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Sample records for rhodium deposits poor

  1. Nanostructured rhodium films produced by pulsed laser deposition for nuclear fusion applications

    NASA Astrophysics Data System (ADS)

    Passoni, M.; Dellasega, D.; Grosso, G.; Conti, C.; Ubaldi, M. C.; Bottani, C. E.

    2010-09-01

    In this paper the possibilities offered by pulsed laser deposition (PLD) for the production of nanostructured rhodium films with improved properties are explored. Thanks to its high reflectivity and low sputtering yield, rhodium is one of the best candidates for the development of thin films to be used in first mirrors, which are crucial components in many diagnostic systems of thermonuclear magnetic fusion machines, like tokamaks. Due to the features of PLD, by varying the process parameters it is possible to tailor both the structure, i.e. the nanocrystalline domain size of the deposited films, down to less than 5 nm and separately control the other relevant physical properties. This leads to modifications in growth regime and annealing dynamics, in such a way that both morphology and reflectivity achieve the properties demanded to use these films as mirrors for fusion applications, opening at the same time new possibilities for the future improvement of thermo-mechanical and adhesion properties.

  2. Degradation of nonmodified and rhodium modified aluminide coating deposited on CMSX 4 superalloy.

    PubMed

    Zagula-Yavorska, Maryana; Wierzbińska, Małgorzata; Gancarczyk, Kamil; Sieniawski, Jan

    2016-07-01

    The Ni-base superalloy CMSX 4 used in the turbine blades of aircraft engines was coated with rhodium layer (0.5-μm thick). Next coated CMSX 4 superalloy was aluminized by the CVD method. The rhodium modified aluminide coating and nonmodified aluminide coating were oxidized at 1100°C at the air atmosphere. The rhodium modified aluminide coating showed about twice better oxidation resistance than the nonmodified one. The spallation equal 62% of the total area was observed on the surface of the nonmodified coating whereas only 36% spallation area was observed on the surface of the rhodium modified aluminide coating after the oxidation test. The oxide layer formed on the surface of the nonmodified coating was composed of nonprotective (Ni,Cr)Al2 O4 and (Ni,Cr)O phases. Aluminium in the coating reacts with oxygen, forming a protective α-Al2 O3 oxide on the surface of the rhodium modified aluminide coating. When the oxide cracks and spalls due to oxidation, additional aluminium from the coating diffuses to the surface to form the oxide. The presence of protective Al2 O3 oxide on the surface of the rhodium modified aluminide coating slows coating degradation. Therefore, rhodium modified aluminide coating has better oxidation resistance than the nonmodified one. © 2016 The Authors Journal of Microscopy © 2016 Royal Microscopical Society.

  3. Microstructure and oxidation behaviour investigation of rhodium modified aluminide coating deposited on CMSX 4 superalloy.

    PubMed

    Zagula-Yavorska, Maryana; Morgiel, Jerzy; Romanowska, Jolanta; Sieniawski, Jan

    2016-03-01

    The CMSX 4 superalloy was coated with rhodium 0.5-μm thick layer and next aluminized by the CVD method. The coating consisted of two layers: the additive and the interdiffusion one. The outward diffusion of nickel from the substrate turned out to be a coating growth dominating factor. The additive layer consists of the β-NiAl phase, whereas the interdiffusion layer consists of the β-NiAl phase with precipitates of σ and μ phases. Rhodium has dissolved in the coating up to the same level in the matrix and in the precipitates. The oxidation test proved that the rhodium modified aluminide coating showed about twice better oxidation resistance than the nonmodified one.

  4. P(CH)P pincer rhodium(I) complexes: the key role of electron-poor imidazoliophosphine extremities.

    PubMed

    Barthes, Cécile; Lepetit, Christine; Canac, Yves; Duhayon, Carine; Zargarian, Davit; Chauvin, Remi

    2013-01-07

    The coordination chemistry of a potentially pincer-type dicationic meta-phenylene-bis(imidazoliophosphine) ligand 3 to neutral and cationic carbonylrhodium(I) centers has been investigated. Similarly to what was observed previously for its ortho-phenylene counterpart, 3 was found to bind to the RhCl(CO) fragment in a trans-chelating manner that makes possible a weak Rh-C(H) interaction, inferred from the nonbonding but relatively short Rh-C and Rh-H contacts observed in the solid state structure of the dicationic adduct (3)RhCl(CO) (5). Formation of the target PCP-type pincer complex could not be triggered despite multiple attempts to deprotonate the central C-H moiety in the initial dicationic adduct 5, or in the tricationic species [(3)Rh(CO)](+) (8) generated by abstraction of the chloride ion from 5. Complex 8 was identified on the basis of NMR and IR analyses as a Rh(I)-stabilized P(CH)P-intermediate en route to the anticipated classical PCP-type pincer complex. Analysis of the electronic structure of this intermediate computed at the density functional level of theory (DFT level) revealed a bonding overlap between a Rh d-orbital and π-orbitals of the m-phenylene ring. NBO analyses and calculated Wiberg indices confirm that this interaction comprises an η(1)-C-Rh bonding mode, with only secondary contributions from the geminal C and H atoms. Although the target PCP-type pincer complex could not be generated, treatment of the tricationic intermediate with methanol induced a P-CN(2) bond cleavage at both imidazoliophosphine moieties, resulting in the formation of a dicationic "open pincer" species, that is, a nonchelated bis((MeO)PPh(2))-stabilized aryl-Rhodium complex that is the κC-only analogue of the putative κP,κC,κP-PCP complex sought initially. Theoretical studies at the DFT level of experimental or putative species relevant to the final C-H activation process ruled out the oxidative addition pathway. Two alternative pathways are proposed to explain

  5. Transition metal oxides deposited on rhodium and platinum: Surface chemistry and catalysis

    SciTech Connect

    Boffa, Alexander Bowman

    1994-07-01

    The surface chemistry and catalytic reactivity of transition metal oxides deposited on Rh and Pt substrates has been examined in order to establish the role of oxide-metal interactions in influencing catalytic activity. The oxides investigated included titanium oxide (TiOx), vanadium oxide (VOx), iron oxide (FeOx), zirconium oxide (ZrOx), niobium oxide (NbOx), tantalum oxide (TaOx), and tungsten oxide (WOx). The techniques used to characterize the sample included AES, XPS, LEED, TPD, ISS, and STM. After characterization of the surface in UHV, the sample was enclosed in an atmospheric reaction cell to measure the influence of the oxide deposits on the catalytic activity of the pure metal for CO and CO2 hydrogenation. The oxide deposits were found to strongly enhance the reactivity of the Rh foil. The rates of methane formation were promoted by up to 15 fold with the maximum in rate enhancement occurring at oxide coverages of approximately 0.5 ML. TiOx TaOx, and NbOx were the most effective promoters and were stable in the highest oxidation states during both reactions (compared to VOx, WOx, and FeOx). The trend in promoter effectiveness was attributed to the direct relationship between oxidation state and Lewis acidity. Bonding at the metal oxide/metal interface between the oxygen end of adsorbed CO and the Lewis acidic oxide was postulated to facilitate C-O bond dissociation and subsequent hydrogenation. 192 refs.

  6. Importance of automobile exhaust catalyst emissions for the deposition of platinum, palladium, and rhodium in the northern hemisphere.

    PubMed

    Rauch, Sebastien; Hemond, Harold F; Barbante, Carlo; Owari, Masanori; Morrison, Gregory M; Peucker-Ehrenbrink, Bernhard; Wass, Urban

    2005-11-01

    An estimated 500 million vehicles worldwide are equipped with an exhaust catalyst that uses platinum group elements (PGE) as the main active components and thus contribute to global PGE emissions. Although PGE emitted from automobile exhaust catalysts were first believed to remain in the roadside environment, we propose here that fine PGE-containing particles in automobile exhaust have resulted in a widespread distribution of emitted PGE. Regional and long-range transport of PGE from automobile exhaust catalysts is supported by elevated PGE deposition in both a peat bog located 250 m from traffic and in central Greenland, respectively. Russian smelters were also found to contribute to PGE contamination in central Greenland. Deposition rates estimated for the roadside environment, the peat bog, and central Greenland were used to provide a first estimate of PGE deposition in the northern hemisphere. The results show that deposition of regionally or long-range transported PGE accounts for a large fraction of total PGE deposition, and PGE deposition in the roadside environment represents less than 5% of the total deposition. Transport at the regional and global scales represents an important component in the environmental cycle of emitted PGE and needs to be further studied to fully assess the environmental fate of PGE from automobile exhaust catalysts.

  7. Overgrowth of Rhodium on Gold Nanorods

    PubMed Central

    2012-01-01

    This study focuses on the deposition and growth mode of rhodium (Rh) on gold (Au) seed nanorods (NRs). Using a combination of scanning transmission electron microscopy imaging, energy-dispersive X-ray spectroscopy, and UV–visible absorption spectroscopy, we show that Rh deposition results in an uneven overlayer morphology on the Au NR seeds, with a tendency for Rh deposition to occur preferentially on the Au NR ends. The results suggest that complex and kinetically driven metal–metal interactions take place in this system. PMID:22582111

  8. The adsorption of acetylene on rhodium-modified colloidal silver, a surface-enhanced Raman study

    NASA Astrophysics Data System (ADS)

    Feilchenfeld, Hannah; Luckier, Miguel; Efron, Leah; Willner, Bilha

    Surface-enhanced Raman scattering (SERS) from molecules adsorbed on rhodium-modified colloidal silver particles is reported for the first time. Deposition of thin layers of metallic rhodium on the silver surface led to fast aggregation of the sol and to modifications of its SERS spectrum. An intense new band, assigned to the RhO stretching vibration of citrate ions bound to rhodium sites, appeared at 530 cm -1 in the Raman spectrum after rhodium addition to the suspension. The spectra of acetylene adsorbed on both unmodified silver particles and silver modified by an overlayer of rhodium indicated that acetylene displaced the citrate ions from their adsorption sites. All acetylene spectra were characterized by weak bands at 1990, 2050 and 2150 cm -1 assigned to σ π-complexes between acetylene and silver, by a silver acetylide peak at 1800 cm -1 and by an intense band at 1550 cm -1 due to C=C containing species formed on the surface. However, on the rhodium-modified colloid an additional band, attributed to acetylene σ π-bound to rhodium sites, was observed at 1910-1920 cm -1. The intensity of the new band was a direct function of the amount of rhodium deposited on the silver. It increased immediately after acetylene adsorption, and later slowly diminished, while simultaneously the 1550 cm -1 peak became more important. This time evolution was ascribed to a reaction taking place on the surface.

  9. Corneal deposits after topical tosufloxacin in a patient with poor tear secretion.

    PubMed

    Kamiya, Kazutaka; Kitahara, Miyuki; Shimizu, Kimiya

    2009-01-01

    To report on severe visual impairment in a patient with decreased tear secretion in whom dense corneal deposits resulted from tosufloxacin treatment after cataract surgery. An 86-year-old woman complained of blurred vision in the left eye. She had been treated with topical applications of tosufloxacin, betamethasone, and diclofenac sodium, all administered 4 times a day as a regimen lasting for 1 month after cataract surgery. In that eye, the best spectacle-corrected visual acuity was 20/200 due to the dense deposits on the cornea. The Schirmer test showed a decrease in basic tear secretion (right eye 2 mm, left eye 1 mm). We removed these deposits surgically and analyzed them by infrared spectrophotometry. The best spectacle-corrected visual acuity markedly improved, to 20/25, after surgical removal of the deposits in the left eye. The spectrophotometric pattern of the deposits was consistent with that of tosufloxacin. Topical application of tosufloxacin may lead to fluoroquinolone drug deposition on the cornea, especially when an antibiotic drug has been used continuously in patients with poor tear secretion.

  10. Role of poorly permeable deposits in the formation of economic yield of groundwaters

    SciTech Connect

    Plugina, T.A.

    1986-05-01

    The formation of the economic yield of groundwaters in layered watersaturated systems represented by an alternation of persistent freely and poorly permeable deposits has a quite complex character. In addition to the water in storage in the exploited aquifer, leakage from adjacent aquifers and surface waters through poorly permeable deposits and drawdown of the water in storage in the latter participate in the formation of the groundwater flow. These factors play a dominant role in the formation of the economic yield. At one of the groundwater reservoirs in the Dnepr-Donetsk artesian basin, the role of the 100-m stratum of Bathonian-Callovian clays in the formation of the economic yield of groundwaters was estimated. The studies presented in this paper were based on pumping tests during which observations were carried out not only in the aquifers but also in the poorly permeable deposits. Refinement of the hydrogeological parameters and analysis of their effect on the formation of groundwater flows were carried out on a digital model. The initial parameters of the model were determined from the data of the experimental groundwater flow studies, thermometry, and compression tests of the clays.

  11. Mesoporous metallic rhodium nanoparticles

    NASA Astrophysics Data System (ADS)

    Jiang, Bo; Li, Cuiling; Dag, Ömer; Abe, Hideki; Takei, Toshiaki; Imai, Tsubasa; Hossain, Md. Shahriar A.; Islam, Md. Tofazzal; Wood, Kathleen; Henzie, Joel; Yamauchi, Yusuke

    2017-05-01

    Mesoporous noble metals are an emerging class of cutting-edge nanostructured catalysts due to their abundant exposed active sites and highly accessible surfaces. Although various noble metal (e.g. Pt, Pd and Au) structures have been synthesized by hard- and soft-templating methods, mesoporous rhodium (Rh) nanoparticles have never been generated via chemical reduction, in part due to the relatively high surface energy of rhodium (Rh) metal. Here we describe a simple, scalable route to generate mesoporous Rh by chemical reduction on polymeric micelle templates [poly(ethylene oxide)-b-poly(methyl methacrylate) (PEO-b-PMMA)]. The mesoporous Rh nanoparticles exhibited a ~2.6 times enhancement for the electrocatalytic oxidation of methanol compared to commercially available Rh catalyst. Surprisingly, the high surface area mesoporous structure of the Rh catalyst was thermally stable up to 400 °C. The combination of high surface area and thermal stability also enables superior catalytic activity for the remediation of nitric oxide (NO) in lean-burn exhaust containing high concentrations of O2.

  12. Could Poor Fens BE More Sensitive than Bogs to Elevated N Deposition in the Oil Sands Region of Northern Alberta?

    NASA Astrophysics Data System (ADS)

    Wieder, R. K.; Vile, M. A.; Scott, K. D.

    2015-12-01

    Bogs and fens cover 29% of the 140,000 km2 Oil Sands Administrative Area (OSAA) in northern Alberta, a region characterized by quite low background N deposition (1-2 kg/ha/yr). However, development of the oil sands resource has led to increasing emission of nitrogen oxides, which are then returned to regional ecosystems as elevated atmospheric N deposition. Given the nutrient deficient nature of bogs and poor fens, elevated N deposition from oil sands development could potentially affect peatland ecosystem structure and function. To evaluate the ecosystem-level effects of N deposition, since 2011, we have experimentally applied N to a bog and a poor fen near Mariana Lakes, Alberta, located far enough from the OSAA to be unaffected by oil sands emissions. Treatments include simulated rainfall equivalent to N deposition of 0, 5, 10, 15, 20, and 25 kg/ha/yr, plus control plots receiving no added water (3 replicate plots per site per N treatment). Concentrations of NH4+-N, NO3- N, and DON at the top of the peatland water table did not increase with increasing N deposition, averaging 0.61, 0.09, and 1.07 mg/L, respectively, in the bog, and 0.53, 0.10, and 0.81 mg/L, respectively, in the poor fen. Ericaceous shrub abundance increased with increasing N deposition in both the bog and the poor fen, although plot-scale greenness (hand-held spectral measurement of the Normalized Difference Red Edge (NDRE) index) increased with N deposition in the poor fen, but not in the bog. Segmented regression indicated that in the poor fen, at N deposition above 14-16 kg/ha/yr, total microbial, bacterial, and fungal biomass in the top 5 cm of peat increased with N deposition, with no effect at lower N deposition. No effect of N deposition on microbial, bacterial, or fungal biomass was observed at 5-10 cm in the poor fen, or at either 0-5 or 5-10 cm in the bog. In the poor fen, microbial, bacterial, and fungal biomass increased with NDRE, but the effect was not significant in the bog

  13. Tumor deposits: markers of poor prognosis in patients with locally advanced rectal cancer following neoadjuvant chemoradiotherapy

    PubMed Central

    Zhang, Lu-Ning; Xiao, Wei-Wei; Xi, Shao-Yan; OuYang, Pu-Yun; You, Kai-Yun; Zeng, Zhi-Fan; Ding, Pei-Rong; Zhang, Hui-Zhong; Pan, Zhi-Zhong; Xu, Rui-Hua; Gao, Yuan-Hong

    2016-01-01

    Background Tumor deposits (TDs) were reported to be poor prognoses in colorectal carcinoma, but the significance in locally advanced rectal cancer (LARC) (T3-4/N+) following neoadjuvant chemoradiotherapy (neo-CRT) and surgery is unclear. Since adjuvant chemotherapy showed no benefit for LARC following neo-CRT, it is of great value to investigate whether TDs can identify the subgroup of patients who may benefit from adjuvant chemotherapy. Methods Between 2004 and 2012, 310 LARC patients following neo-CRT and surgery were retrospectively reviewed. Overall survival (OS), disease-free survival (DFS), distant metastasis free survival (DMFS) and local recurrence free survival (LRFS) were evaluated by Kaplan-Meier method, log-rank test and Cox models. Results TDs-positive patients showed adverse OS, DFS and DMFS (all P≤0.001), but not LRFS (P = 0.273). In multivariate analysis, TDs continued to be associated with poor OS (HR = 2.44, 95% CI 1.32-4.4, P = 0.004) and DFS (HR = 1.99, 95% CI 1.21-3.27, P = 0.007), but not DMFS (HR = 1.77, 95% CI 0.97-3.20, P = 0.061) or LRFS (HR = 1.85, 95% CI 0.58-5.85, P = 0.298). Among TDs-positive patients, adjuvant chemotherapy significantly improved OS (P = 0.045) and DMFS (P = 0.026), but not DFS (P = 0.127) or LRFS (P = 0.862). Conclusions TDs are predictive of poor survival in LARC after neo-CRT. Fortunately, TDs-positive patients appear to benefit from adjuvant chemotherapy. PMID:26695441

  14. Effects of irradiation and annealing on deep levels in rhodium-doped p-GaAs grown by metal-organic chemical-vapor deposition

    SciTech Connect

    Naz, Nazir A.; Qurashi, Umar S.; Iqbal, M. Zafar

    2011-06-01

    This paper reports a detailed study of the effects of irradiation and thermal annealing on deep levels in Rh-doped p-type GaAs grown by low-pressure metal-organic chemical-vapor deposition, using deep level transient spectroscopy (DLTS) technique. It is found upon irradiation with alpha particles that, in addition to the radiation-induced defect peaks, all the Rh-related peaks observed in majority, as well as minority-carrier emission DLTS scans show an increase in their respective concentrations. The usually observed {alpha}-induced defects H{alpha}1, H{alpha}2, and H{alpha}3 are found to have lower introduction rates in Rh-doped samples, as compared to reference samples (not doped with Rh). Alpha-irradiation has been found to decompose the two minority carrier emitting bands (one at low temperature {approx}150 K and the other at {approx}380 K) observed prior to irradiation into distinct peaks corresponding to deep levels Rh1 and Rh2 and EL2 and Rh3, respectively. A similar effect is also observed for the majority-carrier emitting band composed of hole emission from deep levels RhA and RhB, which separate out well upon irradiation. Further, from the double-correlation DLTS measurements, the emission rates of carriers from the radiation-enhanced peaks corresponding to deep levels Rh1, Rh2, Rh3, and RhC were found to be dependent on junction electric field. For RhC, the field dependence data have been analyzed in terms of the Poole-Frenkel model employing a 3-dimensional Coulomb potential with q = 2e (electronic charge). Temperature dependence of the hole capture cross-sections of the levels RhA and RhC was also studied quantitatively. The observed dependence of the hole capture cross-section of RhC on temperature can be interpreted in terms of multiphonon capture model, yielding a capture barrier of 0.2 eV and {sigma}({infinity}) = 2.3 x 10{sup -14} cm{sup 2}. The results of irradiation and isochronal thermal annealing study, in combination with the theoretical

  15. Effects of irradiation and annealing on deep levels in rhodium-doped p-GaAs grown by metal-organic chemical-vapor deposition

    NASA Astrophysics Data System (ADS)

    Naz, Nazir A.; Qurashi, Umar S.; Iqbal, M. Zafar

    2011-06-01

    This paper reports a detailed study of the effects of irradiation and thermal annealing on deep levels in Rh-doped p-type GaAs grown by low-pressure metal-organic chemical-vapor deposition, using deep level transient spectroscopy (DLTS) technique. It is found upon irradiation with alpha particles that, in addition to the radiation-induced defect peaks, all the Rh-related peaks observed in majority, as well as minority-carrier emission DLTS scans show an increase in their respective concentrations. The usually observed α-induced defects Hα1, Hα2, and Hα3 are found to have lower introduction rates in Rh-doped samples, as compared to reference samples (not doped with Rh). Alpha-irradiation has been found to decompose the two minority carrier emitting bands (one at low temperature ˜150 K and the other at ˜380 K) observed prior to irradiation into distinct peaks corresponding to deep levels Rh1 and Rh2 and EL2 and Rh3, respectively. A similar effect is also observed for the majority-carrier emitting band composed of hole emission from deep levels RhA and RhB, which separate out well upon irradiation. Further, from the double-correlation DLTS measurements, the emission rates of carriers from the radiation-enhanced peaks corresponding to deep levels Rh1, Rh2, Rh3, and RhC were found to be dependent on junction electric field. For RhC, the field dependence data have been analyzed in terms of the Poole-Frenkel model employing a 3-dimensional Coulomb potential with q = 2e (electronic charge). Temperature dependence of the hole capture cross-sections of the levels RhA and RhC was also studied quantitatively. The observed dependence of the hole capture cross-section of RhC on temperature can be interpreted in terms of multiphonon capture model, yielding a capture barrier of 0.2 eV and σ(∞) = 2.3 × 10-14 cm2. The results of irradiation and isochronal thermal annealing study, in combination with the theoretical analysis of the field dependence of hole emission data

  16. Formation of supported rhodium clusters from mononuclear rhodium complexes controlled by the support and ligands on rhodium.

    PubMed

    Serna, Pedro; Yardimci, Dicle; Kistler, Joseph D; Gates, Bruce C

    2014-01-21

    Extremely small supported rhodium clusters were prepared from rhodium complexes on the surfaces of solids with contrasting electron-donor properties. The samples were characterized by infrared and extended X-ray absorption fine structure spectroscopies to determine the changes occurring in the rhodium species resulting from treatments in hydrogen. Rhodium cluster formation occurred in the presence of H2, and the first steps are controlled by the electron-donor properties of the support--which acts as a ligand--and the other ligands bonded to the rhodium. The cluster formation begins at a lower temperature when the support is zeolite HY than when it is the better electron-donor MgO, provided that the other ligands on rhodium are ethene. In contrast, when these other ligands are CO, the pattern is reversed. The choice of ligands including the support also allows regulation of the stoichiometry of the surface transformations in H2 and the stability of the structures formed in the presence of other reactants. The combination of MgO as the support and ethene as a ligand allows restriction of the rhodium cluster size to the smallest possible-and these were formed in high yields. The data presented here are among the first characterizing the first steps of metal cluster formation.

  17. Rhodium nanoparticles for ultraviolet plasmonics.

    PubMed

    Watson, Anne M; Zhang, Xiao; Alcaraz de la Osa, Rodrigo; Marcos Sanz, Juan; González, Francisco; Moreno, Fernando; Finkelstein, Gleb; Liu, Jie; Everitt, Henry O

    2015-02-11

    The nonoxidizing catalytic noble metal rhodium is introduced for ultraviolet plasmonics. Planar tripods of 8 nm Rh nanoparticles, synthesized by a modified polyol reduction method, have a calculated local surface plasmon resonance near 330 nm. By attaching p-aminothiophenol, local field-enhanced Raman spectra and accelerated photodamage were observed under near-resonant ultraviolet illumination, while charge transfer simultaneously increased fluorescence for up to 13 min. The combined local field enhancement and charge transfer demonstrate essential steps toward plasmonically enhanced ultraviolet photocatalysis.

  18. Higher lung deposition with Respimat Soft Mist inhaler than HFA-MDI in COPD patients with poor technique.

    PubMed

    Brand, Peter; Hederer, Bettina; Austen, George; Dewberry, Helen; Meyer, Thomas

    2008-01-01

    Aerosols delivered by Respimat Soft Mist Inhaler (SMI) are slower-moving and longer-lasting than those from pressurized metered-dose inhalers (pMDIs), improving the efficiency of pulmonary drug delivery to patients. In this four-way cross-over study, adults with chronic obstructive pulmonary disease (COPD) and with poor pMDI technique received radiolabelled Berodual (fenoterol hydrobromide 50 microg/ipratropium bromide 20 microg) via Respimat SMI or hydrofluoroalkane (HFA)-MDI (randomized order) on test days 1 and 2, with no inhaler technique training. The procedure was repeated on test days 3 and 4 after training. Deposition was measured by gamma scintigraphy. All 13 patients entered (9 males, mean age 62 years; FEV1 46% of predicted) inhaled too fast at screening (peak inspiratory flow rate [IF]: 69-161 L/min). Whole lung deposition was higher with Respimat SMI than with pMDI for untrained (37% of delivered dose vs 21% of metered dose) and trained patients (53% of delivered vs 21% of metered dose) (P(Sign-Test) = 0.15; P(ANOVA) < 0.05). Training also improved inhalation profiles (slower average and peak IF as well as longer breath-hold time). Drug delivery to the lungs with Respimat SMI is more efficient than with pMDI, even with poor inhaler technique. Teaching patients to hold their breath as well as to inhale slowly and deeply increased further lung deposition using Respimat SMI.

  19. Effet de la concentration du cuivre ou de l'argent sur les propriétés des agrégats de rhodium déposés sur silice amorphe dans l'hydrogénation du 1,3 butadiène

    NASA Astrophysics Data System (ADS)

    Ksibi, Z.; Ghorbel1, A.; Bellamy, B.

    1999-02-01

    Some samples with rhodium, rhodium-copper and rhodium-silver deposited on amorphous silica by vapor deposition of the metallic phase under high-vacuum (P < 5.10-7 Pa) have been prepared. The effect of rhodium cluster size and copper or silver addition on catalytic properties of rhodium in the 1,3 butadiène hydrogenation was studied. Results show that the reaction is sensitive to the size of rhodium aggregates and that there is an important difference between the effect of copper and silver on the rhodium properties. Indeed copper forms an alloy with rhodium and provokes a poison effect on the activity of the noble metal, whereas silver exhibits a mask effect on the rhodium particles without forming alloy with it. Des échantillons mono-métalliques au rhodium et bimétalliques rhodium-cuivre et rhodium-argent déposés sur une silice amorphe par vapodéposition d'une phase métallique dans des conditions ultra-vide (P < 5.10-7 Pa) ont été préparés. L'effet de la taille des agrégats de rhodium ainsi que celui de l'addition du cuivre ou de l'argent sur les propriétés catalytiques du rhodium dans l'hydrogénation du 1,3 butadiène ont été étudiés. Les résultats montrent que la réaction étudiée est sensible à la taille des agrégats de rhodium et nous notons une différence importante entre l'effet du cuivre et de l'argent sur les propriétés du rhodium. En effet le cuivre forme un alliage avec le rhodium et provoque un effet poison d?où une modification de l'activité du métal noble, alors que l'argent exerce un effet de masque sur les particules de rhodium sans toutefois former d'alliage avec ce dernier.

  20. A Method to Predict the Thickness of Poorly-Bonded Material Along Spray and Spray-Layer Boundaries in Cold Spray Deposition

    NASA Astrophysics Data System (ADS)

    Li, Yangfan; Hamada, Yukitaka; Otobe, Katsunori; Ando, Teiichi

    2017-02-01

    Multi-traverse CS provides a unique means for the production of thick coatings and bulk materials from powders. However, the material along spray and spray-layer boundaries is often poorly bonded as it is laid by the leading and trailing peripheries of the spray that carry powder particles with insufficient kinetic energy. For the same reason, the splats in the very first layer deposited on the substrate may not be bonded well either. A mathematical spray model was developed based on an axisymmetric Gaussian mass flow rate distribution and a stepped deposition yield to predict the thickness of such poorly-bonded layers in multi-traverse CS deposition. The predicted thickness of poorly-bonded layers in a multi-traverse Cu coating falls in the range of experimental values. The model also predicts that the material that contains poorly bonded splats could exceed 20% of the total volume of the coating.

  1. A Method to Predict the Thickness of Poorly-Bonded Material Along Spray and Spray-Layer Boundaries in Cold Spray Deposition

    NASA Astrophysics Data System (ADS)

    Li, Yangfan; Hamada, Yukitaka; Otobe, Katsunori; Ando, Teiichi

    2016-12-01

    Multi-traverse CS provides a unique means for the production of thick coatings and bulk materials from powders. However, the material along spray and spray-layer boundaries is often poorly bonded as it is laid by the leading and trailing peripheries of the spray that carry powder particles with insufficient kinetic energy. For the same reason, the splats in the very first layer deposited on the substrate may not be bonded well either. A mathematical spray model was developed based on an axisymmetric Gaussian mass flow rate distribution and a stepped deposition yield to predict the thickness of such poorly-bonded layers in multi-traverse CS deposition. The predicted thickness of poorly-bonded layers in a multi-traverse Cu coating falls in the range of experimental values. The model also predicts that the material that contains poorly bonded splats could exceed 20% of the total volume of the coating.

  2. New Fischer carbene complexes of rhodium(i): preparation and 2-cyclopentenone ring synthesis by annelation to alkynes.

    PubMed

    Barluenga, José; Vicente, Rubén; López, Luis A; Rubio, Eduardo; Tomás, Miguel; Alvarez-Rúa, Carmen

    2004-01-21

    A new type of metal carbene complexes of group 9, specifically a cationic Fischer carbene of rhodium(I), has been synthesized from chromium carbene complexes via double transfer of carbene and CO ligands. These complexes reveal a different reactivity than other transition metal carbenes, including their chromium precursors, toward neutral and electron-poor alkynes, giving selectively polysubstituted cyclopentenones.

  3. Superconductivity in zirconium-rhodium alloys

    NASA Technical Reports Server (NTRS)

    Zegler, S. T.

    1969-01-01

    Metallographic studies and transition temperature measurements were made with isothermally annealed and water-quenched zirconium-rhodium alloys. The results clarify both the solid-state phase relations at the Zr-rich end of the Zr-Rh alloy system and the influence upon the superconducting transition temperature of structure and composition.

  4. Do deposit-feeders compete? Isotopic niche analysis of an invasion in a species-poor system

    PubMed Central

    Karlson, Agnes M. L.; Gorokhova, Elena; Elmgren, Ragnar

    2015-01-01

    Successful establishment of invasive species is often related to the existence of vacant niches. Competition occurs when invaders use the same limiting resources as members of the recipient community, which will be reflected in some overlap of their trophic niches. The concept of isotopic niche has been used to study trophic niche partitioning among species. Here, we present a two-year field study comparing isotopic niches of the deposit-feeding community in a naturally species-poor system. The isotopic niche analyses showed no overlap between a recent polychaete invader and any of the native species suggesting that it has occupied a vacant niche. Its narrow isotopic niche suggests specialized feeding, however, the high δ15N values compared to natives are most likely due to isotope fractionation effects related to nitrogen recycling and a mismatch between biological stoichiometry of the polychaete and the sediment nitrogen content. Notably, highly overlapping isotopic niches were inferred for the native species, which is surprising in a food-limited system. Therefore, our results demonstrate that invaders may broaden the community trophic diversity and enhance resource utilization, but also raise questions about the congruence between trophic and isotopic niche concepts and call for careful examination of assumptions underlying isotopic niche interpretation. PMID:25988260

  5. Monodisperse Platinum and Rhodium Nanoparticles as Model Heterogeneous Catalysts

    SciTech Connect

    Grass, Michael Edward

    2008-09-01

    Model heterogeneous catalysts have been synthesized and studied to better understand how the surface structure of noble metal nanoparticles affects catalytic performance. In this project, monodisperse rhodium and platinum nanoparticles of controlled size and shape have been synthesized by solution phase polyol reduction, stabilized by polyvinylpyrrolidone (PVP). Model catalysts have been developed using these nanoparticles by two methods: synthesis of mesoporous silica (SBA-15) in the presence of nanoparticles (nanoparticle encapsulation, NE) to form a composite of metal nanoparticles supported on SBA-15 and by deposition of the particles onto a silicon wafer using Langmuir-Blodgett (LB) monolayer deposition. The particle shapes were analyzed by transmission electron microscopy (TEM) and high resolution TEM (HRTEM) and the sizes were determined by TEM, X-ray diffraction (XRD), and in the case of NE samples, room temperature H2 and CO adsorption isotherms. Catalytic studies were carried out in homebuilt gas-phase reactors. For the nanoparticles supported on SBA-15, the catalysts are in powder form and were studied using the homebuilt systems as plug-flow reactors. In the case of nanoparticles deposited on silicon wafers, the same systems were operated as batch reactors. This dissertation has focused on the synthesis, characterization, and reaction studies of model noble metal heterogeneous catalysts. Careful control of particle size and shape has been accomplished though solution phase synthesis of Pt and Rh nanoparticles in order to elucidate further structure-reactivity relationships in noble metal catalysis.

  6. 103Rh NMR spectroscopy and its application to rhodium chemistry.

    PubMed

    Ernsting, Jan Meine; Gaemers, Sander; Elsevier, Cornelis J

    2004-09-01

    Rhodium is used for a number of large processes that rely on homogeneous rhodium-catalyzed reactions, for instance rhodium-catalyzed hydroformylation of alkenes, carbonylation of methanol to acetic acid and hydrodesulfurization of thiophene derivatives (in crude oil). Many laboratory applications in organometallic chemistry and catalysis involve organorhodium chemistry and a wealth of rhodium coordination compounds is known. For these and other areas, 103Rh NMR spectroscopy appears to be a very useful analytical tool. In this review, most of the literature concerning 103Rh NMR spectroscopy published from 1989 up to and including 2003 has been covered. After an introduction to several experimental methods for the detection of the insensitive 103Rh nucleus, a discussion of factors affecting the transition metal chemical shift is given. Computational aspects and calculations of chemical shifts are also briefly addressed. Next, the application of 103Rh NMR in coordination and organometallic chemistry is elaborated in more detail by highlighting recent developments in measurement and interpretation of 103Rh NMR data, in relation to rhodium-assisted reactions and homogeneous catalysis. The dependence of the 103Rh chemical shift on the ligands at rhodium in the first coordination sphere, on the complex geometry, oxidation state, temperature, solvent and concentration is treated. Several classes of compounds and special cases such as chiral rhodium compounds are reviewed. Finally, a section on scalar coupling to rhodium is provided. 2004 John Wiley & Sons, Ltd.

  7. Light-induced reduction of rhodium(III) and palladium(II) on titanium dioxide dispersions and the selective photochemical separation and recovery of gold(III), platinum(IV), and rhodium(III) in chloride media

    SciTech Connect

    Borgarello, E.; Serpone, N.; Emo, G.; Harris, R.; Pelizzetti, E.; Minero, C.

    1986-12-03

    Irradiation of aqueous TiO/sub 2/ dispersions containing palladium(II) or rhodium(III) chloride salts with AM1 simulated sunlight leads to the photoreduction of these metals, which are deposited on the semiconductor particle surface. Oxygen is detrimental to the photoreduction of rhodium(III) but not the photoreduction of palladium(II). However, in both cases the reduction process is most efficient if the solution contains CH/sub 3/OH, which acts to scavenge valence band holes of the illuminated TiO/sub 2/ semiconductor. The selective photoreduction and recovery of precious metals from a dilute solution (as might be found in industrial wastes) have been investigated for a mixture of gold(III), platinum(IV), and rhodium(III) chloride salts as a function of various parameters (pH, presence or absence of O/sub 2/, presence or absence of a hole scavenger, and the concentration of the semiconductor). At pH 0, gold is easily separated from platinum and rhodium. The rate of photoreduction of gold(III) on TiO/sub 2/ is nearly independent of the concentration of the semiconductor, under the experimental conditions employed; the limiting rate is 2.7 x 10/sup -7/ M s/sup -1/. The potential utility of this selective photochemical technique is discussed.

  8. Vapor deposition of thin films

    DOEpatents

    Smith, David C.; Pattillo, Stevan G.; Laia, Jr., Joseph R.; Sattelberger, Alfred P.

    1992-01-01

    A highly pure thin metal film having a nanocrystalline structure and a process of preparing such highly pure thin metal films of, e.g., rhodium, iridium, molybdenum, tungsten, rhenium, platinum, or palladium by plasma assisted chemical vapor deposition of, e.g., rhodium(allyl).sub.3, iridium(allyl).sub.3, molybdenum(allyl).sub.4, tungsten(allyl).sub.4, rhenium(allyl).sub.4, platinum(allyl).sub.2, or palladium(allyl).sub.2 are disclosed. Additionally, a general process of reducing the carbon content of a metallic film prepared from one or more organometallic precursor compounds by plasma assisted chemical vapor deposition is disclosed.

  9. Rhodium-rhodium interactions in [Rh(β-diketonato)(CO)2] complexes

    NASA Astrophysics Data System (ADS)

    Conradie, Marrigje Marianne; van Rooyen, Petrus H.; Pretorius, Carla; Roodt, Andreas; Conradie, Jeanet

    2017-09-01

    The solid state single crystal structures of [Rh(β-diketonato)(CO)2], where β-diketonato = (R1COCHCOR2)-, with R1, R2 = CF3, C4H3S (1), C4H3S, C4H3S (2), Ph, C4H3S (3) and CF3, Ph (4), show that these complexes in some cases form dinuclear units, which stack in chains with weak metallophilic rhodium-rhodium interactions, while in other cases they produce continuous polymeric units, with equal intermolecular Rh⋯Rh distances. Different solid state structural data is reported herein for these four complexes, including a low temperature comparison with ambient data for (4). In the latter case, weak intermolecular halogen bonding has also been identified, which additionally contributes to the stability of (4) in the solid state. Computational evaluation of the frontier molecular orbitals of both dinuclear and tetranuclear models of complexes (1)-(4), show Rh(dz2)-Rh(dz2) σ bonding and σ* anti-bonding orbitals. An NBO analysis of the dinuclear units, revealed a donor-acceptor interaction between the two rhodium atoms in such a unit, while a QTAIM study identified a bonding path between the two rhodium atoms therein.

  10. Rhodium oxides in unusual oxidation states

    NASA Astrophysics Data System (ADS)

    Reisner, Barbara Alice

    Mixed valence RhIII/RhIV oxides have been proposed as a promising class of candidate compounds for superconductivity. Unfortunately, it is difficult to stabilize rhodates with a formal oxidation state approaching RhIV, as other techniques used for the synthesis of rhodium. oxides favor the most commonly observed formal oxidation state, RhIII. One technique which has been used to stabilize metal oxides in high formal oxidation states is crystallization from molten hydroxides. This thesis explores the use of molten hydroxides to enhance the reactivity of rhodium oxides in order to synthesize rhodates with high formal oxidation states. K0.5RhO2, Rb0.2RhO2, and CsxRhO2 were synthesized from pure alkali metal hydroxides. All crystallized with a previously unobserved polytype in the alkali metal rhodate system. Due to the low activity of dissolved oxygen species in LiOH and NaOH, LiRhO2 and NaRhO2 cannot be crystallized. The formal oxidation state of rhodium in AxRhO2 (A = K, Rb, Cs) is a function of the alkali metal hydroxide used to synthesize these oxides. These materials exhibit remarkable stability for layered metal oxides containing the heavier alkali metals, but all phases are susceptible to intercalation by water. The synthesis, structural characterization, magnetic susceptibility, and reactivity of these oxides are reported. Sr2RhO4 and a new rhodate were crystallized from a KOH-Sr(OH)2 flux. The synthesis and characterization of these materials is reported. Efforts to substitute platinum for rhodium in Sr 2RhO4 are also discussed. Mixed alkali metal-alkaline earth metal hydroxide fluxes were used to crystallize LiSr3RhO6, and NaSr3RhO 6. The synthesis of LiSr3RhO6 and NaSr3RhO 6 represents the first example of the stabilization of a rhodium oxide with a formal oxidation state approaching RhV. X-ray diffraction, electron beam microprobe analysis, thermogravimetric analysis, potentiometric titrations, X-ray photoelectron spectroscopy, and magnetic susceptibility

  11. Chemical Posttranslational Modification with Designed Rhodium(II) Catalysts.

    PubMed

    Martin, S C; Minus, M B; Ball, Z T

    2016-01-01

    Natural enzymes use molecular recognition to perform exquisitely selective transformations on nucleic acids, proteins, and natural products. Rhodium(II) catalysts mimic this selectivity, using molecular recognition to allow selective modification of proteins with a variety of functionalized diazo reagents. The rhodium catalysts and the diazo reactivity have been successfully applied to a variety of protein folds, the chemistry succeeds in complex environments such as cell lysate, and a simple protein blot method accurately assesses modification efficiency. The studies with rhodium catalysts provide a new tool to study and probe protein-binding events, as well as a new synthetic approach to protein conjugates for medical, biochemical, or materials applications.

  12. Structural properties of small rhodium clusters

    SciTech Connect

    Soon, Yee Yeen; Yoon, Tiem Leong; Lim, Thong Leng

    2015-04-24

    We report a systematic study of the structural properties of rhodium clusters at the atomistic level. A novel global-minimum search algorithm, known as parallel tempering multicanonical basin hopping plus genetic algorithm (PTMBHGA), is used to obtain the geometrical structures with lowest minima at the semi-empirical level where Gupta potential is used to describe the atomic interaction among the rhodium atoms. These structures are then re-optimized at the density functional theory (DFT) level with exchange-correlation energy approximated by Perdew-Burke-Ernzerhof (PBE) generalized gradient approximation (GGA). The structures are optimized for different spin multiplicities. The ones with lowest energies will be taken as ground-state structures. In most cases, we observe only minor changes in the geometry and bond length of the clusters as a result of DFT-level re-optimization. Only in some limited cases, the initial geometries obtained from the PTMBHGA are modified by the re-optimization. The variation of structural properties, such as ground-state geometry, symmetry and binding energy, with respect to the cluster size is studied and agreed well with other results available in the literature.

  13. Poor correlation between the removal or deposition of pollen grains and frequency of pollinator contact with sex organs.

    PubMed

    Sakamoto, Ryota L; Morinaga, Shin-Ichi

    2013-09-01

    Pollinators deposit pollen grains on stigmas and remove pollen grains from anthers. The mechanics of these transfers can now be quantified with the use of high-speed video. We videoed hawkmoths, carpenter bees, and swallowtail butterflies pollinating Clerodendrum trichotomum. The number of grains deposited on stigmas did not vary significantly with the number of times pollinators contacted stigmas. In contrast, pollen removal from the anthers increased significantly with the number of contacts to anthers. Pollen removal varied among the three types of pollinators. Also, the three types carried pollen on different parts of their bodies. In hawkmoths and carpenter bees, a large number of contacted body part with anthers differed significantly from the body part that attached a large number of pollen grains. Our results indicate that a large number of contacts by pollinators does not increase either the male or female reproductive success of plants compared to a small number of contacts during a visit.

  14. Poor correlation between the removal or deposition of pollen grains and frequency of pollinator contact with sex organs

    NASA Astrophysics Data System (ADS)

    Sakamoto, Ryota L.; Morinaga, Shin-Ichi

    2013-09-01

    Pollinators deposit pollen grains on stigmas and remove pollen grains from anthers. The mechanics of these transfers can now be quantified with the use of high-speed video. We videoed hawkmoths, carpenter bees, and swallowtail butterflies pollinating Clerodendrum trichotomum. The number of grains deposited on stigmas did not vary significantly with the number of times pollinators contacted stigmas. In contrast, pollen removal from the anthers increased significantly with the number of contacts to anthers. Pollen removal varied among the three types of pollinators. Also, the three types carried pollen on different parts of their bodies. In hawkmoths and carpenter bees, a large number of contacted body part with anthers differed significantly from the body part that attached a large number of pollen grains. Our results indicate that a large number of contacts by pollinators does not increase either the male or female reproductive success of plants compared to a small number of contacts during a visit.

  15. Oxidation-promoted activation of a ferrocene C-H bond by a rhodium complex.

    PubMed

    Labande, Agnès; Debono, Nathalie; Sournia-Saquet, Alix; Daran, Jean-Claude; Poli, Rinaldo

    2013-05-14

    The oxidation of a rhodium(I) complex containing a ferrocene-based heterodifunctional phosphine N-heterocyclic carbene (NHC) ligand produces a stable, planar chiral rhodium(III) complex with an unexpected C-H activation on ferrocene. The oxidation of rhodium(I) to rhodium(III) may be accomplished by initial oxidation of ferrocene to ferrocenium and subsequent electron transfer from rhodium to ferrocenium. Preliminary catalytic tests showed that the rhodium(III) complex is active for the Grignard-type arylation of 4-nitrobenzaldehyde via C-H activation of 2-phenylpyridine.

  16. Experimental and theoretical deposition rates from salt-seeded combustion gases of a Mach 0.3 burner rig

    NASA Technical Reports Server (NTRS)

    Santoro, G. J.; Kohl, F. J.; Stearns, C. A.; Gokoglu, S. A.; Rosner, D. E.

    1984-01-01

    Deposition rates on platinum-rhodium cylindrical collectors rotating in the cross streams of the combustion gases of a salt-seeded Mach 0.3 burner rig were determined. The collectors were internally air cooled so that their surface temperatures could be widely varied while they were exposed to constant combustion gas temperatures. The deposition rates were compared with those predicted by the chemically frozen boundary layer (CFBL) computer program, which is based on multicomponent vapor transport through the boundary layer. Excellent agreement was obtained between theory and experiment for the NaCl-seeded case, but the agreement lessened as the seed was changed to synthetic sea salt, NaNO3, and K2SO4, respectively, and was particularly poor in the case of Na2SO4. However, when inertial impaction was assumed to be the deposition mechanism for the Na2SO4 case, the predicted rates agreed well with the experimental rates. The former were calculated from a mean particle diameter that was derived from the measured intial droplet size distribution of the solution spray. Critical experiments showed that liquid phase deposits were blown off the smooth surface of the platinum-rhodium collectors by the aerodynamic shear forces of the high-velocity combustion gases but that rough or porous surfaces retained their liquid deposits.

  17. Examination of a low-temperature rhodium oxidation mechanism

    SciTech Connect

    Salanov, A.N.; Savchenko, V.I.

    1994-09-01

    The interaction of O{sub 2} with Rh(100) and polycrystalline rhodium at O{sub 2} pressures of 10{sup {minus}5} - 10{sup 3} Pa at 400-600 K is studied by thermodesorption and Auger electron spectroscopy. At P{sub O{sub 2}} = 10{sup {minus}5} - 10{sup {minus}1} Pa, a surface rhodium oxide is formed, whereas at P{sub O{sub 2}} {ge} 10{sup {minus}1} Pa, a bulk rhodium oxide (Rh{sub 2}O{sub 3}) is produced. The bulk oxide film grows by the Cabrera-Mott mechanism of low-temperature metal oxidation. The film growth is dependent on P{sub O{sub 2}} and the sample temperature. The data obtained indicates that the rhodium surface structure has a minor influence on the oxidation process.

  18. Rhodium-Catalyzed Dehydrogenative Borylation of Cyclic Alkenes

    PubMed Central

    Kondoh, Azusa; Jamison, Timothy F.

    2010-01-01

    A rhodium-catalyzed dehydrogenative borylation of cyclic alkenes is described. This reaction provides direct access to cyclic 1-alkenylboronic acid pinacol esters, useful intermediates in organic synthesis. Suzuki-Miyaura cross-coupling applications are also presented. PMID:20107646

  19. Enantioselective rhodium(I)-catalyzed hydrogenation of trifluoromethyl ketones.

    PubMed

    Kuroki, Y; Sakamaki, Y; Iseki, K

    2001-02-08

    [figure: see text] The asymmetric hydrogenation of trifluoromethyl ketones to yield chiral alpha-trifluoromethyl alcohols with enantiomeric excesses up to 98% was achieved in the presence of chiral rhodium-(amidephosphine-phosphinite) complexes.

  20. Polyethylene-bound rhodium(I) hydrogenation catalysts

    SciTech Connect

    Bergbreiter, D.E.; Chandran, R.

    1987-01-07

    Homogeneous, recoverable hydrogenation catalysts were prepared with use of functionalized ethylene oligomers as ligands. Phosphine groups were introduced onto ethylene oligomers following anionic oligomerization of ethylene. The product polyethylenediphenylphosphine ligands were then exchanged with triphenylphosphine or ethylene ligands to prepare ethylene oligomer ligated rhodium(I) complexes. These Rh(I) complexes had the solubility of polyethylene and dissolved at 90-110/sup 0/C in hydrocarbon solvents but quantitatively precipitated at 25/sup 0/C. Less than 0.1% of the charged rhodium was lost in each dissolution precipitation cycle. The rhodium(I) complexes so prepared were shown to have about 80% of the activity of tris(triphenylphosphine)rhodium chloride in hydrogenation of various alkenes including 1-octene, ..delta../sup 2/-cholestene, cyclooctene, cyclododecene, styrene, and ..cap alpha..-methylstyrene. /sup 31/P NMR spectroscopy and reactivity studies were used to characterize these catalysts.

  1. Low gravity containerless processing of immiscible gold rhodium alloys

    NASA Technical Reports Server (NTRS)

    Andrews, J. Barry

    1986-01-01

    Under normal one-g conditions immiscible alloys segregate extensively during solidification due to sedementation of the more dense of the immiscible liquid phases. However, under low-g conditions it should be possible to form a dispersion of the two immiscible liquids and maintain this dispersed structure during solidification. Immiscible (hypermonotectic) gold-rhodium alloys were processed in the Marshall Space Flight Center 105 meter drop tube in order to investigate the influence of low gravity, containerless solidification on their microstructure. Hypermonotectic alloys composed of 65 atomic % rhodium exhibited a tendency for the gold rich liquid to wet the outer surface of the containerless processed samples. This tendency led to extensive segregation in several cases. However, well dispersed microstructures consisting of 2 to 3 micron diameter rhodium-rich spheres in a gold-rich matrix were produced in 23.4 atomic % rhodium alloys. This is one of the best dispersions obtained in research on immiscible alloy-systems to data.

  2. Rhodium-Catalyzed Transannulation of 1,2,3-Triazoles with Nitriles

    PubMed Central

    Horneff, Tony; Chuprakov, Stepan; Chernyak, Natalia

    2009-01-01

    Stable and readily available 1-sulfonyl triazoles are converted to the corresponding imidazoles in good to excellent yields via a rhodium(II)-catalyzed reaction with nitriles. Rhodium iminocarbenoids are proposed intermediates. PMID:18855475

  3. Monodisperse colloidal metal particle from nonaqueous solutions: catalytic behavior in hydrogenation of but-1-ene of platinum, palladium, and rhodium particles supported on pumice

    SciTech Connect

    Boutonnet, M.; Kizling, J.; Mintsa-Eya, V.; Choplin, A.; Touroude, R.; Maire, G.; Stenius, P.

    1987-01-01

    Metal catalysts have been prepared by depositing monodisperse particles of platinum (2-3 nm), rhodium (2-3 nm), or palladium (5 nm) prepared in reversed micellar solutions on pumice. The particles are well dispersed on the support whereas particles deposited from aqueous or alcoholic solution give large aggregates. The catalytic properties of these different catalysts in the deuteration, isomerization, and hydrogen-deuterium exchange of but-1-ene have been compared. The activities calculated per metal surface atom are similar. However, platinum prepared from microemulsions show unusually high selectivity in the isomerization reaction, and for such particles dehydrogenated species are active in the exchange reaction. The specificity of rhodium and palladium catalysts is independent of the mode of preparation. The reaction mechanisms are discussed.

  4. Rhodium(NHC)-catalyzed O-arylation of aryl bromides.

    PubMed

    Kim, Hyun Jin; Kim, Min; Chang, Sukbok

    2011-05-06

    The first example of the rhodium-catalyzed O-arylation of aryl bromides is reported. While the right combination of rhodium species and N-heterocyclic carbene (NHC) offered an effective catalytic system enabling the arylation to proceed, the choice of NHC was determined to be most important. The developed O-arylation protocol has a wide range of substrate scope, high functional group tolerance, and flexibility allowing a complementary route to either N- or O-arylation depending on the choice of NHC.

  5. High pressure synthesis of marcasite-type rhodium pernitride.

    PubMed

    Niwa, Ken; Dzivenko, Dmytro; Suzuki, Kentaro; Riedel, Ralf; Troyan, Ivan; Eremets, Mikhail; Hasegawa, Masashi

    2014-01-21

    Marcasite-type rhodium nitride was successfully synthesized in a direct chemical reaction between a rhodium metal and molecular nitrogen at 43.2 GPa using a laser-heated diamond-anvil cell. This material shows a low zero-pressure bulk modulus of K0 = 235(13) GPa, which is much lower than those of other platinum group nitrides. This finding is due to the weaker bonding interaction between metal atoms and quasi-molecular dinitrogen units in the marcasite-type structure, as proposed by theoretical studies.

  6. H 2 production from CH 4 decomposition: Regeneration capability and performance of nickel and rhodium oxide catalysts

    NASA Astrophysics Data System (ADS)

    Rivas, M. E.; Hori, C. E.; Fierro, J. L. G.; Goldwasser, M. R.; Griboval-Constant, A.

    Nickel-lanthanum (LaNiO 3) and nickel-rhodium-lanthanum (LaNi 0.95Rh 0.05O 3) perovskite-type oxide precursors were synthesized by different methodologies (co-precipitation, sol-gel and impregnation). They were reduced in an H 2 atmosphere to produce nickel and rhodium nanoparticles on the La 2O 3 substrate. All samples were tested in the catalytic decomposition of CH 4. Methane decomposed into carbon and H 2 at reaction temperatures as low as 450 °C-no other reaction products were observed. Conversions were in the range of 14-28%, and LaNi 0.95Rh 0.05O 3 synthesized by co-precipitation was the most active catalyst. All catalysts maintained sustained activity even after massive carbon deposition indicating that these deposits are of the nanotube-type, as confirmed by transmission electron microscopy (TEM). The reaction seems to occur in a way that a nickel or rhodium crystal face is always clean enough to expose sufficient active sites to make the catalytic process continue. The samples were subjected to a reduction-oxidation-reduction cycle and in situ analyses confirmed the stability of the perovskite structure. All diffraction patterns showed a phase change around 400 °C, due to reduction of LaNiO 3 to an intermediate La 2Ni 2O 5 structure. When the reduction temperatures reach 600 °C, this structure collapses through the formation of Ni 0 crystallites deposited on the La 2O 3. Under oxidative conditions, the perovskite system is recomposed with nickel re-entering the LaNiO 3 framework structure accounting for the regenerative capability of these solids.

  7. Radioiodinated and astatinated NHC rhodium complexes: synthesis.

    PubMed

    Rajerison, Holisoa; Guérard, François; Mougin-Degraef, Marie; Bourgeois, Mickael; Da Silva, Isidro; Chérel, Michel; Barbet, Jacques; Faivre-Chauvet, Alain; Gestin, Jean-François

    2014-05-01

    The clinical development of radioimmunotherapy with astatine-211 is limited by the lack of a stable radiolabeling method for antibody fragments. An astatinated N-heterocyclic carbene (NHC) Rhodium complex was assessed for the improvement of radiolabeling methodologies with astatine. Wet harvested astatine-211 in diisopropyl ether was used. Astatine was first reduced with cysteine then was reacted with a chlorinated Rh-NHC precursor to allow the formation of the astatinated analogue. Reaction conditions have been optimized. Astatine and iodine reactivity were also compared. Serum stability of the astatinated complex has been evaluated. Quantitative formation of astatide was observed when cysteine amounts higher than 46.2 nmol/μl of astatine solution were added. Nucleophilic substitution kinetics showed that high radiolabeling yields were obtained within 15 min at 60°C (88%) or within 5 min at 100°C (95%). Chromatographic characteristics of this new astatinated compound have been correlated with the cold iodinated analog ones. The radioiodinated complex was also synthesized from the same precursor (5 min. at 100°C, up to 85%) using [(125)I]NaI as a radiotracer. In vitro stability of the astatinated complex was controlled after 15 h incubation in human serum at 4°C and 37°C. No degradation was observed, indicating the good chemical and enzymatic stability. The astatinated complex was obtained in good yield and exhibited good chemical and enzymatic stability. These preliminary results demonstrate the interest of this new radiolabeling methodology, and further functionalizations should open new possibilities in astatine chemistry. Although there are many steps and pitfalls before clinical use for a new prosthetic group from the family of NHC complexes, this work may open a new path for astatine-211 targeting. Copyright © 2014 Elsevier Inc. All rights reserved.

  8. Electronic and magnetic properties of small rhodium clusters

    SciTech Connect

    Soon, Yee Yeen; Yoon, Tiem Leong; Lim, Thong Leng

    2015-04-24

    We report a theoretical study of the electronic and magnetic properties of rhodium-atomic clusters. The lowest energy structures at the semi-empirical level of rhodium clusters are first obtained from a novel global-minimum search algorithm, known as PTMBHGA, where Gupta potential is used to describe the atomic interaction among the rhodium atoms. The structures are then re-optimized at the density functional theory (DFT) level with exchange-correlation energy approximated by Perdew-Burke-Ernzerhof generalized gradient approximation. For the purpose of calculating the magnetic moment of a given cluster, we calculate the optimized structure as a function of the spin multiplicity within the DFT framework. The resultant magnetic moments with the lowest energies so obtained allow us to work out the magnetic moment as a function of cluster size. Rhodium atomic clusters are found to display a unique variation in the magnetic moment as the cluster size varies. However, Rh{sub 4} and Rh{sub 6} are found to be nonmagnetic. Electronic structures of the magnetic ground-state structures are also investigated within the DFT framework. The results are compared against those based on different theoretical approaches available in the literature.

  9. Recent advances in rhodium-catalyzed asymmetric synthesis of heterocycles.

    PubMed

    Chen, Wen-Wen; Xu, Ming-Hua

    2017-02-01

    Heterocycles are crucial structural motifs that are ubiquitously present in biologically active natural products and pharmaceutically important compounds. Over the past few decades, great attention has been paid to develop efficient methodologies for the construction of diverse enantioenriched heterocyclic frameworks. This review focuses on the recent impressive progress and advances in the asymmetric synthesis of heterocycles under rhodium catalysis.

  10. Discovery of rubidium, strontium, molybdenum, and rhodium isotopes

    SciTech Connect

    Parker, A.M.; Thoennessen, M.

    2012-07-15

    Currently, 31 rubidium, 35 strontium, 35 molybdenum, and 38 rhodium isotopes have been observed and the discovery of these isotopes is described here. For each isotope a brief synopsis of the first refereed publication, including the production and identification method, is presented.

  11. In vitro permeation of platinum and rhodium through Caucasian skin.

    PubMed

    Franken, A; Eloff, F C; Du Plessis, J; Badenhorst, C J; Jordaan, A; Du Plessis, J L

    2014-12-01

    During platinum group metals (PGMs) refining the possibility exists for dermal exposure to PGM salts. The dermal route has been questioned as an alternative route of exposure that could contribute to employee sensitisation, even though literature has been focused on respiratory exposure. This study aimed to investigate the in vitro permeation of platinum and rhodium through intact Caucasian skin. A donor solution of 0.3mg/ml of metal, K2PtCl4 and RhCl3 respectively, was applied to the vertical Franz diffusion cells with full thickness abdominal skin. The receptor solution was removed at various intervals during the 24h experiment, and analysed with high resolution ICP-MS. Skin was digested and analysed by ICP-OES. Results indicated cumulative permeation with prolonged exposure, with a significantly higher mass of platinum permeating after 24h when compared to rhodium. The mass of platinum retained inside the skin and the flux of platinum across the skin was significantly higher than that of rhodium. Permeated and skin retained platinum and rhodium may therefore contribute to sensitisation and indicates a health risk associated with dermal exposure in the workplace.

  12. Rhodium complexes bearing tetradentate diamine-bis(phenolate) ligands

    SciTech Connect

    Liu, Xiang Y; Lokare, Kapil S; Ganesh, Somesh K; Gonzales, Jason M; Oxgaard, Jonas; Goddard, William A; Periana, Roy A

    2011-01-01

    Using tetradentate, dianionic ligands, several new rhodium complexes have been prepared. Some of these diamine-bis(phenolate) compounds, are active for C–H activation of benzene. These complexes are air and thermally stable. All four complexes were characterized by X-ray diffraction.

  13. Impact of simulated atmospheric nitrogen deposition on nutrient cycling and carbon sink via mycorrhizal fungi in two nutrient-poor peatlands

    NASA Astrophysics Data System (ADS)

    Larmola, Tuula; Kiheri, Heikki; Bubier, Jill L.; van Dijk, Netty; Dise, Nancy; Fritze, Hannu; Hobbie, Erik A.; Juutinen, Sari; Laiho, Raija; Moore, Tim R.; Pennanen, Taina

    2017-04-01

    Peatlands store one third of the global soil carbon (C) pool. Long-term fertilization experiments in nutrient-poor peatlands showed that simulated atmospheric nitrogen (N) deposition does not enhance ecosystem C uptake but reduces C sink potential. Recent studies have shown that a significant proportion of C input to soil in low-fertility forests entered the soil through mycorrhizal fungi, rather than as plant litter. Is atmospheric N deposition diminishing peatland C sink potential due to the suppression of ericoid mycorrhizal fungi? We studied how nutrient addition influences plant biomass allocation and the extent to which plants rely on mycorrhizal N uptake at two of the longest-running nutrient addition experiments on peatlands, Whim Bog, United Kingdom, and Mer Bleue Bog, Canada. We determined the peak growing season aboveground biomass production and coverage of vascular plants using the point intercept method. We also analyzed isotopic δ15N patterns and nutrient contents in leaves of dominant ericoid mycorrhizal shrubs as well as the non-mycorrhizal sedge Eriophorum vaginatum under different nutrient addition treatments. The treatments receive an additional load of 1.6-6.4 N g m-2 y-1 either as ammonium (NH4) nitrate (NO3) or NH4NO3 and with or without phosphorus (P) and potassium (K), alongside unfertilized controls. After 11-16 years of nutrient addition, the vegetation structure had changed remarkably. Ten of the eleven nutrient addition treatments showed an increase of up to 60% in total vascular plant abundance. Only three (NH4Cl, NH4ClPK, NaNO3PK) of the nutrient addition treatments showed a concurrent decrease of down to 50% in the relative proportion of ericoid mycorrhizal shrubs to total vascular plant abundance. The response to nutrient load may be explained by the water table depth, the form of N added and whether N was added with PK. Shrubs were strong competitors at the dry Mer Bleue bog while sedges gained in abundance at the wetter Whim bog

  14. Deposition of crystalline hydroxyapatite nano-particle on zirconia ceramic: a potential solution for the poor bonding characteristic of zirconia ceramics to resin cement.

    PubMed

    Azari, Abbas; Nikzad, Sakineh; Yazdani, Arash; Atri, Faezeh; Fazel Anvari-Yazdi, Abbas

    2017-07-01

    The poor bonding strength of zirconia to different dental substrates is one of the challenging issues in restorative dentistry. Hydroxyapatite is an excellent biocompatible material with fine bonding properties. In this study, it was hypothesized that hydroxyapatite coating on zirconia would improve its bond strength. Forty-five zirconia blocks were prepared and randomly divided into three groups: hydroxyapatite coating, sandblasting, and no preparation (control). The blocks were bonded to cement and the micro-shear bond strength was measured following load application. The bond strength values were analyzed with the Kruskal-Wallis test in 3 groups and paired comparisons were made using the Mann-Whitney U test. The failure patterns of the specimens were studied by a stereomicroscope and a scanning electron microscope and then analyzed by the chi-square test (significance level = 0.05). Deposition of hydroxyapatite on the zirconia surface significantly improved its bond strength to the resin cement in comparison with the control specimens (p < 0.0001). Also, the bond strength was similar to the sandblasted group (p = 0.34). The sandblasted and control group only showed adhesive failure, but the hydroxyapatite coated group had mixed failures, indicating the better quality of bonding (p < 0.0001). As a final point, hydroxyapatite coating on the zirconia surface improved the bond strength quality and values.

  15. Interfacial bonding stabilizes rhodium and rhodium oxide nanoparticles on layered Nb oxide and Ta oxide supports.

    PubMed

    Strayer, Megan E; Binz, Jason M; Tanase, Mihaela; Shahri, Seyed Mehdi Kamali; Sharma, Renu; Rioux, Robert M; Mallouk, Thomas E

    2014-04-16

    Metal nanoparticles are commonly supported on metal oxides, but their utility as catalysts is limited by coarsening at high temperatures. Rhodium oxide and rhodium metal nanoparticles on niobate and tantalate supports are anomalously stable. To understand this, the nanoparticle-support interaction was studied by isothermal titration calorimetry (ITC), environmental transmission electron microscopy (ETEM), and synchrotron X-ray absorption and scattering techniques. Nanosheets derived from the layered oxides KCa2Nb3O10, K4Nb6O17, and RbTaO3 were compared as supports to nanosheets of Na-TSM, a synthetic fluoromica (Na0.66Mg2.68(Si3.98Al0.02)O10.02F1.96), and α-Zr(HPO4)2·H2O. High surface area SiO2 and γ-Al2O3 supports were also used for comparison in the ITC experiments. A Born-Haber cycle analysis of ITC data revealed an exothermic interaction between Rh(OH)3 nanoparticles and the layered niobate and tantalate supports, with ΔH values in the range -32 kJ·mol(-1) Rh to -37 kJ·mol(-1) Rh. In contrast, the interaction enthalpy was positive with SiO2 and γ-Al2O3 supports. The strong interfacial bonding in the former case led to "reverse" ripening of micrometer-size Rh(OH)3, which dispersed as 0.5 to 2 nm particles on the niobate and tantalate supports. In contrast, particles grown on Na-TSM and α-Zr(HPO4)2·H2O nanosheets were larger and had a broad size distribution. ETEM, X-ray absorption spectroscopy, and pair distribution function analyses were used to study the growth of supported nanoparticles under oxidizing and reducing conditions, as well as the transformation from Rh(OH)3 to Rh nanoparticles. Interfacial covalent bonding, possibly strengthened by d-electron acid/base interactions, appear to stabilize Rh(OH)3, Rh2O3, and Rh nanoparticles on niobate and tantalate supports.

  16. Plasmonics in the UV range with Rhodium nanocubes

    NASA Astrophysics Data System (ADS)

    Zhang, X.; Gutiérrez, Y.; Li, P.; Barreda, Á. I.; Watson, A. M.; Alcaraz de la Osa, R.; Finkelstein, G.; González, F.; Ortiz, D.; Saiz, J. M.; Sanz, J. M.; Everitt, H. O.; Liu, J.; Moreno, F.

    2016-04-01

    Plasmonics in the UV-range constitutes a new challenge due to the increasing demand to detect, identify and destroy biological toxins, enhance biological imaging, and characterize semiconductor devices at the nanometer scale. Silver and aluminum have an efficient plasmonic performance in the near UV region, but oxidation reduces its performance in this range. Recent studies point out rhodium as one of the most promising metals for this purpose: it has a good plasmonic response in the UV and, as gold in the visible, it presents a low tendency to oxidation. Moreover, its easy fabrication through chemical means and its potential for photocatalytic applications, makes this material very attractive for building plasmonic tools in the UV. In this work, we will show an overview of our recent collaborative research with rhodium nanocubes (NC) for Plasmonics in the UV.

  17. Antitumor effect and toxicity of free rhodium (II) citrate and rhodium (II) citrate-loaded maghemite nanoparticles in mice bearing breast cancer.

    PubMed

    Carneiro, Marcella Lemos Brettas; Peixoto, Raphael C A; Joanitti, Graziela A; Oliveira, Ricardo G S; Telles, Luis A M; Miranda-Vilela, Ana L; Bocca, Anamélia L; Vianna, Leonora M S; da Silva, Izabel C R; de Souza, Aparecido R; Lacava, Zulmira G M; Báo, Sônia N

    2013-02-16

    Magnetic fluids containing superparamagnetic iron oxide nanoparticles represent an attractive platform as nanocarriers in chemotherapy. Recently, we developed a formulation of maghemite nanoparticles coated with rhodium (II) citrate, which resulted in in vitro cytotoxicity enhanced up to 4.6 times when compared to free rhodium (II) citrate formulation on breast carcinoma cells. In this work, we evaluate the antitumor activity and toxicity induced by these formulations in Balb/c mice bearing orthotopic 4T1 breast carcinoma. Mice were evaluated with regard to the treatments' toxicity through analyses of hemogram, serum levels of alanine aminotransferase, iron, and creatinine; DNA fragmentation and cell cycle of bone marrow cells; and liver, kidney and lung histology. In addition, the antitumor activity of rhodium (II) citrate and maghemite nanoparticles coated with rhodium (II) citrate was verified by tumor volume reduction, histology and immunohistochemistry. Regarding the treatments' toxicity, no experimental groups had alterations in levels of serum ALT or creatinine, and this suggestion was corroborated by the histopathologic examination of liver and kidney of mice. Moreover, DNA fragmentation frequency of bone marrow cells was lower than 15% in all experimental groups. On the other hand, the complexes rhodium (II) citrate-functionalized maghemite and free rhodium (II) citrate led to a marked growth inhibition of tumor and decrease in CD31 and Ki-67 staining. In summary, we demonstrated that both rhodium (II) citrate and maghemite nanoparticles coated with rhodium (II) citrate formulations exhibited antitumor effects against 4T1 metastatic breast cancer cell line following intratumoral administration. This antitumor effect was followed by inhibition of both cell proliferation and microvascularization and by tumor tissue injury characterized as necrosis and fibrosis. Remarkably, this is the first published report demonstrating the therapeutic efficacy of maghemite

  18. Antitumor effect and toxicity of free rhodium (II) citrate and rhodium (II) citrate-loaded maghemite nanoparticles in mice bearing breast cancer

    PubMed Central

    2013-01-01

    Background Magnetic fluids containing superparamagnetic iron oxide nanoparticles represent an attractive platform as nanocarriers in chemotherapy. Recently, we developed a formulation of maghemite nanoparticles coated with rhodium (II) citrate, which resulted in in vitro cytotoxicity enhanced up to 4.6 times when compared to free rhodium (II) citrate formulation on breast carcinoma cells. In this work, we evaluate the antitumor activity and toxicity induced by these formulations in Balb/c mice bearing orthotopic 4T1 breast carcinoma. Methods Mice were evaluated with regard to the treatments’ toxicity through analyses of hemogram, serum levels of alanine aminotransferase, iron, and creatinine; DNA fragmentation and cell cycle of bone marrow cells; and liver, kidney and lung histology. In addition, the antitumor activity of rhodium (II) citrate and maghemite nanoparticles coated with rhodium (II) citrate was verified by tumor volume reduction, histology and immunohistochemistry. Results Regarding the treatments’ toxicity, no experimental groups had alterations in levels of serum ALT or creatinine, and this suggestion was corroborated by the histopathologic examination of liver and kidney of mice. Moreover, DNA fragmentation frequency of bone marrow cells was lower than 15% in all experimental groups. On the other hand, the complexes rhodium (II) citrate-functionalized maghemite and free rhodium (II) citrate led to a marked growth inhibition of tumor and decrease in CD31 and Ki-67 staining. Conclusions In summary, we demonstrated that both rhodium (II) citrate and maghemite nanoparticles coated with rhodium (II) citrate formulations exhibited antitumor effects against 4T1 metastatic breast cancer cell line following intratumoral administration. This antitumor effect was followed by inhibition of both cell proliferation and microvascularization and by tumor tissue injury characterized as necrosis and fibrosis. Remarkably, this is the first published report

  19. Asymmetric Arylation of Imines Catalyzed by Heterogeneous Chiral Rhodium Nanoparticles.

    PubMed

    Yasukawa, Tomohiro; Kuremoto, Tatsuya; Miyamura, Hiroyuki; Kobayashi, Shu̅

    2016-06-03

    Asymmetric arylation of aldimines catalyzed by heterogeneous chiral rhodium nanoparticles has been developed. The reaction proceeded in aqueous media without significant decomposition of the imines by hydrolysis to afford chiral (diarylmethyl)amines in high yields with outstanding enantioselectivities. This catalyst system exhibited the highest turnover number (700) in heterogeneous catalysts reported to date for these reactions. The reusability of the catalyst was also demonstrated.

  20. Arylation of Rhodium(II) Azavinyl Carbenes with Boronic Acids

    PubMed Central

    Selander, Nicklas; Worrell, Brady T.; Chuprakov, Stepan; Velaparthi, Subash; Fokin, Valery V.

    2013-01-01

    A highly efficient and stereoselective arylation of in situ generated azavinyl carbenes affording 2,2-diaryl enamines at ambient temperatures has been developed. These transition metal carbenes are directly produced from readily available and stable 1-sulfonyl-1,2,3-triazoles in the presence of a rhodium carboxylate catalyst. In several cases, the enamines generated in this reaction can be cyclized into substituted indoles employing copper catalysts. PMID:22913576

  1. Recovery of rhodium(III) from solutions and industrial wastewaters by a sulfate-reducing bacteria consortium.

    PubMed

    Ngwenya, Nonhlanhla; Whiteley, Chris G

    2006-01-01

    A quantitative analysis of the rate of removal of rhodium(III) by a resting sulfate-reducing bacteria (SRB) consortium under different initial rhodium and biomass concentrations, pH, temperature, and electron donor was studied. Rhodium speciation was found to be the main factor controlling the rate of its removal from solution. SRB cells were found to have a higher affinity for anionic rhodium species, as compared to both cationic and neutral species, which become abundant when speciation equilibrium was reached. Consequently, a pH-dependent rate of rhodium removal from solution was observed. The maximum SRB uptake capacity for rhodium was found to be 66 mg of rhodium per gram of resting SRB biomass. Electron microscopy studies revealed a time-dependent localization and distribution of rhodium precipitates, initially intracellularly and then extracellularly, suggesting the involvement of an enzymatic reductive precipitation process. When a purified hydrogenase enzyme was incubated with rhodium chloride solution under hydrogen, 88% of the rhodium was removed within 1 h, whereas with a soluble extract from SRB 77% was removed within 10 min. Due to the low pH of the industrial effluent (1.31), the enzymatic reduction of rhodium by the purified hydrogenase was greatly limited, and it was apparent that an industrial effluent pretreatment was necessary before the application of an enzymatic treatment. In the present study, however, it was established that SRB are good candidates for the enzymatic recovery of rhodium from both aqueous solution and industrial effluent.

  2. Electronic structure of ternary rhodium hydrides with lithium and magnesium.

    PubMed

    Becker, Jonas Nils; Bauer, Jessica; Giehr, Andreas; Chu, Pui Ieng; Kunkel, Nathalie; Springborg, Michael; Kohlmann, Holger

    2014-01-21

    Chemical bonding in and electronic structure of lithium and magnesium rhodium hydrides are studied theoretically using DFT methods. For Li3RhH4 with planar complex RhH4 structural units, Crystal Orbital Hamilton Populations reveal significant Rh−Rh interactions within infinite one-dimensional ∞ 1 [RhH4] stacks in addition to strong rhodium−hydrogen bonding. These metal−metal interactions are considerably weaker in the hypothetical, heavier homologue Na3RhH4. Both compounds are small-band gap semiconductors. The electronic structures of Li3RhH6 and Na3RhH6 with rhodium surrounded octahedrally by hydrogen, on the other hand, are compatible with a classical complex hydride model according to the limiting ionic formula (M+)3[RhH6]3− without any metal−metal interaction between the 18-electron hydridorhodate complexes. In MgRhH, building blocks of the composition (RhH2)4 are formed with strong rhodium−hydrogen and significant rhodium−rhodium bonding (bond lengths of 298 pm within Rh4 squares). These units are linked together to infinite two-dimensional layers ∞ 2 [(RhH2/2)4] via common hydrogen atoms. Li3RhH4 and MgRhH are accordingly examples for border cases of chemical bonding where the classical picture of hydridometalate complexes in complex hydrides is not sufficient to properly describe the chemical bonding situation.

  3. Time-Resolved, In Situ DRIFTS/EDE/MS Studies on Alumina-Supported Rhodium Catalysts: Effects of Ceriation and Zirconiation on Rhodium–CO Interactions**

    PubMed Central

    Kroner, Anna B; Newton, Mark A; Tromp, Moniek; Roscioni, Otello M; Russell, Andrea E; Dent, Andrew J; Prestipino, Carmelo; Evans, John

    2014-01-01

    The effects of ceria and zirconia on the structure–function properties of supported rhodium catalysts (1.6 and 4 wt % Rh/γ-Al2O3) during CO exposure are described. Ceria and zirconia are introduced through two preparation methods: 1) ceria is deposited on γ-Al2O3 from [Ce(acac)3] and rhodium metal is subsequently added, and 2) through the controlled surface modification (CSM) technique, which involves the decomposition of [M(acac)x] (M=Ce, x=3; M=Zr, x=4) on Rh/γ-Al2O3. The structure–function correlations of ceria and/or zirconia-doped rhodium catalysts are investigated by diffuse reflectance infrared Fourier-transform spectroscopy/energy-dispersive extended X-ray absorption spectroscopy/mass spectrometry (DRIFTS/EDE/MS) under time-resolved, in situ conditions. CeOx and ZrO2 facilitate the protection of Rh particles against extensive oxidation in air and CO. Larger Rh core particles of ceriated and zirconiated Rh catalysts prepared by CSM are observed and compared with Rh/γ-Al2O3 samples, whereas supported Rh particles are easily disrupted by CO forming mononuclear Rh geminal dicarbonyl species. DRIFTS results indicate that, through the interaction of CO with ceriated Rh particles, a significantly larger amount of linear CO species form; this suggests the predominance of a metallic Rh phase. PMID:25044889

  4. Homogeneous hydrogenation of unsaturated organic compounds catalyzed by rhodium complexes containing trioctylamine as a ligand

    SciTech Connect

    Frolov, V.M.; Shuikina, L.P.; Turisbekova, K.K.; Bondarenko, G.N.

    1994-11-01

    Two new types of toluene-soluble rhodium-complex catalysts for hydrogenation of multiple carbon-carbon bonds are synthesized by the reaction of rhodium salts with trioctylamine. The productivity of these catalysts reaches 26000 moles of substrate per gram-atom of rhodium per hour at 20{degrees}C and at a hydrogen pressure of 0.1 MPa. The promoting effect of molecular oxygen and water on homogeneous rhodium-complex catalysts prepared by direct interaction of rhodium trichloride with trioctylamine is established. A scheme for catalyst activation involving the reversible chemisorption of oxygen by the complex is proposed on the basis of IR-spectroscopic data. The kinetics of hydrogenation of unsaturated hydrocarbons is studied.

  5. Free Rhodium (II) citrate and rhodium (II) citrate magnetic carriers as potential strategies for breast cancer therapy.

    PubMed

    Carneiro, Marcella L B; Nunes, Eloiza S; Peixoto, Raphael C A; Oliveira, Ricardo G S; Lourenço, Luiza H M; da Silva, Izabel C R; Simioni, Andreza R; Tedesco, Antônio C; de Souza, Aparecido R; Lacava, Zulmira G M; Báo, Sônia N

    2011-03-28

    Rhodium (II) citrate (Rh(2)(H(2)cit)(4)) has significant antitumor, cytotoxic, and cytostatic activity on Ehrlich ascite tumor. Although toxic to normal cells, its lower toxicity when compared to carboxylate analogues of rhodium (II) indicates (Rh(2)(H(2)cit)(4)) as a promising agent for chemotherapy. Nevertheless, few studies have been performed to explore this potential. Superparamagnetic particles of iron oxide (SPIOs) represent an attractive platform as carriers in drug delivery systems (DDS) because they can present greater specificity to tumor cells than normal cells. Thus, the association between Rh(2)(H(2)cit)(4) and SPIOs can represent a strategy to enhance the former's therapeutic action. In this work, we report the cytotoxicity of free rhodium (II) citrate (Rh(2)(H(2)cit)(4)) and rhodium (II) citrate-loaded maghemite nanoparticles or magnetoliposomes, used as drug delivery systems, on both normal and carcinoma breast cell cultures. Treatment with free Rh(2)(H(2)cit)(4) induced cytotoxicity that was dependent on dose, time, and cell line. The IC(50) values showed that this effect was more intense on breast normal cells (MCF-10A) than on breast carcinoma cells (MCF-7 and 4T1). However, the treatment with 50 μM Rh(2)(H(2)cit)(4)-loaded maghemite nanoparticles (Mag(h)-Rh(2)(H(2)cit)(4)) and Rh(2)(H(2)cit)(4)-loaded magnetoliposomes (Lip-Magh-Rh(2)(H(2)cit)(4)) induced a higher cytotoxicity on MCF-7 and 4T1 than on MCF-10A (p < 0.05). These treatments enhanced cytotoxicity up to 4.6 times. These cytotoxic effects, induced by free Rh(2)(H(2)cit)(4), were evidenced by morphological alterations such as nuclear fragmentation, membrane blebbing and phosphatidylserine exposure, reduction of actin filaments, mitochondrial condensation and an increase in number of vacuoles, suggesting that Rh(2)(H(2)cit)(4) induces cell death by apoptosis. The treatment with rhodium (II) citrate-loaded maghemite nanoparticles and magnetoliposomes induced more specific cytotoxicity

  6. Electrochemical deposition of iridium and iridium-nickel-alloys

    NASA Astrophysics Data System (ADS)

    Näther, J.; Köster, F.; Freudenberger, R.; Schöberl, C.; Lampke, T.

    2017-03-01

    To develop durable and reliable electronic contacts, precious metals are still very important for finish plating of contact surfaces. The lesser-known iridium might be an interesting alternative to substitute gold alloys, platinum or rhodium for applications with highest demands to wear and corrosion resistance such as sliding and plug contacts. As matters stand there is no commercial electrolyte for iridium plating. Initial investigation screened the parameter range for different iridium compounds when an iridium layer occurred on the substrates. This approach showed that the oxidation state of iridium is crucial to reach contenting deposits. Best results came from Ir(IV) electrolyte with high bromine concentration coming from the starting compound, while electrolytes made from Ir(III) compounds gave very poor deposits. In subsequent experiments different organic compounds were added to the electrolytes to improve plating efficiency and stability of the solutions. So found electrolytes gave crack-free deposits up to two microns with a micro-hardness of 600 HV. To reduce the iridium content in the layer, iridium-nickel-alloys were investigated, finding that a nickel-content of 10 wt% raised the layer hardness to more than 900 HV.

  7. Poor Sleep Habits = Poor Grades

    MedlinePlus

    ... https://medlineplus.gov/news/fullstory_166509.html Poor Sleep Habits = Poor Grades Study of college students finds ... socialize, college life seems geared toward an erratic sleep schedule. But new research suggests that an unpredictable ...

  8. Gas-phase chemistry of ruthenium and rhodium carbonyl complexes.

    PubMed

    Cao, Shiwei; Wang, Yang; Qin, Zhi; Fan, Fangli; Haba, Hiromitsu; Komori, Yukiko; Wu, Xiaolei; Tan, Cunmin; Zhang, Xin

    2016-01-07

    Short-lived ruthenium and rhodium isotopes were produced from a (252)Cf spontaneous fission (SF) source. Their volatile carbonyl complexes were formed in gas-phase reactions in situ with the carbon-monoxide containing gas. A gas-jet system was employed to transport the volatile carbonyls from the recoil chamber to the chemical separation apparatus. The gas-phase chemical behaviors of these carbonyl complexes were studied using an online low temperature isothermal chromatography (IC) technique. Long IC columns made up of FEP Teflon were used to obtain the chemical information of the high-volatile Ru and Rh carbonyls. By excluding the influence of precursor effects, short-lived isotopes of (109-110)Ru and (111-112)Rh were used to represent the chemical behaviours of Ru and Rh carbonyls. Relative chemical yields of about 75% and 20% were measured for Ru(CO)5 and Rh(CO)4, respectively, relative to the yields of KCl aerosols transported in Ar gas. The adsorption enthalpies of ruthenium and rhodium carbonyl complexes on a Teflon surface were determined to be around ΔHads = -33(+1)(-2) kJ mol(-1) and -36(+2)(-1) kJ mol(-1), respectively, by fitting the breakthrough curves of the corresponding carbonyl complexes with a Monte Carlo simulation program. Different from Mo and Tc carbonyls, a small amount of oxygen gas was found to be not effective for the chemical yields of ruthenium and rhodium carbonyl complexes. The general chemical behaviors of short-lived carbonyl complexes of group VI-IX elements were discussed, which can be used in the future study on the gas-phase chemistry of superheavy elements - Bh, Hs, and Mt carbonyls.

  9. The promotion of CO dissociation by molybdenum oxide overlayers on rhodium

    NASA Astrophysics Data System (ADS)

    Szenti, Imre; Bugyi, László; Kónya, Zoltán

    2017-03-01

    A considerable promotional effect of MoOx species observed at high pressures on the catalytic activity of rhodium initiated the present UHV model study. The MoOx overlayers formed on Rh films (0.15-20.0 ML) supported by TiO2(110) substrate were characterized by AES, TPD, work function (WF) measurements and CO adsorption. On the mixed oxide support produced by depositing 1.2 ML Mo onto TiO2(110), a new recombinative CO desorption state was observed with Tp=700 K, assigned as β-CO and related to the promotional effect of MoOx species diffused onto Rh particles of 1.0 ML coverage. The development of β-CO needs 0.5-0.7 ML threshold Rh coverage, attributable to particle size effect and geometric factors governing the CO adsorption. The β-CO state with Tp=725-742 K could also be detected on Rh films covered by MoOx moiety formed by the oxidation of Mo overlayers in O2. Remarkably, recombinative CO desorption with Tp=700 K could be observed on the Rh nanoparticles covered by MoOzCy produced from pure Mo deposits by CO adsorption, too. In harmony with the promotional effect of MoOx overlayer found at high pressures, it is established that the dissociation of CO is maximal at 0.2-0.3 ML Mo coverage, attributed to the presence of active sites at the oxide-metal interface. The low desorption peak temperature (700 K) of associative CO desorption observed in the presence of MoOx and MoOzCy overlayers indicates a low activation energy for the reactions of Oa and Ca atoms, allowing high reaction rates for these intermediates. The MoOx species exerted both promotion and inhibition effects on CO adsorption at sub-monolayer coverages, but above 1 ML it completely suppressed the reactivity of rhodium layers towards CO, suggesting that its surface concentration is a critical factor.

  10. The solubility of hydrogen in rhodium, ruthenium, iridium and nickel.

    NASA Technical Reports Server (NTRS)

    Mclellan, R. B.; Oates, W. A.

    1973-01-01

    The temperature variation of the solubility of hydrogen in rhodium, ruthenium, iridium, and nickel in equilibrium with H2 gas at 1 atm pressure has been measured by a technique involving saturating the solvent metal with hydrogen, quenching, and analyzing in resultant solid solutions. The solubilities determined are small (atom fraction of H is in the range from 0.0005 to 0.00001, and the results are consistent with the simple quasi-regular model for dilute interstitial solid solutions. The relative partial enthalpy and excess entropy of the dissolved hydrogen atoms have been calculated from the solubility data and compared with well-known correlations between these quantities.

  11. Rhodium-catalyzed enantioselective cyclopropanation of electron deficient alkenes

    PubMed Central

    Wang, Hengbin; Guptill, David M.; Alvarez, Adrian Varela

    2013-01-01

    The rhodium-catalyzed reaction of electron-deficient alkenes with substituted aryldiazoacetates and vinyldiazoacetates results in highly stereoselective cyclopropanations. With adamantylglycine derived catalyst Rh2(S-TCPTAD)4, high asymmetric induction (up to 98% ee) can be obtained with a range of substrates. Computational studies suggest that the reaction is facilitated by weak interaction between the carbenoid and the substrate carbonyl but subsequently proceeds via different pathways depending on the nature of the carbonyl.. Acrylates and acrylamides result in the formation of cyclopropanation products while the use of unsaturated aldehydes and ketones results in the formation of epoxides. PMID:24049630

  12. Structure of adsorbed organometallic rhodium: model single atom catalysts.

    PubMed

    Bennett, R A; McCavish, N D; Basham, M; Dhanak, V R; Newton, M A

    2007-02-02

    We have determined the structure of a complex rhodium carbonyl chloride [Rh(CO)2Cl] molecule adsorbed on the TiO2(110) surface by the normal incidence x-ray standing wave technique. The data show that the technique is applicable to reducible oxide systems and that the dominant adsorbed species is undissociated with Rh binding atop bridging oxygen and to the Cl found close to the fivefold coordinated Ti ions in the surface. A minority geminal dicarbonyl species, where Rh-Cl bond scission has occurred, is found bridging the bridging oxygen ions forming a high-symmetry site.

  13. Atomic-absorption determination of rhodium in chromite concentrates

    USGS Publications Warehouse

    Schnepfe, M.M.; Grimaldi, F.S.

    1969-01-01

    Rhodium is determined in chromite concentrates by atomic absorption after concentration either by co-precipitation with tellurium formed by the reduction of tellurite with tin(II) chloride or by fire assay into a gold bead. Interelement interferences in the atomic-absorption determination are removed by buffering the solutions with lanthanum sulphate (lanthanum concentration 1%). Substantial amounts of Ag, Al, Au, Bi, Ca, Cd, Co, Cr, Cu, Fe, Ho, Hg, K, La, Mg, Mn, Mo, Na, Ni, Pb, Te, Ti, V, Y, Zn and platinum metals can be tolerated. A lower limit of approximately 0.07 ppm Rh can be determined in a 3-g sample. ?? 1969.

  14. Recyclable rhodium nanoparticles: green hydrothermal synthesis, characterization, and highly catalytic performance in reduction of nitroarenes.

    PubMed

    Lee, Yohan; Jang, Seongwan; Cho, Chang-Woo; Bae, Jong-Seong; Park, Sungkyun; Park, Kang Hyun

    2013-11-01

    In this work, rhodium nanoparticles were synthesized using hydrothermal method that is simple and easy to manipulate reaction and use nontoxic supercritical water. The rhodium nanoparticles were formed in uniform size and shape. These Rh NPs also acted as a efficient heterogenous catalyst in reduction of 4-nitrophenol to 4-aminophenol. Moreover, the rhodium nanoparticles can be recycled without any loss in catalytic activity, and showed highly catalytic activity for various nitroarenes. Therefore, this method will contribute greatly to the development of environmental field and be suitable for use in the industry.

  15. Structural Evolution of a Recoverable Rhodium Hydrogenation Catalyst

    SciTech Connect

    Shaw, Wendy J.; Chen, Yongsheng; Fulton, John L.; Linehan, John C.; Gutowska, Anna; Bitterwolf, Thomas E.

    2008-06-01

    N-isopropylacrylamide was utilized as a ligand to affect recoverability into a rhodium hydrogenation catalyst. The catalyst ligand structure was characterized in situ using NMR, XAFS and IR. Model compounds including glycine, cysteamine and methionine methyl ester were also investigated to aid in the interpretation. The investigation revealed a ligand switch from RNH2 to RSR’ when the catalyst is placed in water as opposed to organic solvents. The catalyst continued to transform with time, creating Rh clusters of up to 4 rhodium atoms, with no Rh metal detected. Over the time and solvents investigated, the catalyst ligands evolve from 1-Cl, 1-NH2, and 2-CO’s to 3-Rh, 1-RSR’ and 1-CO. Upon introduction of the alkene for hydrogenation catalysis, the Rh cluster is lost, favoring instead the interaction with the reactant. The kinetics of the hydrogenation reaction were measured using a novel high pressure flow through NMR system and the catalyst was found to have a TOF of 3000/hr at 25 ºC. This work was supported by the Laboratory Directed Research and Development Program at the Pacific Northwest National Laboratory operated by Battelle for the U.S. Department of Energy.

  16. Crystal structures of fac-tri-chlorido-tris-(tri-methyl-phosphane-κP)rhodium(III) monohydrate and fac-tri-chlorido-tris-(tri-methyl-phosphane-κP)rhodium(III) methanol hemisolvate: rhodium structures that are isotypic with their iridium analogs.

    PubMed

    Merola, Joseph S; Franks, Marion A

    2015-02-01

    The crystal structures of two solvates of fac-tri-chlorido-tris-(tri-methyl-phosphane-κP)rhodium(III) are reported, i.e. one with water in the crystal lattice, fac-[RhCl3(Me3P)3]·H2O, and one with methanol in the crystal lattice, fac-[RhCl3(Me3P)3]·0.5CH3OH. These rhodium compounds exhibit distorted octahedral coordination spheres at the metal and are isotypic with the analogous iridium compounds previously reported by us [Merola et al. (2013 ▶). Polyhedron, 54, 67-73]. Comparison is made between the rhodium and iridium compounds, highlighting their isostructural relationships.

  17. Deep-level transient-spectroscopy study of rhodium in indium phosphide

    NASA Astrophysics Data System (ADS)

    Dadgar, A.; Ammerlahn, D.; Näser, A.; Heitz, R.; Kuttler, M.; Bimberg, D.; Baber, N.; Hyeon, J. Y.; Schumann, H.

    1996-03-01

    The electrical properties of rhodium-related defects in low-pressure metal-organic chemical-vapor-deposition-grown InP:Rh are investigated. Rh concentrations up to 1×1019 cm-3 are achieved without formation of macroscopic RhxPy precipitates. With deep-level transient spectroscopy, two Rh-related deep levels, RhA and RhB, are observed in p-InP:Rh having zero- and low-field activation energies of EV+0.71 and EV+0.62 eV, respectively. Optimization of the growth parameters allows for both traps to obtain electrically active concentrations up to 2×1015 cm-3. Detailed capacitance transient investigations were undertaken to study the field dependence of the emission rates and the hole capture cross sections of both levels. The emission rate is found to be strongly field dependent for both levels. For RhA the experimental data are well fitted with a Poole-Frenkel model employing a three-dimensional square well potential of 7.5 nm. The field-enhanced emission of RhB can be explained by a Coulomb potential in combination with a phonon-assisted tunneling process. Evidence is given that RhA is the Rh3+/2+ deep acceptor level in InP caused by isolated substitutional Rh on In sites. Both traps are suited as compensating acceptors for the growth of semi-insulating InP.

  18. Electrodeposition of Rhodium Nanowires Arrays and Their Morphology-Dependent Hydrogen Evolution Activity

    PubMed Central

    Zhang, Liqiu; Liu, Lichun; Wang, Hongdan; Shen, Hongxia; Cheng, Qiong; Yan, Chao; Park, Sungho

    2017-01-01

    This work reports on the electrodeposition of rhodium (Rh) nanowires with a controlled surface morphology synthesized using an anodic aluminum oxide (AAO) template. Vertically aligned Rh nanowires with a smooth and coarse morphology were successfully deposited by adjusting the electrode potential and the concentration of precursor ions and by involving a complexing reagent in the electrolyte solution. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses were used to follow the morphological evolution of Rh nanowires. As a heterogeneous electrocatalyst for hydrogen evolution reactions (HER), the coarse Rh nanowire array exhibited an enhanced catalytic performance respect to smooth ones due to the larger surface area to mass ratio and the higher density of catalytically active defects, as evidenced by voltammetric measurements and TEM. Results suggest that the morphology of metallic nanomaterials could be readily engineered by electrodeposition. The controlled electrodeposition offers great potential for the development of an effective synthesis tool for heterogeneous catalysts with a superior performance for wide applications. PMID:28467375

  19. Chloride-Bridged Dinuclear Rhodium(III) Complexes Bearing Chiral Diphosphine Ligands: Catalyst Precursors for Asymmetric Hydrogenation of Simple Olefins.

    PubMed

    Kita, Yusuke; Hida, Shoji; Higashihara, Kenya; Jena, Himanshu Sekhar; Higashida, Kosuke; Mashima, Kazushi

    2016-07-11

    Efficient rhodium(III) catalysts were developed for asymmetric hydrogenation of simple olefins. A new series of chloride-bridged dinuclear rhodium(III) complexes 1 were synthesized from the rhodium(I) precursor [RhCl(cod)]2 , chiral diphosphine ligands, and hydrochloric acid. Complexes from the series acted as efficient catalysts for asymmetric hydrogenation of (E)-prop-1-ene-1,2-diyldibenzene and its derivatives without any directing groups, in sharp contrast to widely used rhodium(I) catalytic systems that require a directing group for high enantioselectivity. The catalytic system was applied to asymmetric hydrogenation of allylic alcohols, alkenylboranes, and unsaturated cyclic sulfones. Control experiments support the superiority of dinuclear rhodium(III) complexes 1 over typical rhodium(I) catalytic systems. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Modifiers in rhodium catalysts for carbon monoxide hydrogenation: Structure-activity relationships

    SciTech Connect

    Bhore, N. A.

    1989-05-01

    This report is aimed at identifying interesting modified rhodium systems and elucidating structure-activity relationships in these systems with the overall goal of understanding the scientific issues in the catalytic conversion of syngas to oxygenates. Specific additives (sodium and molybdenum) are selected based on the scoping experiments. The effect of the additives on supported rhodium catalysts is then investigated. Throughout the investigation, experiments and analysis were performed on real systems instead of ideal systems. 374 refs., 82 figs., 57 tabs.

  1. Rhodium-Catalyzed Ketone Methylation Using Methanol Under Mild Conditions: Formation of α-Branched Products**

    PubMed Central

    Chan, Louis K M; Poole, Darren L; Shen, Di; Healy, Mark P; Donohoe, Timothy J

    2014-01-01

    The rhodium-catalyzed methylation of ketones has been accomplished using methanol as the methylating agent and the hydrogen-borrowing method. The sequence is notable for the relatively low temperatures that are required and for the ability of the reaction system to form α-branched products with ease. Doubly alkylated ketones can be prepared from methyl ketones and two different alcohols by using a sequential one-pot iridium- and rhodium-catalyzed process. PMID:24288297

  2. Effect of Sodium Treatment on the Performance of Electrostatic Spray Assisted Vapour Deposited Copper-poor Cu(In,Ga)(S,Se) 2 Solar Cells.

    PubMed

    Wang, Mingqing; Hossain, Md Anower; Choy, Kwang-Leong

    2017-07-28

    In our work, eco-friendly, non-vacuum and low cost Electrostatic Spray Assisted Vapour Deposition (ESAVD) method has been used to produce Cu(In,Ga)(S,Se)2 (CIGS) solar cells. Copper (Cu) deficient (Cu/In + Ga = 0.76) CIGS films were designed to avoid the rather dangerous KCN treatment step for the removal of conductive minor phases of Cu2S/Cu2Se. A simple sodium (Na) treatment method was used to modify the morphology and electronic properties of the absorber and it clearly improved the solar cell performance. The SEM and XRD results testified a slightly increase of the grain size and (112) crystal orientation in the Na-incorporated CIGS thin films. From the Mott-schottky results, it can be seen that the functions of the Na treatment in our non-vacuum deposited CIGS are mainly used for defect passivation and reduction of charge recombination. Photovoltaic characteristics and j-V curve demonstrated that the dipping of CIGS films in 0.2 M NaCl solution for 20 minutes followed by selenization at 550 °C under selenium vapor resulted in the optimum photovoltaic performance, with j sc, V oc, FF and η of the optimized solar cell of 29.30 mA cm(-2), 0.564 V, 65.59% and 10.83%, respectively.

  3. Rhodium Complex and Enzyme Couple Mediated Electrochemical Detection of Adenosine.

    PubMed

    Han, Dawoon; Kim, Hyeong-Mook; Chand, Rohit; Kim, Gyumin; Shin, Ik-Soo; Kim, Yong-Sang

    2015-10-01

    Adenosine is one of the nucleoside which plays an important role in signal transduction and neuromodulation. This work proposes a simple electrochemical assay, comprising two enzymes and rhodium complex based electron transfer mediator, for the detection of adenosine. Sequential reaction of adenosine deaminase and L-glutamic dehydrogenase and the supporting cycle between β-NADH and mediator enable quantitative analysis of adenosine. Role of electron transfer mediator is the conveyance of proton from electrode to β-NAD(+) for regeneration of β-NADH. The electrochemical characteristics of electron transfer mediator were also studied. Real-time adenosine detection was carried out using this multiple enzyme based chronoamperometric assay. The analysis results show a low limit of detection (140 μM) and good correspondence between current signal and the adenosine concentration (R (2) = 0.997).

  4. Thermal effects on Rhodium nanoparticles supported on carbon

    NASA Astrophysics Data System (ADS)

    Agostini, G.; Grisenti, R.; Lamberti, C.; Piovano, A.; Fornasini, P.

    2013-04-01

    EXAFS measurements have been made in the temperature range 5 - 300 K on rhodium nano-clusters of average diameters 15.9 and 11.5 Å (rms dispersion 7.2 and 4.7 Å, respectively) supported on carbon, as well as on a Rh reference foil. The preliminary results of the first shell analysis are presented. The Debye temperature is slightly smaller in n-Rh with respect to bulk and decreases when the cluster size decreases. The results of amplitude analysis (coordination number and static DW) are sensitive to the inclusion of the 4th cumulant. In going from bulk Rh to n-Rh and decreasing the nanocluster size the average coordination number decreases and the static disorder increases. A contraction of the average nearest-neighbour distance is observed at 5 K, -0.004 Å and -0.009 Å for the larger and smaller clusters, respectively, accompanied by a very slight thermal expansion.

  5. Strong Metal-Support Interactions (smsi) in Model Titania-Supported Rhodium Catalysts.

    NASA Astrophysics Data System (ADS)

    Sadeghi, Hassan Roger

    Model catalysts consisting of rhodium particles supported on well characterized, single crystal rutile substrates were used to study the nature of strong metal -support interactions (SMSI) in supported catalyst systems. The use of single crystal supports eliminates many of the complications inherent with powder supported catalysts and greatly simplifies the interpretation of experimental data. A variety of surface sensitive electron spectroscopic techniques, including ultraviolet and x-ray photoemission (UPS and XPS), electron energy loss (ELS) and Auger spectroscopies, low energy electron diffraction (LEED), combined with chemisorption measurements were applied to rhodium on titania model catalysts in order to separate the various phenomena that contribute to SMSI. The properties of the clean titania supports have been determined, including the dynamics of oxidation of reduced surfaces. Model catalysts were then prepared by thermal evaporation of rhodium onto these supports. The high temperature reduction procedures that produce the SMSI state on powder supported catalysts have been used on the model catalysts, and Auger sputter profiles indicate that during high temperature reduction (HTR) a suboxide of titanium migrates onto the rhodium particles, thus blocking carbon monoxide chemisorption. Removal of the suboxide layer by ion bombardment restores the normal chemisorption properties of the catalyst. Model rhodium on titania catalysts fabricated on both fully oxidized and on partially reduced single crystal supports have also been used. In this way it is possible to observe support-to-metal charge transfer in the absence of the encapsulation that accompanies HTR. The experimental results show that reduced titania species and rhodium interact with each other through a partially ionic bond, with electronic charge transferred from the reduced titanium cations to the rhodium. This bonding interaction is part of the driving force that leads to encapsulation of the

  6. Structure and transport behavior of In-filled cobalt rhodium antimonide skutterudites

    SciTech Connect

    Eilertsen, James; Berthelot, Romain; Sleight, Arthur W.; Subramanian, M.A.

    2012-06-15

    The effect of indium icosahedral void-site filling on the transport properties of cobalt and rhodium antimonide solid solutions is investigated. Co{sub 4-x}Rh{sub x}Sb{sub 12} and indium-filled In{sub 0.1}Co{sub 4-x}Rh{sub x}Sb{sub 12} solid solutions were synthesized. Partial rhodium substitution produces a distinct clustering-induced lattice strain that is partly relieved upon indium substitution into the skutterudite icosahedral void-sites. Indium lowers the thermal conductivity of all samples near room temperature. A distinct increase in thermal conductivity is observed in all indium-filled rhodium substituted samples at elevated temperatures and is attributed to bipolar thermal conductivity. In addition, the indium-filled samples were subjected to a 6-day heat treatment at 673 K. Void-site filled indium was found to be metastable at this temperature, and was found to partially precipitate during the 6-day heat treatment; thereby presenting concerns over the long-term stability of thermoelectric devices based on indium-filled skutterudites. - Graphical Abstract: Strain in the cobalt rhodium skutterudite solid solutions decreases upon indium filling. Highlights: Black-Right-Pointing-Pointer Unfilled and indium-filled cobalt and rhodium skutterudite solid solutions were synthesized. Black-Right-Pointing-Pointer Indium filling stabilizes the cobalt and rhodium skutterudite solid solutions. Black-Right-Pointing-Pointer The thermoelectric properties of all compositions are reported. Black-Right-Pointing-Pointer The thermal conductivity of rhodium-rich compositions is strongly affected by indium filling. Black-Right-Pointing-Pointer Void-site filled indium was found to be metastable.

  7. Zeolite-supported rhodium complexes and clusters: switching catalytic selectivity by controlling structures of essentially molecular species.

    PubMed

    Serna, Pedro; Gates, B C

    2011-04-06

    Precise synthesis and characterization of site-isolated rhodium complexes and extremely small rhodium clusters supported on zeolite HY allow control of the catalyst selectivity in the conversion of ethene to n-butene or ethane, respectively, as a result of tuning the structure of the active sites at a molecular level.

  8. Rhodium mediated bond activation: from synthesis to catalysis

    SciTech Connect

    Ho, Hung-An

    2012-01-01

    Recently, our lab has developed monoanionic tridentate ligand, ToR, showing the corresponding coordination chemistry and catalyst reactivity of magnesium, zirconium, zinc and iridium complexes. This thesis details synthetic chemistry, structural study and catalytic reactivity of the ToR-supported rhodium compounds. Tl[ToR] has been proved to be a superior ligand transfer agent for synthesizing rhodium complexes. The salt metathesis route of Tl[ToM] with [Rh(μ-Cl)(CO)]2 and [Rh(μ- Cl)(COE)]2 gives ToMRh(CO)2 (2.2) and ToMRhH(β3-C8H13) (3.1) respectively while Tl[ToM] with [Rh(μ-Cl)(CO)]2 affords ToPRh(CO)2 (2.3). 2.2 reacts with both strong and weak electrophiles, resulting in the oxazoline N-attacked and the metal center-attacked compounds correspondingly. Using one of the metal center-attacked electrophiles, 2.3 was demonstrated to give high diastereoselectivity. Parallel to COE allylic C-H activation complex 3.1, the propene and allylbenzene allylic C-H activation products have also been synthesized. The subsequent functionalization attempts have been examined by treating with Brønsted acids, Lewis acids, electrophiles, nucleophiles, 1,3-dipolar reagents and reagents containing multiple bonds able to be inserted. Various related complexes have been obtained under these conditions, in which one of the azide insertion compounds reductively eliminates to give an allylic functionalization product stoichiometrically. 3.1 reacts with various primary alcohols to give the decarbonylation dihydride complex ToMRh(H)2CO (4.1). 4.1 shows catalytic reactivity for primary alcohol decarbonylation under a photolytic condition. Meanwhile, 2.2 has been found to be more reactive than 4.1 for catalytic alcohol decarbonylation under the same condition. Various complexes and primary

  9. X-ray photoelectron spectroscopy as a probe of rhodium-ligand interaction in ionic liquids

    NASA Astrophysics Data System (ADS)

    Men, Shuang; Lovelock, Kevin R. J.; Licence, Peter

    2016-02-01

    We use X-ray photoelectron spectroscopy (XPS) to identify the interaction between the rhodium atom and phosphine ligands in six 1-octyl-3-methylimidazolium-based ionic liquids ([C8C1Im][X]). The formation of a mono-phosphine rhodium complex based upon addition of triphenylphosphine (PPh3) is confirmed by XPS in all ionic liquids studied herein. Due to the electron donation effect of the ligand, the rhodium atom becomes more negatively charged and thus exhibits a lower measured binding energy. The influence of the anion basicity on the formation of different types of rhodium complexes is also investigated. By introducing a biphosphine ligand, a chelated diphosphine rhodium complex is formed in ionic liquids with more basic anions and verified by both XPS and Infrared Spectroscopy (IR). The measured Rh 3d binding energies are correlated to the reaction selectivity of a hydroformylation reaction which inspires a method to design a metal catalyst to control the chemical reaction towards desired products in the future.

  10. Rhodium chemzymes: Michaelis-Menten kinetics in dirhodium(II) carboxylate-catalyzed carbenoid reactions.

    PubMed

    Pirrung, Michael C; Liu, Hao; Morehead, Andrew T

    2002-02-13

    Rhodium carboxylate-mediated reactions of diazoketones involving cyclopropanation, C-H insertion, and aromatic C-C double bond addition/electrocyclic ring opening obey saturation (Michaelis-Menten) kinetics. Axial ligands for rhodium, including aromatic hydrocarbons and Lewis bases such as nitriles, ethers, and ketones, inhibit these reactions by a mixed kinetic inhibition mechanism, meaning that they can bind both to the free catalyst and to the catalyst-substrate complex. Substrate inhibition can also be exhibited by diazocompounds bearing these groupings in addition to the diazo group. The analysis of inhibition shows that the active catalyst uses only one of its two coordination sites at a time for catalysis. Some ketones exhibit the interesting property that they selectively bind to the catalyst-substrate complex. The similarity of the kinetic constants from different types of reactions with similar diazoketones, regardless of the linking unit or the environment of the reacting alkene, suggests that the rate-determining step is the generation of the rhodium carbenoid. A very useful rhodium carboxylate catalyst for asymmetric synthesis, Rh(2)(DOSP)(4), shows slightly slower kinetic parameters than the achiral catalysts, implying that enantioselectivity of this catalyst is based on slowing reactions from one of the enantiotopic faces of the reactant, rather than any type of ligand-accelerated catalysis. A series of rhodium catalysts derived from acids with pK(a)s spanning 4 orders of magnitude give very similar kinetic constants.

  11. Synthesis of phthalocyanine stabilized rhodium nanoparticles and their application in biosensing of cytochrome c.

    PubMed

    Lokesh, K S; Shivaraj, Y; Dayananda, B P; Chandra, Sudeshna

    2009-06-01

    A single step synthesis route is described for the preparation of rhodium nanoparticles using a cobalt aminophthalocyanine macrocyclic complex as a stabilizer. The results of nanoparticles characterization using electronic absorption, Raman and X-ray spectroscopes as well as transmission electron microscopy are reported. Rhodium nanoparticle modified electrode behavior as examined by cyclic and differential pulse voltammetry is also provided. The nanoparticles were found to be well dispersed and stabilized throughout the macromolecular matrix. TEM studies showed that they have an average diameter of 3 to 5 nm with spherical shape. The colloidal rhodium was then used for electrochemical sensing of cytochrome c using glassy carbon electrode. The results showed that the colloidal rhodium nanoparticles enhanced the electron transfer process between cytochrome c and the electrode. Differential pulse voltammetric measurements of cytochrome c at the colloidal rhodium nanoparticles modified glassy carbon electrode showed a linear relationship with the oxidation peak currents in the concentration range of 100 nM to 3 microM of cytochrome c.

  12. Interaction between water-soluble rhodium complex RhCl(CO)(TPPTS)2 and surfactants probed by spectroscopic methods

    NASA Astrophysics Data System (ADS)

    Zhou, Li-Mei; Guo, Cai-Hong; Fu, Hai-Yan; Jiang, Xiao-Hui; Chen, Hua; Li, Rui-Xiang; Li, Xian-Jun

    The interactions of rhodium complex RhCl(CO)(TPPTS)2 [TPPTS = P(m-C6H4SO3Na)3] with cationic, nonionic, and anionic surfactants have been investigated by UV-vis, fluorescence and 1H NMR measurements. The presence of four different species of RhCl(CO)(TPPTS)2 in cationic cetyltrimethylammonium (CTAB) solution has been demonstrated: free rhodium complex, rhodium complex bound to CTAB monomer, rhodium complex bound to CTAB premicelles, rhodium complex bound to CTAB micelles. The spectroscopy data show that RhCl(CO)(TPPTS)2 can adsorb on the interface of cationic CTAB micelles by strong electrostatic attraction, weakly bind to the nonionic polyoxyethylene (20) sorbitan monolaurate (Tween 20) micelles by hydrophobic interaction, and does not interact with anion sodium dodecyl sulfate (SDS) micelles due to the strong electrostatic repulsion.

  13. Poorly controlled gout: who is doing poorly?

    PubMed Central

    Chia, Faith Li-Ann

    2016-01-01

    Gout, an inflammatory arthritis caused by the deposition of monosodium urate crystals, is commonly seen in primary care and specialist clinics. In recent years, there has been a resurgence of interest in gout due to advances in therapies and the understanding of pathophysiology, with new guidelines being published by international bodies. However, there is still a gap between the goals of treatment and actual day-to-day practice. Barriers that result in poorly controlled gout include patient factors such as lack of understanding of the disease, stigma and nonadherence to treatment, as well as physician factors such as knowledge gaps, inadequate use of allopurinol and lack of ownership of the disease. The medical profession needs to do more to bridge the gap through physician and patient education, identification of treatment targets with appropriate use of drugs, and dissemination of guidelines. PMID:27549096

  14. Poorly controlled gout: who is doing poorly?

    PubMed

    Chia, Faith Li-Ann

    2016-08-01

    Gout, an inflammatory arthritis caused by the deposition of monosodium urate crystals, is commonly seen in primary care and specialist clinics. In recent years, there has been a resurgence of interest in gout due to advances in therapies and the understanding of pathophysiology, with new guidelines being published by international bodies. However, there is still a gap between the goals of treatment and actual day-to-day practice. Barriers that result in poorly controlled gout include patient factors such as lack of understanding of the disease, stigma and nonadherence to treatment, as well as physician factors such as knowledge gaps, inadequate use of allopurinol and lack of ownership of the disease. The medical profession needs to do more to bridge the gap through physician and patient education, identification of treatment targets with appropriate use of drugs, and dissemination of guidelines. Copyright: © Singapore Medical Association.

  15. Inhibition of carrageenin paw edema by pyridinalalkylimine rhodium(I) complexes.

    PubMed

    Sava, G; Pacor, S; Ceschia, V; Zassinovich, G; Mestroni, G

    1989-01-01

    The effects of a series of pyridinalalkyl-1,5-cyclooctadiene Rhodium(I) complexes were studied on the carrageenin paw edema model, using Sprague-Dawley rats. The series of compounds used were administered at 35, 70 and 140 mumol/kg i.p. 1hr before carrageenin application, and the effect was measured 4hr after carrageenin. The 1,5-cyclooctadienepyridinalaldoxime Rhodium(I) complex proved to be the most active compound, effective also when administered 1hr after carrageenin induction of paw swelling. However, the effects of this complex are not superior to those reported for the methyl derivative, and the overall antiinflammatory activity is inferior to that of this latter compound, particularly when the number of dosages causing at least 80% inhibition are compared. These data are consistent with those obtained in a previous investigation indicating that Rhodium(I) complexes have potential antiinflammatory properties, susceptible of further investigations extended also to other models of inflammatory disease.

  16. Rhodium pair-sites on magnesium oxide: Synthesis, characterization, and catalysis of ethylene hydrogenation

    SciTech Connect

    Yang, Dong; Xu, Pinghong; Guan, Erjia; Browning, Nigel D.; Gates, Bruce C.

    2016-06-01

    Supported rhodium acetate dimers were prepared by the reaction of Rh2(OAc)4 (OAc is acetate) with highly dehydroxylated MgO powder and characterized by extended X-ray absorption fine structure and infrared (IR) spectra, which show that the supported species were well represented as Rh2(OAc)3, with each Rh atom on average bonded to one oxygen atom of the MgO surface. Aberration-corrected scanning transmission electron microscopy gave images of Rh atoms in pairs on the MgO. The supported rhodium dimers were probed with a pulse of CO, and the IR spectra indicate a Rh(II) species with weakly bonded carbonyl ligands; the sharpness of the νCO band indicates highly uniform surface species. Further treatment in CO led to breakup of the rhodium dimers into mononuclear species; such fragmentation took place in other treatment gases as well, with the degree of fragmentation decreasing in the order CO > C2H4 > helium. The fragmentation is inferred on the basis of IR spectra to have proceeded through intermediate Rh2 species without acetate ligands. In contrast, rhodium dimers were reduced and not fragmented in the presence of H2 at 353 K, but at higher temperatures the rhodium aggregated to give larger clusters. The supported species catalyzed ethylene hydrogenation at 298 K and 1 bar at a H2 to ethylene molar ratio of 4; after 27 h of catalysis in a once-through flow reactor, acetate ligands were removed from the dimers, and some of them fragmented, as shown by IR spectroscopy. The intermediate dirhodium species without acetate ligands are two or three orders of magnitude more active as catalysts than the supported mononuclear rhodium species or those present predominantly as Rh2(OAc)3, respectively.

  17. Formation of Hexagonal-Close Packed (HCP) Rhodium as a Size Effect.

    PubMed

    Huang, Jing Lu; Li, Zhi; Duan, Hao Hong; Cheng, Zhi Ying; Li, Ya Dong; Zhu, Jing; Yu, Rong

    2017-01-18

    Previous studies on the structural and functional properties of rhodium are based on the face-centered-cubic (fcc) structure in the bulk form. Here we report the first discovery of the hexagonal-close packed (hcp) rhodium in the nanoparticle form. The hcp Rh can be directly synthesized by solvothermal reaction or by electron-beam induced decomposition of Rh monolayers. The hcp Rh nanoparticles are stable under electron beam irradiation. Compared with the fcc structure, the hcp Rh nanoparticles show a large lattice expansion (6% larger atomic volume). The first-principles calculations suggest that the lower surface energy of hcp Rh leads to the size effect in the crystal structure.

  18. Electrochemical Behavior and Electrodeposition of Nanostructured Rhodium from Low-Temperature Carbamide and Acetamide Containing Melts

    NASA Astrophysics Data System (ADS)

    Kochetova, Svetlana; Savchuk, Anastasiya; Shakhnin, Dmytro; Malyshev, Viktor

    2017-05-01

    The electrochemical behavior of rhodium at low-temperature carbamide-chloride and acetamide-chloride melts was investigated. It was found that, during rhodium anodic dissolution in carbamide and acetamide containing chloride melts, mixed complexes [Rh(NH3)4Cl2]+ of quasi-octahedral symmetry D4h are produced. The composition and structure of nascent complex ions have been studied. During electrochemical reduction of [Rh(NH3)4Cl2]+ complexes, the synthesis of Rh nanoparticles, as well as Fe, Cu, and Mo nanocoatings, were realized.

  19. Thermoelectric homogeneity and stability of platinum-rhodium alloyed thermoelements of different compositions

    NASA Astrophysics Data System (ADS)

    Edler, F.; Ederer, P.

    2013-09-01

    This paper discusses the different oxidation behavior of platinum and rhodium and their alloys usable as thermocouple materials. A specially prepared thermocouple containing thermoelements of different platinum-rhodium alloys (Pt-5%Rh, Pt-6%Rh, Pt-13%Rh, Pt-17%Rh and Pt-20%Rh) and a Pt-67 thermoelement was investigated. It was annealed at different temperatures in air. The thermoelectric homogeneity and stability of the thermocouple was tested by measurements of immersion profiles at 400 °C in a salt bath. The alloys of Pt-17%Rh and Pt-20%Rh were found to be the most suitable compositions with regard to thermoelectric homogeneity and stability.

  20. Asymmetric Synthesis of Hydrocarbazoles Catalyzed by an Octahedral Chiral-at-Rhodium Lewis Acid.

    PubMed

    Huang, Yong; Song, Liangliang; Gong, Lei; Meggers, Eric

    2015-12-01

    A bis-cyclometalated chiral-at-metal rhodium complex catalyzes the Diels-Alder reaction between N-Boc-protected 3-vinylindoles (Boc = tert-butyloxycarbonyl) and β-carboxylic ester-substituted α,β-unsaturated 2-acyl imidazoles with good-to-excellent regioselectivity (up to 99:1) and excellent diastereoselectivity (>50:1 d.r.) as well as enantioselectivity (92-99% ee) under optimized conditions. The rhodium catalyst serves as a chiral Lewis acid to activate the 2-acyl imidazole dienophile by two-point binding and overrules the preferred regioselectivity of the uncatalyzed reaction.

  1. Phosphabarrelenes as ligands in rhodium-catalyzed hydroformylation of internal alkenes essentially free of alkene isomerization.

    PubMed

    Fuchs, Evelyn; Keller, Manfred; Breit, Bernhard

    2006-09-06

    Despite significant research efforts in the past, one of the remaining problems to be solved in industrially important hydroformylation is the chemoselective low-pressure hydroformylation of internal alkenes. We report here on a new class of phosphabarrelene/rhodium catalysts 2 that display very high activity towards hydroformylation of internal alkenes with an unusually low tendency towards alkene isomerization. Preparation of new phosphabarrelene ligands, studies of their coordination properties, as well as results obtained in the rhodium-catalyzed hydroformylation of cyclic and acyclic internal alkenes are reported.

  2. Probing the structures of gas-phase rhodium cluster cations by far-infrared spectroscopy

    SciTech Connect

    Harding, D. J.; Gruene, P.; Haertelt, M.; Meijer, G.; Fielicke, A.; Hamilton, S. M.; Hopkins, W. S.; Mackenzie, S. R.; Neville, S. P.; Walsh, T. R.

    2010-12-07

    The geometric structures of small cationic rhodium clusters Rh{sub n}{sup +} (n = 6-12) are investigated by comparison of experimental far-infrared multiple photon dissociation spectra with spectra calculated using density functional theory. The clusters are found to favor structures based on octahedral and tetrahedral motifs for most of the sizes considered, in contrast to previous theoretical predictions that rhodium clusters should favor cubic motifs. Our findings highlight the need for further development of theoretical and computational methods to treat these high-spin transition metal clusters.

  3. N-tosyloxycarbamates as a source of metal nitrenes: rhodium-catalyzed C-H insertion and aziridination reactions.

    PubMed

    Lebel, Hélène; Huard, Kim; Lectard, Sylvain

    2005-10-19

    The rhodium-catalyzed decomposition of N-tosyloxycarbamates to generate metal nitrenes which undergo intramolecular C-H insertion or aziridination reaction is described. Aliphatic N-tosyloxycarbamates produce oxazolidinones with high yields and stereospecificity through insertion in benzylic, tertiary, and secondary C-H bonds. Intramolecular aziridination occurs with allylic N-tosyloxycarbamates to produce aziridines as single diastereomers. The reaction proceeds at room temperature using a rhodium catalyst and an excess of potassium carbonate and does not require the use of strong oxidant, such as hypervalent iodine reagents. A rhodium nitrene species is presumably involved, as both reactions are stereospecific.

  4. Rhodium dihydride (RhH2) with high volumetric hydrogen density.

    PubMed

    Li, Bing; Ding, Yang; Kim, Duck Young; Ahuja, Rajeev; Zou, Guangtian; Mao, Ho-Kwang

    2011-11-15

    Materials with very high hydrogen density have attracted considerable interest due to a range of motivations, including the search for chemically precompressed metallic hydrogen and hydrogen storage applications. Using high-pressure synchrotron X-ray diffraction technique and theoretical calculations, we have discovered a new rhodium dihydride (RhH(2)) with high volumetric hydrogen density (163.7 g/L). Compressing rhodium in fluid hydrogen at ambient temperature, the fcc rhodium metal absorbs hydrogen and expands unit-cell volume by two discrete steps to form NaCl-typed fcc rhodium monohydride at 4 GPa and fluorite-typed fcc RhH(2) at 8 GPa. RhH(2) is the first dihydride discovered in the platinum group metals under high pressure. Our low-temperature experiments show that RhH(2) is recoverable after releasing pressure cryogenically to 1 bar and is capable of retaining hydrogen up to 150 K for minutes and 77 K for an indefinite length of time.

  5. Carbinol derivatives via rhodium-catalyzed addition of potassium trifluoro(organo)borates to aldehydes.

    PubMed

    Pucheault, Mathieu; Darses, Sylvain; Genet, Jean-Pierre

    2005-10-07

    Reaction of potassium aryltrifluoroborates with aldehydes, in the presence of a rhodium catalyst, afforded carbinol derivatives in high yields under mild aqueous conditions; this efficient reaction proved to be general, allowing the production of highly hindered diarylmethanols and aliphatic aldehydes were also reactive under these conditions.

  6. Activating Group Recycling in Action: A Rhodium-Catalyzed Carbothiolation Route to Substituted Isoquinolines

    PubMed Central

    2013-01-01

    A new rhodium(I) catalyst allows practical and efficient alkyne carbothiolation reactions to be achieved on synthetically useful ketone-bearing aryl methyl sulfides. The carbothiolation adducts, featuring a ‘recycled methyl sulfide’ activating group, are convenient precursors to highly substituted isoquinolines. PMID:24083625

  7. Rhodium(II)-Catalyzed Asymmetric Sulfur(VI) Reduction of Diazo Sulfonylamidines

    PubMed Central

    Selander, Nicklas; Fokin, Valery V.

    2013-01-01

    Diazo sulfonylamidines readily undergo enantioselective oxygen transfer from sulfur to carbon atom in the presence of chiral rhodium(II) carboxylates resulting in chiral sulfinylamidines. This unusual asymmetric atom transfer “reduction” occurs rapidly under mild conditions, and sulfinylamidines are obtained in excellent yield. PMID:22233190

  8. A Rhodium Nanoparticle-Lewis Acidic Ionic Liquid Catalyst for the Chemoselective Reduction of Heteroarenes.

    PubMed

    Karakulina, Alena; Gopakumar, Aswin; Akçok, İsmail; Roulier, Bastien L; LaGrange, Thomas; Katsyuba, Sergey A; Das, Shoubhik; Dyson, Paul J

    2016-01-04

    We describe a catalytic system composed of rhodium nanoparticles immobilized in a Lewis acidic ionic liquid. The combined system catalyzes the hydrogenation of quinolines, pyridines, benzofurans, and furan to access the corresponding heterocycles, important molecules present in fine chemicals, agrochemicals, and pharmaceuticals. The catalyst is highly selective, acting only on the heteroaromatic ring, and not interfering with other reducible functional groups.

  9. The rhodium catalyzed three-component reaction of diazoacetates, titanium(IV) alkoxides and aldehydes.

    PubMed

    Lu, Chong-Dao; Liu, Hui; Chen, Zhi-Yong; Hu, Wen-Hao; Mi, Ai-Qiao

    2005-05-28

    The rhodium(II)-catalyzed three-component reaction of diazoacetates, titanium alkoxides and aldehydes is shown to give alpha-alkoxyl-beta-hydroxyl acid derivatives; the novel C-C bond formation reaction is proposed to occur through oxonium ylides derived from diazo compounds and titanium alkoxides, and followed by intermolecular trapping by aldehydes.

  10. Direct C-H alkylation and indole formation of anilines with diazo compounds under rhodium catalysis.

    PubMed

    Mishra, Neeraj Kumar; Choi, Miji; Jo, Hyeim; Oh, Yongguk; Sharma, Satyasheel; Han, Sang Hoon; Jeong, Taejoo; Han, Sangil; Lee, Seok-Yong; Kim, In Su

    2015-12-18

    The rhodium(III)-catalyzed direct functionalization of aniline C-H bonds with α-diazo compounds is described. These transformations provide a facile construction of ortho-alkylated anilines with diazo malonates or highly substituted indoles with diazo acetoacetates.

  11. Toward the Synthesis of Nuphar Sesquiterpene Thioalkaloids: Stereodivergent Rhodium-Catalyzed Synthesis of the Thiolane Subunit.

    PubMed

    Lu, Ping; Herrmann, Aaron T; Zakarian, Armen

    2015-08-07

    A stereodivergent approach to the central thiolane subunit of Nuphar sesquiterpene thioalkaloids has been developed. This approach features a rhodium-catalyzed Stevens-type rearrangement in conjunction with an enzyme resolution reaction. Further elaboration into a polycyclic ring system via alcohol oxidation and ring-closing metathesis is also described.

  12. Rhodium phosphine-π-arene intermediates in the hydroamination of alkenes.

    PubMed

    Liu, Zhijian; Yamamichi, Hideaki; Madrahimov, Sherzod T; Hartwig, John F

    2011-03-02

    A detailed mechanistic study of the intramolecular hydroamination of alkenes with amines catalyzed by rhodium complexes of a biaryldialkylphosphine is reported. The active catalyst is shown to contain the phosphine ligand bound in a κ(1), η(6) form in which the arene is π-bound to rhodium. Addition of deuterated amine to an internal olefin showed that the reaction occurs by trans addition of the N-H bond across the C═C bond, and this stereochemistry implies that the reaction occurs by nucleophilic attack of the amine on a coordinated alkene. Indeed, the cationic rhodium fragment binds the alkene over the secondary amine, and the olefin complex was shown to be the catalyst resting state. The reaction was zero-order in substrate, when the concentration of olefin was high, and a primary isotope effect was observed. The primary isotope effect, in combination with the observation of the alkene complex as the resting state, implies that nucleophilic attack of the amine on the alkene is reversible and is followed by turnover-limiting protonation. This mechanism constitutes an unusual pathway for rhodium-catalyzed additions to alkenes and is more closely related to the mechanism for palladium-catalyzed addition of amide N-H bonds to alkenes.

  13. Rhodium dihydride (RhH[subscript 2]) with high volumetric hydrogen density

    SciTech Connect

    Li, Bing; Ding, Yang; Kim, Duck Young; Ahuja, Rajeev; Zou, Guangtian; Mao, Ho-Kwang

    2012-03-14

    Materials with very high hydrogen density have attracted considerable interest due to a range of motivations, including the search for chemically precompressed metallic hydrogen and hydrogen storage applications. Using high-pressure synchrotron X-ray diffraction technique and theoretical calculations, we have discovered a new rhodium dihydride (RhH{sub 2}) with high volumetric hydrogen density (163.7 g/L). Compressing rhodium in fluid hydrogen at ambient temperature, the fcc rhodium metal absorbs hydrogen and expands unit-cell volume by two discrete steps to form NaCl-typed fcc rhodium monohydride at 4 GPa and fluorite-typed fcc RhH{sub 2} at 8 GPa. RhH{sub 2} is the first dihydride discovered in the platinum group metals under high pressure. Our low-temperature experiments show that RhH{sub 2} is recoverable after releasing pressure cryogenically to 1 bar and is capable of retaining hydrogen up to 150 K for minutes and 77 K for an indefinite length of time.

  14. Rhodium dihydride (RhH2) with high volumetric hydrogen density

    PubMed Central

    Li, Bing; Ding, Yang; Kim, Duck Young; Ahuja, Rajeev; Zou, Guangtian; Mao, Ho-Kwang

    2011-01-01

    Materials with very high hydrogen density have attracted considerable interest due to a range of motivations, including the search for chemically precompressed metallic hydrogen and hydrogen storage applications. Using high-pressure synchrotron X-ray diffraction technique and theoretical calculations, we have discovered a new rhodium dihydride (RhH2) with high volumetric hydrogen density (163.7 g/L). Compressing rhodium in fluid hydrogen at ambient temperature, the fcc rhodium metal absorbs hydrogen and expands unit-cell volume by two discrete steps to form NaCl-typed fcc rhodium monohydride at 4 GPa and fluorite-typed fcc RhH2 at 8 GPa. RhH2 is the first dihydride discovered in the platinum group metals under high pressure. Our low-temperature experiments show that RhH2 is recoverable after releasing pressure cryogenically to 1 bar and is capable of retaining hydrogen up to 150 K for minutes and 77 K for an indefinite length of time. PMID:22039219

  15. Rhodium-catalyzed, efficient deutero- and tritiosilylation of carbonyl compounds from hydrosilanes and deuterium or tritium.

    PubMed

    Rubio, Miguel; Campos, Jesús; Carmona, Ernesto

    2011-10-07

    A cationic rhodium compound which is an active catalyst for both the hydrogen isotope exchange in hydrosilanes and the hydrosilylation of carbonyl compounds permits, in a one-flask, two-step procedure, efficient deutero- and tritiosilylations using SiEt(3)H under D(2) (0.5 bar) or T(2), at low catalyst loadings (0.1-0.5 mol %).

  16. Rhodium Phosphine-π-Arene Intermediates in the Hydroamination of Alkenes

    PubMed Central

    Liu, Zhijian; Yamamichi, Hideaki; Madrahimov, Sherzod T.; Hartwig, John F.

    2011-01-01

    A detailed mechanistic study of the intramolecular hydroamination of alkenes with amines catalyzed by rhodium complexes of a biaryldialkylphosphine are reported. The active catalyst is shown to contain the phosphine ligand bound in a κ1, η6 form in which the arene is π-bound to rhodium. Addition of deuterated amine to an internal olefin showed that the reaction occurs by trans addition of the N-H bond across the C=C bond, and this stereochemistry implies that the reaction occurs by nucleophilic attack of the amine on a coordinated alkene. Indeed, the cationic rhodium fragment binds the alkene over the secondary amine, and the olefin complex was shown to be the catalyst resting state. The reaction was zero-order in substrate, when the concentration of olefin was high, and a primary isotope effect was observed. The primary isotope effect, in combination with the observation of the alkene complex as the resting state, implies that nucleophilic attack of the amine on the alkene is reversible and is followed by turnover-limiting protonation. This mechanism constitutes an unusual pathway for rhodium-catalyzed additions to alkenes and is more closely related to the mechanism for palladium-catalyzed addition of amide N-H bonds to alkenes. PMID:21309512

  17. Ligand Fluorination to Optimize Preferential Oxidation (PROX) of Carbon Monoxide by Water-Soluble Rhodium Porphyrins.

    PubMed

    Biffinger, Justin C; Uppaluri, Shriharsha; Sun, Haoran; Dimagno, Stephen G

    2011-05-18

    Catalytic, low temperature preferential oxidation (PROX) of carbon monoxide by aqueous [5,10,15,20-tetrakis(4-sulfonatophenyl)-2,3,7,8,12,13,17,18-octafluoroporphyrinato]rhodium(III) tetrasodium salt, (1[Rh(III)]) and [5,10,15,20-tetrakis(3-sulfonato-2,6-difluorophenyl)-2,3,7,8,12,13,17,18-octafluoroporphyrinato]rhodium(III) tetrasodium salt, (2[Rh(III)]) is reported. The PROX reaction occurs at ambient temperature in buffered (4 ≤ pH ≤ 13) aqueous solutions. Fluorination on the porphyrin periphery is shown to increase the CO PROX reaction rate, shift the metal centered redox potentials, and acidify ligated water molecules. Most importantly, β-fluorination increases the acidity of the rhodium hydride complex (pK(a) = 2.2 ± 0.2 for 2[Rh-D]); the dramatically increased acidity of the Rh(III) hydride complex precludes proton reduction and hydrogen activation near neutral pH, thereby permitting oxidation of CO to be unaffected by the presence of H(2). This new fluorinated water-soluble rhodium porphyrin-based homogenous catalyst system permits preferential oxidation of carbon monoxide in hydrogen gas streams at 308 °K using dioxygen or a sacrificial electron acceptor (indigo carmine) as the terminal oxidant.

  18. Synthesis of 1H-Indazoles from Imidates and Nitrosobenzenes via Synergistic Rhodium/Copper Catalysis.

    PubMed

    Wang, Qiang; Li, Xingwei

    2016-05-06

    Nitrosobenzenes have been used as a convenient aminating reagent for the efficient synthesis of 1H-indazoles via rhodium and copper catalyzed C-H activation and C-N/N-N coupling. The reaction occurred under redox-neutral conditions with high efficiency and functional group tolerance. Moreover, a rhodacyclic imidate complex has been identified as a key intermediate.

  19. Transmetallation between metal-only Lewis pairs: a new rhodium alane complex.

    PubMed

    Bauer, Jürgen; Braunschweig, Holger; Radacki, Krzysztof

    2012-10-28

    In this communication, synthesis of a rhodium alane Lewis adduct, [Cp(Me(3)P)(2)Rh→AlCl(3)], is reported. Given that direct synthesis using aluminium trichloride failed, a convenient transmetallation reaction was applied. The new MOLP was analysed by single crystal X-ray diffraction, multinuclear NMR spectroscopy and density functional theory calculations.

  20. Ligand Fluorination to Optimize Preferential Oxidation (PROX) of Carbon Monoxide by Water-Soluble Rhodium Porphyrins

    PubMed Central

    Biffinger, Justin C.; Uppaluri, ShriHarsha; Sun, Haoran

    2011-01-01

    Catalytic, low temperature preferential oxidation (PROX) of carbon monoxide by aqueous [5,10,15,20-tetrakis(4-sulfonatophenyl)-2,3,7,8,12,13,17,18-octafluoroporphyrinato]rhodium(III) tetrasodium salt, (1[Rh(III)]) and [5,10,15,20-tetrakis(3-sulfonato-2,6-difluorophenyl)-2,3,7,8,12,13,17,18-octafluoroporphyrinato]rhodium(III) tetrasodium salt, (2[Rh(III)]) is reported. The PROX reaction occurs at ambient temperature in buffered (4 ≤ pH ≤ 13) aqueous solutions. Fluorination on the porphyrin periphery is shown to increase the CO PROX reaction rate, shift the metal centered redox potentials, and acidify ligated water molecules. Most importantly, β-fluorination increases the acidity of the rhodium hydride complex (pKa = 2.2 ± 0.2 for 2[Rh-D]); the dramatically increased acidity of the Rh(III) hydride complex precludes proton reduction and hydrogen activation near neutral pH, thereby permitting oxidation of CO to be unaffected by the presence of H2. This new fluorinated water-soluble rhodium porphyrin-based homogenous catalyst system permits preferential oxidation of carbon monoxide in hydrogen gas streams at 308 °K using dioxygen or a sacrificial electron acceptor (indigo carmine) as the terminal oxidant. PMID:21949596

  1. Anisotropic etching of rhodium and gold as the onset of nanoparticle formation by cathodic corrosion.

    PubMed

    Hersbach, Thomas J P; Mints, Vladislav A; Calle-Vallejo, Federico; Yanson, Alexei I; Koper, Marc T M

    2016-12-12

    Cathodic corrosion is a phenomenon in which negatively polarized metal electrodes are degraded by cathodic etching and nanoparticle formation. Though these changes are dramatic and sometimes even visible by eye, the exact mechanisms underlying cathodic corrosion are still unclear. This work aims to improve the understanding of cathodic corrosion by studying its onset on rhodium and gold electrodes, which are subjected to various constant cathodic potentials in 10 M NaOH. After this polarization, the electrodes are studied using cyclic voltammetry and scanning electron microscopy, allowing a corrosion onset potential of -1.3 V vs. NHE for rhodium and -1.6 V vs. NHE for gold to be defined. The mildness of the potentials on both metals suggests that cathodic corrosion is less extreme and more ubiquitous than expected. Furthermore, we are able to observe well-defined rectangular etch pits on rhodium. Combined with rhodium cyclic voltammetry, this indicates a strong preference for forming (100) sites during corrosion. In contrast, a (111) preference is indicated on gold by voltammetry and the presence of well-oriented quasi-octahedral nanoparticles. This different etching behavior is suggested to be caused by preferential adsorption of sodium ions to surface defects, as is confirmed by density functional theory calculations.

  2. Cyto- and genotoxic effects of coordination complexes of platinum, palladium and rhodium in vitro.

    PubMed

    Bünger, J; Stork, J; Stalder, K

    1996-01-01

    The growing industrial use of platinum group elements as catalysts, especially in automobile exhaust detoxification (trimetal catalytic converters), is causing increasing occupational and environmental pollution. The cytotoxic and mutagenic properties of industrially used coordination complexes of platinum, palladium and rhodium were investigated using the neutral red cytotoxicity assay on two established cell lines and the Salmonella typhimurium/microsome test system (Ames test). Cytotoxic effects of the platinum complexes, measured as ED50, occurred at test concentrations of 0.2 mM. The analogous palladium salts tested were 3 times less toxic with ED50 being 0.6 mM, while the rhodium salts proved to be 30 times less toxic (ED50 = 6 mM). Levels of toxicity of the different complexes of a particular metal did not differ significantly from each other, which indicates that the metal itself is responsible for the toxic effects. In the Ames test, the spontaneous mutation rates increased by factors of 3 to 20 when the four tester strains were exposed to the platinum complexes. The analogous rhodium compounds proved to be considerably less mutagenic, and palladium demonstrated no mutagenic potential. As all of the four tester strains contain different mutations, the mutagenic potential of platinum and rhodium complexes appears to be based on a variety of mechanisms that damage DNA. From these in vitro experiments, it can be concluded that water-soluble complex salts of rhodium are less toxic and have a smaller mutagenic potential than the analogous platinum complexes. For palladium there is no evidence of any mutagenic property. From this point of view, the development of a catalytic converter containing predominantly palladium may be a possible means of minimizing potential health risks from this exhaust detoxification technique.

  3. Determination of phenolic compounds using spectral and color transitions of rhodium nanoparticles.

    PubMed

    Gatselou, Vasiliki; Christodouleas, Dionysios C; Kouloumpis, Antonios; Gournis, Dimitrios; Giokas, Dimosthenis L

    2016-08-17

    This work reports a new approach for the determination of phenolic compounds based on their interaction with citrate-capped rhodium nanoparticles. Phenolic compounds (i.e., catechins, gallates, cinnamates, and dihydroxybenzoic acids) were found to cause changes in the size and localized surface plasmon resonance of rhodium nanoparticles, and therefore, give rise to analyte-specific spectral and color transitions in the rhodium nanoparticle suspensions. Upon reaction with phenolic compounds (mainly dithydroxybenzoate derivatives, and trihydroxybenzoate derivatives), new absorbance peaks at 350 nm and 450 nm were observed. Upon reaction with trihydroxybenzoate derivatives, however, an additional absorbance peak at 580 nm was observed facilitating the speciation of phenolic compounds in the sample. Both absorbance peaks at 450 nm and 580 nm increased with increasing concentration of phenolic compounds over a linear range of 0-500 μM. Detection limits at the mid-micromolar levels were achieved, depending on the phenolic compound involved, and with satisfactory reproducibility (<7.3%). On the basis of these findings, two rhodium nanoparticles-based assays for the determination of the total phenolic content and total catechin content were developed and applied in tea samples. The obtained results correlated favorably with commonly used methods (i.e., Folin-Ciocalteu and aluminum complexation assay). Not the least, the finding that rhodium nanoparticles can react with analytes and exhibit unique localized surface plasmon resonance bands in the visible region, can open new opportunities for developing new optical and sensing analytical applications.

  4. Development of Amperometric α-Ketoglutarate Biosensor based on Ruthenium-Rhodium Modified Carbon Fiber Enzyme Microelectrode

    PubMed Central

    Poorahong, Sujittra; Santhosh, Padmanabhan; Ramírez, Gabriela Valdés; Tseng, Ta-Feng; Wong, Joseph Isaac; Kanatharana, Proespichaya; Thavarungkul, Panote; Wang, Joseph

    2011-01-01

    A rapid and highly sensitive miniaturized amperometric biosensor for the detection α-ketoglutarate (α-KG) based on a carbon fiber electrode (CFE) is presented. The biosensor is constructed by immobilizing the enzyme, glutamate dehydrogenase (GLUD) on the surface of single carbon fiber modified by co-deposition of ruthenium (Ru) and rhodium (Rh) nanoparticles. SEM and EDX shed useful insights into the morphology and composition of the modified microelectrode. The mixed Ru/Rh coating offers a greatly enhanced electrocatalytic activity towards the detection of β-nicotinamide adenine dinucleotide (NADH), with a substantial decrease in overpotential of ~400 mV compared to the unmodified CFE. It also imparts higher stability with minimal surface fouling, common to NADH oxidation. Further modification with the enzyme, GLUD leads to effective amperometric biosensing of α-KG through monitoring of the NADH consumption. A very rapid response to dynamic changes in the α-KG concentrations is observed with a response time of 6s. The current response is linear between 100 and 600 μM with a sensitivity of 42 μA M−1 and a detection limit of 20 μM. This proof of concept study indicates that the GLUD-Ru/Rh-CFE biosensor holds great promise for real-time electrochemical measurements of α-KG. PMID:21334188

  5. Development of amperometric α-ketoglutarate biosensor based on ruthenium-rhodium modified carbon fiber enzyme microelectrode.

    PubMed

    Poorahong, Sujittra; Santhosh, Padmanabhan; Ramírez, Gabriela Valdés; Tseng, Ta-Feng; Wong, Joseph Isaac; Kanatharana, Proespichaya; Thavarungkul, Panote; Wang, Joseph

    2011-04-15

    A rapid and highly sensitive miniaturized amperometric biosensor for the detection of α-ketoglutarate (α-KG) based on a carbon fiber electrode (CFE) is presented. The biosensor is constructed by immobilizing the enzyme, glutamate dehydrogenase (GLUD) on the surface of single carbon fiber modified by co-deposition of ruthenium (Ru) and rhodium (Rh) nanoparticles. SEM and EDX shed useful insights into the morphology and composition of the modified microelectrode. The mixed Ru/Rh coating offers a greatly enhanced electrocatalytic activity towards the detection of β-nicotinamide adenine dinucleotide (NADH), with a substantial decrease in overpotential of ∼ 400 mV compared to the unmodified CFE. It also imparts higher stability with minimal surface fouling, common to NADH oxidation. Further modification with the enzyme, GLUD leads to effective amperometric biosensing of α-KG through monitoring of the NADH consumption. A very rapid response to dynamic changes in the α-KG concentrations is observed with a response time of 6s. The current response is linear between 100 and 600 μM with a sensitivity of 42 μAM(-1) and a detection limit of 20 μM. This proof of concept study indicates that the GLUD-Ru/Rh-CFE biosensor holds great promise for real-time electrochemical measurements of α-KG. Copyright © 2011 Elsevier B.V. All rights reserved.

  6. Burnup of rhodium SPND in VVER-1000: Method for determination of linear energy release by SPND readings

    SciTech Connect

    Kurchenkov, A. Yu.

    2011-12-15

    A method for determination of linear energy release of a VVER fuel assembly near a rhodium self-powered neutron detector (SPND) is described. The dependence of SPND burnup on the charge passing through it is specified.

  7. Asymmetric synthesis of gem-diaryl substituted cyclic sulfamidates and sulfamides by rhodium-catalyzed arylation of cyclic ketimines.

    PubMed

    Nishimura, Takahiro; Ebe, Yusuke; Fujimoto, Hiroto; Hayashi, Tamio

    2013-06-18

    Asymmetric addition of arylboronates to aryl-substituted cyclic ketimines proceeded in the presence of a rhodium catalyst coordinated with a chiral diene ligand to give high yields of sulfamidates and sulfamides with high enantioselectivity (up to 99% ee).

  8. Double hydrophosphination of alkynes promoted by rhodium: the key role of an N-heterocyclic carbene ligand.

    PubMed

    Di Giuseppe, Andrea; De Luca, Roberto; Castarlenas, Ricardo; Pérez-Torrente, Jesús J; Crucianelli, Marcello; Oro, Luis A

    2016-04-25

    The regioselective double hydrophosphination of alkynes mediated by rhodium catalysts is presented. The distinctive stereoelectronic properties of the NHC ligand prevent the catalyst deactivation by diphosphine coordination thereby allowing for the closing of a productive catalytic cycle.

  9. Stabilized rhodium(0) nanoparticles: a reusable hydrogenation catalyst for arene derivatives in a biphasic water-liquid system.

    PubMed

    Schulz, J; Roucoux, A; Patin, H

    2000-02-18

    A colloidal system based on an aqueous suspension of rhodium(o) nanoparticles proved to be an efficient catalyst for the hydrogenation of arene derivatives under biphasic conditions. The rhodium nanoparticles (2-2.5 nm) were synthesized by the reduction of RhCl3 x 3H2O with sodium borohydride and were stabilized by highly water-soluble N-alkyl-N-(2-hydroxyethyl)ammonium salts (HEA-Cn). These surfactant molecules were characterized by measurements of the surface tension and the aqueous dispersions with rhodium were observed by transmission electron cryomicroscopy. The catalytic system is efficient under ultramild conditions, namely room temperature and 1 atm H2 pressure. The aqueous phase which contains the protected rhodium(0) colloids can be reused without significant loss of activity. The microheterogeneous behavior of this catalytic system was confirmed on a mercury poisoning experiment.

  10. Selective catalytic reduction system and process for treating NOx emissions using a palladium and rhodium or ruthenium catalyst

    DOEpatents

    Sobolevskiy, Anatoly [Orlando, FL; Rossin, Joseph A [Columbus, OH; Knapke, Michael J [Columbus, OH

    2011-07-12

    A process for the catalytic reduction of nitrogen oxides (NOx) in a gas stream (29) in the presence of H.sub.2 is provided. The process comprises contacting the gas stream with a catalyst system (38) comprising zirconia-silica washcoat particles (41), a pre-sulfated zirconia binder (44), and a catalyst combination (40) comprising palladium and at least one of rhodium, ruthenium, or a mixture of ruthenium and rhodium.

  11. Ion exchange equilibria in simultaneous extraction of platinum(II, IV) and rhodium(III) from hydrochloric solutions

    NASA Astrophysics Data System (ADS)

    Mel'nikov, A. M.; Kononova, O. N.; Pavlenko, N. I.; Krylov, A. S.

    2012-06-01

    Regularities of sorption extraction of platinum(II, IV) and rhodium(III) by anion exchangers of various physical and chemical structure in the presence of hydrochloric media were studied. It is established that AM-2B, Purolite A 500, and Purolite S 985 ionites adsorb complex anions of platinum metals employing mixed mechanism. A high affinity of the studied anionites for the studied complex anions of platinum and rhodium is established.

  12. Enantioselective Synthesis of Spiroindenes by Enol-Directed Rhodium(III)-Catalyzed C–H Functionalization and Spiroannulation

    PubMed Central

    Reddy Chidipudi, Suresh; Burns, David J; Khan, Imtiaz; Lam, Hon Wai

    2015-01-01

    Chiral cyclopentadienyl rhodium complexes promote highly enantioselective enol-directed C(sp2)-H functionalization and oxidative annulation with alkynes to give spiroindenes containing all-carbon quaternary stereocenters. High selectivity between two possible directing groups, as well as control of the direction of rotation in the isomerization of an O-bound rhodium enolate into the C-bound isomer, appear to be critical for high enantiomeric excesses. PMID:26404643

  13. Intrinsic selectivity and structure sensitivity of Rhodium catalysts for C2+ oxygenate production [On the intrinsic selectivity and structure sensitivity of Rhodium catalysts for C2+ oxygenate production

    DOE PAGES

    Yang, Nuoya; Medford, Andrew J.; Liu, Xinyan; ...

    2016-01-31

    Synthesis gas (CO + H2) conversion is a promising route to converting coal, natural gas, or biomass into synthetic liquid fuels. Rhodium has long been studied as it is the only elemental catalyst that has demonstrated selectivity to ethanol and other C2+ oxygenates. However, the fundamentals of syngas conversion over rhodium are still debated. In this work a microkinetic model is developed for conversion of CO and H2 into methane, ethanol, and acetaldehyde on the Rh (211) and (111) surfaces, chosen to describe steps and close-packed facets on catalyst particles. The model is based on DFT calculations using the BEEF-vdWmore » functional. The mean-field kinetic model includes lateral adsorbate–adsorbate interactions, and the BEEF-vdW error estimation ensemble is used to propagate error from the DFT calculations to the predicted rates. The model shows the Rh(211) surface to be ~6 orders of magnitude more active than the Rh(111) surface, but highly selective toward methane, while the Rh(111) surface is intrinsically selective toward acetaldehyde. A variety of Rh/SiO2 catalysts are synthesized, tested for catalytic oxygenate production, and characterized using TEM. The experimental results indicate that the Rh(111) surface is intrinsically selective toward acetaldehyde, and a strong inverse correlation between catalytic activity and oxygenate selectivity is observed. Furthermore, iron impurities are shown to play a key role in modulating the selectivity of Rh/SiO2 catalysts toward ethanol. The experimental observations are consistent with the structure-sensitivity predicted from theory. As a result, this work provides an improved atomic-scale understanding and new insight into the mechanism, active site, and intrinsic selectivity of syngas conversion over rhodium catalysts and may also guide rational design of alloy catalysts made from more abundant elements.« less

  14. Terminal phosphanido rhodium complexes mediating catalytic P-P and P-C bond formation.

    PubMed

    Geer, Ana M; Serrano, Ángel L; de Bruin, Bas; Ciriano, Miguel A; Tejel, Cristina

    2015-01-07

    Complexes with terminal phosphanido (M-PR2) functionalities are believed to be crucial intermediates in new catalytic processes involving the formation of P-P and P-C bonds. We showcase here the isolation and characterization of mononuclear phosphanide rhodium complexes ([RhTp(H)(PR2)L]) that result from the oxidative addition of secondary phosphanes, a reaction that was also explored computationally. These compounds are active catalysts for the dehydrocoupling of PHPh2 to Ph2P-PPh2. The hydrophosphination of dimethyl maleate and the unactivated olefin ethylene is also reported. Reliable evidence for the prominent role of mononuclear phosphanido rhodium species in these reactions is also provided. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Rhodium-catalyzed ketone methylation using methanol under mild conditions: formation of α-branched products.

    PubMed

    Chan, Louis K M; Poole, Darren L; Shen, Di; Healy, Mark P; Donohoe, Timothy J

    2014-01-13

    The rhodium-catalyzed methylation of ketones has been accomplished using methanol as the methylating agent and the hydrogen-borrowing method. The sequence is notable for the relatively low temperatures that are required and for the ability of the reaction system to form α-branched products with ease. Doubly alkylated ketones can be prepared from methyl ketones and two different alcohols by using a sequential one-pot iridium- and rhodium-catalyzed process. © 2014 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

  16. Allenols versus Allenones: Rhodium-Catalyzed Regiodivergent and Tunable Allene Reactivity with Triazoles.

    PubMed

    Alcaide, Benito; Almendros, Pedro; Cembellín, Sara; Martínez Del Campo, Teresa; Palop, Guillermo

    2017-10-04

    2-Pyrrolines and 6-oxo-hexa-2,4-dienals have been prepared through the divergent reactions of 1-benzenesulfonyl-4-aryl-1,2,3-triazoles with functionalized allenes. The rhodium-catalyzed reactions between allenols and 1-benzenesulfonyl-4-aryl-1,2,3-triazoles yielded 2-pyrrolines. This transformation is compatible with the presence of aliphatic, aromatic, heterocyclic, amide, and halogen functional groups. Interestingly, a reactivity switch took place when the allene-tethered alcohol substrate was replaced by its ketone counterpart. When the rhodium-catalyzed reaction of 1-benzenesulfonyl-4-phenyl-1,2,3-triazole was performed with allenones, acyclic 6-oxo-hexa-2,4-dienals were stereoselectively formed as (2Z,4E) isomers. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Aerobic C-H Oxidation of Arenes Using a Recyclable, Heterogeneous Rhodium Catalyst.

    PubMed

    Matsumoto, Kenji; Tachikawa, Shohei; Hashimoto, Noriko; Nakano, Rina; Yoshida, Masahiro; Shindo, Mitsuru

    2017-04-21

    A novel, practical protocol for the aerobic direct C-H acetoxylation of arenes, employing a recyclable heterogeneous rhodium catalyst, is reported herein. The trifluoroacetoxylation of 2-amido-substituted anthracenes proceeded at the 9-position with exclusive regioselectivity. The oxidation of variously substituted anthracenes and other polycyclic aromatics with molecular oxygen as a terminal oxidant proceeded under mild conditions, providing products in good to excellent yields.

  18. Long Range Materials Research. Appendix 1. Synthesis and Characterization of Supported Organometallic Rhodium (I) Catalysts

    DTIC Science & Technology

    1974-06-30

    support organo - metallic homogeneous catalysts on inert supports. This thesis describes the synthesis of a new chelating ligand for binding...homogeneous catalysts to silica surfaces, a now method using poisons for distinguishing con- ventional heterogeneous catal’,sts from the newer supported organo ...Homogeneous HIydrogenation by Rhodium(l) Complexes Homogeneous catalysts have both served and plagued alchemists and chemists since work began with solutions

  19. Drift as a Function of Temperature in Platinum-Rhodium-Alloyed Thermoelements

    NASA Astrophysics Data System (ADS)

    Webster, E. S.; Edler, F.

    2017-02-01

    Platinum-rhodium-alloyed thermocouples are the most commonly used high-temperature reference thermometer in national measurement institutes, second tier laboratories and industry. Despite the common use of these thermocouples, there is still a great deal that is not known about the drift processes that occur in them. Drift processes in these alloys are known to be made up of three main components: crystallographic changes, rhodium oxidation and migration, and contamination. Through careful use, contamination can be largely avoided; however, the other two processes often cannot. Research on drift in the different platinum-rhodium alloys is important because the largest uncertainty component during calibration of these thermocouple types is due to inhomogeneity, and the same mechanisms responsible for inhomogeneity are responsible for the drift. This study investigates the drift processes as a function of temperature and time for the 5 %, 13 %, 17 %, 20 %, 30 % and 40 % Rh alloys when paired with pure platinum. The use of a linear gradient furnace and high-resolution homogeneity scanner has enabled identification of drift characteristics in the temperature range 100°C to 950°C, where the bulk of reversible drift occurs. The experiments have quantified the drift rates and magnitude for thermoelements given two commonly used annealing procedures: the high-temperature quench anneal and the low-temperature vacancy anneal. Consequently, this study provides users of platinum-rhodium thermoelements with guidance on what levels of drift they should expect and exposure times before re-annealing is required. It also shows that a Pt-Rh alloy of 20 % Rh is by far the most stable and has properties comparable to the Pt-Pd thermocouple.

  20. Catalytic asymmetric synthesis of pyrroloindolines via a rhodium(II)-catalyzed annulation of indoles.

    PubMed

    Spangler, Jillian E; Davies, Huw M L

    2013-05-08

    Herein we report the synthesis of pyrroloindolines via a catalytic enantioselective formal [3+2] cycloaddition of C(3)-substituted indoles. This methodology utilizes 4-aryl-1-sulfonyl-1,2,3-triazoles as carbenoid precursors and the rhodium(II)-tetracarboxylate catalyst Rh2(S-PTAD)4. A variety of aryl-substituted pyrroloindolines were prepared in good yields and with high levels of enantioinduction.

  1. Neutron activation determination of rhodium with preliminary micro-fire-assay concentration into a bismuth collector

    SciTech Connect

    Artem'ev, O.I.; Kabirova, G.M.; Stepanov, V.M.

    1987-09-10

    The authors investigated the possibility of neutron activation determination of rhodium with micro-fire-assay preconcentration (MFAP) in conventional laboratory muffle furnaces or tube furnaces. Lead and bismuth were investigated as collectors. Lead or bismuth alloys obtained by MFAP of the test samples and reference samples (RS) with subsequent cupellation were irradiated along with monitors in the thermal channel of the VVR-K reactor at the Institute of Nuclear Physics (Academy of Sciences of the Kazakh SSR), equipped with a pneumatic transport system, in a flux of approximately 1 x 10/sup 13/ neutrons per square centimeter per second. The monitors were comparison samples of manganese with a concentration of 2 x 10/sup -5/ g. The sample irradiation time was 1 min, measurement time 5 min. The measurements were performed 1.5 min and 1 h after irradiation in a gamma-ray spectrometer with a germanium-lithium detector with a volume of 40 cm/sup 3/. The resolution of the spectrometer was 4.5 keV for the 1332-keV gamma line (/sup 60/Co). The spectra of the monitors were taken under fixed conditions for 3 min, starting 10 min after irradiation. The rhodium content was determined from the area of the photopeak of the gamma line with an energy of 556 keV (/sup 104/Rh + /sup 104m/Rh). With a rhodium content of 10/sup -1/% by weight (concentrates and slimes from copper-nickel ores), when using the cadmium channel (thickness 0.7 mm) with certain samples, rhodium can also be determined by purely instrumental NAA without preconcentration.

  2. Cyclic (Alkyl)(Amino)Carbene Complexes of Rhodium and Nickel and Their Steric and Electronic Parameters.

    PubMed

    Paul, Ursula S D; Sieck, Carolin; Haehnel, Martin; Hammond, Kai; Marder, Todd B; Radius, Udo

    2016-07-25

    N-heterocyclic carbenes (NHCs) and cyclic (alkyl)(amino)carbenes (CAACs) are of great interest, as their electronic and steric properties provide a unique class of ligands and organocatalysts. Herein, substitution reactions involving novel carbonyl complexes of rhodium and nickel were studied to provide a deeper understanding of the fundamental electronic factors characterizing CAAC(methyl) , which were compared with the large array of data available for NHC and sterically more demanding CAAC ligands.

  3. Particle size, precursor, and support effects in the hydrogenolysis of alkanes over supported rhodium catalysts

    SciTech Connect

    Coq, B.; Dutartre, R.; Figueras, F.; Tazi, T. )

    1990-04-01

    A series of Rh catalysts of widely varying dispersion has been prepared using {gamma}-alumina as support and Rh acetylacetonate (Rh(acac){sub 3}) as precursor. The hydrogenolyses of n-hexane (nH), methylcyclopentane (MCP), and 2,2,3,3-tetramethylbutane (TeMB) were investigated as model reactions. Clear dependence of turnover frequency on Rh particle size is observed for nH and MCP hydrogenolysis, but only slight changes of selectivities occur with these alkanes. By contrast, large modifications of both specific activity and selectivity appear when TeMB is reacted. TeMB hydrogenolysis is thus a reliable tool for studying modifications of the surface structure of rhodium particles. This probe was used to investigate the effects of precursor and support on rhodium catalysts. The effect of chlorine is appreciable and shifts the selectivity of TeMB hydrogenolysis toward that of large particles. This is attributed to a different morphology of the rhodium particles. When the effect of dispersion of the metal is taken into account, no support effect is observed when SiO{sub 2} or ZrO{sub 2} is used as support. The different properties of rhodium on MgO can also be attributed to a different morphology of the particles. For Rh/TiO{sub 2} prepared from RhCl{sub 3} {center dot} 3H{sub 2}O, the catalytic properties are similar to those of Rh/Al{sub 2}O{sub 3} of moderate dispersion whatever temperature is used for reduction. Rh/TiO{sub 2} prepared from Rh(acac){sub 3} and reduced at 573 and 773 K simulates the catalytic properties of particles smaller than indeed observed. This effect can be interpreted by a partial coverage of the Rh surface by TiO{sub x} species (SMSI). This SMSI effect disappears upon reduction at 873 K.

  4. Examining Rhodium Catalyst complexes for Use with Conducting Polymers Designed for Fuel Cells in Preparing Biosensors

    SciTech Connect

    Carpio, M.M.; Kerr, J.B.

    2005-01-01

    Biosensing devices are important because they can detect, record, and transmit information regarding the presence of, or physiological changes in, different chemical or biological materials in the environment. The goal of this research is to prepare a biosensing device that is effective, quick, and low cost. This is done by examining which chemicals will work best when placed in a biosensor. The first study involved experimenting on a rhodium catalyst complexed with ligands such as bipyridine and imidazole. The rhodium catalyst is important because it is reduced from RhIII to RhI, forms a hydride by reaction with water and releases the hydride to react with nicotinamide adenine dinucleotide (NAD+) to selectively produce 1,4-NADH, the reduced form of NAD+. The second study looked at different types of ketones and enzymes for the enzyme-substrate reaction converting a ketone into an alcohol. Preliminary results showed that the rhodium complexed with bipyridine was able to carry out all the reactions, while the rhodium complexed with imidazole was not able to produce and release hydrides. In addition, the most effective ketone to use is benzylacetone with the enzyme alcohol dehydrogenase from baker’s yeast. Future work includes experimenting with bis-imidazole, which mimics the structure of bipyridine to see if it has the capability to reduce and if the reduction rate is comparable to the bipyridine complex. Once all testing is completed, the fastest catalysts will be combined with polymer membranes designed for fuel cells to prepare biosensing devices that can be used in a variety of applications including ones in the medical and environmental fields.

  5. Column preconcentration and electrothermal atomic absorption spectrometric determination of rhodium in some food and standard samples.

    PubMed

    Taher, Mohammad Ali; Pourmohammad, Fatemeh; Fazelirad, Hamid

    2015-12-01

    In the present work, an electrothermal atomic absorption spectrometric method has been developed for the determination of ultra-trace amounts of rhodium after adsorption of its 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol/tetraphenylborate ion associated complex at the surface of alumina. Several factors affecting the extraction efficiency such as the pH, type of eluent, sample and eluent flow rates, sorption capacity of alumina and sample volume were investigated and optimized. The relative standard deviation for eight measurements of 0.1 ng/mL of rhodium was ±6.3%. In this method, the detection limit was 0.003 ng/mL in the original solution. The sorption capacity of alumina and the linear range for Rh(III) were evaluated as 0.8 mg/g and 0.015-0.45 ng/mL in the original solution, respectively. The proposed method was successfully applied for the extraction and determination of rhodium content in some food and standard samples with high recovery values.

  6. Catalytic activity of rhodium complex immobilized on AN-31 ion exchanger

    SciTech Connect

    Parshikova, G.N.; Korneva, L.I.; Kononov, Yu.S.

    1995-08-10

    Immobilized platinum-metal complexes are of interest as heterogeneous catalysts. Ion-exchange resins may be used as supports for catalytically active complexes. However, immobilized metal complexes are often unstable, are washed out from supports, and are lost with reaction products. Secure immobilization of metal complexes on supports is possible, for example, via coordination of the central metal by electron-donor groups of the support. This is the case when platinum metals are sorbed from solutions by nitrogen-containing ion exchangers. Complexes thus immobilized have high catalytic activity. Previously the authors demonstrated that rhodium(III) is sorbed from solutions containing rhodium aqua-chloro complexes as stable complexes with AN-31. These complexes were not desorbed with 10 M hydrochloric acid. Stable amino complexes of transition metals sorbed on ion exchangers are known to be active in decomposition of hydrogen peroxide. In this work, the authors have studied catalytic properties of rhodium complex with the ion exchanger under atmospheric pressure at 25-80{degrees}C.

  7. Mild partial deoxygenation of esters catalyzed by an oxazolinylborate-coordinated rhodium silylene

    DOE PAGES

    Xu, Songchen; Boschen, Jeffery S.; Biswas, Abhranil; ...

    2015-08-17

    An electrophilic, coordinatively unsaturated rhodium complex supported by borate-linked oxazoline, oxazoline-coordinated silylene, and N-heterocyclic carbene donors [{κ³-N,Si,C-PhB(OxMe²)(OxMe²SiHPh)ImMes}Rh(H)CO][HB(C₆F₅)₃] (2, OxMe² = 4,4-dimethyl-2-oxazoline; ImMes = 1-mesitylimidazole) is synthesized from the neutral rhodium silyl {PhB(OxMe²)₂ImMes}RhH(SiH2Ph)CO (1) and B(C6F5)3. The unusual oxazoline-coordinated silylene structure in 2 is proposed to form by rearrangement of an unobserved isomeric cationic rhodium silylene species [{PhB(OxMe²)₂ImMes}RhH(SiHPh)CO][HB(C₆F₅)₃] generated by H abstraction. Complex 2 catalyzes reductions of organic carbonyl compounds with silanes to give hydrosilylation products or deoxygenation products. The pathway to these reactions is primarily influenced by the degree of substitution of the organosilane. Reactions with primary silanes give deoxygenationmore » of esters to ethers, amides to amines, and ketones and aldehydes to hydrocarbons, whereas tertiary silanes react to give 1,2-hydrosilylation of the carbonyl functionality. In contrast, the strong Lewis acid B(C₆F₅)₃ catalyzes the complete deoxygenation of carbonyl compounds to hydrocarbons with PhSiH₃ as the reducing agent.« less

  8. Intramolecular Hydroamination of Unbiased and Functionalized Primary Aminoalkenes Catalyzed by a Rhodium Aminophosphine Complex

    PubMed Central

    Julian, Lisa D.; Hartwig, John F.

    2010-01-01

    We report a rhodium catalyst that exhibits high reactivity for the hydroamination of primary aminoalkenes that are unbiased toward cyclization and that possess functional groups that would not be tolerated in hydroaminations catalyzed by more electrophilic systems. This catalyst contains an unusual diaminophosphine ligand that binds to rhodium in a κ3-P,O,P mode. The reactions catalyzed by this complex typically proceed at mild temperatures (room temperature to 70 °C), occur with primary aminoalkenes lacking substituents on the alkyl chain that bias the system toward cyclization, occur with primary aminoalkenes containing chloride, ester, ether, enolizable ketone, nitrile, and unprotected alcohol functionality, and occur with primary aminoalkenes containing internal olefins. Mechanistic data imply that these reactions occur with a turnover-limiting step that is different from that of reactions catalyzed by late transition metal complexes of Pd, Pt, and Ir. This change in the turnover-limiting step and resulting high activity of the catalyst stem from favorable relative rates for protonolysis of the M-C bond to release the hydroamination product vs reversion of the aminoalkyl intermediate to regenerate the acyclic precursor. Probes for the origin of the reactivity of the rhodium complex of L1 imply that the aminophosphine groups lead to these favorable rates by effects beyond steric demands and simple electron donation to the metal center. PMID:20839807

  9. Cell-Selective Biological Activity of Rhodium Metalloinsertors Correlates with Subcellular Localization

    PubMed Central

    Komor, Alexis C.; Schneider, Curtis J.; Weidmann, Alyson G.; Barton, Jacqueline K.

    2013-01-01

    Deficiencies in the mismatch repair (MMR) pathway are associated with several types of cancers, as well as resistance to commonly used chemotherapeutics. Rhodium metalloinsertors have been found to bind DNA mismatches with high affinity and specificity in vitro, and also exhibit cell-selective cytotoxicity, targeting MMR-deficient cells over MMR-proficient cells. Ten distinct metalloinsertors with varying lipophilicities have been synthesized and their mismatch binding affinities and biological activities determined. Although DNA photocleavage experiments demonstrate that their binding affinities are quite similar, their cell-selective antiproliferative and cytotoxic activities vary significantly. Inductively coupled plasma mass spectrometry (ICP-MS) experiments have uncovered a relationship between the subcellular distribution of these metalloinsertors and their biological activities. Specifically, we find that all of our metalloinsertors localize in the nucleus at sufficient concentrations for binding to DNA mismatches. However, the metalloinsertors with high rhodium localization in the mitochondria show toxicity that is not selective for MMR-deficient cells, whereas metalloinsertors with less mitochondrial rhodium show activity that is highly selective for MMR-deficient versus proficient cells. This work supports the notion that specific targeting of the metalloinsertors to nuclear DNA gives rise to their cell-selective cytotoxic and antiproliferative activities. The selectivity in cellular targeting depends upon binding to mismatches in genomic DNA. PMID:23137296

  10. Enantioselective rhodium-catalyzed arylation of cyclic N-sulfamidate alkylketimines: a new access to chiral β-alkyl-β-aryl amino alcohols.

    PubMed

    Chen, Ya-Jing; Chen, Ya-Heng; Feng, Chen-Guo; Lin, Guo-Qiang

    2014-06-20

    The enantioselective rhodium-catalyzed 1,2-addition of arylboronates to cyclic N-sulfamidate alkylketimines was developed. With a rhodium/diene complex as catalyst, high enantioselectivity and broad functional group tolerance were observed. The resulting sulfamidates can easily be converted into chiral β-alkyl-β-aryl amino alcohols.

  11. Enantioselective conjugate addition of phenylboronic acid to enones catalysed by a chiral tropos/atropos rhodium complex at the coalescence temperature.

    PubMed

    Monti, Chiara; Gennari, Cesare; Piarulli, Umberto

    2005-11-14

    A highly enantioselective rhodium-catalysed conjugate addition of phenylboronic acid to cyclic enones has been achieved using a dynamic library of chiral phosphorus ligands; the tropos/atropos nature of the ligands in the rhodium complex has been characterised via 31P-NMR.

  12. Determination of rhodium in metallic alloy and water samples using cloud point extraction coupled with spectrophotometric technique

    NASA Astrophysics Data System (ADS)

    Kassem, Mohammed A.; Amin, Alaa S.

    2015-02-01

    A new method to estimate rhodium in different samples at trace levels had been developed. Rhodium was complexed with 5-(4‧-nitro-2‧,6‧-dichlorophenylazo)-6-hydroxypyrimidine-2,4-dione (NDPHPD) as a complexing agent in an aqueous medium and concentrated by using Triton X-114 as a surfactant. The investigated rhodium complex was preconcentrated with cloud point extraction process using the nonionic surfactant Triton X-114 to extract rhodium complex from aqueous solutions at pH 4.75. After the phase separation at 50 °C, the surfactant-rich phase was heated again at 100 °C to remove water after decantation and the remaining phase was dissolved using 0.5 mL of acetonitrile. Under optimum conditions, the calibration curve was linear for the concentration range of 0.5-75 ng mL-1 and the detection limit was 0.15 ng mL-1 of the original solution. The enhancement factor of 500 was achieved for 250 mL samples containing the analyte and relative standard deviations were ⩽1.50%. The method was found to be highly selective, fairly sensitive, simple, rapid and economical and safely applied for rhodium determination in different complex materials such as synthetic mixture of alloys and environmental water samples.

  13. Influence of particle size and support on the catalytic properties of rhodium for hydrogenolysis of hexanes and methylcyclopentane

    SciTech Connect

    Del Angel, G.; Coq, B.; Dutartre, R.; Figueras, F.

    1984-05-01

    The catalytic properties of rhodium for the hydrogenolysis of C/sub 6/ hydrocarbons have been investigated. Rhodium preferentially cleaves bisecondary and primary-secondary carbon-carbon bonds. Primary-tertiary C-C bonds react much more slowly. Methylcyclopentane (MCP) is converted to methyl-2-pentane, methyl-3-pentane, and n-hexane at temperatures lower than 503 K. The selectivity to n-hexane is low (10%) but measurable on well-dispersed Rh/Al/sub 2/O/sub 3/ catalysts and decreases when the dispersion decreases. Rh/SiO/sub 2/ catalysts have a low selectivity for the formation of n-hexane whatever the dispersion. The specific activity for MCP conversion changes as a function of the dispersion of rhodium and of the support: small rhodium particles are more active than large particles when the support is silica, but the reverse is true on alumina. These changes of activity are consistent with the results reported for C/sub 2/H/sub 6/ hydrogenolysis on Rh/SiO/sub 2/ and for C/sub 5/H/sub 10/ conversion on Rh/Al/sub 2/O/sub 3/. The variations of the catalytic properties for hydrogenolysis may be interpreted as due to the modification of the structure of the small rhodium particles observed on silica.

  14. The structures of the crystalline phase and columnar mesophase of rhodium (II) heptanoate and of its binary mixture with copper (II) heptanoate probed by EXAFS

    NASA Astrophysics Data System (ADS)

    Inb-Elhaj, M.; Guillon, D.; Skoulios, A.; Maldivi, P.; Giroud-Godquin, A. M.; Marchon, J.-C.

    1992-12-01

    EXAFS was used to investigate the local structure of the polar spines of rhodium (II) soaps in the columnar liquid crystalline state. It was also used to ascertain the degree of blending of the cores in binary mixtures of rhodium (II) and copper (II) soaps. For the pure rhodium soaps, the columns are shown to result from the stacking of binuclear metal-metal bonded dirhodium tetracarboxylate units bonded to one another by apical ligation of the metal atom of each complex with one of the oxygen atoms of the adjacent molecule. Mixtures of rhodium (II) and copper (II) soaps give a hexagonal columnar mesophase in which pure rhodium and pure copper columns are randomly distributed.

  15. Poor Americans: How the Poor White Live.

    ERIC Educational Resources Information Center

    Pilisuk, Marc; Pilisuk, Phyllis

    Contents of this book include the following essays which originally appeared in "Transaction" magazine: (1) "Poor Americans: an introduction," Marc Pilisuk and Phyllis Pilisuk; (2) "How the white poor live," Marc Pilisuk and Phyllis Pilisuk; (3) "The culture of poverty," Oscar Lewis; (4) "Life in Appalachia--the case of Hugh McCaslin," Robert…

  16. Poor Americans: How the Poor White Live.

    ERIC Educational Resources Information Center

    Pilisuk, Marc; Pilisuk, Phyllis

    Contents of this book include the following essays which originally appeared in "Transaction" magazine: (1) "Poor Americans: an introduction," Marc Pilisuk and Phyllis Pilisuk; (2) "How the white poor live," Marc Pilisuk and Phyllis Pilisuk; (3) "The culture of poverty," Oscar Lewis; (4) "Life in Appalachia--the case of Hugh McCaslin," Robert…

  17. A rhodium/silicon co-electrocatalyst design concept to surpass platinum hydrogen evolution activity at high overpotentials

    PubMed Central

    Zhu, Lili; Lin, Haiping; Li, Youyong; Liao, Fan; Lifshitz, Yeshayahu; Sheng, Minqi; Lee, Shuit-Tong; Shao, Mingwang

    2016-01-01

    Currently, platinum-based electrocatalysts show the best performance for hydrogen evolution. All hydrogen evolution reaction catalysts should however obey Sabatier's principle, that is, the adsorption energy of hydrogen to the catalyst surface should be neither too high nor too low to balance between hydrogen adsorption and desorption. To overcome the limitation of this principle, here we choose a composite (rhodium/silicon nanowire) catalyst, in which hydrogen adsorption occurs on rhodium with a large adsorption energy while hydrogen evolution occurs on silicon with a small adsorption energy. We show that the composite is stable with better hydrogen evolution activity than rhodium nanoparticles and even exceeding those of commercial platinum/carbon at high overpotentials. The results reveal that silicon plays a key role in the electrocatalysis. This work may thus open the door for the design and fabrication of electrocatalysts for high-efficiency electric energy to hydrogen energy conversion. PMID:27447292

  18. Stripping voltammetric determination of palladium, platinum and rhodium in freshwater and sediment samples from South African water resources.

    PubMed

    van der Horst, C; Silwana, B; Iwuoha, E; Somerset, V

    2012-01-01

    Stripping voltammetry as technique has proved to be very useful in the analysis of heavy and other metal ions due to its excellent detection limits and its sensitivity in the presence of different metal species or interfering ions. Recent assessments of aquatic samples have shown increased levels of platinum group metals (PGMs) in aquatic ecosystems, caused by automobile exhaust emissions and mining activities. The development of an analytical sensor for the detection and characterisation of PGMs were investigated, since there is an ongoing need to find new sensing materials with suitable recognition elements that can respond selectively and reversibly to specific metal ions in environmental samples. The work reported shows the successful application of another mercury-free sensor electrode for the determination of platinum group metals in environmental samples. The work reported in this study entails the use of a glassy carbon electrode modified with a bismuth film for the determination of platinum (Pt(2+)), palladium (Pd(2+)) or rhodium (Rh(2+)) by means of adsorptive cathodic stripping voltammetry. Optimised experimental conditions included composition of the supporting electrolyte, complexing agent concentration, deposition potential, deposition time and instrumental voltammetry parameters for Pt(2+), Pd(2+) and Rh(2+) determination. Adsorptive differential pulse stripping voltammetric measurements for PGMs were performed in the presence of dimethylglyoxime (DMG) as complexing agent. The glassy carbon bismuth film electrode (GC/BiFE) employed in this study exhibit good and reproducible sensor characteristics. Application of GC/BiFE sensor exhibited well-defined peaks and highly linear behaviour for the stripping analysis of the PGMs in the concentration range between 0 and 3.5 μg/L. The detection limit of Pd, Pt and Rh was found to be 0.12 μg/L, 0.04 μg/L and 0.23 μg/L, respectively for the deposition times of 90 s (Pd) and 150 s (for both Pt and Rh). Good

  19. Mechanochemical Rhodium(III)-Catalyzed C-H Bond Functionalization of Acetanilides under Solventless Conditions in a Ball Mill.

    PubMed

    Hermann, Gary N; Becker, Peter; Bolm, Carsten

    2015-06-15

    In a proof-of-principle study, a planetary ball mill was applied to rhodium(III)-catalyzed C-H bond functionalization. Under solventless conditions and in the presence of a minute amount of Cu(OAc)2, the mechanochemical activation led to the formation of an active rhodium species, thus enabling an oxidative Heck-type cross-coupling reaction with dioxygen as the terminal oxidant. The absence of an organic solvent, the avoidance of a high reaction temperature, the possibility of minimizing the amount of the metallic mediator, and the simplicity of the protocol result in a powerful and environmentally benign alternative to the common solution-based standard protocol.

  20. Permeation of platinum and rhodium nanoparticles through intact and damaged human skin

    NASA Astrophysics Data System (ADS)

    Mauro, Marcella; Crosera, Matteo; Bianco, Carlotta; Adami, Gianpiero; Montini, Tiziano; Fornasiero, Paolo; Jaganjac, Morana; Bovenzi, Massimo; Filon, Francesca Larese

    2015-06-01

    The aim of the study was to evaluate percutaneous penetration of platinum and rhodium nanoparticles (PtNPs: 5.8 ± 0.9 nm, RhNPs: 5.3 ± 1.9 nm) through human skin. Salts compounds of these metals are sensitizers and some also carcinogenic agents. In vitro permeation experiments were performed using Franz diffusion cells with intact and damaged skin. PtNPs and RhNPs, stabilized with polyvinylpyrrolidone, were synthesized by reduction of Na2PtCl6 and RhCl3·3H2O respectively. Suspensions with a concentration of 2.0 g/L of PtNPs and RhNPs were dispersed separately in synthetic sweat at pH 4.5 and applied as donor phases to the outer surface of the skin for 24 h. Measurements of the content of the metals in the receiving solution and in the skin were performed subsequently. Rhodium skin permeation was demonstrated through damaged skin, with a permeation flux of 0.04 ± 0.04 μg cm-2 h-1 and a lag time of 7.9 ± 1.1 h, while no traces of platinum were found in receiving solutions. Platinum and rhodium skin-analysis showed significantly higher concentrations of the metals in damaged skin. Rh and Pt applied as NPs can penetrate the skin barrier and Rh can be found in receiving solutions. These experiments pointed out the need for skin contamination prevention, since even a minor injury to the skin barrier can significantly increase penetration.

  1. Synthesis, characterization, and reactivity of rhodium(I) acetylacetonato complexes containing pyridinecarboxaldimine ligands.

    PubMed

    Kanas, Diane A; Geier, Stephen J; Vogels, Christopher M; Decken, Andreas; Westcott, Stephen A

    2008-10-06

    Addition of o-C 6H 4NCHNAr to Rh(coe) 2(acac) (coe = cis-cyclooctene, acac = acetylacetonato) gave several new iminopyridine rhodium(I) complexes of the type Rh(acac)(kappa (2)- o-C 6H 4 NCH NAr) ( 1a Ar = 4-C 6H 4-OMe; 1b Ar = 2,6-C 6H 3-Me 2; 1c Ar = 2,6-C 6H 3-Et 2; 1d Ar = 2,6-C 6H 3- i-Pr 2). All new rhodium complexes have been characterized by a number of physical methods, including multinuclear NMR spectroscopy and X-ray diffraction studies for 1b and 1c. Addition of CHCl 3 to 1a afforded the corresponding rhodium(III) complex trans-Rh(kappa (2)- o-C 6H 4 NCH NAr)(CHCl 2)(Cl)(acac) ( 2). Addition of B 2cat 3 (cat = 1,2-O 2C 6H 4) to 1 gave zwitterionic Rh(eta (6)-catBcat)(kappa (2)- o-C 6H 4 NCH NAr) ( 3). The molecular structure of 3b has been confirmed by a single crystal X-ray diffraction study and shows that the N 2Rh fragment is bound to the catBcat anion via one of the catecholato groups in a eta (6)-fashion. These complexes have also been examined for their ability to catalyze the hydroboration of a series of vinylarenes. Reactions using catecholborane and pinacolborane seem to proceed largely through a dehydrogenative borylation mechanism to give a number of boronated products.

  2. Mild partial deoxygenation of esters catalyzed by an oxazolinylborate-coordinated rhodium silylene

    SciTech Connect

    Xu, Songchen; Boschen, Jeffery S.; Biswas, Abhranil; Kobayashi, Takeshi; Pruski, Marek; Windus, Theresa L.; Sadow, Aaron D.

    2015-08-17

    An electrophilic, coordinatively unsaturated rhodium complex supported by borate-linked oxazoline, oxazoline-coordinated silylene, and N-heterocyclic carbene donors [{κ³-N,Si,C-PhB(OxMe²)(OxMe²SiHPh)ImMes}Rh(H)CO][HB(C₆F₅)₃] (2, OxMe² = 4,4-dimethyl-2-oxazoline; ImMes = 1-mesitylimidazole) is synthesized from the neutral rhodium silyl {PhB(OxMe²)₂ImMes}RhH(SiH2Ph)CO (1) and B(C6F5)3. The unusual oxazoline-coordinated silylene structure in 2 is proposed to form by rearrangement of an unobserved isomeric cationic rhodium silylene species [{PhB(OxMe²)₂ImMes}RhH(SiHPh)CO][HB(C₆F₅)₃] generated by H abstraction. Complex 2 catalyzes reductions of organic carbonyl compounds with silanes to give hydrosilylation products or deoxygenation products. The pathway to these reactions is primarily influenced by the degree of substitution of the organosilane. Reactions with primary silanes give deoxygenation of esters to ethers, amides to amines, and ketones and aldehydes to hydrocarbons, whereas tertiary silanes react to give 1,2-hydrosilylation of the carbonyl functionality. In contrast, the strong Lewis acid B(C₆F₅)₃ catalyzes the complete deoxygenation of carbonyl compounds to hydrocarbons with PhSiH₃ as the reducing agent.

  3. A concise total synthesis of pyrovellerolactone using a rhodium-catalyzed [(3 + 2) + 2] carbocyclization reaction.

    PubMed

    Evans, P Andrew; Inglesby, Phillip A; Kilbride, Kathryn

    2013-04-19

    A concise and highly convergent three-step total synthesis of the lactarane natural product, pyrovellerolactone, is described. The key step involves a regio- and diastereoselective rhodium-catalyzed [(3 + 2) + 2] carbocyclization of an alkenylidenecyclopropane with a 4-hydroxybut-2-ynoate followed by an in situ intramolecular lactonization to generate the tricyclic core in a single operation. This represents the first example of a higher-order [3 + 2 + 2] carbocyclization reaction in total synthesis, which is likely to provide an important strategy for the construction of related targets within this sesquiterpene family.

  4. Hydrolysis of Letrozole catalyzed by macrocyclic Rhodium (I) Schiff-base complexes.

    PubMed

    Reddy, P Muralidhar; Shanker, K; Srinivas, V; Krishna, E Ravi; Rohini, R; Srikanth, G; Hu, Anren; Ravinder, V

    2015-03-15

    Ten mononuclear Rhodium (I) complexes were synthesized by macrocyclic ligands having N4 and N2O2 donor sites. Square planar geometry is assigned based on the analytical and spectral properties for all complexes. Rh(I) complexes were investigated as catalysts in hydrolysis of Nitrile group containing pharmaceutical drug Letrozole. A comparative study showed that all the complexes are efficient in the catalysis. The percent yields of all the catalytic reaction products viz. drug impurities were determined by spectrophotometric procedures and characterized by spectral studies.

  5. Construction of a Chiral Silicon Center by Rhodium-Catalyzed Enantioselective Intramolecular Hydrosilylation.

    PubMed

    Naganawa, Yuki; Namba, Tomoya; Kawagishi, Mayu; Nishiyama, Hisao

    2015-06-22

    Rhodium-catalyzed enantioselective desymmetrizing intramolecular hydrosilylation of symmetrically disubstituted hydrosilanes is described. The original axially chiral phenanthroline ligand (S)-BinThro (Binol-derived phenanthroline) was found to work as an effective chiral catalyst for this transformation. A chiral silicon stereogenic center is one of the chiral motifs gaining much attention in asymmetric syntheses and the present protocol provides cyclic five-membered organosilanes incorporating chiral silicon centers with high enantioselectivities (up to 91 % ee). The putative active Rh(I) catalyst takes the form of an N,N,O-tridentate coordination complex, as determined by several complementary experiments.

  6. Oxidative addition of methane and benzene C--H bonds to rhodium center: A DFT study

    NASA Astrophysics Data System (ADS)

    Bi, Siwei; Zhang, Zhenwei; Zhu, Shufen

    2006-11-01

    A density functional theory study on mechanisms of the oxidative addition of methane and benzene C-H bonds to the rhodium center containing Cp and PMe 3 ligands has been performed. Our calculated results confirm that the C-H bond cleavage from a sigma complex to a hydride alkyl complex is the rate-determining step. Compared with the case of methane C-H bond, the oxidative addition of benzene C-H bond is more favorable kinetically and thermodynamically. Stronger backdonation from metal center to the σ ∗ antibonding orbital of benzene C-H bond is responsible for the observations.

  7. Platinum, palladium, and rhodium analyses of ultramafic and mafic rocks from the Stillwater Complex, Montana

    USGS Publications Warehouse

    Page, Norman J; Riley, Leonard Benjamin; Haffty, Joseph

    1969-01-01

    Analyses by a combination fire- assay-solution-optical-emission spectrographic method of 137 rocks from the Stillwater Complex, Mont., indicate that platinum, palladium, and rhodium are preferentially concentrated in chromitite zones. The A chromitite zone (21 samples) has an average of 988.9 ppb (pans per billion, 10-9) Pt, 2290.2 ppb Pd, and 245.9 ppb Rh and reaches a maximum (to date) of 8,000 ppb Pt, 11,000 ppb Pd, and 1,700 ppb Rh.

  8. AMTEC cell testing, optimization of rhodium/tungsten electrodes, and tests of other components

    NASA Technical Reports Server (NTRS)

    Williams, Roger M.; Ryan, Margaret A.; Jeffries-Nakamura, Barbara; Underwood, Mark L.; O'Connor, Dennis; Kikkert, Stan

    1991-01-01

    Electrodes, current collectors, ceramic to metal braze seals, and metallic components exposed to the high 'hot side' temperatures and sodium liquid and vapor environment have been tested and evaluated in laboratory cells running for hundreds of hours at 1100-1200 K. Rhodium/tungsten electrodes have been selected as the optimum electrodes based on performance parameters and durability. Current collectors have been evaluated under simulated and actual operating conditions. The microscopic effects of metal migration between electrode and current collector alloys as well as their thermal and electrical properties determined the suitability of current collector and lead materials. Braze seals suitable for long term application to AMTEC devices are being developed.

  9. The oxidation of carbon monoxide on polycrystalline rhodium under knudsen conditions. II. Reaction with nitrogen monoxide

    NASA Astrophysics Data System (ADS)

    Lintz, Hans-Günther; Weisker, Tilman

    1985-09-01

    The reaction between carbon monoxide and nitrogen monoxide on a polycrystalline rhodium ribbon under stationary conditions is followed by mass spectrometry. In the temperature range 300 to 1100 K the ratio of the partial pressures of the reactants varies between 0.1 < pNO/ pCO < 100 at values of the total pressure in the reactor from 10 -4 to 10 -5 Torr. The results can be interpreted qualitatively by a simple elementary reaction sequence. Simulation using literature values of the kinetic constants leads to semi-quantitative agreement with experimental results. No isothermal oscillations of the reaction rate could be observed under the stated conditions.

  10. Understanding Rate Acceleration and Stereoinduction of an Asymmetric Giese Reaction Mediated by a Chiral Rhodium Catalyst.

    PubMed

    Tutkowski, Brandon; Meggers, Eric; Wiest, Olaf

    2017-06-21

    The surprising acceleration of the addition of electron-rich radicals to α,β-unsaturated 2-acyl imidazoles by a chiral-at-metal rhodium catalyst is investigated. M06/Lanl2DZ (Rh),6-31G(d) calculations reproduce the observed rate acceleration and shed light on a catalyst design where a rigid chiral pocket with a steric interaction >5 Å from the chiral metal center leads to the observed high stereoinduction. Analysis of the molecular orbitals of two key addition transition states emphasize the role of the catalyst as a Lewis acid without significant charge transfer.

  11. Rhodium(III)-catalyzed indazole synthesis by C-H bond functionalization and cyclative capture.

    PubMed

    Lian, Yajing; Bergman, Robert G; Lavis, Luke D; Ellman, Jonathan A

    2013-05-15

    An efficient, one-step, and highly functional group-compatible synthesis of substituted N-aryl-2H-indazoles is reported via the rhodium(III)-catalyzed C-H bond addition of azobenzenes to aldehydes. The regioselective coupling of unsymmetrical azobenzenes was further demonstrated and led to the development of a new removable aryl group that allows for the preparation of indazoles without N-substitution. The 2-aryl-2H-indazole products also represent a new class of readily prepared fluorophores for which initial spectroscopic characterization has been performed.

  12. Associative Covalent Relay: An Oxadiazolone Strategy for Rhodium(III)-Catalyzed Synthesis of Primary Pyridinylamines.

    PubMed

    Yu, Xiaolong; Chen, Kehao; Wang, Qi; Guo, Shan; Zha, Shanke; Zhu, Jin

    2017-04-05

    A relay formalism is proposed herein for categorizing the interplay among reactants, target product, and catalytic center in transition-metal catalysis, an important factor that can dictate overall catalysis viability and efficiency. In this formalism, transition-metal catalysis can proceed by dissociative relay, associative covalent relay, and associative dative relay modes. An intriguing associative covalent relay process operates in rhodium(III)-catalyzed oxadiazolone-directed alkenyl C-H coupling with alkynes and allows efficient access to primary pyridinylamines. Although the primary pyridinylamine synthesis mechanism is posteriori rationalized, the relay formalism formulated herein can provide an important mechanistic conceptual framework for future catalyst design and reaction development.

  13. Sterilizing the Poor

    ERIC Educational Resources Information Center

    Rothman, Sheila M.

    1977-01-01

    Suggests that freedom for the middle classes may mean vulnerability for the poor. The enthusiasm for sterilization may be so intense as to deprive the poor of their right not to be sterilized. (Author/AM)

  14. The role of macrocyclic compounds in the extraction and possible separation of platinum and rhodium from chloride solutions

    PubMed Central

    Jyothi, Rajesh Kumar; Lee, Jin-Young

    2016-01-01

    Macrocyclic compounds (crown ethers), specifically 18-crown-6 (18-C-6), benzo-15-crown-5 (B-15-C-5), di-benzo-18-crown-6 (DB-18-C-6) and di-cyclohexano-18-crown-6 (DC-18C-6), are used as extractants as well as synergists with amine-group extractants. Platinum and rhodium belong to platinum-group metals (PGMs) and have very similar ionic radii and similar properties. The separation of PGMs is most useful for the preparation of functional materials. Macrocyclic compounds are tested for platinum and rhodium separation and are found to achieve marginal separation. Amines (used as extractants) are paired with macrocyclic compounds (used as synergists), and the separation factor between platinum and rhodium is increased with synergistic enhancement from a chloride solution. The present study discusses extraction chemistry, separation factors and the synergy between platinum and rhodium from chloride solutions. To ensure accurate data, the aqueous samples in this study are analyzed using an inductively coupled plasma optical emission spectrometer (ICP-OES). PMID:27283394

  15. Direct access to ketones from aldehydes via rhodium-catalyzed cross-coupling reaction with potassium trifluoro(organo)borates.

    PubMed

    Pucheault, Mathieu; Darses, Sylvain; Genet, Jean-Pierre

    2004-12-01

    A direct cross-coupling reaction of aromatic aldehydes with potassium trifluoro(organo)borates afforded ketones in high yields and under mild conditions in the presence of a rhodium catalyst and acetone. This new reaction, involving a formal aldehyde C-H bond activation, is believed to proceed via a Heck-type mechanism followed by hydride transfer to acetone.

  16. The role of macrocyclic compounds in the extraction and possible separation of platinum and rhodium from chloride solutions

    NASA Astrophysics Data System (ADS)

    Jyothi, Rajesh Kumar; Lee, Jin-Young

    2016-06-01

    Macrocyclic compounds (crown ethers), specifically 18-crown-6 (18-C-6), benzo-15-crown-5 (B-15-C-5), di-benzo-18-crown-6 (DB-18-C-6) and di-cyclohexano-18-crown-6 (DC-18C-6), are used as extractants as well as synergists with amine-group extractants. Platinum and rhodium belong to platinum-group metals (PGMs) and have very similar ionic radii and similar properties. The separation of PGMs is most useful for the preparation of functional materials. Macrocyclic compounds are tested for platinum and rhodium separation and are found to achieve marginal separation. Amines (used as extractants) are paired with macrocyclic compounds (used as synergists), and the separation factor between platinum and rhodium is increased with synergistic enhancement from a chloride solution. The present study discusses extraction chemistry, separation factors and the synergy between platinum and rhodium from chloride solutions. To ensure accurate data, the aqueous samples in this study are analyzed using an inductively coupled plasma optical emission spectrometer (ICP-OES).

  17. Rhodium(III)-catalyzed C-H activation/annulation with vinyl esters as an acetylene equivalent.

    PubMed

    Webb, Nicola J; Marsden, Stephen P; Raw, Steven A

    2014-09-19

    The behavior of electron-rich alkenes in rhodium-catalyzed C-H activation/annulation reactions is investigated. Vinyl acetate emerges as a convenient acetylene equivalent, facilitating the synthesis of sixteen 3,4-unsubstituted isoquinolones, as well as select heteroaryl-fused pyridones. The complementary regiochemical preferences of enol ethers versus enol esters/enamides is discussed.

  18. Asymmetric cyclopropanation of alkenes catalyzed by a rhodium {open_quotes}chiral fortress{close_quotes} porphyrin

    SciTech Connect

    O`Malley, S.; Kodadek, T.

    1992-06-01

    The authors investigated the use of chiral rhodium porphyrin catalysts for the production of predominantly syn isomers in the cyclopropanation of alkenes. The reactions display good diastereoselectivity on some cases, but only modest enantioselectivities are observed. 15 refs., 3 figs., 1 tab.

  19. Development and testing of a compact basis set for use in effective core potential calculations on rhodium complexes.

    PubMed

    Roscioni, Otello M; Lee, Edmond P F; Dyke, John M

    2012-10-05

    We present a set of effective core potential (ECP) basis sets for rhodium atoms which are of reasonable size for use in electronic structure calculations. In these ECP basis sets, the Los Alamos ECP is used to simulate the effect of the core electrons while an optimized set of Gaussian functions, which includes polarization and diffuse functions, is used to describe the valence electrons. These basis sets were optimized to reproduce the ionization energy and electron affinity of atomic rhodium. They were also tested by computing the electronic ground state geometry and harmonic frequencies of [Rh(CO)(2) μ-Cl](2) , Rh(CO)(2) ClPy, and RhCO (neutral and its positive, and negative ions) as well as the enthalpy of the reaction of [Rh(CO)(2) μ-Cl](2) with pyridine (Py) to give Rh(CO)(2) ClPy, at different levels of theory. Good agreement with experimental values was obtained. Although the number of basis functions used in our ECP basis sets is smaller than those of other ECP basis sets of comparable quality, we show that the newly developed ECP basis sets provide the flexibility and precision required to reproduce a wide range of chemical and physical properties of rhodium compounds. Therefore, we recommend the use of these compact yet accurate ECP basis sets for electronic structure calculations on molecules involving rhodium atoms. Copyright © 2012 Wiley Periodicals, Inc.

  20. Ethylaluminum as an ethylene source for the Mizoroki-Heck-type reaction. Rhodium-catalyzed preparation of stilbene derivatives.

    PubMed

    Tanaka, Shota; Itami, Kazuki; Sunahara, Kazuhiro; Tatsuta, Go; Mori, Atsunori

    2015-02-04

    Treatment of an organoaluminum reagent bearing aryl and ethyl groups furnishes 1,2-diarylethene derivatives in good to excellent yields by the catalysis of a rhodium complex, in which the ethyl group of the aluminum reagent serves as an ethylene source in the product formation.

  1. Development of an improved rhodium catalyst for z-selective anti-markovnikov addition of carboxylic acids to terminal alkynes.

    PubMed

    Wei, Siping; Pedroni, Julia; Meißner, Antje; Lumbroso, Alexandre; Drexler, Hans-Joachim; Heller, Detlef; Breit, Bernhard

    2013-09-02

    To develop more active catalysts for the rhodium-catalyzed addition of carboxylic acids to terminal alkynes furnishing anti-Markovnikov Z enol esters, a thorough study of the rhodium complexes involved was performed. A number of rhodium complexes were characterized by NMR, ESI-MS, and X-ray analysis and applied as catalysts for the title reaction. The systematic investigations revealed that the presence of chloride ions decreased the catalyst activity. Conversely, generating and applying a mixture of two rhodium species, namely, [Rh(DPPMP)2][H(benzoate)2] (DPPMP=diphenylphosphinomethylpyridine) and [{Rh(COD)(μ2-benzoate)}2], provided a significantly more active catalyst. Furthermore, the addition of a catalytic amount of base (Cs2CO3) had an additional accelerating effect. This higher catalyst activity allowed the reaction time to be reduced from 16 to 1-4 h while maintaining high selectivity. Studies on the substrate scope revealed that the new catalysts have greater functional-group compatibility.

  2. Development of Chinese Standard Type of Rhodium-Iron Resistance Thermometer

    NASA Astrophysics Data System (ADS)

    Lin, Peng; Li, Xingwei; Gao, Bo; Yu, Lihong; Huang, Rongjin; Li, Fuhong

    2017-02-01

    New rhodium alloy wires with 0.52 % atomic of iron have been drawn, and several batches of RhFe thermometer with strain-free construction and helium-filled platinum capsule have been made using these new alloy wires and old alloy wires which were made in the 1980s in China. In one of the constructions, the coil of wire is inserted into twisted glass tubes, and in the other, it is laid in grooves on a fused-silica crossed frame. The resistance versus temperature relationship and interpolating characteristic of Chinese RhFe thermometer are similar to those of Tinsley 5187U thermometer from 1.5 K to 27 K. The resistance changes of most thermometers are less than that of equivalent to 0.2 mK at 4.5 K after they are exposed to fifty thermal cycles from room temperature to liquid helium temperature. This standard type of rhodium-iron resistance thermometer is now commercially available. Instead of the regular annealing temperature, which is 750°C, two batches of RhFe thermometers are made with the annealing temperature of 850°C and 950°C. The interpolating characteristics of RhFe thermometers will be studied to find new calibration method.

  3. Mechanisms of catalytic dehydrogenation of alkanes by rhodium clusters Rhn+ probed by isotope labelling

    NASA Astrophysics Data System (ADS)

    Adlhart, Christian; Uggerud, Einar

    2006-03-01

    The regioselectivity for the dehydrogenation of alkanes by rhodium clusters was investigated by reacting Rhn+, n = 1-20, with the isotopically labelled alkanes ethane-1,1,1-d3 and propane-1,1,1,3,3,3-d6. For Rh+ reacting with propane a clear preference for a 1,2- over a 1,1- and 1,3-mechanism was observed. For larger clusters, hydrogen scrambling is faster than hydrogen elimination, which essentially leads to statistical formation of the neutrals H2, HD, and D2. Isotope scrambling with D2 was also used as a structural probe for the reaction products of rhodium clusters with ethane. The intactness of the CH bonds was demonstrated for (n > 6). The studies are completed with a detailed kinetic analysis for the reaction of Rh7+ with ethane and ethane/hydrogen and ethane/helium mixtures. An over-all picture with efficient CH bond activation and fast and reversible hydrogen rearrangements emerges on the basis of these experiments. Some of the dehydrogenation reactions appear to be reversible.

  4. Rhodium-catalyzed formation of stereocontrolled trisubstituted alkenes from Baylis-Hillman adducts.

    PubMed

    Gendrineau, Thomas; Demoulin, Nicolas; Navarre, Laure; Genet, Jean-Pierre; Darses, Sylvain

    2009-01-01

    Efficient and general conditions for the formation of stereodefined trisubstituted alkenes by using the rhodium-catalyzed reaction of unactivated Baylis-Hillman adducts with either organoboronic acids or potassium trifluoro(organo)borates are reported (see scheme).We report here efficient and general conditions for the formation of stereodefined trisubstituted alkenes using the rhodium-catalyzed reaction of unactivated Baylis-Hillman adducts with either organoboronic acids and potassium trifluoro(organo)borates. The use of the [{Rh(cod)OH}(2)] precursor gave very fast coupling reactions under low catalyst loading, very mild reaction conditions (from room temperature up to 50 degrees C) and without the need of additional phosphane ligands. Based on the new reaction conditions, the reaction, originally limited to Baylis-Hillman adducts derived from esters, could be extended to a large variety of Baylis-Hillman adducts, bearing either keto, cyano or amido functionalities. Moreover, the reaction of Baylis-Hillman adducts bearing esters functionality was improved and could be conducted at lower temperature using lower catalyst loading.

  5. The synthesis of rhodium/carbon dots nanoparticles and its hydrogenation application

    NASA Astrophysics Data System (ADS)

    Zhang, Jie; Chen, Yao; Tan, Jing; Sang, Haitao; Zhang, Liqun; Yue, Dongmei

    2017-02-01

    Rhodium (Rh) nanoparticles have been widely used as potent hydrogenation catalysts. Herein, a new convenient method has been developed to synthesize rhodium nanoparticles, in which carbon dots (CDs) were used both as stabilizing and reducing agents. The fluorescent CDs were prepared by microwave-assisted heating method using chitosan as raw material and the presences of hydroxyl and carbonyl on the surface of CDs were supported by FTIR spectra. Subsequently, CDs could directly reduce Rh3+ to Rh0 without additional reducing and stabilizing agents by heating Rh3+ with CDs for 1 h at 120 °C. The resulting Rh nanoparticles have an average size of about 2.8 nm and the Rh/CDs nanoparticles also retain the fluorescent property of CDs. The hydrogenation activities of Rh/CDs nanoparticles were investigated. The results demonstrated that the nanoparticles had highly catalytic activity in the hydrogenation reaction of hydroxyl-terminated polybutadiene (HTPB) and hydroxy-terminated butadiene-acrylonitrile (HTBN). Also, the presence of CDs could improve the fluorescent properties of rubbers after hydrogenation.

  6. Rhodium-catalysed syn-carboamination of alkenes via a transient directing group.

    PubMed

    Piou, Tiffany; Rovis, Tomislav

    2015-11-05

    Alkenes are the most ubiquitous prochiral functional groups--those that can be converted from achiral to chiral in a single step--that are accessible to synthetic chemists. For this reason, difunctionalization reactions of alkenes (whereby two functional groups are added to the same double bond) are particularly important, as they can be used to produce highly complex molecular architectures. Stereoselective oxidation reactions, including dihydroxylation, aminohydroxylation and halogenation, are well established methods for functionalizing alkenes. However, the intermolecular incorporation of both carbon- and nitrogen-based functionalities stereoselectively across an alkene has not been reported. Here we describe the rhodium-catalysed carboamination of alkenes at the same (syn) face of a double bond, initiated by a carbon-hydrogen activation event that uses enoxyphthalimides as the source of both the carbon and the nitrogen functionalities. The reaction methodology allows for the intermolecular, stereospecific formation of one carbon-carbon and one carbon-nitrogen bond across an alkene, which is, to our knowledge, unprecedented. The reaction design involves the in situ generation of a bidentate directing group and the use of a new cyclopentadienyl ligand to control the reactivity of rhodium. The results provide a new way of synthesizing functionalized alkenes, and should lead to the convergent and stereoselective assembly of amine-containing acyclic molecules.

  7. Tracking the shape-dependent sintering of platinum-rhodium model catalysts under operando conditions

    NASA Astrophysics Data System (ADS)

    Hejral, Uta; Müller, Patrick; Balmes, Olivier; Pontoni, Diego; Stierle, Andreas

    2016-03-01

    Nanoparticle sintering during catalytic reactions is a major cause for catalyst deactivation. Understanding its atomic-scale processes and finding strategies to reduce it is of paramount scientific and economic interest. Here, we report on the composition-dependent three-dimensional restructuring of epitaxial platinum-rhodium alloy nanoparticles on alumina during carbon monoxide oxidation at 550 K and near-atmospheric pressures employing in situ high-energy grazing incidence x-ray diffraction, online mass spectrometry and a combinatorial sample design. For platinum-rich particles our results disclose a dramatic reaction-induced height increase, accompanied by a corresponding reduction of the total particle surface coverage. We find this restructuring to be progressively reduced for particles with increasing rhodium composition. We explain our observations by a carbon monoxide oxidation promoted non-classical Ostwald ripening process during which smaller particles are destabilized by the heat of reaction. Its driving force lies in the initial particle shape which features for platinum-rich particles a kinetically stabilized, low aspect ratio.

  8. Correlation between the Stereochemistry and Bioactivity in Octahedral Rhodium Prolinato Complexes.

    PubMed

    Rajaratnam, Rajathees; Martin, Elisabeth K; Dörr, Markus; Harms, Klaus; Casini, Angela; Meggers, Eric

    2015-08-17

    Controlling the relative and absolute configuration of octahedral metal complexes constitutes a key challenge that needs to be overcome in order to fully exploit the structural properties of octahedral metal complexes for applications in the fields of catalysis, materials sciences, and life sciences. Herein, we describe the application of a proline-based chiral tridentate ligand to decisively control the coordination mode of an octahedral rhodium(III) complex. We demonstrate the mirror-like relationship of synthesized enantiomers and differences between diastereomers. Further, we demonstrate, using the established pyridocarbazole pharmacophore ligand as part of the organometallic complexes, the importance of the relative and absolute stereochemistry at the metal toward chiral environments like protein kinases. Protein kinase profiling and inhibition data confirm that the proline-based enantiopure rhodium(III) complexes, despite having all of the same constitution, differ strongly in their selectivity properties despite their unmistakably mutual origin. Moreover, two exemplary compounds have been shown to induce different toxic effects in an ex vivo rat liver model.

  9. Immobilization of rhodium complexes in chiral organic-inorganic hybrid materials.

    PubMed

    Adima, A; Moreau, J J; Wong Chi Man, M

    2000-06-01

    Two new alkoxysilylated derivatives of (-)-(1R,2R)-1, 2-diaminocyclohexane: M = N-[(triethoxysilyl)propyl]-(-)-(1R,2R)-1, 2-diaminocyclohexane and B = N, N'-bis[(triethoxysilyl)propyl]-(-)-(1R,2R)-1,2-diaminocyclohexane have been synthesized. Their complexation with [Rh(cod)Cl]2 in the presence of TEOS = Si(OEt)4, followed by sol-gel hydrolysis-condensation, afforded new catalytic chiral hybrid materials. Evidence for the presence of the organic moieties complexed by rhodium in these solids was obtained by UV-visible spectroscopy, FT-IR studies, solid state 13C and 29Si CP-MAS NMR analysis, energy-dispersive X-ray (EDX) techniques, and elemental analysis. The nitrogen sorption studies and BET analyses ranged these solid gels from nonporous to highly porous materials. The catalytic activities and selectivities of the solid materials have been studied in the asymmetric hydrogen-transfer reduction of prochiral ketones and compared to that of the homogeneous rhodium complexes of the ligands M and B. The hybrid materials appeared interesting supports for enantioselective heterogeneous catalysis leading to chiral alcohols with ee up to 58% in the reduction of acetophenone and up to 98% in the case of the more hindered related ketones. The catalytic properties as a function of the nature of chiral hybrid solid are discussed.

  10. The Role of the Element Rhodium in the hyperbolic law of the Periodic Table of Elements

    NASA Astrophysics Data System (ADS)

    Khazan, Albert

    2009-03-01

    The method of equilateral hyperboles assumes that their tops should be certain with high accuracy by means of Lagrange's theorem. On this basis the scaling factor for transition from the coordinate system usual to mathematicians to that which is to be used in chemistry is calculated. Such an approach has allowed calculating parameters of the last element. The calculation can be checked by means of the first sequel from the hyperbolic law, proceeding only from the atomic mass of the element Rhodium. As it has appeared, the direct and adjacent hyperboles are crossed in a point with the coordinates 205.811; 0.5, which abscissa makes a half of the last element's atomic mass (the deviation is about 0.01%). The real axes of the hyperboles coincide with the tangents and normals, and the scaling factor differs from the first calculation as 0.001%. However these insignificant divergences are so small to the most important conclusion that the validity of the Hyperbolic Law, as calculation on Rhodium our data consists of (Progr. Physics, 2007, v.1, 38; v.2, 83; v.2, 104; 2008, v.3, 56).

  11. Tracking the shape-dependent sintering of platinum–rhodium model catalysts under operando conditions

    PubMed Central

    Hejral, Uta; Müller, Patrick; Balmes, Olivier; Pontoni, Diego; Stierle, Andreas

    2016-01-01

    Nanoparticle sintering during catalytic reactions is a major cause for catalyst deactivation. Understanding its atomic-scale processes and finding strategies to reduce it is of paramount scientific and economic interest. Here, we report on the composition-dependent three-dimensional restructuring of epitaxial platinum–rhodium alloy nanoparticles on alumina during carbon monoxide oxidation at 550 K and near-atmospheric pressures employing in situ high-energy grazing incidence x-ray diffraction, online mass spectrometry and a combinatorial sample design. For platinum-rich particles our results disclose a dramatic reaction-induced height increase, accompanied by a corresponding reduction of the total particle surface coverage. We find this restructuring to be progressively reduced for particles with increasing rhodium composition. We explain our observations by a carbon monoxide oxidation promoted non-classical Ostwald ripening process during which smaller particles are destabilized by the heat of reaction. Its driving force lies in the initial particle shape which features for platinum-rich particles a kinetically stabilized, low aspect ratio. PMID:26957204

  12. Tracking the shape-dependent sintering of platinum-rhodium model catalysts under operando conditions.

    PubMed

    Hejral, Uta; Müller, Patrick; Balmes, Olivier; Pontoni, Diego; Stierle, Andreas

    2016-03-09

    Nanoparticle sintering during catalytic reactions is a major cause for catalyst deactivation. Understanding its atomic-scale processes and finding strategies to reduce it is of paramount scientific and economic interest. Here, we report on the composition-dependent three-dimensional restructuring of epitaxial platinum-rhodium alloy nanoparticles on alumina during carbon monoxide oxidation at 550 K and near-atmospheric pressures employing in situ high-energy grazing incidence x-ray diffraction, online mass spectrometry and a combinatorial sample design. For platinum-rich particles our results disclose a dramatic reaction-induced height increase, accompanied by a corresponding reduction of the total particle surface coverage. We find this restructuring to be progressively reduced for particles with increasing rhodium composition. We explain our observations by a carbon monoxide oxidation promoted non-classical Ostwald ripening process during which smaller particles are destabilized by the heat of reaction. Its driving force lies in the initial particle shape which features for platinum-rich particles a kinetically stabilized, low aspect ratio.

  13. Bimetallic poly- and oligo-nuclear complexes based on a rhodium(III) metalloligand

    NASA Astrophysics Data System (ADS)

    Vasilchenko, Danila B.; Venediktov, Anatoliy B.; Korenev, Sergey V.; Filatov, Evgeniy Yu.; Baidina, Iraida A.; Nadolinnyi, Vladimir A.

    2012-10-01

    Interaction of trans-[Rh(i-Nic)4Cl2]3- anions (i-Nic- - isonicotinate anion) with Cuaq2+ and Coaq2+ cations in water has afforded complex salts Co3[Rh(i-Nic)4Cl2]2·17H2O (1) and Cu3[Rh(i-Nic)4Cl2]2·14H2O (2). Oligonuclear character of 1 and 2 has been established. A coordination polymer Cu5[Rh(i-Nic)4Cl2]2(i-Nic)2(OH)2·2H2O (3) has been crystallized by hydrothermal treatment of 2 at 160 °C, and its structure was determined by X-ray structural analysis. EPR data for the complexes has been collected and interpreted. Thermal decomposition of the salts was studied by c-DTA. Bimetallic alloys rhodium-copper and rhodium-cobalt have been obtained as final products of thermal decomposition.

  14. Reactions of Highly Uniform Zeolite H-Supported Rhodium Complexes: Transient Characterization by Infrared and X-ray Absorption Spectroscopies

    SciTech Connect

    Ogino, I.; Gates, B

    2010-01-01

    A zeolite H-{beta}-supported mononuclear rhodium diethene complex (Rh(C{sub 2}H{sub 4}){sub 2}{l_brace}O{sub 2}Al{r_brace}, where the braces indicate a part of the zeolite) was formed by the reaction of Rh(acac)({eta}{sub 2}-C{sub 2}H{sub 4}){sub 2} (acac = acetylacetonate, C{sub 5}H{sub 7}O{sub 2}{sup -}) with the zeolite. Transient characterization of the sample by X-ray absorption near edge structure (XANES) and infrared (IR) spectroscopies (combined with mass spectrometry of the effluent gas) while the sample was in contact with flowing CO indicates a simple stoichiometric conversion of the supported metal complex into another species, identified by the spectra as the zeolite-supported rhodium gem-dicarbonyl (Rh(CO){sub 2}{l_brace}O{sub 2}Al{r_brace}). The sharpness of the v{sub CO} bands in the IR spectrum indicates a high degree of uniformity of the supported rhodium gem-dicarbonyl, and isosbestic points in the XANES spectra as the transformation was occurring imply that the rhodium diethene complex was also highly uniform. Spectra similarly show that treatment of the supported rhodium gem-dicarbonyl with flowing C{sub 2}H{sub 4} resulted in another stoichiometrically simple transformation, giving a species suggested to be Rh(C{sub 2}H{sub 4})(CO){sub 2}{l_brace}O{sub 2}Al{r_brace}. The intermediate was ultimately transformed when the sample was purged with helium into another highly uniform supported species, inferred on the basis of IR spectra to be Rh(C{sub 2}H{sub 4})(CO){l_brace}O{sub 2}Al{r_brace}. Extended X-ray absorption fine structure spectra characterizing the supported rhodium diethene complex and the species formed from it show how the Rh-O bond distance at the Rh-support interface varied in response to the changes in the ligands bonded to the rhodium.

  15. Adsorptive separation of rhodium(III) using Fe(III)-templated oxine type of chemically modified chitosan

    SciTech Connect

    Alam, M.S.; Inoue, Katsutoshi; Yoshizuka, Kazuharu; Ishibashi, Hideaki

    1998-03-01

    The oxine type of chemically modified chitosan was prepared by the template crosslinking method using Fe(III) as a template ion. Batchwise adsorption of rhodium(III) on this chemically modified chitosan was examined from chloride media in the absence and presence of a large amount of tin(II). It was observed that the Fe(III)-templated oxine type of chemically modified chitosan shows better performance for rhodium adsorption than that of the original chitosan. When Sn(II) is absent from the solution, Rh(III) is hardly adsorbed on the modified chitosan and the order of selectivity of the adsorption of Rh(III), Pt(IV), and Cu(II) was found to be Pt(IV) > Cu(II) {approx} Rh(III). On the other hand, adsorption of rhodium is significantly increased in the presence of Sn(II) and the selectivity order of the adsorption was drastically changed to Rh(III) > Pt(IV) {much_gt} Cu(II), which ensures selective separation of Rh(III) from their mixture. Adsorption of Rh(III) increases with an increase in the concentration of Sn(II) in the aqueous solution, and maximum adsorption is achieved at a molar ratio, [Sn]/[Rh], of >6. The adsorption of Rh(III) decreases at a high concentration of hydrochloric acid. The maximum adsorption capacity was evaluated to be 0.92 mol/kg-dry adsorbent. Stripping tests of rhodium from the loaded chemically modified chitosan were carried out using different kinds of stripping agents containing some oxidizing agent. The maximum stripping of rhodium under these experimental conditions was found to be 72.5% by a single contact with 0.5 M HCl + 8 M HNO{sub 3}.

  16. MERCURY-NITRITE-RHODIUM-RUTHENIUM INTERACTIONS IN NOBLE METAL CATALYZED HYDROGEN GENERATION FROM FORMIC ACID DURING NUCLEAR WASTE PROCESSING AT THE SAVANNAH RIVER SITE - 136C

    SciTech Connect

    Koopman, D.; Pickenheim, B.; Lambert, D.; Newell, J; Stone, M.

    2009-09-02

    Chemical pre-treatment of radioactive waste at the Savannah River Site is performed to prepare the waste for vitrification into a stable waste glass form. During pre-treatment, compounds in the waste become catalytically active. Mercury, rhodium, and palladium become active for nitrite destruction by formic acid, while rhodium and ruthenium become active for catalytic conversion of formic acid into hydrogen and carbon dioxide. Nitrite ion is present during the maximum activity of rhodium, but is consumed prior to the activation of ruthenium. Catalytic hydrogen generation during pre-treatment can exceed radiolytic hydrogen generation by several orders of magnitude. Palladium and mercury impact the maximum catalytic hydrogen generation rates of rhodium and ruthenium by altering the kinetics of nitrite ion decomposition. New data are presented that illustrate the interactions of these various species.

  17. Synergistic rhodium(II) carboxylate and brønsted acid catalyzed multicomponent reactions of enalcarbenoids: direct synthesis of α-pyrrolylbenzylamines.

    PubMed

    Dawande, Sudam Ganpat; Kanchupalli, Vinaykumar; Lad, Bapurao Sudam; Rai, Jyoti; Katukojvala, Sreenivas

    2014-07-18

    The design of a synergistic rhodium(II) carboxylate and BINOL phosphoric acid catalyzed efficient multicomponent reaction of enaldiazo compounds, arylamines, and aryl aldehydes leading to the first transition-metal-catalyzed direct synthesis of valuable α-pyrrolylbenzylamines is disclosed. The reaction is proposed to involve a transient ammonium ylide of a new class of electrophilic rhodium enalcarbenoid, its regioselective Mannich reaction, and a cyclocondensation cascade. The methodology was used in a highly diastereoselective synthesis of a binaphthyl based chiral pyrrole.

  18. 16 CFR 23.7 - Misuse of the words “platinum,” “iridium,” “palladium,” “ruthenium,” “rhodium,” and “osmium.”

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... § 23.7 Misuse of the words “platinum,” “iridium,” “palladium,” “ruthenium,” “rhodium,” and “osmium.” (a) It is unfair or deceptive to use the words “platinum,” “iridium,” “palladium,” “ruthenium,” “rhodium... Platinum, Iridium, Palladium, Ruthenium, Rhodium, and Osmium. (b) The following are examples of markings or...

  19. 16 CFR 23.7 - Misuse of the words “platinum,” “iridium,” “palladium,” “ruthenium,” “rhodium,” and “osmium.”

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... § 23.7 Misuse of the words “platinum,” “iridium,” “palladium,” “ruthenium,” “rhodium,” and “osmium.” (a) It is unfair or deceptive to use the words “platinum,” “iridium,” “palladium,” “ruthenium,” “rhodium... Platinum, Iridium, Palladium, Ruthenium, Rhodium, and Osmium. (b) The following are examples of markings or...

  20. 16 CFR 23.7 - Misuse of the words “platinum,” “iridium,” “palladium,” “ruthenium,” “rhodium,” and “osmium.”

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... § 23.7 Misuse of the words “platinum,” “iridium,” “palladium,” “ruthenium,” “rhodium,” and “osmium.” (a) It is unfair or deceptive to use the words “platinum,” “iridium,” “palladium,” “ruthenium,” “rhodium... Platinum, Iridium, Palladium, Ruthenium, Rhodium, and Osmium. (b) The following are examples of markings or...

  1. 16 CFR 23.7 - Misuse of the words “platinum,” “iridium,” “palladium,” “ruthenium,” “rhodium,” and “osmium.”

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... § 23.7 Misuse of the words “platinum,” “iridium,” “palladium,” “ruthenium,” “rhodium,” and “osmium.” (a) It is unfair or deceptive to use the words “platinum,” “iridium,” “palladium,” “ruthenium,” “rhodium... Platinum, Iridium, Palladium, Ruthenium, Rhodium, and Osmium. (b) The following are examples of markings...

  2. 16 CFR 23.7 - Misuse of the words “platinum,” “iridium,” “palladium,” “ruthenium,” “rhodium,” and “osmium.”

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... § 23.7 Misuse of the words “platinum,” “iridium,” “palladium,” “ruthenium,” “rhodium,” and “osmium.” (a) It is unfair or deceptive to use the words “platinum,” “iridium,” “palladium,” “ruthenium,” “rhodium... Platinum, Iridium, Palladium, Ruthenium, Rhodium, and Osmium. (b) The following are examples of markings...

  3. Heck-type coupling vs. conjugate addition in phosphine-rhodium catalyzed reactions of aryl boronic acids with alpha,beta-unsaturated carbonyl compounds: a systematic investigation.

    PubMed

    Zou, Gang; Guo, Jianping; Wang, Zhiyong; Huang, Wen; Tang, Jie

    2007-07-28

    The competition between Heck-type coupling and conjugate addition in phosphine-rhodium catalyzed reactions of aryl boronic acids with alpha,beta-unsaturated carbonyls has been systematically investigated in a toluene-H(2)O biphasic system. Aside from the intrinsic nature of rhodium and the enolization of carbonyls, the phosphine supporting ligand on rhodium, the ratio of aryl boronic acid to alpha,beta-unsaturated carbonyl and the pH value of the aqueous phase were found to affect the competition significantly. Highly selective rhodium-based catalyst systems have therefore been developed for both Heck-type coupling and conjugate addition by synergistically tuning the supporting ligand, the boronic acid to olefin ratio and other reaction conditions. Conjugate addition with selectivity >99% and Heck-type coupling with selectivity of up to 100%, 98% and 84% for acrylates, acrylamides and methyl vinyl ketone, respectively, could be achieved in the rhodium-catalyzed reactions of aryl boronic acids with alpha,beta-unsaturated carbonyls using the corresponding optimized rhodium-based catalyst systems.

  4. Inference in `poor` languages

    SciTech Connect

    Petrov, S.

    1996-10-01

    Languages with a solvable implication problem but without complete and consistent systems of inference rules (`poor` languages) are considered. The problem of existence of finite complete and consistent inference rule system for a ``poor`` language is stated independently of the language or rules syntax. Several properties of the problem arc proved. An application of results to the language of join dependencies is given.

  5. Rich Donors, Poor Countries

    ERIC Educational Resources Information Center

    Thomas, M. A.

    2012-01-01

    The shifting ideological winds of foreign aid donors have driven their policy towards governments in poor countries. Donors supported state-led development policies in poor countries from the 1940s to the 1970s; market and private-sector driven reforms during the 1980s and 1990s; and returned their attention to the state with an emphasis on…

  6. Catalytic partial oxidation of iso-octane over rhodium catalysts: An experimental, modeling, and simulation study

    SciTech Connect

    Hartmann, M.; Minh, H.D.; Maier, L.; Deutschmann, O.

    2010-09-15

    Catalytic partial oxidation of iso-octane over a rhodium/alumina coated honeycomb monolith is experimentally and numerically studied at short-contact times for varying fuel-to-oxygen ratios. A new experimental set-up with well-defined inlet and boundary conditions is presented. The conversion on the catalyst and in the gas-phase is modeled by detailed reaction mechanisms including 857 gas-phase and 17 adsorbed species. Elementary-step based heterogeneous and homogeneous reaction mechanisms are implemented into two-dimensional flow field description of a single monolith channel. Experiment and simulation provide new insights into the complex reaction network leading to varying product distribution as function of fuel-to-oxygen ratio. At fuel rich conditions, the formation of by-products that can serve as coke precursors is observed and interpreted. (author)

  7. Synthesis of Carbazoles and Carbazole-Containing Heterocycles via Rhodium-Catalyzed Tandem Carbonylative Benzannulations.

    PubMed

    Song, Wangze; Li, Xiaoxun; Yang, Ka; Zhao, Xian-liang; Glazier, Daniel A; Xi, Bao-min; Tang, Weiping

    2016-04-01

    Polycyclic aromatic compounds are important constituents of pharmaceuticals and other materials. We have developed a series of Rh-catalyzed tandem carbonylative benzannulations for the synthesis of tri-, tetra-, and pentacyclic heterocycles from different types of aryl propargylic alcohols. These tandem reactions provide efficient access to highly substituted carbazoles, furocarbazoles, pyrrolocarbazoles, thiophenocarbazoles, and indolocarbazoles. While tricyclic heterocycles could be derived from vinyl aryl propargylic alcohols, tetra- and pentacyclic heterocycles were synthesized from diaryl propargylic alcohols. The tandem carbonylative benzannulation is initiated by a π-acidic rhodium(I) catalyst-mediated nucleophilic addition to alkyne to generate a key metal-carbene intermediate, which is then trapped by carbon monoxide to form a ketene species for 6π electrocyclization. Overall, three bonds and two rings are formed in all of these tandem carbonylative benzannulation reactions.

  8. Synthesis, characterization and antibacterial study of cyclometalated rhodium(III) complex containing dithiocarbamate

    NASA Astrophysics Data System (ADS)

    Mansouri, Ghobad; Heidarizadi, Fateme; Naghipour, Ali; Notash, Behrouz

    2016-10-01

    The novel cyclometalated Rh(III) complex, [Rh(phpy)2(SˆS)], Where phpy is 2-phenylpyridine and (SˆS) is diethyldithiocarbamate, has been prepared and characterized by elemental analysis, IR, 13C and 1H NMR, electronic absorption and Fluorescence spectroscopies, cyclic voltammetry, and X-ray crystallography. The crystal structure of [Rh(phpy)2(SˆS)] shows that the coordination geometry around the Rh(III) is a distorted octahedron, with bite angles of 71.19-81.04° for all three bidentate ligands. Electrochemical analysis by cyclic voltammetry reveals irreversible redox behavior of the rhodium centre. Antibacterial activity of the complex has also been studied by agar disc diffusion method against three Gram-negative bacteria (Pseudomonas aeroginosa, Salmonella typhi and Escherichia coli) and two Gram-positive bacteria (Staphylococcus aureus and Corynebacterium renale).

  9. Determination of palladium, platinum and rhodium in geologic materials by fire assay and emission spectrography

    USGS Publications Warehouse

    Hapfty, J.; Riley, L.B.

    1968-01-01

    A method is described for the determination of palladium down to 4ppb (parts per billion, 109), platinum down to 10 ppb and rhodium down to 5 ppb in 15 g of sample. Fire-assay techniques are used to preconcentrate the platinum metals into a gold bead, then the bead is dissolved in aqua regia and diluted to volume with 1M hydrochloric acid. The solution is analysed by optical emission spectrography of the residue from 200 ??l of it evaporated on a pair of flat-top graphite electrodes. This method requires much less sample handling than most published methods for these elements. Data are presented for G-1, W-1, and six new standard rocks of the U.S. Geological Survey. The values for palladium in W-1 are in reasonable agreement with previously published data. ?? 1968.

  10. Optimization of Rhodium-Based Catalysts for Mixed Alcohol Synthesis – 2012 Progress Report

    SciTech Connect

    Gerber, Mark A.; Gray, Michel J.; Albrecht, Karl O.; Thompson, Becky L.

    2012-11-01

    Pacific Northwest National Laboratory has been conducting research to investigate the feasibility of producing mixed alcohols from biomass-derived synthesis gas (syngas). In recent years, this research has primarily involved the further development of catalysts containing rhodium and manganese based on the results of earlier catalyst screening tests. Testing continued in FY 2012 to further improve the Ir-promoted RhMn catalysts on both silica and carbon supports for producing mixed oxygenates from synthesis gas. This testing re-examined selected alternative silica and carbon supports to follow up on some uncertainties in the results with previous test results. Additional tests were conducted to further optimize the total and relative concentrations of Rh, Mn, and Ir, and to examine selected promoters and promoter combinations based on earlier results. To establish optimum operating conditions, the effects of the process pressure and the feed gas composition also were evaluated.

  11. Optimization of Rhodium-Based Catalysts for Mixed Alcohol Synthesis -- 2011 Progress Report

    SciTech Connect

    Gerber, Mark A.; Gray, Michel J.; Albrecht, Karl O.; Rummel, Becky L.

    2011-10-01

    Pacific Northwest National Laboratory has been conducting research to investigate the feasibility of producing mixed alcohols from biomass-derived synthesis gas (syngas). In recent years, this research has primarily involved the further development of catalysts containing rhodium and manganese based on the results of earlier catalyst screening tests. Research during FY 2011 continued to examine the performance of RhMn catalysts on alternative supports including selected zeolite, silica, and carbon supports. Catalyst optimization continued using both the Davisil 645 and Merck Grade 7734 silica supports. Research also was initiated in FY 2011, using the both Davisil 645 silica and Hyperion CS-02C-063 carbon supports, to evaluate the potential for further improving catalyst performance, through the addition of one or two additional metals as promoters to the catalysts containing Rh, Mn, and Ir.

  12. Optimization of Rhodium-Based Catalysts for Mixed Alcohol Synthesis -- 2009 Progress Report

    SciTech Connect

    Gerber, Mark A.; Gray, Michel J.; Stevens, Don J.; White, J. F.; Rummel, Becky L.

    2010-12-21

    Pacific Northwest National Laboratory (PNNL) has been conducting research for the United States Department of Energy, Energy Efficiency Renewable Energy, Biomass Program to investigate the feasibility of producing mixed alcohols from biomass-derived synthesis gas (syngas). This research has involved the screening of potential catalysts, and optimization of the more promising ones, using laboratory scale reactors. During 2009, the main goal of the testing program focused on optimizing selected supported catalysts containing rhodium (Rh) and manganese (Mn). Optimization involved examining different total concentrations and atomic ratios of Rh and Mn as well as that of the more promising promoters (Ir and Li) identified in the earlier screening studies. Evaluation of catalyst performance focused on attaining improvements with respect to the space-time-yield and converted carbon selectivity to C2+ oxygenates, with additional consideration given to the fraction of the oxygenates that were C2+ alcohols.

  13. Scanning tunneling microscopy studies of organic monolayers adsorbed on the rhodium(111) crystal surface

    SciTech Connect

    Cernota, Paul Davis

    1999-08-01

    Scanning Tunneling Microscopy studies were carried out on ordered overlayers on the (111) surface of rhodium. These adsorbates include carbon monoxide (CO), cyclohexane, cyclohexene, 1,4-cyclohexadiene, para-xylene, and meta-xylene. Coadsorbate systems included: CO with ethylidyne, CO with para- and meta-xylene, and para-xylene with meta-xylene. In the case of CO, the structure of the low coverage (2x2) overlayer has been observed. The symmetry of the unit cell in this layer suggests that the CO is adsorbed in the 3-fold hollow sites. There were also two higher coverage surface structures with (√7x√7) unit cells. One of these is composed of trimers of CO and has three CO molecules in each unit cell. The other structure has an additional CO molecule, making a total of four. This extra CO sits on a top site.

  14. Bifunctional rhodium intercalator conjugates as mismatch-directing DNA alkylating agents.

    PubMed

    Schatzschneider, Ulrich; Barton, Jacqueline K

    2004-07-21

    A conjugate of a DNA mismatch-specific rhodium intercalator, containing the bulky chrysenediimine ligand, and an aniline mustard has been prepared, and targeting of mismatches in DNA by this conjugate has been examined. The preferential alkylation of mismatched over fully matched DNA is found by a mobility shift assay at concentrations where untethered organic mustards show little reaction. The binding site of the Rh intercalator was determined by DNA photocleavage, and the position of covalent modification was established on the basis of the enhanced depurination associated with N-alkylation. The site-selective alkylation at mismatched DNA renders these conjugates useful tools for the covalent tagging of DNA base pair mismatches and new chemotherapeutic design.

  15. Hydrogenation of aniline on a low-percentage, supported rhodium catalyst

    SciTech Connect

    Ualikhanova, A.; Temirbulatova, A.E.

    1992-01-10

    The products of hydrogenation of aniline and their derivatives exhibit biological activity and are used in the pharmaceutical industry for preparation of analgesic, antipyretic, and sulfanilamide drugs. Up to 30% of the total consumption of aniline is for synthesis of drugs. Hydrogenation of aniline on platinum metals supported on carbon was studied by Rylander et al. The authors investigated the catalytic properties of rhodium supported on oxides in saturation of aniline with hydrogen in water. In most cases, the amount of noble metal in the supported catalyst was 5%. Decreasing the concentration of active phase in the catalyst is economically advantageous. The features of hydrogenation of aniline in the presence of 1% Rh/MgO in solutions with wide variation of the technological parameters of the process were investigated in the present study. 19 refs., 3 figs., 2 tabs.

  16. Production of Palladium-103 ( 103Pd) from a thin rhodium foil target - Improved cooling concept

    NASA Astrophysics Data System (ADS)

    Silverman, I.; Lavie, E.; Arenshtam, A.; Kijel, D.; Vaknin, D.; Veinguer, M.; Nagler, A.

    2007-08-01

    Palladium-103 (103Pd) is one of the commonly used radioisotopes for prostate cancer treatment. The current irradiation technique used to produce this radioisotope suffers from several serious inherent drawbacks, of which one is the low beam current due to cooling limitation and the other is the electroplating process used to prepare the target. A liquid-metal jet impingement target cooling system developed at Soreq NRC demonstrated recently a cooling capacity of 8.4 kW/cm2 while the pressure of the cooling liquid on the target back was less than 1 bar. The latter value implies that the target can be made very thin and that the copper back-plate might be removed. Hence, we propose a new target design based on the use of a thin rhodium foil directly cooled by a liquid-metal such as gallium.

  17. Screen-Printed Carbon Electrodes Modified by Rhodium Dioxide and Glucose Dehydrogenase

    PubMed Central

    Polan, Vojtěch; Soukup, Jan; Vytřas, Karel

    2010-01-01

    The described glucose biosensor is based on a screen-printed carbon electrode (SPCE) modified by rhodium dioxide, which functions as a mediator. The electrode is further modified by the enzyme glucose dehydrogenase, which is immobilized on the electrode's surface through electropolymerization with m-phenylenediamine. The enzyme biosensor was optimized and tested in model glucose samples. The biosensor showed a linear range of 500–5000 mg L−1 of glucose with a detection limit of 210 mg L−1 (established as 3σ) and response time of 39 s. When compared with similar glucose biosensors based on glucose oxidase, the main advantage is that neither ascorbic and uric acids nor paracetamol interfere measurements with this biosensor at selected potentials. PMID:21528113

  18. Rhodium-catalyzed acyloxy migration of propargylic esters in cycloadditions, inspiration from the recent "gold rush".

    PubMed

    Shu, Xing-Zhong; Shu, Dongxu; Schienebeck, Casi M; Tang, Weiping

    2012-12-07

    Transition metal-catalyzed acyloxy migration of propargylic esters offers versatile entries to allene and vinyl carbene intermediates for various fascinating subsequent transformations. Most π-acidic metals (e.g. gold and platinum) are capable of facilitating these acyloxy migration events. However, very few of these processes involve redox chemistry, which are well-known for most other transition metals such as rhodium. The coupling of acyloxy migration of propargylic esters with oxidative addition, migratory insertion, and reductive elimination may lead to ample new opportunities for the design of new reactions. This tutorial review summarizes recent developments in Rh-catalyzed 1,3- and 1,2-acyloxy migration of propargylic esters in a number of cycloaddition reactions. Related Au- and Pt-catalyzed cycloadditions involving acyloxy migration are also discussed.

  19. Dimerisation, rhodium complex formation and rearrangements of N-heterocyclic carbenes of indazoles

    PubMed Central

    Guan, Zong; Namyslo, Jan C; Drafz, Martin H H; Nieger, Martin

    2014-01-01

    Summary Deprotonation of indazolium salts at low temperatures gives N-heterocyclic carbenes of indazoles (indazol-3-ylidenes) which can be trapped as rhodium complexes (X-ray analysis). In the absence of Rh, the indazol-3-ylidenes spontaneously dimerize under ring cleavage of one of the N,N-bonds and ring closure to an indazole–indole spiro compound which possesses an exocyclic imine group. The E/Z isomers of the imines can be separated by column chromatography when methanol is used as eluent. We present results of a single crystal X-ray analysis of one of the E-isomers, which equilibrate in solution as well as in the solid state. Heating of the indazole–indole spiro compounds results in the formation of quinazolines by a ring-cleavage/ring-closure sequence (X-ray analysis). Results of DFT calculations are presented. PMID:24778738

  20. Iminophosphanes: Synthesis, Rhodium Complexes, and Ruthenium(II)-Catalyzed Hydration of Nitriles

    PubMed Central

    2017-01-01

    Highly stable iminophosphanes, obtained from alkylating nitriles and reaction of the resulting nitrilium ions with secondary phosphanes, were explored as tunable P-monodentate and 1,3-P,N bidentate ligands in rhodium complexes. X-ray crystal structures are reported for both κ1 and κ2 complexes with the counterion in one of them being an unusual anionic coordination polymer of silver triflate. The iminophosphane-based ruthenium(II)-catalyzed hydration of benzonitrile in 1,2-dimethoxyethane (180 °C, 3 h) and water (100 °C, 24 h) and under solvent free conditions (180 °C, 3 h) results in all cases in the selective formation of benzamide with yields of up to 96%, thereby outperforming by far the reactions in which the common 2-pyridyldiphenylphosphane is used as the 1,3-P,N ligand. PMID:28316361

  1. Optimization of Rhodium-Based Catalysts for Mixed Alcohol Synthesis -- 2010 Progress Report

    SciTech Connect

    Gerber, Mark A.; Gray, Michel J.; Albrecht, Karl O.; White, J. F.; Rummel, Becky L.; Stevens, Don J.

    2010-10-01

    Pacific Northwest National Laboratory has been conducting research for the U.S. Department of Energy, Energy Efficiency Renewable Energy, Biomass Program to investigate the feasibility of producing mixed alcohols from biomass-derived synthesis gas. In recent years this research has primarily involved the further development of a silica-supported catalyst containing rhodium and manganese that was selected from earlier catalyst screening tests. A major effort during 2010 was to examine alternative catalyst supports to determine whether other supports, besides the Davisil 645 silica, would improve performance. Optimization of the Davisil 645 silica-supported catalyst also was continued with respect to candidate promoters iridium, platinum, and gallium, and examination of selected catalyst preparation and activation alternatives for the baseline RhMn/SiO2 catalyst.

  2. Gravimetric preparation and characterization of primary reference solutions of molybdenum and rhodium.

    PubMed

    Kaltenbach, Angela; Noordmann, Janine; Görlitz, Volker; Pape, Carola; Richter, Silke; Kipphardt, Heinrich; Kopp, Gernot; Jährling, Reinhard; Rienitz, Olaf; Güttler, Bernd

    2015-04-01

    Gravimetrically prepared mono-elemental reference solutions having a well-known mass fraction of approximately 1 g/kg (or a mass concentration of 1 g/L) define the very basis of virtually all measurements in inorganic analysis. Serving as the starting materials of all standard/calibration solutions, they link virtually all measurements of inorganic analytes (regardless of the method applied) to the purity of the solid materials (high-purity metals or salts) they were prepared from. In case these solid materials are characterized comprehensively with respect to their purity, this link also establishes direct metrological traceability to The International System of Units (SI). This, in turn, ensures the comparability of all results on the highest level achievable. Several national metrology institutes (NMIs) and designated institutes (DIs) have been working for nearly two decades in close cooperation with commercial producers on making an increasing number of traceable reference solutions available. Besides the comprehensive characterization of the solid starting materials, dissolving them both loss-free and completely under strict gravimetric control is a challenging problem in the case of several elements like molybdenum and rhodium. Within the framework of the European Metrology Research Programme (EMRP), in the Joint Research Project (JRP) called SIB09 Primary standards for challenging elements, reference solutions of molybdenum and rhodium were prepared directly from the respective metals with a relative expanded uncertainty associated with the mass fraction of U rel(w) < 0.05 %. To achieve this, a microwave-assisted digestion procedure for Rh and a hotplate digestion procedure for Mo were developed along with highly accurate and precise inductively coupled plasma optical emission spectrometry (ICP OES) and multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS) methods required to assist with the preparation and as dissemination tools.

  3. Role of Ligand Protonation in Dihydrogen Evolution from a Pentamethylcyclopentadienyl Rhodium Catalyst.

    PubMed

    Johnson, Samantha I; Gray, Harry B; Blakemore, James D; Goddard, William A

    2017-09-01

    Recent work has shown that Cp*Rh(bpy) [Cp* = pentamethylcyclopentadienyl, bpy = 2,2'- bipyridine] undergoes endo protonation at the [Cp*] ligand in the presence of weak acid (Et3NH(+); pKa = 18.8 in MeCN). Upon exposure to stronger acid (e.g., DMFH(+); pKa = 6.1), hydrogen is evolved with unity yield. Here, we study the mechanisms by which this catalyst evolves dihydrogen using density functional theory (M06) with polarizable continuum solvation. The calculations show that the complex can be protonated by weak acid first at the metal center with a barrier of 3.2 kcal/mol; this proton then migrates to the ring to form the detected intermediate, a rhodium(I) compound bearing endo η(4)-Cp*H. Stronger acid is required to evolve hydrogen, which calculations show happens via a concerted mechanism. The acid approaches and protonates the metal, while the second proton simultaneously migrates from the ring with a barrier of ∼12 kcal/mol. Under strongly acidic conditions, we find that hydrogen evolution can proceed through a traditional metal-hydride species; protonation of the initial hydride to form an H-H bond occurs before migration of the hydride (in the form of a proton) to the [Cp*] ring (i.e., H-H bond formation is faster than hydride-proton tautomerization). This work demonstrates the role of acid strength in accessing different mechanisms of hydrogen evolution. Calculations also predict that modification of the bpy ligand by a variety of functional groups does not affect the preference for [Cp*] protonation, although the driving force for protonation changes. However, we predict that exchange of bpy for a bidentate phosphine ligand will stabilize a rhodium(III) hydride, reversing the preference for bound [Cp*H] found in all computed bpy derivatives and offering an appealing alternative ligand platform for future experimental and computational mechanistic studies of H2 evolution.

  4. Rhodium-catalyzed oxygenative [2 + 2] cycloaddition of terminal alkynes and imines for the synthesis of β-lactams.

    PubMed

    Kim, Insu; Roh, Sang Weon; Lee, Dong Gil; Lee, Chulbom

    2014-05-02

    A rhodium-catalyzed oxygenative [2 + 2] cycloaddition of terminal alkynes and imines has been developed, which gives β-lactams as products with high trans diastereoselectivity. In the presence of a Rh(I) catalyst and 4-picoline N-oxide, a terminal alkyne is converted to a rhodium ketene species via oxidation of a vinylidene complex and subsequently undergoes a [2 + 2] cycloaddition with an imine to give rise to the 2-azetidinone ring system. Mechanistic studies suggest that the reaction proceeds through a metalloketene rather than free ketene intermediate. The new method taking advantage of catalytic generation of a ketene species directly from a terminal alkyne provides a novel and efficient entry to the Staudinger synthesis of β-lactams under mild conditions.

  5. Dicarba-closo-dodecarborane-containing half-sandwich complexes of ruthenium, osmium, rhodium and iridium: biological relevance and synthetic strategies.

    PubMed

    Barry, Nicolas P E; Sadler, Peter J

    2012-04-21

    This review describes how the incorporation of dicarba-closo-dodecarboranes into half-sandwich complexes of ruthenium, osmium, rhodium and iridium might lead to the development of a new class of compounds with applications in medicine. Such a combination not only has unexplored potential in traditional areas such as Boron Neutron Capture Therapy agents, but also as pharmacophores for the targeting of biologically important proteins and the development of targeted drugs. The synthetic pathways used for the syntheses of dicarba-closo-dodecarboranes-containing half-sandwich complexes of ruthenium, osmium, rhodium and iridium are also reviewed. Complexes with a wide variety of geometries and characteristics can be prepared. Examples of addition reactions on the metal centre, B-H activation, transmetalation reactions and/or direct formation of metal-metal bonds are discussed (103 references).

  6. Photoinduced cleavage by a rhodium complex at G.U mismatches and exposed guanines in large and small RNAs.

    PubMed

    Chow, Christine S; Cunningham, Philip R; Lee, KangSeok; Meroueh, May; SantaLucia, John; Varma, Shikha

    2002-09-01

    Photoinduced cleavage reactions by the rhodium complex tris(4,7-diphenyl-1,10-phenanthroline)rhodium(III) [Rh(DIP)(3)(3+)] with three RNA hairpins, r(GGGGU UCGCUC CACCA) (16 nucleotide, tetraloop(Ala2)), r(GGGGCUAUAGCUCUAGCUC CACCA) (24 nucleotide, microhelix(Ala)), and r(GGCGGUUAGAUAUCGCC) (17 nucleotide, 790 loop), and full-length (1542 nucleotide) 16S rRNA from Escherichia coli were investigated. The cleavage reactions were monitored by gel electrophoresis and the sites of cleavage by Rh(DIP)(3)(3+) were determined by comparisons with chemical or enzymatic sequencing reactions. In general, RNA backbone scission by the metal complex was induced at G.U mismatches and at exposed G residues. The cleavage activity was observed on the three small RNA hairpins as well as on the isolated 1542-nucleotide ribosomal RNA.

  7. A study on composition, structure and optical properties of copper-poor CIGS thin film deposited by sequential sputtering of CuGa/In and In/(CuGa+In) precursors

    NASA Astrophysics Data System (ADS)

    Park, Seong-Un; Sharma, Rahul; Ashok, K.; Kang, San; Sim, Jae-Kwan; Lee, Cheul-Ro

    2012-11-01

    Copper-poor CIGS thin films were fabricated by using two precursor of CuGa/In and In/(CuGa+In) onto the Mo coated soda-lime glass (SLG) by the sequential sputtering of CuGa and In targets. The CIG precursors were converted into CIGS absorption thin film by selenization process. The X-ray diffraction (XRD) patterns of CIGS absorber from CuGa/In precursor exhibits strong (112) preferred orientation that is more stable than (220)/(204) as compared to In/(CuGa+In) precursor. The elemental composition uniformity onto the surface and along depth were extensively analyzed with energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectroscopy (SIMS). For as-fabricated CIGS thin films from In/(CuGa+In) and CuGa/In precursors, the atomic (at%) composition values of [Cu]//[In+Ga]/=1.14, 1.08 and [Ga]/[In+Ga]=0.33, 0.20 were observed, respectively that is well matched for highest efficient CIGS-based solar cell so far. SIMS confirmed that the Ga profile is not through the depth of CIGS thin film attributed a consistent band gap of 1.04 and 1.08 eV. Further, PL spectrum of CIGS absorber formed by CuGa/In precursor exhibits relatively narrow emission peak as compared to In/(CuGa+In) precursor. It is attributed to decrease defect density with uniform composition in the CIGS absorber. The carrier concentration (Np) found to increase from 1020 to 1021 cm-3 orders with the increase of Cu/(In+Ga) at.% from 0.93 to 1.02, which is related to the increasing carrier concentration for stoichiometric CIGS films.

  8. Sequential rhodium/palladium catalysis: enantioselective formation of dihydroquinolinones in the presence of achiral and chiral ligands.

    PubMed

    Zhang, Lei; Qureshi, Zafar; Sonaglia, Lorenzo; Lautens, Mark

    2014-12-08

    Compatible combinations of achiral and chiral ligands can be used in rhodium/palladium catalysis to achieve highly enantioselective domino reactions. The difference in rates of catalysis and minimal effects of ligand interference confer control in the domino sequence. The "all-in-one" 1,4-conjugate arylation and C-N cross-coupling through sequential Rh/Pd catalysis provides access to enantioenriched dihydroquinolinone building blocks. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Rhodium-catalyzed Asymmetric Hydrogenation of α-Dehydroamino Ketones: A General Approach to Chiral α-amino Ketones.

    PubMed

    Gao, Wenchao; Wang, Qingli; Xie, Yun; Lv, Hui; Zhang, Xumu

    2016-01-01

    Rhodium/DuanPhos-catalyzed asymmetric hydrogenation of aliphatic α-dehydroamino ketones has been achieved and afforded chiral α-amino ketones in high yields and excellent enantioselectives (up to 99 % ee), which could be reduced further to chiral β-amino alcohols by LiAlH(tBuO)3 with good yields. This protocol provides a readily accessible route for the synthesis of chiral α-amino ketones and chiral β-amino alcohols.

  10. Rhodium-catalyzed [(3+2)+1] carbocyclization reactions of alkynylidenecyclopropanes with carbon monoxide: regiospecific construction of polysubstituted phenols.

    PubMed

    Evans, P Andrew; Burnie, Andrew J; Negru, Daniela E

    2014-09-05

    The development of the rhodium-catalyzed [(3+2)+1] carbocyclization reaction of alkynylidenecyclopropanes with carbon monoxide to construct polysubstituted phenols is described. This work offers a convenient method for the selective formation of tetra- and pentasubstituted phenols, which provide important intermediates for target directed synthesis. Finally, the ability to regiospecifically functionalize the phenols using conventional methods further illustrates the utility of this process.

  11. Photocatalytic carbon dioxide reduction with rhodium-based catalysts in solution and heterogenized within metal-organic frameworks.

    PubMed

    Chambers, Matthew B; Wang, Xia; Elgrishi, Noémie; Hendon, Christopher H; Walsh, Aron; Bonnefoy, Jonathan; Canivet, Jérôme; Quadrelli, Elsje Alessandra; Farrusseng, David; Mellot-Draznieks, Caroline; Fontecave, Marc

    2015-02-01

    The first photosensitization of a rhodium-based catalytic system for CO2 reduction is reported, with formate as the sole carbon-containing product. Formate has wide industrial applications and is seen as valuable within fuel cell technologies as well as an interesting H2 -storage compound. Heterogenization of molecular rhodium catalysts is accomplished via the synthesis, post-synthetic linker exchange, and characterization of a new metal-organic framework (MOF) Cp*Rh@UiO-67. While the catalytic activities of the homogeneous and heterogeneous systems are found to be comparable, the MOF-based system is more stable and selective. Furthermore it can be recycled without loss of activity. For formate production, an optimal catalyst loading of ∼10 % molar Rh incorporation is determined. Increased incorporation of rhodium catalyst favors thermal decomposition of formate into H2 . There is no precedent for a MOF catalyzing the latter reaction so far. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Catalytic wet oxidation of ammonia solution: activity of the nanoscale platinum-palladium-rhodium composite oxide catalyst.

    PubMed

    Hung, Chang-Mao

    2009-04-15

    Aqueous solutions of 400-1000 mg/L of ammonia were oxidized in a trickle-bed reactor (TBR) in this study of nanoscale platinum-palladium-rhodium composite oxide catalysts, which were prepared by the co-precipitation of H(2)PtCl(6), Pd(NO(3))(3) and Rh(NO(3))(3). Hardly any of the dissolved ammonia was removed by wet oxidation in the absence of any catalyst, whereas about 99% of the ammonia was reduced during wet oxidation over nanoscale platinum-palladium-rhodium composite oxide catalysts at 503 K in an oxygen partial pressure of 2.0 MPa. A synergistic effect exists in the nanoscale platinum-palladium-rhodium composite structure, which is the material with the highest ammonia reduction activity. The nanometer-sized particles were characterized by TEM, XRD and FTIR. The effect of the initial concentration and reaction temperature on the removal of ammonia from the effluent streams was also studied at a liquid hourly space velocity of under 9 h(-1) in the wet catalytic processes.

  13. Poor school performance.

    PubMed

    Karande, Sunil; Kulkarni, Madhuri

    2005-11-01

    Education is one of the most important aspects of human resource development. Poor school performance not only results in the child having a low self-esteem, but also causes significant stress to the parents. There are many reasons for children to under perform at school, such as, medical problems, below average intelligence, specific learning disability, attention deficit hyperactivity disorder, emotional problems, poor socio-cultural home environment, psychiatric disorders and even environmental causes. The information provided by the parents, classroom teacher and school counselor about the child's academic difficulties guides the pediatrician to form an initial diagnosis. However, a multidisciplinary evaluation by an ophthalmologist, otolaryngologist, counselor, clinical psychologist, special educator, and child psychiatrist is usually necessary before making the final diagnosis. It is important to find the reason(s) for a child's poor school performance and come up with a treatment plan early so that the child can perform up to full potential.

  14. Confronting Poor Performance.

    ERIC Educational Resources Information Center

    Dennis, Bruce L.

    Responsible and effective administrative leadership requires confronting those members of the teaching staff who are a negative influence on the institution. Importantly, the absence of expressed appreciation for good work can have a devastating impact on a principal's image if he or she suddenly begins to confront poor performances. Actually, the…

  15. The Poor Pay More.

    ERIC Educational Resources Information Center

    Folse, Kimberly A.

    2002-01-01

    Describes a sociology experiential learning assignment where students learned why people living in poverty can sometimes pay more for products than people with better incomes. Focuses specifically on the rent to own concept. States students achieved the goal of learning how life constraints of poverty can hinder the poor from overcoming their…

  16. The Poor Pay More.

    ERIC Educational Resources Information Center

    Folse, Kimberly A.

    2002-01-01

    Describes a sociology experiential learning assignment where students learned why people living in poverty can sometimes pay more for products than people with better incomes. Focuses specifically on the rent to own concept. States students achieved the goal of learning how life constraints of poverty can hinder the poor from overcoming their…

  17. GROWING UP POOR.

    ERIC Educational Resources Information Center

    CHILMAN, CATHERINE S.

    PRIMARILY AN OVERVIEW AND ANALYSIS OF RESEARCH ON CHILD-REARING AND FAMILY LIFE PATTERNS, THIS BOOK FOCUSES ON THE LIFE OF THE VERY POOR AND COMPARES THEIR LIFE PATTERNS AND PRACTICES WITH THOSE OF MIDDLE-CLASS FAMILIES. THE TWO SETS OF PATTERNS ARE ANALYZED UNDER FIVE HEADINGS--MENTAL HEALTH, EDUCATION, "MORAL" CHARACTER, SOCIAL ACCEPTABILITY,…

  18. Morphosyntax in Poor Comprehenders

    ERIC Educational Resources Information Center

    Adlof, Suzanne M.; Catts, Hugh W.

    2015-01-01

    Children described as "poor comprehenders" (PCs) have reading comprehension difficulties in spite of adequate word reading abilities. PCs are known to display weakness with semantics and higher-level aspects of oral language, but less is known about their grammatical skills, especially with regard to morphosyntax. The purpose of this…

  19. Synthesis and structures of a pincer-type rhodium(iii) complex: reactivity toward biomolecules.

    PubMed

    Milutinović, Milan M; Bogojeski, Jovana V; Klisurić, Olivera; Scheurer, Andreas; Elmroth, Sofi K C; Bugarčić, Živadin D

    2016-10-04

    A novel rhodium(iii) complex [Rh(III)(H2L(tBu))Cl3] (1) (H2L(tBu) = 2,6-bis(5-tert-butyl-1H-pyrazol-3-yl)pyridine) containing a pincer type, tridentate nitrogen-donor chelate system was synthesized. Single crystal X-ray structure analysis revealed that 1 crystallizes in the orthorhombic space group Pbcn with a = 20.7982(6), b = 10.8952(4), c = 10.9832(4) Å, V = 2488.80(15) Å(3), and eight molecules in the unit cell. The rhodium center in the complex [Rh(III)(H2L(tBu))Cl3] (1) is coordinated in a slightly distorted octahedral geometry by the tridentate N,N,N-donor and three chloro ligands, adopting a mer arrangement with an essentially planar ligand skeleton. Due to the tridentate coordination of the N,N,N-donor, the central nitrogen atom N1 is located closer to the Rh(III) center. The reactivity of the synthesized complex toward small biomolecules (l-methionine (l-Met), guanosine-5'-monophosphate (5'-GMP), l-histidine (l-His) and glutathione (GSH)) and to a series of duplex DNAs and RNA was investigated. The order of reactivity of the studied small biomolecules is: 5'-GMP > GSH > l-Met > l-His. Duplex RNA reacts faster with the [Rh(III)(H2L(tBu))Cl3] complex than duplex DNA, while shorter duplex DNA (15mer GG) reacts faster compared with 22mer GG duplex DNA. In addition, a higher reactivity is achieved with a DNA duplex with a centrally located GG-sequence than with a 22GTG duplex DNA, in which the GG-sequence is separated by a T base. Furthermore, the interaction of this metal complex 1 with calf thymus DNA (CT-DNA) and bovine serum albumin (BSA) was examined by absorption (UV-Vis) and emission spectral studies (EthBr displacement studies). Overall, the studied complex exhibited good DNA and BSA interaction ability.

  20. Letting the poor speak.

    PubMed

    2000-09-29

    This paper comments on two documents prepared by the Washington-based World Bank: the "World Development Report" and the three-volume study "Voices of the Poor." The author provides a brief overview of these documents then examines their potential impact on the delegates to the annual meetings of the World Bank and the International Monetary Fund in Prague on September 19-28, 2000. The author further examines the implication of the new strategies embraced by the global lenders--"opportunity, empowerment, security." Apart from these strategies, the World Bank sets out other strategies like spreading the benefits of technology, as it calls for the elimination of absolute poverty by 2015. However, the most crucial tack is the one illustrated by the way the reports were made: letting the poor speak and responding to their cries.

  1. Combination of supported bimetallic rhodium-molybdenum catalyst and cerium oxide for hydrogenation of amide

    NASA Astrophysics Data System (ADS)

    Nakagawa, Yoshinao; Tamura, Riku; Tamura, Masazumi; Tomishige, Keiichi

    2015-02-01

    Hydrogenation of cyclohexanecarboxamide to aminomethylcyclohexane was conducted with silica-supported bimetallic catalysts composed of noble metal and group 6-7 elements. The combination of rhodium and molybdenum with molar ratio of 1:1 showed the highest activity. The effect of addition of various metal oxides was investigated on the catalysis of Rh-MoOx/SiO2, and the addition of CeO2 much increased the activity and selectivity. Higher hydrogen pressure and higher reaction temperature in the tested range of 2-8 MPa and 393-433 K, respectively, were favorable in view of both activity and selectivity. The highest yield of aminomethylcyclohexane obtained over Rh-MoOx/SiO2 + CeO2 was 63%. The effect of CeO2 addition was highest when CeO2 was not calcined, and CeO2 calcined at >773 K showed a smaller effect. The use of CeO2 as a support rather decreased the activity in comparison with Rh-MoOx/SiO2. The weakly-basic nature of CeO2 additive can affect the surface structure of Rh-MoOx/SiO2, i.e. reducing the ratio of Mo-OH/Mo-O- sites.

  2. Vapour phase hydrogenation of phenol over rhodium on SBA-15 and SBA-16.

    PubMed

    Giraldo, Liliana; Bastidas-Barranco, Marlon; Moreno-Piraján, Juan Carlos

    2014-12-10

    In the present work, mesoporous SBA-15 and SBA-16 were synthesised using classical methods, and their physicochemical properties were investigated by X-ray diffraction (XRD), FTIR, TEM and N2 adsorption-desorption. Rhodium (Rh, 1 wt %) was loaded on the mesoporous SBA-15 and SBA-16 by an impregnation method. The Rh surface coverage, dispersion and crystallite size were determined by room temperature H2 chemisorption on reduced samples. The catalytic activity of Rh supported on mesoporous SBA-15 and SBA-16 was evaluated for the first time in the hydrogenation of phenol in vapour phase in a temperature range between 130 and 270 °C at atmospheric pressure. The reaction over Rh/SBA-15 at 180 °C produced cyclohexanone as the major product (about 60%) along with lower amounts of cyclohexanol (about 35%) and cyclohexane (about 15%). The influences of temperature, H2/phenol ratio, contact time and the nature of the solvent on the catalytic performance were systematically investigated. The Rh/SBA-16 system offered lower phenol conversion compared to Rh/SBA-15, but both have a very high selectivity for cyclohexanone (above 60%).

  3. Reactivity Control of Rhodium Cluster Ions by Alloying with Tantalum Atoms.

    PubMed

    Mafuné, Fumitaka; Tawaraya, Yuki; Kudoh, Satoshi

    2016-02-18

    Gas phase, bielement rhodium and tantalum clusters, RhnTam(+) (n + m = 6), were prepared by the double laser ablation of Rh and Ta rods in He carrier gas. The clusters were introduced into a reaction gas cell filled with nitric oxide (NO) diluted with He and were subjected to collisions with NO and He at room temperature. The product species were observed by mass spectrometry, demonstrating that the NO molecules were sequentially adsorbed on the RhnTam(+) clusters to form RhnTam(+)NxOx (x = 1, 2, 3, ...) species. In addition, oxide clusters, RhnTam(+)O2, were also observed, suggesting that the NO molecules were dissociatively adsorbed on the cluster, the N atoms migrated on the surface to form N2, and the N2 molecules were released from RhnTam(+)N2O2. The reactivity, leading to oxide formation, was composition dependent: oxide clusters were dominantly formed for the bielement clusters containing both Rh and Ta atoms, whereas such clusters were hardly formed for the single-element Rhn(+) and Tam(+) clusters. DFT calculations indicated that the Ta atoms induce dissociation of NO on the clusters by lowering the dissociation energy, whereas the Rh atoms enable release of N2 by lowering the binding energy of the N atoms on the clusters.

  4. Carbon monoxide rich methanation kinetics on supported rhodium and nickel catalysts. Final report

    SciTech Connect

    Keehan, D.

    1988-08-01

    The utilization of carbon dioxide reforming of methane in a solar-based Chemical Energy Transmission System (CETS) relies greatly upon the development of suitable catalysts for both the endothermic and exothermic reactions. Carbon dioxide reforming of methane produces hydrogen and carbon monoxide at a ratio of about one, thus requiring the methanation reaction on the other side of the closed loop CETS to utilize this feed. H/sub 2//CO ratios lower than three favor the formation of carbon with industrial methanation catalysts. Preliminary tests performed on methanation with rhodium and nickel catalysts produced two, 0.5% Rh/A1/sub 2/O/sub 3/ and Ni/A1/sub 2/O/sub 3/, for further study. Kinetic experiments were conducted in an isothermal continuous stirred tank reactor constructed of a copper alloy which prevented carbon formation on reactor parts. These experiments were performed on pelleted 0.5% Rh/A1/sub 2/O/sub 3/ in the 400 to 500 C range and pelleted 70% Ni/A1/sub 2/O/sub 3/ in the 300 to 500 C temperature range. In most experiments steam was added to the reactor feed to inhibit carbon formation.

  5. Investigation on 50 Ω Rhodium-Iron Sensors with Ceramic Shell

    NASA Astrophysics Data System (ADS)

    Yu, Lihong; Yao, Chuanfa; Zhang, Qinggeng; Huang, Zan

    2011-01-01

    Rhodium-iron sensors with a ceramic shell and 0.03 mm diameter wires drawn from 0.05 mm diameter wires have been investigated. Results indicate that a proper annealing process is required for the drawn wires to be used in the sensor. The stability of the 30 thermometers made in this way were investigated after being exposed to 20 thermal cycles between 4.2K and room temperature. The thermometers remained stable at 273.15K within 10mK. A standard reference curve was obtained by 58 calibration points from 1.2K to 300K for ten thermometers. With this curve, the R- T relationship was fitted for the other sensors in the same batch within 0.1K accuracy with just a few temperature points. Finally, the self-heating effect was discussed. The results indicated that the performance of the thermometers with drawn wires are the same as that of the thermometers with the original 0.03 mm diameter wires.

  6. MgF2 prism/rhodium/graphene: efficient refractive index sensing structure in optical domain.

    PubMed

    Mishra, Akhilesh Kumar; Mishra, Satyendra Kumar

    2017-04-12

    A theoretical study of a noble surface plasmon resonance (SPR) based sensing probe has been carried out. The sensing probe consists of a magnesium fluoride (MgF2) prism with its base coated with rarely used noble metal rhodium (Rh) and a bio-compatible layer of graphene. The refractive indices (RIs) of the sensing medium vary from 1.33 to 1.36 refractive index unit (RIU). The thickness of Rh and the number of graphene layers have been optimized for maximum sensitivity in a constraint set by the detection accuracy (DA). For the operating wavelength of 632 nm, the optimized sensing probe Rh (12 nm)/graphene (single layer) demonstrates sensitivity of ~259 degree/RIU with corresponding DA of ~0.32 degree(-1) while for 532 nm of excitation, the optimized sensing probe Rh (12 nm)/graphene (three layer) exhibits sensitivity of ~240 degree/RIU and DA of ~0.27 degree(-1).

  7. Base-Catalyzed Insertion of Dioxygen into Rhodium-Hydrogen Bonds: Kinetics and Mechanism

    SciTech Connect

    Szajna-Fuller, Ewa; Bakac, Andreja

    2009-10-27

    The reaction between molecular oxygenm and rhodium hydrides L(OH)RhH{sup +} (L = (NH{sub 3}){sub 4}, trans-L{sup 1}, and cis-L{sup 1}, where L{sup 1} = cyclam) in basic aqueous solutions rapidly produces the corresponding hydroperoxo complexes. Over the pH range 8 < pH < 12, the kinetics exhibit a first order dependence on [OH{sup -}]. The dependence on [O{sub 2}] is less than first order and approaches saturation at the highest concentrations used. These data suggest an attack by OH{sup -} at the hydride with k = (1.45 {+-} 0.25) x 10{sup 3} M{sup -1} s{sup -1} for trans-L{sup 1}(OH)RhH{sup +} at 25 C, resulting in heterolytic cleavage of the Rh-H bond and formation of a reactive Rh(I) intermediate. A competition between O{sub 2} H{sub 2}O for Rh(I) is the source of the observed dependence on O{sub 2}.

  8. Synthesis of Benzodihydrofurans by Asymmetric C-H Insertion Reactions of Donor/Donor Rhodium Carbenes.

    PubMed

    Lamb, Kellan N; Squitieri, Richard A; Chintala, Srinivasa R; Kwong, Ada J; Balmond, Edward I; Soldi, Cristian; Dmitrenko, Olga; Castiñeira Reis, Marta; Chung, Ryan; Addison, J Bennett; Fettinger, James C; Hein, Jason E; Tantillo, Dean J; Fox, Joseph M; Shaw, Jared T

    2017-09-04

    Metal carbenes appended with two electron-donating groups, known as "donor/donor" carbenes, undergo diastereo- and enantioselective rhodium-catalyzed C-H insertion reactions with ether substrates to form benzodihydrofurans. Unlike the reactions of metal carbenes with electron-withdrawing groups attached, the attenuated electrophilicity enables these reactions to be conducted in Lewis basic solvents (e.g., acetonitrile) and in the presence of water. The diazo precursors for these species are prepared in situ from hydrazone using a mild and chemoselective oxidant (MnO2 ). Although this sequence often can be performed in one-pot, control experiments have elucidated why a "two-pot" process is often more efficient. A thorough screening of achiral catalysts demonstrated that sterically encumbered catalysts are optimal for diastereoselective reactions. Although efficient insertion into allylic and propargylic C-H bonds is observed, competing dipolar cycloaddition processes are noted for some substrates. The full substrate scope of this useful method of benzodihydrofuran synthesis, mechanisms of side reactions, and computational support for the origins of stereoselectivity are described. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. MgF2 prism/rhodium/graphene: efficient refractive index sensing structure in optical domain

    NASA Astrophysics Data System (ADS)

    Mishra, Akhilesh Kumar; Mishra, Satyendra Kumar

    2017-04-01

    A theoretical study of a noble surface plasmon resonance (SPR) based sensing probe has been carried out. The sensing probe consists of a magnesium fluoride (MgF2) prism with its base coated with rarely used noble metal rhodium (Rh) and a bio-compatible layer of graphene. The refractive indices (RIs) of the sensing medium vary from 1.33 to 1.36 refractive index unit (RIU). The thickness of Rh and the number of graphene layers have been optimized for maximum sensitivity in a constraint set by the detection accuracy (DA). For the operating wavelength of 632 nm, the optimized sensing probe Rh (12 nm)/graphene (single layer) demonstrates sensitivity of ~259 degree/RIU with corresponding DA of ~0.32 degree‑1 while for 532 nm of excitation, the optimized sensing probe Rh (12 nm)/graphene (three layer) exhibits sensitivity of ~240 degree/RIU and DA of ~0.27 degree‑1.

  10. Ligand-controlled regioselectivity in the hydrothiolation of alkynes by rhodium N-heterocyclic carbene catalysts.

    PubMed

    Di Giuseppe, Andrea; Castarlenas, Ricardo; Pérez-Torrente, Jesús J; Crucianelli, Marcello; Polo, Victor; Sancho, Rodrigo; Lahoz, Fernando J; Oro, Luis A

    2012-05-16

    Rh-N-heterocyclic carbene compounds [Rh(μ-Cl)(IPr)(η(2)-olefin)](2) and RhCl(IPr)(py)(η(2)-olefin) (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-carbene, py = pyridine, olefin = cyclooctene or ethylene) are highly active catalysts for alkyne hydrothiolation under mild conditions. A regioselectivity switch from linear to 1-substituted vinyl sulfides was observed when mononuclear RhCl(IPr)(py)(η(2)-olefin) catalysts were used instead of dinuclear precursors. A complex interplay between electronic and steric effects exerted by IPr, pyridine, and hydride ligands accounts for the observed regioselectivity. Both IPr and pyridine ligands stabilize formation of square-pyramidal thiolate-hydride active species in which the encumbered and powerful electron-donor IPr ligand directs coordination of pyridine trans to it, consequently blocking access of the incoming alkyne in this position. Simultaneously, the higher trans director hydride ligand paves the way to a cis thiolate-alkyne disposition, favoring formation of 2,2-disubstituted metal-alkenyl species and subsequently the Markovnikov vinyl sulfides via alkenyl-hydride reductive elimination. DFT calculations support a plausible reaction pathway where migratory insertion of the alkyne into the rhodium-thiolate bond is the rate-determining step.

  11. Asymmetric Suzuki-Miyaura coupling of heterocycles via Rhodium-catalysed allylic arylation of racemates

    NASA Astrophysics Data System (ADS)

    Schäfer, Philipp; Palacin, Thomas; Sidera, Mireia; Fletcher, Stephen P.

    2017-06-01

    Using asymmetric catalysis to simultaneously form carbon-carbon bonds and generate single isomer products is strategically important. Suzuki-Miyaura cross-coupling is widely used in the academic and industrial sectors to synthesize drugs, agrochemicals and biologically active and advanced materials. However, widely applicable enantioselective Suzuki-Miyaura variations to provide 3D molecules remain elusive. Here we report a rhodium-catalysed asymmetric Suzuki-Miyaura reaction with important partners including aryls, vinyls, heteroaromatics and heterocycles. The method can be used to couple two heterocyclic species so the highly enantioenriched products have a wide array of cores. We show that pyridine boronic acids are unsuitable, but they can be halogen-modified at the 2-position to undergo reaction, and this halogen can then be removed or used to facilitate further reactions. The method is used to synthesize isoanabasine, preclamol, and niraparib--an anticancer agent in several clinical trials. We anticipate this method will be a useful tool in drug synthesis and discovery.

  12. Alcohols synthesis from carbon oxides and hydrogen on palladium and rhodium catalysts. Study of active species

    SciTech Connect

    Kiememann, A.; Hindermann, J.P.; Breault, R.; Idries, H.

    1986-03-01

    The synthesis of primary chemical products and/or gasoline additives of high octane number from synthesis gas obtained by coal gasification has received much attention these past years. Actually, even if methanol has been the most important oxygenated product, intensive research is being carried out for the direct synthesis of higher alcohols: ethanol for organic synthesis, or an alcohol mixture, from C/sub 1/ to C/sub 5/, as an additive to gasoline. For the methanol synthesis, copper-based catalysts, have long been considered as the only effective catalysts. Meanwhile Poutsma et al., showed the possible obtaining of methanol with palladium; this last metal has always been considered inactive for directing production of methane from CO-H/sub 2/. It is also true that the selectivity and activity vary greatly with the support. Even if other factors like the particle size was evoked to explain the change in the selectivity, the support effect seems to be primordial. It can play different roles on: the acidity and basicity, the structure of the active sites, the stabilization of intermediates and the formation of an intimate contact between metallic particles and sodium or lithium ions, a strong metal support interaction (SMSI); in particular with rhodium catalysts.

  13. Rhodium-Catalyzed Dehydrogenative Silylation of Acetophenone Derivatives: Formation of Silyl Enol Ethers versus Silyl Ethers.

    PubMed

    Garcés, Karin; Lalrempuia, Ralte; Polo, Víctor; Fernández-Alvarez, Francisco J; García-Orduña, Pilar; Lahoz, Fernando J; Pérez-Torrente, Jesús J; Oro, Luis A

    2016-10-04

    A series of rhodium-NSiN complexes (NSiN=bis (pyridine-2-yloxy)methylsilyl fac-coordinated) is reported, including the solid-state structures of [Rh(H)(Cl)(NSiN)(PCy3 )] (Cy=cyclohexane) and [Rh(H)(CF3 SO3 )(NSiN)(coe)] (coe=cis-cyclooctene). The [Rh(H)(CF3 SO3 )(NSiN)(coe)]-catalyzed reaction of acetophenone with silanes performed in an open system was studied. Interestingly, in most of the cases the formation of the corresponding silyl enol ether as major reaction product was observed. However, when the catalytic reactions were performed in closed systems, formation of the corresponding silyl ether was favored. Moreover, theoretical calculations on the reaction of [Rh(H)(CF3 SO3 )(NSiN)(coe)] with HSiMe3 and acetophenone showed that formation of the silyl enol ether is kinetically favored, while the silyl ether is the thermodynamic product. The dehydrogenative silylation entails heterolytic cleavage of the Si-H bond by a metal-ligand cooperative mechanism as the rate-determining step. Silyl transfer from a coordinated trimethylsilyltriflate molecule to the acetophenone followed by proton transfer from the activated acetophenone to the hydride ligand results in the formation of H2 and the corresponding silyl enol ether.

  14. Synthesis and Conformational Behavior of Rhodium(I) Metallohosts Derived from Diphenylglycoluril.

    PubMed

    Coolen, Hein K. A. C.; van Leeuwen, Piet W. N. M.; Nolte, Roeland J. M.

    1996-07-12

    The design and synthesis of molecules containing both a substrate-binding cavity and a nearby catalytically active metal center is a useful approach to the development of synthetic systems that function according to the principles of enzymes. To this end the receptor molecule 2a, derived from diphenylglycoluril, was functionalized with triaryl phosphite ligands to give the receptor ligand 2d. Exchange reactions of 2d with (diketonate)Rh(CO)(2), (diketone = acetylacetone, dibenzoylmethane, or dipivaloylmethane) led to the formation of the metallohosts 3a-c, respectively. The properties and conformational behavior of these metal complexes were studied by NMR techniques. Reaction of compounds 3 with H(2) in the presence of a small excess of additional triphenyl phosphite yields the rhodium(I) hydride complex 5. The metallohosts are capable of binding dihydroxybenzene guests in their cavities by hydrogen bonding and pi-pi stacking interactions. On binding a substrate the conformational behavior of hosts 3a-c was affected considerably.

  15. Synthesis of colloidal dispersions of rhodium nanoparticles under high temperatures and high pressures.

    PubMed

    Harada, Masafumi; Abe, Daisuke; Kimura, Yoshifumi

    2005-12-01

    Colloidal dispersions of rhodium (Rh) nanoparticles have been synthesized by the reduction of Rh ions (III) in high-temperature and high-pressure water, ethanol, or water-ethanol mixture under the existence of the protective polymer of poly(N-vinyl-2-pyrrolidone). The possibility of the regulation of the particle size and size distribution has been tested under several solvents at various temperatures and pressures. At 473 K and 25 MPa, particularly, concentrated colloidal dispersions of Rh particles of 2.5+/-0.5 nm were synthesized from the ionic solution of ethanol ([Rh]=15 mM) within a few seconds. Dilute colloidal dispersions of Rh particles were also synthesized from the dilute ionic solution ([Rh]=1.5 mM) with a diameter of 2.0+/-0.4 nm. From the water solution, Rh particles tended to form aggregates, especially for the lower concentration solution. In the case of solutions in water and ethanol mixture, the average diameter of Rh particles tended to be larger than in ethanol solution, and their distribution became broad.

  16. Nanofiltration of rhodium tris(triphenylphosphine) catalyst in ethyl acetate solution

    NASA Astrophysics Data System (ADS)

    Shaharun, Maizatul S.; Mustafa, Ahmad K.; Taha, Mohd F.

    2012-09-01

    Solvent resistant nanofiltration (SRNF) using polymer membranes has recently received enhanced attention due to the search for cleaner and more energy-efficient technologies. The large size of the rhodium tris(triphenylphosphine) [HRh(CO)(PPh3)3] catalyst (>400 Da) - relative to other components of the hydroformylation reaction provides the opportunity for a membrane separation based on retention of the catalyst species while permeating the solvent. The compatibility of the solvent-polyimide membrane (DuraMem{trade mark, serif} 200 and DuraMem{trade mark, serif} 500) combinations was assessed in terms of the membrane stability in solvent plus non-zero solvent flux at 2.0 MPa. Good HRh(CO)(PPh3)3 rejection (>0.95) and solvent fluxes of 9.9 L/m2ṡh1 at 2.0 MPa were obtained in the catalyst-ethyl acetate-DuraMem 500 system. The effect of pressure and catalyst concentration on the solvent flux and catalyst rejection was conducted on the catalyst-ethyl acetate-membrane systems. Increasing pressure substantially improved both solvent flux and catalyst rejection, while increasing catalyst concentration was found to be beneficial in terms of substantial increases in catalyst rejection without significantly affecting solvent flux.

  17. Synthesis and characterization of polymer-protected rhodium and palladium sols in mixed media.

    PubMed

    Jaine, Jacob E; Mucalo, Michael R

    2012-06-01

    A series of polymer-protected rhodium and palladium sols were generated in mixed (organic/aqueous) dispersion media. Protecting polymers used were PAA, PVP, PVA and an oligosaccharide-based protecting agent, arabinogalactan. This is the first systematic study of colloids generated in mixed solvent dispersion media with these protecting agents. The sols were characterized by TEM, UV/Vis spectrophotometry and Photon Correlation Spectroscopy (PCS). In general, the macroscopic stability of the sols depended on the protecting agent/organic cosolvent combination used, with a nonlinear dependence on cosolvent concentration. Observed sol stabilities correlated well with pre-existing hydrodynamic data for the protective polymers, e.g. radius of gyration data. Average particle size and polydispersity of all sols examined decreased as cosolvent concentration increased, with actual cosolvent concentration, protecting agent and reducing agent used influencing the extent of decrease. Sol particle sizes ranged from 0.8 nm to 6.0 nm with sol turbidities decreasing in parallel with the particle sizes. Hydrodynamic sizes (from PCS) tended to reflect the sols' macroscopic stabilities. FTIR studies using adsorbed CO as a spectroscopic surface probe indicated decreases in the ν(CO)(ads) stretching frequency with an increase in cosolvent concentration due to competitive adsorption of CO with the cosolvent molecules on the metal colloid surfaces. Copyright © 2012 Elsevier Inc. All rights reserved.

  18. Intrinsic selectivity and structure sensitivity of Rhodium catalysts for C2+ oxygenate production [On the intrinsic selectivity and structure sensitivity of Rhodium catalysts for C2+ oxygenate production

    SciTech Connect

    Yang, Nuoya; Medford, Andrew J.; Liu, Xinyan; Studt, Felix; Bligaard, Thomas; Bent, Stacey F.; Nørskov, Jens K.

    2016-01-31

    Synthesis gas (CO + H2) conversion is a promising route to converting coal, natural gas, or biomass into synthetic liquid fuels. Rhodium has long been studied as it is the only elemental catalyst that has demonstrated selectivity to ethanol and other C2+ oxygenates. However, the fundamentals of syngas conversion over rhodium are still debated. In this work a microkinetic model is developed for conversion of CO and H2 into methane, ethanol, and acetaldehyde on the Rh (211) and (111) surfaces, chosen to describe steps and close-packed facets on catalyst particles. The model is based on DFT calculations using the BEEF-vdW functional. The mean-field kinetic model includes lateral adsorbate–adsorbate interactions, and the BEEF-vdW error estimation ensemble is used to propagate error from the DFT calculations to the predicted rates. The model shows the Rh(211) surface to be ~6 orders of magnitude more active than the Rh(111) surface, but highly selective toward methane, while the Rh(111) surface is intrinsically selective toward acetaldehyde. A variety of Rh/SiO2 catalysts are synthesized, tested for catalytic oxygenate production, and characterized using TEM. The experimental results indicate that the Rh(111) surface is intrinsically selective toward acetaldehyde, and a strong inverse correlation between catalytic activity and oxygenate selectivity is observed. Furthermore, iron impurities are shown to play a key role in modulating the selectivity of Rh/SiO2 catalysts toward ethanol. The experimental observations are consistent with the structure-sensitivity predicted from theory. As a result, this work provides an improved atomic-scale understanding and new insight into the mechanism, active site, and intrinsic selectivity of syngas conversion over rhodium catalysts and may also guide rational design of alloy catalysts made from more abundant elements.

  19. Recent Advances in the Synthesis of Heterocycles and Related Substances Based on α-Imino Rhodium Carbene Complexes Derived from N-Sulfonyl-1,2,3-triazoles.

    PubMed

    Jiang, Yu; Sun, Run; Tang, Xiang-Ying; Shi, Min

    2016-12-12

    In recent years, α-imino rhodium carbene complexes derived by ring-opening of N-sulfonyl-1,2,3-triazoles have attracted much attention from organic chemists. Many transformations of these species have been reported that involve, in most cases, nucleophilic attack at the carbene center of the α-imino rhodium carbene, facilitating the synthesis of a wide range of novel and useful compounds, particularly heterocycles. This Minireview mainly focuses on advances in the transformation of N-sulfonyl-1,2,3-triazoles during the past two years.

  20. One-pot synthesis of 2,5-dihydropyrroles from terminal alkynes, azides, and propargylic alcohols by relay actions of copper, rhodium, and gold.

    PubMed

    Miura, Tomoya; Tanaka, Takamasa; Matsumoto, Kohei; Murakami, Masahiro

    2014-12-01

    Relay actions of copper, rhodium, and gold formulate a one-pot multistep pathway, which directly gives 2,5-dihydropyrroles starting from terminal alkynes, sulfonyl azides, and propargylic alcohols. Initially, copper-catalyzed 1,3-dipolar cycloaddition of terminal alkynes with sulfonyl azides affords 1-sulfonyl-1,2,3-triazoles, which then react with propargylic alcohols under the catalysis of rhodium. The resulting alkenyl propargyl ethers subsequently undergo the thermal Claisen rearrangement to give α-allenyl-α-amino ketones. Finally, a gold catalyst prompts 5-endo cyclization to produce 2,5-dihydropyrroles. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Stereochemical features making deoxycholic acid derived tropos biphenylphosphites efficient chiral ligands for rhodium: the asymmetric hydrogenation of dimethylitaconate as a case study.

    PubMed

    Iuliano, Anna; Losi, Debora; Facchetti, Sarah

    2007-10-26

    Different deoxycholic acid derived biphenylphosphites, whose tropos nature was ascertained by NMR and CD measurements, were used in the rhodium-catalyzed asymmetric hydrogenation of dimethylitaconate achieving enantiomeric excesses up to 91%. The comparison of these results to those obtained using the corresponding atropoisomeric binaphthyl analogues, together with NMR and CD measurements on the rhodium complexes of some phosphites, allowed us to shed light on the nature of the active catalytic species and on the asymmetric induction process and hence to recognize the most appropriate stereochemical features to reach good levels of enantioselectivity.

  2. Rhodium nanocatalysts stabilized by various bipyridine ligands in nonaqueous ionic liquids: influence of the bipyridine coordination modes in arene catalytic hydrogenation.

    PubMed

    Léger, Bastien; Denicourt-Nowicki, Audrey; Olivier-Bourbigou, Hélène; Roucoux, Alain

    2008-10-06

    Rhodium nanoparticles stabilized by 2,2'-, 3,3'-, 4,4'-bipyridine ligands were prepared in various ionic liquids according to a chemical reduction approach. Zerovalent nanospecies in the size range of 2.0-2.5 nm were characterized. The nature of the bipyridine and its influence on the coordination environment of rhodium nanoparticles were investigated in various nonaqueous ionic liquids according to the cation and anion. The hydrogenation of various aromatic compounds by these colloidal suspensions was carried out at 80 degrees C and under 40 bar of H 2. A first structural explanation based on bipyridine coordination modes is proposed to justify the observed different activities.

  3. Simultaneous determination of rhodium and ruthenium by high-resolution continuum source graphite furnace atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Zambrzycka-Szelewa, Elżbieta; Lulewicz, Marta; Godlewska-Żyłkiewicz, Beata

    2017-07-01

    In the present paper a fast, simple and sensitive analytical method for simultaneous determination of rhodium and ruthenium by high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GFAAS) was developed. Among six pairs of absorption atomic lines of Rh and Ru, which are close enough to enable their simultaneous detection, two pairs were selected for further studies. Best results were obtained for measurements of the resonance line of rhodium at 343.489 nm and the adjacent secondary line of ruthenium at 343.674 nm (23% intensity of this line). For evaluated lines, the absorbance values were obtained using three pixels. The pyrolysis and atomization temperatures were 1200 °C and 2600 °C, respectively. Under these conditions the limits of detection achieved for Rh and Ru were found to be 1.0 μg L- 1 and 1.9 μg L- 1, respectively. The characteristic mass was 12.9 pg for Rh and 71.7 pg for Ru. Repeatability of the results expressed as a relative standard deviation was typically below 6%. The trueness of the method was confirmed by analysis of the certified reference material - platinum ore (SARM 76). The recovery of Rh and Ru from the platinum ore was 93.0 ± 4.6% and 90.1 ± 2.5%, respectively. The method was successfully applied to the direct simultaneous determination of trace amounts of rhodium and ruthenium in spiked river water, road runoff, and municipal sewage. Separation of interfering matrix on cation exchange resin was required before analysis of road dust and tunnel dust (CW-7) by HR-CS GFAAS.

  4. Complexation of heteroaromatic N-oxides with rhodium(II) tetracarboxylates in solution: DFT and NMR investigations

    NASA Astrophysics Data System (ADS)

    Głaszczka, Rafał; Jaźwiński, Jarosław

    2014-03-01

    Complexation of rhodium(II) tetraacetate and rhodium(II) tetrakistrifluoroacetate with a set of heteroaromatic N-oxides containing additional functional groups was investigated by means of density functional theory (DFT) calculations, and 1H, 13C and 15N nuclear magnetic resonance (NMR) spectroscopy in CDCl3 solutions. Chemical shifts for five N-oxides and their 1:1 adducts with rhodium tetraacetate were computed at the B3PW91/[6-311++G(2d,p), Stuttgart ECP)//B3LYP/[6-31G(2d), LANL2DZ] theory level applying IEF PCM (CHCl3) solvation model and taking into account various complexation modes and conformational variety. Calculated values were used for the estimation of complexation shifts Δδ (Δδ = δadduct - δligand). The largest negative complexation shift were estimated for heteroatoms bonded to Rh, from -37 to -70 ppm (N), from -100 to -160 ppm (O in NO group), from -13 to -23 ppm (O in OCH3 group), and from -12 to -22 ppm (Cl). For the remaining heteroatoms in adducts, the corresponding Δδ values ranged from -22 to +8.2 ppm (N), from +3 to +58 ppm (O) and from +6 to +51 ppm (Cl). The Δδ(1H) usually did not exceed 1 ppm, whereas Δδ(13C) varied from ca. -1 to +7 ppm. Some trends useful for the determination of the complexation site were extracted from calculated data sets. Theoretical findings were applied to analyse experimental NMR data.

  5. Rhodium-catalyzed allylic substitution with an acyl anion equivalent: stereospecific construction of acyclic quaternary carbon stereogenic centers.

    PubMed

    Evans, P Andrew; Oliver, Samuel; Chae, Jungha

    2012-11-28

    A highly regio- and stereospecific rhodium-catalyzed allylic alkylation of tertiary allylic alcohol derivatives with a cyanohydrin pronucleophile is described. This direct and operationally simple protocol provides a fundamentally novel approach toward the synthesis of α-quaternary substituted ketones and circumvents many of the inherent problems associated with conventional enolate alkylation reactions. The stereospecific variant of this reaction provides the enantiomerically enriched α-quaternary substituted allylic aryl ketone, which is a particularly challenging intermediate for more conventional enolate-based strategies.

  6. Diastereoselective rhodium-catalyzed ene-cycloisomerization reactions of alkenylidenecyclopropanes: total synthesis of (-)-α-kainic acid.

    PubMed

    Evans, P Andrew; Inglesby, Phillip A

    2012-02-29

    The rhodium-catalyzed ene-cycloisomerization of alkenylidenecyclopropanes provides an atom-economical approach to five-membered carbo- and heterocycles that contain two new stereogenic centers. A key and striking feature of this protocol is that the alkene geometry does not impact the efficiency and diastereocontrol, which provides excellent synthetic versatility. For instance, (E)- and (Z)-allylic alcohols furnish the corresponding aldehydes with similar efficiency and selectivity. This process facilitates the construction of a key intermediate in an eight-step total synthesis of (-)-α-kainic acid. © 2012 American Chemical Society

  7. Rhodium(I)-Catalyzed Highly Enantioselective Insertion of Carbenoid into Si-H: Efficient Access to Functional Chiral Silanes.

    PubMed

    Chen, Diao; Zhu, Dong-Xing; Xu, Ming-Hua

    2016-02-10

    The first rhodium(I)-catalyzed enantioselective Si-H insertion reaction of α-diazoesters and α-diazophosphonates has been developed. The use of a C1-symmetric chiral diene ligand enabled the asymmetric reaction to proceed under exceptionally mild conditions and give versatile chiral α-silyl esters and phosphonates with excellent enantioselectivities (up to 99% ee). The mechanism and stereochemical pathway of this novel Rh(I)-carbene-directed Si-H insertion was investigated by deuterium kinetic isotope effect experiments and DFT calculations.

  8. Double-Stereodifferentiation in Rhodium-Catalyzed [2 + 2 + 2] Cycloaddition: Chiral Ligand/Chiral Counterion Matched Pair.

    PubMed

    Augé, Mylène; Feraldi-Xypolia, Alexandra; Barbazanges, Marion; Aubert, Corinne; Fensterbank, Louis; Gandon, Vincent; Kolodziej, Emilie; Ollivier, Cyril

    2015-08-07

    The first enantioselective metal-catalyzed [2 + 2 + 2] cycloaddition involving a double asymmetric induction has been devised. It relies on the use of an in situ generated chiral cationic rhodium(I) catalyst with a matched chiral ligand/chiral counterion pair. Careful optimization of the catalytic system, as well as of the reaction conditions, led to atroposelective [2 + 2 + 2] pyridone cycloadducts with high ee's up to 96%. This strategy outperformed those previously described involving a chiral ligand only or a chiral counterion only.

  9. Rhodium(III)-Catalyzed Enantiotopic C-H Activation Enables Access to P-Chiral Cyclic Phosphinamides.

    PubMed

    Sun, Yang; Cramer, Nicolai

    2017-01-02

    Compounds with stereogenic phosphorus atoms are frequently used as ligands for transition-metal as well as organocatalysts. A direct catalytic enantioselective method for the synthesis of P-chiral compounds from easily accessible diaryl phosphinamides is presented. The use of rhodium(III) complexes equipped with a suitable atropochiral cyclopentadienyl ligand is shown to enable an enantiodetermining C-H activation step. Upon trapping with alkynes, a broad variety of cyclic phosphinamides with a stereogenic phosphorus(V) atom are formed in high yields and enantioselectivities. Moreover, these can be reduced enantiospecifically to P-chiral phosphorus(III) compounds.

  10. Rhodium-catalyzed asymmetric addition of arylboronic acids to β-nitroolefins: formal synthesis of (S)-SKF 38393.

    PubMed

    Huang, Kung-Chih; Gopula, Balraj; Kuo, Ting-Shen; Chiang, Chien-Wei; Wu, Ping-Yu; Henschke, Julian P; Wu, Hsyueh-Liang

    2013-11-15

    An efficient enantioselective addition of an array of arylboronic acids to various β-nitrostyrenes catalyzed by a novel and reactive rhodium-diene catalyst (S/C up to 1000) was developed, providing β,β-diarylnitroethanes in good to high yields (62-99%) with excellent enantioselectivities (85-97% ee). The method was extended to 2-heteroarylnitroolefins and 2-alkylnitroolefins similarly providing the desired products with high enantioselectivities and yields. The usefulness of this method was demonstrated in the formal synthesis of the enantiomer of the dopamine receptor agonist and antagonist, SKF 38393.

  11. Rhodium fluorapatite catalyst for the synthesis of trisubstituted olefins via cross coupling of Baylis-Hillman adducts and arylboronic acids.

    PubMed

    Kantam, M Lakshmi; Kumar, K B Shiva; Sreedhar, B

    2008-01-04

    Treatment of fluorapatite (prepared by incorporating basic species F(-) in apatite in situ by coprecipitation) with an aqueous solution of RhCl(3) resulted in rhodium-exchanged fluorapatite catalyst (RhFAP), which successfully promoted cross coupling of Baylis-Hillman adducts with arylboronic acids to yield trisubstituted olefins. A variety of arylboronic acids and Baylis-Hillman adducts were converted to the corresponding trisubstituted olefins, demonstrating the versatility of the reaction. The reaction is highly stereoselective. RhFAP was recovered quantitatively by simple filtration and reused with almost consistent activity.

  12. Rhodium(III)-triphenylphosphine complex with NNS donor thioether containing Schiff base ligand: Synthesis, spectra, electrochemistry and catalytic activity

    NASA Astrophysics Data System (ADS)

    Biswas, Sujan; Sarkar, Deblina; Kundu, Subhankar; Roy, Puspendu; Mondal, Tapan Kumar

    2015-11-01

    New rhodium(III)-triphenylphosphine complex, [Rh(PPh3)(L)Cl2](PF6) (1) with thioether containing NNS donor ligand (L) (L = 2-(methylthio)-N-((pyridine-2-yl)methylene)benzenamine) has been synthesized and characterized. The pseudo octahedral geometry of the complex has been confirmed by single crystal X-ray analysis. The electronic structure, redox properties, absorption and emission properties of the complexes have been interpreted by DFT and TDDFT calculations. The complex effectively catalyzed the transfer hydrogenation reaction of ketones in 2-propanol and oxidation of alcohols in presence of NMO.

  13. Poor ovarian reserve

    PubMed Central

    Jirge, Padma Rekha

    2016-01-01

    Poor ovarian reserve (POR) is an important limiting factor for the success of any treatment modality for infertility. It indicates a reduction in quantity and quality of oocytes in women of reproductive age group. It may be age related as seen in advanced years of reproductive life or may occur in young women due to diverse etiological factors. Evaluating ovarian reserve and individualizing the therapeutic strategies are very important for optimizing the success rate. Majority or women with POR need to undergo in vitro fertilization to achieve pregnancy. However, pregnancy rate remains low despite a plethora of interventions and is associated with high pregnancy loss. Early detection and active management are essential to minimize the need for egg donation in these women. PMID:27382229

  14. Half-sandwich iridium- and rhodium-based organometallic architectures: rational design, synthesis, characterization, and applications.

    PubMed

    Han, Ying-Feng; Jin, Guo-Xin

    2014-12-16

    CONSPECTUS: Over the last two decades, researchers have focused on the design and synthesis of supramolecular coordination complexes, which contain discrete functional structures with particular shapes and sizes, and are similar to classic metal-organic frameworks. Chemists can regulate many of these systems by judiciously choosing the metal centers and their adjoining ligands. These resulting complexes have unusual properties and therefore many applications, including molecular recognition, supramolecular catalysis, and some applications as nanomaterials. In addition, researchers have extensively developed synthetic methodologies for the construction of discrete self-assemblies. One of the most important challenges for scientists in this area is to be able to synthesize target structures that can be controlled in both length and width. For this reason, it is important that we understand the factors leading to special shapes and sizes of such architectures, especially how starting building blocks and functional ligands affect the final conformations and cavity sizes of the resulting assemblies. Towards this goal, we have developed a wide range of different organometallic architectures by rationally designing metal-containing precursors and organic ligands. In this Account, we present our recent work, focusing on half-sandwich iridium- and rhodium-based organometallic assemblies that we obtained through rational design. We discuss their synthesis, structures, and applications for the encapsulation of guests and enzyme-mimicking catalysis. We first describe a series of self-assembled organometallic metallarectangles and metallacages, which we constructed from preorganized dinuclear half-sandwich molecular clips and suitable pyridyl ligands. We extended this strategy to tune the size of the obtained rectangles, creating large cavities by introduction of larger molecular clips. The cavity was found to exhibit selective and reversible CH2Cl2 adsorption properties while

  15. Thermodynamic properties of rhodium at high temperature and pressure by using mean field potential approach

    NASA Astrophysics Data System (ADS)

    Kumar, Priyank; Bhatt, Nisarg K.; Vyas, Pulastya R.; Gohel, Vinod B.

    2016-10-01

    The thermophysical properties of rhodium are studied up to melting temperature by incorporating anharmonic effects due to lattice ions and thermally excited electrons. In order to account anharmonic effects due to lattice vibrations, we have employed mean field potential (MFP) approach and for thermally excited electrons Mermin functional. The local form of the pseudopotential with only one effective adjustable parameter rc is used to construct MFP and hence vibrational free energy due to ions - Fion. We have studied equation of state at 300 K and further, to access the applicability of present conjunction scheme, we have also estimated shock-Hugoniot and temperature along principle Hugoniot. We have carried out the study of temperature variation of several thermophysical properties like thermal expansion (βP), enthalpy (EH), specific heats at constant pressure and volume (CP and CV), specific heats due to lattice ions and thermally excited electrons ( and , isothermal and adiabatic bulk moduli (BT and Bs) and thermodynamic Gruneisen parameter (γth) in order to examine the inclusion of anharmonic effects in the present study. The computed results are compared with available experimental results measured by using different methods and previously obtained theoretical results using different theoretical philosophy. Our computed results are in good agreement with experimental findings and for some physical quantities better or comparable with other theoretical results. We conclude that local form of the pseudopotential used accounts s-p-d hybridization properly and found to be transferable at extreme environment without changing the values of the parameter. Thus, even the behavior of transition metals having complexity in electronic structure can be well understood with local pseudopotential without any modification in the potential at extreme environment. Looking to the success of present scheme (MFP + pseudopotential) we would like to extend it further for the

  16. Iridium, platinum and rhodium baseline concentration in lichens from Tierra del Fuego (South Patagonia, Argentina).

    PubMed

    Pino, Anna; Alimonti, Alessandro; Conti, Marcelo Enrique; Bocca, Beatrice

    2010-10-06

    Lichen samples of Usnea barbata were used as possible biomonitors of the atmospheric background level of iridium (Ir), platinum (Pt) and rhodium (Rh) in the remote region of Tierra del Fuego (South Patagonia, Argentina). Lichens were collected in 2006 at 53 sites covering 7 different areas of the region (24 transplanted lichens of the northern region and 29 native lichen samples of the central-southern region). A microwave acidic digestion procedure was used to mineralize the samples and a sector field inductively coupled plasma mass spectrometry method was developed to quantify the elements. The study of the influence of interferences on analyte signals and a quality control procedure were carried out. The analytical protocol was further applied to evaluate Ir, Pt and Rh bioaccumulation in lichens. The detection limits obtained were 0.010 ng g⁻¹, 0.013 ng g⁻¹ and 0.030 ng g⁻¹ for Ir, Pt and Rh, respectively. Recoveries at different fortification levels were between 96.3% and 106% and precision was 3.3% on average. The metals concentration (as dry weight) spanned the following ranges: Ir, <0.010-1.011 ng g⁻¹; Pt, 0.016-2.734 ng g⁻¹; and Rh, 0.063-1.298 ng g⁻¹. Data on 7 areas were similar suggesting that no specific source, for example traffic or anthropogenic activity, influenced directly the metal concentrations in Tierra del Fuego. Values detected are more likely influenced by the long-range atmospheric transport of these pollutants and, in comparison with densely populated areas in the world, they can represent the baseline for low impacted areas.

  17. Base-catalyzed insertion of dioxygen into rhodium-hydrogen bonds: kinetics and mechanism.

    PubMed

    Szajna-Fuller, Ewa; Bakac, Andreja

    2010-02-01

    The reaction between molecular oxygen and rhodium hydrides L(OH)RhH(+) (L = (NH(3))(4), trans-L(1), and cis-L(1), where L(1) = cyclam) in basic aqueous solutions rapidly produces the corresponding hydroperoxo complexes. Over the pH range 8 < pH < 12, the kinetics exhibit a first order dependence on [OH(-)]. The dependence on [O(2)] is less than first order and approaches saturation at the highest concentrations used. These data suggest an attack by OH(-) at the hydride with k = (1.45 +/- 0.25) x 10(3) M(-1) s(-1) for trans-L(1)(OH)RhH(+) at 25 degrees C, resulting in heterolytic cleavage of the Rh-H bond and formation of a reactive Rh(I) intermediate. A competition between O(2) and H(2)O for Rh(I) is the source of the observed dependence on O(2). In support of this mechanism, there is a significant kinetic isotope effect for the initial step, L(1)(OH(D))RhH(D)(+) + OH(D)(-) k(1)/k(-1) L(1)(OH(D))Rh(I) + H(D)(2)O, k(1H)/k(1D) = 1.7, and k(-1H)/k(-1D) = 3.0. The activation parameters for k(1) for trans-L(1)(OH)RhH(+) are DeltaH(++) = 64.6 +/- 1.3 kJ mol(-1) and DeltaS(++) = 40 +/-4 J mol(-1) K(-1).

  18. Structural sensitivity studies of ethylene hydrogenation on platinum and rhodium surfaces

    SciTech Connect

    Quinlan, M.A. |

    1996-01-01

    The catalytic hydrogenation of ethylene and hydrogen on the well characterized surfaces of the noble metals platinum and rhodium has been studied for the purposes of determining the relative activity of these two substrates as well as the degree of structure sensitivity. The Pt(111) and the Rh(755) single crystal surfaces,as well as Pt and Rh foils, were employed as substrates to study the effect of surface step structure on reactivity. In addition, vibrational spectroscopy studies were performed for ethylene adsorption on the stepped Rh(755) surface. The catalytic reaction were obtained using a combined ultrahigh vacuum chamber coupled with an atmospheric pressure reaction chamber that functioned as a batch reactor. Samples could be prepared using standard surface science techniques and characterized for surface composition and geometry using Auger Electron Spectroscopy and Low Energy Electron Diffraction. A comparison of the reactivity of Rh(111) with the results from this study on Rh(755) allows a direct determination of the effect of step structure on ethylene hydrogenation activity. Structure sensitivity is expected to exhibit orders of magnitude differences in rate as surface orientation is varied. In this case, no significant differences were found, confirming the structure insensitivity of this reaction over this metal. The turnover frequency of the Rh(111) surface, 5 {times} 10{sup 1} s{sup {minus}1}, is in relatively good agreement with the turnover frequency of 9 {times} 10{sup 1} s{sup {minus}1} measured for the Rh(755) surface. Rate measurements made on the Pt(111) surface and the Pt foil are in excellent agreement, both measuring 3 {times} 10{sup 2} s{sup minus}1. Likewise, it is concluded that no strong structure sensitivity for the platinum surfaces exists. High Resolution Electron Energy Loss Spectroscopy studies of adsorbed ethylene on the Rh(755) surface compare favorably with the ethylidyne spectra obtained on the Rh(111) and Rh(100) surfaces.

  19. Toxicity of platinum, palladium and rhodium to Daphnia magna in single and binary metal exposure experiments.

    PubMed

    Zimmermann, Sonja; Wolff, Carolina; Sures, Bernd

    2017-02-17

    Mainly due to automobile traffic, but also due to other sources, the platinum group elements (PGE) platinum (Pt), palladium (Pd) and rhodium (Rh) are introduced into aquatic biotopes where they accumulate in sediments of lakes and rivers. However, the toxicity of these noble metals to aquatic organisms is not well understood and especially toxicity studies under standardized condition are lacking. Thus, the toxicity of Pt, Pd and Rh to Daphnia magna was tested in single metal exposure experiments according to OECD guideline 202. Immobility and lethality was recorded after 24 h and 48 h of exposure and EC50 and LC50, respectively, were determined. As the nominal exposure concentration of Pd differed significantly from the quantified concentration, the control of the real exposure concentration by chemical analysis is mandatory, especially for Pd. The toxicity decreased in the order Pd > Pt ≫ Rh with e.g. LC50(48 h) values of 14 μg/L for Pd, 157 μg/L for Pt and 56,800 μg/L for Rh. The exposure period had a clear effect on the toxicity of Pt, Pd and Rh. For Pt and Rh the endpoint immobility was more sensitive than the endpoint lethality whereas Pd toxicity was similar for both endpoints. The Hill slopes, which are a measure for the steepness of the concentration-response curves, showed no significant discrepancies between the different metals. The binary metal exposure to Pt and Pd revealed a more-than-additive, i.e. a synergistic toxicity using the toxic unit approach. The present study is a start to understand the toxicity of interacting PGE. The modes of action behind the synergistic effect are unclear.

  20. Morphosyntax in Poor Comprehenders

    PubMed Central

    Adlof, Suzanne M.; Catts, Hugh W.

    2016-01-01

    Children described as poor comprehenders (PCs) have reading comprehension difficulties in spite of adequate word reading abilities. PCs are known to display weakness with semantics and higher-level aspects of oral language, but less is known about their grammatical skills, especially with regard to morphosyntax. The purpose of this study was to examine morphosyntax in fourth grade PCs and typically developing readers (TDs), using three experimental tasks involving finiteness marking. Participants also completed standardized, norm-referenced assessments of phonological memory, vocabulary, and broader language skills. PCs displayed weakness relative to TDs on all three morphosyntax tasks and on every other assessment of oral language except phonological memory, as indexed by nonword repetition. These findings help to clarify the linguistic profile of PCs, suggesting that their language weaknesses include grammatical weaknesses that cannot be fully explained by semantic factors. Because finiteness markers are usually mastered prior to formal schooling in typical development, we call for future studies to examine whether assessments of morphosyntax could be used for the early identification of children at risk for future reading comprehension difficulty. PMID:27397969

  1. A visible light responsive rhodium and antimony-codoped SrTiO3 powdered photocatalyst loaded with an IrO2 cocatalyst for solar water splitting.

    PubMed

    Asai, Rikako; Nemoto, Hiroaki; Jia, Qingxin; Saito, Kenji; Iwase, Akihide; Kudo, Akihiko

    2014-03-07

    IrO2-loaded SrTiO3 doped with rhodium and antimony synthesized by a conventional solid-state reaction splits water under visible light and simulated sunlight irradiation giving 0.1% of the apparent quantum yield at 420 nm. The response wavelength up to 500 nm is the longest among achieved photocatalytic water splitting with one-step photoexcitation.

  2. Treatment of ammonia by catalytic wet oxidation process over platinum-rhodium bimetallic catalyst in a trickle-bed reactor: effect of pH.

    PubMed

    Hung, Chang-Mao; Lin, Wei-Bang; Ho, Ching-Lin; Shen, Yun-Hwei; Hsia, Shao-Yi

    2010-08-01

    This work adopted aqueous solutions of ammonia for use in catalytic liquid-phase reduction in a trickle-bed reactor with a platinum-rhodium bimetallic catalyst, prepared by the co-precipitation of chloroplatinic acid (H2PtCl6) and rhodium nitrate [Rh(NO3)3]. The experimental results demonstrated that a minimal amount of ammonia was removed from the solution by wet oxidation in the absence of any catalyst, while approximately 97.0% of the ammonia was removed by wet oxidation over the platinum-rhodium bimetallic catalyst at 230 degrees C with an oxygen partial pressure of 2.0 MPa. The oxidation of ammonia has been studied as a function of pH, and the main reaction products were determined. A synergistic effect is manifest in the platinum-rhodium bimetallic structure, in which the material has the greatest capacity to reduce ammonia. The reaction pathway linked the oxidizing ammonia to nitric oxide, nitrogen, and water.

  3. Rhodium-catalyzed oxidative coupling of triarylmethanols with internal alkynes via successive C-H and C-C bond cleavages.

    PubMed

    Uto, Toshihiko; Shimizu, Masaki; Ueura, Kenji; Tsurugi, Hayato; Satoh, Tetsuya; Miura, Masahiro

    2008-01-04

    The rhodium-catalyzed oxidative coupling of triarylmethanols with internal alkynes effectively proceeds in a 1:2 manner via cleavage of C-H and C-C bonds to produce the corresponding naphthalene derivatives. Addition of tri- or tetraphenylcyclopentadiene as a ligand is crucial for the reaction to occur efficiently.

  4. Elucidation of the resting state of a rhodium NNN-pincer hydrogenation catalyst that features a remarkably upfield hydride (1)H NMR chemical shift.

    PubMed

    Hänninen, Mikko M; Zamora, Matthew T; MacNeil, Connor S; Knott, Jackson P; Hayes, Paul G

    2016-01-11

    Rhodium(I) alkene complexes of an NNN-pincer ligand catalyze the hydrogenation of alkenes, including ethylene. The terminal or resting state of the catalyst, which exhibits an unprecedentedly upfield Rh-hydride (1)H NMR chemical shift, has been isolated and a synthetic cycle for regenerating the catalytically active species has been established.

  5. Rhodium(III)-catalyzed allylic C-H bond amination. Synthesis of cyclic amines from ω-unsaturated N-sulfonylamines.

    PubMed

    Cochet, Thomas; Bellosta, Véronique; Roche, Didier; Ortholand, Jean-Yves; Greiner, Alfred; Cossy, Janine

    2012-11-11

    For the first time, intramolecular allylic amination was conducted using rhodium(III) according to an "inner-sphere" type mechanism with amines activated by only one electron-withdrawing group. The activation of C(sp(3))-H bonds was chemoselective and allows the access to a variety of substituted cyclic amines such as pyrrolidines and piperidines.

  6. Rhodium-Catalyzed Oxidative Benzannulation of N-Adamantyl-1-naphthylamines with Internal Alkynes via Dual C-H Bond Activation: Synthesis of Substituted Anthracenes.

    PubMed

    Zhang, Xuan; Yu, Xiaoqiang; Ji, Dingwei; Yamamoto, Yoshinori; Almansour, Abdulrahman I; Arumugam, Natarajan; Kumar, Raju Suresh; Bao, Ming

    2016-09-02

    Rhodium-catalyzed oxidative benzannulation of N-adamantyl-1-naphthylamines with internal alkynes to produce highly substituted anthracenes in satisfactory to good yields was developed. The annulation reaction proceeded smoothly under mild conditions in the presence of [Cp*RhCl2]2 as the precatalyst and Cu(OAc)2 as the oxidant.

  7. Rhodium-catalyzed asymmetric addition of arylboronic acids to cyclic N-sulfonyl ketimines towards the synthesis of α,α-diaryl-α-amino acid derivatives.

    PubMed

    Takechi, Ryosuke; Nishimura, Takahiro

    2015-05-07

    Rhodium/chiral diene complex-catalyzed asymmetric addition of arylboronic acids to cyclic ketimines having an ester group proceeded to give the corresponding α-amino acid derivatives in high yields with high enantioselectivity. The cyclic amino acid derivative was transformed into a linear α,α-diaryl-substituted α-N-methylamino acid ester.

  8. Synthesis of Multifunctionalized 2-Carbonylpyrrole by Rhodium-Catalyzed Transannulation of 1-Sulfonyl-1,2,3-triazole with β-Diketone.

    PubMed

    Cheng, Wanli; Tang, Yanhua; Xu, Ze-Feng; Li, Chuan-Ying

    2016-12-02

    A facile rhodium-catalyzed transannulation of 1-sulfonyl-1,2,3-triazoles with β-diketones was realized, and a series of multisubstituted 2-carbonylpyrroles were synthesized efficiently (up to 94% yield). The protocol features several advantages, such as readily available materials, mild reaction conditions, a concise operating procedure, a broad reaction scope, and excellent regioselectivity when benzoylacetone derivatives were used.

  9. Separation of platinum and rhodium from chloride solutions containing aluminum, magnesium and iron using solvent extraction and precipitation methods.

    PubMed

    Raju, B; Kumar, J Rajesh; Lee, Jin-Young; Kwonc, Hyuk-Sung; Kantam, M Lakshmi; Reddy, B Ramachandra

    2012-08-15

    The solvent extraction and precipitation methods have been used to develop a process to separate platinum and rhodium from a synthetic chloride solutions containing other associated metals such as (mg/L): Pt-364, Rh-62, Al-13880, Mg-6980, Fe-1308 at <1M HCl acidity. At pH 3.4, the quantitative precipitation of Al and Fe was achieved using 10 wt% Na(3)PO(4)·12H(2)O, with ~4% loss of Pt and Rh due to adsorption phenomenon. The selective separation of platinum was carried out with 0.01 M Aliquat 336 (a quaternary ammonium salt) at an aqueous to organic ratio (A/O) of 3.3 in two stages. Stripping of Pt from loaded organic (LO) at O/A ratio 6 with 0.5 M thiourea (tu) and HCl indicated that ~99.9% stripping efficiency. In stripping studies, needle like crystals of Pt were found and identified as tetrakis (thiourea) platinum (II) chloride ([Pt(tu)(4)]Cl(2)). The selective precipitation of rhodium was performed with (NH(4))(2)S from platinum free raffinate with a recovery of >99%. Copyright © 2012 Elsevier B.V. All rights reserved.

  10. Long-Term Testing of Rhodium-Based Catalysts for Mixed Alcohol Synthesis – 2013 Progress Report

    SciTech Connect

    Gerber, Mark A.; Gray, Michel J.; Thompson, Becky L.

    2013-09-23

    The U.S. Department of Energy’s Pacific Northwest National Laboratory has been conducting research since 2005 to develop a catalyst for the conversion of synthesis gas (carbon monoxide and hydrogen) into mixed alcohols for use in liquid transportation fuels. Initially, research involved screening possible catalysts based on a review of the literature, because at that time, there were no commercial catalysts available. The screening effort resulted in a decision to focus on catalysts containing rhodium and manganese. Subsequent research identified iridium as a key promoter for this catalyst system. Since then, research has continued to improve rhodium/manganese/iridium-based catalysts, optimizing the relative and total concentrations of the three metals, examining baseline catalysts on alternative supports, and examining effects of additional promoters. Testing was continued in FY 2013 to evaluate the performance and long-term stability of the best catalysts tested to date. Three tests were conducted. A long-term test of over 2300 hr duration at a single set of operating conditions was conducted with the best carbon-supported catalyst. A second test of about 650 hr duration at a single set of operating conditions was performed for comparison using the same catalyst formulation on an alternative carbon support. A third test of about 680 hr duration at a single set of operating conditions was performed using the best silica-supported catalyst tested to date.

  11. Reversed reactivity of anilines with alkynes in the rhodium-catalysed C–H activation/carbonylation tandem

    PubMed Central

    Midya, Siba P.; Sahoo, Manoj K.; Landge, Vinod G.; Rajamohanan, P. R.; Balaraman, Ekambaram

    2015-01-01

    Development of multicatalytic approach consisting of two or more mechanistically distinct catalytic steps using a single-site catalyst for rapid and straightforward access of structurally complex molecules under eco-benign conditions has significance in contemporary science. We have developed herein a rhodium-catalysed C–H activation strategy which uses an unprotected anilines and an electron-deficient alkynes to C–C bonded products as a potential intermediate in contrast to the archetypical C–N bonded products with high levels of regioselectivity. This is followed by carbonylation of C–H bond activated intermediate and subsequent annulation into quinolines has been described. This rhodium-catalysed auto-tandem reaction operates under mild, environmentally benign conditions using water as the solvent and CO surrogates as the carbonyl source with the concomitant generation of hydrogen gas. The strategy may facilitate the development of new synthetic protocols for the efficient and sustainable production of chemicals in an atom-economic way from simple, abundant starting materials. PMID:26486182

  12. Diastereoselective access to polyoxygenated polycyclic spirolactones through a rhodium-catalyzed [3+2] cycloaddition reaction: experimental and theoretical studies.

    PubMed

    Rodier, Fabien; Rajzmann, Michel; Parrain, Jean-Luc; Chouraqui, Gaëlle; Commeiras, Laurent

    2013-02-11

    The synthetic utility of γ-alkylidenebutenolides is demonstrated as highly competent dipolarophile partners in both intra- and intermolecular rhodium(II)-catalyzed 1,3-dipolar cycloaddition reactions. The strength of this approach lies in the formation of spiro[6,4]lactone moieties with the concomitant construction of quaternary spiro stereocenters. Typically, the construction of spirolactones involves an esterification step, which has often been reported as a "biosynthetic pathway", and often occurs either as or near to the final step of a total synthesis. Furthermore, a convergent and versatile route is reported for the formation of the (5,7) skeleton of molecules that were isolated from the Schisandra genus. Computational studies were performed to provide an overall picture of the mechanism of the intermolecular [3+2] cycloaddition between 2-diazo-1,3-ketoester and protoanemonin and to rationalize the empirical observations. In particular, we have demonstrated for the first time that the rhodium center plays an important role during the cyclization step itself and reacts with the dipolarophile as a complex with the ylide.

  13. Dimethylammonium hexanoate stabilized rhodium(0) nanoclusters identified as true heterogeneous catalysts with the highest observed activity in the dehydrogenation of dimethylamine-borane.

    PubMed

    Zahmakiran, Mehmet; Ozkar, Saim

    2009-09-21

    Herein we report the discovery of a superior dimethylamine-borane dehydrogenation catalyst, more active than the prior best heterogeneous catalyst (Jaska, C. A.; Manners, I. J. Am. Chem. Soc. 2004, 126, 9776) reported to date for the dehydrogenation of dimethylamine-borane. The new catalyst system consists of rhodium(0) nanoclusters stabilized by C(5)H(11)COO(-) anions and Me(2)H(2)N(+) cations and can reproducibly be formed from the reduction of rhodium(II) hexanoate during dehydrogenation of dimethylamine-borane at room temperature. Rhodium(0) nanoclusters in an average particle size of 1.9 +/- 0.6 nm Rh(0)(approximately 190) nanoclusters) provide 1040 turnovers over 26 h with a record initial turnover frequency (TOF) of 60 h(-1) (the average TOF value is 40 h(-1)) in the dehydrogenation of dimethylamine-borane, yielding 100% of the cyclic product (Me(2)NBH(2))(2) at room temperature. The work reported here also includes the full experimental details of the following major components: (i) Characterization of dimethylammonium hexanoate stabilized rhodium(0) nanoclusters by using TEM, STEM, EDX, XRD, UV-vis, XPS, FTIR, (1)H, (13)C, and (11)B NMR spectroscopy, and elemental analysis. (ii) Collection of a wealth of previously unavailable kinetic data to determine the rate law and activation parameters for catalytic dehydrogenation of dimethylamine-borane. (iii) Monitoring of the formation kinetics of the rhodium(0) nanoclusters by a fast dimethylamine-borane dehydrogenation catalytic reporter reaction (Watzky, M. A.; Finke, R. G. J. Am. Chem. Soc. 1997, 119, 10382) at various [Me(2)NH.BH(3)]/[Rh] ratios and temperatures. Significantly, sigmoidal kinetics of catalyst formation was found to be well fit to the two-step, slow nucleation and then autocatalytic surface growth mechanism, A --> B (rate constant k(1)) and A + B --> 2B (rate constant k(2)), in which A is [Rh(C(5)H(11)CO(2))(2)](2) and B is the growing, catalytically active rhodium(0) nanoclusters. (iv) Mercury

  14. Identification of intrinsic high-level resistance to rare-earth oxides and oxyanions in members of the class Proteobacteria: characterization of tellurite, selenite, and rhodium sesquioxide reduction in Rhodobacter sphaeroides.

    PubMed Central

    Moore, M D; Kaplan, S

    1992-01-01

    We have identified intrinsic high-level resistance (HLR) to tellurite, selenite, and at least 15 other rare-earth oxides and oxyanions in the facultative photoheterotroph Rhodobacter sphaeroides grown either chemoheterotrophically or photoheterotrophically. Other members of the class Proteobacteria, including members of the alpha-2 and alpha-3 phylogenetic subgroups, were also shown to effect the reduction of many of these compounds, although genera from the alpha-1, beta-1, and gamma-3 subgroups did not express HLR to the oxyanions examined. Detailed analyses employing R. sphaeroides have shown that HLR to at least one class of these oxyanions, the tellurite class (e.g., tellurate, tellurite, selenate, selenite, and rhodium sesquioxide), occurred via intracellular oxyanion reduction and resulted in deposition of metal in the cytoplasmic membrane. The concomitant evolution of hydrogen gas from cells grown photoheterotrophically in the presence of these oxyanions was also observed. HLR to tellurite class oxyanions in R. sphaeroides was not affected by exogenous methionine or phosphate but was reduced 40-fold by the addition of cysteine to growth media. In contrast HLR to the periodate class oxyanions (e.g., periodate, siliconate, and siliconite) was inhibited by extracellular PO4(3-) but did not result in metal deposition or gas evolution. Finally, we observed that HLR to arsenate class oxyanions (e.g., arsenate, molybdate, and tungstate) occurred by a third, distinct mechanism, as evidenced by the lack of intracellular metal deposition and hydrogen gas evolution and an insensitivity to extracellular PO4(3-) or cysteine. Examination of a number of R. sphaeroides mutants has determined the obligate requirement for an intact CO2 fixation pathway and the presence of a functional photosynthetic electron transport chain to effect HLR to K2TeO3 under photosynthetic growth conditions, whereas functional cytochromes bc1 and c2 were required under aerobic growth conditions

  15. Consequences of Growing Up Poor.

    ERIC Educational Resources Information Center

    Duncan, Greg J., Ed.; Brooks-Gunn, Jeanne, Ed.

    The consequences and correlates of growing up poor as well as the mechanisms through which poverty influences children are explored. This book is organized with a primary focus on research findings and a secondary concern with policy implications. The chapters are: (1) "Poor Families, Poor Outcomes: The Well-Being of Children and Youth" (Jeanne…

  16. Consequences of Growing Up Poor.

    ERIC Educational Resources Information Center

    Duncan, Greg J., Ed.; Brooks-Gunn, Jeanne, Ed.

    The consequences and correlates of growing up poor as well as the mechanisms through which poverty influences children are explored. This book is organized with a primary focus on research findings and a secondary concern with policy implications. The chapters are: (1) "Poor Families, Poor Outcomes: The Well-Being of Children and Youth" (Jeanne…

  17. Precipitate shape and coherency loss mechanisms in rhodium-gold alloys

    NASA Astrophysics Data System (ADS)

    Jing, Peihua

    The strength and creep properties of precipitate strengthened materials are controlled by the interactions of dislocations with obstacles, which depend on precipitate coherency, elastic and thermodynamic properties. Atomistic simulations have been performed to investigate the structure and coherency loss mechanisms of spherical precipitates in the gold--rhodium alloy system, the critical radius of coherency loss, and the interaction between dislocations and non-coherent precipitates. Sutton-Chen embedded atom method interatomic potentials have been derived to describe the elastic properties of Rh and Au, and the alloy thermodynamics. Molecular dynamics (MD) simulations have used the parallel MDCASK code, and have been visualized using the Common Neighbor Analysis (CNA) method and Atomeye software. The MD simulations of oversized Au precipitates and undersized Rh precipitates are discussed and analyzed as a function of precipitate radius. For Au precipitates, even the smallest 1.0 nm radius precipitate had lost coherency, with the defected matrix atoms forming an octahedral structure. Dislocation reaction analysis explains the observed structure of a network of Hirth dislocation and Shockley partial dislocations. As the precipitate size increases, additional Shockley partial dislocation loops emanate from the octahedron. The undersized Rh precipitates, from 1 to 4 nm radius, were also non-coherent. At 1 to 2 nm radius, coherency loss involved an octahedral-type structure in the matrix. However, with increasing Rh precipitate size, the coherency loss transitioned to internal precipitate deformation. Evidently, above a critical size, the excess volume associated with an undersized precipitate allows for significant deformation within the precipitate. MD simulations of an edge dislocation interacting with several obstacles have been analyzed in terms of the partial dislocation reactions using Thompson tetrahedron notation. These include an oversize {100} platelet and a

  18. Mixed N-Heterocyclic Carbene-Bis(oxazolinyl)borato Rhodium and Iridium Complexes in Photochemical and Thermal Oxidative Addition Reactions

    SciTech Connect

    Xu, Songchen; Manna, Kuntal; Ellern, Arkady; Sadow, Aaron D

    2014-12-08

    In order to facilitate oxidative addition chemistry of fac-coordinated rhodium(I) and iridium(I) compounds, carbene–bis(oxazolinyl)phenylborate proligands have been synthesized and reacted with organometallic precursors. Two proligands, PhB(OxMe2)2(ImtBuH) (H[1]; OxMe2 = 4,4-dimethyl-2-oxazoline; ImtBuH = 1-tert-butylimidazole) and PhB(OxMe2)2(ImMesH) (H[2]; ImMesH = 1-mesitylimidazole), are deprotonated with potassium benzyl to generate K[1] and K[2], and these potassium compounds serve as reagents for the synthesis of a series of rhodium and iridium complexes. Cyclooctadiene and dicarbonyl compounds {PhB(OxMe2)2ImtBu}Rh(η4-C8H12) (3), {PhB(OxMe2)2ImMes}Rh(η4-C8H12) (4), {PhB(OxMe2)2ImMes}Rh(CO)2 (5), {PhB(OxMe2)2ImMes}Ir(η4-C8H12) (6), and {PhB(OxMe2)2ImMes}Ir(CO)2 (7) are synthesized along with ToMM(η4-C8H12) (M = Rh (8); M = Ir (9); ToM = tris(4,4-dimethyl-2-oxazolinyl)phenylborate). The spectroscopic and structural properties and reactivity of this series of compounds show electronic and steric effects of substituents on the imidazole (tert-butyl vs mesityl), effects of replacing an oxazoline in ToM with a carbene donor, and the influence of the donor ligand (CO vs C8H12). The reactions of K[2] and [M(μ-Cl)(η2-C8H14)2]2 (M = Rh, Ir) provide {κ4-PhB(OxMe2)2ImMes'CH2}Rh(μ-H)(μ-Cl)Rh(η2-C8H14)2 (10) and {PhB(OxMe2)2ImMes}IrH(η3-C8H13) (11). In the former compound, a spontaneous oxidative addition of a mesityl ortho-methyl to give a mixed-valent dirhodium species is observed, while the iridium compound forms a monometallic allyl hydride. Photochemical reactions of dicarbonyl compounds 5 and 7 result in C–H bond oxidative addition providing the compounds {κ4-PhB(OxMe2)2ImMes'CH2}RhH(CO) (12) and {PhB(OxMe2)2ImMes}IrH(Ph)CO (13). In 12, oxidative addition results in cyclometalation of the mesityl ortho-methyl similar to 10, whereas the iridium compound reacts with the benzene solvent to give a rare crystallographically characterized cis

  19. Access to enantioenriched alpha-amino esters via rhodium-catalyzed 1,4-addition/enantioselective protonation.

    PubMed

    Navarre, Laure; Martinez, Rémi; Genet, Jean-Pierre; Darses, Sylvain

    2008-05-14

    Conjugate addition of potassium trifluoro(organo)borates 2 to dehydroalanine derivatives 1, mediated by a chiral rhodium catalyst and in situ enantioselective protonation, afforded straightforward access to a variety of protected alpha-amino esters 3 with high yields and enantiomeric excesses up to 95%. Among the tested chiral ligands and proton sources, Binap, in combination with guaiacol (2-methoxyphenol), an inexpensive and nontoxic phenol, afforded the highest asymmetric inductions. Organostannanes have also shown to participate in this reaction. By a fine-tuning of the ester moiety, and using Difluorophos as chiral ligand, increased levels of enantioselectivity, generally close to 95%, were achieved. Deuterium labeling experiments revealed, and DFT calculation supported, an unusual mechanism involving a hydride transfer from the amido substituent to the alpha carbon explaining the high levels of enantioselectivity attained in controlling this alpha chiral center.

  20. Rhodium-Catalyzed Acyloxy Migration of Propargylic Esters in Cycloadditions, Inspiration from Recent “Gold Rush”

    PubMed Central

    Shu, Xing-Zhong; Shu, Dongxu; Schienebeck, Casi M.

    2012-01-01

    Transition metal-catalyzed acyloxy migration of propargylic esters offers versatile entries to allene and vinyl carbene intermediates for various fascinating subsequent transformations. Most π-acidic metals (e.g. gold and platinum) are capable of facilitating these acyloxy migration events. However, very few of these processes involve redox chemistry, which are well-known for most other transition metals such as rhodium. The coupling of acyloxy migration of propargylic esters with oxidative addition, migratory insertion, and reductive elimination may lead to ample new opportunities for the design of new reactions. This tutorial review summarizes recent developments in Rh-catalyzed 1,3- and 1,2-acyloxy migration of propargylic esters in a number of cycloaddition reactions. Related Au- and Pt-catalyzed cycloadditions involving acyloxy migration are also discussed. PMID:22895533

  1. Rhodium-Catalyzed Synthesis of Chiral Spiro-9-silabifluorenes by Dehydrogenative Silylation: Mechanistic Insights into the Construction of Tetraorganosilicon Stereocenters.

    PubMed

    Murai, Masahito; Takeuchi, Yutaro; Yamauchi, Kanae; Kuninobu, Yoichiro; Takai, Kazuhiko

    2016-04-18

    Mechanistic insight into the construction of quaternary silicon chiral centers by rhodium-catalyzed synthesis of spiro-9-silabifluorenes through dehydrogenative silylation is reported. The C2 -symmetric bisphosphine ligand, BINAP, was effective in controlling enantioselectivity, and axially chiral spiro-9-silabifluorenes were obtained in excellent yields with high enantiomeric excess. Monitoring of the reaction revealed the presence of a monohydrosilane intermediate as a mixture of two constitutional isomers. The reaction proceeded through two consecutive dehydrogenative silylations, and the absolute configuration was determined in the first silylative cyclization. Competitive reactions with electron-rich and electron-deficient dihydrosilanes indicated that the rate of silylative cyclization increased with decreasing electron density on the silicon atom of the starting dihydrosilane. Further investigation disclosed a rare interconversion between the two constitutional isomers of the monohydrosilane intermediate with retention of the absolute configuration.

  2. Carboxylic acids as traceless directing groups for the rhodium(III)-catalyzed decarboxylative C-H arylation of thiophenes.

    PubMed

    Zhang, Yuanfei; Zhao, Huaiqing; Zhang, Min; Su, Weiping

    2015-03-16

    A rhodium(III)-catalyzed carboxylic acid directed decarboxylative C-H/C-H cross-coupling of carboxylic acids with thiophenes has been developed. With a slight adjustment of the reaction conditions based on the nature of the substrates, aryl carboxylic acids with a variety of substituents could serve as suitable coupling partners, and a broad variety of functional groups were tolerated. This method provides straightforward access to biaryl scaffolds with diverse substitution patterns, many of which have conventionally been synthesized through lengthy synthetic sequences. An illustrative example is the one-step gram-scale synthesis of a biologically active 3,5-substituted 2-arylthiophene by way of the current method.

  3. A monofunctional platinum complex coordinated to a rhodium metalloinsertor selectively binds mismatched DNA in the minor groove.

    PubMed

    Weidmann, Alyson G; Barton, Jacqueline K

    2015-10-05

    We report the synthesis and characterization of a bimetallic complex derived from a new family of potent and selective metalloinsertors containing an unusual Rh-O axial coordination. This complex incorporates a monofunctional platinum center containing only one labile site for coordination to DNA, rather than two, and coordinates DNA nonclassically through adduct formation in the minor groove. This conjugate displays bifunctional, interdependent binding of mismatched DNA via metalloinsertion at a mismatch as well as covalent platinum binding. DNA sequencing experiments revealed that the preferred site of platinum coordination is not the traditional N7-guanine site in the major groove, but rather N3-adenine in the minor groove. The complex also displays enhanced cytotoxicity in mismatch repair-deficient and mismatch repair-proficient human colorectal carcinoma cell lines compared to the chemotherapeutic cisplatin, and it triggers cell death via an apoptotic pathway, rather than the necrotic pathway induced by rhodium metalloinsertors.

  4. Mechanism, reactivity, and regioselectivity in rhodium-catalyzed asymmetric ring-opening reactions of oxabicyclic alkenes: a DFT Investigation

    NASA Astrophysics Data System (ADS)

    Qi, Zheng-Hang; Zhang, Yi; Gao, Yun; Zhang, Ye; Wang, Xing-Wang; Wang, Yong

    2017-01-01

    The origin of the enantio- and regioselectivity of ring-opening reaction of oxabicyclic alkenes catalyzed by rhodium/Josiphos has been examined using M06-2X density functional theory(DFT). DFT calculations predict a 98% ee for the enantioselectivity and only the 1,2-trans product as one regio- and diastereomer, in excellent agreement with experimental results. The solvent tetrahydrofuran(THF) plays a key role in assisting nucleophilic attack. Orbital composition analysis of the LUMO and the NPA atomic charge calculations were conducted to probe the origins of the regioselectivity. The orbital composition analysis reveals two potential electrophilic sites of the Rh-π-allyl intermediate M3 and the NPA atomic charges demonstrate that Cα carries more positive charges than Cγ, which suggests that Cα is the electrophilic site.

  5. Stepwise construction of discrete parallelogram- and prism-shaped organometallic architectures based on half-sandwich rhodium fragments.

    PubMed

    Gao, Wen-Xi; Lin, Yue-Jian; Jin, Guo-Xin

    2017-08-08

    Herein we describe how to take advantage of a multifunctional ligand to conveniently control the shapes and sizes of different types of discrete organometallic assemblies. Using a versatile ligand 2-(pyridin-2-yl)-1H-imidazole-4,5-dicarboxylate (HL(2-)), which features three kinds of chelating sites, together with half-sandwich rhodium fragments, a series of discrete organometallic complexes with tetranuclear parallelogram and hexanuclear trigonal prism shapes were achieved. The isomerization of the hexanuclear assemblies was confirmed by single-crystal X-ray diffraction analysis. The results also reiterate that pyridyl-substituted imidazole-4,5-dicarboxylate ligands can be used as multifunctional organic scaffolds in the construction of elegant architectures.

  6. Study of activation cross-sections of deuteron induced reactions on rhodium up to 40 MeV

    NASA Astrophysics Data System (ADS)

    Ditrói, F.; Tárkányi, F.; Takács, S.; Hermanne, A.; Yamazaki, H.; Baba, M.; Mohammadi, A.; Ignatyuk, A. V.

    2011-09-01

    In the frame of a systematic study of the activation cross-sections of deuteron induced nuclear reactions, excitation functions of the 103Rh(d,x) 100,101,103Pd, 100g,101m,101g,102m,102gRh and 103gRu reactions were determined up to 40 MeV. Cross-sections were measured with the activation method using a stacked foil irradiation technique. Excitation functions of the contributing reactions were calculated using the ALICE-IPPE, EMPIRE-II and TALYS codes. From the measured cross-section data integral production yields were calculated and compared with experimental integral yield data reported in the literature. From the measured cross-sections and previous data, activation curves were deduced to support thin layer activation (TLA) on rhodium and Rh containing alloys.

  7. Design of luminescent biotinylation reagents derived from cyclometalated iridium(III) and rhodium(III) bis(pyridylbenzaldehyde) complexes.

    PubMed

    Leung, Siu-Kit; Kwok, Karen Ying; Zhang, Kenneth Yin; Lo, Kenneth Kam-Wing

    2010-06-07

    A new class of luminescent biotinylation reagents derived from cyclometalated iridium(III) and rhodium(III) bis(pyridylbenzaldehyde) biotin complexes, [Ir(pba)(2)(bpy-C6-biotin)](PF(6)) (1), [Ir(pba)(2)(bpy-TEG-biotin)](PF(6)) (2), and [Rh(pba)(2)(bpy-C6-biotin)](PF(6)) (3), together with their biotin-free counterparts [Ir(pba)(2)(bpy-Et)](PF(6)) (4) and [Rh(pba)(2)(bpy-Et)](PF(6)) (5) [Hpba = 4-(2-pyridyl)benzaldehyde, bpy-C6-biotin = 4-[(6-biotinamido)hexylaminocarbonyl]-4'-methyl-2,2'-bipyridine, bpy-TEG-biotin = 4-[(13-biotinamido-4,7,10-trioxa)tridecylaminocarbonyl]-4'-methyl-2,2'-bipyridine, bpy-Et = 4-(ethylaminocarbonyl)-4'-methyl-2,2'-bipyridine], have been synthesized and characterized and their photophysical and electrochemical properties studied. Upon photoexcitation, the iridium(III) complexes 1, 2, and 4 exhibited intense and long-lived orange-yellow luminescence in fluid solutions at 298 K and in rigid glass at 77 K. The rhodium(III) complexes 3 and 5 were weakly emissive in fluid solutions at 298 K but showed intense luminescence in low-temperature glass. In view of the structured emission profiles and the long lifetimes, the emission of all of the complexes has been assigned to a triplet intraligand ((3)IL) (pi --> pi*) (pba) excited state, which was probably mixed with some triplet metal-to-ligand charge-transfer ((3)MLCT) [dpi(Ir or Rh) --> pi*(pba)] character. To investigate the reactivity of the aldehyde groups, complex 2 was reacted with n-butylamine, resulting in the formation of the complex [Ir(ppy-CH(2)NHC(4)H(9))(2)(bpy-TEG-biotin)](PF(6)) (2a) [Hppy-CH(2)NHC(4)H(9) = 2-[4-[N-(n-butyl)aminomethyl]phenyl]pyridine]. All of the aldehyde complexes have been used to biotinylate bovine serum albumin (BSA) to form bioconjugates 1-BSA-5-BSA. The bioconjugates have been isolated, purified, and characterized and their photophysical properties studied. Upon photoexcitation, all of the bioconjugates were luminescent and the emission has been

  8. Rhodium/Silver Synergistic Catalysis in Highly Enantioselective Cycloisomerization/Cross Coupling of Keto-Vinylidenecyclopropanes with Terminal Alkynes.

    PubMed

    Yang, Song; Rui, Kang-Hua; Tang, Xiang-Ying; Xu, Qin; Shi, Min

    2017-04-07

    A rhodium/silver synergistic catalysis has been established, enabling cycloisomerization/cross coupling of keto-vinylidenecyclopropanes with terminal alkynes toward the regio- and enantioselective formation of diversified tetrahydropyridin-3-ol tethered 1,4-enynes in good yields and high ee values. In this synergistic catalysis, Rh(I) and Ag(I) catalysts selectively activate keto-VDCP substrates and terminal alkynes to generate -allyl Rh(III) complex of oxa-rhodacyclic intermediate and Ag alkynyl intermediate, respectively. The rapid transmetalation of alkynyl groups from Ag to Rh is proposed to play a key role to realize the regioselective cleavage of distal bond of the three-membered ring in this transformation.

  9. Mechanism, reactivity, and regioselectivity in rhodium-catalyzed asymmetric ring-opening reactions of oxabicyclic alkenes: a DFT Investigation

    PubMed Central

    Qi, Zheng-Hang; Zhang, Yi; Gao, Yun; Zhang, Ye; Wang, Xing-Wang; Wang, Yong

    2017-01-01

    The origin of the enantio- and regioselectivity of ring-opening reaction of oxabicyclic alkenes catalyzed by rhodium/Josiphos has been examined using M06-2X density functional theory(DFT). DFT calculations predict a 98% ee for the enantioselectivity and only the 1,2-trans product as one regio- and diastereomer, in excellent agreement with experimental results. The solvent tetrahydrofuran(THF) plays a key role in assisting nucleophilic attack. Orbital composition analysis of the LUMO and the NPA atomic charge calculations were conducted to probe the origins of the regioselectivity. The orbital composition analysis reveals two potential electrophilic sites of the Rh–π-allyl intermediate M3 and the NPA atomic charges demonstrate that Cα carries more positive charges than Cγ, which suggests that Cα is the electrophilic site. PMID:28074930

  10. A Monofunctional Platinum Complex Coordinated to a Rhodium Metalloinsertor Selectively Binds Mismatched DNA in the Minor Groove

    PubMed Central

    Weidmann, Alyson G.; Barton, Jacqueline K.

    2015-01-01

    We report the synthesis and characterization of a bimetallic complex derived from a new family of potent and selective metalloinsertors containing an unusual Rh—O axial coordination. This complex incorporates a monofunctional platinum center containing only one labile site for coordination to DNA, rather than two, and coordinates DNA non-classically through adduct formation in the minor groove. This conjugate displays bifunctional, interdependent binding of mismatched DNA via metalloinsertion at a mismatch as well as covalent platinum binding. DNA sequencing experiments revealed that the preferred site of platinum coordination is not the traditional N7-guanine site in the major groove, but rather N3-adenine in the minor groove. The complex also displays enhanced cytotoxicity in mismatch repair-deficient and mismatch repair-proficient human colorectal carcinoma cell lines compared to the chemotherapeutic cisplatin, and triggers cell death via an apoptotic pathway, rather than the necrotic pathway induced by rhodium metalloinsertors. PMID:26397309

  11. Rhodium(I)-Complexes Catalyzed 1,4-Conjugate Addition of Arylzinc Chlorides to N-Boc-4-pyridone.

    PubMed

    Guo, Fenghai; McGilvary, Matthew A; Jeffries, Malcolm C; Graves, Briana N; Graham, Shekinah A; Wu, Yuelin

    2017-05-01

    Rhodium(I)-complexes catalyzed the 1,4-conjugate addition of arylzinc chlorides to N-Boc-4-pyridone in the presence of chlorotrimethylsilane (TMSCl). A combination of [RhCl(C₂H₄)₂]₂ and BINAP was determined to be the most effective catalyst to promote the 1,4-conjugate addition reactions of arylzinc chlorides to N-Boc-4-pyridone. A broad scope of arylzinc reagents with both electron-withdrawing and electron-donating substituents on the aromatic ring successfully underwent 1,4-conjugate addition to N-Boc-4-pyridone to afford versatile 1,4-adducts 2-substituted-2,3-dihydropyridones in good to excellent yields (up to 91%) and excellent ee (up to 96%) when (S)-BINAP was used as chiral ligand.

  12. Synthesis and application of Amberlite xad-4 functionalized with alizarin red-s for preconcentration and adsorption of rhodium (III)

    PubMed Central

    2012-01-01

    A new chelating resin was prepared by coupling Amberlite XAD-4 with alizarin red-s through an azo spacer, characterized by infra-red spectroscopy and thermal analysis and studied for Rh(III) preconcentration using inductively coupled plasma atomic emission spectroscopy (ICP-AES) for rhodium monitoring in the environment. The optimum pH for sorption of the metal ion was 6.5. The sorption capacity was found 2.1 mg/g of resin for Rh(III). A recovery of 88% was obtained for the metal ion with 1.5 M HCl as eluting agent. Kinetic adsorption data were analyzed by adsorption and desorption times of Rh(III) on modified resin. Scat chard analysis revealed that the homogeneous binding sites were formed in the polymers. The linear regression equation was Q/C = –1.3169Q + 27.222 (R2 = 0.9239), for Rh were formed in the SPE sorbent,Kd and Qmax for the affinity binding sites were calculated to be 0.76 μmol/mL and 20.67 μmol/g, respectively. The equilibrium data and parameters of Rh(III) adsorption on modified resin were analyzed by Langmuir, Freundlich, Temkin and Redlich–Peterson models. The experimental adsorption isotherm was in good concordance with Langmuir and Freundlich models (R2 > 0.998) and based on the Langmuir isotherm the maximum amount of adsorption (qmax) was 4.842 mg/g. The method was applied for rhodium ions determination in environmental samples. with high recovery (>80%). PMID:23369526

  13. Podiform chromite deposits--database and grade and tonnage models

    USGS Publications Warehouse

    Mosier, Dan L.; Singer, Donald A.; Moring, Barry C.; Galloway, John P.

    2012-01-01

    Chromite ((Mg, Fe++)(Cr, Al, Fe+++)2O4) is the only source for the metallic element chromium, which is used in the metallurgical, chemical, and refractory industries. Podiform chromite deposits are small magmatic chromite bodies formed in the ultramafic section of an ophiolite complex in the oceanic crust. These deposits have been found in midoceanic ridge, off-ridge, and suprasubduction tectonic settings. Most podiform chromite deposits are found in dunite or peridotite near the contact of the cumulate and tectonite zones in ophiolites. We have identified 1,124 individual podiform chromite deposits, based on a 100-meter spatial rule, and have compiled them in a database. Of these, 619 deposits have been used to create three new grade and tonnage models for podiform chromite deposits. The major podiform chromite model has a median tonnage of 11,000 metric tons and a mean grade of 45 percent Cr2O3. The minor podiform chromite model has a median tonnage of 100 metric tons and a mean grade of 43 percent Cr2O3. The banded podiform chromite model has a median tonnage of 650 metric tons and a mean grade of 42 percent Cr2O3. Observed frequency distributions are also given for grades of rhodium, iridium, ruthenium, palladium, and platinum. In resource assessment applications, both major and minor podiform chromite models may be used for any ophiolite complex regardless of its tectonic setting or ophiolite zone. Expected sizes of undiscovered podiform chromite deposits, with respect to degree of deformation or ore-forming process, may determine which model is appropriate. The banded podiform chromite model may be applicable for ophiolites in both suprasubduction and midoceanic ridge settings.

  14. The Etiology of Poor Neighborhoods.

    ERIC Educational Resources Information Center

    Greenberg, Stanley B.

    The inner city aggregations of blacks, Appalachian whites, and Mexicans are not simply the focal points for short-term instability or remedial governmental programs: they are the first native American urban poor. The poor neighborhoods of America's inner city are a result of three great population movements. One originated in the Atlantic Coastal…

  15. Federal Supervisors and Poor Performers

    DTIC Science & Technology

    1999-07-01

    This report looks at the prevalence of poor performance in the Federal workplace from the perspective of employees and supervisors. The report also...examines what supervisors do about poor performers, the effects of supervisors’ actions, and the factors that influence supervisors’ decisions about how they will handle inadequate performance.

  16. A DFT based investigation into the electronic structure and properties of hydride rich rhodium clusters.

    PubMed

    Brayshaw, Simon K; Green, Jennifer C; Hazari, Nilay; Weller, Andrew S

    2007-05-14

    Density functional theory has been used to investigate the structures, bonding and properties of a family of hydride rich late transition metal clusters of the type [Rh(6)(PH(3))(6)H(12)](x) (x = 0, +1, +2, +3 or +4), [Rh(6)(PH(3))(6)H(16)](x) (x = +1 or +2) and [Rh(6)(PH(3))(6)H(14)](x) (x = 0, +1 or +2). The positions of the hydrogen atoms around the pseudo-octahedral Rh(6) core in the optimized structures of [Rh(6)(PH(3))(6)H(12)](x) (x = 0, +1, +2, +3 or +4) varied depending on the overall charge on the cluster. The number of semi-bridging hydrides increased (semi-bridging hydrides have two different Rh-H bond distances) as the charge on the cluster increased and simultaneously the number of perfectly bridging hydrides (equidistant between two Rh centers) decreased. This distortion maximized the bonding between the hydrides and the metal centers and resulted in the stabilization of orbitals related to the 2T(2g) set in a perfectly octahedral cluster. In contrast, the optimized structures of the 16-hydride clusters [Rh(6)(PH(3))(6)H(12)](x) (x = +1 or +2) were similar and both clusters contained an interstitial hydride, along with one terminal hydride, ten bridging hydrides and two coordinated H(2) molecules which were bound to two rhodium centers in an eta(2):eta(1)-fashion. All the hydrides were on the outside of the Rh(6) core in the lowest energy structures of the 14-hydride clusters [Rh(6)(PH(3))(6)H(14)] and [Rh(6)(PH(3))(6)H(14)](+), which both contained eleven bridging hydrides, one terminal hydride and one coordinated H(2) molecule. Unfortunately, the precise structure of [Rh(6)(PH(3))(6)H(14)](2+) could not be determined as structures both with and without an interstitial hydride were of similar energy. The reaction energetics for the uptake and release of two molecule of H(2) by a cycle consisting of [Rh(6)(PH(3))(6)H(12)](2+), [Rh(6)(PH(3))(6)H(16)](2+), [Rh(6)(PH(3))(6)H(14)](+), [Rh(6)(PH(3))(6)H(12)](+) and [Rh(6)(PH(3))(6)H(14)](2+) were modelled

  17. CATALYTIC INTERACTIONS OF RHODIUM, RUTHENIUM, AND MERCURY DURING SIMULATED DWPF CPC PROCESSING WITH HYDROGEN GENERATION

    SciTech Connect

    Koopman, D

    2008-10-09

    Simulations of the Defense Waste Processing Facility (DWPF) Chemical Processing Cell (CPC) vessels were performed as part of the ongoing investigation into catalytic hydrogen generation. Rhodium, ruthenium, and mercury have been identified as the principal elemental factors affecting the peak hydrogen generation rate in the DWPF Sludge Receipt and Adjustment Tank (SRAT) for a given acid addition. The primary goal of this study is to identify any significant interactions between the three factors. Noble metal concentrations were similar to recent sludge batches. Rh ranged from 0.0026-0.013% and Ru ranged from 0.010-0.050% in the dried sludge solids, while initial Hg ranged from 0.5-2.5 wt%. An experimental matrix was developed to ensure that the existence of statistically significant two-way interactions could be determined without confounding of the main effects with the two-way interaction effects. The nominal matrix design consisted of twelve SRAT cycles. Testing included: a three factor (Rh, Ru, and Hg) study at two levels per factor (eight runs), two duplicate midpoint runs, and two additional replicate runs to assess reproducibility away from the midpoint. Midpoint testing can identify potential quadratic effects from the three factors. A single sludge simulant was used for all tests. Acid addition was kept effectively constant except to compensate for variations in the starting mercury concentration. Six Slurry Mix Evaporator (SME) cycles were performed to supplement the SME hydrogen generation database. Some of the preliminary findings from this study include: (1) Rh was linked to the maximum SRAT hydrogen generation rate in the first two hours after acid addition in preliminary statistical modeling. (2) Ru was linked conclusively to the maximum SRAT hydrogen generation rate in the last four hours of reflux in preliminary statistical modeling. (3) Increasing the ratio of Hg/Rh shifted the noble metal controlling the maximum SRAT hydrogen generation rate from

  18. Rhodium-catalyzed [(3+2)+2] carbocyclization of alkynylidenecyclopropanes with substituted allenes: stereoselective construction of tri- and tetrasubstituted exocyclic olefins.

    PubMed

    Evans, P Andrew; Negru, Daniela E; Shang, Deju

    2015-04-13

    The development of the stereoselective rhodium-catalyzed [(3+2)+2] carbocyclization of alkynylidenecyclopropanes (ACPs) with substituted allenes is described. This work demonstrates that activated and unactivated allenes preferentially undergo carbometalation at the distal terminus to generate tri- and tetrasubstituted exocyclic olefins with a neutral rhodium catalyst. In addition, this method provides a strategy for the total synthesis of the guaiane family of sesquiterpenes, which are not directly accessible using alkynes as exogenous π-components. Finally, the preparation of the bicyclo[5.4.0]undecane ring system using a homologated ACP tether serves to further illustrate the versatility of this approach. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Partitioning of rhodium and ruthenium between Pd-Rh-Ru and (Ru,Rh)O2 solid solutions in high-level radioactive waste glass

    NASA Astrophysics Data System (ADS)

    Sugawara, Toru; Ohira, Toshiaki; Komamine, Satoshi; Ochi, Eiji

    2015-10-01

    The partitioning of rhodium and ruthenium between Pd-Rh-Ru alloy with a face-centered cubic (FCC) structure and (Ru,Rh)O2 solid solution has been investigated between 1273 and 1573 K at atmospheric oxygen fugacity. The rhodium and ruthenium contents in FCC increase, while the RhO2 content in (Ru,Rh)O2 decreases with increasing temperature due to progressive reduction of the system. Based on the experimental results and previously reported thermodynamic data, the thermodynamic mixing properties of FCC phase and (Ru,Rh)O2 have been calibrated in an internally consistent manner. Phase equilibrium of platinum grope metals in an HLW glass was calculated by using the obtained thermodynamic parameters.

  20. Rhodium-catalyzed acyl-transfer reaction between benzyl ketones and thioesters: synthesis of unsymmetric ketones by ketone CO-C bond cleavage and intermolecular rearrangement.

    PubMed

    Arisawa, Mieko; Kuwajima, Manabu; Toriyama, Fumihiko; Li, Guangzhe; Yamaguchi, Masahiko

    2012-07-20

    In the presence of catalytic amounts of RhH(CO)(PPh3)3 and 1,2-bis(diphenylphosphino)benzene (dppBz), acyl groups were transferred between benzyl ketones and thioesters/aryl esters. The rhodium complex catalyzed the cleavage of ketone CO-C bonds and intermolecular rearrangement giving unsymmetric ketones. The acyl-transfer reaction also occurred with 1-(p-chlorophenyl)-3-(p-cyanophenyl)propane-2-one giving unsymmetric ketones.

  1. Rhodium-Catalyzed NH-Indole-Directed C-H Carbonylation with Carbon Monoxide: Synthesis of 6H-Isoindolo[2,1-a]indol-6-ones.

    PubMed

    Huang, Qiufeng; Han, Qingshuai; Fu, Shurong; Yao, Zizhu; Su, Lv; Zhang, Xiaofeng; Lin, Shen; Xiang, Shengchang

    2016-12-16

    An efficient synthesis of 6H-isoindolo[2,1-a]indol-6-ones through rhodium-catalyzed NH-indole-directed C-H carbonylation of 2-arylindoles with carbon monoxide has been developed. Preliminary mechanistic studies revealed that this reaction proceeds via N-H bond cleavage and subsequent C-H bond cleavage. Reaction monitoring via ESI-MS was used to support the formation of five-membered rhodacycle species in the catalytic cycle.

  2. Oligomeric complexes of some heteroaromatic ligands and aromatic diamines with rhodium and molybdenum tetracarboxylates: 13C and 15N CPMAS NMR and density functional theory studies.

    PubMed

    Leniak, Arkadiusz; Kamieński, Bohdan; Jaźwiński, Jarosław

    2015-05-01

    Seven new oligomeric complexes of 4,4'-bipyridine; 3,3'-bipyridine; benzene-1,4-diamine; benzene-1,3-diamine; benzene-1,2-diamine; and benzidine with rhodium tetraacetate, as well as 4,4'-bipyridine with molybdenum tetraacetate, have been obtained and investigated by elemental analysis and solid-state nuclear magnetic resonance spectroscopy, (13)C and (15)N CPMAS NMR. The known complexes of pyrazine with rhodium tetrabenzoate, benzoquinone with rhodium tetrapivalate, 4,4'-bipyridine with molybdenum tetrakistrifluoroacetate and the 1 : 1 complex of 2,2'-bipyridine with rhodium tetraacetate exhibiting axial-equatorial ligation mode have been obtained as well for comparison purposes. Elemental analysis revealed 1 : 1 complex stoichiometry of all complexes. The (15)N CPMAS NMR spectra of all new complexes consist of one narrow signal, indicating regular uniform structures. Benzidine forms a heterogeneous material, probably containing linear oligomers and products of further reactions. The complexes were characterized by the parameter complexation shift Δδ (Δδ = δcomplex  - δligand). This parameter ranged from around -40 to -90 ppm in the case of heteroaromatic ligands, from around -12 to -22 ppm for diamines and from -16 to -31 ppm for the complexes of molybdenum tetracarboxylates with 4,4'-bipyridine. The experimental results have been supported by a density functional theory computation of (15)N NMR chemical shifts and complexation shifts at the non-relativistic Becke, three-parameter, Perdew-Wang 91/[6-311++G(2d,p), Stuttgart] and GGA-PBE/QZ4P levels of theory and at the relativistic scalar and spin-orbit zeroth order regular approximation/GGA-PBE/QZ4P level of theory. Nucleus-independent chemical shifts have been calculated for the selected compounds. Copyright © 2015 John Wiley & Sons, Ltd.

  3. Rhodium-Catalyzed Hydroacylation of para-Quinone Methides with Salicylaldehydes: An Approach to α,α-Diaryl-2-Hydroxy Acetophenones.

    PubMed

    Yang, Chi; Gao, Shang; Yao, Hequan; Lin, Aijun

    2016-12-02

    A rhodium-catalyzed hydroacylation of para-quinone methides (p-QMs) with salicylaldehydes has been disclosed. This method allows for the construction of α,α-diaryl-2-hydroxy acetophenones through tandem C-H activation/C-C bond formation/aromatization process. Moreover, this unprecedented hydroacylation of trisubstituted alkenes exhibits good yields with broad functional group tolerance as well as gram-scale capacity.

  4. Rhodium, iridium and nickel complexes with a 1,3,5-triphenylbenzene tris-MIC ligand. Study of the electronic properties and catalytic activities

    PubMed Central

    Mejuto, Carmen; Royo, Beatriz

    2015-01-01

    Summary The coordination versatility of a 1,3,5-triphenylbenzene-tris-mesoionic carbene ligand is illustrated by the preparation of complexes with three different metals: rhodium, iridium and nickel. The rhodium and iridium complexes contained the [MCl(COD)] fragments, while the nickel compound contained [NiCpCl]. The preparation of the tris-MIC (MIC = mesoionic carbene) complex with three [IrCl(CO)2] fragments, allowed the estimation of the Tolman electronic parameter (TEP) for the ligand, which was compared with the TEP value for a related 1,3,5-triphenylbenzene-tris-NHC ligand. The electronic properties of the tris-MIC ligand were studied by cyclic voltammetry measurements. In all cases, the tris-MIC ligand showed a stronger electron-donating character than the corresponding NHC-based ligands. The catalytic activity of the tri-rhodium complex was tested in the addition reaction of arylboronic acids to α,β-unsaturated ketones. PMID:26734104

  5. Hydrogen generation from water/methanol under visible light using aerogel prepared strontium titanate (SrTiO3) nanomaterials doped with ruthenium and rhodium metals.

    PubMed

    Kuo, Yenting; Klabunde, Kenneth J

    2012-07-27

    Nanostructured strontium titanate visible-light-driven photocatalysts containing rhodium and ruthenium were synthesized by a modified aerogel synthesis using ruthenium chloride and rhodium nitrate as dopant precursors, and titanium isopropoxide and strontium metal as the metal sources. The well-defined crystalline SrTiO(3) structure was confirmed by means of x-ray diffraction. After calcination at 500 °C, diffuse reflectance spectroscopy shows an increase in light absorption at 370 nm due to the presence of Rh(3 + ); however an increase of the calcination temperature to 600 °C led to a decrease in intensity, probably due to a loss of surface area. An increase in the rhodium doping level also led to an increase in absorption at 370 nm; however, the higher amounts of dopant lowered the photocatalytic activity. The modified aerogel synthesis allows greatly enhanced H(2) production performance from an aqueous methanol solution under visible light irradiation compared with lower surface area conventional materials. We believe that this enhanced activity is due to the higher surface areas while high quality nanocrystalline materials are still obtained. Furthermore, the surface properties of these nanocrystalline aerogel materials are different, as exhibited by the higher activities in alkaline solutions, while conventional materials (obtained via high temperature solid-state synthesis methods) only exhibit reasonable hydrogen production in acidic solutions. Moreover, an aerogel synthesis approach gives the possibility of thin-film formation and ease of incorporation into practical solar devices.

  6. The interaction of hydrazine with an Rh(1 1 1) surface as a model for adsorption to rhodium nanoparticles: A dispersion-corrected DFT study

    NASA Astrophysics Data System (ADS)

    He, Yan Bin; Jia, Jian Feng; Wu, Hai Shun

    2015-02-01

    In recent years, metal nanoparticles were found to be excellent catalysts for hydrogen generation from hydrazine for chemical hydrogen storage. In order to gain a better understanding of these catalytic systems, we have simulated the adsorption of hydrazine on rhodium nanoparticles surfaces by density functional theory (DFT) calculations with dispersion correction, DFT-D3 in the method of Grimme. The rhodium nanoparticles were modeled by the Rh(1 1 1) surface, in addition, the adsorptions at corners and edges sites of nanoparticles were considered by using rhodium adatoms on the surfaces. The calculations showed that hydrazine binds most strongly to the edge of nanoparticle with adsorption energy of -2.48 eV, where the hydrazine bridges adatoms of edge with the molecule twisted to avoid a cis structure; similar adsorption energy was found at the corner of nanoparticle, where the hydrazine bridges corner atom and surface atom with gauche configuration. However, we found that inclusion of the dispersion correction results in significant enhancement of molecule-substrate binding, thereby increasing the adsorption energy, especially the adsorption to the Rh(1 1 1) surface. The results demonstrate that the surface structure is a key factor to determine the thermodynamics of adsorption, with low coordinated atoms which providing sites of strong adsorption from the surface.

  7. Ionic liquid ultrasound assisted dispersive liquid-liquid microextraction method for preconcentration of trace amounts of rhodium prior to flame atomic absorption spectrometry determination.

    PubMed

    Molaakbari, Elaheh; Mostafavi, Ali; Afzali, Daryoush

    2011-01-30

    In this article, we consider ionic liquid based ultrasound-assisted dispersive liquid-liquid microextraction of trace amounts of rhodium from aqueous samples and show that this is a fast and reliable sample pre-treatment for the determination of rhodium ions by flame atomic absorption spectrometry. The Rh(III) was transferred into its complex with 2-(5-bromo-2-pyridylazo)-5-diethylamino phenol as a chelating agent, and an ultrasonic bath with the ionic liquid, 1-octyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide at room temperature was used to extract the analyte. The centrifuged rhodium complex was then enriched in the form of ionic liquid droplets and prior to its analysis by flame atomic absorption spectrometry, 300 μL ethanol was added to the ionic liquid-rich phase. Finally, the influence of various parameters on the recovery of Rh(III) was optimized. Under optimum conditions, the calibration graph was linear in the range of 4.0-500.0 ng mL(-1), the detection limit was 0.37 ng mL(-1) (3S(b)/m, n = 7) and the relative standard deviation was ±1.63% (n = 7, C = 200 ng mL(-1)). The results show that ionic liquid based ultrasound assisted dispersive liquid-liquid microextraction, combined with flame atomic absorption spectrometry, is a rapid, simple, sensitive and efficient analytical method for the separation and determination of trace amounts of Rh(III) ions with minimum organic solvent consumption.

  8. Educational attainment in poor comprehenders

    PubMed Central

    Ricketts, Jessie; Sperring, Rachael; Nation, Kate

    2014-01-01

    To date, only one study has investigated educational attainment in poor (reading) comprehenders, providing evidence of poor performance on national UK school tests at age 11 years relative to peers (Cain and Oakhill, 2006). In the present study, we adopted a longitudinal approach, tracking attainment on such tests from 11 years to the end of compulsory schooling in the UK (age 16 years). We aimed to investigate the proposal that educational weaknesses (defined as poor performance on national assessments) might become more pronounced over time, as the curriculum places increasing demands on reading comprehension. Participants comprised 15 poor comprehenders and 15 controls; groups were matched for chronological age, nonverbal reasoning ability and decoding skill. Children were identified at age 9 years using standardized measures of nonverbal reasoning, decoding and reading comprehension. These measures, along with a measure of oral vocabulary knowledge, were repeated at age 11 years. Data on educational attainment were collected from all participants (n = 30) at age 11 and from a subgroup (n = 21) at 16 years. Compared to controls, educational attainment in poor comprehenders was lower at ages 11 and 16 years, an effect that was significant at 11 years. When poor comprehenders were compared to national performance levels, they showed significantly lower performance at both time points. Low educational attainment was not evident for all poor comprehenders. Nonetheless, our findings point to a link between reading comprehension difficulties in mid to late childhood and poor educational outcomes at ages 11 and 16 years. At these ages, pupils in the UK are making key transitions: they move from primary to secondary schools at 11, and out of compulsory schooling at 16. PMID:24904464

  9. Deposited films with improved microstructures

    DOEpatents

    Patten, James W.; Moss, Ronald W.; McClanahan, Edwin D.

    1984-01-01

    Methods for improving microstructures of line-of-sight deposited films are described. Columnar growth defects ordinarily produced by geometrical shadowing during deposition of such films are eliminated without resorting to post-deposition thermal or mechanical treatments. The native, as-deposited coating qualities, including homogeneity, fine grain size, and high coating-to-substrate adherence, can thus be retained. The preferred method includes the steps of emitting material from a source toward a substrate to deposit a coating non-uniformly on the substrate surface, removing a portion of the coating uniformly over the surface, again depositing material onto the surface, but from a different direction, and repeating the foregoing steps. The quality of line-of-sight deposited films such as those produced by sputtering, progressively deteriorates as the angle of incidence between the flux and the surface becomes increasingly acute. Depositing non-uniformly, so that the coating becomes progressively thinner as quality deteriorates, followed by uniformly removing some of the coating, such as by resputtering, eliminates the poor quality portions, leaving only high quality portions of the coating. Subsequently sputtering from a different direction applies a high quality coating to other regions of the surface. Such steps can be performed either simultaneously or sequentially to apply coatings of a uniformly high quality, closed microstructure to three-dimensional or large planar surfaces.

  10. Surface Finish after Laser Metal Deposition

    NASA Astrophysics Data System (ADS)

    Rombouts, M.; Maes, G.; Hendrix, W.; Delarbre, E.; Motmans, F.

    Laser metal deposition (LMD) is an additive manufacturing technology for the fabrication of metal parts through layerwise deposition and laser induced melting of metal powder. The poor surface finish presents a major limitation in LMD. This study focuses on the effects of surface inclination angle and strategies to improve the surface finish of LMD components. A substantial improvement in surface quality of both the side and top surfaces has been obtained by laser remelting after powder deposition.

  11. Poor smokers, poor quitters, and cigarette tax regressivity.

    PubMed

    Remler, Dahlia K

    2004-02-01

    The traditional view that excise taxes are regressive has been challenged. I document the history of the term regressive tax, show that traditional definitions have always found cigarette taxes to be regressive, and illustrate the implications of the greater price responsiveness observed among the poor. I explain the different definitions of tax burden: accounting, welfare-based willingness to pay, and welfare-based time inconsistent. Progressivity (equity across income groups) is sensitive to the way in which tax burden is assessed. Analysis of horizontal equity (fairness within a given income group) shows that cigarette taxes heavily burden poor smokers who do not quit, no matter how tax burden is assessed.

  12. Understanding of catalyst deactivation caused by sulfur poisoning and carbon deposition in steam reforming of liquid hydrocarbon fuels

    NASA Astrophysics Data System (ADS)

    Xie, Chao

    2011-12-01

    The present work was conducted to develop a better understanding on the catalyst deactivation in steam reforming of sulfur-containing liquid hydrocarbon fuels for hydrogen production. Steam reforming of Norpar13 (a liquid hydrocarbon fuel from Exxon Mobile) without and with sulfur was performed on various metal catalysts (Rh, Ru, Pt, Pd, and Ni) supported on different materials (Al2O3, CeO2, SiO2, MgO, and CeO2- Al2O3). A number of characterization techniques were applied to study the physicochemical properties of these catalysts before and after the reactions. Especially, X-ray absorption near edge structure (XANES) spectroscopy was intensively used to investigate the nature of sulfur and carbon species in the used catalysts to reveal the catalyst deactivation mechanism. Among the tested noble metal catalysts (Rh, Ru, Pt, and Pd), Rh catalyst is the most sulfur tolerant. Al2O3 and CeO2 are much better than SiO2 and MgO as the supports for the Rh catalyst to reform sulfur-containing hydrocarbons. The good sulfur tolerance of Rh/Al2O3 can be attributed to the acidic nature of the Al2O3 support and its small Rh crystallites (1-3 nm) as these characteristics facilitate the formation of electron-deficient Rh particles with high sulfur tolerance. The good catalytic performance of Rh/CeO2 in the presence of sulfur can be ascribed to the promotion effect of CeO2 on carbon gasification, which significantly reduced the carbon deposition on the Rh/CeO2catalyst. Steam reforming of Norpar13 in the absence and presence of sulfur was further carried out over CeO2-Al2O3 supported monometallic Ni and Rh and bimetallic Rh-Ni catalysts at 550 and 800 °C. Both monometallic catalysts rapidly deactivated at 550 °C, iv and showed poor sulfur tolerance. Although ineffective for the Ni catalyst, increasing the temperature to 800 °C dramatically improved the sulfur tolerance of the Rh catalyst. Sulfur K-edge XANES revealed that metal sulfide and organic sulfide are the dominant sulfur

  13. Molecular models of site-isolated cobalt, rhodium, and iridium catalysts supported on zeolites: Ligand bond dissociation energies

    SciTech Connect

    Chen, Mingyang; Serna, Pedro; Lu, Jing; Gates, Bruce C.; Dixon, David A.

    2015-09-28

    The chemistry of zeolite-supported site-isolated cobalt, rhodium, and iridium complexes that are essentially molecular was investigated with density functional theory (DFT) and the results compared with experimentally determined spectra characterizing rhodium and iridium species formed by the reactions of Rh(C2H4)2(acac) and Ir(C2H4)2(acac) (acac = acetylacetonate) with acidic zeolites such as dealuminated HY zeolite. The experimental results characterize ligand exchange reactions and catalytic reactions of adsorbed ligands, including olefin hydrogenation and dimerization. Two molecular models were used to characterize various binding sites of the metal complexes in the zeolites, and the agreement between experimental and calculated infrared frequencies and metal-ligand distances determined by extended X-ray absorption fine structure spectroscopy was generally very good. The calculated structures and energies indicate a metal-support-oxygen (M(I)-O) coordination number of two for most of the supported complexes and a value of three when the ligands include the radicals C2H5 or H. The results characterizing various isomers of the supported metal complexes incorporating hydrocarbon ligands indicate that some carbene and carbyne ligands could form. Ligand bond dissociation energies (LDEs) are reported to explain the observed reactivity trends. The experimental observations of a stronger M-CO bond than M-(C2H4) bond for both Ir and Rh match the calculated LDEs, which show that the single-ligand LDEs of the mono and dual-ligand complexes for CO are similar to 12 and similar to 15 kcal/mol higher in energy (when the metal is Rh) and similar to 17 and similar to 20 kcal/mol higher (when the metal is Ir) than the single-ligand LDEs of the mono and dual ligand complexes for C2H4, respectively. The results provide a foundation for the prediction

  14. Molecular models of site-isolated cobalt, rhodium, and iridium catalysts supported on zeolites: Ligand bond dissociation energies

    DOE PAGES

    Chen, Mingyang; Serna, Pedro; Lu, Jing; ...

    2015-09-28

    The chemistry of zeolite-supported site-isolated cobalt, rhodium, and iridium complexes that are essentially molecular was investigated with density functional theory (DFT) and the results compared with experimentally determined spectra characterizing rhodium and iridium species formed by the reactions of Rh(C2H4)2(acac) and Ir(C2H4)2(acac) (acac = acetylacetonate) with acidic zeolites such as dealuminated HY zeolite. The experimental results characterize ligand exchange reactions and catalytic reactions of adsorbed ligands, including olefin hydrogenation and dimerization. Two molecular models were used to characterize various binding sites of the metal complexes in the zeolites, and the agreement between experimental and calculated infrared frequencies and metal-ligand distancesmore » determined by extended X-ray absorption fine structure spectroscopy was generally very good. The calculated structures and energies indicate a metal-support-oxygen (M(I)-O) coordination number of two for most of the supported complexes and a value of three when the ligands include the radicals C2H5 or H. The results characterizing various isomers of the supported metal complexes incorporating hydrocarbon ligands indicate that some carbene and carbyne ligands could form. Ligand bond dissociation energies (LDEs) are reported to explain the observed reactivity trends. The experimental observations of a stronger M-CO bond than M-(C2H4) bond for both Ir and Rh match the calculated LDEs, which show that the single-ligand LDEs of the mono and dual-ligand complexes for CO are similar to 12 and similar to 15 kcal/mol higher in energy (when the metal is Rh) and similar to 17 and similar to 20 kcal/mol higher (when the metal is Ir) than the single-ligand LDEs of the mono and dual ligand complexes for C2H4, respectively. The results provide a foundation for the prediction of the catalytic properties of numerous supported metal complexes, as summarized in detail here.« less

  15. Dinuclear pyridine-4-thiolate-bridged rhodium and iridium complexes as ditopic building blocks in molecular architecture.

    PubMed

    Ferrer, Montserrat; Gómez-Bautista, Daniel; Gutiérrez, Albert; Miranda, José R; Orduña-Marco, Guillermo; Oro, Luis A; Pérez-Torrente, Jesús J; Rossell, Oriol; García-Orduña, Pilar; Lahoz, Fernando J

    2014-02-03

    A series of dinuclear pyridine-4-thiolate (4-Spy)-bridged rhodium and iridium compounds [M(μ-4-Spy)(diolef)]2 [diolef = 1,5-cyclooctadiene (cod), M = Rh (1), Ir (2); diolef = 2,5-norbornadiene (nbd), M = Rh (3)] were prepared by the reaction of Li(4-Spy) with the appropriate compound [M(μ-Cl)(diolef)]2 (M = Rh, Ir). The dinuclear compound [Rh(μ-4-Spy)(CO)(PPh3)]2 (4) was obtained by the reaction of [Rh(acac)(CO)(PPh3)] (acac = acetylacetonate) with 4-pySH. Compounds 1-4 were assessed as metalloligands in self-assembly reactions with the cis-blocked acceptors [M(cod)(NCCH3)2](BF4) [M = Rh (a), Ir (b)] and [M(H2O)2(dppp)](OTf)2 [M = Pd (c), Pt (d); dppp = 1,3-bis(diphenylphosphino)propane]. The homometallic hexanuclear metallomacrocycles [{M2(μ-4-Spy)2(cod)2}2{M(cod)}2](BF4)2 (M = Rh [(1a)2], Ir [(2b)2]) and the heterometallic hexanuclear metallomacrocycles [{Rh2(μ-4-Spy)2(cod)2}2{Ir(cod)}2](BF4)2 [(1b)2], [{Rh2(μ-4-Spy)2(cod)2}2{M'(dppp)}2](OTf)4 (M' = Pd [(1c)2], Pt [(1d)2]), and [{Ir2(μ-4-Spy)2(cod)2}2{M'(dppp)}2](OTf)4 (M' = Pd [(2c)2], Pt [(2d)2]) were obtained. NMR spectroscopy in combination with electrospray ionization mass spectrometry was used to elucidate the nature of the metalloligands and their respective supramolecular assemblies. Most of the synthesized species were found to be nonrigid in solution, and their fluxional behavior was studied by variable-temperature (1)H NMR spectroscopy. An X-ray diffraction study of the assemblies (1a)2 and (1d)2 revealed the formation of rectangular (9.6 Å × 6.6 Å) hexanuclear metallomacrocycles with alternating dinuclear (Rh2) and mononuclear (Rh or Pt) corners. The hexanuclear core is supported by four pyridine-4-thiolate linkers, which are bonded through the thiolate moieties to the dinuclear rhodium units, exhibiting a bent-anti arrangement, and through the peripheral pyridinic nitrogen atoms to the mononuclear corners.

  16. Security Deposits

    DTIC Science & Technology

    1987-04-01

    Tenant requirements: Provide a forwarding address. Failure by tenant to pay delinquent rent within twenty days after delivery of written demand makes...dispute boards, track down delinquent soldiers, and to actually collect the money back from the soldier. Finance cannot simply withhold pay - it can do...United States, and rents and deposits are notoriously high. Third, Fort Ord happened to be the site of a much publicized suicide by a teenage boy in

  17. Blue metal-poor stars

    NASA Astrophysics Data System (ADS)

    Preston, George W.; Sneden, Christopher

    2004-12-01

    We review the discovery of blue metal-poor (BMP) stars and the resolution of this population into blue stragglers and intermediate-age Main-Sequence stars by use of binary fractions. We show that the specific frequencies of blue stragglers in the halo field and in globular clusters differ by an order of magnitude. We attribute this difference to the different modes of production of these two populations. We report carbon and s-process enrichment among very metal-poor field blue stragglers and discuss how this result can be used to further resolve field blue stragglers into groups formed during RGB and AGB evolution of their erstwhile primary companions.

  18. The management of poor performance

    PubMed Central

    Mayberry, John F

    2007-01-01

    Identification of poor performance is in an integral part of government policy. The suggested approach for the identification of such problems, advocated by the General Medical Council, is that of appraisal. However, traditionally, there has been a reluctance to deal with poor performers, as all doctors have made mistakes and are usually only too ready to forgive and be non‐critical of colleagues. The problems are widespread, and 6% of the senior hospital workforce in any 5‐year period may have problems. PMID:17308213

  19. Standard and Poor's Rich Website

    ERIC Educational Resources Information Center

    DiMaria, Frank

    2006-01-01

    To help parents investigate and locate quality school districts and to help policy-makers, principals, and superintendents to make well-informed decisions about education, Standard and Poor's has launched a website called SchoolMatters.com. It is recognized by the U.S. Department of Education and featured on its website (www.ed.gov/parents).…

  20. Prospects for the Working Poor

    ERIC Educational Resources Information Center

    Miller, S. M.

    1970-01-01

    Based on a chapter entitled "Barriers to Employment of the Disadvantaged by Martin Deutsch and S. M. Miller in "Manpower Report of the President, 1968. Discusses the Nixon proposals for remediating poverty in relation to the socioeconomic factors operating to maintain the condition of being poor while working. (JM)

  1. The Power of Poor Communications

    ERIC Educational Resources Information Center

    Schaub, Alfred R.

    1975-01-01

    Most breakdowns in communications are the result of the quest for power on behalf of organization members, not the result of poor communications training. Organizational power may be accrued by withholding information, sabotaging communications, refusing to communicate bad news to superiors, and avoiding confrontations by not communicating at all.…

  2. Prospects for the Working Poor

    ERIC Educational Resources Information Center

    Miller, S. M.

    1970-01-01

    Based on a chapter entitled "Barriers to Employment of the Disadvantaged by Martin Deutsch and S. M. Miller in "Manpower Report of the President, 1968. Discusses the Nixon proposals for remediating poverty in relation to the socioeconomic factors operating to maintain the condition of being poor while working. (JM)

  3. Educating Canada's Urban Poor Children.

    ERIC Educational Resources Information Center

    Maynes, Bill; Foster, Rosemary

    2000-01-01

    Presents six critical thoughts and questions about educating poor urban children in Canada. These thoughts were derived from the development of a directory of Canadian educational poverty programs. Findings from that study emphasize the increasing diversity of the student population, the importance of temporary and large-scale funding, and the…

  4. Are poor Chinese text comprehenders also poor in written composition?

    PubMed

    Guan, Connie Qun; Ye, Feifei; Meng, Wanjin; Leong, Che Kan

    2013-10-01

    We studied the performance in three genres of Chinese written composition (narration, exposition, and argumentation) of 158 grade 4, 5, and 6 poor Chinese text comprehenders compared with 156 good Chinese text comprehenders. We examined text comprehension and written composition relationship. Verbal working memory (verbal span working memory and operation span working memory) and different levels of linguistic tasks-morphological sensitivity (morphological compounding and morphological chain), sentence processing (syntax construction and syntax integrity), and text comprehension (narrative and expository texts)-were used to predict separately narrative, expository, and argumentation written compositions in these students. Grade for grade, the good text comprehenders outperformed the poor text comprehenders in all tasks, except for morphological chain. Hierarchical multiple regression analyses showed differential contribution of the tasks to different genres of writing. In particular, text comprehension made unique contribution to argumentation writing in the poor text comprehenders. Future studies should ask students to read and write parallel passages in the same genre for better comparison and incorporate both instructional and motivational variables.

  5. Versatile bonding and coordination modes of ditriazolylidene ligands in rhodium(iii) and iridium(iii) complexes.

    PubMed

    Farrell, Kevin; Müller-Bunz, Helge; Albrecht, Martin

    2016-10-12

    Metalation of novel ditriazolium salts containing a trimethylene (-CH2CH2CH2-) or dimethylether linker (-CH2OCH2-) was probed with different rhodium(iii) and iridium(iii) precursors. When using [MCp*Cl2]2, a transmetalation protocol via a triazolylidene silver intermediate was effective, while base-assisted metalation with MCl3via sequential deprotonation of the triazolium salt with KOtBu and addition of the metal precursor afforded homoleptic complexes. The N-substituent on the triazole heterocycle directed the metalation process and led to Ctrz,Ctrz,CPh-tridentate chelating ditriazolylidene complexes for N-phenyl substituents. With ethyl substituents, only Ctrz,Ctrz-bidentate complexes were formed, while metalation with mesityl substituents was unsuccessful, presumably due to steric constraints. Through modification of the reaction conditions for the metalation step, an intermediate species was isolated that contains a Ctrz,CPh-bidentate chelate en route to the formation of the tridentate ligand system. Accordingly, Cphenyl-H bond activation occurs prior to formation of the second metal-triazolylidene bond. Stability studies with a Ctrz,Ctrz,CPh-tridentate chelating ditriazolylidene iridium complex towards DCl showed deuterium incorporation at both N-phenyl groups and indicate that Cphenyl-H bond activation is reversible while the Ctrz-Ir bond is robust. The flexible linker between the two triazolylidene donor sites provides access to both facial and meridional coordination modes.

  6. Heterobimetallic complexes of rhodium dibenzotetramethylaza[14]annulene [(tmtaa)Rh-M]: formation, structures, and bond dissociation energetics.

    PubMed

    Imler, Gregory H; Peters, Garvin M; Zdilla, Michael J; Wayland, Bradford B

    2015-01-05

    A rhodium(II) dibenzotetramethylaza[14]annulene dimer ([(tmtaa)Rh]2) undergoes metathesis reactions with [CpCr(CO)3]2, [CpMo(CO)3]2, [CpFe(CO)2]2, [Co(CO)4]2, and [Mn(CO)5]2 to form (tmtaa)Rh-M complexes (M = CrCp(CO)3, MoCp(CO)3, FeCp(CO)2, Co(CO)4, or Mn(CO)5). Molecular structures were determined for (tmtaa)Rh-FeCp(CO)2, (tmtaa)Rh-Co(μ-CO)(CO)3, and (tmtaa)Rh-Mn(CO)5 by X-ray diffraction. Equilibrium constants measured for the metathesis reactions permit the estimation of several (tmtaa)Rh-M bond dissociation enthalpies (Rh-Cr = 19 kcal mol(-1), Rh-Mo = 25 kcal mol(-1), and Rh-Fe = 27 kcal mol(-1)). Reactivities of the bimetallic complexes with synthesis gas to form (tmtaa)Rh-C(O)H and M-H are surveyed.

  7. Domino rhodium/palladium-catalyzed dehydrogenation reactions of alcohols to acids by hydrogen transfer to inactivated alkenes.

    PubMed

    Trincado, Mónica; Grützmacher, Hansjörg; Vizza, Francesco; Bianchini, Claudio

    2010-03-01

    The combination of the d(8) Rh(I) diolefin amide [Rh(trop(2)N)(PPh(3))] (trop(2)N=bis(5-H-dibenzo[a,d]cyclohepten-5-yl)amide) and a palladium heterogeneous catalyst results in the formation of a superior catalyst system for the dehydrogenative coupling of alcohols. The overall process represents a mild and direct method for the synthesis of aromatic and heteroaromatic carboxylic acids for which inactivated olefins can be used as hydrogen acceptors. Allyl alcohols are also applicable to this coupling reaction and provide the corresponding saturated aliphatic carboxylic acids. This transformation has been found to be very efficient in the presence of silica-supported palladium nanoparticles. The dehydrogenation of benzyl alcohol by the rhodium amide, [Rh]N, follows the well established mechanism of metal-ligand bifunctional catalysis. The resulting amino hydride complex, [RhH]NH, transfers a H(2) molecule to the Pd nanoparticles, which, in turn, deliver hydrogen to the inactivated alkene. Thus a domino catalytic reaction is developed which promotes the reaction R-CH(2)-OH+NaOH+2 alkene-->R-COONa+2 alkane.

  8. Rhodium Complexes Promoting C-O Bond Formation in Reactions with Oxygen: The Role of Superoxo Species.

    PubMed

    Vilella-Arribas, Laia; García-Melchor, Max; Balcells, David; Lledós, Agustí; López, José A; Sancho, Sofía; Villarroya, B Eva; Del Río, M Pilar; Ciriano, Miguel A; Tejel, Cristina

    2017-01-28

    C-O bond formation in reactions of olefins with oxygen is a long standing challenge in chemistry for which the very complicated-sometimes controversial-mechanistic panorama slows down the design of catalysts for oxygenations. In this regard, the mechanistic details of the oxidation of the complex [Rh(cod)(Ph2 N3 )] (1) (cod=1,5-cyclooctadiene) with oxygen to the unique 2-rhodaoxetane compound [{Rh(OC8 H12 )(Ph2 N3 )}2 ] (2) has been investigated by DFT calculations. The results of this study provide evidences for a novel bimetallic mechanism in which two rhodium atoms redistribute the four electrons involved in the cleavage of the O=O bond. Furthermore, both oxygen atoms are used to create two new C-O bonds in a controlled fashion with 100 % atom economy. The key intermediates that we have found in this process are a mononuclear open-shell triplet superoxo compound, an open-shell singlet "μ-(peroxo)" derivative, and a closed-shell singlet "bis(μ-oxo)" complex. Some of the findings are used to predict the reactions of Rh(I) complexes with oxygen, exemplified by that of the complex [Rh(cod)(OnapyMe2 )] (3). Starting from 3, [{Rh(OC8 H12 )(OnapyMe2 )}2 ] (4) has been prepared and characterized, which represents the second example of a 2-rhodaoxetane compound coming from an oxygenation reaction with oxygen.

  9. Rhodium-doped barium titanate perovskite as a stable p-type semiconductor photocatalyst for hydrogen evolution under visible light.

    PubMed

    Maeda, Kazuhiko

    2014-02-12

    Rhodium-doped barium titanate (BaTiO3:Rh) powder was prepared by the polymerized complex (PC) method, and the photocatalytic activity for H2 evolution from water was examined. BaTiO3 is a wide-gap n-type semiconductor having a band gap of 3.0 eV. Doping Rh species into the lattice of BaTiO3 resulted in the formation of new absorption bands in visible light region. Upon visible light (λ > 420 nm), BaTiO3:Rh modified with nanoparticulate Pt as a water reduction promoter was capable of producing H2 from water containing an electron donor such as methanol and iodide. The best material prepared by the PC method exhibited higher activity than that made by a conventional solid-state reaction method. Visible-light-driven Z-scheme water splitting was also accomplished using Pt/BaTiO3:Rh as a building block for H2 evolution in combination with PtOx-loaded WO3 as an O2 evolution photocatalyst in the presence of an IO3(-)/I(-) shuttle redox mediator. Photoelectrochemical analysis indicated that a porous BaTiO3:Rh electrode exhibited cathodic photoresponse due to water reduction in a neutral aqueous Na2SO4 solution upon visible light.

  10. Spectroscopic Investigation of the Species Involved in the Rhodium-Catalyzed Oxidative Carbonylation of Toluene to Toluic Acid

    SciTech Connect

    Zakzeski, Joseph; Burton, Sarah D.; Behn, Andrew; Head-Gordon, Martin P.; Bell, Alexis T.

    2009-11-14

    A spectroscopic investigation of complexes used to catalyze the oxidative carbonylation of toluene to para-toluic acid was conducted. Rhodium complexes were analyzed by 103Rh and 13C NMR, UV-visible spectroscopy, and infrared spectroscopy. In the presence of vanadium and oxygen, the resting state of the Rh catalyst was found to exist as a Rh(III) complex with carbonyl and trifluoroacetate ligands, consistent with the structure Rh(CO)2(TFA)3. The complex exhibited a carbonyl peak with an unusual degree of shielding, which resulted in the appearance of the carbonyl peak at an unprecedented upfield position in the 13C NMR spectrum. This shielding was caused by interaction of the carbonyl group with the trifluoroacetate ligand. In the absence of oxygen, the Rh(III) complex reduced to Rh(I), and the reduced form exhibited properties resembling the catalyst precursor. Structures and spectroscopic properties calculated using Density Functional Theory were in good agreement with experimental results. The vanadium co-catalyst was similarly characterized by 51V NMR and UV-visible spectroscopy. The oxidized species corresponded to [(VO2)(TFA)]2, whereas the reduced species corresponded (VO)(TFA)2. The spectroscopic results obtained in this study confirm the identity of the species that have been proposed to be involved in the Rh-catalyzed oxidative carbonylation of toluene to toluic acid.

  11. Octahedral rhodium(III) complexes as kinase inhibitors: Control of the relative stereochemistry with acyclic tridentate ligands.

    PubMed

    Mollin, Stefan; Riedel, Radostan; Harms, Klaus; Meggers, Eric

    2015-07-01

    Octahedral metal complexes are attractive structural templates for the design of enzyme inhibitors as has been demonstrated, for example, with the development of metallo-pyridocarbazoles as protein kinase inhibitors. The octahedral coordination sphere provides untapped structural opportunities but at the same time poses the drawback of dealing with a large number of stereoisomers. In order to address this challenge of controlling the relative metal-centered configuration, the synthesis of rhodium(III) pyridocarbazole complexes with facially coordinating acyclic tridentate ligands was investigated. A strategy for the rapid synthesis of such complexes is reported, the diastereoselectivities of these reactions were investigated, the structure of several complexes were determined by X-ray crystallography, the high kinetic stability of such complexes in thiol-containing solutions was demonstrated in (1)H-NMR experiments, and the protein kinase inhibition ability of this class of complexes was confirmed. It can be concluded that the use of multidentate ligands is currently maybe the most practical strategy to avoid a large number of possible stereoisomers in the course of exploiting octahedral coordination spheres as structural templates for the design of bioactive molecules.

  12. A preliminary study of factors affecting the calibration stability of the iridium versus iridium-40 percent rhodium thermocouple

    NASA Technical Reports Server (NTRS)

    Ahmed, Shaffiq; Germain, Edward F.; Daryabeigi, Kamran; Alderfer, David W.; Wright, Robert E.

    1987-01-01

    An iridium versus iridium-40% rhodium thermocouple was studied. Problems associated with the use of this thermocouple for high temperature applications (up to 2000 C) were investigated. The metallurgical studies included X-ray, macroscopic, resistance, and metallographic studies. The thermocouples in the as-received condition from the manufacturer revealed large amounts of internal stress caused by cold working during manufacturing. The thermocouples also contained a large amount of inhomogeneities and segregations. No phase transformations were observed in the alloy up to 1100 C. It was found that annealing the thermocouple at 1800 C for two hours, and then at 1400 C for 2 to 3 hours yielded a fine grain structure, relieving some of the strains, and making the wire more ductile. It was also found that the above annealing procedure stabilized the thermal emf behavior of the thermocouple for application below 1800 C (an improvement from + or - 1% to + or - 0.02% within the range of the test parameters used).

  13. Organometallic rhodium(III) and iridium(III) cyclopentadienyl complexes with curcumin and bisdemethoxycurcumin co-ligands.

    PubMed

    Pettinari, Riccardo; Marchetti, Fabio; Pettinari, Claudio; Condello, Francesca; Petrini, Agnese; Scopelliti, Rosario; Riedel, Tina; Dyson, Paul J

    2015-12-21

    A series of half-sandwich cyclopentadienyl rhodium(III) and iridium(III) complexes of the type [Cp*M(curc/bdcurc)Cl] and [Cp*M(curc/bdcurc)(PTA)][SO3CF3], in which Cp* = pentamethylcyclopentadienyl, curcH = curcumin and bdcurcH = bisdemethoxycurcumin as O^O-chelating ligands, and PTA = 1,3,5-triaza-7-phosphaadamantane, is described. The X-ray crystal structures of three of the complexes, i.e. [Cp*Rh(curc)(PTA)][SO3CF3] (5), [Cp*Rh(bdcurc)(PTA)][SO3CF3] (6) and [Cp*Ir(bdcurc)(PTA)][SO3CF3] (8), confirm the expected "piano-stool" geometry. With the exception of 5, the complexes are stable under pseudo-physiological conditions and are moderately cytotoxic to human ovarian carcinoma (A2780 and A2780cisR) cells and also to non-tumorigenic human embryonic kidney (HEK293) cells, but lack the cancer cell selectivity observed for related arene ruthenium(II) complexes.

  14. Adsorption of Ruthenium, Rhodium and Palladium from Simulated High-Level Liquid Waste by Highly Functional Xerogel - 13286

    SciTech Connect

    Onishi, Takashi; Koyama, Shin-ichi; Mimura, Hitoshi

    2013-07-01

    Fission products are generated by fission reactions in nuclear fuel. Platinum group (Pt-G) elements, such as palladium (Pd), rhodium (Rh) and ruthenium (Ru), are also produced. Generally, Pt-G elements play important roles in chemical and electrical industries. Highly functional xerogels have been developed for recovery of these useful Pt-G elements from high - level radioactive liquid waste (HLLW). An adsorption experiment from simulated HLLW was done by the column method to study the selective adsorption of Pt-G elements, and it was found that not only Pd, Rh and Ru, but also nickel, zirconium and tellurium were adsorbed. All other elements were not adsorbed. Adsorbed Pd was recovered by washing the xerogel-packed column with thiourea solution and thiourea - nitric acid mixed solution in an elution experiment. Thiourea can be a poison for automotive exhaust emission system catalysts, so it is necessary to consider its removal. Thermal decomposition and an acid digestion treatment were conducted to remove sulfur in the recovered Pd fraction. The relative content of sulfur to Pd was decreased from 858 to 0.02 after the treatment. These results will contribute to design of the Pt-G element separation system. (authors)

  15. Characteristics of rhodium-iron resistance thermometers and interpolation properties from 0.65 K to 24.5561 K

    NASA Astrophysics Data System (ADS)

    Rusby, R. L.; Tew, W. L.

    2013-09-01

    Resistance thermometers using wires of rhodium with 0.5 mol % of iron (Rh-Fe thermometers or RIRTs) were first made by H Tinsley & Co in 1969 for applications at low temperatures, below the range where standard platinum resistance thermometers can be used, and down to 0.5 K or lower. They were investigated at NPL and found to have good sensitivity and excellent stability. Subsequently RIRTs have been used as the standard thermometers which record and compare the results of experiments in thermometry particularly below 24.5561 K, the triple-point of neon. From 1969 until the early 2000s, when Tinsley ceased to manufacture them, several hundred RIRTs were made and many were calibrated at NPL, NIST and elsewhere. In order to document the resistance-temperature characteristics of the production, and indicate the variability from batch to batch, the present paper analyses representative data for the resistance at the triple-point of water and the low-temperature calibrations of a number of thermometers produced at various times. The opportunity has been taken to include data for three RIRTs which were made independently, two in Russia and one in China.

  16. Inhibition of endonuclease cleavage and DNA replication of E. coli plasmid by the antitumor rhodium(II) complex.

    PubMed

    Rahman, Md Masudur; Yasuda, Hachiro; Katsura, Shinji; Mizuno, Akira

    2007-08-01

    Binding effect of the antitumor complex rhodium(II) acetate [Rh(2)(O(2)CCH(3))(4)] (Rh1) to the plasmid pUC19 DNA has been studied under different molar ratio of Rh1 compound to base pair of pUC19 DNA (R(f)) and reaction time. The Rh1 binding inhibited the activity of restriction enzyme. The binding effect was monitored using gel electrophoresis. The results indicate that at least one Rh1 binds with the recognition sequence and the binding has no preference between A-T and G-C pairs. At high value of R(f)=100, ICP-MS (Inductively Coupled Plasma Mass Spectrometry) measurement confirmed that 46% of Rh1 binds to DNA. PCR amplification of the DNA was also inhibited by the Rh1 binding. The transformation experiment using Escherichia coli suggested that the cell growth was inhibited after binding the Rh1 to the plasmid. These results indicated that DNA synthesis could be inhibited both in vitro and in vivo by the Rh(2)(O(2)CCH(3))(4) binding.

  17. Health solutions for the poor.

    PubMed

    Castro, J L; Fujiwara, P I; Bhambal, P; Emaille-Léotard, N; Harries, A D

    2014-03-21

    The International Union Against Tuberculosis and Lung Disease (The Union) is the oldest international non-governmental organisation involved in the fight against tuberculosis. In 2008, the Institute of The Union was challenged to think boldly about the future and to develop a diverse work portfolio covering a wide spectrum of lung health and other disease-related problems. The vision adopted by The Union at that time was 'Health solutions for the poor'. More recently, there has been lengthy debate about the need for the Union to concentrate just on its core mandate of tuberculosis and lung health and for the Union's vision to reflect this narrower spectrum of activity as 'Lung health solutions for the poor'. In this viewpoint article we outline our reasons for believing that this narrower vision is incompatible with The Union's mission statement, and we argue that making such a change would be a mistake.

  18. Determination of rhodium by resonance light-scattering technique coupled with solid phase extraction using Rh(III) ion-imprinted polymers as sorbent.

    PubMed

    Yang, Bing; Zhang, Ting; Tan, Wenxiang; Liu, Peng; Ding, Zhongtao; Cao, Qiue

    2013-02-15

    A resonance light-scattering method (RLS) for the determination of Rh(III) was initially developed, based on the reaction among Rh(III), WO4(2-) and ethylrhodamine B. The method possesses high sensitivity, but lacks selectivity. Therefore, a Rh(III) ion-imprinted polymer (IIP), prepared by precipitation polymerization using 2-(allylthio)nicotinic acid (ANA) as functional monomer, was used as sorbent to construct a ion-imprint based solid-phase extraction (IIP-SPE) method for separation of rhodium from complicated matrices prior to its determination by RLS. The experimental parameters affecting the extraction efficiency and selectivity of IIP-SPE were studied carefully. Under the optimal conditions, the IIP-SPE column with the enrichment factor (EF) of 10 could be used at least 20 times without decreasing its extraction recovery (above 90%) significantly. The calibration graph for the determination of rhodium by RLS coupled with IIP-SPE procedure was linear in the range of 0.06-1.5 ng mL(-1) with the detection limit of 0.024 ng mL(-1). There is no metal ions tested at the concentration below 10 ng mL(-1) interfered in the determination of 0.8 ng mL(-1) Rh(III). The proposed IIP-SPE-RLS method was successfully applied to the extraction and measurement of trace rhodium in catalyst, water and geochemical samples with the relative standard deviation (RSD) of less than 4.0% (n=4).

  19. Pentamethylcyclopentadienyl-rhodium and iridium complexes containing (N^N and N^O) bound chloroquine analogue ligands: synthesis, characterization and antimalarial properties.

    PubMed

    Ekengard, Erik; Kumar, Kamlesh; Fogeron, Thibault; de Kock, Carmen; Smith, Peter J; Haukka, Matti; Monari, Magda; Nordlander, Ebbe

    2016-03-07

    The synthesis and characterization of twenty new pentamethylcyclopentadienyl-rhodium and iridium complexes containing N^N and N^O-chelating chloroquine analogue ligands are described. The in vitro antimalarial activity of the new ligands as well as the complexes was evaluated against the chloroquine sensitive (CQS) NF54 and the chloroquine resistant (CQR) Dd2 strains of Plasmodium falciparum. The antimalarial activity was found to be good to moderate; although all complexes are less active than artesunate, some of the ligands and complexes showed better activity than chloroquine (CQ). In particular, rhodium complexes were found to be considerably more active than iridium complexes against the CQS NF54 strain. Salicylaldimine Schiff base ligands having electron-withdrawing groups (F, Cl, Br, I and NO2) in para position of the salicyl moiety and their rhodium complexes showed good antiplasmodial activity against both the CQS-NF54 and the CQR-Dd2 strains. The crystal structures of (η(5)-pentamethylcyclopentadienyl){N(1)-(7-chloroquinolin-4-yl)-N(2)-(pyridin-2-ylmethyl)ethane-1,2-diamine)} chlororhodium(III) chloride and (η(5)-pentamethylcyclopentadienyl){(4-chloro-2-(((2-((7-chloroquinolin-4-yl)amino)ethyl)imino)methyl)phenolate)}chlororhodium(III) chloride are reported. The crystallization of the amino-pyridyl complex (η(5)-pentamethylcyclopentadienyl){(N(1)-(7-chloroquinolin-4-yl)-N(2)-(pyridin-2-ylmethyl)ethane-1,2-diamine)}chloroiridium(III) chloride in acetone resulted in the formation of the imino-pyridyl derivative (η(5)-pentamethylcyclopentadienyl){(N1-(7-chloroquinolin-4-yl)-N2-(pyridin-2-ylmethylene)ethane-1,2-diamine)}chloroiridium(III) chloride, the crystal structure of which is also reported.

  20. Intermolecular rhodium-catalyzed [3+2+2] carbocyclization of alkenylidenecyclopropanes with activated alkynes: regio- and diastereoselective construction of cis-fused bicycloheptadienes.

    PubMed

    Evans, P Andrew; Inglesby, Phillip A

    2008-10-01

    Polycyclic structures that contain seven-membered carbocycles constitute important structural motifs that are ubiquitous in several classes of bioactive natural products. We have developed the first regio- and diastereoselective intermolecular rhodium-catalyzed [3+2+2] carbocyclization of carbon- and heteroatom-tethered alkenylidenecyclopropanes with mono- and disubstituted alkynes for the construction of cis-fused bicycloheptadienes. This study delineates some of the critical features for controlling regioselectivity in this process and demonstrates that E-alkenes can be incorporated in a stereospecific manner to afford products with up to three new stereogenic centers. The latter feature is particularly significant given that related carbocyclization reactions are often limited in this respect.

  1. Rhodium/chiral diene-catalyzed asymmetric 1,4-addition of arylboronic acids to chromones: a highly enantioselective pathway for accessing chiral flavanones.

    PubMed

    He, Qijie; So, Chau Ming; Bian, Zhaoxiang; Hayashi, Tamio; Wang, Jun

    2015-03-01

    Chromone has been noted to be one of the most challenging substrates in the asymmetric 1,4-addition of α,β-unsaturated carbonyl compounds. By employing the rhodium complex associated with a chiral diene ligand, (R,R)-Ph-bod*, the 1,4-addition of a variety of arylboronic acids was realized to give high yields of the corresponding flavanones with excellent enantioselectivities (≥97% ee, 99% ee for most substrates). Ring-opening side products, which would lead to erosion of product enantioselectivity, were not observed under the stated reaction conditions.

  2. Rhodium-catalyzed ring-opening reactions of a 3-aza-2-oxabicyclo[2.2.1]hept-5-ene with arylboronic acids.

    PubMed

    Machin, Ben P; Ballantine, Melissa; Mandel, Jérémie; Blanchard, Nicolas; Tam, William

    2009-10-02

    Rhodium-catalyzed ring-opening reactions of a 3-aza-2-oxabicyclo[2.2.1]hept-5-ene with arylboronic acids were investigated. The use of [RhCl(COD)](2), (+/-)-BINAP, and NaHCO(3) in MeOH at 60 degrees C was found to be the optimized conditions for the ring-opening reactions to give the 1,2-ring-opened products. Various arylboronic acids were examined, and low to moderate yields were obtained and stereoselectivities (trans/cis) from 50:50 to 100:0 were observed.

  3. Rhodium-Catalyzed Atroposelective [2 + 2 + 2] Cycloaddition of Ortho-Substituted Phenyl Diynes with Nitriles: Effect of Ortho Substituents on Regio- and Enantioselectivity.

    PubMed

    Kashima, Kenichi; Teraoka, Kota; Uekusa, Hidehiro; Shibata, Yu; Tanaka, Ken

    2016-05-06

    Axially chiral 3-(2-halophenyl)pyridines were successfully synthesized in high yields with excellent enantioselectivity by the cationic rhodium(I)/(S)-H8-BINAP complex-catalyzed atroposelective [2 + 2 + 2] cycloaddition of (o-halophenyl)diynes with nitriles. Interestingly, regio- and enantioselectivity highly depend on ortho substituents on the phenyl group of diynes. When the ortho substituents were methoxy and methoxycarbonyl groups, axially chiral 3-arylpyridines were obtained as a major product, while enantioselectivity was lowered significantly. On the other hand, when the ortho substituents were alkyl groups, regioselectivity was switched to give achiral 6-arylpyridines in high yields.

  4. Some Effects of Exposure to Exhaust-gas Streams on Emittance and Thermoelectric Power of Bare-wire Platinum Rhodium - Platinum Thermocouples

    NASA Technical Reports Server (NTRS)

    Glawe, George E; Shepard, Charles E

    1954-01-01

    Thermocouples were exposed to exhaust gases from the combustion of propane, 72-octane gasoline, and JP-4 fuel. Exposure increased the emissivity of the thermocouple wire, which increased its radiation error. Two methods are presented for determining the emittance of the wires. The emissivity of a clean platinum rhodium-platinum thermocouple was approximately 0.2 in the temperature range investigated, while the emittance of an exposed thermocouple coated with exhaust residue was about 0.5. The exposure caused negligible change in the thermoelectric power of the thermocouples.

  5. Rhodium-Catalyzed Regioselective Domino Azlactone-Alkyne Coupling/Aza-Cope Rearrangement: Facile Access to 2-Allyl-3-oxazolin-5-ones and Trisubstituted Pyridines.

    PubMed

    Kuang, Jinqiang; Parveen, Shaista; Breit, Bernhard

    2017-07-10

    Rhodium-catalyzed regioselective addition of azlactones to internal alkynes combined with aza-Cope rearrangement provides efficient atom economic access to 2-allyl-3-oxazolin-5-one derivatives. Extension to a triple domino process, in which the above process is combined with in situ azlactone formation starting from amino acids renders this process even more attractive. Subsequent thermolysis of the 2-allyl-3-oxazolines enabled the de novo synthesis of trisubstituted pyridines. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. A facile approach for shape selective synthesis of rhodium nanostructures and conductivity studies

    SciTech Connect

    Sathe, Bhaskar R.

    2012-12-15

    Shape selective synthesis of Rh nanostructures has been demonstrated with the help of a single step chemical vapor deposition, where different shapes like cubes at 500 Degree-Sign C, pyramids and hexagons at 500 Degree-Sign C, 700 Degree-Sign C and 900 Degree-Sign C respectively have been obtained as a function of temperature. Scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and four probe conductivity measurements were used to study the morphology, crystallinity and phase purity of the structures. The conductivity values for as synthesised nanostructures have been obtained in the range of 2-7 kS/cm{sup 2}. On the basis of the experimental results, from TGA and XPS studies possible mechanistic pathway for the evolution of Rh nanostructures was discussed.

  7. Grazing incidence reflection coefficients of rhodium, osmium, platinum, and gold from 50 to 300 A

    NASA Technical Reports Server (NTRS)

    Hettrick, M. C.; Edelstein, J.; Flint, S. A.

    1985-01-01

    Reflectance measurements were made of several metals illuminated from various angles with light at 14 wavelengths in the interval 46.5-283 A. The metals, Rh, Os, Pt and Au were deposited as 125 A films on a binding substrate through electron beam epitaxy. Measurements were made with a grazing incidence monochromator and a reflectometer. The data generally showed lowered reflectance with increasing angles of illumination and shorter wavelengths. The reflectance peak, however, was located at wavelengths of 100-160 A, particularly at large grazing incidences. The wavelengths correspond with the 5p to epsilon-d transition in all of the elements. Rh displayed the highest overall reflectance, and both Rh and Os were more efficient than Au or Pt.

  8. Livestock services and the poor.

    PubMed

    Ahuja, V; Redmond, E

    2004-04-01

    This paper reviews the economic framework for the delivery of livestock services to the poor. It is argued that the demand for livestock products is likely to increase rapidly and the ability of the poor to participate in the opportunities presented by this growth is linked critically to the availability of good service support, both on the input and output side. Governments therefore have a responsibility to supply the necessary public goods (including the institutions and legal frameworks), and the market infrastructure for facilitating the emergence of efficient markets for livestock services. The paper further argues that the dynamics of public policy in developing countries are much more complex than the simple application of economic logic. It is the larger political economy that often dictates policy choices. It is therefore important to integrate political economy and governance issues into the economic debate on livestock service delivery. The paper also reviews the context in which the markets for livestock services will need to function. Different countries are facing very different sets of issues, and the identification of possible interventions in livestock service markets would require careful field research and analysis. In this context, the paper suggests the elements of a research agenda for the next few years.

  9. Rhodium as permanent modifier for atomization of lead from biological fluids using tungsten filament electrothermal atomic absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Zhou, Ying; Parsons, Patrick J.; Aldous, Kenneth M.; Brockman, Paul; Slavin, Walter

    2002-04-01

    Rhodium (Rh) was investigated as a permanent modifier for the atomization of Pb from biological fluids in W-filament atomic absorption spectrometry (AAS). Heating the W-filament with a Rh solution provided a protective coating for subsequent determinations of Pb in blood and urine matrices. The W-filament AAS instrumentation used was based on a prototype design that utilized self-reversal background correction scheme and peak area measurements. We found that Rh not only stabilized Pb during the pyrolysis step, but also facilitated the removal of carbonaceous residues during the cleaning step, requiring much less power than with phosphate modifier. Thus, the filament lifetime was greatly extended to over 300 firings. Periodic reconditioning with Rh was necessary every 30 firings or so. Conditioning the filament with Rh also permitted direct calibration using simple aqueous Pb standards. The method detection limit for blood Pb was approximately 1.5 μg dl -1, similar to that reported previously. Potential interferences from concomitants such as Na, K, Ca and Mg were evaluated. Accuracy was verified using lead reference materials from the National Institute of Standards and Technology and the New York State Department of Health. Blood lead results below 40 μg dl -1 were within ±1 μg dl -1 of certified values, and within ±10% above 40 μg dl -1; within-run precision was ±10% or better. Additional validation was reported using proficiency test materials and human blood specimens. All blood lead results were within the acceptable limits established by regulatory authorities in the US. When measuring Pb in urine, sensitivity was reduced and matrix-matched calibration became necessary. The method of detection limit was 27 μg l -1 for urine Pb. Urine lead results were also validated using an acceptable range comparable to that established for blood lead by US regulatory agencies.

  10. An Unusual Ligand Coordination Gives Rise to a New Family of Rhodium Metalloinsertors with Improved Selectivity and Potency

    PubMed Central

    2015-01-01

    Rhodium metalloinsertors are octahedral complexes that bind DNA mismatches with high affinity and specificity and exhibit unique cell-selective cytotoxicity, targeting mismatch repair (MMR)-deficient cells over MMR-proficient cells. Here we describe a new generation of metalloinsertors with enhanced biological potency and selectivity, in which the complexes show Rh–O coordination. In particular, it has been found that both Δ- and Λ-[Rh(chrysi)(phen)(DPE)]2+ (where chrysi =5,6 chrysenequinone diimmine, phen =1,10-phenanthroline, and DPE = 1,1-di(pyridine-2-yl)ethan-1-ol) bind to DNA containing a single CC mismatch with similar affinities and without racemization. This is in direct contrast with previous metalloinsertors and suggests a possible different binding disposition for these complexes in the mismatch site. We ascribe this difference to the higher pKa of the coordinated immine of the chrysi ligand in these complexes, so that the complexes must insert into the DNA helix with the inserting ligand in a buckled orientation; spectroscopic studies in the presence and absence of DNA along with the crystal structure of the complex without DNA support this assignment. Remarkably, all members of this new family of compounds have significantly increased potency in a range of cellular assays; indeed, all are more potent than cisplatin and N-methyl-N′-nitro-nitrosoguanidine (MNNG, a common DNA-alkylating chemotherapeutic agent). Moreover, the activities of the new metalloinsertors are coupled with high levels of selective cytotoxicity for MMR-deficient versus proficient colorectal cancer cells. PMID:25254630

  11. Zeolite-supported Metal Complexes of Rhodium and of Ruthenium: a General Synthesis Method Influenced by Molecular Sieving Effects

    SciTech Connect

    Ogino, I.; Chen, C; Gates , B

    2010-01-01

    A general method for synthesis of supported metal complexes having a high degree of uniformity is presented, whereby organometallic precursors incorporating acetylacetonate (C{sub 5}H{sub 7}O{sub 2}{sup -}, acac) ligands react with zeolites incorporating OHgroups near Al sites. The method is illustrated by the reactions of Rh(acac)(CO){sub 2} and of cis-Ru(acac){sub 2}({eta}{sup 2}-C{sub 2}H{sub 4}){sub 2} with zeolites slurried in n-pentane at room temperature. The zeolites were H-Beta, H-SSZ-42, H-Mordenite, and HZSM-5. Infrared (IR) and extended X-ray absorption fine structure spectra of the zeolites incorporating rhodium complexes indicate the formation of Rh(CO){sub 2}{sup +} bonded near Al sites; similar results have been reported for the formation of zeolite-supported Rh({eta}{sup 2}-C{sub 2}H{sub 4}){sup 2+} from Rh(acac)({eta}{sup 2}-C{sub 2}H{sub 4}){sub 2}. IR spectra of the supported rhodiumgem-dicarbonyls include sharp, well-resolved {nu}{sub CO} bands, demonstrating that the sites surrounding each metal complex are nearly equivalent. The frequencies of the {nu}{sub CO} bands show how the composition of the zeolite influences the bonding of the supported species, demonstrating subtle differences in the roles of the zeolite as ligands. When the zeolite has pore openings larger than the critical diameter of the precursor organometallic compound, the latter undergoes facile transport into the interior of the zeolite, so that a uniform distribution of the supported species results, but when the precursors barely fit through the zeolite apertures, the mass transport resistance is significant and the supported metal complexes are concentrated near the pore mouths.

  12. Rhodium catalyzed oxidative coupling of salicylaldehydes with diazabicyclic olefins: a one pot strategy involving aldehyde C-H cleavage and π-allyl chemistry towards the synthesis of fused ring chromanones.

    PubMed

    Jijy, E; Prakash, Praveen; Shimi, M; Pihko, Petri M; Joseph, Nayana; Radhakrishnan, K V

    2013-08-25

    An efficient one pot strategy for the synthesis of cyclopentene fused chromanone derivatives through the direct oxidative coupling of salicylaldehydes with bicyclic olefins in the presence of a rhodium-copper catalyst system is described. This is the first report on the ring opening-ring closing of bicyclic hydrazines via metal catalyzed oxidative coupling reaction.

  13. [Drug access in poor countries].

    PubMed

    Sebbag, Robert

    2007-11-01

    As a responsible player in the global pharmaceutical industry, Sanofi-Aventis recognizes its special responsibility to provide poor countries with access to drugs and vaccines. This is a key component of the Group's approach to sustainable development. As such, the Access to Medicines department draws on Sanofi-Aventis' expertise in order to address major public health issues, starting with the treatment of malaria, tuberculosis, sleeping sickness, leishmaniasis and epilepsy, as well as access to vaccines. The department has four main activities: research and development of new drugs; improvement of existing treatments; information, communication and education of patients and healthcare professionals; and development of a differential pricing and distribution policy adapted to patients' income, with a "no profit-no loss" equilibrium.

  14. Serving the world's poor, profitably.

    PubMed

    Prahalad, C K; Hammond, Allen

    2002-09-01

    By stimulating commerce and development at the bottom of the economic pyramid, multi-nationals could radically improve the lives of billions of people and help create a more stable, less dangerous world. Achieving this goal does not require MNCs to spearhead global social-development initiatives for charitable purposes. They need only act in their own self-interest. How? The authors lay out the business case for entering the world's poorest markets. Fully 65% of the world's population earns less than $2,000 per year--that's 4 billion people. But despite the vastness of this market, it remains largely untapped. The reluctance to invest is easy to understand, but it is, by and large, based on outdated assumptions of the developing world. While individual incomes may be low, the aggregate buying power of poor communities is actually quite large, representing a substantial market in many countries for what some might consider luxury goods like satellite television and phone services. Prices, and margins, are often much higher in poor neighborhoods than in their middle-class counterparts. And new technologies are already steadily reducing the effects of corruption, illiteracy, inadequate infrastructure, and other such barriers. Because these markets are in the earliest stages of economic development, revenue growth for multi-nationals entering them can be extremely rapid. MNCs can also lower costs, not only through low-cost labor but by transferring operating efficiencies and innovations developed to serve their existing operations. Certainly, succeeding in such markets requires MNCs to think creatively. The biggest change, though, has to come from executives: Unless business leaders confront their own preconceptions--particularly about the value of high-volume, low-margin businesses--companies are unlikely to master the challenges or reap the rewards of these developing markets.

  15. Evaluation of the role of the metal-support interfacial centers in the dry reforming of methane on alumina-supported rhodium catalysts

    SciTech Connect

    Ferreira-Aparicio, P.; Fernandez-Garcia, M.; Guerrero-Ruiz, A.; Rodriguez-Ramos, I.

    2000-03-10

    The reforming of CH{sub 4} with CO{sub 2} (dry reforming) has been studied on a series of Al{sub 2}O{sub 3}-supported Rh-Cu catalysts. The reaction has been found to proceed on these systems through a bifunctional mechanism, in which the activation on methane takes place on the rhodium phase while carbon dioxide is activated on the support surface via formate intermediates. The addition of a metal, such as copper, inactive for methane activation, has allowed the authors to evaluate the role of the interfacial Rh-Al{sub 2}O{sub 3} sites in the reaction. The presence of copper reduces the stability of the catalysts, though it does not have any effect on the initial activity per surface exposed site. It indicates that the dry reforming of methane is not a structure-sensitive reaction and that catalytic activity, largely affected by the alumina support, is dependent on the number of surface exposed rhodium centers.

  16. Total synthesis of (+)-asteriscanolide: further exploration of the rhodium(I)-catalyzed [(5+2)+1] reaction of ene-vinylcyclopropanes and CO.

    PubMed

    Liang, Yong; Jiang, Xing; Fu, Xu-Fei; Ye, Siyu; Wang, Tao; Yuan, Jie; Wang, Yuanyuan; Yu, Zhi-Xiang

    2012-03-05

    The total synthesis of (+)-asteriscanolide is reported. The synthetic route features two key reactions: 1) the rhodium(I)-catalyzed [(5+2)+1] cycloaddition of a chiral ene-vinylcyclopropane (ene-VCP) substrate to construct the [6.3.0] carbocyclic core with excellent asymmetric induction, and 2) an alkoxycarbonyl-radical cyclization that builds the bridging butyrolactone ring with high efficiency. Other features of this synthetic route include the catalytic asymmetric alkynylation of an aldehyde to synthesize the chiral ene-VCP substrate, a highly regioselective conversion of the [(5+2)+1] cycloadduct into its enol triflate, and the inversion of the inside-outside tricycle to the outside-outside structure by an ester-reduction/elimination to enol-ether/hydrogenation procedure. In addition, density functional theory (DFT) rationalization of the chiral induction of the [(5+2)+1] reaction and the diastereoselectivity of the radical annulation has been presented. Equally important is that we have also developed other routes to synthesize asteriscanolide using the rhodium(I)-catalyzed [(5+2)+1] cycloaddition as the key step. Even though these routes failed to achieve the total synthesis, these experiments gave further useful information about the scope of the [(5+2)+1] reaction and paved the way for its future application in synthesis. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Equilibrium thermodynamics to form a rhodium formyl complex from reactions of CO and H2: metal σ donor activation of CO.

    PubMed

    Imler, Gregory H; Zdilla, Michael J; Wayland, Bradford B

    2014-04-23

    A rhodium(II) dibenzotetramethylaza[14]annulene dimer ([(tmtaa)Rh]2) (1) reacts with CO and H2 in toluene and pyridine to form equilibrium distributions with hydride and formyl complexes ((tmtaa)Rh-H (2); (tmtaa)Rh-C(O)H (3)). The rhodium formyl complex ((tmtaa)Rh-C(O)H) was isolated under a CO/H2 atmosphere, and the molecular structure was determined by X-ray diffraction. Equilibrium constants were evaluated for reactions of (tmtaa)Rh-H with CO to produce formyl complexes in toluene (K2(298 K)(tol) = 10.8 (1.0) × 10(3)) and pyridine (K2(298 K)(py) = 2.2 (0.2) × 10(3)). Reactions of 1 and 2 in toluene and pyridine are discussed in the context of alternative radical and ionic pathways. The five-coordinate 18-electron Rh(I) complex ([(py)(tmtaa)Rh(I)](-)) is proposed to function as a nucleophile toward CO to give a two-electron activated bent Rh-CO unit. Results from DFT calculations on the (tmtaa)Rh system correlate well with experimental observations. Reactions of 1 with CO and H2 suggest metal catalyst design features to reduce the activation barriers for homogeneous CO hydrogenation.

  18. Improved antiparasitic activity by incorporation of organosilane entities into half-sandwich ruthenium(II) and rhodium(III) thiosemicarbazone complexes.

    PubMed

    Adams, Muneebah; de Kock, Carmen; Smith, Peter J; Land, Kirkwood M; Liu, Nicole; Hopper, Melissa; Hsiao, Allyson; Burgoyne, Andrew R; Stringer, Tameryn; Meyer, Mervin; Wiesner, Lubbe; Chibale, Kelly; Smith, Gregory S

    2015-02-07

    A series of ferrocenyl- and aryl-functionalised organosilane thiosemicarbazone compounds was obtained via a nucleophilic substitution reaction with an amine-terminated organosilane. The thiosemicarbazone (TSC) ligands were further reacted with either a ruthenium dimer [(η(6-i)PrC6H4Me)Ru(μ-Cl)Cl]2 or a rhodium dimer [(Cp*)Rh(μ-Cl)Cl]2 to yield a series of cationic mono- and binuclear complexes. The thiosemicarbazone ligands, as well as their metal complexes, were characterised using NMR and IR spectroscopy, and mass spectrometry. The molecular structure of the binuclear ruthenium(ii) complex was determined by single-crystal X-ray diffraction analysis. The thiosemicarbazones and their complexes were evaluated for their in vitro antiplasmodial activities against the chloroquine-sensitive (NF54) and chloroquine-resistant (Dd2) Plasmodium falciparum strains, displaying activities in the low micromolar range. Selected compounds were screened for potential β-haematin inhibition activity, and it was found that two Rh(iii) complexes exhibited moderate to good inhibition. Furthermore, the compounds were screened for their antitrichomonal activities against the G3 Trichomonas vaginalis strain, revealing a higher percentage of growth inhibition for the ruthenium and rhodium complexes over their corresponding ligand.

  19. Ammonia Borane Dehydrogenation Promoted by a Pincer-Square-Planar Rhodium(I) Monohydride: A Stepwise Hydrogen Transfer from the Substrate to the Catalyst.

    PubMed

    Esteruelas, Miguel A; Nolis, Pau; Oliván, Montserrat; Oñate, Enrique; Vallribera, Adelina; Vélez, Andrea

    2016-07-18

    The pincer d(8)-monohydride complex RhH{xant(P(i)Pr2)2} (xant(P(i)Pr2)2 = 9,9-dimethyl-4,5-bis(diisopropylphosphino)xanthene) promotes the release of 1 equiv of hydrogen from H3BNH3 and H3BNHMe2 with TOF50% values of 3150 and 1725 h(-1), to afford [BH2NH2]n and [BH2NMe2]2 and the tandem ammonia borane dehydrogenation-cyclohexene hydrogenation. DFT calculations on the ammonia borane dehydrogenation suggest that the process takes place by means of cis-κ(2)-PP-species, through four stages including: (i) Shimoi-type coordination of ammonia borane, (ii) homolytic addition of the coordinated H-B bond to afford a five-coordinate dihydride-boryl-rhodium(III) intermediate, (iii) reductive intramolecular proton transfer from the NH3 group to one of the hydride ligands, and (iv) release of H2 from the resulting square-planar hydride dihydrogen rhodium(I) intermediate.

  20. Realistic energy surfaces for real-world systems: an IMOMO CCSD(T):DFT scheme for rhodium-catalyzed hydroformylation with the 6-DPPon ligand.

    PubMed

    Gellrich, Urs; Himmel, Daniel; Meuwly, Markus; Breit, Bernhard

    2013-11-25

    The hydroformylation of terminal alkenes is one of the most important homogeneously catalyzed processes in industry, and the atomistic understanding of this reaction has attracted enormous interest in the past. Herein, the whole catalytic cycle for rhodium-catalyzed hydroformylation with the 6-diphenylphosphinopyridine-(2H)-1-one (6-DPPon) ligand 1 was studied. This catalytic transformation is challenging to describe computationally, since two requirements must be met: 1) changes in the hydrogen-bond network must be modeled accurately and 2) bond-formation/bond-breaking processes in the coordination sphere of the rhodium center must be calculated accurately. Depending on the functionals used (BP86, B3LYP), the results were found to differ strongly. Therefore, the complete cycle was calculated by using highly accurate CCSD(T) computations for a PH3 model ligand. By applying an integrated molecular orbital plus molecular orbital (IMOMO) method consisting of CCSD(T) as high level and DFT as low-level method, excellent agreement between the two functionals was achieved. To further test the reliability of the calculations, the energetic-span model was used to compare experimentally derived and computed activation barriers. The accuracy of the new IMOMO method apparently makes it possible to predict the catalytic potential of real-world systems.

  1. Essentially Molecular Metal Complexes Anchored to Zeolite: Synthesis and Characterization of Rhodium Complexes and Ruthenium Complexes Prepared from Rh(acac)(2-C2H4)2 and cis-Ru(acac)2( -C2H4)2

    SciTech Connect

    Ogino, I.; Gates, B

    2010-01-01

    Mononuclear complexes of rhodium and of ruthenium, Rh(acac)({eta}{sup 2}-C{sub 2}H{sub 4}){sub 2} and cis-Ru(acac)2({eta}{sup 2}-C{sub 2}H{sub 4}){sub 2} (acac = C{sub 5}H{sub 7}O{sub 2}{sup -}), were used as precursors to synthesize metal complexes bonded to zeolite {beta}. Infrared (IR) and extended X-ray absorption fine structure (EXAFS) spectra show that the species formed from Rh(acac)({eta}{sup 2}-C{sub 2}H{sub 4}){sub 2} was Rh({eta}{sup 2}-C{sub 2}H{sub 4}){sub 2}{sup +}, which was bonded to the zeolite at aluminum sites via two Rh-O bonds. Reaction of this supported rhodium complex with CO gave the supported rhodium gem-dicarbonyl Rh(CO){sub 2}{sup +}, which was characterized by two {nu}{sub CO} bands in the IR spectrum, at 2048 and 2115 cm{sup -1}, that were sharp (fwhm of 2115-cm{sup -1} band = 5 cm{sup -1}), indicating a high degree of uniformity of the supported species. Nearly the same result was observed (Liang, A. et al. J. Am. Chem. Soc. 2009, 131, 8460) for the isostructural rhodium complex supported on dealuminated HY zeolite, which was characterized by frequencies of the {nu}{sub CO} bands that were 4 and 2 cm{sup -1}, respectively, greater than those characterizing the zeolite {beta}-supported complex. This comparison indicates that the Rh atoms in Rh({eta}{sup 2}-C{sub 2}H{sub 4}){sub 2}{sup +} anchored on zeolite {beta} were slightly more electron-rich than those on zeolite Y. This inference is supported by EXAFS results showing shorter Rh-C bonds in the zeolite {beta}-supported rhodium ethene complex than in the zeolite Y-supported rhodium ethene complex. In contrast to these supported rhodium complexes, the zeolite {beta}-supported ruthenium samples were shown by IR and EXAFS spectroscopies to consist of mixtures of mononuclear ruthenium complexes with various numbers of acac ligands; when CO reacted with the supported ruthenium complexes, the resultant ruthenium carbonyls were characterized by {nu}{sub CO} spectra characteristic of both

  2. Thermal and shape stability of high-index-faceted rhodium nanoparticles: a molecular dynamics investigation.

    PubMed

    Zeng, Xiang-Ming; Huang, Rao; Wen, Yu-Hua; Sun, Shi-Gang

    2015-02-28

    Nanosized noble metallic particles enclosed by high-index facets exhibit superior catalytic activity because of their high density of low-coordinated step atoms at the surface, and thus have attracted growing interest over the past decade. In this article, we employed molecular dynamics simulations to investigate the thermodynamic evolution of tetrahexahedral Rh nanoparticles respectively covered by {210}, {310}, and {830} facets during the heating process. Our results reveal that the {210} faceted nanoparticle exhibits better thermal and shape stability than the {310} and {830} faceted ones. Meanwhile, because the {830} facet consists of {210} and {310} subfacets, the stability of the {830} faceted Rh nanoparticle is dominated by the {310} subfacet, which possesses a relatively poor stability. Furthermore, the shape transformation of these nanoparticles occurs much earlier than their melting. Further analyses indicate that surface atoms with higher coordination numbers display lower surface diffusivity, and are thus more helpful for stabilizing the particle shape. This study offers an atomistic understanding of the thermodynamic behaviors of high-index-faceted Rh nanoparticles.

  3. Preparation and Electrocatalytic Application of Composites Containing Gold Nanoparticles Protected with Rhodium-Substituted Polyoxometalates.

    PubMed

    Wiaderek, Kamila M; Cox, James A

    2011-04-01

    Substitution of a metal center of phosphomolybdate, PMo(12)O(40) (3-) (PMo(12)), or its tungsten analogue with dirhodium(II) and subsequent stabilization of gold nanoparticles, AuNPs, with Rh(2)PMo(11) is demonstrated. The AuNP-Rh(2)PMo(11) mediates oxidations but adsorbs too weakly for direct modification of electrode materials. Stability in quiescent solution was achieved by modifying glassy carbon (GC) with 3-aminopropyltriethoxysilane (APTES) and then electrostatically assembling AuNP-Rh(2)PMo(11). At GC|APTES|AuNP-Rh(2)PMo(11), cyclic voltammetry showed the expected set of three reversible peak-pairs for PMo(11) in the range -0.2 to 0.6 vs (Ag/AgCl)/V and the reversible Rh(II,III) couple at 1.0 vs (Ag/AgCl)/V. The presence of AuNPs increased the current for the reduction of bromate by a factor of 2.5 relative to that at GC|Rh(2)PMo(11), and the electrocatalytic oxidation of methionine displayed characteristics of synergism between the AuNP and Rh(II). To stabilize AuNP-Rh(2)PMo(11) on a surface in a flow system, GC was modified by electrochemically assisted deposition of a sol-gel with templated 10-nm pores prior to immobilizing the catalyst in the pores. The resulting electrode permitted determination of bromate by flow-injection amperometry with a detection limit of 4.0 × 10(-8) mol dm(-3).

  4. Effect of support on iron promoted rhodium nanocatalysts for ethanol synthesis from CO hydrogenation

    NASA Astrophysics Data System (ADS)

    Carrillo Sanchez, Pamela Carolina

    Depleting fossil fuel sources coupled with the deleterious effects of petroleum-based fuel combustion have led to the development of sustainable ways for energy production. One alternative is the production of biofuels like ethanol. Ethanol's biggest advantages are its high energy density, biodegradability and carbon neutrality. A potential scalable process is the conversion of synthetic gas (syngas: CO, CO2, H 2) produced from gasification of biomass with the use of Rh-based catalysts. The work presented in this thesis aimed to study the effect of the introduction of 1, 5, and 10 wt % CeO2 into a TiO2 support on Fe promoted-Rh catalysts for ethanol production from CO hydrogenation. The mixed-oxide CeO2-TiO2 support was synthesized by a sol-gel method where Rh and Fe nanoparticles were deposited by wet incipient impregnation. Reactivity studies were carried under CO hydrogenation conditions with the use of gas chromatography. Characterization of the bare support and the catalyst that showed the best ethanol selectivity were performed by in-situ X-ray diffraction synchrotron experiments. Ethanol selectivity increases with ceria content with a shift on product distribution and CO conversion rates compared to Rh supported on single TiO2 and CeO2. This could be explained by a synergetic effect between CeO2 and TiO2 and to the to the formation of amorphous and mobile species of CeOx that can act as dispersing agents for the Rh particles increasing catalytic sites for CO insertion and for the stabilization of HCOx species. XRD characterization analysis of 10%CeO2-90%TiO2 identified three crystallographic phases: anatase, TiO2(B), and cerianite. The unpromoted 2%Rh/10%CeO2-90%TiO2 in-situ XRD analysis showed an absence of Rh0 under CO hydrogenation conditions. Conversely, the addition of Fe to the different mixed-oxide compositions showed comparable ethanol selectivity at the expense of methane formation. Therefore, the introduction of ceria into the titania support on

  5. Atmospheric organic nitrogen deposition explored at workshop

    NASA Astrophysics Data System (ADS)

    Church, Thomas M.

    Atmospheric organic nitrogen (AON) is an important nitrogen component with significant deposition in many natural waters. The range and quality of the data are varied, but deposited organic nitrogen (DON) is ubiquitous globally, both in extent and magnitude.The Environmental Protection Agency's Chesapeake Bay Program (CBP) sponsored a workshop last year to determine what is known about organic nitrogen in atmospheric deposition and to establish research priorities needed to obtain an adequate database for coastal waters such as Chesapeake Bay Working groups at the meeting concluded that AON represents a poorly quantified array of broadly reactive natural and pollutant species; that because of compromises in collection, preservation, and analysis, wet deposition of total organic nitrogen is inadequately quantified and dry deposition is not quantified at all; and that because of a lack of data on bioactive species, the effect of AON and DON on ecosystems is largely unknown.

  6. Poor Outcomes in Hepatic Amyloidosis: A Report of 2 Cases

    PubMed Central

    Kertowidjojo, Elizabeth; Zhang, Yue; Patel, Pruthvi

    2016-01-01

    Hepatic amyloidosis is a rare disease entity that results from insoluble amyloid protein deposition in the liver. The disease often presents with vague, nonspecific clinical features. Currently, there is little literature describing treatment outcomes for biopsy-proven hepatic amyloidosis and current treatment guidelines recommend that patients enroll in a clinical trial due to insufficient evidence to suggest an optimal treatment regimen. Here, we present two cases of hepatic amyloidosis at an academic medical center and describe their presentation, treatment, and outcomes. These cases highlight the poor outcomes and difficult management of hepatic amyloidosis. Further understanding and investigation of this rare disease are warranted. PMID:27774327

  7. Deposition head for laser

    DOEpatents

    Lewis, Gary K.; Less, Richard M.

    1999-01-01

    A deposition head for use as a part of apparatus for forming articles from materials in particulate form in which the materials are melted by a laser beam and deposited at points along a tool path to form an article of the desired shape and dimensions. The deposition head delivers the laser beam and powder to a deposition zone, which is formed at the tip of the deposition head. A controller comprised of a digital computer directs movement of the deposition zone along the tool path and provides control signals to adjust apparatus functions, such as the speed at which the deposition head moves along the tool path.

  8. Novel interconnect deposition technology

    NASA Astrophysics Data System (ADS)

    Speckman, D. M.; Wendt, J. P.

    1991-12-01

    A new series of experiments was initiated to improve current interconnect deposition technology for integrated circuits. Preliminary aluminum deposition experiments were carried out using trimethylamine(alane) as the precursor, and some mildly reflective, uniform aluminum films were successfully deposited on glass slides, suggesting that chemical vapor deposition (CVD) will be a practicable deposition technique for advanced integrated circuit interconnect films. CVD studies of aluminum and zirconium- and hafnium-diboride thin films are continuing.

  9. Aqua-bis-(4-methyl-benzene-sulfonato-κO)(η(5)-penta-methyl-cyclo-penta-dien-yl)rhodium(III) monohydrate.

    PubMed

    Roy, Christopher P; Boyer, Pauline M; Merola, Joseph S

    2013-05-01

    The title half-sandwich rhodium(III) complex, [Rh(C10H15)(C7H7O3S)2(H2O)]·H2O, consists of a π-bonded penta-methyl-cyclo-penta-dienyl group, two σ-bonded tosyl-ate groups and an aqua ligand. The structure displays both inter- and intra-molecular O-H⋯O hydrogen bonding. The inter-molecular hydrogen bonding results in an extended helical chain along a 21 screw axis parallel to c, due to hydrogen bonding from the coordinating water ligand to the lattice water mol-ecule and then to a sulfonate O atom of a different asymmetric unit.

  10. Regio- and stereospecific rhodium-catalyzed allylic alkylation with an acyl anion equivalent: an approach to acyclic α-ternary β,γ-unsaturated aryl ketones.

    PubMed

    Turnbull, Ben W H; Chae, Jungha; Oliver, Samuel; Evans, P Andrew

    2017-05-01

    The regio- and stereospecific rhodium-catalyzed allylic alkylation of secondary allylic carbonates with cyanohydrin pronucleophiles facilitates the direct construction of acyclic α-ternary β,γ-unsaturated aryl ketones. Interestingly, this study illustrates the impact of deaggregating agents on regiocontrol and the electronic nature of the aryl component to suppress olefin isomerization. In addition, we demonstrate that the dimethylamino substituent, which modulates the pKa of the α-ternary β,γ-unsaturated aryl ketone, provides a useful synthetic handle for further functionalization via Kumada cross-coupling of the aryl trimethylammonium salt. Finally, the stereospecific alkylation of a chiral nonracemic secondary allylic carbonate affords the enantioenriched α-ternary aryl ketone, which was employed in a formal synthesis of trichostatic acid to illustrate that the allylic alkylation proceeds with net retention of configuration.

  11. Synthesis and crystal structure of the rhodium(I) cyclooctadiene complex with bis(3- tert-butylimidazol-2-ylidene)borate ligand

    NASA Astrophysics Data System (ADS)

    Chen, F.; Shao, K.-J.; Xiao, Y.-C.; Pu, X.-J.; Zhu, B.; Jiang, M.-J.

    2015-12-01

    The rhodium(I) cyclooctadiene complex with the bis(3- tert-butylimidazol-2-ylidene)borate ligand [H2B( Im t Bu)2]Rh(COD) C22H36BN4Rh, has been prepared, and its crystal structure is determined by X-ray diffraction. Complex exhibits slightly distorted square planar configurations around the metal center, which is coordinated by the bidentate H2B( Im t Bu)2 and one cyclooctadiene group. The Rh-Ccarbene bond lengths are 2.043(4) and 2.074(4) Å, and the bond angle C-Rh1-C is 82.59°. The dihedral angle between two imidazol-2-ylidene rings is 67.30°.

  12. Synthesis and crystal structure of the rhodium(I) cyclooctadiene complex with bis(3-tert-butylimidazol-2-ylidene)borate ligand

    SciTech Connect

    Chen, F.; Shao, K.-J.; Xiao, Y.-C.; Pu, X.-J.; Zhu, B.; Jiang, M.-J.

    2015-12-15

    The rhodium(I) cyclooctadiene complex with the bis(3-tert-butylimidazol-2-ylidene)borate ligand [H{sub 2}B(Im{sup t}Bu){sup 2}]Rh(COD) C{sup 22}H{sup 36}BN{sup 4}Rh, has been prepared, and its crystal structure is determined by X-ray diffraction. Complex exhibits slightly distorted square planar configurations around the metal center, which is coordinated by the bidentate H{sup 2}B(Im{sup t}Bu){sub 2} and one cyclooctadiene group. The Rh–C{sub carbene} bond lengths are 2.043(4) and 2.074(4) Å, and the bond angle C–Rh1–C is 82.59°. The dihedral angle between two imidazol-2-ylidene rings is 67.30°.

  13. Atomic force microscopy on phase-control pulsed force mode in water: Imaging and force analysis on a rhodium-octaethylporphyrin layer on highly oriented pyrolytic graphite

    NASA Astrophysics Data System (ADS)

    Maeda, Yasushi; Yamazaki, Shin-ichi; Kohyama, Masanori

    2014-06-01

    We developed phase-control pulsed force mode (p-PFM) as the operation mode for atomic force microscopy (AFM). The p-PFM allowed us to observe soft or weakly adsorbed materials in a liquid environment using a conventional AFM apparatus, and allowed for force curve mapping (FCM) after offline data processing. We applied the p-PFM to a rhodium-octaethylporphyrin (RhOEP) layer on highly oriented pyrolytic graphite (HOPG), which is applicable to anode catalysts of fuel cells. The RhOEP/HOPG system was stably observed in water by this mode. In the p-PFM image, we found both large and small protrusions, which were not observed in the dynamic force mode, in air. The detailed force analysis suggested that these protrusions are nanobubbles located on the HOPG substrate exposed in holes or pits of the RhOEP layer.

  14. The role of fluctuations in bistability and oscillations during the H{sub 2} + O{sub 2} reaction on nanosized rhodium crystals

    SciTech Connect

    Grosfils, P.; Gaspard, P.; Visart de Bocarmé, T.

    2015-08-14

    A combined experimental and theoretical study is presented of fluctuations observed by field ion microscopy in the catalytic reaction of water production on a rhodium tip. A stochastic approach is developed to provide a comprehensive understanding of the different phenomena observed in the experiment, including burst noise manifesting itself in a bistability regime, noisy oscillations, and nanopatterns with a cross-like oxidized zone separating the surface into four quadrants centered on the (111) facets. The study is based on a stochastic model numerically simulating the processes of adsorption, desorption, reaction, and transport. The surface diffusion of hydrogen is described as a percolation process dominated by large clusters corresponding to the four quadrants. The model reproduces the observed phenomena in the ranges of temperature, pressures, and electric field of the experiment.

  15. Synthesis of iridium and rhodium complexes with new chiral phosphine-NHC ligands based on 1,1'-binaphthyl framework and their application in asymmetric hydrogenation.

    PubMed

    Gu, Peng; Zhang, Jun; Xu, Qin; Shi, Min

    2013-10-07

    The first series of chiral phosphine-imidazole carbene ligands based on a 1,1'-binaphthyl framework were synthesized from (R)-2-amine-2'-(diphenylphosphino)-1,1'-binaphthyl (1) in a four-step pathway. After deprotonation of these phosphine-imidazolium salts with LiO(t)Bu, and subsequent complexation with [Ir(COD)Cl]2 and anion exchange with NaBArF, phosphine-carbene chelated iridium complexes (R)-6a and (R)-6b were obtained. Their structures have been characterized by NMR and X-ray diffraction analysis. The NHC-phosphine rhodium complex (R)-6c has been also obtained by a similar synthetic method. These iridium complexes have been applied to catalyze the asymmetric hydrogenation of alkenes to give the corresponding products in moderate to excellent conversion (up to 99%) and moderate enantioselectivities under mild conditions (up to 61% ee).

  16. New ammonium surfactant-stabilized rhodium(0) colloidal suspensions: influence of novel counter-anions on physico-chemical and catalytic properties.

    PubMed

    Bilé, Elodie Guyonnet; Sassine, Rita; Denicourt-Nowicki, Audrey; Launay, Franck; Roucoux, Alain

    2011-06-28

    Novel anionic species, such as hydrogen carbonate (HCO(3)(−)), fluoride (F(−)), triflate (CF(3)SO(3)(−)), tetrafluoroborate (BF(4)(−)) and chloride (Cl(−)) were investigated as new partners of water soluble N,N-dimethyl-N-cetyl-N-(2-hydroxyethyl) ammonium salts, used as a protective agent of rhodium colloids. The effect of the surfactant polar head on the micellar behavior, size and morphology of the nanospecies was studied by adapted physico-chemical experiments (surface tension measurements, dynamic light scattering, thermogravimetric and TEM analyses) and discussed in terms of strong or weak stabilization of the growing nanoparticles surface. Finally, the influence of the nanoenvironment generated by the surfactant with various counter-anions was evaluated via the hydrogenation of aromatics.

  17. Deposit model for volcanogenic uranium deposits

    USGS Publications Warehouse

    Breit, George N.; Hall, Susan M.

    2011-01-01

    The International Atomic Energy Agency's tabulation of volcanogenic uranium deposits lists 100 deposits in 20 countries, with major deposits in Russia, Mongolia, and China. Collectively these deposits are estimated to contain uranium resources of approximately 500,000 tons of uranium, which amounts to 6 percent of the known global resources. Prior to the 1990s, these deposits were considered to be small (less than 10,000 tons of uranium) with relatively low to moderate grades (0.05 to 0.2 weight percent of uranium). Recent availability of information on volcanogenic uranium deposits in Asia highlighted the large resource potential of this deposit type. For example, the Streltsovskoye district in eastern Russia produced more than 100,000 tons of uranium as of 2005; with equivalent resources remaining. Known volcanogenic uranium deposits within the United States are located in Idaho, Nevada, Oregon, and Utah. These deposits produced an estimated total of 800 tons of uranium during mining from the 1950s through the 1970s and have known resources of 30,000 tons of uranium. The most recent estimate of speculative resources proposed an endowment of 200,000 tons of uranium.

  18. Sediment-Hosted Copper Deposits of the World: Deposit Models and Database

    USGS Publications Warehouse

    Cox, Dennis P.; Lindsey, David A.; Singer, Donald A.; Diggles, Michael F.

    2003-01-01

    Introduction This publication contains four descriptive models and four grade-tonnage models for sediment hosted copper deposits. Descriptive models are useful in exploration planning and resource assessment because they enable the user to identify deposits in the field and to identify areas on geologic and geophysical maps where deposits could occur. Grade and tonnage models are used in resource assessment to predict the likelihood of different combinations of grades and tonnages that could occur in undiscovered deposits in a specific area. They are also useful in exploration in deciding what deposit types meet the economic objectives of the exploration company. The models in this report supersede the sediment-hosted copper models in USGS Bulletin 1693 (Cox, 1986, and Mosier and others, 1986) and are subdivided into a general type and three subtypes. The general model is useful in classifying deposits whose features are obscured by metamorphism or are otherwise poorly described, and for assessing regions in which the geologic environments are poorly understood. The three subtypes are based on differences in deposit form and environments of deposition. These differences are described under subtypes in the general model. Deposit models are based on the descriptions of geologic environments and physical characteristics, and on metal grades and tonnages of many individual deposits. Data used in this study are presented in a database representing 785 deposits in nine continents. This database was derived partly from data published by Kirkham and others (1994) and from new information in recent publications. To facilitate the construction of grade and tonnage models, the information, presented by Kirkham in disaggregated form, was brought together to provide a single grade and a single tonnage for each deposit. Throughout the report individual deposits are defined as being more than 2,000 meters from the nearest adjacent deposit. The deposit models are presented here as

  19. Colloidal stability, surface characterisation and intracellular accumulation of Rhodium(II) citrate coated superparamagnetic iron oxide nanoparticles in breast tumour: a promising platform for cancer therapy

    NASA Astrophysics Data System (ADS)

    da Silva Nunes, Eloiza; Carneiro, Marcella Lemos Brettas; de Oliveira, Ricardo Guirelli Simões; Báo, Sônia Nair; de Souza, Aparecido Ribeiro

    2013-06-01

    The colloidal stability of a rhodium(II) citrate, Rh2(H2cit)4, coating on the surface of maghemite (γ-Fe2O3) nanoparticles was studied and compared in different dispersion media. The adsorption of Rh2(H2cit)4 at the water-maghemite interface was evaluated as a function of pH and complex concentration. A slight pH-dependent adsorption of the complex was observed with a maximum at pH 3. The colloidal stability of the functionalised nanoparticles with different amounts of Rh2(H2cit)4 as a function of pH was evaluated using dynamic light scattering measurements. The particles have a mean magnetic core size of 5.6 nm and the hydrodynamic diameters are approximately 60 nm, which remained unchanged in the pH range in which the samples were a stable sol. The tolerance to different dispersion media, which were deionised water, saline, phosphate-buffered saline (PBS), foetal bovine serum (FBS) and NaCl solutions with different concentrations, was investigated. At moderate ionic strength, the colloidal stability of the dispersions was similar in saline and in PBS compared to the stability of dispersions diluted in water. Moreover, the intracellular accumulation of nanoparticles in 4T1 breast tumour was examined by ultrastructural analysis performed by transmission electron microscopy. The rhodium(II) citrate-coated nanoparticles were found mostly in the cytoplasm and nucleus. Thus, we suggest that these SPIO nanoparticles functionalized with Rh2(H2Cit)4 can be potential tools for anticancer therapy.

  20. Metallogenic evolution of uranium deposits in the Middle East and North Africa deposits

    NASA Astrophysics Data System (ADS)

    Howari, Fares; Goodell, Philip; Salman, Abdulaty

    2016-02-01

    This paper is briefly involved in classification and distributions of the Middle East and North Africa (MENA) uranium deposits. The study of these mineral systems can significantly contribute to our further understanding of the metallogeny of known and poorly explored deposits. This provides contribution to, and further enhancement of, current classifications and metallogenic models of uranium systems, allowing researchers to emphasize on unknown or poorly studied mineral systems found in MENA. The present study identified eight metallogenic types of uranium associated with: 1) the Archean rocks and intra-cratonic basins, 2) the Pan-African granites and rhyolites which are characterized by igneous activity, 3) Phanerozoic (Paleozoic) clastics, these deposits are the sedimentological response to Pan African magmatism, 4) Mesozoic (basal) clastics type e.g. Nubia sandstones which are characterized by uranium minerals, 5) regional sedimentary phosphate deposits which are categorized as geosynclinal, or continental margin deposits, on the shelf of the Tethys Ocean, 6) Cenozoic Intracratonic Felsic Magmatism of the Tibesti and Hoggar, and the sandstone U deposits of adjoining Niger. These are similar to the Pan-African magmatism metallogenic, 7) Calcretes, and 8) Resistate minerals which are often enriched in rare earth elements, sometimes including uranium. They are thus sometimes considered as U resources but poorly explored in the MENA region. These metallogenic types are described and discussed in the current paper.

  1. Rhodium self-powered neutron detector as a suitable on-line thermal neutron flux monitor in BNCT treatments

    SciTech Connect

    Miller, Marcelo E.; Sztejnberg, Manuel L.; Gonzalez, Sara J.; Thorp, Silvia I.; Longhino, Juan M.; Estryk, Guillermo

    2011-12-15

    Purpose: A rhodium self-powered neutron detector (Rh SPND) has been specifically developed by the Comision Nacional de Energia Atomica (CNEA) of Argentina to measure locally and in real time thermal neutron fluxes in patients treated with boron neutron capture therapy (BNCT). In this work, the thermal and epithermal neutron response of the Rh SPND was evaluated by studying the detector response to two different reactor spectra. In addition, during clinical trials of the BNCT Project of the CNEA, on-line neutron flux measurements using the specially designed detector were assessed. Methods: The first calibration of the detector was done with the well-thermalized neutron spectrum of the CNEA RA-3 reactor thermal column. For this purpose, the reactor spectrum was approximated by a Maxwell-Boltzmann distribution in the thermal energy range. The second calibration was done at different positions along the central axis of a water-filled cylindrical phantom, placed in the mixed thermal-epithermal neutron beam of CNEA RA-6 reactor. In this latter case, the RA-6 neutron spectrum had been well characterized by both calculation and measurement, and it presented some marked differences with the ideal spectrum considered for SPND calibrations at RA-3. In addition, the RA-6 neutron spectrum varied with depth in the water phantom and thus the percentage of the epithermal contribution to the total neutron flux changed at each measurement location. Local (one point-position) and global (several points-positions) and thermal and mixed-field thermal neutron sensitivities were determined from these measurements. Thermal neutron flux was also measured during BNCT clinical trials within the irradiation fields incident on the patients. In order to achieve this, the detector was placed on patient's skin at dosimetric reference points for each one of the fields. System stability was adequate for this kind of measurement. Results: Local mixed-field thermal neutron sensitivities and global

  2. Rhodium self-powered neutron detector as a suitable on-line thermal neutron flux monitor in BNCT treatments.

    PubMed

    Miller, Marcelo E; Sztejnberg, Manuel L; González, Sara J; Thorp, Silvia I; Longhino, Juan M; Estryk, Guillermo

    2011-12-01

    A rhodium self-powered neutron detector (Rh SPND) has been specifically developed by the Comisión Nacional de Energía Atómica (CNEA) of Argentina to measure locally and in real time thermal neutron fluxes in patients treated with boron neutron capture therapy (BNCT). In this work, the thermal and epithermal neutron response of the Rh SPND was evaluated by studying the detector response to two different reactor spectra. In addition, during clinical trials of the BNCT Project of the CNEA, on-line neutron flux measurements using the specially designed detector were assessed. The first calibration of the detector was done with the well-thermalized neutron spectrum of the CNEA RA-3 reactor thermal column. For this purpose, the reactor spectrum was approximated by a Maxwell-Boltzmann distribution in the thermal energy range. The second calibration was done at different positions along the central axis of a water-filled cylindrical phantom, placed in the mixed thermal-epithermal neutron beam of CNEA RA-6 reactor. In this latter case, the RA-6 neutron spectrum had been well characterized by both calculation and measurement, and it presented some marked differences with the ideal spectrum considered for SPND calibrations at RA-3. In addition, the RA-6 neutron spectrum varied with depth in the water phantom and thus the percentage of the epithermal contribution to the total neutron flux changed at each measurement location. Local (one point-position) and global (several points-positions) and thermal and mixed-field thermal neutron sensitivities were determined from these measurements. Thermal neutron flux was also measured during BNCT clinical trials within the irradiation fields incident on the patients. In order to achieve this, the detector was placed on patient's skin at dosimetric reference points for each one of the fields. System stability was adequate for this kind of measurement. Local mixed-field thermal neutron sensitivities and global thermal and mixed

  3. Rhodium-Catalyzed C-C Bond Formation via Heteroatom-Directed C-H Bond Activation

    SciTech Connect

    Colby, Denise; Bergman, Robert; Ellman, Jonathan

    2010-05-13

    Once considered the 'holy grail' of organometallic chemistry, synthetically useful reactions employing C-H bond activation have increasingly been developed and applied to natural product and drug synthesis over the past decade. The ubiquity and relative low cost of hydrocarbons makes C-H bond functionalization an attractive alternative to classical C-C bond forming reactions such as cross-coupling, which require organohalides and organometallic reagents. In addition to providing an atom economical alternative to standard cross - coupling strategies, C-H bond functionalization also reduces the production of toxic by-products, thereby contributing to the growing field of reactions with decreased environmental impact. In the area of C-C bond forming reactions that proceed via a C-H activation mechanism, rhodium catalysts stand out for their functional group tolerance and wide range of synthetic utility. Over the course of the last decade, many Rh-catalyzed methods for heteroatom-directed C-H bond functionalization have been reported and will be the focus of this review. Material appearing in the literature prior to 2001 has been reviewed previously and will only be introduced as background when necessary. The synthesis of complex molecules from relatively simple precursors has long been a goal for many organic chemists. The ability to selectively functionalize a molecule with minimal pre-activation can streamline syntheses and expand the opportunities to explore the utility of complex molecules in areas ranging from the pharmaceutical industry to materials science. Indeed, the issue of selectivity is paramount in the development of all C-H bond functionalization methods. Several groups have developed elegant approaches towards achieving selectivity in molecules that possess many sterically and electronically similar C-H bonds. Many of these approaches are discussed in detail in the accompanying articles in this special issue of Chemical Reviews. One approach that has

  4. Computational Exploration of Rh(III)/Rh(V) and Rh(III)/Rh(I) Catalysis in Rhodium(III)-Catalyzed C-H Activation Reactions of N-Phenoxyacetamides with Alkynes.

    PubMed

    Yang, Yun-Fang; Houk, K N; Wu, Yun-Dong

    2016-06-01

    The selective rhodium-catalyzed functionalization of arenes is greatly facilitated by oxidizing directing groups that act both as directing groups and internal oxidants. We report density functional theory (B3LYP and M06) investigations on the mechanism of rhodium(III)-catalyzed redox coupling reaction of N-phenoxyacetamides with alkynes. The results elucidated the role of the internal oxidizing directing group, and the role of Rh(III)/Rh(I) and Rh(III)/Rh(V) catalysis of C-H functionalizations. A novel Rh(III)-Rh(V)-Rh(III) cycle successfully rationalizes recent experimental observations by Liu and Lu et al. ( Liu , G. Angew. Chem. Int. Ed. 2013 , 52 , 6033 ) on the reactions of N-phenoxyacetamides with alkynes in different solvents. Natural Bond Orbital (NBO) analysis confirms the identity of Rh(V) intermediate in the catalytic cycle.

  5. Family Structure and Employment Characteristics Differentiate Poor from Near-Poor Workers.

    ERIC Educational Resources Information Center

    Dagata, Elizabeth M.

    1997-01-01

    Current Population Survey data indicate that rural workers were more likely than urban workers to be poor or near-poor. Poor and near-poor rural workers were more likely than other workers to be southern, young, and in a minority group. Barriers to livable-wage employment included low educational attainment, being a single mother, and having young…

  6. Do Middle-Class Students Perceive Poor Women and Poor Men Differently?

    ERIC Educational Resources Information Center

    Cozzarelli, Catherine; Tagler, Michael J.; Wilkinson, Anna V.

    2002-01-01

    Examined college students' attitudes and stereotypes regarding poor women, attributions for their poverty, and whether those thoughts and feelings differed from those about poor men. Attitudes and stereotypes were significantly more positive regarding poor women than poor men. Participants endorsed internal attributions for both women's and men's…

  7. Rh(III)-Catalyzed Cascade Annulation/C-H Activation of o-Ethynylanilines with Diazo Compounds: One-Pot Synthesis of Benzo[a]carbazoles via 1,4-Rhodium Migration.

    PubMed

    Guo, Songjin; Yuan, Kai; Gu, Meng; Lin, Aijun; Yao, Hequan

    2016-10-05

    A Rh(III)-catalyzed cascade annulation/C-H activation of o-ethynylanilines with diazo compounds has been developed. This concise method allows for the rapid formation of a number of benzo[a]carbazoles in high yields, exhibiting good functional group tolerance and scalability. The key to the success of this approach involves one C-N bond and two C-C bond formation, and an aryl-to-aryl 1,4-rhodium migration.

  8. Physical deposit measures and commercial potential: The case of titanium-bearing heavy-mineral deposits

    USGS Publications Warehouse

    Attanasi, E.D.; DeYoung, J.H.

    1988-01-01

    Physical measures of mineral deposit characteristics, such as grade and tonnage, long have been used in both subjective and analytic models to predict favorability of areas for the occurrence of mineral deposits of particular types. After a deposit has been identified, however, the explorationist must decide whether to continue data collection, begin an economic feasibility study, or abandon the prospect. The decision maker can estimate the probability that a deposit will be commercial by examining physical measures. The amount of sampling data required before such a probability estimate can be considered reliable can be determined. A logit probability model estimated from onshore titanium-bearing heavy-mineral deposit data identifies and quantifies the relative influence of a deposit's physical measures on the chances of the deposit becoming commercial. A principal conclusion that can be drawn from the analysis is that, along with a measure of deposit size, the characteristics most important in predicting commercial potential are grades of the constituent minerals. Total heavy-mineral-bearing sand grade or even total titanium grade (without data on constituent mineral grades) are poor predictors of the deposit's commercial potential. ?? 1988 International Association for Mathematical Geology.

  9. An automatic collector to monitor insoluble atmospheric deposition: application for mineral dust deposition

    NASA Astrophysics Data System (ADS)

    Laurent, B.; Losno, R.; Chevaillier, S.; Vincent, J.; Roullet, P.; Bon Nguyen, E.; Ouboulmane, N.; Triquet, S.; Fornier, M.; Raimbault, P.; Bergametti, G.

    2015-07-01

    Deposition is one of the key terms of the mineral dust cycle. However, dust deposition remains poorly constrained in transport models simulating the atmospheric dust cycle. This is mainly due to the limited number of relevant deposition measurements. This paper aims to present an automatic collector (CARAGA), specially developed to sample the total (dry and wet) atmospheric deposition of insoluble dust in remote areas. The autonomy of the CARAGA can range from 25 days to almost 1 year depending on the programmed sampling frequency (from 1 day to 2 weeks respectively). This collector is used to sample atmospheric deposition of Saharan dust on the Frioul islands in the Gulf of Lions in the Western Mediterranean. To quantify the mineral dust mass in deposition samples, a weighing and ignition protocol is applied. Almost 2 years of continuous deposition measurements performed on a weekly sampling basis on Frioul Island are presented and discussed with air mass trajectories and satellite observations of dust. Insoluble mineral deposition measured on Frioul Island was 2.45 g m-2 for February to December 2011 and 3.16 g m-2 for January to October 2012. Nine major mineral deposition events, measured during periods with significant MODIS aerosol optical depths, were associated with air masses coming from the southern Mediterranean Basin and North Africa.

  10. Cascadia Tsunami Deposit Database

    USGS Publications Warehouse

    Peters, Robert; Jaffe, Bruce; Gelfenbaum, Guy; Peterson, Curt

    2003-01-01

    The Cascadia Tsunami Deposit Database contains data on the location and sedimentological properties of tsunami deposits found along the Cascadia margin. Data have been compiled from 52 studies, documenting 59 sites from northern California to Vancouver Island, British Columbia that contain known or potential tsunami deposits. Bibliographical references are provided for all sites included in the database. Cascadia tsunami deposits are usually seen as anomalous sand layers in coastal marsh or lake sediments. The studies cited in the database use numerous criteria based on sedimentary characteristics to distinguish tsunami deposits from sand layers deposited by other processes, such as river flooding and storm surges. Several studies cited in the database contain evidence for more than one tsunami at a site. Data categories include age, thickness, layering, grainsize, and other sedimentological characteristics of Cascadia tsunami deposits. The database documents the variability observed in tsunami deposits found along the Cascadia margin.

  11. Chlorido(dimethyl 2,2'-bipyridine-4,4'-dicarboxylate-κ2N,N')(η5-pentamethylcyclopentadienyl)rhodium(III) chloride 1-hydroxypyrrolidine-2,5-dione disolvate.

    PubMed

    Sivanesan, Dharmalingam; Kim, Hyung Min; Sungho, Yoon

    2013-06-01

    The title complex, [Rh(C10H15)Cl(C14H12N2O4)]Cl·2C4H5NO3, has been synthesized by a substitution reaction of the precursor [bis(2,5-dioxopyrrolidin-1-yl) 2,2'-bipyridine-4,4'-dicarboxylate]chlorido(pentamethylcyclopentadienyl)rhodium(III) chloride with NaOCH3. The Rh(III) cation is located in an RhC5N2Cl eight-coordinated environment. In the crystal, 1-hydroxypyrrolidine-2,5-dione (NHS) solvent molecules form strong hydrogen bonds with the Cl(-) counter-anions in the lattice and weak hydrogen bonds with the pentamethylcyclopentadienyl (Cp*) ligands. Hydrogen bonding between the Cp* ligands, the NHS solvent molecules and the Cl(-) counter-anions form links in a V-shaped chain of Rh(III) complex cations along the c axis. Weak hydrogen bonds between the dimethyl 2,2'-bipyridine-4,4'-dicarboxylate ligands and the Cl(-) counter-anions connect the components into a supramolecular three-dimensional network. The synthetic route to the dimethyl 2,2'-bipyridine-4,4'-dicarboxylate-containing rhodium complex from the [bis(2,5-dioxopyrrolidin-1-yl) 2,2'-bipyridine-4,4'-dicarboxylate]rhodium(III) precursor may be applied to link Rh catalysts to the surface of electrodes.

  12. Determination of Ultra-trace Rhodium in Water Samples by Graphite Furnace Atomic Absorption Spectrometry after Cloud Point Extraction Using 2-(5-Iodo-2-Pyridylazo)-5-Dimethylaminoaniline as a Chelating Agent.

    PubMed

    Han, Quan; Huo, Yanyan; Wu, Jiangyan; He, Yaping; Yang, Xiaohui; Yang, Longhu

    2017-03-24

    A highly sensitive method based on cloud point extraction (CPE) separation/preconcentration and graphite furnace atomic absorption spectrometry (GFAAS) detection has been developed for the determination of ultra-trace amounts of rhodium in water samples. A new reagent, 2-(5-iodo-2-pyridylazo)-5-dimethylaminoaniline (5-I-PADMA), was used as the chelating agent and the nonionic surfactant TritonX-114 was chosen as extractant. In a HAc-NaAc buffer solution at pH 5.5, Rh(III) reacts with 5-I-PADMA to form a stable chelate by heating in a boiling water bath for 10 min. Subsequently, the chelate is extracted into the surfactant phase and separated from bulk water. The factors affecting CPE were investigated. Under the optimized conditions, the calibration graph was linear in the range of 0.1-6.0 ng/mL, the detection limit was 0.023 ng/mL for rhodium and relative standard deviation was 3.67% (c = 1.0 ng/mL, n = 11).The method has been applied to the determination of trace rhodium in water samples with satisfactory results.

  13. Wet Dust Deposition Across Texas, USA

    NASA Astrophysics Data System (ADS)

    Collins, J. D., Jr.; Ponette-González, A.; Gill, T. E.; Glass, G. A.; Weathers, K. C.

    2016-12-01

    Atmospheric dust deposition is of critical importance in terrestrial biogeochemical cycles, supplying essential limiting nutrients, such as calcium and phosphorus as well as pollutants, such as lead, to ecosystems. Dust particles are delivered to terrestrial ecosystems directly as dry deposition or in precipitation (wet deposition) as a result of rainout (particles incorporated into cloud droplets) and washout (particles that collide with raindrops as they fall). Compared to dry deposition, wet dust deposition (dissolved + particulate) is a poorly understood yet potentially significant pathway for dust input, especially in humid regions. We quantified wet dust deposition to two National Atmospheric Deposition Monitoring (NADP) sites across Texas-one in west (Guadalupe Mountains) and one in east (near Houston) Texas-with contrasting climate/dust regimes and land cover. We focused on 2012 during one of the most severe droughts in Texas since 1895. Dust event days (DEDs) were identified using meteorological data for stations within 150 km of the NADP sites where wet deposition was sampled weekly. DEDs were defined using the following criteria: visibility <10 km, <30% relative humidity, and wind speed >50 km, supplemented with other Saharan dust incursion and dust observations. A total of 34 DEDs (20 sample weeks) were identified for the west and 5 DEDs (4 sample weeks) for the east Texas sites. Bulk elemental composition of washout particles is analyzed using Particle Induced X-ray Emission (PIXE) spectroscopy and X-ray Fluorescence (XRF) spectroscopy. Using these data, we will examine differences in the chemical composition of rainwater and aerosol particles filtered from rain samples for dust versus non-dust event days at each study site. Deposition fluxes for dust and non-dust event weeks are also compared. Quantifying the magnitude of wet dust deposition is necessary to improve evaluation of dust impacts on biogeochemical cycles.

  14. The Crisis of the Near Poor

    ERIC Educational Resources Information Center

    Newman, Katherine S.; Tan Chen, Victor

    2007-01-01

    This article focuses on the "missing class," the near poor whose incomes place them above the poverty line, but well below the middle class. Near-poor families with two parents and two children subsist on $20,000 to $40,000 a year, which disqualifies them for virtually all public subsidies, but is a far cry from what they need to be…

  15. Cognitive Profiles of Korean Poor Readers

    ERIC Educational Resources Information Center

    Cho, Jeung-Ryeul; Ji, Yu-Kyong

    2011-01-01

    This study compared the performance of 30 poor readers in the third grade with those of 30 average readers of the same age and 30 younger readers matched with the same reading level on phonological, visuo-perceptual, orthographic, and naming speed tasks. Individual data revealed heterogeneous profiles for the poor readers: six (20%) exhibited…

  16. RADAR OBSERVATION CONDITIONS OF POOR VISIBILITY,

    DTIC Science & Technology

    Ship navigational radar is an effective means for revealing above-water objects in conditions of poor visibility. A radar image of the surrounding...radar observation and with the competent operation of the set, radar is a reliable means of detection of encountered vessels in conditions of poor

  17. Poor Rural Children Attract Close Study

    ERIC Educational Resources Information Center

    Viadero, Debra

    2008-01-01

    Growing up poor in isolated rural areas and small towns is qualitatively different from growing up poor in the city. Yet most of what experts know about the effects of poverty on children's development comes from studies conducted in big cities. Now, an ambitious project run by universities in Pennsylvania and North Carolina is putting what some…

  18. Phonological Coding in Good and Poor Readers.

    ERIC Educational Resources Information Center

    Briggs, Pamela; Underwood, Geoffrey

    1982-01-01

    A set of four experiments investigates the relationship between phonological coding and reading ability, using a picture-word interference task and a decoding task. Results with regard to both adults and children suggest that while poor readers possess weak decoding skills, good and poor readers show equivalent evidence of direct semantic and…

  19. BIRTH CONTROL, CULTURE AND THE POOR.

    ERIC Educational Resources Information Center

    RIESSMAN, CATHERINE KOHLER

    EVIDENCE FROM STUDIES INDICATE THAT THE POOR DESIRE TO CONTROL THEIR FAMILY SIZE AND PREFER TO USE BIRTH CONTROL DEVICES (PILLS OR INTERUTERINE DEVICES) WHICH ARE NOT COITUS-CONNECTED AND ANTITHETICAL TO THEIR SEXUAL ATTITUDES AND TRADITIONS. CONTRARY TO THE BELIEF THAT THE POOR ARE LESS LIKELY TO UTILIZE EXISTING HEALTH FACILITIES OR TO TAKE PART…

  20. The Crisis of the Near Poor

    ERIC Educational Resources Information Center

    Newman, Katherine S.; Tan Chen, Victor

    2007-01-01

    This article focuses on the "missing class," the near poor whose incomes place them above the poverty line, but well below the middle class. Near-poor families with two parents and two children subsist on $20,000 to $40,000 a year, which disqualifies them for virtually all public subsidies, but is a far cry from what they need to be…

  1. The Chronically Poor: Breaking the Cycle.

    ERIC Educational Resources Information Center

    Morris-Bilotti, Sharon

    This question-and-answer format paper looks at some of the basic issues surrounding the chronically poor and initiatives and services designed to break the poverty cycle. A first section explores some of the myths and realities surrounding the characteristics of the chronically poor population and notes that this population is comprised of…

  2. Poor Rural Children Attract Close Study

    ERIC Educational Resources Information Center

    Viadero, Debra

    2008-01-01

    Growing up poor in isolated rural areas and small towns is qualitatively different from growing up poor in the city. Yet most of what experts know about the effects of poverty on children's development comes from studies conducted in big cities. Now, an ambitious project run by universities in Pennsylvania and North Carolina is putting what some…

  3. Cognitive Profiles of Korean Poor Readers

    ERIC Educational Resources Information Center

    Cho, Jeung-Ryeul; Ji, Yu-Kyong

    2011-01-01

    This study compared the performance of 30 poor readers in the third grade with those of 30 average readers of the same age and 30 younger readers matched with the same reading level on phonological, visuo-perceptual, orthographic, and naming speed tasks. Individual data revealed heterogeneous profiles for the poor readers: six (20%) exhibited…

  4. Soil-like deposits observed by Sojourner, the Pathfinder rover

    USGS Publications Warehouse

    Moore, Henry J.; Bickler, Donald B.; Crisp, Joy A.; Eisen, Howard J.; Gensler, Jeffrey A.; Haldemann, Albert F.C.; Matijevic, Jacob R.; Reid, Lisa K.; Pavlics, Ferenc

    1999-01-01

    Most of the soil-like materials at the Pathfinder landing site behave like moderately dense soils on Earth with friction angles near 34°-39° and are called cloddy deposits. Cloddy deposits appear to be poorly sorted with dust-sized to granule-sized mineral or rock grains; they may contain pebbles, small rock fragments, and clods. Thin deposits of porous, compressible drifts with friction angles near 26°-28° are also present. Drifts are fine grained. Cohesions of both types of deposits are small. There may be indurated soil-like deposits and/or coated or crusted rocks. Cloddy deposits may be fluvial sediments of the Ares-Tiu floods, but other origins, such as ejecta from nearby impact craters, should be considered. Drifts are probably dusts that settled from the Martian atmosphere. Remote-sensing signatures of the deposits inferred from rover observations are consistent with those observed from orbit and Earth.

  5. Time estimation in good and poor sleepers.

    PubMed

    Fichten, Catherine S; Creti, Laura; Amsel, Rhonda; Bailes, Sally; Libman, Eva

    2005-12-01

    Time estimation was examined in 148 older good and poor sleepers in analogue and naturalistic sleep settings. On analogue tasks, both "empty" time and time listening to an audiobook were overestimated by both good and poor sleepers. There were no differences between groups. "Empty" time was experienced as "dragging." In the sleep setting, most poor sleepers underestimated nocturnal sleep and overestimated awake times related to their own sleep problem: sleep onset vs. sleep maintenance insomnia. Good sleepers did the opposite. Severity of sleep problem and size of time estimation errors were unrelated. Greater night-to-night wake time variability was experienced by poor than by good sleepers. Psychological adjustment was unrelated to time estimations and to magnification or minimization of sleep problems. The results suggest that for poor sleepers who magnify their sleep problem, self-monitoring can be of benefit by demonstrating that the sleep problem is not as severe as believed.

  6. Magmatic ore deposits in layered intrusions - Descriptive model for reef-type PGE and contact-type Cu-Ni-PGE deposits

    USGS Publications Warehouse

    Zientek, Michael L.

    2012-01-01

    Layered, ultramafic to mafic intrusions are uncommon in the geologic record, but host magmatic ore deposits containing most of the world's economic concentrations of platinum-group elements (PGE) (figs. 1 and 2). These deposits are mined primarily for their platinum, palladium, and rhodium contents (table 1). Magmatic ore deposits are derived from accumulations of crystals of metallic oxides, or immiscible sulfide, or oxide liquids that formed during the cooling and crystallization of magma, typically with mafic to ultramafic compositions. "PGE reefs" are stratabound PGE-enriched lode mineralization in mafic to ultramafic layered intrusions. The term "reef" is derived from Australian and South African literature for this style of mineralization and used to refer to (1) the rock layer that is mineralized and has distinctive texture or mineralogy (Naldrett, 2004), or (2) the PGE-enriched sulfide mineralization that occurs within the rock layer. For example, Viljoen (1999) broadly defined the Merensky Reef as "a mineralized zone within or closely associated with an unconformity surface in the ultramafic cumulate at the base of the Merensky Cyclic Unit." In this report, we will use the term PGE reef to refer to the PGE-enriched mineralization, not the host rock layer. Within a layered igneous intrusion, reef-type mineralization is laterally persistent along strike, extending for the length of the intrusion, typically tens to hundreds of kilometers. However, the mineralized interval is thin, generally centimeters to meters thick, relative to the stratigraphic thickness of layers in an intrusion that vary from hundreds to thousands of meters. PGE-enriched sulfide mineralization is also found near the contacts or margins of layered mafic to ultramafic intrusions (Iljina and Lee, 2005). This contact-type mineralization consists of disseminated to massive concentrations of iron-copper-nickel-PGE-enriched sulfide mineral concentrations in zones that can be tens to hundreds

  7. Glacial atmospheric phosphorus deposition

    NASA Astrophysics Data System (ADS)

    Kjær, Helle Astrid; Dallmayr, Remi; Gabrieli, Jacopo; Goto-Azuma, Kumiko; Hirabayashi, Motohiro; Svensson, Anders; Vallelonga, Paul

    2016-04-01

    Phosphorus in the atmosphere is poorly studied and thus not much is known about atmospheric phosphorus and phosphate transport and deposition changes over time, though it is well known that phosphorus can be a source of long-range nutrient transport, e.g. Saharan dust transported to the tropical forests of Brazil. In glacial times it has been speculated that transport of phosphorus from exposed shelves would increase the ocean productivity by wash out. However whether the exposed shelf would also increase the atmospheric load to more remote places has not been investigated. Polar ice cores offer a unique opportunity to study the atmospheric transport of aerosols on various timescales, from glacial-interglacial periods to recent anthropogenic influences. We have for the first time determined the atmospheric transport of phosphorus to the Arctic by means of ice core analysis. Both total and dissolved reactive phosphorus were measured to investigate current and past atmospheric transport of phosphorus to the Arctic. Results show that glacial cold stadials had increased atmospheric total phosphorus mass loads of 70 times higher than in the past century, while DRP was only increased by a factor of 14. In the recent period we find evidence of a phosphorus increase over the past 50 yrs in ice cores close to human occupation likely correlated to forest fires. References: Kjær, Helle Astrid, et al. "Continuous flow analysis method for determination of dissolved reactive phosphorus in ice cores." Environmental science & technology 47.21 (2013): 12325-12332. Kjær, Helle Astrid, et al. "Greenland ice cores constrain glacial atmospheric fluxes of phosphorus." Journal of Geophysical Research: Atmospheres120.20 (2015).

  8. Dry deposition velocities

    SciTech Connect

    Sehmel, G.A.

    1984-03-01

    Dry deposition velocities are very difficult to predict accurately. In this article, reported values of dry deposition velocities are summarized. This summary includes values from the literature on field measurements of gas and particle dry deposition velocities, and the uncertainties inherent in extrapolating field results to predict dry deposition velocities are discussed. A new method is described for predicting dry deposition velocity using a least-squares correlation of surface mass transfer resistances evaluated in wind tunnel experiments. 14 references, 4 figures, 1 table.

  9. Biomimetic thin film deposition

    NASA Astrophysics Data System (ADS)

    Rieke, P. C.; Campbell, A. A.; Tarasevich, B. J.; Fryxell, G. E.; Bentjen, S. B.

    1991-04-01

    Surfaces derivatized with organic functional groups were used to promote the deposition of thin films of inorganic minerals. These derivatized surfaces were designed to mimic the nucleation proteins that control mineral deposition during formation of bone, shell, and other hard tissues in living organisms. By the use of derivatized substrates control was obtained over the phase of mineral deposited, the orientation of the crystal lattice and the location of deposition. These features are of considerable importance in many technically important thin films, coatings, and composite materials. Methods of derivatizing surfaces are considered and examples of controlled mineral deposition are presented.

  10. The Interaction of Carbon Monoxide with Rhodium on Potassium-Modified CeO2(111)

    DOE PAGES

    Mullins, David R.

    2016-02-03

    The adsorption and reactions of CO adsorbed on Rh particles deposited on K-covered CeO2(111) were studied by temperature programmed desorption and photoelectron spectroscopy. K deposited on CeO2(111) forms a KOX over-layer by extracting O from the ceria and partially reducing some of the Ce4+ to Ce3+. CO does not adsorb on the KOX / CeO2-X(111) surface in the absence of Rh particles. CO adsorbed on Rh / K / CeO2(111) adsorbs molecularly on the Rh at 200 K. As the surface is heated the CO spills-over and reacts with the KOX to form carbonate. The carbonate decomposes at elevated temperaturemore » to produce CO and CO2. The carbonate stabilizes the KOX so that K desorbs at a higher temperature than it would in the absence of CO. When the Rh and K deposition are reversed so that K is deposited on both the Rh and the CeO2(111), CO adsorbs as CO2- at 200 K. The CO2- decomposes below 350 K to produce gas phase CO and adsorbed CO32- and CO. The CO is stabilized by the K on the Rh and desorbs above 540 K. The carbonate decomposes into gas phase CO and CO2.« less

  11. The interaction of carbon monoxide with rhodium on potassium-modified CeO2(111)

    NASA Astrophysics Data System (ADS)

    Mullins, David R.

    2016-10-01

    The adsorption and reactions of CO adsorbed on Rh particles deposited on K-covered CeO2(111) were studied by temperature programmed desorption and photoelectron spectroscopy. K deposited on CeO2(111) forms a KOX over-layer by extracting O from the ceria and partially reducing some of the Ce4 + to Ce3 +. CO does not adsorb on the KOX/ CeO2 - X(111) surface in the absence of Rh particles. CO adsorbed on Rh/K/CeO2(111) adsorbs molecularly on the Rh at 200 K. As the surface is heated the CO spills-over and reacts with the KOX to form carbonate. The carbonate decomposes at elevated temperature to produce CO and CO2. The carbonate stabilizes the KOX so that K desorbs at a higher temperature than it would in the absence of CO. When the Rh and K deposition are reversed so that K is deposited on both the Rh and the CeO2(111), CO adsorbs as CO2- at 200 K. The CO2- decomposes below 350 K to produce gas phase CO and adsorbed CO32 - and CO. The CO is stabilized by the K on the Rh and desorbs above 540 K. The carbonate decomposes into gas phase CO and CO2.

  12. Selective synthesis and characterization of single-site HY zeolite-supported rhodium complexes and their use as catalysts for ethylene hydrogenation and dimerization

    NASA Astrophysics Data System (ADS)

    Khivantsev, Konstantin

    Single-site Rh(CO)2, Rh(C2H4)2 and Rh(NO)2 complexes anchored on various dealuminated HY zeolites can be used as precursors for the selective surface mediated synthesis of well-defined site-isolated Rh(CO)(H)x complexes. DFT calculations and D 2 isotope exchange experiments provide strong evidence for the formation of a family of site isolated mononuclear rhodium carbonyl hydride complexes (including the first examples of RhH complexes with undissociated H2 ligands): Rh(CO)(H2), Rh(CO)(H)2, and Rh(CO)(H). The fraction of each individual complex formed varies significantly with the Si/Al ratio of the zeolite and the nature of the precursor used. HY zeolite-supported mononuclear Rh(CO)2 complexes are very active in ethylene hydrogenation and ethylene dimerization under ambient conditions. There is strong evidence for the cooperation mechanism between mononuclear rhodium complexes and Bronsted acid sites of the zeolite support in C-C bond formation process, as well as ethane formation. Finally, it is shown that the dimerization pathway selectivity can be progressively tuned (and completely switched off) by modifying the number of Bronsted acid sites on the zeolite surface. HY zeolite-supported mononuclear Rh(NO)2 complexes can be selectively formed upon exposure of Rh(CO)2/HY to the gas phase NO/He. They are structurally similar to Rh(CO)2/HY with Rh(I) retaining square planar geometry and nitrosyl ligands adopting a linear configuration. Rh(NO)2/HY30 is active in ethylene hydrogenation and ethylene dimerization under ambient conditions. This is the first unprecedented example of a supported transition-metal nitrosyl complex capable of performing a catalytic reaction. Moreover, this is the first example of a site-isolated Rh complex with ligands other than ethylene or carbonyl, which can catalyze both ethylene hydrogenation and dimerization. Unlike its dicarbonyl counterpart, dinitrosyl rhodium complex has a uniquely different reactivity towards ethylene and hydrogen

  13. Energy and minorities, women, and the poor

    SciTech Connect

    Perry, H.L.; Perry, E.B.

    1980-01-01

    A comprehensive, up-to-date (1975 to 1980) bibliography of articles, books and other publications is presented dealing with the subject of energy and minorities, women and the poor. Included are academic, popular, and government publications as well as publications by private groups and organizations. It is intended for political scientists, sociologists, economists, home economists, energy planners, energy managers and others interested in the interface of minorities, women, and the poor with energy. Following a brief introduction, there is a general listing. Also included are references dealing with energy and black Americans, native Americans (Indians), the poor, and women. (MJJ)

  14. An automatic collector to monitor insoluble atmospheric deposition: an application for mineral dust deposition

    NASA Astrophysics Data System (ADS)

    Laurent, B.; Losno, R.; Chevaillier, S.; Vincent, J.; Roullet, P.; Bon Nguyen, E.; Ouboulmane, N.; Triquet, S.; Fornier, M.; Raimbault, P.; Bergametti, G.

    2015-03-01

    Deposition is one of the key processes controlling the mass budget of the atmospheric mineral dust concentration. However, dust deposition remains poorly constrained in transport models simulating the atmospheric dust cycle. This is mainly due to the limited number of relevant deposition measurements. This paper aims at presenting an automatic collector (CARAGA), specially developed to sample the total (dry and wet) atmospheric deposition of insoluble dust in remote areas. The autonomy of the CARAGA can range from 25 days to almost 1 year depending on the programed sampling time step (1 day and 2 weeks sampling time steps, respectively). This collector is used to sample atmospheric deposition on Frioul Island which is located in the Gulf of Lions in the Western Mediterranean Basin over which Saharan dust can be transported and deposited. To quantify the mineral dust mass in deposition samples, a weighing and ignition protocol is applied. Two years of continuous deposition measurements performed on a weekly time step sampling on Frioul Island are presented and discussed with in-situ measurements, air mass trajectories and satellite observations of dust.

  15. Stability and dynamic processes in 16VE iridium(III) ethyl hydride and rhodium(I) σ-ethane complexes: experimental and computational studies.

    PubMed

    Walter, Marc D; White, Peter S; Schauer, Cynthia K; Brookhart, Maurice

    2013-10-23

    Iridium(I) and rhodium(I) ethyl complexes, (PONOP)M(C2H5) (M = Ir (1-Et), Rh (2-Et)) and the iridium(I) propyl complex (PONOP)Ir(C3H7) (1-Pr), where PONOP is 2,6-(tBu2PO)2C5H3N, have been prepared. Low-temperature protonation of the Ir complexes yields the alkyl hydrides, (PONOP)Ir(H)(R) (1-(H)(Et)(+) and 1-(H)(Pr)(+)), respectively. Dynamic (1)H NMR characterization of 1-(H)(Et)(+) establishes site exchange between the Ir-H and Ir-CH2 protons (ΔG(exH)(‡)(-110 °C) = 7.2(1) kcal/mol), pointing to a σ-ethane intermediate. By dynamic (13)C NMR spectroscopy, the exchange barrier between the α and β carbons ("chain-walking") was measured (ΔG(exC)(‡)(-110 °C) = 8.1(1) kcal/mol). The barrier for ethane loss is 17.4(1) kcal/mol (-40 °C), to be compared with the reported barrier to methane loss in 1-(H)(Me)(+) of 22.4 kcal/mol (22 °C). A rhodium σ-ethane complex, (PONOP)Rh(EtH) (2-(EtH)(+)), was prepared by protonation of 2-Et at -150 °C. The barrier for ethane loss (ΔG(dec)(‡)(-132 °C) = 10.9(2) kcal/mol) is lower than for the methane complex, 2-(MeH)(+), (ΔG(dec)(‡)(-87 °C) = 14.5(4) kcal/mol). Full spectroscopic characterization of 2-(EtH)(+) is reported, a key feature of which is the upfield signal at -31.2 ppm for the coordinated CH3 group in the (13)C NMR spectrum. The exchange barrier of the hydrogens of the coordinated methyl group is too low to be measured, but the chain-walking barrier of 7.2(1) kcal/mol (-132 °C) is observable by (13)C NMR. The coordination mode of the alkane ligand and the exchange pathways for the Rh and Ir complexes are evaluated by DFT studies. On the basis of the computational studies, it is proposed that chain-walking occurs by different mechanisms: for Rh, the lowest energy path involves a η(2)-ethane transition state, while for Ir, the lowest energy exchange pathway proceeds through the symmetrical ethylene dihydride complex.

  16. Airfoil deposition model

    NASA Technical Reports Server (NTRS)

    Kohl, F. J.

    1982-01-01

    The methodology to predict deposit evolution (deposition rate and subsequent flow of liquid deposits) as a function of fuel and air impurity content and relevant aerodynamic parameters for turbine airfoils is developed in this research. The spectrum of deposition conditions encountered in gas turbine operations includes the mechanisms of vapor deposition, small particle deposition with thermophoresis, and larger particle deposition with inertial effects. The focus is on using a simplified version of the comprehensive multicomponent vapor diffusion formalism to make deposition predictions for: (1) simple geometry collectors; and (2) gas turbine blade shapes, including both developing laminar and turbulent boundary layers. For the gas turbine blade the insights developed in previous programs are being combined with heat and mass transfer coefficient calculations using the STAN 5 boundary layer code to predict vapor deposition rates and corresponding liquid layer thicknesses on turbine blades. A computer program is being written which utilizes the local values of the calculated deposition rate and skin friction to calculate the increment in liquid condensate layer growth along a collector surface.

  17. Poor Sleep May Worsen Suicidal Thoughts

    MedlinePlus

    ... https://medlineplus.gov/news/fullstory_166928.html Poor Sleep May Worsen Suicidal Thoughts Treating insomnia might help ... 28, 2017 WEDNESDAY, June 28, 2017 (HealthDay News) -- Sleep problems may provide early clues about worsening suicidal ...

  18. Constraining the Evolution of Poor Clusters

    NASA Astrophysics Data System (ADS)

    Broming, Emma J.; Fuse, C. R.

    2012-01-01

    There currently exists no method by which to quantify the evolutionary state of poor clusters (PCs). Research by Broming & Fuse (2010) demonstrated that the evolution of Hickson compact groups (HCGs) are constrained by the correlation between the X-ray luminosities of point sources and diffuse gas. The current investigation adopts an analogous approach to understanding PCs. Plionis et al. (2009) proposed a theory to define the evolution of poor clusters. The theory asserts that cannibalism of galaxies causes a cluster to become more spherical, develop increased velocity dispersion and increased X-ray temperature and gas luminosity. Data used to quantify the evolution of the poor clusters were compiled across multiple wavelengths. The sample includes 162 objects from the WBL catalogue (White et al. 1999), 30 poor clusters in the Chandra X-ray Observatory archive, and 15 Abell poor clusters observed with BAX (Sadat et al. 2004). Preliminary results indicate that the cluster velocity dispersion and X-ray gas and point source luminosities can be used to highlight a weak correlation. An evolutionary trend was observed for multiple correlations detailed herein. The current study is a continuation of the work by Broming & Fuse examining point sources and their properties to determine the evolutionary stage of compact groups, poor clusters, and their proposed remnants, isolated ellipticals and fossil groups. Preliminary data suggests that compact groups and their high-mass counterpart, poor clusters, evolve along tracks identified in the X-ray gas - X-ray point source relation. While compact groups likely evolve into isolated elliptical galaxies, fossil groups display properties that suggest they are the remains of fully coalesced poor clusters.

  19. How School Taught Me I Was Poor

    ERIC Educational Resources Information Center

    Sapp, Jeff

    2009-01-01

    In this article, the author recounts how school taught him that he was poor. For him, third grade was the year in which he learned in school that he was poor. The author's story reminds everyone that all children do not experience school in the same way. Their social class (in the case described in this article), as well as their race, gender,…

  20. Nanoprecipitation for poorly water-soluble drugs.

    PubMed

    Tran, Thao

    2017-10-04

    Approximately 60% of the active pharmaceutical ingredients (APIs) in today's pharmaceutical industry are poorly water soluble drugs, and they are classified as BCS (Biopharmaceutics Classification System) class II compounds. Within the scope of this review, nanoprecipitation methods for poorly water soluble drugs as well as solvent removal techniques will be discussed. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

  1. Ichnologic signature of oxygen-depleted deposits

    SciTech Connect

    Ekdale, A.A.; Mason, T.R.

    1987-05-01

    The sedimentologic record of oxygen-poor depositional environments commonly includes trace fossils, especially those produced by deposit-feeding organisms that must have had broad oxygen tolerances. Endostratal fodinichnial and pascichnial traces indicate lack of oxygen within the substrate. Complex fodinichnia, such as Chondrites and Zoophycos, may form in anoxic sediment some distance below the water-sediment interface. The deposit-feeding animals can circulate oxygenated bottom water from the sea floor down through semipermanent shafts to permit respiration while they feed on unoxidized organic matter in the subsurface. Endostratal pascichnia, such as Helminthoida and Spirophycus, typically lack a continuous connection with the water-sediment interface, so interstitial water cannot be totally devoid of oxygen or else the animals cannot respire. However, endostratal pascichnia normally do not occur in oxidized sediment where digestible organic detritus has decomposed completely. In totally oxidized substrates, which typify higher energy depositional environments, permanent dwellings (domichnia) of filter-feeding organisms predominate. The ichnologic signature of oxygen-depleted deposits is a very high-density, very low-diversity association of deposit-feeding trace fossils. They suggest an oxygen-controlled trace fossil model in which increasing oxygen concentration of the interstitial water parallels a transition from fodinichnia-dominated through pascichnia-dominated to domichnia-dominated trace fossil associations. This model provides an alternative to the more traditional depth-controlled trace fossil distribution model in certain situations.

  2. Ionized cluster beam deposition

    NASA Technical Reports Server (NTRS)

    Kirkpatrick, A. R.

    1983-01-01

    Ionized Cluster Beam (ICB) deposition, a new technique originated by Takagi of Kyoto University in Japan, offers a number of unique capabilities for thin film metallization as well as for deposition of active semiconductor materials. ICB allows average energy per deposited atom to be controlled and involves impact kinetics which result in high diffusion energies of atoms on the growth surface. To a greater degree than in other techniques, ICB involves quantitative process parameters which can be utilized to strongly control the characteristics of films being deposited. In the ICB deposition process, material to be deposited is vaporized into a vacuum chamber from a confinement crucible at high temperature. Crucible nozzle configuration and operating temperature are such that emerging vapor undergoes supercondensation following adiabatic expansion through the nozzle.

  3. ElectroSpark Deposition

    DTIC Science & Technology

    2007-01-25

    ElectroSpark Deposition Hard Chrome Alternatives Team Joint Cadmium Alternatives Team Canadian Hard Chrome Alternatives Team Joint Group on Pollution...00-2007 to 00-00-2007 4. TITLE AND SUBTITLE ElectroSpark Deposition 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S...Processes, Inc. ElectroSpark Deposition (ESD) Results of Materials Testing and Technology Insertion January 25, 2007 Advanced Surfaces And Processes, Inc. 3

  4. The Interaction of Carbon Monoxide with Rhodium on Potassium-Modified CeO2(111)

    SciTech Connect

    Mullins, David R.

    2016-02-03

    The adsorption and reactions of CO adsorbed on Rh particles deposited on K-covered CeO2(111) were studied by temperature programmed desorption and photoelectron spectroscopy. K deposited on CeO2(111) forms a KOX over-layer by extracting O from the ceria and partially reducing some of the Ce4+ to Ce3+. CO does not adsorb on the KOX / CeO2-X(111) surface in the absence of Rh particles. CO adsorbed on Rh / K / CeO2(111) adsorbs molecularly on the Rh at 200 K. As the surface is heated the CO spills-over and reacts with the KOX to form carbonate. The carbonate decomposes at elevated temperature to produce CO and CO2. The carbonate stabilizes the KOX so that K desorbs at a higher temperature than it would in the absence of CO. When the Rh and K deposition are reversed so that K is deposited on both the Rh and the CeO2(111), CO adsorbs as CO2- at 200 K. The CO2- decomposes below 350 K to produce gas phase CO and adsorbed CO32- and CO. The CO is stabilized by the K on the Rh and desorbs above 540 K. The carbonate decomposes into gas phase CO and CO2.

  5. Rhodium-coordinated poly(arylene-ethynylene)-alt-poly(arylene-vinylene) copolymer acting as photocatalyst for visible-light-powered NAD⁺/NADH reduction.

    PubMed

    Oppelt, Kerstin T; Gasiorowski, Jacek; Egbe, Daniel Ayuk Mbi; Kollender, Jan Philipp; Himmelsbach, Markus; Hassel, Achim Walter; Sariciftci, Niyazi Serdar; Knör, Günther

    2014-09-10

    A 2,2'-bipyridyl-containing poly(arylene-ethynylene)-alt-poly(arylene-vinylene) polymer, acting as a light-harvesting ligand system, was synthesized and coupled to an organometallic rhodium complex designed for photocatalytic NAD(+)/NADH reduction. The material, which absorbs over a wide spectral range, was characterized by using various analytical techniques, confirming its chemical structure and properties. The dielectric function of the material was determined from spectroscopic ellipsometry measurements. Photocatalytic reduction of nucleotide redox cofactors under visible light irradiation (390-650 nm) was performed and is discussed in detail. The new metal-containing polymer can be used to cover large surface areas (e.g. glass beads) and, due to this immobilization step, can be easily separated from the reaction solution after photolysis. Because of its high stability, the polymer-based catalyst system can be repeatedly used under different reaction conditions for (photo)chemical reduction of NAD(+). With this concept, enzymatic, photo-biocatalytic systems for solar energy conversion can be facilitated, and the precious metal catalyst can be recycled.

  6. Rhodium nanoparticle-modified screen-printed graphite electrodes for the determination of hydrogen peroxide in tea extracts in the presence of oxygen.

    PubMed

    Gatselou, Vasiliki A; Giokas, Dimothenis L; Vlessidis, Athanasios G; Prodromidis, Mamas I

    2015-03-01

    In this work we describe the fabrication of nanostructured electrocatalytic surfaces based on polyethyleneimine (PEI)-supported rhodium nanoparticles (Rh-NP) over graphite screen-printed electrodes (SPEs) for the determination of hydrogen peroxide in the presence of oxygen. Rh-NP, electrostatically stabilized by citrate anions, were immobilized over graphite SPEs, through coulombic attraction on a thin film of positively charged PEI. The functionalized sensors, polarized at 0.0 V vs. Ag/AgCl/3 M KCl, exhibited a linear response to H2O2 over the concentration range from 5 to 600 μmol L(-1) H2O2 in the presence of oxygen. The 3σ limit of detection was 2 μmol L(-1) H2O2, while the reproducibility of the method at the concentration level of 10 μmol L(-1) H2O2 (n=10) and between different sensors (n=4) was lower than 3 and 5%, respectively. Most importantly, the sensors showed an excellent working and storage stability at ambient conditions and they were successfully applied to the determination of H2O2 produced by autooxidation of polylphenols in tea extracts with ageing. Recovery rates ranged between 97 and 104% suggesting that the as-prepared electrodes can be used for the development of small-scale, low-cost chemical sensors for use in on-site applications. Copyright © 2014 Elsevier B.V. All rights reserved.

  7. Interception and characterization of catalyst species in rhodium bis(diazaphospholane)-catalyzed hydroformylation of octene, vinyl acetate, allyl cyanide, and 1-phenyl-1,3-butadiene.

    PubMed

    Nelsen, Eleanor R; Brezny, Anna C; Landis, Clark R

    2015-11-11

    In the absence of H2, reaction of [Rh(H) (CO)2(BDP)] [BDP = bis(diazaphospholane)] with hydroformylation substrates vinyl acetate, allyl cyanide, 1-octene, and trans-1-phenyl-1,3-butadiene at low temperatures and pressures with passive mixing enables detailed NMR spectroscopic characterization of rhodium acyl and, in some cases, alkyl complexes of these substrates. For trans-1-phenyl-1,3-butadiene, the stable alkyl complex is an η(3)-allyl complex. Five-coordinate acyl dicarbonyl complexes appear to be thermodynamically preferred over the four-coordinate acyl monocarbonyls at low temperatures and one atmosphere of CO. Under noncatalytic (i.e., no H2 present) reaction conditions, NMR spectroscopy reveals the kinetic and thermodynamic selectivity of linear and branched acyl dicarbonyl formation. Over the range of substrates investigated, the kinetic regioselectivity observed at low temperatures under noncatalytic conditions roughly predicts the regioselectivity observed for catalytic transformations at higher temperatures and pressures. Thus, kinetic distributions of off-cycle acyl dicarbonyls constitute reasonable models for catalytic selectivity. The Wisconsin high-pressure NMR reactor (WiHP-NMRR) enables single-turnover experiments with active mixing; such experiments constitute a powerful strategy for elucidating the inherent selectivity of acyl formation and acyl hydrogenolysis in hydroformylation reactions.

  8. Polymer-Supported Optically Active fac(S)-Tris(thiotato)rhodium(III) Complex for Sulfur-Bridging Reaction With Precious Metal Ions.

    PubMed

    Aizawa, Sen-Ichi; Tsubosaka, Soshi

    2016-01-01

    The optically active mixed-ligand fac(S)-tris(thiolato)rhodium(III) complexes, ΔL -fac(S)-[Rh(aet)2 (L-cys-N,S)](-) (aet = 2-aminoethanethiolate, L-cys = L-cysteinate) () and ΔLL -fac(S)-[Rh(aet)(L-cys-N,S)2 ](2-) were newly prepared by the equatorial preference of the carboxyl group in the coordinated L-cys ligand. The amide formation reaction of with 1,10-diaminodecane and polyallylamine gave the diamine-bridged dinuclear Rh(III) complex and the single-chain polymer-supported Rh(III) complex with retention of the ΔL configuration of , respectively. These Rh(III) complexes reacted with Co(III) or Co(II) to give the linear-type trinuclear structure with the S-bridged Co(III) center and the two Δ-Rh(III) terminal moieties. The polymer-supported Rh(III) complex was applied not only to the CD spectropolarimetric detection and determination of a trace of precious metal ions such as Au(III), Pt(II), and Pd(II) but also to concentration and extraction of these metal ions into the solid polymer phase. Chirality 28:85-91, 2016. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.

  9. A Standardized Interpolation of Temperature Using Rhodium-Iron Resistance Thermometers Over the Interval 4.2 K to 24.5 K

    NASA Astrophysics Data System (ADS)

    Tew, W. L.; Rusby, R. L.; Lin, P.; Lipinski, L.; Steur, P. P. M.; Ricketson, B. W. A.

    2015-08-01

    The worldwide history and present state of development of rhodium-iron resistance thermometers (RIRTs) is briefly reviewed. A standardized interpolation method using RIRTs with the nominal composition of 0.5 % Fe (by mole) is presented, with examples using data taken from 60 RIRTs made from a variety of wire batches and sources worldwide over the last 40 years. The parameterization exploits the favorable characteristics of the Cragoe reduced resistance and a suitably reduced temperature . A reference function which approximates the average characteristics of selected wire is derived for use over the interval 0.65 K to 24.5561 K on the ITS-90. The deviations of real RIRT data from this reference function are examined, and simple four-parameter Fourier-series solutions for the resulting deviation curves are presented. Despite the fact that the wire samples may be of different origins or state-of-anneal, it was found that the interpolations are successful for most of the samples studied over the 4.2 K to 24.5561 K interval, at the level of 1 standard uncertainty or less. This method would allow for calibrations of most RIRTs over this interval using only six calibration points, permitting an efficiency not achievable using the common least-squares curve-fitting calibration methods. The potential of this formalism for a standardized interpolation scheme using RIRTs is discussed.

  10. Hollow-shell-structured nanospheres: a recoverable heterogeneous catalyst for rhodium-catalyzed tandem reduction/lactonization of ethyl 2-acylarylcarboxylates to chiral phthalides.

    PubMed

    Liu, Rui; Jin, Ronghua; An, Juzeng; Zhao, Qiankun; Cheng, Tanyu; Liu, Guohua

    2014-05-01

    Chiral organorhodium-functionalized hollow-shell-structured nanospheres were prepared by immobilization of a chiral N-sulfonylated diamine-based organorhodium complex within an ethylene-bridged organosilicate shell. Structural analysis and characterization reveal its well-defined single-site rhodium active center, and transmission electron microscopy images reveal a uniform dispersion of hollow-shell-structured nanospheres. As a heterogenous catalyst, it exhibits excellent catalytic activity and enantioselectivity in synthesis of chiral phthalides by a tandem reduction/lactonization of ethyl 2-acylarylcarboxylates in aqueous medium. The high catalytic performance is attributed to the synergistic effect of the high hydrophobicity and the confined chiral organorhodium catalytic nature. The organorhodium-functionalized nanospheres could be conveniently recovered and reused at least 10 times without loss of catalytic activity. This feature makes it an attractive catalyst in environmentally friendly organic reactions. The results of this study offer a new approach to immobilize chiral organometal functionalities within the hollow-shell-structured nanospheres to prepare materials with high activity in heterogeneous asymmetric catalysis. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Separation and preconcentration of trace amounts of rhodium using a dispersive liquid-liquid microextraction method and its determination by flame atomic absorption spectrometry.

    PubMed

    Mirrahimi, Fateme; Taher, Mohammad Ali

    2014-01-01

    A sensitive and selective method for the determination of low levels of rhodium (Rh) in environmental samples is needed. In the proposed method, an extracting solvent with a lower toxicity and density than the other solvents typically used in dispersive liquid-liquid microextraction was used to extract trace amounts of Rh from aqueous samples. Rh ions were complexed with 1-(2-pyridylazo)-2-naphthol in the pH range of 3.2-4.7 and extracted with dispersive liquid-liquid microextraction. The type and volume of the extracting solvent and dispersive solvent, centrifugation time, pH, amount of the chelating agent, and sample ionic strength were carefully studied. Under the optimal conditions, the LOD and RSD were 0.36 ng/mL (3Sb/m, n = 7) and +/-2.0% (n = 7), respectively. The calibration curve was linear in the range of 4.0-800 ng/mL. The method was applied to the determination of Rh in well and tap water, and spiked recoveries were in the range of 96-103.7%.

  12. Toward new organometallic architectures: synthesis of carbene-centered rhodium and palladium bisphosphine complexes. stability and reactivity of [PC(BIm)PRh(L)][PF6] pincers.

    PubMed

    Plikhta, Andriy; Pöthig, Alexander; Herdtweck, Eberhardt; Rieger, Bernhard

    2015-10-05

    In this article, we report the synthesis of a tridentate carbene-centered bisphosphine ligand precursor and its complexes. The developed four-step synthetic strategy of a new PC(BIm)P pincer ligand represents the derivatization of benzimidazole in the first and third positions by (diphenylphosphoryl)methylene synthone, followed by phosphine deprotection and subsequent insertion of a noncoordinating anion. The obtained ligand precursor undergoes complexation, with PdCl2 and [μ-OCH3Rh(COD)]2 smoothly forming the target organometallics [PC(BIm)PPdCl][PF6] and [PC(BIm)PRh(L)][PF6] under mild hydrogenation conditions. A more detailed study of the rhodium complexes [PC(BIm)PRh(L)][PF6] reveals significant thermal stability of the PC(BIm)PRh moiety in the solid state as well as in solution. The chemical behavior of 1,3-bis(diphenylphosphinomethylene)benzimidazol-2-ylrhodium acetonitrile hexafluorophosphate has been screened under decarbonylation, hydrogenation, and hydroboration reaction conditions. Thus, the PC(BIm)PRh(I) complex is a sufficiently stable compound, with the potential to be applied in catalysis.

  13. Merging rhodium-catalysed C–H activation and hydroamination in a highly selective [4+2] imine/alkyne annulation

    PubMed Central

    Manan, Rajith S.; Zhao, Pinjing

    2016-01-01

    Catalytic C–H activation and hydroamination represent two important strategies for eco-friendly chemical synthesis with high atom efficiency and reduced waste production. Combining both C–H activation and hydroamination in a cascade process, preferably with a single catalyst, would allow rapid access to valuable nitrogen-containing molecules from readily available building blocks. Here we report a single metal catalyst-based approach for N-heterocycle construction by tandem C–H functionalization and alkene hydroamination. A simple catalyst system of cationic rhodium(I) precursor and phosphine ligand promotes redox-neutral [4+2] annulation between N–H aromatic ketimines and internal alkynes to form multi-substituted 3,4-dihydroisoquinolines (DHIQs) in high chemoselectivity over competing annulation processes, exclusive cis-diastereoselectivity, and distinct regioselectivity for alkyne addition. This study demonstrates the potential of tandem C–H activation and alkene hydrofunctionalization as a general strategy for modular and atom-efficient assembly of six-membered heterocycles with multiple chirality centres. PMID:27321650

  14. Depositional processes in large-scale debris-flow experiments

    USGS Publications Warehouse

    Major, J.J.

    1997-01-01

    This study examines the depositional process and characteristics of deposits of large-scale experimental debris flows (to 15 m3) composed of mixtures of gravel (to 32 mm), sand, and mud. The experiments were performed using a 95-m-long, 2-m-wide debris-flow flume that slopes 31??. Following release, experimental debris flows invariably developed numerous shallow (???10 cm deep) surges. Sediment transported by surges accumulated abruptly on a 3?? runout slope at the mouth of the flume. Deposits developed in a complex manner through a combination of shoving forward and shouldering aside previously deposited debris and through progressive vertical accretion. Progressive accretion by the experimental flows is contrary to commonly assumed en masse sedimentation by debris flows. Despite progressive sediment emplacement, deposits were composed of unstratified accumulations of generally unsorted debris; hence massively textured, poorly sorted debris-flow deposits are not emplaced uniquely en masse. The depositional process was recorded mainly by deposit morphology and surface texture and was not faithfully registered by interior sedimentary texture; homogeneous internal textures could be misinterpreted as the result of en masse emplacement by a single surge. Deposition of sediment by similar, yet separate, debris flows produced a homogenous, massively textured composite deposit having little stratigraphic distinction. Similar deposit characteristics and textures are observed in natural debris-flow deposits. Experimental production of massively textured deposits by progressive sediment accretion limits interpretations that can be drawn from deposit characteristics and casts doubt on methods of estimating flow properties from deposit thickness or from relations between particle size and bed thickness.

  15. Poor housing quality: Prevalence and health effects.

    PubMed

    Baker, Emma; Lester, Laurence H; Bentley, Rebecca; Beer, Andrew

    2016-01-01

    Housing is a central component of productive, healthy, and meaningful lives, and a principle social determinant of health and well-being. Surprisingly, though, evidence on the ways that housing influences health in Australia is poorly developed. This stems largely from the fact that the majority of the population are accommodated in good quality housing. The dominance of a "good housing paradigm" means that households living in poor quality and unhealthy housing are doubly disadvantaged-by the quality of their housing and because policy makers in Australia do not acknowledge the health effects of housing. In this article, we examine the relationship between health outcomes and quality of housing. We base our analysis on data from the Household Income and Labour Dynamics in Australia (HILDA) survey, a panel dataset that is representative across Australia. We find a sizeable, policy-important, and to date under-acknowledged cohort of Australians whose health is influenced by poor-condition dwellings.

  16. The Asset Cost of Poor Health

    PubMed Central

    Poterba, James; Venti, Steven; Wise, David A.

    2017-01-01

    This paper examines the correlation between poor health and the evolution of wealth for households in the first nine waves of the Health and Retirement Survey (HRS). It complements previous studies that have enumerating specific financial costs of poor health, such as out of pocket medical expenses or lost earnings. Because poor health can affect wealth accumulation through several channels, the “asset cost” measure can provide additional insight on the health-wealth nexus. We develop a simple measure of health status based on the first principal component of HRS survey responses on self-reported health status, diagnoses, ADLs, IADLs, and other indicators of underlying health. We find a large and substantively important correlation between this health measure and wealth accumulation. Within each 1994 asset quintile, individuals in the top third of the 1994 health status distribution averaged 50 percent more wealth in 2010 than those in the bottom third of that distribution. PMID:21604611

  17. Deposition, Chapter 3

    Treesearch

    K.C. Weathers; J.A. Lynch

    2011-01-01

    To determine the effects of air pollution on ecological systems using the critical load approach, accurate estimates of total nitrogen (N) deposition are essential. Empirical critical loads are set by relating observed ecosystem responses to N deposition (measured, experimentally manipulated, or modeled).

  18. Radionuclide deposition control

    DOEpatents

    Brehm, William F.; McGuire, Joseph C.

    1980-01-01

    The deposition of radionuclides manganese-54, cobalt-58 and cobalt-60 from liquid sodium coolant is controlled by providing surfaces of nickel or high nickel alloys to extract the radionuclides from the liquid sodium, and by providing surfaces of tungsten, molybdenum or tantalum to prevent or retard radionuclide deposition.

  19. Domestic phosphate deposits

    USGS Publications Warehouse

    McKelvey, V.E.; Cathcart, J.B.; Altschuler, Z.S.; Swanson, R.W.; Lutz, Katherine

    1953-01-01

    Most of the worlds phosphate deposits can be grouped into six types: 1) igneous apatite deposits; 2) marine phosphorites; 3) residual phosphorites; 4) river pebble deposits; 5) phosphatized rock; and 6) guano. The igneous apatites and marine phosphorites form deposits measurable in millions or billions of tons; the residual deposits are measurable in thousands or millions; and the other types generally only in thousands of tons. Igneous apatite deposits have been mined on a small scale in New York, New Jersey, and Virginia. Marine phosphorites have been mined in Montana, Idaho, Utah, Wyoming, Arkansas, Tennessee, North Carolina, South Carolina, Georgia, and Florida. Residual phosphorites have been mined in Tennessee, Pennsylvania, and Florida. River pebble has been produced in South Carolina and Florida; phosphatized rock in Tennessee and Florida; and guano in New Mexico and Texas. Present production is limited almost entirely to Florida, Tennessee, Montana, Idaho, and Wyoming. Incomplete but recently partly revised estimates indicate the presence of about 5 billion tons of phosphate deposits in the United States that is minable under present economic conditions. Deposits too lean in quality or thickness to compete with those in the western and southeastern fields probably contain tens of billions of tons.

  20. Poor sleep quality and resistant hypertension.

    PubMed

    Bruno, Rosa Maria; Palagini, Laura; Gemignani, Angelo; Virdis, Agostino; Di Giulio, Alessia; Ghiadoni, Lorenzo; Riemann, Dieter; Taddei, Stefano

    2013-11-01

    We aimed to determine the relationship between sleep quality and treatment-resistant hypertension (RH). In our cross-sectional cohort study, 270 consecutive essential hypertensive patients were recruited at the Outpatient Hypertension Unit, University of Pisa, Italy. The Pittsburgh Sleep Quality Index (PSQI), Beck Depression Inventory (BDI), and State-Trait Anxiety Inventory (STAI-Y2) were administered to all subjects. RH was defined as office blood pressure (BP) >140/90 mmHg with three or more antihypertensive drugs or controlled BP with four or more drugs. Poor sleep quality was defined as PSQI >5, depressive symptoms as BDI >10, and trait anxiety as STAI-Y2 >40. Patients with other sleep disorders were excluded. Complete data were available for 222 patients (50.9% men; mean age, 56.6±12.5 y; RH, 14.9%). Poor sleep quality had a prevalence of 38.2% in the overall population. RH was associated with poor sleep quality, increased sleep latency and reduced sleep efficiency. No significant relationship was found between RH and short sleep duration or depressive symptoms and trait anxiety. Poor sleep quality was more prevalent in resistant vs nonresistant hypertensive women (70.6% vs 40.2%; P=.02) but not in resistant vs nonresistant men (43.8% vs 29.2%; P=.24). In women poor sleep quality was an independent predictor of RH, even after adjustment for cardiovascular and psychiatric comorbidities (odds ratio [OR], 5.3 [confidence interval {CI}, 1.1-27.6), explaining 4.7% of its variance. In men age, diabetes mellitus (DM), and obesity were the only variables associated with RH. Poor sleep quality is significantly associated with resistance to treatment in hypertensive women, independent of cardiovascular and psychiatric confounders. Copyright © 2013 Elsevier B.V. All rights reserved.

  1. Is American business working for the poor?

    PubMed

    Bane, M J; Ellwood, D T

    1991-01-01

    At first glance, poverty seems to have little to do with business. When most people--managers included--think about poverty, they assume that people are poor because they are isolated from the mainstream economy, not productive participants in it. But according to Harvard University professors Mary Jo Bane and David Ellwood, this is a misleading image of the true face of poverty in the United States today. Most poor adults--and a full 90% of poor children--live in families where work is the norm, not the exception. Poor people often work or want to work. But at the low-wage end of the American economy, having a job is no guarantee of avoiding poverty. Poverty is a business issue, then, because the American poor are part of the American work force. And this poses a problem for managers. In a more competitive and fast-changing economic environment, the performance of companies increasingly depends on the capabilities of their employees. In response to this human-resource challenge, more and more managers are embracing the language of "empowerment". And yet how can low-wage employees believe empowerment when their experience of work is, quite literally, impoverishment? It is unlikely that American companies can create the work force of the future with the poverty policies of the past. Fortunately, there are some simple policy mechanisms that can assist the working poor without putting an undue burden on business. Enacting them, however, requires managers to see poverty policy as one part of a national human-resource strategy that links the strategic concerns of companies to a broad social agenda.

  2. Solution deposition assembly

    SciTech Connect

    Roussillon, Yann; Scholz, Jeremy H; Shelton, Addison; Green, Geoff T; Utthachoo, Piyaphant

    2014-01-21

    Methods and devices are provided for improved deposition systems. In one embodiment of the present invention, a deposition system is provided for use with a solution and a substrate. The system comprises of a solution deposition apparatus; at least one heating chamber, at least one assembly for holding a solution over the substrate; and a substrate curling apparatus for curling at least one edge of the substrate to define a zone capable of containing a volume of the solution over the substrate. In another embodiment of the present invention, a deposition system for use with a substrate, the system comprising a solution deposition apparatus; at heating chamber; and at least assembly for holding solution over the substrate to allow for a depth of at least about 0.5 microns to 10 mm.

  3. Trouvelot Crater Deposit

    NASA Image and Video Library

    2002-12-04

    Like many of the craters in the Oxia Palus region of Mars, Trouvelot Crater, shown in this NASA Mars Odyssey image, hosts an eroded, light-toned, sedimentary deposit on its floor. Compared with the much larger example in Becquerel Crater to the NE, the Trouvelot deposit has been so eroded by the scouring action of dark, wind-blown sand that very little of it remains. Tiny outliers of bright material separated from the main mass attest to the once, more really extensive coverage by the deposit. A similar observation can be made for White Rock, the best known example of a bright, crater interior deposit. The origin of the sediments in these deposits remains enigmatic but they are likely the result of fallout from ash or dust carried by the thin martian atmosphere. http://photojournal.jpl.nasa.gov/catalog/PIA04017

  4. Stratiform chromite deposit model

    USGS Publications Warehouse

    Schulte, Ruth F.; Taylor, Ryan D.; Piatak, Nadine M.; Seal, Robert R., II

    2010-01-01

    Stratiform chromite deposits are of great economic importance, yet their origin and evolution remain highly debated. Layered igneous intrusions such as the Bushveld, Great Dyke, Kemi, and Stillwater Complexes, provide opportunities for studying magmatic differentiation processes and assimilation within the crust, as well as related ore-deposit formation. Chromite-rich seams within layered intrusions host the majority of the world's chromium reserves and may contain significant platinum-group-element (PGE) mineralization. This model of stratiform chromite deposits is part of an effort by the U.S. Geological Survey's Mineral Resources Program to update existing models and develop new descriptive mineral deposit models to supplement previously published models for use in mineral-resource and mineral-environmental assessments. The model focuses on features that may be common to all stratiform chromite deposits as a way to gain insight into the processes that gave rise to their emplacement and to the significant economic resources contained in them.

  5. Plasma deposition of tungsten

    SciTech Connect

    Greenberg, K.E.

    1986-12-01

    Tungsten films were plasma-deposited using an abnormal glow discharge through a mixture of tungsten hexafluoride, hydrogen, and argon. The films adhered well to silicon, silicon dioxide, gallium arsenide, and aluminum substrates placed directly on the discharge cathode. Typical deposition rates were on the order of 160 Angstroms/minute with as-deposited film resistivities of 40 to 70 microohm-cm. The tungsten was analyzed using a number of techniques including x-ray diffraction, scanning electron microscopy, and Auger spectroscopy. Low-resistivity (<10 microohm-cm) films that adhered well to silicon dioxide were obtained with a two-step process utilizing plasma deposition and conventional chemical vapor deposition.

  6. Tsunami Deposit Data Base

    NASA Astrophysics Data System (ADS)

    Keating, B. H.; Wanink, M.

    2007-05-01

    A digital database has been established describing tsunami deposits around the world (3 phases; 15 months). The projects involved the review and tabulation of data derived from books, catalogs, journals, preprints, citations and abstracts (currently 1000 references), into a database designed to provide a comprehensive review of the types of tsunami deposits, their geographic distribution and location, sedimentary characteristics, fossil content, age, preservation, run-up, wave height and inundation observations, etc. (34 parameters). The tsunami occurrences can be divided into many subjects, e.g., Volcanogenic (N=375), Seismites (N=49), Co-seismic (N=258), K/T Boundary Impact-triggered debris flows (N=97), Landslides (N=43), etc. Numerous publications compare tsunami deposits to storm deposits (N=38), or analyze the origin of megaboulders (N=22). Tsunami deposits occur throughout geologic time (Pre-Cambrian to present day), and because of plate tectonics, they occur along plate margins (primarily subduction zones) as well as interior to plates. In addition, they occur in epi-continental seas, fjords, etc. Few publications describe depositional processes. Deposits generated by tsunamis occur in multiple environments such as the marine, fresh water, and subaerial. Common characteristics of tsunami deposits include: 1) Deposition of thin sand sheets (can be normal, massive, inversely graded, chaotic or bimodal). 2) Erosional: basal uncomformity, mud balls, rip-up clasts, reworked fossils produced by scouring. 3) Lithology: Stacks of couplets reflecting marine incursions (often sands) into fresh water or subaerial environments (mud, soil, peat). 4) Fossil: Couplets reflects marine fossils, fresh water fossils or a mixed assemblage. 5) Geomorphology: The sand sheets taper landward and can rise in elevation. 6) Deformation: syn-depositional (soft sediments) and intraformational (stiff sediments).

  7. Surface properties of pulsed laser deposited Ir, Rh, and Ir 0.9Rh 0.1 thin films for use as microelectrode arrays in electroanalytical heavy metal trace sensors

    NASA Astrophysics Data System (ADS)

    Le Drogoff, B.; El Khakani, M. A.; Silva, P. R. M.; Chaker, M.; Ross, G. G.

    1999-11-01

    Pulsed laser deposition (PLD) of iridium, rhodium, and Ir 0.9Rh 0.1 thin films onto a-SiC:H-coated silicon substrates for use in heavy metal sensors has been achieved by ablating iridium and/or rhodium targets with a KrF excimer laser. The deposited films are polycrystalline and exhibited very smooth surfaces with an average roughness value ( Ra) of ˜1 nm. The wettability by mercury of their surface was investigated by means of the contact angle measurement technique, and compared to that of Ag and Pt films. The PLD films (whether Ir, Rh, or Ir 0.9Rh 0.1) were found to present an almost identical Hg-wetting behavior, which is characterized by a high static contact angle of 132±2°. Moreover, in contrast to the cases of Pt or Ag films, where amalgamation with Hg rapidly occurs during the contact angle measurements, no evident interaction of Hg with the surface of the PLD films was observed. Microelectrode arrays of each of the three films (Ir, Rh and Ir 0.9Rh 0.1) were fabricated and used as a conducting base onto which Hg microdrops are electroplated. Reproducible and uniform Hg deposits on the microelectrode arrays were obtained. The electroanalytical performance of these Hg-electroplated microelectrode arrays based sensors was then evaluated by means of Square Wave Anodic Stripping Voltammetry (SWASV), in synthetic solutions containing Zn, Cd and Pb ion traces. Over a concentration range as wide as 0.2-20 ppb, the detected signals are found to exhibit a strong linear correlation with ion concentration. For a preconcentration time of only 5 min, detection limits as low as 0.2 ppb for both Cd and Pb, and 0.5 ppb for Zn were achieved.

  8. The structure of the deposit produced by sedimentation of polydisperse suspensions

    NASA Astrophysics Data System (ADS)

    Dorrell, R. M.; Hogg, A. J.; Sumner, E. J.; Talling, P. J.

    2011-03-01

    To interpret the deposits from particle-laden flows it is necessary to understand particle settling at their base. In this paper a quantitative model is developed that not only captures how particles settle out of suspension but also the composition of the final deposit in terms of its vertical distribution of grain sizes. The theoretical model is validated by comparison to published experimental data that has been used to interpret the field deposits of submarine sediment-laden flows (Amy et al., 2006). The model explains two intriguing features of the experimental deposits that are also observed in natural deposits. First, deposits commonly have an ungraded, or poorly normally graded, region overlain by a strongly normally graded region. Second, the normalized thickness of the ungraded region increases as the initial concentration of the suspension is increased. In the theoretical model, the poorly normally graded region results from a constant mass flux into the bed that persists until the largest grain size present within the flow has been completely deposited. The effect of increasing the concentration of the initial suspension is to increase the thickness of the poorly graded part of the deposit and to decrease its average grain size. This work suggests that deposits with relatively thick, poorly graded bases can form from relatively high-concentration polydisperse suspensions, when the initial volume fraction of sediment is greater than approximately 20% and indicates that it is important to include these hindered settling effects in models of depositing flows.

  9. Candidate Tsunami Deposits at Carpinteria Salt Marsh, Southern California

    NASA Astrophysics Data System (ADS)

    Peters, R.; Jaffe, B. E.; Buckley, M.; Watt, S. G.

    2008-12-01

    Carpinteria Salt Marsh, 15 km southeast of Santa Barbara, California preserves geologic evidence of possible past tsunami inundation along the southern California coast. The proximity of the Santa Barbara coastline to the Goleta slide complex and to numerous offshore faults in the Santa Barbara basin suggests a potential for moderate to large tsunamis. A field investigation in February 2008 collected more than 60 cores and examined 8 cutbank exposures throughout the marsh. Sand layers consistent with tsunami deposition were found at depths from 35 to 96 cm in cores from four areas within the marsh. The sand layers, which range from 1 cm to 35 cm thick and extend up to 630 m inland, had sharp lower contacts and were often normally graded. In addition, in some cores there were one or more intervening mud layers within the sand layer. Composition and angularity of the sand is similar to sands found in the surrounding beach, dune, and nearshore environments. While the sand layers occur at similar depths in the cores, they were concentrated in four areas that were isolated by regions with no evidence of tsunami deposition. The deposits may represent spatially discontinuous deposition from one event, spatially continuous deposition from one event with poor preservation of the deposits, or deposition from more than one event. Discontinuous deposition from one event is in contrast to spatially continuous sheet deposition characteristic of moderate to large tsunamis, but may represent isolated deposition by a smaller tsunami along channel banks. The deposit is more consistent with tsunami deposition than deposition by other event-driven processes such as storms or floods. However, marsh processes that may create normally graded sand layers such as channel migration must also be considered before accepting a tsunami origin for the deposits.

  10. Katharine Drexel: Learning to Love the Poor

    ERIC Educational Resources Information Center

    Murray, Cecilia

    2006-01-01

    Although born into privilege, Katharine Drexel was blessed with parents, siblings, friends, and spiritual guides who kept her rooted in a deep, Eucharistic faith. Responding to the needs of the poor was a responsibility of the rich, and Katharine learned this value at the hands of her parents at an early age. With the good counsel of popes and…

  11. Promoting Upward Mobility for the Working Poor.

    ERIC Educational Resources Information Center

    Rupured, Michael

    2000-01-01

    The working poor are typically defined by researchers as individuals who work at least part of the year and earn less than a given percentage of the federal poverty level. This definition tends to understate the problem. In 1997, 15.8 million employed parents had incomes below 200 percent of the federal poverty level. The federal Earned Income Tax…

  12. From Many Lands. Voices of the Poor.

    ERIC Educational Resources Information Center

    Narayan, Deepa, Ed.; Petesch, Patti, Ed.

    This book, the last volume in a three-part series, draws on a large-scale worldwide poverty study to present the views, experiences, and aspirations of poor people in 14 selected countries. In each country, interviews and discussion groups were held in 8-15 rural and urban communities that reflected the most prevalent poverty groups and the…

  13. Direct multiangle solution for poorly stratified atmospheres

    Treesearch

    Vladimir Kovalev; Cyle Wold; Alexander Petkov; Wei Min Hao

    2012-01-01

    The direct multiangle solution is considered, which allows improving the scanning lidar-data-inversion accuracy when the requirement of the horizontally stratified atmosphere is poorly met. The signal measured at zenith or close to zenith is used as a core source for extracting optical characteristics of the atmospheric aerosol loading. The multiangle signals are used...

  14. COMPREHENSIVE HEALTH SERVICES FOR THE RURAL POOR.

    ERIC Educational Resources Information Center

    LOGSDON, DONALD N.

    SEVERAL WRITERS HAVE DEPICTED AGRICULTURAL MIGRANTS AS BEING ONE OF THE MOST DEPRIVED GROUPS IN OUR COUNTRY. HOWEVER, THE NON-MIGRANT AGRICULTURAL WORKERS, WHO FAR OUTNUMBER THE MIGRANTS, ALSO LIVE IN EXTREMELY POOR CIRCUMSTANCES AND ARE VIRTUALLY UNNOTICED BECAUSE THEY DO NOT DRAW ATTENTION THROUGH MIGRATION. BOTH OF THESE GROUPS ARE IN DIRE NEED…

  15. Runway hazard detection in poor visibility conditions

    NASA Astrophysics Data System (ADS)

    Jiang, Bo; Rahman, Zia-ur

    2012-01-01

    More recently, research on enhancing the situational awareness of pilots, especially in poor visibility flight conditions, gains more and more interests. Since pilots may not be able to spot the runway clearly in poor visibility conditions, such as fog, smoke, haze or dim lighting conditions, aviation landing problem can occur due to the (unexpected) presence of objects on the runway. Complicated and trivial instruments, switches, bottoms, plus sudden happenings are enough for the pilots to take care of during landing approach. Therefore, an automatic hazard detection approach that combines non-linear Multi-scale Retinex (MSR) image enhancement, edge detection with basic edge pattern analysis, and image analysis is investigated. The effect of applying the enhancement method is to make the image of the runway almost independent from the poor atmospheric conditions. The following smart edge detection process extracts edge information, which can also reduce the storing space, the comparison and retrieval time, and the effect of sensor noise. After analyzing the features existing in the edge differences occurring in the runway area by digital image processing techniques, the existing potential hazard will be localized and labeled. Experimental results show that the proposed approach is effective in runway hazard detection in poor visibility conditions.

  16. Resilient Learners in Schools Serving Poor Communities

    ERIC Educational Resources Information Center

    Frempong, G.; Visser, M.; Feza, Nosisi; Winnaar, L.; Nuamah, S.

    2016-01-01

    Introduction: Through the education for all initiative, a number of education systems have been able to provide access to their students at the basic education level. The major challenge is that most of these learners, especially, those from poor families who attend schools with limited resources are often not successful. However, in South Africa,…

  17. From Many Lands. Voices of the Poor.

    ERIC Educational Resources Information Center

    Narayan, Deepa, Ed.; Petesch, Patti, Ed.

    This book, the last volume in a three-part series, draws on a large-scale worldwide poverty study to present the views, experiences, and aspirations of poor people in 14 selected countries. In each country, interviews and discussion groups were held in 8-15 rural and urban communities that reflected the most prevalent poverty groups and the…

  18. Planning Behaviour in Good and Poor Readers

    ERIC Educational Resources Information Center

    Mahapatra, Shamita

    2016-01-01

    A group of 50 good readers and a group of 50 poor readers of Grade 5 matched for age and intelligence and selected on the basis of their proficiency in reading comprehension were tested for their competence in word reading and the process of planning at three different levels, namely, perceptual, memory and conceptual in order to study the…

  19. Resilient Parenting: Overcoming Poor Parental Bonding

    ERIC Educational Resources Information Center

    Travis, Wendy J.; Combs-Orme, Terri

    2007-01-01

    This study identified groups of mothers with varying patterns of adaptive functioning and bonds with their own parents. These patterns were related to mothers' parenting of their own children to understand how some mothers avoid repeating the cycle of poor parenting. Data from 210 new mothers were analyzed before hospital discharge about bonding…

  20. Correcting Poor Posture without Awareness or Willpower

    ERIC Educational Resources Information Center

    Wernik, Uri

    2012-01-01

    In this article, a new technique for correcting poor posture is presented. Rather than intentionally increasing awareness or mobilizing willpower to correct posture, this approach offers a game using randomly drawn cards with easy daily assignments. A case using the technique is presented to emphasize the subjective experience of living with poor…

  1. Who Are The Poor In Puerto Rico?

    ERIC Educational Resources Information Center

    Levine, Barry B.; de Cintron, Celia F.

    Dichotomous poverty is defined by taking an arbitrary standard of consumption capability as a dividing line between rich and poor. An investigation into dichotomous poverty below the 2000 dollar level will be worthwhile, since, in 1953, the Planning Board announced as a goal the attempt to lift all families above this margin. In 1953, 78 percent…

  2. EEG Power Spectra of Adolescent Poor Readers.

    ERIC Educational Resources Information Center

    Ackerman, Peggy T.; McPherson, W. Brian; Oglesby, D. Michael; Dykman, Roscoe A.

    1998-01-01

    Electroencephalographic power spectra were studied in two poor-reading adolescent groups (n=38), dysphonetic and phonetic. Significant Group x Hemisphere effects were found in the alpha and beta bands, with the phonetic group showing right greater than left asymmetry. Results suggest more circumscribed and mature processing in the phonetically…

  3. Resilient Learners in Schools Serving Poor Communities

    ERIC Educational Resources Information Center

    Frempong, G.; Visser, M.; Feza, Nosisi; Winnaar, L.; Nuamah, S.

    2016-01-01

    Introduction: Through the education for all initiative, a number of education systems have been able to provide access to their students at the basic education level. The major challenge is that most of these learners, especially, those from poor families who attend schools with limited resources are often not successful. However, in South Africa,…

  4. The Other Poor: Rural Poverty and Education.

    ERIC Educational Resources Information Center

    Books, Sue

    1997-01-01

    This paper argues that rural poverty remains relatively invisible because, although shameful, it is profitable, and the rural poor pose little threat to their suburban neighbors. This is illustrated via interrogation concerning a rural poultry plant fire. The paper examines implications of this case for foundations scholars and educational…

  5. Resilient Parenting: Overcoming Poor Parental Bonding

    ERIC Educational Resources Information Center

    Travis, Wendy J.; Combs-Orme, Terri

    2007-01-01

    This study identified groups of mothers with varying patterns of adaptive functioning and bonds with their own parents. These patterns were related to mothers' parenting of their own children to understand how some mothers avoid repeating the cycle of poor parenting. Data from 210 new mothers were analyzed before hospital discharge about bonding…

  6. Text Comprehension Strategy Instruction with Poor Readers.

    ERIC Educational Resources Information Center

    van den Bos, Kees P.; Brand-Gruwel, Saskia; Aarnoutse, Cor A. J.

    1998-01-01

    Investigates effects of teaching text-comprehension strategies to children with decoding and reading-comprehension problems and with a poor or normal listening ability. Finds no differential program effects for the two listening levels. Finds no stable evidence of transfer of comprehension strategy-training to standardized general listening and…

  7. Correcting Poor Posture without Awareness or Willpower

    ERIC Educational Resources Information Center

    Wernik, Uri

    2012-01-01

    In this article, a new technique for correcting poor posture is presented. Rather than intentionally increasing awareness or mobilizing willpower to correct posture, this approach offers a game using randomly drawn cards with easy daily assignments. A case using the technique is presented to emphasize the subjective experience of living with poor…

  8. The Other Poor: Rural Poverty and Education.

    ERIC Educational Resources Information Center

    Books, Sue

    1997-01-01

    This paper argues that rural poverty remains relatively invisible because, although shameful, it is profitable, and the rural poor pose little threat to their suburban neighbors. This is illustrated via interrogation concerning a rural poultry plant fire. The paper examines implications of this case for foundations scholars and educational…

  9. Rhodium-catalyzed double [2 + 2 + 2] cycloaddition of 1,4-bis(diphenylphosphinoyl)buta-1,3-diyne with tethered diynes: a modular, highly versatile single-pot synthesis of NU-BIPHEP biaryl diphosphines.

    PubMed

    Doherty, Simon; Knight, Julian G; Smyth, Catherine H; Harrington, Ross W; Clegg, William

    2007-11-08

    Rhodium-catalyzed double [2 + 2 + 2] cycloaddition of 1,4-bis(diphenylphosphinoyl)buta-1,3-diyne with tethered diynes provides a straightforward, single-pot procedure for the synthesis of a new class of tropos biaryl diphosphine, NU-BIPHEP. This methodology represents a significant improvement on existing multistep procedures. Enantiopure Lewis acid platinum complexes of these diphosphines are highly efficient catalysts for carbonyl-ene and Diels-Alder reactions, and ruthenium diphosphine-diamine complexes catalyze the asymmetric reduction of ketones to give ee's that rival those obtained with their BINAP counterpart.

  10. Rhodium-catalyzed [5 + 2 + 1] cycloaddition of ene-vinylcyclopropanes and CO: reaction design, development, application in natural product synthesis, and inspiration for developing new reactions for synthesis of eight-membered carbocycles.

    PubMed

    Wang, Yi; Yu, Zhi-Xiang

    2015-08-18

    Practical syntheses of natural products and their analogues with eight-membered carbocyclic skeletons are important for medicinal and biological investigations. However, methods and strategies to construct the eight-membered carbocycles are limited. Therefore, developing new methods to synthesize the eight-membered carbocycles is highly desired. In this Account, we describe our development of three rhodium-catalyzed cycloadditions for the construction of the eight-membered carbocycles, which have great potential in addressing the challenges in the synthesis of medium-sized ring systems. The first reaction described in this Account is our computationally designed rhodium-catalyzed two-component [5 + 2 + 1] cycloaddition of ene-vinylcyclopropanes (ene-VCPs) and CO for the diastereoselective construction of bi- and tricyclic cyclooctenones. The design of this reaction is based on the hypothesis that the C(sp(3))-C(sp(3)) reductive elimination of the eight-membered rhodacycle intermediate generated from the rhodium-catalyzed cyclopropane cleavage and alkene insertion, giving Wender's [5 + 2] cycloadduct, is not easy. Under CO atmosphere, CO insertion may occur rapidly, converting the eight-membered rhodacycle into a nine-membered rhodacycle, which then undergoes an easy C(sp(2))-C(sp(3)) reductive elimination process and furnishes the [5 + 2 + 1] product. This hypothesis was supported by our preliminary DFT studies and also served as inspiration for the development of two [7 + 1] cycloadditions: the [7 + 1] cycloaddition of buta-1,3-dienylcyclopropanes (BDCPs) and CO for the construction of cyclooctadienones, and the benzo/[7 + 1] cycloaddition of cyclopropyl-benzocyclobutenes (CP-BCBs) and CO to synthesize the benzocyclooctenones. The efficiency of these rhodium-catalyzed cycloadditions can be revealed by the application in natural product synthesis. Two eight-membered ring-containing natural products, (±)-asterisca-3(15),6-diene and (+)-asteriscanolide, have been

  11. Differences in Nutrient Adequacy among Poor and Non-Poor Children.

    ERIC Educational Resources Information Center

    Cook, John T.; Martin, Katie S.

    This study compared the proportion of 1- to 5-year-olds in poor and non-poor households whose intakes of key nutrients were inadequate. Data were obtained from the 1986 United States Department of Agriculture Nationwide Food Consumption Survey and Continuing Survey of Food Intakes by Individuals. An intake below 70 percent of the Recommended Daily…

  12. Parenting Efficacy and the Early School Adjustment of Poor and Near-Poor Black Children

    ERIC Educational Resources Information Center

    Jackson, Aurora P.; Choi, Jeong-Kyun; Bentler, Peter M.

    2009-01-01

    This short-term longitudinal study investigates whether maternal educational attainment, maternal employment status, and family income affect African American children's behavioral and cognitive functioning over time through their impacts on mothers' psychological functioning and parenting efficacy in a sample of 100 poor and near-poor single…

  13. Longitudinal stability and predictors of poor oral comprehenders and poor decoders.

    PubMed

    Elwér, Sa; Keenan, Janice M; Olson, Richard K; Byrne, Brian; Samuelsson, Stefan

    2013-07-01

    Two groups of fourth-grade children were selected from a population sample (N=926) to be either poor oral comprehenders (poor oral comprehension but normal word decoding) or poor decoders (poor decoding but normal oral comprehension). By examining both groups in the same study with varied cognitive and literacy predictors, and examining them both retrospectively and prospectively, we could assess how distinctive and stable the predictors of each deficit are. Predictors were assessed retrospectively at preschool and at the end of kindergarten, Grade 1, and Grade 2. Group effects were significant at all test occasions, including those for preschool vocabulary (worse in poor oral comprehenders) and rapid automatized naming (RAN) (worse in poor decoders). Preschool RAN and vocabulary prospectively predicted Grade 4 group membership (77-79% correct classification) within the selected samples. Reselection in preschool of "at-risk" poor decoder and poor oral comprehender subgroups based on these variables led to significant but relatively weak prediction of subtype membership at Grade 4. Implications of the predictive stability of our results for identification and intervention of these important subgroups are discussed. Copyright © 2012 Elsevier Inc. All rights reserved.

  14. Parenting Efficacy and the Early School Adjustment of Poor and Near-Poor Black Children

    ERIC Educational Resources Information Center

    Jackson, Aurora P.; Choi, Jeong-Kyun; Bentler, Peter M.

    2009-01-01

    This short-term longitudinal study investigates whether maternal educational attainment, maternal employment status, and family income affect African American children's behavioral and cognitive functioning over time through their impacts on mothers' psychological functioning and parenting efficacy in a sample of 100 poor and near-poor single…

  15. Longitudinal Stability and Predictors of Poor Oral Comprehenders and Poor Decoders

    PubMed Central

    Elwér, Åsa; Keenan, Janice M.; Olson, Richard K.; Byrne, Brian; Samuelsson, Stefan

    2012-01-01

    Two groups of 4th grade children were selected from a population sample (N= 926) to either be Poor Oral Comprehenders (poor oral comprehension but normal word decoding), or Poor Decoders (poor decoding but normal oral comprehension). By examining both groups in the same study with varied cognitive and literacy predictors, and examining them both retrospectively and prospectively, we could assess how distinctive and stable the predictors of each deficit are. Predictors were assessed retrospectively at preschool, at the end of kindergarten, 1st, and 2nd grades. Group effects were significant at all test occasions, including those for preschool vocabulary (worse in poor oral comprehenders) and rapid naming (RAN) (worse in poor decoders). Preschool RAN and Vocabulary prospectively predicted grade 4 group membership (77–79% correct classification) within the selected samples. Reselection in preschool of at-risk poor decoder and poor oral comprehender subgroups based on these variables led to significant but relatively weak prediction of subtype membership at grade 4. Implications of the predictive stability of our results for identification and intervention of these important subgroups are discussed. PMID:23528975

  16. Differences in Nutrient Adequacy among Poor and Non-Poor Children.

    ERIC Educational Resources Information Center

    Cook, John T.; Martin, Katie S.

    This study compared the proportion of 1- to 5-year-olds in poor and non-poor households whose intakes of key nutrients were inadequate. Data were obtained from the 1986 United States Department of Agriculture Nationwide Food Consumption Survey and Continuing Survey of Food Intakes by Individuals. An intake below 70 percent of the Recommended Daily…

  17. EDITORIAL: Atomic layer deposition Atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Godlewski, Marek

    2012-07-01

    The growth method of atomic layer deposition (ALD) was introduced in Finland by Suntola under the name of atomic layer epitaxy (ALE). The method was originally used for deposition of thin films of sulphides (ZnS, CaS, SrS) activated with manganese or rare-earth ions. Such films were grown for applications in thin-film electroluminescence (TFEL) displays. The ALE mode of growth was also tested in the case of molecular beam epitaxy. Films grown by ALD are commonly polycrystalline or even amorphous. Thus, the name ALE has been replaced by ALD. In the 80s ALD was developed mostly in Finland and neighboring Baltic countries. Deposition of a range of different materials was demonstrated at that time, including II-VI semiconductors (e.g. CdTe, CdS) and III-V (e.g. GaAs, GaN), with possible applications in e.g. photovoltaics. The number of publications on ALD was slowly increasing, approaching about 100 each year. A real boom in interest came with the development of deposition methods of thin films of high-k dielectrics. This research was motivated by a high leakage current in field-effect transistors with SiO2-based gate dielectrics. In 2007 Intel introduced a new generation of integrated circuits (ICs) with thin films of HfO2 used as gate isolating layers. In these and subsequent ICs, films of HfO2 are deposited by the ALD method. This is due to their unique properties. The introduction of ALD to the electronics industry led to a booming interest in the ALD growth method, with the number of publications increasing rapidly to well above 1000 each year. A number of new applications were proposed, as reflected in this special issue of Semiconductor Science and Technology. The included articles cover a wide range of possible applications—in microelectronics, transparent electronics, optoelectronics, photovoltaics and spintronics. Research papers and reviews on the basics of ALD growth are also included, reflecting a growing interest in precursor chemistry and growth

  18. Carbonate Deposition on Antarctic Shelves

    NASA Astrophysics Data System (ADS)

    Frank, T. D.; James, N. P.; Malcolm, I.

    2011-12-01

    Limestones associated with glaciomarine deposits occur throughout the geologic record but remain poorly understood. The best-described examples formed during major ice ages of the Neoproterozoic and Late Paleozoic. Quaternary analogs on Antarctic shelves have received comparatively little study. Here, we report on the composition, spatial distribution, and stratigraphic context of carbonate sediments contained in piston cores from the Ross Sea. The goals of this work are to (1) document the nature and distribution of carbonate sediments on the Ross Sea continental shelf and (2) examine temporal relationships to Quaternary glaciation. Results will be used to develop criteria that will improve understanding of analogous deposits in the ancient record. All carbonate-rich intervals in piston cores from the Ross Rea, now housed at the Antarctic Marine Geology Research Facility at Florida State University, were examined and described in detail. Sediment samples were disaggregated and sieved into size fractions before description with paleontological analysis carried out on the coarsest size fraction (>250 microns). Carbonate-rich sediments are concentrated in the northwestern Ross Sea, along the distal margins of Mawson and Pennell Banks. Calcareous facies include a spectrum of lithologies that range from fossiliferous mud, sand, and gravel to skeletal floatstone-rudstone and bafflestone. Floatstone-rudstone and bafflestone is most abundant along western-facing slopes in areas protected from the Antarctic Coastal Current. Sand-prone facies dominate the tops of banks and mud-prone, often spicultic, facies occur in deeper areas. The carbonate factory is characterized by a low-diversity, heterozoan assemblage that is dominated by stylasterine hydrocorals, barnacles, and bryozoans. Molluscs and echinoids are present but not abundant. Planktic and benthic foraminifera are ubiquitous components of the sediment matrix, which is locally very rich in sponge spicules. Biota rarely

  19. Gold deposits of the Carajás mineral province: deposit types and metallogenesis

    NASA Astrophysics Data System (ADS)

    NetunoVillas, Raimundo; Santos, Marcio

    2001-07-01

    The Carajás mineral province is located in the south-eastern part of the Amazon craton and is divided into the southern and northern tectonic blocks, which are referred to as the Rio Maria granitoid-greenstone terrane and the Itacaiúnas shear belt, respectively. The geological evolution of this province occurred almost entirely in the Archean, with no tectonism from ~2.4 to 1.9 Ga and then an episode of very extensive intraplate granitic magmatism. Distinct types of gold deposits, most associated with Archean metavolcano-sedimentary sequences, including greenstone belts as old as 2.9 Ga, comprise (1) Fe-oxide-poor Cu-Au, (2) Fe-oxide-Cu-Au-U-REE, (3) shear-zone related lode-gold, and (4) sedimentary rock-hosted Au-PGE. The shear-zone related deposits are more typical of the Rio Maria granitoid-greenstone terrane, whereas the other types are more abundant in the Itacaiunas shear belt. The first type, represented by the Serra Verde deposit, shows most characteristics of volcanogenic massive sulfide (VMS) deposits, except for the dominance of chalcopyrite over pyrite and/or pyrrhotite. Some deposits of the second type (Igarapé Salobo and Igarapé Bahia) are also syngenetic, but their ore mineralogy and paucity of pyrite and/or pyrrhotite are inconsistent with, or at least unusual for, classic VMS deposits. Other Fe-oxide-Cu-Au-U-REE deposits, such as the Cristalino and Sossego, occur as epigenetic stockwork mineralization related to Archean granitoid stocks. Most shear-zone related lode-gold deposits are classified as orogenic gold deposits (e.g. Sapucaia, Babaçu and Tucumã) that cut greenstone belt rocks. The Cumaru deposit is also hosted by a shear zone, but may have a genetic association with a granitoid intrusion. The Águas Claras deposit, although also hosted in a shear zone and perhaps intrusion-related, differs from the orogenic gold deposits by its extensional tectonic setting, lack of CO2 in the ore fluids, and voluminous chalcopyrite. The sedimentary

  20. Automatic Payroll Deposit System.

    ERIC Educational Resources Information Center

    Davidson, D. B.

    1979-01-01

    The Automatic Payroll Deposit System in Yakima, Washington's Public School District No. 7, directly transmits each employee's salary amount for each pay period to a bank or other financial institution. (Author/MLF)