Journal articles: 'Rhodium catalysts'

1

Xing, Hai Lin, Hao Zhou, Li Qun Zhang, Wei Ming Wang, and Dong Mei Yue. "Remove Rhodium Catalysts from HNBR Solution." Advanced Materials Research 311-313 (August 2011): 1152–56. http://dx.doi.org/10.4028/www.scientific.net/amr.311-313.1152.

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Rhodium complex is excellent catalyst for nitrile-butadiene rubber homogeneous hydrogenation with difficulties in its recovery. A new extraction method for recovery noble metal catalysts from hydrogenated nitrile-butadiene rubber solution was investigated. Rhodium metal catalysts can be efficiently, easily removed from hydrogenated nitrile-butadiene rubber solution using amine as ligand and hydrogen peroxide as oxidant. The condition of removing noble metal catalysts from hydrogenated nitrile-butadiene rubber solution was carefully studied, including oxidant, reaction temperature, and the concentration of amine. The removal rate of the rhodium catalyst over 96% with the optimal conditions.1H-NMR characterization showed that there was no change in the structure and nitrile group of hydrogenated nitrile-butadiene rubber after rhodium catalysts were removed.

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Hanf, Schirin, Luis Alvarado Rupflin, Roger Gläser, and Stephan Schunk. "Current State of the Art of the Solid Rh-Based Catalyzed Hydroformylation of Short-Chain Olefins." Catalysts 10, no. 5 (May 6, 2020): 510. http://dx.doi.org/10.3390/catal10050510.

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The hydroformylation of olefins is one of the most important homogeneously catalyzed processes in industry to produce bulk chemicals. Despite the high catalytic activities and selectivity’s using rhodium-based homogeneous hydroformylation catalysts, catalyst recovery and recycling from the reaction mixture remain a challenging topic on a process level. Therefore, technical solutions involving alternate approaches with heterogeneous catalysts for the conversion of olefins into aldehydes have been considered and research activities have addressed the synthesis and development of heterogeneous rhodium-based hydroformylation catalysts. Different strategies were pursued by different groups of authors, such as the deposition of molecular rhodium complexes, metallic rhodium nanoparticles and single-atom catalysts on a solid support as well as rhodium complexes present in supported liquids. An overview of the recent developments made in the area of the heterogenization of homogeneous rhodium catalysts and their application in the hydroformylation of short-chain olefins is given. A special focus is laid on the mechanistic understanding of the heterogeneously catalyzed reactions at a molecular level in order to provide a guide for the future design of rhodium-based heterogeneous hydroformylation catalysts.

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Konuspayev, Sapar, Minavar Shaimardan, Nurlan Annas, T. S. Abildin, and Y. Y. Suleimenov. "Hydrogenation of benzene and toluene over supported rhodium and rhodium-gold catalysts." MATEC Web of Conferences 340 (2021): 01026. http://dx.doi.org/10.1051/matecconf/202134001026.

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Rhodium and rhodium-gold catalysts supported on amorphous aluminosilicates (ASA), titanium dioxide (rutile, TiO2) was prepared in two different ways: absorption and colloidal method. The catalysts were characterized by an inductively coupled plasma optical emission spectrometer (ICP-OES), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The activity and selectivity of the prepared catalysts were tested by the hydrogenation of benzene and toluene. Hydrogenation was conducted at a pressure of 4 MPa and a temperature 80 °C. The bimetallic Rh-Au/ASA catalyst prepared by the absorption method showed higher activity and selectivity in benzene hydrogenation reaction, the same catalyst prepared by the colloidal method demonstrated lower selectivity.

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Konuspaev, S. R., and A. Nurlan. "Influence of the Au-Rh /ASA catalyst preparation method on the benzene hydrogenation reaction." BULLETIN of the L.N. Gumilyov Eurasian National University. Chemistry. Geography. Ecology Series 136, no. 3 (2021): 35–44. http://dx.doi.org/10.32523/2616-6771-2021-136-3-35-44.

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Comparative hydrogenation of benzene and toluene in ethanol under hydrogen pressure on rhodium and gold supported on synthetic amorphous aluminosilicate (ASA, trade name is siral-40) with a developed surface area prepared by two methods: impregnation by using the incipient wetness technique and colloidal method. Moreover, the catalysts were prepared by impregnation in two versions: co-impregnation and sequential impregnation of rhodium and gold salts. The catalysts are characterized by inductively coupled plasma-optical emission spectroscopy (ICP-OES) methods. It is shown that the catalysts prepared by impregnation according to the incipient wetness technique were the most acceptable for selective hydrogenation of benzene. The activity of the catalyst depends on the amount of rhodium on the surface of the available surface for the activation of benzene and toluene. On catalysts prepared by the colloidal method, the active metal rhodium goes inside the pores, and gold on the surface, so the activity is low, while on catalysts prepared by impregnation, the amount of rhodium on the surface is close to the theoretically possible amount. The selectivity of benzene hydrogenation in the presence of toluene on this catalyst is 84%.

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Shi, Libin, Suitao Qi, Tianyou Jiao, Jifeng Qu, Xiao Tan, Chunhai Yi, and Bolun Yang. "Catalytic Decomposition of Nitrogen Oxides by Bimetallic Catalysts Synthesized by Dielectric Barrier Discharge Plasma Technology." E3S Web of Conferences 53 (2018): 01032. http://dx.doi.org/10.1051/e3sconf/20185301032.

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Nitrous oxide (N2O) is a common greenhouse gas and urgent need to be contained. Direct catalytic decomposition of N2O by high activity catalyst into N2 and O2 is a low-cost and harmless method. Bimetallic catalysts show good catalytic activity in many classes of reactions, and plasma technologies, applied to prepare of catalyst, are considered to be a promising method. In our contribution, DBD cold plasma is applied to synthesize Rhodium and Cobalt bimetallic catalysts for catalytic N2O decomposition. The influence of cobalt and rhodium content on N2O decomposition activity shows that the optimal amount of metal is determined as 5wt. % cobalt and 0.5wt. % rhodium loaded on Al2O3. The best working voltage is determined as 18kV. The results indicated that the Rh/Al2O3 catalysts prepared by atmospheric-pressure DBD cold plasma showed smaller size and high dispersion of Rh particles, so that the metal-support interaction and the catalytic activity are enhanced. Atmospheric-pressure DBD cold plasma is proved to be an environmentally friendly and efficient method for preparing high performance Rhodium and Cobalt bimetallic catalysts for catalytic N2O decomposition.

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Sedláček, Jan, and Jiří Vohlídal. "Controlled and Living Polymerizations Induced with Rhodium Catalysts. A Review." Collection of Czechoslovak Chemical Communications 68, no. 10 (2003): 1745–90. http://dx.doi.org/10.1135/cccc20031745.

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In the last fifteen years, a large variety of specialty polymers of diverse chemical structure and functionality have been synthesized with the rhodium-based catalysts. The high tolerance to the reaction medium and functional groups of monomers, as well as ability to control various structure features of the polymer formed are typical properties of these catalysts. In addition, some rhodium catalysts can be anchored to inorganic or organic supports or dissolved in ionic liquids to form heterophase polymerization systems, which opens the way to pure, well-defined polymers free of the catalyst residues, as well as to recycling rhodium catalysts. This review provides a survey on the polymerization reactions induced with rhodium-based catalysts, in which one or more structure attributes of the polymer formed are subject to control. The structure attributes considered are (i) sequential arrangement of monomeric units along polymer chains; (ii) head-tail isomerism of polymer molecules; (iii) configurational structure of polymer molecules; (iv) conformation of polymer molecules; and (v) molecular weight and molecular-weight distribution of the polymer formed. A review with 188 references.

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7

Kenzhin, Roman M., Evgeny A. Alikin, Sergey P. Denisov, and Aleksey A. Vedyagin. "Study on Thermal Stability of Ceria-Supported Rhodium Catalysts." Materials Science Forum 950 (April 2019): 190–94. http://dx.doi.org/10.4028/www.scientific.net/msf.950.190.

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In the present work, the impact of the rhodium deposition on the thermal stability of ceria-based catalysts was studied. The samples were prepared by an incipient wetness impregnation of the support with aqueous solution of rhodium nitrate. The loading of Rh was 0.1 and 1 wt.%. The textural characteristics of the samples were examined by a low-temperature nitrogen adsorption. It was shown that the addition of rhodium intensifies the process of ceria agglomeration, which leads to the lower values of specific surface area along with increased average pore diameter after the aging at 1000 °C. Stability of the catalysts was investigated by means of a prompt thermal aging procedure. The high-loaded catalyst (1 wt.% Rh/CeO2) was more active than the 0.1 wt.% Rh/CeO2sample, while the stability of both the catalysts was excellent. It should be emphasized that the alumina-based reference samples with the similar rhodium loading were significantly less active and poorly stable.

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Storey, Caroline M., Audrius Kalpokas, Matthew R. Gyton, Tobias Krämer, and Adrian B. Chaplin. "A shape changing tandem Rh(CNC) catalyst: preparation of bicyclo[4.2.0]octa-1,5,7-trienes from terminal aryl alkynes." Chemical Science 11, no. 8 (2020): 2051–57. http://dx.doi.org/10.1039/c9sc06153c.

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9

Alikin, Evgeny A., Sergey P. Denisov, Konstantin V. Bubnov, and Aleksey A. Vedyagin. "Self-Regeneration Effect of Three-Way Catalysts during Thermal Aging Procedure." Catalysts 10, no. 11 (October 30, 2020): 1257. http://dx.doi.org/10.3390/catal10111257.

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One of the most important features of the three-way catalysts is their long-term stability. However, quite often, promising catalytic compositions with excellent activity become deactivated after a relatively short period of exploitation due to various reasons. Therefore, a study on the onboard regeneration of the deactivated three-way catalysts remains its actuality. The present work is mainly focused on the self-regeneration effect of the rhodium-containing component. Aging of the catalysts in the standard and model engine braking regimes revealed the difference in the catalytic performance. Deactivated rhodium species turned to the active state as a result of rapid cooling in air flow from 1200 to 600 °C. The regenerated catalyst shows improved activity towards NOx reduction and, therefore, widened operation window, which indicates higher accessibility of the rhodium species. X-ray diffraction analysis of the aged catalysts does not reveal any noticeable phase changes. Contrary, significant changes in the Rh oxidation state were registered by X-ray photoelectron spectroscopy. The observed effect opens new horizons for the development of the onboard purification systems with prolonged exploitation lifetime.

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10

Zinner, Sandra C., Mei Zhang-Preße, Wolfgang A. Herrmann, and Fritz E. Kühn. "Enantioselective Hydrosilylation with a Chiral N-Heterocyclic Carbene Complex of Rhodium(I) [1]." Zeitschrift für Naturforschung B 64, no. 11-12 (December 1, 2009): 1607–11. http://dx.doi.org/10.1515/znb-2009-11-1246.

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Both enantiomers of the chiral rhodium-NHC complex [(4X, 5X)-1,3-bis[2,6-diisopropyl-phenyl]- 4,5-ditert-butylimidazolidine-2-ylidene][1,5-cyclooctadiene]-iodo-rhodium(I) with X = R, S were applied as catalysts for the asymmetric hydrosilylation of prochiral ketones. The influence of employed solvent, substrate, silane, and catalyst enantiomer on the catalytic activity and the enantioselectivity of the desired product was investigated

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11

Pan, M. "Observation of in situ reduction of ceria-supported rhodium catalysts by electron beam irradiation." Proceedings, annual meeting, Electron Microscopy Society of America 49 (August 1991): 1022–23. http://dx.doi.org/10.1017/s0424820100089421.

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In rhodium catalysts supported on lanthanide oxides, significant difference in rhodium dispersions has been observed between cerium dioxide (CeO2) and sesquioxides (Ln2O3) by high resolution electron microscopy (HREM). This has been attributed to the different behaviors of the oxide supports during their impregnation with aqueous solution of rhodium nitrate (Rh(NO3)3). In the acid media, cerium dioxide has a higher reducibility while the sesquioxides have a higher solubility. So studying the catalyst precursor and the reduction process can provide an understanding of its interaction with the support during the impregnation stage and the metal dispersion on the oxide supports. Results on cerium dioxide support are presented here.The catalyst precursor was prepared by incipient wetness impregnation method as reported elsewhere. The rhodium loading was 2.4 wt%. The HREM work was performed in JEOL 4000EX electron microscope (point resolution of 1.7 Å). The typical current density used during observation was ∼6.5A/cm2 at the specimen. The vacuum in the column of the microscope was ∼10-7 torr.

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12

Hegedűs, László, Tien Thuy Thanh Nguyen, Krisztina Lévay, Krisztina László, György Sáfrán, and Andrea Beck. "Poisoning and Reuse of Supported Precious Metal Catalysts in the Hydrogenation of N-Heterocycles, Part II: Hydrogenation of 1-Methylpyrrole over Rhodium." Catalysts 12, no. 7 (July 1, 2022): 730. http://dx.doi.org/10.3390/catal12070730.

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Poisoning effect of nitrogen on heterogeneous, supported precious metal catalysts, along with their recycling, was further examined in the liquid-phase hydrogenation of 1-methylpyrrole (MP) to 1-methylpyrrolidine (MPD) over rhodium on carbon or γ-alumina, in methanol, under non-acidic conditions, at 25–50 °C and 10 bar. Reusing a spent, unregenerated 5% Rh/C or 5% Rh/γ-Al2O3 catalyst, it was found that the conversion of this model substrate and the activity of the catalyst were strongly dependent on the amount of catalyst, the type of support, the catalyst pre- or after-treatment, the temperature, and the number of recycling, respectively. An unexpected catalytic behaviour of rhodium was observed when it was used in a prehydrogenated form, because no complete conversion of MP was achieved over even the fresh Rh/C or Rh/γ-Al2O3, contrary to the untreated one. In addition, there was a significant difference in the reusability and activity of these rhodium catalysts, depending on their supports (activated carbon, γ-alumina). These diversions were elucidated by applying dispersion (O2- and H2-titration), temperature-programmed desorption of ammonia (NH3-TPD), and transmission electron microscopy (TEM) measurements.

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Panagiotopoulos, Athanassios A., Efthymios G. Fasoulakis, Eleftheria E. Vardalachaki, and Athanassios G. Coutsolelos. "Photocatalytic hydrogen production based on a water-soluble porphyrin derivative as sensitizer and a series of Wilkinson type complexes as catalysts." Journal of Porphyrins and Phthalocyanines 20, no. 08n11 (August 2016): 1200–1206. http://dx.doi.org/10.1142/s1088424616500905.

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Herein, we report photochemical hydrogen evolution systems consisting of various rhodium based catalysts with Wilkinson type structures, Zn metalated porphyrins and fluorescein as photosensitizers and triethanolamine as a sacrificial electron donor in acetonitrile/H2O (1:1) solution. Since rhodium complexes 1 and 2 are used for the first time as catalysts in this type of systems, a systematic study was performed in order to elucidate the best conditions for H2 production. Upon visible irradiation hydrogen production was detected and the best results were obtained at pH 7 when dye P3 and catalyst 1 were used with a TON of 61, after 48 h and in the presence of dye P1 and catalyst 2 with a TON of 69, after the 48 h.

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14

José-Yacamán, M., M. Marín-Almazo, and J. A. Ascencio. "High Resolution TEM Studies On Palladium, Rhodium Nanoparticles." Microscopy and Microanalysis 7, S2 (August 2001): 1100–1101. http://dx.doi.org/10.1017/s1431927600031573.

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The field of catalysis is one of the most important areas of the nano-sciences for many years. in deed the goal of having a catalyst, with the maximum active area exposed to a chemical reaction, has produced enormous amount of research in nanoparticles. Particularly, the metal nanoparticles study is a very important field in catalysis. Electron Microscopy is one of the techniques that have played a mayor role on studding nanoparticles. Since bright field images, dark field techniques, to the high-resolution atomic images of nanoparticles and more recently the High Angle Annular dark field images or Z-contrast. However this technique provides only indirect evidence of the atomic arrangements on the particles. High Resolution Electron Microscopy (HREM) still appears as a very powerful technique to study nanoparticles and their internal structure. Among the most interesting metals to study is the palladium, which acts for instance as excellent catalyst for hydrogenation of unsaturated hydrocarbons and has many other applications such as environmental catalysts.

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Gao, Hanrong, and Robert J. Angelici. "Rh2Cl2(CO)4 adsorbed and tethered on gold powder: IR spectroscopic characterization and olefin hydrogenation activity." Canadian Journal of Chemistry 79, no. 5-6 (May 1, 2001): 578–86. http://dx.doi.org/10.1139/v00-190.

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Catalysts were prepared by adsorbing Rh2Cl2(CO)4 directly on gold powder or on gold that contained the tethered ligands 2-(diphenylphosphino)ethane-1-thiol (DPET) or methyl 2-mercaptonicotinate (MMNT). Infrared (IR) studies (diffuse reflectance infrared Fourier transform (DRIFT)) of the catalyst RhAu prepared by adsorbing Rh2Cl2(CO)4 directly on Au indicate that a RhI(CO)2 species is present. IR studies of RhDPET-Au suggest that tethered cis-Rh(DPET)(CO)2Cl is the major species at relatively high Rh2Cl2(CO)4 loadings, but trans-Rh(DPET)2(CO)Cl is observable at low Rh2Cl2(CO)4 loadings. Spectral investigations of the catalyst RhMMNT-Au prepared by adsorbing Rh2Cl2(CO)4 on MMNT-Au suggest that tethered [cis-Rh(MMNT)2(CO)2]+Cl and (or) Rh(MMNT)(CO)2Cl are the major species at low Rh2Cl2(CO)4 loadings, while a new unidentified species predominates at high Rh2Cl2(CO)4 loadings. All three catalysts are active 1-hexene hydrogenation catalysts under the mild conditions of 40°C and 1 atm of H2; they are much more active than Au powder or Rh2Cl2(CO)4 in solution. Of the three catalysts, RhAu is the most active with a maximum turnover frequency (TOF) of 800 mol H2 per mol Rh per min while its turnover (TO) is 29 600 mol H2 per mol Rh during a 2-hour run. Under the conditions of 1-hexene hydrogenation, the catalysts lose their CO ligands. Thus, it appears that a form of Rh metal on Au is the catalytically active species.Key words: catalysis, olefin hydrogenation, gold powder, tethered rhodium complexes, infrared studies, adsorption, rhodium complexes.

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Hartwig, J. F. "Development of catalysts for the hydroamination of olefins." Pure and Applied Chemistry 76, no. 3 (January 1, 2004): 507–16. http://dx.doi.org/10.1351/pac200476030507.

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Studies on the development of palladium, nickel, and rhodium catalysts for the hydroamination of dienes and vinylarenes are described. Enantioselective catalysts based on palladium have been developed for the addition of arylamines to dienes and for Markovnikov addition of arylamines to vinylarenes. In addition, nickel catalysts for the addition of aliphatic amines to dienes have been developed, and rhodium catalysts for the first transition metal-catalyzed aminations of vinylarenes that generate terminal amines as the major product are described. Mechanistic data on the hydroamination of vinylarenes with palladium and rhodium is also provided.

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17

Hajdu, Viktória, Emőke Sikora, Ferenc Kristály, Gábor Muránszky, Béla Fiser, Béla Viskolcz, Miklós Nagy, and László Vanyorek. "Palladium Decorated, Amine Functionalized Ni-, Cd- and Co-Ferrite Nanospheres as Novel and Effective Catalysts for 2,4-Dinitrotoluene Hydrogenation." International Journal of Molecular Sciences 23, no. 21 (October 30, 2022): 13197. http://dx.doi.org/10.3390/ijms232113197.

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2,4-diaminotoluene (TDA) is one of the most important polyurethane precursors produced in large quantities by the hydrogenation of 2,4-dinitrotoluene using catalysts. Any improvement during the catalysis reaction is therefore of significant importance. Separation of the catalysts by filtration is cumbersome and causes catalyst loss. To solve this problem, we have developed magnetizable, amine functionalized ferrite supported palladium catalysts. Cobalt ferrite (CoFe2O4-NH2), nickel ferrite (NiFe2O4-NH2), and cadmium ferrite (CdFe2O4-NH2) magnetic catalyst supports were produced by a simple coprecipitation/sonochemical method. The nanospheres formed contain only magnetic (spinel) phases and show catalytic activity even without noble metals (palladium, platinum, rhodium, etc.) during the hydrogenation of 2,4-dinitrotoluene, 63% (n/n) conversion is also possible. By decorating the supports with palladium, almost 100% TDA selectivity and yield were ensured by using Pd/CoFe2O4-NH2 and Pd/NiFe2O4-NH2 catalysts. These catalysts possess highly favorable properties for industrial applications, such as easy separation from the reaction medium without loss by means of a magnetic field, enhanced reusability, and good dispersibility in aqueous medium. Contrary to non-functionalized supports, no significant leaching of precious metals could be detected even after four cycles.

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18

Moya, Juan Francisco, Christian Rosales, Inmaculada Fernández, and Noureddine Khiar. "Pyrene-tagged carbohydrate-based mixed P/S ligand: spacer effect on the Rh(i)-catalyzed hydrogenation of methyl α-acetamidocinnamate." Organic & Biomolecular Chemistry 15, no. 27 (2017): 5772–80. http://dx.doi.org/10.1039/c7ob01085k.

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The chain length between the pyrene group and the rhodium atom in mixed P/S catalysts is crucial in the enantioselective hydrogenation of enamides, and the most active catalyst can be used in catch and release process.

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Medici, Serenella, Massimiliano Peana, Alessio Pelucelli, and Maria Antonietta Zoroddu. "Rh(I) Complexes in Catalysis: A Five-Year Trend." Molecules 26, no. 9 (April 27, 2021): 2553. http://dx.doi.org/10.3390/molecules26092553.

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Rhodium is one of the most used metals in catalysis both in laboratory reactions and industrial processes. Despite the extensive exploration on “classical” ligands carried out during the past decades in the field of rhodium-catalyzed reactions, such as phosphines, and other common types of ligands including N-heterocyclic carbenes, ferrocenes, cyclopentadienyl anion and pentamethylcyclopentadienyl derivatives, etc., there is still lively research activity on this topic, with considerable efforts being made toward the synthesis of new preformed rhodium catalysts that can be both efficient and selective. Although the “golden age” of homogeneous catalysis might seem over, there is still plenty of room for improvement, especially from the point of view of a more sustainable chemistry. In this review, temporally restricted to the analysis of literature during the past five years (2015–2020), the latest findings and trends in the synthesis and applications of Rh(I) complexes to catalysis will be presented. From the analysis of the most recent literature, it seems clear that rhodium-catalyzed processes still represent a stimulating challenge for the metalloorganic chemist that is far from being over.

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Zhang, Lian Zi, and Hao Yuan Sun. "Development of Catalysts for Synthesizing Methanol from Syngas." Materials Science Forum 1053 (February 17, 2022): 165–69. http://dx.doi.org/10.4028/p-0eor9r.

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At present, methanol is one of the most basic organic chemical raw materials and energy storage media. With the development of chemical technology and energy storage technology, its application becomes more and more extensive, and the methanol market prospects are unlimited. Industrial-scale methanol is generally prepared by using synthesis gas containing hydrogen, carbon monoxide, and carbon dioxide as raw materials and reacting under a certain pressure, temperature, and catalyst. Therefore, the development of the methanol industry largely depends on the development of catalysts and the improvement of their performance. Metal catalysts are mainly used in the industry for reaction. This article reviews several metal catalysts used to synthesize methanol from syngas. Copper-based and iron-based catalysts are widely used, and the emerging rhodium and its ligand catalysts exhibit good catalytic performance in low-temperature catalysis. In the future, the scientific research team will focus on in-depth research on preparation methods, active centers, catalytic reaction kinetics, durability, metal ligands, raw material prices, etc., to lay a solid foundation for the industrial application of syngas to methanol in advance.

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Siedle, A. R., C. G. Markell, P. A. Lyon, K. O. Hodgson, and A. L. Roe. "Bifunctional rhodium-oxometalate catalysts." Inorganic Chemistry 26, no. 2 (January 1987): 219–20. http://dx.doi.org/10.1021/ic00249a002.

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Merckle, Christof, Simone Haubrich, and Janet Blümel. "Immobilized rhodium hydrogenation catalysts." Journal of Organometallic Chemistry 627, no. 1 (May 2001): 44–54. http://dx.doi.org/10.1016/s0022-328x(01)00696-9.

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Cabello, J. A., J. M. Campelo, A. Garcia, D. Luna, and J. M. Marinas. "AlPO4-supported rhodium catalysts." Journal of Catalysis 94, no. 1 (July 1985): 1–9. http://dx.doi.org/10.1016/0021-9517(85)90076-4.

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Brunner, Henri. "Enantioselective Rhodium(II) Catalysts." Angewandte Chemie International Edition in English 31, no. 9 (September 1992): 1183–85. http://dx.doi.org/10.1002/anie.199211831.

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Kovalčík, Jakub, Martin Straka, Peter Kačmáry, and Tomáš Pavlík. "CATALYST PROCESSING AND RECYCLING." Acta Tecnología 7, no. 3 (September 30, 2021): 99–104. http://dx.doi.org/10.22306/atec.v7i3.118.

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Discussed auto catalysts contain interesting quantities of platinum noble metals, palladium and rhodium according to the type of auto catalyst, thereby becoming a possible source of these metal aims to acquaint themselves with catalysts in general, their history and last but not least the possibilities of processing and obtaining noble metals for further use. The article deals with knowledge at the theoretical level of use of methods in processing depleted catalysts. It is pyrometallurgical and hydrometallurgical methods. The platinum group metals (PGMs) palladium, platinum, and rhodium represent the key materials for automotive exhaust gas treatment. Since there are currently no adequate alternatives, the importance of these metals for the automotive industry is steadily rising. The high value of PGMs in spent catalysts justifies their recycling. The state-of the-art technology is to melt the ceramic carrier and collect the precious fraction in a liquid metal bath. As the feed material has quite high melting points, huge amounts of energy are required for this process. Hydrometallurgical treatments of the spent catalysts offer the possibility to recycle the PGMs with less energy and time demands. Moreover, automotive catalysts contain further valuable materials to improve the exhaust gas treatment. These compounds, like cerium oxide, cannot be recovered in pyrometallurgical processes.

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Yakoumis, Iakovos, Εkaterini Polyzou, and Anastasia Maria Moschovi. "PROMETHEUS: A Copper-Based Polymetallic Catalyst for Automotive Applications. Part II: Catalytic Efficiency an Endurance as Compared with Original Catalysts." Materials 14, no. 9 (April 26, 2021): 2226. http://dx.doi.org/10.3390/ma14092226.

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PROMETHEUS catalyst, a copper-based polymetallic nano-catalyst has been proven to be suitable for automotive emission control applications. This novel catalyst consists of copper, palladium and rhodium nanoparticles as active phases, impregnated on an inorganic oxide substrate, CeO2/ZrO2 (75%, 25%). The aim of PROMETHEUS catalyst’s development is the substitution of a significant amount (85%) of Platinum Group Metals (PGMs) with copper nanoparticles while, at the same time, presenting high catalytic efficiency with respect to the commercial catalysts. In this work, an extensive investigation of the catalytic activity of full scale PROMETHEUS fresh and aged catalyst deposited on ceramic cordierites is presented and discussed. The catalytic activity was tested on an Synthetic Gas Bench (SGB) towards the oxidation of CO and CH4 and the reduction of NO. The loading of the washcoat was 2 wt% (metal content) on Cu, Pd, Rh with the corresponding metal ratio at 21:7:1. The concentration of the full-scale monolithic catalysts to be 0.032% total PGM loading for meeting Euro III standard and 0.089% for meeting Euro IV to Euro VIb standards. The catalytic activity of all catalysts was tested both in rich-burn (λ = 0.99) and lean-burn conditions (λ = 1.03).

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Saleh, Jehad, Ahmed Sadeq Al-Fatesh, Ahmed Aidid Ibrahim, Francesco Frusteri, Ahmed Elhag Abasaeed, Anis Hamza Fakeeha, Fahad Albaqi, et al. "Stability and Activity of Rhodium Promoted Nickel-Based Catalysts in Dry Reforming of Methane." Nanomaterials 13, no. 3 (January 29, 2023): 547. http://dx.doi.org/10.3390/nano13030547.

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The rhodium oxide (Rh2O3) doping effect on the activity and stability of nickel catalysts supported over yttria-stabilized zirconia was examined in dry reforming of methane (DRM) by using a tubular reactor, operated at 800 °C. The catalysts were characterized by using several techniques including nitrogen physisorption, X-ray diffraction, transmission electron microscopy, H2-temperature programmed reduction, CO2-temperature programmed Desorption, and temperature gravimetric analysis (TGA). The morphology of Ni-YZr was not affected by the addition of Rh2O3. However, it facilitated the activation of the catalysts and reduced the catalyst’s surface basicity. The addition of 4.0 wt.% Rh2O3 gave the optimum conversions of CH4 and CO2 of ~89% and ~92%, respectively. Furthermore, the incorporation of Rh2O3, in the range of 0.0–4.0 wt.% loading, enhanced DRM and decreased the impact of reverse water gas shift, as inferred by the thermodynamics analysis. TGA revealed that the addition of Rh2O3 diminished the carbon formation on the spent catalysts, and hence, boosted the stability, owing to the potential of rhodium for carbon oxidation through gasification reactions. The 4.0 wt.% Rh2O3 loading gave a 12.5% weight loss of carbon. The TEM images displayed filamentous carbon, confirming the TGA results.

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28

Nagel, Ulrich, and Christoph Roller. "Enantioselective Catalysis, XVII [1]. Enantioselective Catalytic Hydrogenation of Unfunctionalized Ketones." Zeitschrift für Naturforschung B 53, no. 3 (March 1, 1998): 267–70. http://dx.doi.org/10.1515/znb-1998-0301.

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Abstract Three diastereomeric rhodium bisphosphane complexes have been applied to asymmetric hydrogenation of unfunctionalized, non-chelating aliphatic and aromatic ketones. The ee values of the catalysis products differ considerably for the diastereomerical catalysts. 70% ee were obtained in hydrogenating butyrophenone, and 83.7% ee for pinacoline. The results depend strongly on the solvent used.

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29

Xu, Rui, Mingyu Zhang, Yuyan Zhang, and Hongge Jia. "Synthesis of rhodium catalysts with amino acid or triazine as a ligand, as well as its polymerization property of phenylacetylene." Heterocyclic Communications 28, no. 1 (January 1, 2022): 149–56. http://dx.doi.org/10.1515/hc-2022-0014.

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Abstract Three novel rhodium complexes, with l-tyrosine (l-Tyr), l-arginine (l-Arg), or 2,4-diamino-6-phenyl-1,3,5-triazine (Dpt) as a ligand, named as [Rh(cod)(l-Tyr)], [Rh(cod)(l-Arg)], and [Rh(cod)(Dpt)2], respectively, had been synthesized for catalyzing the polymerization of phenylacetylene. Their yields were 62.34, 54.87, and 58.21%, respectively, by the most suitable synthesis conditions at 25°C for 4 h. The structures and purity of these complexes were proved by 1H NMR, element analysis, and scanning electron microscope (SEM). It has been examined that phenylacetylene could be polymerized by the three complexes as catalysts with high degrees of polymerization (n = 368, 385, and 664, respectively) and yields (about 87.62, 88.39, and 59.67%, respectively). In conclusion, compared with traditional [Rh–N] type catalysts, the novel [N–Rh–N] type catalyst ([Rh(cod)(Dpt)2]) gained better catalytic performance. By comparing the yield, Mw, and degree of their polymerization, the polymerization mechanism was found under the [N–Rh–N] type rhodium catalyst system.

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30

Hood, Drew M., Ryan A. Johnson, Alex E. Carpenter, Jarod M. Younker, David J. Vinyard, and George G. Stanley. "Highly active cationic cobalt(II) hydroformylation catalysts." Science 367, no. 6477 (January 30, 2020): 542–48. http://dx.doi.org/10.1126/science.aaw7742.

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The cobalt complexes HCo(CO)4 and HCo(CO)3(PR3) were the original industrial catalysts used for the hydroformylation of alkenes through reaction with hydrogen and carbon monoxide to produce aldehydes. More recent and expensive rhodium-phosphine catalysts are hundreds of times more active and operate under considerably lower pressures. Cationic cobalt(II) bisphosphine hydrido-carbonyl catalysts that are far more active than traditional neutral cobalt(I) catalysts and approach rhodium catalysts in activity are reported here. These catalysts have low linear-to-branched (L:B) regioselectivity for simple linear alkenes. However, owing to their high alkene isomerization activity and increased steric effects due to the bisphosphine ligand, they have high L:B selectivities for internal alkenes with alkyl branches. These catalysts exhibit long lifetimes and substantial resistance to degradation reactions.

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31

Reiss, Jiří, and Jiří Hetflejš. "Rhodium-diphosphine tosylate complexes as hydrogenation catalysts." Collection of Czechoslovak Chemical Communications 51, no. 2 (1986): 340–46. http://dx.doi.org/10.1135/cccc19860340.

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Novel rhodium-diphosphine tosylate complexes of the type [Rh(COD)L2]+ (O3SC6H4CH3-p)- (L2 = diphos, prophos, buphos, (-)-DIOP) have been prepared in high yields (87-92%) by the displacement of acac ligand from Rh(COD)(acac)by p-toluenesulphonic acid in the presence of L2. The complexes were found to be efficient hydrogenation catalysts comparable in activity to know cationic rhodium complexes. Some differences in the catalytic behaviour of both systems are reported, using hydrogenation of 1-octene and Z-α-acetamidocinnamic acid as model reactions.

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32

Borrmann, Thomas, Andrew McFarlane, Uwe Ritter, and James Johnston. "Rhodium catalysts build into the structure of a silicate support in the hydroformylation of alkenes." Open Chemistry 11, no. 4 (April 1, 2013): 561–68. http://dx.doi.org/10.2478/s11532-012-0186-z.

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AbstractRhodium is build into a nano-structured calcium silicate during the synthesis of the silicate. Thereby, it was desired to create a robust heterogeneous catalyst, which does not suffer from catalyst leaching like rhodium impregnated on a pre-formed silicate. While this was achieved, the silicate structure was adversely affected by the incorporation of rhodium — the surface area and pore volume of the material were found to be comparatively low. Alcohol and acid washing were tested to address this issue. The alcohol treatment proved detrimental as catalytic material was leached from the silicate. The acid washed rhodium containing calcium silicate was quite active in the hydroformylation of alkenes and did not suffer loss of catalyst into the product phase. Acid treated rhodium containing silicates were more active than their untreated counterparts but less selective due to access to the rhodium centers being opened.

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33

Feldman, Julian, and Milton Orchin. "Membrane-supported rhodium hydroformylation catalysts." Journal of Molecular Catalysis 63, no. 2 (December 1990): 213–21. http://dx.doi.org/10.1016/0304-5102(90)85145-8.

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34

Kamer, Paul C. J., Joost N. H. Reek, and Piet W. N. M. Van Leeuwen. "ChemInform Abstract: Rhodium Phosphite Catalysts." ChemInform 32, no. 52 (May 23, 2010): no. http://dx.doi.org/10.1002/chin.200152256.

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35

Su, Penghe, Ya Chen, Xiaotong Liu, Hongyuan Chuai, Hongchi Liu, Baolin Zhu, Shoumin Zhang, and Weiping Huang. "Preparation and Characterization of Rh/MgSNTs Catalyst for Hydroformylation of Vinyl Acetate: The Rh0 was Obtained by Calcination." Catalysts 9, no. 3 (February 26, 2019): 215. http://dx.doi.org/10.3390/catal9030215.

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A simple and practical Rh-catalyzed hydroformylation of vinyl acetate has been synthesized via impregnation-calcination method using silicate nanotubes (MgSNTs) as the supporter. The Rh0 (zero valent state of rhodium) was obtained by calcination. The influence of calcination temperature on catalytic performance of the catalysts was investigated in detail. The catalysts were characterized in detail by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectrometer (XPS), atomic emission spectrometer (ICP), and Brunauer–Emmett–Teller (BET) surface-area analyzers. The Rh/MgSNTs(a2) catalyst shows excellent catalytic activity, selectivity and superior cyclicity. The catalyst could be easily recovered by phase separation and was used up to four times.

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36

Alberico, Möller, Horstmann, Drexler, and Heller. "Activation, Deactivation and Reversibility Phenomena in Homogeneous Catalysis: A Showcase based on the Chemistry of Rhodium/Phosphine Catalysts." Catalysts 9, no. 7 (June 30, 2019): 582. http://dx.doi.org/10.3390/catal9070582.

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In the present work, the rich chemistry of rhodium/phosphine complexes, which are applied as homogeneous catalysts to promote a wide range of chemical transformations, has been used to showcase how the in situ generation of precatalysts, the conversion of precatalysts into the actually active species, as well as the reaction of the catalyst itself with other components in the reaction medium (substrates, solvents, additives) can lead to a number of deactivation phenomena and thus impact the efficiency of a catalytic process. Such phenomena may go unnoticed or may be overlooked, thus preventing the full understanding of the catalytic process which is a prerequisite for its optimization. Based on recent findings both from others and the authors’ laboratory concerning the chemistry of rhodium/diphosphine complexes, some guidelines are provided for the optimal generation of the catalytic active species from a suitable rhodium precursor and the diphosphine of interest; for the choice of the best solvent to prevent aggregation of coordinatively unsaturated metal fragments and sequestration of the active metal through too strong metal–solvent interactions; for preventing catalyst poisoning due to irreversible reaction with the product of the catalytic process or impurities present in the substrate.

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37

Tang, Jie, Wenjin Dong, Fushan Chen, Li Deng, and Mo Xian. "Rhodium catalysts with cofactor mimics for the biomimetic reduction of CN bonds." Catalysis Science & Technology 11, no. 16 (2021): 5564–69. http://dx.doi.org/10.1039/d1cy00904d.

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Bio-inspired reduction of CN bonds was successfully performed using rhodium catalysts containing cofactor mimics. The intramolecular cooperation between rhodium and cofactor mimics enabled the transformation with good selectivity. A plausible mechanism was also proposed.

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38

Huang, Taisheng, Sripathy Venkatraman, Yue Meng, Tien V. Nguyen, Daniel Kort, Dong Wang, Rui Ding, and Chao-Jun Li. "Quasi-nature catalysis. Rhodium-catalyzed CC bond formation in air and water." Pure and Applied Chemistry 73, no. 8 (August 1, 2001): 1315–18. http://dx.doi.org/10.1351/pac200173081315.

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Transition-metal catalysis is out-grown from dry-boxes where the use of inert gas atmosphere and the exclusion of moisture have been essential. Such a restriction undoubtedly imposes limitations in the application of these reactions in organic synthesis and in the recycling of the catalysts. This article discusses some recent advances of rhodium-catalyzed carboncarbon bond formations under the natural conditions of air and water.

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39

Kihlman, Johanna, and Pekka Simell. "Carbon Formation in the Reforming of Simulated Biomass Gasification Gas on Nickel and Rhodium Catalysts." Catalysts 12, no. 4 (April 7, 2022): 410. http://dx.doi.org/10.3390/catal12040410.

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Biomass gasification gas contains hydrocarbons that must be converted to CO and H2 prior to the utilization of the gas in a synthesis unit. Autothermal or steam reforming operating with a nickel or noble metal catalyst is a feasible option to treat the gas, but the harsh reaction conditions may lead to the formation of solid carbon. This study discusses the effects of pressure, time-on-stream, and ethylene content on the carbon formation on nickel and rhodium catalysts. The experiments were carried out with laboratory-scale equipment using reaction conditions that were closely simulated after a pilot-scale biomass gasifier. The results indicated that ethylene content above 20,000 vol-ppm and the increased pressure would increase the carbon formation, although there were differences between the rhodium and nickel catalysts. However, carbon formation was significantly more pronounced on the nickel catalyst when the reaction time was increased from 5 h to 144 h. The type of carbon was found to be primarily encapsulating and graphitic. The formation of whisker carbons (also known as carbon nanotubes) was not observed, which is consistent with the literature as the feed gas contained H2S. It was concluded that utilizing a noble metal catalyst as the front layer of the catalyst bed could lower the risk for carbon formation sufficiently to provide stable long-term operation.

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40

Al-Rubaie, Ali Z., Zaki N. Kadhim, Majeed Y. Al-Luaibi, and Luma Sabri. "Synthesis of some new Rhodium complexes containing diaryl chalcogenide ligands and their uses as catalysts in hydrosilylation of alkenes." Journal of Physics: Conference Series 2063, no. 1 (November 1, 2021): 012022. http://dx.doi.org/10.1088/1742-6596/2063/1/012022.

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Abstract Diaryl Chalcogenides (i.e. Ar2E where Ar = 4-CH3C6H4, 4-BrC6H4, E= S, Se and Te) were reacted with [RhCl(CO)2]2 and rhodium(III) chloride trihydrate to give compounds of type [RhCl(CO)2(Ar2E)] and [RhCl3(Ar2E)3], respectively. All compounds were characterized by IR, NMR, and mass spectroscopic data. Attempts to prepare hydroxyapatite (HAp) supported rhodium catalyst by using different methods were unsuccessful. Complexes [RhCl(CO)2((4-R-C6H4)2S)], [RhCl(CO)2((4-R-C6H4)2Se)] and [RhCl(CO)2((4-R-C6H4)2Te), where R= CH3 or Br], were evaluated as catalysts for hydrosilylation of allyl phenyl ether and 1-decene. They showed good catalytic activities for hydrosilylation of alkenes with triethoxysilane.

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41

Itoda, Marino, Yuki Naganawa, Makoto Ito, Hiroshi Nonaka, and Shinsuke Sando. "Structural exploration of rhodium catalysts and their kinetic studies for efficient parahydrogen-induced polarization by side arm hydrogenation." RSC Advances 9, no. 32 (2019): 18183–90. http://dx.doi.org/10.1039/c9ra02580d.

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42

Hannagan, Ryan T., Georgios Giannakakis, Romain Réocreux, Julia Schumann, Jordan Finzel, Yicheng Wang, Angelos Michaelides, et al. "First-principles design of a single-atom–alloy propane dehydrogenation catalyst." Science 372, no. 6549 (June 24, 2021): 1444–47. http://dx.doi.org/10.1126/science.abg8389.

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The complexity of heterogeneous catalysts means that a priori design of new catalytic materials is difficult, but the well-defined nature of single-atom–alloy catalysts has made it feasible to perform unambiguous theoretical modeling and precise surface science experiments. Herein we report the theory-led discovery of a rhodium-copper (RhCu) single-atom–alloy catalyst for propane dehydrogenation to propene. Although Rh is not generally considered for alkane dehydrogenation, first-principles calculations revealed that Rh atoms disperse in Cu and exhibit low carbon-hydrogen bond activation barriers. Surface science experiments confirmed these predictions, and together these results informed the design of a highly active, selective, and coke-resistant RhCu nanoparticle catalyst that enables low-temperature nonoxidative propane dehydrogenation.

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43

Lyman, C. E., R. E. Lakis, and H. G. Stenger. "Composition-size distribution diagrams for alloy catalysts." Proceedings, annual meeting, Electron Microscopy Society of America 53 (August 13, 1995): 404–5. http://dx.doi.org/10.1017/s0424820100138397.

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Catalyst microstructure and catalytic properties can be directly correlated using a composition-size distribution diagram that maps the phases of small alloy particles by composition and size. The application of this diagram given here concerns Pt-Rh/alumina catalysts for reduction of NO in hydrogen at low temperatures. The composition-size diagram provides an understanding of why some alloy catalysts perform worse than pure Pt in the NO reduction reaction, while other preparations exhibit the several times the activity of pure Pt. The composition-size diagram can be used to "fingerprint" active and less active alloy catalysts. Analytical electron microscopy (AEM) has been used to determine the Pt-Rh particle composition-size distribution.Catalysts were prepared by aqueous impregnation of platinum chloride into gamma-alumina particles with a 4 nm average pore size. After impregnation and air drying, the catalyst was calcined in air at 500°C for 3 hr. Subsequently, rhodium was impregnated from its chloride into the same support material, and the preparation was air-dried.

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44

Müller, Paul, Corine Baud, and Yvan Jacquier. "The rhodium(II)-catalyzed aziridination of olefins with {[(4-nitrophenyl)sulfonyl]imino}phenyl-lambda3-iodane." Canadian Journal of Chemistry 76, no. 6 (June 1, 1998): 738–50. http://dx.doi.org/10.1139/v98-058.

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The aziridination of olefins with {(4-nitrophenylsulfonyl)imino}phenyl-lambda3-iodane, NsN==IPh (1c), in the presence of [Rh2(OAc)4] proceeds in yields of up to 85% when the olefin is used in large excess. Under optimized conditions, styrene (4a) is aziridinated with 1 equiv. of NsN==IPh (1c) in 64% yield with 2 mol% of catalyst. The aziridines derived from electron-rich olefins undergo ring-opening under the conditions of the aziridination and afford rearrangement products or pyrrolidines. The aziridination is sterospecific with 1,2-dialkyl- and 1,2-arylalkyl-disubstituted olefins, but nonstereospecific with stilbene.The rho -value for aziridination of substituted styrenes is -0.61. No ring-opened products are observed upon aziridination of vinylcyclopropanes. In the presence of chiral RhII catalysts, the aziridination is enantioselective, affording an ee of 73% with cis- β -methylstyrene (4k) and Pirrungs [Rh2{(R)-(-)-bnp}4] catalyst. The experimental results are consistent with a one-step mechanism for transfer of the nitrenoid moiety from the catalyst to the olefin.Key words: aziridination, nitrene transfer, rhodium catalysis.

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45

Charette, André B., and Jean-Emmanuel Bouchard. "Catalytic asymmetric synthesis of cyclopropylphosphonates Catalysts' scope and reactivity." Canadian Journal of Chemistry 83, no. 6-7 (June 1, 2005): 533–42. http://dx.doi.org/10.1139/v05-074.

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The transition metal-catalyzed cyclopropanation of alkenes using α-diazomethylphosphonates leads to cyclopropylphosphonate derivatives in high yields. The reaction proceeds well with copper, rhodium, and ruthenium catalysts. The best catalysts for the enantioselective version are either Evans' Cu·bis(oxazoline) or Nishiyama's Ru·pybox.Key words: cyclopropylphosphonic acids, copper catalysts, ruthenium catalysts, cyclopropanation, diazo reagents.

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46

Bernal, S., F. J. Botana, J. J. Calvino, G. Cifredo, R. García, S. Molina, and J. M. Rodríguez-Izquierdo. "HREM characterization of lanthana-supported rhodium catalysts." Proceedings, annual meeting, Electron Microscopy Society of America 48, no. 4 (August 1990): 246–47. http://dx.doi.org/10.1017/s0424820100174369.

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Metals supported on rare earth sesquioxides present a non- conventional behavior. Ordinary H2 and-or CO chemisorption techniques cannot be straightforwardly used to characterize this group of catalysts. The assessement to the data of metallic dispersions and the establishment of the occurrence and extent of metal-support interaction phenomena are determinant in order to interpret the properties of these catalysts in hydrogenation reactions. In this work HREM is proposed as a powerfull technique for the study of lanthana supported rhodium catalysts. Such catalysts would be considered as representative of a series of metals supported on rare earth sesquioxides.

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47

Weng-Sieh, Zara, Ronald Gronsky, and Alexis T. Bell. "Microstructural evolution of γ-alumina supported rhodium catalysts." Proceedings, annual meeting, Electron Microscopy Society of America 53 (August 13, 1995): 400–401. http://dx.doi.org/10.1017/s0424820100138373.

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In an era of increasing environmental awareness, stricter federal and state regulation of pollutant emissions are emerging. A major source of pollution arises from automobiles which inadvertently form gaseous products such as nitric oxide (NOx), carbon monoxide (CO), and hydrocarbons (HC). Since the early 1980's, these effluents have been converted to safer forms using a three-way catalytic converter that employs a high dispersion of rhodium and platinum particles supported on a large surface area of transitional γ-phase alumina. Unfortunately such a converter is susceptible to decreased performance over time, and this degradation has been attributed to changes in the catalyst microstructure. The nanoscaled nature of the transition metal catalysts and the submicron-scaled size of the transitional alumina necessitates the use of the high spatial resolution analyses made possible by transmission electron microscopy.

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48

Azad, Abdul-Majeed, and Desikan Sundararajan. "A Phenomenological Study on the Synergistic Role of Precious Metals in the Steam Reforming of Logistic Fuels on Bimetal-Supported Catalysts." Advances in Materials Science and Engineering 2011 (2011): 1–12. http://dx.doi.org/10.1155/2011/496038.

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Fuel processors are required to convert sulfur-laden logistic fuels into hydrogen-rich reformate and deliver to the fuel cell stack with little or no sulfur. Since sulfur poisons and deactivates the reforming catalyst, robust sulfur-tolerant catalysts ought to be developed. In this paper, the development, characterization and evaluation of a series of reforming catalysts containing two noble metals (with total metal loading not exceeding 1 weight percent) supported on nanoscale ceria for the steam-reforming of kerosene is reported. Due to inherent synergy, a bimetallic catalyst is superior to its monometallic analog, for the same level of loading. The choice of noble metal combination in the bimetallic formulations plays a vital and meaningful role in their performance. Presence of ruthenium and/or rhodium in formulations containing palladium showed improved sulfur tolerance and significant enhancement in their catalytic activity and stability. Rhodium was responsible for higher hydrogen yields in the logistic fuel reformate. Duration of steady hydrogen production was higher in the case of RhPd (75 h) than for RuPd (68 h); hydrogen generation was stable over the longest period (88 h) with RuRh containing no Pd. A mechanistic correlation between the characteristic role of precious metals in the presence of each other is discussed.

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49

Vogels, Christopher M., Andreas Decken, and Stephen A. Westcott. "Rhodium(I) acetylacetonato complexes containing phosphinoalkynes as catalysts for the hydroboration of vinylarenes." Canadian Journal of Chemistry 84, no. 2 (February 1, 2006): 146–53. http://dx.doi.org/10.1139/v05-242.

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Three novel rhodium(I) acetylacetonato (acac) complexes bearing phosphinoalkynes (Ph2PC≡C-t-Bu, Ph2PC≡CPPh2, and Ph2PC≡CC≡CPPh2) have been prepared and characterized fully. Addition of B2cat3 (cat = 1,2-O2C6H4) to Rh(acac)(Ph2PC≡C-t-Bu)2 (1a) led to zwitterionic Rh(η6-catBcat)(Ph2PC≡C-t-Bu)2 (2a), the first example of this type of compound to contain monodentate phosphine ligands. All new rhodium complexes have been investigated for their ability to catalyse the hydroboration of vinylarenes.Key words: catalysis, hydroboration, phosphinoalkynes, regioselectivity, rhodium.

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50

Burwell, Robert L. "Supported platinum, palladium, and rhodium catalysts." Langmuir 2, no. 1 (January 1986): 2–11. http://dx.doi.org/10.1021/la00067a001.

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Journal articles on the topic 'Rhodium catalysts'

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