Rhodium-on-alumina, catalyzed

In a study on the influence of supports on rhodium, the amount of dicyclohexylamine was found to decrease in the order carbon > barium carbonate > alumina > barium sulfate > calcium carbonate. Plain carbon added to rhodium-on-alumina-catalyzed reactions was found to cause an increase in the amount of dicyclohexylamine, suggesting that carbon catalyzes the formation of the intermediate addition product (59). 

Rhodium-on-alumina, catalyzed reduction of aromatic nuclei, 51, 105... 

REDUCTIVE AMINATION WITH SODIUM CYANOBOROHYDRIDE N.N-DIMETHYLCY-CLOHEXYLAMINE, 52, 124 Reference electrode for electrolytic reduction, 52, 28 Resorcinol dimethyl ether, 50,52 Rhodium-on-alumina, catalyzed reduction of aromatic nuclei, 51, 105... 

Copper chromite tends to catalyze the reduction of the heterocyclic ring and any readily reduced substituents, whereas rhodium on alumina is an effective catalyst for the hydrogenation of the pyrrole ring under very mild conditions (B-77MI30505, B-77MI30507,79CJC1977). 

This preparation illustrates the alkylation of malononitrile under acid-catalyzed conditions, and the use of diborane for the reduction of a dinitrile to a diamine. The procedure for the preparation of tert-butylmalononitrile has been outlined briefly by Boldt and co-workers.2 The generation of diborane in situ and the general method for nitrile reduction is that described by Brown and co-workers.3 Attempts to reduce the dinitrile to the diamine by other methods including catalytic hydrogenation (5% rhodium on alumina, 5 atm.), lithium aluminum hydride, and lithium aluminum hydride-aluminum chloride were singularly unsuccessful. 

Automobile and Hydrocarbon Emissions. The oxidation of carbon monoxide and hydrocarbons is catalyzed by platinum/palladium/rhodium on alumina. If catalyst poisons such as lead and phosphorus are not present, the major problems become initiation of oxidation at low temperature, thermal stability at high temperature, resistance to thermal schock, and a high external surface area catalyst configuration. 

Rhodium-catalyzed Additions. The title compound has been a test reagent in several rhodium-catalyzed additions to the triple bond. For example, a rhodium-catalyzed silylcarbamoylation in the presence of a secondary amine afforded the silylated product in reasonable yield (eq 40). In the presence of a CO atmosphere and with 5% rhodium on alumina as catalyst, stereoselective hydrosilylation has been reported (eq 41). ... 

PAMAM itself was used as a multivalent macromolecular ligand, probably due to its multiple amino groups, in order to complex and immobilize metal ions, complexes, and nanoparticles with catalytic capabilities. Thus, Kawi and coworkers used PAMAM-on-silica and PAMAM-on-alumina templates to immobilize Rh(l) complexes as hydroformy-lation catalysts. Passivation of the silica OH sites outside the pores of SBA-15 silica resulted in a tighter binding of rhodium complexes inside the pores and led to a series of catalysts that displayed a positive dendritic effect up to the second PAMAM generation." Sreekumar and Krishnan used PAMAM on polystyrene to complex Mn(ll) precursors and catalyze the oxidation of secondary alcohols." " ... 

The stmctural complexity and biological activity of the cyathane family of diterpenes has stimulated considerable interest from synthetic chemists, as reflected in the number and diversity of approaches reported thus far [42]. Our own strategy for cyathane synthesis is based on a rhodium-catalyzed [5+2] cycloaddition. The precursor for this reaction was fashioned ultimately from commercially available and inexpensive (S)-(-)-limonene. Treatment of the ketone 139 with 5 mol% [RhCl(CO)2]2 in 1,2-dichloro-ethane gave cycloadduct 140 (Scheme 13.14) in 90% yield and in analytically pure form after simple filtration through a plug of neutral alumina [43]. 

Since 1981, three-way catalytic systems have been standard in new cars sold in North America.6,280 These systems consist of platinum, palladium, and rhodium catalysts dispersed on an activated alumina layer ( wash-coat ) on a ceramic honeycomb monolith the Pt and Pd serve primarily to catalyze oxidation of the CO and hydrocarbons, and the Rh to catalyze reduction of the NO. These converters operate with a near-stoichiometric air-fuel mix at 400-600 °C higher temperatures may cause the Rh to react with the washcoat. In some designs, the catalyst bed is electrically heated at start-up to avoid the problem of temporarily excessive CO emissions from a cold catalyst. Zeolite-type catalysts containing bound metal atoms or ions (e.g., Cu/ZSM-5) have been proposed as alternatives to systems based on precious metals. 

Al-Ammar AS, Webb G (1978) Hydrogenation of acetylene over supported metal catalysts Part 1 - Adsorption of [ C] Acetylene and [ C] ethylene on silica supported rhodium, iridium and palladium and alumina supported palladium. J Chem Soc Earaday Trans 74 195 Al-Ammar AS, Webb G (1979) Hydrogenation of acetylene over supported metal catalysts Part 3 - [ C] tracer studies of the effect of added ethylene and carbon monoxide on the reaction catalyzed by silica-supported palladium, rhodium and iridium. J Chem Soc Faraday Trans 75 1900... 

A palladium derivative of an oligo-p-phenylenetereph-thamide performed better as a catalyst for the reduction of phenylacetylene to ethylbenzene than palladium on carbon or silica or alumina catalysts.207 A rhodium(I) complex of the polyamide (5.48) was used to catalyze the addition of silanes to 1,3-dienes with good regio- and stereoselectivity.208 Rhodium is one of the metals that is so expensive that losses must be kept at an absolute minimum. 

Dehydration of propargyl alcohols occurs commonly on mononuclear ruthenium complexes.[ l Water is formed from the terminal alkynic hydrogen and by the alcoholic OH this is the more common dehydration process (it is denoted Route A). These reactions afford organic intermediates leading to cumulene complexes useful for the synthesis of doped polyacetylenes or of non-linear optic materials. Dehydration of rhodium-coordinated propargyl alcohols " leads to free or coordinated cumulenes and can be catalyzed by alumina and chloride ions, Fig. 16. 

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