Tris- chlororhodium

Halpern J and Wong C S 1973 Hydrogenation of tris(triphenylphosphine)chlororhodium(l) Chem. Commun. 629-30... 

Gonjugation of polyunsaturated fats Methyl linoleate with tris(triphenylphosphine) chlororhodium. J.Am. Oil Chem. Soc., 48, 21-24. 

The 1,4-reduction of a,/3-unsaturated aldehydes is best carried out with diphenylsilane in the presence of zinc chloride and tetrakis(triphenylphosphine) palladium436 or a combination of triethylsilane and tris(triphenylphosphine) chlororhodium 437 Other practical approaches use phenylsilane with nickel (0) and triphenylphosphine438 and diphenylsilane with cesium fluoride.83 It is possible to isolate the initial silyl enol ether intermediate from the 1,4-hydrosilylation of o, /3-unsaturated aldehydes (Eq. 264).73,411 The silyl enol ethers are produced as a mixture of E and Z isomers. 

Besides solid transition metals, certain soluble transition-metal complexes are active hydrogenation catalysts.4. The most commonly used example is tris(triphenylphosphine)-chlororhodium, which is known as Wilkinson s catalyst.5 This and related homogeneous catalysts usually minimize exchange and isomerization processes. Hydrogenation by homogeneous catalysts is believed to take place by initial formation of a rc-complex, followed by transfer of hydrogen from rhodium to carbon. 

Reduction of 5a-Cholest-2-ene with Deuterium and Tris-(tri-phenylphosphine)-chlororhodium... 

Previous work has shown that the electronic characteristics of the benzene substituent in triarylphosphine chlororhodium complexes have a marked influence on the rate of olefin hydrogenation catalyzed by these compounds. Thus, in the hydrogenation of cyclohexene using L3RhCl the rate decreased as L = tri-p-methoxyphenylphosphine > triphenylphosphine > tri-p-fluorophenylphosphine (14). In the hydrogenation of 1-hexene with catalysts prepared by treating dicyclooctene rhodium chloride with 2.2-2.5 equivalents of substituted triarylphosphines, the substituent effect on the rate was p-methoxy > p-methyl >> p-chloro (15). No mention could be found of any product stereochemistry studies using this type of catalyst. 

Wilkinson catalyst, tris (triphenylphosphine) chlororhodium (I). With this in mind, it will be helpful to review briefly a few facts about [(C6H5)3P] 3RhCl before discussing the asymmetric rhodium catalysts in greater detail. 

The dihydrido complexes (Table 62) can be obtained by the oxidative addition of molecular hydrogen to rhodium(I) complexes (equation 186).10,119,922""926 The tri(f-butyl)phosphine complexes can be prepared either from the chlororhodium(I) complex,923 or rhodium trichloride.927 The former method seems more reliable since the latter reports the complex as a matt green substance, a color uncharacteristic of tertiary phosphine rhodium(III) complexes. Indeed, Masters and Shaw report that the related tertiary phosphines PBu2R (R = Et, Pr) give green rhodium(II) complexes in this reaction (see Section 48.5.2.1 above).268,269... 

Tire reaction of carbon dioxide, hydrogen and methyloxirane Iras been desenbed by Koiiiunra (173, 174]. I, 2 Propanedtol formates were prepared in the presence of iri (triphenylphosphine)chlororhodium or tris (tripheny I phosphine) dichlororutheniunr as catalysts. No cocatalysl is required. 

Alternatively, the gem-dibromo group represents a masked carbonyl group. Thus treatment of (8) with. sodium methoxide gives (9) when this is allowed to react with methanolic silver nitrate, the bromine atoms are replaced by methoxyl groups to generate the succinaldehyde ester (10). Hydrolysis of (10) leads to the aldehyde (11). Reduction with tris(triphenylphosphine)chlororhodium (1, 1252 2, 448-453 3, 325-329 this volume) effects decarbonylation to give (12). 

A different type of cyclizalion by means of the rhodium complex is observed in the case of a compound containing a I-al-6-ene system. Thus reaction of (-l-)-citTonellal (4) with I eq. of tris(triphenylphosphine)chlororhodium in freshly distilled chloroform at room temperature for 15 hr. results in the formation of (-t-)-neoisopulegol (5) and (—)-isopulegDl (6) in the ratio of 3 1. 

Reduction of diazoniumfluoroborates. Tris(triphenylphosphine)chlororhodium, [(CsHjjjPJjRhCI, and also [(C HjjjPjjRhCUCO) catalyze the reduction of aryl diazonium fluoroborates by DMF (room temperature for 2 days or 80 for 1 day). 

Akohofysis of dkurylsUanes." Tris(lriphenylphosphine)chlororhodium and di-chlorotris(triphenylphosphine)ruthenium are cflcctivc catalysts for alcoholysis of diary Isilanes ... 

CYCLIZATION Boron trifluoride etherate. Dibenzoyl peroxide. Dimethylcopperlithi-um. Dimethylformormide dimethyl acetal. Mercuric tiifluoroacetate. Polyphos-phoricacid. Sodium hydride. Sodium methylsulfinyUnethylide. Sulfuric acid. Tris( triphenyl phosphine)chlororhodium. 

Tris(triphenylphosphine)chlororhodium(I). The homogenous catalysis of the hydrogenation of ethylene and other olefins by RhCl( PPha) a, recently discovered by Wilkinson and co-workers (6J), probably involves a dihydride intermediate. A plausible mechanism for this reaction, involving steps of the type already described, is shown in Reaction 36. 

Fiuorenone from benzoic anhydride,s Tris(triphenylphosphine)chlororhodium catalyzes the conversion of benzoic anhydride into fiuorenone. The reaction proceeds at about 240°. 

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