Wilkinson's catalyst
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| Wilkinson's catalyst | |
|---|---|
| Molecular formula | [RhCl(PPh3)3] |
| Molar mass | 925.22 g/mol |
| CAS number | |
| EINECS number | 238-744-5 |
| Solubility | C6H6 |
| Melting point | 254-50 °C |
| [Chemical infoboxDisclaimer and references] | |
Wilkinson's catalyst is the common name for chlorotris(triphenylphosphine)rhodium(I), named after the late organometallic chemist and 1973 Nobel Laureate, Sir Geoffrey Wilkinson. The compound is a square planar, 16-electron complex, and is usually isolated in the form of a red-violet crystalline solid with a melting point of 247-252 °C. Wilkinson's catalyst is prepared by heating rhodium(III) chloride trihydrate and triphenylphosphine. in ethanol.1 The ethanol serves as the reducing agent.
The most common use of Wilkinson's catalyst is as a homogeneous catalyst in the hydrogenation of alkenes,2 the mechanism of which involves the initial dissociation of one or two triphenylphosphine ligands to give 14 or 12-electron complexes, respectively, followed by oxidative addition of H2 to the metal. Subsequent π-complexation of alkene, intramolecular hydride transfer, and reductive elimination results in extrusion of the alkane product, e.g.:
Other applications of Wilkinson’s catalyst include: catalytic hydroboration of alkenes using catecholborane and pinacolborane,3 and the selective 1,4-reduction of α, β-unsaturated carbonyl compounds in concert with triethylsilane.4 When the triphenylphosphine ligands are replaced by chiral phosphines (e.g. Chiraphos, DIPAMP, DIOP), the catalyst becomes chiral and is capable of making chiral alkanes from prochiral alkenes through asymmetric hydrogenation.5
References
- J. A. Osborn, F. H. Jardine, J. F. Young, G. Wilkinson, J. Chem. Soc. A. 1966: 1711.
- (a) A. J. Birch, D. H. Williamson, Org. React. 24:1 (1976); (b) B.R. Jones, Homogeneous Hydrogenation. John Wiley & Sons, New York, 1973.
- D. A. Evans, G. C. Fu, and A. H. Hoveyda, J. Am. Chem. Soc. 110: 6917 (1988).
- I. Ojima, T. Kogure, Y. Nagai, Tetrahedron Lett. 1972: 5035.
- W. S. Knowles, Adv. Synth. Catal. 2003, 345(1&2), 3-13.
External links
- For a full list of external links to MSDSs, spectroscopic data, commercial chemicals suppliers etc. for this compound, see [Chemical sources].
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