This MedLibrary.org supplementary page on Wilkinson's catalyst is provided directly from the open source Wikipedia as a service to our readers. Please see the note below on authorship of this content, as well as the Wikipedia usage guidelines. To search for other content from our encyclopedia supplement, please use the form below:
Related Sponsors
| Wilkinson's catalyst | |
|---|---|
 |
|
 |
|
 |
|
| IUPAC name | (SP-4)chloridotris(triphenylphosphane) rhodium |
| Other names | Rhodium(I) tris- (triphenylphosphine) chloride, Wilkinson’s catalyst, Tris(triphenylphosphine)- rhodium chloride |
| Identifiers | |
| CAS number | 14694-95-2 |
| EINECS number | |
| RTECS number | none |
| Properties | |
| Molecular formula | C54H45ClP3Rh |
| Molar mass | 925.22 g/mol |
| Appearance | red solid |
| Melting point |
245-250 °C |
| Solubility in water | insoluble |
| Solubility in other solvents | benzene |
| Structure | |
| Coordination geometry |
square planar |
| Hazards | |
| Main hazards | none |
| R-phrases | none |
| S-phrases | S22 S24/25 |
| Related compounds | |
| Related compounds | triphenylphosphine Pd(PPh3)4 IrCl(CO)[P(C6H5)32 |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox references |
|
Wilkinson's catalyst is the common name for chlorotris(triphenylphosphine)rhodium(I), a chemical compound with the formula RhCl(PPh3)3 (Ph = phenyl). It is named after the late organometallic chemist and 1973 Nobel Laureate, Sir Geoffrey Wilkinson who popularized its use.
Contents |
Structure and basic properties
The compound is a square planar, 16-electron complex and is usually isolated in the form of a red-violet crystalline solid from the reaction of rhodium(III) chloride with triphenylphosphine. The synthesis is conducted in refluxing ethanol.1 Ethanol serves as the reducing agent.
- RhCl3(H2O)3 + CH3CH2OH + 3 PPh3 → RhCl(PPh3)3 + CH3CHO + 2 HCl + 3 H2O
Catalytic applications
Wilkinson's catalyst catalyzes the hydrogenation of alkenes,23 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 (olefin insertion), and reductive elimination results in extrusion of the alkane product, e.g.:
Other applications of Wilkinson’s catalyst includes the catalytic hydroboration of alkenes with catecholborane and pinacolborane,4 and the selective 1,4-reduction of α, β-unsaturated carbonyl compounds in concert with triethylsilane.5 When the triphenylphosphine ligands are replaced by chiral phosphines (e.g., chiraphos, DIPAMP, DIOP), the catalyst becomes chiral and convert prochiral alkenes into enantiomerically enriched alkanes via the process called asymmetric hydrogenation.6
Other reactions of RhCl(PPh3)3
RhCl(PPh3)3 reacts with CO to give RhCl(CO)(PPh3)2, which is structurally analogous to Vaska's complex but much less reactive. The same complex arises from the decarbonylation of aldehydes, although the reaction is stoichiometric:
- RhCl(PPh3)3 + RCHO → RhCl(CO)(PPh3)2 + RH + PPh3
Upon stirring in benzene solution, RhCl(PPh3)3 converts to the poorly soluble red-colored species Rh2Cl2(PPh3)4. This conversion further demonstrates the lability of the triphenylphosphine ligands.
References
- ^ Osborn, J. A.; Jardine, F. H.; Young, J. F.; Wilkinson, G. (1966). "The Preparation and Properties of Tris(triphenylphosphine)halogenorhodium(I) and Some Reactions Thereof Including Catalytic Homogeneous Hydrogenation of Olefins and Acetylenes and Their Derivatives". Journal of the Chemical Society A: 1711–1732. doi:.
- ^ A. J. Birch, D. H. Williamson (1976). Organic Reactions 24: 1ff.
- ^ B.R. James, Homogeneous Hydrogenation. John Wiley & Sons, New York, 1973.
- ^ D. A. Evans, G. C. Fu and A. H. Hoveyda (1988). "Rhodium(I)-catalyzed hydroboration of olefins. The documentation of regio- and stereochemical control in cyclic and acyclic systems". J. Am. Chem. Soc. 110 (20): 6917–6918. doi:.
- ^ I. Ojima, T. Kogure, Y. Nagai (1972). "Selective reduction of α,β-unsaturated terpene carbonyl compounds using hydrosilane-rhodium(I) complex combinations". Tetrahedron Lett. 13 (49): 5035–5038. doi:.
- ^ W. S. Knowles (2003). "Asymmetric Hydrogenations (Nobel Lecture 2001)". Advanced Synthesis and Catalysis 345: 3–13. doi:.
Wikipedia content modification information:
- This page was last modified on 17 July 2008, at 16:11.
Wikipedia Authorship and Review
Wikipedia content provided here is not reviewed directly by MedLibrary.org. Wikipedia content is authored by an open community of volunteers and is not produced by or in any way affiliated with MedLibrary.org.
Wikipedia Usage Guidelines
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article on "Wilkinson's catalyst".
The URL for this specific entry is:
All Wikipedia text is available under the terms of the GNU Free Documentation License. (See Copyrights for details). Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc.