Wilkinson's catalyst 1

Wilkinson's catalyst

Wilkinson's catalyst

Identifiers

CAS number 14694-95-2 [1]

EC number 238-744-5 [2]

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 in water

Solubility in other solvents benzene

Structure

Coordinationgeometry

square planar

Hazards

R-phrases none

S-phrases S22 S24/25

Main hazards none

Wilkinson's catalyst 2

Related compounds

Related compounds triphenylphosphinePd(PPh3)4IrCl(CO)[P(C6H5)3]2

  (verify) [3] (what is:  / ?)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 coordinationcompound with the formula RhCl(PPh3)3 (Ph = phenyl). It is named after the chemist and Nobel Laureate, SirGeoffrey Wilkinson who popularized its use.

Structure and basic propertiesThe compound is a square planar, 16-electron complex. It is usually obtained in the form of a red-violet crystallinesolid from the reaction of rhodium(III) chloride with excess triphenylphosphine.[4] The synthesis is conducted inrefluxing ethanol which helps with the reduction.[5] Triphenylphosphine serves as the reducing agent yieldingtriphenylphosphine oxide.

RhCl3(H2O)3 + 4 PPh3 → RhCl(PPh3)3 + O=PPh3 + 2 HCl + 2 H2O

Catalytic applicationsWilkinson's catalyst catalyzes the hydrogenation of alkenes.[6][7] The mechanism of this reaction involves the initialdissociation of one or two triphenylphosphine ligands to give 14- or 12-electron complexes, respectively, followedby 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.:

Wilkinson's catalyst 3

Other applications of Wilkinson’s catalyst includes the catalytic hydroboration of alkenes with catecholborane andpinacolborane,[8] and the selective 1,4-reduction of α, β-unsaturated carbonyl compounds in concert withtriethylsilane.[9] When the triphenylphosphine ligands are replaced by chiral phosphines (e.g., chiraphos, DIPAMP,DIOP), the catalyst becomes chiral and converts prochiral alkenes into enantiomerically enriched alkanes via theprocess called asymmetric hydrogenation.[10]

Other reactions of RhCl(PPh3)3RhCl(PPh3)3 reacts with CO to give trans-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:

RhCl(PPh3)3 + RCHO → RhCl(CO)(PPh3)2 + RH + PPh3Upon 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[1] http:/ / www. commonchemistry. org/ ChemicalDetail. aspx?ref=14694-95-2[2] http:/ / esis. jrc. ec. europa. eu/ lib/ einecs_IS_reponse. php?genre=ECNO& entree=238-744-5[3] http:/ / en. wikipedia. org/ wiki/ Special%3Acomparepages?rev1=401247156& page2=%3AWilkinson%27s+ catalyst[4] Bennett, M. A.; Longstaff, P. A. Complexes of Rhodium(I) with Triphenylphosphine. Chem. Ind. (London) 1965, p. 846.[5] 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 andAcetylenes and Their Derivatives". Journal of the Chemical Society A: 1711–1732. doi:10.1039/J19660001711.

[6] A. J. Birch, D. H. Williamson (1976). Organic Reactions 24: 1ff.[7] B.R. James, Homogeneous Hydrogenation. John Wiley & Sons, New York, 1973.[8] 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:10.1021/ja00228a068.[9] I. Ojima, T. Kogure (1972). "Selective reduction of α,β-unsaturated terpene carbonyl compounds using hydrosilane-rhodium(I) complex

combinations". Tetrahedron Lett. 13 (49): 5035–5038. doi:10.1016/S0040-4039(01)85162-5.[10] W. S. Knowles (2003). "Asymmetric Hydrogenations (Nobel Lecture 2001)". Advanced Synthesis and Catalysis 345 (12): 3–13.

doi:10.1002/adsc.200390028.

Article Sources and Contributors 4

Article Sources and ContributorsWilkinson's catalyst  Source: http://en.wikipedia.org/w/index.php?oldid=502181644  Contributors: Albris, Armando-Martin, Axiosaurus, Beetstra, Benjah-bmm27, Brichcja, Chem-awb, Chiufrederick, Christian75, EdChem, Edgar181, HappyCamper, Japanese Searobin, Keenan Pepper, Kupirijo, Makecat, MarSch, Materialscientist, Nanotube7, Nirmos, Olaf2, Physchim62, Rifleman82, Smokefoot, Stone, TMaster, Tassedethe, Terpenoid, V8rik, WVhybrid, Walkerma, Xcomradex, 21 anonymous edits

Image Sources, Licenses and ContributorsImage:Wilkinson's-catalyst-2D.png  Source: http://en.wikipedia.org/w/index.php?title=File:Wilkinson's-catalyst-2D.png  License: Public Domain  Contributors: Benjah-bmm27Image:Wilkinson's-catalyst-no-hydrogens-3D-balls.png  Source: http://en.wikipedia.org/w/index.php?title=File:Wilkinson's-catalyst-no-hydrogens-3D-balls.png  License: Public Domain Contributors: Benjah-bmm27Image:Wilkinson's-catalyst-3D-vdW.png  Source: http://en.wikipedia.org/w/index.php?title=File:Wilkinson's-catalyst-3D-vdW.png  License: Public Domain  Contributors: Benjah-bmm27Image:Wilkinson's Cataylst-powder2.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Wilkinson's_Cataylst-powder2.jpg  License: Creative Commons Zero  Contributors:en:user:TMasterFile:Yes check.svg  Source: http://en.wikipedia.org/w/index.php?title=File:Yes_check.svg  License: Public Domain  Contributors: AnomieImage:X mark.svg  Source: http://en.wikipedia.org/w/index.php?title=File:X_mark.svg  License: Public Domain  Contributors: User:GmaxwellImage:RevisedCatCycle.png  Source: http://en.wikipedia.org/w/index.php?title=File:RevisedCatCycle.png  License: Public Domain  Contributors: Nanotube7

LicenseCreative Commons Attribution-Share Alike 3.0 Unported//creativecommons.org/licenses/by-sa/3.0/