Wilkinson's catalyst

Wilkinson's catalyst

Names
IUPAC name (SP-4)chloridotris(triphenylphosphane)rhodium
Other names Rhodium(I) tris(triphenylphosphine) chloride, Wilkinson's catalyst, Tris(triphenylphosphine)rhodium(I) chloride
Identifiers
CAS Number	14694-95-2
3D model (Jmol)	Interactive image
ECHA InfoCard	100.035.207
EC Number	238-744-5
PubChem CID	84599
RTECS number	none
SMILES [Rh+](P(C1=CC=CC=C1)(C2=CC=CC=C2)C3=CC=CC=C3)(P(C4=CC=CC=C4)(C5=CC=CC=C5)C6=CC=CC=C6)P(C7=CC=CC=C7)(C8=CC=CC=C8)C9=CC=CC=C9.[Cl-]
Properties
Chemical formula	C54H45ClP3Rh
Molar mass	925.22 g/mol
Appearance	red solid
Melting point	245 to 250 °C (473 to 482 °F; 518 to 523 K)
Solubility in water	insoluble in water
Solubility in other solvents	20 g/L (CHCl3, CH2Cl2), 2 g/L (benzene, toluene)
Structure
Coordination geometry	square planar
Hazards
Main hazards	none
R-phrases (outdated)	none
S-phrases (outdated)	S22 S24/25
Related compounds
Related compounds	triphenylphosphine Pd(PPh3)4 IrCl(CO)[P(C6H5)3]2
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Y  (what is YN ?)
Infobox references

Wilkinson's catalyst, is the common name for chloridotris(triphenylphosphane)rhodium(I), an coordination complex of rhodium with the formula RhCl(PPh₃)₃ (Ph = phenyl). It is a rouge-colored solid that is soluble in hydrocarbon solvents such as benzene, and more so in tetrahydrofuran or chlorinated solvents such as dichloromethane. The compound is widely used as a catalyst for hydrogenation of alkenes. It is named after chemist and Nobel Laureate, Sir Geoffrey Wilkinson, who first popularized its use.

Historically, Wilkinson's catalyst has been a paradigm in catalytic studies leading to several advances in the field such as the implementation of the some of the first heteronuclear magnetic resonance studies for its structural elucidation in solution (31P),parahydrogen-induced polarization spectroscopy to determine the nature of transient reactive species, or one of the first detailed kinetic investigation by Halpern to elucidate the mechanism. Furthermore, the catalytic and organometallic studies on Wilkinson's catalyst also played a significant role on the subsequent development of cationic Rh- and Ru-based asymmetric hydrogenation transfer catalysts which set the foundations for modern asymmetric catalysis.

According to single crystal X-ray diffraction the compound adopts a slightly distorted square planar structure.

In analyzing the bonding, it is a complex of Rh(I), a d⁸transition metal ion. From the perspective of the 18 electron rule, the four ligands each provides two electrons, for a total of 16-electrons. As such the compound is coordinatively unsaturated. Furthermore, in solution the complex undergoes fast dynamic exchange processes both intermolecular (one of the PPh3 is labile and is constantly exchanged between the inner coordination Rh sphere and the solution, although this fast equilibrium is really balanced towards the starting triphosphine complex, K = 10 Exp (-5) M) and intramolecular (fluxionality).

Wilkinson's catalyst is usually obtained by treating rhodium(III) chloride hydrate with an excess of triphenylphosphine in refluxing ethanol.Triphenylphosphine serves as a two-electron reducing agent that oxidizes itself from oxidation state (III) to (V). In the synthesis, three equivalents of triphenylphosphine become ligands in the product, while the fourth reduces rhodium(III) to rhodium(I).