Chloro(cyclopentadienyl)bis(triphenylphosphine)ruthenium

Chloro(cyclopentadienyl)bis(triphenylphosphine)ruthenium is the organoruthenium half-sandwich compound with formula RuCl(PPh3)2(C5H5). It as an air-stable orange crystalline solid that is used in a variety of organometallic synthetic and catalytic transformations. The compound has idealized Cs symmetry. It is soluble in chloroform, dichloromethane, and acetone.

Preparation
Chloro(cyclopentadienyl)bis(triphenylphosphine)ruthenium was first reported in 1969 when it was prepared by reacting dichlorotris(triphenylphosphine)ruthenium(II) with cyclopentadiene.


 * RuCl2(PPh3)3 + C5H6 →   RuCl(PPh3)3(C5H5) + HCl

It is prepared by heating a mixture of ruthenium(III) chloride, triphenylphosphine, and cyclopentadiene in ethanol.

Reactions
Chloro(cyclopentadienyl)bis(triphenylphosphine)ruthenium(II) undergoes a variety of reactions often by involving substitution of the chloride. With phenylacetylene it gives the phenyl vinylidene complex:
 * (C5H5)(PPh3)2RuCl + HC2Ph + NH4[PF6] →  [Ru(C:CHPh)(PPh3)2(C5H5)][PF6] + NH4Cl

Displacement of one PPh3 by carbon monoxide affords a chiral compound.


 * (C5H5)(PPh3)2RuCl +  CO   →   (C5H5)(PPh3)(CO)RuCl  +  PPh3

The compound can also be converted into the hydride:
 * (C5H5)(PPh3)2RuCl + NaOMe  →   (C5H5)(PPh3)2RuH + NaCl + CH2O

A related complex is tris(acetonitrile)cyclopentadienylruthenium hexafluorophosphate, which has three labile MeCN ligands.

Applications
Chloro(cyclopentadienyl)bis(triphenylphosphine)ruthenium(II) serves as a catalyst for a variety of specialized reactions. For example, in the presence of NH4PF6 it catalyzes the isomerisation of allylic alcohols to the corresponding saturated carbonyls.