Dangling phosphine complexes: Phosphine exchange in pentacarbonyl tungsten complexes of bis(diphenylphosphinomethyl)phenylphosphine

Abstract

The reaction of [W(CO)5NH2Ph] with Ph2PCH2PPhCH2PPh2 under mild conditions and stoichiometric control leads to two sets of linkage isomers: [(OC)5W{κ1-PPh(CH2PPh2)2}] 6a and [(OC)5W(κ1- PPh2CH2PPhCH2PPh2)] 6b; [(OC)5W{μ-PPh2CH2PPh(CH2PPh2)}W(CO)5] 7a and [(OC)5W(μ-PPh2CH2PPhCH2PPh2)W(CO)5] 7b. Isomers 6a and 6b exist in solution in equilibrium with K = 4.35 for 6b/6a in CDCl3 at 55 °C. Under the same conditions, the rate of isomerization of 6a to 6b is 4.32 × 10−6 s−1. Isomerization is thought to proceed by an initial attack of a carbonyl group by a pendant phosphine followed by ring opening and a 1,2-phosphine shift. At higher temperatures, chelated complexes with four- and six-membered rings are formed: [(OC)5W{μ-κ1-, κ2-PPh2CH2 (PhPCH2PPh2)W(CO)4 }] 9a, [(OC)5W{μ-κ1-, κ2-PPh (CH2PPh2)2}W(CO)4 }] 9b, and [(OC)4W{κ2-(PPh2CH2)2PPh}] 10b. X-ray crystal structures of 6a, 7b, and 9b have been determined.