Synthesis and structure of some binuclear carbonyl complexes of platinum(I)

Abstract

The complex [Pt₂Cl₂(µ-CO)(µ-dppm)₂][2; dppm = bis(diphenylphosphino)methane] has been prepared by the reversible reaction of [Pt₂Cl₂(µ-dppm)₂] with carbon monoxide and also by the reaction of [NPr₄]₂[Pt₂Cl₄(CO)₂] with dppm. In polar solvents (2) isomerises to give the ion [Pt₂Cl(CO)(µ-dppm)₂]⁺, isolated as the [PF₆]^– salt (3b). The i.r., Raman, and ¹H and ³¹P n.m.r. spectra of these complexes are discussed. On the basis of its exceptionally low i.r. frequency, it is proposed that the carbonyl group in complex (2) is acting as an unsymmetrical four-electron bridging ligand. An arsine complex [Pt₂Cl₂(µ-CO)(µ-dpam)₂][dpam = bis(diphenylarsino) methane] analogous to (2) has been prepared from [Pt₂Cl₄(CO)₂]^2–.