Substituted metal carbonyls. Part 21. [M(CO)5(dppf-P)] [M = Cr, Mo or W; Dppf = Fe(C5H4PPh2)2] as a metalloligand in heteropolymetallic aggregates of AuI, PdII and PtII. Crystal and molecular structures of [PtCl2{(μ-dppf)W(CO)5}2] and [Mo(CO)5(dppf-P)]

Abstract

The complexes [M(CO)5(dppf-P)] [M = Cr, Mo or W; dppf = 1,1′-bis(diphenylphosphino)ferrocene] behave like a monodentate phosphine ligand and displace the labile ligands from [AuCl(SMe2)], trans-[PdCl2(PhCN)2] and cis-[PtCl2(dmso)2] (dmso = dimethyl sulfoxide) to yield the corresponding dppf-bridged heteropolymetallic complexes of general formula [M′Clx{(μ-dppf)M(CO)5}y] (M′ = Au, x = y = 1; M′ = Pd or Pt, x = y = 2). Only the trans isomers have been isolated for PdII and PtII. Isomerisation of the M′ = Pt, M = Cr complex to the cis form, followed by partial elimination of [Cr2(CO)10(μ-dppf)] to form [PtCl2(dppf-P,P′)], after 3 d in CDCl3 was revealed by NMR spectroscopy. The solution characteristics of both geometrical isomers of the representative M′ = Pt, M = Cr complex have been established by two-dimensional NMR studies. UV-Photolytic degradation of the M′ = Pd or Pt, M complexes generally gave [M(CO)6], [M(CO)4(dppf-P,P′)], [M2(CO)10(μ-dppf)] and [M′Cl2(dppf)]. The molecular structures of trans-[PtCl2{(μ-dppf)W(CO)5}2] and [Mo(CO)5(dppf-P)] have been determined. The former represents a trimetallic pentanuclear aggregate and the latter a metalloligand with a pendant phosphine on a bimetallic complex. Cyclic voltammetry of all the complexes has been examined and generally reveals one chemically reversible phosphinoferrocene-based oxidation, followed by an irreversible oxidation of the complex.