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′Cl_x{(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 Pd^II and Pt^II. 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.