p-Toluenesulphinate ion as a terminal and as a bridging ligand in platinum(II) complexes

Abstract

The p-toluenesulphinatoplatinum(II) complexes, cis- and trans-[PtX(SO₂tol)(PR₃)₂], [Pt₂Cl₂(SO₂tol)₂(PR₃)₂], [Pt₂(SnCl₃)₂(SO₂tol)₂(PR₃)₂], [Pt₂Cl₃(SO₂tol)(PR₃)₂], and [Pt₂Cl(SnCl₃)₂(SO₂tol)(PR₃)₂](X = Cl or Br; PR₃= tertiary phosphine and tol =p-tolyl) have been prepared and their configurations assigned from ¹H n.m.r. and i.r. spectral data. The latter shows that the sulphinato-group is attached to platinum through the sulphur atom, and has a similar trans-influence to that of the tertiary phosphines. This indicates a strong inductive release in the S–Pt σ-bond in contrast to previous suggestions that in the complexes of other metals the sulphinato-group is a weak σ-donor and a strong π-acceptor. In boiling toluene trans-[PtCl(SO₂tol)(PMe₂Ph)₂] loses sulphur dioxide to form the complex trans-[PtCl(tol)(PMe₂Ph)₂]. In platinum(II) complexes the p-toluenesulphinate ion is even more weakly bridging than chloride ion. It takes up bridging positions, to give a solid product, only in association with SnCl₃^– in the complex [(PEt₃)(SnCl₃)Pt(SO₂tol)₂Pt(SnCl₃)(PEt₃)]. Its low affinity for the bridging position contrasts strongly with that of the diphenylphosphinate ion.