Metal complexes of sulphur ligands. Part 14. Reaction of palladium(II) and platinum(II) dithioacid complexes with tertiary phosphinites, and the crystal and molecular structure of dimethylphosphinodithioato(diphenylphosphinito)(diphenylphosphinous acid)palladium(II)

Abstract

Prolonged reaction of [Pd(S₂PMe₂)₂] with excess PPh₂(OR)(R = Me or Et) in either methylene chloride or benzene gives the four-co-ordinate complex [Pd(S₂PMe₂)(PPh₂O){PPh₂(OH)}](1a) shown by spectroscopic evidence and X-ray structural analysis to contain the symmetrically hydrogen-bonded Ph₂POHOPPh₂ ligand. Crystals of (1a) are monoclinic, space group P2₁/m, with a= 6.86(1), b= 22.12(2), c= 9.69(1)Å, β= 111.5(2)°. The acidic hydrogen atom links two equivalent diphenylphosphinite groups with O ⋯ O 2.41 Å. Similar complexes [M(S–S)(PPh₂O){PPh₂(OH)}](M = Pd, S–S^–=[S₂PPh₂]^– or [S₂CNEt₂]^–; M = Pt, S–S^–=[S₂PMe₂]^– or [S₂CNEt₂]^–) have been prepared by reaction of [M(S–S)₂] with PPh₂(OR) or, for M = Pd, by reaction of [{PdCl(PPh₂O)[PPh₂(OH)]}₂] with the appropriate dithioacid anion (1 : 2 molar ratio). A careful study of the [Pt(S₂CNEt₂)₂]–PPh₂(OMe) reaction has resulted in the isolation of the intermediates [Pt(S₂CNEt₂){PPh₂(OMe)}₂]X (2; X =[BPh₄]^– or Cl^–) and [Pt(S₂CNEt₂)(PPh₂O){PPh₂(OMe)}](3) and a mechanism of formation of [Pt(S₂CNEt₂)(PPh₂O)(PPh₂(OH)}](1b) involving both nucleophilic attack on a P–OMe bond and subsequent hydrolysis of a P–OMe bond is proposed. In contrast, reaction of [M(S₂COPrⁱ)₂] with PPh₂(OEt) gives [M(S₂CO){PPh₂(OEt)}₂](M = Pd or Pt), although [Pd(S₂COPrⁱ)(PPh₂O){PPh₂(OH)}](PPh₂O)[PPh₂(OH)]}₂] and K[S₂COPrⁱ](1 : 2 molar ratio).