Metal complexes of sulphur ligands. Part III. Reaction of platinum(II)NN-dialkyldithiocarbamates, O-ethyl dithiocarbonate (xanthate), and OO′-diethyl dithiophosphate with tertiary phosphines

Abstract

Evidence is presented to show that the reaction of all M(S–S)₂ compounds [M = Pt, Pd; (S–S)^–=^–S₂CNR₂(R = Me, Et), ^–S₂COR (R = Et, PhCH₂), ^–S₂P(OEt)₂, and ^–S₂PR₂(R = Me, Et, Ph)] with tertiary phosphines occurs by stepwise cleavage of metal–sulphur bonds to generate four-co-ordinate compounds of formulae [M(S–S)₂PR′₃] and [M(S–S)(PR′₃)₂](S–S) with unidentate/bidentate (III) and ionic/bidentate (IV) co-ordination respectively. All the ionic compounds readily revert to the [M(S–S)₂PR′₃] complexes in the presence of non-polar solvents via nucleophilic attack by (S–S)^– on the metal. In addition, for (S–S)^–=^–S₂COR, ^–S₂P(OEt)₂, nucleophilic attack can also occur on a co-ordinated alkoxy group to give the novel compounds [(R′₃P)₂MS₂CO](I) and [(R′₃P)₂MS₂P(O)OEt](II) respectively.

For [M(S–S)(PR′₃)₂](S–S) compounds containing ^–S₂CNR₂, the presence of excess PR′₃ catalyses the reaction between dithiocarbamate ion and dichloromethane, giving CH₂(S₂CNR₂)₂ and [M(S₂CNR₂)(PR′₃)₂]Cl, H₂O. These conclusions are based on extensive physico-chemical studies and, in particular, the use of variable temperature ¹H n.m.r. spectroscopy.