Transition-metal complexes containing phosphorus ligands. Part VIII. Sulphur dioxide derivatives of rhodium, iridium, palladium, and platinum

Abstract

The palladium and platinum complexes, M(PPh₃)₄, react with sulphur dioxide under anaerobic conditions to afford dark purple air-sensitive derivatives, M(SO₂)(PPh₃)₃; these products undergo aerobic oxidation to form sulphatocomplexes, M(SO₄)(PPh₃)₂,H₂O. The rhodium and iridium hydrides, M′H (CO)(PPh₃)₃, on treatment with sulphur dioxide yield the first sulphur dioxide–hydride derivatives, ‘M′H(SO₂)(CO)(PPh₃)₂’. The anomalous spectroscopic features of these last-named complexes are tentatively interpreted in terms of a tautomeric equilibrium involving hydride migration between the central metal atom and the co-ordinated sulphur dioxide ligand.