Unexpected substitution reactions of bis(phosphine)platinum ethene complexes

Reaction of [Pt(C2H4)(PR3)2](R = Ph or C6H4Me-4) with moderately bulky phosphines at low temperatures did not give the expected tris- or tetrakis-phosphine complexes. Instead, mixed-phosphine complexes of the type [Pt(C2H4)(PR3)(PR′3)](R′= C6H11, C6H4OMe-4, C6H4OMe-2, C6H4Me-4 or CH2Ph) were formed. With less bulky phosphines, chelating diphosphines or phosphites, mixed tetrakis complexes, many of them prone to disproportionation, were formed. The complexes were characterised by 31P and 195Pt NMR spectroscopy in solution.