MIXED LIGAND COMPLEXES OF ZEROVALENT PLATINUM, PALLADIUM AND NICKEL CONTAINING A CHELATING OLEFINIC TERTIARY PHOSPHINE

Article abstract of DOI:10.1016/0022-328X(85)80353-3

The potentially chelating ligand (2-vinylphenyl)diphenylphosphine, o-CH2=CHC6H4PPh2(SP) reacts either with M(PPh3)2(C2H4) (M = Pt, Pd, Ni), or with M(1,5-COD)2 (M = Pt, Ni) and triphenylphosphine in a 1/2 mol ratio, to give mixed ligand complexes M(PPh3)2(SP).The platinum and palladium compounds can be isolated, whereas the nickel compound has been identified in solution by 1H and 31P NMR spectroscopy.All the complexes disproportionate readily, the palladium complex immediately on dissolution giving Pd(PPh3)(SP)2 and Pd(PPh3)3, the platinum and nickel complexes more slowly in solution to M(SP)2, M(PPh3)3 and PPh3.The platinum and nickel complexes contain bidentate SP and are probably tetrahedral, whereas Pd(PPh3)2(SP) in the solid state has a free vinyl group.In contrast to Ni(PPh3)2(SP), Pt(PPh3)2(SP) undergoes an intramolecular process in solution, probably one-ended dissociation of the vinyl group, which equivalences the triphenylphosphine ligands; this process can be frozen at -117 deg C.Both Ni(PPh3)2(SP) and Pt(PPh3)2(SP) undergo intermolecular ligand exchange, above -50 deg C in the case of platinum, above -30 deg C in the case of nickel; the triphenylphosphine ligands of Ni(PPh3)2(SP) exchange at different rates.The results can be correlated with the trend in equilibrium constants for the reaction M(PPh3)3+C2H4<*>M(PPh3)2(C2H4)+PPh3(M = Ni > Pt > Pd).