Use of electron-rich η6-arylphosphine complexes of molybdenum (0) as ligands in group 6 metal carbonyl complexes

Article abstract of DOI:10.1016/0022-328X(88)80159-1

The reactions of M(CO)6 M = Cr, Mo, W and Mo(η⁵-PhPPh2)(dppe(L), dppe = PPh2CH2CH2PPh2, L = CO, (L1CO), L = PMe3, (L1P) in benzene under photolysis lead to the following dimeric species M(CO)5(L2CO) and M(CO)5(L1P).Here the free phosphorus of the donor complex coordinates to M(CO)5 without metal-metal bond formation; a Cotton-Kraihanzel force constant analysis indicates that the ordering of e-donor ability is L2P > L1CO > PPh3.Similarly treating the new complex Mo(η⁶-PhPMePh)(dppe)(P(OMe)3), (L2P) with Mo(CO)6 under photolysis gives the dimer Mo(CO)5(L2P).Heating individual solutions of complexes L1CO, L1PMo(η⁶-PhPMePh)(dppe)(CO), (L2CO) and L2P in the presence of stoichiometric equivalents of M(CO)4(pip)2, M = Mo or W, pip = piperidine yields Mo(CO)4(pip)(L1CO), W(CO)4(pip)(L1CO), Mo(CO)4(pip)(L1P), W(CO)4(pip)(L2CO) and Mo(CO)4(pip)(L2P).The futher thermal reactions of W(CO)4(pip)(L1CO), W(CO)4(pip)(L2CO) and Mo(CO)4(pip)(L2P) with phophines or phosphite result in the substitution of the piperidine ligand and formation of W(CO)4(PMe2Ph)(L1CO), W(CO)4(PMe2Ph)(L2CO), Mo(CO)4(P(OMe)3)(L2P) and Mo(CO)4(PMe3)(L2P).Complexes are characterised by IR, 1H and 31P<1H> NMR spectroscopy.The cone angle for L1CO is determined to be 155 +/- 5 deg by comparing the cis/trans equilibrium ratio for its complex W(CO)4(PMe2Ph)(L2CO) to literature values for other W(CO)4(PMe2Ph)(L) complexes.The bimetallics containing L1CO or L2CO show an irreversible one electron oxidation wave associated with the metallophosphine ligand; those containing L1P or L2P show one reversible oxidation at a more positive potential to that of the free metallophosphine ligands and a second irreversible oxidation.