PHOTOCHEMICAL HYDROFORMYLATION CATALYSIS USING RUTHENIUM COMPLEXES

Article abstract of DOI:10.1016/S0022-328X(00)99720-1

The catalytic hydroformylation of ethylene and propylene is promoted photochemically by the ruthenium(0) complexes Ru(CO)3(PPh3)2, Ru(CO)4(PPh3) and Ru3(CO)12 under UV irradiation at low pressure (ca. 500 torr H2/CO, 1/1) and ambient temperature.Subsequent hydrogenation of the aldehydes is also observed.The photolyses are performed in benzene solution and result in competitive hydroformylation and hydrogenation of the olefin to yield a product mixture of alkane, aldehydes and alcohols.The use of 13CO shows that the ligands in Ru(CO)3(PPh3)2 exchange readily under photolysis, and that under catalytic conditions Ru(CO)3(PPh3)2 is slowly converted to Ru(CO)4(PPh3) as the only observable Ru species in solution.Incorporation of 13C into the carbonyl position of propanal and the C(1) position of 1-propanol is observed directly by NMR spectroscopy.The tetracarbonyl complex exchanges CO readily at ambient temperature, and upon irradiation under H2 forms the unstable dihydride complex RuH2(CO)3(PPh3).A mechanism is proposed for the observed hydroformylation in which the photochemical step is thought to be generation of a coordinatively unsaturated Ru species.