Organometallic Ruthenium Complexes: Application in the Olefination of Carbonyl Compounds

Ruthenium compounds of general formula Cp'RuX(PR2R')(2) (Cp' = eta(5)-C5H5 (Cp), eta(5)-C9H7 (Ind), eta(5)-C-5(CH3)(5) (Cp*); X = Cl, CF3C(O)O; R = C6H5 (Ph), C6H4(CH3) (m-tolyl); R' = C6H5, C6H11 (Cy), C6H4(CH3) (m-tolyl, o-tolyl)) are examined as catalysts for the aldehyde olefination starting from diazo compounds, phosphanes, and aldehydes. Cp*RuCl(PPh3)(2) is highly active for the olefination of several aldehydes, displaying a very high E-selectivity, as well as for ketone olefination (with benzoic acid as cocatalyst). The reaction's mechanism is substantiated by the isolation of a catalytic active reaction species, namely, a mixed carbene/phosphane ruthenium complex, Cp*RuCl(=CHCO2Et)(PPh3) (8). Spectroscopic studies reveal that the latter compound reacts with PPh3 to produce the phosphorus ylide Ph3P=CHCO2Et, which further reacts with the aldehyde to produce the olefin.