Further studies on the homogeneous hydroformylation of alkenes by use of ruthenium complex catalysts

The use of several tertiary-phosphine–ruthenium complexes in the catalytic hydroformylation of alkenes is described. For mononuclear complexes the conversions into aldehyde, as well as the ratios of straight- to branched-chain aldehyde are essentially constant; the ruthenium complex recovered from the reactions is invariably tricarbonylbis(triphenylphosphine) ruthenium(0), Ru(CO)3(PPh3)2. The dependence of conversion and aldehyde ratios on catalyst concentration, temperature, partial and total pressures, nature of the substrate, and addition of excess of triphenylphosphine and other ligands in hydroformylation with Ru(CO)3(PPh3)2 is also described. Based on these results, a mechanism involving Ru(H)2(CO)2(PPh3) as the principal active catalytic species is suggested.