The application of the potassium hydrido(ph0sphine)ruthenate complexes K+[(Ph3P)2Ph2-PC6H4RuH2]-.CloHs.(C2H~)z0 (1) and K2' [(Ph3P)3(PhzP)Ru2H4]2-.2C6H1403 (2) as catalysts for the homogeneous phasehydrogenation of a variety of unsaturated organic compounds is described. Ketones and aldehydes are catalytically hydrogenated with 1 and 2 typically at 85 OC and under 620 kPa of hydrogen, to yield the corresponding alcohols as well as minor aldol condensation byproducts. The hydrogenation of acrolein, depending on conditions, can give either propionaldehyde or mixtures of propionaldehyde and allyl alcohol. Carboxylic acid esters, which are activated by adjacent electron-withdrawing groups, e.&, CF3C02CH3, CF3C02CH2CF3, (-CO*CHJ2, can be hydrogenated, with 1 and 2, to yield, respectively, CF3CH20H and CH30H, CF3CH20H, and HOCHzCOZCH3. Methyl acetate diluted with toluene (1:lO (v/v)) in the presence of 2 is hydrogenated (at 90 OC, under 620 kPa of H,) giving methanol, ethanol, and ethyl acetate (formed by trans-esterification with the ethanol product). This represents the first instance of a homogeneous catalytic hydrogenation of a simple aliphatic ester. Nitriles are hydrogenated with 1 and 2 (at 90 OC, 620 kPa of H2) to give, selectively, primary amines. The rates and achievable conversions for these reactions are dependent upon the solvent medium used and on the nature of the cation associated with the hydridometalate catalysts. . In the previous paperlc we described the synthesis, composition, and basic chemical properties of the potassium hydrido(phosp h i n e ) r u t h e n a t e c o m p 1 e x e s , K+[(Ph3P),Ph2-I (1) (a) A'MH-t A -O T ( A+MH--A t M : o f H O T ( A+MH-A t M L O f H t H2 MH2 t dO-+H t -MHz t At . -+ A+ = cation; M = transition metal with associated ligands.