Synthesis, characterization and reactivity of tetranuclear ruthenium hydrido clusters containing chiral phosphine ligands

The chiral clusters [H4Ru4(CO)(12-n)(L)(n)] (n = 1, 2; L = NMDPP), 1,1-[H4Ru4(CO)(10)(L - L)] (L - L = DUPHOS, DIPAMP), 1,2-[H4Ru4(CO)(10)(DIOP)] and [{H4Ru4(CO)(10)(DIOP)}(2)] have been synthesized by derivatizing the parent carbonyl cluster [H4Ru4(CO)(12)] with the appropriate mono- or didentate chiral phosphine ligand. The phosphine-substituted clusters were found to be able to catalyze the ( asymmetric) hydrogenation of tiglic acid albeit with relatively low selectivity (enantiomeric excesses varying from 0 to 23%). It was found that the stability of the chiral ruthenium hydride clusters and the product distribution obtained in the catalytic reactions are dependent on the nature of the chiral phosphine. The crystal structures of [H4Ru4(CO)(12-n)(L)(n)] (n = 1, 2; L = NMDPP), 1,1-[H4Ru4(CO)(10)(L-L)] (L - L = DUPHOS, O-DUPHOS ( partially oxygenated ligand), DIPAMP), 1,2-[H4Ru4(CO)(10)(DIOP)] and [{H4Ru4(CO)(10)(DIOP)}(2)] are presented.