The chemistry and catalytic properties of ruthenium and osmium compounds. Part 7. Regioselective hydrogenation of cinnamaldehyde (3-phenyl-2-propenal) catalyzed by Ru and Os triphenylphosphine complexes in homogeneous solution and by meta-sulfonatophenyl-diphenyldiphosphine (TPPMS) and tris-meta-sulfonato-phenylphosphine (TPPTS) derivatives in an aqueous biphasic system

Abstract NMR data for two Ru-TPPMS complexes previously described as unsaturated monomeric species have led to their reformulation as the chloro-bridged dimers [RuCl(TPPMS) 2 (μ-Cl)] 2 (1) and [RuH(TPPMS) 2 (μ-Cl)] 2 (2) ; three new water-soluble complexes OsH 4 (TPPMS) 3 (3) , OsHCl(CO)(TPPMS) 2 (4) , and [OsCl(TPPMS) 2 (μ-Cl)] 2 (5) have been synthesized and characterized. Complexes 1–5 , as well as mixtures of Ru and Os salts with TPPMS and TPPTS catalyze the hydrogenation of cinnamaldehyde under mild reaction conditions in aqueous biphasic systems; the activities and selectivities of these catalysts have been compared with those of homogeneous PPh 3 analogues. In general there is a clear advantage in using the aqueous biphasic mixtures over their analogous homogeneous solutions, since catalyst recovery and recycling are easy and because the regioselectivity towards the production of the α, β-unsaturated alcohol is considerably enhanced on going from the homogeneous PPh 3 to the biphasic TPPMS and TPPTS systems, particularly in the case of Ru.