Synthesis of Dicarbonylruthenium(II) Complexes of Functionalized P,S‐Chelating Diphosphane Ligands and Their Catalytic Transfer Hydrogenation

The reaction of P,S‐chelating diphosphane ligands [bis(2‐diphenylphosphanylphenyl)ether monosulfide] ( a ) and [9,9‐dimethyl‐4,5‐bis(diphenylphosphanyl)xanthene monosulfide] ( b ) with [Ru(CO) 2 Cl 2 ] n in a 1:1 molar ratio affords two new ruthenium(II) complexes of the type [Ru(CO) 2 Cl 2 (P∩S)] ( 1a , 1 b ), where P∩S = a , b . The compounds are characterized by elemental analyses, mass spectrometry, thermal studies, and IR and NMR spectroscopy, together with single‐crystal X‐ray structure determination of bis(2‐diphenylphosphanylphenyl)ether (DPEphos), a , 1a , and 1b . The ruthenium atom in both 1a and 1b occupies the center of a slightly distorted octahedral environment formed by a P atom, an S atom, two Cl atoms, and two CO groups. The crystal structures of a and 1a highlights an interesting feature, in which the P(2)–P(1)–S(1) spatial angle (ca. 174.7°) in free ligand a is reduced to around 46° upon complexation, which indicates a very high flexibility of the angle. Complex 1a also exhibits some hemilabile behavior in solution because of its flexible ligand backbone, while ligand b in complex 1b remains rigid in solution. Complexes 1a and 1b are thermally stable up to about 300 °C and show high catalytic activities in the transfer hydrogenation of aldehydes and ketones to the corresponding alcohols. The highest conversion (about 99 %) with the corresponding TOF value of about 1000 h –1 was obtained for 1a in the case of benzaldehyde. The catalytic efficiency of 1a is found to be much higher than 1b , which might result from the hemilabile behavior of ligand a .