Ruthenium(II) Complexes with Triphosphane Ligands Combining Planar, Phosphorus, and Carbon Chirality: Application to Asymmetric Reduction of Trifluoroacetophenone

Dichloro-, bis(acetonitrile)chloro-, and tris(acetonitrile)ruthenium( II) complexes with the triphosphane ligands (R)C- (S)Fe-(S)P-P3Chir and (R)C-(S)Fe-(R)P-P3Chir, combining planar, phosphorus, and carbon chirality, were prepared and structurally characterized in solution. The complexes were tested as catalyst precursors for the reduction of trifluoroacetophenone to (R)-α-(trifluoromethyl)benzyl alcohol by either hydrogenation or hydrogen transfer from iPrOH. The best conversion and enantioselectivity was obtained with the tris(acetonitrile) precursor [{(R)C-(S)Fe-(S)P-P3Chir}Ru- (CH3CN)3](PF6)2 in hydrogen-transfer conditions using a basic co-catalyst.