Synthesis of Ruthenium Hydride Complexes Containing beta-Aminophosphine Ligands Derived from Amino Acids and their use in the H2-Hydrogenation of Ketones and Imines

Abstract

The new complexes RuHCl(PPh2CH2CHRNH2)2 and RuHCl(PPh2CH2CHRNH2)(R- binap), R=H (Pgly), R=Me [(R)-Pala] were prepared by the substitution of the PPh3 ligands in RuHCl(PPh3)3 or RuHCl(PPh3)[(R)-binap] with beta-aminophosphines derived from amino acids. The complex trans-RuHCl(Pgly)[(R)-binap] has been characterized by X-ray crystallography. The complex trans-RuHCl[(S)-Ppro]2 where (S)-Ppro is derived from proline was also prepared and characterized by X-ray crystallography. These were used as catalyst precursors in the presence of a base (KOPr-i or KOBu-t) for the hydrogenation of various ketones and imines to the respective alcohols and amines with H2 gas (1–11 atm) at room temperature. Acetophenone was hydrogenated to (S)-1-phenylethanol in low ee (up to 40%) when catalyzed by the enantiomerically pure complexes. These complexes are especially active in the hydrogenation of sterically congested and electronically deactivated ketones and imines and are selective for the hydrogenation of CO bonds over CC bonds.