Ferrocene based chiral binuclear ?6-benzene-Ru(II)-phosphinite complexes: Synthesis, characterization and catalytic activity in asymmetric reduction of ketones

Abstract

In the present study, a series of chiral C-2-symmetric ferrocenyl based binuclear (6)-benzene-Ru(II) complexes bearing diphenylphosphinite and diisopropylphosphinite moieties have been synthesised. The new binuclear (6)-benzene-Ru(II)-phosphinite complexes were characterised based on nuclear magnetic resonance (H-1, C-13, P-31-NMR), FT-IR spectroscopy and elemental analysis. Then, these complexes have been screened as catalytic precursors in the transfer hydrogenation of acetophenone with 2-propanol as both the hydrogen source and solvent in the presence of KOH. The corresponding optically active secondary alcohols were obtained in excellent conversion rates between 96 and 99% and moderate to good enantioselectivities (up to 78% ee). The complex 5 was the most efficient catalyst among the four new complexes investigated herein.