Ru-η6-benzene-phosphine complex-catalyzed transfer hydrogenation of ketones

Three Ru-eta(6)-benzene-phosphine complexes bearing tri-(p-methoxyphenyl)phosphine, triphenylphosphine and tri-(p-trifluoromethylphenyl)phosphine were synthesized and characterized by P-31{H-1} NMR, H-1 NMR, C-13{H-1} NMR and elemental analyses. Complex 1 was further identified by X-ray crystallography. These complexes exhibit good to excellent activities for the transfer hydrogenation of ketones in refluxing 2-propanol, and the highest turnover frequency (TOF) is up to 5940 h(-1). The effect of electronic factors of these complexes on the transfer hydrogenation of ketones reveals that the catalytic activity is promoted by electron-donating phosphine and the catalyst stability is improved by electron-withdrawing phosphine. Copyright (C) 2011 John Wiley & Sons, Ltd.