Ruthenium(II) carbonyl complexes of P,P and P,O donor diphosphine ligands, Ph2P(CH2)(n)PPh2 and Ph2P(CH2)(n)P(O)Ph-2, n=2, 3 and their activities in catalytic transfer hydrogenation reactions

摘要

The polymeric precursor [RuCl2(CO)(2)](n) reacts with the ligands, PP (a, b) and PO (c, d), in 1:1 M ratio to generate six-coordinate complexes [RuCl2(CO)(2)(?(2)-PP)] (1a, 1b) and [RuCl2(CO)(2)(?(2)-PO)] (1c, 1d), where PP: Ph2P(CH2)(n)PPh2, n=2(a), 3(b); PO: Ph2P(CH2)(n)P(O)Ph-2, n=2(c), 3(d). The complexes are characterized by elemental analyses, mass spectrometry, thermal studies, IR, and NMR spectroscopy. 1a-1d are active in catalyzed transfer hydrogenation of acetophenone and its derivatives to corresponding alcohols with turnover frequency (TOF) of 75-290h(-1). The complexes exhibit higher yield of hydrogenation products than catalyzed by RuCl3 itself. Among 1a-1d, the Ru(II) complexes of bidentate phosphine (1a, 1b) show higher efficiency than their monoxide analogs (1c, 1d). However, the recycling experiments with the catalysts for hydrogenation of 4-nitroacetophenone exhibit a different trend in which the catalytic activities of 1a, 1b, and 1d decrease considerably, while 1c shows similar activity during the second run.