Synthesis and Structures of Ruthenium Carbonyl Complexes Bearing Pyridine-Alkoxide Ligands and Their Catalytic Activity in Alcohol Oxidation

Reaction of Ru(3)(CO)(12) with two equiv of 6-bromopyridine alcohols 6-bromopyCHROH [(R = C(6)H(5) (L1); R = 4-CH(3)C(6)H(4) (L2); R = 4-OMeC(6)H(4) (L3); R = 4-ClC(6)H(4) (L4); (R = 4-CF(3)C(6)H(4) (L5); R = 2-OMeC(6)H(4) (L6); R = 2-CF(3)C(6)H(4) (L7)] and 6-bromopyC(Me)(2)OH (L8) in refluxing xylene afforded novel trinuclear ruthenium complexes [6-bromopyCHRO](2)Ru(3)(CO)(8) (1a-1g) and [6-bromopyC(Me)(2)O](2)Ru(3)(CO)(8) (1h). These complexes were characterized by FT-IR and NMR spectroscopy as well as elemental analysis. The structures of all the complexes were further confirmed by X-ray crystallographic analysis. In the presence of tert-butyl hydroperoxide (TBHP) as the source of oxidant, complexes 1a-1h displayed high catalytic activities for oxidation of primary and secondary alcohols and most of oxidation reactions could be completed within 1 h at room temperature.