Immobilization of ruthenium in organic-inorganic hybrid copolymers: A reusable heterogeneous catalyst for oxidation of alcohols with molecular oxygen

A novel organ ic-inorganic hybrid ruthenium (HB Ru) catalyst for the oxidation of alcohols with molecular oxygen has been developed. The catalyst was prepared from a polystyrene-based copolymer, which includes a trimethoxysilyl functionality, and dichlorotris(triphenylphosphine)ruthenium, [RuCl2(PPh3)(3)], as the metal source. A sol-gel process was employed for heterogenization of the catalyst. The choice of both ruthenium species and trialkoxysilyl-bearing monomers was found to be important for high catalytic activity. In the presence of HB Ru corresponding to 5 mol % loading of ruthenium, the alcohols were oxidized with molecular oxygen or air at atmospheric pressure without any additives to afford the corresponding aldehydes or ketones in good to excellent yields. The catalyst could be recovered and reused at least five times without loss of activity.