Highly efficient homogeneous and heterogenized ruthenium catalysts for transfer hydrogenation of carbonyl compounds

[Ru(acac)(2)(CH3CN)(2)] was synthesized from [Ru(acac)(3)] by refluxing it with zinc powder in ethanol-acetonitrile mixture. The prepared catalyst was characterized by FT-IR, H-1 and C-13 NMR techniques. The silica supported catalyst ('SiO2'-NH2-Ru-II) was prepared by stirring [Ru(acac)(2)(CH3CN)(2)] with 'SiO2'-NH2 in a 1 : 1 mixture of CH2Cl2-toluene for 3 days at room temperature. It was characterized by FT-IR, SEM, solid state NMR, ICP and BET surface area methods. The transfer hydrogenation reaction of carbonyl compounds was carried out separately using [Ru(acac)(2)(CH3CN)(2)] and 'SiO2'-NH2-Ru-II as catalysts. The reaction conditions were optimized with different solvents, bases, catalyst amounts and temperatures using acetophenone as a model system. The scope of the reaction was extended to various substituted aryl ketones including heteroaryl ketones.