N-heterocyclic carbene (NHC) based ruthenium complexes were studied as transfer hydrogenation catalysts of carbonyl compounds. The influence of bis versus mono NHC ligands and the role of pendant ether groups were investigated. Ruthenium complexes containing a monodentate NHC ligand with a tethered diethyl ether N-substituent, ImEt,CH2CH2OEtRu(Cl)2(arene),  (arene = benzene (1  ), p-cymene (2  ), hexamethylbenzene (3  )) and a ruthenium complex with a bis-NHC ligand, [RuCl(methylenebis(N-ethylIm)2)(p-cymene)]PF6  (4  ) were synthesized (Im = Imadazole). X- ray crystal structures of complexes 1  , 2  , and 4  were obtained. These complexes are active transfer hydrogenation catalysts for the reduction of acetophenone in basic isopropanol with complex 1  being the most active. It was found that electron deficient ketones were the most easily reduced. Synthesis of ruthenium complexes containing chiral NHC ligands as catalysts for enantioselective transfer hydrogenation is in progress. Organometallic catalysts for water oxidation are also being investigated.

Synthesis of ruthenium N-heterocyclic carbene (NHC) complexes as catalysts for transfer hydrogenation of carbonyl compounds

243rd National Meeting (2012)

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