Abstract:
A new series of ruthenium(II) N-heterocyclic carbene complexes [RuL 1,2,3(p-cymene)Cl2] (3a-c) (where L is a N-heterocyclic carbene), have been synthesized via transmetalation. The new ruthenium(II)-NHC complexes were applied to transfer hydrogenation of acetophenone derivatives and aldehydes using 2-propanol as a hydrogen source and KOH as a co-catalyst. The results show that the corresponding alcohols could be obtained in good yield with high catalyst activity (up to 100%) under mild conditions. [RuL 1(p-cymene)Cl2] (3a) is much more active than the other complexes in transfer hydrogenation. Reactions, catalyzed by 3a-c, showed the highest reaction rates and yields of alcohol when the substrates bear more electron-withdrawing substituents. All new compounds were characterized by IR, elemental analysis, LC-MS (ESI), and NMR spectroscopy. © 2014 Taylor & Francis.