Novel ruthenium(II) complexes with chelating 1,2,4-triazole NHC ligands and their catalytic activity in the transfer hydrogenation of ketones

A series of novel ruthenium(II) complexes with nitron-type N-heterocyclic carbene ligands containing chelating (N-arylcarbamoyl)methyl or carboxymethyl groups have been synthesized. Their evaluation as precatalysts in the hydrogenation of ketones has revealed that the complex containing three N-mesityl groups (one on the carbamoyl- methyl moiety and two on the triazole moiety) is the most efficient one.