Synthesis and Reactivity of Bis(protic N-heterocyclic carbene)iridium(III) Complexes

Abstract

A nonfunctionalized bis(imidazole) ligand precursor has been directly metalated using IrCp*(OAc)2, leading to a mixture of bis(protic N-heterocyclic carbene) (bisPNHC) complexes (2a,b). Treatment of 2a,b with HCl gas in CH2Cl2 gave a bisPNHC complex (3a), which has been transformed into a hydride bisPNHC complex. Complex 3a underwent ligand and counterion exchange reactions to afford acetonitrile and ethylamine bisPNHC complexes (5 and 6). Furthermore, these bisPNHC complexes have been tested as catalysts in transfer hydrogenation reactions of ketones and unsaturated ketones.