Oxidation-induced C–H bond activation in iridium pincer complexes

Abstract

Dehydrogenation reactions that produce molecular hydrogen are thermodynamically unfavourable. Desired is to couple them with a green driving force, such as oxidation with oxygen or an electric current. This, in turn, requires understanding of the catalyst's redox properties. Here we report oxidation of the iridium pincer complexes (POCOP)IrHCl (POCOP = 2,6-(^tBu₂PO)₂C₆H₃; 1a) and (PCP)IrHCl (PCP = 2,6-(^tBu₂PCH₂)₂C₆H₃; 1c) that induced intramolecular C–H activation, followed by the formation of complexes with a cyclometallated tert-butyl group. Based on an electrochemical study and DFT calculations, we propose a mechanism that involves H⁺ loss from hydrochlorides 1a and 1c to give a highly reactive (pincer)IrCl⁺ compound.