Electrochemical C-H bond activation: Via cationic iridium hydride pincer complexes

Abstract

A C-H bond activation strategy based on electrochemical activation of a metal hydride is introduced. Electrochemical oxidation of (tBu4PCP)IrH4 (tBu4PCP is [1,3-(tBu2PCH2)-C6H3]-) in the presence of pyridine derivatives generates cationic Ir hydride complexes of the type [(tBu4PCP)IrH(L)]+ (where L = pyridine, 2,6-lutidine, or 2-phenylpyridine). Facile deprotonation of [(tBu4PCP)IrH(2,6-lutidine)]+ with the phosphazene base tert-butylimino-tris(pyrrolidino)phosphorane, tBuP1(pyrr), results in selective C-H activation of 1,2-difluorobenzene (1,2-DFB) solvent to generate (tBu4PCP)Ir(H)(2,3-C6F2H3). The overall electrochemical C-H activation reaction proceeds at room temperature without need for chemical activation by a sacrificial alkene hydrogen acceptor. This rare example of undirected electrochemical C-H activation holds promise for the development of future catalytic processes.