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.