Formate-driven catalysis and mechanism of an iridium–copper complex for selective aerobic oxidation of aromatic olefins in water

Abstract

A hetero-dinuclear Ir^III–Cu^II complex with two adjacent sites was employed as a catalyst for the aerobic oxidation of aromatic olefins driven by formate in water. An Ir^III–H intermediate, generated through formate dehydrogenation, was revealed to activate terminal aromatic olefins to afford an Ir-alkyl species, and the process was promoted by a hydrophobic [Ir^III–H]-[substrate aromatic ring] interaction in water. The Ir-alkyl species subsequently reacted with dioxygen to yield corresponding methyl ketones and was promoted by the presence of the Cu^II moiety under acidic conditions. The Ir^III–Cu^II complex exhibited cooperative catalysis in the selective aerobic oxidation of olefins to corresponding methyl ketones, as evidenced by no reactivities observed from the corresponding mononuclear Ir^III and Cu^II complexes, as the individual components of the Ir^III–Cu^II complex. The reaction mechanism afforded by the Ir^III–Cu^II complex in the aerobic oxidation was disclosed by a combination of spectroscopic detection of reaction intermediates, kinetic analysis, and theoretical calculations.