Iron-Catalyzed Aerobic Carbonylation of Methane via Ligand-to-Metal Charge Transfer Excitation

The integration of ligand-to-metal charge transfer (LMCT) catalytic paradigms with radical intermediates has transformed the selective functionalization of inert C-H bonds, facilitating the use of nonprecious metal catalysts in demanding transformations. Notably, aerobic C-H carbonylation of methane to acetic acid remains formidable due to the rapid oxidation of methyl radicals, producing undesired C1 oxygenates. We present an iron terpyridine catalyst utilizing LMCT to achieve exceptional C2/C1 selectivity through synergistic photoexcitation, methyl radical generation, and carbonylation. Mechanistic studies highlight the critical roles of Fe(II) and Fe-carbonyl complexes in bypassing methyl radical oxidation via a radical rebound-like pathway, unlocking unprecedented efficiency in methane aerobic carbonylation.