Ligand-to-Metal Charge Transfer (LMCT) Catalysis: Harnessing Simple Cerium Catalysts for Selective Functionalization of Inert C–H and C–C Bonds

Abstract

Chemists have long pursued harnessing light energy and photoexcitation processes for synthetic transformations. Ligand-to-metal charge transfer (LMCT) in high-valent metal complexes often triggers bond homolysis, generating oxidized ligand-centered radicals and reduced metal centers. While photoinduced oxidative activations can be enabled, this process, typically seen as photochemical decomposition, remains underexplored in catalytic applications. To mitigate decomposition during LMCT excitation, we developed a catalytic cycle integrating in situ coordination, LMCT, and ligand homolysis to activate ligated alcohols transiently into alkoxy radicals. This catalytic approach leverages Ce(IV) LMCT excitation and highly reactive alkoxy radical intermediates for selective functionalizations of C(sp³)–H and C(sp³)–C(sp³) bonds under mild conditions. In this Account, we discuss these advancements, highlighting the practical utility of cost-effective cerium salts as catalysts and their potential to develop innovative transformations, addressing long-standing synthetic challenges.