LMCT-driven electron relay unlocks alcohols as tunable reductants for nickel-catalyzed cross-electrophilic couplings.

Abstract

Photoinduced electron transfer is fundamental to both biological and synthetic processes; however, modulating back electron transfer (BET) remains a formidable challenge in achieving more efficient photocatalytic transformations. In this work, we present a strategy to regulate electron transfer dynamics via ligand-to-metal charge transfer (LMCT) catalysis, wherein the rapid β-scission of alkoxy radicals is harnessed to suppress BET, thereby facilitating the efficient transfer of reducing equivalents to drive transition metal-mediated reductive cross-coupling reactions. By strategically utilizing a diverse array of alcohol reductants, such as methanol and pinacol, we employ a cerium benzoate catalyst to enable reductive processes not through modulation of redox potentials, but by promoting synchronized electron transfer. Detailed mechanistic investigations reveal that the photoinduced electron relay process, governed by LMCT-BET, plays a pivotal role in effectively delivering reducing equivalents to catalytic sites, underscoring its significance in optimizing catalytic efficiency.