Selective Aerobic Peroxidation of Styrene Catalyzed by a Cobalt tert-Butylperoxo Complex

Selective oxidation of styrene to desired products is essential and challenging. In this study, we elucidate a unique pathway for the selective oxidation of styrene to polystyrene peroxo species, catalyzed by the cobalt(III) tert-butylperoxo complex, [CoIII(OOtBu)(qpy)(NCCH3)]2+ (1), under ambient conditions. Mechanistic investigations, including the structural determination of the diperoxo complex, [CoIII(qpy)(OOCH(Ph)CH2OOtBu)(NCCH3)]2+ (2), by X-ray analysis and theoretical calculations reveal that the reaction begins with the nucleophilic addition of styrene to the CoIII–OOtBu moiety in 1. This step is followed by an addition with an O2 molecule, forming a diperoxyl radical (PhCOO•(H)CH2OOtBu), which subsequently rebounds with CoII(qpy) to yield 2. In the presence of excess O2, complex 2 can further react with additional styrene molecules, leading to the formation of cobalt(III) polystyrene peroxo species.