Selective Aerobic Peroxidation of Styrene Catalyzed by a Cobalt <i>tert</i>-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) <i>tert</i>-butylperoxo complex, [Co^III(OO ^<i>t</i> Bu)(qpy)(NCCH₃)]²⁺ (<b>1</b>), under ambient conditions. Mechanistic investigations, including the structural determination of the diperoxo complex, [Co^III(qpy)(OOCH(Ph)CH₂OO ^<i>t</i> Bu)(NCCH₃)]²⁺ (<b>2</b>), by X-ray analysis and theoretical calculations reveal that the reaction begins with the nucleophilic addition of styrene to the Co^III-OO ^<i>t</i> Bu moiety in <b>1</b>. This step is followed by an addition with an O₂ molecule, forming a diperoxyl radical (PhCOO^•(H)CH₂OO^tBu), which subsequently rebounds with Co^II(qpy) to yield <b>2</b>. In the presence of excess O₂, complex <b>2</b> can further react with additional styrene molecules, leading to the formation of cobalt(III) polystyrene peroxo species.