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

Abstract

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, [Co^III(OO ^t Bu)(qpy)(NCCH₃)]²⁺ (1), under ambient conditions. Mechanistic investigations, including the structural determination of the diperoxo complex, [Co^III(qpy)(OOCH(Ph)CH₂OO ^t Bu)(NCCH₃)]²⁺ (2), by X-ray analysis and theoretical calculations reveal that the reaction begins with the nucleophilic addition of styrene to the Co^III-OO ^t Bu moiety in 1. 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 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.