The Cobalt Porphyrin−Lewis Base System:  A Highly Selective Catalyst for Alternating Copolymerization of CO2 and Epoxide under Mild Conditions

The use of a cobalt porphyrin ((TPP)CoCl, 1) in combination with dimethylaminopyridine (DMAP) for the alternating copolymerization of CO2 and epoxide is described. The (TPP)CoCl (1)−DMAP system quantitatively produced the alternating copolymer from CO2 and cyclohexene oxide (CHO) under optimized conditions (50 atm, 80 °C). This calatyst system also worked satisfactorily for the alternating copolymerization of CO2 and a terminal epoxide, e.g., propylene oxide (PO), without formation of cyclic carbonate to give the polycarbonate. The alternating copolymerization of CO2 and epoxide (CHO, PO) was achieved under very mild conditions, such as at ambient temperature and under CO2 at 1 atm, by using the 1−DMAP catalyst system.