(Salen)Cr~IIIX Catalysts for the Copolymerization of Carbon Dioxide and Epoxides:Role of the Initiator and Cocatalyst

摘要

The copolymerization of C0_2 and cyclohexene or propylene oxide has been examined employing(salen)Cr~IIINu complexe(Nu=Cl or N_3)as catalysts.The addition of various cocatalysts,including phosphines and PPN~+ or Bu_4N~+Cl~- salts serves to greatly enhance the rate of copolymer production.In these instances,the mech-anism of the initiation step appears to be unimolecular in catalyst concentration,unlike the bimolecular process cocatalyzed by N-methylimidazole.The copolymers were produced with>95% carbonate linkages with TOFs in the range 39-494 mol epoxide consumed/mol Oh.In the presence of phosphine cocatalysts,no cyclic carbonate was produced as a byproduct.