(Tetramethyltetraazaannulene)chromium Chloride:A Highly Active Catalyst for the Alternating Copolymerization of Epoxides and Carbon Dioxide

摘要

A tetramethyltetraazaannulene complex incorporating a chromium-(III) metal center has been shown to be highly active toward the copolymerization of cyclohexene oxide and carbon dioxide to afford poly(cyclohexene carbonate) in the presence of [PPN]N3 [PPN+ = bis(triphenylphosphoranylidene)ammonium] as a cocatalyst.An asymptotical rate increase was observed,leveling at 2 equiv of cocatalyst with a maximum turnover frequency of 1300 h~(-1) at 80 °C.A benefit of this new catalyst system over that of the previously studied less-active (salen)CrX system is that the (tmtaa)-CrCI catalyst has a much lower propensity toward the formation of a cyclic carbonate byproduct throughout the copolymerization reaction.