Quaternary Phosphonium Halides As Cocatalysts For Cyclohexene Oxide/CO2 Copolymerization

The quaternary organic phosphonium salts 1, 2 and 3 have been tested in conjunction with a chromium Salen complex in the alternating copolymerization of CO2 and cyclohexene oxide, CHO. Of these, triphenyl(4-pyridinylmethyl)phosphonium chloride hydrochloride 1 can compete with the more traditional PPNCl cocatalyst. Highly efficient formation, in terms of TON and selectivity over cyclic carbonate, of atactic polycarbonates characterized by narrow distribution and molecular weights comparable to those obtained with the reference salts was achieved. Remarkably, the use of FTIR/ATR spectroscopy on the pretreated catalytic system can reliably predict the success of the copolymerization before the actual introduction of the epoxide monomer.