Stereoregular Polycarbonate Synthesis: Alternating Copolymerization of CO2 with Aliphatic Terminal Epoxides Catalyzed by Multichiral Cobalt(III) Complexes

Completely stereoregular polycarbonate synthesis was achieved with the use of unsymmetric multichiral cobalt-based complexes bearing a derived chiral BINOL and an appended 1,5,7-triabicyclo[4.4.0] dec-5-ene as catalyst for the copolymerization of CO2 and aliphatic terminal epoxides at mild conditions. The (S,S,S)-Co(III) complex 1c with sterically hindered substituent group is more stereoregular catalyst for the copolymerization of CO2 and racemic propylene oxide to afford a perfectly regioregular poly(propylene carbonate) (PPC), with >99% head-to-tail linkages, >99% carbonate link-ages, and a K-rel of 24.4 for the enchainment of (R)-epoxide over (S)-epoxide. The isotactic PPC exhibits an enhanced glass transition temperature of 47 degrees C, which is 10-12 degrees C higher than that of the corresponding irregular polycarbonate. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 4894-4901, 2011