Synthesis of Diverse Polycarbonates by Organocatalytic Copolymerization of CO and Epoxides: From High Pressure and Temperature to Ambient Conditions.

Organophosphazenes combined with triethylborane (TEB) were selected as binary organocatalyts for the copolymerization of CO and epoxides. Both the activity and selectivity were highly dependent on the nature of phosphazenes. 2,4,6-Tris[tri(1-pyrrolidinyl)-iminophosphorane]-1,3,5-triazine (C N -Py-P ) with a relatively low basicity (pK =26.5 in CD CN) and a bulky molecular size (φ=1.3 nm) exhibited an unprecedented efficiency (TON up to 12240) and selectivity (>99 % polymer selectivity and >99 % carbonate linkages) toward copolymerization of CO and cyclohexene oxide (CHO), and produced CO -based polycarbonates (CO -PCs) with high molar masses (M up to 275.5 kDa) at 1 MPa of CO and 80 °C. Surprisingly, this binary catalytic system achieved efficient CO /CHO copolymerization with TOF up to 95 h at 1 atm pressure and room temperature.