Ring opening polymerization and copolymerization for polyester and polycarbonate formation by a diamino-bis(phenolate) chromium(iii) catalyst

The diamino-bis(phenolate) chromium(III) complex, CrCl[L], 1 where [L] = dimethylaminoethylamino-N,N-bis(2-methylene-4,6-tert-butylphenolate) when pre-contacted with cocatalyst, bis(triphenylphosphine)iminium chloride, formed the bis(triphenylphosphine)iminium chromium(III) dichloride ate complex, 2. Complex 2 shows good activity for the ring-opening polymerization (ROP) of rac-lactide (rac-LA) and ε-caprolactone (ε-CL), ring-opening copolymerization (ROCOP) of cyclohexene oxide (CHO) and phthalic anhydride (PA), ROCOP of epoxides and CO2, and synthesis of terpolymers containing polylactide or polycaprolactone, polycarbonate, and polyester segments. For example, polyester-b-polycarbonates can be obtained through controlled ROCOP of PA and CHO, giving moderate molar mass polymers with narrow dispersity (e.g. Mn = 8.7 kg mol−1 and Đ = Mw/Mn = 1.14), followed by addition of CO2 to generate polycarbonate chains and an increase in Mn to 17.6 kg mol−1 with Đ = 1.13.