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. M_n = 8.7 kg mol⁻¹ and Đ = M_w/M_n = 1.14), followed by addition of CO₂ to generate polycarbonate chains and an increase in M_n to 17.6 kg mol⁻¹ with Đ = 1.13.