Ring-Opening Copolymerization Using a Chromium Complex with a Readily Available Aminotriphenolate Ligand

A new chromium(III) complex (2) with a readily available aminotriphenolate ligand (LtBu,tBu) was developed as an efficient catalyst for alternating ring-opening copolymerization of cyclic epoxides and anhydrides to afford polyesters. The single-crystal structure of 2 exhibits an octahedral geometry despite the high steric profile of LtBu,tBu. After the reaction conditions were optimized, complex 2 in the presence of a cocatalyst produced perfectly alternating polyesters with high molecular weights (up to Mn = 44.2 kg/mol) and low dispersity at high conversion. In addition, various polyesters prepared using combinations of comonomers exhibited relatively high glass transition temper-atures.