Synthesis and Catalytic Activity of Gallium Schiff‐base Complexes in the Ring‐Opening Homo‐ and Copolymerization of Cyclic Esters

Tetranuclear Ga(III) complexes L1–32Ga4(t‐Bu)8 1–3 are synthesized and characterized (elemental analysis, IR, 1H, 13C, DOSY NMR spectroscopy, XRD) and their activity in the ring‐opening polymerization (ROP) of lactide (LA) and ϵ‐caprolactone (ϵ‐CL) is reported. Complex 1 is the most active homopolymerization catalyst in the presence of benzyl alcohol (BnOH), yielding isotactic‐enriched polylactides (PLAs) with Pm (probably of mesomerism) values up to 0.72 by a first order kinetic with respect to the monomer concentration. The living character of the polymerization process was confirmed by a polymerization resumption experiment. Complexes 1–3 are also active catalysts in the copolymerization of LA and ϵ‐CL, and sequential addition of both monomers gave well‐defined block copolymers with narrow Đ values (distributions of molecular weight).