Comparison of the Catalytic Activity of Mono‐ and Multinuclear Ga Complexes in the ROCOP of Epoxides and Cyclic Anhydrides

Tetranuclear Schiff-base complexes L21-3Ga4(t-Bu)(8) 1-3 are highly active and selective (>99 %) catalyst in the alternating ring-opening copolymerization (ROCOP) of epoxides and anhydrides, yielding polyesters with high molecular weights (M-n) and narrow dispersity (D). The thermal properties (T-g) of the resulting polyester range from 18 degrees C to 124 degrees C and increase with increasing steric bulk or rigidity along the polymer backbone. Comparative studies using structurally related complexes (LGa)-Ga-4(t-Bu)(2) 4, [(LGaR2)-Ga-5](2) (R=t-Bu 5, R=Me 6) and (LGa)-Ga-6(t-Bu)(2) 7 proved that the Ga2O2 core of catalyst 1 is the catalytically active species.