Isotactic rac ‐Lactide Polymerization with Copper Complexes: The Influence of Complex Nuclearity

Diiminopyrrolide copper alkoxide complexes, LCuOR (OR 1 = N , N ‐dimethylamino ethoxide, OR 2 =2‐pyridyl methoxide), are active for the polymerization of rac ‐lactide at ambient temperature in benzene to yield polymers with M w / M n =1.0–1.2. X‐ray diffraction studies showed bridged dinuclear complexes in the solid state for both complexes. While LCuOR 1 provided only atactic polylactide, LCuOR 2 produced partially isotactic polylactide ( P m =0.7). The difference in stereocontrol is attributed to a dinuclear active species for LCuOR 2 in contrast to a mononuclear species for LCuOR 1 .