Divergent [{ONNN}Mg–Cl] complexes in highly active and living lactide polymerization† †Electronic supplementary information (ESI) available: Experimental data regarding the synthesis and characterization of the ligands, complexes and PLA polymers. CCDC 1537631–1537632. For ESI and crystallographic data in CIF format or other electronic format see DOI: 10.1039/c7sc01514c Click here for additional data file. Click here for additional data file. Click here for additional data file.

Chloro-magnesium complexes of divergent tetradentate-monoanionic {ONNN}-type ligands which formed as either mononuclear or dinuclear complexes are reported. These complexes catalyze the ringopening polymerization of lactide with high activity and in a living manner, and enable the synthesis of well-defined stereo-diblock copolymers with Mn > 200 kDa, as well as stereo-n-block copolymers (n 1⁄4 tri, tetra) with high molecular weights by sequential monomer addition. Thermal and crystallographic characterizations revealed that even the very high molecular weight PLA copolymers crystallized in a stereocomplex phase, and that their degradation temperature was as high as 354 C.