Magnesium, zinc, and calcium complexes based on tridentate nitrogen ligands: Syntheses, structures, and catalytic activities to the ring opening polymerization of rac-lactide

A series of magnesium, zinc, and calcium monoalkyl or monoamide complexes containing tridentate nitrogen ligands, CH3C(2,6-(iPr)2C6H3N)CHC(CH3) (NCH2CH2–D) (D = NMe2, N((CH2CH2)2CH2)), have been synthesized, and six of which were characterized by single-crystal X-ray diffraction. The X-ray diffraction results show that the metal complexes are all solvent-free monomers and the pendant arm D bonds to the metal ion. These metal complexes are highly active for the ring-opening polymerization of rac-lactide and give preference for heterotactic polylactide.