Homoleptic and heteroleptic ketodiiminate zinc complexes for the ROP of cyclic l-lactide

Homo- and heteroleptic ketodiiminate zinc complexes L Zn (1, L = [Me NC H NC(Me)CH] CO), L (ZnCp) (2, L = [Me NC H NC(Me)CH] CO, Cp = C H ) and L HZnCp* (3, Cp* = C Me ) were synthesized and characterized by H and C NMR and IR spectroscopy as well as by elemental analysis and single crystal X-ray diffraction (sc-XRD, 2, 3). The catalytical activity of heteroleptic complexes 2 and 3 were tested in the ring-opening polymerization (ROP) of l-lactide. Homobimetallic complex 2 showed the highest activity and selectivity for the synthesis of cyclic polylactide (cPLLA; TOF = 17 460 h ) at 100 °C in toluene solution, while linear polymers are formed with mononuclear complex 3.