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

Homo- and heteroleptic ketodiiminate zinc complexes L 1 2 Zn 2 (1, L 1 = [Me 2 NC 2 H 4 NC(Me)CH] 2 CO), L 2 (ZnCp) 2 (2, L 2 = [Me 2 NC 3 H 6 NC(Me)CH] 2 CO, Cp = C 5 H 5 ) and L 2 HZnCp* (3, Cp* = C 5 Me 5 ) were synthesized and characterized by 1 H and 13 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 -1 ) at 100 °C in toluene solution, while linear polymers are formed with mononuclear complex 3.