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.