Binuclear ketodiiminate magnesium complexes for the ROP of cyclic l-Lactide and ε-Caprolactone

Abstract

In contrast to well-established linear and branched polyesters, which find widespread biomedical and materials applications, cyclic polyesters have been less explored. We report on ketodiiminate magnesium complexes L12Mg3Cp+MgCp3- (1), L1(MgCp*)2 (2) and L2(MgCp)2 (3) (L1 = (Me2NC2H4NC(Me)CH)2CO, L2 = (Me2NC3H6NC(Me)CH)2CO), which were spectroscopically characterized (1H, 13C NMR, IR) as well as by elemental analysis and single crystal X-ray diffraction (sc-XRD). Complexes 1–3 were used in the ring-opening polymerization (ROP) of l-lactide (L-LA) and ε-caprolactone (ε-CL) under mild reaction conditions. Catalyst 2 showed excellent reactivity and selectivity for the synthesis of cyclic polylactide (cPLA; TOF = 17820 h−1) and cyclic polycaprolactone (cPCL; 712800 h−1).