Making the cut: Monopyrrolidine-based complexes for the ROP of lactide

A series of monopyrrolidine metal complexes have been prepared with the aim of elucidating structure-to-activity relationships for the ROP of lactide. Complexes of Li(I), Mg(II), Zn(II) and Zr(IV) were synthesised and fully characterised. Structural comparisons are made to the bipyrrolidine analogues. These monopyrrolidine complexes were found to be active towards the ROP of lactide under both solution and melt conditions. The zirconium complexes were found to have reduced and opposing stereocontrol compared to the bipyrrolidine analogues. The zinc and magnesium complexes demonstrated good activity and control under immortal polymerisation conditions.