Novel Ti(IV) and Zr(IV) complexes and their application in the ring-opening polymerisation of cyclic esters

A series of group 4 amine tris(phenolate) complexes have been prepared and characterised by single crystal X-ray diffraction and multinuclear NMR spectroscopy. It was found that the ligands afforded monomeric titanium complexes and dimeric zirconium structures in the solid-state. The complexes have been tested for the ring-opening polymerisation of rac-lactide under both solution and melt conditions, which showed varying degrees of selectivity and control, with PDIs in the range of 1.09-2.07. The initiators were also tested for the production of copolymers containing rac-lactide and isosorbide. From NMR spectroscopic analysis and MALDI-TOF mass spectrometry the isosorbide is incorporated into the polymer. The complexes were also screened for the ring-opening polymerisation of 1,3-dioxan-2-one to produce a polycarbonate with good conversions (24-99%).