Titanium complexes supported by bis(aryloxo) ligand: Structure and lactide polymerization activities

Titanium bis(aryloxo) complexes, [Ti2(μ-OEt)2(edbp)2(OEt)2] (1) and [Ti(edbp)(OiPr)2] (2) (edbp-H2 = 2,2′-ethylidenebis(4,6-di-tert-butylphenol) have been prepared and characterized. It was shown that compounds 1 and 2 were efficient initiators in a process of ring-opening polymerization (ROP) of cyclic esters. The catalytic behavior of complexes 1 and 2 in the polymerization of l- and rac-lactide (l-LA and rac-LA) was studied in toluene at 70 °C with a monomer to initiator ratio fixed at 100. The dimeric complex 1 initiated polymerization of lactide in 90% conversion within 2.5 h to afford polylactide (PLA) with Mn of 17,500 and PDI of 1.06. The parameters of PLA obtained with the monomeric complex 2 were similar (Mn = 18,000, PDI = 1.08). Microstructures of polymers obtained from rac-LA for both initiators were assigned as heterotactic.

Catalytic properties of titanium bis(aryloxo) complexes with 2,2′-ethylidenebis(4,6-di-tert-butylphenol) (edbp-H2) towards polymerization of cyclic esters are reported. Figure optionsDownload as PowerPoint slide