Titanium bis(aryloxo) complexes, [Ti-2(mu-OEt)(2)(edbp)(2)(OEt)(2)] (1) and [Ti(edbp)((OPr)-Pr-i)(2)] (2) (edbp-H-2=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 degrees 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 M-n of 17,500 and PDI of 1.06. The parameters of PLA obtained with the monomeric complex 2 were similar (M-n = 18,000, PDI = 1.08). Microstructures of polymers obtained from rac-LA for both initiators were assigned as heterotactic. (c) 2006 Elsevier B.V. All rights reserved.