Controlled hydrolysis of [Ti(O-2,4,6-Br<inf>3</inf>C<inf>6</inf>H <inf>2</inf>)<inf>2</inf>(O-iPr)<inf>2</inf>]<inf>2</inf>: Synthesis, structural characterization and studies on bulk polymerization of cyclic esters and lactide

Controlled hydrolysis of [Ti(O-2,4,6-Br3C6H 2)2(O-iPr)2]2 with water results in the formation of the Ti-oxo cluster Ti8O24C 66H58Br24 (1). This compound has a very interesting cage structure. The crystal structure consists of centrosymmetric neutral octamers containing two planar Ti4 layers, interlinked by four linear oxo-bridges. The four independent Ti atoms have three different coordination environments. The four unique Ti centers are rigidly coplanar, giving a unique configuration. The bridging oxygen atoms linking the two inversion-center related Ti atoms give a novel assemblage reminiscent of an inverse "cake-plate". Compound 1 is an active initiator for the polymerization of cyclic ester monomers and lactide resulting in polymers with moderate number average molecular weights (Mn) and close to narrow molecular weight distribution (MWD). © 2011 Elsevier B.V. All rights reserved.