摘要
Magnesium catalysts incorporated by sterically bulky benzotriazole- phenoxide ligands ( CMe2Ph BTP - , t-Bu BTP - and TMCl BTP - ) are synthesized and structurally characterized. The reaction of Mg n Bu 2 with CMe2Ph BTP-H (2.0 mol Eq) in THF produces penta-coordinated monomeric magnesium complex [( CMe2Ph BTP) 2 Mg(THF)] (1). However, six-coordinated bis-adduct magnesium complexes [( t-Bu BTP) 2 Mg(THF) 2 ] (2) and [( TMCl BTP) 2 Mg(THF) 2 ] (3) result from treatments of Mg n Bu 2 with t-Bu BTP-H and TMCl BTP-H in THF under the same stoichiometric proportion, in which each Mg center is coordinated by two THF molecules. Optical properties and catalytic studies for l-lactide polymerizations of magnesium complexes 1-3 are investigated. Magnesium complex 3 catalyzes the ring-opening polymerization effectively not only in a controlled fashion but also in an immortal manner, giving polymers with the expected molecular weights and narrow molecular weight distributions. © 2012 Elsevier B.V. All rights reserved.