Synthesis and structural characterization of magnesium complexes bearing benzotriazole phenoxide ligands: Photoluminescent properties and catalytic studies for ring-opening polymerization of L-lactide

Magnesium catalysts incorporated by sterically bulky benzotriazole-phenoxide ligands ((BPT-)-B-CMe2Ph, t-BuBTP- and (BTP-)-B-TMCl) are synthesized and structurally characterized. The reaction of (MgBu2)-Bu-n with (BTP)-B-CMe2Ph-H (2.0 mol Eq) in THF produces penta-coordinated monomeric magnesium complex [((BTP)-B-CMe2Ph)(2)Mg(THF)] (1). However, six-coordinated bis-adduct magnesium complexes [(t-BuBTP)(2)Mg(THF)(2)] (2) and [((BTP)-B-TMCl)(2) Mg(THF)(2)] (3) result from treatments of (MgBu2)-Bu-n with t-BuBTP-H and (BTP)-B-TMCl-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. (C) 2012 Elsevier B.V. All rights reserved.