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

摘要

Magnesium catalysts incorporated by sterically bulky benzotriazole-phenoxide ligands (~(CMe2Ph)BTP~-, ~(t-Bu)BTP~-and ~(TMCI)BTP~-) are synthesized and structurally characterized. The reaction of Mg~nBu2 with ~(CMe2Ph)BTP-H (2.0 mol Eq) in THF produces penta-coordinated monomeric magnesium complex [(~(CMe2Ph)BTP)2Mg(THF)] (1). However, six-coordinated bis-adduct magnesium complexes [(~(t-Bu)BTP2Mg(THF)2] (2) and [(~(TMCI)BTP)2 Mg(THF)2] (3) result from treatments of Mg~(n)Bu2 with ~(t-Bu)BTP-H and ~(TMCI)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.