摘要
Aluminium complexes bearing sterically bulky benzotriazole-phenoxide ligands are synthesized and characterized structurally. The reaction of 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol ( CMe2Ph BTP-H) or 2-(2H-benzotriazol-2-yl)-4,6-di-tert-butylphenol ( t-Bu BTP-H) with AlMe 3 (1.2 molar equiv.) in toluene yields [( CMe2Ph BTP)AlMe 2 ] (1) or [( t-Bu BTP) AlMe 2 ] (2) as a four-coordinated monomeric aluminium complex. Compound 1 reacts further with CMe2Ph BTP-H in a stoichiometric proportion, affording penta-coordinated monomeric aluminium methyl complex [( CMe2Ph BTP) 2 AlMe] (3). Complex 3 is also obtained directly upon treatment of AlMe 3 with CMe2Ph BTP-H (two molar equiv.) in refluxing toluene in high yield. In the presence of H 2 O (half a molar equiv.), hydrolysis of 3 in a mixed solvent of THF and toluene at ambient temperature affords [{( CMe2Ph BTP) 2 Al} 2 (μ-O)] (4), in which the oxo ligand acts as a chelating group linearly bridging two aluminium centers. Air-stable alumoxane 4 is an efficient catalyst for the ring-opening polymerization of l-lactide (l-LA) in the presence of 9-anthracenemethanol (9-AnOH). Complex 4 catalyzes the polymerization of l-LA in a controlled manner, yielding PLLAs with the expected molecular weights and narrow polydispersity indices (PDIs). © The Royal Society of Chemistry 2011.