Aluminum complexes with benzoxazolphenolate ligands: Synthesis, characterization and catalytic properties for ring-opening polymerization of cyclic esters

A family of bidentate ligands, 1–3, were synthesized by the reactions of 5-diethylamino-2-nitrosophenol with bromomethylphenol derivatives. Treatment of the ligands 1–3 with one equivalent of AlMe3 gave the corresponding aluminum complexes 4–6, respectively. All the complexes were characterized by 1H and 13C NMR spectroscopy, along with elemental analysis. Single crystal X-ray diffraction analysis of complex 5 revealed that the Al complex has a distorted tetrahedral geometry around the metal center. All the aluminum complexes are efficient initiators for the ring-opening polymerization of ε-caprolactone and lactide in the presence of benzyl alcohol in a living fashion. The aluminum complexes produced PLA with a slight heterotactic bias.

Benzoxazolphenolate ligands and their aluminum complexes have been synthesized and fully characterized. All of the aluminum complexes were tested in the ring-opening polymerization of cyclic esters. The aluminum complexes produced PLA with a slight heterotactic bias.Figure optionsDownload as PowerPoint slide