Five- or six-membered aluminum metallocyclic complexes containing N, N bidentate oxazolinyl-indolate chelate ring: Synthesis, structural, and catalytic studies

Treatment of two classes of oxazolinyl-indolate ligand precursors with an equivalent trimethylaluminum reagent afforded four corresponding aluminum dimethyl complexes. Intramolecular functional groups were employed to switch coordination behaviors, resulting in the formation of two classes of five- or six-membered aluminum metallocyclic complexes. The screening of the prepared aluminum complexes, mediated by 9-anthracenemethanol as the initiating reagent in the ring-opening polymerization of epsilon-caprolactone, showed significant activities at room temperature. The aluminum compound ligated by 2-(1H-indol-2-yl)-4,4-dimethyl-4,5-dihydrooxazole possessed a suitable chelated ring size, and its intrinsic electronic properties maintained higher activity.