Aluminum Complexes Containing the C-O-Al-O-C Framework as Efficient Initiators for Ring-Opening Polymerization of epsilon-Caprolactone

Three aluminum complexes, LAl(OCH2C6H4-2-NH2)(2) (2), LAl(9-OC13H9)(2) (3), and LAl(OC6H10-4-NH2)(2) (4), were synthesized in good yield by reacting one equivalent of LAlH2 (1) (L = HC(CMeNAr)(2), Ar = 2,6-iPr(2)C(6)H(3)) with two equivalents of 2-aminobenzyl alcohol, 9-hydroxyfluorene, and trans-4-aminocyclohexanol, respectively. All complexes (2, 3, and 4) contain the COAlOC framework. These complexes have been characterized by IR, H-1 and C-13 NMR, elemental analyses, and single-crystal X-ray structural analysis. Furthermore, the excellent catalytic activities of 2, 3, and 4 for ring-opening polymerization of e-caprolactone in the presence of isopropyl alcohol were investigated.