Aluminium metal complexes supported by amine bis-phenolate ligands as catalysts for ring-opening polymerization of ε-caprolactone

A family of aluminium complexes supported by dianionic amine bis(phenolate) ligands are described. Treatment of ligand precursors H2O2NNPy or H2O2NNMe [H2O2NNPy = (2-C5H4N)CH2N(CH2-2-HO-3,5-C6H2(tBu)2)2; H2O2NNMe = Me2NCH2CH2N(CH2-2-HO-3,5-C6H2(tBu)2)2] with 1.1 molar equivalent of AlMe3 in toluene affords MeAl(O2NNPy) (1) and MeAl(O2NNMe) (2) as five-coordinate aluminium methyl complexes, which further react with one equivalent of benzyl alcohol affording (C6H5CH2O)Al(O2NNPy) (3) and (C6H5CH2O)Al(O2NNMe) (4) as five-coordinate aluminium benzyloxy complexes. The molecular structures are reported for compounds 1 and 4. Compounds 3 and 4 show excellent catalytic activity toward the ring-opening polymerization of ε-caprolactone.