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

Abstract

A family of aluminium complexes supported by dianionic amine bis(phenolate) ligands are described. Treatment of ligand precursors H₂O₂NN^Py or H₂O₂NN^Me [H₂O₂NN^Py = (2-C₅H₄N)CH₂N(CH₂-2-HO-3,5-C₆H₂(^tBu)₂)₂; H₂O₂NN^Me = Me₂NCH₂CH₂N(CH₂-2-HO-3,5-C₆H₂(^tBu)₂)₂] with 1.1 molar equivalent of AlMe₃ in toluene affords MeAl(O₂NN^Py) (1) and MeAl(O₂NN^Me) (2) as five-coordinate aluminium methyl complexes, which further react with one equivalent of benzyl alcohol affording (C₆H₅CH₂O)Al(O₂NN^Py) (3) and (C₆H₅CH₂O)Al(O₂NN^Me) (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.