Al(iii)–homopiperazine complexes and their exploitation for the production of polyesters

Abstract

In this paper we report the synthesis and characterisation of a series of Al(III)–homopiperazine complexes. The ortho substituent has been varied from H, Me, tBu to investigate the effect this has on the solid-state structures and on the catalytic activity. Aluminium–methyl complexes involving ligands 1H₂, 3H₂ and 5H₂ have been characterised in the solid-state and the aluminium centres are in pseudo trigonal bipyramidal geometries. The aluminium–methyl complexes were further reacted with benzyl alcohol to generate alkoxide complexes, which have been fully characterised by multinuclear NMR spectroscopy and elemental analysis. The alkoxide complexes were tested in the ring opening polymerisation of rac-lactide, δ-valerolactone and ε-caprolactone. Furthermore, triblock polyesters were also prepared with these initiators.