Synthesis, structural, and ε-caprolactone polymerization studies of heteroleptic derivatives of aluminum(III)

<div><p>A series of metallo-organic complexes of Al(III), [(CH₃COCHCOCH₃)₂Al(OR)]₂ [where R = <i>o</i>-MeC₆H₄ (<b>1</b>), <i>m</i>-MeC₆H₄ (<b>2</b>), <i>p</i>-MeC₆H₄ (<b>3</b>), C₆H₅CH₂ (<b>4</b>), <i>o</i>-ClC₆H₄CH₂ (<b>5</b>), <i>m</i>-ClC₆H₄CH₂ (<b>6</b>), and <i>p</i>-ClC₆H₄CH₂ (<b>7</b>), were synthesized quantitatively by treating Al(OPrⁱ)₃ with CH₃COCH₂COCH₃ and the phenols (<i>o</i>-MeC₆H₄OH, <i>m</i>-MeC₆H₄OH, and <i>p</i>-MeC₆H₄OH) concerned as well as phenylmethanols (C₆H₅CH₂OH, <i>o</i>-ClC₆H₄CH₂OH, <i>m</i>-ClC₆H₄CH₂OH, and <i>p</i>-ClC₆H₄CH₂OH) in suitable stoichiometry using benzene as solvent. All these complexes were soluble in common organic solvents, having sharp melting points, and they were characterized by elemental analysis, IR, and NMR (¹H and ¹³C) spectral studies. Single-crystal XRD followed by ORTEP diagram of solvated complex (<b>1a</b>) revealed its dimeric nature and the existence of six-coordinate aluminum. The complexes were studied in ring-opening polymerization of ε-caprolactone. The molecular weight and polydispersity index values of polycaprolactone were obtained by gel permeation chromatography analysis.</p>