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

<div><p>A series of metallo-organic complexes of Al(III), [(CH<sub>3</sub>COCHCOCH<sub>3</sub>)<sub>2</sub>Al(OR)]<sub>2</sub> [where R = <i>o</i>-MeC<sub>6</sub>H<sub>4</sub> (<b>1</b>), <i>m</i>-MeC<sub>6</sub>H<sub>4</sub> (<b>2</b>), <i>p</i>-MeC<sub>6</sub>H<sub>4</sub> (<b>3</b>), C<sub>6</sub>H<sub>5</sub>CH<sub>2</sub> (<b>4</b>), <i>o</i>-ClC<sub>6</sub>H<sub>4</sub>CH<sub>2</sub> (<b>5</b>), <i>m</i>-ClC<sub>6</sub>H<sub>4</sub>CH<sub>2</sub> (<b>6</b>), and <i>p</i>-ClC<sub>6</sub>H<sub>4</sub>CH<sub>2</sub> (<b>7</b>), were synthesized quantitatively by treating Al(OPr<sup>i</sup>)<sub>3</sub> with CH<sub>3</sub>COCH<sub>2</sub>COCH<sub>3</sub> and the phenols (<i>o</i>-MeC<sub>6</sub>H<sub>4</sub>OH, <i>m</i>-MeC<sub>6</sub>H<sub>4</sub>OH, and <i>p</i>-MeC<sub>6</sub>H<sub>4</sub>OH) concerned as well as phenylmethanols (C<sub>6</sub>H<sub>5</sub>CH<sub>2</sub>OH, <i>o</i>-ClC<sub>6</sub>H<sub>4</sub>CH<sub>2</sub>OH, <i>m</i>-ClC<sub>6</sub>H<sub>4</sub>CH<sub>2</sub>OH, and <i>p</i>-ClC<sub>6</sub>H<sub>4</sub>CH<sub>2</sub>OH) 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 (<sup>1</sup>H and <sup>13</sup>C) 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></div>