Synthesis and catalytic application of aluminium anilido-pyrazolate complexes

A series of aluminium complexes containing anilido-pyrazolate ligands is described. Reactions of four anilido-pyrazolate ligand precursors, HNPhPz, HNPh^TriMePz, HNPh^OMePz, or HNPh^SMePz [HNPhPz = ortho-C₆H₄(NH-phenyl)(1-pyrazole); HNPh^TriMePz = ortho-C₆H₄(NH-2,4,6-trimethylphenyl)(1-pyrazole); HNPh^OMePz = ortho-C₆H₄(NH-2-methoxyphenyl)(1-pyrazole); HNPh^SMePz = ortho-C₆H₄(NH-2-methylthiophenyl)(1-pyrazole)], with one molar equivalent of AlMe₃ in toluene give the aluminium dimethyl complexes, (NArPz)AlMe₂ [Ar = phenyl, (NPhPz)AlMe₂ (1); Ar = 2,4,6-trimethylphenyl, (NPh^TriMePz)AlMe₂ (2); Ar = 2-methoxyphenyl, (NPh^OMePz)AlMe₂ (3); Ar = 2-methylthiophenyl, (NPh^SMePz)AlMe₂ (4)], respectively. The molecular structures are reported for compounds 1 and 3. Their catalytic activities toward the ring opening polymerisation reaction of ε-caprolactone in the presence of BnOH are also under investigation.