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, HNPhTriMePz, HNPhOMePz, or HNPhSMePz [HNPhPz = ortho-C6H4(NH-phenyl)(1-pyrazole); HNPhTriMePz = ortho-C6H4(NH-2,4,6-trimethylphenyl)(1-pyrazole); HNPhOMePz = ortho-C6H4(NH-2-methoxyphenyl)(1-pyrazole); HNPhSMePz = 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, (NPhTriMePz)AlMe2 (2); Ar = 2-methoxyphenyl, (NPhOMePz)AlMe2 (3); Ar = 2-methylthiophenyl, (NPhSMePz)AlMe2 (4)], respectively. The molecular structures are reported for compounds 1 and 3. Their catalytic activities toward the ring opening polymerisation reaction of e-caprolactone in the presence of BnOH are also under investigation.