Organoaluminum complexes containing a pyrrolylaldiminate pincer ligand

Organoaluminum chemistry employing the pyridine functionalized pyrrolylaldiminate ligand N-(2-pyridylmethyl)-5-tert-butyl-pyrrol-2-ylaldiminate ([PyIm-py]−) is described. The ligand precursor H[PyIm-py] was prepared in nearly quantitative yield from the condensation reaction of 5-tert-butylpyrrole-2-carbaldehyde with 2-aminomethylpyridine. Alkane elimination reactions of H[PyIm-py] with AlR3 (R = Me, Et, iBu) in toluene at −35 °C generated corresponding organoaluminum derivatives [PyIm-py]AlR2 in moderate to high yields. The 1H NMR studies of [PyIm-py]AlEt2 and [PyIm-py]AliBu2 revealed the diastereotopic nature of their α-hydrogen atoms. The solid state structures of [PyIm-py]AlMe2 and [PyIm-py]AlEt2 were determined by X-ray crystallography. Complex [PyIm-py]AlMe2 is an active catalyst in controlled ring-opening polymerization of ε-caprolactone.