Aluminum alkyl complexes containing bidentate, mono- or di-anionic pyrrolyl ligands: Intramolecular elimination of methane and 1-hexene polymerization

A series of aluminum alkyl complexes were synthesized and their catalytic polymerization reactivity toward 1-hexene was studied. Aluminum complexes, [C₄H₃N(CH₂NHMe)-2]AlR₂ (1a, R = Me; 1b, R = Et), containing substituted pyrrolyl ligand can be prepared by reacting AlR₃ with one equiv of C₄H₃NH(CH ₂NHMe)-2 in diethyl ether at room temperature. Dimeric aluminum complexes, {[C₄H₃N(CH₂NMe)-2]AlR}₂ (2a, R = Me; 2b, R = Et), can be obtained via metathesis by heating AlR ₃ and with one equiv of [C₄H₃NH(CH ₂NHMe)-2] in toluene for 24 h or via intramolecular methane elimination by heating 1 and 2 at 90 °C in toluene. Complexes 1a, 1b, 2a, and 2b have been characterized by NMR spectroscopy and by X-ray crystallography. Complexes 1a and 2a have shown moderate reactivity for 1-hexene polymerization in the presence of MAO.