Unusual Enhancement of Ethylene Polymerization Activity of Benzyl Zirconium Complexes by Benzylation of the Imino Moiety of 2-(N-Aryliminomethyl)pyrrolyl Ligand

Reaction of Zr(CH2Ph)4 (1) with one equiv. of 2-(N-aryliminomethyl)pyrrolyl ligands (2a–e) in toluene afforded two types of products, depending upon the bulkiness of the aryl moiety. The reactions of 1 with two equiv. of the most sterically bulky 2e afforded complex 5e, whose pseudo octahedral geometry around the zirconium atom and totally dissymmetric cis-dibenzyl structure were elucidated. The high catalytic activity for ethylene polymerization was obtained by using complexes 3a and 3b.