Active Intermediates of Ethylene Polymerization over 2,6-Bis(imino)pyridyl Iron Complex Activated with Aluminum Trialkyls and Methylaluminoxane

Abstract

The intermediates of olefin polymerization over homogeneous catalysts based on bis(imino)pyridine iron(II) chloride (LFeCl2, L = 2,6-bis[(1-2,6-dimethylphenylimino)ethyl]pyridine) with different activators (trimethyl-, triisobutyl-, trioctylaluminum and MAO) have been studied by 1H and 2H NMR. In conditions approaching real polymerization, neutral species of the type [LFe(II)Cl(μ-R)2AlR2] or [LFe(II)R(μ-R)2AlR2] dominate in the reaction solution in LFeCl2+AlR3 systems, whereas in LFeCl2/MAO systems, ion pairs [LFe(II)(μ-Me)(μ-Cl)AlMe2]+[Me-MAO]- (at Al/Fe < 200) and [LFe(II)(μ-Me)2AlMe2]+[Me-MAO]- (at Al/Fe > 500) are the predominant species.