Mono and bimetallic nickel bromide complexes bearing azolate-imine ligands: Synthesis, structural characterization and ethylene polymerization studies

The synthesis of N-(1-(3,5-dimethylpyrazol-1-yl)ethylidene)-2,6-diisopropylaniline (1) and N-(1-(indazol-2-yl)ethylidene)-2,6-diisopropylaniline (2) allowed access to new transition metal complexes. When reacted with dibromo(2,2′-dimethoxyethylether)nickel(II) the complexes [NiBr2{N-(1-(3,5-dimethylpyrazol-1-yl)ethylidene)-2,6-diisopropylaniline}] (3) and [Ni2Br2(μ-Br)2{N-(1-(indazol-1-yl)ethylidene)-2,6-diisopropylaniline}2] (4) are yielded, respectively. The addition of MAO generates catalytically active species for the homopolymerization of ethylene. The polymer products were low molecular weight (3–6 K) and a monomodal molecular weight distribution, consistent with the presence of a single active site. In addition, the catalyst was found to efficiently oligomerize higher olefins to high molecular weights with narrow PDIs.

Graphical abstractThe synthesis of two new organometallic species, compounds 3 and 4, allows for the investigation of MAO activation, and ligand conjugation effect on the ethylene catalytic reactivity. Compound 3 and 4 are active components for the homopolymerization of ethylene. The resulting low molecular weight polymers are described by a single molecular weight distribution, consistent with the presence of a single active metal site. The products also possess high concentrations of internal olefins which are characteristic of chain walking and β-hydrogen elimination.Figure optionsDownload full-size imageDownload as PowerPoint slide