Nickel pre-catalysts bearing [(N)-imidoylamidine] ligands; influence of the presence of pyridine and pentafluorophenyl groups in ligand backbone on the reactivity in ethylene polymerizations

In this contribution the synthesis and polymerization activity of the nickel complexes [NiBr2{N′-(2,6-diisopropylphenyl)-N-[1-(2,6-diisopropylphenylimine)ethyl]-N-(2,3,4,5,6-pentafluorophenyl)acetamidine}] (2), [NiBr2{N′-(2,6-diisopropylphenyl)-N-[1-(2,6-diisopropylphenylimine)ethyl]-N-(2,3,4,5,6-pentafluorophenylimine)ethylacetamidine}] (2a) and [NiBr2{N-(2,6-diisopropylphenyl)-N-[1-(2,6-diisopropylphenylimine)]-N-(pyridin-4-yl)acetamidine}] (3) are reported. The variation of the phenyl substituents on the β amine was found to influence the polymerization activity of the complexes. The electron withdrawing/donating capacity of the substituted ring was found to be correlated with the polymerization activity, with the pentafluoro substituted ring increasing the polymerization activity and the pyridine ring decreasing the activity. The ligands and complexes were characterized using standard techniques and the polymer properties analyzed.

Graphical abstractThe synthesis and polymerization activity of nickel complexes bearing substituted imidoylamidine ligands are discussed with an emphasis on the effect of substitution on the polymerization activity and polymer properties.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► New compounds based on substituted imidoylamidine ligands were synthesized. ► The compounds were active for the polymerization of ethylene. ► Electron withdrawing groups on the ligand increased polymerization activity.