Ethylene polymerization by 2,3-diiminobutylnickel bromide pre-catalysts bearing remote benzhydryl substituents

•Newly synthesized remote benzhydryl-substituted 2,3-diiminobutane compounds.•2,3-Diiminobutylnickel bromide complexes and its molecular structure.•Highly active polymerization of ethylene.•Catalytic influences of the nickel complexes by their ligands' substituents.•Higher molecular weights and fewer branches of obtained polyethylenes.

A series of remote benzhydryl-substituted 2,3-diiminobutane derivatives (L1–L5) was synthesized and used to react with (DME)NiBr2 to form the corresponding 2,3-diiminobutylnickel bromide complexes (Ni1–Ni5). All compounds were characterized by FT-IR spectroscopy and elemental analysis as well as additional NMR measurements for organic compounds and single crystal X-ray diffraction study for a representative complex Ni1. Upon activation with cocatalyst Et2AlCl, all nickel complexes exhibited high activity toward ethylene polymerization, producing polyethylenes with high molecular weights and narrow polydispersity. The existence of remote para-benzhydryl substituent probably retarded chain migration, which led to polyethylenes with high molecular weights and high linearity.

Graphical abstractThe 2,3-diiminobutylnickel bromide complexes having remote benzhydryl-substituents, upon activation with cocatalyst Et2AlCl, exhibited high activity toward ethylene polymerization, producing polyethylenes with high molecular weights and narrow polydispersity. The existence of remote para-benzhydryl-substituent likely retarded chain migration and resulted polyethylenes with high molecular weights and high linearity.Figure optionsDownload full-size imageDownload as PowerPoint slide