Tailoring polymers through interplay of ligands within precatalysts: 8‐(Nitro/benzhydryl‐arylimino)‐7, 7‐dimethyl‐5, 6‐dihydroquinolylnickel halides in ethylene polymerization. Issue 12 (16th April 2017)

• Record Type: Journal Article
• Authors: Huang, Chuanbing; Zeng, Yanning; Flisak, Zygmunt; Zhao, Zhijuan; Liang, Tongling; Sun, Wen‐Hua
• Is Part Of: Journal of polymer science. Volume 55:Issue 12(2017)
• Page Start: 2071
• Page End: 2083
• Publication Date: 2017-04-16
• Subjects: homogeneous catalysis -- nickel -- nitro substituent -- polymerization -- vinylene group; 547
• DOI: 10.1002/pola.28595
• Languages: English
• ISSNs: 0887-624X

Abstract

ABSTRACT: A series of 8‐(nitro/benzhydryl‐substituted arylimino)‐7, 7‐dimethyl‐5, 6‐dihydroquinolines and the corresponding nickel halide complexes were synthesized and characterized. Molecular structures of representative nickel complexes were determined by single crystal X‐ray diffraction, showing the dinuclear dimers with distorted square‐pyramidal geometry around the nickel center. The binding energies determined by X‐ray photoelectron spectroscopy (XPS) indicate the effective coordination between the sp 2 ‐nitrogen and nickel atoms as well as the influence of both the halogen ligands and the substituents within dihydroquinolines on the strength of the NiN bond. Ethylene polymerization with the nickel precatalysts in presence of either methylaluminoxane or diethylaluminum chloride was explored in detail. For the complexes containing the nitro substituent within the organic ligand, the catalytic activity is inversely proportional to the electron density around the nickel core determined by XPS; such phenomenon is consistent with the conclusion of the computational study stating that the activity of precatalysts is correlated with the net charge on the metal center. In the polymerization process, unimodal and branched polyethylenes containing vinyl or vinylene groups were obtained. The nickel precatalysts bearing bulky benzhydryl within the organic ligand as well as bromide rather than chloride attached to the nickel atom produce polymers with relatively large amount of vinylene groups. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem.2017, 55, 2071–2083 Abstract : The 8‐arylimino‐7, 7‐dimethyl‐5, 6‐dihydroquinolylnickel bromides (Ni1–Ni4 ) exhibit rigid geometry and high activity towards ethylene polymerization in the presence of either MAO or Et2 AlCl. Depending on the nitro/benzhydryl‐substituents within the precursor, branched polyethylenes of the low molecular weight and high contents of unsaturated groups will be produced.