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Nickel complexes bearing substituted 2-(naphthylen-1-yl)iminopyridines as catalysts for the formation of highly branched unsaturated PE waxes

journal contribution
posted on 2023-05-25, 10:08 authored by Wenhua Lin, Qiuyue Zhang, Liping Zhang, Gregory A Solan, Yanping Ma, Xiang Hao, Wen-Hua Sun

A set of six 2-iminopyridine-nickel(II) complexes, [2-{C(Me)=NAr}C5H4N]NiCl2 (Ar = 1-C10H7 Ni1, 2-Me-1-C10H6 Ni2, 2-(CHMePh)-1-C10H6 Ni3, 4-(NNC6H5)-1-C10H6 Ni4, 4-(NNC6H4-4-Me)-1-C10H6 Ni5, 4-(NNC6H4-4-F)-1-C10H6 Ni6), all N-functionalized with naphthalen-1-yl or its substituted alkyl or aryldiazenyl derivatives, have been readily synthesized from their corresponding free N,N-ligand, L1 – L6. On crystallization of Ni3, the chloride-bridged trimetallic species, [(L3)3Ni3Cl6(OH2)], was identified as an aqua adduct by single crystal X-ray diffraction. When activated with either MAO or MMAO, high catalytic activity for ethylene polymerization was achieved using Ni1–Ni6 (up to 10.1 × 106 g (PE) mol−1 h−1 for Ni3/MAO), affording low molecular weight polyethylene (Mw range: 0.81–3.50 kg mol−1) with low melting temperature and narrow dispersity. 13C NMR spectroscopic analyses of these polyethylenic waxes revealed the formation of branched macromolecules with branching densities up to 69 per 1000 carbons. Further analysis revealed these polymers to contain predominantly methyl branches (%Me range: 7.8–9.0), with lower levels of longer chain branching and some branch-on branch structure (%sec-Bu range: 0.07–0.12%). Moreover, their 1H and 13C NMR spectra showed various levels of unsaturated functionality in the form of terminal and internal olefins.

History

Author affiliation

Department of Chemistry, University of Leicester

Version

  • AM (Accepted Manuscript)

Published in

Polymer

Volume

277

Pagination

125994

Publisher

Elsevier BV

issn

0032-3861

Copyright date

2023

Available date

2024-04-26

Language

en

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