Issue 5, 2019

Plastomeric-like polyethylenes achievable using thermally robust N,N′-nickel catalysts appended with electron withdrawing difluorobenzhydryl and nitro groups

Abstract

A new set of five unsymmetrical N,N′-diiminoacenaphthenes, 1-[2,6-{(4-FC6H4)2CH}2-4-NO2C6H4N]-2-(ArN)C2C10H6 (Ar = 2,6-Me2C6H3L1, 2,6-Et2C6H3L2, 2,6-iPr2C6H3L3, 2,4,6-Me3C6H2L4, 2,6-Et2-4-MeC6H2L5), have been synthesized and used to prepare their corresponding nickel(II) halide complexes, LNiBr2 (Ni1–Ni5) and LNiCl2 (Ni6–Ni10). The molecular structures of Ni3(OH2) and Ni4 reveal distorted square pyramidal and tetrahedral geometries, respectively, while the 1H NMR spectra of all the nickel(II) (S = 1) complexes show broad paramagnetically shifted peaks. Upon activation with either methylaluminoxane (MAO) or ethylaluminum sesquichloride (Et3Al2Cl2, EASC), Ni1–Ni10 displayed very high activities for ethylene polymerization with the optimal performance being observed using 2,6-dimethyl-containing Ni1 in combination with EASC (1.66 × 107 g PE mol−1 (Ni) h−1 at 50 °C) which produced high molecular weight plastomeric polyethylene (Mw = 3.93 × 105 g mol−1, Tm = 70.6 °C) with narrow dispersity (Mw/Mn = 2.97). Moreover, Ni1/EASC showed good thermal stability by operating effectively at an industrially relevant 80 °C with a level of activity (6.01 × 106 g of PE mol−1 (Ni) h−1) that exceeds previously disclosed N,N′-nickel catalysts under comparable reaction conditions. This improved thermal stability and activity has been ascribed to the combined effects imparted by the para-nitro and fluoride-substituted benzhydryl ortho-substituents.

Graphical abstract: Plastomeric-like polyethylenes achievable using thermally robust N,N′-nickel catalysts appended with electron withdrawing difluorobenzhydryl and nitro groups

Supplementary files

Article information

Article type
Paper
Submitted
07 Қар. 2018
Accepted
23 Жел. 2018
First published
26 Жел. 2018

Dalton Trans., 2019,48, 1878-1891

Plastomeric-like polyethylenes achievable using thermally robust N,N′-nickel catalysts appended with electron withdrawing difluorobenzhydryl and nitro groups

R. Zhang, Z. Wang, Y. Ma, G. A. Solan, Y. Sun and W. Sun, Dalton Trans., 2019, 48, 1878 DOI: 10.1039/C8DT04427A

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