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

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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-Me2C6H3 L1, 2,6-Et2C6H3 L2, 2,6-iPr2C6H3 L3, 2,4,6-Me3C6H2 L4, 2,6-Et2-4-MeC6H2 L5), 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

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Publication details

The article was received on 07 Nov 2018, accepted on 23 Dec 2018 and first published on 26 Dec 2018


Article type: Paper
DOI: 10.1039/C8DT04427A
Citation: Dalton Trans., 2019, Advance Article
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    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, Advance Article , DOI: 10.1039/C8DT04427A

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