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ortho-Cycloalkyl substituted N,N′-diaryliminoacenaphthene-Ni(II) catalysts for polyethylene elastomers; exploring ring size and temperature effects

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Abstract

A family of six unsymmetrical N,N′-diiminoacenaphthene-nickel(II) bromide complexes, [1-{2,6-(Ph2CH)2-4-MeC6H2N}-2-(ArN)C2C10H6]NiBr2 (Ar = 2-(C6H11)-6-MeC6H2 Ni1, 2-(C5H9)-6-MeC6H2 Ni2, 2-(C8H15)-6-MeC6H2 Ni3, 2-(C6H11)-4,6-Me2C6H2 Ni4, 2-(C5H9)-4,6-Me2C6H2 Ni5, 2-(C8H15)-4,6-Me2C6H2 Ni6), each bearing one ring-size variable 4-R-2-methyl-6-cycloalkyl-substituted N-aryl group and one N′-4-methyl-2,6-dibenzhydrylphenyl group, have been prepared and fully characterized. The molecular structures of Ni1, Ni2, Ni3 and Ni5 reveal distorted tetrahedral geometries with different degrees of steric protection imparted by the two inequivalent N-aryl groups. On activation with either EASC or MMAO, all the precatalysts are highly active (up to 17.45 × 106 g PE mol−1 (Ni) h−1) for ethylene polymerization at 20–50 °C with their activities correlating with the type of cycloalkyl ortho-substituent: cyclooctyl (Ni6, Ni3) > the cyclopentyl (Ni5, Ni2) > cyclohexyl (Ni4, Ni1) for either R = H or Me. Moderately branched to hyperbranched polyethylenes (Tm's as low as 44.2 °C) can be obtained with molecular weights in the range 2.14–6.68 × 105 g mol−1 with the branching content enhanced by the temperature of the polymerization. Dynamic mechanical analysis (DMA) and monotonic tensile stress–strain tests have been employed on the polyethylene samples and reveal the more branched materials to show good elastic recovery properties (up to 75.5%).

Graphical abstract: ortho-Cycloalkyl substituted N,N′-diaryliminoacenaphthene-Ni(ii) catalysts for polyethylene elastomers; exploring ring size and temperature effects

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Publication details

The article was received on 10 Sep 2017, accepted on 16 Oct 2017 and first published on 25 Oct 2017


Article type: Paper
DOI: 10.1039/C7DT03362A
Citation: Dalton Trans., 2017, Advance Article
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    ortho-Cycloalkyl substituted N,N′-diaryliminoacenaphthene-Ni(II) catalysts for polyethylene elastomers; exploring ring size and temperature effects

    H. Suo, I. V. Oleynik, C. Huang, I. I. Oleynik, G. A. Solan, Y. Ma, T. Liang and W. Sun, Dalton Trans., 2017, Advance Article , DOI: 10.1039/C7DT03362A

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