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Issue 17, 2018
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Methylene-bridged bimetallic bis(imino)pyridine-cobaltous chlorides as precatalysts for vinyl-terminated polyethylene waxes

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Abstract

Four examples of phenol-substituted methylene-bridged bis(imino)pyridines, CH(C6H4-4-OH){2′-(4-C6H2-2,6-R22N[double bond, length as m-dash]CMe)-6′-(2′′,6′′-R12C6H3N[double bond, length as m-dash]CMe)C5H3N}2 [R1 = R2 = Me L1, R1 = R2 = Et L2, R1 = Et, R2 = Me L3, R1 = iPr, R2 = Me L4], have been synthesized and fully characterized. Treatment of L1–L4 with two equivalents of cobaltous chloride affords the bimetallic complexes, [(L)Co2Cl4] (L = L1Co1, L2Co2, L3Co3, L4Co4), in good yield. The molecular structure of Co1 shows the two metal centers to be separated by a distance of 13.339 Å with each cobalt displaying a distorted trigonal bipyramidal geometry. On activation with either MAO or MMAO, Co1–Co4 exhibited high activities for ethylene polymerization (up to 1.46 × 107 g(PE) mol−1(Co) h−1 at 50 °C) with their relative values influenced by the steric properties of the N-aryl groups: Co1 > Co3 > Co4 > Co2. Highly linear polyethylenes incorporating high degrees of vinyl end-groups are a feature of all the materials produced with the molecular weights of the MAO-promoted systems (Mw range = 2–8 kg mol−1) generally higher than seen with MMAO (Mw range = 1–3 kg mol−1), while the distributions using MMAO are narrower (PDI < 2.0).

Graphical abstract: Methylene-bridged bimetallic bis(imino)pyridine-cobaltous chlorides as precatalysts for vinyl-terminated polyethylene waxes

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Publication details

The article was received on 09 Mar 2018, accepted on 09 Apr 2018 and first published on 10 Apr 2018


Article type: Paper
DOI: 10.1039/C8DT00907D
Citation: Dalton Trans., 2018,47, 6124-6133
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    Methylene-bridged bimetallic bis(imino)pyridine-cobaltous chlorides as precatalysts for vinyl-terminated polyethylene waxes

    Q. Chen, W. Zhang, G. A. Solan, T. Liang and W. Sun, Dalton Trans., 2018, 47, 6124
    DOI: 10.1039/C8DT00907D

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