Self-immobilizing binuclear neutral nickel catalyst for ethylene polymerization: Synthesis and catalytic studies

• The ally-functionalized binuclear neutral Ni complex has been synthesized.
• The complex can be used as a self-immobilizing catalyst for polymerization of ethylene.
• High-molecular-weight branching PEs was obtained.

A allyl-substituted salicylaldimine proligand (Scheme 1, Compound 5) was prepared by a condensation reaction, which reacted with trans-[NiCl(Ph)(PPh3)2] to give a binuclear neutral nickel (II) complex [((4-Allyl-2,6-iPr2C6H2) NCH)C6H3ONi(PPh3)Ph]2 (Scheme 1, Complex 6). The structure of the complex was characterized by 1H NMR, 13C NMR and elemental analysis. This novel complex bearing allyl groups can be used as a self-immobilizing catalyst for the polymerization of ethylene and does not need a cocatalyst for their catalytic performance. The self-immobilizing catalytic systems not only possess high activity (up to 5.23 × 105 g of PE/(mol of Ni h)) but also can produce high-molecular-weight polyethylenes (Mw = (0.42–0.71) × 106) with relatively broad molecular weight distributions (MWD = 2.83–3.11). According to the 13C NMR analyses, the resultant polyethylenes contain a few branched chains mainly consisting of methyl branches.

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