| Summary: | Among various catalyst design strategies used in the α-diimine nickel(II) and palladium(II) catalyst systems, the unsymmetrical strategy is an effective and widely utilized method. In this contribution, unsymmetrical nickel and palladium α-diimine catalysts (<b>Ipty/<i><sup>i</sup></i>Pr-Ni</b> and <b>Ipty/<i><sup>i</sup></i>Pr-Pd</b>) derived from the dibenzobarrelene backbone were constructed via the combination of pentiptycenyl and diisopropylphenyl substituents, and investigated toward ethylene (co)polymerization. Both of these catalysts were capable of polymerizing ethylene in a broad temperature range of 0–120 °C, in which <b>Ipty/<i><sup>i</sup></i>Pr-Ni</b> could maintain activity in the level of 10<sup>6</sup> g mol<sup>−1</sup> h<sup>−1</sup> even at 120 °C. The branching densities of polyethylenes generated by both nickel and palladium catalysts could be modulated by the reaction temperature. Compared with symmetrical <b>Ipty-Ni</b> and <b><i><sup>i</sup></i>Pr-Ni</b>, <b>Ipty/<i><sup>i</sup></i>Pr-Ni</b> exhibited the highest activity, the highest polymer molecular weight, and the lowest branching density. In addition, <b>Ipty/<i><sup>i</sup></i>Pr-Pd</b> could produce copolymers of ethylene and methyl acrylate, with the polar monomer incorporating both on the main chain and the terminal of branches. Remarkably, the ratio of the in-chain and end-chain polar monomer incorporations could be modulated by varying the temperature.
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