Achieving Linear α‑Macro-olefins in Ethylene\nPolymerization through Precisely Tuned Bis(imino)pyridylcobalt Precatalysts\nwith Steric and Electronic Parameters

Synthesis of functional polyethylene\nfrom ethylene alone is tricky\nand heavily dependent on both the type and structure of the precatalyst\nand the choice of cocatalyst used in the polymerization. In the present\nstudy, a series of cobalt precatalysts was prepared and investigated\nfor ethylene polymerization under various conditions. By incorporation\nof strong electron-withdrawing groups (F and NO<sub>2</sub>) and a\nsteric component (benzhydryl) into the parent bis(imino)pyridine ligand,\nthe catalytic performance of these precatalysts was optimized. On\nactivation with MAO or MMAO, these precatalysts with relatively open\nstructure achieved unprecedented ethylene polymerization rates at\n60 °C (up to 27.6 × 10<sup>6</sup> g mol<sup>–1</sup> h<sup>–1</sup>) and remained effective at temperatures up\nto 100 °C. Chain growth reactions were moderate, resulting in\npolyethylene with molecular weights up to 61.0 kg/mol and broad bimodal\ndispersity index. High crystallinity and melt temperature indicated\na strictly linear microstructure, as further confirmed by high-temperature <sup>1</sup>H/<sup>13</sup>C NMR measurements. Of significant note that\nchain termination predominantly occurred through β-elimination\n(up to 84.5%), yielding vinyl-terminated long-chain olefins. These\nfunctional α-macro-olefins are valuable as precursors for postfunctionalization,\nexpanding the potential applications of polyethylene across various\nsectors.