CGC-Scandium-Mediated Copolymerization of Ethylene\nwith Amine-Functionalized Cyclic Olefins

Direct\ncoordination copolymerization of polar monomers with olefin\nshould be the most atom- and energy-efficient strategy to prepare\nfunctional polyolefins, which encounters challenges to trade-off the\nactivity and polar monomer incorporation and molecular weight of the\nafforded product. Herein, we report that using the fluorenyl-modified <i>N</i>-heterocyclic carbene-ligated scandium complex, the copolymerization\nof ethylene with <i>N</i>-(phenyl)-<i>cis</i>-5-norbornene-endo-2,3-dimethylene\n(NPh) was achieved with high activity (2580 kg·mol<sub>Sc</sub><sup>–1</sup>·h<sup>–1</sup>) and high incorporation\nof NPh (31.6%). The investigation of several amine-substituted polar\nmonomers indicated that the high activity and incorporation ability\nwere attributed to the moderate steric and weak basicity of the amine\ngroup, which not only ensure the coordination priority of NPh but\nalso facilitate its swift swing from the Sc–σ–N\nchelation mode to the Sc–π–CC polymerization\nmode illustrated by density functional theory (DFT) calculation. This\nestablished a new polar group self-assisted mechanism, which will\ngive inspirations to tackle the challenging issue in the copolymerization\nof olefin with polar monomers.