CGC-Scandium-Mediated Copolymerization of Ethylene with Amine-Functionalized Cyclic Olefins

Direct
coordination copolymerization of polar monomers with olefin
should be the most atom- and energy-efficient strategy to prepare
functional polyolefins, which encounters challenges to trade-off the
activity and polar monomer incorporation and molecular weight of the
afforded product. Herein, we report that using the fluorenyl-modified N-heterocyclic carbene-ligated scandium complex, the copolymerization
of ethylene with N-(phenyl)-cis-5-norbornene-endo-2,3-dimethylene
(NPh) was achieved with high activity (2580 kg·molSc–1·h–1) and high incorporation
of NPh (31.6%). The investigation of several amine-substituted polar
monomers indicated that the high activity and incorporation ability
were attributed to the moderate steric and weak basicity of the amine
group, which not only ensure the coordination priority of NPh but
also facilitate its swift swing from the Sc–σ–N
chelation mode to the Sc–π–CC polymerization
mode illustrated by density functional theory (DFT) calculation. This
established a new polar group self-assisted mechanism, which will
give inspirations to tackle the challenging issue in the copolymerization
of olefin with polar monomers.