N-heterocyclic Carbene Scandium Complexes: Synthesis, Structure, and Catalytic Performance for α-Olefin Polymerization and Copolymerization with 1,5-Hexadiene

Abstract

The N-heterocyclic carbene ligated scandium trialkyl complexes [{2,6-C6H3R2NCH}2CSc(CH2SiMe3)3] (R = Me (1); R = iPr (2)) were synthesized by the reaction of 1 equiv of [Sc(CH2SiMe3)3(THF)2] with the corresponding ligand [{2,6-C6H3R2NCH}2C]. Their molecular structures have been established by single-crystal X-ray diffraction. Upon activation with 2 equiv of [Ph3C][B(C6F5)4], complexes 1 and 2 exhibited high activities up to 2520 (kg of polymer) (mol of Sc)−1 h–1 for 1-hexene homopolymerization, affording polymers with moderate molecular weight (18–46 kg mol–1) at room temperature. The use of a low reaction temperature of −30 °C resulted in high molecular weight (up to 631 kg mol–1). The catalyst systems based on complex 1 or 2 also showed excellent activities for 1-octene or 1-decene polymerization. Moreover, in the presence of 2 equiv of [Ph3C][B(C6F5)4], complex 1 proved to be an excellent catalyst for copolymerization of 1-hexene (H) with 1,5-hexadiene (HD) to give random atactic H/HD copolymers with a...