Alkyl Effects on the Chain Initiation Efficiency of Olefin Polymerization by Cationic Half-Sandwich Scandium Catalysts: A DFT Study

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• 作者：Xiaohui Kang ; Guangli Zhou ; Xingbao Wang ; Jingping Qu ; Zhaomin Hou ; Yi Luo
• 刊名：Organometallics
• 出版年：2016
• 出版时间：March 28, 2016
• 年：2016
• 卷：35
• 期：6
• 页码：913-920
• 全文大小：478K
• ISSN：1520-6041

文摘

The effect of alkyls on the chain initiation efficiency of ethylene, propene, 1-hexene, styrene, butadiene, and isoprene polymerizations catalyzed by the half-sandwich cationic rare-earth-metal alkyl complexes [(η⁵-C₅Me₅)ScR]⁺ (R = CH₂SiMe₃, 1; R = o-CH₂C₆H₄NMe₂, 2; R = η³-C₃H₅, 3) has been studied by using a DFT approach. It has been found that 2 with the largest sterically demanding aminobenzyl group results in the lowest initiation efficiency and thus longest induction period among the three catalysts investigated. In contrast, 1 with CH₂SiMe₃ displays the best chain initiation ability, and 3 with η³-allyl gives moderate chain initiation activity, mainly due to the most stable resulting coordination complex. Species 1 and 3 have better regioselectivity in the chain initiation of styrene polymerization than species 2. In addition, species 1′ ([(η⁵-C₅Me₅)Sc(CH₂SiMe₃)THF]⁺) with a THF ligand has better chain initiation efficiency in styrene and isoprene polymerizations than species 2 but is reasonably worse than the analogue 1 without a THF ligand.