ω-Alkenyltrimethylsilanes of different alkenyl moieties, i.e., 3-butenyltrimethylsilane, 5-hexenyltrimethylsilane, and 7-octenyltrimethylsilane, are used as model compounds to study the alkenyl length effect in copolymerization of ethylene with steric-hindered tri-substituted silane-functionalized α-olefins over MgCl₂/TiCl₄ catalysts. The experimental results reveal that 3-butenyltrimethylsilane tops the three α-olefins in incorporation rate into PE while 7-octenyltrimethylsilane is slightly better than 5-hexenyltrimethylsilane. The coordination-insertion events for different ω-alkenyltrimethylsilanes are investigated by DFT simulation. The results suggest that the three ω-alkenyltrimethylsilanes encounter similar energy barriers during insertion, with similar repulsive interactions between the bulky trimethylsilane substituent and growing PE chain found in the energy decomposition of transition state configuration. However, complexation abilities at the Ti active site for the three ω-alkenyltrimethylsilanes follow the order of 3-butenyltrimethylsilane > 5-hexenyltrimethylsilane > 7-octenyltrimethylsilane, in line with their molecular compactness, which are deemed to be where the alkenyl length effect originates in the ω-alkenyltrimethylsilane/ethylene copolymerization.

中文翻译：

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MgCl2/TiCl4 催化剂下 ω-烯基三甲基硅烷与乙烯的共聚：烯基长度对共聚单体结合的影响

以不同烯基部分的ω-烯基三甲基硅烷，即3-丁烯基三甲基硅烷、5-己烯基三甲基硅烷和7-辛烯基三甲基硅烷为模型化合物，研究了乙烯与空间位阻三取代硅烷官能化α-共聚过程中的烯基长度效应。 MgCl ₂ /TiCl ₄催化剂上的烯烃。实验结果表明，3-丁烯基三甲基硅烷在PE中的掺入率在三种α-烯烃中最高，而7-辛烯基三甲基硅烷略优于5-己烯基三甲基硅烷。通过DFT模拟研究了不同ω-烯基三甲基硅烷的配位插入事件。结果表明，三种ω-烯基三甲基硅烷在插入过程中遇到相似的能垒，在过渡态构型的能量分解中发现大体积的三甲基硅烷取代基和生长的PE链之间存在相似的排斥相互作用。然而，三种ω-烯基三甲基硅烷在Ti活性位点的络合能力遵循3-丁烯基三甲基硅烷> 5-己烯基三甲基硅烷> 7-辛烯基三甲基硅烷的顺序，与其分子紧密度一致，这被认为是烯基长度效应的起源。 ω-烯基三甲基硅烷/乙烯共聚。