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首页> 外文期刊>Organometallics >DFT Study of Ethylene Polymerization by Zirconocene-Boron Catalytic Systems. Effect of Counterion on the Kinetics and Mechanism of the Process
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DFT Study of Ethylene Polymerization by Zirconocene-Boron Catalytic Systems. Effect of Counterion on the Kinetics and Mechanism of the Process

机译：锆茂-硼催化体系进行乙烯聚合的DFT研究。抗衡离子对过程动力学和机理的影响

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摘要

The effect of counterion on the kinetics and mechanism of ethylene polymerization by the zirconocene-boron catalytic system was examined using the density functional theory approach. A comparative study of three model catalytic species, namely, ethylzirconocene cation, Cp_2ZrEt~+, and two ion pairs of composition Cp_2ZrEt~+A~- (A~- = CH_3B(C_6F_50_3~_, B(C_6F_5)_4~-) was carried out. It was shown that the nature of counterion affects mainly the ratio between the most stable #beta#-agostic and nonagostic Cp_2ZrEt~+A~- isomers, the thermodynamic and kinetic characteristics of ethylene addition to the Cp_2ZrEt~+A~- ion pairs, and the chain propagation kinetics. The weaker the nucleophilicity of the counterion, the higher the fraction of the #beta#-agostic isomer, the higher the exotermicity, and the lower the activation bararier to ethylene addition to Cp_2ZrEt~+A~-, and the lower the activation bararier to ethylene addition to Cp_2ZrEt~+A~-, and the lower the activation energy of chain propagation. All possible pathways of the interaction between Cp_2ZrEt~+CH_3B(C_6F_5)_3~- and ethylene molecule were examined and compared. Among all species of composition Cp_2ZrEt~+CH_3B(C_6F_5)_3~-, the nonagostic isomer was found to be the most reactive toward ethylene.
机译：用密度泛函理论方法研究了抗衡离子对锆茂-硼催化体系乙烯聚合反应动力学和机理的影响。比较了三种模式催化物种乙基锆茂正阳离子Cp_2ZrEt〜+和组成Cp_2ZrEt〜+ A〜-（A〜-= CH_3B（C_6F_50_3〜_，B（C_6F_5）_4〜-）的两个离子对的比较研究。结果表明，抗衡离子的性质主要影响最稳定的β-β-声波和非声波Cp_2ZrEt〜+ A〜-异构体之间的比例，以及乙烯向Cp_2ZrEt〜+ A〜-中添加乙烯的热力学和动力学特性。抗衡离子的亲核性越弱，＃beta＃-亲和异构体的分数越高，放热性越高，并且向Cp_2ZrEt〜+ A〜中添加乙烯的活化障碍越低-，Cp_2ZrEt〜+ A〜-对乙烯的激活障碍越低，链增长的活化能越低，Cp_2ZrEt〜+ CH_3B（C_6F_5）_3〜-与乙烯分子相互作用的所有可能途径为在所有组成成分中Cp_2ZrEt〜+ C H_3B（C_6F_5）_3〜-，发现非弹性异构体对乙烯的反应性最高。

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