钯配合物催化降冰片烯聚合反应机理的理论研究

摘要

(η3-allyl) Pd (PCy3)2] [PF6] and [{(η3-allyl) Pd (PCy3)}2 (μ-Cl)] [PF6] Catalytic norbornene (NB) polymerization is studied with DFT, and the stable point and transition state geometry and free energy are calcu-lated in the reaction process. And then the microscopic mechanism of the reaction is concluded. The calculations demonstrate that: (A) for both of the catalysts, the real active center is [(η3-allyl)Pd(PCy3)+]; (B) the exo insert of norbernene is the more favorite than the endo insert, and the present conclusion agrees with the experimental fact;(C) the energy barrier of the NB insertion into the Pd-allyl bond is very close to that into the Pd-NB bond; (D) the barrier of the chain propagation is higher than the barrier of the initial step, and there is no β-H elimination in the chain propagation, so the reaction process is living polymerization.%应用DFT方法研究了[(η3-allyl)Pd(PCy3)2][PF6]和[{(η3-allyl)Pd(PCy3)}2(μ-Cl)][PF6]催化降冰片烯(NB)聚合反应，计算了反应过程中稳定点及过渡态的几何结构和自由能，进而给出了反应的微观机理。计算结果表明：(1)两种催化剂具有相同的催化活性体[(η3-allyl)Pd(PCy3)2]+，验证了实验预想；(2)NB单体endo方向的插入能垒远高于exo方向的插入能垒，因此聚合物链中只包含以exo方插入的NB单体，与实验结论一致；(3)在引发步与链增长步降冰片烯双键插入Pd-C键的插入能垒接近，且引发步产物需要异构化后才能进行链增长；(4)过程中的链循环步的能垒高于引发步的反应能垒，且反应过程中没有发生链终止的β-H存在，聚合反应属于活性聚合。