钒离子与乙烷反应的理论研究  

Theoretical Studies of the Reaction of Vanadium Monocation with Ethane

作　　者：张冬菊[1] 冯大诚[1] 

机构地区：[1]山东大学理论化学研究所,济南250100

出　　处：《化学学报》2003年第1期17-21,共5页Acta Chimica Sinica

基　　金：国家自然科学基金 (No.2 99730 2 1 );山东大学青年科学基金资助项目

摘　　要：用量子化学方法在UB3LYP/ 6 311+ +G(3df ,3pd)水平上研究了一价钒离子与乙烷的反应 ,找到了 [VC2 H6 ] +势能面上各驻点的结构 ,分析了反应过程中有关的电子转移性质 ,给出了CH4 和H2 的还原消除机理 .结果表明 :CH4 消除反应一般按加成 -消除机理进行 ,在高能条件下也可按协同机理进行 ;H2 分子消除反应 ,一般按 1,2 H2 分子消除机理进行 ,在高能条件下也可按 1,1 H2 分子消除机理进行 .计算表明 :能量最有利的反应通道是V++C2 H6 →V(C2 H4 ) ++H2 ,该反应放热11The reaction of V+ with C2H6 which represents a prototype of the activation of C-C and C-H bonds in alkane by transition metal cations, has been investigated by employing the recently suggested density functional theory/Hartree-Fock hydrid method B3LYP combined with reasonable large one-particle basis set. The calculated results show that three activation branches, C-H activation branches, C-C activation branches, and synchronous C-H and C-C activation branches, are available along the reaction coordinate. And two new mechanisms are found: one is the 1,1-H-2 elimination mechanism and the other is the concerted elimination mechanism of CH4. These two new reaction mechanisms could be alternative pathways at high-energy conditions for H-2 and CH4 eliminations from the reaction of V+ with C2H6. The energetically most favorable channel in the reaction of V+ with C2H6 is V+ + C2H6 -->1-->TS1-4-->4-->TS4-5-->V ( C2H4)(+) + H-2, which is exothermic by 49.49 kJ/mol relative to the reactants. Compared to 1, 2-H-2 elimination reaction, CH4 elimination reaction is energetically more unfavorable. The barrier height of C-H activation is 123.14 kJ/mol, while that of C-C bond activation is 181.40 kJ/mol.

关 键 词：钒离子 乙烷 反应机理 密度泛函理论 量子化学 有机化学反应 

分 类 号：O621.25[理学—有机化学]