气相中CrO_2^+和H_2反应的理论研究  

Theoretical Study of Gas-phase Reaction of CrO_2^+ with H_2

作　　者：陈晓霞[1] 王永成[1] 耿志远[1] 高立国[1] 方冉[1] 张兴辉[1] 

机构地区：[1]西北师范大学化学化工学院,甘肃省高分子材料重点实验室,兰州730070

出　　处：《物理化学学报》2006年第1期59-64,共6页Acta Physico-Chimica Sinica

摘　　要：用密度泛函UB3LYP/6-311++G(3df,3pd)//6-311G(2d,p)方法计算研究了在二重态和四重态两个势能面上的气相反应:CrO2++H2→CrO++H2O.对影响反应机理和反应速率的势能面交叉进行了讨论,并运用Hammond假设和Yoshizawa等的内禀反应坐标(IRC)单点垂直激发计算的方法找出了势能面交叉点(crossingpoint(CP)).运用碎片分子轨道(fragmentmolecularorbital(FMO))理论,对初始复合物2IM1和4IM1的轨道相关进行了分析,解释了CrO2+活化H—Hσ键及H2迁移的机理.The gas-phase reaction of CrO2^＋（^2A1 / ^4A＂） with H2 to yield CrO^＋（^2∑8 /^4∑8） and H2O is selected as a representative system of activation of H--H σ bond by MO2^＋. The reaction mechanism has been investigated with density functional theory（DPT） at the UB3LYP/6-311＋＋G（3df, 3pd）//6-311G（2d, p） level. The geometries for reactants, the transition states, and the products were completely optimized. All the transition states were verified by the vibrational analysis and the intrinsic reaction coordinate calculations. The H--H bond has been activated by CrO2＋（^2A1） on the doublet PES（potential energy surface） while dihydrogen transfer from Cr to O （in longer Cr--O） on the quartet PES. The involving potential energy curve-crossing, with dramatically affecs reaction mechanism and reaction rate, has been discussed in detail. The crossing points （CPs） are localized by means of the Hammond postulate and the intrinsic reaction coordinate（IRC） approach. The formation of the transition metal dihydrogen complex （H2）CrO2^＋（^2MI and ^4IMI） involves donation of the H2 σ bonding orbital to the metal and the back-donation by the metal electron to the H2 σ^＊ antibonding orbital, as illustrated by the fragment molecular orbital（FMO）. In addition, the orbital analysis on the activation of the H--H bond and dihydrogen transfer has been carried out by FMO.

关 键 词：活化H—H键 势能面交叉 碎片分子轨道 

分 类 号：O643.1[理学—物理化学]