物理化学学报 >> 2013, Vol. 29 >> Issue (02): 279-286.doi: 10.3866/PKU.WHXB201212061

理论与计算化学 上一篇    下一篇

金(I)配合物催化乙烯加氢的反应机理

仇毅翔, 万明达, 陈先阳, 王曙光   

  1. 上海交通大学化学化工学院 上海 200240
  • 收稿日期:2012-06-27 修回日期:2012-12-04 发布日期:2013-01-14
  • 通讯作者: 王曙光 E-mail:sgwang@sjtu.edu.cn
  • 基金资助:

    国家自然科学基金(20973109), 国家大学生创新性实验计划(S110ITP5009)和上海交通大学大学生创新实践计划(IPP6123, IPP6128)资助项目

Reaction Mechanisms of Ethylene Hydrogenation Catalyzed by Gold(I) Complexes

QIU Yi-Xiang, WAN Ming-Da, CHEN Xian-Yang, WANG Shu-Guang   

  1. School of Chemistry and Chemical Technology, Shanghai Jiaotong University, Shanghai 200240
  • Received:2012-06-27 Revised:2012-12-04 Published:2013-01-14
  • Supported by:

    The project was supported by the National Natural Science Foundation of China (20973109), National Undergraduate Innovation Program, China (S110ITP5009), and Undergraduate Innovation Program of Shanghai Jiaotong University, China (IPP6123, IPP6128).

摘要:

采用密度泛函理论B3LYP方法, 对两类金(I)配合物AuX (X=F, Cl, Br, I)和AuPR3+(R=F, Cl, Br, I, H, Me,Ph)催化C2H4加氢反应的机理进行了理论研究. 计算显示Au(I)配合物对C2H4氢化具有较好的催化效果, 其作用下的加氢反应存在“活化H―H键后再与C2H4反应”和“活化C=C键后再与H2反应”两种途径, 前者的活化能较后者低90-120 kJ·mol-1, 因而具有明显的能量优势. 研究表明AuPR3+ 的催化能力明显强于AuX. 此外, X/PR3基团供、吸电子能力的变化对配合物的催化能力也具有较为显著的影响. 电子结构分析显示Au(I)配合物在C2H4 加氢反应中不仅能够削弱H―H、C=C 键的强度, 还使H2 σH―H*、C2H4 πC=C* 轨道能级下降, 从而缩小了πC=CH―H*或σH―H-πC=C*轨道间的能级差, 促进了C2H4-H2反应中的电子离域, 从而降低禁阻反应发生的难度.σH―H*πC=C*轨道能级改变量与加氢反应活化能Ea的降低值之间存在较好的一致性关系, 因此使上述轨道能级下降幅度越大的Au(I)配合物可以获得较好的催化效果.

关键词: 密度泛函理论, 乙烯加氢, 金(I)配合物, 反应机理, 电子结构

Abstract:

The reaction mechanisms of ethylene hydrogenation catalyzed by Au(I) complexes AuX (X=F, Cl, Br, I) and AuPR3+ (R = F, Cl, Br, I, H, Me, Ph) were investigated using density functional theory at the B3LYP level. The calculated results indicated that Au(I) complexes were effective catalysts in the hydrogenation of ethylene. AuPR3+ showed higher catalytic activity than AuX and the effect of changing the electron donating or withdrawing ability of the ligand on catalytic activity was large. Natural bond orbital analysis indicated that the interactions between the Au(I) complex and H2/C2H4 not only weakened the H― H/C=C bond strength, but also decreased the energy of the σH―H*πC=C* orbital level. As a result, the energy differences of πC=CH―H*H―H-πC=C* decreased, and ethylene hydrogenation was facilitated. A linear correlation was observed between the activation energies and πC=CH―H*H―H-πC=C*. The more an Au(I) complex affected the σH―H*/πC=C* orbital levels, the higher its catalytic activity.

Key words: Density functional theory, Ethylene hydrogenation, Gold(I) complex, Reaction mechanism, Electronic structure

MSC2000: 

  • O641