物理化学学报 >> 2012, Vol. 28 >> Issue (04): 811-817.doi: 10.3866/PKU.WHXB201202082

理论与计算化学 上一篇    下一篇

IB 族金属-乙烯配合物[N{(Me)C(Ph)N}2]M-C2H4 (M=Cu, Ag, Au)的电子结构

仇毅翔, 王曙光   

  1. 上海交通大学化学化工学院, 上海 200240
  • 收稿日期:2011-11-14 修回日期:2012-01-12 发布日期:2012-03-21
  • 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)资助项目

Electronic Structures of Group IB Metal-Ethylene Complexes [N{(Me)C(Ph)N}2]M-C2H4 (M=Cu, Ag, Au)

QIU Yi-Xiang, WANG Shu-Guang   

  1. School of Chemistry and Chemical Technology, Shanghai Jiao Tong University, Shanghai 200240, P. R. China
  • Received:2011-11-14 Revised:2012-01-12 Published:2012-03-21
  • Contact: WANG Shu-Guang E-mail:sgwang@sjtu.edu.cn
  • Supported by:

    The project was supported by the National Natural Science Foundation of China (20973109).

摘要: 采用从头算Hartree-Fock (HF), Møller-Plesset 微扰(MP2), 二级近似耦合簇(CC2)和密度泛函理论(DFT)方法, 对IB 族金属-乙烯配合物LM-C2H4 (L=[N{(Me)C(Ph)N}2]; M=Cu, Ag, Au)的几何结构、电子结构以及LM与C2H4之间的结合能进行了理论研究. MP2、CC2和密度泛函方法对C2H4配位前后C=C键长的变化情况都给出了正确的描述. 电子结构分析显示LM与C2H4之间主要以C2H4→LM“σ-给予”和LM→C2H4π-反馈”方式协同成键, 这种成键方式使C2H4配体π轨道上的电子密度下降, π*轨道上的电子密度增加, 并使得C=C键长增加、键能下降, 从而达到活化C=C键的目的. 自然电荷布居和能量分解分析显示LM-C2H4中的“σ-给予”作用弱于“π-反馈”作用, 若使用“σ-给予”作用强于“π-反馈”作用的M+-C2H4体系作为LM-C2H4的简化模型进行理论研究是不合适的. LM-C2H4中金属原子M的改变对C=C键长、C2H4电荷布居以及LM与C2H4之间的结合能等性质影响显著. LAu与LCu、LAg相比其接受和反馈电子的能力最强, 使C2H4配体π轨道电子密度减少的程度和π*轨道电子密度增加的程度也最大, 因此LAu对C2H4中C=C键的活化效果最好. 螯合配体取代基供、吸电能力的改变对上述性质的影响则非常有限.

关键词: 金属-乙烯配合物, 从头算, 密度泛函理论, 电子结构, 能量分解分析

Abstract: The geometries, electronic structures, and bonding energies of coinage metal-ethylene complexes LM-C2H4 (L=[N{(Me)C(Ph)N}2]; M=Cu, Ag, Au) were investigated by Hartree-Fock, Møller- Plesset perturbation (MP2), second-order approximate coupled-cluster (CC2), and density functional theory (DFT) methods. The MP2, CC2, and DFT methods performed well in reproducing the experimental geometric features of LM-C2H4. The bonding in LM-C2H4 can be described as a synergistic combination of σ-donor and π-acceptor interactions between the LM and C2H4 π-system. Both σ-donor and π-acceptor contributions increased the C=C bond length and decreased the C=C bond strength by removing electron density from the bonding π orbital and increasing electron density in the anti-bonding π* orbital, respectively. The results of natural population analysis and energy decomposition analysis show that the LM→C2H4 back-donation contribution to the LM-C2H4 bonding is higher than that of the C2H4→LM donation, but this order is reversed in the M+-C2H4 systems. Therefore, it is not appropriate to use M+-C2H4 as a computational model for electronic structures studies of LM-C2H4. The effects of changing the metal on the structural and electronic properties, such as C=C bond length, charge populations of C2H4, and LM-C2H4 interactions, were large. Compared with LCu and LAg, LAu had the strongest ability to accept and donate electrons. Consequently, it showed the maximum reduction in the π orbital electron density and increase in the π* orbital density. Therefore, activation of the C=C bond by LAu was more effective than by LCu and LAg. However, the effects of electron donating or withdrawing ability of the auxiliary ligands on the above properties were small.

Key words: Metal-ethylene complex, Ab initio, Density functional theory, Electronic structure, Energy decomposition analysis

MSC2000: 

  • O641