化学学报 ›› 2012, Vol. 70 ›› Issue (18): 1930-1938.DOI: 10.6023/A12040084 上一篇    下一篇

研究论文

三(五甲基环戊二烯基)稀土金属配合物(C5Me5)3Ln (Ln=Sc, Y, La)的量子化学理论研究

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:2012-04-01 出版日期:2012-09-28 发布日期:2012-08-06
  • 通讯作者: 王曙光
  • 基金资助:

    项目受国家自然科学基金(No. 20973109)资助.

Theoretical Investigations on Tris(pentamethylcyclopentadienyl) Rare Earth Metal Complexes (C5Me5)3Ln (Ln=Sc, Y, La)

Qiu Yixiang, Wang Shuguang   

  1. School of Chemistry and Chemical Technology, Shanghai Jiaotong University, Shanghai 200240
  • Received:2012-04-01 Online:2012-09-28 Published:2012-08-06
  • Supported by:

    Project supported by the National Natural Science Foundation of China (No. 20973109).

采用从头计算方法和密度泛函理论方法, 对三(五甲基环戊二烯基)稀土金属配合物(C5Me5)3Ln (Ln=Sc, Y, La)的几何结构、电子结构以及Ln-C5Me5 之间的结合能进行了研究. (C5Me5)3Ln 的电子结构符合过渡金属配合物“18 电子规则”的描述, 因而具有较好的稳定性. Ln 原子的(n-1)d、ns 轨道能够与C5Me5 的π 轨道较好的重叠并组成强成键轨道. 研究发现(C5R5)3Ln (R=H, Me)的几何结构受到“Ln-C5R5 成键效应”和“C5R5-C5R5 位阻效应”两个相反因素的影响, 其稳定性则受到“Ln 原子半径-(C5R5)3 孔径尺寸”匹配关系的制约. 在C5R5 上引入特定的取代基后可以从轨道能级、金属原子-配体距离、配体-配体距离等多方面直接或间接的影响Ln-C5R5 间的成键强度, 进而实现对(C5R5)3Ln 稳定性和反应活性的控制.

关键词: 三茂基稀土金属配合物, 从头计算, 密度泛函理论, 电子结构, 金属-配体结合能

The molecular geometric and electronic structures of tris(pentamethylcyclopentadienyl) rare earth metal complexes (C5Me5)3Ln (Ln=Sc, Y, La) were investigated by means of ab initio HF, MP2 and density functional theory (DFT) methods. The bonding energies of Ln-C5Me5 were also analyzed on the basis of calculations. To study the effect of the exchange-correlation (XC) functional on the structural parameters and bonding energies, LDA (Xα, SVWN3, SVWN5), GGA (BP86, BLYP), meta-GGA (TPSS) and hybrid (B3LYP, PBE0, TPSSh, M06, M06-HF, M06-2X) functionals have been used. Calculations were carried out with the TZVPP basis sets. The geometry structural parameters from the different methods were compared to the experimental values. The Ln-C distance of (C5Me5)3Ln shows a dramatic reduction of about 15 pm from HF to MP2 level. These differences demonstrates the importance of electron correlation on the Ln-C5Me5 bonds. In (C5Me5)3Ln complexes, the geometric parameters differ much for different DFT exchange-correlation functional. For the Ln-C bond length, the theoretical values closest to the experiment were the M06-2X and M06 methods, with the deviation of only 1.2 and 2.5 pm, respectively. Thus, the M06-2X methods appear to be the most reliable for predicting the molecular structures of (C5Me5)3Ln. The studies of the electronic structures showed that the (C5Me5)3Ln satisfied the 18-electron rule, so these complexes had high stability. The (n-1)d and ns orbitals of Ln atom had a better overlap with the π orbitals of C5Me5. Our calculations revealed that the geometries of (C5R5)3Ln (R=H, Me) were influenced significantly by the “Ln-C5R5 bonding effect” and “C5R5-C5R5 steric effect”, while the thermal stabilities were influenced by whether atomic radius of Ln was suitable for the ring size of (C5R5)3. Therefore, the introduction of specific substituents into C5R5 could affect the π orbital energies, Ln-C5R5 distance and C5R5-C5R5 distance, and then control the Ln-C5R5 bonding strength and stability of (C5R5)3Ln.

Key words: tris(pentamethylcyclopentadienyl) rare earth metal complexes, ab initio, density functional theory, electronic structure, metal-ligand bonding energy