Pandey Krishna K, Lledós Agustí
School of Chemical Sciences, Devi Ahilya University Indore, Indore, India 452017.
Inorg Chem. 2009 Apr 6;48(7):2748-59. doi: 10.1021/ic801072g.
The electronic and molecular structures of the complexes [(eta(5)-C(5)H(5))(CO)(2)M[triple bond]EMe] and [(eta(5)-C(5)H(5))(CO)(3)M-EMe] (M = Cr, Mo, W; E = Si, Sn, Pb) are calculated at the density-functional theory (DFT) level using the exchange correlation functionals B3LYP and BP86. The theoretically predicted bond lengths and angles of the model compounds are in excellent agreement with experimental values. The calculations reveal the presence of a strong M[triple bond]E triple (sigma + 2pi) bond in [(eta(5)-C(5)H(5))(CO)(2)M[triple bond]EMe]. The M-E bond lengths in [(eta(5)-C(5)H(5))(CO)(3)M-EMe] are longer than those expected for a single bond. The nature of the M[triple bond]EMe and M-EMe interactions was analyzed with charge and energy decomposition methods. In the M[triple bond]EMe bond, the M-E sigma-bonding orbitals are always polarized toward the silicon, tin, and lead atoms, and the polarization increases from chromium to tungsten. In contrast, in the M-EMe bond, the M-E sigma-bonding orbitals are significantly polarized toward the metal atom. The hybridization at the metal atoms in the M[triple bond]E bonds has d character in the range 60.6-68.8%, while in the M-E bonds has large d character which is always >86% of the total atomic orbital contribution. In the complexes [(eta(5)-C(5)H(5))(CO)(2)M[triple bond]EMe], the contributions of the electrostatic interactions, DeltaE(elstat), and the covalent bonding, DeltaE(orb), have nearly the same values for silylidyne and germylidyne complexes, while for the stannylidyne and plumbylidyne complexes, the electrostatic interactions, DeltaE(elstat), are greater than the orbital interaction, DeltaE(orb). The covalent bonding has a high degree of pi-character. The total interaction energy DeltaE(int) in the compound [(eta(5)-C(5)H(5))(CO)(3)M-EMe] is less attractive than those in the complexes [(eta(5)-C(5)H(5))(CO)(2)M[triple bond]EMe]. The M-ER bonds have a slightly lower degree of covalent bonding (34.9-44.9%) than the M[triple bond]EMe bonds (42.1-50.2%). The drastic difference between the two classes of compounds are found for the degree of a'' (pi) bonding. The contribution of DeltaE(pi) to the covalent term DeltaE(orb) is much higher in the M[triple bond]EMe bonding (41.6-42.6%) than in the M-EMe bonding (17.1-20.4%). While the pi bonding contribution in [(eta(5)-C(5)H(5))(CO)(3)M-EMe] are weaker than those in [(eta(5)-C(5)H(5))(CO)(2)M[triple bond]EMe], the sigma-bonding contribution in the former compounds are stronger than those in the latter.
使用交换相关泛函B3LYP和BP86在密度泛函理论（DFT）水平上计算配合物[(η⁵-C₅H₅)(CO)₂M≡EMe]和[(η⁵-C₅H₅)(CO)₃M-EMe]（M = Cr、Mo、W；E = Si、Sn、Pb）的电子和分子结构。模型化合物的理论预测键长和键角与实验值非常吻合。计算结果表明[(η⁵-C₅H₅)(CO)₂M≡EMe]中存在强的M≡E三键（σ + 2π）。[(η⁵-C₅H₅)(CO)₃M-EMe]中的M-E键长比单键预期的要长。用电荷和能量分解方法分析了M≡EMe和M-EMe相互作用的本质。在M≡EMe键中，M-E σ键轨道总是向硅、锡和铅原子极化，并且极化程度从铬到钨逐渐增加。相反，在M-EMe键中，M-E σ键轨道明显向金属原子极化。M≡E键中金属原子的杂化具有60.6 - 68.8%的d特征，而在M-E键中具有大的d特征，总是占总原子轨道贡献的>86%。在配合物[(η⁵-C₅H₅)(CO)₂M≡EMe]中，硅亚烷基和锗亚烷基配合物的静电相互作用贡献ΔE(elstat)和共价键贡献ΔE(orb)的值几乎相同，而对于锡亚烷基和铅亚烷基配合物，静电相互作用ΔE(elstat)大于轨道相互作用ΔE(orb)。共价键具有高度的π特征。化合物[(η⁵-C₅H₅)(CO)₃M-EMe]中的总相互作用能ΔE(int)比配合物[(η⁵-C₅H₅)(CO)₂M≡EMe]中的吸引力小。M-ER键的共价键程度（34.9 - 44.9%）比M≡EMe键（42.1 - 50.2%）略低。发现两类化合物在a''（π）键程度上有显著差异。ΔE(π)对共价项ΔE(orb)的贡献在M≡EMe键（41.6 - 42.6%）中比在M-EMe键（17.1 - 20.4%）中高得多。虽然[(η⁵-C₅H₅)(CO)₃M-EMe]中的π键贡献比[(η⁵-C₅H₅)(CO)₂M≡EMe]中的弱，但前一类化合物中的σ键贡献比后一类中的强。
