稀土夹心化合物的SCF-X_α-SW研究 Ⅰ.Cp_2Sm、Cp_2Yb和Cp_3Sm

SCF-X_α-SW Calculations on Lanthanide Metallocenes Ⅰ. Cp_2Sm, Cp_2Yb and Cp_3Sm

对Cp_2Sm、Cp_2Yb和Cp_3Sm进行了非相对论和相对论SCF-X_α-SW计算,用轨道相互作用、分子轨道图形、布居数分析等方法讨论了化学键图象。在Cp_2Ln(Ln=稀土元素)中以Cp为主要成分的轨道能级两种方案结果变化不大。而相对论间接效应的存在,使Ln4f能级明显升高,与Cp_2Ln易被氧化的实验结果一致。二价的Cp_2Ln成键轨道中Ln成分是d>f>p>s,与三价的Cp_3Sm、LnF_3比较,Ln的s、p、d成分变化不大,而Lnf成分明显减少,使Cp_2Ln共价性明显地低于Cp_3Sm和LnF_3。

SCF-X_a-SW ealculations are carried out on Cp_2Sm, Cp_2Yb and Cp_3Sm, both of the nonrelativistic and relativistic schemes have been tried. The bonding pictures are discussed from interaetions of the orbitals, the orbital maps and the populations. In Cp_2Ln (Ln=Lanthanide) there are little differences in the levels of which orbitals involve dominantly Cp components between the two schemes, but due to relativistic indirect effect, Ln 4f level rises up notably, which is consistent with the experimental results that Cp_2Ln is easily oxidized. Ln orbital components for the bonding orbitals of Cp_2Ln are in the order d>f>p>s, those of Cp_3Ln are f>d>p>s. Comparing each other, s, p and d components almost vary a little bit but f one decreases obviously in Cp_2Ln. So the covalent bonding strength of Cp_2Ln is evidently weaker than those of Cp_3Sm and LnF_3.