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采用EHMO法计算了Cp_2ZrX_2(Cp:环戊二烯基;X:F,CI,I)的分子轨道能量组成并计算了这类络合物在可见-紫外光区的电子跃迁.为了检验我们的计算结果,测定了Cp_2ZrCl_2在可见-紫外光区的吸收光谱.计算结果如下:(1)三种络合物的能级图都非常相似,HOMO都是10b_2,LUMO都是13_(α1).能级差按F,Cl,I的顺序减少,分别为1.51,1.47和1.37eV.(2)能量最低的一组空轨道主要是由Zr的d轨道组成,它们的能量都和Zr的d轨道能量接近.在填满轨道中,没有以Zr的d轨道为主体的分子轨道,这一点与通常认为这类络合物是d~0体系的看法一致.卤素配位体的改变对能级高低和轨道组成有一定影响.(3)随卤素配位体的改变,Zr原子上的正电荷和卤素配位体上的负电荷,按F,Cl,I的顺序减少,而两个环戊二烯配位体上的负电荷则变化不大.(4)计算了这类络合物在可见-紫外光区的电子跃迁,发现在可见光区有一个吸收带,在紫外光区有三个吸收带.对产生这些谱带的跃迁性质进行了探讨.(5)实验测定了Cp_2ZrCl_2在四氢呋喃溶剂中的紫外吸收光谱,得到三个吸收带.计算结果与实验数据十分符合.
The molecular orbital energies of Cp_2ZrX_2 (Cp: cyclopentadienyl group; X: F, CI, I) were calculated by EHMO method and the electronic transitions of these complexes in the visible-ultraviolet region were calculated. The calculated results are as follows: The absorption spectra of Cp_2ZrCl_2 in the visible-UV region are obtained. The calculated results are as follows: (1) The energy levels of the three complexes are very similar, HOMO is 10b_2 and LUMO is 13_ (α1) The order of difference decreases in the order of F, Cl and I, which are 1.51, 1.47 and 1.37eV, respectively. (2) A group of empty orbits with the lowest energies are mainly composed of Zr d orbitals whose energies are close to those of Zr d orbital In the filled orbit, there is no molecular orbitals dominated by Zr d orbitals, which is consistent with the notion that such complexes are generally believed to be in the d 0 system. (3) With the change of the halogen ligand, the positive charge on the Zr atom and the negative charge on the halogen ligand decrease in the order of F, Cl and I, and the two cyclopentadienyl (4) The electronic transition of these complexes in the visible-UV region was calculated and found to have an absorption band in the visible region An outer zone has three absorption bands. These bands produced on transition probabilities are discussed. (5) experiment measured in tetrahydrofuran solvent Cp_2ZrCl_2 ultraviolet absorption spectrum, absorption bands obtained three calculated result is in line with the experimental data.