过渡金属双核化合物Cr_2(O_2CH)_4、Mo_2(O_2CH)_4及CrMo(O_2CH)_4的从头计算研究

Ab initio Study on Transition Metal Binuclear Complexes MM' (O_2CH)_4(M,M' = Cr, Mo)

用从头计算方法研究双核过渡金属化合物Cr_2(O_2CH)_4、MO_2(O_2CH)_4及CrMo(O_2CH)_4的金属—金属多重键性质,计算优化键长与实验值符合很好,原子布居表明Mo_2(O_2CH)_4和CrMo(O_2CH)_4中Mo—Mo、Cr—Mo键分别为σ~2π~4δ~2与σ~2δ~2π~4四重键,同时金属-d与氧和碳-p电子间的电荷重叠对分子稳定有相当贡献。对Cr_2(O_2CH)_4在优化键长下3种组态σ~2δ~2δ^(*2)σ^(*2)、π~4π^(*4)及σ~2δ~2π~4的电子结构、原子布居、总能量及电离能的计算进行比较,讨论了Cr—Cr的成键性质,指出描述Cr—Cr间金属多重键本质必须考虑电子相关效应的影响。

In this paper, the ab initio calculations are performed on the metal-metal multiple bonds of the binuclear transition metal complexes MM'(O2CH)4, namely, Cr2(O2CH)4, Mo2(O2CH)4 and CrMo(O2CH)4. The optimized bond lengthes are in good agreement with the experimental values. The calculated results indicate that the Mo-Mo and Cr-Mo bonds are quadruple bonds which correspond to the configurations σ2π4δ2 and σ2δ2π4 in Mo2(O2CH)4 and CrMo(O2CH)4, respectively. For Cr2(O2CH)4, the bonding property of Cr-Cr bond is explored by comparing the calculated results of three configurations . It is shown that a more rigorous theoretical calculation is needed in order to correctly describe the Cr-Cr multiple bonding essence.