多中心d-pπ键与高氧化态钼簇合物的几何构型——(Ⅰ)“碎片结构”模型及分子轨道研究

本文通过对不同构型的二核钼簇合物簇胳结构的分子轨道计算,揭示了Mo—B(T)原子间的多中心d-p π键与该结构的稳定性及结构参数α、θ和R之间的内在联系,提出了2～6核高氧化态钼簇合物的簇胳由“碎片结构”组合而成的设想,该模型对以μ_2-S_2为桥的三核钼簇合物中的“共面—异面”规则和簇胳为Mo_4S_3O]~(6+)的钼簇中的反常Mo—Mo键距给出合理解释,确认了桥原子对Mo—Mo键长和键强的决定作用。

The Multiple Center d-p π Bond and the Configuration of Molybdenum Cluster Compounds in Higher Oxidation States (Ⅰ) "Fragmental Structer" Model and Research of Molecular Orbital

In this paper,the internal relations between the multiple centre d-p π bonding of the Mo -B(T)atoms and the structural stability, as well as the structural parameters a, θ and R have been revealed,and a block-building conception from the "fragmental structure" for the cluster skeleton of 2-6 nuclear Mo clusters in higher oxidation states has been elucidated by the MO calculation ofthe cluster skeleton with various bridging atoms and α,θ values.Based on the model, several reasonable interpretations have been given for the "in- and out- of plane" rule in the trinuclear Mo clusters with μ2-S2 and the anomalous bond length (Mo-Mo) of some clusters with a core Mo4S3O]6+. It is confirmed that the indirect bonding through bridge atoms is the primary influence factor for the R(Mo-Mo) and Mo-Mo bond strength.