An Isolable Bisma­benzene: Synthesis, Structure, and Reactivity

A stable bisma­benzene
was synthesized, isolated, and structurally
characterized. The prospective aromaticity of this heavy benzene,
bearing a sixth-row element, was examined by X-ray crystallography
and NMR and UV–vis spectroscopy, as well as theoretical DFT
calculations. Structural analysis of this bisma­benzene revealed
a planar ring containing unsaturated Bi–C and C–C bonds.
As bond alternations could not be observed, these results are consistent
with the formal criteria of aromaticity. Theoretical calculations
also support the aromatic nature of this bisma­benzene, which
reacted with an alkyne to form the corresponding [4+2] cycloadduct,
thus demonstrating a small yet tangible aromatic stabilization energy.

本研究合成、分离并表征了一种稳定的铋苯（bismabenzene）。针对该含第六周期元素的重苯类化合物的潜在芳香性，研究人员通过X射线晶体学、核磁共振（NMR）波谱、紫外-可见（UV–vis）分光光度法，以及密度泛函理论（Density Functional Theory）计算开展了系统考察。对该铋苯的结构分析显示，其环骨架呈平面构型，包含不饱和的铋-碳（Bi–C）与碳-碳（C–C）键。由于未观察到键长交替现象，上述结果符合芳香性的正式判定标准。理论计算同样支持该铋苯的芳香性本质；该化合物可与炔烃反应生成相应的[4+2]环加合物，由此证明其具备虽微小却切实可测的芳香稳定化能。