A Trigonal-Prismatic Hexanuclear Technetium(II) Bromide Cluster: Solid-State Synthesis and Crystallographic and Electronic Structure

The
compound Na­{[Tc6Br12]2Br} has been
obtained from the decomposition of TcBr4 under vacuum in
a Pyrex ampule at 450 °C. The stoichiometry of the compound has
been confirmed by energy-dispersive X-ray spectroscopy and its structure
determined by single-crystal X-ray diffraction. The compound contains
a trigonal-prismatic hexanuclear [Tc6Br12] cluster.
The cluster is composed of two triangular Tc3Br6 units linked by multiple Tc–Tc bonds. In the Tc3Br6 unit, the average Tc–Tc distance [2.6845(5)
Å] is characteristic of Tc–Tc single bonds, while the
average Tc–Tc distance between the two triangular units [2.1735(5)
Å] is characteristic of TcTc triple bonds. The electronic
structure of the [Tc6Br12] cluster was studied
by first-principles calculations, which confirm the presence of single
and triple Tc–Tc bonds in the cluster.

化合物Na{[Tc₆Br₁₂]₂Br}通过在450℃真空条件下于派热克斯（Pyrex）玻璃安瓿中分解TcBr₄制得。该化合物的化学计量比通过能量色散X射线能谱（energy-dispersive X-ray spectroscopy）得以确认，其晶体结构通过单晶X射线衍射法解析。该化合物包含一个三角棱柱形六核[Tc₆Br₁₂]团簇。
该团簇由两个三角形Tc₃Br₆结构单元通过多重Tc-Tc键连接而成。在Tc₃Br₆结构单元中，Tc-Tc键的平均键长为2.6845(5) Å，与Tc-Tc单键的键长特征一致；而两个三角形结构单元之间的Tc-Tc平均键长为2.1735(5) Å，其数值符合Tc≡Tc三键的特征。
通过第一性原理计算对[Tc₆Br₁₂]团簇的电子结构开展了研究，结果证实该团簇中同时存在Tc-Tc单键与三键。