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.