The Telluraboranes closo-TeB5Cl5 and closo-TeB11Cl11 with Exceptionally Long Body Diagonals: Synthetic and Bonding Motifs for Innovative Octahedral and Icosahedral Geometries

Six-vertex closo-TeB₅Cl₅ ( 1 ) and twelve-vertex closo-TeB₁₁Cl₁₁ ( 2 ) telluraboranes have been prepared via co-pyrolysis of B₂Cl₄ with TeCl₄ in vacuo at temperatures between 360 °C and 400 °C. Both compounds are sublimable, off-white solids, and they have been characterized by one- and two-dimensional ¹¹B NMR and high-resolution mass spectroscopy. Both ab initio/GIAO/NMR and DFT/ZORA/NMR computations support octahedral and icosahedral geometries for 1 and 2 , respectively, as expected due to their closo-electron counts. The octahedral structure of 1 has been confirmed by single-crystal X-ray diffraction on an incommensurately modulated crystal. The corresponding bonding properties have been analyzed in terms of the intrinsic bond orbital (IBO) approach. 1 is the first example of a polyhedral telluraborane with a cluster size smaller than 10 vertices.