Cages such as fullerenes, as well as similar saturated species such as hydrogenated fullerenes (fulleranes) or edge-fused oligoadamantanes (diamondoids) are interesting subjects in nanochemistry. Much less is known about analogues of these compounds with the heavier silicon instead of carbon. There are, e.g., no examples of silicon-based fullerene analogues in the condensed phase. Saturated silafulleranes such as siladodecahedrane (Si₂₀H₂₀) could be more stable, and thus, promising targets for synthesis.

Stefan Grimme, University of Bonn, Germany, Matthias Wagner, University of Frankfurt am Main, Germany, and colleagues have synthesized siladodecahedrane with an encapsulated chloride ion, [Cl@Si₂₀H₂₀]⁻ (pictured). The team started from [ⁿBu₄N][Cl@Si₃₂Cl₄₄], which contains a Si₂₀ dodecahedron. This precursor was desilylated via a reaction with pinacol to give [Cl@Si₂₀H₁₂Cl₈]⁻. Then, a hydrogenation reaction with ⁱBu₂AlH gave the desired siladodecahedrane.

The team found that [Cl@Si₂₀H₂₀]⁻ can be perchlorinated by treating it with CDCl₃ to give [Cl@Si₂₀Cl₂₀]⁻. They characterized both of these compounds using X-ray diffraction, mass spectrometry (MS), as well as ¹H, ²⁹Si, and ³⁵Cl NMR spectroscopy and confirmed their highly symmetric structures.

• [Cl@Si₂₀H₂₀]⁻: Parent Siladodecahedrane with Endohedral Chloride Ion,
  Marcel Bamberg, Markus Bursch, Andreas Hansen, Matthias Brandl, Gabriele Sentis, Lukas Kunze, Michael Bolte, Hans-Wolfram Lerner, Stefan Grimme, Matthias Wagner,
  J. Am. Chem. Soc. 2021.
  https://doi.org/10.1021/jacs.1c05598