Molecular Rods Combining o‑Carborane and Bicyclo[1.1.1]pentane Cages: An Insertion of the Triple Bond Located Next to a Highly Strained Cage

Octacarbonyl dicobalt and bis­(dimethyl sulfide)­decaborane B₁₀H₁₂(Me₂S)₂ were successfully added to 1,3-diethynylbicyclo[1.1.1]­pentane in good yields. This is an interesting example of a cycloaddition reaction achieved next to the bicyclopentane cage that tends to rearrange in many other cases. It proves that both reagents attack the triple bond in a more or less concerted manner that prevents the rearrangement. Products of the latter reaction are of a particular interest because the bicyclopentane and o-carborane cages are immediately linked in their rodlike structures. The new kind of molecular rotors was thus constructed. ¹H and ¹³C nuclear magnetic resonance spectra in solution reveal an averaged rotational symmetry of the molecules with a well-defined geometry that has been confirmed by X-ray structural analysis in several examples.