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.