A stable tetranuclear boron dication with a rhomboid B4 skeleton has been formed by B–B coupling between two diborane cations. In the course of this unusual reaction — which is not feasible for the isolobal ethyl cation analogues — two electron-precise B–B bonds are converted into two B–B–B three-centre bonds.
- Sebastian Litters
- Elisabeth Kaifer
- Hans-Jörg Himmel