BH6+: Revisiting borohydride cation with negatively charged boron and its possible implications for hydrogen storage

Boron is usually an electropositive element and its hydrides are known for unusual bonding with excellent hydrogen storage capacity. In this paper, we reinvestigated a borohydride cation, BH6+ using the state-of-the-art DFT and ab initio methods. We noticed that its global minimum structure has two covalent 2c-2e bonds and two polar 3c-2e bonds as revealed by the QTAIM analysis. It has indeed negatively charged boron as verified by various population schemes. ADMP simulation-based trajectory analysis of BH6+ for 40 ps confirmed that this cation is kinetically stable over a wide range of temperatures from 100 to 500 K. The superatomic feature of the BH6+ cluster has also been revealed. We also notice that the addition of electrons to BH6+ leads to its dehydrogenation. This may implicate its possible application in high-capacity hydrogen storage.