Gas-phase ion chemistry of [B12X12]2-(X = F, Cl, Br, I, CN). A brief review of twelve years of researching twelve-vertexed dianions and their fragments

The closo-dodecaborate dianions [B12X12]2- (X = halogen, CN) have been recognized in recent years for their outstanding physical and chemical properties. Gas-phase ion chemistry and spectroscopy have contributed to the understanding and further development of their record stability, which is applied to stabilize highly reactive cations. Fragment ions generated by collision induced dissociation provide access to a large variety of boronbased structures previously not available in the condensed phase and have challenged common chemical concepts (e.g., the discovery of "superelectrophilic anions"). This has opened new avenues for noble gas chemistry and direct functionalization of alkyl groups with covalently bound "charge tags". Furthermore, the interactions with neutral molecules in the gas phase, e.g., host-guest chemistry, complements the fundamental understanding of solvation effects in solution and association with large neutral molecules, which is highly relevant for the biochemical applications of these compounds. Future perspectives, in particular the special role of these ions and their fragments in preparative mass spectrometry, are discussed.