Polyhalogenated Decaborate and 1-Ammoniododecaborate Ions: An Improved Synthesis with Elemental Halogens, and Physicochemical and Chemical Properties

Currently, the whole area of polyhalogenated polyhedral anions is undergoing a renaissance due to their high stability, the kinetic inertness of the cage B-X (X = F, Cl, Br, I) bonds and facile tuning of the physicochemical properties (stability, polarity, lipophilicity, pK(a), solubility, electrochemical potentials, etc.). Herein, we report on specific procedures that facilitate the polyhalogenation of basic 10- and 12-vertex borate anions. Newly improved preparative methods for the perhalogenation of the [B10H10](2-) ion in aqueous solution that easily and almost quantitatively produce [B10X10](2-) species (X = Cl, Br, I) have been developed using elemental halogens in a glass pressure vessel. Moreover, attention has also been paid to similar reactions leading to derivatives with mixed substitutions with heavier halogens and an ammonium group, that is, to the series of [1-NH3B12X11](-) (X = Cl, Br, I). The X-ray structure of the [1-NH3B12I11](-) derivative is presented and the spectral, electrochemical and physicochemical properties of these polyhalogenated systems are outlined along with specific insights into the properties of the -NH3 group and its substitution chemistry.