Caesium dodecaborate is an inorganic compound with the formula Cs<sub>2</sub>B<sub>12</sub>H<sub>12</sub>. It is a salt composed of caesium and dodecaborate(12) ions. The [B<sub>12</sub>H<sub>12</sub>]<sup>2âÂÂ</sup> anion has been of great theoretical interest to the chemistry community.
The [B<sub>12</sub>H<sub>12</sub>]<sup>2âÂÂ</sup> anion's B<sub>12</sub> core is a regular icosahedron. The [B<sub>12</sub>H<sub>12</sub>]<sup>2âÂÂ</sup> as a whole also has icosahedral molecular symmetry, and it belongs to the molecular point group I<sub>h</sub>. Its icosahedral shape is consistent with the classification of this cage as "closo" in polyhedral skeletal electron pair theory.
Crystals of Cs<sub>2</sub>B<sub>12</sub>H<sub>12</sub> feature Cs<sup>+</sup> ions in contact with twelve hydrides provided by four B<sub>12</sub>H<sub>12</sub><sup>2âÂÂ</sup>. The B-B bond distances are 178 pm, and the B-H distances are 112 pm. Many other salts are known.
The dodecaborate anion was first prepared in modest yield by Pitochelli and Hawthorne from iododecarborane. It is more conventienly prepared in two steps from sodium borohydride. First the borohydride is converted into a triborate anion using the etherate of boron trifluoride:
Pyrolysis of the triborate gives the twelve boron cluster as the sodium salt, which is then treated with caesium hydroxide to precipitate Cs<sub>2</sub>B<sub>12</sub>H<sub>12</sub>.
Salts of B<sub>12</sub>H<sub>12</sub><sup>2âÂÂ</sup> have been investigated for boron neutron capture therapy and as fuels for airbags.
Salts of B<sub>12</sub>H<sub>12</sub><sup>2âÂÂ</sup> are precursors to related derivatives including B<sub>12</sub>(OH)<sub>12</sub><sup>2âÂÂ</sup> and B<sub>12</sub>(CH<sub>3</sub>)<sub>12</sub><sup>2âÂÂ</sup>. This closo boron hydride resists degradation more so than the isoelectronic carboranes.