Caesium dodecaborate

Caesium dodecaborate
IUPAC name Caesium dodecaborate
Properties
Molar mass	407.61.21 g/mol
Appearance	Colourless solid
Melting point	>650 °C
Solubility in water	low
Solubility	good in ethers
Hazards
Main hazards	flammable
Related compounds
Y dodecaborate (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Caesium dodecaborate is an inorganic compound with the formula Cs₂B₁₂H₁₂. It is a salt, with caesium cations and [B₁₂H₁₂]²⁻ anions.

Structure

The [B₁₂H₁₂]²⁻ anion's B₁₂ core is a regular icosahedron. The [B₁₂H₁₂]²⁻ as a whole also has icosahedral molecular symmetry, and it belongs to the molecular point group I_h. Its icosahedral shape is consistent with the classification of this cage as "closo" in polyhedral skeletal electron pair theory.

Crystals of Cs₂B₁₂H₁₂ feature Cs⁺ ions in contact with twelve hydrides provided by four B₁₂H₁₂²⁻. The B-B bond distances are 178 pm, and the B-H distances are 112 pm.^[1] Many other salts are known.^[2]

Preparation

It is prepared in two steps from sodium borohydride. First the borohydride is converted into a triborate anion using the etherate of boron trifluoride:

4 NaBH₄ + BF₃ → NaB₃H₈ + 3 NaF + 4 H₂

Pyrolysis of the triborate gives the twelve boron cluster as the sodium salt, which is then treated with caesium hydroxide to precipitate Cs₂B₁₂H₁₂.

Applications

Salts of B₁₂H₁₂^2– have been investigated for boron neutron capture therapy and as fuels for airbags.^[3]

Salts of B₁₂H₁₂²⁻ are precursors to related derivatives including B₁₂(OH)₁₂²⁻ and B₁₂(CH₃)₁₂²⁻. This closo boron hydride resists degradation more so than the isoelectronic carboranes.

References

1. ^ Tiritiris, Ioannis; Schleid, Thomas; Müller, Klaus; Preetz, Wilhelm (2000). "Strukturelle Untersuchungen an Cs₂[B₁₂H₁₂]". Zeitschrift für anorganische und allgemeine Chemie 626 (2): 323–325. doi:10.1002/(SICI)1521-3749(200002)626:2<323::AID-ZAAC323>3.0.CO;2-Q. 
2. ^ Tiritiris, Ioannis; Van, Nguyen-Duc; Schleid, Thomas (2004). "Synthesis and Crystal Structure of [Ni(H₂O)₆][B₁₂H₁₂]·6 H₂O". Zeitschrift für anorganische und allgemeine Chemie 630 (11): 1763. doi:10.1002/zaac.200470138. 
3. ^ Sivaev, Igor B.; Bregadze, Vladimir I.; Sjöberg, Stefan (2002). "Chemistry of closo-Dodecaborate Anion [B₁₂H₁₂]^2–: A Review". Collection of Czechoslovak Chemical Communications 67 (6): 679. doi:10.1135/cccc20020679.