Caesium dodecaborate

Caesium dodecaborate

Names
IUPAC name Caesium dodecaborate
Identifiers
CAS Number	12008-75-2^Y
3D model (JSmol)	Interactive image
EC Number	601-668-1
PubChem CID	71306871
InChI InChI=1S/B12H12.2Cs/c1-3-5-7-9-11-12-10-8-6-4-2;;/h1-12H;;/q+2;2*-1 Key: WMUPFLCRVFMECH-UHFFFAOYSA-N
SMILES [Cs+].[Cs+].[BH]1234[BH]567[BH]189[BH]2%10%11[BH]8%12%13[BH]%10%14%15[BH]%16%17%18[BH]35([BH]6%16%19[BH]%12%14%17[BH-]79%13%19)[BH-]4%11%15%18
Properties
Chemical formula	B12H12Cs2
Molar mass	407.63 g·mol^−1
Appearance	Colourless solid
Melting point	>650 °C
Solubility in water	low
Solubility	good in ethers
Hazards
Occupational safety and health (OHS/OSH):
Main hazards	flammable
GHS labelling:
Signal word	Danger
Hazard statements	H228, H315, H319, H335
Precautionary statements	P101, P102, P103, P210, P231+P232, P280, P403+P233, P501
Related compounds
Structure
Point group	Ih
Dipole moment	0 D
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y verify (what is ^YN ?) Infobox references

Caesium dodecaborate is an inorganic compound with the formula Cs₂B₁₂H₁₂. It is a salt composed of caesium and dodecaborate(12) ions. The [B₁₂H₁₂]²⁻ anion has been of great theoretical interest to the chemistry community.^[1]

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.^[2] Many other salts are known.^[3]

Preparation

The dodecaborate anion was first prepared in modest yield by Pitochelli and Hawthorne from iododecarborane.^[4] 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:

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.^[5]

Reactions and proposed applications

Salts of B₁₂H₁₂²⁻ have been investigated for boron neutron capture therapy and as fuels for airbags.^[6]

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.

See also

• Neutron capture therapy of cancer

References

1. Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
2. 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.
3. 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.
4. Anthony R. Pitochelli, Frederick M. Hawthorne "The Isolation of Icosahedral B₁₂H₁₂²⁻ Ion" J. Am. Chem. Soc. 1960, volume 82, pp 3228–3229. doi:10.1021/ja01497a069
5. H. C. Miller, E. L. Muetterties "Borane Anions" Inorganic Syntheses, 1967, Volume 10, pp. 81-91. doi:10.1002/9780470132418.ch16
6. 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.