Dodecaborate

Dodecaborate

Names
Other names Dodecahydrododecaborate(2-) Dodecahydro-closo-dodecaborate(2−)
Identifiers
CAS Number	12356-13-7  Y
3D model (JSmol)	Interactive image Interactive image
ChEBI	CHEBI:33594
Gmelin Reference	3407
InChI InChI=1S/B12H12/c1-2-3(1)5(1)6(1)4(1,2)8(2)7(2,3)9(3,5)11(5,6)10(4,6,8)12(7,8,9)11/h1-12H/q-2 Key: CHOGGIOVKODKET-UHFFFAOYSA-N
SMILES [BH-]1234[BH]5%12%13[BH]1%10%11[BH]289[BH]367[BH]145[BH]6%14%15[BH]78%16[BH]9%10%17[BH]%11%12%18[BH]1%13%14[BH-]%15%16%17%18 [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	B12H2−12
Molar mass	141.9504 g/mol
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

The dodecaborate(12) anion, [B₁₂H₁₂]²⁻, is a boron hydride cluster anion. It forms a variety of colorless salts with alkali metal and quaternary ammonium cations. The cluster has a distinctive icosahedral structure with 12 boron atoms at the vertices, each boron atom is attached to a hydrogen atom. Its symmetry is classified by the molecular point group I_h.

Synthesis and reactions

The existence of the dodecaborate(12) anion, [B₁₂H₁₂]²⁻, was predicted by H. C. Longuet-Higgins and M. de V. Roberts in 1955. ^[1] Hawthorne and Pitochelli first made it 5 years later, by the reaction of 2-iododecaborane with triethylamine in benzene solution at 80 °C. ^[2] It is more conveniently prepared in two steps from sodium borohydride. First the borohydride is converted into a triborate anion using the etherate of boron trifluoride:

5 NaBH₄ + BF₃ → 2 NaB₃H₈ + 3 NaF + 2 H₂

Pyrolysis of the triborate gives the twelve-boron cluster as the sodium salt. ^[3] A variety of other synthetic methods have been published.

Salts of the dodecaborate ion are stable in air and do not react with hot aqueous sodium hydroxide or hydrochloric acid. The anion can be electrochemically oxidised to [B₂₄H₂₃]³⁻. ^[4]

Substituted derivatives

Salts of B
_¹²H²⁻
₁₂ undergo hydroxylation with hydrogen peroxide to give salts of [B₁₂(OH)₁₂]²⁻. ^[5] The hydrogen atoms in the ion [B₁₂H₁₂]²⁻ can be replaced by the halogens with various degrees of substitution. The following numbering scheme is used to identify the products. The first boron atom is numbered 1, then the closest ring of five atoms around it is numbered anticlockwise from 2 to 6. The next ring of boron atoms is started from 7 for the atoms closest to number 2 and 3, and counts anticlockwise to 11. The atom opposite the original is numbered 12. A related derivative is [B₁₂(CH₃)₁₂]²⁻. The icosahedron of boron atoms is aromatic in nature.^{[ citation needed ]}

Under kilobar pressure of carbon monoxide [B₁₂H₁₂]²⁻ reacts to form the carbonyl derivatives [B₁₂H₁₁CO]⁻ and the 1,12- and 1,7-isomers of B₁₂H₁₀(CO)₂. The para disubstitution at the 1,12 is unusual. In water the dicarbonyls appear to form carboxylic ions: [B₁₂H₁₀(CO)CO₂H]⁻ and [B₁₂H₁₀(CO₂H)₂]²⁻.^{[ citation needed ]}

A perfluoroborane derivative (with the hydrogen atoms replaced by fluorine atoms) is also known. ^[6]

Proposed applications

Compounds based on the ion [B₁₂H₁₂]²⁻ have been evaluated for solvent extraction of the radioactive ions ¹⁵²Eu³⁺ and ²⁴¹Am³⁺. ^[7]

[B₁₂H₁₂]²⁻, [B₁₂(OH)₁₂]²⁻ and [B₁₂(OMe)₁₂]²⁻ was investigated for use in drug delivery. ^[8]

Salts of [B₁₂H₁₂]²⁻ have been proposed for use in boron neutron capture therapy. The closo-dodecaborate increase the specificity of neutron irradiation treatment. Neutron irradiation of boron-10 leads to the emission of an alpha particle near the tumor. ^[9]

References

1. Longuet-Higgins, Hugh Christopher; Roberts, M. de V. (June 1955). "The electronic structure of an icosahedron of boron atoms". Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences. 230 (1180): 110–119. Bibcode:1955RSPSA.230..110L. doi:10.1098/rspa.1955.0115. S2CID   98533477.
2. Pitochelli, Anthony R.; Hawthorne, Frederick M. (June 1960). "The Isolation of Icosahedral B
   _¹²H²⁻
   ₁₂ Ion". Journal of the American Chemical Society. 82 (12): 3228–3229. doi:10.1021/ja01497a069.
3. Miller, H. C.; Muetterties, E. L.; Boone, J. L.; Garrett, P.; Hawthorne, M. F. (2007). "Borane Anions". Inorganic Syntheses. pp. 81–91. doi:10.1002/9780470132418.ch16. ISBN   978-0-470-13241-8.
4. 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): 679–727. doi:10.1135/cccc20020679.
5. Clayton, Joshua R.; King, Benjamin T.; Zharov, Ilya; Fete, Matthew G.; Volkis, Victoria; Douvris, Christos; et al. (2010). "Boron Cluster Compounds". In Rauchfuss, Thomas B. (ed.). Inorganic Syntheses. Vol. 35. pp. 56–66. doi:10.1002/9780470651568.ch2. ISBN   9780471682554.
6. Shackelford, Scott A.; Belletire, John L.; Boatz, Jerry A.; Schneider, Stefan; Wheaton, Amanda K.; Wight, Brett A.; et al. (18 June 2010). "Bridged Heterocyclium Dicationic closo- Icosahedral Perfluoroborane, Borane, and Carborane Salts via Aqueous, Open-Air Benchtop Synthesis" . Organic Letters. 12 (12): 2714–2717. doi:10.1021/ol100752y. ISSN   1523-7060. PMID   20499850.
7. Bernard, R.; Cornu, D.; Grüner, B.; Dozol, J.-F.; Miele, P.; Bonnetot, B. (September 2002). "Synthesis of [B₁₂H₁₂]^2– based extractants and their application for the treatment of nuclear wastes". Journal of Organometallic Chemistry. 657 (1–2): 83–90. doi:10.1016/S0022-328X(02)01540-1.
8. Axtell, J. C. (2018). "Synthesis and Applications of Perfunctionalized Boron Clusters". Inorganic Chemistry. 57 (5): 2333–2350. doi:10.1021/acs.inorgchem.7b02912. PMC   5985200 . PMID   29465227.
9. Tachikawa, Shoji; Miyoshi, Tatsuro; Koganei, Hayato; El-Zaria, Mohamed E.; Vinas, Clara; Suzuki, Minoru; et al. (2014). "Spermidinium closo-dodecaborate-encapsulating liposomes as efficient boron delivery vehicles for neutron capture therapy". Chemical Communications. 50 (82): 12325–12328. doi: 10.1039/c4cc04344h . PMID   25182569.