Ortho-Carborane
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| Names | |
|---|---|
| Other names
1,2-Dicarbadodecaborane(12)
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| Identifiers | |
| ECHA InfoCard | 100.037.164 |
CompTox Dashboard (EPA)
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| Properties | |
| C2H12B10 | |
| Molar mass | 144.22 g·mol−1 |
| Appearance | colorless solid |
| Melting point | 320 °C (608 °F; 593 K) |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Ortho-carborane is the organoboron compound with the formula C2B10H12. The prefix orthois derived from ortho. It is the most prominent carborane. This derivative has been considered for a wide range of applications from heat-resistant polymers to medical applications. It is a colorless solid that melts, without decomposition, at 320 °C.
Preparation
The preparation of closo-dicarbadodecaboranes was reported independently by groups at Olin Corporation and the Reaction Motors Division of Thiokol Chemical Corporation working under the U.S. Air Force and published in 1963.These groups demonstrated the high stability in air of 1,2-closo-dodecaborane and related compounds, presented a general synthesis, described the transformation of substituents without destroying the carborane cluster, and demonstrated the ortho to meta isomerization.[1] The cluster has C2v symmetry.[2]
Preparation
The 1,2- isomer (aka ortho-dicarbadodecaborane) can be produced in a two-step process from decaborane:
- nido-B10H14 + 2SEt2 → B10H12(SEt2)2 + H2
- B10H12(SEt2)2 + C2H2→ closo-1,2-C2B10H12 +2SEt2 + H2
Reactions
Upon heating to 420 °C, it rearranges to form the meta isomer. The para- isomer is produced by heating to temperatures above 600 °C.
Base degradation of ortho carborane gives dianionic 11-vertex derivative. This degradation occurs for all three isomeric dicarbadecaboranes, but the ortho derivative has been most heavily studied. The reaction is conducted in two-steps, first "decapitation" and second deprotonation:[3]
- C2B10H12 + NaOEt + 2 EtOH → Na+C2B9H12- + H2 + B(OEt)3
- Na+C2B9H12- + NaH → (Na+)2C2B8H112- + H2
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The use of dicarbollides (C2B8H112-) as ligands was developed by M. Frederick Hawthorne and co-workers.[4] The dianion forms sandwich compounds, bis(dicarbollides). Dicarbollides, being strong electron donors, stabilize higher oxidation states, e.g. Ni(IV).
ortho-Carborane can be converted to highly reactive carborynes with the formula B10C2H10.
See also
References
- ^ Heying, T. L.; Ager, J. W.; Clark, S. L.; Mangold, D. J.; Goldstein, H. L.; Hillman, M.; Polak, R. J.; Szymanski, J. W. (1963). "A New Series of Organoboranes. I. Carboranes from the Reaction of Decaborane with Acetylenic Compounds". Inorganic Chemistry. 2 (6): 1089–1092. doi:10.1021/ic50010a002.
- ^ "Definitive crystal structures of ortho-, meta- and para-carboranes: supramolecular structures directed solely by C–H⋯O hydrogen bonding to hmpa (hmpa = hexamethylphosphoramide)". Chem. Commun.: 2285–2286. 1996. doi:10.1039/CC9960002285.
{{cite journal}}: Unknown parameter|authors=ignored (help) - ^ Plešek, J.; Heřmánek, S.; Štíbr, B. (1983). "Potassium dodecahydro-7,8-dicarba-nido-undecaborate(1-), k[7,8-C2B9H12], intermediates, stock solution, and anhydrous salt". Inorganic Syntheses. 22: 231–234. doi:10.1002/9780470132531.ch53.
- ^ Hawthorne, M. F.; Young, D. C.; Wegner, P. A. (1965). "Carbametallic Boron Hydride Derivatives. I. Apparent Analogs of Ferrocene and Ferricinium Ion". Journal of the American Chemical Society. 87 (8): 1818–1819. doi:10.1021/ja01086a053.