Decaborane

Decaborane, also called decaborane(14), is the borane with the chemical formula B10H14. This white crystalline compound is one of the principal boron hydride clusters, both as a reference structure and as a precursor to other boron hydrides. It is toxic and volatile, with a foul smelling odor.[3]

Decaborane
Names
Other names
decaborane
decaboron tetradecahydride
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.037.904
EC Number
  • 241-711-8
UNII
Properties
B10H14
Molar mass 122.22 g/mol
Appearance White crystals
Odor bitter, chocolate-like[1]
Density 0.94 g/cm3[1]
Melting point 97–98 °C (207–208 °F; 370–371 K)
Boiling point 213 °C (415 °F; 486 K)
Solubility in other solvents Slightly, in cold water.
Vapor pressure 0.2 mmHg[1]
Hazards
Main hazards may ignite spontaneously on exposure to air[1]
GHS pictograms
GHS Signal word Danger
H228, H301, H310, H316, H320, H330, H335, H336, H370, H372
P210, P240, P241, P260, P261, P262, P264, P270, P271, P280, P284, P301+310, P302+350, P304+340, P305+351+338, P307+311, P310, P312, P314, P320, P321, P322, P330, P332+313, P337+313
NFPA 704 (fire diamond)
Flammability code 2: Must be moderately heated or exposed to relatively high ambient temperature before ignition can occur. Flash point between 38 and 93 °C (100 and 200 °F). E.g. diesel fuelHealth code 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasReactivity code 2: Undergoes violent chemical change at elevated temperatures and pressures, reacts violently with water, or may form explosive mixtures with water. E.g. white phosphorusSpecial hazard W: Reacts with water in an unusual or dangerous manner. E.g. sodium, sulfuric acid
2
3
2
Flash point 80 °C; 176 °F; 353 K
149 °C (300 °F; 422 K)
Lethal dose or concentration (LD, LC):
276 mg/m3 (rat, 4 hr)
72 mg/m3 (mouse, 4 hr)
144 mg/m3 (mouse, 4 hr)[2]
NIOSH (US health exposure limits):
PEL (Permissible)
 TWA 0.3 mg/m3 (0.05 ppm) [skin][1]
REL (Recommended)
 TWA 0.3 mg/m3 (0.05 ppm) ST 0.9 mg/m3 (0.15 ppm) [skin][1]
IDLH (Immediate danger)
 15 mg/m3[1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Handling, properties and structure

The physical characteristics of decaborane(14) resemble those of naphthalene and anthracene, all three of which are volatile colorless solids. Sublimation is the common method of purification. Decaborane is highly flammable, but, like other boron hydrides, it burns with a bright green flame. It is not sensitive to moist air, although it hydrolyzes in boiling water, releasing hydrogen and giving a solution of boric acid. It is soluble in cold water as well as a variety of non-polar and moderately polar solvents.[3]

In decaborane, the B10 framework resembles an incomplete octadecahedron. Each boron has one "radial" hydride, and four boron atoms near the open part of the cluster feature extra hydrides. In the language of cluster chemistry, the structure is classified as "nido".

Synthesis and reactions

It is commonly synthesized via the pyrolysis of smaller boron hydride clusters. For example, pyrolysis of B2H6 or B5H9 gives decaborane, with loss of H2.[4] On a laboratory scale, sodium borohydride is treated with boron trifluoride to give NaB11H14, which is acidified to release borane and hydrogen gas.[3]

It reacts with Lewis bases (L) such as CH3CN and Et2S, to form adducts:[5][6]

B10H14 + 2 L → B10H12L2 + H2

These species, which are classified as "arachno" clusters, in turn react with acetylene to give the "closo" ortho-carborane:

B10H12·2L + C2H2 → C2B10H12 + 2 L + H2

Decaborane(14) is a weak Brønsted acid. Monodeprotonation generates the anion [B10H13]−, with again a nido structure.

Applications

Decaborane has no significant applications, although the compound has often been investigated.

Since the molecule decomposes in a plasma, yielding monatomic boron ions, decaborane is potentially useful as a fuel for aneutronic fusion.[7] In 2018, LPP Fusion announced plans for using the material in its next round of fusion experiments.[8] Decaborane has been assessed for low energy ion implantation of boron in the manufacture of semiconductors. It has also been considered for plasma-assisted chemical vapor deposition for the manufacture of boron-containing thin films. In fusion research, the neutron-absorbing nature of boron has led to the use of these thin boron-rich films to "boronize" the walls of the tokamak vacuum vessel to reduce recycling of particles and impurities into the plasma and improve overall performance.[9]

Decaborane was also developed as an additive to special high-performance rocket fuels. Its derivates were investigated as well, e.g. ethyl decaborane.

Decaborane is an effective reagent for the reductive amination of ketones and aldehydes.[10]

Safety

Decaborane, like pentaborane, is a powerful toxin affecting the central nervous system, although decaborane is less toxic than pentaborane. It can be absorbed through skin.

Purification by sublimation require a dynamic vacuum to remove evolved gases. Crude samples explode near 100 °C.[6]

It forms an explosive mixture with carbon tetrachloride, which caused an often-mentioned explosion in a manufacturing facility.[11]

References
  1. NIOSH Pocket Guide to Chemical Hazards. "#0175". National Institute for Occupational Safety and Health (NIOSH).
  2. "Decaborane". Immediately Dangerous to Life and Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
  3. Gary B. Dunks, Kathy Palmer-Ordonez, Eddie Hedaya "Decaborane(14)" Inorg. Synth. 1983, vol. 22, pp. 202–207. doi:10.1002/9780470132531.ch46
  4. Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
  5. Charles R. Kutal David A. Owen Lee J. Todd (1968). "closo‐1,2‐Dicarbadodecaborane(12)". Inorganic Syntheses. 11: 19–24. doi:10.1002/9780470132425.ch5.CS1 maint: uses authors parameter (link)
  6. M. Frederick Hawthorne, Timothy D. Andrews, Philip M. Garrett, Fred P. Olsen, Marten Reintjes, Fred N. Tebbe, Les F. Warren, Patrick A. Wegner, Donald C. Young (1967). "Icosahedral Carboranes and Intermediates Leading to the Preparation of Carbametallic Boron Hydride Derivatives". Inorganic Syntheses. 10: 91–118. doi:10.1002/9780470132418.ch17.CS1 maint: uses authors parameter (link)
  7. Lerner, E. J.; Terry, R. E. (2005). "Advances towards pB11 fusion with the dense plasma focus" (pdf).
  8. Wang, Brian (2018-03-27). "LPP Fusion has funds try to reach nuclear fusion net gain milestone | NextBigFuture.com". NextBigFuture.com. Retrieved 2018-03-27.
  9. Nakano, T.; Higashijima, S.; Kubo, H.; Yagyu, J.; Arai, T.; Asakura, N.; Itami, K. "Boronization effects using deuterated-decaborane (B10D14) in JT-60U". 15th PSI Gifu, P1-05. Sokendai, Japan: National Institute for Fusion Science. Archived from the original on 2004-05-30.
  10. Jong Woo Bae; Seung Hwan Lee; Young Jin Cho; Cheol Min Yoon (2000). "A reductive amination of carbonyls with amines using decaborane in methanol". J. Chem. Soc., Perkin Trans. 1: 145–146. doi:10.1039/A909506C.
  11. "Condensed version of the 79th Faculty Research Lecture Presented by Professor M. Frederick Hawthorne". UCLA.

Further reading
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