Sodium borohydride
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| Names | |
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Preferred IUPAC name
Sodium tetrahydridoborate (1–)
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Systematic IUPAC name
Sodium boranuide
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| Identifiers | |
16940-66-2  15681-89-7 (2D4)
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| 3D model (Jmol) | Interactive image |
| ChEBI |
CHEBI:50985
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| ChemSpider |
26189 9052313 (2D4) 9312193 (3T4)
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| ECHA InfoCard | 100.037.262 |
| EC Number | 241-004-4 |
| 23167 | |
| MeSH | Sodium+borohydride |
| PubChem |
4311764 23673181 (2D4) 23671303 (3T4) |
| RTECS number | ED3325000 |
| UN number | 1426 |
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| Properties | |
| NaBH4 | |
| Molar mass | 37.83 g/mol |
| Appearance | white crystals hygroscopic |
| Density | 1.0740 g/cm3 |
| Melting point | 400 °C (752 °F; 673 K) |
| Boiling point | 500 °C (932 °F; 773 K) (decomposes) |
| soluble, reacts with water | |
| Solubility | soluble in liquid ammonia, amines, pyridine |
| Hazards | |
| H260, H301, H311, H314 | |
| P223, P231, P232, P280, P301+310, P370+378, P422 | |
| R-phrases | R49, R15, R23/24/25, R42/43, R68, R51/53, R60, R61 |
| NFPA 704 | |
| Flash point | 70 °C (158 °F; 343 K) |
| ca. 220 °C (428 °F; 493 K) | |
| Explosive limits | 3% |
| Lethal dose or concentration (LD, LC): | |
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LD50 (median dose)
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160 mg/kg (Oral - Rat) 230 mg/kg (Dermal - Rabbit) |
| Related compounds | |
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Other anions
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Sodium cyanoborohydride Sodium hydride Sodium borate Borax |
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Other cations
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Lithium borohydride |
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Related compounds
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Lithium aluminium hydride Sodium triacetoxyborohydride |
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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 (what is  ?) |
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| Infobox references | |
Sodium borohydride, also known as sodium tetrahydridoborate and sodium tetrahydroborate, is an inorganic compound with the formula NaBH4. This white solid, usually encountered as a powder, is a versatile reducing agent that finds wide application in chemistry, both in the laboratory and on a technical scale. It has been tested as pretreatment for pulping of wood, but is too costly to be commercialized. The compound is soluble in alcohols and certain ethers but reacts with water in the absence of a base.
The compound was discovered in the 1940s by H. I. Schlesinger, who led a team that developed metal borohydrides for wartime applications (in particular, looking for a uranium compound more volatile than the hexafluoride to be used in isotope separation by gaseous diffusion; this line of research did not yield useful results). Their work was declassified and published only in 1953.
Sodium borohydride is an odorless white to gray-white microcrystalline powder which often forms lumps. It can be purified by recrystallization from warm (50 °C) diglyme. Sodium borohydride is soluble in protic solvents such as water and lower alcohols; it will also react with these solvents to produce H2; however, these reactions are fairly slow. Complete decomposition in excess methanol can take nearly 90 min at 20 °C. It will decompose in neutral or acidic aqueous solutions but is stable at pH 14. These conditions can be exploited to allow sodium borohydride to react in a homogeneous manner, with reduced lifespan being traded against increased reactivity.
NaBH4 is a salt, consisting of the tetrahedral BH4− anion. The solid is known to exist as three polymorphs: α, β and γ. The stable phase at room temperature and pressure is α-NaBH4, which is cubic and adopts an NaCl-type structure, in the Fm3m space group. At a pressure of 6.3 GPa, the structure changes to the tetragonal β-NaBH4 (space group P421c) and at 8.9 GPa, the orthorhombic γ-NaBH4 (space group Pnma) becomes the most stable.
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