Potassium borohydride

Potassium borohydride, also known as potassium tetrahydroborate, is an inorganic compound with the formula KBH₄.

Potassium borohydride

Names
IUPAC name Potassium tetrahydroborate
Other names Potassium tetrahydridoborate Borate(1-), tetrahydro-, potassium (1:1)
Identifiers
CAS Number	13762-51-1 Y
3D model (JSmol)	Interactive image
ChemSpider	55580 Y
ECHA InfoCard	100.033.949
EC Number	237-360-5
PubChem CID	4192641
UNII	0WS230DTGF
UN number	1870 (POTASSIUM BOROHYDRIDE)
CompTox Dashboard (EPA)	DTXSID50929853
InChI InChI=1S/BH4.K/h1H4;/q-1;+1 Y Key: ICRGAIPBTSPUEX-UHFFFAOYSA-N Y
SMILES [BH4-].[K+]
Properties
Chemical formula	K[BH4]
Molar mass	53.94 g·mol−1
Appearance	colorless solid
Density	1.17 g/mL
Melting point	607 °C (1,125 °F; 880 K) decomposes
Solubility in water	19g/100g
Solubility in methanol	3.9g/100g
Hazards
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H261, H301, H311, H314, H331
Precautionary statements	P280, P305+P351+P338, P309, P310, P370+P378, P402+P404
Related compounds
Other anions	Potassium hydride
Other cations	Lithium borohydride Sodium borohydride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Preparation

It can be obtained through the reaction of sodium borohydride with aqueous potassium hydroxide in a methanol or water solvent:^[1]

NaBH₄ + KOH → KBH₄ + NaOH

Properties

Potassium is a colorless solid that is stable at room temperature and in an aqueous alkaline solution.^[2] Potassium borohydride has a hydrogen desorption temperature of 584 °C, higher than for lithium borohydride or sodium borohydride.^[1]

Like the related Na⁺, Rb⁺, and Cs⁺ salts, potassium borohydride crystallizes in a sodium chloride lattice type, space group Fm3m.^[3][4]

As a reagent

Often potassium borohydride behaves similarly to the more common sodium borohydride, but solubility considerations sometimes recommend the potassium salt. One example is the synthesis of potassium trispyrazolylborate (KTp). The procedure involves heating potassium borohydride and pyrazole without a solvent.^[5]

KBH₄ + 3 C₃N₂H₄ → KHB(C₃N₂H₃)₃ + 3 H₂

Diborane is produced by treating potassium borohydride with phosphoric acid.^[6]

In combination with bismuth trichloride, it forms a reagent for the reduction of nitro group to the hydroxylamine.^[7]