Potassium borohydride

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

Preparation

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

Properties

Potassium is a colorless solid that is stable at room temperature and in an aqueous alkaline solution. Potassium borohydride has a hydrogen desorption temperature of 584 °C, higher than for lithium borohydride or sodium borohydride.
Like the related Na⁺, Rb⁺, and Cs⁺ salts, potassium borohydride crystallizes in a sodium chloride lattice type, space group Fm3m.

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. The procedure involves heating potassium borohydride and pyrazole without a solvent.
Diborane is produced by treating potassium borohydride with phosphoric acid.
In combination with bismuth trichloride, it forms a reagent for the reduction of nitro group to the hydroxylamine.