Potassium tetraphenylborate explained

Potassium tetraphenylborate is the salt with the formula KB(C₆H₅)₄). It is a colourless salt that is a rare example of a water-insoluble salt of potassium.

The salt has a low solubility in water of only 1.8×10⁻⁴ g/L. It is, however, soluble in organic solvents. The insolubility of this compound has been used to determine the concentration of potassium ions by precipitation and gravimetric analysis:^[1]

K⁺ + NaB(Ph)₄ → KB(Ph)₄ + Na⁺

The compound adopts a polymeric structure with bonds between the phenyl rings and potassium. As such it is classified as an organopotassium compound.^[2]

External links

• Potassium tetraphenylborate Jmol Page

Notes and References

1. Engelbrecht . R. M. . McCoy . F. A. . Determination of Potassium by Tetraphenylborate Method . . 28 . 1772 . 1956 . 10.1021/ac60119a040 . 11.
2. Ulrich Behrens, Frank Hoffmann, and Falk Olbrich "Solid-State Structures of Base-Free Lithium and Sodium Tetraphenylborates at Room and Low Temperature: Comparison with the Higher Homologues MB(C₆H₅)₄ (M = K, Rb, Cs)" Organometallics 2012, volume 31, p. 905−913.