Potassium tetraphenylborate

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Potassium tetraphenylborate
Potassium tetraphenylborate.png
CAS number 3244-41-5
PubChem 6432333
ChemSpider 4937589 YesY
Jmol-3D images Image 1
Molecular formula C24H20BK
Molar mass 358.3249
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

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]


  1. ^ Engelbrecht, R. M.; McCoy, F. A. (1956). "Determination of Potassium by Tetraphenylborate Method". Anal. Chem. 28 (11): 1772. doi:10.1021/ac60119a040. 
  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. doi:10.1021/om200943n

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