Potassium hexafluoronickelate(IV) explained

Potassium hexafluoronickelate(IV) is an inorganic compound with the chemical formula . It can be produced through the reaction of potassium fluoride, nickel dichloride, and fluorine.

It reacts violently with water, releasing oxygen. It dissolves in anhydrous hydrogen fluoride to produce a light-red solution. Potassium hexafluoronickelate(IV) decomposes at 350 °C, forming potassium hexafluoronickelate(III), nickel(II) fluoride, and fluorine:^{[1] [2]}

\rm 3 K _{2NiF} _{6} \xrightarrow{\Delta} 2 K _{3NiF} _{6} + NiF _{2} + F _{2}

Potassium hexafluoronickelate is a strong oxidant. It can turn chlorine pentafluoride and bromine pentafluoride into and, respectively:^[3]

\rm K _{2NiF} _{6} + 5 AsF _{5} + XF _{5} \xrightarrow{aHF} XF _{6AsF} _{6} + Ni(AsF _{6)} _{2} + 2 KAsF _{6}

(X = Cl or Br, -60 °C, aHF = anhydrous hydrogen fluoride).

Potassium hexafluoronickelate decomposes at high temperatures to release fluorine gas; like terbium(IV) fluoride, the emitted fluorine is primarily monatomic rather than the typical diatomic.^[4]

It adopts the structure seen for K₂PtCl₆ and Mg₂FeH₆.^[5]

Notes and References

1. Book: 《无机化学丛书》第九卷：锰分族、铁系、铂系. P333. 张青莲. 7-03-002238-6. 北京. 科学出版社.
2. Stein . Lawrence . Neil . John M. . Alms . Gregory R. . November 1969 . Properties of potassium hexafluoronickelates(III) and -(IV). Absorption spectra of nickel(III) and -(IV) in hydrogen fluoride solutions . Inorganic Chemistry . en . 8 . 11 . 2472–2476 . 10.1021/ic50081a045 . 0020-1669.
3. 10.1021/ic001024. Novel Synthesis of ClF₆⁺ and BrF₆⁺ Salts. 2001. Schroer. Thorsten. Christe. Karl O.. Inorganic Chemistry. 40. 10. 2415–9. 11327921.
4. Rau . J. V. . Chilingarov . N. S. . Leskiv . M. S. . Sukhoverkhov . V. F. . Rossi Albertini . V. . Sidorov . L. N. . Transition and rare earth metal fluorides as thermal sources of atomic and molecular fluorine . Le Journal de Physique IV . August 2001 . 11 . PR3 . Pr3–109–Pr3-113 . 10.1051/jp4:2001314.
5. Taylor, J. C. "A comparison of profile decomposition and Rietveld methods for structurtal refinement with powder diffraction data" Zeitschrift für Kristallographie 1987, volume 181, p151-160.