View source for Chemistry:Potassium hexafluoronickelate(IV)

{{Chembox
| ImageFile = K2NiF6.svg
| ImageSize = 
| IUPACName = potassium hexafluoronickelate(IV)
| OtherNames = 
|Section1={{Chembox Identifiers
| CASNo =  17218-47-2
| CASNo_Ref = {{cascite|correct|scifinder}}
| PubChem = 
| EINECS = 625-130-0
| ChemSpiderID = 21241633
| SMILES = [K+].[K+].F[Ni-2](F)(F)(F)(F)F
| InChI = InChI=1S/6FH.2K.Ni/h6*1H;;;/q;;;;;;2*+1;+4/p-6
  }}
|Section2={{Chembox Properties
| Formula = K<sub>2</sub>NiF<sub>6</sub>
| MolarMass = 250.880
| Appearance = 
| Density = 
| MeltingPt = 
| BoilingPt = 
| Solubility =
  }}
|Section3={{Chembox Hazards
| Hazards_ref = <ref name=sds>{{cite web|title = Potassium Hexafluoronickelate(IV)|url =https://www.americanelements.com/potassium-hexafluoronickelate-iv-17218-47-2|publisher = American Elements|accessdate = December 19, 2018}}</ref>
| ExternalSDS = [https://www.americanelements.com/printpdf/potassium-hexafluoronickelate-iv-17218-47-2/sds External SDS]
| GHSPictograms = {{GHS06}}{{GHS07}}{{GHS08}}
| GHSSignalWord = Danger
| HPhrases = {{H-phrases|302|312|317|331|350}}
| PPhrases = {{P-phrases|201|261|280|304+340|405|501}}
| MainHazards = 
| FlashPt = 
| AutoignitionPt =
  }}
}}
'''Potassium hexafluoronickelate(IV)''' is an inorganic compound with the chemical formula {{chem|K|2|NiF|6}}.  It can be produced through the reaction of [[Chemistry:Potassium fluoride|potassium fluoride]], nickel dichloride, and [[Chemistry:Fluorine|fluorine]].

It reacts violently with water, releasing oxygen.  It dissolves in anhydrous [[Chemistry:Hydrogen fluoride|hydrogen fluoride]] to produce a light-red solution.  Potassium hexafluoronickelate(IV) decomposes at 350&nbsp;°C, forming potassium hexafluoronickelate(III), [[Chemistry:Nickel(II) fluoride|nickel(II) fluoride]], and [[Chemistry:Fluorine|fluorine]]:<ref>{{in lang|zh-hans}}{{cite book|title=《无机化学丛书》第九卷：锰分族、铁系、铂系|pages=P333|author=张青莲|isbn=7-03-002238-6|location=北京|publisher=科学出版社}}</ref>{{better source needed|date=December 2013}}<ref>{{Cite journal |last=Stein |first=Lawrence |last2=Neil |first2=John M. |last3=Alms |first3=Gregory R. |date=November 1969 |title=Properties of potassium hexafluoronickelates(III) and -(IV). Absorption spectra of nickel(III) and -(IV) in hydrogen fluoride solutions |url=https://pubs.acs.org/doi/abs/10.1021/ic50081a045 |journal=Inorganic Chemistry |language=en |volume=8 |issue=11 |pages=2472–2476 |doi=10.1021/ic50081a045 |issn=0020-1669}}</ref>

:<math>\rm \ 3 K_2NiF_6 \xrightarrow{\Delta} 2 K_3NiF_6 + NiF_2 + F_2</math>
[[Image:Mg2FeH6 from X-ray.jpg|thumb|left|120px|Chemical structure of solid K<sub>2</sub>NiF<sub>6</sub> as determined by X-ray crystallography.]]

Potassium hexafluoronickelate is a strong oxidant. It can turn [[Chemistry:Chlorine pentafluoride|chlorine pentafluoride]] and [[Chemistry:Bromine pentafluoride|bromine pentafluoride]] into {{chem|ClF|6|+}} and {{chem|BrF|6|+}}, respectively:<ref>{{cite journal|doi=10.1021/ic001024|title=Novel Synthesis of ClF<sub>6</sub><sup>+</sup> and BrF<sub>6</sub><sup>+</sup> Salts|year=2001|last1=Schroer|first1=Thorsten|last2=Christe|first2=Karl O.|journal=Inorganic Chemistry|volume=40|issue=10|pages=2415–9|pmid=11327921}}</ref>

:<math>\rm \ K_2NiF_6 + 5 AsF_5 + XF_5 \xrightarrow{aHF} XF_6AsF_6 + Ni(AsF_6)_2 + 2KAsF_6</math>
:( X = Cl or Br , -60 °C , aHF = anhydrous hydrogen fluoride).

Potassium hexafluoronickelate decomposes at high temperatures to release fluorine gas; like [[Chemistry:Terbium(IV) fluoride|terbium(IV) fluoride]], the emitted fluorine is primarily monatomic rather than the typical diatomic.<ref>{{cite journal |last1=Rau |first1=J. V. |last2=Chilingarov |first2=N. S. |last3=Leskiv |first3=M. S. |last4=Sukhoverkhov |first4=V. F. |last5=Rossi Albertini |first5=V. |last6=Sidorov |first6=L. N. |title=Transition and rare earth metal fluorides as thermal sources of atomic and molecular fluorine |journal=Le Journal de Physique IV |date=August 2001 |volume=11 |issue=PR3 |pages=Pr3–109–Pr3-113 |doi=10.1051/jp4:2001314}}</ref>

It adopts the structure seen for K<sub>2</sub>PtCl<sub>6</sub> and Mg<sub>2</sub>FeH<sub>6</sub>.<ref>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.</ref>

== References ==
{{reflist}}
{{potassium compounds}}
{{Nickel compounds}}

[[Category:Potassium compounds]]
[[Category:Nickel complexes]]
[[Category:Fluoro complexes]]



{{Sourceattribution|Potassium hexafluoronickelate(IV)}}