Caesium hexafluorocuprate(IV)

{{Use American English|date=January 2019}}

{{Use mdy dates|date=January 2019}}

{{Short description|Chemical compound with +4 oxidized copper}}

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| ImageFile = CCs2CuF6.svg

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| OtherNames = Cesium hexafluorocuprate; Dicesium hexafluorocuprate

| Section1 = {{Chembox Identifiers

| CASNo = 43070-30-0

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| PubChem =

| SMILES = [Cs+].[Cs+].F[Cu-2](F)(F)(F)(F)F

| StdInChI=1S/2Cs.Cu.6FH/h;;;6*1H/q2*+1;+4;;;;;;/p-6

| StdInChIKey=JSYFPWMRKBASLN-UHFFFAOYSA-H

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| Section2 = {{Chembox Properties

| Formula = Cs₂CuF₆

| MolarMass = 443.35 g/mol

| Appearance = Red orange solid{{Cite book | title = Dictionary of Inorganic Compounds | page = 3100 | editor = Jane E. Macintyre | publisher = CRC Press | date = 1992 | isbn = 9780412301209}}

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Caesium hexafluorocuprate is the inorganic compound with the chemical formula {{chem2|Cs2CuF6}}. It is a red solid that degrades upon contact with water. It was first prepared by heating {{chem|CsCuCl|3}} and caesium fluoride at 410°C under 350 atmospheres of fluorine:{{cite journal | doi = 10.1002/anie.197305822 | title = Tetravalent Copper: Cs2[CuF6] | year = 1973 | last1 = Harnischmacher | first1 = Werner | last2 = Hoppe | first2 = Rudolf | author-link2 =Rudolf Hoppe| journal = Angewandte Chemie International Edition in English | volume = 12 | issue = 7 | pages = 582–583}}

:2 CsCuCl₃ + 2 CsF + 5 F₂ → 2 Cs₂CuF₆ + 3 Cl₂

The anion [CuF₆]^2- is a rare example of a copper(IV) complex. In terms of its electronic structure, the anion has a low-spin d⁷ configuration. It is thus susceptible to Jahn-Teller distortion.{{cite journal | doi = 10.1016/S0022-1139(00)81198-7 | title = Some physical properties of d-transition metal fluorides in unusual oxidation states | year = 1984 | last1 = Grannec | first1 = J.|last2=Tressaud|first2=A.|last3=Hagenmuller|first3=P. | journal = Journal of Fluorine Chemistry | volume = 25 | issue = 1 | pages = 83–90 | bibcode = 1984JFluC..25...83G }}