View source for Cobalt(III) fluoride

{{Chembox
| Verifiedfields = changed
| Watchedfields = changed
| verifiedrevid = 417786650
| Name = Cobalt(III) fluoride
| ImageFile = Aluminium-trifluoride-3D-polyhedra.png
| ImageClass = bg-transparent
| ImageName = Cobalt(III) fluoride
| ImageFile1 = Cobalt(III) fluoride.png
| ImageSize1 =
| OtherNames = Cobalt trifluoride<br />Cobaltic fluoride<br />Cobalt fluoride<br />Cobaltic trifluoride
|Section1={{Chembox Identifiers
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 59593
| InChI = 1/Co.3FH/h;3*1H/q+3;;;/p-3
| InChIKey = WZJQNLGQTOCWDS-DFZHHIFOAL
| SMILES = F[Co](F)F
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/Co.3FH/h;3*1H/q+3;;;/p-3
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = WZJQNLGQTOCWDS-UHFFFAOYSA-K
| CASNo_Ref = {{cascite|correct|??}}
| CASNo = 10026-18-3
| CASNo2 = 54496-71-8
| CASNo2_Comment = dihydrate
| UNII_Ref = {{fdacite|changed|FDA}}
| UNII = O3R680UKNX
| PubChem = 66208
| EINECS = 233-062-4
 }}
|Section2={{Chembox Properties
| Formula = {{chem2|CoF3}}
| Appearance = brown powder
| MolarMass = 115.928 g/mol
| Density = 3.88 g/cm<sup>3</sup>
| MeltingPtC = 927
| Solubility = reacts
| MagSus = +1900.0·10<sup>−6</sup> cm<sup>3</sup>/mol
 }}
|Section3={{Chembox Structure
| CrystalStruct = hexagonal
 }}
|Section4={{Chembox Hazards
| NFPA-H = 3
| NFPA-F = 0
| NFPA-R = 2
| NFPA-S = 
 }}
|Section5={{Chembox Related
| OtherAnions = [[cobalt(III) oxide]], [[cobalt(III) chloride]]
| OtherCations = [[iron(III) fluoride]], [[rhodium(III) fluoride]]
| OtherCompounds = [[cobalt(II) fluoride]] }}
}}
'''Cobalt(III) fluoride''' is the [[inorganic compound]] with the formula {{chem2|CoF3}}. [[Hydrate]]s are also known. The anhydrous compound is a hygroscopic brown solid.  It is used to synthesize [[organofluorine chemistry|organofluorine]] compounds.<ref name=Coe>{{cite encyclopedia|author=Coe, P. L.|title=Cobalt(III) Fluoride|encyclopedia=Encyclopedia of Reagents for Organic Synthesis|year=2004|publisher=J. Wiley|doi=10.1002/047084289X.rc185|isbn=0471936235}}</ref>

The related [[cobalt(III) chloride]] is also known but is extremely unstable.<ref name=chester>Arthur W. Chester, El-Ahmadi Heiba, Ralph M. Dessau, and William J. Koehl Jr. (1969): "The interaction of cobalt(III) with chloride ion in acetic acid". ''Inorganic and Nuclear Chemistry Letters'', volume 5, issue 4, pages 277-283. {{doi|10.1016/0020-1650(69)80198-4}}</ref> Cobalt(III) bromide and cobalt(III) iodide have not been synthesized.

==Structure==

===Anhydrous===
Anhydrous cobalt trifluoride crystallizes in the [[rhombohedral]] group, specifically according to the [[aluminium trifluoride]] motif, with ''a'' = 527.9 [[picometre|pm]], ''α'' = 56.97°.  Each cobalt atom is bound to six fluorine atoms in octahedral geometry, with Co–F distances of 189 pm. Each fluoride is a doubly bridging ligand.<ref name=levason/>

===Hydrates===
A hydrate {{chem2|CoF3*3.5H2O}} is known.  It is conjectured to be better described as {{chem2|[CoF3(H2O)3]*0.5H2O}}.<ref name=levason/>

There is a report of an hydrate {{chem2|CoF3*3.5H2O}}, isomorphic to {{chem2|AlF3*3H2O}}.<ref name=levason/>

==Preparation==
Cobalt trifluoride can be prepared in the laboratory by treating [[cobalt(II) chloride|{{chem2|CoCl2}}]] with [[fluorine]] at 250&nbsp;°C:<ref name=priest>H. F. Priest (1950): "Anhydrous Metal Fluorides". In ''Inorganic Syntheses'', McGraw-Hill, volume 3, pages 171-183. {{doi|10.1002/9780470132340.ch47}}</ref><ref name=levason/>
:{{chem2|CoCl2}}  +  3/2 {{chem2|F2}}  →    {{chem2|CoF3}}  +  {{chem2|Cl2}}
In this redox reaction, {{chem2|Co(2+)}} and {{chem2|Cl(-)}} are oxidized to {{chem2|Co(3+)}} and {{chem2|Cl2}}, respectively, while {{chem2|F2}} is reduced to {{chem2|F(-)}}. Cobalt(II) oxide (CoO) and cobalt(II) fluoride ({{chem2|CoF2}}) can also be converted to cobalt(III) fluoride using fluorine.<ref name=levason>W. Levason and C. A. McAuliffe (1974): "Higher oxidation state chemistry of iron, cobalt, and nickel". ''Coordination Chemistry Reviews'', volume 12, issue 2, pages 151-184. {{doi|10.1016/S0010-8545(00)82026-3}}</ref>

The compound can also be formed by treating {{chem2|CoCl2}} with [[chlorine trifluoride]] {{chem2|ClF3}} or [[bromine trifluoride]] {{chem2|BrF3}}.<ref name=levason/>

==Reactions==
{{chem2|CoF3}} decomposes upon contact with water to give oxygen:
:4 {{chem2|CoF3}}  +  2 H<sub>2</sub>O →  4 HF  +  4 Co{{chem2|F2}}  +  O<sub>2</sub>

It reacts with fluoride salts to give the anion [CoF<sub>6</sub>]<sup>3−</sup>, which is also features high-spin, octahedral cobalt(III) center.

==Applications==
{{chem2|CoF3}} is a powerful fluorinating agent. Used as slurry, {{chem2|CoF3}} converts [[hydrocarbon]]s to the [[perfluorocarbons]]:
:2 {{chem2|CoF3}}  +  R-H  →  2 Co{{chem2|F2}}  +  R-F  +  HF
[[Cobalt(II) fluoride|Co{{chem2|F2}}]] is the byproduct.

Such reactions are sometimes accompanied by rearrangements or other reactions.<ref name=Coe/> The related reagent KCoF<sub>4</sub> is more selective.<ref>Coe, P. L. "Potassium Tetrafluorocobaltate(III)" in Encyclopedia of Reagents for Organic Synthesis (Ed: L. Paquette) 2004, J. Wiley & Sons, New York. {{doi|10.1002/047084289X.rp251}}.</ref>

==Gaseous {{chem2|CoF3}}==
In the gas phase, {{chem2|CoF3}} is calculated to be planar in its ground state, and has a 3-fold rotation axis (point group D<sub>3h</sub>). The {{chem2|Co(3+)}} ion has a ground state of 3d<sup>6</sup> <sup>5</sup>D. The fluoride ligands split this state into, in energy order, <sup>5</sup>A', <sup>5</sup>E", and <sup>5</sup>E' states. The first energy difference is small and the <sup>5</sup>E" state is subject to the [[Jahn-Teller effect]], so this effect needs to be considered to be sure of the ground state. The energy lowering is small and does not change the energy order.<ref>{{cite journal | last1=Yates | first1 =J. H. | last2=Pitzer | first2 = R. M. | date=1979 | title = Molecular and Electronic Structure of Transition Metal Trifluorides | journal = J. Chem. Phys. | volume = 70 | issue = 9 | pages = 4049–4055 | doi = 10.1063/1.438027| bibcode =1979JChPh..70.4049Y }}</ref> This calculation was the first treatment of the [[Jahn-Teller effect]] using calculated energy surfaces.

==References==
<references/>

==External links==
{{Commons category|Cobalt(III) fluoride}}
*[https://web.archive.org/web/20060219230038/http://www.npi.gov.au/database/substance-info/profiles/26.html National Pollutant Inventory - Cobalt fact sheet]
*[https://web.archive.org/web/20060116134617/http://www.npi.gov.au/database/substance-info/profiles/44.html National Pollutant Inventory - Fluoride and compounds fact sheet]

{{Cobalt compounds}}
{{fluorides}}

[[Category:Fluorides]]
[[Category:Metal halides]]
[[Category:Cobalt(III) compounds]]
[[Category:Fluorinating agents]]