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
Cobaltic fluoride
Cobalt fluoride
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/cm3
| MeltingPtC = 927
| Solubility = reacts
| MagSus = +1900.0·10−6 cm3/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}}. Hydrates are also known. The anhydrous compound is a hygroscopic brown solid. It is used to synthesize organofluorine compounds.{{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}}
The related cobalt(III) chloride is also known but is extremely unstable.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}} 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 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.
=Hydrates=
Preparation
Cobalt trifluoride can be prepared in the laboratory by treating cobalt(II) chloride with fluorine at 250 °C:H. F. Priest (1950): "Anhydrous Metal Fluorides". In Inorganic Syntheses, McGraw-Hill, volume 3, pages 171-183. {{doi|10.1002/9780470132340.ch47}}
:{{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.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}}
The compound can also be formed by treating {{chem2|CoCl2}} with chlorine trifluoride {{chem2|ClF3}} or bromine trifluoride {{chem2|BrF3}}.
Reactions
{{chem2|CoF3}} decomposes upon contact with water to give oxygen:
:4 {{chem2|CoF3}} + 2 H2O → 4 HF + 4 Co{{chem2|F2}} + O2
It reacts with fluoride salts to give the anion [CoF6]3−, which is also features high-spin, octahedral cobalt(III) center.
Applications
{{chem2|CoF3}} is a powerful fluorinating agent. Used as slurry, {{chem2|CoF3}} converts hydrocarbons to the perfluorocarbons:
:2 {{chem2|CoF3}} + R-H → 2 Co{{chem2|F2}} + R-F + HF
Cobalt(II) fluoride is the byproduct.
Such reactions are sometimes accompanied by rearrangements or other reactions. The related reagent KCoF4 is more selective.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}}.
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 D3h). The {{chem2|Co(3+)}} ion has a ground state of 3d6 5D. The fluoride ligands split this state into, in energy order, 5A', 5E", and 5E' states. The first energy difference is small and the 5E" 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.{{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 }} This calculation was the first treatment of the Jahn-Teller effect using calculated energy surfaces.
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}}