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_fluoride.png) | |
| Names | |
|---|---|
| Other names Cobalt trifluoride Cobaltic fluoride Cobalt fluoride Cobaltic trifluoride | |
| Identifiers | |
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3D model (JSmol) | |
| ChemSpider |
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| ECHA InfoCard | 100.030.045 |
| EC Number |
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| UNII | |
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| Properties | |
| CoF3 | |
| Molar mass | 115.928 g/mol |
| Appearance | brown powder |
| Density | 3.88 g/cm3 |
| Melting point | 927 °C (1,701 °F; 1,200 K) |
| reacts | |
| +1900.0·10−6 cm3/mol | |
| Structure | |
| hexagonal | |
| Hazards | |
| NFPA 704 (fire diamond) | |
| Related compounds | |
Otheranions | cobalt(III) oxide,cobalt(III) chloride |
Othercations | iron(III) fluoride,rhodium(III) fluoride |
Related compounds | cobalt(II) fluoride |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Cobalt(III) fluoride is theinorganic compound with the formulaCoF3.Hydrates are also known. The anhydrous compound is a hygroscopic brown solid. It is used to synthesizeorganofluorine compounds.[1]
The relatedcobalt(III) chloride is also known but is extremely unstable.[2] Cobalt(III) bromide and cobalt(III) iodide have not been synthesized.
Anhydrous cobalt trifluoride crystallizes in therhombohedral group, specifically according to thealuminium trifluoride motif, witha = 527.9pm,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.[3]
A hydrateCoF3·3.5H2O is known. It is conjectured to be better described as[CoF3(H2O)3]·0.5H2O.[3]
There is a report of an hydrateCoF3·3.5H2O, isomorphic toAlF3·3H2O.[3]
Cobalt trifluoride can be prepared in the laboratory by treatingCoCl2 withfluorine at 250 °C:[4][3]
In this redox reaction,Co2+ andCl− are oxidized toCo3+ andCl2, respectively, whileF2 is reduced toF−. Cobalt(II) oxide (CoO) and cobalt(II) fluoride (CoF2) can also be converted to cobalt(III) fluoride using fluorine.[3]
The compound can also be formed by treatingCoCl2 withchlorine trifluorideClF3 orbromine trifluorideBrF3.[3]
CoF3 decomposes upon contact with water to give oxygen:
It reacts with fluoride salts to give the anion [CoF6]3−, which is also features high-spin, octahedral cobalt(III) center.
CoF3 is a powerful fluorinating agent. Used as slurry,CoF3 convertshydrocarbons to theperfluorocarbons:
CoF2 is the byproduct.
Such reactions are sometimes accompanied by rearrangements or other reactions.[1] The related reagent KCoF4 is more selective.[5]
In the gas phase,CoF3 is calculated to be planar in its ground state, and has a 3-fold rotation axis (point group D3h). TheCo3+ ion has a ground state of 3d65D. The fluoride ligands split this state into, in energy order,5A',5E", and5E' states. The first energy difference is small and the5E" state is subject to theJahn-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.[6] This calculation was the first treatment of theJahn-Teller effect using calculated energy surfaces.
