Английская Википедия:Cobalt(III) fluoride
Шаблон:Chembox Cobalt(III) fluoride is the inorganic compound with the formula Шаблон:Chem2. Hydrates are also known. The anhydrous compound is a hygroscopic brown solid. It is used to synthesize organofluorine compounds.[1]
The related cobalt(III) chloride is also known but is extremely unstable.[2] 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.[3]
Hydrates
A hydrate Шаблон:Chem2 is known. It is conjectured to be better described as Шаблон:Chem2.[3]
There is a report of an hydrate Шаблон:Chem2, isomorphic to Шаблон:Chem2.[3]
Preparation
Cobalt trifluoride can be prepared in the laboratory by treating [[cobalt(II) chloride|Шаблон:Chem2]] with fluorine at 250 °C:[4][3]
- Шаблон:Chem2 + 3/2 Шаблон:Chem2 → Шаблон:Chem2 + Шаблон:Chem2
In this redox reaction, Шаблон:Chem2 and Шаблон:Chem2 are oxidized to Шаблон:Chem2 and Шаблон:Chem2, respectively, while Шаблон:Chem2 is reduced to Шаблон:Chem2. Cobalt(II) oxide (CoO) and cobalt(II) fluoride (Шаблон:Chem2) can also be converted to cobalt(III) fluoride using fluorine.[3]
The compound can also be formed by treating Шаблон:Chem2 with chlorine trifluoride Шаблон:Chem2 or bromine trifluoride Шаблон:Chem2.[3]
Reactions
Шаблон:Chem2 decomposes upon contact with water to give oxygen:
- 4 Шаблон:Chem2 + 2 H2O → 4 HF + 4 CoШаблон:Chem2 + O2
It reacts with fluoride salts to give the anion [CoF6]3−, which is also features high-spin, octahedral cobalt(III) center.
Applications
Шаблон:Chem2 is a powerful fluorinating agent. Used as slurry, Шаблон:Chem2 converts hydrocarbons to the perfluorocarbons:
- 2 Шаблон:Chem2 + R-H → 2 CoШаблон:Chem2 + R-F + HF
[[Cobalt(II) fluoride|CoШаблон:Chem2]] is the byproduct.
Such reactions are sometimes accompanied by rearrangements or other reactions.[1] The related reagent KCoF4 is more selective.[5]
Gaseous Шаблон:Chem2
In the gas phase, Шаблон:Chem2 is calculated to be planar in its ground state, and has a 3-fold rotation axis (point group D3h). The Шаблон:Chem2 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.[6] This calculation was the first treatment of the Jahn-Teller effect using calculated energy surfaces.
References
- ↑ 1,0 1,1 Шаблон:Cite encyclopedia
- ↑ 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. Шаблон:Doi
- ↑ 3,0 3,1 3,2 3,3 3,4 3,5 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. Шаблон:Doi
- ↑ H. F. Priest (1950): "Anhydrous Metal Fluorides". In Inorganic Syntheses, McGraw-Hill, volume 3, pages 171-183. Шаблон:Doi
- ↑ Coe, P. L. "Potassium Tetrafluorocobaltate(III)" in Encyclopedia of Reagents for Organic Synthesis (Ed: L. Paquette) 2004, J. Wiley & Sons, New York. Шаблон:Doi.
- ↑ Шаблон:Cite journal
External links
- National Pollutant Inventory - Cobalt fact sheet
- National Pollutant Inventory - Fluoride and compounds fact sheet
Шаблон:Cobalt compounds Шаблон:Fluorides
