Cobalt(III) fluoride is the

inorganic compound In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as '' inorganic chemis ...

with the formula .

Hydrate In chemistry, a hydrate is a substance that contains water or its constituent elements. The chemical state of the water varies widely between different classes of hydrates, some of which were so labeled before their chemical structure was understo ...

s are also known. The anhydrous compound is a hygroscopic brown solid. It is used to synthesize

organofluorine Organofluorine chemistry describes the chemistry of the organofluorines, organic compounds that contain the carbon–fluorine bond. Organofluorine compounds find diverse applications ranging from oil and water repellents to pharmaceuticals, r ...

compounds. 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. Cobalt(III) bromide and cobalt(III) iodide have not been synthesized.

Structure

Anhydrous

Anhydrous cobalt trifluoride crystallizes in the

rhombohedral In geometry, a rhombohedron (also called a rhombic hexahedron or, inaccurately, a rhomboid) is a three-dimensional figure with six faces which are rhombi. It is a special case of a parallelepiped where all edges are the same length. It can be us ...

group, specifically according to the

aluminium trifluoride Aluminium fluoride refers to inorganic compounds with the formula AlF3·''x''H2O. They are all colorless solids. Anhydrous AlF3 is used in the production of aluminium metal. Several occur as minerals. Occurrence and production Aside from anhydr ...

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

A hydrate is known. It is conjectured to be better described as . There is a report of an hydrate , isomorphic to .

Preparation

Cobalt trifluoride can be prepared in the laboratory by treating with

fluorine Fluorine is a chemical element with the symbol F and atomic number 9. It is the lightest halogen and exists at standard conditions as a highly toxic, pale yellow diatomic gas. As the most electronegative reactive element, it is extremely reactiv ...

at 250 °C:H. F. Priest (1950): "Anhydrous Metal Fluorides". In ''Inorganic Syntheses'', McGraw-Hill, volume 3, pages 171-183. : + 3/2 → + In this redox reaction, and are oxidized to and , respectively, while is reduced to . Cobalt(II) oxide (CoO) and cobalt(II) fluoride () 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. The compound can also be formed by treating with

chlorine trifluoride Chlorine trifluoride is an interhalogen compound with the formula ClF3. This colorless, poisonous, corrosive, and extremely reactive gas condenses to a pale-greenish yellow liquid, the form in which it is most often sold (pressurized at room temp ...

bromine trifluoride Bromine trifluoride is an interhalogen compound with the formula BrF3. At room temperature, it is a straw-coloured liquid with a pungent odor which decomposes violently on contact with water and organic compounds. It is a powerful fluorinating a ...

Reactions

decomposes upon contact with water to give oxygen: :4 + 2 H₂O → 4 HF + 4 Co + O₂ It reacts with fluoride salts to give the anion oF₆sup>3−, which is also features high-spin, octahedral cobalt(III) center.

Applications

is a powerful fluorinating agent. Used as slurry, converts

hydrocarbon In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and hydrophobic, and their odors are usually weak or ...

s to the perfluorocarbons: :2 + R-H → 2 Co + R-F + HF Co is the byproduct. Such reactions are sometimes accompanied by rearrangements or other reactions. The related reagent KCoF₄ is more selective.

Gaseous

In the gas phase, is calculated to be planar in its ground state, and has a 3-fold rotation axis (symmetry notation D_3h). The 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. This calculation was the first treatment of the Jahn-Teller effect using calculated energy surfaces.

References

External links

National Pollutant Inventory - Cobalt fact sheet
{{fluorine compounds Fluorides Metal halides Cobalt(III) compounds Fluorinating agents