Chromium(III) fluoride is an

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

with the

chemical formula A chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, such as pare ...

. It forms several

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. The compound is a green crystalline solid that is insoluble in common solvents, but the hydrates (violet) and (green) are soluble in water. The anhydrous form

sublimes Sublimation is the Phase transition, transition of a substance directly from the solid to the gas state, without passing through the liquid state. The verb form of sublimation is ''sublime'', or less preferably, ''sublimate''. ''Sublimate' ...

at 1100–1200 °C.

Structures

Like almost all compounds of chromium(III), these compounds feature

octahedral In geometry, an octahedron (: octahedra or octahedrons) is any polyhedron with eight faces. One special case is the regular octahedron, a Platonic solid composed of eight equilateral triangles, four of which meet at each vertex. Many types of i ...

Cr centres. In the anhydrous form, the six coordination sites are occupied by fluoride

ligand In coordination chemistry, a ligand is an ion or molecule with a functional group that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's el ...

s that bridge to adjacent Cr centres. In the hydrates, some or all of the fluoride ligands are replaced by water.

Production

Chromium(III) fluoride is produced from the reaction of

chromium(III) oxide Chromium(III) oxide (or chromia) is an inorganic compound with the formula . It is one of the principal oxides of chromium and is used as a pigment. In nature, it occurs as the rare mineral eskolaite. Structure and properties has the corundum s ...

and

hydrofluoric acid Hydrofluoric acid is a solution of hydrogen fluoride (HF) in water. Solutions of HF are colorless, acidic and highly corrosive. A common concentration is 49% (48–52%) but there are also stronger solutions (e.g. 70%) and pure HF has a boiling p ...

:Gerd Anger, Jost Halstenberg, Klaus Hochgeschwender, Christoph Scherhag, Ulrich Korallus, Herbert Knopf, Peter Schmidt, Manfred Ohlinger, "Chromium Compounds" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2005. : The anhydrous form is produced from

hydrogen fluoride Hydrogen fluoride (fluorane) is an Inorganic chemistry, inorganic compound with chemical formula . It is a very poisonous, colorless gas or liquid that dissolves in water to yield hydrofluoric acid. It is the principal industrial source of fluori ...

and

chromic chloride Chromium(III) chloride (also called chromic chloride) is an inorganic chemical compound with the chemical formula . This crystalline salt forms several hydrates with the formula , among which are hydrates where ''n'' can be 5 (chromium(III) chlori ...

: : Another method of synthesis of involves

thermal decomposition Thermal decomposition, or thermolysis, is a chemical decomposition of a substance caused by heat. The decomposition temperature of a substance is the temperature at which the substance chemically decomposes. The reaction is usually endothermic ...

of ( ammonium hexafluorochromate(III)): : A mixed valence compound (chromium(II,III) fluoride) is also known.

Uses

Chromium(III) fluoride finds some applications as a

mordant A mordant or dye fixative is a substance used to set (i.e., bind) dyes on fabrics. It does this by forming a coordination complex with the dye, which then attaches to the fabric (or tissue). It may be used for dyeing fabrics or for intensifying ...

textiles Textile is an Hyponymy and hypernymy, umbrella term that includes various Fiber, fiber-based materials, including fibers, yarns, Staple (textiles)#Filament fiber, filaments, Thread (yarn), threads, and different types of #Fabric, fabric. ...

and as a

corrosion inhibitor A corrosion inhibitor or anti-corrosive is a chemical compound added to a liquid or gas to decrease the corrosion rate of a metal that comes into contact with the fluid. The effectiveness of a corrosion inhibitor depends on fluid composition and ...

. Chromium(III) fluoride

catalyzes Catalysis () is the increase in rate of a chemical reaction due to an added substance known as a catalyst (). Catalysts are not consumed by the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recycles quick ...

the

fluorination In chemistry, halogenation is a chemical reaction which introduces one or more halogens into a chemical compound. Halide-containing compounds are pervasive, making this type of transformation important, e.g. in the production of polymers, drugs. ...

chlorocarbons Organochlorine chemistry is concerned with the properties of organochlorine compounds, or organochlorides, organic compounds that contain one or more carbon–chlorine bonds. The chloroalkane class (alkanes with one or more hydrogens substituted ...

by HF.Ruh R. P.; Davis R. A. Proceess for Fluorinating Aliphatic Halohydrocarbons with a Chromium Fluoride catalyst and process for preparing the catalyst. U.S. Patent 2,745,886, May 15, 1956; n.a.

References

{{fluorides Fluorides Metal halides Chromium(III) compounds