Chromium(II) fluoride is an inorganic compound with the formula CrF₂. It exists as a blue-green iridescent solid. Chromium(II) fluoride is sparingly soluble in water, almost insoluble in alcohol, and is soluble in boiling

hydrochloric acid Hydrochloric acid, also known as muriatic acid, is an aqueous solution of hydrogen chloride. It is a colorless solution with a distinctive pungent smell. It is classified as a strong acid Acid strength is the tendency of an acid, symbol ...

, but is not attacked by hot distilled sulfuric acid or

nitric acid Nitric acid is the inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but older samples tend to be yellow cast due to decomposition into oxides of nitrogen. Most commercially available nitri ...

. Like other chromous compounds, chromium(II) fluoride is oxidized to

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 ...

in air.

Preparation and structure

The compound is prepared by passing anhydrous hydrogen fluoride over anhydrous

chromium(II) chloride Chromium(II) chloride describes inorganic compounds with the chemical formula, formula Chromium, CrChlorine, Cl2(H2O)n. The anhydrous solid is white when pure, however commercial samples are often grey or green; it is hygroscopic and readily disso ...

. The reaction will proceed at room temperature but is typically heated to 100-200 °C to ensure completion: :CrCl₂ + 2 HF → CrF₂ + 2 HCl Like many difluorides, CrF₂ adopts a structure like

rutile Rutile is an oxide mineral composed of titanium dioxide (TiO2), the most common natural form of TiO2. Rarer polymorphs of TiO2 are known, including anatase, akaogiite, and brookite. Rutile has one of the highest refractive indices at visib ...

with octahedral molecular geometry about Cr(II) and trigonal geometry at F⁻. Two of the six Cr–F bonds are long at 2.43 Å, and four are short near 2.00 Å. This distortion is a consequence of the

Jahn–Teller effect The Jahn–Teller effect (JT effect or JTE) is an important mechanism of spontaneous symmetry breaking in molecular and solid-state systems which has far-reaching consequences in different fields, and is responsible for a variety of phenomena in sp ...

that arises from the d⁴ electron configuration of the chromium(II) ion.

External links

Crystal Structure

References

Chromium(II) compounds Fluorides Metal halides Fluorine compounds {{Inorganic-compound-stub

Preparation and structure

See also

External links

References