Mercury(I) fluoride or mercurous fluoride is the

chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...

composed of

mercury Mercury commonly refers to: * Mercury (planet), the nearest planet to the Sun * Mercury (element), a metallic chemical element with the symbol Hg * Mercury (mythology), a Roman god Mercury or The Mercury may also refer to: Companies * Merc ...

and

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 reacti ...

with the

formula In science, a formula is a concise way of expressing information symbolically, as in a mathematical formula or a ''chemical formula''. The informal use of the term ''formula'' in science refers to the general construct of a relationship betwee ...

Hg₂F₂. It consists of small yellow cubic crystals, which turn black when exposed to light.

Synthesis

Mercury(I) fluoride is prepared by the reaction of mercury(I) carbonate with

hydrofluoric acid Hydrofluoric acid is a Solution (chemistry), solution of hydrogen fluoride (HF) in water. Solutions of HF are colourless, acidic and highly Corrosive substance, corrosive. It is used to make most fluorine-containing compounds; examples include th ...

: :Hg₂CO₃ + 2 HF → Hg₂F₂ + CO₂ + H₂O

Reactions

When added to water, mercury(I) fluoride hydrolyzes to elemental liquid mercury,

mercury(II) oxide Mercury(II) oxide, also called mercuric oxide or simply mercury oxide, is the inorganic compound with the formula Hg O. It has a red or orange color. Mercury(II) oxide is a solid at room temperature and pressure. The mineral form montroydite is v ...

, and hydrofluoric acid: :Hg₂F₂ + H₂O → Hg + HgO + 2 HF It can be used in the

Swarts reaction Swarts fluorination is a process whereby the chlorine atoms in a compound – generally an organic compound, but experiments have been performed using silanes – are replaced with fluorine, by treatment with antimony trifluoride in the presence o ...

to convert

alkyl halide The haloalkanes (also known as halogenoalkanes or alkyl halides) are alkanes containing one or more halogen substituents. They are a subset of the general class of halocarbons, although the distinction is not often made. Haloalkanes are widely ...

s into alkyl fluorides: :2 R-X + Hg₂F₂ → 2 R-F + Hg₂X₂ :where X = Cl, Br, I

Structure

In common with other Hg(I) (mercurous) compounds which contain linear X-Hg-Hg-X units, Hg₂F₂ contains linear FHg₂F units with an Hg-Hg bond length of 251 pm (Hg-Hg in the metal is 300 pm) and an Hg-F bond length of 214 pm.Wells A.F. (1984) ''Structural Inorganic Chemistry'' 5th edition Oxford Science Publications The overall coordination of each Hg atom is a distorted

octahedron In geometry, an octahedron (plural: octahedra, octahedrons) is a polyhedron with eight faces. The term is most commonly used to refer to the regular octahedron, a Platonic solid composed of eight equilateral triangles, four of which meet at ea ...

; in addition to the bonded F and other Hg of the molecule, there are four other F atoms at 272 pm. The compound is often formulated as Hg₂²⁺ 2F⁻.

References

{{fluorine compounds Mercury(I) compounds Fluorides Metal halides