Mercury(I) fluoride

Mercury(I) fluoride or mercurous fluoride is the chemical compound composed of mercury and fluorine with the formula Hg2F2. It consists of small yellow cubic crystals, which turn black when exposed to light.[1]

Mercury(I) fluoride
Names
IUPAC name
Dimercury difluoride
Other names
Mercury(I) fluoride
Mercurous fluoride
Identifiers
3D model (JSmol)
ECHA InfoCard 100.034.302
UNII
Properties
Hg2F2
Molar mass 439.177 g/mol
Appearance yellow cubic crystals
Density 8.73 g/cm³, solid
decomposes[1]
−26.5·10−6 cm3/mol
Hazards
Very toxic (T+)
Dangerous for
the environment (N)
R-phrases (outdated) R26/27/28, R33, R50/53
S-phrases (outdated) S13, S28, S45, S60, S61[2]
NFPA 704 (fire diamond)
Flammability code 0: Will not burn. E.g. waterHealth code 4: Very short exposure could cause death or major residual injury. E.g. VX gasReactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
0
4
0
Flash point non-flammable
Related compounds
Other anions
 Mercury(I) chloride
Mercury(I) bromide
Mercury(I) iodide
Other cations
 Zinc fluoride
Cadmium fluoride
Related compounds
 Mercury(II) fluoride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is YN ?)
Infobox references

Synthesis

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

Hg2CO3 + 2 HF → Hg2F2 + CO2 + H2O

Reactions

When added to water, mercury(I) fluoride hydrolyzes to elemental liquid mercury, mercury(II) oxide, and hydrofluoric acid:[1]

Hg2F2 + H2O → Hg + HgO + 2 HF

It can be used in the Swarts reaction to convert alkyl halides into alkyl fluorides:[3]

2 R-X + Hg2F2 → 2 R-F + Hg2X2
where X = Cl, Br, I

Structure
Unit cell of Hg2F2, with F from adjacent molecules coordinating the Hg atoms

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.[4] The overall coordination of each Hg atom is a distorted octahedron; in addition to the bonded F and other Hg of the molecule, there are four other F atoms at 272 pm.[4] The compound is often formulated as Hg22+ 2F−.[5]

References
  1. Perry, Dale L.; Phillips, Sidney L. (1995), Handbook of Inorganic Compounds, CRC Press, p. 256, ISBN 0-8493-8671-3, retrieved 2008-06-17
  2. 339318 Mercury(I) fluoride technical grade, Sigma-Aldrich, retrieved 2008-06-17
  3. Beyer, Hans; Walter, Wolfgang; Lloyd, Douglas (1997), Organic Chemistry, Horwood Publishing, p. 136, ISBN 1-898563-37-3, retrieved 2008-06-17
  4. Wells A.F. (1984) Structural Inorganic Chemistry 5th edition Oxford Science Publications ISBN 0-19-855370-6
  5. Cotton, F. Albert; Wilkinson, Geoffrey; Murillo, Carlos A.; Bochmann, Manfred (1999), Advanced Inorganic Chemistry (6th ed.), New York: Wiley-Interscience, ISBN 0-471-19957-5
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