Difluoride

Order and disorder in difluorides
A parallelogram-shaped outline with space-filling diatomic molecules (joined circles) arranged in two layers cube of 8 yellow atoms with white ones at the holes of the yellow structure
The fluorite structure Beryllium fluoride glass

Difluorides are chemical compounds with two fluorine atoms per molecule (or per formula unit).

Metal difluorides are all ionic. Despite being highly ionic, the alkali earth metal difluorides generally have extremely high lattice stability and are thus insoluble in water. One exception is beryllium difluoride. In addition, many transition metal difluorides are water-soluble.

Calcium difluoride is a notable compound. In the form of the mineral fluorite it is the major source of commercial fluorine. It also has an epynomic crystal structure, which is an end member of the spectrum starting from bixbyite and progressing through pyrochlore.

Solubility-related constants of alkaline earth metal fluorides
Metal
 M2+ HE[1] F− HE[2] "MF2" unit
HE		 MF2 lattice
energies (−kJ/mol)[3] 		Solubility
(mol/L)[4]
Be 2,455 458 3,371 3,526 soluble
Mg 1,922 458 2,838 2,978 0.0012
Ca 1,577 458 2,493 2,651 0.0002
Sr 1,415 458 2,331 2,513 0.0008
Ba 1,361 458 2,277 2,373 0.006

List of the difluorides

Examples of the difluorides include:

Metal difluorides

Compounds of the form MF2:

Bifluorides

The bifluorides contain the two fluorine atoms in a covalently bound HF2− polyatomic ion rather than as F− anions.

Nonmetal difluorides

Organic difluorides

References

  1. ↑ Wiberg, Wiberg & Holleman 2001, pp. XXXVI–XXXVII.
  2. ↑ Wiberg, Wiberg & Holleman 2001, p. XXXVI.
  3. ↑ Lide 2004, p. 12-23.
  4. ↑ Wiberg, Wiberg & Holleman 2001, p. 1073.

Bibliography

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