difluoride

A difluoride is a chemical compound that contains two fluoride (F−) ligands or atoms in its formula. In inorganic chemistry, the term is most often applied to binary compounds with the general formula MF2, in which a metal cation M is coordinated by two fluoride anions. The surrounding structure and bonding can vary from highly ionic in many metal difluorides to more covalent or polymeric in certain early‑stage metals (for example, BeF2 is a polymeric network).

Examples and properties. Well‑known difluorides include calcium difluoride (CaF2), magnesium difluoride (MgF2), strontium difluoride (SrF2), and barium difluoride (BaF2). These compounds are typically crystalline solids with relatively high melting points and, for many, limited solubility in water. BeF2 is exceptional among difluorides for its covalent, polymeric character rather than a simple ionic lattice. Some transition‑ and post‑transition‑metal difluorides also exist, with a range of magnetic and optical properties.

Occurrence and uses. CaF2, the mineral fluorite, occurs naturally and is widely used as an optical material due to its transparency in the ultraviolet and visible ranges. MgF2 and BaF2 are also used in optics and coatings; BaF2 has applications in scintillation detectors. In many cases, difluorides are prepared synthetically and may serve as precursors to other fluoride compounds or as components in ceramic or optical materials.

Synthesis and safety. Difluorides are typically produced by fluorination of the corresponding metal or metal oxide, or by metathesis reactions involving fluoride sources. Fluorides can be toxic; fluoride exposure and handling of fluorinating agents (such as fluorine gas or hydrofluoric acid) require appropriate safety precautions.