Cobalt(II) fluoride is a chemical compound with the formula (CoF2). It usually appears as a white or pale yellow solid. It is a pink crystalline solid compound which is antiferromagnetic at low temperatures (TN=37.7 K). It is soluble in water and can form a variety of hydrates. It is used in various applications, including as a catalyst in organic reactions and in the preparation of other cobalt compounds.
CoF2 is used in oxygen-sensitive fields, namely metal production. In low concentrations, it has public health uses. CoF2 is sparingly soluble in water. The compound can be dissolved in warm mineral acid, and will decompose in boiling water. Like some other metal difluorides, CoF2 crystallizes in the rutile structure, which features octahedral Co centers and planar fluorides.
Properties
- Chemical formula: CoF2
- Molar mass: 96.93 g/mol
- Appearance: Red crystalline solid
- Density: 4.46 g/cm3 (anhydrous), 2.22 g/cm3 (tetrahydrate)
- Melting point: 1,217 °C (2,223 °F; 1,490 K)
- Boiling point: 1,400 °C (2,550 °F; 1,670 K)
- Solubility in water: 1.4 g/100 mL (25 °C)
- Solubility: soluble in HF, insoluble in alcohol, ether, benzene
Preparation
Cobalt(II) fluoride can be prepared from anhydrous cobalt(II) chloride or cobalt(II) oxide in a stream of hydrogen fluoride:
CoCl2 + 2HF → CoF2 + 2HCl
CoO + 2HF → CoF2 + H2O
It is produced in the reaction of cobalt (III) fluoride with water.
The tetrahydrate cobalt(II) fluoride is formed by dissolving cobalt(II) in hydrofluoric acid. The anhydrous fluoride can be extracted from this by dehydration. Other synthesis can occur at higher temperatures. It has been shown that at 500 °C fluorine will combine with cobalt producing a mixture of CoF2 and CoF3.
Natural Sources
Cobalt(II) fluoride is not commonly found in nature as a pure mineral. Instead, cobalt is typically found in minerals like cobaltite (CoAsS) and erythrite (Co3(AsO4)2·8H2O).
Industrial Production
Cobalt(II) fluoride can be synthesized in the laboratory and is used in various applications, including:
- Electrochemistry: It serves as a source of cobalt ions in battery applications.
- Catalysis: It can act as a catalyst in chemical reactions.
Uses
Cobalt(II) fluoride can be used as a catalyst to alloy metals. It is also used for optical deposition, of which it tremendously improves optical quality. Cobalt(II) fluoride is available in most volumes in an ultra high purity composition. High purity compositions improve optical qualities and its usefulness as a standard.
