Cobalt(II) fluoride is prepared by heating anhydrous cobalt(II) chloride or oxide in a stream of hydrogen fluoride:
CoCl2 + 2HF → CoF2 + 2HCl
CoO + 2HF → CoF2 + 2H2O
Also, cobalt(II) fluoride can be prepared as a tetrahydrate, CoF2•4H2O by dissolving cobalt(II) hydroxide in hydrofluoric acid. The tetrahydrate is then dehydrated to anhydrous fluoride. Elemental fluorine combines with cobalt at 450°C forming mixtures of cobalt(II)–and cobalt(III) fluorides.
Rose-red crystals or powder. Soluble in cold
water and hydrofluoric acid. Decomposes in hot
water. Ammine complexes can be prepared from
the hydrate.
Red tetragonal crystal; density 4.46 g/cm3; melts at 1,127°C; vaporizes around 1,400°C; sparingly soluble in water; soluble in warm mineral acids; decomposes in boiling water. Tetrahydrate is red orthogonal crystal; density 2.22 g/cm3; decomposes on heating; soluble in water; di- and trihydrates are soluble in water.
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. The compound may be used in dental care.
Catalyst for organic reactions.
Violet to red solid. Sinks and mixes slowly with water.
Cobalt(II) fluoride is a toxic, light brown crystalline material, when exposed to water Cobalt(II) fluoride forms highly corrosive hydrofluoric acid. When heated to decomposition Cobalt(II) fluoride emits toxic fumes of metallic cobalt and fluorides [Lewis, 3rd ed., 1993, p. 344].
INHALATION: Inhalation of dust may cause pulmonary symptoms. EYES: Irritation. SKIN: Skin rashes, dermatitis. INGESTION: Nausea and vomiting caused by local irritation.
LD50 oral (rat): 150 mg/kg
Poison by ingestion.
When heated to decomposition it emits
toxic fumes of Co and F-.
