Cobalt(III) fluoride is the chemical compound with the formula CoF3. This highly reactive, hygroscopic brown solid is used to synthesize organofluorine compounds. CoF3 is a powerful fluorinating agent, the product being CoF2. It decomposes upon contact with water to give oxygen.
CoF3 is prepared in the laboratory by treating CoCl2 with fluorine at 250 °C:
CoF3 is hygroscopic and can be converted to the anion [CoF6]3-, a rare example of a high-spin, octahedral cobalt(III) complex.
Such reactions are sometimes accompanied by rearrangements or other reactions. The related reagent KCoF4 is more selective.