코발트(III)불화물

The heat of formation is —187 kcal mole-1 and the magnetic moment is 1-60 B.M. at 90°K rising to 2.46 B.M. at 293°K; it is thus a high spin compound but not magnetically dilute. Anhydrous cobalt(III) fluoride turns dark in the presence of traces of water and reacts violently with the liquid-evolving oxygen. When heated in an inert atmosphere above 350°, cobalt(II) fluoride is formed. It reacts vigorously with many elements, e.g. Al, P, As, S, I, being reduced to cobalt(II) fluoride. It is insoluble in alcohol, ether and benzene and is a useful fluorinating agent in organic chemistry.

Cobalt(III) fluoride may be prepared by reaction of elemental fluorine with cobalt(II) fluoride, cobalt(II) chloride or cobalt(III) oxide at 300 to 400°C. 2CoF2 + F2 → 2CoF3 2CoCl2 + 3F2 → 2CoF3 + 2Cl2 It should be stored in a sealed glass ampule, free from moisture. Electrolytic oxidation of cobalt(II) fluoride in 40% hydrofluoric acid yields hydrated cobalt(III) fluoride, CoF3·3.5H2O (3.5 is the stoichiometric amount of water per CoF3 molecule in the crystal lattice).