Vanadium(III) fluoride

Vanadium(III) fluoride is the chemical compound with the formula VF₃. This yellow-green, refractory solid is obtained in a two-step procedure from V₂O₃. Similar to other transition-metal fluorides (such as MnF₂), it exhibits magnetic ordering at low temperatures (e.g. V₂F₆.4H₂O orders below 12 K).

Preparation

The first step entails conversion to the hexafluorovanadate(III) salt using ammonium bifluoride:

V₂O₃ 6 (NH₄)HF₂ → 2 (NH₄)₃VF₆ 3 H₂O

In the second step, the hexafluorovanadate is thermally decomposed.

(NH₄)₃VF₆ → 3 NH₃ 3 HF VF₃

The thermal decomposition of ammonium salts is a relatively common method for the preparation of inorganic solids.

VF₃ can also be prepared by treatment of V₂O₃ with HF. VF₃ is a crystalline solid with 6 coordinate vanadium atoms with bridging fluorine atoms. The magnetic moment indicates the presence of two unpaired electrons.

References

• Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.