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Niobium(V) fluoride

Niobium(V) fluoride, also known as niobium pentafluoride, is the inorganic compound with the formula NbF<sub>5</sub>. It is a colorless solid.

Preparation and structure

Niobium pentafluoride is obtained by treatment of any niobium compound with fluorine:

2 Nb + 5 F<sub>2</sub> → 2 NbF<sub>5</sub>
2 NbCl<sub>5</sub> + 5 F<sub>2</sub> → 2 NbF<sub>5</sub> + 5 Cl<sub>2</sub>

As shown by X-ray crystallography, the solid consists of tetramers [NbF<sub>5</sub>]<sub>4</sub>. This structure is related to that for WOF<sub>4</sub>.

Reactions

It reacts with hydrogen fluoride to give H<sub>2</sub>NbF<sub>7</sub>, a superacid. In hydrofluoric acid, NbF<sub>5</sub> converts to [NbF<sub>7</sub>]<sup>2-</sup> and [NbF<sub>5</sub>O]<sup>2-</sup>. The relative solubility of (M = Nb, Ta) is the basis of the Marignac process for separation of Nb and Ta.

NbCl<sub>5</sub> forms a dimeric structure (edge-shared bioctahedron) in contrast to the corner-shared tetrameric structure of the fluoride.

References

External links