Manganese niobium fluoride

Manganese Niobium Fluoride, 3NbFs.5MnF2.5HF.28H20 or Nb8Mh5F2s-28H20, forms rose-coloured, long prisms, which are obtained similarly to the cadmium salt. 

In the case of a mixture of hydrofluoric and sulfuric acids, the process is more complex. It can be noted that sulfuric acid most probably interacts mainly with iron and manganese, whereas hydrofluoric acid serves mostly in the dissolution of tantalum and niobium and their conversion into soluble fluoride complexes. Nevertheless, due to the high acidity of the solution, here too the formation of hexafluorotantalate and hexafluoroniobate complex ions, TaF6" and NbF6, is expected. Hence, it is noted that the acid dissolution of tantalum-and niobium-containing raw material leads to the formation of hexafluoro-acids — HTaF6 and HNbF6. 

The cake is leached with water in order to dissolve tantalum and niobium (and other related compounds) in the form of fluoride salts of ammonium. Ammonium fluoroferrate and fluoromanganate are unstable in aqueous solutions of low acidity. It is assumed that iron and manganese will form precipitates of insoluble fluorides or oxyfluorides that can be separated from the solution by filtration. 

It is convenient here to include fluorides with a metal-to-fluorine ratio of 1 2.5. There are three examples. The chromium (53) and manganese (54) compounds, which are not isostructural, can be considered of the type, MF2,MF3, containing di- and trivalent metals. The niobium compound (35) is the only example of a metal cluster fluoride reported as yet. 

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