Alkali fluorides, protactinium

Table IV. Some Alkali Fluoride Protactinium ( V ), Uranium ( V ), Neptunium(V), Plutonium(V) Fluoride Complexes"...

Table I. Alkali Fluoride Complexes of Tetravalent Protactinium...

Complex fluorides containing tetravalent protactinium and the alkali fluorides (Li, Na, K, Rb, and NH4) were prepared from MF -j- PaF4 starting mixtures and by reducing MF-PaF compounds at 400°—500°C. using pure hydrogen, obtained from UH3. The x-ray results on compounds obtained by these methods are presented in Table I. 

A recent study of the alkali metal/uranium fluoride complex systems has shown that KriUFo, K3UF7, and K UFs are isomorphous (99), the crystal symmetry being unaffected by the fluoride ion absences. The structure of K PaFy has been determined only recently (39), and it has been shown that each protactinium atom is surrounded by nine fluorine atoms in what is effectively a trigonal prism with three added equatorial fluorine atoms the PaFo groups are linked in infinite chains by two fluorine bridges. 

Protactinium(V) octafluoro complexes, MlPaF, have been prepared (5, 35, 37, 59) by precipitation from aqueous hydrofluoric acid (M = Li, Na, and Rb), by heating the alkali metal fluoride with the corresponding heptafluoro complex in argon (M = K and Cs) or by fluorinating the product obtained by evaporation of a hydrofluoric acid solution containing 3 1 mixtures of MF and Pa(V). 

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