Protactinium(V) fluoride explained

Protactinium(V) fluoride is a fluoride of protactinium with the chemical formula PaF5.

Preparation

Protactinium(V) fluoride can be obtained by reacting protactinium(V) oxide with bromine trifluoride or bromine pentafluoride at 600 °C:

3 Pa2O5 + 10 BrF3 (6 BrF5) -> 6 PaF5 + 5 Br2 (3 Br2) + 7.5 O2

It can also be obtained by reacting protactinium(V) chloride or protactinium(IV) fluoride with fluorine gas at 700 °C:

2 PaF4 + F2 -> 2 PaF5

The hydrate form of protactinium(V) fluoride can be formed by the reaction of protactinium(V) oxide and hydrofluoric acid in an aqueous solution:

Pa2 O5 + 10 HF -> 2 PaF5 . 2 H2O + 6 H2O

It can also be decomposed from fluorine-containing protactinium complexes.[1]

Properties

Protactinium(V) fluoride is a white, volatile, extremely hygroscopic solid that is partially soluble in water and soluble in hydrofluoric acid. It has a tetragonal crystal structure of the β-uranium pentafluoride type with the space group I42d (space group no. 122) with the lattice parameters a = 1153 pm, c = 510 pm. Quartz and Pyrex are attacked by the compound at higher temperatures. As a dihydrate, it is a colourless, hygroscopic, crystalline solid that is waxy in nature. It is soluble in water and hydrofluoric acid. It reacts with phosphorus trifluoride to form protactinium(IV) fluoride.[2] The dihydrate cannot be converted into the anhydrous form in air, hydrogen fluoride or fluorine at low temperatures. Instead, diprotactinium(V) oxide octafluoride (Pa2OF8) is formed. At higher temperatures around 325 °C, a mixture of the diprotactinium(V) oxide octafluoride and protactinium(V) fluoride is formed.

Notes and References

  1. Book: G. Meyer . Lester R. Morss . Synthesis of Lanthanide and Actinide Compounds . Springer . 77 . 1991 . 9780792310181 . de .
  2. Book: Lester R. Morss . Norman M. Edelstein . J. Fuger . The Chemistry of the Actinide and Transactinide Elements . Springer . 1 . 198 . 978-94-0070211-0 . 2010 . de.