Protactinium(IV) chloride explained

Protactinium(IV) chloride is an inorganic compound. It is an actinide halide, a salt composed of protactinium and chlorine. It is radioactive, and has the chemical formula of PaCl₄. It is a chartreuse-coloured (yellowish-green) crystal of the tetragonal crystal system.

Preparation

Protactinium(IV) chloride can be prepared by the reduction of protactinium(V) chloride:^[1]

2 PaCl5 + H2 -> 2 PaCl4 + 2 HCl

3 PaCl5 + Al -> 3 PaCl4 + AlCl3

It can also be obtained by the chlorination of protactinium(IV) oxide:^[1]

PaO2 + 2 CCl4 -> PaCl4 + 2 COCl2

It can also be formed during the thermal decomposition of protactinium oxychloride at 500 °C in a vacuum:

2 PaOCl2 -> PaCl4 + PaO2

Properties

Protactinium(IV) chloride is a chartreuse, hygroscopic, crystalline solid that can be sublimed at 400 °C in a vacuum. It is soluble in strong mineral acids, forming green solutions. The complex PaCl₄·4CH₃CN is formed with acetonitrile. It has a tetragonal crystal structure with the space group I4₁/amd (space group no. 141) and the lattice parameters a = 837.7 pm, c = 747.9 pm^[1] of the uranium(IV) chloride type.^[2]

Notes and References

1. Georg Brauer (Hrsg.), unter Mitarbeit von Marianne Baudler u. a.: Handbuch der Präparativen Anorganischen Chemie. 3., umgearbeitete Auflage. Band I, Ferdinand Enke, Stuttgart 1975,, pp. 1176.
2. Lester R. Morss, Norman M. Edelstein, J. Fuger (Hrsg.): . Bände 1-6. Springer, Dordrecht 2010,, S. 201 (English, https://books.google.com/books?id=9vPuV3A0UGUC&pg=PA201 in Google Books).