Protactinium tetraiodide

Protactinium tetraiodide is a binary inorganic compound of protactinium metal and iodine with the chemical formula PaI4.

Synthesis
Protactinium tetraiodide can be prepared by reducing the pentaiodide with aluminum at about 400 °C:
 * 3PaI5 + Al -> 3PaI4 + AlI3

Also, a reaction of hydrogen reduction of protactinium(V) iodide at 400 °C:


 * 2PaI5 + H2 -> 2PaI4 + 2HI

Physical properties
The compound forms black or dark green crystals. The structure is not known.

Chemical properties
The compound is oxidized by antimony trioxide when heated in a vacuum:
 * 3PaI4 + Sb2O3 -> 3PaOI2 + 2SbI3

The compound also reacts with quartz when heated:
 * 2PaI4 + SiO2 -> 2PaOI2 + SiI4