Neptunium(IV) phosphide

Neptunium(IV) phosphide is a binary inorganic compound of neptunium metal and phosphorus with the chemical formula Np3P4.

Preparation
Neptunium(IV) phosphide can be formed from the fusion of stoichiometric amounts of neptunium and red phosphorus in an evacuated and sealed quartz tube at 750 °C:
 * 3Np + 4P -> Np3P4

Physical properties
Neptunium(IV) phosphide forms black crystals of cubic crystal system, spatial group I 43d. Isostructural with Th3P4.

It does not dissolve in water.

Chemical properties
The compound reacts with concentrated HCl to give a green solution:
 * Np3P4 + 12HCl -> 3NpCl4 + 4PH3