Neptunium(III) bromide

Neptunium(III) bromide is a bromide of neptunium, with the chemical formula of NpBr3.

Preparation
Neptunium(III) bromide can be prepared by reacting neptunium dioxide and aluminium bromide:


 * 6 NpO2 + 8 AlBr3 -> 6 NpBr3 + 4 Al2O3 + 3 Br2

Properties
Neptunium(III) bromide is a green solid. It can crystallize in two crystal systems:


 * α-NpBr3 is hexagonal with lattice parameters a = 791.7 pm and c = 438.2 pm. It has the same structure as uranium trichloride.


 * β-NpBr3 is orthorhombic with lattice parameters a = 411 pm, b = 1265 pm and c = 915 pm. It has the same structure as the bromides from plutonium to californium.

Neptunium(III) bromide also has a green hexahydrate, which is monoclinic.

Reactions
At 425 °C, neptunium(III) bromide bromide can be further brominated by bromine to form neptunium(IV) bromide.


 * 2 NpBr3 + Br2 -> 2 NpBr4