Rhenium(III) bromide is a chemical compound with the formula Re<sub>3</sub>Br<sub>9</sub>. It is a black lustrous crystalline solid. This compound reacts with water to form rhenium(IV) oxide and is isostructural with rhenium(III) chloride.
This compound is prepared by the reaction of rhenium metal and bromine gas at 500 ðC under nitrogen:
If there is oxygen in the atmosphere, it will instead form rhenium(III) oxybromide.
However, the most common method of producing this compound is by first reacting potassium hexabromorhenate(IV) with silver nitrate, which forms silver hexabromorhenite(IV), then this compound is heated to 600 ðC to form rhenium(III) bromide.
An alternative method is a thermal decomposition of rhenium(V) bromide.