Niobium Oxytribromide, NbOBr₃

Niobium Oxytribromide, NbOBr₃, is prepared by the action of bromine on a mixture of niobium pentoxide and carbon. The method is that by which the pentabromide is produced, but in this case the proportion of carbon present is much smaller. The product is distilled in an atmosphere of bromine or nitrogen. It is a bright yellow, voluminous substance, which sublimes without melting in an atmosphere of bromine, but is converted completely into niobium pentoxide on being sublimed in an atmosphere of carbon dioxide. It fumes in damp air and is decomposed by water with formation of niobic acid and hydrobromic acid. It is soluble in hot concentrated sulphuric and hydrochloric acids, in absolute alcohol and dry ethyl bromide.

These correspond exactly to the double salts of niobium oxytrichloride described above, and are prepared by analogous methods. The following are known:

NbOBr₃.2RbBr Small, dark red octahedra.
NbOBr₃.2CsBr Pale yellow octahedra.
NbOBr₃.C₅H₅N.HBr Orange-red crystals.
NbOBr₃.C₉H₇N.HBr Orange-red prisms.
These double salts are even more unstable in damp air than the corresponding chlorine compounds.