The compound Co(NH3)4BrSO4 exhibits Ionization Isomerism.

Ionization isomerism occurs when a ligand inside the coordination sphere exchanges places with an ion outside the coordination sphere. In this case, the bromide ion ($\text{Br}^-$) and the sulfate ion ($\text{SO}_4^{2-}$), both of which can act as ligands, swap positions between the inner and outer coordination spheres.

The central metal ion is $\text{Co}^{3+}$. Ammonia ($\text{NH}_3$) is a neutral ligand. Bromide ($\text{Br}^-$) is a monodentate ligand. Sulfate ($\text{SO}_4^{2-}$) can act as a monodentate or bidentate