Octahedral Co(NH3)4Br2Cl shows ionisation and geometrical isomerism. In ionisation isomerism ligands show different coordination sphere and the anions present outside the coordination sphere. [Co(NH3)4Br2]Cl[Co(NH3)4Br2]++Cl− [Co(NH3)4BrCl]Br[Co(NH3)4BrCl]++Br−
In geometrical isomerism, coordination number of central atom is six and shape is octahedral.