The complex $[\mathrm{Co}(\mathrm{NH}{}_3){}_5(\mathrm{NO}{}_2)]\mathrm{Cl}{}_2$ can exist as an isomer in which the ligand is attached through oxygen. This type of isomerism is called

The nitro and nitrito forms differ only in the donor atom (N or O) of the ambidentate $\mathrm{NO}{}_2{}^{-}$ ligand, which is linkage isomerism. The other types involve exchange of ions between the sphere and counter ion, between two complex ions, or water inside and outside.