Coordination-sphere Isomers
These result from interchange of ligands / ions from within and outside the coordination sphere.
eg. [Co(NH3)5Br]Cl and [Co(NH3)5Cl]Br
Hydrate isomerism is a special case
of
coordination-sphere isomerisation:
eg. [Cr(H2O)6]Cl3
[Cr(H2O)5Cl]Cl2.H2O
[Cr(H2O)4Cl2]Cl.2H2O