Editing Coordination complex (section)

====Structural isomerism====
[[Structural isomerism]] occurs when the bonds are themselves different. Four types of structural isomerism are recognized: ionisation isomerism, solvate or hydrate isomerism, linkage isomerism and coordination isomerism.
# '''Ionisation isomerism''' – the isomers give different ions in solution although they have the same composition. This type of isomerism occurs when the counter ion of the complex is also a potential ligand. For example, pentaamminebromocobalt(III) sulphate {{chem2|[Co(NH3)5Br]SO4}} is red violet and in solution gives a precipitate with barium chloride, confirming the presence of sulphate ion, while pentaamminesulphatecobalt(III) bromide {{chem2|[Co(NH3)5SO4]Br}} is red and tests negative for sulphate ion in solution, but instead gives a precipitate of AgBr with silver nitrate.<ref name=Huheey>Huheey, James E., ''Inorganic Chemistry'' (3rd ed., Harper & Row 1983), p.524–5 {{ISBN|0-06-042987-9}}</ref>
# [[Hydration isomerism|Solvate or hydrate isomerism]] – the isomers have the same composition but differ with respect to the number of molecules of solvent that serve as ligand vs simply occupying sites in the crystal. Examples: {{chem2|[Cr(H2O)6]Cl3}} is violet colored, {{chem2|[CrCl(H2O)5]Cl2·H2O}} is blue-green, and {{chem2|[CrCl2(H2O)4]Cl*2H2O}} is dark green. See [[water of crystallization]].<ref name=Huheey/>
# '''[[Linkage isomerism]]''' occurs with ligands with more than one possible donor atom, known as [[ambidentate ligand]]s.<ref name=Jolly>{{cite book |last1=Jolly |first1=William L. |title=Modern Inorganic Chemistry |date=1984 |publisher=McGraw-Hill |isbn=0-07-032760-2 |pages=357–9}}</ref> For example, [[nitrite]] can coordinate through O or N.<ref>Huheey, James E., ''Inorganic Chemistry'' (3rd ed., Harper & Row 1983), p.513–24 {{ISBN|0-06-042987-9}}</ref> One pair of nitrite linkage isomers have structures {{chem2|(NH3)5CoNO2(2+)}} (nitro isomer) and {{chem2|(NH3)5CoONO(2+)}} (nitrito isomer).<ref name=Jolly/>
# '''[[Coordination isomerism]]''' occurs when both positive and negative ions of a salt are complex ions and the two isomers differ in the distribution of ligands between the cation and the anion. For example, {{chem2|[Co(NH3)6][Cr(CN)6]}} and {{chem2|[Cr(NH3)6][Co(CN)6]}}.<ref name=Huheey/>