What kind of isomerism exists between [Cr(H2O)6]Cl3 (violet) and [Cr(H2O)5Cl]Cl2.H2O (greyish-green)?
The number of water molecules inside and outside the coordination complex differs. So, it has to be solvate isomerism. Solvate isomers tell us if the solvent is attached to the central atom or is outside the coordination sphere and free.
Ligands that have two different bonding sites are called ambident ligands. Few examples are SCN-,NO2 etc…
SCN-→ Metal or NCS→Metal
So, [Pd(C6H5)2(SCN)2] and [Pd(C6H5)2(NCS)2] are linkage isomers because they differ in the binding site of the ligands which leads to different linkage.
Whereas, a coordination isomer is a form of structural isomerism in which the composition of the complexion varies. In a coordination isomer the total ratio of ligand to metal remains the same, but the ligands attached to a specific metal ion change.
For Example: A solution containing ([Co(NH3)6]3+) and [Cr(CN)6]3- is a coordination isomer with a solution containing ([Cr(NH3)6] and [Co(CN)6]).
Ionisation Isomers: These are identical except for a ligand has exchanged places with an anion or neutral molecule that was originally outside the coordination complex. The central ion and the other ligands are identical.
