Structural Isomerism in coordination compounds

 

Structural Isomerism-

·      structural isomers having same chemical formula but different structure.

·      This isomerism arises due to difference in structures of coordination compounds.

a). Linkage isomerism:

·      This type of isomerism occurs in complex compounds which contain ambidentate ligands like NO₂^-, SCN^-, CN^-

·      These ligands have two donor atoms but at a time only one atom is directly linked to the central metal atom of the complex.

Example

[Co (NH₃)₅N0₂] Cl₂                     <----->        [Co(NH₃)₅ONO]Cl₂

           Pentaamminenitrito-N-cobalt(III)          Pentaamminenitrito-O-cobalt(III)

                           chloride (yellow)                                  chloride (red)

b). Coordination position isomerism:

·      This type of isomerism is exhibited by polynuclear complexes by changing the position of ligands with respect to different metal atoms present in the complex

Example-

 [Co(NH₃)₆][Cr(CN)₆]  <------->  [Cr(NH₃)₆][Co(CN)₆]      

c). Ionisation isomerism :

·      this form of isomerism arises when the counter ion in a complex salt is itself a potential ligand and can displace a ligand which can become the counter ion.

Example-

[Co (NH₃)₅Br]SO₄       ------>  [Co (NH₃)₅SO₄]Br

 

d) solvate isomerism

·   This form of isomerism is known as hydrate isomerism when water is involved as a solvent.

·   This is similar to ionisation isomerism solvate isomer differ by whether or not a solvent molecule is directly bonded to the metal ion or merely present as free solvent molecules in the crystal lattice.

·    when different number of water molecules are present inside and outside the coordination sphere.

Example-

[Cr(H2O)₆] Cl₃          --------->[Cr(H₂O)₅Cl]C1₂·H₂O