Linkage isomerism example are explained with all details in this article.
Isomerism shown by this ambidentate ligands are called linkage isomerism. In otherwise linkage isomerism is the isomerism shown by ligands that can donate electron pair from two different sites.
Examples of complexes with linkage isomerism is listed and described below.
- [Co(NH3)NO2]Cl2 and [Co(NH3)ONO]Cl2
- [Cr SCN(H2O)]2+ and [Cr NCS(H2O)]2+
- [Pd (PPh3)2 (NCS)2] and [Pd (PPh3)2 (SCN)2]
- [Co(NH3)5SCN]2+ and [Co(NH3)5NCS]2+
- [Fe Cl5 (NO2)]3- and [Fe Cl5(ONO)]3-
- [Co(CN)5 SCN]3- and [Co(CN)5 NCS]3-
- [Ru(NH3)5 OS]3+ and [Ru(NH3)5 SO]3+
Some compounds have same chemical formula but are different in the arrangement of atoms. Such compounds are called isomers and the phenomenon is called isomerism.
Due to this property, these compounds are differ in one or more physical and chemical properties even though they are identical in their chemical formula. This property of isomerism is mainly shown by coordination compounds.
There are two principal types of isomerism and its sub classifications.
Stereo isomerism is the isomerism shown by compounds with same chemical formula and bonds but differ in their spatial arrangement of atoms.
Structural isomerism is the isomerism due to the difference in the structure of coordination compounds. Structural isomerism is divided into different types like ionisation, linkage, coordination and solvate isomerism.
Before going to linkage isomerism it is important to understand about ambidentate ligand. Ambidentate ligands are monodentate ligands which are capable of ligating through two different donor atoms present in them.
For example; In NO2 or Nitro group it can coordinate with the metal through either Nitrogen atom or through Oxygen atom. If it coordinates to the metal through nitrogen then it is represented as nitro or nitrito – N. If it is coordinated to the metal through oxygen then represented as nitrito – O. It is written as O-N=O.
Another examples for ambidentate ligands are SCN,CN, SeCN,SO32-.In the case of SCN, if sulphur is the donor atom then it is named as thiocyanate and if nitrogen id donor then it is isothiocyanate.
So the isomerism shown by this ambidentate ligands are called linkage isomerism or linkage isomerism is the isomerism shown by ligands that can donate electron pair from two different sites.
[Co(NH3)NO2]Cl2 and [Co(NH3)ONO]Cl2
Here the ambidentate ligand is nitro group so it can coordinate to the metal cobalt through nitrogen atom and oxygen. So this two different types of coordination results two different complexes. The first one is yellow in colour while the other is in red. This is due to the coordination of the nitro group with central metal atom.
[Cr SCN(H2O)]2+ and [Cr NCS(H2O)]2+
Here the ambidentate ligand is SCN so it can coordinate to the metal cobalt through sulphur atom and nitrogen atom. So this two different types of coordination results two different complexes.
In the first one sulphur is coordinated which is violet in colour while in the second nitrogen is the coordinated to the metal which is orange colour. This is due to the coordination of the thiocyanate and isothiocyanate groups with central metal atom respectively.
Figures of other examples showing linkage isomerism is shown below.
[Pd (PPh3)2 (NCS)2] and [Pd (PPh3)2 (SCN)2]
[Co(NH3)5SCN]2+ and [Co(NH3)5NCS]2+
[Fe Cl5 (NO2)]3- and [Fe Cl5(ONO)]3-
[Co(CN)5 SCN]3- and [Co(CN)5 NCS]3-
[Ru(NH3)5 OS]3+ and [Ru(NH3)5 SO]3+
From all these examples and its detailed structures we can conclude that linkage isomerism is the isomerism shown by certain ligands that has more than one donor atoms present in it.
Hi… I am Aparna Dev, a chemistry Postgraduate with a good understanding of chemistry concepts. I am working in Kerala Minerals and Metals Limited Kollam with experience in the development of electrocatalysts as a part of post graduate thesis.
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