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Isomers of Coordination Compounds:























Chem 116 page

















Coordination Isomer
form of Structural Isomer
Coordination isomers vary according to which anions are coordinated to the metal (inner sphere) and which are acting as counterions to the complex ion (outer sphere)

In one example the choloride is bound to the cobalt and bromide is the counter ion. In the other coordination isomer the bromide is coordinated to the cobalt and chloride is the counter ion













Linkage Isomer
form of Structural Isomer 

Linkage isomers contain the same ligands but one or more of the ligands are coordinated to the metal through a different atoms. These ligands are said to be ambidentate. A ligand that has lone pairs on two different atoms can potentially be ambidentate

In this example, nitrite ion NO2- is ambidentate and may be bound through either the lone pair on the central nitrogen atom or the lone pare on the oxygen. This gives rise to two linkage isomers.







Geometric Isomer
form of Stereo-Isomer
Often refered to as cis/trans isomerism. The ligands are coordinated through the same atoms but their spatial orientation varies. Most common forms are:
similar ligands are ~90 degs apart
similar ligands are ~180 degs apart






Optical Isomer
form of Stereo-Isomer

In this case, the spatial orientation of ligands is such that the two isomers are non-super imposable mirror images of one another. There are two common occurences of this type of isomerism

(i) cis-isomers of octahedral complexes with 2 bidentate ligands and 2 monodentate ligands (cis-bis chelates)
(ii) octahedral complexes with 3 bidentate ligands (tris chelates)

Note that trans isomers cannot be optical isomers


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Created 04/30/99
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