Geometric isomerism is a type of stereoisomerism that is also known as cis-trans isomerism or E-Z isomerism.
Definition
Geometrical isomerism is not possible in 2-coordinated complexes, 3-coordinated complexes, or 4-coordinated tetrahedral complexes. This is because there are no cis positions in 2-coordinated complexes.
cis-trans isomerism is very common in many 4-coordinated square planar complexes and 6-coordinated octahedral complexes.
Geometrical isomerism in square planar complex
[Pt(NH3)2Cl2],
This is the type [Ma2b2] ,where a and b are monodentate ligands.
There are cis and trans isomers of square planar complexes
Cis and Trans isomers of [Pt(NH3)2Cl2]
Geometrical Isomerism in Octahedral complexes
[Co3+(NH3)4(H2O)Cl]2+ ion is an important example of this type of complex. This ion has cis- and trans-isomers