Isomerism is the phenomenon in which more than one compounds have the same chemical formula but different chemical structures. Chemical compounds that have identical chemical formulae but differ in properties and the arrangement of atoms in the molecule are called isomers.
Geometrical isomerism is a type of stereoisomerism having the same molecular formula and same structure but differ in the relative arrangement of atoms. Geometrical Isomerism, which arises commonly in heteroleptic complexes. This type of isomerism arises due to the different possible geometric arrangements for the ligand.
In one case, the CH3 groups are on opposite sides of the double bond, and in the other case, they are on the same side.
- Cis-Trans Isomers
Many diazenes and diphosphates are known to have cis-trans isomers. Coordination complexes having square planar or octahedral geometries also display cis-trans isomerism based on the position of the ligands. When two identical groups occupy adjacent positions, the isomer is called cis and when arranged opposite to one another, the isomer is called trans.[Pt(NH3)2Cl2]The similar ligands are positioned near each other in the cis isomer, but they are positioned on opposite sides in the corresponding trans isomer.