Question

Explain with a suitable example geometrical isomerism in coordination compounds.

Answer 1

Geometrical isomerism arises in coordination compounds due to the different spatial arrangements of ligands around the central metal ion, especially in square planar and octahedral complexes.

It is not possible in tetrahedral complexes due to equivalent positions of all ligands.

For example, the cis and trans forms of complex diamminedichloridoplatinum (II), [PtCl₂(NH₃)₂] are shown:

\[\begin{array}{cc}
\phantom{..}\ce{Cl \phantom{....}NH3}\\
\backslash\phantom{...}/\phantom{}\\
\ce{Pt}\\
/\phantom{...}\backslash\\
\ce{\underset{Cis}{\phantom{...}Cl\phantom{....}NH3}}
\end{array}\]     \[\begin{array}{cc}
\ce{H3N \phantom{....}Cl}\phantom{..}\\
\backslash\phantom{...}/\phantom{}\\
\ce{Pt}\\
/\phantom{...}\backslash\\
\ce{\underset{Trans}{\phantom{...}Cl \phantom{....}NH3}}
\end{array}\] 

The complex [PtCl₂(NH₃)₂] shows geometrical isomerism due to its square planar geometry, resulting in cis and trans forms with distinct structures and chemical/biological properties.