Question

The complexes \[\left[ {{\rm{Co(N}}{{\rm{H}}_{\rm{3}}}{{\rm{)}}_{\rm{6}}}} \right]\left[ {{\rm{Cr(CN}}{)_6}} \right]\] and \[\left[ {{\rm{Cr(N}}{{\rm{H}}_{\rm{3}}}{)_6}} \right]\left[ {{\rm{Co(CN}}{{\rm{)}}_{\rm{6}}}} \right]\] are the example of which type of isomerism?
A. Coordination
B. Geometrical
C. Linkage
D. Ionisation

Answer 1

Hint: Isomerism defines a phenomenon where molecules possess different structures but the same chemical formula. And these molecules possessing different structures but the same chemical formula are termed isomers.

Complete Step by Step Answer:
Let’s understand coordination isomerism. The coordination isomerism occurs in those coordination compounds that possess both anionic and cationic complex ions. In this isomerism, ligands of anions and cations are exchanged. For example, \[\left[ {{\rm{Pt}}{{\left( {{\rm{N}}{{\rm{H}}_{\rm{3}}}} \right)}_{\rm{4}}}} \right]\left[ {{\rm{CuC}}{{\rm{l}}_{\rm{4}}}} \right]\] and \[\left[ {{\rm{Cu}}{{\left( {{\rm{N}}{{\rm{H}}_{\rm{3}}}} \right)}_{\rm{4}}}} \right]\left[ {{\rm{PtC}}{{\rm{l}}_{\rm{4}}}} \right]\].

Here, the given compounds have complex cations and anions. Therefore, coordination isomerism is observed in the compounds.
Hence, option A is right.

Additional Information: Let’s discuss some other types of isomerism. Linkage isomerism is seen in complexes possessing ambidentate ligands. Ambidentate ligands bind through two sites, such as in NO₂, binding through N and O atoms occurs. Therefore, in \[{{\rm{K}}_{\rm{3}}}\left[ {{\rm{Co}}{{\left( {{\rm{N}}{{\rm{O}}_{\rm{2}}}} \right)}_{\rm{6}}}} \right]\] and \[{{\rm{K}}_{\rm{3}}}\left[ {{\rm{Co}}{{\left( {{\rm{ONO}}} \right)}_{\rm{6}}}} \right]\], linkage isomerism is observed. Ionisation isomerism occurs due to the production of different ions by the coordination compounds in the solution. The geometric isomerism is of two types, namely cis and trans. The geometrical isomerism is due to the difference in the arrangement of ligands in the coordination sphere around the central metal atom.

Note: The four characteristics of isomers are, that they have a different boiling point, different melting point, and different structure and they show differences in solubility in the same solvent. So, we can say that isomers possess different physical and chemical properties.