Question

$\left[ Co{{\left( N{{H}_{3}} \right)}_{5}}Br \right]S{{O}_{4}}$ and $\left[ Co{{\left( N{{H}_{3}} \right)}_{5}}S{{O}_{4}} \right]Br$ are examples of which type of isomerism?
A) Linkage
B) Geometrical
C) Ionization
D) Optical

Answer 1

Hint: The coordination compounds sometimes result in isomerism in which the ions outside the coordination sphere get exchanged with the ligands present within the coordination sphere. This type of isomerism is categorized under structural isomerism because the bonding to the central metal ion gets changed.

Complete answer:Ionization isomers: The coordination complex in which the molecular formula of the complex is the same but the ligands attached to the central metal ions are different. Those complexes are known as ionization isomers and the phenomenon is known as ionization isomerism.

The only way to identify these isomers is that a ligand gets exchanged with the anion or the neutral molecule which was initially outside the coordination sphere. This isomerism is usually observed when the counterion in the coordination complex itself is a potential ligand and can replace the position of the existing ligand.

Some of the examples of Ionization isomerism are as follows:

1. $\left[ Co{{\left( N{{H}_{3}} \right)}_{5}}Br \right]S{{O}_{4}}\,\,\And \,\,\,\left[ Co{{\left( N{{H}_{3}} \right)}_{5}}S{{O}_{4}} \right]Br\,$
2. $\left[ Co{{\left( N{{H}_{3}} \right)}_{4}}C{{l}_{2}} \right]N{{O}_{2}}\,\,\And \,\,\,\left[ Co{{\left( N{{H}_{3}} \right)}_{4}}N{{O}_{2}}Cl \right]Cl\,$
3. $\left[ Co{{\left( N{{H}_{3}} \right)}_{5}}N{{O}_{3}} \right]S{{O}_{4}}\,\,\And \,\,\,\left[ Co{{\left( N{{H}_{3}} \right)}_{5}}S{{O}_{4}} \right]N{{O}_{3}}\,$
Therefore, it is clearly observed that the complexes given in the question are experiencing a change in ligands and ions outside the coordination sphere. Thus, the given complexes i.e., $\left[ Co{{\left( N{{H}_{3}} \right)}_{5}}Br \right]S{{O}_{4}}$ and $\left[ Co{{\left( N{{H}_{3}} \right)}_{5}}S{{O}_{4}} \right]Br$ are example of Ionization isomerism and hence, the correct answer is option (C).

Note: It is important to note that the ions inside the coordination sphere of the coordination complex do not dissolve in the aqueous solution i.e., we can only extract the ions which are present outside the coordination sphere along with the complex ion. Thus, by dissolving ionization isomerism in an aqueous solution, different ions are obtained.