$[Co(NH_{3})_{5}SO_{4}]Br$ and $[Co(NH_{3})_{5}Br]SO_{4}$ shows which type of isomerism?

Question

Accepted Answer

The compounds $[Co(NH_{3})_{5}SO_{4}]Br$ and $[Co(NH_{3})_{5}Br]SO_{4}$ exhibit ionization isomerism. This type of isomerism occurs when the counter ion in a complex salt is capable of exchanging places with a ligand within the coordination sphere. In these two compounds, the sulfate ion (SO₄²⁻) and the bromide ion (Br⁻) are interchanged between the coordination sphere and the counter ion position.

1. **Explanation for Option 1 (Ionization isomerism):**
   - In $[Co(NH_{3})_{5}SO_{4}]Br$, the sulfate ion is coordinated to the cobalt center, and the bromide ion is the counter ion. In $[Co(NH_{3})_{5}Br]SO_{4}$, the bromide ion is coordinated to the cobalt center, and the sulfate ion is the counter ion. This exchange of positions between the ligand and the counter ion is characteristic of ionization isomerism. Therefore, Option 1 is correct.

2. **Explanation for why other options are incorrect:**

- **Option 2 (Coordination isomerism):** Coordination isomerism occurs in compounds where both cationic and anionic parts are complex ions, and there is an exchange of ligands between these complex ions. In the given compounds, there is no such exchange between complex ions, as there is only one complex ion in each compound. Thus, this option is incorrect.

- **Option 3 (Linkage isomerism):** Linkage isomerism occurs when a ligand can coordinate to the metal center through different atoms. For example, NO₂⁻ can bind through nitrogen or oxygen. In the given compounds, there is no such ligand capable of binding through different atoms. Therefore, this option is incorrect.

- **Option 4 (Optical isomerism):** Optical isomerism occurs when a compound can exist in two forms that are non-superimposable mirror images of each other, typically due to chirality. The given compounds do not exhibit chirality or optical activity, as they do not have the necessary structural features for optical isomerism. Hence, this option is incorrect.

In conclusion, the correct type of isomerism exhibited by the compounds $[Co(NH_{3})_{5}SO_{4}]Br$ and $[Co(NH_{3})_{5}Br]SO_{4}$ is ionization isomerism, making Option 1 the correct choice.