Which of the following complexes ionization isomerism ?

Options

A. `[Cr(NH_(3))_(6)]Cl_(3)`
B. `[Cr(en)_(2)]Cl_(2)`
C. `[Cr(en)_(3)]Cl_(3)`
D. `[Co(NH_(3))_(5)Br]SO_(4)`

Explanation

To determine which of the given complexes exhibits ionization isomerism, we need to understand what ionization isomerism is and analyze each complex accordingly.

### Step-by-Step Solution:

1. **Understanding Ionization Isomerism**:
- Ionization isomerism occurs when two or more coordination compounds have the same molecular formula but yield different ions in solution upon dissociation. This typically involves the exchange of anionic ligands with counter ions.

2. **Analyzing the First Complex**:
- The first complex has NH3 (a neutral ligand) inside the coordination sphere and Cl⁻ (a counter ion) outside.
- Since NH3 is neutral, there are no anionic ligands present in the coordination sphere. Therefore, this complex **does not show ionization isomerism**.

3. **Analyzing the Second Complex**:
- The second complex contains ethylene diamine (EN), which is also a neutral ligand, inside the coordination sphere.
- Again, there are no anionic ligands present. Thus, this complex **does not show ionization isomerism**.

4. **Analyzing the Third Complex**:
- Similar to the previous complexes, this one also has a neutral ligand inside the coordination sphere and a counter ion outside.
- Since there are no anionic ligands, this complex **does not show ionization isomerism**.

5. **Analyzing the Fourth Complex**:
- The fourth complex contains Br⁻ (an anionic ligand) inside the coordination sphere and SO4²⁻ (also an anionic counter ion) outside.
- Here, both the anionic ligand and the counter ion can potentially exchange places, leading to different ions in solution. Therefore, this complex **can show ionization isomerism**.

6. **Conclusion**:
- The only complex that exhibits ionization isomerism is the fourth complex.

### Final Answer:
The complex that shows ionization isomerism is **Option 4**.

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