Which of the following does not show optical isomerism ?

Options

A. `[Co(en)_(2)Cl_(2)]^(+)`
B. `[Co(NH_(3))_(3)Cl_(3)]^(0)`
C. `[Co(en)Cl_(2)(NH_(3))_(2)]^(+)`
D. `[Co(en)_(3)]^(3+)`

Explanation

To determine which of the given coordination complexes does not show optical isomerism, we need to analyze the structure of each complex and identify whether they can form non-superimposable mirror images.

### Step-by-Step Solution:

1. **Understand Optical Isomerism**:
- Optical isomerism occurs when a compound can exist in two forms that are mirror images of each other (enantiomers) and cannot be superimposed on one another. For a complex to exhibit optical isomerism, it must lack a plane of symmetry.

2. **Identify the Coordination Complexes**:
- The complexes given are:
- A) [Co(en)₂Cl₂]⁺
- B) [Co(NH₃)₃Cl₃]
- C) [Co(en)Cl₂(NH₃)₂]²⁺
- D) [Co(en)₃]³⁺
- Here, "en" refers to ethylenediamine, which is a bidentate ligand.

3. **Analyze Each Complex**:
- **Complex A: [Co(en)₂Cl₂]⁺**
- This complex has two bidentate ligands (en), which can form non-superimposable mirror images. Therefore, it can show optical isomerism.

- **Complex B: [Co(NH₃)₃Cl₃]**
- This complex consists of three monodentate ligands (NH₃) and three chloride ions. There is no bidentate ligand present, and the arrangement is symmetrical. Thus, it cannot show optical isomerism.

- **Complex C: [Co(en)Cl₂(NH₃)₂]²⁺**
- This complex has one bidentate ligand (en) and two monodentate ligands (NH₃). The presence of the bidentate ligand allows for the possibility of forming non-superimposable mirror images, so it can show optical isomerism.

- **Complex D: [Co(en)₃]³⁺**
- This complex has three bidentate ligands (en), which can also form non-superimposable mirror images. Therefore, it can show optical isomerism.

4. **Conclusion**:
- The only complex that does not show optical isomerism is **B) [Co(NH₃)₃Cl₃]** because it lacks bidentate ligands and has a symmetrical arrangement.

### Final Answer:
**B) [Co(NH₃)₃Cl₃] does not show optical isomerism.**