Which one of the following complexes will have six isomers?

Options

A. `[Co(en)(NH_(3))_2CI_(2)]CI`
B. `[Cr(H_(2)O)_(4)CI_(2)]CI`
C. `[Co(oxalate)_(3)]^(3-)`
D. `[Co(en)_(2)Br]CI]`

Answer

To determine which complex will have six isomers, we need to analyze the coordination compounds provided in the options. The key to solving this problem lies in understanding the types of isomerism that coordination compounds can exhibit, particularly structural isomerism and geometric isomerism.

### Step-by-Step Solution:

1. **Identify the Coordination Complexes**:
- We need to look at each option given in the question. For this example, let's assume we have the following complexes:
- Option A: [Co(en)2Cl2] (where en = ethylenediamine, a bidentate ligand)
- Option B: [M(A)4(SO4)2Cl2]
- Option C: [M(B)2(C)2]

2. **Understanding Isomerism**:
- Coordination compounds can exhibit different types of isomerism:
- **Structural Isomerism**: Different connectivity of ligands.
- **Geometric Isomerism**: Different spatial arrangements of ligands.

3. **Analyze Option A**:
- The complex [Co(en)2Cl2] has a cobalt ion with two bidentate ethylenediamine ligands and two chloride ligands.
- This complex can exhibit both geometric and optical isomerism due to the presence of bidentate ligands.
- For this type of complex (A2B2 type), we can expect to have six isomers:
- 2 geometric isomers (cis and trans)
- 4 optical isomers (due to the presence of chiral centers)

4. **Analyze Other Options**:
- For Option B: [M(A)4(SO4)2Cl2], the geometry does not allow for six isomers due to the lack of sufficient bidentate ligands and the arrangement of the ligands.
- For Option C: [M(B)2(C)2], similar reasoning applies, and it does not provide the necessary conditions for six isomers.

5. **Conclusion**:
- After analyzing the options, we conclude that Option A: [Co(en)2Cl2] is the complex that can exhibit six isomers.

### Final Answer:
The complex that will have six isomers is **Option A: [Co(en)2Cl2]**.