Which one of the following complexes will have six isomers ?

Options

A. `[Co(en)NH_(3)Cl_(2)]Cl`
B. `[Cr(PPh_(3))_(2)(H_(2)O)_(2)Cl_(2)]Cl `
C. `[Co(o x)_(3)]^(3-)`
D. `[Co(en)_(2)Br]Cl`

Answer

To determine which complex will have six isomers, we need to analyze the types of coordination complexes and their isomerism.

### Step-by-Step Solution:

1. **Understanding Isomerism in Coordination Compounds**:
- Coordination compounds can exhibit two main types of isomerism: geometrical (cis-trans) and optical isomerism.
- The number of isomers can be predicted based on the coordination number and the types of ligands present in the complex.

2. **Identifying Complex Types**:
- The complexes that typically show six isomers are of the type MA2B2C2, where M is the metal center, and A, B, and C are different types of ligands.
- In this case, we need to find a complex that fits this formula.

3. **Analyzing the Given Options**:
- Look at each option provided in the question and determine if they fit the MA2B2C2 type.
- For each complex, check if they can exhibit geometrical isomers (cis-trans) and optical isomers.

4. **Evaluating Each Complex**:
- **Option 1**: If it is of type MA2B2C2 but contains a bidentate ligand (like ethylenediamine), it may not show six isomers.
- **Option 2**: If it is a complex with two bidentate ligands and two monodentate ligands, it can potentially show six isomers.
- **Option 3**: If it is a complex that does not fit the MA2B2C2 type, it will not show six isomers.
- **Option 4**: Similar to Option 3, if it does not fit the required structure, it will not show six isomers.

5. **Conclusion**:
- After evaluating the options, the correct answer is the complex that fits the MA2B2C2 type and can exhibit six isomers, which is **Option 2**.