Facial-meridional isomers is associated with which one of the following complex (`M =`central metal) .

Options

A. `[M(A A)_(2)]`
B. `[MA_(3)B_(3)]`
C. `[MABCD]`
D. `[M(A A)_(3)]`

Answer

To determine which complex is associated with facial and meridional isomers, we need to analyze the provided options and understand the characteristics of these isomers.

### Step-by-Step Solution:

1. **Understanding Facial and Meridional Isomers**:
- Facial (fac) and meridional (mer) isomers are types of stereoisomers that occur in octahedral complexes with three identical ligands and three other ligands.
- In the facial isomer, the three identical ligands occupy two adjacent corners of the octahedron, creating a "face."
- In the meridional isomer, the three identical ligands are arranged in a plane that divides the octahedron into two equal halves.

2. **Analyzing the Options**:
- **Option A: MAA2** - This complex has two identical ligands and one different ligand. It does not fit the criteria for facial and meridional isomers.
- **Option B: MA3B3** - This complex has three identical ligands (A) and three different ligands (B). This configuration allows for the formation of both facial and meridional isomers.
- **Option C: MABCD** - This complex has four different ligands. It cannot exhibit facial or meridional isomerism as there are no identical ligands.
- **Option D: MAA3** - This complex has three identical ligands and one different ligand, which does not allow for facial and meridional isomerism.

3. **Conclusion**:
- Based on the analysis, the complex that exhibits facial and meridional isomers is **Option B: MA3B3**.

### Final Answer:
**Option B: MA3B3** is the correct answer as it allows for the formation of facial and meridional isomers.