Which of the following complexes form facial and meridional isomers?

Options

A. `[Cr(H_(2)O)_(5)CI]^(+2)`
B. `[Cr(NH_(2))_(5)Br]SO_(4)`
C. `[Cr(NH_(3))_(3)(NO_(2))_(3)]`
D. `[Cr(ox_(3)]^(3-)`

Answer

To determine which complexes can form facial and meridional isomers, we need to focus on the coordination number and the types of ligands involved in the complexes. Specifically, we are looking for complexes of the type MA3B3 or MAB3, where 'A' represents monodentate ligands and 'B' represents bidentate ligands with different donor atoms.

### Step-by-Step Solution:

1. **Identify the Complexes**:
We need to analyze the given complexes to see if they can be classified as MA3B3 or MAB3.

2. **Understanding Isomer Types**:
- **Facial Isomer (fac)**: In this isomer, three identical ligands (A) occupy one face of the octahedron, while the other three (B) occupy the opposite side.
- **Meridional Isomer (mer)**: In this isomer, the three identical ligands (A) are arranged in a plane that divides the octahedron into two equal halves.

3. **Examine Each Complex**:
- **Complex 1: CrH2O5Cl**: This complex has 5 water molecules (monodentate) and 1 chloride ion (monodentate). It does not fit the MA3B3 or MAB3 pattern, so it cannot form facial and meridional isomers.

- **Complex 2: Cr(NH3)3(NO2)3**: This complex has 3 ammonia (NH3) ligands (monodentate) and 3 nitro (NO2) ligands (bidentate). It fits the MA3B3 pattern, allowing for both facial and meridional isomers.

- **Complex 3: Cr(C2O4)3**: This complex has oxalate ligands (C2O4) which are bidentate but identical. Since all ligands are the same, it cannot form facial and meridional isomers.

4. **Conclusion**:
The only complex that can form facial and meridional isomers is **Cr(NH3)3(NO2)3**.

### Final Answer:
The complex that can form facial and meridional isomers is **Cr(NH3)3(NO2)3**.