The ionization isomer of `[Cr(H_2O)_4Cl(NO_2)]Cl` is

Options

A. `[Cr(H_2O)_4(NO_2)]Cl_2`
B. `[Cr(H_2O)_4Cl_2]NO_2`
C. `[Cr(H_2O)_4Cl(ONO)]Cl`
D. `[Cr(H_2O)_3Cl_2(NO_2)]H_2O`

Answer

To find the ionization isomer of the complex `[Cr(H2O)4Cl(NO2)]Cl`, we need to understand the concept of ionization isomers. Ionization isomers have the same molecular formula but differ in the ions that are released when the compound dissolves in water.

### Step-by-Step Solution:

1. **Identify the Coordination Complex**:
The given complex is `[Cr(H2O)4Cl(NO2)]Cl`. Here, chromium (Cr) is the central metal atom, surrounded by four water molecules (H2O), one chloride ion (Cl), and one nitrite ion (NO2).

2. **Determine the Coordination Number**:
The coordination number is the total number of ligand attachments to the central metal atom. In this complex, we have:
- 4 from H2O
- 1 from Cl
- 1 from NO2
Thus, the coordination number is 6.

3. **Understand Ionization Isomers**:
In ionization isomers, the overall formula remains the same, but the ions released in solution differ. For example, one ionization isomer may release a different combination of ions when dissolved.

4. **Analyze Possible Isomers**:
- **Option A**: `[Cr(H2O)4(NO2)Cl]Cl2` - This has a coordination number of 5, which is not valid since the coordination number must remain 6.
- **Option B**: `[Cr(H2O)4Cl(NO2)]Cl` - This maintains the coordination number of 6, and the formula is the same as the original complex. This is a valid ionization isomer.
- **Option C**: `[Cr(H2O)4Cl(O)Cl]` - Here, NO2 is acting as a bidentate ligand, which indicates a linkage isomer rather than an ionization isomer.
- **Option D**: `[Cr(H2O)3Cl2(NO2)(H2O)]` - This suggests that H2O is outside the coordination sphere, which is not possible since it is part of the crystallization water.

5. **Conclusion**:
The only valid ionization isomer that maintains the same coordination number and formula is **Option B**: `[Cr(H2O)4Cl(NO2)]Cl`.

### Final Answer:
The ionization isomer of `[Cr(H2O)4Cl(NO2)]Cl` is `[Cr(H2O)4Cl(NO2)]Cl`.