The ionisation isomer of `[Co(H_(2)O)_(4)Cl_(2)]NO_(2)`
(a) `[Co(H_(2)O)_(4)(NO_(2))]CI_(2)`
(b) `[Co(H_(2)O)_(4)CI_(2)]NO_(2)`
`[Co(H_(2)O)_(4)CI(ONO)]CI`
(d )`[Co(H_(2)O)_(4)CI_(2)(NO_(2))]H_(2)O` .

Answer

To find the ionization isomer of the complex `[Co(H₂O)₄Cl₂]NO₂`, 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 solution.

### Step-by-Step Solution:

1. **Identify the Given Complex**:
The complex given is `[Co(H₂O)₄Cl₂]NO₂`. Here, cobalt (Co) is the central metal ion, surrounded by four water (H₂O) molecules and two chloride (Cl) ions, with a nitrite (NO₂) ion outside the coordination sphere.

2. **Understanding Ionization Isomers**:
Ionization isomers differ in the ions that are released into solution. In this case, we need to consider how the chloride and nitrite ions can be rearranged between the coordination sphere and the outside of the complex.

3. **Analyze the Options**:
We have the following options to consider:
- (a) `[Co(H₂O)₄(NO₂)]Cl₂`
- (b) `[Co(H₂O)₄Cl₂]NO₂`
- (c) `[Co(H₂O)₄Cl(ONO)]Cl`
- (d) `[Co(H₂O)₄Cl₂(NO₂)]H₂O`

4. **Determine the Correct Ionization Isomer**:
- **Option (a)**: `[Co(H₂O)₄(NO₂)]Cl₂` - This has the nitrite ion inside the coordination sphere and two chloride ions outside. This is a valid ionization isomer.
- **Option (b)**: `[Co(H₂O)₄Cl₂]NO₂` - This is the original complex and not an isomer.
- **Option (c)**: `[Co(H₂O)₄Cl(ONO)]Cl` - This has a different arrangement of ions and is not a valid ionization isomer.
- **Option (d)**: `[Co(H₂O)₄Cl₂(NO₂)]H₂O` - This also has the nitrite ion inside the coordination sphere and is not a valid ionization isomer.

5. **Conclusion**:
The correct ionization isomer of `[Co(H₂O)₄Cl₂]NO₂` is **(a) `[Co(H₂O)₄(NO₂)]Cl₂`** because it has the same molecular formula but differs in the ions released in solution.