`[Co(NH_3)_5NO_2]Cl_2` and `[Co(NH_3)_5(ONO)Cl_2]` are related to each other as

Options

A. (a) Geometrical isomers
B. (b) Optical isomers
C. (c) Linkage isomers
D. (d) Coordination isomers

Explanation

To determine the relationship between the two coordination compounds `[Co(NH_3)_5NO_2]Cl_2` and `[Co(NH_3)_5(ONO)Cl_2]`, we can follow these steps:

### Step 1: Identify the Ligands
Both complexes contain the same metal ion, cobalt (Co), and the same ammonia ligands (NH₃). However, the key difference lies in the ligands NO₂ and ONO.

### Step 2: Analyze the Ligands
- In the complex `[Co(NH_3)_5NO_2]Cl_2`, the ligand NO₂ is acting as a nitro ligand, where the nitrogen atom (N) is the donor atom that coordinates to the cobalt ion.
- In the complex `[Co(NH_3)_5(ONO)Cl_2]`, the ligand ONO is acting as a nitrito ligand, where the oxygen atom (O) is the donor atom that coordinates to the cobalt ion.

### Step 3: Determine the Type of Isomerism
The difference in the donor atoms (N in NO₂ vs. O in ONO) indicates that the two complexes have different connectivity between the metal and the ligands. This type of isomerism, where the same ligands are present but the point of attachment to the metal ion is different, is known as linkage isomerism.

### Step 4: Conclusion
The two complexes `[Co(NH_3)_5NO_2]Cl_2` and `[Co(NH_3)_5(ONO)Cl_2]` are therefore related to each other as linkage isomers.

### Final Answer:
The relationship between `[Co(NH_3)_5NO_2]Cl_2` and `[Co(NH_3)_5(ONO)Cl_2]` is that they are linkage isomers.

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