Question

The complex ions \([Co(NH_3)_5(NO_2)]^{2+}\) and \([Co(NH_3)_5(ONO)]^{2+}\) are called

• A. Ionization isomers
• B. Linkage isomers
• C. Co-ordination isomers
• D. Geometrical isomers

Hint:

In linkage isomerism, a ligand can attach to a metal through different atoms, resulting in isomers with the same formula but different structures.

Answer 1

The Correct Option is B

To solve the problem, we need to identify the relationship between the complex ions \([Co(NH_3)_5(NO_2)]^{2+}\) and \([Co(NH_3)_5(ONO)]^{2+}\).

1. Analyzing the Complex Ions:
Both complexes have the same formula: Co, 5 NH\(_3\) ligands, and a nitro group, with a 2+ charge. The difference lies in the ligand:
- In \([Co(NH_3)_5(NO_2)]^{2+}\), the NO\(_2\) ligand is coordinated via the nitrogen atom (nitro, -NO\(_2\)).
- In \([Co(NH_3)_5(ONO)]^{2+}\), the NO\(_2\) ligand is coordinated via an oxygen atom (nitrito, -ONO).

2. Identifying the Type of Isomerism:
The two complexes have the same molecular formula but differ in how the NO\(_2\) ligand is attached to the metal center. This type of isomerism, where the same ligand binds through different atoms, is called linkage isomerism. The NO\(_2\)/ONO\(^-\) ligand is ambidentate, meaning it can coordinate via either the N or O atom, leading to these two forms.

3. Considering Other Types of Isomerism:
- Coordination isomerism involves swapping ligands between cation and anion, but here both are cations with the same ligands.
- Geometric isomerism (e.g., cis-trans) is not applicable, as \([Co(NH_3)_5X]\) (with 5 identical ligands) lacks the necessary symmetry for such isomerism.
Linkage isomerism is the correct classification.

Final Answer:
The complex ions \([Co(NH_3)_5(NO_2)]^{2+}\) and \([Co(NH_3)_5(ONO)]^{2+}\) are called linkage isomers.