Question

The complex compounds [Co(NH₃)₅SO₄]Br and [Co(NH₃)₅Br]SO₄ are:

• A. Coordination isomers
• B. Geometrical isomers
• C. Optical isomers
• D. Ionisation isomers

Hint:

[Co(NH₃)₅SO₄]Br and [Co(NH₃)₅Br]SO₄ are ionisation isomers, differing by the exchange of anions inside and outside the coordination sphere.

Answer 1

The Correct Option is D

Let's analyze the question to determine the correct classification of the given complex compounds:

• The first compound is \([\text{Co(NH}_3)_5\text{SO}_4]\text{Br}\). 
• The second compound is \([\text{Co(NH}_3)_5\text{Br}]\text{SO}_4\).

In coordination chemistry, isomers are compounds that have the same chemical formula but a different arrangement of atoms. Let's explore the options provided:

1. Coordination isomers: These isomers involve the interchange of ligands between the cationic and anionic parts of a coordination complex. The given complexes do not fit this description as the ligand is being exchanged with the counter-ion, not between cation and anion parts.
2. Geometrical isomers: These are compounds with the same formula but different spatial arrangements of atoms within a coordination sphere. The compounds given have different counter-ions, hence, they are not geometrical isomers.
3. Optical isomers: These are isomers that are non-superimposable mirror images of each other. The difference in these compounds is not related to their optical activity but rather to the counter-ions.
4. Ionisation isomers: These isomers occur when a ligand in a coordination compound exchanges places with an anion or cation outside the coordination sphere. In the given compounds, the \(\text{SO}_4^{2-}\) group and \(\text{Br}^-\;\) ion have exchanged positions between the coordination sphere and the counter-ion.

Given this explanation, the correct classification for the compounds \([\text{Co(NH}_3)_5\text{SO}_4]\text{Br}\) and \([\text{Co(NH}_3)_5\text{Br}]\text{SO}_4\) is ionisation isomers.

Therefore, the correct answer is: Ionisation isomers.