Question

Which type of isomerism is shown by the complexes \([Co(NH_3)_5Br]SO_4\) and \([Co(NH_3)_5SO_4]Br\) ?

• A. Linkage
• B. Ionisation
• C. Optical
• D. Solvate

Hint:

Ionisation isomers yield different ions in solution even though they have the same composition.

Answer 1

The Correct Option is B

Step 1: Ionisation isomerism occurs when two complexes differ in the counter ions present inside and outside the coordination sphere.
Step 2: In \([Co(NH_3)_5Br]SO_4\), the bromide ion is coordinated to cobalt, and sulfate is the counter ion.
In \([Co(NH_3)_5SO_4]Br\), the sulfate ion is coordinated to cobalt, and bromide is the counter ion.
Step 3: These two complexes produce different ions in solution:
- The first gives \( Br^- \) inside the complex and \( SO_4^{2-} \) as free ion.
- The second gives \( SO_4^{2-} \) inside the complex and \( Br^- \) as free ion.
Step 4: Therefore, they are ionisation isomers.