Question

The compounds \( [\text{PtCl}_2(\text{NH}_3)_4]\text{Br}_2 \) and \( [\text{PtBr}_2(\text{NH}_3)_4]\text{Cl}_2 \) constitute a pair of:

• A. \( \text{Coordination isomers} \)
• B. \( \text{Linkage isomers} \)
• C. \( \text{Ionization isomers} \)
• D. \( \text{Optical isomers} \)

Hint:

To identify ionization isomers, compare the ions present in the outer ionic sphere and the coordination sphere. These isomers dissociate into different ions when dissolved in solution, making their identification straightforward.

Answer 1

The Correct Option is C

Step 1: Compound Structure Identification.
The compounds \( [\text{PtCl}_2(\text{NH}_3)_4]\text{Br}_2 \) and \( [\text{PtBr}_2(\text{NH}_3)_4]\text{Cl}_2 \) are coordination complexes centered on \( \text{Pt(NH}_3\text{)}_4 \). The key distinction is the location of \( \text{Cl}^- \) and \( \text{Br}^- \) ions, specifically whether they are within the coordination sphere or the ionic sphere.

Step 2: Ionization Isomerism Analysis.
Ionization isomers result from the exchange of ions between the coordination sphere and the ionic sphere. These isomers share a molecular formula but yield distinct ions upon dissolution. For example: \[ [\text{PtCl}_2(\text{NH}_3)_4]\text{Br}_2 \xrightarrow[]{\text{Dissociation}} 2\text{Br}^- + [\text{PtCl}_2(\text{NH}_3)_4] \] \[ [\text{PtBr}_2(\text{NH}_3)_4]\text{Cl}_2 \xrightarrow[]{\text{Dissociation}} 2\text{Cl}^- + [\text{PtBr}_2(\text{NH}_3)_4] \] Observations: - In \( [\text{PtCl}_2(\text{NH}_3)_4]\text{Br}_2 \), bromide ions are external to the coordination sphere, while chloride ions are directly bonded to the platinum. - In \( [\text{PtBr}_2(\text{NH}_3)_4]\text{Cl}_2 \), chloride ions are external, and bromide ions are within the coordination sphere. 

Step 3: Differentiation from Other Isomerism Types.
- Coordination isomerism: Involves ligand exchange between multiple metal centers, not applicable here due to a single metal center. - Linkage isomerism: Occurs when a ligand binds via different atoms (e.g., \( \text{NO}_2^- \) through N or O). This is not relevant for the given ligands. - Optical isomerism: Requires non-superimposable mirror images, which are absent in these square-planar complexes. Therefore, the two compounds demonstrate ionization isomerism. 

Final Answer: \[ \boxed{\text{Ionization isomers}} \]