Which of the following can show coordination isomerism? 

Coordination isomerism occurs when two or more coordination compounds have the same molecular formula but differ in the distribution of ligands between the cationic and anionic parts of the complex.

Analysis of the Given Options

1. Cu(CN)₄PtCl₄:
   • This complex consists of a cationic part, [Cu(CN)₄]²⁻, and an anionic part, [PtCl₄]²⁻.
   • Coordination isomerism is possible here by interchanging the ligands between the cation and anion.
   • Example of Coordination Isomer: [CuCl₄]²⁻ and [Pt(CN)₄]²⁻
2. Fe(NH₃)₆²⁺Pt(CN)₆²⁻:
   • This complex comprises [Fe(NH₃)₆]²⁺ and [Pt(CN)₆]²⁻.
   • Coordination isomerism can occur by swapping the ligands between the cation and anion.
   • Example of Coordination Isomer: [Fe(CN)₆]²⁻ and [Pt(NH₃)₆]²⁺
3. Pt(NH₃)₄Cl₄:
   • This complex contains a single metal center with four NH₃ ligands and four Cl⁻ ions.
   • Coordination isomerism is not applicable here as there is no exchange of ligands between different metal centers.
4. Pt(NH₃)₃Cl₃Py:
   • This complex involves a single metal center with three NH₃ ligands, three Cl⁻ ions, and one pyridine (Py) ligand.
   • Coordination isomerism is not possible here due to the absence of multiple metal centers.

Final Answer

The complexes that can exhibit coordination isomerism are:

• Cu(CN)₄PtCl₄
• Fe(NH₃)₆²⁺Pt(CN)₆²⁻

These complexes have multiple metal centers, allowing for the interchange of ligands between the cationic and anionic parts, thereby demonstrating coordination isomerism.