Question

The number of possible isomers for \( [Pt(\text{py})(NH_3)BrCl] \) is .......... (py is pyridine)
 

Hint:

In coordination chemistry, the number of possible isomers depends on the spatial arrangement and symmetry of the ligands around the metal center.

Answer 1

Correct Answer: 3

Determining the Number of Isomers:

The complex \( [Pt(\text{py})(NH_3)BrCl] \) consists of a square planar platinum coordination environment. Square planar complexes can exhibit different types of isomerism such as geometric isomerism.

Geometric Isomerism: In square planar complexes, geometric isomerism arises due to the arrangement of different ligands around the central metal atom. The possible arrangements for the four different ligands (py, NH₃, Br, Cl) can lead to various isomers.

• cis-isomers: Two identical or similar groups are adjacent.
• trans-isomers: Two identical or similar groups are opposite each other.

Evaluation of Possible Isomers:

1. cis-\((NH_3, \text{py})\), trans-(Br, Cl): Two arrangements where NH₃ and py are adjacent while Br and Cl are opposite.

2. cis-(Br, Cl), trans-\(NH_3, \text{py}\): Another set of arrangements where Br and Cl are adjacent while NH₃ and py are opposite.

In this case, different positions of the ligands around Pt will result in the possible formation of exactly three distinct isomers. These constitute:

Isomer Type	Arrangement
cis-isomer 1	NH3 adjacent to py
cis-isomer 2	Br adjacent to Cl
trans-isomer	NH3 opposite py

Conclusion: The number of possible isomers for \( [Pt(\text{py})(NH_3)BrCl] \) is 3