Isomerism In Coordination Compounds

Correct answer: diamminedichloridoplatinum(II)

The compound cis-Platin has the formula:

IUPAC naming rules applied:

• Neutral ligands like NH₃ are named as ammine.
• Negative ligands like Cl^- are named as chlorido.
• Ligands are listed in alphabetical order, regardless of charge: ammine before chlorido.
• The oxidation state of platinum here is +2, hence denoted as (II).

So, the correct name is: diamminedichloridoplatinum(II)

Step 1: Analyze the Complexes for Isomerism
We are looking for a complex cation that exhibits two isomers. Let’s analyze each option:
:
This complex has only one possible structure, as all ligands are the same ( ). So, it does not have isomers.
:
This complex can only exhibit ionization isomerism if another counter ion is present within the complex to exchange positions with the ligand. With only one , there’s no possibility of isomerism here.
:
This complex can exhibit linkage isomerism because the ligand can coordinate to the metal ion through either the nitrogen atom (nitro isomer) or the oxygen atom (nitrito isomer). Thus, it has two isomers.
:
Same explanation as (2), no isomerism is possible
Conclusion
The correct option is (3): , which exhibits two isomers (nitro and nitrito isomers).

Analysis of the Complexes:

[NiCl Br ] :

• The oxidation state of Ni is , with a configuration.
• Since and are weak field ligands, the complex adopts a tetrahedral geometry.
• Tetrahedral complexes with the formula do not exhibit geometrical isomerism and are optically inactive.

[PtCl Br ] :

• The oxidation state of Pt is , with a configuration.
• Being a 5d series element, forms square planar complexes due to strong ligand field stabilization.
• Square planar complexes of the type can exhibit cis and trans isomers (geometrical isomers).
• However, optical isomerism is not observed in this case due to the symmetry of the ligands.
• The change in geometry from tetrahedral ( ) to square planar ( ) alters the crystal field splitting, affecting the magnetic properties.

Conclusion:

Geometry (A), Geometrical isomerism (B), and Magnetic properties (D) are expected to change.