Question

If Ni^2– is replaced by Pt^2– in the complex NiCl₂Br₂] ^2– , which of the following properties are expected to get changed?
A. Geometry
B. Geometrical isomerism
C. Optical isomerism
D. Magnetic properties

• A. A, B and C
• B. B and D
• C. B and C
• D. A, B and D

Answer 1

The Correct Option is D

Analysis of the Complexes:

[NiCl\(_2\)Br\(_2\)]\( ^{2-} \):

• The oxidation state of Ni is \( \text{Ni}^{2+} \), with a \( d^8 \) configuration.
• Since \( \text{Cl}^- \) and \( \text{Br}^- \) are weak field ligands, the complex adopts a tetrahedral geometry.
• Tetrahedral complexes with the formula \( \text{MA}_2\text{B}_2 \) do not exhibit geometrical isomerism and are optically inactive.

[PtCl\(_2\)Br\(_2\)]\( ^{2-} \):

• The oxidation state of Pt is \( \text{Pt}^{2+} \), with a \( d^8 \) configuration.
• Being a 5d series element, \( \text{Pt}^{2+} \) forms square planar complexes due to strong ligand field stabilization.
• Square planar complexes of the type \( \text{MA}_2\text{B}_2 \) 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 (\( \text{NiCl}_2\text{Br}_2^{2-} \)) to square planar (\( \text{PtCl}_2\text{Br}_2^{2-} \)) alters the crystal field splitting, affecting the magnetic properties.

Conclusion:

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