Question

Which of the following complexes shows zero crystal field stabilization energy?

• A. [Co(H\(_2\)O)\(_6\)]\(^{3+}\)
• B. [Fe(H\(_2\)O)\(_6\)]\(^{3+}\)
• C. [Co(H\(_2\)O)\(_6\)]\(^{2+}\)
• D. [Mn(H\(_2\)O)\(_6\)]\(^{3+}\)

Hint:

CFSE is zero when the metal ion has no significant splitting of d-orbitals, often seen in high-spin or weak field complexes.

Answer 1

The Correct Option is D

Step 1: Crystal Field Stabilization Energy (CFSE)
The crystal field stabilization energy (CFSE) is a measure of the energy stability in coordination complexes, resulting from the splitting of d-orbitals in a metal ion due to the ligand field.
A zero CFSE means that the d-orbitals do not split significantly, or the metal ion is in a high-spin state where the energy difference between orbitals is negligible.
Step 2: Analyzing the Options
In option (a) [Co(H\(_2\)O)\(_6\)]\(^{3+}\), the d-orbitals experience significant splitting, resulting in non-zero CFSE.

In option (b) [Fe(H\(_2\)O)\(_6\)]\(^{3+}\), the metal is also high-spin, with non-zero CFSE.

In option (c) [Co(H\(_2\)O)\(_6\)]\(^{2+}\), there is splitting of the d-orbitals and non-zero CFSE.
In option (d) [Mn(H\(_2\)O)\(_6\)]\(^{3+}\), the \( \text{Mn}^{3+} \) ion has a \( d^4 \) electron configuration, which does not result in significant d-orbital splitting, giving a CFSE of zero.

Step 3: Conclusion \ \ Thus, the complex [Mn(H\(_2\)O)\(_6\)]\(^{3+}\) shows zero crystal field stabilization energy.