Question

In which of the following octahedral complexes of Co (At no. 27), will the magnitude of \( \Delta_o \) be the highest?

• A. \( [\text{Co(CN)}_6]^{3-} \)
• B. \( [\text{Co(CO)}_6]^{3-} \)
• C. \( [\text{Co(H}_2\text{O})_6]^{3+} \)
• D. \( [\text{Co(NH}_3)_6]^{3+} \)

Hint:

Strong field ligands like CN\(^-\) and CO induce greater splitting of the d-orbitals, leading to a higher \( \Delta_o \).

Answer 1

The Correct Option is A

Step 1: Ligand effect on splitting.
CO and CN\(^-\) are strong field ligands, but CN\(^-\) is known to cause a greater splitting in the d-orbitals of the central metal ion, resulting in a higher \( \Delta_o \).
Step 2: Conclusion.
Thus, the magnitude of \( \Delta_o \) is highest for the complex \( [\text{Co(CN)}_6]^{3-} \).
Final Answer: \[ \boxed{A} \]