Question

In which of the following complex ion, the central metal ion is in a state of \( sp^{3}d^{2} \) hybridisation?

• A. $[CoF_{6}]^{3-}$
• B. $[Co(NH_{3})_{6}]^{3+}$
• C. $[Fe(CN)_{6}]^{3-}$
• D. $[Cr(NH_{3})_{6}]^{3+}$

Hint:

Weak field ligands $\rightarrow$ High spin $\rightarrow$ Outer orbital ($sp^{3}d^{2}$).

Answer 1

The Correct Option is A

Step 1: Concept
$sp^{3}d^{2}$ hybridization indicates an outer orbital octahedral complex.
Step 2: Analysis
$F^{-}$ is a weak field ligand and cannot pair up electrons in $Co^{3+}$, forcing the use of outer $4d$ orbitals. Strong ligands like $NH_{3}$ and $CN^{-}$ typically form $d^{2}sp^{3}$ complexes.
Step 3: Conclusion $$
$[CoF₆]³-$ uses $4s, 4p,$ and $4d$ orbitals for $sp³d²$ hybridization.
Final Answer: (A)