Which of the following complexes exhibits the highest crystal field splitting energy in an octahedral geometry?

Solution

1. The magnitude of crystal field splitting ${\Delta }_o$ depends on the spectrochemical series.
2. The order of field strength is ${\text{F}}^{-}<{\text{H}}_2\text{O}<{\text{NH}}_3<{\text{CN}}^{-}$.
3. Stronger ligands cause larger splitting of d-orbitals.
4. Hence the answer is (C).