Question

Transition metal complex with highest value of crystal field splitting $(Δ_0)$ will be

• A. $[Cr(H_2O)_6]3^+$
• B. $[Mo(H_2O)_6]3^+$
• C. $[Fe(H_2O)_6]3^+$
• D. $[Os(H_2O)_6]3^+$

Answer 1

Answer: (D)

$[Os(H_2O)_6]3^+$

Answer 2

Crystal field splitting $(Δ_0)$ for octahedral complexes depends on oxidation state of the metal as well as to which transition series the metal belongs.
For the same oxidation state, the crystal field splitting $(Δ_0)$increases as we move from $3d → 4d → 5d$.

$Cr^{3+}$ and $Fe^{3+}$ belong to 3d series, $Mo^{3+}$ belongs to 4d series and $Os^{3+}$ belongs to $5d$ series.

Hence, crystal field splitting $(Δ_0)$ is highest for $[Os(H_2O)_6]^{3+}$.