Question

For an octahedral complex, which of the following d-electron configuration will give minimum CFSE?

• A. High spin with $d^{6}$ configuration
• B. Low spin with $d^{4}$ configuration
• C. Low spin with $d^{5}$ configuration
• D. High spin with $d^{7}$ configuration

Answer 1

Answer: (C)

For octachedral complex $\mathrm{CFSE}=\mathrm{n}_{\mathrm{t}_{2 \mathrm{~g}}} \times\left(-0.4 \Delta_0\right)+\mathrm{n}_{\mathrm{eg}}+\left(0.6 \Delta_0\right)$

A. High spin with $d^{6}$ configuration $t_{2 g}^{4}$ and $e_{g}^{2}$ CFSE = - 0.4 $\Delta _{0}$

B. Low spin with $d^{4}$ configuration $t_{2 g}^{4}$ and $e_{g}^{0}$ CFSE = - 1.6 $\Delta _{0}$

C. Low spin with $d^{5}$ configuration $t_{2 g}^{5}$ and $e_{g}^{0}$ CFSE = - 2 $\Delta _{0}$

D. High spin with $d^{7}$ configuration $t_{2 g}^{5}$ and $e_{g}^{2}$ CFSE = - 0.8 $\Delta _{0}$