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 $t_{2g}^4$ and $e_g^2$ CFSE = - 0.4 ${\Delta }_0$

B. Low spin with $d^4$ configuration $t_{2g}^4$ and $e_g^0$ CFSE = - 1.6 ${\Delta }_0$

C. Low spin with $d^5$ configuration $t_{2g}^5$ and $e_g^0$ CFSE = - 2 ${\Delta }_0$

D. High spin with $d^7$ configuration $t_{2g}^5$ and $e_g^2$ CFSE = - 0.8 ${\Delta }_0$