Question

Low spin complex of $d^5$- cation in an octahedral field will have the following energy.
(${\Delta }_0=$ CFSE,$P=$ Electron pairing energy)

• A. $-2{\Delta }_0+P$
• B. $-2{\Delta }_0+2P$
• C. $\frac{-2}{5}{\Delta }_0+2P$
• D. $-2{\Delta }_0+3P$

Answer 1

The correct option is B $-2{\Delta }_0+2P$

In octahedral complexes with the configuration of $d^5$ and having low spin will have the electrons in the orbitals $t_2{g}^{5}e{g}^0$. Hence the CFSE will be : (-0.4${\Delta }_o$ $\times$ 5) + electron pairs $\times$ pairing energy $=-2\Delta {}_o+2P$. Hence option $B$ is correct.