Chemistry - Coordination Chemistry Question with Solution | TestHub

The brown ring complex is $[\mathrm{Fe}({\mathrm{H}}_2\mathrm{O}{)}_5\mathrm{NO}]{\mathrm{SO}}_4$.

The oxidation state of Fe is $+1$.

The electronic configuration of ${\mathrm{Fe}}^{+1}$ is $3d^7$.

NO acts as a strong field ligand (NO⁺).

The complex is octahedral.

For $d^7$ in an octahedral field, the electron configuration is $t_{2g}^5{e}_g^2$.

CFSE $=(-0.4\times 5+0.6\times 2){\Delta }_0=(-2.0+1.2){\Delta }_0=-0.8{\Delta }_0$.

Given ${\Delta }_0=7200{\mathrm{cm}}^{-1}$.

CFSE $=-0.8\times 7200=-5760{\mathrm{cm}}^{-1}$.

Thus, X = -5760.