Chemistry - Coordination Chemistry Question with Solution | TestHub

As$\mathrm{S}\mathrm{C}{\mathrm{N}}^{-}$and$\mathrm{C}{\mathrm{N}}^{-}$are weak and strong ligands respectively so during complex formation their behaviours are different.

$\mathrm{S}\mathrm{C}{\mathrm{N}}^{-}$being a weak ligand can not pair inner 3d electrons so

$\mathrm{F}{\mathrm{e}}^{3+}$i.e.${\left[\mathrm{A}\mathrm{r}\right]}_{18}3{\mathrm{d}}^5$

For weak ligand,${\mathrm{t}}_{2\mathrm{g}}^3\mathrm{e}{\mathrm{g}}^2,$i.e. n = 5

As$\mathrm{C}{\mathrm{N}}^{-}$being a strong ligand can pair inner 3d electrons so

For strong ligand,${\mathrm{t}}_{2\mathrm{g}}^5\mathrm{e}{\mathrm{g}}^0$, i.e. n = 1

Magnetic moment$=\sqrt{\mathrm{n}(\mathrm{n}+2)}\mathrm{B}.\mathrm{M}.$

$=\sqrt{5(5+2)}=\sqrt{35}\mathrm{B}.\mathrm{M}.$for weak ligand.

Magnetic moment for strong ligand$=\sqrt{1(1+2)}=\sqrt{3}\mathrm{B}.\mathrm{M}.$

Difference in magnetic moment$=\sqrt{35}-\sqrt{3}=4$