Chemistry - Coordination Chemistry Question with Solution | TestHub

$\mathbf{P}={\left[{\mathbf{FeF}}_6\right]}^{3-}$

ox. no. of $\mathrm{Fe}=+3$,

configuration : $-3{\mathrm{d}}^{5}4{\mathrm{s}}^0$ .

As ${\mathrm{F}}^{-}$is weak ligand, pairing does not take place. so it has 5 unpaired electron.

$\mathrm{Q}={\left[\mathrm{V}{\left({\mathrm{H}}_2\mathrm{O}\right)}_6\right]}^{2+}$ ox. no. of $\mathrm{V}=+2,$ configuration $3{\mathrm{d}}^{3}4{\mathrm{s}}^0$ It has 3 unpaired electrons. $\mathrm{R}={\left[\mathrm{Fe}{\left({\mathrm{H}}_2\mathrm{O}\right)}_6\right]}^{2+},$ ox. no. of $\mathrm{Fe}=+2,$ configuration $3{\mathrm{d}}^6,4{\mathrm{s}}^0$ .

As ${\mathrm{H}}_2\mathrm{O}$ is weak ligand, pairing does not take place, so it has 4 unpaired electron $\Rightarrow$ order of spin only magnetic moment

$\Rightarrow Q<R<P$

so, answer is (B).