Question

$\begin{array}{ccccc}N{a}_{2}S& +& X& ⟶& N{a}_2\left[Fe\right(CN{)}_5\left(NOS\right)]\\ & & & & purplecolor\end{array}$

The reason of color of X is :

• A. d-d transition
• B. charge transfer
• C. colorless compound
• D. None

Answer 1

The correct option is B charge transfer

here X is,
$N{a}_2\left[Fe\right(CN{)}_5\left(NO\right)]$
+2 +1
so $F{e}^{+2}=d^6$ , due to strong ligand pairing happens and low spin complex forms.
So it have zero unpaired electron and zero magnetic moment.
Also, as electron gets paired so it have 6 electron in non axial d-orbitals.
And color of compoud is due to $chargetransfer$.