The complex ion ${\left[\mathrm{Fe}(\mathrm{CN}{)}_6\right]}^{4-}$ contains:

${\left[\mathrm{Fe}(\mathrm{CN}{)}_6\right]}^{4-}\text{ contains total of }36\text{ electrons on }{\mathrm{Fe}}^{2+}\text{ cation. }$
$\begin{array}{l}\text{ EAN }=\mathrm{Z}-\text{ O. S. }+2\times \text{ C.N. }\\ =26-2+2\times 6\\ =24+12\to 36\end{array}$
${\mathrm{d}}^2{\mathrm{sp}}^3\text{ hybridisation; total of }108\text{ electrons and }12\text{ sigma bonds. }$