The d-electron configuration of $\left[\mathrm{Ru}{\left(\mathrm{en}\right)}_3\right]{\mathrm{Cl}}_2$ and$\left[\mathrm{Fe}{\left({\mathrm{H}}_2\mathrm{O}\right)}_6\right] {\mathrm{Cl}}_2$ respectively are:

Fe and Ru belong to same group and their ions ${\mathrm{Fe}}^{2+}$ and ${\mathrm{Ru}}^{2+}$  in the given complex have d⁶configuration. In $\left[\mathrm{Ru}{\left(\mathrm{en}\right)}_3\right]\mathrm{C}{\mathcal{l}}_2$, the electrons rearrange having ${\mathrm{t}}_{2\mathrm{g}}^6{\mathrm{eg}}^0$. In  ${\left[\mathrm{Fe}{\left({\mathrm{H}}_2\mathrm{O}\right)}_6\right]}^{2+}$since  ${\mathrm{H}}_2\mathrm{O}$ is weak ligand electrons do not rearrange. So have ${\mathrm{t}}_{2\mathrm{g}}^4{\mathrm{eg}}^2$.