# The d-electron configuration of

Question:

The d-electron configuration of $\left[\mathrm{Ru}(\mathrm{en})_{3}\right] \mathrm{Cl}_{2}$ and $\left[\mathrm{Fe}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right] \mathrm{Cl}_{2}$, respectively are :

1. $\mathrm{t}_{2 \mathrm{~g}}^{4} \mathrm{e}_{\mathrm{g}}^{2}$ and $\mathrm{t}_{2 \mathrm{~g}}^{6} \mathrm{e}_{\mathrm{g}}^{0}$

2. $\mathrm{t}_{2 \mathrm{~g}}^{6} \mathrm{e}_{\mathrm{g}}^{0}$ and $\mathrm{t}_{2 \mathrm{~g}}^{6} \mathrm{e}_{\mathrm{g}}^{0}$

3. $\mathrm{t}_{2 \mathrm{~g}}^{6} \mathrm{e}_{\mathrm{g}}^{0}$ and $\mathrm{t}_{2 \mathrm{~g}}^{4} \mathrm{e}_{\mathrm{g}}^{2}$

4. $\mathrm{t}_{2 \mathrm{~g}}^{4} \mathrm{e}_{\mathrm{g}}^{2}$ and $\mathrm{t}_{2 \mathrm{~g}}^{4} \mathrm{e}_{\mathrm{g}}^{2}$

Correct Option: 3,

Solution:

$\left[\mathrm{Ru}(\mathrm{en})_{3}\right] \mathrm{Cl}_{2}$

$\mathrm{R}_{\mathrm{u}} \Rightarrow 4 \mathrm{~d}$ series

en $\Rightarrow$ chelating ligand

$\mathrm{CN}=6$, octahedral splitting hence laye splitting of d-subshell

$\left[\mathrm{Fe}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right] \mathrm{Cl}_{2} \Rightarrow \mathrm{H}_{2} \mathrm{O} \Rightarrow$ Weak filled ligand

$\mathrm{Fe}^{+2} \Rightarrow[\mathrm{Ar}] 3 \mathrm{~d}^{6} 4 \mathrm{~s}^{0}$

less plitting

$\mathrm{CN}=6$ octahedral splitting