Which one of the following complexes will have $\Delta_0=0$ and $\mu=5.96$ B.M.?

Question

Aicharya · Accepted Answer

(1) $\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_6\right]^{3+} \quad \mathrm{Co}^{3+} \Rightarrow 3 \mathrm{~d}^6 4 \mathrm{~s}^0$

$=[-0.4 \times 6+0.6 \times(0)] \Delta_0=-2.4 \Delta_0$
(2)
$\begin{aligned}
& {\left[\mathrm{Mn}(\mathrm{SCN})_6\right]^4} \\
& \mathrm{Mn}^{2+} \Rightarrow 3 \mathrm{~d}^5 4 \mathrm{~s}^0
\end{aligned}$

$\begin{aligned}
& \mu=\sqrt{35} \text { B.M. }=5.96 \text { B.M. } \\
& \mathrm{CFSE}=(-0.4 \times 3+0.6 \times 2) \Delta_0
\end{aligned}$
So $\Delta_0=0$
(3)
$\begin{aligned}
& {\left[\mathrm{Fe}(\mathrm{CN})_6\right]^{-4} \quad \mathrm{Fe}^{2+} \Rightarrow 3 \mathrm{~d}^6 4 \mathrm{~s}^0}
\end{aligned}$

$\mathrm{CFSE}=-2.4 \Delta_0$
(4) $\left[\mathrm{FeF}_6\right]^{4-}$
$\mathrm{Fe}^{2+} \Rightarrow 3 \mathrm{~d}^6 4 \mathrm{~s}^0$

$\begin{aligned}
& \mu=\sqrt{24} \text { B.M. }=4.89 \text { B.M. } \\
& \text { CFSE }=(-0.4 \times 4+0.6 \times 2) \Delta_0=-1.2 \Delta_0
\end{aligned}$

Which one of the following complexes will have $\Delta_0=0$ and $\mu=5.96$ B.M.?

Solution