Question

The crystal field stabilisation energy (CFSE) and the spin-only magnetic moment in Bohr Magneton (BM) for the complex $K_3\left[Fe\right(CN{)}_6]$ are, respectively:

• A. $0.0{\Delta }_o$ and $\sqrt{35}DM$
• B. $-2.0{\Delta }_o$ and $\sqrt{3}BM$
• C. $-1.6{\Delta }_o$ and $\sqrt{24}BM$
• D. $-2.4{\Delta }_o$ and $0BM$

Answer 1

The correct option is B $-2.0{\Delta }_o$ and $\sqrt{3}BM$

$K_3\left[Fe\right(CN{)}_6]$

$Fe\to +3$ oxidation state.

$Fe\to 3d^5$ (Valence shell configuration).

Since $C{N}^{-}$ is a strong field ligand so pairing takes place.

${\mu }_B=\sqrt{n(n+2)}$

$\Rightarrow n=1$

$\Rightarrow {\mu }_B=\sqrt{3}BM$

CFSE $=n_{eg}\times 0.6-n_{t_{2}g}\times 0.4$

$=0\times 0.6-5\times 0.4$

$\therefore$ CFSE$=-2.0{\Delta }_o$