Question

(a) For the complex $\left[Fe\right(CN{)}_6{]}^{4-}$, write the hybridisation, magnetic character and spin type of the complex. (At. number: Fe=26)
(b) Draw one of the geometrical isomers of the complex $\left[Co\right(en{)}_{2}C{l}_2{]}^{+}$ which is optically active.

Answer 1

Part (a): Hybridisation, magnetic character and spin type of the complex

Complex: $\left[Fe\right(CN{)}_6{]}^{4-}$

Let the oxidation state of $Fe=x$

$x+6(-1)=-4$

$x=+2$

The electronic configuration of $Fe=\left[Ar\right]3d^{6}4s^2$

The electronic configuration of $F{e}^{2+}=\left[Ar\right]3d^{6}4s^0$

$C{N}^{-}$ is a strong field ligand. So, due to the presence of strong-field ligands, the pairing of $3d-$ electrons takes place.

Hybridization: $d^{2}s{p}^3$

Magnetic character: Diamagnetic

Spin: Low spin complex

Part (b): Geometrical isomer which is optically active

The cis isomer of the following compound is optically active.

The complex does not have a plane of symmetry. It exists in d and l form, it forms non-superimposable mirror images. So, the complex is optically active.