Discuss the nature of bonding and magnetic behaviour in the `[Fe(CN)_(6)]^(4-)` Co-ordination entities on the basis of valence bond theory.

Explanation

`[Fe(CN)_(6)]^(4-)` : In this complex Fe is present as `Fe^(2+)`.
`Fe=[Ar]3d^(6)4s^(2)`
Outer configuration of `Fe^(2+)=3d^(6)4s^(0)`

`CN^(-)` being strong field ligand, pair up the unpaired d electrons Thus, two 3d-orbital are now available for `CN^(-)` ions.

Since, all the electrons are paired, the complex is diamagnetic. Moreover (n - 1) dorbitals are involved in bonding, so, it is an inner orbital or low spin complex.