In $[FeF_{6}]^{3-}$ and $[Fe(CN)_{6}]^{30}$ both, Fe is present as $Fe^{3+}$ $F^{-}$ being a weak field ligand, is not capable to pair up these unpaired electrons but $CN^{-}$ does this Hence, is case of $[FeF_{6}]^{3-}=[Ar]$
Number of unpaired electrons $=5$ Magnetic moment, $\mu_{1}=\sqrt{5\left(5+2\right)}=\sqrt{35}$ In case of $\left[Fe \left(CN\right)_{6}\right]^{3-} =\left[Ar\right]$
Number of unpaired electron $=1$ Magnetic moment, $\mu_{2}=\sqrt{1\left(1+2\right)}=\sqrt{3}$ Ratio of $\mu_{1}$ and $\mu_{2}\cdot \frac{\mu_{1}}{\mu_{2}}=\frac{\sqrt{35}}{\sqrt{3}}$ $=3.41=3$
The metal-carbon bond possesses both the σ and π character in a metal carbonyl. The synergic effect produced by the metal-ligand bond strengthens the bond between the carbonyl molecule and the metal. The types of bonding that exist in metal carbonyls are as follows:
Structure of Metal Carbonyls:
Due to the donation of electrons by the carbonyl molecules to the vacant orbitals of the metal, a metal-carbon σ bond is formed.
Due to the donation of a pair of electrons from a filled d orbital metal into the vacant anti bonding π orbital of carbonyl ligand, a metal-carbon π bond is formed.
Stability of Coordination Compounds:
They are found to dissociate in various solutions. The stability of a coordination compound in a solution mainly depends on the degree of association between the two species involved in the state of equilibrium. For the formation of the compound quantitatively the stability of any complex is given by the magnitude of the equilibrium constant. For instance,
