Give the electronic configuration of d-orbitals of K3 [Fe(Cn)6] and K3[FeF6] and explain why these complexes give different colour with - Chemistry - The d-and f-Block Elements

Question

Give the electronic configuration of d-orbitals of K3 [Fe(Cn)6]
and K3[FeF6] and explain why these complexes give different colour
with same solution

Kirti Gogia · Accepted Answer

In both K3[Fe(CN)6] and
K3[FeF6], iron is in +3 oxidation state, that
is the number of d-electrons in Fe3+ ion is 5 However,
the ligand field strength in both these complexes would be
different since the cyanide ion (CN- ion) is a strong
ligand while the F- ion is a weak ligand Hence,
CN- would cause the pairing of electrons because of
which the electronic arrangement in Fe in
K3[Fe(CN)6] will be
(t2g5)(eg)
On the other hand, the F- ion being a weak ligand
will not cause the pairing of electrons, because of which the
electronic arrangement of Fe in K3[FeF6] will
be (t2g3)(eg2)
In both these complexes, iron possesses different number of
unpaired electrons Hence both these complexes will show different
d-d transitions and therefore exhibit different colours in same
solution

Give the electronic configuration of d-orbitals of K3 [Fe(Cn)6] and K3[FeF6] and explain why these complexes give different colour with same solution.