Question

Discuss the nature of bonding in the following coordination entities on the basis of valence bond theory:
$(i) [Fe(CN)_6]^{4-}$
$(ii) [FeF_6]^{3-}$
$(iii) [Co(C_2O_4)_3]^{3-}$
$(iv) [CoF_6]^{3-}$

Answer 1

$(i) [Fe(CN)_6]^{4-}$
In the above coordination complex, iron exists in the +II oxidation state.
$Fe^{ 2+}$ : Electronic configuration is $3d ^{6}$
Orbitals of $Fe^{ 2+}$ ion:

Hence, the geometry of the complex is octahedral and the complex is diamagnetic (as there are no unpaired electrons).

$(ii) [FeF_6]^{ 3-}$
In this complex, the oxidation state of Fe is +3.
Orbitals of $Fe^{+3}$ ion:

$(iii) [Co(C_2O_4)_3]^{ 3-}$
Cobalt exists in the +3 oxidation state in the given complex
Orbitals of $Co ^{3+}$ ion:

$(iv) [CoF_6]^{ 3-}$
Cobalt exists in the $+3$ oxidation state.
Orbitals of $Co^{3+}$ ion: