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: