Discuss the nature of bonding in the following coordination entities on the basis of valence bond theory:
\((i) [Fe(CN)_6]^{4-} \)
\((ii) [FeF_6]^{3-}\)
\((iii) [Co(C_2O_4)_3]^{3-} \)
\((iv) [CoF_6]^{3-}\)
\((i) [Fe(CN)_6]^{4-} \)
\((ii) [FeF_6]^{3-}\)
\((iii) [Co(C_2O_4)_3]^{3-} \)
\((iv) [CoF_6]^{3-}\)
Solution and Explanation
\((i) [Fe(CN)_6]^{4-}\)
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: 
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Concepts Used:
Applications of Coordination Compounds
There are three applications of coordination compounds:
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- Copper-complex enzymes important to iron storage and producing pigments in hair, skin, and eyes.
- Nickel-complex enzymes as part of the enzymes urease and hydrogenase