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-)`

Explanation

To discuss the nature of bonding in the given coordination entities based on Valence Bond Theory (VBT), we will analyze each compound step by step.

### (i) `[Fe(CN)_6]^(4-)`

1. **Determine the Oxidation State of Iron (Fe)**:
- The charge of the complex is -4.
- Let the oxidation state of Fe be \( x \).
- The cyanide ion (CN^-) has a charge of -1, and there are 6 cyanide ligands.
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