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_(2)O_(4))_(3)]^(3-)`
(iv) `[CoF_(6)]^(3-)`

Explanation

(i). `[Fe(CN)_6]^(4-)` `-d^(2)sp^(3)` octahedral, diamagnetic
(ii). `[FeF_6]^(3-)` `-sp^(3)d^(2)`, octahedral, paramagnetic
(iii). `[Co(C_2O_4)_3]^(3-)` `-d^(2)sp^(3)` octahedral diamagnetic
`(C_2O_4^(2-)` is a stong ligand)
(iv). `[CoF_6]^(3-)` `-sp^(3)d^(2)`, octahedral, paramagnetic.