In which of the following coordination entites the magnitude of `Delta_(0)` (CFSE in octehedral field) will be maximum.
`(At. No .Co = 27)`

Options

A. `[Co(H_(2)O)_(6)]^(3+)`
B. `[Co(NH_(3))_(6)]^(3+)`
C. `[Co(CN)_(6)]^(3-)`
D. `[Co(C_(2)O_(4))_(3)]^(3-)`

Answer

C

Explanation

The magnitude of `Delta _(0) ` ( the crystal field splitting energy ) is decided by the nature of ligand strong ligand has highest `Delta _(0) ` . The increasing field strength is as
`l^(-) lt Br^(-) lt F^(-) lt OH^(-) lt C_(2)O_(4)^(2-) lt NH_(3)lt en lt NO_(2)^(-) lt CN^(-)`
The `CN^(-)` is the strongest ligand among the given , hence the magnitude of `Delta _(0)` will be maximum in `[ Co(CN)_(6)]^(3-)`.