In which of the following octahedral complexes of Co (at. no. 27), will the magnitude of `Delta_o` be the highest?

Options

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

Answer

A

Explanation

CFSE ( crystal field splitting energy ) for octahedral complex , `Delta _(0) ` depands on the the strength of negative ligand . Spectrochemically, it has been found that the strength of splitting is as follows :
` CO gt underline ( CN^(-)) gt NO_(2)^(-) gt underline (NH_(3))gt py gt `
` NCS ^(-) H_(2) O gt O_(2) gt Ox^(2-) gt OH^(-) gt F^(-) gt `
` Cl ^(-) gt SCN^(-) gt S^(2-) gt Br^(-) gt I^(-)`
therefore , magnitude of ` Delta _(0) ` will be highest in case of ` [Co (CN)_(6) ]^(3-)`.