Question

In which of the following octahedral complexes of Co (At. no. 27), will the magnitude of $\Delta_{0}$ be the highest?

• A. $[Co(CN)_6]^{3-}$
• B. $[Co(C_2O_4)_3]^{3-}$
• C. $[Co(H_2O)_6]^{3+}$
• D. $[Co(NH_3)_6]^{3+}$

Answer 1

Answer: (A)

Spectrochemical series. According to the strength of splitting is as :
$CO > CN^{-} > NO^{-}_{2} > en > NH_{3} > py > NCS^{-}$
$> H_{2}O > O^{2-} > oX^{2-} > OH^{-} > F > Cl^{-}$
$ > SCN^{-} > S^{2-} > Br^{-} > I^{-}$
Crystal field stabilisation energy (CFSE) foroctahedral complex, $\Delta^{\circ}$ depends on the strengthof negative ligand. [Higher the strength morewill be the CFSE]