Question

In which of the following octahedral complex species the magnitude of $\Delta_{o}$ will be maximum ?

• A. $\left[Co \left(H_{2}O\right)_{6}\right]^{2+}$
• B. $\left[Co \left(CN\right)_{6}\right]^{3-}$
• C. $\left[Co \left(C_{2}O_{4}\right)_{3}\right]^{3-}$
• D. $\left[Co\left(NH_{3}\right)_{6}\right]^{3+}$

Answer 1

Answer: (B)

Crystal field splitting depends upon the nature of ligand. The nature of ligand $\Delta$ decreases as shown below
$C_{2}O_{4} -<\, H_{2}O <\, NH_{3} <\, CN^{-}$
hence the crystal field splitting will be maximum for $\left[Co \left(CN\right)_{6}\right]^{3-}$