Question

Carbon donor ligands are strong ligands and usually forms low spin complexes. Among the complexes given below, select the high spin complex.

• A. $\left[Fe\right(CN{)}_6{]}^{3-}$
• B. $\left[Fe\right(CN{)}_6{]}^{4-}$
• C. $\left[Fe\right(C_2{O}_4{)}_3{]}^{3-}$
• D. none of these

Answer 1

The correct option is A $\left[Fe\right(CN{)}_6{]}^{3-}$

The complex among the given complexes which shows high spin is $\left[Fe\right(C_2{O}_4{)}_3{]}^{3-}$. This is because the $\left(C_2{O}_4\right)$ is a weak field sigma donar ligand which do not pair up the electrons as CN ligand in the other complexes.