Question

Out of the complexes ${\left[Fe\left(H_{2}O{)}_6\right)\right]}^{3+}$, ${\left[Fe{\left(CN\right)}_6\right]}^{3-}$, ${\left[Fe{\left(C_2{O}_4\right)}_3\right]}^{3-}$ and ${\left[Fe{\left(Cl\right)}_6\right]}^{3-}$, the most stable one is:

• A. ${\left[Fe\left(H_{2}O{)}_6\right)\right]}^{3+}$
• B. ${\left[Fe{\left(CN\right)}_6\right]}^{3-}$
• C. ${\left[Fe{\left(C_2{O}_4\right)}_3\right]}^{3-}$
• D. ${\left[Fe{\left(Cl\right)}_6\right]}^{3-}$

Answer 1

The correct option is C ${\left[Fe{\left(C_2{O}_4\right)}_3\right]}^{3-}$

In ${\left[Fe{\left(C_2{O}_4\right)}_3\right]}^{3-}$, the ligand is a bidentate ligand and hence, binds more strongly to the central atom as per the chelate effect which provides more stability to the complex.

Option C is correct.