Question

Choose incorrect statement(s) regarding following complex ion.

${\left[Fe{\left(ox\right)}_3\right]}^{3-}$ and ${\left[Fe{\left(N{O}_2\right)}_6\right]}^{3-}$

• A. ${\left[Fe{\left(ox\right)}_3\right]}^{3-}$ complex ion is more stable than ${\left[Fe{\left(N{O}_2\right)}_6\right]}^{3-}$
• B. Both complex ions are optically inactive
• C. Both follow Sidwick's rule of E.A.N
• D. Both are paramagnetic

Answer 1

Answer: (A), (C)

${\left[Fe{\left(ox\right)}_3\right]}^{3-}$ complex ion is more stable than ${\left[Fe{\left(N{O}_2\right)}_6\right]}^{3-}$
Both follow Sidwick's rule of E.A.N

The incorrect statement(s) regarding following complex ion ${\left[Fe{\left(ox\right)}_3\right]}^{3-}$ and ${\left[Fe{\left(N{O}_2\right)}_6\right]}^{3-}$ are the statements A, B and C respectively.
(A) ${\left[Fe{\left(ox\right)}_3\right]}^{3-}$ complex ion is less stable than ${\left[Fe{\left(N{O}_2\right)}_6\right]}^{3-}.$. The oxalate ions are bidentate ligands and form metal chelates which are more stable than non chelates.
(B) The complex ${\left[Fe{\left(ox\right)}_3\right]}^{3-}$ is optically active. It exists in the form of d and l isomers and the complex ${\left[Fe{\left(N{O}_2\right)}_6\right]}^{3-}$ is optically inactive.
(C) Both do not follow Sidwick's rule of E.A.N.
$EAN=26-3+12=35$
(D) Both are para-magnetic due to presence of unpaired electrons. In both the complexes, the Fe atom has +3 oxidation state and $3d^5$ electronic configuration.