JEE Main 2025 Apr 3 Shift 1, Chemistry Q23: Isomerism In Co-ordination Compounds

Oxalate (${\text{C}}_2{\text{O}}_4^{2-}$) is a symmetric bidentate ligand. With ${\text{Fe}}^{3+}$ in basic conditions, three oxalate ligands chelate the metal to form the tris-chelate complex $[\text{Fe}({\text{C}}_2{\text{O}}_4{)}_3{]}^{3-}$.

A $[{\text{M(AA)}}_3]$ complex with three identical symmetric bidentate ligands is octahedral and chiral; it lacks any improper symmetry element. It exists as two non-superimposable mirror images ($\Delta$ and $\Lambda$ enantiomers).

$\therefore$ Number of optical isomers $=2$.