The stabilization of coordination compounds due to chelation is called the chelate effect. Which of the following is the most stable complex species?

1. Fe(CO)5
2. \(Fe(CN)_{6}^{3-}\)
3. \(Fe(C_{2}O_{3})_{3}^{3-}\)
4. \([Fe(H_{2}O)_{6}]^{3+}\)

Hint: Bidentate ligand can show chelating effect

Chelation (formation of cycle by linkage between metal ion and ligand) stabilises the Coordination compound. The ligand which chelates the metal ion are known as
chelating ligand.
Here, only Fe(C2O4)33- is a coordination compound which contains oxalate ion as a
chelating ligand, Hence, it stabilises coordination compound by chelating Fe3+ ion.
Chelating ligands are generally bidentate.