Question

Which of the following ligands forms a chelate complex?

• A. C\(_2\)O\(_4^{2-}\)
• B. Cl\(^{-}\)
• C. NO\(_2^{-}\)
• D. NH\(_3\)

Hint:

Chelate complexes are more stable because they form cyclic structures that resist ligand dissociation.

Answer 1

The Correct Option is A

The oxalate ion (C\(_2\)O\(_4^{2-}\)) acts as a bidentate ligand, capable of coordinating to a metal ion at two sites (via two oxygen atoms). This coordination results in the formation of a stable five-membered chelate ring.

- The chelate effect, an entropy-driven stabilization, enhances the stability of the metal complex.
- Notable metal-oxalate complexes comprise:
- [Fe(C\(_2\)O\(_4\))\(_3\)]^{3-} (Ferric oxalate)
- [Cr(C\(_2\)O\(_4\))\(_3\)]^{3-} (Chromium(III) oxalate)