Textbook 9C5 Part B

[Elsie_Lin_2K]

Why is CO3 2- a mono-or bidentate ligand instead of a tridentate ligand? It has three oxygens with lone pairs.

[Nathan Tran 1B]

So for that one it has a trigonal planar structure and contains no spacer molecules. Therefore, while it must wrap around a molecule to be able to be polydentate the structure of the molecule only allows it to be bidentate. Furthermore, it would only be bidentate if the Cation that it was bonding to was very small therefore it is usually monodentate.