denticity

[Tanvi Akula 2K]

Why is the oxalate ion bidentate? It has 4 Oxygens with lone pairs, so wouldn't it have 4 binding sites?

[505771920]

I think that because of it's shape it would be impossible for all four oxygens to bind to the same metal. Only two would be able to bind to the same metal molecule.

[Charlie Gravereaux]

If you draw out the lewis structure of the oxalate ion, you find that there is resonance with two of the oxygen carbon bonds being double bonded. This means that that bond is rigid and could not form more than two bonds with the central atom (only where there are single C-O bonds). This means the molecular geometry of oxalate inhibits it being tetra dentate.

[Gavin Trent 2F]

There must be at least two atoms between the first atom with a lone pair and the second atom with a lone pair, so that the geometry allows for both sites to bind.

[Adithi Ayyala 2G]

Hi!
For the oxalate ion because the oxygens are double-bonded, there is no rotating of the bonds as there would be with single bonds. As a result, because of this rigid shape, only two oxygens can bond to one transition metal, making the ion bidentate.
Hope this helps!

[Desiree Eshraghi 3A]

Shape and structure is another thing to think about when considering these hypotheticals,