Polydentate Potential

[ahuang]

How do you know if a ligand can be polydentate? I know that the metal can bond to the lone pairs but for example in Oxalate (C2O4 2-), it can be bidentate, but why is it not tetradentate?

[Andrew Liang 1I]

Oxalate (C2O4 2-) can only be a bidentate because when you draw the lewis structure there are only 2 lone pairs in the molecule (one on each farthest oxygen atom). In order to be a tridentate, the ligand must have at least 3 lone pairs.

[PriscillaLi_3G]

How do you know if a ligand can be polydentate? I know that the metal can bond to the lone pairs but for example in Oxalate (C2O4 2-), it can be bidentate, but why is it not tetradentate?

If you draw the lewis structure and do the formal charges, you will notice that there are only 2 atoms in which there is a formal charge of -1. Thus these are the only two possible bonding sites, which makes it a bidentate.