(CO3)2- polydentate ligand

[Tylor McGrew 1J]

How come for (CO3)2-, this is either monodentate or bidentate? When do we know, which type of polydentate it is going to be?

[Nishma Chakraborty 1J]

Hey!

(CO3)-2 can either be a bidentate or monodentate due to its Lewis structure and resonance. When we draw the lewis structures for (CO3)2-, there are two possibilities, with one structure having a C=O bond and two C-O^-1 bonds. With this structure, the two O^-1's can bond to a metal at two different places, making it a bidentate. In another structure, there is a double bond between two Carbon and Oxygen bonds. Consequentially, only one Oxygen can bind to a metal, making this form of (CO3)2- a monodentate.

Because (CO3)-2 is a small molecule, I think most of the time it acts as a monodentate.

Hope this helps! :)