Help understanding polydentate

[Ella Bouris]

I'm having trouble just understanding how to determine if a molecule is mono, bi, etc dentate. Do I need to draw a Lewis structure?

[Cali Rauk1D]

you can determine this by seeing if the ligand can bind to a central metal atom at 1,2, or many sites.

[Alex Nechaev 1I]

^What process do we need to use to determine this though? Is there a way to see without drawing the Lewis structures?

[Ella Bouris]

I've been looking it up and my understanding is that for something to be polydentate, there has to be multiple molecules each with a lone e- pair available for bonding. So for something to be bidentate, it doesn't just have to have two lone pairs but one lone pair each on two atoms to make them available for bonding, so my guess is that the Lewis structure would be the most reliable way to find this out, but I haven't really found a conclusive answer on this yet.

[Ramya Natarajan 1D]

you're right--the way to determine whether an atom is polydenate or not is to draw out the lewis structure and see whether multiple atoms have lone pairs available for bonding. These long pairs must be on different atoms, and they must make geometrical sense. For example, in the example we have in the notes, [PtCl2(NH3)2], only the cis form of this is polydentate because it can actually reach the binding site. Basically, you just need to determine if the ligand can bond to the central atom at more than one point.