Textbook problem 9C.5

[Xinyue Zou 2K]

I'm a little confused on how to determine polydentate ligands for this problem:
Which of the following ligands can be polydentate? If the ligand can be polydentate, give the maximum number of places on the ligand that can bind simultaneously to a single metal center:
a.) HN(CH2CH2NH2)2
b.) CO3 2-
c.) H20
and d.) oxalate.

[Rhea Jain 2I]

When determining whether a ligand is polydentate, I find it helpful to draw out the Lewis structure. This way, you can see if an atom has extra lone pairs that would allow it to bond again. The answers to the questions are listed below.

a) yes, tridentate -> 3 N atoms each with a lone pair
b) yes, mono/bidentate -> resonance structure with 1 or 2 O atoms with lone pairs
c) no, monodentate -> known monodentate
d) yes, bidentate -> 2 O atoms with lone pairs

Hopefully this helps!