9C5

[Carla Bruebach 1C]

Can someone explain this question? (especially part a) Thanks!

9C.5 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) H2O
(d) oxalate.

[Rhea Jain 2I]

I recommend drawing out the Lewis structures when determining whether a ligand is polydentate. If more than one binding atom has lone pairs, it should be polydentate unless there are special circumstances, like for H2O. According to this, here are the answers:

a) yes, tridentate -> 3 N atoms each with a lone pair
b) yes, mono/bidentate -> resonance structures 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!