Question 9C.5

[Lauren Haight 1E]

The question asks 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)
CO32−
;
c) H2O;
(d) oxalate.

How are we able to tell that a ligand will be polydentate based on its formula? Do we have to construct a Lewis Structure and see how many lone pairs the molecule has?

[Alexa Mugol 3I]

You would draw the Lewis structure and see how many atoms in the molecule have a lone pair/lone pairs.
For example, HN(CH2CH2NH2)2 has three nitrogens each with lone pairs. Therefore, there are three sites for bonding and the molecule is tridentate.
Water only has one oxygen atom with lone pairs, so it's monodentate.