Chelates

[VZX]

What properties contribute to forming chelating complexes and what prevents chelates to form? Can only molecules within an angle in between them form chelates because of the strain on the bonds?

[305597516]

Chelating complexes are essentially like your normal coordinate complex, except the ligands are able to form more than one bond (bidentate, tridentate, etc.) so that they form a sort of ring. One property that they must have is that there is space in between the lone pairs (where the bonds will take place) so that the repulsion of the electrons will not prevent a bond from forming.

Take ethylene diamine (en) for example; there are two nitrogens, and you know that nitrogen has one lone pair of electrons each. Therefore each nitrogen can form one bond each. Why is it that the repulsion of electrons does not prevent it from forming two bonds? If you draw out the Lewis structure of this molecule, there is at least two atoms of space in between the two, allowing these bonds to form. Because this ligand can form a bond with both the transition metal AND another molecule, it is able to form a ring shape, which makes up a chelating complex.