What is meant by the chelate effect? Give an example.

Explanation

When a bidentate or a polydentate ligand contains donor atoms positioned in such a way that when they coordinate with the central metal ion, a five a or a six membered ring is formed. As a result, the stability of the complex so formed increases. This is known as chelaze effect.
For exmple, the complex of `Ni^(2+)` with en is more stable than with `NH_3`
`Ni^(2+) (aq) + 6 NH_3 (aq) harr [Ni(NH_3)_6]^(2+), log beta = 8.61`
`Ni^(2+) (aq) + 3 en (ag) harr [Ni(en)_3]^(2+), log beta = 18.28`
Another example of chelation and stability is given below: