Formation constant `K_(f)` for the two complex ions are :
`[Ni(en)_(3)]^(2+), K_(f)=1.1 xx 10^(18)` and `[Ni(NH_(3))_(6)]^(2+), K_(f) = 5.3 xx 10^(8)`
Explain the relative stability of these complexes.

Explanation

In the first complex: `en` is didentate ligand and has much larger formation constant than 'ammine' present in the second complex which is only a unidenate ligand. Moreover, `en` is also involved in the formation of chelate (chelation effect) and the complex has extra stability.