Chelate Effect
The greater stability of a complex containing a multidentate ligand compared with one containing equivalent monodentate ligands.
Formula / equation
ΔS favourable
Unit
kJ/mol
In depth
The effect is largely entropic: replacing six separate water molecules with one hexadentate ligand releases six particles while consuming one, so the number of free species increases and entropy rises. Enthalpy changes are usually similar for the two cases.
Examples in the real world
[Ni(en)₃]²⁺ is about 10¹⁰ times more stable than [Ni(NH₃)₆]²⁺ despite very similar donor atoms.