Step 1: A ligand that grips the metal at more than one point (like a claw) creates a closed ring; such ligands are called chelating ligands.
Step 2: Complexes built from these chelating ligands have unusually large stability constants; this enhancement over comparable monodentate complexes is termed the chelate effect.
Step 3: The driving force is largely entropic: replacing six separate \(NH_3\) molecules with three bidentate \(en\) molecules releases more particles into solution, raising disorder and lowering free energy.
Step 4: For instance, \([Fe(EDTA)]^{-}\), where a single hexadentate EDTA wraps around the iron, is exceptionally stable, illustrating the chelate effect.