Ligands
It is an ion or molecule capable of donating a pair of electrons to the central atom via a donor atom.
Types of ligands
Unidentate ligands: Ligands with only one donor atom, e.g. NH3, Cl-, F- etc.
Bidentate ligands:Ligands with two donor atoms, e.g. ethylenediamine, C2O42- (oxalate ion) etc.
Tridentate ligands:Ligands which have three donor atoms per ligand, e.g. (dien) diethyl triamine.
Hexadentate ligands:Ligands which have six donor atoms per ligand, e.g. EDTA.
Chelating Ligands:Multidentate ligand simultaneously co-ordinating to a metal ion through more than one site is called chelating ligand. These ligands produce a ring like structure called chelate. Chelation increases the stability of complex. This effect is called chelation effect.
Example:
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H2C — NH2 O = C — O :
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H2C — NH2 O = C — O :
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