Ligands: The ions or molecules bound to the central atom/ion in the coordination entity are called ligands. These may be simple ions such as Cl-, small molecules such as H2O or NH3, larger molecules such as H2N CH2CH2 NH2 or N(CH2CH2NH3)3 or even macromolecules such as unidentate proteins.
When a ligand is bound to a metal through a single donor atoms such as Cl-, H2O or NH3, the ligand is said to be unidentate Eg.- Cl, H2O
Bidentate: When a ligand is bound through two donor atoms, the ligand is called bidentate ligands.
Eg.- H2N, CH2CH2NH2 or C2O42-
Polydentate: N(CH2CH2NH2) Hexadentate ligand - (EDTA4+)
