Hapticity

              Hapticity is a term describing how a group of contiguous atoms are bonded to a central atom of a coordination compound. Each atom of the contiguous group is bound only once to the central atom. The Hapticity of a ligand is indicated by the Greak character ' eta ' . 'eta' denotes the number of contiguous atoms of the ligand that are bound to the metal.
Example :
             Ferrocene is a molecule with two cyclopentadienyl rings bound to a central iron m olecule. Five contiguous carbon atoms are bound to the central iron atom, the hapticity is five.