Ligand what is ligand all types of ligands

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Ligand :

The natural molecules that surrounded the central metal ion in a complex by coordinate linkages are known as ligands (Latin : Ligare = bind ) . Ligands are generally polar molecules or anions having at least one unshared pair of valence electrons , which they donate to the central metal atom through co - ordination bond . These Ligands have donor atoms or ions and may contain one or more unshared pair of electron , known as donor site (s) of the ligand. Depending upon the number of donor atoms the ligands may be classified as : 

Unidentate or Monodentate ligands : 

Ligands which can coordinate with the central metal  ion or atom through only one donor atom are known as Unidentate or Monodentate ligands.

Bidentate ligands :

Ligands which can co - ordinate with central metal atom through two donor atoms are known as Bidentate ligands .

Polydentate ligands : 

Ligands having more than two donor atoms are called polydentate ligands . These may be called as tridentate , tetradent, pentadentate and hexadentate depending upon the number of donor atom present in them.

Chelating ligands :

When ligands containing two or more donor atoms simultaneously coordinate to a metal ion in such a way that a ring like structure is obtained , then such ligands are called Chelating ligands.

Ambidentate ligands :

The ligands having two or more donor sites but joining to the metal ion or atom at one site only are called Ambidentate ligands .

Bridging ligands : 

Some Monodentate ligands which bridge simultaneously with two centres of coordination forming a bridge between two centres are called Bridging ligands .

π Acid ligands : 

Many ligands like Co ,No etc . Have lone pair electron as well as π or π* orbitals . These ligands from a normal bond through the lone pair electron and the vacant π or π* orbitals of the ligands are involved in the Formation of π - bond with the central metal atom by accepting lone pair electron . These ligands are also Known as π - acceptor ligands .

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