Denticity of ligands

What is the meaning of denticity of ligands?

The denticity of the ligand is defined as the number of pairs of electrons shared with the metal atom or ion.

Ligands can be classified as monodentate and polydentate ligands depending upon the number of ligand donor atoms that attach to the metal atom or ion.

Table of Contents

• Monodentate ligands
• Bidentate ligands
• Tridentate ligands
• Tetradentate ligands
• Pentadentate ligands
• Hexadentate ligands
• Frequently asked questions

Monodentate ligands 

A ligand which shares an electron pair of a single donor atom with a metal atom or ion is called monodentate ligand. The common monodentate ligands are shown below:

Bidentate ligands

These ligands have two donor atoms which can attach to a single metal cation or atom. A bidentate ligand forms one 5- or 6- membered ring with a metal ion. Some examples of bidentate ligands are. 

Bidentate ligands	Name as ligand
NH2CH2CH2NH2	Ethylenediamine (en)
	oxalato
NH2CH2COO–	glycinato
	Propylenediamine (pn)
	Dimethylglyoximato (dmg)-

Note: The ligands like CO32-, NO2-, NO3-, NCS- etc. have two donor atoms but in general, they act as monodentate ligands. They form four or three membered rings including metal cation or atoms there will be repulsion between donor atoms and their electron pairs which causes the ring to be stained and hence unstable.

Tridentate ligands 

These ligands have three donor atoms which can attach to a single metal cation or atom. Some examples of tridentate ligands are.

 Tetradentate ligands

These ligands have four donor atoms which can attach to a single metal cation or atom. Some examples of tetradentate ligands are

Pentadentate ligands

These ligands have five donor atoms which can attach to a single metal cation or atom. Some examples of pentadentate ligands are

Hexadentate ligands

These ligands have six donor atoms which can attach to a single metal cation or atom. Some examples of hexadentate ligands are

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