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 

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:

Negative ligands  Name as ligand
F Fluorido (fluoro)
I Iodide (iodo)
Cl Chlorido (chloro)
OH hydroxo
O22- peroxo
O2 superoxo
CH3COO acetato
CO32- carbonato
SO42- sulphato
SO32- sulphito
SCN thiosulphato-S
NCS isothiocyanato-N
Neutral ligands 
H2O aqua
NH3 ammine
CO carbonyl
NO nitrosyl
CS thiocarbonyl
Positive ligands 
NO2+ nitonium
H2NNH3+ hydrazinium
NO+ nitrosonium

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.

terpy 1

 Tetradentate ligands

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

   trien 1      

 

Pentadentate ligands

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

Ligand

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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Frequently Asked Questions -FAQs

Q1

1. How do you find the denticity of a ligand?

Denticity of a ligand is the no. of lone pairs donated to the central metal atom or ion by a ligand atom or molecule. 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.

Q2

2. What is the denticity of EDTA ligand?

The denticity of ethylenediaminetetraacetate (EDTA) is six.

Q3

3. What denticity Is the oxalate ligand?

The denticity of oxalate ligand is two. It is a bidentate ligand.

Q4

4. What is the denticity of ethylenediamine?

The denticity of ethylenediamine is two. It is a bidentate ligand.

Q5

5. Is bipyridine a neutral ligand?

Bipyridine is a neutral ligand having a density of two.

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