Chelate complex-definition-examples-chelating and π-acid ligand’s .

Chelate complex definition in co-ordination chemistry.

When a bidentate or poly dentate ligand is attached to the central metal atom or ion through two or more donor atoms, resulting in the formation of a ring structure  complex in the co-ordination sphere ,then the resulting complex is known as chelating complex .

Chelate complex examples in co-ordination chemistry.

There are few well known chelating complex in co-ordination chemistry. Such as Ni( DMG )₂ , [ Fe ( C₂O₄ )₃ ]^3– etc .

Dimethyl  glyoxime (dmg ), a chelating ligand which forms a neutral chelate complex with nickel metal .

Besides, ethylene diamine , a bidentate ligand which is also a chelating ligand . It forms chelate cation with Cu ²⁺ ion .

Similarly, oxalate anion acts as a chelating ligand in the formation of a chelate anion, [ Fe ( C₂O₄ )₃ ]^3–.

What is meant by chelating ligand’s?

When a bidentate or poly dentate ligand is attached to the central metal atom or ion through two or more donor atoms forming a ring structure in the co-ordination sphere, then these type of ligand’s are called chelating ligand’s .

Such as glycinate anion ( gly^– ) , oxalate anion ( Ox ^2– ) , dimethyl glyoximato anion ( dmg^– ) , acetyl acetonate anion (acac^– ) , ethylene diamine (en ) , 2,2’dipyridyl ( dipy ) , ethylene diamine tetraacetic acid (EDTA)  etc .

Why does ethylene diamine is called chelating ligand?

Ethylene diamine , a bidentate ligand . When it co-ordinates with Cu ²⁺ ion through both the nitrogen atoms , it forms  a ring structure complex cation in co-ordination sphere . Hence ethylene diamine is called chelating ligand.

Why does oxalate anion is called chelating ligand ?

Oxalate anion, a bidentate ligand. When it co-ordinates with Fe ³⁺ ion through both the oxygen atoms, it forms a ring structure complex anion in co-ordination sphere, [ Fe ( C₂O₄ )₃ ]^3–. Hence oxalate anion is called chelating ligand.

Significance of chelate formation .

( I ) The  quantitative estimation and identification of some metal ions [ Cu ²⁺, Ni ²⁺, Mg ²⁺ , Al ³⁺ etc ] are done by the formation of chelate complexes.

( II ) The permanent hardness of water can be removed by the formation of chelate complexes. Such as Mg ²⁺ , Ca ²⁺ etc ions in hard water can be removed through the formation of Ca – EDTA  or Mg – EDTA chelate complex.

( III ) Separation  of lanthanides elements from actinides elements is possible through the formation of chelate complex .

( IV ) Metal ion toxicity increases due to incorporation of different metal ion [Hg ²⁺,Pb ²⁺ ,  Cd ²⁺ etc ]  in our human body. These toxic metal ions are eliminated from our body through the formation of chelate complex .

In this purpose , EDTA –chelating ligand is used to remove the above said ions. Besides, for Pb ²⁺ ion toxicity, Na₂[Ca ( EDTA )] agent is used to remove Pb ²⁺ ion from human body .

( V ) Chelating complex formation process is also used to preservative of different food and solvent extraction .

What is π-acid or π-acceptor ligand’s ?

The π-acceptor ligand’s are those which possess vacant p-orbitals in addition to the lone pair of electrons .

These ligands donate their lone pair to the metal to form a normal sigma( σ ) bond with the latter.

In addition to it , the vacant orbitals accept electrons from the filled metal orbitals to form a type of π-bond which suppliments the sigma bond . 

These ligand’s are thus called π-acid ligand’s or π-acceptor ligand’s.The π-acid ligand’s are also called π-bonding ligand’s .

Examples of π-acid ligand’s.

The common examples of π-acid ligand’s are CO , R–NC , NO , PR₃ etc .

Summary

Chelate complex definition in co-ordination chemistry . 

Chelate complex examples in  co-ordination chemistry .

What is meant by chelating ligand’s ? 

Why does ethylene diamine is called chelating ligand ?

Why does oxalate anion is called chelating ligand ?

Significance of chelate formation .

What is π-acid or π-acceptor ligand’s ?

Ligand  definition and types of ligand  in chemistry.