Type of Legands:-

Legands are e- donors means nucleophile and their denticity depends on presence of lone pairs which can be co-ordinated.

Generally legands are anion or natural but sometimes they can be positively charged.

According  to denticity there are 6 type of legands from unidentate to hexadentate.

Unidentate

  1. Unidentate or Monodentate:- One lone pair donor.

a) Cationic:-

b).Neutral:-

CO->Carbonyl

CS ->Thio Carbonyl

H2O->Aqua, Aquo

c) Negatively Charged:-

F-->Fluorido

Cl-->Clorido

Br-->Bromido

I- ->Iodido

OH- ->Hydroxo

NH2-->Amido

NO2-->Nitro

O‑ -NOO –-> Nitro

O--CN->Cyanoto

N- CO->Iso cyanoto

S-CN ->Thio cyanoto

N- CS ->Iso Thio cyanoto

N3-->Azido

PH2- ->Phosphido

C-N ->Isocyano

O2-2->Per oxo

2. Bidentate:

Two lone pair donor

Note: All Bidentate have oxidation state -1.

And for (en) it is Zero.

3 .Tridentate:-

Dien      ->     Diethylene triamine

Terpy    --> Tripyridine

denticity means donation of lone pair.

nda        -->   nitrilodiacetato

4. Tetra dentate

Tetra dentate or Quadridentate:-

Trien      -->         Triethylene  tetramine

nitrilo triacetato

5.  Penta dentate

ethylene diamine triacetate

6. Hexa dentate

Hexa dentate:- EDTA

Ethylene diamine tetra acetato

Ambidentate  legand

In this more than one lone pair ore present at a time only one lone pair can be Co-ordinate their lone pair 3 or 4 membered ring is prepared which is highly unstable.

e.g.:-

All ambidentate are pseudo

Flexi dentate

Flexi dentate:- All polydentate legand are flexi legand because they can show more than one type of denticity.

Ethylene diamine  is bidentate legand but can also behave as unidentate.

Chelating legand 

 

Chelating Legand:-

It is non-cyclic legand but form cycle complex. Generally chilates are more stable than normal complexes but not always (because stabililty is decided by crystal filed theory).

Macrocyclic legand

It is a cycle legand which form cyclic complex. Macrocyclic are more stable than chilates.

  • Hb and chloropyll are Macrocycle.
  • All crown ethers are macrocycle.

 

 

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12    PMT    Chemistry    Coordination Compounds    Types of Legands