Types of Ligands Preparation and Properties
Types of Ligands :
Ligands are classified on the basis of number of donor atoms:
Monodentate ligands or unidentate ligands
They have one donor atom ie, they supply only one electron pair to central metal atom or ion. Some unidentate ligands are given in table 9.1:
Table 9.1: Some common monodentate ligands
Name of ligand | Name | Donor atom | Charge |
H2O | Aqua | O | 0 |
NH3 | Am mine | N | 0 |
CO | Carbonyl | O | 0 |
C5H5N or Py | Pyridine | N | 0 |
(C6H5)3 P or Ph3P | Triphenyl phosphine | P | 0 |
NO | Nitrosyl | N | 0 |
X– | Halo | X | -1 |
OH– | Hydroxo | O | -1 |
CN– | Cyano | C | -1 |
NC– | Isocyano | N | -1 . |
NO–2 | Nitro | N | -1 |
ONO– | Nitrito | O | -1 |
H– | Hydrido | H | -1 |
NH–2 | Amido | N | -1 |
O2-2 | Peroxo | O | -1 |
O-2 . | Oxo | O | -2 |
CO32- | Carbonato | O | -2 |
SO42- | Sulphato | O | -2 |
NH-2 | Imido | N | -2 |
S-2 | Sulphido | S | -2 |
N3– | Azido | N | -3 |
p-3 | Phosphido | P | -3 |
Bidentate Ligands
The ligands which contain two donor atoms or ions through which they are bonded to the central ion are called bidentate ligands.
Tridentate Ligands
Ligands which have three donor atoms are called tridentate ligands.
Tetradentate Ligand
Tetradenate ligands bind with four donor atoms.
Pentadentate Ligand
Ligands which have five donor atoms are called pentadentate ligand.
Ethylenediaminetriacetato (EDTA)-3
Hexadentate Ligand
Ligands which have six donor atoms.
Example: Ethylenediaminetetracetato