The number of atoms through which the ligands can donate a pair of electrons is called denticity of a ligand. Ligands on this basis can be unidentate, tredentate or polydentate.
When coordination of central metal atom or ion with ligand takes place from two or more groups of the same ligands in such a way that five or six membered rings are formed with metal atom or ion then it is called chelation and such ligands is called chelating ligands.
Therefore all didentate or polydentate ligands are chelating ligands.
On the basis of the following observations made with aqueous solutions, assign primary and secondary valencies to metals in the following compounds:
|
Formula |
Motes of AgCl precipitated with excess AgNO3 |
|
(i) PdCl2.4NH3 |
2 |
|
(ii) NiCl2.6H2O |
2 |
|
(iii) PtCl4.2HCl |
0 |
|
(iv) CoCl3.4NH3 |
1 |
|
(v) PtCl2.2NH3 |
0 |
.
