Definitions of some terms related to Coordination Compounds Preparation and Properties
Definition of Some Terms Related to Coordination Compounds :
→ Ambidentate Ligand : Ligands which can ligate (link) through two or more different donor atoms present in it are called ambidentate ligand. Although at a time only one atom can link with central metal atom.
Example : NO2–, and SCN– NO2– can link through N as well as O while SCN– can link through S as well as N atom.
→ Chelate Ligand : Polydentate ligands use their one or more donor atoms to from co-ordinate bond with central metal so as to give a ring like structure. This ring is called chelate ring and the ligand is called chelate ligand.
Example : Ethylenediammine and oxalato ion etc.
→ Co-ordination Number : It is defined as the total number of coordinate bonds formed by central metal atom with the ligands. For example, the co-ordination number of cobalt in [Co (NH3)4]3+ is 4.
→ Similarly, the co-ordination number of Ag+ in [Ag(NH3)2]+ is 2, that of Cu2+ in [Cu(NH3)4]2+ is 4, and that of Fe3+ is [Fe(CN)6]3- is 6.
Example :
| [Ag(NH3)2]Cl | C.N. = 2 | [Cu(NHa)4]S04 | C.N. = 4 |
| [Fe(NH3)6]Cl3 | C.N. = 6 | [Ni(en)*]Cl9. | C.N. = 4 |
| Na[Co(ox)3] | C.N. = 6 | Na2 [Co(acac)2Cl2] | C.N. = 6 |
| [Co(dien)2] | C.N. = 6 | [Co(EDTA)]-2 | C.N. = 6 |
→ The most common coordination number exhibited by metal ions are 2, 4 and 6.
Familier coordination number of some common metal ions :
→ Coordination number of metal ion is responsible for geometry of complex.
- C.N. = 2 → Linear
- C.N. = 3 → Triangular planar
- C.N. = 4 → Tetrahedral or square planar
- C.N. = 5 → Triangular bipyramidal
- C.N. = 6 → Octahedral