Q. Show the Nomenclature compounds?
In the earlier days naming of complexes was based on the colour of the complex. For example:
Compound Colour Name
CoCI3, 4NH3, Green Praseocobaltic chloride
CoCI3, 5NH3 Purple Perpureocobaltic chloride
CoCI3, 5NH3,H20 Red Roseocobaltic chloride
CoCI3, 6NH3, Orange-yellow Luteocobaltic chloride
It is apparent that this system of naming cannot be useful when we are dealing with a large number of compounds. A summary of the rules of nomenclature as recommended by the International Union of Pure and Applied Chemistry (IUPAC) is given below:
If the complex is a salt, the cation is named first followed by the name of the anion. For example, in naming K2[PtCl6] we shall name potassium first followed by the name of the anion. In another example of [Cu (NH3)4] Cl2, the name of the cation, [CU (NH3)5 will be placed before chloride ion.
For the complex entity, whether it is in cationic, anionic or neutral form, the name of the ligand(s) is put before the name of the metal atom. However, the reverse order is followed in writing the formula of the compound. For example in Cu(NH3)4]Cl2, we shall name the four ammonla molecules first followed by copper and finally the presence of chloride is mentioned; but in writing the formula copper is written before ammonia molecules.