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.