Purpureo cobaltic chloride

Another procedure that was used in the early days of coordination chemistry was to refer to the compound by its color. For example, [Co(NH3)6]C13, an intensely yellow compound, was known as luteo cobaltic chloride because the prefix luteo indicates the yellow color. Similarly, [Co(NH3)5C1]C1 was known as purpureo cobaltic chloride because of its purple color, but this is not a satisfactory system of nomenclature to deal with a very large number of compounds. 

Three years later, Sommaruga3 made seven analyses of purpureo-cobaltic chloride by heating it until cobaltous chloride remained, and reducing this salt in a stream of hydrogen ... 

In 1871, Lee7 determined the percentage of cobalt in brucine eobalti-cyanide, strychnine cobalti-cyanide, and purpureo-cobaltic chloride ... 

Heating removes one-sixth of the ammonia, and only two-thirds of the chlorine in the resulting purpureo cobaltic chloride ([CoCl(NH3)5]Cl2) is precipitable by silver nitrate. Considering that halogen atoms bonded to the metal atom through other groups such as ammonia are precipitable by silver nitrate, while those bonded directly to the metal atom are not, Jorgensen proposed formula (2) for the luteo salt. 

In order to account for this difference in reactivity, Jorgensen proposed, as Wemer did after him, that the imre-active or masked chlorine is bonded directly to the metal atom. The stmctmes that they proposed, (5) and (6), are both compatible with the experimental facts but again differ in the mode of attachment of the reactive chlorine atoms. JOTgensen considered these atoms as linked to the metal atom through ammonia molecules, whereas Wemer considered them as not linked to any particular atom but attracted by electrostatic forces to the complex cation as a whole. According to Werner s stmcture, a solution of purpureo cobaltic chloride should furnish three ions, a fact confirmed... 

Bromo purpureo cobaltic bromide Chloro tetra amine cobaltic chloride CoBr(NH3),Br, CoC1(NH,),(OB,)C1, 16 0.19 2.50... 

---