13859-51-3

brick red crystal(s) [KIR79] [ALD94]

Chloropentaamminecobalt (III) Chloride is obtained by oxidation of an ammoniacal CoCl3 solution, and purified via [Co(NH3)sH2O]2(C2O4)3 ? 4H3O.
A solution of 20 g. of precipitated cobalt carbonate in some 1:1 HCl is prepared, filtered and cooled; a mixture of 250 ml. of cone, ammonia and 50 g. of (NH4)3CO3 dissolved in 250 ml. of H3O is then added. The mixture is oxidized for three hours by bubbling in a stream of air. After addition of 150 g. of NH4Cl the solution is evaporated to sirup consistency on the steam bath. Dilute HCl is added to drive off the CO 2 and produce a weakly acid reaction; then ammonia is added to give a weakly basic solution, followed by 10 ml. of additional cone, ammonia. The liquid, whose volume at this point is 400-500 ml., is heated on the steam bath until all the tetraammine salt disappears; it is then treated with 300 ml. of cone. HCl and heated for 30-45 minutes on the steam bath. The [Co(NH3)5- Cl]Cl2 precipitates on cooling. It is filtered off and washed with 1:1 HCl until free of NH4Cl, then with alcohol until free of acid. The salt still contains some [Co(NH3) 5]Cl3. Yield: 34.5 g.