Editing Cobalt(II) chloride (section)

===Oxidation to cobalt(III)===
Compounds of cobalt in the +3 oxidation state exist, such as [[cobalt(III) fluoride]] {{chem|CoF|3}}, [[cobalt(III) nitrate|nitrate]] {{chem|Co|(|NO|3|)|3}}, and [[cobalt(III) sulfate|sulfate]] {{chem|Co|2|(|SO|4|)||3}}; however, [[cobalt(III) chloride]] {{chem|CoCl|3}} is not stable in normal conditions, and would decompose immediately into {{chem|CoCl|2}} and [[chlorine]].<ref>''Handbook of Chemistry and Physics'', 71st edition, CRC Press, Ann Arbor, Michigan, 1990.</ref>

On the other hand, cobalt(III) chlorides can be obtained if the cobalt is bound also to other ligands of greater Lewis basicity than chloride, such as [[amine]]s.  For example, in the presence of [[ammonia]], cobalt(II) chloride is readily [[redox|oxidised]] by atmospheric [[oxygen]] to [[hexamminecobalt(III) chloride]]:
:4 {{chem|CoCl|2}}·6{{chem|H|2|O}} + 4 {{chem|NH|4}}Cl + 20 {{chem|NH|3}} + {{chem|O|2}} → 4 {{chem|[|Co|(|NH|3|)|6|]|Cl|3}} + 26 {{chem|H|2|O}}
Similar reactions occur with other [[amine]]s.  These reactions are often performed in the presence of [[carbon|charcoal]] as a catalyst, or with [[hydrogen peroxide]] {{chem|H|2|O|2}} substituted for atmospheric oxygen. Other highly basic ligands, including [[carbonate]], [[acetylacetone|acetylacetonate]], and [[oxalate]], induce the formation of Co(III) derivatives. Simple carboxylates and halides do not.{{cn|date=September 2023}}

Unlike Co(II) [[Complex (chemistry)|complexes]], Co(III) complexes are very slow to exchange [[ligand]]s, so they are said to be ''kinetically inert''. The German chemist [[Alfred Werner]] was awarded the [[Nobel Prize]] in 1913 for his studies on a series of these cobalt(III) compounds, work that led to an understanding of the structures of such [[Complex (chemistry)|coordination compounds]].{{cn|date=September 2023}}