pentaamminechlorocobaltIII

Pentaamminechlorocobalt(III) is an inorganic coordination compound with the chemical formula [Co(NH₃)₅Cl]²⁺. It is a cation and exists as a salt with various counterions, such as chloride or nitrate. This compound is a member of the ammine complexes of cobalt, where ammonia molecules (NH₃) act as ligands coordinated to a central cobalt ion. In this specific complex, five ammonia ligands and one chloride ligand are bound to the cobalt ion. The cobalt ion is in the +3 oxidation state.

The synthesis of pentaamminechlorocobalt(III) typically involves reacting a cobalt(II) salt with ammonia and an oxidizing agent in the presence of chloride ions. Common synthetic routes include the oxidation of cobalt(II) in aqueous ammonia with hydrogen peroxide or air, followed by the addition of hydrochloric acid. The resulting complex can then be isolated as a salt, for example, pentaamminechlorocobalt(III) chloride, [Co(NH₃)₅Cl]Cl₂.

This complex is often used in the study of coordination chemistry and reaction mechanisms. It serves as a precursor for the synthesis of other cobalt(III) complexes, such as those with different amine or halide ligands, through ligand substitution reactions. The geometric isomerism of cobalt(III) ammine complexes is also an area of interest, and while pentaamminechlorocobalt(III) itself exists as a single geometric isomer due to the arrangement of the ligands around the central metal ion, related complexes can exhibit cis and trans isomerism.