hexamminecobaltIII

Hexamminecobalt(III) refers to the coordination complex [Co(NH3)6]3+. In this complex cobalt is in the +3 oxidation state and is coordinated by six ammonia ligands in an octahedral arrangement. It commonly forms salts, for example [Co(NH3)6]Cl3, where three chloride ions balance the charge.

The complex is a low-spin d6 system, resulting in a diamagnetic species with no unpaired electrons. This electronic configuration contributes to substantial kinetic inertness: ligand substitution at cobalt(III) centers is slow compared with many other coordination compounds, making the complex relatively inert to reaction.

Synthesis and occurrence: Hexamminecobalt(III) can be prepared by oxidation of cobalt(II) ammine species under controlled conditions or by treating cobalt(III) salts with excess ammonia to form the hexaammine complex. In practical contexts, the salt form is most commonly encountered.

Properties: As a cation, [Co(NH3)6]3+ is typically soluble in water and forms salts with various counterions. Because all ligands are neutral, changes in the counterion mainly affect crystallization behavior and solubility rather than the coordination sphere.

Reactivity: Substitution at cobalt(III) centers remains slow, illustrating the kinetic inertness characteristic of many cobalt(III) ammine complexes. The complex serves as a standard model in coordination chemistry for ligand-field theory and the study of substitution kinetics.

Safety: Cobalt compounds can be toxic; appropriate handling and disposal procedures should be followed.

See also: hexamminecobalt(III) chloride, [Co(NH3)6]3+ salts, cobalt(III) ammine complexes.