CobaltIV

Cobalt(IV) refers to cobalt in the +4 oxidation state. In formal notation it is written as Co4+ or cobalt(IV). It is one of the less common oxidation states of cobalt and tends to be stabilized only under strongly oxidizing conditions, typically in certain solid-state oxides or in coordination complexes with robust ligands.

Electronic structure and spin states: In a typical octahedral or near-octahedral environment, cobalt(IV) has a d5 electron configuration. Depending on ligand field strength, the ion can be low-spin (t2g5, S = 1/2) or high-spin (t2g3 eg2, S = 5/2). The actual spin state influences magnetic and spectroscopic properties and can affect reactivity.

Occurrence and stabilization: Co4+ is stabilized in solid-state oxides and perovskite cobaltates, such as SrCoO3, where cobalt is formally in the +4 state. It also appears in highly oxidized coordination complexes with strong π-acceptor ligands or oxoanions that delocalize charge. Isolated cobalt(IV) centers are uncommon in aqueous solution due to their tendency to reduce to lower oxidation states.

Preparation and reactivity: Co4+ species are typically generated by chemical or electrochemical oxidation of lower-valent cobalt compounds or by high-temperature synthesis of oxides under oxidizing conditions. They are strong oxidants and can participate in oxidation of organic substrates, as well as catalyze oxygen evolution reactions on oxide surfaces.

See also: cobalt oxide, perovskite cobaltates, cobalt fluorides, oxidation state chemistry.