copperIV

Copper(IV) refers to the oxidation state of copper with a formal oxidation number of +4. It is one of the highest oxidation states observed for copper, which more commonly exists as Cu(I) or Cu(II). Cu(IV) species are relatively rare and are typically stabilized only under highly oxidizing, non-aqueous conditions and with ligands or lattice environments that support high oxidation states. In solution, Cu(IV) is generally unstable and tends to be reduced or to undergo reactions that move it to lower oxidation states.

A well-characterized class of Cu(IV) compounds comprises fluoride-rich salts, such as hexafluorocuprate(IV) species. Examples include salts like K2CuF6 and Cs2CuF6, which contain the [CuF6]2− anion in which copper is in the +4 oxidation state. These solids are stable in the absence of moisture and are typically prepared and studied under strictly anhydrous conditions. Beyond fluorides, Cu(IV) has been observed in other oxide- and fluoride-containing materials and in rare coordination environments in non-aqueous media, where the ligand field and lattice energy help stabilize the high oxidation state.

In chemical research, Cu(IV) is discussed as a highly oxidizing intermediate in certain catalytic and stoichiometric oxidation reactions. Its existence helps explain unusual oxidation chemistry and informs proposed mechanisms for copper-catalyzed fluorination and oxygen-transfer processes. While important for understanding copper redox versatility, Cu(IV) compounds remain far less common and more conditions-dependent than Cu(I) or Cu(II) species.

See also: Copper chemistry, oxidation states of copper, hexafluorocuprate(IV).