NickelIII

Nickel(III), or Ni(III), refers to nickel in the +3 oxidation state. It is much less common than Ni(II) and is often short-lived in solution, stabilized only by particular ligands or solid-state environments. Ni(III) species are more oxidizing than Ni(II) and can act as one-electron oxidants in various chemical processes. In many systems, Ni(III) forms are transient and prone to disproportionation, such as 2 Ni(III) → Ni(II) + Ni(IV), or reduction back to Ni(II).

Electronic structure and coordination chemistry: Nickel(III) has a d7 electron configuration. In octahedral or similar coordination environments, the electronic arrangement can be low-spin or high-spin depending on the ligand field strength. Low-spin Ni(III) complexes (often with strong-field ligands) may have one unpaired electron, while other environments yield more unpaired electrons. This variety influences magnetic properties and spectroscopic signatures, and Ni(III) centers are frequently studied by EPR spectroscopy and related methods.

Formation, stability, and materials: Ni(III) species are typically generated by chemical or electrochemical oxidation of Ni(II) precursors. They are usually stabilized by robust ligands such as cyanides, polypyridines, or other strong-field donors, and are more common in nonaqueous media. In solid-state materials, Ni in the +3 state appears in layered oxides used in energy storage, such as certain nickel-containing battery materials, where Ni cycles between oxidation states during charge and discharge.

Applications and context: Ni(III) intermediates appear in catalytic cycles for cross-coupling and oxidation reactions, and in electrocatalysis. They also serve as transient species in enzymatic systems and other high-valent nickel chemistries.