IIIcatalyzed

IIIcatalyzed is a descriptor used in chemistry to refer to catalytic processes that are driven by a metal center in the +3 oxidation state. It is not a formal IUPAC category, but rather a contextual label appearing in the literature when oxidation-state considerations are central to the mechanism or design of the catalyst. The term can apply to both transition-metal systems such as iron(III), chromium(III), aluminum(III), and other +3 species, as well as to heterogeneous or supported catalysts that present a +3 oxidation state at the active site. Researchers may use this shorthand to distinguish +3-catalysis from +2-, +4-, or organocatalytic routes.

Mechanistic themes in IIIcatalyzed processes vary. Some cycles rely on redox changes of the metal (for example Fe(III)/Fe(II) pairs) to enable electron transfer and substrate activation. Others are dominated by Lewis acidity, where the +3 metal center activates substrates through coordination and polarization without undergoing significant redox changes. Radical intermediates may be generated in some cases, while in others the catalysis progresses through ionic pathways. Ligand environments, coordination geometry, and substrate electronics all influence selectivity and turnover.

Applications reported under the IIIcatalyzed label span oxidation, cycloaddition, hydrofunctionalization, C–H activation, and biomass conversion, among other transformations. The approach is valued for access to reactive intermediates under relatively mild conditions, the potential for high regio- and stereocontrol with appropriate ligands, and the use of abundant metals in some systems. Specific catalysts and conditions are described in primary literature, where the active oxidation state and the exact mechanism are detailed.

Because IIIcatalyzed is not a standardized term, its meaning can vary between studies. When encountered, it should be interpreted in the context of the reported metal, ligands, solvent, and proposed catalytic cycle to determine the exact nature of the active species and the scope of the transformation.