SbIII

SbIII denotes antimony in the +3 oxidation state, commonly written as Sb3+. It is one of the principal oxidation states of the element antimony (Sb) and forms a variety of inorganic and coordination compounds. In aqueous solutions, Sb(III) species are typically present as Sb(III) ions or hydrolyzed species such as Sb(OH)3, depending on pH.

Common Sb(III) compounds include antimony trichloride (SbCl3), antimony tribromide (SbBr3), and antimony trifluoride (SbF3). The oxide Sb2O3 has two polymorphs, valentinite and senarmontite, both of which contain Sb in the +3 oxidation state. The principal sulfide mineral containing Sb(III) is stibnite (Sb2S3). In water, Sb(III) readily hydrolyzes to form Sb(OH)3.

Chemically, Sb(III) behaves as a Lewis acid and forms complexes with halide, oxide, and sulfide ligands. It can be oxidized to Sb(V) by oxidants, establishing a redox couple Sb(III)/Sb(V) that is relevant in environmental chemistry and detoxification. Sb(III) compounds are generally less stable in air than Sb(V) compounds and are often more toxic.

Applications and safety: Sb(III) compounds have uses as Lewis acid catalysts and reagents in organic synthesis; SbCl3, for example, is employed in various Friedel–Crafts-type reactions. Sb2O3 is used as an opacifying agent in glass and ceramics and as a flame retardant additive. Toxicology: exposure to Sb(III) compounds can be hazardous, affecting gastrointestinal and cardiovascular systems and potentially causing other adverse effects; appropriate handling and ventilation are required. In medicine, pentavalent antimony compounds are used to treat leishmaniasis, and these agents can be reduced to Sb(III) species in vivo.