ManganeseIII

Manganese(III), or Mn3+, is the oxidation state of manganese with an oxidation number of +3. It occurs in various coordination compounds and some solid-state oxides, but in aqueous solution Mn3+ is relatively unstable because it rapidly disproportionates to Mn2+ and Mn4+. This tendency to disproportionate limits the stability of many Mn3+ salts in water, unless stabilized by strong ligands or confined in solid matrices.

Electronic structure and geometry: Mn3+ is a d4 ion. In octahedral coordination it is typically high-spin, and Jahn-Teller distortions are common, leading to elongation of some Mn–ligand bonds and a characteristic geometry that influences reactivity and color.

Chemistry and applications: Manganese(III) compounds are generally strong one-electron oxidants and are used in organic synthesis and catalysis. They can oxidize substrates and mediate radical or ionic reactions. Common Mn3+ reagents include manganese(III) acetate (Mn(OAc)3) and metal complexes such as Mn(acac)3 and Mn(III) porphyrins, which are employed as oxidants and catalysts under certain conditions.

Occurrence and preparation: In minerals, Mn exists in multiple oxidation states; Mn3+ appears in oxides and phosphates where Mn3+/Mn4+ coexist, and Mn2O3 is a solid oxide containing Mn3+. In the laboratory Mn3+ salts are prepared by oxidizing Mn2+ salts with suitable non-nucleophilic oxidants or by substitution in preformed Mn3+ complexes. Solid Mn3+ compounds can be more stable than their aqueous counterparts.

Safety: Mn3+ compounds are oxidizers and can pose health and environmental hazards; appropriate safety measures are required when handling them.