manganous

Manganous is the adjective for manganese in the +2 oxidation state, denoted Mn(II). In older nomenclature, manganous distinguished Mn2+ from manganic Mn3+. The term is applied to manganese compounds containing the Mn2+ ion and to processes involving this oxidation state.

In aqueous solution Mn2+ forms the hexaaqua complex [Mn(H2O)6]2+. The ion is paramagnetic with five unpaired electrons and typically participates in octahedral coordination chemistry. Manganous salts, such as manganese(II) sulfate and manganese(II) chloride, are common laboratory reagents. Solutions of Mn2+ are often colorless or pale pink, depending on ligands and concentration.

Manganous ions are easily oxidized to manganic Mn3+ or, more commonly, to insoluble manganese dioxide MnO2 under oxidizing conditions or at elevated pH. This redox behavior drives many manganese-containing reactions and is exploited in qualitative analysis and some industrial processes. Mn2+ forms a variety of coordination compounds with organic ligands and biological molecules.

Occurrence and applications: Mn2+ occurs widely in minerals and is produced industrially from manganese oxides and other manganese minerals. In biology, Mn2+ is an essential trace element acting as a cofactor for various enzymes, including Mn-dependent superoxide dismutase. In agriculture, Mn2+ is supplied as a micronutrient to correct soil deficiencies. Manganous salts are used as reagents, in plating, and in certain chemical syntheses, while care is taken to avoid excessive exposure due to potential toxicity.