Manganate

Manganate refers to the manganate(VI) anion, MnO4^(2-), in which manganese is in the +6 oxidation state. The ion has a tetrahedral arrangement of four oxygens and is green in aqueous solution. Salts such as potassium manganate (K2MnO4) and sodium manganate (Na2MnO4) are commonly encountered. In strongly alkaline media manganate is relatively stable, but it decomposes in acidic conditions, yielding permanganate and manganese dioxide.

Preparation and properties: Manganate is typically formed by partial reduction of permanganate in strongly basic solution or by controlled electrochemical methods in alkaline media. In basic solutions manganate acts as a moderate oxidizing agent, though its utility is limited by its instability in acidic or reducing environments. It tends to revert or disproportionate under unfavorable conditions, and solutions are typically stored under basic conditions away from heat and reducing agents.

Reactions and applications: In alkaline media manganate oxidizes various substrates, such as sulfites to sulfates and iodide to iodine, though it is less commonly used than permanganate due to stability concerns. It can serve as an intermediate in the industrial preparation of permanganate, where manganate is converted to MnO4^- under appropriate conditions. Historically, manganate chemistry contributed to early demonstrations of redox titration and alkaline oxidation chemistry. Safety considerations include treating manganate salts as oxidizers; they should be handled with appropriate precautions to prevent contact with reducing materials or organic compounds.

Overall, manganate is a relatively unstable, green manganese(VI) oxide anion primarily encountered in basic chemical contexts, with activities largely superseded by permanganate in modern practice.