Manganate

Some liquids are a dark green color.

These liquids are made of a metal. They are called manganates.

This metal is called manganese. People can make them in a lab. They stir things in a liquid for a long time. They may also use heat to make them. These green liquids can help change other things. It is a very special kind of matter.

Manganates are special parts of matter. They have a metal called manganese at their center.

Most people use this name for a specific kind called manganate(VI). This type is dark green in color.

You can see this color in a liquid solution.

Manganates have a shape called a tetrahedron. This means they look like a four-sided pyramid. Their shape is like other things called sulfates or chromates. Scientists first saw this in 1831.

People make these in a lab. They stir certain things in a strong liquid. They might do this for 24 hours. They may also use heat to help. In big factories, they use heat and air to make potassium manganate.

Manganates can help change other things. We call them oxidizing agents. This means they help turn one thing into another. For example, they can turn alcohols into acids. Some types, like barium manganate, do not dissolve in water. This makes them useful for science work. They are not always stable. In most liquids, they break apart into other things. They only stay steady in very strong alkaline liquids.

Manganates are special parts of matter. They have a metal called manganese at their center.

Scientists often use this name for one specific type called manganate(VI). This type is a dark green color. You can see this color in a liquid solution.

These compounds are important in the study of chemistry. They help us understand how metals and oxygen work together.

This type of manganate has a very specific shape. It is a tetrahedron. A tetrahedron looks like a pyramid with four sides. This shape is very similar to things called sulfates or chromates.

In this shape, the manganese-oxygen distance is 165.9 pm. This is about 3 pm longer than in permanganate. The shape stays very steady even when scientists look closely. It is a very neat way for atoms to sit together.

People have studied these shapes for a long time. A scientist named Eilhard Mitscherlich first noted this shape in 1831. He saw how they were like other common structures.

Since then, many people have learned more about them. They have found other types too. These include hypomanganate, permanganate, and dimanganate. Each one has its own special way of working.

Making manganates is a careful job. In a lab, people stir permanganate in a strong liquid. They might do this for 24 hours. They might use heat to help the process.

In big factories, they make potassium manganate in a different way. They dissolve manganese dioxide in hot potassium hydroxide. They also use air or potassium nitrate to help. This makes the potassium manganate needed for other things.

Manganates can be used to change other substances. We call them oxidizing agents. This means they help turn one chemical into another.

For example, they can turn primary alcohols into aldehydes. They can also turn them into carboxylic acids. Some types, like barium manganate, do not dissolve in water. This makes them very useful for science work in a lab. They are not always steady, though. In most liquids, they break apart into other things. They only stay steady in very strong alkaline liquids.

In the field of inorganic nomenclature, a manganate is a negatively charged molecular entity. It features manganese as its central atom.

While the term can describe several different ions, it usually refers to the tetraoxidomanganate(2−) anion. This specific ion is also called manganate(VI). This name comes from its +6 oxidation state. Manganates are unique because they are the only known manganese(VI) compounds. They are essential for understanding how transition metal oxyanions behave in chemistry.

The structure of the manganate(VI) ion is a tetrahedron. This means it forms a shape like a pyramid with four triangular sides.

This shape is isostructural with sulfates and chromates. This term means they share the same geometric arrangement. The manganese–oxygen distance in this structure is 165.9 pm. This distance is about 3 pm longer than the distance found in permanganate. Because it is a d1 ion, it is paramagnetic. This means it is attracted to magnetic fields. Although it should show Jahn–Teller distortion, the deviation from its tetrahedral shape is too small to detect with X-ray crystallography.

Scientists have identified several different types of manganate ions. These are distinguished by their oxidation states. There is hypomanganate, also known as manganate(V). There is also permanganate, which is manganate(VII). Another type is the dimanganate(III) ion. Scientists have even prepared a manganate(IV) anion. They did this through the radiolysis of dilute permanganate solutions.

In dilute solutions, the manganate(VI) ion appears as a dark green liquid. It shows a strong absorption in the ultraviolet spectrum. It also shows a weaker absorption at 650 nm. Its visible absorption maximum is at 606 nm.

Research into these structures began in the early 19th century. In 1831, the scientist Eilhard Mitscherlich noted that manganates share structures with sulfates and chromates. This discovery helped chemists understand how different elements can form similar shapes. Since then, scientists have used advanced tools like Raman spectroscopy to study them. They have also used pulse radiolysis techniques to estimate chemical constants. For example, they estimated the second acid dissociation constant for the hypothetical manganic acid. This constant, known as pKa, is 7.4 ± 0.1.

Manganates are often prepared through specific chemical processes. In a laboratory, scientists can make sodium and potassium manganates. They do this by stirring permanganate in a concentrated solution of hydroxide. This solution is usually 5–10 M. The stirring process can take 24 hours or involve heating.

On an industrial scale, potassium manganate is produced as an intermediate. It is made to create potassium permanganate. To do this, manganese dioxide is dissolved in molten potassium hydroxide. An oxidizing agent, such as air or potassium nitrate, is added to the mixture.

These compounds are very useful as oxidizing agents in organic synthesis. An oxidizing agent is a substance that causes other chemicals to lose electrons.

Barium manganate, BaMnO4, is particularly useful because it is insoluble. It can oxidize primary alcohols into aldehydes. These aldehydes can then be turned into carboxylic acids. It can also turn secondary alcohols into ketones. Additionally, barium manganate can oxidize hydrazones into diazo compounds.

Despite their uses, manganates are not always stable. They are prone to a process called disproportionation. This happens when a single substance breaks down into different products. This occurs in all aqueous solutions unless they are very alkaline. The ultimate products of this breakdown are permanganate and manganese dioxide. The exact mechanism is complex. It may involve species that are protonated or involve manganese(V). Finally, the term "manganite" is sometimes used for related compounds. These were once thought to contain the Mn(III) anion. However, most are actually mixed oxides with structures like perovskite, spinel, or sodium chloride.