Cobalt Oxalate: Properties And Applications Of An Important Chemical Compound

Cobalt Oxalate

Cobalt oxalate is an inorganic compound with the formula CoC2O4. In this article, we will discuss the structure, properties, production methods and applications of cobalt oxalate.

Structure and Bonding

Cobalt oxalate has a dihydrate formula of CoC2O4·2H2O. Its structure can be described as molecular, with Co2+ cations coordinated to oxalate (C2O42-) anions in a a 1:2 ratio. The Co2+ cations are coordinated in a distorted octahedral geometry with four oxygen atoms from two bidentate oxalate ligands and two water molecules. The oxalate anions and water molecules interconnect the Co2+ centers through hydrogen bonding interactions to form a three-dimensional network structure.

The bonding between Cobalt Oxalate  ligands is primarily ionic/coordination in nature, with partial covalent character. The electron density is polarized towards the more electronegative oxygen and carbon atoms of the oxalate ligand. This ionic/coordination bonding gives cobalt oxalate its crystalline insoluble nature in water and common organic solvents.

Production

Cobalt oxalate can be produced by direct reaction of cobalt salts like cobalt chloride, cobalt nitrate with sodium or potassium oxalate solutions:

CoCl2 + K2C2O4 → CoC2O4 + 2KCl

This precipitation reaction is carried out at room temperature with constant stirring. The precipitate is filtered, washed with water to remove impurities and dried. Cobalt oxalate produced this way typically has very high purity above 98%.

Another production method involves oxidation of cobalt metal in the presence of oxalic acid:

3Co + 4H2C2O4 → Co3(C2O4)2 + 4H2

Here, oxalic acid acts as both oxidizing as well as complexing agent. The reaction is carried out by boiling a mixture of cobalt powder, oxalic acid and water. The crude product obtained is purified by recrystallization.

Properties

Some of the important physical and chemical properties of cobalt oxalate are:

- It is a light pink crystalline powder insoluble in water and common organic solvents.

- Melting point is around 190°C with decomposition.

- It is stable under normal conditions but starts decomposing above 150°C releasing carbon dioxide.

- Sparingly soluble in dilute acids and soluble in concentrated acids and bases.

- Magnetic in nature due to presence of cobalt cations.

- Non-hygroscopic but absorbs moisture from air over long exposure.

Applications

Due to its distinctive properties, cobalt oxalate finds various applications:

Catalysts
Cobalt oxalate and its derivatives are used as oxidation catalysts. They catalyze oxidative reactions like air oxidation of alcohols, oxidation of hydrocarbons etc. with high selectivity.

Pigments and Ceramics
It imparts beautiful light pink color and is used as pigment in glazes and ceramic products. The color strength and hue depends on particle size.

Rechargeable Batteries
Cobalt oxalate and its lithiated/hydrated forms find uses as cathode materials in lithium-ion batteries due to good electrochemical properties.

Medical Uses
Cobalt complexes are known to have antibacterial, antifungal properties. Research is ongoing to develop cobalt oxalate based drugs/wound dressings.

In summary, cobalt oxalate is an important coordination compound with versatile applications in catalysis, pigments and energy storage owing to its distinctive structural, chemical and physical properties. Though inexpensive to produce, it still remains an active area of research for developing improved catalysts and high-capacity battery materials. Further studies on cobalt oxalate complexes may also lead to novel applications in the medical field.

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