Rhenium trioxide

Rhenium trioxide

Red to purple solid

Fixed

6.9 to 7.4 g · cm -3

400 ° C ( decomposition)

Insoluble in water

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Rhenium ( VI) oxide ReO3 is a chemical compound and is one of the oxides of rhenium. There is a red crystalline solid. It is known rhenium (VI ) oxide, mainly because of its crystal structure, which is used as a structural type. Rhenium ( VI) oxide is the only stable manganese oxide group in the VI oxidation state.

Production and representation

Rhenium ( VI) oxide can be obtained by reduction of rhenium (VII ) oxide. The reaction is for example possible with carbon monoxide at about 200 ° C or at 400 ° C. elemental rhenium.

Rhenium ( VI) oxide is (VII ) oxide are recovered with dioxane, and water with slight warming of the reaction of rhenium. The resulting intermediate dioxane complex is decomposed at 145 ° C, the complex at about 100 ° C., first melts to a colorless to blue- green liquid, which decomposes after a short time to red rhenium (VI ) oxide and volatile rhenium - free products.

Properties

Physical Properties

Rhenium ( VI) oxide is a moisture- sensitive red, purple to violet odorless solid, with green gloss in transmitted light.

Rhenium ( VI) oxide has a characteristic crystal structure similar to the perovskite structure. From this it differs only by the absence of the central atom ( in perovskite calcium). Here, each rhenium atom is octahedrally surrounded by oxygen atoms, while the oxygen atoms are each located between two rhenium atoms. It is thus a primitive cubic unit cell with the space group and the lattice parameters a = 374.8 pm.

Rhenium ( VI) oxide has some metallic properties, so the resistivity is very low, and decreases with falling temperatures. Rhenium has (VI ) oxide metallic luster.

Chemical Properties

Rhenium ( VI) oxide in water and dilute acids and bases are not soluble. When cooking in hot alkaline wash it disproportionates ReO2 and ReO4 -.

It reacts with oxygen at elevated temperature to rhenium (VII ) oxide. In concentrated nitric acid, the reaction is carried out to perrhenic acid. It disproportionates in vacuo at temperatures above 300 ° C to rhenium ( IV) oxide, and rhenium (VII ) oxide.