Rhenium(IV) oxide

Rhenium dioxide

Gray-black solid

Fixed

11.4 g · cm -3

1000 ° C ( decomposition)

Insoluble in water

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Rhenium ( IV) oxide is an inorganic chemical compound of the rhenium from the group of oxides.

Production and representation

Rhenium ( IV) oxide can be obtained by reaction of rhenium, rhenium ( VI) oxide.

The display is also possible by heating ammonium perrhenate in a stream of dry nitrogen, argon, or under vacuum, wherein, depending on temperature, the monoclinic or orthorhombic modification occurs.

By reduction of rhennate (VII ) solutions to get it as a hydrate, which can be easily dehydrate.

Properties

Rhenium (IV ) oxide is a gray-black solid. The resulting and stable below 300 ° C. α - modification transforms irreversibly at temperatures above 300 ° C in the β - modification to. The α - modification has a monoclinic crystal structure ( a = 558 pm, b = 481 pm, c = 558 pm, β = 120.9 ° ) of molybdenum (IV ) oxide and tungsten ( IV) oxide type. The β - modification has an orthorhombic crystal structure with space group Pbcn (a = 480.9 pm, b = 564.3 pm, c = 460.1 pm ). Both modifications exhibit metallic conductivity. They are insoluble in water, bases, non-oxidizing acids. Hydrogen halide acids, they are soluble, with hydrogen peroxide and nitric acid react to form perrhenic acid. A reaction with oxygen to rhenium (VII ) oxide, and in a vacuum at temperatures above 850 ° C is carried out at elevated temperature disproportionation to rhenium and rhenium (VII ) oxide. Metal (II) oxide, it forms a double oxide Me (II ) ReO3 with perovskite structure. There is also a hydrate, is in the form of a brown- black powder X-ray amorphous. It loses at 500 ° C in vacuum and water goes into the anhydrous form.