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Rhenium(VI) oxide has an appearance similar to that of copper. Rhenium(IV) oxide (or rhenium dioxide) is an oxide of rhenium, with the formula ReO 2. This gray to black crystalline solid is a laboratory reagent that can be used as a catalyst. It adopts the rutile structure. It forms via comproportionation: [4] 2 Re 2 O 7 + 3 Re → 7 ReO 2
Rhenium compounds are known for all the oxidation states between −3 and +7 except −2. The oxidation states +7, +4, and +3 are the most common. [32] Rhenium is most available commercially as salts of perrhenate, including sodium and ammonium perrhenates. These are white, water-soluble compounds. [33] Tetrathioperrhenate anion [ReS 4] − is ...
This compound reacts with water to produce perrhenic acid and nitric acid. [1] When heated above 75 °C, it decomposes to rhenium heptoxide, nitrogen dioxide, and oxygen: [1] 4 ReO 3 NO 3 → 2 Re 2 O 7 + 2 NO 2 + O 2. A graphite intercalation compound can be produced by reacting a mixture of rhenium trioxynitrate and dinitrogen pentoxide with ...
Rhenium trioxide is insoluble in water, as well as dilute acids and bases. Heating it in base results in disproportionation to give ReO 2 and ReO − 4, while reaction with acid at high temperature affords Re 2 O 7. In concentrated nitric acid, it yields perrhenic acid. Upon heating to 400 °C under vacuum, it undergoes disproportionation: [2]
Rhenium(IV) oxide or rhenium dioxide is the inorganic compound with the formula ReO 2. This gray to black crystalline solid is a laboratory reagent that can be used as a catalyst . It adopts the rutile structure.
Rhenium(VII) oxide is formed when metallic rhenium or its oxides or sulfides are oxidized at 500–700 °C (900–1,300 °F) in air. [4] Re 2 O 7 dissolves in water to give perrhenic acid. Heating Re 2 O 7 gives rhenium dioxide, a reaction signalled by the appearance of the dark blue coloration: [5] 2Re 2 O 7 → 4ReO 2 + 3O 2
They are readily reduced to nitrous oxide and nitric oxide by sulfur dioxide, to hyponitrous acid with tin(II), and to ammonia with hydrogen sulfide. Salts of hydrazinium N 2 H + 5 react with nitrous acid to produce azides which further react to give nitrous oxide and nitrogen.
These salts are prepared by oxidation of rhenium compounds with nitric acid followed by neutralization of the resulting perrhenic acid. [2] [3] [4] Addition of tetrabutylammonium chloride to aqueous solutions of sodium perrhenate gives tetrabutylammonium perrhenate, which is soluble in organic solvents. [5]