Rhenium(IV) oxide or rhenium dioxide is the inorganic compound with the formula ReO2. This gray to black crystalline solid is a laboratory reagent that can be used as a catalyst. It adopts the rutile structure.
Synthesis and reactions It forms via comproportionation:G. Glemser "Rhenium (IV) Oxide" Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 1480. 2 Re2O7 + 3 Re → 7 ReO2 Single crystals are obtained by chemical transport, using iodine as the transporting agent.: ReO2 + I2 ReO2I2
At high temperatures it undergoes disproportionation: 7ReO2 → 2Re2O7 + 3Re
It forms rhenates with alkaline hydrogen peroxide and oxidizing acids. In molten sodium hydroxide it forms sodium rhenate:G. Glemser "Sodium Rhenate (IV)" Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 1483.
2NaOH + ReO2 → Na2ReO3 + H2O
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