Editing Group 7 element (section)

==== Rhenium ====

Rhenium's main oxides are [[rhenium(IV) oxide]] and [[rhenium(VII) oxide]]. Rhenium(IV) oxide is a gray to black crystalline solid that can be formed by [[comproportionation]].<ref>G. Glemser "Rhenium (IV) Oxide" Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 1480.</ref> At high temperatures it undergoes [[disproportionation]]. It is a laboratory reagent that can be used as a [[catalyst]]. It adopts the [[rutile structure]]. It forms [[perrhenate]]s with alkaline [[hydrogen peroxide]] and [[oxidizing acid]]s.<ref>{{cite web |url=http://www.aaamolybdenum.com/RheniumDioxide.html |title=RHENIUM DIOXIDE - Manufacturer |publisher=Aaamolybdenum.com |accessdate=2012-08-06 |url-status=dead |archiveurl=https://web.archive.org/web/20030209232809/http://www.aaamolybdenum.com/RheniumDioxide.html |archivedate=2003-02-09 }}</ref> In molten sodium hydroxide it forms sodium rhenate:<ref>G. Glemser "Sodium Rhenate (IV)" Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 1483.</ref>

: 2{{nbsp}}NaOH  +  ReO<sub>2</sub>   →   Na<sub>2</sub>ReO<sub>3</sub>  +  H<sub>2</sub>O

Rhenium(VII) oxide can be formed when rhenium or its oxides or sulfides are oxidized a 500-700&nbsp;°C in air.<ref name=Schmidt>{{cite book |title=Inorganic Syntheses |year=1967 |volume=9 |last1=Schmidt |first1=Max |last2=Schmidbaur |first2=Hubert |chapter=Trimethylsilyl Perrhenate |pages=149–151 |isbn=9780470132401 |doi=10.1002/9780470132401.ch40}}</ref> It dissolves in water to give [[perrhenic acid]]. Heating Re<sub>2</sub>O<sub>7</sub> gives rhenium(IV) oxide, signalled by the appearance of the dark blue coloration.<ref name="Brauer" /> In its solid form, Re<sub>2</sub>O<sub>7</sub> consists of alternating octahedral and tetrahedral Re centres. It is the raw material for all rhenium compounds, being the volatile fraction obtained upon roasting the host ore.<ref>{{Ullmann|doi=10.1002/14356007.a23_199|title=Rhenium and Rhenium Compounds|year=2000|last1=Georg Nadler|first1=Hans|isbn=3527306730}}</ref>

Rhenium, in addition to the +4 and +7 oxidation states, also forms a [[rhenium trioxide|trioxide]]. It can be formed by reducing rhenium(VII) oxide with [[carbon monoxide]] at 200&nbsp;C or elemental rhenium at 4000&nbsp;C.<ref>{{Citation |last1=Nechamkin |first1=H. |title=Rhenium(VI) Oxide (Rhenium Trioxide) |date=Jan 1950|url=https://onlinelibrary.wiley.com/doi/10.1002/9780470132340.ch49 |work=Inorganic Syntheses |volume=3 |pages=186–188 |editor-last=Audrieth |editor-first=Ludwig F. |access-date=2023-08-26 |edition=1 |publisher=Wiley |language=en |doi=10.1002/9780470132340.ch49 |isbn=978-0-470-13162-6 |last2=Hiskey |first2=C. F. |last3=Moeller |first3=Therald |last4=Shoemaker |first4=C. E.|url-access=subscription }}</ref> It can also be reduced with [[dioxane]].<ref name="Glemser">{{cite book|author1=O. Glemser|author2=R. Sauer|chapter=Rhenium(VI) Oxide|title=Handbook of Preparative Inorganic Chemistry, 2nd Ed. |editor=G. Brauer|publisher=Academic Press|year=1963|place=NY, NY |volume=2 |pages=1482 }}</ref> It is a red solid with a metallic lustre that resembles [[copper]] in appearance, and is the only stable [[trioxide]] of the group 7 elements.