Editing Ruthenium (section)

== Chemical compounds ==
{{See also|Category:Ruthenium compounds}}
The [[oxidation state]]s of ruthenium range from 0 to +8, and −2. The properties of ruthenium and osmium [[Chemical compound|compounds]] are often similar. The +2, +3, and +4 states are the most common. The most prevalent precursor is [[ruthenium trichloride]], a red solid that is poorly defined chemically but versatile synthetically.<ref name="cotton" />

=== Oxides and chalcogenides ===
Ruthenium can be [[oxidation|oxidized]] to [[ruthenium(IV) oxide]] (RuO<sub>2</sub>, oxidation state +4), which can, in turn, be oxidized by [[Sodium periodate|sodium metaperiodate]] to the volatile yellow tetrahedral [[ruthenium tetroxide]], RuO<sub>4</sub>, an aggressive, strong oxidizing agent with structure and properties analogous to [[osmium tetroxide]]. RuO<sub>4</sub> is mostly used as an intermediate in the purification of ruthenium from ores and radiowastes.<ref>{{cite journal|author1=Swain, P. |author2=Mallika, C. |author3=Srinivasan, R. |author4=Mudali, U. K. |author5=Natarajan, R. |s2cid=95804621|title=Separation and recovery of ruthenium: a review|journal=J. Radioanal. Nucl. Chem. |year=2013|volume=298|issue=2|pages=781–796|doi=10.1007/s10967-013-2536-5|bibcode=2013JRNC..298..781S }}</ref>

Dipotassium ruthenate (K<sub>2</sub>RuO<sub>4</sub>, +6) and potassium perruthenate (KRuO<sub>4</sub>, +7) are also known.{{sfnp|Greenwood|Earnshaw|1997|p={{page needed|date=October 2023}}}} Unlike osmium tetroxide, ruthenium tetroxide is less stable, is strong enough as an oxidising agent to oxidise dilute [[hydrochloric acid]] and organic solvents like [[ethanol]] at room temperature, and is easily reduced to ruthenate ({{chem|RuO|4|2-}}) in aqueous alkaline solutions; it decomposes to form the dioxide above 100&nbsp;°C. Unlike iron but like osmium, ruthenium does not form oxides in its lower +2 and +3 oxidation states.{{sfnp|Greenwood|Earnshaw|1997|pp=1080–1081}} Ruthenium forms di[[chalcogenide]]s, which are diamagnetic semiconductors crystallizing in the [[pyrite]] structure.{{sfnp|Greenwood|Earnshaw|1997|pp=1080–1081}} Ruthenium sulfide (RuS<sub>2</sub>) occurs naturally as the mineral [[laurite]].

Like iron, ruthenium does not readily form oxoanions and prefers to achieve high coordination numbers with hydroxide ions instead. Ruthenium tetroxide is reduced by cold dilute [[potassium hydroxide]] to form black potassium perruthenate, KRuO<sub>4</sub>, with ruthenium in the +7 oxidation state. Potassium perruthenate can also be produced by oxidising potassium ruthenate, K<sub>2</sub>RuO<sub>4</sub>, with chlorine gas. The perruthenate ion is unstable and is reduced by water to form the orange ruthenate. Potassium ruthenate may be synthesized by reacting ruthenium metal with molten potassium hydroxide and [[potassium nitrate]].{{sfnp|Greenwood|Earnshaw|1997|p=1082}}

Some mixed oxides are also known, such as M<sup>II</sup>Ru<sup>IV</sup>O<sub>3</sub>, Na<sub>3</sub>Ru<sup>V</sup>O<sub>4</sub>, Na{{su|b=2}}Ru{{su|p=V|b=2}}O{{su|b=7}}, and M{{su|p=II|b=2}}Ln{{su|p=III}}Ru{{su|p=V}}O{{su|b=6}}.{{sfnp|Greenwood|Earnshaw|1997|p=1082}}

=== Halides and oxyhalides ===
The highest known ruthenium halide is the [[ruthenium hexafluoride|hexafluoride]], a dark brown solid that melts at 54&nbsp;°C. It hydrolyzes violently upon contact with water and easily disproportionates to form a mixture of lower ruthenium fluorides, releasing fluorine gas. [[Ruthenium pentafluoride]] is a tetrameric dark green solid that is also readily hydrolyzed, melting at 86.5&nbsp;°C. The yellow [[ruthenium tetrafluoride]] is probably also polymeric and can be formed by reducing the pentafluoride with [[iodine]]. Among the binary compounds of ruthenium, these high oxidation states are known only in the oxides and fluorides.{{sfnp|Greenwood|Earnshaw|1997|p=1083}}

[[Ruthenium trichloride]] is a well-known compound, existing in a black α-form and a dark brown β-form: the trihydrate is red.{{sfnp|Greenwood|Earnshaw|1997|p=1084}} Of the known trihalides, trifluoride is dark brown and decomposes above 650&nbsp;°C, tribromide is dark-brown and decomposes above 400&nbsp;°C, and triiodide is black.{{sfnp|Greenwood|Earnshaw|1997|p=1083}} Of the dihalides, difluoride is not known, dichloride is brown, dibromide is black, and diiodide is blue.{{sfnp|Greenwood|Earnshaw|1997|p=1083}} The only known oxyhalide is the pale green ruthenium(VI) oxyfluoride, RuOF<sub>4</sub>.{{sfnp|Greenwood|Earnshaw|1997|p=1084}}

=== Coordination and organometallic complexes ===
{{Main|Organoruthenium chemistry}}
[[File:Tris(bipyridine)ruthenium(II)-chloride-powder.jpg|thumb|Tris(bipyridine)ruthenium(II) chloride]]
[[File:Grubbs catalyst Gen2.svg|alt=Skeletal formula of Grubbs' catalyst.|thumb|220x220px|[[Grubbs' catalyst]], which earned a Nobel Prize for its inventor, is used in [[alkene metathesis]] reactions.]]
Ruthenium forms a variety of coordination complexes. Examples are the many pentaammine derivatives [Ru(NH<sub>3</sub>)<sub>5</sub>L]<sup>n+</sup> that often exist for both Ru(II) and Ru(III). Derivatives of [[bipyridine]] and [[terpyridine]] are numerous, best known being the [[luminescence|luminescent]] [[tris(bipyridine)ruthenium(II) chloride]].

Ruthenium forms a wide range compounds with carbon–ruthenium bonds. [[Grubbs' catalyst]] is used for alkene metathesis.<ref>Hartwig, J. F. (2010) ''Organotransition Metal Chemistry, from Bonding to Catalysis'', University Science Books: New York. {{ISBN|1-891389-53-X}}</ref> [[Ruthenocene]] is analogous to [[ferrocene]] structurally, but exhibits distinctive redox properties. The colorless liquid [[ruthenium pentacarbonyl]] converts in the absence of CO pressure to the dark red solid [[triruthenium dodecacarbonyl]]. [[Ruthenium(III) chloride|Ruthenium trichloride]] reacts with carbon monoxide to give many derivatives including RuHCl(CO)(PPh<sub>3</sub>)<sub>3</sub> and Ru(CO)<sub>2</sub>(PPh<sub>3</sub>)<sub>3</sub> ([[Roper's complex]]). Heating solutions of ruthenium trichloride in alcohols with [[triphenylphosphine]] gives [[tris(triphenylphosphine)ruthenium dichloride]] (RuCl<sub>2</sub>(PPh<sub>3</sub>)<sub>3</sub>), which converts to the hydride complex chlorohydridotris(triphenylphosphine)ruthenium(II) (RuHCl(PPh<sub>3</sub>)<sub>3</sub>).<ref name="cotton" />