View source for Ruthenium

{{distinguish|rubidium|rutherfordium}}
{{Use dmy dates|date=February 2021}}
{{infobox ruthenium|phase=solid}}

'''Ruthenium''' is a [[chemical element]]; it has [[Symbol (chemistry)|symbol]] '''Ru''' and [[atomic number]]&nbsp;44. It is a rare [[transition metal]] belonging to the [[platinum group]] of the [[periodic table]]. Like the other metals of the platinum group, ruthenium is unreactive to most chemicals. [[Karl Ernst Claus]], a Russian scientist of Baltic-German ancestry, discovered the element in 1844 at [[Kazan State University]] and named it in honor of [[Russian Empire|Russia]], using the Latin name ''[[Ruthenia]]''. Ruthenium is usually found as a minor component of [[platinum]] ores; the annual production has risen from about 19&nbsp;[[tonne]]s in 2009<ref name=JMM>{{cite web |title=Ruthenium (summary) |year=2009 |department=Market review |page=9 |website=platinum.matthey.com |url=http://www.platinum.matthey.com/services/market-research/market-review-archive/platinum-2009 }}</ref> to some 35.5&nbsp;tonnes in 2017.<ref>{{cite web |title=Platinum group metals (PGM) market report |date=May 2018 |department=Market research |page=30 |website=platinum.matthey.com |url=http://www.platinum.matthey.com/services/market-research/pgm-market-reports }}</ref> Most ruthenium produced is used in wear-resistant electrical contacts and thick-film resistors. A minor application for ruthenium is in platinum [[alloy]]s and as a chemical [[catalysis|catalyst]]. A new application of ruthenium is as the capping layer for extreme ultraviolet [[photomask]]s. Ruthenium is generally found in ores with the other platinum group metals in the [[Ural Mountains]] and in [[North America|North]] and [[South America]]. Small but commercially important quantities are also found in [[pentlandite]] extracted from [[Sudbury, Ontario]], and in [[pyroxenite]] deposits in [[South Africa]].{{sfnp|Haynes|2016|p=4.31}}

==Characteristics==
===Physical properties===
[[File:Ruthenium crystals.jpg|thumb|left|Gas phase grown crystals of ruthenium metal]]

Ruthenium, a [[Valence (chemistry)#Common valences|polyvalent]] hard white metal, is a member of the [[platinum group]] and is in [[group 8 element|group&nbsp;8]] of the periodic table:

{| class="wikitable"
! [[Atomic number|Z]] !! [[Chemical element|Element]] !! [[Electron shell|No. of electrons/shell]]
|-
| 26 || [[iron]] || 2, 8, 14, 2
|-
| 44 || ruthenium || 2, 8, 18, 15, 1
|-
| 76 || [[osmium]] || 2, 8, 18, 32, 14, 2
|-
| 108 || [[hassium]] || 2, 8, 18, 32, 32, 14, 2
|}

Whereas all other group 8 elements have two electrons in the outermost shell, in ruthenium the outermost shell has only one electron (the final electron is in a lower shell). This anomaly is also observed in the neighboring metals [[niobium]]&nbsp;(41), [[molybdenum]]&nbsp;(42), and [[rhodium]]&nbsp;(45).

===Chemical properties===
Ruthenium has four crystal modifications and does not tarnish at ambient conditions; it oxidizes upon heating to {{convert|800|C|K}}. Ruthenium dissolves in fused alkalis to give ruthenates ({{chem|RuO|4|2-}}). It is not attacked by acids (even [[aqua regia]]) but is attacked by sodium hypochlorite at room temperature, and [[halogen]]s at high temperatures.{{sfnp|Haynes|2016|p=4.31}} Ruthenium is most readily attacked by oxidizing agents.{{sfnp|Greenwood|Earnshaw|1997|p=1076}} Small amounts of ruthenium can increase the hardness of [[platinum]] and [[palladium]]. The [[corrosion]] resistance of [[titanium]] is increased markedly by the addition of a small amount of ruthenium.{{sfnp|Haynes|2016|p=4.31}} The metal can be plated by [[electroplating]] and by thermal decomposition. A ruthenium–[[molybdenum]] alloy is known to be [[superconductivity|superconductive]] at temperatures below 10.6&nbsp;[[Kelvin|K]].{{sfnp|Haynes|2016|p=4.31}} Ruthenium is the only 4d&nbsp;transition metal that can assume the group oxidation state&nbsp;+8, and even then it is less stable there than the heavier congener osmium: this is the first group from the left of the table where the second and third-row transition metals display notable differences in chemical behavior. Like iron but unlike osmium, ruthenium can form aqueous cations in its lower oxidation +2 and +3&nbsp;states.{{sfnp|Greenwood|Earnshaw|1997|p=1078}}

Ruthenium is the first in a downward trend in the melting and boiling points and atomization enthalpy in the 4d&nbsp;transition metals after the maximum seen at [[molybdenum]], because the 4d&nbsp;subshell is more than half full and the electrons are contributing less to metallic bonding. ([[Technetium]], the previous element, has an exceptionally low value that is off the trend due to its half-filled [Kr]4d<sup>5</sup>5s<sup>2</sup> configuration, though it is not as far off the trend in the 4d series as [[manganese]] in the 3d&nbsp;transition series.){{sfnp|Greenwood|Earnshaw|1997|p=1075}} Unlike the lighter congener iron, ruthenium is [[paramagnetic]] at room temperature, as iron also is above its [[Curie point]].{{sfnp|Greenwood|Earnshaw|1997|p=1074}}

The reduction potentials in acidic aqueous solution for some common ruthenium species are shown below:{{sfnp|Greenwood|Earnshaw|1997|p=1077}}
{|class=wikitable
!Potential!!colspan=2|Reaction
|-
| 0.455 V ||Ru<sup>2+</sup> + 2e<sup>−</sup>|| ↔ Ru
|-
| 0.249 V ||Ru<sup>3+</sup> + e<sup>−</sup>|| ↔ Ru<sup>2+</sup>
|-
| 1.120 V ||RuO<sub>2</sub> + 4H<sup>+</sup> + 2e<sup>−</sup>|| ↔ Ru<sup>2+</sup> + 2H<sub>2</sub>O
|-
| 1.563 V ||{{chem|RuO|4|2-}} + 8H<sup>+</sup> + 4e<sup>−</sup>|| ↔ Ru<sup>2+</sup> + 4H<sub>2</sub>O
|-
| 1.368 V ||{{chem|RuO|4|-}} + 8H<sup>+</sup> + 5e<sup>−</sup>|| ↔ Ru<sup>2+</sup> + 4H<sub>2</sub>O
|-
| 1.387 V || RuO<sub>4</sub> + 4H<sup>+</sup> + 4e<sup>−</sup> || ↔ RuO<sub>2</sub> + 2H<sub>2</sub>O
|}

=== Isotopes ===
{{Main|Isotopes of ruthenium}}

Naturally occurring ruthenium is composed of seven stable [[isotope]]s. Additionally, 34 [[radioactive isotopes]] have been discovered. Of these [[radioisotope]]s, the most stable are <sup>106</sup>Ru with a [[half-life]] of 373.59&nbsp;days, <sup>103</sup>Ru with a half-life of 39.26&nbsp;days and <sup>97</sup>Ru with a half-life of 2.9 days.<ref name="n1" /><ref name="n2" />

Fifteen other radioisotopes have been characterized with [[atomic weight]]s ranging from {{val|89.93|ul=Da}} (<sup>90</sup>Ru) to 114.928&nbsp;Da (<sup>115</sup>Ru). Most of these have half-lives that are less than five minutes; the exceptions are <sup>95</sup>Ru (half-life 1.643&nbsp;hours) and <sup>105</sup>Ru (half-life 4.44&nbsp;hours).<ref name="n1" /><ref name="n2" />

The primary [[decay mode]] before the most abundant isotope, <sup>102</sup>Ru, is [[electron capture]] while the primary mode after is [[beta emission]]. The primary [[decay product]] before <sup>102</sup>Ru is [[technetium]] and the primary decay product after is [[rhodium]].<ref name="n1">{{RubberBible86th}} Section&nbsp;11, Table of the Isotopes</ref><ref name="n2">{{NUBASE 2003}}</ref>

<sup>106</sup>Ru is a product of fission of a nucleus of [[uranium]] or [[plutonium]]. High concentrations of detected atmospheric <sup>106</sup>Ru were associated with an alleged [[Airborne radioactivity increase in Europe in autumn 2017|undeclared nuclear accident in Russia]] in 2017.<ref name="pnas2019">
{{cite journal
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 | last30 = Kövendiné Kónyi    | first30 = J.     | display-authors = 6
 | year = 2019
 | title = Airborne concentrations and chemical considerations of radioactive ruthenium from an undeclared major nuclear release in 2017
 | journal = Proceedings of the National Academy of Sciences
 | volume = 116 | issue = 34 | pages = 16750–16759
 | doi = 10.1073/pnas.1907571116  | doi-access = free
 | pmc = 6708381  | bibcode = 2019PNAS..11616750M  | pmid = 31350352
}}
</ref>

=== Occurrence ===
{{See also|Category:Ruthenium minerals}}
Ruthenium is found in about 100&nbsp;[[parts per trillion]] in the Earth's crust, making it the [[Abundance of the chemical elements|78th most abundant element]].{{sfnp|Greenwood|Earnshaw|1997|p=1071}} It is generally found in ores with the other platinum group metals in the [[Ural Mountains]] and in North and South America. Small but commercially important quantities are also found in [[pentlandite]] extracted from [[Greater Sudbury|Sudbury]], [[Ontario]], Canada, and in [[pyroxenite]] deposits in [[South Africa]]. The native form of ruthenium is a very rare mineral (Ir replaces part of Ru in its structure).<ref name="USGS-YB-2006">{{cite web |url = http://minerals.usgs.gov/minerals/pubs/commodity/platinum/myb1-2006-plati.pdf |publisher = United States Geological Survey USGS |access-date = 2008-09-16|title = 2006 Minerals Yearbook: Platinum-Group Metals | first = Micheal W.|last = George}}</ref><ref name="USGS-CS-2008">{{cite web |url = http://minerals.usgs.gov/minerals/pubs/commodity/platinum/mcs-2008-plati.pdf |publisher = United States Geological Survey USGS|access-date = 2008-09-16 |title = Commodity Report: Platinum-Group Metals }}</ref> Ruthenium has a relatively high [[fission product yield]] in nuclear fission; and given that its most long-lived radioisotope has a half life of "only" around a year, there are often proposals to recover ruthenium in a new kind of [[nuclear reprocessing]] from [[spent fuel]]. An unusual ruthenium deposit can also be found at the [[natural nuclear fission reactor]] that was active in [[Oklo]], Gabon, some two billion years ago. Indeed, the isotope ratio of ruthenium found there was one of several ways used to confirm that a nuclear fission chain reaction had indeed occurred at that site in the geological past. Uranium is no longer mined at Oklo, and there have never been serious attempts to recover any of the platinum group metals present there.

== Production ==
Roughly 30&nbsp;tonnes of ruthenium are mined each year,<ref name=usgs/> and world reserves are estimated at 5,000&nbsp;tonnes.<ref name=Emsley>{{cite book |last=Emsley |first=J. |year=2003 |title=Nature's Building Blocks: An A-Z guide to the elements |publisher=Oxford University Press |isbn=978-0-19-850340-8 |location=Oxford, UK |pages=[https://archive.org/details/naturesbuildingb0000emsl/page/368 368]–370 |chapter=Ruthenium |chapter-url=https://archive.org/details/naturesbuildingb0000emsl/page/368 |via=archive.org }}</ref> The composition of the mined [[platinum group metal]] (PGM) mixtures varies widely, depending on the geochemical formation. For example, the PGMs mined in South Africa contain on average 11% ruthenium while the PGMs mined in the former USSR contain only 2% (1992).<ref>{{cite book |editor1 = Hartman, H. L. |editor2 = Britton, S. G. |year = 1992 |title = SME mining engineering handbook |publisher = Society for Mining, Metallurgy, and Exploration |location = Littleton, CO |page =69 |isbn = 978-0-87335-100-3 |url = https://books.google.com/books?id=Wm6QMRaX9C4C&pg=PA69 |via = Google }}</ref><ref>{{cite journal |last1=Harris |first1=Donald C. |last2=Cabri |first2=Louis J. |date=August 1973 |title=The nomenclature of the natural alloys of osmium, iridium and ruthenium based on new compositional data of alloys from world-wide occurrences |journal=The Canadian Mineralogist |volume=12 |issue=2 |pages=104–112 |id={{NAID|20000798606}} |url=https://pubs.geoscienceworld.org/canmin/article-abstract/12/2/104/10913/The-nomenclature-of-the-natural-alloys-of-osmium }}</ref> Ruthenium, osmium, and iridium are considered the minor platinum group metals.{{sfnp|Greenwood|Earnshaw|1997|p=1074}}

Ruthenium, like the other platinum group metals, is obtained commercially as a by-product from processing of [[nickel]], [[copper]], and platinum metal ore. During [[Copper extraction techniques#Electrorefining|electrorefining of copper]] and nickel, noble metals such as silver, gold, and the platinum group metals precipitate as ''anode mud'', the [[feedstock]] for the extraction.<ref name=USGS-YB-2006/><ref name=USGS-CS-2008/> The metals are converted to ionized solutes by any of several methods, depending on the composition of the feedstock. One representative method is fusion with [[sodium peroxide]] followed by dissolution in [[aqua regia]], and solution in a mixture of [[chlorine]] with [[hydrochloric acid]].<ref name=ullmann-pt>
{{cite book
 |last1=Renner       |first1=Hermann      |last2=Schlamp  |first2=Günther
 |last3=Kleinwächter |first3=Ingo         |last4=Drost    |first4=Ernst
 |last5=Lüschow      |first5=Hans Martin  |last6=Tews     |first6=Peter
 |last7=Panster      |first7=Peter        |last8=Diehl    |first8=Manfred
 |last9=Lang         |first9=Jutta        |last10=Kreuzer |first10=Thomas
 |last11=Knödler     |first11=Alfons      |last12=Starz   |first12=Karl Anton
 |last13=Dermann     |first13=Klaus       |last14=Rothaut |first14=Josef
 |last15=Drieselmann |first15=Ralf        |last16=Peter   |first16=Catrin
 |last17=Schiele     |first17=Rainer
 |display-authors=6
 |year=2001
 |chapter=Platinum group metals and compounds
 |title=Ullmann's Encyclopedia of Industrial Chemistry
 |isbn=978-3-527-30673-2 |doi=10.1002/14356007.a21_075
}}
</ref><ref name=kirk-pt>{{cite book |first1 = R.J. |last1 = Seymour |last2 = O'Farrelly |first2 = J.I. |year=2001 |chapter=Platinum-group metals |title=Kirk Othmer Encyclopedia of Chemical Technology |publisher=Wiley |isbn = 978-0471238966 |doi=10.1002/0471238961.1612012019052513.a01.pub2 }}</ref> [[Osmium]] (Os), ruthenium (Ru), [[rhodium]] (Rh), and [[iridium]] (Ir) are insoluble in aqua regia and readily precipitate, leaving the other metals in solution. Rhodium is separated from the residue by treatment with molten sodium bisulfate. The insoluble residue, containing Ru, Os, and Ir is treated with sodium oxide, in which Ir is insoluble, producing dissolved Ru and Os salts. After oxidation to the volatile oxides, {{chem|RuO|4}} is separated from {{chem|OsO|4}} by precipitation of (NH<sub>4</sub>)<sub>3</sub>RuCl<sub>6</sub> with ammonium chloride or by distillation or extraction with organic solvents of the volatile osmium tetroxide.<ref>{{cite journal |first = Raleigh |last = Gilchrist |year = 1943 |title = The platinum metals |journal = Chemical Reviews |volume = 32 |issue = 3 |pages = 277–372 |doi = 10.1021/cr60103a002 | s2cid=96640406 }}</ref> [[Hydrogen]] is used to reduce [[ammonium]] ruthenium chloride, yielding a powder.{{sfnp|Haynes|2016|p=4.31}}<ref name=cotton>{{cite book |last = Cotton |first = Simon |year = 1997 |title = Chemistry of Precious Metals |pages = 1–20|publisher = Springer-Verlag |place=New York, NY |isbn = 978-0-7514-0413-5 |url = https://books.google.com/books?id=6VKAs6iLmwcC&pg=PA2 }}</ref> The product is reduced using hydrogen, yielding the metal as a powder or [[sponge metal]] that can be treated with [[powder metallurgy]] techniques or [[argon]]-[[arc welding]].{{sfnp|Haynes|2016|p=4.31}}<ref name="Hunt 1969 126–138">{{cite journal |first1=L.B. |last1=Hunt |last2=Lever |first2=F.M. |year=1969 |journal=Platinum Metals Review |volume=13 |issue=4 |pages=126–138 |title=Platinum metals: A survey of productive resources to industrial uses |doi=10.1595/003214069X134126138 |s2cid=267561907 |url=http://www.platinummetalsreview.com/pdf/pmr-v13-i4-126-138.pdf |url-status=dead |access-date=2 June 2009 |archive-url=https://web.archive.org/web/20081029205825/http://www.platinummetalsreview.com/pdf/pmr-v13-i4-126-138.pdf |archive-date=29 October 2008 }}</ref>

Ruthenium is contained in [[spent nuclear fuel]], both as a direct [[fission product]] and as a product of [[neutron absorption]] by [[long-lived fission product]] {{Chem|99|Tc| link= Technetium-99}}. After allowing the unstable [[isotopes of ruthenium]] to decay, chemical extraction could yield ruthenium for use in all applications of ruthenium.<ref>{{cite journal |last1=Swain |first1=Pravati |last2=Mallika |first2=C. |last3=Srinivasan |first3=R. |last4=Mudali |first4=U. Kamachi |last5=Natarajan |first5=R. |date=November 2013 |title=Separation and recovery of ruthenium: A review |journal=Journal of Radioanalytical and Nuclear Chemistry |volume=298 |issue=2 |pages=781–796 |doi=10.1007/s10967-013-2536-5 |bibcode=2013JRNC..298..781S |s2cid=95804621 }}</ref><ref>{{cite journal |last1=Johal |first1=Sukhraaj Kaur |last2=Boxall |first2=Colin |last3=Gregson |first3=Colin |last4=Steele |first4=Carl |title=Ruthenium Volatilisation from Reprocessed Spent Nuclear Fuel – Studying the Baseline Thermodynamics of Ru(III) |journal=ECS Transactions |date=24 July 2015 |volume=66 |issue=21 |pages=31–42 |doi=10.1149/06621.0031ecst |bibcode=2015ECSTr..66u..31J |url=https://eprints.lancs.ac.uk/id/eprint/78523/2/SJohal_CBoxall_ECSTrans_Paper_16_July_2015_Final_v2.pdf }}</ref>

Ruthenium can also be produced by deliberate [[nuclear transmutation]] from {{chem|99|Tc}}. Given its relatively long half life, high [[fission product yield]] and high chemical mobility in the environment, {{chem|99|Tc}} is among the most often proposed non-[[actinide]]s for commercial scale nuclear transmutation. {{Chem|99|Tc}} has a relatively large [[neutron cross section]], and because technetium has no stable isotopes, there would not be a problem of [[neutron activation]] of stable isotopes. Significant amounts of {{chem|99|Tc}} are produced in nuclear fission. They are also produced as a byproduct of the use of {{chem|99m|Tc| link= Technetium-99m}} in [[nuclear medicine]], because this isomer decays to {{chem|99|Tc}}. Exposing the {{chem|99|Tc}} target to strong enough [[neutron radiation]] will eventually yield appreciable quantities of ruthenium, which can be chemically separated while consuming {{chem|99|Tc}}.<ref>{{cite journal |last1=Konings |first1=R.J.M. |last2=Conrad |first2=R. |date=September 1999 |title=Transmutation of technetium – results of the EFTTRA-T2 experiment |journal=Journal of Nuclear Materials |volume=274 |issue=3 |pages=336–340 |doi=10.1016/S0022-3115(99)00107-5 |bibcode=1999JNuM..274..336K }}</ref><ref>{{cite journal |last1=Peretroukhine |first1=Vladimir |last2=Radchenko |first2=Viacheslav |last3=Kozar' |first3=Andrei |last4=Tarasov |first4=Valeriy |last5=Toporov |first5=Iury |last6=Rotmanov |first6=Konstantin |last7=Lebedeva |first7=Lidia |last8=Rovny |first8=Sergey |last9=Ershov |first9=Victor |display-authors=6 |date=December 2004 |title=Technetium transmutation and production of artificial stable ruthenium |journal=Comptes Rendus Chimie |volume=7 |issue=12 |pages=1215–1218 |doi=10.1016/j.crci.2004.05.002 |url=https://comptes-rendus.academie-sciences.fr/chimie/articles/10.1016/j.crci.2004.05.002/ }}</ref>

== 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" />

== History ==
Though naturally occurring platinum alloys containing all six [[platinum-group metal]]s were used for a long time by [[pre-Columbian]] Americans and known as a material to European chemists from the mid-16th century, not until the mid-18th century was platinum identified as a pure element. That natural platinum contained palladium, rhodium, osmium and iridium was discovered in the first decade of the 19th century.<ref name="Weeks8">{{cite journal|doi = 10.1021/ed009p1017|title = The discovery of the elements. VIII. The platinum metals|date = 1932|last1 = Weeks|first1 = Mary Elvira|author-link1=Mary Elvira Weeks|journal = Journal of Chemical Education|volume = 9|page = 1017|bibcode = 1932JChEd...9.1017W|issue = 6}}</ref> Platinum in [[alluvium|alluvial sands]] of Russian rivers gave access to raw material for use in plates and medals and for the minting of [[ruble]] [[coins]], starting in 1828.<ref name="Roubles">{{cite journal |journal=Platinum Metals Review |volume=48 |issue=2 |date=2004 |pages=66–69 |title=The Minting of Platinum Roubles. Part I: History and Current Investigations |first=Christoph J. |last=Raub |doi=10.1595/003214004X4826669 |doi-access=free }}</ref> Residues from platinum production for coinage were available in the Russian Empire, and therefore most of the research on them was done in Eastern Europe.

It is possible that the [[Poland|Polish]] chemist [[Jędrzej Śniadecki]] isolated element 44 (which he called "vestium" after the asteroid [[4 Vesta|Vesta]] discovered shortly before) from South American platinum ores in 1807. He published an announcement of his discovery in 1808.<ref>{{cite book |last1=Śniadecki |first1=Jędrzej |title=Rosprawa o nowym metallu w surowey platynie odkrytym |trans-title=A case about a new metal in raw platinum discovered |language=pl |date=1808 |publisher=Nakładém i Drukiém Józefa Zawadzkiego |url=https://www.dbc.wroc.pl/publication/5247 |oclc=739088520 }}</ref> His work was never confirmed, however, and he later withdrew his claim of discovery.<ref name="Emsley" />

[[Jöns Berzelius]] and [[Gottfried Osann]] nearly discovered ruthenium in 1827.<ref>{{cite journal |title=New metals in the Uralian platina |journal=The Philosophical Magazine |date=1 November 1827 |volume=2 |issue=11 |pages=391–392 |doi=10.1080/14786442708674516 |url=https://books.google.com/books?id=x57C3yhRPUAC&pg=PA391 }}</ref> They examined residues that were left after dissolving crude platinum from the [[Ural Mountains]] in [[aqua regia]]. Berzelius did not find any unusual metals, but Osann thought he found three new metals, which he called pluranium, ruthenium, and polinium.{{sfnp|Haynes|2016|p=4.31}} This discrepancy led to a long-standing controversy between Berzelius and Osann about the composition of the residues.<ref name="DiscoRu">{{cite journal | title = The Discovery of Ruthenium| first = V. N. | last = Pitchkov | journal = Platinum Metals Review | volume = 40 | issue = 4 | year = 1996 | pages =181&ndash;188 | doi = 10.1595/003214096X404181188 | url = http://www.platinummetalsreview.com/dynamic/article/view/pmr-v40-i4-181-188}}</ref><ref name="Claus, Karl 1845 157–163">{{cite journal |author = Claus, Karl |title=О способе добывания чистой платины из руд |trans-title=On the method of extracting pure platinum from ores |journal=Горный журнал (Mining Journal) |year=1845 | volume = 7 | issue = 3 | pages = 157–163 |language=ru}}</ref> As Osann was not able to repeat his isolation of ruthenium, he eventually relinquished his claims.<ref name="DiscoRu" /><ref name="Osann2">{{cite journal | author = Osann, Gottfried | title = Berichtigung, meine Untersuchung des uralschen Platins betreffend | journal = [[Annalen der Physik|Poggendorffs Annalen der Physik und Chemie]] | volume = 15 | year = 1829 | page = 158 | url = http://gallica.bnf.fr/ark:/12148/bpt6k15100n.image.f168.langDE| doi = 10.1002/andp.18290910119 }}</ref> The name "ruthenium" was chosen by Osann because the analysed samples stemmed from the Ural Mountains in Russia.<ref name="Osann">{{cite journal |last1=Osann |first1=G. |title=Fortsetzung der Untersuchung des Platins vom Ural |trans-title=Continuation of the study of platinum from the Urals |language=de |journal=Annalen der Physik |date=1828 |volume=89 |issue=6 |pages=283–297 |doi=10.1002/andp.18280890609 |bibcode=1828AnP....89..283O |url=https://zenodo.org/record/1423520 }}</ref>

In 1844, [[Karl Ernst Claus]], a Russian scientist of [[Baltic German]] descent, showed that the compounds prepared by Gottfried Osann contained small amounts of ruthenium, which Claus had [[discovery of the chemical elements|discovered]] the same year.{{sfnp|Haynes|2016|p=4.31}}<ref name="Weeks8" /> Claus isolated ruthenium from the platinum residues of rouble production while he was working in [[Kazan University]], [[Kazan]],<ref name="DiscoRu" /> the same way its heavier congener osmium had been discovered four decades earlier.{{sfnp|Greenwood|Earnshaw|1997|p=1071}} Claus showed that ruthenium oxide contained a new metal and obtained 6&nbsp;grams of ruthenium from the part of crude platinum that is insoluble in [[aqua regia]].<ref name="DiscoRu" /> Choosing the name for the new element, Claus stated: "I named the new body, in honour of my Motherland, ruthenium. I had every right to call it by this name because Mr. Osann relinquished his ruthenium and the word does not yet exist in chemistry."<ref name="DiscoRu" /><ref name="Claus, Karl 1845 157–163"/> The name itself derives from the Latin word ''[[Ruthenia]]''.<ref name=Lewis2019/><!-- ref def in Template:infobox ruthenium--><ref name=Pitchkov1996/><!-- ref def in Template:infobox ruthenium-->
In doing so, Claus started a trend that continues to this day – naming an element after a country.<ref name="Meija">{{cite journal |last1=Meija |first1=Juris |title=Politics at the periodic table |journal=Nature Chemistry |date=September 2021 |volume=13 |issue=9 |pages=814–816 |doi=10.1038/s41557-021-00780-5 |pmid=34480093 |bibcode=2021NatCh..13..814M |s2cid=237405162 }}</ref>

== Applications ==
Approximately 30.9 tonnes of ruthenium were consumed in 2016, 13.8 of them in electrical applications, 7.7 in catalysis, and 4.6 in electrochemistry.<ref name="usgs">Loferski, Patricia J.; Ghalayini, Zachary T. and Singerling, Sheryl A. (2018) [https://d9-wret.s3-us-west-2.amazonaws.com/assets/palladium/production/atoms/files/myb1-2016-plati.pdf Platinum-group metals]. ''2016 Minerals Yearbook''. USGS. p. 57.3.</ref>

Because it hardens platinum and palladium alloys, ruthenium is used in [[Switch#Contacts|electrical contacts]], where a thin film is sufficient to achieve the desired durability. With its similar properties to and lower cost than rhodium,<ref name="Hunt 1969 126–138" /> electric contacts are a major use of ruthenium.<ref name="USGS-YB-2006"/><ref>{{cite journal |doi=10.1016/j.ccr.2004.08.015 |title=Chemical and electrochemical depositions of platinum group metals and their applications |date=2005 |author=Rao, C. |journal=Coordination Chemistry Reviews |volume=249 |page=613 |last2=Trivedi |first2=D. |issue=5–6}}</ref> The ruthenium plate is applied to the electrical contact and electrode base metal by electroplating<ref>{{cite journal |doi=10.1016/S0026-0576(00)83089-5 |title=Ruthenium plating |date=1999 |author=Weisberg, A. |journal=Metal Finishing |volume=97 |page=297}}</ref> or [[sputtering]].<ref>{{cite book |isbn=978-0-87170-285-2| url=https://books.google.com/books?id=EkStW7v8VPkC&pg=RA3-PA550 |page=184 |collaboration=ASM International Handbook Committee |author=Merrill L. Minges |date=1989 |publisher=ASM International |location=Materials Park, OH |title=Electronic materials handbook}}</ref>

Ruthenium dioxide with [[lead]] and [[bismuth]] ruthenates are used in thick-film chip resistors.<ref>{{cite journal|doi =10.1007/s10854-006-0036-x|title =Microstructure development and electrical properties of RuO<sub>2</sub>-based lead-free thick film resistors|date =2006|author =Busana, M. G.|journal =Journal of Materials Science: Materials in Electronics|volume =17|page =951|last2 =Prudenziati|first2 =M.|last3 =Hormadaly|first3 =J.|s2cid =135485712|issue =11|hdl =11380/303403}}</ref><ref>{{cite journal|doi = 10.1016/j.matlet.2006.05.015|title = Environment friendly perovskite ruthenate based thick film resistors|date = 2007|author = Rane, Sunit|journal = Materials Letters|volume = 61|page = 595|last2 = Prudenziati|first2 = Maria|last3 = Morten|first3 = Bruno|issue = 2| bibcode=2007MatL...61..595R |hdl = 11380/307664}}</ref><ref>{{cite book|isbn = 978-0-8247-1934-0| url = https://books.google.com/books?id=c2YxCCaM9RIC&pg=PA184|pages = 184, 345|editor = Slade, Paul G.|date = 1999|publisher = Dekker|location = New York, NY|title = Electrical contacts : principles and applications}}</ref><!--http://md1.csa.com/partners/viewrecord.php?requester=gs&collection=TRD&recid=N8113268AH--> These two electronic applications account for 50% of the ruthenium consumption.<ref name="Emsley" />

Ruthenium is seldom alloyed with metals outside the platinum group, where small quantities improve some properties. The added corrosion resistance in [[titanium]] alloys led to the development of a special alloy with 0.1% ruthenium.<ref>{{cite journal |last1=Schutz |first1=R. W. |title=Ruthenium Enhanced Titanium Alloys |journal=Platinum Metals Review |date=April 1996 |volume=40 |issue=2 |pages=54–61 |doi=10.1595/003214096X4025461 |citeseerx=10.1.1.630.7411 |s2cid=267551174 }}</ref> Ruthenium is also used in some advanced high-temperature single-crystal [[superalloy]]s, with applications that include the turbines in [[jet engines]]. Several nickel based superalloy compositions are described, such as EPM-102 (with 3% Ru), TMS-162 (with 6% Ru), TMS-138,<ref>{{cite news| title=Fourth generation nickel base single crystal superalloy. TMS-138 / 138A |url=http://sakimori.nims.go.jp/catalog/TMS-138-A.pdf |date=July 2006|work=High Temperature Materials Center, National Institute for Materials Science, Japan|archive-url=https://web.archive.org/web/20130418105851/http://sakimori.nims.go.jp/catalog/TMS-138-A.pdf|archive-date=18 April 2013}}</ref> and TMS-174,<ref>{{cite journal|author=Koizumi, Yutaka |display-authors=etal |title=Development of a Next-Generation Ni-base Single Crystal Superalloy |url=http://nippon.zaidan.info/seikabutsu/2003/00916/pdf/igtc2003tokyo_ts119.pdf |journal=Proceedings of the International Gas Turbine Congress, Tokyo 2–7 November 2003 |archive-date=10 January 2014 |archive-url=https://web.archive.org/web/20140110170053/http://nippon.zaidan.info/seikabutsu/2003/00916/pdf/igtc2003tokyo_ts119.pdf}}</ref><ref>{{cite news| title=Joint Development of a Fourth Generation Single Crystal Superalloy |author=Walston, S. |author2=Cetel, A. |author3=MacKay, R. |author4=O'Hara, K. |author5=Duhl, D. |author6=Dreshfield, R. |date=December 2004 |work=NASA |url=https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20050019231_2005000097.pdf}}</ref> the latter two containing 6% [[rhenium]].<ref>{{cite journal|doi = 10.1007/s11041-006-0099-6|title = Effect of high-gradient directed crystallization on the structure and properties of rhenium-bearing single-crystal alloy|date = 2006|last1 = Bondarenko |first1 = Yu. A.|journal = Metal Science and Heat Treatment|volume = 48|page = 360|last2 = Kablov|first2 = E. N.|last3 = Surova|first3 = V. A.|last4 = Echin|first4 = A. B.|s2cid = 136907279|issue = 7–8|bibcode = 2006MSHT...48..360B}}</ref> [[Fountain pen]] nibs are frequently tipped with ruthenium alloy. From 1944 onward, the [[Parker 51]] fountain pen was fitted with the "RU" nib, a 14K gold nib tipped with 96.2% ruthenium and 3.8% [[iridium]].<ref>{{cite journal |url=http://www.nibs.com/article4.html |journal=The PENnant |volume=XIII |issue=2 |date=1999 |title=Notes from the Nib Works—Where's the Iridium? |author=Mottishaw, J. |archive-url=https://web.archive.org/web/20020604135505/http://www.nibs.com/article4.html|archive-date=4 June 2002}}</ref>

Ruthenium is a component of [[mixed-metal oxide]] (MMO) anodes used for cathodic protection of underground and submerged structures, and for electrolytic cells for such processes as [[Chlorine production|generating chlorine]] from salt water.<ref>{{cite book|title =Materials Handbook: A Concise Desktop Reference|chapter-url = https://books.google.com/books?id=ArsfQZig_9AC&pg=PT612|pages = 581–582| first1 = François|last1 = Cardarelli|chapter = Dimensionally Stable Anodes (DSA) for Chlorine Evolution|isbn = 978-1-84628-668-1|date =2008|publisher =Springer|location =London}}</ref> The [[fluorescence]] of some ruthenium complexes is quenched by oxygen, finding use in [[optode]] sensors for oxygen.<ref>{{cite book|title = Chemical sensors in oceanography|chapter = Oxygen Microoptode|page = 150|first1 = Mark S.|last1 = Varney|date = 2000|isbn = 978-90-5699-255-2|publisher = Gordon & Breach|location = Amsterdam}}</ref> [[Ruthenium red]], [(NH<sub>3</sub>)<sub>5</sub>Ru-O-Ru(NH<sub>3</sub>)<sub>4</sub>-O-Ru(NH<sub>3</sub>)<sub>5</sub>]<sup>6+</sup>, is a [[biological stain]] used to stain [[polyanion]]ic molecules such as [[pectin]] and [[nucleic acids]] for [[light microscopy]] and [[electron microscopy]].<ref>{{cite book|title = Stains and cytochemical methods|chapter = Ruthenium red|first1 = M. A.|last1 = Hayat|chapter-url = https://books.google.com/books?id=oGj7MLioFlQC&pg=PA305|pages = [https://archive.org/details/stainscytochemic0000haya/page/305 305–310]|isbn = 978-0-306-44294-0|date = 1993|publisher = Plenum Press|location = New York, NY|url = https://archive.org/details/stainscytochemic0000haya/page/305}}</ref> The beta-decaying isotope 106 of ruthenium is used in radiotherapy of eye tumors, mainly [[malignant melanoma]]s of the [[uvea]].<ref>{{cite book|url = https://books.google.com/books?id=Aa83RoXCNk0C&pg=PA97|title = Radiotherapy of ocular disease, Ausgabe 13020|first1 = T.|last1 = Wiegel|isbn = 978-3-8055-6392-5|date = 1997|publisher = Karger|location = Basel, Freiburg}}</ref> Ruthenium-centered complexes are being researched for possible anticancer properties.<ref>{{cite journal |last1=Richards |first1=Adair D. |last2=Rodger |first2=Alison |title=Synthetic metallomolecules as agents for the control of DNA structure |journal=Chem. Soc. Rev. |date=2007 |volume=36 |issue=3 |pages=471–483 |doi=10.1039/b609495c |pmid=17325786 |url=http://wrap.warwick.ac.uk/2189/1/WRAP_Richards_Revised_article1.pdf }}</ref> Compared with platinum complexes, those of ruthenium show greater resistance to hydrolysis and more selective action on tumors.{{citation needed|date = April 2012}}

[[Ruthenium tetroxide]] exposes latent fingerprints by reacting on contact with fatty oils or fats with sebaceous contaminants and producing brown/black ruthenium dioxide pigment.<ref>[https://www.ncjrs.gov/App/publications/abstract.aspx?ID=172645 NCJRS Abstract – National Criminal Justice Reference Service] {{Webarchive|url=https://web.archive.org/web/20220620131906/https://www.ncjrs.gov/App/publications/abstract.aspx?ID=172645 |date=20 June 2022 }}. Ncjrs.gov. Retrieved on 2017-02-28.</ref>

=== Electronics ===
Electronics is the largest use of ruthenium.<ref name="usgs"/> Ru metal is particularly nonvolatile, which is advantageous in [[microelectronic]] devices.  Ru and its main oxide RuO<sub>2</sub> have comparable electrical resistivities.<ref>{{cite journal |last1=Kwon |first1=Oh-Kyum |last2=Kim |first2=Jae-Hoon |last3=Park |first3=Hyoung-Sang |last4=Kang |first4=Sang-Won |title=Atomic Layer Deposition of Ruthenium Thin Films for Copper Glue Layer |journal=Journal of the Electrochemical Society |date=2004 |volume=151 |issue=2 |pages=G109 |doi=10.1149/1.1640633 |bibcode=2004JElS..151G.109K }}</ref> Copper can be directly electroplated onto ruthenium,<ref>{{cite journal |last1=Moffat |first1=T. P. |last2=Walker |first2=M. |last3=Chen |first3=P. J. |last4=Bonevich |first4=J. E. |last5=Egelhoff |first5=W. F. |last6=Richter |first6=L. |last7=Witt |first7=C. |last8=Aaltonen |first8=T. |last9=Ritala |first9=M. |last10=Leskelä |first10=M. |last11=Josell |first11=D. |title=Electrodeposition of Cu on Ru Barrier Layers for Damascene Processing |journal=Journal of the Electrochemical Society |date=2006 |volume=153 |issue=1 |pages=C37 |doi=10.1149/1.2131826 |bibcode=2006JElS..153C..37M |url=https://zenodo.org/record/1236224 }}</ref> particular applications include [[barrier layer]]s, transistor gates, and interconnects.<ref>{{cite journal |doi=10.1149/2.0281901jes|title=Review—Ruthenium as Diffusion Barrier Layer in Electronic Interconnects: Current Literature with a Focus on Electrochemical Deposition Methods|year=2019|last1=Bernasconi|first1=R.|last2=Magagnin|first2=L.|journal=Journal of the Electrochemical Society|volume=166|issue=1|pages=D3219–D3225|bibcode=2019JElS..166D3219B|s2cid=104430143|doi-access=free}}</ref>  Ru films can be deposited by [[chemical vapor deposition]] using volatile complexes such as [[ruthenium tetroxide]] and the [[organoruthenium compound]] ([[cyclohexadiene]])Ru(CO)<sub>3</sub>.<ref>{{cite journal |doi=10.1134/S106373971001004X|title=Low-temperature pulsed CVD of ruthenium thin films for micro- and nanoelectronic applications, Part 1: Equipment and methodology|year=2010|last1=Vasilyev|first1=V. Yu.|journal=Russian Microelectronics|volume=39|pages=26–33|s2cid=122854468}}</ref>

=== Catalysis ===
Many ruthenium-containing compounds exhibit useful catalytic properties. Solutions containing [[ruthenium trichloride]] are highly active for [[olefin metathesis]]. Such catalysts are used commercially for the production of polynorbornene for example.<ref name="KO">{{cite encyclopedia |encyclopedia=Kirk-Othmer Encyclopedia of Chemical Technology |author1=Delaude, Lionel |author2=Noels, Alfred F. |year=2005| doi=10.1002/0471238961.metanoel.a01 |place=Weinheim|publisher=Wiley-VCH |chapter=Metathesis|isbn=978-0471238966}}</ref> Well defined ruthenium [[carbene]] and [[alkylidene]] complexes show similar reactivity but are only used on small-scale.<ref>{{cite journal|doi = 10.1002/1521-3773(20000901)39:17<3012::AID-ANIE3012>3.0.CO;2-G|title=Olefin Metathesis and Beyond|author=Fürstner, Alois|journal=Angewandte Chemie International Edition|volume=39 |issue=17|date=2000|pages=3012–3043 |pmid=11028025|bibcode=2000AngCh..39.3012F }}</ref> The [[Grubbs' catalyst]]s for example have been employed in the preparation of drugs and advanced materials.

: [[File:Polynbornene.png|thumb|center|upright=2|RuCl<sub>3</sub>-catalyzed [[ring-opening metathesis polymerization]] reaction giving polynorbornene]]

Some ruthenium complexes are highly active catalysts for [[transfer hydrogenation]]s (sometimes referred to as "borrowing hydrogen" reactions).  [[Chiral]] ruthenium complexes, introduced by [[Ryoji Noyori]], are employed for the [[asymmetric hydrogenation|enantioselective hydrogenation]] of [[ketone]]s, [[aldehyde]]s, and [[imine]]s.<ref name="citation 21">{{citation |author1=Noyori, R. |author2=Ohkuma, T. |author3=Kitamura, M. |author4=Takaya, H. |author5=Sayo, N. |author6=Kumobayashi, H. |author7=Akutagawa, S. |journal=[[Journal of the American Chemical Society]]|title=Asymmetric Hydrogenation of β-Keto Carboxylic Esters. A Practical, Purely Chemical Access to β-Hydroxy Esters in High Enantiomeric Purity|year=1987|volume=109|issue=19 |pages=5856|doi=10.1021/ja00253a051|bibcode=1987JAChS.109.5856N }}</ref> A typical catalyst is (cymene)Ru(S,S-Ts[[DPEN]]):<ref>{{OrgSynth | author = Ikariya, Takao; Hashiguchi, Shohei; Murata, Kunihiko and [[Ryōji Noyori|Noyori, Ryōji]]| title = Preparation of Optically Active (R,R)-Hydrobenzoin from Benzoin or Benzil| vol = 82 | pages = 10 | year = 2005 | prep = v82p0010}}</ref><ref>{{Cite journal | title = Synthesis of Optically Active 1,2,3,4-Tetrahydroquinolines via Asymmetric Hydrogenation Using Iridium-Diamine Catalyst|journal=Org. Synth.|volume = 92 | pages = 213–226 | year = 2015 | doi = 10.15227/orgsyn.092.0213|last1=Chen|first1=Fei|doi-access = free}}</ref> A [[Nobel Prize in Chemistry]] was awarded in 2001 to [[Ryōji Noyori]] for contributions to the field of [[asymmetric hydrogenation]].

: [[File:RuCl(S,S-TsDPEN)(cymene)-catalysed R,R-hydrobenzoin synthesis.svg|thumb|upright=2|center| [RuCl(''S'',''S''-TsDPEN)(cymene)]-catalysed (''R'',''R'')-hydrobenzoin synthesis (yield 100%, [[Enantiomeric excess|ee]] >99%)]]

Ruthenium-promoted cobalt catalysts are used in [[Fischer–Tropsch process|Fischer–Tropsch synthesis]].<ref>{{cite journal|doi=10.1016/S0926-860X(99)00160-X|title=Short history and present trends of Fischer–Tropsch synthesis|journal=Applied Catalysis A: General|volume=186|issue=1–2|pages=3–12|year=1999|last1=Schulz|first1=Hans}}</ref>

===Emerging applications===
Ruthenium-based compounds are components of [[dye-sensitized solar cell]]s, which are proposed as [[low-cost solar cell]] system.<ref>{{cite journal|doi =10.1021/ja058540p|title =High Molar Extinction Coefficient Heteroleptic Ruthenium Complexes for Thin Film Dye-Sensitized Solar Cells|date =2006|last1 =Kuang|first1 =Daibin|last2 =Ito|first2 =Seigo|last3 =Wenger|first3 =Bernard|last4 =Klein|first4 =Cedric|last5 =Moser|first5 =Jacques-E|last6 =Humphry-Baker|first6 =Robin|last7 =Zakeeruddin|first7 =Shaik M.|last8 =Grätzel|first8 =Michael|s2cid =39111991|journal =Journal of the American Chemical Society|volume =128|pages =4146–54|pmid =16551124|issue =12|bibcode =2006JAChS.128.4146K}}</ref>

== Health effects ==
Little is known about the health effects of ruthenium<ref name=":0">{{Cite web|title=Ruthenium|url=https://www.espimetals.com/index.php/msds/237-Ruthenium|access-date=2020-07-26|website=espimetals.com}}</ref> and it is relatively rare for people to encounter ruthenium compounds.<ref name=":1">{{Cite web|title=Ruthenium (Ru) - Chemical properties, Health and Environmental effects|url=https://www.lenntech.com/periodic/elements/ru.htm|access-date=2020-07-26|website=lenntech.com}}</ref> Metallic ruthenium is [[Chemically inert|inert]] (is not [[Reactivity (chemistry)|chemically reactive]]).<ref name=":0" /> Some compounds such as [[RuO4|ruthenium oxide (RuO<sub>4</sub>)]] are highly toxic and volatile.<ref name=":1" />

== See also ==

* [[Airborne radioactivity increase in Europe in autumn 2017]]

== Notes ==
{{notelist}}

== References ==
{{reflist|25em}}

== Bibliography ==
* {{Greenwood&Earnshaw2nd}}
* {{cite book | editor-last= Haynes |editor-first=William M. | date = 2016| title = CRC Handbook of Chemistry and Physics | edition = 97th | publisher = [[CRC Press]] | isbn = 9781498754293| title-link = CRC Handbook of Chemistry and Physics}}

== External links ==
{{Commons|Ruthenium}}
{{Wiktionary|ruthenium}}
* [http://www.periodicvideos.com/videos/044.htm Ruthenium] at ''[[The Periodic Table of Videos]]'' (University of Nottingham)
* [http://www.brightsurf.com/news/headlines/32014/Nano-layer_of_ruthenium_stabilizes_magnetic_sensors.html Nano-layer of ruthenium stabilizes magnetic sensors] {{Webarchive|url=https://web.archive.org/web/20160405094548/http://www.brightsurf.com/news/headlines/32014/nano-layer_of_ruthenium_stabilizes_magnetic_sensors.html |date=5 April 2016 }}
{{clear}}
{{Periodic table (navbox)}}
{{Ruthenium compounds}}
{{good article}}

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[[Category:Ruthenium| ]]
[[Category:Chemical elements]]
[[Category:Noble metals]]
[[Category:Precious metals]]
[[Category:Transition metals]]
[[Category:Native element minerals]]
[[Category:Chemical elements with hexagonal close-packed structure]]
[[Category:Platinum-group metals]]