Ruthenium

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Ruthenium, 44Ru
Ruthenium a half bar.jpg
Ruthenium
Pronunciation /rˈθniəm/ (roo-THEE-nee-əm)
Appearancesilvery white metallic
Standard atomic weight Ar, std(Ru)101.07(2) [1]
Ruthenium in the periodic table
Hydrogen Helium
Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon
Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon
Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton
Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon
Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon
Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson
Fe

Ru

Os
technetiumrutheniumrhodium
Atomic number (Z)44
Group group 8
Period period 5
Block d-block
Element category   Transition metal
Electron configuration [ Kr ] 4d7 5s1
Electrons per shell2, 8, 18, 15, 1
Physical properties
Phase at  STP solid
Melting point 2607  K (2334 °C,4233 °F)
Boiling point 4423 K(4150 °C,7502 °F)
Density (near r.t.)12.45 g/cm3
when liquid (at m.p.)10.65 g/cm3
Heat of fusion 38.59  kJ/mol
Heat of vaporization 619 kJ/mol
Molar heat capacity 24.06 J/(mol·K)
Vapor pressure
P (Pa)1101001 k10 k100 k
at T (K)258828113087342438454388
Atomic properties
Oxidation states −4, −2, 0, +1, [2] +2, +3, +4, +5, +6, +7, +8 (a mildly acidic oxide)
Electronegativity Pauling scale: 2.2
Ionization energies
  • 1st: 710.2 kJ/mol
  • 2nd: 1620 kJ/mol
  • 3rd: 2747 kJ/mol
Atomic radius empirical:134  pm
Covalent radius 146±7 pm
Color lines in a spectral range Ruthenium spectrum visible.png
Color lines in a spectral range
Spectral lines of ruthenium
Other properties
Natural occurrence primordial
Crystal structure hexagonal close-packed (hcp)
Hexagonal close packed.svg
Speed of sound thin rod5970 m/s(at 20 °C)
Thermal expansion 6.4 µm/(m·K)(at 25 °C)
Thermal conductivity 117 W/(m·K)
Electrical resistivity 71 nΩ·m(at 0 °C)
Magnetic ordering paramagnetic [3]
Magnetic susceptibility +39·10−6 cm3/mol(298 K) [3]
Young's modulus 447 GPa
Shear modulus 173 GPa
Bulk modulus 220 GPa
Poisson ratio 0.30
Mohs hardness 6.5
Brinell hardness 2160 MPa
CAS Number 7440-18-8
History
Namingafter Ruthenia (Latin for: medieval Kyivska Rus' region)
Discovery and first isolation Karl Ernst Claus (1844)
Main isotopes of ruthenium
Iso­tope Abun­dance Half-life (t1/2) Decay mode Pro­duct
96Ru5.54% stable
97Ru syn 2.9 d ε 97Tc
γ
98Ru1.87%stable
99Ru12.76%stable
100Ru12.60%stable
101Ru17.06%stable
102Ru31.55%stable
103Rusyn39.26 d β 103Rh
γ
104Ru18.62%stable
106Rusyn373.59 dβ 106Rh
| references

Ruthenium is a chemical element with the symbol Ru and atomic number 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 inert to most other chemicals. Russian-born scientist of Baltic-German ancestry Karl Ernst Claus discovered the element in 1844 at Kazan State University and named ruthenium in honor of Russia (Ruthenia is the Latin name of Rus). Ruthenium is usually found as a minor component of platinum ores; the annual production has risen from about 19 tonnes in 2009 [4] to some 35.5 tonnes in 2017. [5] Most ruthenium produced is used in wear-resistant electrical contacts and thick-film resistors. A minor application for ruthenium is in platinum alloys and as a chemistry catalyst. A new application of ruthenium is as the capping layer for extreme ultraviolet photomasks. Ruthenium 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 Sudbury, Ontario and in pyroxenite deposits in South Africa. [6]

Contents

Characteristics

Physical properties

Gas phase grown crystals of ruthenium metal. Ruthenium crystals.jpg
Gas phase grown crystals of ruthenium metal.

Ruthenium, a polyvalent hard white metal, is a member of the platinum group and is in group 8 of the periodic table:

Z Element No. of electrons/shell
26 iron 2, 8, 14, 2
44ruthenium2, 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 observed in the neighboring metals niobium (41), molybdenum (42), and rhodium (45).

Ruthenium has four crystal modifications and does not tarnish at ambient conditions; it oxidizes upon heating to 800 °C (1,070 K). Ruthenium dissolves in fused alkalis to give ruthenates (RuO2−
4
), is not attacked by acids (even aqua regia) but is attacked by halogens at high temperatures. [6] Indeed, ruthenium is most readily attacked by oxidizing agents. [7] 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. [6] The metal can be plated by electroplating and by thermal decomposition. A ruthenium-molybdenum alloy is known to be superconductive at temperatures below 10.6 K. [6] Ruthenium is the last of the 4d transition metals that can assume the group oxidation state +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 states of +2 and +3. [8]

Ruthenium is the first in a downward trend in the melting and boiling points and atomization enthalpy in the 4d transition metals after the maximum seen at molybdenum, because the 4d 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]4d55s2 configuration, though it is not as far off the trend in the 4d series as manganese in the 3d transition series.) [9] Unlike the lighter congener iron, ruthenium is paramagnetic at room temperature, as iron also is above its Curie point. [10]

The reduction potentials in acidic aqueous solution for some common ruthenium ions are shown below: [11]

0.455 VRu2+ + 2e↔ Ru
0.249 VRu3+ + e↔ Ru2+
1.120 VRuO2 + 4H+ + 2e↔ Ru2+ + 2H2O
1.563 VRuO2−
4
+ 8H+ + 4e
↔ Ru2+ + 4H2O
1.368 VRuO
4
+ 8H+ + 5e
↔ Ru2+ + 4H2O
1.387 VRuO4 + 4H+ + 4e↔ RuO2 + 2H2O

Isotopes

Naturally occurring ruthenium is composed of seven stable isotopes. Additionally, 34 radioactive isotopes have been discovered. Of these radioisotopes, the most stable are 106Ru with a half-life of 373.59 days, 103Ru with a half-life of 39.26 days and 97Ru with a half-life of 2.9 days. [12] [13]

Fifteen other radioisotopes have been characterized with atomic weights ranging from 89.93 u (90Ru) to 114.928 u (115Ru). Most of these have half-lives that are less than five minutes except 95Ru (half-life: 1.643 hours) and 105Ru (half-life: 4.44 hours). [12] [13]

The primary decay mode before the most abundant isotope, 102Ru, is electron capture and the primary mode after is beta emission. The primary decay product before 102Ru is technetium and the primary decay product after is rhodium. [12] [13]

Occurrence

As the 74th most abundant element in Earth's crust, ruthenium is relatively rare, [14] found in about 100  parts per trillion. [15] This element 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 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). [16] [17]

Production

Roughly 30 tonnes of ruthenium are mined each year [18] with world reserves estimated at 5,000 tonnes. [14] 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). [19] [20] Ruthenium, osmium, and iridium are considered the minor platinum group metals. [10]

Ruthenium, like the other platinum group metals, is obtained commercially as a by-product from nickel, and copper, and platinum metals ore processing. During 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. [16] [17] 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. [21] [22] Osmium, ruthenium, rhodium, and iridium 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, RuO
4
is separated from OsO
4
by precipitation of (NH4)3RuCl6 with ammonium chloride or by distillation or extraction with organic solvents of the volatile osmium tetroxide. [23] Hydrogen is used to reduce ammonium ruthenium chloride yielding a powder. [6] [24] 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. [6] [25]

Chemical compounds

The oxidation states of ruthenium range from 0 to +8, and −2. The properties of ruthenium and osmium 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. [24]

Oxides and chalcogenides

Ruthenium can be oxidized to ruthenium(IV) oxide (RuO2, oxidation state +4) which can in turn be oxidized by sodium metaperiodate to the volatile yellow tetrahedral ruthenium tetroxide, RuO4, an aggressive, strong oxidizing agent with structure and properties analogous to osmium tetroxide. RuO4 is mostly used as an intermediate in the purification of ruthenium from ores and radiowastes. [26]

Dipotassium ruthenate (K2RuO4, +6), and potassium perruthenate (KRuO4, +7) are also known. [27] Unlike osmium tetroxide, ruthenium tetroxide is less stable and 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 (RuO2−
4
) in aqueous alkaline solutions; it decomposes to form the dioxide above 100 °C. Unlike iron but like osmium, ruthenium does not form oxides in its lower +2 and +3 oxidation states. [28] Ruthenium forms dichalcogenides, which are diamagnetic semiconductors crystallizing in the pyrite structure. [28] Ruthenium sulfide (RuS2) 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, KRuO4, with ruthenium in the +7 oxidation state. Potassium perruthenate can also be produced by oxidising potassium ruthenate, K2RuO4, 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. [29]

Some mixed oxides are also known, such as MIIRuIVO3, Na3RuVO4, Na
2
RuV
2
O
7
, and MII
2
LnIII
RuV
O
6
. [29]

Halides and oxyhalides

The highest known ruthenium halide is the hexafluoride, a dark brown solid that melts at 54 °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 °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. [30]

Ruthenium trichloride is a well-known compound, existing in a black α-form and a dark brown β-form: the trihydrate is red. [31] Of the known trihalides, trifluoride is dark brown and decomposes above 650 °C, tetrabromide is dark-brown and decomposes above 400 °C, and triiodide is black. [30] Of the dihalides, difluoride is not known, dichloride is brown, dibromide is black, and diiodide is blue. [30] The only known oxyhalide is the pale green ruthenium(VI) oxyfluoride, RuOF4. [31]

Coordination and organometallic complexes

Tris(bipyridine)ruthenium(II) chloride. Tris(bipyridine)ruthenium(II)-chloride-powder.jpg
Tris(bipyridine)ruthenium(II) chloride.
Grubbs' catalyst, which earned a Nobel Prize for its inventor, is used in alkene metathesis reactions. Grubbs catalyst Gen2.svg
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 pentammine derivatives [Ru(NH3)5L]n+ that often exist for both Ru(II) and Ru(III). Derivatives of bipyridine and terpyridine are numerous, best known being the luminescent tris(bipyridine)ruthenium(II) chloride.

Ruthenium forms a wide range compounds with carbon-ruthenium bonds. Grubbs' catalyst is used for alkene metathesis. [32] 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 trichloride reacts with carbon monoxide to give many derivatives including RuHCl(CO)(PPh3)3 and Ru(CO)2(PPh3)3 (Roper's complex). Heating solutions of ruthenium trichloride in alcohols with triphenylphosphine gives tris(triphenylphosphine)ruthenium dichloride (RuCl2(PPh3)3), which converts to the hydride complex chlorohydridotris(triphenylphosphine)ruthenium(II) (RuHCl(PPh3)3). [24]

History

Though naturally occurring platinum alloys containing all six platinum-group metals 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. [33] Platinum in 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. [34] 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 Polish chemist Jędrzej Śniadecki isolated element 44 (which he called "vestium" after the asteroid Vesta discovered shortly before) from South American platinum ores in 1807. He published an announcement of his discovery in 1808. [35] His work was never confirmed, however, and he later withdrew his claim of discovery. [14]

Jöns Berzelius and Gottfried Osann nearly discovered ruthenium in 1827. [36] 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. [6] This discrepancy led to a long-standing controversy between Berzelius and Osann about the composition of the residues. [37] As Osann was not able to repeat his isolation of ruthenium, he eventually relinquished his claims. [37] [38] The name "ruthenium" was chosen by Osann because the analysed samples stemmed from the Ural Mountains in Russia. [39] The name itself derives from Ruthenia, the Latin word for Rus', a historical area that included present-day Ukraine, Belarus, western Russia, and parts of Slovakia and Poland.

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 discovered the same year. [6] [33] Claus isolated ruthenium from the platinum residues of rouble production while he was working in Kazan University, Kazan, [37] the same way its heavier congener osmium had been discovered four decades earlier. [15] Claus showed that ruthenium oxide contained a new metal and obtained 6 grams of ruthenium from the part of crude platinum that is insoluble in aqua regia. [37] 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." [37] [40]

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. [18]

Because it hardens platinum and palladium alloys, ruthenium is used in electrical contacts, where a thin film is sufficient to achieve the desired durability. With similar properties and lower cost than rhodium, [25] electric contacts are a major use of ruthenium. [16] [41] The ruthenium plate is applied to the electrical contact and electrode base metal by electroplating [42] or sputtering. [43]

Ruthenium dioxide with lead and bismuth ruthenates are used in thick-film chip resistors. [44] [45] [46] These two electronic applications account for 50% of the ruthenium consumption. [14]

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. [47] Ruthenium is also used in some advanced high-temperature single-crystal superalloys, 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, [48] and TMS-174, [49] [50] the latter two containing 6% rhenium. [51] 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. [52]

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 generating chlorine from salt water. [53] The fluorescence of some ruthenium complexes is quenched by oxygen, finding use in optode sensors for oxygen. [54] Ruthenium red, [(NH3)5Ru-O-Ru(NH3)4-O-Ru(NH3)5]6+, is a biological stain used to stain polyanionic molecules such as pectin and nucleic acids for light microscopy and electron microscopy. [55] The beta-decaying isotope 106 of ruthenium is used in radiotherapy of eye tumors, mainly malignant melanomas of the uvea. [56] Ruthenium-centered complexes are being researched for possible anticancer properties. [57] Compared with platinum complexes, those of ruthenium show greater resistance to hydrolysis and more selective action on tumors.[ citation needed ]

Ruthenium tetroxide exposes latent fingerprints by reacting on contact with fatty oils or fats with sebaceous contaminants and producing brown/black ruthenium dioxide pigment. [58]

Catalysis

Halloysite nanotubes intercalated with ruthenium catalytic nanoparticles. Ru-intercalated halloysite nanotubes 3.jpg
Halloysite nanotubes intercalated with ruthenium catalytic nanoparticles.

Many ruthenium-containing compounds exhibit useful catalytic properties. The catalysts are conveniently divided into those that are soluble in the reaction medium, homogeneous catalysts, and those that are not, which are called heterogeneous catalysts.

Ruthenium nanoparticles can be formed inside halloysite. This abundant mineral naturally has a structure of rolled nanosheets (nanotubes), which can support both the Ru nanocluster synthesis and its products for subsequent use in industrial catalysis. [59]

Homogeneous catalysis

Solutions containing ruthenium trichloride are highly active for olefin metathesis. Such catalysts are used commercially for the production of polynorbornene for example. [60] Well defined ruthenium carbene and alkylidene complexes show comparable reactivity and provide mechanistic insights into the industrial processes. [61] The Grubbs' catalysts for example have been employed in the preparation of drugs and advanced materials.

RuCl3-catalyzed ring-opening metathesis polymerization reaction giving polynorbornene.. Polynbornene.png
RuCl3-catalyzed ring-opening metathesis polymerization reaction giving polynorbornene..

Ruthenium complexes are highly active catalysts for transfer hydrogenations (sometimes referred to as "borrowing hydrogen" reactions). This process is employed for the enantioselective hydrogenation of ketones, aldehydes, and imines. This reaction exploits using chiral ruthenium complexes introduced by Ryoji Noyori. [62] For example, (cymene)Ru(S,S-TsDPEN) catalyzes the hydrogenation of benzil into (R,R)-hydrobenzoin. In this reaction, formate and water/alcohol serve as the source of H2: [63] [64]

[RuCl(S,S-TsDPEN)(cymene)]-catalysed (R,R)-hydrobenzoin synthesis (yield 100%, ee >99%) RuCl(S,S-TsDPEN)(cymene)-catalysed R,R-hydrobenzoin synthesis.svg
[RuCl(S,S-TsDPEN)(cymene)]-catalysed (R,R)-hydrobenzoin synthesis (yield 100%, ee >99%)

A Nobel Prize in Chemistry was awarded in 2001 to Ryōji Noyori for contributions to the field of asymmetric hydrogenation.

In 2012, Masaaki Kitano and associates, working with an organic ruthenium catalyst, demonstrated ammonia synthesis using a stable electride as an electron donor and reversible hydrogen store. [65] Small-scale, intermittent production of ammonia, for local agricultural use, may be a viable substitute for electrical grid attachment as a sink for power generated by wind turbines in isolated rural installations.[ citation needed ]

Heterogeneous catalysis

Ruthenium-promoted cobalt catalysts are used in Fischer-Tropsch synthesis. [66]

Emerging applications

Some ruthenium complexes absorb light throughout the visible spectrum and are being actively researched for solar energy technologies. For example, Ruthenium-based compounds have been used for light absorption in dye-sensitized solar cells, a promising new low-cost solar cell system. [67]

Many ruthenium-based oxides show very unusual properties, such as a quantum critical point behavior, [68] exotic superconductivity (in its strontium ruthenate form), [69] and high-temperature ferromagnetism. [70]

Applications of ruthenium thin films in microelectronics

Relatively recently, ruthenium has been suggested as a material that could beneficially replace other metals and silicides in microelectronics components. Ruthenium tetroxide (RuO4) is highly volatile, as is ruthenium trioxide (RuO3). [71] By oxidizing ruthenium (for example with an oxygen plasma) into the volatile oxides, ruthenium can be easily patterned. [72] [73] [74] [75] The properties of the common ruthenium oxides make ruthenium a metal compatible with the semiconductor processing techniques needed to manufacture microelectronics.

To continue miniaturization of microelectronics, new materials are needed as dimensions change. There are three main applications for thin ruthenium films in microelectronics. The first is using thin films of ruthenium as electrodes on both sides of tantalum pentoxide (Ta2O5) or barium strontium titanate ((Ba, Sr)TiO3, also known as BST) in the next generation of three-dimensional dynamic random access memories (DRAMs). [76] [77] [78] Ruthenium thin-film electrodes could also be deposited on top of lead zirconate titanate (Pb(ZrxTi1−x)O3, also known as PZT) in another kind of RAM, ferroelectric random access memory (FRAM). [79] [80] Platinum has been used as the electrodes in RAMs in laboratory settings, but it is difficult to pattern. Ruthenium is chemically similar to platinum, preserving the function of the RAMs, but in contrast to Pt patterns easily. The second is using thin ruthenium films as metal gates in p-doped metal-oxide-semiconductor field effect transistors (p-MOSFETs). [81] When replacing silicide gates with metal gates in MOSFETs, a key property of the metal is its work function. The work function needs to match the surrounding materials. For p-MOSFETs, the ruthenium work function is the best materials property match with surrounding materials such as HfO2, HfSiOx, HfNOx, and HfSiNOx, to achieve the desired electrical properties. The third large-scale application for ruthenium films is as a combination adhesion promoter and electroplating seed layer between TaN and Cu in the copper dual damascene process. [82] [83] [84] [85] [86] Copper can be directly electroplated onto ruthenium, [87] in contrast to tantalum nitride. Copper also adheres poorly to TaN, but well to Ru. By depositing a layer of ruthenium on the TaN barrier layer, copper adhesion would be improved and deposition of a copper seed layer would not be necessary.

There are also other suggested uses. In 1990, IBM scientists discovered that a thin layer of ruthenium atoms created a strong anti-parallel coupling between adjacent ferromagnetic layers, stronger than any other nonmagnetic spacer-layer element. Such a ruthenium layer was used in the first giant magnetoresistive read element for hard disk drives. In 2001, IBM announced a three-atom-thick layer of the element ruthenium, informally referred to as "pixie dust", which would allow a quadrupling of the data density of current hard disk drive media. [88]

Environmental pollution October 2017

In October 2017, monitoring stations in many European countries including France, Germany, Austria, Romania, and Bulgaria detected high atmospheric concentrations of ruthenium-106. An international investigation concluded that it was the result of massive atmospheric release of radioactive material caused by a sizeable undeclared nuclear accident during the reprocessing of nuclear fuel. [89] The study identified the Russian Mayak nuclear complex as the likely source, [89] which also had a major nuclear accident in 1957. [90]

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An oxide is a chemical compound that contains at least one oxygen atom and one other element in its chemical formula. "Oxide" itself is the dianion of oxygen, an O2– atom. Metal oxides thus typically contain an anion of oxygen in the oxidation state of −2. Most of the Earth's crust consists of solid oxides, the result of elements being oxidized by the oxygen in air or in water. Hydrocarbon combustion affords the two principal carbon oxides: carbon monoxide and carbon dioxide. Even materials considered pure elements often develop an oxide coating. For example, aluminium foil develops a thin skin of Al2O3 (called a passivation layer) that protects the foil from further corrosion. Individual elements can often form multiple oxides, each containing different amounts of the element and oxygen. In some cases these are distinguished by specifying the number of atoms as in carbon monoxide and carbon dioxide, and in other cases by specifying the element's oxidation number, as in iron(II) oxide and iron(III) oxide. Certain elements can form many different oxides, such as those of nitrogen. other examples are silicon, iron, titanium, and aluminium oxides.

Rhenium Chemical element with atomic number 75

Rhenium is a chemical element with the symbol Re and atomic number 75. It is a silvery-gray, heavy, third-row transition metal in group 7 of the periodic table. With an estimated average concentration of 1 part per billion (ppb), rhenium is one of the rarest elements in the Earth's crust. Rhenium has the third-highest melting point and highest boiling point of any stable element at 5903 K. Rhenium resembles manganese and technetium chemically and is mainly obtained as a by-product of the extraction and refinement of molybdenum and copper ores. Rhenium shows in its compounds a wide variety of oxidation states ranging from −1 to +7.

Osmium tetroxide chemical compound

Osmium tetroxide (also osmium(VIII) oxide) is the chemical compound with the formula OsO4. The compound is noteworthy for its many uses, despite its toxicity and the rarity of osmium. It also has a number of unusual properties, one being that the solid is volatile. The compound is colourless, but most samples appear yellow. This is most likely due to the presence of the impurity OsO2, which is yellow-brown in colour.

Noble metal Metals resistant to corrosion and oxidation

In chemistry, the noble metals are metals that are resistant to corrosion and oxidation in moist air. The short list of chemically noble metals comprises ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag), osmium (Os), iridium (Ir), platinum (Pt), and gold (Au).

The platinum-group metals are six noble, precious metallic elements clustered together in the periodic table. These elements are all transition metals in the d-block.

Superalloy Alloy with higher durability than normal metals

A superalloy, or high-performance alloy, is an alloy that exhibits several key characteristics: excellent mechanical strength, resistance to thermal creep deformation, good surface stability, and resistance to corrosion or oxidation. A superalloy's most defining feature is its ability to operate at a high fraction of its melting point. The crystal structure is typically face-centered cubic austenitic. Examples of such alloys are Hastelloy, Inconel, Waspaloy, Rene alloys, Incoloy, MP98T, TMS alloys, and CMSX single crystal alloys.

Periodate chemical compounds containing periodate anion

Periodate is an anion composed of iodine and oxygen. It is one of a number of oxyanions of iodine and is the highest in the series, with iodine existing in oxidation state +7. Unlike other perhalogenates, such as perchlorate, it can exist in two forms: metaperiodateIO
4
and orthoperiodateIO5−
6
. In this regard it is comparable to the tellurate ion from the adjacent group. It can combine with a number of counter ions to form periodates, which may also be regarded as the salts of periodic acid.

Ruthenium(III) chloride chemical compound

Ruthenium(III) chloride is the chemical compound with the formula RuCl3. "Ruthenium(III) chloride" more commonly refers to the hydrate RuCl3·xH2O. Both the anhydrous and hydrated species are dark brown or black solids. The hydrate, with a varying proportion of water of crystallization, often approximating to a trihydrate, is a commonly used starting material in ruthenium chemistry. The compound is also widely regarded as a prime candidate to realize Kitaev quantum spin liquid state with Majorana Fermion excitations.

Tetrapropylammonium perruthenate chemical compound

Tetrapropylammonium perruthenate (TPAP or TPAPR) is the chemical compound described by the formula N(C3H7)4RuO4. Sometimes known as the Ley–Griffith reagent, this ruthenium compound is used as a reagent in organic synthesis. This salt consists of the tetrapropylammonium cation and the perruthenate, RuO4 anion. Ruthenium tetroxide is a highly aggressive oxidant, but its one-electron reduced derivative is a mild oxidizing agent for the conversion of alcohols to aldehydes. This oxidizing agent can also be used to oxidize primary alcohols all the way to the carboxylic acid. Use of a higher catalyst loading, larger amount of the co-oxidant, and addition of two equivalents of water. In this situation, the aldehyde reacts with water to form the geminal-diol hydrate, which is then oxidized again.

Dihydroxylation is the process by which an alkene is converted into a vicinal diol. Although there are many routes to accomplish this oxidation, the most common and direct processes use a high-oxidation-state transition metal. The metal is often used as a catalyst, with some other stoichiometric oxidant present. In addition, other transition metals and non-transition metal methods have been developed and used to catalyze the reaction.

Ruthenium tetroxide is the inorganic compound with the formula RuO4. It is a yellow volatile solid that melts near room temperature. Samples are typically black due to impurities. The analogous OsO4 is more widely used and better known. One of the few solvents in which RuO4 forms stable solutions is CCl4.

Ruthenium(IV) oxide chemical compound

Ruthenium(IV) oxide is the inorganic compound with the formula RuO2. This black solid is the most common oxide of ruthenium. It is widely used as an electrocatalyst for producing chlorine, chlorine oxides, and O2 catalyst is ruthenium(IV) oxide. Like many dioxides, RuO2 adopts the rutile structure.

Organoruthenium chemistry

Organoruthenium chemistry is the chemistry of organometallic compounds containing a carbon to ruthenium chemical bond. Several organoruthenium catalysts are of commercial interest and organoruthenium compounds have been considered for cancer therapy. The chemistry has some stoichiometric similarities with organoiron chemistry, as iron is directly above ruthenium in group 8 of the periodic table. The most important reagents for the introduction of ruthenium are ruthenium(III) chloride and triruthenium dodecacarbonyl.

Combustion chemical vapor deposition (CCVD) is a chemical process by which thin-film coatings are deposited onto substrates in the open atmosphere.

Chemical vapor deposition of ruthenium is a method to deposit thin layers of ruthenium on substrates by Chemical vapor deposition (CVD).

Ruthenium anti-cancer drugs are coordination complexes of ruthenium complexes that have anticancer properties. They promise to provide alternatives to platinum-based drugs for anticancer therapy. No ruthenium anti-cancer drug has been commercialized.

Lithium ruthenate chemical compound

Lithium ruthenate, Li2RuO3, is a chemical compound of lithium, ruthenium and oxygen. It has a layered honeycomb crystal structure, and can be prepared by direct calcination of Ru metal and lithium carbonate at ca. 700 °C. It is a potential lithium-ion battery electrode material, though this application is hindered by the high costs of Ru, as compared to the cheaper Li2MnO3 alternative.

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