Ruthenium
In 1844, Karl Ernst Claus worked inside a laboratory at Kazan State University to isolate six grams of a new metal from crude platinum residues. He had been examining the insoluble remains left after dissolving Russian river sands in aqua regia. This work followed a decades-old dispute involving Gottfried Osann, who claimed to have found three new metals in 1827. Osann named one of his discoveries ruthenium, but he could not repeat his isolation and eventually withdrew his claim. Berzelius dismissed Osann's findings as errors, leaving the scientific community confused for nearly two decades. Claus proved that Osann's samples contained small amounts of this new element. He chose the name ruthenium to honor Russia, using the Latin word Ruthenia for Motherland. Claus stated he had every right to use the name because Osann had relinquished it. The decision started a trend of naming elements after countries that continues today.
Ruthenium appears as a hard white metal with four distinct crystal modifications. It does not tarnish under ambient conditions but oxidizes when heated above 100 degrees Celsius. The outermost shell holds only one electron, creating an anomaly seen in other transition metals between atomic numbers 41 and 45. Unlike iron, ruthenium is usually paramagnetic at room temperature. A metastable tetragonal phase created on single crystal molybdenum becomes ferromagnetic at room temperature. Small amounts added to platinum or palladium increase hardness significantly. Adding ruthenium to titanium markedly increases corrosion resistance. A ruthenium-molybdenum alloy becomes superconductive below 10.6 Kelvin. The metal dissolves in fused alkalis to produce ruthenates. It resists attack by acids including aqua regia but reacts with sodium hypochlorite at room temperature. Halogens attack the metal at high temperatures. Oxidizing agents provide the most ready path to reaction.
The Earth's crust contains about 100 parts per trillion of this element, making it the 78th most abundant substance globally. Most deposits exist within ores containing other platinum group metals found in the Ural Mountains. North and South America also host significant geological formations. Commercially important quantities come from pentlandite extracted in Sudbury, Ontario. Pyroxenite deposits in South Africa yield small but vital amounts. Roughly 30 tonnes are mined each year while world reserves total around 5,000 tonnes. Platinum group mixtures vary widely depending on geochemical formation. South African ore averages 11% ruthenium content compared to just 2% in former Soviet Union mines from 1992. Noble metals precipitate as anode mud during electrorefining of copper and nickel. This mud serves as feedstock for extraction processes involving fusion with sodium peroxide followed by dissolution in aqua regia. Osmium, ruthenium, rhodium, and iridium remain insoluble in aqua regia and readily precipitate out.
Approximately 13.8 tonnes of consumed ruthenium went into electrical applications in 2016 alone. Thick-film chip resistors use ruthenium dioxide mixed with lead and bismuth ruthenates. These two electronic uses account for half of all global consumption. A thin film applied via electroplating or sputtering achieves durability in electrical contacts. The metal's non-volatile nature benefits microelectronic devices significantly. Copper can be directly electroplated onto ruthenium barrier layers used in transistor gates. Interconnects benefit from comparable electrical resistivities between the metal and its main oxide RuO2. Advanced high-temperature single-crystal superalloys contain ruthenium for jet engine turbines. EPM-102 contains 3% ruthenium while TMS-162 holds 6%. Fountain pen nibs frequently feature a 96.2% ruthenium alloy tipped on 14K gold since 1944. Mixed-metal oxide anodes protect underground structures through cathodic protection systems. Fluorescence quenching by oxygen enables optode sensors for detecting air quality levels.
Solutions containing ruthenium trichloride show high activity for olefin metathesis reactions. Commercial production of polynorbornene relies on such catalysts. Grubbs' catalysts earned their inventor a Nobel Prize for work in alkene metathesis. These compounds prepare drugs and advanced materials on small scales. Chiral ruthenium complexes introduced by Ryoji Noyori enable enantioselective hydrogenation of ketones, aldehydes, and imines. A typical catalyst formula includes cymene and S,S-TsDPEN ligands. The Nobel Committee awarded Ryōji Noyori the Chemistry prize in 2001 for asymmetric hydrogenation contributions. Ruthenium-promoted cobalt catalysts drive Fischer, Tropsch synthesis processes. Dye-sensitized solar cells utilize ruthenium-based compounds as low-cost alternatives. Transfer hydrogenations sometimes called borrowing hydrogen reactions employ highly active ruthenium complexes. Tris(bipyridine)ruthenium(II) chloride serves as a luminescent derivative used in various applications. The colorless liquid ruthenium pentacarbonyl converts to dark red solid triruthenium dodecacarbonyl without carbon monoxide pressure.
Naturally occurring ruthenium consists of seven stable isotopes including mass numbers 96 through 104. Thirty-four synthetic radioactive isotopes have been discovered since natural forms were cataloged. Ruthenium-106 possesses a half-life of 371.8 days while Ruthenium-103 lasts 39.245 days. Ruthenium-97 decays within 2.837 days. Fifteen other radioisotopes range from 85Ru to 125Ru with most lasting less than five minutes. Exceptions include 94Ru at 51.8 minutes and 105Ru at 4.44 hours. High concentrations detected over Europe in 2017 linked to an alleged undeclared nuclear accident in Russia. This isotope appears as a fission product of uranium or plutonium. Chemical extraction from spent nuclear fuel could yield usable ruthenium after unstable isotopes decay. Deliberate nuclear transmutation from technetium-99 offers commercial-scale production potential. Technetium has no stable isotopes, avoiding neutron activation problems for stable forms. Significant amounts produce as byproducts of technetium-99m used in nuclear medicine.
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Common questions
Who discovered ruthenium and when was it isolated?
Karl Ernst Claus isolated six grams of the new metal in 1844 at Kazan State University. He extracted the element from crude platinum residues found in Russian river sands dissolved in aqua regia.
What is the chemical symbol and atomic number for ruthenium?
Ruthenium has the chemical symbol Ru and occupies position 44 on the periodic table. It appears as a hard white metal with four distinct crystal modifications that do not tarnish under ambient conditions.
Where are the largest deposits of ruthenium located globally?
Most deposits exist within ores containing other platinum group metals found in the Ural Mountains. North and South America also host significant geological formations including pentlandite from Sudbury, Ontario and pyroxenite deposits in South Africa.
How much ruthenium is consumed annually for electrical applications?
Approximately 13.8 tonnes of consumed ruthenium went into electrical applications in 2016 alone. Thick-film chip resistors use ruthenium dioxide mixed with lead and bismuth ruthenates to account for half of all global consumption.
Which Nobel Prize winners utilized ruthenium compounds in their research?
Grubbs' catalysts earned their inventor a Nobel Prize for work in alkene metathesis while Ryōji Noyori won the Chemistry prize in 2001 for asymmetric hydrogenation contributions. Chiral ruthenium complexes introduced by Ryoji Noyori enable enantioselective hydrogenation of ketones, aldehydes, and imines.