See also: Category:Ruthenium 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.
Ruthenium can be oxidized to ruthenium(IV) oxide (RuO2, oxidation state +4) which can in turn be oxidized by sodium metaperiodate to ruthenium tetroxide, RuO4, a strong oxidizing agent with structure and properties analogous to osmium tetroxide. Like osmium tetroxide, ruthenium tetroxide is a potent fixative and stain for electron microscopy of organic materials, and is mostly used to reveal the structure of polymer samples.Dipotassium ruthenate (K2RuO4, +6), and potassium perruthenate (KRuO4, +7) are also known.
Coordination and organometallic complexes
Main article: Organoruthenium chemistry
Ruthenium forms a variety of coordination complexes. Examples are the many pentammine derivatives [Ru(NH3)5L]n+ which often exist in both Ru(II) and Ru(III). Derivatives of bipyridine and terpyridine are numerous, best known being the luminescent tris(bipyridine)ruthenium(II) chloride.
Ruthenium form a wide range compounds with carbon-ruthenium bonds. Ruthenocene is analogous to ferrocene structurally, but exhibits distinctive redox properties. A large number of complexes of carbon monoxide are known, the parent being triruthenium dodecacarbonyl. The analogue of iron pentacarbonyl, ruthenium pentacarbonyl is unstable at ambient conditions. Ruthenium trichloridecarbonylates (reacts with carbon monoxide) to give mono- and diruthenium(II) carbonyls from which many derivatives have been prepared such as RuHCl(CO)(PPh3)3 and Ru(CO)2(PPh3)3 (Roper’s complex). Heating solutions of ruthenium trichloride in alcohols with triphenylphosphine givestris(triphenylphosphine)ruthenium dichloride (RuCl2(PPh3)3), which converts to the hydride complex chlorohydridotris(triphenylphosphine)ruthenium(II) (RuHCl(PPh3)3).
In the area of fine chemical synthesis, Grubbs’ catalyst is used for alkene metathesis.
Metal ruthenides (Ru2−) are very rare, but are commonly found in superconductor applications, especially with regard to lanthanide metals e.g.cerium ruthenide (CeRu2).
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, it took until the mid-18th century for platinum to be identified as a pure element. The discovery that natural platinum contained palladium, rhodium, osmium and iridium occurred in the first decade of the 19th century. 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. Residues of platinum production for minting 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”) from platinum ores in 1807. He published an announcement of his discovery in the Polish language in article “Rosprawa o nowym metallu w surowey platynie odkrytym” in 1808. His work was never confirmed, however, and he later withdrew his claim of discovery. Jöns Berzeliusand Gottfried Osann nearly discovered ruthenium in 1827. 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, pluranium, ruthenium and polinium. This discrepancy led to a long-standing controversy between Berzelius and Osann about the composition of the residues.
In 1844, the Baltic German scientist Karl Ernst Claus showed that the compounds prepared by Gottfried Osann contained small amounts of ruthenium, which Claus had discovered the same year. Claus isolated ruthenium from the platinum residues of the rouble production while he was working in Kazan University, Kazan. 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.
The name itself derives from Ruthenia, the Latin word for Rus’, a historical area which includes present-day western Russia, Ukraine, Belarus, and parts of Slovakia and Poland. Claus used the name proposed by Gottfried Osann in 1828, who had chosen the element’s name in honor of his birthland, as he was born in Tartu, Estonia, which was at the time a part of the Russian Empire.
Because of its ability to harden platinum and palladium, ruthenium is used in platinum and palladium alloys to make wear-resistant electrical contacts. In this application, only thin plated films are used to achieve the necessary wear-resistance. Because of its lower cost and similar properties compared to rhodium, the use as plating material for electric contacts is one of the major applications. The thin coatings are either applied by electroplating or sputtering.
Ruthenium dioxide and lead and bismuth ruthenates are used in thick-film chip resistors. These two electronic applications account for 50% of the ruthenium consumption.
Only a few ruthenium alloys are used other than those with other platinum group metals. Ruthenium is often used in small quantities in those alloys to improve some of their properties. The beneficial effect on the corrosion resistance of titanium alloys led to the development of a special alloy containing 0.1% ruthenium. Ruthenium is also used in some advanced high-temperature single-crystal superalloys, with applications including the turbine blades in jet engines. Several nickel based superalloy compositions are described in the literature. Among them are EPM-102 (with 3% Ru) and TMS-162 (with 6% Ru), as well as TMS-138 and TMS-174. both containing 6% rhenium. Fountain pen nibs are frequently tipped with alloys containing ruthenium. From 1944 onward, the famous Parker 51 fountain pen was fitted with the “RU” nib, a 14K gold nib tipped with 96.2% ruthenium and 3.8% iridium.
Ruthenium is a component of mixed-metal oxide (MMO) anodes used for cathodic protection of underground and submerged structures, and for electrolytic cells for chemical processes such as generating chlorine from salt water. The fluorescence of some ruthenium complexes is quenched by oxygen, which has led to their use as optode sensors for oxygen. 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. The beta-decaying isotope 106 of ruthenium is used in radiotherapy of eye tumors, mainly malignant melanomas of the uvea. Ruthenium-centered complexes are being researched for possible anticancer properties. Compared with platinum complexes, those of ruthenium show greater resistance to hydrolysis and more selective action on tumors. NAMI-A andKP1019 are two drugs undergoing clinical evaluation against metastatic tumors and colon cancers.
Ruthenium is a versatile catalyst. Hydrogen sulfide can be split by light by using an aqueous suspension of CdS particles loaded with ruthenium dioxide. This may be useful in the removal of H2Sin oil refineries and other industrial processing facilities. Organometallic ruthenium carbene and alkylidene complexes have been found to be highly efficient catalysts for olefin metathesis, a process with important applications in organic and pharmaceutical chemistry.
Solar energy conversion
Some ruthenium complexes absorb light throughout the visible spectrum and are being actively researched in various, potential, 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.
Chemical vapor deposition of ruthenium is used as a method to produce thin films of pure ruthenium on substrates. These films show promising properties for the use in microchips and for thegiant magnetoresistive read element for hard disk drives. Ruthenium was also suggested as a possible material for microelectronics because its use is compatible with semiconductor processing techniques.
Many ruthenium based oxides show very unusual properties, such as a quantum critical point behavior, exotic superconductivity, and high temperature ferromagnetism.