Ruthenium

History, Occurrence, and Uses

Ruthenium was recognized as a new element by G.W. Osann in 1828. He found it in insoluble residues from aqua regia extract of native platinum from alluvial deposits in the Ural mountains of Russia. He named it Ruthen after the Latin name Ruthenia for Russia. The discovery of this element, however, is credited to Klaus who in 1844 found that Osann’s ruthenium oxide was very impure and isolated pure Ru metal from crude platinum residues insoluble in aqua regia.
Ruthenium occurs in nature natively, found in minor quantities associated with other platinum metals. Its abundance in the earth’s crust is estimated to be 0.001 mg/kg, comparable to that of rhodium and iridium.
Ruthenium alloyed to platinum, palladium, titanium and molybdenum have many applications. It is an effective hardening element for platinum and palladium. Such alloys have high resistance to corrosion and oxidation and are used to make electrical contacts for resistance to severe wear. Ruthenium–palladium alloys are used in jewelry, decorations, and dental work. Addition of 0.1% ruthenium markedly improves corrosion resistance of titanium. Ruthenium alloys make tips for fountain pen nibs, instrument pivots, and electrical goods. Ruthenium catalysts are used in selective hydrogenation of carbonyl groups to convert aldehydes and ketones to alcohols.

Chemical Properties

Ruthenium is a hard, white-colored member of the PGE with a BP of 4150 °C (Lide, 2006). Like osmium, it can be used to create a hardened alloy with platinum or palladium. The addition of a small quantity of ruthenium to titanium makes an alloy with increased corrosion resistance (Lide, 2006). Ruthenium is also a versatile catalyst.

Physical Properties

Hard silvery-white metal; hexagonal close-packed crystal structure; density 12.41 g/cm3 at 20°C; melts at 2,334°C; vaporizes at 4,150°C; electrical resistivity 7.1 microhm-cm at 0°C; hardness (annealed) 200-350 Vickers units; Young’s modulus 3.0×104 tons/in2; magnetic susceptibility 0.427 cm3/g; thermal neutron absorption cross section 2.6 barns; insoluble in water, cold or hot acids, and aqua regia; can be brought into aqueous phase by fusion of finely divided metal with alkaline hydroxides, peroxides, carbonates and cyanides.

Production

Ruthenium is derived from platinum metal ores. Method of production depends on the type of ore. However, the extraction processes are similar to those of other noble metals (see Platinum, Rhodium and Iridium). Ruthenium, like Rhodium, may be obtained from accumulated anode sludges in electrolytic refining of nickel or copper from certain types of ores. Also, residues from refining nickel by Mond carbonyl process contain ruthenium and other precious metals at very low concentrations. The extraction processes are very lengthy, involving smelting with suitable fluxes and acid treatments.
Metals, such as gold, platinum, and palladium, are separated by digesting refining residues with aqua regia. These metals are soluble in aqua regia, leaving ruthenium, rhodium, iridium, osmium, and silver in the insoluble residue.
The treatment of this insoluble residue may vary. In one typical process, residue is subjected to fusion with sodium peroxide. Ruthenium and osmium are converted to water-soluble sodium ruthenate and osmate, which are leached with water. The aqueous solution is treated with chlorine gas and heated. The ruthenate and the osmate are converted to their tetroxides. Ruthenium tetroxide is distilled out and collected in hydrochloric acid. The tetroxide is converted into ruthenium chloride. Traces of osmium are removed from ruthenium chloride solution by boiling with nitric acid.
Nitric acid converts osmium to volatile osmium tetroxide but forms a nitrosyl complex with ruthenium that remains in the solution. After removal of trace osmium, the solution is treated with ammonium chloride. This precipitates ruthenium as crystals of ammonium chlororuthenate, NH4RuCl6. The precipitate is washed, dried, and ignited to form ruthenium black. This is reduced with hydrogen at 1,000°C to form very pure ruthenium powder.

Reactions

When heated in air at 500 to 700°C, ruthenium converts to its dioxide, RuO2, a black crystalline solid of rutile structure. A trioxide of ruthenium, RuO3, also is known; formed when the metal is heated above 1,000°C. Above 1,100°C the metal loses weight because trioxide partially volatilizes. Ruthenium also forms a tetroxide, RuO4, which, unlike osmium, is not produced by direct union of the elements.
Halogens react with the metal at elevated temperatures. Fluorine reacts with ruthenium at 300°C forming colorless vapors of pentafluoride, RuF5, which at ordinary temperatures converts to a green solid. Chlorine combines with the metal at 450°C to form black trichloride, RuCl3, which is insoluble in water. Ru metal at ambient temperature is attacked by chlorine water, bromine water, or alcoholic solution of iodine.
Ruthenium is stable in practically all acids including aqua regia. Fusion with an alkali in the presence of an oxidizing agent forms ruthenate, RuO42– and perruthenate, RuO4¯.
When finely-divided Ru metal is heated with carbon monoxide under 200 atm pressure, ruthenium converts to pentacarbonyl, Ru(CO)5, a colorless liquid that decomposes on heating to diruthenium nonacarbonyl, Ru2(CO)9, a yellow crystalline solid. Ruthenium reacts with cyclopentadiene in ether to form a sandwich complex, a yellow crystalline compound, bis(cyclopentadiene) ruthenium(0), also known as ruthenocene.

Chemical Properties

Elemental ruthenium has a close-packed hexagonal crystal structure. The seven stable isotopes are 96Ru, 98Ru through 102Ru, and 104Ru.

Chemical Properties

Ruthenium, a transition element, belongs to group VIII (iron) of the periodic classification and to the light platinum metals triad. It is a hard and brittle metal that resembles platinum. It crystallizes in hexagonal form and occurs in the form of seven stable isotopes: 96 (5.46%), 98 (1.87%), 99 (12.63%), 100 (12.53%), 101 (17.02%), 102 (31.6%), and 104 (18.87%). There are also several radioactive isotopes—93, 94, 95, 97, 103, 105, 106, 107, and 108—of which the 106 isotope characterized by strong β radiation and has a half-life of 368 days; since it is produced in large quantities in the nuclear reactors, it deserves special attention. Ruthenium is the rarest of the platinum group elements (abundance in the Earth’s crust ～0.0004 ppm). In chemical compounds, it occurs at oxidation states from +2 to +8; the most frequent is +3 in ruthenium compounds. Rutheniumis resistant to acids and aqua regia, it is not oxidized in the air at room temperature, and in the form of powder it reacts with oxygen at elevated temperatures. It is dissolved in molten strong alkalis and reacts with alkaline metal peroxides and perchlorides. Ruthenium powder reacts with chlorine above 200°C and with bromine at 300– 700°C.
Ruthenium compounds are usually dark brown (ranging from yellow to black). Ruthenium forms alloys with platinum, palladium, cobalt, nickel, and tungsten.

Physical properties

Ruthenium is a rare, hard, silvery-white metallic element located in group 8, just aboveosmium and below iron, with which it shares some chemical and physical properties.Both ruthenium and osmium are heavier and harder than pure iron, making them morebrittle and difficult to refine. Both ruthenium and osmium are less tractable and malleable than iron. Although there are some similar characteristics between ruthenium and iron,ruthenium’s properties are more like those of osmium. Even so, ruthenium is less stablethan osmium. They are both rare and difficult to separate from minerals and ores that containother elements. These factors make it more difficult to determine ruthenium’s accurateatomic weight.
The oxidation state of +8 for ruthenium and its “mate” osmium is the highest oxidationstate of all elements in the transition series. Ruthenium’s melting point is 2,310°C, its boilingpoint is 3,900°C, and its density is 12.45 g/cm³.

Isotopes

There are 37 isotopes for ruthenium, ranging in atomic mass numbers from87 to 120. Seven of these are stable isotopes. The atomic masses and percentage ofcontribution to the natural occurrence of the element on Earth are as follows: Ru-96 =5.54%, Ru-98 = 1.87%, Ru-99 = 12.76%, Ru-100 = 12.60%, Ru-101 = 17.06%, Ru-102 = 31.55%, and Ru-104 = 18.62%.

Origin of Name

“Ruthenium” is derived from the Latin word Ruthenia meaning “Russia,” where it is found in the Ural Mountains.

Occurrence

Ruthenium is a rare element that makes up about 0.01 ppm in the Earth’s crust. Even so, itis considered the 74th most abundant element found on Earth. It is usually found in amountsup to 2% in platinum ores and is recovered when the ore is refined. It is difficult to separatefrom the leftover residue of refined platinum ore.
Ruthenium is found in South America and the Ural Mountains of Russia. There are someminor platinum and ruthenium ores found in the western United States and Canada. All ofthe radioactive isotopes of ruthenium are produced in nuclear reactors.

Characteristics

Ruthenium also belongs to the platinum group, which includes six elements with similarchemical characteristics. They are located in the middle of the second and third series of thetransition elements. The platinum group consists of ruthenium, rhodium,palladium, osmium, iridium, and platinum.
Ruthenium is a hard brittle metal that resists corrosion from all acids but is vulnerable tostrong alkalis (bases). Small amounts, when alloyed with other metals, will prevent corrosionof that metal.

History

Berzelius and Osann in 1827 examined the residues left after dissolving crude platinum from the Ural mountains in aqua regia. While Berzelius found no unusual metals, Osann thought he found three new metals, one of which he named ruthenium. In 1844 Klaus, generally recognized as the discoverer, showed that Osann’s ruthenium oxide was very impure and that it contained a new metal. Klaus obtained 6 g of ruthenium from the portion of crude platinum that is insoluble in aqua regia. A member of the platinum group, ruthenium occurs native with other members of the group of ores found in the Ural mountains and in North and South America. It is also found along with other platinum metals in small but commercial quantities in pentlandite of the Sudbury, Ontario, nickel-mining region, and in pyroxinite deposits of South Africa. Natural ruthenium contains seven isotopes. Twenty-eight other isotopes and isomers are known, all of which are radioactive. The metal is isolated commercially by a complex chemical process, the final stage of which is the hydrogen reduction of ammonium ruthenium chloride, which yields a powder. The powder is consolidated by powder metallurgy techniques or by argon-arc welding. Ruthenium is a hard, white metal and has four crystal modifications. It does not tarnish at room temperatures, but oxidizes in air at about 800°C. The metal is not attacked by hot or cold acids or aqua regia, but when potassium chlorate is added to the solution, it oxidizes explosively. It is attacked by halogens, hydroxides, etc. Ruthenium can be plated by electrodeposition or by thermal decomposition methods. The metal is one of the most effective hardeners for platinum and palladium, and is alloyed with these metals to make electrical contacts for severe wear resistance. A ruthenium–molybdenum alloy is said to be superconductive at 10.6 K. The corrosion resistance of titanium is improved a hundredfold by addition of 0.1% ruthenium. It is a versatile catalyst. Hydrogen sulfide can be split catalytically by light using an aqueous suspension of CdS particles loaded with ruthenium dioxide. It is thought this may have application to removal of H2S in oil refining and other industrial processes. Compounds in at least eight oxidation states have been found, but of these, the +2. +3. and +4 states are the most common. Ruthenium tetroxide, like osmium tetroxide, is highly toxic. In addition, it may explode. Ruthenium compounds show a marked resemblance to those of osmium. The metal is priced at about $25/g (99.95% pure).

Uses

Ruthenium is used in wear-resistant electrical contacts and the production of thick-film resistors. Its use in some platinum alloys, and as a catalyst. It is a most effective hardeners for platinum and palladium. It is also used in some advanced high-temperature single-crystal super alloys, with applications including the turbine blades in jet engines and fountain pen nibs.

Uses

Since ruthenium is rare and difficult to isolate in pure form, there are few uses for it. Itsmain uses are as an alloy to produce noncorrosive steel and as an additive to jewelry metalssuch as platinum, palladium, and gold, making them more durable.
It is also used as an alloy to make electrical contacts harder and wear longer, for medicalinstruments, and more recently, as an experimental metal for direct conversion of solar cellmaterial to electrical energy.
Ruthenium is used as a catalyst to affect the speed of chemical reactions, but is not alteredby the chemical process. It is also used as a drug to treat eye diseases.

Uses

As substitute for platinum in jewelry; for pen nibs; as hardener in electrical contact alloys, electrical filaments; in ceramic colors; catalyst in synthesis of long chain hydrocarbons.

Definition

A transition metal that occurs naturally with platinum. It forms alloys with platinum that are used in electrical contacts. Ruthenium is also used in jewelry alloyed with palladium.Symbol: Ru; m.p. 2310°C; b.p. 3900°C; r.d. 12.37 (20°C); p.n. 44; r.a.m. 101.07.

Production Methods

Elemental ruthenium occurs in native alloys of iridium and osmium (irridosmine, siskerite) and in sulfide and other ores (pentlandite, laurite, etc.) in very small quantities that are commercially recovered.
The element is separated from the other platinum metals by a sequence involving treatment with aqua regia (separation of insoluble osmium, rhodium, ruthenium, and iridium), fusion with sodium bisulfate (with which rhodium reacts), and fusion with sodium peroxide (dissolution of osmium and ruthenium). The resulting solution of ruthenate and osmate is treated with ethanol to precipitate ruthenium dioxide. The ruthenium dioxide is purified by treatment with hydrochloric acid and chlorine and reduced with hydrogen gas to pure metal.
Ruthenium is recovered from exhausted catalytic converters or, in a similar manner, from the waste produced during platinum and nickel ore processing.

Definition

ruthenium: Symbol Ru. A hardwhite metallic transition element;a.n. 44; r.a.m. 101.07; r.d. 12.3; m.p.2310°C; b.p. 3900°C. It is found associatedwith platinum and is used as acatalyst and in certain platinum alloys.Chemically, it dissolves in fusedalkalis but is not attacked by acids. Itreacts with oxygen and halogens at high temperatures. It also formscomplexes with a range of oxidationstates. The element was isolated byK. K. Klaus in 1844.

General Description

This product has been enhanced for energy efficiency.

Hazard

The main hazard is the explosiveness of ruthenium fine power or dust. The metal willrapidly oxidize (explode) when exposed to oxidizer-type chemicals such as potassium chlorideat room temperature. Most of its few compounds are toxic and their fumes should beavoided.

Flammability and Explosibility

Not classified

Pharmaceutical Applications

Ruthenium is the chemical element with the symbol Ru and atomic number 44. It occurs as a minor side product in the mining of platinum. Ruthenium is relatively inert to most chemicals. Its main applications are in the area of specialised electrical parts. The success of cisplatin, together with the occurrence of dose-limiting resistances and severe side effects such as nausea and nephrotoxicity, encouraged the research into other metal-based anticancer agents. Ruthenium is one of those metals under intense research, and first results look very promising, with two candidates – NAMI-A and KP1019 – having entered clinical trials.

Safety Profile

Most ruthenium compounds are poisons. Ruthenium is retained in the bones for a long time. Flammable in the form of dust when exposed to heat or flame. Violent reaction with ruthenium oxide. Explosive reaction with aqua rega + potassium chlorate. When heated to decomposition it emits very toxic fumes of RuO, and Ru, which are hghly injurious to the eyes and lung and can produce nasal ulcerations. See also RUTHENIUM COMPOUNDS.