Ruthenium

Atomic Number:

44

Melting Point: 2334 ºC
Atomic Symbol: Ru Boiling Point:  4150 ºC
Atomic Weight: 101.07 amu Density: 12370 kg/m 3
Atomic Radius:

134 pm

Oxidation States: 3
Covalent Radius: 126 pm Electron Configuration: [Kr]5s14d7
van der Waals Radius:

--

State of Matter:  solid

History

(L. Ruthenia: Russia) In 1827, Berzelius and Osann 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.

Properties

Ruthenium is a hard, white metal and has four crystal modifications. It does not tarnish at room temperatures, but oxidizes explosively. It is attacked by halogens, hydroxides, etc. Compounds in at least eight oxidation states have been found, but of these, the +2, +3, and +4 states are the most common. Ruthenium compounds show a marked resemblance to those of cadmium.

Sources

A member of the platinum group, ruthenium occurs native with other members of the group in 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 in the Sudbury, Ontario nickel-mining region, and in the pyroxinite deposits of South Africa.

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.

Uses

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 from oil refining and other industrial processes.

Organometallic ruthenium carbene and allenylidene complexes have recently been found as highly efficient catalysts for olefin metathesis with important applications in organic and pharmaceutical chemistry.

Recently, large metallo-organic complexes of ruthenium have been found to exhibit anti-tumor activity and the first of a new group of anti-cancer medicine are now in the stage of clinical trials.

Some ruthenium complexes absorb light throughout the visible spectrum and are being actively researched in various, potential, solar energy technologies.

Isotopes

Naturally occurring ruthenium is composed of seven isotopes. The most stable radioisotopes are Ru-106 with a half-life of 373.59 days, Ru-103 with a half-life of 39.26 days and Ru-97 with a half-life of 2.9 days.

Fifteen other radioisotopes have been characterized with atomic weights ranging from 89.93 amu (Ru-90) to 114.928 (Ru-115). Most of these have half-lifes that are less than five minutes except for two, Ru-95 and Ru-105.

Hazards

The compound ruthenium tetroxide RuO4, similar to osmium tetroxide, is highly toxic and may explode. Ruthenium plays no biological role but does strongly stain human skin, may be carcinogenic and bio-accumulates in bone.