Ruthenium

Vapor pressure
44	technetium ← Ruthenium → rhodium
	periodic table
General
Name, Symbol, Number	Ruthenium, Ru, 44
Chemical series	transition metals
Group, Period, Block	8, 5, d
Appearance	silvery white metallic ;
Atomic mass	101.07(2) g/mol
Electron configuration	[Kr] 4d7 5s1
Electrons per shell	2, 8, 18, 15, 1
Physical properties
Density (near r.t.)	12.45 g/cm³
Liquid density at m.p.	10.65 g/cm³
Melting point	2607 K; (2334 °C, 4233 °F)
Boiling point	4423 K; (4150 °C, 7502 °F)
Heat of fusion	38.59 kJ/mol
Heat of vaporization	591.6 kJ/mol
Heat capacity	(25 °C) 24.06 J/(mol·K)
Atomic properties
Crystal structure	hexagonal
Oxidation states	2, 3, 4, 6, 8; (mildly acidic oxide)
Electronegativity	2.2 (Pauling scale)
Ionization energies	1st: 710.2 kJ/mol
	2nd: 1620 kJ/mol
	3rd: 2747 kJ/mol
Atomic radius	130 pm
Atomic radius (calc.)	178 pm
Covalent radius	126 pm
Miscellaneous
Electrical resistivity	(0 °C) 71 nΩ·m
Thermal conductivity	(300 K) 117 W/(m·K)
Thermal expansion	(25 °C) 6.4 µm/(m·K)
Speed of sound (thin rod)	(20 °C) 5970 m/s
Speed of sound (thin rod)	(r.t.) 447 m/s
Shear modulus	173 GPa
Bulk modulus	220 GPa
Poisson ratio	0.30
Mohs hardness	6.5
Brinell hardness	2160 MPa
CAS registry number	7440-18-8
Notable isotopes

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Ruthenium (chemical symbol Ru, atomic number 44) is a rare, hard, white metal. It is a member of the platinum group of elements and is found associated with platinum ores. It is used as a catalyst in some alloys with platinum.

Occurrence and isolation

This element is generally found in ores with the other platinum group metals in the Ural Mountains of western Russia and in parts of North and South America. Small but commercially important quantities are also found in the mineral pentlandite (iron-nickel sulfide) extracted from Sudbury, Ontario (Canada), and in deposits of pyroxenite rock (containing silicate minerals) in South Africa.

This metal is commercially isolated through a complex chemical process in which hydrogen is used to reduce ammonium ruthenium chloride, yielding a powder. The powder is then consolidated by powder metallurgy techniques or by argon-arc welding.

It is also possible to extract ruthenium from spent nuclear fuel, which contains an average of 2 kilograms of ruthenium per metric ton. Ruthenium produced in such a way contains radioactive isotopes, some with a half-life of up to 373.59 days. Therefore this ruthenium has to be stored for at least 10 years in a secured area to allow it to become stable.

History

Jöns Berzelius and Gottfried Osann nearly discovered ruthenium in 1827. They obtained crude platinum (from alluvial deposits in the Ural Mountains), treated it with aqua regia (a 3:1 mixture of concentrated hydrochloric acid and nitric acid), and examined the insoluble residues. Berzelius did not detect any unusual elements, but Osann thought he found three new metals and named them pluran, ruthen, and polin.

Later, in 1844, Karl Klaus demonstrated that Osann had obtained impure ruthenium oxide and went on to isolate the new element from platinum ore. For his work, Klaus is generally credited as the discoverer of ruthenium. Klaus named the element after Ruthenia, a latinized name for Russia, in recognition of the work of Osann and in honor of his own birthland—Klaus was born in Tartu, which was then a part of the Russian Empire.

It is also possible that Polish chemist Jedrzej Sniadecki isolated this element from platinum ores in 1807. He called it vestium. His work, however, was never confirmed and he later withdrew his discovery claim.

Notable characteristics

A polyvalent hard white metal, ruthenium is a member of the platinum group, has four crystal modifications and does not tarnish at normal temperatures, but does oxidize explosively. Ruthenium dissolves in fused alkalis, is not attacked by acids but is attacked by halogens at high temperatures. 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.

This metal can be plated either through electrodeposition or by thermal decomposition methods. One ruthenium-molybdenum alloy has been found to be superconductive at 10.6 K. The oxidation states of ruthenium range from +1 to +8, and -2 is known, though oxidation states of +2, +3, and +4 are most common.

Isotopes

Naturally occurring ruthenium is composed of seven isotopes. The most stable radioisotopes 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.

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

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 mode after is rhodium.

Applications

Due to its highly effective ability to harden platinum and palladium, ruthenium is used in Pt and Pd alloys to make severe wear-resistant electrical contacts. It is sometimes alloyed with gold in jewelry.

0.1% ruthenium is added to titanium to improve its corrosion resistance a hundredfold.

Ruthenium is also a versatile catalyst: Hydrogen sulfide can be split by light by using an aqueous suspension of Cd S particles loaded with ruthenium dioxide. This may be useful in the removal of H₂S from oil refineries and from 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.

Ruthenium will also be used in some advanced high-temperature single-crystal superalloys, with applications including the turbine blades in jet engines.

Ruthenium red, [(NH₃)₅Ru-O-Ru(NH₃)₄-O-Ru(NH₃)₅]⁶⁺, is a biological stain used to visualize polyanionic areas of membranes.

Fountain pen nibs are frequently tipped with alloys containing ruthenium. From 1944 onward, the famous Parker 51 fountain pen was outfitted with the "RU" nib, a 14K gold nib tipped with 96.2% ruthenium, 3.8% iridium.

Compounds

Ruthenium compounds are often similar in properties to those of osmium and exhibit at least eight oxidation states, but the +2, +3, and +4 states are the most common.

See also Ruthenium compounds.

Organometallic chemistry

It is quite easy to form compounds with carbon ruthenium bonds, these compounds tend to be darker and react more quickly than the osmium compounds. Recently Prof Tony Hill and his co-workers have been making compounds of ruthenium in which a boron atom binds to the metal atom.

The organometallic ruthenium compound that is easiest to make is RuHCl(CO)(PPh₃)₃. This compound has two forms (yellow and pink) that are identical once they are dissolved but different in the solid state.

An organometallic compound similar to ruthenocene, bis(2,4-dimethylpentadienyl)ruthenium, is readily synthesized in near quantitative yields and has applications in vapor-phase deposition of metallic ruthenium, as well as in catalysis, including Fischer-Tropsch synthesis of transportation fuels.

Important catalysts based on ruthenium are Grubbs' catalyst and Roper's complex.

Precautions

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.

References
ISBN links support NWE through referral fees

Los Alamos National Laboratory – Ruthenium

External links

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