Difference between revisions of "Ruthenium" - New World Encyclopedia

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

Revision as of 20:11, 7 November 2006

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

Ruthenium is classified as a transition metal. In the periodic table, it lies in period 5 just ahead of rhodium and palladium and is closely related to the latter two elements. In addition, it is situated in group 8 (former group 8B), between iron and osmium.

A hard, white metal, ruthenium does not tarnish at normal temperatures, but under certain conditions it oxidizes explosively. It has four crystal modifications. It is a member of the platinum group and is relatively inert. It is not attacked by acids but dissolves in fused (molten) alkalis. Halogens can attack it at high temperatures. Small amounts of ruthenium can increase the hardness of platinum and palladium. Also, the corrosion resistance of titanium can be increased markedly by adding a small amount of ruthenium.

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

Isotopes

Seven stable isotopes of ruthenium have been found in nature: ⁹⁶Ru, ⁹⁸Ru, ⁹⁹Ru, ¹⁰⁰Ru, ¹⁰¹Ru, ¹⁰²Ru, and ¹⁰⁴Ru. Among the radioactive isotopes, the three with the longest half-lives 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. Many other radioactive isotopes are known, with atomic mass numbers ranging from 87 to 120, but their half-lives are much shorter.

Applications

Ruthenium is a highly effective hardener in alloys with platinum and palladium, and such alloys are used to make electrical contacts that are resistant to severe wear.

It is sometimes alloyed with gold in jewelry.

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

For wear resistance, fountain pen nibs are often tipped with alloys containing ruthenium. For instance, from 1944 onward, the famous Parker 51 fountain pen was outfitted with the "RU" nib, a 14-carat gold nib tipped with 96.2% ruthenium, 3.8% iridium.

Ruthenium and its compounds are versatile catalysts. For instance, hydrogen sulfide (H₂S) can be split by light in the presence of an aqueous suspension of cadmium sulfide (CdS) particles loaded with ruthenium dioxide. This may be a useful method of removing H₂S from oil refining and other industrial processes.

Organometallic complexes of ruthenium (carbene and allenylidene complexes) have recently been found as highly efficient catalysts for certain chemical reactions (called olefin metathesis) that have important applications in organic and pharmaceutical chemistry.

Recently, large organometallic complexes of ruthenium have been found to exhibit anti-tumor activity, and a new group of anti-cancer medicines is now in the stage of clinical trials.

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

Some ruthenium complexes absorb light throughout the visible spectrum and are being actively studied for their potential in solar energy technologies.

Ruthenium may also be used in advanced, high-temperature, single-crystal superalloys, with applications that include the turbine blades of jet engines.

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 compounds

Ruthenium readily forms organometallic compounds in which its atoms are directly bonded to carbon atoms. These compounds tend to be darker and react more quickly than osmium compounds.

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

An organometallic compound called bis(2,4-dimethylpentadienyl)ruthenium can be readily synthesized at high yields and can be used for the vapor-phase deposition of metallic ruthenium and to catalyze chemical reactions (including the Fischer-Tropsch synthesis of transportation fuels).

Grubbs' catalyst and Roper's complex are two of the important organometallic catalysts based on ruthenium.

Precautions

Ruthenium plays no known biological role but it strongly stains human skin. It may be carcinogenic and may bioaccumulate in bone. The compound ruthenium tetroxide (RuO₄), similar to osmium tetroxide, is highly toxic and may explode.

References
ISBN links support NWE through referral fees

Los Alamos National Laboratory – Ruthenium
Greenwood, N. N.; & Earnshaw, A. (1997). Chemistry of the Elements, 2nd Ed., Oxford: Butterworth-Heinemann. ISBN 0-7506-3365-4.
Cotton, S. A. (1997). Chemistry of the Precious Metals. Chapman&Hall. ISBN 0-7514-0413-6.
Canterford, J. H.; & Colton, R. (1968). Halides of the Second and Third Row Transition Metals. London: Wiley-Interscience.

External links

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@@ Line 114: / Line 114: @@
 ''See also [[:category:Ruthenium compounds|Ruthenium compounds]].''
-== Organometallic chemistry ==
+== Organometallic compounds ==
-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.
+Ruthenium readily forms organometallic compounds in which its atoms are directly bonded to carbon atoms. These compounds tend to be darker and react more quickly than [[osmium]] compounds.
-The [[organometallic]] ruthenium compound that is easiest to make is RuHCl(CO)(PPh<sub>3</sub>)<sub>3</sub>. This compound has two forms (yellow and pink) that are identical once they are dissolved but different in the solid state.
+The ruthenium [[organometallic]]* compound easiest to make is RuHCl(CO)(PPh<sub>3</sub>)<sub>3</sub>. This compound has two forms (yellow and pink) that are identical when in solution 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.
+An [[organometallic]]* compound called bis(2,4-dimethylpentadienyl)ruthenium can be readily synthesized at high yields and can be used for the vapor-phase deposition of metallic ruthenium and to catalyze chemical reactions (including the [[Fischer-Tropsch synthesis]]* of transportation fuels).
-Important [[catalyst]]s based on ruthenium are [[Grubbs' catalyst]] and [[Roper's complex]].
+[[Grubbs' catalyst]]* and [[Roper's complex]]* are two of the important organometallic [[catalyst]]s based on ruthenium.
 == Precautions ==
-The compound [[ruthenium tetroxide]], RuO<sub>4</sub>, similar to [[osmium tetroxide]], is highly [[toxic]] and may explode. Ruthenium plays no biological role but does strongly stain human skin, may be [[carcinogen]]ic and [[bio-accumulate]]s in bone.
+Ruthenium plays no known biological role but it strongly stains human skin. It may be [[carcinogen]]ic and may [[bioaccumulate]]* in bone. The compound [[ruthenium tetroxide]]* (RuO<sub>4</sub>), similar to [[osmium tetroxide]]*, is highly [[toxic]]* and may explode.
 ==References==
 *[http://periodic.lanl.gov/elements/44.html Los Alamos National Laboratory &ndash; Ruthenium]
+*{{cite book | author=Greenwood, N. N.; & Earnshaw, A. |
+title=Chemistry of the Elements | edition=2nd Ed. |
+location=Oxford | publisher=Butterworth-Heinemann | year=1997 | id=ISBN 0-7506-3365-4}}
+*{{cite book | author=Cotton, S. A. | title=Chemistry of the Precious Metals | publisher=Chapman&Hall | year=1997 | id=ISBN 0-7514-0413-6}}
+*{{cite book | author=Canterford, J. H.; & Colton, R. | title=Halides of the Second and Third Row Transition Metals | location=London | publisher=Wiley-Interscience | year=1968}}
 == External links ==