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.