Ruthenium

ruthenium is a chemical element with atomic number 44 located in group 8 of the periodic table of elements. Its symbol is Ru. It is a rare transition metal of the platinum group. It is commonly found in platinum mines and is used as a catalyst in some platinum alloys.

It is a rare transition metal that belongs to the platinum group of the periodic table of elements. Like the other platinum group metals, ruthenium is inert to most other chemicals. Russian-born scientist of Baltic-German descent Karl Ernst Claus discovered the element in 1844 at Kazan State University and named it ruthenium after Russia. Ruthenium is generally found as a minor component of platinum ores; annual production has increased from around 19 tonnes in 2009 to around 35.5 tonnes in 2017. Most of the ruthenium produced is used in wear-resistant electrical contacts and thick-film resistors. A minor application of ruthenium is in platinum alloys and as a chemical catalyst. A new application for ruthenium is as a protective coating for extreme ultraviolet photomasks. Ruthenium is generally found in ores with the other platinum group metals in the Ural Mountains and in North and South America. Small but commercially important quantities are also found in pentlandite mined from Sudbury, Ontario, and in pyroxenite deposits in South Africa.

Main features

Physical Properties

Crystals cultivated in the gaseous phase of metallic rust.

It is a hard and brittle white metal; It presents four different crystalline forms. It dissolves in molten bases, and is not attacked by acids at room temperature. At high temperatures it reacts with halogens and hydroxides. Palladium and platinum can be hardened with small amounts of ruthenium. Likewise, the addition of small amounts increases the corrosion resistance of titanium significantly. A superconducting ruthenium-molybdenum alloy has been found at 10.6 K.

The most common oxidation states are +2, +3, and +4. There are compounds in which it has an oxidation state from 0 to +8, and also -2. Ruthenium tetroxide, RuO₄ (oxidation state +8), is highly oxidizing, more so than the osmium analogue, and decomposes violently at high temperatures.

Chemical Properties

Ruthenium has four crystal modifications and does not tarnish in ambient conditions; oxidizes when heated to 800 °C (1070 K). Ruthenium dissolves in fused alkalis to give ruthenates (RuO2−
4), is not attacked by acids (even aqua regia) but is attacked by halogens at high temperatures. In fact, ruthenium is more easily attacked by oxidizing agents. Small amounts of ruthenium can increase the hardness of platinum and palladium. The corrosion resistance of titanium is greatly increased by the addition of a small amount of ruthenium. The metal can be plated by electroplating and by thermal decomposition. An alloy of ruthenium and molybdenum is known to be superconducting at temperatures below 10.6 K. Ruthenium is the only 4d transition metal that can assume the +8 group oxidation state, and even then it is less stable than Osmium, a heavier congener: This is the first group on the left of the table where the second and third row transition metals show striking differences in chemical behavior. Like iron but unlike osmium, ruthenium can form aqueous cations in its lower oxidation states of +2 and +3.

Ruthenium is first in a downward trend in melting and boiling points and enthalpy of atomization in the 4d transition metals after the maximum observed in molybdenum, because the 4d subshell is filled to more than half and the electrons contribute less to the metallic bond. Technetium, the element above, has an exceptionally low value that is out of trend due to its half-filled [Kr]4d⁵5s² configuration, although it is not as away from trending in the 4d series like manganese in the 3d series transition series. Unlike the lighter congener iron, ruthenium is paramagnetic at room temperature, since iron is also above its Curie point.

The reduction potentials in acidic aqueous solution for some common ruthenium ions are shown below:

Isotopes

Seven isotopes of ruthenium are found in nature. The most stable radioisotopes of ruthenium are ¹⁰⁶Ru, with a half-life of 373.59 days, ¹⁰³Ru with a half-life of 39.26 days, and ⁹⁷Ru, with 2.9 days.

Fifteen other radioisotopes with atomic weights from 89.93 amu (⁹⁰Ru) to 114.928 amu (¹¹⁵Ru) have been characterized. Most of these have half-lives of less than five minutes, except for ⁹⁵Ru (1.643 h) and ¹⁰⁵Ru (4.44 h).

The main decay mode of isotopes with A<102 (i.e., lower mass numbers than the more abundant isotope, ¹⁰²Ru) is electron capture, and for those with A>102 it is beta decay. The main product obtained for the former is technetium, while for the latter it is rhodium.

Presence

As the 78th most abundant element in the Earth's crust, ruthenium is relatively rare, found at about 100 parts per trillion. This element is generally found in minerals with the other platinum group metals in the Ural Mountains and in North and South America. Small but commercially important quantities are also found in pentlandite mined from Sudbury, Ontario Canada and in pyroxenite deposits in South Africa. The native form of ruthenium is a very rare mineral.

Applications

• Due to its great effectiveness to harden the palate and platinum, it is used in alloys of these metals used in electrical contacts with high wear resistance.
• It is incorporated into titanium as a alloy element to increase corrosion resistance. 0.1% improvement in a hundred times.
• Like other elements of the platinum group, it can be used as a catalyst in different processes. Hydrogen sulfide, H₂S, it can be broken down by the light using Ruthenium oxide in an aqueous suspension of CdS particles. This can be useful in removing H₂S of oil refineries and other industrial processes.
• Recently, it has been found that some organometallic compounds of Ruthenium have antitumoral activity.

History

Ruthenium (from medieval Latin Ruthenia, meaning "Russia") was discovered by Karl Ernst Claus in 1844. He observed that platinum oxide contained a new metal and he obtained six grams of ruthenium from the part of platinum that is insoluble in aqua regia.

Jöns Berzelius and Gottfried Osann nearly discovered it in 1827. They examined the residues left by dissolving a sample of platinum from the Urals with aqua regia. Osann thought that he had found three new metals, to which he gave names, one of them being ruthenium.

Polish chemist Jedrzej Sniadecki may have isolated this element in 1807, but this fact has not been confirmed.

Although natural platinum alloys containing all six platinum group metals were long used by pre-Columbian Americans and were known as a material by European chemists since the mid-century XVI, it was not until the middle of the XVIII century that platinum was identified as a pure element. That natural platinum contained palladium, rhodium, osmium, and iridium was discovered in the first decade of the 19th century. Platinum in the alluvial sands of Russian rivers gave access to the raw material for use in plaques and medals and for minting ruble coins, beginning in 1828. Residues from platinum production for minting were available in the Empire Russian and therefore most of the research on them was done in Eastern Europe.

Polish chemist Jędrzej Śniadecki may have isolated element 44, which he called "vestium" by the asteroid Vesta discovered shortly before, from South American platinum ores in 1807. He published an announcement of his discovery in 1808. His work, however, was never confirmed and he later withdrew the discovery claim from him.

Berzelius did not find any unusual metals, but Osann thought he found three new metals, which he named pluranium, ruthenium, and pollinium. This discrepancy led to a long-running controversy between Berzelius and Osann over the composition of the residues. As Osann was unable to repeat his isolation of ruthenium, eventually giving up his claims.

In 1844, Karl Ernst Claus a Russian scientist of Baltic German descent demonstrated that compounds prepared by Gottfried Osann contained small amounts of ruthenium, which Claus had discovered that same year. Claus isolated ruthenium from platinum residues of the ruble's production while working at Kazan University, Kazan, in the same way that its heavier congener, osmium, had been discovered four decades earlier. Claus showed that ruthenium oxide contained a new metal and obtained 6 grams of ruthenium from the part of crude platinum that is insoluble in aqua regia. In choosing the name for the new element, Claus stated: I named the new body, after my Motherland, ruthenium. He had every right to call it that because Mr. Osann gave up his ruthenium and the word doesn't exist in Chemistry yet. In doing so, Claus started a trend that continues to this day: naming an element after the name of a country.

Abundance and obtaining

It is found in few minerals and they are not commercial; in laurite, RuS₂, anduoite, RuOsAs2, platarsite, and in small amounts in pentlandite, (FeNi)₉S₈. This element is generally found together with others from the platinum group, in the Urals and in America, forming alloys.

The elements of the platinum group, which are normally together, are separated from each other through a series of chemical processes, different depending on how they are found, taking advantage of the chemical differences between each element.

After processing the minerals with aqua regia, the osmium and ruthenium that are not soluble in said mixture are separated. The ruthenium, in turn, is separated by reduction with alcohol as tetravalent oxide, which in turn is reduced with hydrogen. It is purified by distillation of ruthenium tetroxide at 100ºC.

Compounds

In its compounds, ruthenium presents several oxidation states, reaching +8, although the most common are +2, +3 and +4.

There are some similarities with the osmium compounds, in the same group, but the chemistry of both differs quite a bit from that of iron, also in the same group.

• Ruthenium tetroxide, Ruo₄, it is very oxidizing, rather than the ape analogue, and violently breaks down at high temperatures.
• Some Ru complexes⁺² and Ru⁺³ can be used in cancer treatments. For example, H(im)[RuCl₄(im)₂], being im = imidazole.

Precautions

Ruthenium tetroxide, RuO₄, similar to osmium tetroxide, is highly toxic and can explode. Ruthenium has no biological role, but it may be carcinogenic and can accumulate in bone.