ruthenium

ruthenium
Name	ruthenium
Number	44
Category	transition metal
Appearance	silvery white metallic
Standard atomic weight	101.07(2)
Electron configuration	[Kr] 4d7 5s1
Phase	solid
Melting point K	2607
Boiling point K	4423
Density gpcm3	12.45
Oxidation states	−4, −2, 0, +1, +2, +3, +4, +5, +6, +7, +8
Crystal structure	hexagonal close-packed

ruthenium. A hard, silvery-white member of the platinum group metals, it is a rare transition metal found in period 5 of the periodic table. Discovered in the mid-19th century, it is prized for its remarkable corrosion resistance and its ability to harden other metals like platinum and palladium. While not abundant, it plays critical roles in advanced industrial applications, from wear-resistant electrical contacts to sophisticated catalysts in the chemical industry.

Properties

Ruthenium possesses a high melting point, exceeded among the platinum group metals only by osmium and iridium. It is unaffected by aqua regia at room temperature but dissolves in molten alkalis and reacts with halogens at elevated temperatures. The metal exhibits a wide range of oxidation states, with the +4 state being particularly stable and common in its coordination chemistry. Its hexagonal close-packed crystal structure contributes to its hardness and brittleness, though it becomes more ductile when very pure. Ruthenium is a versatile catalyst, often used in processes like the Haber process for ammonia synthesis and various hydrogenation reactions in organic chemistry.

History

The discovery of ruthenium is credited to Karl Ernst Claus, a Baltic German scientist working at Kazan University in the Russian Empire in 1844. He isolated the new element from residues left after dissolving crude platinum from the Ural Mountains in aqua regia. Claus named the element after Ruthenia, a historical region encompassing parts of modern Ukraine, Belarus, and Russia. Earlier, in 1827, Jöns Jacob Berzelius and Gottfried Osann had examined similar residues from Tartu University but could not definitively identify the new metal. Claus's meticulous work, published in the Saint Petersburg Academy of Sciences, secured his priority and the element's place on the periodic table.

Occurrence and production

Ruthenium is one of the rarest elements in the Earth's crust, typically found alloyed with other platinum group metals in specific geological formations. Primary sources include nickel and copper sulfide ores from the Sudbury Basin in Canada and the Norilsk complex in Siberia. It is also obtained as a by-product from platinum ore mined in the Bushveld Igneous Complex in South Africa and the Great Dyke in Zimbabwe. Commercial production involves complex extraction and refining processes, often beginning with the collection of anode slimes from electrorefining of nickel and copper. Subsequent steps employ techniques like solvent extraction and ion exchange to separate ruthenium from its sister metals like osmium, rhodium, and iridium.

Applications

Major uses of ruthenium exploit its hardness, stability, and catalytic properties. Small additions significantly increase the corrosion resistance and wearability of titanium alloys and platinum jewelry. In electronics, thin films are sputtered onto hard disk drive platters to increase data storage density. Ruthenium-based compounds are pivotal in the chlorine industry for the anodes in the chloralkali process. The Grubbs' catalyst, developed by Robert H. Grubbs, revolutionized olefin metathesis in polymer chemistry and pharmaceuticals, earning the Nobel Prize in Chemistry. Emerging applications include its use in dye-sensitized solar cells and as a potential replacement for copper in advanced semiconductor interconnects.

Biological role and precautions

Ruthenium has no known biological role in any organism. However, certain ruthenium complexes are under intense investigation in medicinal chemistry as potential anticancer agents, with some entering clinical trials; these compounds, such as those studied at the University of Edinburgh, can interact with DNA and induce apoptosis. Metallic ruthenium is generally considered inert and low in toxicity, but its powder and certain volatile compounds, like ruthenium tetroxide, are hazardous. Ruthenium tetroxide is a strong oxidizer and highly toxic if inhaled, requiring handling in specialized fume hoods under protocols established by organizations like the Occupational Safety and Health Administration.

Chemical compounds

Ruthenium forms a diverse array of chemical compounds across multiple oxidation states. Ruthenium(IV) oxide is a conductive material used in thick-film resistors. The brightly colored compound ruthenium red is a histological stain used to visualize pectin in plant cell walls and glycosaminoglycans in animal tissues. Organoruthenium chemistry is rich, with complexes like cyclopentadienyl derivatives and carbonyl clusters being widely studied. Perruthenate and ruthenate ions are powerful oxidizing agents in organic synthesis. The compound ruthenocene, analogous to ferrocene, is a staple in organometallic chemistry research at institutions like the California Institute of Technology.

Category:Chemical elements Category:Transition metals Category:Platinum group metals