Properties and Overview of Ruthenium

Overview:

Ruthenium (Ru) is a rare, silver-white metal with the atomic number 44 and the symbol Ru. It is one of the transition metals in Group 8 of the periodic table. It is part of the platinum group metals (PGMs), including platinum, palladium, rhodium, osmium, and iridium. Discovered in 1844 by the Russian scientist Karl Ernst Claus, ruthenium was named after "Ruthenia," the Latin name for Russia, reflecting the region where it was first isolated. Ruthenium is among the rarest elements in the Earth's crust, with an average concentration of about 0.001 parts per million. It is typically found in ores containing other platinum group metals, particularly in South Africa, Russia, and North America deposits. Physically, ruthenium is a hard, brittle metal with a high melting point of 2,334°C and a boiling point of 4,150°C. It has a density of 12.45g/cm³, comparable to other platinum group metals but less dense than osmium and iridium. Ruthenium has a hexagonal close-packed (hcp) crystal structure, contributing to its hardness and brittleness. The metal is resistant to corrosion and oxidation, even at high temperatures, a characteristic feature of noble metals. Ruthenium's resistance to chemical attack by acids and other chemicals makes it particularly valuable in applications where durability and longevity are critical.
Chemically, ruthenium exhibits a range of oxidation states, from -2 to +8, with +2, +3, and +4 being the most common in its compounds. Its versatility in its oxidation states allows ruthenium to form various chemical compounds, including oxides, chlorides, and organometallic complexes. Ruthenium is notable for its ability to form stable complexes with ligands, which is valuable in catalysis and materials science. One of the most well-known ruthenium compounds is ruthenium(III) chloride (RuCl₃), which is used as a precursor in the synthesis of various ruthenium-based catalysts. Additionally, ruthenium forms several oxides, such as ruthenium dioxide (RuO₂), which is known for its hardness and electrical conductivity and is used in resistors and electrical contacts. Ruthenium also forms complexes with carbon monoxide and other ligands, making it a versatile catalyst in organic synthesis, particularly in hydrogenation, oxidation, and olefin metathesis reactions.
Safety considerations regarding ruthenium depend primarily on the form in which it is encountered. As a metal, ruthenium is relatively inert and poses minimal health risks under normal handling conditions. However, some of its compounds, particularly ruthenium tetroxide (RuO₄), are highly toxic and volatile. Ruthenium tetroxide is a powerful oxidizing agent and can cause severe respiratory irritation, skin burns, and eye damage upon contact. It is highly reactive and can explode upon contact with organic materials or reducing agents. Therefore, strict safety precautions must be taken when working with ruthenium compounds, including the use of appropriate personal protective equipment (PPE), such as gloves, safety goggles, and fume hoods. It is also essential to handle ruthenium tetroxide in well-ventilated areas to prevent inhalation of its fumes. Due to certain ruthenium compounds' potential toxicity and reactivity, handling and disposal must comply with relevant safety regulations and guidelines.

Production:

Ruthenium is primarily obtained as a byproduct of the mining and refining other platinum group metals, particularly platinum and palladium. The extraction process involves several steps, including crushing and grinding the ore, followed by froth flotation to concentrate the metal content. Ruthenium and other PGMs are then separated from the base metals using various chemical and physical processes, such as precipitation, solvent extraction, and ion exchange. The final purification step involves electrorefining or chemical reduction to produce pure ruthenium metal. Due to the complex and multi-step nature of its extraction, ruthenium is produced in relatively small quantities, with annual global production estimated to be around 20 to 30 metric tons.

Applications:

Ruthenium has a variety of industrial and technological applications driven by its unique chemical and physical properties. One of the primary uses of ruthenium is as a catalyst in chemical reactions. Ruthenium-based catalysts are employed in a wide range of industrial processes, including ammonia production through the Haber-Bosch process, hydrogenation reactions, and the oxidation of alcohols to aldehydes or ketones. In addition to its role in catalysis, ruthenium is also used in the electronics industry, where its compounds are employed in producing thick-film resistors and electrical contacts. Ruthenium dioxide (RuO₂), in particular, is valued for its high electrical conductivity and durability, making it ideal for use in resistors, electrical contacts, and chip resistors.
In materials science, ruthenium is used as an alloying agent to improve other metals' hardness, corrosion resistance, and wear resistance, particularly platinum and palladium. Small amounts of ruthenium are added to platinum to enhance its hardness and durability, which is particularly useful in applications such as jewelry, thermocouples, and electrodes. Ruthenium is also used in producing superalloys, which are employed in high-temperature applications such as jet engines and gas turbines due to their ability to maintain strength and resist oxidation at elevated temperatures.
Ruthenium also finds applications in the emerging field of nanotechnology, where it is used to produce thin-film coatings for data storage devices such as hard disk drives. These thin films help increase the storage density of hard disks by improving the magnetic properties of the recording medium. Additionally, ruthenium complexes are being explored for use in dye-sensitized solar cells, which serve as light-absorbing dyes to enhance solar energy conversion efficiency.

Summary:

Ruthenium is a rare, silver-white transition metal known for its hardness, corrosion resistance, and versatility in chemical reactions. Its ability to form various compounds with various oxidation states makes it valuable in catalysis and materials science. While generally safe as a metal, certain ruthenium compounds, particularly ruthenium tetroxide, are highly toxic and require careful handling. Ruthenium is primarily produced as a byproduct of platinum and palladium refining and has a range of applications in catalysis, electronics, materials science, and nanotechnology. The unique properties of ruthenium continue to drive interest in its use in advanced technologies and industrial processes.

See a comprehensive list of atomic, electrical, mechanical, physical and thermal properties for ruthenium below: