Ruthenium trichloride
[CAS# 10049-08-8]

Identification

• Classification: Inorganic chemical industry >> Inorganic salt >> Metal halides and halides >> Metal chlorides and salts
• Name: Ruthenium trichloride
• Synonyms: trichlororuthenium
• Molecular Formula: RuCl₃
• Molecular Weight: 207.43
• CAS Registry Number: 10049-08-8
• EC Number: 233-167-5
• SMILES: Cl[Ru](Cl)Cl

Properties

• Density: 3.11 g/mL
• Melting point: 500 °C
• Water solubility: INSOLUBLE

Safety Data

• Hazard Symbols: GHS05;GHS07;GHS09 Danger
• Risk Statements: H290-H302-H314-H318-H411-H412
• Safety Statements: P234-P260-P264-P264+P265-P270-P273-P280-P301+P317-P301+P330+P331-P302+P361+P354-P304+P340-P305+P354+P338-P316-P317-P321-P330-P363-P390-P391-P405-P406-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Skin corrosion	Skin Corr.	1B	H314
Acute toxicity	Acute Tox.	4	H302
Serious eye damage	Eye Dam.	1	H318
Chronic hazardous to the aquatic environment	Aquatic Chronic	2	H411
Chronic hazardous to the aquatic environment	Aquatic Chronic	3	H412
Substances or mixtures corrosive to metals	Met. Corr.	1	H290
Chronic hazardous to the aquatic environment	Aquatic Chronic	4	H413
Skin corrosion	Skin Corr.	1A	H314
Chronic hazardous to the aquatic environment	Aquatic Chronic	1	H410
Acute hazardous to the aquatic environment	Aquatic Acute	1	H400
Skin corrosion	Skin Corr.	1C	H314
Specific target organ toxicity - single exposure	STOT SE	3	H335
Acute toxicity	Acute Tox.	3	H301

• Transport Information: UN 3260

Discovery and Applications

Ruthenium trichloride is an inorganic compound with the formula RuCl₃, commonly encountered as its hydrate, RuCl₃·xH₂O. It consists of ruthenium in the +3 oxidation state coordinated by three chloride ligands. The compound is a dark reddish-brown to black solid, highly soluble in water and various organic solvents. Ruthenium trichloride is a foundational compound in the chemistry of ruthenium and serves as a precursor to a wide range of ruthenium coordination complexes and organometallic compounds.

The earliest documented studies of ruthenium trichloride date back to the 19th century, following the isolation of ruthenium as an element in 1844 by Karl Ernst Claus. As part of systematic investigations into the platinum group elements, the various oxidation states and halides of ruthenium, including RuCl₃, were synthesized and characterized. The hydrated form of ruthenium trichloride has been more commonly used and studied due to its solubility and ease of handling.

Commercially available ruthenium trichloride is typically obtained as a hydrate, produced by dissolving ruthenium metal or ruthenium dioxide (RuO₂) in hydrochloric acid, often with the aid of an oxidizing agent such as chlorine gas. The resulting aqueous solution contains RuCl₃·xH₂O, which can be isolated by evaporation. The exact number of water molecules varies, and the hydrate is often a mixture rather than a single well-defined compound.

In solid state, anhydrous RuCl₃ adopts a layered structure similar to that of chromium trichloride, with each ruthenium atom octahedrally coordinated by six chloride ions. The compound exhibits interesting magnetic properties and has been the subject of research in solid-state physics and materials chemistry, particularly in relation to low-dimensional magnetic systems and potential quantum materials.

Ruthenium trichloride has broad utility in chemical synthesis. It is a key starting material for the preparation of numerous ruthenium(III), ruthenium(II), and ruthenium(IV) complexes. For example, it reacts with various phosphine, nitrogen, and carbonyl ligands to form stable coordination complexes used in catalysis and inorganic research. Among these, compounds such as [RuCl₂(PPh₃)₃] and [RuCl₂(DMSO)₄] are prepared from RuCl₃ and used as precursors in homogeneous catalytic systems.

In catalysis, ruthenium trichloride is used directly or indirectly in several types of reactions, including hydrogenation, oxidation, and olefin metathesis. The compound is a precursor to Grubbs-type catalysts and other ruthenium-based complexes that catalyze the formation of carbon–carbon double bonds. It is also involved in the synthesis of compounds used for water oxidation, a critical step in artificial photosynthesis.

Ruthenium trichloride has been studied for applications in electrochemical systems and materials science. It has been used to prepare ruthenium-containing thin films, mixed oxides, and electrode materials with potential applications in catalysis, energy storage, and fuel cells. In these applications, RuCl₃ often serves as the soluble ruthenium source for deposition or high-temperature conversion processes.

Characterization of ruthenium trichloride and its derivatives is typically done by a combination of techniques including UV-visible spectroscopy, infrared spectroscopy, X-ray diffraction, and nuclear magnetic resonance spectroscopy. The oxidation state of ruthenium and the ligand environment can be tailored by reactions involving RuCl₃, allowing for fine control of complex properties.

Ruthenium trichloride must be handled with care, as ruthenium compounds can be toxic and may pose risks upon inhalation, ingestion, or skin contact. Appropriate safety measures include the use of gloves, lab coats, and working under a fume hood. Waste materials containing ruthenium must be disposed of in accordance with hazardous waste regulations.

In summary, ruthenium trichloride is a versatile compound widely used in the preparation of ruthenium complexes and catalysts. Its role as a precursor in coordination and organometallic chemistry, as well as in materials science, underpins its importance in both fundamental research and industrial applications.

References

2010. Ruthenium-Catalyzed Synthesis of Functional Conjugated Dienes via Addition of Two Carbene Units to Alkynes. Journal of the American Chemical Society, 132(18).
DOI: 10.1021/ja101064b

2019. Synthesis, structure and biological evaluation of ruthenium(III) complexes of triazolopyrimidines with anticancer properties. Journal of biological inorganic chemistry : JBIC : a publication of the Society of Biological Inorganic Chemistry, 24(8).
DOI: 10.1007/s00775-019-01743-5

2000. Ruthenium-based compounds and tumour growth control (review). International Journal of Oncology, 17(2).
DOI: 10.3892/ijo.17.2.353