Ruthenium(III) chloride hydrate
[CAS# 14898-67-0]

Identification

• Classification: Inorganic chemical industry >> Inorganic salt >> Metal halides and halides >> Metal chlorides and salts
• Name: Ruthenium(III) chloride hydrate
• Synonyms: Ruthenium trichloride
• Molecular Formula: RuCl₃.xH₂O
• Molecular Weight: 207.43
• CAS Registry Number: 14898-67-0
• EC Number: 604-667-4
• SMILES: Cl[Ru](Cl)Cl.O

Properties

• Melting point: 100 °C (Decomposes) (Expl.)
• Water solubility: soluble

Safety Data

• Hazard Symbols: GHS05;GHS07;GHS09 Danger
• Risk Statements: H302-H314-H411
• Safety Statements: P260-P264-P270-P273-P280-P301+P312+P330-P301+P330+P331-P303+P361+P353-P304+P340+P310-P305+P351+P338+P310-P363-P391-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Serious eye damage	Eye Dam.	1	H318
Acute toxicity	Acute Tox.	4	H302
Substances or mixtures corrosive to metals	Met. Corr.	1	H290
Chronic hazardous to the aquatic environment	Aquatic Chronic	3	H412
Skin corrosion	Skin Corr.	1A	H314
Skin corrosion	Skin Corr.	1B	H314
Acute hazardous to the aquatic environment	Aquatic Acute	1	H400
Chronic hazardous to the aquatic environment	Aquatic Chronic	1	H410
Skin irritation	Skin Irrit.	2	H315
Chronic hazardous to the aquatic environment	Aquatic Chronic	2	H411

• Transport Information: UN 3260

Discovery and Applications

Ruthenium(III) chloride hydrate is a widely used inorganic compound with the general formula RuCl₃·xH₂O, where *x* typically ranges from 1 to 3 depending on the preparation method and storage conditions. It appears as a dark reddish-brown or maroon crystalline solid that is highly soluble in water and alcohols, forming dark red or brown solutions. This hydrate is the most common commercially available form of ruthenium(III) chloride and serves as an important starting material in ruthenium chemistry.

The anhydrous form, RuCl₃, is obtained by heating ruthenium metal or ruthenium dioxide in a stream of chlorine gas at elevated temperatures. However, the hydrate is more commonly prepared by dissolving the anhydrous compound in water or by reacting ruthenium metal with hydrochloric acid under oxidative conditions, often involving chlorine gas or other oxidizing agents. The precise composition of the hydrate can vary, and the compound often exists as a mixture of polymeric and monomeric species in aqueous solution.

Structurally, ruthenium(III) chloride hydrate is typically composed of octahedrally coordinated Ru³⁺ ions surrounded by chloride ligands and water molecules. In solution, RuCl₃·xH₂O can dissociate or hydrolyze to give a variety of species, including [Ru(H₂O)₆]³⁺, [RuCl₂(H₂O)₄]⁺, and [RuCl₆]³⁻, depending on pH and concentration. These species are often in equilibrium, contributing to the chemical versatility of the compound.

Ruthenium(III) chloride hydrate is extensively used as a precursor in the synthesis of a wide range of ruthenium complexes. These include catalysts, coordination compounds, and organometallic species with applications in organic synthesis, electrochemistry, and materials science. One of the most notable uses is in the preparation of Grubbs' catalysts, which are ruthenium-based complexes used in olefin metathesis reactions. In this context, RuCl₃·xH₂O is treated with phosphine ligands, alkylidene compounds, and other reagents to generate the active catalytic species.

In homogeneous catalysis, ruthenium(III) chloride hydrate is used as a precursor to various oxidation and hydrogenation catalysts. For example, in transfer hydrogenation reactions, RuCl₃·xH₂O can be converted to active complexes with ligands such as phosphines or N-heterocyclic carbenes that are capable of catalyzing the reduction of ketones and imines under mild conditions. Additionally, ruthenium catalysts derived from this hydrate are employed in the oxidation of alcohols, alkenes, and sulfides using environmentally friendly oxidants such as hydrogen peroxide or molecular oxygen.

The compound also plays a role in materials chemistry and nanotechnology. It has been used to prepare ruthenium nanoparticles and thin films, often through thermal decomposition or chemical reduction methods. These materials have applications in electronics, catalysis, and sensor technology. Furthermore, RuCl₃·xH₂O is used in the synthesis of conductive polymers and as a doping agent in the preparation of superconducting or semiconducting oxides.

In analytical chemistry, ruthenium(III) chloride hydrate is used in redox titrations and in the preparation of luminescent ruthenium complexes for spectroscopic and electrochemical studies. Certain ruthenium polypyridyl complexes derived from RuCl₃·xH₂O exhibit strong photoluminescence and are studied for use in solar cells, light-emitting devices, and biological imaging.

Although ruthenium(III) chloride hydrate is generally considered to have low toxicity, it should be handled with care due to the potential health risks associated with heavy metal exposure. It may cause irritation upon contact with the skin or eyes, and appropriate protective equipment should be used when handling the compound. Waste disposal should comply with local environmental regulations to prevent contamination.

In summary, ruthenium(III) chloride hydrate is a versatile and widely used compound in coordination and materials chemistry. Its ease of dissolution, reactivity with various ligands, and role as a precursor to numerous ruthenium complexes make it essential for research and industrial applications involving catalysis, materials development, and analytical methodologies.

References

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