Chlorobis(ethylene)rhodium (I) dimer
[CAS# 12081-16-2]

Identification

• Classification: Organic raw materials >> Organometallic compound >> Organic rhodium
• Name: Chlorobis(ethylene)rhodium (I) dimer
• Synonyms: mu-Dichlorotetraethylene dirhodium(I)
• Molecular Formula: C₈H₁₆Cl₂Rh₂
• Molecular Weight: 388.93
• CAS Registry Number: 12081-16-2
• EC Number: 235-145-0
• SMILES: C=C.C=C.C=C.C=C.[Cl-].[Cl-].[Rh].[Rh]

Safety Data

• Hazard Symbols: GHS07 Warning
• Risk Statements: H315-H319
• Safety Statements: P264-P264+P265-P280-P302+P352-P305+P351+P338-P321-P332+P317-P337+P317-P362+P364

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Skin irritation	Skin Irrit.	2	H315
Eye irritation	Eye Irrit.	2	H319

Discovery and Applications

Chlorobis(ethylene)rhodium(I) dimer is an organometallic complex with the chemical formula [RhCl(C₂H₄)₂]₂. It consists of two rhodium(I) centers bridged by chloride ligands, each rhodium atom being coordinated by two ethylene (C₂H₄) ligands. The compound is typically a red-orange crystalline solid that is soluble in common organic solvents such as benzene and dichloromethane.

This complex was first synthesized and characterized in the mid-20th century during the exploration of rhodium’s coordination chemistry, especially with unsaturated hydrocarbons like ethylene. It played a key role in advancing the understanding of transition metal-alkene bonding and catalysis. X-ray crystallography confirmed its dimeric structure, featuring square planar rhodium centers bridged by two chloride ligands.

Chlorobis(ethylene)rhodium(I) dimer is commonly prepared by treating rhodium(I) chloride complexes with ethylene gas under controlled pressure and temperature, often starting from rhodium trichloride or other rhodium precursors reduced under ethylene atmosphere. The synthesis typically involves substitution of ligands by ethylene molecules and formation of the chloride-bridged dimer.

The complex serves as a versatile precursor in homogeneous catalysis. It is used to generate active rhodium catalysts for reactions such as olefin hydrogenation, hydroformylation, and carbon-carbon coupling. The coordinated ethylene ligands can be displaced by other ligands (e.g., phosphines or carbonyls), allowing formation of diverse rhodium species tailored for specific catalytic functions.

In addition to catalysis, chlorobis(ethylene)rhodium(I) dimer is employed in mechanistic studies of alkene coordination and activation at transition metal centers. It is valuable in the development of new catalytic processes and organometallic methodologies.

Handling requires care due to the toxicity and air sensitivity of rhodium(I) complexes. The compound should be stored under inert atmosphere and handled with appropriate personal protective equipment in a well-ventilated laboratory environment.

In summary, chlorobis(ethylene)rhodium(I) dimer is a fundamental rhodium(I) organometallic complex with two ethylene ligands and bridging chloride atoms. It is an important catalyst precursor and model compound in the study and application of rhodium-mediated homogeneous catalysis.

References

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