Norbornadiene rhodium chloride dimer
[CAS# 12257-42-0]

Identification

• Classification: Organic raw materials >> Organometallic compound >> Organic rhodium
• Name: Norbornadiene rhodium chloride dimer
• Synonyms: Bis((mu-chloro)(norbornadiene)rhodium); Bis(chloro(eta4-norbornadiene)rhodium); Bis(mu-chloro)bis(norbornadiene)dirhodium; Bis(mu-chloro)bis[(norbornadiene)rhodium]; Bis[chloro(norbornadiene)rhodium]; Chloronorbornadiene rhodium dimer; Di-mu-chlorobis(norbornadiene)dirhodium; Di-mu-chlorobis(eta4-norbornadiene)dirhodium(I); Dichloro(norbornadiene)dirhodium; Dichlorobis(norbornadiene)dirhodium
• Molecular Formula: C₁₄H₁₆Cl₂Rh₂
• Molecular Weight: 460.99
• CAS Registry Number: 12257-42-0
• EC Number: 235-510-4
• SMILES: C1C2C=CC1C=C2.C1C2C=CC1C=C2.[Cl-].[Cl-].[Rh+2]

Properties

• Melting point: 240 °C (decomp) ^*

^* Baumgaertel, Otto

Safety Data

• Hazard Symbols: GHS02;GHS07 Danger
• Risk Statements: H228-H251-H302+H312+H332-H302-H312-H315-H319-H332-H335-H413
• Safety Statements: P210-P235-P240-P241-P261-P264-P264+P265-P270-P271-P273-P280-P301+P317-P302+P352-P304+P340-P305+P351+P338-P317-P319-P321-P330-P332+P317-P337+P317-P362+P364-P370+P378-P403+P233-P405-P407-P410-P413-P420-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Chronic hazardous to the aquatic environment	Aquatic Chronic	4	H413
Acute toxicity	Acute Tox.	4	H312
Acute toxicity	Acute Tox.	4	H332
Eye irritation	Eye Irrit.	2	H319
Acute toxicity	Acute Tox.	4	H302
Skin irritation	Skin Irrit.	2	H315

Discovery and Applications

Norbornadiene rhodium chloride dimer is an organometallic complex with the formula [RhCl(C₇H₈)]₂, where each rhodium(I) center is coordinated by a norbornadiene (bicyclo[2.2.1]hepta-2,5-diene) ligand and two chloride ligands bridge the two rhodium atoms. The compound typically appears as an orange to red crystalline solid that is soluble in common organic solvents such as dichloromethane and toluene.

This complex was first synthesized and characterized during investigations of rhodium(I) coordination chemistry in the mid-20th century, when researchers explored the bonding of unsaturated hydrocarbons like norbornadiene to transition metals. X-ray crystallography revealed the dimeric structure with two bridging chloride ligands and bidentate coordination of norbornadiene to each rhodium center in a square planar geometry, typical of d⁸ rhodium(I).

Norbornadiene rhodium chloride dimer is commonly prepared by reacting rhodium(III) chloride hydrate or rhodium trichloride complexes with norbornadiene under reducing conditions or by ligand substitution starting from other rhodium(I) precursors. The formation of the chloride-bridged dimer stabilizes the rhodium(I) centers and facilitates isolation of the complex.

The compound serves as an important precursor in homogeneous catalysis and organometallic synthesis. The coordinated norbornadiene ligands are labile and readily displaced by other ligands such as phosphines, amines, or olefins, allowing the generation of catalytically active monomeric rhodium species. These catalysts find applications in hydrogenation, hydroformylation, carbonylation, and carbon-carbon bond-forming reactions.

In addition, the complex is used in mechanistic studies to understand ligand substitution and catalytic cycles involving rhodium(I). Its solubility and stability make it valuable for preparative and research purposes in synthetic chemistry.

From a safety perspective, norbornadiene rhodium chloride dimer should be handled with care, as rhodium compounds can be toxic and may cause irritation. Use of gloves, eye protection, and working under a fume hood are recommended.

In summary, norbornadiene rhodium chloride dimer is a well-characterized, dimeric rhodium(I) complex with bridging chloride ligands and coordinated norbornadiene. It is widely employed as a catalyst precursor in organometallic chemistry and homogeneous catalysis due to its stability and ligand exchange properties.

References

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