Metal clusters in catalysis: Hydrocarbon reactions
K G Caulton1, M G Thomas, B A Sosinsky
1Department of Chemistry, Indiana University, Bloomington, Ind., 47401.
Summary
Metal carbonyl clusters, including ruthenium, osmium, and iridium, were tested as catalysts for hydrocarbon reactions. While ineffective for hydrogenation, they showed activity in H-D exchange, skeletal rearrangements, and isomerization of hexenes.
Area of Science:
- Organometallic Chemistry
- Catalysis
- Hydrocarbon Transformations
Background:
- Metal carbonyl clusters are versatile compounds with potential catalytic applications.
- Understanding their activity in various hydrocarbon reactions is crucial for developing new catalytic processes.
Purpose of the Study:
- To evaluate the catalytic performance of ruthenium, osmium, and iridium carbonyl clusters in a range of hydrocarbon reactions.
- To compare the activity and selectivity of these clusters for skeletal rearrangement, metathesis, dehydrogenation, hydrogenation, isomerization, and H-D exchange.
Main Methods:
- Synthesis and characterization of ruthenium(3) carbonyl, osmium(3) carbonyl, and iridium(4) carbonyl clusters.
- Testing catalytic activity in hydrocarbon reactions under varying temperature conditions.
- Analysis of reaction products to determine conversion, selectivity, and reaction mechanisms.
Main Results:
- None of the clusters were effective hydrogenation catalysts for olefins.
- Osmium(3) carbonyl catalyzed H-D exchange with benzene at 195°C, while ruthenium(3) carbonyl required higher temperatures.
- Iridium(4) carbonyl effectively converted cyclohexadiene to cyclohexene and benzene.
- Ruthenium and osmium clusters catalyzed linear hexene isomerization, with ruthenium being more active.
- Osmium and iridium clusters induced skeletal reactions of 2-hexene at high temperatures.
Conclusions:
- Metal carbonyl clusters exhibit varied catalytic activities depending on the metal and reaction type.
- These clusters are not generally suitable for olefin hydrogenation but show promise in H-D exchange and skeletal rearrangement reactions.
- Further research into tuning cluster properties could lead to more efficient hydrocarbon transformations.
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