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Accessing Valuable Ligand Supports for Transition Metals: A Modified, Intermediate Scale Preparation of 1,2,3,4,5-Pentamethylcyclopentadiene
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Potential energy surface for (retro-)cyclopropanation: metathesis with a cationic gold complex
Alexey Fedorov1, Laurent Batiste, Andreas Bach
1Laboratorium für Organische Chemie, ETH Zürich, Wolfgang-Pauli-Strasse 10, CH-8093 Zürich, Switzerland.
Journal of the American Chemical Society
|June 24, 2011
Summary
Quantum-chemical calculations explain gold-ylidene reactions with olefins. A deep potential minimum clarifies cyclopropanation and metathesis, including gas-phase rates and solution-phase retro-cyclopropanation.
Area of Science:
- Organometallic Chemistry
- Computational Chemistry
- Reaction Mechanisms
Background:
- Ligand-supported gold arylidenes exhibit cyclopropanation and metathesis reactivity with electron-rich olefins.
- Understanding these reaction pathways is crucial for catalyst design and mechanistic elucidation.
Purpose of the Study:
- To elucidate the gas-phase cyclopropanation and metathesis mechanisms of gold arylidenes using quantum-chemical calculations.
- To correlate theoretical findings with experimental observations, including electronic effects and product ratios.
Main Methods:
- Density Functional Theory (DFT) calculations were employed to map the potential energy surface.
- Analysis of transition states and intermediates to determine rate-determining steps.
Main Results:
- A deep potential minimum for a metal-bound cyclopropane adduct was identified, aligning with experimental energies.
- Gas-phase cyclopropanation is limited by Lewis-acidic metal fragment dissociation.
- Metathesis pathway involves multiple rate-limiting transition states near product dissociation.
Conclusions:
- The calculated potential energy surface accurately explains observed gas-phase and solution-phase reactivities.
- Electronic effects of arylidenes and phosphorus ylid ligands influence product distributions.
- The study provides a comprehensive mechanistic understanding of gold-catalyzed cyclopropanation and metathesis.
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