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Bimetallic C-C Bond-Forming Reductive Elimination from Nickel
Hongwei Xu1, Justin B Diccianni1, Joseph Katigbak1
1Department of Chemistry, New York University , 100 Washington Square East, New York, New York 10003, United States.
Journal of the American Chemical Society
|March 24, 2016
Summary
This study directly observed bimolecular reductive elimination in nickel-catalyzed cross-coupling reactions. Distinct pathways were identified for sp(3)-sp(3) ethane and sp(2)-sp(2) biphenyl formation, clarifying key reaction mechanisms.
Area of Science:
- Organometallic Chemistry
- Catalysis
- Organic Synthesis
Background:
- Nickel-catalyzed cross-coupling reactions are vital in organic synthesis.
- Characterizing key steps like reductive elimination is challenging.
- Bimolecular pathways were proposed but lacked experimental support.
Purpose of the Study:
- To directly observe and characterize bimolecular reductive elimination in nickel catalysis.
- To elucidate the distinct mechanisms for sp(3)-sp(3) and sp(2)-sp(2) C-C bond formation.
- To provide experimental evidence for proposed bimolecular pathways.
Main Methods:
- Preparation of well-defined (pyridine-pyrrolyl)Ni monomethyl and monophenyl complexes.
- Direct observation of reductive elimination reactions.
- Kinetic studies involving oxidants and donor ligands.
Main Results:
- Direct observation of ethane (sp(3)-sp(3)) and biphenyl (sp(2)-sp(2)) formation via bimolecular reductive elimination.
- Oxidant-promoted Ni(III) dimerization is key for methyl coupling to ethane.
- Bidentate ligand coordination facilitates biphenyl formation.
Conclusions:
- The study provides direct experimental evidence for bimolecular reductive elimination in nickel catalysis.
- Distinct mechanistic pathways are operative for sp(3)-sp(3) and sp(2)-sp(2) couplings.
- Understanding these pathways advances the design and efficiency of cross-coupling reactions.
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