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Naked d-orbital in a centrochiral Ni(II) complex as a catalyst for asymmetric [3+2] cycloaddition
Yoshihiro Sohtome1,2, Genta Nakamura1,3, Atsuya Muranaka2,4
1Synthetic Organic Chemistry Laboratory, RIKEN, Wako, Saitama, 351-0198, Japan.
Nature Communications
|April 7, 2017
Summary
This study reveals how a chiral nickel catalyst activates substrates in asymmetric synthesis. The catalyst's electronic structure and a cooperative mechanism involving its orbitals and ligands are key to its function.
Area of Science:
- Organometallic Chemistry
- Asymmetric Catalysis
- Reaction Mechanisms
Background:
- Chiral metal catalysts are crucial for asymmetric transformations.
- Understanding catalyst electronic structure's role in substrate activation is limited.
Purpose of the Study:
- Investigate the catalytic activation process in Ni(II)-catalyzed asymmetric [3+2] cycloaddition.
- Elucidate the link between electronic structure and catalytic activity.
Main Methods:
- Empirical approach using electron density distribution analysis.
- Solid and solution state analyses.
- Theoretical calculations.
Main Results:
- Distorted Ni(II) center creates a partially 'naked' dz² orbital.
- Labile acetate ligand coordinates via electrostatic interaction.
- Electron-deficient dz² orbital and acetate cooperatively deprotonate α-ketoesters, forming a Ni(II)-enolate.
Conclusions:
- Electronic structure of the Ni(II) complex directly correlates with catalytic activity.
- A cooperative mechanism involving enolate binding and outer-sphere hydrogen bonding activation is proposed.