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Preparation of SNS CobaltII Pincer Model Complexes of Liver Alcohol Dehydrogenase

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Chi Chen¹, Thomas R Dugan, William W Brennessel

¹Department of Chemistry, University of Rochester , 120 Trustee Road, Rochester, New York 14627, United States.

Journal of the American Chemical Society

|January 7, 2014

Summary

Researchers developed cobalt(II) catalysts that selectively isomerize simple alkenes to less stable Z-isomers. This breakthrough offers a new method for controlling stereochemistry in alkene synthesis.

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Area of Science:

Organometallic Chemistry
Catalysis
Stereoselective Synthesis

Background:

Alkene isomerization typically favors more stable E-isomers.
Selective synthesis of Z-alkenes is challenging due to thermodynamic preferences.

Purpose of the Study:

To develop a catalytic system for selective Z-alkene formation via isomerization.
To elucidate the mechanism of cobalt-catalyzed alkene isomerization.

Main Methods:

Utilized cobalt(II) catalysts with bulky β-diketiminate ligands.
Employed isotopic labeling experiments to study reaction intermediates.
Developed a steric model to explain stereoselectivity.

Main Results:

Achieved selective isomerization of 1-alkenes to Z-2-alkenes.
Identified a three-coordinate cobalt(II) alkyl complex as the resting state.
Demonstrated catalyst efficacy with various substrates including silanes and ethers.

Conclusions:

Cobalt(II) catalysts with bulky ligands enable kinetic control for Z-alkene synthesis.
The mechanism involves rapid β-hydride elimination and [1,2]-insertion steps.
Steric factors in the transition state dictate Z-stereoselectivity.