Iron-based cyclopentadienone catalysts are characterized by natural abundance and low cost. Air-stable iron tricarbonyl compounds structurally similar to Shvo’s catalyst have been shown to catalyze the transfer hydrogenation of aldehydes and ketones and the dehydrogenation of alcohols using the solvent (acetone or isopropanol) as the terminal oxidant or reductant. One advantage to this approach is that a strong reducing or oxidizing agent is not needed. Previous studies showed that the substituents on the cyclopentadienone can dramatically affect the reactivity of the catalyst. We chose to probe how the electronics of the substituents affect catalyst reactivity with a goal of ultimately using this insight to develop a more active iron catalyst. After successfully synthesizing iron catalysts containing electron-withdrawing or electron-donating groups, kinetic studies of acetophenone reductions and 4-phenyl-2-butanol oxidations were carried out. Reaction conversions were monitored by GC and suggested less electron density on the cyclopentadienone decreased the catalyst’s reactivity. Kinetic studies of electronically varied p-substituted acetophenone reductions and p-substituted 1-phenylethanol oxidations further confirmed that electron-withdrawing groups decreased the reactivity of the catalyst and suggested that hydride transfer between iron center and substrate is the rate limiting step of both transfer hydrogenations and dehydrogenations.

Electronic effects of (cyclopentadienone)iron tricarbonyl bifunctional catalysts on transfer hydrogenation and dehydrogenation reactions

2019 Spring National Meeting

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.