On the mechanism of carbonyl hydrogenation catalyzed by iron catalyst

Abstract

Density functional theory calculations have been performed to investigate the detailed mechanism of the carbonyl hydrogenation catalyzed by the first well-defined bifunctional iron catalyst. The catalytic reaction proceeds by hydrogen transfer and dihydrogen activation. The hydrogen transfer reaction occurs via the bifunctional mechanism in which the two hydrogen atoms attached on the Fe and O of the catalyst are transferred to the oxygen and carbon atom of the carbonyl compound concertedly. Both the alcohol-mediated and nonalcohol-mediated dihydrogen activation processes are explored.

Bifunctional (Cyclopentadienone)Iron–Tricarbonyl Complexes: Synthesis, Computational Studies and Application in Reductive Amination

“…This hydroxyl group can play the role of a Brönsted acid and activate the imine by means of hydrogen bonding (intermediate V ). The hydrogenation of the imine furnishes the amine and regenerates the unsaturated iron(0) complex II 43–45…”

“…The hydrogenation of the imine furnishes the amine and regenerates the unsaturated iron(0) complex II. [43][44][45] In more detail, the first step involves the activation of the pre-catalyst by a release of a CO ligand. The typically endothermic dissociation of CO (27.2 kcal mol À1 ) becomes an exothermic reaction when it is assisted by the external oxidant.…”

Iron/Brønsted Acid Catalyzed Asymmetric Hydrogenation: Mechanism and Selectivity‐Determining Interactions

“…[20] Also for iron-mediated aldehyde and ketone hydrogenation, the formed alcohol product has been proposed to coordinate to the iron complex. [15,36,35] In our calculations, coordination of the amine is highly favourable (by around 14 kcal/mol), making the relative energy of the Fe(0)-N complex comparable to that of the resting state, Fe(II)-H,OH. Hence, in presence of amine, H2 addition and splitting is only slightly exergonic (-2.3 kcal/mol, B3LYP-D2, Scheme 1B).…”

Using computational methods to explore improvements to Knölker's iron catalyst

“…13,27,28 In this catalytic hydrogenation, the substrate PhCHO and catalyst 1a first interact to form intermediate 3a through transition state 2aTS which corresponds to a concerted hydrogen-transfer mechanism. Intermediate 3a is a complex composed of 4a and an alcohol using a Fe⋯H agostic interaction and a hydrogen bond between the oxygen of the Cp group and the hydroxy hydrogen.…”