Mechanistic Studies on Iron-Catalyzed Dehydrogenation of Amines Involving Cyclopentadienone Iron ComplexesEvidence for Stepwise Hydride and Proton Transfer

• Published in: ACS catalysis Vol. 13; no. 13; pp. 8477 - 8484
• Main Authors: Manna, Srimanta, Peters, Joannes, Bermejo-López, Aitor, Himo, Fahmi, Bäckvall, Jan-E.
• Format: Journal Article
• Language: English
• Published: American Chemical Society 07.07.2023
• Subjects: amines; dehydrogenation; DFT calculations; hydrogen transfer; iron catalysis; kinetic isotope effects; amines; dehydrogenation; iron catalysis; hydrogen transfer; kinetic isotope effects; DFT calculations
• ISSN: 2155-5435; 2155-5435
• DOI: 10.1021/acscatal.3c01779

The mechanism of dehydrogenation of amines catalyzed by (cyclopentadienone)­iron carbonyl complexes was studied by means of kinetic isotope effect (KIE) measurements, intermediate isolation, and density functional theory calculations. The (cyclopentadienone)­iron–amine intermediates were isolated and characterized by 1H and 13C NMR spectroscopy as well as X-ray crystallography. The isolated iron–amine complexes are quite stable and undergo a formal β-hydride elimination to produce imine and iron hydride complexes. The KIEs observed for the iron-catalyzed dehydrogenation of 4-methoxy-N-(4-methylbenzyl)­aniline are in accordance with stepwise dehydrogenation. The density functional calculations corroborate a stepwise mechanism involving a rate-determining hydride transfer from amine to iron to yield a metal hydride and an iminium intermediate, followed by a proton transfer from the iminium ion to the oxygen of the cyclopentadienone ligand.