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02/25/15

"Bifunctional hydrogenation - moving from ruthenium- to iron-based catalysts"

Prof. Robert H. Morris (University of Toronto)
Small Lecture Hall, 11:00

Abstract

Catalysts based on ruthenium(II) and iridium(I/III) are well known to efficiently and selectively catalyze the asymmetric hydrogenation of prochiral ketones and imines to alcohols and amines of value to the pharmaceutical, fragrances and fine chemical industry. This lecture will demonstrate that iron, a cheaper, more abundant, non toxic metal, can be used instead by applying the principles of metal-ligand cooperativity.
A family of iron(II) catalysts containing tetradentate P-NH-N-P ligands very efficiently transfers hydrogen from the solvent isopropanol to ketones and certain imines (TON 6000, TOF up to 200 s-1 at 28 °C), and less efficiently, from hydrogen gas to give reduced products in greater than 90% ee in several cases. Iron(II) complexes with enantiomerically pure tridentate P-N-P’ ligands are precatalysts for the asymmetric hydrogenation of ketones and imines (TON 5000, TOF up to 2000 h-1 at 50 °C) using hydrogen pressures of 10-50 atm. There is nuclear magnetic resonance and density functional theory evidence for hydridoamine iron(II) and amido iron(II) bifunctional moieties within the catalytic cycle in each of these systems.