Tue, Nov. 17, 2015, 4:30pm - 6:00pm
Frick Chemistry Laboratory, Taylor Auditorium
Catalysis enabled by metal-ligand cooperation
This lecture will describe our development of iron-based homogeneous catalysts for the asymmetric transfer hydrogenation (ATH) and asymmetric pressure hydrogenation (AH) of ketones and imines. These chemical processes allow the preparation of enantiopure alcohols and amines for use in the pharmaceutical, agrochemical and fragrance industries while avoiding the use of conventional platinum-metal based catalysts. In the catalyst design we apply the principle of cooperation between the metal and the nitrogen donor of phosphorus-nitrogen or N-heterocyclic carbene-nitrogen ligands to the activation of alcohols, dihydrogen or aqueous formate in order to generate H-M-N-H units with exceptional bifunctional reactivity toward the polar bonds of carbonyl and imine compounds. A modular, iron-templated synthesis provides access to a wide range of enantiopure tetradentate and tridentate phosphorus and nitrogen ligand metal precatalysts, providing the correct structure for highly enantioselective hydrogenations for several classes of substrates. DFT modelling of the catalytic cycle is useful in understanding the source of the high activity of these catalysts and the sense of enantioinduction. A simple method of estimating the acidity of hydride and dihydrogen complexes helps to understand and possibly design these and many other catalytic processes.