Heterogeneous and Homogeneous Catalysts to Transform Organic Molecules
Department of Chemistry and Biochemistry
University of Oregon
We are a group of chemists who study catalysis
We explore the reactivity of organic molecules with transition metal centers both in solution and on surfaces
We care about sustainability and green chemistry
We discover and improve reactions that are relevant to the chemical industry
We employ principles of physical organic and inorganic chemistry to understand reaction mechanisms
Catalysts are agents used to enhance the rate of reactions and control selectivity of reactions.
There are two main categories of catalysts: homogeneous and heterogeneous. Homogeneous catalysts are in the same phase as the reactants, and conversely, heterogeneous catalysts are in a different phase than the reactants.
Catalysts used in industry are primarily heterogeneous and in the solid state. This preference arises because of some intrinsic properties of heterogeneous reactions: they are easily separable from the liquid phase, easy to recycle, and stable to high temperatures and pressures.
However, heterogeneous catalysts can have some disadvantages. Namely, they are not typically synthesized with molecular control of the structure of the active site. This imprecision often results in many types of active sites within one catalytic material, which in turn leads to unselective reactions (multiple products forming) and limits our understanding of the relationship between structure and activity.
In the Cook lab, we strive to synthesize both homogeneous and heterogeneous catalysts with molecular control. We accomplish this by using the knowledge of inorganic, organometallic, and organic chemistry and applying it to molecular and surface chemistry. In doing so, we can make new catalysts for old and new transformations.
Because the catalysts we make are structurally well-characterized, we can probe the mechanism of the transformation. The tools of physical organic and inorganic chemistry are used to elucidate the catalytic cycle, develop structure-activity relationships, and make improvements in catalysis.
We control the activity and selectivity of homogeneous catalysts by tuning the electronic and steric parameters of ancillary ligands.
The structure of the active sites in heterogeneous catalysts can be controlled using an approach called Surface Organometallic Chemistry (SOMC). This strategy enables control of the density, oxidation state, and coordination site of the active site metal center.
Catalysts for alkenyl chain functionalization
A primary challenge in catalysis is the selective functionalization of inert alkyl chains. We propose to control site selectivity using catalysts for alkene migration, then using the alkenes as reactive handles for further functionalization. Using judicious choice of catalyst, the site of functionalization can be controlled.
New ways to support active sites
Heterogeneous catalysts are mainly composed of a support, like silica or alumina, and an active site, such as a transition metal. The active site is linked to the support typically through covalent or ionic bonding.
One aim of research in the Cook lab is to make new solid catalysts by rethinking how the active site (a transition metal, in our case) is bound to the support (metal oxides like silica and alumina, in our case). This will be particularly valuable for those transition metals that don’t have strong interactions with unmodified supports. Creating new linkages between the active site and the support will increase the durability of the solid catalysts and allow for otherwise unattainable active sites to be synthesized.
With these new materials, we can explore their use as catalysts for the transformation of organic molecules. We will target reactions of potential industrial utility, because of industry’s great interest in solid catalysts.
Catalysts for reduction reactions
On prebiotic Earth, at the bottom of the ocean, it is hypothesized that the first organic molecules were synthesized by carbon dioxide reduction at hydrothermal vents. The chimney structures of hydrothermal vents are composed of minerals with transition metals such as Fe, Ni, and Co, along with sulfur, silica, and silicates. It is thought that these transition metal-sulfide and -silicate minerals acted as the catalysts for carbon dioxide reduction to Earth’s first organic molecules.
Research in the Cook lab uses this hypothesis, from a chemical perspective, as inspiration for the development of new catalysts for the reduction of polar, unsaturated bonds. We utilize those elements and functional groups present in the hydrothermal vents within our new materials, and we evaluate their catalytic activity.
The themes of mechanism elucidation, understanding structure-activity relationships, and organic chemistry reaction development are carried throughout this project.
^ indicates undergraduate student; * indicates corresponding author
At the University of Oregon
Kawamura, K. E.; Chang, A. S.; ^Martin, D. J.; Smith, H. M.; ^Morris, P. T.; *Cook, A. K. "A Selective and Modular Ni(0)/HSiR3 Catalytic System for the Isomerization of Alkenes" submitted.
Hurst, M. R.; Zakharov, L.; *Cook, A. K. "The Mechanism of Oxidative Addition of Pd(0) to Si–H bonds: Electronic Effects, Reaction Mechanism, and Hydrosilylation" submitted.
Before the University of Oregon
Cook, A. K., *Copéret, C. “Alkyne Hydroamination Catalyzed by Silica-Supported Isolated Zn(II) Sites” Organometallics 2018, 37, 1342.
Estes, D. P.; Cook, A. K.; *Copéret, C. “Understanding the Lewis Acidity of Co(II) Sites on a Silica Surface” Inorg. Chem. 2017, 56, 7731.
Cook, A. K.; Schimler, S. D.; Matzger, A. J.; *Sanford, M. S. “Catalyst-Controlled Selectivity in the C–H Borylation of Methane and Ethane” Science 2016, 351, 1421.
Cook, A. K.; *Sanford, M. S. “Mechanism of the Palladium-Catalyzed Arene C–H Acetoxylation: A Comparison of Catalysts and Ligand Effects” J. Am. Chem. Soc. 2015, 137, 3109.
Cook, A. K.; *Sanford, M. S. “C-Halogen Bond Formation by Arene C–H Activation” in Catalytic Transformations via C–H Activation, Science of Synthesis 2015, 2, 183.
Cook, A. K.; Emmert, M. H.; *Sanford, M. S. “Steric Control of Site Selectivity in the Pd-Catalyzed C–H Acetoxylation of Simple Arenes” Org. Lett. 2013, 15, 5428.
Gary, J. B.; Cook, A. K.; *Sanford, M. S. “Palladium Catalysts Containing Pyridinium-Substituted Pyridine Ligands for the C–H Oxygenation of Benzene with K2S2O8” ACS Catalysis 2013, 3, 700.
Emmert, M.; Cook, A. K.; ^Xie, Y. J.; *Sanford, M. S. “Remarkably High Reactivity of Pd(OAc)2/Pyridine Catalysts: Nondirected C–H Oxygenation of Arenes” Angew. Chem., Int. Ed. 2011, 50, 9409.
Podhajsky, S. M.; Iwai, Y.; ^Cook-Sneathen, A.; *Sigman, M. S. “Asymmetric Palladium-Catalyzed Hydroarylation of Styrenes and Dienes” Tetrahedron 2011, 67, 4435.
From left to right: Daryl Martin (UG4), Michael Hurst (G5), Shiva Moaven (PD), Alison Chang (G4), Amanda Cook (PI), Kiana Kawamura (G5), Victor Salpino (UG4), Jack Greene (G2), Josh Dvorak (G2), Parker Morris (UG4)
Missing: Zach Silvas (G2), Max Bogdanov (UG4), Lucas Thigpen (UG4), Hayden Henness (UG4), Robel Clifton (REU/UG4)
Contact Information and Links
Our labs and offices are located in Klamath Hall and the Lewis Integrative Sciences Building at the University of Oregon
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The Cook lab is a part of the University of Oregon's Materials Science Institute