个人简介

Aaron Sadow, Associate Professor of Chemistry, received his B.S. in 1997 from Pennsylvania State University, where he worked in the group of Prof. Ayusman Sen on palladium-catalyzed co- and terpolymerizations. He earned his Ph.D. from the University of California, Berkeley in 2003 under the guidance of Prof. T. Don Tilley, primarily focused on the development of new catalytic C–H bond functionalizations. Following postdoctoral work at the Swiss Federal Institute of Technology (ETH Zürich) with Antonio Togni investigating catalytic asymmetric hydroamination and hydrophosphination, Aaron joined the chemistry faculty at Iowa State University. He was promoted to associate professor in 2011.

研究领域

Organometallic Chemistry and Asymmetric Catalysis

The Sadow Group investigates main group element, rare earth element, and transition-metal organometallic chemistry. Our work involves ligand design, organometallic synthesis, development of catalytic chemistry, and study of organometallic reaction mechanisms. These activities are applied in catalytic conversions for chemical synthesis, materials preparations, and energy-related transformations. Oxazoline and Borate Ligands. The ancillary ligands studied in the Sadow Group contain multiple oxazoline donors linked by a monoanionic borate center. The borate center provides an anionic charge to the ligand and increases the electron donating power of the oxazoline groups. Oxazolines are chosen as donors because they are readily obtained in enantiopure form and they are resistant to oxidation and racemization. The tris(oxazolinyl)borate ligands prepared in the Sadow Group have been coordinated to transition-metal, main-group, and rare earth metal centers to make catalysts for a variety of transformations. Alkyl ligands with beta Si–H Groups. Beta-hydrogen elimination is a common reaction pathway for transition-metal alkyl compounds that gives unsaturated organic molecules and a metal-hydrogen bond. This reaction often occurs under very mild conditions for transition-metals, whereas main group alkyls typically resist beta elimination. Our work has shown that beta-C–H and beta-Si–H bonds of main group alkyl and silyl ligands are reactive, even though elimination is not the favored pathway. We are creating new catalytic reactions based on the reaction pathways that become available in the absence of beta-elimination. Catalytic Hydroamination. We are investigating early transition-metal and main group metal compounds as catalysts for C–N bond formations. Chiral amines are important in natural products, pharmaceuticals, materials, and agrichemicals. In this work, we've prepare new catalysts that provide chiral amines with exceptional enantioselectivity. Kinetics, isolated intermediates, and effects of isotopic substitution on enantioselectivity provide evidence for concerted N–C and C–H bond formation in the transition state. This mechanistic insight allows design of new catalysts for a range of carbon-element bond formations. Silicon-element bond formations. Silicones -(SiR2–O)n-, silylethers (R3Si-OR), silazanes (R3Si–NR2), and silanes (R3Si–SiR3) are technologically important materials and are valuable in organic and inorganic chemistry. However, traditional syntheses generate significant wastes, use hydrolytically sensitive halosilanes as starting materials, and mixtures are often obtained. We are developing organometallic compounds to catalyze the formation of Si–O, Si–N, Si–C, and Si–Si bonds to address stereochemical issues, reduce waste production, and employ air-stable precursors. We are also investigating these bond forming reactions for selective transformations of small molecules. C-H, C-C, and C-O Bond activation reactions. The oxidation/reduction chemistry of transition metals is central to catalytic conversions of organic molecules, from highly reduced hydrocarbons through oxygenated carbohydrates to carbon dioxide. We are studying transition-metal-mediated C-H oxidation and C-O reduction to develop catalytic transformations relevant to fuel and chemical production.

近期论文

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Mukherjee, D.; Ellern, A.; Sadow, A. D. "Magnesium-catalyzed Hydroboration of Esters via a New Zwitterionic Mechanism" Chem. Sci. 2014, 5, 959-964. Edge Article. http://dx.doi.org/10.1039/C3SC52793J Sadow A.D. "Stereoselective C-N Bond Formation by Hydroamination of Olefins, Alkynes, Allenes, and Dienes." In: J. Reedijk and K. Poeppelmeier, Eds. Comprehensive Inorganic Chemistry II, Vol 6. Oxford: Elsevier; 2013. p. 487-520. Yan, K.; Duchimaza Heredia, J. J.; Ellern, A.; Gordon, M. S.; Sadow, A. D. "Lewis Base Mediated β-Elimination and Lewis Acid Mediated Insertion Reactions of Disilazido Zirconium Compounds." J. Am. Chem. Soc. 2013, 135, 15225-15227. http://dx.doi.org/10.1021/ja407950e Yan, K.; Upton, B. M.; Zhu, J.; Ellern, A.; Sadow, A. D. "Nucleophilicity of Neutral versus Cationic Magnesium Silyl Compound." Organometallics, 2013, 32, 6834–6843. http://dx.doi.org/10.1021/om400447q Manna, K.; Everett, W. S.; Schoendorff, G.; Ellern, A.; Windus, T. L.; Sadow, A. D. "Highly enantioselective zirconium catalyzed cyclization of aminoalkenes." J. Am. Chem. Soc. 2013, 135, 7235-7250. http://dx.doi.org/10.1021/ja4000189 Yan, K.; Schoendorff, G.; Everett, W.; Ellern, A.; Windus, T.; Sadow, A. D. "Intermolecular β-hydrogen abstractions in ytterbium, calcium, and potassium tris(dimethylsilyl)methyl compounds" Organometallics, 2013, 32, 1300-1316. http://dx.doi.org/10.1021/om3010299 Yan, K.; Sadow, A. D. "C-H Bond activation by a zirconacycle" Chem. Commun. 2013, 49, 3212-3214. http://dx.doi.org/10.1039/c3cc40774h Mukherjee, D.; Lampland, N. L.; Yan, K.; Dunne, J. F.; Ellern, A.; Sadow, A. D. "Divergent reaction pathways of tris(oxazolinyl)borato zinc and magnesium silyl compounds" Chem. Commun. 2013, 49, 4334-4336. http://dx.doi.org/10.1039/C2CC36953B Jana, B.; Hovey, M.; Ellern, A.; Pestovsky, O.; Sadow, A. D.; Bakac, A.: Unusual structural motif in a zwitterionic Fe(II) complex of a tetradentate phosphine. Dalton Trans. 2012, 41, 12781-12785. http://dx.doi.org/10.1039/C2DT31437A Mukherjee, D.; Ellern, A.; Sadow, A. D. "Remarkably Robust Monomeric Alkylperoxyzinc Compounds from Tris(oxazolinyl)boratozinc Alkyls and O2." J. Am. Chem. Soc., 2012, 134, 13018-13026. http://dx.doi.org/10.1021/ja303440n Ho, H.-A.; Manna, K.; Sadow, A. D. "Acceptorless Photocatalytic Dehydrogenation for Alcohol Decarbonylation and Imine Synthesis. Angew. Chem. Int. Ed. 2012, 51, 8607-8610. http://dx.doi.org/10.1002/anie.201203556 Yan, K.; Ellern, A.; Sadow, A. D. "Non-classical β-Hydrogen Eliminations from Hydrosilazido Zirconium Compounds via Direct Hydrogen Transfer." J. Am. Chem. Soc., 2012, 134, 9154-9156. http://dx.doi.org/10.1021/ja302226c Zhu, J.; Mukherjee, D.; Sadow, A. D. "Abstractions of β-hydrogen vs. alkyl groups in reactions of dialkylzinc compounds and bis(oxazolinyl)borane." Chem. Commun. 2012, 48, 464-466. http://dx.doi.org/10.1039/C1CC16113J Manna, K.; Kruse, M. L.; Sadow, A. D. "Concerted C-N/C-H Bond Formation in Highly Enantioselective Yttrium(III)-Catalyzed Hydroamination." ACS Catalysis, 2011, 1, 1637-1642. http://dx.doi.org/10.1021/cs200511z Dunne, J. F.; Neal, S. R.; Engelkemier, J.; Ellern, A.; Sadow, A. D. "Tris(oxazolinyl)boratomagnesium-catalyzed Cross-dehydrocoupling of Organosilanes with Amines, Hydrazine, and Ammonia" J. Am. Chem. Soc. 2011, 133, 16782-16785. http://dx.doi.org/10.1021/ja207641b Chintareddy, V. R.; Ho, H.-A. Sadow, A. D.; Verkade,* J. G. "Polymer-mounted N3=P(MeNCH2CH2)3N: a green, efficient, and recyclable catalyst for room-temperature transesterifications and amidations of unactivated esters" Tetrahedron Lett., 2011, 52, 6523-6529. http://dx.doi.org/10.1016/j.tetlet.2011.09.102 Mukherjee, D.; Thompson, R.; Ellern, A. Sadow, A. D. "A Coordinatively Saturated Tris(oxazolinyl)borato Zinc Hydride-Catalyzed Cross Dehydrocoupling of Silanes and Alcohols." ACS Catalysis, 2011, 1, 698-702. Special issue dedicated to Victor Lin. http:/dx.doi.org/10.1021/cs2001016 Ho, H.-A.; Gray, T. S.; Baird, B.; Ellern, A.; Sadow, A. D. "Allylic C–H Bond Activation and Functionalization Mediated by Tris(oxazolinyl)borato Rhodium(I) and Iridium(I) Compounds." Dalton Trans., 2011, 40, 6500 - 6514. http://dx.doi.org/10.1039/C1DT10249D Wu, K.; Mukherjee, D.; Ellern, A.; Sadow, A. D.; Geiger, W. E. "Anodic Electrochemical Behavior of New Mn and Re Tricarbonyl Complexes of Tris(oxazolinyl)phenyl borate Ligands: Comparison to Analogous Tris(pyrazolyl) borate Complexes" New Journal of Chemistry, New J. Chem., 2011, 35, 2169-2178. http://dx.doi.org/10.1039/C1NJ20222G Jana, B.; Ellern, A.; Pestovsky, O. Sadow, A. D. Bakac, A. "Synthesis of Monomeric Fe(II) and Ru(II) Complexes of Tetradentate Phosphines" Inorg. Chem., 2011, 50, 3010-3016. http://dx.doi.org/10.1021/ic102510c