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Nitrene Transfer Reactions Mediated by Transition Metal Scorpionate Complexes

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Nitrene Transfer Reactions Mediated by Transition Metal Scorpionate Complexes A dissertation presented to the faculty of the College of Arts and Sciences of Ohio University In partial fulfillment of the requirements for the degree Doctor of Philosophy Shengwen Liang August 2012 © 2012 Shengwen Liang. All Rights Reserved. 2 This dissertation titled Nitrene Transfer Reactions Mediated by Transition Metal Scorpionate Complexes by SHENGWEN LIANG has been approved for the Department of Chemistry and Biochemistry and the College of Arts and Sciences by Michael P. Jensen Associate Professor of Chemistry Howard Dewald Interim Dean, College of Arts and Sciences 3 ABSTRACT LIANG, SHENGWEN, Ph.D., August 2012, Chemistry Nitrene Transfer Reactions Mediated by Transition Metal Scorpionate Complexes Director of Dissertation: Michael P. Jensen Transition metal catalyzed C=C bond aziridination and C-H bond amination reactions are powerful synthetic methods for forming C-N bonds directly from unfunctionalized hydrocarbons, and have enormous synthetic potential in chemical processes leading to natural products, pharmaceuticals and materials. Catalytic C-H bond amination also offers a way to achieve functionalization with clean and environmentally sustainable atom efficiency. This work will focus on olefin aziridinations and C-H bond aminations catalyzed by transition metal complexes. We employed N 3-tripod scorpionate ligands to support different transition metal centers. Therefore, complexes [(L)M(NCCH 3)3](BF 4)n (L = tris{3,5-dimethylpyrazol-1-yl}methane, Tpm Me,Me , M = Mn, Fe, Co, Ni, n = 2; L = tris{3- phenylpyrazol-1-yl}methane, Tpm Ph , M = Mn, Fe, Co, Ni, n = 2; L = hydrotris{3,5- dimethylpyrazol-1-yl}borate, Tp Me,Me , M = Fe, Co, Ni, n = 1; L = hydrotris{3-phenyl-5- methylpyrazol-1-yl}borate, Tp Ph,Me , M = Mn, Co, Fe, Ni, n = 1) were prepared and characterized. These complexes were utilized as metal catalysts for nitrene transfer from phenyl-N-tosyliminoiodinane (i.e., PhI=NTs) to variety of organic substrates, resulting in olefin aziridination and C-H bond amination with varying degrees of efficiency. A wide range of organic products was obtained and fully characterized, and reaction mechanisms were probed with Hammett and kinetic isotope effects. Meanwhile, a masked Lewis acid 4 [Fe(NCMe) 6](BF 4)2 was found to catalyze [2+1+2] and [3+2] cycloaddition reactions, leading to the formation of various five-membered nitrogen-containing compounds. Approved: _____________________________________________________________ Michael P. Jensen Associate Professor of Chemistry 5 To My Parents Xiuzhen Qiu and Guoping Liang 6 ACKNOWLEDGMENTS This dissertation, and all of my research work at Ohio University, would not have been possible without the time and support of quite a few people. I need to begin with thanking my advisor Prof. Michael P. Jensen for giving me the opportunity to work in his laboratory on such an interesting research project. He has been a wonderful mentor offering me patience and guidance throughout the past five years. It seems to me that I gain valuable lessons not only on chemistry but also on scientific method, logic, and interpersonal relationships that would be valuable for my future career. In addition, I would like to thank the members of my committee, Prof. Jeffrey J. Rack, Prof. Hao Chen and Prof. R. Guy Riefler. Prof. Rack in particular has been a valuable source of knowledge for my research. I would like to thank Prof. Jeffrey L. Petersen at West Virginia University and Dr. Victor G. Young, Jr. at University of Minnesota for solving the crystal structures. And I also would like to thank Prof. Stephen C. Bergmeier and his graduate student Fang Fang for the valuable discussion about nitrene chemistry. Also, I want to thank my labmates, faculty and staff from the Department of Chemistry and Biochemistry, my research work has become much easier with generous support from these people. Last but not least, I would like to thank my deeply loved parents Xiuzhen Qiu and Guoping Liang, who have given me the support and encouragement to complete my Ph.D. in chemistry. 7 TABLE OF CONTENTS Page Abstract ............................................................................................................................... 3 Dedication ........................................................................................................................... 5 Acknowledgments............................................................................................................... 6 List of Tables .................................................................................................................... 10 List of Figures ................................................................................................................... 12 List of Schemes ................................................................................................................. 15 Chapter 1: Introduction ..................................................................................................... 17 General Aspects ............................................................................................................ 17 C-H Bond Amination Reactions ................................................................................... 20 Aziridination of C=C Bonds and Applications of Aziridine ........................................ 26 Structures and Applications of Late Metal Imido Complexes ...................................... 30 References ..................................................................................................................... 43 Chapter 2: Synthesis and Characterization of Transition Metal Scorpionate Complexes 50 Introduction ................................................................................................................... 50 Experimental Details ..................................................................................................... 51 Results and Discussion ................................................................................................. 61 Characterization of [(L)M(NCMe) 3](BF 4)n .................................................................. 63 A. X-ray Crystallography .......................................................................................... 63 B. Electronic Spectroscopy ....................................................................................... 74 C. 1H NMR Spectroscopy ......................................................................................... 85 D. FT-IR Spectroscopy ............................................................................................. 93 E. Magnetic Properties ............................................................................................ 101 References ................................................................................................................... 103 Chapter 3: Nitrene Transfer Catalysis Mediated by Transition Metal Scorpionate Complexes....................................................................................................................... 108 Aziridination Reactions of Olefins ............................................................................. 110 Aziridination of para -Substituented Styrenes ............................................................ 118 C-H bond Amination of Tetrahydrofuran ................................................................... 121 C-H bond Amination of Aromatic Substrates ............................................................. 127 8 References ................................................................................................................... 131 Chapter 4: Masked Lewis Acid [Fe(NCMe) 6](BF 4)2 Catalyzed Cycloaddition Reactions ......................................................................................................................................... 134 [2+1+2] Cycloaddition of Alkenes with PhI=NTs ..................................................... 139 [3+2] Cycloadditon of Aziridine with Alkenes, Aldehydes, Ketones and Alkynes ... 144 Experimental Procedures for Chapter 3 and Chapter 4 .............................................. 151 References ................................................................................................................... 154 Chapter 5: Oxene and Nitrene Chemistry of Ni(0) Mediated by Tris(3,5-dimethylpyrazol- 1-yl)methane ................................................................................................................... 156 Experimental ............................................................................................................... 157 Results and Discussion ............................................................................................... 163 References ................................................................................................................... 179 Appendix 1: NMR Spectrum of 2 ................................................................................... 184 Appendix 2: NMR Spectrum of 52 ................................................................................. 185 Appendix 3: NMR Spectrum of 53 ................................................................................. 186 Appendix 4: NMR Spectrum of 17 ................................................................................. 187 Appendix 5: NMR Spectrum of 15 ................................................................................
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