SYNTHESIS AND REACTIVITY OF CHROMIUM α-DIIMINE COMPLEXES AND 1,4-DIMETHYL-OXA-NORBORNENE by Lan Wang A dissertation submitted to the Faculty of the University of Delaware in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Chemistry and Biochemistry Winter 2018 © 2018 Lan Wang All Rights Reserved SYNTHESIS AND REACTIVITY OF CHROMIUM α-DIIMINE COMPLEXES AND 1,4-DIMETHYL-OXA-NORBORNENE by Lan Wang Approved: __________________________________________________________ Brian J. Bahnson, Ph.D. Chair of the Department of Chemistry and Biochemistry Approved: __________________________________________________________ George H. Watson, Ph.D. Dean of the College of Arts and Sciences Approved: __________________________________________________________ Ann L. Ardis, Ph.D. Senior Vice Provost for Graduate and Professional Education I certify that I have read this dissertation and that in my opinion it meets the academic and professional standard required by the University as a dissertation for the degree of Doctor of Philosophy. Signed: __________________________________________________________ Klaus H. Theopold, Ph.D. Professor in charge of dissertation I certify that I have read this dissertation and that in my opinion it meets the academic and professional standard required by the University as a dissertation for the degree of Doctor of Philosophy. Signed: __________________________________________________________ Mary P. Watson, Ph.D. Member of dissertation committee I certify that I have read this dissertation and that in my opinion it meets the academic and professional standard required by the University as a dissertation for the degree of Doctor of Philosophy. Signed: __________________________________________________________ Svilen S. Bobev, Ph.D. Member of dissertation committee I certify that I have read this dissertation and that in my opinion it meets the academic and professional standard required by the University as a dissertation for the degree of Doctor of Philosophy. Signed: __________________________________________________________ Raul F. Lobo, Ph.D Member of dissertation committee ACKNOWLEDGMENTS First I would like to thank my advisor, Dr. Klaus H. Theopold, for his academic guidance, support and offering me the opportunity to conduct my research in his laboratory. I’m also grateful to my research group members both in Dr. Theopold’s group and in Catalysis Center for Energy Innovation, past and present, for their time and help to me professionally and personally. I’m also greatly indebted to Dr. Glenn P. A. Yap for helping me to pick up crystals and to solve structures. I would like to thank my dissertation committee members for taking the time out of their schedules to advise me in the preparation and presentation of this research. Furthermore, I want to thank the Chemistry and Biochemistry departmental staff for their help and support. I am grateful to the University of Delaware for providing me with excellent academic and research services as well as the opportunity to earn this degree. Lastly, I would like to thank the National Science Foundation and Department of Energy for their continued financial support of my research career at the University of Delaware. iv TABLE OF CONTENTS LIST OF TABLES ....................................................................................................... vii LIST OF SCHEMES ..................................................................................................... ix LIST OF FIGURES ...................................................................................................... xii ABSTRACT ................................................................................................................. xv Chapter 1 INTRODUCTION .............................................................................................. 1 2 THE REACTIVITY OF A QUINTUPLE-BONDED CHROMIUM DIMER SUPPORTED BY α-DIIMINE LIGANDS ...................................................... 13 2.1 Introduction ............................................................................................. 13 2.2 Results and Discussion ............................................................................ 19 2.3 Experimental ............................................................................................ 41 2.3.1 General Considerations ............................................................... 41 H iPr 2.3.2 Preparation of [ L Cr]2(µ-CO) (1) ............................................ 42 2.3.3 Preparation of (L-CO2)2Cr2 (2) .................................................... 42 H iPr 2 2 2.3.4 Preparation of [ L Cr]2(µ-ƞ :ƞ -CS)(µ-S) (3) ........................... 43 2.3.5 General considerations for X-ray diffraction .............................. 43 2.3.6 Single crystal X-ray diffraction studies ....................................... 44 3 THE SYNTHESIS OF THE DINUCLEAR CHROMIUM ALKYL/ARYL HYDRIDE COMPLEXES SUPPORTED BY α-DIIMINE LIGANDS .......... 50 3.1 Introduction ............................................................................................. 50 3.2 Results and Discussion ............................................................................ 56 3.3 Experimental .......................................................................................... 126 3.3.1 General Considerations ............................................................. 126 H iPr 3.3.2 Preparation of ( L Cr)2(µ-H)2 (4) ............................................ 127 H iPr - + 3.3.3 Preparation of [( L Cr)2(µ-Me)(µ-H)2] [Li(THF)4] (5) ......... 128 H iPr - + 3.3.4 Preparation of [( L Cr)2(µ-Ph)(µ-H)2] [Li(THF)4] (6) .......... 129 H iPr - 3.3.5 Preparation of [( L Cr)2(µ-CH2TMS)(µ-H)2] + [Li(THF)3(Et2O)] (7) ................................................................ 129 v H iPr t - 3.3.6 Preparation of [( L Cr)2(µ-CH2 Bu)(µ-H)2] + [Li(THF)3(Et2O)] (8) ................................................................ 130 H iPr - + 3.3.7 Preparation of [( L Cr)2(µ-CH2Ph)(µ-H)2] [Li(THF)4] (9) ... 130 H iPr - + 3.3.8 Preparation of [( L Cr)2(µ-Me)2(µ-H)] [Li(THF)3(Et2O)] (10) ............................................................................................ 131 H iPr - + 3.3.9 Preparation of [( L Cr)2(µ-Ph)2(µ-H)] [Li(THF)] (11) .......... 132 H iPr Me,H2 iPr 3.3.10 Preparation of ( L Cr) ( L Cr)(µ-CH2TMS)(µ-H)2 (12) . 132 3.3.11 General considerations for X-ray diffraction ............................ 133 3.3.12 Single crystal X-ray diffration studies ....................................... 133 4 SYNTHESIS, ISOLATION AND CHARATERIZATION OF DIMETHYL-OXA-NORBORNENE AND CATALYSTS SEARCH FOR AROMATIZATION AND DIELAS-ALDER REACTIONS ........................ 139 4.1 Introduction ........................................................................................... 139 4.2 Results and Discussion .......................................................................... 142 4.3 Experimental .......................................................................................... 175 4.3.1 General Considerations ............................................................. 175 4.3.2 Preparation of 1,4-dimethyl-7-oxa-bicyclo[2,1]hept-2-ene-5- endo-carboxyl-acid (13) ............................................................ 175 4.3.3 Preparation of 1,4-dimethyl-7-oxa-bicyclo[2,1]heptane-5- endo-carboxyl-acid (14) ............................................................ 176 4.3.4 Preparation of 1,4-dimethyl-7-oxa-bicyclo[2,1]hept-2-ene (15) ............................................................................................ 176 4.3.5 Typical Aromatization Procedure for reactions ........................ 177 4.3.6 Typical retro-Diels-Alder procedure for reactions .................... 178 Appendix ABBREVIATION .......................................................................................... 183 vi LIST OF TABLES Table 2.1 Bond distances (Å) of the α-diimine backbone for the α-diimine ligand in various oxidation states. ...................................................................... 18 H iPr Table 2.2 Interatomic distances (Å) and angles (°) for [ L Cr](µ-CO) (1). .......... 21 1 1 Table 2.3 Interatomic distances (Å) and angles (°) for (µ-ƞ :ƞ -L`)2Cr2 (2). .......... 27 H iPr 2 2 Table 2.4 Interatomic distances (Å) and angles (°) for [ L Cr]2(µ-ƞ :ƞ -CS)(µ- S) (3). ....................................................................................................... 33 Table 2.5 Crystallographic data for complexes 1-3 ................................................. 45 H iPr Table 3.1 Interatomic distances (Å) and angles (°) for ( L Cr)2(µ-H)2 (4) ........... 58 H iPr - Table 3.2 Interatomic distances (Å) and angles (°) for [( L Cr)2(µ-Me)(µ-H)2] + [Li(THF)4] (5) ........................................................................................ 69 H iPr - Table 3.3 Interatomic distances (Å) and angles (°) for [( L Cr)2(µ-Ph)(µ-H)2] + [Li(THF)4] (6) ........................................................................................ 75 H iPr Table 3.4 Interatomic distances (Å) and angles (°) for [( L Cr)2(µ- - + CH2TMS)(µ-H)2] [Li(THF)3(Et2O)] (7) ................................................ 81 H iPr t Table 3.5 Interatomic distances (Å) and angles (°) for [( L Cr)2(µ-CH2 Bu)(µ- - + H)2] [Li(THF)3(Et2O)] (8) ...................................................................... 85 H iPr Table 3.6 Interatomic distances (Å) and angles (°) for [( L Cr)2(µ-CH2Ph)(µ- - + H)2] [Li(THF)4]