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University of Oklahoma Graduate College The UNIVERSITY OF OKLAHOMA GRADUATE COLLEGE THE EFFECT OF LIGAND DENTICITY IN STABILIZING ACTINIDE-ELEMENT MULTIPLE BOND FUNCTIONALITIES A DISSERTATION SUBMITTED TO THE GRADUATE FACULTY in partial fulfillment of the requirements for the Degree of DOCTOR OF PHILOSOPHY By BRIAN C. STOBBE Norman, Oklahoma 2017 THE EFFECT OF LIGAND DENTICITY IN STABILIZING ACTINIDE-ELEMENT MULTIPLE BOND FUNCTIONALITIES A DISSERTATION APPROVED FOR THE DEPARTMENT OF CHEMISTRY AND BIOCHEMISTRY BY ______________________________ Dr. Robert Thomson, Chair ______________________________ Dr. Lloyd Bumm ______________________________ Dr. Kenneth Nicholas ______________________________ Dr. Ronald Halterman ______________________________ Dr. Charles Rice © Copyright by BRIAN C. STOBBE 2017 All Rights Reserved. For my grandfather, Marco Rodriguez, a man of science. Acknowledgements I would like to thank the University of Oklahoma and the Department of Chemistry and Biochemistry for allowing me to pursue my Ph.D. studies. Additionally, I would like to formally thank the members of my committee: Dr. Halterman, Dr. Nicholas, Dr. Rice and Dr. Bumm for their guidance and assistance with my development as a scientist. Importantly, I would like to thank my research advisor, Dr. Robert K. Thomson, for giving me the opportunity to pursue my Ph.D. research in his lab. I am eternally grateful for his guidance and continued support, for without it, I would not have been nearly as successful in my endeavors. Additionally, I would like to thank Dr. Thomson for helping me to develop not only my laboratory research skills, but my presentation skills as they will be extremely useful to me in the future. Again, I am extremely grateful for all of the assistance and guidance provided to me by Dr. Thomson. I also would like to thank the members of the Thomson Lab – both past and present – for their friendship and fruitful research discussions and for helping to push me to become the best chemist I can be. I am eternally grateful to my parents, Andy and Yoky Stobbe, for their continued support, as well as their encouragement to keep pushing on even when times were tough. On this note, words cannot express my gratitude for the support, encouragement, and advice my fiancé, Tiffany, has provided me with, as it is because of this support that I have been successful thus far. iv Table of Contents Acknowledgements ............................................................................................iv List of Tables ......................................................................................................xi List of Figures ................................................................................................... xiii List of Schemes ................................................................................................ xix Abbreviations ................................................................................................... xxii Abstract ........................................................................................................... xxv Chapter 1 Introduction ........................................................................................ 1 1.1: U.S. energy demands and the search for a more sustainable fuel source .............................................................................................. 2 1.2: Concerns with nuclear energy as a long-term, sustainable fuel source ........................................................................................................ 5 1.2.1: Public opinion and economic concerns with nuclear energy .. 5 1.2.2: Concerns with radioactive nuclear waste ............................... 6 1.2.3: Management of high level radioactive waste and funding initiatives for actinide science .................................................. 8 1.3: Important breakthroughs in fundamental actinide science .............. 10 1.3.1: Understanding the inverse trans influence (ITI) ................... 10 1.3.2: Prior research into the inverse trans influence (ITI) ............. 13 1.3.3: Understanding methods of quantifying actinide covalency .. 14 v 1.4: Project goals ................................................................................... 16 1.5: References ..................................................................................... 18 Chapter 2 Synthesis and characterization of uranium(IV) & thorium(IV) tris(trimethylsilyl(anilido)) complexes: Divergent chemistry influenced by alkali metal salt identity .......................................................................... 23 2.1: Background..................................................................................... 24 2.2: Stabilization of U(IV) complexes using amido ligands .................... 27 2.3: Synthesis and characterization of chloro tris(anilido) uranium complexes ..................................................................................... 36 2.4: Synthesis and characterization of bromo anilido uranium complexes ...................................................................................................... 43 2.5: Attempts to generate (F)U[N(SiMe3)(3,5-(CH3)2(C6H3)]3 ................. 56 2.6: Synthesis of Th[N(SiMe3)(3,5-(CH3)2)(C6H3)]4 ................................ 63 1 2.7: Analysis of H NMR chemical shift trends for the [L]3U(X) series ... 70 2.8: Attempts to generate uranium-element multiple bonds using halo tris(anilido) uranium platform ......................................................... 73 2.9: Concluding remarks ........................................................................ 89 2.10: Experimental ................................................................................. 92 2.10.1: General experimental procedures ...................................... 92 2.10.2: Synthesis of [K][N(SiMe3)(3,5-(CH3)2(C6H3)] ...................... 93 vi 2.10.3: Synthesis of [L]3U(I) (2.1) from [Li][N(Si(CH3)3)(3,5- dimethylphenyl)] .................................................................... 94 2.10.4: Synthesis of [Li(Cl)(THF)2][[L]3U(Cl)] (2.2) ......................... 94 2.10.5: Synthesis of [L]3U(Cl) (2.3) ................................................ 95 2.10.6: Synthesis of [L]3U(Br) (2.4) ................................................ 95 2.10.7: Synthesis of [L]2U(Br)(μ-Br)3U(Br)[L]2 (2.5) ........................ 96 2.10.8: Synthesis of [L]4U from K[L] (2.6) ...................................... 96 2.10.9: Synthesis of [L]4Th (2.7) .................................................... 97 2.10.10: Synthesis of [L]3U(THF) (2.8) via reduction pathway ....... 97 2.10.11: Synthesis of [L]3U(THF) (2.8) from K[L] ........................... 98 2.11: References ................................................................................... 98 Chapter 3 An unexpected alkylation: Redox non-innocent ligand reactivity of a bis(amido)pyridine uranium complex ................................................... 107 3.1: Exploring the use of a new ligand framework ............................... 108 3.2: An unexpected alkylation resulting in [BDPPʹ]U(CH2Ph)2 ............. 109 3.3: Rational synthesis of [K][BDPP՛]U(CH2Ph)2 from [BDPP]U(CH2Ph)2 .................................................................................................... 115 3.4: Attempts at elucidating a mechanism for the observed alkylation. 118 3.5: Scope of nucleophilicity ................................................................ 121 vii 3.6: Concluding Remarks .................................................................... 127 3.7: Experimental ................................................................................. 128 3.7.1: General experimental procedures ...................................... 128 3.7.2: Synthesis of K[BDPP']U(CH2(C6H5))2 (3.1) from U(CH2Ph)4 ............................................................................................ 129 3.7.3: Synthesis of [K][BDPP']U(CH2Ph)2 (3.1) from [BDPP]U(CH2Ph)2 ................................................................ 130 3.7.4: Synthesis of [BDPP]U(CD2C6D5)2 ...................................... 130 3.7.5: Synthesis of K[BDPP']U(CD2C6D5)2 ................................... 131 3.8: References ................................................................................... 131 Chapter 4 A new hope for generating An=E functionalities: Synthesis, characterization and reactivity of Th(IV) and U(IV) dichloro Schiff base complexes ........................................................................................... 136 4.1: Background................................................................................... 137 4.2: Synthesis and characterization of [L]An(Cl)2(Solv)2 complexes .... 140 4.3: Salt metathesis reactivity of the [L]An(Cl)2(Solv)2 complexes with NaN3 ............................................................................................ 149 4.4: Salt metathesis reactivity of [L]An(Cl)2(Solv)2 complexes with carbon nucleophiles ................................................................................. 158 viii 4.5: σ-Bond metathesis reactivity of [L]An(Cl)2(Solv)2 complexes with Me3Si-Br ...................................................................................... 174 4.6: Attempts at generating [L]An=E functionalities via oxidative pathways .................................................................................................... 183 4.7: Concluding remarks ...................................................................... 197 4.8:
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