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Synthesis and Reactivity Studies of Chromium

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Synthesis and Reactivity Studies of Chromium SYNTHESIS AND REACTIVITY STUDIES OF CHROMIUM COMPLEXES SUPPORTED BY �–DIKETIMINATE LIGANDS by Yu-Ting Hung 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 Fall 2017 © 2017 Yu-Ting Hung All Rights Reserved SYNTHESIS AND REACTIVITY STUDIES OF CHROMIUM COMPLEXES SUPPORTED BY �–DIKETIMINATE LIGANDS by Yu-Ting Hung 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: __________________________________________________________ Svilen 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: __________________________________________________________ Andrew V. Teplyakov, 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: __________________________________________________________ Lawrence R. Sita, Ph.D. Member of dissertation committee ACKNOWLEDGMENTS The most important person that I would like to express my sincere gratitude to is my research advisor, Professor Klaus Theopold. It has been an extremely great honor to work with him for the duration of my Ph.D. studies. Not only does he have a vast knowledge of chemistry, but he is also an amazing educator, greater than I could have asked for. His never-ending patience, encouragement, and supportive guidance toward my research has allowed me to expand my knowledge in chemistry. Klaus has proven himself as a role model of a chemist through his encouraging attitude these past five years. This has made my entire learning experience very rewarding. Overall, during this journey Klaus has also shown the kindness, enthusiasm, and wide wisdom of life, which are, and will always be invaluable throughout my life. In addition to my advisor, I would like to thank the members of my dissertation committee, Professor Svilen Bobev, Professor Andrew Teplyakov, and Professor Lawrence Sita, for their involvement and comments during my Ph.D. studies. My special thanks goes to Dr. Glenn Yap for his help in X-ray crystallography throughout my time conducting research. I am also very grateful for all the facilities and staff in this department. I’m especially thankful for Dr. Steve Bai for his help in NMR techniques. I would like to thank my lab mates, both past and present, for all of their help and support. I am also very appreciative for the friendships I have created here. They have made this journey more delightful. Lastly, I would like to thank my entire family back in Taiwan for all their spiritual support, especially my parents and brothers. The special bonding in this journey will never be forgotten. iv TABLE OF CONTENTS LIST OF TABLES ......................................................................................................... ix LIST OF FIGURES ..................................................................................................... xii LIST OF SCHEMES ................................................................................................ xviii LIST OF ABBREVIATIONS .................................................................................... xxii TECHNIQUES USED IN THE DISSERTATION .................................................. xxiii ABSTRACT ............................................................................................................... xxiv Chapter 1 USE OF DIAZOALKANES IN CHROMIUM ORGANOMETALLIC CHEMISTRY ..................................................................................................... 1 1.1 Introduction ................................................................................................ 1 1.2 Results and Discussion .............................................................................. 5 1.3 Experimental ............................................................................................ 49 1.3.1 General Considerations ................................................................ 49 Me 1.3.2 Alternative preparation of (L Cr)2(µ-H)2 (2) ............................. 50 1.3.3 Preparation of complexes 3-8 ...................................................... 50 Me 1.3.4 Isolation of [L Cr(THF)]3(µ-N2)3 (3) ........................................ 50 Me Me 1.3.5 Isolation of (L Cr)4(µ-N2)4 (4) and (L Cr)2(µ-N)(µ-H) (5) ..... 51 Me Me 1.3.6 Isolation of (L Cr)3(µ-N2)3(µ-N)CrL (6) ............................... 52 Me 1.3.7 Isolation of (L Cr)2(µ-NSiMe3)(µ-H) (7) .................................. 52 Me 1.3.8 Isolation of (L Cr)2(µ-NCH2)(µ-NH) (8) .................................. 52 iPr 1.3.9 Preparation of (L Cr)2(µ-N)(µ-N(H)NC(H)SiMe3) (9) ............. 53 REFERENCES ............................................................................................................. 57 2 BINUCLEAR ALKYL HYDRIDES OF CHROMIUM AND THEIR REACTION WITH HYDROCARBONS ......................................................... 59 2.1 Introductions ............................................................................................ 59 2.2 Results and Discussion ............................................................................ 64 2.2.1 Synthesis of chromium(II) alkyls and their thermal decomposition products ............................................................... 64 v 2.2.2 Synthesis of chromium alkyl hydrides and their characterizations .......................................................................... 90 2.2.3 Thermal stability of chromium alkyl hydrides ........................... 101 2.2.4 C-H bond activation reaction exploration .................................. 103 2.2.5 Synthesis of chromium aryl hydride .......................................... 107 2.2.6 Mechanistic studies on C-H bond activation reaction ............... 120 2.3 Conclusions ............................................................................................ 132 2.4 Experimental .......................................................................................... 133 2.4.1 General Considerations .............................................................. 133 Me 2.4.2 Preparation of L Cr(CH2SiMe3)(THF) (10) ............................ 134 Me 2.4.3 Preparation of L Cr(CH2CMe3)(THF) (11) ............................. 134 Me 2 2.4.4 Preparation of L Cr(η -CH2C6H5) (12) .................................... 135 2.4.5 Preparation of LMeCr(µ- CH2SiMe3)CrNArC(CH3)CHC(CH3)N-Me-C6H3(µ-CH2) (13). Ar = 2,6-dimethylphenyl. ........................................................... 135 2.4.6 Preparation of LMeCr(µ- CH2CMe3)CrNArC(CH3)CHC(CH3)N-Me-C6H3(µ-CH2) (14). Ar = 2,6-dimethylphenyl. ........................................................... 136 2.4.7 Preparation of [ArNC(CH3)CHC(CH3)N-Me-C6H3]Cr(µ2- CH2)Cr[NArC(CH3)CHC(CH3)N-Me-C6H3](µ1-CH2) (15). Ar = 2,6-dimethylphenyl. ................................................................ 137 Me 2.4.8 Preparation of (L Cr)2(µ-CH2CMe3)(µ-H) (16) ...................... 137 Me 2.4.9 Preparation of (L Cr)2(µ-CH2C6H5)(µ-H) (17) ....................... 138 Me 2.4.10 Preparation of (L Cr)2(µ-C6H5)(µ-H) (18) .............................. 138 Me 2.4.11 Preparation of (L Cr)2(µ-m-CH3C6H4)(µ-H) (19) ................... 139 Me 2.4.12 Preparation of L Cr(C6H5)(THF) (20) ..................................... 140 Me 6 6 2.4.13 Preparation of (L Cr)2(µ2-η :η -C6H5Ph) (22) ......................... 141 REFERENCES ........................................................................................................... 146 3 SYNTHESIS OF CHROMIUM NITRIDO COMPLEXES SUPPORTED BY β–DIKETIMINATE LIGANDS, AND THEIR RELATIONSHIPS TO ISOMERIC DINITROGEN COMPLEXES ................................................... 147 3.1 Introduction ............................................................................................ 147 3.2 Results and Discussion .......................................................................... 156 3.2.1 Preliminary results of irradiation of Cr(II) azide supported by LiPr .............................................................................................. 156 3.2.2 Synthesis and structures of additional Cr(II) azides .................. 160 vi 3.2.3 Formation of nitride/dinitrogen complexes by irradiation of azides .........................................................................................
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