PHOTOREACTIVITY OF N-HETEROCYCLIC CARBENE-BORANES AND THE REACTIVITY OF PYRIDO[2,1-A]ISOINDOLE by Sean M. McDonald A thesis submitted to the Department of Chemistry In conformity with the requirements for the degree of Doctor of Philosophy Queen’s University Kingston, Ontario, Canada (June, 2018) Copyright ©Sean M. McDonald, 2018 Dedicated to my wife, Larissa Smith ii Abstract N-heterocyclic carbene (NHC) borane systems have become an important topic in main group chemistry. Finding uses as catalysts, coordinators for radical polymerizations, and reagents in a variety of reactions, NHCs have become a very important ligand for fundamental research. However, there have been relatively few studies on NHC-boranes over the last fifty years. This thesis will make new strides in the understanding and reactivity of NHC-boranes with UV light. Modeling after a previous result, NHC-BH3 systems were investigated for their photoreactivity. The systems investigated were found to decompose under irradiation. The systems were shifted to NHC-BH2R where the R group has a -hydrogen relative to the boron center. When exposed to UV light a facile reaction occurred, akin to a -hydrogen elimination reaction. The resulting products are an NHC-BH3 and the corresponding alkene from the elimination. BMes2 moieties chelated by an NHC were synthesized, analogous to previous work. When irradiated by UV light, mesitylene was eliminated, yielding a new B-C -bond. This new system contains an imbedded 1,3-azaborine within its multicyclic structure and is the first example of this type. When the precursor was heated, the boron moiety was eliminated and the ring closed to make a new 1H-imidazo[1,2- a]indole. This new compound shows a striking similarity to pyrido[2,1-a]isoindole (iczH). Like iczH, there is a new highly nucleophilic carbon center at the apex of the new 5-membered ring. Due to synthetic ease, iczH was selected to test nucleophilicity in place of the 1H-imidazo[1,2- a]indole. The reactivity of iczH as a nucleophile was explored with a variety of transition metals and main group elements. A normal adduct was formed when reacted with a platinum(II) center, while an 6 complex was formed with a chromium(0) center. When iczH was reacted with group 11 metals(I), a redox reaction took place, producing the solid metal, protonation iczH, and a dimer of iczH. A chlorophosphines was found to be very reactive with iczH once again resulting in protonated iczH while also producing an icz- functionalized phosphine. Despite the HOMO residing on the carbon of the icz unit, the phosphorous atom iii (dominant in HOMO-1) was still the favoured nucleophile when reacted with borane, producing a new borane-phosphine adduct. These new compounds were fully characterized by NMR and X-ray crystallographic analysis. iv Co-Authorship Chapter 2: The X-ray crystallography data collection and analysis was performed by Dr. Suning Wang. All other synthesis, characterization and analysis were performed by me. Chapter 3: The X-ray crystallography data collection and analysis was performed by Dr. Suning Wang. The DFT and TD-DFT calculations were performed by Soren K. Mellerup. All other synthesis, characterization and analysis were performed by me. Chapter 4: The X-ray crystallography data collection and analysis was performed by Dr. Suning Wang. The DFT and TD-DFT calculations were performed by Soren K. Mellerup. All other synthesis, characterization and analysis were performed by me. v Acknowledgements To begin, I would like to thank my supervisor, Professor Suning Wang, for all her hard work in guiding and supporting my research during my PhD program at Queen’s University. She provided freedom for me to work in my own way and to pursue topics that interested me. She also provided beneficial and constructive criticisms and advice for how to proceed in a variety of areas. Moreover, she cares about the well-being and interests of her students. Likewise, she cares about the success of all her students and wants them to graduate and do great things. I would like to thank my research committee members, Professor Anne Petitjean and Professor P. Andrew Evans for their help, advice, and commitment to helping me succeed as a researcher. I would also like to thank Dr. Françoise Sauriol and Dr. Jia-Xi Wang for their technical support for NMR spectroscopy, and for mass spectrometry, respectively. I would also like to thank Dr. Igor Kozin for his help with solid state IR measurements. My years in the Wang group were filled with numerous talented labmates with whom I was lucky to share time with and collaborate, as well as to push one another to greater heights. I’d like to thank all Wang group members, past and present, in no particular order: Dr. Ying-Li Rao, Dr. Nan Wang, Dr. Yufei Li, Dr. Xiang Wang, Dr. Barry Blight, Dr. Allison Brazeau, Dr. Soo-Byung Ko, Dr. Hee-Jun Park, Dr. Jinbao Peng, Dr. Kamrul Hasan, Dr. Dengtao Yang, Maria Varlan, Larissa Smith, Julian Radtke, Soren Mellerup, Kang Yuan, Haijun Li, Zhechang (Logan) He, Faraz Hussain, Lei Dong, Ulrich Makanda, and Cally Li. I would also like to thank the undergraduate students Valerie Chiykowski and Coleen McIlwain that worked under me over the past years and provided new experiences in teaching and mentoring. I would like to also thank my close friends and family for their support and help in balancing my life. I would like to thank my parents, step-parents, sister, step-siblings, and the rest of my family for seeing me through this long track through all my schooling. I would like to thank a few of my friends who vi have stuck by me through many years: Bryan and Kathy Launier, Adam Corsaut, Greg Vanderzyde, Ethan Heming, and Emily Withers. Finally, I would like to thank my wife, Larissa Smith. Larissa has been with me through the best and worse times. We’ve been together since our first year of undergraduate study and attended many of the same classes and graduated with the same degree. We both joined the Wang group and while we worked on different projects she was always ready to hear out my problems and help me work through them. Since then she graduated with her Masters and has gone on to be more of the breadwinner in the family while I continued on the path to my PhD. She is and will always be the love of my life and I would like to dedicate this thesis to her for all the things she’s had to put up with. vii Statement of Originality I hereby certify that all of the work described within this thesis is the original work of the author. Published (or unpublished) ideas and/or techniques from the work of others are fully acknowledged in accordance with the standard referencing practices. (Sean McDonald) (06, 2018) viii Table of Contents Abstract ........................................................................................................................................................ iii Co-Authorship............................................................................................................................................... v Acknowledgements ...................................................................................................................................... vi List of Figures ............................................................................................................................................. xii List of Tables ............................................................................................................................................. xix List of Abbreviations .................................................................................................................................. xx Chapter 1 Introduction .................................................................................................................................. 1 1.1 Lewis Acid and Base Chemistry ......................................................................................................... 1 1.2 N-Heterocyclic Carbenes .................................................................................................................... 4 1.2.1 Fundamental Understanding of Carbenes .................................................................................... 4 1.2.2 History of N-Heterocyclic Carbenes ............................................................................................ 7 1.2.3 N-Heterocyclic Carbenes as a Ligand in Main Group and Transition Metal Chemistry ............. 8 1.3 Photoactivity of Boron Compounds .................................................................................................. 12 1.4 Azaborines ........................................................................................................................................ 18 1.5 Pyrido[2,1-a]isoindole ...................................................................................................................... 26 1.6 Scope of Thesis ................................................................................................................................. 30 1.7 List of New Compounds and Important Known Compounds ........................................................... 31 1.7.1 New Compounds in This Thesis ................................................................................................ 31 1.7.2 Known Compounds Featured in This Thesis ............................................................................. 32 1.8 References ........................................................................................................................................