Neutral and Cationic Organoantimony(V) Lewis Acids As
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NEUTRAL AND CATIONIC ORGANOANTIMONY(V) LEWIS ACIDS AS FLUORIDE RECEPTORS AND CATALYSTS A Dissertation by MASATO HIRAI Submitted to the Office of Graduate and Professional Studies of Texas A&M University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Chair of Committee, François P. Gabbaï Committee Members, Marcetta Y. Darensbourg Oleg V. Ozerov Jodie L. Lutkenhaus Head of Department, Simon W. North August 2016 Major Subject: Chemistry Copyright 2016 Masato Hirai ABSTRACT It is known that SbF5 and SbCl5 are highly robust and show stronger acidic behavior than their boron counterparts, BF3 and BCl3, respectively. This effect is caused by the polarizability and the electropositivity of these heavy elements as well as a lowering of the element-centered σ* orbitals. These larger elements are also able to accept more ligands in their coordination sphere, thus promoting Lewis base coordination. However, antimony pentahalides violently react with water to generate the corresponding hydrohalic acids, which limits the scope of applications in which they can be employed. By replacing the Sb-X (X = F or Cl) bonds with carbon and/or oxygen substituents, this corrosive nature of antimony pentahalide species could be suppressed and become significantly more stable. As a drawback, displacement of electron-withdrawing halide substituents may also result in a decrease of Lewis acidity. It is therefore significant to design organoantimony(V) species that bear sufficient ligand functionalities to balance both reactivity and stability. In this dissertation, we will present our recent developments of both neutral and cationic organoantimony(V) compounds as sensors for small anions specifically in aqueouse media, reagents to activate molecules such as organic carbonyls, and potential ligands for heavy transition metals. ii DEDICATION For Grandma iii ACKNOWLEDGEMENTS I would first like to thank my high school chemistry teacher, Mr. Rudi Jansen, for his passion towards education and for introducing me to the enthusiastic world of chemistry (I would also like to use this opportunity to apologize for talking too much in class). I would also like to thank Prof. Marcetta Y. Darensbourg for not only serving as my PhD committee member but for consistently giving me advice and encouragement throughout my career as both an undergraduate and a graduate student. I would not have been where I am at today without the two of you and I am extremely grateful for that. I would also like to acknowledge my other two committee members Prof. Oleg V. Ozerov and Prof. Jodie L. Lutkenhaus for spending extensive amount of their valuable time for me. I was incredibly fortunate for being able to work with members of the Gabbaï research group, past and present: Dr. Mitsukuni Tsunoda, Prof. Min Hyung Lee, Dr. Baofei Pan, Dr. Kewei Huang, Dr. Boris Vabre, Dr. Daniel Tofan, Dr. Guillaume Bélanger-Chabot, Lauren Leamer, Haifeng Yang, Anna Marie Christianson, Srobona Sen, Chang-Hong Chen, Elham Tabei, Mengxi (Moncy) Yang, Ying-Hao Lo, Di You, Gregory Day, Christina Lollar, Minji Kim, Merid Haile, Samantha Brewer, Andrian Maker, Xu Ye, Nilanjana Pati and Austin Williamson. I would particular like to thank Prof. Casey Wade, Dr. Tzu-Pin Lin, Dr. Haiyan Zhao and Dr. Iou-Sheng Ke for their mentorship in my earlier years of PhD, and Dr. Kantapat Chansaenpak and James (Stuart) Jones for being great friends and colleagues of mine since the beginning. My everlasting friendship goes iv outside of lab as well. I could not have been able to complete my PhD without my former roommates and best friends Dr. Andrew Brown, John Patrick and Chandra-Mouli Palit. Thanks for hanging out with me whenever I needed a break. My special thanks also goes to the Phi Lambda Upsilon (PLU) 2012-2013 officers whom I had the privilege to work with: Dr. Natalie Harvey, Dr. Jessica DeMott, and Darrell Martin. The same respect applies to Dr. Amanda David who invited me to be a part of Organization for Cultural Diversity in Chemistry (OCDC). My appreciation also goes to all of the wonderful professors and staff members who gave me sufficient advice and assistance: Prof. Abraham Clearfield, Prof. Donald J. Darensbourg, Prof. Kim R. Dunbar, Prof. Timothy R. Hughbanks, Prof. Dong-Hee Son, Prof. Coran M. H. Watanabe, Dr. Holly C. Gaede, Dr. Joanna G. Pellois, Dr. Nattamai Bhuvanesh, Dr. Joseph H. Reibenspies, Dr. Vladimir Bakhmoutov, Dr. K. P. Sarathy, Steve K. Silber, Dr. Gregory P. Wylie, Dr. Lisa Perez, Ron Carter, Sandy Horton, Valerie McLaughlin, Dennis Havemann, Curtis Lee, Melvin Williams, and Phillip Wymola. My extended gratitude goes to all of the assistants from the department who have become great friends of mine: Kim Holder, Angie Wilson, Andrezza Silva Mello Cesar An and Ethel Mejia. Words cannot describe how thankful I am to my family back in Japan. My mom and dad gave me the freedom to study whatever I want and gave me the opportunity to go to school in the U.S. since I was 20 years old. I love you both dearly. My brother and I are completely the different but we understand each other the most. Although we do not converse as often, he is my only and the best brother a man could ask for. Thanks for v being such a cool bro. Many thanks goes to my friends back in my home country as well. My special gratitude goes to Natsuko Danjo who has continually encouraged me throughout the hard times. I have been using your Christmas gift every day. I would also like to show my appreciation to the National Science Foundation, the Welch Foundation, Eastman Chemical, PLU and the Department of Chemistry for research funding and travel grants. Finally, my greatest thanks goes to my research advisor, Prof. François P. Gabbaï. Working under him made me realize how much I love what I do in lab. I may not have been the best student but he never gave up on me and led me to where I am at right now. Not only do I respect him as an advisor, a professor or a chemist, I respect him as a person, a human being who cares so much about all of us and the department. I could not have asked for a better boss. Thank you so much Boss! vi TABLE OF CONTENTS Page ABSTRACT .......................................................................................................................ii DEDICATION ................................................................................................................. iii ACKNOWLEDGEMENTS .............................................................................................. iv TABLE OF CONTENTS .................................................................................................vii LIST OF FIGURES ............................................................................................................ x LIST OF TABLES .......................................................................................................... xix CHAPTER I INTRODUCTION TO ANTIMONY LEWIS ACIDS FOR MOLECULAR ANION RECOGNITION AND CATALYSIS ........................................ 1 1.1 Introduction to organoantimony(V) Lewis acids ............................................... 1 1.2 Main-group Lewis acids as fluoride sensors .................................................... 17 1.3 Organoantimony(V) Lewis acids as organic transformation catalysts ............. 31 1.4 Objectives ......................................................................................................... 42 CHAPTER II LEWIS ACIDIC STIBORAFLUORENES FOR THE FLUORESCENCE TURN-ON SENSING OF FLUORIDE IN DRINKING WATER AT PPM CONCENTRATIONS ....................................................................... 43 2.1 Introduction ...................................................................................................... 43 2.2 Fluoride binding properties of spirocyclic stiboranes ...................................... 45 2.3 Spirocyclic stiboranes as fluoride sensors in water/CH2Cl2 mixture ............... 57 2.4 Determination of fluoride concentrations of water samples ............................ 59 2.5 Conclusion ........................................................................................................ 60 2.6 Experimental section ........................................................................................ 61 vii CHAPTER III SQUEEZING FLUORIDE OUT OF WATER WITH A NEUTRAL BIDENTATE ANTIMONY(V) LEWIS ACID ............................................................... 74 3.1 Introduction ...................................................................................................... 74 3.2 Synthesis and characterization of distibine and distiborane ............................. 76 3.3 Fluoride binding property of distiborane in water ........................................... 80 3.4 Reaction of the distiborane with fluoride ions ................................................. 84 3.5 Conclusion ........................................................................................................ 87 3.6 Experimental section ........................................................................................ 88 CHAPTER IV 1-PYRENYL- AND 3-PERYLENYL-ANTIMONY(V) DERIVATIVES FOR THE FLUORESCENCE TURN-ON SENSING OF FLUORIDE IONS IN WATER AT SUB-PPM CONCENTRATIONS .......................... 98 4.1 Introduction ...................................................................................................... 98 4.2 Synthesis and characterization of tetraaryl stibonium bromide salts ............. 100 4.3 Fluoride binding properties of tetraarylstibonium