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Hydrosilylation of Alkenes Catalyzed by Bis-N-Heterocyclic Carbene Rh(I) Complexes a Density Functional Theory Study

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Hydrosilylation of Alkenes Catalyzed by Bis-N-Heterocyclic Carbene Rh(I) Complexes a Density Functional Theory Study TECHNISCHE UNIVERSITÄT MÜNCHEN FACHGEBIET FÜR THEORETISCHE CHEMIE Hydrosilylation of Alkenes Catalyzed by Bis-N-Heterocyclic Carbene Rh(I) Complexes A Density Functional Theory Study Dipl. –Chem. Univ. Yin Wu Vollständiger Abdruck der von der Fakultät für Chemie der Technische Universität München zur Erlangung des akademischen Grades eines Doktors der Naturwissenschaften (Dr. rer. nat.) genehmigten Dissertation. Vorsitzender: Univ.–Prof. Dr. K. Köhler Prüfer der Dissertation: 1. Univ.–Prof. Dr. Dr. h.c. N. Rösch, i. R. 2. Univ.–Prof. Dr. Dr. h.c. B. Rieger Die Dissertation wurde am 14.04.2014 bei der Technischen Universität München eingereicht und durch die Fakultät für Chemie am 08.05.2014 angenommen. i Acknowledgment First and foremost, I want to give my deepest thanks to my Doktorvater, Prof. Dr. Notker Rösch, for giving me the opportunity to do the doctoral thesis in his research group. This dissertation would not have been completed without his guidance and support. Under his supervision, I learned a lot about how to meet academic challenges. The knowledge I gained over these years is very valuable to me. I owe a debt of gratitude to Dr. Alexander Genest, without whose help I would never have learned how to approach a scientific task and resolve essential problems. He also showed me how to communicate efficiently in a team. I am truly thankful to Prof. Dr. Rieger and all colleagues from the Wacker Institute of Silicon Chemistry for the interdisciplinary discussions. It is a pleasure to thank Dr. Virve Karttunen for providing me with the background knowledge about this interesting and complex topic, and for her patience and encouragement, especially in the initial phase of this project. I would like to thank Dr. Ion Chiorescu for helping me improve my calculation skills and for many inspiring discussions. I thank Dr. Sven Krüger for many general scientific discussions and administrative supports. I appreciate deeply administrative support by Dr. Miriam Häberle, Dr. Agnes Mirescu, Ms. Annemarie Meinel, Ms. Barbara Asam, and Ms. Elisabeth Wurm. I thank my colleagues for sharing their scientific interests with me in group seminar and other talks, and for various help with both scientific and non-scientific issues. I thank Dr. Duygu Başaran, Dr. Konstantina Damianos, Dr. Wilhelm Eger, Dr. Alena Kremleva, Dr. Alexei Matveev, Dr. Remi Marchal, Dr. Astrid Nikodem, Dr. Shane Parker, Dr. Zhijian Zhao, Dr. Shranbani Dinda, Dr. Agalya Govindasamy, Dr. Xiufang Ma, Dr. Suwit Suthirakun, Dr. Lili Zhao, Cheng-Chau Chiu, Chun-Ran Chang, Bo Li, Thomas Soini, Benjamin Chen, and Boxiao Zheng, as well as those not mentioned here. I want to give special thanks to my friends for many memorable moments, Mrs. Katia Rodewald, Dr. Heiner Eckert, Dr. Zer-Rur Huang, Dr. Shiang-Bor Huang, Dr. Lei Lei, Dr. Yun Zhang, Dr. Bo Zhang, Yang Liu, Katharina Wussow, Xiaoxiao Du, Nan Zou, Tongyu Wang, Dr. Xiaojun Liu, Ping Lu, Hong Li, Thi-Thoa Nguyen, Gia Hoang, Daniel Nguyen, Puyee Wong, Shuomei Huang, Huiyi Loy, Will Chua, Pricilla Chua, Ying Yuan Wong, and many more. I am grateful to the Plum Village Sangha in Munich, Waldbröl, and Singapore. I also thank all sisters and brothers I met in Fo Guang Shan and Tzu Chi. My warmest thanks are due to my mother who gives me a great deal of understanding and freedom. Finally, I gratefully acknowledge Wacker Chemie AG for awarding me a scholarship. ii “Is the Master out of his mind?” she asked me. I nodded. “And he's taking you with him?” I nodded again. “Where?” she asked. I pointed towards the center of the earth. “Into the cellar?” exclaimed the old servant. “No,” I said, “farther down than that.” Jules Verne, Journey to the Center of the Earth iii Contents 1 Introduction ................................................................................................................... 1 2 Background .................................................................................................................... 3 2.1 Hydrosilylation ....................................................................................................... 3 2.2 Mechanisms for the Catalyzed Hydrosilylation of Alkene ....................................... 8 2.2.1 Chalk-Harrod Mechanism ................................................................................ 9 2.2.2 Modified Chalk-Harrod Mechanism ............................................................... 11 2.2.3 σ-Bond Metathesis Mechanism ...................................................................... 12 2.2.4 Glaser-Tilley Mechanism ............................................................................... 15 2.2.5 Oxidative Addition of Silane .......................................................................... 17 2.3 N-Heterocyclic Carbenes ...................................................................................... 19 2.3.1 Early Synthesis of NHC ................................................................................. 20 2.3.2 Development of the TM-NHC Complexes ..................................................... 23 2.3.3 Stability and Aromaticity of NHC .................................................................. 27 2.3.4 Steric Properties of NHC................................................................................ 31 2.3.5 Stability and Reactivity of the TM-NHC Bond ............................................... 33 2.3.6 Free NHCs ..................................................................................................... 38 3 Computational Methods ............................................................................................... 39 4 Full Pathways of the Mechanisms ................................................................................ 42 4.1 GT Pathway .......................................................................................................... 44 4.1.1 GT: the Silylene Complex .............................................................................. 46 4.2 CH and mCH Pathways......................................................................................... 49 4.2.1 Variants of the Initial Phase ........................................................................... 50 4.2.2 Formation of the Product................................................................................ 53 4.2.3 Elimination of the Product ............................................................................. 55 4.2.4 CH: bis-NHC and trans-Effect ....................................................................... 56 4.3 SBM Pathway ....................................................................................................... 58 4.3.1 SBM: Change in the Coordination Sphere ...................................................... 61 4.4 Performance of the bis-NHC Ligand ..................................................................... 62 4.5 Conclusion ............................................................................................................ 67 5 Method Dependence of Competing Mechanisms .......................................................... 68 5.1 Differences between B3LYP and BP86 for the Four Mechanisms ......................... 71 iv 5.2 Optimization of Eight Selected Barriers by Five Functionals ................................. 75 5.2.1 Ranking of Barriers ........................................................................................ 75 5.2.2 Performances of Density Functionals ............................................................. 78 5.3 Optimization of Four Selected Barriers by 12 Density Functionals ........................ 81 5.3.1 Mechanism Preference between CH and SBM ............................................... 81 5.3.2 A Closer Look at the Barrier gt2 .................................................................... 84 5.4 Conclusion ............................................................................................................ 87 6 Regioselectivity Induced by Catalyst Modification ....................................................... 88 6.1 Location and Energetic Features of the Regioselective Step .................................. 89 6.2 Modification of the Catalyst Ligand ...................................................................... 93 6.3 Impact of the Modifications .................................................................................. 94 6.3.1 Length of the Linkage .................................................................................... 94 6.3.2 Substitution on the Nitrogen Atoms ............................................................... 95 6.3.3 Modification of the C−C backbone ................................................................ 97 6.4 Analyses of the Reaction Kinetics ......................................................................... 99 6.5 Conclusion .......................................................................................................... 106 7 Summary ................................................................................................................... 107 8 List of Abbreviation ................................................................................................... 111 9 Appendix ................................................................................................................... 113 10 References ................................................................................................................. 125 v Introduction 1 Introduction Hydrosilylation
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