Metal-containing and Metal-free systems for small molecule activation by Yanxin Yang A thesis submitted in conformity with the requirements for the degree of Doctor of Philosophy Department of Chemistry University of Toronto © Copyright by Yanxin Yang 2017 Metal-containing and metal-free systems toward small molecule activation Yanxin Yang Doctor of Philosophy Department of Chemistry University of Toronto 2017 Abstract The objective of this thesis is to investigate small molecule activation with metal-containing and metal-free systems. Chapter 2 describes a tri-aryl benzene ligand scaffold for multimetallic N2 activation. A RuCp* complex was synthesized and characterized by NMR and X-ray crystallography. It offered an easy entry to understanding of the ligand coordination environment. Additionally, several multi-iron complexes were also obtained even though they were not the desired products. However, they still demonstrated the feasibility of using this ligand to effect multimetallic chemistry. Chapters 3 to 5 describe a series of compounds with charge-separation feature. These compounds could not only bind CO2 reversibly, but also catalyze the hydroboration of CO2 with a wide borane scope. In Chapter 3, a possible intermediate from the catalytic cycle was isolated and it partly revealed the mechanism of the catalytic reaction. ii Acknowledgments At the beginning, I want to thank my PhD supervisor, Prof. Datong Song. The projects he gave me were very interesting but also challenging. His guidance and encouragement helped me overcome those difficulties in my chemistry journey. I feel truly grateful for him to give me continuous support. I also acknowledge the funding agencies that support our projects, including National Science and Engineering Research Council of Canada (NSERC), Ontario government for Ontario Trillium Scholarship, Digital Specialty Chemicals, and University of Toronto. I also thank my committee members, Prof. Doug Stephan, Prof. Bob Morris, and Prof. Ulrich Fekl for their insightful advices. I acknowledge the assistance from the departmental staff, Anna Liza Villavelez, Dmitry Pichugin, Darcy Burns, Tim Burrows, Jack Sheng, Sergiy Nokhrin, Rose Balazs, and Alan Lough. Thanks for the past and current Song group members, including Xiaofei Li, Runyu Tan, Yu Li, Shaolong Gong, Tara Cho, Rhys Batcup, Vince Annibale, Kim Osten, Celia G-Herndon, Adam Pantaleo, Tongen Wang, Trevor Janes, Charlie Kivi, Walter Liang, Dong Wang, Mengxin Zhao. The undergraduate students working with me also provided a lot of help. I feel grateful for them, Maotong Xu, Pavel Zatsepin, Arcturus Phoon, Linfan Yan, Qinyu Xie. Finally, I want to thank my parents. Your support gives me the encouragement to fulfill my PhD study. iii Table of Contents Acknowledgments..................................................................................................................... iii Table of Contents ...................................................................................................................... iv List of Tables .......................................................................................................................... viii List of Figures ........................................................................................................................... ix List of Schemes..................................................................................................................... xviii List of Abbreviations and Symbols...........................................................................................xxi 1 Introduction ........................................................................................................................... 1 1.1 N2 activation................................................................................................................... 1 1.1.1 Mo complexes for N2 activation .......................................................................... 1 1.1.2 N2 activation by iron systems .............................................................................. 3 1.1.3 Polynuclear systems for multi-electron process ................................................... 6 1.2 CO2 activation and conversion ........................................................................................ 9 1.2.1 Activation of CO2 in a stoichiometric manner.....................................................10 1.2.2 Catalytic reduction of CO2 by metal-free molecules ...........................................17 1.3 4,5-Diazafluorenide ligand chemistry.............................................................................22 1.4 Scope and objectives......................................................................................................24 1.5 References .....................................................................................................................25 2 Chapter 2 Multimetallic systems towards N2 activation.........................................................28 2.1 Abstract .........................................................................................................................28 2.2 Introduction ...................................................................................................................28 2.3 Results and Discussion ..................................................................................................30 2.4 Conclusion.....................................................................................................................35 2.5 Experimental .................................................................................................................36 2.5.1 General procedures.............................................................................................36 iv 2.5.2 Synthesis of 2.1..................................................................................................36 2.5.3 Synthesis of 2.2..................................................................................................38 2.5.4 Synthesis of 2.3..................................................................................................40 2.5.5 Synthesis of 2.4..................................................................................................42 2.5.6 Formation of 2.5.................................................................................................44 2.5.7 Formation of 2.6.................................................................................................45 2.5.8 Synthesis of 2.7..................................................................................................45 2.6 References .....................................................................................................................48 3 Chapter 3 Catalytic hydroboration of CO2 with a carbon-centered organocatalyst .................49 3.1 Abstract .........................................................................................................................49 3.2 Introduction ...................................................................................................................49 3.3 Results and discussion ...................................................................................................50 3.4 Conclusion.....................................................................................................................58 3.5 Experimental .................................................................................................................59 3.5.1 General procedures.............................................................................................59 13 3.5.2 Reaction between 9-BBN and CO2 in the presence of catalyst 3.1 at 70 °C ......60 13 3.5.3 Reaction between HBcat and CO2 in the presence of catalyst 3.1 at 70 °C .......60 3.5.4 Reaction between 9-BBN and CO2 in the presence of catalyst 3.1 at 25 °C.........61 3.5.5 Reaction between 9-BBN and CO2 in the presence of catalyst 3.1 at 70 °C.........63 3.5.6 Reaction between HBcat and CO2 in the presence of catalyst 3.1 at 25 °C ..........64 3.5.7 Reaction between HBcat and CO2 in the presence of catalyst 3.1 at 70 °C ..........66 3.5.8 Reaction between HBcat and CO2 in the presence of catalyst 3.1 at 70 °C ..........67 3.5.9 Reaction between HBpin and CO2 in the presence of catalyst 3.1 at 100 °C........69 3.5.10 Reaction between BH3·SMe2 and CO2 in the presence of catalyst 3.1 at 25 °C ...70 3.5.11 Reaction between BH3·SMe2 and CO2 in the presence of catalyst 3.1 at 70 °C ...72 3.5.12 Synthesis of 3.2..................................................................................................73 v 3.5.13 Reaction between HBcat and CO2 in the presence of catalyst 3.2 at 25 °C ..........76 3.5.14 Formation of 3.3.................................................................................................78 3.6 References .....................................................................................................................79 4 Chapter 4 Catalytic hydroboration of CO2 with a pyrindine derivative ..................................81 4.1 Abstract .........................................................................................................................81 4.2 Introduction ...................................................................................................................81 4.3 Results and discussion ...................................................................................................83