Synthesis of Novel Cyclopentadienyl Cobalt(I)-Complexes and their Application in [2+2+2] Cycloaddition Reactions Dissertation to obtain the academic degree „Doktor der Naturwissenschaften“ (Dr. rer. nat.) submitted at the Mathematisch-Naturwissenschaftlichen Fakultät an der Universität Rostock submitted by MSc. Indre Thiel born on November 27th 1987 in Düsseldorf Rostock, September 13th 2013 I The work of this thesis was conducted between January 2011 and October 2013 under the supervision of Dr. Marko Hapke and Professor Dr. Uwe Rosenthal at the Leibniz-Institut für Katalyse an der Universität Rostock. Referees: 1st Referee: Professor Dr. Uwe Rosenthal, Leibniz-Institut für Katalyse e.V. and der Universität Rostock 2nd Referee: Professor Dr. Matthias Tamm, Technische Universität Braunschweig Thesis Submission: September 13th 2013 PhD Defense: December 3rd 2013 II III Acknowledgement Writing a dissertation takes all kinds of support. Therefore I would like to express my sincere gratitude to all those who made it possible and generously gave their time and expertise. First and foremost I am deeply indebted to my supervisor Dr. Marko Hapke for making me part of his group and providing me with this interesting research project but also giving me the space to pursue my own ideas. His endless believe in me made it possible to push through all the rough stretches that are part of research. My sincere appreciation for many helpful and complaisant discussions and continuous guidance goes to Professor Dr. Uwe Rosenthal. A huge “Thank you” goes to my group members and former group members Fabian Fischer, Phillip Jungk, Dr. Karolin Kral and Dr. Nico Weding. I could not have wished for a better group to share all my experimental successes as well as failures with. Working with you guys never seemed quite as much work than rather great times spend with friends! I will miss you! For creating a warm and welcoming working atmosphere I want to thank the entire Rosenthal group: Kai Altenburger, Dr. Perdita Arndt, Lisanne Becker, Dr. Torsten Beweries, Laura Dura, Christian Godemann, Marc Gongoll, Martin Hähnel, Dr. Sven Hansen, Dr. Katharina Kaleta, Dr. Marcus Klahn, Dr. Monty Kessler, Dr. Bernd H. Müller, Dr. Normen Peulecke, Kathleen Schubert, Johannes Thomas and Ute von Zweydorf. Special thanks are directed towards Dr. Guido Walther, not only because his help with the in situ NMR spectroscopy was essential but also for inspiring as well as diverting conversations. Without the Analytical Department this dissertation would not have been possible. Therefore I want to thank PD Dr. Wolfgang Baumann for all the extraordinary NMR measurements. Susann Buchholz, Kathrin Fiedler, Sigrun Rossmeisl, Susanne Schareina and Dr. Christine Fischer I owe thanks for all the chiral HPLC and mass spectroscopic analyses. I am indebted to Dr. Anke Spannenberg, who was able to determine all X-ray structures even if challenged with infinitely tiny crystals. And last but not least I am grateful to Astrid Lehmann IV and Anja Simmula for all elemental analyses. I would also like to recognize the help and interest extended to me along the way by all those that have not been mentioned explicitly. Finally I do owe more gratitude than I can express to both my parents, who supported me throughout everything and continuously encouraged me to pursue my own path and ideas. Thank you for always being there for me! All my friends I have to acknowledge for the good times and great memories outside the institute! And last but not least I am grateful to the Fonds der Chemischen Industrie for all the financial support throughout my dissertation in the form of a Kekulé scholarship. V Aspects of this thesis have already been published: 1. I. Thiel, H. Jiao, A. Spannenberg, M. Hapke, Chem. Eur. J. 2013, 19, 2548-2554. 2. I. Thiel, M. Hapke, Angew. Chem. 2013, 125, 6030-6032; Angew. Chem. Int. Ed. 2013, 52, 5916–5918. 3. I. Thiel, M. Lamác, H. Jiao, A. Spannenberg, M. Hapke, Organometallics 2013, 32, 11, 3415–3418. 4. I. Thiel, A. Spannenberg, M. Hapke, ChemCatChem 2013, 5, 2865–2868. 5. I. Thiel, M. Hapke, J. Mol. Catal. A: Chem 2014, DOI:10.1016/j.molcata.2013.12.002. Presentations at national and international conferences: Oral Presentations: 1. I. Thiel, CO2 – Vom Schornstein in den Kolben, 3. Mainzer Wissenschaftsgespräche, Mainz, Germany, September 30th - October 1st 2011 (invited speaker) 2. I. Thiel, M. Hapke, Activity versus Stability – A Compromise, 15th Nordic Symposium on Catalysis, Mariehamn, Åland, Finland, June 10th - 12th 2012, O52 3. I. Thiel, M. Hapke, Two Sides of the (Cobalt-) Medal: Activity vs. Stability, CaSus Workshop, Rostock, Germany, September 16th - 18th 2013, T15 4. I. Thiel, M. Hapke, Two Sides of the (Cobalt-) Medal, YoungChem 2013, Poznan, Poland, October 9th - 13th 2013 Poster Presentations: 1. I. Thiel, N. Weding, M. Hapke, Neue Übergangsmetallkomplexe in der Katalyse von [2+2+2]-Cycloadditionsreaktionen, HTI (7. Tagung Hochschule trifft Industrie – Ein Dialog), Schlangenbad, Germany, September 14th - 16th 2011, P2 (invitation) 2. I. Thiel, M. Hapke, New Transition Metal Complexes for [2+2+2] Cycloaddition Reactions, 15th JCF Frühjahrssymposium, Rostock, Germany, March 18th - 21th 2012, P185 VI 3. I. Thiel, M. Hapke, Ligand Influence on the Stability and Activity of Novel Cobalt Complexes for [2+2+2] Cycloaddition Reactions, International Conference Catalysis in Organic Synthesis, Moscow, Russia, September 15th - 20th 2012, P255 4. I. Thiel, M. Hapke, Ligand Influence on the Stability and Activity of Novel Cobalt Complexes for [2+2+2] Cycloaddition Reactions, Frontiers of Organometallic Chemistry (Post-Conference Symposium), St. Petersburg, Russia, September 21st - 22nd 2012, P83 5. I. Thiel, M. Hapke, Ligand Influence on the Stability and Activity of Novel Cobalt Complexes for [2+2+2] Cycloaddition Reactions, ORCHEM, Weimar, Germany, September 24th - 26th 2012, P9 VII “The most exciting phrase to hear in science, the one that heralds the most discoveries is not ‘Eureka!’ but ‘That's funny...’.” Isaac Asimov (1920-1992) VIII IX Table of Contents 1. INTRODUCTION ................................................................................................................ 1 1.1 Benzene and Pyridine as Motives in Natural Substances – Synthetic Approaches ............. 2 1.2 [2+2+2] Cycloaddition ......................................................................................................... 4 1.2.1 Mechanism.................................................................................................................... 4 1.2.2 DFT Calculations .......................................................................................................... 5 1.2.3 Effect of the Ligands .................................................................................................... 8 1.3 Further Modifications of Cobalt(I)-Complexes ................................................................. 12 2. INTENTION OF THIS THESIS ...................................................................................... 17 3. RESULTS AND DISCUSSION ......................................................................................... 19 3.1 Synthesis of Novel CpCo(I)-Complexes for [2+2+2] Cycloaddition Reactions................ 19 3.1.1 Synthesis of [CpCo(H2C=CHSiMe3)(phosphite)]-Complexes – Variation of Phosphites .................................................................................................................. 19 3.1.2 Synthesis of [CpCo(phosphite)2]-Complexes ............................................................. 20 3.1.3 Synthesis of [CpCo(olefin)(phosphite)]-Complexes – Variation of Olefins .............. 22 3.1.4 Synthesis of CpCo-Complexes with Chelating Phosphite-Olefin Ligands ................ 25 3.2 Catalytic Screening ............................................................................................................ 30 3.2.1 Catalytic Screening of the Synthesized CpCo(I)-Complexes ..................................... 30 3.2.2 Performance of 18 and 25 under Various Conditions ................................................ 34 3.2.3 Performance of 19, 23, 25 and 7 under Conventional Heating Conditions and Irradiation with Light ................................................................................................. 34 3.2.4 Comparison of the Reactivity of 6, 11 and 18 ............................................................ 38 3.2.5 Substrate Screening .................................................................................................... 39 3.3 Recycling Experiments ...................................................................................................... 44 3.4 DFT Calculations ............................................................................................................... 46 3.4.1 DFT Calculations for the Synthesis of Complexes Starting from 6 ........................... 46 3.4.2 DFT Calculations for the Synthesis of Complexes Starting from 1 ........................... 48 3.4.3 DFT Calculations for the Synthesis of Chelating Complexes Starting from 1 .......... 49 3.5 In situ NMR Spectroscopy of Photocatalytic Cycloaddition Reactions ............................ 51 3.5.1 Reaction of 3 to 18...................................................................................................... 52 3.5.2 Reaction of 23 to 25.................................................................................................... 54 X 3.5.3 Reaction of 31 to