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Organocuprate Aggregation and Reactivity: Decoding the 'Black Box'

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Organocuprate Aggregation and Reactivity: Decoding the 'Black Box' Dissertation zur Erlangung des Doktorgrades der Fakultät für Chemie und Pharmazie der Ludwig-Maximilians-Universität München Organocuprate Aggregation and Reactivity: Decoding the ‘Black Box’ Aliaksei Putau aus Vitebsk, Weißrussland 2012 Erklärung Diese Dissertation wurde im Sinne von § 7 der Promotionsordnung vom 28. November 2011 von Herrn Prof. Dr. Konrad Koszinowski betreut, und von Herrn Prof. Dr. Mayr von der Fakultät für Chemie und Pharmazie vertreten. Eidesstattliche Versicherung Diese Dissertation wurde selbständig, ohne unerlaubte Hilfe erarbeitet. München, 11.06.2012 _______________________ Aliaksei Putau Dissertation eingereicht am: 12.06.2012 1. Gutachter Prof. Dr. Herbert Mayr 2. Gutachter Prof. Dr. Konrad Koszinowski Mündliche Prüfung am: 20.07.2012 Acknowledgements It is a pleasure to thank the many people who made this project possible. My gratitude to my PhD supervisor, Prof. Dr. Konrad Koszinowski, is difficult to overstate. His sound advice, good company, and enthusiasm for trying new things ensured the tropical sunny climate in our group that is so necessary for fruitful (and, above all, enjoyable) research. Besides, his involvement in the group life outside the lab made all of us group members feel like team members, not just a loose bunch of colleagues. I am also deeply indebted to Prof. Dr. Herbert Mayr, not only for his continuous generous support and help, but also for running such a cool, all-star research group, which provided a great many social occasions. I thank SFB 749 for the financial support of this project, specifically Mrs. Birgit Carell, for her support and understanding of my worries and troubles of all kinds. Furthermore, my sincere gratitude goes to Prof. Dr. Hendrik Zipse, Prof. Dr. Manfred Heuschmann, Prof. Dr. Konstantin Karaghiosoff and Prof. Dr. Paul Knochel for showing interest in this manuscript by accepting to be referees. This work would have hardly been imaginable without my teammates, Katharina Böck, Christina Müller and Julia Fleckenstein, whose friendship, help and motivation made me feel at home. Finally, last but not least, I would like to thank my wife and family for their endless love and support. Parts of the results of this thesis have been published in: Probing Cyanocuprates by Electrospray Ionization Mass Spectrometry A. Putau, K. Koszinowski, Organometallics 2010, 29, 3593-3601; Addition/correction: A. Putau, K. Koszinowski, Organometallics 2010, 29, 6841-6842; Association and Dissociation of Lithium Cyanocuprates in Ethereal Solvents A. Putau, K. Koszinowski, Organometallics 2011, 30, 4771-4778; Tetraalkylcuprates(III): Formation, Association, and Intrinsic Reactivity A. Putau, H. Brand, K. Koszinowski, J. Am. Chem. Soc. 2012, 134, 613-622. Table of Contents 1 Abstract......................................................................................................................... 1 2 Introduction ................................................................................................................ 3 2.1 Overview.......................................................................................................................... 3 2.2 Aggregation and Structure of Cyanocuprates................................................................. 5 2.3 Coupling Reactions.......................................................................................................... 7 2.4 Conjugate Addition Reactions......................................................................................... 9 2.5 Objectives....................................................................................................................... 10 3 Instrumentation and Methods............................................................................. 11 . 3.1 Electrospray Ionization Mass Spectrometry (ESI-MS).................................................. 11 3.1.1 Theoretical Overview.............................................................................................. 11 3.1.2 Potential and Limitations of ESI-MS...................................................................... 16 3.1.2 Experimental Part................................................................................................... 17 3.2 Electrical Conductivity Measurements........................................................................... 23 3.3 Theoretical Calculations on Tetraalkylcuprates(III)...................................................... 25 3.4 Analysis of Energy-Dependent Fragmentation Reactions............................................. 26 4 Results and Discussion............................................................................................ 29 4.1 Aggregation and Structure of Cyanocuprates................................................................ 29 4.1.1 Negative-Ion Mode ESI Mass Spectrometry........................................................... 29 4.1.2 Positive-Ion Mode ESI Mass Spectrometry............................................................ 39 4.1.3 Electrical Conductivity Measurements.................................................................... 42 4.1.4 General Trends........................................................................................................ 45 4.1.5 Equilibria Operative................................................................................................ 46 4.1.6 Effect of the Solvent............................................................................................... 49 4.1.7 Effect of the Organyl Substituent........................................................................... 51 4.1.8 Effect of the Temperature....................................................................................... 53 4.1.9 Comparison of Analytical Methods........................................................................ 53 4.2 Gas-Phase Reactivity of Cyanocuprates......................................................................... 55 4.2.1 Gas-Phase Fragmentation Reactions....................................................................... 55 4.2.2 Gas-Phase Hydrolysis Reactions............................................................................ 63 4.3 Cross-Coupling Reactions............................................................................................... 69 4.3.1 Reactions of Dialkylcuprates with Organyl Halides................................................ 69 4.3.2 Association Equilibria of Lithium Tetraalkylcuprates............................................ 77 4.3.3 Unimolecular Reactivity of Tetraalkylcuprates...................................................... 82 4.4 Conjugate Addition Reactions........................................................................................ 93 4.4.1 Reactions of Diorganylcuprates with Acrylonitrile................................................ 93 4.4.2 Reactions of Diorganylcuprates with Fumaronitrile............................................... 93 4.4.3 Reactions of Diorganylcuprates with 1,1-Dicyanoethylene.................................... 96 4.4.4 Reactions of Diorganylcuprates with Tricyanoethylene.......................................... 96 4.4.5 Reactions of Diorganylcuprates with Tetracyanoethylene................................... 99 4.4.5 Substrate Structure-Reactivity Relationships....................................................... 102 5 Conclusions and Outlook.................................................................................... 104 6 Appendix.................................................................................................................... 108 6.1 Analytical Data.............................................................................................................. 108 6.2 Synthesis........................................................................................................................ 109 6.2.1 General Considerations......................................................................................... 109 6.2.2 Synthesis of Organocuprate Reagents.................................................................. 109 13 6.2.3 Synthesis of Cu CN............................................................................................. 111 6.2.4 Synthesis of Cyanoethylene Substrates................................................................ 112 6.3 Determination of Background Water Concentration................................................... 115 7 References and Notes............................................................................................. 116 1 Abstract 1 Abstract A broad range of organocopper intermediates in different aggregation states were characterized by electrospray ionization (ESI) mass spectrometry, which provided valuable information on these fluxional species. To complement the mass spectrometric data, electrical conductivity measurements and theoretical calculations were employed. Tetrahydrofuran (THF) solutions of CuCN/(RLi)m stoichiometry (m = 0.5, 0.8, 1.0, and 2.0 and R = Me, Et, nBu, sBu, tBu, Ph) were analyzed by ESI mass spectrometry, and organocuprate anions were detected for all cases. The composition of these species showed – clear dependence on the amount of RLi used. Thus, while cyanide-free Lin–1CunR2n anions – completely predominated for CuCN/(RLi)2 solutions, cyanide-containing Lin–1CunRn(CN)n complexes prevailed for CuCN/(RLi)m reagents with m ≤ 1. Ligand mixing studies on n s t LiCuMe2·LiCN and LiCuR2·LiCN systems (R = Et, Bu, Bu, Bu,
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