A Mechanistic Insight into the Nickel-Catalyzed Homocoupling Reaction of Terminal Alkynes vom Fachbereich Chemie der Technischen Universität Kaiserslautern zur Verleihung des akademischen Grades 'Doktor der Naturwissenschaften' eingereichte Dissertation D 386 vorgelegt von Subrata Ghosh, M.Sc. Betreuer Prof. Hans-Jörg Krüger, Ph. D. Tag der wissenschaftlichen Aussprache: 29. 01. 2018 Kaiserslautern 2018 Promotionskommission: Vorsitzender: Prof. Dr. Stefan Kubik Berichterstatter: Prof. Hans-Jörg Krüger, Ph. D. Berichterstatter: Prof. Dr. Helmut Sitzmann Datum der wissenschaftlichen Aussprache: 29. 01. 2018 Die vorliegende Arbeit entstand in der Zeit zwischen November 2010 und September 2017 in den Laboratorien des Fachbereichs Chemie an der Technische Universität Kaiserslautern. Eidesstattliche Erklärung Hiermit versichere ich, dass ich die vorliegende Arbeit eigenständig verfasst, keine anderen als die angegebenen Quellen und Hilfsmittel verwendet und Literaturzitate kenntlich gemacht habe. Ich erkläre außerdem, dass diese Arbeit weder in gleicher noch in ähnlicher Form bereits in einem anderen Prüfungsverfahren vorgelegen hat. Kaiserslautern, den Subrata Ghosh To my parents Abbreviations A Absorbance Ad Adamantly ANAP Acenaphthylene Avg. Average Bu Butyl tBu tert-Butyl Cat. Catalyst CO Carbon monoxide COD 1,5-Cyclooctadiene CT Charge transfer Cy Cyclohexyl Chemical shift d Doublet DCE 1,2-Dichloroethene DFT Density functional theory DMF Dimethylformamide dppe 1,2-Bis(diphenylphosphino)ethane Molar extinction coefficient Equiv. Equivalent EPR Electron paramagnetic resonance ESI MS Electrospray ionization mass spectrometry Et Ethyl EtCN Propionitrile Et3N Triethylamine Et2O Diethyl ether EXAFS Extended X-ray absorption fine structure Fc Ferrocene H Magnetic field strength HIV Human immunodeficiency virus I Nuclear spin IR Infrared K Kelvin Wavelength LMCT Ligand to metal charge transfer L-N4Me2 N,N-Dimethyl-2,11-diaza[3.3](2,6)pyridinophan Me Methyl MeCN Acetonitrile MeOH Methanol MLCT Metal to ligand charge transfer mT Militesla m/z Mass-to-charge ratio MW Molecular weight NaH Sodium hydride NIR Near infrared NMR Nuclear magnetic resonance Ph Phenyl PMe3 Trimethylphosphine PPh3 Triphenylphosphine Pr Propyl iPr iso-Propyl Py Pyridine RT Room temperature s Singlet SCE Saturated calomel electrode SQUID Superconducting quantum interference device t Triplet T Temperature TBAP Tetrabutylammonium perchlorate TMEDA N,N,N,N-tetramethylethylenediamine UV-Vis Ultraviolet visible ̃ Wavenumber v Velocity vs Versus M Molar susceptibility Table of Contents 1 Introduction .................................................................................................................. 1 1.1 Copper-Catalyzed Homocoupling of Terminal Alkynes ............................................. 4 1.2 Palladium-Catalyzed Homocoupling of Terminal Alkynes ......................................... 7 1.3 Nickel-Catalyzed Homocoupling of Terminal Alkynes ............................................... 9 1.4 Nickel-O2 Chemistry .................................................................................................. 13 1.5 Motivation .................................................................................................................. 19 2 Result and Discussions ............................................................................................... 21 2.1 Synthesis and Characterization of [Ni(L-N4Me2)(MeCN)2](ClO4)2 (1) .................... 21 2.2 Synthesis and Characterization of Dinuclear Nickel(I)-Diyne Complexes ............... 27 2.2.1 Synthesis ............................................................................................................. 28 2.2.2 X-ray Structures Analysis .................................................................................. 28 2.2.3 Magnetochemistry .............................................................................................. 45 2.2.4 Spectroscopic Studies ......................................................................................... 51 2.2.5 Electrochemistry ................................................................................................. 63 2.2.6 Stoichiometric Reaction in Presence of Radical Inhibitor ................................. 67 2.2.7 Stoichiometric Reaction at Low Temperature ................................................... 69 2.3 Synthesis and Characterization of [Ni(L-N4Me2)(PhC2Ph)](ClO4) MeOH (3) ....... 71 2.3.1 Synthesis ............................................................................................................. 71 2.3.2 X-Ray Structure Analysis ................................................................................... 72 2.3.3 Spectroscopic Studies ......................................................................................... 75 2.3.4 Electrochemistry ................................................................................................. 78 2.4 Reactivity of [{Ni(L-N4Me2)}2(-RC4R)](ClO4)2 [R = Ph] (2a) with Molecular Oxygen ....................................................................................................................... 80 2.4.1 Spectroscopic Studies ......................................................................................... 80 2.4.2 Reactivity in Presence of Lithium Perchlorate ................................................... 90 2.5 Reactivity of [Ni(L-N4Me2)(PhC2Ph)](ClO4) MeOH (3) with Molecular Oxygen . 91 + 2.6 Generation and Characterization of [Ni(L-N4Me2)(O2)] (5)..................................... 99 2.7 Nickel-Mediated Catalytic Reaction ........................................................................ 104 2.8 Spectroscopy Studies on Catalytic Reaction ............................................................ 105 2.9 Proposed Mechanism ............................................................................................... 108 3 Summary .................................................................................................................. 110 4 Experimental Section ............................................................................................... 112 4.1 Physical Methods ..................................................................................................... 112 4.2 Starting Materials ..................................................................................................... 114 4.3 Experimental Details ................................................................................................ 115 4.3.1 Synthesis of [Ni(L-N4Me2)(MeCN)2](ClO4)2 (1) ............................................. 115 4.3.2 Synthesis of [{Ni(L-N4Me2)}2(-RC4R)](ClO4)2 (2a-2g) ................................ 116 4.3.3 Stoichiometric Reaction in Presence of Radical Inhibitor TEMPO ................. 122 4.3.4 Stoichiometric Reaction at Low Temperature to Room Temperature ............. 123 4.3.5 Synthesis of [Ni(L-N4Me2)(PhC2Ph)](ClO4) MeOH (3) ................................ 125 4.3.6 Reactivity of [{Ni(L-N4Me2)}2(-RC4R)](ClO4)2 [R= Ph] (2a) with Molecular Oxygen ............................................................................................................. 127 4.3.7 Reactivity of [{Ni(L-N4Me2)}2(-RC4R)](ClO4)2 [R= Ph] (2a) with Molecular Oxygen in Presence of Lithium Perchlorate .................................................... 127 4.3.8 Reactivity of [Ni(L-N4Me2)(PhC2Ph)](ClO4)MeOH (3) with Molecular Oxygen .......................................................................................................................... 128 + 4.3.9 Generation of [Ni(L-N4Me2)(O2)] .................................................................. 129 4.3.10 Nickel-Mediated Catalytic Reaction ................................................................ 131 5 Literature .................................................................................................................. 132 6 Acknowledgement .................................................................................................... 143 7 Appendix .................................................................................................................. 144 7.1 [Ni(L-N4Me2)(MeCN)2](ClO4)2 (1) ......................................................................... 144 7.2 [{Ni(L-N4Me2)}2(-RC4R)](ClO4)2 (2a-2g) ............................................................ 147 7.2.1 [{Ni(L-N4Me2)}2(-RC4R)](ClO4)2 [R = Ph] (2a) ........................................... 147 7.2.2 [{Ni(L-N4Me2)}2(-RC4R)](ClO4)2 [R = C6H4Me-4] (2b) .............................. 154 7.2.3 [{Ni(L-N4Me2)}2(-RC4R)](ClO4)2 [R = C6H4F-4] (2c) ................................. 161 7.2.4 [{Ni(L-N4Me2)}2(-RC4R)](ClO4)2 [R = C6H4OMe-4] (2d) ........................... 168 7.2.5 [{Ni(L-N4Me2)}2(-RC4R)](ClO4)2 [R = C6H4NMe2-4] (2e) .......................... 175 n 7.2.6 [{Ni(L-N4Me2)}2(-RC4R)](ClO4)2 [R = C3H7] (2f) ...................................... 182 7.2.7 [{Ni(L-N4Me2)}2(-RC4R)](ClO4)2 EtOH [R = Fc] (2g) ............................... 188 7.3 [Ni(L-N4Me2)(PhC2Ph)](ClO4) MeOH (3) ............................................................ 198 7.4 Reactivity of [{Ni(L-N4Me2)}2(-RC4R)](ClO4)2 [R = Ph] (2a) with Oxygen ....... 201 7.5 Reactivity of [Ni(L-N4Me2)(PhC2Ph)](ClO4)MeOH (3) with Oxygen ................... 203 + 7.6 [Ni(L-N4Me2)(O2)] (4) ............................................................................................ 205 7.7 Nickel-Mediated Catalytic Reaction .......................................................................