Science, Faculty of
Chemistry, Department of
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UBCV
Walsgrove, Henry
Doctor of Philosophy - PhD
University of British Columbia
The investigation of macromolecules containing phosphorus(III) atoms is an active area of research due to the functionality imparted by the heteroatom. Additionally, molecular Pᶦᶦᶦ-compounds are pervasive in synthetic chemistry due to their use as ligands for metal centers. This thesis outlines the investigation of the reactivity of a unique class of low-coordinate Pᶦᶦᶦ-compounds, 1-phosphabutadienes (P=C−C=C), which are phosphorus-containing analogues of organic butadienes. Chapter 1 acquaints the reader with the background and functionality of unique low-coordinate phosphorus compounds. An in-depth examination of the prior art in the polymerization, cyclization and coordination chemistries of these compounds is provided. Chapter 2 focuses on the anionic polymerization of 1-phosphaisoprene [Mes*P=C(Me)−CH=CH₂; Mes* = 2,4,6-tri-t-butylphenyl] to furnish poly(1-phosphaisoprene). Molecular model studies including isolation of the propagating anion and models displaying both 4,3- and trans-4,1-enchainment are presented. The structural data gained from these molecular models are placed into the context of the microstructure of poly(1-phosphaisoprene). Chapter 3 reports the reaction of poly(1-phosphaisoprene) with [Pd(cod)Cl₂] and [Pd(η³-C₃H₅)(μ-Cl)]₂. It is shown that a concentrated solution of the former can undergo reversible gelation. The gelation does not occur upon treatment of poly(1-phosphaisoprene) with [Pd(η³-C₃H₅)(µ-Cl)]₂, indicating that cross-linking within the polymer network is responsible for gel formation. The study is complemented with molecular models. Chapter 4 focuses on cyclization reactions of 1-phosphabutadienes. Specifically, a [4+2] adduct of 1-phosphaisoprene with unique regiochemistry is disclosed and the observed reactivity is complemented by DFT calculations. Furthermore, the synthesis and [2+2] cyclization of a novel 1-phosphabutadiene, Mes*P=C(Me)−C(Me)=CH₂, is reported. Chapter 5 focuses on the synthesis and characterization of Mes*P=C(Si(CH₃)₃)−CH=CH₂. It is shown that this compound undergoes an E/Z-isomerization in the presence of n-BuLi. The compound was also found to isomerize upon exposure to light. Chapter 6 discloses muon spin spectroscopy studies of three 1-phosphabutadienes. The major radical products in each case are identified as delocalized 1-phosphaallyl radicals. This study represents the first model of radical addition to a 1-phosphabutadiene. Chapter 7 contains concluding remarks and a summary of the work presented in this thesis. Taken together, these discoveries mark a significant advancement in the chemistry of these unique P=C−C=C species.
Modeling the Polymerization of 1-Phosphaisoprene: Explorations of the Synthesis and Reactivity of 1-Phosphabutadienes by Henry Walsgrove MSci., The University of Nottingham, 2016 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY in THE FACULTY OF GRADUATE AND POSTDOCTORAL STUDIES (Chemistry) THE UNIVERSITY OF BRITISH COLUMBIA (Vancouver) April 2023 © Henry Walsgrove, 2023 ii The following individuals certify that they have read, and recommend to the Faculty of Graduate and Postdoctoral Studies for acceptance, the dissertation entitled: Modeling the Polymerization of 1-Phospahisoprene: Explorations of the Synthesis and Reactivity of 1-Phosphabutadienes submitted by Henry Walsgrove in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Chemistry Examining Committee: Derek Gates, Professor, Chemistry, UBC Supervisor Mark MacLachlan, Professor, Chemistry, UBC Supervisory Committee Member Andrew MacFarlane, Professor, Chemistry, UBC University Examiner Zac Hudson, Associate Professor, Chemistry, UBC University Examiner Additional Supervisory Committee Members: Pierre Kennepohl, Professor, Chemistry, University of Calgary Supervisory Committee Member Martin Tanner, Professor, Chemistry, UBC Supervisory Committee Member iii Abstract The investigation of macromolecules containing phosphorus(III) atoms is an active area of research due to the functionality imparted by the heteroatom. Additionally, molecular PIII-compounds are pervasive in synthetic chemistry due to their use as ligands for metal centers. This thesis outlines the investigation of the reactivity of a unique class of low-coordinate PIII-compounds, 1-phosphabutadienes (P=C−C=C), which are phosphorus-containing analogues of organic butadienes. Chapter 1 acquaints the reader with the background and functionality of unique low-coordinate phosphorus compounds. An in-depth examination of the prior art in the polymerization, cyclization and coordination chemistries of these compounds is provided. Chapter 2 focuses on the anionic polymerization of 1-phosphaisoprene [Mes*P=C(Me)−CH=CH2; Mes* = 2,4,6-tri-t-butylphenyl] to furnish poly(1-phosphaisoprene). Molecular model studies including isolation of the propagating anion and models displaying both 4,3- and trans-4,1-enchainment are presented. The structural data gained from these molecular models are placed into the context of the microstructure of poly(1-phosphaisoprene). Chapter 3 reports the reaction of poly(1-phosphaisoprene) with [Pd(cod)Cl2] and [Pd(η3-C3H5)(μ-Cl)]2. It is shown that a concentrated solution of the former can undergo reversible gelation. The gelation does not occur upon treatment of poly(1-phosphaisoprene) with [Pd(η3-C3H5)(µ-Cl)]2, indicating that cross-linking within the polymer network is responsible for gel formation. The study is complemented with molecular models. Chapter 4 focuses on cyclization reactions of 1-phosphabutadienes. Specifically, a [4+2] adduct of 1-phosphaisoprene with unique regiochemistry is disclosed and the observed reactivity is complemented by DFT calculations. Furthermore, the synthesis and [2+2] cyclization of a novel 1-phosphabutadiene, Mes*P=C(Me)−C(Me)=CH2, is reported. Chapter 5 focuses on the synthesis and characterization of Mes*P=C(Si(CH3)3)−CH=CH2. It is shown that this compound undergoes iv an E/Z-isomerization in the presence of n-BuLi. The compound was also found to isomerize upon exposure to light. Chapter 6 discloses muon spin spectroscopy studies of three 1-phosphabutadienes. The major radical products in each case are identified as delocalized 1-phosphaallyl radicals. This study represents the first model of radical addition to a 1-phosphabutadiene. Chapter 7 contains concluding remarks and a summary of the work presented in this thesis. Taken together, these discoveries mark a significant advancement in the chemistry of these unique P=C−C=C species. v Lay Summary Phosphorus, the fifteenth element of the periodic table, is one of the most diverse elements and is present in all aspects of modern life, from our DNA, to fertilizers, to our television screens. Therefore, it is important to advance discoveries in the field of phosphorus chemistry. A particular aspect of phosphorus chemistry that is relatively underdeveloped is the reactivity of molecules containing phosphorus-carbon double bonds [termed phosphaalkenes (P=C) or 1-phosphabutadienes (P=C−C=C)]. In this thesis, the synthesis and reactivity of 1-phosphabutadienes are explored. Specifically, rare examples of polymers (i.e. long chains of molecules linked together) with P=C bonds in the polymer chain are synthesized and their reactivity is reported. Furthermore, the unique chemistry of 1-phosphabutadienes in cyclization and isomerization reactions is reported. Lastly, the applications of these molecules and polymers toward binding transition metals are disclosed. vi Preface Sections of this thesis have been published in peer reviewed scientific journals. The synthesis, characterization and writing were carried out by me, apart from the contributions listed below. Chapter 1 was written by me. Chapter 2 is being written as a full paper to be submitted to a peer reviewed journal. The crystals of [Li(12-crown-4)2][endo-2.1] were grown by undergraduate student Max Eaton under my supervision. Two-dimensional NMR spectroscopic data for [Li(12-crown-4)2][endo-2.1], [Li(12-crown-4)2][exo-2.1] and PPI were obtained by Dr. Zhicheng (Paul) Xia and Yuki Liang of UBC Chemistry NMR Facility. NMR spectroscopic data for [2.7(AuCl)2] were obtained by Dr. Maria Ezhova of UBC Chemistry NMR Facility. The data for all crystal structures were collected and solved by Dr. Brian O. Patrick of the UBC Chemistry X-ray Facility. The manuscript is being prepared by me under the supervision of Prof. Derek P. Gates. Chapter 3 has been accepted for publication as a full paper in The European Journal of Inorganic Chemistry. The crystals of [Pd(PI)(η3-C3H5)Cl] were grown by undergraduate student Rodella Chowdhury working under my direction and crystals and characterization data of meso-trans-3.1 were obtained by exchange student Philipp Dabringhaus under my supervision. VT NMR measurements were carried out by Oleg Sannikov of UBC Chemistry NMR Facility. Crystal structure data were collected and solved by Dr. Brian O. Patrick of the UBC Chemistry X-ray Facility. The manuscript was prepared by me under the supervision of Prof. Derek P. Gates. Citation: Walsgrove, H. T. H.; Chowdhury, K. K.; Dabringhaus, P.; Patrick, B. O.; Gates, D. P. Eur. J. Inorg. Chem.2023, manuscript accepted; doi: 10.1002/ejic.202300182. Chapter 4 was partly published as a communication in Chemical Communications. Only compounds that were synthesized by me are included in the chapter. The DFT calculations were vii carried out by Prof. Yoshihiro Hayashi at the Tokyo Institute of Technology, Japan. The manuscript was prepared by me and Prof. Derek P. Gates in collaboration with Prof. Shigekazu Ito and his coworkers. Citation: Ohtsuki, K.; Walsgrove, H. T. G.; Hayashi, Y.; Kawauchi, S.; Patrick, B. O.; Gates, D. P.; Ito, S. Chem. Commun. 2020, 56, 774-777. Sections of chapter 4 were also published as a full paper in Organometallics. Dr. Zeyu Han collected and solved the crystal structure data for [4.1(AuCl)2]; all other crystal structure data were collected and solved by Dr. Brian O. Patrick of the UBC Chemistry X-ray Facility. Variable temperature NMR measurements were collected with the help of Oleg Sannikov and the 13C{1H} NMR spectrum of [Au(PI)Cl] was obtained by Dr. Maria Ezhova. The manuscript was prepared by me under the supervision of Prof. Derek P. Gates. Citation: Walsgrove, H. T. G.; Patrick, B. O.; Gates, D. P. Organometallics 2022, 41, 3399-3410. A version of chapter 5 was published as a full paper in the Canadian Journal of Chemistry. Philipp Dabringhaus, an exchange student from the University of Freiburg, Germany, grew crystals and obtained characterization data of Z-5.1 and E-5.1, and carried out the anion-mediated isomerization experiment. The crystal structure data were collected and solved by Dr. Brian O. Patrick of the UBC Chemistry X-ray Facility. The manuscript was prepared by me under the guidance of Prof. Derek P. Gates. Citation: Walsgrove, H. T. G.; Dabringhaus, P; Patrick, B. O.; Gates, D. P. Can. J. Chem. 2020, 98, 373-378. Chapter 6 is being written as a full paper to be submitted to a peer reviewed journal. All synthetic work was carried out by me. The muon spin spectroscopy measurements and DFT calculations were carried out by our collaborator, Prof. Paul Percival from TRIUMF and Simon Fraser University. The μSR data analysis and interpretation were done by me under the direction viii of Prof. Derek Gates and Prof. Paul Percival. The manuscript is being prepared by me under the supervision of Prof. Derek P. Gates and Prof. Paul Percival. Chapter 7 was written by me. ix Table of Contents Abstract ......................................................................................................................................... iii Lay Summary .................................................................................................................................v Preface ........................................................................................................................................... vi Table of Contents ......................................................................................................................... ix List of Tables .............................................................................................................................. xvi List of Figures ............................................................................................................................ xvii List of Schemes ...........................................................................................................................xxx List of Charts .......................................................................................................................... xxxiii List of Abbreviations and Symbols ...................................................................................... xxxiv Acknowledgements ................................................................................................................ xxxix Dedication ..................................................................................................................................... xl Chapter 1: Introduction to Low-Coordinate Phosphorus Compounds and Their Reactivity and Polymers ..................................................................................................................................1 1.1 Phosphorus ...................................................................................................................... 1 1.2 Low-coordinate phosphorus compounds ........................................................................ 2 1.2.1 The phosphorus-carbon analogy ................................................................................. 5 1.2.2 Phosphaalkenes as ligands for transition metals ......................................................... 6 1.2.3 1-Phosphabutadienes................................................................................................... 9 1.2.4 Cycloaddition reactions of 1-phosphabutadienes ..................................................... 11 1.3 Polymers ....................................................................................................................... 13 1.3.1 Polybutadienes .......................................................................................................... 13 1.3.2 Addition polymerization ........................................................................................... 15 x 1.3.3 Addition polymerization of P=C bonds .................................................................... 16 1.3.4 Commercial polymers containing main-group elements .......................................... 21 1.3.5 Organophosphorus polymers .................................................................................... 22 1.3.6 Polymers containing P=C bonds ............................................................................... 24 1.3.7 Poly(1-phosphaisoprene) (PPI) ................................................................................. 29 1.4 Outline of Thesis ........................................................................................................... 31 Chapter 2: The Microstructure of Poly(1-Phosphaisoprene): Stepwise Modeling of an Addition Polymerization .............................................................................................................32 2.1 Introduction ................................................................................................................... 32 2.2 Results and Discussion ................................................................................................. 33 2.2.1 Modeling the anionic initiation of PPI ...................................................................... 33 2.2.2 Modeling the end-group of PPI................................................................................. 37 2.2.3 Modeling trans-4,1-enchainment in PPI ................................................................... 40 2.2.4 Modeling 4,3-enchainment in PPI ............................................................................ 41 2.2.5 Linear dimerization of PI .......................................................................................... 46 2.2.6 Investigating the anionic polymerization of PI ......................................................... 49 2.3 Conclusion .................................................................................................................... 59 2.4 Experimental Section .................................................................................................... 60 2.4.1 General methods ....................................................................................................... 60 2.4.2 X-ray crystallography ............................................................................................... 61 2.4.3 Preparation of PI ....................................................................................................... 62 2.4.4 Preparation of [Li(12-crown-4)2][endo-2.1] and [Li(12-crown-4)2][exo-2.1] .......... 62 2.4.5 Preparation of 2.2 ...................................................................................................... 64 xi 2.4.6 Preparation of [Au(2.2)Cl] ........................................................................................ 65 2.4.7 Preparation of 2.3 ...................................................................................................... 66 2.4.8 Preparation of [Au(2.3)Cl] ........................................................................................ 67 2.4.9 Preparation of 2.4 ...................................................................................................... 68 2.4.10 Preparation of [Au(2.4)Cl] .................................................................................... 69 2.4.11 Preparation of 2.5 and 2.6 ..................................................................................... 71 2.4.12 Preparation of [Au(2.5)Cl] and [Au(2.6)Cl] ......................................................... 72 2.4.13 Preparation of [2.7(AuCl)2] .................................................................................. 74 2.4.14 Preparation of 2.8 .................................................................................................. 76 2.4.15 Preparation of [Au(2.8)Cl] .................................................................................... 77 2.4.16 General procedure for the anionic polymerization of PI ...................................... 78 2.4.17 Anionic polymerization of PI................................................................................ 78 2.4.18 Preparation of PPI·[AuCl]0.96n .............................................................................. 79 Chapter 3: Palladium(II) Complexes of 1-Phosphaisoprene Molecules and Polymers: Reversible Cross-Linking of a Phosphorus-Containing Polymer ...........................................81 3.1 Results and Discussion ................................................................................................. 82 3.1.1 Coordination of poly(1-phosphaisoprene) (PPI) to PdII ............................................ 82 3.1.2 Molecular models for macromolecular PdII-complexes ........................................... 87 3.1.3 Mechanistic investigations of the C−H activation .................................................... 93 3.1.4 Reversible gelation of poly(1-phosphaisoprene) (PPI) with [Pd(cod)Cl2] ............. 100 3.2 Conclusion .................................................................................................................. 104 3.3 Experimental Section .................................................................................................. 104 3.3.1 General considerations ............................................................................................ 104 xii 3.3.2 X-ray crystallography ............................................................................................. 106 3.3.3 Anionic polymerization of 1-phosphaisoprene (PI) ................................................ 106 3.3.4 Reaction of PPI with [Pd(η3-C3H5)(µ-Cl)]2 (Pd:P = 1.0) ........................................ 107 3.3.5 Reaction of PPI with [Pd(cod)Cl2] (Pd:P = 0.5) ..................................................... 107 3.3.6 Reaction of PPI with [Pd(η3-C3H5)(µ-Cl)]2 (Pd:P = 0.30) ...................................... 108 3.3.7 Reaction of PPI with [Pd(cod)Cl2] (Pd:P = 0.15) ................................................... 109 3.3.8 Preparation of [Pd(PI)(η3-C3H5)Cl] ........................................................................ 109 3.3.9 Preparation of 3.1 .................................................................................................... 110 3.3.10 NMR tube reaction of PI with [Pd(cod)Cl2] ....................................................... 112 3.3.11 Qualitative rate of reaction for PI with [Pd(cod)Cl2] (NMR tubes).................... 113 3.3.12 Qualitative rate of reaction for PI with [Pd(cod)Cl2] (vials)............................... 113 3.3.13 Reaction of 3.2 with [Pd(cod)Cl2] ...................................................................... 113 3.3.14 NMR monitoring of PPI·[PdCl2]0.09n .................................................................. 115 3.3.15 Gelation of PPI with [Pd(cod)Cl2] ...................................................................... 115 3.3.16 Control gelation attempt of PPI with [Pd(η3-C3H5)(µ-Cl)]2 ............................... 116 Chapter 4: Cyclization Reactions of 1-Phosphabutadienes: Selective Formation of P=C-substituted Phosphacyclohexene or 1-Phosphet-2-ene Ligands. ...........................................117 4.1 Introduction ................................................................................................................. 117 4.2 Results and Discussion ............................................................................................... 118 4.2.1 [4+2] Cycloaddition of PI ....................................................................................... 118 4.2.2 Selective intramolecular cyclization of Mes*P=C(Me)−C(Me)=CH2 (4.2) ........... 128 4.2.3 X-ray crystallographic data for AuI and PdII complexes of 1-phosphet-2-ene (4.3) 137 xiii 4.2.4 Detection of intermediates in [2+2] intramolecular cyclization reactions .............. 139 4.3 Conclusion .................................................................................................................. 142 4.4 Experimental Methods ................................................................................................ 143 4.4.1 General procedures ................................................................................................. 143 4.4.2 X-ray crystallography ............................................................................................. 144 4.4.3 DFT calculations ..................................................................................................... 145 4.4.4 Preparation of 4.1 .................................................................................................... 145 4.4.5 Preparation of [Pd(4.1)Cl2] ..................................................................................... 146 4.4.6 Preparation of [Au(PI)Cl] ....................................................................................... 147 4.4.7 Preparation of [4.1(AuCl)2] .................................................................................... 147 4.4.8 Preparation of 4.2 .................................................................................................... 149 4.4.9 Preparation of [Au(4.3)Cl] ...................................................................................... 150 4.4.10 NMR-monitoring of the reaction of 4.2 with [Au(tht)Cl] ................................... 151 4.4.11 Preparation of [Pd(4.3)(η3-C3H5)Cl] ................................................................... 151 4.4.12 NMR monitoring of the reaction of 4.2 with [Pd(η3-C3H5)(μ-Cl)]2 ................... 152 4.4.13 Preparation of [Pd(4.3)2Cl2] ................................................................................ 153 4.4.14 NMR monitoring of the reaction of 4.2 with [Pd(cod)Cl2] ................................. 155 Chapter 5: Chemical- and Light-Induced Isomerization of the P=C Bond of a 1-Phosphabutadiene ......................................................................................................................156 5.1 Introduction ................................................................................................................. 156 5.2 Results and Discussion ............................................................................................... 157 5.2.1 Preparation of Z-5.1 ................................................................................................ 157 5.2.2 n-BuLi-mediated E/Z-isomerization of Z-5.1 ......................................................... 159 xiv 5.2.3 Light-mediated E/Z-isomerization of Z-5.1 ............................................................ 163 5.3 Summary ..................................................................................................................... 165 5.4 Experimental ............................................................................................................... 165 5.4.1 General procedures ................................................................................................. 165 5.4.2 X-ray crystallography ............................................................................................. 166 5.4.3 DFT calculations ..................................................................................................... 166 5.4.4 Synthesis of Z-5.1 ................................................................................................... 166 5.4.5 Synthesis of E-5.1 ................................................................................................... 167 5.4.6 Light-mediated isomerization of Z-5.1 ................................................................... 168 Chapter 6: Probing Radical Addition to 1-Phosphabutadienes using Muon Spin Spectroscopy (μSR) ....................................................................................................................169 6.1 Introduction ................................................................................................................. 169 6.2 Results and Discussion ............................................................................................... 170 6.2.1 Transverse-field (TF)-μSR ...................................................................................... 170 6.2.2 Avoided-level crossing (μALCR) investigations .................................................... 178 6.2.3 Muon (Mu+) addition .............................................................................................. 183 6.3 Conclusion .................................................................................................................. 184 6.4 Experimental Section .................................................................................................. 185 6.4.1 General procedures ................................................................................................. 185 6.4.2 μSR measurements .................................................................................................. 185 6.4.3 DFT calculations ..................................................................................................... 186 6.4.4 Preparation of E/Z-Mes*P=C(CD3)Br .................................................................... 186 6.4.5 Preparation of PI-d3................................................................................................. 187 xv Chapter 7: Conclusion ...............................................................................................................189 7.1 Introduction ................................................................................................................. 189 7.2 Future work ................................................................................................................. 189 7.3 Concluding remarks .................................................................................................... 194 References ...................................................................................................................................195 Appendices ..................................................................................................................................207 Appendix A Supplementary material for chapter 2 ................................................................ 207 Appendix B Supplementary material for chapter 3 ................................................................ 237 Appendix C Supplementary material for chapter 4 ................................................................ 253 Appendix D Supplementary material for chapter 5 ................................................................ 269 Appendix E Supplementary material for chapter 6 ................................................................. 273 xvi List of Tables Table 2.1: Comparison of the 1H and 13C{1H} NMR spectroscopic signals assigned to PPI and model compounds. Multiplicities are omitted for clarity. ............................................................. 55 Table 2.2: Comparison of the 1H and 13C{1H} NMR spectroscopic signals assigned to PPI·[AuCl]0.96n and model compounds. Multiplicities are omitted for clarity. ............................ 59 Table 6.1: Assignment and comparison of experimental and computed hyperfine constants (MHz) for PId, PI-d3d and 6.1d. ................................................................................................... 182 Table A.1: X-ray crystallographic data for [Li(12-Crown-4)2][endo-2.1], [Au(2.2)Cl], [Au(2.3)Cl] and [Au(2.4)Cl]. ...................................................................................................... 235 Table A.2: X-ray crystallographic data for [Au(2.5)Cl], [Au(2.6)Cl] and [2.7(AuCl)2]. ........... 236 Table B.1: X-ray crystallographic data for [Pd(PI)(η3-C3H5)Cl] and 3.1. .................................. 252 Table C.1: X-ray crystallographic data for 4.1, [Pd(4.1)Cl2], [Au(PI)Cl] and [4.1(AuCl)2]. ..... 267 Table C.2: X-ray crystallographic data for 4.2, [Pd(4.3)Cl2], [Pd(4.3)(η3-C3H5)Cl] and [Au(4.3)Cl].................................................................................................................................. 268 Table D.1: Crystallographic data for Z-5.1 and E-5.1. ............................................................... 272 xvii List of Figures Figure 2.1: 31P NMR spectra (162 MHz, 25 °C) of the reaction mixtures of: (a) a THF solution of PI and n-BuLi (1 equiv); (b) the same reaction in Et2O solution after addition of 12-crown-4 (2 equiv). ........................................................................................................................................... 35 Figure 2.2 Molecular structure of compound [Li(12-crown-4)2][endo-2.1]. Thermal ellipsoids are represented at 50% probability level. Hydrogen atoms are omitted for clarity. ........................... 36 Figure 2.3: Molecular structure of [Au(2.2)Cl]. Thermal ellipsoids are presented at 50% probability level. Hydrogen atoms are omitted for clarity. ........................................................... 39 Figure 2.4: 31P NMR spectra (THF, 162 MHz, 25 ⁰C) showing the progress of reaction between Li·2.1 and H2C=CPh2 (1.0 equiv). ................................................................................................ 42 Figure 2.5: Molecular structure of [Au(2.5)Cl]. Thermal ellipsoids are presented at 50% probability level. Hydrogen atoms (except H1−H4) are omitted for clarity. Only P1(R),C2(S) isomer is shown............................................................................................................................. 43 Figure 2.6: Molecular structure of [Au(2.6)Cl]. Thermal ellipsoids are presented at 50% probability level. Hydrogen atoms are omitted for clarity (except H1-H4). ................................ 45 Figure 2.7: Molecular structure of [2.7(AuCl)2]. Thermal ellipsoids are presented at 50% probability level. Hydrogen atoms are omitted for clarity. Only P2(R),C2(R) isomer is shown.. 47 Figure 2.8: 31P NMR spectra (162 MHz, 25 ⁰C) showing the progress of reaction between PI and n-BuLi (2 mol%). All spectra are in THF apart from purified PPI which is in CDCl3. ............... 51 Figure 2.9: 1H,13C-HSQC NMR spectrum (CDCl3, 25 ⁰C) of PPI (Mn = 15,000 g mol−1, Ð = 1.02). Dashed lines indicate correlated 1H (x axis) and 13C (y axis) NMR spectroscopic signals........................................................................................................................................................ 54 Figure 2.10: 31P NMR spectra (162 MHz, CDCl3, 25 ⁰C) of (a) PPI; (b) PPI·[AuCl]0.96n. ........... 57 xviii Figure 3.1: 31P NMR spectra (CH2Cl2, 162 MHz, 25 ⁰C) of: (a) PPI; (b) reaction mixture of PPI and [Pd(η3-C3H5)(µ-Cl)]2 (Pd:P ratio = 0.30) after 24 h to afford PPI·[Pd(η3-C3H5)Cl]0.21n; (c) reaction mixture of PPI and [Pd(cod)Cl2] (Pd:P ratio = 0.15) after 24 h to afford PPI·[PdCl2]0.09n........................................................................................................................................................ 85 Figure 3.2: Molecular structure of [Pd(PI)(η3-C3H5)Cl]·CH2Cl2. Thermal ellipsoids are presented at 50% probability level. Hydrogen atoms and solvent of crystallization are omitted for clarity. 88 Figure 3.3: Molecular structure of meso-trans-3.1·(2  CH2Cl2) [P1(R),P2(S) isomer is shown]. Thermal ellipsoids are presented at 50% probability level. Hydrogen atoms and solvents of crystallization are omitted for clarity. ........................................................................................... 91 Figure 3.4: 31P NMR spectra (CDCl3, 162 MHz, 25 °C) of: a) a solution of the crystals of meso-trans-3.1 recorded immediately after dissolution; b) the same solution after 3 d at room temperature. .................................................................................................................................. 92 Figure 3.5: 31P NMR spectra (CD2Cl2, 162 MHz, 25 ⁰C) showing the progress of reaction between PI and [Pd(cod)Cl2] (0.5 equiv) at room temperature. API = [Pd(PI)2Cl2], BPI = trans-[Pd(PI)(PI')Cl2]. ............................................................................................................................ 94 Figure 3.6: 31P NMR spectra (CD2Cl2, 162 MHz, 25 ⁰C) showing the progress of reaction between 3.2 and [Pd(cod)Cl2] (0.5 equiv) at room temperature. A3.2 = [Pd(3.2)2Cl2], B3.2 = trans-[Pd(3.2)(3.2')Cl2]. ......................................................................................................................... 99 Figure 3.7: Photographs showing the cross-linking process for PPI in CH2Cl2 containing: (a) a solution of PPI; (b) a solution of PPI with [Pd(cod)Cl2] (Pd:P = 0.05) after 1 h; (c) a solution of PPI with [Pd(cod)Cl2] (Pd:P = 0.10) after 1 h; (d) a solution of PPI with [Pd(cod)Cl2] (Pd:P = 0.15) after 1 h; (e) a solution of PPI with [Pd(cod)Cl2] (Pd:P = 0.15) after 12 h. Inset: an inverted xix solution of PPI with [Pd(cod)Cl2] (Pd:P = 0.15) after 12 h showing gelation; (f) a solution of PPI with [Pd(cod)Cl2] (Pd:P = 0.15) immediately after addition of PMe3 (1 drop). ......................... 101 Figure 3.8: 31P NMR spectra (162 MHz, 25⁰C) of (a) a CH2Cl2 solution PPI (1.31 M in P) with [Pd(cod)Cl2] (Pd:P = 0.15) immediately after addition of PMe3 (1 drop, ca. 1 P equiv); (b) a CH2Cl2 solution of PPI (1.31 M in P) with [Pd(cod)Cl2] (Pd:P = 0.15) after addition of PMe3 (6 drops). ......................................................................................................................................... 103 Figure 4.1: Molecular structure of 4.1 [only C2(S),P2(S) diastereomer shown]. Thermal ellipsoids are presented at 50% probability level. Hydrogen atoms are omitted for clarity. ...... 119 Figure 4.2: Molecular structure of [Pd(4.1)Cl2] dimer [C2(R),P2(S) diastereomer is shown]. Thermal ellipsoids are presented at 50% probability level. Hydrogen atoms and solvent of crystallization (2 × CH2Cl2) are omitted for clarity. ................................................................... 121 Figure 4.3: Molecular structure of [Au(PI)Cl]. Thermal ellipsoids are presented at 50% probability level. Hydrogen atoms are omitted for clarity. ......................................................... 124 Figure 4.4: Molecular structure of [4.1(AuCl)2]. [C2(S),P2(R) isomer is shown]. Thermal ellipsoids are presented at 50% probability level. Hydrogen atoms are omitted for clarity. ...... 126 Figure 4.5: Molecular structure of 4.2. Thermal ellipsoids are presented at 50% probability level. Hydrogen atoms are omitted for clarity. ..................................................................................... 130 Figure 4.6: Molecular structure of [Au(4.3)Cl]. Thermal ellipsoids are shown at 50% probability level. Hydrogen atoms are omitted for clarity. ........................................................................... 131 Figure 4.7: Molecular structures of [Pd(4.3)(η3-C3H5)Cl]·0.72 CH2Cl2·0.32 CDCl3 [for clarity, only Isomer 1 (R,endo) with occupancy 0.617 and Isomer 2 (R,exo) with occupancy 0.383 are shown; the enantiomers (S,endo and S,exo) are present, but not shown]. Thermal ellipsoids are presented at the 50% probability level. Solvents of crystallization and hydrogen atoms are xx omitted for clarity. Inset: structures of R,endo-[Pd(4.3)(η3-C3H5)Cl]·0.72 CH2Cl2·0.32 (left box) and R,exo-[Pd(4.3)(η3-C3H5)Cl]·0.72 CH2Cl2·0.32(right box). .................................................. 134 Figure 4.8: Molecular structure of meso-trans-[Pd(4.3)2Cl2] [P1(S),P1'(R) isomer is shown]. Thermal ellipsoids are presented at the 50% probability level. Hydrogen atoms are omitted for clarity. ......................................................................................................................................... 135 Figure 4.9: 31P{1H} NMR spectra (162 MHz, 25 ⁰C) showing the progress of the reaction between 4.2 (1 equiv) and [Au(tht)Cl] (1 equiv) in CH2Cl2. The spectrum for recrystallized [Au(4.3)Cl] was recorded in CDCl3............................................................................................ 140 Figure 4.10: 31P{1H} NMR spectra (162 MHz, 25 ⁰C) showing the progress of the reaction between 4.2 (1 equiv) and [Pd(η3-C3H5)(μ-Cl)]2 (0.5 equiv) in CDCl3. ..................................... 141 Figure 4.11: 31P{1H} NMR spectra (162 MHz, 25 ⁰C) showing the progress of the reaction between 4.2 (1 equiv) and [Pd(cod)Cl2] (0.5 equiv) in CH2Cl2. The spectrum for recrystallized [Pd(4.3)2Cl2] was recorded in CDCl3.......................................................................................... 142 Figure 5.1: Molecular structure of Z-5.1. Hydrogen atoms are omitted for clarity. Thermal ellipsoids are shown at the 50% probability level. ..................................................................... 159 Figure 5.2: 31P NMR spectra (THF, 162 MHz, 25 ⁰C) of a) Z-5.1; b) E-5.1. ............................. 160 Figure 5.3: 1H NMR spectra (CDCl3, 400 MHz, 25 ⁰C) of a) Z-5.1; b) E-5.1. ........................... 161 Figure 5.4: Molecular structure of E-5.1. Hydrogen atoms are omitted for clarity. Thermal ellipsoids are shown at the 50% probability level. ..................................................................... 162 Figure 5.5: 31P NMR spectra (THF, 162 MHz, 25 °C) of: a) a solution of Z-5.1 after 4 d in the dark, b) a solution of Z-5.1 that has been irradiated for 4 d. ....................................................... 164 Figure 6.1: Transverse-field μSR spectrum obtained from a 0.5 M solution of PI in THF at 25 °C with a 14.45 kG field. ................................................................................................................. 171 xxi Figure 6.2: Transverse-field μSR spectrum obtained from a 0.5 M solution of PI-d3 in THF at 25 °C with a 14.45 kG field. ............................................................................................................ 172 Figure 6.3: Transverse-field μSR spectrum obtained from a 0.5 M solution of 6.1 in THF at 25 °C with a 14.45 kG field. ............................................................................................................ 172 Figure 6.4: Reaction pathway energies [i.e. E(radical)−E(parent)−E(H)] for the reaction of Mu with PI (R = H) and 6.1 (R = Me). The reaction of Mu with PI-d3 is omitted as the reference geometries of PI and PI-d3 are identical within the Born-Oppenheimer approximation. ........... 174 Figure 6.5: Calculated hyperfine constants for the postulated muoniated radicals formed from PI (R = H) and 6.1 (R = Me). .......................................................................................................... 176 Figure 6.6: Segment of the μALCR spectrum of the radical formed from exposure of a 0.5 M THF solution of PI to a muon beam. Two resonances are observed at 5.179 ± 0.007 and 5.603 ± 0.006 kG, obtained from a fit of the spectrum using Microsoft Excel. ...................................... 178 Figure 6.7: Segment of the μALCR spectrum of the radicals formed from exposure of a 0.5 M THF solution of PI-d3 to a muon beam. Two resonances are observed at 5.185 ± 0.005 and 5.592 ± 0.005 kG, obtained from a fit of the spectrum using Microsoft Excel. ................................... 179 Figure 6.8: Segment of the μALCR spectrum of the radicals formed from exposure of a 0.5 M THF solution of 6.1 to a muon beam. Two overlapping resonances are observed at 5.270 ± 0.008 and 5.523 ± 0.003 kG, obtained from a fit of the spectrum using Microsoft Excel. .................. 179 Figure 6.9: Segment of the μALCR spectrum of the radicals formed from exposure of a 0.5 M THF solution of PI to a muon beam. A resonance is observed at 3.796 ± 0.019 kG, obtained from a fit of the spectrum using Microsoft Excel. ............................................................................... 181 xxii Figure A.1: 1H NMR spectrum (C6D6, 400 MHz, 25 °C) of [Li(12-crown-4)2][2.1]. * = C6D5H...................................................................................................................................................... 207 Figure A.2: 13C{1H} NMR spectrum (C6D6, 101 MHz, 25 °C) of [Li(12-crown-4)2][2.1]. * = C6D6. ........................................................................................................................................... 207 Figure A.3: 31P NMR spectrum (C6D6, 162 MHz, 25 °C) of [Li(12-crown-4)2][2.1]. ............... 208 Figure A.4: 1H NMR spectrum (CDCl3, 400 MHz, 25 °C) of 2.2. * = CHCl3. .......................... 208 Figure A.5: 13C{1H} NMR spectrum (CDCl3, 101 MHz, 25 °C) of 2.2. * = CDCl3. ................. 209 Figure A.6: 31P NMR spectrum (CDCl3, 162 MHz, 25 °C) of 2.2. ............................................ 209 Figure A.7: 1H NMR spectrum (CDCl3, 400 MHz, −40 °C) of 2.2. * = CHCl3. ........................ 210 Figure A.8: 13C{1H} NMR spectrum (CDCl3, 101 MHz, −40 °C) of 2.2. * = CDCl3. ............... 210 Figure A.9: 1H NMR spectrum (CDCl3, 400 MHz, 25 °C) of [Au(2.2)Cl]. * = CHCl3. ............ 211 Figure A.10: 13C{1H} NMR spectrum (CDCl3, 101 MHz, 25 °C) of [Au(2.2)Cl]. * = CDCl3. . 211 Figure A.11: 31P NMR spectrum (CDCl3, 162 MHz, 25 °C) of [Au(2.2)Cl]. ............................ 212 Figure A.12: 1H NMR spectrum (CDCl3, 400 MHz, 25 °C) of 2.3. * = CHCl3. ........................ 212 Figure A.13: 13C{1H} NMR spectrum (CDCl3, 101 MHz, 25 °C) of 2.3. * = CDCl3. ............... 213 Figure A.14: 31P NMR spectrum (CDCl3, 162 MHz, 25 °C) of 2.3. .......................................... 213 Figure A.15: Molecular structure of [Au(2.3)Cl]. Thermal ellipsoids are presented at 50% probability level. Hydrogen atoms are omitted for clarity. ......................................................... 214 Figure A.16: 1H NMR spectrum (CDCl3, 400 MHz, 25 °C) of [Au(2.3)Cl]. * = CHCl3. .......... 214 Figure A.17: 13C{1H} NMR spectrum (CDCl3, 101 MHz, 25 °C) of [Au(2.3)Cl]. * = CDCl3. . 215 Figure A.18: 31P NMR spectrum (CDCl3, 162 MHz, 25 °C) of [Au(2.3)Cl]. ............................ 215 Figure A.19: 1H NMR spectrum (CDCl3, 400 MHz, −40 °C) of [Au(2.3)Cl]. * = CHCl3. ........ 216 Figure A.20: 13C{1H} NMR spectrum (CDCl3, 101 MHz, −40 °C) of [Au(2.3)Cl]. * = CDCl3.216 xxiii Figure A.21: 1H NMR spectrum (CDCl3, 400 MHz, 25 °C) of 2.4. * = CHCl3. ........................ 217 Figure A.22: 13C{1H} NMR spectrum (CDCl3, 101 MHz, 25 °C) of 2.4. * = CDCl3. ............... 217 Figure A.23: 31P NMR spectrum (CDCl3, 162 MHz, 25 °C) of 2.4. .......................................... 218 Figure A.24: Molecular structure of [Au(2.4)Cl]. Thermal ellipsoids are presented at 50% probability level. Hydrogen atoms are omitted for clarity. ......................................................... 218 Figure A.25: 1H NMR spectrum (CDCl3, 400 MHz, 25 °C) of [Au(2.4)Cl]. * = CHCl3. .......... 219 Figure A.26: 13C{1H} NMR spectrum (CDCl3, 101 MHz, 25 °C) of [Au(2.4)Cl]. * = CDCl3. . 219 Figure A.27: 31P NMR spectrum (CDCl3, 162 MHz, 25 °C) of [Au(2.4)Cl]. ............................ 220 Figure A.28: 1H NMR spectrum (CDCl3, 400 MHz, −40 °C) of [Au(2.4)Cl]. * = CHCl3. ........ 220 Figure A.29: 1H NMR spectrum (CDCl3, 400 MHz, 25 °C) of 2.5 and 2.6. * = CHCl3. ........... 221 Figure A.30: 13C{1H} NMR spectrum (CDCl3, 101 MHz, 25 °C) of 2.5 and 2.6. * = CDCl3. .. 221 Figure A.31: 31P NMR spectrum (CDCl3, 162 MHz, 25 °C) of 2.5 and 2.6. ............................. 222 Figure A.32: 1H NMR spectrum (CDCl3, 400 MHz, 25 °C) of [Au(2.5)Cl]. * = CHCl3. .......... 222 Figure A.33: 13C{1H} NMR spectrum (CDCl3, 101 MHz, 25 °C) of [Au(2.5)Cl]. * = CDCl3. . 223 Figure A.34: 31P NMR spectrum (CDCl3, 162 MHz, 25 °C) of [Au(2.5)Cl]. ............................ 223 Figure A.35: 1H NMR spectrum (CDCl3, 400 MHz, 25 °C) of [Au(2.6)Cl]. * = CHCl3. .......... 224 Figure A.36: 13C{1H} NMR spectrum (CDCl3, 101 MHz, 25 °C) of [Au(2.6)Cl]. * = CDCl3. . 224 Figure A.37: 31P NMR spectrum (CDCl3, 162 MHz, 25 °C) of [Au(2.6)Cl]. ............................ 225 Figure A.38: 1H NMR spectrum (CDCl3, 400 MHz, 25 °C) of 2.7. * = CHCl3. ........................ 225 Figure A.39: 31P NMR spectrum (CDCl3, 162 MHz, 25 °C) of 2.7. .......................................... 226 Figure A.40: 1H NMR spectrum (CDCl3, 400 MHz, 25 °C) of [2.7(AuCl)2]. * = CHCl3. ......... 226 Figure A.41: 13C{1H} NMR spectrum (CDCl3, 101 MHz, 25 °C) of [2.7(AuCl)2]. * = CDCl3. 227 Figure A.42: 1H NMR spectrum (CDCl3, 400 MHz, −50 °C) of [2.7(AuCl)2]. * = CHCl3. ...... 227 xxiv Figure A.43: 31P NMR spectrum (CDCl3, 162 MHz, −50 °C) of [2.7(AuCl)2]. ......................... 228 Figure A.44: 31P{1H} NMR spectrum (CDCl3, 162 MHz, −50 °C) of [2.7(AuCl)2]. ................. 228 Figure A.45: 1H NMR spectrum (CDCl3, 400 MHz, 25 °C) of 2.8. * = CHCl3. ........................ 229 Figure A.46: 13C{1H} NMR spectrum (CDCl3, 101 MHz, 25 °C) of 2.8. * = CDCl3. ............... 229 Figure A.47: 31P NMR spectrum (CDCl3, 162 MHz, 25 °C) of 2.8. .......................................... 230 Figure A.48: 1H NMR spectrum (CDCl3, 400 MHz, 25 °C) of [Au(2.8)Cl]. * = CHCl3. .......... 230 Figure A.49: 13C{1H} NMR spectrum (CDCl3, 101 MHz, 25 °C) of [Au(2.8)Cl]. * = CDCl3. . 231 Figure A.50: 31P NMR spectrum (CDCl3, 162 MHz, 25 °C) of [Au(2.8)Cl]. ............................ 231 Figure A.51: 1H NMR spectrum (CDCl3, 400 MHz, 25 °C) of PPI. Mn = 15,000 g mol−1, Đ = 1.02, dn/dc = 0.169 mL g−1. * = CHCl3. ..................................................................................... 232 Figure A.52: 13C{1H} NMR spectrum (CDCl3, 101 MHz, 25 °C) of PPI. Mn = 15,000 g mol−1, Đ = 1.02, dn/dc = 0.169 mL g−1. * = CDCl3. .................................................................................. 232 Figure A.53: GPC chromatogram of PPI (Mn = 15,000 g mol−1, Ð = 1.02, dn/dc = 0.169). ...... 233 Figure A.54: 1H NMR spectrum (CDCl3, 400 MHz, 25 °C) of PPI·[AuCl]0.96n. Mn = 40,200 g mol−1; Ð = 1.03; dn/dc = 0.17 mL g−1. * = CHCl3, † = CH2Cl2. ................................................ 233 Figure A.55: 13C{1H} NMR spectrum (CDCl3, 101 MHz, 25 °C) of PPI·[AuCl]0.96n. Mn = 40,200 g mol−1; Ð = 1.03; dn/dc = 0.17 mL g−1. * = CDCl3. .................................................................. 234 Figure A.56: GPC chromatogram of PPI·[AuCl]0.96n. Molecular weight data were estimated using the dn/dc* of PPI (Mn = 40,200 g mol−1, Ð = 1.03, *dn/dc = 0.17). ................................. 234 Figure B.1: 1H NMR spectrum (CDCl3, 400 MHz, 25 °C) of [Pd(PI)(η3-C3H5)Cl]. * = CHCl3.237 Figure B.2: 13C{1H} NMR spectrum (CDCl3, 101 MHz, 25 °C) of [Pd(PI)(η3-C3H5)Cl]. * = CDCl3. ......................................................................................................................................... 237 Figure B.3: 31P NMR spectrum (CDCl3, 162 MHz, 25 °C) of [Pd(PI)(η3-C3H5)Cl]. ................. 238 xxv Figure B.4: 1H NMR spectrum (CDCl3, 400 MHz, −30 °C) of [Pd(PI)(η3-C3H5)Cl]. * = CHCl3...................................................................................................................................................... 238 Figure B.5: 1H NMR spectrum (CD2Cl2, 400 MHz, 25 °C) after 12 min showing the reaction progress between PI and [Pd(cod)Cl2] (0.5 equiv) to afford intermediate A and “free” COD. For PI and API assignments, the labels H, H' and H" refer to the –CH=CH'H" moiety where H' is cis-H and H" is trans-H. * = CDHCl2. ............................................................................................. 239 Figure B.6: 1H NMR spectrum (CDCl3, 400 MHz, 25 °C) of meso-trans-3.1. * = CHCl3, † = CH2Cl2......................................................................................................................................... 239 Figure B.7: 31P NMR spectrum (CDCl3, 162 MHz, 25 °C) of meso-trans-3.1. ......................... 240 Figure B.8: 1H NMR spectrum (CDCl3, 600 MHz, 25 °C) of meso-trans- and rac-trans-3.1. * = CHCl3, † = CH2Cl2. ..................................................................................................................... 240 Figure B.9: 31P NMR spectrum (CDCl3, 162 MHz, 25 °C) of meso-trans- and rac-trans-3.1. . 241 Figure B.10: 13C{1H} NMR spectrum (CDCl3, 151 MHz, 25 °C) of rac-trans- and meso-trans-3.1. * = CDCl3; † = CH2Cl2. ....................................................................................................... 241 Figure B.11: 31P NMR spectrum (CD2Cl2, 162 MHz, 25 °C) of intermediate A3.2. ................... 242 Figure B.12: 1H NMR spectrum (CD2Cl2, 400 MHz, 25 °C) of intermediate A3.2. * = CDHCl2, † = COD. ........................................................................................................................................ 242 Figure B.13: 13C{1H} NMR spectrum (CD2Cl2, 101 MHz, 25 °C) of intermediate A3.2. * = CD2Cl2, † = COD. ....................................................................................................................... 243 Figure B.14: 1H NMR spectrum (CD2Cl2, 400 MHz, 25 °C) of the reaction between 3.2 and [Pd(cod)Cl2] (0.5 equiv) after 18 d. * = CDHCl2. ...................................................................... 243 Figure B.15: 31P NMR spectrum (CDCl3, 162 MHz, 25 °C) of meso-trans- and rac-trans-3.3. 244 xxvi Figure B.16: 1H NMR spectrum (CDCl3, 600 MHz, 25 °C) of meso-trans- and rac-trans-3.3. * = CHCl3. ......................................................................................................................................... 244 Figure B.17: 13C{1H} NMR spectrum (CDCl3, 151 MHz, 25 °C) of meso-trans- and rac-trans-3.3. * = CDCl3. ............................................................................................................................ 245 Figure B.18: 31P NMR spectrum (CDCl3, 162 MHz, 25 °C) of PPI. .......................................... 245 Figure B.19: 1H NMR spectrum (CDCl3, 400 MHz, 25 °C) of PPI. * = CHCl3. ....................... 246 Figure B.20: Inverse-gated 13C{1H} NMR spectrum (CDCl3, 101 MHz, 25 °C) of PPI. * = CDCl3. ......................................................................................................................................... 246 Figure B.21: 31P NMR spectrum (CDCl3, 162 MHz, 25 °C) of PPI·[Pd(η3-C3H5)Cl]0.21n. ........ 247 Figure B.22: 1H NMR spectrum (CDCl3, 400 MHz, 25 °C) of PPI·[Pd(η3-C3H5)Cl]0.21n ·* = CHCl3, † = [Pd(η3-C3H5)(μ-Cl)]2, ‡ = hexanes, § = silicone grease. .......................................... 247 Figure B.23: 13C{1H} NMR spectrum (CDCl3, 101 MHz, 25 °C) of PPI·[Pd(η3-C3H5)Cl]0.21n. * = CDCl3, † = [Pd(η3-C3H5)(μ-Cl)]2, ‡ = silicone grease. ............................................................... 248 Figure B.24: 31P NMR spectrum (CDCl3, 162 MHz, 25 °C) of PPI·[PdCl2]0.09n. ...................... 248 Figure B.25: 1H NMR spectrum (CDCl3, 400 MHz, 25 °C) of PPI·[PdCl2]0.09n. * = CHCl3, † = silicone grease. ............................................................................................................................ 249 Figure B.26: 13C{1H} NMR spectrum (CDCl3, 101 MHz, 25 °C) of PPI·[PdCl2]0.09n. * = CDCl3, † = silicone grease. ...................................................................................................................... 249 Figure B.27: GPC chromatogram of poly(1-phosphaisoprene) (PPI) [Mn = 21,800 g mol−1, dn/dc = 0.173, Ð = 1.02]. dn/dc determined using 100% mass recovery method. .............................. 250 Figure B.28: GPC chromatogram of PPI·[Pd(η3-C3H5)Cl]0.21n [Mn = 26,000 g mol−1, dn/dc = 0.17*, Ð = 1.02]. Mass recovery estimated to be 43.2% based on the dn/dc of PPI(*) which was used as a rough approximation to the actual dn/dc of 2·[Pd(η3-C3H5)Cl]0.21n. ........................... 250 xxvii Figure B.29: Photographs showing the control gelation experiment for poly(1-phosphaisoprene) PPI in CH2Cl2 containing: (a) a solution of PPI; (b) a solution of PPI with [Pd(η3-C3H5)(μ-Cl)]2 (Pd:P = 0.10) after 1 h; (c) a solution of PPI with [Pd(η3-C3H5)(μ-Cl)]2 (Pd:P = 0.20) after 1 h; (d) a solution of PPI with [Pd(η3-C3H5)(μ-Cl)]2 (Pd:P = 0.30) after 1 h; (e) a solution of PPI with [Pd(η3-C3H5)(μ-Cl)]2 (Pd:P = 0.30) after 12 h. ........................................................................... 251 Figure B.30: 31P NMR spectrum (CDCl3, 162 MHz, 25 °C) of PPI with [Pd(η3-C3H5)(μ-Cl)]2 (Pd:P = 0.30). .............................................................................................................................. 251 Figure C.1: 1H NMR spectrum (CDCl3, 400 MHz, 25 °C) of 4.1. * = CHCl3. ........................... 253 Figure C.2: 13C{1H} NMR spectrum (CDCl3, 101 MHz, 25 °C) of 4.1. .................................... 253 Figure C.3: 1H NMR spectrum (CDCl3, 400 MHz, 25 °C) of [Pd(4.1)Cl2]. * = CHCl3; † = CH2Cl2......................................................................................................................................... 254 Figure C.4: 31P{1H} NMR spectrum (CDCl3, 162 MHz, 25 °C) of [Pd(4.1)Cl2]. ...................... 254 Figure C.5: 1H NMR spectrum (CDCl3, 400 MHz, 25 °C) of [Au(PI)Cl]. * = CHCl3. .............. 255 Figure C.6: 13C{1H} NMR spectrum (CDCl3, 101 MHz, 25 °C) of [Au(PI)Cl]. * = CDCl3. ..... 255 Figure C.7: 31P NMR spectrum (CDCl3, 162 MHz, 25 °C) of [Au(PI)Cl]. ................................ 256 Figure C.8: 1H NMR spectrum (CD2Cl2, 400 MHz, 25 °C) of [4.1(AuCl)2]. * = CDHCl2. ....... 256 Figure C.9: 13C{1H} NMR spectrum (CD2Cl2, 101 MHz, 25 °C) of [4.1(AuCl)2]. * = CD2Cl2. 257 Figure C.10: 31P NMR spectrum (CD2Cl2, 162 MHz, 25 °C) of [4.1(AuCl)2]. .......................... 257 Figure C.11: 1H NMR spectrum (CDCl3, 400 MHz, 25 °C) of 4.2. * = CHCl3. ........................ 258 Figure C.12: 13C{1H} NMR spectrum (CDCl3, 101 MHz, 25 °C) of 4.2. * = CDCl3. ............... 258 Figure C.13: 31P NMR spectrum (CDCl3, 162 MHz, 25 °C) of 4.2. .......................................... 259 Figure C.14: 1H NMR spectrum (CDCl3, 400 MHz, 25 °C) of [Au(4.3)Cl]. * = CHCl3. .......... 259 Figure C.15: 13C{1H} NMR spectrum (CDCl3, 101 MHz, 25 °C) of [Au(4.3)Cl]. * = CDCl3. . 260 xxviii Figure C.16: 31P NMR spectrum (CDCl3, 162 MHz, 25 °C) of [Au(4.3)Cl]. ............................ 260 Figure C.17: 1H NMR spectrum (CDCl3, 400 MHz, 25 °C) of [Pd(4.3)(η3-C3H5)Cl].* = CHCl3...................................................................................................................................................... 261 Figure C.18: 13C{1H} NMR spectrum (CDCl3, 101 MHz, 25 °C) of [Pd(4.3)(η3-C3H5)Cl]. * = CDCl3. ......................................................................................................................................... 261 Figure C.19: 31P NMR spectrum (CDCl3, 162 MHz, 25 °C) of [Pd(4.3)(η3-C3H5)Cl]. .............. 262 Figure C.20: 1H NMR spectrum (CDCl3, 400 MHz, 25 °C) of meso-trans-[Pd(4.3)2Cl2]. * = CHCl3. ......................................................................................................................................... 262 Figure C.21: 13C{1H} NMR spectrum (CDCl3, 101 MHz, 25 °C) of meso-trans-[Pd(4.3)2Cl2]. * = CDCl3. ......................................................................................................................................... 263 Figure C.22: 31P{1H} NMR spectrum (CDCl3, 162 MHz, 25 °C) of meso-trans-[Pd(4.3)2Cl2]. 263 Figure C.23: 1H NMR spectrum (CDCl3, 400 MHz, 25 °C) of rac-trans- and meso-trans-[Pd(4.3)2Cl2]. * = CHCl3. ............................................................................................................ 264 Figure C.24: 13C{1H} NMR spectrum (CDCl3, 101 MHz, 25 °C) of rac-trans- and meso-trans-[Pd(4.3)2Cl2]. * = CDCl3. ............................................................................................................ 264 Figure C.25: 31P{1H} NMR spectrum (CDCl3, 162 MHz, 25 °C) of rac-trans- and meso-trans-[Pd(4.3)2Cl2]................................................................................................................................ 265 Figure C.26: 1H NMR spectrum (CDCl3, 400 MHz, −5 °C) of rac-trans- and meso-trans-[Pd(4.3)2Cl2]. * = CHCl3. ............................................................................................................ 265 Figure C.27: 13C{1H} NMR spectrum (CDCl3, 101 MHz, −5 °C) of rac-trans- and meso-trans-[Pd(4.3)2Cl2]. * = CDCl3. ............................................................................................................ 266 Figure C.28: 31P{1H} NMR spectrum (CDCl3, 162 MHz, −5 °C) of rac-trans- and meso-trans-[Pd(4.3)2Cl2]................................................................................................................................ 266 xxix Figure D.1: 13C{1H} NMR spectrum (CDCl3, 101 MHz, 25 °C) of Z-5.1. ................................ 269 Figure D.2: 31P{1H} NMR spectrum (CDCl3, 162 MHz, 25 °C) of Z-5.1. ................................. 269 Figure D.3: 29Si NMR Spectrum (CDCl3, 80 MHz, 25 °C) of Z-5.1. ......................................... 270 Figure D.4: 31P NMR Spectrum (CDCl3, 101 MHz, 25 °C) of E-5.1. ........................................ 270 Figure D.5: 13C{1H} NMR Spectrum (CDCl3, 162 MHz, 25 °C) of E-5.1. ............................... 271 Figure D.6: 29Si NMR spectrum (CDCl3, 80 MHz, 25 ⁰C) of E-5.1. .......................................... 271 Figure E.1: 1H NMR spectrum (CDCl3, 400 MHz, 25 °C) of PI-d3. * = CHCl3. ....................... 273 Figure E.2: 2H NMR spectrum (CHCl3, 61 MHz, 25 °C) of PI-d3. * = CDCl3. ......................... 273 Figure E.3: 13C{1H} NMR spectrum (CDCl3, 151 MHz, 25 °C) of PI-d3. * = CDCl3. .............. 274 Figure E.4: 31P NMR spectrum (CDCl3, 162 MHz, 25 °C) of PI-d3. ......................................... 274 Figure E.5: 1H NMR spectrum (C6D6, 600 MHz, 25 °C) of E/Z-Mes*P=C(CD3)Br. * = C6D5H..................................................................................................................................................... 275 Figure E.6: 13C{1H} NMR spectrum (C6D6, 151 MHz, 25 °C) of E/Z-Mes*P=C(CD3)Br. * = C6D6. ........................................................................................................................................... 275 Figure E.7: 31P NMR spectrum (C6D6, 400 MHz, 25 °C) of E/Z-Mes*P=C(CD3)Br. ............... 276 xxx List of Schemes Scheme 1.1: Preparation of the first examples of compounds with a localized P=C bond. ........... 5 Scheme 1.2: Synthetic routes to 1-phosphabutadienes. ................................................................ 10 Scheme 1.3: Pd0-mediated nucleophilic substitution of E/Z-Mes*P=C(H)Br. ............................. 11 Scheme 1.4: Cycloaddition reactions of 1-phosphabutadienes..................................................... 12 Scheme 1.5: Preparation and microstructures of polybutadiene and polyisoprene. ..................... 14 Scheme 1.6: Anionic addition polymerization of a generic olefin. I = initiator. .......................... 15 Scheme 1.7: Polymerization of MesP=CPh2 1.6a to afford poly(methylene phosphine) 1.28 and the preparation of molecular models 1.29a−f. .............................................................................. 17 Scheme 1.8: Addition-isomerization pathway for [Au(1.6a)Cl] with TEMPO. ........................... 19 Scheme 1.9: Reaction of 1.6a with n-BuLi and trityl chloride to afford C−H activated product 1.32. Trt = triphenylmethyl. .......................................................................................................... 20 Scheme 1.10: Reversible formation of poly(2-phosphanaphthalene)s 1.34a,b. ........................... 21 Scheme 1.11: Formation of E/Z-poly(p-phenylene phosphaalkene) (1.35) and Z-poly(p-phenylene phosphaalkene) (1.36). ................................................................................................ 25 Scheme 1.12: Formation of E-poly(p-phenylene phosphaalkene)s 1.37a−d and 1.38a−c via phospha-Wittig reactions. ............................................................................................................. 26 Scheme 1.13: Synthesis of poly(fluorenylidene phosphaalkene)s 1.39 and 1.39·[AuCl]n. .......... 27 Scheme 1.14: Preparation of diphosphinidenecyclobutene (DPCB)-containing polymers 1.40 and 1.41a−c and their PdII complexes.................................................................................................. 29 Scheme 1.15: Polymerization of 1-phosphaisoprene (PI) to afford poly(1-phosphaisoprene) (PPI; only three possible microstructures are shown). ........................................................................... 30 Scheme 1.16: Preparation of PPI·[AuCl]n. For clarity, only microstructure x is shown. .............. 31 xxxi Scheme 2.1: Anionic polymerization of PI to afford PPI. ............................................................ 32 Scheme 2.2: Preparation of cis/trans allyl anions formed from the reaction of isoprene with n-BuLi. ............................................................................................................................................. 33 Scheme 2.3: (a) Preparation of [Li·(12-crown-4)2][endo-2.1]. For clarity, the structures of Li·[exo-2.1] and [Li(12-crown-4)2][exo-2.1] are not shown; (b) structures of endo-2.1 and exo-2.1.................................................................................................................................................. 34 Scheme 2.4: Preparation of [Au(2.2)Cl] from Li·2.1 via 2.2. ...................................................... 38 Scheme 2.5: Preparation of [Au(2.3Cl] and [Au(2.4)Cl] from Li·2.1. ......................................... 40 Scheme 2.6: Formation of 2.5 and 2.6 from the reaction of Li·2.1 with H2C=CPh2 and methanol {2.5 and 2.6 were isolated as AuI salts [Au(2.5)Cl] and [Au(2.6)Cl], respectively}. ................... 42 Scheme 2.7: Preparation of linear dimers 2.7 and [2.7(AuCl)2]. .................................................. 47 Scheme 2.8: Formation of [Au(2.8)Cl] via 2.8. ............................................................................ 49 Scheme 2.9: Assignments of the propagating anion and end-group of H terminated PPI, the NMR spectroscopic signals are shown in Figure 2.8. ............................................................................. 51 Scheme 2.10: Preparation of PPI·[AuCl]0.96n. Only microstructures x and y are shown. ............. 56 Scheme 3.1: Synthesis of PPI·[Pd(η3-C3H5)Cl]an and PPI·[PdCl2]bn from the reaction of PPI with [Pd(η3-C3H5)(µ-Cl)]2 and [Pd(cod)Cl2], respectively. .................................................................. 83 Scheme 3.2: Preparation of complex [Pd(PI)(η3-C3H5)Cl]. .......................................................... 87 Scheme 3.3: Formation of [Pd(PI')2Cl2] (3.1) from PI and [Pd(cod)Cl2]. .................................... 90 Scheme 3.4: Formation of 3.3 from 3.2 and [Pd(cod)Cl2]. ........................................................... 98 Scheme 3.5: Reversible cross-linking of PPI using [Pd(cod)Cl2] and PMe3. ............................. 101 Scheme 4.1: Formation 4.1 and [Pd(4.1)Cl2]. ............................................................................. 119 Scheme 4.2: Reactions of 1-phosphaisoprene with AuI. ............................................................. 123 xxxii Scheme 4.3: (a) Transition state calculations for the [4+2] dimerization of PI; (b) favored regiochemical outcome of intermolecular dimerization of MeP=CH−CH=CH2 to afford a Type I scaffold. ....................................................................................................................................... 128 Scheme 4.4: Preparation of 4.2 from E/Z-Mes*P=C(Me)Br. ..................................................... 129 Scheme 4.5: Preparation of 1-phosphet-2-ene gold(I) complex [Au(4.3)Cl]. ............................ 131 Scheme 4.6: Preparation of 1-phosphet-2-ene palladium(II) complexes. ................................... 133 Scheme 5.1: Pd(0) catalyzed synthesis of Z-5.1 and n-BuLi or light-mediated E/Z isomerization of Z-5.1 to E-5.1. ......................................................................................................................... 158 Scheme 6.1: Possible muoniated products from the reaction of PI and 6.1 with Mu. ................ 173 Scheme 6.2: Hypothetical products arising from Mu+ addition to PI and 6.1. Syn and anti denote the relative orientations of the Mes* and Mu substituents. ........................................................ 183 Scheme 7.1: Formation of cross-linked networks via the binding of PPI to multivalent transition metals. ......................................................................................................................................... 190 Scheme 7.2: Preparation of random and block copolymers of PI and organic monomers to afford functional commodity polymers. ................................................................................................ 191 Scheme 7.3: Reaction scheme showing (a) adducts of 7.1a/b with BH3·THF (b) the postulated reaction pathway of PPI and BH3·THF. For clarity, only microstructure x is shown. ............... 192 Scheme 7.4: Postulated formation of Rind substituted PPI. ....................................................... 193 Scheme 7.5: Formation of: (a) C-aromatic substituted phosphaalkenes reported by Ito and coworkers; (b) postulated formation of polyaromatic substituted 1-phosphabutadienes and the turn-on fluorescence of the resultant polymers. .......................................................................... 194 xxxiii List of Charts Chart 1.1: Generic examples of important phosphorus(III)-containing compounds. ..................... 2 Chart 1.2: Representation of p-orbital overlap for phosphaalkenes, alkenes and imines. .............. 3 Chart 1.3: First reported examples of structurally characterized compounds containing a P=C bond................................................................................................................................................. 4 Chart 1.4: Early examples of P=C transition metal complexes. ..................................................... 7 Chart 1.5: Examples of P=C-metal complexes and complexes used in catalytic transformations; inset top left: generic structure of diphosphinidenecyclobutene (DPCB). ..................................... 8 Chart 1.6: Common commodity polymers.................................................................................... 13 Chart 1.7: Commercialized main-group polymers: polyphosphazenes and silicones. ................. 22 Chart 1.8: Selected examples of PIII-containing polymers. Linker may or may not be present. .. 23 Chart 3.1: Schematic illustrating the existing binding types for phosphorus polymers toward transition metals and the simple cross-linking described herein. ................................................. 82 Chart 4.1: Cycloaddition pathways of 1-phosphabutadienes. ..................................................... 118 Chart 4.2: Diastereomers of [Pd(4.3)(η3-C3H5)Cl]: endo and exo refer to the relative arrangement of the two atoms with red dots. ................................................................................................... 134 Chart 5.1: Selected examples of P=C-containing compounds that undergo E/Z-isomerization: i) monophosphaalkenes; ii) bisphosphaalkenes; iii) trisphosphaalkenes; iv) diphosphabutadienes...................................................................................................................................................... 157 Chart 6.1: The 1-phosphabutadienes selected for this μSR study............................................... 170 xxxiv List of Abbreviations and Symbols Å angstrom (1 x 10−10 meters) ALCR avoided level-crossing resonance APT attached Proton Test (NMR spectroscopy) Ar aryl br broad (NMR spectroscopy) Bu butyl C Celsius ca. circa cal calories calcd calculated CCDC Cambridge Crystallographic Data Centre cf. compare cis same side (double bond geometry) cod/COD cyclooctadiene COSY correlated spectroscopy (NMR) cy cyclohexyl (substituent) d day(s) (time) or doublet (NMR spectroscopy) d1 relaxation delay (NMR spectroscopy) DCM dichloromethane Δ heat δ chemical shift in parts per million xxxv δ+/δ− partial positive or negative charge DFT density functional theory dn/dc refractive index increment X̅n number average degree of polymerization Đ dispersity E entgegen (configuration) Ea activation energy e.g. exempli gratia (for example) Elem. Anal. elemental analysis equiv equivalents Et2O diethyl ether eV electron volt exo outside Fc ferrocenyl FD field desorption (mass spectrometry) g gram GPC gel permeation chromatography {1H} proton decoupled (NMR spectroscopy) h hour(s) HMBC heteronuclear multiple bond correlation (NMR spectroscopy) xxxvi HSQC heteronuclear single quantum correlation (NMR spectroscopy) HOMO highest occupied molecular orbital HRMS high-resolution mass spectrometry Hz Hertz i.e. id est (in other words) i iso (as in i-Pr) in situ in place or in the reaction in vacuo in a vacuum init. initiator J coupling constant (NMR spectroscopy) K Kelvin Kα spectral line KIE kinetic isotope effect LRMS low-resolution mass spectrometry LUMO lowest unoccupied molecular orbital µ micro (10−6) or muon m/z mass-to-charge ratio m milli (10−3)/ meter/ multiplet (NMR spectroscopy) M mega (106)/ molarity (moles per liter) [M]:[I] monomer to initiator ratio MALS multi-angle light scattering xxxvii Me methyl Mes 2,4,6-trimethylphenyl (substituent) Mes* 2,4,6-tri-t-butylphenyl (substituent) min minute(s) Mn number average molecular weight Mw weight average molecular weight MW molecular weight mol mole(s) n normal (i.e. n-BuLi) or number of repeat units (polymer) N nano NMR nuclear magnetic resonance o degrees o ortho p para Ph phenyl (substituent) PI 1-phosphaisoprene PMP poly(methylene phosphine) PPI poly(1-phosphaisoprene) ppm parts per million PPV poly(p-phenylene vinylene) PPYP poly(p-phenylenediethynylene phosphine) Pr Propyl (substituent) xxxviii R generic substituent rt room temperature s singlet (NMR spectroscopy) or seconds SADABS Siemens Area Detector Absorption Correction Program t tertiary T triplet (NMR spectroscopy) TEMPO (2,2,6,6-tetramethylpiperidin-1-yl)oxyl thf tetrahydrofuran tht tetrahydrothiophene TMS trimethylsilyl (substituent) TOCSY total correlation spectroscopy tol tolyl (substituent) trans opposite side (double bond) UBC University of British Columbia UV ultraviolet μSR muon spin spectroscopy V viscometry VAZO-88 1,1′-azobis(cyclohexanecarbonitrile) vide infra see below vide supra see above vis visible Z zusammen (configuration) xxxix Acknowledgements Firstly, I would like to thank Prof. Derek P. Gates for his guidance, encouragement and supervision over the course of my Ph.D. I am also grateful for the opportunity Derek afforded me to participate in multiple conferences throughout my time at UBC which have been a particular highlight. Lastly, without those numerous, multiple-hour sessions in your office writing papers, I would never have got this far. May your radio never go silent. To my supervisory committee members Prof. Mark MacLachlan, Prof. Martin Tanner and Prof. Pierre Kennepohl for their input throughout the years. To the Gates group members past and present, who helped me find my feet in the lab and made this whole process very enjoyable, I am very grateful. To name but a few: Ben Rawe, Khatera Hazin, Zeyu Han, Kerim Samedov, Anna Bennett, Harvey Mackenzie, Jeffrey Suen, Tian Zhang, Rebecca Yang, Ming Li, Aaron Mitchell and Zhaoxiang Liu. Additionally, I would like to thank all the undergraduate and exchange students I have had the pleasure of working alongside. Namely Philipp Dabringhaus, David Roehner, Chieko Yamazawa, Brina Kim, Max Eaton and Rodella Chowdhury. Special shout out to the D-wing lunch crew: Corey Sanz, Ethan Sauvè and Jennifer Yuan (honorary member). I also thank my partner, Amanda, for her love, support and patience over the years and the many, many late nights I spent in the lab when I promised I would come home at a reasonable time. Also, to the Wongs for being my second family here in Vancouver, I appreciate you all. Lastly, I must thank my parents, Christine and Tim, for their support and belief in me. Also, my siblings, although if I try to list all of them, I am going to run out of space. xl Dedication To Mum & Dad1 Chapter 1: Introduction to Low-Coordinate Phosphorus Compounds and Their Reactivity and Polymers 1.1 Phosphorus Discovered in 1669 by Hennig Brandt in the search for the fabled "Philosopher's Stone", white phosphorus (or P4) was a fascinating material due to its chemiluminescence in the presence of oxygen: a mysterious ability to glow in the dark.1 Now known as one of the most important and diverse elements on the periodic table, phosphorus is integral to life as we know it, with phosphates forming the backbone of our DNA and bones. Phosphorus is also an essential element in fertilizers, alongside nitrogen and potassium, and has proved a crucial ingredient for agriculture and food production, which has contributed to feeding an ever-expanding global population.2 Ironically, this element that is crucial for life also has a vast capacity for destruction, having been used extensively during times of war to inflict suffering.3 Thus, the study of this unique element has produced numerous impactful discoveries relevant to modern life. From the viewpoint of a synthetic chemist, phosphorus is a highly versatile element due to the range of oxidation states and bonding geometries available, and the electronic properties that it can impart into molecules. One particular aspect of synthetic chemistry where phosphorus-containing compounds have had extensive impact is the use of phosphines (PR3, Chart 1.1) as ligands for transition metals in catalytic applications. Phosphorus has often been the donor atom of choice due to its lone pair that binds strongly to late-transition metals.4 A remarkable demonstration of the importance of phosphorus-containing compounds as ligands is the awarding of three Nobel prizes (2001, 2005 and 2010) to transition metal-catalyzed processes, in which ancillary phosphine ligands play a crucial role. Thus, a vast library of mono-, bi- and polydentate 2 phosphine ligands has been developed, with the aim of generating efficient catalysts for important catalytic transformations, notably through tuning the steric and electronic environment of the phosphine center. Chart 1.1: Generic examples of important phosphorus(III)-containing compounds. 1.2 Low-coordinate phosphorus compounds Synthetic chemists have investigated unsaturated phosphaalkenes (RP=CR2) and phosphaalkynes (RC≡P) in the interest of exploiting their unique electronic properties for binding transition metals.5-8 Given that the work contained within this thesis focuses on low-coordinate phosphorus compounds, an in-depth discussion of these molecules is presented in chapter 1. Early investigations into low-coordinate phosphorus compounds were hampered by the inherent reactivity of unsaturated phosphorus-carbon π-bonds. For instance, in 1961, Gier and coworkers detected the parent phosphaalkyne, HC≡P, at −196 °C.9 However, upon warming to −130 °C, polymerization occurred to afford a highly pyrophoric polymeric material. Later, Kroto and coworkers were able to observe the "unstable" phosphaalkenes CF2=PH, CH2=PCl and CH2=PH by microwave spectroscopy.10 The difficulty in isolating these compounds under ambient conditions stems from the instability of P=C π-bonds with respect to oligomerization or polymerization reactions. Specifically, the π-bond strength of HP=CH2 was calculated at the MCSCF/631-G(d) level of theory to be 43 kcal mol−1, which was significantly weaker than that in ethylene (H2C=CH2, 65 kcal mol−1).11 The relative weakness of P=C π-bonds relative to C=C bonds can be attributed to the poor 3p−2p orbital overlap in the former (Chart 1.2). 3 Chart 1.2: Representation of p-orbital overlap for phosphaalkenes, alkenes and imines. In order to isolate these reactive P=C-containing compounds, researchers turned to methods to stabilize the π-bond with respect to oligomerization reactions. One such method was to delocalize the P=C π-bond by incorporating it into a conjugated system. The first example of an isolable molecule containing a P=C bond displayed this type of stabilization. Specifically, the seminal report by Dimroth and Hoffman in 1964 disclosed the synthesis of phosphamethine cyanines 1.1a−d and 1.2a,b (Chart 1.3), by the reaction of 2-chlorobenzothiazolium and 2-chloroquinolinium salts with P(CH2OH)3.12 The material was highly colored, and X-ray crystallographic analysis a year later by Allman found the P−C double bond lengths (1.76 Å) were much shorter than typical P−C single bonds (e.g. 1.83 Å in PPh3).13 Later in 1966, Märkl reported the first phosphinine (or phosphabenzene) 1.3, presented as a phosphorus-analogue of organic benzene.14 The parent phosphinine was then synthesized five years later in 1971 by Ashe.15 Electron diffraction data collected on the parent phosphinine indicated that the length of the P=C π-bonds was 1.73 Å which is shorter than that for the P−C single bonds in PMe3 (1.84 Å).16 Furthermore, the carbon-carbon bond lengths (avg 1.398 Å) were relatively unchanged from those of organic benzene (1.395 Å) and the ring was planar. Taken together, these data indicated that the phosphinine ring was aromatic. In 1988, DFT calculations confirmed the aromaticity of phosphinine to be 88% that of pyridine.17 4 Chart 1.3: First reported examples of structurally characterized compounds containing a P=C bond. Another method developed to enable isolation of reactive P=C compounds is via kinetic stabilization, whereby the use of sterically bulky substituents [e.g. Mes (2,4,6-trimethylphenyl) or Mes* (2,4,6-tri-t-butylphenyl)] inhibits oligomerization and polymerization reactions. Utilizing sterically bulky substituents, in 1976, Becker synthesized the first isolable compound with a localized bond between carbon and a heavier main-group element (phosphorus, Scheme 1.1).18 Specifically, it was reported that treatment of RPTMS2 (R = Me, t-Bu, Cy, Ph) with pivaloyl chloride resulted in the formation of acyl phosphines 1.4a−d which underwent a 1,3-silyl migration to afford phosphaalkenes 1.5a−d. This success was closely followed two years later by Bickelhaupt, who reported the first all-carbon substituted phosphaalkenes, RP=CPh2 (1.6a,b) via a 1,2-elimination of the appropriate chlorophosphine precursors.19 Attempts to isolate phosphaalkenes with smaller substituents at phosphorus (PhP=CPh2 and o-tolylP=CPh2) were unsuccessful and instead "polymeric material" was isolated. The phosphaalkene PhP=CPh2 was later demonstrated to be in equilibrium in solution with the cyclic head-to-head dimer PhPCPh2CPh2PPh, demonstrating the finely balanced steric environment of these highly reactive systems with respect to oligomerization.20 An interesting feature of the all-carbon phosphaalkenes 5 is the chemical shift observed in the 31P NMR spectrum of these compounds (>200 ppm, e.g. 1.6a: δ = 233). Scheme 1.1: Preparation of the first examples of compounds with a localized P=C bond. Inspired by the success in isolating compounds containing P=C bonds by incorporating sterically bulky substituents at the π-bond, further examples of stable molecules containing heavier unsaturated main-group elements were isolated. For example, in 1981, landmark syntheses were reported, including a diphosphene (P=P) by Yoshifuji and coworkers,21 a disilene (Si=Si) by West and coworkers,22 a phosphasilene (P=Si) by Brook and coworkers23 and a phosphaalkyne (P≡C) by Becker and coworkers.24 1.2.1 The phosphorus-carbon analogy As the chemistry of phosphaalkenes has developed, a close parallel between the reactivity of P=C and C=C bonds has been established.25, 26 The σ-framework polarity of the P=C bond follows the expected Pδ+−Cδ− indicated by the differences in the Pauling electronegativity scale (2.5 for C vs 2.1 for P). In contrast, their imine (N=C) congeners display the opposite polarity (σ-framework: Nδ—Cδ+). The π-bond of H2C=PH was calculated to be essentially apolar due to the similar π-electronegativities of phosphorus and carbon.27, 28 Additionally, UV photoelectron spectroscopy measurements revealed that the HOMO of HP=CH2 describes the P=C π-bond (−10.3 eV) with the phosphorus lone pair having slightly lower energy (−10.7 eV).29 This result also contrasts with 6 imines where the HOMO describes the lone pair at N. Hence, the reactivity of P=C bonds resembles C=C bonds more closely than N=C-containing molecules. Thus, numerous examples of reactions of P=C bonds that are analogous to transformations of olefins have been reported, including electrophilic addition,30 hydroboration,31 catalytic hydrogenation,32 metathesis,33 Cope rearrangements,34 epoxidation,35 cycloadditions36 and polymerization (see Section 1.3.3). 1.2.2 Phosphaalkenes as ligands for transition metals The reluctance of phosphorus to form hybrid orbitals is well documented and can be attributed to the poor overlap of the atomic 3s and 3p orbitals.8 This inability to hybridize manifests in the R−P=C angle of phosphaalkenes being ca. 100° which is much smaller than the ideal 120° expected for sp2-hybridized species. Furthermore, the lone pair at P in HP=CH2 was calculated to have 66% s-character, whereas, for HN=CH2, the lone pair was calculated to have 39% s-contribution. Additionally, the electropositive character of the phosphorus atom in phosphaalkenes (+0.42e in HP=CH2) imparts excellent π-accepting properties. Acyclic phosphaalkenes can bind both end-on (η1) through the P-lone pair and side-on (η2) through the π-bond (Chart 1.4). For example, In 1981, Bickelhaupt and coworkers described the synthesis of η1-P=C Cr(CO)5 complex 1.7.37 While uncoordinated 1.6a (MesP=CPh2) is air- and moisture-sensitive, it was found that coordination of the P-lone pair to Cr(0) in 1.7 rendered the molecule stable to atmospheric oxygen and moisture. Furthering the study of the coordination chemistry of 1.6a, in 1984, an equilibrium was observed between η1-[(MesP=CPh2)Pt(PPh3)2] (1.8) and its η2 π-bound isomer 1.9.38 It was found that the η2-coordinated 1.9 was favored by 4 kcal mol−1 and predominated at lower temperatures (< 0 °C). However, at higher temperatures, end-on η1-binding was favored due to entropy effects. In the same year, a complex featuring both η1 and η2-binding modes of Mes*P=CH2 (1.10) was isolated by Appel and coworkers.39 7 Chart 1.4: Early examples of P=C transition metal complexes. Many examples of acyclic P=C-complexes have been subsequently utilized to good effect in catalytic transformations.6, 8, 40, 41 Salient examples of the use of phosphaalkenes as ligands in catalysis are discussed in this section (Chart 1.5). The diphosphinidenecyclobutene ligand scaffold [DPCB, Chart 1.5 (inset)] was first reported by Appel in 1987 as the product of a Cope rearrangement.42 Derivatives of DPCB ligands were heavily investigated owing to the unique π-accepting ability of these ligands with their extremely low-lying π*-orbitals, making them attractive ligands for electron-rich transition metals.40 For example, 1.11a−c were utilized as ligands for PdII in the direct conversion of allylic alcohols.43 Catalytic activity was observed in ambient atmosphere at room temperature with low catalyst loading (0.1 mol%) to provide high conversion to product (>85%). In contrast, previously reported allylation catalysts required higher temperatures and catalyst loadings. Variations of the DPCB ligand scaffold have also been widely used in catalytic transformations such as ethylene polymerization,44, 45 alkoxycyclizations,46 1,6-enyne cycloisomerizations,47-49 activation-free hydration of alkynes,47 hydrosilylations,50-52 cyclodehydrations,53 conjugate addition of benzyl carbamate to α,β-unsaturated ketones,54 Stille couplings,55 (de)allylations,56, 57 (hydro)aminations,58-60 dehydrogenative silylations,61 and Sonogashira couplings.62 8 Chart 1.5: Examples of P=C-metal complexes and complexes used in catalytic transformations; inset top left: generic structure of diphosphinidenecyclobutene (DPCB). Further examples of the incorporation of phosphaalkene substituents into complex ligand scaffolds with utility in catalytic transformations have been reported. For example, the cycloisomerization of 1,6-enynes has been demonstrated utilizing phosphaalkene-AuI complexes 1.12a−c and 1.13a,b.63, 64 DFT calculations indicated that the strong binding of the π-accepting P=C unit to AuI was key to the observed reactivity. Chelating hybrid P/N and P/S ligands have 9 also been developed and employed as efficient ligands for catalysis. For instance, Brookhart and coworkers showed that complexes 1.14a,b and 1.15a,b were effective catalysts for the polymerization of ethylene.65 It was found that the complexes are more stable under the polymerization conditions than their imine congers and displayed moderate to high activity. Furthermore, Ozawa and coworkers have explored the coordination chemistry and catalytic activity of PNP-pincer ligands.41 For instance, complex 1.16 has found use in the N-alkylation of amines66 and 1.17a,b (EIND = 1,1,3,3,5,5,7,7-octaethyl-1,2,3,4,5,6,7-hexahydro-s-indacen-4-yl) have been demonstrated to be efficient catalysts for the hydrogenation and hydrosilylation of CO2.67 Additional examples of these PNP pincer complexes show activity as catalysts in the N-alkylation of amines68, 69 and the conjugate addition of carbamates to enones.70 Lastly, our group has used the chelating sp2/sp2 P/N ligand 1.18 in Overman-Claisen rearrangements with isolated yields of up to 91%.71 We have also reported on the catalytic activity of enantiomerically pure P/N chelating ligand 1.19 for use in asymmetric catalysis. Specifically, asymmetric allylic alkylation of 1,3-diphenyl-2-propenyl acetate proceeded with yields of 73–95% with enantiomeric excesses (ee) of 79−92%.72 1.2.3 1-Phosphabutadienes In contrast to phosphaalkenes containing an isolated P=C bond, examples of 1-phosphabutadienes, which contain a C=C bond in conjugation with a P=C bond (i.e. P=C−C=C), are relatively rare. The first examples were reported by Appel and coworkers in 1984 using a "Becker-type" condensation of silyl phosphines with α,β-unsaturated acid chlorides (Scheme 1.2, A).73 Another early strategy to afford 1-phosphabutadienes utilized a 1,2-elimination of the appropriate allylchlorophosphine (B).74-78 The pyrolysis of bis-allyl phosphines has also been shown to result in the formation of a transient 1-phosphabutadiene which was unsubstituted in the carbon chain 10 (C).79, 80 More recently, Pd0-mediated nucleophilic substitutions of Mes*-substituted bromophosphaalkenes by vinyl Grignard reagents have been shown to afford 1-phosphabutadienes (D).81, 82 Lastly, Mathey and coworkers have reported the synthesis of coordinated 1-phosphabutadienes via both a "Phospha-Wittig" methodology (E)83, 84 and phosphinidene/carbene coupling reactions (F).85 The authors stated that coordination of the P=C−C=C skeletons to a transition metal center facilitated isolation of 1-phosphabutadiene ligands with relatively little steric bulk on the P=C−C=C scaffold, however, no attempts were made to isolate the free ligands. Scheme 1.2: Synthetic routes to 1-phosphabutadienes. All 1-phosphabutadienes reported in this thesis were synthesized utilizing the method first reported by van der Sluis et al. in 1997.82 It was shown that the addition of Grignard reagents 11 (RMgBr) to a mixture of E/Z-Mes*P=C(H)Br in the presence of a Pd0 catalyst resulted in the formation of a trans-configured coupling product Mes*P=C(H)R (i.e. trans-Mes*-to-R). An example is given in Scheme 1.3, which shows the synthesis of the 1-phosphabutadiene Mes*P=CH−CH=CH2 (1.22). A mechanistic study revealed that, instead of the expected oxidative addition product 1.20, the reaction proceeded via palladacycle 1.21. The nucleophilic addition of the Grignard reagent to the carbon substituent then occurred trans to the sterically bulky Mes*-substituent. Scheme 1.3: Pd0-mediated nucleophilic substitution of E/Z-Mes*P=C(H)Br. 1.2.4 Cycloaddition reactions of 1-phosphabutadienes Perhaps unsurprisingly, given the widespread cycloaddition reactions in the chemistry of organic butadienes, and the proclivity of reactive P=C-containing species to oligomerize, the reactivity of 1-phosphabutadienes is dominated by intra- and intermolecular cycloaddition reactions. Moreover, the presence of the P heteroatom in the diene and/or dienophile necessitates additional consideration of the regiochemistry of the cyclization products. For example, the [4+2] cycloaddition of 1-phosphabutadiene 1.23a afforded 1,2-diphosphacyclohex-3,4-ene 1.24 (Scheme 1.4).73 In the same report, seven further examples with Ph, Me and Cy substituents at P were shown to undergo an analogous [4+2] cycloaddition. Alternatively, when a t-Bu group was 12 employed at P (1.23b), a head-to-head [2+2] dimer, 1.25, was isolated that contained a 1,2-diphosphacyclobutane scaffold. The [4+2] cycloaddition reaction that furnishes 1,2-diphosphacyclohex-3,4-ene products of type 1.2479, 80, 86-89 is more prevalent than the symmetry-forbidden [2+2] cycloaddition furnishing the 1,2-diphosphacyclobutane of type 1.25.73, 90 Furthermore, the intramolecular [2+2] electrocyclization of a 1-phosphabutadiene to afford a 1-phosphet-2-ene (or 1,2-dihydrophosphete) has also been reported.91, 92 Specifically, the transient 1-phosphabutadiene 1.26 underwent a ring closure reaction to afford 1-phosphet-2-ene 1.27. Additional examples of the electrocyclization of uncoordinated,77 coordinated83, 93-96 and oxidized75, 76 1-phosphabutadienes have been reported. Building on this work, the cycloaddition chemistry of novel 1-phosphabutadienes is investigated in chapter 4 of this thesis. Scheme 1.4: Cycloaddition reactions of 1-phosphabutadienes. 13 1.3 Polymers Polymers, macromolecules that comprise many small molecules linked together to form a chain, are ubiquitous in modern society. In the 1840s, Charles Goodyear discovered the vulcanization of natural rubber (predominantly cis-1,4-polyisoprene), isolated from the hevea braziliensis tree, which produced a hard and highly durable material.97 The robust physical properties of this substance have enabled its use in a vast array of applications, from car tires to medical devices. Decades later in 1909, the first plastic, Bakelite, was synthesized by Leo Baekeland via the condensation of phenol and formaldehyde.98 However, it wasn't until 1920 that German chemist Hermann Staudinger's seminal report on macromolecules correctly postulated the chemical structure of these materials.99 Contemporary demand for commodity polymers is immense, with natural rubber being produced at a scale of 14 million tons in 2021.100 Other commodity polymers such as polyvinylchloride, polyethylene, polypropylene, polyesters and polyamides are also produced on a huge scale (ca. 400 million tons in 2021),101 demonstrating the large role these materials play in our lives (Chart 1.6). Chart 1.6: Common commodity polymers. 1.3.1 Polybutadienes As a class of polymers, polybutadienes [formally poly(buta-1,3-dienes)] are heavily investigated due to their applications as elastomers.102 In particular the anion-initiated polymerizations of 14 butadiene (H2C=CH−CH=CH2) and isoprene (H2C=C(Me)−CH=CH2) have attracted significant attention. These polymerization reactions can afford multiple microstructures, a selection of which is shown in Scheme 1.5. The microstructures of polybutadiene and polyisoprene are dependent on the polymerization conditions including counterion, temperature, pressure and solvent.103-106 For example, the anionic polymerization of isoprene in aliphatic solvents, e.g. cyclohexane, affords up to 95% cis/trans-1,4-enchainment. By contrast, when the polymerization is performed in THF the predominant microstructure is 3,4 (74%).106 Importantly, the physical properties of polybutadienes are heavily dependent upon the prevalent microstructure. Thus, the glass transition temperature (Tg; the temperature below which the amorphous domains of the polymer exhibit brittle glass-like properties) for polyisoprene (Mn = 6,400 g mol−1) which contains 11% 3,4-linkages is −70.5 °C, whereas a sample (Mn = 7,700 g mol−1) with 38% 3,4-linkages exhibits a Tg of −47 °C.107 The authors attributed the increase in Tg with higher 3,4-enchainment content to steric hindrance of the vinyl side chain increasing the stiffness of the polymer. Additionally, simple tailoring of the ratios of 1,4- and 3,4-enchainments in samples of polyisoprene has been shown to result in self-healing behavior of this material without external intervention.108 A portion of the work reported in this thesis focuses on the synthesis and characterization of a phosphorus-containing analogue of polyisoprene and its use in materials science. Scheme 1.5: Preparation and microstructures of polybutadiene and polyisoprene. 15 1.3.2 Addition polymerization A powerful method to generate macromolecules is the addition polymerization of olefins (Scheme 1.6). Typically, a compound containing a C=C double bond is reacted with a substoichiometric amount of initiator (for example, an anion) which then attacks one end of the C=C bond, resulting in a reactive site at the other end (Scheme 1.6, initiation). This reactive site then adds to another C=C-containing molecule to enlarge the chain length in a process called propagation. Using high-purity monomers and solvents, anionic polymerization can be "living". The term "living" was first coined by Swarcz in 1956 while investigating the polymerization of unsaturated monomers by anionic methods.109 Essentially, in the absence of a termination step, the chain end of the polymer is "living" and the addition of subsequent monomers will cause the chain to grow further. Since the first proposal of this phenomenon for anionic methods, "living" (or controlled) polymerization has also been proposed for both cation-110 and radical-111initiated systems. Living polymerization reactions allow accurate control of the molecular weight and represent a powerful method to construct complex macromolecules, such as block copolymers. Scheme 1.6: Anionic addition polymerization of a generic olefin. I = initiator. 16 1.3.3 Addition polymerization of P=C bonds Analogous to the polymerization of olefins, the addition polymerization of phosphaalkenes represents an ideal route to afford functional PIII-containing polymers. Furthermore, particularly relevant to the work presented in this thesis, the addition polymerization of 1-phosphabutadienes is a powerful method to furnish functional phosphorus-containing analogues of polybutadienes (see Section 1.3.7). However, the bulky substituents necessary to enable isolation of these reactive species serve to inhibit oligomerization/polymerization reactions.112 Thus, the kinetic stabilization provided by the bulky substituents on the P=C bond must be sufficient to facilitate isolation of the monomer, but insufficient to prevent polymerization upon introduction of an initiator. In other words, the balance of kinetics and thermodynamics is critical to the success of addition polymerization of unsaturated phosphorus-containing molecules. The first successful well-defined addition polymerization of a phosphaalkene was reported by our group in 2003. Namely, polymerization of 1.6a (MesP=CPh2) furnished a polymer containing phosphine units in the repeating unit (1.28, Scheme 1.7).113 Serendipitously, the polymer was recovered from the residue of a distillation of 1.6a at elevated temperature under vacuum. Gel-permeation chromatographic (GPC) analysis revealed an estimated Mn of 11,500 g mol−1 (Ð = 1.25) which represented a degree of polymerization (X̅n) of ca. 36. The polymer was demonstrated to be relatively air-stable in the solid state, however, in solution it slowly oxidized in air. Quantitative oxidation of 1.28 was demonstrated by reaction with H2O2 or S8 to yield the corresponding phosphine oxide (1.28·O) or sulfide (1.28·S), respectively. Additionally, TGA measurements of 1.28 revealed it was stable to weight loss until 265 °C. We also disclosed that polymerization of 1.6a could also be conducted using a radical VAZO initiator at 200 °C for 48 h. 17 Analysis of radical-initiated 1.28 by 31P NMR spectroscopy revealed two broad signals, suggesting both head-to-head and head-to-tail enchainment in the polymer. Scheme 1.7: Polymerization of MesP=CPh2 1.6a to afford poly(methylene phosphine) 1.28 and the preparation of molecular models 1.29a−f. In the same report, anion-initiated 1.28 was prepared using MeLi and BuLi as initiators for the polymerization of 1.6a. The resultant polymers were isolated with Mn 6,600 and 5,400 g mol−1 with Ð = 1.15 and 1.55, respectively. Subsequently, a living polymerization of 1.6a in glyme using n-BuLi as an anionic initiator was reported.114, 115 The rate of propagation for 1.6a (kp = 21 L mol−1 h−1) was extremely slow (cf. vinyl mesitylene: kp = 1.2×103 L mol−1 h−1). The polymeric phosphine oxides, 1.28·O, initiated by MeLi and quenched with methanol, were analyzed by both MALDI-TOF116 and ESI-MS117 whereby oligomers up to n = 11 and n = 20 were observed, respectively. Initially, the addition polymerization of 1.6a was expected to proceed via a regioregular P−C−P−C addition pathway. Early explorations into the reactivity of 1.6a with organolithium reagents suggested nucleophilic attack at P from the R− moiety to form Mes(R)P−CPh2−, followed by addition of a proton at the carbanion to afford 1.29a, which represents a molecular model for 18 1.28.118 Additional studies by our group produced analogous molecular models for P−C−P−C enchainment in 1.28. Specifically, reaction of R1Li (R1 = Me, n-Bu) with 1.6a followed by the addition of electrophiles R2X (R2 = H, Me, NEt2, SiMe3, SiHMe2; X = Cl, I, OH, MeO) resulted in the isolation of the expected 1,2-addition products Mes(R1)P−C(R2)Ph2 (1.29b−f).119 Our group then investigated the microstructure of radical-initiated 1.28 by utilizing (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO)-derived initiators and models (Scheme 1.8).120 Remarkably, treatment of [Au(1.6a)Cl] with two equiv TEMPO did not result in the expected addition product 1.30. Instead, addition-isomerization product 1.31 was isolated, arising from activation of the ortho-methyl group of the Mes substituent. Detailed NMR spectroscopic analysis of polymer 1.28, using a higher field NMR spectrometer (i.e. 600 MHz) than was available in the initial report (300 MHz), led to a new postulate that the predominant microstructure of radical initiated 1.28 was x in Scheme 1.8. 19 Scheme 1.8: Addition-isomerization pathway for [Au(1.6a)Cl] with TEMPO. The discovery of this intriguing addition-isomerization mechanism prompted further investigation of the microstructure of anion-initiated 1.28. Addition of n-BuLi to 1.6a followed by reaction with trityl chloride (trityl = triphenylmethyl) resulted in the isolation of 1.32, analogous to 1.31.121 Additionally, 1.6a-d9 was synthesized containing deuterated methyl groups on the Mes substituent and the polymerization was monitored by 31P NMR spectroscopy. A kinetic isotope effect (KIE) of ≥23 was observed for the polymerization which indicated that the rate-determining step was the activation of the ortho-methyl substituent of the Mes group. 20 Scheme 1.9: Reaction of 1.6a with n-BuLi and trityl chloride to afford C−H activated product 1.32. Trt = triphenylmethyl. The functionality imparted by the PIII-centers of 1.28 and its derivatives was demonstrated extensively. For example, the P atoms were bound to gold(I) to form a highly metalated polymer.122 Additionally, treatment of 1.28 with BH3 and MeI formed a borane adduct and phosphonium-containing polymer, respectively.123 Block copolymers of 1.28 with styrene,114, 124 methyl methacrylate125 and isoprene126 have also been synthesized. In the case of the latter, the block copolymers were shown to form self-assembled nanostructures upon coordination to AuI and dissolution in heptane. Radical-initiated random copolymers of 1.28 and styrene were utilized in polymer-supported catalysis for a Suzuki coupling reaction.127 Additionally, copolymers of styrene and poly(methylene phosphine) containing a chiral substituent were used as ligands for rhodium(I).128 Lastly, a ferrocene-containing poly(methylene phosphine) was synthesized and a reversible one-electron reduction was observed, consistent with a ferrocene-ferrocenium couple.129 More recently, Grützmacher and coworkers have developed the polymerization of phosphanaphthalenes 1.33a,b.130 Specifically, treatment of 1.33a,b with CuX (X = Cl, Br) afforded polymeric 1.34a−c·[CuX]n that were isolated as brittle yellow solids. The polymers 1.34a−c·[CuX]n were analyzed by GPC to reveal Mn values ranging from 14,400 to 34,200 g mol−1 and dispersities (Đ) of 1.88 to 2.41. Addition of competing PR3 (R = Me, Ph) ligands resulted in de-coordination of 1.34a−c·[CuX]n to afford uncoordinated polymers 1.34a,b. Interestingly, 21 quantitative de-polymerization of 1.34a,b was observed under the stimulus of heat or light. An Arrhenius plot determined Ea(depolymerization) to be 32.9 ± 5.3 and 39.8 ± 7.9 kJ mol−1 for 1.34a and 1.34b, respectively, which are much smaller values than those reported for olefins (200 to 300 kJ mol−1). The polymerization/de-polymerization cycle could be reproducibly repeated many times, demonstrating the utility of 1.34a,b as fully recyclable polymers. Scheme 1.10: Reversible formation of poly(2-phosphanaphthalene)s 1.34a,b. 1.3.4 Commercial polymers containing main-group elements While synthetic methods to generate organic polymers are well-established, aided by the sophisticated techniques developed in the field of organic chemistry, strategies to link together main-group elements into long chains are relatively less mature. For this reason, there is a dearth of main-group polymers compared to their organic counterparts. Nevertheless, two classes of main-group polymers have been commercialized and are shown in Chart 1.7. Polyphosphazenes are highly versatile polymers due to the tunability of the R groups which arises from facile substitution of the poly(chlorophosphazene) precursors. These tunable R groups can render the polymers crystalline, amorphous, hydrophobic or hydrophilic.131 Thus, polyphosphazenes have found applications in the medicinal industry, fire retardant polymers, ceramics, dyes and resins.132 Furthermore, silicones, which contain very strong Si−O bonds in the backbone, have excellent 22 thermal and chemical resistance and thus have been used in applications ranging from building materials to personal care products.133 Chart 1.7: Commercialized main-group polymers: polyphosphazenes and silicones. 1.3.5 Organophosphorus polymers As demonstrated for polyphosphazenes and silicones, the incorporation of main-group elements into polymeric systems can impart favorable properties to the materials. In particular, the incorporation of PIII groups into polymer chains has been explored due to the ability of this center to undergo oxidation, coordinate metals and participate in conjugation. A selection of phosphorus(III)-containing polymers with diverse applications is shown in Chart 1.8. Polystyrene-supported phosphines have been used extensively as catalyst supports for catalytic transformations.134 For example, enantiomerically pure polystyrene-derived PIII ligands have been shown to have moderate to good activity for the asymmetric hydrogenation of alkenes with reported enantiomeric excesses of up to 89%.135 The polymeric nature of the ligand resulted in facile separation of the catalyst from the substrates after the reaction. Additionally, poly(ferrocenyl phosphines) have been employed as ligands for transition metals and catalyst supports.136-139 Additionally, they have been used as precursors to novel nanostructured materials.138, 140 For instance, polyferrocenylphosphine-block-polyferrocenylsilane copolymers have been shown to undergo microphase separation in thin films, forming spherical or cylindrical structures depending on the ratio of the blocks in the copolymer.141 23 Chart 1.8: Selected examples of PIII-containing polymers. Linker may or may not be present. Metallized phosphane-ene networks have also been used as precursors to ceramic materials.142 The material was demonstrated to have excellent shape retention after metallization with Al, Ge or Co post-pyrolysis. Furthermore, conjugated polyphospholes, first reported by Tilley and coworkers in 1997,143 have been investigated for the functionality imparted by the PIII-centers.144 For example, a thiophene-spaced polyphosphole displayed a bathochromic shift (Δλonset = 38 nm) upon oxidation with S8, demonstrating its use as a sensor for chalcogens.145 Additionally, conjugated poly(p-phenylene phosphine)s146, 147 display tunable photophysical properties rendered by the PIII groups in the main-chain, for example via oxidation.148 Lastly, poly(p-phenylenediethynylene phosphine)s, analogues of the organic poly(p-phenylene ethynylene), have been investigated for their sensing properties. These polymers display "turn-on" fluorescence upon 24 oxidation149, 150 or coordination to AuI.151 These examples illustrate that the incorporation of phosphine groups within a polymer chain can offer desirable properties and functions. 1.3.6 Polymers containing P=C bonds In contrast to the phosphine-containing polymers described above, macromolecules containing P=C bonds are rare, although the few reported examples demonstrate the unique properties imparted by the presence of the P=C bond in the main- or side-chain. The first example of such a macromolecule containing P=C bonds was reported by our group in 2002. Specifically, we disclosed the formation of E/Z-poly(p-phenylene phosphaalkene) 1.35, a phosphorus analogue of π-conjugated poly(phenylene vinylene) (PPV) (Scheme 1.11).152 The molecular weights across four trials were determined to be Mn = 2,900 to 10,500 g mol−1 (X̅n = 5 to 21). Polymer 1.35 was analyzed by absorption spectroscopy to reveal a bathochromic shift of the absorption maximum relative to monomeric model compounds, indicating increased conjugation in the polymers. Following this study, the preparation of Z-poly(p-phenylene phosphaalkene) was disclosed (Scheme 1.11).153 The Z-configured polymer 1.36 was isolated in 88% yield and displayed a larger bathochromic shift relative to molecular models in its absorption spectrum compared to 1.35. This result was attributed to enhanced conjugation in the Z-configured 1.36. 25 Scheme 1.11: Formation of E/Z-poly(p-phenylene phosphaalkene) (1.35) and Z-poly(p-phenylene phosphaalkene) (1.36). Protasiewicz and coworkers have also harnessed the unusual properties of P=C bonds in macromolecules by generating 1.37a−d via a phospha-Wittig reaction with difunctional monomers (Scheme 1.12).154 Polymers 1.37a−c with small, conjugated linkers were insoluble in common solvents. However, 1.37d was isolated as a moderately air-stable orange powder and was soluble in hexanes, allowing it to be analyzed in solution. The approximate molecular weight was 6,500 g mol−1 with X̅n = 6, as found by end-group analysis. Polymer 1.37d exhibited a bathochromic shift in the absorption spectrum when compared with organic PPV and exhibited weak fluorescence (only 8% that of stilbene). 26 Scheme 1.12: Formation of E-poly(p-phenylene phosphaalkene)s 1.37a−d and 1.38a−c via phospha-Wittig reactions. The same group has prepared further PPV analogues 1.38a−c, which contained a 1:1 ratio of linear P=C and C=C bonds.155 The molecular weights ranged from 5,000 to 7,300 g mol−1 which corresponded to X̅n = 4.5 to 6.5. Polymers 1.38a−c displayed a hypsochromic shift in the absorption maxima relative to 1.37d and exhibited superior fluorescence due to the presence of fewer P atoms in the chains. A systematic study on the incorporation of P=C units into oligomers of PPV revealed 27 that the presence of P=C groups in the structure can support electronic communication across the conjugated system.156 More recently, Orthaber and coworkers have described the electropolymerization of a fluorenylidenephosphaalkene to afford 1.39 (Scheme 1.13) which exhibited reversible electrochromic behavior.157 Specifically, the neutral system displayed a yellow-green color, whereas, upon oxidation to form a radical cation, it became a deep-blue color. The availability of the lone pair at P in 1.39 was demonstrated by coordination of this moiety to AuI to afford 1.39·[AuCl]n. Subsequent investigation of the absorption spectrum of 1.39·[AuCl]n revealed a bathochromic shift in the absorption maximum (Δλmax = 153 nm). Scheme 1.13: Synthesis of poly(fluorenylidene phosphaalkene)s 1.39 and 1.39·[AuCl]n. In addition to imparting attractive photophysical properties to polymeric systems, the presence of P=C bonds in macromolecules facilitates the binding of transition metals. In the interest of generating polymeric diphosphinidenecyclobutene (DPCB) ligands (see section 1.13), 28 Yoshifuji and coworkers synthesized polymer 1.40 (Scheme 1.14).158 The polymer was soluble in common organic solvents (THF, chloroform). However, treatment of 1.40 with PdII resulted in the formation of an insoluble material which was not analyzed further. Building on this work, the same group reported the synthesis of 1.41a−c.159, 160 Coordination of 1.41a−c to PdII afforded coordination polymers 1.41a−c·[PdCl2]xn [x = 1 (1.41b,c) or 2 (1.41a)]. Interestingly, elemental analysis of PdII-coordinated 1.41a showed good agreement with the presence of two PdCl2 centers per repeating unit (i.e. 1.41a·[PdCl2]2n), however, no information was obtained pertaining to the coordination state of 1.41a·[PdCl2]2n. The catalytic activity of 1.41a·[PdCl2]2n was evaluated for a Sonogashira coupling reaction. Specifically, 4-bromonitrobenzene was reacted with ethynyltrimethylsilane in the presence of 1.41a·[PdCl2]2n, CuI and NEt3 at 100 °C for 24 h. The average yield obtained from two runs was 83% and the polymer was easily separated from the substrates post-reaction. 29 Scheme 1.14: Preparation of diphosphinidenecyclobutene (DPCB)-containing polymers 1.40 and 1.41a−c and their PdII complexes. 1.3.7 Poly(1-phosphaisoprene) (PPI) Our group recently reported the anionic polymerization of Mes*P=C(Me)−CH=CH2 [1-phosphaisoprene, henceforth referred to as PI; Mes* = 2,4,6-tri-t-butylphenyl] to afford poly(1-phosphaisoprene) (henceforth referred to as PPI), a phosphorus-containing analogue of natural rubber (Scheme 1.15).161 Investigations of the reactivity of Polymer PPI form a central theme of this Thesis. In the same report, we disclosed the polymerization of the less bulky 1-phosphabutadiene (Mes*P=CH−CH=CH2, 1.22 in Scheme 1.3) to afford poly(1-30 phosphabutadiene), however, the monomer was unstable under ambient conditions and so was generated in-situ. The downfield resonances of the 31P NMR spectroscopic signals assigned to PPI (δ = 235 and 225) suggested the presence of P=C-substituents in the major microstructure (i.e. x). Thus, it was reasoned that the polymerization proceeded predominantly via addition across the C=C bond, consistent with the anion-mediated addition polymerization of organic isoprene in ethereal solvents.106 Numerous microstructures are possible for PPI, three of which are depicted in Scheme 1.15. Scheme 1.15: Polymerization of 1-phosphaisoprene (PI) to afford poly(1-phosphaisoprene) (PPI; only three possible microstructures are shown). Given that PPI is formally an analogue of polyisoprene (natural rubber), its physical properties are of considerable interest. TGA measurements revealed that PPI was stable to weight loss until 272 °C at which temperature a sharp step was observed to give a ceramic yield of 3.3%. A broad Tg was observed in the DSC trace (Tg onset = 95 °C, Tg midpoint = 110 °C). This value was much higher than the reported Tg of polyisoprene (−70.5 to −36 °C, depending on the microstructure),107 presumably due to the presence of the rigid Mes* substituents. The samples of n-BuLi-initiated PPI ranged in molecular weight from 2,400 to 120,000 g mol−1 with Ð = 1.05 to 1.28. As an initial demonstration of the chemical functionality imparted by the incorporation of PIII-centers into the polymer, macromolecular AuI complex PPI·[AuCl]n was formed by treatment of PPI with [Au(tht)Cl] (Scheme 1.16). 31 Scheme 1.16: Preparation of PPI·[AuCl]n. For clarity, only microstructure x is shown. 1.4 Outline of Thesis The initial goal of the research project was to study the anionic polymerization of 1-phosphaisoprene (PI) via molecular models for the initiation and propagation steps and the end-group. Along the way, many discoveries have been made regarding the unique reactivity of PI and analogous 1-phosphabutadienes. In chapter 2, the microstructure of PPI is evaluated via molecular models and both 4,3- and trans-4,1-addition pathways are revealed. A comparison of the characterization data of these models to PPI is presented. The coordination chemistry of PPI with PdII is explored in chapter 3 and the reversible formation of a gel is disclosed. The study is complemented by molecular models. Chapter 4 reveals a unique [4+2] dimerization pathway for PI and the divergent cyclization chemistry of an analogous 1-phosphabutadiene, Mes*P=C(Me)−C(Me)=CH2. Chapter 5 details the synthesis and unusual anion-mediated isomerization of a 1-phosphabutadiene, Mes*P=C(Si(CH3)3)−CH=CH2. Radical addition to PI, Mes*P=C(CD3)−CH=CH2 and Mes*P=C(Me)−C(Me)=CH2 through muon spin resonance/rotation is presented in chapter 6. The tentative structures of the muoniated radicals formed are postulated using comparison to DFT calculations. Lastly, chapter 7 provides a summary of this thesis and details the future direction of the research. 32 Chapter 2: The Microstructure of Poly(1-Phosphaisoprene): Stepwise Modeling of an Addition Polymerization 2.1 Introduction For an in-depth discussion of the addition polymerization of P=C-compounds, the reader is referred to chapter 1. Our group has recently reported the polymerization of 1-phosphaisoprene (PI) to afford poly(1-phosphaisoprene) (PPI), a phosphorus version of natural rubber (Scheme 2.1).161 Analogous to fully organic polyisoprene, PPI has a fascinating range of possible microstructures, three of which are shown in Scheme 2.1. Attractive properties of organic polyisoprene elastomers, such as self-healing without external intervention, are attainable through tailoring the relative proportions of the cis-1,4 and 3,4 microstructures.108 Therefore, it is of great importance to study the microstructure of PPI to control this novel polymer's physical and chemical properties. Scheme 2.1: Anionic polymerization of PI to afford PPI. Organic polyisoprene is usually described as containing up to four microstructures [cis-1,4; trans-1,4; 1,2; and 3,4 (see chapter 1)]. However, molecular model studies have shown that the addition of n-BuLi to isoprene occurs at the 4-position to afford cis/trans allyl anions (Scheme 2.2).162 Little distinction appears to be made between 4,1 and 1,4, and 3,4 and 4,3-enchainment of polyisoprene in the literature. Indeed, chemical microstructures of polyisoprene ostensibly 33 containing "1,4" microstructures have been reported that display both 4,1108- and 1,4-163enchainments. Nonetheless, for the work contained in chapter 2, an important distinction will be made between 4,1- and 1,4, and 4,3 and 3,4-enchainment with respect to PI. Scheme 2.2: Preparation of cis/trans allyl anions formed from the reaction of isoprene with n-BuLi. Herein we report a study on the anionic initiation, propagation and end-group of the polymerization of PI. A 1-phosphaallyl propagating anion is isolated and resultant quenching studies display both trans-4,1- and 4,3-enchainments, including a linear dimer of PI. A comparison of the characterization data for the model compounds and PPI is presented and evidence for the presence of microstructures x and y (Scheme 2.1) is provided. 2.2 Results and Discussion 2.2.1 Modeling the anionic initiation of PPI As a starting point in our investigations into the anionic polymerization of PI, this initiation reaction was modeled. In our original report, DFT calculations were performed to evaluate the energetic favorability of addition of Me− to each position of the P=C−C=C skeleton of PI.161 The calculations indicated that addition of Me− at the 4-position of PI to afford a delocalized 1-phosphaallyl anion was the lowest energy product by 13.6 kcal mol−1. A strategy for modeling the propagation and/or termination steps would be the subsequent addition of electrophiles to this initiated structure. To this end, n-butyllithium (1 equiv) was added to a pale-yellow solution of PI, forming a deep-red reaction mixture [Scheme 2.3(a)]. Analysis of the reaction mixture by 31P NMR spectroscopy revealed the signal assigned to PI (δ = 264.8) had been fully consumed and was 34 replaced by five signals [δ = 223.1 (2%), −31.1 (2%), −34.1 (85%), −36.9 (11%) and −43.6 (3%)] [Figure 2.1(a)]. Scheme 2.3: (a) Preparation of [Li·(12-crown-4)2][endo-2.1]. For clarity, the structures of Li·[exo-2.1] and [Li(12-crown-4)2][exo-2.1] are not shown; (b) structures of endo-2.1 and exo-2.1. 35 Figure 2.1: 31P NMR spectra (162 MHz, 25 °C) of the reaction mixtures of: (a) a THF solution of PI and n-BuLi (1 equiv); (b) the same reaction in Et2O solution after addition of 12-crown-4 (2 equiv). The volatiles were removed in vacuo to afford a gummy red material from which no solid product could be obtained. This crude material was dissolved in Et2O and 12-crown-4 (2 equiv) was added. The 31P NMR spectrum was recorded to reveal two broad signals at −20.7 (83%) and −17.0 (15%) ppm alongside a small sharp signal at 221.3 (2%) ppm [Figure 2.1(b)]. A red solid was obtained by slow diffusion of hexanes into the reaction mixture at −35 °C for 3 d (yield = 55%). Crystals of this solid suitable for X-ray analysis were grown from a saturated toluene/hexanes solution at −35 °C. The molecular structure is shown in Figure 2.2. 36 Figure 2.2 Molecular structure of compound [Li(12-crown-4)2][endo-2.1]. Thermal ellipsoids are represented at 50% probability level. Hydrogen atoms are omitted for clarity. The X-ray analysis revealed the compound to be 1-phosphaallyl anion [Li(12-crown-4)2][endo-2.1]. The P1−C1 bond length of [Li(12-crown-4)2][endo-2.1] is 1.800(5) Å which is closer to that expected for a P−C single bond [1.82−1.87 Å]164 than that expected for a P=C double bond [1.60−1.70 Å].7 This result suggests a degree of localization of the π-electrons between C1−C2. Further evidence for this localization is gleaned from the C1−C2 bond length [1.343(7) Å] which is in the range expected for a C=C bond. For comparison, the analogous bond lengths in the 1-phosphaallyl anion [Li(dme)3][Mes*PC(Ph)CH(Ph)] are 1.758(6) Å and 1.366(6) Å, respectively.165 The molecular structure also shows the n-butyl substituent at the 4-position (C3) which is in agreement with the DFT calculations in the original report.161 A C6D6 solution of [Li(12-crown-4)2][endo-2.1] was analyzed by 31P NMR spectroscopy to reveal two signals at −23.4 (81%) and −16.7 (12%) ppm that were assigned to isomers [Li(12-crown-4)2][endo-2.1] and [Li(12-crown-4)2][exo-2.1] [Scheme 2.3 (b)], alongside a signal 37 assigned to quenched product 2.2 [δ = −54.9 (3%, d, 1JPH = 223 Hz), vide infra] and two unidentified products [δ = 226.3 (2%) and 220.9 (2%)]. The formation of endo and exo-isomers of 2.1 is consistent with previous reports on [Li(dme)3][Mes*PC(Ph)C(Ph)] and [Li(dme)3][PhPC(Ph)C(Ph)].165, 166 After 14 d in solution, the signals at −16.7 and −23.4 ppm constituted 39 and 44% of the mixture, respectively. The 1H NMR spectrum revealed signals at 4.97 (dt, 1H, 3JPH = 13 Hz, 3JHH = 5 Hz) and 3.67 (br s, 1H) that were assigned to the P−C−CH groups. These signals were correlated by 1H,13C-HSQC NMR spectroscopy to 13C{1H} resonances at 105.7 and 109.3 ppm, respectively. Furthermore, broad signals at 1.77 and 2.13 (d, 3JPH = 14 Hz, P−C−CH3) ppm were assigned to the P−C−CH3 groups. Taken together, these data are consistent with the formulations of [Li(12-crown-4)2][endo-2.1] and [Li(12-crown-4)2][exo-2.1]. The structures of anions endo-2.1 and exo-2.1 represent the initiated anion in the polymerization of PI. Based on the 31P NMR signals assigned to Li·[endo-2.1] and Li·[exo-2.1] constituting 96% of the reaction mixture in Figure 2.1(a), it is evident that the major initiation pathway of PI with n-Bu− is through nucleophilic addition at the 4-position. This result is consistent with the anionic initiation of organic isoprene which proceeds via an allyl anion.162 2.2.2 Modeling the end-group of PPI Satisfied with the identification of Li·2.1, our attention turned to modeling the end-group of PPI via the addition of methanol to Li·2.1. Electrophilic addition to 1-phosphaallyl anions has been shown to occur through both the P-167, 168 and C-termini169 and the regiochemistry of electrophilic addition to Li·2.1 has important implications for the microstructure and end-group of PPI. Thus, n-BuLi (1.1 equiv) was added to a solution of PI in THF. Subsequently, excess deoxygenated methanol was added (Scheme 2.4). The 31P NMR spectrum of the reaction mixture revealed four signals [δ = 235.9 (3%), 234.8 (3%), −55.0 (d, 1JPH = 229 Hz, 91%) and −72.4 (d, 1JPH = 227 Hz, 38 4%)]. The minor signals at 235.9 and 234.8 ppm were consistent with the presence of a P=C bond (i.e. 4,3-addition, microstructure x). However, the upfield shift of the major signal at −55.0 (d, 1JPH = 229 Hz, 91%) ppm was inconsistent with that assigned to microstructure x of PPI (δ = 237, Δδ = −292). The large JPH was also consistent with a P−H bond in the product. We therefore postulated that a 4,1-addition had occurred to afford secondary phosphine 2.2. After work-up, the compound was isolated as a viscous oil from which no solid material could be obtained. Scheme 2.4: Preparation of [Au(2.2)Cl] from Li·2.1 via 2.2. To aid in the identification of this product, it was reasoned that coordination of the P-lone pair to AuI would result in a material that could be characterized crystallographically. Thus, a CH2Cl2 solution of [Au(tht)Cl] (0.8 equiv) was added to a solution of the crude oil (1 equiv) in CH2Cl2, forming an orange reaction mixture. The 31P NMR spectrum of the reaction solution revealed a broad singlet at −18.3 ppm. The downfield shift of this signal relative to that assigned to the uncoordinated starting material (Δδ = 36.7) was consistent with the shift observed when R3P phosphines are coordinated to AuI (R = Ph,170 o-tolyl,171 Me,172 i-Pr,172 t-Bu;173 Δδ = 28 to 52.3). The volatiles were removed in vacuo to afford a gummy yellow solid which was washed with pentane at −35 °C to afford a pure material that was characterized as [Au(2.2)Cl] (yield = 61%). Crystals of the solid suitable for X-ray analysis were grown by slow evaporation of a CDCl3 solution. The molecular structure is shown in Figure 2.3. 39 Figure 2.3: Molecular structure of [Au(2.2)Cl]. Thermal ellipsoids are presented at 50% probability level. Hydrogen atoms are omitted for clarity. The molecular structure confirmed our suspicion that the product displayed 4,1-enchainment [i.e. n-Bu substituent at C3 (4-position) and the H substituent at P1 (1-position)]. The P1−C1 bond length [1.825(2) Å] is in the range expected for a P−C single bond.164 Furthermore, the C1−C2 and C1−C8 bond lengths [1.337(3) and 1.506(3) Å, respectively] are consistent with the presence of a double and single bond in these positions,174 respectively, and the double bond is trans-configured. Analysis of a CDCl3 solution of [Au(2.2)Cl] by 31P NMR spectroscopy revealed a broad doublet resonance at −4.7 ppm (1JPH = 390 Hz). The 1H NMR spectrum revealed signals at 6.60 (d, 1H, 1JPH = 390 Hz) and 6.39 (dt, 1H, 3JPH = 27 Hz, 3JHH = 7 Hz) ppm that were assigned to the P−H and P−C=CH substituents, respectively. Taken together, these data are consistent with the formulation of [Au(2.2)Cl]. Full spectroscopic assignments can be found in the Experimental Section. This trans-4,1-addition structure represents a model for the end-group of H terminated PPI. Given that the signal assigned to 2.2 in the reaction of Li·2.1 with methanol 40 constituted 91% of the reaction mixture by 31P NMR spectroscopy, it appears there is a high selectivity for trans-4,1-addition in this reaction. 2.2.3 Modeling trans-4,1-enchainment in PPI Interested by this apparent selectivity toward trans-4,1-addition, additional molecular models were targeted by the reaction of alternative small electrophiles with Li·2.1. Analogous, separate reactions using methyl iodide and ethyl bromide to react with Li·2.1, followed by treatment with [Au(tht)Cl], resulted in the isolation of [Au(2.3)Cl] and [Au(2.4)Cl] in 70 and 86% yield, respectively (Scheme 2.5). In each case, the 31P NMR spectroscopic signals assigned to 2.3 (δ = − 29.6, 93%) and 2.4 (δ = −8.4, 89%) constituted the major products in the reaction mixtures, indicating a high selectivity for trans-4,1-addition in these reactions. These results contrast with the anionic polymerization of organic isoprene, whereby cis-1,4-enchainment is favored under similar conditions (see chapter 1).106 [Au(2.3)Cl] and [Au(2.4)Cl] were characterized by X-ray crystallography, 1H, 31P, and 13C{1H} NMR spectroscopy, mass spectrometry and elemental analysis which were consistent with their structures. The crystallographic data of [Au(2.3)Cl] and [Au(2.4)Cl] were analogous to those of [Au(2.2)Cl] and the molecular structures are shown in Appendix D. The relevant NMR spectroscopic data are discussed below (vide infra). Scheme 2.5: Preparation of [Au(2.3Cl] and [Au(2.4)Cl] from Li·2.1. 41 2.2.4 Modeling 4,3-enchainment in PPI We were intrigued by the discrepancy between the selective trans-4,1-enchainments (models for microstructure y and the end-group of PPI) observed in [Au(2.2)Cl], [Au(2.3)Cl] and [Au(2.4)Cl], and the apparent major microstructure x of PPI which contains P=C bonds. Given this difference, it was decided to investigate the addition of larger, unsaturated electrophiles to anion Li·2.1 to afford models for the propagation step in the anionic polymerization of PI. To this end, n-BuLi (1.0 equiv) was added to a solution of PI in THF (Scheme 2.6). The red reaction mixture was analyzed by 31P NMR spectroscopy to reveal signals assigned to Li·2.1 (Figure 2.4, top spectrum). Subsequently, H2C=CPh2 (1.0 equiv) was added and the 31P NMR spectrum recorded after 48 h revealed three signals [δ = −19.8 (92%), −34.1 (5%) and −36.9 (3%)]. The addition of excess methanol resulted in the formation of a yellow solution. 31P NMR spectroscopic analysis of this solution showed three major signals [δ = 234.1 (34%) and overlapping doublets δ = −62.2 (d, JPH = 228 Hz, 28%) and −62.4 (d, JPH = 228 Hz, 28%)] alongside a minor signal assigned to 2.2 [δ = −55.1 (d, 1JPH = 223 Hz, 5%)] and further unidentified minor products (5%) (Figure 2.4, bottom spectrum). The signal at 234.1 was indicative of a compound containing a P=C bond (δ > 200),7 while the large magnitudes of the JPH values for the signals at −62.2 (228 Hz) and −62.4 (228 Hz) were indicative of P−H bonds in these products. After work-up, a viscous oil was isolated. 42 Scheme 2.6: Formation of 2.5 and 2.6 from the reaction of Li·2.1 with H2C=CPh2 and methanol {2.5 and 2.6 were isolated as AuI salts [Au(2.5)Cl] and [Au(2.6)Cl], respectively}. Figure 2.4: 31P NMR spectra (THF, 162 MHz, 25 ⁰C) showing the progress of reaction between Li·2.1 and H2C=CPh2 (1.0 equiv). 43 A CH2Cl2 solution of this crude product was added to a CH2Cl2 solution of [Au(tht)Cl] (0.46 equiv) and the 31P NMR spectrum was recorded. Resonances were observed that were assigned to uncoordinated starting material at 232.3 (41%) and −62.3 (br d, 14%) ppm alongside new signals at −21.4 (d, 1JPH = 397 Hz, 20%), −23.9 (d, 1JPH = 397 Hz, 21%) and 182.9 (4%) ppm. The volatiles were removed in vacuo and the crude material was recrystallized from pentane at −35 °C to afford yellow crystals suitable for X-ray analysis. The molecular structure of the product is shown in Figure 2.5. Figure 2.5: Molecular structure of [Au(2.5)Cl]. Thermal ellipsoids are presented at 50% probability level. Hydrogen atoms (except H1−H4) are omitted for clarity. Only P1(R),C2(S) isomer is shown. The X-ray analysis revealed the product to be alkenyl phosphine [Au(2.5)Cl] (Scheme 2.6). This structure is consistent with the addition of H2C=CPh2 at the 3-position (C2) of Li·2.1 (i.e. a 4,3-addition to PI), however, the isolated product contains an alkenyl phosphine group, rather than 44 the expected phosphaalkene substituent (i.e. 2.6 in Scheme 2.6). Analysis of a CDCl3 solution of the crystals of [Au(2.5)Cl] by 31P NMR spectroscopy revealed two broad doublet signals at −21.5 ppm (d, 1JPH = 398 Hz) and −23.5 ppm (d, 1JPH = 400 Hz) in a 50:50 ratio assigned to diastereomers of [Au(2.5)Cl] {[Au(2.5A)Cl] and [Au(2.5B)Cl], respectively}. The 1H NMR spectrum revealed two doublet signals at 6.79 (1H, 1JPH = 398 Hz) and 6.73 (1H, 1JPH = 400 Hz) that were assigned to the P−H groups of [Au(2.5A)Cl] and [Au(2.5B)Cl], respectively. The products were characterized further by 1H, 13C{1H}, 31P and two-dimensional NMR spectroscopies and mass spectrometry, which are consistent with the formulation of [Au(2.5)Cl]. Encouraged by the isolation of [Au(2.5)Cl], displaying a 4,3-enchainment, our focus turned to the identity of the product responsible for the signal at 234.1 ppm, which we postulated to contain a P=C bond (Figure 2.4, bottom spectrum). The filtrate from the recrystallization of [Au(2.5)Cl] was passed through a bed of Celite™ and the volatiles were removed in vacuo to afford a yellow solid. The solid was dissolved in CH2Cl2 and [Au(tht)Cl] (0.7 equiv) was added. Analysis of the reaction mixture by 31P NMR spectroscopy revealed a signal at 182.9 ppm. The upfield chemical shift of this signal relative to that of the signal assigned to uncoordinated material (Δδ = −49.4) is in the range reported for related phosphaalkenes upon coordination to AuI [Δδ = −31.5 to −87.1).49, 120, 157, 175-180 The volatiles were removed in vacuo and the residual solid was washed with pentane at −35 °C to afford a pure white solid in 60% yield. Crystals of this solid suitable for X-ray analysis were grown by slow evaporation of a CH2Cl2/heptane solution. The molecular structure is shown in Figure 2.6. 45 Figure 2.6: Molecular structure of [Au(2.6)Cl]. Thermal ellipsoids are presented at 50% probability level. Hydrogen atoms are omitted for clarity (except H1-H4). The X-ray analysis revealed the product to be phosphaalkene-AuI complex [Au(2.6)Cl], which is a tautomer of [Au(2.5)Cl], and represents a model for 4,3-enchainment (i.e. microstructure x of PPI). Analysis of a CDCl3 solution of [Au(2.6)Cl] by 31P NMR spectroscopy revealed a signal at 183.2 ppm. Moreover, A doublet signal in the 13C{1H} spectrum at 180.2 (1JPC = 68 Hz) ppm was assigned to the P=C substituent. Further discussion of the pertinent NMR spectroscopic assignments is presented below (vide infra) and full assignments of the NMR spectra, alongside HRMS analysis, for [Au(2.6)Cl] are given in the Experimental Section. Analysis of the X-ray data for [Au(2.5)Cl] and [Au(2.6)Cl] was consistent with the structure of each compound. For instance, the P1−C1 bond length in [Au(2.5)Cl] is 1.811(11) Å which is indicative of a P−C single bond in this position.164 The C1−C8 bond length [1.298(17) Å] is reflective of a C=C double bond and the angles at C1 [Σangles = 360(2)°] indicate sp2 hybridization at this position. By contrast, the P1−C1 bond length in [Au(2.6)Cl] [1.655(6) Å] is 46 in the range expected for a P=C double bond (1.60−1.70 Å).7 Additionally the C1−C8 bond length [1.504(10) Å] is consistent with a C−C single bond in this position.174 Furthermore, the angles at P1 and C1 [Σangles = 359.8(4) and 360.0(8)°, respectively] are indicative of sp2 hybridization at these positions. Tautomerization of phosphaalkenes is known181, 182 and two tautomeric products have previously been isolated as W(CO)5 complexes.183 2.2.5 Linear dimerization of PI Encouraged by the isolation of models displaying both 4,3- and trans-4,1-enchainment (models for microstructures x and y of PPI, respectively), it was decided to target a linear dimer of PI as a model for propagation. To this end, n-BuLi (0.5 equiv) was added to a solution of PI in THF (Scheme 2.7). Analysis of the reaction mixture by 31P NMR spectroscopy revealed six signals [δ = 226.5 (5%), 226.0 (5%), 230.0 (29%), 209.1 (3%), −31.2 (36%) and −34.2 (23%)]. The signal at −34.2 ppm was assigned to Li·2.1 and the signals at 230.0 and −31.2 were tentatively assigned to an anionic linear dimer. Methyl iodide was added and the red color dissipated in favor of yellow. Subsequent recording of the 31P NMR spectrum revealed five signals [δ = 234.3 (6%), 232.7 (6%), 231.9 (31%), −28.9 (14%) and −29.6 (43%)]. After work-up, a viscous yellow oil was isolated. The oil was dissolved in CH2Cl2 and [Au(tht)Cl] (2 equiv) was added. Analysis of the yellow reaction mixture by 31P NMR spectroscopy revealed two signals at 184.7 (31%) and 34.7 (69%) ppm. The volatiles were removed in vacuo and the residual yellow solid was washed with pentane at −35 °C to afford an off-white solid in 54% yield {this solid contained ca. 30% [Au(2.3)Cl], as determined by integration of the 1H NMR spectrum}. Crystals suitable for X-ray analysis were grown by slow evaporation of a CH2Cl2/heptane solution. The molecular structure is shown in Figure 2.7. 47 Scheme 2.7: Preparation of linear dimers 2.7 and [2.7(AuCl)2]. Figure 2.7: Molecular structure of [2.7(AuCl)2]. Thermal ellipsoids are presented at 50% probability level. Hydrogen atoms are omitted for clarity. Only P2(R),C2(R) isomer is shown. The X-ray analysis revealed the crystals to be linear dimer [2.7(AuCl)2]. This structure is a model for both microstructures x (4,3-addition, C3−C2−C1−P1) and y (trans-4,1-addition, C9−C10−C11−P2) of PPI. The n-Bu substituent is attached at the 4-position (C3), consistent with 48 the previous examples. The second equivalent of PI (C9−C10−C11−P2) is located at the 3-position (C2). Addition of methyl iodide to the intermediate 1-phosphaallyl anion in Scheme 2.7 resulted in P-alkylation, analogous to model 2.3. The P1−C1 bond length in [2.7(AuCl)2] [1.68(2) Å] indicated the presence of a P=C bond in this position.7 Further evidence for the presence of a P=C bond was gleaned from the sums of the bond angles at P1 and C1 [Σangles = 360(2) and 360(4)°, respectively] which are consistent with sp2 hybridization at these positions. Additionally, the C1−C2 and C1−C8 bond lengths [1.47(3) and 1.48(4) Å, respectively] are as expected for C−C single bonds and the C10−C11 bond length [1.345(11) Å] is consistent with a C=C bond in this position.174 The P2−C11 bond length [1.813(7) Å] indicates a P−C single bond164 and the angles at C11 [Σangles = 359(1)°] are consistent with sp2 hybridization. The double bond between C10 and C11 is trans-configured, analogous to [Au(2.2)Cl], [Au(2.3)Cl] and [Au(2.4)Cl] (vide supra). Analysis of a CDCl3 solution of [2.7(AuCl)2] by 31P NMR spectroscopy at room temperature revealed broad signals at 185.1 (34%) and 33.1 (66%) ppm. The 1H and 13C{1H} NMR spectra also contained broad signals from which multiplicities could not be extracted. Upon cooling to −50 °C, the 31P NMR spectrum revealed broad signals at 182.0 (30%) and 33.1 (70%). The 31P{1H} NMR spectrum revealed five sharper signals [δ = 182.2 (9%), 182.0 (21%), 33.3 (7%), 33.1 (46%) and 32.8 (17%)]. The signal at 33.1 ppm was assigned to [Au(2.3)Cl]. Unfortunately, we were unable to separate [Au(2.3)Cl] (ca. 30% contamination measured by integration of the 1H NMR spectrum) from [2.7(AuCl)2]. Nonetheless, we tentatively assigned two pairs of signals at 182.0 and 32.8, and 182.2 and 33.3 ppm to diastereomers of [2.7(AuCl)2] {[2.7A(AuCl)2] and [2.7B(AuCl)2], respectively} using 1H, 13C{1H} and related two-dimensional NMR spectroscopies. For example, the 1H NMR spectrum displayed signals at 6.93 (dt, 1H, 3JPH = 23 Hz, 3JHH = 7 Hz) and 7.00 ppm (m, 1H) which were assigned to the P−C=CH substituents of 49 [2.7A(AuCl)2] and [2.7B(AuCl)2], respectively. These signals were correlated by 1H,13C-HSQC NMR spectroscopy to resonances at 141.5 (d, 2JPC = 26 Hz) and 142.6 ppm which were assigned to the P−C=CH carbons. Further relevant NMR spectroscopic details are discussed below (vide infra) and assignments are provided in the Experimental Section. Given the difficulty in synthesizing pure linear dimer [2.7(AuCl)2], 2.8 and [Au(2.8)Cl] were synthesized via an independent route as final models for microstructure x of PPI (Scheme 2.8). To this end, ethylmagnesium bromide (5 equiv) in THF was added to a flask containing Mes*P=C(Me)Br (1 equiv) and [Pd(PPh3)4] (0.04 equiv). After work-up, 2.8 was isolated in 45% yield, contaminated with 5% MesP=C(H)Me, and was characterized by 1H, 13C{1H} and 31P NMR spectroscopy and elemental analysis. To a solution of 2.8 in CH2Cl2 was added [Au(tht)Cl] (0.9 equiv), forming an orange solution. The 31P NMR spectrum was recorded and revealed two signals at 179.3 (96%) and 217.4 (4%) ppm. The signal at 179.3 ppm was assigned to the desired [Au(2.8)Cl]. After work-up, [Au(2.8)Cl] was isolated in 94% yield and was characterized by 1H, 31P, 13C{1H} and related two-dimensional NMR spectroscopies and elemental analysis which can be found in the Experimental Section. The relevant NMR spectroscopic assignments are presented below (vide infra). Scheme 2.8: Formation of [Au(2.8)Cl] via 2.8. 2.2.6 Investigating the anionic polymerization of PI With these models in hand, the anionic polymerization of PI was investigated. Thus, n-BuLi (2 mol%) was added to a THF solution of PI and the deep-red reaction mixture was transferred to a 50 J. Young NMR tube and monitored by 31P NMR spectroscopy (Figure 2.8). After 15 min, the spectrum showed sharp signals assigned to PI (δ = 264.8, 46%), the Z-isomer of PI (Z-PI; δ = 244.8, 17%) and an unknown product (δ = 224.1, 2%). The presence of Z-PI in the reaction mixture is consistent with the results presented in chapter 5, where n-BuLi will be shown to facilitate E/Z isomerization of the P=C bond of a 1-phosphabutadiene. Additionally, two broad signals at 237 (27%) and −15 (5%) ppm were present and assigned to microstructures x, and y or z, of PPI, respectively. In contrast, when the polymerization was performed at 50 °C in our original report,161 the signal at −15 ppm was absent, suggesting a temperature dependence on the microstructure of PPI, with 4,3-addition favored at lower temperatures. Remarkably, a broad signal was observed at −34 (2%) ppm that persists until the polymerization is quenched with methanol. This chemical shift is very close to that of the major signal assigned to 2.1 (δ = −34.1) and the approximate integral of this signal compares favorably to the stoichiometry of initiator used (2 mol%). Given these data, this signal was tentatively assigned to the propagating anions (Scheme 2.9). Further evidence for this assignment comes from the 31P NMR spectrum recorded after the addition of methanol to quench the polymerization (vide infra). 51 Figure 2.8: 31P NMR spectra (162 MHz, 25 ⁰C) showing the progress of reaction between PI and n-BuLi (2 mol%). All spectra are in THF apart from purified PPI which is in CDCl3. Scheme 2.9: Assignments of the propagating anion and end-group of H terminated PPI, the NMR spectroscopic signals are shown in Figure 2.8. As the polymerization progressed, an additional broad shoulder was observed at 227 ppm. Unfortunately, overlap of the signal assigned to Z-PI with the broad signals assigned to PPI 52 precluded determination of the rate of propagation for this polymerization. After 4 h 30 min, the signal assigned to PI had been fully consumed by 31P NMR spectroscopy. Degassed methanol (1 drop) was added and the reaction mixture became colorless. The 31P NMR spectrum of the reaction solution revealed that the signal at −34 ppm was no longer present and had been replaced by a broad signal at −53 ppm. This signal at −53 ppm is comparable to that assigned to 2.2 [δ = −55.0 (d, 1JPH = 223 Hz)] and was tentatively assigned to the P−H end-groups of PPI. The volatiles were removed in vacuo and the residual polymer was dissolved in CH2Cl2 and precipitated into deoxygenated isopropanol (× 3). PPI was isolated as an off-white powder in 50% yield. Analysis of the polymer by gel-permeation chromatography equipped with triple detection (GPC-MALS-V) revealed a number-average molecular weight (Mn) of 15,000 g mol-1 and a dispersity (Đ) of 1.02. This observed molecular weight was close to the expected value [Mn (calcd) = 16,583 g/mol]. These data could be indicative of a living polymerization, although a rigorous study would be needed to test this hypothesis. The 31P NMR spectrum of a CDCl3 solution of PPI displayed broad signals at 237 and 226 (93% total), and −13 (7%) ppm. The major signal at 237 ppm was tentatively assigned to microstructure x. For comparison, the chemical shifts of the signals assigned to the P=C groups of 2.6 and 2.8 in CDCl3 solution were 232.9 and 223.3 ppm, respectively. The minor signal at 226 ppm, assigned to P=C substituents, could arise from E/Z-isomerization of the P=C bond in PPI. The chemical shift of the signal at −13 ppm is comparable to the signals assigned to 2.3 and 2.4 (δ = −29.5 and −8.9, respectively). Given the crystallographic characterization of [Au(2.3)Cl] and [Au(2.4)Cl] as trans-4,1-enchainments, and the lack of molecular models that can be assigned to microstructure z or other structures, the signal at −13 ppm was tentatively assigned to microstructure y. Unfortunately, the resonance assigned to the end-groups (−53 ppm) had 53 diminished in the 31P NMR spectrum of the polymer after work-up. New signals (δ = 45 and 13) were present which could indicate oxidation of these groups through the precipitation procedure. No resonances were observed that could be attributed to alkenyl-phosphine tautomerization products of microstructure x to afford structures analogous to 2.5 [δ = −62.2 (d, 1JPH = 228 Hz) and −62.4 (d, 1JPH = 228 Hz)]. Analysis of the 1H and 13C{1H} NMR spectra revealed broad signals typical of a polymeric material. Important correlations were observed in the 1H,13C-HSQC NMR spectrum shown in Figure 2.9. Specifically, a signal at 5.38 ppm in the 1H NMR spectrum was correlated to a resonance at 129.5 ppm in the 13C{1H} NMR spectrum (Figure 2.9, red line). Additionally, a correlation was observed between resonances at 7.54 (1H) and 127.0 (13C{1H}) ppm which were attributed to the meta-CH and CH substituents, respectively, of microstructure y (Figure 2.9, blue line). The signal assigned to the P=C−CH3 and P−C(CH3)=CH substituents of microstructures x and y, respectively, was observed as a broad resonance at 20.2 ppm in the 13C{1H} NMR spectrum. This signal was correlated to a resonance at 1.28 ppm in the 1H NMR spectrum (Figure 2.9 yellow line). Resonances at 2.93 (1H) and 45.9 (13C{1H}) ppm were strongly correlated and assigned to backbone CH and CH groups of microstructure x (Figure 2.9, green line). For comparison, the analogous signals in 2.6 were at 2.71 (m, 1H, P=C−CH) and 47.3 (d, 2JPC = 39 Hz, P=C−CH) ppm. Lastly, a broad resonance was observed in the 13C{1H} spectrum of PPI at 187.6 ppm that was assigned to the P=C groups of microstructure x. A summary of these data and the comparable signals in models 2.3, 2.4, 2.6 and 2.8 is given in Table 2.1. Taken together, the data are consistent with the presence of microstructures x and y in PPI. However, microstructure z and/or other microstructures (e.g. tautomeric products) cannot be unequivocally ruled out. 54 Figure 2.9: 1H,13C-HSQC NMR spectrum (CDCl3, 25 ⁰C) of PPI (Mn = 15,000 g mol−1, Ð = 1.02). Dashed lines indicate correlated 1H (x axis) and 13C (y axis) NMR spectroscopic signals. 55 Table 2.1: Comparison of the 1H and 13C{1H} NMR spectroscopic signals assigned to PPI and model compounds. Multiplicities are omitted for clarity. CA CB CC CD HA HC HD PPI 20.2 187.6 45.9 129.5 1.28 2.93 5.38 2.3 15.4 − − 129.6 1.22 − 5.09 2.4 16.0 − − 129.6 1.30 − 5.28 2.6 19.6 187.0 47.3 − 1.28 2.71 − 2.8 23.4 187.7 − − 1.24 − − Given that the molecular model compounds were characterized crystallographically as AuI complexes, we decided to target polymer PPI·[AuCl]n to gain further information about its microstructure. Thus, a solution of PPI (Mn = 33,600 g mol−1; Đ = 1.18) in CH2Cl2 was added to a solution of [Au(tht)Cl] (1 P equiv) in CH2Cl2 (Scheme 2.10). Analysis of the reaction mixture by 31P NMR spectroscopy revealed broad signals at 239 (10%), 186 (85%) and 42 (5%) ppm. The volatiles were removed in vacuo and the residual orange solid was dissolved in CH2Cl2 and precipitated twice into deoxygenated methanol to afford an off-white solid in 49% yield. The 56 polymer was analyzed using the refractive index increment (dn/dc) calculated from PPI (0.17) as an estimation for the dn/dc of PPI·[AuCl]n which gave a mass recovery of 21%, indicating that the polymer was interacting with the GPC columns. Thus, no further attempts were made to obtain molecular weight data for PPI·[AuCl]n to avoid damaging the instrument. Scheme 2.10: Preparation of PPI·[AuCl]0.96n. Only microstructures x and y are shown. The 31P NMR spectra of CDCl3 solutions of uncoordinated PPI and PPI·[AuCl]n are shown in Figure 2.10. The 31P NMR spectrum PPI·[AuCl]n revealed a broad signal at 187 (89%) ppm which was assigned to the coordinated phosphaalkene substituents. The upfield chemical shift of this signal relative to uncoordinated P=C groups of PPI (δ = 237 and 226, Δδ = −50 and −39, respectively) is in the range reported for molecular P=C compounds upon coordination to AuI [Δδ = −31.5 to −87.1).49, 120, 157, 175-180 The spectrum also revealed a signal assigned to uncoordinated PPI (δ = 237, 4%) and multiple signals between 52 and −9 ppm (7%) which were tentatively assigned to coordinated phosphine groups based on the downfield chemical shift of these signals relative to that assigned to uncoordinated PPI (δ = −13, Δδ = 4 to 65). For reference, R3P phosphines (R = Ph,170 o-tolyl,171 Me,172 i-Pr,172 t-Bu)173 shift downfield by 28 to 52.3 ppm upon coordination to AuI. Integration of the signals assigned to AuI-coordinated PPI in Figure 2.10(b) suggests that 96% of the P atoms are bound to AuI and allow a formulation of the polymer as PPI·[AuCl]0.96n. The numerous signals observed between 52 and −9 ppm are an indication that there is more than one environment for these substituents. The molecular models [Au(2.2)Cl], 57 [Au(2.3)Cl] and [Au(2.4)Cl] and [2.7(AuCl)2] provide evidence for the presence of microstructure y, however, cis-4,1-enchainments, 1,2-enchainments (i.e. microstructure z), tautomeric products {i.e. [Au(2.5)Cl]} may also contribute to these signals. Figure 2.10: 31P NMR spectra (162 MHz, CDCl3, 25 ⁰C) of (a) PPI; (b) PPI·[AuCl]0.96n. The 1H NMR spectrum of a CDCl3 solution of PPI·[AuCl]0.96n revealed very broad signals. A resonance at 2.92 ppm was assigned to the backbone CH and CH2 groups of microstructures x and y by comparison to the analogous signals in the molecular models {C=C−CH2: δ = 2.05 ([Au(2.3)Cl]), 2.09 ([Au(2.4)Cl]), 2.26 ([2.7A(AuCl)2]) and 2.24 ([2.7B(AuCl)2]); P=C−CH: δ = 3.35 ([Au(2.6)Cl] ) and 3.50 ([2.7A(AuCl)2]); P=C−CH2: δ = 2.76 ([Au(2.8)Cl])}. Furthermore, a signal at 6.25 ppm was tentatively attributed to P−C=CH substituent of microstructure y and was 58 compared to the analogous signals in [Au(2.3)Cl], [Au(2.4)Cl], [2.7A(AuCl)2] and [2.7B(AuCl)2] (δ = 6.90, 6.96, 6.93 and 7.00, respectively). The 13C{1H} NMR spectrum also revealed broader signals than that of uncoordinated PPI. A resonance at 179.4 ppm was attributed to the P=C substituents by comparison to the signals assigned to this group in the relevant molecular models {δ = 180.2 ([Au(2.6)Cl]), 178.5 ([2.7A(AuCl)2]), 179.7 ([2.7B(AuCl)2]) and 180.8 ([Au(2.8)Cl])}. Additionally, a broad signal was observed at 42.5 ppm that was assigned to backbone CH and CH2 groups of microstructures x and y {cf: δ(P=C−CH) = 46.9 ([Au(2.6)Cl]) and 48.6 ([2.7A(AuCl)2]); δ(P=C−CH2) = 33.9 ([Au(2.8)Cl]); δ(C=CH−CH2) = 29.3 ([Au(2.3)Cl]) and 29.4 [Au(2.4)Cl)]}. Lastly, a broad resonance at 22.0 ppm was assigned to P=C−CH3 and P−C(CH3)=CH substituents of microstructures x and y, respectively. This signal had a comparable chemical shift to those assigned to the analogous substituents of the relevant molecular model compounds {δ(P=C−CH3) = 18.2 ([Au(2.6)Cl]), 18.1 ([2.7A(AuCl)2]), 18.1 ([2.7B(AuCl)2]) and 22.1 ([Au(2.8)Cl]); δ(P−C(CH3)=CH) = 13.5 ([Au(2.3)Cl]), 13.1 [Au(2.4)Cl]), 14.0 ([2.7A(AuCl)2]) and 14.0 ([2.7B(AuCl)2])}. The broadness of the 1H and 13C{1H} NMR spectra was attributed to the polymeric nature of PPI·[AuCl]0.96n and the presence of quadrupolar 197Au atoms184 and precluded analysis of PPI·[AuCl]0.96n by two-dimensional NMR spectroscopy. Consequently, we were unable to observe NMR spectroscopic signals attributable to the CH3 substituents of microstructures x and y or the P−C(CH3)=CH groups of microstructure y. Nonetheless, a summary of the comparison of the NMR spectroscopic data for PPI·[AuCl]0.96n and the analogous signals for molecular models [Au(2.3)Cl], [Au(2.4)Cl], [Au(2.6)Cl], [2.7(AuCl)2] and [Au(2.8)Cl] is given in Table 2.2 and provides evidence for the presence of 4,3- and trans-4,1-enchainments in PPI·[AuCl]0.96n (i.e. microstructures x and y). 59 Table 2.2: Comparison of the 1H and 13C{1H} NMR spectroscopic signals assigned to PPI·[AuCl]0.96n and model compounds. Multiplicities are omitted for clarity. CA CB CC HC HD PPI·[AuCl]0.96n 22.0 179.4 42.5 2.92 6.25 [Au(2.3)Cl] 13.5 − 29.3 2.05 6.90 [Au(2.4)Cl] 13.1 − 29.4 2.09 6.96 [Au(2.6)Cl] 18.2 180.2 46.9 3.35 − [2.7A(AuCl)2] 18.1 and 14.0 178.5 48.6 2.26 and 3.50 6.93 [2.7B(AuCl)2] 18.1 and 14.0 179.7 − 2.23 7.00 [Au(2.8)Cl] 22.1 180.8 33.9 2.76 − 2.3 Conclusion In closing, the microstructure of PPI has been investigated in detail using both model compound studies and NMR spectroscopic measurements. The initiation product of PI and n-BuLi was 60 isolated and characterized crystallographically, constituting a 1-phosphaallyl anion. Furthermore, model compounds displaying a trans-4,1-enchainment (i.e. microstructure y) were isolated and characterized as AuI salts. Additional models displaying a 4,3-enchainment (i.e. microstructure x) were isolated as AuI salts. PPI was synthesized via anionic methods and coordinated to AuI to afford macromolecular complex PPI·[AuCl]0.96n. The propagating anion and end-group of PPI were detected by 31P NMR spectroscopic monitoring of the polymerization. A comparison of the NMR spectroscopic data for the models, PPI and PPI·[AuCl]0.96n facilitated tentative assignment of microstructures x and y in PPI. 2.4 Experimental Section 2.4.1 General methods All manipulations of air- and/or moisture-sensitive compounds were conducted using standard Schlenk or glovebox techniques. Tetrahydrofuran was dried over sodium/benzophenone ketyl and distilled prior to use. Hexanes, dichloromethane, toluene and diethyl ether were degassed and passed through an activated alumina column prior to use. Mes*P=C(Me)Br was synthesized according to a literature procedure.185 1H, 13C{1H}, and 31P NMR spectra were measured at room temperature on a Bruker AVANCE III HD 400 MHz. Chemical shifts of 1H NMR spectra were expressed in parts per million downfield from residual CHCl3 (δ = 7.26) or C6D5H (δ = 7.15). Chemical shifts of 13C{1H} NMR spectra were expressed in parts per million downfield from CDCl3 (δ = 77.16) or C6D5H (δ = 128.06). Chemical shifts of 31P NMR spectra were expressed in parts per million downfield from 85% H3PO4 as an external standard (δ = 0). Integrals of 31P NMR spectra give only approximate ratios (d1 = 2 s, cf. t1 = 0.613 s for PI). All integrals were phased using Topspin 4.0 software. Polymer molecular weights were determined by gel permeation chromatography with multi-angle light scattering and viscometer detectors (GPC-MALS-V) 61 equipped with an Agilent 1200 series isocratic pump, Agilent 1200 series standard autosampler, Phenomenex Phenogel 5 mm narrow bore columns (4.6 × 300 mm) with sizes of 104, 103 and 500 Å and a Wyatt Optilab T-rEx differential refractometer (λ = 658 nm, 40°C). A flow rate of 0.5 mL/min was used and samples were dissolved in THF (ca. 1 mg/mL). 100 μL of this solution was injected into the Styragel™ columns. Absolute molecular weight data were obtained using the 100% mass recovery method and samples were measured in triplicate to ensure reproducibility. ESI low-resolution mass spectra were recorded on Bruker HCT ion trap mass spectrometer equipped with an electrospray ion source. ESI high-resolution mass spectra were obtained on an Agilent 6545 QTOF mass spectrometer equipped with an Agilent Jet Stream (AJS) electrospray ion source. For accurate mass measurement, commercial reference solutions from Agilent were used as reference compounds. FD mass spectra were recorded on Jeol AccuTOF-GCv 4G, a GC-TOF MS instrument equipped with a Field Desorption/Ionization (FD/FI) ion source. All mass spectra were acquired in the positive ion mode. 2.4.2 X-ray crystallography All single crystals were immersed in oil and mounted on a mylar loop. Data were collected on a Bruker X8 APEX II diffractometer with Mo Kα radiation, integrated using the Bruker SAINT software package186 and corrected for absorption effects using SADABS.187 All structures were solved by direct methods and subsequent Fourier difference techniques. All data sets were corrected for Lorentz and polarization effects. All structure solutions were performed using SHELXT.188 All refinements were performed using SHELXL189 via the Olex2 interface.190 Compound [Au(2.3)Cl] crystallizes as a two-component split crystal. Both domains were integrated and scaled, with all subsequent calculations performed using a single component deconvoluted HKLF4 format data set. The pentyl chain of [Au(2.4)Cl] was disordered and 62 modeled in two orientations. One phenyl and one t-Bu group and the pentyl chain of [Au(2.5)Cl] were disordered and modeled in two orientations. Compound [Au(2.6)Cl] crystallizes as a two-component twin which was solved using a conventional one-component HKLF4 format data set. [2.7(AuCl)2] crystallizes with disorder in one Mes*P−Au−Cl substituent and the pentyl chain which were each modeled in two orientations. 2.4.3 Preparation of PI This compound was synthesized according to a modified literature procedure.81 To a stirred dark-orange colored solution of Mes*P=C(Me)Br (11.17 g, 29 mmol) and vinylmagnesium bromide (35 mL, 35 mmol, 1 M in THF) in THF (150 mL) was added a yellow solution of [Pd(PPh3)4] (617 mg, 0.53 mmol) in THF (30 mL). Upon addition, the reaction mixture immediately deepened in color. The flask was covered in aluminum foil to preclude light-induced E/Z isomerization of the P=C bond of PI. Analysis of the reaction mixture by 31P NMR spectroscopy after five min revealed a singlet at 264.8 ppm. The volatiles were removed in vacuo and the dark-orange residue was dissolved in hexanes and eluted through a silica plug (3 × 10 cm). A yellow fraction was collected and the solvent was removed in vacuo to afford a yellow solid. The solid was recrystallized from CH2Cl2/CH3CN (1:1) at −35 °C to afford pale yellow crystals. Yield = 6.50 g, 67%. The spectroscopic data matched those previously reported. 2.4.4 Preparation of [Li(12-crown-4)2][endo-2.1] and [Li(12-crown-4)2][exo-2.1] To a pale-yellow solution of PI (300 mg, 0.91 mmol) in THF (10 mL) was added n-BuLi (0.57 mL, 0.91 mmol, 1.6 M in hexanes) forming a deep-red solution. Analysis of the reaction mixture by 31P NMR spectroscopy revealed five signals [δ = 223.1 (2%), −31.1 (2%), −34.1 (85%), −36.9 (11%) and −43.6 (3%)]. The volatiles were removed in vacuo to afford a gummy red solid. The solid was dissolved in Et2O (5 mL) and a solution of 12-crown-4 (320 mg, 1.82 mmol) in Et2O (5 63 mL) was added. Analysis of the reaction mixture by 31P NMR spectroscopy revealed signals at −20.7 (83%), −17.0 (15%) and 221.3 (2%) ppm. The solvent was reduced to 3 mL and hexanes (3 mL) was carefully added, and the solution was stored at −35 °C. After 3 d, a red solid had formed which was filtered and washed with hexanes (3 × 2 mL). Yield = 370 mg, 55%. Crystals suitable for X-ray analysis were grown from a saturated toluene/hexanes (1:1) solution at −35 °C. Some NMR spectroscopic assignments were made using a 1H,13C-HSQC NMR experiment. [Li(12-crown-4)2][2.1] (isomer 1). 31P NMR (C6D6, 162 MHz, 25 °C) δ −16.7 (br s); 1H NMR (C6D6, 400 MHz, 25 °C) δ 7.67 (s, 2H, Mes*H), 4.97 (dt, 1H, 3JPH = 13 Hz, 3JHH = 5 Hz, P−C−CH), 3.29 (s, 32H, 12-crown-4 × 2), 2.70 (br s, 2H, CH−CH2), 2.28 (s, 18H, o-C(CH3)3), 1.85 (m, 2H, CH2), 1.77 (br s, 3H, P−C−CH3), 1.67 (m, 2H, CH2), 1.53 (m, 2H, CH2), 1.50 (s, 9H, p-C(CH3)3), 1.03 (t, 3H, 3JHH = 7 Hz, CH2−CH3); 13C{1H} NMR (C6D6, 101 MHz, 25 °C) δ 157.8 (s, o-Mes*), 151.0 (br, ipso-Mes*), 144.8 (br s, p-Mes*), 119.5 (s, m-Mes*), 105.7 (s, P−C−CH), 67.5 (s, 12-crown-4 × 2), 40.2 (s, o-C(CH3)3), 35.0 (s, p-C(CH3)3), 34.1 (d, 4JPC = 10 Hz, o-C(CH3)3), 32.25 (s, p-C(CH3)3), 31.7 (s, CH2), 27.8 (br s, CH2 or P−C−CH3), 14.84 (s, CH2−CH3); signals for: CH2−CH2 and P−C−CH were not able to be assigned. [Li(12-crown-4)2][2.1] (isomer 2). 31P NMR (C6D6, 162 MHz, 25 ⁰C) δ −23.4 (br s); 1H NMR (C6D6, 400 MHz, 25 ⁰C) δ 7.76 (s, 2H, Mes*H), 3.67 (br s, 1H, P−C−CH), 3.29 (s, 32H, 12-crown-4 × 2), 2.40 (dt, 2H, 3JHH = 7 Hz, 3JHH = 7 Hz, CH−CH2), 2.28 (s, 18H, o-C(CH3)3), 2.13 (br d, 3H, 3JPH = 14 Hz, P−C−CH3), 1.49 (s, 9H, p-C(CH3)3), 1.48 (m, 2H, CH2), 1.42 (m, 2H, CH2), 1.36 (m, 2H, CH2), 0.94 (t, 3H, 3JHH = 7 Hz, CH2−CH3); 13C{1H} NMR (C6D6, 101 MHz, 25 ⁰C) δ 158.0 (s, o-Mes*), 148.8 (d, 1JPC = 50 Hz, ipso-Mes*), 144.5 (s, p-Mes*), 120.6 (s, m-Mes*), 109.3 (s, P−C−CH), 67.5 (s, 12-crown-4 × 2), 40.0 (s, o-C(CH3)3), 35.1 (s, p-C(CH3)3), 34.0 (d, 4JPC = 9 Hz, o-C(CH3)3), 32.18 (s, p-C(CH3)3), 30.8 (s, CH−CH2), 20.1 (d, 2JPC = 50 Hz, 64 P−C−CH3), 23.5 (s, CH2), 14.78 (s, CH2−CH3); signals for: CH2−CH2 and P−C−CH were not able to be assigned. Satisfactory elemental analysis could not be obtained: Anal. Calcd for C42H76O8PLi: C, 67.53; H, 10.26. Found: C, 64.29; H, 9.54. 2.4.5 Preparation of 2.2 To a pale-yellow solution of PI (169 mg, 0.51 mmol) in THF (10 mL) was added n-BuLi (0.35 mL, 0.56 mmol, 1.6 M in hexanes), forming a deep-red solution. Analysis of the reaction mixture by 31P NMR spectroscopy showed a broad major signal at −34.1 ppm. Deoxygenated methanol (0.1 mL, excess) was added, resulting in the dissipation of the red color in favor of pale-yellow. Analysis of the reaction mixture by 31P NMR spectroscopy showed a major doublet resonance (δ = −55.0, 1JPH = 223 Hz, 91%) alongside minor signals [δ = 235.9 (3%), 234.8 (3%) and −72.4 (JPH = 227 Hz, 4%)]. The volatiles were removed in vacuo and the resulting pale-yellow oil was dissolved in pentane and filtered through celite™. The solvent was removed in vacuo to afford a crude viscous pale-yellow oil. Yield = 186 mg, 94%. 31P NMR (CDCl3, 162 MHz, 25 ˚C) δ −55.0 (ddq, 1JPH = 226 Hz, 3JHH = 11 Hz, 3JHH = 8 Hz); 1H NMR (CDCl3, 400 MHz, 25 ˚C) δ 7.45 (br s, 2H, Mes*H), 5.37 (d, 1H, 1JPH = 226 Hz, P−H), 4.30 (dt, 1H, 3JPH = 8 Hz, 3JHH = 8 Hz, P−C=CH), 1.91 (dt, 2H, 3JHH = 8 Hz, 3JHH = 7 Hz, C=CH−CH2), 1.61 (d, 3H, 3JPH = 11 Hz, P−C−CH3), 1.55 (br s, 18H, o-C(CH3)3), 1.36 (s, 9H, p-C(CH3)3), 1.27−1.04 (m, 6H, CH2−CH2−CH2), 0.85 (t, 3H, 3JHH = 7 Hz, CH2−CH3); 13C{1H} NMR (CDCl3, 101 MHz, 25 ˚C) δ 155.8 (br s, o-Mes*) 150.0 (s, p-Mes*) 134.7 (d, 2JPC = 11 Hz, P−C=CH), 133.4 (d, 1JPC = 15 Hz, P−C=CH), 129.6 (d, 1JPC = 29 Hz, ipso-Mes*), 122.0 (br, s, m-Mes*), 38.4 (br s, o-C(CH3)3), 35.2 (s, p-C(CH3)3), 33.5 (br s, o-C(CH3)3), 31.5 (s, p-C(CH3)3), 31.4 (s, CH2), 29.0 (s, CH2), 28.6 (d, 3JPC = 5 Hz, C=CH−CH2), 22.7 (s, CH2), 16.6 (d, 2JPC = 25 65 Hz, P−C−CH3), 14.2 (s, CH2−CH3). Some broad signals were resolved upon cooling of the solution: 1H NMR (CDCl3, 400 MHz, −40 ˚C) δ 7.45 (br s, 1H, Mes*H), 7.41 (br s, 1H, Mes*H), 5.34 (d, 1H, 1JPH = 229 Hz, P−H), 4.07 (br s, 1H, P−C=CH), 1.85 (m, 2H, 3JHH = 8 Hz, 3JHH = 7 Hz, C=CH−CH2), 1.61 (d, 3H, 3JPH = 12 Hz, P−C−CH3), 1.56 (s, 9H, o-C(CH3)3), 1.43 (s, 9H, o-C(CH3)3), 1.31 (s, 9H, p-C(CH3)3), 1.19-0.95 (m, 6H, CH2−CH2−CH2), 0.79 (t, 3H, 3JHH = 7 Hz, CH2−CH3); 13C{1H} NMR (CDCl3, 101 MHz, −40 ˚C) δ 156.1 (d, 2JPC = 20 Hz, o-Mes*), 154.4 (d, 2JPC = 4 Hz, o-Mes*), 149.9 (s, p-Mes*), 134.1 (d, 2JPC = 7 Hz, P−C=CH), 132.8 (d, 1JPC = 13 Hz, P−C=CH), 129.3 (d, 1JPC = 28 Hz, ipso-Mes*), 122.6 (s, m-Mes*), 121.7 (d, 3JPC = 8 Hz, m-Mes*), 38.5 (d, 3JPC = 3 Hz o-C(CH3)3), 38.2 (s, o-C(CH3)3), 35.1 (s, p-C(CH3)3), 33.4 (d, 4JPC = 14 Hz, o-C(CH3)3), 33.1 (s, o-C(CH3)3), 31.3 (s, p-C(CH3)3), 31.2 (s, CH2), 29.0 (s, CH2), 28.4 (d, 3JPC = 4 Hz, C=CH−CH2), 22.7 (s, CH2), 16.6 (d, 2JPC = 27 Hz, P−C−CH3), 14.5 (s, CH2−CH3); EI-MS [M−H]+ 387 (100), 386 (54), 395 (77). HRMS (EI, positive mode) calcd for C26H44P, 387.3181, found 387.3179. 2.4.6 Preparation of [Au(2.2)Cl] To a pale-yellow solution of 2.2 (78 mg, 0.20 mmol) in CH2Cl2 (1 mL) was added a solution of [Au(tht)Cl] (51 mg, 0.16 mmol) in CH2Cl2 (1 mL), forming an orange solution. Immediate analysis by 31P NMR spectroscopy revealed a signal at −18.3 ppm. The solvent was removed in vacuo to afford a gummy yellow solid. The solid was washed with pentane (2 mL) at −35 °C and a white solid was isolated after filtration. Yield = 60 mg, 61%. Yellow crystals suitable for X-ray analysis were grown by slow evaporation of a CDCl3 solution. 31P NMR (CDCl3, 400 MHz, 25 °C) δ −4.7 (br d, 1JPH = 390 Hz); 1H NMR (CDCl3, 400 MHz, 25 ˚C) δ 7.45 (br s, 1H, Mes*H), 7.44 (br s, 1H, Mes*H), 6.60 (d, 1H, 1JPH = 390 Hz, P−H), 6.39 (dt, 1H, 3JPH = 27 Hz, 3JHH = 7 Hz, P−C=CH), 2.08 (m, 2H, C=CH−CH2), 1.56 (s, 18H, 66 o-C(CH3)3), 1.38-1.18 (m, 6H, CH2-CH2-CH2), 1.30 (s, 9H, p-C(CH3)3), 1.20 (d, 3H, 3JPH = 13 Hz, P−C−CH3), 0.86 (t, 3H, 3JHH = 7 Hz, CH2−CH3); 13C{1H} NMR (CDCl3, 101 MHz, 25 ˚C) δ 157.9 (s, o-Mes*), 156.9 (d, 2JPC = 8 Hz, o-Mes*), 153.0 (d, 4JPC = 3 Hz, p-Mes*), 148.3 (d, 2JPC = 20 Hz, P−C=CH) 126.6 (d, 1JPC = 57 Hz, P−C=CH), 125.1 (d, 3JPC = 11 Hz, m-Mes*), 123.2 (d, 3JPC = 9 Hz, m-Mes*), 119.0 (d, 1JPC = 52 Hz, ipso-Mes*), 39.6 (s, o-C(CH3)3), 38.8 (s, o-C(CH3)3), 35.1 (s, p-C(CH3)3), 34.7 (d, 4JPC = 3 Hz, o-C(CH3)3), 34.2 (d, 4JPC = 2 Hz, o-C(CH3)3), 31.6 (s, CH2), 31.2 (s, p-C(CH3)3), 29.5 (d, 3JPC = 17 Hz, C=CH−CH2), 28.0 (d, JPC = 2 Hz, CH2), 22.5 (s, CH2), 15.3 (d, 2JPC = 10 Hz, P−C−CH3), 14.1 (s, CH2−CH3). FD-MS [M+] 620.1 (100), 621.1(29), 622.1 (39), 623.1 (10). HRMS (FD+) calcd for C26H45PAuCl, 620.2613, found 620.2607. Satisfactory elemental analysis could not be obtained: Anal. Calcd for C26H45PAuCl: C, 50.28; H, 7.30. Found: C, 52.31; H, 7.75. 2.4.7 Preparation of 2.3 To a pale-yellow solution of PI (164 mg, 0.50 mmol) in THF (10 mL) was added n-BuLi (0.34 mL, 0.54 mmol, 1.6 M in hexanes), forming a deep-red solution. Analysis of the reaction mixture by 31P NMR spectroscopy revealed a major signal at −34.1 ppm. Iodomethane (0.04 mL, 0.64 mmol) was added, resulting in the dissipation of the red color in favor of pale-yellow. Analysis of the reaction mixture by 31P NMR spectroscopy showed two signals [δ = −29.6 (93%) and −34.6 (7%)]. The volatiles were removed in vacuo to afford a pale-yellow oil. The oil was dissolved in hexanes and filtered through celite™. The solvent was removed in vacuo to afford a viscous pale-yellow oil. Yield = 183 mg, 92%. 31P NMR (CDCl3, 162 MHz, 25 ˚ C) δ −29.5 (s); 1H NMR (CDCl3, 400 MHz, 25 ˚ C) δ 7.37 (d, 2H, 4JPH = 2 Hz, Mes*H), 5.09 (dt, 1H, 3JPH = 7 Hz, 3JHH = 7 Hz, P−C=CH), 2.00 (m, 2H, C=C−CH2), 1.74 (d, 3H, 2JPH = 7 Hz, P−CH3), 1.50 (s, 18H, o-C(CH3)3), 1.31 (s, 9H, p-C(CH3)3), 67 1.31-1.24 (m, 6H, CH2−CH2−CH2), 1.22 (br d, 3H, 3JPH = 10 Hz, P−C−CH3), 0.88 (t, 3H, 3JHH = 7 Hz, CH2−CH3); 13C{1H} NMR (CDCl3, 101 MHz, 25 ˚C) δ 159.0 (d, 2JPC = 13 Hz, o-Mes*), 150.0 (d, 4JPC = 3 Hz, p-Mes*), 137.2 (d, 1JPC = 19 Hz, P−C=CH), 131.2 (d, 1JPC = 43 Hz, ipso-Mes*), 129.6 (d, 2JPC = 15 Hz, P−C=CH), 122.6 (d, 3JPC = 7 Hz, m-Mes*), 39.5 (d, 3JPC = 4 Hz, o-C(CH3)3), 34.9 (s, p-C(CH3)3), 34.0 (d, 4JPC = 8 Hz, o-C(CH3)3), 31.8 (s, CH2), 31.4 (s, o-C(CH3)3), 29.2 (d, JPC = 4 Hz, CH2), 28.9 (d, 3JPC = 2 Hz, C=CH−CH2), 22.7 (s, CH2), 15.4 (d, 2JPC = 26 Hz, P−C−CH3), 14.2 (s, CH2−CH3), 12.5 (d, 1JPC = 28 Hz, P−CH3). FD-MS [M+] 402.4 (100), 403.4 (32), 404.4 (5). HRMS (FD+) calcd for C27H47P, 402.3431, found 402.3415. 2.4.8 Preparation of [Au(2.3)Cl] To a pale-yellow solution of 2.3 (91 mg, 0.23 mmol) in CH2Cl2 (1 mL) was added a solution of [Au(tht)Cl] (58 mg, 0.18 mmol) in CH2Cl2 (1 mL). The orange reaction mixture was analyzed by 31P NMR spectroscopy to reveal three signals [δ = 46.3 (14%), 34.6 (78%) and 30.0 (9%)]. The solvent was removed in vacuo to afford a gummy yellow solid. The solid was washed with hexanes (2 mL) at −35 °C. After filtration, a white solid was isolated. Yield = 80 mg, 70%. Crystals suitable for X-ray crystallographic analysis were grown from a CH2Cl2/heptane (1:1) solution at −35 °C. 31P NMR (CDCl3, 162 MHz, 25 °C) δ 34.3 (s); 1H NMR (CDCl3, 400 MHz, 25 ˚C) δ 7.25 (br s, 2H, Mes*H), 6.90 (br s, 1H, P−C=CH), 2.05 (m, 2H, C=C−CH2), 1.70 (br d, 3H, 2JPH = 8 Hz, P−CH3), 1.43 (br s, 18H, o-C(CH3)3), 1.42 (m, 2H, CH2), 1.29 (m, 2H, CH2), 1.26 (s, 9H, p-C(CH3)3), 1.25 (m, 2H, CH2), 0.95 (br s, 3H, P−C−CH3), 0.85 (br t, 3H, 3JHH = 7 Hz, CH2−CH3); 13C{1H} NMR (CDCl3, 101 MHz, 25 ˚C) δ 159.3 (br s, o-Mes*), 151.2 (s, p-Mes*), 147.3 (br s, P−C=CH), 132.6 (d, 1JPC = 61 Hz, P−C=CH), 123.7 (br s, m-Mes*), 123.4 (d, 1JPC = 53 Hz, ipso-Mes*), 40.2 (br s, o-C(CH3)3), 34.5 (s, p-C(CH3)3), 34.0 (br s, o-C(CH3)3), 31.8 (s, CH2), 31.1 (s, p-C(CH3)3), 29.3 (d, 3JPC = 18 Hz, C=C−CH2), 27.8 (s, CH2), 23.1 (d, 1JPC = 43 Hz, P−CH3), 22.5 68 (s, CH2), 14.0 (s, CH2−CH3), 13.5 (br s, P−C−CH3). Some broad signals were resolved upon cooling of the solution: 1H NMR (CDCl3, 400 MHz, −40 ˚C) δ 7.27 (dd, 1H, 4JPH = 2 Hz, 4JHH = 2 Hz, Mes*H), 7.19 (dd, 1H, 4JPH = 4 Hz, 4JHH = 2 Hz, Mes*H), 6.90 (dt, 1H, 3JPH = 26 Hz, 3JPH = 7 Hz, P−C=CH), 2.04 (m, 2H, C=C−CH2), 1.70 (d, 3H, 2JPH = 8 Hz, P−CH3), 1.46 (s, 9H, o-C(CH3)3), 1.39 (m, 2H, CH2), 1.37 (s, 9H, o-C(CH3)3), 1.26 (s, 9H, p-C(CH3)3), 1.25 (m, 2H, CH2), 1.20 (m, 2H, CH2), 0.95 (d, 3H, 3JPH = 10 Hz, P−C−CH3), 0.86 (t, 3H, 3JHH = 7 Hz, CH2−CH3); 13C{1H} NMR (CDCl3, 101 MHz, −40 ˚C) δ 159.1 (d, 2JPC = 4 Hz, o-Mes*), 158.6 (d, 2JPC = 3 Hz, o-Mes*), 150.8 (d, 4JPC = 3 Hz, p-Mes*), 147.5 (d, 2JPC = 23 Hz, P−C=CH), 132.0 (d, 1JPC = 61 Hz, P−C=CH), 123.8 (d, 3JPC = 10 Hz, m-Mes*), 123.4 (d, 3JPC = 9 Hz, m-Mes*), 123.1 (d, 1JPC = 53 Hz, ipso-Mes*), 40.2 (d, 3JPC = 1 Hz, o-C(CH3)3), 39.9 (d, 3JPC = 1 Hz, o-C(CH3)3), 34.5 (s, p-C(CH3)3), 33.9 (br s, o-C(CH3)3), 33.7 (br s, o-C(CH3)3), 31.9 (s, CH2), 31.1 (s, p-C(CH3)3), 29.3 (d, 3JPC = 18 Hz, C=C−CH2), 27.8 (s, CH2), 23.0 (d, 1JPC = 43 Hz, P−CH3), 22.6 (s, CH2), 14.3 (s, CH2−CH3), 13.5 (d, 2JPC = 6 Hz, P−C−CH3). FD-MS [M+] 634.3 (100), 635.3 (33), 636.3 (40), 637.3 (13). HRMS (FD+) calcd for C27H47PAuCl, 634.2769, found 634.2790. Satisfactory elemental analysis could not be obtained: Anal. Calcd for C27H47PAuCl: C, 51.07; H, 7.46. Found: C, 51.69; H, 7.68. 2.4.9 Preparation of 2.4 To a pale-yellow solution of PI (174 mg, 0.53 mmol) in THF (10 mL) was added n-BuLi (0.36 mL, 0.58 mmol, 1.6 M in hexanes), forming a deep-red solution. Analysis of the reaction mixture by 31P NMR spectroscopy revealed the major signal at −34.1 ppm. Bromoethane (50 μL, 0.67 mmol) was added, resulting in the dissipation of the red color in favor of pale-yellow. Analysis of the reaction mixture by 31P NMR spectroscopy showed three signals [δ = 231.6 (6%), −8.4 (89%) and −12.4 (6%)]. The volatiles were removed in vacuo to afford a pale-yellow oil. The oil was 69 dissolved in hexanes and filtered through celite™. The solvent was removed in vacuo to afford a viscous pale-yellow oil. Yield = 214 mg, 98%. 31P NMR (CDCl3, 162 MHz, 25 ˚C) δ −8.9 (s); 1H NMR (CDCl3, 400 MHz, 25 ˚C) δ 7.37 (d, 2H, 4JPH = 2 Hz, Mes*H), 5.28 (dt, 1H, 3JPH = 7 Hz, 3JHH = 7 Hz, P−C=CH), 2.20 (m, 1H, P−CHaHb−CH3), 2.04 (m, 2H, C=C−CH2), 2.01 (m, 1H, P−CHaHb−CH3), 1.50 (s, 18H, o-C(CH3)3), 1.33−1.27 (m, 6H, CH2−CH2−CH2), 1.31 (s, 9H, p-C(CH3)3), 1.30 (br d, 3H, 3JPH = 7 Hz, P−C−CH3), 1.14 (dt, 3H, 3JPH = 20 Hz, 3JHH = 8 Hz, P−CHaHb−CH3 ), 0.89 (t, 3H, 3JHH = 7 Hz, CH2−CH2−CH3); 13C{1H} NMR (CDCl3, 101 MHz, 25 ˚C) δ 159.0 (d, 2JPC = 13 Hz, o-Mes*), 149.8 (d, 4JPC = 2 Hz, p-Mes*), 135.4 (d, 1JPC = 22 Hz, P−C=CH2), 130.6 (d, 1JPC = 43 Hz, ipso-Mes*), 129.6 (d, 2JPC = 14 Hz, P−C=CH), 122.9 (d, 3JPC = 7 Hz, m-Mes*), 39.5 (d, 3JPC = 4 Hz, o-C(CH3)3), 34.8 (s, p-C(CH3)3), 34.1 (d, 4JPC = 7 Hz, o-C(CH3)3), 31.8 (s, CH2), 31.4 (s, p-C(CH3)3) 29.2 (d, JPC = 4 Hz, CH2), 28.9 (d, 3JPC = 2 Hz, C=CH−CH2), 22.8 (s, CH2), 20.7 (d, 1JPC = 24 Hz, P−CHaHb−CH3), 16.0 (d, 2JPC = 26 Hz, P−C−CH3), 14.3 (s, CH2−CH2−CH3), 12.8 (d, 2JPC = 30 Hz, P−CHaHb−CH3). FD-MS [M+] 416.5 (100), 417.5 (32), 418.5 (5). HRMS (FD+) calcd for C28H49P, 416.3572, found 416.3562. 2.4.10 Preparation of [Au(2.4)Cl] To a solution of 2.4 (103 mg, 0.25 mmol) in CH2Cl2 (1 mL) was added a solution of [Au(tht)Cl] (63 mg, 0.20 mmol) CH2Cl2 (1 mL). The orange reaction mixture was analyzed by 31P NMR spectroscopy to reveal two signals at 54.0 and 65.4 ppm in a 4:1 ratio. The volatiles were removed in vacuo to afford a gummy yellow solid. The solid was washed with hexanes (2 mL) at −35 °C. After filtration, a white solid was isolated. Yield = 110 mg, 86%. Crystals suitable for X-ray crystallographic analysis were grown from a CH2Cl2/heptane (1:1) solution at −35 °C. 70 31P NMR (CDCl3, 162 MHz, 25 ˚C) δ 53.7 (s); 1H NMR (CDCl3, 400 MHz, 25 ˚C) δ 7.25 (br s, 1H, Mes*H), 7.21 (br s, 1H, Mes*H), 6.96 (br d, 1H, 3JPH = 26 Hz, P−C=CH), 2.30 (m, 1H, P−CHaHb−CH3), 2.09 (dt, 2H, 3JHH = 7 Hz, 3JHH = 7 Hz, C=C−CH2), 1.45 (s, 9H, o-C(CH3)3), 1.41 (m, 2H, CH2), 1.38 (s, 9H, o-C(CH3)3), 1.37 (m, 1H, P−CHaHb−CH3), 1.29−1.26 (m, 4H, CH2−CH2), 1.25 (s, 9H, p-C(CH3)3), 0.91 (dt, 3H, 3JPH = 21 Hz, 3JHH = 7 Hz, P−CHaHb−CH3), 0.88 (d, 3H, 3JPH = 8 Hz, P−C−CH3), 0.85 (t, 3H, 3JHH = 7 Hz, CH2−CH2−CH3); 13C{1H} NMR (CDCl3, 101 MHz, 25 ˚C) δ 159.3 (s, o-Mes*), 159.1 (s, o-Mes*), 151.1 (d, 4JPC = 3 Hz, p-Mes*), 151.0 (d, 2JPC = 20 Hz, P−C=CH), 128.2 (d, 1JPC = 58 Hz, P−C=CH), 123.6 (br s, m-Mes*), 121.7 (d, 1JPC = 52 Hz, ipso-Mes*), 40.6 (s, o-C(CH3)3), 40.1 (s, o-C(CH3)3), 34.4 (s, p-C(CH3)3), 34.2 (s, o-C(CH3)3), 33.8 (s, o-C(CH3)3), 31.8 (s, CH2), 31.1 (s, p-C(CH3)3), 29.4 (d, 3JPC = 18 Hz, C=CH−CH2), 27.8 (d, JPC = 1 Hz, CH2), 24.6 (br d, 1JPC = 40 Hz, P−CHaHb−CH3), 22.4 (s, CH2), 14.0 (s, CH2−CH2−CH3), 13.1 (br s, P−C−CH3), 9.7 (d, 2JPC = 5 Hz, P−CHaHb−CH3). Some broad signals were resolved upon cooling of the solution: 1H NMR (CDCl3, 400 MHz, −40 °C) δ 7.23 (br s, 1H, Mes*H), 7.19 (br s, 1H, Mes*H), 6.93 (dt, 1H, 3JPH = 25 Hz, 3JHH = 7 Hz, P−C=CH), 2.30 (m, 1H, P−CHaHb−CH3), 2.09 (dt, 2H, 3JHH = 7 Hz, 3JHH = 7 Hz, C=C−CH2), 1.45 (s, 9H, o-C(CH3)3), 1.36 (s, 9H, o-C(CH3)3), 1.40 (m, 2H, CH2), 1.36 (m, 1H, P−CHaHb−CH3), 1.28−1.24 (m, 4H, CH2−CH2), 1.24 (s, 9H, p-C(CH3)3), 0.89 (dt, 3H, 3JPH = 21 Hz, 3JHH = 7 Hz, P−CHaHb−CH3), 0.86 (d, 3H, 3JPH = 8 Hz, P−C−CH3), 0.85 (t, 3H, 3JHH = 7 Hz, CH2−CH2−CH3). FD-MS [M+] 648.3 (100), 649.4 (32), 650.3 (37), 651.3 (11). HRMS (FD+) calcd for C28H49PAuCl, 648.2926, found 648.2901. Anal. Calcd for C28H49PAuCl: C, 51.81; H, 7.61. Found: C, 51.61; H, 7.69. 71 2.4.11 Preparation of 2.5 and 2.6 To a solution of PI (376 mg, 1.1 mmol) in THF (10 mL) was added n-BuLi (0.71 mL, 1.1 mmol, 1.6 M in hexanes) forming a deep-red solution. Analysis of the reaction mixture by 31P NMR spectroscopy revealed a major signal at −34.1 ppm. To this reaction mixture was added a solution of H2C=CPh2 (205 mg, 1.1 mmol) in THF (5 mL) and the red solution was monitored by 31P NMR spectroscopy. After 48 h, the 31P NMR spectrum showed three signals [δ = −19.8 (92%), −34.1 (5%) and −36.9 (3%)]. Deoxygenated methanol (1 mL) was added and the red color dissipated in favor of pale-yellow. Analysis of the reaction mixture by 31P NMR spectroscopy revealed seven signals [δ = 239.7 (2%), 238.3 (2%), 236.2 (1%), 234.1 (34%), −55.1 (d, JPH = 223 Hz, 5%), −62.2 (d, JPH = 228 Hz, 28%) and −62.4 (d, JPH = 228 Hz, 28%)]. The volatiles were removed in vacuo and the residual yellow oil was dissolved in hexanes and filtered through a bed of Celite™. The solvent was removed in vacuo to afford a yellow oil. Yield = 440 mg, 68%. 2.5: Due to overlap of the NMR resonances, absolute assignment of signals to either 2.5A or 2.5B could not be accomplished, and the assignments of the signals for each compound are given together: 31P NMR (CDCl3, 162 MHz, 25 °C) δ −63.0 (d, 1JPH = 231 Hz) and −63.2 (d, 1JPH = 231 Hz); 1H NMR (CDCl3, 400 MHz, 25 °C) δ 7.50 (s, 2H, Mes*H, overlapping signals), 5.47 and 5.42 (d, 1JPH = 231 Hz, P−H), 5.13 (br m, 1H, P−C=CHaHb, overlapping signals), 4.13 and 4.06 (dd, 1H, 3JHH = 9 Hz, 3JHH = 7 Hz, CHPh2), 3.77 (br m, 1H, P−C=CHaHb, overlapping signals), 2.13 (m, 1H, P−C−CH, overlapping signals); 13C{1H} NMR (CDCl3, 101 MHz, 25°C) δ 121.9 (m-Mes*, overlapping signals), 118.9 (d, 2JPC = 22 Hz, P−C=CHaHb, overlapping signals), 48.88 and 48.86 (s, CHPh2), 44.8 and 44.6 (d, 2JPC = 8 Hz, P−C−CH). 2.6 Only well-resolved signals were assigned: 31P NMR (CDCl3, 162 MHz, 25 °C) δ 232.9 (s); 1H NMR (CDCl3, 400 MHz, 25 °C) δ 7.48 (s, 2H, Mes*H), 4.19 (dd, 1H, 3JHH = 8 Hz, 3JHH = 72 8 Hz, CHPh2), 2.71 (m, 1H, P=C−CH), 1.28 (d, 3H, 3JPH = 14 Hz, P=C−CH3); 13C{1H} NMR (CDCl3, 101 MHz, 25 °C) δ 187.0 (d, 1JPC = 45 Hz, P=C), 121.9 (s, m-Mes*), 47.8 (s, CHPh2), 47.3 (d, 2JPC = 39 Hz, P=C−CH), 19.6 (d, 2JPC = 16 Hz, P=C−CH3). 2.4.12 Preparation of [Au(2.5)Cl] and [Au(2.6)Cl] To a solution of [Au(tht)Cl] (110 mg, 0.34 mmol) in CH2Cl2 (2 mL) was added a solution of the above oil (420 mg, 0.74 mmol) in CH2Cl2 (2 mL) forming an orange solution. Analysis of the reaction mixture by 31P NMR spectroscopy revealed five signals [δ = 232.3 (41%), 182.9 (4%), −21.4 (d, JPH = 397 Hz, 20%), −23.9 (d, JPH = 397 Hz, 21%) and −62.3 (br d, 14%)]. The reaction mixture was filtered through Celite™ and the volatiles were removed in vacuo to afford an orange oil. The oil was recrystallized from pentane at −35 °C to afford yellow crystals suitable for X-ray analysis. Yield of [Au(2.5)Cl] = 90 mg, 33%. The filtrate from the recrystallization was filtered through Celite™ and the volatiles were removed in vacuo to afford a yellow oil. To a yellow solution of this oil (75 mg, 0.13 mmol) in CH2Cl2 (1 mL) was added a solution of [Au(tht)Cl] (30 mg, 0.09 mmol) in CH2Cl2 (1 mL), forming an orange solution. Analysis of the reaction mixture by 31P NMR spectroscopy revealed a signal at 182.9 ppm. The reaction mixture was filtered through Celite™ and the volatiles were removed in vacuo to afford a gummy yellow solid. The solid was washed with pentane (3 × 1 mL) at −35 °C to afford a white solid. Yield of [Au(2.6)Cl] = 45 mg, 60%. Crystals of the solid suitable for X-ray analysis were grown by slow evaporation of a CH2Cl2/heptane (1:1) solution. [Au(2.5A)Cl]: 31P NMR (162 MHz, CDCl3, 25 ˚C) δ −21.5 (d, 1JPH = 398 Hz); 1H NMR (CDCl3, 400 MHz, 25 ˚C) δ 7.51 (m, 2H, Mes*H), 7.38−7.12 (m, 10H, phenyl-CH), 6.79 (d, 1H, 1JPH = 398 Hz, P−H), 5.616 (d, 1H, 3JPH = 41 Hz, P−C=CHaHb), 4.67 (d, 1H, 3JPH = 20 Hz, P−C=CHaHb), 3.94 (t, 1H, 3JHH = 8 Hz, CHPh2), 2.42 (m, 2H, P−C−CH and 73 CH−CHcHd−CHPh2), 2.19 (m, 1H, CH−CHcHd−CHPh2), 1.69 (s, 9H, o-C(CH3)3), 1.50 (m, 2H, CH2), 1.46 (s, 9H, o-C(CH3)3), 1.33 (s, 9 H, p-C(CH3)3), 1.31−1.09 (m, 6H, CH2-CH2−CH2), 0.88 (t, 3H, 3JHH = 7 Hz, CH3); 13C{1H} NMR (CDCl3, 101 MHz, 25 ˚C) δ 157.8 (d, 2JPC = 1 Hz, o-Mes*), 156.9 (d, 2JPC = 9 Hz, o-Mes*), 153.6 (d, 4JPC = 3 Hz, p-Mes*), 145.2 (d, 1JPC = 47 Hz, P−C=CHaHb), 144.3 (s, phenyl-C), 143.9 (s, phenyl-C), 129.1−128.8 (phenyl-CH), 128.0 (d, 2JPC = 60 Hz, P−C=CHaHb), 128.0−127.8 (phenyl-CH), 126.8−126.6 (phenyl-CH), 124.5 (d, 3JPC = 11 Hz, m-Mes*), 123.5 (d, 3JPC = 9 Hz, m-Mes*), 117.4 (d, 1JPC = 51 Hz, ipso-Mes*), 48.78 (s, CHPh2), 43.3 (d, 2JPC = 17 Hz, P−C−CH), 39.8 (d, 3JPC = 3 Hz, o-C(CH3)3), 39.5 (d, 3JPC = 6 Hz, CH−CHcHd−CHPh2), 38.35 (d, 3JPC = 2 Hz, o-C(CH3)3), 35.32 (s, p-C(CH3)3), 35.27 (d, 4JPC = 3 Hz, o-C(CH3)3), 34.2 (d, 4JPC = 2 Hz, o-C(CH3)3), 33.3 (d, JPC = 4 Hz, CH2), 31.8 (s, CH2), 31.2 (s, p-C(CH3)3), 25.8 (s, CH2), 22.68 (s, CH2), 14.1 (s, CH3). [Au(2.5B)Cl]: 31P NMR (CDCl3, 162 MHz, 25 ˚C) δ −23.5 (d, 1JPH = 400 Hz); 1H NMR (CDCl3, 400 MHz, 25 ˚C) δ 7.54 (m, 1H, Mes*H), 7.49 (m, 1H, Mes*H), 7.38−7.12 (m, 10H, phenyl-CH), 6.73 (d, 1H, 1JPH = 400 Hz, P−H), 5.610 (d, 1H, 3JPH = 41 Hz, P−C=CHaHb), 4.64 (d, 1H, 3JPH = 20 Hz, P−C=CHaHb), 3.88 (t, 1H, 3JHH = 8 Hz, CHPh2), 2.42 (m, 1H, P−C−CH), 2.31 (m, 2H, CH−CHcHd-CHPh2), 1.66 (s, 9H, o-C(CH3)3), 1.53 (s, 9H, o-C(CH3)3), 1.50 (m, 2H, CH2), 1.33 (s, 9H, p-C(CH3)3), 1.31−1.09 (m, 6H, CH2−CH2−CH2), 0.83 (t, 3H, 3JHH = 7 Hz, CH3); 13C{1H} NMR (CDCl3, 101 MHz, 25 ˚C) δ 157.5 (d, 2JPC = 1 Hz, o-Mes*), 157.0 (d, 2JPC = 9 Hz, o-Mes*), 153.6 (d, 4JPC = 3 Hz, p-Mes*), 145.3 (d, 1JPC = 47 Hz, P−C=CHaHb), 144.5 (s, phenyl-C), 143.9 (s, phenyl-C), 129.1−128.8 (phenyl-CH), 128.0 (d, 2JPC = 60 Hz, P−C=CHaHb), 128.0−127.8 (phenyl-CH), 126.8−126.6 (phenyl-CH), 124.4 (d, 3JPC = 11 Hz, m-Mes*), 123.6 (d, 3JPC = 9 Hz, m-Mes*), 117.1 (d, 1JPC = 51 Hz, ipso-Mes*), 48.84 (s, CHPh2), 43.2 (d, 2JPC = 17 Hz, CH−CHcHd−CHPh2), 40.1 (d, 3JPC = 5 Hz, CH−CHcHd−CHPh2), 39.7 (d, 3JPC = 3 Hz, o-74 C(CH3)3), 38.44 (d, 3JPC = 2 Hz, o-C(CH3)3), 35.32 (s, p-C(CH3)3), 35.1 (d, 4JPC = 3 Hz, o-C(CH3)3), 34.3 (d, 4JPC = 2 Hz, o-C(CH3)3), 33.7 (d, JPC = 4 Hz, CH2), 31.9 (s, CH2), 31.2 (s, p-C(CH3)3), 26.3 (s, CH2), 22.71 (s, CH2), 14.2 (s,CH3). FD-MS [M+] 800.3 (100), 801.3 (40), 802.3 (40), 803.3 (20). HRMS (FD+) calcd for C40H57PAuCl, 800.3552, found 800.3583. [Au(2.6)Cl]: 31P NMR (162 MHz, CDCl3, 25 ˚C) δ 183.2 (s); 1H NMR (CDCl3, 400 MHz, 25 ˚C) δ 7.54 (br m, 2H, Mes*H), 7.38−7.18 (m, 10H, Phenyl-CH), 3.98 (t, 3H, 3JHH = 8 Hz, CHPh2), 3.35 (m, 1H, P=C−CH), 2.18 (m, 2H, CH−CHaHb-CHPh2), 1.68 (s, 9H, o-C(CH3)3), 1.59 (s, 9H, o-C(CH3)3), 1.46 (m, 2H, CH2), 1.34 (s, 9H, p-C(CH3)3), 1.34 (d, 3H, 3JPH = 29 Hz, P=C−CH3), 1.28−1.20 (m, 6H, CH2−CH2−CH2), 0.87 (t, 3H, 3JHH = 7 Hz, CH3); 13C{1H} NMR (CDCl3, 101 MHz, 25 ˚C) δ 180.2 (d, 1JPC = 68 Hz, P=C), 156.2 (d, 2JPC = 2 Hz, o-Mes*), 156.0 (d, 2JPC = 2 Hz, o-Mes*), 153.9 (d, 4JPC = 3 Hz, p-Mes*), 144.0 (s, phenyl-C), 143.7 (s, phenyl-C), 129.2−126.7 (s, phenyl-CH), 124.2 (d, 1JPC = 29 HZ, ipso-Mes*), 123.6 (d, 3JPC = 9 Hz, m-Mes*), 123.5 (d, 3JPC = 9 Hz, m-Mes*), 49.1 (s, CHPh2), 46.9 (d, 2JPC = 19 Hz, P=C−CH), 39.5 (d, 3JPC = 16 Hz, CH−CHaHb-CHPh2), 39.0 (br s, o-C(CH3)3), 35.4 (s, p-C(CH3)3), 34.1 (br s, o-C(CH3)3), 33.4 (d, JPC = 16 Hz, CH2), 31.8 (s, CH2), 31.2 (s, p-C(CH3)3), 27.5 (s, CH2), 22.6 (s, CH2), 18.2 (d, 2JPC = 7 Hz, P=C−CH3), 14.2 (s, CH3). FD-MS [M+] 800.4 (100), 801.3 (45), 802.4 (40), 803.4(15). HRMS (FD+) calcd for C40H57PAuCl, 800.3552, found 800.3572. 2.4.13 Preparation of [2.7(AuCl)2] To a pale-yellow solution of PI (204 mg, 0.62 mmol) in THF (10 mL) was added n-BuLi (193 μL, 0.31 mmol, 1.6 M in hexanes), forming a deep-red solution. Analysis of the reaction mixture by 31P NMR spectroscopy revealed six signals [δ = 226.5 (5%), 226.0 (5%), 230.0 (29%), 209.1 (3%), 75 −31.2 (36%) and −34.2 (23%)]. Iodomethane (20 μL, 0.32 mmol) was added and the red color dissipated in favor of pale-yellow. The 31P NMR spectrum was recorded to reveal five signals [δ = 234.3 (10%), 232.7 (10%), 231.9 (31%), −28.9 (14%) and −29.6 (43%)]. The volatiles were removed in vacuo and the product was dissolved in hexanes and filtered through a bed of Celite™ to afford a crude yellow oil. To a solution of the crude oil (113 mg, 0.15 mmol) in CH2Cl2 (3 mL) was added a solution of [Au(tht)Cl] (100 mg, 0.31 mmol) in CH2Cl2 (3 mL) forming an orange solution. Analysis of the reaction mixture by 31P NMR spectroscopy revealed two broad signals [δ = 184.7 (31%) and 34.7 (69%)]. The reaction mixture was filtered through Celite™ and the volatiles were removed in vacuo to afford an off-white solid. The solid was washed with pentane at −35 °C to afford the product [2.7(AuCl)2] which was contaminated with [Au(2.3)Cl] (ca. 30% by integration of the 1H NMR spectrum). Yield = 100 mg, 54%. Some NMR spectroscopic assignments were made using 1H,13C-HSQC and HMBC NMR experiments. [2.7A(AuCl)2]: 31P{1H} NMR (162 MHz, CDCl3, −50°C) δ 182.0 (s), 32.8 (s); 1H NMR (CDCl3, 400 MHz, −50 °C) δ 7.49 (br s, 2H, Mes*H), 7.29 (br s, 2H, Mes*H), 6.93 (dt, 1H, 3JPH = 23 Hz, 3JHH = 7 Hz, P−C=CH), 3.50 (dt, 1H, 3JPH = 24 Hz, 3JHH = 7 Hz, P=C−CH), 2.26 (br m, 2H, C=CH−CH2), 1.86 (d, 3H, 2JPH = 8 Hz, P−CH3), 1.65 (s, 9H, o-C(CH3)3), 1.56 (s, 9H, o-C(CH3)3), 1.40 (s, 9H, o-C(CH3)3), 1.38 (d, 3H, 3JPH = 29 Hz, P=C−CH3), 1.11 (d, 3H, 3JPH = 10 Hz, P−C−CH3); signals for: o-C(CH3)3, 2 × p-C(CH3)3 and CH2−CH2−CH2−CH2−CH3 were not able to be assigned. 13C{1H} NMR (CDCl3, 400 MHz, 25 °C) δ 178.5 (d, 1JPC = 92 Hz, P=C), 141.5 (d, 2JPC = 26 Hz, P−C=CH), 137.8 (d, 1JPC = 70 Hz, P−C=CH), 123.6 (m-Mes*), 48.6 (d, 2JPC = 21 Hz, P=C−CH), 40.0 (o-C(CH3)3), 39.1 (o-C(CH3)3), 38.7 (o-C(CH3)3), 34.0 (3 × o-C(CH3)3), 33.0 (C=CH−CH2), 23.3 (P−CH3), 18.1 (P=C−CH3), 14.0 (d, 2JPC = 8 Hz, P−C−CH3); 76 signals for: p-Mes*, o-Mes*, ipso-Mes*, o-C(CH3)3, o-C(CH3)3, 2 × p-C(CH3)3, 2 × p-C(CH3)3 and CH2−CH2−CH2−CH2−CH3 were not able to be assigned. [2.7B(AuCl)2]: 31P{1H} NMR (162 MHz, CDCl3, −50°C) δ 182.2 (s), 33.3 (s); 1H NMR (CDCl3, 400 MHz, −50 °C) δ 7.51 (br s, 2H, Mes*H), 7.00 (m, 1H, P−C=CH), 2.23 (m, 2H, C=CH−CH2), 1.77 (d, 3H, 2JPH = 8 Hz, P−CH3), 1.33 (d, 3H, 3JPH = 31 Hz, P=C−CH3), 1.05 (d, 3H, 3JPH = 10 Hz, >P−C−CH3); signals for: 4 × o-C(CH3)3, 2 × p-C(CH3)3, Mes*H, P=C−CH and CH2−CH2−CH2−CH2−CH3 were not able to be assigned. 13C{1H} NMR (CDCl3, 400 MHz, 25 °C) δ 179.7 (d, 1JPC = 79 Hz, P=C), 142.6 (P−C=CH), 136.5 (d, 1JPC = 66 Hz, P−C=CH), 123.6 (m-Mes*), 33.0 (C=CH−CH2), 23.2 (P−CH3), 18.1 (P=C−CH3), 14.0 (d, 2JPC = 8 Hz, P−C−CH3); signals for: p-Mes*, o-Mes*, ipso-Mes*, P=C−CH, 4 × o-C(CH3)3, 4 × o-C(CH3)3, 2 × p-C(CH3)3, 2 × p-C(CH3)3 and CH2−CH2−CH2−CH2−CH3 were not able to be assigned. 2.4.14 Preparation of 2.8 Magnesium turnings (0.50 g, 21 mmol) were added to a Schlenk flask and flame dried. Bromoethane (0.5 mL, 0.74 g, 7 mmol), THF (15 mL) and an iodine crystal were added, and the reaction mixture was heated to reflux for 30 min. A separate Schlenk flask was charged with Mes*P=C(Me)Br (500 mg, 1.3 mmol), [Pd(PPh3)4] (60 mg, 0.05 mmol) and THF (15 mL), forming an orange solution. The reaction flask was covered in foil to preclude light-induced E/Z-isomerization of the P=C bond. To this solution was added the Grignard solution via cannula to afford a dark-orange reaction mixture that was stirred for 10 min. Analysis of the reaction mixture by 31P NMR spectroscopy revealed a signal at 252.3 (17%) and 224.8 (83%) ppm. The volatiles were removed in vacuo to afford a dark-orange solid. The crude solid was eluted through a silica plug (3 × 10 cm, hexanes) and a yellow fraction was collected. The solvent was removed in vacuo 77 and the residual yellow solid was recrystallized from CH2Cl2/CH3CN (1:1) to afford colorless crystals. Yield = 197 mg, 45%. 31P NMR (CDCl3, 162 MHz, 25 °C) δ 223.3 (tq, 3JPH = 21 Hz, 3JPH = 14 Hz); 1H NMR (CDCl3, 400 MHz, 25 °C) δ 7.40 (s, 2H, Mes*H), 2.50 (dq, 2H, 3JPH = 21 Hz, 3JHH = 7 Hz, P=C(CH3)−CH2−CH3), 1.49 (s, 18H, o-C(CH3)3), 1.34 (s, 9H, p-C(CH3)3), 1.24 (d, 3H, 3JPH = 14 Hz, P=C(CH3)−CH2−CH3), 1.16 (td, 3H, 3JHH = 7 Hz, 4JPH = 1 Hz, P=C(CH3)−CH2−CH3); 13C{1H} NMR (CDCl3, 101 MHz, 25 °C) δ 187.7 (d, 1JPC = 41 Hz, P=C(CH3)−CH2−CH3), 153.7 (d, 2JPC = 1 Hz, o-Mes*), 149.5 (s, p-Mes*), 138.3 (d, 1JPC = 59 Hz, ipso-Mes*), 121.5 (s, m-Mes*), 38.2 (s, o-C(CH3)3), 35.1 (s, p-C(CH3)3), 34.8 (d, 2JPC = 42 Hz, P=C(CH3)−CH2−CH3), 32.6 (d, 3JPC = 7 Hz, o-C(CH3)3), 31.6 (s, p-C(CH3)3), 23.4 (d, 2JPC = 17 Hz, P=C(CH3)−CH2−CH3), 14.0 (d, 3JPC = 17 Hz, P=C(CH3)−CH2−CH3). Anal. Calcd for C22H37P: C, 79.47; H, 11.22. Found: C, 79.64; H, 11.35. 2.4.15 Preparation of [Au(2.8)Cl] A vial was charged with 2.8 (100 mg, 30 mmol), [Au(tht)Cl] (88 mg, 27 mmol) and CH2Cl2 (2 mL) to form an orange solution. Analysis of the reaction mixture by 31P NMR spectroscopy revealed two signals at 179.3 (br, 96%) and 217.4 (4%) ppm. The reaction mixture was filtered through Celite™ to remove dark insoluble material. The volatiles were removed in vacuo to afford a yellow solid. The solid was washed with hexanes (2 mL) at −35 °C and the supernatant was removed to yield an off-white solid. Yield = 145 mg, 94%. 31P NMR (CDCl3, 162 MHz, 25 °C) δ 177.5 (br s); 1H NMR (CDCl3, 400 MHz, 25 °C) δ 7.52 (d, 2H, 4JPH = 4 Hz, Mes*H), 2.76 (dq, 2H, 3JPH = 32 Hz, 3JHH = 7 Hz, P=C(CH3)−CH2−CH3), 1.59 (s, 18H, o-C(CH3)3), 1.37 (d, 3H, 3JPH = 29 Hz, P=C(CH3)−CH2−CH3), 1.33 (s, 9H, p-C(CH3)3), 1.15 (t, 3H, 3JHH = 7 Hz, P=C(CH3)−CH2−CH3); 13C{1H} NMR (CDCl3, 101 MHz, 25 78 °C) δ 180.8 (d, 1JPC = 71 Hz, P=C(CH3)−CH2−CH3), 156.1 (d, 2JPC = 2 Hz, o-Mes*), 154.0 (d, 4JPC = 3 Hz, p-Mes*), 124.4 (d, 1JPC = 31 Hz, ipso-Mes*), 123.2 (d, 3JPC = 9 Hz, m-Mes*), 38.9 (s, o-C(CH3)3), 35.4 (s, p-C(CH3)3), 33.9 (s, P=C(CH3)−CH2−CH3), 33.7 (d, 3JPC = 2 Hz, o-C(CH3)3), 31.2 (s, p-C(CH3)3), 22.1 (d, 2JPC = 7 Hz, P=C(CH3)−CH2−CH3), 13.2 (d, 3JPC = 19 Hz, P=C(CH3)−CH2−CH3). Anal. Calcd for C22H37PAuCl: C, 46.77; H, 6.60. Found: C, 46.67; H, 6.25. 2.4.16 General procedure for the anionic polymerization of PI THF was distilled over sodium benzophenone/ketyl and then stored over CaH2 overnight. The THF was then distilled into a dried flask and sealed with a Teflon™ stopcock and stored over activated molecular sieves (4 Å) for 24 h before use. 1-Phosphaisoprene (PI) was ground to a fine white powder and dried in vacuo at 40 °C for 4 h before use. 1H NMR spectroscopy was used to confirm purity. All glassware was soaked in TMSCl/toluene (1:10 v/v) overnight, rinsed three times with deionized water and then dried at 200 °C overnight before use. 2.4.17 Anionic polymerization of PI In a beaker in the glovebox, PI (1.00 g, 3.0 mmol) was dissolved in THF (6 mL) forming a pale-yellow solution that was rapidly stirred. To this solution was added n-BuLi (38 μL, 0.06 mmol, 1.6 M in hexanes) and the color immediately changed to deep-red. The reaction mixture was transferred to a flask that was sealed with a Teflon™ stopcock. An aliquot was removed, transferred to a J. Young NMR tube and monitored by 31P NMR spectroscopy until the signals assigned to PI (δ= 264.8 and 244.8) were fully consumed (4 h 30 min). Deoxygenated methanol (1 drop) was added and the deep-red color dissipated in favor of yellow. The volatiles were removed in vacuo and the residual yellow solid was dissolved in CH2Cl2 (5 mL) and precipitated into deoxygenated isopropanol (50 mL). Precipitation was repeated twice more to afford an off-white solid. Yield = 500 mg, 50%. 79 31P NMR (CDCl3, 162 MHz, 25 ⁰C) δ 237 (br, P=C), 226 (br, P=C), −13 (br, >P−C); 1H NMR (CDCl3, 400 MHz, 25 ⁰C) δ 7.54 (br, Mes*H of microstructure y), 7.45 (br, Mes*H of microstructure x) 5.38 (br, P−C=CH), 2.93 (br, P=C−CH), 2.41 (br, CH2 of microstructures x and y), 1.56 (br, o-C(CH3)3 of microstructures x and y), 1.42 (br, p-C(CH3)3 of microstructures x and y), 1.28 (br, P=C−CH3 of microstructure x and P−C−CH3 of microstructure y); 13C{1H} NMR (CDCl3, 101 MHz, 25 ⁰C) δ 187.6 (br, P=C), 159.3 (br, o-Mes* of microstructure y), 154.0 (br, o-Mes* of microstructure x), 149.3 (br, p-Mes* of microstructure x), 137.9 (br, ipso-Mes* of microstructure x), 132.0 (br, ipso-Mes* of microstructure y), 129.5 (br, P−C=CH), 127.0 (br, m-Mes* of microstructure y), 121.5 (br, m-Mes* of microstructure x), 45.9 (br, P=C−CH), 38.3 (br, o-C(CH3)3 of microstructures x and y), 35.1 (br, p-C(CH3)3 of microstructures x and y), 33.3 (br, o-C(CH3)3 of microstructures x and y), 31.6 (br, p-C(CH3)3 of microstructures x and y), 20.2 (br, P=C−CH3 of microstructure x and P−C−CH3 of microstructure y). GPC: Mn = 15,000 g mol−1, Đ = 1.02, dn/dc = 0.169 mL g−1. Satisfactory elemental analysis could not be obtained: Anal. Calcd for C22H35P: C, 79.97; H, 10.70. Found: C, 78.61; H, 10.04. 2.4.18 Preparation of PPI·[AuCl]0.96n To a solution of [Au(tht)Cl] (290 mg, 0.90 mmol) in CH2Cl2 (3 mL) was added a solution of poly(1-phosphaisoprene) PPI (299 mg, Mn = 33,600 g mol-1, Đ = 1.18) in CH2Cl2 (3 mL), forming an orange solution. Analysis of the reaction mixture by 31P NMR spectroscopy revealed three broad signals [δ = 239 (10%), 186 (85%) and 42 (5%)]. The volatiles were removed in vacuo and the residual orange solid was dissolved in CH2Cl2 (1.5 mL) and precipitated into deoxygenated methanol (15 mL). The precipitation was repeated once more to afford an off-white solid. Yield = 251 mg, 49%. 80 31P NMR (CDCl3, 162 MHz, 25 ⁰C) δ 237 (br, P=C), 187 (br, Au−P=C), 52 to −9 (br, >P(Au)−C); 1H NMR (CDCl3, 400 MHz, 25 ⁰C) δ 7.55 (br, Mes*H), 6.25 (br, P−C=CH), 2.92 (br, CH and CH2), 1.69 (br, o-C(CH3)3), 1.35 (br, p-C(CH3)3 and CH3); 13C{1H} NMR (CDCl3, 101 MHz, 25 ⁰C) δ 179.4 (br, P=C), 154.9 (br, o- and p-Mes*), 123.9 (br, ipso- and m-Mes*), 42.5 (br, CH and CH2), 39.2 (br, o-C(CH3)3), 35.5 (br, p-C(CH3)3), 34.9 (br, o-C(CH3)3), 31.2 (br, p-C(CH3)3), 22.0 (br, CH3). GPC: Mn = 40,200 g mol−1; Ð = 1.03; dn/dc = 0.17 mL g−1; mass recovery = 21%. Satisfactory elemental analysis could not be obtained: Anal. Calcd for C22H35PAu0.96Cl0.96: C, 47.73; H, 6.37. Found: C, 48.85; H, 6.37. 81 Chapter 3: Palladium(II) Complexes of 1-Phosphaisoprene Molecules and Polymers: Reversible Cross-Linking of a Phosphorus-Containing Polymer For an overview of the metal coordination chemistry of P=C-containing macromolecules, the reader is directed to chapter 1. To further investigate the coordination chemistry of PPI, we hypothesized that the addition of a metal center with two vacant coordination sites would result in the formation of a cross-linked network (Chart 3.1: This work). These cross-linked networks would be of great interest for use in functional materials. There has been growing interest in the development of self-healing polymers, where the healing takes place through the facile cleavage and reforming of the cross-linking groups between polymer chains.191-198 Recently, linear P-containing polymers have been the subject of novel cross-linking studies using covalent linkages or frustrated Lewis pair strategies involving nonmetals.199-203, 204 Despite the potential advantages of exploiting labile dative covalent bonds to cross-link polymeric ligands with transition metals, this strategy has been limited primarily to N- and O-based donors.191-198 Although P-containing macromolecules have been utilized as ligand supports for metal-catalyzed organic transformations (Chart 3.1: Intramolecular),134, 135, 205-209 the use of transition metals to deliberately link macromolecular P-ligands is rare and remains limited to phosphine ditelechelic poly(tetrahydrofuran) (Chart 3.1: Intermolecular).210-213 Versions of sections of this chapter have been published: Walsgrove, H. T. H.; Chowdhury, K. K.; Dabringhaus, P.; Patrick, B. O.; Gates, D. P. Eur. J. Inorg. Chem. 2023, manuscript accepted; doi: 10.1002/ejic.202300182 82 Chart 3.1: Schematic illustrating the existing binding types for phosphorus polymers toward transition metals and the simple cross-linking described herein. Chapter 3 reports the formation of macromolecular complexes of poly(1-phosphaisoprene) (PPI) with PdII including the reversible formation of a cross-linked polymer gel by taking advantage of the lability of the dative P-metal bonds. To model the coordination chemistry of PPI, we have investigated the ligand behavior of monomer PI with [Pd(η3-C3H5)(μ-Cl)]2 and [Pd(cod)Cl2] (COD = 1,5-cyclooctadiene). 3.1 Results and Discussion 3.1.1 Coordination of poly(1-phosphaisoprene) (PPI) to PdII To further explore the coordination chemistry of polymer PPI, it was decided to target reactions with PdII salts that can accept either one or two P-ligands. To this end, PI was polymerized with 83 n-BuLi (2 mol%) in THF solution at room temperature following a similar procedure that reported in chapter 2. PPI was isolated in 75% yield after precipitation of a CH2Cl2 solution into deoxygenated 2-propanol. Analysis of the polymer by gel permeation chromatography equipped with a multi-angle light scattering detector and viscometer (GPC-MALS-V) indicated the absolute number average molecular weight (Mn) was 21,800 g mol–1 (Ð = 1.02) which was larger than that predicted from the monomer-to-initiator ratio [Mn (calcd) = 16,583 g mol–1]. To investigate the coordination chemistry of PPI with PdII, PPI was treated with [Pd(η3-C3H5)(µ-Cl)]2 (0.5 equiv, i.e. Pd:P = 1.0) in CH2Cl2 solution and the reaction was monitored by 31P NMR spectroscopy (Trial 1 in Scheme 3.1). After 24 h, two new signals were observed at 197 (27%) and 30 (2%) ppm, alongside the signals previously assigned to PPI [δ = 239 (67%) and −15 (5%)]. In a separate experiment, polymer PPI was treated with [Pd(cod)Cl2] (Pd:P = 0.5) in CH2Cl2 solution (Trial 1' in Scheme 3.1). After 24 h, the 31P NMR spectrum of the reaction mixture showed two new signals at 185 (26%) and 43 ppm (2%) in addition to signals assigned to remaining uncoordinated P atoms in PPI [δ = 239 (68%) and −15 (4%)]. Both observations suggest that ~30% of the P atoms in PPI were bound to PdII and no further coordination was observed even when the reaction mixtures were heated to reflux for 24 h. Scheme 3.1: Synthesis of PPI·[Pd(η3-C3H5)Cl]an and PPI·[PdCl2]bn from the reaction of PPI with [Pd(η3-C3H5)(µ-Cl)]2 and [Pd(cod)Cl2], respectively. 84 In the case of the reaction of PPI with [Pd(η3-C3H5)(µ-Cl)]2, the crude solid product was soluble in common organic solvents (alcohols, ethers, alkanes) which precluded purification by precipitation methods. We reasoned that reactions with lower stoichiometries of PdII (Trial 2 and 2' in Scheme 3.1) would facilitate purification by reducing PdII impurities in the crude polymer in addition to being more atom economical. Thus, a colorless CH2Cl2 solution of PPI was mixed with a yellow CH2Cl2 solution of [Pd(η3-C3H5)(µ-Cl)]2 (Pd:P = 0.30). The initially yellow reaction mixture gradually changed to orange over the first 30 min. Analogous to that described above for the 1:1 reaction, 31P NMR spectroscopic analysis of the present reaction mixture revealed similar differences between the spectra before and after treatment with PdII [Figure 3.1(a) and (b), respectively]. These data are consistent with a macromolecular coordination complex PPI·[Pd(η3-C3H5)Cl]xn where 18% of the P=C and 3% of the phosphine groups in PPI are bound to PdII. Overall, approximately 21% (i.e. 18% + 3%) of the P atoms in PPI are bound to PdII, giving a tentative formulation as PPI·[Pd(η3-C3H5)Cl]0.21n. Based on the Pd:P stoichiometry, a maximum of 30% of the P atoms in PPI could be coordinated by PdII. Due to the high solubility in common organic solvents, we were also unable to purify polymer PPI·[Pd(η3-C3H5)Cl]0.21n by precipitation. Therefore, crude PPI·[Pd(η3-C3H5)Cl]0.21n was dissolved in hexanes and filtered through a bed of Celite™ to remove dark insoluble material. Following the removal of the volatiles in vacuo, an orange solid was isolated in 87% yield. 85 Figure 3.1: 31P NMR spectra (CH2Cl2, 162 MHz, 25 ⁰C) of: (a) PPI; (b) reaction mixture of PPI and [Pd(η3-C3H5)(µ-Cl)]2 (Pd:P ratio = 0.30) after 24 h to afford PPI·[Pd(η3-C3H5)Cl]0.21n; (c) reaction mixture of PPI and [Pd(cod)Cl2] (Pd:P ratio = 0.15) after 24 h to afford PPI·[PdCl2]0.09n. The isolated solid was further characterized by 1H and 13C{1H} NMR spectroscopy in CDCl3 solution. The spectra revealed broad resonances consistent with the formulation of PPI·[Pd(η3-C3H5)Cl]0.21n. Specifically, resonances were observed in the 1H NMR spectrum ( = 5.35, 4.63, 3.57 and 2.80) that were tentatively assigned to the η3-C3H5 group. Due to their breadth and partial overlap with unreacted [Pd(η3-C3H5)(µ-Cl)]2, these signals could not be integrated. The resonances assigned to the aliphatic and aromatic region differed slightly from those for 86 uncoordinated PPI. For example, the signals in the 1H NMR spectrum assigned to the Mes* substituent of PPI·[Pd(η3-C3H5)Cl]0.21n [δ = 7.35 (br, Mes*H), 1.45 (br, o-C(CH3)3) and 1.33 (br, p-C(CH3)3] are slightly shifted from those for uncoordinated PPI [δ = 7.43 (br, Mes*H), 1.53 (br, o-C(CH3)3) and 1.41 (br, p-C(CH3)3)]. A broad signal at 116.1 ppm in the 13C{1H} NMR spectrum was assigned to the η3-CH(CH2)2 substituents in PPI·[Pd(η3-C3H5)Cl]0.21n by comparison to molecular model [Pd(PI)(η3-C3H5)Cl] (vide infra). In an effort to obtain molecular weight data, macromolecular complex PPI·[Pd(η3-C3H5)Cl]0.21n was analyzed by gel permeation chromatography (GPC). Thus, a dilute (0.61 mg mL–1) solution in THF was filtered through a 0.22 µm PTFE filter and injected onto the Styragel™ size exclusion columns. Unfortunately, the sample did not fully elute with an estimated mass recovery of ca. 40%. No further GPC analyses of these PdII-containing polymers could be performed due to the potential to damage the instrument. However, using the dn/dc value for PPI (0.17), an estimation for molecular weight and dispersity was obtained (Mn = 26,000 g mol−1, Ð = 1.02). In a separate experiment, PPI was dissolved in CH2Cl2 and mixed with a yellow solution of [Pd(cod)Cl2] (Pd:P = 0.15) in CH2Cl2. The reaction mixture was stirred for 24 h at room temperature over which time it became dark-red. The 31P NMR spectrum was recorded and revealed two new broad resonances at 185 ppm (17%) and 43 ppm (1%) in addition to signals assigned to uncoordinated PPI ( = 239, 75%; –15, 7%) [Figure 3.1(c)]. Analogous to those described for the Pd:P = 0.5:1 experiment, these new signals are consistent with the formation of complex PPI·[PdCl2]n in which ca. 18% of the P atoms are bound to PdII through both the phosphaalkene and phosphine units. Presuming that each PdII is bound by two P ligands, a formulation of the product as PPI·[PdCl2]0.09n may be proposed. The volatiles were removed in 87 vacuo to afford a dark-red solid. This solid was purified by precipitation of a CH2Cl2 solution into methanol to afford PPI·[PdCl2]0.09n as an orange solid (yield = 52%). 3.1.2 Molecular models for macromolecular PdII-complexes Given the challenges in characterizing the coordination complexes of polymer PPI, monomer 1-phosphaisoprene (PI) was employed as a molecular model ligand. Thus, a pale-yellow solution of PI in CH2Cl2 was treated with a yellow solution of [Pd(η3-C3H5)(μ-Cl)]2 (0.43 equiv) in CH2Cl2 (Scheme 3.2). After 30 min, the reaction mixture was analyzed by 31P NMR spectroscopy to reveal a new singlet resonance at 214.9 ppm (83%) assigned to complex [Pd(PI)(η3-C3H5)Cl] in addition to a signal at 264.3 ppm (17%) assigned to PI. Although there is no reported 31P NMR chemical shift for a phosphaalkene−[Pd(η3-C3H5)Cl] complex, the upfield shift for [Pd(PI)(η3-C3H5)Cl] compared to PI ( = –49.4) is similar to those found for [{Mes*P=CH(o-(MeO)C6H4)}Pd(η3-C3H5)OTf] ( = –55)214 and related PdII complexes containing chelating phosphaalkenes (range:  = –69.7 to –11.7).71, 72, 215, 216 Importantly, the signal assigned to the phosphaalkene-PdII substituents in polymer PPI·[Pd(η3-C3H5)Cl0.21n was similarly shifted upfield from that of uncoordinated PPI (Δδ = –44). Scheme 3.2: Preparation of complex [Pd(PI)(η3-C3H5)Cl]. The crude product was isolated as a yellow solid and washed with cold hexanes (–35 °C) to remove residual PI. Recrystallization of the solid from a saturated CH2Cl2 solution at –35 °C afforded yellow crystals suitable for X-ray crystallographic analysis. The molecular structure is 88 shown in Figure 3.2 and confirms the identity of the product as the expected P-bound PdII complex [Pd(PI)(η3-C3H5)Cl]. Isolated complex [Pd(PI)(η3-C3H5)Cl] was further characterized by 1H, 13C and 31P NMR spectroscopy and elemental analysis. Detailed assignments are given in the Experimental Section. The data are mostly unremarkable, although the 13C{1H} NMR spectrum revealed that the signal assigned to the P=C carbon in [Pd(PI)(η3-C3H5)Cl] ( = 173.8) is upfield shifted with respect to the analogous signal for PI (Δδ = −5.8). Figure 3.2: Molecular structure of [Pd(PI)(η3-C3H5)Cl]·CH2Cl2. Thermal ellipsoids are presented at 50% probability level. Hydrogen atoms and solvent of crystallization are omitted for clarity. The room temperature 1H NMR spectrum of complex [Pd(PI)(η3-C3H5)Cl] showed five broad signals assigned to the protons of the η3-C3H5 ligand, however, the coupling constants could not be measured. The sample was cooled to –30 °C and the signals sharpened. Broadening of the allyl resonances at room temperature has been observed previously for [(η3-C3H5)Pd(Pi-Pr3)Cl] and has been attributed to interconversion of the localized σ-π and π-σ bonding modes of the allyl 89 ligand to PdII.217 The chemicals shifts of these signals for [Pd(PI)(η3-C3H5)Cl] ( = 5.55, 4.73, 3.87, 3.74, 2.97) are similar to those of PPI·[Pd(η3-C3H5)Cl]0.21n ( = 5.35, 4.63, 3.57 and 2.80), although the signals were not fully resolved in the polymer. A search of the Cambridge Crystallographic Database found no examples of phosphaalkene-Pd(η3-C3H5)Cl complexes. However, the P=C bond length in [Pd(PI)(η3-C3H5)Cl] [1.693(2) Å] is similar to that of PI [1.687(5) Å].81 For comparison, the P=C bond length in the related triflate [{Mes*P=CH(o-(MeO)C6H4)}Pd(η3-C3H5)OTf] was 1.661(2) Å.214 The P=C−C=C group in [Pd(PI)(η3-C3H5)Cl] shows only minimal distortion from planarity [P1–C1–C2–C3 = 177.35(15)°] when compared to PI [P1–C1–C2–C3 = 180.0(4)°].81 The best plane of the P=C–C=C group is also twisted with respect to the PdII square plane [43.53(12)°]. Given the success in modeling PPI·[Pd(η3-C3H5)Cl]0.21n with molecular [Pd(PI)(η3-C3H5)Cl], our attention turned to synthesizing a model for PPI·[PdCl2]0.09n. To this end, a solution of PI in CH2Cl2 was added to a stirred solution of [Pd(cod)Cl2] (0.5 equiv) in CH2Cl2 (Scheme 3.3). After 48 h, the 31P NMR spectrum of the reaction mixture showed that the signal assigned to PI (δ = 264.3) was no longer present and in its place were two new signals (δ = 37.1 and 36.5; 46:54 ratio). In contrast to the reaction of PI with [Pd(η3-C3H5)(μ-Cl)]2, the large upfield shift in the signals observed for the present reaction (Δδ = –227.2, –227.8 respectively) were inconsistent with end-on binding through the P-lone pair in PI. In addition, this upfield shift was significantly different from that observed for PPI upon formation of PPI·[PdCl2]0.09n (Δδ = −56) suggesting a different type of complex. After work-up, yellow single crystals of the model system were isolated from a saturated CH2Cl2 solution at −35 °C (yield = 37%). A crystal was selected for X-ray crystallographic analysis which revealed that the product was racemic phosphine-PdII complex 90 meso-trans-3.1 involving C–H activation of the t-Bu substituent to give phosphine ligand PI'. The molecular structure is shown in Figure 3.3. Scheme 3.3: Formation of [Pd(PI')2Cl2] (3.1) from PI and [Pd(cod)Cl2]. 91 Figure 3.3: Molecular structure of meso-trans-3.1·(2  CH2Cl2) [P1(R),P2(S) isomer is shown]. Thermal ellipsoids are presented at 50% probability level. Hydrogen atoms and solvents of crystallization are omitted for clarity. The crystals of meso-trans-3.1 were further characterized by 31P, 1H and 13C{1H} NMR spectroscopy, including one- and two-dimensional experiments to facilitate assignments. The 31P NMR spectrum of the crystals recorded immediately after dissolution in CDCl3 showed a singlet resonance at 36.4 ppm, assigned to meso-trans-3.1 [Figure 3.4(a)]. After 3 d in solution at room temperature, the 31P NMR spectrum of the same solution showed singlet resonances at 36.4 and 36.9 ppm in a 55:45 ratio, respectively [Figure 3.4(b)]. These observations are consistent with an isomeric mixture of meso-trans-3.1 and rac-trans-3.1 resulting from phosphine ligand exchange and this conclusion was further confirmed by 1H and 13C{1H} NMR analysis to assign the resonances of both species. An analogous ligand exchange is reported in chapter 4. The ready 92 ligand scrambling in 3.1 illustrates the potential of using labile dative covalent bonds to reversibly cross-link polymer PPI. Figure 3.4: 31P NMR spectra (CDCl3, 162 MHz, 25 °C) of: a) a solution of the crystals of meso-trans-3.1 recorded immediately after dissolution; b) the same solution after 3 d at room temperature. The molecular structure of meso-trans-3.1 is typical of symmetrically substituted trans-diphosphine PdII square planar complexes. The P−Pd bond lengths [P1−Pd1 = 2.3279(10) and P2−Pd1 = 2.3306(11) Å] in meso-trans-3.1 are similar to that of [{Mes*P=CH(o-(MeO)C6H4)}Pd(η3-C3H5)OTf] [P−Pd = 2.3344(7) Å] and are in the range found for related trans-configured [(R3P)2PdCl2] complexes [R = Ph,218 o-Tolyl,219 m-Tolyl,220 Cy,221 and Et;222 range = 2.186(2) to 2.3639(9) Å]. The P1−C1 and P2−C9 bond lengths [1.815(5) and 1.821(5) Å, 93 respectively] are in the range expected for a P−C single bond.164 The C1−C2 and C9−C10 bond lengths [1.337(7) and 1.327(6) Å, respectively] are as expected for a C=C bond.174 Furthermore, analysis of the C2−C3 and C10−C11 bond lengths [1.501(7) and 1.506(7) Å, respectively] indicate the presence of a single bond in this position. This is consistent with the formulation of the ligand as alkenyl phosphine PI'. 3.1.3 Mechanistic investigations of the C−H activation To ascertain the intermediacy of P=C complex, [Pd(PI)2Cl2] (API), in the reaction of PI and [Pd(cod)Cl2], the reaction progress was carefully monitored by NMR spectroscopy. Thus, a solution of PI in CD2Cl2 was added to a solution of [Pd(cod)Cl2] (0.5 equiv) in CD2Cl2 and the reaction mixture was transferred to an NMR tube. Selected 31P NMR spectra are shown in Figure 3.5. After 10 min, the 31P NMR spectrum of the red reaction mixture was recorded. In addition to a singlet resonance at 264.3 ppm, assigned to unreacted PI, a singlet resonance was observed at 197.1 ppm (API) along with a set of strongly coupled doublets at 212.6 and 41.7 ppm (2JPP = 614 Hz; BPI). Integration of the spectrum gave approximate ratios of the three species as PI (49%), API (47%) and BPI (4%). 94 Figure 3.5: 31P NMR spectra (CD2Cl2, 162 MHz, 25 ⁰C) showing the progress of reaction between PI and [Pd(cod)Cl2] (0.5 equiv) at room temperature. API = [Pd(PI)2Cl2], BPI = trans-[Pd(PI)(PI')Cl2]. A tentative formulation of [Pd(PI)2Cl2] for intermediate API was obtained by analyzing the 1H NMR spectrum recorded immediately following the 31P NMR spectrum (ca. 12 min after mixing the reagents). The spectrum displayed resonances 7.87 (ddt, 1H, 3Jtrans = 17 Hz, 3Jcis = 11 Hz, JPH = 8 Hz), 5.41 (dt, 1H, 3Jtrans = 17 Hz, JPH = 5 Hz) and 5.31 (dt, 1H, 3Jcis = 11 Hz, JPH = 3 Hz) ppm that were correlated by 1H,31P-HMBC NMR spectroscopy to the signal at 197.1 ppm. Integration of these signals, assigned to P=C−CH=CH2 substituents of API, against the analogous resonances assigned to PI suggested a 44:56 ratio of PI to API. This ratio is similar to 49:47 95 estimated by 31P NMR spectroscopy. In addition, the ratio of [Pd(cod)Cl2] to COD was estimated to be 46:54 from the integrated ratio of signals assigned to free COD [δ = 5.56 (s), 2.36 (s)] to those of COD in [Pd(cod)Cl2] [δ = 6.26 (m), 2.89 (m), 2.55 (m)] in the 1H NMR spectrum. Given these data, the initial stoichiometry of PI and [Pd(cod)Cl2] of 2:1 and the fact that COD takes up two binding sites on PdII, there must be a 2:1 ratio of P:Pd in API. Thus, the tentative formulation of [Pd(PI)2Cl2] was supported for intermediate API. For the next 21 d, the reaction progress was monitored by NMR spectroscopy over which time the color slowly changed from red to pale orange. In contrast, the reaction from which 3.1 was initially isolated was conducted in a vial with a stirbar in the glovebox and took 48 h to reach completion at the same concentration as the reaction in the NMR tube ([PI] = 0.12 M; [Pd(cod)Cl2] = 0.06 M). Both reaction rates were reproducible. Hypothesizing that either the stirbar, glass surface or impurities were catalyzing the reaction in the vial, four repetitions of the reaction were performed at identical concentrations to the original reactions: one in a vial with no stir bar, and three in vials that were soaked overnight in either 1 M TMSCl, HCl or NaOH in ethanol, before rinsing thoroughly and drying. In each case, after 48 h the 31P NMR spectra showed only two signals at 36.5 and 37.1 ppm, consistent with our first reaction in the vial. Unfortunately, no conclusion can be made about the reasons for the slower reaction rate in the NMR tube than the vial. After 21 d, product 3.1 was isolated in pure form after recrystallization from CH2Cl2 at −35 °C. It remained to confirm the identity of intermediate BPI, tentatively formulated as [Pd(PI)(PI')Cl2], which displayed two sets of doublet resonances with a large coupling constant in its 31P NMR spectrum (δ = 212.6, 41.7; 2JPP = 614 Hz). Analysis of the 1H,31P-HMBC NMR spectrum after 200 min permitted the elucidation of key signals assigned to the PI and PI' ligands 96 in BPI. In particular, the doublet centered at 212.6 ppm in the 31P NMR spectrum showed correlations to three signals in the 1H NMR spectrum at 7.91, 5.34 and 5.21 ppm. These signals are similar to, and overlap with, those assigned to the vinyl group in PI and API. Thus, they were assigned to the P=C−CH=CH2 protons of ligand PI in BPI. Unfortunately, the overlap of these signals with those of free PI and API precluded determination of multiplicity and coupling constants. The 1H,31P-HMBC NMR spectrum further revealed that the doublet resonance at 41.7 ppm in the 31P NMR spectrum showed a correlation to a proton resonance at 5.61 (1H, dq, 3JPH = 21 Hz, 3JHH = 7 Hz) which was assigned to the P–C(CH3)=CH−CH3 group by analogy to that described above for ligand PI' in meso-trans-3.1 [δ = 5.45 (2H, dq, 3JPH = 15, 3JHH = 8 Hz)]. Additional correlations were observed to proton resonances at 3.16 (1H, dd, 2JHH = 14 Hz, 2JPH = 7 Hz) and 2.26 ppm (1H, dd, 2JHH = 14 Hz, 2JPH = 3 Hz). These signals were assigned to the diastereotopic P–CH2 group of the benzophospholane ring. For comparison, the analogous signals assigned to the P–CH2 in meso-trans-3.1 were observed as coupled doublets at 3.19 and 2.13 ppm (2JHH = 14 Hz). Thus, we conclude that intermediate BPI contains both phosphaalkene and phosphine substituents and may be formulated as [Pd(PI)(PI')Cl2]. The intramolecular cyclization of Mes*−P=C substituents to furnish a benzophospholane has previously been observed upon coordination of these species to transition metals69, 223-232 or main group Lewis acids.233-235 In these cases, the end result is that the P=C bond inserts into a C–H bond of an ortho-t-Bu group of the Mes* substituent. Of particular interest, one study reported the C–H activation of a Mes* substituted phosphaalkene at group 10 metal centers.228 Specifically, treatment of a Mes*P=C(H)Ph with [Ni(cod)2] afforded the uncoordinated 1-P-benzylbenzophospholane. Based on experimental and in silico studies, the authors invoke an η4-97 complex involving the P=C−C=C substituent (the C=C comes from the Ph group) as a key intermediate. Given that we do not observe an analogous C−H activation of polymer PPI·[PdCl2]0.09n, even after 60 d in CDCl3 solution [0.23 M in P], we decided to assess the possible role of 4-complexation of the P=C−C=C backbone of PI in this process by targeting Mes*P=CH2 (3.2) as a more suitable model for PPI. Thus, a yellow solution of 3.2 (1 equiv) was added to a yellow solution of [Pd(cod)Cl2] (0.5 equiv) in CD2Cl2 to afford an orange solution (Scheme 3.4). The reaction progress was monitored by 31P NMR spectroscopy and after 10 min the doublet of doublets assigned to 3.2 [δ = 289.1 (dd, 2JPH = 33 Hz, 2JPH = 28 Hz)] had been replaced by a broad resonance at 230.3 ppm, tentatively assigned to complex A3.2 {i.e. [Pd(3.2)2Cl2], Figure 3.6}. Further reaction monitoring showed that after 8 d, a doublet-of-doublets was observed at 242.9 ppm (2JPP = 644 Hz, 2JPH = 33 Hz) along with a broad doublet at 22.3 ppm (2JPP = 644 Hz). These signals were very similar to those described above for intermediate BPI and were assigned to B3.2, [Pd(3.2)(3.2')Cl2], the large coupling constant being suggestive of a trans-configured isomer. After 18 d, the reaction was complete and the signals assigned to both A3.2 and B3.2 had been replaced by resonances at 15.8 and 15.4 ppm in a 3:2 ratio, assigned to 3.3. After work-up, a yellow powder of complex 3.3 was isolated in 50% yield. 98 Scheme 3.4: Formation of 3.3 from 3.2 and [Pd(cod)Cl2]. 99 Figure 3.6: 31P NMR spectra (CD2Cl2, 162 MHz, 25 ⁰C) showing the progress of reaction between 3.2 and [Pd(cod)Cl2] (0.5 equiv) at room temperature. A3.2 = [Pd(3.2)2Cl2], B3.2 = trans-[Pd(3.2)(3.2')Cl2]. Importantly, intermediate A3.2 is longer-lived than intermediate API. This result shows that, although η4-complexation is not necessary for C−H activation to occur, the presence of a π-conjugated C=C group increases the C−H activation rate. Overall, these mechanistic studies of the coordination reactions of molecular models PI and 3.2 with [Pd(cod)Cl2] support the formation of macromolecular complex PPI·[PdCl2]bn and provide some rationale for the absence of C−H activation for the polymeric PdII-complex even after 60 d in solution. 100 3.1.4 Reversible gelation of poly(1-phosphaisoprene) (PPI) with [Pd(cod)Cl2] During our attempt to observe C−H activation with a 0.23 M in P solution of PPI·[PdCl2]0.09n, we noted the formation of a precipitate that we tentatively attributed to cross-linked polymer. To further evaluate the possibility of using this potentially cross-linked PPI in materials applications (Scheme 3.5), a highly concentrated solution of PPI (1.31 M in P) was prepared in CH2Cl2 and solid [Pd(cod)Cl2] (0.05 P equiv, Pd:P = 0.05) was added. We reasoned that the higher concentration would favor inter-chain binding of P=C substituents of PPI to PdII rather than intra-chain binding (i.e. chelation) to PdII. The reaction mixture was stirred for 30 min and then stopped for 30 min at room temperature. During this period, the color changed from colorless to orange and the solution became more viscous [Figure 3.7(a) vs. (b)]. The process was repeated for the addition of a second portion of [Pd(cod)Cl2] (0.05 P equiv, overall Pd:P = 0.10) and the color was more intense and the solution more viscous than before. A third portion of solid [Pd(cod)Cl2] (0.05 P equiv, overall Pd:P = 0.15) was added and the mixture was allowed to stand for 12 h at room temperature. Remarkably, the solution formed a gel. This is evident from the photographs showing that the reaction mixture held its shape upon inversion of the vial [Figure 3.7(e) and inset]. These observations, combined with the NMR spectroscopic data (vide supra and infra), are consistent with PPI being cross-linked via binding of the phosphaalkene and/or phosphine groups within polymer PPI to PdII. Further evidence that the cross-linking of PPI causes gelation comes from an identical treatment of PPI with [Pd(η3-C3H5)(µ-Cl)]2 which can only accept one P-ligand. No gelation was observed (see Figure C.29, Appendix C). 101 Scheme 3.5: Reversible cross-linking of PPI using [Pd(cod)Cl2] and PMe3. Figure 3.7: Photographs showing the cross-linking process for PPI in CH2Cl2 containing: (a) a solution of PPI; (b) a solution of PPI with [Pd(cod)Cl2] (Pd:P = 0.05) after 1 h; (c) a solution of PPI with [Pd(cod)Cl2] (Pd:P = 0.10) after 1 h; (d) a solution of PPI with [Pd(cod)Cl2] (Pd:P = 0.15) after 1 h; (e) a solution of PPI with [Pd(cod)Cl2] (Pd:P = 0.15) after 12 h. Inset: an inverted solution of PPI with [Pd(cod)Cl2] (Pd:P = 0.15) after 12 h showing gelation; (f) a solution of PPI with [Pd(cod)Cl2] (Pd:P = 0.15) immediately after addition of PMe3 (1 drop). The cross-linking of PPI using ligand-to-metal bonds is exciting given the potential lability of these cross-links. We reasoned that this may result in a reversible process. This potential 102 reversibility was evaluated by attempting to replace the macromolecular complexed P atoms with a molecular phosphine. To test this hypothesis, PMe3 (1 drop, ca. 1 P equiv) was added to the vial containing the cross-linked gel and an immediate decrease in viscosity was observed [Figure 3.7(f)]. Upon inversion of the vial, the deep-red-orange solution flowed again. The solution was transferred to an NMR tube and analyzed by 31P NMR spectroscopy [Figure 3.8(a)]. The spectrum revealed new signals at –0.6 and –10.8 ppm assigned to cis/trans-[Pd(PMe3)2Cl2].236 Interestingly, signals assigned to PPI·[PdCl2]bn (δ = 239, 185, 43 and −15) were also still present in the 31P NMR spectrum. This result suggests that full de-coordination of PPI from PdII is not required to break down the gel. 103 Figure 3.8: 31P NMR spectra (162 MHz, 25⁰C) of (a) a CH2Cl2 solution PPI (1.31 M in P) with [Pd(cod)Cl2] (Pd:P = 0.15) immediately after addition of PMe3 (1 drop, ca. 1 P equiv); (b) a CH2Cl2 solution of PPI (1.31 M in P) with [Pd(cod)Cl2] (Pd:P = 0.15) after addition of PMe3 (6 drops). To test whether uncoordinated PPI can be re-generated from PPI·[PdCl2]bn, five more drops of PMe3 were added (ca. 5 P equiv, 6 P equiv total) and the solution became yellow with a dark-red precipitate. Analysis of the solution by 31P NMR spectroscopy revealed only signals at 239 and −15 ppm assigned to uncoordinated PPI and signals at −8.0 assigned to [Pd(PMe3)xCl]+ and 37.2 which was assigned to Me3P=O237 [Figure 3.8(b)]. The absence of signals assignable to coordinated PPI·[PdCl2]bn suggests that the binding to PdII is fully reversible. After addition of 6 104 more drops of PMe3 (12 total), the chemical shift of the 31P resonance assigned to [Pd(PMe3)xCl]+ was −27.0 ppm. Such dynamic behavior of the 31P NMR signal of these complexes has been observed previously, and was attributed to rapid exchange of free PMe3 and [Pd(PMe3)nCl]+ (n = 3, 4) at room temperature.236 Thus, a variety of PdII complexes are expected which are sensitive to the amount of PMe3 added. Nevertheless, the reversible cross-linking of poly(1-phosphaisoprene) PPI by coordination to PdII has been demonstrated in the present study. 3.2 Conclusion It has been demonstrated that PPI can function as both macromolecular phosphaalkene and phosphine ligand for PdII. To model the binding of macromolecule PPI to PdII, detailed studies of the reactions of 1-phosphaisoprene monomer (PI) with [Pd(η3-C3H5)(µ-Cl)]2 and [Pd(cod)Cl2] were performed. Both the well-defined phosphaalkene-PdII complex [Pd(PI)(η3-C3H5)Cl] and C–H activated bis(benzophospholane)-PdII complex 3.1 have been characterized crystallographically. In contrast to these model studies, PPI does not show any evidence of intramolecular C–H activation in solution and instead affords complexes PPI·[Pd(η3-C3H5)Cl]0.21n and PPI·[PdCl2]0.09n. It is particularly noteworthy that treating concentrated solutions of PPI with [Pd(cod)Cl2] affords gels that are postulated to be cross-linked via PdCl2 units bridging between the phosphaalkene and/or phosphine substituents of two adjacent polymer chains. We demonstrate this gelation process can be reversed by adding PMe3 which we reasoned competes with PPI for the binding sites of PdII. 3.3 Experimental Section 3.3.1 General considerations All manipulations of air- and/or moisture-sensitive compounds were conducted using standard Schlenk or glovebox techniques. Hexanes and dichloromethane were degassed and passed through 105 an activated alumina column prior to use. [Pd(cod)Cl2] and [Pd(η3-C3H5)(µ-Cl)]2 were purchased from Sigma Aldrich and used as received. Mes*P=C(Me)Br185 and Mes*P=CH2233, 238 (3.2) were synthesized according to literature procedures. 1H, 13C{1H}, and 31P NMR spectra were measured at room temperature on a Bruker AVANCE III HD 400 MHz spectrometer or a Bruker AVANCE III 600 MHz spectrometer equipped with a TXI probe. All NMR spectra were recorded at room temperature unless otherwise specified. Chemical shifts of 1H NMR spectra were expressed in parts per million downfield from residual CHCl3 (δ = 7.26) or CDHCl2 (δ = 5.32). Chemical shifts of 13C{1H} NMR spectra were expressed in parts per million downfield from CDCl3 (δ = 77.16) or CD2Cl2 (δ = 53.84). Chemical shifts of 31P NMR spectra were expressed in parts per million downfield from 85% H3PO4 as an external standard (δ = 0). Integrals of 31P NMR spectra give only approximate ratios (d1 = 2 s, cf. t1 = 0.613 s for PI). All integrals were phased using Topspin 4.0 software. Polymer molecular weights were determined by gel permeation chromatography with multi-angle light scattering and viscometer detectors (GPC-MALS-V) equipped with an Agilent 1200 series isocratic pump, Agilent 1200 series standard autosampler, Phenomenex Phenogel 5 mm narrow bore columns (4.6×300 mm) with sizes of 104, 103 and 500 Å and a Wyatt Optilab T-rEx differential refractometer (λ = 658 nm, 40°C). A flow rate of 0.5 mL/min was used and samples were dissolved in THF (ca. 1 mg/mL). 100 μL of this solution was injected into the Styragel™ columns. Absolute molecular weight data were obtained using the 100% mass recovery method. GPC samples for PPI were run in triplicate to ensure reproducibility. ESI low-resolution mass spectra were recorded on Bruker HCT ion trap mass spectrometer equipped with an electrospray ion source. ESI high-resolution mass spectra were obtained on an Agilent 6545 QTOF mass spectrometer equipped with an Agilent Jet stream (AJS) electrospray ion source. For accurate mass measurement, commercial reference solutions from Agilent were used as reference compounds. 106 FD mass spectra were recorded on Jeol AccuTOF-GCv 4G, a GC-TOF MS instrument equipped with a Field Desorption/Ionization (FD/FI) ion source. All mass spectra were acquired in the positive ion mode. 3.3.2 X-ray crystallography All single crystals were immersed in oil and mounted on a mylar loop. Data were collected on a Bruker X8 APEX II diffractometer with Mo Kα radiation, integrated using the Bruker SAINT software package186 and corrected for absorption effects using SADABS.187 All structures were solved by direct methods and subsequent Fourier difference techniques. All data sets were corrected for Lorentz and polarization effects. All structure solutions were performed using SHELXT.188 All refinements were performed using SHELXL189 via the Olex2 interface.190. Compound [Pd(PI)(η3-C3H5)Cl] crystallizes with disorder in the orientation of the allyl ligand that was modeled in two orientations using SADI restraints. Additionally, one CH2Cl2 molecule crystallizes in the asymmetric unit. Compound 3.1 crystallizes with two molecules of CH2Cl2 in the asymmetric unit. 3.3.3 Anionic polymerization of 1-phosphaisoprene (PI) In a dried flask in the glovebox, PI (2.0 g, 6.1 mmol) was dissolved in THF (12 mL) forming a pale-yellow solution. n-BuLi (76 μL, 0.12 mmol, 1.6 M in hexanes) was added quickly using a 100 μL microsyringe to afford a deep-red solution. The reaction mixture was transferred to a flask that was sealed with a Teflon™ stopcock. Analysis of the reaction mixture by 31P NMR spectroscopy after 3.5 h showed two broad signals at 237 and −15 ppm. The solution was stirred at room temperature for a further 20 h and was then quenched with deoxygenated methanol (1 drop). The reaction mixture immediately became yellow. The volatiles were removed in vacuo and the yellow crude polymer was dissolved in CH2Cl2 (5 mL) and precipitated into deoxygenated 2-107 propanol (50 mL). The supernatant was removed to afford an off-white powder which was dried in vacuo. Yield = 1.50 g, 75%. 31P NMR (CDCl3, 162 MHz, 25 ⁰C) δ 237 (br, P=C), −13 (br, >P−C), −52 (>P−H end-group); 1H NMR (CDCl3, 400 MHz, 25 ⁰C) δ 7.43 (br, Mes*H), 5.38 (br, C=CH), 2.93 (br, CH−CH2 and P=C(CH3)), 1.53 (br, o-C(CH3)3), 1.41 (br, p-C(CH3)3); inverse-gated 13C{1H} NMR (CDCl3, 101 MHz, 25 ⁰C) δ 187.8 (br, P=C), 153.8 (br, o-Mes*), 149.2 (br, p-Mes*), 137.8 (br, ipso-Mes*), 121.5 (br, m-Mes*), 44.6 (br, CH−CH2), 38.3 (br, o-C(CH3)3), 35.0 (br, p-C(CH3)3), 33.2 (br, o-C(CH3)3), 31.6 (br, p-C(CH3)3), 20.4 (br, P=C(CH3)). GPC: PPI (13.6 mg) was dissolved in THF (10 mL) to afford a colorless solution. The solution was filtered through a 0.22 μm PTFE syringe filter and 100 μL of this solution was injected into the Styragel™ columns. The absolute molecular weight data (using 100% mass recovery) were as follows: Mn = 21,800 g/mol; Ð = 1.02; dn/dc = 0.173. 3.3.4 Reaction of PPI with [Pd(η3-C3H5)(µ-Cl)]2 (Pd:P = 1.0) To a colorless solution of PPI (208 mg, 0.63 mmol P, Mn = 21,800 g mol−1) in CH2Cl2 (2 mL) was added a pale-yellow solution of [Pd(η3-C3H5)(µ-Cl)]2 (115 mg, 0.31 mmol) in CH2Cl2 (2 mL) to afford a yellow solution. The reaction mixture was stirred for 24 h and became orange. Analysis of the reaction mixture by 31P NMR spectroscopy revealed four broad signals at 239 (67%), 197 (27%), 30 (2%) and −15 (5%) ppm. No change was observed in the 31P NMR spectrum of the reaction mixture after it was heated to reflux at 50 °C for 24 h. 3.3.5 Reaction of PPI with [Pd(cod)Cl2] (Pd:P = 0.5) To a colorless solution of PPI (106 mg, 0.32 mmol P, Mn = 21,800 g mol−1) in CH2Cl2 (2 mL) was added a yellow solution of [Pd(cod)Cl2] (46 mg, 0.16 mmol) in CH2Cl2 (2 mL). The reaction mixture was stirred for 24 h and became a dark-red-orange color. Analysis of the reaction solution 108 by 31P NMR spectroscopy revealed four broad resonances at 239 (68%), 185 (26%), 43 (2%) and −15 (4%) ppm. No change in the 31P NMR spectrum was observed after the reaction mixture was heated to reflux at 50 °C for 24 h. 3.3.6 Reaction of PPI with [Pd(η3-C3H5)(µ-Cl)]2 (Pd:P = 0.30) To a pale-yellow solution of [Pd(η3-C3H5)(µ-Cl)]2 (25 mg, 0.07 mmol) in CH2Cl2 (1 mL) was added a colorless solution of PPI (150 mg, 0.45 mmol P, Mn = 21,800 g mol−1) in CH2Cl2 (1 mL) to afford a yellow solution. The reaction mixture was stirred for 30 min and became orange. Analysis of the reaction mixture by 31P NMR spectroscopy after it was stirred for 24 h revealed four broad signals at 239 (72%), 197 (18%), 30 (3%) and −15 (6%) ppm. The volatiles were removed in vacuo and the residual solid was dissolved in hexanes (20 mL) and filtered through Celite™. The solvent was removed in vacuo to afford a dark-orange solid. Yield = 145 mg, 87% based on a postulated formulation of PPI·[Pd(η3-C3H5)Cl]0.21n. 31P NMR (CDCl3, 162 MHz, 25 ⁰C) δ 237 (br, P=C), 200 (br, Pd−P=C), 29 (br, >P(Pd)−C), −13 (br, >P−C); 1H NMR (CDCl3, 400 MHz, 25 ⁰C) δ 7.35 (br, Mes*H), 5.35 (br, C=CH and allyl-CH), 4.63 (br, allyl-CH2), 3.57 (br, allyl-CH2), 2.80 (br, CH−CH2, P=C(CH3) and allyl-CH2), 1.45 (br, o-C(CH3)3), 1.33 (br, p-C(CH3)3); 13C{1H} NMR (CDCl3, 101 MHz, 25 ⁰C) δ 187.5 (br, P=C), 153.5 (br, o-Mes*), 149.3 (br, p-Mes*), 137.2 (br, ipso-Mes*), 121.4 (br, m-Mes*), 116.1 (br, allyl-CH), 44.9 (br, CH−CH2), 38.2 (br, o-C(CH3)3), 35.0 (br, p-C(CH3)3), 33.4 (br, o-C(CH3)3), 31.7 (br, p-C(CH3)3), 19.9 (br, P=C(CH3)). GPC: PPI·[Pd(η3-C3H5)Cl]0.21n (6.1 mg) was dissolved in THF (10 mL) to afford an orange solution. This solution was filtered through a 0.22 μm PTFE syringe filter and 100 μL was injected into the columns. The observed mass recovery of the trace was 43.2% when using the dn/dc of PPI (0.17) that was obtained from the 100% mass recovery method. 109 3.3.7 Reaction of PPI with [Pd(cod)Cl2] (Pd:P = 0.15) To a yellow solution of [Pd(cod)Cl2] (26 mg, 0.09 mmol) in CH2Cl2 (2 mL) was added a colorless solution of PPI (200 mg, 0.60 mmol P, Mn = 21,800 g mol−1) in CH2Cl2 (2 mL). The reaction mixture was stirred for 24 h and became dark-red. Analysis of the solution by 31P NMR spectroscopy revealed four broad resonances at 239 (75%), 185 (17%), 43 (1%) and −15 (7%) ppm. The volatiles were removed in vacuo to afford a dark-red solid. The solid was dissolved in CH2Cl2 (2 mL) and precipitated into deoxygenated methanol (20 mL). After filtration, a dark-orange powder was isolated. Yield = 110 mg, 52% based on a postulated formulation of PPI·[PdCl2]0.09n. 31P NMR (CDCl3, 162 MHz, 25 ⁰C) δ 237 (br, P=C), 186 (br, Pd−P=C), 45 (br, >P(Pd)−C), −13 (br, >P−C); 1H NMR (CDCl3, 400 MHz, 25 ⁰C) δ 7.34 (br, Mes*H), 5.26 (br, =CH), 2.93 (br, CH−CH2 and P=C(CH3)), 1.43 (br, o-C(CH3)3), 1.32 (br, p-C(CH3)3); 13C{1H} NMR (CDCl3, 101 MHz, 25 ⁰C) δ 187.5 (br, P=C), 153.8 (br, o-Mes*), 149.3 (br, p-Mes*), 137.5 (br, ipso-Mes*), 121.6 (br, m-Mes*), 44.7 (br, CH−CH2), 38.2 (br, o-C(CH3)3), 35.0 (br, p-C(CH3)3), 33.4 (br, o-C(CH3)3), 31.7 (br, p-C(CH3)3), 20.9 (br, P=C(CH3)). 3.3.8 Preparation of [Pd(PI)(η3-C3H5)Cl] To a pale-yellow solution of PI (115 mg, 0.35 mmol) in CH2Cl2 (1 mL) was added a pale yellow solution of [Pd(η3-C3H5)(µ-Cl)]2 (55 mg, 0.15 mmol) in CH2Cl2 (1 mL). The yellow reaction mixture was stirred for 30 min. Analysis of the reaction mixture by 31P NMR spectroscopy revealed singlet resonances at 264.3 (17%) and 214.9 (83%) ppm. The volatiles were removed in vacuo and the residual yellow solid was washed with hexanes (2 mL) at −35 °C. The supernatant was removed to afford a pure yellow solid. Yield = 115 mg, 74%. Crystals suitable for X-ray diffraction were grown from a saturated solution in CH2Cl2 at −35 °C. 110 31P NMR (CDCl3, 162 MHz, 25 °C) δ 212.1 (s); 1H NMR (CDCl3, 400 MHz, 25 °C) δ 7.64 (ddd, 1H, 3Jtrans = 17 Hz, 3JPH = 16 Hz, 3Jcis = 11 Hz, P=C(CH3)−CH=CHcisHtrans), 7.49 (br s, 2H, Mes*H), 5.55 (5-line multiplet, 1H, JHH = 10 Hz , allyl-CH), 5.34 (dd, 1H, 3Jtrans = 17 Hz, 4JPH = 10 Hz, P=C(CH3)−CH=CHcisHtrans trans to H), 5.25 (dd, 1H, 3Jcis = 11 Hz, 4JPH = 8 Hz, P=C(CH3)−CH=CHcisHtrans cis to H), 4.73 (br s, 1H, allyl-CH2), 3.87 (br s, 1H, allyl-CH2), 3.74 (br s, 1H, allyl-CH2), 2.97 (br s, 1H, allyl-CH2), 1.54 (s, 18H, o-C(CH3)3), 1.48 (d, 3H, 3JPH = 24 Hz, P=C(CH3)−CH=CHcisHtrans), 1.32 (s, 9H, p-C(CH3)3); 1H NMR (CDCl3, 400 MHz, −30 °C) δ 7.64 (ddd, 1H, 3Jtrans= 17 Hz, 3JPH = 17 Hz, 3Jcis = 11 Hz, P=C(CH3)−CH=CHcisHtrans), 7.49 (s, 1H, Mes*H), 7.46 (s, 1H, Mes*H), 5.58 (7-line multiplet, 1H, allyl-CH), 5.36 (dd, 1H, 3Jtrans = 17 Hz, 4JPH = 10 Hz, P=C(CH3)CH=CHcisHtrans trans to H), 5.29 (dd, 1H, 3Jcis = 11 Hz, 4JPH = 8 Hz, P=C(CH3)−CH=CHcisHtrans cis to H), 4.76 (dd, 1H, 3JPH = 7 Hz, JHH = 7 Hz, allyl-CH2), 3.86 (d, 1H, JHH = 5 Hz, allyl-CH2), 3.77 (dd, 1H, JPH = 13 Hz, JHH = 13 Hz, allyl-CH2), 2.97 (d, 1H, JHH = 12 Hz, allyl-CH2), 1.53 (s, 18H, o-C(CH3)3), 1.47 (d, 3H, 3JPH = 24 Hz, P=C(CH3)−CH=CHcisHtrans), 1.30 (s, 9H, p-C(CH3)3); 13C{1H} NMR (CDCl3, 101 MHz, 25 °C) δ 173.8 (d, 1JPC = 34 Hz, P=C), 154.5 (br s, o-Mes*), 152.1 (s, p-Mes*), 139.1 (d, 2JPC = 17 Hz, P=C(CH3)−CH=CH2), 128.8 (br s, ipso-Mes*), 123.4 (br s, m-Mes*), 116.0 (br s, allyl-CH), 114.0 (d, 3JPC = 45 Hz, P=C(CH3)−CH=CH2), 77.8 (br s, allyl-CH2), 63.4 (br s, allyl-CH2), 38.9 (s, o-C(CH3)3), 35.1 (s, p-C(CH3)3), 33.8 (s, o-C(CH3)3), 31.2 (s, p-C(CH3)3), 19.4 (d, 2JPC = 14 Hz, P=C(CH3)−CH=CH2). Satisfactory elemental analysis could not be obtained: Anal Calcd for C25H40PPdCl: C, 58.48; H, 7.85. Found C, 60.07; H, 8.07. 3.3.9 Preparation of 3.1 To a yellow solution of [Pd(cod)Cl2] (43 mg, 0.15 mmol) in CH2Cl2 (1.25 mL) was added a pale-yellow solution of PI (100 mg, 0.30 mmol) in CH2Cl2 (1.25 mL). The reaction mixture was stirred 111 for 48 h and analyzed by 31P NMR spectroscopy. The spectrum showed two signals at 36.5 (54%) and 37.1 (46%) ppm. The volatiles were removed in vacuo and the residual solid was washed with hexanes (2 mL) at −35 °C to afford a yellow solid. Yellow crystals suitable for X-ray analysis were grown by recrystallization from a saturated CH2Cl2 solution at −35 °C. Yield = 47 mg, 37%. Meso-trans-3.1. 31P NMR (CDCl3, 162 MHz, 25 ⁰C) δ 36.4 (s); 1H NMR (CDCl3, 600 MHz, 25 ⁰C) δ 7.46 (br s, 2H, ArH), 7.05 (br s, 2H, ArH), 5.45 (dq, 2H, 3JPH = 15 Hz, 3JHH = 8 Hz, P−C(CH3)=CH−CH3), 3.19 (d, 2H, 2Jgem = 14 Hz, P−CH2), 2.13 (d, 2H, 2Jgem = 14 Hz, P−CH2), 1.87 (t, 6H, JPH = 6 Hz, P−C(CH3)=CH−CH3), 1.74 (s, 18H, o-C(CH3)3), 1.58 (d, 6H, 3JHH = 7 Hz, P−C(CH3)=CH−CH3), 1.45 (s, 6H, C(CH3)2), 1.33 (s, 18H, p-C(CH3)3), 1.19 (s, 6H, C(CH3)2); 13C{1H} NMR (CDCl3, 151 MHz, 25 ⁰C) δ 158.3 (t, JPC = 9 Hz, o-Ar), 154.2 (s, p-Ar), 153.5 (t, JPC = 5 Hz, o-Ar), 137.2 (br t, JPC = 3 Hz, P−C(CH3)=CH−CH3), 130.7 (t, JPC = 19 Hz, P−C(CH3)=CH−CH3), 123.9 (t, JPC = 4 Hz, m-Ar), 123.3 (t, JPC = 21 Hz, ipso-Ar), 119.3 (t, JPC = 4 Hz, m-Ar), 44.5 (s, C(CH3)2), 37.9 (t, JPC = 15 Hz, P−CH2), 37.8 (s, o-C(CH3)3), 35.2 (s, p-C(CH3)3), 33.6 (s, o-C(CH3)3), 32.6 (t, JPC = 4 Hz, C(CH3)2), 31.8 (s, C(CH3)2), 31.4 (s, p-C(CH3)3), 16.3 (t, JPC = 8 Hz, P−C(CH3)=CH−CH3), 14.8 (t, JPC = 6 Hz, P−C(CH3)=CH−CH3). Rac-trans-3.1. 31P NMR (CDCl3, 162 MHz, 25 ⁰C) δ 36.9 (s); 1H NMR (CDCl3, 600 MHz, 25 ⁰C) δ 7.46 (br s, 2H, ArH), 7.07 (s, 2H, ArH), 5.45 (dq, 2H, 3JPH = 15 Hz, 3JHH = 8 Hz, P−C(CH3)=CH−CH3), 3.07 (d, 2H, 2Jgem = 14 Hz, P−CH2), 2.11 (d, 2H, 2Jgem = 14 Hz, P−CH2), 1.96 (t, 6H, JPH = 6 Hz, P−C(CH3)=CH−CH3), 1.76 (s, 18H, o-C(CH3)3), 1.59 (d, 6H, 3JHH = 7 Hz, P−C(CH3)=CH−CH3), 1.38 (s, 6H, C(CH3)2), 1.32 (s, 18H, p-C(CH3)3), 1.18 (s, 6H, C(CH3)2); 13C{1H} NMR (CDCl3, 151 MHz, 25 ⁰C) δ 158.3 (t, JPC = 8 Hz, o-Ar), 154.3 (s, p-Ar) 153.5 (t, JPC = 5 Hz, o-Ar), 137.2 (br t, JPC = 3 Hz, P−C(CH3)=CH−CH3), 130.7 (t, JPC = 19 Hz, P−C(CH3)=CH−CH3), 123.9 (t, JPC = 4 Hz, m-Ar), 123.3 (t, JPC = 21 Hz, ipso-Ar), 119.3 (t, JPC = 112 4 Hz, m-Ar), 44.5 (s, C(CH3)2), 38.2 (t, JPC = 16 Hz, P−CH2), 37.8 (s, o-C(CH3)3), 35.2 (s, p-C(CH3)3), 33.6 (s, o-C(CH3)3), 32.5 (t, JPC = 4 Hz, C(CH3)2), 31.7 (s, C(CH3)2), 31.4 (s, p-C(CH3)3), 16.5 (t, JPC = 8 Hz, P−C(CH3)=CH−CH3), 14.8 (t, 3JPC = 6 Hz, P−C(CH3)=CH−CH3). MS (ESI/TOF, positive mode): [M−Cl+] m/z = 810 (4), 809 (10), 808 (7), 807 (26), 806 (30), 805 (59), 804 (48), 803 (100), 802 (63), 801 (89), 800 (48), 799 (15). HRMS (ESI/TOF, positive mode): Calcd for C44H70ClP2Pd: 803.3680. Found: 803.3679; satisfactory elemental analysis could not be obtained: Anal. Calcd for C44H70Cl2P2Pd: C, 63.04; H, 8.42. Found: C 63.60; H, 8.59. 3.3.10 NMR tube reaction of PI with [Pd(cod)Cl2] To a yellow solution of [Pd(cod)Cl2] (43 mg, 0.15 mmol) in CD2Cl2 (1.25 mL) was added a pale-yellow solution of PI (100 mg, 0.30 mmol) in CD2Cl2 (1.25 mL) to afford a yellow solution. The reaction mixture was transferred to an NMR tube and monitored by 31P, 1H, 1H{31P} 1H, 1H- and 31P,31P-COSY and 1H,31P-HMBC NMR spectroscopies. API: 31P NMR (CD2Cl2, 162 MHz, 25 ⁰C) δ 197.1(s); 1H NMR (CD2Cl2, 400 MHz, 25 ⁰C) δ 7.87 (ddt, 2H, 3Jtrans = 17 Hz, 3Jcis = 11 Hz, JPH = 8 Hz, P=C(CH3)−CH=CHcisHtrans), 7.59 (br s, 4H, Mes*H), 5.41 (dt, 2H, 3Jtrans = 17 Hz, JPH = 5 Hz, P=C(CH3)−CH=CHcisHtrans trans to H), 5.31 (dt, 2H, 3Jcis = 11 Hz, JPH = 3 Hz, P=C(CH3)−CH=CHcisHtrans cis to H), 1.74 (d, 6H, JPH = 28 Hz, P=C(CH3)−CH=CHcisHtrans), 1.68 (s, 36H, o−C(CH3)3), 1.37 (s, 18H, p-C(CH3)3). BPI: 31P NMR (CD2Cl2, 162 MHz, 25 ⁰C) δ 212.6 (d, 2JPP = 614 Hz), 41.7 (d, 2JPP = 614 Hz); 1H NMR (CD2Cl2, 400 MHz, 25 ⁰C) δ 7.91 (m, 1H, P=C(CH3)−CH=CHcisHtrans), 7.57 (s, 2H, Mes*H), 7.57 (s, 1H, ArH), 7.15 (s, 1H, ArH), 5.61 (dq, 1H, 3JPH = 21 Hz, 3JHH = 7 Hz, P−C(CH3)=CH−CH3), 5.34 (m, 1H, P=C(CH3)−CH=CHcisHtrans trans to H), 5.21 (m, 1H, P=C(CH3)−CH=CHcisHtrans cis to H), 3.16 (dd, 1H, 2Jgem = 14 Hz, 2JPH = 7 Hz, P−CH2), 2.26 (dd, 113 1H, 2Jgem = 14 Hz, 2JPH = 3 Hz, P−CH2), 1.95 (d, 3H, 3JPH = 16 Hz, P−C(CH3)=CH−CH3), 1.64 (s, 18H, o−C(CH3)3), 1.63 (d, 3H, 3JHH = 7 Hz, P=C(CH3)−CH=CH2). Signals could not be unambiguously assigned to the o- and p-C(CH3)3 substituents and the C(CH3)2 in ligand PI' of BPI due to overlap with aliphatic signals assigned to PI, API, and 3.1. 3.3.11 Qualitative rate of reaction for PI with [Pd(cod)Cl2] (NMR tubes) Three NMR tubes were soaked in 1 M Si(CH3)3Cl, NaOH and HCl in ethanol overnight, respectively. The NMR tubes were thoroughly rinsed with ethanol. In the glovebox, the NMR tubes were each charged with PI (50 mg, 0.15 mmol), [Pd(cod)Cl2] (21 mg, 0.07 mmol) and CH2Cl2 (1.25 mL). The reaction progress was monitored by 31P NMR spectroscopy and followed a similar profile to the NMR tube reaction of PI with [Pd(cod)Cl2] taking 21 d to go to completion. 3.3.12 Qualitative rate of reaction for PI with [Pd(cod)Cl2] (vials) Three vials were soaked in 1 M Si(CH3)3Cl, NaOH and HCl in ethanol overnight, respectively. The vials were thoroughly rinsed with ethanol and dried. A separate vial was used without soaking and loaded with a Teflon™-coated stir bar. In the glovebox, each of the four vials was charged with PI (50 mg, 0.15 mmol), [Pd(cod)Cl2] (21 mg, 0.07) and CH2Cl2 (1.25 mL). The reaction progress was monitored by 31P NMR spectroscopy and followed a similar profile to the reaction of PI and [Pd(cod)Cl2] in a vial taking 48 h to go to completion. 3.3.13 Reaction of 3.2 with [Pd(cod)Cl2] To a yellow solution of Pd(cod)Cl2 (20 mg, 0.07 mmol) in CD2Cl2 (0.75 mL) was added a yellow solution of 3.2 (40 mg, 0.14 mmol) in CD2Cl2 (0.75 mL) in an NMR tube. Analysis of the orange reaction mixture after 10 min by 31P NMR spectroscopy revealed a singlet at 230.3 ppm. Analysis after 8 d revealed two sets of coupled signals at 242.9 (dd, 2JPP = 644 Hz, 2JPH = 33 Hz) and 22.3 (d, 2JPP = 644 Hz) ppm. After 18 d, the spectrum showed two signals at 15.8 and 15.4 ppm in a 3:2 114 ratio, respectively. The volatiles were removed in vacuo and the residual yellow solid was washed with hexanes at −35 °C to afford a yellow powder (26 mg, 49%). A3.2: 31P NMR (CD2Cl2, 162 MHz, 25 ⁰C) δ 230.3 (br s); 1H NMR (CD2Cl2, 400 MHz, 25 ⁰C) δ 7.69 (d, 2H, 2Jgem = 5 Hz, P=CHcisHtrans trans to Mes*), 7.55 (br t, 4H, JPH = 1 Hz, Mes*H), 6.54 (td, 2H, JPH = 9 Hz, 2Jgem = 5 Hz, P=CHcisHtrans cis to Mes*), 1.68 (s, 36H, o-C(CH3)3), 1.36 (s, 18H, p-C(CH3)3); 13C{1H} NMR (CD2Cl2, 101 MHz, 25 ⁰C) δ 155.0 (br s, o-Mes*), 153.4 (s, p-Mes*), 143.4 (t, JPC = 32 Hz, P=C), 125.9 (t, JPC = 12 Hz, ipso-Mes*), 124.2 (t, JPC = 5 Hz, m-Mes*), 39.7 (s, o-C(CH3)3), 35.5 (s, p-C(CH3)3), 35.2 (s, o-C(CH3)3), 31.2 (s, p-C(CH3)3). B3.2: 31P NMR (CD2Cl2, 162 MHz, 25 ⁰C) δ 242.9 (dd, 2JPP = 644 Hz, 2JPH = 33 Hz), 22.3 (br d, 2JPP = 644 Hz); 1H NMR (CD2Cl2, 400 MHz, 25 ⁰C) δ 7.62 (dd, 1H, 2JPH = 5 Hz, 2Jgem = 5 Hz, P=CHcisHtrans trans to Mes*), 7.54 (s, 2H, Mes*H), 7.53 (d, 1H, 4JPC = 3 Hz, ArH), 7.17 (br s, 1H, ArH), 6.63 (ddd, 1H, 2JPH = 33 Hz, 4JPH = 12 Hz, 2Jgem = 5 Hz, P=CHcisHtrans cis to Mes*), 3.10 (ddd, 1H, 2Jgem = 15 Hz, 2JPH = 6 Hz, 4JPH = 3 Hz, P−CH2), 2.19 (dd, 1H, 2Jgem = 15 Hz, 2JPH = 4 Hz, P−CH2), 1.86 (dd, 3H, 3JPH = 11 Hz, 5JPH = 3 Hz, P−CH3), 1.71 (s, 9H, o-C(CH3)3), 1.68 (s, 9H, o-C(CH3)3), 1.64 (s, 9H, o-C(CH3)3), 1.50 (s, 3H, C(CH3)2), 1.40 (s, 3H, C(CH3)2), 1.35 (s, 9H, p-C(CH3)3), 1.34 (s, 9H, p-C(CH3)3). 3.3 (isomer 1). 31P NMR (CDCl3, 162 MHz, 25 ⁰C) δ 15.5 (s); 1H NMR (CDCl3, 600 MHz, 25 ⁰C) δ 7.44 (br s, 2H, ArH), 7.08 (br s, 2H, ArH), 3.07 (d, 2H, 2Jgem = 14 Hz, P−CH2), 2.04 (d, 2H, 2Jgem = 14 Hz, P−CH2), 1.78 (t, 6H, JPH = 4 Hz, P−CH3), 1.68 (s, 18H, o-C(CH3)3), 1.50 (s, 6H, C(CH3)2), 1.39 (s, 6H, C(CH3)2), 1.32 (s, 18H, p-C(CH3)3); 13C{1H} NMR (CDCl3, 151 MHz, 25 ⁰C) δ 157.7 (t, JPC = 9 Hz, o-Ar), 154.1 (s, p-Ar), 152.7 (t, JPC = 5 Hz, o-Ar), 126.4 (t, JPC = 21 Hz, ipso-Ar), 124.1 (t, JPC = 5 Hz, m-Ar), 118.9 (t, JPC = 5 Hz, m-Ar), 44.8 (s, C(CH3)2), 41.7 (t, 115 JPC = 15 Hz, P−CH2), 37.7 (s, o-C(CH3)3), 35.2 (s, p-C(CH3)3), 33.8 (s, C(CH3)2), 33.5 (s, o-C(CH3)3), 32.5 (t, JPC = 3 Hz, C(CH3)2), 31.4 (s, p-C(CH3)3), 16.7 (t, JPC = 14 Hz, P−CH3). 3.3 (isomer 2). 31P NMR (CDCl3, 162 MHz, 25 ⁰C) δ 15.6 (s); 1H NMR (CDCl3, 600 MHz, 25 ⁰C) δ 7.44 (br s, 2H, ArH), 7.06 (br s, 2H, ArH), 3.01 (d, 2H, 2Jgem = 14 Hz, P−CH2), 2.04 (d, 2H, 2Jgem = 14 Hz, P−CH2), 1.79 (t, 6H, JPH = 4 Hz, P−CH3), 1.72 (s, 18H, o-C(CH3)3), 1.43 (s, 6H, C(CH3)2), 1.37 (s, 6H, C(CH3)2), 1.31 (s, 18H, p-C(CH3)3); 13C{1H} NMR (CDCl3, 151 MHz, 25 ⁰C) δ 157.8 (t, JPC = 9 Hz, o-Ar), 154.2 (s, p-Ar), 152.5 (t, JPC = 5 Hz, o-Ar), 126.6 (t, JPC = 21 Hz, ipso-Ar), 123.9 (t, JPC = 4 Hz, m-Ar), 119.0 (t, JPC = 5 Hz, m-Ar), 44.9 (s, C(CH3)2), 41.6 (t, JPC = 16 Hz, P−CH2), 37.7 (s, o-C(CH3)3), 35.2 (s, p-C(CH3)3), 33.9 (s, C(CH3)2), 33.4 (s, o-C(CH3)3), 32.6 (t, JPC = 3 Hz, C(CH3)2), 31.4 (s, p-C(CH3)3), 16.6 (t, JPC = 13 Hz, P−CH3). MS (FD, positive mode): [M+] m/z = 764 (4), 763 (7), 762 (21), 761 (26), 760 (68), 759 (42), 758 (100), 757 (56), 756 (82), 755 (51), 754 (21). HRMS (FD, positive mode): Calcd for C38H62Cl2P2Pd: 758.2743. Found: 758.2757. Satisfactory elemental analysis could not be obtained: Anal. Calcd for C38H62Cl2P2Pd: C, 60.20; H, 8.24. Found: C 57.48; H, 7.64. 3.3.14 NMR monitoring of PPI·[PdCl2]0.09n Polymer PPI·[PdCl2]0.09n (40 mg, 0.12 mmol P) was dissolved in CH2Cl2 (0.5 mL) to afford a dark-red solution. The solution was monitored by 31P NMR spectroscopy for 60 d and no change was observed to the signals assigned to PPI·[PdCl2]0.09n (δ = 239, 185, 43 and −15). 3.3.15 Gelation of PPI with [Pd(cod)Cl2] In a vial in the glovebox, PPI (87 mg, 0.26 mmol P, Mn = 21,800 g mol−1) was dissolved in CH2Cl2 (0.2 mL) to afford a colorless solution. [Pd(cod)Cl2] (4 mg, 0.014 mmol) was added and the reaction solution became orange. The reaction mixture was stirred for 30 min and then left to stand for 30 min. Inversion of the vial revealed an increase in viscosity. This process was repeated with 116 two additional portions of [Pd(cod)Cl2] (each portion: 4 mg, 0.014 mmol, i.e. total added: 12 mg, 0.042 mmol). The reaction mixture became more viscous. After standing for 12 h at 25 °C, inversion of the vial confirmed that the reaction mixture did not flow. PMe3 (1 drop, ca. 0.30 mmol) was added to the immobile gel and the gel immediately became mobile, as confirmed by inversion of the vial. The deep-red-orange reaction mixture was diluted with CH=CL2 (0.3 mL) and analyzed by 31P NMR spectroscopy to reveal four broad signals at 239, 185, 43 and −15 ppm and two sharp signals at −0.6 and −10.8 ppm. A further 5 drops (ca. 1.50 mmol) were added to afford a yellow solution with a dark precipitate. Analysis of the reaction mixture by 31P NMR spectroscopy revealed two broad signals at 239 and −15 ppm and two sharp signals at −8.0 and 37.2 ppm 3.3.16 Control gelation attempt of PPI with [Pd(η3-C3H5)(µ-Cl)]2 In a vial in the glovebox, PPI (87 mg, 0.26 mmol P, 21,800 g mol−1) was dissolved in CH2Cl2 (0.2 mL) to afford a colorless solution. [Pd(η3-C3H5)(µ-Cl)]2 (5 mg, 0.014 mmol) was added and the reaction solution became orange. The reaction mixture was stirred for 30 min and then left to stand for 30 min. Inversion of the vial revealed no increase in viscosity. This process was repeated with two additional portions of [Pd(η3-C3H5)(µ-Cl)]2 (each portion: 5 mg, 0.14 mmol, i.e. total added: 15 mg 0.042 mmol). The orange color of the reaction mixture became more intense. After standing for 12 h at 25 °C, inversion of the vial showed no increase in viscosity of the reaction mixture. The orange solution was diluted with CH2Cl2 (0.3 mL), transferred to an NMR tube and analyzed by 31P NMR spectroscopy which revealed broad signals at 239, 197, 30 and −15 ppm. 117 Chapter 4: Cyclization Reactions of 1-Phosphabutadienes: Selective Formation of P=C-substituted Phosphacyclohexene or 1-Phosphet-2-ene Ligands. 4.1 Introduction As is the case with olefins, the cycloaddition reactions of phosphaalkenes represent a powerful means to construct larger architectures. Moreover, the presence of phosphorus provides unique reactivity and a functional group that can often be employed as a ligand for transition metals. As discussed in chapter 1, 1-phosphabutadienes, formally P-containing analogues of the ubiquitous 1,3-butadienes, show unique cycloaddition behavior compared to fully organic dienes (Chart 4.1). For instance, 1-phosphabutadienes have been shown to undergo intramolecular [4+2] cycloadditions (type I) which are analogous to the classical Diels-Alder reaction yet display unique regiochemistry due to the presence of a heteroatom.73, 79, 80, 86-89 In addition, intermolecular [2+2] cycloadditions (type II) have been observed for 1-phosphabutadienes to afford P(sp3)-heterocyclic compounds.73, 90 The intramolecular [2+2] cycloaddition (type III) of 1-phosphabutadienes has also been observed as a route to 1-phosphet-2-enes (or 1,2-dihydrophosphetes).75-77, 83, 91-96 Versions of sections of this chapter have been published: Walsgrove, H. T. G.; Patrick, B. O.; Gates, D. P. Organometallics 2022, 41, 3399-3410; Copyright 2022 American Chemical Society. Additionally: Ohtsuki, K.; Walsgrove, H. T. G.; Hayashi, Y.; Kawauchi, S.; Patrick, B. O.; Gates, D. P.; Ito, S. Chem. Commun. 2020, 56, 774-777. 118 Chart 4.1: Cycloaddition pathways of 1-phosphabutadienes. In chapter 4, the novel [4+2] cycloaddition of PI to afford a phosphaalkene substituted phosphacyclohexene is reported. The utility of this dimer as a P(sp2)/P(sp3)-hybrid ligand for PdII is demonstrated. Furthermore, we report the synthesis of the metal complex [Au(PI)Cl] and show that it undergoes an analogous [4+2] cyclization. In stark contrast, the 1-phosphabutadiene Mes*P=C(Me)–C(Me)=CH2 (4.2), which contains an additional methyl group in the C3 position, affords a transient [Au(4.2)Cl] complex that selectively undergoes an electrocyclization of type III. This quantitative formation of a 1-phosphet-2-ene ligand at AuI also occurs in the presence of PdII to afford the first examples of 1-phosphet-2-ene-PdII complexes. 4.2 Results and Discussion 4.2.1 [4+2] Cycloaddition of PI To investigate the cycloaddition chemistry of PI, a 0.3 M solution in THF was heated to 60 °C and the reaction mixture was monitored by 31P NMR spectroscopy (Scheme 4.1). After 3 d, the 31P NMR spectrum revealed two major signals in a 1:1 ratio at 238.2 (32%) and −16.1 (32%) ppm, alongside a signal assigned to PI (δ = 265.2, 17%) and multiple other minor unidentified signals. The volatiles were removed in vacuo and the crude material was recrystallized from a saturated 119 Et2O solution at −35 °C to afford yellow crystals in 50% yield. Analysis of a crystal by X-ray diffraction revealed the product to be 4.1 (Figure 4.1). Scheme 4.1: Formation 4.1 and [Pd(4.1)Cl2]. Figure 4.1: Molecular structure of 4.1 [only C2(S),P2(S) diastereomer shown]. Thermal ellipsoids are presented at 50% probability level. Hydrogen atoms are omitted for clarity. The molecular structure revealed an unprecedented [4+2] dimer of PI to furnish a phosphaalkene-substituted phosphacyclohexene. Analysis of a CDCl3 solution of 4.1 by 31P{1H} 120 NMR spectroscopy revealed coupled doublets at 236.7 and −16.5 ppm (3JPP = 31 Hz) assigned to the P=C and >P (phosphine) groups, respectively. The 1H NMR spectrum revealed a broad multiplet at 5.67 ppm which was assigned to the >P−C=CH substituent. This signal was correlated by 1H,13C-HSQC NMR spectroscopy to a doublet at 127.3 ppm (2JPC = 10 Hz). Additionally, a broad signal was observed at 4.52 ppm which was assigned to the >P−CH substituent that was correlated to a doublet of doublets at 48.0 ppm (1JPC = 42 Hz, 2JPC = 29 Hz). Full NMR spectroscopic characterization data of 4.1 can be found in the Experimental Section. The X-ray data of 4.1 are consistent with the proposed structure. For example, the P1−C1 bond length [1.6815(18) Å] is in the typical range expected for P=C bonds (1.60-1.70 Å),7 indicative of a phosphaalkene substituent at this position. Furthermore, the angles at C1 and C6 [Σangles = 359.81(23) and 359.84(26)°, respectively] are consistent with a sp2-hybridized centers. The angles at P2 are indicative of a distorted tetrahedral structure. For example, the C2−P2−C6 angle [100.87(8)°] is more acute than the expected 109.5°, reflecting the strain within the phosphacyclohexene ring. Taken together, these data are consistent with the structure of 4.1. As mentioned in the introduction, the intermolecular cycloaddition chemistry of 1-phosphabutadienes had thus far been limited to the [4+2] cycloadditions to form 1,2-diphosphacyclohex-3-enes73, 79, 80, 86-89 and [2+2] cycloadditions to form 1,2-diphosphacyclobutanes.73, 90 The novel regiochemistry of dimer 4.1 warrants further investigation of the coordination properties of this unprecedented scaffold as a P(sp2)/(sp3)-hybrid chelating ligand. To this end, a solution of [Pd(cod)Cl2] (0.93 equiv) in CH2Cl2 was added to a solution of 4.1 in CH2Cl2 (Scheme 4.1) and the reaction mixture was monitored by 31P{1H} NMR spectroscopy. After 3 h, the spectrum revealed two major signals at 212.1 and 62.6 ppm (2JPP = 18 Hz), which were consistent with the formation of complex [Pd(4.1)Cl2]. For instance, the 121 difference in chemical shift of the signal assigned to the P=C moiety of [Pd(4.1)Cl2] (δ = 212.1) compared to that assigned to 4.1 (δ = 236.7, Δδ = −24.6) is in the range reported for related PdII complexes containing chelating phosphaalkenes upon coordination to PdII (range:  = –70.1 to –11.7).71, 72, 215, 216, 239 Surprisingly, the downfield chemical shift of the signal at 62.6 ppm relative to that assigned to 4.1 (δ = −16.5,  = 79.1) is much larger than the range for related chelating phosphine-phosphaalkene ligands (Δδ = −18.4 to 38.9).215, 216, 239 The volatiles were removed in vacuo and crystals suitable for X-ray analysis were isolated in 71% yield after work-up. The molecular structure is shown in Figure 4.2. Figure 4.2: Molecular structure of [Pd(4.1)Cl2] dimer [C2(R),P2(S) diastereomer is shown]. Thermal ellipsoids are presented at 50% probability level. Hydrogen atoms and solvent of crystallization (2 × CH2Cl2) are omitted for clarity. 122 As predicted, the X-ray analysis revealed the structure to be chelating PdII-complex [Pd(4.1)Cl2]. Analysis of a CDCl3 solution of [Pd(4.1)Cl2] by 31P{1H} NMR spectroscopy revealed two coupled doublets at 213.5 and 62.5 ppm (2JPP = 17 Hz). For comparison the 2JPP coupling constant for reported cis-configured phosphine-phosphaalkene-PdII complexes are: cis-[(Mes*P=CMe–PPh2)PdCl2] (52 Hz)239 cis-[(Mes*P=CMe–PPh2)Pd(η3-C3H5)]OTf: (11 Hz)216 and cis-[(Fc(CHPMes*)PAr2)Pd(η3-C3H5)]OTf (Ar = Ph, Naph): 2JPP = (72–74 Hz).215 The 1H NMR spectrum revealed broad signals at 6.26 and 5.93 (d, 2JPH = 29 Hz) that were assigned to the P−C=CH and P−CH groups, respectively. Overall, these data are consistent with the structure of [Pd(4.1)Cl2]. The P1−C1 bond length [1.671(3) Å] does not differ significantly from that in uncoordinated 4.1 [1.6815(18) Å]. The absence of lengthening of this bond upon coordination to an electron-rich metal center may seem somewhat surprising, given the established π-accepting character of P=C ligands.8 Cain and coworkers have attributed this result to a rehybridization of the P-center whereupon the P−C σ-bonds have increased s-character in the complex, thereby giving a shorter -bond that cancels out the lengthening due to π-acceptance.223, 240, 241 This rehybridization can also be observed in the shortening of the Mes*−P1 bond length upon coordination to PdII {1.8601(17) Å in 4.1 vs 1.827(3) Å in [Pd(4.1)Cl2]} and an increase in the Mes*−P1−C1 angle in [Pd(4.1)Cl2] [109.42(14)°] relative to 4.1 [102.85(8)°]. The angles at Pd1 [Σangles = 361.4(1)°] are typical of a square planar PdII center, with the P1−Pd1−P2 angle [81.61(3)°] being the most acute. It was then decided to test whether coordination to a metal center would affect the dimerization chemistry of PI. Hence, a solution of PI in CH2Cl2 was treated with [Au(tht)Cl] (0.93 equiv) in CH2Cl2 (Scheme 4.2). After 5 min, the orange reaction mixture was analyzed by 31P 123 NMR spectroscopy to reveal a broad singlet at 200.5 ppm. The volatiles were removed in vacuo to afford an orange solid. This crude solid was washed with cold hexanes (−35 °C) to dissolve excess PI and the remaining off-white solid was dried in vacuo (yield = 88%). The 31P NMR spectrum of a CDCl3 solution of the solid showed a sharp singlet resonance at 196.5 ppm assigned to [Au(PI)Cl]. The upfield chemical shift relative to that of PI (Δδ = −67.8) is in the range expected for known phosphaalkene-AuI complexes (Δδ = −31.5 to −87.1).49, 120, 157, 175-180 Scheme 4.2: Reactions of 1-phosphaisoprene with AuI. A single crystal grown by cooling a saturated CH2Cl2 solution of the product to −35 °C was analyzed by X-ray diffraction to reveal the structure to be [Au(PI)Cl] (Figure 4.3). The P1−C1, C1−C2 and C2−C3 bond lengths [1.684(3), 1.449(3) and 1.342(5) Å, respectively] are not significantly different from those of uncoordinated PI [1.687(5), 1.458(7) and 1.322(8) Å, respectively].81 The aforementioned rehybridization of the P-center upon coordination to AuI is manifested in an increase in the Mes*−P=C angle in [Au(PI)Cl] [108.23(14)°] compared to PI [103.4(2)°] and a shortening of the Mes*−P bond {[Au(PI)Cl]: 1.822(3); PI 1.860(4) Å}. 124 Figure 4.3: Molecular structure of [Au(PI)Cl]. Thermal ellipsoids are presented at 50% probability level. Hydrogen atoms are omitted for clarity. Analysis of a CDCl3 solution of [Au(PI)Cl] by 1H NMR spectroscopy revealed three resonances assigned to the CH=CH2 group [δ = 7.36 (ddd, 1H, 3JPH = 20 Hz, 3Jtrans = 17 Hz, 3Jcis = 11 Hz), 5.53 (dd, 1H, 3Jtrans = 17 Hz, 4JPH = 10 Hz) and 5.40 (dd, 1H, 3Jcis = 11 Hz, 4JPH = 8 Hz)]. These resonances are shifted downfield from those of PI (Δδ = 0.32, 0.32 and 0.35, respectively).81 The 13C{1H} spectrum of this solution revealed a signal at 170.3 (d, 1JPC = 77 Hz) ppm, which was assigned to the P=C substituent. This signal was shifted upfield from the analogous signal in uncomplexed PI and displayed a large increase in coupling constant (Δδ = −9.3, ΔJPC = 41 Hz). The product was further characterized by LRMS, HRMS and elemental analysis. 125 With [Au(PI)Cl] in hand, it was decided to investigate the effect of AuI-coordination on the dimerization chemistry of this novel complex. Thus, a reaction mixture of PI (0.3 M) and [Au(tht)Cl] (0.3 M) in CH2Cl2 was prepared {cf. 0.1 M for the above preparation of [Au(PI )Cl]} (Scheme 4.2). The reaction mixture was monitored by 31P NMR spectroscopy at room temperature. After 24 h, as compared to 3 h for the preparation of [Au(PI)Cl], the recorded spectrum revealed multiple signals [δ = 199.6 (21%), 196.6 (30%), 189.2 (10%), 23.1 (29%) and −30.6 (d, JPH = 393 Hz, 10%)]. A 31P,31P-COSY NMR spectrum was recorded and showed that the signals at 199.6 and 23.1 ppm were coupled, consistent with the formation of a ligand scaffold analogous to 4.1 The signal at 196.6 ppm was assigned to [Au(PI)Cl]. The signals at 189.2 and –30.6 with a total integrated ratio of ca. 20% of the total remain unidentified. The volatiles were removed in vacuo and the residual dark solid was recrystallized from diethyl ether at −35 °C to afford colorless crystals in 18% yield. Analysis of a crystal by X-ray diffraction revealed the product to be compound [4.1(AuCl)2]. The molecular structure is shown in Figure 4.4. 126 Figure 4.4: Molecular structure of [4.1(AuCl)2]. [C2(S),P2(R) isomer is shown]. Thermal ellipsoids are presented at 50% probability level. Hydrogen atoms are omitted for clarity. The P1−Au1 bond length [2.2076(18) Å] in [4.1(AuCl)2] is in the range reported for phosphaalkene-AuI complexes [2.20(5) to 2.242(11) Å].49, 120, 157, 175-180 The P1−C1 bond length in [4.1(AuCl)2] [1.674(8) Å] is comparable to that of uncoordinated 4.1 [1.6815(18) Å] and is in the range reported for known phosphaalkene-AuI complexes [1.665(3) to 1.74(4) Å].49, 120, 157, 175-180 Analogous to the observations in the coordination of PI to AuI, the Mes*−P1−C1 angle in 4.1 becomes larger upon coordination to AuI {4.1 102.85(8), [4.1(AuCl)2] 113.0(3)°}. Additionally, the Mes*−P1 bond length decreases upon coordination by 0.034(7) Å. The P2−C2 bond [1.870(6) Å] is shorter than the P2−C6 bond [1.816(7) Å], typical of P–C(sp3) and P–C(sp2) bonds.164, 174 The C2−P2−C6 angle [97.1(3)°] is relatively acute compared to the Mes*−P2−C2 and Mes*−P2−C6 angles [101.8(3) and 107.4(4)°, respectively]. The analogous angles in 127 uncoordinated dimer 4.1 [C6−P2−C2 100.87(8), Mes*−P2−C2 108.87(8) and Mes*−P2−C6 110.19(8)°] are all slightly larger [Δ = 3.77(3), 7.07(3) and 2.79(4)°, respectively]. Presumably, coordination to AuI causes steric congestion at P2 and results in more acute angles for the complex. Analysis of a CD2Cl2 solution of [4.1(AuCl)2] by 31P NMR spectroscopy revealed a doublet of quartets resonance at 199.5 ppm (3JPP = 65 Hz, 3JPH = 26 Hz) which was assigned to the phosphaalkene substituent. The upfield shift of this signal relative to 4.1 (Δδ = −37.2) is in the range expected for related P=C compounds upon coordination to AuI (Δδ −31.5 to −87.1).49, 120, 157, 175-180 Additionally, a signal was observed at 23.1 ppm (br d, 3JPP = 65 Hz), assigned to the phosphine−AuCl group, which was shifted downfield by 39.5 ppm relative to the analogous signal in 4.1. For reference the signals assigned to related phosphines (PR3: R = Me172, i-Pr172, t-Bu173, o-tolyl171, Ph170) shift downfield upon coordination to AuI (Δδ = 28.0 to 52.3). The complex was further analyzed by 1H and 13C{1H} NMR spectroscopy, including two-dimensional experiments, to permit assignments. Notably, the resonance assigned to the P=C substituent was observed at 174.3 ppm (d, 1JPC = 71 Hz) and was shifted upfield from the analogous signal in 4.1 [δ = 187.4 (dd, 1JPC = 45 Hz, 2JPC = 14 Hz)]. A large increase in the 1JPC coupling constant (Δ1JPC = 26 Hz) was also observed upon coordination to AuI, analogous to that described for [Au(PI)Cl]. To gain insight into the mechanism of this unprecedented [4+2] cycloaddition reaction, DFT calculations were undertaken by Prof. Yoshihiro Hayashi at the Tokyo Institute of Technology. Two types of [4+2] Diels-Alder dimerization are possible between a P=C−C=C moiety and the C=C of another P=C-C=C unit [shown as TS1 and TS2 in Scheme 4.3(a)]. Due to unfavorable interactions between the bulky Mes* substituent and the P=C−C=C diene during approach in TS2(endo/exo), these transition states were 2.2 and 2.8 kCal mol−1 higher than TS1, respectively. The endo pathway of TS1 could not be modeled. From these calculations, it is clear 128 that the steric bulk provided by the large Mes* substituent is responsible for the observed regiochemistry of the [4+2] dimerization of PI. Interestingly, DFT modeling of (Me)P=CH−CH=CH2, which contains a smaller Me substituent at P, revealed the favored dimerization product to be of Type I [Scheme 4.3(b)]. Scheme 4.3: (a) Transition state calculations for the [4+2] dimerization of PI; (b) favored regiochemical outcome of intermolecular dimerization of MeP=CH−CH=CH2 to afford a Type I scaffold. 4.2.2 Selective intramolecular cyclization of Mes*P=C(Me)−C(Me)=CH2 (4.2) To explore the generality and selectivity of this novel coordination chemistry, a new P=C−C=C diene was prepared with increased steric encumbrance on the ligand framework. It is shown above that the steric profile of the P=C−C=C scaffold dictates which cycloaddition/oligomerization pathway is favored as evaluated by density functional theory (DFT). Moreover, 1-phosphabutadiene Mes*P=CH−CH=CH2, which does not have a methyl group in the 2-position, is not isolable at room temperature and spontaneously polymerizes to afford poly(1-phosphabutadiene), whereas PI [Mes*P=C(Me)−CH=CH2] is isolable and can be stored in pure 129 form for long periods.161 We therefore hypothesized that additional steric bulk on the P=C−C=C ligand may favor intramolecular cycloaddition to afford 1-phosphet-2-ene structures (type III in Chart 4.1) as opposed to intermolecular processes (types I, II or polymerization). To this end, we targeted Mes*P=C(Me)−C(Me)=CH2, 4.2, which has a methyl group in the 3-position. A solution of freshly prepared 2-propenylmagnesium bromide (3.3 equiv) was added to a solution of Mes*P=C(Me)Br (1 equiv) and [Pd(PPh3)4] (0.04 equiv) in THF (Scheme 4.4). As a precaution, the reaction flask was covered in aluminum foil to preclude light-induced E/Z-isomerization of the product which has been previously observed for P=C−C=C compounds (see chapter 5). Analysis of the reaction mixture by 31P NMR spectroscopy after 20 min revealed only a singlet at 256.1 ppm. Following work-up, single crystals were isolated in 70% yield. The crystals were characterized as 4.2 using 1H, 31P, 13C{1H} and two-dimensional NMR spectroscopies, LRMS, HRMS, elemental analysis, and single-crystal X-ray diffraction. Scheme 4.4: Preparation of 4.2 from E/Z-Mes*P=C(Me)Br. The molecular structure of 4.2 is shown in Figure 4.5. Consistent with previous reports, the palladium-mediated nucleophilic substitution of E/Z-Mes*P=C(Me)Br by 2-propenylmagnesium bromide proceeds stereoselectively to exclusively produce the E-configured P=C bond.81, 82, 242 The P1−C1, C1−C2 and C2−C3 bond lengths [1.692(3), 1.476(4) and 1.340(4) Å, respectively] are similar to those of related 1-phosphabutadienes [Mes*P=C(R)−CH=CH2 (R = Me, Si(CH3)3) (ranges): P1−C1 1.687(5) to 1.694(1); C1−C2 1.457(4) to 1.477(2); C2−C3 1.323(8) to 1.341(2) 130 Å].81 The P=C−C=C torsion angle [171.5(2)°] reflects a slightly less planar phosphabutadiene unit than in related Mes*P=C(R)−CH=CH2 compounds [R = CH3: 180.0(4)°; R = Si(CH3)3 (Z-isomer): 180.00(5)°; R = Si(CH3)3 (E-isomer): 173.7(4)°]. Figure 4.5: Molecular structure of 4.2. Thermal ellipsoids are presented at 50% probability level. Hydrogen atoms are omitted for clarity. With the new 1-phosphabutadiene in hand, 4.2 (1 equiv) was treated with [Au(tht)Cl] (1 equiv) in CH2Cl2 and the resultant pale-yellow solution was evaluated by 31P NMR spectroscopy (Scheme 4.5). After 48 h the analysis revealed only a singlet resonance at 38.4 ppm and its high field chemical shift suggested that the product no longer contained a P=C bond. Single crystals were grown from CH2Cl2/pentane (1:1) at −35 °C and were analyzed by X-ray diffraction. As hypothesized, the greater degree of steric bulk of 4.2 led selectively to the intramolecular type III cyclized product [Au(4.3)Cl] (Figure 4.6). AuI complexes of 1-phosphet-2-enes are rare yet have been of interest for their potential luminescent applications.243 131 Scheme 4.5: Preparation of 1-phosphet-2-ene gold(I) complex [Au(4.3)Cl]. Figure 4.6: Molecular structure of [Au(4.3)Cl]. Thermal ellipsoids are shown at 50% probability level. Hydrogen atoms are omitted for clarity. Analysis of a CDCl3 solution of compound [Au(4.3)Cl] by 31P NMR spectroscopy revealed a singlet resonance at 38.4 ppm. Furthermore, the 1H NMR spectrum revealed two sets of doublet of doublets [δ = 3.07 (1H, 2Jgem = 15 Hz, 2JPH = 8 Hz) and 2.60 (1H, 2Jgem = 15 Hz, 2JPH = 15 Hz)] that were assigned to the diastereotopic P−CH2 protons. These signals both correlated by 1H,13C-HSQC NMR spectroscopy to a 13C{1H} doublet at 42.9 ppm (1JPC = 49 Hz). Two additional signals were observed at 1.92 (d, 3H, 3JPH = 14 Hz) and 1.68 (s, 3H) ppm which were assigned to the CH3 substituents of the 1-phosphet-2-ene heterocycle. These signals were correlated by 1H,13C-HSQC NMR spectroscopy to 13C{1H} resonances at 14.8 (d, 2JPC = 6 Hz) and 17.3 (d, 3JPC = 24 Hz) ppm, respectively. Notably, two doublet signals were observed at 150.1 (2JPC = 5 Hz) and 137.7 (1JPC = 132 51 Hz) ppm and were assigned to the C=C substituent of the 1-phosphet-2-ene ring. For comparison, the signals assigned to the C=C group in the related [C(=CPh2)–CaH=CbPh-P(AuCl)Ph] resonated at 143.0 ppm (JPC = 7 Hz, Ca) and 130.8 ppm (JPC = 7 Hz, Cb).243 Given the interest in developing 1-phosphet-2-ene scaffolds due to their desirable ligand properties and potential applications in optoelectronic materials,244 the scope of this novel intramolecular cyclization was investigated. As there are no reported PdII complexes of 1-phosphetenes and the role of PdII in catalytic transformations, we targeted the readily available complexes [Pd(η3-C3H5)(μ-Cl)]2 and [Pd(cod)Cl2]. In both cases, treatment with 4.2 promoted the [2+2] intramolecular cycloaddition in ca. 1 h to afford complexes of 1-phosphet-2-ene 4.3 as determined by 31P NMR spectroscopy (Scheme 4.6). After work-up, the isolated complexes [Pd(4.3)(η3-C3H5)Cl] and [Pd(4.3)2Cl2] were characterized by 1H, 13C{1H} and 31P NMR spectroscopies, X-ray crystallography, elemental analysis, low- and high-resolution MS {only [Pd(4.3)(η3-C3H5)Cl]}. 133 Scheme 4.6: Preparation of 1-phosphet-2-ene palladium(II) complexes. The molecular structures of [Pd(4.3)(η3-C3H5)Cl] are shown in Figure 4.7. Additionally, the molecular structure of the crystallized isomer meso-trans-[Pd(4.3)2Cl2] is shown in Figure 4.8. The molecular structure of [Pd(4.3)(η3-C3H5)Cl] displays disorder of the allyl ligand such that two sets of diastereomers are observed [R,endo and S,endo with occupancy 0.617(7) and R,exo and S,exo with occupancy 0.383(7)]. In Figure 4.7, the two isomers with R-configuration at P are shown and are named exo or endo to mark the relationship between the relative orientations of C4 and C7 (opposite side is endo).245 All four isomers are shown in Chart 4.2. This type of isomerism for Pd-allyl complexes bearing chiral substituents is well-established.246-253 134 Figure 4.7: Molecular structures of [Pd(4.3)(η3-C3H5)Cl]·0.72 CH2Cl2·0.32 CDCl3 [for clarity, only Isomer 1 (R,endo) with occupancy 0.617 and Isomer 2 (R,exo) with occupancy 0.383 are shown; the enantiomers (S,endo and S,exo) are present, but not shown]. Thermal ellipsoids are presented at the 50% probability level. Solvents of crystallization and hydrogen atoms are omitted for clarity. Inset: structures of R,endo-[Pd(4.3)(η3-C3H5)Cl]·0.72 CH2Cl2·0.32 (left box) and R,exo-[Pd(4.3)(η3-C3H5)Cl]·0.72 CH2Cl2·0.32(right box). Chart 4.2: Diastereomers of [Pd(4.3)(η3-C3H5)Cl]: endo and exo refer to the relative arrangement of the two atoms with red dots. PMes*PdMeMeClPMes*PdMeMeClPMes*PdMeClMeR,endo R,exo S,exoS,endoPMes*PdMeClMe135 Figure 4.8: Molecular structure of meso-trans-[Pd(4.3)2Cl2] [P1(S),P1'(R) isomer is shown]. Thermal ellipsoids are presented at the 50% probability level. Hydrogen atoms are omitted for clarity. The 31P NMR spectrum of a solution of the crystals of [Pd(4.3)(η3-C3H5)Cl] in CDCl3 revealed two signals at 42.6 (ca. 60 %) and 41.6 (ca. 40 %) ppm. These ratios are identical to those observed in the reaction mixture and to the ratio of disorder of the allyl ligand in the crystal structure (0.617:0.383). In addition, all the expected signals detected in the 1H and 13C{1H} NMR spectra could be assigned to either the endo or the exo isomer with the aid of standard two-dimensional NMR spectroscopic experiments. The integrals in the 1H NMR spectra suggested a similar isomeric ratio (ca. 60:40). For instance, the integrated ratio of the well-resolved doublet resonances at 2.86 ppm (JHH = 12 Hz) assigned to one H of the CH2 of the η3-C3H5 group in the endo isomer and at 2.73 (JHH = 12 Hz) assigned to the same proton in the exo isomer was 62:38. 136 Notably, the 13C{1H} spectrum of [Pd(4.3)(η3-C3H5)Cl] in CDCl3 revealed four signals that could be assigned to the C=C group of the 1-phosphet-2-ene ring [δ = 148.3 (d, 2JPC = 5 Hz) and 139.5 (d, 1JPC = 34 Hz) (Endo); 147.3 (d, 2JPC = 5 Hz) and 139.6 (d, 1JPC = 35 Hz) (exo)]. For comparison, the analogous signals in [Au(4.3)Cl] resonated at 150.1 (2JPC = 5 Hz) and 137.7 (1JPC = 51 Hz) ppm. In addition, two doublet resonances were observed at 42.4 (1JPC = 41 Hz, endo) and 42.6 (1JPC = 39 Hz, exo) ppm assigned to the P−CH2 substituent. Analysis of a CDCl3 solution of meso-trans-[Pd(4.3)2Cl2] by 31P{1H} NMR spectroscopy at room temperature immediately after dissolution revealed a singlet at 48.1 ppm. The 1H NMR spectrum revealed two sets of doublets at 3.31 (2H, 2Jgem = 13 Hz) and 2.36 (br 2H, 2Jgem = 13 Hz) ppm that were assigned to the diastereotopic P−CH2 protons. Furthermore, two signals were observed at 2.00 (t, 6H, 3JPH/5JPH = 5 Hz) and 1.67 (br s, 6H) ppm that were assigned to the CH3 substituents of the 1-phosphet-2-ene ring. The 13C{1H} NMR spectrum revealed two signals [δ = 149.3 (s) and 138.6 (t, 1JPC/3JPC = 19 Hz)] assigned to the C=C moiety and an apparent triplet assigned to the P−CH2 substituent was observed at 42.37 ppm (t, 1JPC/3JPC = 21 Hz). These assignments were consistent with the AuI and PdII complexes of ligand 4.3 described above. Interestingly, after 48 h, the 31P{1H} NMR spectrum of the crystals of meso-trans-[Pd(4.3)2Cl2] revealed two signals at 48.1 (s) and 48.2 (br s) ppm with approximately equal ratios. We tentatively assign the signal at 48.2 ppm to rac-trans-[Pd(4.3)2Cl2], resulting from exchange of the R- and S-4.3 ligands. Evidence for this assignment was garnered from the 1H and 13C{1H} NMR spectra after 48 h, including variable temperature, compared to the spectra of the crystals immediately after dissolution. Specifically, new signals observed at 3.28 (d, 2H, 2Jgem = 11 Hz) and 2.35 (br d, 2H, 2Jgem = 11 Hz) ppm could be assigned to diastereotopic P−CH2 protons. Furthermore, signals were observed at 1.99 (t, 6H, 3JPH/5JPH = 5 Hz) and 1.67 (br s, 6H) ppm that 137 were assigned to CH3 substituents. These signals were correlated by 1H,13C-HMBC NMR spectroscopy to 13C{1H} resonances at 149.2 (s) and 138.3 (t, 1JPC /3JPC = 19 Hz) that were assigned to the C=C moiety of the rac-trans-[Pd(4.3)2Cl2] isomer. Also, a signal assigned to the P−CH2 group was observed as an apparent triplet [δ = 42.41 (t, 1JPC = 21 Hz)]. Further evidence for the assignment of this second isomer as rac-trans-[Pd(4.3)2Cl2] comes from the presence of triplet resonances for the C substituents of the phosphines in the 13C{1H} spectrum. The observation of triplets rather than the expected doublet of doublets is typical of trans-configured PdII-diphosphines.254 Moreover, phosphine ligand scrambling in solution of this type has been previously observed for mixtures of trans-[PhPd(PPh3)2I] and trans-[PhPd(PPh2Me)2I].255 Due to overlap of many of the signals assigned to meso-trans- and rac-trans-[Pd(4.3)2Cl2], we were unable to determine the precise ratio of the two isomers, but it was approximately 50:50. 4.2.3 X-ray crystallographic data for AuI and PdII complexes of 1-phosphet-2-ene (4.3) In each crystal structure, the asymmetric 1-phosphet-2-ene ligand (4.3) necessitates stereochemical considerations. Namely, both enantiomers were present in the crystal lattice of [Au(4.3)Cl], two sets of diastereomers in the case of (endo/exo)-[Pd(R/S-4.3)(η3-C3H5)Cl] and selectively the meso-trans-[Pd(4.3)2Cl2] isomer. The PC3-ring of the 1-phosphet-2-ene ligand (4.3) is essentially planar in each case with the maximum distance from the best plane of the four atoms of the 1-phosphet-2-ene scaffold being at the C2 atom {distance of C2 from the best plane (Å): [Au(4.3)Cl] = 0.0274(19); [Pd(4.3) (η3-C3H5)Cl] = 0.0126(11); [Pd(4.3)2Cl2] = 0.0046(16)}. This results in a slight puckering of the ring with C2 and P being slightly above the best plane and C1 and C3 being below the best plane of the ring. The largest deviation from planarity occurs with [Au(4.3)Cl] as judged by the aforementioned distance from the best plane and also the P1−C1−C2−C3 dihedral angles {[Au(4.3)Cl] = −3.8(3); [Pd(4.3)(η3-C3H5)Cl] = 1.75(15); [Pd(4.3)2Cl2] = −0.7(2)°}. 138 The sum of the angles within the 1-phosphet-2-ene ring show minimal deviation from the idealized 360° for a planar four-membered ring {[Au(4.3)Cl] = 359.8(5); [Pd(4.3)(η3-C3H5)Cl] = 360.0(3); [Pd(4.3)2Cl2] = 360.0(5)°}. For comparison, the sum of the ring angles within known 1-phosphet-2-ene W0 and AuI complexes range from 358.8(4) to 360(1)°.93, 96 256-259 The C1−P1−C3 angles are the most acute within the 1-phosphet-2-ene ring {angle (°): [Au(4.3)Cl] = 75.11(19); [Pd(4.3)(η3-C3H5)Cl] = 74.51(9); [Pd(4.3)2Cl2] = 73.40(18)}. This is in agreement with the aforementioned known 1-phosphet-2-ene-W0 and AuI complexes [range = 70.9(2) to 75.4(1)°]. The P1−C1−C2 and C1−C2−C3 angles are much more acute than expected for an sp2 center and suggest considerable ring strain is present {[Au(4.3)Cl] = 92.5(3), 105.6(3); [Pd(4.3)(η3-C3H5)Cl] = 93.70(15), 104.69(17); [Pd(4.3)2Cl2] = 96.0(2), 104.3(4)°, respectively}. The best plane of the PC3 1-phosphet-2-ene ring in each PdII complex is nearly orthogonal to the PdII square plane {angle between planes (°): [Pd(4.3)(η3-C3H5)Cl] endo = 91.10(18), exo = 83.4(3); [Pd(4.3)2Cl2] = 88.34(10)}. Interestingly, the Mes* ring in each case is slightly folded with the ipso-C being significantly out of the best plane of the other five ring atoms {distance from ipso-C to Mes* plane (Å) = 0.204(5) in [Au(4.3)Cl]; 0.199(2) in [Pd(4.3)(η3-C3H5)Cl]; 0.190(3) in [Pd(4.3)2Cl2]}. In each case, this folding occurs towards the plane of the 1-phosphet-2-ene ring. The AuI center deviates slightly from linearity in [Au(4.3)Cl] [P1−Au1−Cl1 = 176.56(4)°] and the PdII center is planar with the sum of the angles near the expected 360° {Σangles (°) = 360.5(7) in [Pd(4.3)(η3-C3H5)Cl]; 360.0(6) in [Pd(4.3)2Cl2]}. For comparison, the range for [R3P−Pd(η3-C3H5)Cl] complexes is 359.6 to 360.0° (R = Ph260, Cy261, Me262) and for trans-configured [(R3P)2PdCl2] complexes range from 360.0 to 360.1° (R = Ph,218 o-tolyl,219 m-tolyl,220 Cy,221 Et222). The P–Au bond length in [Au(4.3)Cl] [2.2325(8) Å] is similar to that found in the only other structurally characterized AuI-phosphet-2-ene [2.224(2) Å].243 Although no previous 1-139 phosphet-2-ene complexes of PdII have been reported, the P−Pd bond lengths can be compared to those of related phosphine complexes. For instance, the P–Pd bond lengths in [Pd(4.3)2Cl2] and [Pd(4.3)(η3-C3H5)Cl] [2.3322(8) and 2.3245(6) Å, respectively] are at the long end of the range for trans-configured [(R3P)2PdCl2] complexes [R = Ph,218 o-tolyl,219 m-tolyl,220 Cy,221 Et;222 range = 2.186(2) to 2.3629(9) Å] and [R3P−Pd(η3-C3H5)Cl] complexes [R = Ph,260 Cy,261 Me;262 range = 2.2728(15) to 2.314(5) Å]. 4.2.4 Detection of intermediates in [2+2] intramolecular cyclization reactions To gain insight into the mechanism of these novel electrocyclization reactions, all three were monitored by 31P and 31P{1H} NMR spectroscopy. A stack plot showing the progress of reaction of 4.2 (1 equiv) with [Au(tht)Cl] (1 equiv) along with the recrystallized product is shown in Figure 4.9. This reaction was the slowest of the three. The 31P{1H} NMR spectrum of the pale-yellow reaction mixture after 2 h showed that the signal for 4.2 was no longer present and two major signals at 177.0 and 38.4 ppm in a 3:1 ratio were observed alongside two minor signals 171.9 and 18.0 ppm. The signal at 177.0 ppm ( = −77.8 from 4.2) was assigned to intermediate [Au(4.2)Cl] complex {cf. [Au(PI)Cl]:  =196.5;  = −67.8 from PI }. The signal assigned to [Au(4.2)Cl] disappeared over 48 h and the signal assigned to [Au(4.3)Cl] was observed (δ = 38.4) in near quantitative conversion except for the minor signal at 18.0 ppm (unidentified). 140 Figure 4.9: 31P{1H} NMR spectra (162 MHz, 25 ⁰C) showing the progress of the reaction between 4.2 (1 equiv) and [Au(tht)Cl] (1 equiv) in CH2Cl2. The spectrum for recrystallized [Au(4.3)Cl] was recorded in CDCl3. The reaction of 4.2 with [Pd(η3-C3H5)(μ-Cl)]2 (0.5 equiv) in CDCl3 was much faster than the reaction of 4.2 and [Au(tht)Cl], and was monitored by 31P{1H}, 1H, 1H{31P} and related two-dimensional NMR spectroscopies. After 10 min, the 31P{1H} NMR spectrum showed a small signal at 196.3 ppm (19%) assigned to [Pd(4.2)(η3-C3H5)Cl] and signals at 42.6 (47%) and 41.6 ppm (34%) assigned to isomers of product [Pd(4.3)(η3-C3H5)Cl]. Additional support for these assignments comes from the 1H,31P-HMBC NMR spectrum of the reaction mixture after 10 min. Specifically, a correlation between the 31P signal at 196.3 ppm and a signal at 1.44 (d, 3JPH = 27 Hz) in the 1H NMR spectrum was observed. This resonance was assigned to the P=C(CH3)−C(CH3)=CH2 substituent of [Pd(4.2)(η3-C3H5)Cl]. Moreover, two more correlations were observed to broad singlets at 5.35 and 4.94 ppm that were assigned to the P=C(CH3)−C(CH3)=CH2 group. Additionally, five signals were observed that were consistent with the presence of the η3-C3H5 ligand [δ = 5.47 (overlapping multiplet), 4.66 (br s), 3.96 (br s), 3.64 141 (br s) and 2.97 (br s)]. Taken together, these data are consistent with the formulation of the intermediate as [Pd(4.2)(η3-C3H5)Cl]. Figure 4.10: 31P{1H} NMR spectra (162 MHz, 25 ⁰C) showing the progress of the reaction between 4.2 (1 equiv) and [Pd(η3-C3H5)(μ-Cl)]2 (0.5 equiv) in CDCl3. In contrast to the two previous reactions, careful monitoring of the reaction of 4.2 and [Pd(cod)Cl2] (0.5 equiv) to form meso-trans- and rac-trans-[Pd(4.3)2Cl2] did not reveal intermediates by 31P{1H} NMR spectroscopy. It appears that any intermediate species {e.g. [Pd(4.2)2Cl2]}, if indeed involved in the [2+2] cycloaddition, is consumed faster than it is formed from 4.2 and [Pd(cod)Cl2]. 142 Figure 4.11: 31P{1H} NMR spectra (162 MHz, 25 ⁰C) showing the progress of the reaction between 4.2 (1 equiv) and [Pd(cod)Cl2] (0.5 equiv) in CH2Cl2. The spectrum for recrystallized [Pd(4.3)2Cl2] was recorded in CDCl3. 4.3 Conclusion In closing, we have reported a series of cyclization reactions of 1-phosphabutadienes. The hitherto unknown regioselective [4+2] dimerization of PI affords a phosphaalkene substituted phosphacyclohexene ligand scaffold. This dimer is shown to act as a hybrid P(sp2)/P(sp3) chelating P-ligand for PdII. Furthermore, PI formed complex [Au(PI)Cl] upon reaction with [Au(tht)Cl]. This complex was shown to undergo the same intermolecular [4+2] cycloaddition to afford [4.1(AuCl)2] when the reaction was conducted at higher concentration. In contrast to the intermolecular cyclization observed for PI, the more sterically hindered 1-phosphabutadiene 4.2 underwent an intramolecular [2+2] cycloaddition to afford [Au(4.3)Cl] (4.3 = 1-phosphet-2-ene). Analogous cyclizations to afford 1-phosphet-2-ene ligands also occurred when 4.2 was treated with either [Pd(cod)Cl2] or [Pd(η3-C3H5)(μ-Cl)]2. Namely, racemic [Pd(4.3)2Cl2] and [Pd(4.3)(η3-143 C3H5)Cl], respectively, were isolated and structurally characterized. NMR spectroscopic studies detected transient intermediates, [Au(4.2)Cl] and [Pd(4.2)(η3-C3H5)Cl], in the reactions of 4.2 with [Au(tht)Cl] and [Pd(η3-C3H5)(μ-Cl)]2, respectively. No intermediates were observed for the reaction of 4.2 with [Pd(cod)Cl2]. The present work provides a facile route to chiral phosphorus ligands which are of interest as non-traditional ligands for transition metals and may permit access to complexes that have utility in catalysis. 4.4 Experimental Methods 4.4.1 General procedures All manipulations of air- and/or moisture-sensitive compounds were conducted using standard Schlenk or glovebox techniques. Tetrahydrofuran (THF) was dried over sodium/benzophenone ketyl and distilled prior to use. Hexanes, dichloromethane, and diethyl ether were degassed and passed through an activated alumina column prior to use. [Pd(cod)Cl2] and [Pd(η3-C3H5)(μ-Cl)]2 were purchased from Sigma Aldrich and used as received. Mes*P=C(Me)Br was synthesized according to a literature procedure.185 1H, 13C{1H} and 31P NMR spectra were measured at room temperature on a Bruker AVANCE III HD 400 spectrometer. Chemical shifts of 1H NMR spectra were expressed in parts per million downfield from residual CHCl3 (δ = 7.26) or CDHCl2 (δ = 5.32). Chemical shifts of 13C{1H} NMR spectra were expressed in parts per million downfield from CDCl3 (δ = 77.16) or CD2Cl2 (δ = 53.84). Chemical shifts of 31P NMR spectra were expressed in parts per million downfield from 85% H3PO4 as an external standard (δ = 0). Integrals of 31P NMR spectra give only approximate ratios (d1 = 2 s, cf. t1 = 0.613 s for PI). All integrals were phased using Topspin 4.0 software. ESI low-resolution mass spectra were recorded on a Bruker HCT ion trap mass spectrometer equipped with an electrospray ion source. ESI high-resolution mass spectra were obtained on an Agilent 6545 QTOF mass spectrometer equipped with an Agilent 144 Jet stream (AJS) electrospray ion source. For accurate mass measurement, commercial reference solutions from Agilent were used as reference compounds. FD mass spectra were recorded on Jeol AccuTOF-GCv 4G, a GC-TOF MS instrument equipped with a field desorption/ionization (FD/FI) ion source. All mass spectra were acquired in the positive ion mode. 4.4.2 X-ray crystallography All single crystals were immersed in oil and mounted on a mylar loop. Data were collected on a Bruker X8 APEX II diffractometer with Mo Kα radiation, integrated using the Bruker SAINT software package186 and corrected for absorption effects using SADABS.187 All structures were solved by direct methods and subsequent Fourier difference techniques. All data sets were corrected for Lorentz and polarization effects. All structure solutions were performed using SHELXT.188 All refinements were performed using SHELXL189 via the Olex2 interface.190 Compound 4.2 was refined as a 4-component twin using an HKLF5 format data set with complete data from the largest domain and overlapped reflections from the three smaller domains. Compound [4.1(AuCl)2] was resolved as a two-component twin and crystallized with CH2Cl2 in the lattice that was too badly disordered to be reasonably modeled. As a result, the PLATON/SQUEEZE263 program was used to generate a 'solvent-free' data set. For meso-trans-[Pd(4.3)2Cl2], the 1-phosphete-2-ene fragment is disordered and was modeled in two orientations. Also, one of the t-Bu groups is disordered in two orientations and was modeled with mild restraints to maintain reasonable geometries. For [Pd(4.3)(η3-C3H5)Cl], the allyl group is disordered and was modeled in two orientations. [Pd(4.3)(η3-C3H5)Cl] also crystallizes with both dichloromethane and chloroform in the lattice, occupying the same site and modeled as disordered. The occupancy of the central carbon refined to exactly 1.0; therefore, it was assumed that the sum of the occupancies 145 of the different solvent fragments is 1.0. Three dichloromethane fragments and one chloroform fragment were located and modeled. 4.4.3 DFT calculations All geometry optimizations and transition state calculations were performed by Prof. Yoshihiro Hayashi at the ωB97X-D264/6-311G(d,p) level using Gaussian 16, Revision B.01.265 All calculated transition states were checked using Intrinsic Reaction Coordinate calculations. 4.4.4 Preparation of 4.1 PI (500 mg, 1.5 mmol) was dissolved in THF (5 mL) resulting in a yellow solution. The reaction was stirred at 60 °C resulting in a gradual change from a yellow to orange color. Monitoring by 31P NMR spectroscopy after 3 d showed two new resonances in a 1:1 ratio [δ = 238.2 (32%) and –16.1 (32%)]. The solvent was removed in vacuo to afford a crude yellow solid. Yellow crystals suitable for X-ray analysis were grown from a saturated Et2O solution at −35 °C. Yield = 250 mg, 50%. 31P{1H} NMR (CD2Cl2, 162 MHz, 25 ⁰C) δ 236.7 (d, 3JPP = 31 Hz), −16.5 (d, 3JPP = 31 Hz); 1H NMR (CD2Cl2, 400 MHz, 25 ⁰C) δ 7.45 (s, 1H, Mes*H), 7.40 (s, 1H, Mes*H), 7.36 (s, 1H, Mes*H), 7.32 (s, 1H, Mes*H), 5.67 (br m, 1H, C=CH), 4.52 (br, 1H, P−CH), 2.53 (br, 1H, CHaHb), 2.25 (br m, 2H, CH2), 2.05 (br m, 1H, CHaHb), 1.62 (s, 18H, o-C(CH3)3), 1.50 (s, 9H, o-C(CH3)3), 1.41 (d, 3H, 3JPH = 14 Hz, P=C−CH3), 1.34 (s, 9H, p-C(CH3)3), 1.32 (s, 9H, p-C(CH3)3), 1.29 (d, 3H, 3JPH = 5 Hz, P−C−CH3), 1.22 (s, 9H, o-C(CH3)3); 13C{1H} NMR (101 MHz, CD2Cl2, 25 ⁰C) δ 187.4 (dd, 1JPC = 45 Hz, 2JPC = 14 Hz, P=C), 160.5 (d, 2JPC = 34 Hz, o-Mes*), 157.6 (d, 2JPC = 7 Hz, o-Mes*), 153.9 (s, o-Mes*), 153.5 (s, o-Mes*), 149.8 (d, 4JPC = 2 Hz, p-Mes*), 149.5 (s, o-Mes*), 138.0 (d, 1JPC = 31 Hz, ipso-Mes*), 137.5 (d, 1JPC = 5 Hz, C=CH), 131.1 (d, 1JCP = 55 Hz, ipso-Mes*), 127.3 (d, 2JPC = 10 Hz, C=CH), 124.3 (s, m-Mes*), 122.6 (s, m-Mes*), 121.6 (s, m-146 Mes*), 121.4 (s, m-Mes*), 48.0 (dd, 1JPC = 42 Hz, 2JPC = 29 Hz, P−CH), 39.8 (s, o-C(CH3)3), 39.6 (d, 3JPC = 7 Hz, o-C(CH3)3), 38.3 (s, o-C(CH3)3), 37.8 (s, o-C(CH3)3), 35.1 (br d, 4JPC = 16 Hz, o-C(CH3)3), 35.0 (s, p-C(CH3)3), 34.9 (s, p-C(CH3)3), 34.7 (br, o-C(CH3)3), 32.9 (d, 4JPC = 8 Hz, o-C(CH3)3), 32.6 (d, 4JPC = 7 Hz, o-C(CH3)3), 32.0 (dd, JPC = 13 Hz, JPC = 13 Hz, CH2), 31.5 (s, p-C(CH3)3), 31.4 (s, p-C(CH3)3), 27.8 (s, CH2), 23.5 (d, 2JPC = 14 Hz, P−C−CH3), 20.9 (dd, 2JPC = 16 Hz, 3JPC = 11 Hz, P=C−CH3). ESI-MS [M+H+] 661.4 (100), 662.4 (50), 663.4 (10). HRMS (ESI, positive mode) calcd for C44H71P2, 661.5031, found 661.5033. 4.4.5 Preparation of [Pd(4.1)Cl2] To a solution of 4.1 (30 mg, 45 µmol) in CH2Cl2 (1 mL) was added [Pd(cod)Cl2] (12 mg, 42 µmol) resulting in an orange solution. After 3 h, 31P{1H} NMR spectroscopic analysis of the reaction mixture showed two doublets (δ = 212.1, 62.6, 2JPP = 18 Hz) in a 1:1 ratio. Slow evaporation of the solvent at room temperature afforded yellow crystals suitable for X-ray analysis. The crystals were washed with pentane. Yield = 25 mg, 71%. 31P{1H} NMR (CDCl3, 162 MHz, 25 ⁰C) δ 213.5 (d, 2JPP = 17 Hz), 62.5 (d, 2JPP = 17 Hz); 1H NMR (CDCl3, 400 MHz, 25 ⁰C) δ 7.52 (br s, 1H, Mes*H), 7.46 (br s, 1H, Mes*H), 7.32 (br s, 1H, Mes*H), 7.27 (br s, 1H, Mes*H), 6.26 (br s, 1H, C=CH), 5.93 (br d, 1H, 2JPH = 29 Hz, P−CH), 2.90 (d, 3H, 3JPH = 13 Hz, P−C−CH3), 2.84 (br m, 2H, CH2), 2.66 (br m, 2H, CH2), 1.72 (s, 9H, o-C(CH3)3), 1.62 (s, 9H, o-C(CH3)3), 1.53 (s, 9 H, o-C(CH3)3), 1.45 (s, 9H, o-C(CH3)3), 1.29 (d, 3H, 3JPH = 26.0 Hz, P=C−CH3), 1.29 (s, 18H, p-C(CH3)3 and p-C(CH3)3). FD-MS [M+] 832.4 (3), 833.4 (3), 834.4 (24), 835.4 (55), 836.4 (86), 837.4 (66), 838.4 (100), 839.4 (48), 840.4 (66), 841.4 (28), 842.4 (24), 843.4 (10). HRMS (FD+) calcd for C44H70P2Cl2Pd, 838.3369, found 838.3378. 147 4.4.6 Preparation of [Au(PI)Cl] PI (100 mg, 0.30 mmol) was dissolved in CH2Cl2 (1 mL) forming a pale-yellow solution. To this solution was added a solution of [Au(tht)Cl] (90 mg, 0.28 mmol) in CH2Cl2 (2 mL) to afford an orange solution. The reaction mixture was stirred for 5 min and analyzed by 31P NMR spectroscopy to reveal a broad signal at 200.5 ppm. The solvent was removed in vacuo and the residue was washed with hexanes (2 mL) at −35 °C. The supernatant was removed and the resultant off-white solid was dried in vacuo. Yield = 140 mg, 88%. Yellow crystals suitable for X-ray analysis were grown from a saturated CH2Cl2 solution at −35 °C. 31P NMR (CDCl3, 162 MHz, 25 ⁰C) δ 196.5 (s); 1H NMR (CDCl3, 400 MHz, 25 ⁰C) δ 7.54 (d, 2H, 2JPH = 4 Hz, Mes*H), 7.36 (ddd, 1H, 3JPH = 20 Hz, 3Jtrans = 17 Hz, 3Jcis = 11 Hz, P=C(CH3)−CH=CH2), 5.53 (dd, 1H, 3Jtrans = 17 Hz, 4JPH = 10 Hz, P=C(CH3)−CH=CHcisHtrans trans to H), 5.40 (dd, 1H, 3Jcis = 11 Hz, 4JPH = 8 Hz, P=C(CH3)−CH=CHcisHtrans cis to H), 1.56 (s, 18H, o-C(CH3)3), 1.41 (d, 3H, 3JPH = 28 Hz, P=C(CH3)−CH=CH2), 1.33 (s, 9H, p-C(CH3)3); 13C{1H} NMR (CDCl3, 101 MHz, 25 ⁰C) δ 170.3 (d, 1JPC = 77 Hz, P=C(CH3)−CH=CH2), 156.6 (s, o-Mes*), 154.5 (d, 4JPC = 2 Hz, p-Mes*), 137.6 (d, 2JPC = 15 Hz, P=C(CH3)−CH=CH2), 123.4 (d, 3JPC = 10 Hz, m-Mes*), 123.1 (d, 1JPC = 35 Hz, ipso-Mes*), 117.3 (d, 3JPC = 48 Hz, P=C(CH3)−CH=CH2), 38.9 (d, 3JPC = 2 Hz, o-C(CH3)3), 35.5 (s, p-C(CH3)3), 33.8 (s, o-C(CH3)3), 31.2 (s, p-C(CH3)3), 17.9 (d, 2JPC = 8 Hz, P=C(CH3)−CH=CH2). FD-MS [M+] 562.2 (100), 563.2 (26), 564.2 (37), 565.2 (25). HRMS (FD+) calcd. for C22H35AuPCl, 562.1830; found: 562.1843. Anal. Calcd for C22H35PAuCl: C, 46.94; H, 6.27. Found: C, 47.25; H, 6.54. 4.4.7 Preparation of [4.1(AuCl)2] A flask was charged with PI (100 mg, 0.30 mmol) and [Au(tht)Cl)] (97 mg, 0.30 mmol) and CH2Cl2 (1 mL) was added forming a yellow solution which was stirred for 24 h. Analysis of the 148 reaction mixture revealed five signals [δ = 199.6 (21%), 196.6 (30%), 189.2 (10%), 23.1 (29%) and −30.6 (d, JPH = 393 Hz, 10%)]. The volatiles were removed in vacuo to afford a dark solid. The crude product was recrystallized from Et2O at −35 °C to afford colorless crystals suitable for X-ray analysis. Yield = 30 mg, 18%. 31P NMR (CD2Cl2, 162 MHz, 25 ⁰C) δ 199.5 (dq, 3JPP = 65 Hz, 3JPH = 26 Hz), 23.1 (br d, 3JPP = 65 Hz); 1H NMR (CD2Cl2, 400 MHz, 25 ⁰C) δ 7.59 (s, 1H, Mes*H), 7.55 (s, 1H, Mes*H), 7.33 (s, 1H, Mes*H), 7.25 (s, 1H, Mes*H), 6.54 (br d, 1H, 2JPH = 28 Hz, C=CH), 4.31 (ddd, 1H, 2JPH = 25 Hz, 3JHH = 8 Hz, 3JPH = 8 Hz, P−CH), 2.36 (d, 3H, 3JPH = 15 Hz, P−C−CH3), 1.80 (s, 9H, o-C(CH3)3), 1.71 (s, 9H, o-C(CH3)3), 1.57 (s, 9H, o-C(CH3)3), 1.55 (d, 3H, 3JPH = 26 Hz, P=C−CH3), 1.45 (br s, 2H, CH2), 1.43 (s, 9H, o-C(CH3)3), 1.37 (br s, 2H, CH2), 1.33 (s, 9H, p-C(CH3)3), 1.32 (s, 9H, p-C(CH3)3); 13C{1H} NMR (CD2Cl2, 101 MHz, 25 ⁰C) δ 174.3 (d, 1JPC = 71 Hz, P=C), 160.04 (br d, 2JPC = 2 Hz, o-Mes*), 159.97 (d, 2JPC = 5 Hz, o-Mes*), 157.3 (br s, o-Mes*), 155.7 (s, o-Mes*), 154.8 (d, 4JPC = 2 Hz, p-Mes*), 152.6 (d, 4JPC = 4 Hz, p-Mes*), 147.7 (br s, C=CH), 132.1 (d, 1JPC = 44 Hz, C=CH), 124.8 (d, 3JPC = 10 Hz, m-Mes*), 124.4 (d, 3JPC = 10 Hz, m-Mes*), 124.3 (d, 1JPC = 48 Hz, ipso-Mes*), 124.1 (d, 3JPC = 10 Hz, m-Mes*), 123.6 (d, 1JPC = 32 Hz, ipso-Mes*), 123.3 (d, 3JPC = 11 Hz, m-Mes*), 47.9 (dd, 1JPC = 32 Hz, 2JPC = 15 Hz, P−CH), 43.7 (s, o-C(CH3)3), 40.4 (s, o-C(CH3)3), 39.7 (s, o-C(CH3)3), 39.3 (s, o-C(CH3)3), 36.2 (s, o-C(CH3)3), 35.6 (s, p-C(CH3)3), 35.2 (s, o-C(CH3)3), 34.8 (br, s, p-C(CH3)3), 34.4 (s, o-C(CH3)3), 33.7 (s, o-C(CH3)3), 31.23 (s, p-C(CH3)3), 31.16 (s, p-C(CH3)3), 27.5 (d, 2JPC = 20 Hz, >P−C−CH3), 26.9 (dd, 2JPC = 17 Hz, 3JPC = 6 Hz, P=C−CH3) 23.5 (overlapping signals, CH2−CH2). ESI-MS [M−Cl+] 1089.4 (100), 1090.4 (44), 1091.4 (38), 1092.4 (13). HRMS (FD+) calcd for C44H70P2Au2Cl2, 1124.3661, found 1124.3627. 149 4.4.8 Preparation of 4.2 A dried flask was charged with magnesium turnings (2.40 g, 99 mmol), an iodine crystal and THF (110 mL). A reflux condenser was added and the dark solution was heated to 80 °C. 2-bromopropene (4.0 g, 33 mmol) in THF (10 mL) was slowly added over a period of 30 min. Upon addition, a color change from dark to colorless was observed. The reaction was refluxed for a further 30 min. To a separate flask, Mes*P=C(Me)Br (4.0 g, 10 mmol) and [Pd(PPh3)4] (500 mg, 0.43 mmol) were dissolved in THF (100 mL), forming a yellow solution. The cooled Grignard solution was added quickly to this flask via filter cannula to afford a dark solution. 31P NMR spectroscopic analysis after 10 min showed two signals at 243.5 and 256.1 ppm. After 20 min, the only signal present in the 31P NMR spectrum was at 256.1 ppm. The volatiles were removed in vacuo and the dark residue was dissolved in hexanes and passed through a silica plug (3 × 10 cm). The yellow fraction was collected and the volatiles were removed in vacuo, producing a yellow solid. Crystals suitable for X-ray analysis were grown from CH2Cl2:CH3CN (4 mL:4 mL) at −35 °C. Yield = 2.53 g, 70%. 31P NMR (CDCl3, 162 MHz, 25 ⁰C) δ 254.9 (s); 1H NMR (CDCl3, 400 MHz, 25 ⁰C) δ 7.45 (br s, 2H, Mes*H), 5.13 (br d, 1H, 4JPH = 4 Hz, P=C(CH3)−C(CH3)=CHcisHtrans trans to Me), 4.91 (br s, 1H, P=C(CH3)−C(CH3)=CHcisHtrans cis to Me), 2.29 (br s, 3H, P=C(CH3)−C(CH3)=CH2), 1.49 (s, 18H, o-C(CH3)3), 1.38 (d, 3H, 3JPH = 13 Hz, P=C(CH3)−C(CH3)=CH2), 1.37 (s, 9H, p-C(CH3)3); 13C{1H} NMR (CDCl3, 101 MHz, 25 ⁰C) δ 181.7 (d, 1JPC = 43 Hz, P=C(CH3)−C(CH3)=CH2), 153.7 (s, o-Mes*), 150.0 (s, p-Mes*), 147.3 (d, 2JPC = 23 Hz, P=C(CH3)−C(CH3)=CH2), 138.1 (d, 1JPC = 57 Hz, ipso-Mes*), 121.8 (s, m-Mes*), 110.7 (d, 3JPC = 27 Hz, P=C(CH3)−C(CH3)=CH2), 38.2 (s, o-C(CH3)3), 35.2 (s, p-C(CH3)3), 32.6 (d, 4JPC = 7 Hz, o-C(CH3)3), 31.6 (s, p-C(CH3)3), 22.5 (d, 3JPC = 27, P=C(CH3)−C(CH3)=CH2), 21.3 (d, 2JPC = 15 150 Hz, P=C(CH3)−C(CH3)=CH2). FD-MS [M+] 344.3 (100), 345.3 (27). HRMS (FD+) calcd for C23H37P, 344.2633; found 344.2648. Anal. Calcd for C23H37P: C, 80.18; H, 10.83. Found: C, 80.10; H, 10.77. 4.4.9 Preparation of [Au(4.3)Cl] Compound 4.2 (50 mg, 0.15 mmol) and [Au(tht)Cl] (47 mg, 0.15 mmol) were dissolved in CH2Cl2 (1 mL). The resultant pale-yellow solution was analyzed by 31P NMR spectroscopy after 48 h. The spectrum revealed a signal at 38.4 ppm. The volatiles were removed in vacuo. The residual yellow solid was washed with hexanes at −35 °C and the supernatant removed by filtration to afford a white powder. Yield = 70 mg, 83%. Colorless crystals suitable for X-ray analysis were isolated from a saturated CH2Cl2/pentane solution (1:1) at −35 °C. 31P NMR (CDCl3, 162 MHz, 25 ⁰C) δ 38.4 (s); 1H NMR (CDCl3, 400 MHz, 25 ⁰C) δ 7.32 (d, 2H, 4JPH = 3 Hz, Mes*H), 3.07 (dd, 1H, 2Jgem = 15 Hz, 2JPH = 8 Hz, P−CH2), 2.60 (dd, 1H, 2Jgem = 15 Hz, 2JPH = 15 Hz, P−CH2), 1.92 (d, 3H, 3JPH = 14 Hz, P−C(CH3)=C(CH3)), 1.68 (s, 3H, P−C(CH3)=C(CH3)), 1.54 (s, 18H, o-C(CH3)3), 1.30 (s, 9H, p-C(CH3)3); 13C{1H} NMR (CDCl3, 101 MHz, 25 ⁰C) δ 155.5 (d, 2JPC = 4 Hz, o-Mes*), 151.2 (d, 4JPC = 3 Hz, p-Mes*), 150.1 (d, 2JPC = 5 Hz, P−C(CH3)=C(CH3)), 137.7 (d, 1JPC = 51 Hz, P−C(CH3)=C(CH3)), 125.8 (d, 1JPC = 30 Hz, ipso-Mes*), 124.3 (br d, 3JPC = 8 Hz, m-Mes*), 42.9 (d, 1JPC = 49 Hz, P−CH2), 40.0 (s, o-C(CH3)3), 34.7 (d, 4JPC = 3 Hz, o-C(CH3)3 and p-C(CH3)3), 31.2 (s, p-C(CH3)3), 17.3 (d, 3JPC = 24 Hz, P−C(CH3)=C(CH3)), 14.8 (d, 2JPC = 6 Hz, P−C(CH3)=C(CH3)). Satisfactory elemental analysis could not be obtained. Anal. Calcd for C23H37PAuCl: C, 47.88; H, 6.46. Found: C, 47.25; H, 6.48. 151 4.4.10 NMR-monitoring of the reaction of 4.2 with [Au(tht)Cl] An NMR tube was charged with 4.2 (50 mg, 0.15 mmol), [Au(tht)Cl] (47 mg, 0.15 mmol) and CH2Cl2 (1 mL) to afford a pale-yellow solution. The reaction mixture was monitored by 31P and 31P{1H} NMR spectroscopies for 48 h. 4.4.11 Preparation of [Pd(4.3)(η3-C3H5)Cl] To a yellow solution of [Pd(η3-C3H5)(μ-Cl)]2 (53 mg, 0.14 mmol) in CH2Cl2 (1 mL) was added a colorless solution of 4.2 (100 mg, 0.29 mmol) in CH2Cl2 (1 mL). The resultant yellow solution was analyzed by 31P NMR spectroscopy after 1 h to reveal two major signals at 43.1 and 42.4 ppm in a 3:2 ratio. The volatiles were removed in vacuo and the residual yellow solid was washed with hexanes (2 mL) at −35 °C. After filtration, the product was isolated as a yellow powder. Yield = 145 mg, 95%. Crystals suitable for X-ray analysis were grown from a saturated CH2Cl2 solution at −35 °C. Endo-[Pd(4.3)(η3-C3H5)Cl] (59%). 31P NMR (CDCl3, 162 MHz, 25 ⁰C) δ 42.6 (s); 1H NMR (CDCl3, 400 MHz, 25 ⁰C) δ 7.32 (br s, 2H, Mes*H), 5.48 (m, 1H, allyl-CH), 4.58 (dd, 1H, 3JPH = 7 Hz, 3JHH = 7 Hz, allyl−CH2), 3.50 (d, 1H, 3JPH = 11 Hz, allyl-CH2), 3.38 (d, 1H, 3JHH = 7 Hz, allyl-CH2), 3.25 (d, 1H, 2Jgem = 14 Hz, P−CH2), 2.86 (d, 1H, 3JHH = 12 Hz, allyl-CH2), 2.21 (dd, 1H, 2Jgem = 14 Hz, 2JPH = 10 Hz, P−CH2), 1.98 (d, 3H, 3JPH = 12 Hz, P−C(CH3)=C(CH3)), 1.72 (s, P−C(CH3)=C(CH3)), 1.52 (s, 18H, o-C(CH3)3), 1.30 (s, 9H, p-C(CH3)3); 13C{1H} NMR (CDCl3, 101 MHz, 25 ⁰C) δ 153.7 (br s, o-Mes*), 149.5 (br s, p-Mes*), 148.3 (d, 2JPC = 5 Hz, P−C(CH3)=C(CH3)), 139.5 (d, 1JPC = 34 Hz, P−C(CH3)=C(CH3)), 131.1 (d, 1JPC = 3 Hz, ipso-Mes*), 123.8 (br s, m-Mes*), 116.5 (d, 2JPC = 5 Hz, allyl-CH), 76.3 (d, 2JPC = 33 Hz, allyl-CH2), 58.9 (br s, allyl-CH2), 42.4 (d, 1JPC = 41 Hz, P−CH2), 39.3 (br, o-C(CH3)3), 34.4 (s, p-C(CH3)3), 34.3 (s, o-C(CH3)3), 31.1 (s, p-C(CH3)3), 16.3−15.8 (overlapping multiplets, P−C(CH3)=C(CH3)). 152 Exo-[Pd(4.3)(η3-C3H5)Cl] (41%). 31P NMR (CDCl3, 162 MHz, 25 ⁰C) δ 41.6 (s); 1H NMR (CDCl3, 400 MHz, 25 ⁰C) δ 7.32 (br s, 2H, Mes*H), 5.48 (m, 1H, allyl-CH), 4.53 (dd, 1H, 3JPH = 7 Hz, 3JHH = 7 Hz, allyl−CH2), 3.53 (d, 1H, 3JPH = 11 Hz, allyl-CH2) 3.49 (br s, 1H, allyl-CH2), 3.17 (d, 1H, 2Jgem = 14 Hz, P−CH2), 2.73 (d, 1H, 3JHH = 12 Hz, allyl-CH2), 2.41 (dd, 1H, 2Jgem = 14 Hz, 2JPH = 10 Hz, P−CH2), 1.90 (d, 3H, 3JPH = 12 Hz, P−C(CH3)=C(CH3)), 1.69 (s, 3H, P−C(CH3)=C(CH3)), 1.54 (s, 18H, o-C(CH3)3), 1.30 (s, 9H, p-C(CH3)3); 13C{1H} NMR (CDCl3, 101 MHz, 25 ⁰C) δ 153.9 (br s, o-Mes*), 149.5 (br s, p-Mes*), 147.3 (d, 2JPC = 5 Hz, P−C(CH3)=C(CH3)), 139.6 (d, 1JPC = 35 Hz, P−C(CH3)=C(CH3)), 130.0 (br s, ipso-Mes*), 123.8 (br s, m-Mes*), 116.2 (d, 2JPC = 5 Hz, allyl-CH), 75.7 (d, 2JPC = 33 Hz, allyl-CH2) 58.9 (br s, allyl-CH2), 42.6 (d, 1JPC = 39 Hz, P−CH2), 39.3 (br, o-C(CH3)3), 34.4 (s, p-C(CH3)3), 34.3 (s, o-C(CH3)3), 31.1 (s, p-C(CH3)3), 16.3−15.8 (overlapping multiplets, P−C(CH3)=C(CH3)). ESI-MS [M−Cl+] 488.1 (4), 489.1 (28), 490.1 (72), 491.1 (100), 492.1 (24), 493.1 (80), 494.1 (20), 495.1 (36), 496.1 (8). HRMS (ESI-TOF) calcd for C26H42PPd: 491.2059, found: 491.2071. Satisfactory elemental analysis could not be obtained. Anal. Calcd for C26H42PPdCl: C, 59.20; H, 8.03. Found: C, 60.38; H, 8.08. 4.4.12 NMR monitoring of the reaction of 4.2 with [Pd(η3-C3H5)(μ-Cl)]2 An NMR tube was charged with 4.2 (50 mg, 0.15 mmol), [Pd(η3-C3H5)(μ-Cl)]2 (27 mg, 0.07 mmol) and CDCl3 (2 mL). The yellow reaction mixture was monitored by 31P, 31P{1H}, 1H and two-dimensional NMR spectroscopies for 40 min. Intermediate [Pd(4.2)(η3-C3H5)Cl]. 31P NMR (CDCl3, 162 MHz, 25 ⁰C) δ 196.3 (s); 1H NMR (CDCl3, 400 MHz, 25 ⁰C) δ 7.48 (s, 2H, Mes*H), 5.47 (overlapping m, 1H, allyl-CH), 5.35 (br s, 1H, P=C(CH3)−C(CH3)=CHcisHtrans trans to Me), 4.94 (br s, 1H, P=C(CH3)−C(CH3)=CHcisHtrans cis to Me), 4.66 (br s, 1H, allyl-CH2), 3.96 (br s, 1H, allyl-CH2), 153 3.64 (br s, 1H, allyl-CH2), 2.97 (br s, 1H, allyl-CH2), 1.93 (br s, 3H, P=C(CH3)−C(CH3)=CH2), 1.44 (d, 3H, 3JPH = 27 Hz, P=C(CH3)−C(CH3)=CH2), 1.32 (s, 9H, p-C(CH3)3). Due to overlap with the signals assigned to 4.2 and [Pd(4.3)(η3-C3H5)Cl], the o-C(CH3)3 signal could not be unequivocally assigned. 4.4.13 Preparation of [Pd(4.3)2Cl2] To a yellow solution of [Pd(cod)Cl2] (41 mg, 0.14 mmol) in CH2Cl2 (2 mL) was added a colorless solution of 4.2 (100 mg, 0.29 mmol) in CH2Cl2 (2 mL). After 1 h, the yellow reaction solution was analyzed by 31P{1H} NMR spectroscopy to reveal the formation of two new signals (δ = 48.1, 48.0). The volatiles were removed in vacuo and the yellow solid was washed with hexanes (2 mL) at −35 °C. After filtration, a pure yellow powder was obtained. Yield = 97 mg, 78%. Recrystallization from CH2Cl2 at −35 °C resulted in the isolation of X-ray quality crystals. Yield = 40 mg, 32%. Meso-trans-[Pd(4.3)2Cl2]. 31P{1H} NMR (CDCl3, 162 MHz, 25 ⁰C) δ 48.1 (s); 1H NMR (CDCl3, 400 MHz, 25 ⁰C) δ 7.33 (br s, 4H, Mes*H), 3.31 (d, 2H, 2Jgem = 13 Hz, P−CH2), 2.36 (br d, 2H, 2Jgem = 13 Hz, P−CH2), 2.00 (t, 6H, JPH = 5 Hz, P−C(CH3)=C(CH3)), 1.67 (br s, 6H, P−C(CH3)=C(CH3)), 1.63 (br s, 36H, o-C(CH3)3), 1.29 (br s, 18H, p-C(CH3)3); 13C{1H} NMR (CDCl3, 101 MHz, 25 ⁰C) δ 154.0 (br s, o-Mes*), 149.5 (s, p-Mes*), 149.3 (s, P−C(CH3)=C(CH3)), 138.6 (t, JPC = 19 Hz, P−C(CH3)=C(CH3)), 127.4 (t, JPC = 7 Hz, ipso-Mes*), 126.5 (br, m-Mes*), 42.37 (t, JPC = 21 Hz, P−CH2), 40.0 (br, o-C(CH3)3), 34.6 (s, p-C(CH3)3), 34.5 (br s, o-C(CH3)3), 31.2 (s, p-C(CH3)3), 16.5 (t, JPC = 3 Hz, P−C(CH3)=C(CH3)), 15.2 (t, JPC = 11 Hz, P−C(CH3)=C(CH3)). Some broad signals were resolved upon cooling of the solution: 31P{1H} NMR (CDCl3, 162 MHz, −5 ⁰C) δ 48.5 (br s); 1H NMR (CDCl3, 400 MHz, −5 ⁰C) δ 7.37 (br s, 2H, Mes*H), 7.28 (br s, 2H, Mes*H), 3.29 (d, 2H, 2Jgem = 13 Hz, P−CH2), 2.37 (br d, 2H, 2Jgem = 13 154 Hz, P−CH2), 2.00 (br s, 6H, P−C(CH3)=C(CH3)), 1.67 (br s, 24H, P−C(CH3)=C(CH3) and o-C(CH3)3 overlapping signals), 1.57 (s, 18H, o-C(CH3)3), 1.28 (s, 18H, p-C(CH3)3); 13C{1H} NMR (CDCl3, 101 MHz, −5 ⁰C) δ 154.0 (br s, o-Mes*), 153.3 (br s, o-Mes*), 149.5 (s, p-Mes*), 149.3 (s, P−C(CH3)=C(CH3)), 138.4 (t, JPC = 18 Hz, P−C(CH3)=C(CH3)), 127.3 (t, JPC = 7 Hz, ipso-Mes*), 126.0 (br s, m-Mes*), 122.8 (br s, m-Mes*), 42.20 (t, JPC = 21 Hz, P−CH2), 40.7 (s, o-C(CH3)3), 38.4 (s, o-C(CH3)3), 35.2 (br s, o-C(CH3)3), 34.6 (s, p-C(CH3)3), 33.9 (br s, o-C(CH3)3), 31.2 (s, p-C(CH3)3), 16.5 (t, JPC = 3 Hz, P−C(CH3)=C(CH3)), 15.26 (t, JPC = 11 Hz, P−C(CH3)=C(CH3)). Rac-trans-[Pd(4.3)2Cl2]. 31P{1H} NMR (CDCl3, 162 MHz, 25 ⁰C) δ 48.2 (s); 1H NMR (CDCl3, 400 MHz, 25 ⁰C) δ 7.33 (br s, 4H, Mes*H), 3.28 (d, 2H, 2Jgem = 11 Hz, P−CH2), 2.35 (br d, 2H, 2Jgem = 11 Hz, P−CH2), 1.99 (t, 6H, JPH = 5 Hz, P−C(CH3)=C(CH3)), 1.67 (br s, 6H, P−C(CH3)=C(CH3)), 1.63 (br s, 36H, o-C(CH3)3), 1.29 (br s, 18H, p-C(CH3)3); 13C{1H} NMR (CDCl3, 101 MHz, 25 ⁰C) δ 154.0 (br s, o-Mes*), 149.5 (s, p-Mes*), 149.2 (s, P−C(CH3)=C(CH3)) 138.3 (t, JPC = 19 Hz, P−C(CH3)=C(CH3)), 127.2 (t, JPC = 7 Hz, ipso-Mes*), 126.5 (br, m-Mes*), 42.41 (t, JPC = 21 Hz, P−CH2), 40.0 (br, o-C(CH3)3) 34.6 (s, p-C(CH3)3), 34.5 (br s, o-C(CH3)3), 31.2 (s, p-C(CH3)3), 16.4 (t, JPC = 3 Hz, P−C(CH3)=C(CH3)), 15.2 (t, JPC = 11 Hz, P−C(CH3)=C(CH3)). Some broad signals were resolved upon cooling of the solution: 31P{1H} NMR (CDCl3, 162 MHz, −5 ⁰C) δ 48.5 (br s); 1H NMR (CDCl3, 400 MHz, −5 ⁰C) δ 7.37 (br s, 2H, Mes*H), 7.28 (br s, 2H, Mes*H), 3.26 (d, 2H, 2Jgem = 13 Hz, P−CH2), 2.34 (br d, 2H, 2Jgem = 13 Hz, P−CH2), 2.00 (br s, 6H, P−C(CH3)=C(CH3)), 1.67 (br s, 24H, P−C(CH3)=C(CH3) and o-C(CH3)3 overlapping signals), 1.57 (s, 18H, o-C(CH3)3), 1.28 (s, 18H, p-C(CH3)3); 13C{1H} NMR (CDCl3, 101 MHz, −5 ⁰C) δ 154.0 (br s, o-Mes*), 153.5 (s, o-Mes*), 149.5 (s, p-Mes*), 149.3 (s, P−C(CH3)=C(CH3)), 138.1 (br s, P−C(CH3)=C(CH3)), 127.1 (br s, ipso-Mes*), 126.0 (br s, m-155 Mes*), 122.8 (br s, m-Mes*), 42.3 (t, JPC = 21 Hz, P−CH2), 40.7 (br s, o-C(CH3)3) , 38.4 (br s, o-C(CH3)3), 35.2 (br s, o-C(CH3)3), 34.6 (s, p-C(CH3)3), 33.9 (br s, o-C(CH3)3), 31.2 (s, p-C(CH3)3), 16.5 (br s, P−C(CH3)=C(CH3)), 15.30 (t, JPC = 11 Hz, P−C(CH3)=C(CH3)). Satisfactory elemental analysis could not be obtained. Anal. calcd for C46H74P2PdCl2: C, 63.77; H, 8.61. Found: C, 62.76; H, 8.74 4.4.14 NMR monitoring of the reaction of 4.2 with [Pd(cod)Cl2] An NMR tube was charged with 4.2 (50 mg, 0.15 mmol), [Pd(cod)Cl2] (21 mg, 0.07 mmol) and CH2Cl2 (2 mL). The yellow reaction mixture was monitored by 31P and 31P{1H} NMR spectroscopies for 1 h. 156 Chapter 5: Chemical- and Light-Induced Isomerization of the P=C Bond of a 1-Phosphabutadiene 5.1 Introduction One intriguing aspect of phosphaalkenes is their ability to undergo E/Z-isomerization in solution. Such an isomerization process could play an important role in the polymerization of P=C monomers. In addition, it was imagined that polymers featuring P=C bonds, such as poly(1-phosphaisoprene) (PPI), may have intriguing photoswitchable properties by analogy to well-established azobenzene polymers.266, 267 The E/Z-isomerization of phosphaalkenes has been studied extensively for systems bearing a range of substituents (Chart 5.1).268-285 The isomerization of the P=C bond is most commonly induced by visible or UV light irradiation or in some instances mild thermolysis. The chemically induced isomerization of P=C bonds is much less common, with a few reports of iodine-mediated cis/trans-isomerization.286, 287 In one case, a proton-mediated isomerization was postulated for the Z-to-E-isomerization of Mes*P=CH(CH2)2P(Mes*)(DBNH)]Br [DBN = 1,5-diazabicyclo[4.3.0]non-5-ene].288 Versions of sections of this chapter have been published: Walsgrove, H. T. G.; Dabringhaus, P.; Patrick, B. O.; Gates, D. P. Can. J. Chem. 2020, 98, 373-378. 157 Chart 5.1: Selected examples of P=C-containing compounds that undergo E/Z-isomerization: i) monophosphaalkenes; ii) bisphosphaalkenes; iii) trisphosphaalkenes; iv) diphosphabutadienes. In chapter 5, the synthesis and characterization of the E- and Z-isomers of 2-trimethylsilyl-1-phosphabutadiene (5.1) are reported. Surprisingly, it is shown that solutions of the Z-isomer undergo E/Z isomerization in the presence of n-BuLi (10 mol%). This isomerization can also be mediated by irradiation with sunlight. 5.2 Results and Discussion 5.2.1 Preparation of Z-5.1 To aid in the interrogation of the initiation step of the anionic polymerization of 1-phosphaisoprene, the 2-trimethylsilyl substituted 1-phosphabutadiene (Z-5.1) was prepared as a model system (Scheme 5.1). A THF solution of Mes*P=C(Br)Si(CH3)3289-291 [97% trans-Si(CH3)3; 3% cis-Si(CH3)3] was treated with vinylmagnesium bromide (1.2 equiv) in the presence of catalytic [Pd(PPh3)4] (2 mol%). The reaction progress was monitored by 31P NMR spectroscopy of aliquots removed from the reaction mixture. Over the course of 3 h, the signal assigned to Mes*P=C(Br)Si(CH3)3 (δ = 304.8) was replaced by signals attributed to the new compound 5.1 (δ = 316.7, 90%) and byproduct Mes*P=C(H)Si(CH3)3 [ = 338.5 (d, 2JPH = 20 Hz, 10%)].290 After work-up, yellow crystals of Z-5.1 were isolated in 46% yield. 158 Scheme 5.1: Pd(0) catalyzed synthesis of Z-5.1 and n-BuLi or light-mediated E/Z isomerization of Z-5.1 to E-5.1. The identity of the product as 1-phosphabutadiene Z-5.1 was confirmed by X-ray crystallography. Its molecular structure is shown in Figure 5.1 and confirms the cis disposition of the bulky Si(CH3)3 and Mes* substituents about the P=C bond. This observed stereochemistry is consistent with previous Pd(0)-catalyzed reactions of E/Z-Mes*P=C(R)Br (R = H, Me) with nucleophiles (nuc) which afford only the cis-configured product, Mes*P=C(nuc)R [i.e. cis-Mes-to-R].81, 82, 185, 292 The metrical parameters are consistent with a π-conjugated P1−C3−C2−C1 unit which lies in a mirror plane. Consistent with this conclusion is the slight elongation of the P=C bond and shortening of the C–C bond [P1–C3 = 1.6940(14) Å; cf. 1.643(3) Å in Mes*P=CH2;233 C3–C2 = 1.4767(19) Å; cf. a typical C–C bond =1.53 Å].174 Notably, the P=C−Si bond angle [P1−C3−Si1 = 133.47(8)°] is widened considerably from the 120⁰ predicted for sp2 hybridization, presumably reflecting steric repulsion of the cis Si(CH3)3 and Mes* groups. However, the Mes*−P=C angle [C4–P1–C3 = 109.05(6)°] is slightly more acute than in Mes*P=CH2 [110.1(2)°]. 159 Figure 5.1: Molecular structure of Z-5.1. Hydrogen atoms are omitted for clarity. Thermal ellipsoids are shown at the 50% probability level. 5.2.2 n-BuLi-mediated E/Z-isomerization of Z-5.1 To probe reactions of Si(CH3)3 substituted 1-phosphabutadiene with anionic initiators, a THF solution of Z-5.1 was treated with n-BuLi (10 mol%). Analogous to the anionic polymerization of PI161 and MesP=CPh2114, 115 the initially colorless solution immediately turned a very deep-red or purple color. However, 31P NMR spectroscopic analysis of the reaction mixture after 24 h did not reveal any broad signals which would be expected for a polymeric species. In contrast, a new sharp resonance was observed. Specifically, the resonance assigned to Z-5.1 [δ = 316.7 ppm, Figure 5.2(a)] disappeared and was replaced by a sharp resonance at 305.7 ppm [Figure 5.2(b)], consistent with retention of the P=C bond. The addition of deoxygenated methanol resulted in the immediate dissipation of the dark-red/purple color in favor of a pale-yellow solution. After work-up, pale-yellow crystals were isolated in high yield (96%). 160 Figure 5.2: 31P NMR spectra (THF, 162 MHz, 25 ⁰C) of a) Z-5.1; b) E-5.1. The 1H NMR spectrum of the product is shown in Figure 5.3(b) and for comparison the spectrum of the starting material (Z-5.1) is shown in Figure 5.3(a). Signals were observed that could be attributed to the Mes* substituent, the Si(CH3)3 and a vinyl group, suggesting that both compounds had very similar constitutions. Thus, it was speculated that the product was E/Z isomerization product E-5.1. Support for this assignment was gained by comparing the 1H NMR spectrum of the product to that of Z-5.1. For example, the resonance assigned to Si(CH3)3 protons was downfield shifted to 0.32 ppm compared to the analogous signal for Z-5.1 (δ = −0.34). Such a downfield shift in trimethylsilyl groups has previously been observed for cis-to-trans isomerizations of C-Si(CH3)3 substituted phosphaalkenes and was attributed to the absence of shielding of the Si(CH3)3 group when trans to aromatic Mes*.290 Furthermore, the signals assigned to the vinyl protons in Z-5.1 [δ = 6.91, 5.39 and 4.97; Figure 5.3(a), inset] were upfield shifted to 161 5.62, 4.94 and 4.69, respectively [Figure 5.3(b), inset]. Presumably, these upfield shifts result from increased shielding of the vinyl protons when cis to Mes* in E-5.1. Furthermore, the smaller 3JPH coupling constant of the P=C(Si(CH3)3)−CH=CH2 proton in E-5.1 when compared to Z-5.1 (3JPH = 11 and 21 Hz, respectively) is consistent with previous observations that a cis configuration between this C substituent and 3p lone pair will have a larger 3JPH than the trans isomer.289, 293, 294 Figure 5.3: 1H NMR spectra (CDCl3, 400 MHz, 25 ⁰C) of a) Z-5.1; b) E-5.1. Analysis of the crystals using X-ray diffraction confirmed our suspicion that the product was E-5.1 (Figure 5.4). In contrast to the planar 1,3-diene moiety of Z-5.1, the P=C–C=C unit of E-5.1 is slightly twisted with a torsion angle of 173.7(4)°. Notably, the bond angles within the diene unit are significantly closer to the 120⁰ predicted for sp2 hybridization in E-5.1 when compared to Z-5.1. For instance, the P=C−C bond angle in E-5.1 is 124.55(18)° compared to the 162 analogous angle in Z-5.1 [P1−C3−C2 = 109.38(10)°]. Likewise, the C–C=C angle in E-5.1 is 126.2(2)° compared to 128.1(2)° in Z-5.1. The P=C–Si bond angle in E-5.1 [P1−C3−Si1 = 114.55(14)°] is considerably smaller than in Z-5.1 [P1−C3−Si1 = 133.47(8)°]. The decrease in this bond angle is most likely a consequence of the weaker steric repulsion between the trans-configured Si(CH3)3 and Mes* groups in E-5.1. The Mes*–P=C angle is dramatically more acute in E-5.1 [Mes*–P1–C3 = 102.94(12)°] when compared to Z-5.l [Mes*–P1–C3 = 109.05(6)] and Mes*P=CH2 [110.1(2)°]. Despite the changes in angles, the bond lengths of the P=C−C=C diene unit in E-5.1 are largely unchanged from those of Z-5.1. Only a small increase in the C–C bond length is observed [C3−C2 = 1.458(3) Å, cf. 1.477(2) Å in Z-5.1], perhaps indicative of slightly reduced conjugation in the former. Figure 5.4: Molecular structure of E-5.1. Hydrogen atoms are omitted for clarity. Thermal ellipsoids are shown at the 50% probability level. 163 5.2.3 Light-mediated E/Z-isomerization of Z-5.1 As mentioned in the introduction, the E/Z-isomerization of phosphaalkenes is rarely induced through a chemical process. Therefore, the observed n-BuLi-mediated isomerization of Z-5.1 is highly unusual especially given the near-quantitative conversion of Z-5.1 to E-5.1 observed herein. In contrast, light-promoted E/Z isomerization has been widely reported in myriad low-coordinate phosphorus systems (vide supra). Thus, we wondered whether the isomerization of Z-5.1 could be induced by light irradiation. To this end, a THF solution of Z-5.1 (0.1 M) in an NMR tube was exposed to ambient sunlight and was monitored via 31P NMR spectroscopy. After 4 d, the solution reached a Z:E ratio of 1:9 by integration of the 31P NMR spectrum [Figure 5.5(b)]. Further irradiation of the sample with sunlight resulted in no additional change in the 31P NMR spectrum. A control experiment was performed with Z-5.1 (0.1 M in THF) where the solution was kept in the dark. Monitoring for 4 d using 31P NMR spectroscopy revealed no change in the spectrum [i.e. Z-5.1 did not isomerize in the dark, Figure 5.5(a)]. This result confirms the hypothesis that light will promote this isomerization, however, the isomerization is not quantitative as in the case of Z-5.1 and n-BuLi. 164 Figure 5.5: 31P NMR spectra (THF, 162 MHz, 25 °C) of: a) a solution of Z-5.1 after 4 d in the dark, b) a solution of Z-5.1 that has been irradiated for 4 d. Given that the structural evidence suggests that E-5.1 might be slightly less conjugated than Z-5.1 in the solid state, we postulate that the release of steric strain is an important factor favoring the conversion of Z-5.1 to E-5.1. In particular, E-5.1 has the bulky Si(CH3)3 substituent in a trans-configuration with respect to the sterically encumbering Mes* group. To gain insight into the isomerization, DFT calculations (B3LYP/295, 296def2−TZVPP297-300) were performed by exchange student Phillipp Dabringhaus to estimate the relative energies of the two isomers. Consistent with the experimental observations, the Z-to-E-isomerization was determined to be 165 thermodynamically favorable in the gas phase [G0 (25 °C) = –10.2 kJ mol−1, H° = –6.9 kJ mol−1]. 5.3 Summary In closing, a novel 1-phosphabutadiene system, Z-2-trimethylsilyl-1-phosphabutadiene (Z-5.1) was synthesized and characterized. Reaction with n-BuLi resulted in a surprising isomerization to E-5.1. This represents a rare example of a chemically-mediated isomerization of a phosphaalkene. Both isomers were isolated and characterized using high-resolution mass spectrometry, 1H, 31P, 13C{1H} and 29Si NMR spectroscopy and X-ray crystallography. Irradiation with sunlight was also effective to promote the isomerization of Z-5.1 to E-5.1. DFT studies were consistent with the experimental observations and indicated the Z-to-E-isomerization was thermodynamically favorable. 5.4 Experimental 5.4.1 General procedures All manipulations of air- and/or moisture-sensitive compounds were conducted using standard Schlenk or glovebox techniques. Tetrahydrofuran was dried over sodium/benzophenone ketyl and distilled prior to use. Hexanes and dichloromethane were degassed and passed through an activated alumina column prior to use. Pentane and trimethylsilyl chloride were dried over CaH2 and distilled prior to use. Vinylmagnesium bromide (1.0 M in THF) and n-butyllithium (1.6 M in hexanes) and tetrakis(triphenylphosphine)palladium(0) were purchased from Sigma Aldrich and used as received. 1H NMR, 13C{1H} NMR, 31P NMR, and 29Si NMR spectra were measured on a Bruker AVANCE III HD 400 spectrometer. Chemical shifts of 1H NMR were expressed in parts per million downfield from residual CHCl3 (δ = 7.26) in CDCl3. Chemical shifts of 13C{1H} NMR were expressed in parts per million downfield from CDCl3 as an internal standard (δ = 77.16). 166 Chemical shifts of 31P NMR were expressed in parts per million downfield from 85% H3PO4 as an external standard (δ = 0). Chemical shifts of 29Si NMR were expressed in parts per million downfield from tetramethylsilane as an external standard in CDCl3 (δ = 0). Mass spectra were measured on a JEOL AccuTOF GCv 4G spectrometer. 5.4.2 X-ray crystallography All single crystals were immersed in oil and mounted on a mylar loop. Data were collected on a Bruker X8 or Duo APEX II diffractometer with graphite-monochromated Mo Kα radiation, integrated using the Bruker SAINT software package186 and corrected for absorption effects using SADABS.187 All structures were solved by direct methods and subsequent Fourier difference techniques. All non-hydrogen atoms were refined anisotropically. All data sets were corrected for Lorentz and polarization effects. All structure solutions were performed using SHELXT.188 All refinements were performed using SHELXL189 via the Olex2 interface.190 5.4.3 DFT calculations All DFT calculations were performed by Phillipp Dabringhaus at the B3LYP/295, 296def2−TZVPP297, 298 level of theory using Orca software.301 5.4.4 Synthesis of Z-5.1 To a solution of E/Z-Mes*P=C(Si(CH3)3)Br (4.20 g, 9.51 mmol) and [Pd(PPh3)4] (0.22 g, 0.19 mmol) in THF (100 mL) was added vinylmagnesium bromide (11.4 mL, 11.4 mmol, 1.0 M in THF). After 3 h, analysis of the reaction mixture by 31P NMR spectroscopy revealed two signals at 338.5 (d, 2JPH = 20 Hz, 10%) and 316.7 (s, 90%) ppm. The reaction mixture was cooled to −78 ˚C and methanol (10 mL, deoxygenated) was added dropwise. The dark solution was warmed to room temperature and the volatiles were removed in vacuo. The crude dark product was dissolved in hexanes (50 mL) and filtered through a silica frit. The yellow filtrate was washed with 167 water (3 × 50 mL, deoxygenated), dried over MgSO4 and the solvent was removed in vacuo to afford a crude orange solid. The solid was recrystallized three times from boiling pentane at −35 ˚C. Yield = 1.70 g, 46%. 31P NMR (CDCl3, 162 MHz, 25 ˚ C) δ 312.3 (s); 1H NMR (CDCl3, 400 MHz, 25 ˚C) δ 7.36 (s, 2H, Mes*H), 6.91 (ddd, 1H, 3JPH = 21 Hz, 3Jtrans = 17 Hz, 3Jcis = 10 Hz, P=C−CH=CHcisHtrans), 5.39 (ddd, 1H, 3Jtrans = 17 Hz, 4JPH = 6 Hz, 2Jgem = 2 Hz, P=C−CH=CHcisHtrans), 4.97 (ddd, 1H, 3Jcis = 10 Hz, 4JPH = 6 Hz, 2Jgem = 2 Hz, P=C−CH=CHcisHtrans), 1.53 (s, 18H, o-C(CH3)3), 1.33 (s, 9H, p-C(CH3)3), −0.34 (s, 9H, Si(CH3)3); 13C{1H} NMR (CDCl3, 101 MHz, 25 ˚C) δ 187.9 (d, 1JPC = 54 Hz, P=C−CH=CHcisHtrans), 154.3 (d, 2JPC = 2 Hz, o-Mes*), 150.6 (s, p-Mes*), 142.9 (d, 2JPC = 31 Hz, P=C−CH=CHcisHtrans), 139.0 (d, 1JPC = 64 Hz, ipso-Mes*), 121.8 (s, m-Mes*), 112.6 (d, 3JPC = 34 Hz, P=C−CH=CHcisHtrans), 38.5 (s, o-C(CH3)3), 35.2 (s, p-C(CH3)3), 33.7 (d, 4JPC = 8 Hz, o-C(CH3)3), 31.5 (s, p-C(CH3)3), −1.4 (s, Si(CH3)3); 29Si NMR (CDCl3, 80 MHz, 25 ˚C) δ −6.7 (d, 2JPSi = 16.4 Hz). FD-MS [M+] 388.2 (100), 389.2 (36), 390.2 (7). HRMS (FD+) calcd for C24H41PSi, 388.2715, found 388.2699. 5.4.5 Synthesis of E-5.1 To a solution of Z-5.1 (0.47 g, 1.2 mmol) in THF (2 mL) was added n-BuLi (1.6 M in hexanes, 76 μL, 120 μmol). The red reaction mixture was stirred for 24 h at room temperature. 31P NMR spectroscopic analysis of the reaction mixture showed a resonance at 305.7 ppm. Methanol (1 mL, deoxygenated) was added and the volatiles were removed in vacuo. The yellow residue recrystallized from CH2Cl2 at −35 ˚C to afford yellow crystals suitable for X-ray analysis. Yield = 0.45 g, 96%. 31P NMR (CDCl3, 162 MHz, 25 ˚ C) δ 303.1 (s); 1H NMR (CDCl3, 400 MHz, 25 ˚ C) δ 7.39 (s, 2H, Mes*H), 5.62 (ddd, 1H, 3Jtrans = 18 Hz, 3Jcis = 11 Hz, 3JPH = 11 Hz, P=C−CH=CHcisHtrans), 168 4.94 (ddd, 1H, 3Jtrans = 18 Hz, 4JPH = 4 Hz, 2Jgem = 1 Hz, P=C−CH=CHcisHtrans), 4.69 (ddd, 1H, 3Jcis = 11 Hz, 4JPH = 5 Hz, 2Jgem = 1 Hz, P=C−CH=CHcisHtrans), 1.44 (s, 18H, o-C(CH3)3), 1.34 (s, 9H, p-C(CH3)3), 0.32 (d, 9H, 4JPH = 2 Hz, Si(CH3)3); 13C{1H} NMR (CDCl3, 101 MHz, 25 ˚C) δ 182.1 (d, 1JPC = 73 Hz, P=C−CH=CHcisHtrans), 153.6 (d, 2JPC = 2 Hz, o-Mes*), 149.8 (s, p-Mes*), 139.3 (d, 2JPC = 18 Hz, P=C−CH=CHcisHtrans), 138.2 (d, 1JPC = 39 Hz, ipso-Mes*), 121.7 (s, m-Mes*), 113.5 (d, 3JPC = 26 Hz, P=C−CH=CHcisHtrans), 38.2 (s, o-C(CH3)3), 35.2 (s, p-C(CH3)3), 33.1 (d, 4JPC = 8 Hz, o-C(CH3)3), 31.6 (s, p-C(CH3)3), 0.8 (d, 3JPC = 13 Hz, Si(CH3)3); 29Si NMR (CDCl3, 80 MHz, 25 ˚ C) δ −4.7 (d, 2JPSi = 40 Hz). FD-MS [M+] 382.2 (100), 389.2 (30), 390.2 (7). HRMS (FD+) calcd for C24H41PSi, 388.2706, found 388.2714. 5.4.6 Light-mediated isomerization of Z-5.1 Z-5.1 (20 mg, 0.05 mmol) was dissolved in THF (0.5 mL) in a J. Young NMR tube. The NMR tube was placed in sunlight and monitored via 31P NMR. Gradually, the signal assigned to Z-5.1 (δ = 316.7) was consumed and a new signal assigned to E-5.1 (δ = 305.7) was observed. After 4 d, a ratio of 1:9 (Z:E) was reached and no further change in the ratio was observed. 169 Chapter 6: Probing Radical Addition to 1-Phosphabutadienes using Muon Spin Spectroscopy (μSR) 6.1 Introduction Our group has previously achieved success in polymerizing P=C monomers via radical methods. Thus, we are curious to investigate the reactivity of PI with radical species, with a view to generating radical-initiated PPI. Additionally, free radical reactions of P=C−C=C systems are unprecedented; the most closely related report to this work is the study of the one-electron oxidation of a 2-phosphabutadiene to afford a radical cation.302 Therefore, the radical reactivity of 1-phosphabutadienes is also of fundamental interest to synthetic chemists. A useful technique for studying the radical reactivity of unsaturated main-group compounds is muon spin spectroscopy (μSR). This technique involves irradiating samples with a beam of positive muons (μ+) to generate muoniated radicals. The positive muon has spin ½ and the muonium atom (i.e. μ+ + e− = Mu) can be viewed as a light isotope of 1H.303-305 μSR has many advantageous features: the muoniated radicals are produced in situ as opposed to being prepared prior to measurement, therefore, transient radicals can be detected; the muons are spin-polarized meaning the technique is highly sensitive (1011 × more sensitive than NMR); the muon lifetime is 2.2 μs, therefore, secondary bimolecular reactions can generally be disregarded.306, 307 The first reports of Mu addition to main-group molecules focused on unsaturated organosilicon radicals,308-314 however, more recently, unsaturated phosphorus-containing molecules have also been reacted with Mu.307, 315-318 Chapter 6 reports the μSR study of three 1-phosphabutadienes Mes*P=C(Me)−CH=CH2 (PI), Mes*P=C(CD3)−CH=CH2 (PI-d3) and Mes*P=C(Me)−C(Me)=CH2 [6.1 (first reported as 170 compound 4.2 in chapter 4)]. Two muoniated radicals are identified by transverse-field (TF)-μSR and the major products are identified as delocalized 1-phosphaallyl radicals resulting from addition of a Mu atom at the 4-position of the P=C−C=C skeletons. 6.2 Results and Discussion 6.2.1 Transverse-field (TF)-μSR As a starting point for our μSR study of 1-phosphabutadienes, we selected PI, 6.1 and PI-d3 (Chart 6.1). We reasoned that changing the spin-active substituents on the P=C−C=C backbone may aid in our assignment of any muoniated products. The synthesis of PI-d3 is described in the Experimental Section. The characterization data were as described for PI,81 except the signal assigned to the CD3 substituent in the 13C{1H} NMR spectrum (CDCl3) was observed as a doublet of septets resonance at 17.7 (1JCD = 19Hz, 2JPC = 16 Hz) ppm. Additionally, the 2H NMR spectrum (CHCl3) revealed a broad singlet at 1.31 ppm that was assigned to the Mes*P=C(CD3)−CH=CH2 group. Chart 6.1: The 1-phosphabutadienes selected for this μSR study. To investigate the reactivity of these 1-phosphabutadienes with muonium atoms, 0.5 M THF solutions of PI, 6.1 and PI-d3 were separately exposed to muon beams. The transverse-field (TF) μSR spectra of the reaction solutions each showed five precession frequencies, consistent with the formation of two radicals in each case. Specifically, the spectra of the radicals formed from each 1-phosphabutadiene displayed a major product {muon hyperfine constant [Aμ (MHz) = 90.6 ± 0.1 (PI, Figure 6.1), 90.7 ± 0.04 (PI-d3, Figure 6.2) and 90.0 ± 0.04 (6.1, Figure 6.3)]}. 171 Additionally, signals assigned to minor radical products were observed [Aμ(MHz) = 261.6 ± 0.1 (PI), 261.3 ± 0.1 (PI-d3) and 284.4 ± 0.04 (6.1)]. The magnitude of the muon hyperfine constant is a measure of the interaction between the spins of the muon and the unpaired electron in the radical species. Hence, the large difference in Aμ between the major and minor radicals formed from PI, PI-d3 and 6.1 suggested very different interactions between the muon and unpaired electron in each case. Figure 6.1: Transverse-field μSR spectrum obtained from a 0.5 M solution of PI in THF at 25 °C with a 14.45 kG field. 172 Figure 6.2: Transverse-field μSR spectrum obtained from a 0.5 M solution of PI-d3 in THF at 25 °C with a 14.45 kG field. Figure 6.3: Transverse-field μSR spectrum obtained from a 0.5 M solution of 6.1 in THF at 25 °C with a 14.45 kG field. In consideration of the four most likely initial intermediates that could result from the addition of a muonium atom to the P=C–C=C system, density functional theory (DFT) calculations 173 were performed to aid the assignment of the muoniated radicals formed from these 1-phosphabutadienes. The calculations were performed at the UB3LYP295, 296/def2-TZVP297-300 level of theory by Professor Paul Percival at Simon Fraser University. Since PI and PI-d3 differ only by isotopic substitution of the methyl-substituent, their reference geometries are identical within the Born-Oppenheimer approximation. Therefore, separate calculations for the reactions of PI and PI-d3 with Mu were not performed and only the products derived from PI will be discussed in detail. Intuitively, the addition of Mu to a 1-phosphabutadiene (analogous to the addition of a H atom to a 1-phosphabutadiene) is expected to afford one or more muoniated radical(s) (a−d, Scheme 6.1). Scheme 6.1: Possible muoniated products from the reaction of PI and 6.1 with Mu. The calculated reaction energies [i.e. E(radical)−E(parent)−E(H)] for the reactions of PI and 6.1 with Mu are shown in Figure 6.4. The most energetically favorable product from the reaction of PI with Mu was 1-phosphaallyl radical PId. The second lowest in energy was phosphinyl radical PIb (+43 kJ mol−1 relative to PId). The reaction pathways forming PIa and PIc were the least energetically favorable (+71 and +126 kJ mol−1 relative to PId, respectively). The calculated energy pathways for the reaction of 6.1 with Mu followed an analogous trend (6.1d < 6.1b < 6.1a < 6.1c). 174 Figure 6.4: Reaction pathway energies [i.e. E(radical)−E(parent)−E(H)] for the reaction of Mu with PI (R = H) and 6.1 (R = Me). The reaction of Mu with PI-d3 is omitted as the reference geometries of PI and PI-d3 are identical within the Born-Oppenheimer approximation. With this information in hand, the muon, phosphorus and proton hyperfine constants (Aμ, AP and AH, respectively) for each radical were calculated using DFT in order to aid our assignment of the major and minor muoniated radical products. A summary of the results is shown in Figure 6.5. The value of 82 MHz for Aμ(calcd) of PId represents the high-temperature free rotation limit of this hyperfine constant. Calculation of Aμ for PId at 0 K gave a value of 112 MHz, which increased to 130 MHz upon vibrational averaging over the anharmonic C−Mu modes. The value of 130 MHz represents the maximum overlap of C−Mu with the π-orbital containing the unpaired electron within PId. As the temperature increases, a larger range of dihedral angles is accessed for the CH2Mu substituent and Aμ(calcd) decreases to 82 MHz at the free-rotation temperature limit. 175 Therefore, for radical PId, Aμ at room temperature is expected to be between 82 and 130 MHz. The experimental Aμ of the major muoniated radical formed from PI at room temperature was within this range [Aμ = 90.6 ± 0.1 MHz (or 90.7 ± 0.04 MHz for the radical formed from PI-d3)]. Additionally, an inverse correlation of the experimental Aμ of the major radical with temperature was observed. Specifically, when the TF spectrum of the radicals formed from the reaction of PI with Mu was recorded at 4 ⁰C, Aμ of the major radical increased to 92.1 ± 0.04 MHz (ΔAμ = 1.5 ± 0.1 MHz). An analogous increase was observed when the TF-μSR spectrum of the reaction of PI-d3 with Mu was recorded at 4 ⁰C [ΔAμ(major) = 1.3 ± 0.1 MHz]. These results provide evidence for radical structures PId and PI-d3d, containing a muoniated methyl substituent. We have previously observed such an effect in the reaction of Mu with MesP=CPh2307 and it is known for muoniated alkyl radicals.319, 320 176 . Figure 6.5: Calculated hyperfine constants for the postulated muoniated radicals formed from PI (R = H) and 6.1 (R = Me). Furthermore, the experimental Aμ for the major muoniated radical formed from 6.1 (90.0 ± 0.04 MHz) falls within the calculated range [Aμ(calcd) = 77 (T = ∞ K) to 144 (T = 0 K) MHz)]. Given the calculated energetic favorability of the formation of PId (or PI-d3d) and 6.1d from PI (or PI-d3) and 6.1, respectively, and the good correlation between the calculated and experimental Aμ values, the major radical in each reaction was tentatively assigned to structure PId, PI-d3d and 6.1d, respectively. The magnitude of these Aμ values may be indicative of a degree of localization of the unpaired spin density of PId, PI-d3d and 6.1d at the polarizable P substituents that is far removed from the muon. Contrastingly, the muoniated radicals MesP(H)−Ċ(CH3)CH2Mu, 177 MesṖ−C(CH3)2Mu and MesP(H)−C(CH3)(Mu)ĊH2, which have localized spin density vicinal to the muon, display larger experimental Aμ values of 304, 135 and 254 MHz, respectively.307 Our attention then turned to the structure of the minor muoniated radicals formed from each 1-phosphabutadiene. Calculation of Aμ by DFT for radicals PIa PIb and PIc provided values of 215, 193 and 130 MHz, respectively. These values did not correlate well with the observed experimental Aμ of 261.6 ± 0.1 MHz (or 261.3 ± 0.1 MHz for PI-d3) of the minor radical. Similarly, Aμ(calcd) for 6.1a, 6.1b and 6.1c was 176, 192 and 280 MHz, respectively. Aμ(calcd) for 6.1a and 6.1b did not correlate well with the experimental Aμ (284.4 ± 0.04 MHz). Contrastingly, Aμ(calcd) for 6.1c was comparable to the experimentally observed value, however, the reaction to form this primary radical was calculated to be too energetically unfavorable relative to 6.1d (+128 kJ mol−1) and thus was ruled out. Therefore, we were unable to assign the structure of the minor radical in each case to any of these structures, due to the disagreement between the DFT-calculated and experimentally observed hyperfine constants. Although there is no accepted error margin for comparison of the calculated and experimental hyperfine constants, one can rule-out possible radical products based on a combined analysis of both the computed energetics of the reaction to form the radical, and the comparison of the calculated and experimental hyperfine constants. It was then considered that the unsaturated Mes* substituent could accept Mu to form a delocalized cyclohexadienyl-type radical. However, such species have much larger Aμ (>400 MHz) than we observe for the minor radical.321-323 Indeed, the addition of Mu to Mes*H in THF formed a radical with Aμ = 468.4 MHz.317 Therefore, addition of Mu to the Mes* substituent of PI, PI-d3 and 6.1 was ruled out. Unfortunately, given the disagreement between the calculated and experimental Aμ values, the tentative assignment of the structures of the minor radicals was not possible from these data. 178 6.2.2 Avoided-level crossing (μALCR) investigations Nevertheless, to gain further evidence for the assignment of the major radicals as PId, PI-d3d and 6.1d, the avoided level-crossing resonance (μALCR) spectra were recorded. μALCR allows the determination of hyperfine constants assigned to spin-active nuclei other than Mu.306 The signals from μALCR measurements display differential-type line shapes due to field modulation.317 Two resonances were observed for the muoniated radicals formed from PI at 5.179 ± 0.007 and 5.603 ± 0.006 kG (Figure 6.6) that correspond to AP (phosphorus hyperfine constant) values of 212.0 ± 0.2 and 222.0 ± 0.2 MHz, respectively. One of these signals was assigned as AP of radical PId due to the comparability of these values with Ap(calcd) (231 MHz for PId). However, there is ambiguity as to which of these resonances is AP of PId. This ambiguity arises from the unknown structure of the minor radical (Aμ = 261.6 ± 0.1 MHz) which precludes assignment of all observed μALCR signals in this experiment. Therefore, absolute assignment of AP for PId was not possible. Figure 6.6: Segment of the μALCR spectrum of the radical formed from exposure of a 0.5 M THF solution of PI to a muon beam. Two resonances are observed at 5.179 ± 0.007 and 5.603 ± 0.006 kG, obtained from a fit of the spectrum using Microsoft Excel. 179 Figure 6.7: Segment of the μALCR spectrum of the radicals formed from exposure of a 0.5 M THF solution of PI-d3 to a muon beam. Two resonances are observed at 5.185 ± 0.005 and 5.592 ± 0.005 kG, obtained from a fit of the spectrum using Microsoft Excel. Figure 6.8: Segment of the μALCR spectrum of the radicals formed from exposure of a 0.5 M THF solution of 6.1 to a muon beam. Two overlapping resonances are observed at 5.270 ± 0.008 and 5.523 ± 0.003 kG, obtained from a fit of the spectrum using Microsoft Excel. 180 Similarly, the μALCR spectrum obtained from the reaction of PI-d3 with Mu displayed two resonances at 5.185 ± 0.005 and 5.592 ± 0.005 kG (Figure 6.7). These values correspond to AP = 212.1 ± 0.1 or 221.7 ± 0.1 MHz, respectively, which are comparable to AP(calcd) for PI-d3d (231 MHz). The spectrum obtained from the reaction of 6.1 with Mu displayed overlapping signals which were fitted as two resonances at 5.270 ± 0.008 and 5.523 ± 0.003 kG (Figure 6.8). These field values give AP = 213.5 ± 0.2 or 219.4 ± 0.1 MHz, respectively, which correlate favorably with AP(calcd) for 6.1d (211 MHz). For the reasons given above (vide supra), absolute assignment of AP for these radicals was not possible. The μALCR spectrum collected from the reaction of PI with Mu also revealed a broad signal at 3.796 ± 0.019 kG (Figure 6.9) that was attributed to the CH2Mu protons of PId (AH = 19.8 MHz). The assignment of this signal was aided by comparison to the DFT calculated AH value of 26 MHz for this resonance. Signals assigned to the other spin-active nuclei of PId [i.e., C(Me) and CH] were not observed. AH(calcd) for the C(Me) protons (−8 MHz) is too small to be observed experimentally (<10 MHz), hence the absence of a μALCR signal that could be assigned to this position. Analysis of all observed signals in the μALCR spectra of this sample did not reveal any signals close to AH(calcd) of the CH proton (−20 Hz). Fitting of this signal to a muon hfc of Aμ = 90.6 MHz revealed a predicted signal with very low amplitude, presumably rendering it unobservable under these experimental conditions. 181 Figure 6.9: Segment of the μALCR spectrum of the radicals formed from exposure of a 0.5 M THF solution of PI to a muon beam. A resonance is observed at 3.796 ± 0.019 kG, obtained from a fit of the spectrum using Microsoft Excel. Likewise, no signals were observed that could be assigned to AH or AD of PI-d3d or 6.1d. AD(calcd) for PI-d3d was estimated by taking the corresponding AH(calcd) for PId (−8 MHz) and dividing it by the ratio of the gyromagnetic ratios of a proton and deuteron (ca. 7) which would result in AD = ca. −1 MHz. Such a small hyperfine constant would not be observable experimentally (<10 MHz). Furthermore, AH(calcd) for the P−C(Me)−C(Me) protons of 6.1d (−8 MHz) was also too small to be detected experimentally. A summary of the calculated and experimental hfc values is given in Table 6.1. 182 Table 6.1: Assignment and comparison of experimental and computed hyperfine constants (MHz) for PId, PI-d3d and 6.1d. Radical Assignment Exp[a] Calcd PId CH2Mu 90.6 ± 0.1 82 P 212.0 ± 0.2 or 222.0 ± 0.2[c] 231[b] C(Me) Not observed −8[b] CH−CH2Mu Not observed −20[b] CH2Mu 19.8 ± 0.4 26 PI-d3d CH2Mu 90.7 ± 0.1 82 P 212.1 ± 0.01 or 221.7 ± 0.02[c] 231[b] C(CD3) Not observed −1[d] CH−CH2Mu Not observed −20[b] CH2Mu Not observed 26 6.1d CH2Mu 90.0 ± 0.1 77 P 213.5 ± 0.2 or 219.4 ± 0.1[c] 211[b] P−C(Me)−C(Me) Not observed −8[b] C(Me)−CH2Mu Not observed 15[b] CH2Mu Not observed 24 [a] 298 K; [b] 0 K; [c] ambiguous assignments (vide supra); [d] calculated using the ratio of the gyromagnetic ratios of 1H and 2H, i.e. 267.6/41.1 = ca. 7. 183 6.2.3 Muon (Mu+) addition Given the difficulty in assigning the structure of the minor muoniated radicals formed on exposure of PI and 6.1 to muon beams (Aμ = 261.6 ± 0.1, and 284.4 ± 0.1 MHz, respectively), it was decided to investigate the possibility of Mu+ (i.e. μ+) addition to these 1-phosphabutadienes, as opposed to neutral Mu atom addition [Scheme 6.2(a)]. Such reaction mechanisms involving Mu+ addition to substrate, followed by electron capture to form muoniated radicals, have been reported for addition to unsaturated organic molecules.324, 325 It was found that the formation of PId(cat) was the lowest energy reaction pathway, analogous to Mu addition to PI. The second lowest energy pathway was via addition of Mu+ at the 3-position to afford cyclic cation PIe(cat) [Scheme 6.2(b)] which formed spontaneously during geometry optimization of PIc(cat) [+23 kJ mol−1 relative to PId (cat)]. Similarly, the lowest energy addition pathway for Mu+ to 6.1 gave 1-phosphaallyl cation 6.1d(cat) and the second most favorable pathway was to form 6.1e(cat) [+24 kJ mol−1 relative to PId(cat)]. Scheme 6.2: Hypothetical products arising from Mu+ addition to PI and 6.1. Syn and anti denote the relative orientations of the Mes* and Mu substituents. 184 Neutralization of PIe(cat) and 6.1e(cat) via electron capture would afford PIe and 6.1e, respectively. Aμ(calcd) = 293 (syn) and 342 (anti) MHz for PIe, the lower of which is close to the experimentally observed value for the minor radical (Aμ of 261.6 ± 0.1 MHz) formed from PI. Additionally, Aμ(calcd) = 285 (syn) and 354 (anti) MHz for 6.1e. These calculated Aμ values are close to the observed 284.4 ± 0.1 MHz for the minor muoniated radical formed from 6.1. The DFT calculations also indicated AP > 200 MHz for PIe and 6.1e which would correspond to observed μALCR resonances in very low fields (<1 kG) with large widths (>0.6 kG) for Aμ = 261.6 ± 0.1 and 284.4 ± 0.1 MHz, respectively. These signals would be very difficult to observe using μALCR spectroscopy, however, we do observe a sloping baseline at low fields which could indicate the presence of these resonances. The speculative reactions described in section 6.2.3 are potential avenues for trying to elucidate the structure of the minor radical formed from the reaction of Mu with PI, PI-d3 and 6.1. However, we also observe more signals in the μALCR spectra in each reaction than can be accounted for by the presence of two radicals of type d and e. Given this reality, we pursued further DFT calculations of the hyperfine constants of the myriad possible stereochemical isomers of the radicals presented in this chapter. Unfortunately, none have resulted in calculated hyperfine constants that are consistent with the experimentally observed minor radicals. Due to these complications, we are thus far unable to confidently assign the structures of the minor radicals. Further computation and experiments are required to fully elucidate the constitution of the minor radicals. 6.3 Conclusion In closing, THF solutions of 1-phosphabutadienes Mes*P=C(Me)−CH=CH2 (PI), Mes*P=C(CD3)−CH=CH2 (PI-d3) and Mes*P=C(Me)−C(Me)=CH2 (6.1) were exposed to beams 185 of muons. The transverse-field spectra of each sample revealed the formation of two radicals in each case. The major muoniated radical product in each experiment was identified as a 1-phosphaallyl radical (type d) with the aid of DFT calculations and μALCR measurements. The structures of the minor radicals formed from PI, PI-d3 and 6.1 were unable to be unambiguously assigned and require further investigation to determine their constitution. 6.4 Experimental Section 6.4.1 General procedures All manipulations of air- and/or moisture-sensitive compounds were conducted using standard Schlenk or glovebox techniques. Tetrahydrofuran was dried over sodium/benzophenone ketyl and distilled prior to use. Dichloromethane was degassed and passed through an activated alumina column prior to use. Mes*P=C(Me)Br was synthesized according to a literature procedure.185 1H, 13C{1H}, and 31P NMR spectra were measured at room temperature on a Bruker AVANCE III HD 400 MHz spectrometer or a Bruker AVANCE III 600 MHz spectrometer equipped with a TXI probe. All NMR spectra were recorded at room temperature. Chemical shifts of 1H NMR spectra were expressed in parts per million downfield from residual CHCl3 (δ = 7.26), or C6D5H (δ = 7.15). Chemical shifts of 13C{1H} NMR spectra were expressed in parts per million downfield from CDCl3 (δ = 77.16) or C6D6 (δ = 128.06). Chemical shifts of 31P NMR spectra were expressed in parts per million downfield from 85% H3PO4 as an external standard (δ = 0). FD mass spectra were recorded on Jeol AccuTOF-GCv 4G, a GC-TOF MS instrument equipped with a field desorption/ionization (FD/FI) ion source in positive mode. 6.4.2 μSR measurements For a typical experiment, in a glovebox, the sample (PI, PI-d3 or 6.1) was dissolved in THF to afford a 0.5 M solution. This solution was transferred to a stainless-steel sample cell which 186 contained a thin steel window for μSR analysis. Muon experiments were performed in Vancouver, Canada at the TRIUMF particle accelerator. For a detailed explanation of the experimental setup, see our previous report.307 6.4.3 DFT calculations Optimized molecular geometries and hyperfine constants were calculated at the UB3LYP296/TZVP297, 298 level. Separate energies for PI and PI-d3 were not calculated as they are the same within the Born-Oppenheimer approximation. The calculations were performed using Gaussian 16, Revision B.01.265 6.4.4 Preparation of E/Z-Mes*P=C(CD3)Br Mes*P=CBr2 (5.10 g, 11 mmol) was dissolved in THF (150 mL) and the orange reaction mixture was cooled to −78 °C. To this solution was added n-BuLi (5.0 mL, 13. mmol, 2.5 M in hexanes) forming a dark reaction mixture which was stirred for 15 min. Methyl Iodide-d3 (0.84 mL, 13 mmol) was dissolved in THF (20 mL) and this solution was added to the reaction mixture dropwise. The reaction was warmed to room temperature and analyzed by 31P NMR spectroscopy to reveal two singlets at 234.6 and 238.2 ppm in a 10:1 ratio. The volatiles were removed in vacuo and the residual orange solid was dissolved in hexanes (100 mL) and washed with water (100 mL). The aqueous layer was further extracted with hexanes (2 × 100 mL) and the organic layers were combined and dried over MgSO4. The solvent was removed in vacuo and the residual solid was recrystallized from a saturated refluxing ethanol solution at −35 °C to afford orange crystals. Yield = 3.36 g, 76%. Z-Mes*P=C(CD3)Br (91%). 31P NMR (C6D6, 162 MHz, 25 ⁰C) δ 243.4 (s); 1H NMR (C6D6, 600 MHz, 25 ⁰C) δ 7.54 (s, 2H, Mes*H), 1.56 (s, 18H, o-C(CH3)3), 1.33 (s, 9H, p-C(CH3)3); 13C{1H} NMR (C6D6, 151 MHz, 25 ⁰C) δ 162.0 (d, 1JPC = 58 Hz, P=C), 153.5 (d, 2JPC 187 = 2 Hz, o-Mes*), 151.03 (s, p-Mes*), 139.3 (d, 1JPC = 52 Hz, ipso-Mes*), 122.4 (s, m-Mes*), 38.2 (s, o-C(CH3)3), 35.3 (s, p-C(CH3)3), 33.0 (d, 4JPC = 7 Hz, o-C(CH3)3), 31.7 (s, p-C(CH3)3), 30.5 (m, CD3); E-Mes*P=C(CD3)Br (9%). 31P NMR (C6D6, 162 MHz, 25 ⁰C) δ 237.8 (s); 1H NMR (C6D6, 600 MHz, 25 ⁰C) δ 7.47 (s, 2H, Mes*H), 1.47 (s, 18H, o-C(CH3)3), 1.26 (s, 9H, p-C(CH3)3); 13C{1H} NMR (C6D6, 151 MHz, 25 ⁰C) δ 166.1 (d, 1JPC = 58 Hz, P=C), 154.1 (d, 2JPC = 2 Hz, o-Mes*), 151.01 (s, p-Mes*), 137.8 (d, 1JPC = 60 Hz, ipso-Mes*), 122.1 (s, m-Mes*), 38.1 (s, o-C(CH3)3), 35.2 (s, p-C(CH3)3), 32.8 (d, 4JPC = 7 Hz, o-C(CH3)3), 31.5 (s, p-C(CH3)3), not found: CD3; FD-MS [M+] 385.2 (100), 386.3 (27), 387.2 (100), 388.3 (20). HRMS (FD+) calcd for C20H29D3PBr 385.1613; found 385.1601. Satisfactory elemental analysis could not be obtained: Anal. Calcd for C20H29D3PBr: C, 62.17; H, 9.13. Found: C, 62.82; H, 8.35. 6.4.5 Preparation of PI-d3 To a solution of E/Z-Mes*P=C(CD3)Br (2.92 g, 8 mmol) in THF (40 mL) was added vinylmagnesium bromide (16 mL, 16 mmol, 1.0 M in THF), forming a dark solution. To this reaction mixture was added a solution of [Pd(PPh3)4] (400 mg, 0.3 mmol) in THF (20 mL). Analysis of the reaction mixture after 10 min revealed a major singlet at 264.8 ppm. The volatiles were removed in vacuo to afford a dark solid. The solid was eluted through a silica plug (10 × 3 cm, hexanes) and a yellow fraction was collected. The volatiles were removed in vacuo to afford a yellow solid which was recrystallized twice from CH2Cl2/CH3CN (1:1) at −35 °C. Yield 1.56 g, 62%. 31P NMR (CDCl3, 162 MHz, 25 ⁰C) δ 264.4 (s); 1H NMR (CDCl3 400 MHz, 25 ⁰C) δ 7.42 (br s, 1H, Mes*H), 7.02 (ddd, 1H, 3JPH = 13 Hz, 3Jtrans = 17 Hz, 3Jcis = 11 Hz, P=C−CH=CHcisHtrans), 5.19 (dd, 1H, 3Jtrans = 17 Hz, 4JPH = 7 Hz, P=C−CH=CHcisHtrans trans to 188 H), 5.04 (dd, 1H, 3Jcis = 11 Hz, 4JPH = 5 Hz, P=C−CH=CHcisHtrans cis to H), 1.45 (s, 18H, o-C(CH3)3), 1.34 (s, 9 H, p-C(CH3)3); 13C{1H NMR (CDCl3, 151 MHz, 25 ⁰C) δ 179.7 (d, 1JPC = 36 Hz, P=C−CH=CHcisHtrans), 154.0 (s, o-Mes*), 150.1 (s, p-Mes*), 141.5 (d, 2JPC = 44 Hz, P=C−CH=CHcisHtrans), 137.0 (d, 1JPC = 56 Hz ipso-Mes*), 121.6 (s, m-Mes*), 110.5 (d, 3JPC = 41 Hz, P=C−CH=CHcisHtrans), 38.1 (s, o-C(CH3)3), 35.2 (s, p-C(CH3)3), 32.7 (d, 4JPC = 7 Hz, o-C(CH3)3), 31.7 (s, p-C(CH3)3), 17.7 (d of septets, 1JCD = 19Hz, 2JPC = 16 Hz, CD3); 2H NMR (CHCl3, 61 MHz) δ 1.29 (br s). FD-MS [M+] 332.3 (19), 333.3 (100), 334.3 (25). HRMS (FD+) calcd for C22H33D3P, 334.2743, found 334.2729. Anal. Calcd for C22H32D3P: C, 79.23; H, 11.48. Found: C, 79.49; H, 10.79. 189 Chapter 7: Conclusion 7.1 Introduction The primary goal of this thesis was to investigate the anionic polymerization of 1-phosphaisoprene, Mes*P=C(Me)−CH=CH2 (PI), a phosphorus-containing analogue of the commodity organic monomer isoprene. Through the isolation of molecular structures via the reaction of PI with n-BuLi and electrophiles, both phosphaalkene- and phosphine-containing microstructures of poly(1-phosphaisoprene) (PPI) were modeled. An understanding of these microstructures is crucial to predicting the reactivity of PPI, as demonstrated by the reversible gelation of the polymer utilizing the labile dative bonds between PPI and PdII. This result demonstrates the potential applications of PPI in materials chemistry. Beyond the polymerization of PI, the project evolved into a wider investigation of the unique reactivity of 1-phosphabutadienes, of which there is a wealth of undiscovered chemistry available for investigation. This thesis, therefore, additionally reports novel ligand scaffolds formed through dimerization of the P=C−C=C skeletons, an unprecedented anion-mediated isomerization reaction and the characterization of radicals formed from muonium addition to 1-phosphabutadienes. Overall, these results have expanded the field of low-coordinate phosphorus chemistry and are of great interest to materials, synthetic and fundamental chemists alike. Additionally, the results contained herein lay the groundwork for further worthwhile discoveries of the reactivity of these unique P=C−C=C species. 7.2 Future work Given the extensive possibilities for the functionalization of poly(1-phosphaisoprene) (PPI), further investigations into the reactivity of this polymer are warranted. For example, in chapter 4, the formation of a gel through coordination bonds in PPI·[PdCl2]0.09n is described. The dative bonds that are postulated to be involved in this gel formation are not unique to 190 phosphaalkene/phosphine-PdII complexes. As phosphaalkenes are excellent ligands for various transition metals,8 the coordination chemistry of PPI can be explored further and the properties of the resulting materials evaluated (Scheme 7.1). Furthermore, the catalytic activity of coordination complexes of PPI can be evaluated. The polymeric nature of the metal complex has the potential to facilitate easy separation of the catalyst from the substrates post-polymerization. Moreover, PIII-containing polymers have been used as transition metal scavengers326, 327 and PPI, an unusual macromolecule containing coordinating P=C substituents, warrants investigation for the same application. Scheme 7.1: Formation of cross-linked networks via the binding of PPI to multivalent transition metals. The attractive coordination properties of PPI are enticing, however, owing to the challenging synthesis of PI, the large-scale production of PPI would not be easily realized. As is common for inorganic polymers, with the notable exceptions of polyphosphazenes and silicones, the commercialization of these macromolecules is hampered by difficulty in synthesizing them. This difficulty can be circumvented by incorporating the functionality provided by the PIII groups of PPI into well-established, mass-produced polymers via the synthesis of copolymers (random or 191 block) with commodity monomers. For reference, the copolymerization of MesP=CPh2 with organic monomers has been demonstrated for styrene (random),127 isoprene126 (block) and methyl methacrylate125 (block). Subsequently, the P atoms could be cross-linked via metal coordination. Such cross-linked networks would represent functional organic polymers (Scheme 7.2). Scheme 7.2: Preparation of random and block copolymers of PI and organic monomers to afford functional commodity polymers. Furthermore, the presence of P=C moieties in macromolecule PPI imparts not only the functionality of the P-lone pair, but also a reactive P=C π-bond which can undergo further transformations. For instance, Yoshifuji and coworkers reported the hydroboration of molecular phosphaalkenes [Scheme 7.3(a)].31 The initial products were detected as phosphaalkene-borane adducts 7.2a,b that undergo hydroboration with a second equivalent of BH3·THF to afford 7.3a,b. Importantly, the hydroboration adducts were found to further react upon concentration of the reaction solution to afford six-membered rings 7.4a,b. A similar reaction pathway for PPI with BH3·THF is shown in Scheme 7.3b. An analogous reaction with the P=C substituents of PPI would result in the intra- or inter-chain cross-linking of the polymer chains, which could be reversed by the subsequent addition of excess BH3·THF. The resulting cross-linked polymers could be of 192 interest in materials chemistry. Further cross-linking strategies for PPI (e.g. vulcanization and epoxidation) can also be explored. Scheme 7.3: Reaction scheme showing (a) adducts of 7.1a/b with BH3·THF (b) the postulated reaction pathway of PPI and BH3·THF. For clarity, only microstructure x is shown. Additionally, given that the polymers contained within this thesis are synthesized solely via anionic methods, there is a wealth of exploration available using other initiation methods (i.e. radical or cationic). However, as has been shown in chapter 4, the Mes* substituent is not always inert and can undergo intramolecular C−H activation to afford benzophospholanes. Such a process has been observed for the addition of H+ to Mes*P=CH2233, 234 which suggests that, if cationic initiators are employed to polymerize PI ¸an analogous intramolecular cyclization will occur. This cyclization has also been observed when Mes* substituted phosphaalkenes have been exposed to radicals.328, 329 Given the tendency of the Mes* substituent to C−H-activate upon addition of radicals or cations, it would be necessary to substitute this sterically bulky protecting group for another to generate radical- or cation-initiated PPI. For example, the "Rind" substituents have 193 found use as protecting groups with similar steric bulk to Mes*, however, they are unable to undergo an analogous C−H activation (Scheme 7.4).330 These groups have been utilized to isolate structures that were unattainable using Mes* substituted phosphaalkenes.331 Although the syntheses of the "Rind" substituents are more synthetically challenging than Mes*, they would potentially enable access to cation- and radical-initiated PPI, which may have a different major microstructure and physical properties. Scheme 7.4: Postulated formation of Rind substituted PPI. Lastly, our group has created fluorescent polymers for use in oxygen sensing by attaching fluorescent substituents to PIII-containing macromolecules.332 The presence of the P-lone pair in each repeat unit quenches the fluorescence and, upon oxidation, the fluorescence "turns on". Employing a similar strategy with PPI could result in the isolation of polymers with novel photophysical properties. The synthesis of 1-phosphabutadienes containing pendant fluorescent groups can be achieved through the strategy employed by Ito and coworkers [Scheme 7.5(a)].242 Analogous Pd0-catalyzed substitution of Mes*P=CBr2 using aryl grignards with fluorescent aryl groups could be followed by the established synthetic route to afford 1-phosphabutadienes 194 [Scheme 7.5(b)].82 The polymerization of these materials and the evaluation of their photophysical properties would be of great interest to the materials chemistry community [Scheme 7.5(c)]. Scheme 7.5: Formation of: (a) C-aromatic substituted phosphaalkenes reported by Ito and coworkers; (b) postulated formation of polyaromatic substituted 1-phosphabutadienes and the turn-on fluorescence of the resultant polymers. 7.3 Concluding remarks Through the work contained herein, I have conveyed the versatility of 1-phosphabutadienes as building blocks for functional materials. These curious low-coordinate phosphorus compounds, Mes*P=C−C=C (1-phosphabutadienes), had initially been described as being "sterically protected to the point of being completely unreactive".77 As the reader comes to the end of my thesis, I hope that an appreciation for the unique reactivity and applications of these unusual species has been gained. 195 References (1) Gleason, W. JOM 2007, 59, 17-19. (2) Cordell, D.; Drangert, J. O.; White, S. Glob. Environ. Change 2009, 19, 292-305. (3) Ashley, K.; Cordell, D.; Mavinic, D. Chemosphere 2011, 84, 737-746. (4) Kamer, P. C.; van Leeuwen, P. W., Phosphorus (III) ligands in homogeneous catalysis: design and synthesis. John Wiley & Sons: 2012. (5) Yoshifuji, M. Molecules 2022, 27. (6) Dugal-Tessier, J.; Conrad, E. D.; Gates, D. P., Phosphorus(III) ligands in homogeneous catalysis design and synthesis. Wiley: Hoboken, N.J., 2012. (7) Mathey, F. Angew. Chem., Int. Ed. 2003, 42, 1578-1604. (8) Le Floch, P. Coord. Chem. Rev. 2006, 250, 627-681. (9) Gier, T. E. J. Am. Chem. Soc. 1961, 83, 1769-&. (10) Hopkinson, M. J.; Kroto, H. W.; Nixon, J. F.; Simmons, N. P. C. J. Chem. Soc., Chem. Commun. 1976, 513-514. (11) Schmidt, M. W.; Truong, P. N.; Gordon, M. S. J. Am. Chem. Soc. 1987, 109, 5217. (12) Dimroth, K.; Hoffmann, P. Angew. Chem., Int. Ed. 1964, 3, 384-&. (13) Allman, R. Angew. Chem. 1965, 77, 134. (14) Markl, G. Angew. Chem., Int. Ed. 1966, 5, 846-&. (15) Ashe, A. J. J. Am. Chem. Soc. 1971, 93, 3293-&. (16) Wong, T. C.; Bartell, L. S. J. Chem. Phys. 1974, 61, 2840-2849. (17) Baldridge, K. K.; Gordon, M. S. J. Am. Chem. Soc. 1988, 110, 4204-4208. (18) Becker, G. Z. Anorg. Allg. Chem. 1976, 423, 242-254. (19) Klebach, T. C.; Lourens, R.; Bickelhaupt, F. J. Am. Chem. Soc. 1978, 100, 4886-4888. (20) Wang, S.; Samedov, K.; Serin, S. C.; Gates, D. P. Eur. J. Inorg. Chem. 2016, 2016, 4144-4151. (21) Yoshifuji, M.; Shima, I.; Inamoto, N.; Hirotsu, K.; Higuchi, T. J. Am. Chem. Soc. 1981, 103, 4587-4589. (22) West, R.; Fink, M. J.; Michl, J. Science 1981, 214, 1343-1344. (23) Brook, A. G.; Abdesaken, F.; Gutekunst, B.; Gutekunst, G.; Kallury, R. K. J. Chem. Soc., Chem. Commun. 1981, 191-192. (24) Becker, G.; Gresser, G.; Uhl, W. Z. Naturforsch. B 1981, 36, 16-19. (25) Dillon, K. B.; Mathey, F.; Nixon, J. F., Phosphorus: the Carbon Copy. Wiley: Chichester; New York, 2001. (26) Simpson, M. C.; Protasiewicz, J. D. Pure Appl. Chem. 2013, 85, 801-815. (27) Schoeller, W. W. J. Chem. Soc., Chem. Commun. 1985, 334-335. (28) Waluk, J.; Klein, H. P.; Ashe, A. J.; Michl, J. Organometallics 1989, 8, 2804-2808. (29) Lacombe, S.; Gonbeau, D.; Cabioch, J. L.; Pellerin, B.; Denis, J. M.; Pfister-Guillouzo, G. J. Am. Chem. Soc. 1988, 110, 6964-6967. (30) Vanderknaap, T. A.; Klebach, T. C.; Visser, F.; Bickelhaupt, F.; Ros, P.; Baerends, E. J.; Stam, C. H.; Konijn, M. Tetrahedron 1984, 40, 765-776. (31) Yoshifuji, M.; Takahashi, H.; Toyota, K. Heteroatom Chem. 1999, 10, 187-196. (32) Devaumas, R.; Marinetti, A.; Mathey, F. J. Organomet. Chem. 1991, 413, 411-417. (33) Han, Z.; Gates, D. P. Chem. - Eur. J. 2021, 27, 14594-14599. 196 (34) Appel, R.; Barth, V.; Knoll, F.; Ruppert, I. Angew. Chem., Int. Ed. Engl. 1979, 18, 873-874. (35) Bauer, S.; Marinetti, A.; Ricard, L.; Mathey, F. Angew. Chem., Int. Ed. Engl. 1990, 29, 1166-1167. (36) Trauner, H.; Delacuesta, E.; Marinetti, A.; Mathey, F. Bulletin De La Societe Chimique De France 1995, 132, 384-393. (37) Klebach, T. C.; Lourens, R.; Bickelhaupt, F.; Stam, C. H.; Vanherk, A. J. Organomet. Chem. 1981, 210, 211-221. (38) Vanderknaap, T. A.; Bickelhaupt, F.; Kraaykamp, J. G.; Vankoten, G.; Bernards, J. P. C.; Edzes, H. T.; Veeman, W. S.; Deboer, E.; Baerends, E. J. Organometallics 1984, 3, 1804-1811. (39) Appel, R.; Casser, C.; Knoch, F. J. Organomet. Chem. 1985, 293, 213-217. (40) Ozawa, F.; Yoshifuji, M. Dalton Trans. 2006, 4987-4995. (41) Ozawa, F.; Nakajima, Y. Chem. Rec. 2016, 16, 2314-2323. (42) Appel, R.; Winkhaus, V.; Knoch, F. Chem. Ber. 1987, 120, 243. (43) Ozawa, F.; Okamoto, H.; Kawagishi, S.; Yamamoto, S.; Minami, T.; Yoshifuji, M. J. Am. Chem. Soc. 2002, 124, 10968-10969. (44) Ikeda, S.; Ohhata, F.; Miyoshi, M.; Tanaka, R.; Minami, T.; Ozawa, F.; Yoshifuji, M. Angew. Chem., Int. Ed. 2000, 39, 4512-+. (45) Ozawa, F.; Kawagishi, S.; Ishiyama, T.; Yoshifuji, M. Organometallics 2004, 23, 1325-1332. (46) Ito, S.; Nanko, M.; Shinozaki, T.; Kojima, M.; Aikawa, K.; Mikami, K. Chem. - Asian J. 2016, 11, 823-827. (47) Ito, S.; Nanko, M.; Mikami, K. ChemCatChem 2014, 6, 2292-2297. (48) Ito, S.; Freytag, M.; Liang, H.; Nishide, K.; Yoshifuji, M. Phosphorus, Sulfur Silicon Relat. Elem. 2008, 183, 555-557. (49) Freytag, M.; Ito, S.; Yoshifuji, M. Chem. Asian J. 2006, 1, 693-700. (50) Hayashi, A.; Yoshitomi, T.; Umeda, K.; Okazaki, M.; Ozawa, F. Organometallics 2008, 27, 2321-2327. (51) Nagao, M.; Asano, K.; Umeda, K.; Katayama, H.; Ozawa, F. J. Org. Chem. 2005, 70, 10511-10514. (52) Katayama, H.; Nagao, M.; Nishimura, T.; Matsui, Y.; Umeda, K.; Akamatsu, K.; Tsuruoka, T.; Nawafune, H.; Ozawa, F. J. Am. Chem. Soc. 2005, 127, 4350-4353. (53) Murakami, H.; Matsui, Y.; Ozawa, F.; Yoshifuji, M. J. Organomet. Chem. 2006, 691, 3151-3156. (54) Jensen, R. S.; Umeda, K.; Okazaki, M.; Ozawa, F.; Yoshifuji, M. J. Organomet. Chem. 2007, 692, 286-294. (55) Gajare, A. S.; Jensen, R. S.; Toyota, K.; Yoshifuji, M.; Ozawa, F. Synlett 2005, 144-148. (56) Murakami, H.; Minami, T.; Ozawa, F. J. Org. Chem. 2004, 69, 4482-4486. (57) Ozawa, F.; Ishiyama, T.; Yamamoto, S.; Kawagishi, S.; Murakami, H. Organometallics 2004, 23, 1698-1707. (58) Gajare, A. S.; Toyota, K.; Yoshifuji, M.; Ozawa, F. J. Org. Chem. 2004, 69, 6504-6506. (59) Gajare, A. S.; Toyota, K.; Yoshifuji, M.; Ozawa, F. Chem. Commun. 2004, 1994-1995. (60) Minami, T.; Okamoto, H.; Ikeda, S.; Tanaka, R.; Ozawa, F.; Yoshifuji, M. Angew. Chem., Int. Ed. 2001, 40, 4501-+. 197 (61) Ozawa, F.; Yamamoto, S.; Kawagishi, S.; Hiraoka, M.; Ikeda, S.; Minami, T.; Ito, S.; Yoshifuji, M. Chem. Lett. 2001, 972-973. (62) Toyota, K.; Masaki, K.; Abe, T.; Yoshifuji, M. Chem. Lett. 1995, 221-222. (63) Kato, M.; Ueta, Y.; Ito, S. Chem. Eur. J. 2021, 27, 2469-2475. (64) Ito, S.; Kusano, S.; Morita, N.; Mikami, K.; Yoshifuji, M. J. Organomet. Chem. 2010, 695, 291-296. (65) Daugulis, O.; Brookhart, M.; White, P. S. Organometallics 2002, 21, 5935-5943. (66) Chang, Y. H.; Tanigawa, I.; Taguchi, H.; Takeuchi, K.; Ozawa, F. Eur. J. Inorg. Chem. 2016, 754-760. (67) Takeuchi, K.; Tanaka, Y.; Tanigawa, I.; Ozawa, F.; Choi, J. C. Dalton Trans. 2020, 49, 3630-3637. (68) Nakajima, Y.; Okamoto, Y.; Chang, Y. H.; Ozawa, F. Organometallics 2013, 32, 2918-2925. (69) Chang, Y. H.; Nakajima, Y.; Ozawa, F. Organometallics 2013, 32, 2210-2215. (70) Hayashi, A.; Okazaki, M.; Ozawa, F. Organometallics 2007, 26, 5246-5249. (71) Dugal-Tessier, J.; Dake, G. R.; Gates, D. P. Organometallics 2007, 26, 6481-6486. (72) Dugal-Tessier, J.; Dake, G. R.; Gates, D. P. Org. Lett. 2010, 12, 4667-4669. (73) Appel, R.; Knoch, F.; Kunze, H. Chem. Ber. 1984, 117, 3151-3159. (74) Pellon, P.; Himdikabbab, S.; Rault, I.; Tonnard, F.; Hamelin, J. Tetrahedron Lett. 1990, 31, 1147-1150. (75) Boyd, B. A.; Thoma, R. J.; Neilson, R. H. Tetrahedron Lett. 1987, 28, 6121-6124. (76) Neilson, R. H.; Boyd, B. A.; Dubois, D. A.; Hani, R.; Scheide, G. M.; Shore, J. T.; Wettermark, U. G. Phosphorus Sulfur Silicon Relat. Elem. 1987, 30, 463-466. (77) Boyd, B. A.; Thoma, R. J.; Watson, W. H.; Neilson, R. H. Organometallics 1988, 7, 572-574. (78) Neilson, R. H. Phosphorus Sulfur Silicon Relat. Elem. 1983, 18, 43-46. (79) Martin, G.; Ocando-Mavarez, E. Heteroatom Chem. 1991, 2, 651-654. (80) Martin, G.; Ocando-Mavarez, E.; Osorio, A.; Laya, M.; Canestrari, M. Heteroatom Chem. 1992, 3, 395-401. (81) Öberg, E.; Orthaber, A.; Santoni, M. P.; Howard, F.; Ott, S. Phosphorus Sulfur Silicon Relat. Elem. 2013, 188, 152-158. (82) van der Sluis, M.; Klootwijk, A.; Wit, J. B. M.; Bickelhaupt, F.; Veldman, N.; Spek, A. L.; Jolly, P. W. J. Organomet. Chem. 1997, 529, 107-119. (83) Marinetti, A.; Ricard, L.; Mathey, F. Organometallics 1990, 9, 788-793. (84) Marinetti, A.; Bauer, S.; Ricard, L.; Mathey, F. J. Chem. Soc., Dalton Trans. 1991, 597-602. (85) Huy, N. H. T.; Fischer, J.; Mathey, F. J. Am. Chem. Soc. 1987, 109, 3475-3477. (86) Delauzon, G.; Charrier, C.; Bonnard, H.; Mathey, F.; Fischer, J.; Mitschler, A. J. Chem. Soc., Chem. Commun. 1982, 1272-1273. (87) Delauzon, G.; Charrier, C.; Bonnard, H.; Mathey, F. Tetrahedron Lett. 1982, 23, 511-514. (88) Charrier, C.; Bonnard, H.; Delauzon, G.; Mathey, F. J. Am. Chem. Soc. 1983, 105, 6871-6877. (89) Appel, R.; Knoch, F.; Zimmermann, R. Chem. Ber. 1985, 118, 814-824. (90) Ocando-Mavarez, E.; Martin, G.; Andrade, A. Heteroatom Chem. 1997, 8, 91-96. 198 (91) Ionkin, A. S.; Marshall, W. J.; Fish, B. M.; Schiffhauer, M. F.; McEwen, C. N. Chem. Commun. 2008, 5432-5434. (92) Ionkin, A. S.; Marshall, W. J.; Fish, B. M. Dalton Trans. 2009, 10574-10580. (93) Slootweg, J. C.; Krill, S.; de Kanter, F. J. J.; Schakel, M.; Ehlers, A. W.; Lutz, M.; Spek, A. L.; Lammertsma, K. Angew. Chem., Int. Ed. 2005, 44, 6579-6582. (94) Huy, N. H. T.; Mathey, F. Heteroatom Chem. 1990, 1, 33-35. (95) Huy, N. H. T.; Mathey, F. Tetrahedron Lett. 1988, 29, 3077-3078. (96) Huy, N. H. T.; Ricard, L.; Mathey, F. Organometallics 1988, 7, 1791-1795. (97) “Improvement in India-Rubber Fabrics”, C. Goodyear, US3633, 1844. (98) (99) Staudinger, H. Ber. Dtsch. Chem. Ges. 1920, 53, 1073-1085. (100) (101) (102) Hadjichristidis, N.; Hirao, A., Anionic Polymerization. Springer: Tokyo, Japan, 2015. (103) Morita, H.; Tobolsky, A. V. J. Am. Chem. Soc. 1957, 79, 5853-5855. (104) Vinogradova, L. V.; Sgonnik, V. N.; Nikolaev, N. I.; Vetchinova, E. P. Eur. Poly. J. 1980, 16, 799-801. (105) Jenner, G. J. Macromol. Sci. A 1975, A 9, 83-93. (106) Worsfold, D. J.; Bywater, S. Can. J. Chem. 1964, 42, 2884-&. (107) Widmaier, J. M.; Meyer, G. C. Macromolecules 1981, 14, 450-452. (108) Wang, H. B.; Yang, Y.; Nishiura, M.; Hong, Y. L.; Nishiyama, Y.; Higaki, Y.; Hou, Z. M. Angew. Chem., Int. Ed. 2022, 61. (109) Szwarc, M. Nature 1956, 178, 1168-1169. (110) Miyamoto, M.; Sawamoto, M.; Higashimura, T. Macromolecules 1984, 17, 265-268. (111) Wang, J. S.; Matyjaszewski, K. J. Am. Chem. Soc. 1995, 117, 5614-5615. (112) Manners, I. Angew. Chem., Int. Ed. 1996, 35, 1602-1621. (113) Tsang, C. W.; Yam, M.; Gates, D. P. J. Am. Chem. Soc. 2003, 125, 1480-1481. (114) Noonan, K. J. T.; Gates, D. P. Angew. Chem., Int. Ed. 2006, 45, 7271-7274. (115) Noonan, K. J. T.; Gates, D. P. Macromolecules 2008, 41, 1961-1965. (116) Gillon, B. H.; Gates, D. P. Chem. Commun. 2004, 1868-1869. (117) Gillon, B. H.; Gates, D. P.; Henderson, M. A.; Janusson, E.; McIndoe, J. S. Can. J. Chem. 2017, 95, 239-242. (118) Vanderknaap, T. A.; Bickelhaupt, F. Tetrahedron Lett. 1982, 23, 2037-2040. (119) Gillon, B. H.; Noonan, K. J. T.; Feldscher, B.; Wissenz, J. M.; Kam, Z. M.; Hsieh, T.; Kingsley, J. J.; Bates, J. I.; Gates, D. P. Can. J. Chem. 2007, 85, 1045-1052. (120) Siu, P. W.; Serin, S. C.; Krummenacher, I.; Hey, T. W.; Gates, D. P. Angew. Chem., Int. Ed. 2013, 52, 6967-6970. (121) Rawe, B. W.; Priegert, A. M.; Wang, S.; Schiller, C.; Gerke, S.; Gates, D. P. Macromolecules 2018, 51, 2621-2629. (122) Gillon, B. H.; Patrick, B. O.; Gates, D. P. Chem. Commun. 2008, 2161-2163. (123) Noonan, K. J. T.; Feldscher, B.; Bates, J. I.; Kingsley, J. J.; Yam, M.; Gates, D. P. Dalton Trans. 2008, 4451-4457. (124) Zhang, T.; Conrad, E. D.; Gates, D. P. Polymer 2022, 249. (125) Chen, L. X.; Rawe, B. W.; Adachi, K.; Gates, D. P. Chem. Eur. J. 2018, 24, 18012-18019. 199 (126) Noonan, K. J. T.; Gillon, B. H.; Cappello, V.; Gates, D. P. J. Am. Chem. Soc. 2008, 130, 12876-+. (127) Tsang, C. W.; Baharloo, B.; Riendl, D.; Yam, M.; Gates, D. P. Angew. Chem., Int. Ed. 2004, 43, 5682-5685. (128) Serin, S. C.; Dake, G. R.; Gates, D. P. Dalton Trans. 2016, 45, 5659-5666. (129) Noonan, K. J. T.; Patrick, B. O.; Gates, D. P. Chem. Commun. 2007, 3658-3660. (130) Mei, Y. B.; Gamboa-Carballo, J. J.; Bao, Y. Y.; Wu, N.; Le Corre, G.; Grützmacher, H. Sci. Adv. 2021, 7. (131) Honeyman, C. H.; Manners, I.; Morrissey, C. T.; Allcock, H. R. J. Am. Chem. Soc. 1995, 117, 7035-7036. (132) Amin, A. M.; Wang, L.; Wang, J. J.; Yu, H. J.; Huo, J.; Gao, J. M.; Xiao, A. G. Designed Monomers and Polymers 2009, 12, 357-375. (133) Weinhold, F.; West, R. J. Am. Chem. Soc. 2013, 135, 5762-5767. (134) Leadbeater, N. E.; Marco, M. Chem. Rev. 2002, 102, 3217-3273. (135) den Heeten, R.; Swennenhuis, B. H. G.; van Leeuwen, P.; de Vries, J. G.; Kamer, P. C. J. Angew. Chem., Int. Ed. 2008, 47, 6602-6605. (136) Fellmann, J. D.; Garrou, P. E.; Withers, H. P.; Seyferth, D.; Traficante, D. D. Organometallics 1983, 2, 818-825. (137) Mizuta, T.; Onishi, M.; Miyoshi, K. Organometallics 2000, 19, 5005-5009. (138) Cao, L.; Manners, I.; Winnik, M. A. Macromolecules 2001, 34, 3353-3360. (139) Peckham, T. J.; Massey, J. A.; Honeyman, C. H.; Manners, I. Macromolecules 1999, 32, 2830-2837. (140) Cao, L.; Winnik, M. A.; Manners, I. J. Inorg. Organomet. Polym. 1998, 8, 215-224. (141) Patra, S. K.; Whittell, G. R.; Nagiah, S.; Ho, C. L.; Wong, W. Y.; Manners, I. Chem. Eur. J. 2010, 16, 3240-3250. (142) Beland, V. A.; Ragogna, P. J. Acs Appl. Mater. Inter. 2020, 12, 27640-27650. (143) Mao, S. S. H.; Tilley, T. D. Macromolecules 1997, 30, 5566-5569. (144) Green, J. P.; Orthaber, A., Organophosphorus Polymers. John Wiley and Sons, Ltd.: Hoboken, NJ, 2019. (145) Sebastian, M.; Hissler, M.; Fave, C.; Rault-Berthelot, J.; Odin, C.; Reau, R. Angew. Chem., Int. Ed. 2006, 45, 6152-6155. (146) Lucht, B. L.; St Onge, N. O. Chem. Commun. 2000, 2097-2098. (147) Jin, Z.; Lucht, B. L. J. Organomet. Chem. 2002, 653, 167-176. (148) Jin, Z.; Lucht, B. L. J. Am. Chem. Soc. 2005, 127, 5586-5595. (149) Rawe, B. W.; Gates, D. P. Angew. Chem., Int. Ed. 2015, 54, 11438-11442. (150) Rawe, B. W.; Scott, M. R.; Brown, C. M.; MacKenzie, H. K.; Gates, D. P. Macromolecules 2017, 50, 8916-8927. (151) Mackenzie, H. K.; Rawe, B. W.; Samedov, K.; Walsgrove, H. T. G.; Uva, A.; Han, Z. Y.; Gates, D. P. J. Am. Chem. Soc. 2020, 142, 10319-10324. (152) Wright, V. A.; Gates, D. P. Angew. Chem., Int. Ed. 2002, 41, 2389-2392. (153) Wright, V. A.; Patrick, B. O.; Schneider, C.; Gates, D. P. J. Am. Chem. Soc. 2006, 128, 8836-8844. (154) Smith, R. C.; Chen, X. F.; Protasiewicz, J. D. Inorg. Chem. 2003, 42, 5468-5470. (155) Smith, R. C.; Protasiewicz, J. D. J. Am. Chem. Soc. 2004, 126, 2268-2269. (156) Smith, R. C.; Protasiewicz, J. D. Eur. J. Inorg. Chem. 2004, 998-1006. 200 (157) Salazar, D. M.; Mijangos, E.; Pullen, S.; Gao, M.; Orthaber, A. Chem. Commun. 2017, 53, 1120-1123. (158) Yamada, N.; Toyota, K.; Yoshifuji, M. Chem. Lett. 2001, 248-249. (159) Toyota, K.; Ujita, J.; Kawasaki, S.; Abe, K.; Yamada, N.; Yoshifuji, M. Tetrahedron Lett. 2004, 45, 7609-7612. (160) Kawasaki, S.; Ujita, J.; Toyota, K.; Yoshifuji, M. Chem. Lett. 2005, 34, 724-725. (161) Dück, K.; Rawe, B. W.; Scott, M. R.; Gates, D. P. Angew. Chem., Int. Ed. 2017, 56, 9507-9511. (162) Schue, F.; Worsfold, D. J.; Bywater, S. Journal of Polymer Science Part B-Polymer Letters 1969, 7, 821-&. (163) Chen, M. K.; Zhao, Y. H.; Zhang, R.; Yang, Y.; Cao, J.; Tang, M. Z.; Huang, G. S.; Xu, Y. X. Chem. Eng. J. 2023, 452, 139130. (164) Becker, G.; Herrmann, W. A.; Kalcher, W.; Kriechbaum, G. W.; Pahl, C.; Wagner, C. T.; Ziegler, M. L. Angew. Chem., Int. Ed. 1983, 22, 413-414. (165) Niecke, E.; Nieger, M.; Wenderoth, P. J. Am. Chem. Soc. 1993, 115, 6989. (166) Niecke, E.; Nieger, M.; Wenderoth, P. Angew. Chem., Int. Ed. Engl. 1994, 33, 1953-1955. (167) Gaumont, A. C.; Morise, X.; Denis, J. M. J. Org. Chem. 1992, 57, 4292-4295. (168) Marinetti, A.; Bauer, S.; Ricard, L.; Mathey, F. Organometallics 1990, 9, 793-798. (169) Ito, S.; Kimura, S.; Yoshifuji, M. Chem. Lett. 2002, 708-709. (170) Brooner, R. E. M.; Brown, T. J.; Widenhoefer, R. A. Chem. Eur. J. 2013, 19, 8276-8284. (171) Nieto-Oberhuber, C.; Lopez, S.; Echavarren, A. M. J. Am. Chem. Soc. 2005, 127, 6178-6179. (172) Angermaier, K.; Zeller, E.; Schmidbaur, H. J. Organomet. Chem. 1994, 472, 371-376. (173) Schmidbaur, H.; Brachthauser, B.; Steigelmann, O.; Beruda, H. Chem. Ber. 1992, 125, 2705-2710. (174) Characteristic Bond Lengths in Free Molecules. CRC Handbook of Chemistry and Physics, 84th ed.; CRC: Boca Raton, FL, 2003 (175) Ito, S.; Zhai, L. L.; Mikami, K. Chem. Asian J. 2011, 6, 3077-3083. (176) Öberg, E.; Orthaber, A.; Lescop, C.; Reau, R.; Hissler, M.; Ott, S. Chem. Eur. J. 2014, 20, 8421-8432. (177) Orthaber, A.; Lofas, H.; Öberg, E.; Grigoriev, A.; Wallner, A.; Jafri, S. H. M.; Santoni, M. P.; Ahuja, R.; Leifer, K.; Ottosson, H.; Ott, S. Angew. Chem., Int. Ed. 2015, 54, 10634-10638. (178) Wells, J. A. L.; Shameem, M. A.; Gupta, A. K.; Orthaber, A. Inorg. Chem. Front. 2020, 7, 4052-4061. (179) Green, J. P.; Salazar, D. M.; Gupta, A. K.; Orthaber, A. J. Org. Chem. 2020, 85, 14619-14626. (180) Ito, S.; Freytag, M.; Yoshifuji, M. Dalton Trans. 2006, 710-713. (181) Yam, M.; Tsang, C. W.; Gates, D. P. Inorg. Chem. 2004, 43, 3719-3723. (182) Mercier, F.; Hugellegoff, C.; Mathey, F. Tetrahedron Lett. 1989, 30, 2397-2398. (183) Gaumont, A. C.; Guillemin, J. C.; Denis, J. M. J. Chem. Soc., Chem. Commun. 1994, 945-946. (184) Marbella, L. E.; Millstone, J. E. Chem. Mater. 2015, 27, 2721-2739. (185) Orthaber, A.; Öberg, E.; Jane, R. T.; Ott, S. Z. Anorg. Allg. Chem. 2012, 638, 2219-2224. (186) SAINT, version 8.34A; Bruker AXS Inc.: Madison, WI, 2013. 201 (187) Krause, L.; Herbst-Irmer, R.; Sheldrick, G. M.; Stalke, D. J. Appl. Crystallogr. 2015, 48, 3-10. (188) Sheldrick, G. M. Acta Crystallogr. A 2015, 71, 3-8. (189) Sheldrick, G. M. Acta Crystallogr. C Struct. Chem. 2015, 71, 3-8. (190) Dolomanov, O. V.; Bourhis, L. J.; Gildea, R. J.; Howard, J. A. K.; Puschmann, H. J. Appl. Crystallogr. 2009, 42, 339-341. (191) Gotz, S.; Zechel, S.; Hager, M. D.; Newkome, G. R.; Schubert, U. S. Prog. Polym. Sci. 2021, 119. (192) Scheutz, G. M.; Lessard, J. J.; Sims, M. B.; Sumerlin, B. S. J. Am. Chem. Soc. 2019, 141, 16181-16196. (193) Li, H.; Yang, P.; Pageni, P.; Tang, C. B. Macromol. Rapid Commun. 2017, 38. (194) Heinzmann, C.; Weder, C.; de Espinosa, L. M. Chem. Soc. Rev. 2016, 45, 342-358. (195) Voorhaar, L.; Hoogenboom, R. Chem. Soc. Rev. 2016, 45, 4013-4031. (196) Roy, N.; Bruchmann, B.; Lehn, J. M. Chem. Soc. Rev. 2015, 44, 3786-3807. (197) Billiet, S.; Hillewaere, X. K. D.; Teixeira, R. F. A.; Du Prez, F. E. Macromol. Rapid Commun. 2013, 34, 290-309. (198) Wojtecki, R. J.; Meador, M. A.; Rowan, S. J. Nat. Mater. 2011, 10, 14-27. (199) Wang, M.; Holland, J.; Horton, T. A. R.; Yolsal, U.; Shaver, M. P. Polymer 2022, 242. (200) Horton, T. A. R.; Wang, M.; Shaver, M. P. Chem. Sci. 2022, 13, 3845-3850. (201) Yolsal, U.; Horton, T. A. R.; Wang, M.; Shaver, M. P. J. Am. Chem. Soc. 2021, 143, 12980-12984. (202) Yolsal, U.; Wang, M.; Royer, J. R.; Shaver, M. P. Macromolecules 2019, 52, 3417-3425. (203) Wang, M.; Nudelman, F.; Matthes, R. R.; Shaver, M. P. J. Am. Chem. Soc. 2017, 139, 14232-14236. (204) Knights, A. W.; Chitnis, S. S.; Manners, I. Chem. Sci. 2019, 10, 7281-7289. (205) Chen, M. J.; Zhang, Z. M.; Yu, Z. Z.; Qiu, H. L.; Ma, B.; Wu, H. H.; Zhang, J. L. Acs Catalysis 2015, 5, 7488-7492. (206) Akai, Y.; Konnert, L.; Yamamoto, T.; Suginome, M. Chem. Commun. 2015, 51, 7211-7214. (207) Corkum, E. G.; Kalapugama, S.; Hass, M. J.; Bergens, S. H. RSC Adv. 2012, 2, 3473-3476. (208) Hu, Q. S.; Lu, Y.; Tang, Z. Y.; Yu, H. B. J. Am. Chem. Soc. 2003, 125, 2856-2857. (209) Li, G. Y.; Fagan, P. J.; Watson, P. L. Angew. Chem., Int. Ed. 2001, 40, 1106-+. (210) Paulusse, J. M. J.; Sijbesma, R. P. Chem. Commun. 2008, 4416-4418. (211) Paulusse, J. M. J.; van Beek, D. J. M.; Sijbesma, R. P. J. Am. Chem. Soc. 2007, 129, 2392-2397. (212) Paulusse, J. M. J.; Huijbers, J. P. J.; Sijbesma, R. P. Chem. Eur. J. 2006, 12, 4928-4934. (213) Paulusse, J. M. J.; Sijbesma, R. P. Angew. Chem., Int. Ed. 2004, 43, 4460-4462. (214) Deschamps, B.; Le Goff, X.; Ricard, L.; Le Floch, P. Heteroatom Chem. 2007, 18, 363-371. (215) Takita, R.; Takada, Y.; Jensen, R. S.; Okazaki, M.; Ozawa, F. Organometallics 2008, 27, 6279-6285. (216) Liang, H. Z.; Ito, S.; Yoshifuji, M. Org. Lett. 2004, 6, 425-427. (217) Krause, J.; Goddard, R.; Mynott, R.; Porschke, K. R. Organometallics 2001, 20, 1992-1999. 202 (218) Pons, J.; Garcia-Anton, J.; Solans, X.; Font-Bardia, M.; Ros, J. Acta Crystallogr. E 2008, 64, M621-U163. (219) Vuoti, S.; Autio, J.; Laitila, M.; Haukka, M.; Pursiainen, J. Eur. J. Inorg. Chem. 2008, 397-407. (220) Meijboom, R.; Muller, A.; Roodt, A. Acta Crystallogr. E 2006, 62, M1603-M1605. (221) Grushin, V. V.; Bensimon, C.; Alper, H. Inorg. Chem. 1994, 33, 4804-4806. (222) Woisetschlager, O. E. B., W.; Polborn, K. CSD Communication 2005. (223) Nakashige, M. L.; Loristo, J. I. P.; Wong, L. S.; Gurr, J. R.; O'Donnell, T. J.; Yoshida, W. Y.; Rheingold, A. L.; Hughes, R. P.; Cain, M. F. Organometallics 2019, 38, 3338-3348. (224) Taguchi, H. O.; Sasaki, D.; Takeuchi, K.; Tsujimoto, S.; Matsuo, T.; Tanaka, H.; Yoshizawa, K.; Ozawa, F. Organometallics 2016, 35, 1526-1533. (225) Chang, Y. H.; Takeuchi, K.; Wakioka, M.; Ozawa, F. Organometallics 2015, 34, 1957-1962. (226) Taguchi, H.; Chang, Y. H.; Takeuchi, K.; Ozawa, F. Organometallics 2015, 34, 1589-1596. (227) Chang, Y. H.; Nakajima, Y.; Tanaka, H.; Yoshizawa, K.; Ozawa, F. J. Am. Chem. Soc. 2013, 135, 11791-11794. (228) Houdard, R.; Mezailles, N.; Le Goff, X. F.; Le Floch, P. Organometallics 2009, 28, 5952-5959. (229) Septelean, R.; Nemes, G.; Escudie, J.; Silaghi-Dumitrescu, I.; Ranaivonjatovo, H.; Petrar, P.; Gornitzka, H.; Silaghi-Dumitrescu, L.; Saffon, N. Eur. J. Inorg. Chem. 2009, 628-634. (230) Liang, H. Z.; Ito, S.; Yoshifuji, M. Org. Biomol. Chem. 2003, 1, 3054-3058. (231) David, M. A.; Alexander, J. B.; Glueck, D. S.; Yap, G. P. A.; Liable-Sands, L. M.; Rheingold, A. L. Organometallics 1997, 16, 378-383. (232) David, M. A.; Paisner, S. N.; Glueck, D. S. Organometallics 1995, 14, 17-19. (233) Tsang, C. W.; Rohrick, C. A.; Saini, T. S.; Patrick, B. O.; Gates, D. P. Organometallics 2004, 23, 5913-5923. (234) Tsang, C. W.; Rohrick, C. A.; Saini, T. S.; Patrick, B. O.; Gates, D. P. Organometallics 2002, 21, 1008-1010. (235) Karsch, H. H.; Reisacher, H. U.; Muller, G. Angew. Chem., Int. Ed. Engl. 1986, 25, 454-455. (236) Favez, R.; Roulet, R. Inorg. Chem. 1981, 20, 1598-1601. (237) Hilliard, C. R.; Bhuvanesh, N.; Gladysz, J. A.; Blumel, J. Dalton Trans. 2012, 41, 1742-1754. (238) Appel, R.; Casser, C.; Immenkeppel, M.; Knoch, F. Angew. Chem., Int. Ed. Engl. 1984, 23, 895-896. (239) Liang, H. Z.; Nishide, K.; Ito, S.; Yoshifuji, M. Tetrahedron Lett. 2003, 44, 8297-8300. (240) Magnuson, K. W.; Oshiro, S. M.; Gurr, J. R.; Yoshida, W. Y.; Gernbicky, M.; Rheingold, A. L.; Hughes, R. P.; Cain, M. F. Organometallics 2016, 35, 855-859. (241) Miura-Akagi, P. M.; Nakashige, M. L.; Maile, C. K.; Oshiro, S. M.; Gurr, J. R.; Yoshida, W. Y.; Royappa, A. T.; Krause, C. E.; Rheingold, A. L.; Hughes, R. P.; Cain, M. F. Organometallics 2016, 35, 2224-2231. (242) Ito, S.; Shinozaki, T.; Mikami, K. ChemistrySelect 2016, 1, 5260-5264. (243) Chen, H.; Pascal, S.; Wang, Z. Y.; Bouit, P. A.; Wang, Z. S.; Zhang, Y. L.; Tondelier, D.; Geffroy, B.; Reau, R.; Mathey, F.; Duan, Z.; Hissler, M. Chem. Eur. J. 2014, 20, 9784-9793. (244) Lauwick, H.; Duffy, M. P.; Bouit, P. A.; Hissler, M. Coord. Chem. Rev. 2021, 433, 213759. 203 (245) Poli, G.; Prestat, G.; Liron, F.; Kammerer-Pentier, C., Selectivity in Palladium-Catalyzed Allylic Substitution. In Transition Metal Catalyzed Enantioselective Allylic Substitution in Organic Synthesis, Kazmaier, U., Ed. Springer: New York, 2011; Vol. 38, pp 2-52. (246) Albert, J.; Bosque, R.; Cadena, J. M.; Delgado, S.; Granell, J.; Muller, G.; Ordinas, J. I.; Bardia, M. F.; Solans, X. Chem. Eur. J. 2002, 8, 2279-2287. (247) Franco, D.; Gomez, M.; Jimenez, F.; Muller, G.; Rocamora, M.; Maestro, M. A.; Mahia, J. Organometallics 2004, 23, 3197-3209. (248) Camus, J. M.; Andrieu, J.; Richard, P.; Poli, R. Eur. J. Inorg. Chem. 2004, 1081-1091. (249) Grabulosa, A.; Muller, G.; Ordinas, J. I.; Mezzetti, A.; Maestro, M. A.; Font-Bardia, M.; Solans, X. Organometallics 2005, 24, 4961-4973. (250) Platero-Prats, A. E.; Perez, S.; Lopez, C.; Solans, X.; Font-Bardia, M.; van Leeuwen, P.; van Strijdonck, G. P. F.; Freixa, Z. J. Organomet. Chem. 2007, 692, 4215-4226. (251) Clavero, P.; Grabulosa, A.; Font-Bardia, M.; Muller, G. Journal of Molecular Catalysis a-Chemical 2014, 391, 183-190. (252) Biosca, M.; Margalef, J.; Caldentey, X.; Besora, M.; Rodriguez-Escrich, C.; Salto, J.; Carnbeiro, X. C.; Maseras, F.; Pamies, O.; Dieguez, M.; Pericas, M. A. Acs Catalysis 2018, 8, 3587-3601. (253) Deegan, M. M.; Muldoon, J. A.; Hughes, R. P.; Glueck, D. S.; Rheingold, A. L. Organometallics 2018, 37, 1473-1482. (254) Nelson, J. H. Concepts Magn. Reson. 2002, 14, 19-78. (255) Morita, D. K.; Stille, J. K.; Norton, J. R. J. Am. Chem. Soc. 1995, 117, 8576-8581. (256) Doxsee, K. M.; Hanawalt, E. M.; Shen, G. S.; Weakley, T. J. R.; Hope, H.; Knobler, C. B. Inorg. Chem. 1991, 30, 3381-3389. (257) Streubel, R.; Wilkens, H.; Rohde, U.; Ostrowski, A.; Jeske, J.; Ruthe, F.; Jones, P. G. Eur. J. Inorg. Chem. 1999, 1567-1579. (258) Marinetti, A.; Fischer, J.; Mathey, F. J. Am. Chem. Soc. 1985, 107, 5001-5002. (259) Perez, J. M.; Klein, M.; Kyri, A. W.; Schnakenburg, G.; Streubel, R. Organometallics 2011, 30, 5636-5640. (260) Gubin, S. P. K., L. G.; Polyakova, L. A.; Churakov, A. V. CSD Communication 1998. (261) Faller, J. W.; Sarantopoulos, N. Organometallics 2004, 23, 2179-2185. (262) Wu, J. G.; Green, J. C.; Hazari, N.; Hruszkewycz, D. P.; Incarvito, C. D.; Schmeier, T. J. Organometallics 2010, 29, 6369-6376. (263) Spek, A. L. Acta Crystallogr. C Struct. Chem. 2015, 71, 9-18. (264) Chai, J. D.; Head-Gordon, M. Phys Chem Chem Phys 2008, 10, 6615-6620. (265) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Petersson, G. A.; Nakatsuji, H.; Li, X.; Caricato, M.; Marenich, A. V.; Bloino, J.; Janesko, B. G.; Gomperts, R.; Mennucci, B.; Hratchian, H. P.; Ortiz, J. V.; Izmaylov, A. F.; Sonnenberg, J. L.; Williams; Ding, F.; Lipparini, F.; Egidi, F.; Goings, J.; Peng, B.; Petrone, A.; Henderson, T.; Ranasinghe, D.; Zakrzewski, V. G.; Gao, J.; Rega, N.; Zheng, G.; Liang, W.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Vreven, T.; Throssell, K.; Montgomery Jr., J. A.; Peralta, J. E.; Ogliaro, F.; Bearpark, M. J.; Heyd, J. J.; Brothers, E. N.; Kudin, K. N.; Staroverov, V. N.; Keith, T. A.; Kobayashi, R.; Normand, J.; Raghavachari, K.; Rendell, A. P.; Burant, J. C.; Iyengar, S. S.; Tomasi, J.; Cossi, M.; Millam, J. M.; Klene, M.; Adamo, C.; Cammi, R.; Ochterski, J. W.; Martin, 204 R. L.; Morokuma, K.; Farkas, O.; Foresman, J. B.; Fox, D. J. Gaussian 16 Rev. C.01, Wallingford, CT, 2016. (266) Wang, D. R.; Wang, X. G. Prog. Polym. Sci. 2013, 38, 271-301. (267) Sun, S. D.; Liang, S. F.; Xu, W. C.; Xu, G. F.; Wu, S. Polym. Chem. 2019, 10, 4389-4401. (268) Sasamori, T.; Hirano, K.; Miyake, H.; Tokitoh, N. Chem. Lett. 2015, 44, 1240-1242. (269) Gudimetla, V. B.; Rheingold, A. L.; Payton, J. L.; Peng, H.-L.; Simpson, M. C.; Protasiewicz, J. D. Inorg. Chem. 2006, 45, 4895-4901. (270) Ito, S.; Yoshifuji, M. Chem. Commun. 2001, 1208-1209. (271) Kawanami, H.; Toyota, K.; Yoshifuji, M. J. Organomet. Chem. 1997, 535, 1. (272) Yoshifuji, M.; Kawanami, H.; Kawai, Y.; Toyota, K.; Yasunami, M.; Niitsu, T.; Inamoto, N. Chem. Lett. 1992, 1053-1056. (273) Yoshifuji, M.; Toyota, K.; Murayama, M.; Yoshimura, H.; Okamoto, A.; Hirotsu, K.; Nagase, S. Chem. Lett. 1990, 2195. (274) Yoshifuji, M.; Niitsu, T.; Toyota, K.; Inamoto, N.; Karsch, H. H.; Reisacher, H. U. Tetrahedron Lett. 1988, 29, 333-336. (275) Yoshifuji, M.; Toyota, K.; Matsuda, I.; Niitsu, T.; Inamoto, N.; Hirotsu, K.; Higuchi, T. Tetrahedron 1988, 44, 1363-1367. (276) Yoshifuji, M.; Toyota, K.; Inamoto, N. Tetrahedron Lett. 1985, 26, 1727. (277) Yoshifuji, M.; Toyota, K.; Inamoto, N. Phosphorus and Sulfur 1985, 25, 237. (278) Yoshifuji, M.; Toyota, K.; Inamoto, N.; Hirotsu, K.; Higuchi, T. Tetrahedron Lett. 1985, 26, 6443-6446. (279) Yoshifuji, M.; Toyota, K.; Shibayama, K.; Inamoto, N. Chem. Lett. 1983, 1653. (280) Jouaiti, A.; Badri, A. A.; Geoffroy, M.; Bernardinelli, G. J. Organomet. Chem. 1997, 529, 143. (281) Jouaiti, A.; Geoffroy, M.; Terron, G.; Bernardinelli, G. J. Am. Chem. Soc. 1995, 117, 2251. (282) Appel, R.; Niemann, B.; Schuhn, W.; Siabalis, N. J. Organomet. Chem. 1988, 347, 299. (283) Appel, R.; Hünerbein, J.; Siabalis, N. Angew. Chem., Int. Ed. Engl. 1987, 26, 779-780. (284) Appel, R.; Menzel, J.; Knoch, F.; Voltz, P. Z. Anorg. All. Chem. 1986, 100. (285) Szkop, K. M.; Jupp, A. R.; Razumkov, H.; Stephan, D. W. Dalton Trans. 2020, 49, 885-890. (286) Yamada, N.; Abe, K.; Toyota, K.; Yoshifuji, M. Org. Lett. 2002, 4, 569-572. (287) Toyota, K.; Tashiro, K.; Abe, T.; Yoshifuji, M. Heteroat. Chem. 1994, 5, 549. (288) Ionkin, A. S.; Marshall, W. J.; Fish, B. M.; Schiffhauer, M. F.; Davidson, F.; McEwen, C. N.; Keys, D. E. Organometallics 2007, 26, 5050-5058. (289) Appel, R.; Casser, C.; Immenkeppel, M. Tetrahedron Lett. 1985, 26, 3551-3554. (290) van der Sluis, M.; Wit, J. B. M.; Bickelhaupt, F. Organometallics 1996, 15, 174-180. (291) Shameem, M. A.; Esfandiarfard, K.; Öberg, E.; Ott, S.; Orthaber, A. Chem. Eur. J. 2016, 22, 10614-10619. (292) van der Sluis, M.; Beverwijk, V.; Termaten, A.; Bickelhaupt, F.; Kooijman, H.; Spek, A. L. Organometallics 1999, 18, 1402-1407. (293) Appel, R.; Casser, C. Tetrahedron Lett. 1984, 25, 4109-4112. (294) Appel, R.; Immenkeppel, M. Z. Anorg. Allg. Chem. 1987, 553, 7-14. (295) Becke, A. D. J. Chem. Phys. 1993, 98, 5648-5652. (296) Lee, C. T.; Yang, W. T.; Parr, R. G. Phys Rev B 1988, 37, 785-789. (297) Weigend, F.; Ahlrichs, R. Phys Chem Chem Phys 2005, 7, 3297-3305. 205 (298) Weigend, F. Phys Chem Chem Phys 2006, 8, 1057-1065. (299) Grimme, S.; Antony, J.; Ehrlich, S.; Krieg, H. J. Chem. Phys. 2010, 132. (300) Grimme, S.; Ehrlich, S.; Goerigk, L. J. Comput. Chem. 2011, 32, 1456-1465. (301) Neese, F. Wiley Interdisciplinary Reviews-Computational Molecular Science 2012, 2, 73-78. (302) Sharma, M. K.; Blomeyer, S.; Glodde, T.; Neumann, B.; Stammler, H. G.; Hinz, A.; van Gastel, M.; Ghadwal, R. S. Chem. Sci. 2020, 11, 1975-1984. (303) Rhodes, C. J. J. Chem. Soc., Perkin Trans. 2 2002, 1379-1396. (304) Macrae, R. M. Sci. Prog. 2013, 96, 237-293. (305) Walker, D. C. J. Chem. Soc., Faraday Trans. 1998, 94, 1-9. (306) McKenzie, I. Annu. Rep. Prog. Chem., Sect. C: Phys. Chem. 2013, 109, 65-112. (307) Chandrasena, L.; Samedov, K.; McKenzie, I.; Mozafari, M.; West, R.; Gates, D. P.; Percival, P. W. Angew. Chem., Int. Ed. 2019, 58, 297-301. (308) McCollum, B. M.; Abe, T.; Brodovitch, J.-C.; Clyburne, J. A. C.; Iwamoto, T.; Kira, M.; Percival, P. W.; West, R. Angew. Chem., Int. Ed. 2008, 47, 9772-9774. (309) McCollum, B. M.; Brodovitch, J.-C.; Clyburne, J. A. C.; Mitra, A.; Percival, P. W.; Tomasik, A.; West, R. Chem. - Eur. J. 2009, 15, 8409. (310) McCollum, B. M.; Brodovitch, J.-C.; Clyburne, J. A. C.; Percival, P. W.; West, R. Phys. B 2009, 404, 940-942. (311) Mitra, A.; Brodovitch, J. C.; Krempner, C.; Percival, P. W.; Vyas, P.; West, R. Angew. Chem., Int. Ed. 2010, 49, 2893-2895. (312) Percival, P. W.; Brodovitch, J. C.; Mozafari, M.; Mitra, A.; West, R.; Ghadwal, R. S.; Azhakar, R.; Roesky, H. W. Chem. Eur. J. 2011, 17, 11970-11973. (313) Percival, P. W.; McCollum, B. M.; Brodovitch, J.-C.; Driess, M.; Mitra, A.; Mozafari, M.; West, R.; Xiong, Y.; Yao, S. Organometallics 2012, 31, 2709-2714. (314) Samedov, K.; West, R.; Percival, P. W.; Brodovitch, J.-C.; Chandrasena, L.; Mozafari, M.; Tacke, R.; Junold, K.; Kobelt, C.; Samuel, P. P.; Azhakar, R.; Mondal, K. C.; Roesky, H. W.; Driess, M.; Wang, W. Organometallics 2015, 34, 3532-3537. (315) Ito, S.; Akama, H.; Ueta, Y.; McKenzie, I.; Kojima, K. M. Bull. Chem. Soc. Jpn. 2021, 94, 2970-2972. (316) Koshino, K.; Kojima, K. M.; McKenzie, I.; Ito, S. Angew. Chem., Int. Ed. 2021, 60, 24034-24038. (317) Ito, S.; Ueta, Y.; Koshino, K.; Kojima, K. M.; McKenzie, I.; Mikami, K. Angew. Chem., Int. Ed. 2018, 57, 8608-8613. (318) Samedov, K.; Heider, Y.; Cai, Y.; Willmes, P.; Muehlhausen, D.; Huch, V.; West, R.; Scheschkewitz, D.; Percival, P. W. Angew. Chem., Int. Ed. 2020, 59, 16007-16012. (319) Ramos, M. J.; McKenna, D.; Webster, B. C.; Roduner, E. J. Chem. Soc., Faraday Trans. 1 1984, 80, 267-274. (320) Percival, P. W.; Brodovitch, J. C.; Leung, S. K.; Yu, D.; Kiefl, R. F.; Luke, G. M.; Venkateswaran, K.; Cox, S. F. J. Chem. Phys. 1988, 127, 137-147. (321) Roduner, E.; Brinkman, G. A.; Louwrier, P. W. F. Chem. Phys. 1982, 73, 117-130. (322) Yu, D.; Percival, P. W.; Brodovitch, J. C.; Leung, S. K.; Kiefl, R. F.; Venkateswaran, K.; Cox, S. F. J. Chem. Phys. 1990, 142, 229. (323) Roduner, E.; Brinkman, G. A.; Louwrier, P. W. F. Chem. Phys. 1984, 88, 143-153. (324) Roduner, E. Radiat. Phys. Chem. 1986, 28, 75-84. 206 (325) Hill, A.; Symons, M. C. R.; Cox, S. F. J.; Derenzi, R.; Scott, C. A.; Bucci, C.; Vecli, A. J. Chem. Soc., Faraday Trans. 1 1985, 81, 433-448. (326) Hajirahimkhan, S.; Chapple, D. E.; Gholami, G.; Blacquiere, J. M.; Xu, C. B.; Ragogna, P. J. Chem. Commun. 2020, 56, 10357-10360. (327) Guino, M.; Hii, K. K. M. Tetrahedron Lett. 2005, 46, 6911-6913. (328) Bhat, S. N.; Berclaz, T.; Jouaiti, A.; Geoffroy, M. Helvetica Chimica Acta 1994, 77, 372-382. (329) Bhat, S. N.; Berclaz, T.; Geoffroy, M.; Jouaiti, A. J. Phys. Chem. 1995, 99, 15864-15869. (330) Matsuo, T.; Kobayashi, M.; Tamao, K. Dalton Trans. 2010, 39, 9203-9208. (331) Takeuchi, K.; Taguchi, H.; Tanigawa, I.; Tsujimoto, S.; Matsuo, T.; Tanaka, H.; Yoshizawa, K.; Ozawa, F. Angew. Chem., Int. Ed. 2016, 55, 15347-15350. (332) Rawe, B. W.; Brown, C. M.; MacKinnon, M. R.; Patrick, B. O.; Bodwell, G. J.; Gates, D. P. Organometallics 2017, 36, 2520-2526. 207 Appendices Appendix A Supplementary material for chapter 2 Figure A.1: 1H NMR spectrum (C6D6, 400 MHz, 25 °C) of [Li(12-crown-4)2][2.1]. * = C6D5H. Figure A.2: 13C{1H} NMR spectrum (C6D6, 101 MHz, 25 °C) of [Li(12-crown-4)2][2.1]. * = C6D6. 208 Figure A.3: 31P NMR spectrum (C6D6, 162 MHz, 25 °C) of [Li(12-crown-4)2][2.1]. Figure A.4: 1H NMR spectrum (CDCl3, 400 MHz, 25 °C) of 2.2. * = CHCl3. 209 Figure A.5: 13C{1H} NMR spectrum (CDCl3, 101 MHz, 25 °C) of 2.2. * = CDCl3. Figure A.6: 31P NMR spectrum (CDCl3, 162 MHz, 25 °C) of 2.2. 210 Figure A.7: 1H NMR spectrum (CDCl3, 400 MHz, −40 °C) of 2.2. * = CHCl3. Figure A.8: 13C{1H} NMR spectrum (CDCl3, 101 MHz, −40 °C) of 2.2. * = CDCl3. 211 Figure A.9: 1H NMR spectrum (CDCl3, 400 MHz, 25 °C) of [Au(2.2)Cl]. * = CHCl3. Figure A.10: 13C{1H} NMR spectrum (CDCl3, 101 MHz, 25 °C) of [Au(2.2)Cl]. * = CDCl3. 212 Figure A.11: 31P NMR spectrum (CDCl3, 162 MHz, 25 °C) of [Au(2.2)Cl]. Figure A.12: 1H NMR spectrum (CDCl3, 400 MHz, 25 °C) of 2.3. * = CHCl3. 213 Figure A.13: 13C{1H} NMR spectrum (CDCl3, 101 MHz, 25 °C) of 2.3. * = CDCl3. Figure A.14: 31P NMR spectrum (CDCl3, 162 MHz, 25 °C) of 2.3. 214 Figure A.15: Molecular structure of [Au(2.3)Cl]. Thermal ellipsoids are presented at 50% probability level. Hydrogen atoms are omitted for clarity. Figure A.16: 1H NMR spectrum (CDCl3, 400 MHz, 25 °C) of [Au(2.3)Cl]. * = CHCl3. 215 Figure A.17: 13C{1H} NMR spectrum (CDCl3, 101 MHz, 25 °C) of [Au(2.3)Cl]. * = CDCl3. Figure A.18: 31P NMR spectrum (CDCl3, 162 MHz, 25 °C) of [Au(2.3)Cl]. 216 Figure A.19: 1H NMR spectrum (CDCl3, 400 MHz, −40 °C) of [Au(2.3)Cl]. * = CHCl3. Figure A.20: 13C{1H} NMR spectrum (CDCl3, 101 MHz, −40 °C) of [Au(2.3)Cl]. * = CDCl3. 217 Figure A.21: 1H NMR spectrum (CDCl3, 400 MHz, 25 °C) of 2.4. * = CHCl3. Figure A.22: 13C{1H} NMR spectrum (CDCl3, 101 MHz, 25 °C) of 2.4. * = CDCl3. 218 Figure A.23: 31P NMR spectrum (CDCl3, 162 MHz, 25 °C) of 2.4. Figure A.24: Molecular structure of [Au(2.4)Cl]. Thermal ellipsoids are presented at 50% probability level. Hydrogen atoms are omitted for clarity. 219 Figure A.25: 1H NMR spectrum (CDCl3, 400 MHz, 25 °C) of [Au(2.4)Cl]. * = CHCl3. Figure A.26: 13C{1H} NMR spectrum (CDCl3, 101 MHz, 25 °C) of [Au(2.4)Cl]. * = CDCl3. 220 Figure A.27: 31P NMR spectrum (CDCl3, 162 MHz, 25 °C) of [Au(2.4)Cl]. Figure A.28: 1H NMR spectrum (CDCl3, 400 MHz, −40 °C) of [Au(2.4)Cl]. * = CHCl3. 221 Figure A.29: 1H NMR spectrum (CDCl3, 400 MHz, 25 °C) of 2.5 and 2.6. * = CHCl3. Figure A.30: 13C{1H} NMR spectrum (CDCl3, 101 MHz, 25 °C) of 2.5 and 2.6. * = CDCl3. 222 Figure A.31: 31P NMR spectrum (CDCl3, 162 MHz, 25 °C) of 2.5 and 2.6. Figure A.32: 1H NMR spectrum (CDCl3, 400 MHz, 25 °C) of [Au(2.5)Cl]. * = CHCl3. 223 Figure A.33: 13C{1H} NMR spectrum (CDCl3, 101 MHz, 25 °C) of [Au(2.5)Cl]. * = CDCl3. Figure A.34: 31P NMR spectrum (CDCl3, 162 MHz, 25 °C) of [Au(2.5)Cl]. 224 Figure A.35: 1H NMR spectrum (CDCl3, 400 MHz, 25 °C) of [Au(2.6)Cl]. * = CHCl3. Figure A.36: 13C{1H} NMR spectrum (CDCl3, 101 MHz, 25 °C) of [Au(2.6)Cl]. * = CDCl3. 225 Figure A.37: 31P NMR spectrum (CDCl3, 162 MHz, 25 °C) of [Au(2.6)Cl]. Figure A.38: 1H NMR spectrum (CDCl3, 400 MHz, 25 °C) of 2.7. * = CHCl3. 226 Figure A.39: 31P NMR spectrum (CDCl3, 162 MHz, 25 °C) of 2.7. Figure A.40: 1H NMR spectrum (CDCl3, 400 MHz, 25 °C) of [2.7(AuCl)2]. * = CHCl3. 227 Figure A.41: 13C{1H} NMR spectrum (CDCl3, 101 MHz, 25 °C) of [2.7(AuCl)2]. * = CDCl3. Figure A.42: 1H NMR spectrum (CDCl3, 400 MHz, −50 °C) of [2.7(AuCl)2]. * = CHCl3. 228 Figure A.43: 31P NMR spectrum (CDCl3, 162 MHz, −50 °C) of [2.7(AuCl)2]. Figure A.44: 31P{1H} NMR spectrum (CDCl3, 162 MHz, −50 °C) of [2.7(AuCl)2]. 229 Figure A.45: 1H NMR spectrum (CDCl3, 400 MHz, 25 °C) of 2.8. * = CHCl3. Figure A.46: 13C{1H} NMR spectrum (CDCl3, 101 MHz, 25 °C) of 2.8. * = CDCl3. 230 Figure A.47: 31P NMR spectrum (CDCl3, 162 MHz, 25 °C) of 2.8. Figure A.48: 1H NMR spectrum (CDCl3, 400 MHz, 25 °C) of [Au(2.8)Cl]. * = CHCl3. 231 Figure A.49: 13C{1H} NMR spectrum (CDCl3, 101 MHz, 25 °C) of [Au(2.8)Cl]. * = CDCl3. Figure A.50: 31P NMR spectrum (CDCl3, 162 MHz, 25 °C) of [Au(2.8)Cl]. 232 Figure A.51: 1H NMR spectrum (CDCl3, 400 MHz, 25 °C) of PPI. Mn = 15,000 g mol−1, Đ = 1.02, dn/dc = 0.169 mL g−1. * = CHCl3. Figure A.52: 13C{1H} NMR spectrum (CDCl3, 101 MHz, 25 °C) of PPI. Mn = 15,000 g mol−1, Đ = 1.02, dn/dc = 0.169 mL g−1. * = CDCl3. 233 Figure A.53: GPC chromatogram of PPI (Mn = 15,000 g mol−1, Ð = 1.02, dn/dc = 0.169). Figure A.54: 1H NMR spectrum (CDCl3, 400 MHz, 25 °C) of PPI·[AuCl]0.96n. Mn = 40,200 g mol−1; Ð = 1.03; dn/dc = 0.17 mL g−1. * = CHCl3, † = CH2Cl2. 0 5 10 15 20Retention Time (min)234 Figure A.55: 13C{1H} NMR spectrum (CDCl3, 101 MHz, 25 °C) of PPI·[AuCl]0.96n. Mn = 40,200 g mol−1; Ð = 1.03; dn/dc = 0.17 mL g−1. * = CDCl3. Figure A.56: GPC chromatogram of PPI·[AuCl]0.96n. Molecular weight data were estimated using the dn/dc* of PPI (Mn = 40,200 g mol−1, Ð = 1.03, *dn/dc = 0.17). 0 5 10 15 20Retention Time (min)235 Table A.1: X-ray crystallographic data for [Li(12-Crown-4)2][endo-2.1], [Au(2.2)Cl], [Au(2.3)Cl] and [Au(2.4)Cl]. [Li(12-Crown-4)2][endo-2.1] [Au(2.2)Cl] [Au(2.3)Cl] [Au(2.4)Cl] Formula C42H76LiO8P C26H45AuClP C27H47AuClP C28H49AuClP FW 746.93 621 635.03 649.06 Crys Syst monoclinic triclinic triclinic monoclinic Space group P21/m P-1 P-1 P21/c a/Å 12.722(3) 10.0061(6) 10.2830(7) 10.4419(3) b/Å 11.455(2) 10.3354(6) 11.0840(7) 25.7242(8) c/Å 14.854(3) 14.8474(9) 13.8949(8) 10.9026(4) α/° 90 69.6360(10) 70.503(2) 90 β/° 93.967(7) 82.543(2) 71.470(2) 96.0310(10) γ/° 90 71.1910(10) 81.594(2) 90 Volume/Å3 2159.6(8) 1362.37(14) 1414.06(16) 2912.33(16) Z 2 2 2 4 ρcalcg/cm3 1.149 1.514 1.491 1.48 μ/mm-1 0.111 5.566 5.364 5.211 F(000) 820 624 640 1312 No. Rflns 11625 32521 7056 40260 GOF 1.038 1.052 1.056 1.215 R1[a][I>=2σ(I)] 0.061 0.0184 0.0284 0.0341 wR2[all data][b] 0.1712 0.0411 0.0705 0.0592 [a]R1 = ∑∥Fo| − |Fc∥/∑|Fo|. [b]wR2(F2 [all data]) = {∑[w(Fo 2 − Fc 2 ) 2 ]/∑[w(Fo2)2]}1/2 236 Table A.2: X-ray crystallographic data for [Au(2.5)Cl], [Au(2.6)Cl] and [2.7(AuCl)2]. [Au(2.5)Cl] [Au(2.6)Cl] [ (AuCl)2] Formula C40H57AuClP C40H57AuClP C49H82Au2Cl2P2 FW 801.24 801.24 1197.91 Crys Syst triclinic monoclinic triclinic Space group P-1 P21 P-1 a/Å 9.4331(4) 9.1078(9) 10.9103(7) b/Å 9.7595(4) 21.417(2) 12.7455(8) c/Å 21.5633(8) 10.0771(10) 19.4329(12) α/° 85.4824(12) 90 78.347(2) β/° 82.7388(12) 108.071(2) 75.829(2) γ/° 72.4912(12) 90 87.680(2) Volume/Å3 1876.27(13) 1868.7(3) 2565.9(3) Z 2 2 2 ρcalcg/cm3 1.418 1.424 1.55 μ/mm-1 4.059 4.076 5.907 F(000) 816 816 1196 No. Rflns 4791 11452 85933 GOF 1.056 1.028 1.043 R1[a][I>=2σ(I)] 0.0549 0.0319 0.0461 wR2[all data][b] 0.1107 0.0802 0.1123 [a]R1 = ∑∥Fo| − |Fc∥/∑|Fo|. [b]wR2(F2 [all data]) = {∑[w(Fo 2 − Fc 2 ) 2 ]/∑[w(Fo2)2]}1/2 237 Appendix B Supplementary material for chapter 3 Figure B.1: 1H NMR spectrum (CDCl3, 400 MHz, 25 °C) of [Pd(PI)(η3-C3H5)Cl]. * = CHCl3. Figure B.2: 13C{1H} NMR spectrum (CDCl3, 101 MHz, 25 °C) of [Pd(PI)(η3-C3H5)Cl]. * = CDCl3. 238 Figure B.3: 31P NMR spectrum (CDCl3, 162 MHz, 25 °C) of [Pd(PI)(η3-C3H5)Cl]. Figure B.4: 1H NMR spectrum (CDCl3, 400 MHz, −30 °C) of [Pd(PI)(η3-C3H5)Cl]. * = CHCl3. 239 Figure B.5: 1H NMR spectrum (CD2Cl2, 400 MHz, 25 °C) after 12 min showing the reaction progress between PI and [Pd(cod)Cl2] (0.5 equiv) to afford intermediate A and “free” COD. For PI and API assignments, the labels H, H' and H" refer to the –CH=CH'H" moiety where H' is cis-H and H" is trans-H. * = CDHCl2. Figure B.6: 1H NMR spectrum (CDCl3, 400 MHz, 25 °C) of meso-trans-3.1. * = CHCl3, † = CH2Cl2. 240 Figure B.7: 31P NMR spectrum (CDCl3, 162 MHz, 25 °C) of meso-trans-3.1. Figure B.8: 1H NMR spectrum (CDCl3, 600 MHz, 25 °C) of meso-trans- and rac-trans-3.1. * = CHCl3, † = CH2Cl2. 241 Figure B.9: 31P NMR spectrum (CDCl3, 162 MHz, 25 °C) of meso-trans- and rac-trans-3.1. Figure B.10: 13C{1H} NMR spectrum (CDCl3, 151 MHz, 25 °C) of rac-trans- and meso-trans-3.1. * = CDCl3; † = CH2Cl2. 242 Figure B.11: 31P NMR spectrum (CD2Cl2, 162 MHz, 25 °C) of intermediate A3.2. Figure B.12: 1H NMR spectrum (CD2Cl2, 400 MHz, 25 °C) of intermediate A3.2. * = CDHCl2, † = COD. 243 Figure B.13: 13C{1H} NMR spectrum (CD2Cl2, 101 MHz, 25 °C) of intermediate A3.2. * = CD2Cl2, † = COD. Figure B.14: 1H NMR spectrum (CD2Cl2, 400 MHz, 25 °C) of the reaction between 3.2 and [Pd(cod)Cl2] (0.5 equiv) after 18 d. * = CDHCl2. 244 Figure B.15: 31P NMR spectrum (CDCl3, 162 MHz, 25 °C) of meso-trans- and rac-trans-3.3. Figure B.16: 1H NMR spectrum (CDCl3, 600 MHz, 25 °C) of meso-trans- and rac-trans-3.3. * = CHCl3. 245 Figure B.17: 13C{1H} NMR spectrum (CDCl3, 151 MHz, 25 °C) of meso-trans- and rac-trans-3.3. * = CDCl3. Figure B.18: 31P NMR spectrum (CDCl3, 162 MHz, 25 °C) of PPI. 246 Figure B.19: 1H NMR spectrum (CDCl3, 400 MHz, 25 °C) of PPI. * = CHCl3. Figure B.20: Inverse-gated 13C{1H} NMR spectrum (CDCl3, 101 MHz, 25 °C) of PPI. * = CDCl3. 247 Figure B.21: 31P NMR spectrum (CDCl3, 162 MHz, 25 °C) of PPI·[Pd(η3-C3H5)Cl]0.21n. Figure B.22: 1H NMR spectrum (CDCl3, 400 MHz, 25 °C) of PPI·[Pd(η3-C3H5)Cl]0.21n ·* = CHCl3, † = [Pd(η3-C3H5)(μ-Cl)]2, ‡ = hexanes, § = silicone grease. 248 Figure B.23: 13C{1H} NMR spectrum (CDCl3, 101 MHz, 25 °C) of PPI·[Pd(η3-C3H5)Cl]0.21n. * = CDCl3, † = [Pd(η3-C3H5)(μ-Cl)]2, ‡ = silicone grease. Figure B.24: 31P NMR spectrum (CDCl3, 162 MHz, 25 °C) of PPI·[PdCl2]0.09n. 249 Figure B.25: 1H NMR spectrum (CDCl3, 400 MHz, 25 °C) of PPI·[PdCl2]0.09n. * = CHCl3, † = silicone grease. Figure B.26: 13C{1H} NMR spectrum (CDCl3, 101 MHz, 25 °C) of PPI·[PdCl2]0.09n. * = CDCl3, † = silicone grease. 250 Figure B.27: GPC chromatogram of poly(1-phosphaisoprene) (PPI) [Mn = 21,800 g mol−1, dn/dc = 0.173, Ð = 1.02]. dn/dc determined using 100% mass recovery method. Figure B.28: GPC chromatogram of PPI·[Pd(η3-C3H5)Cl]0.21n [Mn = 26,000 g mol−1, dn/dc = 0.17*, Ð = 1.02]. Mass recovery estimated to be 43.2% based on the dn/dc of PPI(*) which was used as a rough approximation to the actual dn/dc of 2·[Pd(η3-C3H5)Cl]0.21n. 0 5 10 15 20Retention time (min)0 5 10 15 20Retention Time (min)251 Figure B.29: Photographs showing the control gelation experiment for poly(1-phosphaisoprene) PPI in CH2Cl2 containing: (a) a solution of PPI; (b) a solution of PPI with [Pd(η3-C3H5)(μ-Cl)]2 (Pd:P = 0.10) after 1 h; (c) a solution of PPI with [Pd(η3-C3H5)(μ-Cl)]2 (Pd:P = 0.20) after 1 h; (d) a solution of PPI with [Pd(η3-C3H5)(μ-Cl)]2 (Pd:P = 0.30) after 1 h; (e) a solution of PPI with [Pd(η3-C3H5)(μ-Cl)]2 (Pd:P = 0.30) after 12 h. Figure B.30: 31P NMR spectrum (CDCl3, 162 MHz, 25 °C) of PPI with [Pd(η3-C3H5)(μ-Cl)]2 (Pd:P = 0.30). 252 Table B.1: X-ray crystallographic data for [Pd(PI)(η3-C3H5)Cl] and 3.1. [Pd(PI)(η3-C3H5)Cl] 3.1 Formula C26H42Cl3PPd C46H74Cl6P2Pd FW 598.31 1008.09 Crys Syst monoclinic monoclinic Space group P21/c Pc a/Å 17.3009(7) 14.8733(11) b/Å 9.4030(4) 10.1643(8) c/Å 17.7385(7) 17.1663(12) α/° 90 90 β/° 97.421(2) 97.697(2) γ/° 90 90 Volume/Å3 2861.5(2) 2571.8(3) Z 4 2 ρcalcg/cm3 1.389 1.302 μ/mm-1 0.997 0.764 F(000) 1240 1056 No. Rflns 44219 40952 GOF 1.029 1.025 R1[a][I>=2σ(I)] 0.0247 0.0411 wR2[all data][b] 0.0577 0.0880 [a]R1 = ∑∥Fo| − |Fc∥/∑|Fo|. [b]wR2(F2 [all data]) = {∑[w(Fo 2 − Fc 2 ) 2 ]/∑[w(Fo2)2]}1/2 253 Appendix C Supplementary material for chapter 4 Figure C.1: 1H NMR spectrum (CDCl3, 400 MHz, 25 °C) of 4.1. * = CHCl3. Figure C.2: 13C{1H} NMR spectrum (CDCl3, 101 MHz, 25 °C) of 4.1. 254 Figure C.3: 1H NMR spectrum (CDCl3, 400 MHz, 25 °C) of [Pd(4.1)Cl2]. * = CHCl3; † = CH2Cl2. Figure C.4: 31P{1H} NMR spectrum (CDCl3, 162 MHz, 25 °C) of [Pd(4.1)Cl2]. 255 Figure C.5: 1H NMR spectrum (CDCl3, 400 MHz, 25 °C) of [Au(PI)Cl]. * = CHCl3. Figure C.6: 13C{1H} NMR spectrum (CDCl3, 101 MHz, 25 °C) of [Au(PI)Cl]. * = CDCl3. 256 Figure C.7: 31P NMR spectrum (CDCl3, 162 MHz, 25 °C) of [Au(PI)Cl]. Figure C.8: 1H NMR spectrum (CD2Cl2, 400 MHz, 25 °C) of [4.1(AuCl)2]. * = CDHCl2. 257 Figure C.9: 13C{1H} NMR spectrum (CD2Cl2, 101 MHz, 25 °C) of [4.1(AuCl)2]. * = CD2Cl2. Figure C.10: 31P NMR spectrum (CD2Cl2, 162 MHz, 25 °C) of [4.1(AuCl)2]. 258 Figure C.11: 1H NMR spectrum (CDCl3, 400 MHz, 25 °C) of 4.2. * = CHCl3. Figure C.12: 13C{1H} NMR spectrum (CDCl3, 101 MHz, 25 °C) of 4.2. * = CDCl3. 259 Figure C.13: 31P NMR spectrum (CDCl3, 162 MHz, 25 °C) of 4.2. Figure C.14: 1H NMR spectrum (CDCl3, 400 MHz, 25 °C) of [Au(4.3)Cl]. * = CHCl3. 260 Figure C.15: 13C{1H} NMR spectrum (CDCl3, 101 MHz, 25 °C) of [Au(4.3)Cl]. * = CDCl3. Figure C.16: 31P NMR spectrum (CDCl3, 162 MHz, 25 °C) of [Au(4.3)Cl]. 261 Figure C.17: 1H NMR spectrum (CDCl3, 400 MHz, 25 °C) of [Pd(4.3)(η3-C3H5)Cl].* = CHCl3. Figure C.18: 13C{1H} NMR spectrum (CDCl3, 101 MHz, 25 °C) of [Pd(4.3)(η3-C3H5)Cl]. * = CDCl3. 262 Figure C.19: 31P NMR spectrum (CDCl3, 162 MHz, 25 °C) of [Pd(4.3)(η3-C3H5)Cl]. Figure C.20: 1H NMR spectrum (CDCl3, 400 MHz, 25 °C) of meso-trans-[Pd(4.3)2Cl2]. * = CHCl3. 263 Figure C.21: 13C{1H} NMR spectrum (CDCl3, 101 MHz, 25 °C) of meso-trans-[Pd(4.3)2Cl2]. * = CDCl3. Figure C.22: 31P{1H} NMR spectrum (CDCl3, 162 MHz, 25 °C) of meso-trans-[Pd(4.3)2Cl2]. 264 Figure C.23: 1H NMR spectrum (CDCl3, 400 MHz, 25 °C) of rac-trans- and meso-trans-[Pd(4.3)2Cl2]. * = CHCl3. Figure C.24: 13C{1H} NMR spectrum (CDCl3, 101 MHz, 25 °C) of rac-trans- and meso-trans-[Pd(4.3)2Cl2]. * = CDCl3. 265 Figure C.25: 31P{1H} NMR spectrum (CDCl3, 162 MHz, 25 °C) of rac-trans- and meso-trans-[Pd(4.3)2Cl2]. Figure C.26: 1H NMR spectrum (CDCl3, 400 MHz, −5 °C) of rac-trans- and meso-trans-[Pd(4.3)2Cl2]. * = CHCl3. 266 Figure C.27: 13C{1H} NMR spectrum (CDCl3, 101 MHz, −5 °C) of rac-trans- and meso-trans-[Pd(4.3)2Cl2]. * = CDCl3. Figure C.28: 31P{1H} NMR spectrum (CDCl3, 162 MHz, −5 °C) of rac-trans- and meso-trans-[Pd(4.3)2Cl2]. 267 Table C.1: X-ray crystallographic data for 4.1, [Pd(4.1)Cl2], [Au(PI)Cl] and [4.1(AuCl)2]. 4.1 [Pd(4.1)Cl2] [Au(PI)Cl] [4.1(AuCl)2] Formula C44H70P2 C46H74Cl6P2Pd C22H35PClAu C44H70Au2Cl2P2 FW 660.94 1008.09 562.88 1125.77 Crys Syst monoclinic monoclinic monoclinic monoclinic Space group P21/n P21/n P21/c P21/c a/Å 20.2458(6) 9.4889(5) 10.2811(11) 17.1459(18) b/Å 10.1920(3) 22.8642(11) 25.342(3) 18.7669(19) c/Å 39.8543(11) 23.9461(11) 9.5757(11) 17.1151(17) α/° 90 90 90 90 β/° 95.5090(10) 101.0020(10) 114.767(3) 111.979(6) γ/° 90 90 90 90 Volume/Å3 8185.8(4) 5099.8(4) 2265.4(4) 5107.0(9) Z 8 4 4 4 ρcalcg/cm3 1.073 1.313 1.65 1.464 μ/mm-1 0.134 0.77 6.685 5.931 F(000) 2912 2112 1112 2224 No. Rflns 80792 59508 65227 16762 GOF 0.998 1.014 1.272 1.052 R1[a][I>=2σ(I)] 0.0441 0.0469 0.0257 0.0489 wR2[all data][b] 0.1021 0.0972 0.0552 0.1204 CCDC no. 1953755 1954573 2182934 2182939 [a]R1 = ∑∥Fo| − |Fc∥/∑|Fo|. [b]wR2(F2 [all data]) = {∑[w(Fo 2 − Fc 2 ) 2 ]/∑[w(Fo2)2]}1/2 . 268 Table C.2: X-ray crystallographic data for 4.2, [Pd(4.3)Cl2], [Pd(4.3)(η3-C3H5)Cl] and [Au(4.3)Cl]. 4.2 [Pd(4.3)Cl2] [Pd(4.3)(η3-C3H5)Cl] [Au(4.3)Cl] Formula C23H37P C46H74Cl2P2Pd C27.04H43.76Cl3.4PPd C23H37PClAu FW 344.49 866.29 626.52 576.91 Crys Syst monoclinic triclinic triclinic monoclinic Space group P21/n P-1 P-1 P21/c a/Å 6.2560(2) 8.819(3) 10.5196(4) 10.7290(4) b/Å 25.8591(7) 10.123(3) 11.2072(5) 24.9034(10) c/Å 13.6996(4) 14.772(5) 14.0528(6) 9.9009(4) α/° 90 105.764(9) 91.6560(10) 90 β/° 95.425(2) 94.059(10) 111.1740(10) 116.3980(10) γ/° 90 114.584(10) 101.9520(10) 90 Volume/Å3 2206.32(11) 1128.4(7) 1501.62(11) 2369.56(16) Z 4 1 2 4 ρcalcg/cm3 1.037 1.275 1.386 1.617 μ/mm-1 1.083 0.63 0.987 6.394 F(000) 760 460 649 1144 No. Rflns 4068 36375 50631 67331 GOF 1.021 1.059 1.056 1.04 R1[a][I>=2σ(I)] 0.0588 0.0355 0.0297 0.0305 wR2[all data][b] 0.1500 0.0825 0.0726 0.0673 CCDC no. 2182936 2182938 2182935 2182937 [a]R1 = ∑∥Fo| − |Fc∥/∑|Fo|. [b]wR2(F2 [all data]) = {∑[w(Fo 2 − Fc 2 ) 2 ]/∑[w(Fo2)2]}1/2 . 269 Appendix D Supplementary material for chapter 5 Figure D.1: 13C{1H} NMR spectrum (CDCl3, 101 MHz, 25 °C) of Z-5.1. Figure D.2: 31P{1H} NMR spectrum (CDCl3, 162 MHz, 25 °C) of Z-5.1. 270 Figure D.3: 29Si NMR Spectrum (CDCl3, 80 MHz, 25 °C) of Z-5.1. Figure D.4: 31P NMR Spectrum (CDCl3, 101 MHz, 25 °C) of E-5.1. 271 Figure D.5: 13C{1H} NMR Spectrum (CDCl3, 162 MHz, 25 °C) of E-5.1. Figure D.6: 29Si NMR spectrum (CDCl3, 80 MHz, 25 ⁰C) of E-5.1. 272 Table D.1: Crystallographic data for Z-5.1 and E-5.1. Z-5.1 E-5.1 Formula C24H41PSi C24H41PSi FW 388.63 388.63 Crys Syst orthorhombic orthorhombic Space group Pna21 Pnma a/Å 9.2540(11) 19.4369(11) b/Å 19.676(2) 13.4180(8) c/Å 13.7783(16) 9.2875(5) α/° 90 90 β/° 90 90 γ/° 90 90 Volume/Å3 2508.8(5) 2422.2(2) Z 4 4 ρcalcg/cm3 1.029 1.066 μ/mm-1 0.163 0.169 F(000) 856 856 No. Rflns 20233 50239 GOF 1.03 1.05 R1[a][I>=2σ(I)] 0.0383 0.0347 wR2[all data][b] 0.091 0.1009 [a]R1 = ∑∥Fo| − |Fc∥/∑|Fo|. [b]wR2(F2 [all data]) = {∑[w(Fo 2 − Fc 2 ) 2 ]/∑[w(Fo2)2]}1/2 273 Appendix E Supplementary material for chapter 6 Figure E.1: 1H NMR spectrum (CDCl3, 400 MHz, 25 °C) of PI-d3. * = CHCl3. Figure E.2: 2H NMR spectrum (CHCl3, 61 MHz, 25 °C) of PI-d3. * = CDCl3. 274 Figure E.3: 13C{1H} NMR spectrum (CDCl3, 151 MHz, 25 °C) of PI-d3. * = CDCl3. Figure E.4: 31P NMR spectrum (CDCl3, 162 MHz, 25 °C) of PI-d3. 275 Figure E.5: 1H NMR spectrum (C6D6, 600 MHz, 25 °C) of E/Z-Mes*P=C(CD3)Br. * = C6D5H Figure E.6: 13C{1H} NMR spectrum (C6D6, 151 MHz, 25 °C) of E/Z-Mes*P=C(CD3)Br. * = C6D6. 276 Figure E.7: 31P NMR spectrum (C6D6, 400 MHz, 25 °C) of E/Z-Mes*P=C(CD3)Br.
Thesis/Dissertation
eng
Chemistry
Vancouver : University of British Columbia Library
Attribution-NonCommercial-NoDerivatives 4.0 International
Graduate
Gates, Derek P.
Modeling the polymerization of 1-phosphaisoprene : explorations of the synthesis and reactivity of 1-phosphabutadienes
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