PATHWAYS TO FUNCTIONALIZED SILOXANES FROM POLYHEDRAL OLIGOMERIC SILSESQUIOXANES By Badru-Deen Barry A DISSERTATION Submitted to Michigan State University in partial fulfillment of the requirements for the degree of Chemistry—Doctor of Philosophy 2021 ABSTRACT PATHWAYS TO FUNCTIONALIZED SILOXANES FROM POLYHEDRAL OLIGOMERIC SILSESQUIOXANES By Badru-Deen Barry This dissertation is an account of my efforts toward developing strategies for the synthesis of novel functionalized polyhedral oligomeric silsesquioxanes (POSS). These organic/inorganic nanomaterials date back to 1946 and the pioneering work of Scott’s synthesis of octamethylsilsesquioxane. POSS cages constitute a framework of silicon- oxygen polyhedron with reactive or inert organic coronae. These hybrid nanostructures are versatile precursors that find applications in polymer chemistry, catalysis, engineering, medicine, and electronics. Their properties are partly dictated by the peripheral organic groups. They are generally benign and easily processible into composite materials with high thermal degradation temperatures, low dielectric constants and superior mechanical properties. These features of POSS compounds have prompted growing interest in their exploration, particularly their use as models for the synthesis of the next generation hybrid nanocomposites. POSS molecules come in different cage sizes with condensed and incompletely condensed structures. The completely condensed analogues are denoted as Tn, where n = number of silicon atoms in the cage and n ≥ 6. Whereas the cubic/condensed silsesquioxanes were the initially discovered compounds, most explorations today are focused on the incompletely condensed di-, tri-, and tetra-functional scaffolds because of the ability to derivatize them into more functional materials for a myriad of applications. Even with the partially condensed structures, current research focus on this family of compounds has been dominated by the highly symmetric tetrafunctional octasilsesquioxane otherwise known as the double-decker oligomeric silsesquioxane. This functional POSS precursor has enormous potential for the synthesis of nanosized hybrid clusters with defined shape, structure, and physicochemical properties. In this study, efforts have been made to disclose strategies for the synthesis of asymmetrically functionalized double-decker shaped silsesquioxanes that can serve as nano-linkers to two dissimilar polymer matrices. The conversion of dead-end silsesquioxanes into more functional cage precursors, and surface transformation of cubic and functionalized DDSQs into modifiable precursors for the synthesis of well-defined 3D networks well among my aims. POSS cages used in these investigations were obtained either from commercially available cages or cage-like precursors or were synthesized from monomeric trialkoxy- (or trichloro-)silanes by hydrolytic condensation. Products obtained from this study could open an avenue for the exploration of new structure/property relationships and provide a unique way by which cages can be used as linkers to form both linear POSS/polymer and 3D networks. This research promises to open a new research direction for the synthesis of novel materials that combine three unconventional materials into hybrid POSS/polymer composites. With the asymmetric POSS cage as the building block, unprecedented properties may emerge from the synergy of these building blocks. To my parents, wife and two daughters iv ACKNOWLEDGEMENTS My inclination for a doctoral degree had been an inimitable aspiration in my life. Even though the path to this goal was hectic, the vision is materialized with the inspirations, guidance, and mentorship of an adorable class of people that merit commendations. The contributions of these eminent scientists, professors and scholars, research colleagues and friends made this struggle worth undertaking. To this end, I would like to acknowledge the following people for their diverse roles in helping me transform this dream into reality. First and foremost, I am grateful to the Michigan State University for offering me the opportunity to pursue my graduate studies and to the Chemistry department particularly for the tutelage and research exposure that have positively impacted my life, both from an academic and multicultural viewpoint. I would also want to thank the Office of Naval Research (ONS) for funding part of this study under grant number N00014-16- 2109. My special thanks go to my advisor Dr Robert E. Maleczka Jr. and collaborator, Dr Andre Lee of the Department of Chemical Engineering and Material Science, MSU, for their outstanding mentorship, tenacity, and courage in aiding me through my graduate studies. Accomplishing this goal would have been impossible had it not been for their priceless support. They did not only accept me into their joint research group, but they also gave their support, priceless and insightful comments, criticisms, guidance, and motivations that has transformed me into a better researcher and chemist. They encouraged me to explore various areas of my research and shaped my faculty by v critiquing my work from experimental details to quality of work and results. Having them as my supervisors was truly intriguing and phenomenal and for which reason, I consider them as the finest elites I have ever been fortunate to work with. To these two professors, I am truly grateful. Next, I would like to extend my sincere gratitude to my committee for their boundless contributions. Dr. James Ned Jackson, Dr. Kevin D. Walker, and Dr. Aaron L. Odom have been very supportive in my struggle. Their commitment to attend to my concerns and proffer suggestions whenever I am challenged with research problems is amazing. Having them on my committee was a thing to my advantage and is part of the reasons that irrefutably made my research objectives to be attained. I was also blessed to have come across special friends and lab mates in the Maleczka and Lee research groups during my graduate studies. From the moments we shared our research pains to taking a break from lab activities by playing board games on weekends are memories that will ever linger in my mind. My appreciation therefore goes to both past and present lab mates including Susanne Miller, Chachurika Jayasundara, Jonathan E. Dannatt, David F Vogelsang, Fangyi Shen, Jose Montero, Emmanuel Maloba, Aditya Patil, Arzoo Chhabra, Thomas Oleskey, and Austin K. King. Together we created an ambiance of a healthy workplace that served as a panacea to soothing our research and academic struggles. On the technical wing, I am heavily indebted to three prominent scholars in the Chemistry Department at MSU - Dr. Dan Holmes, Dr. Xie Li (both of the NMR facility) and Dr. Richard Staples (X-Ray Crystallographer). These gentlemen always had their offices open to me to answer to some of my questions based on NMR and X-ray crystallography. vi Further, I am grateful to all the secretaries from the Chair’s office to those in the graduate office for their invaluable and timely duties in keeping all graduate students abreast with news, events and needs of the graduate school. To Heidi, Tiphani, Anna, Mary and Brenda, I say thank you for your assistance since my entry into graduate school to date. You guys have been amazing. Most importantly, my experience in the graduate school started with the inspiration of two distinguished country mates of mine - Dr Patrick K. Lukulay and Dr Thomas B. R. Yormah. The success of this work owes its genesis to these gentlemen whom for the most times in their lives are invigorated to promote education in their country. These people would be always remembered for providing me this opportunity to pursue graduate studies at the Michigan State University and for giving me all necessary support that made my career a reality. To these two influential people, I say kudos. Lastly, I cannot end this section without recognizing the loving support and courage demonstrated by my wife and two kids. We came and we conquered together. I am therefore most pleased with my wife and two daughters for their motivation and fortitude during this struggle. Their roles have been truly supportive and irreplaceable. Thank you all for been with me in thick and thin. vii TABLE OF CONTENTS LIST OF TABLES ........................................................................................................... xii LIST OF FIGURES ........................................................................................................ xiv LIST OF SCHEMES .................................................................................................... xxiv CHAPTER 1.0 ................................................................................................................. 1 1.1 Introduction ............................................................................................................ 1 1.2 Background ............................................................................................................ 1 1.2.1 Silsesquioxanes ............................................................................................... 1 1.2.2 Classification and Nomenclature of Silsesquioxanes....................................... 1 1.2.2.1 Classification ............................................................................................ 1 1.2.2.2 Nomenclature ........................................................................................... 2 1.3 Polyhedral Oligomeric Silsesquioxanes (POSS) .................................................... 4 1.3.1 Synthesis of Polyhedral Oligomeric Silsesquioxanes (POSS) ......................... 6 1.4 Incompletely Condensed Polyhedral Oligomeric Silsesquioxanes ......................... 7 1.5 Synthesis of Condensed Difunctional Double-Decker Shaped Silsesquioxanes .. 10 1.6 Motivation and Research Goals ........................................................................... 11 1.7 Dissertation Summary .......................................................................................... 13 REFERENCES .............................................................................................................. 15 CHAPTER 2.0: Synthesis of Asymmetrically Functionalized Double-Decker Shaped Silsesquioxanes ............................................................................................................ 23 2.1 Introduction .......................................................................................................... 24 2.2 Results and Discussions ...................................................................................... 29 2.2.1 Solubility of DDSQ(OH)4 in Various Organic Solvents ................................... 31 2.2.2 Optimization of the Selective Borylation for the Generation of (p- MeOC6H4B)DDSQ(OH)2 3 ...................................................................................... 32 2.2.3 Substrate Scope for Asymmetrically Functionalized Double-Decker Shaped Silsesquioxanes...................................................................................................... 34 2.2.4 Structural Analysis of Asymmetric DDSQs (6) by Si-NMR............................. 36 2.3 Conclusions ......................................................................................................... 50 2.4 Experimental Details ............................................................................................ 51 2.4.1. General Information ...................................................................................... 51 2.4.1.1 General Experimental Procedure for the Synthesis of DDSQ Boronate Esters ................................................................................................................. 53 2.4.1.2 Deborylation of DDSQ Bis-boronate Ester with Pinacol.......................... 54 2.4.1.3 General Procedure for Solubility Test for DDSQ(OH)4 in Different Organic Solvents .............................................................................................................. 54 2.4.1.4 General Experimental Procedures for the Multi-step Synthesis of Asymmetrically Functionalized DDSQs .............................................................. 55 2.4.1.4.1 Mono-borylation of DDSQ(OH)4 with p-MeOC6H4B(OH)2 (Step 1) .... 55 viii 2.4.1.4.2 General Procedure for the First Silylation of Mono-borylated DDSQ(OH)2 (3) - (Step 2) ................................................................................ 56 2.4.1.4.3 General Procedure for the Deborylation of a Mixture of (p- MeOC6H4B)- DDSQSiR1R2 and (p-MeOC6H4B)2DDSQ (Step 3) ..................... 57 2.4.1.4.4 General Procedure for the Second Silylation of Monosilylated DDSQ (5) .................................................................................................................... 58 2.4.2 Synthetic Scope for Asymmetrically Functionalized Double-Decker Shaped Silsesquioxanes...................................................................................................... 59 APPENDIX .................................................................................................................... 60 REFERENCES ............................................................................................................ 125 CHAPTER 3.0: Synthesis of Incompletely Condensed Asymmetrically Functionalized Double-Decker Shaped Silsesquioxane Disilanols ‘Bird Nest-Shaped Silsesquioxanes’ .................................................................................................................................... 129 3.1 INTRODUCTION................................................................................................ 129 3.2 Modifications of Incompletely Condensed POSS Cages.................................... 131 3.2.1 Tetrafunctional Polyhedral Oligomeric Silsesquioxanes and their Derivatives ............................................................................................................................. 133 3.2.2 Asymmetrically Functionalized DDSQs ....................................................... 135 3.3 Results and Discussions .................................................................................... 140 3.3.1 Optimization of (p-MeOC6H4B)2DDSQ(OH)2 (3) .......................................... 140 3.3.2 Substrate Scope .......................................................................................... 141 3.3.3 Transformation of Monosilylated DDSQ diol into Condensed Asymmetric DDSQs (7) ............................................................................................................ 143 3.3.4 Spectral Data for Asymmetric R1R2DDSQ(OH)2 .......................................... 144 3.3.5 Structural Characterization by 29Si NMR Spectroscopy .............................. 149 3.3.6 NMR and Mass Spectral Data for Condensed Asymmetric D2T8 Silsesquioxanes.................................................................................................... 159 3.3.7 Structural Characterization of Completely Condensed Asymmetric D2T8 Silsesquioxanes by 29Si NMR Spectroscopy ........................................................ 163 3.4 Conclusion ......................................................................................................... 170 3.5 Experimental Details .......................................................................................... 170 3.5.1 Materials and Methods ................................................................................ 170 3.5.2 General Experimental Procedure for the Synthesis of DDSQ Bis-boronate Ester (2) ................................................................................................................ 172 3.5.3 Partial Deborylation of DDSQ Bis-boronate Ester with Pinacol ................... 173 3.5.4 General Experimental Procedure for the Multi-step Synthesis of monosilylated DDSQ diol............................................................................................................. 175 3.6 Synthetic Modifications of Monosilylated DDSQ diols (5) into Fully Condensed Asymmetric DDSQs of the D2T8 type (7) ................................................................ 178 APPENDIX .................................................................................................................. 179 REFERENCES ............................................................................................................ 224 Chapter 4.0: Base-Promoted Hydroylsis of Dodecaphenyl Silsesquioxane into Partially Condensed Octaphenyl Silsesquioxane ...................................................................... 230 4.1 Abstract .............................................................................................................. 230 ix 4.2 Introduction ........................................................................................................ 231 4.3 Research Hypothesis ......................................................................................... 233 4.4 Proposed Reaction Mechanism for the Formation of Double-decker Octaphenyl silsesquioxanetetraol (5) .......................................................................................... 234 4.4.1 Hydrolysis of Ph12T12 (1) into [(PhSiO)8(O)2(OTMS)4] (3) ............................ 235 4.4.2 Time-course Study for the Hydrolysis of 1 into 3 ......................................... 237 4.4.3 Synthesis of [(PhSiO)8(O)2(OH)4] (5) from Ph12T12 (1) ................................. 240 4.4.4 Condition Screening Results for the Synthesis of (PhSiO)8(O)2(OH)4 5 from Ph12T12 (1) ............................................................................................................ 241 4.5 Single Crystal X-ray Structures .......................................................................... 242 4.6 Experimental Section ......................................................................................... 246 4.6.1 Materials and Methods ................................................................................ 246 4.6.1.1 Synthesis of 5,11,14,17-tetrakis(trimethylsilyl)octaphenyltetracyclo[7.3.3. 33;7]octasilsesquioxane (3) from DodecaphenylT12 [Ph12T12] (1)....................... 248 4.6.1.2. Time-course Study for the Hydrolysis of 1 followed by TMS Capping to Afford 3 ............................................................................................................. 250 4.6.1.3 Synthesis of 5,11,14,17-Tetra(hydro)octaphenyltetracyclo[7.3.3.33;7] octasilsesquioxane [(PhSiO)8(O)2(OH)4] 5 from Dodecaphenyl Silsesquioxane [Ph12T12] 1......................................................................................................... 251 4.6.1.4 Screening Conditions for the Synthesis of (PhSiO)8(O)2(OH)4 3 from 1 252 APPENDIX .................................................................................................................. 253 REFERENCES ............................................................................................................ 294 Chapter 5.0: De novo construction of Double-Decker Shaped Silsesquioxanes with Modifiable Surface Functionalities ............................................................................... 298 5.1 Introduction ........................................................................................................ 298 5.1.1 Styrenyl functionalized Polyhedral Oligomeric Silsesquioxanes .................. 300 5.1.2 Corner-capping DDSQ(OH)4 with styrenyl and styryl groups ....................... 304 5.1.3 Styryl functionalized Polyhedral Oligomeric Silsesquioxanes ...................... 306 5.1.4 p-Bromophenyl functionalized Polyhedral Oligomeric Silsesquioxanes ....... 308 5.2 Experimental Section ......................................................................................... 313 5.2.1 Materials and Methods ................................................................................ 313 5.2.1.1 Synthesis of dichloro(methyl)(4-vinylphenyl)silane (2) from 4- bromostyrene (1) .............................................................................................. 315 5.2.1.2 Synthesis of [[(styryl)(Me)}2DDSQ] from DDSQ(OH)4 (3) and styryl(Me)SiCl2 (2) ............................................................................................ 316 5.2.2 Synthesis of Tn styryl Silsesquioxanes ........................................................ 317 5.2.3 Synthesis of 5,11,14,17-tetrakis((trimethylsilyl)oxy)-1,3,5,7,9,11,14,17-octakis (4-vinylphenyl)-2,4,6,8,10,12,13,15,16,18-decaoxa-1,3,5,7,9,11,14,17-octasilatricyc- lo[7.3.3.33,7]octadecane (9) ................................................................................. 319 5.2.4 Synthesis of 2,4,6,8-tetrakis(4-bromophenyl)-2,4,6,8-tetrakis((trimethylsilyl)- oxy)-1,3,5,7,2,4,6,8-tetraoxatetrasilocane ............................................................ 321 5.2.5 Borylation of [4-BrC6H4Si(OTMS)]4 .............................................................. 322 5.2.6 Synthesis of tetra-n-butylammonium octa(4-bromophenyl)octasilsesqui- oxane fluoride .................................................................................................................. 323 x 5.2.7 Synthesis of 1,3,5,7,9,11,14,17-octakis(4-bromophenyl)-5,11,14,17- tetrakis((tr-imethylsilyl)oxy)-2,4,6,8,10,12,13,15,16,18-decaoxa-1,3,5,7,9,11,14,17- octasilatricy- clo[7.3.3.33,7]octadecane ................................................................. 325 APPENDIX .................................................................................................................. 327 REFERENCES ............................................................................................................ 348 CHAPTER 6: Conclusions and Future Direction ......................................................... 355 6.1 Conclusions ....................................................................................................... 355 6.2 Future Directions ................................................................................................ 356 xi LIST OF TABLES Table 2-1: Full Protection of DDSQ(OH)4 1 with p-substituted Phenylboronic Acid ...... 29 Table 2-2: Crystal Structures of Bis-boronated DDSQ Esters 2 (Displacement ellipsoid contour probability drawn at 50%) ................................................................................. 30 Table 2-3: Solubility Tests for DDSQ(OH)4 (1) in Organic Solvents.............................. 32 Table 2-4: Optimization of Monoboronate Ester Formation .......................................... 33 Table 2-5: Scope for Asymmetrically Functionalized DDSQs ....................................... 34 Table 2-6: Crystal Data and Structure Refinement for Compounds 2A - 2C............... 105 Table 2-7: Bond Lengths in Å for CCDC 1843217 ...................................................... 106 Table 2-8: Bond Angles in ° for CCDC 1843217 ......................................................... 108 Table 2-9: Hydrogen Fractional Atomic Coordinates (×104) and Equivalent Isotropic Displacement Parameters (Å2×103) for CCDC 1843217. Ueq is defined as 1/3 of the trace of the orthogonalised Uij .............................................................................................. 110 Table 2-10: Bond Lengths in Å for CDCC 1823844 .................................................... 112 Table 2-11: Bond Angles in ° for CDCC 1823844 ....................................................... 114 Table 2-12: Hydrogen Fractional Atomic Coordinates (×104) and Equivalent Isotropic Displacement Parameters (Å2×103) for CCDC 1823844. Ueq is defined as 1/3 of the trace of the orthogonalised Uij. ............................................................................................. 116 Table 2-13: Bond Lengths in Å for CCDC 1850462 .................................................... 118 Table 2-14: Bond Angles in ° for CCDC 1850462 ....................................................... 120 Table 2-15: Hydrogen Fractional Atomic Coordinates (×104) and Equivalent Isotropic Displacement Parameters (Å2×103) for CCDC 1850462. Ueq is defined as 1/3 of the trace of the orthogonalised Uij .............................................................................................. 123 Table 3-1: Optimization for the partial deborylation of (p-MeOC6H4B)2DDSQ (2) for the synthesis of monoborylated DDSQ diol (3) ................................................................. 140 Table 3-2: Substrate scope for the synthesis of asymmetric monosilylated DDSQ(OH) 2 (5) ................................................................................................................................ 142 Table 3-3: Post Functionalization of asymmetric monosilylated DDSQ(OH)2 (5) into Completely Condensed Asymmetric DDSQs of the D2T8 Type ................................... 143 xii Table 3-4: Crystal Data and Structure Refinement for Asymmetric DDSQ Diols 5a, 5b, 5e and 5f .......................................................................................................................... 206 Table 3-5: Crystal Data and Structure Refinement for Asymmetric DDSQ 7a ............ 223 Table 4-1: LCMS-G2-XS QTof time course analysis of data for selected intermediates obtained from the hydrolysis of 1 followed by silylation with TMSCl ............................ 237 Table 4-2: Relative intensity of Species in Table 4.1 expressed as a percentage ...... 238 Table 4-3: Synthesis of [(PhSiO)8(O)2(OTMS)4] (3) from Ph12T12 (1) .......................... 239 Table 4-4: Hydrolysis of 12 with Acetic Acida.............................................................. 241 Table 4-5: Crystal and Experimental Data for 5,11,14,17-tetrakis(trimethylsilyl)- octaphenyltetracyclo[7.3.3.-33,7]octasilsesquioxane (3) (CCDC 299794a) ................... 285 Table 4-6: Crystal and Experimental Data for 5,11,14,17-tetra(hydro)octaphenyl tetracyclo[7.3.3.-33;7]octasilsesquioxane (C48H44O14Si8) (5) ........................................ 286 Table 4-7: Bond Lengths in Å for 5,11,14,17-tetra(hydro)octaphenyltetracyclo[7.3.3.- 33;7]octasilsesquioxane (5)......................................................................................... 287 Table 4-8: Bond Angles in ° for 5,11,14,17-tetra(hydro)octaphenyltetracyclo[7.3.3.- 33;7]octasilsesquioxane (5)......................................................................................... 289 Table 4-9: Hydrogen Fractional Atomic Coordinates (×104) and Equivalent Isotropic Displacement Parameters (Å2×103) for 5,11,14,17-tetra(hydro)octaphenyltetracyclo [7.3.3.-33;7]octasilsesquioxane (5). Ueq is defined as 1/3 of the trace of the orthogonalised Uij ................................................................................................................................ 292 Table 4-10: Hydrogen Bond information for 5,11,14,17-tetra(hydro)octaphenyltetra- cyclo[7.3.3.-33;7]octasilsesquioxane (5) ....................................................................... 293 Table 5-1: Crystal and Experimental Data for 9,19-dimethyl-1,3,5,7,11,13,15,17- octaphenyl-9,19-bis(4-vinylphenyl)-2,4,6,8,10,12,14,16,18,20,21,22,23,24-tetradecaoxa- 1,3,5,7,9,11,13,15,17,19-decasilapentacyclo[11.7.1.13,11.15,17.17,15]tetracosane (4) .................................................................................................................................... 344 Table 5-2: Crystal and Experimental Data for 2,4,6,8-tetrakis(4-bromophenyl)-2,4,6,8- tetrakis((trimethylsilyl)oxy)-1,3,5,7,2,4,6,8-tetraoxatetrasilocane65-67 .......................... 346 xiii LIST OF FIGURES Figure 1-1: Different architectures of (RSiO3/2)n ............................................................. 2 Figure 1-2: Systematic/trivial nomenclature of Silsesquioxanes..................................... 3 Figure 1-3: Cubic octameric silsesquioxane ................................................................... 5 Figure 1-4: Methacrylate heptaphenylPOSS .................................................................. 5 Figure 1-5: Incompletely condensed POSS frameworks25-27 .......................................... 7 Figure 1-6: Octaphenyl tetrasilanolPOSS [DDSQ(OH)4] ................................................ 9 Figure 2-1: Double-decker oligomeric silsesquioxane tetraol (1) and (b) R7-trisilanol POSS ............................................................................................................................ 25 Figure 2-2: Designed Graphical Pathway to Asymmetrically Functionalized DDSQs ... 31 Figure 2-3: Stacked 29Si NMR of AB 6a, AA 7a and BB 8a .......................................... 37 Figure 2-4: Stacked 29Si NMR of AB 6b, AA 7b and BB 8b ......................................... 39 Figure 2-5: Stacked 29Si NMR of AB 6c, Symmetric AA 7c and BB 8c ........................ 41 Figure 2-6: Stacked 29Si NMR of AB 6d, AA 7d and BB 8d ......................................... 42 Figure 2-7: Stacked 29Si NMR of AB 6f, AA 7f and BB 8f ............................................ 44 Figure 2-8: Stacked 29Si NMR of AB 6g, AA 7g and BB 8g ......................................... 45 Figure 2-9: Stacked 29Si NMR of AB 6h, AA 7h and BB 8h ......................................... 47 Figure 2-10: Stacked 29Si NMR of AB 6i and AA 7i...................................................... 49 Figure 2-11: 1H NMR (500 MHz, CDCl3) of (p-MeOC6H4B)2DDSQ 2a ......................... 71 Figure 2-12: 11B NMR (160 MHz, CDCl3) of (p-MeOC6H4B)2DDSQ 2a ........................ 72 Figure 2-13: 13C NMR (126 MHz, CDCl3) of (p-MeOC6H4B)2DDSQ 2a ........................ 72 Figure 2-14: 29Si NMR (99 MHz, CDCl3) of (p-MeOC6H4B)2DDSQ 2a ......................... 73 Figure 2-15: 1H NMR (500 MHz, CDCl3) of (C6H4B)2DDSQ 2b .................................... 74 Figure 2-16: 11B NMR (160 MHz, CDCl3) of (C6H4B)2DDSQ 2b ................................... 75 xiv Figure 2-17: 13C NMR (126 MHz, CDCl3) of (C6H4B)2DDSQ 2b ................................... 75 Figure 2-18: 29Si NMR (99 MHz, CDCl3) of (C6H4B)2DDSQ 2b .................................... 76 Figure 2-19: 1H NMR (500 MHz, CDCl3) of (p-MeC6H4B)2DDSQ 2c ............................ 77 Figure 2-20: 11B NMR (160 MHz, CDCl3) of (p-MeC6H4B)2DDSQ 2c ........................... 78 Figure 2-21: 13C NMR (126 MHz, CDCl3) of (pMeC6H4B)2DDSQ 2c ............................ 78 Figure 2-22: 29Si NMR (99 MHz, CDCl3) of (C6H4B)2DDSQ 2c .................................... 79 Figure 2-23: 1H NMR (500 MHz, CDCl3) of AB 6a........................................................ 80 Figure 2-24: 13C NMR (126 MHz, CDCl3) of AB 6a ...................................................... 81 Figure 2-25: 29Si NMR (99 MHz, CDCl3) of AB 6a ........................................................ 81 Figure 2-26: 1H NMR (500 MHz, CDCl3) of AB 6b ....................................................... 82 Figure 2-27: 13C NMR (126 MHz, CDCl3) of AB 6b ...................................................... 83 Figure 2-28: 29Si NMR (99 MHz, CDCl3) of AB 6b........................................................ 83 Figure 2-29: 1H NMR (500 MHz, CDCl3) of AB 6c........................................................ 84 Figure 2-30: 13C NMR (126 MHz, CDCl3) of AB 6c ...................................................... 85 Figure 2-31: 29Si NMR (99 MHz, CDCl3) of AB 6c ........................................................ 85 Figure 2-32: 1H NMR (500 MHz, CDCl3) of AB 6d ....................................................... 86 Figure 2-33: 13C NMR (126 MHz, CDCl3) of AB 6d ...................................................... 87 Figure 2-34: 29Si NMR (99 MHz, CDCl3) of AB 6d........................................................ 87 Figure 2-35: 1H NMR (500 MHz, CDCl3) of AB 6f ........................................................ 88 Figure 2-36: 13C NMR (126 MHz, CDCl3) of AB 6e ...................................................... 89 Figure 2-37: 29Si NMR (99 MHz, CDCl3) of AB 6f......................................................... 89 Figure 2-38: 1H NMR (500 MHz, CDCl3) of AB 6g ....................................................... 90 Figure 2-39: 13C NMR (126 MHz, CDCl3) of AB 6g ...................................................... 91 Figure 2-40: 29Si NMR (99 MHz, CDCl3) of AB 6g........................................................ 91 Figure 2-41: 1H NMR (500 MHz, CDCl3) of AB 6h ....................................................... 92 xv Figure 2-42: 13C NMR (126 MHz, CDCl3) of AB 6h ...................................................... 93 Figure 2-43: 29Si NMR (99 MHz, CDCl3) of AB 6h........................................................ 93 Figure 2-44: 1H NMR (500 MHz, CDCl3) of AB 6i......................................................... 94 Figure 2-45: 13C NMR (126 MHz, CDCl3) of AB 6i ....................................................... 95 Figure 2-46: 29Si NMR (99 MHz, CDCl3) of AB 6i ......................................................... 95 Figure 2-47: Mass Spec of AB 6a ................................................................................ 96 Figure 2-48: Mass Spec of AB 6b ................................................................................ 97 Figure 2-49: Mass Spec of AB 6c ................................................................................. 98 Figure 2-50: Mass Spec of AB 6d ................................................................................ 99 Figure 2-51: Mass Spec of AB 6f ............................................................................... 100 Figure 2-52: Mass Spec of AB 6g .............................................................................. 101 Figure 2-53: Mass Spec of AB 6h .............................................................................. 102 Figure 2-54: Mass Spec of AB 6i ................................................................................ 103 Figure 3-1: Representative Incompletely Condensed Silsesquioxanes ...................... 129 Figure 3-2: Tetrafunctional Polyhedral Oligomeric Silsesquioxanes .......................... 134 Figure 3-3: Monborylated DDSQ(OH)2 ....................................................................... 138 Figure 3-4: Stacked 29Si NMR of AB diol 5a and AA 6a ............................................. 150 Figure 3-5: Stacked 29Si NMR of AB diol 5b and AA 6b ............................................. 151 Figure 3-6: Stacked 29Si NMR of AB diol 5c and AA 6c ............................................. 152 Figure 3-7: Stacked 29Si NMR of AB diol 5d and AA 6d ............................................. 153 Figure 3-8: Stacked 29Si NMR of AB diol 5e and AA 6e ............................................. 154 Figure 3-9: Stacked 29Si NMR of AB diol 5f and AA 6f ............................................... 155 Figure 3-10: Stacked 29Si NMR of AB diol 5g and AA 6g ........................................... 156 Figure 3-11: 29Si NMR of AB diol 5h ........................................................................... 158 Figure 3-12: 29Si NMR of 7a stacked with its symmetric AA and BB .......................... 163 xvi Figure 3-13: Stacked 29Si NMR of AA, AB and BB (7b) ............................................. 165 Figure 3-14: Stacked 29Si NMR of AA and BB (7c) .................................................... 167 Figure 3-15: Stacked 29Si NMR of AA, AB(7d) and BB .............................................. 169 Figure 3-16: 1H NMR of 2a (CDCl3 + 1%TMS, 500 MHz) ........................................... 180 Figure 3-17: 13C NMR of 2a (CDCl3 + 1%TMS, 126 MHz) ......................................... 181 Figure 3-18: 11B NMR of 2a (CDCl3 + 1%TMS, 160 MHz) ......................................... 181 Figure 3-19: 29Si NMR of 2a (CDCl3 + 1%TMS, 99 MHz) ........................................... 182 Figure 3-20: 1H NMR of 5a (CDCl3 + 1%TMS, 500 MHz) ........................................... 183 Figure 3-21: 13C NMR of 5a (CDCl3 + 1%TMS, 126 MHz) ......................................... 184 Figure 3-22: 29Si NMR of 5a (CDCl3 + 1%TMS, 99 MHz) ........................................... 184 Figure 3-23: Mass spec of 5a ..................................................................................... 185 Figure 3-24: 1H NMR of 5b (CDCl3 + 1%TMS, 500 MHz) .......................................... 186 Figure 3-25: 13C NMR of 5b (CDCl3 + 1%TMS, 126 MHz) ......................................... 187 Figure 3-26: 29Si NMR of 5b (CDCl3 + 1%TMS, 99 MHz) .......................................... 187 Figure 3-27: Mass spec of 5b..................................................................................... 188 Figure 3-28: 1H NMR of 5c (CDCl3 + 1%TMS, 500 MHz) ........................................... 189 Figure 3-29: 13C NMR of 5c (CDCl3 + 1%TMS, 126 MHz) ......................................... 190 Figure 3-30: 29Si NMR of 5c (CDCl3 + 1%TMS, 99 MHz) ........................................... 190 Figure 3-31: Mass spec of 5c ..................................................................................... 191 Figure 3-32: 1H NMR of 5d (CDCl3 + 1%TMS, 500 MHz) .......................................... 192 Figure 3-33: 13C NMR of 5d (CDCl3 + 1%TMS, 126 MHz) ......................................... 193 Figure 3-34: 29Si NMR of 5d (CDCl3 + 1%TMS, 99 MHz) .......................................... 193 Figure 3-35: Mass spec of 5d..................................................................................... 194 Figure 3-36: 1H NMR of 5e (CDCl3 + 1%TMS, 500 MHz) ........................................... 195 Figure 3-37: 13C NMR of 5e (CDCl3 + 1%TMS, 126 MHz) ......................................... 196 xvii Figure 3-38: 29Si NMR of 5e (CDCl3 + 1%TMS, 99 MHz) ........................................... 196 Figure 3-39: Mass spec of 5e ..................................................................................... 197 Figure 3-40: 1H NMR of 5f (CDCl3 + 1%TMS, 500 MHz) ........................................... 198 Figure 3-41: 13C NMR of 5f (CDCl3 + 1%TMS, 126 MHz) .......................................... 199 Figure 3-42: 29Si NMR of 5f (CDCl3 + 1%TMS, 99 MHz) ........................................... 199 Figure 3-43: Mass spec of 5f...................................................................................... 200 Figure 3-44: 1H NMR of 5g (CDCl3 + 1%TMS, 500 MHz) .......................................... 201 Figure 3-45: 13C NMR of 5g (CDCl3 + 1%TMS, 126 MHz) ......................................... 202 Figure 3-46: 29Si NMR of 5g (CDCl3 + 1%TMS, 99 MHz) .......................................... 202 Figure 3-47: 1H NMR of 5h (CDCl3 + 1%TMS, 500 MHz) .......................................... 203 Figure 3-48: 13C NMR of 5h (CDCl3 + 1%TMS, 126 MHz) ......................................... 204 Figure 3-49: 29Si NMR of 5h (CDCl3 + 1%TMS, 99 MHz) .......................................... 204 Figure 3-50: Mass spec of 5h..................................................................................... 205 Figure 3-51: Single Crystal Structure of 5a (Displacement ellipsoid contour probability drawn at 50%) ............................................................................................................. 207 Figure 3-52: The following hydrogen bonding interactions with a maximum D-D distance of 2.9 Å and a minimum angle of 120 ° are present in 5a: O4–O10: 2.767 Å, O10–O4_1: 2.738 Å ........................................................................................................................ 207 Figure 3-53: Single Crystal Structure of 5b (Displacement ellipsoid contour probability drawn at 50%) ............................................................................................................. 208 Figure 3-54: The following hydrogen bonding interactions with a maximum D-D distance of 3.1 Å and a minimum angle of 110 ° are present in REN1220D: O13–O14_1: 2.741 Å, O14–O13: 2.767 Å ...................................................................................................... 208 Figure 3-55: Single Crystal Structure of 5e (Displacement ellipsoid contour probability drawn at 50%) ............................................................................................................. 209 Figure 3-56: The following hydrogen bonding interactions with a maximum D-D distance of 2.9 Å and a minimum angle of 120 ° are present in 5e: O1–O2_1: 2.721 Å, O2–O1: 2.724 Å ........................................................................................................................ 209 Figure 3-57: Single Crystal Structure of 5f (Displacement ellipsoid contour probability drawn at 50%) ............................................................................................................. 210 xviii Figure 3-58: The following hydrogen bonding interactions with a maximum D-D distance of 2.9 Å and a minimum angle of 120 ° are present in REM221BB: O4–O10: 2.777 Å, O10–O4_1: 2.787 Å .................................................................................................... 210 Figure 3-59: 1H NMR (CDCl3 + 1%TMS, 500 MHz).................................................... 211 Figure 3-60: 13C NMR (CDCl3 + 1%TMS, 126 MHz) .................................................. 212 Figure 3-61: 29Si NMR (CDCl3 + 1%TMS, 99 MHz) .................................................... 212 Figure 3-62: Mass spec of 7a ..................................................................................... 213 Figure 3-63: 1H NMR (CDCl3 + 1%TMS, 500 MHz).................................................... 214 Figure 3-64: 13C NMR (CDCl3 + 1%TMS, 126 MHz) .................................................. 215 Figure 3-65: 29Si NMR (CDCl3 + 1%TMS, 99 MHz) .................................................... 215 Figure 3-66: Mass spec of 7b..................................................................................... 216 Figure 3-67: 1H NMR (CDCl3 + 1%TMS, 500 MHz).................................................... 217 Figure 3-68: 13C NMR (CDCl3 + 1%TMS, 126 MHz) .................................................. 218 Figure 3-69: 29Si NMR (CDCl3 + 1%TMS, 99 MHz) .................................................... 218 Figure 3-70: Mass spec of 7c ..................................................................................... 219 Figure 3-71: 1H NMR (CDCl3 + 1%TMS, 500 MHz).................................................... 220 Figure 3-72: 13C NMR (CDCl3 + 1%TMS, 126 MHz) .................................................. 221 Figure 3-73: 29Si NMR (CDCl3 + 1%TMS, 99 MHz) .................................................... 221 Figure 3-74: Single Crystal Structure of 7a (Displacement ellipsoid contour probability drawn at 50%) ............................................................................................................. 222 Figure 4-1: Structures of cage-like Silsesquioxanes - dodecaphenylT12 (1), octaphenylT8 (2), tetrakis(trimethylsilyl)octaphenylT8 (3), and heptaphenylT7 triol (4) ...................... 231 Figure 4-2: Graph of relative intensity (%) vs hydrolysis time ..................................... 238 Figure 4-3: Compound 3 showing two molecules of THF solvent per molecule of interest (Displacement ellipsoid contour probability drawn at 50%) ......................................... 243 Figure 4-4: Single molecule of 3 in the asymmetric unit, which is represented by the reported sum (Z is 4 and Z' is 1).................................................................................. 243 Figure 4-5: Packing diagram of 3 ............................................................................... 243 xix Figure 4-6: Compound 5 with two THF molecules co-crystallized per molecule of interest (Displacement ellipsoid contour probability drawn at 50%) ......................................... 244 Figure 4-7: Single molecule of 5 in the asymmetric unit, which is represented by the reported sum formula (Z is 2 and Z' is 1) ..................................................................... 244 Figure 4-8: Hydrogen bonding interactions in 5 .......................................................... 245 Figure 4-9: Packing diagram of 5,11,14,17-tetra(hydro)octaphenyltetracyclo[7.3.3.- 33;7]octasilsesquioxane (5) .......................................................................................... 246 Figure 4-10: 5,11,14,17-tetra(sodio)octaphenyltetracyclo[7.3.3.33;7]octasilsesquioxano- late (12) ....................................................................................................................... 249 Figure 4-11: 1H NMR of 3 (500 MHz, CDCl3) ............................................................. 254 Figure 4-12: 13C NMR of 3 (126 MHz, CDCl3) ............................................................ 255 Figure 4-13: 29Si NMR of 3 (99 MHz, CDCl3) ............................................................. 255 Figure 4-14: 1H NMR of 5 (500 MHz, CDCl3) ............................................................. 256 Figure 4-15: 13C NMR of 5 (126 MHz, CDCl3) ............................................................ 256 Figure 4-16: 29Si NMR of 5 (99 MHz, CDCl3) ............................................................. 257 Figure 4-17: 1H NMR of 3 – 16h (500 MHz, CDCl3) ................................................... 258 Figure 4-18: 29Si NMR of 3 – 16h (99 MHz, CDCl3).................................................... 259 Figure 4-19: 1H NMR of 3 – 24h (500 MHz, CDCl3) ................................................... 260 Figure 4-20: 29Si NMR 3 – 24h (99 MHz, CDCl3) ....................................................... 261 Figure 4-21: 1H NMR 3 – 36h (500 MHz, CDCl3) ....................................................... 262 Figure 4-22: 29Si NMR 3 – 36h (99 MHz, CDCl3) ....................................................... 263 Figure 4-23: 1H NMR 3 – 48h (500 MHz, CDCl3) ....................................................... 264 Figure 4-24: 29Si NMR 3 – 48h (99 MHz, CDCl3) ....................................................... 265 Figure 4-25: 1H NMR 3 – 72h (500 MHz, CDCl3) ....................................................... 266 Figure 4-26: 29Si NMR 3 – 72h (99 MHz, CDCl3) ....................................................... 267 Figure 4-27: Stacked 1H NMR of 5,11,14,17-tetrakis(trimethylsilyl)octaphenyltetracyclo- [7.3.3.-33,7]octasilsesquioxane (3) from 16 to 72 Hydrolysis of 1 (500 MHz, CDCl3) ... 268 xx Figure 4-28: Stacked 29Si NMR of 5,11,14,17-tetrakis(trimethylsilyl)octaphenyltetracyclo- [7.3.3.-33,7]octasilsesquioxane (3) from 16 to 72 Hydrolysis of 1 (99 MHz, CDCl3) ..... 269 Figure 4-29: 1H NMR of commercial 1 (500 MHz, Toluene-d8)................................... 270 Figure 4-30: 29Si NMR of commercial 1 (99 MHz, CDCl3) .......................................... 271 Figure 4-31: 1H NMR of recovered 1 (500 MHz, Toluene-d8) ..................................... 272 Figure 4-32: 29Si NMR of recovered 1 (99 MHz, CDCl3)............................................. 273 Figure 4-33: Stacked 1H NMR of Commercial Ph12T12 (1) and Recovered Ph12T12 (1) (500 MHz, Toluene-d8) ........................................................................................................ 274 Figure 4-34: Stacked 29Si NMR of Commercial Ph12T12 (1) and Recovered Ph12T12 (1) (99 MHz, CDCl3).......................................................................................................... 275 Figure 4-35: Stacked 1H NMR of Resinous product from the acid hydrolysis of intermediate salt (12) (500 MHz, CDCl3) ..................................................................... 276 Figure 4-36: Stacked 29Si NMR of Resinous product from the acid hydrolysis of intermediate salt 12 (99 MHz, CDCl3) ......................................................................... 277 Figure 4-37: DOESY NMR Spectra of resinous product (500 MHz, CDCl3) ............... 278 Figure 4-38: DOSY Spectra for 5,11,14,17-tetrakis(trimethylsilyl)octaphenyltetracyclo- [7.3.3.-33,7]octasilsesquioxane (3) (500 MHz, CDCl3) .................................................. 279 Figure 4-39: Commercial Ph12T12 (1) .......................................................................... 280 Figure 4-40: 5,11,14,17-tetrakis(trimethylsilyl)octaphenyltetracyclo[7.3.3.-33,7]octasilses- quioxane (3) from 16 h hydrolyzed 12 ......................................................................... 280 Figure 4-41: 5,11,14,17-tetrakis(trimethylsilyl)octaphenyltetracyclo[7.3.3.-33,7]octasilses- quioxane (3) from 24 h hydrolyzed 12 ......................................................................... 281 Figure 4-42: 5,11,14,17-tetrakis(trimethylsilyl)octaphenyltetracyclo[7.3.3.-33,7]octasilses- quioxane (3) from 36 h hydrolyzed 12 ......................................................................... 281 Figure 4-43: 5,11,14,17-tetrakis(trimethylsilyl)octaphenyltetracyclo[7.3.3.-33,7]octasilses- quioxane (3) from 48 h hydrolyzed 12 ......................................................................... 282 Figure 4-44: 5,11,14,17-tetrakis(trimethylsilyl)octaphenyltetracyclo[7.3.3.-33,7]octasilses- quioxane (3) from 72 h hydrolyzed 12 ......................................................................... 282 Figure 4-45: MS Spectra for 0 – 2 h hydrolyzed 12 .................................................... 283 Figure 4-46: MS Spectra for 4 – 8 h hydrolyzed 12 .................................................... 283 xxi Figure 4-47: MS Spectra for 36 – 72 h hydrolyzed 12 ................................................ 284 Figure 4-48: Mass Spectral Data for Resinous Mixture .............................................. 284 Figure 5-1: GC/MS – styrene ..................................................................................... 328 Figure 5-2: 1H NMR of 2 (CDCl3 + 1%TMS, 500 MHz)............................................... 328 Figure 5-3: 13C NMR of 2 (CDCl3 + 1%TMS, 126 MHz) ............................................. 329 Figure 5-4: 29Si NMR of 2 (99 MHz, CDCl3) ............................................................... 329 Figure 5-5: 1H NMR of 4 (CDCl3 + 1%TMS, 500 MHz)............................................... 330 Figure 5-6: 29Si NMR of 4 (99 MHz, CDCl3) ............................................................... 331 Figure 5-7: Mass spec of 4 ......................................................................................... 331 Figure 5-8: 1H NMR of 6 (CDCl3 + 1%TMS, 500 MHz)............................................... 332 Figure 5-9: 13C NMR of 6 (CDCl3 + 1%TMS, 126 MHz) ............................................. 332 Figure 5-10: 29Si NMR of 6 (99 MHz, CDCl3) ............................................................. 333 Figure 5-11: Mass spec of 6 ....................................................................................... 333 Figure 5-12: 1H NMR of 7 (CDCl3 + 1%TMS, 500 MHz) ............................................. 334 Figure 5-13: 13C NMR of 7 (CDCl3 + 1%TMS, 126 MHz) ........................................... 334 Figure 5-14: 29Si NMR of 7 (99 MHz, CDCl3) ............................................................. 335 Figure 5-15: Mass spec of 7 ....................................................................................... 335 Figure 5-16: 1H NMR of 12 (CDCl3 + 1%TMS, 500 MHz) ........................................... 336 Figure 5-17: 13C NMR of 12 (CDCl3 + 1%TMS, 126 MHz) ......................................... 337 Figure 5-18: 29Si NMR of 12 (99 MHz, CDCl3) ........................................................... 337 Figure 5-19: 1H NMR of 13 (CDCl3 + 1%TMS, 500 MHz) ........................................... 338 Figure 5-20: 11B NMR of 13 (CDCl3 + 1%TMS, 160 MHz) ......................................... 338 Figure 5-21: 29Si NMR of 13 (99 MHz, CDCl3) ........................................................... 339 Figure 5-22: 1H NMR of 14 (Acetone-d6, 500 MHz) .................................................... 339 Figure 5-23: 13C NMR of 14 (126 MHz, Acetone-d6) .................................................. 340 xxii Figure 5-24: 19F NMR of 14 (Acetone-d6, 471 MHz) ................................................... 340 Figure 5-25: 29Si NMR of 14 (Acetone-d6, 99 MHz) .................................................... 341 Figure 5-26: 1H NMR of 14 (CDCl3 + 1%TMS, 500 MHz) ........................................... 342 Figure 5-27: 13C NMR of 14 (CDCl3 + 1%TMS, 500 MHz) ......................................... 342 Figure 5-28: 29Si NMR of 14 (CDCl3 + 1%TMS, 99 MHz) ........................................... 343 Figure 5-29: Crystal Structure of 4 ............................................................................. 344 Figure 5-30: Packing diagram of 9,19-dimethyl-1,3,5,7,11,13,15,17-octaphenyl-9,19- bis(4-vinylphenyl)-2,4,6,8,10,12,14,16,18,20,21,22,23,24-tetradecaoxa- 1,3,5,7,9,11,13,1 5,17, 19-decasilapentacyclo[11.7.1.13,11.15,17.17,15]tetracosane (4) (Displacement ellipsoid contour probability drawn at 50%) ......................................... 345 Figure 5-31: Crystal Structure of 12 ........................................................................... 346 Figure 5-32: Packing diagram of 2,4,6,8-tetrakis(4-bromophenyl)-2,4,6,8-tetrakis((tri- methylsilyl)oxy)-1,3,5,7,2,4,6,8-tetraoxatetrasilocane ................................................. 347 xxiii LIST OF SCHEMES Scheme 1-1: Hydrolytic Polycondensation of RSiX3 ....................................................... 6 Scheme 1-2: Acid/base promoted cleavage of Completely Condensed Silsesquioxanes ........................................................................................................................................ 6 Scheme 1-3: Hydrolysis and condensation of RSiX3 ...................................................... 7 Scheme 1-4: Corner-capping trisilanol POSS with trifunctional monomers .................... 9 Scheme 1-5: Hydrolytic condensation of phenyltrimethoxysilane ................................. 10 Scheme 1-6: Condensation of DDSQ(ONa)4 with Me2SiCl2 ......................................... 11 Scheme 1-7: Condensation of DDSQ(OH)4 with R1R2SiCl2, where R1 ≠ R2 ................. 11 Scheme 2-1: Styryl-POSS macromonomer synthesis and its polymerization12 ............ 24 Scheme 2-2: Synthesis of organic–inorganic polyimide with DDSQ in the main chain23 ...................................................................................................................................... 25 Scheme 2-3: Ruthenium catalyzed silylative coupling of divinyl-substituted silsesqui- oxanes DDSQ-2ViSi with two different styrenes ........................................................... 26 Scheme 2-4: Side capping of DDSQ tetraol with two different chlorosilanes ................ 27 Scheme 2-5: (A) Bis-protection of DDSQ(OH)4 (1) with a boronic acid, (B) bis- deprotection of 2 with pinacol, and (C) stability of boronic acid protecting group under standard silylation conditions ........................................................................................ 28 Scheme 2-6: Monoborylation of DDSQ(OH)4 1 with p-MeO-C6H4B(OH)2..................... 28 Scheme 2-7: Synthesis of DDSQ Bis-boronate Esters 2 .............................................. 53 Scheme 2-8: Deborylation of (p-MeOC6H4B)2DDSQ with Pinacol ................................ 54 Scheme 2-9: Monoborylation of DDSQ(OH)4 1 with p-MeO-C6H4B(OH)2..................... 55 Scheme 2-10: Silylation of Mono-borylated Product, (p-MeOC6H4B)DDSQ(OH)2 with R1R2SiCl2 ...................................................................................................................... 56 Scheme 2-11: Deborylation of (p-MeOC6H4B)DDSQSiR1R2 and (p-MeOC6H4B)2DDSQ with Pinacol ................................................................................................................... 57 xxiv Scheme 2-12: Second Silylation of Monosilylated Precursor, R1R2SiDDSQ(OH)2 ....... 58 Scheme 2-13: Substrate Scope of the Multistep Pathway for the Synthesis of Asymmetrically Functionalized DDSQ ........................................................................... 59 Scheme 3-1: Hydrolysis of cyclopentyltrichlorosilane into heptacyclopentyl POSS trisilanol ....................................................................................................................... 130 Scheme 3-2: Selective cleavage of completely condensed octacyclohexyl silsesquioxane for the synthesis of octacyclohexyl POSS disilanol (Path A) and heptacyclohexyl POSS trisilanol (Path B) ........................................................................................................ 130 Scheme 3-3: Condensation of DDSQ(OH)4 with diphenyldichlorosilane .................... 131 Scheme 3-4: Condensation of DDSQ(OH)4 with 3-cyanopropyl(methyl)dichlorosilane .................................................................................................................................... 132 Scheme 3-5: Synthesis of difunctional POSS, phenyl7anilinePOSS from heptaphenylPOSS trisilanol ......................................................................................... 132 Scheme 3-6: Condensation of trisilanol POSS for the synthesis of metallasilsesquioxane .................................................................................................................................... 133 Scheme 3-7: Functionalization of POSS endo disilanol with MeHSiCl2 and subsequent hydrosilylation ............................................................................................................. 133 Scheme 3-8: Known routes into asymmetrically functionalized DDSQs ..................... 137 Scheme 3-9: Synthetic route into R1R2SiDDSQ(OH)2 (5) ........................................... 139 Scheme 3-10: Optimal deborylation of 2 with pinacol for the synthesis of 3 ............... 140 Scheme 3-11: Synthesis of asymmetrically functionalized R1R2SiDDSQ(OH)2 (5) .... 141 Scheme 3-12: Synthesis of 9,19-bis(4-methoxyphenyl)-1,3,5,7,11,13,15,17-octaphenyl- 2,4,6,8,10,12,14,16,18,20,21,22,23,24-tetradecaoxa-1,3,5,7,11,13,15,17-octasila-9,19- diborapentacyclo[11.7.1.13,11.15,17.17,15]tetracosane (2) ....................................... 172 Scheme 3-13: Complete Deborylation of (p-MeOC6H4B)2DDSQ (2) with Pinacol .... 173 Scheme 3-14: Partial Deborylation of (p-MeOC6H4B)2DDSQ (2) with Pinacol ......... 173 Scheme 3-15: Synthesis of asymmetrically functionalized monosilylated DDSQ(OH)2 .................................................................................................................................... 175 Scheme 3-16: Synthesis of completely condensed asymmetrically functionalized D 2T8 .................................................................................................................................... 178 xxv Scheme 4-1: Prior strategies for the partial cleavage of completely condensed (a) octaphenylT8, (b) hexacyclohexylT6 ............................................................................ 232 Scheme 4-2: Hydrolysis of Ph12T12 (1) for the synthesis of 5,11,14,17-tetrakis(trime- thylsilyl)octaphenyltetracyclo[7.3.3.33;7]octasilsesquioxane (3) ................................... 233 Scheme 4-3: Base cleavage of 1 with NaOH followed by acid hydrolysis of intermediate 12 with AcOH to give 5 ................................................................................................ 234 Scheme 4-4: Proposed route to 5 from 1.................................................................... 234 Scheme 4-5: Synthesis of 5,11,14,17-tetrakis(trimethylsilyl)octaphenyltetracyclo- [7.3.3.- 33,7]octasilsesquioxane [(PhSiO)8(O)2(OTMS)4] (3) from Ph12T12 (1) .......................... 235 Scheme 4-6: Time-course analysis for the synthesis of 3 from 1 ............................... 237 Scheme 4-7: Synthesis of 5 from 1 ............................................................................ 240 Scheme 4-8: Optimal Conditions for the Synthesis of (PhSiO)8(O)2(OH)4 (5) ............ 241 Scheme 4-9: Hydrolysis of Ph12T12 (1) for the synthesis of 15,11,14,17-tetrakis(tri- methylsilyl)octaphenyltetracyclo[7.3.3.33;7]octasilsesquioxane (3) .............................. 248 Scheme 4-10: Time-course study for the synthesis of 3 from 1.................................. 250 Scheme 4-11: Base hydrolysis of [Ph12T12] 1 for the synthesis of [(PhSiO)8(O)2(OH)4] 5 .................................................................................................................................... 251 Scheme 4-12: Optimization for the synthesis of (PhSiO)8(O)2(OH)4 (5) ..................... 252 Scheme 5-1: Silylative coupling and cross metathesis of octavinylT8 with styrenes ... 300 Scheme 5-2: Hydrosilylation of POSS-OSi(Me)2H with ethynylbenzene .................... 301 Scheme 5-3: Elaboration of OctavinylT8 for the synthesis of a variety of different POSS .................................................................................................................................... 302 Scheme 5-4: Fluoride catalyzed rearrangement of polysilsesquioxanes to mixed T10 and T12 isomers .................................................................................................................. 303 Scheme 5-5: Metathesis of mixed VinylT10 and VinylT12 for thesynthesis of styrenylT10/12 cages........................................................................................................................... 304 Scheme 5-6: Synthesis of 3,13-dianilino DDSQ from phenyltrimethoxysilane ............ 305 Scheme 5-7: Synthesis of asymmetric styrenylDDSQs from the silylative coupling of divinylDDSQ with substituted styrenes ........................................................................ 306 xxvi Scheme 5-8: Synthesis of [(styryl(Me)}2DDSQ] .......................................................... 306 Scheme 5-9: Route to styryl-functionalized Tn cage silsesquioxanes ......................... 307 Scheme 5-10: Synthesis of styryl-functionalised T8-F Cage ....................................... 307 Scheme 5-11: Synthesis of Brominated Octaphenylsilsesquioxanes (BrxOPS), x = the average number of bromines per molecule ................................................................. 309 Scheme 5-12: Selective self-catalyzed bromination of octa(phenyl)silsesquioxane (OPS) for the selective synthesis of octabrominated OPS ..................................................... 309 Scheme 5-13: Synthesis of octa(dibromophenyl)silsesquioxane ................................ 310 Scheme 5-14: Synthesis of sodium cyclotetrasiloxanolates from para-substituted phenyltriethoxysilane ................................................................................................... 310 Scheme 5-15: Synthesis of sodium and potassium cyclosiloxanolates based on trisiloxanolate cycles with vinyl and alkyl substituents ................................................. 311 Scheme 5-16: Synthesis of Br-T8 from all-cis-Br-T4-tetraol......................................... 312 Scheme 5-17: Synthesis of tetra-n-butylammonium octa(para-bromophenyl)octasilses- quioxane fluoride ......................................................................................................... 312 Scheme 5-18: Synthesis of dichloro(methyl)(4-vinylphenyl)silane (2) via Grignard .... 315 Scheme 5-19: Capping of DDSQ(OH)4 (3) with dichloro(methyl)(4-vinylphenyl)silane (2) .................................................................................................................................... 316 Scheme 5-20: Synthesis of sty8T8 (6), sty10T10 (7) and sty12T12 (8) from styryltrimethoxy- silane (5) ..................................................................................................................... 317 Scheme 5-21: Hydrolysis of sty8T8 with sodium hydroxide ......................................... 319 Scheme 5-22: Synthesis of 2,4,6,8-tetrakis(4-bromophenyl)-2,4,6,8-tetrakis((trimethyl- silyl)oxy)-1,3,5,7,2,4,6,8-tetraoxatetrasilocane (12) from the sodium hydroxide hydrolysis of 4-bromophenyltrimethoxysilane (10) ....................................................................... 321 Scheme 5-23: Synthesis of 2,4,6,8-tetrakis(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2- yl)phenyl)-2,4,6,8-tetrakis((trimethylsilyl)oxy)-1,3,5,7,2,4,6,8-tetraoxatetrasilocane .... 322 Scheme 5-24: Synthesis of fluoride ion entrapped octa(4-bromophenyl)octa- silsesquioxane (14) ..................................................................................................... 323 Scheme 5-25: Cleavage of 14 for the synthesis of 1,3,5,7,9,11,14,17-octakis(4- bromophenyl)-5,11,14,17-tetrakis((trimethylsilyl)oxy)-2,4,6,8,10,12,13,15,16,18-decaoxa -1,3,5,7,9,11,14,17-octasilatricyclo[7.3.3.33,7]octadecane (15) .................................. 325 xxvii KEY TO ABBREVIATIONS AA = Symmetric double-decker shaped silsesquioxane AB = Asymmetric double-decker shaped silsesquioxane ACN = acetonitrile APCI = Atmospheric Pressure Chemical Ionization Ar = Argon BB = Symmetric double-decker shaped silsesquioxane Bpin = 4,4,5,5-Tetramethyl-1,3,2-dioxaborolane B2pin2 = bis(pinacolato)diboron bpy = 2,2′-bipyridine CDCl3 = deuterated chloroform CHB = C–H activation borylation Chex = cyclohexyl °C = Degrees Celsius COD cyclooctadiene DCM = dichloromethane DDSQ = Double Decker Oligomeric Silsesquioxane DDSQ(OH)4 = Tetrasilanol double-decker shaped silsesquioxane DDSQ(ONa)4 = Tetrasodium double-decker shaped silsesquioxane DSC = Differential Scanning Calorimetry DPS = Diphenyl-functionalized Silsesquioxane dtbpy = 4,4′-di-tert-butyl-2,2′-bipyridine EtOAc = ethyl acetate FC = Fractional crystallization GC-MS Gas chromatography – Mass spectroscopy h = hour ICBM = Intercontinental Ballistic Missile xxviii Ir = iridium LC/MS = Liquid Chromatography-Mass Spectrometry m = multiplet peak in NMR spectrum M+ = molecular ion peak in mass spectrum m/z = mass divided by charge of an ion Me = methyl mg = milligrams MHz = mega hertz mL = milliliter mmol = millimole mp = melting point N2 = nitrogen MS = Mass Spectrometry MW = Molecular Weight NASA = National Aeronautics and Space Administration NMR = Nuclear Magnetic Resonance Spectroscopy OIBS = Octa-isobutyl Silsesquioxane OIBS-EDN = Octa-isobutyl Silsesquioxane Endo-disilanol OPS = Octaphenyl Silsesquioxane ORTEP = Oak Ridge Thermal Ellipsoid Plot Ph = Phenyl PFG = Pulse-Field Gradient POSS = Polyhedral Oligomeric Silsesquioxane ppm = parts per million rt = room temperature s = singlet peak in NMR spectrum T4 = Tetraphenylsilsesquioxane T6 = Hexaphenylsilsesquioxane xxix T8 = Octaphenylsilsesquioxane T10 = Decaphenylsilsesquioxane T12 = Dodecaphenylsilsesquioxane THF = tetrahydrofuran Td = Decomposition temperature Tg = Glass Transition Temperature Tm = Melting temperature TGA = Thermogravimetric Analysis TLC = Thin layer chromatography TMS = tetramethylsilane TPS = Thermal Protection System xxx CHAPTER 1.0 1.1 Introduction This chapter presents some background information on the growth of silsesquioxane chemistry, particularly previous literature related to the work described in this study. The chapter also reviews recent developments in this chemistry, pinpointing the motivations that led to our overall goal and objectives. 1.2 Background 1.2.1 Silsesquioxanes Silsesquioxanes are a diverse class of organosilicon compounds with the empirical formula RSiO3/2; where R can be hydrogen, alkyl or aryl group. The term is a portmanteau of three Latin syllables; ‘sil’ for silicon, ‘sesqui’ for three-halves typifying a Si:O ratio of 1:1.5 per unit molecule and ‘oxane’ for oxygen.1 The compounds contain several well- defined 3D structures with tunable physical and chemical properties. The arrangement of the Si–O–Si framework, analogous to that of the silica architecture, makes silsesquioxanes model nanofillers and polymer modifiers.2–4 1.2.2 Classification and Nomenclature of Silsesquioxanes 1.2.2.1 Classification Early classification of silsesquioxanes was based on their structures. Following the first isolation of some volatile silsesquioxanes from the co-hydrolysis products of Me2SiCl2 and MeSiCl3 by Scott in 1945,5 and the confirmation of their polyhedral nature by Barry and Gilkey,6 several other studies corroborated the fact that the condensation of trifunctional organosilanes produces a range of products with general formula, (RSiO 3/2)n. The resulting frameworks can be (i) random silsesquioxanes having no regular 1 arrangement of the Si-O-Si linkages, (ii) ladder structures where two siloxane chains are oxygen-linked at regular intervals with no polyhedra, (iii) fully condensed cages that are completely closed structures, or (iv) incompletely condensed cages that can serve as precursors to completely condensed structures.13 The random and ladder structures constitute the polysilsesquioxanes (also known as T-resins) and the closed and partial cage structures the polyhedral oligomeric silsesquioxane (POSS) (Figure 1-1). Figure 1-1: Different architectures of (RSiO3/2)n However, unlike the polysilsesquioxanes that lack regularity, the well-defined rigid frameworks of the polyhedral oligomeric silsesquioxanes make them a more interesting class of silsesquioxanes for the synthesis of new materials. The surge in research interest is particularly skewed towards the cubic T8 architecture due to its high symmetry and stability. 1.2.2.2 Nomenclature Silsesquioxanes are generally named using either the IUPAC system of nomenclature or the systematic (otherwise known as the trivial) nomenclature. The latter is more conveniently adopted because it describes only the number of silsesquioxane units, SiO3/2 in a molecule and the type of R group(s) on the silicon vertices unlike the IUPAC systems which requires details that makes the process cumbersome.1,7 For instance, the compound (iBuSiO3/2)8 is octaisobutylsilsesquioxane based on the 2 systematic name, and 1,3,5,7,9,11,13,15-octaisobutyl-2,4,6,8,10,12,14,16,17,18,19,20- dodecaoxa-1,3,5,7,9,11,13,15-octasilapentacyclo[9.5.1.13,9.15,15.17,13] icosane, based on the IUPAC system. For cases where the number of substituents is less than the number of silsesquioxane units, Rn-1R’(SiO3/2)n, as in (CH3)7vinyl(SiO3/2)8, the systematic and IUPAC names become heptamethylvinylsilsesquioxane and 1,3,5,7,9,11,13- heptamethyl-15-vinyl-2,4,6,8,10,12,14,16,17,18,19,20-dodecaoxa-1,3,5,7,9,11,13,15- octasilapentacyclo [9.5.-1.13,9.15,15.17,13]icosane respectively. A more convenient nomenclature also used to overcome the difficulty with the IUPAC system is to adopt the nomenclature as in siloxane chemistry. Here upper-case letters and numerical subscripts are used to describe the type of silicon atoms found in the polyhedra and in some cases, a superscript to denote the substituent on the silicon vertices. Based on this system, the letters M, D, T and Q are used as shorthand notations for the number of oxygen atoms bound to a silicon. Thus, silicon sites in POSS molecules are classified as an M-siloxane if the silicon atom is bound to one oxygen (R3SiO), D- siloxane when the silicon is bound to two oxygens (R2SiO2), T-siloxane when it is bound to 3 oxygens (RSiO3) and Q-siloxane when it is bound to 4 oxygen atoms (SiO4) (Figure 1-2).8 Figure 1-2: Systematic/trivial nomenclature of Silsesquioxanes Applying this system to the examples above, (iBuSiO3/2)8 becomes iBu8T8 or T8iBu and (CH3)7vinyl(SiO3/2)8 becomes Me7T7(CH2=CH)T or T7MeTvi 3 1.3 Polyhedral Oligomeric Silsesquioxanes (POSS) Polyhedral Oligomeric Silsesquioxanes are a class of hybrid organic-inorganic nanoparticles with the basic molecular composition of (RSiO3/2)n, where R is hydrogen or an organic group and n = 6,8,10,12,…Structurally, the compounds are made of several fused rings of Si-O-Si frameworks having each silicon atom bound to an organic group and three oxygens to form an Si-O based polyhedron.9 They are considered as the smallest particles of silica (nanostructural dimension of 1 – 3 nm in diameter) with tunable ability to offer material properties that are typical to both the core inorganic siloxane and the peripheral organic units.9–11 Consequently, both the composite rigidity and stability that comes from the inorganic core, and the toughness and processability from the organic coronae are tenable from a single material. The organic groups in the structure can be derivatized into more functional materials and used as binders or linkers to polymer matrices. The presence of various types of functionalities on the POSS core allows their easy incorporation onto surfaces to obtain composite materials with unique properties.12,13 Thus, the hybrid nature of these nanoparticles provides the property synergy that are intermediate to those of classical ceramics and polymers resulting in the generation of advanced engineering materials. Polyhedral oligomeric silsesquioxanes are therefore important building blocks for the design of new materials in polymer chemistry, material science, medicine, catalysis, and engineering. Depending on the value of n, there can be several different well-defined 3D structures of known silsesquioxanes, the most explored being the cubic silsesquioxane with an n value of 8 (Figure 1-3).12 4 Figure 1-3: Cubic octameric silsesquioxane Like other completely condensed POSS cages, octameric silsesquioxanes have a unique rigid silica core bearing eight organic functional groups anchored on the silicon vertices. They have an internal diameter of 0.53 nm, a sphere-like organic-inorganic molecular diameter of 1-2 nm and a volume that is less than 2 nm3. 12 These cage derivatives are highly symmetrical and easy to handle and modify. They are synthesized from the hydrolysis and condensation reactions of various trifunctional silanes. 3,8,12,14–16 However, cubic octafunctional POSS with mixed functionalities have also been obtained from the corner capping of various trisilanol POSS cages. Such POSS cages display different substitution patterns with different groups on the vertices as in the case of methacrylate heptaphenyl POSS derivative below (Figure 1-4).17 methacrylate heptaphenylPOSS Figure 1-4: Methacrylate heptaphenylPOSS POSS molecules are easy to disperse into polymer matrices. 17 The incorporation of POSS into polymer matrices causes significant property enhancement due to the strong interactions between the polymer chain and the nanoparticle. The strong nano 5 effects impacted by the POSS cage restricts the segmental motion of the polymer and hence leads to significant property enhancement in the composite. POSS/Polymer nanocomposites are obtained from either physical blending or chemical copolymerization courtesy of the reactive functional groups on both the polymer and POSS. 1.3.1 Synthesis of Polyhedral Oligomeric Silsesquioxanes (POSS) POSS compounds have been synthesized from the hydrolytic polycondensation of trifunctional organosilicon monomers, RSiX3, where R is a stable organic group and X, a very reactive halogen or alkoxide group (Scheme 1-1).15,16,18–23 Scheme 1-1: Hydrolytic Polycondensation of RSiX3 Whereas this approach affords both completely and incompletely condensed POSS cages, a higher yielding route specific to partially condensed products involves the base/acid promoted cleavage of fully condensed POSS (Scheme 1-2).24–27 Scheme 1-2: Acid/base promoted cleavage of Completely Condensed Silsesquioxanes Formation of silsesquioxanes from the hydrolysis of trichloro/trialkoxysilanes is a consecutive two-step process involving (i) the rapid hydrolysis of the trifunctional monomer into trisilanol, followed by (ii) polycondensations yielding different silsesquioxane frameworks (Scheme 1-3). 6 Scheme 1-3: Hydrolysis and condensation of RSiX3 Formation of various architectures is condition dependent and as a complicated process, reaction parameters such as initial monomer concentration, the nature of solvent, the nature of the R and X substituents, and the amount of water to be added requires careful considerations. For instance, the type of X group used can influence the reaction kinetics and polycondensations conducted at higher temperatures favors the formation of completely condensed cages over other frameworks. 1.4 Incompletely Condensed Polyhedral Oligomeric Silsesquioxanes Incompletely condensed polyhedral oligomeric silsesquioxanes are important building blocks for the synthesis of silsequioxane-containing polymers, silica-supported catalyst, electronic materials, and network solids.21,28–38 Since the first synthesis and isolation of heptacyclohexyl trisilanolPOSS by Brown and Vogt in 1965,19 there has being a rapidly expanding library of different partially condensed POSS cages including the difunctional, trifunctional or tetrafunctional silsesquioxanes (Figure 1-5). Figure 1-5: Incompletely condensed POSS frameworks25-27 7 Majority of the work in this field is credited to the Feher group for their tremendous efforts in developing procedures to access various types of partially condensed POSS cages. This class of silsesquioxanes has been accessed from both the hydrolytic condensation of functional organosilicon monomer19,21,30,39–41 and via the controlled partial hydrolysis of fully condensed POSS frameworks.30 However, whereas the former approach affords complex resins and/or polyhedral oligosilsesquioxanes (i.e., [RSiO 3/2]n), in addition to the incompletely-condensed frameworks, the latter using fully condensed POSS precursors offers a better route that is devoid of the undesired T-gels. The poorer yields obtained from monomeric chloro/alkoxy-silanes is a result of the formation of unstable intermediates that are very difficult to isolate from the crude. In addition, the synthetic procedures for the hydrolytic condensations of cyclohexyltrichlorosilane, cyclopentyltrichlorosilane and cycloheptyltrichlorosilane require long gestation periods that may vary from one partially condensed POSS to another.39 Compared to other 3D macromolecular systems like fullerenes and carboranes, incompletely condensed POSS cages are easier to functionalize and incorporate into polymer systems due to their solubility and the flexibility of the core siloxane cage. 42–44 Modification of various trifunctional precursors has been achieved via corner-capping reactions with functionalized trichloro- or trialkoxy-silanes.4,21,45,46 The process involves condensation of the terminal silanols or other reactive functionalities on the open end of the cage with chloro- or alkoxysilanes to yield completely condensed monofunctional POSS compounds (Scheme 1-4). 8 Scheme 1-4: Corner-capping trisilanol POSS with trifunctional monomers Monofunctionalized POSS cages have found huge applications as important synthetic precursors for the synthesis of POSS/polymer composites with high shear storage modulus (E′), high glass transition (Tg), melting (Tm), and decomposition (Td) temperatures.31,47–49 Lately, a special type of polyhedral oligomeric silsesquioxane with a unique symmetry, the so-called double-decker oligomeric silsesquioxane (DDSQ) has emerged as an even more interesting nanobuilding block precursor. This partially condensed cage bearing four dangling reactive groups symmetrically aligned in the molecule was discovered by Yoshida and coworkers in 2004.50 Modifications of their strategy leading to better yields of this compound were later reported by the Kawakami group. 24,51 This unique open POSS cage has two parallel cyclic siloxane rings arranged in planes that are linked by two oxygen atoms with phenyl coronae and four silanols (Figure 1-6). Figure 1-6: Octaphenyl tetrasilanolPOSS [DDSQ(OH)4] The position of the silanols offers this compound the added advantages of not only broadening the applications of POSS cages but also the ability to better impact the 9 physico-chemical properties including material flammability, viscosity, oxidative resistance, and thermal stability of polymers.28,52–58 The two reactive ends of the DDSQ(OH)4 can be derivatized via condensation reactions with various chlorosilanes into open DDSQ cages with four M-silicons and eight-silicons (M4T8 = DDSQ-4OSi) or condensed siloxanes with ten silicons, eight of which are T, and two D (D 2T8 = DDSQ- 2Si.59,60 Functionalized DDSQs of such frameworks are easy to incorporate into linear polymer backbones as in ‘beads-on-chain’. However, compared to monofunctionalized POSS which can only be pendant to polymer matrices, the ability of the functionalized DDSQs to link two or more polymer matrices makes their design better nano-precursors that can enhance the composite material properties by effectively retarding the backbone motion of polymers.57,61–63 Double-decker oligomeric silsesquioxane is synthesized from the hydrolysis of phenyltrimethoxysilane with sodium hydroxide and water in refluxing isopropanol followed by acid workup (Scheme 1-5).50,51 Scheme 1-5: Hydrolytic condensation of phenyltrimethoxysilane Functionalization of the open ends with suitable chlorosilanes can afford closed POSS derivatives that are ideal comonomers for incorporation into polymer matrices. 1.5 Synthesis of Condensed Difunctional Double-Decker Shaped Silsesquioxanes Condensation of DDSQ(OH)4 with mono-, di- or tri-functional capping agents in the presence of Et3N can afford either open DDSQs of the M4T8 framework or closed derivatives of the D2T8 architecture. Based on the reagent used for capping, the 10 functionalized DDSQs can either be a single compound or one that is made up of a mixture of geometric isomers (cis and trans). Formation of a single compound can result if, for instance, the bridging dichlorosilane has identical R substituents (R2SiCl2) (Scheme 1-6)51 whereas geometric isomers are obtained with difunctional chlorosilanes with two different R groups (Scheme 1-7).64 Scheme 1-6: Condensation of DDSQ(ONa)4 with Me2SiCl2 Scheme 1-7: Condensation of DDSQ(OH)4 with R1R2SiCl2, where R1 ≠ R2 Isolation of the cis/trans isomers had been a challenge until recently when various groups used both fractional crystallization (FC) and liquid chromatographic techniques.54,65–67 Interestingly, the structural differences between the geometric isomers (cis- and trans-forms) impacts differences on the physico-chemical properties of the POSS/polymer composite.52 1.6 Motivation and Research Goals Since the discovery of polyhedral oligomeric silsesquioxanes, much of the research focus had been on derivatizations leading to bifunctional nano-precursors that are integrated into polymer matrices.54,55,57,62,68–71 For this specific purpose, investigations on the applications of completely condensed POSS systems, the partially condensed 11 POSS trisilanols (RSiO1.5)7(OH)3, and the double-decker shaped tetrasilanol DDSQ(OH)4 have predominated in research laboratories and industries. This is so because of their nanometric dimensions which upon incorporation into polymer systems retard the chain mobility and hence boost their physico-chemical and mechanical properties. These structures have been functionalized with a range of groups via corner capping, side- capping, and derivatization of the organic peripherals on the silicon atoms.12,24,45 Functionalized double-decker shaped silsesquioxanes with the DDSQ-2(R1R2) architecture are particularly used as model building blocks for the synthesis of linear POSS/polymer composites.55,56,69,70,72–74 Their integration into polymer systems results in composites with enhanced physico-chemical properties including the glass transition temperature (Tg), dielectric properties and chemical resistance. However, these compounds have also been used to a limited extent as amphiphilic molecules,75 and as support for heterogeneous catalysts.76 In contrast, the synthesis and study of products resulting from the side-capping of incompletely condensed DDSQ(OH)4 cages with two different polymerizable groups (A/B systems) has remained a challenge. To this end, my dissertation is devoted to uncovering strategies and methods for the synthesis of novel POSS nano-precursors. Specifically, my research aims to synthesize symmetric and asymmetrically functionalized double- decker shaped silsesquioxanes with capping agents bearing Si, B, or C atoms. My goals are: (i) Synthesis and characterization of asymmetrically functionalized DDSQs that can link two dissimilar polymer matrices. 12 (ii) Study of the fissure patterns of dodecaphenylsilsesquioxane (Ph 12T12) as an alternative route for the synthesis of ‘Octaphenyl Double-Decker shaped Silsesquioxane. (iii) Development of protocol(s) for the synthesis of DDSQs with cage substituents that can be synthetically modified. 1.7 Dissertation Summary This dissertation is a collection of our strides towards developing protocols for the synthesis of novel functionalized Polyhedral Oligomeric Silsesquioxanes (POSS) as promising materials with scientific and engineering benefits. Special attention is focused on transforming cubic and/or DDSQ(OH)4 precursors into unique derivatives via complete or partial condensation approaches. Alternative approaches to access the highly desirable and expensive octaphenyl tetrasilanolPOSS precursors were also explored using cheaper starting materials. Chapter 1 gives a compendium of some relevant background to this research that enables the identification of explorable gaps as outlined in our research aim and objectives. Chapter 2 presents a synthetic route for the synthesis of asymmetrically functionalized double-decker shaped silsesquioxanes that has the potential to bridge two dissimilar polymer matrices. Chapter 3 discloses our efforts toward developing a general route into a crucial intermediate that is ideal for the efficient synthesis of condensed asymmetrically functionalized DDSQs and as a ligand for solid support. Chapter 4 outlines an economically viable route into the most coveted and costly DDSQ(OH)4 using the dead-end cubic dodecasilsesquioxane (Ph12T12) as a precursor. Chapter 5 reveals our preliminary attempts to expand the library of symmetrical incompletely condensed octa-functional double-decker shaped silsesquioxanes bearing unhindered styryl or p-bromophenyl substituents on the silicon vertices. 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Rev. 2013, 42, 4083–4097. 22 CHAPTER 2.0: Synthesis of Asymmetrically Functionalized Double-Decker Shaped Silsesquioxanes Parts of this chapter are published under the title “A general diversity-oriented synthesis of asymmetric double-decker shaped silsesquioxanes’’ with the following citation: Barry, B.-D.; Dannatt, J. E.; King, A. K.; Lee, A.; Maleczka Jr., R. E. Chem. Commun., 2019, 55, 8623–8626. 23 2.1 Introduction Silsesquioxanes have attracted significant research interest for the synthesis of materials with properties that meet medicinal, synthetic, industrial and materials science demands.1–4 Over the years, explorations in this field have been dominated by the manipulation of cubic-like silsesquioxanes for the synthesis of hybrid polymers.2,5–7 This is due to the well-defined spatial dimensions, the presence of seven relatively inert peripheral organic moieties to accommodate solubility and processability, and one polymerizable reactive organic group.8–14 Such silsesquioxane frameworks are accessed by corner-capping incompletely condensed R7-trisilanol POSS with R’-trichlorosilanes.12– 16 The resulting condensed structure bears a polymerizable R’ group that can be incorporated as a pendant nanostructure to a linear polymer chain. Scheme 2-1: Styryl-POSS macromonomer synthesis and its polymerization12 After the first synthesis of DDSQ-tetraol (1),17,18 two reactive edges could be accessed via the condensation of 1 with various chlorosilane capping agents.8,19,20 24 (a) DDSQ-tetraol (1) (b) R7-trisilanol POSS Figure 2-1: Double-decker oligomeric silsesquioxane tetraol (1) and (b) R7-trisilanol POSS Unlike the monofunctionalized POSS where the nano-precursor acts as a pendant, this framework allows incorporation into a linear polymer backbone (Scheme 2-2).21–24 Incorporating silsesquioxanes in this manner may provide more effective retardation to the backbone motion of a linear polymer, which in turn could allow a more efficient approach to property enhancement.23–26 Scheme 2-2: Synthesis of organic–inorganic polyimide with DDSQ in the main chain23 It is noteworthy, however, that in all the cases above the two lengths of polymer bridged by the silsesquioxane linker are from the same monomer. This results from the fact that DDSQ tetraol is symmetrically capped. We believe that silsesquioxanes bridging two distinct polymers will offer an interesting new class of materials. To produce and explore such materials requires the symmetry in 1 to be broken. Certainly, synthetically 25 accessing such asymmetric DDSQ systems presents a significant challenge due to the nanometer scale distance between capping sites. Recently, two routes to asymmetric DDSQs have been reported. In 2018 the Zak and Marciniec team developed an olefin metathesis catalyst able to selectively couple one vinyl group on a symmetrically capped divinyl-substituted DDSQ with various styrene derivatives.27 After this mono-functionalization, a second styrene derivative was added to afford an asymmetric AB system (Scheme 2-3). Scheme 2-3: Ruthenium catalyzed silylative coupling of divinyl-substituted silsesqui- oxanes DDSQ-2ViSi with two different styrenes While this ground-breaking work effectively provided an AB system, major limitations include the necessity of the vinyl and styryl coupling partners, the requirement of ruthenium-based catalyst and lack of a reason for asymmetry. A more general synthetic route must be one that is amenable to a broader range of functionalities. Thus, in our previous attempt to develop a methodology that supports a diverse array of functional groups we explored the capping of DDSQ tetraol with a premixture of two chlorosilanes. 28 In that study, we demonstrated that the AB system could be isolated if one of the chlorosilanes is a trichloromethylsilane. The latter upon workup, provided a silane and the 26 resultant polarity difference between the symmetric by-products and the desired asymmetric system enabling separation by HPLC (Scheme 2-4). Scheme 2-4: Side capping of DDSQ tetraol with two different chlorosilanes Again, this technique was limited in that it requires HPLC and is thus scale limited, it generated significant symmetric by-product waste, and it required differences in polarity between the by-products and desired asymmetric material. To improve on current methodologies, we sought a synthetic route where all chlorosilane capping agents are tolerated, excess DDSQ tetraol can be recovered then recycled, and symmetric by-products are minimized. To this end, a protecting group strategy was envisioned. If 1 could be mono protected by masking two silanol groups, silylation of the free silanol edge, followed by deprotection and capping with another chlorosilane would afford the desired asymmetric material. To achieve this goal, we first had to identify an effective protecting group. The desired protecting group would be able to protect two silanols simultaneously, be easily installed and removed without impacting the DDSQ framework and tolerate standard capping conditions (Scheme 2-5). 27 Scheme 2-5: (A) Bis-protection of DDSQ(OH)4 (1) with a boronic acid, (B) bis- deprotection of 2 with pinacol, and (C) stability of boronic acid protecting group under standard silylation conditions Once this is achieved, we can next seek optimal conditions that could lead to the mono-protected 1 (Scheme 2-6). Scheme 2-6: Monoborylation of DDSQ(OH)4 1 with p-MeO-C6H4B(OH)2 28 2.2 Results and Discussions All reactions were followed using 1H, 11B, 13C and 29Si spectroscopy and the final asymmetric products were purified by flash chromatography. The isolated compounds were all characterized by 1H, 11B, 13C and 29Si NMR spectroscopy (Appendix). The asymmetrically functionalized DDSQs 6 were obtained almost exclusively with minor symmetric AA 7 and BB 8 by-products. The asymmetric products (6) are denoted AB implying that these products are composed of one of each of the A and B capping silyl groups. In addition to the spectral data, single X-ray crystal structures were obtained for all bis-borylated DDSQs (Appendix). Table 2-1: Full Protection of DDSQ(OH)4 1 with p-substituted Phenylboronic Acid After initial evaluation it was found that 1 could be bis-protected with a variety of boronic acids under Dean-Stark conditions in high isolated yields. Among the boronic acids explored, 4-methoxyphenylboronic acid allowed simple spectroscopic analysis due to its distinct methoxy protons while also affording the highest yield of 98% (entry 1). Recrystallization of the bis-boronate DDSQ esters from DCM/hexane (1:3) provided single crystals suitable for X-ray analysis (Table 2-2). 29 Table 2-2: Crystal Structures of Bis-boronated DDSQ Esters 2 (Displacement ellipsoid contour probability drawn at 50%) Deborylation of 2 was achieved by stirring with pinacol providing a high yield of pure 1 (Scheme 2-5B). To our knowledge, this is the first report of a boronic acid used as a protecting group for silanols; however, borosiloxane cages have been reported. 21 Excitingly, compound 2 was stable under the capping reaction conditions with one alteration. Using pyridine as opposed to the more common triethylamine provided a nearly quantitative recovery of bis-protected material (Scheme 2-5C). In our hands, pyridine had 30 no adverse effects on the capping of 1. However, even with this development, it is worth mentioning that borylation of 1 for the synthesis of 3 afforded a mixture of borylated cages (Scheme 2-9) that were difficult to isolate in their pure forms. As a result, a pictorial outline (Figure 2-2) was designed for the multistep synthesis of the asymmetric compounds. The route consists of four (4) steps, viz: (i) Selective protection with boronic acid; (ii) First silylation with ‘A’ di-chlorosilane; (iii) Deprotection with pinacol and (iv) Second silylation with ‘B’ di-chlorosilane. Figure 2-2: Designed Graphical Pathway to Asymmetrically Functionalized DDSQs For this pathway to be effective by minimizing the generation of undesired symmetric products, the unreacted 1 in steps 1 and 3 must be quantitatively recovered. 2.2.1 Solubility of DDSQ(OH)4 in Various Organic Solvents DDSQ(OH)4 1 is least soluble in toluene (Table 2-3, entry 3) followed by chloroform (Table 2-3, entry 2) and is most soluble in acetone (Table 2-3, entry 7). However, because of the challenges to remove toluene from the reaction mixture owing to its high boiling point (111 ⁰C), chloroform was chosen as the solvent for the deborylation in step 3. Unreacted 1 was efficiently recovered in both steps 1 and 3 by filtration due to the poor solubility of 1 in chloroform. 31 Table 2-3: Solubility Tests for DDSQ(OH)4 (1) in Organic Solvents 2.2.2 Optimization of the Selective Borylation for the Generation of (p- MeOC6H4B)DDSQ(OH)2 3 With a suitable protecting group determined, optimal conditions leading to mono- protected 3 were sought (Table 2-4). Although all conditions screened could not exclusively afford mono-protected 1, it was found that addition of 1 equivalent of p-MeO- C6H4B(OH)2 under Dean-Stark conditions for 2 h afforded 42% recovered 1 and 58% of an inseparable mixture which by 1H and 29Si NMR spectroscopy consisted of mono- borylated 3 and bis-borylated 2 in a ratio of 1:3 (Scheme 2-9). While the ratio of compound 3 to compound 2 is not optimal, it was reasoned this mixture could be carried forward without significant loss of material as compound 2 could be recovered as starting material, 1, after global deprotection (Scheme 2-9). Note that in both steps 1 and 3 (Scheme 2-9) compound 1 is recovered by filtration, which is enabled by its poor solubility in chloroform. 32 Table 2-4: Optimization of Monoboronate Ester Formation aExperimental conditions: DDSQ(OH)4 1 (0.53g, 0.51mmol), p-methoxyphenylboronic acid ('x' mmol), toluene (10 mL) nitrogen, 115 °C, 'y' h. bRecovered DDSQ(OH)4 1 in grams; cMass of filtrate in grams; dLoss in mass of starting DDSQ(OH)4 1 in grams; eRatio of mono- to bis-borylated product based on crude 29Si NMR. 33 2.2.3 Substrate Scope for Asymmetrically Functionalized Double-Decker Shaped Silsesquioxanes Table 2-5: Scope for Asymmetrically Functionalized DDSQs aYields reported are based on the calculated amount of compound 3 generated in step 1. Yields in parenthesis are based on the total amount of compounds 2 and 3 generated in step 1. bYields for 7 and 8 are based on the total amount of compounds 2 and 3 generated in step 1. The percentage of recovered 1 includes material from steps 1 and 3. cIsolated as a cis/trans mixture. In our efforts to explore the scope of this multistep route, the reactions were scaled to DDSQ(OH)4 1 (1.96 mmol, 2 g), p-MeO-C6H4B(OH)2 (1 equiv), chlorosilane (1 equiv based on 3), pyridine (2 equiv based on 3), and pinacol (1 equiv based on original p-MeO- C6H4B(OH)2 added. With this route, the identity of the chlorosilanes used in steps 2 and 4 (Scheme 2-13) is unrestricted unlike prior synthetic routes.27,28 Overall, moderate to 34 high isolated yields were achieved with an average relative isolated yield of 65%. The high recovery of 1 is a key element of this strategy; namely the recyclability of compound 2 back to 1. Symmetric by-products will only arise from inefficiencies in removing 1 in steps 1 and 3. Besides, the 29Si NMR data is more informative. Spectra of compounds 6a–6i exhibited six or eight characteristic peaks depending on if cis/trans isomers were present, and the high-resolution mass spectrometry are in excellent agreement with calculated theoretical molecular exact masses (Appendix). While some of the AB cages contain moieties that can serve as polymer end-cap groups (6a, 6b, 6d, 6e, and 6i), others possess moieties that enable them to bridge two distinct polymers (6c, 6f, and 6g). Asymmetric product 6h is quite unique in that it bears three reactive polymerizable groups. Reversing the order in which chlorosilanes were added had little effect on isolated yields and had no observed effect on the amounts of symmetric by-products isolated (6d and 6e). This experiment suggests the symmetric by-products can only be attributed to the small amounts of 1 passing through the filtration in steps 1 and 3 and is independent of the capping agent used. The variation of isolated symmetric materials throughout (Table 2-5) is attributed to the ability of the symmetric material to pass through the flash chromatography after the final step. It was observed that asymmetric products with a significant difference in polarity at the capping site afforded better yields of the isolated asymmetric products (6b, 6d, 6e, 6g, and 6h). This is not surprising as the success in separating the mixture by column chromatography relies on the interaction of the various components in the mixture with the stationary phase and the eluting solvent (mobile phase). It is also noteworthy that in Table 2-5 (entries 2, 8, and 9) the corresponding symmetric by-product 8 was not isolated. This is likely because these symmetric products 35 are quite polar and thus will only slowly pass through the silica column. The symmetric product 8a (entry 1), on the other hand, should readily pass through the silica. We expect in this case the mass of generated symmetric material may be low enough that it is difficult to detect. 2.2.4 Structural Analysis of Asymmetric DDSQs (6) by Si-NMR In addition to literature reports and other spectroscopic data, the structures of the asymmetrically functionalized DDSQs were resolved by matching with spectra of symmetric products obtained from using the same capping agents as in the asymmetric products. The silicon atoms in each structure are numbered for clarity, with those in the same chemical environment bearing the same number. 36 6a: (1r,3R,11s,13S)-9,9,19-trimethyl-1,3,5,7,11,13,15,17-octaphenyl-2,4,6,8,10,12,14, 16,18,20,21,22,23,24-tetradecaoxa-1,3,5,7,9,11,13,15,17,19-decasilapentacyclo[11.7.1. 13,11.15,17.17,15]tetracosane. Figure 2-3: Stacked 29Si NMR of AB 6a, AA 7a and BB 8a Spectra for 6a C51H50Si10O14 reveals six (6) peaks characteristic of the chemically different Si atoms present in the structure. Figure 2-3 above shows a stacked spectrum of the symmetric tetramethyl capped cage (top), asymmetric AB 6a (middle) and symmetric dimethyl dihydrido-capped DDSQ (bottom). Si#1 is the D-silicon with two Me substituents bridging one side of the DDSQ and shows up at -16.48 ppm. Si#2 is the other D-silicon with a methyl and hydrogen substituent capping the other end of the cage and 37 peaks at -32.87 ppm. The remaining Si atoms are T-silicons and as expected, have their chemical shifts in the T-silicon range (-77.8 to -79.8 ppm). Thus, by matching with the symmetric AA and BB cages, it can be delineated that the signal at -77.89 ppm denotes the two silicon atoms (Si#3) close to Si#2, and that at -78.61 ppm designate the two silicon atoms (Si#4) next to Si#1. The remaining signals between -79.28 to -79.74 represent the internal silicons (Si#5 and Si#6) that can interchange chemical shift values illustrating the different configurations of AB 6a based on the orientation of the substituents on Si#1 and Si#2. 38 6b: (1r,3R,11s,13S)-9,19,19-trimethyl-1,3,5,7,11,13,15,17-octaphenyl-2,4,6,8,10,12,14, 16,18,20,21,22,23,24-tetradecaoxa-1,3,5,7,9,11,13,15,17,19-decasilapentacyclo[11.7.1. 13,11.15,17.17,15]tetracosan-9-ol. Figure 2-4: Stacked 29Si NMR of AB 6b, AA 7b and BB 8b The 29Si-NMR for AB 6b C51H50Si10O15 shows six (6) peaks (Figure 2-4). The spectrum itself is stacked with that for the symmetric tetramethyl- AA 7b and symmetric dimethyl-dihydroxyl-capped cages BB 8b. The silicon atom having two methyl groups (Si#1), the only D-silicon in the structure, bridges one side of the DDSQ and appears upfield at -16.38 ppm. The other bridging group is a T-silicon bearing a free hydroxyl group (Si#2) gives a peak at -54.01 ppm (a region that is symbolic of Si atoms bearing 39 OH groups). The spectrum also indicates that the compound was isolated in its cis/trans form and thus, the environments of the remaining Si atoms can change depending on the orientation of the substituents on the capping chlorosilane, hence accounting for the remaining Si peaks in the -78.00 to -79.50 ppm region. The peak at -78.52 ppm represent the two T-silicon atoms (Si#3) bound to the Me2SiO2- group. That at -78.68 ppm (Si#4) denotes the other two T-silicon atoms linked to the Me(OH)SiO2- group. The remaining four Si-atoms (Si#5/6) are the four internal silicons that can assume two different environments based on the orientation of the substituents on Si#1 ans Si#2. The cis configuration has the Me and OH groups on Si#1 and Si#2 on the same face. 40 6c: 4-((1r,3R,11s,13S)-9,19-dimethyl-1,3,5,7,11,13,15,17-octaphenyl-2,4,6,8,10,12, 14,16,18,20,21,22,23,24-tetradecaoxa-1,3,5,7,9,11,13,15,17,19-decasilapentacyclo- [11.7.1. 13,11.15,17.17,15]tetracosan-9-yl)butanenitrile. Figure 2-5: Stacked 29Si NMR of AB 6c, Symmetric AA 7c and BB 8c AB 6c C54H53Si10NO14 also has six (6) peaks, showing the different types of silicon atoms in the structure (Figure 2-5). AB 6c (middle) is stacked with the symmetric AA (bottom) and BB (top) cages. For 6c, the spectra show two D-silicons (Si#1 and Si#2), both appearing in the D-silicon region as expected. The silicon bonded to an Me and H groups (Si#1), appears upfield at -32.86 ppm and the other with the Me and 3-CNPr group (Si#2) appears downfield at -19.16 ppm. The spectra also illustrate that the compounds were isolated in their cis/trans forms. The environments of the remaining Si atoms can 41 thus change based on the orientation of the substituents on the capping chlorosilane as is shown by the signals between the -77.00 to -79.50 ppm region. Thus, the peak at - 77.92 ppm (2Si) denotes Si#3, -78.30 ppm (2Si) Si#4, -79.24 ppm (1Si), signals at -79.29 ppm (1Si), -79.45 ppm (1Si), and -79.49 ppm (1Si) denotes one of each of the four internal silicons (Si#5 or Si#6 with cis/trans configuration), 6d: 4-((1r,3R,11s,13S)-9,19,19-trimethyl-1,3,5,7,11,13,15,17-octaphenyl-2,4,6,8,10, 12,14,16,18,20,21,22,23,24-tetradecaoxa-1,3,5,7,9,11,13,15,17,19-decasilapentacy- clo[11. 7.1.13,11.15,17.17,15] tetracosan-9-yl)butanenitrile. Figure 2-6: Stacked 29Si NMR of AB 6d, AA 7d and BB 8d 42 Spectra for AB 6d C55H55Si10NO14 displays six (6) peaks for the six different Si atoms present in the structure. AB 7d (middle) is stacked with the symmetric AA 7d (bottom) and BB 8d (top) cages (Figure 2-6). Like is seen in its structure, the spectra shows two D-silicons (Si#1 and Si#2), found in the expected ppm range of -16.48 for the Me2SiO2- silicon (Si#1) and -19.24 for the (Me)(3-CNPr)SiO2- (Si#2). Because the environments of the remaining Si atoms are affected by the orientation of the substituents on Si#1 and Si#2 and based on the stacked spectra above, the T-silicons in the structure are distributed thus: Signal at -78.36 ppm for the two Si#4 closest to Si#2, -78.63 ppm for the two Si#3 next to Si#1, -79.48 ppm for the internal silicons (Si#5 or Si#6) with a cis configuration for the Me groups on both Si#1 and Si#2, and -79.53 ppm for the internal silicons (Si#5 or Si#6) when substituents on Si#1 and Si#3 are trans. It must be mentioned that AB 6d and AB 6e are the same compounds that resulted by reversing the order of addition of the chlorosilanes to DDSQ tetraol. Whilst, the addition order was Me2SiCl2 first and then Me(3CNPr)SiCl2 for 6d, that for 6e was the reverse. 43 6f: 4-((1s,3R,11r,13S)-9,19-dimethyl-1,3,5,7,11,13,15,17-octaphenyl-19-vinyl-2,4,6,8, 10,12,14,16,18,20,21,22,23,24-tetradecaoxa-1,3,5,7,9,11,13,15,17,19-decasilapenta- cyclo [11.7.1.13,11.15, 17.17,15]tetracosan-9-yl)butanenitrile. Figure 2-7: Stacked 29Si NMR of AB 6f, AA 7f and BB 8f Spectra for AB 6f C56H55Si10NO14 also shows six (6) peaks as seen in its stacked 29Si-NMR with that of symmetric AA 7f (top) and BB 8f (bottom) cages (Figure 2-7). Here also, AB 6f has two D-silicon peaks at -19.23 and -31.38 ppm in line with (C2H3)(Me)SiO2- (Si#1) and (Me)(3-CNPr)SiO2- (Si#2) respectively. All the T-silicons in the structure are found in the -78.35 to -79.51 ppm range. By matching with spectra for 7f and 8f cages, - 44 78.35 ppm peak denotes the two Si#4 close to Si#2 and -78.43 ppm the two Si#3 atoms nearest to Si#1. Signals at -79.47 and -79.51 are symbolic of the four internal silicon atoms (Si#5 and Si#6) that can assume complementary signals based on the orientation of the substituents on Si#1/Si#2 (cis/trans). Clearly, the signal at -79.47 ppm is for the cis configuration of the Me groups on Si#1 and Si#2 and the -79.51 the trans configuration. 6g: (1r,3R,11s,13S)-9,19-dimethyl-1,3,5,7,11,13,15,17-octaphenyl-9-vinyl-2,4,6,8,10, 12,14,16,18,20,21,22,23,24-tetradecaoxa-1,3,5,7,9,11,13,15,17,19-decasilapentacy- clo[11. 7.1.13,11.15,17.17,15]tetracosane Figure 2-8: Stacked 29Si NMR of AB 6g, AA 7g and BB 8g 45 Spectra for AB 6f C52H50Si10O14 similarly displays six (6) peaks. AB 6f (middle) is stacked with the symmetric AA (top) and BB (bottom) cages (Figure 2-8). The two D- silicon atoms in the structure give peaks at -31.37 and -32.91 ppm denoting one Si each for Si#1 having a Me and H substituents and Si#2 bearing a Me and vinyl substituents respectively. The T-silicons in the structure are found upfield between -77.90 and -79.56 ppm. These peaks are assigned to the T-silicons by matching with the spectra for 7g and 8g. Thus, the -77.90 ppm peak stems from the two Si#3 close to Si#1 and the -78.36 ppm peak the two Si#4 nearest to Si#2. Similarly, signals at -79.35 and -79.56 ppm are consistent with the four internal silicon atoms (Si#5 and Si#6) that can assume complementary signals based on the orientation of the substituents on Si#1/Si#2 (cis/trans). The signal at -79.35 ppm is for the cis configuration of the Me groups on Si#1 and Si#2 and the peak at -79.56, the trans configuration. It is worth mentioning that the divinylDDSQ cage (top) was isolated as the trans isomer only as is disclosed by the single peak at -79.56 ppm. 46 6h: (1r,3R,11s,13S)-19-methyl-1,3,5,7,11,13,15,17-octaphenyl-9-vinyl-2,4,6,8,10,12, 14,16,18,20,21,22,23,24-tetradecaoxa-1,3,5,7,9,11,13,15,17,19-decasilapentacyclo- [11.7.1. 13,11.15,17.17,15]tetracosan-9-ol. Figure 2-9: Stacked 29Si NMR of AB 6h, AA 7h and BB 8h Unlike the spectra for AB 6a to AB 6g, those for AB 6h (Figure 2-9) C51H48Si10O15 and AB 6i (Figure 2-10) C54H54Si10O15 are quite unique. They display eight peaks instead of six and were isolated as geometric isomers (cis/trans forms). This is expected because the substituents on Si#1 and Si#2 are all different from one another and hence, make their internal silicons (Si#5 and Si#6) even more chemically different. As always, asymmetric 6h (middle) is stacked with 7h (top) and 8h (bottom). The structure of AB 6h has one distinct D-silicon capping one end of the DDSQ with a shift at -32.80 ppm that is consistent for Si#1. The second bridging Si on the other end of the cage, a T-silicon (Si#2) 47 appearing at -69.88 ppm is consistent for the region of T-silicons bearing a hydroxyl group. All other T-silicons in the structure appeared upfield between -77.86 and -79.43 ppm. These peaks are assigned to the T-silicons by matching with spectra for the AA and BB cages. Clearly, the -77.86 ppm peak denotes the two Si#3 close to Si#1 and the peak at -78.49 ppm, the two Si#4 nearest to Si#2. The remaining signals [-79.16 (1Si), -79.23 (1Si), -79.36 (1Si), -79.43 (1Si)] ppm are characteristic of each of the internal silicons (two Si#5 and two Si#6) which can assume complimentary signals based on the orientation of the substituents on Si#1/Si#2 (cis/trans). 48 6i: (1r,3R,11s,13S)-9-isopropyl-19-methyl-1,3,5,7,11,13,15,17-octaphenyl-19-vinyl-2, 4,6,8,10,12,14,16,18,20,21,22,23,24-tetradecaoxa-1,3,5,7,9,11,13,15,17,19-decasila- pentacyclo[11.7.1.13, 11.15,17.17,15]tetracosan-9-ol. Figure 2-10: Stacked 29Si NMR of AB 6i and AA 7i Spectra for AB 6i discloses 8 signals in line with the different kinds of silicon atoms in its structure (Figure 2-10). Asymmetric AB 6i (bottom) is stacked with the symmetric AA (top). The isopropyltrichlorosilane capped DDSQ (BB cages) was not isolated, hence its absence from the stacked spectra. Like in AB 6h, the structure of AB 6i has one distinct D-silicon with a shift at -31.34 ppm typical of D-silicons with Me and vinyl substituents (Si#1). The other DDSQ bridging silicon is Si#2, a T-silicon having an isopropyl and OH 49 substituents exhibiting a peak at -55.89 ppm (Si#2); the expected range for T-silicons with one free hydroxyl group. The remaining silicons in the structure are all T-silicons showing up in the -78.36 to -79.51 ppm range. These peaks are assigned to the various T-silicons by matching. Thus, the signal at -78.36 ppm represents the two Si#3 close to Si#1 bearing the Me and vinyl substituents and the one at -78.98 ppm designates the two Si#4 close to Si#2. Signals at -79.38, -79.51 ppm each denotes two of the internal silicons (Si#5 and Si#6) that can interchange values based on the orientation of the substituents on Si#1/Si#2 (cis/trans). 2.3 Conclusions In conclusion, a strategically novel synthesis of nano-sized, asymmetrically functionalized double-decker shaped silsesquioxanes (DDSQ) is reported. The technique relied on the protection of two silanol groups on DDSQ tetraol (1) using boronic acid. Importantly, the protocol discloses the effectiveness of pyridine as a base, which unlike the more commonly used triethylamine is inert to the boron protected cage. Additionally, pinacol chemoselectively demasks the boron protecting group without compromising the cage architecture. The protocol is general, robust and allows the assemblage of a wide range of functionalized asymmetrically functionalized DDSQs. Eight asymmetric compounds were synthesized and characterized as pure compounds by 1H, 13C, and 29Si NMR and mass spectroscopy. Over 50% of the starting DDSQ tetraol (1) that could have otherwise contributed toward the synthesis of unwanted side products is recovered with a high purity and can be used in another cycle of synthesis. Efforts to use these compounds as nano-linkers to two different block copolymers are underway in our lab. 50 2.4 Experimental Details 2.4.1. General Information All manipulations were done under a nitrogen atmosphere using standard Schlenk techniques except otherwise stated. Tetrasilanol POSS (DDSQ tetraol) or (C6H5)8Si8O10(OH)4 or DDSQ(OH)4 was purchased from Hybrid Plastics. Dimethyldichlorosilane, methyldichlorosilane, vinylmethyldichlorosilane, 3-chloro- propylmethyldichlorosilane, 3-chloropropylmethyldichlorosilane, vinyltrichlorosilane, isopropyltrichlorosilane, and isobutyltrichlorosilane were purchased from Gelest. Methyltrichlorosilane (CH3)SiCl3 was purchased from Sigma-Aldrich. Triethylamine (Et3N) was purchased from Avantor and distilled over calcium hydride before use. Deuterated chloroform with 1% (v/v) TMS and tetrahydrofuran-d8 were purchased from Cambridge isotopes laboratories. Dichloromethane, trichloromethane, tetrahydrofuran, ethyl acetate, acetone, acetonitrile, methanol, isopropanol, 2,4,6-trimethylpyridine, and anhydrous magnesium sulfate were purchased from Aldrich. THF was distilled over benzophenone and sodium metal at a temperature of 50 ⁰C under nitrogen. Toluene was distilled over calcium hydride at a temperature of 120 ⁰C. The other solvents were used as purchased without further purification. Glassware was oven-dried and solvents such as tetrahydrofuran (THF) and toluene were freshly distilled prior to use. All 1H, 11B, 13C and 29Si NMR were acquired on an Agilent DirectDrive2 500 MHz NMR spectrometer equipped with a OneProbe operating at 500 MHz for 1H NMR, 160 MHz for 11B NMR, 126 MHz for 13C NMR, and 99 MHz for 29Si NMR CDCl3 or deuterated THF and recorded at 25 ⁰C. 1H-NMR spectra were recorded with 8-32 scans, a relaxation delay of 1s, and a pulse angle of 45⁰ and referenced to the residual protonated solvent in CDCl3 (7.24 ppm). 51 13C-NMR spectra were collected with 254 scans, a relaxation delay of 0.1 s, and a pulse angle 45⁰. 29Si NMR spectra were recorded with either 256 or 512 scans, a relaxation delay of 12 s and a pulse angle of 45⁰. Column chromatography was performed on EMD Millipore silica gel 60 columns of 40–63 Å silica, 230–400 mesh. Thin-layer chromatography (TLC) was performed on plates of EMD 250-µm silica 60-F254. High resolution mass spectroscopy was performed with APCI mass spectra recorded on a Finnigan LCQ Deca (ThermoQuest) technologies with LC/MS/MS (quadrupole/time-of- flight) and Waters Xevo G2-XS UPLC/MS/MS inert XL MSD with SIS Direct Insertion Probe. Melting points for all products were measured with a Thomas HOOVER capillary uni-melt melting point apparatus and are uncorrected. X-ray diffraction measurements were performed on a Stoe IPDS2 or a Bruker-AXS SMART APEX 2 CCD diffractometer using graphite-monochromated MoKα radiation. The structures were solved using direct methods (SHELXL-97) and refined by fullmatrix least-squares techniques against F2 (SHELXL-97). Cell parameters were retrieved using the SAINT (Bruker, V8.34A, S3 after 2013) software and refined using SAINT (Bruker, V8.34A, after 2013) on 5941 reflections, 47 % of the observed reflections. Data reduction was performed using the SAINT (Bruker, V8.34A, after 2013) software which corrects for Lorentz polarization. The yields reported are calculated by two methods. The first is based on the amount of compound 3 after step 1 in Scheme 2-13. This yield shows the overall efficiency of the route from the monoprotected material to the desired asymmetric product. The second method is based on the combined amounts of compounds 2 and 3 generated in step 1 of the same scheme for the yields of the symmetric products. 52 2.4.1.1 General Experimental Procedure for the Synthesis of DDSQ Boronate Esters Scheme 2-7: Synthesis of DDSQ Bis-boronate Esters 2 An oven-dried 100 mL round bottom flask equipped with a magnetic stir bar was charged with DDSQ tetraol 1 (1.96 mmol, 2.1g) and p-substituted phenylboronic acid (2.5 equiv, 5 mmol). The flask was fitted with a Dean-Stark apparatus and filled with nitrogen atmosphere. Toluene (40 mL) was added, and the mixture stirred over a pre-heated oil bath at a temperature of 115 ⁰C for 24 h or until full conversion of the DDSQ tetraol 1 was detected by TLC. The solvent was evaporated under reduced pressure to afford a white solid. Isopropanol (20 mL) was added to the flask bearing a magnetic stir bar and the mixture heated at 40 ⁰C for 20 minutes. The mixture was cooled to room temperature and filtered through a fine filter frit. The residue was washed with isopropanol (2 x 10 mL) and dried at reduced pressure to afford a pure white solid of the bis-protected cage (Table 2- 1). From this product, fine crystals appropriate for crystallographic analysis were obtained from a mixture of DCM/hexanes (1:3) of the Bis-boronate esters 2 (Table 2-2). The solid was characterized by 1H, 13C, 11B, 29Si NMR X-ray crystallography and LCMS measurements. The structures investigated in this study are listed in Figure 2-1 and Table 2-2. NMR, mass spectral and crystallographic data are shown in Appendix. 53 2.4.1.2 Deborylation of DDSQ Bis-boronate Ester with Pinacol Scheme 2-8: Deborylation of (p-MeOC6H4B)2DDSQ with Pinacol An oven-dried 50 mL round bottom flask bearing a magnetic stir bar was charged with p-MeO-C6H4B)2DDSQ (2) (0.65 g, 0.5 mmol) and pinacol (0.1182 g, 1 mmol, 2 equiv). The flask was placed under a nitrogen atmosphere and CHCl3 (10 mL) added to it. The reaction mixture was stirred at room temperature for 24 h. The heterogenous mixture was then filtered through a Buchner funnel using an aspirator. The residue was washed with 2 x 10 mL CHCl3, transferred to a beaker, and dried in an oven at 80 ⁰C for 5 h. The solid 1 (0.46 mmol, 92%) was analyzed by 1H, 13C, 11B and 29Si NMR. NMR data for the products are shown in Appendix. 2.4.1.3 General Procedure for Solubility Test for DDSQ(OH)4 in Different Organic Solvents Into a 20 mL vial bearing a stir bar was added 0.2 g of DDSQ tetraol (1) and the solvent (10 mL). The vial was sealed with a cap and the reaction mixture stirred at room temperature for 2 minutes. The mixture was suction filtered through a fine frit filter funnel. The filtrate was transferred to an oven-dried pre-weighed 20 mL vial and the solvent evaporated with a rotary evaporator. The vial was cooled to room temperature and the weight determined (Table 2-3). 54 2.4.1.4 General Experimental Procedures for the Multi-step Synthesis of Asymmetrically Functionalized DDSQs 2.4.1.4.1 Mono-borylation of DDSQ(OH)4 with p-MeOC6H4B(OH)2 (Step 1) Scheme 2-9: Monoborylation of DDSQ(OH)4 1 with p-MeO-C6H4B(OH)2 An oven-dried 100 mL round bottom flask equipped with a magnetic stir bar was charged with DDSQ(OH)4 1 (1.96 mmol, 2.1g) and p-methoxyphenylboronic acid (1 equiv, 1.96 mmol, 0.30 g). The flask was fitted with a Dean-Stark apparatus and filled with a nitrogen atmosphere. Toluene (40 mL) was added, and the mixture stirred in a pre-heated oil bath at 115 ⁰C. After 2 h, the resulting heterogeneous mixture was cooled to room temperature and suction filtered using a fine-fritted funnel and filter flask to isolate the unreacted DDSQ(OH)4. The residue was washed with toluene (2 x 10 mL) and filtered. The combined filtrate was evaporated under reduced pressure to afford a white solid. This solid is a mixture of both the mono- and bis-borylated cage and trace amounts of DDSQ(OH)4. Chloroform (20 mL) was added to dissolve the solid in the flask. The contents were cooled in a refrigerator at -5 ⁰C for 1 h and suction filtered using a fine- fritted funnel and a Buchner flask. The filtrate was dried by rotary evaporation to give a white solid. This dissolution in chloroform, refrigeration and filtration processes were repeated two times and the filtrate dried each time by rotary evaporation to give a white solid consisting of the bis- and mono-borylated cages in an average ratio of 3:1. The 55 resulting crude product was analyzed by 1H 11B, and 29Si NMR spectroscopy. It must be mentioned that all attempts to isolate the pure mono-borylated cage were unsuccessful. 2.4.1.4.2 General Procedure for the First Silylation of Mono-borylated DDSQ(OH)2 (3) - (Step 2) Scheme 2-10: Silylation of Mono-borylated Product, (p-MeOC6H4B)DDSQ(OH)2 with R1R2SiCl2 After isolating the recovered 1 by filtration, the crude product mixture (Scheme 2- 9) was charged into a pre-dried 100 mL round bottom flask bearing a magnetic stir bar and sealed with a septum. The flask was purged with dry nitrogen for 30 min and THF (20 mL) added to it. The flask was immersed into an ice bath and the contents stirred vigorously under nitrogen for 1 h. R1R2SiCl2 (x mmol, 1 equiv. based on the mono- borylated cage) in 5 mL THF was added first followed by dropwise addition of pyridine (2x mmol, 2 equiv. based on the mono-borylated cage) over a period of 10 minutes. The reaction mixture was stirred at 0 ⁰C for 4 h and at room temperature for 20 h. The suspension was filtered through a glass frit, the residue washed with THF (3 x 5 mL) and the solvent together with other volatiles removed from the filtrate by rotary evaporation to afford a white solid. This crude solid is a mixture of the bis-boronate DDSQ ester and the silylated mono-boronate DDSQ ester that forms the substrate for the next step. Reaction was followed by both 1H and 29Si NMR. 56 2.4.1.4.3 General Procedure for the Deborylation of a Mixture of (p-MeOC6H4B)- DDSQSiR1R2 and (p-MeOC6H4B)2DDSQ (Step 3) Scheme 2-11: Deborylation of (p-MeOC6H4B)DDSQSiR1R2 and (p-MeOC6H4B)2DDSQ with Pinacol The crude product mixture (Scheme 2-10) was charged into a pre-dried 100 mL round bottom flask bearing a magnetic stir bar, pinacol (2 mmol) and chloroform (10 mL) were added to the flask under nitrogen and the reaction mixture stirred vigorously at room temperature for 24 h. The crude mixture was initially completely soluble in chloroform, but gradually turned to a colloidal solution over time. After 24 h, the resulting white suspension was filtered with a fine-fritted filter funnel and a Buchner flask. The white powdered residue was washed with chloroform (3 x 5 mL), filtered, dried in an oven at 80 ⁰C for 5 h and characterized by 1H and 29Si NMR spectroscopy. The solvent and other volatiles were removed from the filtrate by rotary evaporation to afford a white solid/oily liquid which was similarly characterized by 1H, 11B, 13C and 29Si NMR spectroscopy. The solid from the crude filtrate which is mostly the monsilylated DDSQ(OH)2 and p-MeOC6H4Bpin was used as starting material for the next silylation. 57 2.4.1.4.4 General Procedure for the Second Silylation of Monosilylated DDSQ (5) Scheme 2-12: Second Silylation of Monosilylated Precursor, R1R2SiDDSQ(OH)2 The crude product mixture after isolating the DDSQ tetraol 1 (Scheme 2-11) was charged into an oven-dried 100 mL round bottom flask bearing a magnetic stir bar and a septum. The flask was purged with dry nitrogen for 30 min and THF (20 mL) added to it. The flask was immersed into an ice bath and the mixture stirred vigorously under nitrogen for 1 h. A suitable mono or di-substituted chlorosilane bearing R groups different from the former, R3R4SiCl2 (‘x’ equiv as in Step 1) in 5 mL THF was added followed by dropwise addition of pyridine (‘2x’ equiv) over a period of 10 minutes. The reaction mixture was stirred at 0 ⁰C for 4 h and at room temperature for 20 h. The suspension was filtered through a glass frit funnel, the residue washed with THF (3 x 5 mL) and the solvent together with other volatiles removed from the filtrate by rotary evaporation to afford a white solid/oil. This crude solid/oil is mostly the asymmetrically functionalized DDSQ cage and p-MeOC6H4Bpin. Reaction was followed by both 1H and 29Si NMR. All products were purified by flash column chromatography (ethylacetate:hexanes = 1:9 and in some cases ethylacetate:hexane = 1:16) and analyzed by 1H, 13C, 29Si and LCMS measurement. The chromatographed products were washed with hexanes to remove the p-MeOC6H4Bpin. The asymmetrically functionalized DDSQs synthesized in this study are listed in Table 2- 5 and the NMR data in Appendix. Copies of NMR and mass spectra are given in Appendix. 58 2.4.2 Synthetic Scope for Asymmetrically Functionalized Double-Decker Shaped Silsesquioxanes Scheme 2-13: Substrate Scope of the Multistep Pathway for the Synthesis of Asymmetrically Functionalized DDSQ To demonstrate the synthetic scope, the asymmetric products (Table 2-4) were synthesized following the route described above (Scheme 2-13). Two yields are reported for the asymmetric material. The first yield is based on the amount of compound 3 after step 1. This yield shows the overall efficiency of the route from the monoprotected material to the desired asymmetric product. The yield in parenthesis and the yields of symmetric by-products are based on the combined amounts of compounds 2 and 3 generated in step 1. Finally, the reported yield for compound 1 is based on the amount of material recovered in steps 1 and 3. 59 APPENDIX 60 NMR and Mass Spectral Data of Isolated Products Bis-borylated DDSQ (2) 9,19-bis(4-methoxyphenyl)-1,3,5,7,11,13,15,17-octaphenyl-2,4,6,8,10,12,14,16,18, 20,21,22,23,24-tetradecaoxa-1,3,5,7,11,13,15,17-octasila-9,19-diborapentacyclo[11. 7.1.13,11.15,17.17,15]tetracosane (2a) {(p-MeOC6H4B)2DDSQ} This product was isolated as a white crystalline solid in 2.50 g, 1.92 mmol (98%). mp 293 – 295 °C 1H NMR (500 MHz, CDCl3) δ (ppm) 7.74 – 7.61 (m, 8H), 7.60 – 7.54 (m, 4H), 7.53 – 7.15 (m, 32H), 6.75 – 6.64 (m, 4H), 3.71 (s, 6H). 11B NMR (160 MHz, CDCl3) δ (ppm) 29.9 13C NMR (126 MHz, CDCl3) δ (ppm) 138.12, 134.55, 134.52, 129.40, 128.59, 128.37, 128.34, 128.33, 128.14, 128.10, 125.69, 21.75. 29Si NMR (99 MHz, CDCl3) δ (ppm) -78.62, -80.38. 1,3,5,7,9,11,13,15,17,19-decaphenyl-2,4,6,8,10,12,14,16,18,20,21,22,23,24-tetrade- caoxa-1,3,5,7,11,13,15,17-octasila-9,19-diborapentacyclo[11.7.1.13,11.15,17.17,15] tetracosane (2b) {(C6H5B)2DDSQ} This product was isolated as a white crystalline solid in 2.31 g, 1.86 mmol (95%). mp 279 – 281 °C 1H NMR (500 MHz, CDCl3) δ (ppm) 7.67 – 7.61 (m, 10H), 7.54 – 7.11 (m, 41H). 13C NMR (126 MHz, CDCl3) δ (ppm) 135.80, 134.15, 134.13, 131.41, 131.26, 130.69, 130.59, 130.30, 127.97, 127.73, 127.54. 11B NMR (160 MHz, CDCl3) δ (ppm) 29.57 29Si NMR (99 MHz, CDCl3) δ (ppm) -78.62, -80.33. 61 1,3,5,7,11,13,15,17-octaphenyl-9,19-di-p-tolyl-2,4,6,8,10,12,14,16,18,20,21,22,23,24, tetradecaoxa-1,3,5,7,11,13,15,17-octasila-9,19-diborapentacyclo[11.7.1.13,11.15, 17.17,15]tetracosane (2c) {(p-tolylC6H4B)2DDSQ} This product was isolated as a white crystalline solid in 2.39 g, 1.88 mmol (96%). mp 289 – 291 °C 1H NMR (500 MHz, CDCl3) δ (ppm) 7.75 – 7.57 (m, 8H), 7.52 (d, J = 7.6 Hz, 4H), 7.50 – 7.18 (m, 32H), 6.99 (d, J = 7.7 Hz, 4H), 2.28 (s, 6H). 11B NMR (160 MHz, CDCl3) δ (ppm) 21.35 13C NMR (126 MHz, CDCl3) δ (ppm) 141.61, 135.91, 134.14, 131.37, 130.62, 130.35, 128.35, 127.68, 21.62. 29Si NMR (99 MHz, CDCl3) δ (ppm) -78.67, -80.39. Asymmetrically Functionalized DDSQs (6) (1r,3R,11s,13S)-9,9,19-trimethyl-1,3,5,7,11,13,15,17-octaphenyl-2,4,6,8,10,12,14,16, 18,20,21,22,23,24-tetradecaoxa-1,3,5,7,9,11,13,15,17,19-decasilapentacyclo[11.7.1. 13,11.15,17.17,15]tetracosane. (6a) Formula: C51H50O14Si10 This product was isolated as a white solid in 0.31 g, 0.27 mmol (79%). mp 266-268 °C 62 1H NMR (500 MHz, CDCl3) δ 7.57 – 7.16 (m, 40H), 4.98 (p, J = 1.5 Hz, 1H), 0.37 (t, J = 1.4 Hz, 3H), 0.30 (d, J = 1.2 Hz, 6H). 13C NMR (126 MHz, CDCl3) δ (ppm) δ 134.08, 133.93, 131.66, 127.83, 0.63, 0.56 29Si NMR (99 MHz, CDCl3) δ (ppm) -16.47 (1Si), -32.90 (1Si), -77.91 (2Si), -78.56 (2Si), -79.37 (2Si), -79.57 (2Si). LC/MS QTof: exact mass for C51H51O15Si10 [M+H]+ calculated m/z 1167.0966 found m/z 1167.0891 (1r,3R,11s,13S)-9,19,19-trimethyl-1,3,5,7,11,13,15,17-octaphenyl-2,4,6,8,10,12,14, 16,18,20,21,22,23,24-tetradecaoxo-1,3,5,7,9,11,13,15,17,19-decasilapentacyclo[11. 7.1.13,11.15,17.17,15]tetracosan-9-ol. (6b) Formula: C51H50O15Si10 This product was isolated as a white solid in 0.23 g, 0.19 mmol (61%). mp 256-258 °C 1H NMR (500 MHz, CDCl3) δ 7.57 – 7.16 (m, 40H), 0.35 (s, 3H), 0.30 (s, 6H). 13C NMR (126 MHz, CDCl3) δ 134.05, 131.99, 130.40, 127.83, 0.53, -3.90. 29Si NMR (99 MHz, CDCl3) δ -16.40 (1Si), -54.01 (1Si), -78.54 (2Si), -78.70 (2Si), -79.33 (2Si), -79.45 (2Si). LC/MS QTof: exact mass for C51H51O15Si10 [M+H]+ calculated m/z 1182.0842 found m/z 1183.0823 63 4-((1r,3R,11s,13S)-9,19-dimethyl-1,3,5,7,11,13,15,17-octaphenyl-2,4,6,8,10,12,14, 16,18,20,21,22,23,24-tetradecaoxa-1,3,5,7,9,11,13,15,17,19-decasilapentacyclo [11.7.1.13, 11.15,17.17,15]tetracosan-9-yl)butanenitrile. (6c) Formula: C54H53NO14Si10 This product was isolated as a white solid in 0.21 g, 0.17 mmol (52%). mp 204 - 206 1H NMR (500 MHz, CDCl3) δ (ppm) 7.55 – 7.18 (m, 40H), 4.98 (s, 1H), 2.17 (t, J = 7.0 Hz, 2H), 1.76 – 1.69 (m, 2H), 0.88 – 0.85 (m, 2H), 0.37 (s, 3H), 0.33 (s, 3H). 13C NMR (126 MHz, CDCl3) δ (ppm) 133.80, 131.60, 130.52, 127.84, 119.47, 29.70, 20.02, 19.43, 16.14. 29Si NMR (99 MHz, CDCl3) δ (ppm) -19.16 (1Si), -32.86 (1Si), -77.92 (2Si), -78.30 (2Si), -79.24 (1Si), -79.29 (1Si), -79.45 (1Si), -79.49 (1Si). LC/MS QTof: exact mass for for C54H53KNO14Si10 [M+K]+calculated m/z 1258.0790 found m/z 1259.0798 64 4-((1r,3R,11s,13S)-9,19,19-trimethyl-1,3,5,7,11,13,15,17-octaphenyl-2,4,6,8,10,12, 14,16,18,20,21,22,23,24-tetradecaoxa-1,3,5,7,9,11,13,15,17,19-decasilapentacy- clo[11.7.1.13,11.15,17.17,15]tetracosan-9-yl)butanenitrile. (6d) Formula: C55H55NO14Si10 This product was isolated as a white solid in 0.32 g, 0.26 mmol (81%). mp 218 – 220 1H NMR (500 MHz, CDCl3) δ (ppm) 7.54 – 7.17 (m, 40H), 2.17 (t, J = 7.0 Hz, 2H), 1.77 – 1.68 (m, 2H), 0.88 – 0.82 (m, 2H), 0.32 (s, 3H), 0.30 (s, 6H). 13C NMR (126 MHz, CDCl3) δ (ppm) 134.00, 133.99, 133.90, 133.82, 131.96, 131.67, 130.85, 130.53, 130.47, 130.39, 130.37, 127.90, 127.79, 127.74, 127.67, 20.03, 19.44, 16.14, 0.52, -0.89. 29Si NMR (99 MHz, CDCl3) δ (ppm) -16.48 (1Si), -19.24 (1Si), -78.36 (2Si), -78.63 (2Si), -79.48 (2Si), -79.53 (2Si). LC/MS QTof: exact mass for for C55H55KNO14Si10 [M+K]+ calculated m/z 1272.0947 found m/z 1273.0958 65 4-((1r,3R,11s,13S)-9,19,19-trimethyl-1,3,5,7,11,13,15,17-octaphenyl-2,4,6,8,10,12, 14,16,18,20,21,22,23,24-tetradecaoxa-1,3,5,7,9,11,13,15,17,19-decasilapentacy- clo[11.7.1.13,11.15,17.17,15]tetracosan-9-yl)butanenitrile. (6e) Formula: C55H55NO14Si10 This product was isolated as a white solid in 0.31 g, 0.25 mmol (74%). mp 218 – 220 1H NMR (500 MHz, CDCl3) δ (ppm) 7.59 – 7.15 (m, 40H), 2.17 (t, J = 7.0 Hz, 2H), 1.76 – 1.69 (m, 2H), 0.86 (dd, J = 7.4, 4.0 Hz, 2H), 0.32 (s, 3H), 0.30 (6H). 13C NMR (126 MHz, CDCl3) δ (ppm) 134.02, 131.98, 130.90, 130.40, 127.70, 119.50, 29.72, 19.46, 16.16, 14.16. 29Si NMR (99 MHz, CDCl3) δ (ppm) -16.48 (1Si), -19.24 (1Si), -78.36 (2Si), -78.63 (2Si), -79.48 (2Si), -79.53 (2Si). LC/MS QTof: exact mass for C55H55KNO14Si10 [M+K]+ calculated m/z 1272.0947 found m/z 1273.0958 66 4-((1s,3R,11r,13S)-9,19-dimethyl-1,3,5,7,11,13,15,17-octaphenyl-19-vinyl-2,4,6,8,10,12, 14,16,18,20,21,22,23,24-tetradecaoxa-1,3,5,7,9,11,13,15,17,19-decasilapentacyclo[11. 7.1.13,11.15,17.17,15]tetracosan-9-yl)butanenitrile. (6f) Formula: C56H55NO14Si10 This product was isolated as a white solid in 0.28 g, 0.22 mmol (65%). mp 220-222 1H NMR (500 MHz, CDCl3) δ (ppm) 7.54 – 7.18 (m, 40H), 6.13 (d, J = 20.2 Hz, 1H), 5.96 (d, J = 16.4 Hz, 2H), 2.17 (t, J = 7.0 Hz, 2H), 1.72 (dt, J = 16.6, 7.3 Hz, 2H), 0.87 (d, J = 5.5 Hz, 2H), 0.37 (s, 3H), 0.32 (s, 3H). 13C NMR (126 MHz, CDCl3) δ (ppm) 134.02, 133.83, 131.66, 130.42, 127.92, 127.80, 119.49, 29.71, 19.45, 16.15, 14.14, -1.16. 29Si NMR (99 MHz, CDCl3) δ (ppm) -19.23 (1Si), -31.38 (1Si), -78.35 (2Si), -78.43 (2Si), -79.47 (2Si) (d, J = 1.2 Hz), -79.51 (2Si) (d, J = 1.5 Hz). LC/MS QTof: exact mass for C56H55KNO14Si10 [M+K]+ calculated m/z 1284.0947 found m/z 1285.0961 67 (1r,3R,11s,13S)-9,19-dimethyl-1,3,5,7,11,13,15,17-octaphenyl-9-vinyl-2,4,6,8,10,12, 14,16,18,20,21,22,23,24-tetradecaoxa-1,3,5,7,9,11,13,15,17,19-decasilapentacyclo [11.7.1. 13,11.15,17.17,15]tetracosane. (6g) Formula: C52H50O14Si10 This product was isolated as a white solid in 0.19 g, 0.16 mmol (50%). mp 235-237 °C 1H NMR (500 MHz, CDCl3) δ (ppm) 7.59 – 7.14 (m, 40H), 6.15 (dd, J = 20.2, 15.0 Hz, 1H), 6.02 – 5.90 (m, 2H), 4.98 (s, 1H), 0.37 (s, 6H). 13C NMR (126 MHz, CDCl3) δ (ppm) 133.95, 131.88, 131.64, 130.40, 127.80, 127.63, - 1.15. 29Si NMR (99 MHz, CDCl3) δ (ppm) -31.37 (1Si), -32.91 (1Si), -77.90 (2Si), -78.36 (2Si), -79.35 (2Si), -79.56 (2Si). LC/MS QTof: exact mass for C52H51Si10NO14 [M+H]+ calculated m/z 1179.0966 found m/z 1181.0642 68 (1r,3R,11s,13S)-19-methyl-1,3,5,7,11,13,15,17-octaphenyl-9-vinyl-2,4,6,8,10,12,14, 16,18,20,21,22,23,24-tetradecaoxa-1,3,5,7,9,11,13,15,17,19-decasilapentacyclo [11.7.1.13, 11.15,17.17,15]tetracosan-9-ol. (6h) Formula: C51H48O15Si10 This product was isolated as a white solid in 0.27 g, 0.23 mmol (68%). Mp 235-237 °C 1H NMR (500 MHz, CDCl3) δ (ppm) 7.61 – 7.13 (m, 40H), 6.11 – 6.06 (m, 2H), 5.82 (m, 1H), 4.99 – 4.97 (m, 1H), 0.37 (d, J = 1.6 Hz, 3H). 13C NMR (126 MHz, CDCl3) δ (ppm) 136.90, 134.08, 133.98, 131.52, 130.51, 127.84, 14.14. 29Si NMR (99 MHz, CDCl3) δ (ppm) ¬-32.80 (1Si), -69.88 (1Si), -77.86 (2Si), -78.49 (2Si), -79.16 (1Si), -79.23 (1Si), -79.36 (1Si), -79.43 (1Si). LC/MS QTof: exact mass for C51H49Si10O15 [M+H]+ calculated m/z 1181.0759 found m/z 1181.0642 69 (1r,3R,11s,13S)-9-isopropyl-19-methyl-1,3,5,7,11,13,15,17-octaphenyl-19-vinyl-2,4,6, 8,10,12,14,16,18,20,21,22,23,24-tetradecaoxa-1,3,5,7,9,11,13,15,17,19-decasilapen- tacyclo[11.7.1.13,11.15,17.17,15]tetracosan-9-ol. (6i) Formula: C54H54O15Si10 This product was isolated as a white solid in 0.22 g, 0.18 mmol (56%). mp 228-230 °C 1H NMR (500 MHz, CDCl3) δ (ppm) 7.65 – 7.10 (m, 40H), 6.15 (m, 1H), 6.02 – 5.91 (m, 2H), 1.05 (d, J = 2.1 Hz, 6H), 0.38 – 0.33 (m, 3H). 13C NMR (126 MHz, CDCl3) δ (ppm) 134.07, 131.82, 131.53, 130.39, 127.81, 127.62, 16.90, 12.01, -1.18. 29Si NMR (99 MHz, CDCl3) δ (ppm) -31.34 (1Si), -55.89 (1Si), -78.36 (2Si), -78.96 (2Si), -79.38 (2Si), -79.51 (2Si). 70 Copies of NMR Spectra Bis-Boronate Esters (2) 9,19-bis(4-methoxyphenyl)-1,3,5,7,11,13,15,17-octaphenyl-2,4,6,8,10,12,14,16,18,- 20,21,22,23,24-tetradecaoxa-1,3,5,7,11,13,15,17-octasila-9,19-diborapentacyclo[11. 7.1.13,11.15,17.17,15]tetracosane (2a) Figure 2-11: 1H NMR (500 MHz, CDCl3) of (p-MeOC6H4B)2DDSQ 2a 71 Figure 2-12: 11B NMR (160 MHz, CDCl3) of (p-MeOC6H4B)2DDSQ 2a Figure 2-13: 13C NMR (126 MHz, CDCl3) of (p-MeOC6H4B)2DDSQ 2a 72 Figure 2-14: 29Si NMR (99 MHz, CDCl3) of (p-MeOC6H4B)2DDSQ 2a 73 1,3,5,7,9,11,13,15,17,19-decaphenyl-2,4,6,8,10,12,14,16,18,20,21,22,23,24-tetra decaoxa-1,3,5,7,11,13,15,17-octasila-9,19-diborapentacyclo[11.7.1.13,11.15,17.17, 15]tetracosane (2b) Figure 2-15: 1H NMR (500 MHz, CDCl3) of (C6H4B)2DDSQ 2b 74 Figure 2-16: 11B NMR (160 MHz, CDCl3) of (C6H4B)2DDSQ 2b Figure 2-17: 13C NMR (126 MHz, CDCl3) of (C6H4B)2DDSQ 2b 75 Figure 2-18: 29Si NMR (99 MHz, CDCl3) of (C6H4B)2DDSQ 2b 76 1,3,5,7,11,13,15,17-octaphenyl-9,19-di-p-tolyl-2,4,6,8,10,12,14,16,18,20,21,22,23,24- tetradecaoxa-1,3,5,7,11,13,15,17-octasila-9,19-diborapentacyclo[11.7.1.13,11.15, 17.17,15]tetracosane (2c) Figure 2-19: 1H NMR (500 MHz, CDCl3) of (p-MeC6H4B)2DDSQ 2c 77 Figure 2-20: 11B NMR (160 MHz, CDCl3) of (p-MeC6H4B)2DDSQ 2c Figure 2-21: 13C NMR (126 MHz, CDCl3) of (pMeC6H4B)2DDSQ 2c 78 Figure 2-22: 29Si NMR (99 MHz, CDCl3) of (C6H4B)2DDSQ 2c 79 Asymmetrically Functionalized Products (6) (1r,3R,11s,13S)-9,9,19-trimethyl-1,3,5,7,11,13,15,17-octaphenyl-2,4,6,8,10,12,14,16, 18,20,21,22,23,24-tetradecaoxa-1,3,5,7,9,11,13,15,17,19-decasilapentacyclo[11.7.1. 13,11.15, 17.17,15]tetracosane (6a) Figure 2-23: 1H NMR (500 MHz, CDCl3) of AB 6a 80 Figure 2-24: 13C NMR (126 MHz, CDCl3) of AB 6a Figure 2-25: 29Si NMR (99 MHz, CDCl3) of AB 6a 81 (1r,3R,11s,13S)-9,19,19-trimethyl-1,3,5,7,11,13,15,17-octaphenyl-2,4,6,8,10,12,14, 16, 18,20,21,22,23,24-tetradecaoxa-1,3,5,7,9,11,13,15,17,19-decasilapentacyclo [11.7.1. 13,11.15,17.17,15]tetracosan-9-ol (6b) Figure 2-26: 1H NMR (500 MHz, CDCl3) of AB 6b 82 Figure 2-27: 13C NMR (126 MHz, CDCl3) of AB 6b Figure 2-28: 29Si NMR (99 MHz, CDCl3) of AB 6b 83 4-((1r,3R,11s,13S)-9,19-dimethyl-1,3,5,7,11,13,15,17-octaphenyl-2,4,6,8,10,12,14, 16,18,20,21,22,23,24-tetradecaoxa-1,3,5,7,9,11,13,15,17,19-decasilapentacyclo [11.7.1. 13,11.15,17.17,15]tetracosan-9-yl)butanenitrile (6c) Figure 2-29: 1H NMR (500 MHz, CDCl3) of AB 6c 84 Figure 2-30: 13C NMR (126 MHz, CDCl3) of AB 6c Figure 2-31: 29Si NMR (99 MHz, CDCl3) of AB 6c 85 4-((1r,3R,11s,13S)-9,19,19-trimethyl-1,3,5,7,11,13,15,17-octaphenyl-2,4,6,8,10,12, 14,16,18,20,21,22,23,24-tetradecaoxa-1,3,5,7,9,11,13,15,17,19-decasilapentacyclo [11.7.1.13,11.15,17.17,15]tetracosan-9-yl)butanenitrile (6d) Figure 2-32: 1H NMR (500 MHz, CDCl3) of AB 6d 86 Figure 2-33: 13C NMR (126 MHz, CDCl3) of AB 6d Figure 2-34: 29Si NMR (99 MHz, CDCl3) of AB 6d 87 4-((1s,3R,11r,13S)-9,19-dimethyl-1,3,5,7,11,13,15,17-octaphenyl-19-vinyl-2,4,6,8,10, 12,14,16,18,20,21,22,23,24-tetradecaoxa-1,3,5,7,9,11,13,15,17,19-decasilapentacy- clo[11.7.1.13,11.15,17.17,15]tetracosan-9-yl)butanenitrile (6f) Figure 2-35: 1H NMR (500 MHz, CDCl3) of AB 6f 88 Figure 2-36: 13C NMR (126 MHz, CDCl3) of AB 6e Figure 2-37: 29Si NMR (99 MHz, CDCl3) of AB 6f 89 (1r,3R,11s,13S)-9,19-dimethyl-1,3,5,7,11,13,15,17-octaphenyl-9-vinyl-2,4,6,8,10,12, 14,16,18,20,21,22,23,24-tetradecaoxa-1,3,5,7,9,11,13,15,17,19-decasilapentacyclo [11.7.1.13,11.15,17.17,15]tetracosane (6g) Figure 2-38: 1H NMR (500 MHz, CDCl3) of AB 6g 90 Figure 2-39: 13C NMR (126 MHz, CDCl3) of AB 6g Figure 2-40: 29Si NMR (99 MHz, CDCl3) of AB 6g 91 (1r,3R,11s,13S)-19-methyl-1,3,5,7,11,13,15,17-octaphenyl-9-vinyl-2,4,6,8,10,12,14, 16,18,20,21,22,23,24-tetradecaoxa-1,3,5,7,9,11,13,15,17,19-decasilapentacyclo[11. 7.1.13, 11.15,17.17,15]tetracosan-9-ol (6h) Figure 2-41: 1H NMR (500 MHz, CDCl3) of AB 6h 92 Figure 2-42: 13C NMR (126 MHz, CDCl3) of AB 6h Figure 2-43: 29Si NMR (99 MHz, CDCl3) of AB 6h 93 (1r,3R,11s,13S)-9-isopropyl-19-methyl-1,3,5,7,11,13,15,17-octaphenyl-19-vinyl-2,4,6, 8,10,12,14,16,18,20,21,22,23,24-tetradecaoxa-1,3,5,7,9,11,13,15,17,19-decasilapen- tacyclo[11.7.1.13, 11.15,17.17,15]tetracosan-9-ol (6i) Figure 2-44: 1H NMR (500 MHz, CDCl3) of AB 6i 94 Figure 2-45: 13C NMR (126 MHz, CDCl3) of AB 6i Figure 2-46: 29Si NMR (99 MHz, CDCl3) of AB 6i 95 Copies of Mass Spectra of Asymmetrically Functionalized DDSQs (6) (1r,3R,11s,13S)-9,9,19-trimethyl-1,3,5,7,11,13,15,17-octaphenyl-2,4,6,8,10,12,14,16, 18,20,21,22,23,24-tetradecaoxa-1,3,5,7,9,11,13,15,17,19-decasilapentacyclo[11.7.1. 13, 11.15,17.17,15]tetracosane (6a) col 280 AB1 Me2T8MeH XS2_2012019_002 45 (0.471) 1: TOF MS AP+ 1107.0511 5.35e5 100 1167.0891 968.9725 % 908.9347 848.8972 1250.0891 0 m/z 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 2200 2300 2400 2500 2600 2700 2800 2900 Figure 2-47: Mass Spec of AB 6a 96 (1r,3R,11s,13S)-9,19,19-trimethyl-1,3,5,7,11,13,15,17-octaphenyl-2,4,6,8,10,12,14, 16, 18,20,21,22,23,24-tetradecaoxa-1,3,5,7,9,11,13,15,17,19-decasilapentacyclo [11.7.1.13,11.15,17.17,15]tetracosan-9-ol (6b) BDB 261 SPOT 2 ME2T8ME(OH) XS2_1232019_002 103 (1.049) Cm (103:120) 1: TOF MS AP+ 1044.9994 3.88e6 100 984.9651 1107.0342 1183.0829 % 924.9304 947.9427 846.8845 786.8481 663.4523 1238.1150 0 m/z 650 700 750 800 850 900 950 1000 1050 1100 1150 1200 1250 1300 1350 1400 1450 1500 1550 1600 1650 1700 1750 Figure 2-48: Mass Spec of AB 6b 97 4-((1r,3R,11s,13S)-9,19-dimethyl-1,3,5,7,11,13,15,17-octaphenyl-2,4,6,8,10,12,14, 16, 18,20,21,22,23,24-tetradecaoxa-1,3,5,7,9,11,13,15,17,19-decasilapentacyclo [11.7.1.13,11.15,17.17,15]tetracosan-9-yl)butanenitrile (6c) 270B XS2_121418_010 17 (0.222) Cm (17:26) 1: TOF MS AP+ 1259.0798 2.03e6 100 1260.0795 1258.0779 1261.0791 % 1262.0780 1238.1499 1237.1477 1263.0770 1082.0331 1021.9985 1084.0363 1264.0768 929.1948 1024.0006 1085.0355 1151.2467 838.2244 961.9639 1076.2255 1299.2805 1373.2986 1447.3167 1465.3236 0 m/z 850 900 950 1000 1050 1100 1150 1200 1250 1300 1350 1400 1450 Figure 2-49: Mass Spec of AB 6c 98 4-((1r,3R,11s,13S)-9,19,19-trimethyl-1,3,5,7,11,13,15,17-octaphenyl-2,4,6,8,10,12, 14,16,18,20,21,22,23,24-tetradecaoxa-1,3,5,7,9,11,13,15,17,19-decasilapentacyclo [11.7.1. 13,11.15,17.17,15]tetracosan-9-yl)butanenitrile (6d) 267 XS2_121418_007 17 (0.222) Cm (15:27) 1: TOF MS AP+ 1273.0958 2.37e6 100 1274.0952 1272.0939 1252.1663 1251.1643 1275.0951 % 1276.0941 1277.0934 1018.0062 1096.0543 1038.0173 1099.0542 1278.0939 975.9808 1039.0176 1157.0925 1326.1206 855.9089 915.9457 957.9707 1156.0902 1345.0314 1391.30381465.3280 0 m/z 850 900 950 1000 1050 1100 1150 1200 1250 1300 1350 1400 1450 Figure 2-50: Mass Spec of AB 6d 99 4-((1s,3R,11r,13S)-9,19-dimethyl-1,3,5,7,11,13,15,17-octaphenyl-19-vinyl-2,4,6,8,10, 12,14,16,18,20,21,22,23,24-tetradecaoxa-1,3,5,7,9,11,13,15,17,19-decasilapentacy- clo[11.7.1.13,11.15,17.17,15]tetracosan-9-yl)butanenitrile (6f) 269 XS2_121418_008 18 (0.230) Cm (17:24) 1: TOF MS AP+ 1285.0961 2.44e6 100 1286.0952 1284.0938 1287.0955 % 1264.1658 1263.1641 1288.0947 1289.0935 1108.0532 1048.0164 1290.0919 1111.0540 987.9819 1030.0066 1051.0176 1169.0916 927.9448 1254.1403 1291.0940 1371.11191391.3020 871.1788 1113.0524 1465.3219 0 m/z 850 900 950 1000 1050 1100 1150 1200 1250 1300 1350 1400 1450 Figure 2-51: Mass Spec of AB 6f 100 (1r,3R,11s,13S)-9,19-dimethyl-1,3,5,7,11,13,15,17-octaphenyl-9-vinyl-2,4,6,8,10,12, 14,16,18,20,21,22,23,24-tetradecaoxa-1,3,5,7,9,11,13,15,17,19-decasilapentacyclo [11.7.1.13,11.15,17.17,15]tetracosane (6g) BDB 277AB* MEHT8VI(OH) XS2_1232019_011 30 (0.320) Cm (30:39) 1: TOF MS AP+ 1181.0642 1.36e6 100 1144.0450 % 1205.0833 1236.1040 1163.0555 1198.0883 1228.1013 1171.0526 0 m/z 1135 1140 1145 1150 1155 1160 1165 1170 1175 1180 1185 1190 1195 1200 1205 1210 1215 1220 1225 1230 1235 1240 Figure 2-52: Mass Spec of AB 6g 101 19-methyl-1,3,5,7,11,13,15,17-octaphenyl-9-vinyl-2,4,6,8,10,12,14,16,18,20,21,22, 23,24-tetradecaoxa-1,3,5,7,9,11,13,15,17,19-decasilapentacyclo[11.7.1.13,11.15, 17.17,15]tetracosan-9-ol (6h) BDB 277AB3 MEHT8VI(OH) XS2_1232019_014 42 (0.446) Cm (42:50) 1: TOF MS AP+ 945.9255 1042.9840 5.45e6 100 982.9486 885.8904 1005.9614 922.9129 1103.0194 904.9016 964.9365 % 1181.0613 825.8556 844.8669 1084.0054 1144.0430 862.8776 784.8318 1205.0802 765.8198 802.8412 1236.1013 0 m/z 750 800 850 900 950 1000 1050 1100 1150 1200 1250 1300 1350 1400 1450 1500 Figure 2-53: Mass Spec of AB 6h 102 (1r,3R,11s,13S)-9-isopropyl-19-methyl-1,3,5,7,11,13,15,17-octaphenyl-19-vinyl-2,4, 6,8,10,12,14,16,18,20,21,22,23,24-tetradecaoxa-1,3,5,7,9,11,13,15,17,19-decasila- pentacyclo[11.7.1.13,11.15,17.17,15]tetracosan-9-ol (6i) BDB 278AA MEVIT8iPR(OH) XS2_1232019_017 108 (1.103) 1223.1230 100 1261.1302 % 1246.1342 1286.1372 1234.1124 1277.1365 1313.1740 1303.1536 1212.0759 1337.1385 1350.1311 0 1210 1220 1230 1240 1250 1260 1270 1280 1290 1300 1310 1320 1330 1340 1350 1360 1370 1380 Figure 2-54: Mass Spec of AB 6i 103 Copies of X-Ray Chrystallographic Data Crystallographic data for the three crystal structures reported in this manuscript have been deposited with the Cambridge Crystallographic Data Centre as supplementary publication no. CCDC-1843217 for C62H54B2O16Si8 (2a), 1823844 for C60H50B2O14Si8 (2b) and 1850462 C62H54B2O14Si8 (2c) Copies of the data can be obtained free of charge via the CCDC Website. 104 Table 2-6: Crystal Data and Structure Refinement for Compounds 2A - 2C 105 Table 2-7: Bond Lengths in Å for CCDC Atom Atom Length/Å 1843217 C21A C22A 1.394(7) Atom Atom Length/Å C22A C23A 1.369(9) Si1A O1A 1.598(3) C23A C24A 1.379(9) Si1A O4A 1.613(3) C24A C25A 1.376(7) Si1A O5A 1.613(3) C26A C27A 1.401(6) Si1A C8A 1.851(4) C26A C31A 1.389(6) Si2A O4A 1.610(3) C27A C28A 1.366(7) Si2A O6A 1.620(3) C28A C29A 1.382(7) Si2A O7A 1.613(3) C29A C30A 1.375(7) Si2A C14A 1.841(4) C30A C31A 1.388(6) Si3A O5A 1 1.615(3) Si1B O1B 1.614(3) Si3A O6A 1.599(3) Si1B O4B 1.617(3) Si3A O8A 1.612(3) Si1B O5B 1.611(3) Si3A C20A 1.843(5) Si1B C8B 1.842(4) Si4A O2A 1.610(3) Si2B O4B 1.617(3) Si4A O7A1 1.619(3) Si2B O6B 1.611(3) Si4A O8A 1.623(3) Si2B O7B 1.608(3) Si4A C26A 1.842(4) Si2B C14B 1.839(4) O1A B1A 1.335(6) Si3B O5B2 1.614(3) O2A B1A 1.358(6) Si3B O6B 1.609(3) O3A C4A 1.372(5) Si3B O8B 1.617(3) O3A C7A 1.440(7) Si3B C20B 1.847(4) O5A Si3A1 1.615(3) Si4B O2B 1.603(3) O7A Si4A 1 1.619(3) Si4B O7B2 1.616(3) C1A C2A 1.395(6) Si4B O8B 1.616(3) C1A C6A 1.418(6) Si4B C25B 1.852(4) C1A B1A 1.555(6) O1B B1B 1.357(6) C2A C3A 1.387(6) O2B B1B 1.363(6) C3A C4A 1.389(6) O3B C4B 1.369(5) C4A C5A 1.388(7) O3B C7B 1.407(6) C5A C6A 1.374(6) O5B Si3B2 1.614(3) C8A C9A 1.390(6) O7B Si4B2 1.616(3) C8A C13A 1.375(7) C1B C2B 1.396(6) C9A C10A 1.389(6) C1B C6B 1.399(6) C10A C11A 1.382(7) C1B B1B 1.558(6) C11A C12A 1.358(7) C2B C3B 1.391(6) C12A C13A 1.387(7) C3B C4B 1.382(6) C14A C15A 1.374(6) C4B C5B 1.379(6) C14A C19A 1.405(6) C5B C6B 1.406(6) C15A C16A 1.384(7) C8B C9B 1.379(6) C16A C17A 1.369(8) C8B C13B 1.366(7) C17A C18A 1.371(7) C9B C10B 1.376(7) C18A C19A 1.376(7) C10B C11B 1.340(8) C20A C21A 1.391(7) C11B C12B 1.365(9) C20A C25A 1.395(7) C12B C13B 1.384(8) 106 Table 2-7 (cont’d) Atom Atom Length/Å C14B C15B 1.383(6) C14B C19B 1.393(6) C15B C16B 1.380(7) C016 C20B 1.389(6) C016 C24B 1.388(6) C16B C17B 1.354(9) C17B C18B 1.349(9) C18B C19B 1.378(6) C20B C21B 1.387(6) C21B C22B 1.402(6) C22B C23B 1.369(7) C23B C24B 1.377(7) C25B C26B 1.388(6) C25B C30B 1.376(6) C26B C27B 1.383(7) C27B C28B 1.368(8) C28B C29B 1.369(8) C29B C30B 1.377(7) –––– 12-x,-y,1-z; 21-x,1-y,1-z 107 Table 2-8: Bond Angles in ° for CCDC Atom Atom Atom Angle/° 1843217 C9A C8A Si1A 120.9(3) C13A C8A Si1A 121.1(4) Atom Atom Atom Angle/° C13A C8A C9A 117.9(4) O1A Si1A O4A 107.8(2) C10A C9A C8A 121.6(5) O1A Si1A O5A 109.98(19) C11A C10A C9A 118.6(5) O1A Si1A C8A 109.32(18) C12A C11A C10A 120.5(4) O4A Si1A O5A 109.15(16) C11A C12A C13A 120.4(5) O4A Si1A C8A 111.88(19) C8A C13A C12A 121.0(5) O5A Si1A C8A 108.70(18) C15A C14A Si2A 121.0(4) O4A Si2A O6A 109.07(17) C15A C14A C19A 116.5(4) O4A Si2A O7A 110.70(17) C19A C14A Si2A 122.4(3) O4A Si2A C14A 107.91(18) C14A C15A C16A 122.3(5) O6A Si2A C14A 110.33(18) C17A C16A C15A 119.8(5) O7A Si2A O6A 106.65(16) C16A C17A C18A 119.9(5) O7A Si2A C14A 112.16(18) C17A C18A C19A 120.1(5) O5A1 Si3A C20A 107.70(17) C18A C19A C14A 121.5(5) O6A Si3A O5A1 108.70(17) C21A C20A Si3A 120.4(4) O6A Si3A O8A 109.50(16) C21A C20A C25A 118.3(5) O6A Si3A C20A 110.71(19) C25A C20A Si3A 121.0(4) O8A Si3A O5A1 108.94(16) C20A C21A C22A 119.9(6) O8A Si3A C20A 111.23(19) C23A C22A C21A 120.6(6) O2A Si4A O7A1 111.01(17) C22A C23A C24A 120.2(6) O2A Si4A O8A 108.15(17) C25A C24A C23A 119.6(6) O2A Si4A C26A 108.03(17) C24A C25A C20A 121.4(6) O7A1 Si4A O8A 110.67(16) C27A C26A Si4A 120.5(3) O7A1 Si4A C26A 109.62(18) C31A C26A Si4A 122.3(4) O8A Si4A C26A 109.30(18) C31A C26A C27A 117.3(4) B1A O1A Si1A 170.7(3) C28A C27A C26A 121.9(5) B1A O2A Si4A 152.4(3) C27A C28A C29A 119.9(5) C4A O3A C7A 117.3(4) C30A C29A C28A 119.7(5) Si2A O4A Si1A 150.6(2) C29A C30A C31A 120.2(5) Si1A O5A Si3A1 146.3(2) C30A C31A C26A 121.0(5) Si3A O6A Si2A 157.5(2) O1A B1A O2A 121.5(4) Si2A O7A Si4A1 144.3(2) O1A B1A C1A 120.7(4) Si3A O8A Si4A 150.8(2) O2A B1A C1A 117.7(4) C2A C1A C6A 116.9(4) O1B Si1B O4B 109.46(17) C2A C1A B1A 120.9(4) O1B Si1B C8B 110.34(18) C6A C1A B1A 122.2(4) O4B Si1B C8B 108.09(18) C3A C2A C1A 122.6(4) O5B Si1B O1B 107.99(16) C2A C3A C4A 118.4(4) O5B Si1B O4B 110.12(15) O3A C4A C3A 123.1(5) O5B Si1B C8B 110.83(17) O3A C4A C5A 115.6(4) O4B Si2B C14B 111.79(17) C5A C4A C3A 121.2(4) O6B Si2B O4B 108.22(17) C6A C5A C4A 119.5(4) O6B Si2B C14B 107.46(17) C5A C6A C1A 121.5(4) O7B Si2B O4B 109.20(15) 108 Table 2-8 (cont’d) C13B C8B Si1B 122.6(4) Atom Atom Atom Angle/° C13B C8B C9B 116.7(5) O7B Si2B O6B 109.90(15) C10B C9B C8B 121.6(5) O7B Si2B C14B 110.24(18) C11B C10B C9B 120.8(6) O5B 2 Si3B O8B 108.44(15) C10B C11B C12B 119.1(6) O5B2 Si3B C20B 110.40(16) C11B C12B C13B 120.3(6) O6B Si3B O5B2 107.59(15) C8B C13B C12B 121.4(6) O6B Si3B O8B 110.15(16) C15B C14B Si2B 123.2(4) O6B Si3B C20B 109.71(17) C15B C14B C19B 116.3(4) O8B Si3B C20B 110.49(17) C19B C14B Si2B 120.4(3) O2B Si4B O7B2 108.94(17) C16B C15B C14B 121.4(5) O2B Si4B O8B 110.27(16) C24B C016 C20B 121.5(4) O2B Si4B C25B 110.73(18) C17B C16B C15B 120.4(6) O7B 2 Si4B O8B 109.51(15) C18B C17B C16B 120.1(5) O7B2 Si4B C25B 109.64(17) C17B C18B C19B 120.0(6) O8B Si4B C25B 107.73(17) C18B C19B C14B 121.7(5) B1B O1B Si1B 143.0(3) C016 C20B Si3B 120.4(3) B1B O2B Si4B 165.0(3) C21B C20B Si3B 121.3(3) C4B O3B C7B 117.9(4) C21B C20B C016 118.1(4) Si2B O4B Si1B 146.4(2) C20B C21B C22B 120.5(4) Si1B O5B Si3B2 153.9(2) C23B C22B C21B 119.9(5) Si3B O6B Si2B 145.35(18) C22B C23B C24B 120.6(5) Si2B O7B Si4B2 162.2(2) C23B C24B C016 119.3(5) Si4B O8B Si3B 144.57(19) C26B C25B Si4B 119.3(3) C2B C1B C6B 117.3(4) C30B C25B Si4B 122.6(4) C2B C1B B1B 121.9(4) C30B C25B C26B 117.8(4) C6B C1B B1B 120.6(4) C27B C26B C25B 121.1(5) C3B C2B C1B 121.5(4) C28B C27B C26B 119.4(5) C4B C3B C2B 119.8(4) C27B C28B C29B 120.5(5) O3B C4B C3B 115.0(4) C28B C29B C30B 119.7(5) O3B C4B C5B 124.3(4) C25B C30B C29B 121.4(5) C5B C4B C3B 120.7(4) O1B B1B O2B 123.2(4) C4B C5B C6B 119.0(4) O1B B1B C1B 118.0(4) C1B C6B C5B 121.6(4) O2B B1B C1B 118.8(4) C9B C8B Si1B 120.5(3) –––– 12-x,-y,1-z; 21-x,1-y,1-z 109 Table 2-9: Hydrogen Fractional Atomic Coordinates (×104) and Equivalent Isotropic Displacement Parameters (Å2×103) for CCDC 1843217. Ueq is defined as 1/3 of the trace of the orthogonalised Uij. Atom x y z Ueq H2A 9395 1192 195 46 H3A 8890 1696 -1274 53 H5A 7590 1657 724 54 H6A 8096 1154 2176 48 H7AA 7812 2368 -2812 136 H7AB 8202 1807 -2694 136 H7AC 8400 2425 -2157 136 H9A 8277 1678 4376 51 H10A 7401 2026 4597 59 H11A 6759 1394 5333 65 H12A 6990 444 5842 79 H13A 7857 93 5580 67 H15A 9435 2024 6022 70 H16A 9538 2942 6892 94 H17A 9990 3031 8725 88 H18A 10326 2200 9695 79 H19A 10242 1286 8811 54 H21A 11031 1577 6776 74 H22A 11690 2307 7102 99 H23A 12269 2541 5662 103 H24A 12206 2046 3876 90 H25A 11570 1306 3554 67 H27A 10803 1489 1842 55 H28A 11352 1804 415 74 H29A 11613 1150 -1018 78 H30A 11294 188 -1037 71 H31A 10737 -132 402 56 H2B 6508 3432 2466 60 H3B 6838 2639 1436 65 H5B 6027 1512 3423 50 H6B 5661 2315 4400 45 H7BA 6821 723 1552 88 H7BB 6232 893 1949 88 H7BC 6745 928 2870 88 H9B 5063 2772 7059 58 H10B 4575 2115 8111 78 H11B 3653 2057 7819 102 H12B 3208 2665 6445 147 H13B 3695 3315 5352 103 H15B 2993 4553 4095 74 H016 5623 6194 1478 50 110 Table 2-9 (cont’d) Atom x y z Ueq H16B 2213 4428 2891 105 H17B 2265 4140 974 101 H18B 3094 4015 212 89 H19B 3882 4192 1360 61 H21B 4268 5247 720 48 H22B 4149 5734 -1089 60 H23B 4766 6440 -1596 65 H24B 5495 6688 -304 65 H26B 6542 5702 2767 66 H27B 7419 5995 2410 87 H28B 8144 5389 2964 84 H29B 8000 4494 3858 76 H30B 7126 4199 4193 58 111 Table 2-10: Bond Lengths in Å for CDCC Atom Atom Length/Å 1823844 C22 C23 1.380(5) Atom Atom Length/Å C23 C24 1.377(5) Si1 O1 1.599(3) C25 C26 1.397(5) Si1 O3 1.619(2) C25 C30 1.392(5) Si1 O4 1.607(2) C26 C27 1.382(5) Si1 C7 1.838(4) C27 C28 1.376(6) Si2 O3 1.611(2) C28 C29 1.371(6) Si2 O5 1.616(2) C29 C30 1.383(5) Si2 O6 1.617(2) Si5 O9 1.602(3) Si2 C13 1.836(4) Si5 O10 1.597(3) Si3 O2 1 1.621(2) Si5 O11 1.608(3) Si3 O5 1.610(2) Si5 C37 1.845(4) Si3 O7 1.622(3) Si6 O10 1.615(3) Si3 C19 1.842(4) Si6 O12 1.612(2) Si4 O4 1.621(2) Si6 O13 1.615(3) Si4 O61 1.620(2) Si6 C43 1.845(4) Si4 O7 1.619(2) Si7 O112 1.614(3) Si4 C25 1.828(4) Si7 O12 1.618(2) O1 B1 1.364(5) Si7 O14 1.610(3) O2 Si31 1.621(2) Si7 C49 1.823(4) O2 B1 1.377(5) Si8 O8 1.607(3) O6 Si4 1 1.620(2) Si8 O132 1.614(3) B1 C1 1.554(5) Si8 O14 1.608(3) C1 C2 1.385(5) Si8 C55 1.841(4) C1 C6 1.395(5) O8 B2 1.373(5) C2 C3 1.386(5) O9 B2 1.356(5) C3 C4 1.366(7) O11 Si72 1.614(3) C4 C5 1.355(8) O13 Si82 1.614(3) C5 C6 1.394(6) B2 C31 1.547(6) C7 C8 1.388(5) C31 C32 1.364(5) C7 C12 1.385(5) C31 C36 1.375(6) C8 C9 1.373(6) C32 C33 1.382(6) C9 C10 1.381(7) C33 C34 1.339(7) C10 C11 1.358(7) C34 C35 1.344(7) C11 C12 1.382(6) C35 C36 1.384(7) C13 C14 1.397(5) C37 C38 1.379(6) C13 C18 1.396(5) C37 C42 1.398(5) C14 C15 1.370(6) C38 C39 1.378(6) C15 C16 1.366(6) C39 C40 1.345(8) C16 C17 1.366(6) C40 C41 1.363(7) C17 C18 1.368(5) C41 C42 1.383(6) C19 C20 1.399(5) C43 C44 1.365(5) C19 C24 1.392(5) C43 C48 1.388(5) C20 C21 1.390(5) C44 C45 1.399(6) C21 C22 1.375(5) C45 C46 1.357(6) 112 Table 2-10 (cont’d) Atom Atom Length/Å C46 C47 1.367(6) C47 C48 1.384(5) C49 C50 1.528(10) C49 C50A 1.455(10) C49 C54 1.340(14) C49 C54A 1.292(15) C50 C51 1.395(12) C50A C51A 1.400(12) C51 C52 1.372(14) C51A C52A 1.308(15) C52 C53 1.399(19) C52A C53A 1.348(18) C53 C54 1.375(18) C53A C54A 1.385(19) C55 C56 1.399(5) C55 C60 1.389(5) C56 C57 1.379(5) C57 C58 1.372(6) C58 C59 1.367(6) C59 C60 1.390(5) –––– 11-x,1-y,2-z; 2-x,2-y,1-z 113 Table 2-11: Bond Angles in ° for CDCC Atom Atom Atom Angle/° 1823844 C12 C7 Si1 120.7(3) Atom Atom Atom Angle/° C12 C7 C8 117.9(4) O1 Si1 O3 108.08(14) C9 C8 C7 121.6(4) O1 Si1 O4 110.32(14) C8 C9 C10 119.8(5) O1 Si1 C7 110.94(15) C11 C10 C9 119.0(4) O3 Si1 C7 108.91(15) C10 C11 C12 121.8(5) O4 Si1 O3 109.44(13) C11 C12 C7 119.9(4) O4 Si1 C7 109.13(15) C14 C13 Si2 123.6(3) O3 Si2 O5 109.05(13) C18 C13 Si2 120.0(3) O3 Si2 O6 108.37(13) C18 C13 C14 116.4(4) O3 Si2 C13 112.28(14) C15 C14 C13 120.7(4) O5 Si2 O6 107.92(13) C16 C15 C14 121.2(4) O5 Si2 C13 109.61(15) C15 C16 C17 119.8(4) O6 Si2 C13 109.51(15) C16 C17 C18 119.5(4) O2 1 Si3 O7 108.60(13) C17 C18 C13 122.5(4) O21 Si3 C19 108.46(14) C20 C19 Si3 121.4(3) O5 Si3 O21 108.67(13) C24 C19 Si3 121.7(3) O5 Si3 O7 109.33(13) C24 C19 C20 116.9(3) O5 Si3 C19 111.04(15) C21 C20 C19 121.7(3) O7 Si3 C19 110.68(14) C22 C21 C20 119.5(4) O4 Si4 C25 109.67(15) C21 C22 C23 120.1(4) O6 1 Si4 O4 108.82(13) C24 C23 C22 120.1(4) O61 Si4 C25 109.72(15) C23 C24 C19 121.7(4) O7 Si4 O4 110.40(13) C26 C25 Si4 121.3(3) O7 Si4 O61 108.31(12) C30 C25 Si4 121.9(3) O7 Si4 C25 109.89(15) C30 C25 C26 116.8(3) B1 O1 Si1 157.5(3) C27 C26 C25 121.8(4) B1 O2 Si31 136.9(2) C28 C27 C26 119.7(4) Si2 O3 Si1 150.84(17) C29 C28 C27 120.2(4) Si1 O4 Si4 154.12(17) C28 C29 C30 119.9(4) Si3 O5 Si2 158.92(17) C29 C30 C25 121.7(4) Si2 O6 Si41 140.59(16) O9 Si5 O11 107.35(15) Si4 O7 Si3 145.11(16) O9 Si5 C37 110.88(16) O1 B1 O2 120.4(3) O10 Si5 O9 110.27(16) O1 B1 C1 120.1(3) O10 Si5 O11 110.76(14) O2 B1 C1 119.4(3) O10 Si5 C37 108.41(16) C2 C1 B1 121.8(4) O11 Si5 C37 109.19(16) C2 C1 C6 117.8(4) O10 Si6 O13 108.61(15) C6 C1 B1 120.3(4) O10 Si6 C43 111.27(15) C1 C2 C3 120.8(4) O12 Si6 O10 108.88(13) C4 C3 C2 120.4(5) O12 Si6 O13 109.95(14) C5 C4 C3 120.1(5) O12 Si6 C43 108.34(15) C4 C5 C6 120.5(5) O13 Si6 C43 109.78(15) C5 C6 C1 120.4(4) O112 Si7 O12 107.87(14) C8 C7 Si1 120.9(3) O112 Si7 C49 111.48(18) 114 Table 2-11 (cont’d) Atom Atom Atom Angle/° Atom Atom Atom Angle/° C50 C49 Si7 115.2(4) O12 Si7 C49 109.14(18) C50A C49 Si7 116.8(5) O14 Si7 O112 109.01(15) C54 C49 Si7 130.7(6) O14 Si7 O12 107.68(13) C54 C49 C50 112.0(7) O14 Si7 C49 111.52(17) C54A C49 Si7 124.7(7) O8 Si8 O132 109.58(14) C54A C49 C50A 115.2(8) O8 Si8 O14 108.88(14) C51 C50 C49 120.0(8) O8 Si8 C55 110.53(16) C51A C50A C49 119.4(9) O132 Si8 C55 109.37(15) C52 C51 C50 120.3(10) O14 Si8 O132 108.80(15) C52A C51A C50A 121.3(10) O14 Si8 C55 109.65(15) C51 C52 C53 120.7(9) B2 O8 Si8 142.6(3) C51A C52A C53A 117.6(12) B2 O9 Si5 158.4(3) C54 C53 C52 117.6(11) Si5 O10 Si6 160.10(19) C52A C53A C54A 123.0(15) Si5 O11 Si72 153.91(19) C49 C54 C53 127.5(12) Si6 O12 Si7 138.67(16) C49 C54A C53A 121.6(13) Si8 2 O13 Si6 152.60(19) C56 C55 Si8 118.6(3) Si8 O14 Si7 155.16(18) C60 C55 Si8 124.1(3) O8 B2 C31 119.1(3) C60 C55 C56 117.2(3) O9 B2 O8 121.4(3) C57 C56 C55 121.8(4) O9 B2 C31 119.4(3) C58 C57 C56 119.5(4) C32 C31 B2 122.2(4) C59 C58 C57 120.2(4) C32 C31 C36 115.2(4) C58 C59 C60 120.3(4) C36 C31 B2 122.5(4) C55 C60 C59 120.8(4) C31 C32 C33 123.3(4) –––– 11-x,1-y,2-z; 2-x,2-y,1-z C34 C33 C32 120.1(5) C33 C34 C35 118.5(5) C34 C35 C36 121.6(5) C31 C36 C35 121.2(5) C38 C37 Si5 122.3(3) C38 C37 C42 116.6(4) C42 C37 Si5 121.0(3) C39 C38 C37 121.3(5) C40 C39 C38 121.0(5) C39 C40 C41 120.1(5) C40 C41 C42 119.7(5) C41 C42 C37 121.4(5) C44 C43 Si6 121.1(3) C44 C43 C48 117.4(4) C48 C43 Si6 121.4(3) C43 C44 C45 120.8(4) C46 C45 C44 120.6(4) C45 C46 C47 119.9(4) C46 C47 C48 119.2(4) C47 C48 C43 122.0(4) 115 Table 2-12: Hydrogen Fractional Atomic Coordinates (×104) and Equivalent Isotropic Displacement Parameters (Å2×103) for CCDC 1823844. Ueq is defined as 1/3 of the trace of the orthogonalised Uij. Atom x y z Ueq H2 3063 9469 7708 56 H3 3104 10617 6604 87 H4 4565 10098 5713 118 H5 5961 8412 5899 114 H6 5915 7210 6987 73 H8 5019 5574 7090 59 H9 5445 4668 6127 86 H10 6988 3044 6083 82 H11 7972 2284 7048 79 H12 7552 3170 8023 58 H14 4544 3283 8100 51 H15 4291 1915 7669 73 H16 3818 494 8436 76 H17 3638 404 9661 67 H18 3870 1770 10106 51 H20 6545 1791 9090 41 H21 7580 220 8580 48 H22 8997 -1176 9156 50 H23 9418 -973 10217 53 H24 8349 554 10746 45 H26 8784 5142 8397 47 H27 10665 4909 8116 57 H28 11888 3867 8946 56 H29 11223 3098 10065 58 H30 9343 3327 10349 49 H32 5004 8128 3489 80 H33 6880 7114 3371 95 H34 7703 5991 4348 92 H35 6646 5952 5444 163 H36 4769 6985 5577 115 H38 2696 5979 6192 93 H39 3033 4695 7227 109 H40 2749 5246 8305 91 H41 2053 7111 8378 77 H42 1645 8424 7352 59 H44 1174 12282 6426 62 H45 1387 12864 7424 87 H46 691 12201 8554 64 H47 -207 10925 8709 58 H48 -383 10314 7720 56 H50 -261 13928 5135 78 H50A -1003 13916 3865 81 116 Table 2-12 (cont’d) Atom x y z Ueq H51 -8 15636 4679 85 H51A -732 15589 3303 85 H52 1182 15835 3638 81 H52A 1001 15697 3082 81 H53 1881 14440 2921 68 H53A 2410 14261 3599 78 H54 1749 12734 3424 61 H54A 2183 12606 4165 101 H56 469 11663 2785 50 H57 728 12815 1718 60 H58 2521 12663 1164 64 H59 4038 11281 1632 64 H60 3794 10138 2716 54 117 Table 2-13: Bond Lengths in Å for CCDC Atom Atom Length/Å 1850462 C24 C25 1.389(3) Atom Atom Length/Å C26 C27 1.398(3) Si1 O2 1.6169(13) C26 C31 1.396(3) Si1 O3 1.6159(13) C27 C28 1.383(3) Si1 O51 1.6098(13) C28 C29 1.381(4) Si1 C8 1.8507(18) C29 C30 1.377(3) Si2 O3 1.6162(13) C30 C31 1.387(3) Si2 O4 1.6256(12) Si5 O8 1.6165(14) Si2 O71 1.6156(13) Si5 O10 1.6063(15) Si2 C14 1.841(2) Si5 O132 1.6155(14) Si3 O4 1.6143(14) Si5 C39 1.8483(19) Si3 O5 1.6163(13) Si6 O10 1.6101(15) Si3 O6 1.6146(12) Si6 O11 1.6153(14) Si3 C20 1.8437(17) Si6 O12 1.6195(13) Si4 O1 1.6100(13) Si6 C45 1.838(2) Si4 O6 1.6223(13) Si7 O12 1.6148(12) Si4 O7 1.6126(13) Si7 O13 1.6145(15) Si4 C26 1.8421(18) Si7 O14 1.6190(14) O1 B1 1.362(3) Si7 C51 1.8493(18) O2 B1 1.366(3) Si8 O9 1.6072(16) C1 C2 1.398(3) Si8 O112 1.6164(14) C1 C6 1.391(3) Si8 O14 1.6105(14) C1 B1 1.559(2) Si8 C57 1.8486(19) C2 C3 1.398(3) O8 B2 1.370(3) C3 C4 1.379(4) O9 B2 1.352(3) C4 C5 1.390(4) C32 C33 1.391(3) C4 C7 1.514(3) C32 C37 1.387(3) C5 C6 1.385(3) C32 B2 1.552(3) C8 C9 1.402(3) C33 C34 1.384(3) C8 C13 1.399(3) C34 C35 1.368(3) C9 C10 1.387(3) C35 C36 1.377(4) C10 C11 1.381(3) C35 C38 1.506(3) C11 C12 1.381(3) C36 C37 1.385(4) C12 C13 1.390(3) C39 C40 1.392(3) C14 C15 1.398(3) C39 C44 1.404(3) C14 C19 1.396(3) C40 C41 1.391(3) C15 C16 1.379(4) C41 C42 1.378(4) C16 C17 1.378(4) C42 C43 1.374(4) C17 C18 1.377(4) C43 C44 1.393(3) C18 C19 1.386(3) C45 C46 1.395(5) C20 C21 1.395(3) C45 C46A 1.560(5) C20 C25 1.385(3) C45 C50 1.324(5) C21 C22 1.386(3) C45 C50A 1.337(5) C22 C23 1.377(4) C46 C47 1.386(6) C23 C24 1.368(4) C46A C47A 1.396(6) 118 Table 2-13 (cont’d) Atom Atom Length/Å C47 C48 1.359(11) C47A C48A 1.366(10) C48 C49 1.366(10) C48A C49A 1.388(9) C49 C50 1.372(7) C49A C50A 1.384(8) C51 C52 1.395(3) C51 C56 1.389(3) C52 C53 1.391(3) C53 C54 1.379(3) C54 C55 1.382(3) C55 C56 1.393(3) C57 C58 1.394(3) C57 C62 1.396(3) C58 C59 1.386(3) C59 C60 1.372(4) C60 C61 1.374(4) C61 C62 1.395(3) –––– 11-x,-y,2-z; 2-x,1-y,1-z 119 Table 2-14: Bond Angles in ° for CCDC Atom Atom Atom Angle/° 1850462 C13 C8 C9 117.21(17) Atom Atom Atom Angle/° C10 C9 C8 121.38(18) O2 Si1 C8 108.34(7) C11 C10 C9 120.1(2) O3 Si1 O2 108.56(7) C12 C11 C10 119.95(19) O3 Si1 C8 109.69(8) C11 C12 C13 119.93(19) O5 1 Si1 O2 108.65(7) C12 C13 C8 121.45(19) O51 Si1 O3 110.09(7) C15 C14 Si2 121.16(16) O5 1 Si1 C8 111.45(8) C19 C14 Si2 121.38(16) O3 Si2 O4 108.62(7) C19 C14 C15 117.4(2) O3 Si2 C14 109.58(8) C16 C15 C14 121.1(2) O4 Si2 C14 109.67(7) C17 C16 C15 120.5(2) O71 Si2 O3 110.52(7) C18 C17 C16 119.7(2) O7 1 Si2 O4 108.40(7) C17 C18 C19 120.1(2) O71 Si2 C14 110.01(8) C18 C19 C14 121.3(2) O4 Si3 O5 108.27(7) C21 C20 Si3 119.35(14) O4 Si3 O6 107.99(7) C25 C20 Si3 122.89(14) O4 Si3 C20 109.37(8) C25 C20 C21 117.68(17) O5 Si3 C20 109.14(8) C22 C21 C20 121.4(2) O6 Si3 O5 108.89(7) C23 C22 C21 119.5(2) O6 Si3 C20 113.07(7) C24 C23 C22 120.2(2) O1 Si4 O6 108.24(7) C23 C24 C25 120.3(2) O1 Si4 O7 110.73(7) C20 C25 C24 120.9(2) O1 Si4 C26 110.80(8) C27 C26 Si4 121.05(15) O6 Si4 C26 108.17(7) C31 C26 Si4 119.98(14) O7 Si4 O6 109.85(7) C31 C26 C27 118.30(17) O7 Si4 C26 109.01(8) C28 C27 C26 120.8(2) B1 O1 Si4 151.40(13) C29 C28 C27 119.9(2) B1 O2 Si1 143.99(13) C30 C29 C28 120.4(2) Si1 O3 Si2 150.75(9) C29 C30 C31 120.0(2) Si3 O4 Si2 140.19(8) C30 C31 C26 120.7(2) Si1 1 O5 Si3 157.38(9) O1 B1 O2 121.78(16) Si3 O6 Si4 151.34(9) O1 B1 C1 120.04(17) Si4 O7 Si21 153.32(10) O2 B1 C1 118.18(17) C2 C1 B1 121.59(18) O8 Si5 C39 110.41(9) C6 C1 C2 117.41(18) O10 Si5 O8 108.30(8) C6 C1 B1 120.93(18) O10 Si5 O132 108.65(9) C1 C2 C3 120.7(2) O10 Si5 C39 111.24(9) C4 C3 C2 121.1(2) O132 Si5 O8 109.37(8) C3 C4 C5 118.30(19) O132 Si5 C39 108.84(8) C3 C4 C7 121.1(2) O10 Si6 O11 108.53(8) C5 C4 C7 120.6(2) O10 Si6 O12 107.46(7) C6 C5 C4 120.8(2) O10 Si6 C45 110.77(10) C5 C6 C1 121.6(2) O11 Si6 O12 109.23(8) C9 C8 Si1 120.90(14) O11 Si6 C45 111.96(9) C13 C8 Si1 121.88(14) O12 Si6 C45 108.78(8) 120 Table 2-14 (cont’d) Atom Atom Atom Angle/° Atom Atom Atom Angle/° C47A C46A C45 120.7(4) O12 Si7 O14 109.80(7) C48 C47 C46 119.8(5) O12 Si7 C51 107.76(8) C48A C47A C46A 121.0(5) O13 Si7 O12 109.49(7) C47 C48 C49 121.0(6) O13 Si7 O14 108.68(7) C47A C48A C49A 119.5(8) O13 Si7 C51 109.11(8) C48 C49 C50 119.1(6) O14 Si7 C51 111.96(8) C50A C49A C48A 120.1(8) O9 Si8 O112 107.07(8) C45 C50 C49 120.0(5) O9 Si8 O14 110.87(8) C45 C50A C49A 127.7(5) O9 Si8 C57 110.95(9) C52 C51 Si7 121.38(14) O112 Si8 C57 108.36(8) C56 C51 Si7 120.69(14) O14 Si8 O112 110.98(8) C56 C51 C52 117.89(17) O14 Si8 C57 108.59(8) C53 C52 C51 121.21(19) B2 O8 Si5 140.62(15) C54 C53 C52 120.0(2) B2 O9 Si8 163.59(16) C53 C54 C55 119.7(2) Si5 O10 Si6 154.42(10) C54 C55 C56 120.2(2) Si6 O11 Si82 152.04(10) C51 C56 C55 121.01(19) Si7 O12 Si6 141.03(8) C58 C57 Si8 120.76(17) Si7 O13 Si52 148.89(10) C58 C57 C62 117.82(19) Si8 O14 Si7 163.75(10) C62 C57 Si8 121.27(16) C33 C32 B2 120.73(18) C59 C58 C57 121.2(2) C37 C32 C33 116.0(2) C60 C59 C58 120.1(3) C37 C32 B2 123.3(2) C59 C60 C61 120.2(2) C34 C33 C32 122.3(2) C60 C61 C62 120.1(3) C35 C34 C33 120.9(2) C61 C62 C57 120.7(2) C34 C35 C36 117.7(2) O8 B2 C32 116.76(18) C34 C35 C38 121.0(2) O9 B2 O8 122.3(2) C36 C35 C38 121.3(2) O9 B2 C32 120.95(18) C35 C36 C37 121.6(2) –––– 11-x,-y,2-z; 2-x,1-y,1-z C36 C37 C32 121.5(2) C40 C39 Si5 124.41(16) C40 C39 C44 118.02(19) C44 C39 Si5 117.53(16) C41 C40 C39 120.9(2) C42 C41 C40 120.0(2) C43 C42 C41 120.5(2) C42 C43 C44 119.9(2) C43 C44 C39 120.7(2) C46 C45 Si6 117.0(2) C46A C45 Si6 117.7(2) C50 C45 Si6 118.8(2) C50 C45 C46 121.3(3) C50A C45 Si6 131.2(3) C50A C45 C46A 111.1(3) C47 C46 C45 117.1(4) 121 Table 2-15: Hydrogen Fractional Atomic Coordinates (×104) and Equivalent Isotropic Displacement Parameters (Å2×103) for CCDC 1850462. Ueq is defined as 1/3 of the trace of the orthogonalised Uij Atom x y z Ueq H2 5472.33 2326.14 6841.24 42 H3 5069.34 3522.87 5788.71 54 H5 2678.34 5666.91 6898.42 47 H6 3023.42 4453.26 7942.55 37 H7A 3730.98 6121.1 5507.75 87 H7B 2742.43 5669.69 5550.22 87 H7C 3938.97 5091.66 5147.28 87 H9 1723.92 4305.69 9298.6 37 H10 685.44 5885.49 9763.15 44 H11 1065.1 6184.68 10780.78 43 H12 2490.68 4897.75 11335.36 42 H13 3535.7 3313.04 10873.76 33 H15 738.61 1617.16 9742.36 47 H16 -1127.97 1871.61 10043.43 63 H17 -1843.75 1062.59 11143.89 58 H18 -678.29 -3.64 11951.14 54 H19 1193.49 -244.98 11663.81 39 H21 3812.79 -3171.07 10047.08 46 H22 3640.03 -4509.88 9547.49 68 H23 3943.31 -4362.31 8321.11 71 H24 4425.49 -2897.52 7601.42 64 H25 4569.72 -1538.65 8096.03 41 H27 5125.04 481.73 7083.98 34 H28 5529.54 -594.71 6221.69 49 H29 6897.94 -2288.37 6306.44 57 H30 7863.18 -2915.2 7251.62 51 H31 7460.23 -1850.69 8123.03 36 H33 5005.83 3457.58 3525.16 44 H34 6802.25 2328.48 3336.72 50 H36 6311.42 515.63 5244.53 90 H37 4522.19 1659.67 5449.85 73 H38A 8140.77 478.62 3657.45 83 H38B 8001.39 -126.26 4462.78 83 H38C 8394.45 930.55 4260.51 83 H40 3843.41 5338.95 2756.93 48 H41 4114.44 6451.74 1664.28 60 H42 2615.48 7647.47 1148.51 58 H43 844.52 7696.52 1692.11 52 H44 559.16 6549.53 2769.77 42 H46 -175.24 8597.18 3441.09 43 H46A -92.49 8978.78 5108.92 41 H47 429.72 10119.8 2921.37 55 123 Table 2-15 (cont’d) Atom x y z Ueq H47A 407.37 10556.91 4666.36 54 H48 1852.59 10313.15 3309.13 61 H48A 1523.73 10740.89 3581.47 60 H49 2651.99 9064.48 4228.02 77 H49A 2191.51 9313.98 2928.52 77 H50 2034.67 7572.9 4739.02 57 H50A 1744.96 7748.92 3346.16 59 H52 -257.85 5142.88 7702.74 42 H53 -105.48 5784.39 8664.32 51 H54 497.96 7290.48 8477.22 54 H55 944.08 8156.64 7324.97 55 H56 762.95 7535.34 6362.11 42 H58 2731.27 1065.54 6244.47 50 H59 3134.45 -149.54 7285.12 67 H60 2735.46 489.6 8344.81 68 H61 1915.54 2344.74 8374.31 63 H62 1495.31 3578.73 7334.88 46 124 REFERENCES 125 REFERENCES (1) Ye, Q.; Zhou, H.; Xu, J. 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(33) Software for the Integration of CCD Detector System Bruker Analytical X-ray Systems, Bruker axs, Madison, WI (after 2013). 128 CHAPTER 3.0: Synthesis of Incompletely Condensed Asymmetrically Functionalized Double-Decker Shaped Silsesquioxane Disilanols ‘Bird Nest- Shaped Silsesquioxanes’ 3.1 INTRODUCTION Incompletely condensed silsesquioxanes constitute a class of organosilicon hybrid materials with exceptional physico-chemical properties not realized from pure organic and inorganic compounds.1–13 They are generally three-dimensional cage-like nanostructures with free transformable moieties that are amenable to numerous functional groups (Figure 3-1). The structural arrangement of atoms/groups in these compounds makes them ideal precursors for several applications including their utility as ligands in catalysis, as drug delivery agents in medicine and as fillers for the synthesis of telechelic, hemitelechelic and beads-on-chain composite architectures. The tetrafuntional, trifunctional and various bifunctional analogues are known.14–18 Figure 3-1: Representative Incompletely Condensed Silsesquioxanes These compounds can be accessed from both monomeric trifunctional organo chloro/alkoxy silanes5 (Scheme 3-1) or from the fully condensed POSS cages under both acidic7,19,20 (Scheme 3-2 Path A) and basic8 (Scheme 3-2 Path B) conditions. 129 Scheme 3-1: Hydrolysis of cyclopentyltrichlorosilane into heptacyclopentyl POSS trisilanol Scheme 3-2: Selective cleavage of completely condensed octacyclohexyl silsesquioxane for the synthesis of octacyclohexyl POSS disilanol (Path A) and heptacyclohexyl POSS trisilanol (Path B) Credit for the synthesis of such compounds from fully condensed precursors is given to Feher and coworkers for developing not only the first synthetic modification of these cages via selective cleavage of one Si-O-Si linkage but also for demonstrating various other routes that have led to the increased pool of incompletely condensed POSS compounds. In their seminal report, Feher and coworkers disclosed that the treatment of cubic silsesquioxanes of the R8Si8O12 type with strong acids (HX) afforded open cage structures, which upon hydrolysis yielded the R8Si8O11(OH)2 frameworks.7 Such POSS scaffolds are flexible starting materials for the synthesis of a wide range of functional silsesquioxane and metallasilsesquioxane frameworks.2,8,21,22 Prior to 130 their work, only a handful of synthetically useful incompletely condensed POSS cages bearing bulky organic groups were known and these were solely obtained from the hydrolytic condensation of trifunctional silanes.23 However, with the discoveries8,10,20 that fully-condensed [RSiO3/2]n frameworks can undergo selective cleavage by strong acids and bases, a wide range of novel incompletely-condensed frameworks were obtained. Compared to other nanoparticles, their unique thermal stability, chemical/oxidative resistance, low dielectric constant and mechanical properties have found applications in polymer and material sciences. More applications emerged after the discovery of the double-decker oligomeric silsesquixane in 2004.14,21–26 3.2 Modifications of Incompletely Condensed POSS Cages There are quite a good number of transformations that have been conducted on various incompletely condensed POSS compounds leading to the generation of new functional materials for various applications. The symmetric tetrafunctional double decker has for instance been modified into fully condensed bifunctional siloxanes using suitable chlorosilanes. Depending on the type of capping agent used, products obtained from the side-capping can either be a single compound (Scheme 3-3) or one that displays geometric isomerism (Schemes 3-4).15,27–33 Scheme 3-3: Condensation of DDSQ(OH)4 with diphenyldichlorosilane 131 Scheme 3-4: Condensation of DDSQ(OH)4 with 3-cyanopropyl(methyl)dichlorosilane The cis/trans forms have been isolated by various groups and shown to display different properties like solubility and melting temperatures.34,35 Similarly, incompletely condensed trisilanols have been modified via corner-capping with various reactive groups leading to condensed structures with complete control over the functionalized POSS architecture (Scheme 3-5). Scheme 3-5: Synthesis of difunctional POSS, phenyl7anilinePOSS from heptaphenylPOSS trisilanol Metal-bearing POSS structures are also obtained via similar corner-capping approaches (Scheme 3-6)36–38 132 Scheme 3-6: Condensation of trisilanol POSS for the synthesis of metallasilsesquioxane Difunctional POSS precursors have also been transformed into various derivatives via the addition of unique difunctional organic groups to generate materials with properties that are distinct from those of the constituent reactants (Scheme 3-7). Like other incompletely condensed POSS cages, such modified POSS-based functional materials also impact intrinsic properties including thermal stability and mechanical properties on the nanocomposite. Scheme 3-7: Functionalization of POSS endo disilanol with MeHSiCl2 and subsequent hydrosilylation 3.2.1 Tetrafunctional Polyhedral Oligomeric Silsesquioxanes and their Derivatives The tetrafunctional POSS frameworks generally come in three forms; the half cube with the basic molecular composition of R4T4(OH)4,39,40 the homologated analogue with R6T6(OH)44 and the unique double-decker bearing two well-defined cyclic 133 tetraphenylsiloxane decks linked together by two oxygen atoms with the four drooping functional groups symmetrically arranged in pairs on opposite ends (Figure 3-2).14 Figure 3-2: Tetrafunctional Polyhedral Oligomeric Silsesquioxanes These cage-like silsesquioxanes have been obtained from both the monomeric trifunctional chloro/alkoxy silane and the cubic POSS precursors. However, among them, the symmetric nature of DDSQ(OH)4 with its rigid three-dimensional framework bearing phenyl coronae is particularly interesting. The well-defined assembly of the atoms accords this compound the molecular flexibility for easy functionalization via side-capping. By virtue of its size and structure, transformation affords macromolecular frameworks that are useful for a myriad of applications. The modified materials have a low dielectric constant and excellent thermal and oxidative stability, good optical and mechanical properties.31,41–49 The growing appeal for these properties on composite materials makes the double- decker oligomeric silsesquioxane tetrasilanol the most explored of the tetrafunctional polyhedral oligomeric silsesquioxanes. Whereas research opportunities keep growing for the synthesis of novel symmetrically functionalized condensed POSS templates, the silsesquioxane bearing two distinct reactive functionalities could be an even more intriguing molecular template. We recently reported a route (Chapter 2) using protecting group strategies with aryl boronic acid to selectively mask two silanols on the 134 DDSQ(OH)4. Even though this technique was superior to prior routes, it suffered from the generation of unwanted symmetric byproduct. One way we envisioned to address this limitation was to isolate either the monoborylated DDSQ diol or the one-side silylated DDSQ(OH)2. In this study, we developed a route that yields the POSS disilanol equivalent with some modifications to our previous protocol. The disilanols synthesized in this study offered the asymmetrically capped products in excellent yields upon post functionalization. Their architecture also makes them ideal precursors for modifying solid supports like carbon fibres. 3.2.2 Asymmetrically Functionalized DDSQs Until recently, functionalized DDSQs were exclusively the closed bifunctional siloxanes that are often incorporated into the polymer backbone as ‘beads-on-a- chain.27,44,45,50–53 The well-defined architecture of the double-decker precursor allows their transformation into diverse functional macromers ideal for post functional elaboration. From an application viewpoint, the post functionalized derivatives are limited to linking identical polymers on either side of the functionalized cages. Even though siloxanes bridging polymers in this manner have shown to reinforce the composite properties such as strength, modulus, dielectric properties, oxidative resistance, flammability and glass transition temperature (Tg),27,54,55 attempts to cluster analogous POSS linkers that are able to link dissimilar polymers has been a long-standing challenge. One way to overcome this problem is to destroy the symmetry in DDSQ(OH)4 by transforming it into the asymmetrically functionalized equivalent. Whilst formation of symmetric bi-functional DDSQs appears simple, the selective reactivity of the silanols in DDSQ against different capping agents remains a serious challenge. The few 135 modification strategies known to date are via O-silylation, hydrosilylation and O-borylation of the silanol groups with chlorosilanes and boronic acids respectively to afford either closed T8D232,49,56 or T8D257,58 or open polymeric58 siloxane frameworks. An illustration of some of these strategies is shown in Scheme 3-8. These preliminary discoveries laid the platform for the resulting siloxanes to be grafted to the backbone of two different polymer matrices.32,49,56 One route currently undergoing development in our laboratory involves accessing condensed asymmetric DDSQs via controlled hydrosilylation of bi- functionalized cages. The Marciniec group also reported a Grubb’s catalyzed metathesis of a pre-functionalized DDSQ cage.56 Our group also recently reported two routes for the synthesis of these type of POSS cages; one involving addition of a premixture of different capping/coupling agents to DDSQ(OH)432 and the other, a protecting group strategy.49 136 Scheme 3-8: Known routes into asymmetrically functionalized DDSQs These developments opened the avenue to a new class of POSS cages that have potential to modulate the performance of the POSS/polymer composite by regulating the motions of the dissimilar polymeric matrices to which these cages are anchored. Unfortunately, all these approaches have their associated limitations. The hydrosilylation pathway, still under development in our lab is restricted to prefunctionalized 137 MeHSiDDSQSiMeH and allyl-containing reagents for elaboration; the metathesis route by Zac et al. is limited to a pre-functionalized symmetric R(vi)SiDDSQSiR(vi), styryl coupling partners; the chlorosilane pre-mixture path is restrained by its requirement of a trichlorosilane as a second coupling partner and the generation of a large amount of unwanted symmetrically functionalized DDSQs; and lastly, the boronic acid course, requires multiple steps and also generates symmetric products to ̴ 8%. Figure 3-3: Monborylated DDSQ(OH)2 Efforts to improve the latter protocol via various attempts to isolate the key monoborylated DDSQ(OH)2 (Figure 3-3) have been unsuccessful to date. However, we modified our previous strategy to enable us isolate the asymmetric T 8D1 monosilylated DDSQ(OH)2 after the first silylation. Herein, we present for the first time a strategy to modify DDSQ(OH)4 for the selective synthesis of asymmetric monosilylated DDSQ(OH)2. Such functionalized DDSQs are versatile precursors for the efficient synthesis of a wide range of asymmetric DDSQs, several metallasilsesquioxanes and ligands for solid supports. The starting material in this study is the bisborylated DDSQ which is obtained from the DDSQ(OH)4. The approach herein referred to as the “reverse approach” consists of three steps, viz. (i) selective deprotection, (ii) silylation and finally (iii) global deprotection. The bis-borylated ester is first subjected to partial deborylation, then silylated with an appropriate di-/tri-chlorosilane and the resulting crude mixture finally exposed to global deborylation affording the targeted monosilylated DDSQ disilanol 138 (Scheme 3-9). Illustrations of their synthetic utility as model precursors for the synthesis of completely condensed asymmetrically functionalized DDSQs afforded excellent yields. Scheme 3-9: Synthetic route into R1R2SiDDSQ(OH)2 (5) It is worth mentioning here that in steps (i) and (iii), DDSQ(OH)4 (1) is isolated and used to synthesize more bisborylated DDSQ starting material. Unlike our previously reported protocol “the forward approach”,49 this strategy yields more of the key intermediate monoborylated DDSQ (3) (mono:bis-boronate ester 〜 1:2) and is free from adventitious boronic acid that may alter the composition of the crude in step 1. 139 3.3 Results and Discussions 3.3.1 Optimization of (p-MeOC6H4B)2DDSQ(OH)2 (3) Scheme 3-10: Optimal deborylation of 2 with pinacol for the synthesis of 3 Table 3-1: Optimization for the partial deborylation of (p-MeOC6H4B)2DDSQ (2) for the synthesis of monoborylated DDSQ diol (3) Reaction conditions: 0.25 mmol 2, pinacol (x equiv). Residue from crude mixture is pure 1 obtained after filtration. Amounts of 2 and 3 were determined from 1H-NMR. Selective deborylation with varying amounts of pinacol at different reaction times never exclusively afford the target monoborylated DDSQ(OH)2 (3). In all cases, a product mixture consisting of the partially deborylated DDSQ (3), the completely deborylated cage (1) and some starting materials (2) were obtained. Even though 1 can be separated from this mixture due to its poor solubility in chloroform, attempts to isolate 3 from 2 using various techniques has been unsuccessful. Interesting though, good nmr ratios of 2:3 was obtained with good throughputs using conditions in entries 3, 5 and 6. Conditions in entry 140 3 were deemed optimal because of the high ratio of 2:3 (0.096 mmol:0.071 mmol) and because these conditions afforded the highest throughput (0.21 g) of product that could be taken to the next step. With this route, symmetric AA in negligible amounts could only arise from adventitious 1 that may have escaped during the filtration process (solubility of 1 in CHCl3 = 5.8 mg/mL). 3.3.2 Substrate Scope Scheme 3-11: Synthesis of asymmetrically functionalized R1R2SiDDSQ(OH)2 (5) All reactions were monitored using 1H, 11B, and 29Si spectroscopy. The target R1R2SiDDSQ(OH)2 were further purified by flash chromatography using ethylacetate:hexane (1:9) as the eluting solvent. 141 Table 3-2: Substrate scope for the synthesis of asymmetric monosilylated DDSQ(OH) 2 (5) Conditions: aReactions were run on 1 mmol scale of 2, btotal amount of 1 generated in steps I and III, cyields of 5 are based on 3, dyields of 6 are obtained after subtracting the amount of 1 generated from 1 mmol of 2 in step 1. The yields of 5 are calculated based on the amount of 3 obtained in step 1, and those for 6, after subtracting the amount of 1 obtained in this same step from the starting material (2). It is noteworthy that the recovery of 1 is crucial as this material can always be used to make the bis-boronate DDSQ ester (2). The strategy is amenable to a wide range of capping agents affording moderate to high yields of 5 (Table 3-2). The spectral data for all functionalized 5 shows resonances that are in agreement with the proposed structures and the high-resolution mass spectrometry are in excellent agreement with the calculated theoretical masses (Appendix). 142 3.3.3 Transformation of Monosilylated DDSQ diol into Condensed Asymmetric DDSQs (7) Table 3-3: Post Functionalization of asymmetric monosilylated DDSQ(OH)2 (5) into Completely Condensed Asymmetric DDSQs of the D2T8 Type Conditions: Reactions were run on 0.1 mmol scale of 5, Yields of 7 are obtained after washing the crude with hexanes and pentanes without further purifications. 143 3.3.4 Spectral Data for Asymmetric R1R2DDSQ(OH)2 15-Methyl-1,3,5,7,9,11,13,17-octaphenyl-2,4,6,8,10,12,14,16,18,19,20,21-dodecaoxa- 1,3,5,7,9,11,13,15,17-nonasilatetracyclo[9.7.1.15,17.17,13]henicosane-3,9-diol (5a) C49H46O14Si9 This product was isolated as a white solid in 52% yield (0.16 mmol). mp 189–192 ⁰C. 1H NMR (500 MHz, CDCl3) δ (ppm) 7.53 – 7.14 (m, 40H), 5.06 (s, 2H), 4.97 (q, J = 1.6 Hz, 1H), 0.36 (d, J = 1.6 Hz, 3H). 13C NMR (126 MHz, CDCl3) δ (ppm) 134.24, 134.10, 134.07, 134.06, 133.90, 131.46, 130.88, 130.71, 130.59, 130.48, 130.43, 127.86, 127.80, 127.65, 127.62, 0.61. 29Si NMR (99 MHz, CDCl3) δ (ppm) -32.83, -68.57, -77.94, -79.06, -79.25. 15,15-Dimethyl-1,3,5,7,9,11,13,17-octaphenyl-2,4,6,8,10,12,14,16,18,19,20,21-dode- caoxa-1,3,5,7,9,11,13,15,17-nonasilatetracyclo[9.7.1.15,17.17,13]henicosane-3,9-diol (5b) C50H48O14Si9 This product was isolated as a white solid in 58% yield (0.15 mmol). mp 179–182 ⁰C. 1H NMR (500 MHz, CDCl3) δ (ppm) 7.52 – 7.14 (m, 40H), 5.04 (s, 2H), 0.29 (s, 6H). 144 13C NMR (126 MHz, CDCl3) δ (ppm) 134.22, 134.08, 133.89, 131.96, 130.85, 130.80, 130.61, 130.36, 130.33, 127.80, 127.75, 127.62., 0.51. 29Si NMR (99 MHz, CDCl3) δ (ppm) -16.48, -68.63, -78.65, -79.30. 15,15-Diethyl-1,3,5,7,9,11,13,17-octaphenyl-2,4,6,8,10,12,14,16,18,19,20,21-dodeca- oxa-1,3,5,7,9,11,13,15,17-nonasilatetracyclo[9.7.1.15,17.17,13]henicosane-3,9-diol (5c) C52H52O14Si9 This product was isolated as a white solid in 52% yield (0.14 mmol). mp 147–150 ⁰C. 1H NMR (500 MHz, CDCl3) δ (ppm) 7.51 – 7.13 (m, 40H), 0.98 (t, J = 7.9 Hz, 6H), 0.70 (q, J = 8.0 Hz, 4H). 13C NMR (126 MHz, CDCl3) δ (ppm) 134.26, 134.23, 134.13, 134.12, 134.10, 134.07, 134.03, 133.90, 133.86, 132.05, 130.91, 130.88, 130.60, 130.43, 130.34, 130.28, 127.80, 127.78, 127.75, 127.71, 127.68, 127.63, 127.61, 6.89, 6.32. 29Si NMR (99 MHz, CDCl3) δ (ppm) -16.80, -68.69, -78.91, -79.37. 145 4-(3,9-Dihydroxy-15-methyl-1,3,5,7,9,11,13,17-octaphenyl-2,4,6,8,10,12,14,16,18,19, 20,21-dodecaoxa-1,3,5,7,9,11,13,15,17-nonasilatetracyclo[9.7.1.15,17.17,13]henico- san-15-yl)butanenitrile (5d). C53H51NO14Si9 This product was isolated as a white solid in 51% yield (0.14 mmol). mp 128–131 ⁰C. 1H NMR (500 MHz, CDCl3) δ (ppm) 7.52 – 7.12 (m, 40H), 5.20 (s, 2H), 2.25 (m, 2H), 1.81 – 1.59 (m, 2H), 0.84 (ddd, J = 8.4, 6.1, 2.8 Hz, 2H), 0.34 (s, 3H). 13C NMR (126 MHz, CDCl3) δ (ppm) 134.22, 134.14, 134.11, 134.04, 134.03, 133.95, 133.80, 131.50, 130.70, 130.55, 130.47, 127.94, 127.90, 127.87, 127.85, 127.81, 127.74, 127.74, 127.68, 127.62, 20.03, 19.41, 16.12. 29Si NMR (99 MHz, CDCl3) δ (ppm) -19.19, -68.59, -78.37, -79.18 (d, J = 3.7 Hz). 15-Methyl-1,3,5,7,9,11,13,17-octaphenyl-15-vinyl-2,4,6,8,10,12,14,16,18,19,20,21-do- decaoxa-1,3,5,7,9,11,13,15,17-nonasilatetracyclo[9.7.1.15,17.17,13]henicosane-3,9-diol (5e) C51H48O14Si9 This product was isolated as a white solid in 61% yield (0.18 mmol). mp 148–150 ⁰C. 146 1H NMR (500 MHz, CDCl3) δ (ppm) 7.54 – 7.17 (m, 40H), 6.18 – 6.09 (m, 1H), 6.01 – 5.89 (m, 2H), 0.38 – 0.34 (m, 3H). 13C NMR (126 MHz, CDCl3) δ (ppm) 134.49, 134.22, 134.08, 133.92, 131.75, 130.87, 130.73, 130.64, 130.39, 127.82, 127.75, 127.63, 127.58, -1.20. 29Si NMR (99 MHz, CDCl3) δ (ppm) -31.37, -68.61, -78.45, -79.28 (d, J = 1.7 Hz). 15-Allyl-15-methyl-1,3,5,7,9,11,13,17-octaphenyl-2,4,6,8,10,12,14,16,18,19,20,21-do- decaoxa-1,3,5,7,9,11,13,15,17-nonasilatetracyclo[9.7.1.15,17.17,13]henicosane-3,9-diol (5f) C52H50O14Si9 This product was isolated as a white solid in 58% yield (0.11 mmol). mp 183–186 ⁰C. 1H NMR (500 MHz, CDCl3) δ (ppm) 7.52 – 7.15 (m, 40H), 5.76 (ddt, J = 16.9, 10.1, 8.0 Hz, 1H), 5.03 (s, 2H), 4.85 (dq, J = 17.0, 1.6 Hz, 1H), 4.75 (ddt, J = 10.2, 2.2, 1.1 Hz, 1H), 1.83 – 1.68 (m, 2H), 0.29 (s, 3H). 13C NMR (126 MHz, CDCl3) δ (ppm) 134.22, 134.07, 133.93, 132.66, 131.73, 130.82, 130.74, 130.73, 130.64, 130.40, 130.37, 127.81, 127.74, 127.63, 114.84, 24.53, -1.66. 29Si NMR (99 MHz, CDCl3) δ (ppm) -22.00, -68.64, -78.69, -79.30 (d, J = 2.5 Hz). 147 15-Methyl-1,3,5,7,9,11,13,17-octaphenyl-2,4,6,8,10,12,14,16,18,19,20,21-dodecaoxa- 1,3,5,7,9,11,13,15,17-nonasilatetracyclo[9.7.1.15,17.17,13]henicosane-3,9,15-triol (5g) C49H46O15Si9 This product was isolated as a white solid in 55% yield (0.16 mmol). mp 193–196 ⁰C. 1H NMR (500 MHz, CDCl3) δ (ppm) 7.58 – 7.12 (m, 40H), 0.34 (s, 3H). 13C NMR (126 MHz, CDCl3) δ (ppm)134.22, 134.11, 134.09, 134.07, 134.04, 134.03, 134.00, 133.95, 130.70, 130.61, 130.58, 130.54, 130.52, 130.49, 127.87, 127.86, 127.83, 127.82, 127.72, 127.69, 127.67, 127.64, -3.87, -3.90. 29Si NMR (99 MHz, CDCl3) δ (ppm)-54.05 (1Si), -68.54 (2Si), -78.72 (2Si), -79.02 (2Si), - 79.12 (2Si). 15-Isopropyl-1,3,5,7,9,11,13,17-octaphenyl-2,4,6,8,10,12,14,16,18,19,20,21-dodeca- oxa-1,3,5,7,9,11,13,15,17-nonasilatetracyclo[9.7.1.15,17.17,13]henicosane-3,9,15-triol (5h) C51H50O15Si9 This product was isolated as a white solid in 58% yield (0.16 mmol). mp 164–167 ⁰C. 148 1H NMR (500 MHz, CDCl3) δ (ppm) 7.54 – 7.07 (m, 40H), 5.52 (s, 2H), 1.03 (d, J = 1.6 Hz, 6H), 0.88 (ddt, J = 11.6, 9.9, 4.6 Hz, 1H). 13C NMR (126 MHz, CDCl3) δ (ppm) 134.16, 134.13, 134.08, 134.04, 134.00, 133.93, 131.38, 130.69, 130.65, 130.62, 130.58, 130.44, 130.42, 130.40, 127.83, 127.78, 127.72, 127.68, 127.63, 127.59, 16.87, 11.97. 29Si NMR (99 MHz, CDCl3) δ (ppm) -55.95, -68.72, -79.02, -79.14, -79.27. 3.3.5 Structural Characterization by 29Si NMR Spectroscopy Characterization of the product cages was based on identifying chemically equivalent silicon atoms in the structures displayed. Color coding/numbers on the silicon atoms is used to match the various silicons in the proposed structure to that of the resonances in the spectra. 149 5a C49H46O14Si9 5a Figure 3-4: Stacked 29Si NMR of AB diol 5a and AA 6a Figure 3-4 is the stacked spectra for symmetric Me(H)SiDDSQSiMe(H) (6a) (bottom) and the asymmetric Me(H)SiDDSQ diol (5a) (top). Spectra for 5a displays five (5) peaks characteristic of the five chemically different Si atoms in the structure; one D- silicon and four different pairs of T-silicons. Symmetric 6a shows three chemically equivalent Si atoms (two D-silicons and two different sets of four T-silicons) with the triplet resonance at -79 ppm indicating the cis/trans configurations of the two D-silicons relative 150 to the internal silicons (purple). The unique peak at -68 ppm (top) is characteristic of the silanol silicons (Si#5) in 5a. 5b C50H48O14Si9 Figure 3-5: Stacked 29Si NMR of AB diol 5b and AA 6b Figure 3-5 gives the stacked 29Si NMR spectra for asymmetric Me2SiDDSQ(OH)2 (5b) (top) and symmetric Me2SiDDSQSiMe2 6b (bottom). 5b shows four different sets of silicon atoms; one D-silicon (Si#1) and three sets of chemically equivalent silicons (Si#2, Si#3 and Si#4). Symmetric 6b displays 3 different sets of silicons; two D-silicons (blue), 151 the four silicons next to the D-silicons (green) and the four internal silicons (purple). The unique resonance at δ -69 ppm denotes the two silanol silicons (Si#4) in 5b. 5c C52H52O14Si9 Figure 3-6: Stacked 29Si NMR of AB diol 5c and AA 6c Figure 3-6, the stacked 29Si NMR spectra for asymmetric Et2SiDDSQ(OH)2 (5c) (bottom) and symmetric Et2SiDDSQSiEt2 6c (bottom). There are four chemically equivalent silicons in 5c corresponding to the four different signals in the spectra (bottom) with the matching color codes. The symmetric analogue, 6c (top), has three different silicons; two D-silicons (blue) and two sets of T-silicons (green and purple). The unique peak at δ -68 ppm denotes the two silanol silicons in 5c (Si#4, bottom) shows four different 152 sets of silicon atoms; one D-silicon (Si#1) and three sets of chemically equivalent silicons (Si#2, Si#3 and Si#4). Symmetric 6c displays three different sets of silicons; two D- silicons (blue), the four silicons next to the D-silicons (green) and the four internal silicons (purple). The unique resonance at δ -69 ppm denotes the two silanol silicons (Si#4) in 5c. 5d C53H51NO14Si9 Figure 3-7: Stacked 29Si NMR of AB diol 5d and AA 6d Figure 3-7, the stacked 29Si NMR spectra for asymmetric (3CNPr)(Me)SiDDSQ(OH)2 (5d) (bottom) and symmetric (3CNPr)(Me)SiDDSQSi(3CNPr)(Me) 6d (top). 5d has four chemically equivalent silicons; 153 one D-silicon (Si#1) and three sets of T-silicons (Si#2, Si#3 and Si#4) corresponding to the resonances in the spectra (bottom). 6d on the other hand (top) has three signals: two D-silicons (blue) and two sets of T-silicons (green and purple). However, unlike 6d, 5d shows a unique peak at δ -68 ppm corresponding to the two silanol silicons on 5d. 5e C51H48OSi9 Figure 3-8: Stacked 29Si NMR of AB diol 5e and AA 6e Figure 3-8, the stacked 29Si NMR spectra for asymmetric Me(vinyl)SiDDSQ(OH)2 (5e) (bottom) and symmetric Me(vinyl)SiDDSQSiMe(vinyl) 6e (top). There are four 154 chemically equivalent silicons in 5e corresponding to the four different signals in the spectra (bottom) with the matching color codes. The symmetric analogue, 6e (top), has three different silicons; two D-silicons (blue) and two sets of T-silicons (green and purple). The T-silicon signal at δ -79 ppm (purple) is a triplet denoting the cis/trans configuration of the two D-silicons relative to the internal silicons (purple). The unique peak at δ -68 ppm denotes the two silanol silicons in 5e (Si#4, bottom). 5f C52H50O14Si9 Figure 3-9: Stacked 29Si NMR of AB diol 5f and AA 6f 155 Figure 3-9 is the stacked 29Si NMR spectra for asymmetric (allyl)(Me)SiDDSQ(OH)2 (5f) (top) and symmetric (allyl)(Me)SiDDSQSi(allyl)(Me) 6f (bottom). 5f has four chemically equivalent silicons; one D-silicon (Si#1) and three sets of T-silicons (Si#2, Si#3 and Si#4) corresponding to the resonances in the spectra (top). Unlike 5f, 6f (bottom) has three signals: two D-silicons (blue) and two sets of T-silicons (green and purple). However, 5f shows a unique peak at δ -68 ppm corresponding to the two silanol silicons on the structure. 5g C49H46O15Si9 Figure 3-10: Stacked 29Si NMR of AB diol 5g and AA 6g 156 Figure 3-10 shows the 29Si NMR spectra for symmetric (Me)(OH)SiDDSQSi(OH)(Me) 6g (top) stacked with that for the asymmetric (Me)(OH)SiDDSQ(OH)2 (5g) (bottom). 5g exhibits five Si resonances, all of which are T- silicons. All resonances are upfield shifted in the T-silicon region, with the most downfield signal at -54.05 ppm being the bridging silicon having the Me and OH group. (blue, Si#1), and the signal at -68.54 ppm denoting the two silanol silicons (pink, Si#5). Si#2 (green) are the two T-silicons next to Si#1. The remaining signals in the 78.70 – 79.15 ppm range are two sets of chemically equivalent silicons (2 x Si#3, red and 2 x Si#4, purple) depending on the orientation of the groups on Si#1. On the other hand, 6g (top) has four unique signals; all being T-silicons: Two bridging silicon (blue) for the resonance at - 54.22, four green silicons at -78.64 ppm, and two sets of internal silicons (red and purple) in the -79.12 to -79.24 range with silicons consistent to the cis/trans conformation on the blue silicons. 157 5h C51H50O15Si9 Figure 3-11: 29Si NMR of AB diol 5h Figure 3-11 is the 29Si NMR spectra of asymmetric (Me)(OH)SiDDSQ(OH)2 (5h). 5h has five Si resonances, all of which are T-silicons. Like 5g which also has exclusively T-silicons, all resonances are relatively upfield shifted. Si#1 (blue), the most downfield signal at -55.95 ppm is the bridging silicon having the iPr and OH group. The signal at - 68.72 ppm denotes the two silanol silicons (pink, Si#5). Si#2 (green) at -79.02 ppm is the bridging T-silicons next to Si#1. The remaining signals at -79.14 (Si#3, red) and 79.27 158 (Si#5, light red) ppm are the four interchangeable innermost silicons relative to the orientation of the iPr and OH substituents on Si#1. 3.3.6 NMR and Mass Spectral Data for Condensed Asymmetric D2T8 Silsesquioxanes 9-(3-Isocyanatopropyl)-9,19-dimethyl-1,3,5,7,11,13,15,17-octaphenyl-2,4,6,8,10,12, 14,16,18,20,21,22,23,24-tetradecaoxa-1,3,5,7,9,11,13,15,17,19-decasilapentacyclo [11.7.1.13,11.15,17.17,15]tetracosane (7a) C54H53NO15Si10 This product was isolated as a white solid (81%). mp 196-199 ⁰C. 1H NMR (500 MHz, CDCl3) δ (ppm) 7.55 – 7.18 (m, 40H), 4.98 (p, J = 1.6 Hz, 1H), 3.13 (t, J = 6.8 Hz, 2H), 1.67 (ddt, J = 11.2, 8.3, 6.8 Hz, 2H), 0.78 – 0.72 (m, 2H), 0.37 (t, J = 1.5 Hz, 3H), 0.31 (s, 3H). 13C NMR (126 MHz, CDCl3) δ (ppm) 134.03, 134.01, 134.00, 133.98, 133.92, 133.83, 131.52, 130.49, 130.47, 130.42, 127.88, 127.86, 127.83, 127.72, 127.69, 127.65, 127.64, 45.34, 24.87, 13.76, 0.62, 0.20, -0.89. 29Si NMR (99 MHz, CDCl3) δ (ppm) -18.30 (1Si), -32.87 (1Si), -77.93 (2Si), -78.41 (2Si), -79.31 (d, J = 3.0 Hz, 2Si), -79.51 (d, J = 3.1 Hz, 2Si). LC/MS QTof: exact mass for C54H54NO15Si10 [M+H]+ calculated m/z 1236.1181 found m/z 1236.1089 159 9,9,19-Trimethyl-1,3,5,7,11,13,15,17-octaphenyl-19-vinyl-2,4,6,8,10,12,14,16,18,20, 21,22,23,24-tetradecaoxa-1,3,5,7,9,11,13,15,17,19-decasilapentacyclo[11.7.1.13, 11.15, 17.17,15]tetracosane (7b) C53H52O14Si10 This product was isolated as a white solid (100%). mp 250–253 ⁰C. 1H NMR (500 MHz, CDCl3) δ (ppm) 7.55 – 7.16 (m, 40H), 6.15 (dd, J = 20.2, 15.0 Hz, 1H), 6.04 – 5.87 (m, 2H), 0.37 (s, 3H), 0.30 (s, 6H). 13C NMR (126 MHz, CDCl3) δ (ppm) 145.64, 141.70, 134.46, 134.05, 134.03, 133.94, 133.90, 132.08, 131.89, 130.98, 130.37, 130.35, 130.31, 127.79, 127.65, 127.60, 127.36, -1.17. 29Si NMR (99 MHz, CDCl3) δ (ppm) -16.54 (1Si), -31.42 (1Si), -78.43 (2Si), -78.63 (2Si), -79.61 (d, J = 1.3 Hz, 4Si). LC/MS QTof: exact mass for C53H52NaO14Si10 [M+Na]+ calculated m/z 1215.0942 found m/z 1216.0813 160 9-Cyclohexyl-9,19,19-trimethyl-1,3,5,7,11,13,15,17-octaphenyl-2,4,6,8,10,12,14,16,18, 20,21,22,23,24-tetradecaoxa-1,3,5,7,9,11,13,15,17,19-decasilapentacyclo[11.7.1.13, 11.15, 17.17,15]tetracosane (7c) C57H60O14Si10 This product was isolated as a white solid (72%). mp 273–276 ⁰C. 1H NMR (500 MHz, CDCl3) δ (ppm) 7.63 – 7.12 (m, 40H), 1.76 (d, J = 12.8 Hz, 6H), 1.15 (dd, J = 39.4, 10.0 Hz, 4H), 0.83 (d, J = 12.6 Hz, 1H), 0.37 – 0.26 (m, 6H), 0.24 (s, 3H). 13C NMR (126 MHz, CDCl3) δ (ppm) 134.05, 134.03, 133.94, 132.19, 132.14, 131.14, 131.08, 130.27, 127.76, 127.74, 127.61, 127.59, 27.45, 26.70, 26.30, -3.03. 29Si NMR (99 MHz, CDCl3) δ (ppm) -16.72 (1Si), -18.90 (1Si), -78.69 (2Si), -78.93 (2Si), -79.64 (2Si), -79.74 (2Si). LC/MS QTof: exact mass for C53H53O14Si10 [M+H]+ calculated m/z 1249.1748 found m/z 1249.1677 161 9,9-Diethyl-19,19-dimethyl-1,3,5,7,11,13,15,17-octaphenyl-2,4,6,8,10,12,14,16,18,20, 21,22,23,24-tetradecaoxa-1,3,5,7,9,11,13,15,17,19-decasilapentacyclo[11.7.1.13, 11.15, 17.17,15]tetracosane (7d) C54H56O14Si10 This product was isolated as a white solid (71%). mp 263–268 ⁰C. 1H NMR (500 MHz, CDCl3) δ (ppm) 7.55 – 7.17 (m, 40H), 1.00 (t, J = 7.9 Hz, 6H), 0.70 (q, J = 7.9 Hz, 4H), 0.30 (s, 6H). 13C NMR (126 MHz, CDCl3) δ (ppm) 134.02, 133.93, 133.92, 132.19, 131.12, 130.32, 130.28, 127.78, 127.76, 127.62, 6.90, 6.33, 0.54. 29Si NMR (99 MHz, CDCl3) δ (ppm) -16.64 (1Si), -16.88 (1Si), -78.66 (2Si), -78.91 (2Si), -79.69 (4Si). 162 3.3.7 Structural Characterization of Completely Condensed Asymmetric D2T8 Silsesquioxanes by 29Si NMR Spectroscopy 9-(3-Isocyanatopropyl)-9,19-dimethyl-1,3,5,7,11,13,15,17-octaphenyl-2,4,6,8,10,12, 14,16,18,20,21,22,23,24-tetradecaoxa-1,3,5,7,9,11,13,15,17,19-decasilapentacyclo [11.7.1.13,11.15,17.17,15]tetracosane (7a) Figure 3-12: 29Si NMR of 7a stacked with its symmetric AA and BB Figure 3-12 shows the 29Si NMR spectra of asymmetric 7a (middle) stacked with its symmetric counterparts; Me(H)SiDDSQSi(H)Me (5a) (top) and 163 PrNCO)(Me)SiDDSQSi(Me)(PrNCO) (bottom). 7a has six (6) chemically equivalent Si- atoms corresponding to the six resonances in its spectra (middle). This structure has two D-silicons and 4 x 2 T-silicons with signals in the spectra consistent with these atoms. The D-silicon at δ -18 ppm (red, Si#6) is the Si bearing the (PrNCO)(Me) groups and that at δ -32 ppm (blue, Si#1) is the one with the (Me)(H) groups. T-silicons (Si#2 and Si#5) at δ -78 and -78.4 ppm are the T-silicons next to Si#1 and Si#6 respectively. 7a was isolated as a mixture of its cis/trans forms and so the environments of the internal silicons (Si#3 and Si#4) can change based on the orientation of the substituents on the capping sites (Si#1 and Si#6) as is seen in the signals between the -79.00 to -79.80 ppm region. Thus, the doublet peak at -79.30 ppm (2Si) denotes Si#3 and that at -79.60 ppm (2Si) are the silicon atoms denoted as Si#4. 164 9,9,19-trimethyl-1,3,5,7,11,13,15,17-octaphenyl-19-vinyl-2,4,6,8,10,12,14,16,18,20,21, 22,23,24-tetradecaoxa-1,3,5,7,9,11,13,15,17,19-decasilapentacyclo[11.7.1.13,11.15, 17.17,15]tetracosane (7b) Figure 3-13: Stacked 29Si NMR of AA, AB and BB (7b) Figure 3-13 shows the stacked spectra of asymmetric 7b (middle) with its symmetric counterparts; Me(vinyl)SiDDSQSi(vinyl)Me (6b) (top) and Me2SiDDSQSiMe2. 7b has six chemically different Si atoms consistent with the resonances in its spectra (middle). Like in 7a, asymmetric 7b has two distinct D-silicons with a shift at -16.58 ppm typical of D-silicons with two Me groups (Si#1, blue) and one at -32.50 ppm symbolic of 165 the Si with the Me and vinyl substituents (Si#6, red). Si#2 (purple) and Si#5 (green) are the silicons next to Si#1 and Si#6 respectively. The remaining silicons (Si#3 and Si#4) are the internal T-silicons with δ 79.55 (purple) for cis orientation of both the two Me groups on Si#1 and Si#6 relative to Si#3 and the one with δ 79.60 for the D-silicons with Me and vinyl groups facing Si#4. 166 9-Cyclohexyl-9,19,19-trimethyl-1,3,5,7,11,13,15,17-octaphenyl-2,4,6,8,10,12,14,16,18, 20,21,22,23,24-tetradecaoxa-1,3,5,7,9,11,13,15,17,19-decasilapentacyclo[11.7.1.13, 11.15,17.17,15]tetracosane (7c) Figure 3-14: Stacked 29Si NMR of AA and BB (7c) Figure 3-14 is the stacked spectra asymmetric 7c (top) and symmetric Me2SiDDSQSiMe2. 6c. 7c has six chemically different Si atoms, two D-silicons and 4 x 2 sets of T-silicons. Signal at -16.58 ppm is identical to the D-silicon with two methyl substituents (blue, Si#1) and the one at -18.38 ppm is symbolic of the D-silicon with the 167 cyclohexyl and methyl groups (red, Si#6). Si#2 (purple) and Si#5 (green) are the T- silicons next to Si#1 and Si#6 respectively. The internal signal with δ -79.65 (orange, Si#4) are the two T-silicons on the same face with the two methyl substituents on the capping D-silicons and the one at δ 79.75 (grey, Si#3) are for the two T-silicons having the same orientation with the Me and cyclohexyl substituents on the capping D-silicons. 168 9,9-Diethyl-19,19-dimethyl-1,3,5,7,11,13,15,17-octaphenyl-2,4,6,8,10,12,14,16,18,20, 21,22,23,24-tetradecaoxa-1,3,5,7,9,11,13,15,17,19-decasilapentacyclo[11.7.1.13, 11.15,17.17,15]tetracosane (7d) Figure 3-15: Stacked 29Si NMR of AA, AB(7d) and BB Figure 3-15 is the stacked spectra asymmetric 7d (middle), symmetric Et2SiDDSQSiEt2 (6d) (top) and symmetric Me2SiDDSQSiMe2 (8d) (bottom). 7d has five chemically different Si atoms, two D-silicons with resonances at – 16.78 ppm for Si#1 (blue) bearing the two ethyl groups and the other at – 16.58 ppm for the one with two 169 methyl groups (Si#5, red). The remaining six silicons are T-silicons with the resonances at -78.60 ppm for the two Si#4 (green) next to D-silicon Si#5, δ 78.80 for the other two Si#3 (purple) next to Si#1, δ 79.65 for the four internal silicons (Si#3, grey). 3.4 Conclusion This protocol discloses a strategically novel approach into partially condensed bis- capped monosilylated double-decker shaped silsesquixanes. By strategically using boronic acid to mask two silanol groups, a wide range of bifunctional DDSQs were obtained in good to high yields. About 50 % of the clean starting material was recovered upon deborylation in the first and second steps. These unique monosilylated DDSQ scaffolds are interesting synthetic precursors for a variety of functional materials including condensed asymmetric DDSQs, ligands in catalysis, surface modifiers, and nano- medicine carriers. An illustration of the post-modification of these cages for the synthesis of condensed asymmetrically functionalized DDSQs afforded excellent yields of the pure targets. With this approach, formation of unwanted BB products is completely evaded, and no further purifications of the D2T8 POSS cages are required. However, even though the route is amenable to a broad range of substrates, capping the DDSQ(OH) 4 with dicyclohexyldichlorosilane was unsuccessful, probably due to increasing steric at the α- carbon of the cyclohexyl ring. Further investigations to reasonably account for this challenge is ongoing in our laboratory. 3.5 Experimental Details 3.5.1 Materials and Methods All reactions were carried out with dry solvents under a nitrogen atmosphere using standard techniques except otherwise stated. DDSQ(OH)4 was obtained from Hybrid 170 Plastics. Pyridine, ethyl acetate, hexanes, acetonitrile, methanol, and isopropanol were used as received. THF was distilled over benzophenone and sodium metal at a temperature of 50 °C under nitrogen prior to use. Glassware was oven dried. Reactions were monitored by thin-layer chromatography (TLC) on silica gel plates or a Hydrion Insta-Chek pH pH 0-14 and. 1H, 11B, 13C, and 29Si NMR spectra were acquired on an Agilent DirectDrive2 500 MHz NMR spectrometer equipped with a OneProbe operating at 500 MHz for 1H NMR, 160 MHz for 11B NMR, 126 MHz for 13C NMR, and 99 MHz for 29Si NMR CDCl3 and recorded at 25 °C. 1H-NMR spectra were recorded with 8 scans, a relaxation delay of 1s, and a pulse angle of 45° and referenced to tetramethylsilane in CDCl3 (0.00 ppm). 13C-NMR spectra were collected with 254 scans, a relaxation delay of 0.1 s, and a pulse angle 45°. 29Si NMR spectra were recorded with either 256 or 512 scans, a relaxation delay of 12 s and a pulse angle of 45°. Thin-layer chromatography (TLC) was performed on plates of EMD 250-μm silica 60-F254. High-resolution mass spectroscopy was performed with APCI mass spectra recorded on a Finnigan LCQ Deca (ThermoQuest) technologies with LC/MS/MS (quadrupole/time-of-flight) and Waters Xevo G2-XS UPLC/MS/MS inert XL MSD with SIS Direct Insertion Probe. Melting points for all products were measured with a Thomas HOOVER capillary uni-melt melting point apparatus and are uncorrected. X-ray diffraction measurements were performed on a Stoe IPDS2 or a Bruker-AXS SMART APEX 2 CCD diffractometer using graphite- monochromated Mo Kα radiation. The structures were solved using direct methods (SHELXL-97) and refined by full-matrix least-squares techniques against F2 (SHELXL- 97). Cell parameters were retrieved using the SAINT (Bruker, V8.34A, after 2013) software and refined using SAINT (Bruker, V8.34A, after 2013) on 5941 reflections, 47% 171 of the observed reflections. Data reduction was performed using the SAINT (Bruker, V8.34A, after 2013) software which corrects for Lorentz polarization. 3.5.2 General Experimental Procedure for the Synthesis of DDSQ Bis-boronate Ester (2) Scheme 3-12: Synthesis of 9,19-bis(4-methoxyphenyl)-1,3,5,7,11,13,15,17-octaphenyl- 2,4,6,8,10,12,14,16,18,20,21,22,23,24-tetradecaoxa-1,3,5,7,11,13,15,17-octasila-9,19- diborapentacyclo[11.7.1.13,11.15,17.17,15]tetracosane (2) The starting material, bis-boronate ester 2, was synthesized following a procedure we reported earlier.49 An oven-dried 500 mL round bottom flask equipped with a magnetic stir bar was charged with DDSQ(OH)4 1 (10 mmol, 10.69 g) and p-MeOC6H4B(OH)2 (2.2 equiv, 22 mmol). The flask was fitted with a Dean-Stark apparatus and its contents placed under a nitrogen atmosphere. Toluene (120 mL) was added, and the setup stirred over a pre-heated oil bath at a temperature of 115 ⁰C for 24 h. The solvent was evaporated under reduced pressure, the resulting crude then was washed with isopropanol (20 mL), filtered with a filter frit and flask and dried again at reduced pressure to afford a white solid. From this product, fine crystals appropriate for crystallographic analysis were obtained from a mixture of DCM/hexanes (1:3) of the Bis-boronate esters 2 in 98% yield. The solid was characterized by 1H, 13C, 11B, 29Si NMR X-ray crystallography and LCMS measurements. 1H NMR (500 MHz, CDCl3 + 1%TMS) δ 7.70 – 7.60 (m, 8H), 7.59 – 7.53 (m, 4H), 7.50 – 7.19 (m, 32H), 6.75 – 6.65 (m, 4H), 3.74 (s, 6H). 172 13C NMR (126 MHz, CDCl3 + 1%TMS) δ 137.68, 134.14, 134.11, 131.43, 130.62, 130.53, 130.38, 127.94, 127.68, 113.04, 55.01. 11B NMR (160 MHz, CDCl3 + 1%TMS) δ 20.09. 29Si NMR (99 MHz, CDCl3 + 1%TMS) δ -78.70, -80.45. 3.5.3 Partial Deborylation of DDSQ Bis-boronate Ester with Pinacol Complete transesterification of the bis-boronate ester with pinacol was described in our previous work (Scheme 3-11).49 Scheme 3-13: Complete Deborylation of (p-MeOC6H4B)2DDSQ (2) with Pinacol In line with this, optimization for the synthesis of the monoborylated DDSQ disilanol was done following the same procedure with some modifications (Scheme 3-14). Scheme 3-14: Partial Deborylation of (p-MeOC6H4B)2DDSQ (2) with Pinacol An oven-dried 50 mL round bottom flask bearing a magnetic stir bar was charged with p-MeO-C6H4B)2DDSQ (2) (0.65 g, 0.5 mmol) and pinacol (0.8 mmol). The flask was capped with a septum, its content placed under nitrogen atmosphere and CHCl 3 (5 mL) was added to it. The reaction mixture was stirred at room temperature for 5 h (Scheme 173 3-14). The solvent was next evaporated using a rotary evaporator. The crude solid was dissolved in CHCl3 (5 mL) and kept in a refrigerator at -5 °C for 5 h. The resulting heterogeneous mixture was suction filtered using a fine-frit funnel and filter flask to isolate the unreacted DDSQ tetraol. The residue was washed with CHCl3 (2 x 5 mL), filtered, and dried in the oven at 80 ⁰C for 5 h. The solid 1 was analyzed by 1H, 13C, 11B and 29Si NMR. NMR data for the products are shown in Appendix. The combined filtrate was evaporated under reduced pressure to afford a white solid. This solid is a mixture of the mono- and bis-borylated cage and a trace amount of DDSQ tetraol. The combined filtrate was dried by rotary evaporation to give a white solid. The dissolution in CHCl3, refrigeration, filtration and rotary evaporation processes were repeated two or more times until the mixture was free of DDSQ tetraol. The final white crude obtained is a mixture of the bis- and mono- borylated cages in an approximate ratio of 2:1 (Table 3-1). The resulting crude product was analyzed by 1H, 11B, and 29Si NMR spectroscopy. It must be mentioned that all attempts to isolate the pure mono-borylated cage were unsuccessful. 174 3.5.4 General Experimental Procedure for the Multi-step Synthesis of monosilylated DDSQ diol Scheme 3-15: Synthesis of asymmetrically functionalized monosilylated DDSQ(OH)2 Step 1: Partial deborylation An oven-dried 100 mL round bottom flask bearing a magnetic stir bar was charged with p-MeO-C6H4B)2DDSQ (2) (1.3 g, 1.00 mmol) and pinacol (0.8 equiv, 0.0944 g). The flask was capped with a septum, its content placed under a nitrogen atmosphere and CHCl3 (10 mL) was added. The reaction mixture was stirred at room temperature for 5 h (Scheme 3-15, step I). The solvent was next evaporated using a rotary evaporator. The crude solid was then dissolved in CHCl3 (10 mL) and kept in a refrigerator at -5 °C for 5 h. The resulting heterogeneous mixture was suction filtered using a fine-frit funnel and filter flask to isolate the generated DDSQ tetraol (1). The residue was washed with CHCl3 (2 x 5 mL), filtered, and dried in the oven at 80 ⁰C for 5 h. The combined filtrate was evaporated under reduced pressure to afford a white solid. The white solid was redissolved in CHCl3 (10 mL), kept in a refrigerator at -5 ⁰C for 5 h and filtered with a fine 175 frit funnel. This solid is a mixture of the mono- and bis-borylated cage and trace amount of DDSQ tetraol. The dissolution in CHCl3, refrigeration, filtration and rotary evaporation processes were repeated two or more times until the mixture was free of 1. The resulting crude products (residue and filtrate) were analyzed by 1H, 11B, and 29Si NMR spectroscopy. The final white crude obtained from the filtrate is a mixture of the bis- and mono-borylated cages in an approximate ratio of 2:1. The residue was the completely deborylated boronate ester or DDSQ tetraol (1). NMR data for the products are shown in Appendix. Step 2: Silylation The crude filtrate mixture (Scheme 3-15, step I) was charged into a pre-dried 100 mL round bottom flask bearing a magnetic stir bar and sealed with a septum. The flask was purged with dry nitrogen for 30 min and THF (20 mL) was added. The flask was immersed into an ice bath and its contents stirred vigorously under nitrogen for 20 min. R1R2SiCl2 (x mmol, 1.2 equiv. based on the mono-borylated cage) in 1 mL THF was added first followed by dropwise addition of pyridine (2x mmol, 2.4 equiv. based on the mono-borylated cage) over a period of 5 minutes. The reaction mixture was stirred at 0 ⁰C for 4 h and at room temperature for 20 h (Scheme 3-15, step II). The suspension was filtered through a glass frit, the residue washed with THF (3 x 5 mL) and the solvent together with other volatiles removed from the filtrate by rotary evaporation. This crude product is a mixture of the bis-boronate DDSQ ester (2) and the silylated mono-boronate DDSQ ester (4) that forms the substrate for the next step. Reaction was followed by both 1H, 13B, and 29Si NMR. 176 Step 3: Global Transesterification The crude product mixture (Scheme 3-15, step II) was charged into a pre-dried 100 mL round bottom flask bearing a magnetic stir bar and pinacol (1.5 mmol based on the monoborylated/monosilylated DDSQ) added to it. Chloroform (10 mL) was added to the flask under nitrogen and the reaction mixture stirred vigorously at room temperature for 24 h (Scheme 3-15, step III). After 24 h, the resulting white suspension was filtered through a fine-fritted filter funnel. The white powdered residue was washed with chloroform (3 x 5 mL), filtered, dried in an oven at 80 ⁰C for 5 h and characterized by 1H and 29Si NMR spectroscopy. The solvent and other volatiles were removed from the filtrate by rotary evaporation to afford a white solid or oil which was similarly characterized by 1H, 11B, 13C and 29Si NMR spectroscopy. Final products in step III were further purified by flash column chromatography (ethylacetate:hexanes = 1:9) and analyzed by 1H, 13C, 29Si and LCMS measurement. The chromatographed products were washed with hexanes to remove the p-MeOC6H4Bpin. Fine crystals suitable for X-ray crystallography were obtained by crystallization from a mixture of dichloromethane:hexanes ~ 1:3. The asymmetrically functionalized DDSQ diols (5) synthesized in this study are listed in Table 3-2. Copies of NMR, mass spectra and X-ray crystal data are given in Appendix. 177 3.6 Synthetic Modifications of Monosilylated DDSQ diols (5) into Fully Condensed Asymmetric DDSQs of the D2T8 type (7) Scheme 3-16: Synthesis of completely condensed asymmetrically functionalized D2T8 An oven-dried 100 mL round bottom flask bearing a magnetic stir bar was charged with the 0.5 mmol of monosilylated DDSQ diol (5) and capped with a septum. The flask was purged with dry nitrogen for 10 min and THF (20 mL) was added. The flask was immersed into an ice bath and the mixture stirred vigorously for 30 min under N 2. A suitable di-substituted chlorosilane bearing R groups different from those on the starting material R3R4SiCl2 (1.5 equiv) in 5 mL THF was added first followed by dropwise addition of pyridine or Et3N (3.0 equiv) over a period of 10 minutes. The reaction mixture was stirred at 0 ⁰C for 1 h and at room temperature for 23 h. The suspension was filtered through a glass frit funnel, the residue washed with THF (3 x 5 mL) and the solvent together with other volatiles removed from the filtrate by rotary evaporation. This crude product is washed with hexanes (2 x 10 mL) and then pentane (10 mL). The solvent was evaporated at reduced pressure to afford the pure fully condensed D 2T8 asymmetric DDSQ in good to excellent yields. Products were analyzed directly by 1H, 13C, 29Si and LCMS measurement without further purifications. A list of the asymmetrically functionalized D2T8 DDSQs are listed in Table 3-3. Copies of the NMR and mass spectra are given in Appendix and X-ray crystallographic data in Appendix. 178 APPENDIX 179 Copies of NMR and Mass Spectra – Bis-boronate Ester and Asymmetrically Silylated DDSQ Diol 9,19-Bis(4-methoxyphenyl)-1,3,5,7,11,13,15,17-octaphenyl-2,4,6,8,10,12,14,16,18,20, 21,22,23,24-tetradecaoxa-1,3,5,7,11,13,15,17-octasila-9,19-diborapentacyclo[11.7.1. 13, 11.15,17.17,15]tetracosane (2a) Figure 3-16: 1H NMR of 2a (CDCl3 + 1%TMS, 500 MHz) 180 Figure 3-17: 13C NMR of 2a (CDCl3 + 1%TMS, 126 MHz) Figure 3-18: 11B NMR of 2a (CDCl3 + 1%TMS, 160 MHz) 181 Figure 3-19: 29Si NMR of 2a (CDCl3 + 1%TMS, 99 MHz) 182 15-Methyl-1,3,5,7,9,11,13,17-octaphenyl-2,4,6,8,10,12,14,16,18,19,20,21-dodecaoxa- 1,3,5,7,9,11,13,15,17-nonasilatetracyclo[9.7.1.15,17.17,13]henicosane-3,9-diol (5a) Figure 3-20: 1H NMR of 5a (CDCl3 + 1%TMS, 500 MHz) 183 Figure 3-21: 13C NMR of 5a (CDCl3 + 1%TMS, 126 MHz) Figure 3-22: 29Si NMR of 5a (CDCl3 + 1%TMS, 99 MHz) 184 Figure 3-23: Mass spec of 5a 185 15,15-dimethyl-1,3,5,7,9,11,13,17-octaphenyl-2,4,6,8,10,12,14,16,18,19,20,21-dode- caoxa-1,3,5,7,9,11,13,15,17-nonasilatetracyclo[9.7.1.15,17.17,13]henicosane-3,9-diol (5b) Figure 3-24: 1H NMR of 5b (CDCl3 + 1%TMS, 500 MHz) 186 Figure 3-25: 13C NMR of 5b (CDCl3 + 1%TMS, 126 MHz) Figure 3-26: 29Si NMR of 5b (CDCl3 + 1%TMS, 99 MHz) 187 Figure 3-27: Mass spec of 5b 188 15,15-diethyl-1,3,5,7,9,11,13,17-octaphenyl-2,4,6,8,10,12,14,16,18,19,20,21-dodeca- oxa-1,3,5,7,9,11,13,15,17-nonasilatetracyclo[9.7.1.15,17.17,13]henicosane-3,9-diol. (5c) Figure 3-28: 1H NMR of 5c (CDCl3 + 1%TMS, 500 MHz) 189 Figure 3-29: 13C NMR of 5c (CDCl3 + 1%TMS, 126 MHz) Figure 3-30: 29Si NMR of 5c (CDCl3 + 1%TMS, 99 MHz) 190 Figure 3-31: Mass spec of 5c 191 4-(3,9-Dihydroxy-15-methyl-1,3,5,7,9,11,13,17-octaphenyl-2,4,6,8,10,12,14,16,18,19, 20,21-dodecaoxa-1,3,5,7,9,11,13,15,17-nonasilatetracyclo[9.7.1.15,17.17,13]henico- san-15-yl)butanenitrile. (5d) Figure 3-32: 1H NMR of 5d (CDCl3 + 1%TMS, 500 MHz) 192 Figure 3-33: 13C NMR of 5d (CDCl3 + 1%TMS, 126 MHz) Figure 3-34: 29Si NMR of 5d (CDCl3 + 1%TMS, 99 MHz) 193 Figure 3-35: Mass spec of 5d 194 15-Methyl-1,3,5,7,9,11,13,17-octaphenyl-15-vinyl-2,4,6,8,10,12,14,16,18,19,20,21-dod- ecaoxa-1,3,5,7,9,11,13,15,17-nonasilatetracyclo[9.7.1.15,17.17,13]henicosane-3,9-diol (5e) Figure 3-36: 1H NMR of 5e (CDCl3 + 1%TMS, 500 MHz) 195 Figure 3-37: 13C NMR of 5e (CDCl3 + 1%TMS, 126 MHz) Figure 3-38: 29Si NMR of 5e (CDCl3 + 1%TMS, 99 MHz) 196 Figure 3-39: Mass spec of 5e 197 15-Allyl-15-methyl-1,3,5,7,9,11,13,17-octaphenyl-2,4,6,8,10,12,14,16,18,19,20,21- dodecaoxa-1,3,5,7,9,11,13,15,17-nonasilatetracyclo[9.7.1.15,17.17,13]henicosane-3,9- diol (5f) Figure 3-40: 1H NMR of 5f (CDCl3 + 1%TMS, 500 MHz) 198 Figure 3-41: 13C NMR of 5f (CDCl3 + 1%TMS, 126 MHz) Figure 3-42: 29Si NMR of 5f (CDCl3 + 1%TMS, 99 MHz) 199 Figure 3-43: Mass spec of 5f 200 15-Methyl-1,3,5,7,9,11,13,17-octaphenyl-2,4,6,8,10,12,14,16,18,19,20,21dodecaoxa- 1,3,5,7,9,11,13,15,17-nonasilatetracyclo[9.7.1.15,17.17,13]henicosane-3,9,15-triol (5g) C49H46O15Si9 Figure 3-44: 1H NMR of 5g (CDCl3 + 1%TMS, 500 MHz) 201 Figure 3-45: 13C NMR of 5g (CDCl3 + 1%TMS, 126 MHz) Figure 3-46: 29Si NMR of 5g (CDCl3 + 1%TMS, 99 MHz) 202 15-Isopropyl-1,3,5,7,9,11,13,17-octaphenyl-2,4,6,8,10,12,14,16,18,19,20,21-dodeca- oxa-1,3,5,7,9,11,13,15,17-nonasilatetracyclo[9.7.1.15,17.17,13]henicosane-3,9,15-triol (5h) Figure 3-47: 1H NMR of 5h (CDCl3 + 1%TMS, 500 MHz) 203 Figure 3-48: 13C NMR of 5h (CDCl3 + 1%TMS, 126 MHz) Figure 3-49: 29Si NMR of 5h (CDCl3 + 1%TMS, 99 MHz) 204 Figure 3-50: Mass spec of 5h 205 Single X-Ray Crystallographic Data of 5 Table 3-4: Crystal Data and Structure Refinement for Asymmetric DDSQ Diols 5a, 5b, 5e and 5f 5a 5b 5e 5f CCDC 2064703 2052368 1986063 - Formula C49.5H47Cl0.5O14Si9 C50.5H50O14.5Si9 C51H48O14Si9 C51.57H50.57O14Si9 Dcalc./ g cm-3 1.379 1.390 1.398 1.359 μ/mm-1 2.821 2.619 2.634 2.543 Formula Weight 1136.40 1141.71 1137.70 1147.17 Colour colourless colourless colourless colourless Shape needle needle needle needle Size/mm3 0.27×0.07×0.05 0.44×0.07×0.03 0.25×0.05×0.04 0.35×0.21×0.15 T/K 100.0(4) 101(2) 100.00(10) 100.01(10) Crystal System monoclinic monoclinic monoclinc monoclinic Space Group P21/c P21/c P21/c P21/c a/Å 10.86380(10) 10.84639(7) 11.04925(11) 10.90427(11) b/Å 25.5534(3) 25.56527(16) 14.90570(19) 26.0236(3) c/Å 19.7196(2) 19.68348(14) 32.8348(3) 19.8193(2) /° 90 90 90 90 / ° 91.7170(10) 92.0317(6) 91.5123(9) 94.2165(10) /° 90 90 90 90 V/Å3 5471.84(10) 5454.62(6) 5405.90(10) 5608.86(11) Z 4 4 4 4 Z’ 1 1 1 1 Wavelength/Å 1.54184 1.54184 1.54184 1.54184 Radiation type Cu K Cu K Cu K Cu K min/° 2.831 2.834 2.692 2.807 max/° 77.004 77.115 77.372 80.173 Measured Refl's. 33813 73347 41543 45620 Indep't Refl's 10231 11423 11055 11532 Refl's I≥2 (I) 9188 10309 9379 10109 Rint 0.0329 0.0420 0.0405 0.0380 Parameters 683 688 734 736 Restraints 3 0 1 0 Largest Peak 0.780 0.537 0.810 0.454 Deepest Hole -0.806 -0.912 -0.775 -0.564 GooF 1.018 1.065 1.041 1.065 wR2 (all data) 0.1154 0.1250 0.1344 0.1106 wR2 0.1124 0.1217 0.1287 0.1073 R1 (all data) 0.0460 0.0495 0.0606 0.0444 R1 0.0417 0.0446 0.0515 0.0388 206 15-Methyl-1,3,5,7,9,11,13,17-octaphenyl-2,4,6,8,10,12,14,16,18,19,20,21-dodecaoxa- 1,3,5,7,9,11,13,15,17-nonasilatetracyclo[9.7.1.15,17.17,13]henicosane-3,9-diol (5a) Figure 3-51: Single Crystal Structure of 5a (Displacement ellipsoid contour probability drawn at 50%) CCDC 2064703 contains the supplementary crystallographic data for 5a. The data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/structures. There is a single molecule in the asymmetric unit, which is represented by the reported sum formula. In other words: Z is 4 and Z' is 1. Figure 3-52: The following hydrogen bonding interactions with a maximum D-D distance of 2.9 Å and a minimum angle of 120 ° are present in 5a: O4–O10: 2.767 Å, O10–O4_1: 2.738 Å 207 15,15-Dimethyl-1,3,5,7,9,11,13,17-octaphenyl-2,4,6,8,10,12,14,16,18,19,20,21-dode- caoxa-1,3,5,7,9,11,13,15,17-nonasilatetracyclo[9.7.1.15,17.17,13]henicosane-3,9-diol (5b) Figure 3-53: Single Crystal Structure of 5b (Displacement ellipsoid contour probability drawn at 50%) CCDC 2052368 contains the supplementary crystallographic data for 5b. The data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/structures. There is a single molecule in the asymmetric unit, which is represented by the reported sum formula. In other words: Z is 4 and Z' is 1. Figure 3-54: The following hydrogen bonding interactions with a maximum D-D distance of 3.1 Å and a minimum angle of 110 ° are present in REN1220D: O13–O14_1: 2.741 Å, O14–O13: 2.767 Å 208 15-Methyl-1,3,5,7,9,11,13,17-octaphenyl-15-vinyl-2,4,6,8,10,12,14,16,18,19,20,21- dodecaoxa-1,3,5,7,9,11,13,15,17-nonasilatetracyclo[9.7.1.15,17.17,13]henicosane-3,9- diol (5e) Figure 3-55: Single Crystal Structure of 5e (Displacement ellipsoid contour probability drawn at 50%) CCDC 1986063 contains the supplementary crystallographic data for this paper. The data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/structures. There is a single molecule in the asymmetric unit, which is represented by the reported sum formula. In other words: Z is 4 and Z' is 1. Figure 3-56: The following hydrogen bonding interactions with a maximum D-D distance of 2.9 Å and a minimum angle of 120 ° are present in 5e: O1–O2_1: 2.721 Å, O2–O1: 2.724 Å 209 15-Allyl-15-methyl-1,3,5,7,9,11,13,17-octaphenyl-2,4,6,8,10,12,14,16,18,19,20,21- dodecaoxa-1,3,5,7,9,11,13,15,17-nonasilatetracyclo[9.7.1.15,17.17,13]henicosane-3,9- diol (5f) Figure 3-57: Single Crystal Structure of 5f (Displacement ellipsoid contour probability drawn at 50%) Crystal structure for REM221BB does not clearly determine if this is dimethyl, diAllyl or methyl-Allyl substituted on the Si atom. X-ray Diffraction model suggests mixture but need more chemical information to know for sure. There is a single molecule in the asymmetric unit, which is represented by the reported sum formula. In other words: Z is 4 and Z' is 1. Figure 3-58: The following hydrogen bonding interactions with a maximum D-D distance of 2.9 Å and a minimum angle of 120 ° are present in REM221BB: O4–O10: 2.777 Å, O10–O4_1: 2.787 Å 210 NMR and Mass Spectra of Completely Condensed Asymmetric D2T8 Silsesquioxanes 9-(3-Isocyanatopropyl)-9,19-dimethyl-1,3,5,7,11,13,15,17-octaphenyl-2,4,6,8,10,12, 14,16,18,20,21,22,23,24-tetradecaoxa-1,3,5,7,9,11,13,15,17,19-decasilapentacyclo- [11.7.1. 13,11.15,17.17,15]tetracosane. (7a) Figure 3-59: 1H NMR (CDCl3 + 1%TMS, 500 MHz) 211 Figure 3-60: 13C NMR (CDCl3 + 1%TMS, 126 MHz) Figure 3-61: 29Si NMR (CDCl3 + 1%TMS, 99 MHz) 212 Figure 3-62: Mass spec of 7a 213 9,9,19-Trimethyl-1,3,5,7,11,13,15,17-octaphenyl-19-vinyl-2,4,6,8,10,12,14,16,18,20, 21,22,23,24-tetradecaoxa-1,3,5,7,9,11,13,15,17,19-decasilapentacyclo[11.7.1.13, 11.15, 17.17,15]tetracosane. (7b) Figure 3-63: 1H NMR (CDCl3 + 1%TMS, 500 MHz) 214 Figure 3-64: 13C NMR (CDCl3 + 1%TMS, 126 MHz) Figure 3-65: 29Si NMR (CDCl3 + 1%TMS, 99 MHz) 215 Figure 3-66: Mass spec of 7b 216 9-cyclohexyl-9,19,19-trimethyl-1,3,5,7,11,13,15,17-octaphenyl-2,4,6,8,10,12,14,16, 18,20,21,22,23,24-tetradecaoxa-1,3,5,7,9,11,13,15,17,19-decasilapentacyclo[11.7. 1.13, 11.15,17.17,15]tetracosane (7c) Figure 3-67: 1H NMR (CDCl3 + 1%TMS, 500 MHz) 217 Figure 3-68: 13C NMR (CDCl3 + 1%TMS, 126 MHz) Figure 3-69: 29Si NMR (CDCl3 + 1%TMS, 99 MHz) 218 Figure 3-70: Mass spec of 7c 219 9,9-Diethyl-19,19-dimethyl-1,3,5,7,11,13,15,17-octaphenyl-2,4,6,8,10,12,14,16,18,20, 21,22,23,24-tetradecaoxa-1,3,5,7,9,11,13,15,17,19-decasilapentacyclo[11.7.1.13, 11.15, 17.17,15]tetracosane (7d) Figure 3-71: 1H NMR (CDCl3 + 1%TMS, 500 MHz) 220 Figure 3-72: 13C NMR (CDCl3 + 1%TMS, 126 MHz) Figure 3-73: 29Si NMR (CDCl3 + 1%TMS, 99 MHz) 221 Characteristic Single Crystal Structure of Compounds 7 9-(3-isocyanatopropyl)-9,19-dimethyl-1,3,5,7,11,13,15,17-octaphenyl-2,4,6,8,10,12, 14,16,18,20,21,22,23,24-tetradecaoxa-1,3,5,7,9,11,13,15,17,19-decasilapentacyclo [11.7. 1.13,11.15,17.17,15]tetracosane (7a) Figure 3-74: Single Crystal Structure of 7a (Displacement ellipsoid contour probability drawn at 50%) CCDC 2073474 contains the supplementary crystallographic data for 7a. 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NaOH affords an intermediate, which upon derivatization with TMSCl gives a ‘double-decker’ shaped silsesquioxane. Time-resolved mass spectroscopic studies indicates Ph12T12 is transformed to the partially condensed octaphenylT8. This is the first report of Ph12T12 as a precursor to a partially condensed lower cage framework. Parts of this chapter is under preparation for publication in Green Chemistry. 230 4.2 Introduction Fully condensed oligomeric silsesquioxanes can form nanosized model organosilicon compounds with a well-defined 3D inner siloxy cage, having a general formula (RSiO3/2)n, where n= 6, 8, 10, 12, 14, etc.1-7 The peripheral organic moieties, R, on the silicon vertices promote miscibility and hence allow for synthetic elaboration.1,8-12 Cage-like silsesquioxanes come in two variations; (i) completely condensed cages,3,8,13-16 e.g. 1 and 2 and (ii) their partially condensed counterparts 3 and 4 (Figure 4.1). 17-20 Figure 4-1: Structures of cage-like Silsesquioxanes - dodecaphenylT12 (1), octaphenylT8 (2), tetrakis(trimethylsilyl)octaphenylT8 (3), and heptaphenylT7 triol (4) Even though both classes of compounds are pivotal building blocks for the synthesis of advanced inorganic-organic materials, the latter category is more interesting because the structures allow tunability for a range of engineering applications. 3,10,21-23 Several groups have cleaved completely condensed silsesquioxanes (SQ) to obtain different types of partially condensed cages (Scheme 4.1). Feher et al., reported acid19 and base24 promoted partial cleavage of fully condensed [RSiO 3/2]n frameworks and further illustrated the manipulation of the resulting functional groups for use as precursors to inorganic-organic hybrid materials. Li and Kawakami20 also reported the formation of partially condensed double-decker shaped octaphenyl silsesquioxane 231 (DDSQ) from the hydrolysis of the completely condensed precursor 2. Half cubes have also been obtained from the base hydrolysis of cubic octasilsesquioxanes. 27, 28 For instance, Laine et al.28 demonstrated the formation and transformation of the sodium phenylsiloxanolate half cube into well-defined bi-functional ‘’Janus’’ cubes by directly treating a methanol solution of the salt with MeSiCl3 followed by acid hydrolysis. Scheme 4-1: Prior strategies for the partial cleavage of completely condensed (a) octaphenylT8, (b) hexacyclohexylT6 (a) Selected strategies for the cleavage of octaphenylT8 (b) Cleavage of completely condensed hexacyclohexylT619 Rikowski and Marsmann28 disclosed that various functional octasilsesquioxanes can undergo base catalyzed rearrangement of the cage into the higher deca- and dodeca- 232 analogues. Similar analogues were also reported by Ervithayasuporn et al. via the nucleophilic reaction of condensed octa-functional silsesquioxanes with substituted sodium phenoxide salts.6 However, to date, all syntheses of partially condensed polyhedral oligomeric silsesquioxane cages from completely condensed precursors started with T6 or T8 silsesquioxanes and none from condensed T10 or T12.5,19,20,24 4.3 Research Hypothesis Stimulated by the foregoing lacuna, and prior art on the hydrolysis of completely condensed octaphenylT8 to yield the double-decker tetrasodium derivative,20 we hypothesized that reacting completely condensed Ph12T12 (1) with NaOH could affect the selective fissure of Si-O-Si bonds. Were this to be realized, opening and/or reorganization of the cage architecture could afford discreet partially condensed products. To test this idea, Ph12T12 (1) was treated with four equivalents of aqueous NaOH in isobutanol at 90 °C for 24 h.20 To aid in the identification of the reaction products, we silylated the crude reaction product with TMSCl (Scheme 4.2). Scheme 4-2: Hydrolysis of Ph12T12 (1) for the synthesis of 5,11,14,17-tetrakis(trime- thylsilyl)octaphenyltetracyclo[7.3.3.33;7]octasilsesquioxane (3) This sequence resulted in the generation of a material that crystallized from hexanes at –30 °C. To our surprise, characterization of this material by 1H, 13C, and 29Si NMR spectroscopy, MS, and single-crystal X-ray indicated that the product was 5,11,14,17- tetrakis(trime- thylsilyl)octaphenyltetracyclo[7.3.3.33;7]octasilsesquioxane (3).17 233 To better understand the process of affording 3 from Ph12T12 (1), we conducted a time-course experiment. With that information in hand, we next sought to isolate the more useful double-decker octaphenyl silsesquioxanetetraol (5) by protonating the resultant hydrolysis intermediate in step 1 (Scheme 4.3) with AcOH.17 Scheme 4-3: Base cleavage of 1 with NaOH followed by acid hydrolysis of intermediate 12 with AcOH to give 5 Detailed synthetic procedures, isolations and characterization techniques for all products synthesized here are described in the experimental section below. 4.4 Proposed Reaction Mechanism for the Formation of Double-decker Octaphenyl silsesquioxanetetraol (5) Based on the structure of 1 and our experimental data, we suggest 5 results from first the cleavage of two Si–O–Si bonds in 1 to give linear (PhSi(ONa)2)2O (13) fragments, which dimerizes to afford the tetrameric cyclic sym-cis tetraphenyl tetrasiloxane species 14. Intermolecular condensation of 14 would result in 5 (Scheme 4.4). Scheme 4-4: Proposed route to 5 from 1 234 This proposal agrees with the kinetic and mechanistic studies conducted by the Hwang group14 with PhSi(OMe)3 as a precursor. They detected the transient (PhSi(OH)2)O species and its subsequent disappearance due to formation of 1 by 29Si NMR. In our case, formation of (PhSiO)4(OH)2(ONa)2 (14), which could result from the dimerization of 13 is supported by mass spectrometric data obtained for (PhSiO)4(OTMS)4 during the time-course experiments (Table 4.1) on the cleavage of 1. In conclusion, we have established a new route to the lower, highly symmetrical, partially condensed double-decker shaped octaphenyl silsesquioxane framework starting with dodecaphenylT12 (Ph12T12). Mass spectral data from a time-resolved study point to early formation of a tetracyclosiloxane as a key intermediate for the formation of the ‘double-decker’ shaped silsesquioxane. This result demonstrates the first use of dodecaphenylT12 as precursor to the lower functionalized partially condensed octaphenylT8 frameworks.4 Results and Discussions 4.4.1 Hydrolysis of Ph12T12 (1) into [(PhSiO)8(O)2(OTMS)4] (3) Scheme 4-5: Synthesis of 5,11,14,17-tetrakis(trimethylsilyl)octaphenyltetracyclo- [7.3.3.- 33,7]octasilsesquioxane [(PhSiO)8(O)2(OTMS)4] (3) from Ph12T12 (1) Following the sequence of reactions outlined in Scheme 4.5, a white solid was generated that crystallized at –30 ⁰C overnight. To our surprise, characterization of this material by 1H, 13C, and 29Si NMR spectroscopy, MS, and single-crystal X-ray indicated 235 that the product was 5,11,14,17-tetrakis(trimethylsilyl)octaphenyl-tetracyclo[7.3.3.- 33,7]octasilsesquioxane (3). Moreover, based on moles of 1, as opposed to silicon equivalents, 3 was formed in 89% yield (1.87 g, 1.38 mmol). Yields are calculated based on the starting material that reacted (i.e. after subtracting the recovered Ph 12T12). However, it is worth mentioning that a white suspension was obtained prior to the recrystallization step. This solid in the organic phase separated by filtration using a fine frit funnel was shown to be the unreacted dodecaphenylT12 1 based on proton and silicon NMR. 5,11,14,17-tetrakis(trimethylsilyl)octaphenyltetracyclo[7.3.3.-33,7]octasilsesquioxane [(PhSiO)8(O)2(OTMS)4] 3 Chemical Formula: C60H74O14Si12 This product is a white crystalline solid. mp 225 – 228 1H NMR (500 MHz, CDCl3 + 1% TMS) δ (ppm) 7.47 – 7.43 (m, 8H), 7.38 – 7.08 (m, 32H). 13C NMR (126 MHz, CDCl3 + 1% TMS) δ (ppm) 134.34, 133.59, 131.78, 130.08, 129.71, 127.42, 1.90. 29Si NMR (99 MHz, CDCl3 + 1% TMS) δ (ppm) 10.53 (4Si), -76.09 (4Si), -78.92 (4Si). 236 4.4.2 Time-course Study for the Hydrolysis of 1 into 3 Scheme 4-6: Time-course analysis for the synthesis of 3 from 1 Table 4-1: LCMS-G2-XS QTof time course analysis of data for selected intermediates obtained from the hydrolysis of 1 followed by silylation with TMSCl Compound time Relative m/z [M + H]+ m/z [M + NH4]+ m/z [M + Na]+ Int. (%) (Calc’d) (Found) (Calc’d) (Found) (Calc’d) (Found) Ph12T12 (1) 0h 100 11549.1111549.13 1566.14 1567.12 1571.09 1571.12 Ph12T12 (1) 1h 100 1549.11 1549.13 1566.14 1567.12 1571.09 1571.12 Ph12T12 (1) 2h 89 1549.11 1549.13 1566.14 1566.12 1571.09 1571.12 [(PhSiO)4(OTMS)4] (7) 2h 11 858.25 858.97 – – – – Ph12T12 (1) 4h 45 1549.11 1549.13 1566.14 1566.12 1571.09 1571.12 [(PhSiO)8(O)2(OTMS)4](3) 4h 54 1357.25 1357.24 1374.28 1374.27 – – [(PhSiO)4(OTMS)4](7) 4h 1 – – 859.25 858.96 863.20 863.15 Ph12T12 (1) 8h 41 1549.11 1549.08 – – – – [(PhSiO)8(O)2(OTMS)4] (3) 8h 58 – – 1374.28 1374.99 1379.24 1379.61 [(PhSiO)4(OTMS)4] (7) 8h 1 841.22 841.18 859.25 858.96 863.20 862.84 Ph12T12 (1) 16 h 7 1549.11 1549.08 1566.14 1567.25 1571.09 1570.24 [(PhSiO)8(O)2(OTMS)4] (3) 16 h 90 1357.25 1357.13 – – 1571.09 1570.24 [(PhSiO)4(OTMS)4] (7) 16 h 3 841.22 840.95 859.25 858.96 863.20 861.95 Ph12T12 (1) 24 h 2 1549.11 1549.08 1566.14 1567.25 1571.09 1571.12 [(PhSiO)8(O)2(OTMS)4] (3) 24 h 96 1357.25 1357.14 – – 1379.24 1379.23 [(PhSiO)4(OTMS)4] (7) 24 h 2 841.22 840.95 859.25 858.96 – – Ph12T12 (1) 36 h 2 1549.11 1549.08 1566.14 1566.07 [(PhSiO)8(O)2(OTMS)4] (3) 36 h 95 1357.25 1357.24 1374.28 1374.99 1379.24 380.23 [(PhSiO)4(OTMS)4] (7) 36 h 3 841.22 840.95 859.25 858.96 – – Ph12T12 (1) 48 h 6 1549.11 1549.08 1566.14 1567.10 – – [(PhSiO)8(O)2(OTMS)4] (3) 48 h 91 1357.25 1357.24 1374.28 1374.90 1379.24 1380.23 [(PhSiO)4(OTMS)4] (7) 48 h 3 841.22 840.95 859.25 858.96 863.20 861.95 Ph12T12 (1) 72 h 3 1549.11 1549.08 – – 1571.09 1571.01 [(PhSiO)8(O)2(OTMS)4] (3) 72 h 94 1357.25 1357.24 1374.28 1374.99 1379.24 380.23 [(PhSiO)4(OTMS)4] (7) 72 h 3 841.22 840.95 859.25 858.96 – – 237 Atomic pressure chemical ionization mass spectrometry (APCI MS) was used to monitor reaction progress. This analysis showed the loss of 1 being met with an increase in the formation of 3. Notably, the mass spectral data indicated (PhSiO)4(OTMS)4 (7) as an intermediate species prior to the formation of 3. Table 4.2 details the presence of these selected species at different reaction times. This table gives the MS data of selected species for the hydrolysis and silylation of 1 at various time intervals. Table 4-2: Relative intensity of Species in Table 4.1 expressed as a percentage Time (h)/Relative Intensity (%) Entry Species 0 1 2 4 8 16 24 36 48 72 1 Ph12T12 (1) 100 100 89 45 41 7 2 2 6 3 2 [(PhSiO)4(OTMS)4] (7) 0 0 11 1 1 3 2 3 3 3 3 [(PhSiO)8(O)2(OTMS)4] (3) 0 0 0 54 58 90 96 95 91 94 A graphical plot of this data showing the consumption of 1 and formation of 3 is shown in Figure 4.2 Figure 4-2: Graph of relative intensity (%) vs hydrolysis time 238 At the 2-hour point, APCI-MS indicated the presence of 1 and 7 but provided no evidence for the presence of 3. Compound 3 was first detected at the 4- and 8-hour time points. By the 16-hour time point, the mass peak for 3 was predominant. In practice, the optimal yield of 3 was 89% and obtained when silylation occurred after the base hydrolysis of 1 had run for 48 h (Table 4.2). Table 4-3: Synthesis of [(PhSiO)8(O)2(OTMS)4] (3) from Ph12T12 (1) aReaction done in two consecutive steps; hydrolysis with NaOH to give intermediate (12) which was treated with TMSCl. bAmount of 3 isolated. cYields are calculated based on mmols of reacted 1. After product isolation, characterization by 1H, 13C, and 29Si NMR spectroscopy, MS, and single-crystal X-ray diffraction analysis with X-ray refinement parameters for 3 are consistent with the literature.20 This result indicates that the NaOH hydrolysis of 1 affords the double-decker octaphenyl silsesquioxanetetraol tetrasodium salt 12 (Figure 4.2) as the Scheme 4.5 intermediate. It is noteworthy here that order than MS, other spectroscopic data did not show evidence of any rearrangement for shorter hydrolysis time. However, despite the early detection of 3 from the mass spectral data, isolation of pure 3 was achieved for the silylation of all hydrolyzed intermediates from 16-72 h (Table 4.3). It should be noted that the APCI-MS data were only a measure of the soluble product. Indeed, insoluble solids remained in the reaction and once isolated proved to be unreacted 1, as judged by 1H, 13C, 29Si NMR and mass spectral data (Appendix). 239 4.4.3 Synthesis of [(PhSiO)8(O)2(OH)4] (5) from Ph12T12 (1) Scheme 4-7: Synthesis of 5 from 1 Following neutralization with AcOH and filtration of the insoluble material, MeCN was added. The addition of MeCN caused a precipitation. That precipitate proved to be 5,11,14,17-tetra(hydro)octaphenyltetracyclo[7.3.3.-33;7]octasilsesquioxane (5). The amount of 5 isolated represented a 61% yield from 1. The product was characterized by 1H, 13C and 29Si NMR, X-ray crystallography and APCI+ QTof LCMS Measurements. Chemical Formula: C48H44O14Si8 This product is a white solid. 1H NMR (500 MHz, CDCl3 + 1% TMS) δ 7.60 – 7.51 (m, 8H), 7.47 – 7.28 (m, 16H), 7.18 (dt, J = 25.2, 7.6 Hz, 16H) 13C NMR (126 MHz, CDCl3 + 1% TMS) δ 134.23, 132.32, 131.53, 130.40, 127.78, 127.53 29Si NMR (99 MHz, CDCl3 + 1% TMS) δ -69.08 (4Si), -79.26 (4Si). 240 4.4.4 Condition Screening Results for the Synthesis of (PhSiO)8(O)2(OH)4 5 from Ph12T12 (1) Scheme 4-8: Optimal Conditions for the Synthesis of (PhSiO)8(O)2(OH)4 (5) Results of efforts to optimize the yield of 5 are given in Table 4.4. Table 4-4: Hydrolysis of 12 with Acetic Acida aReaction conditions: Ph12T12 (1), NaOH, H2O, iBuOH, 90 °C 24 h. The hydrolysis step was done with AcOH and work up with MeCN. b%Yields of 5 are calculated based on moles of Reacted 1. cResin from MeCN solution. dInsoluble solid recombined with fresh 1. The results from the acid hydrolysis show that optimal conditions for the formation of 5 are those listed in entry 2, Table 4.4. However, this yield (66%) did not compare to the optimal 89% yield observed for the silylated product 3. This is due to 5 being slight solubility in MeCN (solubility in MeCN at 25 °C = 1.32 x 10-2g/10 mL) and thus lost to the filtrate. Indeed, mass spectral analysis of the filtrate confirmed the presence of 5. The filtrate also contained a resinous material. Though the exact structure of this product was 241 not established, mass spectral data and DOSY NMR suggested a resinous oligomer. This would not be surprising as 1 is made up of two pairs of fused cyclic tetrasiloxanes and fused cyclic pentasiloxanes.6,26 Subjection of such an oligomer to base hydrolysis could conceivably afford cage structures. Unfortunately, the material remained as a resin when treated with aqueous NaOH. In contrast, when the insoluble solid obtained prior to the MeCN treatment was recombine with fresh 1 and then subjected to the NaOH conditions, 5 was obtained (Table 4.3, entry 5) in 73% yield. This confirmed that this insoluble material is unreacted 1. 4.5 Single Crystal X-ray Structures Crystallographic structures for compound 3 (CCDC-299794) was reported by Lee and Kawakami based on single crystal X-ray. The same group reported a powder XRD structure for compound 5.20 In our specific case, the structure of compound 5 (CCDC- 1901262) was resolved based on single crystal X-ray crystallography. Data for these crystal structures obtained in our lab and used in this manuscript have been deposited with the Cambridge Crystallographic Data Centre as supplementary publication number CCDC-1912552 for C60H76O14Si12 (3) and CCDC-1901262 for C56H60O16Si8 (5). Copies of the data can be obtained free of charge via the CCDC Website (www.ccdc.cam.ac.uk/structures). 242 6.1. 5,11,14,17-Tetrakis(trimethylsilyl)octaphenyltetracyclo[7.3.3.-33,7]octasilsesquio- xane (C60H76O14Si12) (3) Figure 4-3: Compound 3 showing two molecules of THF solvent per molecule of interest (Displacement ellipsoid contour probability drawn at 50%) Figure 4-4: Single molecule of 3 in the asymmetric unit, which is represented by the reported sum (Z is 4 and Z' is 1) Figure 4-5: Packing diagram of 3 243 5,11,14,17-Tetra(hydro)octaphenyltetracyclo[7.3.3.-33;7]octasilsesquioxane (C48H44O14Si8) (5) Figure 4-6: Compound 5 with two THF molecules co-crystallized per molecule of interest (Displacement ellipsoid contour probability drawn at 50%) Figure 4-7: Single molecule of 5 in the asymmetric unit, which is represented by the reported sum formula (Z is 2 and Z' is 1) 244 Figure 4-8: Hydrogen bonding interactions in 5 The following hydrogen bonding interactions with a maximum D-D distance of 2.9 Å and a minimum angle of 120 ° are present in 5,11,14,17-tetra(hydro)octaphenyltetra- cyclo[7. 3.3.-33;7]octasilsesquioxane (5): O1A–O1S: 2.645 Å, O4A–O1A_1: 2.782 Å, O1B–O2S: 2.647 Å, O4B–O1B_2: 2.743 Å. 245 Figure 4-9: Packing diagram of 5,11,14,17-tetra(hydro)octaphenyltetracyclo[7.3.3.- 33;7]octasilsesquioxane (5) Notes: Jonathan E Dannatt is thanked for his significant contributions to this project during our silicon group meetings. 4.6 Experimental Section 4.6.1 Materials and Methods All reactions were carried out with dry solvents under a nitrogen atmosphere using standard techniques except otherwise stated. DodecaphenylT12 was obtained from Hybrid Plastics. Triethylamine (Et3N) was distilled over calcium hydride before use. Ethyl acetate, hexanes, diethyl ether, acetonitrile, methanol, isopropanol, isobutanol, and acetic acid were used as received. THF was distilled over benzophenone and sodium metal at a temperature of 50 °C under nitrogen prior to use. Glassware was oven dried. Reactions were monitored thin-layer chromatography (TLC) on silica gel plates or a Hydrion Insta-Chek pH pH 0-14 and. 1H, 13C, and 29Si NMR spectra were acquired on an Agilent DirectDrive2 500 MHz NMR spectrometer equipped with a OneProbe operating 246 at 500 MHz for 1H NMR, 126 MHz for 13C NMR, and 99 MHz for 29Si NMR CDCl3 or toluene-d8 and recorded at 25 °C. 1H-NMR spectra were recorded with 8 scans, a relaxation delay of 1s, and a pulse angle of 45° and referenced to tetramethylsilane in CDCl3 (0.00 ppm). 13C-NMR spectra were collected with 254 scans, a relaxation delay of 0.1 s, and a pulse angle 45°. 29Si NMR spectra were recorded with either 256 or 512 scans, a relaxation delay of 12 s and a pulse angle of 45°. Thin-layer chromatography (TLC) was performed on plates of EMD 250-µm silica 60-F254. High-resolution mass spectroscopy was performed with APCI mass spectra recorded on a Finnigan LCQ Deca (ThermoQuest) technologies with LC/MS/MS (quadrupole/time-of-flight) and Waters Xevo G2-XS UPLC/MS/MS inert XL MSD with SIS Direct Insertion Probe. Melting points for all products were measured with a Thomas HOOVER capillary uni-melt melting point apparatus and are uncorrected. X-ray diffraction measurements were performed on a Stoe IPDS2 or a Bruker-AXS SMART APEX 2 CCD diffractometer using graphite- monochromated Mo Kα radiation. The structures were solved using direct methods (SHELXL-97) and refined by full-matrix least-squares techniques against F2 (SHELXL- 97). Cell parameters were retrieved using the SAINT (Bruker, V8.34A, after 2013) software and refined using SAINT (Bruker, V8.34A, after 2013) on 5941 reflections, 47% of the observed reflections. Data reduction was performed using the SAINT (Bruker, V8.34A, after 2013) software which corrects for Lorentz polarization. 247 4.6.1.1 Synthesis of 5,11,14,17-tetrakis(trimethylsilyl)octaphenyltetracyclo[7.3.3. 33;7]octasilsesquioxane (3) from DodecaphenylT12 [Ph12T12] (1) Scheme 4-9: Hydrolysis of Ph12T12 (1) for the synthesis of 15,11,14,17-tetrakis(tri- methylsilyl)octaphenyltetracyclo[7.3.3.33;7]octasilsesquioxane (3) Step I: Hydrolysis of Ph12T12 (1) with NaOH. Hydrolysis of dodecaphenylT12 (1) was carried out under basic conditions following the literature procedure described by Kawakami and Li with slight modifications. 20 Into a 100 mL round bottom flask equipped with a stir bar was charged with Ph 12T12 (1) (2 mmol, 3.17 g) and NaOH (8 mmol, 4 equiv, 0.32 g). The flask was sealed with a septum, its contents placed under a nitrogen atmosphere, and charged with isobutanol (30 mL). Next, water (4 mmol, 2 equiv, 0.075 mL) was added. The reaction flask was placed in a pre- heated oil bath at 90 ⁰C and then the reaction mixture was stirred for 24 h. The flask was cooled to room temperature and the heterogenous mixture filtered through a fine frit filter funnel. The residue was washed several times with isopropanol and dried in an oven at 105 °C for 5 h. The dried white solid (12) was next silylated (Step II) with TMSCl and characterized. 248 Figure 4-10: 5,11,14,17-tetra(sodio)octaphenyltetracyclo[7.3.3.33;7]octasilsesquioxano- late (12) Step II: Silylation of Intermediate (12) into 5,11,14,17-tetrakis(trimethylsilyl)octa- phenyltetracyclo[7.3.3.-33,7]octasilsesquioxane [(PhSiO)8(O)2(OTMS)4] (3). A 100 mL oven-dried round bottom flask containing the white product (12) obtained from the hydrolysis of 2 mmol of Ph12T12 (step 1 above) was equipped with a magnetic stirrer and its contents placed under a nitrogen atmosphere. The flask was placed in an ice bath and charged with THF (20 mL). TMSCl (5.38 mL, 42.4 mmol, 21.2 equiv based on mmol of Ph12T12) and triethylamine (Et3N) (4.96 mL, 35.6 mmol, 17.8 equiv based on mmol of Ph12T12) were added to flask and the reaction mixture stirred vigorously at room temperature for 3 h. Deionized water (20 mL) was added, and the reaction mixture was further stirred for 10 min before being extracted with hexanes (3 x 10 mL). The insoluble solid in the organic phase was separated by filtration using a fine frit funnel. This solid (0.63 g, 0.41 mmol) proved to be the unreacted dodecaphenylT 12 (1) based on proton and silicon NMR. To the hexanes filtrate was added n-hexane (40 mL) and the solution left to stand in a –30 °C refrigerator overnight. The precipitated solid was filtered off and dried at reduced pressure to afford 1.70 g (1.25 mmol, 79% yield based on recovered 1) of pure 5,11,14,17-tetrakis(trimethylsilyl)octaphenyltetracyclo[7.3.3.-33,7]octasilses quioxane [(PhSiO)8(O)2(OTMS)4] (3) as a white crystalline solid (mp 225–228 °C). Note: Yields are calculated based on the starting material. Products are characterized by 1H, 249 13C, 29Si NMR, X-ray crystallography, APCI+ QTof LCMS. Analytical results are provided in Appendix (NMR, X-ray crystallography and mass spectral data). 4.6.1.2. Time-course Study for the Hydrolysis of 1 followed by TMS Capping to Afford 3 Scheme 4-10: Time-course study for the synthesis of 3 from 1 Ten 100 mL round bottom flasks containing 1 (1 mmol), NaOH (4 equiv), H2O (2 equiv) and isobutanol (15 mL) were subjected to the base hydrolysis procedure described in Step I of section 4.6.1.1. These individual reactions were stopped at ten different time points; 0 h, 1 h, 2 h, 4 h, 8 h, 16 h, 24 h, 36 h, 48 h and 72 h respectively. The resulting white precipitates (12) were filtered through a fine frit funnel, washed several times with 2-propanol, and the residues dried in an oven at 105 °C for 5 h. Product identification was done by converting the intermediates into their TMS derivatives as described in Step II (Section 4.6.1.1). The individual products were analyzed by 1H,13C, 29Si NMR and MS (Table 4.1). 250 4.6.1.3 Synthesis of 5,11,14,17-Tetra(hydro)octaphenyltetracyclo[7.3.3.33;7] octasilsesquioxane [(PhSiO)8(O)2(OH)4] 5 from Dodecaphenyl Silsesquioxane [Ph12T12] 1 Scheme 4-11: Base hydrolysis of [Ph12T12] 1 for the synthesis of [(PhSiO)8(O)2(OH)4] 5 Step I: Hydrolysis of Ph12T12 1 with NaOH See step 1, section 4.4.1.1 above. Step II: Acid Hydrolysis of Int I with AcOH Acetic acid (0.48 g, 8 mmol) was added dropwise to a THF (20 mL) dispersion of 12 (obtained from the hydrolysis in step I) under nitrogen atmosphere. The reaction mixture was stirred at room temperature for 1 h. The solution was next neutralized with saturated aqueous sodium hydrogen carbonate (10 mL) and washed with deionized water (20 mL). The mixture was extracted with Et2O (3 x 10 mL) and the heterogenous organic layer was filtered with a fine frit funnel. The residue was dried in an oven at 105 °C for 5 h and analyzed by 1H, 13C, 29Si NMR and APCI+ QTof LCMS Measurements. Results from these analyses showed that the residue was the unreacted Ph12T12 (1). The filtrate was dried over anhydrous magnesium sulfate, filtered and the solvent evaporated under reduced pressure. The resulting solid was washed with acetonitrile from which a white insoluble solid was isolated as pure (PhSiO)8(O)2(OH)4 5 in 0.50 g (0.47 mmol, 61%). Yields were calculated based on the exact amount of 1 that reacted (i.e after deducting 251 the amount of recovered 1). The product was characterized by 1H, 13C and 29Si NMR, X- ray crystallography and APCI+ QTof LCMS Measurements (Appendix). 4.6.1.4 Screening Conditions for the Synthesis of (PhSiO)8(O)2(OH)4 3 from 1 Scheme 4-12: Optimization for the synthesis of (PhSiO)8(O)2(OH)4 (5) Step I: Hydrolysis of Ph12T12 1 with NaOH See step 1, section 4.4.1.1 above for experimental procedure. Cleavage of 1 with NaOH was done following the procedure outlined in step I of section 4.4.1.1 except that the amounts of NaOH used were varied (Table 4.3). Step II: Acid Hydrolysis of Int-I with AcOH Acid hydrolysis of the intermediate from step I, section 4.4.1.1 above was carried out with AcOH following procedure as outlined in step II of section 4.4.1.3. A series of reactions were run with varied amounts of 1, NaOH, AcOH and reaction time. Results from this screening are shown in Table 4.3. 252 APPENDIX 253 Copies of 1H, 13C, 29Si NMR Spectra Figure 4-11: 1H NMR of 3 (500 MHz, CDCl3) 254 Figure 4-12: 13C NMR of 3 (126 MHz, CDCl3) Figure 4-13: 29Si NMR of 3 (99 MHz, CDCl3) 255 Figure 4-14: 1H NMR of 5 (500 MHz, CDCl3) Figure 4-15: 13C NMR of 5 (126 MHz, CDCl3) 256 Figure 4-16: 29Si NMR of 5 (99 MHz, CDCl3) 257 Spectral Data from Time-Course Experiment 1H NMR (500 MHz, Chloroform-d) δ 7.46 – 7.07 (m, 40H), 0.08 (s, 36H). Figure 4-17: 1H NMR of 3 – 16h (500 MHz, CDCl3) 258 29Si NMR (99 MHz, Chloroform-d) δ 10.54 – 10.50, -76.11, -78.94. Figure 4-18: 29Si NMR of 3 – 16h (99 MHz, CDCl3) 259 1H NMR (500 MHz, Chloroform-d) δ 7.46 – 7.07 (m, 40H), 0.06 (s, 36H). Figure 4-19: 1H NMR of 3 – 24h (500 MHz, CDCl3) 260 29Si NMR (99 MHz, Chloroform-d) δ 10.52, -76.11, -78.94. Figure 4-20: 29Si NMR 3 – 24h (99 MHz, CDCl3) 261 1H NMR (500 MHz, Chloroform-d) δ 7.46 – 7.07 (m, 40H), 0.06 (s, 36H). Figure 4-21: 1H NMR 3 – 36h (500 MHz, CDCl3) 262 29Si NMR (99 MHz, Chloroform-d) δ 10.52, -76.11, -78.94. Figure 4-22: 29Si NMR 3 – 36h (99 MHz, CDCl3) 263 1H NMR (500 MHz, Chloroform-d) δ 7.46 – 7.08 (m, 40H), 0.06 (s, 36H). Figure 4-23: 1H NMR 3 – 48h (500 MHz, CDCl3) 264 29Si NMR (99 MHz, Chloroform-d) δ 10.51, -76.12, -78.95. Figure 4-24: 29Si NMR 3 – 48h (99 MHz, CDCl3) 265 1H NMR (500 MHz, Chloroform-d) δ 7.47 – 7.07 (m, 41H), 0.06 (s, 36H). Figure 4-25: 1H NMR 3 – 72h (500 MHz, CDCl3) 266 29Si NMR (99 MHz, Chloroform-d) δ 10.52, -76.11, -78.94. Figure 4-26: 29Si NMR 3 – 72h (99 MHz, CDCl3) 267 Stacked 1H NMR of 5,11,14,17-tetrakis(trimethylsilyl)octaphenyltetracyclo[7.3.3.- 33,7]octasilsesquioxane (3) from 16 to 72 Hydrolysis of 1 Figure 4-27: Stacked 1H NMR of 5,11,14,17-tetrakis(trimethylsilyl)octaphenyltetracyclo- [7.3.3.-33,7]octasilsesquioxane (3) from 16 to 72 Hydrolysis of 1 (500 MHz, CDCl3) 268 Stacked 29Si NMR of 5,11,14,17-tetrakis(trimethylsilyl)octaphenyltetracyclo[7.3.3.- 33,7]octasilsesquioxane (3) from 16 to 72 Hydrolysis of 1 Figure 4-28: Stacked 29Si NMR of 5,11,14,17-tetrakis(trimethylsilyl)octaphenyltetracyclo- [7.3.3.-33,7]octasilsesquioxane (3) from 16 to 72 Hydrolysis of 1 (99 MHz, CDCl3) 269 1H and 29Si NMR of Commercial Dodecaphenylsilsesquioxane (Ph12T12) (1) 1H NMR (500 MHz, Toluene-d8) δ 8.15 – 7.84 (m, 24H), 7.40 – 7.17 (m, 36H). Figure 4-29: 1H NMR of commercial 1 (500 MHz, Toluene-d8) 270 29Si NMR (99 MHz, Toluene-d8) δ -73.63, -75.77 Figure 4-30: 29Si NMR of commercial 1 (99 MHz, CDCl3) 271 Recovered Ph12T12 (1) from the hydrolysis of 1 with NaOH 1H NMR (500 MHz, Toluene-d8) δ 8.21 – 7.74 (m, 24H), 7.38 – 7.19 (m, 36H). Figure 4-31: 1H NMR of recovered 1 (500 MHz, Toluene-d8) 272 29Si NMR (99 MHz, Toluene-d8) δ -73.63, -75.77. Figure 4-32: 29Si NMR of recovered 1 (99 MHz, CDCl3) 273 Stacked 1H NMR of Commercial Ph12T12 (1) and Recovered Ph12T12 (1) Figure 4-33: Stacked 1H NMR of Commercial Ph12T12 (1) and Recovered Ph12T12 (1) (500 MHz, Toluene-d8) 274 Stacked 29Si NMR of Commercial Ph12T12 (1) and Recovered Ph12T12 (1) Figure 4-34: Stacked 29Si NMR of Commercial Ph12T12 (1) and Recovered Ph12T12 (1) (99 MHz, CDCl3) 275 Figure 4-35: Stacked 1H NMR of Resinous product from the acid hydrolysis of intermediate salt (12) (500 MHz, CDCl3) The aromatic protons in the 6.5–8.0 ppm is attributed to phenyl groups.3 The peaks in this region are broader due to a higher molecular weight suggesting that the material could be a resin from Ph12T12. 276 Stacked 29Si NMR of Resinous product from the acid hydrolysis of intermediate salt 12 Figure 4-36: Stacked 29Si NMR of Resinous product from the acid hydrolysis of intermediate salt 12 (99 MHz, CDCl3) The broad siloxane peak centered about -80 ppm is characteristic of the T3 unit Ph-Si(O-Si-)3 denoting a polysilsesquioxane fragment.3,4 The sharp peaks between -77 and -79 ppm are ascribed to some fully condensed siloxane structures lost into the MeCN solvent. 277 DOESY NMR Spectra of resinous product. Figure 4-37: DOESY NMR Spectra of resinous product (500 MHz, CDCl3) 278 DOSY Spectra for 5,11,14,17-tetrakis(trimethylsilyl)octaphenyltetracyclo[7.3.3.- 33,7]octasilsesquioxane (3). Figure 4-38: DOSY Spectra for 5,11,14,17-tetrakis(trimethylsilyl)octaphenyltetracyclo- [7.3.3.-33,7]octasilsesquioxane (3) (500 MHz, CDCl3) 279 Selected Mass Spectra Figure 4-39: Commercial Ph12T12 (1) Figure 4-40: 5,11,14,17-tetrakis(trimethylsilyl)octaphenyltetracyclo[7.3.3.-33,7]octasilses- quioxane (3) from 16 h hydrolyzed 12 280 Figure 4-41: 5,11,14,17-tetrakis(trimethylsilyl)octaphenyltetracyclo[7.3.3.-33,7]octasilses- quioxane (3) from 24 h hydrolyzed 12 Figure 4-42: 5,11,14,17-tetrakis(trimethylsilyl)octaphenyltetracyclo[7.3.3.-33,7]octasilses- quioxane (3) from 36 h hydrolyzed 12 281 Figure 4-43: 5,11,14,17-tetrakis(trimethylsilyl)octaphenyltetracyclo[7.3.3.-33,7]octasilses- quioxane (3) from 48 h hydrolyzed 12 Figure 4-44: 5,11,14,17-tetrakis(trimethylsilyl)octaphenyltetracyclo[7.3.3.-33,7]octasilses- quioxane (3) from 72 h hydrolyzed 12 282 Figure 4-45: MS Spectra for 0 – 2 h hydrolyzed 12 Figure 4-46: MS Spectra for 4 – 8 h hydrolyzed 12 283 Figure 4-47: MS Spectra for 36 – 72 h hydrolyzed 12 Figure 4-48: Mass Spectral Data for Resinous Mixture 284 X-ray crystallographic data Table 4-5: Crystal and Experimental Data for 5,11,14,17-tetrakis(trimethylsilyl)- octaphenyltetracyclo[7.3.3.-33,7]octasilsesquioxane (3) (CCDC 299794a) Compound 5,11,14,17-tetrakis(trimethylsilyl)octaphenyltetracyclo [7.3.3.-33,7]octasilsesquioxane (3) Dcalc./ g cm-3 1.239 μ/mm-1 2.317 Formula Weight 1502.49 Color colourless Shape block Size/mm3 0.41×0.30×0.22 T/K 173(2) Crystal System monoclinic Space Group P2/n a/Å 12.8512(2) b/Å 18.5351(5) c/Å 16.9170(3) α/° 90 / ° 91.2150(10) /° 90 V/Å3 4028.69(14) Z 2 Z' 0.5 Wavelength/Å 1.541838 Radiation type CuK min/° 3.538 max/° 68.573 Measured Refl. 13317 Independent Refl. 13317 Reflections with I > 2(I) 11099 Rint . Parameters 440 Restraints 0 Largest Peak 0.631 Deepest Hole -0.535 GooF 1.087 wR2 (all data) 0.1878 wR2 0.1750 R1 (all data) 0.0737 R1 0.0603 aCrystllographic data are those obtained in this study but the CDCC number is that from Kawakami and Lee.20 285 Table 4-6: Crystal and Experimental Data for 5,11,14,17-tetra(hydro)octaphenyl tetracyclo[7.3.3.-33;7]octasilsesquioxane (C48H44O14Si8) (5) Compound 5,11,14,17-Tetra(hydro)octaphenyltetracyclo[7.3.3.-33;7] octasilsesquioxane (5) CCDC 1901262 Formula C56H60O16Si8 Dcalc./ g cm-3 1.339 μ/mm-1 2.238 Formula Weight 1213.76 Color colourless Shape needle Size/mm3 0.28×0.10×0.04 T/K 173(2) Crystal System triclinic Space Group P-1 a/Å 10.9096(2) b/Å 15.1731(3) c/Å 18.3358(3) /° 83.1970(10) /° 88.0820(10) /° 88.1450(10) V/Å3 3010.88(10) Z 2 Z' 1 Wavelength/Å 1.541838 Radiation type CuK ° 2.428 min/ max/° 72.185 Measured Refl. 45542 Independent Refl. 11525 Reflections with I > 2(I) 7020 Rint 0.1531 Parameters 725 Restraints 0 Largest Peak 0.543 Deepest Hole -0.414 GooF 1.013 wR2 (all data) 0.1589 wR2 0.1338 R1 (all data) 0.1140 R1 0.0594 286 Table 4-7: Bond Lengths in Å for 5,11,14,17-tetra(hydro)octaphenyltetracyclo[7.3.3.- 33;7]octasilsesquioxane (5) Atom Atom Length (Å) Si1A O1A 1.631(3) Si1A O2A 1.613(3) Si1A O6A 1 1.618(3) Si1A C0AA 1.839(4) Si2A O3A 1.620(3) Si2A O4A 1.613(3) Si2A O7A 1 1.619(3) Si2A C6AA 1.852(4) Si3A O2A 1.622(3) Si3A O3A 1.600(3) Si3A O5A 1.606(3) Si3A C2BA 1.848(4) Si4A O5A 1.608(3) Si4A O6A 1.611(3) Si4A O7A 1.612(3) Si4A C00S 1.847(4) C0AA C1AA 1.384(6) C0AA C5AA 1.392(6) C0BA C1BA 1.384(7) C0BA C9AA 1.378(8) C00S C012 1.377(6) C00S C015 1.394(6) C1AA C2AA 1.401(6) C01B C01I 1.367(7) C01B C01O 1.358(7) C1BA C6AA 1.387(6) C01I C015 1.390(6) C01O C012 1.407(7) C2AA C3AA 1.371(7) C2BA C3BA 1.398(6) C2BA C7BA 1.381(6) C3AA C4AA 1.361(7) C3BA C4BA 1.393(6) C4AA C5AA 1.393(6) C4BA C5BA 1.379(8) C5BA C6BA 1.354(7) C6AA C7AA 1.404(6) C6BA C7BA 1.390(7) C7AA C8AA 1.382(7) C8AA C9AA 1.381(9) Si1B O1B 1.621(3) Si1B O2B 1.624(3) Si1B O7B 2 1.618(3) 287 Table 4-7 (cont’d) Atom Atom Length (Å) Si1B C1A 1.844(4) Si2B O3B 1.620(3) Si2B O4B 1.606(3) Si2B O6B2 1.628(3) Si2B C7A 1.843(4) Si3B O2B 1.619(3) Si3B O3B 1.602(3) Si3B O5B 1.605(3) Si3B C13A 1.859(4) Si4B O5B 1.615(3) Si4B O7B 1.613(3) Si4B C19A 1.837(4) C1A C2A 1.394(6) C1A C6A 1.397(6) C2A C3A 1.393(6) C3A C4A 1.382(7) C4A C5A 1.368(7) C5A C6A 1.381(6) C7A C8A 1.383(7) C7A C12A 1.394(7) C8A C9A 1.398(8) C9A C10A 1.373(10) C10A C11A 1.369(10) C11A C12A 1.379(7) C13A C14A 1.385(7) C13A C18A 1.385(7) C14A C15A 1.385(7) C15A C16A 1.378(10) C16A C17A 1.368(10) C17A C18A 1.410(7) C19A C20A 1.396(6) C19A C24A 1.398(6) C20A C21A 1.390(6) C21A C22A 1.375(7) C22A C23A 1.372(7) C23A C24A 1.386(6) O1S C1S 1.435(6) O1S C4S 1.423(7) C1S C2S 1.483(8) C2S C3S 1.511(8) C3S C4S 1.485(8) 288 Table 4-8: Bond Angles in ° for 5,11,14,17-tetra(hydro)octaphenyltetracyclo[7.3.3.- 33;7]octasilsesquioxane (5) Atom Atom Atom Angle (°) O1A Si1A C0AA 112.23(17) O2A Si1A O1A 105.51(15) O2A Si1A O6A 1 111.33(15) O2A Si1A C0AA 110.80(17) O6A 1 Si1A O1A 109.87(16) O6A1 Si1A C0AA 107.18(16) O3A Si2A C6AA 109.33(18) O4A Si2A O3A 109.95(16) O4A Si2A O7A 1 109.97(18) O4A Si2A C6AA 108.95(18) O7A 1 Si2A O3A 108.39(16) O7A1 Si2A C6AA 110.24(18) O2A Si3A C2BA 111.61(17) O3A Si3A O2A 109.26(16) O3A Si3A O5A 109.59(16) O3A Si3A C2BA 109.92(18) O5A Si3A O2A 107.61(15) O5A Si3A C2BA 108.81(17) O5A Si4A O6A 110.25(16) O5A Si4A O7A 108.38(16) O5A Si4A C00S 107.60(17) O6A Si4A O7A 110.06(16) O6A Si4A C00S 110.08(18) O7A Si4A C00S 110.42(17) Si1A O2A Si3A 150.4(2) Si3A O3A Si2A 163.0(2) Si3A O5A Si4A 153.4(2) Si4A O6A Si1A1 153.3(2) Si4A O7A Si2A 1 149.0(2) C1AA C0AA Si1A 123.3(3) C1AA C0AA C5AA 118.1(4) C5AA C0AA Si1A 118.7(3) C9AA C0BA C1BA 120.6(5) C012 C00S Si4A 123.5(3) C012 C00S C015 117.6(4) C015 C00S Si4A 118.8(3) C0AA C1AA C2AA 120.6(5) C01O C01B C01I 121.2(5) C0BA C1BA C6AA 121.0(5) C01B C01I C015 118.8(5) C01B C01O C012 119.9(5) 289 Table 4-8 (cont’d) Atom Atom Atom Angle (°) C3AA C2AA C1AA 119.8(5) C3BA C2BA Si3A 121.3(3) C7BA C2BA Si3A 121.6(3) C7BA C2BA C3BA 117.1(4) C4AA C3AA C2AA 120.7(4) C4BA C3BA C2BA 120.7(5) C3AA C4AA C5AA 119.8(5) C5BA C4BA C3BA 120.0(5) C0AA C5AA C4AA 121.1(4) C6BA C5BA C4BA 120.3(5) C1BA C6AA Si2A 122.0(3) C1BA C6AA C7AA 118.2(4) C7AA C6AA Si2A 119.7(3) C5BA C6BA C7BA 119.7(5) C8AA C7AA C6AA 120.0(5) C2BA C7BA C6BA 122.2(5) C9AA C8AA C7AA 121.2(6) C0BA C9AA C8AA 118.9(5) C00S C012 C01O 120.6(5) C01I C015 C00S 121.9(4) O1B Si1B O2B 104.20(14) O1B Si1B C1A 111.67(17) O2B Si1B C1A 110.98(16) O7B 2 Si1B O1B 111.21(15) O7B2 Si1B O2B 110.92(15) O7B 2 Si1B C1A 107.90(17) O3B Si2B O6B2 108.00(15) O3B Si2B C7A 110.53(17) O4B Si2B O3B 109.46(16) O4B Si2B O6B2 111.49(16) O4B Si2B C7A 108.32(18) O6B2 Si2B C7A 109.06(19) O2B Si3B C13A 111.65(17) O3B Si3B O2B 109.17(15) O3B Si3B O5B 109.57(16) O3B Si3B C13A 109.82(19) O5B Si3B O2B 107.97(15) O5B Si3B C13A 108.64(18) O5B Si4B C19A 109.32(16) O6B Si4B O5B 109.22(15) O6B Si4B O7B 110.68(15) O6B Si4B C19A 110.06(17) O7B Si4B O5B 109.27(16) O7B Si4B C19A 108.27(17) 290 Table 4-8 (cont’d) Atom Atom Atom Angle (°) Si3B O2B Si1B 146.72(18) Si3B O3B Si2B 167.1(2) Si3B O5B Si4B 155.21(19) Si4B O6B Si2B2 144.03(19) Si4B O7B Si1B2 149.74(19) C2A C1A Si1B 122.5(3) C2A C1A C6A 117.7(4) C6A C1A Si1B 119.9(3) C3A C2A C1A 121.1(4) C4A C3A C2A 119.3(5) C5A C4A C3A 120.5(4) C4A C5A C6A 120.1(5) C5A C6A C1A 121.2(4) C8A C7A Si2B 121.4(4) C8A C7A C12A 118.0(4) C12A C7A Si2B 120.7(4) C7A C8A C9A 121.3(6) C10A C9A C8A 118.8(7) C11A C10A C9A 121.0(6) C10A C11A C12A 119.9(7) C11A C12A C7A 121.0(6) C14A C13A Si3B 120.4(4) C14A C13A C18A 118.7(4) C18A C13A Si3B 120.8(4) C13A C14A C15A 122.0(6) C16A C15A C14A 118.3(6) 17A C16A C15A 121.6(5) C16A C17A C18A 119.4(6) C13A C18A C17A 119.8(6) C20A C19A Si4B 121.7(3) C20A C19A C24A 117.1(4) C24A C19A Si4B 121.1(3) C21A C20A C19A 121.5(4) C22A C21A C20A 119.7(4) C23A C22A C21A 120.2(4) C22A C23A C24A 120.3(5) C23A C24A C19A 121.2(4) C4S O1S C1S 106.8(4) O1S C1S C2S 105.0(4) C1S C2S C3S 102.0(5) C4S C3S C2S 103.3(5) C5S C6S C7S 103.9(4) –––– 11-x,1-y,1-z; 2-x,2-y,2-z 291 Table 4-9: Hydrogen Fractional Atomic Coordinates (×104) and Equivalent Isotropic Displacement Parameters (Å2×103) for 5,11,14,17-tetra(hydro)octaphenyltetracyclo [7.3.3.-33;7]octasilsesquioxane (5). Ueq is defined as 1/3 of the trace of the orthogonalised Uij Atom x y z Ueq H1A 4555.44 4990.65 2757.58 54 H4A 6551.4 4018.68 6578.17 60 H0BA 8563.17 430.43 6312.28 79 H1AA 3312.2 2342.31 3922.91 57 H01B -1747.43 5915.8 7143.67 66 H1BA 8118.58 1916.35 6424.62 54 H01I -1531.02 5077.63 6167.07 60 H01O -70.31 6525.63 7597.44 77 H2AA 3290.7 1040.03 3347.79 72 H3AA 4532.78 901.61 2314.87 61 H3BA 1242.08 3149.68 4927.78 50 H4AA 5796.42 2035.04 1844.59 58 H4BA 67.48 1887.28 5217.45 66 H5AA 5846.61 3328.67 2418.06 48 H5BA 879.23 647.78 5930.3 70 H6BA 2818.08 676.04 6385.93 70 H7AA 5646.85 1982.02 4816.92 61 H7BA 3997.48 1926.96 6100.59 56 H8AA 6101.12 493.04 4720.37 85 H9AA 7584.54 -284.29 5446.17 90 H012 1877.79 6374.44 7027.09 58 H015 406.31 4895.87 5614.73 50 H1B 350.66 11237 7911.04 49 H4B -1605.04 8424.38 11168.95 52 H2A -1153.79 9075.56 7336.24 51 H3A -783.61 8321.46 6305.69 70 H4AB 1230.54 8076.6 5891.55 66 H5A 2858.38 8492.06 6539.12 58 H6A 2501.97 9240 7562.72 47 H8A -1225.21 6346.38 10422.81 93 H9A -1572.43 5095.27 9826.1 129 H10A -2514.42 5282.31 8697.84 115 H11A -3013.66 6687.03 8134.88 111 H12A -2623.67 7929.2 8709.37 81 H14A 899.13 7235.77 8958.05 71 H15A 2036.07 5978.42 8692.84 97 H16A 4041.2 5779.58 9090.44 105 H17A 4924.26 6819.32 9717.3 98 H18A 3742.62 8066.16 10021.59 67 H20A 4781.37 10277.05 10575.04 46 292 Table 4-9 (cont’d) Atom x y z Ueq H21A 6591.13 9826.28 11169.34 56 H22A 6505.63 9026.49 12332.51 55 H23A 4623.85 8671.41 12898.81 58 H24A 2812.75 9087.4 12300.42 46 H1SA 7111.46 5778.75 1745.11 76 H1SB 6716.28 5562.96 2600.05 76 H2SA 6796.81 7168.88 2072.46 79 H2SB 5640.17 6874.28 2608.03 79 H3SA 4600.03 7422.58 1584.78 94 H3SB 5699.85 7153.41 1036.87 94 H4SA 3808.73 6107.29 1647.95 104 H4SB 4687.07 5946.06 953.39 104 H5SA -1274.97 12214.5 8512.18 72 H5SB -2186.69 12571.88 7864.9 72 H6SA -947.49 13631.76 8603.98 78 H6SB -1537.69 13950.12 7818.78 78 H7SA 485.5 14174.66 7498.21 71 H7SB 951.51 13365.31 8085.29 71 H8SA -172.08 13230.14 6711.43 68 H8SB 1050.13 12707.29 7014.88 68 Table 4-10: Hydrogen Bond information for 5,11,14,17-tetra(hydro)octaphenyltetra- cyclo[7.3.3.-33;7]octasilsesquioxane (5) D H A d(D-H) (Å) d(H-A) (Å) d(D-A) (Å) D-H-A (°) O1A H1A O1S 0.84 1.82 2.645(5) 168.6 O4A H4A O1A1 0.84 1.95 2.782(4) 172.1 O1B H1B O2S 0.84 1.84 2.647(4) 161.2 O4B H4B O1B2 0.84 1.91 2.743(4) 169.5 –––– 11-x,1-y,1-z; 2-x,2-y,2-z 293 REFERENCES 294 REFERENCES (1) Tanaka, K.; Chujo, Y. 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Oxford Scholarship Online, 2018. 297 Chapter 5.0: De novo construction of Double-Decker Shaped Silsesquioxanes with Modifiable Surface Functionalities 5.1 Introduction There is a growing demand for novel hybrid materials with the double-decker shaped architecture that can inspire new technological applications in chemistry and engineering. With the extensive research efforts reported so far,1,2 the only known double decker is the octaphenyl double-decker shaped silsesquioxane (DDSQ).3–5 In the past several years, this cage has been functionalized in diverse ways on its open ends leading to the generation of condensed symmetric and asymmetric DDSQs.6–11 The development of methodologies that can mimic this nanocage, particularly those bearing transformable groups as the silica coronae, would be intriguing molecular templates that may afford tunable multifunctional nanocomposites through modifications of its sides and surfaces. Such molecular designs are promising precursors in materials and polymer chemistry for the generation of linear POSS/polymer composites and the formation of 3D networks. To actualize such a vision, the manipulation of trifunctional silanes or caged silsesquioxanes decorated with transformable organic peripherals on the silicon vertices should be explored. Generally, cage silsesquioxanes bearing various silica coronae have been obtained from the hydrolytic condensation of trifunctional silanes, and various benzyltrimethyl- ammonium hydroxide (BzTMAH) or tetrabutylammonium fluoride (TBAF) catalyzed condensation reactions.2,12–20 Lately, cages with reactive functionalities on the silicon vertices have attracted interest for surface functionalization and for their plausible utility as precursors to various incompletely condensed nanohybrid functional 298 materials.21–31 Reactive POSS cages bearing ortho-, meta- and para- functional moieties on the phenyl groups are quite promising candidates32–37 for the generation of 3D composites. Thus, part of our efforts to design hybrid functional nanoparticles was to explore possible routes for the synthesis of DDSQs with defined symmetry and surface functionalities that are based on peripherals other than phenyl. Inspired by the works of the Ohgum and Kawakami groups on the synthesis of the octaphenyl double-decker shaped silsesquioxane,3,4 and the recent report by the Unno group on the assembly of styryl-functionalized Tn cages, we envisioned that a DDSQ with styryl or halophenyl functionalities as coronae could be quite interesting. Such double- decker shaped silsesquioxanes, if realized, would enable a wide range of corner capping and surface modifications that could afford nanobuilding materials with superior properties. To fabricate such compounds, our efforts were focused on obtaining the incompletely condensed octafunctional double-decker oligomeric silsesquioxanes trimmed on the silicon vertices with styryl and 4-bromophenyl motifs. Such molecular frameworks will offer multifunctional sites for modification into more interesting classes of nano-precursors with perfect symmetry. Thus, we intended to either directly assemble the substituted phenylDDSQ(OH)4 from the monomeric chloro/alkoxysilane or from the controlled cleavage of the fully condensed substituted octafunctional POSS. The unhindered substituent on the phenyl moiety and the free silanol groups will provide the necessary molecular design for multi functionalization using various chemistries including epoxidation, hydrosilylation, thioetherification, polymerization, and other reactions typical of alkenes and cross-coupling reactions into a variety of products for various applications. 299 5.1.1 Styrenyl functionalized Polyhedral Oligomeric Silsesquioxanes The direct synthesis of POSS cages with styryl and styrenyl substituents has been a longstanding challenge. Lately however, several groups have reported indirect procedures to access styrenyl POSS. For instance, Itami, et al. reported the synthesis of octastyrenyl POSS via the transformation of a pre-assembled octavinylsilsesquioxane (octavinylT8) using both a ruthenium carbene complexed–silylative coupling and cross- metathesis with various substituted styrenes (Scheme 5-1).38,39 Scheme 5-1: Silylative coupling and cross metathesis of octavinylT8 with styrenes The resultant POSS cage is an octastyrenyl POSS in which the styrene is bound onto the POSS core via the alkenyl moiety. Starting with a terminal aryl alkyne, the Ye group also reported the synthesis of an octastyrenyl POSS from the hydrosilylation of an octasilanePOSS (POSS-OSi(Me)2H) with ethynylbenzene. A rigid octastyrenyl POSS with alkenylsilane linkages was obtained from the treatment of an equimolar ratio of [Si-H]:[C=C] = (1:1) (Scheme 5-2).40 300 Scheme 5-2: Hydrosilylation of POSS-OSi(Me)2H with ethynylbenzene The Cole-Hamilton group in 2008 disclosed a myriad of techniques for the elaboration of octavinylsilsesquioxane into various functionalized cubic octastyrenyl- and octastyrethynyl-silsesquioxanes. A demonstration of the versatility of their work was illustrated by the successful modification of all eight peripheral vinyl groups in octavinylT8 using various techniques including the palladium catalyzed Heck coupling, ruthenium catalyzed cross metathesis, Karstedt’s catalyzed hydrosilylation and Sonogashira coupling reactions (Scheme 5-3) therein designated as POSS-A through H.41 301 Scheme 5-3: Elaboration of OctavinylT8 for the synthesis of a variety of different POSS Reaction conditions: (i) 4-bromostyrene, Grubbs’ catalyst (1st gen., 4 mol%), CH2Cl2; (ii) (3,5-dibromophenyl)dimethylsilane, Karstedt’s catalyst (75 µL), Et 2O; (iii) 4- bromophenyl(dimethyl)silane, Karstedt’s catalyst (75 µL), Et 2O; (iv) trimethylsilylacetylene, [Pd(PPh3)2Cl2] (78 mol%), CuI (1.59 equiv), PPh3, Et3N/THF; (v) 302 iodobenzene, [Pd(OAc)2] (40 mol%), PPh3, Et3N/THF; (vi) 4-(4,4,5,5-tetramethyl-1,3,2- dioxaborolan-2-yl)styrene, Grubbs’ catalyst (1st gen., 6 mol%), CH2Cl2; (vii) 4-vinybenzyl chloride, Grubbs’ catalyst (1st gen. 3 mol%), CH2Cl2. The presence of olefinic, acetylenic, chloro, bromo or Bpin groups in these functional compounds make them ideal nanobuilding blocks for further transformation into novel interesting materials with useful chemical and mechanical properties. In contrast to a protocol reported by the Laine group for the iron-catalyzed synthesis of brominated POSS, this procedure allows for the precise number and location of bromine atoms per unit molecule. Octafunctionalized POSS trimmed with aryl borate groups ideal for Suzuki cross coupling were also obtained (Scheme 5-3, (iv)). Styrenyl functionalized POSSs have also been obtained from vinyl substituted polysilsesquioxanes, −[vinylSiO1.5]n−. For instance, the Laine group reported a fluoride ion catalyzed rearrangement of oligomeric and polymeric polyvinylsilsesquioxanes (PVS) in THF44,45 for the synthesis of a mixture of T10, T12 and T14 vinyl functionalized cages (Scheme 5-4). Scheme 5-4: Fluoride catalyzed rearrangement of polysilsesquioxanes to mixed T10 and T12 isomers Elaboration of these cages by metathesis with p-R-styrene afforded the styrenyl analogues therein referred to as the generation 1 compounds (GEN1) (Scheme 5-5).44 303 Scheme 5-5: Metathesis of mixed VinylT10 and VinylT12 for thesynthesis of styrenylT10/12 cages Further modification of these cages via Heck reaction with p-substituted-styrenes gave the p-substituted-stilbenevinylT10/12 GEN2 derivatives in excellent yields. 5.1.2 Corner-capping DDSQ(OH)4 with styrenyl and styryl groups Attempts have also been made to functionalize DDSQ(OH)4 with styryl and styrenyl groups, but these transformations have so far been limited to the open ends of the cage. For instance, pre-functionalized divinyl(Me)DDSQs have been transformed into styrenyl DDSQs by various groups. The Zheng group in 2016 introduced styrenyl groups 304 onto the DDSQ(OH)4 indirectly via a Heck coupling reaction of a pre-fabricated 3,13- divinyloctaphenyl double decker silsesquioxane (3,13-divinyl DDSQ) with 4-bromoaniline (Scheme 5-6).43 The precursor, 3,13-divinyloctaphenyl double decker silsesquioxane (3,13-divinyl DDSQ) was obtained from the silylation of octaphenyldicycloocatasiloxane tetrasodium silanolate with methylvinyldichlorosilane. Scheme 5-6: Synthesis of 3,13-dianilino DDSQ from phenyltrimethoxysilane Recently, Zac et al.9,46 reported a ruthenium catalyzed metathesis of divinyl- capped DDSQs with several substituted styrenes for the synthesis of asymmetrically functionalized styrenyl D2T8 silsesquioxanes (Scheme 5-7). The [RuHCl(CO)(NHC)(PCy3)] in the presence of CuCl was highly efficient with exclusive (E)- selective silylative coupling of various para-substituted styrenes and the divinylDDSQ. However, in this work, the styryl group was grafted to the cage by the vinyl moiety affording a condensed DDSQ with hindered ethynyl groups. 305 Scheme 5-7: Synthesis of asymmetric styrenylDDSQs from the silylative coupling of divinylDDSQ with substituted styrenes Lately our laboratory was able to corner cap DDSQ(OH)4 with a pre-synthesized styryl(Me)SiCl2 providing a D2T8 DDSQ with unhindered styryl groups for the first time (Scheme 5-8). Even with this development, the system only afforded a condensed styryl functionalized D2T8 DDSQ with unhindered vinyl groups for post-modification. Scheme 5-8: Synthesis of [(styryl(Me)}2DDSQ] 5.1.3 Styryl functionalized Polyhedral Oligomeric Silsesquioxanes Until the latest work by Unno and coworkers in 2020,47 styryl decorated cages linked to the Tn POSS via the phenyl group were unknown (Scheme 5-9). However, several groups have reported the successful synthesis of monofunctionalized styryl POSS via corner-capping of a trisilanol POSS48 and by Grubbs’ catalyzed metathesis of a pre-monofunctionalized vinyl POSS with substituted styrenes,49 the styryl Tn garnished systems with unhindered vinylic groups have the advantage of making the vinylic moiety easily accessible for further modifications. 306 Scheme 5-9: Route to styryl-functionalized Tn cage silsesquioxanes Like other POSS cages, the well-defined structures of styryl Tn POSS make them potential nano-linkers to polymer matrices with good thermal and oxidative stabilities. Their benignity and nano-structural dimensions (approximately 3 Å) could equally make them effective templates as nanocarriers in medicine, catalysis, and electronics. The sterically unhindered styryl group provides the opportunity for post-modifications and/or their utility as synthons for the synthesis of 3D cross-linked polymers. Styryl functionalized POSS cages with an encapsulated fluoride ion (T8-F) in the siloxy core has also been reported by Man and coworkers (Scheme 5-10).50 The fluoride ion was extracted from the cage using various approaches, in most cases leading to improved yields of the T8 compound.14,16,50,51 Scheme 5-10: Synthesis of styryl-functionalised T8-F Cage 307 Some common approaches include dissolution of the cage in THF followed by stirring in the presence of either LiCl or CaCl2, or washing with a saturated solution of CaCl2, or addition of CaCl2 to the reaction mixture prior to workup to sequester the fluoride anion by the Ca2+. Post-functionalizations of this material via metathesis, silylative coupling, Heck coupling, thiol-ene click reactions, etc. have offered more useful products that find applications in catalysis,52,53 optical materials54,55 and coatings.56 Based on literature reports, alkoxysilanes with electron-donating sp3-hybridized organic groups will only give T8 cages without entrapped fluoride whereas those with electron withdrawing sp 3 or sp2 hybridized groups affords T8-F compound.47,50,57,58 Interestingly further attempts to modify these cages have remained a challenge. However, other POSS cages with entrapped fluoride ions are known. The Bassindale’s group for instance, reported the first successful encapsulation of a fluoride ion in the void of a cubic octaphenyl-functionalized POSS.59 5.1.4 p-Bromophenyl functionalized Polyhedral Oligomeric Silsesquioxanes Cubic brominated octaphenyl silsesquioxanes have been obtained from the monomeric alkoxysilane and from the bromination of octaphenyl POSS using Br2/Fe. The iron catalyzed route with molecular bromine reported by the Brick et al. is controlled by the reaction stoichiometry.60 The process is complicated and, depending on the reaction stoichiometry, can lead to a mixture of multibrominated-phenyl substitution products. The initial bromination occurs at the para position of the phenyl groups followed by subsequent intramolecular rearrangement that affords the 2,5-dibrominated species as the major product (Scheme 5-11). Such brominated T8 POSS can undergo various coupling reactions to generate a range of inorganic-organic nanohybrid materials. 308 Scheme 5-11: Synthesis of Brominated Octaphenylsilsesquioxanes (BrxOPS), x = the average number of bromines per molecule Further exploration of this chemistry by way of manipulating reaction parameters such as choice of catalyst, temperature, concentration and order of reagents addition led this same group to discover a better route for the synthesis of octa-, hexadeca- and tetraicosa-brominated octaphenylsilsesquioxane, [PhSiO1.5]8 or OPS.61 Two mechanisms have been proposed for these 3-D brominated cages; one with an external catalyst and the other without. They observed that even in the absence of a Lewis catalyst, OPS can auto-catalyze its bromination in DCM to give a high selective ortho:para brominated cage of 85:15 (Scheme 5-12). Scheme 5-12: Selective self-catalyzed bromination of octa(phenyl)silsesquioxane (OPS) for the selective synthesis of octabrominated OPS To account for this surprising bromination of the unactivated phenyl groups, they opined that the cage, being electrophilic forms a complex with molecular bromine. This 309 results in the polarization of the Br2 with the partially positive bromine (Br+) being proximal to the ortho position relative to the silicon atom which in turn promotes the bromination at the ortho position of the phenyl groups. However, if the bromination is done for a prolonged reaction time or in the presence of a Lewis acid catalyst, the doubly, or multiply brominate Br16OPS (Scheme 5-13) and Br24OP silsesquioxanes are formed. Scheme 5-13: Synthesis of octa(dibromophenyl)silsesquioxane Half-cube p-substituted phenyl cyclosiloxanes have also been reported by several groups including the Zucchi and Shchegolikhina groups. Ronchi et al for example, 62 reported the synthesis of a generation of functionalized sodium para-substituted phenylcyclotetrasiloxanolates that are potential silica supports to second order NLO active or fluorescent organic chromophores (Scheme 5-14). Scheme 5-14: Synthesis of sodium cyclotetrasiloxanolates from para-substituted phenyltriethoxysilane The single crystal structures of the trimethylsiloxy derivatives of these 2D scaffolds have all phenyl rings in a cis orientation. Interestingly, this same group was faced with 310 challenges in their efforts to obtain similar scaffolds following the route reported by Shchegolikhina et al. for alkyl and vinyl trialkoxysilane derivatives (Scheme 5-15).63 Scheme 5-15: Synthesis of sodium and potassium cyclosiloxanolates based on trisiloxanolate cycles with vinyl and alkyl substituents The complex mixture of oligomers and resinous materials obtained using para- substituted phenyltriethoxysilane as starting material in the Shchegolikhina approach was ascribed to the sensitivity of cyclotetrasiloxane rings to reaction conditions such as amount of water, nature of solvent, and base content that could affect their separation due to solubility. Picking up from the efforts of Ronchi and Shchegolikhina 63 and also the pioneering art of Brown for the synthesis of the first tetraphenyltetrasiloxanetetraol 64 the Kawakami group elaborated on the sodium 4-bromophenylcyclotetrasiloxanolates half cube for the synthesis of pure cubic octa(4-bromo-substituted phenyl)octasilsesquioxane.18 Thus acidification of sodium 4-bromophenylcyclotetrasiloxanolate with acetic acid followed by treatment of the resulting condensate in benzene with benzyltrimethylammonium hydroxide (BzTMAH) afforded pure crystalline 4-bromo-substituted phenylsilsesquioxane (Scheme 5-16).18 311 Scheme 5-16: Synthesis of Br-T8 from all-cis-Br-T4-tetraol This route is quite unique from the standpoint that the precise location of the transformable group (i.e. the Br atom) in the cage is known, and unlike previously reported procedures where the brominated products are obtained from bromination of octaphenylsilsesquioxane. An alternative route to this was a procedure reported by Taylor et al. involving the TBAF catalyzed synthesis of the fluoride-encapsulated brominated octasilsesquioxane cage (Scheme 5-17).14 In that report, both the synthesis of the fluoride encapsulated octasilsesquioxane cages and methods for the migration of the fluoride anion out of the cage using strong acids and lithium salts without distorting the cage architecture was disclosed. Scheme 5-17: Synthesis of tetra-n-butylammonium octa(para-bromophenyl)octasilses- quioxane fluoride 312 Despite these tremendous advances reported to date on the synthesis of these types of POSS cages, there are no reports in the literature for synthesis of the double- decker parity bearing styryl or bromophenyl substituents as pendants. Thus, with the desire to obtain a styryl or bromophenyl trimmed DDSQ(OH)4 being our goal, we sought to develop strategies that can fabricate such compounds by either the selective and symmetric cleavage of two Si-O bond in the fully condensed POSS precursor or direct synthesis of the partially condensed cages from their respective trichloro/alkoxy silanes. Such cages, if realized, will extend post-functionalization to both its surfaces and corners. 5.2 Experimental Section 5.2.1 Materials and Methods All reactions were carried out with dry solvents under a nitrogen atmosphere using standard techniques except otherwise stated. 4-bromophenyltrimethoxysilane was purchased from Gilest Inc. and styryltrimethoxysilane from Shin-Etsu Chemical Co. Ltd. Triethylamine (Et3N) and toluene were distilled over calcium hydride before use. Acetic acid, hexanes, acetonitrile, methanol, isopropanol, and isobutanol were used as received. THF was distilled over benzophenone and sodium metal at a temperature of 50 °C under nitrogen prior to use. Glassware was oven dried. Reactions were monitored thin-layer chromatography (TLC) on silica gel plates or a Hydrion Insta-Chek pH pH 0-14 and. 1H, 13C, 19F, and 29Si NMR spectra were acquired on an Agilent DirectDrive2 500 MHz NMR spectrometer equipped with a OneProbe operating at 500 MHz for 1H NMR, 126 MHz for 13C NMR, 471.82 MHz for 19F NMR, and 99 MHz for 29Si NMR with CDCl3 or acetone-d6 and recorded at 25 °C. 1H-NMR spectra were recorded with 8 scans, a relaxation delay of 1s, and a pulse angle of 45° and referenced to tetramethylsilane in CDCl 3 (0.00 ppm). 313 13C-NMR spectra were collected with 254 scans, a relaxation delay of 0.1 s, and a pulse angle of 45°. 19F NMR spectra were collected with 32 Scans, a relaxation delay of 25 s, and a pulse angle of 60 ⁰. 29Si NMR spectra were recorded with either 256 or 512 scans, a relaxation delay of 12 s and a pulse angle of 45°. Thin-layer chromatography (TLC) was performed on plates of EMD 250-µm silica 60-F254. High-resolution mass spectroscopy was performed with APCI mass spectra recorded on a Finnigan LCQ Deca (ThermoQuest) technologies with LC/MS/MS (quadrupole/time-of-flight) and Waters Xevo G2-XS UPLC/MS/MS inert XL MSD with SIS Direct Insertion Probe. Melting points for all products were measured with a Stuart SMP30 melting point apparatus and are uncorrected. X-ray diffraction measurements were performed on a Stoe IPDS2 or a Bruker-AXS SMART APEX 2 CCD diffractometer using graphite-monochromated Mo Kα radiation. The structures were solved using direct methods (SHELXL-97) and refined by full-matrix least-squares techniques against F2 (SHELXL-97). Cell parameters were retrieved using the SAINT (Bruker, V8.34A, after 2013) software and refined using SAINT (Bruker, V8.34A, after 2013) on 5941 reflections, 47% of the observed reflections. Data reduction was performed using the SAINT (Bruker, V8.34A, after 2013) software which corrects for Lorentz polarization. 314 5.2.1.1 Synthesis of dichloro(methyl)(4-vinylphenyl)silane (2) from 4-bromostyrene (1) Scheme 5-18: Synthesis of dichloro(methyl)(4-vinylphenyl)silane (2) via Grignard Magnesium powder (0.58 g, 24 mmol) was added onto an oven dried 100 mL two- necked round bottom bearing a stir bar and fitted with a dropping funnel. The flask was dried under vacuum (1 mmHg) and filled with pure argon. The magnesium was activated with a few crystals of I2 and THF (10 mL) was added to the flask. The mixture was placed in an ice bath, stirred continuously and a few drops of 4-bromostyrene added to allow the exothermic reaction to occur slowly. Once the system returned to room temperature, the remaining 4-bromostyrene making the total volume of 2.61 mL (3.66 g, 20 mmol) was added slowly through the dropping funnel to prevent polymerization (Scheme 5-18, step 1). The reaction was allowed to react under the inert Ar atmosphere and at room temperature for 4 h. An aliquot of the crude quenched with MeOH and analyzed by GC/MS showed full conversion of 1 into the Grignard product. Into another pre-heated 100 mL round bottom flask equipped with a stir bar and an argon atmosphere was added freshly distilled MeSiCl3 (2.82 mL, 24 mmol) in 10 mL THF. The Grignard solution prepared above was next cannulated dropwise over a period of 20 minutes into the flask bearing the MeSiCl3 (Scheme 5-18, step 2). The mixture was left to stir at room temperature for 24 h at which time GC/MS showed full conversion into 2. This product was isolated as a colorless oil in 77% yield (1.8 mL, 15.4 mmol). 315 1H NMR (500 MHz, CDCl3 + 1% TMS) δ (ppm): 7.71 – 7.65 (m, 2H), 7.48 – 7.45 (m, 2H), 6.80 – 6.62 (m, 2H), 5.86 – 5.81 (m, 1H), 5.34 (dd, J = 10.9, 0.8 Hz, 1H), 1.01 (s, 3H). 13C NMR (126 MHz, CDCl3 + 1% TMS) δ (ppm) 140.66, 136.16, 133.34, 126.04, 125.86, 116.06, 5.53. 29Si NMR (99 MHz, CDCl3 + 1% TMS) δ (ppm) 18.50 (1Si) 5.2.1.2 Synthesis of [[(styryl)(Me)}2DDSQ] from DDSQ(OH)4 (3) and styryl(Me)SiCl2 (2) Scheme 5-19: Capping of DDSQ(OH)4 (3) with dichloro(methyl)(4-vinylphenyl)silane (2) DDSQ(OH)4 (1.05 g, 1.0 mmol) was charged into a pre-dried 100 mL round bottom flask bearing a magnetic stir bar and sealed with a septum. The flask was purged with dry nitrogen and THF (10 mL) was added. The flask was immersed into an ice bath and styryl(Me)SiCl2 (0.23 mL, 2 equiv) in 3 mL THF was added followed by dropwise addition of pyridine (0.32 mL, 4 equiv). The reaction mixture was stirred at 0 ⁰C for 2 h and at room temperature for 22 h (Scheme 5-19). The suspension was filtered through a glass frit, the residue washed with THF (3 x 5 mL) and the solvent together with other volatiles removed from the filtrate by rotary evaporation. This crude was further purified by flash column chromatography with ethylacetate/hexane:1/3 to give a white solid. The product was isolated as a white solid in 38% yield (0.53 g, 0.39 mmol) and was analyzed by 1H, 13C, 29Si, single X-ray crystallography and LCMS measurement. mp 265 – 268 °C. 316 1H NMR (500 MHz, CDCl3 + 1% TMS) δ (ppm) 1H NMR (500 MHz, Chloroform-d) δ 7.62 – 7.03 (m, 41H), 6.80 – 6.55 (m, 2H), 5.85 – 5.63 (m, 2H), 5.35 – 5.18 (m, 2H), 0.51 (d, J = 5.3 Hz, 6H). 13C NMR (126 MHz, CDCl3 + 1% TMS) δ (ppm) 136.90, 134.31, 134.17, 133.82, 131.97, 131.30, 130.37, 127.87, 127.78, 127.56, 127.49, 125.71, 114.58, -0.41 29Si NMR (99 MHz, CDCl3 + 1% TMS) δ (ppm) -30.87 (2Si), -78.40 (4Si), -79.21 (1Si), - 79.57 (2Si), -79.84 (1Si). LCMS (APCI) m/z calcd for C66H60KO14Si10+ [M + K]+ 1395.1307, obs’d 1395.1235 5.2.2 Synthesis of Tn styryl Silsesquioxanes Scheme 5-20: Synthesis of sty8T8 (6), sty10T10 (7) and sty12T12 (8) from styryltrimethoxy- silane (5) In an oven-dried round bottom flask equipped with a stir bar was added a solution of trimethoxy(4-vinylphenyl)silane (3.7 mL, 17.5 mmol) in DCM (400 mL). The flask was placed over a pre-heated oilbath at 30 ⁰C and water (160 μL, 8.75 mmol, 0.5 equiv) was added followed by dropwise addition of TBAF solution in THF (10 mL, 10 mmol). After 48 h reaction time, anhydrous CaCl2 (1.2 g, 11 mmol) was then added to the solution and stirred for a further 16 h (Scheme 5-20). The resulting crude reaction mixture was filtered, washed three times with water (3 x 100 mL), and dried over anhydrous Na 2SO4. The 317 solvent was removed by rotary evaporation affording a crude reaction mixture containing styryl-T8, T10 and T12 cage Silsesquioxanes. Products were further purified by flash column chromatography using dichloromethane/hexane:1/4. Octastyryl silsesquioxane (sty8T8) (6): This product was isolated as a white solid in 10% yield (0.26g, 0.21 mmol). mp > 400 ⁰C, 1H NMR (500 MHz, CDCl3 + 1% TMS) δ (ppm) 7.73 – 7.69 (m, 16H), 7.42 – 7.39 (m, 16H), 6.70 (dd, J = 17.6, 10.9 Hz, 8H), 5.80 (dd, J = 17.6, 0.9 Hz, 8H), 5.29 (dd, J = 10.8, 0.9 Hz, 8H). 13C NMR (126 MHz, CDCl3 + 1% TMS) δ (ppm) 139.77, 136.66, 134.47, 129.47, 125.68, 115.06. 29Si NMR (99 MHz, CDCl3 + 1% TMS) δ (ppm) -78.31 (8Si). LCMS (Qtof) calculated for C64H57O12Si8 [M + H]+ 1241.1999, found 1241.1703. Decastyryl silsesquioxane (sty10T10) (7): This product was isolated as a white solid in 11% yield (0.29 g, 0.19 mmol). mp > 400 ⁰C. 1H NMR (500 MHz, CDCl3 + 1% TMS) δ (ppm) 7.57 (d, J = 7.7 Hz, 16H), 7.30 (d, J = 7.7 Hz, 16H), 6.67 (dd, J = 17.6, 10.9 Hz, 8H), 5.76 (d, J = 17.6 Hz, 8H), 5.26 (d, J = 10.9 Hz, 8H). 13C NMR (126 MHz, CDCl3 + 1% TMS) δ (ppm) 139.53, 136.69, 134.41, 129.90, 125.55, 114.90. 29Si NMR (99 MHz, CDCl3 + 1% TMS) δ (ppm) -79.68 (10Si). LCMS (APCI) m/z calcd for C80H70NaO15Si10+ [M + Na]+ 1573.2300, obs’d 1573.2207 318 Dodecastyryl silsesquioxane (sty12T12) (8): This product was not isolated as a pure compound. 5.2.3 Synthesis of 5,11,14,17-tetrakis((trimethylsilyl)oxy)-1,3,5,7,9,11,14,17-octakis (4-vinylphenyl)-2,4,6,8,10,12,13,15,16,18-decaoxa-1,3,5,7,9,11,14,17-octasilatricyc- lo[7.3.3.33,7]octadecane (9) Step 1: Attempted cleavage of octasyrylsilsesquioxane (sty8T8) (6) for the synthesis of sodium 1,3,5,7,9,11,14,17-octakis(4-vinylphenyl)-2,4,6,8,10,12,13,15,16,18-decaoxa-1, 3,5,7,9,11,14,17-octasilatricyclo[7.3.3.33,7]octadecane-5,11,14,17-tetrakis(olate) Scheme 5-21: Hydrolysis of sty8T8 with sodium hydroxide Step 1: Synthesis of from [(stySiO)8(ONa)4] (9) from octastyryl8T8 (6) To a 100 mL round bottom flask equipped with a stir bar was added styryl8T8 (0.05 g, 0.04 mmol) and NaOH (0.064 g, 4 equiv). The reaction mixture was placed under nitrogen and 15 mL of iso-propanol added. Next 0.0014 mL (2 equiv) of water was added, and the mixture stirred at 70 ⁰C for 24 h. The resulting white precipitate was filtered, washed several times with 2-propanol and dried under vacuum at 70 ⁰C for 24 h. Product identification was done by derivatizing the siloxanolate intermediate to the TMS derivative and characterized by 1H, 13C, 29Si NMR and MS. 319 Step 2: Synthesis of tetrakis(trimethylsilyl) octastyrylsilsesquioxane [(stySiO)8(OTMS)4] (9) from [(stySiO)8(ONa)4] The intermediate obtained from the NaOH hydrolysis of the octasyrylsilsesquioxane (Scheme 5-21, step 1) was charged into a 100 mL oven-dried round bottom flask equipped with a magnetic stirrer. The flask was purged with nitrogen gas for 30 minutes and THF (20 mL) added to it. Trimethylchlorosilane (0.092 g, 0.11 mL, 21.2 equiv) was then added followed by dropwise addition of triethylamine (0.071 g, 0.10 mL, 17.6 equiv) for 1 minute (Scheme 5-21, step 2). The reaction mixture was stirred at room temperature for 3 h. Deionized water (5 mL) was added to dissolve any NaCl produced and to hydrolyze unreacted Me3SiCl. The organic layer was separated by means of a separating funnel, n-hexane (5 mL) was added, and the organic layer repeatedly washed with deionized water. n-Hexane (20 mL) was added to this solution which was then kept in a freezer at -30 ⁰C overnight. However, the 1H NMR obtained for this product shows that the product is a mixture of compounds. 1H NMR (500 MHz, CDCl3 + 1% TMS) δ (ppm) 7.58 – 7.50 (m, 7H), 7.49 – 7.43 (m, 8H), 7.38 – 7.30 (m, 6H), 7.30 – 7.27 (m, 8H), 6.70 (ddd, J = 17.7, 10.9, 9.1 Hz, 8H), 5.83 – 5.71 (m, 8H), 5.29 – 5.22 (m, 8H), 0.07 (s, 28H), 0.05 (s, 32H). 13C NMR (126 MHz, CDCl3 + 1% TMS) δ (ppm) 137.03, 134.26, 125.24, 114.05, 1.70. 29Si NMR (99 MHz, CDCl3 + 1% TMS) δ (ppm) 9.08, -79.94, -90.14. 320 5.2.4 Synthesis of 2,4,6,8-tetrakis(4-bromophenyl)-2,4,6,8-tetrakis((trimethylsilyl)- oxy)-1,3,5,7,2,4,6,8-tetraoxatetrasilocane Scheme 5-22: Synthesis of 2,4,6,8-tetrakis(4-bromophenyl)-2,4,6,8-tetrakis((trimethyl- silyl)oxy)-1,3,5,7,2,4,6,8-tetraoxatetrasilocane (12) from the sodium hydroxide hydrolysis of 4-bromophenyltrimethoxysilane (10) Step 1: Controlled alkaline hydrolysis of p-bromophenyltrimethoxysilane (10) To a mixture of EtOH (4.4 mL), NaOH (0.263 g, 6.57 mmol, 1 equiv) and H 2O (0.118 g, 0.12 mL, 6.67 mmol, 1 equiv) was added (4-BrC6H4)Si(OMe)3 (1.82 g, 6.57 mmol). The reaction mixture was stirred under a nitrogen stream for about an hour when the solvent volume reduced to half (Scheme 22, step 1). The resulting white precipitate was washed and centrifuged three times with anhydrous n-hexane and dried in vacuo to afford crude sodium 4-bromophenylcyclotetrasiloxanolate as a white solid in 24% yield (1.51 g, 1.58 mmol). Step 2: Synthesis of 2,4,6,8-tetrakis(4-bromophenyl)-2,4,6,8-tetrakis((trimethylsilyl)oxy)- 1,3,5,7,2,4,6,8-tetraoxatetrasilocane (12) from Sodium 4-bromophenylcyclotetrasilo- xanolate (11) To a 100 mL round bottom flask containing the sodium salt (11) (0.62 g, 0.65 mmol) above in anhydrous hexanes (60 mL) was added Me3SiCl (1.65 mL, 13.0 mmol, 20 equiv) and pyridine (0.55 mL, 6.5 mmol, 10 equiv). The suspension was refluxed for 2 h under 321 a nitrogen atmosphere and after cooling to room temperature, the pyridinium salt was filtered off and washed with deionized water until the mixture is chloride free. The mixture was dried over MgSO4, filtered and the solvent removed by rotary evaporation to afford the crude product as an oil in 71% yield (0.54 g, 0.46 mmol). This crude product was characterized by 1H, 13C and 29Si NMR. 1H NMR (500 MHz, CDCl3 + 1% TMS) δ (ppm) 7.31 – 7.28 (m, 8H), 7.13 – 7.09 (m, 8H), 0.17 (s, 36H). 13C NMR (126 MHz, CDCl3 + 1% TMS) δ (ppm) 135.27 (2C), 131.52 (1C), 130.85 (2C), 125.08 (1C), 1.78 (12C). 29Si NMR (99 MHz, CDCl3 + 1% TMS) δ (ppm) 11.59 (4Si), -79.97 (4Si). 5.2.5 Borylation of [4-BrC6H4Si(OTMS)]4 Scheme 5-23: Synthesis of 2,4,6,8-tetrakis(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2- yl)phenyl)-2,4,6,8-tetrakis((trimethylsilyl)oxy)-1,3,5,7,2,4,6,8-tetraoxatetrasilocane Onto a flask equipped with a magnetic stirrer in a glove box was added PdCl2(PPh3)2 (3 mol%), Ph3P (6 mol%), KOAc (3 equiv), bis(pinacolato)diboron (6 equiv), toluene (6 mL), and 2,4,6,8-tetrakis(4-bromophenyl)-2,4,6,8-tetrakis((trimethylsilyl)oxy)- 1,3,5,7,2,4,6,8-tetraoxatetrasilocane (12) (0.20 g, 0.17 mmol). The mixture was placed over a preheated mantle at 50 °C and stirred for 12 h.62 The mixture was left to cool to room temperature and then extracted three times with water and benzene. The combined 322 organic layer washed with brine and dried over anhydrous MgSO 4. The crude pinacolyl boronate (13) (0.18 g, 0.13 mmol, 76%) was then analyzed by 1H, 11B, 13C and 29Si NMR. 1H NMR (500 MHz, CDCl3 + 1% TMS) δ (ppm) 7.25 (t, J = 7.5 Hz, 8H), 7.18 – 7.15 (m, 8H), 2.35 (s, 11H), 1.36 – 1.31 (m, 12H), 1.26 (s, 48H), 0.17 (t, J = 6.7 Hz, 12H). 11B NMR (160 MHz, CDCl3 + 1% TMS) δ (ppm) 22.27. 29Si NMR (99 MHz, CDCl3 + 1% TMS) δ (ppm) 10.80 (4Si), -79.99 (4Si). 5.2.6 Synthesis of tetra-n-butylammonium octa(4-bromophenyl)octasilsesqui- oxane fluoride Scheme 5-24: Synthesis of fluoride ion entrapped octa(4-bromophenyl)octa- silsesquioxane (14) Octa(para-bromophenyl)octasilsesquioxane with an entrapped fluoride anion was synthesized following the procedure developed by Taylor et al. 14 using 4- bromophenyltrimethoxysilane. A 100 mL round bottom flask bearing a magnetic stirrer was sealed with a septum and purged with N2 gas for 20 min. 4- Bromophenyltrimethoxysilane (2.77 g, 10 mmol, 2 equiv) and toluene (40 mL) were then added and the reaction mixture stirred for a further 20 minutes. Next tetra-n- butlyammonium fluoride (5.0 mL of 1 M solution in THF with 5% water, 1 equiv). was added and the mixture stirred at room temperature (Scheme 5-24). After 24 h reaction 323 time, the solvent was evaporated with a rotary evaporator and the resulting brown liquid was further dried under vacuum at a temperature of 80 ◦C and a pressure of 70 mbar for 20 minutes to afford a yellow solid. The solid was further purified by flash column chromatography on silica gel (acetone/hexane: 3/7) to afford a white solid in 0.88 g (37 % yield). mp > 400 ◦C. 1H NMR (500 MHz, Acetone-d6) δ (ppm) 7.75 – 7.62 (m, 16H), 7.59 – 7.45 (m, 16H), 3.46 – 3.39 (m, 8H), 1.81 (tt, J = 8.1, 6.2 Hz, 8H), 1.43 (h, J = 7.4 Hz, 8H), 0.97 (t, J = 7.4 Hz, 12H). 13C NMR (126 MHz, Acetone-d6) δ (ppm) 135.90, 135.51, 130.58, 123.61, 58.44, 19.50, 12.98. 19F NMR (470 MHz, Acetone-d6) δ -27.28. 29Si NMR (99 MHz, Acetone-d6) δ -80.82. 324 5.2.7 Synthesis of 1,3,5,7,9,11,14,17-octakis(4-bromophenyl)-5,11,14,17-tetrakis((tr- imethylsilyl)oxy)-2,4,6,8,10,12,13,15,16,18-decaoxa-1,3,5,7,9,11,14,17-octasilatricy- clo[7.3.3.33,7]octadecane Step 1: Attempted cleavage of tetra-n-butylammonium octa(p-bromophenyl)octa- silsesquioxanolate fluoride with sodium hydroxide Scheme 5-25: Cleavage of 14 for the synthesis of 1,3,5,7,9,11,14,17-octakis(4- bromophenyl)-5,11,14,17-tetrakis((trimethylsilyl)oxy)-2,4,6,8,10,12,13,15,16,18-decaoxa -1,3,5,7,9,11,14,17-octasilatricyclo[7.3.3.33,7]octadecane (15) To a 100 mL round bottom flask equipped with a stir bar was added (4-BrC6H4)8T8 (0.50 g, 0.30 mmol) and NaOH (0.048 g, 4 equiv). The reaction mixture was placed under nitrogen and 24 mL of iso-butanol added. Next 0.01 mL (2 equiv) of water was added, and the mixture stirred at 90 ⁰C for 24 h (Scheme 5-25). The resulting white precipitate was filtered, washed several times with 2-propanol and dried under vacuum at 70 ⁰C for 24 h. Product identification was done by derivatizing the sodium salt to the [(p- BrC6H4)8(SiO)8(OTMS)4] and characterized by 1H, 13C, 29Si NMR and MS. 325 Step 2: Synthesis of tetrakis(trimethylsilyl) octa(p-bromophenyl)silsesquioxane [(p- BrC6H4)8(SiO)8(OTMS)4] from [[(p-BrC6H4)8(SiO)8(ONa)4] The intermediate obtained from the NaOH hydrolysis of 14 (Scheme 5-25, step 1) above was charged into a 100 mL oven-dried round bottom flask equipped with a magnetic stirrer. The flask was purged with nitrogen gas for 30 minutes and THF (20 mL) added to it. Trimethylchlorosilane (21.2 equiv) was then added followed by dropwise addition of triethylamine (17.6 equiv) for 1 minute (Scheme 5-25, step 2). The reaction mixture was stirred at room temperature for 3 h. Deionized water (5 mL) was added to dissolve any NaCl produced and to hydrolyze unreacted Me3SiCl. The organic layer was separated by means of a separating funnel. n-Hexane (5 mL) was added, and the organic layer repeatedly washed with deionized water. n-Hexane (20 mL) was added to this solution, and the solution left standing at -30 ⁰C in a refrigerator overnight. The precipitated solid was filtered off and dried at reduced pressure to afford a white impure solid (0.43 g) that was characterized by 1H, 13C and 29Si NMR. 1H NMR (500 MHz, CDCl3 + 1%TMS) δ 7.62 – 7.57 (m, 16H), 7.45 – 7.38 (m, 16H), 2.45 – 2.36 (m, 8H), 1.20 (p, J = 7.3 Hz, 8H), 1.15 – 1.06 (m, 8H), 0.90 (t, J = 7.2 Hz, 12H). 13C NMR (126 MHz, CDCl3) δ 135.99, 135.63, 130.49, 123.80, 23.57, 19.64, 13.65. 29Si NMR (99 MHz, CDCl3) δ -81.45. 326 APPENDIX 327 Copies of GC/MS, MS, 1H, 11B, 13C, 19F and 29Si NMR Spectra GC/MS for styrene Figure 5-1: GC/MS – styrene Figure 5-2: 1H NMR of 2 (CDCl3 + 1%TMS, 500 MHz) 328 Figure 5-3: 13C NMR of 2 (CDCl3 + 1%TMS, 126 MHz) Figure 5-4: 29Si NMR of 2 (99 MHz, CDCl3) 329 Figure 5-5: 1H NMR of 4 (CDCl3 + 1%TMS, 500 MHz) 330 Figure 5-6: 29Si NMR of 4 (99 MHz, CDCl3) Figure 5-7: Mass spec of 4 331 Figure 5-8: 1H NMR of 6 (CDCl3 + 1%TMS, 500 MHz) Figure 5-9: 13C NMR of 6 (CDCl3 + 1%TMS, 126 MHz) 332 Figure 5-10: 29Si NMR of 6 (99 MHz, CDCl3) Figure 5-11: Mass spec of 6 333 Figure 5-12: 1H NMR of 7 (CDCl3 + 1%TMS, 500 MHz) Figure 5-13: 13C NMR of 7 (CDCl3 + 1%TMS, 126 MHz) 334 Figure 5-14: 29Si NMR of 7 (99 MHz, CDCl3) Figure 5-15: Mass spec of 7 335 Figure 5-16: 1H NMR of 12 (CDCl3 + 1%TMS, 500 MHz) 336 Figure 5-17: 13C NMR of 12 (CDCl3 + 1%TMS, 126 MHz) Figure 5-18: 29Si NMR of 12 (99 MHz, CDCl3) 337 Figure 5-19: 1H NMR of 13 (CDCl3 + 1%TMS, 500 MHz) Figure 5-20: 11B NMR of 13 (CDCl3 + 1%TMS, 160 MHz) 338 Figure 5-21: 29Si NMR of 13 (99 MHz, CDCl3) Figure 5-22: 1H NMR of 14 (Acetone-d6, 500 MHz) 339 Figure 5-23: 13C NMR of 14 (126 MHz, Acetone-d6) Figure 5-24: 19F NMR of 14 (Acetone-d6, 471 MHz) 340 Figure 5-25: 29Si NMR of 14 (Acetone-d6, 99 MHz) 341 Figure 5-26: 1H NMR of 14 (CDCl3 + 1%TMS, 500 MHz) Figure 5-27: 13C NMR of 14 (CDCl3 + 1%TMS, 500 MHz) 342 Figure 5-28: 29Si NMR of 14 (CDCl3 + 1%TMS, 99 MHz) 343 Table 5-1: Crystal and Experimental Data for 9,19-dimethyl-1,3,5,7,11,13,15,17- octaphenyl-9,19-bis(4-vinylphenyl)-2,4,6,8,10,12,14,16,18,20,21,22,23,24-tetradecaoxa- 1,3,5,7,9,11,13,15,17,19-decasilapentacyclo[11.7.1.13,11.15,17.17,15]tetracosane (4) Figure 5-29: Crystal Structure of 4 344 Figure 5-30: Packing diagram of 9,19-dimethyl-1,3,5,7,11,13,15,17-octaphenyl-9,19- bis(4-vinylphenyl)-2,4,6,8,10,12,14,16,18,20,21,22,23,24-tetradecaoxa- 1,3,5,7,9,11,13,1 5,17, 19-decasilapentacyclo[11.7.1.13,11.15,17.17,15]tetracosane (4) (Displacement ellipsoid contour probability drawn at 50%) The value of Z' is 0.5. This means that only half of the formula unit is present in the asymmetric unit, with the other half consisting of symmetry equivalent atoms. CCDC 1917847 contains the supplementary crystallographic data for 4. The data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/structures. 345 Figure 5-31: Crystal Structure of 12 Table 5-2: Crystal and Experimental Data for 2,4,6,8-tetrakis(4-bromophenyl)-2,4,6,8- tetrakis((trimethylsilyl)oxy)-1,3,5,7,2,4,6,8-tetraoxatetrasilocane65-67 There is a single molecule in the asymmetric unit, which is represented by the reported sum formula. In other words: Z is 4 and Z' is 1.65-67 CCDC 2051116 contains the supplementary crystallographic data for this 346 structure. The data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/structures. 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Thus, following recommendations from our group on previous studies, this research work recorded the following feats: • Use of a protecting group approach that afforded asymmetrically functionalized double-decker shaped silsesquioxanes in good yields. In this strategy, we employed a bidentate boronic acid that benignly and selectively masked the silanol groups of the DDSQ(OH)4 providing a model for the functionalization with different chlorosilanes. Unlike other protecting groups which are generally challenging on deprotection, pinacol chemoselectively demasked the boronic acid without compromising the cage architecture. • A protocol, which in close relation to the above, outlines an approach toward the synthesis of asymmetric monosilylated DDSQ disilanols [R1R2SiDDSQ(OH)2]. Such partially functionalized DDSQs are ideal molecular templates for the effective synthesis of condensed asymmetric D2T8 siloxanes, various metallasilsesquioxanes and for modification of solid supports. An illustration of its synthetic utility for the synthesis of the D2T8 siloxane is herein disclosed. • Demonstration of the base promoted hydrolysis of cubic dodecaphenylsilsesquioxane (Ph12T12) for the synthesis of the more desirable and highly symetrical ‘double-decker’ shaped silsesquioxane. Whereas other research groups have recorded the synthesis of higher cage frameworks starting from lower 355 cage Silsesquioxanes, this work serves as the first report of the conversion of dead-end Ph12T12 into the partially condensed double-decker shaped silsesquioxane tetraol [DDSQ(OH)4]. • Progress on the synthesis of novel ‘double-decker’ shaped Silsesquioxanes bearing transformable silicon coronal groups. In this work, efforts were directed to cages with styryl or bromophenyl groups that could provide avenues for multifunctionalization on the sides and surfaces. 6.2 Future Directions Our desire to explore strategies for the synthesis and modifications of siloxanes keeps growing as some realizations are met. Thus, the recommendations made herein are in no way exhaustive but based on our materials’ development drive, the achievements and challenges faced during this study. Even though a considerable progress is recorded, the following proposals are thought-provoking: • Exploration of an atom-economic and non-protecting group route for the synthesis of asymmetrically functionalized D2T8 ‘double-decker’ shaped silsesquioxanes. Based on preliminary results from our investigations, the use of solvents in which the DDSQ(OH)4 has very poor solubility seems promising. • Applications of the asymmetrically functionalized DDSQs as nano-linkers to two different block copolymers. Studies of the property enhancement relative to symmetric POSS/polymer composites should also be explored. • Use of the asymmetric R1R2SiDDSQ(OH)2 as precursors in nanomedicine, catalysis and for the modification of solid supports should be given due considerations. 356 • Surface modification of the phenyl groups in pre-synthesized condensed D2T8 POSS will result to a molecular design with pendants that are ideal for the formation of 3D networks. • Venture towards the applications of C-H borylation chemistry to functionalize the cage phenyl groups on the commercially available cubic cages or the tetrasilonolPOSS or condensed functionalized DDSQs to generate compounds that are susceptible to a variety of transformations that could result to a host of previously unexplored cages. • Exploration of routes for the synthesis of ‘double-decker shaped Silsesquioxanes that are based on other coronae order than phenyl. This area, being so nascent can be approached from either the trichloro/alkoxysilane or backward, from the selective fissure of two Si-O-Si linkages. 357