Alternative Synthetic Methodologies for the Synthesis Of

Home , Sulfuryl chloride, Thionyl chloride

ALTERNATIVE SYNTHETIC METHODOLOGIES FOR THE SYNTHESIS OF

ORGANOSILICON COMPOUNDS

PLOUSIA E. VASSILARAS

Submitted in partial fulfillment of the requirements

for the degree of Doctor of Philosophy

Thesis Advisor: Dr. Malcolm E. Kenney

Department of Chemistry

CASE WESTERN RESERVE UNIVERSITY

August, 2011 CASE WESTERN RESERVE UNIVERSITY

SCHOOL OF GRADUATE STUDIES

We hereby approve the thesis/dissertation

Plousia Vassilaras______

candidate for the Ph.D. degree *.

(signed) John Protasiewicz ______(chair of the committee)

______Irene Lee______

Eve. F. Fabrizio______

John Stuehr______

Malcolm E. Kenney______

(date) ______7-5-2011______

*We also certify that written approval has been obtained for any proprietary material contained therein.

Dedicated to my parents

Sofia and Elia

and my brothers

Dimitri, George and Yianni for always being next to me.

Table of Contents

page

LIST OF TABLES ix

LIST OF FIGURES xiii

LIST OF SCHEMES xvi

LIST OF SYMBOLS AND ABBREVIATIONS xviii

ACKNOWLEDGMENTS xix

ABSTRACT xx

CHAPTER 1. INTRODUCTION TO THE SYNTHESIS OF SiCl4 AND 1 CHLOROSILANES Silicon 2

Uses of Silicon 4

Silicon Tetrachloride 5

Uses of Silicon Tetrachloride 8

Objectives 9

CHAPTER 2. PREPARATION AND CHARACTERIZATION FOR THE 10 SYNTHESIS OF SiCl4 AND CHLOROSILANES Reagents and Solvents 11

Instruments and Apparatus 11

29Si Nuclear Magnetic Resonance Spectroscopy 11

Processing Methods 11

CHAPTER 3. SYNTHETIC PROCEDURES FOR THE SYNTHESIS OF 12 SiCl4 AND CHLOROSILANES

Currell’s Approach Experiments

Attempts to Reproduce Reported Pyridine HCl-Catalyzed Syntheses 13 of Silicon Tetrachloride from Tetraalkoxysilanes and Thionyl Chloride

Exploratory Experiments

Uncatalyzed Synthesis of Silicon Tetrachloride from Tetramethoxysilane and 15 Chlorinating Agents

Variously Catalyzed Syntheses of Silicon Tetrachloride from 16 Tetramethoxysilane and Chlorinating Agents

Detailed Experiments

Catalyzed Alkoxysilane-Thionyl Chloride Investigations

DMF-Catalyzed Synthesis of Methylchlorosilanes from Methylmethoxysilanes 18 and Thionyl Chloride

DMF-Catalyzed Synthesis of Methylchlorosilanes from Methylethoxysilanes 21 and Thionyl Chloride

DMF-Catalyzed Synthesis of Ethylchlorosilanes from Ethylalkoxysilanes 22 and Thionyl Chloride

DMF-Catalyzed Synthesis of Silicon Tetrachloride from Tetramethoxysilane 23 and Thionyl Chloride

Variously Catalyzed Synthesis of Silicon Tetrachloride from Tetramethoxysilane 27 and Thionyl Chloride

DMF-Catalyzed Synthesis of Silicon Tetrachloride from Tetramethoxysilane 30 and Thionyl Chloride with Vent-Line Traps

Catalyzed Synthesis of Silicon Tetrachloride from Higher Tetraalkoxysilanes 33 and Thionyl Chloride

Alkoxysilane-Aqueous HCl Investigations

Uncatalyzed Synthesis of Trimethylchlorosilane from Trimethylmethoxysilane 36 and Aqueous HCl

Uncatalyzed Synthesis of Trimethylchlorosilane from Trimethylethoxysilane 37 and Aqueous HCl

Uncatalyzed Synthesis of Triethylchlorosilane from Triethylethoxysilane 38 and Aqueous HCl

Alkoxysilane-HCl Gas Investigations

Uncatalyzed Synthesis of Methylchlorosilanes from Methylmethoxysilanes 39 and HCl Gas

Uncatalyzed and Catalyzed Synthesis of Methylchlorosilanes from 41 Methylethoxysilanes and HCl Gas

Uncatalyzed Synthesis of Ethylchlorosilanes from an Ethylmethoxysilanes 43 and HCl Gas

Uncatalyzed Synthesis of Ethylchlorosilanes from an Ethylethoxysilanes 44 and HCl Gas

Uncatalyzed and Catalyzed Synthesis of Methoxychlorosilanes from 45 Tetramethoxysilanes and HCl Gas

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Uncatalyzed Synthesis of Alkoxychlorosilanes from Higher Tetraalkoxysilanes 49 and HCl Gas

Uncatalyzed Synthesis of Alkoxychlorosilanes from Tetramethoxysilane 50 and Liquid HCl

Acetoxysilane-Thionyl Chloride Investigations

Uncatalyzed Synthesis of Triacetoxychlorosilane and Diacetoxydichlorosilane 51 from Tetraacetoxysilane and Thionyl Chloride

Catalyzed Synthesis of Silicon Tetrachloride from Tetraacetoxysilane and 52 Thionyl Chloride

Metal Silicate-Chlorinating Agent Investigations

Attempted Synthesis of Silicon Tetrachloride from Silicates and 54 Chlorinating Agents

Silicon Dioxide-Chlorinating Agent Investigations

Attempted Synthesis of Silicon Tetrachloride from Silica and Chlorinating 55 Agents

CHAPTER 4. RESULTS AND DISCUSSION OF THE SYNTHESIS OF SiCl4 56 AND CHLOROSILANES

Currell’s Approach Experiments

Attempts to Reproduce Reported Pyridine HCl-Catalyzed Syntheses of Silicon 57 Tetrachloride from Tetramethoxysilane and Thionyl Chloride

Exploratory Experiments

Uncatalyzed Synthesis of Silicon Tetrachloride from Tetramethoxysilane and 63 Chlorinating Agents

Variously Catalyzed Synthesis of Silicon Tetrachloride from Tetramethoxysilane 67 and Chlorinating Agents

Detailed Experiments

Catalyzed Alkoxysilane-Thionyl Chloride Investigations

DMF-Catalyzed Synthesis of Methylchlorosilanes from Methylmethoxysilanes 92 and Thionyl Chloride

DMF-Catalyzed Synthesis of Methylchlorosilanes from Methylethoxysilanes 94 and Thionyl Chloride

DMF-Catalyzed Synthesis of Ethylchlorosilanes from Ethylalkoxysilanes 95 and Thionyl Chloride

DMF-Catalyzed Synthesis of Silicon Tetrachloride from Tetramethoxysilane 96 and Thionyl Chloride

Variously Catalyzed Syntheses of Silicon Tetrachloride from Tetramethoxysilane 98 and Thionyl Chloride

DMF-Catalyzed Synthesis of Silicon Tetrachloride from Tetramethoxysilane 99 and Thionyl Chloride with Vent-Line Traps

Catalyzed Synthesis of Silicon Tetrachloride from Higher Tetraalkoxysilanes 100 and Thionyl Chloride

Alkoxysilane-Aqueous HCl Investigations

Uncatalyzed Synthesis of Trimethylchlorosilane from Trimethylmethoxysilane 109 and Aqueous HCl

Uncatalyzed Synthesis of Trimethylchlorosilane from Trimethylethoxysilane 111 and Aqueous HCl

Uncatalyzed Synthesis of Triethylchlorosilane from Triethylethoxysilane 112 and Aqueous HCl

Alkoxysilane-HCl Gas Investigations

Silicon Tetrachloride from Tetramethoxysilane and HCl Gas 114

Uncatalyzed Synthesis of Methylchlorosilanes from Methylmethoxysilanes 115 and HCl Gas

Uncatalyzed and Catalyzed Synthesis of Methylchlorosilanes from 117 Methylethoxysilanes and HCl Gas

Uncatalyzed Synthesis of Ethylchlorosilanes from an Ethylmethoxysilanes 119 and HCl Gas

Uncatalyzed Synthesis of Ethylchlorosilanes from an Ethylethoxysilanes 120 and HCl Gas

Uncatalyzed and Catalyzed Synthesis of Alkoxychlorosilanes from 122 Tetramethoxysilane and HCl Gas

Uncatalyzed Synthesis of Alkoxychlorosilanes from Higher Tetraalkoxysilanes 124 and HCl Gas

Acetoxysilane-Thionyl Chloride Investigations

Uncatalyzed Synthesis of Triacetoxychlorosilane and Diacetoxydichlorosilane 133 from Tetraacetoxysilane and Thionyl Chloride

Catalyzed Synthesis of Silicon Tetrachloride from Tetraacetoxysilane and 136 Thionyl Chloride

Metal Silicate-Chlorinating Agent Investigations

Attempted Synthesis of Silicon Tetrachloride from Silicates and 139 Chlorinating Agents

Metal Silicate-Chlorinating Agent Investigations

Attempted Synthesis of Silicon Tetrachloride from Silica and Chlorinating 144 Agents

CHAPTER 5. SUMMARY AND CONCLUSIONS FOR THE SYNTHESIS OF 147 SiCl4 AND CHLOROSILANES

CHAPTER 6. INTRODUCTION TO THE HIGH-ASPECT-RATIO, 160 CONDUCTING AND SEMICONDUCTING NANOWIRES FROM SCROLL POLYMERS Scroll Polymers 161

Objectives 166

CHAPTER 7. PREPARATION AND CHARACTERIZATION OF THE HIGH- 167 ASPECT-RATIO, CONDUCTING AND SEMICONDUCTING NANOWIRES FROM SCROLL POLYMERS Materials and Procedures 168

Instruments and Apparatus 168

Powder X-ray Diffractometry 169

Transmission Electron Microscopy 169

Processing Methods 169

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CHAPTER 8. EXPERIMENTAL PROCEDURES FOR HIGH-ASPECT-RATIO, 170 CONDUCTING AND SEMICONDUCTING NANOWIRES FROM SCROLL POLYMERS Synthesis of Scroll Polymers

Chrysotile Preparation 171

[((CH3)3SiO)x(OH)1-xSiO1.5]n, C-M3 171

C-M3 Fibers Partially Filled with Lead Sulfide 172

C-M3 Fibers Partially Filled with Platinum 173

CHAPTER 9. RESULTS AND DISCUSSION OF THE HIGH-ASPECT-RATIO, 174 CONDUCTING AND SEMICONDUCTING NANOWIRES FROM SCROLL POLYMERS Scroll Nanowires 175

CHAPTER 10. SUMMARY AND CONCLUSIONS OF THE HIGH-ASPECT-RATIO, 180 CONDUCTING AND SEMICONDUCTING NANOWIRES FROM SCROLL POLYMERS APPENDIX A. SELECTED 29Si NMR SPECTRA 182

REFERENCES 208

BIBLIOGRAPHY 213

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List of Tables

Table 1. Boiling Points of Compounds, p 20.

Table 2. Reported Pyridine HCl-Catalyzed Synthesis of Silicon Tetrachloride from Tetraalkoxysilanes and Thionyl Chloride – Reaction Conditions and Results, p 60.

Table 3. Reported Pyridine HCl-Catalyzed and Nonpyridine Catalyzed Synthesis of Silicon Tetrachloride from Tetraalkoxysilanes and Thionyl Chloride – Reaction Conditions and Results, p 61.

Table 4. Reported Pyridine HCl-Catalyzed and Synthesis of Silicon Tetrachloride from Tetraalkoxysilanes and Thionyl Chloride – Reaction Conditions and Results, p 61.

Table 5. Attempts to Reproduce Currell’s Reported Pyridine HCl-Catalyzed Syntheses of Silicon Tetrachloride from Tetraalkoxysilanes and Thionyl Chloride, p 62.

Table 6. Silanes from a Mixture of Si(OCH3)4 and Various Chlorinating Agents at Various Reaction Times and at Room Temperature - Reaction Mixtures, p 65.

Table 7. Silanes from a Mixture of Si(OCH3)4 and Various Chlorinating Agents at Various Reaction Times and at Room Temperature – Results, p 66.

Table 8. Silanes from a Mixture of Si(OCH3)4 and Excess of SOCl2 with Thirteen Potential Catalysts and at Various Reaction Times and at Room Temperature - Reaction Mixtures, pp 71 - 72.

Table 9. Silanes from a Mixture of Si(OCH3)4 and Excess of SOCl2 with Thirteen Potential Catalysts and at Various Reaction Times and at Room Temperature –Results, pp 73 – 74.

Table 10. Silanes from a Stoichiometric Mixture of Si(OCH3)4 and stoichiometric SOCl2 with Seven Potential Catalysts and at Various Reaction Times and at Room Temperature - Reaction Mixtures, p 75.

Table 11. Silanes from a Stoichiometric Mixture of Si(OCH3)4 and stoichiometric SOCl2 with Seven Potential Catalysts and at Various Reaction Times and at Room Temperature – Results, p 76.

Table 12. Approximate Cost of Catalysts, p 77.

Table 13. Approximate Cost of Chlorinating Agents, p 78.

Table 14. Silanes from a Mixture of Si(OCH3)4 and Excess SO2Cl2 with Five Potential Catalysts at Various Reaction Times and at Room Temperature - Reaction Mixtures, p 79.

Table 15. Silanes from a Mixture of Si(OCH3)4 and Excess SO2Cl2 with Five Potential Catalysts at Various Reaction Times and at Room Temperature – Results, p 80.

Table 16. Silane Products from a Mixture of Si(OCH3)4 and PCl3 with Four Potential Catalysts at Various Reaction Times and at Room Temperature - Reaction Mixtures, p 81.

Table 17. Silane Products from a Mixture of Si(OCH3)4 and PCl3 with Four Potential Catalysts at Various Reaction Times and at Room Temperature – Results, p 82.

Table 18. Silane Products from Mixtures of Si(OCH3)4 and Various Amounts of PCl5 with a Dimethylformamide Catalyst at Various Reaction Times and at Room Temperature – Reaction Mixtures, p 83.

Table 19. Silane Products from Mixtures of Si(OCH3)4 and Various Amounts of PCl5 with a Dimethylformamide Catalyst at Various Reaction Times and at Room Temperature – Results, p 84.

Table 20. Silane Products from a Mixture of Si(OCH3)4 and Excess POCl3 with Four Potential Catalysts at Various Reaction Times and at Room Temperature – Reaction Mixtures, p 85.

Table 21. Silane Products from a Mixture of Si(OCH3)4 and Excess POCl3 with Four Potential Catalysts at Various Reaction Times and at Room Temperature – Results, p 86.

Table 22. Silane Products from a Mixture of Si(OCH3)4 and Excess of HCl with Five Catalysts at Various Reaction Times and at Room Temperature - Reaction Mixtures, p 87.

Table 23. Silane Products from a Mixture of Si(OCH3)4 and Excess of HCl with Five Catalysts at Various Reaction Times and at Room Temperature – Results, p 88.

Table 24. DMF-Catalyzed Synthesis of Methylchlorosilanes from Methylmethoxysilanes and Excess Thionyl Chloride, p 102.

Table 25. DMF-Catalyzed Methylchlorosilanes from Methylalkoxysilanes and Excess Thionyl Chloride, p 103.

Table 27. DMF-Catalyzed Synthesis of Silicon Tetrachloride from Tetramethoxysilane and Excess Thionyl Chloride, p 104.

Table 28. Variously Catalyzed Syntheses of Silicon Tetrachloride from Tetramethoxysilane and Excess Thionyl Chloride, p 105.

Table 29. DMF-Catalyzed Synthesis of Silicon Tetrachloride from Tetramethoxysilane, and Excess of Thionyl Chloride with Vent-Line Traps - Reaction Mixtures, p 106.

Table 30. DMF-Catalyzed Synthesis of Silicon Tetrachloride from Tetramethoxysilane and Excess of Thionyl Chloride with Vent-Line Traps – Results, p 107.

Table 31. Catalyzed Synthesis of Silicon Tetrachloride from Higher Tetraalkoxysilanes and Excess Thionyl Chloride, p 108.

Table 32. Uncatalyzed Synthesis of Trialkylchlorosilanes from Trialkylalkoxysilanes and Excess Aqueous HCl in Hexanes, p 113.

Table 33. Uncatalyzed Synthesis of Methylchlorosilanes from Methylmethoxysilanes and HCl Gas, p 126.

Table 34. Uncatalyzed and Catalyzed Synthesis of Methylchlorosilanes from Methylethoxysilanes and HCl Gas – Variables, p 127.

Table 35. Uncatalyzed Synthesis of Ethylchlorosilanes from an Ethylmethoxysilane and HCl Gas, p 128.

Table 36. Uncatalyzed Synthesis of Ethylchlorosilanes from Ethylethoxysilanes and HCl Gas, p 129.

Table 37. Uncatalyzed and Catalyzed Synthesis of Alkoxychlorosilanes from Tetramethoxysilane and HCl Gas, p 130.

Table 38. Uncatalyzed and Catalyzed Synthesis of Alkoxychlorosilanes from Tetramethoxysilane and HCl Gas – Results, p 131.

Table 39. Uncatalyzed Synthesis of Alkoxychlorosilanes from Higher Tetraalkoxysilanes and HCl Gas, p 132.

Table 40. Uncatalyzed Synthesis of Alkoxychlorosilanes from Tetramethoxysilane and Liquid HCl, p 132.

Table 41. Uncatalyzed Synthesis of Triacetoxychlorosilane, and Diacetoxydichlorosilane from Tetraacetoxysilane and Excess Thionyl Chloride, p 135.

Table 42. Catalyzed Synthesis of Silicon Tetrachloride from Tetraacetoxysilane and Excess Thionyl Chloride, p 137.

Table 43. Approximate Cost of Silicon Reactants, p 138.

Table 44. Attempted Synthesis of SiCl4 from Silicates and Excess Chlorinating Agents - Reaction Mixtures, pp 140 – 141.

Table 45. Attempted Synthesis of SiCl4 from Silicates and Excess Chlorinating Agents – Results, pp 142 – 143.

Table 46. Attempted Synthesis of SiCl4 from Silica and Excess Chlorinating Agents - Reaction Mixtures, p 145.

Table 47. Attempted Synthesis of SiCl4 from Silica and Excess Chlorinating Agents – Results, p 146.

Table 48. Catalyzed Alkoxysilane-Thionyl Chloride Runs, p 157.

Table 49. Alkoxysilane-HCl Runs, p 158.

Table 50. Acetoxysilane-Thionyl Chloride Runs, p 159.

Table 51. Intrasheet Spacing in Scroll Polymers, p 164.

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List of Figures

Figure 1. Relative intensity of 29Si resonances of chlorinated silanes at 16:1 and 4:1

SOCl2:TMOS ratios, and 0.2 and 0.05 DMF:TMOS ratios at three reaction times, p 89.

29 Figure 2. Relative intensity of Si resonances of chlorinated silanes at a SOCl2:TMOS ratio of 16:1, a catalyst:TMOS ratio of 0.2 and a time of 0.5 h, p 90.

29 Figure 3. Relative intensity of Si resonances of chlorinated silanes at SOCl2:TMOS ratio of 16:1, a catalyst:TMOS ratio of 0.2 and a time of 2 h, p 91.

Figure 4. The structure of chrysotile, p 161.

Figure 5. (a) Sheet silicate anion in chrysotile, (b) scroll in chrysotile formed by steric-hindrance enforced furling of its sheet, p 162.

Figure 6. Schematic representation of the protonation and silylation of a chrysotile scroll, p 163.

Figure 7. Sheet polymer in C-M3, p 163.

Figure 8. Intrasheet spacing in a scroll polymer, p 164.

Figure 9. Multisheet scroll polymer, p 164.

Figure 10. Structure of Pt[((CH2=CH)(CH3)2Si)2O]1.5 (Karstedt’s catalyst), p 166.

Figure 11. The infrared spectrum and X-ray powder pattern of the C-M3 used in the platinum- and lead-filling studies, p 176.

Figure 12. Transmission electron micrograph of C-M3 scrolls with lead-acetate cores, p 175.

Figure 13. XEDS scan showing the excitation edge of sulfur at 165 – 185 eV, p 177.

Figure 14. Transmission electron micrographs of lead-sulfide filled C-M3, p 178.

Figure 15. Transmission electron micrograph of platinum filled C-M3, p 179.

29 Figure 16. Si NMR spectrum of Si(OMe)3Cl and Si(OMe)2Cl2 from Si(OMe)4 with pyridinium chloride and SOCl2, p 183.

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29 Figure 17. Si NMR spectrum of Si(OMe)Cl3, Si(OMe)2Cl2 and Si(OMe)3Cl from Si(OMe)4 with pyridinium chloride and SOCl2, p 184.

29 Figure 18. Si NMR spectrum of SiCl4 from Si(OMe)4 with pyridine and SOCl2 (4 fold excess), p 185.

29 Figure 19. Si NMR spectrum of SiCl4 and Si(OMe)Cl3 from Si(OMe)4 with pyridine and SOCl2 (stoichiometric), p 186.

29 Figure 20. Si NMR spectrum of Me3SiCl from Me3SiOMe with DMF and SOCl2, p 187.

29 Figure 21. Si NMR spectrum of Me2SiCl2 from Me2Si(OMe)2 with DMF and SOCl2, p 188.

29 Figure 22. Si NMR spectrum of MeSiCl3 from MeSi(OMe)3 with DMF and SOCl2, p 189.

29 Figure 23. Si NMR spectrum of SiCl4 from Si(OMe)4 with DMF and SOCl2, p 190.

29 Figure 24. Si NMR spectrum of SiCl4 and Si(OMe)Cl3 from Si(OMe)4 with Et3N and SOCl2, p 191.

29 Figure 25. Si NMR spectrum of SiCl4 from Si(OMe)4 with DMF and SOCl2, p 192.

29 Figure 26. Si NMR spectrum of SiCl4 from Si(OEt)4 with DMF and SOCl2, p 193

29 Figure 27. Si NMR spectrum of SiCl4 from Si(OPr)4 with DMF and SOCl2, p 194.

29 Figure 28. Si NMR spectrum of SiCl4 from Si(OBu)4 with DMF and SOCl2, p 195.

29 Figure 29. Si NMR spectrum of Me3SiCl from Me3SiOMe with HClaq, p 196.

29 Figure 30. Si NMR spectrum of Me3SiCl from Me3SiOEt with HClaq, p 197.

29 Figure 31. Si NMR spectrum of Et3SiCl from Et3SiOEt with HClaq, p 198.

29 Figure 32. Si NMR spectrum of Me3SiCl from Me3SiOMe with HClg, p 199.

29 Figure 33. Si NMR spectrum of Me2SiCl2 and Me2Si(OMe)Cl from Me2Si(OMe)2 with HClg, p 200.

29 Figure 34. Si NMR spectrum of MeSi(OMe)Cl2 and MeSi(OMe)2Cl from MeSi(OMe)3 with HClg, p 201.

29 Figure 35. Si NMR spectrum of Si(OMe)3Cl from Si(OMe)4 with HClg, p 202.

29 Figure 36. Si NMR spectrum of Si(OEt)3Cl from Si(OEt)4 with HClg, p 203.

29 Figure 37. Si NMR spectrum of Si(OPr)3Cl from Si(OPr)4 with HClg, p 204.

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29 Figure 38. Si NMR spectrum of Si(OMe)3Cl from Si(OMe)4 with HCll, p 205.

29 Figure 39. Si NMR spectrum of Si(OAc)3Cl and Si(OAc)2Cl2 from Si(OAc)4 with SOCl2, p 206.

29 Figure 40. Si NMR spectrum of SiCl4 from Si(OAc)4 with SOCl2, p 207.

List of Schemes

Scheme 1. Pyridine HCl-Catalyzed Synthesis of Alkoxychlorosilanes from Tetraalkoxysilanes and Thionyl Chloride at 100oC

Scheme 2. Pyridine HCl-Catalyzed Synthesis of Alkoxychlorosilanes from Tetraalkoxysilanes and Thionyl Chloride at Room Temperature

Scheme 3. Silicon Tetrachloride from Tetramethoxysilane, SOCl2 and Dimethylformamide

Scheme 4. Methylchlorosilanes from Methylmethoxysilanes, SOCl2 and Dimethylformamide

Scheme 5. Methylchlorosilanes from Methylethoxysilanes, SOCl2 and Dimethylformamide

Scheme 6. Ethylchlorosilanes from Ethylalkoxysilanes, SOCl2 and Dimethylformamide

Scheme 7. Silicon Tetrachloride from Tetramethoxysilane, SOCl2 and Dimethylformamide

Scheme 8. Silicon Tetrachloride from Higher Tetraalkoxides, SOCl2 and Dimethylformamide

Scheme 9. Trimethylchlorosilane from Trimethylmethoxysilane and Aqueous HCl and a Possible Methyl(chloromethyl)dimethoxysilane from Dimethyldimethoxysilane and Aqueous HCl

Scheme 10. Trimethylchlorosilane from Trimethylethoxysilane and Aqueous HCl and a Possible Methyl(chloromethyl)diethoxysilane from Dimethyldiethoxysilane and Aqueous HCl

Scheme 11. Triethylchlorosilane from Triethylethoxysilane and Aqueous HCl

Scheme 12. Silicon Tetrachloride from Tetramethoxysilane and HCl Gas

Scheme 13. Methylchlorosilanes from Methylmethoxysilanes and HCl Gas

Scheme 14. Methylchlorosilanes from Methylethoxysilanes and HCl Gas

Scheme 15. Ethylchlorosilanes from an Ethylmethoxysilane and HCl Gas

Scheme 16. Ethylchlorosilane from Ethylethoxysilanes and HCl Gas

Scheme 17. Alkoxychlorosilanes from Tetramethoxysilane and HCl Gas

Scheme 18. Alkoxychlorosilanes from Higher Tetralkoxysilanes and HCl Gas

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Scheme 19. Alkoxychlorosilanes from Tetramethoxysilane and Liquid HCl

Scheme 20. Triacetoxychlorosilane and Diacetoxydichlorosilane from Tetraacetoxysilane and Thionyl Chloride Scheme 21. Silicon Tetrachloride from Tetraacetoxysilane and Thionyl Chloride

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List of Symbols and Abbreviations

BuCl n-butyl chloride cat catalyst imin (chloromethylene) dimethyliminium chloride

DMA N, N- dimethylacetamide

DMF N, N- dimethylformamide xs excess py pyridine rel relative stoich stoichiometric temp temperature

Et3N triethylamine unk unknown var variable vol volume

XRD X-ray diffraction

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ACKNOWLEDGMENTS

I would like to express my sincerest gratitude to Professor Malcolm E. Kenney for his encouragement, guidance, enthusiasm and mentoring throughout the course of this work. Our collaboration taught me that even the impossible can be accomplished.

I would like to express my heartfelt thanks to my parents, Sofia and Elia, and my brothers, Dimitri, George and Yianni, for all their love, patience and support. Their continuous encouragement and understanding helped me to fulfill my dream.

I would like to thank my committee members Dr. John Protasiewicz, Dr. Irene Lee, Dr.

John Stuehr and Dr. Eve Fabrizio for their valuable advice, help and support. Also, current and former co-workers, Dr. Junhwan Kim, Dr. Jun Li, Dr. Ming Guo, Dr. Ping Zhang, Dr. Yun Liu,

Mr. Yang Yang, Mr. Jacob Miller for their advice and friendship. Special thanks to Dr. Nicholas

Leventis for his encouragement and guidance to achieve a Ph. D. in Chemistry.

Appreciation is extended to our collaborator at Dow Corning, Dr. Dimitris E. Katsoulis, for his interest and support to this work. The financial support of Dow Corning Corporation is gratefully acknowledged.

I would also like to thank members of the faculty and staff of the Departments of

Chemistry, Macromolecular Science and Engineering, Materials Science and Engineering,

School of Medicine, and NASA Glenn Research Center for their kind help in characterization of samples and discussions related to my work.

xix

Alternative Synthetic Methodologies for the Synthesis of Organosilicon Compounds

Abstract

PLOUSIA E. VASSILARAS

Methods for making SiCl4 under mild conditions from tetramethoxysilane and other readily available materials in high yields by routes which present few major engineering challenges have been investigated. Much of the emphasis of the work is on the synthesis of

SiCl4 from tetramethoxysilane and SOCl2 with dimethylformamide as a catalyst. This synthesis gives SiCl4 in good yields at atmospheric pressure and moderate temperatures. Some emphasis is on the use of catalysts other than dimethylformamide including dimethylacetamide, triethylamine, and (chloromethylene)dimethyliminiumchloride all of which are effective catalysts, and on the use of higher tetraalkoxysilanes. The higher tetraalkoxysilanes investigated serve as good reactants. The byproduct of the tetraalkoxysilane-SOCl2 reactions is the alkyl chloride, methyl chloride when tetramethoxysilane is used.

Emphasis is given also to the uncatalyzed synthesis of SiCl4 from tetramethoxysilane and

HCl gas. This work shows that one methoxy group of tetramethoxysilane can be displaced by a chloro group under mild conditions. Additional work shows that the displacement of one methoxy group can be achieved with liquid HCl at low temperatures. These results suggest that the replacement of all four methoxy groups by chloro groups can be achieved with the use of a dehydrating agent, appropriate temperatures and pressures, and suitable adjustment of reactant and product flows in the reaction vessel.

In separate work, methods for the preparation of silicate scroll polymers with trimethylsiloxy groups grafted on one side of the scroll, a diameter of several hundred Å, and a core of about 50 Å which is filled with PbS have been investigated. In this work, the unfilled scroll polymer was made, partially unfurled, filled with Pb(OAc)4, and treated with thioacetamide and H2S gas. This gave the PbS-filled scroll polymer. In related work, the cores of the same scroll polymer were filled with platinum by treating the partially unfurled polymer with a platinum catalyst, Karstedt’s catalyst, and then heating the treated polymer. This work opens the way to make silicone-insulated nanorods of semiconductors such as CdS and CdSe, and silicone-insulated nanowires of highly conducting metals such as silver.

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Chapter 1

Synthesis of SiCl4 and Chlorosilanes

Introduction

Silicon

Silicon crystallizes in the diamond structure. It melts at 1414 oC and boils at ~2355 oC.

The density of silicon is 2.33 g/cm3 and its Si-Si bond energy is 340 kJ/mol. It is a semiconductor with large band gap, 1.11 eV. Silicon is shiny blue-gray and has a metallic luster.1,2,3

It is relatively unreactive at room temperature. However, it reacts with oxygen in the air above 900 oC to give silica, and with nitrogen in the air above 1400 oC to give silicon nitride. It dissolves in a mixture of HNO3 and HF to give SiF4, and in hot aqueous NaOH to give the orthosilicate ion. 2

Si + O2 SiO2 (1)

3 Si + 2 N2 Si3N4 (2)

- + - Si + NO3 + 4 H + 4 F SiF4 + NO + 2 H2O (3)

- 4- Si + 4 OH SiO4 + 2 H2 (4)

4a Silicon was first isolated by reducing SiF4 with molten potassium. Other methods which

4b,5,6 have been used include the reduction of silicon tetrachoride with zinc or H2.

SiF4 + 4 K Si + 4 KF (5)

SiCl4 + 2 Zn Si + 2 ZnCl2 (6)

SiCl4 + 2 H2 Si + 4 HCl (simplified) (7)

Industrially, metallurgical-grade silicon is produced on a massive scale (686 x 103 metric tons in 2005) by the high-temperature reduction (~1700 oC) of quartz with coke in a three- electrode, ac submerged-arc electric furnace.4b,7

SiO2 + 2 C Si + 2 CO (8)

The leading producers of metallurgical silicon include Elkem Metals (US), Globe

Metallurgical (US), Simcala (US), PEM/Invensil (France).refs Leading producers of electronic- grade polycrystalline silicon are Hemlock Semiconductor (US), OCI (South Korea), LG (South

Korea), Wacker Chemie (Germany), and Tokuyama Soda (Japan).8-12

Uses of Silicon

The metallurgical silicon produced is used as an intermediate in the manufacture of silicon chemicals (particularly organosilicon compounds), aluminum casting alloys, and to a small extent electronic-grade silicon.1

Silicon Tetrachloride

o o SiCl4 belongs to the Td point group, melts at -69 C and boils at 57 C. It has the lowest

3 density (1.48 g/cm ) and the highest Si-X bond energy (381 kJ/mol) of the SiX4 series. It is colorless and dissolves in many organic solvents.13

Because of the polarity of the Si-Cl bond, the Si-Cl bond in SiCl4 is susceptible to nucleophilic attack. This underlies the broad reactivity of SiCl4, notably towards protic species.

With excess water it immediately yields silica and HCl. Under controlled conditions it can yield species such as Cl3SiOSiCl3 and (Cl3SiO)2SiCl2. Other examples of its reactivity include its reaction with alcohols and amines.13,14

SiCl4 + 2 H2O SiO2 + 4 HCl (9)

2 SiCl4 + H2O Cl3SiOSiCl3 + 2 HCl (10)

SiCl4 + 4 CH3CH2OH Si(OCH2CH3)4 + 4 HCl (11)

SiCl4 + excess HN(CH3)2 Si(N(CH3)2)4 + 4 HN(CH3)2·HCl (12) 5

The substitution reactions of SiCl4 are facilitated by the removal of the byproduct HCl, and typically are reversible.

SiCl4 was first made by the reaction of silica, carbon and chlorine. It has also been made by the reaction of pyrolyzed rice hulls (which are rich in silica), chlorine and carbon; silicon carbide and chlorine; and silica, silicon carbide and chlorine. Another route is the reaction of

15-20a tetraethylsilane and AlCl3.

SiO2 + 2 C + 2 Cl2 SiCl4 + 2 CO (13)

SiC + 2 Cl2 SiCl4 + C (14)

SiO2 + 2 SiC + 6 Cl2 3 SiCl4 + 2 CO (15)

Et4Si + 4 AlCl3 SiCl4 + 4 EtAlCl2 (16)

An attempt to make it by treating tetramethoxysilane with thionyl chloride and pyridine has been described.21

py Si(OMe)4 + 4 SOCl2 SiCl4 + 4 MeCl + 4 SO2 (17)

Technical grade SiCl4 is made industrially by treating metallurgical silicon with chlorine.

Very pure SiCl4 is made industrially by careful distillation of technical SiCl4. This pure SiCl4 is used for the production of semiconductor grade silicon by reduction with hydrogen.4b,16,22

Si + 2 Cl2 SiCl4 (18)

SiCl4 + 2 H2 Si + 4 HCl (19)

Byproduct SiCl4 is made industrially in a step in the trichlorosilane process for making very pure silicon. In this process metallurgical silicon is treated with HCl to make trichlorosilane, and this is carefully distilled and then pyrolyzed.16,23

Si + n HCl HSiCl3 + SiCl4 (20)

4 HSiCl3 3 SiCl4 + Si + 2 H2 (21)

The leading producers of technical SiCl4 are Dow Corning (US), General Electric (US),

Shin-Etsu (Japan), Tokuyama Soda (Japan), and Mitsubishi Materials (Japan), Wacher Chemie

13 (Germany) and Huls (Europe). Much of the pure SiCl4 is made in captive processes.

Uses of Silicon Tetrachloride

The industrial uses of SiCl4 are large and broad. Much is used in making high-surface area (fumed) silica. Very importantly, it is used in the production of very pure polycrystalline silicon for the photovoltaic industry and very pure single-crystal silicon for the semiconductor industry. It is also used in the manufacture of optical fibers.24-29

Objectives

As indicated above a very large amount of energy is used in making silicon by the carbothermic reduction of silica, and thus an undesirably large amount of energy used in making

SiCl4 via the commonly used silicon-chlorination route. Further, the amount of byproduct SiCl4 available is variable. With this in mind, a search was undertaken for a process for making SiCl4 which uses relatively little energy, gives high yields, uses mild reaction conditions and presents only moderate engineering challenges.

Chapter 2

Synthesis of SiCl4 and Chlorosilanes

Preparation and Characterization

Reagents and Solvents

The commercial reagents and solvents used in the SiCl4 work were generally of reagent grade quality or better. Most of the organosilicon reagents were purchased from commercial sources (generally Gelest, Tullytown, PA and Aldrich, Milwaukee, WI), and most of the organic reagents were purchased from reagent chemical vendors (e.g., Aldrich, Fisher Scientific,

Pittsurgh, PA; and Gelest). Most of the silicates were already in the laboratory and most of the minerals had been purchased previously from a minerals vendor (Ward’s Natural Science

Establishment, Rochester, NY).

The glassware was oven-dried (110 oC) for 24 h and then cooled in the atmosphere.

Instruments and Apparatus

29Si Nuclear Magnetic Resonance Spectroscopy

The 29Si NMR spectra were collected with a 600 MHz Varian Inova NMR spectrometer.

On a typical run, 128 scans were taken. The processing was done with a line broadening of 10.

Typical instrument settings were: temperature, 25 oC; spinning rate, 23 Hz; pulse width, 5

s; spectrum width 60 kHz; recycle delay, 3 sec; and gated decoupled acquisition time, 1.0 sec.

Processing Methods

Some reaction mixtures used in the synthesis of silicon tetrachloride were sonicated with an ultrasonic cleaner (2510, Branson, Inc. Danbury, CT). 11

Chapter 3

Synthesis of SiCl4 and Chlorosilanes

Synthetic Procedures

Currell’s Approach Experiments

Attempts to Reproduce Reported Pyridine HCl-Catalyzed Synthesis of Silicon Tetrachloride from Tetraalkoxysilanes and Thionyl Chloride

o Run 1, Si(OCH3)2Cl2, and Si(OCH3)3Cl. A warmed (100 C) mixture of Si(OCH3)4

(51.0 mL, 0.343 mol), SOCl2 (100 mL, 1.37 mol) (SOCl2/silane 4/1, stoichiometric) and pyridinium chloride (1.58 g, 0.0137 mol) was stirred for 17 h, and the product was sampled. 29Si

NMR (CDCl3): -54 (Si(OCH3)2Cl2), -66 (Si(OCH3)3Cl).

o Run 2, Si(OC2H5)2Cl2, and Si(OC2H5)4. A warmed (100 C) mixture of Si(OC2H5)4

(76.6 mL, 0.343 mol), SOCl2 (100 mL, 1.37 mol) (SOCl2/silane 4/1, stoichiometric) and pyridinium hydrochloride (1.58 g, 0.0137 mol) was stirred for 25 h, and the product was

29 sampled. Si NMR (CDCl3): -68 (Si(OC2H5)3Cl), - 2H5)4).

Run 3, Si(OCH3)Cl3, Si(OCH3)2Cl2, and Si(OCH3)3Cl. A room temperature mixture of

Si(OCH3)4 (51.0 mL, 0.343 mol), SOCl2 (100 mL, 1.37 mol) (SOCl2/silane 4/1, stoichiometric) and pyridinium hydrochloride (1.58 g, 0.0137 mol) was stirred for 17 h, and the product was

29 sampled. Si NMR (CDCl3): - 3)Cl3), -54 (Si(OCH3)2Cl2), -66 (Si(OCH3)3Cl).

Run 4, Si(OC2H5)2Cl2, and Si(OC2H5)3Cl. A room temperature mixture of Si(OC2H5)4

(76.6 mL, 0.343 mol), SOCl2 (100 mL, 1.37 mol) (SOCl2/silane 4/1, stoichiometric) and pyridinium hydrochloride (1.58 g, 0.0137 mol) was stirred for 25 h, and the product was

29 sampled. Si NMR (CDCl3): -56 (Si(OC2H5)2Cl2), -68 (Si(OC2H5)3Cl).

Exploratory Experiments

Uncatalyzed Synthesis of Silicon Tetrachloride from Tetramethoxysilane and Chlorinating Agents

Runs 5 – 7, Typical Attempt, at Uncatalyzed Synthesis of Silicon Tetrachloride from

Tetramethoxysilane and Chlorinating Agents, Excess Thionyl Chloride; Si(OCH3)2Cl2, and

Si(OCH3)3Cl. A solution of tetramethoxysilane (0.26 mL, 1.7 mmol), and SOCl2 (2.0 mL, 27 mmol) (SOCl2/silane, 16/1, 4-fold excess) was allowed to stand in a vial at room temperature for

48 h. Samples of the mixture were taken at 2 hours and at the end of the run. Two Hour Sample,

29 29 Si NMR (CDCl3): -66 (Si(OCH3)3Cl), no other Si resonances observed. Forty-Eight Hour

29 29 Sample, Si NMR (CDCl3): -66 (Si(OCH3)3Cl), -54 (Si(OCH3)2Cl2), no other Si resonances observed.

Runs 60 – 61, 72 – 73, 86 – 87, and 96 – 97, Other Attempts with Thionyl Chloride and Chlorinating Agents. Other attempted syntheses of SiCl4 with thionyl chloride and other chlorinating agents were carried out in a similar fashion.

Variously Catalyzed Synthesis of Silicon Tetrachloride from Tetramethoxysilane and Chlorinating Agents

Runs 34 – 36, Typical Attempt, at Variously Catalyzed Synthesis of Silicon

Tetrachloride from Tetramethoxysilane and Chlorinating Agents, Excess Thionyl

Chloride; Si(OCH3)Cl3, and Si(OCH3)2Cl2. A solution of tetramethoxysilane (0.26 mL, 1.7 mmol), and SOCl2 (2.0 mL, 27 mmol) (SOCl2/silane, 16/1, 4-fold excess) with 1,3-dimethyl-2- imidazolidone (38 mL, 0.35 mmol) was allowed to stand in a vial at room temperature for 48 h.

Samples of the mixture were taken at 0.5 hour and at the end of the run. Half Hour Sample, 29Si

29 NMR (CDCl3): -54 (Si(OCH3)2Cl2), -38 (Si(OCH3)Cl3), -18 (SiCl4), no other Si resonances

29 29 observed. Forty-Eight Hour Sample, Si NMR (CDCl3): -18 (SiCl4), no other Si resonances observed.

Runs 58 – 59, Typical Attempt, at Variously Catalyzed Synthesis of Silicon

Tetrachloride from Tetramethoxysilane and Chlorinating Agents, Stoichiometric Thionyl

Chloride; Si(OCH3)Cl3, Si(OCH3)2Cl2, Si(OCH3)3Cl. A solution of tetramethoxysilane (1.1 mL, 7.1 mmol), and SOCl2 (2.0 mL, 27 mmol) (SOCl2/silane, 4/1, stoichiometric) with 1,3- dimethyl-2-imidazolidone (38 mL, 0.35 mmol) was allowed to stand in a vial at room temperature for 48 h. Samples of the mixture were taken at 0.5 hour and at the end of the run.

29 Half Hour Sample, Si NMR (CDCl3): -66 (Si(OCH3)3Cl), -54 (Si(OCH3)2Cl2), -38

29 29 (Si(OCH3)Cl3), no other Si resonances observed. Forty-Eight Hour Sample, Si NMR

29 (CDCl3): -54 (Si(OCH3)2Cl2), -38 (Si(OCH3)Cl3), -18 (SiCl4), no other Si resonances observed.

Runs 8 – 106, Other Attempts with Various Chlorinating Agents and Potential

Catalysts. Other attempted syntheses of SiCl4 from Si(OCH3)4 with various chlorinating agents and various potential catalysts were carried out in a similar fashion. The chlorinating agents used were SOCl2, SO2Cl2, PCl3, PCl5, POCl3, and 4 M solution of HCl in dioxane. The potential catalysts used were benzene, pyridine, quinoline, 2,3,5-collidine, cyanuric chloride, trimethylamine, triethylamine, butylamine, dibutylamine, tributylamine, dimethylformamide, dimethylacetamide, dimethylaniline, 2-imidazolidone, 1,3-dimethyl-2-imidazolidone,

(chloromethylene)dimethyliminium chloride (iminium chloride), N-chlorosuccinimide, and zinc chloride.

Detailed Experiments

Catalyzed Alkoxysilane-Thionyl Chloride Investigations

DMF-Catalyzed Synthesis of Methylchlorosilanes from Methylmethoxysilanes and Thionyl Chloride

o Run 107, No Methoxysilanes. A warmed (55 C) mixture of Si(CH3)4 (11.6 mL, 0.085 mol), SOCl2 (100 mL, 1.37 mol) (SOCl2/silane, 16/1, 4-fold excess) and dimethylformamide

29 (2.75 mL, 0.0355 mol) was refluxed for 28 h and cooled (~98 mL). Si NMR (CDCl3):

29 (Si(CH3)4), no other Si resonances observed.

o Run 108, (CH3)3SiCl. A warmed (55 C) mixture of (CH3)3SiOCH3 (11.8 mL, 0.086 mol), SOCl2 (100 mL, 1.37 mol) (SOCl2/silane, 16/1, 16-fold excess) and dimethylformamide

(2.75 mL, 0.0355 mol) was refluxed for 0.5 h and cooled (~105 mL). The reaction mixture was fractionally distilled (29 cm column, glass helices packing, atmospheric pressure), and the

o 29 fraction distilling in the 53-62 C range (7.4 mL) was collected (75 %). Si NMR (CDCl3):

29 32.1 ((CH3)3SiCl), no other Si resonances observed (~60 % as inferred from NMR).

The reaction mixture in this and similar runs was sampled periodically during the experiment and the experiment was terminated when the reaction was complete.

o Run 109, (CH3)2SiCl2. A warmed (55 C) mixture of (CH3)2Si(OCH3)2 (11.9 mL, 0.087 mol), SOCl2 (100 mL, 1.37 mol) (SOCl2/silane, 16/1, 8-fold excess) and dimethylformamide

29 (2.75 mL, 0.0355 mol) was refluxed for 0.5 h and cooled (~98 mL). Si NMR (CDCl3): 33.2

29 ((CH3)2SiCl2), no other Si resonances observed (~60 % as inferred from NMR). The reaction mixture was fractionally distilled (29 cm column, glass helices packing, atmospheric pressure), but no fraction composed predominately of (CH3)2SiCl2 was obtained.

Because of the closeness of the boiling points of some of the species involved in this run,

Table 1, yield determination by fractional distillation proved difficult. Accordingly, resort was made to estimating yields in this and other like cases on the basis of the relative intensities of the resonances in the 29Si spectra of the reaction products. While only qualitative, this procedure did give approximate yields.

o Run 110, CH3SiCl3. A warmed (55 C) mixture of CH3Si(OCH3)3 12.2 mL, 0.085 mol),

SOCl2 (100 mL, 1.37 mol) (SOCl2/silane, 16/1, 5.3-fold excess) and dimethylformamide (2.75

29 mL, 0.0355 mol) was refluxed for 2 h and cooled (~89 mL). Si NMR (CDCl3): 12.5

29 (CH3SiCl3), no other Si resonances observed (~60 % as inferred from NMR). The reaction mixture was fractionally distilled (29 cm column, glass helices packing, atmospheric pressure), but no fraction composed predominately of CH3SiCl3 was obtained.

Table 1. Boiling Points of Compounds Type increasing bp (oC) (oC) Si(CH3)4 26 CH3Cl -24 SiCl4 57 SO2 -10 CH3SiCl3 66 Si(CH3)4 26

C2H5SiCl3 99 (CH3)3SiOCH3 57 (CH ) SiCl 70 SiCl 57 3 2 2 4 (CH3)3SiCl 57 (CH3)3SiCl 57 Si(OCH3)4 121 CH3SiCl3 66 Si(OC2H5)4 168 (CH3)2SiCl2 70 Si(OC3H7)4 94 PCl3 74 Si(OC4H9)4 275 (CH3)3SiOC2H5 75 2 CH3Si(OCH3)3 102 BuCl 77 CH3Si(OC2H5)3 141 SOCl2 79 C2H5Si(OCH3)3 123 (CH3)2Si(OCH3)2 81 4 C2H5Si(OC2H5)3 158 Et3N 88 (CH3)2Si(OCH3)2 81 Si(OC3H7)4 94 (CH3)2Si(OC2H5)2 114 C2H5SiCl3 99 (CH3)3SiOCH3 57 CH3Si(OCH3)3 102 (CH3)3SiOC2H5 75 POCl3 105

SOCl2 79 (CH3)2Si(OC2H5)2 114 PCl 74 Si(OCH ) 121 3 3 4 POCl3 105 C2H5Si(OCH3)3 123 1 DMF 153 CH3Si(OC2H5)3 141 BuCl2 77 DMF1 153 3 DMA 164 C2H5Si(OC2H5)3 158 4 3 Et3N 88 DMA 164 CH3Cl -24 Si(OC2H5)4 168 SO2 -10 Si(OC4H9)4 275 1DMF, dimethylformamide. 2BuCl, n-butyl chloride. 3 4 DMA, dimethylacetamide. Et3N, triethylamine.

DMF-Catalyzed Synthesis of Methylchlorosilanes from Methylethoxysilanes and Thionyl Chloride

o Run 111, (CH3)3SiCl. A warmed (55 C) mixture of (CH3)3Si(OC2H5) (13.4 mL, 0.086 mol), SOCl2 (100 mL, 1.37 mol) (SOCl2/silane, 16/1, 16-fold excess) and dimethylformamide

29 (2.75 mL, 0.0355 mol) was refluxed for 0.5 h and cooled (~105 mL). Si NMR (CDCl3): 32.1

29 ((CH3)3SiCl), no other Si resonances observed (~60% as inferred from NMR). The reaction mixture was fractionally distilled (29 cm column, glass helices packing, atmospheric pressure), but no fraction composed predominately of (CH3)3SiCl was obtained.

o Run 112, (CH3)2SiCl2. A warmed (55 C) mixture of (CH3)2Si(OC2H5)2 (15.1 mL, 0.088 mol), SOCl2 (100 mL, 1.37 mol) (SOCl2/silane, 16/1, 8-fold excess) and dimethylformamide

29 (2.75 mL, 0.0355 mol) was refluxed for 0.5 h and cooled (~107 mL). Si NMR (CDCl3): 32.8

29 ((CH3)2SiCl2), no other Si resonances observed (~60% as inferred from NMR). The reaction mixture was fractionally distilled (29 cm column, glass helices packing, atmospheric pressure), but no fraction composed predominately of (CH3)2SiCl2 was obtained.

o Run 113, CH3SiCl3. A warmed (55 C) mixture of CH3Si(OC2H5)3 (17.0 mL, 0.086 mol), SOCl2 (100 mL, 1.37 mol) (SOCl2/silane, 16/1, 5.3-fold excess) and dimethylformamide

29 (2.75 mL, 0.0355 mol) was refluxed for 7 h and cooled (~95 mL). Si NMR (CDCl3): 12.4

29 (CH3SiCl3), no other Si resonances observed (~60% as inferred from NMR). The reaction

mixture was fractionally distilled (29 cm column, glass helices packing, atmospheric pressure), but no fraction composed predominately of CH3SiCl3 was obtained.

DMF-Catalyzed Synthesis of Ethylchlorosilanes from Ethylalkoxysilanes and Thionyl Chloride

o Run 114, C2H5SiCl3. A warmed (55 C) mixture of C2H5Si(OCH3)3 (13.7 mL, 0.086 mol), SOCl2 (100 mL, 1.37 mol) (SOCl2/silane, 16/1, 5.3-fold excess) and dimethylformamide

29 (2.75 mL, 0.0355 mol) was refluxed for 3 h and cooled (~88 mL). Si NMR (CDCl3): 14.9

29 (C2H5SiCl3), no other Si resonances observed (~60% as inferred from NMR). The reaction mixture was fractionally distilled (29 cm column, glass helices packing, atmospheric pressure), but no fraction composed predominately of C2H5SiCl3was obtained.

o Run 115, C2H5SiCl3. A warmed (55 C) mixture of C2H5Si(OC2H5)3 (18.4 mL, 0.086 mol), SOCl2 (100 mL, 1.37 mol) (SOCl2/silane, 16/1, 5.3-fold excess) and dimethylformamide

29 (2.75 mL, 0.0355 mol) was refluxed for 7 h and cooled (~97 mL). Si NMR (CDCl3): 14.9

DMF-Catalyzed Synthesis of Silicon Tetrachloride from Tetramethoxysilane and Thionyl Chloride

o Run 116, SiCl4. A warmed (55 C) mixture of Si(OCH3)4 (12.7 mL, 0.086 mol), SOCl2

(100 mL, 1.37 mol) (SOCl2/silane, 16/1, 4-fold excess) and dimethylformamide (2.75 mL,

0.0355 mol) was refluxed for 8 h and cooled. The reaction mixture was fractionally distilled (29 cm column, glass helices packing, atmospheric pressure), and the fraction distilling in the 53-62 o 29 29 C range (6.2 mL) was collected 63 %). Si NMR (CDCl3): -18.8 (SiCl4), no other Si resonances observed.

o Run 117, SiCl4. A warmed (55 C) mixture of Si(OCH3)4 (25.5 mL, 0.171 mol), SOCl2

(100 mL, 1.37 mol) (SOCl2/silane, 8/1, 2-fold excess) and dimethylformamide (2.75 mL, 0.0355 mol) was refluxed for 17 h and cooled. The reaction mixture was fractionally distilled (29 cm column, glass helices packing, atmospheric pressure), and the fraction distilling in the 53-62 oC

29 29 range (8.5 mL) was collected (43 %). Si NMR (CDCl3): -18.8 (SiCl4), no other Si resonances observed.

o Run 118, SiCl4. A warmed (55 C) mixture of Si(OCH3)4 (12.7 mL, 0.086 mol), SOCl2

(100 mL, 1.37 mol) (SOCl2/silane, 16/1, 4-fold excess) and dimethylformamide (1.38 mL,

0.0178 mol) was refluxed for 17 h and cooled. The reaction mixture was fractionally distilled

(29 cm column, glass helices packing, atmospheric pressure), and the fraction distilling in the 53-

o 29 29 62 C range (5.3 mL) was collected (54 %). Si NMR (CDCl3): -18.8 (SiCl4), no other Si resonances observed.

o Run 119, SiCl4. A warmed (45 C) mixture of Si(OCH3)4 (12.7 mL, 0.086 mol), SOCl2

(100 mL, 1.37 mol) (SOCl2/silane, 16/1, 4-fold excess) and dimethylformamide (2.75 mL,

0.0355 mol) was refluxed for 17 h and cooled. The reaction mixture was fractionally distilled

(29 cm column, glass helices packing, atmospheric pressure), and the fraction distilling in the 53-

o 29 29 62 C range (5.6 mL) was collected (57 %). Si NMR (CDCl3): -18.8 (SiCl4), no other Si resonances observed.

o Run 120, SiCl4. A warmed (35 C) mixture of Si(OCH3)4 (12.7 mL, 0.086 mol), SOCl2

(100 mL, 1.37 mol) (SOCl2/silane, 16/1, 4-fold excess) and dimethylformamide (2.75 mL,

0.0355 mol) was refluxed for 21 h and cooled. The reaction mixture was fractionally distilled

(29 cm column, glass helices packing, atmospheric pressure), and the fraction distilling in the 53-

o 29 29 62 C range (5.2 mL) was collected (53 %). Si NMR (CDCl3): -18.8 (SiCl4), no other Si resonances observed.

o Run 121, SiCl4. A warmed (35 C) mixture of Si(OCH3)4 (12.7 mL, 0.086 mol), SOCl2

(100 mL, 1.37 mol) (SOCl2/silane, 16/1, 4-fold excess) and dimethylformamide (2.75 mL,

0.0355 mol) was refluxed for 25 h and cooled. The reaction mixture was fractionally distilled

(29 cm column, glass helices packing, atmospheric pressure), and the fraction distilling in the 53- 24

o 29 29 62 C range (5.2 mL) was collected (53 %). Si NMR (CDCl3): -18.8 (SiCl4), no other Si resonances observed.

Run 122, SiCl4. A room temperature mixture of Si(OCH3)4 (12.7 mL, 0.086 mol), SOCl2

(100 mL, 1.37 mol) (SOCl2/silane, 16/1, 4-fold excess) and dimethylformamide (2.75 mL,

0.0355 mol) was refluxed for 96 h and cooled. The reaction mixture was fractionally distilled

(29 cm column, glass helices packing, atmospheric pressure), and the fraction distilling in the 53-

o 29 29 62 C range (5.2 mL) was collected (53 %). Si NMR (CDCl3): -18.8 (SiCl4), no other Si resonances observed.

o Run 123, SiCl4. A warmed (55 C) mixture of Si(OCH3)4 (25.5 mL, 0.171 mol), SOCl2

(100 mL, 1.37 mol) (SOCl2/silane, 8/1, 2-fold excess) and dimethylformamide (1.38 mL, 0.0178 mol) was refluxed for 28 h and cooled. The reaction mixture was fractionally distilled (29 cm column, glass helices packing, atmospheric pressure), and the fraction distilling in the 53-62 oC

29 29 range (9.7 mL) was collected (50 %). Si NMR (CDCl3): -18.8 (SiCl4), no other Si resonances observed.

o Run 124, SiCl4. A warmed (38 C) mixture of Si(OCH3)4 (25.5 mL, 0.171 mol), SOCl2

(100 mL, 1.37 mol) (SOCl2/silane, 8/1, 2-fold excess) and dimethylformamide (1.38 mL, 0.0178 mol) was refluxed for 71 h and cooled. The reaction mixture was fractionally distilled (29 cm column, glass helices packing, atmospheric pressure), and the fraction distilling in the 53-62 oC 25

29 29 range (8.9 mL) was collected (45 %). Si NMR (CDCl3): -18.8 (SiCl4), no other Si resonances observed.

Run 125, SiCl4. A room temperature mixture of Si(OCH3)4 (25.5 mL, 0.171 mol), SOCl2

(100 mL, 1.37 mol) (SOCl2/silane, 8/1, 2-fold excess) and dimethylformamide (1.38 mL, 0.0178 mol) was refluxed for 168 h and cooled. The reaction mixture was fractionally distilled (29 cm column, glass helices packing, atmospheric pressure), and the fraction distilling in the 53-62 oC

29 29 range (9.5 mL) was collected (48 %). Si NMR (CDCl3): -18.8 (SiCl4), no other Si resonances observed.

o Run 126, SiCl4. A warmed (55 C) mixture of Si(OCH3)4 (6.4 mL, 0.043 mol), SOCl2

(50 mL, 0.69 mol) (SOCl2/silane, 16/1, 4-fold excess) and dimethylformamide (1.38 mL, 0.0178 mol) was refluxed for 17 h and cooled. The reaction mixture was fractionally distilled (29 cm column, glass helices packing, atmospheric pressure), and the fraction distilling in the 53-62 oC

29 29 range (3.2 mL) was collected (65 %). Si NMR (CDCl3): -18.8 (SiCl4), no other Si resonances observed.

Variously Catalyzed Synthesis of Silicon Tetrachloride from Tetramethoxysilane and Thionyl Chloride

Run 127, Si(OCH3)3Cl. A room temperature mixture of Si(OCH3)4 (12.7 mL, 0.086

29 mol), SOCl2 (100 mL, 1.37 mol) (SOCl2/silane, 16/1, 4-fold excess) was stirred for 48 h. Si

29 NMR (CDCl3): -68.7 (Si(OCH3)3Cl), no other Si resonances observed.

o Run 128, SiCl4. A warmed (55 C) mixture of Si(OCH3)4 (12.7 mL, 0.086 mol), SOCl2

(100 mL, 1.37 mol) (SOCl2/silane, 16/1, 4-fold excess) and dimethylacetamide (1.65 mL, 0.0177 mol) was refluxed for 24 h and cooled (the reaction mixture color turned dark red within minutes). The reaction mixture was fractionally distilled (29 cm column, glass helices packing, atmospheric pressure), and the fraction distilling in the 53-62 oC range (5.4 mL) was collected

29 29 (55 %). Si NMR (CDCl3): -18.8 (SiCl4), no other Si resonances observed.

o Run 129, SiCl4. A warmed (55 C) mixture of Si(OCH3)4 (12.7 mL, 0.086 mol), SOCl2

(100 mL, 1.37 mol) (SOCl2/silane, 16/1, 4-fold excess) and triethylamine (2.5 mL, 0.017 mol) was refluxed for 32 h and cooled. The reaction mixture was fractionally distilled (29 cm column, glass helices packing, atmospheric pressure), and the fraction distilling in the 53-62 oC range (6.3

29 29 mL) was collected (64 %). Si NMR (CDCl3): -18.8 (SiCl4), no other Si resonances observed.

o Run 130, SiCl4. A warmed (55 C) mixture of Si(OCH3)4 (12.7 mL, 0.086 mol), SOCl2

(100 mL, 1.37 mol) (SOCl2/silane, 16/1, 4-fold excess) and triethylamine (5.0 mL, 0.034 mol) was refluxed for 8 h and cooled. The reaction mixture was fractionally distilled (29 cm column, glass helices packing, atmospheric pressure), and the fraction distilling in the 53-62 oC range (6.8

29 29 mL) was collected (70 %). Si NMR (CDCl3): -18.8 (SiCl4), no other Si resonances observed.

o Run 131, SiCl4. A warmed (55 C) mixture of Si(OCH3)4 (12.7 mL, 0.086 mol), SOCl2

(100 mL, 1.37 mol) (SOCl2/silane, 16/1, 4-fold excess) and (chloromethylene)dimethyliminium chloride, ClCH=N(CH3)2Cl, (2.28 g, 0.0178 mol) was refluxed for 17 h and cooled. The reaction mixture was fractionally distilled (29 cm column, glass helices packing, atmospheric pressure), and the fraction distilling in the 53-62 oC range (6.1 mL) was collected (62 %). 29Si NMR

29 (CDCl3): -18.8 (SiCl4), no other Si resonances observed.

o Run 132, SiCl4. A warmed (55 C) mixture of Si(OCH3)4 (12.7 mL, 0.086 mol), SOCl2

(100 mL, 1.37 mol) (SOCl2/silane, 16/1, 4-fold excess) and (chloromethylene)dimethyliminium chloride, ClCH=N(CH3)2Cl, (4.56 g, 0.035 mol) was refluxed for 8 h and cooled. The reaction mixture was fractionally distilled (29 cm column, glass helices packing, atmospheric pressure), and the fraction distilling in the 53-62 oC range (6.4 mL) was collected (65 %). 29Si NMR

29 (CDCl3): -18.8 (SiCl4), no other Si resonances observed.

o Run 133, SiCl4. A warmed (55 C) mixture of Si(OCH3)4 (12.7 mL, 0.086 mol), SOCl2

(100 mL, 1.37 mol), (SOCl2/silane, 16/1, 4-fold excess) dimethylformamide (2.75 mL, 0.0355 mol) and n-C4H9Cl (6 mL, 0.06 mol) was refluxed for 11 h and cooled. The reaction mixture was fractionally distilled (29 cm column, glass helices packing, atmospheric pressure), and the

o 29 fraction distilling in the 53-62 C range (5.9 mL) was collected (60 %). Si NMR (CDCl3):

29 -18.8 (SiCl4), no other Si resonances observed.

o Run 134, SiCl4. A warmed (55 C) mixture of Si(OCH3)4 (25.5 mL, 0.171 mol), SOCl2

(100 mL, 1.37 mol), (SOCl2/silane, 8/1, 2-fold excess) dimethylformamide (2.75 mL, 0.0355 mol) and n-C4H9Cl (6 mL, 0.06 mol) was refluxed for 17 h and cooled. The reaction mixture was fractionally distilled (29 cm column, glass helices packing, atmospheric pressure), and the

o 29 fraction distilling in the 53-62 C range (11.1 mL) was collected (57 %). Si NMR (CDCl3):

29 -18.8 (SiCl4), no other Si resonances observed.

DMF-Catalyzed Synthesis of Silicon Tetrachloride from Tetramethoxysilane and Thionyl Chloride with Vent-Line Traps

Run 135, SiCl4. In a setup in which the vent line of the apparatus contained three cooled

o o o o traps (ice, 0 C; CO2-acetone, -77 C; CO2-acetone, -77 C), a warmed (55 C) mixture of

Si(OCH3)4 (12.7 mL, 0.086 mol), SOCl2 (100 mL, 1.37 mol) (SOCl2/silane, 16/1, 4-fold excess) and dimethylformamide (2.75 mL, 0.0355 mol) was refluxed for 8 h and cooled. The product in

29 29 trap 1 (2.2 mL) was collected (22 %). Si NMR (CDCl3): -18.8 (SiCl4), no other Si resonances observed. The product in trap 2, probably CH3Cl (25 mL, 0.49 mol if CH3Cl), was lost because of its volatility. Trap 3 did not contain any product. The reaction mixture was fractionally distilled (29 cm column, glass helices packing, atmospheric pressure), and the

o 29 fraction distilling in the 53-62 C range (6.8 mL) was collected (70 %). Si NMR (CDCl3): -

29 18.8 (SiCl4), no other Si resonances observed (total yield 22 + 70 = 92 %).

Run 136, SiCl4. In a setup in which the vent line of the apparatus contained three cooled

o o o o traps (ice, 0 C; CO2-CCl4, -23 C; CO2-CH3CN, -42 C), a warmed (55 C) mixture of

Si(OCH3)4 (12.7 mL, 0.086 mol), SOCl2 (100 mL, 1.37 mol) (SOCl2/silane, 16/1, 4-fold excess) and dimethylformamide (2.75 mL, 0.0355 mol) was refluxed for 11 h and cooled. The product

29 29 in trap 1 (2.0 mL) was collected (20 %). Si NMR (CDCl3): -18.8 (SiCl4), no other Si resonances observed. The product in trap 2, probably CH3Cl (30 mL, 0.49 mol if CH3Cl), was lost because of its volatility. Trap 3 did not contain any product. The reaction mixture was

fractionally distilled (29 cm column, glass helices packing, atmospheric pressure), and the

o 29 fraction distilling in the 53-62 C range (5.7 mL) was collected (58 %). Si NMR (CDCl3): -

29 18.8 (SiCl4), no other Si resonances observed (total yield 20 + 58 = 78 %).

o Run 137, SiCl4. In a setup in which the vent line contained four traps (ice, 0 C; empty;

o o 11 M aqueous NaOH, room temperature; CO2-CH3CN, -42 C), a warmed (55 C) mixture of

Si(OCH3)4 (12.7 mL, 0.086 mol), SOCl2 (100 mL, 1.37 mol) (SOCl2/silane, 16/1, 4-fold excess) and dimethylformamide (2.75 mL, 0.0355 mol) was refluxed for 8 h and cooled. The product in

29 29 trap 1 (1.3 mL) was collected (13 %). Si NMR (CDCl3): -18.8 (SiCl4), no other Si resonances observed. The product in trap 3 was a white precipitate (product was absent in traps

2 and 4). The reaction mixture was fractionally distilled (29 cm column, glass helices packing, atmospheric pressure), and the fraction distilling in the 53-62 oC range (6.8 mL) was collected

29 29 (70 %). Si NMR (CDCl3): -18.8 (SiCl4), no other Si resonances observed (total yield 13 +

70 = 83 %).

o Run 138, SiCl4. In a setup in which the vent line contained three cooled traps (ice, 0 C;

o o o CO2-CH3CN, -42 C; CO2-CH3CN, -42 C), a warmed (55 C) mixture of Si(OCH3)4 (12.7 mL,

0.086 mol), SOCl2 (100 mL, 1.37 mol) (SOCl2/silane, 16/1, 4-fold excess) and dimethylformamide (2.75 mL, 0.0355 mol) was refluxed for 12 h and cooled. The product in

29 29 trap 1 (2.0 mL) was collected (20 %). Si NMR (CDCl3): -18.8 (SiCl4), no other Si resonances observed. The product in trap 2, probably CH3Cl (27 mL, 0.49 mol if CH3Cl), was

lost because of its volatility. Trap 3 did not contain any product. n-C4H9Cl was added to the reaction product (6.0 mL, 0.057 mol), and the mixture was fractionally distilled (29 cm column, glass helices packing, atmospheric pressure). The fraction distilling in the 53-62 oC range (5.7

29 29 mL) was collected (58 %). Si NMR (CDCl3): -18.8 (SiCl4), no other Si resonances observed

(total yield 20 + 58 = 78 %).

Catalyzed Synthesis of Silicon Tetrachloride from Higher Tetraalkoxysilanes and Thionyl Chloride

o Run 139, SiCl4. A warmed (55 C) mixture of Si(OC2H5)4 (19.1 mL, 0.086 mol), SOCl2

(100 mL, 1.37 mol) (SOCl2/silane, 16/1, 4-fold excess) and dimethylformamide (2.75 mL,

0.0355 mol) was refluxed for 15 h and cooled. The reaction mixture was fractionally distilled

(29 cm column, glass helices packing, atmospheric pressure), and the fraction distilling in the 53-

o 29 29 62 C range (4.2 mL) was collected (43 %). Si NMR (CDCl3): -18.8 (SiCl4), no other Si resonances observed.

o Run 140, SiCl4. A warmed (55 C) mixture of Si(n-OC3H7)4 (24.7 mL, 0.086 mol),

SOCl2 (100 mL, 1.37 mol) (SOCl2/silane, 16/1, 4-fold excess) and dimethyformamide (2.75 mL,

0.0355 mol) was refluxed for 32 h and cooled. The reaction mixture was fractionally distilled

(29 cm column, glass helices packing, atmospheric pressure), and the fraction distilling in the 43-

o o 53 C range (27 mL, n-C4H9Cl by NMR, 90 %) and distilling in the 53-62 C range (4.5 mL,

29 29 SiCl4, 46 %) were collected. Si NMR (CDCl3): -18.8 (SiCl4), no other Si resonances observed.

o Run 141, SiCl4. A warmed (55 C) mixture of Si(n-OC4H9)4 (30.5 mL, 0.086 mol),

SOCl2 (100 mL, 1.37 mol) (SOCl2/silane, 16/1, 4-fold excess) and dimethyformamide (2.75 mL,

0.0355 mol) was refluxed for 64 h and cooled. The reaction mixture was fractionally distilled

(29 cm column, glass helices packing, atmospheric pressure), and the fraction distilling in the 53-

o 29 29 62 C range (7.2 mL) was collected (73 %). Si NMR (CDCl3): -18.8 (SiCl4), no other Si resonances observed. The distillation was continued but no fraction composed predominately of n-C4H9Cl (as determined by NMR) was obtained.

o Run 142, SiCl4. A warmed (55 C) mixture of Si(OC2H5)4 (9.6 mL, 0.043 mol), SOCl2

(100 mL, 1.37 mol) (SOCl2/silane, 32/1, 8-fold excess) and dimethylformamide (1.38 mL, 0.018 mol) was refluxed for 24 h and cooled. The reaction mixture was fractionally distilled (29 cm column, glass helices packing, atmospheric pressure), and the fraction distilling in the 53-62 oC

29 29 range (1.6 mL) was collected (33 %). Si NMR (CDCl3): -18.8 (SiCl4), no other Si resonances observed.

o Run 143, SiCl4. A warmed (55 C) mixture of Si(OC2H5)4 (38.3 mL, 0.171 mol), SOCl2

(100 mL, 1.37 mol) (SOCl2/silane, 8/1, 2-fold excess) and dimethylformamide (2.75 mL, 0.0355 mol) was refluxed for 41 h and cooled. The reaction mixture was fractionally distilled (29 cm column, glass helices packing, atmospheric pressure), and the fraction distilling in the 53-62 oC

29 29 range (6.8 mL) was collected (35 %). Si NMR (CDCl3): -18.8 (SiCl4), no other Si resonances observed.

o Run 144, SiCl4. A warmed (55 C) mixture of Si(OC2H5)4 (38.3 mL, 0.171 mol), SOCl2

(100 mL, 1.37 mol) (SOCl2/silane, 8/1, 2-fold excess) and dimethylformamide (1.38 mL, 0.0178 34

mol) was refluxed for 120 h and cooled. The reaction mixture was fractionally distilled (29 cm column, glass helices packing, atmospheric pressure), and the fraction distilling in the 53-62 oC

29 29 range (11.5 mL) was collected (58 %). Si NMR (CDCl3): -18.8 (SiCl4), no other Si resonances observed.

o Run 145, SiCl4. A warmed (55 C) mixture of Si(OC2H5)4 (19.1 mL, 0.086 mol), SOCl2

(100 mL, 1.37 mol) (SOCl2/silane, 16/1, 4-fold excess) and dimethylformamide (1.38 mL,

0.0178 mol) was refluxed for 45 h and cooled. The reaction mixture was fractionally distilled

(29 cm column, glass helices packing, atmospheric pressure), and the fraction distilling in the 53-

o 29 29 62 C range (4.8 mL) was collected (49 %). Si NMR (CDCl3): -18.8 (SiCl4), no other Si resonances observed.

o Run 146, SiCl4. A warmed (55 C) mixture of Si(OC2H5)4 (9.6 mL, 0.043 mol), SOCl2

(100 mL, 1.37 mol) (SOCl2/silane, 32/1, 8-fold excess) and dimethyacetamide (1.65 mL, 0.0177 mol) was refluxed for 24 h and cooled. The reaction mixture was fractionally distilled (29 cm column, glass helices packing, atmospheric pressure), and the fraction distilling in the 53-62 oC

29 29 range (1.8 mL) was collected (37 %). Si NMR (CDCl3): -18.8 (SiCl4), no other Si resonances observed.

Alkoxysilane-Aqueous HCl Investigations

Uncatalyzed Synthesis of Trimethylchlorosilane from Trimethylmethoxysilane and Aqueous HCl

o Run 147, (CH3)3SiCl. A portion of cold (0 C) aqueous HCl (12 N, 39 mL, 0.47 mol) was treated with a solution of (CH3)3SiOCH3 (6.9 mL, 0.050 mol) (HCl/silane, 9.4/1, 4.7-fold excess) and hexanes (10 mL, 0.076 mol) over 1 h, stirred for 2 h, and separated. The organic

29 layer was sampled. Si NMR (CDCl3): CH3)3SiCl), 11.4 (unknown).

o Run 148, CH3(CH2Cl)Si(OCH3)2 ?. A portion of cold (0 C) aqueous HCl (12 N, 39 mL,

0.47 mol) was treated with a solution of (CH3)2Si(OCH3)2 (6.9 mL, 0.050 mol) (HCl/silane,

9.4/1, 2.4-fold excess) and hexanes (10 mL, 0.076 mol) over 1 h, stirred for 2 h, and separated.

29 The organic layer was sampled. Si NMR (CDCl3): -15, -17.3, -17.6 (all three resonances unknown, one possibly CH3(CH2Cl)Si(OCH3)2).

Uncatalyzed Synthesis of Trimethylchlorosilane from Trimethylethoxysilane and Aqueous HCl

o Run 149, (CH3)3SiCl. A portion of cold (0 C) aqueous HCl (12 N, 39 mL, 0.47 mol) was treated with a solution of (CH3)3SiOC2H5 (7.8 mL, 0.050 mol) (HCl/silane, 9.4/1, 4.7-fold excess) and hexanes (10 mL, 0.076 mol) over 1 h, stirred for 2 h, and separated. The organic

29 layer was sampled. Si NMR (CDCl3): 77.2 (unknown), 33.7 ((CH3)3SiCl), 11.4 (unknown).

o Run 150, CH3(CH2Cl)Si(OEt)2 ?. A portion of cold (0 C) aqueous HCl (12 N, 39 mL,

0.47 mol) was treated with a solution of (CH3)2Si(OC2H5)2 (8.6 mL, 0.050 mol) (HCl/silane,

9.4/1, 2.4-fold excess) and hexanes (10 mL, 0.076 mol) over 1 h, stirred for 2 h, and separated.

29 The organic layer was sampled. Si NMR (CDCl3): -19.2, -21.5 (both unknown, one possibly

CH3(CH2Cl)Si(OEt)2).

Uncatalyzed Synthesis of Triethylchlorosilane from Triethylethoxysilane and Aqueous HCl

o Run 151, (C2H5)3SiCl. A portion of cold (0 C) aqueous HCl (12 N, 39 mL, 0.47 mol) was treated with a solution of (C2H5)3SiOC2H5 (9.8 mL, 0.050 mol) (HCl/silane, 9.4/1, 4.7-fold excess) and hexanes (10 mL, 0.076 mol) over 1 h, stirred for 2 h, and separated. The organic

29 layer was sampled. Si NMR (CDCl3): 35.3 ((C2H5)3SiCl).

Alkoxysilane-HCl Gas Investigations

Uncatalyzed Synthesis of Methylchlorosilanes from Methylmethoxysilanes and HCl Gas

o Run 152, (CH3)3SiCl. A cold (0 C) portion of (CH3)3SiOCH3 (2.5 mL, 0.018 mol) was treated with a stream of HCl gas (~78 mL/min) (0.21 mol, HCl/silane, 11.5/1, 5.8-fold excess)

29 for 1 h, and the product was sampled. Si NMR (CDCl3): CH3)3SiCl).

o Run 153, (CH3)2SiCl2, and (CH3)2Si(OCH3)Cl. A cold (0 C) portion of

(CH3)2Si(OCH3)2 (2.5 mL, 0.018 mol) was treated with a stream of HCl gas (~78 mL/min) (0.21 mol, HCl/silane, 11.4/1, 2.8-fold excess) for 1 h, and the product was sampled. 29Si NMR

(CDCl3): ((CH3)2SiCl2), 21.1 ((CH3)2Si(OCH3)Cl), 11.1 (unknown), 8.5

((CH3)2Si(OCH3)2) .

o Run 154, CH3Si(OCH3)Cl2, and CH3Si(OCH3)2 Cl. A cold (0 C) portion of

CH3Si(OCH3)3 (2.5 mL, 0.018 mol) was treated with a stream of HCl gas (~78 mL/min) (0.21 mol, HCl/silane, 11.9/1, 2.0-fold excess) for 1 h, and the product was sampled. 29Si NMR

(CDCl3): - (CH3Si(OCH3)Cl2), -24.7 (CH3Si(OCH3)2 Cl), -34.1 (CH3Si(OCH3)3), -47.2

(CH3Si(OCH3)3).

Run 155, (CH3)3SiCl. A room temperature portion of (CH3)3SiOCH3 (2.5 mL, 0.018 mol) was treated with a stream of HCl gas (~78 mL/min) (0.21 mol, HCl/silane, 11.5/1, 5.8-fold

29 excess) for 1 h, and the product was sampled. Si NMR (CDCl3): CH3)3SiCl).

Run 156, (CH3)2SiCl2, and (CH3)2Si(OCH3)Cl. In a reaction setup in which the vent line of the apparatus contained a cooled trap (ice, 0 oC), a room temperature portion of

(CH3)2Si(OCH3)2 (2.5 mL, 0.018 mol) was treated with a stream of HCl gas (~78 mL/min) (0.42 mol, HCl/silane, 22.8/1, 5.7-fold excess) for 2 h. The product was sampled but did not show any

29 29 Si resonances. Trap 1 contained a liquid which was sampled. Si NMR (CDCl3):

((CH3)2SiCl2), 16.9 ((CH3)2Si(OCH3)Cl), 7.3 ((CH3)2Si(OCH3)2).

Run 157, CH3Si(OCH3)Cl2, and CH3Si(OCH3)2 Cl. A room temperature portion of

CH3Si(OCH3)3 (2.5 mL, 0.018 mol) was treated with a stream of HCl gas (~78 mL/min) (0.21 mol, HCl/silane, 11.9/1, 2.0-fold excess) for 1 h, and the product was sampled. 29Si NMR

(CDCl3): -3.5 (CH3Si(OCH3)Cl2), -20.7 (CH3Si(OCH3)2 Cl), -34.1 (CH3Si(OCH3)3), -43.3

(CH3Si(OCH3)3).

Uncatalyzed and Catalyzed Synthesis of Methylchlorosilanes from Methylethoxysilanes and HCl Gas

o Run 158, (CH3)3SiCl. A cold (0 C) portion of (CH3)3SiOC2H5 (2.5 mL, 0.016 mol) was treated with a stream of HCl gas (~78 mL/min) (0.21 mol, HCl/silane, 13.0/1, 6.5-fold excess)

29 for 1 h, and the product was sampled. Si NMR (CDCl3): 35.3 ((CH3)3SiCl).

o Run 159, (CH3)2SiCl2, and (CH3)2Si(OC2H5)Cl. A cold (0 C) portion of

(CH3)2Si(OC2H5)2 (2.5 mL, 0.015 mol) was treated with a stream of HCl gas (~78 mL/min) (0.21 mol, HCl/silane, 14.3/1, 3.6-fold excess) for 1 h, and the product was sampled. 29Si NMR

(CDCl3): 32.3 ((CH3)2SiCl2), 13.7 ((CH3)2Si(OC2H5)Cl), 6.9 ((CH3)2Si(OC2H5)2).

o Run 160, CH3Si(OC2H5)Cl2, and CH3Si(OC2H5)2Cl. A cold (0 C) portion of

CH3Si(OC2H5)3 (2.5 mL, 0.013 mol) was treated with a stream of HCl gas (~78 mL/min) (0.21 mol, HCl/silane, 16.6/1, 2.8-fold excess) for 1 h, and the product was sampled. 29Si NMR

(CDCl3): -5.9 (CH3Si(OC2H5)Cl2), -23.5 (CH3Si(OC2H5)2Cl).

Run 161, (CH3)3SiCl. A room temperature portion of (CH3)3SiOC2H5 (2.5 mL, 0.016 mol) was treated with a stream of HCl gas (~78 mL/min) (0.21 mol, HCl/silane, 13.0/1, 6.5-fold

29 excess) for 1 h, and the product was sampled. Si NMR (CDCl3): 35.6 ((CH3)3SiCl). 41

o Run 162, (CH3)2SiCl2, and (CH3)2Si(OC2H5)Cl. A warmed (35 C) portion of

(CH3)2Si(OC2H5)2 (2.5 mL, 0.015 mol) was treated with a stream of HCl gas (~78 mL/min) (0.21 mol, HCl/silane, 14.3/1, 3.6-fold excess) for 1 h, and the product was sampled. 29Si NMR

(CDCl3): 32.3 ((CH3)2SiCl2), 13.7 ((CH3)2Si(OC2H5)Cl), 6.9 ((CH3)2Si(OC2H5)2), 4.0

(unknown), -19 (unknown).

Run 163, (CH3)Si(OC2H5)Cl2, and (CH3)Si(OC2H5)2Cl. A room temperature portion of

CH3Si(OC2H5)3 (2.5 mL, 0.013 mol) was treated with a stream of HCl gas (~78 mL/min) (0.21 mol, HCl/silane, 16.6/1, 2.8-fold excess) for 1 h, and the product was sampled. 29Si NMR

(CDCl3): -6.2 ((CH3)Si(OC2H5)Cl2), -23.7 ((CH3)Si(OC2H5)2Cl), 38.0 ((CH3)Si(OC2H5)3).

Run 164, (CH3)2SiCl2, and (CH3)2Si(OC2H5)Cl. A room temperature portion of

(CH3)2Si(OC2H5)2 (2.5 mL, 0.015 mol) was treated with a stream of HCl gas (~78 mL/min) (0.21 mol, HCl/silane, 14.3/1, 3.6-fold excess) for 1 h, and the product was sampled. 29Si NMR

(CDCl3): 36.8 ((CH3)2SiCl2), 18.1 ((CH3)2Si(OC2H5)Cl), 11.0 (unknown), 8.8

((CH3)2Si(OC2H5)2).

Run 165, (CH3)2SiCl2, and (CH3)2Si(OC2H5)Cl. A room temperature mixture of

(CH3)2Si(OC2H5)2 (2.5 mL, 0.015 mol) and AlCl3 (0.04 g, 0.3 mmol, Si:Al 1:50) was treated

with a stream of HCl gas (~78 mL/min) (0.21 mol, HCl/silane, 14.3/1, 3.6-fold excess) for 1 h,

29 and the product was sampled. Si NMR (CDCl3): 36.9 ((CH3)2SiCl2), 18

((CH3)2Si(OC2H5)Cl), 11.6 ((CH3)2Si(OC2H5)2).

Uncatalyzed Synthesis of Ethylchlorosilanes from an Ethylmethoxysilanes and HCl Gas

o Run 166, C2H5Si(OCH3)Cl2, and C2H5Si(OCH3)2Cl. A cold (0 C) portion of

C2H5Si(OCH3)3 (2.5 mL, 0.016 mol) was treated with a stream of HCl gas (~78 mL/min) (0.21 mol, HCl/silane, 13.2/1, 2.2-fold excess) for 1 h, and the product was sampled. 29Si NMR

(CDCl3): -2.5 (C2H5Si(OCH3)Cl2), -19.9 (C2H5Si(OCH3)2Cl), -20.6 (C2H5Si(OCH3)2Cl), -29.7

(C2H5Si(OCH3)3).

Run 167, C2H5Si(OCH3)Cl2, and (C2H5Si(OCH3)2Cl. In a reaction setup in which the vent line of the apparatus contained a cooled trap (ice, 0 oC), a room temperature portion of

C2H5Si(OCH3)3 (2.5 mL, 0.016 mol) was treated with a stream of HCl gas (~78 mL/min) (0.42 mol, HCl/silane, 26.5/1, 4.4-fold excess) for 2 h, and the product was sampled. 29Si NMR

(CDCl3): -6.9 (C2H5Si(OCH3)Cl2), -24.9 (C2H5Si(OCH3)2Cl), -33.9 (C2H5Si(OCH3)3), -40.5

(C2H5Si(OCH3)3), -48.59 (C2H5Si(OCH3)3). Trap 1 contained only traces of the product. These were insufficient for sampling

Uncatalyzed Synthesis of Ethylchlorosilanes from an Ethylethoxysilanes and HCl Gas

o Run 168, (C2H5)3SiCl. A cold (0 C) portion of (C2H5)3SiOC2H5 (2.5 mL, 0.013 mol) was treated with a stream of HCl gas (~78 mL/min) (0.21 mol, HCl/silane, 16.4/1, 8.2-fold

29 excess) for 1 h, and the product was sampled. Si NMR (CDCl3): 39.9 ((C2H5)3SiCl).

o Run 169, C2H5Si(OC2H5)Cl2, and C2H5Si(OC2H5)2Cl. A cold (0 C) portion of

C2H5Si(OC2H5)3 (2.5 mL, 0.012 mol) was treated with a stream of HCl gas (~78 mL/min) (0.21 mol, HCl/silane, 18.0/1, 3.0-fold excess) for 1 h, and the product was sampled. 29Si NMR

(CDCl3): -5.3 (C2H5Si(OC2H5)Cl2), -23.9 (C2H5Si(OC2H5)2Cl), -24.7 (C2H5Si(OC2H5)2Cl), -

32.0 (C2H5Si(OC2H5)3).

Run 170, (C2H5)3SiCl. A room temperature portion of (C2H5)3SiOC2H5 (2.5 mL, 0.013 mol) was treated with a stream of HCl gas (~78 mL/min) (0.21 mol, HCl/silane, 16.4/1, 8.2-fold

29 excess) for 1 h, and the product was sampled. Si NMR (CDCl3): 39.9 ((C2H5)3SiCl).

Run 171, C2H5Si(OC2H5)Cl2, and C2H5Si(OC2H5)2Cl. A room temperature portion of

(C2H5)Si(OC2H5)3 (2.5 mL, 0.012 mol) was treated with a stream of HCl gas (~78 mL/min) (0.21

mol, HCl/silane, 18.0/1, 3.0-fold excess) for 1 h, and the product was sampled. 29Si NMR

(CDCl3): -5.5 (C2H5Si(OC2H5)Cl2), -24.3 (C2H5Si(OC2H5)2Cl), -32.0 (C2H5Si(OC2H5)3).

Uncatalyzed and Catalyzed Synthesis of Methoxychlorosilanes from Tetramethoxysilanes and HCl Gas

o Run 172, Si(OCH3)3Cl. A cold (0 C) portion of Si(OCH3)4 (2.5 mL, 0.017 mol) was treated with a stream of HCl gas (~78 mL/min) (0.10 mol, HCl/silane, 6.2/1, 0.8-fold excess) for

29 0.5 h, and the product was sampled. Si NMR (CDCl3): - (Si(OCH3)3Cl), -78.7

(Si(OCH3)4).

Run 173, Si(OCH3)3Cl. A room temperature portion of Si(OCH3)4 (2.5 mL, 0.017 mol) was treated with a stream of HCl gas (~78 mL/min) (0.10 mol, HCl/silane, 6.2/1, 0.8-fold

29 excess) for 0.5 h, and the product was sampled. Si NMR (CDCl3): - (Si(OCH3)3Cl), -

78.7 (Si(OCH3)4), -85 (unknown).

Run 174, Si(OCH3)3Cl. In a reaction setup in which the vent line of the apparatus contained two cooled traps (ice, 0 oC, empty; ice, 0 oC, undecane filled), a room temperature portion of Si(OCH3)4 (2.5 mL, 0.017 mol) was treated with a stream of HCl gas (~78 mL/min)

(0.84 mol, HCl/silane, 49.7/1, 6.2-fold excess) for 4 h, and the product was sampled. 29Si NMR

(CDCl3): - Si(OCH3)3Cl), -78.7 (Si(OCH3)4), -85 (unknown). Trap 1 contained a liquid

29 which was also sampled. Si NMR (CDCl3): - Si(OCH3)3Cl), -78.7 (Si(OCH3)4), -85

29 (unknown). Trap 2 likewise contained a liquid which was sampled. Si NMR (CDCl3): -

(Si(OCH3)3Cl).

Run 175, Si(OCH3)3Cl. In a reaction setup in which the vent line of the apparatus contained two cooled traps, (ice, 0 oC, empty; ice, 0 oC, undecane filled), a room temperature mixture of Si(OCH3)4 (2.5 mL, 0.017 mol) and Pt on Al2O3 spheres (Escat 226, 0.5 wt % Pt,

0.045 g, Pt to Si 6.9 x 105) was treated with a stream of HCl gas (~78 mL/min) (0.84 mol,

29 HCl/silane, 49.7/1, 6.2-fold excess) for 4 h, and the product was sampled. Si NMR (CDCl3):

- (Si(OCH3)3Cl), -78.7 (Si(OCH3)4), -85.7 (unknown). Traps 1 and 2 contained only traces of the product. These were insufficient for sampling.

Run 176, Si(OCH3)3Cl. In a reaction setup in which the vent line of the apparatus contained two cooled traps, (ice, 0 oC, empty; ice, 0 oC, undecane filled), a room temperature mixture of Si(OCH3)4 (2.5 mL, 0.017 mol) and Pt on carbon (10 wt % Pt on activated carbon,

0.043 g, Pt to Si 130 x 105) was treated with a stream of HCl gas (~78 mL/min) (0.84 mol,

29 HCl/silane, 49.7/1, 6.2-fold excess) for 4 h, and the product was sampled. Si NMR (CDCl3):

29 - (Si(OCH3)3Cl), -78.4 (Si(OCH3)4). Trap 1 contained a liquid which was also sampled. Si

NMR (CDCl3): - (Si(OCH3)3Cl), -78.4 (Si(OCH3)4). Trap 2 contained only traces of the product. These were insufficient for sampling.

Run 177, Si(OCH3)3Cl. In a reaction setup in which the vent line of the apparatus contained two cooled traps, (ice, 0 oC, empty; ice, 0 oC, undecane filled), a warmed (35 oC) portion of Si(OCH3)4 (2.5 mL, 0.017 mol) was treated with a stream of HCl gas (~78 mL/min)

(0.84 mol, HCl/silane, 49.7/1, 6.2-fold excess) for 4 h, and the product was sampled. 29Si NMR

(CDCl3): - Si(OCH3)3Cl), -78.7 (Si(OCH3)4), -85 (unknown). Trap 1 contained a liquid

29 which was also sampled. Si NMR (CDCl3): - (Si(OCH3)3Cl), -78.7 (Si(OCH3)4). Trap 2

29 likewise contained a liquid which was sampled. Si NMR (CDCl3): - (Si(OCH3)3Cl).

Run 178, Si(OCH3)3Cl. In a reaction setup in which the vent line of the apparatus contained two cooled traps, (ice, 0 oC, empty; ice, 0 oC, undecane filled), a warmed (50 oC) of

Si(OCH3)4 (2.5 mL, 0.017 mol) and Pt on Al2O3 spheres (Escat 226, 0.5 wt % Pt, 0.050 g, Pt to Si 7.5 x 105) was treated with a stream of HCl gas (~78 mL/min) (0.84 mol, HCl/silane,

29 49.7/1, 6.2-fold excess) for 4 h, and the product was sampled. Si NMR (CDCl3): -

(Si(OCH3)3Cl), -78.7 (Si(OCH3)4), -85.7 (unknown). Trap 1 contained a liquid which was also

29 sampled. Si NMR (CDCl3): - (Si(OCH3)3Cl), -78.7 (Si(OCH3)4), -85.7 (unknown). Trap

2 contained only traces of the product. These were insufficient for sampling.

Run 179, Si(OCH3)3Cl. In a reaction setup in which the vent line of the apparatus contained two cooled traps, (ice, 0 oC, empty; ice, 0 oC, undecane filled), a warmed (50 oC) portion of Si(OCH3)4 (2.5 mL, 0.017 mol) was treated with a stream of HCl gas (~78 mL/min)

(0.84 mol, HCl/silane, 49.7/1, 6.2-fold excess) for 1.5 h, and the product was sampled. 29Si

NMR (CDCl3): - Si(OCH3)3Cl), -78.7 (Si(OCH3)4), -85 (unknown). Traps 1 and 2 contained only traces of the product. These were insufficient for sampling.

Run 180, Si(OCH3)3Cl. In a reaction setup in which the vent line of the apparatus contained two two cooled traps, (ice, 0 oC, empty; ice, 0 oC, undecane filled), a warmed (50 oC) mixture of Si(OCH3)4 (2.5 mL, 0.017 mol) and Pt on carbon (10 wt % Pt on activated carbon,

0.050 g, Pt to Si 160 x 105) was treated with a stream of HCl gas (~78 mL/min (0.84 mol,

HCl/silane, 49.7/1, 6.2-fold excess) for 4 h. The product was sampled but did not show any 29Si

29 29 resonances. Trap 1, Si NMR (CDCl3): -66.3 (Si(OCH3)3Cl), -78.4 (Si(OCH3)4). Trap 2, Si

NMR (CDCl3): - (Si(OCH3)3Cl), -78.4 (Si(OCH3)4).

Uncatalyzed Synthesis of Alkoxychlorosilanes from Higher Tetraalkoxysilanes and HCl Gas

Run 181, Si(OC2H5)3Cl. A room temperature portion of Si(OC2H5)4 (2.5 mL, 0.011 mol) was treated with a stream of HCl gas (~78 mL/min) (0.84 mol, HCl/silane, 74.6/1, 9.3-fold

29 excess) for 4 h, and the product was sampled. Si NMR (CDCl3): - (Si(OC2H5)3Cl), -81.8

(Si(OC2H5)4).

Run 182, Si(OC3H7)3Cl. A room temperature portion of Si(OC3H7)4 (2.5 mL, 0.009 mol) was treated with a stream of HCl gas (~78 mL/min) (0.84 mol, HCl/silane, 96.6/1, 12.1-fold

29 excess) for 4 h, and the product was sampled. Si NMR (CDCl3): - (Si(OC3H7)3Cl), -81.9

(Si(OC3H7)4).

Run 183, Si(OC4H9)3Cl. A room temperature portion of Si(OC4H9)4 (2.5 mL, 0.007 mol) was treated with a stream of HCl gas (~78 mL/min) (0.84 mol, HCl/silane, 119.2/1, 14.9-fold

29 excess) for 4 h, and the product was sampled. Si NMR (CDCl3): - (Si(OC4H9)3Cl), -82.3

(Si(OC4H9)4).

Uncatalyzed Synthesis of Alkoxychlorosilanes from Tetramethoxysilane and Liquid HCl

Run 184, Si(OCH3)3Cl. HCl gas was passed (~78 mL/min) into a liquid nitrogen cooled

o (-195 C) trap for 20 min. A room temperature portion of Si(OCH3)4 (1.0 mL, 0.007 mol) (0.07 mol, HCl/silane, 4.1/1, 0.5-fold excess) was added to the liquid HCl formed and the remaining

29 solution was sampled. Si NMR (CDCl3): -66.6 Si(OCH3)3Cl), -78.7 (Si(OCH3)4), -85

(unknown).

Acetoxysilane-Thionyl Chloride Investigations

Uncatalyzed Synthesis of Triacetoxychlorosilane and Diacetoxydichlorosilane from Tetraacetoxysilane and Thionyl Chloride

Note: Tetraacetoxysilane was obtained from various vendors (Aldrich, Gelest, and Alfa

Aesar). In run 1 of this section and runs 2 - 5 of the next section, only tetraacetoxysilane which melted as expected (near 111 oC)35 was used. Most of this came from one batch supplied by

Aldrich.

o Run 185, Si(OAc)2Cl2, and Si(OAc)3Cl. A warmed (120 C) portion of

o tetraacetoxysilane (m.p. 111-115 C, 0.15 g, 0.57 mmol) was treated with SOCl2 (4.2 mL, 0.057 mol) (SOCl2/acetate 100/1, 25-fold excess) and stirred for 5.5 h; and the product was sampled.

29 Si NMR (CDCl3): - 2Cl2), -76 (Si(OAc)3Cl), -96 (Si(OAc)4).

Catalyzed Synthesis of Silicon Tetrachloride from Tetraacetoxysilane and Thionyl Chloride

Note: Please see entry at the beginning of the preceding section.

o Run 186, SiCl4. A warmed (120 C) portion of tetraacetoxysilane (0.11 g, 0.40 mmol) was treated with SOCl2 (1.5 mL, 0.021 mol) (SOCl2/acetate 50/1, 12.5-fold excess) and dimethylformamide (10 L, 0.013 mmol) and stirred for 10 min; and the product was sampled.

29 Si NMR (CDCl3): -18 (SiCl4).

o Run 187, SiCl4. A warmed (120 C) portion of tetraacetoxysilane (0.13 g, 0.48 mmol) was treated with SOCl2 (1.8 mL, 0.024 mol), (SOCl2/acetate 50/1, 12.5-fold excess) PCl3 (0.63 mL, 0.007 mol) and dimethylformamide (20 L, 0.026 mmol) and stirred for 10 min; and the

29 product was sampled. Si NMR (CDCl3): -18 (SiCl4).

o Run 188, SiCl4. A warmed (120 C) portion of tetraacetoxysilane (0.13 g, 0.48 mmol) was treated with SOCl2 (1.8 mL, 0.024 mol) (SOCl2/acetate 50/1, 12.5-fold excess) and pyridine

29 (10 L, 0.012 mmol) and stirred for 10 min; and the product was sampled. Si NMR (CDCl3):

-18 (SiCl4).

o Run 189, SiCl4. A warmed (120 C) portion of tetraacetoxysilane (0.13 g, 0.48 mmol) was treated with SOCl2 (1.8 mL, 0.024 mol) (SOCl2/acetate 50/1, 12.5-fold excess) and CHCl3

29 (10 L, 0.012 mmol) and stirred for 10 min; and the product was sampled. Si NMR (CDCl3):

-18 (SiCl4).

Metal Silicates-Chlorinating Agent Investigations

Attempted Synthesis of Silicon Tetrachloride from Silicates and Chlorinating Agents

Run 190, Typical Attempt, at Synthesis of Silicon Tetrachloride from Silicate and a

Chlorinating Agent . A mixture of alite, Ca3SiO5, (0.25 g, 1.1 mmol) and a solution of HCl in dioxane (4 M, 10 mL, 40 mmol HCl) (HCl/alite 36/1, 3.6 fold excess) was refluxed for 84 h and

29 29 cooled. Si NMR (CDCl3): no Si resonances.

Runs 191 – 228, Attempts with Other Silicates. Other attempted syntheses of SiCl4 from silicates were carried out in a similar fashion. The additional silicates studied were magnesium silicate, Mg2Si3O8; dioptase, Cu6Si6O18·6 H2O; fayalite, Fe2SiO4; hardystonite,

Ca2ZnSi2O7; hemimorphite, Zn4Si2O7(OH)2·H2O; laumontite, Ca(AlSi2O6)2·4 H2O; lithium metasilicate, Li4SiO3; lithium orthosilicate, Li4SiO4; muscovite, KAl2(AlSi3O10)(F,OH)2; olivine,

3,9 5,15 7,13 Mg2SiO4; octakis(tetramethylammonium) pentacyclo[9.5.1.1 .1 .1 ]octasiloxane-

1,3,5,7,9,11,13,15-octakis(yloxide) hydrate, C32H96N8O20Si8; sodalite, Na4Al3(SiO4)3Cl; sodium metasilicate, Na2SiO3; sodium calcium silicate, Na4Ca4Si8O18; and willemite, Zn2SiO4. The chlorinating agents used were HCl in dioxane, SOCl2, and PCl5. The solvents used were glacial acetic acid; acetyl chloride; 1-chloronaphthalene; 1,2,4-trichlorobenzene; and acetylacetone, and the potential catalysts were dimethylformamide and aqueous ammonium hydroxide.

Silicon Dioxide-Chlorinating Agent Investigations

Attempted Synthesis of Silicon Tetrachloride from Silica and Chlorinating Agents

Run 229, Typical Attempt, at Synthesis of Silicon Tetrachloride from Silica and

® Chlorinating Agents. A mixture of Celite 545 , SiO2, (1.2 g, 20 mmol) and a solution of HCl in dioxane (4 M, 20 mL, 80 mmol HCl) (HCl/celite 4/1) was stirred at room temperature for 24 h.

29 29 Si NMR (CDCl3): no Si resonances.

Runs 230 – 235, Attempts with Silica Gel. The other attempted syntheses of SiCl4 from silica were carried out in a similar fashion. The silica studied in these was silica gel, SiO2. The chlorinating agents used were HCl in dioxane, SOCl2, and PCl5. The solvents used were 1- chloronaphthalene, and 1,2,4-trichlorobenzene, and the potential catalyst was dimethylformamide.

Chapter 4

Synthesis of SiCl4 and Chlorosilanes

Results and Discussion

Currell’s Approach Experiments

Attempts to Reproduce Reported Pyridine HCl-Catalyzed Syntheses of Silicon Tetrachloride from Tetraalkoxysilanes and Thionyl Chloride

As mentioned in the Introduction, Currell et al. reported that the reaction of tetramethoxysilane, tetraethoxysilane and tetrabutoxysilane with thionyl chloride in presence of pyridinium hydrochloride produced silicon tetrachloride: “It was found that the separation of silicon tetrachloride from the reaction mixtures which contained alkyl chloride, thionyl chloride and alkoxychlorosilanes by distillation was protracted: but by the addition of excess pyridine in n-pentane, the silicon tetrachloride-pyridine complex was precipitated, filtered, washed dried and weighted and then the silicon tetrachloride calculated”.21 This account of the reactions is ambiguous and leaves open the question of whether silicon tetrachloride was already present in the reaction mixture and was merely complexed upon the addition of the pyridine, or whether the excess pyridine reacted with a chlorosilane precursor in the reaction mixture to give the silicon tetrachloride-pyridine complex. In any event, no direct claim was made for the isolation of silicon tetrachloride. A summary of the reaction conditions used by Currell is given in Table 2.

For completeness, the other reactions carried out by Currell between tetraalkoxysilanes and thionyl chloride in the presence or absence of pyridinium hydrochloride are listed in Tables

3 and 4. In none of these was the production of silicon tetrachloride reported.

A set of four runs, Schemes 1 and 2, was made to help clarify the ambiguity in the results of runs a1, a2 and a3. In runs 1 and 2, Table 5, the reaction-mixture mole ratios, temperature and times used by Currell in his tetramethoxysilane and tetraethoxysilane runs were duplicated.

Runs 3 and 4 were the same except that the temperature was reduced to room temperature. As is seen, run 1 yielded monochlorotrimethoxysilane and dichlorodimethoxysilane while run 2 yielded only monochlorotrimethoxysilane. The room temperature runs, runs 3 and 4, yielded the mono-, di- and trichlorosilanes, and the mono- and dichlorosilanes, respectively. In no case was silicon tetrachloride detected. Thus, this work did not support Currell’s report that the pyridine hydrochloride-catalyzed reaction of tetraalkoxysilanes and thionyl chloride produces silicon tetrachloride.

Scheme 1. Pyridine HCl-Catalyzed Synthesis of Alkoxychlorosilanes from

Tetraalkoxysilanes and Thionyl Chloride at 100oC

py·HCl Si(OCH3)4 + SOCl2 Si(OCH3)2Cl2 + Si(OCH3)3Cl + CH3Cl + SO2

py·HCl Si(OC2H5)4 + SOCl2 Si(OC2H5)3Cl + C2H5Cl + SO2

Scheme 2. Pyridine HCl-Catalyzed Synthesis of Alkoxychlorosilanes from

Tetraalkoxysilanes and Thionyl Chloride at Room Temperature

py·HCl Si(OCH3)4 + SOCl2 Si(OCH3)Cl3 +Si(OCH3)2Cl2 + Si(OCH3)3Cl + CH3Cl + SO2

py·HCl Si(OC2H5)4 + SOCl2 Si(OCH3)2Cl2 + Si(OCH3)3Cl + CH3Cl + SO2

Table 2. Reported Pyridine HCl-Catalyzed Synthesis of Silicon Tetrachloride from Tetraalkoxysilanes and Thionyl Chloride – Reaction Conditions and Results 1 2 1 3 variable silane SOCl2 py·HCl SOCl2 / SOCl2 xs py·HCl / temp time product R formula vol mol vol mol silane silane SiCl4 (mL) (mL) (g) (fold) (oC) (h) (%) a1 CH3 Si(OMe)4 149 1.0 292 4.0 0.8 4 stoich 0.007 100 17 0

a2 C2H5 Si(OEt)4 223 1.0 292 4.0 0.8 4 stoich 0.007 100 25 0

a3 n-C4H9 Si(OBu)4 357 1.0 292 4.0 0.8 4 stoich 0.007 100 42 0 1By moles. 2Based on assumed equations. 3See discussion for yield data.

Table 3. Reported Pyridine HCl-Catalyzed and Nonpyridine Catalyzed Synthesis of Silicon Tetrachloride from Tetraalkoxysilanes and Thionyl Chloride – Reaction Conditions and Results 1 2 1 variable silane SOCl2 py·HCl SOCl2 / SOCl2 xs py·HCl / temp time product R formula vol mol vol mol silane silane (BuO)3SiCl (BuO)2SiCl2 mmol (mL) (mL) (g) (fold) (oC) (h) (g) (g) b1 n-C4H9 Si(OBu)4 357 1.0 146 2.0 0.8 2 0.5 0.007 120 32 7.4 13.6 26 55

b2 n-C4H9 Si(OBu)4 357 1.0 146 2.0 0.0 2 0.5 100 1 2.6 9

b3 n-C4H9 Si(OBu)4 357 1.0 146 2.0 0.0 2 0.5 160 57 4.9 17 1By moles. 2Based on assumed equations.

Table 4. Reported Pyridine HCl-Catalyzed and Synthesis of Silicon Tetrachloride from Tetraalkoxysilanes and Thionyl Chloride – Reaction Conditions and Results 1 2 1 variable silane SOCl2 py·HCl SOCl2 / SOCl2 xs py·HCl / temp time product R formula vol mol vol mol silane silane (RO)3SiCl mmol (mL) (mL) (g) (fold) (oC) (h) (g) c1 n-C4H9 Si(OEt)4 223 1.0 73 1.0 0.2 1 0.25 0.002 120 0.5 13.4 70

c2 i-C4H9 Si(OBu)4 357 1.0 73 1.0 0.8 1 0.25 120 10 17.8 63 1By moles. 2Based on assumed equations.

Table 5. Attempts to Reproduce Currell’s Reported Pyridine HCl-Catalyzed Syntheses of Silicon Tetrachloride from Tetraalkoxysilanes and Thionyl Chloride 1 2 1 3 variable silane SOCl2 py·HCl SOCl2 / SOCl2 xs py·HCl / temp time product R formula vol mol vol mol silane silane Si(OR)4 (RO)3SiCl (RO)2SiCl2 ROSiCl3 SiCl4 (mL) (mL) (g) (fold) (oC) (h)

1 CH3 Si(OMe)4 51 0.34 100 1.4 1.6 4 stoich 0.04 100 17 10 2

2 C2H5 Si(OEt)4 77 0.34 100 1.4 1.6 4 stoich 0.04 100 25 9 10

3 CH3 Si(OMe)4 51 0.34 100 1.4 1.6 4 stoich 0.04 RT 17 4 10 1

4 C2H5 Si(OEt)4 77 0.34 100 1.4 1.6 4 stoich 0.04 RT 25 10 6 1By moles. 2Based on assumed equations. 3Relative intensity of reactant and product 29Si resonances with 10 being the most intense.

Exploratory Experiments

Uncatalyzed Synthesis of Silicon Tetrachloride from Tetramethoxysilane and Chlorinating Agents

A series of small-scale exploratory uncatalyzed reactions of tetramethoxysilane and various chlorinating agents having the potential to convert the tetramethoxysilane into SiCl4 under mild conditions was investigated to find areas where more intensive work would be useful.

The agents investigated were SOCl2, SO2Cl2, PCl3, POCl3, and HCl.

Thionyl Chloride; Si(OCH3)2Cl2 and Si(OCH3)3Cl. The uncatalyzed reaction of tetramethoxysilane with a 4-fold excess of thionyl chloride and reaction times of 2, 3 and 48 hours was investigated, runs 5 – 7, Tables 6 and 7. At 48 hours, this led to the production of

Si(OCH3)3Cl and Si(OCH3)2Cl2, and suggested promise for the use of SOCl2 as a chlorinating agent for Si(OCH3)4.

Sulfuryl Chloride; Si(OCH3)2Cl2. In an another set of experiments, the uncatalyzed reaction of tetramethoxysilane with sulfuryl chloride and reaction times of 3 and 48 hours, was investigated, runs 60 and 61. Inspection of the data showed that at 48 hours Si(OCH3)2Cl2 was produced. This suggested possible promise for the use of SO2Cl2 as a chlorinating agent for

Si(OCH3)4.

Phosphorus Trichloride; Si(OCH3)2Cl2 and Si(OCH3)3Cl. A set of experiments was also carried out on the uncatalyzed reaction of tetramethoxysilane and PCl3, runs 72 and 73.

From the results it was seen that at 48 hours both Si(OCH3)3Cl and Si(OCH3)2Cl2 were produced.

Again this agent showed possible promise.

Phosphorus Oxychloride; Si(OCH3)2Cl2 and Si(OCH3)3Cl. Further experiments were done on the uncatalyzed reaction of tetramethoxysilane and POCl3, runs 86 and 87. At 48 hours both Si(OCH3)3Cl and Si(OCH3)2Cl2 were produced. From these experiments it was concluded that POCl3 had some potential as a chlorinating agent for Si(OCH3)4.

HCl in Dioxane; Si(OCH3)3Cl. Finally, experiments were done on the uncatalyzed reaction of tetramethoxysilane and HCl in dioxane, runs 96 and 97. At 48 hours Si(OCH3)4

Si(OCH3)3Cl were produced. These results indicated that anhydrous HCl had some potential.

Table 6. Silanes from a Mixture of Si(OCH ) and Various Chlorinating Agents at Various 3 4 Reaction Times and at Room Temperature - Reaction Mixtures 1 2 Si(OMe)4 chlorinating agent agent / agent xs volume mmol formula volume mmol silane (mL) (mL) (fold) 5 0.26 1.7 SOCl2 2.0 27 16 4

6 0.26 1.7 SOCl2 2.0 27 16 4 7 0.26 1.7 SOCl 2.0 27 16 4 2

60 0.26 1.7 SO2Cl2 2.2 27 16 4 61 0.26 1.7 SO2Cl2 2.2 27 16 4

72 0.26 1.7 PCl3 2.4 27 16 4 73 0.26 1.7 PCl3 2.4 27 16 4

86 0.26 1.7 POCl3 2.5 27 16 4 87 0.26 1.7 POCl3 2.5 27 16 4

96 0.20 1.3 HCl/diox 1.0 4 3 0.4 97 0.20 1.3 HCl/diox 1.0 4 3 0.4 1 2 By moles. Based on assumed equations.

Table 7. Silanes from a Mixture of Si(OCH3)4 and Various Chlorinating Agents at Various Reaction Times and at Room Temperature - Results chlorinating agent1 time reactant4 product4 2 3 compound agent / agent xs Si(OMe)4 Si(OMe)3Cl Si(OMe)2Cl2 Si(OMe)Cl3 SiCl4 silane (fold ) (h) 5 SOCl2 16 4 0.5 6 SOCl2 16 4 2 10 7 SOCl2 16 4 48 10 4

60 SO2Cl2 16 4 3 10 2 61 SO2Cl2 16 4 48 10

72 PCl3 16 4 2 10 2 73 PCl3 16 4 48 10 4

86 POCl3 16 4 2 1 10 87 POCl3 16 4 48 10 8

96 HCl/diox 3 0.4 2 10 8 97 HCl/diox 3 0.4 48 10 9 1Reaction mixtures are given in Table 6. 2By moles. 3Based on assumed equations. 4Relative intensity of reactant and product 29Si resonances with 10 being the most intense.

Variously Catalyzed Synthesis of Silicon Tetrachloride from Tetramethoxysilane and Chlorinating Agents

A further series of small-scale exploratory experiments was carried out in which the catalyzed reaction of Si(OCH3)4 with various chlorinating agents. The chlorinating agents investigated were SOCl2, SO2Cl2, PCl3, PCl5, POCl3, and HCl, and the potential catalysts were benzene, pyridine, quinoline, 2,3,5-collidine, cyanuric chloride, trimethylamine, triethylamine, butylamine, dibutylamine, tributylamine, dimethylformamide, dimethylacetamide, dimethylaniline, 2-imidazolidone, 1,3-dimethyl-2-imidazolidone,

(chloromethylene)dimethyliminium chloride (iminium chloride), N-chlorosuccinimide, and zinc chloride.

Excess Thionyl Chloride; SiCl4 to Si(OCH3)3Cl. The catalyzed reaction of Si(OCH3)4 and SOCl2 with thirteen potential catalysts at a 4-fold excess of SOCl2, a catalyst-to-Si(OCH3)4 ratio of 1 to 0.2 and reaction times of 0.5, 2 and 48 hours was investigated, runs 8 - 45, Tables 8 and 9, Figures 1-3. Under the conditions used, as is seen, the aromatic bases pyridine, quinoline, and 2,3,5-collidine showed promise at 48 hours. Also the amides dimethylformamide, dimethylacetamide, the related compounds 2-imidazolidone, and 1,3-dimethyl-2-imidazolidone showed promise at 48 hours. The promise of the amides and their two analogues was expected because it has been reported that the combination of SOCl2 as a chlorinating agent with dimethylformamide as a catalyst can increase the reactivity of the agent.30 Further, iminium chloride showed promise. This was expected because based on the work of others it appears that

31 an intermediate of the reaction of SOCl2 with dimethylformamide is the iminium chloride. 67

Stoichiometric Thionyl Chloride; SiCl4 to Si(OCH3)3Cl. In additional work, the use of milder conditions was investigated. Here, a mixture of Si(OCH3)4 and SOCl2 catalyzed with seven of the potential catalysts at a stoichiometric SOCl2-to-Si(OCH3)4 ratio, a catalyst-to-

Si(OCH3)4 ratio of 0.05 and reaction times of 0.5 and 48 hours was surveyed, runs 46 – 59,

Tables 10 and 11. At a reaction time of 48 hours and under these SOCl2-to-silane and catalyst- to-silane ratios, the aromatic bases pyridine, quinoline and collidine still showed promise. In addition, dimethylformamide, dimethylacetamide, and 1,3-dimethylimidazolidone also still showed promise. At a reaction time of 0.5 hours, dimethylacetamide and the dimethylimidazolidine continued to show modest promise.

These results and the cost of the various catalysts (based on the prices of laboratory chemicals by Aldrich, and Alfa Aesar and Acros), Table 12, make the selection of the reaction of

Si(OCH3)4 and SOCl2 catalyzed with dimethylacetamide, dimethylformamide and 1,3-dimethyl-

2-imidazolidone reasonable choices for more intensive investigation. Ultimately it was decided to focus on dimethylformamide. However, work with dimethylacetamide, 2-imidazolidone, and

1,3-dimethyl-2-imidazolidone holds potential.

Sulfuryl Chloride; Si(OCH3)Cl3 to Si(OCH3)3Cl. In an another set of experiments, the reaction of Si(OCH3)4 with SO2Cl2 catalyzed with five potential catalysts was studied at a

SO2Cl2-to-Si(OCH3)4 ratio of 1 to 16, a catalyst-to-Si(OCH3)4 ratio of 1 to 0.2, and reaction times of 0.5, 2 or 3 and 48 hours, runs 62 – 71, Tables 14 and 15. Inspection of the table shows

that SO2Cl2 by itself did not give silicon tetrachloride. While the amine catalysts helped, again none gave silicon tetrachloride. Thus with these data and the SO2Cl2 cost data, Table 13, SO2Cl2 seems to hold little promise.

Phosphorus Trichloride; SiCl4 to Si(OCH3)3Cl. A set of experiments was also carried out on the reaction of Si(OCH3)4 and PCl3 catalyzed with four potential catalysts under the conditions shown in runs 72 – 81, Tables 16 and 17. From the data it is seen that the reaction catalyzed by dimethylformamide showed some promise. However, it was slow. Thus, with these data and the PCl3 cost data, Table 8, the use of the dimethylformamide-catalyzed reaction of

Si(OCH3)4 and PCl3 does not appear as attractive as those based on SOCl2.

Phosphorus Pentachloride; Si(OCH3)Cl3 to Si(OCH3)3Cl. Experiments were done on the reaction of Si(OCH3)4 with PCl5 catalyzed with dimethylformamide under the conditions shown in runs 82 – 85, Tables 18 and 19. The data suggest that dimethylformamide can catalyze the reaction but that the reaction does not go to completion under the conditions used. With these data and the PCl5 cost data, Table 13, the dimethylformamide-catalyzed reaction of

Si(OCH3)4 with PCl5 thus do not appear to offer the promise of the catalyzed SOCl2 reactions.

Phosphorus Oxychloride; Si(OCH3)Cl3 to Si(OCH3)3Cl. Further, experiments were done on the reaction of Si(OCH3)4 with POCl3 catalyzed with four catalysts under with conditions shown in runs 86 – 95, Tables 20 and 21. The results show that the reaction is 69

catalyzed somewhat with triethyl amine, dimethyl formamide and iminium chloride. However, on the basis of these data and the cost data, Table 13, the catalyzed reaction of tetramethoxysilane and POCl3 does not seem a promising approach on the basis of the data at hand.

HCl in Dioxane; Si(OCH3)3Cl. Finally, experiments were done on the reaction of

Si(OCH3)4 and HCl in dioxane catalyzed with five catalysts at an HCl-to-tetramethoxysilane ratio of 3 to 1, a catalyst-to-tetramethoxysilane ratio of 1 to 0.25 and reaction times of 2 and 48 hours, Tables 22 and 23. The results show that the reaction either uncatalyzed or the catalyzed does not give chlorinated products beyond trimethoxychlorosilane under the conditions used.

Therefore, the HCl in dioxane approach under these conditions does not seem a promising for the synthesis of silicon tetrachloride.

Table 8. Silanes from a Mixture of Si(OCH3)4 and Excess of SOCl2 with Thirteen Potential Catalysts and at Various Reaction Times and at Room Temperature - Reaction Mixtures 1 2 1 Si(OMe)4 SOCl2 agent / agent xs catalyst catalyst / volume mmol volume mmol silane structure name amount silane (mL) (mL) (fold) (g) ( L) 5 0.26 1.7 2.0 27 16 4 no cat 6 0.26 1.7 2.0 27 16 4 7 0.26 1.7 2.0 27 16 4

8 0.13 0.85 1.0 14 16 4 benzene 16 0.2 9 0.13 0.85 1.0 14 16 4 10 0.13 0.85 1.0 14 16 4

11 0.13 0.85 1.0 14 16 4 pyridine 14 0.2 12 0.26 1.7 2.0 27 16 4 29 13 0.13 0.85 1.0 14 16 4 N 14

14 0.13 0.85 1.0 14 16 4 quinoline 21 0.2 15 0.13 0.85 1.0 14 16 4 16 0.13 0.85 1.0 14 16 4 N

17 0.13 0.85 1.0 14 16 4 2,3,5-collidine 23 0.2 18 0.13 0.85 1.0 14 16 4 19 0.13 0.85 1.0 14 16 4 N

20 0.26 1.7 2.0 27 16 4 Cl cyanuric chloride 0.07 0.2 21 0.26 1.7 2.0 27 16 4 N N 22 0.26 1.7 2.0 27 16 4 Cl N Cl

23 0.26 1.7 2.0 27 16 4 N triethylamine 50 0.2 24 0.26 1.7 2.0 27 16 4 3

Table 8. Silanes from a Mixture of Si(OCH3)4 and Excess of SOCl2 with Thirteen Potential Catalysts and at Various Reaction Times and at Room Temperature - Reaction Mixtures (con’t) 1 2 1 Si(OMe)4 SOCl2 agent / agent xs catalyst catalyst / volume mmol volume mmol silane structure name amount silane (mL) (mL) (fold) (g) ( L) 25 0.13 0.85 1.0 14 16 4 H dimethylformamide 14 0.2 26 0.26 1.7 2.0 27 16 4 O 28 N 27 0.13 1.7 2.0 27 16 4 14

28 0.13 0.85 1.0 14 16 4 O dimethylacetamide 17 0.2 29 0.26 1.7 2.0 27 16 4 N 30 0.13 0.85 1.0 14 16 4

31 0.26 1.7 2.0 27 16 4 NH 2-imidazolidone 0.03 0.2 32 0.26 1.7 2.0 27 16 4 O NH 33 0.26 1.7 2.0 27 16 4

34 0.26 1.7 2.0 27 16 4 1,3-dimethyl-2- 38 0.2 N O imidazolidone 35 0.26 1.7 2.0 27 16 4 N 36 0.26 1.7 2.0 27 16 4

37 0.26 1.7 2.0 27 16 4 Cl iminium chloride 0.04 0.2 N Cl 38 0.26 1.7 2.0 27 16 4 H 39 0.26 1.7 2.0 27 16 4

40 0.26 1.7 2.0 27 16 4 O N-chlorosuccinimide 0.05 0.2 41 0.26 1.7 2.0 27 16 4 42 0.26 1.7 2.0 27 16 4 N Cl

O 43 0.13 0.85 1.0 14 16 4 zinc chloride 16 0.2 44 0.13 0.85 1.0 14 16 4 ZnCl2 45 0.13 0.85 1.0 14 16 4 1By moles. 2Based on assumed equations.

Table 9. Silanes from a Mixture of Si(OCH3)4 and Excess of SOCl2 with Thirteen Potential Catalysts and at Various Reaction Times and at Room Temperature - Results 1 2 3 2 4 4 catalyst SOCl2 / agent xs cat / time reactant product structure name amount silane silane Si(OMe)4 Si(OMe)3Cl Si(OMe)2Cl2 Si(OMe)Cl3 SiCl4 (g) ( L) (fold) (h) 5 no cat 16 4 0.5 6 16 4 2 10 7 16 4 48 10 4

8 benzene 16 16 4 0.2 0.5 9 16 16 4 0.2 2 4 10 10 16 16 4 0.2 48 10 8

11 pyridine 14 16 4 0.2 0.5 10 2 12 29 16 4 0.2 2 10 1 1 13 14 16 4 0.2 48 10 N

14 quinoline 21 16 4 0.2 0.5 10 3 15 21 16 4 0.2 2 16 N 21 16 4 0.2 48 10

17 2,3,5-collidine 23 16 4 0.2 0.5 10 1 18 23 16 4 0.2 2 19 23 16 4 0.2 48 10 N

20 Cl cyanuric chloride 0.07 16 4 0.2 0.5 21 N N 0.07 16 4 0.2 2 4 10 22 0.07 16 4 0.2 48 10 Cl N Cl

23 N triethylamine 50 16 4 0.2 0.5 24 3 50 16 4 0.2 2 3 10

Table 9. Silanes from a Mixture of Si(OCH3)4 and Excess of SOCl2 with Thirteen Potential Catalysts and at Various Reaction Times and at Room Temperature - Results (con’t) 1 2 3 2 4 4 catalyst SOCl2 / agent xs cat / time reactant product structure name amount silane silane Si(OMe)4 Si(OMe)3Cl Si(OMe)2Cl2 Si(OMe)Cl3 SiCl4 (g) ( L) (fold) (h) 25 H dimethylformamide 14 16 4 0.2 0.5 10 4 26 O 28 16 4 0.2 3 4 10 7 N 27 14 16 4 0.2 48 10

28 dimethylacetamide 17 16 4 0.2 0.5 10 4 O 29 N 17 16 4 0.2 3 4 10 7 30 17 16 4 0.2 48 10

31 NH 2-imidazolidone 0.03 16 4 0.2 0.5 2 10 3 32 O 0.03 16 4 0.2 2 33 NH 0.03 16 4 0.2 48 10 8

34 1,3-dimethyl-2- 38 16 4 0.2 0.5 4 10 3 N imidazolidone O 35 N 38 16 4 0.2 2 36 38 16 4 0.2 48 10

37 Cl iminium chloride 0.04 16 4 0.2 0.5 N Cl 38 H 0.04 16 4 0.2 2 5 10 7 39 0.04 16 4 0.2 48 10

40 O N-chlorosuccinimide 0.05 16 4 0.2 0.5 41 0.05 16 4 0.2 2 10 4 42 N Cl 0.05 16 4 0.2 48 3 10

43 ZnCl2 zinc chloride 16 16 4 0.2 0.5 44 16 16 4 0.2 2 10 45 16 16 4 0.2 48 10 1 2 3 4 29 Reaction mixtures are given in Table 8. By moles. Based on assumed equations. Relative intensity of reactant and product Si resonances with 10 being the most intense.

Table 10. Silanes from a Stoichiometric Mixture of Si(OCH3)4 and stoichiometric SOCl2 with Seven Potential Catalysts and at Various Reaction Times and at Room Temperature - Reaction Mixtures 1 2 1 Si(OMe)4 SOCl2 agent / agent xs catalyst catalyst / volume mmol volume mmol silane structure name amount silane (mL) (mL) (fold) (g) ( L) 46 0.51 3.4 1.0 14 4 stoich pyridine 14 0.05 47 0.51 3.4 1.0 14 4 stoich N 48 0.51 3.4 1.0 14 4 stoich quinoline 21 0.05 49 0.51 3.4 1.0 14 4 stoich N 50 0.51 3.4 1.0 14 4 stoich 2,3,5-collidine 23 0.05 51 0.51 3.4 1.0 14 4 stoich N 52 0.51 3.4 1.0 14 4 stoich H dimethylformamide 14 0.05 53 0.51 3.4 1.0 14 4 stoich O N

54 0.51 3.4 1.0 14 4 stoich O dimethylacetamide 17 0.05 55 0.51 3.4 1.0 14 4 stoich N

56 1.1 7.1 2.0 27 4 stoich NH 2-imidazolidone 0.03 0.05 57 1.1 7.1 2.0 27 4 stoich O NH

58 1.1 7.1 2.0 27 4 stoich N 1,3-dimethyl-2- 38 0.05 O imidazolidone 59 1.1 7.1 2.0 27 4 stoich N

1By moles. 2Based on assumed equations.

Table 11. Silanes from a Stoichiometric Mixture of Si(OCH3)4 and stoichiometric SOCl2 with Seven Potential Catalysts and at Various Reaction Times and at Room Temperature - Results 1 2 3 2 4 4 catalyst SOCl2 / agent xs cat / time reactant product structure name amount silane silane Si(OMe)4 Si(OMe)3Cl Si(OMe)2Cl2 Si(OMe)Cl3 SiCl4 (g) ( L) (fold) (h) 46 pyridine 14 4 stoich 0.05 0.5 10 3 47 14 4 stoich 0.05 48 8 10 N

48 quinoline 21 4 stoich 0.05 0.5 4 10 1 49 21 4 stoich 0.05 48 10 7

50 2,3,5-collidine 23 4 stoich 0.05 0.5 3 10 2 51 23 4 stoich 0.05 48 10 9 N

52 H dimethylformamide 14 4 stoich 0.05 0.5 4 10 1 53 O 14 4 stoich 0.05 48 4 10 2 N

54 dimethylacetamide 17 4 stoich 0.05 0.5 1 10 4 O 55 N 17 4 stoich 0.05 48 10 6

56 NH 2-imidazolidone 0.03 4 stoich 0.05 0.5 7 10 1 57 O 0.03 4 stoich 0.05 48 10 8 NH

58 1,3-dimethyl-2 38 4 stoich 0.05 0.5 1 10 4 N O imidazolidone 59 N 38 4 stoich 0.05 48 2 10 4

1Reaction mixtures are given in Table 10. 2By moles. 3Based on assumed equations. 4Relative intensity of reactant and product 29Si resonances with 10 being the most intense. 76

1 Table 12. Approximate Cost of Catalysts $/100 mL $/100 g $/1 mol butylamine 19 19 cyanuric chloride ~14 26 N-chlorosuccinimide 20 27 benzene 34 31 dimethylformamide 43 33 2-imidazolidone ~40 35 triethylamine 25 35 dibutylamine 21 36 tributylamine 15 36 dimethylacetamide 42 39 trimethylamine 71 42 1,3-dimethyl-2-imidazolidone 42 45 quinoline 40 52 pyridine 77 59 dimethylaniline 57 70 2,3,5-collidine 247 298 iminium chloride 492 631

1Based on prices of laboratory chemicals listed by Aldrich, Alfa Aesar and Acros in 2011.

1 Table 13. Approximate Cost of Chlorinating Agents

amount cost (L) (kg) ($) 4 M HCl-dioxane solution 1 418.00 sulfuryl chloride 1 110.00 thionyl chloride 1 110.00 phosphorus trichloride 1 90.00 phosphorus pentachloride 1 80.00 phosphorus oxychloride 1 80.00 1Based on prices of laboratory chemicals listed by Aldrich in 2011.

Table 14. Silanes from a Mixture of Si(OCH3)4 and Excess SO2Cl2 with Five Potential Catalysts and at Various Reaction Times and at Room Temperature - Reaction Mixtures 1 2 1 Si(OMe)4 SO2Cl2 agent / agent xs catalyst catalyst / volume mmol volume mmol silane structure name amount silane (mL) (mL) (fold) (g) ( L) 60 0.26 1.7 2.2 27 16 4 no cat 61 0.26 1.7 2.2 27 16 4

62 0.26 1.7 2.2 27 16 4 NH2 butylamine 35 0.2 63 0.26 1.7 2.2 27 16 4

64 0.26 1.7 2.2 27 16 4 NH dibutylamine 60 0.2 65 0.26 1.7 2.2 27 16 4 2

66 0.26 1.7 2.2 27 16 4 N tributylamine 85 0.2 67 0.26 1.7 2.2 27 16 4 3

68 0.26 1.7 2.2 27 16 4 N triethylamine 50 0.2 69 0.26 1.7 2.2 27 16 4 3

70 0.26 1.7 2.2 27 16 4 H dimethylformamide 56 0.4 71 0.26 1.7 2.2 27 16 4 O N

1By moles. 2Based on assumed equations.

Table 15. Silanes from a Mixture of Si(OCH3)4 and Excess SO2Cl2 with Five Potential Catalysts and at Various Reaction Times and at Room Temperature - Results 1 2 3 2 4 4 catalyst SO2Cl2 / agent xs cat / time reactant product structure name amount silane silane Si(OMe)4 Si(OMe)3Cl Si(OMe)2Cl2 Si(OMe)Cl3 SiCl4 (g) ( L) (fold) (h) 60 no cat 16 4 0.2 3 10 2 61 16 4 0.2 48 10

62 butylamine 35 16 4 0.2 2 2 10 7 63 NH2 35 16 4 0.2 48 3 3 10 6

64 dibutylamine 60 16 4 0.2 2 3 10 8 65 NH 60 16 4 0.2 48 5 1 10 6 2

66 tributylamine 85 16 4 0.2 2 7 1 10 67 N 85 16 4 0.2 48 8 8 10 3

68 triethylamine 50 16 4 0.2 2 7 3 10 69 N 50 16 4 0.2 48 10 6 7 3

70 H dimethylformamide 56 16 4 0.4 3 5 10 71 O 56 16 4 0.4 48 10 N

1Reaction mixtures are given in Table 14. 2By moles. 3Based on assumed equations. 4Relative intensity of reactant and product 29Si resonances with 10 being the most intense.

Table 16. Silane Products from a Mixture of Si(OCH3)4 and PCl3 with Four Potential Catalysts and at Various Reaction Times and at Room Temperature - Reaction Mixtures 1 2 1 Si(OMe)4 PCl3 agent / agent xs catalyst catalyst / volume mmol volume mmol silane structure name amount silane (mL) (mL) (fold) (g) ( L) 72 0.26 1.7 2.4 27 16 4 no cat 73 0.26 1.7 2.4 27 16 4

74 0.26 1.7 2.4 27 16 4 pyridine 29 0.2 75 0.26 1.7 2.4 27 16 4 N

76 0.26 1.7 2.4 27 16 4 triethylamine 50 0.2 77 0.26 1.7 2.4 27 16 4 N

78 0.26 1.7 2.4 27 16 4 H dimethylformamide 28 0.2 79 0.26 1.7 2.4 27 16 4 O N

80 0.26 1.7 2.4 27 16 4 Cl iminium chloride 0.04 0.2 N Cl 81 0.26 1.7 2.4 27 16 4 H

1By moles. 2Based on assumed equations.

Table 17. Silane Products from a Mixture of Si(OCH3)4 and PCl3 with Four Potential Catalysts and at Various Reaction Times and at Room Temperature - Results 1 2 3 2 4 4 catalyst PCl3 / agent xs cat / time reactant product structure name amount silane silane Si(OMe)4 Si(OMe)3Cl Si(OMe)2Cl2 Si(OMe)Cl3 SiCl4 (g) ( L) (fold) (h) 72 no cat 16 4 0.2 2 10 2 73 16 4 0.2 48 10 4

74 pyridine 29 16 4 0.2 2 10 1 75 29 16 4 0.2 72 9 10 N

76 triethylamine 50 16 4 0.2 2 10 77 N 50 16 4 0.2 72 10 2 3

78 H dimethylformamide 28 16 4 0.2 2 1 10 6 79 O 28 16 4 0.2 48 1 10 5 2 N

80 Cl iminium chloride 0.04 16 4 0.2 2 10 2 N Cl 81 H 0.04 16 4 0.2 48 10 6

1Reaction mixtures are given in Table 16. 2By moles. 3Based on assumed equations. 4Relative intensity of reactant and product 29Si resonances with 10 being the most intense.

Table 18. Silane Products from Mixtures of Si(OCH3)4 and Various Amounts of PCl5 with a Dimethylformamide Catalyst and at Various Reaction Times and at Room Temperature – Reaction Mixtures 1 2 1 Si(OMe)4 PCl5 agent / agent xs catalyst DMF / volume mmol weight mmol silane structure name amount silane (mL) (g) (fold) (g) ( L) 82 0.26 1.7 1.0 4.8 3 0.37 H dimethylformamide 28 0.2 O N 83 0.26 1.7 0.36 1.7 1 0.12 dimethylformamide 28 0.2

84 0.26 1.7 0.074 0.35 0.2 0.025 dimethylformamide 28 0.2

85 0.26 1.7 0.074 0.35 0.2 0.025 dimethylformamide 28 0.2 1By moles. 2Based on assumed equations.

Table 19. Silane Products from Mixtures of Si(OCH3)4 and Various Amounts of PCl5 with a Dimethylformamide Catalyst and at Various Reaction Times and at Room Temperature - Results 1 2 3 2 4 4 catalyst PCl5 / agent xs DMF / time reactant product structure name amount silane silane Si(OMe)4 Si(OMe)3Cl Si(OMe)2Cl2 Si(OMe)Cl3 SiCl4 (g) ( L) (fold) (h) 82 H dimethylformamide 28 3 0.37 0.2 0.5 10 8 O N 83 dimethylformamide 28 1 0.12 0.2 0.5 2 10 4

84 dimethylformamide 28 0.2 0.025 0.2 22 5 10

85 dimethylformamide 28 0.2 0.025 0.2 0.5 4 10 1 1Reaction mixtures are given in Table 18. 2By moles. 3Based on assumed equations. 4Relative intensity of reactant and product 29Si resonances with 10 being the most intense.

Table 20. Silane Products from a Mixture of Si(OCH3)4 and Excess POCl3 with Four Potential Catalysts and at Various Reaction Times and at Room Temperature – Reaction Mixtures 1 2 1 Si(OMe)4 POCl3 agent / agent xs catalyst catalyst / volume mmol volume mmol silane structure name amount silane (mL) (mL) (fold) (g) ( L) 86 0.26 1.7 2.5 27 16 4 no cat 87 0.26 1.7 2.5 27 16 4

88 0.26 1.7 2.5 27 16 4 pyridine 29 0.2 89 0.26 1.7 2.5 27 16 4 N

90 0.26 1.7 2.5 27 16 4 triethylamine 50 0.2 91 0.26 1.7 2.5 27 16 4 N

92 0.26 1.7 2.5 27 16 4 H dimethylformamide 28 0.2 93 0.26 1.7 2.5 27 16 4 O N

94 0.26 1.7 2.5 27 16 4 Cl iminium chloride 0.04 0.2 N Cl 95 0.26 1.7 2.5 27 16 4 H

1By moles. 2Based on assumed equations.

Table 21. Silane Products from a Mixture of Si(OCH3)4 and Excess POCl3 with Four Potential Catalysts and at Various Reaction Times and at Room Temperature – Results 1 2 3 2 4 4 catalyst POCl3 / agent xs cat / time reactant product structure name amount silane silane Si(OMe)4 Si(OMe)3Cl Si(OMe)2Cl2 Si(OMe)Cl3 SiCl4 (g) ( L) (fold) (h) 86 no cat 16 4 0.2 2 1 10 87 16 4 0.2 48 10 8

88 pyridine 29 16 4 0.2 2 9 10 89 29 16 4 0.2 72 10 N

90 triethylamine 50 16 4 0.2 2 10 8 91 N 50 16 4 0.2 72 10 4

92 H dimethylformamide 28 16 4 0.2 2 6 10 93 O 28 16 4 0.2 48 1 10 2 N

94 Cl iminium chloride 0.04 16 4 0.2 3 10 9 N Cl 95 H 0.04 16 4 0.2 48 2 10 3

1Reaction mixtures are given in Table 20. 2By moles. 3Based on assumed equations. 4Relative intensity of reactant and product 29Si resonances with 10 being the most intense.

Table 22. Silane Products from a Mixture of Si(OCH3)4 and Excess of HCl with Five Catalysts and at Various Reaction Times and at Room Temperature - Reaction Mixtures 1 2 1 Si(OMe)4 HCl agent / agent xs catalyst catalyst / volume mmol volume mmol silane structure name amount silane ( L) (mL) (fold) (g) ( L) 96 200 1.34 1.0 4 3 0.4 no cat 97 200 1.34 1.0 4 3 0.4

98 200 1.34 1.0 4 3 0.4 pyridine 29 0.26 99 200 1.34 1.0 4 3 0.4 N

100 200 1.34 1.0 4 3 0.4 quinoline 42 0.26 101 200 1.34 1.0 4 3 0.4 N

102 200 1.34 1.0 4 3 0.4 trimethylamine 34 0.26 N 103 200 1.34 1.0 4 3 0.4 3

104 200 1.34 1.0 4 3 0.4 H dimethylformamide 28 0.26 O N

105 200 1.34 1.0 4 3 0.4 N dimethylaniline 44 0.26 106 200 1.34 1.0 4 3 0.4

1By moles. 2Based on assumed equations.

Table 23. Silane Products from a Mixture of Si(OCH3)4 and Excess of HCl with Five Catalysts and at Various Reaction Times and at Room Temperature - Results catalyst1 HCl2/ agent xs3 cat2/ time reactant3 product3 structure name amount silane silane Si(OMe)4 Si(OMe)3Cl Si(OMe)2Cl2 Si(OMe)Cl3 SiCl4 (g) ( L) (h) 96 no cat 3 0.4 2 10 8 97 3 0.4 48 10 9

98 pyridine 29 3 0.4 0.26 2 10 4 99 29 3 0.4 0.26 48 10 4

100 quinoline 42 3 0.4 0.26 2 10 5 101 42 3 0.4 0.26 48 10 4 N

102 trimethylamine 34 3 0.4 0.26 2 10 6 N 103 3 34 3 0.4 0.26 48 10 7

104 H dimethylformamide 28 3 0.4 0.26 2 10 6 O N

105 N dimethylaniline 44 3 0.4 0.26 2 10 5 106 44 3 0.4 0.26 48 10 4

1Reaction mixtures are given in Table 22. 2By moles. 3Based on assumed equations. 4Relative intensity of reactant and product 29Si resonances with 10 being the most intense.

10 16:1 8

29Si 6 rel 4 int 2 Cl2 Cl3 Cl2 Cl3 Cl4 Cl4 0

10 4:1 8 6 29Si rel 4 int 2 Cl2 Cl3 Cl3 Cl4 0 0.5 3 48 h

Figure 1. Relative intensity of 29Si resonances of chlorinated silanes at 16:1 and 4:1 SOCl :TMOS ratios, and 0.2 and 0.05 2 DMF:TMOS ratios at three reaction times.

29Si rel int 4

Cl3 Cl3 Cl4 Cl Cl Cl Cl Cl Cl3 Cl T T Cl 2 Cl 2 Cl 2 Cl Cl 3 0 2 2 pyridine quinoline collidine 2-imidazolidone DMA DMF dimethyl

29 imidazolidone Figure 2. Relative intensity of Si resonances of chlorinated silanes at a SOCl2:TMOS ratio of 16:1, a catalyst:TMOS

ratio of 0.2 and a time of 0.5 h (collidine, 2,3,5-collidine, ; 2-imidazolidone, ;

N O 90

DMA, N,N-dimethylacetamide, CH CON(CH ) ; dimethylimidazolidone, 1,3-dimethyl-2-imidazolidone, N ). 3 3 2

29 Si rel int

Cl4 Cl4 Cl Cl Cl2 Cl Cl Cl Cl 3 3 Cl 2 Cl T T T T Cl Cl Cl2 2 0 pyridine N-chloro cyanuric benzene zinc triethyl iminium DMF

succinimide chloride chloride amine chloride 29 Figure 3. Relative intensity of Si resonances of chlorinated silanes at SOCl2:TMOS ratio of 16:1, a catalyst:TMOS

ratio of 0.2 and a time of 2 h (cyanuric chloride, ; iminium chloride, (chloromethylene) dimethyliminium chloride, 91

Cl (CH3)2N C Cl H ).

Detailed Experiments

Catalyzed Alkoxysilane-Thionyl Chloride Investigations

The work done with the small-scale exploratory experiments on the synthesis of SiCl4 led to the conclusion that a promising area for work on an efficient synthesis of SiCl4 could be based on the reaction of alkoxysilanes with SOCl2 in the presence of a catalyst such as dimethylformamide, Scheme 3. As a part of the work in this area, model studies were done on alkylalkoxysilanes, SOCl2 and dimethylformamide.

Scheme 3. Silicon Tetrachloride from Tetramethoxysilane, SOCl2 and

Dimethylformamide

DMF Si(OCH3)4 + 4 SOCl2 SiCl4 + 4 CH3Cl + 4 SO2

DMF-Catalyzed Synthesis of Methylchlorosilanes from Methylmethoxysilanes and Thionyl Chloride

To support studies on the synthesis of SiCl4 from Si(OCH3)4, the dimethylformamide catalyzed reaction of Si(CH3)4; and three methylmethoxysilanes, (CH3)3Si(OCH3,

(CH3)2Si(OCH3)2, and CH3Si(OCH3)3 with SOCl2 was investigated, Scheme 4. In these runs,

runs 107 – 110, Table 24, the SOCl2 was in a 4, 5.3, 8, 16-fold excess, the ratio of

o dimethylformamide to Si(OCH3)4 was 1 : 0.4, the temperature was 55 C and the time was 0.5 to

28 h, Table 24.

Scheme 4. Methylchlorosilanes from Methylmethoxysilanes, SOCl2 and

Dimethylformamide

DMF (CH3)4Si + SOCl2 no reaction

DMF (CH3)3Si(OCH3) + SOCl2 (CH3)3SiCl + CH3Cl + SO2

DMF (CH3)2Si(OCH3)2 + 2 SOCl2 (CH3)2SiCl2 + 2 CH3Cl + 2 SO2

DMF CH3Si(OCH3)3 + 3 SOCl2 CH3SiCl3 + 3 CH3Cl + 3 SO2

Tetramethylsilane proved to be inert and gave no chlorosilanes, as expected. The three methoxysilanes all yielded full displacement of their alkoxy groups, with a longer reaction reaction time being required for the displacement of three alkoxy groups. The successful synthesis of the methylchlorosilanes from the methylmethoxysilanes in acceptable yields shows that the Si-OCH3 bond can be readily displaced by the Si-Cl bond under mild conditions. This finds precedents in the literature.20b The displacement is not surprising because the bond energy of the Si-O bond, 452 kJ/mol, is not substantially higher than that of the Si-Cl bond, 381 kJ/mol.32

DMF-Catalyzed Synthesis of Methylchlorosilanes from Methylethoxysilanes and Thionyl Chloride

The effect of ethoxy groups in place of methoxy groups, Scheme 5, was investigated by carrying out runs 111 - 113. As is seen, Table 25, the ethoxysilanes gave results similar to those from the methoxy silanes except for a lengthening of the reaction time in the case of the triethoxysilane.

Scheme 5. Methylchlorosilanes from Methylethoxysilanes, SOCl2 and

Dimethylformamide

DMF (CH3)3Si(OC2H5) + SOCl2 (CH3)3SiCl + C2H5Cl + SO2

DMF (CH3)2Si(OC2H5)2 + 2 SOCl2 (CH3)2SiCl2 + 2 C2H5Cl + 2 SO2

DMF CH3Si(OC2H5)3 + 3 SOCl2 CH3SiCl3 + 3 C2H5Cl + 3 SO2

DMF-Catalyzed Synthesis of Ethylchlorosilanes from Ethylalkoxysilanes and Thionyl Chloride

To determine the effect of using ethyl groups in place of methyl groups, Scheme 6, runs

114 - 115 were carried out. As expected, the substitution of ethyl groups for a methyl groups had little effect, Table 26.

Scheme 6. Ethylchlorosilanes from Ethylalkoxysilanes, SOCl2 and

Dimethylformamide

DMF C2H5Si(OCH3)3 + 3 SOCl2 (C2H5)SiCl3 + 3 C2H5Cl + 3 SO2

DMF C2H5Si(OC2H5)3 + 3 SOCl2 (C2H5)SiCl3 + 3 C2H5Cl + 3 SO2

DMF-Catalyzed Synthesis of Silicon Tetrachloride from Tetramethoxysilane and Thionyl Chloride

A set of runs was made to examine the products of the treatment of a mixture Si(OCH3)4 with SOCl2 and with dimethylformamide as a catalyst, Scheme 7. In one experiment, run 116,

Table 27, the excess of SOCl2 was 4-fold, the ratio of dimethylformamide to Si(OCH3)4 was

o 1 : 0.4, the temperature was 55 C and the time was 8 h. This gave SiCl4 in 63 % yield with no incompletely chlorinated byproducts.

Scheme 7. Silicon Tetrachloride from Tetramethoxysilane, SOCl2 and

Dimethylformamide

DMF Si(OCH3)4 + 4 SOCl2 SiCl4 + 4 CH3Cl + 4 SO2

In addition, a group of experiments was carried out to determine the effect of variations in the conditions used in the synthesis of SiCl4 from Si(OCH3)4 in runs 117 - 126, Table 27.

Reduction of the SOCl2 to Si(OCH3)4 and DMF to Si(OCH3)4 Ratios. To investigate the effect of a decrease in the SOCl2/Si(OCH3)4 and DMF/ Si(OCH3)4 ratios used in run 116, run

117 was carried out. In this reaction, the excess of SOCl2 was dexreased to 2-fold, and the ratio of dimethylformamide to Si(OCH3)4 was decreased to 0.2. As expected, the lower SOCl2-to-Si(O

CH3)4 and dimethylformamide-to-Si(OCH3)4 ratios gave a lower yield and took a longer time.

Reduction of the DMF to Si(OCH3)4 Ratio. To determine the effect of reducing the excess of dimethylformamide over Si(OCH3)4 while keeping the SOCl2/Si(OCH3)4 ratio constant, run 118 was carried out. In this run, the ratio was lowered from 0.4 to 0.2. Under these conditions, the yield was lowered and the reaction time was increased. These results show the effectiveness of the dimethylformamide as a catalyst.

Reduction of Temperature. The effect of temperature on the reaction was investigated with runs 116 and 119 to 122. In these, the temperature was reduced stepwise from the 55 oC of run 116 to 25 oC. The results show that the reactions are significantly slowed at lower temperatures, as expected.

Reduction of Temperature at Reduced SOCl2 to Si(OCH3)4 and DMF to Si(OCH3)4

Ratios. The effect of a reduction of the temperature at lower excess of SOCl2/Si(OCH3)4 and a lower DMF/Si(OCH3)4 ratio is shown with runs 123 to 125. The same trend is found as that in runs 116 and 119 to 122.

Reduction of Scale. Run 126 was carried out and compared to run 116 to determine the effect of scale. Here a reaction was run at half scale. The result shows that, as expected, scale has no appreciable effect on yield. (The apparent effect on reaction time is ascribed to variables associated with apparatus differences.)

Variously Catalyzed Synthesis of Silicon Tetrachloride from Tetramethoxysilane and Thionyl Chloride

Alternative Catalysts. The effect of alternative catalysts was investigated by substituting dimethylacetamide (DMA), triethylamine (Et3N), and (chloromethylene) dimethyliminium chloride (imin) (mp 132 oC) for dimethylformamide in runs patterned on run 116. The results, runs 128 – 132, Table 28, show that all three catalysts are effective. The effectiveness of DMA is as expected. The effectiveness of Et3N shows that a moderately strong organic base can also catalyze the reaction. Most interesting is the efficacy of the iminium chloride. This chloride has

31 been shown to be formed by the reaction of dimethylformamide with SOCl2.

Addition of n-Butyl Chloride. The effect of adding n-butyl chloride as a distillation aid was investigated by carrying out a run that was the same as run 116 except for the addition of n-butyl chloride before the start of the distillation, run 133, Table 28. This did not have a large effect on the reaction time or yield. A parallel modification of run 117 showed little effect on reaction time, run 134.

DMF-Catalyzed Synthesis of Silicon Tetrachloride from Tetramethoxysilane and Thionyl Chloride with Vent-Line Traps

To determine if the yield of SiCl4 from the reaction of Si(OCH3)4 and a 4-fold excess of

SOCl2 catalyzed by dimethylformamide, Scheme 7, was lowered as a result of loss of SiCl4 vapor through the vent line of the chlorination apparatus, a set of experiments was done in which traps were placed in the line, runs 135 - 137, Tables 29 and 30. This work showed that the yield was reduced by vent-line loss. It further showed that with a suitable trap the yield of the

Si(OCH3)4-SOCl2-DMF reaction was high and probably could be increased still more. An additional experiment, run 138, showed that the addition of the distillation aid butyl chloride did not affect the yield arising from the use of the traps.

Catalyzed Synthesis of Silicon Tetrachloride from Higher Tetraalkoxysilane and Thionyl Chloride

Higher Alkoxides. To investigate the effect of the use of higher tetraalkoxides on the synthesis of SiCl4, Scheme 8, a set of comparative runs, runs 139 - 141, Table 31, was made. The reference run again was run 116. As is seen, Table 30, the reaction time required increased with the larger alkyl groups. This is as expected.

Scheme 8. Silicon Tetrachloride from Higher Tetraalkoxides, SOCl2 and

Dimethylformamide

DMF Si(OR)4 + 4 SOCl2 SiCl4 + 4 RCl + 4 SO2

The effect of reaction variables was investigated with runs 139 - 146.

Increase of the SOCl2 to Si(OR)4 Ratio. The effect of an 8-fold excess of SOCl2 relative to Si(OR)4 was an increase in reaction time, runs 139 and 142, Table 31.

Reduction of the SOCl2 to Si(OR)4 and DMF to Si(OR)4 Ratios. The effect of a smaller excess of SOCl2 and a smaller amount of dimethylformamide was to increase the reaction time as before, compare runs 116 and 117 with runs 139 and 143, and runs 116 and 117 with runs 139 and 144. 100

Reduction of the DMF to Si(OR)4 Ratio. The effect of a reduction in the amount of catalyst was an increase in reaction time as before, compare runs 116 and 118 with runs 139 and

145.

Exchange of DMF for DMA. The effect of the exchange of dimethylformamide for dimethylacetamide is not significant, as expected, compare runs 116 and 128 with runs 142 and

146. (although run 142 is only an approximate match to run 116).

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Table 24. DMF-Catalyzed Synthesis of Methylchlorosilanes from Methylmethoxysilanes and Excess of Thionyl Chloride 1 2 3 2 variable silane SOCl2 DMF SOCl2 / SOCl2 xs DMF / temp time reaction product formula volume mol volume mol Silane silane silane vol yield (mL) (mL) (mL) (fold) (oC) (mL) (%) 107 no. of R SiMe4 11.6 0.085 100 1.37 2.75 16 4 0.4 55 28 none 0 4 108 Me3SiOMe 11.8 0.086 100 1.37 2.75 16 16 0.4 55 0.5 Me3SiCl 7.4 75 5 109 Me2Si(OMe)2 11.9 0.087 100 1.37 2.75 16 8 0.4 55 0.5 Me2SiCl2 ~60 5 110 MeSi(OMe)3 12.2 0.085 100 1.37 2.75 16 5.3 0.4 55 2 MeSiCl3 ~57 1DMF, dimethylformamide. 2By moles. 3Based on assumed equations. 4Estimated by fractional distillation. 5Estimated from 29Si NMR spectra.

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Table 25. DMF-Catalyzed Methylchlorosilanes from Methylalkoxysilanes and Excess of Thionyl Chloride 1 2 3 2 variable silane SOCl2 DMF SOCl2 / SOCl2 xs DMF / temp time reaction product formula volume mol volume mol silane silane silane vol yield (mL) (mL) (mL) (fold) (oC) (mL) (%) 4 108 OR Me3SiOMe 11.8 0.086 100 1.37 2.75 16 16 0.4 55 0.5 Me3SiCl 7.4 75 5 111 Me3SiOEt 13.4 0.086 100 1.37 2.75 16 16 0.4 55 0.5 Me3SiCl ~60

5 109 Me2Si(OMe)2 11.9 0.087 100 1.37 2.75 16 8 0.4 55 0.5 Me2SiCl2 ~60 5 112 Me2Si(OEt)2 15.1 0.088 100 1.37 2.75 16 8 0.4 55 0.5 Me2SiCl2 ~60

5 110 MeSi(OMe)3 12.2 0.085 100 1.37 2.75 16 5.3 0.4 55 2 MeSiCl3 ~60 5 113 MeSi(OEt)3 17.0 0.086 100 1.37 2.75 16 5.3 0.4 55 7 MeSiCl3 ~60 1DMF, dimethylformamide. 2By moles. 3Based on assumed equations. 4Estimated by fractional distillation. 5Estimated from 29Si NMR spectra.

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Table 27. DMF-Catalyzed Synthesis of Silicon Tetrachloride from Tetramethoxysilane and Excess Thionyl Chloride 1 2 3 2 variable Si(OMe)4 SOCl2 DMF SOCl2 / SOCl2 xs DMF / temp time SiCl4 4 vol mol vol mol Si(OMe)4 Si(OMe)4 volume yield (mL) (mL) (mL) (fold) (oC) (h) (mL) (%) 116 SOCl2/Si(OMe)4 & 12.7 0.086 100 1.37 2.75 16 4 0.4 55 8 6.2 63 117 DMF/Si(OMe)4 25.5 0.171 100 1.37 2.75 8 2 0.2 55 17 8.5 43

116 DMF/Si(OMe)4 12.7 0.086 100 1.37 2.75 16 4 0.4 55 8 6.2 63 118 12.7 0.086 100 1.37 1.38 16 4 0.2 55 17 5.3 54

116 temp 12.7 0.086 100 1.37 2.75 16 4 0.4 55 8 6.2 63 119 12.7 0.086 100 1.37 2.75 16 4 0.4 45 17 5.6 57 120 12.7 0.086 100 1.37 2.75 16 4 0.4 35 21 5.2 53 121 12.7 0.086 100 1.37 2.75 16 4 0.4 35 25 5.2 53 122 12.7 0.086 100 1.37 2.75 16 4 0.4 25 96 5.2 53

123 temp 25.5 0.171 100 1.37 1.38 8 2 0.1 55 28 9.7 50 124 25.5 0.171 100 1.37 1.38 8 2 0.1 38 71 8.9 45 125 25.5 0.171 100 1.37 1.38 8 2 0.1 25 168 9.5 48

116 scale 12.7 0.086 100 1.37 2.75 16 4 0.4 55 8 6.2 63 126 6.4 0.043 50 0.69 1.38 16 4 0.4 55 17 3.2 65 1DMF, dimethylformamide. 2By moles. 3Based on assumed equations. 4Estimated from 29Si NMR spectra.

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Table 28. Variously Catalyzed Synthesis of Silicon Tetrachloride from Tetramethoxysilane and Excess Thionyl Chloride 4 5 4 6 variable Si(OMe)4 SOCl2 catalyst SOCl2 / SOCl2 xs cat / temp time BuCl SiCl4 1 2 3 8 vol mol vol mol DMF DMA Et3N imin Si(OMe)4 Si(OMe)4 volume yield (mL) (mL) (mL) (mL) (mL) (g) (fold) (oC) (h) (mL) (%) 127 cat 12.7 0.086 100 1.37 16 4 25 48 0.0 0 116 12.7 0.086 100 1.37 2.75 16 4 0.4 55 8 6.2 63 128 12.7 0.086 100 1.37 1.65 16 4 0.2 55 24 5.4 55 129 12.7 0.086 100 1.37 2.5 16 4 0.2 55 32 6.3 64 130 12.7 0.086 100 1.37 5.0 16 4 0.4 55 8 6.8 70 131 12.7 0.086 100 1.37 2.28 16 4 0.2 55 17 6.1 62 132 12.7 0.086 100 1.37 4.56 16 4 0.4 55 8 6.4 65

116 dist aid 12.7 0.086 100 1.37 2.75 16 4 0.4 55 8 6.2 63 133 12.7 0.086 100 1.37 2.75 16 4 0.4 55 11 6.07 5.9 60

116 dist aid 25.5 0.171 100 1.37 2.75 8 2 0.2 55 17 8.5 43 134 25.5 0.171 100 1.37 2.75 8 2 0.2 55 17 6.07 11.1 57 1DMF, dimethylformamide. 2DMA, dimethylacetamide. 3imin, (chloromethylene)dimethyliminium chloride. 4By moles. 5Based on assumed equations. 6BuCl, n-butyl chloride. 7n-Butyl chloride was added after the reaction and before the distillation. 8Estimated by fractional distillation.

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Table 29. DMF-Catalyzed Synthesis of Silicon Tetrachloride from Tetramethoxysilane, and Excess of

Thionyl Chloride with Vent-Line Traps - Reaction Mixtures 1 2 3 2 4 variable Si(OMe)4 SOCl2 DMF SOCl2 / SOCl2 xs DMF / BuCl vol mol vol mol Si(OMe)4 Si(OMe)4 (mL) (mL) (mL) (fold) 116 traps 12.7 0.086 100 1.37 2.75 16 4 0.4 135 traps 12.7 0.086 100 1.37 2.75 16 4 0.4 136 traps 12.7 0.086 100 1.37 2.75 16 4 0.4 137 traps 12.7 0.086 100 1.37 2.75 16 4 0.4 138 traps 12.7 0.086 100 1.37 2.75 16 4 0.4 6.0

1DMF, dimethylformamide. 2By moles. 3Based on assumed equations. 4BuCl, n-butyl chloride.

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Table 30. DMF-Catalyzed Synthesis of Silicon Tetrachloride from Tetramethoxysilane and Excess of Thionyl Chloride with Vent-Line Traps – Results1 2 3 3 4 var Si(OMe)4 SOCl2 DMF SOCl2 / DMF / temp time BuCl reaction traps total SiCl4 Si(OMe)4 Si(OMe)4 SiCl4 1 2 3 9 vol yield temp SiCl4 temp Me Cl/SO2 temp vol yield vol yield10 vol yield11 vol (mL) (mL) (mL) (oC) (h) (mL) (%) (oC) (mL) (%) (oC) (mL) (%) (oC) (mL) (mL) (%) 116 t12 12.7 100 2.75 16 0.4 55 8 6.2 63 6.2 63 135 t 12.7 100 2.75 16 0.4 55 8 6.8 70 05 2.2 22 -776 25 66 -776 - 9.0 92 136 t 12.7 100 2.75 16 0.4 55 11 5.7 58 05 2.0 20 -237 30 80 -429 - 7.7 78 137 t 12.7 100 2.75 16 0.4 55 8 6.8 70 05 1.3 13 RT8 0 0 -429 - 8.1 83 138 t 12.7 100 2.75 16 0.4 55 12 6.0 5.7 58 05 2.0 20 -429 27 72 -429 - 7.7 79 1 2 3 4 5 6 Reaction mixtures are given in Table 29. DMF, dimethylformamide. By moles. BuCl, n-butyl chloride. Ice slurry trap. CO2/ace, dry ice/acetone slurry. 7CO /CCl , dry ice/carbon tetrachloride slurry. 8Aqueous NaOH (11 M). 9CO /CH CN, dry ice/acetonitrile slurry. 10Estimated by fractional distillation. 2 4 2 3 11Assuming the product in trap 2 is 50% MeCl. 12t, traps.

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Table 31. Catalyzed Synthesis of Silicon Tetrachloride from Higher Tetraalkoxysilane and Excess Thionyl Chloride 3 4 3 variable Si(OR)4 R SOCl2 catalyst SOCl2 / SOCl2 xs catalyst / temp time SiCl4 RCl 1 2 4 5 vol mol vol mol DMF DMA Si(OR)4 Si(OR)4 vol yield vol yield (mL) (mL) (mL) (mL) (fold) (oC) (h) (mL) (%) (mL) (%) 116 R 12.7 0.086 CH3 100 1.37 2.75 16 4 0.4 55 8 6.2 63 139 19.1 0.086 C2H5 100 1.37 2.75 16 4 0.4 55 15 4.2 43 140 24.7 0.086 C3H7 100 1.37 2.75 16 4 0.4 55 32 4.5 46 27 90 141 30.5 0.086 C4H9 100 1.37 2.75 16 4 0.4 55 64 7.2 73

139 SOCl2/Si(OR)4 19.1 0.086 C2H5 100 1.37 2.75 16 4 0.4 55 15 4.2 43 142 9.6 0.043 C2H5 100 1.37 1.38 32 8 0.4 55 24 1.6 33

116 SOCl2/Si(OR)4 & 12.7 0.086 CH3 100 1.37 2.75 16 4 0.4 55 8 6.2 63 117 DMF/ Si(OR)4 25.5 0.171 CH3 100 1.37 2.75 8 2 0.2 55 17 8.5 43 139 19.1 0.086 C2H5 100 1.37 2.75 16 4 0.4 55 15 4.2 43 143 38.3 0.171 C2H5 100 1.37 2.75 8 2 0.2 55 41 6.8 35

116 SOCl2/Si(OR)4 & 12.7 0.086 CH3 100 1.37 2.75 16 4 0.4 55 8 6.2 63 117 DMF/ Si(OR)4 25.5 0.171 CH3 100 1.37 2.75 8 2 0.2 55 17 8.5 43 139 19.1 0.086 C2H5 100 1.37 2.75 16 4 0.4 55 15 4.2 43 144 38.3 0.171 C2H5 100 1.37 1.38 8 2 0.1 55 120 11.5 58

116 DMF/Si(OR)4 12.7 0.086 CH3 100 1.37 2.75 16 4 0.4 55 8 6.2 63 118 12.7 0.086 CH3 100 1.37 1.38 16 4 0.2 55 17 5.3 54 139 19.1 0.086 C2H5 100 1.37 2.75 16 4 0.4 55 15 4.2 43 145 19.1 0.086 C2H5 100 1.37 1.38 16 4 0.2 55 45 4.8 49

116 cat 12.7 0.086 CH3 100 1.37 2.75 16 4 0.4 55 8 6.2 63 128 12.7 0.086 CH3 100 1.37 1.65 16 4 0.2 55 24 5.4 55 142 9.6 0.043 C2H5 100 1.37 1.38 32 8 0.4 55 24 1.6 33 146 9.6 0.043 C2H5 100 1.37 1.65 32 8 0.4 55 24 1.8 37 1DMF, dimethylformamide. 2DMA, dimethylacetamide. 3By moles. 4Based on assumed equations. 5Estimated by fractional distillation.

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Alkoxysilane-Aqueous HCl Investigations

Uncatalyzed Synthesis of Trimethylchlorosilane from Trimethylmethoxysilane and Aqueous HCl

The preparation of trimethylchlorosilane from trimethylmethoxysilane and aqueous HCl without a catalyst was achieved at ice temperature, Scheme 9 and Table 32. Thus reaction finds precedent in the literature with the synthesis of, for example, triethylchlorosilane from triethylmethoxysilane, and triisopropylchlorosilane from triisopropylmethoxysilane under mild conditions.33 While treatment of dimethyldimethoxysilane with aqueous HCl gave a 29Si spectra with resonance which could have belonged to methyl(methylchloro)dimethoxysilane, no clear evidence for the preparation of dimethyldichlorosilane from dimethyldimethoxysilane was obtained. Also, no evidence for the preparation of methyltrichlorosilane from methyltrimethoxysilane and aqueous HCl, or silicon tetrachloride from tetramethoxysilane and aqueous HCl was obtained. This is not surprising since the concentration of water in the reaction mixtures was high and methylchlorosilanes are easily hydrolyzed to methylsiloxanes, and silicon tetrachloride is very readily hydrolyzed to silica.

However, the fact that trimethylchlorosilane can easily be prepared from trimethylmethoxysilanes and HCl under mild conditions shows that the Si-O bond can be displaced by the Si-Cl bond under mild conditions in spite of the lower bond energy of the Si-Cl bond versus that of the Si-O bond (381 versus 452 kJ/mol). This suggests that the synthesis of

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silicon tetrachloride from a tetramethoxysilane or a similar compound such as a tetraalkoxysilane or a tetracarboxysilane with a chlorinating agent such as anhydrous HCl might be possible.

Scheme 9. Trimethylchlorosilane from Trimethylmethoxysilane and Aqueous HCl and a Possible Methyl(chloromethyl)dimethoxysilane from Dimethyldimethoxysilane and

Aqueous HCl

(CH3)3SiOCH3 + 2 HClaq (CH3)3SiCl + CH3Cl + H2O

(CH3)2Si(OCH3)2 + HClaq CH3(CH2Cl)Si(OCH3)2 ? + H2

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Uncatalyzed Synthesis of Trimethylchlorosilane from Trimethylethoxysilane and Aqueous HCl

The reaction of trimethylethoxysilane and aqueous HCl is similar to that of trimethylmethoxysilane and aqueous HCl, Scheme 10 and Table 32, as expected, and needs no further comment.

The reaction of dimethyldiethoxysilane and aqueous HCl is apparently similar to that of dimethyldimethoxysilane and aqueous HCl but again the product was not positively identified.

Scheme 10. Trimethylchlorosilane from Trimethylethoxysilane and Aqueous HCl and a Possible Methyl(chloromethyl)diethoxysilane from Dimethyldiethoxysilane and

Aqueous HCl

(CH3)3SiOC2H5 + 2 HClaq (CH3)3SiCl + C2H5Cl + H2O

(CH3)2Si(O C2H5)2 + HClaq CH3(CH2Cl)Si(O C2H5)2 ? + H2

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Uncatalyzed Synthesis of Triethylchlorosilane from Triethylethoxysilane and Aqueous HCl

Also as expected, the reaction of triethylethoxysilane and aqueous HCl is similar to that of both trimethylmethoxysilane and trimethylethoxysilane with aqueous HCl, Scheme 11 and

Table 32, and further discussion is unnecessary.

Scheme 11. Triethylchlorosilane from Triethylethoxysilane and Aqueous HCl

(C2H5)3SiOC2H5 + 2 HClaq (C2H5)3SiCl + C2H5Cl + H2O

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Table 32. Uncatalyzed Synthesis of Trialkylchlorosilanes from Trialkylalkoxysilanes and Excess Aqueous HCl in Hexanes reactant temp time HCl1/ HCl xs2 product3 4 silane HCl silane Me3SiCl Et3SiCl unknown compound vol mol vol mol (mL) (mL) (oC) (h) (fold) 147 Me3SiOMe 6.9 0.05 39 0.47 0 3 9.4 4.7 4 10

148 Me2Si(OMe)2 6.9 0.05 39 0.47 0 3 9.4 2.4 10

149 Me3SiOEt 7.8 0.05 39 0.47 0 3 9.4 4.7 4 10

150 Me2Si(OEt)2 8.6 0.05 39 0.47 0 3 9.4 2.4 10

151 Et3SiOEt 9.8 0.05 39 0.47 0 3 9.4 4.7 10 1By moles. 2Based on assumed equations. 3Relative intensity of reactant and product 29Si resonances with 10 being the most intense. 4Largest unknown 29Si resonance.

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Alkoxysilane-HCl Gas Investigations

Silicon Tetrachloride from Tetramethoxysilane and HCl Gas

As a simpler alternative to the synthesis of SiCl4 from Si(OCH3)4 and SOCl2, its synthesis from Si(OCH3)4 and HCl gas was investigated, Scheme 12. While SiCl4 was not made from

Si(OCH3)4 in this study, data were collected which indicated this should be possible.

Scheme 12. Silicon Tetrachloride from Tetramethoxysilane and HCl Gas

Si(OCH3)4 + 8 HCl SiCl4 + 4 CH3Cl + 4 H2O

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Uncatalyzed Synthesis of Methylchlorosilanes from Methylmethoxysilanes and HCl Gas

The treatment of (CH3)3SiOCH3, (CH3)2Si(OCH3)2, and CH3Si(OCH3)3 with HCl gas was investigated as a part of this study, Scheme 13. In these runs the rate of addition of HCl was approximately 78 mL/min, the temperature was 0 oC, and the time was either 0.5 or 1 h.

Scheme 13. Methylchlorosilanes from Methylmethoxysilanes and HCl Gas

(CH3)3SiOCH3 + 2 HClg (CH3)3SiCl + CH3Cl + H2O

(CH3)2Si(OCH3)2 + HClg CH3)2SiCl2 + (CH3)2Si(OCH3)Cl + CH3Cl + H2O

(CH3)Si(OCH3)3 + HClg CH3Si(OCH3)Cl2 + CH3Si(OCH3)2Cl + CH3Cl + H2O

All three silanes gave a monochlorosilane species. Dimethyldimethoxysilane gave, in addition, an approximately equal amount of a dichloro species. However, methyltrimethoxysilane did not give a trichloro species, runs 152 - 154, Table 33.

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These results show that under mild conditions HCl can effect the replacement of at least one methoxy group of a methoxysilane with a chloro group. The synthesis of a dichloro species from (CH3)2Si(OCH3)2, suggests that electron donation by the methyl groups may ease the displacement of methoxy groups.

A set of experiments was carried to help determine the effect of reaction variables on the synthesis of chlorosilanes from methylmethoxysilanes and HCl gas, Table 33.

Increased Reaction Time and Temperature. Runs 155 – 157 were done to determine the effect of an increase in reaction time, an increase in reaction temperature, or an increase in both reaction time and reaction temperature. In one of the three room-temperature reactions, vent-line traps were used to capture gaseous products.34

The more demanding conditions used in the increased time and/or temperature reactions did not result in significant changes in the product distribution. This suggests that without catalysts, considerably more demanding conditions are required for the displacement of more than two methoxy groups.

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Uncatalyzed and Catalyzed Synthesis of Methylchlorosilanes from Methylethoxysilanes and HCl Gas

A study of the reaction of three methylethoxysilanes, trimethylethoxysilane,

(CH3)3SiOC2H5; dimethyldiethoxysilane, (CH3)2Si(OC2H5)2; and methyltriethoxysilane

(CH3)Si(OC2H5)3; and HCl gas was done to investigate the effect of replacement of the methoxy groups with the ethoxy groups, Scheme 14.

Scheme 14. Methylchlorosilanes from Methylethoxysilanes and HCl Gas

(CH3)3SiOC2H5 + 2 HClg (CH3)3SiCl + C2H5Cl + H2O

(CH3)2Si(OC2H5)2 + HClg (CH3)2SiCl2 + (CH3)2Si(OC2H5)Cl + C2H5Cl + H2O

CH3Si(OC2H5)3 + HClg CH3Si(OC2H5)Cl2 + CH3Si(OC2H5)2Cl + C2H5Cl + H2O

Unsurprisingly, the trends observed here, runs 158 - 160, Table 34 were quite similar to those from the corresponding methoxy group runs, runs 152 - 154.

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A group of runs was done to examine the effect of reaction variables on the synthesis of methylchlorosilanes from methylethoxysilanes and HCl gas, Table 34.

Increased Reaction Temperature. In three paired runs, the effect of reaction temperature on the synthesis of the corresponding chlorosilanes was studied, runs 159 – 162.

The results obtained are similar to those for the corresponding methoxy compounds, runs 155 –

157, except for the triethoxide. Probably the difference with the triethoxide was due to an uncontrolled reaction variable, although even here the same species were produced and only the amounts of them were different.

Addition of an Aluminum Chloride Catalyst. In a pair of runs, the effect of AlCl3 as a catalyst was investigated, runs 164 and 165. The results showed that AlCl3 did not increase the displacement of the alkoxy groups under the conditions used.

Exchange of Methoxy for Ethoxy Groups. Runs 159 and 160 permitted the study of the effect of the exchange of methoxy for ethoxy groups. The results showed that this exchange had little effect, as was expected.

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Uncatalyzed Synthesis of Ethylchlorosilanes from an Ethylmethoxysilanes and HCl Gas

Runs were made which allowed investigation of the effect of reaction variables on the reaction of an ethylmethoxysilane and HCl gas, Scheme 15.

Scheme 15. Ethylchlorosilanes from an Ethylmethoxysilane and HCl Gas

C2H5Si(OCH3)3 + HClg C2H5Si(OCH3)Cl2 + C2H5Si(OCH3)2Cl + CH3Cl + H2O

Increased Reaction Time and Temperature. In runs 166 and 167, Table 35, the reaction temperature and time were varied. The results showed that more demanding reaction conditions had little effect.

Exchange of Ethyl for Methyl Groups. Run 166 also permitted an examination of the effect of exchange of ethyl for methyl groups. This examination showed that the ethyl compound might have given a slight increase in the amount of dichloro product.

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Uncatalyzed Synthesis of Ethylchlorosilanes from an Ethylethoxysilanes and HCl Gas

In an extension of the work with methylethoxysilanes, a study of two ethylethoxysilanes and HCl gas was done, Scheme 16.

Scheme 16. Ethylchlorosilane from Ethylethoxysilanes and HCl Gas

(C2H5)3SiOC2H5 + 2 HClg (C2H5)3SiCl + C2H5Cl + H2O

C2H5Si(OC2H5)3 + HClg C2H5Si(OC2H5)Cl2 + C2H5Si(OC2H5)2Cl + C2H5Cl + H2O

This work gave results, runs 166 and 169, Table 36, parallel to those with the methylethoxysilanes runs 154 and 160, as expected.

A group of runs was done on the synthesis of ethylchlorosilanes from ethylethoxysilanes and HCl gas to determine the effect of reaction variables, Table 36.

Increased Reaction Temperature. When the reaction temperature was varied, the results showed that a small increase had little effect, runs 168 – 171.

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Exchange of Ethoxy for Methoxy Groups. With run 169, the effect of exchanging ethoxy for methoxy groups was investigated. This exchange had little effect as expected.

Exchange of Ethyl for Methyl Groups. Runs 168 and 169 permitted the study of the effect of exchanging ethyl for methyl groups. Again the exchange had little effect as expected.

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Uncatalyzed and Catalyzed Synthesis of Alkoxychlorosilanes from Tetramethoxysilane and HCl Gas

A study of the reaction of Si(OCH3)4 and HCl gas was carried out to investigate the product of this reaction, Scheme 17.

In run 175, Tables 37 and 38, both trimethoxychlorosilane and dimethoxydichlorosilane were obtained. This result showed that the treatment of tetramethylsilane with HCl with the aim of making SiCl4 has promise.

Scheme 17. Alkoxychlorosilanes from Tetramethoxysilane and HCl Gas

Si(OCH3)4 + HClg Si(OCH3)2Cl2 + Si(OCH3)3Cl + CH3Cl + H2O

Increased Reaction Temperature and Time. Runs 173 and 174 together with run 172 made possible investigation of the effect of varying the reaction temperature and time. As is seen these variables within the range used had little effect.

Addition of Platinum Catalysts. The effect of platinum catalysts on the reaction between Si(OCH)4 and HCl was investigated by adding platinum-on-aluminum or platinum-on-

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carbon catalysts to reaction mixtures, and comparing the results with those from similar runs without the added platinum, runs 174 – 180. The results, while not definitive, suggest that under the conditions used these catalysts had little effect.

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Uncatalyzed Synthesis of Alkoxychlorosilanes from Higher Tetraalkoxysilanes and HCl Gas

Three runs were carried out to determine the effect of the replacement of the methoxy groups in tetramethoxysilane by higher alkoxy groups, Scheme 18.

Scheme 18. Alkoxychlorosilanes from Higher Tetralkoxysilanes and HCl Gas

Si(OC2H5)4 + 2 HClg Si(OC2H5)3Cl + C2H5Cl + H2O

Si(OC3H7)4 + 2 HClg Si(OC3H7)3Cl + C3H7Cl + H2O

Si(OC4H9)4 + 2 HClg Si(OC4H9)3Cl + C4H9Cl + H2O

In this work, three higher higher tetraalkoxysilanes tetraethoxysilane, Si(OEt)4; tetra-n- propoxysilane, Si(O-n-Pr)4; and tetra-n-butoxysilane, Si(O-n-Bu)4; were treated with HCl gas, runs 181 – 183, Table 39. The results indicated that the replacement of alkoxy groups by chloro groups became more sluggish as the size of the group increased, as expected.

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In supplementary work, the use of liquid HCl was investigated, Scheme 19.

Scheme 19. Alkoxychlorosilanes from Tetramethoxysilane and Liquid HCl

Si(OCH3)4 + HClg Si(OCH3)2Cl2 + Si(OCH3)3Cl + CH3Cl + H2O

Here tetramethoxysilane was treated with liquid HCl at below -85 oC. Under these conditions, liquid HCl yielded the monochloro species, run 184, Table 40. Thus, it gave results similar to those from HCl gas at 0 oC, run 172. Again it appears that harsher conditions are required to obtain complete exchange of chloro for alkoxy groups with tetraalkoxysilanes.

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Table 33. Uncatalyzed Synthesis of Methylchlorosilanes from Methylmethoxysilanes and HCl Gas variable reactant HCl1/ HCl xs2 temp time reaction product3 silane HCl silane flask trap4 type vol mol mol react5 mono6 di7 react5 mono6 di7 (mL) (mL/min) (oC) (h) 152 no. of OMe Me3SiOMe 2.5 0.018 78 0.21 11.5 5.8 0 1 0 10 0 153 Me2Si(OMe)2 2.5 0.018 78 0.21 11.4 2.8 0 1 3 10 9 154 MeSi(OMe)3 2.5 0.017 78 0.21 11.9 2.0 0 1 1 10 1

152 temp/time Me3SiOMe 2.5 0.018 78 0.21 11.5 5.8 0 1 0 10 0 155 Me3SiOMe 2.5 0.018 78 0.21 11.5 5.8 RT 1 0 10 0

153 Me2Si(OMe)2 2.5 0.018 78 0.21 11.4 2.8 0 1 3 10 9 156 Me2Si(OMe)2 2.5 0.018 78 0.42 22.8 5.7 RT 2 0 0 0 3 10 6

154 MeSi(OMe)3 2.5 0.017 78 0.21 11.9 2.0 0 1 1 10 1 157 MeSi(OMe)3 2.5 0.017 78 0.21 11.9 2.0 RT 1 2 10 1 1By moles. 2Based on assumed equations. 3Relative intensity of reactant and product 29 Si resonances with 10 being the most intense. 4 trap; empty, ice- cooled. 5 react, reactant. 6mono, monochloro substituted silane.7di, dichloro substituted silane.

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Table 34. Uncatalyzed and Catalyzed Synthesis of Methylchlorosilanes from Methylethoxysilanes and HCl Gas - Variables variable reactant HCl1/ HCl xs2 temp time catalyst reaction product3 4 5 6 silane HCl silane AlCl3 Al/ react mono di type vol mol mol Si (mL) (mL/min) (oC) (h) (mg) 158 no. of OEt Me3SiOEt 2.5 0.016 78 0.21 13.0 6.5 0 1 0 10 0 159 Me2Si(OEt)2 2.5 0.015 78 0.21 14.3 3.6 0 1 2 10 9 160 MeSi(OEt)3 2.5 0.013 78 0.21 16.6 2.8 0 1 0 10 2

158 temp Me3SiOEt 2.5 0.016 78 0.21 13.0 6.5 0 1 0 10 161 Me3SiOEt 2.5 0.016 78 0.21 13.0 6.5 RT 1 0 10

159 Me2Si(OEt)2 2.5 0.015 78 0.21 14.3 3.6 0 1 2 10 9 162 Me2Si(OEt)2 2.5 0.015 78 0.21 14.3 3.6 35 1 3 10 2

160 MeSi(OEt)3 2.5 0.013 78 0.21 16.6 2.8 0 1 0 10 2 163 MeSi(OEt)3 2.5 0.013 78 0.21 16.6 2.8 RT 1 1 1 10

164 Al cat Me2Si(OEt)2 2.5 0.015 78 0.21 14.3 3.6 RT 1 1 10 6 165 Me2Si(OEt)2 2.5 0.015 78 0.21 14.3 3.6 RT 1 40 0.02 3 10 4

152 OR Me3SiOMe 2.5 0.018 78 0.21 11.5 5.8 0 1 0 10 158 Me3SiOEt 2.5 0.016 78 0.21 13.0 6.5 0 1 0 10

153 Me2Si(OMe)2 2.5 0.018 78 0.21 11.4 2.8 0 1 3 10 9 159 Me2Si(OEt)2 2.5 0.015 78 0.21 14.3 3.6 0 1 2 10 9

154 MeSi(OMe)3 2.5 0.017 78 0.21 11.9 2.0 0 1 1 10 1 160 MeSi(OEt)3 2.5 0.013 78 0.21 16.6 2.8 0 1 0 10 2 1By moles. 2Based on assumed equations. 3Relative intensity of reactant and product 29 Si resonances with 10 being the most intense. 4react, reactant. 5mono, monochloro substituted silane.6di, dichloro substituted silane.

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Table 35. Uncatalyzed Synthesis of Ethylchlorosilanes from an Ethylmethoxysilane and HCl Gas variable reactant HCl1/ HCl xs2 temp time reaction product3 silane HCl silane flask trap4 type vol mol mol react5 mono6 di7 react5 mono6 di7 (mL) (mL/min) (oC) (h) 166 time/temp EtSi(OMe)3 2.5 0.016 78 0.21 13.2 2.2 0 1 3 10 3 167 EtSi(OMe)3 2.5 0.016 78 0.42 26.5 4.4 RT 2 1 10 2 0 0 0

154 temp/time MeSi(OMe)3 2.5 0.017 78 0.21 11.9 2.0 0 1 1 10 1 166 EtSi(OMe)3 2.5 0.016 78 0.21 13.2 2.2 0 1 3 10 3 1By moles. 2Based on assumed equations. 3Relative intensity of reactant and product 29 Si resonances with 10 being the most intense. 4 trap; empty, ice- cooled. 5react, reactant. 6mono, monochloro substituted silane.7di, dichloro substituted silane.

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Table 36. Uncatalyzed Synthesis of Ethylchlorosilanes from Ethylethoxysilanes and HCl Gas Table 36. Uncatalyzed Synthesis of Ethylchlorosilanes from Ethylethoxysilanes and HCl Gas variable reactant HCl1/ HCl xs2 temp time reaction product3 silane HCl silane react4 mono5 di 6 type vol mol mol (mL) (mL/min) (oC) (h) 158 Me3SiOEt 2.5 0.016 78 0.21 13.0 6.5 0 1 0 10 0 160 MeSi(OEt)3 2.5 0.013 78 0.21 16.6 2.8 0 1 0 10 2

168 Et3SiOEt 2.5 0.013 78 0.21 16.4 8.2 0 1 0 10 169 EtSi(OEt)3 2.5 0.012 78 0.21 18.0 3.0 0 1 2 10 3

168 temp Et3SiOEt 2.5 0.013 78 0.21 16.4 8.2 0 1 0 10 170 Et3SiOEt 2.5 0.013 78 0.21 16.4 8.2 RT 1 0 10

169 EtSi(OEt)3 2.5 0.012 78 0.21 18.0 3.0 0 1 2 10 3 171 EtSi(OEt)3 2.5 0.012 78 0.21 18.0 3.0 RT 1 1 10 2

166 OR EtSi(OMe)3 2.5 0.016 78 0.21 13.2 2.2 0 1 3 10 3 169 EtSi(OEt)3 2.5 0.012 78 0.21 18.0 3.0 0 1 2 10 3

158 R Me3SiOEt 2.5 0.016 78 0.21 13.0 6.5 0 1 0 10 168 Et3SiOEt 2.5 0.013 78 0.21 16.4 8.2 0 1 0 10

160 MeSi(OEt)3 2.5 0.013 78 0.21 16.6 2.8 0 1 0 10 2 169 EtSi(OEt)3 2.5 0.012 78 0.21 18.0 3.0 0 1 2 10 3 1By moles. 2Based on assumed equations. 3Relative intensity of reactant and product 29 Si resonances with 10 being the most intense. 4react, reactant.5mono, monochloro substituted silane.6di, dichloro substituted silane.

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Table 37. Uncatalyzed and Catalyzed Synthesis of Alkoxychlorosilanes from Tetramethoxysilane and HCl Gas Table 37. Uncatalyzed and Catalyzed Synthesis of Alkoxychlorosilanes from Tetramethoxysilane and HCl Gas variable reactant HCl1/ HCl xs2 temp time catalyst silane HCl silane Pt-Al3 Pt-C4 Pt5/ type vol mol mol Si (mL) (mL/min) (oC) (h) (mg) (mg) 172 temp/time Si(OMe)4 2.5 0.017 78 0.10 6.2 0.8 0 0.5 173 Si(OMe)4 2.5 0.017 78 0.10 6.2 0.8 RT 0.5 174 Si(OMe)4 2.5 0.017 78 0.84 49.7 6.2 RT 4

174 Pt cat Si(OMe)4 2.5 0.017 78 0.84 49.7 6.2 RT 4 175 Si(OMe)4 2.5 0.017 78 0.84 49.7 6.2 RT 4 45 6.9

174 Si(OMe)4 2.5 0.017 78 0.84 49.7 6.2 RT 4 176 Si(OMe)4 2.5 0.017 78 0.84 49.7 6.2 RT 4 40 130

177 Si(OMe)4 2.5 0.017 78 0.84 49.7 6.2 35 4 178 Si(OMe)4 2.5 0.017 78 0.84 49.7 6.2 50 4 50 7.5

179 Si(OMe)4 2.5 0.017 78 0.31 18.6 2.3 50 1.5 180 Si(OMe)4 2.5 0.017 78 0.31 18.6 2.3 50 1.5 50 160 1 2 3 4 By moles. Based on assumed equations. Pt -Al2O3, Escat 226, 0.5 wt % Pt on alumi na spheres. Pt-C, 10 wt % Pt on activated carbon. 5Pt/Si, mol of Pt over mol of Si x 105.

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Table 38. Uncatalyzed and Catalyzed Synthesis of Alkoxychlorosilanes from Tetramethoxysilane and HCl Gas - Results variable reactant1 temp time catalyst reaction product2 silane HCl Pt-Al3 Pt-C4 Pt 5/ flask trap 16 trap 27 type vol Si react8 mono9 di10 react8 mono9 di10 react8 mono9 di10 (mL) (mL/min) (oC) (h) (mg) (mg) 172 temp/time Si(OMe)4 2.5 78 0 0.5 7 10 0 173 Si(OMe)4 2.5 78 RT 0.5 10 7 0 174 Si(OMe)4 2.5 78 RT 4 9 10 0 10 9 0 0 10 0

174 Pt cat Si(OMe)4 2.5 78 RT 4 9 10 0 10 9 0 0 10 0 175 Si(OMe)4 2.5 78 RT 4 45 6.9 9 10 0 0 0 0 0 0 0

174 Si(OMe)4 2.5 78 RT 4 9 10 0 10 9 0 0 10 0 176 Si(OMe)4 2.5 78 RT 4 40 130 10 9 0 10 9 0 0 0 0

177 Si(OMe)4 2.5 78 35 4 10 6 0 7 10 0 0 0 0 178 Si(OMe)4 2.5 78 50 4 50 7.5 10 3 0 10 9 0 0 0 0

179 Si(OMe)4 2.5 78 50 1.5 10 3 0 0 0 0 0 0 0 180 Si(OMe)4 2.5 78 50 1.5 50 160 0 0 0 7 10 0 10 8 0 1 2 29 3 Reaction mixtures are given in Table 37. Relative intensity of reactant and product Si resonances with 10 being the most intense. Pt-Al2O3, Escat 226, 0.5 wt % Pt on alumina spheres. 4Pt-C, 10 wt % Pt on activated carbon. 5Pt/Si, mol of Pt over mol of Si x 105. 6trap 1; empty, ice-cooled. 7trap 2; undecane- filled, ice-cooled. 8react, reactant. 9mono, monochloro substituted silane. 10di, dichloro substituted silane.

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Table 39. Uncatalyzed Synthesis of Alkoxychlorosilanes from Higher Tetraalkoxysilanes and HCl Gas Table 39. Uncatalyzed Synthesis of Alkoxychlorosilanes from Higher Tetraalkoxysilanes and HCl Gas variable reactant HCl1/ HCl xs2 temp time reaction product3 silane HCl silane react4 mono5 di 6 type vol mol mol (mL) (mL/min) (oC) (h) 174 OR Si(OMe)4 2.5 0.017 78 0.84 49.7 6.2 RT 4 9 10 0 181 Si(OEt)4 2.5 0.012 78 0.84 74.6 9.3 RT 4 5 10 0 182 Si(OPr)4 2.5 0.009 78 0.84 96.6 12.1 RT 4 6 10 0 183 Si(OBu)4 2.5 0.007 78 0.84 119.2 14.9 RT 4 7 10 0 1By moles. 2Based on assumed equations. 3Relative intensity of reactant and product 29 Si resonances with 10 being the most intense. 4react, reactant.5mono, monochloro substituted silane.6di, dichloro substituted silane.

Table 40. Uncatalyzed Synthesis of Alkoxychlorosilanes from Tetramethoxysilane and Liquid HCl Table 40. Uncatalyzed Synthesis of Alkoxychlorosilanes from Tetramethoxysilane and Liquid HCl variable reactant HCl1/ HCl xs2 temp time reaction product3 silane HCl silane react4 mono5 di 6 type vol mol mol (mL) (mL/min) (oC) (h) 172 HCl phase Si(OMe)4 2.5 0.017 78 0.10 6.2 0.8 0 0.5 7 10 0 184 Si(OMe)4 2.5 0.017 78 0.07 4.1 0.5 <-85 0.3 7 10 0 1By moles. 2Based on assumed equations. 3Relative intensity of reactant and product 29 Si resonances with 10 being the most intense. 4react, reactant.5mono, monochloro substituted silane.6di, dichloro substituted silane.

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Acetoxysilane-Thionyl Chloride Investigations

Uncatalyzed Synthesis of Triacetoxychlorosilane and Diacetoxydichlorosilane from Tetraacetoxysilane and Thionyl Chloride

While the main focus of this work was on the preparation of silicon tetrachloride from tetramethoxysilane and SOCl2, efforts were also devoted to preparing it from other silicon compounds and various chlorinating agents. One of these efforts focused on the use of tetraacetoxysilane. Considerable difficulties were encountered in this work. In large part these centered on the problem of securing and maintaining a supply of the acetate that had not been significantly hydrolyzed by atmospheric moisture. Most of the tetraacetoxysilane used came from one batch supplied by Aldrich. The rest came from other batches that initially melted as expected at about 111 oC,35 but soon hydrolyzed to material which did not melt. Only tetraacetoxysilane which melted near the expected melting point was used in the run yielding triacetoxychlorosilanes and diacetoxydichlorosilane discussed in this section and in the runs yielding silicon tetrachloride discussed in the next section. (Attempts to prepare tetraacetoxysilane by a procedure in the literature failed). 35,36

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The uncatalyzed synthesis of the acetoxychlorosilanes from tetraacetoxysilane and

SOCl2, Scheme 20 and Table 41, is not surprising since alkoxysilanes and acetoxysilanes react in similar ways, and in view of the synthesis of methoxychlorosilanes from the uncatalyzed reaction of tetramethoxysilane and thionyl chloride.20c,37A reaction temperature of 120 oC was chosen so as to have a temperature above the melting point of the acetate (111 oC).

Scheme 20. Triacetoxychlorosilane and Diacetoxydichlorosilane from

Tetraacetoxysilane and Thionyl Chloride

Si(OAc)4 + 4 SOCl2 2 Si(OAc)3Cl + Si(OAc)2Cl2 + 4 SO2 + 4 AcCl

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Table 41. Uncatalyzed Synthesis of Triacetoxychlorosilane, and Diacetoxydichlorosilane from Tetraacetoxysilane and Excess Thionyl Chloride 1 2 3 3 reactants SOCl2 / SOCl2 xs temp time reactant product Si(OAc)4 SOCl2 Si(OAc)4 Si(OAc)4 Si(OAc)3Cl Si(OAc)2Cl2 Si(OAc)Cl3 SiCl4 (g) (mL) (fold) (oC) (h) 185 0.15 4.2 100 25 120 5.5 7 10 5

1By moles. 2Based on assumed equations. 3Relative intensity of silane 29Si resonances with 10 being the most intense.

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Catalyzed Synthesis of Silicon Tetrachloride from Tetraacetoxysilane and Thionyl Chloride

The catalyzed synthesis of SiCl4 from tetraacetoxysilane and SOCl2, Scheme 21 and runs

186 – 189, Table 42, is also not surprising in view of the already mentioned similarity of the reactions of alkoxysilanes and acetoxysilanes.20c,37 The fact that the reaction of tetraacetoxysilane and SOCl2 can be catalyzed by dimethylformamide and pyridine finds parallels in the dimethylformamide- and pyridine-catalyzed reactions of tetramethoxysilane and thionyl chloride (see above). While the catalyzed tetraacetoxysilane–thionyl chloride reaction does produce silicon tetrachloride under mild conditions, it is not an attractive alternative to the catalyzed reaction of tetramethoxysilane and SOCl2 because the acetate is less available Table

43, is a solid, and is difficult to store.

Scheme 21. Silicon Tetrachloride from Tetraacetoxysilane and Thionyl Chloride

Si(OAc)4 + 4 SOCl2 SiCl4 + 4 SO2 + 4 AcCl

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Table 42. Catalyzed Synthesis of Silicon Tetrachloride from Tetraacetoxysilane and Excess Thionyl Chloride 1 2 1 2 2 reactants catalyst SOCl2 / SOCl2 xs cat / temp time reactant product Si(OAc)4 SOCl2 DMF PCl3 py CHCl3 Si(OAc)4 Si(OAc)4 Si(OAc)4 Si(OAc)3Cl Si(OAc)2Cl2 Si(OAc)Cl3 SiCl4 (g) (mL) ( L) ( L) ( L) ( L) (fold) (oC) (h) 186 0.11 1.5 10 50 12.5 0.03 120 0.2 10

187 0.13 1.8 20 600 50 12.5 0.05 15 120 0.2 10

188 0.13 1.8 10 50 12.5 0.025 120 0.2 10

189 0.13 1.8 10 50 12.5 0.026 120 0.2 10 1By moles. 2Based on assumed equations. 3Relative intensity of silane 29Si resonances with 10 being the most intense.

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1 Table 43. Approximate Cost of Silicon Reactants $/L $/kg $/mol tetraacetoxysilane 1276 336

tetramethoxysilane 288 133

1Based on prices of laboratory chemicals listed by Aldrich and Alfa Aesar (2011).

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Metal Silicate-Chlorinating Agent Investigations

Attempted Synthesis of Silicon Tetrachloride from Silicates and Chlorinating Agents

The attempts to convert silicates and silica directly to silicon tetrachloride with various chlorinating agents were unsuccessful. In no case was any silicon tetrachloride detected by 29Si

NMR. In part this failure is attributed to the insolubility of the essentially ionic silicates and silica in the reaction mixtures.38 However, the problem probably is deeper than this. It may be that insufficiently harsh reaction conditions were used since the bond energies of the Si-O bond and the Si-Cl bond are not greatly different, 452 and 381 kJ/mol.32 Whether conditions that are harsh enough to work and not so harsh as to be unacceptable can be found is unclear.

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Table 44. Attempted Synthesis of SiCl4 from Silicates and Excess Chlorinating Agents - Reaction Mixtures silicate chlorinating agents solvent catalyst name formula weight mmol compound amount mmol compound vol compound vol mmol (g) (mL)(g) (mL) (mL)

190 alite Ca3SiO5 0.25 1.1 HCl 10 40 191 0.25 1.1 HCl 10 40 DMF 0.5 6.5 192 3.1 14 SOCl2 20 274 193 1.6 7 SOCl2 20 274 DMF 0.27 3.6 194 0.32 1.4 SOCl2 15 206 1-chloronaphthalene 25 195 0.055 0.24 SOCl2,PCl5 10 0.38 137 1.8 1,2,4-trichlorobenzene 10 196 0.10 0.44 PCl5 0.34 1.6 25

197 magnesium silicate Mg2Si3O8 0.054 0.21 acetylacetone 5

198 dioptase Cu6Si6O18·6 H2O 0.0024 0.0025 SOCl2 1 14

199 fayalite Fe2SiO4 0.037 0.18 SOCl2 10 137 200 0.036 0.18 SOCl2 10 137 DMF 0.27 3.6 201 0.026 0.13 SOCl2 25 343 1,2,4-trichlorobenzene 15

202 hardystonite Ca2ZnSi2O7 0.026 0.083 SOCl2 2 27 203 1.55 4.9 SOCl2 20 274 DMF 0.27 3.6

204 hemimorphite Zn4Si2O7(OH)2·H2O 0.10 0.21 HCl 2 8 acetyl chloride 1 205 0.10 0.21 HCl 2 8 acetyl chloride 1 NH4OH 1.0 0.025 206 0.0059 0.012 SOCl2 1 14

207 laumontite Ca(AlSi2O6)2·4 H2O 0.05 0.11 SOCl2 20 274

208 lithium metasilicate Li2SiO3 0.25 2.8 SOCl2 20 274 209 0.25 2.8 SOCl2 20 274 DMF 0.27 3.6

210 lithium orthosilicate Li4SiO4 0.015 0.12 SOCl2 2 27

211 muscovite KAl2(AlSi3O10)(F,OH)2 0.022 0.050 SOCl2 10 137 212 0.029 0.066 SOCl2 10 137 DMF 0.27 3.6 213 0.0075 0.017 SOCl2 25 343 1,2,4-trichlorobenzene 15 214 0.0076 0.017 SOCl2 10 137 1-chloronaphthalene 20

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Table 44. Attempted Synthesis of SiCl4 from Silicates and Excess Chlorinating Agents - Reaction Mixtures (con’t) silicate chlorinating agents solvent catalyst name formula weight mmol compound amount mmol compound vol compound vol mmol (g) (mL)(g) (mL) (mL)

215 olivine Mg2SiO4 1.2 8.5 SOCl2 20 274 DMF 0.27 3.6

1 216 PSS C32H96N8O20Si8 0.02 0.018 SOCl2 2 27 217 0.02 0.018 SOCl2 2 27 DMF 1.0 0.013

218 Sodalite Na4Al3(SiO4)3Cl 0.054 0.11 HCl 1 4 219 0.052 0.11 SOCl2 1 14

220 sodium metasilicate Na2SiO3 0.19 1.55 SOCl2 20 274 221 0.21 1.7 SOCl2 20 274 DMF 0.27 3.6

222 sodium calcium silicate Na4Ca4Si8O18 0.15 0.2 SOCl2 20 274 DMF 0.27 3.6

223 willemite Zn2SiO4 0.10 0.45 SOCl2 20 274 224 0.05 0.22 SOCl2 10 137 DMF 0.27 3.6 225 0.11 0.49 SOCl2 15 206 1-chloronaphthalene 25 226 0.11 0.49 SOCl2 15 206 1,2,4-trichlorobenzene 25 227 0.06 0.27 SOCl2, PCl5 15 0.27 206 1.3 1,2,4-trichlorobenzene 12 228 0.01 0.045 PCl5 0.20 1.0 1,2,4-trichlorobenzene 25 1PSS, octakis(tetramethylammonium) pentacyclo[9.5.1.13,9.15,15.17,13]octasiloxane-1,3,5,7,9,11,13,15-octakis(yloxide) hydrate,.

O O O O Si Si O O + Si Si O CH3 O O O H3C N CH3 O O O Si CH3 O Si O O O 8 . xH O Si Si 2 O O O .

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Table 45. Attempted Synthesis of SiCl4 from Silicates and Excess Chlorinating Agents - Results 1 2 1 3 silicate chlorinating agents solvent catalyst agents / agents xs catalyst / temp time SiCl4 name formula silicate silicate (fold) (oC) (h) 190 alite Ca3SiO5 HCl 36 3.6 110 84 0 191 HCl DMF 36 3.6 6 110 84 0 192 SOCl2 20 4 85 3 0 193 SOCl2 DMF 40 8 0.5 75 48 0 194 SOCl2 1-chloronaphthalene 147 29 100 3 0 195 SOCl2, PCl5 1,2,4-trichlorobenzene 570 7.5 114 3.8 200 5 0 196 PCl5 3.6 1.8 200 5 0

197 magnesium silicate Mg2Si3O8 SOCl2 acetylacetone 140 4 0

198 dioptase Ca6Si6O18·6 H2O SOCl2 5600 311 RT 24 0

199 fayalite Fe2SiO4 SOCl2 761 190 70 26 0 200 SOCl2 DMF 761 190 20 70 26 0 201 SOCl2 1,2,4-trichlorobenzene 2638 659 80 2 0

202 hardystonite Ca2ZnSi2O7 SOCl2 338 48 80 6 0 203 SOCl2 DMF 56 8 100 4 0

204 hemimorphite Zn4Si2O7(OH)2·H2O HCl acetyl chloride 40 2.5 RT 24 0 205 HCl acetyl chloride NH4OH 40 2.5 0.125 RT 24 0 206 SOCl2 1167 146 RT 24 0

207 laumontite Ca(AlSi2O6)2·4 H2O SOCl2 2491 208 75 24 0

208 lithium metasilicate Li2SiO3 SOCl2 98 33 70 72 0 209 SOCl2 DMF 98 33 1.3 70 72 0

210 lithium Li4SiO4 SOCl2 225 56 75 4 0 orthosilicate

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Table 45. Attempted Synthesis of SiCl4 from Silicates and Excess Chlorinating Agents – Results (con’t) 1 2 1 3 silicate chlorinating agents solvent catalyst agents / agents xs catalyst / temp time SiCl4 name formula silicate silicate (fold) (oC) (h) 211 muscovite KAl2(AlSi3O10)(F,OH)2 SOCl2 2740 228 78 48 0 212 SOCl2 DMF 2740 228 78 48 0 213 SOCl2 1,2,4-trichlorobenzene 20176 1681 90 2 0 214 SOCl2 1-chloronaphthalene 8059 672 170 12 0

215 olivine Mg2SiO4 SOCl2 DMF 32 8 0.4 RT 3 0

4 216 PSS C32H96N8O20Si8 SOCl2 1500 RT 24 0 217 SOCl2 DMF 1500 RT 24 0

218 sodalite Na4Al3(SiO4)3Cl HCl 36 1.5 RT 24 0 219 SOCl2 127 11 RT 24 0

220 sodium metasilicate Na2SiO3 SOCl2 177 59 75 96 0 221 SOCl2 DMF 161 54 2 75 96 0

222 sodium calcium Na4Ca4Si8O18 SOCl2 DMF 1370 114 18 RT 3 0 silicate

223 willemite Zn2SiO4 SOCl2 609 152 70 26 0 224 SOCl2 DMF 623 156 16 70 26 0 225 SOCl2 1-chloronaphthalene 420 105 115 3 0 226 SOCl2 1,2,4-trichlorobenzene 420 105 120 7 0 227 SOCl2, PCl5 1,2,4-trichlorobenzene 763 4.8 191 0.6 200 8 0 228 PCl5 1,2,4-trichlorobenzene 22 2.8 115 5 0 1 By mmoles. 2 Based on assumed equations. 3Relative intensity of reactant and product 29Si resonances with 10 being the most intense. 4PSS, octakis(tetramethylammonium) pentacyclo[9.5.1.13,9.15,15.17,13]octasiloxane-1,3,5,7,9,11,13,15-octakis(yloxide) hydrate,

O O O O Si Si O O + Si Si O CH3 143 O O O H3C N CH3 O O O Si CH3 O Si O O O 8 . xH O Si Si 2 O O O . Silicon Dioxide-Chlorinating Agent Investigations

Attempted Synthesis of Silicon Tetrachloride from Silica and Chlorinating Agents

Again attempts to convert silica directly to silicon tetrachloride with various chlorinating agents were not successful, Tables 46 and 47, runs 229 - 235. The reasons for this are probably similar to those in the case of the attempted conversion of silicates to silicon tetrachloride.38

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Table 46. Attempted Synthesis of SiCl4 from Silica and Excess Chlorinating Agents - Reaction Mixtures silicate chlorinating agents solvent catalyst run name formula weight mmol compound vol mmol compound vol compound vol mmol (g) (mL) (mL) (mL) ® 229 Celite 545 SiO2 1.2 20 HCl 20 80

230 4.1 68 SOCl2 20 274

231 silica gel SiO2·xH2O 0.44 7.3 SOCl2 20 274

232 0.46 7.7 SOCl2 20 274 DMF 0.27 3.6

233 0.054 0.89 SOCl2 15 206 1-chloronaphthalane 25

234 0.054 0.89 SOCl2 15 206 1,2,4-trichlorobenzene 25

235 0.054 0.89 SOCl2 PCl5 15 0.26 206 1.2 1,2,4-trichlorobenzene 12

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Table 47. Attempted Synthesis of SiCl4 from Silica and Excess Chlorinating Agents - Results 1 2 1 3 silicate chlorinating agents solvent catalyst agents / agent xs catalyst / temp time SiCl4 name formula silicate silicate (fold) (oC) (h) ® 229 Celite 545 SiO2 HCl 4 stoich RT 24 0

230 SOCl2 4 2 85 2 0

231 silica gel SiO2·xH2O SOCl2 37 19 78 48 0

232 SOCl2 DMF 35 18 0.47 78 48 0

233 SOCl2 1-chloronaphthalane 231 116 100 3 0

234 SOCl2 1,2,4-trichlorobenzene 231 116 100 6 0

235 SOCl2 PCl5 1,2,4-trichlorobenzene 231 1.3 116 0.3 200 6 0 1 By mmoles. 2Based on assumed equations. 3Relative intensity of reactant and product 29Si resonances with 10 being the most intense.

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Chapter 5

Synthesis of SiCl4 and Chlorosilanes

Summary and Conclusions

147

Summary and Conclusions

Fifty years ago Currell and coworkers reported that the reaction of tetramethoxysilane and thionyl chloride in the presence of pyridinium hydrochloride gave silicon tetrachloride.21

However, they gave experimental evidence only for the isolation of a silicon tetrachloride complex upon the addition of excess pyridine to the reaction product, and did not give direct experimental evidence for the production of silicon tetrachloride, Table 2, runs a1- a3. Attempts to produce silicon tetrachloride using Currell’s reactants and conditions with analysis of the reaction mixture by 29Si NMR spectroscopy failed, Table 5, runs 1-4. Currell et al. conditions were also used by Frohn et al. for the synthesis of pentafluorophenyltrichlorosilane from pentafluorophenyltriethoxysilane.21a

However, exploratory work done as a part of the present investigation did show that the reaction of silicon tetrachloride and SOCl2 catalyzed with pyridine, dimethyformamide and other catalysts when done under suitable conditions and with analysis by 29Si NMR spectroscopy did give silicon tetrachloride, Table 11, run 47 and Table 5, run 1 (for convenience these two runs and the other runs discussed in this section are relisted in Tables 48 – 50). Ultimately, taking into account factors such as efficacy, availability and cost, it was decided to focus on dimethylformamide as a catalyst. As is shown on the following mechanism is believed that the reaction between thionyl chloride and dimethylformamide gives the

(chloromethylene)dimethyliminium chloride intermediate. This intermediate is responsible for

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the chlorination reaction of the methoxy group of tetramethoxysilane. The byproduct of this reaction can be rearranged in order for the dimethylformamide to be regenerated.

O + Cl O N + S Cl- + SO2 N Cl Cl H

OCH OCH 3 Cl 3 + OCH3 + + Cl Si OCH3 + N N - H3CO Si OCH3 - H Cl H Cl OCH3 OCH3

O CH H + 3 N O + Cl- CH3Cl H N

Some model work in this investigation was done with alkylalkoxysilanes. This showed that, for example, methyltrimethoxysilane and SOCl2 with dimethylformamide as a catalyst yielded methyltrichlorosilane, and thus that the methoxy groups of an alkylsilane could be readily replaced with chloro groups using SOCl2 and dimethylformamide as a catalyst.

The main emphasis of the work was on the reaction of tetramethoxysilane and SOCl2 with dimethylformamide as a catalyst. This work demonstrated that this reaction mixture under

149

the proper conditions gave silicon tetrachloride in good yield, Table 28, run 116 (Table 48).

Because there was concern that silicon tetrachloride was being lost in the vent stream, experiments were done in which traps were placed in the vent line. These showed that silicon tetrachloride was lost in the vent stream and that its yield could be considerably enhanced by using traps, Table 30, run 135 (Table 48). In addition, a fraction was trapped in one run, run

135, which was assumed to be about half methyl chloride and half liquid SO2. This fraction provided some direct evidence for the production of methyl chloride as a byproduct. Methyl chloride would be a valuable byproduct if, as appears likely, it is produced because it could be used as a reactant in the widely used direct (Rochow), process for the industrial production of methylchlorosilanes.

Some emphasis was also put on the use of catalysts other than dimethylformamide for the tetramethoxysilane-SOCl2 reaction. Dimethylacetamide, triethylamine and

(chloromethylene)dimethyliminium chloride were examined, Table 28, runs 128, 130 and 131

(Table 48). These all proved to be good catalysts. This result was expected for dimethylacetamide since it is a direct analogue of dimethylformamide. The efficacy of triethylamine showed that amines can act as catalysts. Most interesting was the fact that

(chloromethylene)dimethyliminium chloride was a good catalyst since it has been reported to be

31 formed when dimethylformamide and SOCl2 react. It appears likely that it is the real catalyst when dimethylformamide is used in the tetramethoxysilane-SOCl2 reaction.

150

Finally, attention was given to the reaction of higher tetraalkoxysilanes and SOCl2 in the presence of dimethylformamide. The results showed that higher tetraalkoxysilanes such as tetrapropoxysilane work well, Table 31, run 140 (Table 48). This reaction was interesting because the boiling points of the tetrapropoxysilane and the byproduct permitted separation of product and byproduct by fractional distillation. Proton NMR analysis of the byproduct showed that it was propyl chloride, and thus provided direct evidence that the major organic byproduct of the tetraalkoxysilane-SOCl2 reaction is the alkyl chloride.

Attention was also given to the uncatalyzed reaction of tetraalkoxysilanes and HCl.

Model work was done with methylmethoxysilanes. For example, trimethylmethoxysilane was treated with 12 N aqueous HCl, Table 32, run 147 (Table 49). This showed that even in aqueous solution a methoxy group can be replaced with a chloro group in spite of the ease of hydrolysis of chlorosilanes.33

Work was likewise done on the uncatalyzed reaction of methyltrichlorosilane and HCl gas, Table 33, run 157 (Table 49). This showed that HCl gas can displace a methoxy group of a methylmethoxysilane.

In further work, the uncatalyzed reaction of tetramethoxysilane and HCl gas was studied,

Table 38, run 173 (Table 49). With the results from this reaction, it was apparent that replacement of a methoxy group by the chloro group is again possible. 151

Finally, work on uncatalyzed reaction of tetramethoxysilane and liquid HCl was investigated, Table 40, run 184 (Table 49). This showed that the liquid HCl can be used to displace a methoxy group with a chloro group

In an effort to find alternatives to alkoxysilanes as a silicon source, work with tetraacetoxysilane was done. In one run, the uncatalyzed reaction of tetraacetoxysilane and

SOCl2 was investigated, Table 41, run 185 (Table 50). This showed that tetraacetoxysilane has some potential as a replacement for tetramethoxysilane. A run with these two reagents and dimethylformamide as a catalyst (Table 42, run 186), (Table 50) gave a little better result and verified the modest potential of tetraacetoxysilane. However, this potential is not high because tetraacetoxysilane is a very hydrolytically sensitive solid and this is more difficult to handle than silicon tetrachloride;

The sum of these results leads to the conclusion that two attractive ways for making silicon tetrachloride are at hand. In one, the first step is to make tetramethoxysilane from a metal silicate.

Ca2SiO4 + 4 MeOH + 4 HCl Si(OMe)4 + 2 CaCl2 + 4 H2O (22)

152

This is then converted to silicon tetrachloride by treatment with SOCl2 in the presence of a dimethylformamide catalyst.

DMF Si(OMe)4 + 4 SOCl2 SiCl4 + 4 SO2 + 4 MeCl (23)

The first step in this route is based on work showing that a number of silicate minerals and commercial silicates can be converted to fully alkoxylated monomeric silanes and oligomeric siloxanes by treatment with alcohol and HCl.39 For example:

Ca2SiO4 + 4 EtOH + 4 HCl Si(OEt)4 + 2 CaCl2 + 4 H2O (24)

The second step is based on the dimethylformamide-catalyzed tetramethoxysilane-SOCl2 work summarized above.

This route is advantageous because both steps are conducted under moderate temperature and at atmospheric pressure. In addition, the route can utilize any one of the several common silicates as the silicon source. Further, the intermediate tetramethoxysilane and product silicon tetrachloride are easily separated from the byproducts of the reactions producing them. In addition, the byproduct methyl chloride of the second step is a starting material in the direct

153

process for making methylchlorosilanes and thus is a valuable material in its own right. The fact that the intermediate tetramethoxysilane is a liquid with a moderate boiling point and, as a consequence, is easy to handle further adds to the attractiveness of the route. In sum, the route is an easy to carry out, is energy efficient and requires only readily available materials.

As pointed out in Chapter 1, this route is in contrast to the route often currently used to supply silicon tetrachloride.7,16,22 This route is:

SiO2 + 2 C Si + 2 CO (25)

Si + 2 Cl2 SiCl4 (26)

The first step in this route is energy-intensive, requires very high temperatures and is demanding to carry out. The second step requires the dissipation of much energy. In sum, the process involves a wasteful reduction and reoxidation of silicon and presents complex engineering problems. The tetramethoxysilane-SOCl2 process does not have either of these deficiencies.

The second attractive way for making silicon tetrachloride suggested by the current work is a tetramethoxysilane-HCl route:

154

Ca2SiO4 + 4 MeOH + 4 HCl Si(OMe)4 + 2 CaCl2 + 4 H2O (27)

Si(OMe)4 + 8 HCl SiCl4 + 4 MeCl + 4 H2O (28)

This route is not yet fully developed. More work needs to be done to provide direct evidence that the chlorination of tetramethoxysilane with HCl can be carried beyond monochlorination to tetrachlorination.40 However, on the basis of the results obtained so far with the very mild conditions used in run 147 Table 32, run 157 Table 33, run 173 Table 38 and run

184 Table 4, (Table 49), it appears that this can be achieved through the application of more robust reaction conditions. Further, a patent shows that the residues of the direct process for making methylchlorosilanes can be converted to silicon tetrachloride by treatment with HCl under pressure at elevated temperatures.41 If this can be done then it seems likely that conditions can be found to fully chlorinate tetramethoxysilane with HCl.

This route would be very attractive for various reasons. It would use tetramethoxysilane as an intermediate just as does the tetramethoxysilane-SOCl2 route, and thus would have the advantages that come from using this moderate boiling, moderately-reactive liquid as the intermediate. Further, since it would use HCl as the chlorinating agent in the second step, the

155

chlorinating agent would be less expensive than the SOCl2 used in the tetramethoxysilane-SOCl2 route. As with the tetramethoxysilane-SOCl2 route, the conditions required would much milder than those used in the current silicon-chlorine route. In sum, this tetramethoxysilane-HCl route would be easy to carry out, be energy efficient and utilize low cost reactants.

Finally, it appears that is should be possible to devise a route that is a hybrid of the two routes. In it, HCl would be used as the main chlorinating agent and SOCl2 would be used as an auxiliary chlorinating agent. This route can be approximated as:

Ca2SiO4 + 4 MeOH + 4 HCl Si(OMe)4 + 2 CaCl2 + 4 H2O (29)

Si(OMe)4 + 2 SOCl2 + 4 HCl SiCl4 + 2 SO2 + 4 MeCl + 4 H2O (30)

Here just enough SOCl2 would be used to reduce the maximum amount of byproduct water to that which can be tolerated in the HCl reaction. The fact that some water can be tolerated is based on the fact that tetramethoxysilane and HCl give trimethoxychlorosilane and water at room temperature and atmospheric pressure (Table 38, run 173).

Si(OMe)4 + HCl Si(OMe)3Cl + H2O (31)

156

Thus, it is apparent that not all the water has to be removed from the reaction product if the HCl concentration is high enough. Accordingly, it appears that the supplementation of the HCl with a moderate amount of SOCl2 would yield silicon tetrachloride. This route would have the advantage of using reaction conditions that are similar to the mild conditions used in the tetramethoxysilane-SOCl2 route and of using low cost HCl for most of the chlorination. The

SOCl2 used would yield methyl chloride as a byproduct and this would be of value.

Other reagents or materials probably could be used to trap the water instead of SOCl2.

For example, a suitable zeolite might act to selectively trap water.

157

Table 48. Selected Catalyzed Alkoxysilane-Thionyl Chloride Runs 1 table run reactants cat SOCl2 xs temp time silane alkylchloride silane Cl agent compound yield compound yield (fold)2 (oC) (h) (%) (%) 3 5 1 Si(OMe)4 SOCl2 py·HCl 4 100 17 -

4 24 110 MeSi(OMe)3 SOCl2 DMF 4 55 2 MeSiCl3 ~60

5 28 116 Si(OMe)4 SOCl2 DMF 4 55 8 SiCl4 63

5,6 7 30 135 Si(OMe)4 SOCl2 DMF 4 55 8 SiCl4 92 MeCl 66

3 8,9 11 47 Si(OMe)4 SOCl2 py stoich RT 48 SiCl4 10

5 28 128 Si(OMe)4 SOCl2 DMA 4 55 24 SiCl4 55

5 28 130 Si(OMe)4 SOCl2 Et3N 4 55 8 SiCl4 70

5 28 131 Si(OMe)4 SOCl2 imin 4 55 17 SiCl4 62

5 31 140 Si(OPr)4 SOCl2 DMF 4 55 32 SiCl4 46 PrCl 90 1 2 silane; most highly chlorinated silane produced. fold; the number of times of the stoichiometrically required amount of SOCl2. 3Currell’s reaction stoichiometry. 4Determined by 29Si NMR. 5Determined by distillation. 6Total yield from reaction flask and trap. 7 8 9 Estimated on assumption that trap contained 50% MeCl and 50% SO2. Exploratory experiment. Relative intensity of reactant and product with 29Si resonances.

158

Table 49. Alkoxysilane-HCl Runs 2 table run reactants cat HCl xs temp time silane silane Cl agent compound rel amount3 o (fold) ( C) (h) 1 32 147 Me3SiOMe 12 N HCl none 5 0 3 Me3SiCl 4

33 157 MeSi(OMe)3 HClg none 2 RT 1 MeSi(OMe)2Cl 10

38 173 Si(OMe)4 HClg none 0.8 RT 0.5 Si(OMe)3Cl 7

40 184 Si(OMe)4 HCll none 0.5 < -85 0.3 Si(OMe)3Cl 10 1Approximate HCl concentration of 78 mL/min. 2fold; the number of times of the stoichiometrically required amount of HCl. 3rel amount; relative intensity of product 29Si resonances with 10 being the most intense.

159

Table 50. Acetoxysilane-Thionyl Chloride Runs 1 table run reactants cat SOCl2 xs temp time silane silane Cl agent compound rel amount2 (fold) (oC) (h) 41 185 Si(OAc)4 SOCl2 none 25 120 6 Si(OAc)2Cl2 5

42 186 Si(OAc)4 SOCl2 DMF 13 120 0.2 SiCl4 10 1 2 fold; the number of times of the stoichiometrically required amount of SOCl2. rel amount; relative intensity of product 29Si resonances with 10 being the most intense..

160

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High-Aspect-Ratio, Conducting and Semiconducting Nanowires Derived from Scroll Polymers

Introduction

161

Introduction

Siloxane scroll polymers have been prepared from chrysotile, a scroll silicate,

Figures 4 and 5, by a process that has as its first step the excision of its silicate scroll with acid.42-50 The scroll silicic acid produced is then subjected to the addition of organic or organosilicon pendent groups by a grafting process. The overall process in the case of the

42,51 polymer having trimethoxysiloxy groups (C-M3) can be summarized as:

Mg3(OH)4Si2O5 + HCl + (CH3)3SiCl [((CH3)3SiO)x(OH)1-xSiO1.5]n (1)

chrysotile C-M3 scroll polymer

Figure 4. The structure of chrysotile (adapted from Guo, M. Synthesis and Characterization of Silicon Phthalocyanines for Photodynamic Therapy. Ph.D. Thesis, Case Western Reserve University, Cleveland, OH, 2008, used with permission).

162

- - - - -

------

(a) (b)

Figure 5. (a) Sheet silicate anion in chrysotile, (b) scroll in chrysotile formed by steric- hindrance enforced furling of its sheet (adapted from Boucher, M. Processable Sheet, Scroll, and Tube Organosilicon Polymers. Ph.D. Thesis, Case Western Reserve University, Cleveland, OH, 2003, used with permission).

It is believed that the excision and grafting processes take place simultaneously on a single sheet, and that the scrolls only partially unfurl during these two processes, Figure

6.52

The scroll architecture of the scroll polymers comes from steric interactions arising because all of the pendent groups are grafted on one side of the silicic acid sheet,

Figure 7.53-56 The size of the pendent group governs the spacing between the scroll sheets, Figure 8 and Table 51.53,42 A hollow core runs down the center of the scrolls.52

In general, chrysotile scrolls have several layers rolled up together, and as a consequence, scroll polymers derived from chrysotile also have several layers rolled up together,

Figure 9.43,52 163

Figure 6. Schematic representation of the protonation and silylation of a chrysotile scroll (adapted from Boucher, M. Processable Sheet, Scroll, and Tube Organosilicon Polymers. Ph.D. Thesis, Case Western Reserve University, Cleveland, OH, 2003, used with permission).

Figure 7. Sheet polymer in C-M3 (from Linsky, J. P.; Paul, T. R.; Kenney, M. E., Planar Organosilicon Polymers. J. Polym. Sci., 1971, 9, 143-160, used with permission).

164

Table 51. Intrasheet Spacing in Scroll Polymersa pendent group(s) chain length spacing (Å) O C-M3 Si 3 15

O C-CM2 Si CN 7 19

O C-ODM-CM2 Si 20 - 7 23

aAdapted from Boucher, M. Processable Sheet, Scroll, and Tube Organosilicon Polymers Ph.D. Thesis, Case Western Reserve University, Cleveland, OH, 2003.

intrasheet spacing

Figure 8. Intrasheet spacing in a scroll polymer.

Figure 9. Multisheet scroll polymer.

165

The polymers are not soluble in organic solvents but many of them swell to a

considerable extent in some organic solvents such as CCl4. When swollen, the polymers give gels that can be from stiff to fluid depending on the amount of solvent present.57-59

Some of the gels retain their solvent tenaciously. For example, the gel prepared from

60 CCl4 and C-M3 can be kept in a glass-stopper flask for many years.

Earlier work has shown that the hollow cores of C-M3 can be filled with lead acetate by treating a CHCl3 gel of C-M3 with a dimethylformamide solution of lead acetate and then drying the treated grid.61,52

CHCl Pb(OAc) DMF drying C-M 3 C-M gel-suspension 4 C-M /Pb(OAc) 3 3 solution 3 4

Other earlier work has shown that the cores of C-M3 can also be filled with a platinum species by treating a gel of C-M3 with a xylene solution of the platinum catalyst known as Karstedt’s catalyst, Pt[((CH2=CH)(CH3)2Si)2O]1.5, Figure 10 and then drying and heating the gel.61

CCl4 Karstedt’s cat drying C-M3 C-M3 gel heating C-M3/Pt

166

O Si Si Si Pt O Si

Figure 10. Structure of Pt[((CH2=CH)(CH3)2Si)2O]1.5 (Karstedt’s catalyst).

Here the core filling is assumed to be elemental platinum because Karstedt’s catalyst is easily thermally decomposed to platinum.

Objectives

The objectives of this study were to make high-aspect-ratio, highly conducting nanowires with or without organosilicon insulation, and to make high-aspect-ratio, semiconducting wires with or without organosilicon insulation.

167

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High-Aspect-Ratio, Conducting and Semiconducting Nanowires Derived from Scroll Polymers

Preparation and Characterization

168

Materials and Procedures

Scroll Polymers. The chrysotile was from Thetford, Quebec, Canada and was purchased from a minerals vendor (Ward’s Natural Science Establishment, Rochester,

NY). The other reagents and solvents were purchased from chemical vendors (e.g.

Aldrich, Fisher Scientific, and Gelest). Most of the chemicals were of reagent grade or better. The electron microscope specimen grids were 200 mesh gold grids with a Formvar carbon support film (Electron Microscopy Sciences, Fort Washington, PA). The vacuum used for filtration and oven drying (60 – 120 Torr) was from a house vaccuum line. The temperature of the drying oven was 80 oC.

Instruments and Apparatus

Infrared Spectroscopy

Infrared spectra were collected by the diffuse-reflectance technique with a

Spectra One spectrophotometer (Perkin-Elmer) equipped with a diffuse-reflectance accessory. The spectrophotometer was controlled with an Optiplex GX110PC computer

(Dell, Austin, TX). The samples were prepared with powdered KBr. Instrument settings used were: range, 4000 – 400 cm-1; resolution, 4 cm-1; background scans, 8; and sample scans, 8.

169

Powder X-ray Diffractometry

X-ray powder diffraction patterns were collected with a Scintag Model X1 diffractometer (Scintag, Cupertino, CA). The instrument settings used were: generator power, 45 KV, 40 mA; scan mode, continuous; 2 scan rate, 2o/min; 2 step size, 0.02o;

2 range, 1 to 50o; tube slit widths, scatter, 0.5 mm and divergence 1.0 mm; detector slit widths, scatter, 0.3 mm and receiving, 0.2 mm.

Transmission Electron Microscopy

The transmission-electron micrographs were collected with a JEM-

1200EX transmission electron microscope (JEOL, Japan). The filament used was tungsten, and the accelerating voltage was 80 kV.

Processing Methods

Some scroll polymer samples were sonicated with an ultrasonic cleaner (2510,

Branson, Inc. Danbury, CT).

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High-Aspect-Ratio, Conducting and Semiconducting Nanowires Derived from Scroll Polymers

Experimental Procedures

171

Scroll Polymer, C-M3

Chrysotile Preparation. Bulk chrysotile was torn into small pieces with tweezers

(HOOD).

Chrysotile-Derived Trimethylsiloxy Scroll Polymer, [((CH3)3SiO)x(OH)1-

53 xSiO1.5]n, C-M3. This synthesis was modeled on syntheses described in the literature. A mixture of a chrysotile (0.608 g, 2.20 mmol), trimethylchlorosilane (10 mL, 0.079 mol), hydrochloric acid (concentrated, 5 mL) and isopropanol (25 mL) was heated (82 oC) for

24 h, additional trimethylchlorosilane (5.0 mL, 0.04 mol) was added, and the mixture was heated (82 oC) for 7 days. The product was filtered, and the solid was washed

(isopropanol-concentrated HCl solution, 6:1, isopropanol, hexanes, acetone, acetone- water solution, 1:1), vacuum dried (50oC), and weighed (0.375 g, 83 % assuming x =

0.50). IR (diffuse reflectance, KBr, cm-1): 3208 (m, H-bonded OH str), 2963 (m, CH str),

2902 (m, CH str), 1418 (m, CH def), 1255 (m, SiCH2 def), 1077 (s, SiOSi str), 845 (m),

757 (w), 447 (m). XRD d, Å (I/I0): 15 (100).

The polymer is a white, paper-like solid. It is insoluble in CH2Cl2, dimethylformamide, ethanol, toluene, and hexanes. However, it swells in dimethylformamide, dimethyl sulfoxide, 2-nonanone, 10 cSt. polydimethylsiloxane,

CCl4, and n-decane.

172

C-M3 Fibers Partially Filled with Lead Sulfide

A mixture of C-M3 (2.2 mg) and CHCl3 (3.0 mL) (0.05 %), was sonicated for 1 h.

A small amount (several drops/grid) of the resulting fluid gel was placed on grids (gold,

200 mesh with a Formvar support film) and the preparations were allowed to air dry. The dried preparations were treated with a small amount (several drops/grid) of a solution of

Pb(CH3CO2)2·3 H2O (2.4 mg) and dimethylformamide (5.0 mL, 0.05 % Pb(CH3CO2)2·3

H2O) and allowed to air dry.

A set of these dried preparations was treated with a small amount (several drops/grid) of a solution of thioacetamide (2.4 mg) and dimethylformamide (5.0 mL, 0.05

% CH3C(S)NH2) and allowed to air dry.

Another set of these dried preparations was treated with H2S gas for 5 min.

173

C-M3 Fibers Partially Filled with Platinum

C-M3 (6.6 mg) and CCl4 (0.21 mL) (1:50) were mixed, and a portion of the resulting gel (0.2 mg) together with a xylene solution of Pt[((CH2=CH)(CH3)2Si)2O]1.5

(Karstedt’s catalyst, 2.0 - 2.5 % Pt, 0.42 g) was sonicated for 1 h. A small amount of the resulting fluid gel (two drops/grid) was placed on grids (gold, 200 mesh with a Formvar carbon support film), and the preparations were heated (160 oC) under vacuum (0.006

Torr) for 2 h, and then further heated (180 oC) under vacuum (0.006 Torr) for 1 h.

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High-Aspect-Ratio, Conducting and Semiconducting Nanowires Derived from Scroll Polymers

Results and Discussion

175

Results and Discussion

The earlier work on the filling of the cores of C-M3 with lead acetate gave rise to the present work on making C-M3 with cores filled with lead sulfide. The approach involved making C-M3 with lead-acetate filled cores, and then converting this lead- acetate filled C-M3 to lead-sulfide filled C-M3 with thioacetamide or H2S. (The C-M3 used in this work showed the expected infrared spectrum and X-ray powder pattern,

Figure 11).52,53

200 nm

Figure 12. Transmission electron micrograph of C-M3 scrolls with lead-acetate cores. Note their flexibility.

176

C-M3 C-M3

CH 15 Å

Si-CH3

SiO

IR XRD

Figure 11. The infrared spectrum and X-ray powder pattern of the C-M3 used in the platinum- and lead-filling studies.

Preparation of gels of C-M3 with lead-acetate filled cores in this work was patterned on the earlier work. The dried gels were composed of quite flexible fibers,

Figure 12.

The treatment of gels of the lead-acetate filled C-M3 with a thioacetamide solution or H2S gas and drying the product resulted in lead-sulfide filled C-M3. The presence of sulfur in the cores was verified with X-ray electron diffraction spectroscopy (XEDS),

Figure 13.

177

950

850

120 140 160 180 200 220 240 260 750

counts x 103

650

Figure 1 3 . XEDS scan showing the excitation edge of sulfur at 165 – 185 eV.

550

Transmission electron micrographs of the lead-sulfide filled C-M3 showed that in

some of the450 cores the filling was nearly complete, Figure 14. While this work was not extended with an intensive investigation, it does show that the scrolls can be filled with a

metal sulfide.

178

200 nm

(a)

200 nm

(b)

Figure 14. Transmission electron micrographs of lead-sulfide filled C-M3. 179

61 With the earlier work on C-M3 with platinum-filled cores in mind , extensions of it were undertaken. The C-M3 used in this work was the same as that used in the lead sulfide work. The procedure for filling the C-M3 cores with platinum was patterned on the earlier platinum work. Transmission electron micrographs of the platinum-filled

C-M3 made showed that some of the cores were filled with platinum for long distances,

Figure 15. This work was not carried further but it does show that long platinum wires sheathed in a methylsiloxane insulation can be made.

200 nm

Figure 15. Transmission electron micrograph of platinum filled C-M3.

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High-Aspect-Ratio, Conducting and Semiconducting Nanowires Derived from Scroll Polymers

Summary and Conclusions

181

Summary and Conclusions

The work on lead-sulfide filled C-M3 opens the possibility of filling the cores of scroll polymers with semiconductor species such as CdS and CdSe. The resulting semiconducting wires would be interesting because their diameter would be in the nanoparticle range, probably about 50 Å and their aspect ratio would be very high. As a consequence, they would be expected to have properties quite different than those of compact particles of the same semiconductors. If desired, the methylsiloxane scroll sheath of these semiconducting wires could be stripped off with hydrofluoric acid

(assuming the semiconducting wires were resistant to it) and bare semiconducting wires could be made.

The work on platinum filled C-M3 opens a way to make long methylsiloxane- insulated metal wires with nano-range diameters. Such wires could be of use in microelectronics. The insulation on these wires could be stripped off with hydrofluoric acid and thus bare platinum wires made. These could have a variety of uses, for example, in making supple, nonwoven platinum sheets for use as electromagnetic shielding.

182

Appendix A

Selected 29Si NMR Spectra

183

Si(OMe)3Cl

Si(OMe)2Cl2 Si(OMe)4

(ppm)

29 Figure 16. Si NMR spectrum of Si(OMe)3Cl and Si(OMe)2Cl2 from Si(OMe)4 with pyridinium chloride and SOCl2, run 1, Table 5, (CDCl3). 184

Si(OMe)2Cl2

Si(OMe)3Cl

Si(OMe)Cl3

(ppm)

29 Figure 17. Si NMR spectrum of Si(OMe)Cl3, Si(OMe)2Cl2 and Si(OMe)3Cl from Si(OMe)4 with pyridinium chloride and SOCl , run 3, Table 5, (CDCl ). 2 3 185

(ppm)

29 Figure 18. Si NMR spectrum of SiCl4 from Si(OMe)4 with pyridine and SOCl2 (4 fold excess), run 13, Table 9, (CDCl3).

186

SiCl4

Si(OMe)Cl3

(ppm) 29 Figure 19. Si NMR spectrum of SiCl4 and Si(OMe)Cl3 from Si(OMe)4 with pyridine and SOCl2 (stoichiometric), run 47, Table 11, (CDCl3). 187

(ppm)

29 Figure 20. Si NMR spectrum of Me3SiCl from Me3SiOMe with DMF and SOCl2, run 108, Table 24, (CDCl3). 188

(ppm) 29 Figure 21. Si NMR spectrum of Me2SiCl2 from Me2Si(OMe)2 with DMF and SOCl2, run 109, Table 24, (CDCl3). 189

(ppm)

29 Figure 22. Si NMR spectrum of MeSiCl3 from MeSi(OMe)3 with DMF and SOCl2, run 110, Table 24, (CDCl3).

190

(ppm)

29 Figure 23. Si NMR spectrum of SiCl4 from Si(OMe)4 with DMF and SOCl2, run 116, Table 28, (CDCl3). 191

SiCl4

Si(OMe)Cl3

(ppm) 29 Figure 24. Si NMR spectrum of SiCl4 and Si(OMe)Cl3 from Si(OMe)4 with Et3N and SOCl2, run 130, Table 28, (CDCl3). 192

(ppm) 29 Figure 25. Si NMR spectrum of SiCl4 from Si(OMe)4 with DMF and SOCl2, run 135, Table 30, (CDCl3). 193

(ppm) 29 Figure 26. Si NMR spectrum of SiCl4 from Si(OEt)4 with DMF and SOCl2, run 139, Table 31, (CDCl3). 194

(ppm) 29 Figure 27. Si NMR spectrum of SiCl4 from Si(OPr)4 with DMF and SOCl2, run 140, Table 31, (CDCl3). 195

(ppm) 29 Figure 28. Si NMR spectrum of SiCl4 from Si(OBu)4 with DMF and SOCl2, run 141, Table 31, (CDCl3). 196

unk

Me3SiCl

(ppm) 29 Figure 29. Si NMR spectrum of Me3SiCl from Me3SiOMe with HClaq, run 147, Table 32, (CDCl3). 197

unk

Me3SiCl unk

(ppm) 29 Figure 30. Si NMR spectrum of Me3SiCl from Me3SiOEt with HClaq, run 149, Table 32, (CDCl3). 198

(ppm) 29 Figure 31. Si NMR spectrum of Et3SiCl from Et3SiOEt with HClaq, run 151, Table 32, (CDCl3).

199

(ppm) 29 Figure 32. Si NMR spectrum of Me3SiCl from Me3SiOMe with HClg, run 152, Table 33, (CDCl3).

200

Me2Si(OMe)Cl

Me2SiCl2 unk

(ppm) 29 Figure 33. Si NMR spectrum of Me2SiCl2 and Me2Si(OMe)Cl from Me2Si(OMe)2 with HClg, run 153, Table 33, (CDCl3). 201

MeSi(OMe)Cl

MeSi(OMe)3

MeSi(OMe)Cl2

(ppm) 29 Figure 34. Si NMR spectrum of MeSi(OMe)Cl2 and MeSi(OMe)2Cl from MeSi(OMe)3 with HClg, run 154, Table 33, (CDCl3). 202

Si(OMe)4

Si(OMe)3Cl

unk

(ppm)

29 Figure 35. Si NMR spectrum of Si(OMe)3Cl from Si(OMe)4 with HClg, run 173, Table 38, (CDCl3).

203

Si(OEt)3Cl

Si(OEt)4

(ppm)

29 Figure 36. Si NMR spectrum of Si(OEt)3Cl from Si(OEt)4 with HClg, run 181, Table 39, (CDCl3).

204

Si(OPr)3Cl

Si(OPr)4

(ppm)

29 Figure 37. Si NMR spectrum of Si(OPr)3Cl from Si(OPr)4 with HClg, run 182, Table 39, (CDCl3). 205

Si(OMe)4

unk

Si(OMe)3Cl

(ppm) 29 Figure 38. Si NMR spectrum of Si(OMe)3Cl from Si(OMe)4 with HCll, run 184, Table 40, (CDCl3). 206

Si(OAc)3Cl

Si(OAc)2Cl2

(ppm) 29 Figure 39. Si NMR spectrum of Si(OAc)3Cl and Si(OAc)2Cl2 from Si(OAc)4 with SOCl2, run 185, Table 41, (CDCl3).

207

(ppm)

29 Figure 40. Si NMR spectrum of SiCl4 from Si(OAc)4 with SOCl2, run 186, Table 42, (CDCl3). 208

References

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2. Greenwood, N. N.; Earnshaw, A. Silicon. Chemistry of the Elements, 2nd ed.; Butteworth-Heinemann: Oxford, 1997; p 338.

3. Miessler, G. L.; Tarr, D. A. Inorganic Chemistry, 3rd ed.; Pearson Education: Upper Saddle River, N.J., 2004; p 225.

4. Seidel, A. Kirk-Othmer Encyclopedia of Chemical Technology, 5th ed.; Wiley: New York, 2006; Vol. 22 a) p 547; b) p 492-498.

5. Lyon, D. W.; Olson, C. M.; Lewis, E. D. Preparation of Hyper-Pure Silicon. J. Electrochem. Soc. 1949, 96, 359-363.

6. Butler, K. H.; Olson, C. M. Process for the Production of Pure Silicon in a Coarse Crystalline Form. U.S. Patent 2,773,745, Dec 11, 1956.

7. Torrey, H. C.; Whitmer, C. A. Crystal Rectifiers, Goudsmit, S. A., Linford, L. B., Lawson, J. L., Stone, A.M., Eds., McGraw-Hill: New York, 1948; pp 301-303.

8. Minerals Yearbook:Silicon, U.S. Geological Survey, Reston, VA, 2004.

9. Tokuyama Augments Polysilicon Project. Chem. Eng. News, May 16, 2011, p 16.

10. OCI Bets on Polysilicon. Chem. Eng. News, May 2, 2011, p 8.

11. Wacker Will Expand Silicon in Germany. Chem. Eng. News, Mar 21, 2011, p 22.

12. Einhaus, R.; Kraiem, J.; Cocco, F.; Caratini, Y.; Bernou, D.; Sarti, D.; Rey, G.; Monna, R., Trassy, C.; Degoulange, J.; Delannoy, Y.; Martinuzzi, S.; Perichaud, I.; Record, M. C.; Rivat, P. Photosil-Simplified Production of Solar Silicon from Metallurgical Silicon. Proceedings of the 21st European PVSEC, Dresden, 2006, pp 580-583.

13. Kroschwitz, J. Kirk-Othmer Encyclopedia of Chemical Technology, 4th ed.; Wiley: New York, 1991; Vol. 22, pp 31-36.

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14. Cotton, F.A.; Wikinson, G.; Murillo, C. A.; Bochmann, M. Advanced Inorganic Chemistry, 6th ed.; Wiley:New York, 1999; p 271.

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16. Rappoport, Z.; Apeloig, Y. Organosilicon Halides – Synthesis and Properties. In The Chemistry of Organic Silicon Compounds; The Chemistry of Functional Groups; Wiley: New York, 1991; Vol. 3, pp 470-471.

17. Hengge, E. in Gutmann, V. Inorganic Silicon Halides in Halogen Chemistry; Academic Press: New York, 1967; Vol. 2.

18. Basu, P. K. Development of a Process for the Manufacture of Silicon Tetrachloride from Rice Hulls. Ph. D. Thesis, University of California, Berkeley, 1972.

19. Secord, R. N. Manufacture of Silicon Tetrachloride. U.S. Patent 3,173,758, Mar. 16, 1965.

20. Eaborn, C. Organosilicon Compounds, Butterworths: London, 1960; a) p 127; b) p. 304; c) pp 312-318.

21. Currell, B. R.; Frazer, M. J.; Gerrard, W.; Haines, E.; Leader, L. Some Replacement Reactions on Silicon and Sulphur (IV) Atoms. J. Inorg. Nucl. Chem. 1959, 12, 45-48.

21a. Frohn, H. J.; Giesen, M.; Klose, A.; Lewin, A.; Bardin, V. V. A Convenient Preparation of Pentafluorophenyl(fluoro)silanes: Reactivity of Pentafluorophenyltrifluorosilane. J. Organomet. Chem. 1996, 506, 155-164.

22. Andrianov, K. A. Preparation of Silicon Tetrachloride and its Use as a Basis for Obtaining Silicic Acid Esters. Dokl. Akad. Nauk. SSSR 1940, 28, 66-69.

23. Breneman, W. C. In Catalyzed Direct Reactions of Silicon. Lewis, K. M., Rethwish, D. G., Eds.; Elsevier: Amsterdam, 1993, p 441.

24. Feasibility of the Silane Process for Producing Semiconductor Grade Silicon, Jet Propulsion Laboratory Contract 954334, June 1979.

25. White, L. J.; Duffy, G. L. Vapor-Phase Production of Colloidal Silica. Ind. Eng. Chem. 1959, 51(3), 232-238.

26. More Polysilicon for Solar Cells. Chem. Eng. News, Dec 20, 2010, p 10. 210

27. Kleinschmit, P. Silicas and Related Materials. Spec. Publ.- R. Soc. Chem. 1981, 40 (Spec. Inorg. Chem.) 196-225.

28. Seidel, A. Kirk-Othmer Encyclopedia of Chemical Technology, 5th ed.; Wiley: New York, 2004; Vol. 11, 138-139.

29. Li, B. S.; Zhu, X. F.; Zhang, Q. Gas Chromatographic Determination of Trace Trichlorosilane in High-Purity Tetrachlorosilane for Optical Fibers. Sepu 1994, 12(2), pp 108-109.

30. Kazakova, V. V.; Gorbatsevich, O. B.; Skvortsova, S. A.; Demchenko, N. V.; Muzafarov, A. M. Synthesis of Triethoxysilanol. Russ. Chem. Bull. Intern. Ed. 2005, 54(5), 1350-1351.

31. Vinogradova, S. V.; Pankratov, V. A.; Korshak, V. V.; Komarova, L. I.; Investigation of the Reaction of Thionyl Chloride with Dimethylformamide. Russ. Chem. Bull. 1971, 20(3), 450-455.

32. Craig, P. J.; Brinkman, U. K.; Brinkman, F. E. Occurrence and Pathways of Organometallic Compounds in the Environment-General Considerations. In Organometallic Compounds in the Environment: Principles and Reactions; Craig, P. J., Ed.; Wiley: New York, 1986.

33. Masaoka, S.; Banno, T.; Ishikawa, M. The Synthesis of Chlorosilanes from Alkoxysilanes, Silanols, and Hydrosilanes with Bulky Substituents. J. Organomet. Chem. 2006, 691, 174-181.

34. Gerrard, W.; Kilburn, K. D. Correlation between Reactivity of the 1-Carbon Atom in Alcohols, and Certain Properties of Alkoxysilanes. J. Chem. Soc. 1956, 1536- 1539.

35. Balthis, J. H. Silicon Tetraacetate. Inorg. Synth. 1953, 4, 45-47.

36. Mehrotra, R. C.; Pant, B. C. Reaction of Silicon Tetrachloride with Tertiary Butyl Acetate. A Novel Synthesis of Silicon Tetraacetate. Tetr. Letters 1963, 4(5), 321- 322.

37. Hyde, J. F. Chemical Background of Silicones. The Siloxane Linkage as a Structure-Building Device Gives Variety and Versatility to the Silicones. Science, 1965, 147, 829-836.

38. North, H. B.; Hageman, A. M. The Action of Thionyl Chloride on the Oxides of Metals and Metalloids. J. Am. Chem. Soc. 1913, 35(4), 352-356.

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39. Goodwin, G. B.; Kenney, M. E., A New Approach to the Synthesis of Alkyl Silicates and Organosiloxanes. ACS Sym Ser 1988, 360, 238-248.

40. Post, H. W.; Norton, H. M. Studies in Silico-Organic Compounds. IV. The Action of Organic Acid Halides and of Hydrohalogen Acids on Silico-Orthoesters. J. Org. Chem. 1942, 7(6), 528-533.

41. Chadwick, K. M.; Dhaul, A. K.; Halm, R. L.; Johnson, R. G. Catalytic Conversion of Direct Process High-Boiling Component to Chlorosilane Monomers in the Presence of Hydrogen Chloride. U. S. Patent 5, 292,912, Mar 1994.

42. Frazier, S. E.; Bedford, J. A.; Hower, J.; Kenney, M.E. Inherently Fibrous Polymer. Inorg. Chem. 1967, 6, 1693-1696.

43. Liebau, F. Structural Chemistry of Silicates; Springer: Berlin, 1985.

44. Fripiat, J. J.; Mendelovici, E. Organic Derivatives of Silicates. I. Chrysotile Methyl Derivative. Bull. Soc. Chim. Fr. 1968, 483-92.

45. Edwards, H. Study of the Reactions of Surface Hydroxyl Groups of a Crysotile Asbestos with Organic Silanes by Means of Infrared Spectroscopy. J. Appl. Chem. 1970, 20, 76-9.

46. Zapata, L.; Castelein, J.; Mercier, J. P.; Fripiat, J. J. Organic Derivatives of Silicates. II. Vinyl and Allyl Derivatives of Chrysotile and Vermiculite. Bull. Soc. Chim. Fr. 1972, 54-63.

47. Bleiman, C.; Mercier, J. P. Esterification of Chrysotile-Asbestos by Allyl Alcohol. Inorg. Chem. 1975, 14, 2853-4.

48. Yamashita, Y.; Kaziwara, M. Novel Silicon-Containing Resist, SCMR, for EB Lithography. J. Electrochem. Soc. 1990, 137, 3253-7.

49. Fonseca, M.G.; Oliveira, A.S.; Airoldi, C. Silylating Agents Grafted onto Silica Derived from Leached Chrysotile. J. Colloid Interface Sci. 2001, 240, 533-538.

50. Mendelovici, E.; Frost, R. L.; Kloprogge, J. T. Modification of Chrysotile Surface by Organosilanes: An IR-Photoacoustic Spectroscopy Study. J. Colloid Interface Sci. 2001, 238, 273-278.

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51. Lentz, C. W. Silicate Minerals as Sources of Trimethylsilyl Silicates and Silicate Structure Analysis of Sodium Silicate Solutions. Inorg. Chem. 1964, 3, 574-9. 52. Linsky, J. P.; Paul, T. R.; Kenney, M.E. Planar Organosilicon Polymers. J. Polym. Sci., Part A-2 1971, 9, 143-60.

53. Boucher, M.A. Processable Sheet, Scroll and Tube Organosilicon Polymers. Ph.D. Thesis, Case Western Reserve University, Cleveland, OH, August 2003.

54. Yang, J. C.-S. The Growth of Synthetic Chrysotile Fiber. Am. Mineral. 1961, 46, 748-52.

55. Yada, K.; Iishi, K. Growth and Microstructure of Synthetic Chrysotile. Am. Mineral. 1977, 62, 958-65.

56. Falini, G.; Foresti, E.; Lesci, G.; Roveri, N. Structural and Morphological Characterization of Synthetic Chrysotile Single Crystals. Chem. Commun. 2002, 1512-1513.

57. Chen, C.; Katsoulis, D. E.; Kenney, M. E. Sheet and Tube Siloxane Polymers Containing Multiple Pendent Organosilyl Groups. U.S. Patent 5,977,281, Nov 1999.

58. Chen, C.; Katsoulis, D. E.; Kenney, M. E. Silicone Gels and Composites from Sheet and Tube Organofunctional Siloxane Polymers. U.S. Patent 6,013,705, Jan 2000.

59. Chen, C.; Katsoulis, D. E.; Kenney, M. E. Sheet and Tube Siloxane Polymers Containing a Pendent Organo Functional Group. U.S. Patent 5,997,248, Nov 1999.

60. Kenney, M. E. Case Western Reserve University, Personal communication, June 2011.

61. Guo, M. Synthesis and Characterization of Silicon Phthalocyanines for Photodynamic Therapy. Ph.D. Thesis, Case Western Reserve University, Cleveland, OH, May 2008.

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Bibliography

Andrianov, K. A. Preparation of Silicon Tetrachloride and its Use as a Basis for Obtaining Silicic Acid Esters. Dokl. Akad. Nauk. SSSR 1940, 28, 66-69.

Balthis, J. H. Silicon Tetraacetate. Inorg. Synth. 1953, 4, 45-47.

Basu, P. K. Development of a Process for the Manufacture of Silicon Tetrachloride from Rice Hulls. Ph. D. Thesis, University of California, Berkeley, 1972.

Bleiman, C.; Mercier, J. P. Esterification of Chrysotile-Asbestos by Allyl Alcohol. Inorg. Chem. 1975, 14, 2853-4.

Boucher, M.A. Processable Sheet, Scroll and Tube Organosilicon Polymers. Ph.D. Thesis, Case Western Reserve University, Cleveland, OH, August 2003.

Breneman, W. C. In Catalyzed Direct Reactions of Silicon. Lewis, K. M., Rethwish, D. G., Eds.; Elsevier: Amsterdam, 1993, p 441.

Butler, K. H.; Olson, C. M. Process for the Production of Pure Silicon in a Coarse Crystalline Form. U.S. Patent 2,773,745, Dec 11, 1956.

Chadwick, K. M.; Dhaul, A. K.; Halm, R. L.; Johnson, R. G. Catalytic Conversion of Direct Process High-Boiling Component to Chlorosilane Monomers in the Presence of Hydrogen Chloride. U. S. Patent 5, 292,912, Mar 1994.

Chen, C.; Katsoulis, D. E.; Kenney, M. E. Sheet and Tube Siloxane Polymers Containing Multiple Pendent Organosilyl Groups. U.S. Patent 5,977,281, Nov 1999.

Chen, C.; Katsoulis, D. E.; Kenney, M. E. Silicone Gels and Composites from Sheet and Tube Organofunctional Siloxane Polymers. U.S. Patent 6,013,705, Jan 2000.

Chen, C.; Katsoulis, D. E.; Kenney, M. E. Sheet and Tube Siloxane Polymers Containing a Pendent Organo Functional Group. U.S. Patent 5,997,248, Nov 1999.

Cotton, F.A.; Wikinson, G.; Murillo, C. A.; Bochmann, M. Advanced Inorganic Chemistry, 6th ed.; Wiley:New York, 1999; p 271.

Craig, P. J.; Brinkman, U. K.; Brinkman, F. E. Occurrence and Pathways of Organometallic Compounds in the Environment-General Considerations. In 214

Organometallic Compounds in the Environment: Principles and Reactions; Craig, P. J., Ed.; Wiley: New York, 1986.

Currell, B. R.; Frazer, M. J.; Gerrard, W.; Haines, E.; Leader, L. Some Replacement Reactions on Silicon and Sulphur (IV) Atoms. J. Inorg. Nucl. Chem. 1959, 12, 45-48.

Eaborn, C. Organosilicon Compounds, Butterworths: London, 1960; a) p 127; b) p. 304; c) pp 312-318.

Edwards, H. Study of the Reactions of Surface Hydroxyl Groups of a Crysotile Asbestos with Organic Silanes by Means of Infrared Spectroscopy. J. Appl. Chem. 1970, 20, 76-9.

Einhaus, R.; Kraiem, J.; Cocco, F.; Caratini, Y.; Bernou, D.; Sarti, D.; Rey, G.; Monna, R., Trassy, C.; Degoulange, J.; Delannoy, Y.; Martinuzzi, S.; Perichaud, I.; Record, M. C.; Rivat, P. Photosil-Simplified Production of Solar Silicon from Metallurgical Silicon. Proceedings of the 21st European PVSEC, Dresden, 2006, pp 580-583.

Falini, G.; Foresti, E.; Lesci, G.; Roveri, N. Structural and Morphological Characterization of Synthetic Chrysotile Single Crystals. Chem. Commun. 2002, 1512-1513.

Feasibility of the Silane Process for Producing Semiconductor Grade Silicon, Jet Propulsion Laboratory Contract 954334, June 1979.

Fonseca, M.G.; Oliveira, A.S.; Airoldi, C. Silylating Agents Grafted onto Silica Derived from Leached Chrysotile. J. Colloid Interface Sci. 2001, 240, 533-538.

Frazier, S. E.; Bedford, J. A.; Hower, J.; Kenney, M.E. Inherently Fibrous Polymer. Inorg. Chem. 1967, 6, 1693-1696.

Fripiat, J. J.; Mendelovici, E. Organic Derivatives of Silicates. I. Chrysotile Methyl Derivative. Bull. Soc. Chim. Fr. 1968, 483-92.

Frohn, H. J.; Giesen, M.; Klose, A.; Lewin, A.; Bardin, V. V. A Convenient Preparation of Pentafluorophenyl(fluoro)silanes: Reactivity of Pentafluorophenyltrifluorosilane. J. Organomet. Chem. 1996, 506, 155-164.

Gerrard, W.; Kilburn, K. D. Correlation between Reactivity of the 1-Carbon Atom in Alcohols, and Certain Properties of Alkoxysilanes. J. Chem. Soc. 1956, 1536-1539.

215

Gerhartz, W. Ullmann’s Encyclopedia of Industrial Chemistry; Elvers, B., Hawkins, S., Russey, W., Schult, G., Eds., VCH Verlagsgesellschaft: Weinheim, 1986; Vol. A 24, p 8.

Goodwin, G. B.; Kenney, M. E., A New Approach to the Synthesis of Alkyl Silicates and Organosiloxanes. ACS Sym Ser 1988, 360, 238-248.

Greenwood, N. N.; Earnshaw, A. Silicon. Chemistry of the Elements, 2nd ed.; Butteworth-Heinemann: Oxford, 1997; p 338.

Guo, M. Synthesis and Characterization of Silicon Phthalocyanines for Photodynamic Therapy. Ph.D. Thesis, Case Western Reserve University, Cleveland, OH, May 2008.

Hengge, E. in Gutmann, V. Inorganic Silicon Halides in Halogen Chemistry; Academic Press: New York, 1967; Vol. 2.

Hyde, J. F. Chemical Background of Silicones. The Siloxane Linkage as a Structure- Building Device Gives Variety and Versatility to the Silicones. Science, 1965, 147, 829-836.

Kazakova, V. V.; Gorbatsevich, O. B.; Skvortsova, S. A.; Demchenko, N. V.; Muzafarov, A. M. Synthesis of Triethoxysilanol. Russ. Chem. Bull. Intern. Ed. 2005, 54(5), 1350-1351.

Kenney, M. E. Case Western Reserve University, Personal communication, June 2011.

Kleinschmit, P. Silicas and Related Materials. Spec. Publ.- R. Soc. Chem. 1981, 40 (Spec. Inorg. Chem.) 196-225.

Kroschwitz, J. Kirk-Othmer Encyclopedia of Chemical Technology, 4th ed.; Wiley: New York, 1991; Vol. 22, pp 31-36.

Kroschwitz, J. Kirk-Othmer Concise Encyclopedia of Chemical Technology, 4th ed.; Wiley: New York, 1999; pp 1809-1810.

Lentz, C. W. Silicate Minerals as Sources of Trimethylsilyl Silicates and Silicate Structure Analysis of Sodium Silicate Solutions. Inorg. Chem. 1964, 3, 574-9.

Li, B. S.; Zhu, X. F.; Zhang, Q. Gas Chromatographic Determination of Trace Trichlorosilane in High-Purity Tetrachlorosilane for Optical Fibers. Sepu 1994, 12(2), pp 108-109.

Liebau, F. Structural Chemistry of Silicates; Springer: Berlin, 1985. 216

Linsky, J. P.; Paul, T. R.; Kenney, M.E. Planar Organosilicon Polymers. J. Polym. Sci., Part A-2 1971, 9, 143-60.

Lyon, D. W.; Olson, C. M.; Lewis, E. D. Preparation of Hyper-Pure Silicon. J. Electrochem. Soc. 1949, 96, 359-363.

Masaoka, S.; Banno, T.; Ishikawa, M. The Synthesis of Chlorosilanes from Alkoxysilanes, Silanols, and Hydrosilanes with Bulky Substituents. J. Organomet. Chem. 2006, 691, 174-181.

Mehrotra, R. C.; Pant, B. C. Reaction of Silicon Tetrachloride with Tertiary Butyl Acetate. A Novel Synthesis of Silicon Tetraacetate. Tetr. Letters 1963, 4(5), 321-322.

Mendelovici, E.; Frost, R. L.; Kloprogge, J. T. Modification of Chrysotile Surface by Organosilanes: An IR-Photoacoustic Spectroscopy Study. J. Colloid Interface Sci. 2001, 238, 273-278.

Miessler, G. L.; Tarr, D. A. Inorganic Chemistry, 3rd ed.; Pearson Education: Upper Saddle River, N.J., 2004; p 225.

Minerals Yearbook:Silicon, U.S. Geological Survey, Reston, VA, 2004.

More Polysilicon for Solar Cells. Chem. Eng. News, Dec 20, 2010, p 10.

North, H. B.; Hageman, A. M. The Action of Thionyl Chloride on the Oxides of Metals and Metalloids. J. Am. Chem. Soc. 1913, 35(4), 352-356.

OCI Bets on Polysilicon. Chem. Eng. News, May 2, 2011, p 8.

Post, H. W.; Norton, H. M. Studies in Silico-Organic Compounds. IV. The Action of Organic Acid Halides and of Hydrohalogen Acids on Silico-Orthoesters. J. Org. Chem. 1942, 7(6), 528-533.

Rappoport, Z.; Apeloig, Y. Organosilicon Halides – Synthesis and Properties. In The Chemistry of Organic Silicon Compounds; The Chemistry of Functional Groups; Wiley: New York, 1991; Vol. 3, pp 470-471.

Secord, R. N. Manufacture of Silicon Tetrachloride. U.S. Patent 3,173,758, Mar. 16, 1965.

Seidel, A. Kirk-Othmer Encyclopedia of Chemical Technology, 5th ed.; Wiley: New York, 2004; Vol. 11, 138-139.

217

Seidel, A. Kirk-Othmer Encyclopedia of Chemical Technology, 5th ed.; Wiley: New York, 2006; Vol. 22 a) p 547; b) p 492-498.

Tokuyama Augments Polysilicon Project. Chem. Eng. News, May 16, 2011, p 16.

Torrey, H. C.; Whitmer, C. A. Crystal Rectifiers, Goudsmit, S. A., Linford, L. B., Lawson, J. L., Stone, A.M., Eds., McGraw-Hill: New York, 1948; pp 301-303.

Vinogradova, S. V.; Pankratov, V. A.; Korshak, V. V.; Komarova, L. I.; Investigation of the Reaction of Thionyl Chloride with Dimethylformamide. Russ. Chem. Bull. 1971, 20(3), 450-455.

Wacker Will Expand Silicon in Germany. Chem. Eng. News, Mar 21, 2011, p 22.

White, L. J.; Duffy, G. L. Vapor-Phase Production of Colloidal Silica. Ind. Eng. Chem. 1959, 51(3), 232-238.

Yada, K.; Iishi, K. Growth and Microstructure of Synthetic Chrysotile. Am. Mineral. 1977, 62, 958-65.

Yamashita, Y.; Kaziwara, M. Novel Silicon-Containing Resist, SCMR, for EB Lithography. J. Electrochem. Soc. 1990, 137, 3253-7.

Yang, J. C.-S. The Growth of Synthetic Chrysotile Fiber. Am. Mineral. 1961, 46, 748- 52.

Zapata, L.; Castelein, J.; Mercier, J. P.; Fripiat, J. J. Organic Derivatives of Silicates. II. Vinyl and Allyl Derivatives of Chrysotile and Vermiculite. Bull. Soc. Chim. Fr. 1972, 54-63.

218