Table Of Contents

ACKNOWLEDGEMENTS I would like to acknowledge Reed group members, past and present. I am grateful to Kee- Chan Kim, Mark Juhasz, Stephen Hoffman, Yun Zhang, Paul Richardson, James Wright, Gabe Mueck, and Matt Nava. A very special thank you is in order for Evgenii Stoyanov and Irina Stoyanov; both of whom taught me so much! Their insights to synthesis and infrared spectroscopy were invaluable. I am especially grateful to Dr. Christopher Reed, who let me explore synthetic chemistry and guided me wisely throughout the process. I would also like to acknowledge my colleagues at SBVC, Sheri Lillard, Susan Bangasser, John Stanskas, Michael Torrez, and Denise Bailey who have always encouraged me. I am very thankful and dedicate this dissertation to my husband Alvaro, and my children, AJ, Alex, and Andrew. Alvaro- you rock! Thank you for all of your support and for the coffee late at night…

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ABSTRACT OF THE DISSERTATION

Derivatives of the Dodecahalo-Closo-Dodecaborate Di-Anion by Amy Avelar Doctor of Philosophy, Graduate Program in Chemistry University of California, Riverside, December 2009-11-14 Dr. Christopher A. Reed, Chairperson

The di-anion, dodecahalo-closo-dodecaborate, B12X122–, where the X = Cl or Br, has been determined to be a useful weakly coordinating anion, WCA. Despite the dinegative charge, several elusive and reactive cationic species were stabilized with B12X122– as the counterion. Of particular interest was the synthesis of the di-protic acid, H2(B12X12),1 H2(B12X12) is the di-protic analogue to the recently developed strongest isolable mono-protic Brønsted acid, H(CHB11Cl11).2 The basicity of the di-anion, B12Cl122–, was shown to be surprisingly similar to basicity of the carborane anion, CHB11Cl111–, based on the νN-H anion basicity scale.3 The methodology used to synthesize the carborane acids was modified in order to successfully synthesize the di-protic acids, H2(B12X12). Several of the precursors to the acids are new compounds, and the precursors display remarkably similar properties as the analogous carborane compounds. The di-protic acids themselves are superacids due to

v

their ability to protonate arenes, such as benzene and toluene. 1 Also investigated was the stabilization of elusive di-cations with B12X122– counter-ions, and preliminary data are discussed in Chapter 6, including future work.

References 1. “Superacidity of Boron Acids H2(B12X12) (X= Cl, Br)” Avelar, A.; Tham, F.S.; Reed, C.A. Angew. Chem. 2009, 121, 3543-3545. (Angew Chem., Int. Ed. 2009, 48, 34913493.) 2. “The Strongest Isolable Acid,” Juhasz, M.; Hoffmann, S.; Stoyanov, E.; Kim, K.-C.; Reed, C.A. Angew. Chem. Int. Ed. 2004, 43, 5352-5255. 3. “An Infrared νNH Scale for weakly basic anions. Implications for Single-Molecule Acidity and Superacidity,” Stoyanov, E.S.; Kim, K.-C.; Reed, C.A. J. Am. Chem. Soc. 2006, 128, 8500-8508.

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Table of Contents

Acknowledgements ……………………………………………………………………... iv Abstract ………………………………………………………………………………...…v Table of Contents …………………………………………………………………….….vii List of Figures …………………………………………………………………………....xi List of Tables ………………………………………………………………………...…xvi List of Reaction Schemes ………………………………………………………...……xvii

CHAPTER 1 Introduction 1.1

Introduction ……………………………………………………………………….1

1.2

B12X122– (X = H or halogen) …………………………………..………………….3

1.3

Reagents and Reactive Cations …………………………………………………...6 1.3.1

Trityl Salts ………………………………………………………………...6

1.3.2

Silylium Ion-like Compounds ………………..………………….………..6

1.3.3

Brønsted Superacids ………………………………………………………7

1.3.4

Arenium Ions ………………….………………………………………….7

1.3.5

Stabilizing 2+ Cations …………………………………………………….8

1.4

Conclusions ……………………………………………………………………….9

1.5

References ………………………………………………………………………...7

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CHAPTER 2 Synthesis of Dodecahydro-closo-dodecaborate (B12H122–) Anion and its Halogenation 2.1

Introduction ……………………………………………………………………...13

2.2

Experimental …………………………………………………………………….14

2.3

Results and Discussion ………………………………………………………….17

2.4

Conclusions ……………………………………………………………………...27

2.5

References ……………………………………………………………………….28

CHAPTER 3 Synthesis of Trityl Salts and Silylium Derivatives with B12X122– 3.1

Introduction ……………………………………………………………………...30

3.2

Experimental …………………………………………………………………….31

3.3

Results and Discussion ………………………………………………………….34

3.4

Conclusions ……………………………………………………………………...61

3.5

References ……………………………………………………………………….62

CHAPTER 4 Synthesis of H2(B12X12) (X = Cl, Br) 4.1

Introduction ……………………………………………………………………...63

4.2

Experimental …………………………………………………………………….66

4.3

Results and Discussion ………………………………………………………….67

4.4

Conclusions ……………………………………………………………………...82

4.5

References …………………...…………………………………………………. 83

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CHAPTER 5 Isolation of Arenium Ions with B12X122– Counterions (X = Cl, Br) 5.1

Introduction ……………………………………………………………………...84

5.2

Experimental …………………………………………………………………….86

5.3

Results and Discussion ………………………………………………………….88

5.4

Conclusions ………………………………………………………………..…...102

5.5

References ……………………………………………………………………...103

CHAPTER 6 Di-cationic Targets, Methyl Derivatives, and Future Work with B12X122– (X = Cl, Br) 6.1

Introduction ………………………………………..……………………...……104

6.2

Experimental ……………………………………………………………….…..106

6.3

Results and Discussion ………………………………………………………...108

6.4

Conclusions …………………………………………………………………….129

6.5

References ……………………………………………………………………...130

Appendix A. X-ray Structure Determination for [Ph3C]2[B12Br12]·2toluene ………...131 A.1 Experimental Details ………………………………………………………………131 A.2 Structure Data ……………………………………………………………………..134 A.2.1 Crystal structure and refinement data for [Ph3C]2[B12Br12]·2toluene …...134 A.2.2 Atomic Coordinates ……………………………………………………..135 A.2.3 Bond Lengths and Angles ……………………………………………….136 A.2.4 Anisotropic Displacement Parameters .....................................................142

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A.2.5 Hydrogen Coordinates ..............................................................................143 A.3 References ……………………………………………………………………..… 144

Appendix B. X-Ray Structure Determination for [Ph3C]2[B12Cl12]·2C6H4Cl2 …..…..145 B.1 Experimental Details ………………………………………………………………145 B.2 Structure Data ……………………………………………………………………..147 B.2.1 Crystal data and structure refinement for [[C6H5]3C]2[B12Cl12].2[C6H4Cl2] ………………………………………………………………………………….147 B.2.2 Atomic Coordinates …………………………………………………..…149 B.2.3 Bond Lengths and Angles ………………………………………………152 B.2.4 Anisotropic Displacement Parameters ………………..…………………164 B.2.5 Hydrogen Coordinates …………………………………………………..167 B.3 References ………………………………………………………………………....168

Appendix C. X-Ray Structure Determination for ((C2H5)3Si)2(B12Br12)·ODCB …….169 C.1 Experimental Details ………………………………………………………………169 C.2 Structure Data ……………………………………………………………………...170 C.2.1 Crystal structure and refinement data for ((C2H5)3Si)2(B12Br12)·ODCB ..170 C.2.2 Atomic Coordinates ……………………………………………………...171 C.2.3 Bond Lengths and Angles ……………………………………………….173 C.2.4 Anisotropic Displacement Parameters …………………………………..182

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C.2.5 Hydrogen Coordinates …………………………………………………..183 C.3 References …………………………………………………………………………185

Appendix D. X-Ray Structure Determination for ((C2H5)3Si)2(B12Cl2) ……………..186 D.1 Experimental Details ………………………………………………………………186 D.2 Structure Data ……………………………………………………………………..188 D.2.1 Crystal data and structure refinement for ((C2H5)3Si)2(B12Cl12) ………..188 D.2.2 Atomic Coordinates ……………………………………………………..189 D.2.3 Bond Lengths and Angles ……………………………………………….190 D.2.4 Anisotropic Displacement Parameters …………………………………..196 D.2.5 Hydrogen Coordinates …………………………………………………..197 D.3 References …………………………………………………………………………197 List of Figures Figure 1.1

B12X122– where X = H or halogen ………..………………..……………...3

Figure 2.1

11

Figure 2.2

1

Figure 2.3

11

Figure 2.4

1

Figure 2.5

11

Figure 2.6

11

Figure 2.7

1

B NMR spectrum of Na2[B12H12] ...……………………...…………….19

H NMR spectrum of Na2[B12H12] in D2O …………….………………..20 B NMR spectrum of crude Na2[B12H12] (unreferenced) .……...………21

H NMR spectrum of crude Na2[B12H12] in D2O ………….…………….22 B NMR spectrum of Cs2[B12Cl12] in reaction solution (unreferenced) ..23 B NMR spectrum of Na2[B12Br12] in reaction solution (unreferenced) .24

H NMR spectrum of Cs2[B12Cl12] in D2O ……………………………...24

xi

Figure 2.8

1

Figure 2.9

FT-IR spectrum of Ag2[B12Br12] ………………………………………...26

Figure 2.10

FT-IR spectrum of Ag2[B12Cl12] ………………………………………...26

Figure 3.1

1

H NMR spectrum of Na2[B12Br12] in D2O ……………………………..25

H NMR (CD3CN) spectrum of [Ph3C]2[B12Br12] before heating the solid

………………………………………………………………………...… 36 Figure 3.2

1

H NMR (CD3CN) spectrum of [Ph3C]2[B12Br12] after heating the solid

……………………………………………………………………………33 Figure 3.3

11

B NMR (CD3CN) spectrum of [Ph3C]2[B12Br12] after heating the solid

……………………………………………………………………………38 Figure 3.4

FT-IR spectrum of [Ph3C]2[B12Br12] after heating the solid …………….38

Figure 3.5

1

H NMR (CD3CN) spectrum of [Ph3C]2[B12Cl12] before heating the solid

……………………………………………………………………………39 Figure 3.6

1

Figure 3.7

11

Figure 3.8

FT-IR spectrum of [Ph3C]2[B12Cl12] after heating ………………………41

Figure 3.9

Thermal ellipsoid plot of [Ph3C]2[B12Br12]·2 toluene ……..…………….42

Figure 3.10

Thermal ellipsoid plot of [Ph3C]2[B12Cl12]·2 ODCB ……………………44

Figure 3.11

1

Figure 3.12

11

Figure 3.13

1

Figure 3.14

11

Figure 3.15

FT-IR spectrum of (Et3Si)2(B12Br12) synthesized in toluene ....................50

H NMR (CD3CN) spectrum of [Ph3C]2[B12Cl12] after heating the solid. 40 B NMR (CD3CN) spectrum of [Ph3C]2[B12Cl12] after heating the solid.40

H NMR spectrum of (Et3Si)2(B12Br12) in ODCB-d4 ................................47 B NMR spectrum of (Et3Si)2(B12Br12) (unreferenced) ...........................47

H NMR spectrum of (Et3Si)2(B12Cl12) in ODCB-d4 ……………………48 B NMR spectrum of (Et3Si)2(B12Cl12) (unreferenced) ...........................48

xii

Figure 3.16

FT-IR spectrum of [Et3Si–H–SiEt3]+ with B12Br122– ……………………51

Figure 3.17

FT-IR spectrum of [Et3Si–H–SiEt3]+ with B12Cl122–………………...…..51

Figure 3.18

FT-IR spectrum of (Et3Si)2(B12Br12) .........................................................52

Figure 3.19

FT-IR spectrum of (Et3Si)2(B12Cl12) .........................................................53

Figure 3.20

Thermal ellipsoid plot of (Et3Si)2(B12Cl12) ….…………………………..54

Figure 3.21

Thermal ellipsoid plot of (Et3Si)2(B12Br12)·C6H4Cl2 …..………………..56

Figure 4.1

Infrared spectra of the νNH (>3000 cm–1) for trioctylammonium salts with (a) B12Cl122– in CCl4, (b) B12Cl122– in CH2Cl2, and (c) B12Br122– in CH2Cl2 ....................................................................................................................6 9

Figure 4.2

Infrared spectra of the νN–H (>3000 cm–1) for trioctylammonium salts in the solid state with (a)B12Cl122– and (b) B12Br122– ………………………70

Figure 4.3

FT-IR spectrum of Hx(B12Br12) mixture ………………………………...72

Figure 4.4

FT-IR spectrum of H(CHB11Cl11) …………………………………….…73

Figure 4.5

FT-IR spectrum of H2(B12Cl12) ………………………………………….74

Figure 4.6

FT-IR spectrum of H2(B12Cl12) after computer subtraction of impurities.74

Figure 4.7

ATR spectrum of H2(B12Br12) showing a Gaussian fit (green) to one of the bands associated with the bridging proton ………………………………75

Figure 4.8

11

Figure 4.9

1

Figure 4.10

1

Figure 4.11

FT-IR spectrum of H(SO2)2+ with B12Br122– …………………………….78

B NMR spectrum of H2(B12Cl12) in SO2 …………………………..…..76

H NMR spectrum of H2(B12Cl12) in SO2 ……………………………….77 H NMR spectrum of SO2 ……………………………………………….77

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Figure 4.12

11

Figure 4.13

1

Figure 4.14

FT-IR spectrum of air-exposed H2(B12Cl12) showing formation of H5O2+

B NMR spectrum of H(H2O)n(B12Br12) in SO2 ………………………..72

H NMR spectrum of H(H2O)n(B12Br12) in SO2 ………………………...80

and H7O3+ salts .......................…………………………………………...81 Figure 5.1

H0 Scale of Protic Acids and Their Ability to Protonate Arenes ..............85

Figure 5.2

Portions of the FT-IR spectrum of benzenium with B12X122– counterions89

Figure 5.3

FT-IR spectrum of [C6H7]2[B12Cl12] …………………………………….90

Figure 5.4

FT-IR spectrum of [C6H7]2[B12Br12] …………………………………….90

Figure 5.5

1

H NMR spectrum of benzenium dissolved in SO2 with B12Cl122– at -50 °C

……………………………………………………………………………92 Figure 5.6

FT-IR spectrum of toluenium ion salt, [C7H9]2[B12Cl12] ………………..93

Figure 5.7

FT-IR spectrum of toluenium ion salt, [C7H9]2[B12Br12] ………………..93

Figure 5.8

FT-IR spectrum of mesitylenium ion salt, [C9H13]2[B12Cl12] …………...94

Figure 5.9

1

Figure 5.10

1

Figure 5.11

Thermal ellipsoid plot of [C4H9O]2[B12Br12]·C6H6 ……………………..97

Figure 5.12

Di-cationic Target ……………………………………………………….99

Figure 5.13

Thermal

H NMR spectrum of Mesitylenium with B12Br122- in CD2Cl2 at -20 °C .95 H NMR spectrum of Mesitylenium with B12Br122- in CD2Cl2 at 25 °C ..96

ellipsoid

plot

of

the

tetramethylbenzenium

and

pentamethylbenzenium ..…………………………………………….…100 Figure 6.1

13

C NMR spectrum of (CH3)2(B12Br12) containing excess methyl triflate in

SO2 at –60 °C ..........................................................................................110 Figure 6.2

13

C NMR spectrum of methyl triflate in SO2 ..........................................111

xiv

Figure 6.3

13

C NMR spectrum of (CH3)2(B12Br12) containing excess methyl triflate in

SO2 at 25 °C ............................................................................................112 Figure 6.4

Partial 1H NMR spectrum of (CH3)2(B12Br12) containing excess methyl triflate in SO2 at –60 °C ..........................................................................113

Figure 6.5

1

H NMR spectrum of (CH3)2(B12Br12) containing excess methyl triflate in

SO2 at –60 °C ..........................................................................................113 Figure 6.6

1

Figure 6.7

1

H NMR spectrum of methyl triflate in SO2 ...........................................114 H NMR spectrum of (CH3)2(B12Br12) containing excess methyl triflate in

SO2 at 25 °C ............................................................................................115 Figure 6.8

11

B NMR spectrum of (CH3)2(B12Br12) containing excess methyl triflate in

SO2 at –60 °C (external reference BF3·OEt2) .........................................116 Figure 6.9

11

B NMR spectrum of (CH3)2(B12Br12) containing excess methyl triflate in

SO2 at 25 °C ............................................................................................117 Figure 6.10

13

Figure 6.11

1

Figure 6.12

11

Figure 6.13

FT-IR spectrum of (CH3)2(B12Br12) containing excess methyl triflate ...122

Figure 6.14

ATR of neat methyl triflate .....................................................................122

Figure 6.15

FT-IR spectrum of (CH3)2(B12Br12) ........................................................123

Figure 6.16

FT-IR spectrum of (CH3)2(B12Br12) with excess methyl triflate after

C NMR spectrum of (CH3)2(B12Br12) at -60 °C in SO2 .......................118

H NMR spectrum of (CH3)2(B12Br12) in SO2 at –60 °C ........................119 B NMR spectrum of (CH3)2(B12Br12) in SO2 at –60 °C ......................120

pumping ..................................................................................................124 Figure 6.17

11

B NMR spectrum (in SO2 at –40 °C) of MexB12Br12 synthesized at 25 °C

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..................................................................................................................125 Figure 6.18

11

B NMR spectrum (in SO2 at –40 °C) of MexB12Cl12 synthesized at 25 °C

..................................................................................................................12 5 Figure 6.19

ATR of (CH3)2(B12Cl12) synthesized in neat methyl triflate ...................126

Figure 6.20

X-Ray Crystal Structure of [(Et3Si)Me4N2]2[B12Cl12] ............................127

Figure 6.21

X-ray Structure of Monoprotonated Tetramethylhydrazine ...................128

Figure 6.22

Structure of [Et3SiN2(CH3)4][Et3Si(B12Br12)] ………………………..129

List of Tables Table 3.1

Crystal structure and refinement data for [Ph3C]2[B12Br12]·2 toluene .….43

Table 3.2

Crystal structure and refinement data for [Ph3C]2[B12Cl12]·2 ODCB …..45

Table 3.3

Selected Bond Angles ….………………………………………………..54

Table 3.4

Crystal data and structure refinement data for (Et3Si)2(B12Cl12) ………..55

Table 3.5

Crystal structure and refinement data for (Et3Si)2(B12Br12)· ODCB ……57

Table 3.6

Selected Bond Angles …………………………………………………...58

Table 3.7

Key Bonding Distances and Angles of Et3Si compounds with B12X122– Anions……………………………………………………………………59

Table 3.8

Key Bonding Distances and Angles of Et3Si compounds with CHB11X11– (X = halogen or H) Anions ………...……………………………………60

Table 4.1

νN-H, in cm–1, for Octyl3NH+ salts in CCl4 …….....…………………….68

Table 4.2

νN–H, in cm1–, with different anions ………………………...………….71

Table 5.1

Frequencies of Benzenium versus Counter-ion (a: ref. 6; b: ref. 4) …….88 xvi

Table 5.2

Crystal data and structure refinement for [C4H9O]2[B12Br12]·C6H6 …….98

Table 5.3

Crystal data and structure refinement for cr308_0m ………………..…101

Table 6.1

Methyl Group Modes (cm–1) ...................................................................121

List of Reaction Schemes Reaction Scheme 2.1 Synthesis of B12H122– from decaborane ……………………...….13 Reaction Scheme 2.2 Synthesis of M2[B12H12] M = Na or Cs ……………………..…..18 Reaction Scheme 2.3 Halogenation of B12H122–…………………………………...……23 Reaction Scheme 3.1 Synthesis of [(C6H5)3C]2[B12X12] ……………………………….35 Reaction Scheme 3.2 Synthesis of (Et3Si)2(B12X12) ........................................................46 Reaction Scheme 4.1 Protonation of Mesityl Oxide .........................................................65 Reaction Scheme 5.1 Proposed Synthesis of Di-cationic Target ………………………100 Reaction Scheme 6.1 Synthetic Route A to [Me6N2][B12X12] ........................................109 Reaction Scheme 6.2 Synthetic Route B to [Me6N2][B12X12] ........................................109 Reaction Scheme 6.3 Synthesis of [(Et3Si)Me4N2]2[B12X12] ..........................................127

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