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Derivatization chemistry of mono-carboranes

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Derivatization chemistry of mono-carboranes

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Content DERIVATIZATION CHEMISTRY OF MONO-CARBORANES by Janet Hillary Manning A Thesis Presented to the FACULTY OF THE GRADUATE SCHOOL UNIVERSITY OF SOUTHERN CALIFORNIA In Partial Fulfillment of the Requirements for the Degree Master of Science (Chemistry) May 1997 Copyright 1997 Janet Hillary M anning R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. U N IVERSITY O F S O U T H E R N C A L IFO R N IA t h e g r a d u a t e s c h o o l U N IV E R S IT Y P A R K L O S A N G E L E S . C A L IF O R N IA 9 0 0 0 7 This thesis, written by Janet Hillary Manning_______________ under the direction of Thesis Committee, and approved by all its members, has been pre sented to and accepted by the Dean of The Graduate School, in partial fulfillment of the requirements for the degree of Master of Science DateIS^3I.ZAh..JJ.2J THESIS COMMITTEE ^ / f K i b S r V m V — a ■ Chairman R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. In m em ory of my Grandfather, Edward Mills R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. . . .I've finally decided, my future lies beyond the yellow brick ro a d ... . Bemie Taupin Goodbye Yellow Brick Road From the record album of the same name. Copyright 1973 This Record Co. Ltd. R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. ACKNOWLEDGMENTS D uring m y hiatus from industry in returning to pursue an advanced degree, there are a great m any to thank for different reasons. Firstly, to Professor Chris Reed for giving me a wonderful project to w ork on. Though tough at times his guidance has proved invaluable to me. Secondly, I thank past research advisors Professor Tom Flood of U.S.C and Professor Wayne Tikkanen of California State University, Los Angeles. Tom Flood taught me to think as a both an inorganic and organic chemist. Wayne Tikkanen taught me just about everything I know about organometallic chemistry laboratory techniques. Being part of the carborane project in the Reed group was a especially good job. Professor Zuowei Xie, Dr. Rob Reed, and Dr. Raj M athur all were good teachers and fun to work with. I'm lucky to have had advice from Professor Peter Boyd visiting from the University of Auckland. Many of my successful experiments came from ideas discussed w ith him. And in the lab, Rob Reed often proved to be a strong right hand, always willing to help out. I feel I had a great teaching position in organic chemistry with lab director Dr. James Ellem and all my fellow teaching assistants. Their m oral support and friendship, often needed, was greatly appreciated. i v R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. My special thanks and good wishes go to my labmate Raj M athur and his wife M ary Drabnis for their friendship and colorful carpool rides to and from the lab. Sorry Raj, the dishes are all yours to do now. There was alw ays a laugh after hours w ith fellow group members, especially M argaret Kosal, Bob Bolskar, and Marc Hombeck. I will miss having coffee and a good gossip with them. W hen I w asn't in the lab I m ay have been w ith David VanVliet who did his best to make me forget chem istry for awhile. Finally, my love and thanks goes out to my family for their support. My husband, Mark, first opposed me studying his field of boron chem istry, however after seeing how m uch I liked it, backed me completely. My sister Pamela was always there to listen w hen times were less than perfect. And even though she's a political sociologist telling her you had a rough day in class or lab didn't prevent her from understanding and sym pathizing. Pictures of my X-ray crystal structures still hang on her refrigerator. v R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. TABLE OF CONTENTS PAGE DEDICATION.............................................................................................. ii ACKNOWLEDGMENTS.......................................................................... iv LIST OF TABLES........................................................................................ xii UST OF FIGURES...................................................................................... xiv ABSTRACT.................................................................................................. xviii CHAPTER 1- INTRODUCTION: (1-TRIMETHYLAMINE-l-CARBA-CLOSO) DODECABORANE and the 1-CARBA-CLOSO-DODECABORATE ANION.................................................................... 1 1.1 Boranes and Mono-carbon C arboranes 1 1.2 Synthesis of the Parent Carboranes.................... 3 1.3 (1-Trimethylamino-lcarba-cZoso) dodecaborane.......................................................... 5 1.4 Weakly Coordinating Anions............................. 6 1.5 The 1-Carba-doso-dodecaborate Anion........................................................................ 7 1.6 Derivatives of the Parent Carborane, l-Carba-c/oso-dodecaborate: Approaching an Even More W eakly Coordinating Anion.............................................. 7 1.7 Summary.................................................................. 9 1.8 References................................................................. 11 vi R eproduced with perm ission of the copyright owner. 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PAGE CHAPTER 2- DERIVATIVES of (1-TRIMETHYLAMINE-1-CARBA-CL0S0) DODECABORANE............................................... 14 2.1 Introduction............................................................ 14 2.2 Experimental........................................................... 16 2.2.1 Reagents and Technique.......................... 16 2.2.2 C/oso-l-NM e3-12-BrCBnHi0................ 16 2.2.3 Pd(0) Coupling Reaction of C/oso-l-NMe3-12-B rC B nH io with MeMgBr............................................. 17 2.3 Results and Discussion......................................... 17 2.3.1 C/oso-l-NM e3-12BrCBnHio................. 17 2.3.2 Evidence for the Substitution of Closo-l-N M e3-12BrCBnH io.................. 20 2.4 Sum m ary................................................................. 26 2.5 References................................................................ 27 CHAPTER 3- MONO and DI-HALOGENATION OF (CESIUM) (1-CARBA-CLOSO) DODECABORATE................................................ 29 3.1 Introduction............................................................ 29 3.2 Experimental........................................................... 30 3.2.1 Reagents and Technique.......................... 30 vii R eproduced with perm ission of the copyright owner. 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PAGE 3.2.2 Cs[c/oso-12-ICBiiHii].............................. 30 3.2.3 Cs[c/oso-7-I-12-BrCBnHio]................... 30 3.3 Results and Discussion......................................... 31 3.3.1 Cs[doso-12-ICBiiH n].............................. 31 3.3.2 Cs[doso-7-I-12-BrCBnHio]................... 31 3.4 Sum m ary.................................................................. 35 3.5 References................................................................ 36 CHAPTER 4- (CESIUM) (l-CARBA-(7-12)-HEXAIODO) CLOSO-DODECABORATE................................. 37 4.1 Introduction............................................................. 37 4.2 Experimental........................................................... 37 4.2.1 Reagents and Technique.......................... 37 4.2.2 Cs[doso-(7-12)-l6CBnH6]...................... 37 4.3 Results and Discussion......................................... 39 4.3.1 Synthesis..................................................... 39 4.3.2 One- and Two-dimensional NM R 41 4.4 Sum m ary.................................................................. 46 4.5 References................................................................. 47 v iii R eproduced with perm ission of the copyright owner. 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PAGE CHAPTER 5- (SILVER(I)) (l-CARBA-(7-12)-HEXAIODO-CLOSO) DODECABORATE................................................. 48 5.1 Introduction............................................................. 48 5.2 Experimental............................................................ 49 5.2.1 Reagents and Technique......................... 49 5.2.2 Ag[doso-(7-12)-l6CBnH6]....................... 50 5.2.3 Reaction of Ag[c/oso-(7-12)-l6CBnH6l w ith FeCp(CO)2l....................................... 50 5.3 Results and Discussion......................................... 51 5.3.1 Synthesis..................................................... 51 5.3.2 One- and Two-dimensional NM R 51 5.3.3 X-ray Crystallography.............................. 55 5.3.4 IR Spectroscopy......................................... 60 5.4 Sum m ary.................................................................. 66 5.5 References................................................................. 66 CHAPTER 6- (TRESOPROPYLSILYL) (l-CARBA-(7-12)-HEXAIODO-CLOSO) DODECABORATE................................................. 76 6.1 Introduction............................................................. 76 6.2 Experimental............................................................ 77 6.2.1 Reagents and Technique.......................... 77 ix R eproduced with perm ission of the copyright owner. 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PAGE 6.2.2 [Ph3C] [c/oso-(7-12)-I6CBhH6]............... 78 6.2.3 i-Pr3Si[c/oso-(7-12)-l6C B iiH 6]................ 78 6.2.4 NMR Scale Preparation of z-Pr3Si[cZoso-(7-12)-l6C B iiH 6 ]................ 79 6.3 Results and Discussion..................................................... 79 6.3.1 Synthesis...................................................... 79 6.3.2 NMR Spectroscopy of [PI13C] [c/oso-(7-12)-l6CBnH6]............................. 80 6.3.3 NMR Spectroscopy of (i-Pv^Si) [doso-(7-12)-l6CBnH6]............................. 86 6.3.4 X-ray Crystallography of (z-Pr3Si) [doso-(7-12)-l6CBnH6]............................. 87 6.4 Sum m ary................................................................... 96 6.5 References................................................................. 97 CHAPTER 7- CONCLUSION AND FUTURE PROSPECTS.......................................... 108 7.1 Sum m ary................................................................... 108 7.2 References................................................................. I l l SELECTED BIBLIOGRAPHY.................................................................... 112 x R eproduced with perm ission o f the copyright owner. Further reproduction prohibited without perm ission. PAGE APPENDIX 1- REAGENTS AND TECHNIQUE......................... 114 A l.l Reagents................................................................... 114 Al.1.1 Solvents............................................ 114 Al.1.2 Other Materials.............................. 114 A1.2 Technique................................................................ 115 A1.3 References................................................................ 115 APPENDIX 2- PHYSICAL MEASUREMENTS........................... 116 A2.1 Nuclear Magnetic Resonance (NMR) Spectroscopy.......................................................... 116 A2.2 Infrared (IR) Spectroscopy................................... 116 A2.3 Elemental Analysis................................................ 117 A2.4 X-ray Crystallography........................................... 117 A2.5 References................................................................ 117 x i R eproduced with perm ission of the copyright owner. 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LIST OF TABLES TABLE PAGE 1 A bbreviations..................................................................... 10 5.1 Carbonyl Stretching Frequencies for FeCp(CO)2Y Systems......................................................... 49 5.2 Crystal Data for Ag [closo- (7-12)-l6CBnH6]................................................................. 68 5.3 Data Collection for Ag [closo- (7- 12)-l6CBnH6]................................................................ 69 5.4 Solution and Refinement for Ag [closo- (7-12)-I6CB 11H6]................................................................. 70 5.5 Bond Lengths (A) for Ag [closo- (7-12)-I6C B iiH 6I................................................................ 71 5.6 Bond Angles (deg) for Ag [closo- (7-12)-I6C B iiH 6]................................................................ 72 5.7 Atomic Coordinates (xlO^) and Equivalent Isotropic Displacement Coefficients (A^ x 10^) for Ag [c/oso-(7-12)-l6CBnH6]........................................ 74 5.8 Anisotropic Displacement Coefficients (A^ x 10^) for Ag [doso-(7-12)-l6CBnH6]........................................ 75 6.1 Specific Geometrical Parameters for /-Pr3Si[doso- (7-12)-I6C B iiH 6]................................................................ 88 6.2 Collective Key Geometrical Param eters for i-Pr3Si[doso- (7-12)-X6CBnH6]...................................... 91 6.3 Crystal Data for z-Pr3Si[c/oso- (7-12)-I6C B h H 6]................................................................ 99 xii R eproduced with perm ission o f the copyright owner. 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TABLE PAGE 6.4 Data Collection for i-Pr^Si[closo- (7-12)-I6CBiiH6]................................................................. 100 6.5 Solution and Refinement for z-Pr3Si[doso- (7- 12)-I6CBi i H6]................................................................. 101 6.6 Bond Lengths (A) for z'-Pr3Si[doso- (7-12H6CBhH6]................................................................. 102 6.7 Bond Angles (deg) for z-Pr3Si[doso- (7-12)-l6CBnH6]................................................................. 103 6.8 Atomic Coordinates (xlO^) and Equivalent Isotropic Displacement Coefficients (A^ x 10^) for z-Pr3Si[doso-(7-12)-l6C B n H 6]................................. 105 6.9 Anisotropic Displacement Coefficients (A^ x 10^) for z-Pr3Si[doso-(7-12)-l6C B n H 6]................................. 106 6.10 H-Atom Coordinates (xlO^) and Isotropic Displacement Coefficients (A^ x 10^) for z-Pr3Si[doso-(7-12)-l6C B n H 6]......................................... 107 xiii R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. LIST OF FIGURES FIGURE PAGE 1.1 N um bering and Structure of the C B n H nXmZp Fram ework.............................................. 2 1.2 Synthesis of Cs[c/oso-CBhHi2]....................................... 4 1.3 Synthesis of C/oso-l-NMe3- C B n H n ............................ 4 2.1 Proposed Catalytic Cycle in the Reaction of (l-Trim ethylam ine-l-carba-12-brom o-c/oso) dodecaborane with M ethyl M agnesium Bromide................................................................................. 15 2.2 llB NMR (86.7 MHz) of CZoso-l-NMe3- C B n H n . Proton Decoupled Spectrum (lower), Coupled Spectrum (top), in Acetone d£.................. 18 2.3 llB NMR (86.7 MHz) of C/oso-l-NM e3-12- BrCBuHiO- Proton Decoupled Spectrum (lower), Coupled Spectrum (top), in Acetone d6 ....................... 19 2.4 a) llB {lH} NMR (86.7 MHz) of C/oso-l-NM e3-12-B rC B n H io in THF w ith one equivalent (Ph3 P)4P d................................... 21 b) Initial H b {lH} NM R (86.7 MHz) of CZoso-l-NMe3-12-B rC B n H io in THF w ith one equivalent (Ph3P)4Pd and five equivalents of Methyl M agnesium Brom ide........................ 21 c) llB {lH} NMR (86.7 MHz) after two weeks at 65 °C of the C /oso-l-N M e3-12-BrCBnH io, (Ph3 P)4Pd, MeMgBr System in THF................ 22 xiv R eproduced with perm ission o f the copyright owner. Further reproduction prohibited without perm ission. FIGURE PAGE 2.4 d) llB {lH} NMR (86.7 MHz) after three weeks at 65 °C of the Closo-l-N M e3-12-B rC B nH io, (Ph3P)4Pd, MeMgBr System in THF...................................................................... 22 e) llB {lH} NMR (86.7 MHz) after one m onth at 65 °C of the C/0S 0-l-N M e3-12-B rC B nH io, (Ph3P)4Pd, MeMgBr System in THF................ 23 f) llB NMR 86.7 MHz) after one m onth and 72 hrs at 65 °C of the C/oso-l-NMe3 -12- B rC B uH io, (Ph3P)4Pd, MeMgBr System in THF. Proton Decoupled Spectrum (left), Coupled Spectrum (right).................................... 23 3.1 llB NMR (86.7 MHz) of Cs[CZoso-CBnHi2 ]. Proton Decoupled Spectrum (lower), Coupled Spectrum (top), in Acetone d(,........................................ 32 3.2 llB NMR (86.7 MHz) of Cs[cZoso-12-ICBnHn]. Proton Decoupled Spectrum (lower), Coupled Spectrum (top), in Acetone d6........................................ 33 3.3 a) llB NMR {lH} (86.7 MHz) of Cs[c/oso-12-Br- C B iiH n ] in Acetone d&................................................... 34 b) H b NMR {lH} (86.7 MHz) of Cs[cZoso-12-Br-7- IC B uH io] in Acetone ds................................................. 34 4.1 1 : 5 : 5 H b NMR Integration Ratio for the Borons in the [CZoso-CBnHi2]‘ A nion................ 40 4.2 llB NMR (86.7 MHz) of Cs[closo- (7-12)-I6CBhH6]. Proton Decoupled Spectrum (lower), Coupled Spectrum (top), in DME................................................... 42 xv R eproduced with perm ission o f the copyright owner. Further reproduction prohibited without perm ission. FIGURE PAGE 4.3 n B NMR {iH} (160.46 MHz) of Cs[c/oso-CBnHi2] in Acetone ds...................................................................... 43 4.4 2-D H b-11b COSY {^H} NMR (160.46 MHz) of Cs[c/oso-CBnHi2] in Acetone ds................................... 44 4.5 2-D llB -H B COSY {^H} NMR (160.46 MHz) of Cs[c/oso-(7-12)-l6CBnH6] in Acetone d(,..................... 45 5.1 n B {lH} NMR (160.46 MHz) of Ag [c/oso-(7-12)- I6CB11H 6] in Acetonitrile d3.......................................... 52 5.2 n B NMR (86.7 MHz) of A g [closo-(7-12)- I6CB11H 6]. Proton Decoupled (lower), Coupled (top), in M ethanol/DM E................................... 54 5.3 2-D llB -n B COSY {^H} NMR (160.46 MHz) of Ag [c/oso-(7-12)-l6CBnH6] in Acetonitrile d3 ...................................................... 56 5.4 X-ray Crystal Structure of Ag [c/os0-(7-12)-l6C B n H 6]............................... 57 5.5 X-ray Crystal Structure of Ag [closo-(7- 12)-l6CBnH6] displaying the alternating polymeric chain arrangem ent.... 59 5.6 a) IR Spectrum at 48 hrs of FeCp(CO)2l and Ag [c/oso-(7-12)-l6CBnH6] in Toluene 61 b) IR Spectrum of FeCp(CO)2l in Toluene 62 c) E R Spectrum at Time-Zero of FeCp(CO)2l and Ag [c/oso-(7-12)-l6CBnH6] in Toluene.... 63 d) IR Spectrum at 1 & 1 /2 hrs of FeCp(CO)2l and Ag [c/oso-(7-12)-l6CBnH6] in Toluene.... 63 xvi R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. FIGURE PAGE e) IR Spectrum at 3 & 1/2 hrs of FeCp(CO)2l and Ag [closo-(7-l2)-lsCBnHs\ in Toluene.... 64 f) IR Spectrum at 20 hrs of FeCp(CO)2l and Ag [doso-(7-12)-l6CBnH6] in Toluene 64 6.1 n B NMR (86.7 MHz) of [Ph3C] [doso-(7-12)- l6C B n H 6]- Proton Decoupled Spectrum (lower), Coupled Spectrum (top), in Acetone ds....................................................................... 81 6.2 13C {lH} NMR (90.56 MHz) of [PI13C] [doso-(7-12)- I6CB11H 6] in Acetone ds.................................................. 82 6.3 iH NMR (250 MHz) of [PI13C] [doso-(7-12)- I6CB11H 6] displaying the phenyl region in Acetone ds............................................................................ 83 6.4 HB {lH} NMR (86.7 MHz) of z-Pr3Si [closo- (7-l2)-lsC B iiH s] in Toluene dg..................................... 85 6.5 Proposed Interaction betw een the B(7) Iodine and the Tri-isopropyl Silyl Moiety in Toluene dg............................................................................ 86 6.6 X-ray Crystal Structure of z'-Pr3Si [closo- (7- 12)-l6CBnH6].................................................................. 89 6.7 Scheme of the A pproach Towards the Silylium Ion.......................................................................... 93 xvii R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. ABSTRACT Brom ination and evidence for alkylation of the tw elve-position of l-trim ethylam ine-l-carba-doso-dodecaborane is dem onstrated. M onoiodination of the twelve position by a new method, 12-bromo-7- iodo-halogenation, and /iexaiodination of the lower pentagonal belt [7- 12 positions] of cesium 1-carba-doso-dodecaborate has been accomplished. The silver(I), triphenylm ethyl, and triisopropylsilyl complexes of the l-carba-(7-12)-Jie;nziodo-doso-dodecaborate anion have been isolated. Selected one-dim ensional ^H, ^ C , H-B, and two- dim ensional 11B-Hb COSY NMR spectra are presented. The silver(I) and triisopropylsilyl complexes have been analyzed by X-ray crystallography. xviii R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. CHAPTER ONE INTRODUCTION: 1-TRIMETHYLAMINE-l-CARBA-CLOSO-DODECABORANE and the 1-CARBA-CLOSO-DODECABORATE ANION 1.1 Boranes and M ono-Carbon Carboranes Closo- boranes (boron hydrides) have the general formula [BnHn]2 " 1 All skeletal and terminal B-H electron pairs are accounted for as being in bonding sets of molecular orbitals.^ A lthough one could say that these clusters are electron deficient since the bonding is not entirely two-electron-two-centered, they are formally considered electron-precise.^ W hen a B-H unit is replaced by a C-H unit in a borane the num ber of skeletal electrons increases by one. Therefore, the newly form ed carborane of the formula [CBnHn + l] need now only be singly charged: [CBn Hn+ l]_1. The mono-carbon carborane, [doso-C B nH i2]" is of this type and is pseudo-arom atic electronically and chemically. It is show n in Figure 1.1 w ithout the hydrogens on boron or carbon. It's electron count mimics that of benzene in that the fram ework pairs are found entirely in bonding molecular orbitals in which a large HOMO-LUMO gap exists.^ The electrons are considered to be delocalized over the cage fram ew ork w ith some variation in electron density, vida infra? 1 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. Figure 1.1 Num bering and Structure of the C B iiH nXmZp, Framework n + m + p = 12 With the n = 12 geometry, the size of this moiety is equivalent to that bonds undergo many of the aromatic substitution reactions similar to benzene and subsequent reactivity is affected by substituents already on The reactivity of the boron cage may be explained in terms of the difference between borane and isostructrual carborane. Substitution of a two-electron B-H donor with a three-electron C-H donor results in electron density to be relatively greater in the lower pentagonal belt of the cage (positions 7-11, and 12, Figure 1.1).2 Not w ithstanding is the fact the C-H bond is electrophilic in nature owing 0 = b of a benzene ring spinning on its two-fold axis.4 Chemically, the B-H 2 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. to the greater electronegativity of carbon compared to boron, or that carbon is a three electron donor, whereas boron contributes two electrons to the skeletal framework. Recent theoretical calculations show that electron density at the carbon-hydrogen bond is less than at the boron-hydrogen ones.3 The major chemical change at boron is increased nucleophilicity of the lower pentagonal belt and the antipodal 12-boron resulting in the propensity for electrophilic substitution. Nucleophilic C-H substitution occurs. Both B-H and C-H substitution has been accomplished.^'^ 1.2 Synthesis of the Parent Carboranes Both starting materials, c/oso-l-NMe3- C B n H n 9 (the carbon in Figure 1.1 would have a NMe3 group instead of a hydrogen) and the [closo-CB iiH i 2]" ^ are derived from decaborane, B10H 14. Their synthesis is show n in Figures 1.2 and 1.3. As an alternate route to the anion, c/oso-l-NMe3- C B n H n m ay be converted to [doso-C B nH i2]" by Birch reduction (treatm ent w ith sodium in liquid am m onia).7/10 The cage closure step (use of Et3N*BH3 ) is of use in Boron Neutron Capture Therapy (BNCT) w here 10b may be inserted, and in using Et3N:BRH2 (R = alkyl) to form 2-B or 7-B alkylated c/oso-carboranes.H/12 C/oso-l-NMe3- C B n H n is considered zwitterionic since the trim ethylam ine nitrogen is formally four-coordinate. The NM e3 group does not dissociate under norm al circumstances from the carbon of the carborane. 3 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. bm h „ O j r ^ b, o„ j3 _c n 1 ^ 6. NCBioHi32. y g H a . . OH', Me?SOA 1 neutralize^ Csci + 2 NaOH + NMe, + 0.5 H * ' C-^oH^ -NaCl ___ ___ EVBH3 _ Cs Icloso- CBuHjJ Cs [T-CB^H-^] 200" C, 24 hr. Cesium 1-carba-c/oso- dodecaborate Figure 1.2 Synthesis of Cs[ closo- CB1:lH 12] 7-Me3N-7- d) EtjN B Hj, 200* C, 24 hr. CB10HU ► Nfe2HNCB11H11 (2) MeOH (3) NaOH aq J M e2S0 4 , 24 hr. Me3NCB11Hu 1-T rimethylamine- 1- carba-c/oso- dodecaborane Figure 1.3 Synthesis of Closo- l-NMe^-CB11H 11 [C/oso-CBnHi2]" is an anion and may be isolated as its cesium, sodium, potassium, tetraalkylammonium, and trimethylammonium salts. R eproduced with perm ission o f the copyright owner. Further reproduction prohibited without perm ission. Since these two parent carboranes are differently charged and substituted, the chemistry of each is expected to be different i.e. a neutral m olecule vs. an anionic one. In the context of this thesis the reactivity of CZoso-l-NMe3-C B iiH n has been exploited so that eventually a substituted anion may be formed from the initially treated zwitterion. The chemistry of [doso-CBnH i2]" has been dedicated to producing new and unique boron substituted anions, to study their reactivity and subsequently create a more weakly coordinating anion. 1.3 1-Trimethvlamino-l-carba-cZoso-dodecaborane The X-ray crystal structure of this molecule has been r e p o r t e d .13 The synthesis is outlined in Figure 1.3. Cage closure from the nido- carborane precedes complete methylation of the amino group. In fact, a m ethyl group is removed in the closure process. There are synthetic problem s in using a mono- or di-methylated amino group in that they behave as weak N-acids with pKa's of 6.5 and 5.7 respectively.^ Clearly, the need for a trim ethylamino group is needed to prevent unw anted side reactions during substitution of the B-H hydrogens. Similar trim ethylam ine carbon substituted species in which one of the boron hydrogens is replaced by a PhCH2- group (Ph = C6H5) has been reported.H In this case, closure of the cage came after substitution at boron. Cage rearrangem ent of the alkyl containing boron to the 7- position of the closo- molecule occurs in the process. W ithout such rearrangem ent the alkyl group would be at the 2-position of the closo- molecule. It is uncertain whether initial or further substitution may take place through the use of mono-alkyl boranes i.e. RBH2 or 5 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. RBX2 (X = Cl). These have been used in the cage closure of nido- anionic mono-carbon carboranes with the alkyl group on the 2-position of the closo- species. 12,14 Little substitution chemistry of this molecule has been reported, perhaps due to the inertness of the trim ethylated nitrogen in the case of C-substitution, or the difficulty of rem oving the trim ethylam ino group to form the anion. Consequently, there exists a lack of knowledge as to the behavior of a substituted zwitterion upon treatm ent w ith sodium in liquid ammonia in order to cleave the trim ethyl group to yield an anion. 1.4 W eakly Coordinating A nions Interest in anions that only weakly co o rd in ate^ stems from the desire to achieve a higher level of reactivity in a chemical system. Minimal interaction is the key to having a truly weakly coordinating anion. Desirable features of such an anion are large size, low charge, none or few lone electron pairs, chemical inertness, solubility in low dielectric solvents, low nucleophilicity, and suitable therm al stability. Strauss in a recent review outlined the anions, past and present, of chemical interest. 16 Am ong the more popular of these are the tetraarylborates [(C6F5)4B]‘, and [(3,5-CF3-C6H3)4B]‘; the "teflates" of the type B(OTeF5 )4"; Sb2F n ', and the monoanionic closo-carboranes. The usefulness of these anions comes with coordinatively unsaturated cations, such as Zeigler-Natta-type polymerization catalysts.^ R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. 1.5 The 1-Carba-cZoso-dodecaborate Anion O ut of the weakly coordinating anions above, the carboranes perhaps hold the most promise. The fluorinated tetraarylborates are presently competitive but further developm ent is unlikely (plain tetraarylborate anion is prone to decomposition); the teflates dissociate. In contrast [c/oso-CBnHi2]" is large in size, has no lone pairs, and is therm ally stable. First synthesized by Knoth and co-workers in 1967,17,18 debut as "The Least Coordinating Anion" was not until 1986 by Shelly and R e e d 19 where the Fe(TPP) (TPP = tetraphenylporphyrinate) "cation" was compared with I", OCIO3", FSbFs", and [c/oso-CBnHi2 ]" as coordinating anions. Their results show ed that the carborane anion displayed the weakest axial ligand field, resulting in a lowering of the spin multiplicity of Fe(HI) and a contraction of the porphyrin core; implying that it is the weakest binding anion in this system. It's low nucleophilicity is dem onstrated in the formation of a donor-acceptor adduct between Ag[c/oso- CB11H 12] and Vaska’ s com pound (IrCl(CO)(PPh3)2), in contrast to expected metathesis reaction to form silver chloride.20 1.6 Derivatives of the Parent Carborane \Closo-CB n H i 2l“: Approaching an Even M ore W eakly Coordinating A nion Proven as a weakly coordinating anion, the design of derivatives of this parent carborane was a step further towards the isolation of other cations and design of more reactive polym erization systems. In the course of previous work, it was discovered that the silver(I) complex of [c/oso-CBnH i2 ]- is light sensitive and the B-H 7 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. bonds of the lower belt are prone to abstraction (B-12 is the most reactive, followed by B-7).21 This precludes use in m ore highly reactive cationic system s such as the form ation of the trityl salt, [Ph3C ][C B nH i2] w here there is evidence of B-H substitution with the trityl cation to form a 12-B-CPh3 bond on the anion and H+.8 Hexa- halogenation using excess brom ine or chlorine has since yielded the c/0so-(7-12)-Br6CBnH6" and closo-(7- 12)-Cl6CBnH6" anions respectively .6 Treatm ent of these w ith an alkyl lithium reagent followed by addition of an alkyl halide yields the C-alkylated-/ze.r«- halogenated a n i o n .8 N-butyllithium is the base of choice, although MeLi, MeCuLi, or other bases such as MeMgBr or lithium diisopropyl am ide w ould m ost likely be effective as well. By limiting the am ount of reagent or using a m ilder reagent such as N-brom osuccim ide, only the 12-B or 7,12-B positions may be substituted^ These /zexahalogenated anions are considerably m ore stable than [c/oso-CBnH i2]“ as their silver(I) complexes, and they also have been isolated as their trityl reagents. A recent accom plishm ent has been the close approach to the ion-like silylium complex of R3Si,22-24 with the silicon in it's m ost planar geometry to date using c/oso-(7-12)- C l6C B nH 6“ as anion, and R = isopropyl on silicon. Silver(I)closo~(7~ 12)-Br6CBnH6 reacts with Fe(TPP)Br to produce w hat could be term ed a free Fe(TPP)+ cation in the sense that there is no coordination by the new anion: {Ag[c/0so-(7-12)-Br6CBnH6]2}"- It is twice as large as the closo-(7- 12)-Br6CBnH6~ anion with the sam e charge. While this new 8 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. anion is not isolable as a useful metathesis reagent, the synthetic challenge remains to do so. 1.7 S um m ary As enorm ous as the am ount of research in recent times has been, the beauty of this chem istry lies in the wealth of still unexplored areas. Electronic experiments via C- or B-substitution, asymmetric induction by a chiral auxiliary group or chiral carborane itself, novel substitution chem istry (alkyl, halogen, heteroatom or a combination of these), or the building of even bigger forms of the anion for use in reactive cationic systems still rem ain to be studied. Both C-alkyl and heteroatom , and B-mercury and halogen- substitution have been accomplished.^ B-alkylation and B-(7-ll) iodination have been reported,26 however this was after Reed, Xie, and M anning reported fzexaiodination of the lower pentagonal belt of the anion.27 Fluorination of [c/oso-CBnHi2]" has also recently been reported by Strauss and co-workers.28 After the synthesis of hexachloro and hexabromo derivatives of the C B iiH l2 " anion, and the success of the hexabromo anion as a weakly coordinating species, further halogenation using iodine or fluorine became the next step. The obvious test of these would be to isolate the silylium ion, m easure the 29si NMR chemical shift (the m ore downfield shift would show a weaker coordination by the anion in a weakly coordinating solvent such as toluene), the I.R. carbonyl stretching frequency, vCO, of the CpFe(II)(CO)2 moiety with the hexa- iodo carborane as the coordinating anion (the more coordinating the 9 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. anion to Fe(II), the lower the vCO 29) f measure the Hf3 NMR chemical shift of the silver(I) salt in a non-coordinating solvent in order to observe which site was most-coordinating, and finally to obtain the X- ray crystal structure of an [R3Si]+[c/oso-(7,12)-l2CBnHio]" so as to determ ine which of these substituted positions is the m ore coordinating. In the course of research to make a new Ziexahalogenated anion, new i o d i n a t e d 2 4 , 2 7 anci an alkylated species were isolated and observed respectively, and new synthetic methods developed for substitution of both the carborane anion and the 1-trimethylamino zwitterion. Table 1 Abbreviations 1-T rim ethylam ine-l-carb a-closo- dodecaborane.................................... .closo-1 -NM e3-CB 11 H i l l-Trim ethylam ine-l-carba-12-brom o-c/oso- dodecaborane...................................................... c/oso-l-NMe3-12- B rC B nH io 1-Carba-c/oso-dodecaborate anion, [closo-C B iiH i2]" Cesium 1-carba-c/oso-dodecaborate Cs[c/oso-CBiiHi2 ] l-Carba-12-iodo-c/oso-dodecaborate anion [c/oso-12-ICBiiHii]' Cesium l-carba-12-iodo-c/oso-dodecaborate Cs[c/oso-12-ICBnHn] 1 0 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. Table 1 Continued. l-Carba-7-iodo-12-bromo-c/oso- dodecaborate anion..................................................[cZoso-7-I-l2-BrCB 11H 10 ]" Cesium l-carba-7-iodo-12-bromo-c/oso- dodecaborate.......................................................... Cs[closo-7- I-12-BrCBnHio] l-Carba-(7-12)-hexaiodo-c/oso- dodecaborate anion.....................................................[cZoso-(7-12)-l6CBnH6]- or C B nH 6l6“ (hexa iodo) l-Carba-(7-12)-hexabromo-cZoso- dodecaborate anion..................................................[c/oso-(7-12)-Br6CB i \ H6]- or CBnH 6Br6" (hexabromo) l-Carba-(7-12)-hexachloro-cZoso- dodecaborate anion.................................................. [cZoso-(7-12)-Cl6CBnH6]' or CBnH 6C l6" (hexachloro) C esium , or Silver(I), or Trityl or T riisopropylsiiyl l-carba-(7-12)- hexaiodo-cZoso-dodecaborate Cs[cZoso-(7-12)l6CBnH6], or Ag[cZoso-(7-12)l6CBnH6], or [Ph3C] [doso-(7-12)l6CBnH6], or Z-Pr3Si[cZoso-(7-12)l6CBnH6] 1.8 References 1. Purcell, K. F.; Kotz, J. C. Inorganic Chemistry, W. B. Saunders Company, Philadelphia, 1977. 2. Williams, R. E. Chem. Rev. 1992, 92, 177. 3. Green, T. A.; Switendick, A. C.; Emin, D. /. Chem. Phys. 1988,89, 6815. 4. Grimes, R. N. et al. Angezv. Chem. Int. Ed. Engl. 1993, 32, 1289. 11 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. References Continued. 5. Grimes, R. N. Carboranes Academic Press, New York, 1970. 6. Jelinek, T; Plesek, J.; Herm anek, S.; Stibr, B. Collect. Czech. Chem. Commnn. 1984, 52, 819. 7. Plesek, J.; Jelinek, T.; Drdadova, E.; Hermanek, S.; Stibr, B. Collect. Czech. Chem. Comman. 1983, 49, 1559. 8. Jelinek, T.; Baldwin, P.; Scheidt, W. R.; Reed, C. A. Inorg. Chem. 1993, 32, 1982. 9. Knoth, W. H.; Little, J. L.; Lawrence, J. R.; Scholer, F. R.; Todd, L. J. Inorg. Synth. 1968, 11, 33. 10. Plesek, J.; Jelinek, T.; Stibr, B. Polyhedron 1984, 3, 1351. 11. Jelinek, T.; Plesek, J.; Mares, F.; Hermanek, S.; Stibr, B. Polyhedron 1987, 6, 1981. 12. Mair, F. S.; Morris, J. H.; Gaines, D. F.; Powell, D. /. Chem. Soc. Dalton Trans. 1993, 135. 13. Maly, K.; Subrtova, V.; Petricek, V. Acta Cryst. 1987, C43, 593. 14. Mair, F. S.; Martin, A.; Morris, J. H.; Peters, G. S.; Spicer, M. D. /. Chem. Soc., Chem. Commnn. 1993, 1058. 15. Seppelt, K. Angew. Chem. Int. Ed. Engl. 1993, 32, 1025. 16. Strauss, S. H. Chem. Rev. 1993, 93, 927. 17. Knoth, W. H. J. Am. Chem. Soc. 1967, 89, 1274. 18. Knoth, W. H. Inorg. Chem. 1971, 10, 598. 19. Shelly, K.; Reed, C. A. /. Am. Chem. Soc. 1986, 108, 3117. 20. Liston, D. J.; Reed, C. A.; Eigenbrot, C. W.; Scheidt, W. R. Inorg. Chem. 1987, 26, 2739. 12 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. References C ontinued. 21. Shelly, Kenneth, Ph.D. Dissertation, D epartm ent of Chem istry, University of Southern California, 1985. 22. Reed, C. A.; Xie, Z.; Bau, R.; Benesi, A. Science 1993,262, 402. 23. Xie, Z.; Bau, R.; Benesi, A.; Reed, C. A. Organometallics 1995,14,3933. 24. Xie, Z.; Manning, J.; Reed, R. W.; M athur, R.; Boyd, P. D. W.; Benesi, A.; Reed, C. A. /. Am. Chem. Soc. 1996, 118,2922. 25. Xie, Z.; Bau, R.; Reed, C. A. Angew. Chem. Int. Ed. Engl. 1994,33,2433. 26. This reaction has been independently investigated by Janousek, Z.; Griiner, B.; Trammel, M.; Michel, J. 209th ACS Meeting Abstracts, Anaheim, CA 1995, ORG 315. 27. Reed, R. W.; Xie, Z.; Manning, J.; M athur, R.; Bau, R.; Reed, C. A. Phosphorus, Sulfur, Silicon, and the Related Elements 1994, 93, 45. 28. Strauss, S. H. et al. Inorg. Chem. 1995, 34, 6419. 29. Xie, Z.; Jelinek, T.; Bau, R.; Reed, C. A. J. Am. Chem. Soc. 1994,116,1907. R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. CHAPTER 2 DERIVATIVES OF 1-TRIMETHYLAMINE-l-CARBA-CLOSO-DODECABORANE 2.1 Introduction Halogenation of the twelve-position of this zw itterion has not been previously reported. Bromination might be m ore facile w ith the zwitterion, c/oso-l-N M e3-C B iiH n, as the anion precursor. While direct brom ination w ith Br2 may be possible, and has show n to be so in the analogous anionic systems, it is also less selective yielding 7-, 12-, and 7,12-bromo-anions. N-bromosuccimide (NBS) has been show n to be a selective reagent in brominating the allylic position of alkenes.l NBS forms elemental bromine as the reaction proceeds, providing a constant steady source of reagent that may preferentially brom inate at the most reactive 12-position. The general reaction, a single step synthesis, is show n in the equation: Closo-l-N M e3 -C B iiH n + NBS ----------- > C/oso-l-NMe3-12-BrCBnHio The zw itterion once brom inated in the twelve-position is now a suitable candidate for a palladium(O) mediated coupling reaction in the presence Grignard reagent.2'9 The proposed catalytic cycle is show n in Figure 2.1. 1 4 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. Figure 2.1 Proposed Catalytic Cycle in the Reaction of l-Trimethylamine-l-carba-12-bromo-c/oso-dodecaborane with Methyl Magnesium Bromide. CbBr = closo- l-NM^-12-BrCBn H1 0 Pd(Cb) = closo- l-NMe3 -12-PdCBn H1 0 CbMe = closo- l-NM^-12-MeCBn H1 0 CbBr eMgBr CbMe Figure 2.1 is similar to that reported by H aw thorne and co workers for the diiodinated closo-9,12-12-1,2-C2B10H 10 where a Pd(PPh3 )2Cl2 /C u I system is used instead of Pd(PPh3)4.1^ in their scheme the G rignard reagent first reacts with Cul to form CuR, which in turn reacts w ith the oxidative-addition product of iodinated carborane and Pd(0); Pd(0) is formed by reaction of Grignard and Cul with the initial palladium catalyst. 15 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. The catalytic cycle show n in Figure 2.1 is straightforw ard phosphine dissociation, followed by oxidative-addition of the 12-bromo-zwitterion. The subsequent addition of G rignard reagent forms MgBr2 and the Pd(II) carborane/m ethyl complex. Reductive- elim ination allows the form ation of the 12-methyl zw itterion, and regeneration of the Pd(0) catalyst. 2.2 Experim ental 2.2.1 Reagents and Technique The preparation and purification of solvents and other m aterials is described in Appendix 1. Physical m easurem ents were perform ed as described in Appendix 2. 2.2.2 l-N M e3-12-Br-c/oso-CBi i H i n 0.28 g (1.39 mmol) c/oso-l-NMe3-C B n H n was dissolved in 20 mL 1:1, V:V, acetonitrile/toluene solution. To this 0.25 g (1.39 mmol) N-brom osuccim ide (NBS) was added. After 24 hrs HB NMR show ed a mixture of products. A second equivalent (1.39 mmol) NBS was added and the m ixture was refluxed for 24 hr. The solvent was rem oved by rotary evaporation. Recrystallization from acetonitrile gave c/oso-1- NMe3-12-BrCBnHiO as a tan s°lid, 78.9% yield, l^C NMR (90.6 MHz, (CD3)2SO) 8 59.8 N(CH3)3- n B NMR (86.7 MHz, CH3CO, BF3-OEt2 external) 5 - 0.07 [s, IB, B(12)], -11.8 [d, 5B, J BH = 144 Hz, B(7- 11)], -14.6 [d, 5B, / BH = 162 Hz, B(2-6)]. Anal. Calcd for C4H i 9BllBrN : C, 17.16; H, 6.84; N, 4.98. Found: C, 18.61; H, 7.15; N, 4.68. 1 6 R eproduced with perm ission o f the copyright owner. Further reproduction prohibited without perm ission. 2.2.3 Pd(Ot coupling reaction of l-NM e^-12-Br-doso-CBn H i n with MeMgBr NMR scale reaction. 0.03 g (0.1 mmol) c/oso-l-NMe3-12- BrCBuHiO and 0.12 g (0.1 mmol) tetrakis(triphenylphosphine) palladium(O) [(Ph3 P)4Pd] were combined in an 8 mm tube. 2 mL of freshly distilled THF was added. The tube was fitted w ith a rubber septum and purged w ith argon. 500 (iL of a 1.0 molar (0.5 mmol) methyl magnesium brom ide (MeMgBr) in THF was added by syringe. The tube was initially sonicated for 4 hr and then heated at 65 °C (oil bath). The reaction w as monitored by HB NMR. After one month, a new product was show n to form slowly with no traces of starting material remaining. H B NMR (86.7 MHz, THF, BF3-OEt2 external) 5 -4.2 [s, IB, B(12)], -13.9 [d, 5B, / BH = 125 Hz, B(7-ll)], -15.2 [d, 5B, / BH = 130 Hz, B(2-6)]. 2.3 Results and D iscussion 2.3.1 C/oso-l-NMe^-12-BrCBi i H ~| n The llB NMR spectra of starting zwitterion and product, Figures 2.2 and 2.3, clearly show that the desired transform ation has occurred. The difference is seen in chemical shift change and lack of B-H coupling for the 12-B position. The 12-boron is initially at 8 -6.5, w ith a B-H coupling constant of 136 Hz. In the product, the 12-boron is at about 8 -0.1 and rem ains a singlet in the proton coupled spectrum . There are traces of im purity by observing a resonance at -5.46 ppm that becomes greatly broadened in the proton coupled spectrum. 17 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. T 1 ----1 ----1 --- 1 ----1 ----1 ----1 ----1 ----1 ----1 ----1 - 5 . 0 - I Z . 0 - 1 8 . 0 -Z-'r.B PPM TV T 1 --- - 1 2 .0 PPM -I 1 ------ - 6.0 -IB .0 -2-^.0 Figure 2.2 H b NMR (86.7 MHz) of C /oso-l-N M e3-CBnH n- Proton Decoupled Spectrum (lower), Coupled Spectrum (top), in Acetone d& . 18 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. - 1 — i — i — r - 0.0 -i— i — i — i — r - I B . 0 PPM -28.0 £ c. “I— i— i— r —l— i— i— i— i l I l I l ' I 0 . 0 - 8 . 0 -1 B .0 - 2 8 .0 rr*n Figure 2.3 n B NMR (86.7 MHz) of C/oso-l-NM e3-12-BrCBnHio. Proton Decoupled Spectrum (lower), Coupled Spectrum (top), in Acetone dft. 19 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. As seen from experiment, this synthesis is not fast even at elevated tem peratures. The closo-CB11H 12" anion reacts alm ost instantly under am bient tem peratures; this m ay lend some insight into the different nature of the 12-B-H bond betw een the anion and zwitterion. The zw itterion is less reactive presum ably because of the presence of the electron w ithdraw ing trim ethylam ino group and the loss of the overall negative charge. A study of this could be done w ith other groups on the carborane carbon, both electron w ithdraw ing and donating to the cage, and both as zwitterion and anion. 2.3.2 Evidence for the substitution of Closo-l-N M e^-12-Br-CB- ) 1 H i 0 M onitoring by H-B NMR has show n the possibility of alkylation at the 12-boron on the zwitterion. The reaction took one m onth at 65 °C. W hile 13c and NMR spectra were not rim, the overw helm ing change in ^ B chemical shifts, which can be seen over time, clearly indicate a transform ation at the 12-boron. Figures 2.4a-f show the starting material HB NMR spectrum along w ith the spectra upon addition of palladium catalyst and Grignard reagent over a one m onth period. 2 0 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. 1 5 . 0 0 .0 - Z S . 0 rrn Figure 2.4a 11b NMR {lH} (86.7 MHz) of C/oso-l-NMe3-12-BrCBiiHjo in THF with one equivalent (Ph3 P)4 Pd. T T T T T T 1 T T r 15.0 0.0 - 25.0 - ^ 0.0 PPM Figure 2.4b Initial llB {IK} NMR (86.7 MHz) of C/oso-l-NMe3-12- BrCBnH iO in THF with one equivalent (Ph3P)4 Pd and five equivalents of Methyl Magnesium Bromide. R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. 0 .0 -a .0 PPM — 16.0 - 2^.0 Figure 2.4c 11b {iH} NMR (86.7 MHz) after two weeks at 65 °C of the Closo-l-NMe3-12-BrCBnHiO, (Ph3 P)4 Pd, MeMgBr System in THF. T 1 --1 t — i — I — i — r T T T 0 .0 -2 -^.0 PPM Figure 2.4d llB {lH| NMR (86.7 MHz) after three weeks at 65 °C of the C/oso-l-NMe3-12-BrCBnHlO, (Ph3 P)4 Pd, MeMgBr System in THF. 22 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. I -----1 -----1 -----1 -----1 -----1 -----1 0 .0 — 2S.0 PPM Figure 2.4e H b {lH} NMR (86.7 MHz) after one month at 65 °C of the C/oso-l-NMe3-12-BrCBnHiO/ (Ph3P)4Pd, MeMgBr System in THF. T T T T 0 . 0 - 2 S . 0 0 . 0 - 2 S . 0 fpm rrn Figure 2.4f llB NMR 86.7 MHz) after one month and 72 hrs at 65 °C of the C/os0-l-NM e3-12-BrCBnHiO/ (Ph3P)4Pd, MeMgBr System in THF. Proton Decoupled Spectrum (left), Coupled Spectrum (right). 23 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. These spectra show a gradual building in of a resonance around 5 -13.5, and as time progresses, the appearance of a peak at 5 -4.1 that does not become a doublet in the proton coupled spectrum. In the final stages of the reaction, the 12-B resonance at around zero ppm completely disappears and the resonance at 8 -4.3 is clearly visible. At this stage the peak due to borons 7-11 of the 12-brominated starting material on the cage can still be seen; borons 2-6 of product and starting material are apparently accidentally degenerate. After repeated heating and reaction time, the spectrum , show n in Figure 2.4f, rem ained the same. In contrast to the 12-B brom inated spectrum , the ^ B NMR chemical shifts begin to resemble that of the non-brom inated zwitterion; (8 -6.5, -12.7, -14.1 for zwitterion; 8 -0.1, -11.8, -14.6 for 12-B brom inated zwitterion; 8 -4.3,-13.9,-15.2 for product). Even w ith the variance in chemical shift in the T H F/palladium catalyst m edium (8 -0.1, -12.4, -15.4) for the brom inated zwitterion, it is clear that a transform ation at the twelve boron has occurred. There is no data available to com pare to e.g. another 12-B alkylated zwitterion. In the anion, [Me3NH][12-C6F5-c/oso- C B n H ii],H the 12- boron has a H-B NMR chemical shift of -1.55 ppm . Also, in the analogous anion, [Me3NH][12-CF3COOHg-c/oso- C B n H ii],H the H b chemical shift is reported to be -5.38 ppm . Both 12-B resonances are reported as singlets in the proton coupled spectrum . The chemical shift of a bis-carborane, C2 B2 2H 22, B12-B12 coupling product, form ed from the reaction of the silver(I) carborane 24 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. complex and trityl bromide, Xie and R e e d ^ report a ^ B NMR chemical shift of 3.15 ppm. This rules out a carborane coupling product. The brom inated zwitterion also appears to undergo the palladium -m ediated coupling reaction in toluene b u t at the much slower rate of about twice as long. U nder the conditions in Figure 2.1 the c/oso-12-B rC B nH n' anion does not react in the palladium -m ediated reaction. There have been unpublished reports of an iodinated anion of the C B n type undergoing the alkylation.13,14 in this case, an I-B bond may be a better candidate in the reaction for the zwitterion as well as the anion. An indication of this may be the H-B NMR for the 12-B halogenated zwitterion and anions: 8 -2.2 and 8 -17.5 for the 12-B brom inated and iodinated anions respectively. If the 14 electron PdL2 interm ediate is considered electrophilic, then a more electron rich B-I bond would react faster. This pattern of reactivity (I>Br) indicates an electrophilic metal interaction! 5 in contrast to that of a nucleophilic metal undergoing an Sn 2 type mechanism on a polarized B^+-X^“ bond in which there exists no backside nucleophilic entry. An inner-sphere electron transfer/caged radical-pair m echanism ^ is also unlikely due to the lack of coupling product that would form from carborane radical addition. Nevertheless, speculation could be m ade that the 12-B signal is the oxidative-addition product. This seems unlikely due to the precedent of Pd^ m ediated coupling reactio n s^ ,13,14,16,17 and the 25 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. reactivity of Grignard reagent present. One way to test this would be if the PdL2 moiety formed an anion-cation pair, (CbPdL2)+Br", which could be trapped via a Lewis b a s e ; 1 5 subsequently HB NMR spectroscopy could be used to monitor the reaction. The change in H-B NMR chemical shift supports 12-B substitution; the 12-B resonance is now closer to that of the unsubstituted zwitterion. Finally, isolation of the product is key in positive identification by way of both ^ B , ^H, and NMR on a m ethyl substituted twelve-boron. 2.4 Sum m ary Bromination of the zwitterion: C/oso-l-NMe3- C B n H n has been dem onstrated and produced a new substituted zwitterion. The use of NBS rather than brom ine probably affords selective 12-B halogenation. NIS as a selective iodinating reagent should also be utilized since very recent experiments have show n I to be a better leaving group in alkylation.13 Exhaustive brom ination using NBS or bromine w as not tried. However, extensive brom ination and iodination on the zwitterion are future experimental efforts that could lead to partial or complete halogenation and subsequent alkylation. It is clear that B-Br bonds are not as reactive as B-I bonds in the palladium m ediated coupling reaction to methylate the carborane borons. The 12-bromo anion is completely unreactive under the same conditions used for the zwitterion. Nevertheless this work is the first 2 6 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. reported alkylation of a neutral mono-carbon carborane, discovered around the same tim e as alkylation of the m ono-carbon carborane anion.14 2.5 References 1. M orrison, R. T. and Boyd, R. N. Organic Chemistry, 6th ed., Prentice-Hall, Inc., N.J., 1992. 2. Farina, V.; Krishnan, B.; Marshall, D. R.; Roth, G. P.; /. Org. Chem. 1993, 58, 5434. 3. Dieck, H. A.; Heck, F. R.; /. Organomet. Chem. 1975, 93, 259. 4. Trost B. M. Tetrahedron 1977, 32, 2615. 5. Sekiya, A.; Ishikawa, N. J. Organomet. Chem. 1976, 118, 349. 6. Cassar, L. f. Organomet. Chem. 1975, 93, 253. 7. Tunney, S. E.; Stille, J. K. J. Org. Chem. 1987, 52, 748. 8. Yam am ura, M.; Moritani, I.; M urahashi, S. J. Organomet. Chem. 1975, 91, C39. 9. Dang, H.; Linstrumelle, G. Tett. Lett. 1978, 191. 10. Zheng, Z.; Jiang, W; Zinn, A; Knobler, C. B.; H aw thorne, M. F. Inorg. Chem. 1995, 34, 2095. 11. Jelinek, T.; Baldwin, P.; Scheidt, W. R.; Reed, C. A. Inorg. Chem. 1993,32, 1982. 12. Xie, Z.; Jelinek, T.; Bau, R.; Reed, C. A. J. Am. Chem. Soc. 1994,116,1907. 13. M athur, R.; Reed, C. A.; unpublished results. 27 R eproduced with perm ission o f the copyright owner. Further reproduction prohibited without perm ission. References C ontinued. 14. This reaction has been independently investigated by Janousek, Z.; Griiner, B.; Trammel, M.; Michel, J. 209th ACS M eeting Abstracts, Anaheim, CA 1995, ORG 315. 15. Collman, J .P.; Hegedus, L. S.; Norton, J. R.; Finke, R. G. Principles and Applications of Organotransition Metal Chemistry, University Science Books, Mill Valley, California, 1987. 16. Zakharkin, L. I.; Kovredou, A. I.; Ol'shevskaya, V. A.; Shaugum bekova, Zh. S. /. Organomet. Chem. 1982, 226, 217. 17. Li, J.; Logan, C. M.; Jones, M., Jr. Inorg. Chem. 1991, 30, 4866. R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. CHAPTER 3 MONO- and DI-HALOGENATION OF CESIUM 1-CARBA-CLOSO-DODECABORATE 3.1 Introduction Singly and doubly halogenated carborane anions have been know n for the last decade. 12- While attem pting /zexfliodination of [c/oso-CBnHi2]", a new method of singly iodinating the twelve- position, and a mixed halogenated anion synthesis have been carried out. The use of N-iodosuccinimide (NIS)3 as a reagent had not been tried previously. It's utility as a route to a hexa- or greater iodinated anion was explored. As experiment show ed, it was not a strong enough reagent to Iiexaiodinate the anion, yielding mixtures of di-, tri, and perhaps quadruply 7-12 substituted anion. W hat was discovered is that NIS, like NBS, may give a more pure yield of 12-halo substituted anion. Along the same course of reasoning, an already substituted 12- bromo-anion was subjected to the sam e conditions. The reasoning behind using an already substituted anion was that iodination m ay proceed m ore easily with the sm aller brom ine in the twelve-position (0.2 A atomic radius smaller than that of iodine). 2 9 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. 3.2 Experim ental 3.2.1 Reagents and Technique The preparation and purification of solvents and other m aterials is described in Appendix 1. Physical m easurements were perform ed as described in Appendix 2. 3.2.2 Cs fc/oso-12-ICBi i H t | | NMR scale reaction. 10 mg (0.036 mmol) Cs[c/oso-CBnH i2] in an 8 mm tube was dissolved in 1 mL CH 3CN. To this 0.008 g (0.036 mmol) N-iodosuccinimide (NIS) was added. The rubber septum sealed tube was heated at 60 °C (oil bath) for 27 hrs. A nearly quantitative yield in situ of Cs[c/oso-12-ICBnHn] was detected by ^ B NMR. HB NMR (86.7 MHz, CH3CN, BF3*OEt2 external) 5 -11.3 [d, 5 B, / BH = 140 Hz, B(7-ll)], -15.5 [d, 5B, / BH = 153 Hz, B(2-6)], -17.5 [s, IB, B(12)]. 3.2.3 Cs [c/oso-7-Br-12-ICB~ i 1 Hi n] NMR scale reaction. 10 mg (0.036 mmol) Cs[closo- CB11H 12] in an 8 mm tube was dissolved in 1 mL CH 3CN. To this 0.006 g ( 0.036 mmol) N-bromosuccinimide (NBS) was added. After 24 hrs ^ B NMR showed quantitative formation of Cs[c/oso-12-BrCBnHn]. 0.008 g (0.036 mmol) N-iodosuccinimide was added and the tube heated for 2 days at 60 °C (oil bath). A quantitative yield in situ of Cs[c/oso-12-Br-7- ICB11H 10] was detected by H-B NMR. HB NMR (86.7 MHz, CH 3CN, BF3-OEt2 external) 5 -2.2 [s, IB, B(12)], -9.9 [d, 2B, B(8,ll)], -11.8 [d, 2B, B(9,10)], -14.1 [d, 2B, B(2,3)], -16.1 [d, 2B, B(4,6)], -17.4 [d, IB, B(5)], -22.0 [s, IB, B(7)]. 30 R eproduced with perm ission o f the copyright owner. Further reproduction prohibited without perm ission. 3.3 Results and Discussion 3.3.1 Cs [doso-12-ICBi i Hi 11 From the NMR spectra of starting carborane and product, Figures 3.1 and 3.2 respectively, the iodination of the twelve-boron has occurred. The chemical shift of 8 -17.5 for B(12) is consistent w ith results from our lab using 12 in glacial acetic acid, and that reported by Jelinek et al.1 W hat is prom ising about using this reagent instead of 12 is the lack of 7,12-12 product, and the use of acetonitrile rather than acetic acid, which is more difficult to remove once the reaction is complete. There are however traces of starting m aterial and 7-iodo- product which is not surprising since this position is the next easily halogenated. The key to completely pure 12-iodo product m ay be in controlled addition of NIS experimentally. 3.3.2 Cs [c/oso-7-I-12-BrCBi 1 Hi nl The form ation of the 12-bromo- product, Figure 3.3a, is facile and proceeds at room tem perature. In contrast, 12-iodination of the anion, and subsequent 7-iodination of the 12-bromo- anion, is slow er and requires heating at 65 °C. The pattern of the ^ B NMR spectrum , Figure 3.3b is consistent w ith that of 7,12 di-bromo and di-iodo anions previously form ed.1 The assignm ent of the Yl-bromo- boron at 8 -2.2, and the 7-iodo- boron at 8 -22.0 follows from these previous results as well, [(7,12)12 5 -22.0, -16.3];* [(7,12)Br2 8 -7.9, -2.2].2 Two unaccounted resonances at -8 ppm and -19 ppm are consistent with trace am ounts of 31 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. m J v X r — i 1 r ~ — i i—'i— " i < * ■ i 1 1 1 * -s.® -1^.0 -zz.B -30. e ppn - S . 0 f*rn Figure 3.1 llB NMR (86.7 MHz) of Cs[c/oso-CBnHi2]- Proton Decoupled Spectrum (lower), Coupled Spectrum (top), in Acetone d& . R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. c_ T ' ' » " ■ “ — 3 0 . 0 T ’ I 0.0 pm Figure 3.2 11b NMR (86.7 MHz) of Cs[cZoso-12-ICBnHn]. Proton Decoupled Spectrum (lower), Coupled Spectrum (top), in Acetone de- 33 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. 1— I— I— I— I— I— I— I— I— I— I— I— I— I— I— I— I 0.0 - 8 . 0 - i b .0 - e a . 0 rrm Figure 3.3a llB {lH} NMR (86.7 MHz) of Cs[c/oso-12-BrCBnHn] in Acetone d& . T— I— I— I— I— I — I — I — I — I— I — I— I — I— I — I— I 0 . 0 - l * . 0 - Z B . 0 PPM Figure 3.3b 11b (1h) NMR (86.7 MHz) of Cs[c/oso-12-Br-7-ICBnHioJ in Acetone d& . 34 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. the opposite product forming i.e. 7-Br-12-I. Any starting material left appears to have reacted with NIS, however any products (7-1, 12-1, or 7,12-12) w ould share an accidental overlap w ith the predom inant 7-I-12-Br product resonances. The purpose of this was to show that mixed halogenation was possible, and once show n, attem pt full B(7-ll) iodination on the 12- bromo anion. W hile up to a three equivalent excess of NIS was used along with heating at 65 °C, only mixtures of iodinated product were form ed. 3.4 Sum m ary In contrast to halogenation of the zw itterion using NBS, where two equivalents are necessary, the anion reaction utilizing NBS or NIS, appears to require only one equivalent of succinimide reagent. This m ay indicate a reaction pathw ay different from that of Br2 or 12 form ation^ and possibly supports radical or ionic mechanisms since a di-halogen form ing mechanism would yield HBr and HI respectively, which do not react further; unsubstituted anion would be present in the HB NMR. Once 12-iodination of the anion was show n by using one equivalent of NIS, excess (three equivalents per lower pentagonal B-H bond) was used on the unsubstituted anion to see if full 7-12 iodination was possible. Unfortunately this reagent only gave tri-iodinated anions w ith certainty. However, NIS has now been show n to yield nearly spectrally pure 12-iodo anion with no di-substituted carborane with easier product w ork-up. Further recrystallization of predom inant 12- 35 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. iodo product formed could also be a m ethod of elim inating the trace am ounts 7-iodo present. While not being successful in hexa-halogenation by w ay of prior 12-bromo- halogenation, an interesting m ixed 12-bromo-7-iodo- anion was formed. It could be used in X-ray crystallographic studies of the silver(I) or trialkylsilyl complexes to see which of the two halogens coordinates to the cationic center. 3.5 References 1. Jelinek, T; Plesek, J.; Herm anek, S.; Stibr, B. Collect. Czech. Chem. Commiin. 1984, 51, 819. 2. Jelinek, T.; Baldwin, P.; Scheidt, W. R.; Reed, C. A. Inorg. Chem. 1993, 32, 1982. 3. Olah, G. A.; Wang, Q.; Sandford, G.; Prakash, G. K. S. /. Org. Chem. 1993, 58, 3194. 4. Morrison, R. T. and Boyd, R. N. Organic Chemistry, 6th ed., Prentice-Hall, Inc., N.J., 1992. 3 6 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. CHAPTER 4 CESIUM l-CARBA-(7-12)-HEXAIODO-CLOSO-DODECABORANE 4.1 Introduction NIS w as not successful in fully substituting the 7-12 positions of the carborane anion. The next experiment was to use a different source of iodine. It was felt that a more electrophilic source of iodine was necessary to accomplish the synthesis of a hexaiodo anion. Iodine m onochloride (IC1) was a good candidate since the more electronegative chlorine atom leaves iodine positively charged in the molecule (I^+Cl^"). This is ideal owing to the nucleophilic nature of the 7-12 B-H bonds. 4.2 E xperim ental 4.2.1 Reagents and Technique The preparation and purification of solvents and other materials is described in Appendix 1. Physical m easurements were performed as described in Appendix 2. 4.2.2 Cs \doso-(7-12Vl6CBnH6] To a 15 mL reaction tube a slurry of 0.5 g (1.81 mmol) Cs[closo- CB11H 12] and Et2 0 was stirred for 1 hr. The E t20 was then evaporated off in a 30 °C oil bath. The 0.5 g Cs[c/oso-CBnHi2] was dissolved in DME (5 mL). This solution was stirred in a 65 °C oil bath for 20 min. While still w arm , 4.0 g (4.10 mmol) iodine m onochloride (IC1) was added w ith a nickel spatula while stirring. Any rem aining IC1 was dissolved in DME and added to the mixture. The reaction is 37 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. immediate and violent. Caution should be taken i.e. IC1 should be stored under argon and added to the carborane/DM E solution slowly. The reaction was immersed in a 65 °C oil bath with oil covering the tube to the solvent line. A red rubber septum was placed on the tube and the reaction vented to atm osphere every 45 min. for 5 hrs via syringe needle. Alternatively, the septum m ay be periodically removed as long as the reaction is carried out in a proper fume hood. The mixture was left stirring overnight (20 hrs) in an air reflux under solvent and evolved gas pressure. The reaction m ixture was allowed to cool to room tem perature and washed into a 125 mL flask w ith 20 mL DME. While stirring a saturated aqueous solution of sodium sulfite (Na2S0 3 ) was added dropwise until a light yellow clear solution persisted. The pH of this solution was acidic to litmus paper. A ddition of water (H2O) (100 mL) resulted in formation of a white precipitate. After chilling in an ice bath, suction filtration on a fine frit followed by five ice water washings produced 1.71 g of crude Cs[closo-(7-12)~ I6CB11H 6] as a white powder, 91.7%. The product was recrystallized from m ethanol/aqueous saturated cesium chloride (CsC1)/H20 to give bright white crystals of pure Cs[c/oso-(7-12)-l6CBnH6], 64.8% overall yield. HB NMR (86.7 MHz, DME, BF3-OEt2 external) 8 -6.3 [s, IB, B(12)], -14.4 [d, 5B / BH = 166 Hz, B(2-6)], -18.7 [s, 5B, B(7-ll)]. Connectivities from 2-D HB-n B NMR (160.5 MHz, (CD3)2CO, BF3-OEt2 external): B(12) [B(7-11)J; B(2-6) [B(7-ll)]; B(7-ll) [B(12), B(2-6)]. Anal. Calcd for CsCH6B n l6: C, 1.16; H, 0.59. Found: C, 1.54; H 0.51. 3 8 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. 4.3 Results and Discussion 4.3.1 Synthesis From reviewing the experimental section, it is clear that IC1 is a powerful, and successful reagent for iodinating the lower pentagonal belt of the anion, Figure 4.1.1 The use of DME as a solvent allows the HC1 formed in the reaction to have little solubility, and drive the reaction by leaving the reaction mixture; the vapor above the reaction mixture, the mixture itself, and the water work-up were all strongly acidic to litmus. In fact, in other experimental procedures in which neat IC1 was added to parent carborane anion the H-B NMR show ed that the reaction failed to produce the desired 7-12 iodinated anion. Rather, a m ixture of iodinated anions was formed that proved intractable to further substitution. Even upon addition of DMF solvent and prolonged heating the NMR remained the same. Since there is no reason that the less-than-Zzexa-substituted anion should not react to form a fully /^ ^ su b stitu te d one, an explanation could be that under forcing conditions the upper pentagonal belt (positions 2-6) may be iodinated. Once this occurs, steric or electronic factors may preclude full /ie:raiodination of the lower pentagonal belt or lead to hepta substitution i.e. B(2) &B(7-11) iodination. Experimentally two-dim ensional H-B NMR may be able to answ er this question. Furthermore, other researchers have reported a fully- substituted anion [c/oso-l-Me-(2-6)l5-(7-ll)M e 5C B n ]".2 Therefore, the possibility that this is occurring is not unreasonable. 3 9 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. In calculating the ratio of equivalents of I+ to that of carborane anion, the strength of this reagent is seen: a little over two equivalents of IC1 to that of each 7-12 B-H bond of the carborane anion is needed. Upper pentagonal belt B (2-6) Lower pentagonal belt B(7-ll) Antipodal boron B(12) IB Figure 4.1 1:5:5 11B NMR Integration Ratio for the Borons in the [Closo- CBu H1 2 1 Anion. Interestingly, w hen less than two equivalents of ICl^ per 7-11 B- H bond are used, or the reaction mixture is m ore dilute than that of the above reported procedure, only 12-B iodination occurs. It should be noted that both acetonitrile and glacial acetic acid are also solvents in which complete /zexahalogenation occurs.^ There are undesirable effects though; acetonitrile yields an intractable and inseparable polymeric by-products, and the initial experim ental reaction took about a m onth of refluxing w hen performed in acetic acid. U nder m ore 40 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. rigorous conditions /zexaiodination in acetic acid does proceed in under 36 hours, however product isolation is a more tedious procedure. As far as a reasonable mechanism for this transform ation is concerned, most likely I+ in the form of IC1 or a solvated cation reacts at the B-H site. Since synthesis was the goal, the determ ination of a reasonable mechanism was not considered; it could be the basis of future experiments. 4.3.2 One- and Two-dimensional NMR The llB NMR was the first evidence of the new hexaiodinated anion. Figure 4.2 shows the 270 MHz spectrum. It is distinctly different from that of it's parent carborane anion shown in Figure 4.3. Borons 2- 6 have shifted slightly downfield, while borons 7-11 have significantly shifted upfield from 5 -12.2 to -18.6. This upfield shift appears to be consistent with the chemical shifts in 12-1, and 7-12-12 substituted a n i o n s . 5 / 6 What is not so similar is the 12-boron chemical shift now in fact being similar to that of the unsubstituted anion; 8 -6.3 for hexa- iodo, and 8 -5.8 for [doso-C B nH i2]" respectively. It is definitely substituted by inspection of the lH coupled spectrum , Figure 4.2, but is sharply different from the 12-iodo- anion, 8 -17.5. The two-dimensional H b-H b COSY NMR confirm the assignm ent of borons. The 1:5:5 integration (see Figures 4.1 and 4.4) pattern clearly identifies the B-12 boron. By inspection of both 2-D spectra, Figures 4.4 and 4.5, the difference in connectivity patterns is clearly seen. In Figure 4.4 the B-12 is coupled only to the resonance at -12.3 ppm ; the resonance at -12.3 ppm is coupled to both resonances at 41 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. T 1 - 25.0 T T T 1 -- 0 .0 PPM Figure 4.2 n B NMR (86.7 MHz) of Cs[c/oso-(7-12)-l6CBnH6l. Proton Decoupled Spectrum (lower), Coupled Spectrum (top), in DME. 4 2 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. Figure 4.3 llB { 1H} NMR (160.46 MHz) of Cs[c/oso-CBnHi2l m Acetone de- R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. ■ d a Figure 4.4 2-D ^ B - ^ b COSY { l H} NMR (160.46 MHz) of Cs[c/oso-CBhH i2] in Acetone c/6- J v. O ' I . u» I o (U - o k r . . . . . . . . . . . . . . . . . . . . . . . . . . . . T ‘ “ ’ "l r I- - r I -. - 1 r T r , -I , D t i l l 44 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. Figure 4.5 2-D n B-llB COSY {lH} NMR (160.46 MHz) of Cs[c/oso-(7-12)-l6CBnH6] in Acetone d& . A o- I U l ‘ I o I rv j o t w- u» T "f > ................. > | « 1-T > » . » j 4 5 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. -5.8 and -15.3 ppm ; and the resonance at 8 -15.3 is coupled only to the resonance at 8 -12.3. This shows that for the unsubstituted anion B(7- 11) m ust be at 5 -12.3. Since B(12) is at 8 -5.8, it follows that 8 -15.3 is B(2-6). In Figure 4.5, the B-12 boron at 8 -6.3 is coupled only to the resonance at 8 -18.6; the resonance at 8 -14.2 is coupled only to the peak at 8 -18.6; however, the resonance at 8 -18.6 is coupled to both peaks at 8 -14.2 and 8 -6.3. This shows that the resonrnce at 8 -18.6 m ust be borons 7-11, since borons 2-6 would only couple to borons 7-11, and not be detectable to B-12; as well, B-12 would only show coupling to borons 7-11. The 7-11 borons would couple to both borons 2-6 and B-12, Figure 4.1. Therefore, one can assign the following ^ B chemical shifts to Figure 4.5: B-12, -6.3 ppm; B(2-6), -14.2 ppm; B(7-ll), -18.6 ppm. 4.4 Sum m ary Iodine monochloride in DME is now the reagent of choice for hexa-iodination of borons 7-12 in the parent carborane anion. It yields product quickly, with a relatively simple work-up. One-dimensional NMR confirms the iodination of borons 7-12. Two-dimensional NMR successfully assigns the HB chemical shifts of this new molecule. An understanding of the chemical shift change at the 12-boron position in the hexaiodo anion versus the 12-1 or 7,12-12 anions is not presently available. Perhalogenation, e.g. [closo-CBilll2]~, remains an intriguing synthetic challenge. 46 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. 4.5 References 1. Reed, R. W.; Xie, Z.; Manning, J.; M athur, R.; Bau, R.; Reed, C. A. Phosphorus, Sulfur, Silicon, and the Related Elements 1994,93, 45. 2. This reaction has been independently investigated by Janousek, Z.; Griiner, B.; Trammel, M.; Michel, J. 209th ACS Meeting Abstracts, Anaheim, CA 1995, ORG 315. 3. Cotton, F. A.; Wilkinson, G. Sir Advanced Inorganic Chemistry, 5th ed., Wiley-Interscience, N.Y., 1988. 4. Xie, Z.; Manning, J.; Reed, R. W.; M athur, R.; Boyd, P. D. W.; Benesi, A.; Reed, C. A. J. Am. Chem. Soc. 1996, 118,2922. 5. Jelinek, T; Plesek, J.; Hermanek, S.; Stibr, B. Collect. Czech. Chem. Commun. 1984, 51, 819. 6. Jelinek, T.; Baldwin, P.; Scheidt, W. R.; Reed, C. A. Inorg. Chem. 1993, 32, 1982. R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. CHAPTERS SILVERd) l-CARBA-(7-12)-HEXAIODO-CLOSO-DODECABORATE 5.1 Introduction Once the cesium complex of the c/oso-(7-12)I6CBh H 6" anion had been synthesized,^ formation of the silver(I) complex was carried out. One w ay to test the weakly coordinating nature of this anion is by isolation of its trialkyl-silicon complex. The hexabromo complex has been show n to give the closest approach tow ards achieving a planar silicon cation.2-4 It was felt that the larger size and 'softer' nature of iodine as com pared w ith bromine m ight create ideal conditions for an even closer approach to a planar trialkyl-silicon cation. This complex is typically form ed starting from the trityl salt of hexaiodo via the silver reagent. The Ag(I) salts are therefore explored in this chapter. A nother test of this new anion's coordination is the value of the I.R. carbonyl stretching frequency of [Fe(n)Cp(CO)2]+ with hexaiodo as the counterion. The reaction is show n in the equation: Ag[doso-(7-12)-l6CBnH6] + FeCp(CO)2l > Agl + (FeCp(CO)2)+ [c/oso-(7- 12)-I6C B iiH 6]- The m ore coordinating the anion to the iron center, the lower the CO stretching frequency: an indication of donor value of the anion. The rationalization is that the more electron-rich the iron center, the m ore 7 t-backbonding into the CO rc-antibonding orbital; as well, CO a bond is 48 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. weakened, thus lowering the stretching frequency.5/6 Table 5.1 shows reported values for various anions.^ Table 5.1 Carbonyl Stretching Frequencies for FeCp(CO>2Y Systems Y vCO in toluene (cm“l) I- 2038,1994 [CB11H 12]- 2067,2031 C104- 2071,2027 SbF6" 2073,2030 Br6CBnH6" 2128,2088 The reaction to form the silver(I) complex is a simple m etathesis type according to the equation: Cs[doso-(7-12)-l6CBnH6] + AgN0 3 ------- > CsNC>3 + Ag[c/oso-(7-12)-l6CBnH6] The ^ B NMR spectrum in a non-coordinating solvent such as toluene m ight give some insight as to which iodine is most accessible to silver in solution. And finally, an X-ray crystal structure would determine the com position of the new anion as well as the structure of the silver(I) com plex compared to that of the analogous hexabromo one. 5.2 Experim ental 5.2.1 Reagents and Technique The preparation and purification of solvents and other materials is described in Appendix 1. Physical m easurem ents were perform ed as described in Appendix 2. 49 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. 5.2.2 Ag fcIoso-(7-12)-lfi,CB- \ i Hft] 0.43 g (0.42 mmol) Cs[c/oso-(7-12)-l6-CBnH6] was dissolved in 5 mL DME. To this solution 0.20 g (1.2 mmol) silver nitrate (AgNC>3) dissolved in 3 mL H2O was added. A white precipitate formed immediately and the reaction w as stirred for 5 min. in the dark. The m ixture was then filtered through a fine frit and repeatedly washed with water until the last filtrate was clear upon addition of solid sodium chloride (NaCl). The solid was dried in vacuo in the dark for two days. Ag[doso-(7-12)-l6CBnH6] as a dry white powder resulted, 84.6% yield. Crystals suitable for X-ray diffraction were grown in the dark from a 1:1 (by volume) acetonitrile/benzene solution by evaporation of solvent. lH NMR (500 MHz, CD3CN) 8 2.4 - 3.6 [m, B- H], 5 3.4 [s, C-HJ; n B NMR (86.7 MHz, CH3CN, BF3-OEt2 external) 8 -6.0 [s, IB, B(12)], -14.1 [d, 5B,/ BH = 165 Hz, B(2-6), -18.7 [s, 5B, B(7-ll). Connectivities from 2-D H B -H b NMR (160.5 MHz, CD3CN, BF3 -OEt2 external): B(12) [B(7-ll)]; B(2-6) [B(7-11)J; B(7-ll) [B(12), B(2-6)]. Anal. Calcd for AgCH6B n l6: C, 1.19; H, 0.60. Found: C, 1.58; H, 0.51. 5.2.3 Reaction of Ag rdoso-(7-12)-fc;CBn H 6 l with FeCpfCObI 0.01 g (0.10 mmol) Ag [doso-(7-12)-l6CBnH6] was added to 2 mL toluene with stirring. To this, a solution of O.lg (0.33 mmol) FeCp(CO)2l in 1 mL toluene was added. I.R. spectra were recorded at time-zero, 1/2 hour, 1 & 1/2 hours, 3 & 1/2 hours, 20 hours, and 48 hour intervals. A toluene spectrum , from the same sample source, was subtracted from each run. Details concerning the I.R. instrum ent 50 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. may be found in Appendix 2. For each scan, the resolution was 2 cm"l, and 64 scans for each spectrum recorded. 5.3 Results and Discussion 5.3.1 Synthesis The silver(I) complex is easily made. However, it is not completely im m une to light sensitivity. W hen the solid contains some solvent, a brow nish com pound begins to form, in and out of light (probably ow ing to dissolved oxygen a n d /o r water in the solvent). The only way to ensure that decomposition does not occur is to store the completely dry solid in the dark, under inert gas (argon), or in the glove box. In the glove box, light sensitivity does not appear to be a problem in an absence of oxygen and water. The product, if sufficiently washed w ith water, doesn't seem to need further purification by recrystallization, by inspection of the NMR. Furthermore, recrystallization m ay cause decomposition, vida supra. W hen AgNC>3 is used in excess, product seems to form nearly quantitatively, and cleanly. 5.3.2 One- and Two-dimensional NMR The 11b NMR spectrum in acetonitrile appears in Figure 5.1. The chemical shift values are similar to those of the cesium complex, allowing for chemical shift changes (0.2-0.4 ppm ) due to the use of a different solvent), and the B-H coupling constant for the 2-6 borons is virtually the sam e as the cesium complex. The spectrum displays the 5 1 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. Figure 5.1 11{3 NMR {lH} (160.46 MHz) of Ag [closo-(7- 12)-l6CBnH6] in Acetonitrile rf3- r j s y V/ - 1 0 — I— -1 5 — I — -20 5 2 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. familiar 1:5 :5 integration ratio, see Figure 4.1. The integration ratio is not perfectly 1:5:5. This is because of quadrupolar relaxation of the 11-B nucleus which leads to difficulty in obtaining integration accuracy that m ight be expected in a lH spectrum. The lack of change in chemical shift and coupling constant m ight lead to the conclusion that w hen fully dissolved, the metal counterion or solvent, does not have m uch interaction w ith this anion. Attem pts to obtain HB NMR of the silver(I) complex in a non coordinating solvent were not possible. The closest 'non-coordinating' solvent spectrum w as in a dim ethoxyethane/m ethanol solution where the new m aterial was sparingly soluble, Figure 5.2. This spectrum show s that the B-12 boron has a chemical shift of -4.6 ppm ; the chemical shift of the B-12 boron in acetonitrile being about -6.0 ppm. Even allowing a 0.2-0.4 ppm change due to solvent, a 1.0 ppm difference betw een B-12 borons is seen in com paring the spectra. The ^ B NMR chemical shifts of the B-(2-6) and B(7-ll) borons are within a change of solvent margin, allowing hydrogen bonding between the iodine of hexaiodo and methanol (if this was significant, then silver(I) hexaiodo w ould be expected to be much more soluble in polar protic solvents; which it is not). And the cesium hexaiodo complex displays about the sam e H B NMR B(12) chemical shift values w hether in aprotic acetone or protic DME. Thus, there is an indication that in a solution in which Ag[doso-(7-12)-l6CBnH6] is only sparingly soluble a close contact betw een the B(12) B-I bond and silver may exist; this is 5 3 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. ✓ 0 .0 5 ] col T, I - 2 S . e — C 5 * O C O * I 0 3 I I B . B - 2 5 . B PPM Figure 5.2 ^ B NMR (86.7 MHz) of Ag [doso-(7-12)- I6CB11H 6]. Proton Decoupled (lower), Coupled (top), in M ethanol/DM E. 54 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. compared to an Ag-I-B(8) contact seen in the X-ray crystal structure, vida infra. W hat is implied is the B(12)-I bond may be sterically, and electronically preferably accessible, but that in the solid state a closer contact w ith B(8)-I bond is engendered by packing effects A similar effect is seen in the ^ B spectrum of the silver (I) CB11H 12 complex in toluene.® The chemical shifts of all boron atoms are affected. The H-B NMR changes are opposite to that found w ith the CB11H 6I6 complex, especially the B-12 boron. The silver(I) [closo- CB11H 12] complex exhibits shifts consistent with a polarization of charge tow ards the apical boron and lower pentagonal belt, resulting in npfield shifts for borons 7-12, and a downfield shift for borons 2-6. In the analogous CB11H 6I6 complex, the apical boron exhibits a doivnfield shift, while borons 2-6 and 7-11 show little change. In this case, only the 12-B-I bond may be affected. A downfield shift would be consistent with an iodine to silver donation that does not have great influence on the rest of the carborane borons. A two-dimensional 11b-HB COSY {^H} (2-D) experim ent was perform ed for the sake of identity prior to an X-ray structure analysis, (see Figure 5.3). The connectivity patterns from the 2-D spectrum are essentially the same as the cesium-Zzexaiodo spectrum . 5.3.3 X-ray Crystallography Crystals of X-ray quality were easily grown from a benzene/acetonitrile solution by evaporation (benzene m olecules, not shown, are w ithin the crystal lattice). Acetonitrile is necessary to allow 55 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. •d d Figure 5.3 2-D COSY {lH} NMR (160.46 MHz) of Ag [closo-(7- 12)-l6CBnH6] in Acetonitrile £ * 3. iO o- i . u I o I m i to ol . T T T T 56 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. Figure 5.4 X-ray Crystal Structure of Ag [c/oso-(7-12)-l6CBnH6]. C I 1 ) 1 (10) 1 (8) , r i ( 9 ) 1 ( 7 ) 1(12) 1 (10) R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission the silver complex to dissolve; other techniques such as solvent diffusion and solvent layering did not yield suitable crystals. The crystal structure is shown in Figure 5.4. Tables 5.2-8 display the structure determ ination sum m ary. In viewing Figure 5.5, the structure is one of an alternating polymeric chain. Each silver atom is in contact with five iodine atoms from two carborane units, Figure 5.4, in a pseudo square pyram idal type geometry. The coordination about silver alternates up and dow n between each carborane unit. Every carborane contributes five of it’ s iodine atoms to the structure: 1(7, 8, 10, 11, 12); 1(9) is not involved in any interactions; three iodine atoms from one carborane and two iodine atoms from another make up the coordination geometry. 1(10) and 1(11) form one edge of the base of a square pyramid, while 1(7) and 1(12) form the other. The axial atom 1(8) comes from the carborane unit that contributes 1(7) and 1(12). The 1(8),(7),(12) portion is situated in the structure such that 1(8) is tilted away from 1(10) and 1(11). The I(8)-Ag- 1(10) and I(8)-Ag-I(ll) bond angles are 116° and 123.6°, respectively. The I(7)-Ag-I(10) and I(ll)-Ag-I(12) angles are 153.7° and 146.1°, respectively (less than the 180° of a perfect square pyramid). In addition the 1(7,8,12) unit appears to be positioned closer to 1(11) than to 1(10), rather than evenly between those two atoms; I(7)-Ag-I(ll) is 79.4° contrasted to I(10)-Ag-I(12) which is 93.7°. The I-Ag-I angles in terms of iodine atoms on adjacent borons clearly reflect the 5 8 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. Figure 5.5 X-ray Crystal Structure of Ag [c/oso-(7-12)-l6CBnH6] displaying the alternating polymeric chain arrangem ent. 5 9 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. Ag-I bond distances i.e. the sm aller the I-Ag-I angle, the longer the Ag-I bonds are: I(10)-Ag-I(ll) = 92.0° > I(7)-Ag-I(8) = 89.0° > I(8)-Ag-I(12) = 83.1° > I(7)-Ag-I(12) = 80.8° The ordering of Ag-I bond lengths is: 1(12) [3.25 A] > 1(7) [3.12 A] > 1(11) [2.93 A] > 1(10) [2.86 A] > 1(8) [2.85 A] As seen from table 5.5 the B-I bond lengths do not follow any pattern as to the respective Ag-I distances. All are about the same length: 2.16 to 2.20 A. This indicates that there is no stretching of B-I bonds to silver, but rather the position of the carborane unit dictates the Ag-I bond distances. Since the crystals w ere grown from CH3C N /benzene solution, it could have been expected that discrete silver-acetonitrile coordinated cations and hexaiodo anions w ould be formed. Acetonitrile and benzonitrile were the only solvents that dissolved CBnH 6l6"- In considering the polymeric structure it is clear that silver-halogen interactions predom inate in a condensed medium. 5.3.4 I.R. Spectroscopy M easurement of the I.R. carbonyl stretching frequency of the Fe(II)Cp(CO)2 complex of the anion was attempted. While being easy w ith the analogous hexabromo anion, the silver complex of hexaiodo proved to be essentially insoluble in toluene- the non-coordinating solvent of choice; and necessary for legitimate com parison to the other anions already m easured. Figures 5.6a-f displays the I.R. spectra of the 60 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. ftifiN'iH! 1 fHMIt Figure 5.6a IR Spectrum at 48 hrs of FeCp(CO)2l and Ag [closo-(7- 12)-l6CBnH6] in Toluene. WIN • 177S.5 2769.1 - X*K 192.54 121.3 2290 rfflY E N U M B E R tcn-1) 2400 R eproduced with perm ission o f the copyright owner. Further reproduction prohibited without perm ission. Figure 5.6b IR Spectrum of FeCp(CO)2l in Toluene. r 2000 ( c m - 1 ) R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. 11-fin-,m; muni * transmittance Figure 5.6c IR Spectrum at Time-Zero of FeCp(CO)2l and Ag [closo-(7- 12)-l6CBnH6] in Toluene. 1B2.I A S. 09. 2609 Figure 5.6d IR Spectrum at 1 & 1 /2 hrs of FeCp(CO)2 l and Ag [c/oso-(7-12)-l6CBnH6] in Toluene. R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. I M lN S W I I M M C r j- T f tf lN S M lT If lN C E Figure 5.6e IR Spectrum at 3 & 1 /2 hrs of FeCp(CO)2l and Ag [c/oso-(7-12)-l6CBnH6] in Toluene. SS.fl - 7$. i s e c Figure 5.6f IR Spectrum at 20 hrs of FeCp(CO)2 l and Ag [closo-(7- 12)-l6CBnH6] in Toluene. R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. reaction at different time intervals. There appears to be a very small time w indow in which two new vCO peaks are visible. This could be a result of slow reactivity, low solubility, a n d /o r rapid decom position of the iron carbonyl product once formed. Several attem pts w ere undertaken. After 48 hours, a spectrum was obtained in w hich two new peaks shifted to higher wave num bers are present: 2063 and 2023 cm "l, Figure 5.6a. Experimentally, as time progresses, the carborane stretching frequency (approximately 2600 cm"l) is present and increases in intensity with respect to the carbonyl stretching frequency values of the FeCp(CO)2l starting material. Other peaks at 2364 and 2330 c m 'l appear in both initial and final ER spectra, Figures 5.6c and 5.6a. N either of these peaks are present in the IR spectrum of FeCp(CO)2l/toluene alone, Figure 5.6b. The two new carbonyl stretching peaks are present along w ith those characteristic of FeCp(CO)2l at 2038 and 1994 cm 'l. The new peaks at 2063 and 2023 cm"l, tentatively assigned to [FeCp(CO)2 ]+ [c/oso- C B h H i2]’ are fairly close to those reported for the unsubstituted carborane anion: [c/oso-C B nH l2]", see Table 5.1. Apparently, the hexa iodo anion has sim ilar donor ability to the C B n H i2‘ anion. In contrast, it is m uch more donating then the hexabromo anion. In considering the anion, iodine is more polarizable, and iodonium character is more likely than with the hexabromo anion.9 Being about the same in coordination as the [c/oso-C BnH i2]‘ anion could be explained by size versus electron availability. The [c/oso-CBiiH i2 ]" 6 5 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. anion is sm aller, and a closer approach is possible. The hexaiodo anion is larger, yet has electron donating iodine atoms. 5.4 S um m ary In synthesizing the Ag(I) complex of hexaiodo several experim ents were accomplished. Positive identification of the new feexahalogenated anion was confirmed w ith an X-ray structure determ ination. Also, this structure, very sim ilar to that of hexabromo, confirms that Ag-I contact is therm odynam ically favored in the solid state to that of CH3CN with Ag(I), probably ow ing to the symbiotic com patibility of a 'soft' Ag(I) with a 'soft' iodine atom and the form ation of a polymeric structure. 5.5 References 1. Reed, R. W.; Xie, Z.; Manning, J.; M athur, R.; Bau, R.; Reed, C. A. Phosphorus, Sulfur, Silicon, and the Related Elements 1994, 93, 45. 2. Reed, C. A.; Xie, Z.; Bau, R.; Benesi, A. Science 1993,262, 402. 3. Xie, Z.; Bau, R.; Benesi, A.; Reed, C. A. Organometallics 1995,14,3933. 4. Xie, Z.; Manning, J.; Reed, R. W.; M athur, R.; Boyd, P. D. W.; Benesi, A.; Reed, C. A. /. Am. Chem. Soc. 1996, 118, 2922. 5. Lukehart, C. M. Fundamental Transition Metal Organometallic Chemistry, B rooks/C ole Publishing Company, Monterey, CA, 1985. 66 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. References Continued. 6. Collman, J .P.; H egedus, L. S.; Norton, J. R.; Finke, R. G. Principles and Applications of Organotransition Metal Chemistry, University Science Books, Mill Valley, California, 1987. 7. Xie, Z.; Jelinek, T.; Bau, R.; Reed, C. A. J. Am. Chem. Soc. 1994,116,1907. 8. Shelly, Kenneth, Ph.D. Dissertation, Departm ent of Chemistry, University of Southern California, 1985. 9. Olah, G.; Prakash, S. G. K; Sommer, J. Superacids, W iley- Interscience, New York, 1985, pp 193-206. R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. Table 5.2 Crystal Data for Ag [doso-(7-12)-l6CBnH6]. Empirical Formula Color; Habit Crystal s iz e (m m ) Crystal System Space Group Unit Cell Dimensions Volume Z Formula Weight D e n sity (c a lc .) Absorption C oefficien t F(000) colorless, a ir sta b le 0.3*0.2*0.4 Orthorhombic Iba2 a = 15.063(1) A b = 19.584 (2) A c = 14.267(2) A 4208.7(7) A 8 1084 . 3 3.423 Mg/m3 -1 9.752 m m 3792 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. Table 5.3 Data Collection for Ag [c/oso-(7-12)-l6CBnH6]. D i f f r a c t o m e t e r U s e d R a d i a t i o n T e m p e r a t u r e (K) M o n o c h r o m a t o r 2 6 R a n g e S c a n T y p e S c a n S p e e d S c a n R a n g e (to) B a c k g r o u n d M e a s u r e m e n t S t a n d a r d R e f l e c t i o n s I n d e x R a n g e s R e f l e c t i o n s C o l l e c t e d I n d e p e n d e n t R e f l e c t i o n s O b s e r v e d R e f l e c t i o n s A b s o r p t i o n C o r r e c t i o n M i n . / M a x . T r a n s m i s s i o n S i e m e n s P4 MoKor (A = 0 . 7 1 0 7 3 A) 157 H i g h l y o r i e n t e d g r a p h i t e c r y s t a l 2 . 0 t o 4 5 . 0 ° 2 8 — 6 o V a r i a b l e ; 5 . 0 0 t o 3 0 . 0 0 / m i n . i n u o 1 . 2 0 p l u s K a - s e p a r a c i o n S t a t i o n a r y c r y s t a l a n d s t a t i o n a r y c o u n t e r a t b e g i n n i n g a n d e n d o f s c a n , e a c h f o r 50.0% o f t o t a l s c a n t i m e 3 m e a s u r e d e v e r y 97 r e f l e c t i o n s - 1 £ h s 15, - 1 s k £ 19 - 1 £ I £ 14 1579 1354 (R. = 4.36% ) i n t 1253 (F > 4 . Off ( F) ) S e m i - e m p i r i c a l 0 . 4 2 1 8 / 1 . 0 0 0 0 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. Table 5.4 Solution and Refinement for Ag [c/oso-(7-12)-l6CBnH6]. S y s c e m U s e d S o l u t i o n R e f i n e m e n t M e th o d Q u a n t i t y M i n i m i z e d A b s o l u t e S t r u c t u r e E x t i n c t i o n C o r r e c t i o n H y d r o g e n A tom s W e i g h t i n g S c h e m e N u m b e r o f P a r a m e t e r s R e f i n e d F i n a l R I n d i c e s ( o b s . d a t a ) R I n d i c e s ( a l l d a t a ) G o o d n e s s - o f - F i t L a r g e s t a n d Mean &/<r D a t a - t o - P a r a m e t e r R a t i o L a r g e s t D i f f e r e n c e P e a k L a r g e s t D i f f e r e n c e H o le S ie m e n s SHELXTL IR I S D i r e c t M e th o d s F u l l - M a t r i x L e a s t - S q u a r e s I w ( F - F ) 2 o c N/A N/A R i d i n g m o d e l, f i x e d i s o t r o p i c U - 1 2 2 w = a (F) + 0 . 0 0 1 2 F 142 R = 3 . 2 7 *, wR = 4 . 3 7 % R = 3 .7 8 1, wR = 4 . 6 3 % 1.00 4 . 6 5 7 , 0 .2 8 5 8.8:1 0 . 9 4 eA- - 3 -1.01 eA-3 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. Table 5.5 Bond Lengths (A) for Ag [c/oso-(7-12)-l6CBnH6]- 1 ( 7 ) -Ag 3 . 1 1 8 (3) I ( 8 ) -Ag 2 . 8 5 4 (2) 1 ( 9 ) - B (9) 2 . 1 8 7 ( 2 S ) I ( 1 0 ) - B (10) 2 . 1G3 (26) 1 ( 1 1 ) - B ( l l ) 2 . ISO (25) 1 ( 1 2 ) - B (12) 2 . 183 (22) C ( l ) -B (3 ) 1 . 7 0 6 (32) C ( l ) - B (5) 1 . 7 1 1 (35) B ( 2 ) - B (3) 1 .8 1 4 (36) B ( 2 ) - B (7) 1 . 8 4 7 (33) B ( 3 ) - B (4) 1 . 7 9 1 (33) B ( 3 ) - B (8) 1 . 7 8 0 (33) B ( 4 ) - B (8) 1 . 7 1 0 (31) B ( 5 ) - B (6) 1 .8 1 6 (35) B (5 ) - B (10) 1 . 8 2 5 (34) B (6) -B (11) 1 . 7 5 7 (32) B ( 7 ) - B ( l l ) 1 . 8 0 0 (35) B ( 8 ) - B (9) 1 . 7 8 0 (36) B (9) - B (10) 1 . 7 3 9 (38) B ( 1 0 ) - B (11) 1 . 7 8 6 (35) B ( 1 1 ) - B (12) 1 . 7 7 1 (37) C ( 2 ) - C (4) 1 . 4 2 5 (98) C ( 6 ) - C (7) 1 . 3 9 0 (68) 1 ( 7 ) - B (7) 2 . 177 (22) 1 ( 8 ) - 8 ( 8 ) 2 . 2 0 3 (24) 1 ( 1 0 ) -Ag 2 . 8 5 8 (3) 1 ( 1 1 ) -Ag 2 . 927 (3) 1 ( 1 2 ) -Ag 3 .2 5 4 (3) C ( l ) - B (2) 1 . 6 8 5 (32) C ( l ) - B (4) 1. 75 7 (32) C ( l ) - B (6) 1 . 6 7 3 (33) B (2) - B (6) 1 . 727 (36) B ( 2 ) - B (11) 1 . 8 0 9 (35) B ( 3 ) - B (7) 1 . 7 9 8 (31) B ( 4 ) - B (5) 1 . 8 3 6 (35) B ( 4 ) - B {9) 1 . 7 8 6 (32) B ( 5 ) - B (9) 1. 78 9 (35) B ( 6 ) - B (10) 1. 8 3 1 (33) B ( 7 ) - B (8) 1. 79 1 (32) B ( 7 ) - B (12) 1 . 7 5 8 (34) B (8) - B (12) 1 . 8 1 5 (35) B ( 9 ) - B (12) 1. 796 (32) B (10) - B (12) 1. 76 4 (37) C ( 3 ) -C (5 ) 1 . 4 5 4 (98) C ( 4 ) -C (S ) 1 . 390 (75) C ( 6 ) - C (8) 1 . 4 0 9 (68) R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. Table 5.6 Bond Angles (deg) for Ag [closo-{7-l2)-\eCQi\He]. A g - I ( 7 ) - B (7) 88 . S 6) Ag- 1 ( 8 ) - B (8) 9 5 .3 6) A g - I ( 1 0 ) - B (10) 9 9 .7 6) Ag- 1 ( 1 1 ) - B (11) 98 . 3 7) A g - I ( 1 2 ) - B (12) 8 8 . 7 7) I (7 - A g - I (8) 8 9 .0 1) 1 ( 7 ) - A g - I (10) 1 S 3 .7 1) I (8 - A g - I (10) 116 . 0 1) 1 ( 7 ) - A g - I (11) 7 9 .4 1) 1(8 - A g - I (11) 123 .6 1) I ( 1 0 ) - A g - I (11) 9 2 .0 1) 1 (7 - A g - I (12) 8 0 .8 1) 1 ( 8 ) - A g - I (12) 8 3 .1 1) I ( 1 0 ) - A g - I (12) 93 .7 1) 1 ( 1 1 ) - A g - I (12) 1 4 6 .1 1) B (2 - C ( l ) - B (3) 64 .7 14) B ( 2 ) - C ( l ) - B (4) 1 1 6 .7 16) B (3 - C ( l ) - B (4) 6 2 . 2 13) B ( 2 ) - C ( l ) - B (S) 1 1 7 .8 17) B (3 - C ( l ) - B ( S ) 1 1 6 .9 17) B (4) - C ( l ) -B (S) 6 3 . 9 14) B (2 - C ( l ) - B (6) 6 1 . 9 14) B ( 3 ) - C ( l ) - B ( 6 ) 1 1 5 .7 15) B (4 - C ( l ) - B (6) 1 1 6 .7 16) B ( 5 ) - C ( l ) - B ( 6 ) 6 4 . 9 14) C(1 -B (2) -B (3) 5 8 .2 14) C ( l ) - B ( 2 ) - B (6) 58 .7 14) B (3 -B (2) -B (6) 1 0 7 .8 18) C (1) -B (2) -B (7) 1 0 2 .1 17) B (3 -B (2) -B (7) 5 8 .8 13) B (6) -B (2) -B (7) 1 0 6 .4 17) C(1 - B ( 2 ) - B (11) 103 .1 17) B (3) -B (2) -B (11) 1 0 6 .6 17) B (6 -B (2) -B (11) 5 9 .5 14) B (7) -B (2) -B (11) 5 9 .0 13) C(1 -B (3) -B (2) 5 7 .1 13) C ( l ) - B ( 3 ) - B (4) 6 0 .3 13) B (2 -B (3) -B (4) 1 0 8 .8 17) C ( l ) - B ( 3 ) -B (7) 1 0 3 .3 16) B (2 -B (3) -B (7) 6 1 . 5 13) B (4) -B (3) -B (7) 1 0 6 .6 16) C(1 -B (3) -B (8) 1 0 2 .7 16) B ( 2 ) - B ( 3 ) -B (8 ) 1 0 8 .8 16) B(4 -B (3) -B (8) 5 7 .2 12) B (7) -B (3) -B (8) 6 0 . 1 13) C(1 -B (4) -B (3) 5 7 .5 13) C ( l ) - B ( 4 ) - B (5) 5 6 .8 13) B (3 -B (4) -B (S) 1 0 6 .8 16) C ( l ) - B ( 4 ) - B (8) 1 0 3 .4 IS) B (3 -B (4) -B (8) 6 1 . 1 13) B ( 5 ) - B ( 4 ) - B (8) 1 0 8 .7 16) C(1 -B (4) -B (9) 1 0 1 .2 16) B (3) -B (4) -B (9) 108 .4 15) B (5 -B (4) -B (9) 5 9 .2 14) B (8) -B (4) -B (9) 6 1 . 1 13) C(1 -B (5) -B (4) 5 9 .3 13) C ( l ) - B ( 5 ) -B (6) 5 6 .5 13) B (4 - B ( 5 ) - B (6) 1 0 6 .2 17) C ( l ) - B ( S ) - B (9) 103 .0 17) B (4 -B (5) -B (9) 5 9 .0 14) B ( 6 ) - B ( 5 ) - B ( 9 ) ' 1 0 5 .4 16) C(1 -B (5) -B (10) 1 0 2 .6 16) B (4) -B (S) -B (10) 1 0 5 .2 16) B (6 -B (5) -B (10) . 60 .4 13) B(9) -B (S) -B (10) 5 7 .5 14) C(1 -B (6) -B (2) 5 9 .4 14) C ( l ) - B ( 6 ) - B (5) 5 8 .5 14) B (2 -B (6) -B (5) 1 1 0 .3 18) C ( l ) -B (6) -B (10) 1 0 3 .9 17) B (2 -B (6) -B (10) 1 1 0 .2 17) B ( 5 ) - B ( 6 ) - B (10) 6 0 . 1 13) C(1 -B (6) -B (11) 1 0 5 .9 17) B ( 2 ) - B ( 6 ) - B (11) 6 2 .6 14) B (5 -B (6) -B (11) 1 0 9 .1 17) B (10) - B ( S ) - B (11) 5 9 .7 13) 1 (7 -B (7) -B (2) 1 1 7 .3 13) 1 ( 7 ) - B (7) -B (3) 1 2 0 .5 14) B (2 - B ( 7 ) - B (3) 5 9 .7 13) 1 ( 7 ) - B ( 7 ) - B (8) 1 2 6 .4 14) B (2 -B (7) -B (8) 1 0 6 .9 15) B (3) -B (7) -B (8) 5 9 .5 13) 1 (7 -B (7) -B (11) 1 1 9 .8 14) B (2) -B (7) -B (11) 5 9 .5 13) B (3 - B ( 7 ) - B (11) 1 0 7 .6 IS) B ( 8 ) - B ( 7 ) - B ( l l ) 1 0 7 .9 16) 1(7 -B (7) -B (12) 124 .4 13) B (2) -B (7) -B (12) 107 .8 17) B (3 - B ( 7 ) - B (12) 1 0 9 .3 16) B (8) -B (7) -B (12) 6 1 . S 13) B (11) -B (7) -B (12) 5 9 .7 14) 1 ( 8 ) - B ( 8 ) - B (3) 1 2 1 .8 14) 1(8 - B ( 8 ) - B (4) 1 2 1 .4 14) B ( 3 ) - B ( 8 ) - B (4) 6 1 . 7 13) I (8 - B ( 8 ) - B (7) 1 2 0 .0 14) B (3) -B (8) -B (7) 6 0 . 5 13) B (4 - B ( 8 ) - B (7) 1 1 0 .5 16) 1 ( 8 ) - B ( 8 ) - B (9) 12 2 .3 IS) B (3 -B (8) -B (9) 1 0 9 .2 16) B ( 4 ) - B ( 8 ) - B (9) 6 1 .5 13) B (7 -B (8) -B (9) 107 .1 17) 1 (8 ) - B ( 8 ) - B (12) 1 2 0 .2 14) B (3 -B (8) -B (12) 107.6 16) B ( 4 ) - B ( 8 ) - B (12) 1 1 0 .2 17) B (7 -B (8) -B (12) 5 8 .3 13) B (9) -B (8) -B (12) S 9 .9 13) 1 (9 - B ( 9 ) - B (4) 1 1 7 .8 14) 1 ( 9 ) - B ( 9 ) - B (5) 1 1 9 .7 15) B (4 -B (9) -B (5) 6 1 .8 13) 1 ( 9 ) - B ( 9 ) - B (8) 1 2 0 .7 16) B (4 - B ( 9 ) -B (8) 57 . 3 13) B (5) -B (9) -B (8) 1 0 7 .8 17) 1 (9 - B ( 9 ) -B (10) 123 .0 16) R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. Table 5.6 Continued. B (4) - B ( 9 ) - B ( I O ) 1 1 1 .2 17) B (5) -B (9) -B (10) 6 2 . 3 ( 1 4 ) B ( 8 ) - B ( 9 ) -B{10) 1 0 9 .2 17) 1 ( 9 ) - B ( 9 ) - B (12) 1 2 4 .0 (1 4 ) B ( 4 ) - B ( 9 ) - B ( 1 2 ) 1 0 7 .7 17) B ( 5) -B (9) -B (12) 1 0 9 .4 (1 8 ) B (8) -B ( 9) -B (12) 6 1 .0 14) B (10) -B (9) -B (12) 5 9 . 8 ( 1 4 ) B ( 5 ) - B ( 1 0 ) - B (6) S 9 .6 13) B (5) - B ( 1 0 ) - B (9) 6 0 . 2 ( 1 3 ) B (6) -B (10) -B (9) 1 0 6 .9 17) B ( 5 ) - B ( 1 0 ) - B (11) 1 0 7 .4 (1 7 ) B (6) - B ( 1 0 ) - B (11) 5 8 .1 13) B ( 9 ) - B ( 1 0 ) - B (11) 1 0 8 .9 (1 8 ) B ( S ) - B ( 1 0 ) - B ( 1 2 ) 1 0 9 .3 18) B ( 6 ) - B ( 1 0 ) - B (12) 1 0 6 .0 ( 1 7 ) B ( 9 ) - B ( 1 0 ) - B (12) 6 1 .7 14) B ( 1 1 ) - B ( 1 0 ) - B (12) 5 9 . 9 ( 1 4 ) B(S) - B ( 1 0 ) - I (10) 1 1 8 .8 15) B (6) - B ( 1 0 ) - 1 ( 1 0 ) 1 2 1 .0 ( 1 5 ) B (9) - B ( 1 0 ) - 1 ( 1 0 ) 1 2 2 .1 15) B ( 1 1 ) - B ( 1 0 ) - 1 ( 1 0 ) 1 2 2 .8 ( 1 5 ) B ( 1 2 ) - B ( 1 0 ) - 1 ( 1 0 ) 1 2 4 . S 14) B ( 2 ) - B ( 1 1 ) - B (6) 5 7 . 9 ( 1 3 ) B ( 2 ) - B ( l l ) - B (7) 6 1 .5 13) B ( 6 ) - B ( l l ) - B (7) 1 0 7 .1 ( 1 6 ) B ( 2 ) - B ( 1 1 ) -B (1 0 ) 1 0 8 .5 17) B ( 6 ) - B ( l l ) - B ( 1 0 ) 6 2 . 2 ( 1 4 ) B ( 7 ) - B ( 1 1 ) -B (1 0 ) 1 0 6 .8 17) B ( 2 ) - B ( 1 1 ) - B (12) 108 . 9 (18) B ( 6 ) - B ( l l ) - B (12) 1 0 8 .9 17) B ( 7 ) - B ( 1 1 ) - B (12) 58 . 9 (14) B (10) -B (11) -B (12) 5 9 .5 14) B (2) - B ( 1 1 ) - 1 ( 1 1 ) 1 1 8 . 9 (IS) B ( 6 ) - B { 1 1 ) - 1 ( 1 1 ) 1 2 1 .5 16) B ( 7 ) - B ( l l ) - I (11) 1 2 1 .0 ( 1 4 ) B ( 1 0 ) - B ( 1 1 ) - 1 ( 1 1 ) 123 .9 15) B (12) - B ( 1 1 ) - 1 ( 1 1 ) 1 2 3 .1 ( 1 4 ) 1 ( 1 2 ) - B ( 1 2 ) - B (7) 1 2 1 . S 15) 1 ( 1 2 ) - B ( 1 2 ) -B (8) 1 2 1 .5 ( 1 6 ) B (7) -B (12) -B (8) 6 0 .1 13) 1 ( 1 2 ) - B ( 1 2 ) - B (9) 1 2 1 .4 (15) B (7) -B (12) -B (9) 1 0 7 .8 16) B (8) -B (12) -B (9) S 9 .0 (1 4 ) 1 ( 1 2 ) - B ( 1 2 ) -B (1 0 ) 1 2 1 .8 16) B ( 7 ) - B ( 1 2 ) -B (10) 1 0 9 .6 ( 1 7 ) B (8) -B (12) -B (10) 1 0 6 .5 16) B (9) - B ( 1 2 ) - B (10) 5 8 .5 ( 1 4 ) 1 (1 2 ) -B (12) -B (11) 1 2 2 .8 15) B (7) - B ( 1 2 ) - B ( l l ) 6 1 . 4 ( 1 4 ) B (8) -B (12) -B (11) 1 0 8 .1 16) B (9) - B ( 1 2 ) - B (11) 1 0 7 .0 (1 7 ) B (10) -B (12) -B (11) 60 .7 14) C ( 2 ) - C ( 4 ) - C (5) 1 1 8 .4 ( 5 6 ) C ( 3 ) - C ( 5 ) - C ( 4 ) ' 1 1 9 .0 SS) C ( 7 ) - e ( 6 ) - C (8) 1 1 8 .6 (4 9 ) R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. Table 5.7 Atomic Coordinates (xlO4) and Equivalent Isotropic Displacement Coefficients (A^ x 10^) for Ag [closo-{7- 12)-l6CBnH6]- X Y I (7) 7S6(1) 3053 I (8) 1625(1) 1180 I (9) 2164(1) -82 I (10) -1555(1) 935 1(11) -699(1) 2884 I (12) -16(1) 1220 Ag -93(1) 1789 C(l) 3360(12) 2146 B(2) 2562(16) 2747 B (3) 2808(15) 2291 B (4) 3159(14) 1443 B (5) 3163(16) 1384 B (6) 2747(14) 2197 B (7) 1669(14) 2361 B (8) 2092(15) 1571 B (9) 2276 (14) 1027 B (10) 2001(15) 1461 B (11) 1646(16) 2304 B (12) 1344(15) 1598 C (3) 4908(52) 1 C (2) 5044(57) 12 C (4) 5841(40) -3 C (5) 5777(40) 54 C (6) 5907(25) -229 C (7) 5546 (43) -115 C (8) 5371(37) -115 z U(eq) 1) 37 28 (1) 1) 1127(2) 24 (1) 1) -1075(2) 27(1) 1) 1516(2) 31(1) 1) 2248(2) 30(1) 1) -1134(2) 25 (1) 1) 1008 (2) 52 (1) 12) -1341(16) 28 (5) 14) -1392(19) 28 (5) 12) -316(17) 17 (5) 11) -605(16) 11(4) 13) -1890(19) 23 (5) 12) -2317(18) 14 (4) 11) -681(17) 12 (4) 12) -234(17) 14 (4) 13) -1214(20) 21(5) 13) -2237(18) 18 (5) 13) -1940(18) 22 (5) 13) -1231(20) 28 (5) 75) 445(43) 139(8) 76) 2391(37) 157 (8) SO) 1852(38) 145(8) 55) 884(35) 165(8) 49) 1574 (32) 150(8) 39) 691(30) 97 (8) 40) 2368 (32) 86 (8) * Equivalent isotrop ic U defined as one third of the trace of the orthogonalized U .. tensor R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. Table 5.8 Anisotropic Displacement Coefficients (A^ x 10^) for Ag [c/oso-(7-12)-l6CBnH6]- U11 ° 2 2 U33 U 12 U13 U23 1 ( 7 ) 34 (1) 24 (1) 25 (1) 1 1 ( 1 ) 8 ( 1 ) 0 (1) K B ) 30 (1) 23 (1) 1 9 ( 1 ) 1 (1 ) 1 ( 1 ) 6 (1) r (9) 3 1 ( 1 ) 1 0 ( 1 ) 40 (1) -3 (1) 3 ( 1 ) 1 ( 1 ) I (10) 42 (1) 30 (1) 2 1 ( 1 ) 4 (1) 5 ( 1 ) -8 (1) I (11) 26 (1) 3 7 ( 1 ) 27 (1) - 9 ( 1 ) 1 (1 ) 14 (1) 1 ( 1 2 ) 13 (1) 3 0 ( 1 ) 32 (1) - 7 ( 1 ) 0 ( 1 ) 4 (1) Ag 3 7 ( 1 ) 5 9 ( 1 ) 5 9 ( 1 ) 8 ( 1 ) 24 (1) 9 ( 1 ) T h e a n i s o t r o p i c d i s p l a c e m e n t f a c t o r e x p o n e n t t a k e s t h e f o r m : - 2 . 2 ( h 2 . * 20 + . . . + 2 h k a * b * U i 2 > 7 5 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. CHAPTER 6 (TRHSOPROPYLSILYL) l-CARBA-(7-12)-HEXAIODO-CLOSO-DODECABORATE 6.1 Introduction A critical test of the new hexaiodo anion's coordinative ability is the geometry of a trialkyl silicon "cation" with the CB11H 6I6" species as counterion. Generally the C-Si-C bond angles as well as the silicon out- of-plane distance are key factors in comparing hexaiodo with that of the hexabromo and hexachloro anions. The closer the sum of the C-Si-C angles approaches 360°, the greater towards planarity the trialkyl silicon cation becomes. Correspondingly, the out-of-plane distance should decrease as well. A purely planar silicon cation w ould have a zero out-of-plane distance. Observation of the 29Si and ^ B NMR chemical shifts would be of interest as well. A relatively non-coordinating solvent w ould be optim al for 29gi NMR since a donor solvent will coordinate to the silicon center.l The further downfield the 29si chemical shift, the more positive the charge on silicon. Theoretical calculations of a silicon cation in the gas phase reveal the downfield shift to be over 300 ppm .2 Solution 29si NMR in toluene has proven to be difficult due to the low solubility of the trialkylsilicon-Zzcxahalo complexes. While soluble in solvents such as acetonitrile, the 29si chemical shift is less downfield due to solvent coordination. Therefore, solid state NMR is the m ethod of choice for these complexes. 76 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. While 29si NMR in solution is difficult, vicia supra, the H B NMR is possible. The chemical shift can provide inform ation on how the small am ount of complex that is dissolved behaves in solution. This experim ent is sim ilar to that of m easuring the shift of the silver(I)-lzexfliodo complex in a non-coordinating solvent as well, (chapter 5 of this thesis). The triphenylm ethyl (trityl) salt of C B n H 6l6" m ust first be synthesized from the corresponding Ag(I) complex. After the successful isolation, the trityl complex may be reacted w ith a trialkylsilane (R3SLH). The synthesis steps are show n in the following two equations: Ag[c/oso-(7-12)-l6CBnH6] + Ph3CBr ------- > [PI13C] [c/oso-(7-12)-l6CBnH6] + AgBr [PI13C] [c/oso-(7-12)-l6CBiiH6] + R3SLH > R3Si[c/oso-(7-12)-l6C B n H 6] + PI13CH 6.2 Experim ental 6.2.1 Reagents and Technique The preparation and purification of solvents and other m aterials is described in Appendix 1. Physical measurements were perform ed as described in Appendix 2. 77 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. 6.2.2 (PtoC l \closo-(7-l2)-lf> C B 'nHfl] In a glove box 0.30 g (0.30 mmol) Ag[closo-(7-12)-lsCBnHs] was dissolved in 10 mL CH3CN. 0.096 g (0.30 mmol) Ph3CBr was dissolved in 3 mL toluene and added to the CH3CN solution. Over time, the m ixture became bright orange and a gray precipitate formed. The reaction flask was fitted with a jacketless condenser and refluxed for one week in the dark. The mixture was allowed to cool to ambient tem perature and filtered through a fine frit. The filtrate was reduced in volum e until orange crystals began to form. Further cooling to -30 °C resulted in the formation of a large quantity of orange crystals. The chilled m ixture was filtered on a fine frit and the residue washed with chilled toluene three times and chilled hexanes three times. After drying under vacuum 0.24 g [PI13C] [closo-(7-12)-I^CBnH^] was recovered as an orange-red solid, 70%. NMR (360 MHz, (CD3)2CO) 8 7.72 & 7.68 [dd, 6H, metci ], 7.86 [t, 6H, ortho ], 8.25 [t, 3H, para ]; 13C NMR (90.6 MHz, (CD3)2CO) 5 69.2 [carborane C], 127.5 [para C], 128.2 [meta C], 128.7 [ortho C], 154.3 [ipso C], 210.0 [PI13C ]; llB NMR (86.7 MHz, (CD3)2CO BF3*OEt2 external) 8 -6.10 [s, IB, B(12)], -14.0 [d, 5B, / BH = 169 Hz, B(2-6)], -18.3 [s, 5B, B(7-ll)]. Anal. Calcd for C20H 21B11I6: C, 21.04; H, 1.85. Found: C, 20.19 ; H,1.87. 6.2.3 i-PreSi [c/oso-f7-121-l6CBiiH6] This procedure was performed in the glovebox. To a slurry of 0.05 g (0.044 mmol) [Ph3C] [c/oso-(7-12)-l6CBnH6] and 20 mL toluene was added 0.028 g (0.177 mmol) z-Pr3SiH dissolved in 2 mL toluene. The m ixture was allowed to stir under glovebox conditions for one 78 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. week. After this time a colorless cloudy solution formed. This solution was filtered through a fine frit. The now clear colorless solution was subjected to hexanes vapor diffusion. After ten days pale yellow crystals suitable for X-ray diffraction had formed from the hexanes/toluene solution. 6.2.4 NMR Scale Preparation of z-Pr^Si [c/oso-f 7-12)-fcCB'|'iH < 5] This procedure was performed in the glovebox. 10 m g (0.009 mmol) [Ph3C] [c/oso-(7-12)-l6CBnH6] was m easured into a 5 mm Young valve NMR tube. 0.5 mL toluene d% and 10 mg (0.063 mmol) /-Pr3SiH were added. The sealed tube was shaken periodically for one week. The orange color of the trityl complex had disappeared and pale yellow crystals of the triisopropyl complex were present in a clear solution. The solution was not concentrated enough for ^^Si NMR. However, H b NMR was possible. ^ B NMR (86.7 MHz, C6D6, BF3 -OEt2 external) 5 -6.31, -14.12, -17.91, -19.46. 6.3 Results and Discussion 6.3.1 Synthesis Preparing the trityl complex of hexaio&o proved to be more difficult than the corresponding hexabromo one.3 A reaction time of only 1.5 hours at ambient glove box tem perature was sufficient for C B n H 6Br6"- When this method was used for the silver(I) complex of C B n H 6l6"/ the reaction was incomplete, with visible signs of unreacted silver complex present. After several attem pts at longer reaction times e.g. one day to one week, heat was used. As a precaution, to avoid 79 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. decomposition of the starting silver complex, the reaction was done in the dark. The same pattern of slower reactivity was also apparent in the synthesis of the triisopropylsilyl complex of hexaiodo. W hile stirring overnight was enough for the preparation of the hexabvomo triisopropylsilyl comp lex,4 the extreme insolubility of trityl C B nH 6l6" in toluene dem anded a reaction time of one week. The form ation of X- ray quality crystals for CBnH6Br6" required one day, whereas crystal formation for CB11H 6I6" took ten days. 6.3.2 NMR Spectroscopy of [Ph^C] [c/oso-(7-12)-I^CBi i H f ] In addition to ^ B NMR, and spectra w ere also taken; mainly for the identification of the trityl cation. The ^ B NMR spectrum , Figure 6.1 is nearly identical to that of either the cesium or silver complexes (chapters 4 & 5). The indicative resonances are prom inently present. The -^C resonances are nearly the sam e as those reported for hexabromo in the acetone d& the unique trityl carbon appears at 210 ppm . A clear difference is the chemical shift of the carboranyl carbon. In CBnH6Br6", it is reported at 43.5 ppm ;4 in C BnH 6l6", the resonance is present at 69.2 ppm. 8 0 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. 1 1 1 1 1 1 0 . 0 - Z S . 0 PPM Figure 6.1 11b NMR (86.7 MHz) of [PI13C] [closo-(7- 12)-l6CBnH6]. Proton Decoupled Spectrum (lower), Coupled Spectrum (top), in Acetone dfr. 81 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. Figure 6.2 13c {!hJ NMR (90.56 MHz) of [Ph3C] [closo- (7-12)-l6CBnH6] in Acetone r/6- R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. 3./ ‘6.3 6.2 s.: 6 0 1.3 7 8 M Ffv Figure 6.3 *H NMR (250 MHz) of [Ph3C] [c/oso-(7-12)-I6CBhH6] displaying the phenyl region in Acetone dS- 83 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. Therefore, the trityl cation's 13C chemical shifts indicate little contact w ith the anion in either case; the nature of the carborane anion itself can be seen in the difference in carboranyl resonances. The carbon, Figure 6 .2, and proton, Figure 6.3, spectra displayed residual solvent resonances (in both 13c and lH spectra these resonances appear upfield and are not show n so that the peaks of interest are easily seen). W hen the 13c NMR was initially run in CD3CN, the solvent hexanes were clearly visible, but more im portantly the unique trityl carbon was not seen (other trityl and carboranyl resonances were). This could be due to the interaction of the trityl cation with acetonitrile. In addition to this, the trityl salt is not stable for very long in acetone d6 - In Figure 6.2 the 13c spectrum has a resonances at 5 198.2 and in the region of 5 124. A dark solution forms in one day, yielding more obscure resonances in the 13c and lH spectra. A solution of trityl brom ide in acetone also undergoes w hat appears to be a similar change. The unaccounted resonances in the 13c spectrum can most likely be attributed to decom position due to reaction by the trityl cation. 8 4 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. n 0 _ e_ U ) e s H U a I n •i a * I I--------------- 1 ----------------1 --------------- 1 ----------------1 ----------------1 0 . 0 - 1 S . 0 - 2 S . 0 rrn Figure 6.4 1_lB {iH} NMR (86.7 MHz) of i-Pr3Si [closo- (7-12)-l6CBnH6] in Toluene dg. 85 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. 6.3.3 NMR Spectroscopy of i-Pr^Si\closo-(7-12)-l^CB'\ t Hft] The triisopropyl hexaiodo complex is very sparingly soluble in toluene ds■ The H-B {^-H } spectrum , Figure 6.4, shows an extrem ely broadened B(2-6) region at -14.1 ppm , and two resonances are present in the B(7-ll) region at -17.9 and -19.5 ppm . The smaller of these two peaks (-19.5 ppm) is likely B-7 in close contact with the silicon center. The loss of sym m etry and broadened resonances support this. • = C -H o = B-I o = B-H i- Pr3Si Figure 6.5 Proposed Interaction betw een the B(7) Iodine and the Tri-isopropyl Silyl M oiety in Toluene d 8 . If the twelve-position w ere the interacting bond, sym m etry w ould be preserved as dem onstrated by Shelly^ and in chapter five of this thesis with the silver(I) [C B n H i2]" and silver(I) [C B nH 6l6]" complexes, respectively. Since the ^ B NMR chemical shifts are not largely changed, this B(7)-I-Si interaction appears to induce only a small am ount of charge polarization towards B-7 within the carborane cage. 86 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. Upfield llB NMR shifts have been reported for the tri isopropylsilyl hexabromo complex in C6Dg as com pared to those in acetone d$- How ever in both these cases the 1:5:5 sym m etry is preserved. Ionization in acetone would explain this but since separation of the moieties in benzene is unlikely, fluxional behavior of the i-Pr3Si substituent over the 7-11 bromine atom s is a likely explanation. In the case of C B n H 6l6" there is an apparent B(7)-I-Si contact in C6 D6 - B-7 is shifted upfield, and B(8- ll) are shifted downfield supporting a B(7)-I bond polarization w ithout fluxionality. Thus, to a degree, the sym m etry of the anion is lost. This is clearly visible in the 2-6 borons where the resonance is about 8 ppm wide, (-10 to -18 ppm); in the symmetrical anion the peak is about 3-4 ppm wide. The 7-11 boron resonances are sharper than those of the 2-6 borons, where two peaks are present. Borons 8-11 may be less affected by the B(7)-I-Si interaction due to iodine substitution. Figure 6.5 displays the proposed interaction of the B(7)-I bond with the z-Pr3Si moiety. It is consistent with up- and downfield shifts for borons 2-6 and borons 7-11 due to unsym m etrical cage polarization from the B(7)-I-Si interaction leading to broadened and separated resonances. 6.3.4 X-ray Crystallography of i-PriStfcloso-(7-l2)-lACB- \ f Hfi] Pale yellow crystals form as discrete molecular units show n in Figure 6.6 . The crystals are somewhat stable outside of an inert atmosphere, appearing to decompose after about a m onth w hen in Paratone-N oil, outside the glovebox. As in the hexabromo complex, there is a contact between 1(7) of carborane and the silicon center. The 87 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. iodine substituent antipodal to carbon 1(12), m ay be more electron rich but is apparently however being screened by the iodine atoms of the lower pentagonal belt; i.e. it is the least sterically accessible. Thus, the iodine lone pairs on the lower pentagonal belt interact w ith R3Si+. Table 6.1 displays the bond angles and lengths for hexaiodo specifically. X-ray crystal structures on all three triisopropylsilyl Zierahalogenated complexes are now known. Hexabromo and hexacblovo complexes are com pared to hexaio&o in Table 6.2. Tables 6.3 - 6.10 display the various structure determ ination and data collection param eters for the C B n H 6l6" derivative- Table 6.1 Specific Geometrical Parameters fori- Pr3Si[c/oso- (7-12)-l6CBuH6l Si-I(7) (A) 2.661 Si-I-B (deg) 110.3 H o o r d (A) 2.22(2) B-Iuncoord (A) (from pentagonal belt only, excluding 12-position) 2.15-2.18(2) 88 R eproduced with perm ission o f the copyright owner. Further reproduction prohibited without perm ission. Figure 6.6 X-ray Crystal Structure of /-Pr3Si[doso-(7-12)-l6CBnH6]. C(5) C (2) C(8) C(1) 1(9) 1 (8) 1 ( 1 1 ) 1(12) 1(7) 89 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. Table 6.1 Continued. C-Si-C(deg) (Numbers in brackets identify the carbon atoms, Figure 6.6) SC-Si-C (deg) m ean C-Si-C (deg) Si out of C3 plane 112.9 [2,8] 113.2 [2,5] 120.7 [5,8] 346.8(9) 115.6(9) 0.400 Si-C(2) (A) 1.875(21) Si-C(2)-C(3) (deg) 114.1(15) Si-C(2)-C(4) (deg) 116.4(14) C(3)-C(2)-C(4) (deg) 110.0(18) Si-C(5) (A) 1.902(21) Si-C(5)-C(6) (deg) 112.9(14) Si-C(5)-C(7) (deg) 110.3(14) C(6)-C(5)-C(7) (deg) 109.7(17) Si-C(8) (A) 1.872(22) Si-C(8)-C(9) (deg) 120.6(16) Si-C(8)-C(10) (deg) 108.2(15) C(9)-C(8)-C(10) (deg) 111.4(19) 9 0 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. Table 6.2 Collective Key Geometrical Parameters for i - Pr3Si[c/oso-(7-12)-X6CBnH6l Param eter X = C l ref- 6 X = Br ref. 4 X = I Si-X (A) 2.323(3) 2.479(9) 2.661(6) Si-X-B (deg) 122.6(3) 114.7(7) 110.3(5) h-Xcoord (A) 1.88(1) 2.05(3) 2.22(2) B-Xuncoord (A) (from pentagonal belt only, excluding 12-position) 1.77-1.82(1) 1.93-2.02(3) 2.15-2.18(2) C-Si-C (deg) (Numbers in brackets identify the carbon atoms, Figure 6.6) 115.4(4) 111.2(14) 112.9(10) 117.4(4) 119.6(13) 113.2(9) 119.0(4) 120.2(12) 120.7(9) IC -Si-C (deg) 351.8(4) 351.0(13) 346.8(9) mean C-Si-C (deg) 117.3(4) 117.0(13) 115.6(9) Si out of C3 plane 0.307 0.300 0.400 Si-C (A) 1.846(9) 1.86(3) 1.875(21) 1.848(10) 1.91(3) 1.902(21) 1.850(8) 1.80(3) 1.872(22) By reviewing Table 6.1, comparison of i-Pr3Si[c/oso-(7-12)- I6CB11H 6 ] w ith that of a silane of the type R3SiI suggests an 'ion like' nature of the complex due to hexaiodo's lesser coordination. The Si-I bond is about 0.25 A longer than a normal Si-I bond at 2.661(6) A (H3SLI 91 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. has a microwave gas phase m easured Si-I bond length of 2.44 A).^ The silicon out-of-plane distance in Me3SiBr is 0.56 A. In the triisopropylsilyl complexes of C B n H 6Br6" and C B n H 6Cl6‘ the silicon out-of-plane distances are 0.300 A and 0.307 A, respectively. In C B n H 6l6" the out-of-plane distance is 0.400 A. Therefore, in the hexa- iodo complex this distance is closer to those values found in sim ilar hexahalo carboranes than that of organohalosilanes. The average of the three silicon carbon angles is 115.6°. Me3SiBr has an average of 111.3° for the silicon carbon angles and C B n H 6Br6 an average of 117.0°. In addition, if one considers the sum of the carbon silicon angles, a difference is clearly seen. Me3SiBr has a carbon silicon angle sum of 333.9°; the sum in the ideal tetrahedral molecule is 328.5°; the sum in C B n H 6 Br6 " is 351.0°; the sum in the hexaiodo complex is 346.8°; in an ideal trigonal planar molecule the sum w ould be 360°. Again, in com parison the Z C-Si-C° for the C B n H 6l6 “ derivative is closer to values for the C B n H 6Br6" derivative. These values appear to be in between that of a covalently bonded halosilane and a purely sp2 planar R3Si+ cation. The long Si-I bond length and lower out-of plane distance also support an approach to planarity. Therefore, silicon exhibits some ionic character w ith the degree of covalency being determ ined relative to the other /zexahalogenated carborane triisopropyl complexes. As seen in Table 6.2 the smaller the Si-X bond distance, the greater the Si-X-B angle becomes. Since the size of the anion increases as X increases, the overall approach of each anion to the silicon center 92 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. is about the sam e i.e. the approximate van der W aals approach of B-H bonds of the anion to z-propyl groups on silicon. This is reflective of an electrostatic interaction rather than a covalent one. In addition the B(7)-X bonds are minimally extended as com pared to the uncoordinated B(8- ll) bonds, Table 6.1. Therefore, there is little change in the nature of the B-X bonds that could be seen if significant covalency were present between the Si-X interaction. This does not rule out covalency all together, but rather each anion is seen to lie along the continuum of pure tetrahedral to pure trigonal planar cation. “ ■ > A . I+ \ B n C H 6I5f A) Iodonium ion 1 1 5 . 6 f W J f ------ j \ 5 B) Partial Silylium ion 120 H .+ A (Bn CH6I6)- C) Silylium ion Figure 6.7 Schem e o f the Approach T ow ards the Silylium Ion 93 R eproduced with perm ission o f the copyright owner. Further reproduction prohibited without perm ission. A reasonable explanation for the overall approach of the three anions to the silicon center being about the same has recently been given by Xie and Reed.6 They conclude that the nature of the Si-X interaction is different depending on the halogen. In considering the order of first ionization potential of the halogens, iodonium ions are m ore stable than brom onium ions, and more so than chloronium ions.8 It follows that the degree of halonium ion character will increase with increasing halogen size, w ith iodonium character the m ost likely of the three. Therefore, hexaiodo contributes the most halonium ion character, see Figure 6.7. In this sense, the bond distance m ay reflect the degree of covalency in the Si-X interaction (sheer orbital overlap). The B(7)-C1 is about the same net distance aw ay from silicon as B(7)-I (0.25 A) for a covalent bond, however the ratio of net Si-X distance to covalent distance is greater for C B n H 6Cl6" than for C B n H 6l6“- This shows that bonding the Si-Cl contact has the least covalency and most electrostatic interaction; the Si-I contact having the m ost covalency and least electrostatic interaction. Thus, hexachloro has the most silylium ion character and hexaiodo less so. In support of this the H B NMR of z-Pr3Si[c/oso-(7-12)-l6CBnH6] shows definite contact between silicon and 1(7) by loss of sym m etry in the spectrum; this in itself, does not prove greater covalency; an electrostatic interaction could produce the same cage polarization. The B NMR change in coordinated and uncoordinated B-I bonds do not indicate a great change in the B(7)-I bond. A large atom such as iodine m ay not be sp3 hybridized^ in the non-silylium anion; the orbitals are 94 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. large and diffuse, lessening the lone-pair/lone-pair repulsive interaction as well as interaction with borons of the carborane cage. The I(7)-B(7)-B(12) angle is 114.8(11)°. The other I(8-ll)-B (8-ll)- B(12) angles are all about 123-125°; in the silver(I) complex of hexa iodo all I(8-ll)-B(8-ll)-(-B(12) angles are between 120.2°[I(8)] and 124.5°[1(10)]. This would indicate that 1(7) is m oving relative to the carborane cage rather than the whole cage itself tilting tow ards the silicon center. In having a sm aller I(7)-B(7)-B(12) angle the entire anion may more closely approach the cationic silicon center. In this sense iodine may change hybridization or simply form a stronger contact w ith silicon at the expense of a longer and less strong bond with B(7).10 W hether the 1(7) is sim ply polarized via an electrostatic interaction or is involved covalently with silicon, or both: some orbital overlap, w ith some stabilization from an electrostatic interaction, the triisopropylsilyl center displays little C-H hyperconjugation. These lead to planarity: C+-CH3 <—> C=CH2 H+ ref. 11 Since the hexabromo complex is in a condensed m edium , C-H hyperconjugation is helping to stabilize the /-Pr3Si moiety and thus its greater planarity. If it were in the gas phase, planarity would be the geom etry and C-H hyperconjugation stabilizing the cation. In hexa iodo the largest isopropyl carbon-silicon bond angle. C(5)-Si-C(8), is 120.7°, and the C-Si-C angle sum is 346.8°. However, the bond angles of the carbons of the isopropyl groups are all around the 95 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. sp3 hybridized 110°. The hydrogens of the isopropyl carbons are in the correct position to contribute hyperconjugatively; in contrast though the Si-C and C-C bonds are all of tetrahedral length (see Table 6 .6). Thus, while the C(5)-H and C(8)-H bonds could be involved in some stabilization of the silicon center, the X-ray data does not show this. The possibility that both C(5)-H and C(8)-H’ s are interacting w ith the silicon center cannot be precluded. 6.4 Summary While the X-ray crystal structure shows that for the triisopropylsilyl hexaiodo complex the silicon is not in its m ost nearly planar geometry, data indicate that there is an approach to the trigonal planar geometry. H b NMR reflect an anion/cation contact in toluene not seen w ith the analogous hexabromo complex. Thus, the conclusion is made that C B n H 6l6" is more coordinating than C B n H 6 Br6" or C B n H 6Cl6" anions in this medium. Although C-H hyperconjugation is likely present in the hexa bromo complex, allowing greater planarity, and perhaps not as obviously present in hexaiodo, crystal packing factors m ay play a significant part in the lesser planarity of the C B n H 6l6" moiety. To test this other trialkylsilyl complexes could be synthesized. Two extremes w ould be X-ray structural analysis of the tri-f-butyl and trim ethylsilyl complexes. The trimethyl would be smaller, perhaps allowing C-H hyperconjugation, leading to a m ore trigonal planar silicon. In contrast, tri-f-butyl w ould only allow C-C hyperconjugation, and sterically be less likely to have a tetrahedral geometry, leading to an 96 R eproduced with perm ission o f the copyright owner. Further reproduction prohibited without perm ission. overall more electrostatic and less covalent interaction betw een hexa iodo and the silicon center. In isolating the triisopropylsilyl hexaiodo com plex, the com parison of hexahalo carborane anions w ith this m oiety is nearly complete. CBnH 6Cl6" has been show n to be the least coordinating followed by CBnH6Br6" and C B nH 6l6_ in the series. W hat rem ains is the synthesis of a hexafluoro (CB11H 6F6") complex. This anion has yet to be made. 6.5 References 1. Xie, Z.; Reed, C.A. unpublished results. 2. a) Olah, G. A.; Field, L Organometallics 1982, 1 ,1485. b) Grum bine, S. K.; Tilley, T. D.; A rnold, F. P.; Rheingold, A.L. /. Am. Chem. Soc. 1994, 116, 5495. c) Kutzelnigg, W.; Fleischer, U.; Schindler, M. NMR; Basic Principles and Progress; Diel, P.; Fluck, E.; G unther, H.; Kosfeld, R.; Selling, J., Eds.; Springer- Verlag, New York, 1989, Vol. 23. 3. Xie, Z.; Jelinek, T.; Bau, R.; Reed, C. A. /. Am. Chem. Soc. 1994,116,1907. 4. Xie, Z.; Bau, R.; Benesi, A.; Reed, C. A. Organometallics 1995,14, 3933. 5. Shelly, Kenneth, Ph.D. Dissertation, D epartm ent of Chemistry, University of Southern California, 1985. 6. Xie, Z.; M anning, J.; Reed, R. W.; M athur, R.; Boyd, P. D. W.; Benesi, A.; Reed, C. A. J. Am. Chem. Soc. 1996, 118,2922. 97 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. References Continued. 7. Patai, S.; Rappoport, Z eds. The Chemistry of Organic Silicon Compounds, Part I John W iley & Sons, New York, 1989. 8. Olah, G.; Prakash, S. G. K; Sommer, J. Superacids, Wiley- Interscience, New York, 1985, pp 193-206, 9. G ray, H. B. Chemical Bonds: A n Introduction to Atomic and Molecular Structure, B enjam in/C um m ings Publishing Co., Menlo Park, CA 1973. 10. Maly, K.; Subrtova, V.; Petricek, V. Acta Cryst. 1987, C43, 593; Dang, H.; Linstrumelle, G. Tett. Lett. 1978, 191. 11. Lowry, T. H. and Richardson, K. S. Mechanism and Theory in Organic Chemistry, 3rd ed., H arper Collins Publishers, Inc., N.Y., 1987. R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. Table 6.3 Crystal Data for z-Pr3Si[c/oso-(7-12)-l6CBnH6]. Empirical Formula Color; Habit Crystal Size (m m ) Crystal System Space Group Unit Cell Dimensions Volume Z Formula Weight D en sity (ca lc.) Absorption C oefficient F (000) pale-yellow, a ir s e n s itiv e 0 . 4 * 0 . 3 5 * 0 . 3 Orthorhombic Pbca a = 1 8 . 3 6 7 ( 5 ) A b = 1 5 . 7 3 2 (4) A C = 2 0 . 7 9 4 (7) A 6 0 0 8 ( 3 ) A3 8 1 0 5 5 . 7 2 . 3 3 4 Mg/m3 6 . 2 4 4 m m 1 3 7 9 2 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. Table 6.4 Data Collection for i-Pr3Si[c/oso-(7-12)-l6CBnH6]- D i f f r a c t o m e t e r U sed R a d i a t i o n T e m p e r a t u r e (K) M onochrom a t o r 20 R a n g e S c a n T y p e S c a n S p e e d S c a n R a n g e (cj) B a c k g r o u n d M e a s u r e m e n t S t a n d a r d R e f l e c t i o n s I n d e x R a n g e s R e f l e c t i o n s C o l l e c t e d I n d e p e n d e n t R e f l e c t i o n s O b s e r v e d R e f l e c t i o n s A b s o r p t i o n C o r r e c t i o n S i e m e n s P4 MoKor (X = 0 . 7 1 0 7 3 A) 223 H i g h l y o r i e n t e d g r a p h i t e c r y s t a l 2 . 0 t o 4 5 . 0 ° 2 6-0 o V a r i a b l e ; S . 00 t o 3 0 . 0 0 / m i n . m cj o 1 . 2 0 p l u s K o r - s e p a r a t i o n S t a t i o n a r y c r y s t a l a n d s t a t i o n a r y c o u n t e r a t b e g i n n i n g a n d e n d o f s c a n , e a c h f o r 5 0 .0 V o f t o t a l s c a n t i m e ' 3 m e a s u r e d e v e r y 97 r e f l e c t i o n s - 1 s h s I S , - 1 s k s 15 - 1 s t s 20 4 0 2 9 •3215 (R. = 3 .1 8 V ) i n t 2 1 6 5 (F > 4 . O ff(F )) Yes 100 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. Table 6.5 Solution and Refinement for /-Pr3Si[c/oso-(7-12)-l6CBnH6]. S y s t e m U s e d S o l u t i o n R e f i n e m e n t M e th o d Q u a n t i t y M i n i m i z e d A b s o l u t e S t r u c t u r e E x t i n c t i o n C o r r e c t i o n H y d r o g e n Atom s W e i g h t i n g Schem e N um ber o f P a r a m e t e r s R e f i n e d F i n a l R I n d i c e s ( o b s . d a t a ) R I n d i c e s ( a l l d a t a ) • G o o d n e s s - o f - F i t L a r g e s t a n d Mean a / a D a t a - t o - P a r a m e t e r R a t i o L a r g e s t D i f f e r e n c e P e a k L a r g e s t D i f f e r e n c e H o l e S i e m e n s SHELXTL IR IS D i r e c t M e th o d s F u l l - M a t r i x L e a s t - S q u a r e s £ w (F - F ) 2 o c N/A N/A R i d i n g m o d e l , f i x e d i s o t r o p i c U w_1 = a 2 (F) * 0 . 0 0 1 6 F 2 148 R = 4 . 6 6 *, WR = 6 . 1 8 % R = 8 . 1 8 *, wR = 7 . 8 3 % 1 . 0 9 0 . 2 0 2 , 0 . 0 1 9 1 4 . 6 : 1 . - 3 1 . 2 5 eA - 0 . 8 1 eA-3 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. Table 6.6 Bond Lengths (A) for /-Pr3Si[c/oso-(7-12)-l6CBnH6]. 1 ( 7 ) - S i 2 .6 8 1 (6) 1 ( 7 ) - B (7) 2 . 227 (20) I ( 8 ) - B (8) 2 .1 8 4 (20) 1 ( 9 ) - B (9) 2 . 157 (20) 1 ( 1 0 ) - B (10) 2 .1 7 4 (21) 1 ( 1 1 ) - B ( l l ) 2 . 165 (21) I ( 1 2 ) - B (12) 2 .173 (20) S i - C ( 2 ) 1. 875 (21) S i - C ( S ) 1 .9 0 2 (21) S i - C (8) 1 . 8 7 2 (22) C ( l ) - B (2) 1 .7 3 6 (28) C (1) -B (3 ) 1 . 7 1 3 (2 S ) C ( l ) - B (4) 1 .6 7 8 (26) C { 1 ) - B (5) 1. 701 (29) C ( l ) - B (6) 1 .7 0 S (26) C ( 2 ) - C (3) 1 . 559 (33) C ( 2 ) - C (4) 1 .5 0 4 (29) C (5) - C (6) 1 . 5 3 1 (30) C (5 ) -C (7 ) 1 .5 1 9 (30) C ( 8 ) - C (9) 1. 504 (34) C ( 8 ) -C (IO ) 1 .S 5 3 (33) B ( 2 ) - B (3) 1 . 8 0 1 (30) B ( 2 ) - B (6) 1 .8 0 3 (30) B ( 2 ) - B (7) 1 . 7 1 5 (30) B ( 2 ) - B ( l l ) 1 .7 9 6 (31) B ( 3 ) - B (4) 1 . 8 1 1 (28) B ( 3 ) - B (7) 1 .7 5 6 (28) B ( 3 ) - B (8) 1 .8 1 3 (28) B ( 4 ) - B ( S ) 1 .7 4 6 (31) B ( 4 ) - B (8) 1 . 8 0 0 (28) B (4 ) - B (9) 1 .7 6 9 (28) B ( 5 ) - B (6) 1 . 7 1 9 (30) B ( 5 ) - B (9) 1. 774 (31) B ( 5 ) -B (1 0 ) 1 . 7 5 9 (32) B ( 6 ) - B (10) 1 .7 9 0 (29) B ( 6 ) - B (11) 1 . 7 9 2 (29) B (7) - B (8) 1 .8 0 6 (28) B ( 7 ) - B (11) 1 . 7 8 9 (28) B ( 7 ) - B (12) 1 . 8 2 9 (28) B ( 8 ) - B (9) 1 . 7 9 4 (28) B ( 8 ) - B (12) 1 .8 1 0 (28) B ( 9 ) -B (1 0 ) 1 . 772 (29) B (9) - B (12) 1 .8 4 0 (28) B ( 1 0 ) - B ( l l ) 1 . 7 9 2 (29) B ( 1 0 ) - B (12) 1 .7 5 9 (29) B ( 1 1 ) - B (12) 1 . 786 (29) 102 R eproduced with perm ission of the copyright owner. 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Table 6.7 Bond Angles (deg) for /-Pr3Si[c/oso-(7-12)-l6CBiiH6]- S i - I ( 7 ) - B (7) 110. 3 5) 1(7 - S i - C (2) 104 . 3 7) I ( 7 ) - S i - C ( S ) 10 4 .8 6) C (2 -S i-C (S ) 113.2 9) I ( 7 ) - S i - C {8) 9 7 .7 7) C (2 - S i - C (8) 112.9 10) C ( S ) - S i - C ( 8 ) 1 2 0 .7 9) B (2 - C ( l -B (3) 63 .0 11) B ( 2 ) - C ( I ) - B ( 4 ) 1 1 5 .6 14) B (3 - C ( l -B (4) 6 4 .6 11) B ( 2 ) - C ( l ) - B (5) 113 . 5 14) B (3 - C ( l -B (5) 1 1 5 .7 14) B ( 4 ) - C ( l ) - B ( S ) 6 2 .2 12) B (2 -C (l -B (6) 6 3 .2 12) B (3) -C ( I ) -B (6) 1 1 5 .5 14) B (4 - C ( l -B (6) 113.1 14) B ( S ) - C ( l ) - B ( 6 ) 6 0 .6 12) S i - C ( 2 ) - C (3) 114 . 1 15) S i - C (2) - C (4) 1 1 6 .4 14) C (3 -C (2 -C (4 ) 110 . 0 18) S i - C ( 5 ) -C(6) 112. 9 14) S i - C ( S ) - C (7) 110 . 3 14) C ( 6 ) - C ( 5 ) - C (7) 1 0 9 .7 17) S i - C (8) - C (9) 120.6 16) S i - C ( 8 ) - C ( I O ) 1 0 8 .2 15) C (9 -C (8 -C(10) 111.4 19) C ( I ) - B { 2 ) - B (3) 5 7 .9 11) C(1 -B (2 -B (6) 5 7.6 11) B (3) -B (2) -B (6) 1 0 6 .6 IS) C(1 -B (2 -B (7) 103 .4 15) B (3) -B (2) -B (7) S 9 . 9 12) B(6 -B (2 -B (7) 1 0 7 .5 IS) C ( l ) - B ( 2 ) - B (11) 104. 1 15) B (3 -B (2 - B ( l l ) 1 0 9 .0 15) B ( 6 ) - B ( 2 ) - B (I1 ) 5 9 .7 12) B (7 -B (2 - B ( l l ) 6 1 .2 12) C ( l ) -B (3) -B (2) 5 9 .1 11) C(1 -B (3 -B (4) 56 . 8 10) B (2) -B (3) -B (4) 1 0 6 .2 14) C(1 -B (3 -B (7) 102 . 7 13) B (2) -B (3) -B (7) 5 7 .6 11) B (4 -B (3 -B (7) 106 . 8 14) C ( l ) - B ( 3 ) - B (8) 102. 9 13) B (2 -B (3 -B (8) 1 0 6 .6 14) B ( 4 ) - B ( 3 ) -B{8) 5 9 .6 11) B (7 -B (3 -B (8) 6 0 .8 11) C ( l ) - B ( 4 ) - B (3) 5 8 .7 11) C(1 -B (4 -B (5) S9.5 12) B ( 3 ) - B ( 4 ) - B ( 5 ) 1 0 8 .7 14) C(1 -B (4 -B (8) 104 . 9 14) B (3) r B ( 4 ) -B (8) 60. 3 11) B (5 -B (4 -B (8) 1 0 7 .8 IS) C ( l ) - B ( 4 ) -B (9) 1 0 7 .0 14) B (3 -B (4 -B (9) 10 9 .8 14) B ( S ) - B ( 4 ) - B ( 9 ) 6 0 .6 12) B (8 -B (4 -B (9) 6 0 .3 11) C ( l ) - B ( S)-B (4) 5 8 .2 11) C(1 -B (5 -B (6) 5 9 .8 12) B ( 4 ) -B (5 > -B (6 ) 1 0 9 .1 16) C(1 -B (5 -B (9) 1 0 5 .8 IS) B ( 4 ) - B ( 5 ) - B ( 9 ) ’ 6 0 .3 12) B (6 -B (5 -B (9) 1 1 0 .6 16) C (1) -B(S) -B (10) 1 0 6 .7 15) B (4 -B (5 - B (10) 1 0 8 .5 16) B (6) -B (5) -B (10) 6 1 .9 12) B (9 -B (5 -B(10) 6 0 .2 12 j C (1) -B (6) -B (2) 5 9 .3 11) C(1 -B (6 -B(S) 5 9 .6 12) B ( 2 ) - B ( 6 ) - B ( 5 ) 1 0 9 .3 15) C(1 -B (6 -B(10) 1 0 5 .2 14) B ( 2 ) - B ( 6 ) - B (10) 1 0 7 .9 14) B (5 -B (6 -B(10) 6 0 .1 12) C ( l ) - B ( 6 ) - B (11) 1 0 5 .6 14) B (2 -B (6 - B (11) 6 0 .0 12) B(5) - B ( 6 ) - B (11) 1 0 9 .0 15) B ( 1 0 ) - B ( 6 ) - B (11) 6 0 .0 11) 1 (7) -B (7) -B (2) 1 2 5 .6 13) 1 (7 -B (7 -B (3) 1 2 3 .7 12) B (2) -B (7) -B (3) 6 2 .5 12) 1(7 -B (7 -B (8) 117 . 8 11) B (2) -B (7) -B (8) 1 1 0 .8 14) B (3 -B (7 -B (8) 6 1 .2 11) 1 ( 7 ) - B ( 7 ) - B (11) 1 2 0 .0 12) B (2 -B (7 - B (11) 6 1 .6 12) B (3) -B (7) -B (11) 1 1 1 .4 14) B(8 -B (7 - B (11) 107 . 8 14) 1(7) -B (7) -B (12) 1 1 4 .8 11) B (2 -B (7 - B (12) 1 0 9 .8 14) B (3) -B (7) -B (12) 1 1 0 .1 14) B (8 -B (7 - B (12) 5 9 .7 11) B ( 1 1 ) - B ( 7 ) - B (12) 5 9 .1 11) 1(8 -B (8 -B {3) 1 1 8 .1 12) 1 (8) -B (8) -B (4) 1 2 0 .6 12) B(3 -B (8 -B (4) 6 0 .2 11) 1 (8) -B (8) -B (7) 1 2 3 .1 12) B (3 -B (8 -B (7) 5 8 .1 11) B (4) -B (8) -B (7) 1 0 S .2 13) I (8 -B (8 -B (9) 122.8 12) B (3) -B (8) -B (9) 1 0 8 .7 13) B (4 -B (8 -B (9) 5 9 .0 11) B (7) -B (8) -B (9) 1 0 8 .6 14) 1(8 -B (8 - B (12) 124 .6 12) B (3) -B (8) -B (12) 1 0 8 .4 13) B (4 -B (8 - B (12) 10 7 .5 13) B (7) - B (8) -B (12) 6 0 .8 11) B (9 -B (8 - B (12) 6 1 .4 11) 1 ( 9 ) - B ( 9 ) - B (4) 1 2 1 .8 12) 1(9 -B (9 -B (5) 12 1 .8 13) B (4) -B (9) -B (5) 5 9 .0 12) 1 (9 -B (9 -B (8) 123 .2 12) B (4) -B (9) -B (8) 6 0 . 7 11) B(S -B (9 -B (8) 106 . 9 14) R eproduced with perm ission of the copyright owner. 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Table 6.7 Continued. 1 ( 9 ) - B ( 9 ) - B ( 1 0 ) 1 2 2 .1 (1 2 ) B (S> - B ( 9 ) - B ( I O ) 5 9 . 5 ( 1 2 ) 1 ( 9 ) -B < 9 )-B (1 2 ) 1 2 3 .6 (1 2 ) B ( S) - B ( 9 ) - B ( 1 2 ) 1 0 5 .6 (1 4 ) B ( 1 0 ) - B ( 9 ) - B (12) 5 8 .2 ( 1 1 ) 1 ( 1 0 ) - B ( 1 0 ) - B ( 6 ) 1 1 8 .8 (1 2 ) 1 ( 1 0 ) - B ( 1 0 ) - B ( 9 ) 1 2 2 .8 (1 2 ) B ( 6 ) - B ( 1 0 ) - B ( 9 ) 1 0 7 .5 (1 4 ) B ( 5 ) - B ( 1 0 ) - B ( l l ) 1 0 7 .3 (1 5 ) B ( 9 ) - B ( 1 0 ) - B ( l l ) 1 1 0 .5 (1 4 ) B ( 5 ) - B ( 1 0 ) - B (12) 1 0 9 .9 (1 5 ) B ( 9 ) - B ( 1 0 ) - B (12) 6 2 . 8 ( 1 2 ) I ( 1 1 ) - B ( l l ) - B ( 2 ) 1 2 0 .6 (1 3 ) B ( 2 ) - B ( l l ) - B ( 6 ) 6 0 .3 ( 1 2 ) B ( 2 ) - B ( l l ) - B (7) 5 7 .1 ( 1 1 ) 1 ( 1 1 ) - B ( l l ) - B ( 1 0 ) 1 2 3 .4 (1 3 ) B ( 6 ) - B ( l l ) - B ( 1 0 ) 5 9 .9 ( 1 2 ) I ( 1 1 ) - B ( l l ) - B ( 1 2 ) 1 2 2 .3 (1 2 ) B ( 6 ) - B ( l l ) - B ( 1 2 ) 1 0 7 .1 (1 4 ) B ( 1 0 ) - B ( l l ) - B ( 1 2 ) 5 8 . 9 ( 1 1 ) 1 ( 1 2 ) - B ( 1 2 ) - B ( 8 ) 1 2 0 .6 (1 2 ) 1 ( 1 2 ) - B ( 1 2 ) - 8 ( 9 ) 1 2 2 .2 (1 2 ) B ( 8 ) - B ( 1 2 ) - B (9) 5 8 .9 ( 1 1 ) B ( 7 ) - B ( 1 2 ) - B (10) 1 0 6 .3 (1 4 ) B ( 9 ) - B ( 1 2 ) - B (10) 5 9 .0 ( 1 1 ) B ( 7 ) - B ( 1 2 ) - B ( l l ) 5 9 .3 ( 1 1 ) B ( 9 ) - B ( 1 2 ) - B ( l l ) 1 0 7 .7 (1 4 ) B (4) - B (8) - B (4) - B (8) - 1 ( 1 0 ) B (5) - B (5) - 1 (10 ) B (6) - 1 (10 ) B (6) - B (11) K l l ) 1 ( 1 1 ) B (6) - B (2) - B (7) - B (2) - B (7) - 1 ( 1 2 ) B (7) - B (7) - 1 ( 1 2 ) B (8) - 1 ( 1 2 ) B (8) - B (10) B ( 9 ) - B (10) B ( 9 ) -B(10) B ( 9 ) - B (12) B( 9 ) - B (12) - B ( 1 0 ) - B (5) B(10)-B(6) B ( 1 0 ) -B(9) - B ( 1 0 ) - B ( l l ) B ( 1 0 ) - B ( l l ) - B ( 1 0 ) - B (12) B(10)-B(12) - B ( 1 0 ) - B (12) -B ( 1 1 ) - B (6 ) -B (11 ) -B (7 ) B ( 1 1 ) -B(7) B ( 1 1 ) -B(10) B ( 1 1 ) -B(10) B i l l ) - B (12) B(11)-B(12) - B ( 1 2 ) -B (7) B ( 12) -B ( 8 ) B ( 1 2 ) - B (9) - B ( 1 2 ) -B(10) B ( 1 2 ) -B(10) - B (12 ) -B (11 ) B( 1 2 ) - B ( l l ) - B ( 1 2 ) - B ( l l ) 1 0 6 .9 (1 4 ) 106 .4 (14) 1 0 7 .5 (14) 5 9 .7 ( 1 1 ) 1 2 0 .0 (1 3 ) 5 7 .9 ( 1 2 ) 6 0 .3 ( 1 2 ) 1 2 0 .7 (1 2 ) 6 0 .1 ( 1 1 ) 1 2 3 .8 (1 3 ) 1 0 8 .4 (1 4 ) 6 0 .4 ( 1 1 ) 1 2 2 .5 (1 2 ) 1 2 2 .9 (1 3 ) 104 .8 (14) 1 0 8 .1 ( 1 5 ) 1 0 6 .6 ( 1 4 ) 1 0 8 . 1 ( 1 4 ) 6 1 . 5 ( 1 1 ) 1 2 2 .8 (12) 5 9 . 5 (11) 1 0 5 .6 (13) 1 2 3 . 9 ( 1 2 ) 1 0 6 .3 (14) 1 2 2 . 8 ( 1 2 ) 1 0 7 .8 (14) 6 0 . 7 ( 1 1 ) 104 R eproduced with perm ission of the copyright owner. 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Table 6.8 Atomic Coordinates (xlO4) and Equivalent Isotropic Displacement Coefficients (A^ x 103) for z-Pr3Si[c/oso-(7-12)-l6CBnH6]- 1(7) X 428 (1) y 4081 1) z 3976(1) U(eq) 42(1) 1(8) 80 (1) 3919 1) 2056(1) 60 (1) 1(9) 1916 (1) 4916 1) 1160(1) 63 (1) I (10) 3384 (1) 5537 1) 2S67(1) 55 (1) 1(11) 2484 (1) 4972 1) 4318(1) 58 (1) I (12) 1166 (1) 5952 1) 2895(1) 41(1) Si 176 (3) 2763 4) 4746 (3) 41(2) C(l) 2343 (9) 2784 11) 2731 (8) 29 (4) C(2) 846 (11) 2897 13) 5420(10) 50 (4) C (3) 771 (14) 3753 16) 5791(12) 83 (5) C (4) 1632 (11) 2735 13) 5259(9) 49 (4) C(S) 363 (11) 1790 13) 4229(9) 48 (4) C (6) -167 (12) 1705 15) 3664(11) 66 (5) C (7) 339 (12) 989 14) 4637(10) 62 (5) C (8) -776 (12) 3048 14) 4985(10) 58 (5) C (9) -1346 (14) 3214 17) 4481 (13) 90 (5) C(10) -1043 (14) 2387 16) 5487(12) 84 (5) B (2) 2072 (12) 3142 15) 3484(11) 42 (5) B (3) * 1425 (11) 2852 13) 2871(10) 27 (4) B (4) 1842 (11) 3130 13) 2109(10) 29 (4) B (S) 2701 (13) 3562 15) 2259(11) 45 (5) B (6) 2858 (11) 3564 13) 3074(10) 27 (4) B (7) 1350 (11) 3797 12) 3315(10) 26 (4) B (8) 1174 (11) 3827 13) 2461(10) 26 (4) B (9) 1964 (11) 4243 12) 2063(10) 27 (4) B (10) 2589 (12) 4524 14) 2677(10) 30 (4) B (11) 2223 (11) 4270 13) 3453(10) 34 (4) B (12) 1659 (11) 4700 12) 2833(9) 24 (4) * Equivalent isotrop ic U defined as one third of the trace of the orthogonalized U. . tensor 1 0 5 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. Table 6.9 Anisotropic Displacement Coefficients (A^ x 10^) for z-Pr3Si[c/oso-(7-12)-l6CBnH6]. U 11 U22 U33 U 12 U13 U 23 1 (7 ) 45 (1 34 (1) 46 (1 7 ( 1 ) 23 (1) 10(1) 1(8) 3S (1 7 7 ( 1 ) 67 (1 8(1) - 2 1 ( 1 ) - 1 1 ( 1 ) 1 (9 ) 76 (1 8 1 ( 1 ) 3 1 ( 1 3 2 (1 ) 12 (1) 20 (1) I (10) 36 (1 35 (1) 96 (1 - 6 ( 1 ) 12 (1) 18 (1) r (ii) 71 (1 62 (1) 41 (1 - 1 2 ( 1 ) - 1 7 ( 1 ) - 1 2 ( 1 ) 1(12) 4 1 ( 1 2 7 ( 1 ) 5 5 ( 1 8(1) 12 (1) 5 (1) S i 35 (3 4 2 ( 3 ) 46 (3 - 2 ( 3 ) 8 ( 3 ) 14 (3) T h e a n i s o t r o p i c d i s p l a c e m e n t f a c t o r e x p o n e n t t a k e s t h e f o r m : -2ir2 ( h 2 a* . . + 2 h k a * b * U1 2 ) R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. Table 6.10 H-Atom Coordinates (xlO4) and Isotropic Displacement Coefficients (A2 x 103) for /-Pr3Si[c/oso-(7-12)-l6C B n H 6 ]. X y Z U H (1) 716 2459 5750 65 H (2) 1082 3801 6154 95 H (3) 884 4224 5504 95 H (4) 275 3854 5939 95 H (5) 1688 2175 5089 58 H (6) 1782 3138 4951 58 H (7) 1931 2785 5635 58 H (8) 844 1843 4044 62 H (9) -659 1673 3796 75 H (10) -139 2219 3378 75 H (11) -60 1237 3386 75 H (12) -142 909 4810 77 H (13) 450 490 4382 77 H (14) 675 1020 4979 77 H (IS) -745 3616 5206 69 H (16) -1799 3368 4638 96 H (17) -1184 3642 4171 96 H (18) -1400 2692 4224 96 H (19) . -1508' 2561 5687 99 H (20) -1102 1854 5311 99 H (21) -702 2355 5848 99 1 0 7 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. CHAPTER SEVEN CONCLUSION AND FUTURE PROSPECTS 7.1 Summary While the m ain em phasis of this thesis was to dem onstrate the synthesis and identity of the hexaiodo anion and subsequently test it's coordinative properties, the path to this accomplishm ent led to other new experimental findings. In working with both the anion and neutral zw itterion clear differences in reactivity were found. Hopefully a better understanding of the necessary synthetic pathw ays to reach the desired synthetic goals has been achieved. The twelve-bromo zw itterion was synthesized for the first time using NBS. In extending this work, elemental brom ine could also be tried, and in doing so, see if it can brominate the 12-position of the zw itterion as cleanly as NBS. NIS, elemental iodine and elemental chlorine could also be tried. As a result of synthesizing the 12-bromo zw itterion, experimental evidence shows that the 12-position can m ost probably be alkylated. The palladium(O) mediated coupling reaction appears to be m ore facile with iodine-boron bonds than w ith brom ine-boron bonds.1'2 The zwitterion seems to be ignored because it is not charged. However, its use as an anion precursor is available, as well as its use as a 10b enriched m oiety for the use in Boron N eutron C apture Theory. Experimentation into 12-B substituted zwitterions^ {i.e. the 108 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. zwitterionic site is at the twelve-boron) are yet to be explored. The carborane C-H bond could now be substituted. If the twelve-position could be altered such that mono-carborane units could be linked, new 'anticrow n'4 ligands could be formed. On the course to the hexaiodo anion, new reagents (NIS, and IC1) were used to effect 12-iodination, and a mixed-halogen anion was formed [7(I),12(Br)]. This could lead to insight as to the way the anion coordinates in different m edia. Furtherm ore, mixed-halogenated anions m ay have unique electronic, steric, reactive, and solubility properties not shown by those w ith all the same halogen. If 1-C, some (7-12)-B, or even (2-6)B alkylation is combined with a mixed halogenated anion, lower nucleophilicity w ith greater solubility m ay be possible. The lower pentagonal belt of the mono-carborane anion has now been fully iodinated and characterized by 2-D 11b-HB COSY NMR and X-ray crystallography. Its synthesis along with hexabiomo and hexachloro anions was essential in producing a series of lower pentagonal belt halogenated anions that were tested for their weakly coordinating properties. In two key tests, the C B n H 6l6" anion was show n to be more coordinating than C B n H 6Br6" or C B n H 6Cl6" anions. In the I.R. spectrum of the iron(II)cyclopentadienylbiscarbonyl cation w ith hexaiodo anion, the analysis showed it to be about as coordinating as the unsubstituted carborane anion, [closo-C B n H i 2]“. W hile more nucleophilic than hexabromo, it is less so than perchlorate or hexafluoroantim onate anions. In X-ray structure analysis, hexaiodo 109 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. did not produce the most planar geom etry in the triisopropylsilyl complex. However data reveal that it does yield the triisopropylsilyl m oiety in a partial planar geom etry, and is not in this test case significantly different than hexabrom o or chloro anions in it's interaction with the z-Pr3Si moiety. If the C B n H 6l6" anion lies at the more coordinating end of the hexahalo carborane anion spectrum , ultim ately the isolation of the yet unknow n hexafluoro anion m ay yield the least coordinating anion. Fluorinated anions have been show n to be weakly coordinating and active w ork on synthesizing new ones are in p r o g r e s s . 5 / 6 The greatest benefit from isolating the hexaiodo anion is that hexaalkyladon by way of the palladium -m ediated coupling reaction m ay now be realized. The goal of hexa- or greater alkylation of the carborane anion would be the test of a new nearly organic anion as a w eakly coordinating species. W ith the palladium catalyzed reaction now feasible, the push to further iodinate and subsequently alkylate the carborane anion is underw ay. A n alkylated anion would then be used to stabilize electrophiles such as (FeTPP)+, (FeCp(CO)2)+/ and R3 Si+ cations to gauge its coordinating capacity. An alkylated or fluorinated anion may prove to be the most w eakly coordinating and least nucleophilic while still retaining the reactivity to be incorporated in chemical systems.^ In the successful isolation of hexaiodo anion, new pathw ays to achieve an even larger m ore weakly coordinating anion have been realized. 110 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. 7.2 References 1. This reaction has been independently investigated by Janousek, Z.; Griiner, B.; Trammel, M.; Michel, J. 209th ACS Meeting Abstracts, Anaheim, CA 1995, ORG 315. 2. Mathur, R.; Reed, C. A.; Unpublished results. 3. Jelinek, T; Plesek, J.; Hermanek, S.; Stibr, B. Collect. Czech. Chem. Commun. 1984, 51, 819. a) H aw thorne, M. F. et al. Angezv. Chem. Int. Ed. Engl. 1991,30,1507. b) Haw thorne, M. F. et al. Angew. Chem. Int. Ed. Engl. 1992,31,893. c) Haw thorne, M. F. et al. J. Am. Chem. Soc. 1992, 114, 380. d) Grimes, R. N. et al. Angezv. Chem. Int. Ed. Engl. 1993,32,1289. e) Haw thorne, M. F. et al. J. Am. Chem. Soc. 1993, 115, 5320. f) H aw thorne, M. F. et al. J. Am. Chem. Soc. 1993, 115,193. g) H aw thorne, M. F. et al. J. Am. Chem. Soc. 1993, 115, 6981. h) H aw thorne, M. F. et al. }. Am. Chem. Soc. 1994, 116, 7142. i) H aw thorne, M. F. et al. Pure & Appl. Chem. 1994, 66, 245. j) W ade, K. et al. Angezv. Chem. Int. Ed. Engl. 1993, 32, 1328. 5. W ilkinson, J. A. Chem. Rev. 1992, 92, 505. 6. Strauss, S. H. Chem. Rev. 1993, 93, 927. R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. SELECTED BIBLIOGRAPHY Atwood, J. D. Inorganic and Organometallic Reaction Mechanisms, Brooks/Cole Publishing Com pany, M onterey, CA, 1985. Bochmann, M. Organometallics 1, Complexes with Transition Metal-Carbon a-Bonds, Oxford University Press, N.Y., 1994. Bochmann, M. Organometallics 2, Complexes with Transition Metal-Carbon K-Bonds, Oxford University Press, N.Y., 1994. Greenw ood, N. N. and Eam shaw, A. Chemistry of the Elements, Pergamon Press, N.Y., 1984. House, H. O. Modern Synthetic Reactions, 2nd ed., W. A. Benjamin, Inc. Menlo Park, CA, 1972. Brown, H. C. Boranes in Organic Chemistry, Cornell Univ. Press Ltd., London, 1972. Olah, G. A.; Prakash, G. K. S.; Williams, R. E.; Field, L. D.; W ade, K. Hypercarbon Chemistry, John Wiley & Sons, N. Y., 1987. W ilkins, R. G. Kinetics and Mechanism of Reactions of Transition Metal Complexes, 2nd ed., VCH, New York, 1991. Huheey, J. E. Inorganic Chemistry, 3rd ed., H arper & Row, Publishers, N.Y., 1983. Ballhausen, C. J.; Gray, H. B. Molecular Orbital Theory, The Benjam in/Cum m ings Publishing Company, Inc., MA, 1964. Purcell, K. F.; Kotz, J. C. Inorganic Chemistry, W. B. Saunders Company, Philadelphia, 1977. 112 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. Selected Bibliography Continued. Pine, S. H. Organic Chemistry, 5th ed., McGraw-Hill Inc., N.Y., 1987. Weeks, D. P. Pushing Electrons, 2nd ed., Saunders College Publishing, N.Y., 1992. H enderson, R. A. The Mechanisms of Reactions at Transition Metal Sites, Oxford University Press, N.Y., 1993. Kegley, S. E.; Pinhas, A. R. Problems and Solutions in Organometallic Chemistry, U niversity Science Books, Mill- Valley, CA, 1986. Sheldrick, W. S. in The Chemistry of Organic Silicon Compounds, Patai, S.; Rappoport, Z. Eds.; Wiley-Interscience: N ew York, 1989; Vol. 1, pp 227-303. 113 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. APPENDIX I REAGENTS AND TECHNIQUE A l.l Reagents Al.1.1 Solvents For glovebox procedures reagent grade acetonltrile (CH3CN), toluene, and hexanes were double distilled from calcium hydride (CaH 2 ) outside the glovebox; then from CaH 2 (for CH3CN) or sodium benzophenone ketyl (for toluene and hexanes) in the glovebox. 1 Reagent grade tetrahydrofuran (THF) was either distilled from lithium alum inum hydride (LiAlH4 )l or used as received. All other solvents were reagent grade and used as received. Acetone d6 [(CD3)2CO], dim ethylsulfoxide d& [(CD3)2SO], and acetonitrile ds [CD3 CN] were stored over activated 4 A molecular sieves. CD3CN was dried over activated 4 A m olecular sieves, and then passed over activated neutral alum ina (dried at 270-300°C for 24 hours in vacuo) in the glovebox. Toluene d$ was distilled from sodium benzophenone ketyl in the glove box. Al.1.2 O ther Materials Trityl brom ide was recrystallized twice from toluene and stored under argon or in a glovebox. Cs[cZoso-CBnHi2] and c/oso-l-NMe3- CB11H 11 were prepared by modification of previously reported m ethods.^ O ther commercially available chemicals were reagent grade and purchased from Aldrich Chemical Com pany and used as received. 114 R eproduced with perm ission o f the copyright owner. Further reproduction prohibited without perm ission. A1.2 Technique For air- and moisture-sensitive com pounds experimental m anipulations requiring an inert atm osphere were carried out using either standard vacuum^ arid Schlenk techniques^ under argon (pre purified grade), or in an helium atmosphere glovebox (02, H2O <0.5 ppm). A1.3 References 1. Perrin D. D.; Armarego, W. L. F.; Perrin, D. R. Purification of Laboratory Chemicals, 2nd ed., Pergam on Press, New York, 1980. 2. a) Shelly, Kenneth, Ph.D. Dissertation, Departm ent of Chemistry, University of Southern California, 1985. b) Reed, R.W.; Manning, J.; M athur, R.; Xie, Z.; Reed, C.A. Unpublished results. 3. Coyne, G. S. The Laboratory Handbook of Materials, Equipment, and Technique, Prentice-Hall, Inc. New Jersey, 1992. 4. Wayda, A. L.; Darensbourg, M. Y., eds. Experimental Organometallic Chemistry A Practicum in Synthesis and Characterization, American Chemical Society, 1987. 1 1 5 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. APPENDIX 2 PHYSICAL MEASUREMENTS A2.1 Nuclear M agnetic Resonance (NMR) S p e c t r o s c o p y ^ All 5 mm and 10 mm NM R tubes were purchased from W ilm ad Glass Company. HB NMR spectra were recorded on a Bruker WP-270 spectrom eter using BF3 -Et2 0 as external standard (0.0 ppm w ith negative values upfield). HB NM R of Ag[c/oso-(7-12)-l6CBnH6], [Ph3C] [closo-{7- 12)-l6CBnH6]/ and z'-Pr3Si[c/oso-(7-12)-l6C B n H 6] were recorded in 5 mm diam eter NMR tubes. All other HB NMR were recorded in 8 mm diam eter Pyrex tubes fitted into 10 mm diam eter standard NMR tubes. lH and 13c NMR spectra were recorded on a Bruker AC-250, Bruker AM-360, or Bruker AM-500 spectrom eters in 5 m m NMR sample tubes. Proton and carbon chemical shifts were m easured relative to residual lH and 13c in the appropriate deuterated solvent ((CD3)2CO; (CD3)2SO; CD3CN). Two-dimensional (2-D) llg - llB NMR spectra were recorded in 5 mm NMR sample tubes on a Bruker AM-500 spectrometer.3 A2.2 Infrared (IR) Spectroscopy IR spectra were recorded on an IBM IR/30S FT instrum ent. All IR supplies were purchased from M cCarthy Scientific. Solution IR was carried out using the appropriate holder fitted with sodium chloride cells (0.2 mm path length provided by a Teflon spacer). All IR sam ples were prepared in the glovebox. 116 R eproduced with perm ission o f the copyright owner. Further reproduction prohibited without perm ission. A2.3 Elem ental Analysis Elemental analyses w ere perform ed by the University of California, Berkeley Microanalytical Lab, Berkeley, California. A2.4 X-ray Crystallography All crystals were m ounted in thin-walled glass capillaries using Paratone-N oil. Diffraction data w ere collected on a Siemens P4/R A or a Syntex P2i diffractometer under the conditions indicated in Tables 5.2-4 and 6.3-5. Crystallographic examinations led to the cell constants and space groups. Absorption correction procedures were applied to the intensity data. Structures were solved by direct m ethods using Siemens Shelxtl PC ™ software or Shelx86.4 In the final m odel, hydrogen atoms were placed in idealized positions and all non hydrogen atoms were refined anisotropically. Data collection and refinem ent param eters, tables of bond lengths, bond angles, anisotropic therm al param eters, calculated hydrogen atomic coordinates, and final atomic coordinates are given in Tables 5.2-5.8 and 6.3-10. A2.5 References 1. Parish, R. V. NM R, NQR, EPR, and Mdssbauer Spectroscopy in Inorganic Chemistry, Ellis H orw ood, Ltd., England, 1990. 2. G unther, H. NM R Spectroscopy, An Introduction, John Wiley & Sons, Ltd., N.Y., 1987. 3. Venable, L. T.; H utton, W. C.; Grimes, R. N. /. Am. Chem. Soc. 1984, 106, 29. 4. Siemens, Shelxtl PC ™ , Siemens Analytical X-ray Instrum ents, Inc., May, 1990. 1 1 7 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. INFORMATION TO USERS This manuscript has been reproduced from the microfilm master. UMI films the text directly from the original or copy submitted. Thus, some thesis and dissertation copies are in typewriter face, while others may be from any type o f computer printer. The quality of this reproduction is dependent upon the quality of the copy submitted. Broken or indistinct print, colored or poor quality illustrations and photographs, print bleedthrough, substandard margins, and improper alignment can adversely affect reproduction. In the unlikely event that the author did not send UMI a complete manuscript and there are missing pages, these will be noted. Also, if unauthorized copyright material had to be removed, a note will indicate the deletion. Oversize materials (e.g., maps, drawings, charts) are reproduced by sectioning the original, beginning at the upper left-hand comer and continuing from left to right in equal sections with small overlaps. Each original is also photographed in one exposure and is included in reduced form at the back o f the book. Photographs included in the original manuscript have been reproduced xerographically in this copy. Higher quality 6” x 9” black and white photographic prints are available for any photographs or illustrations appearing in this copy for an additional charge. Contact UMI directly to order. UMI A Bell & Howell Information Company 300 North Zeeb Road, Ann Arbor MI 48106-1346 USA 313/761-4700 800/521-0600 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. UMI Number: 1384906 Copyright 1997 by Manning, Janet Hillary All rights reserved. UMI Microform 1384906 Copyright 1997, by UMI Company. All rights reserved. This microform edition is protected against unauthorized copying under Title 17, United States Code. UMI 300 North Zeeb Road Ann Arbor, MI 48103 R eproduced with perm ission of the copyright owner. Further reproduction prohibited without perm ission.

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Asset Metadata

Creator Manning, Janet Hillary (author)

Core Title Derivatization chemistry of mono-carboranes

School Graduate School

Degree Master of Science

Degree Program Chemistry

Degree Conferral Date 1997-05

Publisher University of Southern California (original), University of Southern California. Libraries (digital)

Tag chemistry, inorganic,chemistry, organic,OAI-PMH Harvest

Language English

Contributor Digitized by ProQuest (provenance)

Advisor Reed, Christopher (committee chair), [illegible] (committee member)

Permanent Link (DOI) https://doi.org/10.25549/usctheses-c16-13793

Unique identifier UC11341444

Identifier 1384906.pdf (filename),usctheses-c16-13793 (legacy record id)

Legacy Identifier 1384906.pdf

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Document Type Thesis

Rights Manning, Janet Hillary

Type texts

Source University of Southern California (contributing entity), University of Southern California Dissertations and Theses (collection)

Access Conditions The author retains rights to his/her dissertation, thesis or other graduate work according to U.S. copyright law. Electronic access is being provided by the USC Libraries in agreement with the au...

Repository Name University of Southern California Digital Library

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