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Synthesis of fluorosilanes and gas phase rearrangements of chloromethylsilanes

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Synthesis of fluorosilanes and gas phase rearrangements of chloromethylsilanes
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Simon, Roger Anthony
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68 unnumbered leaves : illustrations, charts, samples ; 28 cm

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Organosilicon compounds ( lcsh )
Organosilicon compounds ( fast )
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bibliography ( marcgt )
theses ( marcgt )
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Includes bibliographical references (leaves 47-49).
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Submitted in partial fulfillment of the requirements for the degree, Master of Science, Department of Chemistry
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by Roger Anthony Simon.

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University of Colorado Denver
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Full Text
SYNTHESES OF FLUOROSILANES AND GAS PHASE REARRANGEMENTS OF
CHLOROMETHYLSILANES
by
Roger Anthony Simon
B.A., Reed College, 1985
A Thesis Submitted to the
Faculty of the Graduate School of the
University of Colorado in partial fullfilment
of the requirements for the degree of
Master of Science
Department of Chemistry
1988


This thesis for the Master of Science Degree by
Roger Anthony Simon
has been approved for the
Department of
Chemistry
by
Dr. Robert Damrauer
Dr. Larry Anderson
Dr. Robert Meglen
Date


m
ABSTRACT
A wide variety of fluorosilanes has been prepared from chlorosilanes using
hexafluorosiliconates, Grignard attack or a combination of both. Ammonium
hexafluorosiliconate and refluxing dimethoxyethane afforded a tractable solution from
which products could be isolated by simple aqueous work-up and evaporation of
solvent. Reaction times were generally fast; crude product yields and purities were
high; isolated yields of pure products were between 54 % and 88 %. Ammonium
hexafluorosiliconate was shown to be a mild reagent, preserving Si-Si, Si-O and Si-H
bonds.
Kinetic activation parameters have been determined for a series of
aryl-substituted methylchloromethyl silanes and aryl-substituted dimethylchloromethyl
silanes using the stirred flow pyrolysis technique. The Arrhenius 'A' factors obtained
support a unimolecular pathway for rearrangement.


ACKNOWLEDGMENTS
Many thanks to a whole bunch of folks who made it much easier.
Dr. Robert Damrauer
, Bonnie K. O'Connell
Vemon E. Yost
Stephen E. Danahey
Michael Clarke
Dr. I.M.T. Davidson
Dr. Gerald Larson
Dr. Bernard Kanner
National Science Foundation Grant
CHE-85-19503 (RD)
NATO Grant (RD and IMTD)


V
DEDICATION
To Dr. Ronda Sandifer Bard:
its your turn this time.


TABLE OF CONTENTS
INTRODUCTION............................................................. 1
CHAPTER 1 PREPARATIONS OF FLUOROSILANES
1.1 Introduction........................................... 3
1.2 Results and Discussion................................. 6
1.2.1 Fluorinations of Chlorosilanes via Fluorosiliconates... 6
1.2.2 Fluorinations of Chlorosilanes using Ammonium Fluoride.... 10
1.2.3 Synthesis of Fluorosilanes by Grignard Substitution.... 12
1.3 Experimental........................................... 15
1.3.1 General Experimental................................... 15
1.3.2 Detailed Experimental.................................. 16
CHAPTER 2 GAS PHASE REARRANGEMENTS OF CHLOROMETHYL-
SILANES
2.1 Introduction........................................... 30
2.2 Results and Discussion................................. 32
2.2.1 Interpretation of A factors and Energies of Activation. 34
2.2.2 Relative Migratory Aptitudes of Silicon Substituents... 35
2.2.3 Electronic Substituent Effects in Rearrangements of Chloro-
methylsilanes.......................................... 36
2.2.4 Considerations on Error Analysis....................... 40
2.2.5 Summation of Results................................... 41
2.3 Experimental........................................... 41


vu
2.3.1 SFR Procedural Considerations.......................... 42
2.3.2 Physical Data for the Silanes Studied.................. 42
2.3.3 Mass Spectral Data for the Product Silanes............. 44
REFERENCES............................................................ 47
APPENDIX
A Useful Equations for Kinetics.......................... 50
B Detailed Kinetic Parameters for Chloromethylsilane
Rearrangements...................................... 52
C Stirred Flow Pyrolysis Apparatus....................... 68


TABLES
TABLE
I. Yields of Fluorosilanes from Reaction of Ammonium Hexa-
fluorosiliconate....................................... 7
n. Yields of Fluorosilanes from Reaction of Sodium Hexa-
fluorosiliconate....................................... 8
HI. Comparison of Fluorosilanes from Reaction of Ammonium
Hexafluorosiliconate and Ammonium Fluoride............. 11
IV. Yields of Fluorosilanes generated through Organometallic
Reagents............................................... 14
V. Temperature Ranges and Substituents for
(X-Ar)SiCH3(Y)(CH2Cl).................................. 33
VI. Kinetic Parameters for the Rearrangement of Compounds a
through i.............................................. 33
VII. Hammett Parameters for Chloromethyl Hydrides at 800 K.. 37
VUI. Hammett Parameters for Chloromethyl Dimethyl Silanes at
800 K.................................................. 39
XIX. Rate and Temperature Values for PhSiMe(H)CH2Cl........... 52
X. Rate and Temperature Values for (p-F-CgH^SiMeCHlC^Cl... 54
XI. Rate and Temperature Values for (m-CF3*C5H4)SiMe(H)CH2Cl. 56
XII. Rate and Temperature Values for (p-Q^-CgH^SiMeCHjC^Cl. 58
XIII. Rate and Temperature Values for PhSih^C^Cl............... 60
XIV. Rate and Temperature Values for (p-F-CgH^Sih^C^Cl...... 62
XV. Rate and Temperature Values for (m-CF3-C6H4)SiMe2CH2Cl... 64


IX
XVI. Rate and Temperature Values for (p-Cf^-C^H^SiJ^Cf^Cl... 66


FIGURES
FIGURE
I. Comparsion of the Conversion Rates of Fluorination of
(n-hex^SiCl............................................. 9
II. Comparsion of the Conversion Rates of Fluorination of
Mes2SiCl2............................................... 9
HI. The Reetz Dyoptropic Intermediary....................... 31
IV. The Hammett Relationship of Chloromethyl Hydrides at
800 K.................................................... 38
V. The Hammett Relationship of Chloromethyl Dimethyl
Silanes at 800 K......................................... 39
VI. The Relationship between log (k) and 1/T for PhSiMe(H)CH2CL 53
VII. The Relationship between log (k/T) and 1/T for
PhSiMe(H)CH2Cl........................................... 53
VIE. The Relationship between log (k) and 1/T for
(p-F-C6H4)SiMe(H)CH2Cl................................... 55
IX. The Relationship between log (k/T) and 1/T for
(p-F-C6H4)SiMe(H)CH2Cl................................... 55
X. The Relationship between log (k) and 1/T for
(m-CF3-C6H4)SiMe(H)CH2Cl................................. 57
XL The Relationship between log (k/T) and 1/T for
(m-CF3-C6H4)SiMe(H)CH2Cl................................. 57
XII. The Relationship between log (k) and 1/T for
(p-CH3-C6H4)SiMe(H)CH2Cl............................... 59
Xm. The Relationship between log (k/T) and 1/T for
(p-CH3-C6H4)SiMe(H)CH2Cl................................. 59


XI
XIV. The Relationship between log (k) and 1/T for PhSiN^CF^Cl... 61
XV. The Relationship between log (k/T) and lyT for PhSiMe2CH2G. 61
XVI. The Relationship between log (k) and 1/T for
(p-F-C6H4)SiMe2CH2Cl................................... 63
XVn. The Relationship between log (k/T) and 1/T for
(p-F-C6H4)SiMe2CH2Cl................................... 63
XVIII. The Relationship between log (k) and 1/T for
(m-CF3-C6H4)SiMe2CH2Cl................................. 65
XIX. The Relationship between log (k/T) and 1/T for
(m-CF3-C6H4)SiMe2CH2Cl................................. 65
XX. The Relationship between log (k) and 1/T for
(p-CH3-C6H4)SiMe2CH2Cl................................. 67
XXI. The Relationship between log (k/T) and 1/T for
(p-CH3-C6H4)SiMe2CH2Cl................................. 67


INTRODUCTION
Chemistry involving fluorosilanes recently began a major revival.
Historically, compounds containing silicon fluorine bonds have received little
attention. Preparation of these compounds traditionally involved processes such as
reaction of silicon tetrafluoride gas with a Grignard reagent1,2,3,4 or fluorination of a
chlorosilane with a reactive metal fluoride.5,6,78,9,10,1112 Because silicon tetrafluoride
is a gas and requires special handling, it is difficult to control the stoichiometry of its
reactions. Metal fluorides (ZnF2, CuF2-..) are very reactive, requiring special
conditions (such as strictly anhydrous environments) and handling.13 Other
preparations of fluorosilanes have also been reported, but these use reactive or toxic
reagents making their use unsatisfactory.2,6,7,8
The first portion of this work addresses the syntheses of a number of
fluorosilanes. While one method of preparation mentioned involves the reaction of
Grignard reagents and silicon fluorides, the main thrust of this portion focuses on a
new modification of an older procedure. This results in an easier, cleaner, relatively
non-hazardous preparation of fluorosilanes from chlorosilanes. Detailed experimental
procedures, yields, and physical data for a number of fluorosilanes are included.
The second chapter of this work attempts to probe the kinetics,
thermodynamics and possible reaction mechanism of the rearrangements of a series of
aryl-substituted chloromethylsilanes in the gas phase at high temperatures using the
Stirred Flow Apparatus, developed by Davidson. Reported are kinetic activation



parameters Ea, A, AH*, AG*, AS* and k. Some mechanistic speculations are included
as well.


CHAPTER 1
PREPARATIONS OF FLUOROSILANES
1.1 Introduction
Silicon chemistry plays an increasingly important role in chemistry today.
Chlorosilanes are used to generate protecting groups in bioorganic pharmaceutical
molecules; siloxanes are the basis for an entire industry of polymeric oils and resins;
and various silicon-containing compounds are used extensively in physical organic
chemistry.
Fluorosilanes are an increasingly important subset of the silane family. While
little was done with them in the past, interest in these compounds has recently
increased. One of their uses is in the formation of pentacoordinate siliconates (R^Si').
From work by Klanberg and Muetterties14 and other groups, many types of
five-coordinated negatively charged silicon species (siliconates) have been
characterized. Their cations, however, were based on tetraalkyl ammonium- or sulfur-
containing groups. This made the compounds sensitive to hydrolysis and difficult to
handle. Recently, Damrauer and Danahey15 changed the cation to potassium /
18-Crown-6 and found a decrease in their sensitivity towards hydrolysis. One such
compound is phenyl(xylyl)trifluorosiliconate (PhXySiF3) with the positive potassium /
18-Crown-6 as cation. They then went on to study kinetic parameters of the
rearrangement of these compounds using dynamic nuclear magnetic resonance


4
spectroscopy. Before they could do any of these studies, however, they needed four
coordinate fluorosilane precursors. Few of these were available commerically.
The need for fluorosiliconates in the Damrauer group, in general developed
from their pentacoordinate work with fluorosiliconates. They typically used Grignard
reagents and silicon tetrafluoride to synthesize four coordinate precursors. A study to
determine kinetic parameters of a series of substituted fluorosiliconates, and then to
apply those paramters to a Hammett study led to the need for asymmetrical fluorisilanes
(i.e. Ph(Xy)SiF2 and Ph(t-Bu)SiF2). These were prepared in two ways, fluorination
of Ph(t-Bu)SiCl2, and reaction of o-xylyl magnesium bromide on PhSiF^. The group
was interested in the Kanner fluorination16,17,18,19,20 method because there were (and
are) some reservations about the toxicity and ease of handling of other methods of
fluorination of chlorosilanes. Antimony trifluoride is classified as toxic,21 as well as
the by-product of reaction, antimony trichloride (which is also water sensitive). Many
of the other methods of fluorination involve highly reactive metals which require special
anhydrous handling conditions.
Another use of fluorosilanes stems from the fact that the Si F bond is more
reactive with lithium or Grignard reagents than the Si Cl bond; hindered Grignard
reagents will not react or react sluggishly with silicon tetrachloride,1 but will react with
silicon tetrafluoride.
Fluorosilanes also have an advantage that is important for industrial
applications. Fluorosilanes are not as labile to hydrolysis as chlorosilanes. They are
stable to the point that many are able to withstand aqueous work-ups in slightly acidic
conditions. Chlorosilanes, on the other hand, are highly reactive with water and, thus,
do not store well. From an industrial standpoint, the shelf lives of fluorosilanes are


5
much longer and require much less special packaging than that of chlorosilanes.
A final note on the synthetic utility of fluorosilanes, is that they can be used as
a protecting group to prepare other halosilanes, siloxanes and silicon hydrides. Using
an amine and a tetrahalosilane, a fluorosilane can also be converted to a chloro-, bromo-
SiY4 + RxSiF4_x -------------- RxSiY4.x + SiF4 (gq 1}
Y Cl, Br or I
or iodo- silane16 (eq. 1). Hydrolysis of fluorosilanes yields siloxanes (eq. 2).
Reduction (i.e. via LiAlH4) gives silicon hydrides2 (eq. 3). These abilities are
H+, H70
2 R3SiF -------------------- R3SiOSiR3 + 2 HF (eq. 2)
important because at times it may not be possible to make a certain silanes directly (case
L i flIH4
R3SiF ------------------ R3SiH (eq.3)
in point, xylyl derivatized compounds).
Among the many current methods for preparation of fluorosilanes, the most
common methods involve fluorination of a chlorosilane with an active metal fluoride
(i.e. ZnF3, CuF2...)5,6,7,89,10,11,12 (see eq. 4). Conditions require anhydrous
environments and
RxSiCl4_x
,,metg' > Rxsif4_
fIuoride x ^ x
(eq.4)
reagents. Other methods of fluorination of chlorosilanes use antimony
trifluoride,2-6.7>8-22.23 ammonium fluoride / sulfuric acid,25,26 hydrogen
fluoride,1,10,24,27,28,29,30 boron trifluoride31 and carbonyl fluoride.32 A
comprehensive review by Pike33 summarzies most of these methods. Another type of


6
preparation is the action of a Grignard or lithium reagent on silicon tetrafluoride or some
other fluorosilane.1,2,3,45,6,7
1.2 Results and Discussion
Fluorosilanes have been prepared using two methods. The first involves
fluorination of a chlorosilane with a hexafluorosiliconate (HFS), while the second
involves substitution of a fluorosilane with an organometallic compound.
1.2.1 Fluorinations of Chlorosilanes via Fluorosiliconates
Three reagents were used in the fluorinations of chlorosilanes: sodium
hexafluorosiliconate (Na2SiFg), ammonium hexafluorosiliconate ((NH^SiFg) and
ammonium fluoride (NH4F). Ammonium HFS gave the most consistent fluorinations
with respect to isolated yield. Table I summarizes the results of fluorinations with
(NH4)2SiF6.
Reaction times, except in cases of highly hindered compounds, were a few
hours or a day. Yields of isolated compounds were good, in many cases above
seventy-five percent. All reactions, except for those where Ph2Si(H)F and BzSiMe2F
are formed, could be worked-up under aqueous conditions to remove ammonium
chloride salts generated in the reaction. Since the silicon hydrogen and silicon -
benzylic carbon bonds are sensitive to water, these two exceptions also required both
anhydrous reaction conditions and work-up. The work-ups went quite smoothly and


TABLE I
Yields of Fluorosilanes from Reaction of Ammonium Hexafluorsiliconate
7
Product Silane Reaction Time / Temperature Method Isolated
__________________________________________________________________Yield
MesoSiF?
(t-BubSiF?
(n-hex)3SiF
BzSiMe^F
Ph2Si(t-£u)F
PhSiF3
Ph2SiF2
Ph3Sih
Ph2Si(H)F
Me3SiSiMe2F
20 hrs / 80C B 80%
3 wks / 80C B 54%
19 hrs / 80C B 88%
1 hr / 22C B 85 %a
120 hrs/80C B 75%
2 hrs / 105C A 80%
1 hr / 80C B 66%
3.6 hrs / 80C B 68%
0.5 hrs / 80C B 96 %a
2 hrs / 80C b 97 %b
a crude yield, >95 % pure
b reaction monitored by gas chromotography, product not isolated; GC yield assuming
RF(x) = 1.
the crude products obtained after solvent evaporation were quite pure, needing very
little subsequent purification. One of the largest benefits of ammonium HFS is its
versatility: silicon silicon, silicon oxygen, silicon hydrogen and silicon benzylic
carbon bonds are all preserved during fluorination.
Sodium hexafluorosiliconate, on the other hand, was a poorer reagent.
Sodium HFS was the first agent used in fluorinating chlorosilanes chronologically;
therefore, this reagent was looked at in a rather sporadic and non-logical way until a
direct sodium versus ammonium comparison was made. As Table II shows, the
results (reacton times and isolated yeilds) were not outstanding:


8
TABLE Q
Yields of Fluorosilanes from Reaction of Sodium Hexafluorsiliconate
Product Silane Reaction Time / Temperature Method Isolated
__________________________________________________________________Yield
PhSiF3
PhoSiF?
Ph2SiF7
MesoSiFn
(p-toi^Sif^
(p-tol)2SiF2
Et3SiF
3 hrs / 120C A 65 %
2 wks/34C B 16%
22 hrs / 80C B 27 %
24 hrs / 80C B 33%
1.5 hrs/ 180 C D 11 %
4 days/120C A 32%
2 wks / 34 C B 24%
Because there are several disadvantages to using sodium HFS, the method
was not studied in detail. Sodium chloride is one of the products of reaction, and there
was usually excess sodium HFS in the final mix. These two salts led to a difficult
aqueous work-up since the salts did not dissolve. Reaction times also were much
slower than with the ammonium compound. A detailed comparison was carried out for
the dimesityldifluorosilane and the tri-n-hexylfluorosilane; Figures I and II are a
comparison of the rates of reaction for the two compounds. Mes2SiCl2 and
(n-hex)3SiCl were chosen as representative compounds, the former being an example
of a sterically hindered chlorosilane. Figures I and II clearly show that ammonium
HFS reacts much faster than sodium HFS, on the order of 5 to 10 times faster.


% conversion % conversion
9
058 conversion (ammonium) 058 conversion (sodium)
100
80
60
40
20
0
0 5 10 15 20 25 30 35 40 45 50
time (hrs)
FIGURE I
Comparison of the Conversion Rates of Fluorination of (n-hex^SiCl.
100
80
60
40
20
0
0 2.5 5 7.5 10 12.5 15 17.5 20
time (hrs)
FIGURE n
conversion (ammonium) 058 conversion (sodium)
1 1 *
o
o
0.....O..
> "i 1 i i -------------------r
Comparison of the Conversion Rates of Fluorination of Mes2SiCl2.


10
With both the ammonium and sodium hexafluorosiliconates, mixed
chlorofluoro- silanes are observed as intermediates in the fluorination of a
dichlorosilane:
R2SiCl2 ----- R2Si(F)Cl -------> R2SiF2 (eq. 5)
R = Ph or t- Bu
The concentration of the mixed halogen intermediate was always extremely small in
comparison to the starting material and final product.
1.2.2 Fluorinations of Chlorosilanes using Ammonium Fluoride
A series of fluorination reactions was also carried out using ammonium
fluoride in an analogous manner to that of ammonium HFS. Work by Wilkins35 and
Payne36 in the early 1950's suggested that ammonium fluoride might be a viable
fluorinating agent. Table III summarizes the results of our experiments and shows a
direct comparison of the ammonium HFS and ammonium fluoride methods; the
products were prepared from the corresponding chlorosilanes. Ammonium fluoride
offers some advantages over ammonium HFS preparation of fluorosilanes in some
cases (di-t-butyl and dimesityl), but not in others (BzSiMe2F and Ph2Si(H)F). Yields
and purities, as with ammonium HFS, are good. Reaction rates behave anomolously.
The more hindered compounds (t-Bu^SiC^ and Mes2SiCl2 react much faster with
NH4F than with ammonium HFS. Note, however, that the fluorination reaction of
diphenylchlorosilane results in diphenyldifluorosilane, not diphenylfluorosilane, a
result quite different from ammonium HFS. Unlike ammonium HFS, ammonium


11
fluoride does not preserve Si H bonds.
TABLE m
Comparison of Fluorosilanes from Reaction of Ammonium HFS and Ammonium
Fluoride
Product (NH4)2SiF6 NH4F
t-Bu2SiF2 DME reflux, 3 weeks (100 g scale) isolated yield: 54 % method D DME relfux, 72 hours (10 g scale; 2 g scale: 1 hr) crude yield: 80 % (90 % pure) method D
Mes2SiF2 DME relfux, 20 hrs isolated yield: 80% method D DME reflux, 3 hrs isolated yield: 83 % method D
Ph3SiF DME reflux, 3.6 hrs isolated yield: 68 % method D DME reflux, 26 hrs isolated yield: 77 % method D
BzSiMe2SiF DME reflux, 1 hr crude yield: 85 % (95 % pure) method C DME reflux, 24 hrs crude yield: 96 % (85 % pure) method C
Ph2Si(H)F DME reflux, 0.5 hrs crude yield: 96 % (98+ % pure) method C 42 % conversion after 6 days DME reflux; also observed Ph2SiF2; rxn stopped and discarded at this point


12
1.2.3 Synthesis of Fluorosilanes bv Grignard Substitution
Another method of preparation of fluorosilanes is through organometallic
substitution on a pre-existing fluorosilane (eq. 6):
R'MgBr
+ or
(eq.6)
R'Li
This reaction is especially useful in preparing highly hindered silanes. As mentioned
earlier, hindered Grignard reagents are slow to react with chlorosilanes;
tetrachlorosilane, in fact, will not react with the Grignard reagent of 2-bromo-m-xylene
while tetrafluorosilane will. The smaller atomic radius of fluorine may allow hindered
reagents to react at silicon. Nucleophiles that will react range from simple Grigard
reagents to organolithium reagents to various alkoxides.
The hindered (2-methylphenyl)(2,6-dimethylphenyl)difluorosilane
((o-tol)(Xy)SiF2) system can potentially be synthesized by two routes:
Route A
SiCl^ + XyMgBr------- XySiClj
(eq.7)
XySiCl3
XySiF^
(eq.8)
XySiF-j + (o-tol)MgBr ----* Xy( o-tol )SiF£
(eq. 9)


13
Route B
Si Cl 4 + (o-tol)MgBr --- (o-tol )$iCl3
(eq.10)
(eq. 11)
Xy( o-tol )$iF2
(eq.12)
Xy = 2,6-dimethylphenyl =
o-tol = 2-methylphenyl =
The first step in route A does not occur; an attempt at preparing
2,6-dimethylphenyl(2-methylphenyl)dichlorosilane by route A failed, giving only
o-tolyl derivatives. Steric hinderance about the silicon by the chlorines and about the
Grignard by the methyl groups may be enough to inhibit reaction. Indeed, it is found
experimentally, that an organofluorosilane can be added neat to the Grignard reagent
formed from 2-bromo-m-xylene in a one to one stoichiometry without risk of
poly-xylylation (eq. 13):
The o-tolyl reagent, however, is less hindered and the reaction with silicon tetrachloride
proceeds easily, but slowly. (o-Tolyl)trichlorosilane is then easily fluorinated.
(o-Tolyl)trifluorosilane subquently reacts quickly with the xylyl Grignard reagent.
Table IV summarizes the results of fluorosilane preparations through Grignard
attack. Preparations of fluorosilanes with the same R groups (a-Np, Xy, p-tol) was
RSiF3 + XyMgBr
(eq. 13)


14
accomplished by reaction of the appropriate Grignard on tetrafluorosilane. Preparations
of fluorosilanes with different R groups (PhXy and Xy(o-tol)) were done by reaction of
the approriate Grignard with phenyltrifluorosilane.
TABLE IV
Yields of Fluorosilanes generated through Organometallic Reagents
Product________________Solvent_____________Isolated Yield
ether 42.4 %
ether 17.8 %
ether 25%
ether 48.4 %
ether 47 %


15
1.3 Experimental
General experimental information about instrumentation is presented in section
1.3.1, while synthetic procedures are in section 1.3.2.
1.3.1 General Experimental
All nuclear magnetic resonance spectra were obtained with an IBM NR80 / B
multinuclear spectrometer. Chemical shift values (8) were determined relative to
tetramethyl silane for proton and carbon-13 spectra, and fluorotrichloromethane for
fluorine-19 spectra. The solvent for NMR determinations was acetone-d^ unless
otherwise noted. Carbon-13 spectra were recorded in proton decoupling mode.
Melting points are uncorrected and were recorded on a Mel-temp apparatus (Laboratory
Devices). Mass spectral information was obtained on a Hewlett-Packard 5890 A Gas
Chromatograph equipped with a cross linked polydimethyl silicone column
approximately 15 feet long interfaced with a Hewlett Packard 5970 Mass Selective
detector. Gas Chromatographic data were obtained with either a Perkin Elmer 3920 B
Gas Chromatograph with flame ionization dectection and an 1/8" x 6 ft 10 % OV-1
silicone oil on chromosorb WHP packed column or a Hewlett Packard 5890 Gas
Chromatograph with flame ionization detection and a 25 meter crosslinked
polydimethylsilicone capillary column. Refractive indices were determined with a
Bausch and Lomb Refractometer. Spinning band distillations were performed with a
Nester / Faust Annular Spinning Band Column or a B/R Micro still. Elemental analyses
were performed by Huffman Laboratories, Golden, Colorado. Numbers in parentheses
next to compounds are laboratory notebook references (i.e. difluorodiphenylsilane


16
(RS-1-143). The term 'ether' refers to diethyl ether unless otherwise specified.
1.3.2 Detailed Experimental:
Method A: Fluorination with Distillation
Into a three necked, round bottom flask equipped with magnetic stirring, short
path distillation head and thermometer with an argon inlet, were added a chlorosilane
and fluorination agent (a hexafluorosiliconate) and a high boiling solvent
(triethyleneglycol dimethyl ether or decahydronapthalene). The reaction mixture was
stirred and heated to a high temperature. The product was distilled out as it was
formed.
Compounds prepared in this manner include:
Phenvltrifluorosilane (RS-1-731:
Phenyltrifluorosilane was distilled from phenyltrichlorosilane (130 g, 616
mmol, Union Carbide), sodium hexafluorosiliconate (231 g, 1.23 mol, Aldrich) and
150 ml decalin; the product was then purified by distillation through a 30 cm Vigreaux
column. Phenyltrifluorosilane (65 %): m/z: 162.00 (mw: 162.01); bp: 96-99C;
nD17: 1.4202; !H NMR: 5 = 7.638 (m), 7.766 (m) ppm; 13CNMR: 5= 129.96,
134.85,135.70 ppm; 19FNMR: 6 = -141.06 ppm (JSiF = 266.49 Hz)
Phenvltrifluorosilane (RS-4-33):
Phenyltrifluorosilane was distilled from phenyltrichlorosilane (414 g, 1.96
mol, Aldrich), ammonium hexafluorosiliconate (523 g, 2.94 mol, Petrarch) and 100 ml


17
triglyme; the product was then purified by distillation through a 20 cm Vigreaux
column. Phenyltrifluorosilane (70 %): bp: 98-100 C; m/z: 161.95 (Mw: 162.01).
Di(4-methvlphenvl)difluorosilane (RS-1 -107):
Dichlorodi-p-tolylsilane (2.83 g, 10.1 mmol, RS-1-93), sodium
hexafluorosiliconate (4.0 g, 21.3 mmol, Aldrich) and decalin gave
difluorodi(p-tolyl)silane, which was purified by vacuum distillation to separate the
silane and the decalin. Difluorodi(p-tolyl)silane (32 %): (p-tol)2SiF2: m/z: 248.00
(mw: 248.08); bp: 88-94C/0.2-0.15 mm Hg; mp: 26-32C; ^NMR: 5 = 2.279
(s, 3H), 7.214 (d, 3JHH = 6.7, 2H), 7.59 (d, 3JHH = 7.8, 2H); 13C NMR: 5= 22.19,
, 125.90 (t, JCF = 30 Hz) 127.84, 130.60, 135.73, 142.83, 142.96 ppm; 19F NMR:
5 = -140.63 ppm (JSiF = 263.05 Hz)
Method B: Fluorination with Aqueous Work-up
Into a three necked, round bottom flask equipped with magnetic stirring and a
reflux condensor with an argon inlet, was added a chlorosilane (21 mmol) and a
fluorosiliconate as fluorinating agent and dimethoxyethane (DME). The mixture was
stirred and heated at DME reflux (80C). Product formation was monitored by gas
chromatography. When starting material was no longer present, the reaction mixture
was cooled and poured into an aqueous saturated solution of ammonium chloride (100
ml), shaken and separated. The aqueous layer was extracted twice with diethyl ether
(100 ml). The combined organic layers were dried over magnesium sulfate; the
solvent was then rotory evaporated to give a crude product
Compounds prepared in this manner include:


18
Difluorodiphenvlsilane: (RS-3-251):
Diphenyldichlorosilane (5 g, 21.2 mmol, Petrarch), sodium
hexafluorosiliconate (4.1 g, 21.8 mmol, Aldrich) and dimethoxyethane as solvent, gave
difluorodiphenylsilane which was purified by vacuum distillation.
Difluorodiphenylsilane (27 %): m/z: 220.10 (mw: 220.05); bp: 54C/0.1mmHg
Difluorodiphenvlsilane: (RS-2-59):
Diphenyldichlorosilane (5 g, 21.2 mmol, Petrarch), ammonium
hexafluorosiliconate (4.0 g, 22.4 mmol, Petrarch), mesitylene (2.4 g, 19.9 mmol,
Fischer; as a GC reference) and dimethoxyethane, gave difluorodiphenylsilane which
was purified by vacuum distillation. Difluorodiphenylsilane (66 %): m/z: 220.1 (mw:
220.05); bp: 63-79C / 0.4-0.27 mm Hg; !HNMR: 8 = 7.550 (m), 7.690 (m) ppm;
13CNMR: 8 = 129.50, 133.27, 135.27 ppm; 19F NMR: 8 =-141.46 ppm (JSiF =
292.3 Hz; JCF = 108.32 Hz ).
Fluorotriphenvlsilane (RS-3-71):
Chlorotriphenylsilane (4.0 g, 13.6 mmol, Petrarch), ammonium
hexafluorosiliconate (1.2 g, 6.7 mmol, Petrarch) and dimethoxyethane gave
fluorotriphenylsilane, which was purified by sublimation. Fluorotriphenylsilane (68
%): m/z: 278.00 (mw: 287.09); mp: 58-58.5C; sub: 80C / 0.1 mm Hg; lH
NMR: 8 = 7.501(m), 7.605 (m) ppm; 13C NMR: 8 = 129.26, 131.99, 133.48 (d,
2JCF = 14 Hz), 135.78 ppm; 19F NMR: 8 = -154.13 ppm (JSiF = 281.11 Hz; JCF =
105.74 Hz)


19
Fluorotriphenvl silane (RS-3-71):
Chlorotriphenylsilane (4.0 g, 13.6 mmol, Petrarch), ammonium fluoride (0.5
g, 13.5 mmol, Aldrich) and dimethoxyethane gave fluorotriphenylsilane, which was
purified by sublimation. Fluorotriphenylsilane (77 %): m/z: 278.10 (mw: 278.09);
sub: 50C /0.10 mm Hg; mp: 57-58C.
tert-Butvldiphenvlfluorosilane (RS-2-95):
tert-Butyldiphenylchlorosilane (10 g, 36 mmol, Petrarch), ammonium
hexafluorosiliconate (9.3 g, 52 mmol, Petrarch) and dimethoxyethane gave tert-
butyldiphenylfluorosilane, which was purified by vacuum distillation.
tert-Butyldiphenylfluorosilane (75 %): m/z: 258.10 (mw: 258.12); bp: 137-142C/
3 mm Hg; sub: 22C/0.10mmHg; mp: 30-31C; 29-30C; nD17: 1.5492; %C =
74.09 (calc: 74.39); % H = 7.27 (calc: 7.41); *H NMR: 5 = 1.077 (d, 4JHF = 1.22
Hz, 9H), 7.440 (m, 6H), 7.733 (m, 4H) ppm; 13CNMR: 8= 19.36 (d, 2JCF = 3.3
Hz), 26.25, 128.84, 131.24, 133.38 (d, 2JCF = 3.3 Hz), 135.09 ppm; 19F NMR: 8
= -141.86 ppm (JSiF = 289.70 Hz; JCF = 106.60 Hz)
Fluorotri(n-hexvl)silane (RS-3-3):
Tri(n-hexyl)chlorosilane (3.0 g, 9.4 mmol, Petrarch), ammonium
hexafluorosiliconate (0.85 g, 4.8 mmol, Petrarch), dimethoxyethane and xylene (1.0 g,
9.4 mmol, Baker; as a GC reference) gave fluorotri(n-hexyl)silane, which was
purified by vacuum distillation. Fluorotri(n-hexyl)silane (88 %): m/z: 302.25
(mw: 302.28); bp: 115-117C / 0.25 mm Hg; nD20: 1.4370; %C =


20
71.44 (calc: 71.45); % H = 12.81 (calc: 12.99); ^NMR: 5 = 0.89 (m, 5H), 1.34
(br. s, 8H) ppm; 13C NMR: 5= 14.25 (d, 2JCF = 31.22 Hz),14.93, 23.22, 32.23,
33.69 ppm; 19F NMR: 5 = -170.08 (t, 3JHF = 5.91 Hz; JSiF = 291.40; JCF = 106.32
Hz).
Difluorodi(2.4.6-trimethvlphenvl)silane (RS-2-871:
Dichlorodi(2,4,6-trimethylphenyl)silane (2.0 g, 5.9 mmol, Petrarch),
ammonium hexafluorosiliconate (2.1 g, 11.8 mmol, Petrarch), o-xylene (5.9 mmol,
Baker, as GC reference) and dimethoxyethane gave
difluorodi(2,4,6-trimethylphenyl)silane after sublimation.
Difluorodi(2,4,6-trimethylphenyl)silane (80 %): sub: 100C / 0.20 mm Hg; mp:
143-144C; lH NMR: 5 = 2.266 (s, 6H), 2.356 (t, 5JHF = 3.66 Hz, 12H), 6.910 (s,
4H) ppm; 13C NMR: 5 = 21.22, 23.04 (t, 4JCF = 5.49 Hz), 130.33, 142.77,
145.53 ppm; 19FNMR: 5 = -122.96 ppm (JSiF = 295.72 Hz; JCF = 106.60 Hz)
Difluorodi(2.4.6-trimethvl phenvDsilane (RS-3-29):
Dichlorodi(2,4,6-trimethyl phenyl)silane (1.0 g, 3.0 mmol, Petrarch),
ammonium hexafluorosiliconate (0.53 g, 3.0 mmol, Petrarch) and dimethoxyethane
gave difluorodi(2,4,6-trimethylphenyl)silane after recrystallization from acetone.
Difluorodi(2,4,6-trimethylphenyl)silane (73 %): mp: 141.5-143 C.
Difluorodi(2.4.6-trimethvlphenyl)silane (RS-3-67):
Dichlorodi(2,4,6-trimethylphenyl)silane (2.0 g, 5.9 mmol, Petrarch),
ammonium fluoride (0.44 g, 11.8 mmol, Aldrich) and dimethoxyethane gave


21
difluorodi(2,4,6-trimethylphenyl)silane after recrystallization from acetone.
Difluorodi(2,4,6-trimethylphenyl)silane (83 %): m/z: 304.15 (mw: 304.15); mp:
141-142C.
E)i(ten-butvl)difIuorosilane (RS-2-103):
Di(tert-butyl)dichlorosilane (100 g, 469 mmol, Petrarch), ammonium
hexafluorosiliconate (125 g, 702 mmol, Petrarch) and dimethoxyethane gave
di(tert-butyl)difluorosilane after purification by spinning band distillation.
Di(tert-butyl)difluorosilane (54 %): (t-Bu)2SiF2: m/z: 180.10 (mw: 180.11); bp:
128-129C / 629 mm Hg; nD17: 1.3886; nD20: 1.1.3871; lH NMR: 6= 1.086 (t,
4jhf = i.95 Hz) ppm; 13C NMR: 5 = 19.58 (t, 3JCF = 15 Hz), 26.22 ppm; 19F
NMR: 8 = -156.38 ppm (d,J = 2.58Hz; JSiF = 324.95 Hz; JCF = 109.18 Hz)
Di(tert-butvl)difluorosilane (RS-2-121):
Di(tert-butyl)dichlorosilane (10 g, 47 mmol, Petrarch), ammonium fluoride
(3.6 g, 97 mmol, Baker) and dimethoxyethane gave di(tert-butyl)difluorosilane after
removal of solvent by fractional distillation through a 30 cm Vigreaux column.
Di(tert-butyl)difluorosilane (80 %): (t-Bu)2SiF2: m/z: 180.10 (mw: 180.11)
Variation on method B: At the point at which the reaction mixture is cooled, the
solution was gravity filtered. The solvent was then driven off with rotory evaporation
to give a crude product.
Compounds prepared in this manner include:


22
Difluorodiphenvlsilane: (RS-1-143):
Diphenyldichlorosilane (34.5 g, 136 mmol, Petrarch), sodium
hexafluorosiliconate (45 g, 186 mmol, Aldrich) and diethyl ether as solvent, gave
difluorodiphenylsilane which was purified by vacuum distillation.
Difluorodiphenylsilane (16 %): m/z: 220.15 (mw: 220.05); nD17: 1.5285; bp:
109-lllC/3.5 mm Hg.
Benzvldimethvlfluorosilane (RS-3-75):
Benzyldimethylchlorosilane (2 g, 10.8 mmol, Petrarch), ammonium
hexafluorosiliconate (1.0 g, 5.7 mmol, Petrarch) and dry dimethoxyethane gave
benzyldimethylfluorosilane (85 % crude yield, 95 % pure, determined by gas
chromatography): m/z: 168.05 (mw: 168.08); NMR: 8 = 0.075 (d, 3JHF =
7.32 Hz, 6H), 2.28 (d, 3JHF = 6.22 Hz, 2H), 7.131 (m, 5H); 19F NMR: 8 =
-160.116 (JHF = 5.91 Hz; JSiF = 275.64; JCF = 86.62)
Benzvldimethvlfluorosilane (RS-3-771:
Benzyldimethylchlorosilane (2 g, 10.8 mmol, Petrarch), ammonium fluoride
(0.4 g, 10.8 mmol, Aldrich) and dry dimethoxy ethane gave benzyldimethylfluorosilane
(96 % crude yield, 85 % pure, determined by gas chromatography ): m/z: 168.00
(mw: 168.09).
Fluorodiphenvlsilane (RS-2-137):
Chlorodiphenylsilane (3 g, 13.7 mmol, Petrarch), ammonium
hexafluorosiliconate (1.2 g, 6.73 mmol, Petrarch) and dry dimethoxyethane gave


23
fluorodiphenylsilane (97 %, crude yield; 95 % pure, determined by gas
chromatography): m/z: 202.10 (mw: 202.06); *HNMR: 8= 5.49 (d, JHF = 54.3
Hz), 7.51 (m); 13C NMR: 5 = 135.15,132.27,129.32; 19FNMR: 8= -173.97
(d,2JHF = 55.13 Hz; JSiF = 333.65; JCF = 232.33)
Fluorotriethylsilane fRS-2-5~):
Chlorotriethylsilane (6.3 g, 42 mmol, Petrarch), sodium hexafluorosiliconate
(15.7 g, 84 mmol, Aldrich) and diethyl ether gave fluorotriethylsilane, which was
purified by simple distillation. Fluorotriethylsilane (24 %): m/z: 134.05 (mw:
134.09); nD17: 1.3965; bp: 28-50C; *H NMR: 8 = 0.720 (quartet, 3JHH = 6.35
Hz, 6H), 0.942 (t, 3JHH = 6.10 Hz, 9H) ppm; 13C NMR: 8 = 5.07, 5.77, 6.28 (d,
JCF = 1.83 Hz), 7.13 ppm; 19F NMR: 8 = -148.31 (quintet, 3JHF = 6.01 Hz; JSiF =
263.05 Hz; 3JCF = 108.00 Hz) ppm
Difluorodif2.4.6-trimethvlphenvDsilane (RS-2-45):
Dichlorodi(2,4,6-trimethylphenyl)silane (2.0 g, 5.9 mmol, Petrarch), sodium
hexafluorosiliconate (3.3 g, 17.5 mmol, Aldrich) and dimethoxyethane gave
difluorodi(2,4,6-trimethylphenyl)silane after sublimation.
difluorodi(2,4,6-trimethylphenyl)silane (33 %): m/z: 304.10 (mw: 304.15); sub:
85-100C / 0.02 mm Hg; mp: 139-143C.
Pentamethvlfluorodisilane (RS-3-13):
Chloropentamethyldisilane (1.05 g, 6.3 mmol, RS-3-7), ammonium
hexafluorosiliconate (0.6 g, 3.4 mmol, Petrarch), hexamethyldisilane (0.85 g, 5.8


24
mmol, RS-3-7, as a GC reference) and dimethoxyethane gave fluoro-
pentamethyldisilane. No product was isolated; Fluoropentamethyldisilane: m/z: 150.2
(mw: 150.07).
Method C: Grignard Method
Into a dry 100 ml 3-necked round bottom flask equipped with a magnetic
stirring unit, addition funnel and a reflux condenser with an argon inlet was charged
magnesium metal (95 mmol) and enough solvent (ether or THF) to cover the metal. A
halide solution (81 mmol) was added dropwise to form a Grignard reagent. One hour
after addition was complete, silicon tetrafluoride gas was bubbled slowly into solution.
The reaction mixture was then stirred overnight. Aqueous work-up with saturated
ammonium chloride (75 ml, 3x), drying of the organic layer over magnesium sulfate
and rotory evaporation of solvent afforded a crude product.
Compounds prepared in this manner include:
Difluorodi(2.6-dimethvlphenvl)silane (RS-1-55. RS-4-35):
2-Bromo-m-xyelene (15 g, 81 mmol, Aldrich) and magnesium metal (2.3 g,
95 mmol, Fischer) in diethylether and silicon tetrafluoride (4.2 g, 40.5 mmol,
Matheson) gave difluorodi(o-xylyl)silane after sublimation. Difluorodi(o-xylyl)silane
(42 %): m/z: 276.05 (mw: 276.11); sub: 65C / 0.25 mm Hg; mp: 57.5-58.0C;
%C = 69.15 (calc: 69.53); % H = 6.60 (calc: 6.56); ^NMR: 8 = 2.401 (t, 3JHH =
2.01 Hz, 6H), 7.071 (d), 7.231 (m, 3H]) ppm ; 13C NMR: 8 = 23.164, 129.543,
132.79, 145.568 ppm; 19F NMR: 8 = -123.074 ppm (JSiF = 299.16 Hz; JCF =
60.18 Hz); recystallized from ethanol: mp: 65.6-66.0 C, %C 69.53 (calc. 69.53),


25
H % 6.78 (6.56).
Difluorodi(a-napthvl)silane (RS-1-59):
1-Bromonapthalene (16.7 g, 81 mmol, Mallinkrodt) and magnesium metal
(2.3 g, 94.6 mmol, Fischer) in ether and silicon tetrafluoride (8 g, 76.8 mmol,
Matheson) gave difluorodi(a-napthyl)silane after sublimation.
Difluorodi(a-napthyl)silane (18 %): m/z: 320.05 (mw: 320.08); sub: 70C/0.01
mm Hg; mp: 77.5-79.5C; *H NMR: 8 = 7.68(m, 3H), 8.22(m, 4H) ppm; 13C
NMR: 5 = 126.23, 127.51, 128.41, 130.24, 134.15, 137.28 ppm; 19F NMR: 5 =
-134.00 ppm (JSiF = 289.7 Hz)
FIuorotri(p-tolvl)silane (RS-1-63):
Bromo-4-methylbenzene (13.8 g, 81 mmol, Matheson) and magnesium metal
(2.3 g, 94.6 mmol, Fischer) in ether and silicon tetrafluoride (8.6 g, 82.6 mmol,
Matheson) gave fluorotri(p-tolyl)silane after sublimation. Fluorotri(p-tolyl)silane (25
%): m/z: 320.15 (mw: 320.14); sub: 72C / 0.05 mm Hg; mp: 101-105C; *H
NMR: 8 = 2.323 (3H), 7.264 (d, 3JHH = 7.93, 2H), 7.542 ( d, 3JHH = 7.93, 2K)
19F NMR: 8 = -155.30 ppm (JSiF = 278.52 Hz; JCF = 91.12 Hz).
Fluorotri(o-anisolvl)silane (RS-1-123):
o-Bromo-anisole (10 g, 54 mmol, Aldrich) and magnesium metal (1.4 g, 58
mmol, Fischer) in ether and silicon tetrafluoride (4.3 g, 41 mmol, Matheson) gave
fluorotri(o-anisolyl)silane after sublimation. Fluorotri(o-anisolyl)silane: m/z: 368.10
(mw: 368.12); mp: 162-170C; *H NMR: 8 = 3.586 (3H), 7.023 (m), 7.294 (m,


26
4H); 19F NMR: 8 = -166.6, -141.4, -139.8 (?)
Variation 1 on method C: The Grignard solution, after anaerobic and
anhydrous transfer to an addition funnel, was added dropwise to a three neck, round
bottom flask under an atmosphere of argon, equipped with magnetic stirring, reflux
condensor and fluorosilane solution (76 mmol). Work-up and purification of the
product is as in method C.
Compounds prepared in this manner include:
Difluorophenvl (2.6-dimethvlphenvPsilane (RS-1-81):
2-Bromo-m-xyelene (9.25 g, 50 mmol, Aldrich) and magnesium metal (1.2 g,
49 mmol, Fischer) and phenyltrifluorosilane (12.4 g, 76 mmol, RS-1-73) in diethyl
ether gave difluorophenyl(xylyl)silane after simple vacuum distillation.
Difluorophenyl(xylyl)silane (48 %): m/z: 248.10 (mw: 248.08); bp: 107-108C/
0.5 mm Hg; nD17: 1.5373; % C = 67.03 (calc: 67.71); % H = 5.75 (calc: 5.68);
*H NMR: 8 = 2.453 (t, 5JHF = 2.44 Hz, 6H), 7.078, 7.434, 7.60 (m, 8H); 13C
NMR: 8 = 24.14, 129.63, 129.87, 133.43, 135.04, 144.66 ppm; 19F NMR: 8 =
-130.30 ppm (JSiF = 293.14 Hz; Jhf = 5.16Hz; JCF = 85.97 Hz ).
Variation 2 on method C: A neat fluorosilane (when liquid), instead of silicon
tetrafluoride, was added dropwise to the Grignard solution of 2-bromo-m-xylene. All
else remains the same.
Compounds prepared in this manner include:


27
Difluoro(2-methvlphenvl)(2.6-dimethvlphevDsilane (RS-4-23. RS-4-43):
2-Bromo-m-xyelene (7.5 g, 41 mmol, Aldrich) and magnesium metal (11 g,
45 mmol, Fischer) and o-tolyltrifluorosilane (6.33 g, 36 mmol, RS-4-21) in diethyl
ether gave difluoro(o-tolyl)(o-xylyl)silane after simple vacuum distillation.
Difluoro(o-tolyl)(o-xylyl)silane (45 %): m/z: 262.15 (mw: 262.10); bp: 84-89C/
0.06 mm Hg; nD20: 1.5372; % C = 68.12 (calc: 68.67); % H = 6.36 (calc: 6.15);
lU NMR: 8 = 2.435 (t, JHF = 2.32 Hz, 9H), 7.038-7.612 (m, 7H); 13C NMR: 8 =
22.25 (t, 4Jcf = 1.23 Hz), 23.46 (t, 4JCF = 3.05 Hz, 126.53, 127.38, 129.26, 130.48,
131.39, 133.06, 136.06, 145.11, 146.17 (t, 2or3JCF = 1.22 Hz); 19F NMR: 8 =
-129.36 (JSiF = 293.36; JCF = 196.47); spinning band distilled: bp: 90-93 C / 0.1
mm Hg, % C 68.66 (calc. 68.67), % H 6.36 (calc. 6.15).
Difluorophenvl(2.6-dimethvlphenvl)silane (RS-4-41):
spinning band distilled: bp: 79 C / 0.09 mm Hg, % C 67.70 (calc. 67.71),
% H 6.01 (calc. 5.68).
Variation 3 on method C: The Grignard solution, after anaerobic and anhydrous
transfer to an addition funnel, was added dropwise to a three neck, round bottom flask
under an atmosphere of argon, equipped with magnetic stirring, reflux condensor and
containing a chlorosilane solution (160 mmol). A crude product was obtained after
Filtration and distillation of solvent.
Compounds prepared in this manner include:


28
Dichlorodi('4-methvlphenvDsilane (RS-1-93):
4-Methylbromobenzene (50 g, 292 mmol, MCB), magnesium metal (7.8 g,
320 mmol, Fischer) and silicon tetrachloride (27.2 g, 160 mmol, Union Carbide) in
ether gave after sublimation to remove (p-tolyl)2, followed by vacuum distillation
dichlorodi(p-tolyl)silane (7 %): m/z: 282.10,280.10 (mw: 280.02); bp: 124-145C
/ 0.2-0.15 mm Hg.
Also obtained was (p-tolyl)trichlorosilane (54 %): m/z: 223.95 (mw:
223.85); bp: 60-79C / 0.9-0.65 mm Hg; !HNMR: 8 = 2.397 (s, 3H), 7.385 (d,
3Jhh = 7.88 Hz, 2H), 7.742 (d, 3JHH = 8.06 Hz, 2H) ppm.
Method D: Fluorosilanes from Chlorosilanes
Into a three neck, round bottom flask under an atmosphere of argon, equipped
with magnetic stirring, reflux condensor was charged a chlorosilane solution. A
Grignard solution prepared from magnesium metal (mmol) and a halide (mmol) in the
usual manner and transfered to an addition funnel using anhydrous and anaerobic
technique was added dropwise to the chlorosilane. The solution is stirred for
approximately 20 hours after addition of the Grignard. The solution is then filtered and
solvent evaporated. A high boiling solvent and hexafluorosiliconate were added and (as
in method B) product distilled away from the solvent.
Compounds prepared in this manner include:


29
Difluorodi^-methvlphenvDsilane fRS-1-77'):
4-Methylbromobenzene (27.4 g, 160 mmol, Matheson), magnesium metal
(4.1 g, 169 mmol, Fischer), silicon tetrachloride (13.7 g, 81 mmol, Union Carbide),
diammonium hexafluorosiliconate (22.7 g, 121 mmol, Petrarch) and decalin (25 ml as
distilling base) gave difluorodi(p-tolyl)silane after vacuum distillation to separate the
silane and the decalin. Difluorodi(p-tolyl)silane (11 %): m/z: 248.10 (mw: 248.08);
bp: 112-134C / 0.8-0.5 mm Hg.
o-ToIvltrifluorosilane (RS-4-21. RS-4-39):
o-Bromotoluene (25 g, 146 mmol, Aldrich), magnesium metal (4 g, 166
mmol, Fischer), silicon tetrachloride (28 g, 185 mmol, Union Carbide), diammonium
hexafluorosiliconate (35 g, 197 mmol, Petrarch) and triglyme (25 ml) gave
o-tolyltrifluorosilane which was distilled out as it was made. o-Tolyltrifluorosilane (19
%): m/z: 176.00 (mw: 176.03).


CHAPTER 2
GAS PHASE REARRANGEMENTS OF CHLOROMETHYLSILANES
2.1 Introduction
In 1973 Brook and co-workers37 studied a series of sealed tube pyrolyses at
different temperatures to probe the kinetics of the interesting rearrangement shown in
eq. 14. Their R groups ranged from phenyl to ethyl to methyl; their X groups included
F, OTos, OAc,Cl, and Br. The R' group was phenyl. They reported that the reaction
occurred via an inverse
6- 5 +
R-3 SiCHR'
3 \ /
X
R3SiCHXR' ------> or ---------------> R2$iXCHR'R (eq. 14)
R7SiCHR'
3 I
X
ylid type of transition state, as opposed to the Reetz dyotropic transition state which
involves both the R and X groups migrating intramolecularly, simultaneously and with
little charge separation.38 Figure III is an example of this Reetz dyotropic transition
state (see page following). This was first applied to a silicon compound by
Hazeldine.37 Brook argued that the near-zero value of AS$ for the rearangement of
Me3SiCBrPh2 was indicative of a loose transition state for the rearrangement. In
contrast, the dyotropic rearrangement, according to Brook, was a tighter formation


31
because of its double bridge and "would be expected to have a very large, negative
AS*."37 The AS* for the rearrangement of MejSiCBrPl^ was reported as -1.3 3
e.u. (log A = 13.9).
\
C
c
/
\
FIGURE HI
The Reetz Dyotropic Transition State
Martin, O'Neal and Ring (1986) have argued that a dyotropic mechanism
holds for the rearrangement of (chloromethyl)dimethylsilane.39 In a static gas phase
reaction at high temperatures (630 680 K), they obtained a log A value of 12.99
0.13 and an Ea of 52.2 4 kcal / mole. Equation 15 details the dyotropic mechanism
they propose for the rearrangement. Similar to the Reetz transition state in figure III,
Martin's mechanism involves a stepwise rearrangement instead of a concerted process.
\
/
y
i
a b
/
\
y
l
a b
/
\
\
a b
I
x
>
<
(eq.15)
They also noted a parallel pathway involving free radicals was in operation. The
dyotropic pathway could be studied in detail by quenching with excess propene.
Davidson and co-workers, in contrast, have studied the same compound in a
Stirred Flow Reactor (SFR),40 and demonstrated first order kinetics throughout a 100
degree temperature range. The kinetics of formation were unaffected by addition of
trapping agents such as butadiene, propene, methanol, methyl chloride or toluene in 10


32
fold excess. They proposed a three center transition state, since the Arrhenius
parameters obtained are similar to those for an a-elimination of a silylene from
chlorodisilanes (log A in the range of 11.7 to 12.5; Ea in the range of 46-50 kcal/mole).
Their log A value for rearrangement was 12.5 0.3; Ea for the reaction was 49.5 1.2
kcal/mole. Davidson indicated that their "experiments do not enable us to comment on
the charge separation in the transition state."40 Nevertheless, he suggested some type
of pentacoordinate silicon as an intermediate.
HMe2SiCH2Cl ------- HMe2$iCH2 --------- Me3$iCl (eq. 16)
Cl
In collaboration with the Davidson group, we have probed the kinetics of
rearrangements of a series of aryl substituted dimethylchloromethyl- and
methylchloromethyl silanes in an attempt to further define the mechanism of these
thermal rearrangements, particularly with regard to the charge separation question.
2.2 Results and Discussic .
The pyrolyses of the compounds listed in Table V were carried out using the
Stirred Flow Technique of Davidson in his laboratories in Leicester, UK. Table V
identifies the compounds and the temperature ranges used in this study. Rates of
reaction at various temperatures were determined from the ratio of products to starting
materials using a SFR/GC interfaced to a data handling and analysis system.


33
TABLE V
Temperature Ranges and Substituent for (X-Ar)SiCH3(Y)(CH2Cl)
X Y Temperature Range Studied (K)
H H (a) 744-828
p-F H (b) 754-811
m-CF3 H (£) 758-838
p-Me H (d) 750-816
H Me (£) 772-849
p-F Me (D 771-849
m-CF3 Me (8) 766-862
p-Me Me (h) 765-844
Table VI presents the kinetic parameters determined from the Arrhenius and
Eyring Equations (presented in various forms in Appendix A) and the temperature / rate
constant data for compunds a through ft.
TABLE VI
Kinetic Parameters for the Rearrangements of Compounds a through ft
compound Ea log A AH* AS* AG*
a 53.5 1.3 13.4 51.8 -1.1 52.7
h 52.7 1.6 13.3 51.2 -1.8 52.6
£ 56.2 1.0 14.1 54.6 1.9 53.1
4 51.7 0.7 13.0 50.7 -2.4 52.6
£ 49.9 1.1 11.8 48.3 -8.7 55.3
I 47.6 1.7 11.2 46.0 -11.3 55.0
a 55.7 1.2 13.1 54.1 -2.4 56.0
li 54.0 1.7 13.0 52.4 -3.2 55.0
Me2Si(H)CH7Cl 49.5 14.4a (hydride migration)
Me3SiSiMe2CH2Cl 49.5 12.5a (methyl migration or TMS migration?)
E AH* and AG*^ in kcal / mole
AS* in e.u.; k = 1.
a data from I.M.T. Davidson


34
The values given for compounds a through d, are for hydride migration (A)
(eq. 17), and the values for compounds £ thorugh h are for migration of the aryl group
(B) (eq. 18):
Ar Me
ArSi(H)Me(CH2Cl) - Me-Si-Cl + ArCH2-$i-H (eq. 17)
Me ci
A (<10 JO
Me Ar
A 1 I
ArSiMe2CH2Cl ArCH2-Si-Cl + Cl-Si-Et (eq. 18)
Me Me
B (<10 JO
Also shown in equations 17 and 18 are secondary migration products. Graphs and
detailed rate data for individual compounds can be found in Appendix B.
2.2.1 Interpretation of A factors and Energies of Activation
Arrhenius 'A' factors obtained from all the above rearrangements range from
10111 to 1014-5, indicative of a unimolecular process37,39,40,41. Log A for gas phase
bimolecular processes typically range between 7 and 10.5, while those for unimoleclar
processes are much higher, according to Benson41. Our A factors, while in the range
of those determined by Davidson and O'Neal, do not allow any clear choice of
mechanism. It is also important to note that the series of compounds studied here is
significantly different than those studied by Brook.
According to Martin, Ring and O'Neal, an A factor of IQ12-810-3 corresponds


35
to an entropy of activation of approximately -3.5 e.u. which is accounted for by the
loss of one internal rotation in a singly bridged transition state.39 A AS^ of
approximately -7 e.u. would, thus, be expected for a doubly bridged dyotropic state.
Except for the X = H, Y = Me and X = p-F, Y = Me cases, AS^ (determined from
Eyring plots) ranged from 1.9 to -3.2 e.u. which is in agreement with the singly
bridged transition state. However, this does not reflect on the possible charge
separation during transition. For the two exceptions, AS^ was -8.7 and -11.6
indicating a potentially doubly bridged system during rearrangement. In any event, it
appears that these two compounds have a tighter transition state than the others.
Large energies of activation (Ea) were obtained as well: 47.5 to 56 kcal /
mole. These are also consistent with a unimolecular rearrangement; bimolecular
energies of activation are typically near 10 kcal / mole41.
If the free energies of rearrangement are compared for the two sets of
compounds, it is also observed that AG* is about 3 kcal higher for the aryl migration as
opposed to the hydride migration. Also observed is that the m-CF3 compounds (both
types) have a larger magnitude than the others in their respective sets.
2.2.2 Relative migratory aptitudes of silicon substituents
If one compares the rate constant for aryl and hydrogen migration at the same
temperature (eq. 17), it is found that the hydrogen migrates approximately one order of
magnitude faster than the aromatic group: k for hydride migration in the m-CFj
hydride (]i) at 828 K is experimentally found to be 0.142 s'1, whereas that for aryl
migration at the same temperature is 0.0103 s'1. For the p-Me dimethyl case (eq. 18),


36
rate constants of 0.0434 s'1 for aryl migration and 0.00345 s'1 for methyl migration are
obtained experimentally at 820 K. This gives a relationship where the ratio of hydride
to aryl to methyl migration is approximately 100:10:1. If the gas chromatographic
spectra are visually inspected, it is verified that for the methyl hydrides, there is a very
small peak approximately ten percent of the area of the product peak when higher
conversion rates are achieved. The same is observed for the dimethyl case, the major
peak being aromatic migration and the minor one, methyl migration.
Attempts at using rates of migration determined from the areas of the
secondary products in an Arrhenius plot were unsuccessful in getting more than a rough
estimate of the rate constant in the temperature range studied. These plots were
unsuccessful due to scatter caused by the small amounts of methyl migration.
If the respective Anrhenius parameters A and Ea are used to calculate the rate
constants for rearrangement at 873 K, values obtained are 1.275 s'1 (H-migration) for
the p-F hydride and 0.161 s'1 (aryl migration) for the p-F dimethyl compounds. These
give a relative migratory ratio of approximately 8:1.
2.2.3 Electronic Substituent Effects in Rearrangements of Chloromethvlsilanes
Distinctions between the various mechanisms for rearrangement are all rather
close and make simple kinetic arguments difficult. On the other hand, we felt that
electronic differences might be used to probe the mechanism. Consider the migration
of an aryl group: if significant charge were developing on the silicon, substituents on
the aromatic ring would assist or destabilize the transition state depending upon whether
they were electron donating or withdrawing. A Hammett study can probe electronic


37
substituent effects to determine the charge distribution in the transition state.
In trying to evaluate if there are electronic effects on the rearrangement of
chloromethyl silanes, a Hammett study was carried out. For the aryl substitutions H,
p-F, m-CF3 and P-CH3, c constants 0, 0.6, 0.47 and -0.17 were used respectively.
The rate constants for reaction were calculated from the derived values of Ea and log(A)
at temperatures of 760 K (for hydride migration) and 800 K for aryl migration. These
temperatures were chosen as representative of approximately 15 percent conversion of
starting material to product.
Table VII and Figure IV give the results of the Hammett study for the hydride
migration. There is essentially no correlation. The p value obtained is-0.29 0.16.
Nothing about the electronic nature of the transition state can be inferred from this
information.
Table Yn
Hammett Parameters for Chloromethyl Hydrides at 760 K
compound sigma rate at 760 K relative rate log (rel. rate)
a 0.00 0.0103 1.00 0.00
h 0.06 0.0139 1.350 0.130
a 0.47 0.00866 0.841 -0.0753
4 -0.17 001355 1.315 0.1188


38
y = -.287x + .069, R-squared: .623
FIGURE IV
The Hammett Relationship of Chloromethyl Hydrides at 760 K
For the dimethyl compounds, a much different correlation exists. Table VIII
and Figure V give the pertinent information for this Hammett study. In this case there
is a better correlation and straight line relationship between the log of the relative rates
and a. p for aryl rearrangement is -0.6 0.1. Despite the correlation in this case,
again, little can be said about the mechanism of reaction. Both sets of compounds give
negative slopes, which is consisitent with a positive center developing next to the
aromatic ring. The magnitude of p, however is very small, indicating there is little
charge separation in the transition state, if indeed there is a real effect. So, while this
result is opposite of Brook's inverse ylid, the magnitude of p does not allow it to be
ruled out.


TABLE Vm
Hammett Parameters for Chloromethyl Dimethyl Silanes at 800 K
39
compound sigma rate at 800 relative rate log (rel. rate)
£ 0.00 0.0147 1.00 0.00
£ 0.06 0.0157 1.068 0.0286
g. 0.47 0.00762 0.518 -0.285
h -0.17 0.0176 1.197 0.0781
y = -.586x + .008, R-squared:.946
Figure VI
The Hammett Relationship of Chloromethyl Dimethyl Silanes at 800 K


40
2.2.4 Considerations on Error Analysis
Error analysis of this project was difficult. Originally data were processed by
the Leicester computer; Ea's and A factors were both returned with uncertainties (i.e.
235 4 kJ / mole and 10141 -3). Since these two values are co-dependent, figuring
out a reasonable error value in the derived rate constants from the Arrhenius equation
was non-trivial. Uncertainties in Ea (from the Statview program) are presented in Table
VI. Uncertanties were also determined through a standard deviation method.42 This
method gave good uncertainties in general in the 5-20 % range (similar to those directly
off the Leicester computer).
If a 5 % uncertainty is assumed, it still has a large effect in the Hammett
comparisons. A value of 1.18 0.06 will give 0.0899 and 0.0531 for the bounds after
transformation to its logarithmic form for the Hammett comparison. With this range,
the uncertainties are so large, essentially any line that is desired could be drawn for a
set of points.
From a more realistic note however, it seems reasonable to assume the
differences in the compounds activation parameters and derived rate constants are real,
since they were all obtained in the same manner experimentally, and analyzed by the
same method. Therefore, they should all have roughly the same types and sources of
uncertainty. Errors in measurments would be the same for all compounds since they
were handled in a nearly identical manner.


41
2.2.5 Summation of Results
Using the A factors and energies of activation, it is clear these rearrangements
are unimolecular (Ea's range from 49.9 to 56.2 kcal/mole; log A ranges from 11.2 to
14.1). Also, when considering AS*, the singly bridged dyotropic mechanism for
rearrangement is supported (AS* ranges from 1.9 to -11.3 e.u.). Electronic effects of
substituents on the aromatic ring are small, if even real, as shown by the magnitude of
p from the Hammett studies (-0.29 and -0.59). Therefore, little can be said about
charge separation, if any in the transition state.
2.3 Experimental
All compounds were purified with a B/R spinning band micro still to a purity
of two parts in ten thousand maximum (liquid phase), as determined by gas
chromotography. Gas chromatographic data were determined with a Hewlett-Packard
5890 Gas Chromatograph with 25 m crosslinked polydimethylsilicone capillary
column. Pyrolysis of the chloromethyl compounds was performed in the Stirred Flow
Reactor in Leicester, UK43,44. Rearrangement products were characterized using a
new Stirred Flow Pyrolysis Reactor interfaced to a Hewlett-Packard 5995C Gas
Chromatograph with Mass Quadrupole Detector. Mass spectra of products were also
obtained through sealed tube pyrolyses of the various silanes, followed by liquid
injection of the product(s) into the mass quadrupole/gas chromatograph.


42
2.3.1 SFR Procedural Considerations
After the sample was degassed completely through a series of freezing and
thawing cycles under high vacuum, a sample of vapor (0.050 to .250 torr) was injected
into the Stirred Flow Reactor with a carrier gas of nitrogen (60 1 / min). Contact time
inside the Reactor was 15 seconds. The Reactor temperature was controlled with a
variac and thermocouple with l.e.d. readout. The temperature of the oven was allowed
to equilibrate a few minutes before injection. After equilibrium in the Stirred Flow
Reactor, the sample was carried into a Gas Chromatograph with 3.5 metre SE 30
packed column. The output of the Chromatograph was coupled with both a chart
recorder and computer program (ARRH) for handling of the data.
A series of response factors for each set of rearrangement products was
determined using (C^H5)SiMe2Cl (for the hydride migration) and
(CgH-jjCF^Silv^Cl (for the aryl migration) as reference products. These values were
incorporated into the computer program before any temperature runs were started.
A second SFR interfaced with a gas chromatograph with mass selective
detector was used for identification of products. When the injection valve on this
instrument was not running properly, or the silane was too non-volatile, sealed tube
pyrolyses of the silane were done with liquid injection to check the products.
2.3.2 Physical Data for the Silanes Studied
I. (CgH^SiM^Cl: bp: 52C/1.4 mm Hg; Petrarch Systems, Inc.;
mw: 170.03; M+ 170.00 (4272), 172.00 (1250); M+ CH3 =
154.90 (10,000), 157.00 (8780).


43
II. (CgH^CH^iMe^l: bp: 52C / 1.4 mm Hg; Petrarch Systems,
Inc.; mw: 184.05; M+ = 184.10 (3771), 186.10 (1190); M+-
PhCH2 = 93.05 (10,000), 94.95 (9071).
III. (C6H5)SiMe(H)(CH2Cl): bp: 66C/1.3 mmHg; VY-II-8/7/87;
mw: 170.03; M+ = 170.00 (268), 172.00 (84); M+ CH2C1 =
121.00 (10,000).
IV. (p-F-C6H4)SiMe(H)(CH2Cl): bp: 68-71C / 1.5 3.0 mm Hg; %
C 51.08 (calc: 50.92), % H 5.47 (calc: 5.34); VY-H-2/20/87 (?);
mw: 188.02; M+ = 188.05 (985), 190.15 (305); M+-CH2C1 =
139.10 (10,000).
V. (p-CH3-C6H4)SiMe(H)(CH2Cl): bp: 75C / 1.5 mm Hg;
VY-n-2/7/84 (?); % C 58.83 (calc: 58.51), % H 7.30 (calc:
7.09); mw: 184.05; M+= 184.10 (621), 186.10 (259); M+-
CH2C1 = 135.05 (10,000).
VI. (m-CF3-C6H4)SiMe(H)(CH2Cl): bp: 68C / 1.3 mm Hg;
VY-II-11/22/86; %C 45.63 (calc: 45.28), % H 4.46 (calc: 4.22);
mw: 238.02; M+ = 238.00 (34), 239.90 (12); M+ CH2C1 =
189.00 (10,000).


44
VII. (C^H5)SiMe2(CH2Cl): bp: 56C / 0.8 mm Hg; Petrarch Systems,
Inc.; mw: 184.05; M+= 184.05 (151), 186.05 (69); M+-
CH2C1 = 135.00 (10,000).
VIII. (p-F-C6H4)SiMe2(CH2Cl): bp: 75C / 1.4 mm Hg; VY-I-8/7/84;
mw: 202.04; M+= 202.10 (407), 204.10 (144); M+-CH2C1 =
153.00 (10,000).
IX. (p-CH3-C6H4)SiMe2(CH2Cl): bp: 91C / 2.5 mm Hg;
VY-I-7/27/84; mw: 198.06; M+= 198.00 (605), 200.10 (264);
M+ CH2C1 = 149.15 (10,000).
X. (m-CF3-C6H4)SiMe2(CH2Cl): bp: 81C/ 1.9 mm Hg;
VY-I-7/30/84; mw: 252.08; M+ = not observed; M+-CH3 =
237.00 (253), 239.00 (89); M+ CH2C1 = 203.10 (10,000).
2.3.3 Mass Spectral Data for the Product Silanes
Pyrolysis of (C6H5)SiMe(H)(CH2Cl):
I. (C6H5)SiMe2Cl (H migration): M+= 170.00 (1487), 172.10
(500); M+ CH3 = 155.00 (10,000), 157.00 (3207).
Pyrolysis of (p-F-C6H4)SiMe(H)(CH2Cl):


45
I. (p-F-C6H4)SiMe2Cl (H migration): M+= 187.90 (1573), 189.90
(543); M+ CH3 = 172.90 (10,000), 174.90 (3422).
II. (p-F-C£H4)CH2SiMeCl (trace Ph migration): M+ = 187.90 (697),
189.90 (239); M+ (p-F-C6H4)CH2 = 78.95 (2702), 80.95
(1105); ,(p-F-C6H4)CH2+ = 109.05 (5192); -(C6H4)CH2+=
90.05 (10,000).
Pyrolysis of (p-F-C6H4)SiMe(H)(CH2Cl):
I. (p-CH3-C6H4)SiMe2Cl (H migration): M+= 184.00(82),
186.00 (271); M+ CH3 = 169.00 (5095), 171.00 (1789).
Pyrolysis of (m-CF3-C6H4)SiMe(H)(CH2Cl):
I. (m-CF3-C6H4)SiMe2Cl (H migration): M+= 237.80(1337),
239.80 (469); M+ CH3 = 222.70 (10,000), 224.70 (3441).
II. (m-CF3-CgH4)CH2SiMeCi (trace Ph migration): M+ = 237.70
(79); M+ CH3 = 222.80 (480), 224.80 (186); M+-CF3CH2 =
154.85 (9220 ), 156.85 (2994).
Pyrolysis of (C^H3)SiMe2(CH2Cl):
I. (C6H5)CH2SiMe2Cl (Ph migration): M+= 183.90(1031),
185.90 (351); M+ -CH2Ph = 92.95 (10,000).


II.
46
(CgH5)Si(Et)(Me)Cl (trace Me migration): M+ = 183.90(1047);
185.90 (376); M+ CH2CH3 = 154.95 (10,000), 156.95 (3544).
Pyrolysis of (p-F-C6H4)SiMe2(CH2Cl):
I. (C6H5)CH2SiMe2Cl (Ph migration): M+= 202,204; M+-
CH2PhF = 93; -CH2Ph+ = 90.
Pyrolysis of (p-CH3-C^H4)SiMe2(CH2Cl):
I. (p-CH3-C^H4)CH2SiMe2Cl (Ph migration): M+ = 198.00
(1404), 200.00 (491); M+ CH3Ph = 93.05 (10,000), 95.05
(3593).
II. (p-CH3-C^H4)Si(Et)(Me)Cl (trace Me migration): M+ = 198.00
(1272); 200.00(411); M+- CH2CH3 = 169.00 (10,000), 171.00
(3403).
Pyrolysis of (m-CF3-CgH4)SiMe2(CH2Cl):
I.
(m-CF3-C^H4)CH2SiMe2Cl (Ph migration): M+ = 252; M+ -
CF3Ph = 93; M+ C6H5C1 = 140.


REFERENCES
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1952, 2846-2849.
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13. According to the 1988-1989 Aldrich Chemical Company
Catalogue/Handbook, zinc (II) fluoride, lead (II) fluoride and aluminum (HI)
fluoride (x hydrate) are all classified as toxic; lead fluoride is corrosive and
toxic, and the zinc and aluminum fluorides are classified as highly toxic.
Copper (A) fluoride is listed as hygroscopic.
14. Klanberg, F.; Muetterties, E.L. Inorg. Chem.. 1968. 7. 155.
15. Damrauer, R.; Danahey, S.E. Organometallics. 1986. 5,1490.
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(Cl. 260 448.2; £A: £1: P8340h).
17.
Damrauer, R; Kanner, B; Simon, R. Organometallics. 1988. 7. 1161-1164.


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18. Bailey, D.L.; Pike, R.M. US Patent 3,020,302, Feb. 6, 1962; see CA:
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20. Kuroda, K.; Ishikawa, N. Nippon Kagaku Zasshi. 1969, 22, 322-323.
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22. Hairston, T.J.; O'brien, D.H. J. Organomet. Chem.. 1971, 22. 79-92.
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41-45.
24. Anderson, H.H.; Hendifar, A. JACS. 1959, SI, 1027-1028; Emeleus,
H.J.; Wilkins, C.J. J. Chem. Soc.. 1944, 454-456.
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P.A.; Whitmore, F.C. JACS. 1948, 22, 433-434.
26. Flood, E.A. JACS. 1933, 55, 1735-1736.
27. Bluestein, B.A. JACS. 1948, 22, 3068-3071.
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Publications, 1960.
29. Pearlson, W.H.; Brice, T.J.; Simons, J.H. JACS. 1945. 67. 1769-1770.
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49
39. Martin, J.G.; Ring, M.A.; O'Neal, H.E. Organometallics. 1986, 5.,
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ML 17.


APPENDIX A
Useful Equations for Kinetics
The Arrhenius Equation
ic A e Efl/RT
log *
log A -
(-)
( 2. 303 )R M/
plot log 1< vs.
k = rate constant
When the graph of log(k) vs. 1 / T is done, b = log A; therefore A = 10^*. The slope is
related to Ea: m = Ea / (2.303) R; Ea = (2.303) R m.
The Ervin g Equation
* = K h. T e-^BT
h
i K e-AG*/RT
T h
L
log = log + log k +
T h
. K T eAS'/B e-AH'/RT
h
= K ~ eAS*/R e-AH*/RT
h
A$* _ AH* l\_
( 2. 303 )R ( 2. 303 )R \T


51
plot log vs. {^yI
When the graph of log(k / T) vs. 1 / T is done, b = log (kb / h) + log K + (AS* / (2.303
* R)); AS* = (2.303) R (b 10.32 log k). m = (AH* / (2.303 R)); AH* =
(2.303) R m.
Also from the Eyring equation is the relationship between AS* and A:
R ln^ Ah_j = AS*
b
. kb AS*/R
A = T e
h
Constants and Miscellaneous
y = mx + b equation for a line
R = 8.3143 J / mole K
= 1.987 cals / mole K
h = 6.626 x 10'34 J / Hz
kb = 1.38 x 10'23 J K
conversion factor: 4.184 J / cal
kb/h = 2.0836 x 1010 s1 K'1
log (kb/h) = 10.32
k = 1, for simple reaction pathways;
for an n path reaction, k = 1 / n
k = rate constant


APPENDIX B
Detailed Kinetic Parameters for Chloromethylsilane Rearrangements
PhSiMe(H)CH2CI
TABLE IX
Rate and Temperature Values for PhSiMe(H)CH2Cl
T(K) k (s'1) 1/T log(k) k/T log(k/T)
744.0 0.005620
745.0 0.005290
764.0 0.016000
766.0 0.018440
772.0 0.022600
776.0 0.024800
777.0 0.027300
783.0 0.034800
793.0 0.048200
796.0 0.054100
796.0 0.057300
798.0 0.072900
805.0 0.094300
816.0 0.156000
828.0 0.197000
0.001344 -2.250264
0.001342 -2.276544
0.001309 -1.795880
0.001305 -1.734239
0.001295 -1.645892
0.001289 -1.605548
0.001287 -1.563937
0.001277 -1.458421
0.001261 -1.316953
0.001256 -1.266803
0.001256 -1.241845
0.001253 -1.137272
0.001242 -1.025488
0.001225 -0.806875
0.001208 -0.705534
0.0000076 -5.1218
0.0000071 -5.1487
0.0000209 -4.6790
0.0000241 -4.6185
0.0000293 -4.5335
0.0000320 -4.4954
0.0000351 -4.4543
0.0000444 -4.3522
0.0000608 -4.2162
0.0000680 -4.1677
0.0000720 -4.1428
0.0000914 -4.0393
0.0001171 -3.9313
0.0001912 -3.7186
0.0002379 -3.6236


log ( k / T ) log k
53
g = -11647.732x + 13.416, R-squared: .993
The Relationship between log (k) vs. 1/T for PhSiMe(H)CH2Cl
y = -11308.049x + 10.088, R-squared: .992
The Relationship between log (k/T) vs. 1/T for PhSiMe(H)CH2Cl


54
(p-F-C6H4)SiMe(H)CH2Cl
TABLE X
Rate and Temperature Values for (p-F-CgH^SiMe/FOCI-^Cl
T (K) k (s'1) 1/T log(k) k/T log (k/T)
754.0 0.009801 0.001326 -2.0087 0.0000130 -4.8861
768.0 0.018820 0.001302 -1.7254 0.0000245 -4.6107
777.0 0.027140 0.001287 -1.5664 0.0000349 -4.4568
783.0 0.031640 0.001277 -1.4998 0.0000404 -4.3935
784.0 0.031850 0.001276 -1.4969 0.0000406 -4.3912
790.0 0.050260 0.001264 -1.2988 0.0000636 -4.1964
791.0 0.050210 0.001264 -1.2992 0.0000635 -4.1974
797.0 0.069750 0.001255 -1.1565 0.0000875 -4.0579
801.0 0.077610 0.001248 -1.1101 0.0000969 -4.0137
802.0 0.078920 0.001247 -1.1028 0.0000984 -4.0070
806.0 0.097540 0.001241 -1.0108 0.0001210 -3.9172
811.0 0.104400 0.001233 -0.9813 0.0001287 -3.8903


log ( k / T )
55
y = -11517.429x + 13.255, R-squared: .99
1 /T
FIGURE VHI
The Relationship between log (k) vs. 1/T for (p-F-C^H^SiMeCFDCH^Cl
y = -11177.464x + 9.927, R-squared: .99
FIGURE IX
The Relationship between log (k/T) vs. 1/T for (p-F-CgH^SiMeCFDCF^Cl


56
(m-CF3-C6H4)SiMe(H)CH2Cl
TABLE XI
Rate and Temperature Values for (m-CFg-C^H^SiMeCf^CF^Cl
T(K) k (s'1) 1/T
758.0 0.007410 0.001319
760.0 0.007556 0.001316
764.0 0.009875 0.001309
770.0 0.012320 0.001299
779.0 0.021200 0.001284
781.0 0.021970 0.001280
784.0 0.027250 0.001276
785.0 0.033500 0.001274
787.0 0.032660 0.001271
797.0 0.047840 0.001255
797.0 0.042030 0.001255
799.0 0.054250 0.001252
805.0 0.069910 0.001242
810.0 0.082490 0.001235
816.0 0.105200 0.001225
818.0 0.016200 0.001222
826.0 0.169700 0.001211
827.0 0.172100 0.001209
828.0 0.142100 0.001208
836.0 0.263300 0.001196
838.0 0.265300 0.001193
log(k) k/T log (k/T)
-2.1302 0.0000098 -5.0099
-2.1217 0.0000099 -5.0025
-2.0055 0.0000129 -4.8886
-1.9094 0.0000160 -4.7959
-1.6737 0.0000272 -4.5652
-1.6582 0.0000281 -4.5508
-1.5646 0.0000348 -4.4589
-1.4750 0.0000427 -4.3698
-1.4860 0.0000415 -4.3820
-1.3202 0.0000600 -4.2217
-1.3764 0.0000527 -4.2779
-1.2656 0.0000679 -4.1681
-1.1555 0.0000868 -4.0613
-1.0836 0.0001018 -3.9921
-0.9780 0.0001289 -3.8897
-0.9739 0.0001298 -3.8866
-0.7703 0.0002054 -3.6873
-0.7642 0.0002081 -3.6817
-0.8474 0.0001716 -3.7654
-0.5795 0.0003150 -3.5018
-0.5763 0.0003166 -3.4995


57
y = -12276.036x + 14.072, R-squared: .994
FIGURE X
The Relationship between log (k) vs. 1/T for (m-CF3-C(5Hi^)SiMe(H)CH2Cl
y = -11929.91 lx 10.736, R-squared: .993
The Relationship between log (k/T) vs. 1/T for (m-CF3-C^H4)SiMe(H)CH2Cl


58
(p-CH3-C6H4)SiMe(H)CH2Cl
TABLE XII
Rate and Temperature Values for (p-CHg-CgH^SiMeCEQCF^Cl
T (K) k (s'1) 1/T log(k) k/T log (k/T)
753.0 0.009254
755.0 0.010510
755.0 0.010480
762.0 0.014980
764.0 0.016380
770.0 0.020970
775.0 0.025910
780.0 0.034030
782.0 0.031450
785.0 0.039570
790.0 0.049390
792.0 0.056950
794.0 0.054150
795.0 0.058190
799.0 0.069530
806.0 0.097920
810.0 0.111700
816.0 0.145800
0.001328 -2.0337
0.001325 -1.9784
0.001325 -1.8245
0.001312 -1.8245
0.001309 -1.7857
0.001299 -1.6784
0.001290 -1.5865
0.001282 -1.4681
0.001279 -1.5024
0.001274 -1.4026
0.001266 -1.3064
0.001263 -1.2445
0.001259 -1.2664
0.001258 -1.2352
0.001252 -1.1578
0.001241 -1.0091
0.001235 -0.9519
0.001225 -0.8362
0.0000123 -4.9105
0.0000139 -4.8563
0.0000139 -4.8576
0.0000197 -4.7064
0.0000214 -4.6688
0.0000272 -4.5649
0.0000334 -4.4758
0.0000436 -4.3602
0.0000402 -4.3956
0.0000504 -4.2975
0.0000625 -4.2040
0.0000719 -4.1432
0.0000682 -4.1662
0.0000732 -4.1355
0.0000870 -4.0604
0.0001215 -3.9155
0.0001379 -3.8604
0.0001787 -3.7479


log k
59
y =-11410.982x + 13.135, R-squared: .997
FIGURE XH
The Relationship between log (k) vs. 1/T for (p-C^-C^H^SiMelHlCI^Cl
y -11071,599x + 9.808, R-squared: .997
The Relationship between log (k/T) vs. 1/T for (p-C^-CgH^SiMeCFQCl^Cl


60
PhSiMe2CH2Cl
TABLE Xm
Rate and Temperature Values for PhSiMe2CH2Cl
T(K) k (S1) 1/T log(k) k/T
772.0 0.005247 0.001295 -2.2801 0.0000068
777.0 0.005934 0.001287 -2.2267 0.0000076
784.0 0.007091 0.001276 -2.1493 0.0000090
788.0 0.008308 0.001269 -2.0805 0.0000105
788.0 0.009812 0.001269 -2.0082 0.0000125
791.0 0.008686 0.001264 -2.0612 0.0000110
792.0 0.009252 0.001263 -2.0338 0.0000117
793.0 0.010250 0.001261 -1.9893 0.0000129
793.0 0.009450 0.001261 -2.0246 0.0000119
793.0 0.009693 0.001261 -2.0135 0.0000122
793.0 0.012290 0.001261 -1.9104 0.0000155
793.5 0.010980 0.001260 -1.9594 0.0000138
799.0 0.015340 0.001252 -1.8142 0.0000192
800.0 0.014730 0.001250 -1.8318 0.0000184
802.0 0.015570 0.001247 -1.8077 0.0000194
807.0 0.016800 0.001239 -1.7747 0.0000208
808.0 0.016530 0.001238 -1.7817 0.0000205
813.0 0.024480 0.001230 -1.6112 0.0000301
815.0 0.021690 0.001227 -1.6637 0.0000266
818.0 0.025660 0.001222 -1.5907 0.0000314
818.0 0.025030 0.001222 -1.6015 0.0000306
822.0 0.030700 0.001217 -1.5129 0.0000373
825.0 0.036920 0.001212 -1.4327 0.0000448
826.0 0.035060 0.001211 -1.4552 0.0000424
830.0 0.036700 0.001205 -1.4353 0.0000442
832.0 0.044520 0.001202 -1.3514 0.0000535
833.0 0.049280 0.001200 -1.3073 0.0000592
834.0 0.051300 0.001199 -1.2899 0.0000615
834.0 0.059940 0.001199 -1.2223 0.0000719
837.0 0.063280 0.001195 -1.1987 0.0000756
841.0 0.068810 0.001189 -1.1623 0.0000818
845.0 0.076300 0.001183 -1.1175 0.0000903
849.0 0.091300 0.001178 -1.0395 0.0001075
log (k / T)
-5.1677
-5.1171
-5.0436
-4.9770
-4.9048
-4.9594
-4.9325
-4.8885
-4.9238
-4.9128
-4.8097
-4.8589
-4.7167
-4.7349
-4.7119
-4.6816
-4.6891
-4.5213
-4.5749
-4.5035
-4.5143
-4.4277
-4.3492
-4.3722
-4.3544
-4.2716
-4.2280
-4.2110
-4.1434
-4.1215
-4.0871
-4.0443
-3.9684


log k
61
y = -10896.481 x + 11.764, R-squared: .986
The Relationship between log (k) vs. 1/T for PhSiN^CP^Cl
y = -10544.416x + 8.421, R-squared: .985
1 /T
FIGURE XV
The Relationship between log (k/T) vs. 1/T for PhSiN^CP^G


62
T (K)
771.0
774.0
779.0
780.0
780.0
783.0
783.0
784.0
791.0
792.0
798.0
799.0
805.0
809.0
817.0
818.0
824.0
829.0
832.0
839.5
841.0
844.0
849.0
(p-F-C6H4)SiMe2CH2Cl
TABLE XIV
Rate and Temperature Values for (p-F-C6H4)SiMe2CH2Cl
k (s1) 1/T log(k) k/T log (k/T)
0.005000 0.001297 -2.3010 0.0000065 -5.1881
0.005950 0.001292 -2.2255 0.0000077 -5.1142
0.007764 0.001284 -2.1099 0.0000100 -5.0015
0.009020 0.001282 -2.0448 0.0000116 -4.9369
0.005460 0.001282 -2.2628 0.0000070 -5.1549
0.010680 0.001277 -1.9714 0.0000136 -4.8652
0.007015 0.001277 -2.1540 0.0000090 -5.0477
0.005580 0.001276 -2.2534 0.0000071 -5.1477
0.012080 0.001264 -1.9179 0.0000153 -4.8161
0.010830 0.001263 -1.9654 0.0000137 -4.8641
0.011960 0.001253 -1.9223 0.0000150 -4.8243
0.014660 0.001252 -1.8339 0.0000183 -4.7364
0.018810 0.001242 -1.7256 0.0000234 -4.6314
0.021445 0.001236 -1.6687 0.0000265 -4.5766
0.026710 0.001224 -1.5733 0.0000327 -4.4855
0.025740 0.001222 -1.5894 0.0000315 -4.5021
0.034220 0.001214 -1.4657 0.0000415 -4.3816
0.043940 0.001206 -1.3571 0.0000530 -4.2757
0.044790 0.001202 -1.3488 0.0000538 -4.2689
0.064120 0.001191 -1.1930 0.0000764 -4.1170
0.06790 0.001189 -1.1695 0.0000805 -4.0943
0.075580 0.001185 -1.1216 0.0000895 -4.0479
0.092290 0.001178 -1.0348 0.0001087 -3.9638


log k
63
y = -10409.782x + 11.19, R-squared: .975
The Relationship between log (k) vs. IT for (p-F-CgH^SilV^Cl^Cl
y = -10058.769X + 7.848, R-squared: .973
The Relationship between log (k/T) vs. 1/T for (p-F-C^H^Sifr^CH^Cl


64
(m-CF3-C6H4)SiMe2CH2Cl
TABLE XV
Rate and Temperature Values for (m-CF3-CgH4)SiMe2CH2Cl
T (K) k (s'1) 1/T
766.0 0.001828 0.001305
771.0 0.002025 0.001297
777.0 0.003537 0.001287
783.0 0.003390 0.001277
788.0 0.003540 0.001269
797.0 0.007003 0.001255
797.0 0.008560 0.001255
804.0 0.012400 0.001244
807.0 0.011600 0.001239
810.0 0.014380 0.001235
816.0 0.019020 0.001225
817.0 0.014170 0.001224
820.0 0.019660 0.001220
824.0 0.028010 0.001214
829.0 0.027516 0.001206
833.0 0.031800 0.001200
834.0 0.037020 0.001199
837.0 0.035590 0.001195
839.0 0.038940 0.001192
843.0 0.046050 0.001186
843.0 0.051630 0.001186
848.0 0.063800 0.001179
853.0 0.072300 0.001172
856.0 0.081680 0.001168
860.0 0.095800 0.001163
862.0 0.104100 0.001160
log(k) k/T log (k/T)
-2.7380 0.0000024 -5.6223
-2.6936 0.0000026 -5.5806
-2.4514 0.0000046 -5.3418
-2.4698 0.0000043 -5.3636
-2.4510 0.0000045 -5.3475
-2.1547 0.0000088 -5.0562
-2.0675 0.0000107 -4.9690
-1.9066 0.0000154 -4.8118
-1.9355 0.0000144 -4.8424
-1.8422 0.0000178 -4.7507
-1.7208 0.0000233 -4.6325
-1.8486 0.0000173 -4.7609
-1.7064 0.0000240 -4.6202
-1.5527 0.0000340 -4.4686
-1.5604 0.0000332 -4.4790
-1.4976 0.0000382 -4.4182
-1.4316 0.0000444 -4.3527
-1.4487 0.0000425 -4.3714
-1.4096 0.0000464 -4.3334
-1.3368 0.0000546 -4.2626
-1.2871 0.0000612 -4.2129
-1.1952 0.0000752 -4.1236
-1.1409 0.0000848 -4.0718
-1.0879 0.0000954 -4.0204
-1.0186 0.0001114 -3.9531
-0.9825 0.0001208 -3.9181


log ( k / T ) lo9 k
65
g = -12176.637x + 13.143, R-squared: .989
The Relationship between log (k) vs. 1/T for (m-CF3*C^H4)SiMe2CH2Cl
y = -11823.223x + 9.797, R-squared: .989
The Relationship between log (k/T) vs. 1/T for (m-CF^-C^H^SiN^CITjCl


66
T(K)
765.0
770.0
775.0
778.0
783.0
788.0
790.0
794.0
799.0
801.0
807.0
812.0
814.0
820.0
822.0
828.0
829.0
836.0
837.0
844.0
(p-CH3-C6H4)SiMe2CH2Cl
TABLE XVI
Rate and Temperature Values for (p-CH3-C6H4)SiMe2CH2Cl
k (s'1) 1/T log(k) k/T log (k/T)
0.003570 0.001307 -2.4473 0.0000047 -5.3310
0.004071 0.001299 -2.3903 0.0000053 -5.2768
0.006700 0.001290 -2.1739 0.0000086 -5.0632
0.006340 0.001285 -2.1979 0.0000081 -5.0889
0.007390 0.001277 -2.1314 0.0000094 -5.0251
0.009430 0.001269 -2.0255 0.0000120 -4.9220
0.010210 0.001266 -1.9910 0.0000129 -4.8886
0.012200 0.001259 -1.9136 0.0000154 -4.8135
0.015890 0.001252 -1.7989 0.0000199 -4.7014
0.018900 0.001248 -1.7235 0.0000236 -4.6272
0.023180 0.001239 -1.6349 0.0000287 -4.5418
0.028300 0.001232 -1.5482 0.0000349 -4.4578
0.022080 0.001229 -1.6560 0.0000271 -4.5666
0.043400 0.001220 -1.3625 0.0000529 -4.2763
0.029500 0.001217 -1.5302 0.0000359 -4.4450
0.051740 0.001208 -1.2862 0.0000625 -4.2042
0.051580 0.001206 -1.2875 0.0000622 -4.2061
0.067720 0.001196 -1.1693 0.0000810 -4.0915
0.076510 0.001195 -1.1163 0.0000914 -4.0390
0.123000 0.001185 -0.9101 0.0001457 -3.8364


67
y = -11799.242x + 12.962, R-squared: .983
The Relationship between log (k) vs. 1/T for (p-CF^-CgH^SiN^CF^Cl
y = -11450.365x + 9.623, R-squtred: .982
The Relationship between log (k/T) vs. 1/T for (p-CB^-CgH^SiN^CF^Cl


STIRRED FLOW PYROLYSIS APPARATUS
flow
controller
thermocouple
port
Barytron
(pressure
guage)
sample loop
r\
sample

fe
oven
stirred flow reactor (SFR)


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