Utility of trichloroisocyanuric acid in the efficient chlorination of silicon hydrides

Article abstract of DOI:10.1016/j.jorganchem.2006.12.032

The potential of trichloroisocyanuric acid (TCCA) as a chlorination agent for efficient conversion of Si-H functional silanes and siloxanes to the corresponding Si-Cl functional moieties was explored. In comparison to methods using other chlorinating agents, TCCA is inexpensive, results in a much faster reaction and produces a high purity product with a conversion that is essentially quantitative. A variety of chloro derivatives of linear and cyclic structures have been synthesized from silicon hydrides using this reagent with impressive yields that typically exceed 90%: PhSiCl₃ (97.5%); PhMeSiCl₂ (95.5%); Ph₃SiCl (97.5%); Vi₃SiCl (98.7%); (EtO)₃SiCl (99.7%); t-Bu₃SiCl (～100%); (MeClSiO)₄ (86.5%); (MeClSiO)₅ (95%); (MeClSiO)₇ (96.5%); Ph(OEt)₂SiCl (98%); ClMe₂SiOSiMe₂Cl (98.6%); ClMe₂SiOSiMeClOSiMe₂Cl (94.6%); ClMe₂Si(OSiMeCl)₂OSiMe₂C l (92.3%); (Me₃SiO)₃SiCl (97%); Me₃SiOSiClPhOSiMe₃ (99%); Me₃SiO(SiMeClO)₃SiMe₃ (95.7%); ClSi(OSiMe₃)₂OSi(OSiMe₃) ₂Cl (93.6%). For monohydridosilanes, dichloromethane (CH₂Cl₂) was a suitable solvent in which nearly quantitative conversion was observed within several minutes following the addition of the silanes to TCCA. For certain cyclic and linear siloxanes, and especially silanes containing multiple hydrogen atoms on the same silicon for which the reaction is sluggish in CH₂Cl₂, tetrahydrofuran (THF) was the preferred solvent. For a sterically demanding silane that did not undergo chlorination even in THF viz., HSi(OSiMe₃)₂O-Si(OSiMe₃)₂H, 1,2-dichloroethane was the best solvent.

Full text of DOI:10.1016/j.jorganchem.2006.12.032

Journal of Organometallic Chemistry 692 (2007) 1892–1897
www.elsevier.com/locate/jorganchem
Utility of trichloroisocyanuric acid in the efficient chlorination
of silicon hydrides
*
Sudarsanan Varaprath , Debra H. Stutts
Dow Corning Corporation, Health and Environmental Sciences, Mail # CO3101, 2200 W. Salzburg Road, Auburn, MI 48611, USA
Received 13 December 2006; received in revised form 21 December 2006; accepted 22 December 2006
Available online 9 January 2007
Abstract
The potential of trichloroisocyanuric acid (TCCA) as a chlorination agent for efficient conversion of Si–H functional silanes and sil-
oxanes to the corresponding Si–Cl functional moieties was explored. In comparison to methods using other chlorinating agents, TCCA is
inexpensive, results in a much faster reaction and produces a high purity product with a conversion that is essentially quantitative. A
variety of chloro derivatives of linear and cyclic structures have been synthesized from silicon hydrides using this reagent with impressive
yields that typically exceed 90%: PhSiCl3 (97.5%); PhMeSiCl2 (95.5%); Ph3SiCl (97.5%); Vi3SiCl (98.7%); (EtO)3SiCl (99.7%); t-Bu3SiCl
(ꢀ100%); (MeClSiO)4 (86.5%); (MeClSiO)5 (95%); (MeClSiO)7 (96.5%); Ph(OEt)2SiCl (98%); ClMe2SiOSiMe2Cl (98.6%); ClMe2SiO-
SiMeClOSiMe2Cl (94.6%); ClMe2Si(OSiMeCl)2OSiMe2C l (92.3%); (Me3SiO)3SiCl (97%); Me3SiOSiClPhOSiMe3 (99%); Me3SiO(SiM-
eClO)3SiMe3 (95.7%); ClSi(OSiMe3)2OSi(OSiMe3) Cl (93.6%).
2
For monohydridosilanes, dichloromethane (CH2Cl2) was a suitable solvent in which nearly quantitative conversion was observed
within several minutes following the addition of the silanes to TCCA. For certain cyclic and linear siloxanes, and especially silanes con-
taining multiple hydrogen atoms on the same silicon for which the reaction is sluggish in CH2Cl2, tetrahydrofuran (THF) was the pre-
ferred solvent. For a sterically demanding silane that did not undergo chlorination even in THF viz., HSi(OSiMe3)2O–Si(OSiMe3)2H,
1,2-dichloroethane was the best solvent.
Ó 2007 Elsevier B.V. All rights reserved.
Keywords: Synthesis of chlorosilanes; Siliconhydrides; Trichloroisocyanuric acid; TCCA
1. Introduction
(for example, octamethylcyclotetrasiloxane, decamethyl-
cyclopentasiloxane, dodecamethylcyclohexasiloxane, hex-
amethyldisiloxane, poly(dimethylsiloxanes) of various
viscosities, etc.) are routinely utilized as tracers in environ-
mental and toxicological investigations [2–10].
One of the common methods used to synthesize chloro-
silanes of interest is via the silicon hydrides. Various chlo-
rinating agents are used to transform the Si–H bond to
Si–Cl: Cl2, HCl, acetylchloride, phosphorous trichloride,
allyl chloride in presence of activated charcoal on palla-
dium etc [11a,11b,11c]. The draw backs in using these chlo-
rinating agents can arise from one or more of the following:
low yield, difficulty in handling the reagent, tedious
workup procedures to obtain pure product.
Among the organosilicon compounds, chlorosilane
materials are the most frequently used for a variety of func-
tional group transformations. Reactions involving nucleo-
philic attack by water, alcohols, organic acids, metallic
oxides or organometallic reagents have been used in the
synthesis of numerous substituted products. For example,
introduction of a radioactive 14C-methyl group into
organosilicon compounds is almost always accomplished
by reaction of chlorosilanes with 14C-labeled methyl Grig-
nard reagents [1a,1b]. The resulting 14C-labeled siloxanes
*
Corresponding author. Tel.: +1 989 496 4795; fax: +1 989 496 5595/
In this context, the use of chloroimides was investigated.
The driving force was the need to develop an efficient reac-
tion involving a simple clean up procedure following the
6609.
E-mail address: sudarsanan.varaprath@dowcorning.com (S. Vara-
prath).
0022-328X/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2006.12.032

S. Varaprath, D.H. Stutts / Journal of Organometallic Chemistry 692 (2007) 1892–1897
1893
reaction which required just a filtration to remove the
2. Experimental
insoluble byproduct. Two chloroimides, N-chlorosuccini-
mide (NCS) and trichloroisocyanuric acid (TCCA) were
investigated. We demonstrated that TCCA worked the best
as a chlorinating agent transforming silicon hydrides to the
chloro derivatives.
2.1. Instrumentation
The Gas Chromatography–Mass spectrometer system
components were as follows: Hewlett-Packard (HP)
5890 series II gas chromatograph; HP 7683 GC/SFC
injector; HP 5970 series Mass Selective Detector. GC–
MS system was equipped with electronic pressure control
units. Data analyses were performed using a MicrosoftÒ
Trichloroisocyanuric acid (TCCA) or 1,3,5-trichloro-
1,3,5-2,4,6,-(1H,3H,5H)-trione), known since 1902, belongs
to the large group of chloroimides. TCCA is produced in
large quantities (>100,000 t/year) and is used primarily as
a disinfectant in swimming pools and water treatment. It
is also used as a dishwashing additive in hotel and food ser-
vices. TCCA is seldom used in organic synthesis. In fact, a
review article in 2002 [12] on TCCA deplored the fact
‘‘TCCA has never had a real breakthrough in organic
chemistry laboratories. It has not found a way into text
books of organic chemistry’’. The following synthetic
applications of TCCA have been reported: chlorination
of cyclic ethers [13], benzene [14], alkenes [15] and ketones,
benzylic chlorination [16], oxidation of secondary alcohols
[17,18], aldehydes [19], oximes [20] and ethers [21], hypo-
halogenation of unsaturated ethers [13] and alkenes [17],
cleavage of acetals [22] and, dehydrogenations of various
N-heterocycles [23,24].
Windows-based
Enhanced
ChemStation
software
G1701BA, version B01.00 GC–MS Acquisition parame-
ters are as follows:
GC-oven: Initial temperature, 70 °C; Initial time, 3 min;
Ramps: 1. Rate, 20.00 °C/min to a final temperature of
210 °C. Held at 210 °C for 5 min; Ramp 2: Rate,
20.00 °C/min to a final temperature of 250 °C. Held at
250 °C for 5 min.
GC-Inlet settings: Temperature, 250 °C; Purge flow,
1.0 mL/min; Purge gas, Helium; Constant flow, ON; Ini-
tial pressure, 7.3 psi at 70 °C; Linear velocity, 39.1 cm/
sec; GC column, HP-5 (5% phenylmethylsilicone) from
Hewlett Packard; Column length, 30 meters; Column
id, 0.25 mm; Film thickness, 0.25 micron. MS Detector
(HP 5970 MSD): Detector temperature, 280 °C; Scan
mass m/z, 50–550.
The review article mentioned above has no specific cita-
tion of the utility of TCCA in Si–H to Si–Cl conversion.
However, a single reference was noted in a multistep syn-
thesis of an alkysilyl-tethered polystyrene resin where
TCCA was used on an intermediate containing Si-H moi-
ety to introduce a chlorine atom following the reaction
shown below [25].
Removal of solvent from the products was carried out
using a rotary evaporator of the following specifications:
Buchi Rotavapor: R-205 ; Buchi Vacuum controller: V-
800 ; Buchi Heating Bath: B-490.
2.2. Materials
*
SiH(Pr-i)2 TCCA
Pr-i
SiCl(Pr-i)2
Pr-i
The following organosilanes were purchased from Gel-
est: Ph3SiH, Vi3SiH, t-Bu3SiH, and Ph(OEt)2SiH. The sil-
anes purchased from Aldrich Chemical Co are the
following: PhSiH3, PhMeSiH2 and (Me3SiO)3SiH. The fol-
lowing were available from Dow Corning Corporation:
(MeHSiO)4, (MeHSiO)5, (MeHSiO)7, HSiMe2OSiMe2H,
HMe2SiOSiMeHOSiMe2H, HMe2Si(OSiMeH)2OSiMe2H,
Me3Si(OSiMeH)3OSiMe3, Me3SiOSiHMeOSiMe3 and
Me3SiOSiPhHOSiMe3. The solvent CH2Cl2 was distilled
over phosphorous pentoxide. Pentane, THF and 1,2-
dimethoxyethane were distilled over lithium aluminum
hydride. 1,2-dichloroethane was distilled over calcium
hydride. The distilled solvents were stored over molecular
Si
MeO
MeO
OMe
Neither the potential of TCCA in achieving multiple
halogenation onto a single silicon atom nor its utility to
halogenate oligomeric linear and cyclic siloxanes contain-
ing Si–H have been explored. The striking aspect of this
reagent is that all the three chlorine atoms present have
comparable reactivity and are equally and completely
available for reaction. This unique feature is due to the
achievement of the lower energy state resulting from aro-
matization following the substitution of all 3 chlorine
atoms by hydrogen atoms.
˚
sieve, 4 A (4–8 mesh).
O
OH
O
Cl
O
Cl
H
H
2.3. General note on the experimental
- 3 Cl
N
N
N
N
N
N
+ 3H from Si-H
N
O
HO
N
OH
O
N
H
O
The reactions were conducted in oven dried glassware
under a dry nitrogen atmosphere. To realize high yields,
care must be exercised to prevent moisture getting into
the system throughout the entire procedure until isolation.
Although the reactions require stoichiometric amounts of
the reagents, a slight excess (10 mole%) of TCCA is
preferred.
Cl
The objective of the paper is to explore the utility and
scope of TCCA in the transformation of silicon hydrides to
the corresponding chlorosilanes, since the latter are needed
to synthesize various functional siloxanes and especially
radioactive 14C-siloxanes involving Grignard reagents.

1894
S. Varaprath, D.H. Stutts / Journal of Organometallic Chemistry 692 (2007) 1892–1897
2.4. The order of addition
2.8. Workup method A
When using CH2Cl2 as the solvent, the silanes were
added to a slurry of TCCA in CH2Cl2. A similar procedure
was used for reactions in 1,2-dimethoxyethane and 1,2-
dichloroethane. However, when THF was used, the
reagents were added in reverse. TCCA was added by means
of a solid addition funnel to the silane dissolved in THF
cooled to À20 °C. The change in the order of addition
for reactions in THF was necessary to minimize chlorina-
tion of THF by TCCA.
To isolate products of very high to moderate volatility,
the condenser on the reaction flask was replaced with a
short-path distillation unit with a vigreux column. The recei-
ver flask (100 mL, 14/20 round-bottom flask) was attached
to a vacuum manifold. The receiver flask was cooled to
À78 °C in a dry ice/acetone bath under nitrogen. The nitro-
gen line was closed and the vaccum was applied carefully and
gently to collect volatiles (solvent and the product). Heating
was then applied to the distillation flask either via a heat gun
or an oil bath until the residue in the flask (excess TCCA and
the byproduct) turned to a dry solid which indicated a com-
plete removal of the product. The solvent in the receiver flask
was removed using a rotary evaporator or by simple distilla-
tion at atmospheric pressure to obtain the product.
2.5. Procedure for reactions in CH2Cl2
The solvent was placed in a 50 mL, 14/20 two-necked
round-bottom flask equipped with a magnetic stir-bar, a
rubber-septum and a condenser. The condenser in turn
was attached in series to a gas-inlet and gas bubbler.
TCCA was then added and the slurry of TCCA in
CH2Cl2 was stirred at ambient temperature. Under a
blanket of nitrogen, the organosilane (either as neat or
as a solution in the reaction medium) was added drop-
wise by means of a gas-tight syringe at a rate to main-
tain a steady reflux of the solvent. After the addition
was over, the flask was heated, if necessary, in an oil
bath maintained at 40 °C until the GC–MS analysis of
a 5–10 lL aliquot of the reaction mixture indicated com-
plete conversion to the product.
2.9. Workup method B
For products of low volatility (high boiling point), the
solvent was removed under vacuum at ambient tempera-
ture following the method A. The residue in the reaction
flask was treated with dry pentane and the contents were
transferred into a centrifuge tube under nitrogen atmo-
sphere. The contents were centrifuged and the clear organ-
ics decanted into another 14/20 one-necked flask. Pentane
extraction of the residue must be repeated twice for com-
plete removal of the products. The combined extracts were
subjected to rotary evaporation to remove the solvent.
2.6. Procedure for reactions in THF
2.10. Workup method C
For reactions in THF, the organosilane and THF were
placed in the reaction flask. The flask was cooled to
À20 °C in an acetone bath, the temperature of which was
maintained by the addition of controlled amounts of dry
ice. TCCA was then added in installments via a solid addi-
tion funnel. After the addition was over, the cold bath was
removed and the reaction mixture was allowed to warm to
ambient temperature. The stirring was continued until GC–
MS analysis indicated a complete conversion of the orga-
nosilane to the desired product.
The contents of the flask can be transferred directly into
a filtration apparatus containing a bed of CeliteÒ. The fil-
tration apparatus is a coarse sintered funnel fitted with
14/20 joints to facilitate direct transfer of the contents from
the reaction flask and allow filtration under vacuum into a
14/20 receiver flask. The filtrate collected is removed of the
solvent using a rotary evaporator. This method is suitable
for isolation of volatile as well as non-volatile products.
2.11. Workup method D (a special case for (MeSiClO)4)
2.7. Monitoring the progress of the reaction
The solvent was removed under vacuum following the
procedure in method A. The distillation unit was replaced
with a sublimation apparatus which was connected to a vac-
uum manifold. Vacuum was applied and the flask heated
with a heat gun to sublime the product on to the cold sur-
face maintained at À10 °C by a circulating bath. The subli-
mation unit was placed in a nitrogen glove bag and product
was scrapped off the cold surface using a spatula.
The reaction mixture (5–10 lL aliquot) was withdrawn
by means of a gas-tight syringe and diluted with dry pen-
tane (1–2 mL) in a 7 mL vial with a screw cap. The vial
was centrifuged for a minute and the clear solution ana-
lyzed by GC–MS. If the mixture remained turbid, Cel-
iteÒ or anhydrous MgSO4 can be added and the
contents centrifuged again. Once it was determined that
the reaction is complete, the entire reaction mixture
can be worked up by one of the three methods described
below depending upon the volatility of the product and
the difference between the boiling point of the product
and the solvent.
3. Results and discussion
Typically, to convert Si–H functional silanes and silox-
anes to the corresponding Si–Cl analogs, chlorine gas, or

S. Varaprath, D.H. Stutts / Journal of Organometallic Chemistry 692 (2007) 1892–1897
1895
allylchloride in presence of palladium on charcoal is used.
3.1. Reaction medium
The method using chlorine gas has been described in detail
previously [1]. In compounds containing multiple hydrogen
atoms, for example (MeHSiO)4, three of the four hydrogen
atoms were readily replaced with chlorine atom, whereas
substitution of the fourth hydrogen atom was very slug-
gish. The same was true of the chlorination of (MeHSiO)5
with chlorine. The experimental set up using chlorine gas is
somewhat involved: (a) dilution of Cl2 with nitrogen or
argon was necessary to moderate the exothermic reaction,
(b) the by-product HCl had to be effectively removed from
the solution and trapped, and (c) temperature control was
necessary to avoid side chain halogenation.
Chlorination using allyl chloride in presence of palla-
dium on charcoal can mitigate some of the inconveniences
mentioned above. However, allyl chloride, a lachrymator is
required in a large excess, and its removal from the prod-
ucts can be cumbersome. It was also observed that contam-
ination from palladium and charcoal is a frequent
occurrence necessitating additional purification.
In view of the issues cited above, chloroimides were con-
sidered for use as chlorination agents. It is known that the
byproducts (imides) are quite insoluble in nonpolar sol-
vents. Hence following chlorination with such reagents,
the byproducts can simply be filtered off to obtain the
product in the reaction medium. The workup to isolate
the product is very much simplified. In this regard use of
N-chlorosuccinimide (NCS) and TCCA were investigated
as chlorinating agent. It became apparent from preliminary
experiments that TCCA chlorinated Si–H compounds
quite rapidly and NCS was relatively sluggish. Conse-
quently the focus was shifted to utilizing TCCA for chlori-
nation and establishing the experimental procedure.
The various silanes converted to the corresponding chlo-
rosilanes are given in Table 1. Though the reaction requires
a stoichiometric amount of TCCA, a slight excess of the
latter was used. For reactions using 5–20 mmol of the
silane, 20–30 mL of solvent was sufficient.
Time and temperature required for completion of the
chlorination reaction was strongly dependant on the med-
ium used for the reaction. In the case of simple silanes con-
taining a single hydrogen on a silicon atom, which are not
sterically demanding (Ph3SiH, Vi3SiH, (EtO)3SiH, etc.),
chlorination was found to take place in CH2Cl2 almost
instantly. The reactions were exothermic and the rate of
addition of silane to TCCA was controlled to maintain a
gentle reflux of the solvent. At the 10 mmol scale of the sil-
anes, the reaction mixtures could be worked up anywhere
from 10 min to an hour of stirring after the addition of
the reagent.
In CH2Cl2 as the reaction medium, silanes containing
more than one hydrogen atom per silicon required longer
reaction time and higher temperature for completion.
PhSiH3, for example, required 5 h of heating at reflux tem-
perature in CH2Cl2 for 95% completion. For such silanes,
THF was found to be a more suitable solvent. In THF,
PhSiH3underwent complete chlorination in 10 min at
ambient temperature. Similarly, cyclic siloxanes in CH2Cl2
also required longer reaction time and heating at reflux
temperature for completion. However, in THF the chlori-
nation proceeded much more rapidly. A 30 min heating
at reflux in THF resulted in complete conversion of (MeH-
SiO)7 to the perchlorinated product, whereas in CH2Cl2, a
5 h heating at reflux was needed.
For a relatively crowded internal Si–H materials, such as
Me3SiO(SiMeHO)3SiMe3, only 68% of the theoretical tri-
chloro substituted product was formed in CH2Cl2 after
one hour at ambient temperature. It required an hour of
reflux and overnight stirring at ambient temperature for
complete conversion. In contrast, 92% of the trichloro
substituted product was formed in 10 min at ambient tem-
perature when the chlorination was conducted in THF.
Heating at 40 °C for 20 min led to complete conversion.
The three hydrogen atoms in the sterically less demanding
HMe2SiOSiMeHOSiMe2H were substituted with chlorine
atoms within an hour of stirring at ambient temperature
It must be noted that reactions in THF must be started
at or below À20 °C, and then allowed to warm to room
temperature. This is to control the very exothermic reac-
tion, and to prevent chlorination, to a small extent, of
THF. At ambient temperature, in the absence of any silane,
TCCA reacted with THF exothermically to form mono
and disubstituted products shown in the equation below:
Table 1
The list of silanes that were converted to the corresponding chlorosilanes
Starting silane
The chlorosilane product
Isolated
yield %
PhSiH3
PhMeSiH2
Ph3SiH
Vi3SiH
PhSiCl3
PhMeSiCl2
Ph3SiCl
97.5
95.5
97.5
98.7
99.7
86.5
95.0
96.5
98.0
98.6
Vi3SiCl
(EtO)3SiH
(EtO)3SiCl
(MeClSiO)4
(MeClSiO)5
(MeClSiO)7
Ph(OEt)2SiCl
ClMe2SiOSiMe2Cl
O
(MeHSiO)4
(MeHSiO)5
(MeHSiO)7
Ph(OEt)2SiH
HMe2SiOSiMe2H
HMe2SiOSiMeHOSiMe2H
Cl
Cl
N
N
+
+
Cl
Cl
O
Cl
O
O
O
N
O
ClMe2Si(OSiMeCl)OSiMe2Cl 94.6
Cl
HMe2Si(OSiMeH)2OSiMe2H ClMe2Si(OSiMeCl)2OSiMe2Cl 92.3
However, no such products were observed when the
ingredients were mixed at 0 °C. Therefore, it is critical that
the reactions in THF are conducted at well below 0 °C
before warming to ambient temperature.
(Me3SiO)3SiH
(Me3SiO)3SiCl
97.0
99.0
95.7
93.6
Me3SiOSiHPhOSiMe3
Me3SiO(SiMeHO)3SiMe3
O[SiH(OSiMe3)2]2
Me3SiOSiClPhOSiMe3
Me3SiO(SiMeClO)3SiMe3
O[SiCl(OSiMe3)2]2

1896
S. Varaprath, D.H. Stutts / Journal of Organometallic Chemistry 692 (2007) 1892–1897
Among the organosilanes investigated, H(OSiMe3)2-
If the product was distillable under low pressure, the sol-
vent and the product were collected in a dry flask cooled to
À78 °C. During the flash distillation, the distillation flask
can be heated rapidly either using an oil bath or by gently
waving a heat gun. It is critical, for quantitative recovery of
product, that the residue (cyanuric acid and the excess
TCCA) in the distillation flask turns very dry to indicate
complete transfer of the product. Cyanuric acid and TCCA
did not distill over under these conditions. The solvent
from the distillate was then removed using a rotary evapo-
rator to obtain the product. Product purity was 95% or
greater in almost all cases, and further purification was
not necessary.
SiOSi(OSiMe3)2H was found to be most sterically
demanding. In both CH2Cl2 and THF, <10% of the com-
pletely chlorinated product was formed after an hour of
heating at the respective reflux temperatures. Prolonged
heating failed to improve the conversion. Hence, two other
solvents – ClCH2CH2Cl in place of CH2Cl2 and MeOCH2-
CH2OMe (DME) in place of THF were attempted. DME
was found to be unsuitable due to incomplete conversion.
However, in ClCH2CH2Cl, a complete conversion to the
desired product was noted after heating for an hour at
80 °C.
3.2. Product isolation
For products such as (MeClSiO)7 that are not readily
distillable, and where filtration was required, it was pre-
ferred to distill off the solvent (CH2Cl2 or THF) first.
The residue was then triturated with dry pentane. Cyanuric
acid and the excess TCCA are practically insoluble in pen-
tane. Both pentane and the insoluble residue were trans-
ferred under nitrogen into a centrifuge tube. Following
centrifugation, the clear pentane extract was collected
and the pentane removed using a rotary evaporator to
obtain the product.
If a stoichiometric amount of TCCA was used for the
chlorination, all that was required, following the comple-
tion of chlorination, was to filter off the insoluble by-prod-
uct (see Method C), cyanuric acid (1,3,5-triazine-2,4,6-
triol). CeliteÒ as a filter aid may be necessary in instances
where the byproduct was very fine and passed through
the filter disk. If an excess of TCCA was used, the isolation
procedures were modified slightly to enable removal of the
trace level of the sparingly soluble TCCA present in the
reaction medium along with the desired product (see Meth-
ods A and B).
The isolation method for (MeClSiO)4 is a special case
since it sublimes readily. In this case, a sublimation unit
was placed on the reaction flask. THF was removed under
Table 2
Experimental condition on the synthesis of chlorosilanes
Starting silane
PhSiH3
Amount silane (g)
2.07
Amount TCCA (g)
4.91
Reaction medium
CH2Cl2
Workup method
A
Conditions for solvent removal
P = 150 mbar
T = 35 °C
PhMeSiH2
2.4
3.41
0.85
0.85
1.7
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
THF
B
P = 200 mbar
T = 23 °C
P = 150 mbar
T = 35 °C
P = 150 mbar
T = 4 °C
P = 200 mbar
T = 5 °C
P = 150 mbar
T = 35 °C
P = 150 mbar
T = 35 °C
P = 200 mbar
T = 35 °C
P = 200 mbar
T = 23 °C
P = 400 mbar
T = 23 °C
P = 200 mbar
T = 10 °C
P = 200 mbar
T = 23 °C
P = 400 mbar
T = 23 °C
Ph3SiH
2.6
B
Vi3SiH
1.1
A
A
D
A
B
(EtO)3SiH
3.28
2.4
(MeHSiO)4
3.4
(MeHSiO)5
3
4.3
THF
(MeHSiO)7
2.1
2.98
2.57
1.86
2.64
3.41
1.74
2.6
THF
Ph(OEt)2SiH
1.96
1.61
1.94
2.54
2.22
2.84
3.42
2.15
CH2Cl2
CH2Cl2
CH2Cl2
THF
A
A
A
A
A
A
A
A
HMe2SiOSiMe2H
HMe2SiOSiMeHOSiMe2H
HMe2Si(OSiMeH)2OSiMe2H
(Me3SiO)3SiH
CH2Cl2
CH2Cl2
THF
Me3SiOSiHPhOSiMe3
Me3SiO(SiMeHO)3SiMe3
O[SiH(OSiMe3)2]2
P = 200 mbar
T = 23 °C
2.6
P = 75 mbar
T = 35 °C
0.85
ClCH2CH2Cl
P = 50 mbar
T = 37 °C

S. Varaprath, D.H. Stutts / Journal of Organometallic Chemistry 692 (2007) 1892–1897
1897
Table 3
Mass spectral characteristics of chlorosilanes
Chlorosilane synthesized
GC–MS retention time (min)
Prominent mass spectral characteristics; m/z
PhSiCl3
PhMeSiCl2
6.17
6.19
210 (M, the parent ion),175 (MÀCl),133,112, 77
190 (M), 175, 77
Ph3SiCl
Vi3SiCl
15.07
2.44
294 (M), 217 (MÀPh), 154
129, 116, 91, 63, 53
(EtO)3SiCl
(MeClSiO)4
(MeClSiO)5
(MeClSiO)7
3.74
197 and 199 (M), 183, 169, 155, 139, 125, 97
361 (MÀCH3), 311, 233, 174
6.76–7.07 (isomers)
8.38–8.63 (isomers)
Centered at 11.13
455 & 457 (MÀCH3), 329, 397, 291, 255, 233, 93
647 (MÀCH3), 517, 389, 367, 343, 307, 247, 207, 187, 113, 93
230 (M), 185 (MÀOEt), 157, 137, 121, 105, 77, 63
187 (MÀCH3), 167 (MÀCl), 151, 137, 113, 93, 63, 45
283 (MÀCH3), 261, 229, 187, 153, 93
Ph(OEt)2SiCl
7.78
2.74
5.57
7.69
6.62
8.32
8.46
8.81
ClMe2SiOSiMe2Cl
ClMe2Si(OSiMeCl)OSiMe2Cl
ClMe2Si(OSiMeCl)2OSiMe2Cl
(Me3SiO)3SiCl
Me3SiOSiClPhOSiMe3
Me3SiO(SiMeClO)3SiMe3
O[SiCl(OSiMe3)2]2
375 (MÀCH3), 247, 93
315 (MÀCH3), 207, 191, 73
303 (MÀCH3), 267, 251, 193, 135, 126, 91, 73
429& 431 (MÀCH3), 321, 301, 269, 249, 167, 93 and 73
483 (MÀCH3), 375, 287, 267, 147 73
[4] K.P. Plotzke, S.D. Crofoot, E.S. Ferdinandi, J.G. Beattie, R.H.
Reitz, D.A. McNett, R.G. Meeks, Drug Metab. Dispos. 28 (2000)
192.
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low pressure at ambient temperature. The sublimation unit
was then cooled to À10 °C or less and the distillation flask
heated either with a heat gun or an oil bath. The product
was scrapped off the sublimation apparatus inside a nitro-
gen glove bag. The experimental details on the reactions
and mass spectra characteristics of the products are given
in Tables 2 and 3 respectively.
[8] S. Varaprath, K.L. Salyers, K.P. Plotzke, S. Nanavati, Drug Metab.
Dispos. 27 (1999) 1267.
4. Conclusion
[9] S. Varaprath, J.M. McMahon, K.P. Plotzke, Drug Metab. Dispos. 31
(2003) 206.
[10] M.B. Reddy, Micaela, M.E. Andersen, P.E. Morrow, I.D. Dobrev,
S. Varaprath, K.P. Plotzke, M.J. Utell, Toxicol. Sci. 72 (2003) 3.
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Elsevier Publishing Company, 1967;
An efficient synthetic methodology was developed for
the conversion of silicon hydrides to chlorosilanes using
inexpensive trichloroisocyanuric acid (TCCA) as the chlo-
rination agent. The conversions were essentially quantita-
tive, and in general, the isolated product yields were 90%
or greater. The workup after the reaction was quite simple,
requiring only a removal of the very insoluble byproduct.
Since the products formed are of high purity (>95%), an
additional purification step (such as distillation) was not
necessary.
(b) H. Uchida, Y. Kabe, K. Yoshino, A. Kawamata, T. Tsumuraya,
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requiring a few minutes to an hour depending upon the ste-
ric demand of the starting silane. For compounds that
reacted sluggishly in CH2Cl2 as the solvent medium, use
of THF drastically reduced the reaction time. For sterically
demanding silanes, chlorination was accomplished using
ClCH2CH2Cl as the solvent.
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