(Iodomethyl)fluorosilanes: Synthesis and Reactions

Article abstract of DOI:10.1134/S1070363218100092

The methods of synthesis of bifunctional (iodomethyl)fluorosilanes of general formula ICH₂SiMe_nF_3–n (n = 0, 2) have been elaborated; the structure was proved by ¹H, ¹³C, ²⁹Si NMR spectroscopy. The reaction of (iodomethyl)dimethylfluorosilane with O-trimethylsilyl derivative of N,N'-dimethylhydrazide of trifluoroacetic acid gives rise to the formation of 2,2,4,4-tetramethyl-6-(trifluoromethyl)-3,4-dihydro-2Н-1,4,5,2-oxadiasilin-4-ium iodide with tetracoordinate silicone atom.

Full text of DOI:10.1134/S1070363218100092

ISSN 1070-3632, Russian Journal of General Chemistry, 2018, Vol. 88, No. 10, pp. 2084–2088. © Pleiades Publishing, Ltd., 2018.
Original Russian Text © B.А. Gostevskii, N.F. Lazareva, 2018, published in Zhurnal Obshchei Khimii, 2018, Vol. 88, No. 10, pp. 1639–1643.
(Iodomethyl)fluorosilanes: Synthesis and Reactions
B. А. Gostevskiia and N. F. Lazarevaa*
a A.E. Favorskii Irkutsk Institute of Chemistry, Siberian Branch, Russian Academy of Sciences,
ul. Favorskogo 1, Irkutsk, 664033 Russia
е-mail: nataliya.lazareva@gmail.com
Received May 24, 2018
Abstract―The methods of synthesis of bifunctional (iodomethyl)fluorosilanes of general formula
1
ICH2SiMenF3–n (n = 0, 2) have been elaborated; the structure was proved by H, 13C, 29Si NMR spectroscopy.
The reaction of (iodomethyl)dimethylfluorosilane with O-trimethylsilyl derivative of N,N'-dimethylhydrazide
of trifluoroacetic acid gives rise to the formation of 2,2,4,4-tetramethyl-6-(trifluoromethyl)-3,4-dihydro-2Н-
1,4,5,2-oxadiasilin-4-ium iodide with tetracoordinate silicone atom.
Keywords: (iodomethyl)trifluorosilane, (iodomethyl)dimethylfluorosilane, (halogenomethyl)halogenosilanes,
α-carbofunctional silanes
DOI: 10.1134/S1070363218100092
Organosilicon
α-carbofunctional
compounds
procedure with SbF3 was not described. (Iodomethyl)-
dimethylfluorosilane was synthesized by splitting the
siloxane bond of (ICH2SiMe2)2O with potassium
bifluoride [8], its yield was not reported. The structure
of the products was proved by the methods of 1Н NMR
and IR spectroscopy.
YCH2SiRnX3–n containing geminal fragment Y–C–Si
(X = Hlg, OR, SR, NRR'; Y = Hal, RO, RR'N, RS; R,
R' = Alk, Ar) demonstrate unique reactivity due to their
structure and are widely used in synthetic organic chemistry
[1–4]. (Chloromethyl)chlorosilanes СlCH2SiRnCl3–n
(n = 0–3) are commercially available compounds and
their reactivity is the most studied among (halomethyl)
halosilanes HalCH2SiRnHal3–n (n = 0–3). Therefore, it is
not surprising that they serve as a basis for the synthesis
of α-carbofunctional silanes with different substituents
at the silicon and the α-carbon atom [1, 5]. However,
special interest attract bifunctional (halomethyl)halo-
silanes containing two different halogen atoms in the
molecule. Thus, (iodomethyl)fluorosilanes ICH2SiRnF3–n
contain the С–I bond capable of nucleophilic sub-
stitution reactions, and one of the strongest bonds in
silicon-containing compounds Si–F (ESi–F = 159.9 kcal/mol
[6]), therefore, their use in organic synthesis may lead to
the synthesis of new compounds and elaboration of
unique synthetic procedures. We failed to find informa-
tion on their reactivity. Apparently, the lack of such
information is due to difficulties of preparation and
isolation of bifunctional (iodomethyl)fluorosilanes.
(Iodomethyl)trifluorosilane ICH2SiF3 was first syn-
thesized by exchange reactions of (iodomethyl)tri-
chlorosilane with KHF2 and SbF3 in 48.7 and 87%
yield, respectively [7]. When treated with potassium
bifluoride, this silane is formed in low yield, and the
The goal of the present work was to elaborate an
effective laboratory method for the synthesis of (iodo-
methyl)fluorosilanes ICH2SiMenF3–n (n = 0, 2) and
investigation of their reactivity. The synthesis of
(iodomethyl)methyldifluorosilane and its properties will
be reported elsewhere. As starting reagents, com-
mercially
available
(chloromethyl)chlorosilanes
ClCH2SiMenCl3–n (n = 0, 2) were chosen, which were
converted to the target products 4 by a sequence of
consecutive reactions via intermediate silanes 1–3
(Scheme 1).
Silanes 1а, 1b were synthesized in good yield by
the reaction of the corresponding (chloromethyl)-
chlorosilanes ClCH2SiMenCl3–n with excess methanol
in diethyl ether in the presence of thoroughly dried
urea. The choice of urea as a hydrogen chloride
acceptor was not accidental: urea hydrochloride
formed in the reaction is a viscous mass or solid,
which allowed simple decanting of ethereal solution of
the product for further treatment. The use of
triethylamine as a hydrogen chloride acceptor is less
preferable because of two reasons. Firstly, the
2084

2085
(IODOMETHYL)FLUOROSILANES: SYNTHESIS AND REACTIONS
Scheme 1.
MeOH,
(H2N)2C=O
NaI
ClCH2SiMenCl3-n
ClCH2SiMen(OMe)3-n
ICH2SiMen(OMe)3-n
MeCN
Et2O
1а, 1b
2а, 2b
SOCl2
SbF3
ICH2SiMenF3-n
4а, 4b
ICH2SiMenCl3-n
3а, 3b
n = 0 (a), 2 (b).
formation of voluminous fine-disperse crystalline salt
Et3N·HCl requires increasing the amount of the used
solvent to perform the stage of filtration and to wash
the precipitate (Et3N·HCl). Secondly, Et3N·HCl is partly
soluble in the reaction mixture; it is sublimed to the
condenser during distillation and contaminates the
product.
formation of (O–Si) chelate or zwitter ionic silicon
compounds attract the attention of chemists during last
decades [11–17]. O-Trimethylsilyl-substituted N,N'-
dimethylhydrazides of carboxylic acids, when reacting
with (chloromethyl)dimethylchlorosilane, form zwitter
ionic heterocycles [18, 19]. In particular, from the
O-trimethylsilyl derivative of N,N'-dimethylhydrazide
of trifluoroacetic acid 5, (O–Si)-chloro-[1-(1,1-di-
methyl-2-trifluoroacetylhydrazonium)methyl]dimethyl-
silane 6 is formed (Scheme 2). The upfield chemical
shift of the silicon atom in the 29Si NMR spectra of the
compound (–42.9 ppm) is indicative of penta-
coordinate state of the silicon atom [19].
The exchange reaction of silanes 1а, 1b with NaI
was performed in thoroughly dried solvent. Unlike a
similar procedure [9], the use of excess NaI, sub-
stantial increase in the reaction time, and washing of
the precipitate during filtration allowed the preparation
of (iodomethyl)(methoxy)silanes 2а, 2b in a high
yield. (Pentafluorophenyl)ethoxysilanes under the
action of thionyl chloride in the presence of pyridine
hydrochloride readily form the corresponding
(pentafluorophenyl)chlorosilanes [10]. Under these
conditions, silanes 2а, 2b were quantitatively converted
to the corresponding (iodomethyl)chlorosilanes 3а, 3b.
To monitor the reactivity of the synthesized silanes,
we have studied the reaction of silanes 2b–4b with
compound 5. Silane 2b does not react with compound
5 even on heating in chloroform (100°С, 3 h). The
reaction of silane 3b with N,N'-dimethylhydrazide of
trifluoroacetic acid is completed at room temperature
after several minutes by the formation of 2,2,4,4-
tetramethyl-6-(trifluoromethyl)-3,4-dihydro-2Н-1,4,5,2-
oxadiazasilin-4-ium iodide 7 (Scheme 3). In contrast to
compound 6, the value of chemical shift of the silicon
atom in the 29Si NMR spectrum of compound 7 is
indicative of its tetracoordinate state (+22.02 ppm).
Earlier, (iodomethyl)trifluorosilane was synthesized
by the exchange reaction of (iodomethyl)trichloro-
silane with SbF3 by addition of SbF3 to the silane [7].
However, the reaction was highly exothermic, so, we
used the reverse order of mixing of the reagents: slow
addition of the silane to SbF3 with vigorous stirring
allowed controlling the process.
Silane 4b in the reaction with hydrazide 5 also
forms compound 7, but in this case the reaction
1
The reactions of bifunctional silanes XCH2SiMe2Y
with N- and/or О-trimethylsilylamides, hydrazides of
carboxylic acids and related compounds leading to the
proceeds much slower. Thus, after 32 h, the Н NMR
spectrum of the reaction mixture contains only traces
of trimethylfluorosilane, and the reaction is completed
after ~72 h. The structure of compound 7 was proved
by 1Н, 13С, and 29Si NMR spectroscopy.
Scheme 2.
The elaborated modified procedures for the syn-
thesis of silanes 1–4 allow the preparation of difficultly
accessible bifunctional silanes in high yields (87–94%)
after purification and can be used in laboratory
practice. At present, the investigation of reactivity of
silanes having two different halogen atoms in
Me
Me
O
Cl
SiMe3
C NNMe2
5
Si
O
+ ClMe2SiCH2Cl
NMe2
F3C
N
F3C
6
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GOSTEVSKII, LAZAREVA
Scheme 3.
Me Me
SiMe3
Si
CHCl3, 20oC, 5 min
O
I−
NMe2
O
+
C NNMe2 XMe2SiCH2I
_ Me3SiX
F3C
F3C
N
7
X = Cl, F.
resilylation and alkylation of amides and hydrazides is
in progress. We expect that variation of the number of
fluorine atoms at silicon atom and the nature of
halogens at carbon atom in silanes HalCH2SiMenF3–n
will allow controlling the selectivity of the processes.
silane 1b was isolated, bp 118°С (720 mmHg), nD20
1.4172. 1Н NMR spectrum, δ, ppm: 0.24 s (6Н,
SiMe2), 2.81 s (2H, CH2Cl), 3.50 s (3H, OMe). 13C
NMR spectrum, δ, ppm: –3.95 (SiMe), 29.20 (CH2Cl),
50.95 (OMe). 29Si NMR spectrum, δ, ppm: 13.45.
Found, %: C 34.92; H 7.58. C4H11ClOSi. Calculated,
%: C 34.65; H 7.99.
EXPERIMENTAL
(Iodomethyl)trimethoxysilane (2a). A mixture of
20.00 g (0.117 mol) of silane 1a, 26.40 g (0.176 mol)
of NaI, and 50 mL of anhydrous acetonitrile was
refluxed with stirring for 15 h. The precipitate was
filtered off, washed with anhydrous Et2O (2×20 mL),
the ethereal solution was combined with the filtrate.
The solvents were removed in a vacuum (20 mmHg),
the residue was distilled in a vacuum to obtain 28.90 g
(0.11 mol, 94%) of compound 2а as pink liquid
(decolorized after addition of 0.1 g of copper powder),
1Н, 13С, and 29Si NMR spectra were registered on
Bruker DPX-400 and Bruker AV-400 spectrometers
(400.13, 100.61, and 161.90 MHz respectively) in
CDCl3 and CD3CN solutions with TMS as an internal
reference.
(Chloromethyl)trichlorosilane and (chloromethyl)di-
methylchlorosilane were distilled before use. The
solvents were dried by known procedures [20]. All
reactions were carried out in dry argon atmosphere.
bp 76–78°С (10 mmHg), nD20 1.4691. Н NMR spec-
1
(Chloromethyl)trimethoxysilane (1a). To
a
trum, δ, ppm: 1.97 s (2Н, СН2), 3.64 s (9Н, 3MeО).
13С NMR spectrum, δ, ppm: –26.83 (СН2), 51.54
(MeО). 29Si NMR spectrum, δ: –53.20 ppm. Found,
%: C 18.59; H 4.78. C4H11IO3Si. Calculated, %: C
18.33; H 4.23.
mixture of 86.00 g (1.43 mol) of dry urea, 45.88 g
(1.43 mol) of anhydrous methanol, and 100 mL of
anhydrous diethyl ether 70.23 g (0.38 mol) of
chloromethyltrichloro-silane was added dropwise at
stirring in the course of 2 h, and the mixture was
refluxed for 2 h. After cooling the ethereal solution
was decanted, ether was removed in a vacuum at
40 mmHg, and silane 2 was isolated by vacuum
distillation. Yield 56.76 g (0.333 mol, 87%), colorless
(Iodomethyl)dimethylmethoxysilane (2b). A mix-
ture of 40.0 g (0.288 mol) of silane 1b, 67.50 g
(0.438 mol) of NaI in 50 mL of anhydrous ethyl
acetate was refluxed at stirring for 93 h. The reaction
mixture was filtered, the precipitate was washed with
anhydrous ether (40 mL), combined filtrates were
evaporated at a reduced pressure, the residue was
distilled with 3 g of copper powder to obtain 55.60 g
(0.242 mol, 83.8%) of silane 2b as colorless liquid, bp
liquid, bp 65°С (30 mmHg), nD20 1.4074. Н NMR
1
spectrum, δ, ppm: 2.83 s (2Н, СН2), 3.65 s (9Н, MeО).
Found, %: C 27.86; H 6.34. C4H11ClO3Si. Cal-
culated, %: C 28.15; H 6.50.
(Chloromethyl)dimethylmethoxysilane (1b). To a
mixture of 18.42 g (0.58 mol) of anhydrous МеОН,
37.70 g (0.58 mol) of urea, and 100 mL of anhydrous
diethyl ether 71.54 g (0.5 mol) of (chloromethyl)-
dimethylchlorosilane was added dropwise in the course
of 2 h and the mixture was refluxed for 2 h. Crystal-
lization of urea hydrochloride was initiated by cooling
the reaction flask bottom by liquid nitrogen. After
decanting of ethereal solution and its distillation at
atmospheric pressure 64.70 g (0.467 mol, 93%) of
74°С (40 mmHg), nD20 1.4870. Н NMR spectrum, δ,
1
ppm: 0.29 s (6Н, SiMe2), 2.04 s (2H, CH2I), 3.49 s
(3H, MeO). 13C NMR spectrum, δ, ppm: –15.60
(CH2I), –3.09 (SiMe), 50.82 (MeO). 29Si NMR spec-
trum, δ, ppm: 14.41. Found, %: C 21.17; H 4.47.
C4H11IOSi. Calculated, %: C 20.88; H 4.82.
(Iodomethyl)trichlorosilane (3a). To a mixture of
18.30 g (0.07 mol) of silane 2a and 1.04 g (9.0 mmol)
of pyridine hydrochloride 50.60 g (0.425 mol) of
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(IODOMETHYL)FLUOROSILANES: SYNTHESIS AND REACTIONS
thionyl chloride was slowly added dropwise at
vigorous stirring in the course of 2 h. Slow addition is
required because of evolution of two gaseous products
(SO2 and HCl). The reaction mixture was stirred for
2 h until the evolution of gaseous products ceased, then
it was refluxed for another 4 h. Such a long reflux is
needed because after a shorter period (2 h) the reaction
95.7 %), colorless liquid, bp 69°С (100 mmHg), nD20
1
1.4720. Н NMR spectrum, δ, ppm: 0.42 d (6Н,
3
3
SiMe2, JHF = 7.2 Hz), 2.09 d (2Н, СН2I, JHF
=
3.0 Hz). 13C NMR spectrum, δ, ppm: –16.97 d
(СН2I, 2JCF = 17.4 Hz), –2.23 d (MeSi, 2JCF = 14.8 Hz).
29Si NMR spectrum, δ, ppm: 26.53 d (JSiF = 281.6 Hz).
Found, %: C 16.19; H 3.24. C3H8FISi. Calculated,
%: C 16.52; H 3.69.
1
mixture, according to Н NMR, contains ~20% of
1
ICH2Si(OMe)Cl2. Н NMR spectrum, δ, ppm: 2.41 s
2,2,4,4-Tetramethyl-6-(trifluoromethyl)-3,4-di-
hydro-2Н-1,4,5,2-oxadiazasilin-4-ium iodide (7).
A mixture of silane 3b 1.36 g (5.96 mmol), 10 mL of
anhydrous chloroform, and 1.27 g (5.41 mmol) of com-
pound 5 was stirred for 30 min at 20°С. Volatile
compounds were removed at a reduced pressure,
solid residue was washed with anhydrous diethyl
(2Н, СН2), 3.73 s (3H, MeO). 13С NMR spectrum, δ,
ppm: –20.25 (СН2), 52.59 (MeO). Excess of thionyl
chloride and volatile products were removed at
20 mmHg, the residue was distilled in a vacuum to
obtain 17.10 g (0.062 mol, 89%) of silane 3a.
Colorless liquid, bp 64–67°С (20 mmHg), nD201.5322.
1Н NMR spectrum, δ, ppm: 2.67 s (2Н, СН2). 13С
ether (2×30 mL) and dried in
a
vacuum
29
NMR spectrum, δ, ppm: –16.21. Si NMR spectrum,
(0.1 mmHg). Yield 1.64 g (4.63 mmol, 85.6%),
colorless crystals, mp (evacuated capillar) 128.5°С.
1Н NMR spectrum (CD3CN), δ, ppm: 0.76 s (6Н,
SiMe2), 3.64 s (6H, NMe2), 4.07 s (2H, CH2). 13C
NMR spectrum (CD3CN), δ, ppm: –0.84 (MeSi),
δ, ppm: 1.81.
(Iodomethyl)dimethylchlorosilane (3b). To a mix-
ture of 26.02 g (0.219 mmol) of thionyl chloride and
1.66 g (0.014 mol) of Py·HCl 27.60 g (0.120 mol) of
silane 2b was added dropwise at stirring for 2 h. The
reaction mixture was refluxed for 3 h. Volatile
products and excess of thionyl chloride were removed
at 40 mmHg, the precipitate of Py·HCl was filtered off,
the residue was distilled over ~3 g of copper powder.
Yield 20.13 g (0.086 mol, 71.6 %), colorless liquid, bp
54.56 (H2CSi), 59.86 (MeN), 116.31 q (CF3, JCF
=
2
278.4 Hz), 152.80 q (OC=N, JCF = 39.4 Hz). 29Si
NMR spectrum (CD3CN), δ, ppm: 22.02. Found, %:
C 23.80; H 3.76; N 7.82; Si 8.01; F 15.96; I 36.02.
C7H14N2OSiF3I. Calculated, %: C 23.74; H 3.98; N
7.91; Si7.93; F 16.09; I 35.83.
74°С (42 mmHg), nD20 1.5073. Н NMR spectrum, δ,
1
ppm: 0.60 s (6Н, SiMe2), 2.24 s (2H, CH2I). 13C NMR
spectrum, δ, ppm: –14.20 (CH2I), 0.96 (SiMe). 29Si
NMR spectrum, δ, ppm: 24.68. Found, %: C 14.91; H
2.98. C3H8ClISi. Calculated, %: C 15.36; H 3.44.
ACKNOWLEDGMENTS
The results were obtained by using analytical
equipment of the Baikal Center for Joint Use, Siberian
Branch of Russian Academy of Sciences.
(Iodomethyl)trifluorosilane (4a). To 10.00 g
(0.056 mol) of SbF3 15.00 g (0.055 mol) of silane 3a
was added dropwise at vigorous stirring in the course
of 1 h and the mixture was stirred for 1 h. After
recondensation to an evacuated Schlenk flask at
0.1 mmHg, 11.36 g (0.050 mol, 92%) of silane 4a was
CONFLICT OF INTERESTS
No conflict of interests was declared by the authors.
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isolated as a slightly pink liquid, nD20 1.4112. Н NMR
1
spectrum, δ, ppm: 2.15 q (2Н, СН2, 3JHF = 2.8 Hz). 13С
NMR spectrum, δ, ppm: –37.12 q (СН2, 2JCF = 23.6 Hz).
29Si NMR spectrum, δ, ppm: –68.41 q (3JSiF = 262.4 Hz).
Found, %: C 4.96; H 0.81. CH2F3ISi. Calculated,
%: C 5.31; H 0.89.
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