1-[N-phenyl(aminomethyl)]silatrane: Synthesis, reactivity and structure

Article abstract of DOI:10.1016/j.jorganchem.2019.120870

1-[N-Phenyl(aminomethyl)]silatrane PhNHCH₂Si(OCH₂CH₂)₃N was prepared and characterized by multinuclear NMR spectroscopy and single-crystal X-ray diffraction analysis. Its reactivity with CCl₄, AgNO

Full text of DOI:10.1016/j.jorganchem.2019.120870

Accepted Manuscript
1-[N-phenyl(aminomethyl)]silatrane: Synthesis, reactivity and structure
N.F. Lazareva, I.V. Sterkhova
PII:
S0022-328X(19)30304-3
https://doi.org/10.1016/j.jorganchem.2019.120870
DOI:
Article Number: 120870
Reference:
JOM 120870
To appear in: Journal of Organometallic Chemistry
Received Date: 6 May 2019
Revised Date: 16 July 2019
Accepted Date: 18 July 2019
Please cite this article as: N.F. Lazareva, I.V. Sterkhova, 1-[N-phenyl(aminomethyl)]silatrane: Synthesis,
reactivity and structure, Journal of Organometallic Chemistry (2019), doi: https://doi.org/10.1016/
j.jorganchem.2019.120870.
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ACCEPTED MANUSCRIPT
1
-[N-PHENYL(AMINOMETHYL)]SILATRANE: SYNTHESIS, REACTIVITY AND
STRUCTURE
N. F. Lazareva* and I. V. Sterkhova
A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Division of the Russian Academy of
Science,1 Favorsky Street, 664033, Irkutsk, Russian Federation, nataly_lazareva@irioch.irk.ru
Abstract
1
-[N-Phenyl(aminomethyl)]silatrane PhNHCH Si(OCH CH ) N was prepared and characterized
2 2 2 3
by multinuclear NMR spectroscopy and single-crystal X-ray diffraction analysis. Its reactivity
with CCl , AgNO , CuCl and α-,β-unsaturated cyclic ketones was investigated.
4
3
2
Keywords: silatrane, 1-[N-phenyl(aminomethyl)]silatrane, NMR spectroscopy, X-Ray
1
. Introduction
Silatranes XSi(OCH CH ) N belong to the important class of the pentacoordinate organosilicon
2
2 3
compounds with the intramolecular N→Si. Since their discovery in 1961 [1], silatranes with
hydrogen, organyl, organoxy, thioorganyl, acyloxy, halogen, pseudohalogen and other groups as
axial substituent X have attracted great interest due to their unique physicochemical properties
and biological activity [2-4 and references cited therein]. Over the last decade there has been a
renaissance in the discovery and development of synthetic [5-12], structural [13-15] and material
chemistry [16] of silatranes. In particular, the new derivatives of 1-(3-aminopropyl)silatrane
H N(CH ) Si(OCH CH ) N with the useful properties and biological activity were obtained [see,
2
2 3
2
2 3
for example 5, 10-12]. The 1-(aminomethyl)silatranes RR’NCH Si(OCH CH ) N are the typical
2
2
2 3
representatives of the α-silylamines RR’NCH SiX possessing unusual properties. These
2
3
compounds have been widely applied as synthons in synthetic organic chemistry and possess the
various and interesting biological properties [17-19 and ref. therein]. The introduction of a silyl
group in the α-position to the heteroatom with the lone pair (N, O or S) decreases of the
oxidation potential of this atom. This effect can be explained by an overlap between the C-Si σ-
orbital and the nonbonding 2p-orbital of heteroatom in the neutral molecule [19]. The depression
of the ionization potential is favourable to the electron transfer driven reactions of α-
aminosilanes under UV irradiation or visible light. In recent years, significant efforts have been
made toward the study of such reactions [see, for example, 20-23]. It is common knowledge that
1

ACCEPTED MANUSCRIPT
the oxidation potential of amine is governed by its structure, the inductive and steric effects of
the substituents[24, 25]. The considerable donor inductive effect of the CH Si(OCH CH ) N
2
2
2 3
group (σ* = –2.24 [26,27] provides the abnormally high basicity of the exocyclic nitrogen atom
28]. The 1-[N,N-dialkyl(aminomethyl)]silatranes RR’NCH Si(OCH CH ) N exhibit enhanced
[
2
2
2 3
reactivity with respect to the polychloromethanes CH Cl4-n (n = 0-2) [29-31]. 1-
n
(
aminomethyl)silatranes rapidly react with CCl under the irradiation of daylight with the
4
formation of the corresponding 1-(aminomethyl)silatranes hydrochloride in high yields. Carbon-
centered radicals of a-silatranylamines are the key intermediates of this reaction and they were
detected by ESR spectroscopy. 1-(Aminomethyl)silatranes react with alcohols and phenols in
inert solvents at room temperature with cleavage of the Si–C bond [32] and reduce salts of some
metals [33]. The data about the synthesis, reactivity and structure of silatranes
RNHCH Si(OCH CH ) N (R = Alk, Ar) with secondary amino group are extremely scarce.
2
2
2 3
Recently the structure and properties of 1-[N-(methyl)aminomethyl]silatrane were explored by
us [34]. The continuation of our work is associated primarily with the investigation of N-
(
silylmethyl)arylamines ArRNCH SiX because the aromatic amines are intriguing compounds
2 3
for theoretical study as well as considerable practical importance. The information about 1-[N-
phenyl(aminomethyl)]silatrane PhNHCH Si(OCH CH ) N is extremely scarce. Procedure of its
2
2
2 3
synthesis is given in patent [35], but there is no any description of its purification and spectral
data. The aim of this work is the investigation of the structure and some properties of 1-[N-
phenyl(aminomethyl)]silatrane PhNHCH Si(OCH CH ) N.
2
2
2 3
2
. Experimental section
2
.1. General
1
13
29
The H, C and Si NMR spectra of 10-20% solutions of compounds in CDCl or CD CN were
3
3
registered on a Bruker DPX 400 spectrometer (400.1, 100.6 and 79.5 MHz respectively) with HMDS
or cyclohexane as internal standard. All reactions were performed in the flame dried glassware
under an atmosphere of dry argon. The used solvents were purified according to standard
procedures [36]. As a further precaution, diethyl ether was dried by filtration through column
packed with neutral alumina under a positive pressure of argon. The solvents were stored under
argon over molecular sieves 4A. Triethanolamine was purified by low-pressure distillation and
stored over molecular sieves 4A. Starting silane ClCH Si(OMe) was obtained according to ref.
2
3
[
37].
2

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2
.2. N-[(trimethoxysilyl)methyl]aniline (1).
A mixture of 8.53 g (50 mmol) (chloromethyl)trimethoxysilane and the excess of aniline 18.6 g
(~200 mmol) was sealed in glass ampoule. During the 20-hour ampoule was heated at
o
temperature 85 C. The ampoule was cooled to room temperature and opened and freshly
.
distilled Et O (150 mL) was added to the residue. The precipitate of PhNH HCl was filtered off,
2
2
washed by ether (35 mL x 2) and the solvent removed from the filtrate by distillation on rotary
evaporator. Compound 1 as yellowish liquid was isolated by vacuum distillation of the resulting
2
5
1
residue (yield 10.92 g, 96 %). Bp 96-99 °C/3 mm Hg, nD = 1.5054. H NMR (CD CN, δ ppm):
3
1
3
2
.54 (s, 2 H, SiCH N), 3.62 (s 9 H, OMe), 4.11 (broad s, 1 H, NH), 6.65-7.11 (m, 5H, Ph). C
2
2
9
NMR (CD CN, δ ppm): 28.20 (SiCH N), 51.78 (OMe), 113.88, 118.75, 130.46, 151.96 (Ph). Si
3
2
NMR (CD CN, δ ppm): - 47.49. Anal. Calcd. for C H NO Si: C, 52.83; H, 7.54; N, 6.16, Si,
3
10 17
3
1
2.35. Found: C, 52.69; H, 7.73; N, 6.11; Si, 12.79.
2
.3. 1-[N-Phenyl(aminomethyl)]silatrane (2).
Triethanolamine 1.49 g (10 mmol) was added dropwise to 2.27 (10 mmol) of N-
(phenylamino)methyl]trimethoxysilane at stirring vigorously. The methanol released in this
[
reaction was removed in vacuum immediately after homogenization of reaction mixture. The
white solid residue was dried in vacuum, yield is 2.69 g (93%). Colorless crystals suitable for
structural analysis were obtained by the recrystallization from benzene. M. p. with the
1
decomposition >199 °C (in a sealed capillary). H NMR (CD CN, δ ppm): 2.01 (s, 2 H,
3
3
3
SiCH N), 2.87 (t, 6 H, NCH , J = 5.9 Hz), 3.73 (t, 6 H, OCH , J = 5.9 Hz), 4.05 (broad s, 1 H,
2
2
2
13
NH), 6.50-7.03 (m, 5H, Ph). C NMR (CD CN, δ ppm): 35.05 (SiCH N), 51.88 (NCH ), 58.37
3
2
2
2
9
(
OCH ), 112.95, 116.41, 130.25, 153.22 (Ph). Si NMR (CD CN, δ ppm): - 77.47. Anal. Calcd.
2
3
for C H N O Si: C, 55.69; H, 7.19; N, 9.99, Si, 10.02. Found: C, 55.21; H, 7.06; N, 10.08; Si,
1
3
20
2
3
1
0.47.
2
.4. 1-[N-Phenyl(aminomethyl)]silatrane hydrochloride (3). The solution of HCl (0.0365 g, 1
mmol) in carefully dried benzene was added dropwise to benzene solution of compound 2 (0.280
о
g, 1 mmol) at 10 С. After 10 minutes the reaction mixture was evaporated to remove the
solvent. The solid residue was purified by the recrystallization in chloroform/benzene (5: 2). M.
1
p. with the decomposition >219 °C (in a sealed capillary). H NMR (CD CN, δ ppm): 2.42 (s, 2
3
3
3
H, SiCH N), 2.94 (t, 6 H, NCH , J = 5.9 Hz), 3.71 (t, 6 H, OCH , J = 5.9 Hz), 6.75 (broad s,
2
2
2
1
3
2
5
H, NH), 7.15-7.63 (m, 5H, Ph). C NMR (CD CN, δ ppm): 46.26 (SiCH N), 51.56 (NCH ),
3 2 2
2
9
7.87 (OCH ), 122.14, 123.80, 130.60, 146.55 (Ph). Si NMR (CD CN, δ ppm): - 84.75. Anal.
2
3
3

ACCEPTED MANUSCRIPT
Calcd. for C H ClN O Si: C, 49.28; H, 6.68; N, 8.84, Si, 8.86. Found: C, 49.02; H, 6.53; N,
1
3
21
2
3
8
.76; Si, 9.31.
2
.5. The reaction of silatrane 2 with CCl4.
The silatrane 2 (0.28 g, 1mmol) was dissolved in MeCN (15 ml). The solution was degassed
three times via freeze–pump–thaw cycles prior to addition of tetrachloromethane (0.16, 1mmol).
The mixture obtained after the introduction of CCl was allowed to stand for 2 days at ambient
4
temperature and natural illumination. Then solvent was evaporated in vacuum. The solid residue
was purified by the recrystallization from chloroform/benzene (5:2). The spectral data were
identical to above for compound 3.
2
.6. The reaction of silatrane 2 with AgNO3.
The silatrane 2 (0.28 g, 1mmol) was dissolved in MeCN (15 ml). The solution was degassed
three times via freeze–pump–thaw cycles before being mixed with the solution of AgNO (0.169
3
g, 1 mmol) in MeCN (15 ml). The formation of the metal silver was observed immediately after
the mixing of the solutions. The reaction mixture was kept for 1 hours at room temperature than
the liquid phase decanted. Solvent was removed from the clear solution in vacuum to give solid
rest. Its recrystallization in chloroform/benzene (2 : 1) yielded compound 4 as a colorless solid
1
3
(
0.19 g, 55%). ). H NMR (CD CN, δ ppm): 2.41 (s, 2 H, SiCH N), 2.93 (t, 6 H, NCH , J = 5.9
3 2 2
3
13
Hz), 3.70 (t, 6 H, OCH , J = 5.9 Hz), 6.15 (broad s, 2H, NH), 7.20-7.68 (m, 5H, Ph). C NMR
2
(CD CN, δ ppm): 46.18 (SiCH N), 51.54 (NCH ), 57.83 (OCH ), 122.12, 123.82, 130.61, 146.57
3 2 2 2
2
9
(
Ph). Si NMR (CD CN, δ ppm): - 85.65. Anal. Calcd. for C H N O Si: C, 45.47; H, 6.16; N,
3
1
3
21
3
6
1
2.24; Si, 8.18. Found: C, 45.22; H, 6.11; N, 12.18; Si, 8.39.
2
.7. The reaction of silatrane 2 with CuCl2.
The silatrane 2 (0.28 g, 1mmol) was dissolved in MeCN (15 ml). The solution was degassed
three times via freeze–pump–thaw cycles before being with the solution of CuCl (0.13 g, 1
2
mmol) in MeCN (15 ml). The reaction mixture was kept for 3 days at room temperature.
Concurrent with the sluggishly disappearing of the brown colouring of the anhydrous CuCl2, the
formation of a white precipitate was observed. was filtered and filtrate was evaporated in
vacuum. Recrystallization from (chloroform/benzene (5:2) was obtained 3 as a colorless solid
(0.29 g, 91%).
4

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2
.8. The reaction of silatrane 2 with α-,β-unsaturated cyclic ketones.
The silatrane 2 (0.14 g, 0.5 mmol) and equivalent amount of α-,β-unsaturated cyclic ketone were
dissolved in the corresponding solvent (20 ml) under the argon atmosphere. The solution was
degassed three times via freeze–pump–thaw cycles prior to addition of CuCl (0.065 g, 0.5
2
mmol). The mixture obtained after the introduction of CuCl was allowed to stand for set time at
2
ambient temperature and natural illumination. Then the reaction mixture was filtered and filtrate
concentrated in vacuum. The residue was purified by column chromatography on silica gel with
o
petroleum ether (B. p. between 30 and 60 C)/ethyl acetate (9:1) as eluent.
1
3
1
2
-(Anilinomethyl)cyclopentanone (7), very viscous liquids, yield 43%. H NMR (CDCl , δ ppm):
3
.60-1.70 (m), 1.91-1.98 (m), 2.13-2.26 (m), 2.28-2.37 (m), 2.40 -2.57 (m) (7H, cycle), 3.18 (d,
13
H, N-CH , J = 7.0 Hz), 4.12 (br s, 1H, NH), 6.57-6.69 (m, 3H, Ph), 7.13-7.17 (m, 2H, Ph). C
2
NMR (CDCl , δ ppm): 27.3 (CH-CH -CH ), 36.9 (CH), 38.1(CH CH C=O), 43.2 (CHCH C=O),
3
2
2
2
2
2
4
8.7 (NCH ), 112.9, 117.8, 129.4, 148.1 (Ar), 218.5 (C=O). Anal. Calcd. for C H NO: C,
2
12 15
7
6.16; H, 7.99; N, 7.40. Found: C, 76.21; H, 8.15; N, 7.52.
3
-(Anilinomethyl)cyclohexanone (8), white powder, yieds are showed in Table 2. M. p. 70-72
o
1
C. H NMR (CDCl , δ ppm): 1.40-1.51 (m), 1.74-1.76 (m), 2.03-2.18 (m), 2.27-2.58 (m) (9H,
3
cycle), 3.08-3.17 (m, 2H), 4.28 (br s, 1H), 6.61-6.73 (m, 3H, Ph), 7.13-7.27 (m, 2H, Ph). Anal.
Calcd. for C H NO: C, 76.81; H, 8.43; N, 6.89. Found: C, 76.59; H, 8.32; N, 6.82.
1
3
17
2
.9. X-Ray analysis
The molecular structures of 1-[N-phenyl(aminomethyl)]silatrane 2 was determined by single-
crystal X-ray diffraction. Suitable single crystals of 2 were obtained by crystallization of
silatrane 2 from benzene (slow cooling of a boiling saturated solution to room temperature).
Crystal data were collected on a Bruker D8 Venture diffractometer with MoKα radiation (λ =
0
.71073) using the ϕ and ω scans. The structures were solved and refined by direct methods
using the SHELX programs set [38]. Data were corrected for absorption effects using the multi-
scan method (SADABS). Non-hydrogen atoms were refined anisotropically using SHELX [38].
Crystallographic data for the structure reported in this paper have been deposited with the
Cambridge Crystallographic Data Centre as supplementary publication CCDC 1843731. These
data can be obtained free of charge from the Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif. Details of crystallographic data and experimental
conditions are presented in Table 1.
5

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Table 1. Crystal data, details of intensity measurements, and structure refinement
for compound 2
Empirical formula
Formula weight / g·mol
Crystal system
Space group
a / Å
C H N O Si
13 20 2 3
280.40
-1
orthorhombic
P 2 2 2
1
1 1
11.1828(3)
b / Å
13.0842(3)
c / Å
18.4813(5)
α, β, γ / ˚
Volume / Å
90
2704.2(1)
3
Z
8
-3
Density (calculated) / g·cm
Absorptions coefficient / mm
Radiation (λ / Å)
1.380
0.180
MoKα (0.71073)
-1
Temperature / K
100(2)
2
Θ range / °
4.79 – 60.18
Crystal size / mm
Crystal habit
0.170 × 0.260 × 0.310
colorless prism
F(000)
1204
Index ranges
-15 ≤ h ≤ 14, -18 ≤ k ≤ 18, -22 ≤ l ≤ 26
Reflections collected
Independent reflections
Min. and max. transmission
Number of ref. parameters
R / wR [I > 2σ(I)]
33538
7917
0.7860 / 0.9500
347
0.0357 / 0.0796
0.0461 / 0.0833
1.034
0.325 / -0.373
w = 1/[σ (F ) + (0.0415 P) + 0.5258 P]
where P = (F + 2F )/3
1
2
R / wR (all data)
Goodness-of-fit on F
1
2
2
-3
Largest diff. peak and hole / e·Å
Weight scheme
2
2
2
o
2
2
o
c
3
. Results and Discussion
3
.1. Synthesis and reactivity
N-[(Phenylamino)methyl]trimethoxysilane
1
was
synthesized
by interaction
of
(chloromethyl)trimethoxysilane with an excess of aniline (Scheme 1).
Scheme 1. Synthesis of silane 1.
The typical procedure for the synthesis of silatranes RSi(OCH CH ) N involves treatment of
2
2 3
respective RSi(OAlk) with triethanolamine N(CH CH OH) [1-4]. The interaction of N-
3
2
2
3
6

ACCEPTED MANUSCRIPT
[
(phenylamino)methyl]trimethoxysilane 1 with triethanolamine led to formation of 1-[N-
phenyl(aminomethyl)]silatrane 2 with high yield without use of any catalyst (Scheme 2). We
have successfully executed this procedure at ambient temperature unlike the early described [35].
The structure of compound 2 was confirmed by multinuclear NMR spectroscopy and single-
crystal X-ray diffraction analysis.
Scheme 2. Synthesis of 1-[N-phenyl(aminomethyl)]silatrane 2.
The electron transfer under light irradiation in the complexes of aromatic amines with
.
..
carbon tetrachloride ArRR'N CCl gives rise to the formation of the pair of the radical cation of
4
amine and radical anion of carbon tetrachloride. It is the first stage of the photochemical
reactions between aromatic amines and carbon tetrachloride [39 and ref. therein]. Under day
light irradiation the reaction of compound 2 with carbon tetrachloride at room temperature in
benzene or acetonitrile afford to 1-[N-phenyl(aminomethyl)]silatrane hydrochloride 3 (Scheme
1
3
). The H NMR monitoring of this reaction in CD CN shows that the signal of chloroform (δ =
3
7
.28 ppm) appears in the spectrum within four hour. The possible mechanism for the reaction
between α-silylamines and CCl has been suggested by us early [30].
4
Scheme 3. Reaction of silatrane 2 with CCl and HCl
4
The spectra of the compound 3 are completely identical to the spectra of 1-
[
(phenyl)aminomethyl]silatrane hydrochloride, which has been synthesized by the interaction of
silatrane 2 with the HCl in dry benzene (Scheme 3). This reaction was carried out by dropwise
o
addition of HCl solution in benzene to silatrane 2 solution in benzene at 10 C. It is significant
that an increase of the temperature of the reaction mixture leads to the cleavage of the Si-O
bonds of atrane skeleton and the formation of a byproducts.
7

ACCEPTED MANUSCRIPT
Early we showed that α-silylamines react with AgNO and CuCl to give the corresponding salts
3
2
-
+
(
R NH CH SiX )X (X = NO or Cl) and at the same time, Ag(I) and Cu(II) are reduced up to
2 2 3 3
Ag(0) and Cu(I) [30]. Radical cations of α-silylamines are intermediates in these single electron
transfer reactions. Note that the reduction of Ag(I) by MeN[CH Si(OCH CH ) N] has given rise
2
2
2 3
2
to formation of Ag(0) as the “silver mirror”. This process could be used as a basis for creating
new techniques to form thin films. The reaction of silatrane 2 with AgNO starts immediately
3
after the mixing their acetonitrile solutions at the room temperature. Unfortunately the thin silver
films did not generate under these conditions. In a few hours the reaction is completed by the
formation of the compound 4 and the grey precipitate of metal silver (Scheme 4). It should be
noted that in contrast to the reduction of Ag(I) by MeN[CH Si(OCH CH ) N] this reaction lead
2
2
2 3
2
to generation of considerable quantities of by-products as the result of the partial cleavage of
silatrane group and the polymerization of aniline group. The conversion of compound 2 to
1
compound 4 is no higher than 60% according to H NMR spectrum of the reaction mixture.
The spectral characteristics of compound 4 and the salt 4 resulting from the reaction between
compound 3 and AgNO (Scheme 4) are identical. It is well known, that a composites of organic
3
material and metallic silver are produced at interaction of aniline or related compounds with
AgNO [40-44]. The oxidation of aromatic amines by silver nitrate has theoretical as well as
3
practical interest and therefore the research of the interaction of compound 2 with AgNO will be
3
continued in our laboratory and results will be reported in due course.
Scheme 4. Reaction of silatrane 2 with AgNO3.
The oxidative action of CuCl on silatrane 2 is a slow process completed over period of 3 days
2
by the formation of the salt 3 with 91 % yield (Scheme 5). It is a remarkable fact that the
generation of amine radical cation is greatly facilitated by reaction of aromatic amines with salts
Cu(II) [45-48]. Oxidative transformations of amines are the important methods for synthesis of
nitrogen-containing compounds, which are very useful building blocks in synthetic and material
chemistry [see for example 49-52].
8

ACCEPTED MANUSCRIPT
Scheme 5. Reaction of silatrane 2 with CuCl2.
α-Silylamines are easy oxidize and are the good candidates for the generation of α-aminoalkyl
radicals along with the desilylation. The addition of α-aminoalkyl radicals generated from a-
silylamines to α-,β-unsaturated ketones under UV irradiation has been extensively studied by P.
Mariano with staff [see, example 53-58]. In particular, the structure of adducts forming at the
interaction of aniline and N-methyl-N-[(trimethylsilyl)methyl]aniline with 4,4-
dimethylcyclohex-2-en-l-one was explored [58]. In this work we study the synthetic aspect of the
reaction of α-silatranylamine 2 with α-,β-unsaturated cyclic ketones in the presence of salt
CuCl . The compound 2 reacts with cyclopent-2-en-1-one 5 or 2-cyclohexen-1-one 6 as typical
2
α-silylamine with the formation of 3-(anilinomethyl)cyclopentanone
7
or 3-
(anilinomethyl)cyclohexanone 8, respectively (Scheme 6). The estimation of the different
reaction conditions for the synthesis of compound 8 shows in Table 2. Based on analysis of our
results and the literature data we concluded that on the first stage cation-radical of α-
silatranylamine was formed at the interaction of silatrane 2 with CuCl . The latter is the reagent
2
so the yield of compound 8 decreases near twofold at the lowering of its content in reaction
mixture (see entry 6). The desilylation of cation-radical of α-silatranylamine leads to the
formation of α-aminoalkyl radical which adds to α-,β-unsaturated cyclic ketones giving
compound 7 and 8. The high oxophilicity of silicon [59,60] is mainly responsible of more high
yield of compound 8 in nucleophilic solvents such as MeOH or MeCN-H O. The yield of
2
compound 8 in pure MeCN was only 17% (entry 7).
Scheme 6. Reaction of silatrane 2 with α-,β-unsaturated cyclic ketones
Table 2. Modification of reaction conditions for synthesis of compound 8.
9

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Entry 2 : 6 : CuCl Solvent t, h Yield, %**
2
1
2
3
4
5
6
7
1 : 1 : 0
1 : 1 : 1
1 : 1 : 1
1 : 1 : 1
1 : 1 : 2
1 : 1 : 0.5
1 : 1 : 1
1 : 1 : 1
MeOH 72
MeOH 72
MeOH 48
MeOH 96
MeOH 72
MeOH 96
MeCN 72
MeCN 72
0
86
52
88
85
41
17
90
8
*
*
*
2 : 6 : CuCl : H O = 1 : 1 : 1 : 1
2 2
* Yield after purification
3
.2. Crystal structure studies
The molecular structure of 1-[N-phenyl(aminomethyl)]silatrane 2 was determined by single
crystal X-ray diffraction (Fig. 1). The selected bond lengths and angles are presented in Tables
1
S (Suppl. Mat). The geometry of the Si coordination center in compound 2 (Fig. 1) is typical for
the silatranes [3 and ref. therein]. The coordination polyhedron of the silicon atom in these
compounds represents a distorted trigonal bipyramid with N atom and C atom in the axial
positions and three oxygen atoms occupying the equatorial positions. All five-membered rings of
silatrane skeleton in molecules of compound 2 adopt an ‘envelope’-like conformation. In the
asymmetric unit cell of silatrane 2 there are two conformers (Fig. 2) which differ by the lengths
of N•••Si dative bond and the value of torsion angle Si-C-N-C (Fig 2b). Moreover, the
differences concern the direction of the angle of rotation β-carbon atom in the five-membered
heterocycles of silatrane 2. Indeed, in one conformer these angles are rotated clockwise but in the
second conformer - counterclockwise (Fig. 2a). A similar picture was observed for N-methyl-N-
(
(3,7,10-trimethylsilatran-1-yl)methyl)acetamide [61], N-(1-silatranylmethyl)indole [62] and l-
4-tolyl)-silatrane [63] which also have two molecules in the asymmetric unit.
(
The N···Si bond distance in conformers of compound 2 are 2.124(2) and 2.130(2) Å, that shorter
on ~0.03-0.05 Å than in studied by us early 1-[N-methyl(aminomethyl)]silatrane (2.159 Å) [34]
and 1-[N-methyl-N-trityl(aminomethyl)]silatrane (2.179 Å) [64], but close to those in N-(1-
silatranylmethyl)phthalimide (2.134 Å) [65]. Average values of Si-O, N-C and C-O bond lengths
in conformers of silatrane 2 consist 1.67, 1.47 and 1.42 Å respectively, that is typical for most
silatranes according to the Cambridge Structural Database data. The displaces of the silicon
atoms relative to the equatorial planes defined by the three oxygen atoms towards the apical
substituent in conformers of compound 2 are 0.173 and 0.170 Å. The deviations of the
endocyclic nitrogen atoms from the plane of the neighboring carbon atoms comprise 0.385 and
1
0

ACCEPTED MANUSCRIPT
Fig. 1. Molecular structure of compound 2 (ORTEP, 50% probability)
a
b
Fig. 2. Two molecules of silatrane 2 in the asymmetric unit: a) anti-clock wise and clock wise
conformers; b) differences in torsion angle Si-C-N-C (H atoms are omitted for clarity).
1
1

ACCEPTED MANUSCRIPT
0
.391 Å in these conformers. These values lie within the typical range for silatranes (0.09–0.24
Å for Si atom and 0.34–0.40 Å for N atom). In the crystal molecules of compound 2 packed in
orthorhombic space group P 2 2 2 , in unit cell there are 8 molecules connected by short contacts
1
1 1
H···H of length 2.294 and 2.385 Å and CH···O of length 2.641 Å (Fig. 1S in Suppl. Mat.).
4
. Conclusion
The synthesis and structural data of 1-[N-phenyl(aminomethyl)]silatrane was described. The
geometry of the Si coordination center of this is typical for the silatranes: polyhedron of the
silicon atom represents a distorted trigonal bipyramid with N atom and C atom in the axial
positions and three oxygen atoms occupying the equatorial positions. In the asymmetric unit cell
of this silatrane there are two conformers which differ by the geometrical parameters. This
compound is a bright representative of α-silylamines. Single electron transfer reactions of 1-[N-
phenyl(aminomethyl)]silatrane with CCl , AgNO and CuCl was discussed. For the first time, a
4
3
2
protocol for the aminomethylation of α-,β-unsaturated cyclic ketones using α-silatranylamine is
described.
These results were obtained using analytical equipment of the Baikal Center for Collective Use
of the SB RAS.
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•
•
•
•
aniline with α-silatranyl group PhNHCH Si(OCH CH ) N was obtained
2
2
2 3
structure was proved by NMR and X-Ray data
reactions of this compound with CCl , AgNO and CuCl was investigated
4
3
2
for the first time, a protocol for the aminomethylation of α-,β-unsaturated cyclic ketones
using α-silatranylamine is described