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R. Singh et al. / Journal of Molecular Structure 982 (2010) 107–112
2.5. X-ray structure determination
2. Experimental
2.1. Materials
Single crystal X-ray diffraction data for 4 was collected on a
Nonius Kappa CCD diffractometer equipped with a CCD detector
and graphite-monochromatized Mo K
a radiation (k = 0.71073 Å).
All the syntheses were carried out under a dry nitrogen atmo-
sphere using vacuum glassline. Organic solvents used were dried
and purified according to standard procedures and stored under
nitrogen. 3-Chloropropyl(triethoxy)silane (Aldrich), sodium azide
(Acros organics) and triethanolamine (Merck) were used as such.
All intensities were corrected for Lorentz and polarization. The
structure was solved by direct methods using SIR97 program
[21] and refined on F2 by full-matrix least-square methods. Crystal
data is given in Table 1 and ORTEPIII [22] view along with atomic
labelling (thermal ellipsoids are drawn at 40% probability) of 4 is
shown in Fig. 1. Non hydrogen atoms were refined anisotropically
apart from N4 and C2, which were found disordered over two al-
most equivalent positions and refined isotropically. The other dis-
ordered atoms C4 and C6 were refined anisotropically with a fixed
occupancy factor of 0.5 (Fig. 1). H atoms were included on calcu-
lated positions. All calculations were performed using SHELXL-97
[23], and PARST [24], as implemented in the WINGX [25] system
of programs.
2.2. Instruments and measurements
Infrared spectra were routinely obtained as thin films or Nujol
mulls and KBr pellet on a Perkin–Elmer RX-I FT IR Spectrophotom-
eter. Mass spectral measurements (EI, 70 eV) were carried out on a
VG Analytical (70-S) spectrometer. C, H and N analyses were ob-
tained on a Perkin–Elmer Model 2400 CHN elemental analyzer.
The solution 1H and 13C NMR spectra were recorded at 25 °C on a
Jeol and Bruker FT NMR (AL 300 MHz and 400 MHz) spectrometer
using CDCl3 as the solvent. Chemical shifts in ppm were deter-
mined relative to internal CDCl3 and external tetramethylsilane
(TMS).
2.6. Theoretical studies
The quantum mechanical calculations were carried out using
the GAUSSIAN 03 series of programs. Geometries were fully opti-
mized at both the Restricted Hartree–Fock (RHF) and Density Func-
tional Theory level (DFT), using Becke’s three parameter hybrid
exchange functional and the correlation functional of Lee, Yang,
and Parr (B3LYP) with 3-21 + Gꢂ and 6-31Gꢂ(d) basis sets.
2.3. Synthesis of 3-azidopropyltriethoxysilane (3)
To a dried 100 mL single-neck round-bottom flask equipped
with reflux condenser, 3-chloropropyltriethoxysilane (4 g,
16.6 mmol), sodium azide (2.16 g, 33.2 mmol) and tetrabutyl
ammonium bromide (1.288 g, 4 mmol) were added in dry acetoni-
trile (50 mL), under nitrogen atmosphere. The reaction mixture
was then brought to stirr under reflux for 18 h. After completion
of the reaction, the solvent was removed under reduced pressure.
The crude mixture was diluted in dry hexane and the suspension
was filtered under vacuum. Solvent was removed from the result-
ing filtrate and the crude oil obtained was distilled under reduced
pressure to give 3-azidopropyltriethoxysilane as a colorless liquid.
Yield: 3.02 g, 74%. IR (Neat, KBr plates cmꢀ1): 2098
(AN@N+@NꢀA); 1H NMR (300 MHz, CDCl3): d 0.60 (t, 2H, CH2Si),
1.15 (t, 9H, CH3), 1.64 (q, 2H, CCH2C), 3.19 (t, 2H, CH2N3), 3.77 (q,
6H, OCH2); 13C NMR (300 MHz, CDCl3) d 7.38 (SiCH2), 18.41
(CCH2C), 22.45 (CH2N3), 53.54 (NCH2), 58.58 (OCH2).
3. Results and discussion
3.1. Synthesis
3-Azidopropyltriethoxysilane can be prepared from 3-chloro-
propyltriethoxysilane and sodium azide by using two alternate
methods, either in the presence or in the absence of catalyst. In
the absence of catalyst, reaction has been carried out by refluxing
the reactants in butanone for 72 h [26]. On the other hand, use of
catalyst such as tetrabutylammonium bromide reduces the reac-
tion time to 18 h [27].
In the present work, 3-azidopropyltriethoxysilane (3) was syn-
thesized in high yield by nucleophilic substitution reaction of 3-
chloropropyltriethoxysilane (1) and sodium azide (2) in the pres-
ence of tetrabutylammoium bromide as catalyst and acetonitrile
as solvent. The compound was isolated as a colorless liquid after
distillation under reduced pressure, which can be used as a precur-
sor for the synthesis of new silatrane (4). Transesterification of
compound (3) with triethanolamine in the presence of a catalytic
2.4. Synthesis of 3-azidopropylsilatrane (4)
To a dried 100 mL single-neck round-bottom flask fitted with
Dean Stark apparatus, 3-azidopropyltriethoxysilane (2.22 g,
8.98 mmol) and triethanolamine (1.34 g, 8.98 mmol) was added
in dry benzene. The contents were refluxed for 5 h in the presence
KOH in catalytic amount. Benzene was removed under vacuum and
dry diethylether was added when white solid was separated out.
The contents were further stirred for 1 h at room temperature.
The solid was filtered under vacuum, washed twice with diethyl-
ether (2 ꢁ 10 mL) and dried. M.pt. 55–57 °C; yield: 1.95 g, 84%.
Anal. Calcd for C9H18N4O3Si: C, 41.84; H, 7.02; N, 21.69; found: C,
Table 1
X-ray crystal data and structure refinement of 4.
Chemical formula
C9H18N4O3Si
Mr
258.36
Orthorhombic, Pna21
13.2149 (2), 12.0619 (3), 8.1850 (3)
1304.66 (6)
4
Crystal system, space group
a, b, c (Å)
V (Å3)
41.10; H, 6.89; N, 21.20; IR (CCl4, KBr plates, cmꢀ1): 2093 vs.
(AN@N+@NꢀA), 583 m
(Si N), 612 m ds (SiO3), ms (Si–C), 936
s, 1087 s, 1105 vs. 1130 vs. (Si–O–C–C), 1180 m (CH2O),
1278 m (CH2O), 1352 m, 1454 m
(CH2N); 1H NMR (400 MHz,
m
Z
Radiation type
Mo Ka
m
l
(mmꢀ1
)
0.18
m
s
Crystal size (mm)
No. of measured, independent
0.41 ꢁ 0.37 ꢁ 0.29
x
x
2700, 2700, 2279
CDCl3): d 0.35 (t, CH2Si), 1.66 (q, CCH2C), 2.75 (t, NCH2), 3.12 (t,
CH2N3), 3.70 (t, OCH2); 13C NMR (400 MHz, CDCl3): d 13.32 (SiCH2),
24.78 (CCH2C), 54.63 (CH2N3), 51.00 (NCH2), 57.62 (OCH2); 29Si
(300 MHz, CDCl3); ꢀ70.24 ppm; MS: m/z (relative abundance, %):
132 (48), 150 (89), 172 (71), 174 (60), 192 (100), 216 (23), 233 (91).
and observed [I > 2r(I)] reflections
R[F2 > 2s(F2)], wR(F2), S
No. of reflections
0.063, 0.200, 1.04
2700
171
0.43, ꢀ0.50
No. of parameters
D
qmax
,
D
qmin (e Åꢀ3
)