Synthesis and reactivity of novel 3-isothiocyanatopropylsilatrane derived from aminopropylsilatrane: X-ray crystal structure and theoretical studies

Article abstract of DOI:10.1016/j.jorganchem.2009.10.013

A novel silatrane {A figure is presented} containing Si ← N bond (2.160 ?), has been synthesized by the reaction of 3-aminopropylsilatrane (1), dicyclohexylcarbodiimide (2) and CS₂. The structure was established by elemental analysis, spectroscopic methods (IR, ¹H NMR, ¹³C NMR and Mass spectroscopy) and X-ray crystallography. It was correlated with theoretical studies such as semiempirical (AM1, PM3, PM3MM and MNDO), Density Functional Theory (B3LYP) and Hartree-Fock at 3-21+G^* and 6-31G^*(d) levels. The reactivity of compound 3 was studied with some Lewis acids and bases that showed the formation of corresponding adducts (4-7), which were characterized by elemental analysis, IR and NMR (¹H, ¹³C) spectroscopy.

Full text of DOI:10.1016/j.jorganchem.2009.10.013

Journal of Organometallic Chemistry 695 (2010) 183–188
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Synthesis and reactivity of novel 3-isothiocyanatopropylsilatrane derived
from aminopropylsilatrane: X-ray crystal structure and theoretical studies
*
Raghubir Singh, Jugal Kishore Puri , Varinder Kaur Chahal, Raj Pal Sharma, Paloth Venugopalan
Department of Chemistry, Panjab University, Chandigarh 160 014, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 6 August 2009
A novel silatrane
containing Si N bond (2.160 Å), has been synthe-
N(CH2CH2O)3SiCH2CH2CH2NCS(3)
Received in revised form 7 October 2009
Accepted 13 October 2009
Available online 13 November 2009
sized by the reaction of 3-aminopropylsilatrane (1), dicyclohexylcarbodiimide (2) and CS2. The structure
was established by elemental analysis, spectroscopic methods (IR, 1H NMR, 13C NMR and Mass spectros-
copy) and X-ray crystallography. It was correlated with theoretical studies such as semiempirical (AM1,
PM3, PM3MM and MNDO), Density Functional Theory (B3LYP) and Hartree–Fock at 3-21+G* and
6-31G*(d) levels. The reactivity of compound 3 was studied with some Lewis acids and bases that showed
the formation of corresponding adducts (4–7), which were characterized by elemental analysis, IR and
NMR (1H, 13C) spectroscopy.
Keywords:
3-Isothiocyanatopropylsilatrane
Pentacoordinated silicon
Crystal structure
Density Functional Theory
Hartree–Fock Theory
Ó 2009 Elsevier B.V. All rights reserved.
1. Introduction
As discussed above, aminopropylsilatranes have captured con-
temporary interest of chemists due to their involvement in the
Silatranes, cyclic organosilicon ethers of tris(2-oxyalkyl)amine,
have been the subject of intense study since their discovery in
1961 [1]. Perhaps the most intriguing aspect of these hypercoordi-
nate silicon compounds is the nature of the silicon–nitrogen inter-
action and the variation in the transannular Si–N distance as a
function of change in the axial silicon substituent [2–9]. Amino-
propylsilatranes are potential precursor materials for the synthesis
of a number of N-derivative silatranes [10–15]. These derivatives of
aminopropylsilatranes find applications as fungicides [13,14], anti-
cancer and antitumour agents [15,16]. The aminopropylsilatranes
have also been used for immobilization of DNA due to less reactiv-
ity, extremely resistant behavior to hydrolysis and polymerization
at neutral pH [17]. They can also function as additives of water-
based metalworking fluids due to their tribological properties.
Semenov et al. reported the coordination of metal salts with
aminopropylsilatrane to form various metal complexes [18].
The X-ray structure and reactivity of a five membered 1-isot-
hiocyanatosilatrane with a direct Si–NCS bond was reported by
Narula et al. [19] and the structure was compared with ab initio
and DFT calculations to examine the precise structure by Chung
et al. [20]. Recently, we have reported the synthesis and reactivity
of six membered 1-isothiocyanatosilatrane, prepared by transethe-
rification reaction of triethoxyisothiocyanatosilane with tris-(2-hy-
droxy-3,5-dimethylbenzyl)amine [21].
synthesis of some novel silatranes by the derivatization of amino
group. In the context of these studies, we aimed at a novel synthe-
sis of 1-(3-isothiocyanatopropyl)-2,8,9-trioxa-5-aza-1-sila-bicy-
clo[3.3.3]undecane (3) from aminopropylsilatrane (1) with the
structural characterization in solid state by X-ray crystallography,
multinuclear NMR (1H, 13C), IR and mass spectroscopy. Theoretical
methods such as DFT and HF theory as well as their extensions are
very important for computing a molecular structure. So, the exper-
imental studies were complemented by computational studies
such as semiempirical (AM1, PM3, PM3MM and MNDO), DFT and
Hartree–Fock methods. The newly synthesized compound 3 was
found to be reactive due to the presence of –NCS moiety and reac-
tivity of the compound towards some of Lewis acids and Lewis
bases to form adducts is also reported in the present paper.
2. Results and discussion
2.1. Synthesis
Amines can be converted into isothiocyanates by reacting
primary amines with thiophosgene or by the decomposition of
1,3-disubstituted thiourea with acids [22]. Isothiocyanates can also
be accessed by the decomposition of dithiocarbamates from pri-
mary amines and CS2 in the presence of heavy metal salts [23] or
dicyclohexylcarbodiimide (DCC) [24], dicyandiamide [25] or cyan-
amide [26]. The use of DCC in nonaqueous systems is advantageous
over other methods.
* Corresponding author. Tel.: +91 9814522681.
E-mail address: prof_jkpuri@yahoo.com (J.K. Puri).
0022-328X/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2009.10.013

184
R. Singh et al. / Journal of Organometallic Chemistry 695 (2010) 183–188
In the present work, 3-isothiocyanatopropylsilatrane (3) is syn-
field, respectively. The peaks appearing at 55.0 and 48.0 ppm in 1
due to d OCH2 and NCH2 are observed at the same position as in 3.
The most common feature of mass spectrum of C-substituted
silatrane is the fragmentation of X–Si bond. Besides the molecular
ion (M+Na, 297) and (M+K, 313), a silatranyl ion (174) peak was
also observed in the mass spectrum. The molecular ion peak was
more abundant as compared to silatranyl ion peak.
thesized from 3-aminopropylsilatrane (1) and DCC (2) as a white
substance which is stable in air and soluble in common organic sol-
vents such as diethylether, chloroform and carbon tetrachloride.
The general reaction scheme for the synthesis of 3 is given below
(Scheme 1). Based on the previous reports [19], reactions of 3 with
some Lewis acids and bases were carried out to yield correspond-
ing adducts (4–7) and the routes followed are summarized in
Scheme 2.
2.3. Crystal structure
The molecular structure of compound with atom numbering
scheme is depicted in Fig. 1. The X-ray data, selected bond dis-
tances and angles of compound 3 are listed in Tables 1 and 2,
respectively. The compound possesses usual skeleton containing
2.2. Spectroscopic data
The IR spectrum of 3 was recorded in the range 4000–400 cmꢀ1
.
The absorption bands were assigned on the basis of literature
[19,25,26]. The IR absorption frequencies are in accordance with
the structure of prepared complex. The absorptions of interest
are those of NCS, Si–O and Si–N bonds. IR spectrum in Nujol/KBr
plates show mas NCS absorption at 2121 cmꢀ1 for 3.
Multinuclear (1H and 13C) NMR spectra are consistent with the
structure of synthesized compound. On comparing 1H NMR spectra
of 3 with those of 1, a downfield shift for the OCH2 and NCH2 pro-
tons of Si(OCH2CH2)3N moiety in 3 is observed. Correspondingly,
triplet due to –CH2–NCS protons is also shifted to downfield as
compared to –CH2NH2 which can be justified on the basis of elec-
tron withdrawing effect of –NCS group. All protons in the com-
pound 3 have been identified and the total number of protons
calculated from the integration curve was found to be equal to ex-
pected number.
In the 13C NMR, d NCS appeared at 177.0 ppm. The effect of –
NCS moiety on the 13C spectra is observed on the signals due to
–CH2NCS and –CH2CH2CH2 which are shifted downfield and up-
Fig. 1. Perspective view of 3 showing atom numbering scheme (thermal ellipsoids
are at 45% probability level).
Table 1
X-ray crystal data and structure refinement of 3-isothiocyanatopropylsilatrane.
Empirical formula
Formula weight
C10H18N2O3SSi
274.41
T (K)
293(2)
Crystal system, space group
Monoclinic, P21/c
Unit cell dimensions
a (Å)
Scheme 1.
7.955(1)
13.204(1)
12.9492(10)
90.150(1)
1360.1(2)
4
b (Å)
c (Å)
b (°)
V (Å3)
Z
Density (calculated) (Mg/m3)
1.340
0.325
Absorption coefficient (mmꢀ1
)
Theta range for data collection 2.20–24.99
(°)
Index ranges
ꢀ9 6 h 6 0, ꢀ15 6 k 6 0, ꢀ15 6 l 6 15
Reflections collected
Independent reflections [R(int)
Refinement method
Data/restraints/parameters
Goodness-of-fit (GOF) on F2
Weighting scheme
2555
]
2376 [0.0270]
Full-matrix least-squares on F2
2376/0/154
1.039
2
1=½r2ðF2oÞ þ ð0:0719PÞ þ 0:83Pꢁ,
P ¼ ðMaxðF2o; 0Þ þ 2 ꢂ F2c Þ=3
R1 = 0.0586, wR2 = 0.1444
Final R indices, 1631
reflections [I > 2r(I)]
R indices (all data)
R1 = 0.0929, wR2 = 0.1590
0.527 and ꢀ0.272
Largest difference peak and
hole (e Åꢀ3
)
Scheme 2.

R. Singh et al. / Journal of Organometallic Chemistry 695 (2010) 183–188
185
Table 2
Selected bond lengths (Å) and angles (°) of 3-isothiocyanatopropylsilatrane.
N(1)–Si
C(7)–Si
C(9)–N(2)
C(10)–N(2)
O(1)-Si
O(2)–Si
O(3)–Si
C(10)–S(1)
N(2)–C(9)–C(8)
N(2)–C(10)–S
2.160(3)
1.882(3)
1.447(5)
1.138(5)
1.663(3)
1.655(3)
1.659(3)
1.575(5)
112.5(3)
176.7(4)
O(1)–Si–O(2)
O(1)–Si–O(3)
O(2)–Si–O(3)
C(8)–C(7)–Si
O(1)–Si–C(7)
O(2)–Si–C(7)
O(3)–Si–C(7)
C(9)–C(8)–C(7)
C(10)–N(2)–C(9)
C(7)–Si–N(1)
118.17(15)
118.06(14)
119.47(16)
117.7(2)
97.92(12)
95.51(14)
97.36(14)
109.8(3)
159.9(4)
178.34(14)
a five-coordinate silicon atom. The stereochemistry of silicon is
distorted trigonal bipyramidal. A comparison with the 1-isothioc-
yanatosilatrane showed a slight lengthening of Si–O bonds with
the contraction of C–C, N–C and O–C bonds. The influence of elec-
tron withdrawing effect of –NCS on the transannular Si–N bond
was found to be less as compared to the silatrane with direct Si–
NCS bond. The reduced electron withdrawing inductive effect of
–NCS due to the intervening –CH2–CH2–CH2– alkyl chain might
be responsible for the longer Si–N distance 2.160(3) Å in 3 when
compared with 1-isothiocyanatosilatrane, which has the shortest
Si–N distance, 2.007(3) Å. The SiO3 pyramid is flattened, the aver-
age values of both O–Si–C and O–Si–N angles being closer to per-
fectly flattened 90° value. This bond angle is an important factor
to illustrate the deviation in the geometry around the Si atom from
a pentacoordinated trigonal bipyramidal structure. The silicon
atom deviates to an extent of ꢀ0.20 Å from the best least square
plane defined by the three O atoms (O1, O2 and O3) that also indi-
cates that the hypercoordination induces significant structural
deviations in the molecule.
Compound 3 crystallizes in a monoclinic crystal system (space
group = P21/c) with four molecules in a unit cell. Although there
are strong hydrogen bond acceptors like O and N atoms in the mol-
ecule, there are no strong hydrogen bond donors like –OH or –
COOH moieties. Besides this, the hydrogen atom to non-hydrogen
atom ratio is relatively low to a value of 1 that prompts the mole-
cules to adopt a packing that utilizes the interactions with hydro-
gen atoms that are most acidic in the structure. These hydrogen
atoms are the one at C9 (bonded to the –NCS group) (Fig. 2) and in-
deed both the hydrogen atoms participate in C–Hꢃ ꢃ ꢃO hydrogen
bonding that play a significant role in the lattice stabilization.
Within the centrosymmetrically related molecules, both O1 and
O3 act as C–Hꢃ ꢃ ꢃO hydrogen bond acceptors of these hydrogen
atoms (C9–H9Aꢃ ꢃ ꢃO1 = 2.516 Å, C9–H9Bꢃ ꢃ ꢃO3 = 2.490 Å) that gen-
erates a zig–zag corrugated ribbon like arrangement that run par-
allel to the ‘a’ axis of the unit cell. Such an arrangement is depicted
in the Fig. 2. The molecules in the corrugated sheet like arrange-
ment are further linked to c glide related molecules through an-
other C–Hꢃ ꢃ ꢃO hydrogen bond involving the third oxygen atom,
O2 and H1B (C1–H1Bꢃ ꢃ ꢃO2 = 2.637 Å). The resulting arrangement
of the molecules viewed down ‘b’ axis is shown in the Fig. 3. It is
to be noted that CH2CH2CH2NCS moiety attached to the silatrane
ring is like an appendage protruding out of a sphere and their clos-
est packing arrangement is achieved if they are arranged in a head
to tail fashion. This indeed happens in the lattice (P21/c space
group, centrosymmetric arrangement). Thus, the Kitaigorodsky
model of close packing is achieved in the lattice and within this
arrangement the C–Hꢃ ꢃ ꢃO hydrogen bonds anchor the molecule
to their respective positions. There are no other significant short
contacts observed in the molecular packing.
Fig. 2. The corrugated sheet formation through C–Hꢃ ꢃ ꢃO hydrogen bonding
involving most acidic hydrogen atoms (H9AA and H9BA). The third oxygen atom
links these sheets through a third C–Hꢃ ꢃ ꢃO hydrogen bond (see Fig. 3).
these studies to semi empirical methods, but a few reports using
ab initio methods have been appeared in the last decade [27–31].
Initially, quantum chemical calculations of 3 were performed by
using semiempirical methods (AM1, PM3, PM3MM and MNDO)
but the accuracy of these methods was found insufficient to de-
scribe transannular N ? Si interaction and appeared to be of little
use. Therefore, optimization of geometry parameters was carried
out by using DFT/B3LYP and HF methods with different basis sets.
The optimized geometrical parameters of 3-isothiocyanatopropyls-
ilatrane with various levels of DFT and RHF methods are summa-
rized in Table 3, respectively.
The Density Functional Theory and Hartree–Fock calculations
were performed at 3-21+G* and 6-31+G(d) basis sets for 3 and
the results were compared with crystal data. The most important
geometrical parameter, N ? Si distance, examined with RHF meth-
od at 3-21+G* and 6-31+G(d) basis sets was found to be signifi-
cantly longer than the crystal data, the values are lower than
other methods when computed with B3LYP at 3-21+G* and 6-
31+G(d) basis sets. The X-ray studies demonstrate the bond angle
N–C–S at around 176.8° which is accordance with the theoretical
value obtained with DFT/B3LYP/6-31G*(d). The variation in other
bond angles is attributed to the denser packing of molecules which
promotes the intensification of crystal field and, hence, compres-
sion of the molecules. As a result, the N ? Si bond length decreases
with the increase of crystal density and packing coefficient. Proba-
bly, stringent packing requirements involving large number of
cooperative C–Hꢃ ꢃ ꢃO hydrogen bonds may compress the molecule
through the N ? Si vector leading to a smaller value (2.16 Å) than
the same observed in an isolated molecule (2.54–2.70 Å) through
theoretical means. However, this bond length is sensitively af-
2.4. Theoretical studies
The limited literature on computational studies on silatranes is
due to the large size of these molecules which restricts largely

186
R. Singh et al. / Journal of Organometallic Chemistry 695 (2010) 183–188
Fig. 3. Close packing of compound 3 viewed down ‘b’ axis of the unit cell. All the dotted lines show C–Hꢃ ꢃ ꢃO type hydrogen bonding within the centrosymmetric arrangement
of the molecules.
Table 3
DFT and HF studies of 3-isothiocyanatopropylsilatrane.
Parameters
DFT, B3LYP 3-21+G*
DFT, B3LYP 6-31G*(d)
RHF, 3-21+G*
RHF, 6-31G*(d)
Total energy (a.u.)
Dipole moment
N(1) ? Si
ꢀ1407.77
9.8
2.54
ꢀ1414.89
8.10
2.59
ꢀ1402.09
9.76
2.70
ꢀ1409.21
8.74
2.67
Si–C(7)
1.87
1.87
1.86
1.87
Si–O av.
1.68
1.67
1.65
1.65
N(1)–C(2,4,6) av.
N(2)–C(10)
1.48
1.18
1.46
1.18
1.46
1.15
1.45
1.15
C(7)–S(1)
1.60
1.60
1.61
1.61
N(2)–C(10)–S(1)
C(9)–N(2)–C(10)
C(7)–C(8)–C(9)
C(8)–C(7)–Si(1)
O(1)–Si(1)–O(2)
O(2)–Si(1)–O(3)
O(3)–Si(1)–O(1)
C(2)–N(1)–C(4)
C(4)–N(1)–C(6)
C(6)–N(1)–C(2)
179.30
174.24
112.91
113.22
114.10
115.38
115.38
116.75
116.68
116.67
176.49
157.41
113.76
115.12
114.74
114.67
113.96
117.70
117.72
117.72
179.85
179.29
112.87
112.69
111.16
112.31
112.06
118.15
118.16
118.12
179.98
179.55
113.91
114.66
112.08
112.90
113.06
118.49
118.48
118.47
fected by adding the electron correlation effect at the B3LYP levels
and showed an increase in the value. The computed Si–C(7) bond
lengths at both RHF and B3LYP levels are equal to the crystallo-
graphic value. Other parameters like Si–O bond length computed
from RHF levels are almost same with the values obtained in the
X-ray crystallographic studies. The slight change observed in other
bond lengths might be because of either the crystal packing forces
in the solid state or an experimental unreliability.
The optimized structure of 3, when compared with the opti-
mized structure of 1-isothiocyanatosilatrane depicted structural
changes in silatrane ring on decreasing the inductive effect of X
moiety [20]. The most drastic change was found in Si–N1 bond dis-
tance for 1-isothiocyanatosilatrane (2.33 Å) at the B3LYP/6-31+G*
level which was very less than the 3 due to direct bond of electron
withdrawing –NCS with silicon.
3. Reactivity
Compound 3 is stable towards atmospheric moisture as com-
pared to 1. It was found that compound 3 readily reacts with Lewis
acids to produce corresponding adducts. The reactions (Scheme 2)
were carried out in accordance with the literature [19] and the
products were analyzed with spectroscopic studies. The reaction
of 3 with equimolar amounts of SnCl4 and TiCl4 leads to the forma-
tion of 4 and 5, respectively. IR spectra suggested the bonding of
adducts 4 and 5 through N atom of NCS. The decrease observed
in the mas NCS absorption band in case of 4 and 5 adducts is due
to the coordination of Lewis acids through N atom of NCS group.
Reaction of 3 with diethylamine yielded the desired product 6.
However, the obtained white product was hygroscopic. The de-
crease in the
m NH in 6 indicated the formation of adduct of 3 with

R. Singh et al. / Journal of Organometallic Chemistry 695 (2010) 183–188
187
diethylamine. A reaction of 3 with AgNO3 gave 7 in which Ag+ is
4.1.4. Theoretical studies
coordinated to S atom of NCS group. The shift of band towards
the higher frequency in adduct 7 supports the bonding through
S. IR spectrum showed mas NCS absorption in the range of 1990–
2190 cmꢀ1 for adducts. In addition, investigation of adducts for
structural fragment of Si–O–C–C is shown by the characteristic fre-
quencies appearing in the region 1480–575 cmꢀ1. The characteris-
tic spectra for pentacoordinated molecular structure and Si N
coordinative bond are observed as medium intensity band in the
The quantum mechanical calculations were carried out using
the GAUSSIAN 03 series of programs. Geometries were fully optimized
at both the Restricted Hartree–Fock (RHF) and Density Functional
Theory level (DFT), using Becke’s three parameter hybrid exchange
functional and the correlation functional of Lee, Yang, and Parr
(B3LYP) with 3-21+G* and 6-31G*(d) basis sets.
4.2. Synthesis of 3-aminopropylsilatrane (1)
region of 570–590 cmꢀ1
.
The starting material 1 was synthesized according to the meth-
od reported in literature [14,15]. 3-Aminopropyl(triethoxy)silane
(5.00 g, 22.5 mmol) was added to triethanolamine (3.36 g,
22.5 mmol) at room temperature in a two-necked flask which
was fitted with a Dean Stark trap. The resulting mixture was re-
fluxed to remove the ethanol formed during the reaction. After
the complete removal of ethanol, when the reaction mixture was
kept in refrigerator for 5 h, white solid was obtained. Dry hexane
was added, stirred for one hour and the solid was filtered and dried
under vacuum.
4. Experimental
4.1. General details
4.1.1. Synthesis
All the syntheses were carried out under a dry nitrogen atmo-
sphere using vacuum glassline. The organic solvents used were
dried and purified according to standard procedures and stored un-
der nitrogen. 3-Aminopropyl(triethoxy)silane (Aldrich), triethanol-
amine (Merck) and DCC (Merck) were used as such. Diethylamine
(Merck) was distilled by refluxing over KOH pellets under dry
nitrogen atmosphere. CS2 (Qualigens) was purified by distillation
prior to use.
4.3. Synthesis of 3-isothiocyanatopropylsilatrane (3)
3-Aminopropylsilatrane (2.00 g, 8.62 mmol) and DCC (1.76 g,
8.62 mmol) dissolved in 50 mL of dry diethylether were taken in
a two-necked round bottom flask. The contents were stirred at
0–5 °C in an ice bath for 15 min and 4 mL of CS2 was added drop-
wise at low temperature. The temperature was allowed to increase
to 20 °C during the stirring for 5 h. The mixture was kept at room
temperature overnight and filtered. The residue was washed with
diethylether and the filtrate was evaporated under reduced pres-
sure. The product obtained was recrystallized from diethylether.
Yield: 1.6 g, 69.6%. Anal. Calc. for C10H18N2O3SSi: C, 43.77; H,
6.61; N, 10.21; S, 11.69; Si, 10.23. Found: C, 43.70; H, 6.59; N,
4.1.2. Characterization
Infrared spectra were routinely obtained as thin films or Nujol
mulls on a Perkin–Elmer RX-I FT IR Spectrophotometer. Mass spec-
tral measurements (EI, 70 eV) were carried out on a VG Analytical
(70-S) spectrometer. C, H and N analyses were obtained on a
Perkin–Elmer Model 2400 CHN elemental analyzer. Cl, S and Si
were estimated by gravimetric methods. The solution 1H and 13C
NMR spectra were recorded at 25 °C on a Jeol FT NMR (AL
300 M Hz) spectrometer using CDCl3 as the solvent. Chemical shifts
in ppm were determined relative to internal CDCl3 and external
tetramethylsilane (TMS).
10.20; S, 11.63; Si, 10.17%. IR (Nujol, cmꢀ1): 2121 vs
456 m d (NCS), 576 m (C@S), 625 m ds
(Si N), 670 m
(SiO3), ms (Si–C), 725 vs, 770 s das (SiO3), 938 s, 975 s, 1085 s,
1115 s, 1152 s (Si–O–C–C), 1175 m (CH2O), 1270 m
(CH2O), 1370 m, 1342 m
(CH2N); 1H NMR (CDCl3): d 3.76 (t,
m (C@N),
m
m
m
s
x
x
4.1.3. X-ray crystallography
OCH2), 2.82 (t, NCH2), 0.42 (t, CH2Si), 1.82 (q, CCH2C), 3.44 (t,
CH2NCS). 13C NMR (CDCl3): d 55.47 (OCH2), 48.91 (NCH2), 11.35
(SiCH2), 24.29 (CCH2C), 45.88 (CH2NCS), 177.05 (NCS); MS (m/z,
assignment): 297 (M+Na), 313 (M+K), 174 (silatranyl ion).
Single crystals of compound 3 suitable for X-ray structure
determination were obtained from its saturated solution in dieth-
ylether and a crystal with dimensions 0.41 ꢄ 0.22 ꢄ 0.31 mm was
mounted along the largest dimension and used for data collec-
tion. Diffraction measurements were carried out on a Siemens
P4 single X-ray crystal diffractometer equipped with molybde-
num sealed tube (k = 0.71073 Å) and highly oriented graphite
monochromator. The lattice parameters and standard deviations
were obtained by least-squares fit to 30 reflections. The data
were collected by 2h–h scan mode with a variable scan speed
ranging from 2° to a maximum of 60° minꢀ1. The stability and
orientation of the crystal were monitored by three reflections
and remeasured after every 97 reflections. The intensities
showed only statistical fluctuations during data collection. The
corrections in the data were made for Lorentz and polarization
factors.
4.4. Synthesis of adducts
Compound 4: To the stirred solution of 3 (0.25 g, 0.90 mmol) in
dry CH2Cl2, tin(IV) chloride (0.1 mL, 0.88 mmol) was added drop-
wise. A white solid was appeared immediately and the contents
were allowed to stir at 25 °C for 4 h. The solid obtained was filtered
and washed with 15 mL of CH2Cl2. The white solid was dried under
vacuum and analyzed with spectroscopic methods. Yield: 0.38 g,
79.2%. Anal. Calc. for C10H18Cl4N2O3SSiSn: C, 22.45; H, 3.39; Cl,
26.51; N, 5.24; S, 5.99; Si, 5.25. Found: C, 21.98; H, 3.28; Cl,
26.60; N, 5.25; S, 5.83; Si, 5.23%. IR (Nujol, cmꢀ1): 2011, 1995 s
m
(C@N), 1H NMR (CDCl3): d 3.75 (t, OCH2), 2.80 (t, NCH2), 0.45 (t,
CH2Si), 1.80 (q, CCH2C), 3.40 (t, CH2NCS). 13C NMR (CDCl3): d
55.40 (OCH2), 48.90 (NCH2), 11.20 (SiCH2), 24.20 (CCH2C), 45.71
(CH2NCS), 177.01 (NCS).
The crystal structure was determined by direct methods using
SHELX-86 and refined by full matrix least-squares using SHELX-97
package [32]. Non-hydrogen atoms were subjected to anisotropic
refinement. The hydrogen atoms were fixed at their ideal positions
with their isotropic U values varying 1.2 times to that of their
respective non-hydrogen atoms and were riding. A weighing
Compound 5: In 25 mL dry CH2Cl2, 3 (0.25 g, 0.9 mmol) was ta-
ken in a round bottom flask and titanium(IV) chloride (0.1 mL,
0.9 mmol) was added dropwise. The contents were stirred for 4 h
at room temperature. The precipitated solid was filtered and
washed with 10 mL CH2Cl2 three times. The solid was dried under
vacuum and characterized. Yield: 0.31 g, 73.8%. Anal. Calc. for
C10H18Cl4N2O3STi: C, 25.88; H, 3.91; Cl, 30.56; N, 6.04; S, 6.91; Si,
2
scheme of the form w ¼ 1=½r2ðF2oÞ þ ðaPÞ þ bPꢁ with a = 0.0719
and b = 0.83 was used. The refinement converged to a final R value
of 0.0586 for 1631 reflections [I > 2r(I)]. The final difference map
was featureless.

188
R. Singh et al. / Journal of Organometallic Chemistry 695 (2010) 183–188
6.05. Found: C, 24.88; H, 3.89; Cl, 30.51; N, 6.01; S, 6.81; Si, 5.98%.
IR (Nujol, cmꢀ1): 2013 s, 1990 s (C@N), 1H NMR (CDCl3): d 3.72 (t,
OCH2), 2.81 (t, NCH2), 0.47 (t, CH2Si), 1.79 (q, CCH2C), 3.41 (t,
CH2NCS). 13C NMR (CDCl3): d 55.43 (OCH2), 48.88 (NCH2), 11.25
(SiCH2), 24.23 (CCH2C), 45.79 (CH2NCS), 177.01 (NCS).
References
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8.08. Found: C, 48.21; H, 8.34; N, 12.05; S, 9.12; Si, 8.00%. IR (Nujol,
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m (NH), 2083 s, m
(C@N), 1H NMR (CDCl3): d 3.02 (t,
OCH2), 2.11 (t, NCH2), 0.40 (t, CH2Si), 1.60 (q, CCH2C), 3.15 (t,
CH2NCS), 2.89 (q, CH2), 1.28 (t, CH3), 8.5 (br, NH); 13C NMR (CDCl3):
d 12.5 (CH3), 42.12 (CH2), 54.23 (OCH2), 46.58 (NCH2), 11.28
(SiCH2), 24.21 (CCH2C), 45.81 (CH2NCS), 177.01 (NCS).
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and dried under vacuum. Yield: 0.30 g, 73.2%. Anal. Calc. for
C10H18AgN3O6SSi: C, 27.03; H, 4.08; N, 9.46; S, 7.22; Si, 6.32.
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m
(C@N), 1H NMR (CDCl3): d 3.69 (t, OCH2), 2.75 (t,
NCH2), 0.36 (t, CH2Si), 1.75 (q, CCH2C), 3.42 (t, CH2NCS). 13C NMR
(CDCl3): d 55.30 (OCH2), 48.78 (NCH2), 11.20 (SiCH2), 24.20
(CCH2C), 45.85 (CH2NCS), 177.01 (NCS).
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Raghubir Singh is thankful to UGC, New Delhi for providing
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Appendix A. Supplementary material
CCDC 742997 contains the supplementary crystallographic data
for 3. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via http://www.ccdc.cam.
ac.uk/data_request/cif. Supplementary data associated with this
article can be found, in the online version, at doi:10.1016/
j.jorganchem.2009.10.013.
[32] G.M. Sheidrick, SHELX97, Program for Crystal Structure Refinement, University
of Gottingen, Germany, 1997.