Silyl stabilized azanes: Reactions of mono- and dilithium bis(trimethylsilyl)hydrazide with dichloro- and tetrachlorostannane

Article abstract of DOI:10.1016/j.jorganchem.2009.03.004

SnCl₄ acts primarily as an oxidant and oxidizes monolithium bis(trimethylsilyl) hydrazide 1 to mainly bis(trimethylsilyl)amine, BSA and tris(trimethylsilyl)hydrazine, TrSH and itself get reduced to SnCl₂. Similarly, reaction of SnCl<

Full text of DOI:10.1016/j.jorganchem.2009.03.004

Journal of Organometallic Chemistry 694 (2009) 2252–2257
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Journal of Organometallic Chemistry
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Silyl stabilized azanes: Reactions of mono- and dilithium
bis(trimethylsilyl)hydrazide with dichloro- and tetrachlorostannane
b
a
a,
J. Kataria a, , P. Mayer , S.K. Vasisht , P. Venugopalan
*
*
a Department of Chemistry, Panjab University, Chandigarh 160 014, India
b Dept. Chemie, Univ. LMU, Butenandt Str. 5-13, Haus-D, 81377-München, Germany
a r t i c l e i n f o
a b s t r a c t
Article history:
SnCl4 acts primarily as an oxidant and oxidizes monolithium bis(trimethylsilyl) hydrazide 1 to mainly
bis(trimethylsilyl)amine, BSA and tris(trimethylsilyl)hydrazine, TrSH and itself get reduced to SnCl2. Sim-
ilarly, reaction of SnCl4 with dilithiumbis(trimethylsilyl) hydrazide 2, oxidizes it to lithium tris(trimeth-
ylsilyl)hydrazide, Li-TrSH. Reaction of dichlorostannane (reduction of oxidation state of tin from +4 to +2)
with 1 gives a simple substitution reaction and give a pale yellow solid, 1,4-bis(trimethylsilyl)-1,2,4,5-
tetraza-3,6-distannacyclohexane, 3b. Whereas, in reaction of 2 with SnCl2 intermediate stannimine
[(Me3Si)2N–N@Sn], tetramerizes and further loses tetrakis(trimethylsilyl)tetrazene, TST to give a cubane
compound [(Me3Si)N–Sn]4, 4.
Received 28 January 2009
Received in revised form 2 March 2009
Accepted 3 March 2009
Available online 12 March 2009
Keywords:
Monolithiumbis(trimethylsilyl)hydrazide
Dilithiumbis(trimethylsilyl) hydrazide
Bis(trimethylsilyl)amine
Ó 2009 Elsevier B.V. All rights reserved.
Lithiumtris(trimethylsilyl)hydrazide
1,4-Bis(trimethylsilyl)-1,2,4,5-tetraza-3,
6-Distannacyclohexane
Stannimine
1. Introduction
tures previously thought impossible might be possible after all.
Especially tantalizing were heterocubanes, single molecules ar-
The synthesis and study of heterocycles containing main-group
elements have played a pivotal role in the development of inor-
ganic chemistry. Current research continues to uncover fascinating
new ring systems which pose intriguing questions with respect to
their bonding or which exhibit unexpected reactivity. Some note-
rayed in a simple unit cell pattern. Such chemical species have lat-
tice energies on the order of ionic salts but with superior mobility,
especially in the gas phase. This ability to store energy has made
heterocubanes prime targets for both high energy density materi-
als (HEDMs) [13] and metal-oxide chemical vapor deposition
(MOCVD) [14]. GaS, GaSe, and various indium heterocubanes have
been used industrially to cleanly produce both cubic and hexago-
nal surfaces for metal–insulator–semiconductor field-effect tran-
sistor (MISFET) applications [14,15]. Because of such interesting
applications, the cubane is an important observed structural motif
in solid-state inorganic chemistry. We envisaged that compounds
1 and 2 could act as potential precursors for the synthesis of vari-
ous inorganic non-alternating heterocycles as we can incorporate a
diazane moiety into a ring by using these compounds. The present
paper deals with the outcome of such studies.
worthy examples include 6p-electron gallium-based systems and
pseudo aromatic cyclic silylenes [1,2], novel cyclic tellurium imi-
des [3] and interesting aluminum–nitrogen heterocycles [4] among
others [5–8]. In addition to the studies on bonding and reactivity, a
further reason for studying inorganic rings is their potential use as
precursors to polymers and solid-state materials. The use of inor-
ganic rings to construct solid-state materials with novel properties
has also been successfully developed. For example, materials with
interesting electronic, magnetic and conductive properties have
been prepared from sulfur–nitrogen or selenium–nitrogen hetero-
cycles [9,10]. Further, inorganic rings have attracted considerable
attention as precursors to ceramics via thermolysis: examples in-
clude the use of aluminum–nitrogen or gallium–arsenic heterocy-
cles to prepare AlN and GaAs, respectively [11,12].
2. Experimental
All experiments were performed in dried glassware under puri-
fied nitrogen using standard inert atmosphere and vacuum line
techniques. Bis(trimethylsilyl)hydrazine [16,17], monolithium-
bis(trimethylsilyl)hydrazide [18–20], dilithiumbis(trimethylsilyl)
hydrazide [18–20] and n-butyllithium [21] were prepared as re-
ported in the literature. Special care was taken in the preparation
of monolithiumbis(trimethylsilyl)hydrazide as it tends to slowly
Heterocubanes are also a part of inorganic heterocycles. With
the synthesis of cubane came the realization that other cubic struc-
* Corresponding authors. Tel.: +91 0172 2534443; fax: +91 0172 2545074
(J. Kataria).
E-mail address: jyotkataria@yahoo.co.in (J. Kataria).
0022-328X/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2009.03.004

J. Kataria et al. / Journal of Organometallic Chemistry 694 (2009) 2252–2257
2253
disproportionate to dilithiumbis(trimethylsilyl)hydrazide and
bis(trimethylsilyl)hydrazine [19]. Therefore it is prepared in n-hex-
ane and at low temperature and the salt was dried as soon as it is
formed to rule out the possibility of disproportionation. Trimethyl-
silylchloride (Aldrich), dichlorostannane (Aldrich), and tetrachlo-
rostannane (Aldrich) were used as such. Diethyl ether and
tetrahydrofuran were dried over sodium benzophenoneketyl and
n-hexane was kept over sodium wire and distilled under nitrogen
prior to use. All NMR spectra were obtained on a Jeol AL 300 MHz
(FT NMR) apparatus using tetramethylsilane (1H, 29Si, 0 ppm), deu-
teriochloroform (13C, 77.1 ppm) and teramethyltin (119Sn, 0 ppm)
as reference standards. The mass spectra on a Jeol Mstation JMS
700 or a Varian MAT CH7 spectrometer. The mass spectrum data
are reported in mass to charge units (m/z) followed by their rela-
tive intensities and fractions lost in parentheses.
and SnCl2) and a pale yellow filtrate. The pale yellow filtrate on
cooling at ꢀ80 °C in liquid N2/acetone slurry gave colorless crystal-
line solid. Recrystallization provided colorless crystals of 5.
2.4. X-ray crystallography
X-ray structure analyses were done on Stoe IPDS. Crystals suit-
able for single crystal diffraction studies were grown by cooling a
saturated solution at ꢀ80 °C in liquid N2/acetone slurry. A plate
like single crystal with dimension 0.39 ꢁ 0.27 ꢁ 0.18 mm was
mounted along the largest dimension and used for data collection.
Single crystal X-ray diffraction data were collected at measure-
ment temperature of 200 K using an image plate detector system
(Stoe IPDS) with graphite monochromated Mo
Ka radiation
(k = 0.71073 Å). The crystal to image distances was set to 60 mm
and u-increment of 1.2° per exposure. The data were collected by
dynamic area detection mode. The data were corrected for Lorentz
and polarization factors and an analytical absorption correction
was also applied. All other relevant information about the data col-
lection is presented in Table 1.
2.1. [Me3Si(H)N-N-Sn]2, 3
Monolithium bis(trimethylsilyl)hydrazide (6.67 g, 36.6 mmol)
dissolved in 30 ml THF, was cooled to ꢀ20 °C and SnCl2 (3.47 g,
18.3 mmol), dissolved in 15 ml THF, was added dropwise with con-
stant stirring. On addition the color of the solution turned yellow to
orange and then to brown. After complete addition, the reaction
mixture was allowed to come to room temperature slowly over-
night. The color of the mixture turned yellow again. The reaction
mixture was evacuated to remove THF and other volatile impuri-
ties. The residue was then treated with 30 ml n-hexane. The mix-
ture was filtered to obtain white residue of LiCl (1.53 g,
36.0 mmol) and a yellow filtrate. 1H NMR of the filtrate showed
one main signal at d 0.10 ppm and small signals at d 0.34, 0.25
and 0.22 ppm. The filtrate was evacuated to remove n-hexane.
Fractional distillation at 100 °C/10ꢀ3 torr provided small amount
of BSH. The yellow solid left after evacuation, was crystallized from
hexane in liquid N2/acetone slurry. It was analyzed and found to be
3.
The structure was solved by Direct Methods using SHELX-97 [22]
package and also refined using the same one. All the non-hydrogen
atoms were refined anisotropically. The hydrogen atoms were re-
fined isotropically by initially fixing their geometrical positions
using the AFIX options in SHELX-97. A weighting scheme of the form
2
1=½r2ðF2oÞ þ ð0:0405PÞ ꢂ was used. The refinement converged to a
final
R value of 0.0331 (wR2 0.0711) for 3659 reflections
[I > 2r(I)]. The final difference Fourier map was featureless. All
other information regarding the refinement is also recorded in
Table 1.
3. Results and discussion
Monolithium bis(trimethylsilyl)hydrazide (1) reacts with
dichlorostannane in a redox reaction to form BSD, which on ther-
molysis [23] provides BSA and TrSH at room temperature. Forma-
tion of BSD is confirmed from 1H NMR recorded at different time
intervals during the course of the reaction. In 1H NMR the signal
2.2. [(Me3Si)N–Sn]4, 4
Dilithium bis(trimethylsilyl)hydrazide (5.17 g, 27.5 mmol), dis-
solved in 30 ml THF, was cooled to ꢀ40 °C and SnCl2 (5.22 g,
27.5 mmol), dissolved in 20 ml THF, was added to it dropwise with
constant stirring. On addition the color of the solution changed
from yellow to brick red to dark red. After complete addition the
reaction mixture was slowly allowed to come to room temperature
overnight. The color of the solution again turned to yellow. 1H NMR
of the clear solution showed one main signal at d 0.22 ppm and
some small signals at d 0.07, 0.11, 22.0 and 0.37 ppm. Evacuated
the reaction mixture thoroughly to remove THF and other volatile
impurities. Thick gelatinous solid was taken in 35 ml n-hexane and
filtered to get white solid of LiCl (2.274 g, 53.5 mmol) and a yellow
filtrate. 1H NMR of the filtrate in n-hexane showed one main signal
at d 0.21 ppm and two small signals at d 0.09 and 0.34 ppm. The fil-
trate was cooled at ꢀ80 °C in liquid N2/acetone slurry to get pale
yellow crystalline solid. Repeated crystallization provided pale yel-
low crystals of pure compound of 4.
Table 1
Crystal data and Structure refinement for 4.
Empirical formula
Formula weight
Temperature
Diffractometer used
Radiation used, wavelength
Crystal system, space group
Unit cell dimensions
C12H36N4Si4Sn4,0.5(C7H8)
869.69
200 K
Stoe IPDS
Mo K
monoclinic, Cc (No. 9)
a = 26.1398(14) Å = 90°
b = 12.0793(8) Å b = 110.262(6)°
a, 0.71073 Å
a
c = 21.8990(12) Å
6486.7(7) Å3
8, 1.781 g/cm3
3.202 mmꢀ1
3336
c = 90°
Volume
Z, Calculated density
Absorption coefficient
F(000)
Crystal size
Theta range for data collection
Index ranges
0.39 ꢁ 0.27 ꢁ 0.18 mm3
2.9–28°
ꢀ34 6 h634, ꢀ15 6 k 6 15,
ꢀ28 6 l 6 28
2.3. [(Me3Si)3N2Li], 5
Reflections collected
27635
Independent reflections
Refinement method
Data/restraints/parameters
Goodness-of-fit on F2
Weighting scheme
Data to parameter ratio
Final R indices, 3659 reflections
[I > 2r(I)]
14647 [Rint = 0.049]
Full-matrix least-squares on F2
14647/0/496
Dilithium bis(trimethylsilyl)hydrazine (6.87 g, 36.7 mmol), sus-
pended in 40 ml n-hexane, was cooled to ꢀ20 °C and SnCl4 (4.84 g,
18.3 mmol), dissolved in 20 ml n-hexane, was added to it dropwise
with constant stirring. After complete addition, the reaction mix-
ture was allowed to come to room temperature slowly overnight.
1H NMR of the reaction mixture showed two prominent signals
at d 0.12 and 0.41 ppm due to TrSH and Me3SiCl, respectively.
The solution was filtered to obtain white solid (mixture of LiCl
0.83
2
1=½r2ðF2oÞ þ ð0:0405PÞ ꢂ, P ¼ Fo2 þ 2 ꢃ F2c
29.53:1
R1 = 0.0331, wR2 = 0.0711
R indices (all data)
Largest difference in peak and hole
R1 = 0.0670, wR2 = 0.0799
0.63 and ꢀ0.70 e Åꢀ3

2254
J. Kataria et al. / Journal of Organometallic Chemistry 694 (2009) 2252–2257
well within the range observed for tin(II) compounds [25–28]. In
the bis(amino)stannylenes, the relative energies of electrons in
at d 0.21 ppm assigned to the methyl protons of (Me3Si)N group of
BSD slowly disappears as the reaction progresses. However, the
main reaction product is a pale yellow solid [(Me3Si)(H)N–N–
Sn)]2, 3 which is formed by a substitution reaction followed
Sn–N
r bonds is lower and therefore, the energy difference be-
tween the ground states and the relevant excited states is larger,
which causes a smaller contribution to the paramagnetic shielding
term in the tin amides than in the organostannylenes where 119Sn
chemical shift values are in the range of 2000–2500 ppm [29].
Its mass spectral analysis shows a molecular ion peak with rel-
ative low intensity at m/z 444. Other significant fragments are ob-
served at m/z 429, 414, 371, 356, 283, 268 indicating the loss of
radicals like Me, 2Me, Me3Si, (Me3Si)NH, (Me3Si)2NH and (Me3-
Si)HN–NH(SiMe3). An important fragment is observed at m/z
237 corresponding to the loss of radical (Me3SiN@Sn) from the
molecular ion. This is also supported by a metastable peak at
m/z 126 which provides evidence for the loss of molecule of (Me3-
SiN@Sn) due to the initial ionization at the largely polar Sn–N
bond.
by elimination. The yellow solid
3 can have two possible
configurations 1,3-bis(trimethylsilylamino)-1,3-diaza-2,4-distan-
nacyclobutane, 3a or 1,4-bis(trimethylsilyl)-1,2,4,5-tetraza-3,6-
distannacyclohexane, 3b.
3a could be formed by simple elimination of LiCl leading to the
formation of [(Me3Si)HN–N(Me3Si)(SnCl)] which further undergoes
intramolecular loss of Me3SiCl to form intermediate stannimine
[(Me3Si)HN–N'Sn]. It immediately dimerises to give 3a. On the
other hand, elimination of LiCl followed by intermolecular loss of
Me3SiCl will provide 3b (see equation).
1H NMR of 3 in benzene (toluene) shows one signal at d 0.23
(0.21) ppm for the methyl protons of (Me3Si)N groups. 13C NMR
in benzene (toluene) also shows a singlet at d ꢀ0.12 (ꢀ0.67) ppm
and 29Si NMR in d8-toluene shows a signal at d 4.06 due to (Me3-
Si)N group. 119Sn NMR indicates a signal at d 786 ppm (N–Sn–N
group). This value is much lower than that for compounds with
four coordinated tin(IV) hydrazine derivatives [24].
Sn
H
N
N
N
H
Me3Si
N
N
N
N
H
m* (calc.) = 126.5
-
Me3SiN Sn
H
SiMe3
Sn
SiMe3
Sn
Me3Si
H
SiMe3
Li
Me3Si
H
SiMe3
SnCl
N
N
N
N
+
SnCl2
-LiCl
X 2
Other important fragments are observed at m/z 222 (Me3SiN2HSn)+,
208 (Me3SiNHSn)+, 134 (NSn)+ and 73 (Me3Si)+. The mass spectral
analysis appears to support the configuration of 3b as 1,4-bis(tri-
methylsilyl)-1,2,4,5-tetraza-3,6-distannacyclohexane. Various at-
tempts to grow good crystals of the product were unsuccessful
and the unequivocal nature of the molecular structure could not
be ascertained.
(1)
Intramolecular
-
Me3SiCl
H
SiMe3
Cl Sn
SiMe3
H
N
N
N
N
Me3Si
SiMe3
Sn Cl Me3Si
N
N
Sn
H
Intermolecular
Stannimine
X 2
Dilithium bis(trimethylsilyl)hydrazide (2) reacts with dichlo-
rostannane leading to the simple elimination of LiCl followed
by anionic rearrangement [30] leading to the formation of
[(Me3Si)2N–N(Li)(SnCl)]. It further undergoes intramolecular loss
of LiCl to form intermediate stannimine [(Me3Si)2N–N@Sn], which
tetramerizes and further loses tetrakis(trimethylsilyl)tetrazene,
[(Me3Si)N]4, TST to give [(Me3Si)N–Sn]4, 4.
- 2 Me3SiCl
Sn
H
Me3Si
N
N
N
N
H
Sn
Me3Si
H
N
N
N
N
H
SiMe3
SiMe3
Sn
Sn
(3a)
(3b)
Me3Si
Me3Si
Me3Si
Li
SiMe3
Li
Me3Si
SiMe3
SnCl
anionic
rearrangement
N
N
N
N
N
N
SnCl2
+
-LiCl
SnCl
Li
Li
(2)
- LiCl
Me3Si
SiMe3
N
Sn
Me3Si
Sn
N
N
N
N
Sn
Sn
Me3Si
N
SiMe3
-
[(Me3Si)N]4
Me3Si
Stannimine
Sn
(4)
Its 1H NMR in toluene (hexane) shows one signal at d 0.25 (0.20)
ppm for the methyl protons of (Me3Si)N group. 13C NMR in toluene
shows a singlet at d ꢀ0.38 ppm for (Me3Si)N group. 29Si NMR in
The literature reports that 119Sn nuclear shielding decreases with
the decrease in the coordination number of tin and this value falls

J. Kataria et al. / Journal of Organometallic Chemistry 694 (2009) 2252–2257
2255
toluene shows a triplet at d 4.19 due to (Me3Si)N group. 119Sn NMR
Table 2
Important bond lengths [Å] and angles [°] in 4.
indicates a singlet at d 783.49 ppm for the Sn–N groups which falls
in the range observed for two coordinated tin(II) amino derivatives
[25–28]. In addition to that the coupling of three 14N nuclei (I = 1)
around each 119Sn atom split the 119Sn signal into a septet with a
coupling constant of 1J (14N, 119Sn) = 101.7 Hz and 2J (117Sn,
119Sn) = 59 Hz.
Sn1–N1
2.187(13)
1.776(17)
2.188(14)
2.276(19)
2.179(16)
2.271(19)
Sn1–N3
Sn1–N4
Sn2–N3
Si4–N4
Sn4–N2
Si1–N1
2.195(18)
2.186(19)
2.228(18)
1.714(18)
2.197(15)
1.773(16)
Si2–N2
Sn2–N2
Sn3–N4
Sn4–N1
Sn4–N3
It is evident from the 119Sn chemical shifts of transition metal
complexes of bis(amino)stannylenes [31], that the engagement of
the lone pair of electrons at the tin atom in M–Sn bonds does not
induce a dramatic shift of the 119Sn NMR signal. Thus, paramag-
netic effects as the result of Bo induced charge circulation involving
the formally unoccupied Sn-pz orbital arises mainly from the lone
pair of electrons at the tin atom. This explains that the dimeriza-
tion of stannylenes causes a marked increase in 119Sn nuclear
shielding since the Sn-pz orbital is now used in donor–acceptor
interaction [25].
Mass spectrum of 4 shows molecular ion peak at m/z 824 and
the observed isotopic pattern agrees quantitatively with that cal-
culated for C12H36N4Si4Sn4. The molecular ion shows the loss of
Me, SiMe3 and SiMe4 at m/z 809, 751 and 736 before losing stanni-
mine (Me3Si)HNN@Sn at m/z 602. This loss is supported by a meta-
stable peak at m/z 440. The molecular ion M0 (m/z = 602) shows
fragment at m/z 572 for the loss of 2Me. The other prominent peak
is observed at m/z 453 indicating the loss of (Me3Si–SiMe3), which
is supported by a metastable peak at m/z 339. Other significant
fragments are observed at m/z 397 [SnN2(SiMe3)3(Me2)], 221 (Me3-
SiNNSn), 192 (Me3SiSn), 147 (Me3Si–SiMe3), 119 (Sn), 100 (Me3-
SiN2), 86 (Me3SiN) and 73 (Me3Si). Base peak is observed at m/z
147 corresponding to (Me3Si–SiMe3). The mass spectrum appears
to support the cubane structure, which is further supported by
X-ray crystallography.
Good single crystals of 4 have been grown by slowly cooling a
saturated solution in n-hexane at ꢀ80 °C in liquid N2/acetone slur-
ry. A perspective ORTEP view of the molecules with atom numbering
scheme is shown in Fig. 1. Details of data collection and structural
refinement are given in Table 1. The molecule crystallizes in mono-
clinic crystal system (Cc space group) with two independent mol-
ecules in the asymmetric unit. The cuboid nature of the (Sn–N)4
moiety is amply evident from figure and this is the first crystal
structure of an inorganic cuboid entirely build up of tin and nitro-
gen atoms synthesized from the hydrazide salts. The cube is not
perfect as can be observed from the selected bond lengths and
bond angles shown in Table 2.
Sn2–N3–Si3
Sn1–N3–Sn2
Sn1–N3–Si3
Sn3–N4–Si4
Sn3–N1–Sn4
Sn1–N1–Sn4
Sn2–N2–Sn3
N–Sn–N
120.5(10)
Sn4–N3–Si3
Sn1–N3–Sn4
Sn2–N3–Sn4
Sn1–N4–Sn3
Sn1–N1–Sn3
Sn1–N1–Si1
Sn4–N2–Si2
118.1(9)
97.5(6)
124.2(11)
116.5(9)
98.5(6)
98.1(6)
98.2(6)
95.2(7)
94.7(7)
95.8(7)
98.9(6)
119.2(9)
118.2(8)
81.1–83.7
In one of the cuboid structures due to the distortion of the cube
to a greater extent the Sn–Sn contacts are 3.299 Å (Sn4ꢄꢄꢄSn1) and
3.296 Å (Sn4ꢄꢄꢄSn3), respectively.
The Sn–N bond length at the edges of the cube has a consider-
able variation and it ranges from 2.139 to 2.276 Å. Similarly the an-
gles vary from 94.7° to 98.9° around the Sn atoms. One of the
bonds associated with the Sn–N being a coordinate bond is slightly
longer than the other two bonds, the maximum difference being
0.137 Å. To avoid the eclipsing interactions of the methyl groups
with Sn–N edges the methyl groups of the –SiMe3 moiety occupies
a staggered position (for example, Sn3–N9–Si8–C18 = 64.3°) as
shown in Fig. 2. In the figure, C18, C27 and C29 carbon atoms are
in between the three Sn atoms at the corners of the cube and this
is true for all the four –SiMe3 groups attached to the corners of the
cube.
It is interesting that there are 0.5 molecules of toluene per one
cuboid moiety in the crystal lattice. These toluene molecules are
incorporated into the lattice upon crystallization. The cuboid struc-
ture of 4 forms linear channels running through the ac plane and
stabilize the lattice (Fig. 3). However there are no short contacts of
hydrogen atoms with heteroatoms (or between the heavier atoms)
observed in the lattice. The lattice structure is hence stabilized
through van der Waal’s interactions. The single crystal x-ray diffrac-
tion study of compound 4 produces a comparable result as reported
by Veith et al. [32]. This group has synthesized the compound from
the reaction of the cyclic diazastannylene 1 with primary silylam-
ines. Another research group of William Jr. have also synthesized
the similar compound using stannylamine and SnCl2 [33].
Fig. 1. A perspective view of one of the cuboid structures of 4 in the asymmetric
unit. Hydrogen atoms are not shown for clarity.
Fig. 2. A projection of the second molecule of 4 down Si8–N8 bond.

2256
J. Kataria et al. / Journal of Organometallic Chemistry 694 (2009) 2252–2257
Fig. 3. Packing of the molecules of 4 viewed down the ac plane.
Me3Si
Li
SiMe3
Li
Me3Si
Li
SiMe3
SiMe3
Tetrachlorostannane reacts with 1 at low temperature to give a
N
N
Me3SiCl
+
N N
blue colored reaction mixture. The blue color disappears slowly as
the reaction mixture is allowed to come to room temperature over
a period of time. Probably SnCl4 oxidizes 1 to form bis(trimethyl-
silyl)diazene, BSD as indicated in the 1H NMR.
- LiCl
(2)
(5)
Compound 5 is a white crystalline solid which catches fire on expo-
sure to traces of air or moisture. Its 1H NMR in benzene shows two
signals at d 0.11 and 0.93 ppm in the intensity ratio 2:1 for (Me3-
Si)2N and (Me3Si)N groups. 13C NMR in benzene shows two signals
at d 0.50 and 0.88. 29Si NMR (1H-decoupled) in CDCl3 also shows two
signal at d 22.78 and 23.51 ppm due to (Me3Si)2N and (Me3Si)N
groups, respectively. Mass spectrum of the molecule shows a
molecular ion peak at m/z 248. Fragments corresponding to the loss
of Me, 2Me, 3Me and Me3Si are quite significant. Base peak in the
spectrum corresponds to (Me3Si–SiMe3)+ at m/z 147.
Synthesis and reactivity of compound 5 is already reported in
the literature [34–37]. Compound 5 dissolves in n-hexane and slow
cooling provided colorless crystals suitable for X-ray crystal struc-
ture determination. Crystal structure of this compound has already
been undertaken by Metzler et al. [38].
Me3Si
SiMe3
N
N
SnCl4
+
Me3Si N N SiMe3
+
SnCl2
-LiCl
-HCl
Li
H
(BSD)
(1)
Bis(trimethylsilyl)diazene, BSD, Me3SiN@NSiMe3 is a well-known
compound which tends to thermolyses above ꢀ30 °C [23] or it
may react further with the Lewis acid at low temperature. The
decomposition products above ꢀ30 °C vary with the reaction condi-
tions and catalytic effects of the Lewis and protic acids. The decom-
position products of BSD are reported and they are TSH, BSA and
TrSH.
On the other hand, dilithiumbis(trimethylsilyl)hydrazide
2
reacts with tetrachlorostannane in a redox manner to form
BSD, which further reacts with SnCl4 to form Me3SiCl and N2 is re-
leased.
4. Summary
Me3Si
SiMe3
Tetrachlorostannane acts primarily as an oxidant and oxidizes 1
to mainly bis(trimethylsilyl)amine, BSA and tris(trimethyl-
silyl)hydrazine, TrSH and itself get reduced to SnCl2. Similarly,
reaction of SnCl4 with 2, oxidizes it to lithium tris(trimethyl-
N
N
SnCl4
+
Me3Si N N SiMe3
+
SnCl2
- 2LiCl
Li
Li
(BSD)
(2)
ꢀ
silyl)hydrazide, 5. It crystallizes in triclinic space group ðP1Þ with
two molecules in the asymmetric unit.
Me3Si
N
N
SiMe3
SnCl 4
+
SnCl2
+ 2Me3SiCl
+ N2
Reaction of dichlorostannane (reduction of oxidation state of
tin from +4 to +2) with 1 gives a simple substitution reaction and
give a pale yellow solid, 1,4-bis(trimethylsilyl)-1,2,4,5-tetraza-
3,6-distannacyclohexane, 3b. Whereas, in reaction of 2 with SnCl2
(BSD)
This Me3SiCl reacts with another molecule of 2 to give lithium
tris(trimethylsilyl)hydrazide, [(Me3Si)3N2Li], Li-TrSH, 5.

J. Kataria et al. / Journal of Organometallic Chemistry 694 (2009) 2252–2257
2257
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intermediate stannimine [(Me3Si)2N–N@Sn], tetramerizes and fur-
ther loses TST, [(Me3Si)N]4 to give [(Me3Si)N–Sn]4, 4. Good single
crystals of 4 have been grown by slowly cooling a saturated solu-
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crystal X-ray structure determination was carried out. The mole-
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two independent molecules in the asymmetric unit. The structure
shows a cuboid architecture in which four tin atoms and four nitro-
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inorganic cuboid entirely build up of tin and nitrogen atoms syn-
thesized from the hydrazide salts.
5. Supplementary material
CCDC 715953 contains the supplementary crystallographic data
for 4. These data can be obtained free of charge from The Cam-
bridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/da-
ta_request/cif.
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