Synthesis and characterization of 2,5,7-trichalcogena-1,3,4,6-tetrasilanorbornanes (RMeSiSiMe)2E3 (R=Me, Ph/E=S, Se, Te)

Article abstract of DOI:10.1016/S0022-328X(01)00741-0

The reactions of the trichlorodisilanes ClRMeSi-SiMeCl₂ (R=Me, Ph) with either H₂S/NEt₃ or Li₂E (E=Se, Te) result in the selective formation of 2,5,7-trichalcogena-1,3,4,6-tetrasilanorbornanes (RMeSiSiMe)₂E₃ (R=Me, Ph/E=S, Se, Te). In the cases of R=Ph, three stereoisomers with different spatial orientations of the phenyl substituents arise. The isomers with both phenyl substituents in equatorial positions are formed preferably. All products have been characterized by multinuclear NMR spectroscopy including ¹J_SiSe and ¹J_SiTe coupling constants. A crystal structure analysis of the isomer of (PhMeSiSiMe)₂S₃ with both phenyl substituents in equatorial positions reveals a very small bond angle at the bridging sulfur atom of 88.5° which is even 4.6° smaller than in the parent norbornane C₇H₁₂.

Full text of DOI:10.1016/S0022-328X(01)00741-0

Journal of Organometallic Chemistry 627 (2001) 144–152
www.elsevier.nl/locate/jorganchem
Synthesis and characterization of
2,5,7-trichalcogena-1,3,4,6-tetrasilanorbornanes (RMeSiSiMe)2E3
(R=Me, Ph/E=S, Se, Te)
U. Herzog a,*, U. Bo¨hme a, G. Rheinwald b
a Institut fu¨r Anorganische Chemie der TU Bergakademie Freiberg, Leipziger Str. 29, D-09596 Freiberg, Germany
b Institut fu¨r Chemie, Lehrstuhl Anorganische Chemie, TU Chemnitz, Straße der Nationen 62, D-09111 Chemnitz, Germany
Received 18 December 2000; received in revised form 16 January 2001; accepted 2 February 2001
Abstract
The reactions of the trichlorodisilanes ClRMeSi–SiMeCl2 (R=Me, Ph) with either H2S/NEt3 or Li2E (E=Se, Te) result in the
selective formation of 2,5,7-trichalcogena-1,3,4,6-tetrasilanorbornanes (RMeSiSiMe)2E3 (R=Me, Ph/E=S, Se, Te). In the cases
of R=Ph, three stereoisomers with different spatial orientations of the phenyl substituents arise. The isomers with both phenyl
substituents in equatorial positions are formed preferably. All products have been characterized by multinuclear NMR
1
1
spectroscopy including JSiSe and JSiTe coupling constants. A crystal structure analysis of the isomer of (PhMeSiSiMe)2S3 with
both phenyl substituents in equatorial positions reveals a very small bond angle at the bridging sulfur atom of 88.5° which is even
4.6° smaller than in the parent norbornane C7H12. © 2001 Elsevier Science B.V. All rights reserved.
Keywords: Norbornane; Silane; Silthiane; Selenium; Tellurium
1. Introduction
Cyclic and polycyclic silthianes and related selenium
and tellurium derivatives have been investigated for
some time but only a small number of reports deals
with structures containing Si–Si bonds [1–5]. In previ-
ous papers we could show that numerous new cyclic
and polycyclic systems can be built starting from suit-
ably substituted oligosilanes [6–9].
All these investigations also reveal that in these sys-
tems five membered rings Si3E2 (E=S, Se, Te) are the
most favoured ring type.
One silthiane having a norbornane skeleton has al-
ready been published by Wojnowski et al. [10]. It is
formed in a surprisingly clean reaction starting from
1,4-dichlorodecamethylcyclohexasilane:
Remarkable is the relatively small angle at the sulfur
,
atom in 1 of 94.9° while the bond lengths SiS (2.17 A)
,
and SiSi (2.34 A) are in the usual range.
2. Results and discussion
The reactions of 1,1,2-trichlorotrimethyldisilane (2a)
with either H2S/NEt3 or Li2Se yield in clean reactions
the norbornanes (Si2Me3)2E3, E=S (3a), E=Se (3b)
while the reaction with Li2Te failed:
* Corresponding author. Tel.: +49-3731-394343; fax: +49-3731-
394058.
E-mail address: herzog@merkur.hrz.tu-freiberg.de (U. Herzog).
0022-328X/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(01)00741-0

U. Herzog et al. / Journal of Organometallic Chemistry 627 (2001) 144–152
145
Fig. 1. ZORTEP plot of the two crystallographically independent
molecules (A left, B right) in the crystal structure of racemic 4a.
NMR spectra of 4–6 show, that all three diastereomers
a–c are formed but in different amounts. Isomer b
gives raise to four different 29Si-NMR chemical shifts
and can therefore be identified unambiguously. The
isomer, which is formed in relatively small amounts (8%
for E=S, 10% for E=Se, 11.5% for E=Te) is likely
to be the isomer c were both phenyl substituents are in
axial positions, which is less favoured due to steric
interactions. The longer Si–Se and Si–Te bonds in
respect to Si–S bonds in 4a–c increase the distance
between the phenyl rings in the isomers c and hence,
the content of this isomer raises from E=S to E=Te.
Density functional theory (DFT) calculations of 3a as
well as the three isomers 4a–c were carried out, see
Table 1. Scheme 2 represents the calculated relative
energies of 4a–c confirming that 4a is the most stable
isomer.
Scheme 1. Stereoisomers of (Si2Me2Ph)2E3, E=S (4a–c), Se (5a–c),
Te (6a–c).
Both compounds are colourless liquids which could
be identified by NMR spectroscopy and mass
spectrometry.
In order to obtain crystalline norbornane derivatives
2a was exchanged for 1-phenyl-1,2-dimethyltrichloro-
disilane (2b). The reactions with H2S/NEt3 and Li2E
(E=Se, Te), respectively, yielded the expected norbor-
nanes (Si2Me2Ph)2E3, E=S (4a–c), Se (5a–c), Te (6a–
c).
Fractional crystallization of 4a–c from a CDCl3–
hexane solution yielded single crystals of 4a, the isomer,
which is formed in 53% amount. Fig. 1 shows the result
of a crystal structure analysis. Both enantiomers of 4a
are present in the asymmetric unit because of crystallo-
graphic symmetry. The asymmetric unit contains two
crystallographic independent molecules with almost
identical bond lengths and angles. The largest differ-
Due to the different spatial orientations of the phenyl
substituents three isomers are formed in each case, see
Scheme 1.
Additionally all norbornanes discussed in this paper
are chiral and consist of pairs of enantiomers. The
Table 1
Calculated total energies and geometry parameters (B3LYP/6-31 G*) of the norbornanes 3a and 4a–c (numbering of Si1–Si4 and S1–S3 are in
analogy to molecule A in Fig. 1)
3a
4a
4b
4c
Total energy (H)
Total energy with zero point correction (H)
−2592.30580
−2592.07037
−2975.77342
−2975.42954
−2975.77183
−2975.42776
−2975.77070
−2975.42647
,
d(Si1–Si2) (A)
2.370
2.187
2.182
2.183
2.372
2.196
2.186
2.182
2.368/2.370
2.199/2.201
2.184/2.185
2.183/2.184
2.368
2.204
2.184
2.186
,
d(Si1–S1) (A)
,
d(Si4–S1) (A)
d(Si2–S3) (A)
,
Ú(Si2–S3–Si4) (°)
Ú(Si1–S1–Si4) (°)
Ú(Si2–Si1–S1) (°)
Ú(Si1–Si2–S2) (°)
Ú(Si1–Si2–S3) (°)
Ú(S2–Si2–S3) (°)
89.1
99.5
102.1
108.9
101.2
109.2
88.9
99.5
102.1
108.9/109.3
101.7/101.9
108.5
89.1
99.7/100.2
101.5
107.8/111.8
99.6/101.6
108.5/109.3
89.3
100.2
101.1
110.8
99.2
109.2

/
627
(
Scheme 2. Calculated (B3LYP/6-31G*) geometries and relative energies of the stereoisomers 4a–c.
144
152

U. Herzog et al. / Journal of Organometallic Chemistry 627 (2001) 144–152
147
ences occur in the orientations of the phenyl rings, what
can be described by the dihedral angles C–C–Si–Si.
While the dihedral angles C(22)–C(17)–Si(5)–Si(6) and
C(30)–C(25)–Si(7)–Si(8) of molecule B are relatively
similar (+63.42 and +76.74°, respectively) the angles
C(2)–C(1)–Si(1)–Si(2) and C(10)–C(9)–Si(3)–Si(4) in
molecule A are quite different (−71.07 and +73.39°,
respectively). Some important bond lengths and angles
are summarized in Table 2. The most interesting feature
of the structure are the angles at the sulfur bridges S3
and S6 which are with 88.5° by 6.4° smaller than in 1
and also 4.6° smaller than the angle of 93.1° at the
bridging methylene unit in the parent hydrocarbon
norbornane C7H12 [11]. A result of these small angles at
S3 and S6 are also small Si–Si distances (Si2–Si4 and
The calculated geometry of 4a (see Table 1) is in a
good agreement with the result of the X-ray structure
analysis, especially in terms of the unusual angle at the
bridging sulfur atom. As the calculations show, this
angle as well as the whole symmetry within the norbor-
nane skeleton remains almost unchanged in the other
isomers 4b–c as well as in the permethylated norbor-
nane 3a. The values of the calculated dihedral angles
C(2)–C(1)–Si(1)–Si(2) and C(10)–C(9)–Si(3)–Si(4) are
with +68.0 and +74.6° similar to the observed angles
in molecule B in the crystal structure, see above. These
dihedral angles allow a maximal distance between the
phenyl rings and the methyl groups at Si2 and Si4,
respectively. Crystal packing forces may be responsible
for the different dihedral angles found for molecule A
in the crystal structure.
,
Si6–Si8), which are with 3.01 A only 28% larger than a
normal Si–Si single bond [12]. Nevertheless there is no
indication of a Si–Si bond by means of NMR
spectroscopy.
As for other silicon sulfur compounds, calculated
previously with the same method [6,9,13], the calculated
,
SiS as well as SiSi bonds are in average 0.02 A longer
On the other hand the angles at the other sulfur
atoms (S1, S2, S4 and S5) are with 98–99° in the usual
range for five-membered rings Si3S2 in polycyclic
silthianes.
than the values found by X-ray analysis.
Tables 3–6 summarize the H-, 13C-, 29Si-, 77Se- and
1
125Te-NMR data of the prepared norbornanes. The
1
1
assignment of the coupling constants JSiSe and JSiTe
was possible unambiguously by observing the satellites
in the 29Si- as well as in the 77Se- and 125Te-NMR
spectra, respectively.
Table 2
,
Selected bond lengths (A) and angles (°) of (a) molecule A and (b)
molecule B in the X-ray structure of 4a
Compared with the 29Si-NMR chemical shifts of the
related acyclic chalcogenobutyl substituted disilanes
(BuE)2SiAMe–SiBMe2(EBu), E=S: lA: 10.3 ppm, lB:
−0.8 ppm [14]; E=Se: lA: 0.8 ppm, lB: −6.0 ppm
[15] having the same first coordination spheres at sili-
con, the chemical shifts in the norbornanes 3a and 3b
are shifted by some 11 ppm (E=S) and 14–20 ppm
(E=Se) to lower field. This confirms the general trends
of lSi in five-membered rings Si3E2 as discussed in detail
in [7]. On the other hand the coupling constants 1JSiSi in
the norbornanes are close to the values in the acyclic
disilanes (BuE)2SiMe–SiMe2(EBu) with the same E. A
comparison of lSe and lTe of analogous E atoms in
5a–c and 6a–c is shown in Fig. 2.
A linear correlation of lSe and lTe with a slope of
2.44 are found for the positions of EB and EC (assign-
ment see Tables 3 and 4). This is in good agreement
with observations in other cyclic and polycyclic silse-
lenides and -tellurides where a slope of 2.49 has been
found [7] whereas the slope increases to 3.16 for the
bridging EA atoms in 5a–c and 6a–c.
Atoms
Bond length
Atoms
Bond angle
(°)
,
(A)
(a)
Si(1)–Si(2)
Si(3)–Si(4)
Si(1)–S(1)
Si(3)–S(2)
Si(2)–S(2)
Si(4)–S(1)
Si(2)–S(3)
Si(4)–S(3)
Si(1)–C(1)
Si(3)–C(9)
Si(1)–C(7)
Si(3)–C(15)
Si(2)–C(8)
Si(4)–C(16)
2.351(3)
2.352(3)
2.164(3)
2.166(3)
2.152(3)
2.141(3)
2.148(3)
2.155(3)
1.867(8)
1.853(7)
1.841(7)
1.872(8)
1.853(8)
1.863(6)
Si(1)–S(1)–Si(4)
Si(3)–S(2)–Si(2)
Si(2)–S(3)–Si(4)
Si(1)–Si(2)–S(2)
Si(3)–Si(4)–S(1)
Si(2)–Si(1)–S(1)
Si(4)–Si(3)–S(2)
Si(1)–Si(2)–S(3)
Si(3)–Si(4)–S(3)
S(1)–Si(4)–S(3)
S(2)–Si(2)–S(3)
C(1)–Si(1)–C(7)
C(9)–Si(3)–C(15)
98.1(1)
98.3(1)
88.6(1)
109.2(1)
108.4(1)
103.1(1)
102.8(1)
101.4(1)
102.3(1)
109.2(1)
109.0(1)
111.6(3)
110.1(3)
(b)
Si(5)–Si(6)
Si(7)–Si(8)
Si(5)–S(4)
Si(7)–S(5)
Si(6)–S(5)
Si(8)–S(4)
Si(6)–S(6)
Si(8)–S(6)
Si(5)–C(17)
Si(7)–C(25)
Si(5)–C(23)
Si(7)–C(31)
Si(6)–C(24)
Si(8)–C(32)
2.353(3)
2.337(3)
2.164(3)
2.162(3)
2.148(3)
2.147(3)
2.155(2)
2.163(3)
1.861(8)
1.868(7)
1.852(7)
1.843(8)
1.870(7)
1.852(6)
Si(5)–S(4)–Si(8)
Si(7)–S(5)–Si(6)
Si(6)–S(6)–Si(8)
Si(5)–Si(6)–S(5)
Si(7)–Si(8)–S(4)
Si(6)–Si(5)–S(4)
Si(8)–Si(7)–S(5)
Si(5)–Si(6)–S(6)
Si(7)–Si(8)–S(6)
S(4)–Si(8)–S(6)
S(5)–Si(6)–S(6)
99.0(1)
98.7(1)
88.5(1)
107.1(1)
108.7(1)
102.4(1)
102.9(1)
102.0(1)
101.8(1)
109.0(1)
109.9(1)
3. Experimental
3.1. NMR and GC–MS measurements
C(17)–Si(5)–C(23) 109.8(3)
C(25)–Si(7)–C(31) 111.6(3)
All NMR spectra in solution were recorded on a
Bruker DPX 400 in CDCl3 solution and TMS as inter-
1
nal standard for H, 13C and 29Si. External Ph2Se2 (lSe:

148
U. Herzog et al. / Journal of Organometallic Chemistry 627 (2001) 144–152
Table 3
29Si-, 13C- and 1H-NMR data of the norbornanes (MeSiSiMeR)2S3 (R=Me (3a), Ph (4a–c))
460 ppm) and Ph2Te2 (lTe: 422 ppm) in CDCl3 were
used as standards for 77Se and 125Te.
ture was solved using direct methods (SIR-97 [19]),
refined using least-squares methods (SHELX-97) and
drawn using ZORTEP [20].
In order to get a sufficient signal/noise ratio of 29Si
1
1
1
1,2
NMR spectra for obtaining JSiC, JSiSi, JSiSe or
J
SiTe
satellites 29Si INEPT spectra were also recorded. 77Se
and 125Te spectra were recorded using an igated pulse
program.
3.3. Theoretical methods
The ab initio molecular orbital calculations were
carried out using the GAUSSIAN-98 series of programs
[21]. Geometries were fully optimized at the DFT level,
using Becke’s three-parameter hybrid exchange func-
tional and the correlation functional of Lee et al.
(B3LYP) [22,23]. Geometry optimizations, harmonic
frequencies, and zero-point vibrational energies were
calculated with the polarized 6-31G* basis set for C, H,
S and Si [24,25]. All structures were identified as true
local minima by their Hessian matrices.
GC–MS spectra were measured on a Hewlett–Pack-
ard 5971 (ionization energy: 70 eV, column: 30 m×
0.25 mm×0.25 mm, phenylmethylpolysiloxane, column
temperature: 100°C (3 min)/20 K min−1, flow: He 0.5
ml min−1).
3.2. Crystal structure analysis
X-ray structure analysis measurements were per-
formed on a Bruker smart CCD. Crystal data of 4a as
well as data collection and refinement details are given
in Table 7.
3.4. Starting materials
The unit cell was determined with the program smart
[16]. For data integration and refinement of the unit cell
the program SAINT [10] was used. The space group was
determined using the program absen [17]. All data were
corrected for absorption using sadabs [18]. The struc-
H2S (N25, Air Liquide), Se, Te, triethylamine, 1 M
LiBEt3H in THF (Super Hydride) were commercially
available. Complex 2a was prepared as described previ-
ously [26]. THF was distilled from sodium potassium
alloy prior to use. The other solvents were dried over

U. Herzog et al. / Journal of Organometallic Chemistry 627 (2001) 144–152
149
Table 4
Table 5
29Si- and 77Se-NMR data of the norbornanes (MeSiSiMeR)2Se3
29Si- and 125Te-NMR data of the norbornanes (MeSiSiMePh)2Te3
(R=Me (3b), Ph (5a–c))
(6a–c)
Table 6
13C- and 1H-NMR data of the norbornanes (MeSiSiMeR)2E3 (R=Me, E=Se (3b); R=Ph, E=Se (5a–c), E=Te (6a–c)) (for assignment of the
silyl units A–D see Tables 4 and 5)
Compound
lC (SiMe)
E=Se
lC (SiPh)
E=Se
–
lH
E=Te
E=Te
E=Se
E=Te
3b
A: 1.97
B: −0.04/0.14
–
–
–
A: 1.11
B: 0.70/0.48
–
−
5a/6a
A: −2.18
B: −0.08
A: −2.65
B: −1.22
i: 135.15
o: 134.17
m: 127.92
p: 129.59
i: 134.66
o: 134.54
m: 127.89
p: 129.39
A: 1.03
B: 0.97
Ph: o: 7.30
m: 7.65
p: 7.35
A: 1.09
B: 0.99
5b/6b
A: −2.48
B: 0.67
C/D: 0.09/0.06
A: −2.83
B: −1.73
C/D: −1.31/−1.33
C: i: 135.18
o: 134.2
m: 127.9
p: 129.60
D: i: 133.64
o: 134.68
m: 127.9
i:
A: 1.02
B: 1.11
C: 0.97
D: 0.76
A: 1.07
B: 1.11
C: 1.01
D: 0.80
o: 134.60
m: 127.9
p: 129.40
i:
o: 135.25
m: 127.9
p: 129.80
p: 129.87
5c/6c
A: 0.75
B: 0.27
A: −1.90
B: −1.26
i: 133.57
o: 135.03
m: 127.9
p: 129.83
i:
A: 1.11
B: 0.74
o: 135.22
m: 127.9
p: 129.79

150
U. Herzog et al. / Journal of Organometallic Chemistry 627 (2001) 144–152
KOH or sodium wire. All reactions were carried out
under argon applying standard Schlenk techniques.
100 ml of diethyl ether (prepared from 16 g (0.10 mol)
PhBr and 2.5 g (0.11 mol) Mg) was slowly added under
stirring to a solution of 27.4 g (0.12 mol) of 1,1,2,2-te-
trachlorodimethyldisilane in 50 ml of diethyl ether. The
solvent was removed in vacuo and replaced by 100 ml
of hexane. The mixture was filtered from precipitated
magnesium salts and distilled under reduced pressure to
give 16.55 g (0.061 mol) 2b, Kp1: 110°C.
3.5. Preparation of
1-phenyl-1,2-dimethyltrichlorodisilane (2b)
A solution of 0.1 mol phenylmagnesium bromide in
3.5.1. PhMeClSiA–SiBCl2Me (2b)
1
29Si-NMR: lA: 3.80 ppm, lB: 23.53 ppm, JSiSi: 127.8
Hz; 13C-NMR: lMeA: −0.61 ppm (1JSiC: 53.7 Hz),
lMeB: 5.81 ppm (1JSiC: 54.4 Hz), Ph: li: 131.49 ppm, lo:
133.68 ppm, lm: 128.44 ppm, lp: 131.07 ppm; 1H-
NMR: lMeA: 0.86 ppm, lMeB: 0.89 ppm, Ph: 7.65 ppm
(2 H), 7.41 (3 H).
GC–MS: 268/270 (M+, 4), 253 (M–Me, 1), 233
(M–Cl, 1), 175 (PhSiCl2, 1), 155 (MePhSiCl, 100), 135
(Me2PhSi, 2), 120 (PhSi, 3), 105 (PhSi, 5), 77 (Ph, 3).
Due to the use of phenylmagnesium bromide the
product contained also small amounts (10% each) of
the two 1-phenyl-1,2-dimethylbromodichlorosilanes
PhMeBrSiA–SiBCl2Me (lSiA: −1.5 ppm, lSiB: 22.3
Fig. 2. Comparison of lSe and lTe in the norbornanes 5a–c (E=Se)
and 6a–c (E=Te) (for assignment of A, B and C see Tables 4 and 5).
ppm) and PhMeClSiA–SiBClBrMe (lSiA
: 3.68/3.64
ppm, lSiB: 18.25/18.05 ppm, two diastereomers in equal
amounts) but this had no consequences for the further
reactions of 2b.
Table 7
Crystal data of 4a as well as data collection and refinement details
4a
The distillation residue (1.5 g) consisted of Ph-
MeXSi–SiXMePh (X=Cl, Br): PhMeClSi–SiClMePh
(40%, lSi: 6.47/6.25 ppm, two diastereomers in equal
amounts), PhMeClSiA–SiBBrMePh (40%, lSiA: 5.86/
5.59 ppm, lSiB: 1.48/1.17 ppm, two diastereomers in
equal amounts), PhMeBrSi–SiBrMePh (20%, lSi: 0.83/
0.43 ppm, two diastereomers in equal amounts).
PhMeClSi–SiClMePh GC–MS: 310 (M+, 2), 275
(M–Cl, 1), 217 (Ph2SiCl, 1), 197 (MePh2Si, 100), 155
(MePhSiCl, 43), 120 (PhSi, 25), 105 (PhSi, 22) (two GC
peaks with identical MS due to the two diastereomers).
Crystal system
Space group
Unit cell dimensions
Monoclinic
P21/c
,
a (A)
16.483(2)
33.464(5)
8.036(1)
100.078(3)
4364.2(11)
8
,
b (A)
,
c (A)
i (°)
3
,
Volume (A )
Z
Dcalc. (g cm−3
)
1.287
0.556
Linear absorption coefficient
(mm−1
)
Radiation used
Mo–Ka
Temperature (K)
173(2)
Scan method
ꢀ-scans
Empirical
0.957/0.851
21 353
10 306
3525
0.1608
1.25–30.65
76.3
3.6. Preparation of 1,3,3,4,6,6-hexamethyl-2,5,7-
trithia-1,3,4,6-tetrasilanorbornane (3a)
Absorption correction
Max./min. transmission
Measured reflections
Independent reflections
Observed reflections (\2|I)
Rint
q Range for collection (°)
Completeness to qmax (%)
Refinement method
A total of 0.52 g (2.5 mmol) of 2a was diluted with
20 ml of hexane and a stream of dried H2S was bubbled
through the stirred solution while 1.04 ml (7.5 mmol) of
NEt3 was slowly added. After filtration from the precip-
itated ammonium salt the solvent was removed in
vacuo and the colourless oily residue, already pure 3a,
could be distilled at 80°C/0.03 Torr without
decomposition.
Full-matrix least-squares on
F2
Final R1 (I\2|(I))
R1 (all data)
0.0724
0.2645
difmap/refall
0.926
0.476/−0.522
H-locating and refining
3a GC–MS (m/e, rel. int.): 298 (M+, 47), 283 (M–
Me, 40), 239 (M–SiMe2H, 24), 223 (Me5S2Si3, 22), 165
(Me3S2Si2, 27), 73 (Me3Si, 100).
Goodness-of-fit on F2
−3
,
Max./min. e-density (e A
)

U. Herzog et al. / Journal of Organometallic Chemistry 627 (2001) 144–152
151
3.7. Preparation of 1,3,3,4,6,6-hexamethyl-2,5,7-
triselena-1,3,4,6-tetrasilanorbornane (3b)
5a, 40% 5b and 10% 5c and 44.5% 6a, 44% 6b and
11.5% 6c, respectively.
A total of 0.42 g (2 mmol) of 2a was added at 0°C to
a suspension of 3 mmol Li2Se, prepared from 0.24 g (3
mmol) of selenium powder and 6 ml of a 1 M LiBEt3H
solution in THF. The solvent was removed in vacuo
and replaced by 10 ml of hexane. The mixture was
filtered from precipitated lithium salts and the solvent
removed in vacuo to give pure 3b as an oily liquid in
approximately 60% yield.
4. Supplementary material
Crystallographic data (excluding structure factors)
for the structural analysis have been deposited with the
Cambridge Crystallographic Data Centre, CCDC no.
156569. Copies of this information may be obtained
free of charge from the Director, CCDC, 12 Union
Road, Cambridge, CB2 1EZ, UK (fax: +44-1223-
336033; e-mail: deposit@ccdc.cam.ac.uk or http://
www.ccdc.cam.ac.uk).
3b GC–MS: 440 (M+, 18), 425 (M–Me, 14), 381
(M–SiMe2H, 4), 365 (M–SiMe3, 1), 319 (Me850Se2Si3,
10), 303 (Me830Se2Si3CH2, 3), 289 (Me830Se2Si3, 2), 261
(Me830Se2Si2, 9), 231 (Me80Se2Si2, 2), 211 (Me5SeSi2, 8),
195 (Me3SeSi2CH2, 9), 281 (Me3SeSi2, 8), 123 (MeSeSi,
7), 73 (Me3Si, 100). The isotopic patterns of all frag-
ments fitted the natural abundance of 76Se:77Se:78Se:
80Se:82Se=9.2:7.6:23.7:49.8:8.8 [27].
Acknowledgements
The authors thank the Deutsche Forschungsgemein-
schaft for financial support. Special thanks are given to
the Computing Centre of the TU Bergakademie
Freiberg for supplying disk space and computing time.
Furthermore, the authors thank Professor H. Lang,
Chair of Inorganic Chemistry, TU Chemnitz for the
access to the X-ray facility used to determine the single-
crystal structures.
3.8. Preparation of 3,6-diphenyl-1,3,4,6-hexamethyl-
2,5,7-trithia-1,3,4,6-tetrasilanorbornane (4a–c, mixture
of stereoisomers)
A total of 0.54 g (2 mmol) of 2b was dissolved in 40
ml of hexane and dried H2S was bubbled through the
stirred reaction mixture while 0.83 ml (6 mmol) of NEt3
was slowly added by a syringe. The mixture was filtered
from precipitated triethylammonium salts (chloride and
some bromide due to the content of bromo-
dichlorophenyl-1,2-dimethyldisilanes, see Section 3.5)
and the solvent was removed from the filtrate in vacuo
to get 4a–c as crystalline product. A 29Si-NMR spec-
trum of a solution in CDCl3 revealed a composition of
53% 4a, 39% 4b and 8% 4c. No by-products have been
detected. Single crystals of 4a could be obtained by
slow concentration of a solution of 4a–c in hexane–
CDCl3.
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