Five- and six-membered ring Group 14 chalcogenides of the types (Me2ME)3 (M=Si, Ge, Sn), E(Si2Me4)2E, Me4Si2(E)2MRx (MRx=C(CH2)5, SiMe2, GeMe2, SnMe2, SnPh2, BPh)

Article abstract of DOI:10.1016/S0022-328X(01)00707-0

The reactions of Me₂MCl₂ (M=Si, Ge, Sn) with either H₂S/NEt₃ or Li₂E (E=Se, Te) yielded the six-membered-ring compounds (Me₂ME)₃. Similarly the treatment of ClMe₂SiSiMe₂Cl (1) with H₂S/NEt₃ or Li₂E resulted in the formation of E(Si₂Me₄)₂E. Mixed species E(Si₂Me₄)₂E′ could be obtained by reaction with mixtures of Li₂E and Li₂E′ or in the presence of traces of moisture (E′=O). Reactions of 1:1 mixtures of Me₂MCl₂ and 1 with Li₂E resulted in exclusive or at least preferred formation of five-membered rings Me₄Si₂(E)₂MMe₂. A carbon analogue, Me₄Si₂(S)₂C(CH₂)₅, was obtained from 1 and (HS)₂C(CH₂)₅. Boron could also be introduced in these ring systems, starting from PhBCl₂ and 1 the compounds PhB(E)₂Si₂Me₄ (E=S, Se) could be synthesized. Mixtures of 1 and Cl₂MeSiSiMeCl₂ yielded, on treatment either with H₂S/NEt₃ or Li₂E (E=Se, Te), the bis(cyclopentyl) compounds [Me₄Si₂(E)₂SiMe-]₂. All products have been characterized by multinuclear NMR (¹H, ¹¹B, ¹³C, ²⁹Si, ⁷⁷Se, ¹¹⁹Sn, ¹²⁵Te) measurements including coupling constants. Trends of chemical shifts and coupling constants are discussed. The crystal structures of E(Si₂Me₄)₂E (E=S, Se) and [Me₄Si₂(S)₂SiMe-]₂ are reported.

Full text of DOI:10.1016/S0022-328X(01)00707-0

Journal of Organometallic Chemistry 627 (2001) 23–36
www.elsevier.nl/locate/jorganchem
Five- and six-membered ring Group 14 chalcogenides of the types
(Me2ME)3 (M=Si, Ge, Sn), E(Si2Me4)2E, Me4Si2(E)2MRx
(MRx=C(CH2)5, SiMe2, GeMe2, SnMe2, SnPh2, BPh) and
[Me4Si2(E)2SiMeꢀ]2 (E=S, Se, Te)
U. Herzog 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 der TU Chemnitz, Straße der Nationen 62, D-09111 Chemnitz, Germany
Received 8 September 2000; accepted 14 December 2000
Abstract
The reactions of Me2MCl2 (M=Si, Ge, Sn) with either H2S/NEt3 or Li2E (E=Se, Te) yielded the six-membered-ring
compounds (Me2ME)3. Similarly the treatment of ClMe2SiSiMe2Cl (1) with H2S/NEt3 or Li2E resulted in the formation of
E(Si2Me4)2E. Mixed species E(Si2Me4)2E% could be obtained by reaction with mixtures of Li2E and Li2E% or in the presence of
traces of moisture (E%=O). Reactions of 1:1 mixtures of Me2MCl2 and 1 with Li2E resulted in exclusive or at least preferred
formation of five-membered rings Me4Si2(E)2MMe2. A carbon analogue, Me4Si2(S)2C(CH2)5, was obtained from 1 and
(HS)2C(CH2)5. Boron could also be introduced in these ring systems, starting from PhBCl2 and 1 the compounds PhB(E)2Si2Me4
(E=S, Se) could be synthesized. Mixtures of 1 and Cl2MeSiSiMeCl2 yielded, on treatment either with H2S/NEt3 or Li2E (E=Se,
Te), the bis(cyclopentyl) compounds [Me4Si2(E)2SiMeꢀ]2.
All products have been characterized by multinuclear NMR (1H, 11B, 13C, 29Si, 77Se, 119Sn, 125Te) measurements including
coupling constants. Trends of chemical shifts and coupling constants are discussed. The crystal structures of E(Si2Me4)2E (E=S,
Se) and [Me4Si2(S)2SiMeꢀ]2 are reported. © 2001 Elsevier Science B.V. All rights reserved.
Keywords: Silthianes; Selenides; Tellurides; Germanium; Tin
far allowing us to conclude, e.g. trends of NMR data
(chemical shifts, coupling constants) in series like
(Me2ME)3, M=Si, Ge, Sn, E=(O), S, Se, Te. On the
other hand, especially a comparison of NMR data of
the same building blocks in five- and six-membered ring
compounds seems to be very interesting. Previous inves-
tigations, for instance, have shown, that the formation
of five-membered rings is accompanied by a strong
down field shift of the 29Si-NMR signals in comparison
with acyclic compounds or six-membered rings contain-
ing the same first coordination sphere at silicon.
DFT calculations on the equilibrium have shown
that the formation of the five-membered ring according
to Eq. (1) lowers the total energy (including vibrational
zero point correction) of the system by 36.0 kJ mol−1
[1]. This means that five-membered rings seem to be the
most stable ring size in these systems.
1. Introduction
In the course of our systematic investigations on
silicon (and other Group 14) chalcogenides [1–4] we
report in this paper on five- and six-membered ring
chalcogenides of Group 14 elements (Si, Ge, Sn). Some
compounds like (Me2SiE)3 (E=S [5], Se [6]),
(Me2SnE)3 (E=S, Se, Te) [7], E(Si2Me4)2E (E=S, Se)
[8], Me4Si2(S)2SiMe2 [1,9] or Me4Sn2(E)2SnMe2 (E=S,
Se, Te) [7] have been reported previously (including
some NMR chemical shifts) but there has not been any
systematic investigation of this class of compounds so
* 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)00707-0

24
U. Herzog, G. Rheinwald / Journal of Organometallic Chemistry 627 (2001) 23–36
2. Results and discussion
2.1. Six-membered ring compounds (Me2ME)3 (M=Si,
Ge, Sn; E=S, Se, Te)
All compounds of this class could be synthesized
starting from the dichlorodimethyl derivatives either by
reaction with H2S/NEt3 or Li2E (E=Se, Te) Eqs. (2)
and (3):
(1)
Crystal structures of (R2ME)3 are only known for
some cyclotrisilthianes with larger substituents R, e.g.
trans-(PhMeSiS)3 (twisted boat conformation, dSiS
:
,
2.13–2.15 A, ÚSiSSi: 104.7–108.0°, ÚSSiS: 112.2–
(2)
112.6° [10]) and for the tin chalcogenides (Me2SnS)3
,
(two modifications reported: tetragonal: dSnS: 2.41 A,
ÚSnSSn: 103°, ÚSSnS: 107.7° [11]; monoclinic: dSnS
:
,
2.41–2.44 A, ÚSnSSn: 102.0–104.4° ÚSSnS: 106.1–
,
108.7° [12]), (Me2SnSe)3 (dSnSe: 2.52–2.54 A, ÚSnSeSn:
100.6, 101.1°, ÚSeSnSe: 107.8, 110.6°) [13], and
(Me2SnTe)3 (dSnTe: 2.72–2.77 A, ÚSnTeSn: 94.9–97.4°,
(3)
,
ÚTeSnTe: 111.3–113.6°) [14] which also adopt unusual
twisted boat conformations. Furthermore the molecular
structures of the five-membered heterocyclic tin com-
pounds Me4SnA2 (Se)2SnBMe2 (envelope conformation,
All products were characterized by multinuclear
NMR spectroscopy, in the cases of E=S MS spectra
could also be recorded. Table 1 summarizes the ob-
served NMR parameters. NMR data of 2a, 2b and
4a–c, as far as they have been published, are in good
agreement with these data. In comparison with the
acyclic compounds Me2Si(SBu)2 (lSi: 24.8 ppm) [17],
Me2Si(SMe)2 (lSi: 28.14 ppm) [18], Me2Si(SeBu)2 (lSi:
18.1 ppm) [19] and Me2Si(TeBu)2 (lSi: −24.6 ppm) [20]
the formation of a six-membered ring is accompanied
by a high field shift of about 3 ppm (compared to the
EBu-derivatives with the same E). Similar effects can
also be observed for the tin compounds. The acyclic
derivatives Me2Sn(SMe)2 and Me2Sn(SeMe)2 exhibit
,
,
dSnSn: 2.77–2.78 A, d
: 2.56–2.58 A, d
: 2.52–
B
Se
A
Sn
Sn
Se
B
,
2.55 A, ÚSnSeSn: 93.3–96.7°, ÚSeSn Se: 106.5–
107.2°) [15] and tBu4Sn2A(E)2SnBtBu2 (E=S: planar,
,
,
,
: 2.40–2.42 A,
B
Sn
dSnSn: 2.88 A, d
: 2.40–2.43 A, d
A
Sn
ÚSnSSn: 107.9–10S8.3°, ÚSSnBS: 115.3;SE=Se: planar,
,
,
,
: 2.52–2.53 A,
B
Se
dSnSn: 2.88 A, d
: 2.52–2.53 A, d
A
Sn
Sn
ÚSnSeSn: 106.3–S1e06.5°, ÚSeSnBSe: 115.1; E=Te:
,
,
,
: 2.74 A,
B
Te
twisted, dSnSn: 2.84 A, d
: 2.75 A, d
A
Sn
Sn
Te
ÚSnTeSn: 101.6–102.3°, ÚTeSnBTe: 114.0–114.3)
[16]; have been reported. The conformations of the
latter are obviously determined by the steric demand of
t
the butyl substituents at the tin atoms.
Table 1
NMR data of the six-membered rings (Me2ME)3; M=Si, Ge, Sn; E=S, Se, Te (chemical shifts in ppm, coupling constants in Hz)
Compound
lE
lM
1JME
lC
1JMC
lH
(Me2SiS)3 (2a)
(Me2SiSe)3 (2b)
(Me2SiTe)3 (2c)
21.1
15.2
−23.7
7.95
8.7
8.8
59.6
55.4
0.69
0.91
1.26
Se: −244
Te: −618
130.7
344.5
49.5
2JTeC: 18.4
3JTeH: 8.8
0.97
(Me2GeS)3 (3a)
(Me2GeSe)3 (3b)
(Me2GeTe)3 (3c)
10.6
11.1
10.3
Se: −182
Te: −476
1.15
1.42
2JTeC: 9.6
405.1
3JTeH: 7.3
0.86
(Me2SnS)3 (4a)
(Me2SnSe)3 (4b)
(Me2SnTe)3 (4c)
133
4.8
4.4
1.9
2JSnSn: 193 a
46
Se: −360
Te: −859
1217
3098
363.5
298
0.99
2JSnSn: 231 a
−192
2JSnH: 57.8
1.17
2JSnSn: 239 a
2JSnH: 52
a 2
J
119Sn117Sn.

U. Herzog, G. Rheinwald / Journal of Organometallic Chemistry 627 (2001) 23–36
25
Fig. 1. NMR chemical shifts in six-membered rings (Me2ME)3 (M=Si, Ge, Sn; E=S, Se, Te).
Fig. 2. Correlation of lSe and lTe in different kinds of silselenanes and siltelluranes and related germanium and tin derivatives (M=Si, Ge, Sn;
E=Se, Te) reported here and in Refs. [3,4] (r=regression coefficient).
119Sn-NMR shifts of 144 [21] and 57 ppm [22], respec-
tively, which are in both cases at a lower field by 11
ppm than the corresponding (Me2SnE)3 derivatives. On
the other hand, the 29Si-NMR signal of Me2Si(TeBu)2
(lSi: −24.6 ppm) [20] is by 0.9 ppm at a higher field
than in the case of the corresponding six-membered
ring 2c.
If several NMR parameters, such as lE, lC or lH of
analogous derivatives of silicon, germanium and tin are
compared, see Fig. 1, it is obvious, that the values of
the germanium compounds do not lie between those of
the silicon and tin derivatives but are shifted in all cases
to a lower field. This trend can also be found in
five-membered rings discussed in Section 2.3.
It can be explained with the higher electronegativity
(2.02) of germanium (values according to Allred and
Rochow [23]) in comparison with those of silicon (1.74)
and tin (1.72).
Concerning the chemical shifts of selenium and tel-
lurium it has already been stated, that in equivalent
compounds the chemical shifts run closely parallel. A
plot of lTe against lSe for a variety of organic deriva-
tives has been found to be linear with a slope of about
1.6 [24,25]. As can be seen from Figs. 2 and 3 again a
1
linear relationship between lSe and lTe as well as JSiSe
1
and JSiTe could be observed but with a steeper slope of
app. 2.6 in both cases. In order to show that this
observation is more general other types of Group 14

26
U. Herzog, G. Rheinwald / Journal of Organometallic Chemistry 627 (2001) 23–36
1
1
Fig. 3. Correlation of JSiSe and JSiTe in different kinds of silselenanes and siltelluranes reported here and in Refs. [3,4] (same compounds as in
Fig. 2).
is formed exclusively by the cleavage of one SiꢀSi bond.
The mixed species O(Si2Me4)2E (E=S (5e), Se (5f),
Te (5g)) have been observed as by-products if the
reactions (Eqs. (4) and (5)) were carried out in the
presence of traces of moisture. Besides NMR-spectro-
scopic evidence also a mass spectrum of 5e could be
recorded. Finally the mixed substituted compounds
S(Si2Me4)2Se (5h), S(Si2Me4)2Te (5i) and Se(Si2Me4)2Te
(5k) were prepared together with the homosubstituted
cycles 5b–d upon treatment of 1 with 1:1 mixtures of
Li2E and Li2E% (E=S, Se; E%=Se, Te).
selenides and tellurides have been included into the
figures, too.
Some deviations in Fig. 2 may arise from the fact
that compounds like (Me2SiSe)3 and (Me2SiTe)3 have
been compared, but to be correct, lSe of (Me2SiSe)3
should be compared with the lTe of Me6Si3Se2Te.
An equivalent correlation like that in Fig. 3 can also
1
1
be observed by comparing JSnSe with JSnTe of equiva-
lent compounds (4b/4c, 6i/6n or the bicyclic compounds
Me2Sn(E)2Si2Me2(E)2SnMe2 [3]) yielding a slope of
2.54.
While 5a is a well known compound [26] (a 29Si-
NMR chemical shift of 2.3 ppm has been reported in
Ref. [27]), the sulfur and selenium derivatives 5b and 5c
have been synthesized by the insertion of elemental
sulfur or selenium (red modification) into the five-mem-
bered rings (Me2Si)4E (obtained from (Me2Si)4 and E8)
[8]. In contrast to observations reported in Ref. [8] we
found both compounds to give relatively stable color-
less crystals in an inert atmosphere but they hydrolyze
on contact with air (5c more rapidly than 5b). The
29Si-NMR shifts given in Ref. [8] differ somewhat from
our results, especially for 5c and the also reported
mixed sulfur selenium compound 5h.
2.2. Six-membered rings E(Si2Me4)2E%; E, E%=O, S, Se,
Te
Starting from 1 the six-membered rings E(Si2Me4)2E
(E=O (5a), S (5b), Se (5c) and Te (5d)) were formed
without any acyclic by-products by reaction with either
H2E/NEt3 or Li2E (Eqs. (4) and (5)):
(4)
(5)
In the synthesis of 5d it is crucial to add 1 to the
THF solution of Li2Te at a temperature below 0°C,
otherwise the five-membered ring Me4Si2(Te)2SiMe2 (6l)
Fig. 4. ZORTEP plot of the molecular structure of 5b.

U. Herzog, G. Rheinwald / Journal of Organometallic Chemistry 627 (2001) 23–36
27
the same space group with almost identical lattice
constants.
The SiꢀS as well as SiꢀSe bond lengths found are
relatively large in comparison with reported values of
other silthianes and silselenanes. But in general the SiꢀS
bond distances decrease with the number of S sub-
stituents at silicon [28] and in 5b there is only one sulfur
atom connected to each silicon atom. The same might
also hold for the SiꢀSe bond lengths but fewer data of
crystal structures are available. Furthermore, the bond
angles at sulfur and selenium are smaller than the
tetrahedral angle but larger than values found previ-
ously in other cyclic silthianes or selenanes or related
germanium and tin compounds. These observations are
confirmed by previously performed DFT calculations
on 5b (B3LYP/6-31G*) which also yielded a relatively
Fig. 5. ZORTEP plot of the molecular structure of 5c.
Crystal structure analyses of 5b and 5c have been
carried out, and Figs. 4 and 5 show the molecular
structures. In contrast to the reported twisted boat
conformations of (MePhSiS)3 [10] and 4a–c [11–14] in
both molecules the six-membered ring adopts a chair
conformation. Some important bond parameters are
summed up in Table 2. Both compounds crystallize in
,
large bond length SiꢀS of 2.187 A and an angle SiꢀSꢀSi
of 109.2° [1].
Table 2
Important bond distances and angles of 5b and 5c
Atoms
Bond length
Atoms
Angles
5b (E=S)
5c (E=Se)
5b (E=S)
5c (E=Se)
Si(1)ꢀSi(2)
Si(1)ꢀE(1)
Si(2a)ꢀE(1)
Si(1)ꢀC(1)
Si(1)ꢀC(2)
Si(2)ꢀC(3)
Si(2)ꢀC(4)
2.3373(4)
2.1562(4)
2.1545(4)
1.8713(11)
1.8869(11)
1.8666(11)
1.8709(11)
2.3306(10)
2.2908(8)
2.2883(8)
1.870(3)
1.863(8)
1.871(3)
1.867(3)
Si(1)ꢀE(1)ꢀSi(2a)
E(1)ꢀSi(1)ꢀSi(2)
E(1a)ꢀSi(2)ꢀSi(1)
C(1)ꢀSi(1)ꢀC(2)
C(3)ꢀSi(2)ꢀC(4)
E(1)ꢀSi(1)ꢀSi(2)ꢀE(1a)
Si(2a)ꢀE(1)ꢀSi(1)ꢀSi(2)
106.45(1)
111.90(2)
113.29(2)
109.21(6)
109.68(5)
−59.65(2)
55.74(2)
105.14(3)
111.37(4)
112.27(3)
110.17(16)
110.65(15)
−62.40(4)
58.17(4)
Table 3
NMR data of the six-membered ring compounds E(SiMe2SiMe2)2E (E=O, S, Se, Te)
Compound
lE
lSi
1JSiE
lC
1JSiC
lH
O(Si2Me4)2O (5a)
S(Si2Me4)2S (5b)
Se(Si2Me4)2Se (5c)
Te(Si2Me4)2Te (5d)
3.7
−4.8
−9.1
2.8
0.21
0.44
0.55
0.72
1.94
1.40
1.00
45.4
44.1
42.3
−369
−885
109.8
−28.9
280.2
2JSiTe: 13
Table 4
NMR data of the six-membered ring compounds E(SiAMe2SiBMe2)2E% (E, E%=O, S, Se; E"E%)
Compound
lE
1JSiE
lSiA
1JSiC
lSiB
1JSiC
1JSiSi
lC
lHA
lHB
O(Si2Me4)2S (5e)
O(Si2Me4)2Se (5f)
O(Si2Me4)2Te (5g)
S(Si2Me4)2Se (5h)
S(Si2Me4)2Te (5i)
Se(Si2Me4)2Te (5k)
4.7
4.1
3.8
−3.9
−2.5
−7.3
58.3
−8.4
43.7
43.2
40.8
45.7
43.7
41.8
100.1
98
95.7
92.8
89.4
88.0
2.31, 1.88
0.26
0.26
0.26
0.45
0.47
0.57
0.38
0.48
0.64
0.54
0.70
0.71
Se: −317
Te: −902
Se: −370
Te: −916
Se: −366
Te: −890
103
−13.6
−35.6
−10.1
−32.8
−31.5
1.85, 1.75
1.48, 1.12
1.81, 1.52
1.73, 0.97
1.37, 0.93
a
255.1
107.9
267.2
112.2
273.1
45.7
b
44.5
c
a 2
J
: 10.2.
: 8.3.
: 8.7.
SiTe
b 2
J
J
SiTe
c 2
SiTe

28
U. Herzog, G. Rheinwald / Journal of Organometallic Chemistry 627 (2001) 23–36
The observed NMR parameters of 5a–k are given in
A carbon analog (6f) has been obtained in a clean
reaction by treatment of 1 with cyclohexane-1,1-dithiol
(Eq. (8)):
Tables 3 and 4. In the row 5a–d (E=O, S, Se, Te) the
29Si- and 13C-NMR signals are shifted to higher field
1
and the values of the JSiC coupling constants decrease
which is consistent with the decreasing electronegativity
of E. On the other hand, lH of the methyl groups
increases, but this trend parallels the increasing
deshielding effect of heavier halogen substituents at
silicon towards methyl protons [29].
(8)
Compared with the acyclic disilane derivatives
BuSꢀSiMe2ꢀSiMe2ꢀSBu [17], BuSeꢀSiMe2ꢀSiMe2ꢀSeBu
[19] and BuTeꢀSiMe2ꢀSiMe2ꢀTeBu [20] the 29Si-NMR
signals of the six-membered rings are more shielded by
3.2 (5b), 2.4 (5c) and 2.9 ppm (5d) whereas the lC
values of the methyl carbon atoms are shifted by 2–3
1,1-Dithiols are accessible from ketones and H2S
according to [30] (Eq. (9)):
(9)
1
ppm to a lower field and lH and JSiC remain almost
unchanged.
The selenium and tellurium containing five-mem-
bered rings 6g–n have been prepared by reaction with
Li2Se or Li2Te. In these cases the reactions yield only
the expected five-membered ring compounds without
six-membered rings (Me2ME)3 and 5c,d as by-products
(Eq. (10)).
In the mixed six-membered ring compounds 5e–k lSi
of the SiMe2 units attached to the more electronegative
E atom is shifted to a lower field while lSi of the other
SiMe2 units are shifted to a higher field in comparison
with lSi in the comparable compounds 5a–d. This
effect increases with increasing difference in the elec-
tronegativities of E and E% and can also be observed for
other unsymmetrically substituted disilanes.
(10)
In the mixed six-membered rings it has also been
1
possible to obtain JSiSi coupling constants. As ex-
pected, the values increase with the electronegativities
of the two chalcogen atoms E and E% and fall in the
expected range.
As stated above, pure Me4Si2(Te)2SiMe2 (6l) is also
observed in the reaction of pure 1 with Li2Te at room
temperature under the cleavage of the SiꢀSi bonds.
Mixed sulfur selenium (6p), sulfur tellurium (6q) as
well as selenium tellurium (6r) five-membered rings
could be detected in the product mixtures besides 6a, 6g
and 6l, if 1:1 mixtures of 1 and Me2SiCl2 were reacted
with 1:1 mixtures of Li2E and Li2E% in THF.
No oxygen containing five-membered rings, but the
O-substituted six-membered rings 5e–g were observed
as by-products when the reactions were carried out in
the presence of traces of moisture. The larger bond
angle SiOSi prevents the formation of the smaller five-
membered rings in this case.
2.3. Fi6e-membered rings Me4Si2(E,E%)2MRx; E
(E%=S, Se, Te; MRx=BPh, C(CH2)5, SiMe2, GeMe2,
SnMe2, SnPh2)
As already reported in Ref. [1], the reaction of 1 in
mixture with Me2SiCl2 yields the five-membered ring
Me4Si2(S)2SiMe2 (6a) as the preferred product. This
reaction can also be used to prepare the corresponding
germanium (6b), tin (6c,d) and boron (6e) containing
cycles (Eqs. (6) and (7)):
The NMR data of all prepared five-membered rings
are given in Tables 5 and 6. 6e has been synthesized
before in a different route [9], but only the 11B- and
1H-NMR shifts were given. The strongly deshielded
selenium NMR signal in 6k compared to all other
selenium compounds of this paper is remarkable. In
contrast to other 77Se-NMR spectra this signal is much
more broadened due to the contact with the quadrupo-
lar nuclei 10B and 11B. The same reason is responsible
for the problems in detecting the ipso carbon atoms of
the phenyl rings in 6e and 6k.
(6)
(7)
Compared with the six-membered heterocycles dis-
cussed before, the 29Si-NMR signals of the same silyl
units in five-membered rings are shifted significantly to

U. Herzog, G. Rheinwald / Journal of Organometallic Chemistry 627 (2001) 23–36
29
Table 5
NMR data of five-membered rings Me4Si2(E)2SiMe2 (E=S, Se, Te)
a lower field. A closer look reveals that this low field
shift increases within the disilanyl unit (in comparison
with 5b–d), if one goes down the row of S, Se and Te,
whereas the opposite is observed for the monosilyl units
Me2Si(Eꢀ)2 (in comparison with 2a–c), see Fig. 6.
In the three tin derivatives Me4Si2(E)2SnMe2 (E=S
(6c), Se (6i), Te (6n)) the 119Sn-NMR signals are shifted
downfield by about 50 ppm in comparison with 4a–c.
The values of lSe and lTe in the five-membered rings
Me4Si2(E)2MMe2 (M=Si, Ge, Sn), where the E atoms
are placed between one disilanyl and one MMe2 unit,
are almost exactly the average between the shifts found
in the comparable six-membered rings 5c,d, 2b–4b and
2c–4c for M=Si, while for M=Ge and Sn the devia-
tions towards higher field increase up to 146 ppm in 6n.
Other NMR parameters do not show significant
changes due to the change in ring size, at best it seems,
that JSiSi in analogous units EꢀSiMe2ꢀSiMe2ꢀE% are in
five-membered rings by 4–5 Hz smaller than in six-
membered rings.
In five-membered rings with two different E atoms
(6p–r) lSi of the unit EꢀMe2SiꢀE% is almost the average
of the chemical shifts of the monosilyl unit in the rings
Si2Me4(E)2SiMe2 and Si2Me4(E%)2SiMe2 while the 29Si-
NMR shifts of the disilanyl units behave like those
already discussed for 5e–k but to a larger extent.
2.4. Bis(cyclopentyl) compounds
Me4Si2(E)2SiMeꢀSiMe(E)2Si2Me4 (E=S (7a), Se (7b),
Te (7c))
In a previous paper [1] we have already reported the
formation and the NMR data of the sulfur compound
7a according to (Eq. (11))
(11)
By changing the starting molar ratio of MeCl2Siꢀ
SiCl2Me:1 from 1:2 to 1:1 the amount of the by-
product 5b could be reduced to 20%. Upon treatment
with H2S and NEt3 excess MeCl2SiꢀSiCl2Me forms
Me6Si6S6 [1], which is insoluble in hexane and can
therefore be removed very easily.
The selenium and tellurium compounds 7b,c are
formed in the reaction of Li2E with a 1:2 mixture of
MeCl2SiꢀSiCl2Me and 1 in THF as main products
besides smaller amounts of 5c,d and the noradaman-
tane Me4Si4Se5 in the case of selenium [4] (Eq. (12)):
1

30
U. Herzog, G. Rheinwald / Journal of Organometallic Chemistry 627 (2001) 23–36
Table 6
NMR data of five-membered ring compounds Me4Si2(E)2MRx (E=S, Se, Te; MRx: GeMe2, SnMe2, SnPh2, C(CH2)5, BPh)

U. Herzog, G. Rheinwald / Journal of Organometallic Chemistry 627 (2001) 23–36
31
Fig. 6. Comparison of lSi of mono and disilyl units in five- and six-membered ring silicon chalcogenides (2a–c, 5b–d and 6a, 6g, 6l).
Table 7
NMR data of the compounds Me4Si2(E)2SiMeꢀSiMe(E)2Si2Me4 (E=S, Se, Te (7a–c))
the SiMe2 units of 7a–c are diastereotopic giving rise to
two different carbon and hydrogen NMR signals. But
the averages of the two signals are close to the values
found in 6a, 6f and 6l, respectively.
Fig. 7 shows the result of the crystal structure analy-
sis of 7a confirming the expected bis(cyclopentyl) skele-
ton. Some important bond lengths and angles are given
in Table 8. The five-membered rings adopt a twisted
(12)
The NMR data of the compounds 7a–c are given in
Table 7.
While the lSi of the Si2Me4 units can be compared
with the disilanyl units of the five-membered rings 6a,
6f and 6l and show only small additional down field
shifts of 1.5–2 ppm the chemical shifts of the central
Si2Me2 units could at best be compared with the com-
pounds C2H4(S)2SiMeꢀSiMe(S)2C2H4 (lSi: 23.8 ppm)
and C6H4(S)2SiMeꢀSiMe(S)2C6H4 (lSi: 20.8 ppm) [2],
which are indeed similar to 7a. But no related selenium
or tellurium compounds are known. In contrast to the
monocyclic five-membered rings the methyl groups in
Fig. 7. ZORTEP plot of the molecular structure of 7a.

32
U. Herzog, G. Rheinwald / Journal of Organometallic Chemistry 627 (2001) 23–36
Table 8
5c and 7a as well as data collection and refinement
details are given in Table 9.
,
Important bond distances (A) and angles (°) of 7a
The unit cells were determined with the program
SMART [31]. For data integration and refinement of the
unit cells the program SAINT [31] was used. The space
groups were determined using the programs XPREP [31]
(5a, 5b) and ABSEN [32]. All data were corrected for
absorption using SADABS [33]. The structures were
solved using direct methods (5a, 5b: SHELX-97 [34], 7a:
SIR-97 [35]), refined using least-squares methods
Atoms
Distances
Atoms
Angles
Si(1)ꢀSi(1a)
Si(1)ꢀS(1)
Si(1)ꢀS(2)
Si(2)ꢀS(1)
Si(3)ꢀS(2)
Si(2)ꢀSi(3)
Si(1)ꢀC(1)
Si(2)ꢀC(2)
Si(2)ꢀC(3)
Si(3)ꢀC(4)
Si(3)ꢀC(5)
2.323(2)
Si(1)ꢀS(1)ꢀSi(2)
Si(1)ꢀS(2)ꢀSi(3)
S(1)ꢀSi(1)ꢀS(2)
S(1)ꢀSi(2)ꢀSi(3)
S(2)ꢀSi(3)ꢀSi(2)
Si(1a)ꢀSi(1)ꢀC(1)
C(2)ꢀSi(2)ꢀC(3)
C(4)ꢀSi(3)ꢀC(5)
104.38(5)
103.85(5)
112.65(5)
103.05(5)
103.65(5)
111.22(14)
110.5(2)
2.1458(12)
2.1409(12)
2.1551(12)
2.1539(13)
2.3310(13)
1.853(4)
1.848(4)
1.860(4)
1.865(4)
1.874(4)
109.1(2)
(SHELX-97) and drawn using ZORTEP [36]. The ellip-
soides at the nonhydrogen atoms are at the 50% proba-
bility level.
3.3. Starting materials
,
conformation. Si(2) and Si(3) are 0.382(2) A above and
,
0.461(2) A below the plane defined by the atoms Si(1),
H2S (N25, Air Liquide), Se, Te, triethylamine, 1 M
Li[BEt3H] in THF (Super Hydride), Me2SiCl2,
Me2GeCl2, Me2SnCl2, Ph2SnCl2, PhBCl2 were commer-
cially available. 1 and SiCl2MeꢀSiCl2Me were prepared
as described previously [37,38]. THF was distilled from
sodium potassium alloy prior to use. The other solvents
were dried over KOH or sodium wire. All reactions
were carried out under argon applying standard
Schlenk techniques.
S(1) and S(2). The angles at the sulfur atoms are larger
than in other silthianes containing five-membered rings
Si3S2 [1] but in this case the five-membered rings are not
incorporated into bi- or polycyclic ring systems, and the
angles are close to the calculated SiꢀSꢀSi angle of
103.8° in 6a (B3LYP/6-31G*, [1]). Also the calculated
angles SꢀSiꢀS and SiꢀSiꢀS of 111.6° and 102.2° for 6a
are mirrored well in the observed angles in 7a. The
bond lengths SiꢀSi, SiꢀS and SiꢀC are in the expected
range. As already observed in other silthianes the SiꢀS
bond length decreases with increasing number of S
substituents at Si. Therefore the SiꢀS bonds at Si(1) are
slightly shorter than the SiꢀS bonds at Si(2) and Si(3).
3.4. Preparation of the six-membered ring compounds
(Me2ME)3 (M=Si, Ge, Sn; E=S, Se, Te) (2a–4c)
3.4.1. Sulfur compounds (2a–4a)
In a typical reaction 2 mmol Me2MCl2 (M=Si, Ge,
Sn) was dissolved in 20 ml hexane and a stream of dried
H2S was passed through the stirred solution while 0.55
ml (4 mmol) NEt3 were slowly added by a syringe. A
white precipitate of Et3NHCl was formed. After filtra-
tion the solvent was removed in vacuo yielding pure
2a–3a as colorless oils and 4a as a semicrystalline
residue in ca. 60% yield.
3. Experimental
3.1. NMR and GC–MS measurements
All NMR spectra were recorded on a Bruker DPX
400 in CDCl3 solution and TMS as internal standard
for 1H, 13C and 29Si. In order to get a sufficient
signal/noise ratio of the 29Si-NMR spectra for obtain-
2a GC–MS m/e (rel. int.): 270 (M+, 21), 255
(Me5Si3S3, 100), 165 (Me3Si2S2), 73 (Me3Si, 35).
3a GC–MS 404 (Me762Ge274GeS3, 13), 389
(Me752Ge724GeS3, 92), 255 (Me372Ge74GeS2, 100), 225
(Me72Ge74GeS2, 12), 151 (Me374GeS, 5), 119 (Me734Ge,
48), 89 (Me74Ge, 14). (The isotopic patterns of all
1
1,2
1,2
ing JSiC
,
1JSiSi
,
J
or
J
satellites also 29Si
SiTe
SiSe
INEPT spectra were recorded. 77Se, 125Te and 119Sn
spectra were recorded using an IGATED pulse program.
External BF3·OEt2, Me4Sn, Ph2Se2 (lSe: 460 ppm)
and Ph2Te2 (lTe: 422 ppm) in CDCl3 were used as
standards for 11B, 119Sn, 77Se and 125Te.
fragments
fitted
the
natural
abundance
of
Mass spectra were measured on a Hewlett–Packard
5971 (ionization energy: 70 eV, column: 30 m×0.25
mm×0.25 mm, phenylmethylpolysiloxane, column tem-
perature: 80°C (3 min)/20 K min−1, flow: He 0.5
ml min−1).
70Ge:72Ge:73Ge:74Ge:76Ge=20.5:27.4:7.8:36.5:7.8 [39].)
4a GC–MS 527 (Me1518Sn120Sn2S3, 16), 497
(Me1318Sn120Sn2S3, 4), 362 (Me1418Sn120SnS2, 20), 347
(Me1318Sn120SnS2, 100), 317 (Me118Sn120SnS2, 63), 302
(
118Sn120SnS2, 19), 270 (118Sn120SnS, 10), 197 (Me3120SnS,
35), 165 (Me3120Sn, 31), 135 (Me120Sn, 19), 120 (120Sn,
15) (The isotopic patterns of all fragments fitted the
natural abundance of 116Sn: 117Sn:118Sn:119Sn:
120Sn:122Sn:124Sn=14.53:7.68:24.22:8.58:32.59:4.63:5.79
[39].)
3.2. Crystal structure analysis
X-ray structure analysis measurements were per-
formed on a Bruker SMART CCD. Crystal data of 5b,

U. Herzog, G. Rheinwald / Journal of Organometallic Chemistry 627 (2001) 23–36
33
3.4.2. Selenium compounds (2b–4b)
which turned light orange. Work-up as described for
the selenium compounds 2b–4b yielded the tellurium
compounds as light yellow viscous oils in ca. 40% yield.
Black selenium powder (0.16 g, 2 mmol) was reacted
with a mixture of 4 ml 1 M solution of Li[BEt3H]
(‘‘Super Hydride’’) in THF and 5 ml THF under stir-
ring. The selenium dissolved within a few seconds with
the formation of a white suspension of Li2Se in THF.
Me2MCl2 (2 mmol) dissolved in 1 ml THF was added
to this mixture. The precipitation of Li2Se disappeared
almost immediately. After stirring for 30 min at room
temperature the THF was removed in vacuo and re-
placed by 10 ml hexane. The solution was separated
from precipitated LiCl. Removal of the solvent pro-
duced 2b and 3b as colorless oils and 4b as a white solid
in ca. 50% yield.
3.5. Preparation of the six-membered ring compounds
E(SiMe2SiMe2)2E (E=O, S, Se, Te) (5a–d) and
mixed compounds E(SiMe2SiMe2)2E% (E"E)%
3.5.1. Synthesis of S(SiMe2SiMe2)2S (5b)
1,2-Si2Me4Cl2 (1) (2.5 g, 13.3 mmol) was dissolved in
100 ml hexane and 3.7 ml (26.6 mol) NEt3 was slowly
added while a stream of dried H2S passed through the
stirred solution. After 1 h the reaction mixture was
filtered from precipitated Et3NHCl and most of the
solvent was removed in vacuo when 5b crystallized in
colorless needles from the solution in yield of 1.6 g
(81%).
3.4.3. Tellurium compounds (2c–4c)
Tellurium powder (0.25 g, 2 mmol (200 mesh)) was
added to a mixture of 4 ml 1 M solution of Li[BEt3H]
(‘‘Super Hydride’’) in THF and 5 ml THF under stir-
ring. After 5 min the tellurium started to react under
the formation of a deep purple solution which became
dark red after 1 h at room temperature.
If the reaction is carried out with H2S, which was not
dried with CaCl2 prior to use, besides 5b the monooxy-
gen and dioxygen six-membered ring compounds 5e
and 5a were formed as by-products, which could also
be proved by GC–MS:
Dichloride Me2MCl2 (2 mmol) dissolved in 1 ml
THF was added to this ‘‘Li2Te’’-solution under stirring,
5b GC–MS: 296 (M+, 23), 281 (Me7Si4S2, 13), 237
(Me5Si3S2CH2, 11), 116 (Me4Si2, 100), 73 (Me3Si, 92).
Table 9
Crystal data of 5b, 5c and 7a as well as data collection and refinement details
5b
5c
7a
Crystal system
Space group
Monoclinic
P21/n
Monoclinic
P21/n
Monoclinic
P21/n
Unit cell dimensions
,
a (A)
6.8132(5)
12.1869(9)
10.1091(8)
90
91.006(2)
90
839.25(11)
2
1.174
6.8672(10)
12.2988(17)
10.2087(15)
90
1.852(3)
90
861.8(2)
2
1.505
6.6431(5)
12.4055(11)
14.7678(12)
90
96.962(2)
90
1208.1(2)
2
1.229
,
b (A)
,
c (A)
h (°)
i (°)
k (°)
3
,
Volume (A )
Z
Density (calc.) in g cm−3
Linear absorption coefficient
0.575
4.541
0.682
(mm−1
)
Radiation used
Mo–Ka
Mo–Ka
Mo–Ka
Temperature
173(2) K
173(2) K
173(2) K
Scan method
v scans
v scans
v scans
Absorption correction
Max/min transmission
Measured reflections
Independent reflections
Observed reflections
R(int)
Empirical
Empirical
Empirical
0.8465/0.6960
5581
2404
2078
0.6118/0.2917
4267
2033
1628
0.9602/0.8756
5306
2619
1520
0.0192
0.0254
0.0547
Theta range for collection (°)
Completeness to qmax (%)
Refinement method
Final R1 (I\2|(I))
R1 (all data)
2.62–30.74
2.59–31.16
2.15–29.55
92.0
73.2
77.3
Full-matrix least-squares on F2
Full-matrix least-squares on F2
Full-matrix least-squares on F2
0.0215
0.0263
0.0292
0.0422
0.0410
0.0989
H-locating and refining
difmap/refall
1.028
0.258/−0.261
difmap/refall
1.000
0.558/−0.715
difmap/refall
0.908
0.354/−0.298
Goodness-of-fit on F2
−3
,
Max/min e-density (e A
)

34
U. Herzog, G. Rheinwald / Journal of Organometallic Chemistry 627 (2001) 23–36
5e GC–MS: 280 (M+, 22), 265 (Me7Si4OS, 16), 221
with two of the already known compounds 5b, 5c and
5d and in the case of 5h also by GC–MS.
(Me7Si3S, 14), 205 (Me7Si3O, 13), 147 (Me5Si2O, 24),
116 (Me4Si2, 100), 101 (Me3Si2, 7), 73 (Me3Si, 57).
5a GC–MS: 264 (M+, 32), 249 (Me7Si4O2, 41), 221
(Me7Si3O2, 7), 205 (Me7Si3O, 97), 191 (Me5Si3O2, 57),
175 (Me5Si3O, 15), 147 (Me5Si2O, 27), 131 (Me5Si2, 12),
117 (Me3Si2O, 18), 91 (35), 73 (Me3Si, 100).
5h GC–MS: 344 (M+, 2), 329 (Me7Si4SSe, 1), 285
(Me5Si3SSeCH2, 2), 239 (Me5Si3Se, 2), 211 (Me5Si2Se,
1), 191 (Me5Si3S, 3), 147 (Me3Si2SCH2, 6), 131 (Me5Si2,
9), 116 (Me4Si2, 100), 101 (Me3Si2, 8), 73 (Me3Si, 66).
3.6. Preparation of the fi6e-membered ring compounds
Me4Si2(E)2MRx
3.5.2. Synthesis of Se(SiMe2SiMe2)2Se (5c)
1 (2 mmol) was added at room temperature to Li2Se
suspension prepared from 2 mmol Se powder, 4 ml 1 M
Li[BEt3H] solution and 5 ml THF and the mixture was
stirred for 1 h before the solvent was removed and
replaced by 10 ml hexane. The hexane solution was
separated from precipitated LiCl and concentrated in
vacuo until needles of 5c crystallized from the solution
in 64% yield (0.25 g).
If this reaction is carried out with THF, which was
not dried very carefully, the monooxygen compound 5f
was obtained as by-product as confirmed by GC–MS.
5c GC–MS: 392 (M+, 2), 377 (Me7Si480Se2, 1), 333
(Me5Si3Se2CH2, 2), 319 (Me5Si3Se2, 0.5), 239 (Me5Si3Se,
3), 211 (Me5Si2Se, 2), 195 (Me3Si2SeCH2, 5), 131
(Me5Si2, 8), 116 (Me4Si2, 100), 101 (Me3Si2, 8), 73
(Me3Si, 74).
3.6.1. Sulfur deri6ati6es Me4Si2(S)2MMe2 (M=Si, Ge,
Sn (6a–c)) and Me4Si2(S)2SnPh2 (6d)
1 (0.28 g, 1.5 mmol) and 1.5 mmol Me2MCl2 (M=
Si, Ge or Sn) or 1.5 mmol Ph2SnCl2 were dissolved in
40 ml hexane (or 25 ml toluene in the cases of the tin
compounds) and 0.83 ml (6 mmol) NEt3 was slowly
added while a stream of dried H2S was bubbled
through the stirred solution. After 1 h the mixture was
filtered from precipitated ammonium salt and the sol-
vent removed in vacuo yielding an oily residue of ca.
55–65% of the desired five-membered ring compound
6a–d besides a mixture of the six-membered rings 2–4a
and 5b.
6a GC–MS: 238 (M+, 50), 223 (Me5Si3S2, 65), 165
(Me3Si2S2, 34), 163 (Me5Si2S, 30), 73 (Me3Si, 100).
6b GC–MS: 284 (M+, 7), 269 (Me5GeSi2S2, 12), 209
(Me5GeSiS; 1), 181 (MeGeSiS2, 2), 163 (Me5Si2S, 10),
119 (Me3Ge, 4), 89 (MeGe, 5), 73 (Me3Si, 100).
6c GC–MS: 330 (M+, 2), 315 (Me5Si2SnS2, 25), 227
(MeSiSnS2, 14), 195 (MeSiSnS, 2), 165 (Me3Sn, 3), 135
(MeSn, 13), 73 (Me3Si, 100).
5f GC–MS: 328 (M+, 3), 313 (Me7Si4OSe), 269
(Me7Si3Se, 4), 255 (Me5Si3OSe), 205 (Me7Si3O, 7), 189
(Me7Si3, 2), 175 (Me5Si3O, 3), 147 (Me5Si2O, 32), 131
(Me5Si2, 12), 116 (Me4Si2, 91), 101 (Si2Me3, 9), 73
(Me3Si, 100). (The isotopic patterns of all fragments
fitted the natural abundance of 76Se:77Se:78Se:80Se:
82Se=9.2:7.6:23.7:49.8:8.8 [39].)
3.6.2. Preparation of Me4Si2(S)2BPh (6e)
PhBCl2 (0.32 g, 2 mmol) and 0.37 g (2 mmol) 1 were
dissolved in 40 ml hexane and 1.11 ml (8 mmol) NEt3
was slowly added while a stream of H2S was passed
through the stirred solution. After 1 h the product
mixture was filtered and the solvent was removed yield-
ing pure 6e as very thin needles unsuitable for X-ray
3.5.3. Synthesis of Te(SiMe2SiMe2)2Te (5d)
The tellurium compound was synthesized essentially
via the same procedure as the selenium compound 5c,
but the disilane 1 was added while the Li2Te suspension
was cooled to the range −40 to −30°C and further
work-up was carried out in an ice bath (0°C). Colorless,
very thin needles of 5d could be obtained which decom-
pose very rapidly, if the sample is heated above room
temperature, but in solid state under Ar they are stable
at 20°C for at least several weeks.
1
analysis. The observed 11B- and H-NMR signals were
1
in good agreement with the H- and 11B-NMR data of
6e published in Ref. [9].
Again, if the reaction is carried out with THF con-
taining traces of moisture, the monooxygen compound
5g could be obtained as by-product.
If the addition of 1 to the Li2Te suspension is done at
room temperature, pure 6l was obtained as a colorless
oil after work-up.
The six-membered rings containing two different
chalcogen atoms (E=S, Se; E%=Se, Te) were prepared
via the same route than 5c and 5d but 2 mmol of 1 was
added to a mixture of Li2E and Li2E% prepared from 1
mmol E, 1mmol E% and 4 ml 1 M Li[BEt3H] in 5 ml
THF. 5h, 5i and 5k were detected by NMR in a mixture
3.6.3. Preparation of Me4Si2(S)2C(CH2)5 (6f)
According to the procedure described in Ref. [30]
10.2 g (0.104 mol) cyclohexanone and 0.86 g (0.01 mol)
morpholine were dissolved in 40 ml methanol and H2S
was bubbled through the mixture for 3 h. The resulting
product was treated with diluted sulfuric acid until two
phases occurred. The oily organic phase was separated,
the solvents were removed in vacuo at room tempera-
1
ture and the product was dried over CaCl2. H- and
13C-NMR spectra revealed that the product is pure
cyclohexane-1,1-dithiol which was used without further
purification, yield: 6.3 g (0.043 mol, 41%).

U. Herzog, G. Rheinwald / Journal of Organometallic Chemistry 627 (2001) 23–36
35
3
1H-NMR (ppm): 2.53 (SH), 1.87 (ortho-CH2, JHH
=
6p GC–MS: 286 (M+, 11), 271 (Me5Si3SSe, 16), 213
(Me3Si2SSe, 10), 211 (Me5Si2Se, 9), 181 (Me3Si2Se, 2),
163 (Me5Si2S, 18), 147 (Me3Si2SCH2, 8), 133 (Me3Si2S,
6), 123 (MeSiSe, 4), 73 (Me3Se, 100).
3
5.9 Hz), 1.52 (meta-CH2), 1.32 (para-CH2, JHH=5.7
Hz). 13C-NMR (ppm): 53.3 (C(SH)2), 45.7 (ortho-CH2),
23.6 (meta-CH2), 24.9 (para-CH2).
Cyclohexane-1,1-dithiol (0.22 g, 1.5 mmol) and 0.28 g
(1.5 mmol) 1 were dissolved in 25 ml hexane and 0.42
ml (3 mmol) NEt3 was slowly added under stirring.
After filtration from precipitated Et3NHCl and removal
of the solvent 0.29 g (74%) pure 6f remained as an oily
residue.
3.7. Preparation of the bis(cyclopentyl) compounds
Me4Si2(E)2Si2Me2(E)2Si2Me4 (E=S, Se, Te (7a–c))
1 (0.37 g, 2 mmol) and 0.46 g (2 mmol) SiCl2Me–
SiCl2Me were dissolved in 50 ml hexane and H2S was
bubbled through the solution while 1.66 ml (12 mmol)
NEt3 was added by a syringe. After 1 h the mixture was
filtered and the solvent removed to yield a crystalline
residue of 75% 7a besides 5b. Single crystals of 7a were
obtained from hexane solution.
GC–MS: 262 (M+, 3), 247 (M−Me, 2), 181
(Me4Si2S2H, 10), 180 (Me4Si2S2, 11), 165 (Me3Si2S2,
100), 149 (Me4Si2SH, 17), 133 (Me3Si2S, 10), 73 (Me3Si,
23).
7b and 7c were obtained by reacting a mixture of
0.187 g (1 mmol) 1 and 0.114 g (0.5 mmol) SiCl2Me–
SiCl2Me dissolved in 1 ml THF with a suspension of 2
mmol Li2E (E=Se, Te, prepared from E and LiBEt3H
as described above) in 5 ml THF at room temperature
(E=Se) or at −20°C (E=Te). After reacting for 30
min the THF was exchanged for hexane and the clear
hexane solution was separated and the solvent removed
to yield 7b as a semicrystalline residue and 7c (which
contained 5d and 6l as by-products) as an oily residue.
3.6.4. Selenium and tellurium deri6ati6es
Me4Si2(Se)2MMe2 (M=Si, Ge, Sn (6g–i)) and
Me4Si2(Te)2MMe2 (6l–n)
Selenium (0.16 g, 2 mmol) or 0.25 g (2 mmol) tel-
lurium powder reacted at room temperature with a
solution of 4 mmol Li[BEt3H] (‘‘Super hydride’’) in 10
ml THF. The selenium dissolved very rapidly and the
initially dark brown solution became a white suspen-
sion of Li2Se within a few minutes. But it took 1–2 h
until the tellurium was completely dissolved and the
initially deep purple solution became a light red suspen-
sion of Li2Te.
4. Supplementary material
A mixture of 0.187 g (1 mmol) 1 and 1 mmol of the
dichlorides Me2MMe2 were dissolved in 2 ml THF and
added to the Li2E suspension under stirring. After 30
min the solvent was removed and exchanged with 10 ml
hexane. The clear solution was separated and the sol-
vent removed to yield the five-membered ring com-
pounds as oils in a 50–70% yield. Only in the case of 6n
some 6l occurred as the by-product as determined by
NMR. 5f or 5g, respectively, were detected as by-prod-
ucts, if the reactions were not carried out under abso-
lute exclusion from oxygen and moisture.
Crystallographic data (excluding structure factors)
for the structural analyses have been deposited at the
Cambridge Crystallographic Data Centre, CCDC nos.
154132, 154133 and 154134 for 5b, 5c and 7a, respec-
tively. Copies of the data can be obtained free of charge
from The Director, CCDC, 12 Union Road, Cam-
bridge CB2 1EZ, UK (Fax: +44 1223336033 or e-mail:
deposit@ccdc.cam.ac.uk or http:// www.ccdc.cam.
ac.uk).
6g GC–MS: 334 (M+, 6), 319 (Me5Si380Se2, 8), 261
(Me3Si2Se2, 3), 246 (Me2Si2Se2, 1), 211 (Me5Si2Se, 17),
195 (Me3Si2SeCH2, 7), 181 (Si2Me3Se, 5), 123 (MeSiSe,
7), 73 (Me3Si, 100).
Acknowledgements
The authors wish to thank the ‘Deutsche
Forschungsgemeinschaft’ for financial support. Special
thanks are given to Prof. H. Lang, Chair of Inorganic
Chemistry, TU, Chemnitz for the access to the X-ray
facility used to determine the single crystal structures.
3.6.5. Mixed fi6e-membered rings Me4Si2(E)(E%)SiMe2
(E=S, E%=Se (6p), E=S, E%=Te (6q), E=Se,
E%=Te (6r))
E (1 mmol) (S or Se) and 1 mmol E% (Se or Te) were
mixed and added to a solution of 4 mmol Li[BEt3H] in
10 ml THF. A mixture of 0.187 g (1 mmol) 1 and 0.129
g (1 mmol) Me2SiCl2 in 2 ml THF was added to the
stirred suspension of Li2E and Li2E%. After work-up as
described in Section 3.6.4 an oily mixture was obtained,
which contained 45–50% 6p, 6q or 6r, respectively,
besides a mixture of two of the homocycles 6a, 6g and
6l.
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