1,2,3,4,5,6,7-Hexathiagermepanes: Synthesis, structures, and the ring contraction to 1,2,3,4,5-tetrathiagermolanes

Article abstract of DOI:10.1246/cl.2001.60

The first 1,2,3,4,5,6,7-hexathiagermepanes Dmp(Ar)GeS₆ [Dmp=2,6-dimesitylphenyl, Ar= Mes, Dep (2,6-diethylphenyl), Tip (2,4,6-triisopropylphenyl)] were synthesized along with 1,2,3,4,5-tetrathiagermolanes by sulfurization of the corresponding dihydrogermanes. The hexathiagermepane Dmp(Tip)GeS₆ slowly converted to the tetrathiagermolane with release of elemental sulfur owing to the steric hindrance.

Full text of DOI:10.1246/cl.2001.60

60
Chemistry Letters 2001
1,2,3,4,5,6,7-Hexathiagermepanes: Synthesis, Structures, and
the Ring Contraction to 1,2,3,4,5-Tetrathiagermolanes
Tsuyoshi Matsumoto, Yosuke Matsui, Yukiko Nakaya, and Kazuyuki Tatsumi*†
Department of Chemistry, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602
†Research Center for Materials Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602
(Received October 18, 2000; CL-000948)
The first 1,2,3,4,5,6,7-hexathiagermepanes Dmp(Ar)GeS6
presumably due to the steric congestion.
[Dmp=2,6-dimesitylphenyl, Ar = Mes, Dep (2,6-diethylphenyl),
Tip (2,4,6-triisopropylphenyl)] were synthesized along with
1,2,3,4,5-tetrathiagermolanes by sulfurization of the correspon-
ding dihydrogermanes. The hexathiagermepane Dmp(Tip)GeS6
slowly converted to the tetrathiagermolane with release of ele-
mental sulfur owing to the steric hindrance.
In a Schlenk tube were mixed the dihydrogermanes 1a–c
with elemental sulfur (30–40 equiv as S8) and heated to
160–170 °C for 15–20 min. Most of excess sulfur was removed
by recrystallization and the residue was chromatographed on
silica gel to afford the new hexathiagermepanes 2a–c along
with the tetrathiagermolanes 3a–c. The selectivity for 2 is high-
er for the reaction of dihydrogermane having a less bulky Ar
group, i.e., Ar=Mes. On the other hand, the total yields of the
germanium polysulfides 2 and 3 increase when a bulkier Ar
group (Ar=Dep, Tip) is attached to germanium. In the case of
sulfurization of Tip2GeH2 the yield of Tip2GeS4 was low (15%)
and many uncharacterizable compounds were generated.5
Thus, it is important to choose a substituent of an appropriate
size in order to isolate polysulfido compounds of germanium.
According to the 1H NMR spectra, the hexathiagermepanes
2 are sterically tighter than the corresponding tetrathiager-
molanes 3. For instance, 2c shows four doublets from 0.78 to
1.10 ppm attributed to four iPr groups of o-positions on Tip,
while only one doublet at 0.83 ppm is observed in 3c. Six
methyl groups of Dmp are observed independently from 1.87 to
2.41 ppm in 2c, despite two singlets at 1.87 and 2.29 ppm in 3c.6
The structures of 2a,b and 3a–c were determined by X-ray
analysis and those of 2b and 3b are shown in Figures 1 and 2,
respectively.7
Although transition metal polysulfides are ubiquitous,1
chemistry of polysulfido compounds of group 14 elements is
less developed.2,3 As an extension of our studies on transition
metal chalcogenides, we have been interested in those having
sterically protected germanium polysulfides. The structurally-
characterized example of germanium polysulfides was limited
to the 1,2,3,4,5-tetrathiagermolane.3a,b Here we report the syn-
thesis and structures of 1,2,3,4,5,6,7-hexathiagermepane,
Dmp(Ar)GeS6, and experimentally made obvious that their ring
size was controlled by steric effect.
The 7-membered ring of 2b assumes a chair conformation,
which is similar to the geometry of reported hexathiepanes, the
carbon analogue.8 The S-Ge-S angle of 2b, 104.68(4)°, is
notably larger than that of 3b, 99.31(3)°, which in turn forces
the other bond angles around Ge to be smaller for 2b.
The dihydrogermanes with bulky substituents 1a–c were
prepared as shown in Scheme 1. Recently Power et al. reported
the high yield synthesis of Dmp2Ge by the reaction of
GeCl2(dioxane) with 2 equiv of DmpLi.4 When we reacted
GeCl4 with DmpLi, which was prepared in ether from DmpI
and n-BuLi, DmpCl (51%) was formed. Addition of HMPA to
the reaction system was found to suppress the formation of
DmpCl, and we were able to synthesize Dmp(Ar)GeH2 in satis-
factory yields by the subsquent treatment with ArMgBr and
reduction by LiAlH4. The substitution by two or more Dmp
groups was not observed even in the presence of excess DmpLi,
Copyright © 2001 The Chemical Society of Japan

Chemistry Letters 2001
61
The Dep ring is situated nearly parallel to one Mes group
of Dmp, and the two ethyl substituents of Dep point away from
the Mes group, probably to avoid steric repulsion. Or, the par-
allelism may be caused by attractive π–π stacking interactions.
The other Mes group of Dmp and the ethyl groups of Dep
appear to protect sterically the 7-membered ring. This arrange-
ment of substituents is also observed in 3b.
Press, New York (1995), Vol. 2, pp.34–37, pp.166–174,
and pp.293–296, and references cited therein.
3
a) N. Tokitoh, H. Suzuki, T. Matsumoto, Y. Matsuhashi, R.
Okazaki, and M. Goto, J. Am. Chem. Soc., 113, 7047
(1991). b) T. Matsumoto, N. Tokitoh, R. Okazaki, and M.
Goto, Organometallics, 14, 1008 (1995). c) H. Suzuki, N.
Tokitoh, R. Okazaki, S. Nagase, and M. Goto, J. Am.
Chem. Soc., 120, 11096 (1998). d) Y. Matsuhashi, N.
Tokitoh, R. Okazaki, M. Goto, and S. Nagase,
Organometallics, 12, 1351 (1993). e) N. Tokitoh, N.
Kano, K. Shibata, and R. Okazaki, Organometallics, 14,
3121 (1995).
4
5
6
R. S. Simons, L. Pu, M. M. Olmstead, and P. P. Power,
Organometallics, 16, 1920 (1997).
T. Matsumoto, Y. Matsui, and K. Tatsumi, unpublished
result.
1
2c: colorless crystals; H NMR(CDCl3, 500 MHz) δ 0.78
(br d, J = 6.9 Hz, 3H), 0.80 (br d, J = 6.9 Hz, 3H), 1.00 (br
d, J = 6.9 Hz, 3H), 1.10 (br d, J = 6.9 Hz, 3H), 1.23 (br d, J
= 6.9 Hz, 6H), 1.87 (s, 3H), 2.02 (s, 3H), 2.23 (s, 3H), 2.30
(s, 3H), 2.33 (s, 3H), 2.41 (s, 3H), 2.82 (sept, J = 6.9 Hz,
1H), 3.09 (br sept, J = 6.9 Hz, 2H), 6.44 (br s, 1H), 6.84 (br
s, 1H), 6.85 (br s, 2H), 6.86 (br s, 1H), 7.02 (br s, 1H), 7.02
(br d, J = 7.6 Hz, 1H), 7.12 (br d, J = 7.6 Hz, 1H), 7.41 (t, J
= 7.6 Hz, 1H). Anal. Found: C, 59.50; H, 5.72; S, 24.89%.
Calcd for C39H48GeS6: C, 59.91; H, 6.19; S, 24.61%. 3c:
1
light yellow crystals; H NMR(CDCl3, 500 MHz) δ 0.83
(d, J = 6.9 Hz, 12H), 1.20 (d, J = 6.9 Hz, 6H), 1.87 (br s,
12H), 2.29 (s, 6H), 2.79 (sept, J = 6.9 Hz, 1H), 2.98 (br
sept, J = 6.9 Hz, 2H), 6.76 (br s, 4H), 6.84 (s, 2H), 7.00 (br
d, J = 7.6 Hz, 2H), 7.43 (t, J = 7.6 Hz, 1H). Anal. Found:
C, 65.59; H, 6.90; S, 17.51%. Calcd for C39H48GeS4: C,
65.27; H, 6.74; S, 17.87%.
The thermodynamic equilibrium between 2 and 3 deserves
comments. The hexathiagermepane 2c slowly converted to 3c
with release of elemental sulfur in hexane at room temperature
while almost no change was discernible for 2a in 2 days. The
transformation was, however, accelarated by heating, and at 60
˚C in hexane in 5 days, it reached to equilibrium in 1:1 (2a : 3a)
and 1:4 (2c : 3c) ratio (Scheme 2). The conversion of 3c to 2c
was also observed in the presence of 1 equiv of S8 in hexane
under reflux.9 The observation indicates that the ring size of
the polysulfides is thermodynamically controlled by the size of
the substituents on germanium.10
7
The data collection was made with a Rigaku-AFC7R dif-
fractometer for 2b and a Rigaku-AFC diffractometer
equipped with a MSC/ADSC Quantum 1 CCD detector for
3b. The structures were solved by a Texsan package.
Crystal data for 2b: C34H38GeS6, Mr = 711.62, monoclinic,
space group P21/n, a = 11.346(5), b = 16.340(9), c =
18.989(7) Å, β = 100.82(3)°, V = 3458(2) Å3, Z = 4, Dcalc
=
1.367 g/cm3, T = 296 K, µ(Mo Kα) = 47.74 cm–1, R =
0.046, Rw = 0.067, GOF = 2.63, 370 variables, 5518 unique
reflections [I > 1σ(I)]. For 3b: C34H38GeS4, Mr = 647.50,
monoclinic, space group P21/c, a = 10.9365(6), b =
10.4258(9), c = 27.5673(7) Å, β = 90.2677(5)°, V =
3143.2(3) Å3, Z = 4, Dcalc = 1.368 g/cm3, T = 193 K, µ(Mo
Kα) = 47.74 cm–1, R = 0.067, Rw = 0.069, GOF = 0.90, 361
variables, 7199 unique reflections (all data). One methyl
group on Dep is disordered.
References and Notes
1
Reviews on polychalcogenido complexes, see: a) A.
Müller, E. Diemann, R. Jostes, and H. Bögge, Angew.
Chem., Int. Ed. Engl., 20, 934 (1981). b) A. Müller, W.
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245 (1982). c) M. Draganjac and T. B. Rauchfuss, Angew.
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Polyhedron, 5, 323 (1986). f) A. Müller and E. Diemann,
Adv. Inorg. Chem., 89, 31 (1987). g) M. R. DuBois, Chem.
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Chem. Rev., 100, 223 (1990). i) J. W. Kolis, Coord. Chem.
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8
9
a) V. F. Fehér and J. Lex, Z. Anorg. Allg. Chem., 423, 103
(1976). b) Y.-N. Jin, A. Ishii, Y. Sugihara, and J.
Nakayama, Heterocycles, 44, 255 (1997).
The equilibrium was reported between 1,2,3,4,5-benzopen-
tathiepines and 1,2,3-benzotrithioles in the presence of
amines. a) N. Tokitoh, H. Ishizuka, and W. Ando, Chem.
Lett., 1988, 657. b) B. L. Chenard, R. L. Harlow, A. L.
Johnson, and S. A. Vladuchick, J. Am. Chem. Soc., 107,
3871 (1985).
10 The steric effect on the ring size was proposed previously.
See ref 3.
2
“Comprehensive Organometallic Chemistry II,” Pergamon