Reaction of an overcrowded distibene with elemental sulfur and crystallographic analysis of the sulfurization products

Article abstract of DOI:10.1246/cl.2004.104

The reaction of a kinetically stabilized distibene bearing 2,6-bis[bis(trimethylsilyl)methyl]-4-[tris(trimethylsilyl)methyl]-phenyl (denoted as Bbt) groups with elemental sulfur resulted in the formation of three types of sulfurization products containing two antimony atoms. The first structural identification of the 1,2,4,3,5-trithiadistibolane derivative was achieved by X-ray crystallographic analysis.

Full text of DOI:10.1246/cl.2004.104

104
Chemistry Letters Vol.33, No.2 (2004)
Reaction of an Overcrowded Distibene with Elemental Sulfur and Crystallographic Analysis
of the Sulfurization Products
Takahiro Sasamori, Eiko Mieda, Nobuhiro Takeda, and Norihiro Tokitohꢀ
Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011
(Received October 29, 2003; CL-031036)
The reaction of a kinetically stabilized distibene bearing
2,6-bis[bis(trimethylsilyl)methyl]-4-[tris(trimethylsilyl)methyl]-
phenyl (denoted as Bbt) groups with elemental sulfur resulted in
the formation of three types of sulfurization products containing
two antimony atoms. The first structural identification of the
1,2,4,3,5-trithiadistibolane derivative was achieved by X-ray
crystallographic analysis.
of the solution gradually changed to yellow. After standing the
solution for 1 h, three types of antimony-containing cyclic poly-
sulfides, 1,2,4,3,5-trithiadistibolane 2 (69%), 1,2,3,5,4,6-tetra-
thiadistibinane 3 (17%), and 1,3,2,4-dithiadistibetane 4 (14%)
were obtained without any other identifiable compounds as
4
1
judged by the H NMR spectrum of the crude solution. It was
very difficult to perform the complete separation of 2, 3, and 4
from each other by HPLC and column chromatography, because
they gradually decomposed through separation procedures.
However, small amounts of pure 2, 3, and 4 were isolated and
identified via persistent purification by recrystallization and col-
umn chromatography. This result contrasts with the case of di-
phosphenes, the lighter analogue of distibenes, which are known
to react with elemental sulfur to give three-membered ring com-
pounds, thiadiphosphiranes.5 We examined the reaction of 1
with 1 equiv. (as S) of elemental sulfur at room temperature in
the hope of obtaining Bbt-substituted thiadistibirane, a possible
intermediate to give 2, 3, and 4. As a result, 1H NMR spectrum
showed that the reaction mixture contained unidentified com-
pound X as a main product together with 1, 2, and 4. Unfortu-
nately, compound X, which might be a thiadistibirane derivative,
could not be isolated because of its extreme sensitivity toward
air and moisture.6
Recent active works on the chemistry of doubly-bonded sys-
tems between heavier group 15 elements have demonstrated that
they are not fictitious any longer and have real existence as stable
compounds even in the case of the heaviest group 15 element,
bismuth, when they are kinetically well stabilized.1 Currently,
there is a widespread interest in the reactivity of these fascinat-
ing doubly-bonded systems. Although several reactions of di-
phosphenes (RP=PR) and diarsenes (RAs=AsR) have been re-
ported,1a,b,d the reactivities of their heavier congeners,
distibenes (RSb=SbR) and dibismuthenes (RBi=BiR), are not
fully explored. Up to date, only three examples of stable disti-
benes and dibismuthenes have been recently reported,2,3 and
we have succeeded in the synthesis and characterization of the
first stable distibene (TbtSb=SbTbt)2b and dibismuthene
(TbtBi=BiTbt)2a by taking advantage of an efficient steric pro-
tection group, 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl (Tbt)
group. In addition, we have already reported the unique oxida-
tion reactions of TbtSb=SbTbt and TbtBi=BiTbt with atmos-
pheric oxygen in the solid state to give the corresponding
1,3,2,4-dioxadipnictogetane derivatives.2 Although further stud-
ies on the reactivities of TbtE=ETbt (E=Sb, Bi) in solution have
been thwarted by their extremely low solubility in common or-
ganic solvents, we have recently succeeded in the synthesis of
soluble distibene and dibismuthene bearing a new substituent,
2,6-bis[bis(trimethylsilyl)methyl]-4-[tris(trimethylsilyl)methyl]-
phenyl (denoted as Bbt) group,2c and started studies on the reac-
tivities of BbtE=EBbt (E=Sb, Bi) in solution. At the first stage
of studies on reactivities of heavier dipnictenes (‘‘pnictogen’’ is
the general term for group 15 elements), we decided to elucidate
the reactivity of the soluble distibene and dibismuthene with el-
emental chalcogens from the viewpoint of comparison with the
oxidation reaction by atmospheric oxygen. Here, we wish to de-
scribe the reaction of BbtSb=SbBbt with elemental sulfur lead-
ing to the formation of three types of antimony-containing cyclic
polysulfides, all of which were structurally characterized by X-
ray crystallographic analysis.
CH(SiMe3)2
Bbt
Sb Sb
Bbt
S
S8
Bbt Sb
Sb Bbt
CX(SiMe3)2
CH(SiMe3)2
C6D6
r.t.
Sn
1
2 (n = 2): 69%
3 (n = 3): 17%
4 (n = 1): 14%
Tbt: X = H
Bbt: X = SiMe3
Scheme 1.
On the other hand, we have already revealed that the reac-
tion of TbtSb=SbTbt (5) with elemental sulfur in THF, in which
5 may be slightly more soluble than in C6D6, did not proceed at
room temperature probably due to the extremely low solubility
of 5. Refluxing the reaction mainly produced a mixture of the
linear polysulfides 8 and 9 (ca. 52%) containing no Sb atom, to-
gether with Tbt-substituted 1,2,4,3,5-trithiadistibolane 6 (31%)
and 1,2,3,5,4,6-tetrathiadistibinane 7 (13%).7 The linear polysul-
fides 8 and 9 are most likely generated via the over reaction of 6
and/or 7 with S8 at such high temperature. Since the soluble dis-
tibene 1 was found to react with S8 easily at room temperature, it
can be concluded that the results of the reaction of BbtSb=SbBbt
(1) with S8 described here might reflect the more inherent reac-
tivity of a distibene with S8.
When a benzene-d6 solution (0.7 mL) of 1 (96 mg,
0.064 mmol), which was easily prepared by reductive coupling
reaction of BbtSbBr2 with Mg in almost quantitative yield,
was mixed with an excess amount of elemental sulfur (S8,
20 mg, 9.8 equiv. as S) at room temperature, deep-orange color
Single crystals of the new 1,2,4,3,5-trithiadistibolane
[2ꢁhexane] were obtained by the recrystallization from hexane,
and its unique molecular structure was revealed by X-ray crys-
tallographic analysis.8 It should be noted that this is the first ex-
Copyright Ó 2004 The Chemical Society of Japan

Chemistry Letters Vol.33, No.2 (2004)
105
of chair-conformations, two Bbt groups on the antimony atoms
are in equatorial positions. The structural parameters of 3 are
similar to those of previously reported 7.10 Although the struc-
tural parameters of 4 were not determined definitively due to
the low quality of the single crystals, the 1,3,2,4-dithiadistibe-
tane skeleton of 4 was confirmed by X-ray crystallographic anal-
ysis.8
It should be noted again that the reaction products of disti-
benes with elemental sulfur are different from those reported
for diphosphenes, though their formation mechanism is not clear
at present. Further elucidation of the chemical properties of
heavier dipnictenes is currently in progress.
Tbt
Sb Sb
Tbt
S
Tbt Sb Sb
Sn
S8
+
Tbt Sn Tbt
Tbt
THF
reflux
5
6 (n = 2): 31%
7 (n = 3): 13%
8 (n = 6)
9 (n = 8)
ca. 52%
Scheme 2.
ample of a 1,2,4,3,5-trithiadistibolane ring system. In Figure 1
are shown the ORTEP drawing and the selected structural pa-
rameters of 2. One can see the half-chair geometry for the central
1,2,4,3,5-trithiadistibolane ring skeleton. The two sulfur atoms
S2 and S3 lie at almost equal distance on both sides of the plane
defined by Sb1, Sb2, and S1 [Figure 1a]. The Sb–S bond lengths
ꢀ
[2.4349(8), 2.4806(7), 2.4398(7), and 2.4833(7) A] in 2 are com-
This work was partially supported by a Grants-in-Aid for
COE Research on Elements Science [No. 12CE2005], the
Scientific Research on Priority Areas [No. 14078213], and the
21 COE Program on Kyoto University Alliance for Chemistry
(Novel Organic Materials Creation & Transformation Project)
from the Ministry of Education, Culture, Sports, Science and
Technology, Japan.
parable with those of W(CO)5 complex of cyclo-R2Sb2S2 [R =
ꢀ
9
CH(SiMe3)2; Sb–S: 2.425(1), 2.428(1) A]. The S–S bond-
ꢀ
length [2.0586(9) A] in 2 is within a range of normal single bond
lengths.
We also succeeded in the structural characterization of 3.8
Figure 2 shows the chair-conformation of the central 1,2,3,5,4,
6-tetrathiadistibinane ring of 3. It was found that the 1,2,3,5,
4,6-tetrathiadistibinane ring was disordered (78:22) due to the
flipping of the six-membered ring. In both cases of the two types
References and Notes
1
For reviews, see: a) L. Weber, Chem. Rev., 92, 1839 (1992). b) M. Yoshifuji,
in ‘‘Multiple Bonds and Low Coordination in Phosphorus Chemistry,’’ ed. by
M. Regitz and O. J. Scherer, Georg Thieme Verlag, Stuttgart, Germany
(1990), p 321. c) A. H. Cowley, J. E. Kilduff, J. G. Lasch, S. K. Mehrotra,
N. C. Norman, M. Pakulski, B. R. Whittlesey, J. L. Atwood, and W. E.
Hunter, Inorg. Chem., 23, 2582 (1984). d) N. Tokitoh, J. Organomet. Chem.,
611, 217 (2000). e) C. Jones, Coord. Chem. Rev., 215, 151 (2001). f) P. P.
Power, Chem. Rev., 99, 3463 (1999).
S3
C31
(a)
(b)
Sb1
Sb2
S1
S2
C1
2
a) N. Tokitoh, Y. Arai, R. Okazaki, and S. Nagase, Science, 277, 78 (1997). b)
N. Tokitoh, Y. Arai, T. Sasamori, R. Okazaki, S. Nagase, H. Uekusa, and Y.
Ohashi, J. Am. Chem. Soc., 120, 433 (1998). c) T. Sasamori, Y. Arai, N.
Takeda, R. Okazaki, Y. Furukawa, M. Kimura, S. Nagase, and N. Tokitoh,
Bull. Chem. Soc. Jpn., 75, 661 (2002).
3
4
B. Twamley, C. D. Sofield, M. M. Olmstead, and P. P. Power, J. Am. Chem.
Soc., 121, 3357 (1999).
All the new products here obtained (2–4) showed satisfactory spectral and an-
alytical data. The spectral data for 2 as the representative are shown as fol-
lows. 2: yellow crystals, mp 186.0–186.7 ꢂC (dec.); 1H NMR (300 MHz,
C6D6) ꢀ 0.34 (s, 126H), 2.59 (s, 4H), 7.04 (s, 4H); 13C NMR (75 MHz, C6D6)
ꢀ 1.70 (q), 1.89 (q), 5.60 (q), 22.74 (s), 34.84 (d), 128.12 (d), 147.61 (s),
147.94 (s), 151.12 (s). HRMS(FAB) m=z Obsd 1589.4515 ([M + H]þ) Calcd
for C60H135S3123Sb2 Si14: 1589.4586. Anal. Found: C, 47.66; H, 9.00%.
Calcd for C60H134S3Sb2Si14ꢁC6H14: C, 47.65; H, 8.95%.
Figure 1. (a) Side view of the Sb2S3 ring in 2. (b) ORTEP
drawing of 2 with thermal ellipsoid plot (50% probability).
The solvated hexane molecule was omitted for clarity. Selected
ꢀ
bond lengths (A) and angles (deg): Sb1–S1 2.4349(8), Sb1–S2
5
6
a) M. Yoshifuji, K. Shibayama, I. Shima, and N. Inamoto, Phosphorus, Sulfur
and Silicon, 18, 11 (1983). b) M. Yoshifuji, K. Shibayama, N. Inamoto, K.
Hirotsu, and T. Higuchi, J. Chem. Soc., Chem. Commun., 1983, 862. c) T.
Sasamori, N. Takeda, and N. Tokitoh, J. Phys. Org. Chem., 16, 450 (2003).
The spectral data for compound X are shown as follows: 1H NMR (300 MHz,
C6D6) ꢀ 0.32 (s, 126H), 2.96(s, 4H), 6.94(s, 4H). Compound X gave a
complicated mixture containing BbtH on exposure to the air and moisture.
N. Tokitoh, Y. Arai, and R. Okazaki, unpublished results (Y. Arai, Thesis,
The University of Tokyo, 1996.)
2.4806(7), Sb2–S1 2.4398(7), Sb2–S3 2.4833(7), S2–S3
2.0586(9), Sb1–S1–Sb2 101.90(3), S1–Sb1–S2 94.40(2), Sb1–
S2–S3 91.04(3), S2–S3–Sb2 91.21(3), S1–Sb2–S3 94.96(2).
7
8
The intensity data for single crystals of [2ꢁhexane], 3 and 4 were collected on
a Rigaku/MSC Mercury CCD diffractometer. Crystallographic data for
1674.78, T ¼ 103ð2Þ K, triclinic,
ꢀ ꢀ
[2ꢁhexane]: C66H148S3Sb2Si14, FW
=
ꢀ
P ꢃ 1 (#2), a ¼ 12:9972ð16Þ A, b ¼ 18:119ð2Þ A, c ¼ 21:906ð2Þ A, ꢁ ¼
69:779ð3Þꢂ, ꢂ ¼ 73:807ð4Þꢂ, ꢃ ¼ 87:957ð5Þꢂ, V ¼ 4638:3ð9Þ A , Z ¼ 2,
ꢀ 3
Dcalcd ¼ 1:199 g cmꢃ3, R1 ¼ 0:0312 [I > 2ꢄðIÞ], wR2 = 0.0781 [all data]
(CCDC222751); 3: C60H134S4Sb2Si14, FW = 1620.67, T ¼ 103ð2Þ K, mono-
ꢀ
ꢀ
ꢀ
clinic, P21=a (#14), a ¼ 24:764ð10Þ A, b ¼ 12:656ð5Þ A, c ¼ 28:522ð12Þ A,
ꢀ 3
ꢂ ¼ 103:468ð4Þꢂ, V ¼ 8693ð6Þ A , Z ¼ 4, Dcalcd ¼ 1:238 g cmꢃ3
,
R1
¼
0:1059 [I > 2ꢄðIÞ], wR2 0.2307 [all data] (CCDC222752); 4:
=
Figure 2. ORTEP drawing of 3 (major part) with thermal ellip-
ꢀ
soid plot (50% probability). Selected bond lengths (A) and an-
C60H134S3Sb2Si14, FW = 1588.61, T ¼ 103ð2Þ K, monoclinic, P21=c (#14),
a ¼ 8:918ð19Þ A, b ¼ 12:90ð3Þ A, c ¼ 36:44ð7Þ A, ꢂ ¼ 91:16ð2Þꢂ, V ¼
ꢀ
ꢀ
ꢀ
4192ð15Þ A , Z ¼ 2, Dcalcd ¼ 1:259 g cmꢃ3
.
H. J. Breunig, L. Ghesner, and E. Lork, Appl. Organomet. Chem., 16, 547
(2002).
ꢀ 3
gles (deg) for the major part: Sb1–S1 2.473(3), Sb1–S4
2.449(4), Sb2–S3 2.455(4), Sb2–S4 2.443 (4), S1–S2 2.067(5),
S2–S3 2.068(5), S1–Sb1–S4 95.18(13), Sb1–S1–S2 95.10(16),
S1–S2–S3 107.4(2), S2–S3–Sb2 97.54(17), S3–Sb2–S4
97.75(13), Sb1–S4–Sb2 93.20(13).
9
10 a) N. Tokitoh, Y. Arai, J. Harada, and R. Okazaki, Chem. Lett., 1995, 959. b)
N. Tokitoh, Y. Arai, T. Sasamori, N. Takeda, and R. Okazaki, Heteroatom
Chem., 12, 244 (2001).
Published on the web (Advance View) January 8, 2004; DOI 10.1246/cl.2004.104