Reactions of 2-germanaphthalene with elemental sulfur and selenium: Synthesis of novel cyclic polychalcogenides containing a germanium, trichalcogenagermolanes

Article abstract of DOI:10.1246/cl.2002.818

Novel five-membered cyclic trichalcogenides containing a germanium atom were synthesized by the reactions of a kinetically stabilized 2-germanaphthalene with elemental sulfur and selenium, and the molecular structure of the triselenide was determined by X

Full text of DOI:10.1246/cl.2002.818

818
Chemistry Letters 2002
Reactions of 2-Germanaphthalene with Elemental Sulfur and Selenium: Synthesis of Novel
Cyclic Polychalcogenides Containing a Germanium, Trichalcogenagermolanes
Norio Nakata, Nobuhiro Takeda, and Norihiro Tokitohꢀ
Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011
(Received May 13, 2002; CL-020410)
Novel five-membered cyclic trichalcogenides containing a
sulfur in THF (Scheme 1).
germanium atom were synthesized by the reactions of a
kinetically stabilized 2-germanaphthalene with elemental sulfur
and selenium, and the molecular structure of the triselenide was
determined by X-ray crystallographic analysis.
The chemistry of cyclic polychalcogenides has attracted
much interest because of their unique structures, reactivities and
biological activities.1 Among them, however, cyclic polychal-
cogenides containing a germanium atom have been little known.
Indeed, there have been only a few reports on tetrathiagermo-
lanes,2 a hexathiagermepane,3 and a tetraselenagermolane.4
Meanwhile, in recent years there has been much attention to
metallaaromatic compounds of heavier group 14 elements,5;6 i.e.,
heavier congeners of aromatic hydrocarbons which occupy a
great part of organic chemistry.7 We have recently succeeded in
the synthesis of the first stable 2-silanaphthalene 1 by taking
advantage of an efficient steric protection group, 2,4,6-
tris[bis(trimethylsilyl)methyl]phenyl (Tbt),8a and revealed that
the reaction of 1 with elemental sulfur afforded the novel
thiasilirane 3 or five-membered trisulfide depending on the
stoichiometry of sulfur.8b Very recently, 2-germanaphthalene 2
bearing a Tbt group, the first example of a stable neutral
germaaromatic compound, was also synthesized and fully
characterized by us.9 Herein, we present the reactions of 2 with
elemental sulfur and selenium leading to the formation of novel
Ge-containing cyclic trisulfide 5 and triselenide 6, respectively.
We also describe the X-ray crystallographic analysis of 6 and
dechalcogenation of 5 and 6.
Scheme 1.
Figure 1. ORTEP drawing of 6 with thermal ellipsoids
ꢀ
(50% probability). Selected bond lengths (A) and
angles(ꢁ): Ge(1)–Se(1) 2.402(1), Se(1)–Se(2) 2.350(1),
Se(2)–Se(3) 2.325(1), Se(3)–C(1) 1.984(4), Ge(1)–C(1)
1.979(5); Ge(1)–Se(1)–Se(2) 93.72(4), Se(1)–Se(2)–
Se(3) 98.54(3), Se(2)–Se(3)–C(1) 96.62(14).
We have revealed that the Ge–C(1) double bond of 2 has high
reactivity towards a variety of addition reactions even though it is
incorporated in the aromatic 2-germanaphthalene ring.12 The
reactivity of 2 with elemental chalcogens here observed is also
anothor experimentaldemonstration for the high reactivity of the
germene moiety.
The structures of cyclic trichalcogenides 5 and 6 were
satisfactorily confirmed by mass spectrometry, elemental analy-
sis, and NMR spectroscopy, and the molecular structure of 6 was
finally determined by X-ray crystallographic analysis.13 In Figure
1 is shown the ORTEP drawing of 6 together with some selected
bond lengths and angles. The CGeSe3 ring of 6 adopts a distorted
half-chair conformation where the Se(2) and Se(3) atoms lie at
opposite sides of the plane containing C(1), Ge(1), and Se(1)
To a benzene solution of 2 was added excess amount of sulfur
at room temperature, and the reaction mixture was stirred for 48 h.
After removalof the solvent, the crude products were separated
by gel permeation liquid chromatography (eluent: CHCl3) and
subsequent preparative thin-layer chromatography (eluent:
hexane) to afford a novel Ge-containing cyclic trisulfide,
1,2,3,4-trithiagermolane 510 as colorless crystals in 55% yield.
The reaction of 2 with 1 equiv (as S atom) of elemental sulfur did
not afford the corresponding Ge-containing three-membered ring
product, i.e., thiagermirane 4, but resulted in the formation of 5 in
12% yield. This result contrasted with the reaction of 1 with 1
equiv (as S atom) of elememtal sulfur giving the corresponding
thiasilirane 3.8b The selenium derivative, a novel Ge-containing
cyclic triselenide 6,11 was also obtained as orange crystals in 57%
yield when elemental selenium was used instead of elemental
ꢀ
atoms with irregular distances from the plane (0.56 A for Se(2)
ꢀ
and 0.75 A for Se(3)). The Se–Se bond lengths (2.325(1),
ꢁ
ꢀ
2.350(1) A), and the Se–Se–Se bond angle (98.54(3) ) of the
4
CGeSe3 ring are roughly similar to those of Tbt(Mes)GeSe4
ꢀ
(2.311(2)–2.327(4) A for the Se–Se bond lengths, 96.94(8), and
96.03(8) ꢁ for the Se–Se–Se bond angles). In the 77Se NMR
spectrum of 6 (in CDCl3), three signals were observed at 296, 531,
and 717 ppm. On the basis of the chemicalshifts of realted
polyselenides,4;14 these signals are assigned to theselenium atoms
Copyright Ó 2002 The ChemicalSociety of Japan

Chemistry Letters 2002
819
References and Notes
of the ꢀ-, ꢁ-, and ꢂ-positions to the germanium atom,
respectively.
1
a) R. Sato, T. Goto, and M. Saito, Yuki Gosei Kagaku Kyokaishi, 48, 797
(1990). b) B. S. Davidson, T. F. Molinski, L. R. Barrows, and C. M. Ireland,
J. Am. Chem. Soc., 113, 4709 (1991). c) M. Litaudon and M. Guyot,
Tetrahedron Lett., 32, 911 (1991). d) A. Ishii and J. Nakayama, Rev.
Heteroat. Chem., 19, 1 (1998). e) R. Okazaki, Phosphorus, Sulfur Silicon
Relat. Elem., 168–169, 41 (2001).
Trisulfide 5 is fairly stable toward air and moisture, and dose
not undergo any decomposition by the thermolysis at 100 ꢁC in
solution and even at 230 ꢁC in the solid state. On the other hand,
triselenide 6 gradually decomposed with liberation of red
selenium on standing in a hexane or CHCl3 solution for a few
hours to give a complex mixture. Of particular note among the
reactivities of 5 and 6 is that they gave quite different products on
dechalcogenation reactions with triphenylphosphine. Desulfur-
ization of 5 with 3 equiv. of Ph3P in C6D6 at 80 ꢁC for 24 h gave
the 2-germanaphthalene 2 (76%) together with Ph3P ¼ S (91%)
as judged by 1H NMR. On the other hand, deselenation of 6 under
similar reaction conditions for 3 h afforded a novel heterocycle, 1-
selena-2,5-digermacyclopentane 7 (82%), as an inseparable
mixture of the structuralisomers together with Ph3P ¼ Se
(80%) (Scheme 2).
2
a) N. Tokitoh, H. Suzuki, T. Matsumoto, Y. Matsuhashi, R. Okazaki, and
M. Goto, J. Am. Chem. Soc., 113, 7047 (1991). b) N. Tokitoh, T.
Matsumoto, and R. Okazaki, Tetrahedron Lett., 32, 6143 (1991). c) T.
Matsumoto, N. Tokitoh, and R. Okazaki, Organometallics, 14, 1008
(1995).
3
4
5
T. Matsumoto, Y. Matsui, Y. Nakaya, and K. Tatsumi, Chem. Lett., 2001,
60.
N. Tokitoh, T. Matsumoto, and R. Okazaki, Tetrahedron Lett., 33, 2531
(1992).
For reviews of silaaromatic compounds, see: a) G. Raabe and J. Michl,
Chem. Rev., 85, 419 (1985). b) G. Raabe and J. Michl, in ‘‘The Chemistry
of Organic Silicon Compounds,’’ ed. by S. Patai and Z. Rappoport, Wiley,
New York (1989), Chap. 17. c) A. G. Brook and M. A. Brook, Adv.
Organomet. Chem., 39, 71 (1996). d) Y. Apeloig and M. Karni, in ‘‘The
Chemistry of Organic Silicon Compounds,’’ ed. by Z. Rappport and Y.
Apeloig, Wiley, New York (1998), Vol. 2.
´
For reviews of germaaromatic compounds, see: a) J. Barrau, J. Escudie,
6
7
8
´
and J. Satge, Chem. Rev., 90, 283 (1990). b) V. Y. Lee, A. Sekiguchi, M.
Ichinohe, and N. Fukaya, J. Organomet. Chem., 611, 228 (2000).
V. J. Minkin, M. N. Glukhovtsev, Y. B. Simkin, in ‘‘Aromaticity and
Antiaromaticity; Electronic and Structural Aspects,’’ Wiley, New York
(1994).
a) N. Tokitoh, K. Wakita, R. Okazaki, S. Nagase, P. v. R. Schleyer, and H.
Jiao, J. Am. Chem. Soc., 119, 6951 (1997). b) K. Wakita, N. Tokitoh, R.
Okazaki, S. Nagase, P. v. R. Schleyer, and H. Jiao, J. Am. Chem. Soc., 121,
11336 (1999).
9
N. Nakata, N. Takeda, and N. Tokitoh, Organometallics, 20, 5507 (2001).
10 5: mp 220–223 ꢁC; 1H NMR (300 MHz, CDCl3) ꢃ À0:10 (s, 9H), À0:06 (s,
9H), 0.02 (s, 18H), 0.05 (s, 9H), 0.09 (s, 9H), 1.32 (s, 1H), 2.12 (br s, 2H),
4.44 (s, 1H), 6.32 (br s, 1H), 6.36 (d, J ¼ 12:9 Hz, 1H), 6.44 (br s, 1H), 7.14
(d, J ¼ 12:9 Hz, 1H), 7.14–7.32 (m, 4H); 13C NMR (75 MHz, CDCl3) ꢃ
0.40 (q), 0.67 (q), 0.69 (q), 0.76 (q), 0.80 (q), 1.14 (q), 29.59 (d), 29.90 (d),
30.64 (d), 46.96 (d), 122.45 (d), 125.45 (s), 127.45 (s), 127.94 (d), 128.12
(d), 128.95 (d), 131.85 (d), 134.13 (d), 134.37 (d), 135.50 (s), 141.49 (d),
146.36 (s), 151.33 (s), 151.66 (s); FABMS m=z 836 [Mþ], 740[(M-S3)þ].
Anal. Calcd for C36H66GeS3Si6: C, 51.71; H, 7.96%. Found: C, 51.63; H,
7.99%.
11 6: mp 203–205 ꢁC (decomp.); 1H NMR (300 MHz, CDCl3) ꢃ À0:11 (s,
9H), À0:07 (s, 9H), 0.01 (s, 18H), 0.09 (s, 9H), 0.12 (s, 9H), 1.30 (s, 1H),
2.22 (s, 2H), 5.06 (s, 1H), 6.30 (br s, 1H), 6.37 (d, J ¼ 12:9 Hz, 1H), 6.42
(br s, 1H), 7.06 (d, J ¼ 12:9 Hz, 1H), 7.07–7.33 (m, 4H); 13C NMR
(75 MHz, CDCl3) ꢃ 0.54 (q), 0.72 (q), 0.95 (q), 1.31 (q), 29.49 (d), 29.75
(d), 30.64 (d), 44.12 (d), 122.58 (d), 124.38 (s), 127.61 (d), 127.65 (d),
127.84 (d), 131.56 (d), 131.71 (d), 133.65 (s), 133.70 (d), 137.16 (s),
139.97 (d), 146.04 (s), 151.34 (s), 151.61 (s); 77Se NMR (57 MHz, CDCl3)
ꢃ 296.0, 531.4, 716.9; FABMS m=z 977 [Mþ], 819[(M-Se2)þ], 740[(M-
Se3)þ]. Anal. Calcd for C36H66GeSe3Si6: C, 44.26; H, 6.81%. Found: C,
44.04; H, 6.82%.
Scheme 2.
The structure of 7 was confirmed by its 1H and 77Se NMR,
high-resolution FAB-MS and elemental analysis.15 In the 1H and
77Se NMR spectra of 7, two structuralisomers were observed
(major : minor ¼ 4 : 3, ꢃSe; À451:2, À447:4). These two isomers
are most likely assigned to 7a and 7b judging from the
consistency with their 1H NMR spectra and the calculated
relative energies for the four isomeric structures 7a–d (Figure 2).
Although the formation mechanism of 7 is not clear at present,
one might be able to postulate the intermediacy of extremely
reactive selenagermirane derivative 8 and/or its ring opened
biradicalisomer 9 and their subsequent coupling reactions with
the exhaustively deselenated product 2 (Scheme 2). The exclusive
formation of the five-membered ring compounds 5 and 6 in the
reactions of 2 may be due to the steric effect of Tbt group and/or
the instability of the chalcogenagermirane skeletons. Further
investigation on the reactivity of 2, 5, and 6 is currently in
progress.
12 N. Nakata, N. Takeda, and N. Tokitoh, Organometallics, submitted.
13 The intensity data for 6 were collected on a Rigaku/MSC Mercury CCD
diffractometer. Crystaldata of
6:
C
36H66GeSe3Si6, fw ¼ 976:90,
ꢁ
ꢀ
T ¼ 103 K, triclinic, space group P1 (#2), a ¼ 9:484ð4Þ A, b ¼
ꢁ
ꢁ
ꢀ
ꢀ
12:021ð4Þ A, c ¼ 22:902ð9Þ A, ꢀ ¼ 75:562ð16Þ , ꢂ ¼ 81:901ð18Þ , ꢁ ¼
68:746ð13Þ ꢁ, V ¼ 2352:8ð15Þ A , Z ¼ 2, Dcalcd ¼ 1:379 g/cm3, R1
ꢀ 3
(I > 2ꢄðIÞÞ ¼ 0:045, wR2 ðall dataÞ ¼ 0:112 (CCDC 187028).
14 S. Ogawa, T. Kikuchi, S. Niizuka, and R. Sato, J. Chem. Soc., Chem.
Commun., 1994, 1593.
15 7: mp 203–205 ꢁC (decomp.); 1H NMR (300 MHz, CDCl3) ꢃ 0.06 (s,
SiMe3, major), 0.13 (s, SiMe3, major), 0.14 (s, SiMe3, minor), 0.26 (s,
SiMe3, minor), 0.27 (s, SiMe3, minor), 0.31 (s, SiMe3, major), 0.34 (s,
SiMe3, minor), 1.42 (s, Tbt-p-methine, major), 1.44 (s, Tbt-p-methine,
minor), 2.03 (br s, Tbt-o-methine, major), 2.28 (br s, Tbt-o0-methine,
major), 2.43 (br s, Tbt-o-methine, minor), 2.69 (br s, Tbt-o0-methine,
minor), 3.43 (s, GeCH, major), 3.93 (s, GeCH, minor), 6.12 (d, J ¼ 7:2 Hz,
Ar, major), 6.50–6.73 (m, Ar, major þ minor), 6.90–7.06 (m, Ar,
major þ minor); 77Se NMR (57 MHz, CDCl3) ꢃ À451:2 (major),
À447:4 (minor). Anal. Calcd for C72H132Ge2SeSi12: C, 55.47; H,
8.53%. Found: C, 55.45; H, 8.50%. HRMS (FAB): found m=z 1561.5237
([M þ H]þ), calcd for C72H133Ge2SeSi12 1561.5167.
Figure 2. Calculated relative energies for the four
isomers of 7 (kcal/mol, B3LYP/6-31G(d)).
This work was partially supported by a Grant-in-Aid for COE
Research on Elements Science (No. 12CE2005) and Grants-in-
Aid for Scientific Research (Nos. 11304045 and 11166250) from
the Ministry of Education, Science, Sports and Culture, Japan.