The first kinetically stabilized germanethiones and germaneselones: Syntheses, structures, and reactivities

Article abstract of DOI:10.1021/ja991147x

The first kinetically stabilized germanethiones (germanium-sulfur double-bond species) and germaneselones (germanium-selenium double-bond species) were synthesized. Dechalcogenation of the novel 1,2,3,4,5-tetrachalcogenagermolane Tbt(TiP)GeX₄ (Tbt = 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl, Tip = 2,4,6-triisopropylphenyl, X = S or Se) with 3 molar equiv of triphenylphosphine gave diaryl-substituted germanethione Tbt(Tip)Ge=S 1a and germaneselone Tbt(Tip)Ge=Se 2a as orange-yellow crystals and red crystals, respectively, which were unstable in air but thermally quite stable. Chalcogenation of germylene Tbt(Dis)Ge: resulted in the isolation of the corresponding germanethione Tbt(Dis)Ge-S 1b and germaneselone Tbt(Dis)Ge=Se 2b (Dis = bis(trimethylsilyl)methyl). The molecular structures of germanethione 1a and germaneselones 2a,b determined by X-ray crystallographic analysis indicate that they have trigonal planar geometies around the germanium atom and a remarkably shorter Ge-S (2.049(3) A for 1a) or Ge-Se bond lengths (2.180(2) A for 2a and 2.173(3) A for 2b), compared with that of typical single bonds. The double-bond characters are also reflected in their spectral data such as UV/vis (1a, 450 nm; 1b, 432 nm; 2a, 519 nm; 2b, 492 nm), Raman (1a, 521 cm^-1; 1b, 512 cm^-1; 2a, 381 cm^-1; 2b, 386 cm^-1), and ⁷⁷Se NMR (2a, 941 ppm; 2b, 872 ppm). The germanethiones and germaneselones underwent [2 + 2] (with phenyl isothiocyanate), [3 + 2] (with mesitonitrile oxide), and [4 + 2] cycloadditions (with 1,3-dienes) to give the corresponding adducts in high yields. The regioselectivities of the [4 + 2] cycloadditions were examined using unsymmetrical dienes such as isoprene and interpreted in terms of the interaction between LUMO of the Ge=X unit and HOMO of the diene part.

Full text of DOI:10.1021/ja991147x

J. Am. Chem. Soc. 1999, 121, 8811-8824
8811
The First Kinetically Stabilized Germanethiones and Germaneselones:
Syntheses, Structures, and Reactivities
Tsuyoshi Matsumoto,† Norihiro Tokitoh,*,‡ and Renji Okazaki*,§
Contribution from the Department of Chemistry, Graduate School of Science, The UniVersity of Tokyo,
7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
ReceiVed April 12, 1999
Abstract: The first kinetically stabilized germanethiones (germanium-sulfur double-bond species) and
germaneselones (germanium-selenium double-bond species) were synthesized. Dechalcogenation of the novel
1,2,3,4,5-tetrachalcogenagermolane Tbt(Tip)GeX4 (Tbt ) 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl, Tip )
2,4,6-triisopropylphenyl, X ) S or Se) with 3 molar equiv of triphenylphosphine gave diaryl-substituted
germanethione Tbt(Tip)GedS 1a and germaneselone Tbt(Tip)GedSe 2a as orange-yellow crystals and red
crystals, respectively, which were unstable in air but thermally quite stable. Chalcogenation of germylene
Tbt(Dis)Ge: resulted in the isolation of the corresponding germanethione Tbt(Dis)GedS 1b and germaneselone
Tbt(Dis)GedSe 2b (Dis ) bis(trimethylsilyl)methyl). The molecular structures of germanethione 1a and
germaneselones 2a,b determined by X-ray crystallographic analysis indicate that they have trigonal planar
geometies around the germanium atom and a remarkably shorter Ge-S (2.049(3) Å for 1a) or Ge-Se bond
lengths (2.180(2) Å for 2a and 2.173(3) Å for 2b), compared with that of typical single bonds. The double-
bond characters are also reflected in their spectral data such as UV/vis (1a, 450 nm; 1b, 432 nm; 2a, 519 nm;
2b, 492 nm), Raman (1a, 521 cm-1; 1b, 512 cm-1; 2a, 381 cm-1; 2b, 386 cm-1), and 77Se NMR (2a, 941
ppm; 2b, 872 ppm). The germanethiones and germaneselones underwent [2 + 2] (with phenyl isothiocyanate),
[3 + 2] (with mesitonitrile oxide), and [4 + 2] cycloadditions (with 1,3-dienes) to give the corresponding
adducts in high yields. The regioselectivities of the [4 + 2] cycloadditions were examined using unsymmetrical
dienes such as isoprene and interpreted in terms of the interaction between LUMO of the GedX unit and
HOMO of the diene part.
Introduction
first isolation of kinetically stabilized germanethione Tbt(Tip)-
GedS 1a8a and germaneselone Tbt(Tip)GedSe 2a,8b along with
some other analogues of double-bond species between group
14 and group 16 elements,8c,9,10 by taking advantage of a very
effective steric protection group, 2,4,6-tris[bis(trimethylsilyl)-
methyl]phenyl (denoted as Tbt11).
This paper describes the detailed account of the isolation,
molecular structure, physical properties, and reactivities of the
diarylgermanethione 1a and diarylgermaneselone 2a as well as
new germanethione Tbt(Dis)GedS 1b and germaneselone Tbt-
(Dis)GedSe 2b, having Dis group [Dis; bis(trimethylsilyl)-
methyl]. The syntheses of 1b and 2b are expected to enable us
Over the past few decades, it had been commonly considered
that double bonds between heavier main-group elements would
not be stable for their weak π-bonds, which was the so-called
“double-bond rule”. In the 1960s, however, the double-bond
species between the heavier groups 14 and 15 elements came
to be proposed via trapping experiments, and the isolation of
compounds with SidC,1 SidSi,2 and PdP3 bonds was achieved
in 1981. After this breakthrough, remarkable progress has been
made in the chemistry of multiply bonded compounds of heavier
main group elements.
Among them are double-bond species between groups 14 and
16 elements, that is, congeners of a carbonyl compound, which
are of current interest. Although many reports have also been
published for transient germanium-chalcogen double-bond
species,4 the examples of stable species are rare. Three Ge-
S5-7 and two Ge-Se double-bond compounds6,7 have been
isolated, but all of them were stabilized by intramolecular
coordination of nitrogen ligands. We preliminarily reported the
(4) For reviews: (a) Barrau, J.; Escudie´, J.; Satge´, J. Chem. ReV. 1990,
90, 283. (b) Satge´, J. AdV. Organomet. Chem. 1982, 21, 241. (c) Rivie`re,
P.; Rivie`re-Baudet, M.; Satge´, J. ComprehensiVe Organometallic Chemistry;
Pergamon Press: New York, 1982; Vol. 2, Chapter 2. (d) Power, P. P. J.
Chem. Soc., Dalton. Trans. 1998, 2939.
(5) (a) Veith, M.; Becker, S.; Huch, V. Angew. Chem., Int. Ed. Engl.
1989, 28, 1237. (b) Veith, M.; Detemple, A.; Huch, V. Chem. Ber. 1991,
124, 1135. (c) Veith, M.; Detemple, A. Phosphorus, Sulfur Silicon Relat.
Elem. 1992, 65, 17.
(6) (a) Kuchta, M. C.; Parkin, G. J. Chem. Soc., Chem. Commun. 1994,
1351. (b) idem, ibid. 1996, 1669.
(7) Ossig, G.; Meller, A.; Bro¨nneke, C.; Mu¨ller, O.; Scha¨fer, M.; Herbst-
Irmer, R. Organometallics 1997, 16, 2116.
(8) (a) Tokitoh, N.; Matsumoto, T.; Manmaru, K.; Okazaki, R. J. Am.
Chem. Soc. 1993, 115, 8855. (b) Matsumoto, T.; Tokitoh, N.; Okazaki, R.
Angew. Chem., Int. Ed. Engl. 1994, 33, 2316. (c) Tokitoh, N.; Matsumoto,
T.; Okazaki, R. J. Am. Chem. Soc. 1997, 119, 2337.
(9) (a) Suzuki, H.; Tokitoh, N.; Nagase, S.; Okazaki, R.; J. Am. Chem.
Soc. 1994, 116, 11578. (b) Suzuki, H.; Tokitoh, N.; Okazaki, R.; Nagase,
S.; Goto, M. J. Am. Chem. Soc. 1998, 120, 11096.
† Present address: Department of Chemistry, Graduate School of Science,
Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan.
‡ Present address: Institute for Fundamental Research of Organic
Chemistry, Kyusyu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-
8581, Japan.
§ Present address: Department of Chemical and Biological Sciences,
Faculty of Science, Japan Women’s University, Mejirodai, Bunkyo-ku,
Tokyo 112-8681, Japan.
(1) Brook, A. G.; Abdesaken, F.; Gutekunst, B.; Gutekunst, G.; Kallury,
R. K. J. Chem. Soc., Chem. Commun. 1981, 191.
(2) West, R.; Fink, M. J.; Michl, J. Science (Washington, D.C.) 1981,
214, 1343.
(3) Yoshifuji, M.; Shima, I.; Inamoto, N.; Hirotsu, K.; Higuchi, T. J.
Am. Chem. Soc. 1981, 103, 4587.
(10) (a) Tokitoh, N.; Saito, M.; Okazaki, R. J. Am. Chem. Soc. 1993,
115, 2065. (b) Saito, M.; Tokitoh, N.; Okazaki, R. J. Organomet. Chem.
1995, 499, 43. (c) idem, Organometallics 1996, 15, 4531. (d) idem, J. Am.
Chem. Soc. 1997, 119, 11124.
10.1021/ja991147x CCC: $18.00 © 1999 American Chemical Society
Published on Web 09/08/1999

8812 J. Am. Chem. Soc., Vol. 121, No. 38, 1999
Matsumoto et al.
to study a possible effect of an aryl group on the properties of
those double-bond species.
Scheme 1
Scheme 2
Scheme 3
Results and Discussion
Synthesis of Diaryl-Substituted Germanethione, Tbt(Tip)-
GedS (1a). We previously reported the synthesis of novel cyclic
polysulfides containing Ge atom, 1,2,3,4,5-tetrathiagermolanes
Tbt(Ar)GeS4 [3, Ar ) 2,4,6-trimethylphenyl (Mes); 4, Ar )
2,6-diethylphenyl (Dep); 5, Ar ) 2,4,6-triisopropylphenyl (Tip)],
which are a useful precursor for the germanethione.12
thermally very stable. It melted at 163-165 °C without
decomposition, no change being observed even after heating
of its hexane solution at 160 °C for 3 days in a sealed tube.
Synthesis of Diaryl-Substituted Germaneselone, Tbt(Tip)-
GedSe (2a).8b Although a cyclic polyselenide containing Ge
atom is considered to be a proper starting material for the
synthesis of germaneselone as in the case of germanethione,
no selenated product was obtained by the direct thermal
selenation of diarylgermane Tbt(Mes)GeH2 10 with elemental
selenium even in refluxing o-dichlorobenzene in the presence
of 1,8-diazabicyclo[5.4.0]undec-7-ene as an activator of the
selenation.16 However, we succeeded in the isolation of the first
1,2,3,4,5-tetraselenagermolane 11 (Scheme 3) by the reaction
of elemental selenium with a germyllithium generated from
dihydrogermane 10 with tert-butyllithium in THF at -20 °C in
the presence of cosolvent, hexamethylphosphoramide (HMPA),
and its structure was revealed by X-ray crystallographic
analysis.17 Deselenation of 11 with triphenylphosphine at 90
°C gave 1,3,2,4-diselenadigermetane 12, a dimer of the corre-
sponding germaneselone Tbt(Mes)GedSe, despite the presence
of excess 2,3-dimethyl-1,3-butadiene as was observed in the
desulfurization of Tbt(Mes)GeS4 3. The molecular structure of
12 is shown in Figure 1 along with selected bond lengths and
angles. Figure 1b shows that the folding of the four-membered
ring releases the steric hindrance effectively as is observed also
in 1,3,2,4-dithiadigermetane 7.13 Dihedral angle between Se-
(1)-Ge(1)-Se(1*) plane and Se(1)-Ge(1*)-Se(1*) plane is
43.8° for 12, whereas the corresponding angle is 37.8° for 7.
The synthesis of Tbt(Tip)GeSe4 13 bearing a bulkier Tip
group was achieved by treatment of the corresponding germyl-
anion with elemental selenium, but the yield was only 7% (13%
conversion yield), probably because of the lower reactivity of
the sterically hindered germylanion and the instability of 13
under the basic reaction conditions unlike the corresponding
tetrathiagermolanes. We then used diarylgermylene Tbt(Tip)-
Ge: 14 as a precursor for the desired tetraselenagermolane,
because a germylene is known to be highly reactive.18 Although
The desulfurization of tetrathiagermolane 3 with 3 equiv of
hexamethylphosphorous triamide at -78 °C gave hydroxy-
(mercapto)germane 6 and cis-1,3,2,4-dithiadigermetane 7. This
indicates the generation of germanethione Tbt(Mes)GedS 8
because the formation of 6 and 7 is reasonably explained in
terms of reaction with water and head-to-tail dimerization of 8,
respectively.13 The desulfurization with hexamethylphosphorus
triamide in a sealed tube in THF at 90 °C afforded the dimer 7
exclusively. Even in the presence of 2,3-dimethyl-1,3-butadiene
as a trapping reagent, only the dimer 7 was obtained, indicating
the very fast self-dimerization of 8 (Scheme 1).14,15
By contrast, the desulfurization of the tetrathiagermolane 5,
having a much bulkier Tip group, exclusively gave hydroxy-
(mercapto)germane Tbt(Tip)Ge(OH)(SH) 9 regardless of the
reaction conditions after usual workup without any precaution
toward water, suggesting the generation of monomeric ger-
manethione Tbt(Tip)GedS 1a. When the desulfurization of 5
by 3 equiv of triphenylphosphine in hexane in a glovebox filled
with pure argon, germanethione 1a was quantitatively yielded
as orange-yellow crystals after filtration of triphenylphosphine
sulfide, which was formed quantitatively and totally insoluble
in hexane (Scheme 2). The molecular structure was confirmed
by spectral data and X-ray structural analysis (vide supra).
Germanethione 1a is very sensitive toward moisture, but
(11) Although 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl group had been
denoted as Tb in our previous papers, we changed this acronym to Tbt in
order to avoid confusion with a symbol of an element (terbium). (a) Okazaki,
R.; Unno, M.; Inamoto, N. Chem. Lett. 1987, 2293. (b) Okazaki, R.; Unno,
M.; Inamoto, N.; Yamamoto, G. Chem. Lett. 1989, 493. (c) Okazaki, R.;
Unno, M.; Inamoto, N. Chem. Lett. 1989, 791.
(12) (a) Tokitoh, N.; Suzuki, H.; Matsumoto, T.; Matsuhashi, Y.; Okazaki,
R.; Goto, M. J. Am. Chem. Soc. 1991, 113, 7047. (b) Matsumoto, T.;
Tokitoh, N.; Okazaki, R.; Goto, M. Organometallics 1995, 14, 1008.
(13) The molecular structure of 7 was determined by X-ray structural
analysis, which revealed the extremely congested cis configuration of four
bulky aryl groups with unprecedentedly large fold angles of the central
rhombic dithiadigermetane ring. Tokitoh, N.; Matsumoto, T.; Ichida, H.;
Okazaki, R. Tetrahedron Lett. 1991, 32, 6877.
(14) The same result was also obtained in the case of Tbt(Dep)GeS4 4
bearing a bulkier group Dep on germanium, the corresponding 1,3,2,4-
dithiadigermetane being formed.
(15) Ando and co-workers reported that dimesitylgermanethione under-
went dimerization to give 1,3,2,4-dithiadigermetane without any formation
of [4 + 2] adduct, even when the germanethione was generated in the
presence of 2,3-dimethyl-1,3-butadiene; see Tsumuraya, T.; Sato, S.; Ando,
W. Organometallics 1988, 7, 2015.
(16) The activation of elemental selenium with amines has been reported;
see (a) Tokitoh, N.; Hayakawa, H.; Goto, M.; Ando, W. Tetrahedron Lett.
1988, 29, 1935. (b) Chenard, B. L.; Miller, T. J. J. Org. Chem. 1984, 49,
1221. (c) Yoshida, H.; Kabe, Y.; Ando, W. Organometallics 1991, 10, 27.
(17) A preliminary communication: Tokitoh, N.; Matsumoto, T.; Oka-
zaki, R. Tetrahedron Lett. 1992, 33, 2531.
(18) Neumann, W. P. Chem. ReV. 1991, 91, 311, and references therein.

Germanethiones and Germaneselones
J. Am. Chem. Soc., Vol. 121, No. 38, 1999 8813
Scheme 4
Scheme 5
Scheme 6
Figure 1. (a) ORTEP drawing of 12 with thermal ellipsoid plot (30%
probability). Selected bond lengths (Å) and angles (deg): Ge(1)-Se(1)
2.397(1), Ge(1)-Se(1*) 2.433(1), Ge(1)-C(1) 2.013(7), Ge(1)-C(2)
1.994(7), Ge(1)-Se(1)-Ge(1*)83.54(4), Se(1)-Ge(1)-Se(1*)88.23(4),
C(1)-Ge(1)-Se(1) 114.3(2), C(1)-Ge(1)-Se(1*) 118.8(2), C(2)-Ge-
(1)-Se(1) 112.9(2), C(2)-Ge(1)-Se(1*) 107.6(2), C(1)-Ge(1)-C(2)
112.7(3). (b) Dihedral angle of 12.
membered polyselenide selectively, as in the case of the
polysulfides 3, 4 and 5.12 As was discussed in the previous
paper,13b the isolation of only five-membered-ring compounds
is probably owing to the steric repulsion between the bulky Tbt
and Ar (Mes or Tip) groups on Ge atom which enlarges the
bond angle of C-Ge-C and hence narrows the angle S-Ge-S
or Se-Ge-Se.
we previously reported the generation of 14 by the reaction of
GeI2 with TbtLi and TipLi,19 the yield was low. We then took
advantage of reductive debromination of dibromogermane Tbt-
(Tip)GeBr2 15 by lithium naphthalenide for the synthesis of
14.20 Treatment of 15 with 2 equiv of lithium naphthalenide in
THF at -78 °C afforded a blue solution (λmax ) 581 nm) of an
expected germylene 14. This absorption maximum is similar,
although relatively red shifted, to those reported for other
diorganogermylenes which are attributed to an n-p transi-
tion.21,22 The large groups substituted on germanium atom
expand the bond angle of R-Ge-R and hence make the
difference between n and p energy levels smaller, resulting in
the red shift of n-p transition. The generation of germylene 14
was also confirmed by a trapping reaction with 2,3-dimethyl-
1,3-butadiene to give germacyclopentene 16 in 68% yield
(Scheme 4).
The germylene 14 also reacted with elemental sulfur to give
1,2,3,4,5-tetrathiagermolane 5 in 68% yield.
Unlike 11, the deselenation of 13 with triphenylphosphine
resulted in the quantitative isolation of the first stable germane-
selone 2a as red crystals (Scheme 5). Dimerization of 2a was
not observed even in refluxing hexane, despite the longer bond
distance of GedSe than that of GedS. Germaneselone 2a is
the first example of a kinetically stabilized germaneselone; it
is extremely sensitive to moisture but thermally very stable like
1a.
Synthesis of Cyclic Polysulfide and Polyselenide bearing
Tbt and Dis. To synthesize Tbt(Dis)GedX, having a bulky
alkyl group Dis instead of Tip, we examined the syntheses of
cyclic polychalcogenides containing Ge atom. Germylene Tbt-
(Dis)Ge: 17 was generated by reductive debromination of
dibromogermane Tbt(Dis)GeBr2 with 2 equiv of lithium naph-
thalenide and confirmed by its UV-vis spectrum (λmax ) 535
nm in THF) and the formation of a trapping product with 2,3-
dimethyl-1,3-butadiene, albeit in low yield probably because
of steric congestion (Scheme 6).
Germylene 17 was allowed to react with an excess amount
of elemental sulfur and selenium to afford the five-membered
1,2,3,4,5-tetrathiagermolane 19 and 1,2,3,4,5-tetraselenager-
molane 20, respectively.23
Synthesis of Alkyl,aryl-Disubstituted Tbt(Dis)GedX (X
) S, Se). Desulfurization of tetrathiagermolane 19 was carried
out using 3 equiv of triphenylphosphine in a manner similar to
that for diarylgermanethione 1a to afford germanethione 1b as
yellow crystals (Scheme 7). The yield was, however, only 62%,
The reaction of 14 with an excess amount of elemental
selenium resulted in the successful isolation of the expected
1,2,3,4,5-tetraselenagermolane 13 in a reasonable yield as orange
crystals. Here it should be noted that any selenation reaction
(see also the formation of 20 in Scheme 6) gave only five-
(19) (a) Tokitoh, N.; Manmaru, K.; Okazaki, R. Organometallics 1994,
13, 167. (b) Tokitoh, N.; Manmaru, K.; Okazaki, R. Nippon Kagaku Kaishi
1994, 240.
(20) Masamune and co-workers reported the reductive coupling of
dichlorodiarylgermanes with lithium naphthalenide to give a cyclotrigermane
from dichloro[bis(2,6-diethylphenyl)]germane and a digermene (germanium-
germanium double-bond species) from dichloro[bis(2,6-diisopropylphenyl)]-
germane. (a) Masamune, S.; Hanzawa, Y.; Williams, D. J. J. Am. Chem.
Soc. 1982, 104, 6136. (b) Snow, J. T.; Murakami, S.; Masamune, S.;
Williams, D. J. Tetrahedron Lett. 1984, 25, 4191. (c) Park, J.; Batcheller,
S. A.; Masamune, S. J. Organomet. Chem. 1989, 367, 39. (d) Tsumuraya,
T.; Batcheller, S. A.; Masamune, S. Angew. Chem., Int. Ed. Engl. 1991,
30, 902.
(21) Some recent examples, see (a) Jutzi, P.; Schmidt, H.; Neumann,
B.; Stammler, H. G. Organometallics 1996, 15, 741. (b) Simons, R. S.; Pu,
L.; Olmstead, M. M.; Power, P. P. Organometallics 1997, 16, 1920. (c)
Jutzi, P.; Becker, A.; Stammler, H. G.; Neumann, B. Organometallics 1991,
10, 1647.
(23) Although the final level has not yet been reached due to the low
quality of the single crystal used, the molecular structure of Tbt(Dis)GeSe4
(20) was preliminarily determined by X-ray crystallographic analysis, whose
configuration of the tetraselenolane ring and the geometry around the Ge
atom were almost similar to those of Tbt(Mes)GeSe4 (11);17 Matsumoto,
T. Doctor Thesis, The University of Tokyo, 1994.
(22) (a) Ando, W.; Itoh, H.; Tsumuraya, T.; Yoshida, H. Organometallics
1988, 7, 1880. (b) Ando, W.; Itoh, H.; Tsumuraya, T. Organometallics 1989,
8, 2759, and references therein.

8814 J. Am. Chem. Soc., Vol. 121, No. 38, 1999
Matsumoto et al.
Scheme 7
Scheme 8
Figure 3. ORTEP drawing of Tbt(Tip)GedSe 2a with thermal ellipsoid
plot (30% probability).
Figure 2. ORTEP drawing of Tbt(Tip)GedS 1a with thermal ellipsoid
plot (30% probability).
owing to the formation of unexpected tetrathiadigermacyclo-
hexane 21 as a white solid totally insoluble in common organic
solvents.24
To obtain the germanethione in higher yield, we used
germirene (germacyclopropene) 22 as the germylene precursor.
We previously reported that the germirene 22, prepared from
germylene 17 and diphenylacetylene as a stable solid, regener-
ated the germylene 17 via cycloreversion on heating to 80 °C.25
Thermolysis of the germirene 22 in the presence of 1/8 equiv
of S8 in C6D6 quantitatively gave germanethione 1b, which was
isolated as yellow crystals in a glovebox filled with argon
(Scheme 8).
Similarly, germaneselone Tbt(Dis)GedSe 2b was synthesized
quantitatively and isolated as orange-red crystals.
Crystal Structures of Germanethione 1a and Germane-
selones 2a, 2b. The molecular structures of 1a and 2a, 2b were
determined by X-ray crystallographic analysis. The ORTEP
drawings (Figures 2, 3, and 4) show that the germanium-
chalcogen units are effectively protected by bulky groups. The
Figure 4. ORTEP drawing of Tbt(Dis)GedSe 2b with thermal
ellipsoid plot (30% probability).
shortest intermolecular distance between Ge and S in 1a is 5.91
Å, which is much longer than the sum of van der Waals radii
(3.90 Å), indicating the absence of intermolecular interaction
even in the solid state. This is also the case with the germane-
selones, in which the intermolecular Ge-Se distances are 5.69
and 8.13 Å for 2a and 2b, respectively.26 The selected bond
lengths and bond angles are summarized in Table 1.
(24) The yield of the germanethione was estimated by the yield of
hydroxy(mercapto)germane Tbt(Dis)Ge(SH)(OH), which was formed by
the addition of water. See Experimental Section.
(25) Tokitoh, N.; Kishikawa, K.; Matsumoto, T.; Okazaki, R. Chem. Lett.
1995, 827.

Germanethiones and Germaneselones
J. Am. Chem. Soc., Vol. 121, No. 38, 1999 8815
Table 1. Selected Bond Lengths (Å) and Angles (deg) of Germanethione 1a and Germaneselones 2a, 2b
Tbt(Tip)GedS 1a
Tbt(Tip)GedSe 2a
Tbt(Dis)GedSe 2b
bond lengths (Å)
Ge(1)-Se(1)
Ge(1)-S(1)
Ge(1)-C(1)
Ge(1)-C(7)
2.049(3)
1.953(9)
1.91(1)
2.180(2)
1.932(9)
1.945(9)
Ge(1)-Se(1)
Ge(1)-C(1)
Ge(1)-C(7)
2.173(3)
1.99(1)
1.92(2)
Ge(1)-C(1)
Ge(1)-C(10)
bond angles (deg)
S(1)-Ge(1)-C(1)
S(1)-Ge(1)-C(7)
C(1)-Ge(1)-C(7)
124.8(3)
116.2(3)
118.4(4)
Se(1)-Ge(1)-C(1)
Se(1)-Ge(1)-C(10)
C(1)-Ge(1)-C(10)
126.4(3)
113.8(3)
119.1(4)
Se(1)-Ge(1)-C(1)
Se(1)-Ge(1)-C(7)
C(1)-Ge(1)-C(7)
122.5(4)
117.8(4)
119.7(6)
Table 2. Dihedral Angles of Germanethione 1a and
Germaneselone 2a
In the germanethione 1a, the intramolecular Ge-S distance
is 2.049(3) Å, which is 9% shorter than typical Ge-S single
bond lengths (2.21 ( 0.04 Å)27 and in good agreement with
the calculated one (2.042 Å for H2GedS).28 The geometry
around the germanium atom is trigonal planer, the sum of the
angles being 359.6°. These facts clearly show that the germa-
nium-sulfur bond in 1a has a double-bond character. The bond
lengths of base-stabilized germathioureas are reported to be
longer [2.063(3) and 2.110(2) Å]5,6 than that of germanethione
1a.
Similar structural properties were observed for the germane-
selones. Their trigonal planar geometry is shown in the sum of
the bond angles around the germanium atom (359.3° for 2a and
360.0° for 2b). The Ge-Se bond distances of 2a [2.180(2) Å]
and 2b [2.173(3) Å] are reduced by 9% compared with those
reported for typical germanium-selenium single bonds29 and
shorter than those of the reported germaselenourea [2.247(1)
and 2.2472(7)].6,7 The calculated GedSe bond length for H2-
GedSe is 2.174 Å,28 which agrees well with these results.
angles (deg)
plane
plane
1a (X ) S)
2a (X ) Se)
Tbt
Tip
Tbt
π (GedX)
π (GedX)
Tip
39
70
89
38
72
89
Table 3. UV-Vis Spectra of Germanethiones 1a,b and
Germaneselones 2a,b
The dihedral angles observed for 1a and 2a are shown in
Table 2. Two aryl groups are arranged almost perpendicular to
each other. The large groups on the ortho position of the
aromatic rings hinder the aryl groups from situating on the
germathiocarbonyl π plane, indicating the absence of significant
conjugative interaction between the two aryl groups and the
GedX double bond in the solid state. In the case of Tbt(Dis)-
GedSe 2b, the dihedral angle between the π-plane of GedSe
and the aryl ring is 56°, being considerably larger than that for
1a (39°) and 2a (38°).
λ
max/nm
solvent
1a
1b
2a
2b
hexane
benzene
Et2O
450
444
451
444
432
427
519
513
492
486
THF
510
noketone).30 One can see that the absorption maxima show only
slight solvent dependency, suggesting no coordination of the
solvent toward the GedX bond. Small red shifts in λmax (n-
π*) on going from Tbt(Tip)GedX to Tbt(Dis)GedX (∆λ )
18 nm for germanethiones and 27 nm for germaneselones)
indicate a minor contribution from conjugation between the aryl
group and the GedX bond in solution.
Physical Properties. (1) Electronic Spectra. The absorption
maxima of the n-π* transition are summarized in Table 3. In
hexane the absorption maxima due to the n-π* transition of
GedSe bond in 2a appears at 519 nm (ꢀ 140), being red-shifted
compared to germanethione 1a (450 nm, ꢀ 100) as is observed
for the corresponding carbon analogues (thioketone vs sele-
(2) Raman Spectra. Raman shifts attributed to the stretching
of the GedS groups were observed at 521 (for 1a) and 512
cm-1 (for 1b). This suggests a fair degree of double-bond
character in this polar bond since the stretching vibrations of
(26) The sum of van der Waals radii of Ge and Se is 4.0 Å.
(27) A search of the Cambridge Crystallographic Database indicates the
following metrical data for Ge-S bond interactions (given in the order of
mean, range, and number of observations in distribution): d(Ge-S) ) 2.26
Å, 2.06-2.84 Å, 145. The bond lengths of organogermane sulfide are
reported to vary within a range of 2.21 ( 0.04 Å. For example, see: (a)
Benno, R. H.; Frichie, C. J. J. Chem. Soc., Dalton Trans. 1973, 543. (b)
Jutzi, P.; Steiner, W.; Ko¨nig, E.; Huttner, G.; Frank, A.; Schubert, U. Chem.
Ber. 1978, 111, 606. (c) Chadha, R. K.; Drake, J. E.; Sarkar, A. B. Inorg.
Chem. 1987, 26, 2885. (d) Ando, W.; Kadowaki, T.; Kabe, Y.; Ishii, M.
Angew. Chem., Int. Ed. Engl. 1992, 31, 59. For a review, see (e) Baines,
K. M.; Stibbs, W. G. Coord. Chem. ReV. 1995, 145, 157.
Ge-S single bonds normally appear near 410 cm-1 31
. Nefedov
and co-workers reported the IR spectrum for dimethylger-
manethione in an argon matrix at 17-18 K and assigned an
absorption at 518 cm-1 to the stretching of the GedS bond.32
Their result is in good agreement with those for 1a and 1b
observed here. In the germaneselones were observed the Raman
shifts at 381 (2a) and 386 cm-1 (2b), that is, at a lower field
compared to the germanethiones. These observed values are in
(28) Calculated with B3LYP/TZ(d, p); see ref 9b.
(30) (a) For thioketones: Duus, F. In ComprehensiVe Organic Chemistry;
Barton, D. H. R., Ollis, W. D., Eds.; Pergamon Press: Oxford, U.K., 1979;
Vol. 3, p 373. (b) For selenoketones: Guziec, F. S., Jr. In The Chemistry
of Organic Selenium and Tellurium Compounds; Patai, S., Ed.; John Wiley
& Sons: New York, 1987; Vol. 2, p 215, and references therein.
(31) (a) Cradock, S. J. Chem. Soc. A 1968, 1426. (b) Goldfarb, T. D.;
Sujishi, S. J. Am. Chem. Soc. 1964, 86, 1679. (c) Schumann, H.; Schmidt,
M. Angew. Chem., Int. Ed. Engl. 1965, 4, 1007. (d) Vyazankin, N. S.;
Bochkarev, M. N.; Sanina, L. P.; Egorochkin, A. N.; Khorshev, S. Ya. Zh.
Obshch. Khim. 1967, 37, 2576 (Russ), 2451 (Engl).
(29) A search of the Cambridge Crystallographic Database indicates the
following metrical data for Ge-Se bond interactions (given in the order of
mean, range, and number of observations in distribution): d(Ge-Se) )
2.37 Å, 2.31-2.77 Å, 38. The bond lengths of organogermane selenides
are reported to vary from 2.337 to 2.421 Å. For example, see: (a)
Weidenbruch, M.; Ritschl, A.; Peters, K.; Schnering, H. G. J. Organomet.
Chem. 1992, 438, 39. (b) Dra¨ger, M.; Ha¨berle, K. ibid. 1985, 280, 183. (c)
Ross, V. L.; Dra¨ger, M. Z. Anorg. Allg. Chem. 1981, 472, 109, and refernces
cited therein. See also ref 27e.

8816 J. Am. Chem. Soc., Vol. 121, No. 38, 1999
Matsumoto et al.
Table 4. [4 + 2] Cycloaddition Reactions of Germanethione 1a
with Dienes
Scheme 9
Scheme 10
keeping with the calculated values (B3LYP/TZ(d,p) level), that
is, 542 cm-1 for H2GedS and 379 cm-1 for H2GedSe.9b
1,3,2-dichalcogenagermetane, and the molecular structure of 25
was determined by single-crystal X-ray diffraction.37
(3) 77Se NMR of the Germaneselones. It is reported that
the 77Se chemical shift of (H3Ge)2Se, having Ge-Se single
bonds, is -612 ppm (relative to (H3C)2Se).33 By contrast, 77Se
NMR of the germaneselones shows a signal at a much lower
field (941 ppm for 2a and 872 ppm for 2b), which is
characteristic of doubly bonded selenium atoms.34 One can see
that Tbt(Tip)GedSe 2a resonates at a lower field than Tbt(Dis)-
GedSe 2b, which agrees with the trend observed in the
electronic spectra,35 although the difference is quite small.
Reactions of Germanethiones and Germaneselones. Ger-
manethione 1a was allowed to react with water to give hydroxy-
(mercapto)germane 9. Exposure of 1a to air also immediately
afforded 9 quantitatively, indicating the high reactivity of the
GedS bond to water. No adduct was obtained in the reaction
with methyl iodide at ambient temperature. This is in contrast
to the results reported for thermodynamically stabilized ger-
manium-sulfur compounds.5-7 The addition of methyllithium
gave 23 or 24 after quenching with ethanol or methyl iodide,
respectively, reflecting the polarization of the GedS bond like
Geδ+dSδ- in contrast to thiocarbonyl compounds, in which
thiophilic reactions were observed (Scheme 9).36
In the reactions of 1a and 2a with mesitonitrile oxide, a 1,3-
dipolar reagent, [3 + 2] cycloaddition proceeded to afford
oxachalcogenazagermole 27 and 28, respectively. The regio-
chemistry of this [3 + 2] cycloaddition was tentatively assigned
on the basis of the mass spectra of the cycloadducts. In the mass
spectrum of the adduct 27 were observed the fragments
corresponding to the mesitylisothiocyanate and germanone Tbt-
(Tip)GedO, which would be expected only from the assigned
structure. The regiochemistry observed here is interpreted in
terms of the orbital interactions between germanethione LUMO
and nitrile oxide HOMO, which will be discussed below in [4
+ 2] cycloaddition reactions.
Dienes reacted with germanethiones and germaneselones to
give [4 + 2] cycloadducts. The results for the reactions of the
germanethione 1a are summarized in Table 4. The yields of
the corresponding adducts are moderate to good, except in the
case of 1,4-disubstituted dienes where no reaction took place.
These are the first examples of Diels-Alder reaction of
germanium-chalcogen double-bond species. The desulfurization
of Tbt(Mes)GeS4 in the presence of an excess amount of 2,3-
dimethyl-1,3-butadiene gave only the dimer 7, no corresponding
[4 + 2] cycloadduct being formed.15
Regiochemistry of the Diels-Alder reactions was examined
using unsymmetrically substituted dienes (entries 2-6). Reaction
with isoprene at 90 °C gave two regioisomers in the ratio of
9:1. Similar selectivity and reaction rate were observed also in
THF (entry 4). The observed regioselectivity is consistent with
the frontier molecular orbital interpretation based on the PM3
calculation concerning the [4 + 2] cycloaddition reaction
between dimethylgermanethione and isoprene.38 The energies
and coefficients of the frontier orbitals in this model reaction
are shown in Figure 5. The calculation shows that the
predominant transition state interaction involves the germathio-
carbonyl LUMO and the diene HOMO and that the favorable
The double-bond character of the GedX bond (X ) S, Se)
in 1 and 2 manifested itself in the cycloaddition reactions with
various 2π and 4π systems. For example, phenyl isothiocyanate
reacted smoothly with 1a and 2a at room temperature to afford
[2 + 2] cycloadduct 25 and 26 in 84% and 61%, respectively
(Scheme 10). These are the first examples of imino-substituted
(32) The IR spectrum of the matrix-isolated dimethylgermanethione
generated by gas-phase pyrolysis of (Me2GeS)3 was reported by Michl and
co-workers to be 605 cm-1 for the GedS stretching. However, immediately
after their report, the assignment was revised to be 518 cm-1 by Nefedov
et al. The observed frequencies and their relative intensities are in good
agreement with those calculated at the ab initio Hartree-Fock level. See
(a) Barrau, J.; Balaji, V.; Michl, J. Organometallics 1989, 8, 2034. (b)
Khabashesku, V. N.; Boganov, S. E.; Zuev, P. S.; Nefedov, O. M. J.
Organomet. Chem. 1991, 402, 161.
(33) McFahrlane, H. C. E.; McFarlane, W. In Multinuclear NMR; Mason,
J., Ed.; Plenum Press: New York, 1987; p 417, and references therein.
(34) The 77Se chemical shifts of most of dialkyl selenoketones are in
the range between 1600 and 2200 ppm. See (a) Wong, T. C.; Guziec, F. S.
Jr.; Moustakis, C. A. J. Chem. Soc., Perkin Trans. 2. 1983, 1471. (b) Cullen,
E. R.; Guziec, F. S., Jr.; Murphy, C. J.; Wong, T. C.; Andersen, K. K. J.
Am. Chem. Soc. 1981, 103, 7055. (c) Okazaki, R.; Ishii, A.; Inamoto, N. J.
Chem. Soc., Chem. Commun. 1983, 1429.
(36) The reactions of thiocarbonyl compounds with organometallic
compounds were reported to proceed via single electron transfer. Whether
the nuclophiles attack on a carbon or sulfur atom depends on the spin density
on each atom of the generated anion radical [R2CdS]•-, which is affected
by the substituents R. See (a) Duus, F. In ComprehensiVe Organic
Chemistry; Barton, D. H. R., Ollis, W. D., Eds.; Pergamon Press: Oxford,
U.K., 1979; Vol. 3, p 373. (b) Ohno, A.; Nakamura, K.; Uohama, M.; Oka,
S.; Yamabe, T.; Nagata, S. Bull. Chem. Soc. Jpn. 1975, 48, 3718.
(37) Tokitoh, N.; Kishikawa, K.; Manmaru, K.; Okazaki, R. Heterocycles
1997, 44 149.
(35) In NMR the shielding constant is correlated to ∆E-1 (∆E ) an
average electron excitation energy), see (a) Pople, J. A. Mol. Phys. 1963,
7, 301. (b) Karplus, M.; Pople, J. A. J. Chem. Phys. 1963, 38, 2803.

Germanethiones and Germaneselones
J. Am. Chem. Soc., Vol. 121, No. 38, 1999 8817
Table 5. [4 + 2] Cycloaddition Reactions of Germaneselone 2a
with Dienesa
a In hexane at room temperature.
Scheme 11
was low (entry 1), but the use of large excess of the dimeth-
ylbutadiene (40 equiv) increased the yield up to 84% (entry 2).
The reactions proceeded under milder conditions than those for
germanethione 1a (∼50-90 °C).
Figure 5. The energies (eV) and coefficients of the frontier orbitals
involved in the [4 + 2] cycloaddition reactions of dimethylgermaneth-
ione and dimethylgermaneselone with isoprene.
Regiochemistry of the Diels-Alder reaction of germaneselone
2a was also examined in the reaction with isoprene, which
afforded two regioisomers 35 and 36 in 51% and 35% yields,
respectively (entry 3). A more favorable regioisomer was the
same as in the case of germanethione 1a. This tendency was
also similar to that in Diels-Alder reactions reported for
selenoaldehydes.40 It is noteworthy that the selectivity was lower
than that observed for germanethione 1a. The low selectivity
is probably explicable in terms of the smaller activation energies
in Diels-Alder and retro Diels-Alder reactions of germane-
selone 2a than those of germanethione 1a, which is in keeping
with the results obtained by the PM3 calculation (Figure 5).
The calculation shows that the predominant transition state
interaction is again that between the germaselenocarbonyl
LUMO and the diene HOMO and that the HOMO-LUMO gap
is smaller for the reaction with dimethylgermaneselone, thus
accelerating the Diels-Alder reaction for a germaneselone
compared to that for a germanethione. The difference in the
LUMO coefficients between germanium and selenium atoms
is slightly smaller than that for dimethylgermanethione, which
would be partly responsible for the lower selectivity in the
reaction with a germaneselone. The occurrence of the [4 + 2]
cycloreversion to 2a was indicated by color change from
colorless to red upon heating of a hexane solution of the adduct
34 at 50 °C. It was chemically confirmed by a trapping reaction
with mesitonitrile oxide to afford 28 in 90% (Scheme 11).
Germanethione 1b also gave cycloadducts with some dienes,
as summarized in Table 6. Since the reaction was slower than
that of Tbt(Tip)GedS 1a, much more of a diene (50 equiv)
was added in other entries. In the reaction with isoprene only
one isomer 38 was obtained (entry 3) and the regiochemistry
was opposite of that of germanethione 1a. These results indicate
larger steric congestion around germanium atom in 1b with Tbt
and Dis groups than 1a with Tbt and Tip groups. In addition,
the regioselectivity is not changed in the reaction at 150 °C,
under whose conditions the retro Diels-Alder reaction should
occur as in the thermolysis of the [4 + 2] cycloadduct of
germanethione 1a. When a colorless hexane solution of the
isoprene adduct 38 was heated to 150 °C, the solution turned
regioisomer would be compound 30, judging from the coef-
ficients on the pertinent molecular orbitals. Regiochemistry
observed here and its interpretation are similar to those already
reported for the cycloaddition of thioaldehydes.39
It is noteworthy that only one isomer was obtained with
2-methyl-1,3-pentadiene and 2,4-dimethyl-1,3-pentadiene (en-
tries 5 and 6). These high regioselectivities are explicable in
terms of steric effect as well as the favorable orbital overlap.
This interpretation is supported by the fact that the reaction with
1,4-disubstituted dienes did not give a corresponding adduct
(entries 7 and 8).
In entry 3, the regioselectivity was lost when the reaction
was carried out at 150 °C. Furthermore, heating of 30 in hexane
at 150 °C afforded 30 and 31 in the ratio of 1:1. These results
clearly show that retro Diels-Alder reaction proceeded at about
150 °C. Examination of the CPK model indicates that there
seems to be no difference between 30 and 31 in the steric
interaction of the methyl group in the diene moiety with the
two aryl groups on the Ge atom. A slight difference in the orbital
coefficients of the 1 and 4 positions of isoprene HOMO is also
consistent with the fact that the regioselectivity is lost in the
reaction at higher temperature.
The occurrence of the retro Diels-Alder reaction was also
shown when compound 32 was heated at 150 °C; the color of
the solution changed from colorless to orange-yellow most
likely due to 1a regenerated, and in the presence of an excess
amount of 2,3-dimethyl-1,3-butadiene, the corresponding adduct
29 was formed.
Diels-Alder reactions with dienes were also examined for
germaneselone 2a. The results are summarized in Table 5. When
germaneselone 2a was allowed to react with 10 equiv of 2,3-
dimethyl-1,3-butadiene, the reaction proceeded at room tem-
perature very slowly and the yield of [4 + 2] cycloadduct 34
(38) PM3 calculations were conducted using standard methods as
implemented in the MOPAC 6.0 semiempirical molecular orbital package.
For the geometry of Me2GedS, the distance between Ge and S was fixed
to 2.049 Å, which is the observed value for 1a. Stewart, J. J. P. QCPE
Bull. 1989, 9, 10.
(39) (a) Vedejs, E.; Perry, D. A. J. Am. Chem. Soc. 1983, 105, 6999. (b)
Rao, V. P.; Chandrasekhar, J.; Ramamurthy, V. J. Chem. Soc., Perkin Trans.
2 1988, 647.
(40) (a) Meinke, P. T.; Krafft, G. A. Tetrahedron Lett. 1987, 5121. (b)
Idem J. Am. Chem. Soc. 1988, 110, 8671. (c) Idem ibid. 1988, 110, 8679.

8818 J. Am. Chem. Soc., Vol. 121, No. 38, 1999
Matsumoto et al.
Table 6. [4 + 2] Cycloaddition Reactions of Germanethione 1b
with Dienes
resolution mass spectral data were obtained on a JEOL SX-102 mass
spectrometer. Electronic spectra were recorded on a JASCO Ubest-50
UV/vis spectrometer. Elemental analyses were performed by the
Microanalytical Laboratory of the Department of Chemistry, Faculty
of Science, The University of Tokyo.
Desulfurization of 5-{2,4,6-Tris[bis(trimethylsilyl)methyl]phenyl}-
5-mesityl-1,2,3,4,5-tetrathiagermolane (3). (1) To a THF solution (20
mL) of 312 (311 mg, 0.357 mmol) was added hexamethylphosphorous
triamide (0.194 mL, 1.07 mmol) at -78 °C. After the solution was
warmed to room temperature over 10 h, the solvent was removed under
reduced pressure and the residue was chromatographed by DCC (SiO2
with 10:1 hexane/CH2Cl2) to afford {2,4,6-tris[bis(trimethylsilyl)methyl]-
phenyl}(hydroxy)(mercapto)(mesityl)germane (6; 121 mg, 49%) and
2,4-bis{2,4,6-tris[bis(trimethylsilyl)methyl]phenyl}-2,4-dimesityl-1,3,2,4-
dithiadigermetane (7; 84.7 mg, 35%). 6: white crystals; mp 131-135
°C; 1H NMR(CDCl3, 500 MHz) δ -0.11 (s, 9H), -0.06 (s, 9H), 0.04
(s, 18H), 0.06 (s, 18H), 0.91 (s, 1H, Ge-SH), 1.31 (s, 1H), 1.50 (s,
1H, Ge-OH), 2.23 (s, 3H), 2.36 (br s, 1H), 2.50 (br s, 1H), 2.52 (s,
6H), 6.27 (br s, 1H), 6.40 (br s, 1H), 6.79 (s, 2H); 13C NMR (CDCl3,
125 MHz) δ 0.75 (q), 0.85 (q), 1.26 (q), 1.54 (q), 20.92 (d), 24.52 (q),
27.60 (d), 27.62 (d), 30.50 (q), 122.99 (d), 127.93 (d), 129.70 (d), 130.98
(s), 138.30 (s), 139.72 (s), 141.94 (s), 145.29 (s), 150.01 (s), 150.25
(s). Anal. found: C, 53.25; H, 8.82; S, 3.94. Calcd for C36H72GeOSSi6‚
H2O: C, 53.23; H, 9.18; S, 3.95. 7: white crystals; mp >300 °C; It
was impossible to assign the NMR data owing to the complexity
resulting from the steric congestion. The final structure was determined
by X-ray structural analysis. Anal. found C, 55.42; H, 8.83; S, 4.26.
Calcd for C84H164S2Si12Ge2: C, 55.71; H, 9.09; S, 4.13. (2) To a THF
solution (0.6 mL) of 3 (117 mg, 0.134 mmol) was added hexameth-
ylphosphorous triamide (88 µL, 0.40 mmol) at room temperature in a
5 mm i.d. Pyrex tube. After five freeze-pump-thaw cycles, the tube
was evacuated and sealed. Heating the solution at 90 °C for 1 day
afforded 7 (98.4 mg, 95%).
Desulfurization of 5-{2,4,6-Tris[bis(trimethylsilyl)methyl]phenyl}-
5-(2,6-diethylphenyl)-1,2,3,4,5-tetrathiagermolane (4). In an 8 mm
i.d. Pyrex glass tube was placed a hexane (1.5 mL) solution of 4 (72.9
mg, 0.0823 mmol) and triphenylphosphine (65.0 mg, 0.248 mmol).
After five freeze-pump-thaw cycles, the tube was evacuated and
sealed. The mixture was heated at 90 °C for 1 min to give a yellow
solution. The mixture was heated at 100 °C for 1 h, during which time
the yellow color disappeared. After removal of the solvent, the residue
was separated by GPLC to give 2,4-bis(2,6-diethylphenyl)-2,4-bis{2,4,6-
tris[bis(trimethylsilyl)methyl]phenyl}-1,3,2,4-dithiadigermetane (56.3
mg, 87%) as white crystals with mp >300 °C (CH2Cl2/EtOH). It was
impossible to assign the NMR data owing to the complexity resulting
from the steric congestion. Anal. found: C, 55.57; H, 9.27; S, 4.85.
Calcd for C74H144Ge2S2Si12‚H2O: C, 55.60 H, 9.21; S, 4.01.
yellow, indicating the formation of 1b. When the solution was
cooled to 90 °C, the color was slowly diminished, indicating
the occurrence of a cycloaddition reaction. This color change
was reversible. These facts suggest that the selectivity observed
in the Diels-Alder reaction with isoprene is thermodynamically
controlled owing to the steric hindrance.
Conclusion
The dechalcogenation of the novel 1,2,3,4,5-tetrathia- and
tetraselenagermolanes Tbt(Tip)GeX4 with triphenyl phosphine
resulted in the successful isolation of the first kinetically
stabilized germanethione Tbt(Tip)GedS 1a and germaneselone
Tbt(Tip)GedSe 2a. A germanium-chalcogen double-bond
species having an alkyl group, Tbt(Dis)GedX (1b, 2b), was
also synthesized by the reaction of germylene [Tbt(Dis)Ge:] with
1 molar equiv of chalcogens. Although one might think that 1
and 2 have rather exotic substituents such as Tbt and Dis, the
results obtained in this study show that they have intrinsic
physical and chemical properties. For example, the bond lengths
of GedS and GedSe determined by X-ray diffraction are quite
close to the calculated values for H2GedS and H2GedSe. The
Raman shifts for the stretching of the GedS bond (521 cm-1
for 1a and 512 cm-1 for 1b) are very similar to the values of
518 cm-1 observed for Me2GedS and 542 cm-1 calculated for
H2GedS. Furthermore, 1 and 2 are highly reactive with regard
to the addition and cycloaddition reactions, despite the presence
of very bulky substituents, thus enabling us to know the intrinsic
reactivity of germanethione and germaneselone.
There is not so much difference between Tbt(Tip)GedX and
Tbt(Dis)GedX (X ) S, Se) in terms of their structural and
spectral properties, but the difference in the chemical reactivities
is obvious. In the former compounds, the dimerization is
prevented by the intermolecular repulsion of the aryl groups,
which interferes in an approach to another Tbt(Tip)GedX
molecule. On the contrary, in the latter compounds, not only
such an effect but also the Dis group itself directly inhibits an
intermolecular attack onto the germanium atom, thus lowering
the chemical reactivity.
Desulfurization of 5-{2,4,6-Tris[bis(trimethylsilyl)methyl]phenyl}-
5-(2,4,6-triisopropylphenyl)-1,2,3,4,5-tetrathiagermolane (5). To a
THF solution (1 mL) of 5 (136 mg, 0.142 mmol) was added
hexamethylphosphorous triamide (93 µL, 0.42 mmol) at -78 °C. After
the solution was warmed to room temperature over 10 h, the solvent
was removed under reduced pressure and the residue was chromato-
graphed by DCC (SiO2 with hexane) to afford {2,4,6-tris[bis(tri-
methylsilyl)methyl]phenyl}(hydroxy)(2,4,6-triisopropylphenyl)(mercapto)-
germane (9; 107 mg, 95%). 9: white crystals; mp 160-165 °C dec
Experimental Section
1
(CH2Cl2/i-PrOH); H NMR (CDCl3, 500 MHz, 300 K) δ -0.12 (s,
9H), -0.05 (s, 9H), 0.05 (s, 9H), 0.06 (s, 9H), 0.11 (s, 9H), 0.15 (s,
9H), 1.01 (br s, 3H), 1.05 (s, 1H, Ge-SH), 1.15 (d, J ) 6.9 Hz, 6H),
1.25 (br s, 3H), 1.32 (s, 1H), 1.33 (br s, 6H), 1.71 (s, 1H, Ge-OH),
2.48 (br s, 1H), 2.65 (br s, 1H), 2.85 (sept, J ) 6.9 Hz, 1H), 2.96 (br
s, 1H), 4.43 (br s, 1H), 6.30 (br s, 1H), 6.43 (br s, 1H), 7.02 (s, 2H),
7.12-7.73 (m, 10H); 13C NMR (CDCl3, 125 MHz, 300 K) δ 0.81 (q),
1.00 (q), 1.20 (q), 1.44 (q), 1.66 (q), 1.94 (q), 22.35 (q × 2), 23.63 (q),
23.89 (q), 24.72 (q × 2), 26.70 (d), 27.19 (d), 27.50 (d), 28.23 (d),
30.53 (d), 34.34 (d), 121.66 (d), 122.84 (d), 123.38 (d), 128.46 (d),
132.09 (s), 137.27 (s), 144.72 (s), 149.48 (s), 149.74 (s), 150.81 (s),
152.80 (s), 152.94 (s). Anal. found: C, 57.50; H, 9.44; S, 4.09. Calcd
for C42H84GeOSSi6: C, 57.43; H, 9.64; S, 3.65.
General Procedure. All melting points are uncorrected. All solvents
used in the reactions were purified by the reported methods. THF was
purified by distillation from benzophenone ketyl before use. All
reactions were carried out under an argon atmosphere unless otherwise
noted. Preparative gel permeation liquid chromatography (GPLC) was
performed by LC-908 with JAI gel 1H and 2H columns (Japan
Analytical Industry) with chloroform as solvent. Dry column chroma-
tography (DCC) was performed with ISN silica DCC 60A. Preparative
thin-layer chromatography (PTLC) was carried out with Merck Kie-
1
selgel 60 PF254 (Art. No. 7747). The H NMR (500 MHz) and 13C
NMR spectra (125 MHz) were measured in CDCl3 or C6D6 with a
Bruker AM-500 spectrometer using CHCl3 or C6H6 as the internal
standard. The 77Se NMR spectra (51.5 MHz) were measured with a
JEOL EX-270 spectrometer using Me2Se as the external standard. High-
Isolation of {2,4,6-Tris[bis(trimethylsilyl)methyl]phenyl}(2,4,6-
triisopropylphenyl)germanethione (1a). To a mixture of 5 (800 mg,

Germanethiones and Germaneselones
J. Am. Chem. Soc., Vol. 121, No. 38, 1999 8819
Table 7. Experimental Crystallographic Data for 1a, 2a, 2b, and 12
1a
2a
2b
12
empirical formula
formula weight
crystal size, mm
temp, K
crystal system
space group
unit cell dimensions
A, Å
C42H82GeSSi6
860.27
C42H82GeSeSi6
C34H78GeSeSi8
C72H140Ge2Se2Si12
1646.02
907.17
863.22
0.40 × 0.10 × 0.50
0.50 × 0.60 × 0.10
0.40 × 0.30 × 0.30
0.50 × 0.30 × 0.30
294
296
296
298
triclinic
triclinic
P1h
triclinic
P1h
monoclinic
C2/c
P1h
13.508(4)
20.722(8)
9.740(3)
96.96(3)
90.01(3)
81.87(3)
2679(3)
2
13.507(2)
20.662(5)
9.468(2)
96.35(2)
89.49(2)
98.49(2)
2597(1)
2
12.696(3)
22.117(6)
9.525(3)
92.16(2)
109.48(2)
86.89(2)
2517(1)
2
20.974(6)
15.243(5)
30.197(3)
B, Å
C, Å
R, deg
â, deg
102.41(1)
γ, deg
V, Å3
9428(4)
4
1.159
2θ - ω
5062
12.75
0.78
-0.95
0.051
0.038
3.97
Z
density (calcd), g cm-3
scan type
1.066
1.160
1.139
2θ - ω
2θ - ω
2θ - ω
no. of obsd reflns
data-to-param ratio
largest diff peak, e Å-3
largest diff hole, e Å-3
R, %
Rw, %
goodness of fit
3454
3395
2185
7.66
0.69
7.53
0.76
5.50
0.55
-0.56
-0.54
-0.43
0.065
0.058
0.050
0.076
0.062
0.060
2.60
2.27
1.44
0.837 mmol) and triphenylphosphine (658 mg, 2.51 mmol) was added
hexane (5 mL), and the solution was refluxed for 2 h. After filtration
of triphenylphosphine sulfide under argon, the residual bright yellow
solution was concentrated in a glovebox filled with argon to give
orange-yellow crystals, which contained 96% of 5 (728 mg, 100%)
and 4% of triphenylphosphine sulfide (52 mg). 1a: orange-yellow
12: white crystals; mp >300 °C (CH2Cl2/EtOH). It was impossible to
assign the NMR data owing to the complexity resulting from the steric
congestion. The final structure was determined by X-ray structural
analysis. Anal. found C, 52.29; H, 8.33; Se, 9.08. Calcd for C84H164
-
Se2Si12Ge2: C, 52.53; H, 8.57; Se, 9.59. High-resolution FAB-MS:
observed m/z 1646.5045 (M+); calcd for C72H14074Ge278Se80SeSi12,
1646.4948.
1
crystals; mp 163-165 °C (hexane); H NMR (C6D6, 500 MHz, 300
K) δ 0.15 (s, 18H), 0.16 (s, 18H), 0.26 (br s, 18H), 1.19 (d, J ) 6.9
Hz, 6H), 1.35 (br d, J ) 6.9 Hz, 6H), 1.48 (d, J ) 6.9 Hz, 6H), 2.74
(sept, J ) 6.9 Hz, 1H), 3.18 (br s, 1H), 3.29 (br s, 1H), 3.30 (sept, J
) 6.9 Hz, 1H), 3.65 (br s, 1H), 6.52 (br s, 1H), 6.70 (br s, 1H), 7.07
(s, 2H); 13C NMR (C6D6, 125 MHz, 300 K) δ 1.08 (q), 1.28 (q), 1.61
(q), 22.32 (q), 24.11 (q × 2), 27.68 (q), 29.56 (d), 29.60 (d), 31.74 (d),
34.83 (d), 37.52 (d), 122.30 (d × 2), 123.89 (d), 128.98 (d), 142.25
(s), 147.50 (s), 147.62 (s), 149.98 (s), 150.99 (s), 151.27 (s × 2), 152.30
Synthesis of 5-{2,4,6-Tris[bis(trimethylsilyl)methyl]phenyl}-5-
(2,4,6-triisopropylphenyl)-1,2,3,4,5-tetraselenagermolane (13). To a
THF solution (20 mL) of {2,4,6-tris[bis(trimethylsilyl)methyl]phenyl}-
(2,4,6-triisopropylphenyl)germane (213 mg, 0.256 mmol) was added
at -78 °C t-BuLi (1.60 M in pentane, 0.32 mL, 0.51 mmol) and then
hexamethylphosphoric triamide (0.23 mL, 1.4 mmol). The solution was
warmed to -20 °C over 3 h and to it was added elemental selenium
(0.20 g, 2.5 mmol). The mixture was warmed to room temperature
over 20 min. Solvent was removed under reduced pressure, and the
residue was separated by flush column chromatography (SiO2 with
hexane at -40 °C) and GPLC to afford 13 (21.5 mg, 7%) along with
the recovery of the starting material (95.4 mg. 45%). 13: orange
(s). FT-Raman (solid, excitation; Nd:YAG laser 1064 nm) 521 cm-1
.
High-resolution FAB-MS: observed m/z 861.4042 ([M + H]+); calcd
for C42H8374GeSSi6 861.4043.
Synthesis of 5-{2,4,6-Tris[bis(trimethylsilyl)methyl]phenyl}-5-
mesityl-1,2,3,4,5-tetraselenagermolane (11). To a THF solution (20
mL) of {2,4,6-tris[bis(trimethylsilyl)methyl]phenyl}(mesityl)germane
(10; 328 mg, 0.439 mmol) was added at -78 °C t-BuLi (1.60 M in
pentane, 0.36 mL, 0.58 mmol) and then hexamethylphosphoric triamide
(0.30 mL, 1.9 mmol). The solution was warmed to -25 °C over 2 h
and to it was added elemental selenium (0.30 g, 3.9 mmol). The mixture
was warmed to room temperature over 2 h. The solvent was removed
under reduced pressure, and the residue was separated by flush column
chromatography (SiO2 with hexane at -10 °C) and GPLC to afford
11 (169 mg, 34%). 11: orange crystals; mp 209 °C dec (CH2Cl2/EtOH);
1H NMR (CDCl3, 500 MHz, 300 K) δ -0.01 (br s, 36H), 0.06 (s,
18H), 1.33 (s, 1H), 2.07 (br s, 1H), 2.13 (br s, 1H), 2.19 (s, 3H), 2.55
(s, 6H), 6.34 (br s, 1H), 6.46 (br s, 1H), 6.76 (s, 2H); 13C NMR (CDCl3,
125 MHz, 300 K) δ 0.83 (q), 1.62 (q), 1.91 (q), 20.82 (q), 26.10 (d),
28.73 (d), 28.91 (d), 30.71 (q), 123.25 (d), 128.46 (d), 130.19 (d), 131.60
(s), 139.34 (s), 140.49 (s), 141.42 (s), 145.74 (s), 151.51 (s), 151.61
(s); 77Se NMR (toluene-d8, 17 MHz, 300 K) δ 443.2, 785.1. Anal.
found: C, 40.51; H, 6.49; Se, 29.49. Calcd for C36H70GeSe4Si6: C,
40.79; H, 6.65; Se, 29.79.
Desulfurization of 1,2,3,4,5-Tetraselenagermolane 11. To a mix-
ture of 11 (31.8 mg, 0.030 mmol) and triphenylphosphine (24.0 mg,
0.090 mmol) in a 5 mm i.d. Pyrex tube was added hexane (0.6 mL)
and 2,3-dimethyl-1,3-butadiene (0.1 mL, 0.88 mmol). After five freeze-
pump-thaw cycles, the tube was evacuated and sealed. The solution
was heated at 90 °C for 1 h. After removal of the solvent, the crude
reaction products were chromatographed by DCC (SiO2 with hexane)
to afford 2,4-dimesityl-2,4-bis{2,4,6-tris[bis(trimethylsilyl)methyl]-
phenyl}-1,3,2,4-diselenadigermetane (12; 23.8 mg, 96%) (Table 7).
1
crystals; mp 215-218 °C dec (CH2Cl2/EtOH); H NMR (CDCl3, 500
MHz, 340 K) δ 0.05 (br s, 36H), 0.73 (s, 18H), 1.13 (br d, J ) 6.9 Hz,
12H), 1.21 (d, J ) 6.9 Hz, 6H), 1.36 (s, 1H), 2.17 (br s, 2H), 2.82
(sept, J ) 6.9 Hz, 1H), 3.96 (br s, 2H), 6.44 (br s, 2H), 7.01 (s, 2H);
13C NMR (CDCl3, 125 MHz, 340 K) δ 1.03 (q), 2.71 (br q), 23.69 (q),
24.76 (q), 28.19 (d), 31.02 (d), 34.22 (d), 35.68 (d), 123.60 (d), 129.30
(d), 135.48 (s), 139.07 (s), 145.14 (s), 150.33 (s), 151.17 (s), 152.50
(s); 77Se NMR (CDCl3, 51.5 MHz, 300 K) δ 411.1, 471.8, 730.2, 841.3.
Anal. found: C, 43.78; H, 7.00; Se, 27.73. Calcd for C42H82GeSe4Si6:
C, 44.09; H, 7.22; Se, 27.61.
Trapping of {2,4,6-Tris[bis(trimethylsilyl)methyl]phenyl}(2,4,6-
triisopropylphenyl)germylene (14) with 2,3-Dimethyl-1,3-butadiene.
To a solution of dibromogermane 1511b (101 mg, 0.102 mmol) in THF
(5 mL) was added lithium naphthalenide (0.38 M in THF, 0.53 mL,
0.20 mmol) at -78 °C. The mixture was warmed to room temperature
over 1 h to give a blue solution of 14, to which was added 2,3-dimethyl-
1,3-butadiene (0.1 mL, 0.88 mmol), and the solution was stirred for 1
h. After removal of the solvent, the residue was chromatographed by
DCC (SiO2 with hexane) to afford 1-{2,4,6-tris[bis(trimethylsilyl)-
methyl]phenyl}-2,5-dihydro-1-(2,4,6-triisopropyl-phenyl)-3,4-dimeth-
ylgermole (16; 57.3 mg, 68%).18a
Synthesis of 1,2,3,4,5-Tetraselenagermolane 13 from Germylene
14. To a solution of dibromogermane 15 (267 mg, 0.245 mmol) in
THF (9 mL) was added lithium naphthalenide (0.47 M in THF, 1.3
mL, 0.61 mmol) at -60 °C, and the solution was warmed to room
temperature over 1.5 h to give a blue solution of 14. After cooling to
-20 °C, elemental selenium (160 mg, 2.0 mmol) was added to this
solution and it was stirred for 2.5 h, during which time it was warmed

8820 J. Am. Chem. Soc., Vol. 121, No. 38, 1999
Matsumoto et al.
to room temperature. After removal of the solvent, the residue was
roughly purified by short column chromatography (SiO2 with CH2Cl2)
and then by GPLC and flush column chromatography (SiO2 with
hexane). The orange solid thus obtained was reprecipitated from CH2-
Cl2/hexane to afford 13 (160 mg, 57%).
Synthesis of 1,2,3,4,5-Tetrathiagermolane 5 from Germylene 14.
To a solution of dibromogermane 15 (1.26 g, 1.28 mmol) in THF (40
mL) was added lithium naphthalenide (0.74 M in THF, 4.1 mL, 3.0
mmol) at -50 °C, and the solution was warmed to room temperature
over 3 h to give a blue solution of 14. To this solution was added
elemental sulfur (390 mg, 1.5 mmol as S8), and the solution was stirred
for 5 h. After removal of the solvent, the residue was roughly purified
by short column chromatography (SiO2 with CH2Cl2) and GPLC. The
yellow solid thus obtained was reprecipitated from CH2Cl2/hexane to
afford 5 (829 mg, 68%).
white crystals. Tbt(Dis)GeH2: white crystals; mp 180-182 °C (CH2-
1
Cl2/EtOH); H NMR (CDCl3, 500 MHz, 300 K) δ -0.20 (t, J ) 3.2
Hz, 1H), 0.03 (s, 18H), 0.06 (s, 18H), 0.07 (s, 18H), 0.15 (s, 18H),
1.28 (s, 1H), 1.94 (s, 1H), 2.18 (s, 1H), 4.55 (d, J ) 3.2 Hz, 2H, Ge-
H), 6.23 (s, 1H), 6.39 (s, 1H); 13C NMR (CDCl3, 125 MHz, 300 K) δ
0.07 (d), 0.85 (q), 1.05 (q), 1.32 (q), 1.99 (q), 28.73 (d), 28.79 (d),
30.26 (d), 122.53 (d), 127.36 (d), 129.57 (s), 143.11 (s), 149.63 (s),
149.78 (s). Anal. found: C, 50.06; H, 10.46. Calcd for C34H80GeSi8‚
2H2O: C, 49.66; H, 10.30.
(3) Bromination of Tbt(Dis)GeH2. To a benzene solution (100 mL)
of Tbt(Dis)GeH2 (3.44 g, 4.38 mmol) obtained as above was added
N-bromosuccinimide (1.7 g, 9.6 mmol) at room temperature, and the
solution was stirred for 10 h. The crude reaction mixture was
chromatographed over SiO2 with benzene. The white solid thus obtained
was dissolved into CH2Cl2, and to the solution was added approximately
the same volume of ethanol. Evaporation of CH2Cl2 at room temperature
under reduced pressure afforded precipitates of Tbt(Dis)GeBr2 (3.3 g,
80%). White crystals; mp 199-201 °C (CH2Cl2/EtOH); 1H NMR
(CDCl3, 500 MHz, 300 K) δ 0.05 (s, 18H), 0.12 (s, 18H), 0.14 (s,
18H), 0.32 (s, 18H), 1.32 (s, 1H), 1.37 (s, 1H), 2.63 (s, 1H), 3.03 (s,
1H), 6.27 (s, 1H), 6.39 (s, 1H); 13C NMR (CDCl3, 125 MHz, 300 K)
δ 0.95 (q), 1.90 (q), 2.03 (q), 3.77 (q), 22.71 (d), 27.00 (d), 27.27 (d),
30.69 (d), 123.98 (d), 128.86 (d), 130.04 (s), 146.12 (s), 149.79 (s),
150.57 (s). Anal. found: C, 43.01; H, 8.24; Br, 16.87. Calcd for C34H78-
Br2GeSi8: C, 43.25; H, 8.33; Br, 16.93. High-resolution FAB-MS:
observed m/z 944.1930 (M+); calcd for C34H7879Br81Br74GeSi8 944.1816.
Trapping of {2,4,6-Tris[bis(trimethylsilyl)methyl]phenyl}[bis-
(trimethylsilyl)methyl]germylene (17) with 2,3-Dimethyl-1,3-buta-
diene. To a solution of the Tbt(Dis)GeBr2 (73.9 mg, 0.0783 mmol) in
THF (3 mL) was added lithium naphthalenide (0.50 M in THF, 0.37
mL, 0.19 mmol) at -55 °C, and the mixture was warmed to room
temperature over 1.5 h. To the resulting purple solution of 17 was added
2,3-dimethyl-1,3-butadiene (0.1 mL, 0.88 mmol), and the solution was
stirred for 1 h. After removal of the solvent, the residue was purified
by GPLC and DCC (SiO2 with hexane) to afford 1-{2,4,6-tris[bis-
(trimethylsilyl)methyl]phenyl}-2,5-dihydro-1-[bis(trimethylsilyl)methyl]-
3,4-dimethylgermole (18) (10%). White crystals; mp 174-176 °C
(CH2Cl2/EtOH); 1H NMR (CDCl3, 500 MHz, 300 K) δ 0.00 (s, 18H),
0.03 (s, 18H), 0.05 (s, 18H), 0.10 (s, 18H), 0.21 (s, 1H), 1.25 (s, 1H),
1.71 (s, 6H), 1.90 (s, 1H), 1.97 (d, J ) 16.1 Hz, 2H), 1.99 (s, 1H),
2.06 (d, J ) 16.1 Hz, 2H), 6.21 (s, 1H), 6.34 (s, 1H); 13C NMR (CDCl3,
125 MHz, 300 K) δ 0.38 (q), 0.94 (q), 1.62 (q), 1.83 (q), 3.71 (q),
5.38 (d), 19.44 (q), 27.74 (d), 29.69 (d), 29.91 (d), 33.71 (t), 122.72
(d), 128.15 (d), 131.32 (d), 133.38 (d), 142.35 (s), 142.61 (s), 149.75
(s), 150.16 (s). Anal. found: C, 55.14; H, 10.44. Calcd for C40H88-
GeSi8: C, 55.45; H, 10.24. High-resolution FAB-MS: observed m/z
867.4466 ([M+H]+); calcd for C40H8974GeSi8 867.4330.
Synthesis of 5-{2,4,6-Tris[bis(trimethylsilyl)methyl]phenyl}-5-
[bis(trimethylsilyl)methyl]-1,2,3,4,5-tetrathiagermolane (19). To a
solution of Tbt(Dis)GeBr2 (155 mg, 0.164 mmol) in THF (6 mL) was
added lithium naphthalenide (0.50 M in THF, 0.78 mL, 0.39 mmol) at
-55 °C, and the solution was warmed to room temperature over 2.5 h
to give a purple solution of germylene 17. To this solution was added
elemental sulfur (50 mg, 0.20 mmol as S8), and the solution was stirred
for 0.5 h. After removal of the solvent, the residue was roughly purified
by short column chromatography (SiO2 with CH2Cl2) and GPLC. The
yellow solid thus obtained was purified by DCC (SiO2 with hexane)
and reprecipitated from CH2Cl2/EtOH to afford 19 (78.7 mg, 53%).
19: pale yellow crystals; mp 206-210 °C dec (CH2Cl2/EtOH); 1H NMR
(CDCl3, 500 MHz, 300 K) δ 0.05 (s, 18H), 0.11 (s, 36H), 0.23 (s,
18H), 1.06 (s, 1H), 1.32 (s, 1H), 2.20 (s, 1H), 2.21 (s, 1H), 6.26 (s,
1H), 6.41 (s, 1H); 13C NMR (CDCl3, 125 MHz, 300 K) δ 0.99 (q),
1.93 (q), 2.23 (q), 4.49 (q), 18.30 (d), 28.69 (d), 28.78 (d), 30.51 (d),
123.42 (d), 128.87 (d), 132.06 (s), 145.31 (s), 150.32 (s), 150.91 (s).
Anal. found: C, 43.58; H, 9.11; S, 13.30. Calcd for C34H78GeS4Si8‚
H2O: C, 43.88; H, 8.67; S, 13.78.
Synthesis of {2,4,6-Tris[bis(trimethylsilyl)methyl]phenyl}(2,4,6-
triisopropylphenyl)germaneselone (2a). To a mixture of 13 (500 mg,
0.437 mmol) and triphenylphosphine (340 mg, 1.30 mmol) was added
hexane (3 mL), and the solution was refluxed for 2 h. After filtration
of triphenylphosphine selenide under argon, the residual red solution
was concentrated in a glovebox filled with argon to give red crystals,
which contained 99% of 2a (392 mg, 100%) and 1% of triphenylphos-
1
phine selenide (8 mg). 2a: red crystals, mp 191-194 °C; H NMR
(C6D6, 500 MHz, 300 K) δ 0.15 (s, 18H), 0.18 (s, 18H), 0.25 (s, 18H),
1.19 (d, J ) 6.9 Hz, 6H), 1.34 (d, J ) 6.9 Hz, 6H), 1.46 (d, J ) 6.9
Hz, 6H), 1.49 (s, 1H), 2.73 (sept, J ) 6.9 Hz, 1H), 3.40 (br s, 1H),
3.41 (sept, J ) 6.9 Hz, 2H), 3.79 (br s, 1H), 6.51 (br s, 1H), 6.68 (brs,
1H), 7.05 (s, 2H); 13C NMR (C6D6, 125 MHz, 300 K) δ 1.11 (q), 1.37
(q), 1.67 (q), 22.28 (q), 24.09 (q × 2), 27.39 (d), 29.08 (br d × 2),
31.83 (d), 34.83 (d), 36.52 (d), 122.64 (d × 2), 124.38 (d), 128.29 (d),
144.04 (s), 147.42 (s), 149.58 (s), 150.06 (s), 150.43 (s), 151.01 (s ×
2), 152.08 (s); 77Se NMR (C6D6, 51.5 MHz, 300 K) δ 940.6. FT-Raman
(solid, excitation; Nd: YAG laser 1064 nm) 382 cm-1. High-resolution
FAB-MS: observed m/z 908.3455 ([M + H]+). Calcd for C42H83
GeSeSi6: 908.3409.
-
74
Preparation of {2,4,6-Tris[bis(trimethylsilyl)methyl]phenyl}-
dibromo[bis(trimethylsilyl)methyl]germane. (1) Synthesis of {2,4,6-
tris[bis(trimethylsilyl)methyl]phenyl}[bis(trimethylsilyl)methyl]-
dihalogermane. To a solution of 1-bromo-2,4,6-tris[bis(trimethyl-
silyl)methyl]benzene11 (TbtBr, 5.0 g, 7.92 mmol) in THF (80 mL) was
added t-BuLi (1.62 M in pentane, 10.5 mL, 17.0 mmol) at -78 °C.
After the reaction solution was stirred for 10 min, GeCl4 (0.95 mL,
8.3 mmol) was added to it at -78 °C. The reaction mixture was warmed
to room temperature over 10 h to give a solution of TbtGeCl3, to which
DisMgCl, prepared from bis(trimethylsilyl)chlorosilane (DisCl; 3.5 mL,
16.0 mmol) and magnesium (580 mg, 24 mmol) in THF, was added at
room temperature. After the solution was refluxed for 10 h, a few drops
of aqueous NH4Cl was added and almost all THF was removed under
reduced pressure. Chloroform and diluted HCl were added to the
residue, and the aqueous layer was extracted by CHCl3 several times.
The organic layer was dried over MgSO4, and the solvent was removed
under reduced pressure. The white solid thus obtained was dissolved
into CH2Cl2, and to the solution was added approximately the same
volume of ethanol. Evaporation of CH2Cl2 at room temperature under
reduced pressure afforded precipitates of {2,4,6-tris[bis(trimethylsilyl)-
methyl]phenyl}[bis(trimethylsilyl)methyl]dihalogermane (4.26 g) as a
mixture of dichlorogermane, bromochlorogermane, and dibromoger-
mane as judged by mass spectrometry and elemental analysis.
(2) Synthesis of {2,4,6-tris[bis(trimethylsilyl)methyl]phenyl}[bis-
(trimethylsilyl)methyl]germane. The mixture of the dihalogermanes
obtained above was dissolved in THF (100 mL), and LiAlH4 (380 mg,
10.0 mmol) was added to it at 0 °C. After being warmed to room
temperature, the mixture was refluxed for 10 h. After being quenched
by aqueous NH4Cl, the organic layer was washed by dilute HCl. The
water layer was extracted with CHCl3 several times. The organic layer
was dried over MgSO4, and all of the solvent was removed under
reduced pressure. The residue was dissolved in CH2Cl2, and ap-
proximately the same volume of ethanol was added to it. Evaporation
of CH2Cl2 at room temperature under reduced pressure afforded
precipitates of {2,4,6-tris[bis(trimethylsilyl)methyl]phenyl}[bis(trimeth-
ylsilyl)methyl]germane (Tbt(Dis)GeH2, 3.44 g, 55% from TbtBr) as
Synthesis of 5-{2,4,6-Tris[bis(trimethylsilyl)methyl]phenyl}-5-
[bis(trimethylsilyl)methyl]-1,2,3,4,5-tetraselenagermolane (20). To
a solution of Tbt(Dis)GeBr2 (213 mg, 0.225 mmol) in THF (8 mL)
was added lithium naphthalenide (0.63 M in THF, 0.90 mL, 0.57 mmol)
at -60 °C, and the solution was warmed to room temperature over 1.5

Germanethiones and Germaneselones
J. Am. Chem. Soc., Vol. 121, No. 38, 1999 8821
h to give a purple solution of germylene 17. To the resulting purple
solution was added elemental selenium (100 mg, 1.3 mmol), and the
solution was stirred for 1 h. After removal of the solvent, the residue
was roughly purified by short column chromatography (SiO2 with
hexane) and GPLC. The orange solid thus obtained was purified by
DCC (SiO2 with hexane) and reprecipitated from CH2Cl2/EtOH to afford
20 (137 mg, 55%). 20: orange crystals; mp 194-198 °C (CH2Cl2/
silyl)methyl]phenyl}-1-[bis(trimethylsilyl)methyl]germirene (22; 378
mg, 45%). 22: white crystals; mp 153-156 °C (CH2Cl2/EtOH); H
1
NMR (CDCl3, 500 MHz, 300 K) δ -0.02 (s, 18H), -0.01 (s, 18H),
0.04 (s, 18H), 0.12 (s, 18H), 0.37 (s, 1H), 1.29 (s, 1H), 2.21 (s, 1H),
2.28 (s, 1H), 6.26 (s, 1H), 6.40 (s, 1H), 7.19-7.22 (m, 2H), 7.27-
7.31 (m, 4H), 7.53-7.55 (m, 4H); 13C NMR (CDCl3, 125 MHz, 300
K) δ 0.97 (q), 1.61 (q), 1.89 (q), 3.51 (q), 9.35 (d), 28.88 (d), 29.03
(d), 30.27 (d), 122.71 (d), 127.11 (d), 128.10 (d), 128.14 (d), 129.09
(d), 133.34 (s), 135.37 (s), 143.32 (s), 150.15 (s), 150.38 (s), 155.21
(s). Anal. found: C, 56.93; H, 9.14. Calcd for C48H88GeSi8‚3H2O: C,
56.71; H, 9.32.
Thermal Reaction of 22 in the Presence of 2,3-Dimethyl-1,3-
butadiene. In a 5 mm i.d. NMR tube was placed a benzene-d6 (1.0
mL) solution of 22 (24.4 mg, 0.0253 mmol) and 2,3-dimethyl-1,3-
butadiene (0.02 mL, 0.18 mmol). After five freeze-pump-thaw cycles,
the tube was evacuated and sealed. The solution was heated at 70 °C
for 3.5 h. 1H NMR of the reaction mixture measured at this stage
indicated that the starting material remained. After being heated at 80
°C for 20 h, the solvent was removed under reduced pressure and the
crude reaction products were chromatographed by PTLC (SiO2 with
hexane) to afford 18 (15.7 mg, 71%) together with diphenylacetylene
(4.4 mg, 97%).
1
EtOH); H NMR (CDCl3, 500 MHz, 300 K) δ 0.05 (s, 18H), 0.12 (s,
36H), 0.24 (s, 18H), 1.31 (s, 1H), 1.34 (s, 1H), 2.25 (s, 1H), 2.26 (s,
1H), 6.27 (br s, 1H), 6.41 (br s, 1H); 13C NMR (CDCl3, 125 MHz, 300
K) δ 1.04 (q), 2.22 (q), 2.52 (q), 4.86(q), 20.04 (d), 28.85 (d), 28.89
(d), 30.48 (d), 123.51 (d), 129.11 (d), 134.22 (s), 144.91 (s), 150.16
(s), 150.76 (s); 77Se NMR (CDCl3, 95.2 MHz, 300 K) δ 405.6, 776.0.
Anal. found: C, 36.55; H, 6.89. Calcd for C34H78GeSe4Si8: C, 36.81;
H, 7.18.
Desulfurization of Tetrathiagermolane 19: Synthesis of {2,4,6-
Tris[bis(trimethylsilyl)methyl]phenyl}[bis(trimethylsilyl)methyl]-
germanethione (1b). To a mixture of 19 (289 mg, 0.317 mmol) and
triphenylphosphine (249 mg, 0.950 mmol) was added hexane (4 mL),
and the solution was refluxed for 3 h. After filtration of the precipitates,
the residual bright yellow solution was concentrated in a glovebox filled
with argon to give yellow crystals, which contained 94% of 1b (166
mg, 62%), 5% of triphenylphosphine (24.1 mg), and 1% of triph-
enylphosphine sulfide (5.6 mg). The yields were determined after the
hydrolysis of germanethione 1b, which gave the corresponding adduct
quantitatively. The white precipitates initially filtered-off were dissolved
into chloroform, and the insoluble white solid was separated by filtration
to give triphenylphosphine sulfide (246 mg, 88% from triphenylphos-
phine) from the filtrate and 3,6-bis[bis(trimethylsilyl)methyl]-3,6-bis-
{2,4,6-tris[bis(trimethylsilyl)methyl]phenyl}-1,2,4,5-tetrathia-3,6-di-
germacyclohexane (21; 82.5 mg, 31%) from the insoluble substances.
Synthesis of {2,4,6-Tris[bis(trimethylsilyl)methyl]phenyl}[bis-
(trimethylsilyl)methyl]germanethione (1b). In a 5 mm i.d. NMR tube
was placed a benzene-d6 (0.8 mL) solution of 22 (23.0 mg, 0.0239
mmol) and elemental sulfur (0.8 mg, 0.003 mmol as S8). After five
freeze-pump-thaw cycles, the tube was evacuated and sealed. The
solution was heated at 90 °C for 7 days to afford a yellow solution.
The quantitative generation of germanethione 1b and diphenylacetylene
1
was observed by H NMR. The solvent was removed in a glovebox
filled with argon to afford 1b together with diphenylacetylene.
Synthesis of {2,4,6-Tris[bis(trimethylsilyl)methyl]phenyl}[bis-
(trimethylsilyl)methyl]germaneselone (2b). In a 5 mm i.d. NMR tube
was placed a benzene-d6 (0.8 mL) solution of 22 (30.9 mg, 0.0321
mmol) and elemental selenium (2.6 mg, 0.033 mmol). After five
freeze-pump-thaw cycles, the tube was evacuated and sealed. The
solution was heated at 90 °C for 7 days to afford an orange-red
solution. The quantitative generation of germaneselone 2b and diphe-
1
1b: yellow crystals; mp 190-193 °C (hexane); H NMR (C6D6, 500
MHz, 300 K) δ 0.14 (s, 9H), 0.27 (br s, 18H), 0.31 (br s, 18H), 0.40
(s, 18H), 1.48 (s, 1H), 2.05 (s, 1H), 2.63 (br s, 1H), 2.73 (br s, 1H),
6.52 (s, 1H), 6.67 (s, 1H); 13C NMR (C6D6, 125 MHz, 300 K) δ 0.95
(q), 1.57 (q), 1.91 (q), 3.92 (q), 31.35 (d), 31.50 (d), 31.81 (d), 40.70
(d), 123.09 (d), 129.50 (d), 143.41 (s), 147.14 (s), 148.39 (s), 148.96
(s). FT-Raman (solid, excitation; Nd: YAG laser 1064 nm) 512 cm-1
.
High-resolution FAB-MS: observed m/z 817.3217 ([M + H]+); calcd
for C34H7974GeSSi8 817.3268. 21: white crystals; mp >300 °C (CHCl3);
1H NMR (CDCl3, 500 MHz, 300 K) δ -0.02 (s, 9H), 0.00 (s, 9H),
0.04 (s, 9H), 0.09 (s, 9H), 0.21 (s, 36H), 0.61 (s, 1H), 1.34 (s, 1H),
2.91 (s, 1H), 3.01 (s, 1H), 6.37 (s, 1H), 6.54 (s, 1H). It was impossible
to measure the 13C NMR owing to its insolubility. Anal. found: C,
47.05; H, 9.58; S, 7.85. Calcd for C68H156Ge2S4Si12‚2H2O: C, 47.13;
H, 9.30; S, 7.40.
1
nylacetylene was observed by H NMR. The solvent was removed in
a glovebox filled with argon to afford 2b together with diphenylacetyl-
1
ene. 2b: red orange crystals; mp 195-198 °C; H NMR (C6D6, 500
MHz, 300 K) δ 0.14 (s, 18H), 0.28 (br s, 18H), 0.31 (br s, 18H), 0.40
(s, 18H), 1.48 (s, 1H), 2.35 (s, 1H), 2.84 (s, 1H), 6.50 (s, 1H), 6.65 (s,
1H); 13C NMR (C6D6, 125 MHz, 300 K) δ 0.97 (q), 1.70 (q), 2.00 (q),
3.98 (q), 30.58 (d), 31.27 (d), 31.55 (d), 44.13 (d), 123.52 (d), 129.49
(d), 145.15 (s), 146.92 (s), 147.88 (s), 148.32 (s); 77Se NMR (C6D6,
51.5 MHz, 300 K) δ 872.7. FT-Raman (solid, excitation; Nd: YAG
laser 1064 nm) 386 cm-1. High-resolution FAB-MS: observed m/z
865.2625 ([M+H]+); calcd for C34H7874GeSeSi8 865.2713.
Hydrolysis of Germanethione 1b. One drop of water was added
to a yellow solution of germanethione 1b (20.0 mg, 0.025 mmol) in
hexane (1 mL). The yellow color immediately disappeared. Separation
by PTLC (SiO2 with 20:1 hexane/CH2Cl2) gave {2,4,6-tris[bis-
(trimethylsilyl)methyl]phenyl}(hydroxy)(mercapto)[bis(trimethylsilyl)-
methyl]germane Tbt(Dis)Ge(SH)(OH) (20.4 mg, 100%). White crystals;
mp 175-180 °C (CH2Cl2/EtOH); 1H NMR (CDCl3, 500 MHz, 300 K)
δ 0.04 (s, 9H), 0.05 (s, 9H), 0.10 (s, 9H), 0.11 (s, 9H), 0.12 (s, 9H),
0.248 (s, 9H), 0.253 (s, 9H), 0.61 (s, 1H), 0.94 (s, 1H, SH), 1.31 (s,
1H), 1.56 (br s, 1H, OH), 2.45 (s, 1H), 2.68 (s, 1H), 6.27 (s, 1H), 6.38
(s, 1H); 13C NMR (CDCl3, 125 MHz, 300 K) δ 0.87 (q), 0.92 (q), 1.54
(q), 1.71 (q × 2), 1.94 (q), 3.608 (q), 3.614 (q), 15.33 (d), 27.03 (d),
27.18 (d), 30.44 (d), 123.52 (d), 128.55 (d), 128.70 (s), 144.96 (d),
149.80 (d), 150.29 (d). Anal. Found: C, 48.02; H, 9.67. Calcd for
C34H80GeOSSi8‚H2O: C, 47.91; H, 9.70. High-resolution FAB-MS:
observed m/z 834.3331 ([M + H]+); calcd for C34H8074GeOSSi8
834.3296.
Reaction of Germylene 17 with Diphenylacetylene. To a solution
of Tbt(Dis)GeBr2 (824 mg, 0.873 mmol) in THF (30 mL) was added
lithium naphthalenide (0.63 M in THF, 3.3 mL, 2.1 mmol) at -55 °C,
and the mixture was warmed to room temperature over 1.5 h. To the
resulting purple solution of germylene 17 was added diphenylacetylene
(200 mg, 1.1 mmol), and the solution was stirred for 10 h. After removal
of the solvent, the residue was chromatographed by GPLC and DCC
(SiO2 with hexane) to afford 2,3-diphenyl-1-{2,4,6-tris[bis(trimethyl-
Hydrolysis of Germanethione 1a. One drop of water was added
to a yellow solution of germanethione 1a (21.0 mg, 0.024 mmol) in
hexane (1 mL). The yellow color immediately dissappeared. Separation
with PTLC (SiO2 with 10:1 hexane/CH2Cl2) gave 9 (21.4 mg, 100%).
Reaction of Germanethione 1a with Methyllithium. (1) To a
mixture of 5 (108 mg, 0.113 mmol) and triphenylphosphine (89.0 mg,
0.340 mmol) was added hexane (0.5 mL), and the solution was refluxed
for 2 h to afford a yellow solution of germanethione 1a. Methyllithium
(0.95 M in ether, 0.20 mL, 0.19 mmol) was added dropwise to this
solution at - 65 °C. The color of the solution disappeared at -20 °C,
and then ethanol (0.01 mL, 0.2 mmol) was added to this solution. After
the solution was warmed to room temperature, the solvent was removed
under reduced pressure and the residue was chromatographed by DCC
(SiO2 with hexane) to afford {2,4,6-tris[bis(trimethylsilyl)methyl]-
phenyl}(2,4,6-triisopropylphenyl)(mercapto)(methyl)germane (23; 68.6
1
mg, 81%). 23: white crystals, mp 212-213 °C (CH2Cl2/EtOH); H
NMR (CDCl3, 500 MHz, 340 K) δ -0.01 (s, 18H), 0.06 (s, 18H),
0.07 (s, 18H), 0.42 (s, 1H, SH), 1.14 (br s, 6H), 1.21 (d, J ) 6.9 Hz,
6H), 1.24 (d, J ) 6.9 Hz, 6H), 1.31 (s, 1H), 1.38 (s, 3H, GeMe), 2.39
(br s, 1H), 2.53 (br s, 1H), 2.83 (sept, J ) 6.9 Hz, 1H), 3.42 (br s, 2H),
6.37 (br s, 2H), 7.00 (br s, 2H); 13C NMR (CDCl3, 125 MHz, 300 K)
δ 0.87 (q), 0.93 (q), 1.89 (q), 1.93 (q), 2.16 (q), 2.23 (q), 17.27 (q,

8822 J. Am. Chem. Soc., Vol. 121, No. 38, 1999
Matsumoto et al.
GeMe), 23.42 (q), 23.83 (q), 24.56 (q), 27.68 (d), 28.20 (d), 30.18 (d),
32.77 (d), 33.37 (d), 34.19 (d), 121.66 (d), 123.44 (d × 2), 128.58 (d),
132.57 (s), 137.59 (s), 143.44 (s), 149.70 (s), 149.76 (s), 150.23 (s),
152.11 (s), 154.05 (s). Anal. found: C, 58.52; H, 9.48; S, 3.72. Calcd
for C43H86GeSSi6: C, 58.93; H, 9.89; S, 3.66. (2) To a mixture of 5
(161 mg, 0.168 mmol) and triphenylphosphine (132 mg, 0.504 mmol)
was added hexane (1.2 mL), and the solution was refluxed for 2 h to
afford a yellow solution of germanethione 1a. Methyllithium (1.0 M
in ether, 0.30 mL, 0.30 mmol) was added dropwise to this solution at
- 65 °C, which was warmed gradually. The color of the solution
disappeared at -20 °C, and methyl iodide (0.05 mL, 0.8 mmol) was
added to the solution. After it was warmed to room temperature, the
solvent was removed under reduced pressure and the residue was
chromatographed by DCC (SiO2 with hexane) to afford {2,4,6-tris-
[bis(trimethylsilyl)methyl]phenyl}(2,4,6-triisopropylphenyl)(methyl)-
(methylthio)germane (24; 123 mg, 69%). 24: white crystals, mp 178-
179 °C (CH2Cl2/EtOH); 1H NMR (CDCl3, 500 MHz, 300 K) δ -0.15
(br s, 9H), -0.04 (br s, 9H), 0.03 (s, 9H), 0.04 (s, 9H), 0.07 (br s, 9H),
0.13 (br s, 9H), 0.83 (d, J ) 6.9 Hz, 3H), 1.18 (d, J ) 6.9 Hz, 3H),
1.19 (d, J ) 6.9 Hz, 6H), 1.23 (d, J ) 6.9 Hz, 3H), 1.27 (s, 1H), 1.30
(s, 3H, GeMe), 1.36 (d, J ) 6.9 Hz, 3H), 1.78 (s, 3H, SMe), 2.20 (br
s, 1H), 2.38 (br s, 1H), 2.81 (sept, J ) 6.9 Hz, 1H), 3.26 (sept, J ) 6.9
Hz, 1H), 3.37 (sept, J ) 6.9 Hz, 1H), 6.28 (s, 1H), 6.39 (s, 1H), 6.97
(s, 1H); 13C NMR (CDCl3, 125 MHz, 300 K) δ 0.85 (q), 1.07 (q), 1.80
(q), 1.85 (q), 2.03 (q), 2.16 (q), 11.72 (q), 12.52 (q), 23.79 (q), 23.89
(q), 25.55 (q), 26.48 (d), 27.22 (d), 30.15 (d), 31.67 (d), 33.84 (d),
34.12 (d), 121.47 (d), 123.52 (d), 124.00 (d), 128.64 (d), 133.38 (s),
134.16 (s), 143.01 (s), 149.69 (s), 149.93 (s), 153.61 (s), 154.83 (s).
Anal. found: C, 59.07; H, 10.08; S, 3.77. Calcd for C43H86GeSSi6: C,
59.35; H, 9.96; S, 3.60.
(d), 124.56 (d), 125.74 (d), 129.00 (d), 129.31 (s), 137.42 (s), 143.77
(s), 145.91 (s), 150.44 (s), 150.86 (s), 150.98 (s), 151.51 (s), 151.63
(s), 151.87 (s); 77Se NMR (CDCl3, 51.5 MHz, 300 K) δ -16.2. High-
resolution FAB-MS: observed m/z 1044.3621 ([M + H]+); calcd for
C49H8874GeNSSeSi6 1044.3631.
Reaction of Germanethione 1a with Mesitonitrile Oxide. To a
mixture of 5 (228 mg, 0.239 mmol) and triphenylphosphine (188 mg,
0.718 mmol) was added hexane (1.0 mL), and the solution was refluxed
for 2 h to afford a yellow solution of germanethione 1a. Mesitonitrile
oxide (60 mg, 0.63 mmol) was added to the solution at room
temperature and the mixture was stirred for 10 h. After removal of the
solvent, the crude reaction products were chromatographed by GPLC
to afford 2-{2,4,6-tris[bis(trimethylsilyl)methyl]phenyl}-2-(2,4,6-tri-
isopropylphenyl)-4-mesityl-1,3,5,2-oxathiazagermole (27; 243 mg,
1
99%). 27: white crystals; mp 213-215 °C (CH2Cl2/EtOH); H NMR
(CDCl3, 500 MHz, 300 K) δ 0.01 (s, 9H), 0.03 (s, 18H), 0.04 (s, 9H),
0.06 (s, 9H), 0.08 (s, 9H), 1.20 (d, J ) 6.9 Hz, 6H), 1.21 (d, J ) 6.9
Hz, 6H), 1.22 (d, J ) 6.9 Hz, 6H), 1.36 (s, 1H), 2.16 (s, 6H), 2.25 (s,
3H), 2.31 (s, 1H), 2.52 (s, 1H), 2.85 (sept, J ) 6.9 Hz, 1H), 3.15 (br
s, 1H), 3.35 (br s, 1H), 6.38 (s, 1H), 6.51 (s, 1H), 6.62 (s, 2H), 7.00 (s,
2H); 13C NMR (CDCl3, 125 MHz, 300 K) δ 1.10 (q), 1.36 (q), 1.45
(q), 1.53 (q), 1.82 (q), 20.62 (q), 21.05 (q), 23.77 (q), 23.85 (q), 28.51
(d), 28.73 (d), 30.87 (d), 31.58 (d), 34.23 (d), 122.80 (d), 124.02 (d),
128.50 (d), 129.33 (d), 129.43 (s), 130.24 (s), 137.07 (s), 137.14 (s),
138.43 (s), 145.84 (s), 150.91 (s), 151.34 (s), 151.20 (s), 151.98 (s),
153.18 (s). Anal. found: C, 60.38; H, 9.12; N, 1.33; S, 3.36. Calcd for
C52H93GeNOSSi6‚0.5H2O: C, 60.60; H, 9.19; N, 1.36; S, 3.11.
Reaction of Germaneselone 2a with Mesitonitrile Oxide. To a
mixture of 13 (60.0 mg, 0.0524 mmol) and triphenylphosphine (41.0
mg, 0.156 mmol) was added hexane (0.5 mL), and the solution was
refluxed for 1.5 h to afford a red solution of germaneselone 2a.
Mesitonitrile oxide (10 mg, 0.062 mmol) was added to the solution at
room temperature, and the mixture was stirred for 5 min. After removal
of the solvent, the crude reaction products were chromatographed by
GPLC and wet column chromotography (SiO2 with CH2Cl2) to afford
2-{2,4,6-tris[bis(trimethylsilyl)methyl]phenyl}-2-(2,4,6-triisopropylphe-
nyl)-4-mesityl-1,3,5,2-oxaselenazagermole (28; 57.0 mg, 100%). 28:
white crystals; mp 237-239 °C (CH2Cl2/EtOH); 1H NMR (CDCl3, 500
MHz, 300 K) δ 0.00 (s, 18H), 0.06 (s, 9H), 0.067 (s, 9H), 0.069 (s,
9H), 0.082 (s, 9H), 1.18 (br s, 6H), 1.22 (d, J ) 6.9 Hz, 6H), 1.29 (br
s, 6H), 1.36 (s, 1H), 2.19 (s, 6H), 2.25 (s, 3H), 2.36 (s, 1H), 2.46 (s,
1H), 2.85 (sept, J ) 6.9 Hz, 1H), 3.22 (br s, 1H), 3.43 (br s, 1H), 6.38
(s, 1H), 6.50 (s, 1H), 6.82 (s, 2H), 7.01 (s, 2H); 13C NMR (CDCl3, 125
MHz, 300 K) δ 1.09 (q), 1.17 (q), 1.39 (q), 1.54 (q), 1.69 (q), 1.93 (q),
20.70 (q), 20.87 (q), 23.67 (q), 23.73 (q), 23.89 (q), 28.12 (d), 28.27
(d), 28.47 (d), 30.84 (d), 34.21 (d), 34.67 (d), 122.87 (br d), 124.13
(d), 128.48 (d), 129.51 (d), 130.56 (s), 131.37 (s), 136.90 (s), 137.11
(s), 138.43 (s), 145.60 (s), 148.79 (s), 150.77 (s), 151.20 (s), 151.32
(s), 152.31 (s), 153.16 (s); 77Se NMR (CDCl3, 51.5 MHz, 300 K) δ
212.4. Anal. found: C, 58.55; H, 8.94; N, 1.44; Se, 7.58. Calcd for
C52H93GeNOSeSi6: C, 58.75; H, 8.77; N, 1.31; Se, 7.39.
Reaction of Germanethione 1a with Phenyl Isothiocyanate. To
a mixture of 5 (74.0 mg, 0.0774 mmol) and triphenylphosphine (60.8
mg, 0.232 mmol) was added hexane (1.0 mL), and the solution was
refluxed for 1.5 h to afford a yellow solution of germanethione 1a.
Phenyl isothiocyanate (0.02 mL, 0.170 mmol) was added to the solution,
which was stirred for 10 h. After removal of the solvent, the crude
reaction products were chromatographed by DCC (SiO2 with 3:1
hexane/CH2Cl2) to afford 2-{2,4,6-tris[bis(trimethylsilyl)methyl]phenyl}-
2-(2,4,6-triisopropylphenyl)-4-phenylimino-1,3,2-dithiagermetane (25;
64.8 mg, 84%). 25: white crystals; mp 150-153 °C dec (CH2Cl2/
1
EtOH); H NMR (CDCl3, 500 MHz, 300 K) δ -0.05 (s, 9H), -0.03
(s, 9H), 0.03 (s, 9H), 0.05 (s, 9H), 0.09 (s, 9H), 1.16 (br s, 3H), 1.20
(br s, 6H), 1.22 (d, J ) 6.9 Hz, 6H), 1.32 (br s, 3H), 1.33 (s, 1H), 2.43
(br s, 1H), 2.87 (sept, J ) 6.9 Hz, 1H), 3.08 (br s, 3H), 6.33 (s, 1H),
6.51 (s, 1H), 6.92 (s, 1H), 6.93 (s, 1H), 7.04-7.29 (m, 5H); 13C NMR
(CDCl3, 125 MHz, 300 K) δ 0.90 (q), 1.58 (q), 1.62 (q), 1.72 (q), 23.12
(br q), 23.58 (q), 28.18 (d), 28.24 (d), 30.82 (d), 34.35 (d), 35.73 (d),
35.85 (d), 121.20 (d), 122.96 (d), 123.81 (d), 124.13 (d), 128.80 (d),
129.03 (d), 129.60 (s), 137.36 (s), 146.16 (s), 149.03 (s), 151.12 (s),
151.68 (s), 151.91 (s), 153.16 (s). Anal. found: C, 58.64; H, 8.51; N,
1.46; S, 6.39. Calcd for C47H87GeNS2Si6‚0.5H2O: C, 58.59; H, 8.83;
N, 1.39; S, 6.39.
Reaction of Germanethione 1a with 2,3-Dimethyl-1,3-butadiene.
To a mixture of 5 (69.2 mg, 0.0724 mmol) and triphenylphosphine
(56.9 mg, 0.217 mmol) in a 5 mm i.d. Pyrex glass tube was added
2,3-dimethyl-1,3-butadiene (0.08 mL, 0.72 mmol) and hexane (0.8 mL)
at room temperature. After five freeze-pump-thaw cycles, the tube
was evacuated and sealed. The solution was heated at 90 °C for 10 h,
during which time the yellow color disappeared. After removal of the
solvent, the crude reaction products were chromatographed by DCC
(SiO2 with hexane) to afford 2-{2,4,6-tris[bis(trimethylsilyl)methyl]-
phenyl}-2-(2,4,6-triisopropylphenyl)-4,5-dimethyl-1-thia-2-germacyclo-
hex-4-ene (29; 57.1 mg, 84%) together with 9 (7.0 mg, 11%). 29: white
Reaction of Germaneselone 2a with Phenyl Isothiocyanate. To a
mixture of 13 (59.6 mg, 0.0521 mmol) and triphenylphosphine (40.0
mg, 0.153 mmol) was added hexane (0.5 mL), and the solution was
refluxed for 1.5 h to afford a red solution of germaneselone 2a. Phenyl
isothiocyanate (0.1 mL, 0.84 mmol) was added to the solution, which
was stirred for 1.5 h. After removal of the solvent, the crude reaction
products were chromatographed by GPLC to afford 2-{2,4,6-tris[bis-
(trimethylsilyl)methyl]phenyl}-2-(2,4,6-triisopropylphenyl)-4-phenylimino-
1,3,2-thiaselenagermetane (26; 33.1 mg, 61%). 26: white crystals; mp
199-203 °C dec (CH2Cl2/EtOH); 1H NMR (CDCl3, 500 MHz, 300 K)
δ -0.06 (s, 9H), -0.03 (s, 9H), 0.04 (s, 9H), 0.047 (s, 9H), 0.051 (s,
9H), 0.11 (s, 9H), 1.12 (br s, 3H), 1.20 (br s, 3H), 1.22 (d, J ) 6.9 Hz,
6H), 1.28 (br s, 6H), 1.33 (s, 1H), 2.45 (br s, 1H), 2.87 (sept, J ) 6.9
Hz, 1H), 2.99 (br s, 1H), 3.18 (br s, 1H), 3.30 (br s, 1H), 6.33 (s, 1H),
6.51 (s, 1H), 6.90-6.92 (m, 2H), 7.03 (s, 2H), 7.08-7.10 (m, 1H),
7.28-7.30 (m, 2H); 13C NMR (CDCl3, 125 MHz, 300 K) δ 0.87 (q),
0.95 (q), 1.60 (q), 1.67 (q), 1.76 (q × 2), 22.96 (q), 23.54 (q), 23.84
(q), 23.89 (q), 27.76 (q), 28.06 (q), 28.20 (d), 28.50 (d), 30.76 (d),
34.34 (d), 35.57 (d), 35.84 (d), 120.67 (d), 122.96 (d), 123.10 (d), 123.82
1
crystals; mp 164-168 °C dec (CH2Cl2/EtOH); H NMR (CDCl3, 500
MHz, 340 K) δ -0.02 (br s, 18H), 0.06 (s, 9H), 0.07 (s, 9H), 0.12 (br
s, 18H), 1.06 (br d, J ) 6.9 Hz, 6H), 1.18 (d, J ) 6.9 Hz, 6H), 1.22
(br s, 6H), 1.32 (s, 1H), 1.39 (br s, 3H), 1.80 (s, 3H), 2.13 (br s, 2H),
2.28 (d, J ) 12.2 Hz, 1H), 2.55 (d, J ) 12.2 Hz, 1H), 2.79 (sept, J )
6.9 Hz, 1H), 3.03 (br s, 1H), 3.16 (d, J ) 13.4 Hz, 1H), 3.30 (d, J )
13.4 Hz, 1H), 4.26 (br s, 1H), 6.39 (br s, 2H), 6.92 (s, 2H); 13C NMR
(CDCl3, 125 MHz, 340 K) δ 1.01 (q), 1.21 (q), 2.16 (q), 2.47 (q), 20.31
(q), 20.96 (q), 23.77 (q), 23.81 (q), 25.59 (q), 26.42 (d), 26.88 (d),

Germanethiones and Germaneselones
J. Am. Chem. Soc., Vol. 121, No. 38, 1999 8823
28.51 (q), 30.47 (d), 31.44 (d), 33.26 (t), 33.49 (t), 33.75 (d), 34.14
(d), 122.72 (d), 122.75 (s), 122.96 (s), 123.16 (d), 128.77 (d), 129.04
(s), 129.81 (d), 135.87 (s), 136.26 (s), 143.16 (s), 149.33 (s), 149.96
(s), 152.76 (s), 155.125 (s). Anal. found: C, 60.38; H, 9.56; S, 3.81.
Calcd for C48H92GeSSi6‚0.5H2O: C, 60.59; H, 9.85; S, 3.37.
1H), 2.77 (sept, J ) 6.9 Hz, 1H), 2.99 (br s, 1H), 3.47 (m, 1H), 4.63
(br s, 1H), 5.47 (m, 1H), 6.40 (br s, 2H), 6.89 (br s, 1H), 6.93 (br s,
1H). It was impossible to assign the 13C NMR data owing to the
complexity resulting from the steric congestion. Anal. found: C, 61.29;
H, 9.52; S, 3.22. Calcd for C48H92GeSSi6: C, 61.17; H, 9.84; S, 3.40.
High-resolution FAB-MS: observed m/z 943.4796 ([M + H]+); calcd
for C48H9374GeSSi6 943.4825.
Reaction of Germanethione 1a with Isoprene at 90 °C. To a
mixture of 5 (102 mg, 0.107 mmol) and triphenylphosphine (84.0 mg,
0.321 mmol) in a 5 mm i.d. Pyrex glass tube was added isoprene (0.11
mL, 1.1 mmol) and hexane (0.8 mL) at room temperature. After five
freeze-pump-thaw cycles, the tube was evacuated and sealed. The
solution was heated at 90 °C for 10 h, during which time the yellow
color disappeared. After removal of the solvent, the crude reaction
products were chromatographed by DCC (SiO2 with hexane) to afford
2-{2,4,6-tris[bis(trimethylsilyl)methyl]phenyl}-2-(2,4,6-triisopropylphe-
nyl)-4-methyl-1-thia-2-germacyclohex-4-ene (30; 69.7 mg, 70%) and
2-{2,4,6-tris[bis(trimethylsilyl)methyl]phenyl}-2-(2,4,6-triisopropylphe-
nyl)-5-methyl-1-thia-2-germacyclohex-4-ene (31; 7.5 mg, 8%) together
with 9 (11.1 mg, 13%). 30: white crystals; mp 166-169 °C dec (CH2-
Reaction of Germanethione 1a with 2,4-Dimethyl-1,3-pentadiene.
The reaction using 5 (84.7 mg, 0.0886 mmol), triphenylphosphine (70.0
mg, 0.267 mmol), and 2,4-dimethyl-1,3-pentadiene (0.20 mL, 1.8 mmol)
in hexane (0.8 mL) at 90 °C for 10 h gave 2-{2,4,6-tris[bis(tri-
methylsilyl)methyl]phenyl}-2-(2,4,6-triisopropylphenyl)-4,6,6-trimethyl-
1-thia-2-germacyclohex-4-ene (33; 42.5 mg, 50%) together with 9 (20.2
mg, 26%). 33: white crystals; mp 168-170 °C dec (CH2Cl2/EtOH);
1H NMR (CDCl3, 500 MHz, 340 K) δ -0.06 (s, 18H), 0.06 (s, 9H),
0.07 (s, 9H), 0.14 (s, 9H), 0.18 (s, 9H), 0.87 (br s, 3H), 1.12 (br s,
3H), 1.179 (d, J ) 6.9 Hz, 3H), 1.182 (d, J ) 6.9 Hz, 3H), 1.24 (d, J
) 6.9 Hz, 6H), 1.32 (s, 1H), 1.35 (s, 3H), 1.54 (s, 3H), 1.55 (br s, 3H),
2.12 (br s, 2H), 2.36 (d, J ) 11.4 Hz, 1H), 2.47 (d, J ) 11.4 Hz, 1H),
2.78 (sept, J ) 6.9 Hz, 1H), 2.91 (br s, 1H), 4.59 (br s, 1H), 5.48 (s,
1H), 6.37 (br s, 2H), 6.88 (s, 1H), 6.96 (s, 1H). It was impossible to
assign the 13C NMR data owing to the complexity resulting from the
steric congestion. Anal. found: C, 61.17; H, 9.77; S, 2.98. Calcd for
C49H94GeSSi6: C, 61.53; H, 9.91; S, 3.35. High-resolution FAB-MS:
observed m/z 957.5008 ([M + H]+); calcd for C49H9574GeSSi6 957.4892.
Reaction of Germanethione 1a with 2,4-Hexadiene. The reaction
of 5 (93.6 mg, 0.0980 mmol), triphenylphosphine (77.0 mg, 0.294
mmol), and 2,4-hexadiene (0.10 mL, 1.0 mmol) in hexane (0.8 mL) at
150 °C over 10 h afforded 9 (86.0 mg, 100%).
Reaction of Germanethione 1a with trans,trans-1,4-Diphenyl-1,3-
butadiene. The reaction of 5 (59.2 mg, 0.0619 mmol), triphenylphos-
phine (49.0 mg, 0.187 mmol), and trans,trans-1,4-diphenyl-1,3-
butadiene (64.0 mg, 0.311 mmol) in hexane (0.8 mL) at 130 °C for 10
h gave 9 (53.3 mg, 98%).
Thermal Reaction of the Diene Adduct 31 in the Presence of
Isoprene. In a 5 mm i.d. Pyrex glass tube was placed a hexane (0.5
mL) solution of 31 (40.0 mg, 0.0431 mmol) and isoprene (0.10 mL,
0.1 mmol). After five freeze-pump-thaw cycles, the tube was
evacuated and sealed. The solution was heated at 150 °C for 10 h.
After removal of the solvent, the crude reaction products were
chromatographed by DCC (SiO2 with hexane) to afford 30 (16.2 mg,
41%), 31 (17.3 mg, 43%), and 9 (5.0 mg, 13%).
1
Cl2/EtOH); H NMR (CDCl3, 500 MHz, 300 K) δ -0.09 (br s, 18H),
0.03 (s, 9H), 0.05 (s, 9H), 0.06 (s, 9H), 0.13 (br s, 9H), 0.92 (br s,
3H), 1.10 (d, J ) 6.9 Hz, 3H), 1.15 (s, 3H), 1.16 (d, J ) 6.9 Hz, 6H),
1.28 (s, 1H), 1.33 (br s, 3H), 1.94 (br s, 1H), 2.12 (br s, 1H), 2.17 (d,
J ) 11.9 Hz, 1H), 2.48 (d, J ) 11.9 Hz, 1H), 3.15 (dd, J1 ) 13.5 Hz,
J2 ) 5.2 Hz, 1H), 3.37 (dd, 1H, J1 ) 13.5 Hz, J2 ) 7.7 Hz), 4.59 (br
s, 1H), 5.74 (m, 1H), 6.29 (s, 1H), 6.40 (s, 1H), 6.67 (s, 1H), 6.92 (s,
1H); 13C NMR (CDCl3, 125 MHz, 300 K) δ 0.91 (q), 1.15 (q), 1.82
(q), 2.01 (q × 2), 2.37 (q), 23.81 (q), 23.87 (q), 25.24 (q), 25.63 (q),
26.17 (d), 26.24 (t), 28.02 (d), 28.09 (d), 30.15 (d), 31.43 (t), 33.57
(d), 34.05 (d), 122.48 (d), 122.76 (d), 123.28 (d), 123.36 (d), 128.67
(d), 135.01 (s), 137.63 (s), 143.11 (s), 149.25 (s), 149.36 (s), 150.16
(s), 152.40 (s), 155.32 (s), 155.37 (s). Anal. found: C, 60.41; H, 9.45;
S, 3.23. Calcd for C47H90GeSSi6: C, 60.80; H, 9.77; S, 3.45. High-
resolution FAB-MS: observed m/z 929.4764 ([M + H]+); calcd for
C47H9174GeSSi6 929.4669. 31: white crystals; mp 177-180 °C dec
(CH2Cl2/EtOH); 1H NMR (CDCl3, 500 MHz, 335 K) δ 0.02 (s, 18H),
0.04 (s, 18H), 0.052 (s, 9H), 0.054 (s, 9H), 1.13 (d, J ) 6.9 Hz, 12H),
1.20 (d, J ) 6.9 Hz, 6H), 1.30 (s, 1H), 1.87 (s, 3H), 2.24 (br s, 2H),
2.25-2.42 (m, 2H), 2.80 (sept, J ) 6.9 Hz, 1H), 3.11 (br s, 1H), 3.14
(s, 2H), 4.12 (br s, 1H), 5.69 (m, 1H), 6.39 (br s, 2H), 6.96 (br s, 2H);
13C NMR (CDCl3, 125 MHz, 300 K) δ 0.93 (q), 0.95 (q), 1.96 (q),
2.21 (q × 2), 2.42 (q), 23.78 (q), 23.81 (q), 23.98 (q), 24.43 (q), 24.65
(d), 25.69 (t), 27.73 (d), 27.96 (d), 29.78 (t), 30.14 (d), 33.75 (d), 34.10
(d), 122.45 (d), 123.08 (d), 123.20 (d), 128.67 (d), 128.80 (d), 134.42
(s), 137.21 (s), 137.58 (s), 143.04 (s), 148.96 (s), 149.81 (s), 150.30
(s), 151.97 (s), 153.86 (s). Anal. found: C, 60.57; H, 9.56; S, 3.41.
Thermal Reaction of Diene Adduct 32 in the Presence of 2,3-
Dimethyl-1,3-butadiene. The reaction of 32 (30.8 mg, 0.0326 mmol)
and 2,3-dimethyl-1,3-butadiene (0.14 mL, 0.98 mmol) at 150 °C for
10 h was similarly carried out to give 29 (22.0 mg, 71%) and 9 (3.6
mg, 13%).
Calcd for C47H90GeSSi6: C, 60.80; H, 9.77; S, 3.45. High-resolution
74
FAB-MS: observed m/z 929.4659 ([M + H]+); calcd for C47H90
GeSSi6 929.4669.
-
Reaction of Germaneselone 2a with 10 and 40 equiv of 2,3-
Dimethyl-1,3-butadiene. The reaction was carried out in a manner
similar to that of 1a. The reaction of 13 (54.7 mg, 0.0478 mmol),
triphenylphosphine (37.0 mg, 0.141 mmol), and 2,3-dimethyl-1,3-
butadiene (0.06 mL, 0.53 mmol) in hexane (0.8 mL) at 90 °C for 10 h,
and then at room temperature for 10 h, afforded 2-{2,4,6-tris[bis-
(trimethylsilyl)methyl]phenyl}-2-(2,4,6-triisopropylphenyl)-4,5-dimethyl-
1-selena-2-germacyclohex-4-ene (34; 10.5 mg, 22%). 34: white crystals,
mp 148-154 °C dec (CH2Cl2/EtOH); 1H NMR (CDCl3, 500 MHz, 350
K) δ -0.02 (br s, 18H), 0.07 (s, 9H), 0.09 (s, 9H), 0.14 (s, 18H), 0.93
(br s, 3H), 1.05 (br s, 3H), 1.19 (d, J ) 6.9 Hz, 6H), 1.21 (br s, 3H),
1.28 (br s, 6H), 1.32 (br s, 6H), 1.33 (s, 1H), 1.79 (s, 3H), 2.14 (br s,
2H), 2.29 (d, J ) 10.8 Hz, 1H), 2.67 (d, J ) 10.8 Hz, 1H), 2.79 (sept,
J ) 6.9 Hz, 1H), 3.07 (br s, 1H), 3.17 (d, J ) 11.8 Hz, 1H), 3.29 (d,
J ) 11.8 Hz, 1H), 4.33 (br s, 1H), 6.40 (br s, 2H), 6.92 (s, 2H); 77Se
NMR (CDCl3, 51.5 MHz, 300 K) δ 30.9, 32.6. It was impossible to
assign the 13C NMR because there were at least two conformers at
room temperature and also 34 gradually decomposed at elevated
temperature. Anal. found: C, 57.74; H, 9.02; Se, 8.33. Calcd for C48H92-
GeSeSi6: C, 58.27; H, 9.37; S, 7.98.
Reaction of Germanethione 1a with Isoprene at 150 °C. A
solution of 1a obtained from 5 (93.2 mg, 0.0975 mmol) in a manner
similar to the above reaction at 90 °C was heated with isoprene (0.11
mL, 1.1 mmol) at 150 °C for 10 h and gradually cooled to room
temperature over 5 h. The products were 30 (32.1 mg, 36%) and 31
(32.7 mg, 36%) together with 9 (11.1 mg, 13%).
Reaction of Germanethione 1a with Isoprene at 90 °C in THF.
Similarly, a THF solution (0.5 mL) of 1a, obtained from 5 (40.4 mg,
0.0423 mmol), was heated with isoprene (0.08 mL, 0.63 mmol) at 80
°C for 10 h, during which time the yellow color disappeared. The
products were 30 (26.6 mg, 76%) and 31 (2.9 mg, 8%).
Reaction of Germanethione 1a with 2-Methyl-1,3-pentadiene. A
similar reaction using 5 (83.7 mg, 0.0876 mmol), triphenylphosphine
(68.8 mg, 0.263 mmol), and 2-methyl-1,3-pentadiene (0.20 mL, 1.8
mmol) in hexane (0.8 mL) at 50 °C for 10 h afforded 2-{2,4,6-tris-
[bis(trimethylsilyl)methyl]phenyl}-2-(2,4,6-triisopropylphenyl)-4,6-di-
methyl-1-thia-2-germacyclohex-4-ene (32; 73.6 mg, 89%) together with
9 (5.2 mg, 7%). 32: white crystals; mp 163-165 °C dec (CH2Cl2/
EtOH); 1H NMR (CDCl3, 500 MHz, 340 K) δ -0.07 (s, 9H), 0.058 (s,
9H), 0.062 (s, 9H), 0.08 (s, 9H), 0.13 (s, 18H), 0.95 (br s, 3H), 1.11
(br s, 3H), 1.17 (d, J ) 6.9 Hz, 6H), 1.21 (d, J ) 6.9 Hz, 3H), 1.23 (s,
3H), 1.317 (s, 1H), 1.323 (d, J ) 6.9 Hz, 3H), 1.54 (d, J ) 6.9 Hz,
3H), 2.10 (br s, 2H), 2.15 (d, J ) 10.5 Hz, 1H), 2.55 (d, J ) 10.5 Hz,
Similarly, the reaction of 13 (68.3 mg, 0.0597 mmol), triphenylphos-
phine (47.0 mg, 0.180 mmol), and 2,3-dimethyl-1,3-butadiene (0.30
mL, 2.6 mmol) in hexane (0.7 mL) at 90 °C for 2 h and then at room
temperature for 10 h gave 34 (49.4 mg, 84%).

8824 J. Am. Chem. Soc., Vol. 121, No. 38, 1999
Matsumoto et al.
Reaction of Germaneselone 2a with Isoprene. The reaction of
isolated germaneselone 2a (52.0 mg, 0.0573 mmol) and isoprene (0.23
mL, 2.3 mmol) in hexane (0.5 mL) at room temperature for 10 h
afforded 2-{2,4,6-tris[bis(trimethylsilyl)-methyl]phenyl}-2-(2,4,6-tri-
isopropylphenyl)-4-methyl-1-selena-2-germacyclohex-4-ene (35; 28.5
mg, 51%) and 2-{2,4,6-tris[bis(trimethylsilyl)methyl]phenyl}-2-(2,4,6-
triisopropylphenyl)-5-methyl-1-selena-2-germacyclohex-4-ene (36; 19.6
mg, 35%). 35: white crystals; mp 126-130 °C dec (CH2Cl2/EtOH);
1H NMR (CDCl3, 500 MHz, 300 K) δ -0.01 (br s, 9H), 0.07 (s, 18H),
0.08 (s, 9H), 0.09 (s, 9H), 0.15 (s, 9H), 0.95 (br s, 3H), 1.11 (br s,
3H), 1.19 (d, J ) 6.9 Hz, 6H), 1.23 (br s, 6H), 1.27 (s, 1H), 1.33 (s,
3H), 2.15 (br s, 2H), 2.26 (d, 1H, J ) 11.4 Hz), 2.66 (d, 1H, J ) 11.4
Hz), 2.79 (sept, J ) 6.9 Hz, 1H), 3.16 (dd, J1 ) 12.1 Hz, J2 ) 5.2 Hz,
1H), 3.40 (dd, J1 ) 12.1 Hz, J2 ) 8.2 Hz, 1H), 4.56 (br s, 1H), 5.71
(m, 1H), 6.42 (br s, 2H), 6.92 (s, 2H). It was impossible to assign the
13C NMR data owing to the complexity resulting from the steric
congestion. Anal. found: C, 57.46; H, 9.11. Calcd for C47H90GeSeSi6:
C, 57.88; H, 9.30. High-resolution FAB-MS: observed m/z 977.4230
([M + H]+); calcd for C49H9574GeSSi6 977.4114. 36: white crystals;
mp 147-150 °C dec (CH2Cl2/EtOH); 1H NMR (CDCl3, 500 MHz, 350
K) δ 0.07 (s, 18H), 0.08 (s, 18H), 0.09 (s, 18H), 1.11 (d, J ) 6.9 Hz,
6H), 1.14 (br d, J ) 6.9 Hz, 6H), 1.20 (d, J ) 6.9 Hz, 6H), 1.32 (s,
1H), 1.88 (s, 3H), 2.27-2.33 (m, 1H), 2.37 (br s, 2H), 2.50-2.55 (m,
1H), 2.80 (sept, J ) 6.9 Hz, 1H), 3.10 (d, J ) 12.0 Hz, 1H), 3.17 (d,
J ) 12.0 Hz, 1H), 3.18 (br s, 1H), 3.96 (br s, 1H), 5.59 (m, 1H), 6.40
(br s, 2H), 6.96 (s, 2H). It was impossible to assign the 13C NMR data
owing to the complexity resulting from the steric congestion. Anal.
found: C, 57.70; H, 9.15. Calcd for C47H90GeSeSi6: C, 57.88; H, 9.30.
High-resolution FAB-MS: observed m/z 977.4203 ([M + H]+); calcd
for C47H9174Ge80SeSi6 977.4114.
was placed in a 8 mm i.d. Pyrex glass tube. To this solution was added
isoprene (0.3 mL, 3.0 mmol), and the solution was heated at 90 °C for
10 h. The solvent was removed under reduced pressure, and the residue
was separated by DCC (SiO2 with hexane) to give 2-{2,4,6-tris[bis-
(trimethylsilyl)methyl]phenyl}-5-methyl-2-[bis(trimethylsilyl)methyl]-
1-thia-2-germa-cyclohex-4-ene (38; 27.5 mg, 62%) together with a
quantitative amount of diphenylacetylene. 38: white crystals; mp 166-
1
169 °C dec (CH2Cl2/EtOH); H NMR (CDCl3, 500 MHz, 300 K) δ
0.036 (s, 9H), 0.039 (s, 9H), 0.08 (s, 9H), 0.10 (s, 18H), 0.125 (s, 9H),
0.134 (s, 9H), 0.18 (s, 9H), 0.40 (s, 1H), 1.28 (s, 1H), 1.85 (s, 3H),
2.06 (dd, J1 ) 13.8 Hz, J2 ) 6.9 Hz, 1H), 2.13 (dd, J1 ) 13.8 Hz, J2
) 7.4 Hz, 1H), 2.37 (s, 1H), 2.44 (s, 1H), 3.07 (d, J ) 13.7 Hz, 1H),
3.10 (d, 13.7 Hz, 1H), 5.64 (m, 1H), 6.19 (s, 1H), 6.35 (s, 1H); 13C
NMR (CDCl3, 125 MHz, 300 K) δ 1.00 (q), 1.04 (q), 1.99 (q), 2.14
(q), 2.37 (q), 2.41 (q), 4.22 (q), 4.95 (q), 10.84 (d), 23.51 (t), 24.51
(q), 27.58 (d), 27.97 (d), 29.68 (t), 29.98 (d), 122.90 (d), 123.11 (d),
128.80 (d), 134.05 (s), 136.34 (s), 143.14 (s), 149.66 (s), 150.10 (s).
Anal. found: C, 52.55; H, 9.68. Calcd for C39H86GeSSi8: C, 52.96; H,
9.80. High-resolution FAB-MS: observed m/z 885.3832 ([M + H]+);
calcd for C39H8774GeSSi8 885.3895.
(2) Reaction at 150 °C. A similar reaction at 150 °C for 10 h gave
38 (29.8 mg, 67%) and a quantitative amount of diphenylacetylene.
X-ray Data Collection. Single crystals of 1a, 2a, and 2b were grown
by the slow evaporation of its saturated solution in hexane at room
temperature in a glovebox filled with argon, and single crystals of 12
were grown by the slow evaporation of its saturated solution in ethanol
and dichloromethane at room temperature. The intensity data were
collected on Rigaku AFC5R (for 1a, 2b) and AFC7R (for 2a, 12)
diffractometers with graphite monochromated Mo KR radiation (λ )
0.71069 Å). The structure was solved by direct methods with SHELXS-
8641 and refined by the full matrix least-squares method. All of the
nonhydrogen atoms were refined anisotropically. The final cycle of
the least-squares refinement was based on 3454 observed reflections
[I > 4σ|I|] and 451 variable parameters for 1a, 3395 observed
reflections [I > 3σ|I|] and 451 variable parameters for 2a, 2185
observed reflections [I > 4σ|I|] and 397 variable parameters for 2b,
and 5062 observed reflections [I > 3σ|I|] and 397 variable parameters
for 12. Atomic coordinates, bond lengths and angles, and themal
parameters have been deposited at the Cambridge Crystallographic Data
Centre.
Thermal Reaction of Diene Adduct 34 in the Presence of
Mesitonitrile Oxide. In a 5 mm i.d. Pyrex glass tube was placed a
hexane (0.6 mL) solution of 34 (20.5 mg, 0.021 mmol) and mesitonitrile
oxide (4.0 mg, 0.025 mmol). After five freeze-pump-thaw cycles,
the tube was evacuated and sealed. The solution was heated at 50 °C
for 2 h. After removal of the solvent, the crude reaction products were
chromatographed by DCC (SiO2 with 5:1 hexane/CH2Cl2) to afford 28
(19.9 mg, 90%).
Reaction of Germanethione 1b with excess 2,3-Dimethyl-1,3-
butadiene. The reaction was carried out in a manner similar to that of
1a. The reaction of 1b (50.0 mg, 0.0548 mmol), triphenylphosphine
(43.1 mg, 0.164 mmol), and 2,3-dimethyl-1,3-butadiene (0.06 mL, 0.53
mmol) in hexane (2.0 mL) at 90 °C for 20 h gave 2-{2,4,6-tris[bis-
(trimethylsilyl)methyl]phenyl}-4,5-dimethyl-2-[bis(trimethylsilyl)methyl]-
1-thia-2-germacyclohex-4-ene (37; 16.2 mg, 33%). 37: white crystals;
mp 160-164 °C dec (CH2Cl2/EtOH); 1H NMR (CDCl3, 500 MHz, 300
K) δ 0.036 (s, 9H), 0.039 (s, 9H), 0.076 (s, 9H), 0.081 (s, 9H), 0.11 (s,
9H), 0.12 (s, 9H), 0.14 (s, 9H), 0.18 (s, 9H), 0.37 (s, 1H), 1.27 (s, 1H),
1.79 (s, 3H), 1.80 (s, 3H), 1.90 (d, J ) 14.4 Hz, 1H), 2.34 (d, J ) 14.4
Hz, 1H), 2.55 (s, 1H), 2.67 (s, 1H), 2.99 (d, J ) 13.8 Hz, 1H), 3.12 (d,
J ) 13.8 Hz, 1H), 6.21 (s, 1H), 6.35 (s, 1H); 13C NMR (CDCl3, 125
MHz, 300 K) δ 1.00 (q), 1.04 (q), 2.10 (q), 2.18 (q), 2.37 (q), 2.45 (q),
3.65 (q), 4.87 (q), 10.49 (d), 20.34 (q), 23.24 (q), 27.45 (d), 27.53 (d),
29.87 (t), 29.94 (d), 32.11 (t), 123.32 (d), 128.16 (s), 128.46 (s), 128.90
(d), 134.32 (s), 142.89 (s), 149.80 (s), 150.28 (s). Anal. found: C, 53.88;
H, 10.04; S, 3.08. Calcd for C40H88GeSSi8: C, 53.47; H, 9.87; S, 3.57.
High-resolution FAB-MS: observed m/z 899.4158 ([M + H]+); calcd
for C40H8974GeSSi8 899.4051.
When a hexane solution (2.0 mL) of 19 (50.0 mg, 0.0548 mmol),
triphenylphosphine (43.1 mg, 0.164 mmol), and 2,3-dimethyl-1,3-
butadiene (0.30 mL, 0.26 mmol) was heated at 90 °C for 70 h, the
product was 37 (24.5 mg, 50%).
Reaction of Germanethione 1b with Isoprene. (1) Reaction at
90 °C. In a 5 mm i.d. NMR tube was placed a benzene-d6 (1.0 mL)
solution of 22 (48.3 mg, 0.0502 mmol) and elemental sulfur (1.6 mg,
0.0063 mmol). After five freeze-pump-thaw cycles, the tube was
evacuated and sealed. The solution was heated at 90 °C for 10 h to
afford a yellow solution. The quantitative generation of germanethione
1b and diphenylacetylene was observed by 1H NMR. The sealed tube
was opened in a glovebox, and the solvent was removed. The yellow
solid thus obtained was dissolved in hexane (0.3 mL), and the solution
Acknowledgment. This work was partially supported by a
Grant-in-Aid for Scientific Research on Priority Area (No.
0536102) from the Ministry of Education, Science, Sports and
Culture, Japan. T.M. is grateful to the Research Fellowship of
the Japan Society for the Promotion of Science for Young
Scientists. We acknowledge Dr. M. Minoura of Hiroshima
University for molecular orbital calculations, Prof. Y. Furukawa
of Waseda University, and Mr. K. Kawauchi of JEOL Ltd. for
the measurement of the FT-Raman spectra. We would also like
to thank ASAI Germanium Research Institute, Shin-etsu Chemi-
cal Co., Ltd., and Tosoh Akzo Co., Ltd. for the generous gifts
of tetrachlorogermane, chlorosilanes, and alkyllithiums, respec-
tively.
Supporting Information Available: Tables of crystal data,
structure solution and refinement, atomic coordinates, bond
lengths and angles, and anisotropic thermal parameters for 1a,
2a, 2b, and 12 (PDF). This material is available free of charge
via the Internet at http://pubs.acs.org.
JA991147X
(41) Sheldrick, G. M. SHELX-86, Program for Crystal Structure Deter-
mination. University of Go¨ttingen, Go¨ttingen, Germany, 1986.