Synthesis and structure of the first alkylidenetelluragermirane

Article abstract of DOI:10.1021/om970812c

The first stable alkylidenetelluragermirane 4 was synthesized by the reaction of an overcrowded diarylgermylene Tbt(Mes)Ge: 2b (Tbt = 2,4,6-tris[bis-(trimethylsilyl)methyl]phenyl; Mes = mesityl) with 9-(dichloromethylene)fluorene, 3, followed by addition of tributylphosphine telluride. X-ray crystallographic analysis of 4 shows that the geometry of its telluragermirane ring can be explained in terms of a π-complex binding model of a tellurium atom to a germaniumcarbon double bond.

Full text of DOI:10.1021/om970812c

© Copyright 1997
Volume 16, Number 24, November 25, 1997
American Chemical Society
Communications
Syn th esis a n d Str u ctu r e of th e F ir st
Alk ylid en etellu r a ger m ir a n e
Kuniyuki Kishikawa, Norihiro Tokitoh,* and Renji Okazaki*
Department of Chemistry, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo,
Bunkyo-ku, Tokyo 113, J apan
Received September 15, 1997X
Summary: The first stable alkylidenetelluragermirane
4 was synthesized by the reaction of an overcrowded
diarylgermylene Tbt(Mes)Ge: 2b (Tbt ) 2,4,6-tris[bis-
(trimethylsilyl)methyl]phenyl; Mes ) mesityl) with
9-(dichloromethylene)fluorene, 3, followed by addition
of tributylphosphine telluride. X-ray crystallographic
analysis of 4 shows that the geometry of its tellurager-
mirane ring can be explained in terms of a π-complex
binding model of a tellurium atom to a germanium-
carbon double bond.
have been widely employed utilizing their insertion or
cycloaddition reactions1b,4 as useful building blocks for
the synthesis of a variety of organogermanium com-
pounds having new skeletons. We have reported some
interesting reactions of extremely bulky germylenes,
Tbt(R)Ge:, 2 (R ) Tip, Mes, Dis), which were generated
by (i) the sequential nucleophilic substitution reactions
of germanium(II) iodide with TbtLi and RLi, (ii) the
reductive dehalogenation of the corresponding dihalo-
germanes 1 with lithium naphthalenide in THF, or (iii)
the thermal retrocycloaddition of the corresponding
germirenes (Tbt ) 2,4,6-tris[bis(trimethylsilyl)methyl]-
phenyl,5 R ) Tip (2,4,6-triisopropylphenyl), Mes (mesi-
tyl), or Dis (bis(trimethylsilyl)methyl)).6 For example,
In recent years, much attention has been paid to the
synthesis, structure, and reactions of three-membered
rings containing group 14 elements because of their
unique structures and high strain energies. Until now,
many of these types of compounds have been synthe-
sized and their reactivities have been investigated.1
Among them, ring compounds bearing an exocyclic
double bond have been drawing special interest, since
the introduction of an exo-methylene group to the three-
membered ring is expected to increase the strain energy.
In contrast to the extensive studies on alkylidenecyclo-
propanes and their heterocyclic analogues, e.g., allene
oxides or allene episulfides,2 the chemistry of germa-
nium analogues has been less explored.3
(2) Ando, W.; Choi, N.; Tokitoh, N. in Comprehensive Heterocyclic
Chemistry II; Padwa, A., Ed.; Pergamon: Oxford, 1996; p 173.
(3) Up to now, some examples of stable alkylidenegermiranes have
been synthesized, see: (a) Ando, W.; Tsumuraya, T. Organometallics
1989, 8, 1467. (b) Ando, W.; Ohgaki, H.; Kabe, Y. Angew. Chem., Int.
Ed. Engl. 1994, 33, 659.
(4) For a review, see: (a) Neumann, W. P. Chem. Rev. 1991, 91,
311. Recently, several stable alkyl- or aryl-substituted germylenes were
isolated and their structures were determined by X-ray analysis. (b)
J utzi, P.; Becker, A.; Stammler, H. G.; Neumann, B. Organometallics
1991, 10, 1647. (c) J utzi, P.; Schmidt, H.; Neumann, B.; Stammler, H.
G. Organometallics 1996, 15, 741. (d) Simons, R. S.; Pu, L.; Olmstead,
M. M.; Power, P. P. Organometallics 1997, 16, 1920. (e) Bender, J . E.,
IV; Holl, M. M. B.; Kampf, J . W. Organometallics 1997, 16, 2743 and
references cited therein.
Meanwhile, divalent germanium compounds (ger-
mylenes) are known to be highly reactive species and
(5) We have recently succeeded in the synthesis of highly reactive
species containing heavier main group elements by taking advantage
of the effective protecting group, Tbt. For example, see: (a) Tokitoh,
N.; Wakita, K.; Okazaki, R.; Nagase, S.; Schleyer, P. v. R.; J iao, H. J .
Am. Chem. Soc. 1997, 119, 6951. (b) Tokitoh, N.; Arai, Y.; Okazaki,
R.; Nagase, S. Science 1997, 277, 78. (c) Takeda, N.; Suzuki, H.;
Tokitoh, N.; Okazaki, R.; Nagase, S. J . Am. Chem. Soc. 1997, 119, 1456
and references cited therein.
X Abstract published in Advance ACS Abstracts, November 15, 1997.
(1) For recent reviews, see: (a) Barrau, J .; Escudie´, J .; Satge´, J .
Chem. Rev. 1990, 90, 283. (b) Tsumuraya, T.; Batcheller, S. A.;
Masamune, S. Angew. Chem., Int. Ed. Engl. 1991, 30, 902. (c) Kabe,
Y.; Ando, W. Adv. Strain Org. Chem. 1993, 3, 59. (d) Driess, M.;
Gru¨tzmacher, H. Angew. Chem., Int. Ed. Engl. 1996, 35, 828. (e)
Baines, K. M.; Stibbs, W. G. Adv. Organomet. Chem. 1996, 39, 275.
S0276-7333(97)00812-1 CCC: $14.00 © 1997 American Chemical Society

5128 Organometallics, Vol. 16, No. 24, 1997
Communications
Sch em e 1
followed by dechlorination with 2 leading to 1-germaal-
lene and subsequent chalcogenation.
Chalcogenagermiranes 4 and 5 represent the first
examples of three-membered ring systems of this kind,
although Ando et al. reported the synthesis of a 3-alkyl-
idene-1,2-thiagermirane via cycloaddition of a ger-
mylene with a thioketene.3a All of the compounds 4-6
are stable at room temperature, even upon exposure to
atmospheric oxygen, light, and moisture. Selena- and
thiagermiranes 5 and 6 were found to be thermally very
stable up to 200 °C, as in the case of the Ando’s
alkylidenethiagermirane which does not decompose at
its melting point (120-121 °C).3a In contrast to these
compounds, telluragermirane 4 gradually decomposed
in solution at 120 °C.
Sch em e 2
The molecular structure of 4 was determined by X-ray
crystallographic analysis.11 The ORTEP drawing is
shown in Figure 1 along with selected bond lengths and
angles.
The length of the Ge(1)-Te(1) bond (2.591(3) Å) in 4
is similar to that of the Ge-Te bond reported for a
we have succeeded in the synthesis of the first stable
oxazagermete derivative by the reaction of 2a (R ) Tip)
with 2,4,6-trimethybenzonitrile oxide, Scheme 1.7 In
this paper, we report the synthesis and structure of the
first stable alkylidenetelluragermirane 4 derived from
diarylgermylene 2b (R ) Mes).
(10) All of the new organogermanium compounds obtained here
showed satisfactory spectral and analytical data, which are described
in the Supporting Information together with the experimental details
for their preparation. In the following, the preparation of diarylger-
mylene 2b and its reaction with 9-(dichloromethylene)fluorene, 3,
followed by addition of tributylphosphine telluride are described as
representative examples. To a solution of Tbt(Mes)Ge:, 2b, prepared
from Tbt(Mes)GeCl2, 1b (1.23 g, 1.51 mmol), and LiNaph (0.60 M, 3
mmol) at -78 °C in THF (50 mL), was added a THF solution (20 mL)
of 9-(dichloromethylene)fluorene, 3 (418 mg, 1.69 mmol), at room
temperature. The solution was stirred for 5 min. To the solution was
added tributylphosphine telluride (303 mg, 0.92 mmol), and the
reaction mixture was stirred overnight. The solution was purified
roughly by short column chromatography (SiO2 with CHCl3). After
removal of the solvent, the reaction residue was subjected to gel
permeation liquid chromatography (GPLC) to remove naphthalene and
tributylphosphine telluride. The orange yellow solid thus obtained was
chromatographed by flash column chromatography (FCC) (SiO2 with
hexane-10/1 hexane/CHCl3) to afford dichlorogermane, 1b (293 mg, 0.36
mmol), and telluragermirane, 4 (153 mg, 0.15 mmol). Other fractions
were further purified by preparative thin-layer chromatography
(PTLC) (SiO2 with hexane) to afford (1-chlorovinyl)germane, 7 (75 mg,
0.076 mmol), and vinylgermane, 8 (174 mg, 0.18 mmol). 4: orange
crystals, mp 209.0-217.0 °C (dec); 1H NMR (500 MHz, CDCl3, 300K)
δ -0.17 (s, 9H), -0.13 (s, 9H), -0.08 (s, 9H), -0.04 (s, 9H), 0.05 (s,
9H), 0.06 (s, 9H), 1.33 (s, 1H, p-CH), 2.22 (s, 3H, p-Me), 2.49 (s, 1H,
o-CH), 2.64 (br s, 3H, o-Me), 2.73 (br s, 3H, o-Me), 2.74 (s, 1H, o-CH),
6.33 (s, 1H, arom H Tbt), 6.42 (s, 1H, arom H Tbt), 6.82 (s, 2H, arom
H Mes), 7.09 (t, J ) 7.6 Hz, 1H), 7.28 (t, J ) 7.6 Hz, 1H), 7.34 (t, J )
7.6 Hz, 1H), 7.38 (t, J ) 7.6 Hz, 1H), 7.49 (d, J ) 7.6 Hz, 1H), 7.66 (d,
To a THF solution of germylene 2b, prepared from
Tbt(Mes)GeCl2, 1b (1.23 g, 1.51 mmol), and 2 equiv of
LiNaph (0.60 M, 5 mL), was added at room temperature
1.1 equiv of 9-(dichloromethylene)fluorene, 38 (418 mg,
1.69 mmol), and then tributylphosphine telluride (303
mg, 0.92 mmol).9 After removal of the solvent, purifica-
tion of the residue afforded dichlorogermane, 1b (24%),
(1-chlorovinyl)germane, 7 (5%), vinylgermane, 8 (12%),
and alkylidenetelluragermirane, 4 (10%, orange crys-
tals).10 The use of elemental tellurium instead of
tributylphosphine telluride as a tellurium source gave
almost similar reaction products, but compound 4 was
not obtained, probably due to the low solubility of
elemental tellurium. On the other hand, the alkylidene-
chalcogenagermiranes 5 and 6, the selenium and sulfur
analogues of 4, were readily obtained together with 1b,
7, and 8 by the reactions of germylene 2b with 9-(dichlo-
romethylene)fluorene, 3, followed by the addition of
elemental sulfur and selenium, respectively, Scheme 2.
The structures of chalcogenagermiranes 4-6 obtained
here were determined by 1H NMR, 13C NMR, and FAB-
MS spectroscopy and elemental analysis. Chalcogen-
agermiranes 4-6 are presumably formed by the initial
insertion of germylene 2 into the C-Cl bond of 3
J ) 7.6 Hz, 1H), 7.72 (d, J ) 7.6 Hz, 1H), 8.36 (d, J ) 7.6 Hz, 1H); 13
C
NMR (126 MHz, CDCl3, 300 K) δ 0.76 (q), 0.88 (q), 1.25 (q), 1.41 (q),
1.62 (q), 1.77 (q), 20.90 (q), 27.84 (d), 28.01 (q × 2), 28.64 (d), 30.73
(d), 119.23 (d), 119.46 (d), 121.90 (s), 122.35 (d), 122.73 (s), 122.83 (d),
123.59 (d), 126.03 (d), 126.75 (d), 127.23 (d), 127.73 (d), 128.46 (d),
129.37 (d × 2), 136.50 (s), 137.53 (s), 138.32 (s), 139.59 (s), 140.64 (s),
140.68 (s), 141.58 (s), 142.39 (s), 143.74 (s), 145.64 (s), 152.87 (s), 153.04
(s); 125Te NMR (158 MHz, CDCl3, Me2Te) δ 13.77. Anal. Calcd for C50
-
H78GeSi6Te: C, 57.31; H, 7.50. Found: C, 57.23; H, 7.41. 1b: white
crystals, mp 216.0-218.0 °C. 5: pale orange crystals, mp 263.0-269.0
°C (dec); 77Se NMR (95 MHz, CDCl3, Me2Se) δ 127.56. 6: yellow
crystals, mp 274.0-276.0 °C (dec). 7: yellow crystals, mp >300 °C. 8:
pale yellow crystals, mp 286-299 °C (dec).
(6) (a) Tokitoh, N.; Manmaru, K.; Okazaki, R. Organometallics 1994,
13, 167. (b) Tokitoh, N.; Kishikawa, K.; Okazaki, R. J . Chem. Soc.,
Chem. Commun. 1995, 1425. (c) Tokitoh, N.; Kishikawa, K.; Matsu-
moto, T.; Okazaki, R. Chem. Lett. 1995, 827. (d) Tokitoh, N.; Matsu-
moto, T.; Okazaki, R. Chem. Lett. 1995, 1087. (e) Tokitoh, N.;
Kishikawa, K.; Manmaru, K.; Okazaki, R. Heterocycles 1997, 44, 149.
(f) Tokitoh, N.; Matsumoto, T.; Okazaki, R. J . Am. Chem. Soc. 1997,
119, 2337.
(7) Matsumoto, T.; Tokitoh, N.; Okazaki, R. Chem. Commun. 1997,
1553.
(8) Combret, J . C.; Villie´ras, J .; Lavielle, G. Tetrahedron Lett. 1971,
12, 1035.
(11) Crystallographic data for 4: C50H78GeSi6Te, fw ) 1047.87,
monoclinic, space group P21/n (No. 14), a ) 12.863(4) Å, b ) 11.012-
(10) Å, c ) 39.56(3) Å, â ) 92.57(5)°, V ) 5598(5) Å3, Z ) 4, Dc ) 1.243
g cm-3, µ(Mo KR) ) 12.16 cm-1, R (Rw) ) 0.085 (0.057). An orange
prismatic crystal of 4 having approximate dimensions of 0.20 × 0.10
× 0.05 mm was mounted on a glass fiber. All measurements were made
on a Rigaku AFC7R diffractometer with graphite-monochromated Mo
KR radiation (λ ) 0.710 69 Å) at 296 K and a rotating anode generator.
The structure was solved by direct methods with SHELXS-86.12 The
non-hydrogen atoms were refined anisotropically. Hydrogen atoms
were included at calculated position but not refined. The final cycle of
full-matrix least-squares refinement was based on 2326 observed
reflections (I > 2.00σ(I)) and 523 variable parameters.
(9) Quite recently, a similar type of reactions (reaction of a ger-
mylene with vinyl chloride) was reported, see: Ohgaki, H.; Ando, W.
J . Orgamomet. Chem. 1996, 521, 387.
(12) Sheldrick, G. M. SHELXS-86, Program for Crystal Structure
Determination; University of Go¨ttingen: Go¨ttingen, Germany, 1986.

Communications
Organometallics, Vol. 16, No. 24, 1997 5129
lar to each other. A dihedral angle between the three-
membered ring and the fluorenyl group is 17.4°. The
sum of the bond angles around the Ge atom (C(1)-Ge-
(1)-C(10), C(1)-Ge(1)-C(19), and C(10)-Ge(1)-C(19))
is 354.4°, suggesting considerable sp2 character of the
germanium center of 4.
In connection with the molecular structure of 4, it
should be pointed out that many examples of diger-
mirane derivatives Ge-Ge-X (X ) S,18 C,19 N,19 and
Te13), show remarkable shortening in their Ge-Ge
bonds compared with a typical Ge-Ge single bond as
well as planarity around the germanium atoms. This
characteristic geometry for digermirane derivatives is
most likely interpreted in terms of a π-complex binding
model of the corresponding digermenes with the chal-
cogen atom, carbene, and nitrene.20 We think that the
shortening of the Ge(1)-C(19) bond and the notable
planarity around the Ge(1) atom in telluragermirane 4
can be explained similarly using the π-complex binding
model of a tellurium atom with a germanium-carbon
double bond of a germaallene. In other words, the Ge-
(1)-C(19) bond in 4 might have a partial π-bond
character.
F igu r e 1. The ORTEP drawing of alkylidenetellurager-
mirane 4 with thermal ellipsoid plots (30% probability).
Selected bond lengths (Å) and angles (deg): Ge(1)-C(19)
1.88(2), Ge(1)-Te(1) 2.591(3), C(19)-Te(1) 2.11(2), C(19)-
Ge(1)-Te(1) 53.5(7), Ge(1)-Te(1)-C(19) 45.8(5), Ge(1)-
C(19)-Te(1) 80.6(7), Ge(1)-C(19)-C(20) 149(1), Te(1)-
C(19)-C(20) 129(1), C(1)-Ge(1)-C(10) 119.7(7), C(1)-
Ge(1)-C(19) 119.5(7), C(10)-Ge(1)-C(19) 115.2(8), Te(1)-
Ge(1)-C(19)-C(20) 179(3).
The chalcogenagermiranes obtained here are poten-
tially useful precursors for the synthesis of a germaal-
lene, a novel class of a germanium-carbon double bond
compound. Investigations on the reactivities of the
newly obtained chalcogenagermiranes 4-6 are currently
in progress.
telluradigermirane (2.597(2) Å).13 The C(19)-Te(1)
bond length (2.11(2) Å) is in the range of Te-C single
bond lengths for two-coordinate tellurium compounds
previously reported (2.025-2.298 Å;14b an average of
2.158 Å).15 However, its length is shorter than that in
Cp*2Ta(η2-TeCH2)H (2.21(2) Å)14b and longer than that
in a tellurocarbonyl η1-tungsten complex (1.987(5) Å).16
The Ge(1)-C(19) bond length (1.88(2) Å) is slightly
shorter than the reported Ge-C single bond length
(1.92-2.07 Å) of germirane derivatives3b or that of the
calculated value for H3GeCHdCH2 (1.943 Å).17 The
interior bond angles at Ge(1), Te(1), and C(19) are
53.5(7)°, 45.8(5)°, and 80.6(7)°, respectively, and the
bond angle of Ge(1)-C(19)-C(20) is 149(1)°. The dihe-
dral angles between the telluragermirane ring plane
and the aromatic planes of Tbt and Mes groups are 71.1°
and 74.5°, respectively. In addition, the two benzene
rings of the Tbt and Mes groups are almost perpendicu-
Ack n ow led gm en t. This work was partially sup-
ported by Grants-in-Aid for Scientific Research (Grant
Nos. 05236102 and 07454193) from the Ministry of
Education, Science, Sports, and Culture of J apan. K.K.
thanks Research Fellowships of the J apan Society for
the Promotion of Science for Young Scientists. We are
also grateful to Shin-etsu Chemical Co., Ltd., and Tosoh
Akzo Co., Ltd., for the generous gift of the chlorosilanes
and alkyllithiums, respectively.
Su p p or tin g In for m a tion Ava ila ble: Text giving detailed
experimental and spectral data for all new compounds, tables
of complete bond lengths and angles, atomic coordinates, and
positional and thermal parameters, and an ORTEP diagram
for 4 (41 pages). Ordering information is given on any current
masthead page.
(13) Tumuraya, T.; Kabe, Y.; Ando, W. J . Chem. Soc., Chem.
Commun. 1990, 1159.
(14) Tellurocarbonyl η2-metal complexes have been reported. See,
for example: (a) Wolf, J .; Zolk, R.; Schubert, U.; Werner, H. J .
Orgamomet. Chem. 1988, 340, 161. (b) Shin, J . H.; Parkin, G.
Organometallics 1994, 13, 2147.
OM970812C
(18) Tsumuraya, T.; Sato, S.; Ando, W. Organometallics 1988, 7,
(15) Allen, F.; Kennard, O.; Watson, D. G.; Brammer, L.; Orpen, A.
G.; Taylor, R. J . Chem. Soc., Perkin Trans. 2 1987, S1.
(16) Minoura, M.; Kawashima, T.; Tokitoh, N.; Okazaki, R. Chem.
Commun. 1996, 123.
(17) Basch, H.; Hoz, T. in The Chemistry of Organic Germanium,
Tin and Lead Compounds; Patai, S., Rappoport, Z., Eds.; Wiley: New
York, 1995; p 1.
2015.
(19) Tsumuraya, T.; Sato, S.; Ando, W. Organometallics 1990, 9,
2061.
(20) Interestingly, the telluradigermirane ring system shows almost
no bond shortening for the Ge-Ge bond as compared with a typical
Ge-Ge single bond but a remarkable planarity at the Ge atoms. See,
ref 13.