First stable germanetellones: Syntheses and crystal structures of the heaviest germanium-chalcogen double-bond compound

Full text of DOI:10.1021/ja963517c

J. Am. Chem. Soc. 1997, 119, 2337-2338
2337
Scheme 1
First Stable Germanetellones: Syntheses and
Crystal Structures of the Heaviest
Germanium-Chalcogen Double-Bond Compound
Norihiro Tokitoh, Tsuyoshi Matsumoto, and Renji Okazaki*
Department of Chemistry
Graduate School of Science
The UniVersity of Tokyo
7-3-1 Hongo, Bunkyo-ku, Tokyo 113, Japan
ReceiVed October 8, 1996
In view of the central importance of the carbonyl group in
organic chemistry, interest in the chemistry of its heavier
chalcogen analogues has remarkably increased in recent years.1
Although thio- and selenocarbonyl compounds have been
actively investigated and reliable synthetic methods for stable
species have been developed,1 very little is known for telluro-
carbonyl compounds except for electronically stabilized2 or
transient short-lived species,3 and no stable telluroketone had
been described until we recently reported the synthesis of
1,1,3,3,-tetramethylindantellone,4 the first telluroketone stable
in solution.
germanium-chalcogen bond lengths indicative of the unam-
biguous double-bond character and complete trigonal planar
geometry around the germanium atom as in the case of ketones.
Here, we present the syntheses and crystal structures of the first
stable germanetellones 3 and 4 which are worthy of note not
only as the heaviest congeners of this family of germanium-
chalcogen double-bond compounds but also as the first examples
of the crystallographic analysis of a tellurium analogue of a
ketone.
For the synthesis of germanetellones 3 and 4, we took
advantage of the direct telluration of germylenes Tbt(R)Ge: (5,
R ) Tip; 6, R ) Dis) with elemental tellurium since we recently
found that 5 and 6 were cleanly and efficiently generated by
the thermal cycloreversion of germirenes 7 and 8 (Scheme 1).8
Thus, germirene 7 and 1 equiv of elemental tellurium were
allowed to react in benzene-d6 at 90 °C in a sealed tube for 9
days, after which time the solution turned green and the 1H NMR
indicated the complete consumption of 7 and the appearance
of new signals in addition to those of diphenylacetylene. The
sealed tube was opened in a glovebox filled with argon, and
mesitonitrile oxide was added to the solution to afford a [3+2]-
cycloadduct, 9, in 94% yield, clearly indicating the generation
of germanetellone 3 in high yield.9,10 The germanetellone 3
thus prepared was also allowed to react with 2,3-dimethyl-1,3-
butadiene to give the corresponding [4+2]-cycloadduct 10 in
70% yield.10 Removal of the solvent from the green solution
without the addition of mesitonitrile oxide gave germanetellone
3 as a stable, green crystalline compound together with the
colorless crystals of diphenylacetylene in almost quantitative
The chemistry of a germanetellone, a germanium analogue
of a tellone, has also been very little explored, and as for the
germanium-tellurium double-bond species there has been only
one report by Parkin et al. on the isolation and characterization
of the terminal tellurido complex of germanium supported by
ligation of the macrocyclic octamethyldibenzotetraza[14]-
annulene dianion.5 Meanwhile, we recently succeeded in the
synthesis of stable germanethione6 and germaneselone7 having
carbon substituents on germanium, i.e., Tbt(Tip)GedX (1, X
) S; 2, X ) Se; Tbt ) 2,4,6-tris[bis(trimethylsilyl)methyl]-
phenyl; Tip ) 2,4,6-triisopropylphenyl) and their X-ray struc-
tural analyses, which revealed a considerable shortening of their
1
yields as judged by H NMR, from which pure crystals of 311
were sorted out, taking advantage of its characteristic green color
(Scheme 1). This is the first isolation of a kinetically stabilized
(1) (a) Duus, F. In ComprehensiVe Organic Chemistry; Barton, D. H.
R., Ollis, W. D., Eds.; Pergamon, Oxford, 1979; Vol. 3, pp 373-487. (b)
Voss, J. In Houben-Weyl Methoden der Organischen Chemie; Klamann,
D., Ed.; George Thieme: Stuttgart, 1985; Bd. E11, pp 181-231. (c)
Magnas, P. D. In ComprehensiVe Organic Chemistry; Barton, D. H. R.,
Ollis, W. D., Eds.; Pergamon: Oxford, 1979; Vol. 3, pp 491-538. (d)
Guziec, F. S., Jr. In Organoselenium Chemistry; Liotta, D., Ed.; John Wiley
& Sons: New York, 1987.
(8) Tokitoh, N.; Kishikawa, K.; Matsumoto, T.; Okazaki, R. Chem. Lett.
1995, 827.
(9) The germanethione 1 and germaneselone 2 also reacted with
mesitonitrile oxide to give the corresponding [3+2]-cycloadducts in excellent
yields.6,7
(10) Experimental procedures and the physical properties of the reaction
products for the cycloaddition reactions of 3 with mesitonitrile oxide and
2,3-dimethyl-1,3-butadiene are described in the Supporting Information.
(11) 3: green crystals, mp 205-210 °C; 1H NMR (C6D6, 500 MHz,
300 K) δ 0.15 (s, 18H), 0.20 (s, 18H), 0.24 (s, 18H), 1.18 (d, J ) 6.9 Hz,
6H), 1.32 (d, J ) 6.9 Hz, 6H), 1.40 (d, J ) 6.9 Hz, 6H), 1.49 (s, 1H), 2.72
(sept, J ) 6.9 Hz, 1H), 3.57 (br s, 1H), 3.67 (sept, J ) 6.9 Hz, 2H), 3.88
(br s, 1H), 6.49 (s, 1H), 6.65 (s, 1H), 7.03 (s, 2H); 13C NMR (C6D6, 125
MHz, 300 K) δ 1.16 (q), 1.57 (q), 1.63 (q), 22.22 (q), 24.09 (q), 26.97 (q),
28.24 (d), 28.50 (d), 32.03 (d), 34.67 (d × 2), 34.81 (d), 123.28 (d × 2),
125.30 (d), 130.49 (d), 146.79 (s), 147.04 (s), 148.95 (s), 149.44 (s), 150.27
(s × 2), 151.64 (s), 155.42 (s); 125Te NMR (C6D6, 85.1 MHz, 300 K) δ
1143; UV-vis (hexane) λmax 640 (ꢀ 180); high-resolution FAB-MS, obsd
m/z 955.3307 ([M + H]+), calcd for C42H8372GeSi6128Te 955.3375. 4: blue-
green crystals, mp 200-203 °C; 1H NMR (C6D6, 500 MHz, 300 K) δ 0.15
(s, 18H), 0.30 (br s, 18H), 0.31 (br s, 18H), 0.48 (s, 18H), 1.48 (s, 1H),
2.93 (s, 1H), 2.98 (br s, 1H), 3.30 (br s, 1H), 6.48 (br s, 1H), 6.63 (br s,
1H); 13C NMR (C6D6, 125 MHz, 300 K) δ 1.02 (q), 1.99 (q), 2.22 (q),
4.24 (q), 29.18 (d), 30.46 (d), 31.64 (d), 50.49 (d), 124.37 (d), 129.82 (d),
146.47 (s), 147.08 (s), 148.35 (s × 2); 125Te NMR (C6D6, 85.1 MHz, 300
K) δ 1009; UV-vis (hexane) λmax 604 (ꢀ 119); high-resolution FAB-MS,
obsd m/z 912.2589 (M+), calcd for C34H7872GeSi8130Te 912.2541 (or
C34H7874GeSi8128Te 912.2514).
(2) (a) Barrett, A. G. M.; Read, R. W.; Barton, D. H. R. J. Chem. Soc.,
Chem. Commun. 1979, 645. (b) Barrett, A. G. M.; Read, R. W.; Barton,
D. H. R. J. Chem. Soc., Perkin Trans. 1 1980, 2191. (c) Severengiz, T.;
du Mont, W.-W. J. Chem. Soc., Chem. Commun. 1987, 820. (d) Lerstrup,
K. A.; Henriksen, L. J. Chem. Soc., Chem. Commun. 1979, 1102. (e)
Lappert, M. F.; Martin, T. R.; McLaughlin, G. M. J. Chem. Soc., Chem.
Commun. 1980, 635. (f) Segi, M.; Kojima, A.; Nakajima, T.; Suga, S.
Synlett. 1991, 2, 105.
(3) (a) Erker, G.; Hock, R. Angew. Chem., Int. Ed. Engl. 1989, 28, 179.
(b) Segi, M.; Koyama, T.; Takata, Y.; Nakajima, T.; Suga, S. J. Am. Chem.
Soc. 1989, 11, 8749. (c) Boese, R.; Haas, A.; Limberg, C. J. Chem. Soc.,
Chem. Commun. 1991, 1378. (d) Haas, A.; Limberg, C. Chimia 1992, 46,
78. (e) Laishev, V. Z.; Petrov, A. A. Zh. Org. Khim. 1981, 17, 2064. (f)
Lakshmikantham, M. V.; Cava, M. P.; Albeck, M.; Engman, L.; Carroll,
P.; Bergman, J.; Wudl, F. Tetrahedron Lett. 1981, 22, 1495.
(4) Minoura, M.; Kawashima, T.; Okazaki, R. J. Am. Chem. Soc. 1993,
115, 7019.
(5) Kucha, M. C.; Parkin, G. J. Chem. Soc., Chem. Commun. 1994, 1351.
(6) Tokitoh, N.; Matsumoto, T.; Manmaru, K.; Okazaki, R. J. Am. Chem.
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S0002-7863(96)03517-2 CCC: $14.00 © 1997 American Chemical Society

2338 J. Am. Chem. Soc., Vol. 119, No. 9, 1997
Communications to the Editor
diarylgermanetellone. Under similar reaction conditions, ger-
mirene 8 bearing a bis(trimethylsilyl)methyl (Dis) group also
reacted with elemental tellurium to afford the expected alkylaryl-
substituted germanetellone 411 as stable blue-green crystals in
a quantitative yield (Scheme 1).
Germanetellones 3 and 4 were very sensitive toward moisture
especially in solution but thermally very stable; 3 and 4 melted
at 205-210 and 200-203 °C, respectively, without decomposi-
tion, and no dimerization was observed in solution up to 90 °C
[1H NMR (C6D6, sealed tube)]. Interestingly, 3 and 4 are quite
stable toward light either in solution or in the solid state in sharp
contrast to the stable telluroketone 1,1,3,3-tetramethylindantel-
lone, which is extremely light sensitive even toward the
fluorescent light.4 Both 3 and 4 showed characteristic absorption
maxima attributed to n-π* transitions of the GedTe unit [636
(for 3) and 599 (for 4) nm in benzene], with the diaryl-
substituted 3 being red shifted (37 nm) compared with the
alkylaryl-substituted 4. These absorption maxima were red
shifted relative to those observed for germanethione 16 and
germaneselone 27 [444 (for 1) and 513 (for 2) nm in benzene].
The 125Te NMR of 3 and 4 in C6D6 showed singlet signals in
the region at 1143 and 1009 ppm, respectively, although it is at
much higher field than that of 1,1,3,3-tetramethylindantellone
(2858 ppm in CDCl3).4
The molecular structures of both 3 and 4 were revealed by
X-ray crystallographic analysis,12 and the ORTEP drawing of
4 is shown in Figure 1. In each case the germatellurocarbonyl
unit is effectively protected by the bulky substituents and no
intermolecular interaction exists even in the solid state; the
shortest intermolecular distances between Ge and Te atoms for
3 and 4 were found to be 5.49 and 7.98 Å, respectively, which
are considerably longer than the sum of the van der Waals radii
of Ge and Te atoms (4.16 Å). The germatellurocarbonyl units
of 3 and 4 have completely trigonal planar geometry, the sum
of bond angles around the germanium atom being 359.5° (for
3) and 360.0° (for 4). The Ge-Te bond distances of 3 and 4
[2.398(1) and 2.384(2) Å] are ca. 8% shorter than those reported
for typical germanium-tellurium single bonds (2.59-2.60 Å)13
and in good agreement with the calculated bond length of H2-
GedTe (2.36 Å),14 showing an unambiguous double-bond
character between germanium and tellurium.15 These values
for 3 and 4 are still shorter than that reported for Parkin’s
compound [2.446(1) Å],5 clearly indicating the double-bond
nature of 3 and 4. In germanetellone 3, there seems to be no
Figure 1. ORTEP drawing of germanetellone Tbt(Dis)GedTe (4) with
thermal ellipsoid plot (30% probability). Selected bond lengths (Å)
and angles (deg): Ge(1)-Te(1) 2.384(2), Ge(1)-C(1) 1.981(9),
Ge(1)-C(7) 1.924(11); Te(1)-Ge(1)-C(1) 123.3(3), Te(1)-Ge(1)-
C(7) 118.7(3), C(1)-Ge(1)-C(7) 118.0(4).
significant conjugation between the two aryl groups and the
GedTe bond in the solid state judging from their dihedral angles
between the aryl planes and the π-plane of the germatelluro-
carbonyl unit, i.e., 39° for the Tbt group and 71° for the Tip
group, the values of which are almost similar to those of
germanethione 16 and germaneselone 2.7 In the case of 4, an
even larger value (57°) was observed for the dihedral angle
between the planes of the Tbt and GedTe groups.
In conclusion, we have synthesized both diaryl- and alkyl-
arylgermanetellones 3 and 4 and determined their crystal-
lographic structures. In view of the fact that no isolable
compound has been reported even for a telluroketone, it should
be noted that 3 and 4 bearing carbon substituents on the Ge
atom can be isolated as thermally and photochemically stable
crystalline compounds which have a Ge-Te double bond as
revealed by X-ray crystallography.
Acknowledgment. This work was partially supported by the
Sumitomo Foundation (N.T.) and a Grant-in-Aid for Scientific Research
(No. 05236102) from the Ministry of Education, Science and Culture,
Japan. We are grateful to ASAI Germanium Research Institute, Shin-
etsu Chemical Co., Ltd., and Tosoh Akzo Co., Ltd., for the generous
gift of tetrachlorogermane, chlorosilanes, and alkyllithiums, respectively.
(12) Crystallographic data for 3: C42H82GeSi6Te, MW ) 955.81, triclinic,
space group P1h, a ) 13.541(7) Å, b ) 20.613(8) Å, c ) 9.778(5) Å, R )
97.14(4)°, â ) 90.81(5)°, γ ) 97.98(4)°, V ) 2683(2) Å3, Z ) 2, Dc )
1.183 g cm-3, µ ) 12.62 cm-1, R (Rw) ) 0.057 (0.042). Crystallographic
data for 4: C34H78GeSi8Te, MW ) 911.86, triclinic, space group P1h, a )
12.841(8) Å, b ) 22.118(8) Å, c ) 9.534(6) Å, R ) 91.73(4)°, â ) 109.49-
(5)°, γ ) 87.82(4)°, V ) 2557(2) Å3, Z ) 2, Dc ) 1.184 g cm-3, µ )
13.65 cm-1, R (Rw) ) 0.046 (0.057). Full details for the crystallographic
analysis of 3 and 4 are described in the Supporting Information.
(13) A search of the Cambridge Crystallographic Database indicates the
following metrical data for Ge-Te single bonds (given in the order of the
mean value, range, and number of observations of the distribution): 2.59
Å, 2.59-2.60 Å, and 8. For example, see: Weidenbruch, M.; Ritschl, A.;
Peters, K.; Schnering, H. G. J. Organomet. Chem. 1992, 437, C25.
(14) Calculated with HF/DZ+d: Suzuki, H.; Tokitoh, N.; Nagase, S.;
Okazaki, R. Manuscript in preparation.
Supporting Information Available: Experimental procedures for
the synthesis and reaction of germanetellone 3 with physical properties
of the starting materials and reaction products 7-9, and crystallographic
data with complete tables of bond lengths, bond angles, and thermal
and positional parameters for 3 and 4 (71 pages). See any current
masthead page for ordering and Internet access instructions.
JA963517C
(15) The sum of the double-bond covalent radii of Ge and Te is 2.39 Å.
Pauling, L. The Nature of The Chemical Bond, 3rd ed.; Cornell University
Press: Ithaca, NY, 1960; p 224.