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Isolation and Structure of a Stable Molecule Containing a Silicon-Carbon Double Bond.

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[3] Preparation of 3 : A solution of l b (814 mg, 4 mmol) and 2 (304 mg, 4
mmol) in petroleum ether (60/90"C) was irradiated in a photolysis apparatus for 40 min. The solution turned from yellow to deep-violet in color.
After filtration and removal of solvent from the filtrate, Ib could be separated from the resulting residue by sublimation in a high vacuum. Recrystallization of the remaining residue from petroleum ether at -30°C afforded analytically pure 3, m.p. 142°C (decomp.).
[4] P2,/n, Z = 8 ; a = 1403.4(3), b = 1081.3(2), c=2044.8(4) p m , p = 100.87(4)",
V=3047.5 x 10' pm'; pGtIc= 1.744 g/cm3, 8=3-24" (MoKa radiation,
graphite monochromator, T = - 80°C). 4490 reflections measured, LP
correction, empirical absorption correction. Direct methods. Refinement
[2265 reflections with 1>3a(1)1 of all atom positions with anisotropic
temperature parameters, cyclopentadienyl C-atoms isotropic; R , = 0.053,
R z = 0.056.298 parameters. Further details of the crystal structure investigation are available on request from the Fachinformationszentrum Energie Physik Mathematik, D-7514 Eggenstein-Leopoldshafen 2, on quoting
the depository number CSD 51 128, the names of the authors, and the full
citation of the journal.
151 Mn-Mn bonds are shorter than 320 pm; cf. 1. Bernal, M. Creswick, W.
A. Herrmann, Z. Natutforsch. 8 3 4 (1979) 1353; W. A. Herrmann, B.
Koumbouris, T. Zahn, M. L. Ziegler, Angew. Chem. 96 (1984) 802; Angew.
Chem. In,. Ed. Engl. 23 (1984) 812.
[6] C. Barbeau, R. J . Dubey, Can. J. Chern. 51 (1973) 3684.
[7] R. J. Lovejoy, J. Colwell, G. D. Halsey, J . Chem. Phys. 35 (1962) 612.
[8] The homologous Te complex [((~'-C,H,)(CO)2Mn},Te]is known; cf. M.
Herberhold, D. Reiner, D. Neugebauer, Angew. Chem. 95 (1983) 46; Ang e w . Chem. Int. Ed. Engl. 22 (1983) 59; Angew. Chem. Suppl. 1983, 10; W.
A. Herrmann, C. Hecht, M. L. Ziegler, B. Balbach, J. Chem. Sac. Chem.
Commun. 1984. 686.
Isolation and Structure of a Stable Molecule
Containing a Silicon-Carbon Double Bond**
benzene (see Experimental Procedure). The silaethene 2
( M a : m/z 300) forms colorless prisms which are stable at
room temperature but decompose above 65 "C over the
course of several days. The 'H-NMR spectrum (90 MHz,
CbD5CD3, 30°C : 6 = 0.55 (very broad, Me2%, Me,Si,
MeSi), 1.26 (sharp, tBu2Si)) indicates a rapid methyl exchange, which was also observed for the silaethene
R = SiMe(tBu)z
shows an essenThe X-ray structure analysis (Fig.
tially planar C2Si=CSi2 skeleton for 2 (the sums of the valence angles at Sil and C1 each 360.0"141).The torsional distortion along the Si=C bond amounts to only 1.6" (Fig. 2).
The deviations of the valence angles at the unsaturated
centers Sil and C1 from standard spz values may be easily
explained by the steric strain exerted by the SiMe, and especially the SiMe(tBu), groups at C I .
By Nils Wiberg*, Gerhard Wagner, and Gerhard MuNer*
The stable, tetrahydrofuran (THF)-containing silaethene
1 is obtained in crystalline form in THF""]. By the same
reaction sequence, the THF-free 2 is formed in diethyl
ether in ca. 60% yield. It could not, however, be isolated
M e SiMe,
F Br
+ Me3SiC1
Me SiMeB
F L i
S i M e ( tBu),
t Bu),
S i M e ( t Bu),
from the reaction mixture in crystalline
Its existence was demonstrated by characteristic trapping experim e n t s t l h . Icl as well as by the formation of 1 upon addition
of T H F to 2 :
Fig. I. Structure of 2 in the crystal (ORTEP, thermal ellipsoids 50"%1).Imporand angles ["I: Sil-CI 1.702(5), Sil-C2 1.851(5), SiI-C3
tant distances
1.842(5), Cl-Si2
1.865(5), CI-Si3
1.890(5), CI-Sil-C2
129.0(2), C2-SiI-C3
104.0(3). Sil-CI-Si2
Sil-C1-Si3 122.8(3), Si2-CI-Si3 117.7(2).
We have now succeeded in converting 1 into crystalline
2 by removing T H F from 1 by azeotropic distillation with
[*] Prof. Dr. N. Wiberg, DipLChem. G. Wagner
Institut fur Anorganische Chemie der Universitat
Meiserstrasse I , D-8000 Munchen 2 (FRG)
Dr. G. Muller
Anorganisch-chemisches lnstitut der Technischen Universitat Munchen
Lichtenbergstrasse 4, D-8046 Garching (FRG)
Part 9, Unsaturated Silicon Compounds: Part 60, Compounds of Silicon. For Part 8 (Part 59) see [Ic].
A n g e w . Chem. I n t . Ed. Engl. 24 (198.7) No. 3
Fig. 2. View of 2 perpendicular to the plane of the double bond (methyl
groups at Si2, C8, C12 with arbitrary radii). Angle of planes
Si 1C lC2C3 -C 1 Si 1 Si2Si3 = 1.6".
0 VCH Verlagsgesells~hafimbH. D-6940 Weinherm 1985
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The length of the Si=C bond, the subject of considerable contr~versy[~"',
is 1.702(5) A in 2 . Thus, it fits astonishingly well into the range of 1.69- 1.71 A predicted theoretically by ab initjo calculations151.Compared to a typical
Si-C bond (1.87 ,A), the observed Si=C distance is shortened by ca. 0.17 A (shortening C-C-C=C:
0.19 A). It is
drastically shorter than the Si=C bond in the silaenol ether
(Me,Si),Si=C(OSiMe,)( I-adamantyl) (1.764(3) ALbl),which
is twisted by 14.6". The reason for the bond length and torsional distortion of this Si=C bond is thought to be the
bulkiness of the substituents as well as the high electronegativity of the OSiMe, groupLs'I. Since the silaethene 2
contains less bulky and not particularly electronegative
substituents, the observed Si=C bond length in 2 should
be representative for silaethenes R2Si=CR2 with moderately bulky substituents R = H, alkyl, :ilyl. The previously
found Si=C bond length of 1.747(5) A in the T H F adduct
had already indicated that the Si=C distance in unsaturated systems like 2 should be shorter than in the aforementioned silaenol ether. The observed double bond
geometry of the silaethenes shows close resemblances to
that of ethenes. This implies a similar bonding situation in
both systems.
Spiroacetal Formation by
Carbene (Carbenoid) Insertion Reaction :
Synthesis of the Major Constituent of
the Sex Attractant of the Olive Fly (Dacus oleae)**
By Udo H. Brink&, Ali Haghani, and Klaus Gomann
The spiroacetal unit is a frequently occurring structural
element in antibiotics and insect pheromones[". Herein we
present a novel strategy for the synthesis of s p i r o a c e t a l ~ [ ~ ~ ,
the key step of which is an intramolecular C-H insertion
reaction of a cyclopropylidene (cyclopropylidenoid)
( A - B). Subsequent selective opening of the three-membered ring in B should enable the synthesis of methylated
spiroacetals and(or) spiroacetals with expanded rings.
Experimental Procedure:
The benzene from a solution of 1.5 mmol of crystalline 1 (prepared according to [la]) in 25 mL of anhydrous benzene contained in a flask A was distilled in high vacuum into a flask B which had been cooled to -78°C and
contained 10 mmol of pure LiBu as a T H F scavenger. By cooling A to
- 78°C and warming B to room temperature, the benzene was distilled back
into A. After repeating this process 40 timea, 1 mL of anhydrous pentane was
distilled onto the benzene-free residue in A. The pentane solution thus obtained was cooled to -90°C for 2-3 d (formation of seed crystals) and subsequently to -78°C. The pentane was decanted off and the crystals were
dried in vacuo.
To test this synthetic concept we chose 1,7-dioxaspiro[5.5]undecane 1, the prototype of some spiroacetals isolated from natural products. 1 is the major constituent of
the sex attractant of the female olive fly Dacus oleae (Gmelin); the biological activity of the racemate has been confirmed by field experiments"].
Received: December 3, 1984 [ Z I096 IE]
German bersion: Angew Chem. 97 (1985) 220
[ I ] a) N. Wiberg, G. Wagner, G. Miiller, J. Riede, J. Organornefal. Chern. 271
(1984) 381; h) N. Wiberg, G. Wagner, Anyew. Chem. 95 (1983) 1027; Anqew. Chem. I n t . E d . Engl. 22 (1983) 1005; c) N. Wiberg, J. Orgonomet.
Chem. 273 (1984) 141.
[2] "C-NMR ( - 7 0 T , C,D,CD,): S=3O.ll (CMe?), 21.80 (CMe,), 7.06
(SiMe,), -2.10 (SiMe(fBu2)), 10.81 and 5.85 (C=SiMe2), 77.20 (C=Si)."Si-NMR ( - 7 O " C , C,D,CD;): 6 = -4.60 (SiMe3), 6.00 (SiMe(rBu2)),
144.2 (Si=C). The spectra were recorded in cooperation with Dr. B.
[3] Crystal structure data of 2 : C,,H,,Si, M,=300.71, space group P2,2,2,,
a=8.109(1), b=14.886(2), ~=16.470(2)A, V=1988.10 A',p,,,t,,, =1.005
g/cm' for 2 = 4 . 3378 measured reflexions of which 2928 were unique
( + h + k + l and FriePel reflections, (sinO/A)m?,,x
=0.572, o-scan, Aw = I O ,
MoKor1=0.71069 A, F(000)=672, T = - 3 5 ° C ) . Direct methods (MULTAN SO); R=0.055, R,, =0.05?( w = k i m ' ( F , , ) , k = 1.8 in last cycle) for 163
refined parameters and 2447 structure factors with F,,>4.00(Fo) (full matrix. non-H atoms anisotropic, H atoms constant,
(final)= +0.451'
-0 36 e/A', SHELX 76). The refinement of the enantiomorphous structure did not result in significant differences. Further details of the crystal
structure analysis are available on request from the Fachinformationszentrum Energie Physik Mathematik, D-7514 Eggenstein-Leopoldshafen 2
(FRC), on quoting the depository number CSD 51 178, the names of the
authors, and the journal citation.
[4] The relatively large thermal parameters of atoms C2/C3 at Si 1 (Fig. 2) do
nor exclude a slight pyramidalization of Sil with disordered methyl
groups. Alternatively, they point to a relatively shallow minimum of the
equilibrium conformation of Sil.
[5] a ) H. F. Schaefer, Acc. Chrm Re.r. 15 (1982) 283 and references cited
therein. b ) Y. Apeloig, M . Karni, J. Chem. SOC. Chem. Commun. 1984,
[6] A. G . Brook, S. C . Nyburg, F. Abdesaken, B. Gutekunst. G. Gutekunst, R.
K. M. R. Kallury, Y . C. Poon, Y.-M. Chang, W. Wong-Ng, J. Am. Chcm.
SOC. 104 (1982) 5667.
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4.3,R = Br; 4b, R = Li
4c. R = H; 4d. R = CH,
[*] Priv.-Doz. Dr. U. H. Brinker, A. Haghani, K. Gomann
Abteilung fur Chemie der Universitat
Universitatsstr. 150, D-4630 Bochum I (FRG)
Carbene Rearrangements, Part 18. This work was supported by the
Fonds der Chemischen Industne. We thank Dr. W . Dicrrrch, Priv.-Doz.
Dr. H Duddeck. and Dr. M. Kaiser. for recording the 2 D - ' H - N M R
(NOESY and COSY) spectra of 6 and Dr. D.Miiller for the GC-MS determinations.-Part 17: [I].
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Angew Chem. I n t . E d . Engl. 24 119851 N o . 3
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bond, structure, containing, isolation, molecules, silicon, double, carbon, stable
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