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Dihydroacepentalenediide the Dianion of Acepentalene.

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distorted tetrahedral array of the centroids of the two cyclopentadienyl rings and the two bridging phosphorus
atoms. At the same time, these two phosphorus atoms together with the two nitrogen atoms of the tmeda ligand
coordinate the lithium atom tetrahedrally. In addition, the
crystal contains one molecule of toluene (disordered) per
two molecules of 2 . The Pl-Lu-P2 and Pl-Li-P2 planes
form an angle of 148.7 i. e., a bent four-membered ring is
formed, as observed in compounds with sulfur['l o r selenium ([Cp,L~(p-SePh),Li(thf)]~'~~)
in place of phosphorus,
By contrast, in the already well-known complexes 7, the
Y b C 5 M e 5 C1
Y b C5Me5 I
Er. C5H5
(Etz0)z [I11
(Etz0)Z 1111
CH3 t m e d a
L n ( ~ - x ) ~ Lmoieties
are planar. The Cp*l-Lu-Cp*2 angle
and the mean value of the ten Lu-C(q5) distances in 2 lie
in the expected range; the cyclopentadienyl rings are planar. The lengths of the organolutetium-phosphorus bonds
(measured for the first time) are 2.782 and 2.813 A.
Dihydroacepentalenediide, the Dianion of
By Thomas Lendvai, Thomas Friedl, Holger Butenschon,
Timothy Clark, * and Armin de Meijere *
Dedicated to Professor Edgar Heilbronner on the occasion
of his 65th birthday
Dihydroacepentalenediide (2 2Q), formally an ethenobridged dihydropentalenediide,".'I should, according to
semiempirical calculations, in analogy to the latter be a
closed-shell system.13] However, the high strain energy in
the cyclic and cross-conjugated skeleton with three angularly annelated five-membered rings could preclude its form a t i ~ n . 'Apparently
all attempts to generate 2 2 Q have
thus far failed, despite the keen interest long shown by
theoretical chemists in acepentalene (cyclopenta[c~pentalene) 2.15]The most recent attempts to reductively eliminate
the two dialkylamino groups from the potentially suitable precursor 4,7-bis(dialkylamino)tricyclo['"]deca1( 10),2,5,8-tetraene~[~]
merely led to 1,4,7-tris(dialkylamiall the more
no)-substituted m o n o a r ~ i o n s . It~ ~is. therefore
surprising that 22Qcan be prepared quite simply and directly from triquinacene 1.
Received: March 13, 1986 [Z 1700 IEI
German version: Angew. Chem. 98 (1986) 726
CAS Registry numbers:
1. 93895-53-5; 2, 103349-56-0; 2 . tC6HSCH,, 103349-57-1 ; 3, 93895-55-7; 4,
103349-58-2; HPPh2, 829-85-6.
I /
When 1 is added to a suspension of n-butyllithium and
potassium tert-amyl alkoxide171 in n-hexane,[81 the mixture
turns deep red within 24 h at room temperature. To complete the reaction, the mixture is boiled under reflux for
24 h. The solvent is then removed from the mixture by suction through a fritted glass under nitrogen, and the excess
base is then removed by washing five times with hexane.
The reddish-brown powder that is recovered along with
potassium hydride on the filter (corresponding to 130135% yield) can be dissolved in tetrahydrofuran (THF). Its
'H-NMR spectrum shows only one singlet (Table I), and,
[I] H. Schumann, H. Jarosch, Z . Anorg. Allgem. Chem. 426 (1976) 127.
[2] H. Schumann, G. M. Frisch, Z. Naturforsch. 836 (1981) 1294.
[ 3 ] G. Bielang, R. D. Fischer, J. Organomet. Chem. 161 (1978) 335.
[4] W. J. Evans, 1. Bloom, W. E. Hunter, J . L. Atwood, Organometallics 2
(1983) 709
[ S ] H. Schumann, F. W. Reier, E. Hahn, 2. Nafurforsch. B40 (1985) 1289.
[6] 2 and 6 gave correct elemental analysis. The NMR spectra were measured at 25°C in C6D6 with a 80-MHz instrument (6('H, "C) relative to
TMS, 6("P) relative to 85% H3P04). 2 : decomposition point= 13OC;
'H-NMR: 6=1.67 ( s ; NCH2), 1.86 (s; NCHs), 6.12 (t, J(HP)=0.8 Hz;
CsHs), 7.0-7.9 (m: C6Hs); "C-NMR: 6=46.28 (s; NCH,), 56.96 (s;
N C H A 109.25 (s; C ~ H S )130
, (m; C6Hs); "P-NMR: 6=9.46. 6 : decomposition point= 122°C; 'H-NMR: 6 = 1.31 and 3.52 (m; THF), 6.14 (t.
J(HP)=0.8 Hz; C,H,), 7.0-7.9 (m; C6H,); "C-NMR: 6=25.33 and
68.65 (THF), 109.54 (s; CsHs), 130 (m; C6H5); "P-NMR: 6=5.68.
Table I. Some characteristic data of the dipotassium acepentalenediide
[7] H. Schumann, H. Lauke, E. Hahn, M. J. Heeg, D. van der Helm, OrgaZZe/2K0 and its trapping products 5 and 6 .
nomerallics 4 (1985) 321
I81 2 ( I ( ~ ~ - C S H , ) ~ L ~ ~ P ( C ~ H S ) ~ } ~ L ~ ~ ( C H , ) , N C H
. )CJhCH,I):
Z C H ~ N ( C H ' ) ~ ~ Z 2 ' : 'H-NMR (400 MHz, [Da]THF): 6=6.16 (s, 6H).-I3C-NMR (100.63
C2/c, ~=36.211(13), b:11.843(3),
c=24.008(8) A, a = y = 9 0 ,
MHz, [DaITHF): 6=109.87 (d, ' J c , ~ = l 4 8 . 8Hz, C-2,3,5,6,8,9), 121.79 (s, Cp= 128.92(2)', V=8011(4) A', 2 = 8 ,
1.40 g c m - ' ; MoKI, radia1,4,7), 140.64 or 159.89 (s, C-10) (see text)
tion, graphite monochromator, 0.8" w-scans in the 2 8 range up to 50" at
5 : 'H-NMR (270 MHz, CGD6): 6=0.07 (s, IsH), 5.26 (s, 5,6-H), 5.44 (d,
- 150°C. 7003 independent reflections, 5744 observed (FoZ 3.50(F)),
Hz, 3,8-H), 5.65 (d, 2,9-H).-MS:
M" calc. 272.14166, obs.
empirical absorption correction (min/max-transmission = 0.4W0.94).
Solution by direct methods and subsequent difference-Fourier tech6 : 'H-NMR (270 MHz, CeDs): 6=0.08 ( s , 9H), 0.20 (s, 9H), 5.37 (s, 2.3-H),
niques, structure refinement by block-cascade methods with idealized
5.56 (d, 3J6(g1.5,9)=5.4Hz, 6,8-H), 5.65 (d, 5,9-H).-MS (NH,-CI): m / z 273
geometry for CsHS- and C,Hs-rings and CH,- and CH2-groups with 1.2(loo%, M e H)
fold isotropic temperature factors for the H-atoms corresponding to the
V,, tensor of the respective C-atoms (391 parameters). All calculations
with the SHELXTL program system: R=0.0382, R,=0.0378
( w - ' =02(F)+0.00037 P ) . Further details of the crystal structure investigation are available on request from the Fachinformationszentrum En[*I Prof. Dr. A. de Meijere, Dr. H. Butenschon, Dipl.-Chem. T. Lendvai
ergie, Physik, Mathematik GmbH, D-7514 Eggenstein-Leopoldshafen2,
Institut fur Organische Chemie der Universitat
on quoting the depository number CSD-51847, the names of the authors,
Martin-Luther-King-Platz 6, D-2000 Hamburg 13 (FRG)
and the full citation of the journal.
Dr. T. Clark, Dip].-Chem. T. Friedl
191 H. Schumann, 1. Albrecht, E. Hahn, Angew Chem. 97 (1985) 991; AnInstitut fur Organische Chemie der Universitat Erlangen-Niirnberg
gew. Chem. Int. Ed. Engl. 24 (1985) 985.
Henkestrasse 42, D-8520 Erlangen (FRG)
[lo] H. Schumann, M. Gallagher, C. Kolax, unpublished.
11 11 P. L. Watson, J . F. Whitney, R. L. Harlow, Inorg. Chem. 20 (1981)
[**I This work was supported by the Stiftung Volkswagenwerk and the
Fonds der Chemischen Industrie.
Anyew. Chrm Int. Ed. Engl. 25 (1986) No. 8
0 VCH Verlagsgesellschaft mbH, 0-6940 Wernherm. 1986
0570-0833/86/0808-0719 $ 02 50/0
7 19
according to the I3C-NMR spectrum, the constitution of
the product recovered is indeed that of the dipotassiurn dihydroacepentalenediide 22Q/2K@(Table l).[91But the assignment of the very weak signal of C-10 is not absolutely
certain because 22Q/2K@slowly decomposes in THF,
even at -40 "C, and hence signals of other products appear in the spectrum. An unequivocal proof of the constitution was, however, provided by the trapping reaction
with chlorotrimethylsilane. When a suspension of 22Q/
2Ke in n-hexane is stirred at room temperature for 48 h
with an approximately equimolar amount of Me3SiC1, decolorization of the mixture occurs, and, after the usual
work-up, a product can be isolated (60-70% yield based o n
1) in which two components with M , = 272 can be detected
by combined GC-MS. According to the 'H-NMR spectrum (Table 1) the components are the isomeric bis(trimethylsilyl)tricyclo['o]decatetraenes 5 and 6 (ratio
It is especially remarkable that 6 is formed along with 5 ,
since the tricycl0[5.2.1.O~~'~]deca-1,3,5,8-tetraeneskeleton
of 6, according to force field calculations, is about 18.2
kcal/mol more strainedt4]than the skeleton of 5 , which is
easily accessible in the form of 4,7-bis(dialkylamino)derivative^.^^^ According to MNDO calculations the charge
distribution in dihydroacepentalenediide 2 2 o is best explained in terms of the structure a, a trisetheno-bridged
trimethylenemethane dianion; structure b plays only a
subordinate role.'31 Hence, the 4-trimethylsilyl anion 3
should be formed first in a kinetically controlled reaction
of Z Z Q with Me3SiC1; this could partially rearrange into
the thermodynamically more stable 10-trimethylsilyl anion
4 with a Ion-perimeter by 1,2- o r 1,5-silatropic
before it reacts further to give the bis(trimethylsily1) derivative. As expected, 5 is thermodynamically more stable than
6 ; under modified conditions 5 and 6 are formed in the
ratio 83:17 o r 1OO:O. The isomer 6 rearranges into 5 , rapidly upon MeSiC1-catalysis at room temperature, but at
best only slowly upon heating above 90 OC.['']
Received: March 24, 1986 [Z 1708 IE]
German version: Angew. Chem. 98 (1986) 734
0 VCH VerlagsgesellschaJi mbH, 0.6940 Weinheim. I986
CAS Registry numbers:
1 , 6053-74-3; 2, 103148-72-7; 5 , 103148-69-2; 6 , 103148-70-5
[ I ] Contrary to the IUPAC rules for nomenclature the dihydropentalenediide has often been called pentalenediide in the literature, cf. T. G.
Katz, M. Rosenberger, J. Am. Chem. SOC.84 (1962) 865.
[2] J. J. Stezowski, H. Hoier, D. Wilhelm, T. Clark, P. von R. Schleyer, J.
Chem. SOC.Chem. Commun. 1985. 1263.
131 H . Butenschon, A. de Meijere, Helu. Chim. Acta 68 (1985) 1658.
[4j Cf. H. Butenschon, A. de Meijere, Chem. Ber. 118 (1985) 2557.
[5] a) A. Streitwieser, Jr.: Molecular Orbital Theory for Organic Chemists,
Wiley, New York 1961, p. 290f.; b) R. Zahradnik, J. Michl, J. Koutecky,
CON. Czech. Chem. Commun. 29 (1964) 1932; c) R. Zahradnik, J. Michl,
ibid. 30 (1965) 3529; d) B. A. Hess, Jr., L. J. Schaad, J. Org. Chem. 36
(1971) 3418; e) F. Tomas, J. 1. Fernandez-Alonso, A n . Quim. 72 (1976)
122; f) 1. Gutman, N. Trinajstic, Croat. Chem. Acta 47 (1975) 35; g) I.
Gutman, M. Milun, N. Trinajstic, J. Am. Chem. SOC. 99 (1977) 1692.
[6] K. Mullen, H. Butenschon, A. de Meijere, unpublished, results.
171 Cf. L. Lochmann, J. Pospisil, D. Lim, Tetrahedron Lett. 1966, 257; cf. M .
Schlosser, S. Strunk, ibid. 25 (1984) 741.
[8] Analogous to the synthesis of numerous polyanions by metalation-elimination: D. Wilhelm, T. Clark, T. Friedl, P. von R. Schleyer, Chem. Ber.
I16 (1983) 751; D. Wilhelm, T. Clark, P. von R. Schleyer, Tetrahedron
Lerr. 23 (1982) 4077.
191 All experimental findings with other systems are consistent with the
presence of a dipotassium salt. Cf. D. Wilhelm, T. Clark, P. von R.
Schleyer, J. L. Courtneidge, A. G. Davies, J . Organomet. Chem. 273
(1984) CI.
[lo] According to MNDO calculations the 10-Me,Si anion 4 is about 2.9
kcal/mol more stable than the 4-Me3Si anion 3. Accordingly, 4 shows
hardly any bonding alternance in the lox-perimeter. T. Clark, unpublished results.
[ I l l This is surprising in view of the reports that the silatropic 1,5-shift o f
cyclopentadienes is lo6 times more rapid than the prototropic shift. C.
A. J. Asche 111, J. Am. Chem. SOC.92 (1970) 1233; S . McLean, G. W. B.
Reed, Can. J. Chem. 48 (1970) 3110; C. W. Spangler, Chem. Rev. 76
(1976) 187.
Bridged I14IAnnulenes with a Phenanthrene-Perimeter :
syn-1,6 :7,12-Bismethano[ 14]annulene**
By Emanuel Vogel,* Wilhelm Piittmann,
Walter Duchatsch, 7'homas Schieb, Hans Schmickler,
and Johann Lex
Dedicated to Professor Heinz A . Staab on the occasion
of his 60th birthday
The syn/anti-isomeric 1,6:8,13-bismethano[l4]annulenes
l1I1and 2['l with an anthracene-perimeter are exemplary
models for correlating aromaticity and molecular geometry.131O n the basis of spectral141and structural chemical criteria, the syn-isomer 1 clearly qualifies as an aromatic
compound, even though the annulene ring is noticeably
bent-mainly as a result of steric repulsion of the internal
bridge hydrogen atoms. In the anti-isomer 2, on the other
hand, the annulene ring is strongly puckered, so that the
cyclic n-electron delocalization can no longer be sustained,
and consequently 2 constitutes a highly reactive olefinic
[*] Prof. Dr. E. Vogel, Dr. W. Piittmann, Dr. W. Duchatsch,
Dr. T. Schieb, Dr. H. Schmickler, Dr. J. Lex
lnstitut fur Organische Chemie der Universitat
Greinstrasse 4, D-5000 Koln 41 (FRG)
This work was supported by the Deutsche Forschungsgemeinschaft
0570-0833/86/0808-0720 $ 02.50/0
Angew. Chem. Int. Ed. Engl. 25 (1986) No. 8
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dihydroacepentalenediide, acepentalene, dianion
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