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Existence of a New C6H6 Isomer Tricyclo[3.1.0

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tively rigid skeletons. We now report the synthesis, thermolysis
kinetics, and intramolecular interactions of the fourfold
bridged benzene dimer (2)['1, which could be expected a
priori to have a greater thermal stability than o,o'- and 0 , ~ ' dibenzenes"!
The relationship between ( 2 ) and benzene is expressed
schematically by ( I ), which also underlines the C2 symmetry
present.
121
111
Treatment of bishomocubanedione (3) with diazomethane
yields a mixture of the homologous diketones (4)[31.Reaction
with tosylhydrazine in tetrahydrofuran leads to the isomeric
hydrazones. The action of n-butyllithium in T H F on the mixture at room temperature affords a 22 % yield of the diene
(2), which is purified by distillation and subsequent gas chromatography. Compound (2) is a colorless, slightly air-sensitive
liquid having an uncharacteristic
f
.
1) T o s - NH- NH2
2l n - B d # . T H F
I21
The predominant fragmentation to benzene induced by electron impact is also observed on heating. After 2 h at 190°C
in hexachlorobutadiene, (2) has decomposed quantitatively
to benzene. The kinetics of the unimolecular reaction was
measured in mesitylene (Table 1).
Table 1. Decomposition of (2) in mesitylene
8.9
18.4
29.2
ii
I
36.9T0.3 kcal/mol
154.2f 1.3 kJ/mol
14.1 To,2
The activation energy of 36.9 kcal/mol is of the same order
of magnitude as the values for basketene (29.7 kcal/m~l)[~"]
and homobasketene (35.3 k ~ a l / m o l ) [ ~The
~ ] . thermal reaction
might involve a [4 + 21 cycloreversion to o,o'-dibenzene and
its [2 + 21 fragmentation to beniene.
The formally nonconjugated double bonds in (2) could
at first sight create the impression that there is no interaction
between them. This is not the case. Although the topology
of the molecule rules out direct n overlap (homoconjugation),
considerable hyperconjugational effects can be expected, Possible transmitters are the 1,s-CJ
bond and the bicyclo[2.2.0]hexane moiety (C atoms 2,5,4,9,10,3),the latter case being without
precedent. CNDO/S calculationd6] predict the energy sequence xs (HOMO, E = - 9.09 eV)> n A (third highest occupied
MO, E = - 9.76 eV). The splitting of 0.7 eV is due to o,n-interaction of ns with 0(1,8) and with the bicyclo[2.2.0]hexane unit.
The perspectively correct structural formula f5)"], which
also contains the n-electron densities of the ns HOMOS, reveals
that both the 1,s-o bond and the four-membered ring bonds
848
Received: August 1, 1978 [Z 78 IE]
German version: Angew. Chem. YO, 901 (1978)
CAS Registry numbers:
(2). 68109-02-4; ( 3 ) , 14725-77-0
141
160.1
166.7
169.5
172.2
179.7
185.3
5,4 and 10,3 could engage in o,n interaction. These model
considerations are confirmed by experiment. The photoelectron spectrum of (2) gives IP1,,=8.30eV and IP2,,=9.35eV;
the second band is more than three times as intense as the first
one. Since basketend'] shows IPl,,= 8.97 eV and the inductive
effect of an additional vinylene group on I P , . , can be neglectedlgl [(2) can be regarded as vinylogous to basketene],
a through-bond interaction of the kind mentioned above is
held responsible for the lowering of IP1,, by AIPzO.7eV.
[l] The designation ansaradienes (ansa, Latin handle; sari, New Greek cube)
is proposed for these bis-vinylogous cubanes. Thus ( 2 ) (point group
C,) i s called Cz-ansaradiene and hence distinguished from the Czvand
DZhisomers.
[2] W Grimme, E. Schneider, Angew. Chem. 89, 754 (1977); Angew. Chem.
Int. Ed. Engl. 16, 717 (1977), and references cited therein.
[3] K . Hirno, E. Abe, 0.Yonemitsu, Tetrahedron Lett. 1975, 4131.
[4] 'H-NMR (CCI4, 90 MHz): 6=2.11 (mc; 4 H ; I-H, 3-H, 4-H, 8-H), 2.53
(m; 2 H ; 2-H, 9-H), 3.40 (m; 2 H ; 5-H, 10-H), 5.94 ("t"; 2 H ; 6-H, 11-H),
6.34 ("t"; 2H; 7-H, 12-H).-MS (70eV): m/e= 156 (I %, M'), 78 (100 %,
M -C6H6).--IR: 1610cm-' (C=C).
151 a) H. H. Wesrberg, E. N . Cain, S. Masamune, J. Am. Chem. SOC.91,
7512 (1969); b) W Mauer, W Grimme, Tetrahedron Lett. 1976, 1835.
[6] H. H. Ja@, Acc. Chem. Res. 2, 136 (1969).
[7] c1! L. Jorgensen, Quantum Chemistry Program Exchange 10,340 (1977).
[S] R. J . Boyd, J.-C. G . Biinzli, J . P . Snyder, J. Am. Chem. SOC.98, 2398
(1976).
[9] Cf. 1,3-cycloheptadiene + bicyclo[4.2.l]nonatriene: P . Bischof, R. Gleiter,
E. Heilbronner, Helv. Chim. Acta 53, 1425 (1970).
Existence of a New C6H6 Isomer:
Tricyclo[3.1.0.02~6]hex-1(6)-ene c*'l
By Ursula Szeimies-Seebach, Joachim Harnisch, Giinter Szeimies, Maurice Van Meerssche, Gabriel Germain, and Jean-Paul
DeclerqI'[
Cumulative evidence has become available for the formation
of tricycl0[4.1.0.0~~~]hept-l(7)-eneas a shortlived interme[*] Priv.-Doz. Dr. G. Szeimies ['I, Dipl.-Chem. U. Szeimies-Seebach, Dr.
J. Harnisch
Institut fur Organiscbe Chemie der Universitat
Karlstrasse 23, D-8000 Miinchen 2 (Germany)
Prof. Dr. M. Van Meerssche, Dr. G. Germain, Dr. J.-P. Declerq
Laboratoire de Chimie Physique et de Cristallographie de I'Universitt
de Louvain
BItiment Lavoisier, Place L. Pasteur, 1, B-1348 Louvain-la-Neuve (Belgium)
['I To whom correspondence should be addressed.
[**I This work was supported by the Deutsche ForschunP~"emeinschaft,
the Fonds der Chemischen Industrie, and the Fonds de la Recherche Fondamentale Collective.
Angew. Chem. I n ? . Ed. Engl. 17 (1978) No. 11
diate"]. We now report experimental results from which we
deduce that the homologous title compound ( 1 ) can also
exist as a reactive species. This new C6H6 isomer has the
carbon skeleton of benzvalene, from which it differs in the
position and energy of its CC double bond.
Ill
131
121
141
I Z I I a
b
c
d
e
R
Li
CI
n-C,,H9
C6H5
I
H
bond, is 0.31
The (C-llk(C-16) bond is significantly
longer at 1.54A than the corresponding bonds in the other
bicyclo[l.l .O]butanes examined so
At 150°C in C&, ( 5 ) undergoes complete rearrangement
within 30min to the diene (6) (cf. ['"]).-Compound (3)
also isomerizes quantitatively at 160°C to the acetylene (7).
161
Tricycl0[3.1.0.0*~~]hexane(2a)['] could be metalated with
n-butyllithium in diethyl ether to give (26), which afforded
a 48 % yield of l-chlorotricyclo[3.1.0.02~6]hexane(2c) on
treatment with p-toluenesulfonyl chloride[3! Compound (2 c)
reacts with organolithium compounds by nucleophilic substitution: n-butyllithium (molar ratio 1 :3) gave an essentially
quantitative yield of I-n-butyltricyclo[3.1.0.02,6]hexane (2 d)
after aqueous workup, and phenyllithium the 1-phenyl derivative (2e) in 65% yield. The preparation of I-(1-tricyclo[3.1 .O.O'. 6]hexyl)tricyclo[4.1.O.O', 'lheptane (3) was accomplished in 25% yield by combination of (2c) and l-tricyclo[4.1 .0.02.'lheptyllithium.
We interpret the course of these reactions as follows: the
I-chloro derivative ( 2 c ) is lithiated at C-6 by the lithium
base to give ( 4 ) , which undergoes LiCl elimination to form
the intermediate (I). The bicyclo[l.l .O]but-l(3)-ene derivative
( I ) adds the lithium base to its highly strained double bond;
aqueous workup then leads to the products [ ( 2 d ) , (Ze),
and (3)].
171
Table 1 lists NMR data of the new compounds.
Table I . NMR data (6 values) of ( Z c ) , ( Z d ) , ( 2 e ) , (3), (S), f6), and
(7).
( 2 c ) : 'H-NMR (C6D6): 0.91-1.53 (m; 4H, 3-H2, 4-H2), 2.10 (t, J = 2 H z ;
1 H, 6-H), 2.22 (d, J = 2 H z ; 2H, 2-H, 5-H)
( 2 d ) : 'H-NMR (CC14): 0.90 (t, J = 6 H z ; 3H, CH,), 1.15-1.47 (m; 10H,
(CH2)3,3-H2,4-H,(lasttwoproton groups as s at 1.23)), 1.53 (br. s; 1 H,
6-H), 1.85 (narrow m; 2H, 2-H. 5-11)
( 2 e ) : 'H-NMR (CCI.,): 1.40 (s; 4H, 3-H2, 4-H2), 2.02 (br. s ; 1 H, 6-H),
2.49(d, J = 2 H z ; 2H, 2-H, 5-H).-13C-NMR (CDCII): 16.94 (d; C-6),
20.40 (s; C-I), 25.84 (t; '2-3, C-4), 37.12 (d; '2-2, C-5); aromatlc C :
124.59 (d), 126.11 (d), 127.89 (d), 137.70 (s)
( 3 ) : 'H-NMR (CCI,): 1.11 (t. J = 3 H z ; I H, 7-H), 1.29 (broadened s , IOH,
3-H2,4-H2,5-H2,3'-H2, 4'-Hz), 1.58(br.s; 1 H, 6-H), 1.97 (d, J = 1.5 Hz;
2H, T-H, 5'-H), 2.28 (m; 2H, 2-H, 6-H).-I3C-NMR (CDCI,): 7.41
(d; C-6), 10.90 (d; C-7), 14.76 (s; C-l'), 16.29 (s; C-l), 20.48 (t; C-3,
C-S), 21.01 (t; C-4), 26.15 (t; C-3', C-4), 37.83 (d; C-2, C-S), 43.78
(d; C-2, C-6)
(5): 'H-NMR (CDCla): 1.37 ( s ; 4H, 13-H2, 14-H~),2.00 (s; 2H, 12-H,
15-H),4.65 ( s ;2H, 9-H, 10-H),6.90-7.47 (AA'BB' system; 8 H, aromatic H).-I3C-NMR (CDCI,): 26.00 (s; C-11, C-16), 27.34 (t; C-13,
C-14), 44.17 (d; C-9, C-lo), 53.21 (d; C-12, C-15); aromatic C: 124.14
(d), 125.75 (d), 142.50 (s)
( 6 ) : 'H-NMR (C6Ds): 1.93 (s; 4H), 4.17 (d, J = 8 Hz; 1 H), 4.70 (S; 1 H),
5.70-6.07 (m; 2H), 6.83-7.42 (m; 8H)
( 7 ) : "CC-NMR (CDCI,): 20.81 (t). 24.77 (t), 27.61 (d), 29.83 (t), 31.97 (t),
32.04 (t), 36.02 (d), 82.50 (s), 83.08 (s), 126.94 (d), 127.99 (d), 130.84
(d), 132.04 (d)
Received: August 4, 1978 [Z 80 IE]
German version: Angew. Chem. 90, 904 (1978)
Fig. 1. Molecul;ir Ctructure of ( 5 ) with the principal bond lengths [A].
The dihedral anglc 111 the bicyclo[l.l.O]butane system is 113". Bond angles:
(c-l2)b(c- 1 1 ) ( C - I ?I.V I ";(c'I O J g C - 1l)+C-l6), 110"; (C-l I)+C-l2)--(C13), 109"; (C-12)-(C-13)-(C-14), 101"; (C-l2)-(C-l l)-(C-16), 59".
Our interpretation of the reaction proceeding via ( I ) as
intermediate is based on the formation of the Diels-Alder
adduct ( 5 ) , which was isolated in 36 % yield from a mixture
of (2 c), lithium 2,2,6,6-tetramethylpiperidide, and anthracene
in tetrahydrofuran at - 20°C (m.p. 155-1 57 "C, from n-pentane).
Structural proof for ( 5 ) is based on spectroscopic data
(Table 1) and on an X-ray analysis depicted in detail in Figure
lL4I. The bridgehead atoms C-I 1 and C-16 of the bicyclo[l .l.O]butane system ofthis (4.1.1]pr0pellane[~'~exhibit the "inverted
tetrahedron" phenomen~n[~],
i. e. C-I 1 and C-16 are each
located outside the tetrahedron formed by their four respective
substituents. Thus the distance between C-11 and the tetrahedral face C-10, C-12, C-15, which intersects the (C-11j ( C - 1 6 )
Angenp. Chem. Int. Ed. Engl. 17 ( 1 978) No. 11
CAS Registry numbers:
(J), 68108-93-0; (ZU), 287-12-7; (Zb), 68108-94-1; ( Z C ) , 68208-95-2; ( Z d ) ,
68108-96-3;(2e),68108-97-4;(3),68108-98-5; ( 5 ) , 68108-99-6;(61,68109-00-2;
(7), 68109-01-3; 1-tricyclo[4.1.0.0z~']heptyllithium. 66464-70-8
[ l ] a) G. Szeimies, J. Harnisch, 0. Baumgurtel, J. Am. Chem. SOC.99, 5183
(1977); b) G. Szeimies, 3. Harnisch, K . - H . Stadfer, Tetrahedron Lett.
1978, 243; c) U . Szeimies-Seebach, G . Szeirnies, J. Am. Chem. SOC.100,
3966 (1978); d) J . Harnisch, H . Legner, U . Szeimies-Seebach, G . Szeimies,
Tetrahedron Lett. 1978, 3683.
[2] M. Christl, G. Briintrup, Chem. Ber. 107, 3908 (1974).
[3] G. Szeimies, F . Phifipp, 0. Eaurngiirtel, J. Harnisch, Tetrahedron Lett.
1977, 2135.
M ( 5 ) forms monoclinic crystals, a = 28.008(18), b = 6.1 14(3),
c = 19.349(13)A;p= 124.15(4),space group C2; Z=8. The structure was
solved by Patterson search with the program written by P . B. Brarm,
J . Hornsrra, and J . I . Leenhouts (Philips Res. Rep. 24, 85 (1969)) and
relined with X-RAY 72 SYSTEM (Tech. Rep. TR-192. Computer Science
Center, University of Maryland 1972) for 2240 reflections, R=0.058
(Syntex P2' diffractometer, MoKx, 2 L =47").
151 K . B. Wiberg, G. J. Burgmaier, K . W Shen, S. J. LaPlaca, W C . Hamilton,
M . D. Newton, J. Am. Chem. SOC.94, 7402 (1972).
C6l The comparable distance in 8,8-dichlorotricyclo[3.2.1.0'~5]octane is
0.093A [5].
849
[7] a) Bicyclo[l.l.O]butane: 1.497A; K . W Cox, M . D. Harmony, G . Nelson,
K . B. H'!hrrg, J . Chem. Phys. 50, 1976 (1969); b) henzvalene: 1.452 A;
R. D. Suenram, M . D. Harmony, J . Am. Chem. Soc. 95, 4506 (1973);
1.483A; C .
c) 6-thiate~racyclo[5.4.0.02~4.03~S]undeca-l(7),8,1O-triene:
Kabuto, 7: Tarsuoka, I . Muruta, Y Kitahara, Angew. Chem. 86, 738
(1974); Angew. Chem. Int. Ed. Engl. 13, 669 (1974); d) 1,5-diphenyltricyclo[2.1.0.0L. s]pent-3-ylp-bromobenzoate: 1.44A; J . Trotter, C. S. Gibbons,
N. Nakarsuku, S. Masamune, J . Am. Chem. Soc. 89, 2792 (1967).
A Stable o/n-Organometallic Radical of Vanadium:
(q 5-C5Me4Et)2V-eC-C6H2Me3 [**I
By Frank H . Kokler, Wolfram Prossdorf, Ulrich Sckubert, and
Dietmar Neugebauer[*]
Dedicated to Professor E. 0. Fiscker on the occasion of his
60th birthday
Vanadocenes bearing an additional o-bonded organic group
on the metal could provide valuable information about the
s t i l l u n k n o w n V 4 bondlength[" "],about thestability ofthis
bond, about Hoffmann's MO concept of bent metallocenes[z],
and about paramagnetic NMR behavior, if only it were possible to adequately stabilize these molecules, which are generally known to be unstable and poorly characteri~able[~I.
We have successfully stabilized such a molecule by peralkylation of the cyclopentadienyl ligands. Starting from 3-ethyl1,2,4,5-tetramethylcyclopentadiene(1)L41, slight modifications
to our previous synthesis[5] yield peralkylated vanadocene
(2) and vanadocene bromide (3). Reaction of (3) with the
sodium salt of mesitylacetylene ( 4 ) gives olive-green, airsensitive bis(ethyltetramethy1-q5-cyclopentadienyl)mesitylethynylvanadium ( 5 ) . While the nonalkylated compound rapidly
decomposes at 25"C[61,compound ( 5 ) melts at 83-84"C,
can be sublimed (leaving a residue), and survives several hours'
heating in boiling toluene without decomposition.
Elemental analysis and mass spectrum (principal metal-containing ions at 70eV and 75°C: M + (32), [ M + 11' (12), [ M (4)]+ (72), [M+2-(1)]+ (loo), [M-(I)]+ (44), [ V - e C C6H2Me3]' (20)) prove the composition of ( 5 ) ; X-ray analysis['] provides proof of its structure (cf. Fig. 1). The vanadium
atom lies in the plane El (C20, MI, M2) and can be regarded
as surrounded by three hydrocarbon groups in an almost
trigonal-planar fashion. Peralkylation of the five-membered
rings does not lead to any significant increase in the metal-ring
distances compared with other (q '-CsHS)-vanadium derivatives['] studied so far; instead, the Ml-V-M2
angle (149.7")
is considerably greater than that in (q 5-CSHs)2VC1(139.5")[8b1.
In spite of this decrease in strain, the methyl groups are
bent out of the planes of the five-membered rings away from
the vanadium by up to 32pm. The bond angles and the
bond lengths of the acetylene moiety are typical['], whereas
no reference data are available for the V"'-C,,
distance of
203.2 pm.
Of particular interest was the question how the plane of the
benzene ring E 2 would be oriented relative to the coordination
plane of the vanadium El. With regard to the metal orbitals,
and especially b2, according to Hoffmann et a/.[21conjugation
might conceivably extend from the vanadium to the benzene
ring, which should lead to a parallel arrangement of El and
Fig. 1. Molecular structure of the organometallic radical ( 5 ) .
__
Distances
[pm]
Angles
r1
V-M 1
V-M2
v-c20
C20-C201
C201-C22
197.6
197 0
203.2 (13)
123.4 (17)
144.7 (14)
M1-V-M2
MI-V-C2O
M2-V-C20
v-c20-c201
C2(tCZOl-C22
149.7 ( I )
105.4 (4)
104.8 (4)
176.6 (10)
175.5 (12)
E2. In contrast, we find these planes to enclose an
angle of 86.8". Thus x-interaction occurs only between
V/C20/C201 on the one hand and between C20/C201/mesityl
on the other.
A well-resolved paramagnetic 'H-NMR spectrum can be
recorded for ( 5 ) . It exhibits broad signals (300-400 and
120Hz wide) having large chemical shifts such as are typical
for protons located CL or
to a cyclopentadienyl ring[5b1:
S~a'a('H-31/41/81/9t~101=
-22.3,
~pam('H-21/51/71/101)=
- 18.2, 6P"ra('H-11/6t)= - 10.3, and hpara('H-12/62)=+0.6.
In addition, signals of 20-80 Hz width are observed for
the bonded acetylene: hpara('H-24/26)=- 20.5, Para(lH231/271)= - 10.1, and SP"'"('H-251)= -8.7. On comparison
with vanadocene halides[5b1,these data show ( 5 ) to be an
organometallic radical possessing two unpaired electrons and
confirm that the vanadium is surrounded only by two nand one o-bonded hydrocarbon groups. Correlation of Kpara
with the distance from vanadium shows that the delocalization
of unpaired electrons is much more pronounced onto the
acetylene than onto the TC ligands. Thus, elucidation of structure
and studies on electron distribution in radicals of the (q5CSH5)2V-R type are seen to be possible by NMR.
Procedure
Sodium mesitylacetylide (0.58 g, 3.5 mmol) is added to a
solution of (3) (1.45g, 3.4mmol) in diethyl ether (50ml). After
removal of ether, the residue is extracted with pentane (30ml),
the olive-green extract treated with ethanol (30ml), and the
pentane removed under reduced pressure. Compound ( 5 )
crystallizesfrom the ethanol solution at - 78 "C. Recrystallization from ethanol (2 x ) and from pentane (3 x ) gives lustrous
black crystals of analytically pure ( 5 ) (0.35 g, 21 %).
Received: August 10, 1978 [ Z 87 IE]
German version: Angew. Chem. 90, 912 (1978)
[*) Doz. Dr. F. H. Kohler, Dr. U. Schubert, DipILChem. W. Prossdorf,
D. Neugebauer
Anorganisch-chemisches Institut der Technischen Universitat Miinchen
Lichtenbergstrasse 4, D-8046 Garching (Germany)
This work was supported by the Deutsche Forschungsgemeinschaft
and the Fonds der Chemischen Industrie.
CAS Registry numbers:
(3), 68185-51-3; (41,68184-34-9; (S), 68185-52-4
[*"I
[l] J . L. Atwood, personal communication; J. L. Atwood, W E . Hunter,
H. Alt, M . D. Rauwh, J . Am. Chem. Soc. 98, 2454 (19761
850
Angew Chem. Int. Ed. Engl. 17 ( 1 9 7 8 ) No. 11
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