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Molecular Structure of 8 11-Dichloro[5]metacyclophane A Strongly Bent Benzene Ring.

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structure analysis['] contain the hitherto unknown radical
cation S4N? (Fig. 1). In contrast to the dication S4N:@,
which occurs as a planar ring (D4,, symmetry) with the
counterions S03Fo or AlCl? and in the boat conformation
((2'") with the counterion SbCl:['], the radical cation S4N:
has a puckered eight-membered ring structure in which the
S-atoms form an almost ideal square; the N-atoms are located alternately 34, - 59, 45, and - 38 pm above and below this square. The SN bonds are almost equal in length
(average 154 pm), the NSN and SNS angles have mean
values of 116.0 and 138.9", respectively. The SN bond
lengths are thus markedly shorter than those in the S4N4
molecule (162 prn)[''], but almost the same length as those
in the S4Nz@cation[']. The NSN angles in the two cations
also differ only slightly (S,N:@: average 119"), whereas
the SNS angle in the S4N: radical ion, with a value of
139", is considerably smaller than that in S4N$@(average
value 1520f2]).
Fig. I. Structure of the S4NF radical cation (in the crystal of S4N4FeC14)
viewed in two directions; ellipsoids of the thermal vibration for 50% prohability at 25°C.
Nonius (Delft): crystallographic data: a =803, b = 1004, c = 1509 pm,
b= 104.7", space group P2,/c, Z=4 . 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 50664. the names of the authors, and fu-ll citation of the journal.
[lo] B. D. Sharma, J. Donohue, Acta Crystallogr. 16 (1963) 891.
[Ill J. W. Lauher, J. A. Ibers, Inory. Chem. 14 (1975) 348.
1121 H. Siebert: Anwendungen der Schwingungsspektroskopie in der anorganischen Chemie, Springer-Verlag, Berlin 1966, p. 66.
[I31 A. T. Sherren, J. R. Ferraro, Inorg. Chim. Acta 22 (1977) 43.
Molecular Structure of
A Strongly Bent Benzene Ring**
By Leonardus W . Jenneskens, Johannes C. Klamer,
Henricus J. R . de Boer, Willem H . de WolJ Friedrich
BickelhaupP, and Caspar H . Stam
Of particular interest in the chemistry of the [n]para-[']
and [n]metacyclophanesL2]with short oligomethylene
bridges, is the high strain and its effect on the geometry
and reactivity of such compounds. Thus, it is conceivable
that the sterically enforced bending of the benzene ring
could lead to a'bond fixation tending towards a cyclohexatriene structure; the increased tendency of some cyclophanes to undergo Diels-Alder reactions has come under
discussion in this s e n ~ e [ ~ " .8,l
~ ] l-Dichloro[5]metacyclo.
phane 1 is a representative of the meta series with the hitherto shortest bridgeL4].
The possibility of the presence of [S4N4]2@[FeC14]2e
be ruled out. The four Fe-Cl bonds in the anion have the
same length, namely 219 pm, corresponding exactly to the
known value for those in FeCl? with various counterions;
in FeCl:@, on the other hand the length is 229 pm["]. This
difference greatly exceeds the limit of error. Equally significant is the IR spectrum: The F2stretching vibration of the
FeCI? anion appears at 388 cm-' (for comparison: FeCl?
385 cm-'['21, FeCl:' 286 ~ m - ' [ ' ~ l )Also
the IR-active SN
stretching vibrations for the S4N$ cation were observed at
other frequencies than quoted for S4Ni@[S4N4(AlC14)2:
1091, 1020,974 ~m-'[*~].
In accord with the general finding
that a smaller positive charge leads to a long-wave shift,
the S4N? vibrations appear at 952, 941, 763, 750, and 715
cm-' ; the greater number of IR-active vibrations is consistent with the lower C1 symmetry of the radical cation.
Received: November 2, 1983 [Z 613 IE]
revised: November 29, 1983
German version: Angew. Chem. 96 (1984) 225
CAS Registry numbers:
(NSCI),, 5964-00-1 : [S4N4]"[FeCI4]', 88928-89-6
[I] J. Weiss, 2. Anorg. Allg. Chem. 333 (1964) 314.
[2] R. J. Gillespie, J. P. Kent, J. F. Sawyer, D. R. Slim, J. D. Tyrer, Inorg.
Chem. 20 (1981) 3799.
[3] T. Chivers, L. Fielding, W. G. Laidlaw, M. Trsic, Inorg. Chem. 18 (1979)
(41 A. C. Hazell, R. G. Hazell, Acra Chem. Scand. 26 (1972) 1987.
[S] A. J. Banister, H. G. Clarke, 1. Rayment, H. M. M. Shearer, Inorg. Nucl.
Chem. Left. 10 (1974) 647.
[6] R. J. Gillespie, P. R. Ireland, J. E. Vekris, Can. J. Chem. 53 (1975)
(71 B. Krebs, G. Henkel, S. Pohl, H. W. Roesky, Chem. Ber. 113 (1980)
[8] H. W. Roesky, M. Witt, J. Schimkowiak, M. Schmidt, M. Noltemeyer, G.
M. Sheldrick, Angew. Chem. 94 (1982) 541; Angew. Chem. Znf. Ed. Engl.
21 (1982) 538; Angew. Chem. Suppl. 1982, 1273.
[9] Structure determination with 1023 independent, observed reflections,
refinementto R = 0.046; MoKnradiation,four-circlediffractometer, Enraf-
0 Verlag Chemie GmbH. 0-6940 Weinheim, 1984
Fig. 1. PLUTO diagram of the structure of 1 in the crystal [5]. Selected bond
lengths [A] and angles ["I: CI-C2 1.569(3), Cl-CIO 1.506(3), C2-C3
1.566(3), C8-C9 1.389(3), C9-CIO 1.400(3), CIO-C11 1.391(2), C8-CI8
1.747(3), CII-CIII 1.754(3): C2-CI-CIO 104.7(2), CI-C2-C3 121.9(2),
122.2(2), C7-C8-C9
120.3(3), C7-CS-CI8
118.8(2), CI-CIO-C9
121.8(2), C1-ClO-CII
C9-ClO-CI1 117.4(2), C6-CII-CIO 118.7(2), C6-CII-CII1 119.7.
[*] Prof. Dr. F. Bickelhaupt, Drs. L. W. Jenneskens, J. C. Klamer,
H. J. R. de Boer, Dr. W. H. de Wolf
Vakgroep Organische Chemie, Vrije Universiteit
De Boelelaan 1083, NL-I081 HV Amsterdam (Netherlands)
Dr. C. H. Stam
Laboratorium voor Kristallografie, Universiteit van Amsterdam (Netherlands)
[**I The investigations were supported by the Netherlands Foundation for
Chemical Research (SON) with a grant (L. W. J.) from the Netherlands
Organization for the Advancement of Pure Research (ZWO).
0270-0833/84/0303-0238 $ 02.50/0
Angew. Chem. Inl. Ed. Engl. 23 (1984) No. 3
In the crystal, the molecule has C, symmetry (Fig. 1); its
conformation essentially corresponds to that which, according to MNDO calculations and NMR data, is the
more stable of the two conformations in
benzene ring has an unsymmetric boat conformation,
whose most striking characteristic is the marked bending
of the "bow" (Fig. 2; al =26.8"); to our knowledge this is
the strongest deviation from planarity known so far in a
benzene ring. The angle at the "stern" is smaller (a2= 12
and the sum al+a2=38.8" is close to that found in the
[6]paracyclophane system (41.3 '[Ia1, 38.9'[Ib1).
A remarkable feature is the large angle Dl =48 ; the strain at the bridgehead carbon atoms C-6 and C-10 also manifests itself in
marked pyramidalization (sum of the bond angles: 354").
are somewhat larger than in the [6]paracyclophane sysFinally, we would like to point out that the MNDO calculations[2q have predicted the geometry of l remarkably
well, even though they are not perfect in detail (e.g.
cW1=32, a,=9,81=41").
Received: November 7, 1983 [Z 615 IE]
German version: Angew. Chem. 96 (1984) 236
Fig. 2. Side view of the structure of 1 in the crystal [5]. a l ,a*,PI, see text.
As has already been observed on several occasions with
cyclophanes[61and acyclic, strongly crowded benzene derivatives['], the boat conformation is preferred over thesterically possible-chair conformation. Perhaps this is
due to the more favorable n-overlap in the boat
This effect also explains the striking finding that all six
atoms bound to the benzene ring lie on the same side of
the ring, namely the convex side, whereas the substituents
in paracyclophynes are, for the same reason, tilted to the
concave side[*].Exceptions to this rule are apparently only
found when steric factors counteract such an arrangement,
as in the case of the phosphorus atom in bis(2,4,6-tri-tertbutylpheny1)phosphinic chloride['].
The bending of the benzene ring manifests itself in an
adjustment of the bond angles in the ring, particularly at
C-6, C-10, and C-11. In contrast, the bond lengths in the
benzene ring are, surprisingly, completely normal (mean
value 1.393 k 0.007 A). On the basis of this criterion, one
must conclude that the aromaticity of the ring is essentially
intact. This hypothesis is supported by the ring current effect in the NMR
These findings are not reconcilable with the postulated cyclohexatriene character,
which was considered to explain the high Diels-Alder
r e a c t i ~ i t y ' ~ ~Apparently,
the destabilization of the aromatic ring, which is reflected both in the chemical reactivity and in the UV spectrum['b,el,is not caused by (partial)
bond fixation.
The pentamethylene bridge consists of sp3-hybridized
carbon atoms and is therefore less rigid than the aromatic
ring. Consequently, the effects of strain are discernible in
the bond lengths as well as in the bond angles. The trend is
similar to that in the short-chain [n]paracy~lophanes['~.
angle at the benzylic carbon atom is remarkably small
(ClO-Cl-C2= 104.7"); the angles at the other bridge
atoms (ca. 122") and the CC bond lengths (1.56-1.57 A)
Angew. Chem. Int. Ed. Engl. 23 (1984) No. 3
[I] a) Y. Tobe, K. Kakiuchi, Y. Odaira, T. Hosaki, Y. Kai, N. Kasai, J. A m .
Chem. SOC.105 (1983) 1376, and references cited therein: b) C. Krieger, J.
Liebe, W. Tochtermann, Tetrahedron Lett. 24 (1983) 707, and references
cited therein.
121 a) S. Hirano, H. Hara, T. Hiyama, S. Fujita, H. Nozaki, Tetrahedron 31
(1975) 2219; b) J. W. van Straten, W. H. de Wolf, F. Bickelhaupt, Tefrahedron Lett. 1977, 4667; c) P. Grice, C. B. Reese, J. Chem. SOC.Chem. Commun. 1980, 424; d) L. A. M. Turkenburg, P. M. L. Blok, W. H. de Wolf, F.
Bickelhaupt, Angew. Chem. 94 (1982) 291; Angew. Chem. Int. Ed. Engl. 21
(1982) 298; e) L. A. M. Turkenburg, W. H. de Wolf, F. Bickelhaupt, Tetruhedron Lett. 24 (1983) 1817; f) L. A. M. Turkenburg, W. H. de Wolf, F.
Bickelhaupt, W. P. Cofino, K. Lammertsma, ibid. 24 (1983) 1821.
[3] A. F. Murad, J. Kleinschroth, H. Hopf, Angew. Chem. 92 (1980) 388; Angew. Chem. Inr. Ed. Engl. 19 (1980) 389.
[4] In the non-benzenoid series, a [4]metatroponophane has been described:
Y. Fujise, T. Shiokawa, Y. Mazaki, Y. Fukazawa, M. Fujii, S. Ito, Tetrahedron Left. 23 (1982) 1601.
[5] Crystallographic data for 1: Space group Pbnm; u =9.399(2),
b = 11.832(3), c=9.176(2) A; 2=4. Nonius CAD4 diffractometer, CuKa
radiation, graphite monochromator; 864 observed reflections
(1>2.5o(I)), no absorption correction. The structure was determined by
the heavy atom method and refined by block-diagonal least squares calculations (anisotropic for C and CI, isotropic for H) to R=0.031. A
weighting w = 1/(6.1 +F0+0.01 E ) was applied and an extinction correction performed. Anomalous scattering of the chlorine was taken into account.-Further details of the crystal structure investigation are available
on request from the Cambridge Crystallographic Data Centre, University
Chemical Laboratory, Lensfield Road, Cambridge CB2 IEW (England).
161 a) F. Vflgtle, P. Neumann, Angew. Chem. 84 (1972) 75: Angew. Chem. Int.
Ed. Engl. 11 (1972) 73, and references cited therein; b) H. Iwamura, H.
Kihara, S. Misumi, Y. Sakata, T. Umemoto, Tetrahedron Left. 1976, 615,
and references cited therein.
[7] M. Yoshifuji, I. Shima, N. Inamoto, T. Aoyama, Tetrahedron Lett. 22
(1981) 3057, and references cited therein.
[8] a) H. Hope, J. Bernstein, K. N. Trueblood, Acta Crystallogr. B28 (1972)
1733; b) M. G. Newton, T. J. Walter, N. L. Allinger, J. A m . Chem. SOC.95
(1973) 5652.
syn-Diastereoselective Homoaldol Reactions:
y-Hydroxyalkylation of Q-ZButenyl Carbarnates
and Synthesis of
0,y-cis-Di- and -Trisubstituted y- Lactones**
By Dieter Hoppe* and Florian Lichtenberg
Diastereoselective homoaldol reactions[']-they correspond to the hydroxyalkylation of homoenolate ions['] to
give y-aldols 3-were first reported very recently. However, the approaches described so far only permit access to
anti[3,41-diastereomers3[']. We have now been able to accomplish the first ~yn[~~'~-selective
version of the homoaldo1 reaction, starting from the (Z)-2-butenyl carbamate Z-
The anti-selective procedures utilize, e.g., a-metalated
(E)-2-butenyl carbamates[la-clE-4a,(E)-2-butenyl ethers E4b[Id1or E - ~ C " ' ~and
, (E)-2-butenylsilanes[IflE-4d as homoenolate reagents; the sequences proceed via l-function-
[*] Prof. Dr. D. Hoppe, Dr. F. Lichtenberg
Institut fur Organische Chemie der Universitiit
Tammannstrasse 2, D-3400 Gattingen (FRG)
[**I Metalated Nitrogen Derivatives of Carbonic Acid in Organic Synthesis,
Part 26. This work was supported by the Deutsche Forschungsgemeinschaft and the Fonds der Chemischen 1ndustrie.-Part 25: [Ic].
0 Verlug Chemie GmbH, 0-6940 Weinheim, 1984
0570-0833/84/0303-0239 $ 02.50/0
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structure, molecular, dichloro, benth, ring, strongly, metacyclophane, benzenes
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