The 'cyclophene' [2.2.2](1,2,4)cyclophan-9-ene

Article abstract of DOI:10.1107/S0108270107050937

In the title compound, C18H16, the [2.2]paracyclo-phane geometry is restrained to a considerable extent despite the introduction of the extra C=C bridge; typical paracyclo-phane features, such as the elongated C - C bridges, are still observed. However, t

Full text of DOI:10.1107/S0108270107050937

organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
report here the preparation and the structural properties of
[2.2.2](1,2,4)cyclophan-9-ene, (III), a triply bridged cyclo-
phane in which one of the ethano bridges of its saturated
analogue has been replaced by a double bond. The unsatu-
rated analogue of superphane, superphene, a hydrocarbon
with six adjacent unsaturated bridges, is so far unknown. A
search of the Cambridge Structural Database (Allen, 2002)
revealed no other cyclophene of the [2.2.2](1,2,4) type.
The molecule of (III) is shown in Fig. 1 and selected mol-
ecular dimensions are presented in Table 1. The molecule may
be regarded as a derivative of [2.2]paracyclophane (bridge-
head atoms C3, C6, C13 and C16); as we have previously noted
in such derivatives with extra bridges (Bondarenko et al.,
2007), the molecular geometry is changed surprisingly little by
the extra bridge. Typical features of [2.2]paracyclophanes are
elongated single bonds in the bridges, widened sp3 angles at
the bridge atoms, narrowed sp2 angles in the six-membered
rings at the bridgehead atoms, and ¯attened boat conforma-
tions of the rings, with the bridgehead atoms displaced by ca
ISSN 0108-2701
The `cyclophene' [2.2.2](1,2,4)cyclo-
phan-9-ene
Klaus Broschinski,a Arunachalam Kannan,a Peter G.
Jones,b* Ina Dixa and Henning Hopfa
aInstitut fur Organische Chemie, Technische Universitat Braunschweig, Postfach
È
È
3329, 38023 Braunschweig, Germany, and bInstitut fur Anorganische und
È
Analytische Chemie, Technische Universitat Braunschweig, Postfach 3329, 38023
È
Braunschweig, Germany
Correspondence e-mail: p.jones@tu-bs.de
Received 16 October 2007
Accepted 17 October 2007
Online 14 November 2007
Ê
0.10±0.15 A from the mean plane of the other four atoms
towards the centre of the molecule. All these features are
observed in (III) (Table 1), except that the deviations of the
In the title compound, C18H16, the [2.2]paracyclophane geom-
etry is restrained to a considerable extent despite the intro-
duction of the extra C C bridge; typical paracyclophane
features, such as the elongated CÐC bridges, are still ob-
served. However, the bridgehead atoms of the C C bridge
Ê
bridgehead atoms are slightly smaller [0.111 (3) A for C3,
Ê
Ê
Ê
0.136 (3) A for C6, 0.146 (4) A for C13 and 0.115 (4) A for
C16].
However, whereas the rings in normal [2.2]paracyclophanes
are parallel, those in (III) are signi®cantly rotated, with an
interplanar angle of 13.7 (2)ꢀ; this is also an effect that we have
noted before (Bondarenko et al., 2007) and is presumably
connected with the extra C9 C10 bridge. The bridge is not
elongated with respect to normal C C distances, but the
angles at the bridge atoms are signi®cantly narrower than
ideal sp2 angles. This leads to an extremely short contact of
Ê
are forced into unusually close proximity [2.657 (3) A], which
in turn causes the rings to be rotated to an interplanar angle of
13.7 (2)ꢀ. The packing involves hexagonally close-packed
layers of molecules parallel to the xy plane, corresponding
to the known `7,11' pattern of paracyclophanes, but without
signi®cant short intermolecular contacts.
Ê
2.657 (3) A between the formally nonbonded atoms C8 and
C11, whereas the ring rotation causes atoms C4 and C5 to be
Comment
Ê
farther than usual (> 3.2 A) from their counterparts (Table 2).
The crystal packing involves layers of molecules parallel to
In contrast to to the [2n]cyclophanes with saturated bridges ±
from [22]paracyclophane (review article: Hopf & Klein-
schroth, 1982) to superphane ([26]paracyclophane; review
1
the xy plane, with four layers per cell at z ' , 38, 85 and 87. One
8
such layer is shown in Fig. 2. The molecules are arranged in a
hexagonally close-packed pattern; connecting the centroids of
adjacent molecules, which are related by the b-glide planes,
Ê
forms a rhombus with sides of ca 7.0 A and angles of 66 and
article: Gleiter & Roers, 2004) ± relatively little is known
about the chemical behavior and the structural properties of
cyclophanes with unsaturated bridges (`cyclophenes'). We
Figure 1
The molecule of (III). Displacement ellipsoids represent 30% probability
levels.
Acta Cryst. (2007). C63, o711±o713
DOI: 10.1107/S0108270107050937
# 2007 International Union of Crystallography o711

organic compounds
bridge); 13C NMR (100.6 MHz, CD2Cl2): ꢁ 141.98, 141.45, 139.60
(3 Â s, quart. C), 139.21, 138.21, 133.47, 130.82 (4 Â s, ArÐC,
±HC CH±), 35.42, 34.29 (t, ethano bridges). Analysis calculated for
C18H16: C 93.06, H 6.94%; found: C 93.16, H 6.85%. Single crystals
were obtained from cyclohexane. Additional spectroscopic data for
(II) and (III) are given in the deposited material.
Crystal data
3
Ê
C18H16
Mr = 232.31
Orthorhombic, Pbca
V = 2422.4 (8) A
Z = 8
Mo Kꢂ radiation
1
Ê
a = 7.6402 (15) A
ꢃ = 0.07 mm
T = 153 (2) K
Ê
b = 11.775 (2) A
Ê
c = 26.927 (5) A
0.7 Â 0.5 Â 0.25 mm
Data collection
Stoe Stadi-4 diffractometer
4154 measured re¯ections
2139 independent re¯ections
1446 re¯ections with I > 2ꢄ(I )
Rint = 0.059
3 standard re¯ections
frequency: 60 min
intensity decay: 5%
Re®nement
R[F2 > 2ꢄ(F2)] = 0.054
wR(F2) = 0.150
S = 1.10
164 parameters
H-atom parameters constrained
Figure 2
3
1
8
Ê
Áꢅmax = 0.23 e A
The packing of (III), viewed parallel to the z axis in the region z ' .
3
Ê
0.24 e A
2139 re¯ections
Áꢅmin
=
113ꢀ. The approximately equidimensional nature of the mol-
ecules of simple [2.2]paracyclophane derivatives often leads to
such layer structures, in which the two cell constants asso-
Table 1
Selected geometric parameters (A, ).
ꢀ
Ê
C1ÐC2
C9ÐC10
1.580 (4)
1.332 (4)
C17ÐC18
1.578 (4)
Ê
ciated with the layer are, as here, often ca 7 and 11 A. We have
called this the `7,11'-packing pattern (El Shaieb et al., 2003;
Jones et al., 2007). In many cases, adjacent molecules are
connected by CÐHÁ Á Áꢀ contacts, sometimes extremely short,
but in (III) there are no HÁ Á Á(C9 C10) contacts shorter than
C16ÐC1ÐC2
C3ÐC2ÐC1
C8ÐC3ÐC4
C7ÐC6ÐC5
C10ÐC9ÐC8
112.4 (2)
112.6 (2)
118.1 (2)
117.2 (2)
115.9 (2)
C9ÐC10ÐC11
C12ÐC13ÐC14
C15ÐC16ÐC11
C13ÐC17ÐC18
C6ÐC18ÐC17
116.6 (2)
116.9 (2)
117.6 (2)
113.8 (2)
114.0 (2)
Ê
Ê
3.17 A and no HÁ Á Áring centroid contacts greater than 3.34 A.
Table 2
Contact distances between cyclophane rings (A).
Experimental
Ê
For the preparation of the bis-tosylhydrazone (II) of the pseudo-
geminal dialdehyde (I) (Bondarenko et al., 2007, and references
therein), a solution of (I) (1.5 g, 5.68 mmol) and p-toluenesulfonic
acid hydrazide (3.0 g, 16.12 mmol) in anhydrous tetrahydrofuran
(250 ml) was re¯uxed for 2 h in the presence of a trace of p-toluene-
sulfonic acid. After cooling to room temperature, the solvent was
removed in vacuo and the raw product puri®ed by plate chromato-
graphy on silica gel with dichloromethane/ethyl acetate (98:2 v/v).
After recrystallization from dichloromethane/ethanol, (II) (3.13 g,
92%) was obtained as colourless needles [m.p. 467 K (decomposi-
tion)]. Analysis calculated for C32H32N4O4S2 (Mr = 600.76): C 63.98,
H 5.36%; found: C 62.94, H 4.98%.
C3Á Á ÁC16
C4Á Á ÁC15
C5Á Á ÁC14
2.737 (3)
3.326 (3)
3.280 (3)
C6Á Á ÁC13
C7Á Á ÁC12
C8Á Á ÁC11
2.807 (3)
2.831 (3)
2.657 (3)
H-atom positions were calculated, after which the H atoms were
2
Ê
re®ned using a riding model with CÐH distances of 0.95 A for sp
3
and 0.99 A for sp C atoms. Uiso(H) values were ®xed at 1.2Ueq of the
Ê
parent C atoms. There is no signi®cant residual electron density that
might suggest disorder of the bridges. A rigid-body libration
correction (Schomaker & Trueblood, 1968) gave an acceptable Rlib of
Ê
0.062 and bond-length corrections of 0.005±0.006 A; corrected bond
For the preparation of (III), a solution of (II) (3.0 g, 5.0 mmol) and
sodium methoxide (3.0 g, 93 mmol) in diglyme (150 ml) was heated
under re¯ux for 3 h. After cooling to room temperature, water
(200 ml) was added and the reaction mixture was extracted with
ether. The organic phase was separated and dried (calcium chloride),
the solvent was removed by rotary evaporation, and the remainder
was puri®ed by plate chromatography on silica gel with tetrachloro-
methane/dichloromethane (9:1 v/v). After recrystallization from
dichloromethane/ethanol, (III) (0.85 g, 73%) was obtained as
colourless plates (m.p. 430±431 K). 1H NMR (400 MHz, CD2Cl2, int.
TMS): ꢁ 7.24 (s, 2H, 9-H), 6.39 (dd, Jo = 7.9 Hz, Jm = 2.1 Hz, 2H, 5-H),
6.33 (d, Jo = 7.9 Hz, 2H, 4-H), 6.23 (d, Jm = 2.1 Hz, 2H, 7-H), 3.05 (m,
4H, ethano bridge), 2.93 (m, 2H, ethano bridge), 2.61 (m, 2H, ethano
lengths are given in the deposited CIF, but uncorrected values are
used in Table 1 and the Comment section.
Data collection: DIF4 (Stoe & Cie, 1992); cell re®nement: DIF4;
data reduction: REDU4 (Stoe & Cie, 1992); program(s) used to solve
structure: SHELXS97 (Sheldrick, 1997); program(s) used to re®ne
structure: SHELXL97 (Sheldrick, 1997); molecular graphics: XP
(Siemens, 1994); software used to prepare material for publication:
SHELXL97.
Supplementary data for this paper are available from the IUCr electronic
archives (Reference: LN3070). Services for accessing these data are
described at the back of the journal.
ꢁ
o712 Broschinski et al.
C18H16
Acta Cryst. (2007). C63, o711±o713

organic compounds
Hopf, H. & Kleinschroth, J. (1982). Angew. Chem. Int. Ed. Engl. 21, 285±
295.
References
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ꢁ
Acta Cryst. (2007). C63, o711±o713
Broschinski et al. C18H16 o713