X-ray crystal structures of p-halogenated 6, 6-diphenylfulvenes

Article abstract of DOI:10.1007/s11224-010-9685-8

Crystal structures of a series of p-halogenated 6, 6-diphenylfulvenes 2-5 are reported and comparatively discussed including the known structure of the nonhalogenate parent compound 1. The molecular structures show twisted conformations of the plane aryl

Full text of DOI:10.1007/s11224-010-9685-8

Struct Chem (2011) 22:95–101
DOI 10.1007/s11224-010-9685-8
ORIGINAL RESEARCH
X-ray crystal structures of p-halogenated 6,6-diphenylfulvenes
•
Anke Schwarzer Wilhelm Seichter
•
Edwin Weber
Received: 28 July 2010 / Accepted: 3 November 2010 / Published online: 26 November 2010
Ó Springer Science+Business Media, LLC 2010
Abstract Crystal structures of a series of p-halogenated
6,6-diphenylfulvenes 2–5 are reported and comparatively
discussed including the known structure of the non-
halogenate parent compound 1. The molecular structures
show twisted conformations of the plane aryl and fulvene
subunits against each other, rather unaffected by the dif-
ferent halogen substituents. The packing structures exclu-
sively involve C–HꢀꢀꢀX (X = F, Cl, p) contacts while
HalꢀꢀꢀHal and p-stacking interactions do not occur.
For reasons of stability, 6,6-diaryl substituted derivatives of
the fulvene are the species normally being investigated in
this regard. Also, as previously demonstrated [9], 6,6-di-
arylfulvenes have proven suitable diene components in
Diels–Alder reactions [10].
Despite the broad interest in this substance class, X-ray
crystal structures of respective compounds are rare and
excepting the metal complexes [3–8] only the crystal
structure of the 6,6-diphenylfulvene (1) (Fig. 1) has been
described [8] and duplicated [11] in the literature. Under
these circumstances and to arrive at potential conclusions
relating to crystal engineering aspects [12, 13], we deter-
mined the crystal structures of a series of differently
p-halogenated 6,6-diphenylfulvenes 2–5 (Fig. 1). In com-
parison with the parent compound 1 [8, 11], the structures of
2–5 will give information about the influence of halogen
substitution on the molecular and packing structures in this
system of compounds that might be applicable to com-
pounds of similar structures.
Keywords 6,6-Diphenylfulvenes ꢀ Halogen compounds ꢀ
X-ray analysis ꢀ Supramolecular interactions
Introduction
Fulvenes, being the condensation products of 1,3-cyclo-
pentadiene with aldehydes or ketones are a very interesting
class of compounds [1]. Due to their structure featuring
three cross-conjugated double bonds, they are distin-
guished by a particular electronic system that can be
regarded as valence isomeric benzoid [2]. Referring to this
property, fulvenes have extensively been studied to show
their behaviour as organic ligands [3–8]. In this respect, a
great variety of organometallic complexes were found
differing in the modes of binding, i.e. whether the metal
centre is coordinated in ene, diene or triene fashion.
Experimental
Chemical synthesis
General remarks
Melting points were measured on a microscope heating
¨
stage PHMK Rapido (Wagetechnik Dresden). IR spectra
were obtained from a Nicolet FT-IR 510 spectrometer as
1
KBr pellet. H and 13C NMR spectra were recorded on
Bruker Avance III 500 at 500.1 and 125.8 MHz, respec-
tively, using TMS as reference. Chemical shifts for proton
and carbon resonances are reported in ppm (d). Solvents
were purified by standard procedures [14].
A. Schwarzer ꢀ W. Seichter ꢀ E. Weber (&)
Institut fu¨r Organische Chemie, TU Bergakademie Freiberg,
Leipziger Straße 29, 09596 Freiberg/Sachs, Germany
e-mail: edwin.weber@chemie.tu-freiberg.de
123

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Struct Chem (2011) 22:95–101
4,40-Dibromobenzophenone was prepared from bromo-
benzene and carbon tetrachloride as described in literature
[15]. 4,40-Diiodobenzophenone was analogously synthe-
sized [15] from iodobenzene and carbon tetrachloride.
4,40-Difluorobenzophenone, 4,40-dichlorobenzophenone and
dicyclopentadiene were purchased from Acros.
General procedure for preparation of fulvenes 2–5
The halogenated diphenylfulvenes 2–5 were obtained from
reaction of the respective benzophenone and freshly dis-
tilled 1,3-cyclopentadiene (from dicyclopentadiene) in a
freshly produced sodium ethanolate solution using the
Fig. 1 Chemical structures of the diarylfulvens studied, with
designation of ring planes
Table 1 Crystallographic data for the compounds studied
Compound
2
3
4
5
Empirical formula
Formula weight (g mol-1
Temperature (K)
C18H12F2
266.28
C18H12Cl2
299.18
C18H12Br2
388.10
C18H12I2
)
482.08
100(2)
93(2)
93(2)
100(2)
˚
Wave length (A)
0.71073
0.71073
0.71073
0.71073
Triclinic, P-1
Crystal system, space group
Unit cell dimensions
Monoclinic, P21/n
Triclinic, P-1
Triclinic, P-1
˚
a (A)
10.2407(9)
8.6735(8)
14.9909(14)
90.00
9.5397(2)
9.5268(3)
11.3248(3)
15.6599(4)
84.3280(10)
76.509(2)
65.2550(10)
1492.06(7)
4
9.5970(2)
˚
b (A)
11.0405(3)
15.5749(4)
84.4580(10)
76.4370(10)
65.0000(10)
1445.24(6)
4
11.6949(3)
15.9312(4)
84.1990(10)
76.1230(10)
66.2450(10)
1588.78(7)
4
˚
c (A)
a (°)
b (°)
c (°)
98.316(4)
90.00
3
˚
V (A )
1317.5(2)
4
Z
Calculated density (g m-3
)
1.342
1.375
1.728
2.015
Absorption coefficient (mm-1
)
0.096
0.435
5.419
3.946
F(000)
Crystal size (mm3)
552
616
760
904
0.35 9 0.26 9 0.25
2.26–29.06
-11 B h C 14
-11 B k C 11
-20 B l C 20
0.60 9 0.40 9 0.30
1.34–39.43
-17 B h C 16
-19 B k C 19
-27 B l C 27
0.45 9 0.44 9 0.16
1.34–35.00
-15 B h C 15
-18 B k C 18
-25 B l C 25
0.25 9 0.19 9 0.05
1.32–25.00
-11 B h C 11
-13 B k C 13
-18 B l C 16
H range for data collection (°)
Limiting indices
Reflections collected/unique
35595/3497
[R(int)] = 0.0421]
83408/17168
[R(int)] = 0.0270]
32223/13118
[R(int)] = 0.0394]
12654/5571
[R(int)] = 0.0270]
Completeness to H (%)
99.5
99.4
99.7
99.7
Refinement method
Full-matrix least
squares on F2
Full-matrix least
squares on F2
Full-matrix least
squares on F2
Full-matrix least
squares on F2
No. of F values used [I [ 2r(I)]
Restraints/parameters
2641
13428
9531
4677
0/181
0/361
0/361
0/361
Goodness-of-fit on F2
1.061
1.075
1.067
0.987
Final R indices [I [ 2r(I)]
R1 = 0.0416,
wR2 = 0.0938
R1 = 0.0616,
wR2 = 0.1025
0.331 and -0.211
R1 = 0.0371,
wR2 = 0.1013
R1 = 0.0548,
wR2 = 0.1135
0.687 and -0.437
R1 = 0.0445,
wR2 = 0.0891
R1 = 0.0722,
wR2 = 0.0937
0.850 and -0.939
R1 = 0.0264,
wR2 = 0.0512
R1 = 0.0356,
wR2 = 0.0542
0.574 and -0.644
R indices (all data)
-3
)
˚
Largest diff peak and hole (e A
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Struct Chem (2011) 22:95–101
97
3
(d, JHH = 8.4 Hz, 4H, H7); 7.16 (d, JHH = 8.4 Hz, 4H,
3
method of Thiele [16]. Details for the individual com-
pounds are given below.
3
3
H6); 6.62 (d, JHH = 6 Hz, 2H, H1); 6.22 (d, JHH
=
6,6-Bis(4-fluorophenyl)fulvene (2). Recrystallisation from
n-hexane yielded 35% bright red crystals (mp 98 °C).
Spectroscopic and other analytical data correspond to the
specifications from literature [17, 18].
6.4 Hz, 2H, H2). 13C NMR (CDCl3): 148.7 (C4); 144.5
(C3); 139.6 (C5); 133.5 (C6); 133.2 (C2); 131.1 (C7);
123.9 (C1); 123.6 (C8).
6,6-Bis(4-iodophenyl)fulvene (5). Recrystallisation from
ethanol yielded 9% bright red crystals (mp 138 °C). IR
(KBr): 3071; 1579; 1058; 1004; 833. H NMR (CDCl3):
6,6-Bis(4-chlorophenyl)fulvene (3). Recrystallisation from
ethanol yielded 62% bright red crystals (mp 112 °C).
Spectroscopic and other analytical data correspond to the
specifications from literature [4, 19, 20].
1
3
7.76 (3JHH = 10 Hz, 4H, H7); 7.06 (d, JHH = 10 Hz, 4H,
H6); 6.63 (d, 3JHH = 5 Hz, 2H, H1); 6.26 (d, 3JHH = 5 Hz,
2H, H2). 13C NMR (CDCl3): 149.1 (C4); 144.5 (C3); 140.2
(C5); 137.2 (C7); 133.8 (C6); 133.3 (C2); 124.0 (C1); 95.7
(C8).
6,6-Bis(4-bromophenyl)fulvene (4). Recrystallisation
from ethanol yielded 58% bright red crystals (mp
128–130 °C, lit. [19] mp 128–130 °C). IR (KBr): 3068;
1633; 1582; 1070; 1009; 832. 1H NMR (CDCl3): 7.52
Crystal structure determination
Table 2 Dihedral angles of compounds 1–5
Crystals of the compounds suitable for X-ray analysis were
formed by slow evaporation of corresponding solutions of
2–5 in ethanol. All crystals were measured on a Bruker
Kappa Apex II using graphite-monochromated Mo Ka
Denotationa 1 [11]
2
3
4
5
A/B
A/C
B/C
a
74.1
78.6
71.67(4) 78.90(3) 74.80(7)
76.23(2) 80.08(8)
80.57(10)
71.98(13)
˚
radiation (k = 0.71073 A). Data collection: SMART;
46.30(6) 44.13(6) 56.68(4) 49.20(12) 58.73(15)
44.74(6) 52.42(3) 57.72(11) 49.56(19)
57.97(6) 54.46(4) 47.58(3) 53.93(8) 47.82(12)
53.22(5) 49.05(4) 47.51(10) 53.05(14)
cell refinement: SMART; data reduction: SAINT [21].
Preliminary structure models were derived by Direct
Methods using SHELXS-97 [22] and were refined with full-
matrix least squares methods against F2 using SHELXL-97
[22]. All non-hydrogen atoms were refined anisotropically.
Designations of the ring mean planes in Fig. 1
Table 3 Selected
intermolecular hydrogen
bonding contacts
Atoms involveda
Symmetry
Angle (°)
˚
Distance (A)
D(DꢀꢀꢀA)
d(HꢀꢀꢀA)
h(D–HꢀꢀꢀA)
1 [11]
C12A–H12AꢀꢀꢀCg6
C16–H16ꢀꢀꢀCg1
C22–H22ꢀꢀꢀCg2
C26A–H26AꢀꢀꢀCg4
1 - x, 1 - y, -z
1 - x, -y, 1 - z
1 - x, -y, 1 - z
1 - x, 1 - y, -z
3.8117
3.5352
3.8584
3.4747
2.91
2.88
2.94
2.86
159
127
163
123
2
3
C9–H9ꢀꢀꢀF2
1 - x, 1 - y, 2 - z
1 - x, 2 - y, 2 – z
-x, -y, -z
3.4508(16)
3.2701(14)
3.4477(14)
3.7006(13)
2.56
2.48
2.81
2.81
157
141
125
157
C15–H15ꢀꢀꢀF2
C6–H6ꢀꢀꢀCg1
C12–H12ꢀꢀꢀCg1
-x, -y, -z
C18–H18ꢀꢀꢀCl2
C33–H33ꢀꢀꢀCl3
C9–H9ꢀꢀꢀCg1
x, -1 ? y, z
3.7795(9)
3.8364(9)
3.7554(17)
3.5265(16)
2.85
2.90
2.99
2.75
168
169
140
142
1 ? x, -1 ? y, z
x, 1 - y, 1 - z
1 - x, 2 - y, -z
C21–H21ꢀꢀꢀCg3
4
5
C21–H21ꢀꢀꢀCg3
C23–H23ꢀꢀꢀCg3
1 - x, 2 - y, -z
-x, 2 - y, -z
3.819(3)
3.527(3)
2.94
2.72
154
143
a
Cg1 is defined as the centre of
the ring with C14–C18, Cg3 is
defined as the centre of the ring
with C32–C36, Cg4 is defined
as the centre of the ring with
C32–C36
C3–H3ꢀꢀꢀCg1
C5–H5ꢀꢀꢀCg1
1 - x, 1 - y, 1 - z
-x, 1 - y, 1 - z
3.611(6)
3.786(5)
2.78
2.91
146
153
123

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Struct Chem (2011) 22:95–101
Structures of halogenated diphenylfulvenes 2–5
Multiscan absorption corrections were applied using the
SADABS program [23]. All non-hydrogen atoms were
refined anisotropically. Geometrical calculations were
performed using PLATON [24] and molecular graphics
were generated using Ortep-3 [25] and SHELXTL [22].
In contrast to the fluorinated diphenylfulvene 2, which
crystallizes in the monoclinic space group P21/n with one
molecule in the asymmetric unit, all the other examined
fulvenes 3–5, and including the parent fulvene 1 [11] were
found to crystallizes with two molecules per asymmetric
unit in the triclinic space group P-1. Without exceptions,
both the phenyl rings (A, B) and the cyclopentadienyl unit
(C) of the molecular structures are planar not deviating
significantly from the least-squares plane of the rings
(Table 2). Considering the bond lengths of the cylopenta-
dienyl ring, this unit presents itself more like a 1,4-diene
than an aromatic system. Bolte and Amon [11] found
that the dihedral angles involving the planes of fulvene (C)
and phenyl rings (A, B) are 46.30° and 57.97° for one
molecule and 44.74°, 53.22° for another one. The present
halogenated diphenylfulvenes behave similar in this
respect. Namely, the torsion angles including the aryl rings
and the fulvene unit range between 44.14° (compound 2)
and 49.56° (compound 5) for the one aryl ring, and from
Results and discussion
Crystallization of the halogenated diphenylfulvenes 2–5
(Fig. 1) from ethanol solution yielded solvent-free species.
Crystal data and details of the refinement of the structures
2–5 are summarized in Table 1. Selected torsion angles for
the diphenylfulvene derivatives that define the principal
molecular conformations are listed in Table 2. Parameters
of the weak intermolecular interactions are specified in
Table 3. Molecular structures 2–5, including atom label-
ling schemes and ring specification are shown in Fig. 2,
while packing illustrations and diagrams involving specific
modes of C–HꢀꢀꢀX interactions are given in Figs. 3, 4,
and 5.
Fig. 2 Perspective views of 2
(a), 3 (b), 4 (c) and 5 (d),
including atom numbering
scheme. Thermal ellipsoids are
at 50% probability level
123

Struct Chem (2011) 22:95–101
99
Fig. 3 Crystalline packings of
1 (a) and 2 (b) viewed down the
crystallographic c-axis.
Noncovalent C–HꢀꢀꢀF
interactions are represented as
broken lines. Non-relevant
hydrogen atoms are omitted
for clarity
Although the framework of the parent 6,6-diphenylful-
vene 1 is composed of three p-electron containing plane
subunits, though twisted against each other, p-stacking
interactions [26] between adjacent molecules are absent in
the crystal structure [11], whereas the packing of 1 is
dominated by several C–Hꢀꢀꢀp contacts [27]. In the same
way behaves the compound 2 since there is no close
intermolecular distance in the crystal structure (closest
˚
distance between adjacent aryl rings 4.7 A) that would
indicate a p-stacking interaction [26]. Instead, a weak
˚
bifurcated C–HꢀꢀꢀF contact [9] (d = 2.56 A, h = 157°,
˚
d = 2.48 A, h = 141°) leads to a zigzag chain along the
crystallographic b-axis. In addition, C–Hꢀꢀꢀp interactions
[27] connect the zigzag chains to a molecular network and
stabilize the crystal structure of the compound 2.
Fig. 4 Crystalline packing of 3 showing the noncovalent C–HꢀꢀꢀCl
interactions represented as broken lines. Non-relevant hydrogen
atoms are omitted for clarity
Substitution of the fluorine atoms in 2 for chlorine in
the molecule 3 does not involve significant changes in the
crystal structure. As before, none of the aryl rings of 3 is
included in p-stacking interaction, but several C–Hꢀꢀꢀp
contacts are found. Moreover, two weak C–HꢀꢀꢀCl
52.42° (compound 3) to 58.73° (compound 5) for the other.
Hence, in no case we see coplanarity of the rings including
the fulvene moiety, suggesting missing conjugation of the
p-systems.
Fig. 5 Crystalline packing of 4
(a) and 5 (b) viewed down the
crystallographic a-axis. All
hydrogen atoms are omitted for
clarity
123

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Struct Chem (2011) 22:95–101
contacts [28, 29] lead to chain formations in the crystal
structure, one being along the crystallographic b-axis, the
other one parallel to the ab plane. However, a remarkable
fact of the crystal structure of 3 is the absence of an
inter-halogen contact [30, 31] which is often found in
the structure of similar chloro containing compounds
[32–34].
interfering with common aspects of crystal engineering
[12, 13].
Supplementary data
CCDC 784790 (2), 784788 (3), 784789 (4) and 784791 (5)
contain the supplementary crystallographic data for this
paper. These data can be obtained free of charge at www.
ccdc.cam.ac.uk/data_request/cif [or from the Cambridge
Crystallographic Data Centre (CCDC), 12 Union Road,
Cambridge CB2 1EZ, UK; fax: ?44(0)1223-336033;
e-mail: deposit@ccdc.cam.ac.uk].
Even in the structure of 4, referring to p-bromo substi-
tuted diphenylfulvene, there is no inter-halogen contact,
although this type of BrꢀꢀꢀBr interaction, both in head-on
and side-on mode [30, 31], is rather frequent for related
compounds [34–37]. Actually, the bromine atoms of 4 are
not involved in any relevant contacts including C–HꢀꢀꢀHal
as before. Only several weak C–Hꢀꢀꢀp contacts are shown
to stabilize the crystal packing. The crystal structure of
the iodo derivative 5 is very similar to 4, also having only
C–Hꢀꢀꢀp contacts for stabilization and lacking halogen
involved contacts.
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A series of 6,6-diphenylfulvenes 2–5 featuring fluorine,
chlorine, bromine and iodine substituents in the p-positions
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