Preparation of donor-acceptor substituted fluorostilbenes and crystal chemistry of fluorinated (E)-4-(4-halogeno-styryl)-benzonitriles

Article abstract of DOI:10.1016/j.jfluchem.2008.09.012

The syntheses and crystal structures of a series of fluoro-substituted halogeno (Cl, Br, I)-cyano-stilbenes containing donor and acceptor groups (D-π-A) are reported. These molecules show a tendency to form antiparallel chain-like structures and herringbone packing, crystallising predominantly in a centric space group. However, second harmonic generation measurements bear evidence for orientational disorder leading to partial polar order below the ordinary X-ray structure determination limit. Some co-crystals are isostructural with their components. The non-fluoro as well as the halogeno-fluoro substituted components of co-crystals seem to impose their crystal structure on the complementary fluoro- or cyano-fluoro substituted components. Co-crystallization enhanced the deviation from centrosymmetry.

Full text of DOI:10.1016/j.jfluchem.2008.09.012

Journal of Fluorine Chemistry 130 (2009) 175–196
Contents lists available at ScienceDirect
Journal of Fluorine Chemistry
journal homepage: www.elsevier.com/locate/fluor
Preparation of donor–acceptor substituted fluorostilbenes and crystal chemistry
of fluorinated (E)-4-(4-halogeno-styryl)-benzonitriles
a
a
a
a
a
a
´
¨
Raul Mariaca , Gael Labat , Norwid-Rasmus Behrnd , Michel Bonin , Fabien Helbling , Patrick Eggli ,
Gae¨tan Couderc a, Antonia Neels b, Helen Stoeckli-Evans b, Ju¨rg Hulliger a,
*
a Department of Chemistry and Biochemistry, University of Berne, Freiestrasse 3, CH-3012 Berne, Switzerland
b
ˆ
Institute of Microtechnique, Jaquet Droz 1, CP 526, CH-2002 Neuchatel, Switzerland
A R T I C L E I N F O
A B S T R A C T
Article history:
The syntheses and crystal structures of a series of fluoro-substituted halogeno (Cl, Br, I)-cyano-stilbenes
Received 21 July 2008
containing donor and acceptor groups (D-p-A) are reported. These molecules show a tendency to form
Received in revised form 23 September 2008
Accepted 24 September 2008
Available online 7 October 2008
antiparallel chain-like structures and herringbone packing, crystallising predominantly in a centric space
group. However, second harmonic generation measurements bear evidence for orientational disorder
leading to partial polar order below the ordinary X-ray structure determination limit. Some co-crystals
are isostructural with their components. The non-fluoro as well as the halogeno-fluoro substituted
components of co-crystals seem to impose their crystal structure on the complementary fluoro- or
cyano–fluoro substituted components. Co-crystallization enhanced the deviation from centrosymmetry.
ß 2008 Published by Elsevier B.V.
Keywords:
Donor acceptor halogenostyryl-
benzonitriles
HWE approach
Heck coupling
Halogen bonding
Co-crystals
SHG
Crystal structure
1. Introduction
molecules pertaining to fundamental studies of fluoro-organic
compounds.
Compared to interactions observed in crystal structures
between arenes, relative strong intermolecular interactions
between arene and perfluoroarenes have been reported in many
areas of chemistry and biochemistry. Binary co-crystals, i.e.
crystals containing complementary pairs of molecules, provide
an interesting class of materials for understanding intermolecular
non-covalent interactions [1]. Some examples such as the co-
crystallization of octafluoronaphtalene with trans-stilbene from
solutions have been reported recently [2]. We have extended this
topic by exploring the formation and structural properties of new
co-crystals based on fluorinated (E)-4-(4-halogenostyryl)-benzo-
nitriles and their corresponding H-analogues [3]. However, many
of the synthetic procedures leading to fluorine containing
materials are not as preponderant as for the hydrogen containing
analogues. They require readily accessible fluorinated materials
and detailed reports on versatile synthetic procedures. In this
contribution we focus on the synthesis of a series of fluorinated
Some molecules we present here show crystal structures
having CNꢀ ꢀ ꢀI interactions that have been described as important
motifs for making co-crystals [4]. Halogen bonding (XB) is a strong,
specific and directional interaction that gives rise to well defined
supramolecular synthons. XB relevance in fields as various as
superconductors has been found [5]. Indeed supramolecular
organic conductors based on halogen-bonded iodotetrathiafulva-
lenes (TTFs) have been reported [6]. Recently, XB has also proven to
be able to form liquid crystals from nonmesomorphic components.
This is the case of the complexes between 4-alkoxystibazoles and
iodopentafluorobenzene [7]. Substrate–receptor bindings allowing
the resolution of racemic compounds i.e. resolution of (rac)-1,2-
dibromo-hexafluoro-propane through halogen-bonded supramo-
lecular helices have been highlighted [8]. Particularly important
reviews on XB issues have been published by Metrangolo et al. [9].
In addition, it has been shown that fluorination of an iodo/
bromo substituted phenyl ring, greatly enhances the electron-
acceptor ability of such substituents [10]. The attractive nature of
the halogen (XB) bonding causes CNꢀ ꢀ ꢀX distances shorter than the
sum of van der Waals radii of involved atoms. The stronger the
interaction, the shorter the CNꢀ ꢀ ꢀX distance is [11].
* Corresponding author. Tel.: +41 31 6314241; fax: +41 31 6314244.
E-mail address: publication.hulliger@iac.unibe.ch (J. Hulliger).
0022-1139/$ – see front matter ß 2008 Published by Elsevier B.V.
doi:10.1016/j.jfluchem.2008.09.012

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R. Mariaca et al. / Journal of Fluorine Chemistry 130 (2009) 175–196
Scheme 2. Preparation of 4-iodobenzaldehyde 3: (a) NaBH4, THF; (b) CrO3/pyridine/
MeCl2.
phosphate with a benzyl halide to produce an alkyl phosphonate.
We have prepared fluorinated stilbenes by using sodium hydride in
tetrahydrofurane or sodium ethanolate in ethanol. The HWE-
precursors have been prepared by using the methods described
below.
Scheme 1. Basic building blocks used to form co-crystals.
Although some tetra- and penta-fluorostilbenes are known
and examples containing fluorinated push–pull stilbenes have
been described in the literature [12], the use of perfluorinated
2.2. Preparation of HWE precursors
aromatic stilbenes A-p-D bearing substituents such as CN (A)
and halogens X (D) represents a new concept. For this reason we
report on the synthesis and crystal structures of an octafluoro
compound featuring acceptor and donor properties, including
particularly hydrogen analogues and tetrafluorinated derivatives
(see Scheme 1)
Precursors like 4-fluoro- and 4-chloro-benzaldehyde were
commercially available. 4-iodobenzaldehyde 3 was prepared as
described in the literature [18], by reduction (NaBH4) followed by
an oxidation step with CrO3/pyridine/MeCl2 (PCC) (Scheme 2).
An efficient synthesis of 2,3,5,6-tetrafluoro-4-halogenatedben-
zaldehyde 5 was developed to obtain chloro or bromo derivatives
as described in the literature [19]. In this procedure, a mixture of
commercial available pentafluoro-benzaldehyde 4 and lithium salt
was heated to 150 8C in absolute N-methylpyrrolidone for 3 h
(Scheme 3).
2. Results and discussion
2.1. Horner–Wadsworth–Emmons approach
For the preparation of 2,3,5,6-tetrafluoro-4-iodo-benzaldehyde
9, we followed the method published in a recent paper [20]
(Scheme 4).
The commercially available starting material 6 was lithiated.
After formylation with an excess of ethyl formate, the obtained
tetrafluorinated benzaldehyde was subsequently protected by
forming the acetal 7, lithiation of compound 7 and subsequent
Horner and coworkers were the first to modify the Wittig
reaction: They reacted phosphoryl-stabilized carbanions with
ketones and aldehydes to make alkenes [13]. Derivatives of
diphenyl-phosphineoxide and diethylbenzyl phosphonate were
used to obtain these particular carbanions. Wadsworth and
Emmons, on the other hand, focused primarily on phosphonate
carbanions to produce olefins [14]. Both phosphonate-mediated
modifications of the Wittig reaction were combined and referred to,
as the Horner–Wadsworth–Emmons (HWE) olefination reaction.
The HWE reaction provides many advantages over the
traditional Wittig reaction. Phosphonate carbanions are recog-
nized to be more nucleophilic than phosphonium ylides, providing
a higher diversity of aldehydes and ketones to react with these
particular carbanions [15]. A problem associated with the Wittig
reaction is the phosphineoxide formed, which is often difficult to
separate from the desired product. The phosphate ion formed from
the HWE reaction is water-soluble, thus providing easier separa-
tion from the final product. Finally, smooth alkylation is possible
on the
a-carbon of the phosphonatecarbanion, whereas phospho-
nium ylides generally do not alkylate well [16].
The preparation of phosphonates takes place through the
Michaelis–Arbuzov reaction [17], i.e. the reaction of trialkyl
Scheme 3. Preparation of 4-chloro-2,3,5,6-tetrafluorobezaldehyde 5: (c) LiCl/NMP,
150 8C.
Scheme 4. Synthetic route for 4-iodo-2,3,5,6-tetrafluorobenzaldehyde 9: (d) n-BuLi; EtO-CHO; HO–CH2–CH2–OH/p-TsOH; (e) n-BuLi, I2; (f) TFA/HCl/H2O.

R. Mariaca et al. / Journal of Fluorine Chemistry 130 (2009) 175–196
177
Scheme 5. Synthetic route for the preparation of 4-(bromomethyl)-2,3,5,6-tetrafluoro-benzonitrile 13: (g) SOCl2/NH4OH; (h) pyridine/POCl3; (i) NBS/CCl4.
iodination of the lithio derivative led to the 4-iodoacetal 8. After
acetal hydrolysis, the desired iodinated aldehyde 9 was isolated.
The preparation of the fluorinated phosphonate 13 as precursor
for the HWE-coupling was already reported [3] by the route
described in Scheme 5.
correspond to the compounds where the I-atom is attached to
the fluorinated phenyl ring [10].
2.4. Heck approach (method C)
Nowadays, the Heck reaction [21] is one of the most valuable C–
C bond-forming process promoted by transition metals offering an
alternative access towards stilbenes, which we used for the
preparation of H-cyanostilbenes 17, 18, as well as F-cyanostilbenes
19 and 25.
2.3. Synthesis of H- and F-stilbenes
HWE reactions were carried out at room temperature using a
base method A and/or method B by stirring overnight. Trans-
stilbenes 16, 17 and 18 were obtained by coupling of 15 with the
corresponding aldehydes described before (Scheme 6). The
progress of the reaction was followed by GC–MS analysis.
Products were obtained (42–70%) and no trace of the cis-isomer
was detected. E-stilbenes 19–21 were prepared similarly by
coupling the aldehydes 4, 5 and 9, with the phosphonate
derivative 15 (16–50%). Compound 13 undergoes the Michae-
lis–Arbuzov reaction to obtain a fluorophosphonate as inter-
mediate, which reacts with the corresponding aldehydes to afford
22–24. In the same way, the synthesis of the octafluorinated
stilbenes 25–27 was performed by HWE coupling of 4, 5 and 9
with 13 (30–50%). Solid products were isolated by crystallization
in dichloromethane or methanol and characterized by their
melting points (Table 1).
Cross-coupling reactions were carried out using a catalyst
composed of Pd(OAc)2, P(o-tolyl)3 each in 1% molar ratio
compared to the aryl halide. A slight excess (1.5 equivalents) of
the appropriate styrene was employed. The reaction took place
during refluxing over 12 h, in dry deoxygenated amine solvents.
The progress of the reactions was monitored by GC–MS, which
could also detect the formation of side products. Using the Heck
coupling, previously tested on the preparation of H-stilbenes,
good results and full conversion of the substrates (Scheme 10),
were obtained. By applying this method on the fluorinated
compounds, however, we observed only partial conversion of the
olefinic substrate, when the entire brominated compound was
consumed. In most of cases, traces of the reduced bromide were
found.
Comparing both series: X–C6F4–CH CH–C6F4–CN and X–C6H4–
CH CH–C6H4–CN, the former showed lower melting temperatures
probably due to weak molecular Fꢀ ꢀ ꢀF interactions and the lack of
Nꢀ ꢀ ꢀI interactions in 25 and 26. Compound 27 makes an exception
and has a higher melting point. The interesting fact is that all iodine
compounds showed higher melting temperatures than the fluoro
and chloro analogues. This might be related to a stronger Nꢀ ꢀ ꢀI
interaction; indeed the highest values (211 8C and 240 8C)
These observations indicate that the olefin and the bromide
are competing in the coordination sphere of Pd(0): coordination-
insertion against oxidative addition. Albeniz et al. [22] observed
that the reaction increases with higher concentration of styrene,
favouring the oxidative addition process. However, a large excess
can stop the reaction. Indeed, for tetrafluoroaryl and penta-
fluoroaryl bromides, these authors could prove that the
coordination-insertion is rate determining, and can be switched
Table 1
Yield, melting point, packing mode, SHG and UV spectra of trans-stilbenes.
Molecule
Packing
SHG
mp (8C)
lmax
emax
Yield (%)
16
17
18
19
20
21
22
23
24
25
26
27
F–C6H4–CH CH–C6H4CN
Cl–C6H4–CH CH–C6H4CN
I–C6H4–CH CH–C6H4CN
F–C6F4–CH CH–C6H4–CN
Cl–C6F4–CH CH–C6H4–CN
I–C6F4–CH CH–C6H4–CN
F–C6H4–CH CH–C6F4–CN
Cl–C6H4–CH CH–C6F4–CN
I–C6H4–CH CH–C6F4–CN
F–C6F4–CH CH–C6F4–CN
Cl–C6F4–CH CH-C6F4–CN
I–C6F4–CH CH–C6F4–CN
Herringbone
Herringbone
–
1D chain-like + 3D network
1D chain-like + 3D network
1D chain-like + 2D network
1D chain-like + 3D network
3D network
+
183–185
174–177
189–195
150–153
185–187
>240
322
329
329
312
318
334
328
332
339
312
318
326
25,000
48,000
67,500
52,400
62,000
25,000
26,100
33,100
66,300
54,000
65,000
72,000
42
56
70
16
57
50
54
66
56
51
31
42
+
ꢁ
+
Herringbone
Herringbone
–
ꢁ
+
1D chain-like + 2D network
1D chain-like + 3D network
1D chain-like + 3D network
1D chain-like + 3D network
3D network
–
ꢁ
ꢁ
+
145–147
212–214
211–213
84–87
Herringbone
Herringbone
Herringbone
Herringbone
–
ꢁ
ꢁ
+
3D network
136–138
211
1D chain-like + 3D network
Br–C6H4CH CH–C6H4CNa
Br–C6F4CH CH–C6H4CNa
Br–C6H4CH CH–C6F4CNa
Br–C6F4CH CHC6F4CNa
Herringbone
3D network
ꢁ
ꢁ
ꢁ
ꢁ
195
150
196
149
–
1D chain-like + 3D network
1D chain-like + 3D network
3D network
Herringbone
–
a
Syntheses and crystal structures described elsewhere [3].

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R. Mariaca et al. / Journal of Fluorine Chemistry 130 (2009) 175–196
Scheme 6. (j) P(OEt)3, 110 8C; (k) NaH/THF; (l) NaOEt/EtOH.
to oxidative addition if a large excess of olefin is used. Thus, the
best reaction conditions can be reached by adjusting the actual
ratio of halo-aryl to olefin for each combination of substrates.
Working with a small olefin excess (1:1.5) led to 12 and 22
(Scheme 7). Despite these limitations, the authors reported about
new catalytic systems for the Heck reaction using an efficient
catalyst including fluorinated precursors [Pd(C6F5)Br(NCMe)2]
and (NBu4)2[Pd2-m-Br)2(C6F5)Br2].

R. Mariaca et al. / Journal of Fluorine Chemistry 130 (2009) 175–196
179
Scheme 7. Heck-coupling for the preparation of 17, 19, 25 and 28: (m) Pd(OAc)2, NEt3/P(o-tolyl)3, dioxane, reflux; (n) Pd(OAc)2, NEt3/P(o-tolyl)3, CH3CN, reflux.
The competition between the HWE and the Heck approach
depends on the ease of the corresponding precursors preparation,
and the robustness of the reaction protocols for these substrates,
often altered in their reactivity if compared to their H-analogues.
For the Heck coupling, the precursors are most of all 4-
halogenated-tetrafluoro-styrenes, which may be obtained over
several reaction steps [23] (Scheme 8). While, for the HWE-
approach, the different 4-bromo- and chloro-tetrafluoro-benzal-
dehydes are often easily accessible by nucleophilic substitution of
the commercially available pentafluoro-benzaldehyde (Schemes 3
and 4).
All the obtained stilbenes were identified by 1H NMR, 13C NMR
and 19F NMR spectroscopy. The chemical displacements of olefinic
protons Ha and Hb and their doublet multiplicities ( = 6.57–7.46
and 6.97–7.60 with large coupling constants of about J = 16 Hz),
were found by 1H NMR, which are specific for trans-stilbenes.
The UV spectra of the perfluorinated X–C6F4–CH CH–C6F4-CN
series (25–27) as well as the partial fluorinated X–C6F4–CH CH–
d

180
R. Mariaca et al. / Journal of Fluorine Chemistry 130 (2009) 175–196
Scheme 8. Synthesis of 4-halo-2,3,5,6-tetrafluoro-styrene 32: (o) Mg, THF; (p) CH3-CHO/THF; (q) distilled over P2O5.
˚
C6H4–CN (19–21) analogues showed a hypsochromic shift (blue
shift) compared to the H-homologues X–C6H4–CH CH–C6H4–CN
(16–18). In contrast, the series X–C6H4–CH CH–C6F4–CN (22–24)
showed a bathochromic shift (red shift) compared to the H-
homologues (16–18). This is due to the inversion of the charge
distribution, which has been described in our previous work on the
subject, calculated for the bromo derivatives [3]. Indeed, when the
acceptors (CN or F) are placed on one side of the benzene ring (22–
24), making up the largest dipole moment, a red shift took place.
Whereas in all cases where the acceptors are placed on both
aromatic rings (19–21 and 25–27; dipole moment being smaller) a
blue shift was observed.
and C Cꢀ ꢀ ꢀPh interactions (dmin = 3.49 A) and hydrogen bonds,
˚
with an interlayer distance of 3.451 A.
2.5.2. (E)-4-(4-chlorostyryl)-benzonitrile 17
Compound 17 crystallized in a centric space group P21/c (Fig. 4).
The structure is similar to that of 16, i.e. molecules are arranged in
˚
parallel chains aligned by short CNꢀ ꢀ ꢀH and Clꢀ ꢀ ꢀH bonds (2.470 A
˚
and 2.908 A). CH8Cl 17 shows a typical herringbone structure with
nearly orthogonally oriented planes (76.158). Stacking along the c-
axis is held through CNꢀ ꢀ ꢀH bonds (2.736 A). Similarly to molecule
˚
16, the crystal structure of 17 reveals orientational disorder over
two positions of Cl and CN. However, contrary to F, Cl produces
intermolecular contacts in the packing. Therefore, three different
graph-set drawings (Fig. 4) are presented below to resume these
interactions. These representations reveal similar infinite chains
C1,1(12), C1,1(23) and rings R2,2(10), R2,2(9). However, some
extra features appear in the first and second level graph-set such as
C1,1(5), C1,1(11), C1,1(7) and R2,2(8), mainly due to the Cl atom
replacing the F atom in 16.
2.5. Crystal structures (see Tables 2 and 3)
2.5.1. (E)-4-(4-fluorostyryl)-benzonitrile 16
Compound 16 crystallized in the non-centrosymmetric space
group P21 (Figs. 1–3). It forms crystals showing
a typical
herringbone pattern with nearly orthogonal oriented planes
(79.268). The packing of this molecule undergoes some orienta-
tional disorder over two positions for F and CN. For clarity on the
graph-set drawing, the F atom is omitted, as it does not create any
special interaction with other atoms. At a first look (first level
graph-set), the crystal structure is characterized by H-bonding
between CPh-H and the cyano group or the F atom of adjacent
molecules, forming endless molecular chains, which are described
as C1,1(12) and C1,1(23) creating parallel chains and C1,1(12)
2.5.3. (E)-4-(4-iodostyryl)-benzonitrile 18
Compound 18 crystallized in the centric space group P21/n
(Figs. 5 and 6). The molecules form antiparallel helicoidal endless
˚
chains through CNꢀ ꢀ ꢀI contacts (3.261 A, 172.068) described at the
first level graph-set as C1,1(13). The individual molecules also
exhibit a dihedral angle between the phenyl rings of 16.488. The
chains are connected by very short interplanar Hꢀ ꢀ ꢀI bonds
˚
˚
creating a herringbone pattern (C–Hꢀ ꢀ ꢀN 2.685 A). At the second
(3.162 A), creating another infinite chain C1,1(10), resulting in
˚
level graph-set, molecules generate ring patterns R2,2(10) or
an interlayer distance of 3.440 A.
R2,2(9) created through the same two C–Hꢀ ꢀ ꢀN hydrogen bonds
˚
˚
˚
˚
(2.431 A and 2.465 A) and C–Hꢀ ꢀ ꢀF motives (3.016 A and 3.069 A)
between two adjacent molecules as for the parallel chains. The
stacks along the a-axis are held together through CNꢀ ꢀ ꢀPh, Fꢀ ꢀ ꢀPh
2.5.4. (E)-4-(4-fluoro-2,3,5,6-tetrafluorostyryl)-benzonitrile 19
Compound 19 crystallized in the centric space group P21/c with
two independent molecules in the unit cell (Figs. 7 and 8). Again,
this compound forms crystals showing a typical herringbone
structure with nearly orthogonally oriented planes (77.488 and
77.958) created by infinite chains C1,1(10), C2,2(15), C2,2(16),
Fig. 1. View of 16 along the c-axis, through the ab-plane.
Fig. 2. View of 16 crystal packing related to its graph-set drawing (Fig. 3).

Table 2
Summary of X-ray diffraction crystal structures.
Sample
16
17
18
19
20
21
22
23
24
25
26
27
[16ꢀ25]
P21/c
[17ꢀ26]
P21/c
[18ꢀ27]
P-1
[21ꢀ24]
P1
Space group
P21
P21/c
P21/n
P21/c
P21/c
P-1
P-1
P21/c
Cc
C2/c
C2/c
P-1
˚
a (A)
4.7403(9) 4.7445(3)
9.970(2)
12.063(2) 12.1462(9) 27.182(2)
6.2058(5)
14.8605(13) 7.7730(7)
7.9947(16) 7.1424(16) 9.3335(12) 20.9120(12) 7.5372(8) 7.6169(15) 7.4365(6)
4.7078(11) 4.7677(10) 7.7885(15) 8.0489(16)
10.229(3) 10.518(2) 13.683(3) 8.6192(17)
˚
b (A)
10.2736(10) 7.5004(8)
10.0540(5) 13.7839(13) 8.401(2)
7.2901(17) 10.7836(10) 17.2400(8) 9.3970(7) 9.3431(19) 8.1145(7)
˚
c (A)
17.1887(16) 12.0296(13) 10.348(3) 12.239(3)
12.5299(17) 13.9210(8) 35.668(4) 37.386(7) 13.7580(11) 12.998(3) 12.914(3) 13.946(3) 10.368(2)
a
b
g
(8)
(8)
(8)
90
90
90
90
90
91.56(3)
94.99(3)
98.886(19) 90
90
90
90
80.017(7)
77.778(7)
61.853(6)
90
90
66.616(14) 92.09(3)
84.745(15) 94.78(3)
74.775(15) 106.89(3)
1316.1(4) 684.5(2)
99.29(3)
90
99.557(6)
90
94.462(9)
90
109.350(7) 92.662(8)
96.147(19) 97.490(10) 127.109(4) 92.797(9) 94.87(3)
99.199(18) 99.09(3)
90
90
107.76(3) 103.197(18) 90
90
90
90
90
90
3
˚
V (A )
(g cmꢁ3
562.63(18) 583.83(8)
1261.37(19) 2423.1(3)
1287.5(2)
1.608
173(2)
658.3(3)
2.034
606.2(3)
1.617
1250.4(3)
1.656
4002.5(4)
2.007
2523.2(4) 2651.0(9) 712.83(10) 617.9(3)
639.4(2)
1.601
173(2)
r
)
1.318
1.363
1.744
1.618
1.933
1.922
2.213
1.56
2.034
1.966
Measurement
temperature
SOF
173(2)
153(2)
173(2)
153(2)
173(2)
173(2)
173(2)
173(2)
153(2)
173(2)
173(2)
173(2)
173(2)
173(2)
0.553(11) n.a.
n.a.
n.a.
n.a.
n.a.
n.a.
n.a.
n.a.
n.a.
n.a.
n.a.
0.534(14) 0.524(10) n.a.
0.845(3)
0.51(6)
5,182
Flack parameter 0(4)
n.a.
n.a.
n.a.
n.a.
n.a.
n.a.
n.a.
0.50(3)
38,546
n.a.
n.a.
n.a.
n.a.
n.a.
n.a.
Reflections
collected
Unique
3,918
8,346
8,573
25,790
18,012
5,131
8,677
15,529
10,272
2,325
13,910
4,383
4,060
22,729
1,941
1,636
1,617
1,558
2,443
1,791
6,419
4,990
3,474
2,615
2,380
1,238
3,273
1,884
3,382
2,934
10,532
8,720
2,263
1,767
2,325
1,731
3,827
3,375
1,091
588
1,106
780
7,144
4,804
4,290
3,667
reflections
Unique
reflections
(I > 2
Rint
Rsigma
s(I))
0.165
0.108
0.1
0.049
0.026
0.076
0.078
0.052
0.05
0.062
0.038
0.052
0.07
0.045
0.026
0.054
0.072
0.134
0.214
0.11
0.048
0.045
0.048
0.092
0.033
0.02
0.076
0.05
0.119
0.072
0.062
0.079
0
0.049
0.034
0.028
0.033
0.084
0.061
0.141
0.19
0.076
0.048
0.1
0.1
0.069
0.047
0.06
0.029
0.108
0.123
0.077
0.053
0.09
R1 (I > 2
s(I))
0.03
0.031
0.037
0.047
0.057
R1 (all
0.108
0.049
0.165
0.124
0.068
reflections)
wR2
Goof
0.294
1.149
0.22
0.16
0.074
0.986
0.82
0.142
1.095
0.38
0.139
1.119
0.27
0.336
1.076
2.71
0.14
0.091
1.032
0.29
0.126
1.075
2.33
0.187
1.059
0.37
0.309
1.138
0.59
0.082
0.666
0.6
0.45
0.297
1.097
0.53
0.157
1.069
1.17
0.152
1.011
1.04
1.3
0.991
0.21
1.594
0.96
ꢁ3
Dr+ (eA ꢁ3
)
0.26
˚
Drꢁ (eA
)
ꢁ0.2
ꢁ0.24
693,730
ꢁ0.58
693,731
ꢁ0.23
693,732
ꢁ0.33
693,733
ꢁ2.14
693,734
ꢁ0.24
693,735
ꢁ0.27
693,736
ꢁ1.81
693,737
ꢁ0.42
ꢁ0.51
ꢁ1.11
693,740
ꢁ0.48
693,741
ꢁ0.34
693,742
ꢁ1.99
693,743
ꢁ1.49
693,744
˚
Nos CCDC
693,729
693,738 693,739

182
R. Mariaca et al. / Journal of Fluorine Chemistry 130 (2009) 175–196
Table 3
Selected geometrical parameters for intermolecular contacts in the crystal structures.
˚
˚
Compound
Interaction
d (A)
u
(8)
Compound
Interaction
d (A)
u (8)
16
C(16)–H(16)ꢀ ꢀ ꢀN(11)
C(6)–H(6)ꢀ ꢀ ꢀN(1)
C(8)–N(1)ꢀ ꢀ ꢀPh
2.431
2.465
3.477
3.493
3.546
3.594
3.429
3.458
2.470
2.908
3.261
3.162
2.645
2.649
2.836
2.708
2.881
2.832
2.937
2.933
3.581
3.294
3.484
3.560
2.548
2.546
2.467
2.977
2.840
2.632
2.568
2.994
2.499
2.633
2.559
2.628
2.604
3.073
2.757
2.773
2.631
2.616
3.466
3.644
3.486
3.541
3.260
3.188
3.170
2.615
2.701
2.745
2.446
2.821
2.881
2.880
2.849
2.864
2.903
2.894
3.086
3.203
3.178
2.922
2.888
2.886
2.919
3.110
3.042
2.925
2.927
2.745
2.906
2.930
161.78
163.57
[17ꢀ26]
C(2)–H(2)ꢀ ꢀ ꢀN(1)
C(2)–H(2)ꢀ ꢀ ꢀCl(1)
C(6)–F(4)ꢀ ꢀ ꢀCl(2)
C(2)–F(1)ꢀ ꢀ ꢀCl(1)
C(2)–F(1)ꢀ ꢀ ꢀN(1)
C(5)–F(3)ꢀ ꢀ ꢀN(1)
C(6)–F(4)ꢀ ꢀ ꢀN(1)
C(6)–F(4)ꢀ ꢀ ꢀF(2)
C(2)–F(1)ꢀ ꢀ ꢀF(1)
C(6)–F(4)ꢀ ꢀ ꢀF(1)
C(6)–F(4)ꢀ ꢀ ꢀCl(1)
C(7)–N(1)ꢀ ꢀ ꢀPh
Cl(1)ꢀ ꢀ ꢀPh
2.805
3.382
3.039
3.077
2.475
2.762
2.783
2.378
2.851
2.751
3.409
3.551
3.584
3.516
3.142
3.214
2.561
2.481
2.54
165.22
157.35
144.96
149.04
156.01
115.39
109.00
142.52
94.32
C(18)–N(11)ꢀ ꢀ ꢀPh
F(1)ꢀ ꢀ ꢀPh
F(11)ꢀ ꢀ ꢀPh
C(7) C(17)ꢀ ꢀ ꢀPh
C(7) C(17)ꢀ ꢀ ꢀPh
C(2)–H(2)ꢀ ꢀ ꢀN(9)
C(2)–H(2)ꢀ ꢀ ꢀCl(10)
C(1)–I(1)ꢀ ꢀ ꢀN(1)
C(14)–H(14A)ꢀ ꢀ ꢀI(1)
C(33)–H(33)ꢀ ꢀ ꢀN(1)
C(13)–H(13)ꢀ ꢀ ꢀCl(11)
C(4)–F(3)ꢀ ꢀ ꢀF(14)
C(24)–F(13)ꢀ ꢀ ꢀF(4)
C(2)–F(1)ꢀ ꢀ ꢀF(13)
C(4)–F(3)ꢀ ꢀ ꢀF(11)
C(5)–F(4)ꢀ ꢀ ꢀF(11)
C(23)–F(12)ꢀ ꢀ ꢀF(4)
C(15)–N(1)ꢀ ꢀ ꢀPh
F(13)ꢀ ꢀ ꢀPh
17
18
19
165.76
160.31
172.06
129.65
148.09
152.44
148.17
151.22
172.73
98.33
125.72
112.98
C(8) C(18)ꢀ ꢀ ꢀPh
C(1)–I(1)ꢀ ꢀ ꢀN(2)
C(16)–I(2)ꢀ ꢀ ꢀN(1)
C(20)–H(20A)ꢀ ꢀ ꢀF(5)
C(22)–H(22A)ꢀ ꢀ ꢀF(4)
C(23)–H(23A)ꢀ ꢀ ꢀF(6)
C(25)–H(25A)ꢀ ꢀ ꢀF(3)
C(2)–F(1)ꢀ ꢀ ꢀF(7)
C(30)–N(2)ꢀ ꢀ ꢀF(7)
C(22) C(23)ꢀ ꢀ ꢀF(2)
F(5)ꢀ ꢀ ꢀF(5)
[18ꢀ27]
176.07
177.77
126.28
150.18
148.46
128.23
139.63
127.50
122.87
2.487
2.901
3.126
3.546
2.816
3.345
3.014
3.031
3.152
2.593
2.479
2.653
2.618
2.421
2.948
3.007
3.161
3.424
3.405
3.370
3.542
3.705
3.650
3.333
3.399
3.370
3.749
3.850
3.864
3.919
3.452
3.540
3.754
3.673
4.064
3.772
3.488
3.738
3.367
3.956
3.816
4.026
C(7) C(8)ꢀ ꢀ ꢀPh
C(27) C(28)ꢀ ꢀ ꢀPh
C(10)–H(10)ꢀ ꢀ ꢀN(1)
C(11)–H(11)ꢀ ꢀ ꢀF(2)
C(14)–H(14)ꢀ ꢀ ꢀF(4)
C(5)–F(3)ꢀ ꢀ ꢀCl(1)
C(3)–F(2)ꢀ ꢀ ꢀF(4)
C(11)–H(11A)ꢀ ꢀ ꢀF(4)
C(13)–H(13A)ꢀ ꢀ ꢀF(2)
C(1)–I(1)ꢀ ꢀ ꢀN(1)
C(6)–H(6)ꢀ ꢀ ꢀN(1)
C(2)–H(2)ꢀ ꢀ ꢀF(1)
C(2)–H(2)ꢀ ꢀ ꢀF(5)
C(6)–H(6)ꢀ ꢀ ꢀF(4)
C(6)–H(6)ꢀ ꢀ ꢀN(1)
C(11)–F(1)ꢀ ꢀ ꢀCl(1)
C(11)–F(1)ꢀ ꢀ ꢀF(1)
C(11)–F(1)ꢀ ꢀ ꢀF(4)
C(2)–H(2)ꢀ ꢀ ꢀF(2)
C(5)–H(5)ꢀ ꢀ ꢀF(4)
C(15)–N(1)ꢀ ꢀ ꢀPh
Cl(1)ꢀ ꢀ ꢀPh
20
158.43
152.48
151.76
169.76
88.32
F(1)ꢀ ꢀ ꢀPh
[21ꢀ24]
C(1)–I(1)ꢀ ꢀ ꢀN(1)
C(21)–I(2)ꢀ ꢀ ꢀN(2)
C(41)–I(22)ꢀ ꢀ ꢀN(22)
C(13)–H(13)ꢀ ꢀ ꢀF(2)
C(31)–H(31)ꢀ ꢀ ꢀF(22)
C(33)–H(33)ꢀ ꢀ ꢀF(52)
C(30)–H(30)ꢀ ꢀ ꢀF(53)
C(31)–H(31)ꢀ ꢀ ꢀF(54)
C(2)–F(1)ꢀ ꢀ ꢀF(22)
C(2)–F(1)ꢀ ꢀ ꢀF(54)
C(26)–F(21)ꢀ ꢀ ꢀF(51)
C(53)–F(53)ꢀ ꢀ ꢀF(51)
C(3)–F(2)ꢀ ꢀ ꢀI(22)
C(22)–F(24)ꢀ ꢀ ꢀI(22)
C(51)–F(52)ꢀ ꢀ ꢀI(22)
C(53)–F(53)ꢀ ꢀ ꢀI(1)
C(26)–F(21)ꢀ ꢀ ꢀI(1)
C(15)–N(1)ꢀ ꢀ ꢀF(54)
C(15)–N(1)ꢀ ꢀ ꢀF(22)
C(35)–N(2)ꢀ ꢀ ꢀF(2)
F(1)ꢀ ꢀ ꢀPh
172.66
168.93
171.28
122.60
121.89
152.22
153.32
145.49
83.96
21
22
141.16
119.24
175.00
154.84
124.51
147.39
123.30
167.01
146.02
91.40
88.63
141.86
132.33
96.93
23
155.53
137.13
95.64
104.09
143.46
142.71
96.22
85.80
93.33
C(7) C(8)ꢀ ꢀ ꢀPh
C(7) C(8)ꢀ ꢀ ꢀPh
C(1)–I(1)ꢀ ꢀ ꢀN(1)
C(21)–I(2)ꢀ ꢀ ꢀN(2)
C(41)–I(3)ꢀ ꢀ ꢀN(3)
C(2)–H(2)ꢀ ꢀ ꢀF(22)
C(3)–H(3)ꢀ ꢀ ꢀF(22)
C(22)–H(22)ꢀ ꢀ ꢀF(2)
C(47)–H(47)ꢀ ꢀ ꢀF(23)
C(10)–F(1)ꢀ ꢀ ꢀF(21)
C(13)–F(3)ꢀ ꢀ ꢀF(23)
C(2)–F(1)ꢀ ꢀ ꢀF(4)
C(3)–F(2)ꢀ ꢀ ꢀF(3)
C(10)–F(5)ꢀ ꢀ ꢀF(9)
C(11)–F(6)ꢀ ꢀ ꢀF(8)
C(12)–F(7)ꢀ ꢀ ꢀF(8)
C(15)–N(1)ꢀ ꢀ ꢀPh
C(2)–F(1)ꢀ ꢀ ꢀCl(1)
C(6)–F(4)ꢀ ꢀ ꢀCl(1)
C(2)–F(1)ꢀ ꢀ ꢀF(4)
C(3)–F(2)ꢀ ꢀ ꢀF(3)
C(13)–F(12)ꢀ ꢀ ꢀF(13)
C(12)–F(11)ꢀ ꢀ ꢀF(14)
C(8)–N(1)ꢀ ꢀ ꢀPh
86.98
24
171.75
163.71
163.62
126.92
122.57
122.59
172.27
142.03
90.57
F(1)ꢀ ꢀ ꢀPh
F(2)ꢀ ꢀ ꢀPh
F(2)ꢀ ꢀ ꢀPh
F(3)ꢀ ꢀ ꢀPh
F(3)ꢀ ꢀ ꢀPh
F(4)ꢀ ꢀ ꢀPh
F(4)ꢀ ꢀ ꢀPh
F(21)ꢀ ꢀ ꢀPh
F(22)ꢀ ꢀ ꢀPh
25
26
161.77
138.90
167.44
135.66
165.20
F(23)ꢀ ꢀ ꢀPh
F(24)ꢀ ꢀ ꢀPh
F(51)ꢀ ꢀ ꢀPh
F(52)ꢀ ꢀ ꢀPh
F(53)ꢀ ꢀ ꢀPh
F(54)ꢀ ꢀ ꢀPh
142.09
148.47
155.59
147.08
146.74
155.77
27
C(1)–I(1)ꢀ ꢀ ꢀN(1)
C(2)–F(1)ꢀ ꢀ ꢀF(7)
C(2)–F(2)ꢀ ꢀ ꢀF(6)
C(5)–F(3)ꢀ ꢀ ꢀF(5)
C(5)–F(3)ꢀ ꢀ ꢀF(6)
C(6)–F(4)ꢀ ꢀ ꢀF(5)
172.46
144.47
81.38
126.28
166.94
119.00

R. Mariaca et al. / Journal of Fluorine Chemistry 130 (2009) 175–196
183
Table 3 (Continued )
˚
˚
Compound
Interaction
d (A)
u
(8)
Compound
Interaction
d (A)
u (8)
F(6)ꢀ ꢀ ꢀPh
3.656
3.732
2.625
2.625
2.247
2.638
2.781
2.468
2.706
2.843
3.497
3.477
3.475
I(1)ꢀ ꢀ ꢀPh
[16ꢀ25]
C(6)–H(2)ꢀ ꢀ ꢀN(1)
C(6)–H(2)ꢀ ꢀ ꢀF(5)
C(6)–F(4)ꢀ ꢀ ꢀN(1)
C(2)–F(1)ꢀ ꢀ ꢀN(1)
C(3)–F(2)ꢀ ꢀ ꢀN(1)
C(2)–F(1)ꢀ ꢀ ꢀF(3)
C(2)–F(1)ꢀ ꢀ ꢀF(4)
C(6)–F(4)ꢀ ꢀ ꢀF(4)
C(7)–N(1)ꢀ ꢀ ꢀPh
F(5)ꢀ ꢀ ꢀPh
168.73
168.73
161.03
151.76
169.76
137.17
132.47
88.91
C(8) C(8)ꢀ ꢀ ꢀPh
C2,2(18), C2,2(19) and rings R1,2(7), R2,2(9). Molecules are
structure created by R2,2(13) rings. However, in the case of
compound 20, the planes dihedral angle is far from orthogonal
(165.428). Adjacent molecules are stacked in 2D antiparallel layers
stacked in endless head to head chains through strong CNꢀ ꢀ ꢀH
˚
˚
˚
˚
(2.645 A and 2.649 A) and Fꢀ ꢀ ꢀF (2.708 A and 2.836 A) contacts as
˚
˚
˚
described at the second level graph-set by 2 rings R2,2(8),
through short CNꢀ ꢀ ꢀH (2.548 A), Fꢀ ꢀ ꢀH (2.467 A and 2.546 A) bonds
˚
˚
˚
˚
˚
˚
R2,2(10). Additional Fꢀ ꢀ ꢀH (2.598 A, 2.609 A, 2.620 A and 2.633 A)
and by head to edge Clꢀ ꢀ ꢀF (2.977 A) contacts that form infinite
˚
˚
˚
and Fꢀ ꢀ ꢀF (2.832 A, 2.881 A, 2.933 A and 2.937 A) interactions with
neighboring molecules form a 3D network. Parallel chains are
stacked and held together through CNꢀ ꢀ ꢀPh, Fꢀ ꢀ ꢀPh and C Cꢀ ꢀ ꢀPh
chains such as C1,1(6), C1,1(9), C2,2(12), C2,2(15), C2,2(17) and
˚
C2,2(18). These layers are connected by short Fꢀ ꢀ ꢀF (2.840 A) and
˚
Cꢀ ꢀ ꢀF (3.109 A) interactions to form a 3D network described in the
˚
interactions with interlayer distances as short as 3.4–3.6 A.
graph-set by endless chains C1,1(5), C1,1(6) and rings R4,4(18).
Molecules are also packed in parallel and antiparallel pairs
through similar interactions.
2.5.6. (E)-4-(4-iodo-2,3,5,6-tetrafluorostyryl)-benzonitrile 21
¯
Compound 21 crystallized in the centric space group P1
2.5.5. (E)-4-(4-chloro-2,3,5,6-tetrafluorostyryl)-benzonitrile 20
Compound 20 crystallized in the centrosymmetric space group
P21/c (Figs. 9 and 10). Molecules are packed in a similar manner as
for compounds 16 and 17, i.e. crystals show a typical herringbone
(Figs. 11 and 12). The CH4F4I molecules form endless C1,1(13)
˚
chains through short CNꢀ ꢀ ꢀI contacts (2.997 A, 174.858). These
˚
chains are arranged in a 2D networks through Fꢀ ꢀ ꢀH bonds (2.568 A
˚
and 2.633 A), creating in the first level of the graph-set endless
Fig. 3. (a) View of 16 crystal structure graph-set, showing the herringbone pattern through CNꢀ ꢀ ꢀH bonds. (b) View of 16 crystal structure graph-set, showing endless chains
formed by CNꢀ ꢀ ꢀH and Fꢀ ꢀ ꢀH contacts.

184
R. Mariaca et al. / Journal of Fluorine Chemistry 130 (2009) 175–196
Fig. 4. (a) View of 17 crystal structure graph-set, showing a 3D network built by Clꢀ ꢀ ꢀH bonds. (b) View of 17 crystal structure graph-set, showing the herringbone pattern
through CNꢀ ꢀ ꢀH bonds. (c) View of 17 crystal structure graph-set, showing endless chains formed by CNꢀ ꢀ ꢀH and Fꢀ ꢀ ꢀH contacts.
˚
˚
chains C1,1(9), C1,1(10), C2,2(11) and C2,2(19), which are related
planes are stacked by short Fꢀ ꢀ ꢀF (2.857 A) and Cꢀ ꢀ ꢀF (3.090 A) and
˚
˚
by an inversion center. These planes are stacked by Cꢀ ꢀ ꢀF (3.051 A
show an interplanar distance of 3.340 A.
˚
and 3.127 A) interactions and feature an interlayer distance of
˚
3.121 A.
2.5.8. (E)-4-(4-chlorostryryl)-2,3,5,6-tetrafluorobenzonitrile 23
Similarly to compounds 17 and 20, 23 crystallized in the
centrosymmetric space group P21/c. Molecules are (like for 17 and
20 Fig. 15), arranged in a typical herringbone packing and form
antiparallel chains, aligned by short CNꢀ ꢀ ꢀH (C1,1(12)) and Clꢀ ꢀ ꢀF
2.5.7. (E)-4-(4-fluorostryryl)-2,3,5,6-tetrafluorobenzonitrile 22
Compound 22 crystallized in the centric space group P1
(Figs. 13 and 14). Molecules form parallel chains aligned by short
¯
˚
˚
˚
CNꢀ ꢀ ꢀH bonds (2.499 A), building antiparallel 2D networks through
bonds (2.604 A and 3.073 A). The herringbone structure, described
on the graph-set by endless chains C2,2(12) and C2,2(18), has
nearly orthogonal oriented planes (70.288). The packing displays
flattened tetramers held together through Fꢀ ꢀ ꢀF short contacts
˚
˚
˚
Fꢀ ꢀ ꢀH bonds (2.559 A, 2.628 A and 2.633 A). All these D–Hꢀ ꢀ ꢀA
hydrogen bonds create (see graph-set) several rings and infinite
chains like R2,2(8), R2,2(20), R4,2(12), R4,4(20), C1,1(12), C2,1(14),
C2,2(10), C2,2(12), C2,2(14), C2,2(16) and C2,2(20). The molecular
˚
˚
(2.757 A and 2.773 A), and other tetramers connected by Fꢀ ꢀ ꢀF
Fig. 5. View of 18 along the a-axis, through the bc-plane.

R. Mariaca et al. / Journal of Fluorine Chemistry 130 (2009) 175–196
185
and specially the molecular dipoles determined physically (see
Fig. 16b). Consequently, one can observe a resulting polarity vector
along the c-axis.
2.5.10. (E)-4-(4-fluoro-2,3,5,6-tetrafluorostyryl)-2,3,5,6-
tetrafluorobenzonitrile 25
This compound 25 crystallizes in the centrosymmetric space
group C2/c (Figs. 18 and 19). The molecules are packed in a
flattened herringbone structure, which shows molecules arranged
˚
as head to head pairs, through Fꢀ ꢀ ꢀF interactions (2.894 A) creating
rings R2,2(8) in the graph-set. These pairs of molecules are
connected side by side to their neighboring pairs by other Fꢀ ꢀ ꢀF
˚
˚
˚
˚
contacts (2.849 A, 2.864 A, 2.880 A and 2.903 A), forming parallel
offset 2D layers described by many infinite chains and rings,
˚
orthogonal to the bc-plane at an interlayer distance of 3.143 A. The
herringbone structure has again nearly orthogonally oriented
Fig. 6. View of 18 crystal structure graph-set, showing a 3D network built by CNꢀ ꢀ ꢀI
and Iꢀ ꢀ ꢀH contacts.
planes (79.268) that are stacked along the b-axis by a CNꢀ ꢀ ꢀPh head
˚
to edge interaction (3.086 A).
2.5.11. (E)-4-(4-chloro-2,3,5,6-tetrafluorostyryl)-2,3,5,6-
tetrafluorobenzonitrile 26
Compound 26 crystallized in the centrosymmetric space group
C2/c (Fig. 20). The structure and graph-set are similar to compound
25, i.e. molecules are packed in a flattened herringbone structure.
Indeed, molecules are piled as head to head pairs in a similar
˚
˚
manner to 25, by Clꢀ ꢀ ꢀF interactions (3.178 A and 3.203 A). These
pairs of molecules are connected side by side to their neighboring
˚
˚
˚
pairs by other Fꢀ ꢀ ꢀF contacts (2.886 A, 2.888 A, 2.919 A and
˚
2.922 A), forming parallel offset 2D layers, orthogonal to the bc-
˚
plane at an interlayer distance of 3.112 A. The herringbone
structure has again nearly orthogonally oriented planes (78.628)
that are stacked along the b-axis by a CNꢀ ꢀ ꢀPh head to edge
˚
interaction (3.110 A).
2.5.12. (E)-4-(4-iodo-2,3,5,6-tetrafluorostyryl)-2,3,5,6-tetrafluoro
benzonitrile 27
In contrary to 25 and 26, compound 27 crystallized in the
¯
centric space group P1 (Fig. 21). The packing is dominated by CNꢀ ꢀ ꢀI
˚
bonds (3.042 A, 172.478), defining a 1D molecular chain C1,1(13).
˚
˚
˚
The additional short Fꢀ ꢀ ꢀF contacts (2.745 A, 2.906 A, 2.925 A and
˚
2.930 A) form 2D layers parallel to the bc-plane, described at the
Fig. 7. View of 19 along the a-axis, through the bc-plane.
first level in the graph-set by endless chains like C1,1(8), C1,1(10),
C2,2(17) and C2,2(18). Each plane is antiparallel to its neighbor
˚
with an interlayer distance of about 3.20 A. Layers are held
˚
˚
˚
˚
˚
short contacts (2.773 A), Fꢀ ꢀ ꢀH bonds (2.616 A) and Phꢀ ꢀ ꢀPh
interactions. The antiparallel chains are stacked by CNꢀ ꢀ ꢀPh,
Clꢀ ꢀ ꢀPh and C Cꢀ ꢀ ꢀPh interactions and short Fꢀ ꢀ ꢀF short contacts
together by Iꢀ ꢀ ꢀPh (3.732 A), Fꢀ ꢀ ꢀPh (3.656 A) and Fꢀ ꢀ ꢀF (2.927 A)
contacts. A 3D-network is built-up by several infinite chains and
rings as shown in the graph-set.
˚
˚
(3.092 A), giving an interplanar distance of 3.471 A. A 3D network
˚
˚
appears through short Fꢀ ꢀ ꢀH bonds (2.616 A and 2.631 A).
2.6. Co-crystallization of stilbenes
2.5.9. (E)-4-(4-iodostryryl)-2,3,5,6-tetrafluorobenzonitrile 24
This compound crystallized in the non-centrosymmetric space
group Cc (Figs. 16 and 17) with three molecules per asymmetric
unit. Among these series of compounds, this is the only polar space
group, also confirmed by a second harmonic generation (SHG)
powder test. The architecture of 24 is dominated by short CNꢀ ꢀ ꢀI
[16ꢀ25]: The molecular formula of this co-crystal [16ꢀ25] should
be read as {[C15H10NF][C15H2NF9]}. Similarly to compounds 17 and
23, [16ꢀ25] crystallized in the centrosymmetric space group P21/c
(Fig. 22). Molecules are arranged in similar fashion as for
compound 16, i.e. molecules form a typical herringbone structure
with nearly orthogonally oriented planes (77.018). The molecular
packing revealed some orientational disorder over two group
positions for F and CN. The molecules are arranged in parallel
˚
˚
˚
bonds (3.260 A, 171.758; 3.188 A, 163.718; 3.170 A, 163.628)
forming antiparallel endless chains (C1,1(13) along the b-axis.
The packing displays a 2D network perpendicular to the ac-plane,
˚
˚
chains aligned by short CNꢀ ꢀ ꢀH (2.625 A) and CNꢀ ꢀ ꢀF (2.247 A)
˚
˚
˚
held together by short CNꢀ ꢀ ꢀI, Fꢀ ꢀ ꢀH bonds (2.446 A, 2.615 A,
bonds, at an interlayer distance of 3.468 A. The stacks along the a-
˚
˚
˚
2.701 A and 2.745 A) and Fꢀ ꢀ ꢀF contacts (2.821 A). The 3D structure
axis are held together through CNꢀ ꢀ ꢀPh, Fꢀ ꢀ ꢀPh and C Cꢀ ꢀ ꢀPh
˚
˚
displays a parallel arrangement of planes in an offset stacked
interactions with dmin = 3.48 A, supported by Fꢀ ꢀ ꢀF (2.468 A,
˚
˚
˚
˚
˚
geometry with interplanar distances as short as 3.20 A and short
2.706 A and 2.843 A) and CNꢀ ꢀ ꢀF (2.638 A and 2.781 A) contacts.
One should note that molecule 16 seems to have imposed its
structural symmetry to compound 25 in the co-crystal [16ꢀ25].
˚
˚
Fꢀ ꢀ ꢀF contacts (2.881 A and 2.933 A). The polarity of this sample is
explained by the molecular arrangement in the crystal structure

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R. Mariaca et al. / Journal of Fluorine Chemistry 130 (2009) 175–196
Fig. 8. (a) View of 19 crystal structure graph-set, showing a 3D network built by Fꢀ ꢀ ꢀH, Fꢀ ꢀ ꢀF, CNꢀ ꢀ ꢀH interactions. (b) View of 19 crystal structure graph-set, showing the
herringbone pattern through CNꢀ ꢀ ꢀH and Fꢀ ꢀ ꢀH contacts.
[17ꢀ26]: The molecular formula of co-crystal [17ꢀ26] should be
read as {[C15H10NCl][C15H2NF8Cl]}. Compound [17ꢀ26] also crys-
tallized in the space group P21/c. Molecules are arranged in the
same fashion as for compound [16ꢀ25]. Therefore, one can observe
comparable interactions, interplanar angles and distances. A
similar observation to compound [16ꢀ25] can be drawn on the
imposed symmetry of 17 to compound 26 in the co-crystal. An
additional observation confirms this hypothesis as the co-crystal
melted at 181 8C, compared to the melting point of the pure
components C15H2NClF8 26 (136–137 8C) and C15H10NCl 17 (182–
183 8C).
two independent molecules in the unit cell. One molecular site is
occupied by compound 27 and the other one by 18. Crystal packing
˚
˚
is dominated by strong CNꢀ ꢀ ꢀI contacts (3.142 A, 176.538; 3.214 A,
177.538) that arrange molecules in chains alternating 18 and 27
˚
˚
˚
species and by edge to edge Fꢀ ꢀ ꢀH bonds (2.481 A, 2.487 A, 2.540 A
˚
and 2.567 A), forming antiparallel offset 2D layers with interplanar
˚
distance of 3.232 A. Planes are stacked together by Fꢀ ꢀ ꢀCN
˚
˚
˚
˚
(3.126 A), Fꢀ ꢀ ꢀC=C (3.546 A), Fꢀ ꢀ ꢀF (2.816 A) and Fꢀ ꢀ ꢀPh (3.345 A)
interactions.
[21ꢀ24]: Co-crystal of {[C15H4NF4I][C15F4NH4I]} [21ꢀ24] crystal-
lized in the triclinic polar space group P1 (Fig. 24). One should
notice that 24 also crystallized in a polar space group. There are
two independent molecules in the unit cell. One of these molecular
sites is fully occupied by compound 21 and the other position is
shared in a 0.8:0.2 ratio by 21 and 24. Crystal packing is dominated,
[18ꢀ27]: Similarly to compound 27, co-crystal of
{[C15H10NI][C15H2NF8I]} [18ꢀ27] crystallized in the centric triclinic
¯
space group P1 (Fig. 23). Molecules are packed in the same fashion
as for 27, meaning that the latter forced molecule 18 to set into its
structural architecture. Indeed, the melting point was lowered
(188 8C) compared to the pure components 18 (197–198 8C) and 27
(200–201 8C), respectively. However, in contrary to the crystal
structure of 27 and co-crystals [16ꢀ25] and [17ꢀ26], here there are
˚
˚
by strong CNꢀ ꢀ ꢀI contacts (3.014 A, 172.668; 3.031 A, 168.938;
˚
3.152 A, 171.288) that arrange molecules in antiparallel chains, and
˚
˚
˚
˚
by edge to edge Fꢀ ꢀ ꢀH bonds (2.421 A, 2.479 A, 2.576 A, 2.618 A and
˚
˚
˚
˚
˚
2.653 A), Fꢀ ꢀ ꢀF (3.161 A, 3.204 A, 3.424 A and 2.973 A) and Fꢀ ꢀ ꢀI
Fig. 9. View of 20 along the c-axis, through the ab-plane.

R. Mariaca et al. / Journal of Fluorine Chemistry 130 (2009) 175–196
187
Scheme 9. Graph-set of molecules 16, 17 and 18. Ten-member rings being drawn by
intermolecular interactions on compounds 16 and 17.
defects. Here, the antiparallel alignment of the dipole moments
may favour a non-polar structure. In the case of [21ꢀ24], there are
complementary stacks without 180 8C orientational disorder.
Adjacent chains take advantage of the complementary charge
distribution in H- and F-aromatic compounds, thus inducing the
formation of polar planes.
2.7. Melting behaviour of single compounds and co-crystals
We have recently published the crystal structures of new
polyfluorinated (E)-4-(4-bromostyryl)-benzonitriles [3]. Here, we
compare the motifs formed by interactions of at least two
molecules of the single compounds of the halogenated stilbenes
from F-, Cl-, Br- and I-derivatives.
The melting point of a solid depends mainly on the strength
of the intermolecular interactions and this dependence cannot
be easily quantified due to the numerous parameters affecting
the crystal packing. Nevertheless, this thermal behaviour may be
taken as an indication of developing specific and relatively
strong intermolecular interactions. For instance, the fluoro-
compound 16 containing CNꢀ ꢀ ꢀH interactions and forming a 10-
member ring may explain a higher melting point (183–185 8C).
The chloro derivative of 17 contains similar 10-member rings
with Nꢀ ꢀ ꢀH and Clꢀ ꢀ ꢀH motifs and shows a relative high melting
point (174–177 8C). In addition, the structures of 17 and 16 are
isomorphic.
Br–C6H4–CH CH–C6H4–CN [3] contains linear Brꢀ ꢀ ꢀBr chains
with complementary Brꢀ ꢀ ꢀH and Nꢀ ꢀ ꢀH motifs. In contrast, the
iodo-analogue 18 forms linear chains with CNꢀ ꢀ ꢀI and interchain
Hꢀ ꢀ ꢀI motifs, but adjacent chains are oriented in an antiparallel
mode. The high melting point of this compound (189–195 8C)
seems to reflect the strength of these interactions (Scheme 9).
The fluoro-compound 19 contains CNꢀ ꢀ ꢀH motifs forming 10-
member rings. The chloro-analogous 20 forms 12-member
rings interactions of Fꢀ ꢀ ꢀCl and Fꢀ ꢀ ꢀH at the one side and 14-
member rings interactions of CNꢀ ꢀ ꢀH and Hꢀ ꢀ ꢀF at the other side
of the molecule. Br–C6F4–CH CH–C6H4–CN and 21 are char-
acterized by CNꢀ ꢀ ꢀBr and CNꢀ ꢀ ꢀI motifs. Both are isomorphous.
The melting points of all these compounds are very high: 150–
153 8C for 19, 212–214 8C for 20 and 240 8C for 21, respectively
(Scheme 10).
Fig. 10. (a) View of 20 crystal structure graph-set, showing the herringbone pattern
through CNꢀ ꢀ ꢀH and Fꢀ ꢀ ꢀH contacts. (b) View of 20 crystal structure graph-set,
showing a tetramer built by Clꢀ ꢀ ꢀF and Fꢀ ꢀ ꢀF interactions.
˚
˚
(3.370 A and 3.542 A) interactions forming antiparallel offset 2D
˚
layers with interplanar distance of 3.232 A. Planes are stacked
˚
˚
˚
˚
together by Fꢀ ꢀ ꢀCN (3.340 A, 3.388 A and 3.479 A), Fꢀ ꢀ ꢀI (3.405 A,
˚
˚
˚
˚
3.650 A and 3.705 A), Fꢀ ꢀ ꢀF (2.948 A and 3.001 A) and Fꢀ ꢀ ꢀPh
(Table 3) interactions. Effects of polarity are well established by
second harmonic generation (SHG) experiments, showing a strong
SHG effect for the co-crystal. The melting point of [21ꢀ24] is 193–
195 8C, which is lower compared to those of the pure components
NC–C6H4–C2H2–C6F4–I 21 (256 8C), NC–C6F4–C2H2–C6H4–I 24
(206 8C), respectively.
Fluoro- and chloro-derivatives 22, 23, and Br–C6H4–CH CH–
C6F4–CN contain the same CNꢀ ꢀ ꢀH motif but different inter-
halogen motifs: Clꢀ ꢀ ꢀF, Brꢀ ꢀ ꢀF and Fꢀ ꢀ ꢀF interactions. Additionally
Hꢀ ꢀ ꢀF interactions are observed. Compound 23 is isomorphous
with Br–C6H4–CH CH–C6F4–CN. Only 24 contains CNꢀ ꢀ ꢀI motifs.
The structures [16ꢀ25], [17ꢀ26] and [18ꢀ27] are showing almost
no SHG effects, which may come up from preferential orientational

188
R. Mariaca et al. / Journal of Fluorine Chemistry 130 (2009) 175–196
Fig. 11. View of 21 along the b-axis, through the ac-plane.
Here also, the melting points are reflecting the strength of the
cyclic interactions (nine-member ring) of 23 (212–213 8C) and
the strong linear CNꢀ ꢀ ꢀI interactions of 24 (211–213 8C) (Scheme
11).
The fluoro compound 25 contains only weak Fꢀ ꢀ ꢀF interactions
forming a typical herringbone structure with lower melting point
(84–87 8C). The chloro-compound 26 contains only Fꢀ ꢀ ꢀCl motifs,
arranged in an eight-member ring (melting point is 136–138 8C).
Besides, Br–C6F4–CH CH–C6F4–CN is isomorphous with the iodo
analogue 27, showing strong CNꢀ ꢀ ꢀBr and CNꢀ ꢀ ꢀI interactions.
Lateral Fꢀ ꢀ ꢀF interactions are also present (Scheme 12).
and Clꢀ ꢀ ꢀF motifs. In contrast, the co-crystals [18ꢀ27] (1:1) showed
only linear CNꢀ ꢀ ꢀI chains (Scheme 13).
In [21ꢀ24] with a stoichiometry 9:1, we find strong interactions
˚
CNꢀ ꢀ ꢀI (3.10 A) complemented by the Hꢀ ꢀ ꢀF and Fꢀ ꢀ ꢀF contacts
(Scheme 14).
2.7.1. Co-crystals
[16ꢀ25] represents an ordered centric structure with 1:1
˚
stoichiometry based on 9-member ring CNꢀ ꢀ ꢀF motifs (2.25 A)
and Nꢀ ꢀ ꢀH and Fꢀ ꢀ ꢀF interactions. The structure of [17ꢀ26] is very
similar to this, featuring also 9-member ring CNꢀ ꢀ ꢀF, CNꢀ ꢀ ꢀH, Fꢀ ꢀ ꢀF
Fig. 12. View of 21 crystal structure graph-set, showing a 2D network built by Fꢀ ꢀ ꢀH,
and CNꢀ ꢀ ꢀI contacts.
Fig. 13. View of 22 along the a-axis, through the bc-plane.

R. Mariaca et al. / Journal of Fluorine Chemistry 130 (2009) 175–196
189
Fig. 14. (a) View of 22 crystal structure graph-set, showing di and trimers built by Fꢀ ꢀ ꢀH bonds. (b) View of 22 crystal structure graph-set, showing bi, tri, tetra and hexamers
built by Fꢀ ꢀ ꢀH bonds.
3. Experimental
frequency of 300 MHz (1H), 100 MHz or 75 MHz (13C, decoupled)
and 375 MHz (19F), respectively. Chemical shifts are reported in
ppm, with the residual or with CFCl3 as external standard (19
F
3.1. Analytical methods
NMR). IR spectra were recorded on a JASCO FT-IR 460 Plus in ATR
modus. GC–MS analyses were performed on a Finnigan Trace GC–
MS spectrometer wit EI source (70 eV) and equipped with a
siloxane-coated column.
1H NMR, 13C NMR and 19F NMR were recorded on a Bruker
AVANCE 300 or Bruker DRX400 spectrometer at a resonance
3.2. Materials
4-iodo-benzoylchloride, 4-fluoro-benzaldehyde, 4-chloro-ben-
zaldehyde, 4-iodo-benzaldehyde, 4-bromo-benzonitrile, 1,2,4,5-
tetrafluoro-benzene, 2,3,4,5,6-pentafluoro-benzaldehyde, 1,3,5,6
tetrafluoro-4-toluolic acid were purchased from Aldrich Che-
mical Company in purum quality and used without further
purification.
All reactions were carried out under argon atmosphere.
Triethylamine was distilled over CaH2 and degassed with argon.
Dioxane was distilled over Na/benzophenone.
3.3. General procedures
3.3.1. Horner–Wadsworth–Emmons approach
3.3.1.1. Method A. A mixture of 13 or 14 (5 mmol), trimethylpho-
sphite (2 ml, 17 mmol) and THF (10 ml) was heated to 150 8C for
2 h. After cooling with dry ice and acetone. A suspension of NaH in
kerosene (60 wt%, 375 mg, 7.5 mmol) was added and after another
30 min, a solution of the aldehyde (5 mmol) in THF (5 ml) followed
dropwise. The mixture was stirred overnight warming slowly to
room temperature. After addition of water the mixture was
extracted with methylene chloride (50 ml). The organic phase was
subsequently washed with 1 M NaOH (10 ml), brine and dried over
Fig. 15. View of 23 crystal structure graph-set, showing the herringbone pattern
through Fꢀ ꢀ ꢀH bonds.

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R. Mariaca et al. / Journal of Fluorine Chemistry 130 (2009) 175–196
Fig. 16. (a) View of 24 along the b-axis, through the ac-plane. (b) View of 24 along the a-axis, onto the bc-plane showing net polarity along the c-axis. The arrows represent
polar vectors, which remain under application of point symmetry.
Na2SO4 and concentrated by evaporation to yield the product,
which was purified by recrystallization.
mixture was poured under stirring into crushed ice (150 g).
Methylene chloride (200 ml) was added. The organic phase was
washed with brine, dried (MgSO4) and distilled under high
vacuum. The crude product was sublimated to give 2.13 g (50%)
3.3.1.2. Method B. 13 or 14 (4.6 mmol) and trimethylphosphite
(0.7 ml, 5.9 mmol) were heated for 4 h to 90 8C. After cooling, the
reaction mixture containing the phosphonic acid dimethylester
was diluted with absolute EtOH (4.20 ml) and mixed with a
solution of the corresponding aldehyde (5.2 mmol) in EtOH
(3.5 ml). A sodium ethanolate solution (sodium: 5.1 mmol, EtOH:
3.5 ml) was added dropwise during 10 min. After 20 h stirring at
room temperature, the precipitate was filtered off at room
temperature and rinsed with EtOH. The product was purified by
recrystallization.
of an orange solid. mp: 101–103 8C; 1H NMR (300 MHz, CDCl3):
10.22 (1H, s); 13C NMR (75 MHz, CDCl3):
182, 149.9, 148.3, 117.2,
112.2; 19F NMR (375 MHz, CDCl3):
d
d
d
ꢁ139.52 (m, 2F), ꢁ144.67 (m,
2F); GC–MS (EI) m/z (rel. int.), 211(M+, 79), 183 (24), 149 (22), 133
(37), 99 (100), 79 (42), 42 (67).
4-(bromomethyl)-2,3,5,6-tetrafluorobenzonitrile 13: 2,3,5,6-tet-
rafluoro-4-methyl-benzonitrile (4.5 g, 23.8 mmol) and dibenzoyl-
peroxyde (0.1 g, 0.4 mmol) were dissolved in dry CCl4 (50 ml). NBS
(6.35 g, 35.7 mmol) was added. The yellow suspension was then
heated to reflux for 65 h under irradiation with a 300 W photo
lamp. After cooling to room temperature, methylene chloride
(30 ml) was added and the organic phase was washed with
aqueous sodiumthiosulfate solution, dried (MgSO4) and concen-
trated under high vacuum. The crude product, orange oil (5.90 g,
92%) was distilled under high vacuum (70–85 8C) with a Bu¨chi
Kugelrohr apparatus to give a white liquid, which solidified at
room temperature (5.70 g, 89%). mp: 35 8C; 1H NMR (300 MHz,
3.3.2. Heck approach
3.3.2.1. Method C. E-4-(4-styryl)benzonitrile 28: 4-bromobenzoni-
trile (182 mg 1.0 mmol) with 20 mg Pd(OAc)2, 60 mg of P(o-tolyl)3
were placed in a flask under argon atmosphere. 0.5 ml of NEt3 and
0.2 ml styrene in 5.0 ml dioxane (distilled over Na) was added and
stirred under reflux over 12 h. The reaction was quenched with
50 ml sat. NH4Cl solution, filtered over Cellite and the residue
extracted with 50 ml ether, washed with saturated NaCl solution,
dried over MgSO4 and the solvent distilled. The dark brown residue
was purified by sublimation in vacuum to yield 1.4 g (80%) of the
CDCl3):
150.9, 146.9, 121.4, 106.9, 89.1; 19F NMR (375 MHz, CDCl3):
d d
4.51 (2H, t, J = 1.3 Hz); 13C NMR (100 MHz, CDCl3):
d
ꢁ132.17 (2F, m), ꢁ139.59 (2F, m); GC–MS (EI) m/z (rel. int.) 268
(M+, 100), 187 (29), 168 (20), 137 (18), 81 (19), 79 (25).
desired product. mp.: 120–121 8C; 1H NMR (300 MHz, CDCl3):
d
(E)-4-(4-fluorostyryl)benzonitrile 16: Method A, 930 mg (42%);
Method C, 350 mg (85%). mp: 183–185 8C, lmax (CH2Cl2)/nm 322
7.09 (1H, d, J = 17 Hz), 7.22 (1H, d, J = 17 Hz), 7.3–7.5 (5H, m), 7.57–
7.64 (4H, dd), J = 8.6 Hz); 13C NMR (100 MHz, CDCl3):
d
111.2,
(25,000); IR (KBr) cmꢁ1
:
n
2228 (nitrile), 1600 (C C), 1482, 1464
(aromatic), 1405, 1070 (C–F), 960 (trans C C), 870, 854, 825, 651,
619; 1H NMR (300 MHz, CDCl3):
7.00 (1H, d, J = 16.1 Hz), 7.07 (1H,
117.9, 127.9, 132.5, 133.3.
4-chloro-2,3,5,6-tetrafluorobenzaldehyde 5: Pentafluorobenzal-
dehyde (3.92 g, 20 mmol) and LiCl (0.93 g, 22 mmol) were
dissolved in absolute N-methylpyrrolidone (30 ml) and heated
under vigorous stirring for 3 h to 150 8C. The hot brown reaction
d
m, J = 8.8 Hz), 7.09 (1H, m, J = 8.5 Hz), 7.17 (1H, d, J = 16.8 Hz), 7.49
(1H, m, J = 4.2 Hz), 7.51 (1H, m, J = 3.9 Hz), 7.56 (2H, m, J = 8.2 Hz),
7.63 (2H, m, J = 8.5 Hz); 13C NMR (100 MHz, CDCl3):
d 110.64,

R. Mariaca et al. / Journal of Fluorine Chemistry 130 (2009) 175–196
191
Fig. 17. (a) View of 24 crystal structure graph-set, showing a 3D network built by Fꢀ ꢀ ꢀH and CNꢀ ꢀ ꢀI interactions. (b) View of 24 crystal structure graph-set, showing endless
chains formed by Fꢀ ꢀ ꢀH contacts.
Fig. 18. View of 25 along the a-axis, through the bc-plane.

192
R. Mariaca et al. / Journal of Fluorine Chemistry 130 (2009) 175–196
Fig. 19. View of 25 crystal structure graph-set, showing a 2D network built by Fꢀ ꢀ ꢀF
interactions.
Fig. 20. View of 26 crystal structure graph-set, showing a 2D network built by Fꢀ ꢀ ꢀF
and Clꢀ ꢀ ꢀF interactions.
Fig. 21. (a) View of 27 crystal structure graph-set, showing a 2D network built by
Fꢀ ꢀ ꢀF and CNꢀ ꢀ ꢀI contacts. (b) View of 27 crystal structure graph-set, showing a 2D
network built by Fꢀ ꢀ ꢀF contacts.
115.76, 115.98, 118.95, 126.77, 128.46, 128.54, 131.12, 132.49,
141.65, 164.10; 19F NMR (375 MHz, CDCl3):
d
ꢁ112.83 (1F, s,); GC–
MS: m/z (EI) (rel. int) 223 (M+, 100), 208 (28), 183 (14), 120 (16), 98
(17), 75 (32), 50 (24), 39 (13); HRMS (EI) for C15H10NF calculated:
223.07, found: 223.08.
(E)-4-(4-chlorostyryl)benzonitrile 17: Method B, 1.25 g (56%);
Method C, 500 mg (70%). mp: 174–177 8C, lmax (CH2Cl2) nm
329(48,000); IR (KBr) cmꢁ1
:
n
3050 (aromatic) 2220 (nitrile), 1600
(C C), 1485, 1413 (aromatic), 1169, 1088, 1009 (C–F), 959 (trans
C), 824, 670; 1H NMR (300 MHz, CDCl3):
7.05 (1H, d,
C
d
J = 16.4 Hz,), 7.16 (1H, d, J = 16.4 Hz,), 7.37 (2H, m, J = 8.5 Hz),
7.47 (1H, m, J = 8.5 Hz), 7.57 (1H, m, J = 8.3 Hz,), 7.64 (1H, m,
J = 8.7 Hz,); 13C NMR (100 MHz, CDCl3):
d 110.81, 118.89, 126.87,
127.28, 128.02, 129.02, 131.00, 132.49, 134.28, 134.76, 141.43;
GC–MS (EI) m/z (rel. int.) 239 (M+, 74), 204 (100), 177 (22), 151
(18), 102 (21), 88 (51), 75 (29), 63 (15), 51 (18), 39 (10); HRMS (EI)
for C15H10NCl calculated: 239.05, found: 239.05.
(E)-4-(4-iodostyryl)benzonitrile 18: Method A: 1.09 g (70%). mp:
189–195 8C, lmax (CH2Cl2)/nm: 329 (67,500); IR (KBr) cmꢁ1
: n
2800–3050 (aromatic), 2221 (nitrile), 1598 (C C), 1500, 1482
(aromatic), 1397, 1326, 1172, 1058, 1004 (C–F), 972, 943 (trans
C
C), 875, 824, 698; 1H NMR (300 MHz, CDCl3):
d 7.07 (1H, d,
J = 16.4 Hz), 7.13 (1H, d, J = 16.4 Hz), 7.26 (2H, d, J = 8.3 Hz), 7.56
(2H, d, J = 8.5 Hz), 7.64 (2H, d, J = 8.5 Hz), 7.71 (2H, d, J = 8.5 Hz);
Fig. 22. View of compound [16ꢀ25] and its orientational disorder, PLUTON and Ortep
[24] drawing at 50% probability [17ꢀ26].
13C NMR (100 MHz, CDCl3):
d 94.13, 110.91, 118.89, 126.92,

R. Mariaca et al. / Journal of Fluorine Chemistry 130 (2009) 175–196
193
J = 16.6 Hz); 13C NMR (100 MHz, CDCl3):
d
143.8, 140.4, 136,1, 132.8,
127.6, 118.9, 118.4, 116.4, 113.1, 112.6; 19F NMR (375 MHz, CDCl3):
d
ꢁ141.2 (2F, m), ꢁ142.4 (2F, m); GC–MS (EI) m/z (rel. int.), 311(M+,
100), 291 (90), 275 (44), 257 (52), 226 (45), 138 (28), 123 (22), 99
(21), 75 (47), 50 (47); HRMS (EI) for C15H6NF4Cl calculated: 311.01,
found: 311.01.
(E)-4-(4-iodo-2,3,5,6-tetrafluorostyryl)-benzonitrile 21: Method
B, 1.0 g (50%). mp: 256 8C;
cmꢁ1
3100–2800 (aromatic), 2229 (nitrile), 1600 (C C), 1469
(aromatic), 1331, 1052 (C–F), 950 (trans C C), 869, 817, 607; 1H
NMR (300 MHz, acetone d-6): 7.23 (1H, d, J = 16.8 Hz), 7.50 (1H,
d, J = 17.0 Hz), 7.71 (2H, m, J = 8.7 Hz), 7.80 (2H, m, J = 8.3 Hz), 13
NMR (100 MHz, CDCl3): 79.18, 128.98, 130.09, 133.90, 207.28;
19F NMR (375 MHz, CDCl3):
lmax (CH2Cl2)/nm 324 (35,000); IR (KBr)
:
n
d
C
d
d
ꢁ140.87 (2F), ꢁ123.04 (2F), MS: m/z
(EI) 405.2 (1.3), 404.2 (18), 403.2 (M+, 100), 402.0 (0.8) 226.2 (58).
HRMS (EI) for C15H6NF4I calculated: 402.95, found: 402.95.
(E)-4-(4-fluorostryryl)-2,3,5,6-tetrafluorobenzonitrile 22: Method
Fig. 23. View of [18ꢀ27] along the b-axis, through the ac-plane [21ꢀ24].
A, 0.80 g (54%). mp: 145–147 8C,
(KBr) cmꢁ1
2800–3100 (aromatic), 2240 (nitrile), 1626 (C C),
1595, 1509, 1484(aromatic), 1333, 1303, 1227, 1164,1027, 1100(C–
lmax (CH2Cl2) nm: 328 (26,100); IR
128.48, 131.19, 132.51, 135.78, 137.95, 141.38; GC–MS m/z (EI)
331 (M+, 100), 203 (82), 176 (37), 151 (15), 127 (16), 102 (19), 88
(31), 75 (25), 63 (19), 50 (26), 39 (11); HRMS (EI) for C15NH10Na
calculated: 353.98, found: 353.97.
: n
F), 974, 945, 927 (trans C C), 829, 643; 1H NMR (300 MHz, CDCl3):
d
6.99 (1H, d, J = 16.8 Hz), 7.09 (1H, m, J = 8.7 Hz), 7.13 (1H, m,
J = 8.5 Hz), 7.54 (1H, m, J = 8.3 Hz), 7.55 (1H, m, J = 8.9 Hz), 7.61 (1H,
(E)-4-(4-fluoro-2,3,5,6-tetrafluorostyryl)-benzonitrile 19: Method
A, 470 mg (16%); Method C in acetonitrile, 174 mg (30%). mp: 150–
d, J = 17.0 Hz); 13C NMR (100 MHz, CDCl3):
d
29.69, 107.70, 112.27,
153 8C,
(aromatic), 2225 (nitrile), 1604 (C C), 1494, 1413 (aromatic), 1228,
1009 (C–F), 960 (trans C C), 877, 845, 734, 653.cmꢁ1 1H NMR
(300 MHz, CDCl3): 7.07 (1H, d, J = 17 Hz), 7.41 (1H, d, J = 17 Hz),
7.59(1H,m,J = 8 Hz), 7.66(2H, m, J = 8 Hz), 7.76(1H,m, J = 8 Hz);13
NMR (100 MHz, CDCl3): 112.17, 116.36, 118.57, 127.32, 127.9,
132.6, 135.05, 136.18, 140.78, 143.38, 146.62; 19F NMR (375 MHz,
CDCl3):
l
max (CH2Cl2) 312 nm: (52,400);IR (KBr) cmꢁ1
:
n
2800–3100
116.17, 129.23, 139.83, 162.48, 164.98; 19F NMR (CDCl3):
d
ꢁ140.64
(2F, m,), ꢁ134.04 (2F, m), ꢁ110.29 (m, 1F), MS (EI) m/z (rel. int.)
295(M+, 64), 275 (100), 244 (25), 226 (20), 199 (8), 137 (8), 124 (11),
96 (38), 75 (32), 57 (24), 50 (22); HRMS (EI) for C15H6NF5 calculated:
295.04, found: 295.04.
;
d
C
d
(E)-4-(4-chlorostryryl)-2,3,5,6-tetrafluorobenzonitrile 23: Method
A, 1.02 g (66%). mp: 212–214 8C,
IR (KBr) cmꢁ1
2800–3100 (aromatic), 2244 (nitrile), 1619, 1590
(C C), 1485 (aromatic), 1330, 1299, 1086, 1009 (C–F), 974 (trans
C), 925, 817, 698, 642; 1H NMR (300 MHz, CDCl3):
7.05 (1H, d,
J = 16.8 Hz), 7.40(2H, m,J = 8.5 Hz), 7.51 (2H, m, J = 8.5 Hz), 7.60 (1H,
d, J = 16.8 Hz); 13C NMR (100 MHz, CDCl3):
139.7, 136.0, 135.9,
134.1, 131.9, 129.2, 128.6, 126.1, 122.4, 118.1, 113.0, 107.6; 19F NMR
(375 MHz, CDCl3):
l
max (CH2Cl2) cmꢁ1: 332 (33,100);
d
ꢁ142.3(m, 2F), ꢁ154.7(m) 1F, ꢁ162.6 (m) 2F; MS (EI) m/z
: n
(rel. int) 295 (M+,100), 275 (84), 244 (38), 226 (44), 192 (18), 122
(18), 75 (20), 50 (20); HRMS (EI) for C15H6NF5 calculated: 295.00,
found: 295.04.
C
d
(E)-4-(4-chloro-2,3,5,6-tetrafluorostyryl)-benzonitrile 20: Method
d
B, 0.41 g (57%). mp: 185–187 8C,
(KBr) cmꢁ1
3000–3100 (aromatic), 2222 (nitrile), 1594, 1507
(C C), 1417 (aromatic), 1230, 1175, 1158, 1096 (C–F), 969 (trans
C), 835, 781; 1H NMR (300MHz, CDCl3):
6.57(1H, d, J = 16.8 Hz),
6.67 (2H, m, J = 8.1 Hz), 6.96 (2H, m, J = 8.5 Hz), 6.97 (1H, d,
lmax (CH2Cl2) nm: 318 (62,000); IR
:
n
d
ꢁ140.45 (m, 2F), ꢁ133.91 (m, 2F), GC–MS (EI)
m/z (rel. int.) 311 (M+, 97), 291 (46), 276 (82), 257 (48), 226 (100),
137 (26), 112 (37), 75 (40), 50 (33); HRMS (EI) for C15H6NF4Cl
calculated: 311.01, found: 311.01.
C
d
Fig. 24. View of [21ꢀ24] along the b-axis, through the ac-plane.

194
R. Mariaca et al. / Journal of Fluorine Chemistry 130 (2009) 175–196
Scheme 11. Graph-set of molecules 22, 23 and 24. Nine-member rings being drawn
by intermolecular interactions on compound 23.
(E)-4-(4-chloro-2,3,5,6-tetrafluorostyryl)-2,3,5,6-tetrafluorobenzo-
nitrile26:MethodB, 0.74 g(42%). mp:136–138 8C;
318 (65,000); IR (KBr) cmꢁ1
2222 (nitrile), 1650, 1630 (C C),
1487, 1414 (aromatic), 1335, 1304 (C–F), 965 (trans C C), 877, 654,
610; 1H NMR (300 MHz, CDCl3):
7.37 (d, 1H, J = 17.1 Hz), 7.49 (d,
1H, J = 17.1 Hz); 13C NMR (100 MHz, CDCl3):
71.8, 103.1, 107.9,
113.1, 114.1, 121.3, 125.3, 142.8, 143.3, 146.2, 148.8; 19F NMR
(375 MHz, CDCl3):
139.7(2F,m), ꢁ133.1; MS (EI) m/z (rel. int.) 383(M+,100), 329 (22),
298 (42), HRMS (EI) for C15H2NF4Cl calculated: 383.01, found:
383.01.
lmax (CH2Cl2)nm
:
n
d
d
d
ꢁ161.8 (2F,m), ꢁ151.9 (2F,m),ꢁ141.2(2F,m),
Scheme 10. Graph-set of molecules 19, 20 and 21. 10 and 12-member rings being
drawn by intermolecular interactions on compounds 19 and 20.
(E)-4-(4-iodostryryl)-2,3,5,6-tetrafluorobenzonitrile 24: Method
(E)-4-(4-iodo-2,3,5,6-tetrafluorostyryl)-2,3,5,6-tetrafluorobenzo-
A, 1.0 g (42%). mp: 211–213 8C;
(KBr) cmꢁ1
2220 (nitrile), 1615 (C C), 1582, 1485 (aromatic),
1329, 1300,1059, 1005 (C–F), 980, 960 (trans C C), 930, 808, 681,
640; 1H NMR (300 MHz, CDCl3):
7.06 (1H, d, J = 16.8 Hz), 7.27 (1H,
m, J = 8.2 Hz), 7.53 (1H, d, J = 16.8 Hz), 7.60 (1H, d, J = 8.5 Hz), 7.74
(1H, dm, J = 8.5 Hz); 13C NMR (100 MHz, CDCl3):
18.41, 30.89,
96.14, 107.61, 113.21, 128.89, 135.14, 138.21, 139.91; 19F NMR
(375 MHz, CDCl3):
l
max (CH2Cl2)/nm: 339 (66,300); IR
nitrile 27: Method A, 1.0 g (42%). mp: 211 8C lmax (CH2Cl2)/nm: 326
:
n
d
d
d
ꢁ140.37 (2F), ꢁ133.94 (2F); GC–MS: m/z (EI):
405.2 (1), 404.2 (13), 403.1 (100), 226.3 (100), 226.2 (58); HRMS
(EI) for C15H6NF4 calculated: 402.95, found: 402.95.
(E)-4-(4-fluoro-2,3,5,6-tetrafluorostyryl)-2,3,5,6-tetrafluoroben-
zonitrile 25: Method B, 860 mg (51%); Method C, 110 mg in dioxane
(30%). mp: 84–87 8C, lmax (CH2Cl2)/nm: 312 (54,000); IR (KBr)
cmꢁ1
:
n
2250 (nitrile), 1650, 1520 (C C), 1491, 1422 (aromatic),
1339, 1302, 1153, 1137, 1110, 1020 (C–F), 961 (trans C C), 721,
660, 613; 1H NMR (300 MHz, CDCl3):
7.39 (1H, d, J = 17.3 Hz),
7.52 (1H, d, J = 17.1 Hz); 13C NMR (100 MHz, CDCl3):
93.01,
107.24, 110.9, 120.8, 122.1, 125.03, 136.2, 139.55, 143.15, 145.62,
149.09; 19F NMR (375 MHz, CDCl3):
d
d
d
ꢁ161.8 (2F, m), ꢁ151.9 (1F,
m), ꢁ141.3 (2F, m), ꢁ139.7 (2F, m), ꢁ133.2 (2F, m); GC–MS (EI) m/
z: 367 (100), 298 (62), 192 (14), 168 (14), 123 (14), 99 (14), 75 (20),
50 (20); HRMS (EI) for C15H2NF9Na calculated: 389.99, found:
389.99.
Scheme 12. Graph-set of molecules 25, 26 and 27. Eight-member rings being drawn
by intermolecular interactions on compounds 25 and 26.

R. Mariaca et al. / Journal of Fluorine Chemistry 130 (2009) 175–196
195
3.3.3.4. Co-crystal of (E)-4-(4-iodo-2,3,5,6-tetrafluorostyryl)-benzo-
nitrile 21 and (E)-4-(4-iodostryryl)-2,3,5,6-tetrafluorobenzonitrile
24. 21 (22 mg) and 24 (37 mg) were dissolved in dichloromethane.
The solvent was evaporated under isothermal conditions and
purged with nitrogen. The obtained crystals melted at 193–195 8C.
GC–MS analysis for [21ꢀ24]: [9:1].
3.4. Crystal structure determination
Data were collected on a Stoe Imaging plate diffractometer
system [25] equipped with a graphite monochromator. Data
collection was performed at ꢁ120 8C using Mo K
a radiation
˚
(l
= 0.71073 A). The structure were solved by direct methods using
SHELXS-97 [26] and refined by full matrix least-squares on F2 with
SHELXL-97 [27]. The hydrogen atoms were included in calculated
positions and treated as riding atoms using SHELXL-97 default
parameters. All non-hydrogen atoms were refined anisotropically.
No absorption correction was applied for 16, 17, 19, 20, 22, 23, 25,
26, [16ꢀ25] and [17ꢀ26] (
m
< 1 mmꢁ1). For all other structures
either a semi-empirical or an empirical absorption correction was
applied using MULABS or DIFABS, respectively, as implemented in
PLATON [28] (Tmin/Tmax = 0.523/0.629 18, 0.441/0.634 21, 0.383/
0.619 24, 0.383/0.642 27, 0.452/0.882 [18ꢀ27], 0.408/0.711
[21ꢀ24]).
Scheme 13. Graph-set of co-crystals [16ꢀ25], [17ꢀ26] and [18ꢀ27]. Nine-member
rings being drawn by intermolecular interactions on compounds [16ꢀ25] and
[17ꢀ26].
4. Summary and conclusion
We have been using the HWE approach for the synthesis of
trans-stilbenes and obtained exclusively E-stereoisomers with
satisfactory yields. By applying the standard Heck coupling
conditions we, however, obtained poor yields and side reactions.
Comparing the H-substituted and F-substituted structures we
have observed a considerable difference. On the one side, the
structures of the p-X-C6H4–CH CH–C6H4–CN series (X = F, Cl, I)
are very different from the analogous p-X-C6F4–CH CH–C6F4–CN
series (X = F, Cl, I), indicating that the fluorine substitution may
change the packing structure completely. On the other hand the
structures of the p-X-C6H4–CH CH–C6F4–CN (X = F, Cl, I) mole-
cules undergo also a different packing compared to p-X–C6F4–
CH CH–C6H4–CN (X = F, Cl, I) molecules, pointing out that the
position of the fluorine substitution has a great influence on
the formation of crystal-packing motifs: Fluorine substitution on
the halogen side of the benzene ring enhances the acceptor nature
of the halogen atoms (X), making the halogen bonding (XB)
Scheme 14. Graph-set of co-crystal [21ꢀ24].
(72,000); IR (KBr) cmꢁ1
(aromatic), 1342, 1303 (C–F), 978, 959, 923 (trans C C), 815, 650,
605; 1H NMR (300 MHz, CDCl3):
7.46 (d, 1H, J = 17.1 Hz), 7.57 (d,
1H, J = 17.1 Hz); 13C NMR (100 MHz, CDCl3): 128.09; 19F NMR
(375 MHz, CDCl3):
: n 2252 (nitrile), 1645 (C C), 1489, 1471
d
d
d
ꢁ140.29 (2F), ꢁ139.68 (2F), ꢁ133.33 (2F),
ꢁ120.79 (2F); MS: m/z (EI) 477.2 (1), 476.2 (12), 475.1 (100), 298.2
(63); HRMS (EI) for C15H2NF8I calculated: 474.91, found: 474.91.
˚
stronger. Nꢀ ꢀ ꢀI distances of 3.04 A were observed in the per-
3.3.3. Co-crystals and solid solutions
˚
fluorinated 27 and 2.99 A in the partially fluorinated 21. At the
3.3.3.1. Co-crystal of (E)-4-(4-fluorostyryl)-benzonitrile 16 and (E)-
4-(4-fluoro-2,3,5,6-tetrafluorostyryl)-2,3,5,6-tetrafluorobenzonitrile
25. 16 (22 mg) and 25 (37 mg) were dissolved in dichloromethane.
The solvent was evaporated under isothermal conditions and
purged with nitrogen. GC–MS analysis for [16ꢀ25]: [1:1].
contrary, fluorine substitution on the benzene ring carrying the CN
group has the tendency to diminish the donor nature of the CN-
˚
group with longer distances (3.23 A). However, all these distances
˚
are shorter than the sum of the Van der Waals radii (3.69 A), which
coincides with those reported in the literature for similar kinds of
structures [8]. The fluorination on the benzene ring carrying the CN
group (24) increases the strength of the intermolecular interac-
tions (Hꢀ ꢀ ꢀF bonds), reflected by higher melting point as compared
to 18. Contrary, the effect of fluorine substitution on the iodine side
(21) strongly shortened the Nꢀ ꢀ ꢀI interaction by improving the
iodine acceptor character due to electron withdrawing, and
consequently increases the melting point. Similarly to compounds
18 and 21 fluorination of the iodo side of 24 improves the Nꢀ ꢀ ꢀI
interactions in 27, which is compensated by weak Fꢀ ꢀ ꢀF inter-
molecular interactions instead of Fꢀ ꢀ ꢀH bonding. Therefore, the
melting point of 24 and 27 may not be really affected. In the same
way, the higher melting point of 21 is due to the absence of fluorine
atoms on the cyano side of the molecule and therefore may be due
to the presence of Hꢀ ꢀ ꢀF bonds, as compared to 27.
3.3.3.2. Co-crystal of (E)-4-(4-chlorostyryl)-benzonitrile 17 and (E)-
4-(4-chloro-2,3,5,6-tetrafluorostyryl)-2,3,5,6-tetrafluorobenzonitrile
26. 17 (22 mg) and 26 (37 mg) were dissolved in dichloromethane.
The solvent was evaporated under isothermal conditions and
purged with nitrogen. The obtained crystals melted at 181 8C. GC–
MS analysis for [17ꢀ26]: [1:1].
3.3.3.3. Co-crystal of (E)-4-(4-iodostyryl)-benzonitrile 18 and (E)-4-
(4-iodo-2,3,5,6-tetrafluorostyryl)-2,3,5,6-tetrafluorobenzonitrile
27. 18 (22 mg) and 27 (37 mg) were dissolved in dichloromethane.
The solvent was evaporated under isothermal conditions and
purged with nitrogen. The obtained crystals melted at 188 8C. GC–
MS analysis for [18ꢀ27]: [1:1].

196
R. Mariaca et al. / Journal of Fluorine Chemistry 130 (2009) 175–196
[3] R. Mariaca, N. Behrnd, P. Eggli, H. Stoeckli-Evans, J. Hulliger, Cryst. Eng. Commun. 8
An interesting comparison appearing in the literature [29] is the
(2006) 222–232.
structure of 40-bromo-20,30,50,60-tetrafluorostilbazole, consisting of
an infinite unimolecular network involving both interchain
stacking and Nꢀ ꢀ ꢀBr halogen bonding. Furthermore, the structure of
halogenated tolans of general formula p-C6H4–CBB C–C6F5 and p-
C6F4–CBB C–C6H5 (X = F, Cl, Br, I) are characterized by arene-
perfluoroarene, halogen–halogen interactions and herringbone
packing [11].
[4] C.B. Aakero¨y, J. Desper, B.A. Helfrich, P. Metrangolo, T. Pilati, G. Resnati, A.
Stevenazzi, Chem. Commun. (2007) 4236–4238.
[5] (a) T. Imakuwo, H. Sawa, R. Kato, Synth. Met. 73 (1995) 117–122;
p–p
´
(b) M. Formigue, P. Batail, Chem. Rev. 104 (2004) 5379–5418;
(c) N. Tajima, M. Tamura, R. Kato, Y. Nishio, K. Kajita, Synth. Met. 181 (2003) 133–
134.
[6] (a) A.S. Batsanov, A.J. Moore, N. Robertson, A. Green, M.R. Bryce, J.A.K. Howard,
A.E. Underhill, J. Mater. Chem. 7 (1997) 387–389;
´
(b) M. Fourmigue, Struct. Bond. 126 (2008) 181–207.
The co-crystal [18ꢀ27] is formed with two species, which are
connected through CNꢀ ꢀ ꢀI chains having different distances
[7] H.L. Nuyen, P.N. Horton, M.B. Hursthouse, A.C. Legon, D.W. Bruce, J. Am. Chem.
Soc. 126 (2004) 16–17.
[8] A. Farina, S.V. Meille, M.T. Messina, P. Metrangolo, G. Resnati, G. Vecchio, Angew.
Chem. Int. Ed. 38 (1999) 2433–2436.
[9] (a) P. Metrangolo, G. Resnati, Chem. Eur. J. 7 (2001) 2511–2520;
(b) P. Metrangolo, F. Meyer, T. Pilati, D.M. Proserpio, G. Resnati, Chem. Eur. J. 13
(2007) 5765–5772;
˚
˚
3.14 A and 3.21 A. The lower melting point (188 8C) of [18ꢀ27]
indicates a different structure compared to the pure compounds
18 (195 8C) and 27 (211 8C). In the case of the co-crystal [17ꢀ26],
interactions CNꢀ ꢀ ꢀF (forming
a 10-member ring) can be
(c) P. Metrangolo, G. Resnati, T. Pilati, R. Liantonio, F. Meyer, J. Polym. Sci. A:
Polym. Chem. 45 (2007), Highlight 1–15;
(d) P. Metrangolo, H. Neukirch, T. Pilati, G. Resnati, Acc. Chem. Res. 38 (2005)
386–395.
compared with those of CNꢀ ꢀ ꢀH (forming a 9-member ring) of
the pure compound 17, because the melting points are very near
(175 and 181 8C). In contrast to the interactions of the pure
compound 16 (Fꢀ ꢀ ꢀF interactions) and 25 (CNꢀ ꢀ ꢀH forming a 10
member ring), the co-crystal [16ꢀ25] shows strong Nꢀ ꢀ ꢀF
interactions (9 member ring), lower as the sum of van der
[10] S.G. Bratsch, J. Chem. Educ. 62 (1985) 101–103.
[11] J.C. Colling, J.M. Burke, P.S. Smith, A.S. Batsanov, J.A.K. Howard, T.B. Marder, Org.
Biomol. Chem. 2 (2004) 3172–3178.
[12] A. Papagni, S. Maiorana, P. Del Buttero, D. Perdicchia, F. Cariati, E. Cariati, W.
Marcolli, Eur. J. Org. Chem. 8 (2002) 1380–1384.
[13] (a) L. Horner, H. Hoffmann, H.G. Wippel, Chem. Ber. 91 (1958) 61–63;
(b) L. Horner, H. Hoffmann, H.G. Wippel, G. Klahre, Chem. Ber. 92 (1959) 2499–
2505.
[14] W.S. Wadsworth, W.D. Emmons, J. Am. Chem. Soc. 83 (1961) 1733–1738.
[15] L. Horner, H. Hoffmann, W. Klink, Chem. Ber. 96 (1963) 3133–3136.
[16] R. Thomas, J. Boutagy, Chem. Rev. 74 (1974) 87–99.
[17] A.E. Arbuzov, A.F. Razumov, J. Russ. Phys. Chem. Soc. 61 (1929) 623–630.
[18] R.M. Acheson, G.C.M. Lee, J. Chem. Soc. Perkin Trans. I (1987) 2321–2332.
[19] (a) A. Ianni, S.R. Waldvogel, Synthesis (2006) 2103–2112;
(b) M.J. Robson, US Patent 5,132,469 (1992);
(b) M.J. Robson, J. Williams, UK patent GB 2,171,994A (1985).
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Chem. 125 (2004) 1379–1382.
˚
Waals radii (2.89 A).
The structure of [21ꢀ24] has been studied in details. It
contains two molecular species (9:1) aligned in 1D polar chains
CNꢀ ꢀ ꢀI, located on two symmetrically independent sites, one site
containing molecules of one species and the other site contains
two molecules (8:2), related by an inversion center. The polarity
of this structure was confirmed by a positive SHG effect and the
polar space group P1. This may be related to the polar properties
found also (i) 24 and (ii) in the solid solutions of [E-4-(4-
bromostyryl)-2,3,5,6-tetrafluorobenzonitrile)]xꢀ[E-4-(4-bromo-
2,3,5,6-tetrafluorostyryl)-benzonitrile]1ꢁx that we had reported
before [3].
[21] (a) J.M. Campagne, D. Prim. Les complexes de palladium en synthe`se organique,
Initiation et guide practique. CNRS editions, 2001;
(b) E. Negishi (Ed.), Handbook of Organopalladium Chemistry for Organic
Synthesis, vols. I and II, Wiley, New York, 2002;
(c) J.J. Li, G.W. Gribble, Palladium in Heterocyclic Chemistry. A Guide for Syn-
thetic Chemist, Elsevier, Oxford, 2000.
In this context one should mention previous partially published
work [30] on the polar structures of p-X–C6F4–CN (X = Cl, Br, I) in
which lateral fluorination was successful to promote the formation
of polar structures. Qualitative measurements of an extended
series confirmed that about. 90% of these structures were SHG
active. However, this study shows clearly, that 8-/9- or 4-fault
fluorination in stilbenes has effected only one polar structure (24)
out of 12. In view of some design principles we have put forward
recently [3], this is quite surprising.
´
[22] A.C. Albeniz, P. Espinet, B. Martin-Ruiz, D. Milstein, Organometallics 24 (2005)
3679–3684.
[23] (a) C. Roscher, PhD Thesis, University of Wu¨ rzburg, 1998;;
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[24] (a) A.L. Spek, PLUTON and ORTEP Platon for Windows Taskbar v 1.10, University
of Utrecht, The Netherlands, 2006;
(b) A.L. Spek, Acta Cryst. A46 (1990) C34.
[25] X-Area V1.17 & X-RED32 V1.04 Software, Stoe & Cie GmbH, Darmstadt, Germany,
2002.
Acknowledgments
[26] (a) G.M. Sheldrick, SHELXS-97, Program for Crystal Structure Determination,
University of Go¨ttingen, Germany, 1997;
(b) G.M. Sheldrick, Acta Cryst. A46 (1990) 267–273.
[27] G.M. Sheldrick, SHELXL-97, Program for Crystal Structure Refinement, University
of Go¨ttingen, Germany, 1997.
We thank PD Dr. Stefan Schu¨rch for the mass spectrometry and
elemental analyses. We thank the Regionale Arbeitsvermittlung
Bern (Lukas Kaltenrieder) for technical assistance in syntheses.
[28] A.L. Spek, J. Appl. Cryst. 36 (2003) 7–13.
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