organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
ISSN 0108-2701
A new precursor for the synthesis
of porphyrazine: 2,3-bis(4-methyl-
phenyl)maleonitrile
Christophe Faulmann,* Patrick Cassoux and Anthony E.
Pullen²
Laboratoire de Chimie de Coordination du CNRS, 205 Route de Narbonne, 31077
Toulouse CEDEX, France
Figure 1
The molecular structure of (II), showing 30% probability displacement
ellipsoids and the atom-numbering scheme. H atoms have been omitted
for clarity.
Correspondence e-mail: faulmann@lcc-toulouse.fr
Received 16 November 1999
Accepted 16 December 1999
coupling of para-substituted benzyl cyanides, we have isolated
not only the trans, (I), but also the cis isomer, 2,3-bis(4-
methylphenyl)maleonitrile, (II), and characterized them by
several methods including X-ray crystallography. Due to the
relative high yields of their syntheses, these latter compounds
are therefore of interest for the preparation of porphyrazines.
Although the structure of the trans isomer, (I), has been
determined, it will not be presented in this article because of
its low quality, mainly due to the thin, needle-shaped crystals
and the poor diffracting power of the samples. The molecule of
the title compound, (II), is not planar: it is distorted from
planarity along the C C bond. This is evident as shown by the
torsion angles along the C C bond (Table 1) and with the
values of the angles between the planes de®ned by C1, C3, C5
and C2, C4, C12 [10.6 (1)ꢁ] and those de®ned by C1, C2, C5,
C12 and C1, C2, C3, C4 [7.43 (2)ꢁ]. A view of the molecule can
be seen in Fig. 1.
Such non-planarity was also observed in the trans-ꢀ,ꢁ-di-
cyanostilbene (Wallwork, 1961), which is the only aryl-
containing disubstituted dinitrile compound reported so far in
the Cambridge Structural Database. Since the accuracy of its
structural determination is not comparable to the present one,
no comparison will be undertaken. The p-methylphenyl
groups are twisted about the C5±C8 and C12±C15 axes and
form an angle of 37.54 (6) and 43.88 (6)ꢁ with the mean plane
built around the C C bond (least-square plane through
atoms C1, C2, C3, C4, C5 and C12). The angle between the two
p-methylphenyl group planes is 56.95 (6)ꢁ.
The structure of the title compound consists of discrete
C18H14N2 molecules in a cis con®guration. The molecules are
distorted from planarity.
Comment
It has been shown that both maleonitrile and fumaronitrile
compounds can be cyclized into porphyrazine macrocycles,
but in very low yields when using the fumaronitrile isomer
(Fitzgerald et al., 1991). The fumaronitriles must ®rst be
thermally isomerized to the maleonitrile cis isomer before
cyclization can occur. It has been reported that dialkyl or
alkyl/aryl-mixed fumaronitriles can be photoisomerized to the
maleonitrile form (Fitzgerald et al., 1991). Diarylfumaro-
nitriles on the contrary have been shown to be unable to be
photoisomerized (Sargent & Timmons, 1963). We had set out
to prepare the porphyrazine precursor molecule 2,3-bis(4-
methylphenyl)maleonitrile but in several reports, each using
different synthetic conditions, only the fumaronitrile isomer
Experimental
Compound (I) (pale yellow needles) was synthesized in 43% yield
using procedures similar to that found for the coupling of related
benzyl cyanide compounds (Baumann et al., 1997). Elemental and
melting-point analyses were in agreement with those previously
reported for this compound (Pochat, 1978; Chatterjea et al., 1966).
Compound (II) was obtained in 15% yield from the ®ltrate of (I) after
the ®ltrate was placed in a freezer at 253 K for 3 d. Well formed
yellow hexagonal plates crystallized, were ®ltered, washed with
MeOH and dried under vacuum (m.p. 432±433 K, uncorrected).
was isolated (Chatterjea et al., 1966; Ogata & Nagura, 1974;
Pochat, 1978; Kurihara et al., 1987). Using a previously
reported procedure (Baumann et al., 1997) for the oxidative
² Present address: Department of Chemistry, Massachusetts Institute of
Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA.
ꢀ
384 # 2000 International Union of Crystallography
Printed in Great Britain ± all rights reserved
Acta Cryst. (2000). C56, 384±385
Faulmann, Christophe
