480
J Chem Crystallogr (2008) 38:479–482
2.51; N, 19.38%. Found: C, 50.04; H, 2.37; N, 19.53%. IR
(KBr pellets, cm-1): v (N–H) 3430, 3169, (C=O) 1724,
1691, (C–S–C) 699. 1H NMR (DMSO-d6): d 7.28
(t, J = 8.4 Hz, 2H, aromatic H), 7.62–7.70 (m, 1H, aro-
matic H), 7.94 (d, J = 5.2 Hz, 2H, pyridyl 3,5-H), 8.75
(d, J = 5.2 Hz, 2H, pyridyl 2,6-H), 11.80 (s, 1H, NH),
12.14 (s, 1H, NH). EI-MS (m/z, %): 361 (M+, 30), 342
(66), 205 (100), 177 (13), 141 (63), 113 (8), 78 (11).
A fully completed Crystallographic Information File
deposited with the CCDC is available (Deposition CCDC
No. 273315).
S
S
N
NNHCNH2
CH
+
H2NNHCNH2
CHO
N
N N
FeCl3· 6H2O
N
NH2
S
1
F
F
O
C
O
(COCl)2
N
C
O
N
NH2
C
DCE, reflux
F
F
2
F
O
O
C
N
N
H
Results and Discussion
1
+
2
C
F
N
N
H
S
1
The data of H NMR, IR, MS and elemental analysis for
3
the product are in good agreement with the structure of the
title compound 3. Table 1 contains crystallographic data of
compound 3, Table 2 gives the selected bond lengths and
angles. Table 3 enumerates the significant hydrogen bonds.
The molecular structure of the title compound 3 is shown in
Fig. 1.
Scheme 1 Procedure of preparing the title compound 3
with TMS as internal standard and DMSO-d6 as the sol-
vent. Mass spectra were recorded on a Finnigan Trace
Mass Spectrometer. Elemental analysis was performed by a
Vario EL III analyzer. Melting point was determined by an
X-4 microscopic melting-point apparatus and uncorrected.
Single crystal X-ray data were collected on a BRUKER
SMART APEX-CCD diffractometer equipped with a
graphite-monochromated MoKa radiation. The structure
was solved by direct Fourier methods. Full-matrix least-
squares refinement was based on F2 with SHELXL-97 [12].
In the title molecule, all of the C–N distances (Table 2)
˚
are between the normal C=N double bond (1.27 A) and
˚
C–N single bond (1.47 A), indicating all the N atoms are
partially characterized by sp2 hybridization. It is deduced
that there exists some degree of p-electron delocalization
around the urea scaffold. The urea linkage unit O(1)–C(7)–
N(1)–C(8)–N(2)–H(2A) adopts the most stable conforma-
tion for the formation of an intramolecular N–HꢀꢀꢀO
hydrogen bond (Fig. 2, Table 3) to give a planar six-
membered ring specified as graph-set motif of S(6), which
is essentially coplanar with the thiadiazole plane with a
dihedral angle of only 8.62(14)°. Compared with unsub-
stitution or para-substitution [15] in the benzene moiety,
the dihedral angle between the benzene ring with the urea
scaffold increases to 42.66(15)°, thus the p-conjugation in
the molecular structure is greatly weakened, as can be
attributed to the existence of two F atoms substituted in the
ortho-positions of the benzene ring. The three rings in the
title molecule are not coplanar, the dihedral angles formed
by the thiadiazole ring with the pyridine and benzene
planes being 11.61(16)° and 39.94(16)°, respectively.
X-ray diffraction analysis reveals that pairs of N–HꢀꢀꢀO
Synthesis of the Compound
All chemicals used for the preparation of the compound
were of reagent grade quality. Solvents were dried by
standard methods and distilled prior to use. The required
2-amino-5-(pyrid-4-yl)-1,3,4-thiadiazole 1 was obtained
via the oxidative cyclization of thiosemicarbazone in the
presence of ferric chloride hexahydrate according to the
literature method [13]. 2,6-Difluorobenzoyl isocyanate 2
was synthesized by refluxing 2,6-difluorobenzamide and an
excess of oxalyl chloride in anhydrous 1,2-dichloroethane
(DCE) by the reported procedure [14]. A solution of 1.83 g
(10 mmol) of 2 in 5 mL of dry dimethylformide was added
to a stirred solution of 1.78 g (10 mmol) of 1 in 12 mL of
dry dimethylformide. The mixture was stirred overnight at
room temperature, the solvent was removed by evaporation
under reduced pressure, and the residue was recrystallized
from ethanol/dimethylformide (1:2, v/v) to give the desired
product 3.
˚
hydrogen bonds (NꢀꢀꢀO 2.867(3) A, N–HꢀꢀꢀO 169.4°)
occurring between centrosymmetrically related molecules
result in the formation of R22(8) motifs [16, 17], where each
H atom also participates in intramolecular N–HꢀꢀꢀF
hydrogen bond, as shown in Fig. 2 and Table 3. The
hydrogen-bond patterns, such as graph-set motifs of S(6)
and R22(8), are similar to those reported in the previous
literatures [18, 19]. Also present are intermolecular p–p
stacking interactions [20] between parallel benzene rings
N-(2,6-difluorobenzoyl)-N0-[5-(pyrid-4-yl)-1,3,4-thia-
diazol-2-yl]urea (3) Color: white. Yield: 83%. m.p.
[300 °C. Anal. required for C15H9F2N5O2S: C, 49.86; H,
123
Song, Xin-Jian
