J Chem Crystallogr (2011) 41:721–726
723
slowly added to a suspension of 0.53 g (0.022 mol) of NaH
(m(C=C), m(C=N), d(C–H) ) [25]. A strong and well-
oop
-
1
in 10 mL of tetrahydrofuran. The solution was stirred at
0
defined band at 3,454 cm
it is also observed, which
6
0 °C for 2 h. 2.75 g (0.010 mol) of a,a -dibromo-o-xylene
corresponds to m(O–H) and it is generally associated to
coordinated water molecules [26]. In the NMR, at room
temperature, the signals attributable to CH group of the
in 10 mL of tetrahydrofuran were the added dropwise and
under vigorous stirring. The resulting mixture was allowed
to stir for 12 h at 60 °C. After cooling to room temperature,
1
13
1
pyrazole ring appear at (d( H) = 5.81 and d( C{ H}) =
105.9 ppm).
1
0 mL of water were added dropwise in order to destroy
excess NaH. The solvents were then evaporated under
reduced pressure. The residue was taken up in water
The ORTEP [27] view of compound L is shown in
Fig. 1. Selected bond lengths and bond angles are pre-
sented in Table 2. The crystal structure, which lies on a
crystallographic inversion centre, consists of one dimeric
molecule formed by two ligands and two molecules of
water (Fig. 2). The two potentially active H atoms (water
molecules) are engaged in intermolecular bonds with the
lone-pair of the N atom of the pyrazolyl group of L, which
acts as a bidentate bridge ligand. Each pair of pyrazole
rings of the molecule L are almost perpendicular to each
other (interplanar angle of 77(9)°) and one of them
coplanar to the benzene groups (interplanar angle of 4(1)°).
The distance between two consecutive oxygen atoms
(
40 mL) and extracted with chloroform (3 9 50 mL). The
chloroform layers were dried with anhydrous MgSO and
4
evaporated. The crystals were obtained by the slow evap-
oration of a solution in dichloromethane/diethyl ether (1:1)
at 293 K.
Yield: 2.60 g (65%). Mp: 68.7–69.9 °C. (C H N O ꢀ
2
2 30 4 2
H O): Anal. Calc.: C, 65.98; H, 8.05; N, 13.99; Found: C,
2
6
5.72; H, 7.94; N, 13.67%. MS(ESI): m/z (%) = 383 (100)
?
-1
L ? H] . IR (KBr, cm ): 3,454 m(O–H), 3,129 m(C–H)ar,
,986, 2,865 m(C–H) , 1,623 d(O–H), 1,556 (m(C=C),
[
2
al
m(C=N)) , 1,422 (d(C=C), d(C=N)) , 1,104 m(C–O–C),
ar
ar
1
˚
(OW1) in the macrocycle is 14.483(4) A. Moreover, the
7
54 d(C–H)oop
.
H
NMR ([D]chloroform solution,
2
50 MHz) d: 7.21 [4H, br, Ph], 5.81 [2H, s, CH(pz), 4.40
4H, s, OCH Ph], 4.15 [4H, t, J = 5.8 Hz, NpzCH2
aromatic rings are parallel planar but do not overlap (their
˚
centroids are displaced by over 4 A), and therefore exhibit
3
[
2
3
CH O], 3.68 [4H, t, J = 5.8 Hz, NpzCH CH O], 2.28
evidence of very slight intramolecular p–p interaction in
the solid state. However, in this system, the free ether
moieties can be envisaged to be applied in host–guest
chemistry because of the similarity with the hetero-crown
ether [28, 29].
2
2
2
1
3
1
[
s, 12H, CH (pz)] ppm. C{ H} NMR ([D]chloroform
3
solution, 63 MHz,) d: 147.5 (pz-C), 140.3 (pz-C), 136.9-
28.5 (Ph), 105.9 (CH(pz)), 73.7 (OCH Ph), 69.1 (NpzCH2
CH O), 49.2 (NpzCH CH O), 12.5 (CH (pz)), 11.4
1
2
2
2
2
3
(
CH (pz)) ppm.
3
A detailed examination of the crystal packing (Fig. 3)
revealed that each dimeric unit is linked to two neigh-
bouring molecules, which all are in the same plane, via four
´
˚
C–HꢀꢀꢀN intermolecular bonding (2.721(2) A). This inter-
Result and Discussion
molecular interaction leads to the formation of a one-
dimensional infinite chain, running approximately along
the b axis. The X–HꢀꢀꢀN (X = C or O) intermolecular
contacts can be considered as ‘‘weak’’ on the basis of the
The synthetic route for the preparation of the ligand
,2-bis[4-(3,5-dimethyl-1H-pyrazol-1-yl)-2-oxobutyl]ben-
1
zene (L) consists of two steps (Scheme 1). The 1-(2-
hydroxyethyl)-3,5-dimethylpyrazole was reacted with NaH
in dry tetrahydrofuran to give the sodium alkoxide. This
sodium salt was converted to ligand L, by reacting it with
0
a,a -dibromo-o-xylene in dry tetrahydrofuran. For L it has
been possible to obtain colourless monocrystals suitable for
X-ray analysis through crystallization from a dichloro-
methane/diethyl ether (1:1) mixture.
The ligand has been fully characterized by melting
1
point, elemental analysis, mass spectrometry, IR, H,
1
3
1
C{ H} NMR spectroscopies and X-ray crystal structure.
The NMR signals were assigned by reference to the liter-
ature [25] and from COSY and HMQC NMR experiments.
Elemental analysis, mass spectrometry and all spectro-
scopic data are consistent with the proposed structure. The
most characteristic bands in the IR spectra are those
attributable to the ether (m(C–O–C)) and pyrazolyl groups
Fig. 1 ORTEP diagram of ligand
L showing atom labelling
scheme. 50% probability amplitude displacement ellipsoids are
shown. Hydrogen atoms are omitted for clarity. See Table 2 for
selected bond lengths, bond angles and torsion angles
123
Guerrero, Miguel
