S. Jianrattanasawat, G. Mezei / Inorganica Chimica Acta 384 (2012) 318–323
319
single crystal mounted atop a glass fiber with a Bruker SMART
APEX II diffractometer using graphite-monochromated Mo K
k = 0.71073 Å) radiation. The structures were solved employing
corresponds to an approximate composition of 47 mol%
3,5-dimethylpyrazole-4-sulfonic acid, 19 mol% methanedisulfonic
acid and 34 mol% sulfoacetic acid. Recrystallization from water
did not change the ratio between the products significantly. Skip-
ping the reflux during the synthesis still led to sulfoacetic acid
a
(
the SHELXTL-direct methods program and refined by full-matrix
2
least-squares on F , using the APEX2 v2008.2-0 software package
[
23]. Crystallographic details are summarized in Table 1.
but only traces of methanedisulfonic acid, and some unreacted
1
3
,5-dimethylpyrazole was detected in the H NMR spectrum. We
have also performed the same reaction under the original condi-
tions without 3,5-dimethyl-pyrazole, and found sulfoacetic acid
2.2. Synthesis
but no methanedisulfonic acid in the resulting reaction mixture
Sulfoacetic acid and methanedisulfonic acid were obtained in
1
by H NMR. The reaction of H
acetic acid) produced similar results, while in the case of H
2
SO
4
and acetic anhydride only (no
SO
4
mixture with 3,5-dimethylpyrazole-4-sulfonic acid during the sul-
fonation of 3,5-dimethylpyrazole with H SO in acetic anhydride/
acetic acid [6], and were used without further purification
Scheme 1). H SO (95–98%, 5.3 ml, 9.8 g, 0.10 mol) was slowly
2
2
4
and acetic acid only (no acetic anhydride), no sulfonation was ob-
served at all. These results show that only the more reactive acetic
anhydride undergoes sulfonation to sulfoacetic acid, even in the
absence of 3,5-dimethyl-pyrazole (via protonation by sulfuric acid
producing acetic acid and acetylsulfuric acid, with the latter under-
going a subsequent rearrangement to sulfoacetic acid [7]). Further
sulfonation to methanedisulfonic acid occurs in the presence of
(
2
4
added to 14.2 ml (15.3 g, 0.15 mol) acetic anhydride under stirring.
After cooling to room temperature, a solution of 9.61 g (0.10 mol)
,5-dimethylpyrazole in 5.0 ml (5.2 g, 0.087 mol) glacial acetic acid
was added dropwise. After stirring for 3 days at room temperature
protected from moisture), the mixture was refluxed for 30 min
3
(
3
,5-dimethylpyrazole.
and then kept in a refrigerator for one day. The resulting solid
1
was filtered, washed with benzene and dried in vacuum. H NMR
(
3
400 MHz, CDCl ): 4.00 (s, 2H, sulfoacetic acid); 3.49 (s, 2H, meth-
anedisulfonic acid); 2.41 (s, 6H, 3,5-dimethylpyrazole-4-sulfonic
acid).
3.2. Description of the crystal structures
3.2.1. Co(O SCH CO )(H O) [Co(SA)(H O) ]
Metal complexes were prepared by dissolving the ligand mix-
3
2
2
2
3
2
3
ture and the corresponding metal compound (CoCO
3
, ZnO, BaCO
3
,
Since the crystals of the cobalt complex turned opaque at 100 K
and did not diffract at that temperature, data collection was carried
out at room temperature (296 K). The Co ion is 6-coordinate, in
an approximately octahedral environment, by three O-atoms from
two different sulfoacetate ligands (two from acetate groups and
PbO and Cs CO ) in water. A few single crystals suitable for X-ray
2
3
2
+
diffraction were grown from those solutions after acetone vapor
diffusion (Zn, Ba and Pb – colorless, Co – red, Cs – yellow). In each
case, crystals with only one type of ligand were obtained, while the
other possible complexes were left dissolved in the mother
liquor.
one from a sulfonate group), and three H O molecules (Fig. 1, Table
2
2). The coordination mode of the SA ligand, which is both chelating
and bridging, can be described as
l-sulfonato-1jO-acetato-
0
1jO:2jO . The resulting coordination polymer consists of planar
3
. Results and discussion
snake-like undulating chains with perpendicularly bound water
molecules on each side, and in-plane water molecules forming in-
tra-chain hydrogen bonds (Fig. 2). The overall 3D structure is the
result of a web of inter-chain hydrogen bonds (Table 3) connecting
the polymeric chains.
3.1. NMR characterization
1H NMR of the crystalline reaction product in CDCl
3
revealed
the presence of three compounds (see reaction equation above).
The signal at 2.41 ppm was assigned to 3,5-dimethylpyrazole-4-
6
sulfonic acid (reported value in DMSO-d
6
is 2.28 ppm), while the
signals at 3.49 ppm and 4.00 ppm were attributed to methanedi-
sulfonic acid and sulfoacetic acid, respectively (a sample of wet
sulfoacetic acid from Aldrich has a chemical shift of 4.04 ppm in
3 2 2 2 3 2 3
3.2.2. Zn(O SCH CO )(H O) [Zn(SA)(H O) ]
The zinc sulfoacetate complex is isostructural with the corre-
sponding cobalt complex (see above), with nearly identical struc-
tural parameters.
3
CDCl ). The integration ratio of 7.33:1:1.73 of those three signals
Table 1
Summary of crystallographic data.
Co(SA)(H
CoO
251.07
monoclinic
P2 /c (No. 14)
6.3701(2)
9.0071(2)
13.5190(4)
90
90.757(1)
90
775.60(4)
4
2
O)
3
Zn(SA)(H
2
O)
3
Ba(SA)(H
BaO5.5
284.44
monoclinic
P2 /n (No. 14)
5.2849(1)
8.2004(2)
13.6441(4)
90
95.614(2)
90
588.48(3)
4
2
O)
Pb(SA)(H
2
O)
Cs
CH
439.97
monoclinic
C2/c (No. 15)
13.3316(2)
8.0022(1)
7.8672(1)
90
91.624(1)
90
838.95(2)
4
2
(MDS)
Formula
C
2
H
8
8
S
2
C H
8
O
8
SZn
C
2
H
3
S
C
H
2 4
O
6
PbS
2
Cs
2
O
6
S
2
Formula weight
Crystal system
Space group
a (Å)
b (Å)
c (Å)
257.51
monoclinic
P2 /c (No. 14)
363.30
monoclinic
C2/m (No. 12)
10.3837(2)
7.1228(1)
9.5745(2)
90
120.680(1)
90
609.02(2)
4
1
1
1
6.4992(1)
8.8577(1)
13.4436(2)
90
90.000(1)
90
773.92(2)
4
2.210
a
(°)
b (°)
(°)
c
3
V (Å )
Z
D
l
calc (gcmꢀ3)
(mm
2.150
2.491
3.211
7.059
3.962
28.014
3.483
9.169
ꢀ
1
)
3.453
Reflections collected/unique
Observed reflections
Goodness-of-fit (on F )
26,815/2420
2090
1.051
10,476/1335
1227
1.077
7697/1648
1195
1.052
7145/1559
1504
1.102
16,563/1767
1570
1.043
2
R(F); R
w
(F) (I > 2
r
(I))
0.0229; 0.0578
0.0184; 0.0431
0.0440; 0.0925
0.0170; 0.0364
0.0179; 0.0355