Influence of steric strain of S,N-heterocycles derivative ligands on the coordination geometry in cadmium(II) nitrato complexes

Article abstract of DOI:10.1016/j.poly.2011.09.033

The new ligands 2-(3,5-dimethyl-1-pyrazolyl)-2-thiazoline (DMPyTn) and 2-(3,5-diphenyl-1-pyrazolyl)-2-thiazoline (DPhPyTn) have been synthesized and characterized, and six cadmium(II) nitrato complexes with these two ligands and four other pyrazole/S,N-he

Full text of DOI:10.1016/j.poly.2011.09.033

Polyhedron 31 (2012) 307–318
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Polyhedron
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Influence of steric strain of S,N-heterocycles derivative ligands on the
coordination geometry in cadmium(II) nitrato complexes
⇑
P. Torres-García, R. Pedrero-Marín, F. Luna-Giles, A.V. Huertas-Sánchez, E. Viñuelas-Zahínos
Departamento de Química Orgánica e Inorgánica, Facultad de Ciencias, Universidad de Extremadura, 06071 Badajoz, Spain
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 16 July 2011
Accepted 17 September 2011
Available online 4 October 2011
The new ligands 2-(3,5-dimethyl-1-pyrazolyl)-2-thiazoline (DMPyTn) and 2-(3,5-diphenyl-1-pyrazolyl)-
2-thiazoline (DPhPyTn) have been synthesized and characterized, and six cadmium(II) nitrato complexes
with these two ligands and four other pyrazole/S,N-heterocyclic derivative ligands with different steric
features, previously reported, have been prepared and structurally characterized by means of elemental
analysis, single crystal X-ray diffraction and IR spectra, with the objective of determining the role played
by the steric strains of the ligands on the metal ion coordination index and geometry. The effect of two
factors has been analyzed: the bulk of the pyrazole ring substituents and the size of the S,N-heterocycle.
The data indicate that there is a clear influence of the size of the organic ligands on the coordination envi-
ronment of the Cd(II) ion.
Keywords:
Cadmium(II) complexes
Thiazine
Thiazoline
Pyrazole
Ó 2011 Elsevier Ltd. All rights reserved.
Crystal structures
1. Introduction
and coordination numbers in their complexes. Because of the large
size of the cadmium(II) ion, it exhibits high coordination numbers,
Polydentate ligands containing N,N or S,N donors have been
extensively used in coordination chemistry, drawing considerable
interest in biological systems due to their versatile chelating ability
towards transition metal ions [1]. In addition, it is fairly well known
that heterocycles with N and/or S atoms are present in the structure
of numerous compounds with pharmacological properties. Among
them, thiazolines constitute building blocks in several drugs and
biologically active natural products, like micacocidin [2], whereas
the 1,3-thiazine ring is contained in the b-lactam antibiotic frame-
work [3]. Besides the medical field, both heterocycles show applica-
tions in other diverse areas, such as the food and agricultural
industries as part of certain food flavors and aromas [4] and as
phytosanitary products [5,6], respectively.
like seven or eight, which are less common in smaller metal ions.
The coordination environment around the central ion may be a
determining factor of the coordination number. Thus, the presence
of chelating ligands in the coordination sphere of a metal ion may
contribute to minimize the possible repulsions in complexes with
a high coordination index. This is probably due to the increase of me-
tal–ligand bond distances with chelation, as it is the case of nitrato
ligands [17–21]. In this way, as can be shown from the Cambridge
Structural Database (CSD) [22], the great majority of cadmium com-
plexes that contain bidentate nitrato ligands in their coordination
sphere present coordination indices of seven and eight, with
Cd(II)–ONO2 bond distances higher than the corresponding ones to
monodentate nitrato ligands.
For these reasons, over the last few years we have carried out a
systematic study on the coordination chemistry of compounds
containing 2-thiazoline or 1,3-thiazine rings [7–12]. More recently,
we have incorporated the pyrazole moiety into these compounds
[13,14], since this aromatic heterocycle is an effective donor atom
system for a wide variety of transition metal ions. In fact, the intro-
duction of the pyrazole ring confers coordination versatility to
these ligands allowing them to act as N,N or S,N-donors through
the N pyrazole atom and the N or S atom from the 2-thiazoline
or 1,3-thiazine heterocycles, depending on the metal ion [15,16].
On the other hand, it is well known that metal ions with a d10 con-
figuration, as for cadmium(II), present a wide variety of geometries
The aim of this work is to elucidate the role played by the steric
strain of chelating ligands in the coordination environment around
the cadmium(II) ion. For this purpose, we have made cadmium ni-
trate react with several ligands with different steric features
(Scheme 1) to be able to analyze both the influence of the bulk
of pyrazole ring substituents and the size of the S,N-heterocycle
on the metal ion coordination index.
Results are reported on the isolation and characterization of two
new ligands: 2-(3,5-dimethyl-1-pyrazolyl)-2-thiazoline (DMPyTn)
and 2-(3,5-diphenyl-1-pyrazolyl)-2-thiazoline (DPhPyTn) and the
solid phases obtained by reaction of Cd(NO3)2 with these ligands,
as well as with 2-(1-pyrazolil)-2-thiazoline (PyTn), 2-(1-pyrazo-
lil)-1,3-thiazine (PzTz), 2-(3,5-dimethyl-1-pyrazolil)-1,3-thiazine
(DMPzTz) and 2-(3,5-diphenyl-1-pyrazolil)-1,3-thiazine (DPhPzTz),
already published in earlier editions of this journal [13,14]. The six
⇑
Corresponding author. Tel.: +34 924 289 395; fax: +34 924 271 149.
E-mail address: emilvin@unex.es (E. Viñuelas-Zahínos).
0277-5387/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2011.09.033

308
P. Torres-García et al. / Polyhedron 31 (2012) 307–318
4000–370 cmÀ1 range and on a Perkin-Elmer FT-IR 1700X spectro-
photometer, from Nujol mull in the 500–150 cmÀ1 range. 1H NMR
spectra for the organic ligands at 400 MHz in CDCl3 and 13C NMR
spectra for the ligands in CDCl3 at 100 MHz were obtained with a
Bruker AM 400 instrument.
2.2. Synthesis of the ligands
The ligands PyTn, PzTz, DMPzTz and DPhPzTz were synthesized
as previously reported [13,14].
2.2.1. Synthesis of 2-(3,5-dimethyl-1-pyrazolyl)-2-thiazoline
(DMPyTn)
Sodium hydride 60% (0.600 g, 0.017 mol) was added to a solution
of 3,5-dimethylpyrazole (0.961 g, 0.010 mol) in glyme (50 mL). The
mixture was stirred at room temperature for 3 h. Then a solution of
3-chloroethylisothiocyanate (1.490 g, 0.010 mol) in glyme (5 mL)
was added and the reaction mixture was refluxed for 4 h and cooled.
After the addition of methanol (5 mL), the solvent was removed in
vacuo. Water was added to the residue and the organic phase was
extracted with chloroform, dried with anhydrous Na2SO4 and the
solvent evaporated. After evaporation, a pale yellow oil was
obtained (1.492 g, 82.3%). Anal. Calc. for C8H11N3SÁ2.5glyme: C,
53.06; H, 6.96; N, 19.32; S, 14.75. Found: C, 53.39; H, 7.31; N,
19.60; S, 14.90%. 1H NMR (400 MHz, CDCl3, 25 °C) d: 5.95 (s, 1H),
4.35 (t, J = 8.0 Hz, 2H), 3.37 (t, J = 8.0 Hz, 2H), 2.47 (s, 3H), 2.14 (s,
3H); 13C NMR (100 MHz, CDCl3, 25 °C) d: 159.1, 151.1, 142.6,
106.8, 62.2, 33.1, 13.9, 13.5. IR (KBr, cmÀ1): thiazoline ring vibrations
Scheme 1. Organic ligands.
cadmium(II) solid phases obtained, [Cd(NO3)2L2], have been charac-
terized through elemental analysis, IR spectroscopy and single crys-
tal X-ray diffraction.
2. Experimental
2.1. General procedures
All reagents were commercial grade materials and used without
any further purification. Chemical analyses of carbon, hydrogen,
nitrogen and sulfur were performed by microanalytical methods
using a Leco CHNS-932 microanalyser. IR spectra were recorded
on a Termo IR-300 spectrophotometer, from KBr pellets in the
1641 [m(C@N)], 985, 932, 794, 762, 661, 582, 523, 441; pyrazole ring
vibrations: 1574, 1410, 1387, 970.
Table 1
Crystal data and structure refinement details for compounds 1–3.
1
2
3
Crystal shape
Color
Prism
Colorless
Prism
Colorless
Prism
Colorless
Size (mm)
Chemical formula
Formula weight
Crystal system
Space group
Unit cell dimensions
a (Å)
0.27 Â 0.16 Â 0.14
0.21 Â 0.16 Â 0.10
C16H22CdN8O6S2
598.95
0.10 Â 0.08 Â 0.02
C74H66Cd2N16O13S4
1740.47
C
12H14CdN8O6S2
542.83
Triclinic
Triclinic
Triclinic
ꢀ
ꢀ
ꢀ
P1
P1
P1
8.219(1)
9.559(1)
12.402(1)
91.07(1)
105.95(1)
100.57(1)
918.5(1)
2
8.025(1)
11.919(1)
12.379(1)
94.79(1)
97.37(1)
104.39(1)
1129.2(1)
2
9.324(1)
b (Å)
c (Å)
19.576(1)
20.942(1)
73.762(1)
88.401(2)
87.035(2)
3664.5(2)
2
a
(°)
b (°)
c
(°)
Cell volume (Å3)
Z
T (K)
100(2)
1.963
1.468
100(2)
1.761
1.203
100(2)
1.577
0.77
Dcalc (g cmÀ3
)
l
(mmÀ1
)
F(000)
540
604
1772
h Range
Index range
1.7–27.9
À10 6 h 6 10,
À12 6 k 6 12,
0 6 l 6 16
4372
1.7–28.4
À10 6 h 6 10,
À15 6 k 6 15,
0 6 l 6 16
5496
2.2–22.8
À11 6 h 6 12,
À25 6 k 6 25, À27 6 l 6 27
Independent reflections
Observed reflections [F > 4.0
Data completeness
16804
r(F)]
4003 [F > 4.0
0.994
r
(F)]
5117 [F > 4.0
0.972
r
(F)]
10461 [F > 4.0
0.994
r(F)]
Maximum/Minimum transmission
No. of reflection parameters
0.820/0.693
257
0.028
0.069
1.047
0.885/0.786
302
0.026
0.059
1.094
0.985/0.927
981
0.056
0.130
1.024
R[F > 4.0
wR[F > 4.0
Goodness-of-fit (GOF)c
r
(F)]a
(F)]b
r
qmax.
;
qmin. (e ÅÀ3
)
1.633; À0.915
0.99; À0.44
2.14; À1.97
P
P
a
b
c
R = ||Fo| À |Fc||/ |Fo|.
P
P
R = { [w(Fo À Fc2)2]/ [w(Fo2)2]}1/2
.
2
P
The goodness-of-fit (GOF) equals { [w(Fo À Fc2)2]/(Nrflns À Nparams)}1/2
.
2

P. Torres-García et al. / Polyhedron 31 (2012) 307–318
309
Table 2
Crystal data and structure refinement details for compounds 4–6.
4
5
6
Crystal shape
Color
Prism
Colorless
Prism
Colorless
Prism
Colorless
Size (mm)
Chemical formula
Formula weight
Crystal system
Space group
Unit cell dimensions
a (Å)
0.16 Â 0.12 Â 0.07
0.85 Â 0.32 Â 0.05
C18H26CdN8O6S2
626.99
Monoclinic
Cc
0.20 Â 0.19 Â 0.19
C38H34CdN8O7.5S2
875.25
Tetragonal
P43212
C
14H18CdN8O6S2
570.88
Monoclinic
C2/c
27.558(1)
8.662(1)
27.167(9)
107.65(1)
6179.3(4)
12
18.09(3)
8.22(1)
17.37(3)
105.04(4)
2496(7)
4
10.047(5)
36.236(5)
b (Å)
c (Å)
b (°)
Cell volume (Å3)
Z
3658(3)
4
T (K)
100(2)
1.841
1.314
293(2)
1.669
1.093
110(2)
1.589
0.771
Dcalc (g cmÀ3
)
l
(mmÀ1
)
F(000)
3432
1272
1748
h Range
Index range
1.6–25.7
À33 6 h 6 32,
0 6 k 6 10,
0 6 l 6 33
5881
2.3–26.1
À22 6 h 6 22,
0 6 k 6 10,
À21 6 l 6 21
4947
2.1–26.3
À12 6 h 6 12,
0 6 k 6 12,
0 6 l 6 45
3747
Independent reflections
Observed reflections [F > 4.0
Data completeness
r(F)]
4189 [F > 4.0
0.994
r
(F)]
3802 [F > 4.0
0.972
r
(F)]
3462 [F > 4.0
0.994
r(F)]
Maximum/Minimum transmission
No. of reflection parameters
0.914/0.817
420
0.048
0.109
1.053
0.947/0.457
320
0.036
0.081
0.969
0.867/0.861
249
0.032
0.069
1.065
R[F > 4.0
wR[F > 4.0
Goodness-of-fit (GOF)c
r
(F)]a
(F)]b
r
qmax.
;
qmin. (e ÅÀ3
)
2.143; À1.275
0.426; À0.474
0.306; À0.282
P
P
a
b
c
R = ||Fo| À |Fc||/ |Fo|.
P
P
R = { [w(Fo À Fc2)2]/ [w(Fo2)2]}1/2
.
2
P
The goodness-of-fit (GOF) equals { [w(Fo À Fc2)2]/(Nrflns À Nparams)}1/2
.
2
Fig. 1. Crystal structure of 1. The thermal ellipsoids are plotted at the 50% probability level.

310
P. Torres-García et al. / Polyhedron 31 (2012) 307–318
Table 3
Table 4
Selected bond lengths (Å), angles (°) and hydrogen bond parameters for compounds
Quantification of the geometry of eight-coordinated complexes.
1–3.a
d1 (°)
d2 (°)
d3 (°)
d4 (°)
1
2
3
Dodecahedron
Square antiprism
Bicapped trigonal prism
1
29.5
0.0
21.8
20.6
29.5
0.0
0.0
29.5
52.4
48.2
34.9
29.5
52.4
48.2
39.5
Cd–N(1)
Cd–N(3)
Cd–N(4)
Cd–N(6)
Cd–O(1)
Cd–O(2)
Cd–O(4)b
Cd–O(5)c
2.370(2)
2.389(2)
2.379(2)
2.461(2)
2.544(2)
2.444(2)
2.375(2)
2.505(2)
2.287(2)
2.502(2)
2.319(2)
2.505(2)
2.335(2)
2.342(4)
2.435(4)
2.373(4)
2.430(4)
2.330(4)
27.4
4
Majority
Minority
5
42.4
32.0
26.1
45.4
32.0
7.2
17.5
71.0
11.1
34.7
71.0
28.2
2.350(2)
2.568(2)
2.524(7)
2.459(8)
N(1)–Cd–N(3)
N(1)–Cd–N(4)
N(1)–Cd–N(6)
N(3)–Cd–N(4)
N(3)–Cd–N(6)
N(4)–Cd–N(6)
N(1)–Cd–O(1)
N(1)–Cd–O(2)
N(1)–Cd–O(4)b
N(1)–Cd–O(5)c
N(3)–Cd–O(1)
N(3)–Cd–O(2)
N(3)–Cd–O(4)b
N(3)–Cd–O(5)c
N(4)–Cd–O(1)
N(4)–Cd–O(2)
N(4)–Cd–O(4)b
N(4)–Cd–O(5)c
N(6)–Cd–O(1)
N(6)–Cd–O(2)
N(6)–Cd–O(4)b
N(6)–Cd–O(5)c
O(1)–Cd–O(2)
O(1)–Cd–O(4)b
O(1)–Cd–O(5)c
O(2)–Cd–O(4)b
O(2)–Cd–O(5)c
O(4)b–Cd–O(5)c
69.2(1)
134.7(1)
84.7(1)
89.8(1)
115.1(1)
68.1(1)
130.0(1)
90.3(1)
132.3(1)
79.7(1)
73.8(1)
81.5(1)
153.5(1)
143.9(1)
123,3(1)
73,0(1)
82.6(1)
125.8(1)
142.4(1)
159.2(1)
85.6(1)
78.6(1)
51.5(1)
79.7(1)
116.8(1)
82.9(1)
80.7(1)
52.5(1)
68.5(1)
96.6(1)
87.5(1)
86.2(1)
142.4(1)
67.8(1)
87.0(1)
67.4(1)
174.1(1)
107.7(1)
110.2(2)
77.3(1)
66.4(1)
105.6(2)
2.2.2. Synthesis of 2-(3,5-diphenyl-1-pyrazolyl)-2-thiazoline
(DPhPyTn)
A solution of 3,5-diphenylpyrazole (2.200 g, 0.010 mol) in tolu-
ene (50 mL) was treated with sodium hydride 60% (0.600 g,
0.0170 mol) and the resulting mixture was stirred 3 h at room tem-
perature. Then, a solution of 3-chloroethylisothiocyanate (1.490 g,
0.010 mol) in toluene (5 mL) was added. The mixture was refluxed
for 4 h and cooled. After addition of 5 mL of methanol, the organic
solvent was removed in vacuo and water was added. Extraction
with chloroform, drying over anhydrous sodium sulfate and con-
centration gave a yellow oil. The product was purified by flash chro-
matography, using a dichloromethane/diethyl ether mixture, 20:1
v/v. The early fractions of the chromatography contained DPhPyTn,
which was recrystallized in diethyl ether/petroleum ether 1:1 v/v,
yielding colorless crystals (1.540 g, 50.4%). Anal. Calc. for
149.8(1)
156.8(1)
118.4(1)
103.5(2)
87.1(2)
85.8(2)
84.3(1)
134.7(1)
154.4(1)
167.8(2)
132.9(2)
79.3(2)
94.0(1)
88.1(1)
87.2(1)
79.6(3)
91.2(2)
132.8(1)
C
19H17N3S: C, 70.79; H, 4.95; N, 13.76; S, 10.50. Found: C, 70.78;
H, 4.78; N, 13.61; S, 10.54%. 1H NMR (400 MHz, CDCl3, 25 °C) d:
7.93 (d, J = 7.6 Hz, 2H), 7.54 (d, J = 7.6 Hz, 2H), 7.48–7.40 (m, 6H),
6.76 (s, 1H), 4.25 (t, J = 8.0 Hz, 2H), 3.43 (t, J = 8.2 Hz, 2H); 13C
NMR (100 MHz, CDCl3, 25 °C) d: 158.9, 153.2, 146.5, 131.8, 130.3,
129.4, 128.9, 128.8, 128.7, 127.9, 108.5, 61.7, 33.7. IR (KBr, cmÀ1):
122.6(1)
73.2(1)
114.0(2)
73.7(3)
95.3(1)
79.3(1)
89.1(2)
140.6(2)
thiazoline ring vibrations 1639 [m(C@N)], 951, 927, 778, 763, 675,
683, 492, 454; pyrazole ring vibrations: 1560, 1408, 1319, 1000.
51.4(1)
51.5(3)
D–HÁ Á ÁA
Position of A
AÁ Á ÁD (Å)
AÁ Á ÁH–D (°)
2.3. Synthesis of the complexes
3
O(13)–H(13)Á Á ÁO(11)
x, y, z
2.864
148.94
The cadmium(II) complexes were prepared by reacting a solu-
tion (2 mL) of Cd(NO3)2Á4H2O (31 mg, 0.1 mmol) in the solvent
specified below with a solution of the organic ligand in the same
solvent, in such a way that the metal–ligand molar ratio was 1:2.
Solid colorless precipitates were obtained upon evaporation or
when the solution was surrounded with ether using a liquid–vapor
diffusion method. The solids were filtered, washed with cold ether
and finally air-dried.
a
b
c
Atom named Cd is Cd(1) for 3.
O(4A) for 3.
O(5A) for 3.
2.3.1. [Cd(NO3)2(PyTn)2] (1)
Yield: 43.05 mg, 79.1%. X-ray quality crystals were grown by
slow evaporation of an ethanol 96% solution. Anal. Calc. for
C
12H14CdN8O6S2: C, 26.55; H, 2.60; N, 20.64; S, 11.81. Found: C,
26.34; H, 2.67; N, 20.35; S, 11.40%. IR (KBr, cmÀ1): thiazoline ring
vibrations 1627 [ (C@N)], 993, 904, 774, 732, 647, 608, 581, 433;
m
pyrazole ring vibrations: 1532, 1358, 993.
2.3.2. [Cd(NO3)2(DMPyTn)2] (2)
Yield: 29.89 mg, 49.9%. Crystals were isolated from an ethanol
96% solution using a liquid–vapor diffusion method. Anal. Calc.
for C16H22CdN8O6S2: C, 32.02; H, 3.69; N, 18.67; S, 10.69. Found:
C, 32.14; H, 3.39; N, 18.40; S, 11.13%. IR (KBr, cmÀ1): thiazoline ring
vibrations 1608 [m(C@N)], 991, 980, 816, 744, 659, 588, 574, 497;
pyrazole ring vibrations: 1574, 1416, 1358, 991, 964.
2.3.3. [Cd(NO3)2(DPhPyTn)2]Á0.5C2H6O (3)
Yield: 55.57 mg, 63.7%. By means of slow evaporation of the
ethanol 96% solution at room temperature, crystals were isolated.
Fig. 2. View of the dodecahedral coordination polyhedron for 1.

P. Torres-García et al. / Polyhedron 31 (2012) 307–318
311
Fig. 3. Crystal structure of 2. The thermal ellipsoids are plotted at the 50% probability level.
solution. Anal. Calc. for C14H18CdN8O6S2: C, 29.45; H, 3.18; N,
Table 5
19.63; S, 11.23. Found: C, 29.54; H, 3.40; N, 19.35; S, 11.38%. IR
(KBr, cmÀ1): thiazine ring vibrations 1623 [
m(C@N)], 946, 918,
Quantification of the geometry of seven-coordinated complexes.
887, 782, 609, 608, 584, 526, 433; pyrazole ring vibrations: 1523,
d1 (°)
d2 (°)
d3 (°)
1330, 1000.
Capped octahedron
Pentagonal bipyramid
Capped trigonal prism
2
24.2
54.4
0.0
24.2
54.4
0.0
24.2
41.5
27.8
2.3.5. [Cd(NO3)2(DMPzTz)2] (5)
55.8
47.2
Yield: 39.1 mg, 62.3%. Good quality crystals were obtained
using a liquid–vapor diffusion method from a methanol solution.
Anal. Calc. for C18H26CdN8O6S2: C, 34.48; H, 4.18; N, 17.87; S,
10.23. Found: C, 34.24; H, 3.79; N, 17.52; S, 10.66%. IR (KBr,
3
Molecule 1
Molecule 2
22.1
45.1
6.9
31.6
cmÀ1): thiazine ring vibrations 1602 [
m(C@N)], 979, 900, 858,
742, 590; pyrazole ring vibrations: 1568, 1419, 1319, 1022.
2.3.6. [Cd(NO3)2(DPhPzTz)2] (6)
Yield: 45.9 mg, 52.4%. Crystals were isolated from an ethanol
96% solution by means of slow evaporation at room temperature.
Anal. Calc. for C38H34CdN8O6S2: C, 48.03; H, 3.91; N, 12.80; S,
7.33. Found: C, 48.09; H, 3.90; N, 12.84; S, 7.25%. IR (KBr cmÀ1):
thiazine ring vibrations 1610 [m(C@N)], 964, 927, 898, 763, 615,
595, 539, 459; pyrazole ring vibrations: 1556, 1411, 1301, 998.
2.4. Crystal structure determinations
X-ray diffraction measurements were performed using a Bruker
APEX or a Bruker SMART CCD diffractometer with MoKa radiation
(k = 0.71073 Å, graphite monochromator). Absorption corrections
were applied using the program SADABS [23]. The structures were
solved by direct methods and subsequent Fourier differences using
the SHELXS-97 [24] program and refined by full-matrix least-squares
on F2 with SHELXL-97 [25], included in WINGX package [26], assum-
ing anisotropic displacement parameters for non-hydrogen atoms.
All crystals were measured at low temperature, except for 5 which
was measured at 293 K because the crystals deteriorated at low
temperature. The crystal structure of complex 3 presented a static
disorder affecting the O(4) and O(5) atoms corresponding to the
bidentate nitrato ligand. Likewise, the C(21) atom corresponding
to one thiazoline ring in the same complex was also disordered.
These disorders were modeled using two sets of positions. For this
procedure the occupancy of two alternate orientations were con-
strained to unity. The refined occupancy was 56% for O(4A) and
O(5A) and 44% for O(4B) and O(5B) in the case of the nitrate group,
Fig. 4. Coordination geometry for 2.
Anal. Calc. for C37H33CdN8O7.5S2: C, 50.78; H, 3.74; N, 12.98; S, 7.43.
Found: C, 50.43; H, 3.40; N, 12.93; S, 7.57%. IR (KBr, cmÀ1): thiaz-
oline ring vibrations 1600 [m(C@N)], 960, 954, 765, 674, 600, 479,
458; pyrazole ring vibrations: 1564, 1408, 1321, 1001.
2.3.4. [Cd(NO3)2(PzTz)2] (4)
Yield: 25.9 mg, 45.4%. Crystals suitable for X-ray diffraction
were obtained by means of slow evaporation of an ethanol 96%

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P. Torres-García et al. / Polyhedron 31 (2012) 307–318
Fig. 5. Crystal structure of the two types of independent molecules of 3. The thermal ellipsoids are plotted at the 50% probability level and hydrogen atoms are omitted for
clarity.
Fig. 6. Coordination geometry in the two types of molecules found for 3.
and 65% and 35% for C(21A) and C(21B), respectively, for the thiaz-
oline ring. The EADP restraints were applied to atoms C(6) and
C(12) in 1 and to atoms N(7), N(8), O(2), O(4) and O(5) in 5 to
achieve convergence during the least squares refinement. All
hydrogen atoms were positioned geometrically, with Uiso values
derived from Ueq values of the corresponding carbon or oxygen
atoms. Graphical representations of the molecular structures were
generated using ORTEP3 [27] for Windows. Experimental details of
the crystal structure determinations are listed in Tables 1 and 2.
which acts as a bidentate ligand and coordinates the metallic atom
through the thiazoline nitrogen atom and the available nitrogen
atom of the pyrazole ring. The other four coordination positions
are occupied by four oxygen atoms corresponding to two bidentate
nitrato ligands. The disposition of the eight donor atoms can be
adequately described as a distorted dodecahedron with O(2) as
the lone capping atom, whereas N(4) and N(6) are the shared cap-
ping atoms (see Fig. 2). Likewise, the two trapezoids which charac-
terize the dodecahedron [28] are defined by the positions of atoms
N(3), N(1), O(5), O(4) and N(4), N(6), O(2), O(1). The angle between
the mean planes of these trapezoids is 86.6°, which is close to the
ideal value. In addition, the value of the d angles (d1, d2, d3, d4) [29]
are also a good test to determine the coordination geometry. The d
angles calculated by using the hard sphere model (HSM) shape
characteristics are listed in Table 4, together with the ideal values
calculated for the most usual coordination geometries found in
eight-coordinated complexes. In this case, the d values indicate
that the coordination polyhedron is best described as a distorted
triangular dodecahedral geometry.
3. Results and discussion
3.1. Crystal structures
X-ray data for 1 reveal that this complex crystallizes in the tri-
clinic system with two molecules per unit cell. A diagram of the
molecular structure of 1 is presented in Fig. 1, while selected bond
lengths and angles for this complex are listed in Table 3. The Cd(II)
ion is eight-coordinated, being bonded to two molecules of PyTn,

P. Torres-García et al. / Polyhedron 31 (2012) 307–318
313
Table 6
The axial positions of the bipyramid are occupied by one oxygen
atom O(1) corresponding to one monodentate nitrato ligand and
by the atom N(4) belonging to one molecule of the organic biden-
tate ligand DMPyTn, while the equatorial plane is formed by nitro-
gen atoms N(1), N(3), N(6) and oxygen atoms O(4) and O(5),
corresponding to the other nitrate group which behaves as a biden-
tate ligand (see Fig. 4).
Selected bond lengths (Å) and angles (°) for compounds 4 and 5.
4
5
Cd(1)–N(1)
Cd(1)–N(3)
Cd(1)–N(4)
Cd(1)–N(6)
Cd(1)–O(1)
Cd(1)–O(2)
Cd(1)–O(4)
Cd(1)–O(5)
2.420(5)
2.339(5)
2.372(5)
2.403(5)
2.396(4)
2.601(5)
2.393(5)
2.569(5)
Cd–N(1)
Cd–N(3)
Cd–N(4)
Cd–N(6)
Cd–O(1)
Cd–O(2)
Cd–O(4)
Cd–O(5)
2.354(5)
2.379(6)
2.342(6)
2.395(7)
2.452(5)
2.590(8)
2.49(1)
With regard to 3, there are two types of independent molecules
in the unit cell. The graphical representation of these molecules is
shown in Fig. 5, while the most relevant bond distances and angles
are indicated in Table 3. One of them presents a seven-coordinated
Cd(II) ion bonded to two molecules of the bidentate ligand
DPhPyTn, one bidentate nitrato ligand and another nitrate group
that behaves as monodentate. However, the other molecule [the
one with the Cd(1) atom] contains a metallic ion coordinated to
two DPhPyTn molecules, one monodentate nitrato ligand and an-
other nitrate group, N(8)–O(4)–O(5)–O(6), which is disordered in
two sets of positions, denoted A and B, with similar occupancy
(see Section 2.4). The nitrato A can be considered as bidentate to-
wards the Cd(II) ion, but in position B the distance Cd(1)–O(4B)
[2.81 Å] is too long, so this group appears to behave as a monoden-
tate ligand. Thus, this last molecule can be described as a mix of
two different coordination complexes: a seven-coordinated one
(with the nitrato N(8)–O(4A)–O(5A) as a bidentate ligand) and a
six-coordinated one (with the nitrato N(8)–O(4B)–O(5B) behaving
as a monodentate ligand). The coordination geometry around the
Cd(II) ion in the six-coordinated complex can be described as a
highly distorted octahedron; likewise, the coordination polyhedra
in both types of seven-coordinated molecules are not the same.
Thus, according to the values of the d angles (Table 5), the geome-
try of one of the molecules seems to be near to a capped octahe-
dron, where atoms N(1), N(4), N(6) and O(1) are located at
equatorial positions, atoms N(3) and O(4A) occupy axial sites,
and oxygen atom O(5A) is the capping atom (see Fig. 6a). However,
the coordination geometry of the other molecule could be de-
scribed as a distorted pentagonal bipyramid, with atom N(9) and
N(12) occupying the axial positions and atoms N(11), N(14),
O(7), O(10) and O(11) forming the equatorial plane (see Fig. 6b).
In the case of 4, the X-ray data reveal that this complex crystal-
lizes in the monoclinic system, and the unit cell contains two types
of independent molecules in a 2:1 ratio. The molecules in the high-
er proportion possess a C1 local symmetry, while the minority mol-
ecules present a C2 symmetry, with the two-fold axis containing
2.438(6)
N(1)–Cd(1)–N(3)
N(1)–Cd(1)–N(4)
N(1)–Cd(1)–N(6)
N(3)–Cd(1)–N(4)
N(3)–Cd(1)–N(6)
N(4)–Cd(1)–N(6)
N(1)–Cd(1)–O(1)
N(1)–Cd(1)–O(2)
N(1)–Cd(1)–O(4)
N(1)–Cd(1)–O(5)
N(3)–Cd(1)–O(1)
N(3)–Cd(1)–O(2)
N(3)–Cd(1)–O(4)
N(3)–Cd(1)–O(5)
N(4)–Cd(1)–O(1)
N(4)–Cd(1)–O(2)
N(4)–Cd(1)–O(4)
N(4)–Cd(1)–O(5)
N(6)–Cd(1)–O(1)
N(6)–Cd(1)–O(2)
N(6)–Cd(1)–O(4)
N(6)–Cd(1)–O(5)
O(1)–Cd(1)–O(2)
O(1)–Cd(1)–O(4)
O(1)–Cd(1)–O(5)
O(2)–Cd(1)–O(4)
O(2)–Cd(1)–O(5)
O(4)–Cd(1)–O(5)
67.9(2)
104.2(2)
89.3(2)
96.4(2)
149.2(2)
68.5(2)
79.5(2)
103.6(2)
165.9(2)
142.0(2)
116.6(2)
85.4(2)
125.3(2)
74.2(2)
144.9(2)
150.7(2)
80.6(2)
76.8(2)
76.8(2)
121.2(2)
80.0(2)
124.3(2)
51.0(1)
89.0(2)
121.7(2)
74.7(2)
75.5(1)
51.7(1)
N(1)–Cd–N(3)
N(1)–Cd–N(4)
N(1)–Cd–N(6)
N(3)–Cd–N(4)
N(3)–Cd–N(6)
N(4)–Cd–N(6)
N(1)–Cd–O(1)
N(1)–Cd–O(2)
N(1)–Cd–O(4)
N(1)–Cd–O(5)
N(3)–Cd–O(1)
N(3)–Cd–O(2)
N(3)–Cd–O(4)
N(3)–Cd–O(5)
N(4)–Cd–O(1)
N(4)–Cd–O(2)
N(4)–Cd–O(4)
N(4)–Cd–O(5)
N(6)–Cd–O(1)
N(6)–Cd–O(2)
N(6)–Cd–O(4)
N(6)–Cd–O(5)
O(1)–Cd–O(2)
O(1)–Cd–O(4)
O(1)–Cd–O(5)
O(2)–Cd–O(4)
O(2)–Cd–O(5)
O(4)–Cd–O(5)
68.2(2)
165.8(2)
99.7(2)
102.4(2)
81.8(2)
67.7(2)
111.4(2)
71.9(2)
112.4(3)
82.3(2)
79.4(2)
90.7(3)
167.6(3)
141.9(2)
75.9(2)
120.0(2)
79.2(3)
101.1(2)
134.0(2)
170.5(2)
109.9(3)
79.9(3)
49.1(2)
89.1(2)
135.7(2)
78.0(3)
102.9(3)
47.9(2)
In the case of 2, the Cd(II) ion presents a seven-coordinated
environment with the metallic atom bonded to two molecules of
the bidentate organic ligand DMPyTn and two nitrato ligands, is
shown in Fig. 3. Selected bond lengths and angles for this complex
are listed in Table 3. The coordination geometry can be adequately
described as a distorted pentagonal bipyramid, as can be deduced
from the value of the d angles [28], which are indicated in Table 5.
Fig. 7. Crystal structure of the majority (a) and minority (b) molecules for 4. The thermal ellipsoids are plotted at the 50% probability level.

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P. Torres-García et al. / Polyhedron 31 (2012) 307–318
Fig. 8. Coordination polyhedra for the majority (a) and minority (b) molecules for 4.
positions of atoms N(11), N(9), O(8), O(7) whereas atoms N(11a),
N(9a), O(8a), O(7a) form the lower square (see Fig. 8b). The angle
between the mean planes of these squares is 10.0°.
In 5 the coordination geometry around the Cd(II) ion (Fig. 9) is
an intermediate between a dodecahedron and a bicapped trigonal
prism, being closer to the first one. Atoms O(4) and O(5), corre-
sponding to one bidentate nitrate group, are the shared capping
atoms, whereas the lone capping atom in this case is N(3). The
trapezoids that define the square dodecahedron are formed by
atoms N(1), N(5), N(4), O(2) and N(3), O(1), O(4), O(5), and the an-
gle between the mean planes of these groups of atoms is 78.2°,
which clearly deviates from the ideal value for a regular dodecahe-
dron. Atoms O(1) and O(2) correspond to another bidentate nitrato
ligand. The other four coordination positions are occupied by the
thiazine and pyrazole nitrogen atoms of two molecules of DMPzTz,
which behaves as a bidentate ligand in a similar way to the rest of
the organic ligands reported in this work. In Fig. 10, a diagram of
the molecular structure of 5 with the atom numbering scheme is
represented and the most relevant bond distances and angles are
listed in Table 6.
In complex 6 the cadmium atom is six-coordinated, bonded to
two oxygen atoms of two monodentate nitrato ligands, two pyra-
zole nitrogen atoms and two thiazine nitrogen atoms correspond-
ing to two molecules of the ligand DPhPzTz, which behaves as
bidentate. The coordination geometry can be described as a dis-
torted octahedron (see Fig. 11), with ligand–metal–ligand angles
varying between 65.5(1)° [N(1)–Cd–N(3)] and 114.9(1)° [O(1)–
Cd–O(1a)]. In Fig. 12 the structure of this complex is represented,
and in Table 7 bond lengths and angles corresponding to the coor-
dination polyhedron are listed.
The average Cd–O bond distances of the bidentate nitrate
groups in complexes 1, 4 and 5 are comparable to the mean value
2.56(11) Å calculated for 29 eight-coordinated Cd(II) complexes
with the chromophore group CdN4O4, obtained from CONQUEST
software [30] from the Cambridge Structural Database (CSD)
[22]. The mean distances in the bidentate nitrato ligands for
compounds 2 and 3 are similar to the average value 2.518(91) Å
obtained for 8 seven-coordinated complexes with a Cd(II) ion
bonded to one bidentate and one monodentate nitrate group, and
four nitrogen atoms. Likewise, the Cd–O bond distance in the
monodentate nitrate group for these two complexes is comparable
to the mean value, 2.463(60) Å, calculated from the aforemen-
tioned search in the CSD. For 6, the Cd–O distance for the
Fig. 9. View of the coordination polyhedron of 5.
the cadmium atom. A selection of the bond lengths and angles for
this complex is presented in Table 6, whereas a diagram of the
structures of the two types of independent molecules is shown in
Fig. 7. The Cd(II) ion is bonded to four oxygen atoms from two ni-
trate groups, which behave as bidentate ligands, and to two mole-
cules of the organic ligand PzTz, which also acts as a bidentate
ligand and coordinates cadmium through the nitrogen atoms of
the thiazine and pyrazole rings in such a way that a five-membered
chelate ring is formed. The coordination geometry around the cad-
mium atom in the molecules in the higher proportion can be de-
scribed as a distorted dodecahedron where N(4) is the lone
capping atom and O(1) and O(2) are the shared capping atoms
(see Fig. 8a). The angle between the interpenetrating trapezoids,
defined by the positions of atoms O(2), O(1), N(6), N(4) and O(4),
O(5), N(3), N(1), is 85.6°. The d angles calculated for this structure
are listed in Table 4. On the other hand, the coordination geometry
of minority molecules could be described as a highly distorted
square antiprism, as can be deduced from the value of the d angles
(Table 4). In this antiprism the upper square is defined by the

P. Torres-García et al. / Polyhedron 31 (2012) 307–318
315
Fig. 10. Crystal structure of 5. The thermal ellipsoids are plotted at the 20% probability level.
where this kind of union is present. Finally, it is remarkable that
only one compound with a Cd(II)–Nthiazine bond, [Cd(NO3)2(InTz)2]
[InTz = N-(5,6-dihydro-4H-1,3-thiazin-2-yl)indazole] [31], has
been reported in the CSD. In 4, one of the Cd–Nthiazine bond dis-
tances is longer while the other is similar to the one found in the
reference complex [2.362(2) Å]. In the case of 5 and 6, the distances
of this type are comparable to the one of [Cd(NO3)2(InTz)2].
According to the X-ray data, it seems that the size of the organic
ligands have some influence on both the coordination index and
the coordination geometry (Fig. 13). Specifically, in the case of
the thiazoline derivative ligands it can be observed that the coordi-
nation index in 1 (whose ligand PyTn contains an unsubstituted
pyrazole ring) is higher than in 2 and 3 (which present a 3,5-disub-
stituted pyrazole ring in their organic ligands). Besides, although 2
and 3 are both seven-coordinated, the distortion of the pentagonal
bipyramidal geometry in 3 is higher than that found in 2. This fact
could be a consequence of the presence of phenyl substituents in
complex 3, which cause a higher steric hindrance than the methyl
groups in 2. In a similar way, in the thiazine derivative compounds
the presence of voluminous substituents, like phenyl rings, leads to
a decrease in the coordination index of 6 (six-coordinated) with re-
spect to 4 and 5 (eight coordinated). Regarding the eight-coordi-
nated complexes 4 and 5, it seems that the presence of methyl
groups in the ligand DMPzTz induces a steric effect that causes a
higher distortion of the dodecahedral geometry in 5.
Fig. 11. View of the coordination polyhedron of 6.
monodentate nitrato ligand is of the same order of the value,
2.423(93) Å, obtained as an average of 48 six-coordinated Cd(II)
complexes with the same chromophore group. With respect to
the Cd–Npyrazole bond lengths, they have been compared with the
average value [2.335(48) Å] found for 63 Cd(II) complexes with this
type of bond, with the result that in complexes 1–3 all these dis-
tances are slightly longer than the calculated mean value, in 4
and 5 one of the Cd–Npyrazole bond lengths is longer and the other
is similar to the mean value found in the CSD, and in 6 the dis-
tances of this type are longer than the mean reference value. On
the other hand, the Cd–Nthiazoline bond lengths for 1–3 are compa-
rable to the mean value calculated for nine cadmium(II) complexes
If we consider the influence of the S,N-heterocycle size, it can be
observed that there are remarkable differences between the thia-
zine derivative ligands (larger S–C–N angle) and the analogous
thiazoline derivative ligands (smaller S–C–N angle). This fact is
especially remarkable in the 3,5-diphenylpyrazole derivative li-
gands; thus, 6, which posses the most voluminous organic ligand
reported in this work, is a six-coordinated complex with a highly
distorted octahedral geometry, whereas its thiazoline analogous
3 presents a higher coordination index (seven), probably due to
the lower size of thiazoline ring with respect to thiazine. On the
other hand, the behavior of PyTn and PzTz in 1 and 4 is similar,
since both complexes are eight-coordinated, as it was expected

316
P. Torres-García et al. / Polyhedron 31 (2012) 307–318
Fig. 12. Crystal structure of 6. The thermal ellipsoids are plotted at the 50% probability level.
since PyTn and PzTz are the smallest ligands in each group; how-
ever, and according to the values of the d angles, the dodecahedral
geometry in 4 is slightly more distorted than in 1. In the case of 2
and 5, the influence of the S,N-heterocycle is not clear, since the
coordination index in complex 5 is higher than in complex 2, but
the distortion of the geometry in 5 is very high, probably as a con-
sequence of the large size of the organic ligand, which is forced to
distort the polyhedron in order to minimize the steric hindrance.
Table 7
Selected bond lengths (Å) and angles (°) for compound 6.
Cd–N(1)
Cd–O(1)
2.393(3)
2.341(2)
Cd–N(3)
2.468(3)
N(1)–Cd–N(3)
N(1)–Cd–N(3a)
N(1)–Cd–N(1a)
N(3)–Cd–N(3a)
N(3)–Cd–N(1a)
O(1)–Cd–N(1a)
68.5(1)
97.(1)
160.5(1)
92.3(1)
97.6(1)
88.9(1)
N(1)–Cd–O(1)
N(1)–Cd–O(1a)
N(3)–Cd–O(1)
N(3)–Cd–O(1a)
O(1)–Cd–N(3a)
O(1)–Cd–O(1a)
101.6(1)
88.9(1)
164.8(1)
77.4(1)
77.4(1)
114.9(1)
3.2. IR spectra
The IR spectra of the cadmium(II) complexes 1–6 in the 4000–
370 cmÀ1 region show the presence of bands due to organic moiety
ring vibrations, with a shift of the bands attributable to thiazoline
1737 cmÀ1 for 4 (
(
D
= 28 cmÀ1) and 1768 and 1733 cmÀ1 for 5
4) combination bands of the
bidentate nitrato ligands, while the bands at 1À7134 and
1716 cmÀ1 for = 18 cmÀ1), 1751 and 1735 cm
for
= 16 cmÀ1) and 1762 and 1751 cmÀ1 for 6 ( = 11 cmÀ1) corre-
4) combination bands of monodentate nitrato
D + m
= 35 cmÀ1) are assigned to (m1
and thiazine ring m(C@N) stretching in-plane vibrations, as well as
the stretching vibrations of the pyrazole heterocycle, when com-
pared with those of the free ligands. It can be noted that there is
a shift to lower frequencies for the bands assigned to the thiazoline
and thiazine ring vibrations, whereas the bands attributable to pyr-
azole ring vibrations suffer a shift in the opposite direction. These
facts confirm the coordination through the pyrazole and thiazoline
or thiazine nitrogen atoms. However, in the case of the complexes
with the 3,5-disubstituted pyrazole ligands, the bands correspond-
ing to the aromatic ring vibrations hardly vary because of the do-
nor effect of the ring substituents [32].
2
(D
3
(D
D
spond to (m1 + m
groups.
In the low frequency (500–150 cmÀ1) region, the C1 symmetry
of complexes 1, 4 and 5 predicts the appearance of eight bands
assignable to metal–ligand stretching vibrations [34,35], of which
only four bands are detected for 1 and 4, and three bands for 5.
In the case of complexes 2 and 3, there should be seven bands of
this type predicted by the C1 symmetry of the complex molecules
[34,35], but only four and three bands are observed, respectively.
Finally, for complex 6, its C2 symmetry point group indicates the
presence of six metal–ligand stretching vibration modes [34,35],
Moreover, according to Lever et al. [33], the bands registered at
1784 and 1764 cmÀ1 for 1 (
(
D
= 22 cmÀ1), 1793 and 1766 cmÀ1 for 2
D D
= 33 cmÀ1), 1782 and 1735 cmÀ1 for 3 ( = 47 cmÀ1), 1765 and

P. Torres-García et al. / Polyhedron 31 (2012) 307–318
317
Fig. 13. Representation of the variation of the coordination number and geometry of Cd(II) nitrato complexes when the size of the organic ligands is increased.
of which only four are registered. Thus, the m(Cd–Npyrazole) vibra-
Appendix A. Supplementary data
tions, registered at 280 (1), 271 (2), 261 (3), 262 (4), 248 (5) and
253 cmÀ1 (6), are in good agreement with literature data [36]. In
addition, the bands at 234 (1), 230 (2) and 236 cmÀ1 (3) can be
CCDC 833007–833012 contain the supplementary crystallo-
graphic data for this paper. These data can be obtained free of
charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or
from the Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail:
deposit@ccdc.cam.ac.uk.
attributed to
detected at 236 (4), 221 (5) and 223 cmÀ1 (6) are assigned to
(Cd–Nthiazine) vibrations [31].
Dealing with (Cd–ONO2) vibrations, they appear, in accord
m(Cd–Nthiazoline) vibrations [37–39], while the bands
m
m
with the consulted bibliography for cadmium(II) nitrato complexes
[38,40], at 219 and 211 for 1, 212 and 195 for 2, 209 and 188 for 3,
206 and 198 for 4, 196 for 5 and finally, 201 and 192 cmÀ1 for 6.
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It is clear that the size of the organic ligands induces a steric ef-
fect which influences both the coordination index and the coordi-
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results reported in this paper, it can be deduced that, in general,
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GR10138) for financial support.

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