Syntheses, characterization and crystal structures of eight Cd(II) carboxylates containing 3,5-dimethylpyrazole

Article abstract of DOI:10.1016/j.poly.2014.02.041

Eight new complexes, namely [Cd(Hdmpz)₂(L1)₂0.5H ₂O]₂ (1) (Hdmpz = 3,5-dimethylpyrazole, L1 = trichloroacetate), [Cd(Hdmpz)₂(L2)₂]·H₂O (2) (L2 = indole-3-acetate), Cd(Hdmpz)₂(L3)₂ (3) (L3 = 4-methylbenzoate), Cd(Hdmpz)₄(L4)₂ (4) (L4 = 3-methylbenzoate), Cd(Hdmpz)₄(L5)₂ (5) (L5 = 4-methoxybenzoate), Cd(Hdmpz)₂(L6)₂ (6) (L6 = 2-chloronicotinate), Cd(Hdmpz)(HL7)₂ (7) (HL7 = 2-hydroxy-5- (phenyldiazenyl)benzoate) and [Cd₂(Hdmpz)₆(L8) ₂]·(Hdmpz)₂ (8) (L8 = o-phthalate) have been prepared by the self-assembly of Cd ions, 3,5-dimethylpyrazole and carboxylic acids at room temperature. All the complexes were characterized by elemental analysis, IR spectra, TG and single crystal X-ray diffraction analysis. The X-ray studies revealed that these complexes display mononuclear to dinuclear structures, with an octahedral geometry around each cadmium ion. The 3,5-dimethylpyrazole ligand in all the compounds is coordinated only in a monodentate fashion by its neutral N group. In 2, 3 and 6, the carboxylate groups behave as chelating bidentate ligands. In 4 and 5, the carboxylate groups act as monodentate ligands. The COO^- group in 1 is coordinated to the Cd centre in both monodentate and bridging bidentate modes. The carboxylates in 7 coordinate to the Cd centre in tridentate chelating bridging and bidentate bridging fashions, simultaneously, while in 8 there exists a tridentate bridging carboxylate ligand. Based on the X-ray crystallographic study, extensive intra- and intermolecular non-covalent interactions, such as classical hydrogen bonds, CH-Cl, CH₃-Cl, ClCl, ClO, CH-N, CH₃-N, C-HO, CH₃O, C-Hπ, CH₂π, CH₃-π and π-π interactions, are analyzed. These compounds display different structures, such as a 0D discrete mononuclear arrangement, sheet, 3D network, and 3D layer network. The thermal stabilities for 1-8 were examined and the results show that the complexes display good thermal stability.

Full text of DOI:10.1016/j.poly.2014.02.041

Polyhedron 74 (2014) 79–92
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Syntheses, characterization and crystal structures of eight Cd(II)
carboxylates containing 3,5-dimethylpyrazole
a
a
b
a
a
a
Shou-Wen Jin a, , Zhang-Hui Lin , Ying Zhou , Da-Qi Wang , Gu-Qing Chen , Zuo-Yi Ji , Tian-Song Huang
⇑
a Tianmu College ZheJiang A & F University, Lin’An 311300, PR China
b Department of Chemistry, Liaocheng University, Liaocheng 252059, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Eight new complexes, namely [Cd(Hdmpz)2(L1)20.5H2O]2 (1) (Hdmpz = 3,5-dimethylpyrazole, L1 = tri-
chloroacetate), [Cd(Hdmpz)2(L2)2]ÁH2O (2) (L2 = indole-3-acetate), Cd(Hdmpz)2(L3)2 (3) (L3 = 4-methylbenzo-
ate), Cd(Hdmpz)4(L4)2 (4) (L4 = 3-methylbenzoate), Cd(Hdmpz)4(L5)2 (5) (L5 = 4-methoxybenzoate),
Cd(Hdmpz)2(L6)2 (6) (L6 = 2-chloronicotinate), Cd(Hdmpz)(HL7)2 (7) (HL7 = 2-hydroxy-5-(phenyldiaze-
nyl)benzoate) and [Cd2(Hdmpz)6(L8)2]Á(Hdmpz)2 (8) (L8 = o-phthalate) have been prepared by the self-assem-
bly of Cd ions, 3,5-dimethylpyrazole and carboxylic acids at room temperature. All the complexes were
characterized by elemental analysis, IR spectra, TG and single crystal X-ray diffraction analysis. The X-ray
studies revealed that these complexes display mononuclear to dinuclear structures, with an octahedral geom-
etry around each cadmium ion. The 3,5-dimethylpyrazole ligand in all the compounds is coordinated only in a
monodentate fashion by its neutral N group. In 2, 3 and 6, the carboxylate groups behave as chelating bidentate
ligands. In 4 and 5, the carboxylate groups act as monodentate ligands. The COOÀ group in 1 is coordinated to
the Cd centre in both monodentate and bridging bidentate modes. The carboxylates in 7 coordinate to the Cd
centre in tridentate chelating bridging and bidentate bridging fashions, simultaneously, while in 8 there exists a
tridentate bridging carboxylate ligand. Based on the X-ray crystallographic study, extensive intra- and intermo-
lecular non-covalent interactions, such as classical hydrogen bonds, CH–Cl, CH3–Cl, ClÁÁÁCl, ClÁÁÁO, CH–N,
Received 22 May 2013
Accepted 19 February 2014
Available online 12 March 2014
Keywords:
Structure
Supramolecules
3,5-Dimethylpyrazole
Carboxylate
Non-covalent bonding interactions
Cadmium
CH3–N, C–HÁÁÁO, CH3ÁÁÁO, C–HÁÁÁ
p, CH2ÁÁÁp, CH3–p and p–p interactions, are analyzed. These compounds
display different structures, such as a 0D discrete mononuclear arrangement, sheet, 3D network, and 3D layer
network. The thermal stabilities for 1–8 were examined and the results show that the complexes display good
thermal stability.
Ó 2014 Elsevier Ltd. All rights reserved.
1. Introduction
covalent bonding interactions, solvent molecules, counterions
and the ratio of the metal salt to the organic ligand also
Recently, metal coordination complexes have aroused great
interest in coordination chemistry because of their intriguing
structures and potential as functional materials [1–3]. Research
in this field has been focused on the design and construction
of novel coordination frameworks and the relationships between
their structures and properties. It is still a great challenge to
predict the exact structures and compositions of the assembly
products built by coordination bonds and/or non-covalent bonds
in crystal engineering. The framework structure of coordination
complexes is primarily dependent upon the coordination
preferences of the central metal ions and the nature of the
ligands. Aside from the coordination bonding interactions, non-
influence the formation of the ultimate architectures. Therefore,
systematic research on this topic is still important for under-
standing the roles of these factors in the formation of coordination
frameworks.
The study on metal carboxylates has always been intriguing in
that they play important roles not only in synthetic chemistry,
with the essence of the labile coordination modes of the carboxyl-
ate group, such as architectures of open and porous frameworks
[4,5], but also with regard to biological activities [6,7] and physio-
logical effects [8,9]. The carboxylate anions can adopt a wide range
of bonding modes, including monodentate, symmetric and asym-
metric chelating, and bidentate and monodentate bridging [10].
Cd(II), being a d10 metal, exhibits a variety of coordination num-
bers and geometries, depending on the crystal packing and on
the ligands [11].
⇑
Corresponding author. Tel./fax: +86 571 6374 6755.
E-mail address: jinsw@zafu.edu.cn (S.-W. Jin).
http://dx.doi.org/10.1016/j.poly.2014.02.041
0277-5387/Ó 2014 Elsevier Ltd. All rights reserved.

80
S.-W. Jin et al. / Polyhedron 74 (2014) 79–92
Pyrazole and its derivatives have been widely employed in
purification. The FT-IR spectra were recorded from KBr pellets in
range 4000–400 cmÀ1 on a Mattson Alpha-Centauri spectrometer.
Microanalytical (C, H, N and S) data were obtained with a Perkin-
Elmer Model 2400II elemental analyzer. Thermogravimetric analy-
ses (TGA) were studied by a Delta Series TA-SDT Q600 in a N2
atmosphere between room temperature and 800 °C (heating rate
10 °C minÀ1) using Al crucibles.
polypyrazolylborates to stabilize a variety of organometallic and
coordination compounds [12]. Up until now, a large number of
complexes containing pyrazole (Hdmpz) ligands have been synthe-
sized and employed in coordination chemistry or organometallic
chemistry [13–15]. Many complexes with simple pyrazoles, both
in terminal as well as in bridging fashions are also available [16–
18]. However, complexes in the presence of carboxylic acids and
pyrazole derivatives are not very common, except some recently
reported examples in the literature [19]. We have been working
on coordination compounds with mixed ligands of carboxylate
and 3,5-dimethylpyrazole [20]. The pyrazole and the carboxylate
ligands appear to possess similar steric requirements and, to a cer-
tain extent, also similar bonding capabilities. In order to know the
influence of the carboxylate residue in the formation of new com-
plexes and the role the weak non-covalent interactions played in
forming the final supramolecular frameworks, we selected carbox-
ylic acids bearing N/NH, OH, Cl and CH3 units, which are good
groups in forming hydrogen bonds and some other non-bonding
interactions [21]. Thus, in the following, we report the synthesis,
structural characterization and thermal behaviour of eight Cd com-
plexes with a combination of 3,5-dimethylpyrazole (Hdmpz) and
different carboxylates (Scheme 1), namely [Cd(Hdmpz)2(L1)20.5H2
O]2 (1) (Hdmpz = 3,5-dimethylpyrazole, L1 = trichloroacetate),
[Cd(Hdmpz)2(L2)2]ÁH2O (2) (L2 = indole-3-acetate), Cd(Hdmpz)2
(L3)2 (3) (L3 = 4-methylbenzoate), Cd(Hdmpz)4(L4)2 (4) (L4 = 3-
methylbenzoate), Cd(Hdmpz)4(L5)2 (5) (L5 = 4-methoxybenzoate),
Cd(Hdmpz)2(L6)2 (6) (L6 = 2-chloronicotinate), Cd(Hdmpz)(HL7)2
(7) (HL7 = 2-hydroxy-5-(phenyldiazenyl)benzoate) and [Cd2
(Hdmpz)6(L8)2]Á(Hdmpz)2 (8) (L8 = o-phthalate).
2.2. Synthesis of the complexes
2.2.1. Synthesis of [Cd(Hdmpz)2(L1)20Á5H2O]2 (1)
A solution of Cd(CH3COO)2Á2H2O (0.0270 g, 0.1 mmol) in 8 mL
of MeOH was added to a MeOH solution (12 mL) containing Hdmpz
(0.0192 g, 0.2 mmol) and trichloroacetic acid (HL1) (0.0654 g,
0.4 mmol), under continuous stirring. The solution was stirred for
about 2 h at room temperature, the solution became turbid, then
a few drops of conc. ammonia were added until the solution be-
came completely clear. The clear solution was filtered into a test
tube and after several days colourless crystals formed, which were
filtered off, washed with MeOH and dried under vacuum to afford
0.0450 g of the product. Yield: 70.49% (based on Hdmpz). Elemen-
tal analysis performed on crystals exposed to the atmosphere, Anal.
Calc. for C28H34Cd2Cl12N8O9 (1276.83): C, 26.32; H, 2.66; N, 8.77.
Found: C, 26.25; H, 2.58; N, 8.73%. IR (KBr, cmÀ1): 3568w,
3322w(
2782w, 1639m(
1451m( s(CO2)), 1382s(
m
as(NH)), 3294w(
as(CO2)), 1599s(
s(CO2)), 1338m, 1287m, 1244m, 1202m,
m
s(NH)), 3154m, 3035m, 2964m, 2880m,
m
m
as(CO2)), 1560m, 1487m,
m
m
1154m, 1101m, 1055m, 998m, 949m, 888m, 831m, 784m, 744m,
695m, 643m, 604m.
2.2.2. Synthesis of [Cd(Hdmpz)2(L2)2]ÁH2O (2)
2. Experimental
A solution of Cd(CH3COO)2Á2H2O (0.0270 g, 0.1 mmol) in 6 mL
of MeOH was added to an EtOH solution (15 mL) containing
Hdmpz (0.0192 g, 0.2 mmol) and indole-3-acetic acid (HL2)
(0.0701 g, 0.4 mmol), under continuous stirring. The solution was
stirred for about 2 h at room temperature and the solution became
turbid. Afterwards, a few drops of conc. ammonia were added until
2.1. Materials and physical measurements
The chemicals and solvents used in this work were of analytical
grade and available commercially, and were used without further
H
N
HO
Cl
O
O
O
Cl
HO
OH
Cl
HL1
HL3
HL2
Cl
O
O
N
OH
O
O
HO
HO
HL5
HL4
HL6
OH
O
O
N
HO
O
N
OH
N
NH
OH
H2L8
Hdmpz
H2L7
Scheme 1. The ligands used in this paper.

S.-W. Jin et al. / Polyhedron 74 (2014) 79–92
81
the solution became clear. The solution was filtered into a test tube
and after several days colorless crystals were formed, which were
filtered off, washed with EtOH and dried under vacuum to afford
0.0510 g of the product. Yield 76.00% (based on Hdmpz). Elemental
analysis performed on crystals exposed to the atmosphere, Anal.
Calc for C30H34CdN6O5 (671.03): C, 53.65; H, 5.07; N, 12.52. Found:
C, 53.56; H, 5.01; N, 12.46%. IR (KBr, cmÀ1): 3606w, 3395w, 3246w,
1234m, 1170m, 1113m, 1066m, 996m, 951m, 898m, 845m,
785m, 726m, 670m, 639m, 600m.
2.2.6. Synthesis of Cd(Hdmpz)2(L6)2 (6)
A solution of Cd(CH3COO)2Á2H2O (0.0270 g, 0.1 mmol) in 6 mL
of MeOH was added to a MeOH solution (8 mL) containing Hdmpz
(0.0192 g, 0.2 mmol) and 2-chloronicotinic acid (HL6) (0.0630 g,
0.4 mmol), under continuous stirring. The solution was stirred for
about 2 h at room temperature, the solution became turbid, then
a few drops of conc. ammonia were added until the solution be-
came completely clear. The clear solution was filtered into a test
tube and after several days colorless block crystals formed, which
were filtered off, washed with MeOH and dried under vacuum to
afford 0.0541 g of the product. Yield: 87.57% (based on Hdmpz).
Elemental analysis performed on crystals exposed to the atmo-
sphere, Anal. Calc. for C22H22CdCl2N6O4 (617.76): C, 42.74; H,
3.56; N, 13.60. Found: C, 42.68; H, 3.49; N, 13.54%. IR (KBr,
3172w, 3057w, 2925m, 2847m, 2768w, 1627s(mas(CO2)), 1574m,
1521m, 1498s( s(CO2)), 1457m, 1424s, 1381m, 1287w, 1234m,
m
1225m, 1116m, 940w, 846m, 805m, 762m, 723, 696m, 645m,
621m.
2.2.3. Synthesis of Cd(Hdmpz)2(L3)2 (3)
A solution of Cd(CH3COO)2Á2H2O (0.0270 g, 0.1 mmol) in 6 mL
of MeOH was added to a MeOH solution (12 mL) containing Hdmpz
(0.0192 g, 0.2 mmol) and 4-methylbenzoic acid (HL3) (0.0545 g,
0.4 mmol), under continuous stirring. The solution was stirred for
about 2 h at room temperature, a small amount of precipitate
formed, then a few drops of conc. ammonia were added until the
precipitate dissolved completely. The clear solution was filtered
into a test tube and after several days colorless block crystals
formed, which were filtered off, washed with MeOH and dried un-
der vacuum to afford 0.0472 g of the product. Yield: 82.09% (based
on Hdmpz). Elemental analysis performed on crystals exposed to
the atmosphere, Anal. Calc. for C26H30CdN4O4 (574.94): C, 54.27;
H, 5.22; N, 9.74. Found: C, 54.21; H, 5.17; N, 9.69%. IR (KBr,
cmÀ1): 3346w(
1583m, 1534m, 1476s(
m
as(NH)), 3245w(
ms(NH)), 2955m, 1613s(mas(COO)),
ms(COO)), 1413m, 1366s, 1306s, 1279w,
1224w, 1170m, 1119m, 1067m, 1012m, 964m, 913m, 865m,
816m, 770m, 723m, 676m, 620m.
2.2.7. Synthesis of Cd(Hdmpz)(HL7)2 (7)
A solution of Cd(CH3COO)2Á2H2O (0.0270 g, 0.1 mmol) in 6 mL
of MeOH was added to a MeOH solution (10 mL) containing Hdmpz
(0.0192 g, 0.2 mmol) and 2-hydroxy-5-(phenyldiazenyl)benzoic
acid (H2L7) (0.0968 g, 0.4 mmol), under continuous stirring. The
solution was stirred for about 2 h at room temperature, the solu-
tion became turbid, then a few drops of conc. ammonia were added
until the solution became completely clear. The clear red solution
was filtered into a test tube and after several days dark red crystals
formed, which were filtered off, washed with MeOH and dried un-
der vacuum to afford 0.0540 g of the product. Yield: 78.15% (based
on Cd(CH3COO)2Á2H2O). Elemental analysis performed on crystals
cmÀ1): 3349w(
2870m, 1610s(
m
as(NH)), 3269w(
m
s(NH)), 3177m, 3032m, 2937m,
m
as(COO)), 1550m, 1484s(
ms(COO)), 1426m, 1404m
1378m, 1293m, 1245m, 1194m, 1176m, 1060m, 1012m, 852m,
801m, 763m, 698m, 656m, 624m, 602m.
2.2.4. Synthesis of Cd(Hdmpz)4(L4)2 (4)
A solution of Cd(CH3COO)2Á2H2O (0.0270 g, 0.1 mmol) in 6 mL
of MeOH was added to a MeOH solution (12 mL) containing Hdmpz
(0.0192 g, 0.2 mmol) and 3-methylbenzoic acid (HL4) (0.0545 g,
0.4 mmol), under continuous stirring. The solution was stirred for
about 2 h at room temperature, the solution became turbid, then
a few drops of conc. ammonia were added until the solution be-
came completely clear. The clear solution was filtered into a test
tube and after several days colourless crystals formed, which were
filtered off, washed with EtOH and dried under vacuum to afford
0.0270 g of the product. Yield: 70.38% (based on Hdmpz). Elemen-
tal analysis performed on crystals exposed to the atmosphere, Anal.
Calc. for C36H46CdN8O4 (767.21): C, 56.31; H, 5.99; N, 14.60. Found:
exposed to the atmosphere, Anal. Calc. for
C31H26CdN6O6
(690.98): C, 53.84; H, 3.76; N, 12.16. Found: C, 53.79; H, 3.65; N,
12.07%. IR (KBr, cmÀ1): 3647w, 3344w, 3290w, 3138m, 3079m,
2988m, 2866m, 1622s(mas(COO)), 1596s(mas(COO)), 1473s
(m
as(COO)), 1438s( as(COO)), 1385m, 1331m, 1286m, 1235s,
m
1178m, 1123m, 1067m, 1014m, 977m, 924m, 862m, 780m,
731m, 684m, 646m, 610m.
2.2.8. Synthesis of [Cd2(Hdmpz)6(L8)2]Á(Hdmpz)2 (8)
A solution of Cd(CH3COO)2Á2H2O (0.0270 g, 0.1 mmol) in 6 mL
of MeOH was added to a MeOH solution (6 mL) containing Hdmpz
(0.0192 g, 0.2 mmol) and o-phthalic acid (H2L8) (0.0332 g,
0.2 mmol) under continuous stirring. The solution was stirred for
2 h at room temperature, the solution became turbid, then a few
drops of conc. ammonia were added until the solution became
clear. The clear solution was filtered into a test tube and after sev-
eral days colorless block crystals formed, which were filtered off,
washed with MeOH, and dried under vacuum to afford 0.0264 g
of the product. Yield: 79.87% (based on Hdmpz). Elemental analysis
performed on crystals exposed to the atmosphere, Anal. Calc. for
C, 56.21; H, 5.87; N, 14.53%. IR (KBr, cmÀ1): 3367w(
3261w( s(NH)), 3156m, 3082m, 2933m, 2858m, 1614s( as(COO)),
1555m, 1489m, 1446m, 1398s( s(COO)), 1342m, 1298m, 1249m,
mas(NH)),
m
m
m
1190m, 1136m, 1065m, 1016m, 881m, 834m, 779m, 720m,
679m, 634m, 605m.
2.2.5. Synthesis of Cd(Hdmpz)4(L5)2 (5)
A solution of Cd(CH3COO)2Á2H2O (0.0270 g, 0.1 mmol) in 6 mL
of MeOH was added to an EtOH solution (4 mL) containing Hdmpz
(0.0192 g, 0.2 mmol) and 4-methoxybenzoic acid (H2L5) (0.0608 g,
0.4 mmol), under continuous stirring. The solution was stirred for
about 2 h at room temperature, the solution became turbid, then
a few drops of conc. ammonia were added until the solution be-
came completely clear. The clear solution was filtered into a test
tube and after several days colourless crystals formed, which were
filtered off, washed with EtOH and dried under vacuum to afford
0.0330 g of the product. Yield: 82.58% (based on Hdmpz). Elemen-
tal analysis performed on crystals exposed to the atmosphere, Anal.
Calc. for C36H46CdN8O6 (799.21): C, 54.05; H, 5.76; N, 14.01. Found:
C
56H72Cd2N16O8 (1322.10): C, 50.83; H, 5.44; N, 16.94. Found: C,
50.75; H, 5.41; N, 16.88%. IR (KBr, cmÀ1): 3326w, 3237w, 3164m,
3068m, 2992m, 2849m, 1627s( as(CO2)),
as(COOÀ)), 1591s(
1547m, 1506m, 1439s( s(CO2)), 1388s(
s(COOÀ)), 1353s, 1299m,
m
m
m
m
1247m, 1201m, 1154m, 1100m, 1059m, 1005m, 951m, 892m,
848m, 789m, 735m, 691m, 657m, 622m.
2.3. X-ray crystallography
C, 53.97; H, 5.69; N, 13.97%. IR (KBr, cmÀ1): 3374m(
3258m( s(NH)), 3087m, 3082m, 2957m, 2896m, 1610s( as(COO)),
1558m, 1503m, 1426m, 1405s( s(COO)), 1386m, 1335m, 1281m,
m
as(NH)),
Suitable crystals were mounted on a glass fiber on a Bruker
SMART 1000 CCD diffractometer operating at 50 kV and 40 mA
using Mo Ka radiation (0.71073 Å). Data collection and reduction
m
m
m

82
S.-W. Jin et al. / Polyhedron 74 (2014) 79–92
were performed using the SMART and SAINT software [22]. The struc-
tures were solved by direct methods and the non-hydrogen atoms
were subjected to anisotropic refinement by full-matrix least
squares on F2 using the SHELXTL package [23]. Hydrogen atom posi-
tions for all of the structures were found in a difference map. Fur-
ther details of the structural analysis are summarized in Tables 1
and 2. Selected bond lengths and angles for complexes 1–8 are
listed in Table S1.
addition of a few drops of conc. ammonia solution. The structure
determination revealed that Cd, L1 and Hdmpz are present in a
1:2:2 ratio in the molecular complex 1, and the asymmetric unit is
shown in Fig. 1. The Cl22, Cl23 and Cl24 atoms are all disordered over
twopositions with an occupancy factor of0.43007. The Cl10, Cl11 and
Cl12 atoms are all disordered over two positions with an occupancy
factor of 0.47514. The Cl1, Cl2, and Cl3 atoms are all disordered over
two positions with an occupancy factor of 0.62186. Due to the pres-
ence of these disorders, the R value for complex 1 is high. Each Cd
ion is octahedrally coordinated by four oxygen atoms from three dif-
ferent L1 ligands and one water molecule, and by two nitrogen atoms
from two different monodentate pyrazole ligands, generating a dis-
torted trigonalprismaticgeometry(Fig. 1). Herein thewatermolecule
acts as a bridging bidentate ligand.
The location of H2, H4, H6 and H8 in 1, bound to nitrogen and
not oxygen atoms, is consistent with the different acidic characters
of pyrazole and trichloroacetic acid [26], and is also confirmed by
the difference electron density map, used to find the H atoms.
The Cd–N distances are 2.21(2)–2.40(2) Å and the Cd–O distances
are 2.28(1)–2.46(1) Å. The angles around the Cd atom range from
79.9(5)° to 176.4(6)°.
Moreover 1 is not an ionic species consisting of a monocationic
Cd(II) complex and carboxylate counterions. Compound 1 is dinu-
clear. There are two kinds of L1 in the dinuclear unit, one kind of L1
is coordinated to the Cd in a monodentate mode, and the other
kind of L1 is coordinated to two Cd atoms in a bridging bidentate
fashion. In the dinuclear aggregate there exist an intramolecular
N–HÁ Á ÁO hydrogen bond between the NH unit of the pyrazole
and the non-bonded O atom of the anion, with an N–O distance
of 2.95(2) Å, together with O–HÁ Á ÁO hydrogen bonds between the
water molecule and the non-bonded O atom with O–O distances
of 2.647(19)–2.650(19) Å. The dinuclear aggregates are linked to-
gether by a CH–O association between the 4-CH group of the pyr-
azole and the non-bonded O atom, with a C-O distance of 3.588 Å,
3. Results and discussion
3.1. Preparation and general characterization
Complexes 1–8 were prepared in MeOH or EtOH at room tem-
perature via the combination of the cadmium acetate, Hdmpz
and the appropriate carboxylic acid. The corresponding crystals,
suitable for X-ray crystallography analysis, were grown upon addi-
tion of a few drops of conc. ammonia solution, with yields of
70.38–87.57%.
During the process the acetate ligands were substituted by car-
boxylate ions and also by the pyrazole group of Hdmpz. The infra-
red spectra of 1-8 are consistent with their molecular
compositions. The IR spectra of 1-8 display characteristic carboxyl-
ate bands in the range 1639–1591 cmÀ1 for
m
as(CO2) and 1498–
1382 cmÀ1 for
m
s(CO2) [24]. Neutral Hmdpz ligands are coordinated
in all of the compounds, which is further confirmed by the pres-
ence of characteristic NH bands in the region 3500–3200 cmÀ1
[25]. Weak absorptions observed at 3000–2800 cmÀ1 can be attrib-
uted to the aromatic C–H group in 1-8.
3.2. Crystal structure description
3.2.1. Crystal and molecular structure of [Cd(Hdmpz)2(L1)2 0.5H2O]2
(1)
Compound 1 was prepared by the reaction of Cd(CH3COO)2Á2H2O,
trichloroacetic acid (HL1) and Hdmpz in a ratio of 1:2:4 with
MeOH as the solvent, yielding pure [Cd(Hdmpz)2(L1)20.5H2O]2 upon
and a CH3–p association between the 3-CH3 group of the pyrazole
and the aromatic ring of the pyrazole, with a C–Cg distance of
3.692 Å, to generate a tetranuclear aggregate. The tetranuclear
Table 1
Summary of X-ray crystallographic data for complexes 1–4.
1
2
3
4
Formula
Formula weight
T (K)
C
28H34Cd2Cl12N8O9
C30H34CdN6O5
671.03
293(2)
C26H30CdN4O4
574.94
293(2)
C36H46CdN8O4
767.21
293(2)
1276.83
293(2)
Wavelength (Å)
Crystal system
Space group
a (Å)
b (Å)
c (Å)
0.71073
0.71073
monoclinic
P2(1)/c
17.6688(18)
8.5825(8)
22.297(3)
90
111.745(2)
90
3140.5(6)
4
1.419
0.742
1376
0.71073
monoclinic
P2(1)/c
10.4478(8)
13.3827(10)
19.9333(19)
90
90.9870(10)
90
2786.7(4)
4
1.370
0.819
1176
0.71073
triclinic
triclinic
ꢀ
ꢀ
P1
P1
10.3708(10)
19.6174(12)
24.729(3)
81.8280(10)
83.9940(10)
89.250(2)
4952.7(8)
4
1.712
1.558
9.4206(6)
9.4690(5)
11.1927(7)
106.126(5)
91.460(5)
102.179(5)
933.79(10)
1
1.364
0.633
398
a
(°)
b (°)
c
(°)
V (Å3)
Z
Dcalcd (Mg/m3)
Absorption coefficient (mmÀ1
F(000)
)
2520
Crystal size, mm
h (°)
Limiting indices
0.40 Â 0.27 Â 0.11
2.49–25.00
À12 6 h 6 12, À23 6 k 6 21,
À29 6 l 6 27
32414
0.31 Â 0.26 Â 0.16
2.57–25.02
À21 6 h 6 17, À6 6 k 6 10,
À26 6 l 6 23
10531
0.29 Â 0.24 Â 0.18
2.47–25.02
À12 6 h 6 12, À15 6 k 6 15,
À23 6 l 6 23
17819
0.30 Â 0.22 Â 0.16
2.79–25.02
À11 6 h 6 10, À11 6 k 6 11,
À13 6 l 6 13
6040
Reflections collected
Reflections independent (Rint
)
17465 (0.1310)
1.077
5539 (0.0701)
1.107
4916 (0.1023)
1.049
3290 (0.0316)
1.046
Goodness-of-fit (GOF) on F2
R indices [I > 2
R indices (all data)
Largest difference in peak and
hole (e ÅÀ3
r
I]
0.1392, 0.3261
0.2553, 0.4429
5.745 and À1.350
0.0887, 0.2109
0.1387, 0.2529
1.783 and À1.304
0.0543, 0.0769
0.1311, 0.1131
1.231 and À0.805
0.0307, 0.0766
0.0320, 0.0779
0.324 and À0.486
)

S.-W. Jin et al. / Polyhedron 74 (2014) 79–92
83
Table 2
Summary of X-ray crystallographic data for complexes 5–8.
5
6
7
8
Formula
Formula weight
T (K)
C
36H46CdN8O6
C22H22CdCl2N6O4
617.76
293(2)
C31H26CdN6O6
690.98
298(2)
C56H72Cd2N16O8
1322.10
293(2)
799.21
293(2)
Wavelength (Å)
Crystal system
Space group
a (Å)
b (Å)
c (Å)
0.71073
triclinic,
P1
0.71073
0.71073
monoclinic
C2/c
32.403(3)
8.9030(7)
23.075(2)
90
0.71073
triclinic
triclinic
ꢀ
ꢀ
ꢀ
P1
P1
9.0378(7)
10.4146(5)
10.8203(8)
11.4181(12)
72.444(6)
11.0827(7)
12.2160(6)
13.1214(8)
83.785(5)
10.8628(9)
10.8658(10)
67.047(8)
a
(°)
b (°)
78.711(7)
84.938(6)
963.21(14)
1
1.378
88.580(6)
85.092(5)
1222.27(17)
2
1.679
118.020(2)
90
5876.5(9)
8
1.562
0.798
65.771(6)
73.324(5)
1551.75(16)
1
1.415
c
(°)
V (Å3)
Z
Dcalcd (Mg/m3)
Absorption coefficient (mmÀ1
F(000)
)
0.620
414
1.154
620
0.749
680
2800
Crystal size, mm
h (°)
Limiting indices
0.37 Â 0.28 Â 0.23
2.81–25.02
À10 6 h 6 10, À12 6 k 6 12,
À11 6 l 6 12
5753
0.42 Â 0.37 Â 0.31
2.71–25.02
À12 6 h 6 12, À11 6 k 6 12,
À7 6 l 6 13
4317
0.34 Â 0.27 Â 0.18
2.40–25.02
À38 6 h 6 34, À10 6 k 6 10,
À14 6 l 6 27
5179
0.45 Â 0.31 Â 0.25
3.06–25.02
À12 6 h 6 13, À14 6 k 6 14,
À15 6 l 6 15
10752
Reflections collected
Reflections independent (Rint
)
3387 (0.0377)
1.041
4317 (0.0000)
1.068
5179 (0.0000)
1.049
5483 (0.0283)
1.092
Goodness-of-fit (GOF) on F2
R indices [I > 2
R indices (all data)
Largest difference in peak and
hole (e ÅÀ3
r
I]
0.0389, 0.0773
0.0444, 0.0811
0.347 and À0.435
0.0696, 0.1777
0.0925, 0.2067
3.033 and À1.261
0.0631, 0.1631
0.0997, 0.1906
0.794 and À0.851
0.0323, 0.0666
0.0414, 0.0736
0.678 and À0.371
)
Fig. 1. Molecular structure of complex 1 at the 30% ellipsoid probability level. Due to the crowded nature of the structure, the atomic numbering is not shown.
aggregates are held together via a CH–Cl association between 4-CH
of the pyrazole and the Cl of CCl3, with a C–Cl distance of 3.716 Å,
to form a chain. The chains are combined together by interchain
Cl–Cl bonds with Cl–Cl separations of 3.399–3.457 Å to form a
sheet extending in a direction that makes a dihedral angle of ca.
60° with the bc plane (Fig. 2). The sheets are further stacked along
the direction that is perpendicular to its extending direction via a
CH–O association between 4-CH of the pyrazole and the non-
bonded O atom of the carboxylate, with a C–O separation of
3.303 Å, CH3–Cl associations between 3-CH3 of the pyrazole and
structure. Herein the neighboring sheets are slipped some distance
from each other along the extending directions.
3.2.2. Crystal and molecular structure of [Cd(Hdmpz)2(L2)2]ÁH2O (2)
Crystals of 2 contain a mononuclear complex of the formulation
[Cd(Hdmpz)2(L2)2]ÁH2O (Fig. 3). Each Cd ion is octahedrally coordi-
nated by four oxygen atoms of two chelating bidentate L2 ligands
and by two nitrogen atoms, belonging to two monodentate pyra-
zole ligands, creating a CdN2O4 binding set. The coordination mode
of the Cd centre is similar to the reported compounds [Cd(La)2
(Hdmpz)2] where La = R-C6H4COO– (R = H, 2-Cl, 4-OH and 2-OH)
[27]. The CdN4O2 unit possesses coordination distances and angles
in the ranges 2.254(6)–2.463(7) Å and 54.3(2)–149.8(2)°,
the Cl of CCl3 with C–Cl distances of 3.579–3.621 Å and a CH3–
p
association between 3-CH3 of the pyrazole and the pyrazole ring,
with a C–Cg distance of 3.561 Å, to form a 3D layer network

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S.-W. Jin et al. / Polyhedron 74 (2014) 79–92
Fig. 2. Packing diagram of compound 1 showing the sheet extending in the direction that makes a dihedral angle of ca. 60° with the bc plane.
Fig. 3. Molecular structure of complex 2 at the 30% ellipsoid probability level. Due to the crowded nature of the structure, the atomic numbering is not shown.
respectively. The two pyrazole ligands and the two carboxylates
coordinated to the same Cd centre are in a cis arrangement.
The rms deviations of the pyrazole rings containing N1 and N2,
and N3 and N4 atoms are 0.0051 and 0.0063 Å, respectively, and
both rings are inclined at an angle of 102.3° to each other. The
rms deviation of the indole ring containing the N5–C(13)–C(20)
atoms is 0.0112 Å, and this ring forms dihedral angles of 10.8°
and 96.4° with the above two pyrazole rings, respectively. The
plane defined by the indole ring is almost perpendicular to the pyr-
azole ring containing the N3 and N4 atoms. The rms deviation of
the indole ring containing the N6–C(23)–C(30) atoms is 0.0076 Å,
and this ring forms dihedral angles of 90.8° and 15.4° with the
above two pyrazole rings, respectively. The two indole rings are in-
clined at an angle of 86.6° with each other. Due to the flexible
bridge between the carboxylate and the pyrrole ring, the plane de-
fined by the carboxylate is perpendicular to the aromatic ring to
which it is attached.
At every mononuclear unit there is a water molecule attached
through an N–HÁ Á ÁOw hydrogen bond arising from the NH unit of
the pyrazole, with an N–O distance of 2.801(9) Å, and an O–HwÁ Á ÁO
hydrogen bond between the water molecule (donor) and the car-
boxylate, with an O–O separation of 2.716(8) Å. The mononuclear

S.-W. Jin et al. / Polyhedron 74 (2014) 79–92
85
units are linked together by an N–HÁ Á ÁO hydrogen bond between
the pyrrole NH and the carboxylate, with an N–O distance of
2.938(9) Å, an N–HÁ Á ÁO hydrogen bond between the NH of the pyr-
azole and the water molecule, with an N–O distance of 2.807(9) Å,
and an O–HwÁ Á ÁO hydrogen bond between the water molecule and
the carboxylate, with an O–O distance of 2.744(8) Å, to form a
chain running along the b axis direction. In the chain the Cd–Cd
separation of neighboring Cd centres in the same chain is
8.582 Å, which is equal to the length of the b axis. The Cd–Cd
distance between two adjacent chains is 11.215 Å, while the
Cd–Cd separation between the third chain and the first chain is
22.297 Å, which is equal to the length of the c axis.
The coordination arrangement around the Cd centre in complex
3 is a distorted octahedron, with coordination angles in the range
54.7(2)–132.6(2)°. The geometrical parameters of this species clo-
sely match those of compound 2.
The root mean square (rms) deviations of the pyrazole rings
containing the N1 and N2 atoms, and the N3 and N4 atoms are
0.0046 and 0.0036 Å, respectively, and the dihedral angle between
the two pyrazole rings is 76.5°. The rms deviations of the phenyl
rings of the anions are 0.0030 Å for the group C12–C17, and
0.0104 Å for the group C20–C25, and the two phenyl rings have a
dihedral angle of 116.9° to each other.
The adjacent mononuclear moieties are connected together
through N–HÁ Á ÁO hydrogen bonds between the NH unit at the pyr-
azole and the carboxylate, with N–O distances of 2.878(7)–
2.904(7) Å, CH3Á Á ÁO interactions between the 5-CH3 of the pyrazole
and the O atom of the anion, with C–O separations of 3.404–
3.461 Å, to form a chain running along the b axis direction. In the
chain the neighboring Cd–Cd distance is 6.746 Å, the distance be-
tween the first Cd and the third Cd centres is 13.383 Å, which is
equal to the length of the b axis. The interchain Cd–Cd distance
is 10.448 Å. The chains are held together by an interchain CHÁ Á ÁO
interaction between the phenyl CH of the anion and the carboxyl-
ate, with a C–O distance of 3.422 Å, and a CH3Á Á ÁO association be-
tween the CH3 of the anion and the carboxylate, with a C–O
distance of 3.483 Å, to form a sheet extending along the ab plane
(Fig. 6). The sheets are further stacked along the c axis direction
The chains are combined together by an interchain CH–p asso-
ciation between the phenyl CH of the anion and the aromatic ring
of the indole-3-acetate, with a C–Cg distance of 3.512 Å, to form a
sheet extending parallel to the bc plane (Fig. 4). Two sheets are
joined together by an intersheet CH–p association between 4-CH
of the pyrazole and the pyrazole ring, with a C–Cg distance of
3.741 Å, to form a double sheet structure. The double sheets are
further stacked along the a axis direction via a CH2–
p association
between the CH2 spacer of the anion and the aromatic ring of the
indole moiety, with a C–Cg distance of 3.647 Å, to form a 3D layer
network structure. Herein the adjacent sheets are slipped some
distance from each other along the b and c axis directions.
3.2.3. Crystal and molecular structure of Cd(Hdmpz)2(L3)2 (3)
via an intersheet CH3–p association between the CH3 group at
The structural determination revealed that compound 3, of the
formula Cd(Hdmpz)2(L3)2, has 4 formula units in the unit cell. As
illustrated in Fig. 5, the asymmetric unit consists of one CdII cation,
two pyrazole molecules and two 4-methylbenzoate ligands. The
pyrazolate unit acts as a monodentate terminal ligand. The carbox-
ylates are coordinated to the CdII cation in a bischelating bidentate
fashion. Similar to compound 2, the Cd centre has a hexa-coordi-
nate geometry with two Cd–N bonds and four Cd–Ocarboxylate
bonds. The Cd–N distances are in the range 2.281(6)–2.304(5) Å.
The Cd–Ocarboxylate distances are in the range 2.282(4)–2.449(5) Å.
the anion and the phenyl ring of the anion, with a C–Cg distance
of 3.508 Å to form a 3D layer network structure. Herein the neigh-
boring sheets are slipped some distance from each other along the
a and b axis directions.
3.2.4. Crystal and molecular structure of Cd(Hdmpz)4(L4)2 (4)
The asymmetric unit of 4, (Cd(Hdmpz)4(L4)2), contains one
octahedrally coordinated Cd(II) ion, two monodentate L4 anions
and four Hdmpz groups, as shown in Fig. 7. The Cd ion is located
Fig. 4. The sheet structure of compound 2 extending parallel to the bc plane.

86
S.-W. Jin et al. / Polyhedron 74 (2014) 79–92
Fig. 5. Molecular structure of complex 3 showing the atomic numbering scheme, at the 30% ellipsoid probability level.
with N–O distances ranging from 2.807(3) to 2.832(3) Å and H–O
distances of 1.98–2.00 Å.
Compound 4 is mononuclear. The mononuclear units are ar-
ranged linearly in the ab plane with
a Cd–Cd distance of
11.865 Å. There are, however no bonding interactions between
these mononuclear units (Fig. 8).
3.2.5. Crystal and molecular structure of Cd(Hdmpz)4(L5)2 (5)
For compound 5, the asymmetric unit of Cd(Hdmpz)4(L5)2 con-
tains one six-coordinated Cd(II) ion, two L5 anions and four Hdmpz
groups, as is shown in Fig. 9. The Cd ion is located at the inversion
center (0.5, 0.5, 0.5). The Cd–O distance are 2.365(2) Å, the Cd–N
distances are 2.362(2) and 2.389(2) Å, which are similar to the cor-
responding bond distances in 4. In this case, the Cd(1)–O(1), and
Cd(1)–N(1) bond lengths are of comparable values.
The root mean square (rms) deviations of the pyrazole ring con-
taining the N1 and N2 atoms, and the N3 and N4 atoms are 0.0021
and 0.0018 Å, respectively, and the dihedral angle between the two
pyrazole rings is 109.1°. The rms deviation of the benzene ring,
C12–C17, of the anion is 0.0027 Å, and this forms dihedral angles
of 65.0° and 48.5° with the above two pyrazole rings, respectively.
In 5, the non-bonded oxygen atoms, far enough from the Cd
ions with distances of 3.688 Å, are involved in two intramolecular
hydrogen bonds, (N(2)–H(2)Á Á ÁO(2) and N(4)–H(4)Á Á ÁO(2), with N–
O distances ranging from 2.706(3) to 2.737(3) Å and H–O distances
of 1.91 Å.
The mononuclear moieties are linked together via CH–
p inter-
Fig. 6. The sheet structure of 3 extending along the ab plane.
actions between the phenyl CH of the anion and the phenyl ring
of the anion, with a C–Cg distance of 3.581 Å, to form chain. The
chains are arranged in parallel in the same plane, that is parallel
to the ab plane, to form a sheet (Fig. 10), yet there are no bonding
interactions between these chains.
at (0.5, 0.5, 0). The molecular structure of 4 resembles complexes 2
and 3.
The CdN4O2 moiety has coordination distances and angles in the
ranges 2.289(2)–2.402(2) Å and 87.24(7)–180.0°, respectively. The
root mean square (rms) deviations of the pyrazole ring containing
the N1 and N2 atoms, and N3 and N4 atoms are 0.0013 and
0.0020 Å, respectively, and the dihedral angle between the two
pyrazole rings is 73.2°. The rms deviation of the phenyl ring of
the anion with C12–C17 is 0.0016 Å, and the phenyl ring intersects
the above two pyrazole rings with angles of 127.0° and 54.0°
respectively. In 4, the non-bonded oxygen atoms, far enough from
the Cd ions with distances of 3.742 Å, are involved in two intramo-
lecular hydrogen bonds, (N(2)–H(2)Á Á ÁO(2) and N(4)–H(4)Á Á ÁO(2),
3.2.6. Crystal and molecular structure of Cd(Hdmpz)2(L6)2 (6)
The structural determination reveals that compound 6, of the
formula Cd(Hdmpz)2(L6)2, crystallizes with 2 formula units in the
unit cell. As illustrated in Fig. 11, the asymmetric unit consists of
one CdII cation, two pyrazole molecules and two carboxylate li-
gands. The pyrazole unit acts as a monodentate terminal ligand,
with Cd–N distances of 2.260(7)–2.275(6) Å. The complex is
mononuclear and the pair of pyrazoles and the anions are in cis
positions. The carboxylate groups coordinate in a chelating biden-
tate manner with Cd–O distances of 2.343(5)–2.398(6) Å. The

S.-W. Jin et al. / Polyhedron 74 (2014) 79–92
87
Fig. 7. Molecular structure of complex 4 at the 30% ellipsoid probability level. Due to the crowded nature of the structure, the atomic numbering is not shown.
Fig. 8. The packing diagram showing the linearly arranged mononuclear units in the ab plane.
coordination arrangement around the Cd centre in complex 6 is a
distorted octahedron with coordination angles in the range
54.9(2)–175.4(2)°. The mononuclear units are linked together
through N–HÁÁÁO hydrogen bonds between the NH unit of the pyr-
azole and the carboxylate, with N–O distances of 2.779(9)–
2.782(9) Å, and a CH3Á Á ÁO interaction between the 5-CH3 group
of the pyrazole and the O atom of the carboxylate, with a C–O sep-
aration of 3.575 Å, to form a chain running along the a axis direc-
tion. In complex 6, there also exist intramolecular Cl–O contacts
between the Cl atom of the anion and the coordinated O atoms
of the carboxylate, with Cl–O distances of 2.995–3.057 Å. In this
case, the Cl–O contact is somewhat stronger than a reported exam-
ple [28]. In the chain, the neighboring Cd–Cd distances are 5.419
and 5.514 Å. The distance between the first Cd and the third Cd
centres are 10.415 Å, which is equal to the length of the a axis,
while the interchain Cd–Cd distances are 12.671 and 15.221 Å.
extending direction via intersheet p–p stacking interactions be-
tween the pyridinic rings, with a Cg–Cg distance of 3.31 Å, to form
a 3D layer network structure. In this regard, neighboring sheets are
also slipped by some distance from each other along the extending
direction.
3.2.7. Crystal and molecular structure of Cd(Hdmpz)(HL7)2 (7)
In compound 7, there are 8 formula units in the unit cell. Each
Cd ion is octahedrally coordinated by five oxygen atoms of four
HL7 ligands and by one nitrogen atom, belonging to the mono-
dentate pyrazole ligand (Fig. 13). The N6, C28, C29, C30 and
C31 atoms are all disordered over two positions with equal occu-
pancy. The carboxylate of one anion is coordinated to two Cd
centres in a tridentate chelating bridging fashion, while the other
anion is coordinated to two Cd centres in a bidentate bridging
mode. The CdNO5 moiety possesses coordination distances and
angles in the ranges 2.177(7)–2.532(6) Å and 55.2(2)–170.1(2)°,
respectively; thus, the overall coordination geometry of the Cd
centre is distorted octahedral. The two pairs of C–N bond dis-
tances related with the azo groups in the two anions are almost
equal to each other, to within the experimental error [N(1)–C(6),
The chains are held together by interchain
p–p interactions be-
tween the pyridinic rings of the anion, with a Cg–Cg distance of
3.249 Å, to form a sheet extending along the direction that makes
an angle of ca. 60° with the ab plane (Fig. 12). The sheets are
further stacked along the direction that is perpendicular with its

88
S.-W. Jin et al. / Polyhedron 74 (2014) 79–92
Fig. 9. Molecular structure of complex 5, at the 30% ellipsoid probability level. Due to the crowded nature of the structure, the atomic numbering is not shown.
Fig. 10. Packing diagram of compound 5 with the sheet structure extending parallel to the ab plane.
1.422(10) Å; N(2)–C(8), 1.427(11) Å; N(3)–C(19), 1.431(9) Å;
N(4)–C(21), 1.434(10) Å], indicating equal orbital overlap be-
tween the N and C atoms. In compound 7 the ligand HL7, (2-hy-
to that found in salicylic acid [29], and in the previously reported
structure of a deprotonated compound based on o-hydroxy ben-
zoic acid derivatives [30]. As expected, the O–O separations,
2.556(8)–2.563(10) Å (mean: 2.559 Å), are essentially in the upper
limit of the documented data [2.531(4)–2.570(4) Å] [31] because of
the planarity of the hydrogen bonded carboxylate unit, but they
are slightly contracted compared with the non-deprotonated
droxy-5-(phenyldiazenyl)benzoate), adopts an
E conformation
about the N@N bond.
There exists an intramolecular hydrogen bond (N(6)–
H(6)Á Á ÁO(5)) in 7 with an N–O distance of 2.934(11) Å and an H–
O distance of 2.15 Å. In addition to the intramolecular N–HÁ Á ÁO
hydrogen bond, there also exists intramolecular O–HÁ Á ÁO hydrogen
bonds between the phenol OH group and the oxygen atoms of the
carboxylate to produce an S11(6) loop motif. This feature is similar
examples (2.547–2.604, mean: 2.588 Å), as
deprotonation.
a result of the
The carboxylate of one anion coordinates to two Cd centres in a
tridentate chelating bridging fashion, while the other anion coordi-

S.-W. Jin et al. / Polyhedron 74 (2014) 79–92
89
3.2.8. Crystal and molecular structure of
[Cd2(Hdmpz)6(L8)2]Á(Hdmpz)2 (8)
Crystals of 8 contain a dinuclear [Cd2(Hdmpz)6(L8)2] moiety
(Fig. 15), and there is 1 formula unit in the unit cell. Each Cd centre
is octahedrally coordinated by three oxygen atoms of two different
L8 anions and by three nitrogen atoms belonging to three mono-
dentate pyrazoles, with a CdN3O3 bonding set. The phthalate anion
coordinates to one metal ion in a chelating form with two of the
four oxygen atoms, and further bridges a neighboring metal ion
with one O of the remaining two oxygen atoms. This coordinating
mode is different from the corresponding compound Zn3(l-
dmpz)4(Hdmpz)2(L8) [20b]. The CdN3O3 unit possesses coordina-
tion distances and angles in the ranges 2.271(2)–2.463(2) Å and
78.48(6)–175.77(7)°, respectively.
The Cd–Cd separation in 8 is 5.333 Å. In the dinuclear units
there are two pyrazole molecules bonded through an N–HÁ Á ÁN
hydrogen bond between the NH group of the coordinated pyrazole
and the ring N of the non-coordinated pyrazole, with an N–N dis-
tance of 2.943(4) Å, and an N–HÁ Á ÁO hydrogen bond between the
NH group of the non-coordinated pyrazole and the O of the carbox-
ylate, with an N–O distance of 2.810(3) Å. The dinuclear moieties,
with the pyrazole ligands, were linked together by a CH3–p associ-
ation between the 3-CH3 group of the coordinated pyrazole and the
aromatic ring of a non-coordinated pyrazole, with a C–Cg distance
of 3.741 Å, to form a chain. In the chain the Cd–Cd separation be-
tween adjacent dinuclear moieties is 9.768 Å. The chains running
parallel in the same plane form a sheet extending along the direc-
tion that makes an angle of ca. 60° with the bc plane (Fig. 16). How-
ever, no associations were found between these chains. The sheets
are further stacked along the direction that is perpendicular with
the extending direction by an intersheet CH3–O association be-
tween the CH3 group of the coordinated pyrazole and the non-
bonded O atom of the carboxylate, with a C–O distance of
3.485 Å, to form a 3D network structure.
Fig. 11. Molecular structure of complex 6 showing the atomic numbering scheme,
at the 30% ellipsoid probability level.
nates to two Cd centres in a bidentate bridging mode. The anions
and the Cd centres form a chain running along the b axis direction.
In this regard the corresponding pyrazole and anions are arranged
antiparallel on both sides of the chain. The Cd–Cd distances along
the chain are 4.027 and 4.895 Å. The pyrazole ligands are attached
to the chain via the Cd–N bonds. There exist an intrachain CH-N
association between the CH group of the benzene ring in the anion
and the azo group, with a C–N separation of 3.630 Å, and a
CH3–O interaction between the 5-CH3 group of the pyrazole and
the phenol unit, with a C–O distance of 3.195 Å. The chains are
3.3. Thermogravimetry (TG)
For 1, the water molecule was released between 94.8 and
115.7 °C (Found 1.32%, Calcd. 1.41%). The weight loss of 29.98%
(Calcd. 30.07%) corresponds to the loss of four Hdmpz molecules
in the temperature range 173.6–269.2 °C, and the weight loss of
50.84% between 292.2 and 457.3 °C arises from the loss of the four
trichloroacetates (Calcd. 50.91%). For 2 the water molecule was lib-
erated between 91.5 and 102.6 °C (Found 2.61%, Calcd. 2.68%). The
joined together by
a CH–O interaction between the 4-CH
group of the pyrazole and the phenol unit, with a C–O distance
of 3.402 Å, and a CH3–N association between the 5-CH3 group
of the pyrazole and the azo group, with
a C–N separation
of 3.651 Å, to form a sheet extending parallel to the bc plane
(Fig. 14).
Fig. 12. The sheet structure of compound 6 extending along the direction that makes an angle of ca. 60° with the ab plane.

90
S.-W. Jin et al. / Polyhedron 74 (2014) 79–92
Fig. 13. Molecular structure of complex 7, at the 30% ellipsoid probability level. Due to the crowded nature of the structure, the atomic numbering is not shown.
Fig. 14. The sheet structure of compound 7 extending parallel to the bc plane.
two Hdmpz molecules were removed in the temperature range
167.4-258.9 °C (Found 28.55%, Calcd. 28.61%) and the carboxylates
were decomposed at 315.7–421.2 °C (Found 51.87%, Calcd.
51.94%). The TGA studies showed that 3 is stable below 160 °C.
Its decomposition begins at 165.2 °C. The weight loss of 33.33%
in the temperature range 165.2–255.8 °C is caused by the loss of
the two pyrazole molecules (Calcd. 33.39%). The weight loss of
46.94% from 320.2 to 427.7 °C arises from the loss of two L3 ligands
(Calcd. 47.05%). For 4, the first weight loss of 49.96% in the temper-
ature range 152.9-249.8 °C is attributed to the loss of four pyrazole
molecules (Calcd. 50.05%). The second weight loss of 35.18% from
289.6 to 409.8 °C is due to the loss of the two L4 ligands
(Calcd. 35.26%). For 5, the first weight loss stage occurs between
163.1 and 256.0 °C and corresponds to the removal of four Hdmpz
ligands (calcd.: 48.05%, found: 47.97%). The second stage between
296.8 and 414.6 °C is accompanied by a mass loss of 37.71% for two
4-methoxybenzoates (calcd.: 37.79%). Complex 6 experiences a
first weight loss of 31.02% in the temperature range 167.6-
260.5 °C, which is due to the loss of two pyrazole molecules (Calcd.
31.08%). The second weight loss of 50.61% was observed between
301.0 and 443.9 °C, which is attributed to the loss of the bonded
carboxylates (Calcd. 50.67%). For 7, the first weight loss between
161.5 and 225.6 °C corresponds to the release of two neutral pyra-
zoles (found: 13.82%, calcd. 13.89%). The carboxylate ligands are

S.-W. Jin et al. / Polyhedron 74 (2014) 79–92
91
Fig. 15. Molecular structure of complex 8, at the 30% ellipsoid probability level. Due to the crowded nature of the structure, the atomic numbering is not shown.
Fig. 16. The sheet structure of compound 8 extending along the direction that makes an angle of ca. 60° with the bc plane.
lost in the second stage in the temperature range 312.8-431.7.0 °C
(found: 69.67%, calcd. 69.76%). For 8, the first weight loss of 58.02%
(Calcd. 58.09%) corresponds to the loss of 8 Hdmpz molecules in
the temperature range 142.7–264.5 °C, and the second weight loss
of 24.73% between 293.3 and 452.1 °C arises from the loss of the
two L8 ligands (Calcd. 24.81%).
N4O2, N3O3, N2O4 and NO5 bonding sets around the Cd centres. In
these complexes, the metal centers are coordinated by 3,5-dimeth-
ylpyrazole, and there are no deprotonated 3,5-dimethylpyrazole
anions. The carboxylate groups behave as monodentate, chelating
bidentate, bidentate bridging and tridentate bridging ligands.
Complexes 1–8 have a great deal of intra- and intermolecular
non-bonding interactions (including classical hydrogen bonds,
CH–Cl, CH3–Cl, ClÁ Á ÁCl, ClÁ Á ÁO, CH–N, CH3–N, C–HÁ Á ÁO, CH3Á Á ÁO, C–
HÁ Á Á
p
, CH2Á Á Á
p, CH3–p and p–p interactions) in their crystals,
4. Summary
which contribute to the formation and stabilization of the final
structures.
In summary, the use of 3,5-dimethylpyrazole and different car-
boxylate ligands afforded a series of mononuclear to dinuclear Cd
complexes. Although synthesized by the same method, they
showed different structures ranging from a 0D discrete mononu-
clear arrangement, sheet, 3D network to a 3D layer network. The
octahedral geometry for Cd was observed in the X-ray studies, with
Acknowledgements
We gratefully acknowledge the financial support of the
Education Office Foundation of Zhejiang Province (project No.

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S.-W. Jin et al. / Polyhedron 74 (2014) 79–92
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Appendix A. Supplementary data
CCDC 927746, 927736, 927738, 927739, 930290, 930292,
937416 and 926288 contains the supplementary crystallographic
data for 1–8. 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, Cam-
bridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail: depos-
it@ccdc.cam.ac.uk. Supplementary data associated with this
article can be found, in the online version, at http://dx.doi.org/
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