Synthesis and characterization of copper(II) complexes incorporating pyrazolyl-derived N,S-donor bidentate ligands

Article abstract of DOI:10.1007/s11243-012-9629-9

The novel bidentate N,S-donor anionic ligands [PhNCSIndz]^-, [PhNCSImz]^-, [PhNCSPzMe3]-, and [EtNCSPz]-, where Indz = indazole, Imz = imidazole, Pz_Me3 = 3,4,5-trimethylpyrazole, and Pz = pyrazole, were synthesized and used

Full text of DOI:10.1007/s11243-012-9629-9

Transition Met Chem (2012) 37:611–617
DOI 10.1007/s11243-012-9629-9
Synthesis and characterization of copper(II) complexes
incorporating pyrazolyl-derived N,S-donor bidentate ligands
•
Moayad Hossaini Sadr Behzad Soltani
•
•
Alireza Jalili Faeghe Nejadghafar
•
•
Reza Kia James T. Engle Christopher J. Ziegler
•
Received: 23 May 2012 / Accepted: 27 June 2012 / Published online: 18 July 2012
ꢀ Springer Science+Business Media B.V. 2012
Abstract The novel bidentate N,S-donor anionic ligands
[PhNCSIndz]-, [PhNCSImz]-, [PhNCSPzMe3]-, and
[EtNCSPz]-, where Indz = indazole, Imz = imidazole,
PzMe3 = 3,4,5-trimethylpyrazole, and Pz = pyrazole, were
synthesized and used to prepare Cu(II) complexes of general
formula [Cu(N^S)2]. The ligands were synthesized via direct
addition of phenylisothiocyanate or ethylisothiocyanate into
THF suspensions of the corresponding sodium-pyrazolate
salts. All of the synthesized compounds, including the
ligands and the complexes, were characterized by physico-
chemical and spectroscopic methods, and crystal structures
of [Cu(EtNCSPz)2] and [Cu(PhNCSPzMe2)2] were deter-
mined by X-ray diffraction analysis, showing a trans-square
planar geometry for [Cu(EtNCSPz)2] and a distorted tetra-
hedral geometry for [Cu(PhNCSPzMe2)2].
Introduction
The chemistry of pyrazole-based heterocyclic ligands has
attracted considerable interest due to their rich coordination
chemistry with transition metal ions [1–3], and some of their
complexes are good models of the active sites of metallo-
enzymes [4]. In addition to the vital roles of metalloproteins
in living systems, a unique feature of metalloproteins is their
ability to discriminate between various metal ions which are
present in their environment. Generally, metalloproteins are
macromolecular systems with complicated structures, and
analysis of their structure and geometry can be very diffi-
cult; therefore, the synthesis of model compounds for the
active sites can provide useful insight into the relationships
between the structure and activity of the active sites of
proteins [4, 5].
Electronic supplementary material The online version of this
article (doi:10.1007/s11243-012-9629-9) contains supplementary
material, which is available to authorized users.
M. Hossaini Sadr (&) Á B. Soltani Á A. Jalili Á F. Nejadghafar
Department of Chemistry, Azarbaijan University of Tarbiat
Moallem, Tabriz, Iran
Inspired by the occurrence of N,S-coordinated copper
ions in a variety of proteins [6], a number of N,S-donor
ligands and their copper complexes have been synthesized
and investigated as models for active sites of the metallo-
proteins such as plastocyanin, azurin, and cytochrome
c oxidase [7, 8]. In continuation of our work on transition
metal complexes with pyrazole-derived ligands [9–11],
recently we have reported some copper complexes con-
taining N,S-donor systems based on pyrazole-derived
ligands, providing a N2S2 coordination environment around
the copper [3, 12]. It is important to mention that copper
complexes with N,S-donor ligands are comparatively rare
[3]. The suitable structure and high stability of pyrazoles,
in addition to the ability of their deprotonated form to act
as powerful nucleophiles in substitution reactions, have
e-mail: Sadr@azaruniv.edu
B. Soltani
e-mail: bh_soltani@yahoo.com
M. Hossaini Sadr Á R. Kia
Department of Chemistry, Science and Research Branch,
Islamic Azad University, Tehran, Iran
R. Kia
X-ray Crystallography Lab., Plasma Physics Research Center,
Science and Research Branch, Islamic Azad University,
Tehran, Iran
J. T. Engle Á C. J. Ziegler
Department of Chemistry, University of Akron,
Akron, OH, USA
123

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Transition Met Chem (2012) 37:611–617
Physical measurements
N
N
IR spectra were obtained on a FT BRUKER VECTOR 22
infrared spectrophotometer using pressed KBr disks with
N
C
N
C
1
Ph
N
S
Ph
N
S
polystyrene as reference. H and 13C-NMR spectra were
obtained using a BRUKER 250 MHz spectrometer.
1
2
Synthesis
Synthesis of Na[PhNCSIndz]
N
C
N
N
C
3
N
S
C2H5
N
S
Ph
N
NaH (55 %, 0.07 g, 1.69 mmol) was added to a solution
of indazole (0.2 g, 1.69 mmol) in THF (30 ml) under a
N2 atmosphere. After stirring for 1 h, PhNCS (0.2 ml,
1.69 mmol) was added to the resulting suspension of NaIndz
and the reaction heated to reflux for 3 h. After filtration, most
of the solvent was removed under vacuum and n-hexane
(10 ml) was added dropwise to induce precipitation. The
white solid Na[PhNCSIndz] was filtered off, washed with
cold THF (10 ml) and n-hexane (2 9 10 ml), and dried in
vacuo. Yield: 0.29 g (68 %). Mp: 215 ꢁC. IR (KBr, cm-1):
3286 (KBr, O–H), 1611 (m), 1591 (m), 1541 (s), 1522 (s),
1465 (m), 1338 (s), 1272 (m), 1221 (s), 1162 (s), 1112 (s),
1068–1011 (m), 963 (s), 929–803 (m), 768 (s), 742 (s),
668–426 (m). 1HNMR (DMSO, 296.5 K): 8.24 ppm (s, 1H,
3-H in Indz), 8.82 ppm (d, J = 8.4 Hz, 1H, 7-H in Indz),
7.8 ppm (d, J = 8.1 Hz, 1H, 4-H in Indz), 7.42 ppm (t,
J = 7.2 Hz, 1H, 5-H in Indz), 7.21–7.30 ppm (m, 1H, 6-H in
Indz, 4H, 2-H, 3-H, 5-H, 6-H in Ph), 7.02 ppm (m, 1H, 4-H in
Ph). 13CNMR (CDCl3): 116.68, 121.18, 122.43, 123, 124.42,
124.38, 128.42, 139.12, 172.36 ppm. Anal. Calc. For
C16H16N3NaS: C, 62.9; H, 5.2; N, 13.6; S, 10.5. Found:
C, 62.8; H, 5.1; N, 13.4; S, 10.4.
4
Scheme 1 Pyrazolyl-based ligands, [PhNCSIndz]- (1), [PhNC-
SImz]- (2), [PhNCSPzMe3 - (3), [EtNCSPz]- (4)
]
made them good candidates for incorporation in the design
of new ligands [13, 14]. In light of the structural and
spectroscopic similarities between our complexes and
active sites of copper proteins, they have been investigated
as model compounds [15–17].
Recently, we have described the synthesis and charac-
terization of some complexes of new N,S-donor ligands
formed via additional reaction of PhNCS and different pyr-
azolate anions such as: Na?[PhNCSPzR2 -
] (R=H, Me, Ph)
[3]. In this paper, we report some new similar bidentate
N,S-donor ligands, abbreviated as [PhNCSIndz]-, [PhNC-
SImz]-, [PhNCSPzMe3]-, and [EtNCSPz]- (Scheme 1), and
their Cu(II) complexes. The coordination environment
around the copper(II) atom in [Cu(EtNCSPz)2], 1, is trans-
N2S2 square planar, while that in [Cu(PhNCSPzMe2)2] is
D2d-flattened tetrahedral (Scheme 2).
Synthesis of Na[PhNCSImz]
Na[PhNCSImz] was prepared in a manner similar to
Na[PhNCSIndz]. Yield: 2.1 g (70.7 %). Mp: 235 ꢁC. IR
(KBr, cm-1): 3123 (KBr, O–H), 1549 (m), 1467 (s), 1263 (s),
1199 (s), 1101 (s), 1065 (s), 1036 (m), 933 (s), 913–615 (m).
1HNMR (DMSO, 296.5 K): 7.23 ppm (d, 1H, 4-H in Imz),
7.26 ppm (d, 1H, 5-H in Imz), 7.63 (s, 1H, 2-H in Imz), 6.8-
7.54 ppm (m, 5H in ph).13CNMR (CDCl3): 118.67, 119.59,
121.11, 121.9, 123, 123.67, 128.58, 129, 135.62, 137.28,
168.671 ppm. Anal. Calc. For C12H14N3NaS: C, 56.4; H,
5.5; N, 16.4; S, 12.5. Found: C, 56.3; H, 4.9; N, 16.2; S, 12.5.
Experimental
General considerations
All operations were carried out under a pure dinitrogen or
argon atmosphere using Schlenk techniques. All reagents
were purchased from commercial sources, and the solvents
for synthesis including tetrahydrofuran, n-hexane, and
acetone were reagent grade or better and were dried by
standard methods [18]. The melting points were deter-
mined using a BarnSteel Electrothermal BI 9300 apparatus
and they are uncorrected. Na[PhNCSPzMe2] (PzMe2 = 3,5-
dimethylpyrazole) and Cu(PhNCSPzMe2)2 were prepared as
previously described [3]. PzMe3 (3,4,5-trimethylpyrazole)
ligand was synthesized by a reported procedure [19].
Synthesis of Na[PhNCSPzMe3
]
This ligand was obtained as Na[PhNCSIndz]. Yield: 2.22 g
(88 %). M.p. = 300 ꢁC (commencement of melting along
with color change and decomposition). IR (KBr, cm-1):
123

Transition Met Chem (2012) 37:611–617
613
Scheme 2 Chemical structures
of the [Cu(EtNCSPz)2] (1), and
[Cu(PhNCSPzMe2)2] (2)
N
N
S
N
N
S
N
S
C2H5
N
Cu
Cu
N
N
N
N
C2H5
S
N
N
1
2
1634 (m), 1606 (m), 1498 (s), 1476 (m), 1447 (m), 1384
(s), 1322 (m), 1135 (m), 999 (vs), 829 (w), 689 (s), 656
(m), 546 (m), 473 (m). 1H-NMR (DMSO-d6, d ppm, J Hz):
2.11 (b, 3 H, CH3 in 3,5-(CH3)2Pz). 2.39 (b, 3 H, CH3 in
the precipitate was washed with MeOH (2 9 15 ml) and
dried in vacuo. IR (KBr, cm-1): 3421 (KBr, O–H), 1582 (s),
1525 (w), 1473 (s), 1340 (m), 1261 (s), 1198 (s), 1105 (m),
1068 (s), 941 (w), 917 (s), 828 (m), 795 (m), 744 (m), 701
(m). Anal. Calc. For C20H16CuN6S2 : C, 51.3; H, 3.4; N,17.9;
S, 13.7. Found: C, 50.9; H, 3.3; N, 17.5; S, 13.5.
3
3,5-(CH3)2Pz), 6.25 (t, JN–H = 4, 1 H, 4-H in 3,5-
3
(CH3)2Pz), 6.85 (t, JH–H = 19, 1 H, 4-H in Ph), 7.00 (d,
JH–H = 18.0, 2 H, 2-H and 6-H in Ph), 7.19 (t, 2 H, 3-H and
5-H in Ph); Anal. Calc. For C15H20N3NaS: C, 66.5; H, 6.7;
N, 14.1; S, 10.7. Found: C, 66.4; H, 6.6; N, 14.0; S, 10.6.
Synthesis of [Cu(PhNCSPzMe3)2], 4
To a solution of Na[PhNCSPzMe3] (0.534 g, 2.0 mmol) in
acetone (15 ml), CuCl2 (0.135 g, 1 mmol) was added and
stirred for 3 h. The resulting deep-violet solution was fil-
tered and the resulting precipitate was washed with acetone
(2 9 15 ml) and dried in vacuo. Yield: 0.42 g (90 %). IR
(KBr, cm-1): 3132 (w) and 3120 (w) t(C–H), 1593 (vs),
1500 (w), 1460 (w), 1431 (s), 1391 (m), 1339 (m), 1278
(m), 1216 (m), 1201 (m), 1102 (m), 1073 (s), 942 (vs), 910
(m), 780 (s), 763 (m), 693 (s), 609 (m). Anal. Calc. For
C26H28CuN6S2: C, 56.5; H, 5.1; N, 15.2; S, 11.6. Found: C,
56.3; H, 4.9; N, 15.9; S, 11.3.
Synthesis of Na[EtNCSPz]
This compound was prepared in a manner similar to the three
ligands mentioned above. Yield: 2.21 g (85 %). Mp: 220 ꢁC
(commencement of melting along with color change and
decomposition). IR (KBr, cm-1): 3331w broad, m(C–H),
1382w, 1237s, 1196s, 1111w, 981s, 939w, 861vs, 836 m,
777w, 675w, 624s, 580m. 1HNMR(CDCl3, 296.5 K): 1.242–
1.369 (t, –CH3), 3.664–3.828 (q, –CH2–), 6.280–7.705 (3H
of pyrazole). Anal. Calc. For C6H8N3NaS: C, 46.7; H, 5.2; N,
27.2; S, 20.7. Found: C, 46.8; H, 5.1; N, 27.1; S, 20.6.
Synthesis of [Cu(PhNCSIndz)2], 5
Synthesis of [Cu(EtNCSPz)2], 1
To a solution of Na[PhNCSIndz] (0.054 g, 0.2 mmol) in
MeOH (10 ml), CuCl2 (0.01 g, 0.1 mmol) in MeOH
(15 ml) was added and heated to reflux for 3 h. The
resulting solution was filtered and solvent was removed by
rotary evaporation. The resulting solid was washed with
n-hexane and dried in vacuo. IR (KBr, cm-1): 3441 (KBr,
O–H), 1619 (s), 1592 (s), 1507 (w), 1422 (s), 1347 (s),
1219 (m), 1143 (m), 939 (s), 766 (w), 753 (s), 697 (m).
Anal. Calc. For C28H20CuN6S2 : C, 59.1; H, 3.5; N, 14.7; S,
11.2. Found: C, 58.9; H, 3.4; N, 14.6; S, 11.0.
To a solution of Na[EtNCSPz] (0.354 g, 2.0 mmol) in
CH3CN/MeOH (2:1) (30 ml), CuCl2 (0.14 g, 1 mmol) was
added and stirred for 12 h. The resulting deep-green solution
was filtered and green crystals were obtained after 1 day by
slow evaporation. They were collected and washed with
diethyl ether and dried in vacuo. Yield: 75 %. Mp: 300 ꢁC.
IR (KBr, cm-1): 3442 (KBr, O–H), 2900–3100 (multiplets),
1604 (vs), 1434 (w), 1393 (s), 1376 (s), 1393 (s), 1269 (m),
1207 (w), 1116 (m), 1052 (s), 952 1 (s), 849 (m), 768 (s), 611
(s). Anal. Calc. For C12H16CuN6S2: C, 38.7; H, 4.3; N, 22.5;
S, 17.2. Found: C, 38.6; H, 4.2; N, 22.4; S, 17.1.
X-ray crystallography
Synthesis complex of [Cu(PhNCSImz)2], 3
X-ray intensity data were measured at 100 K (Bruker
KYRO-FLEX) on a Bruker SMART APEX CCD-based
X-ray diffractometer system equipped with a Mo-target
To a solution of Na[PhNCSImz] (0.15 g, 0.2 mmol) in
MeOH (15 ml), CuCl2 (0.014 g, 0.1 mmol) was added and
stirred for 3 h. The resulting orange solution was filtered and
˚
X-ray tube (k = 0.71073 A) operated at 2000 W power.
123

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Transition Met Chem (2012) 37:611–617
EtNCS, similar to our previously reported analogous
ligands (Na[PhNCSPzx]) (Pzx = pyrazole with substituted
groups on it) [3, 13]. Pyrazoles are dissolved in an aprotic
solvent such as THF, CH2Cl2, n-hexane or acetone, and
NaH is added to the resulting solution to remove the acidic
proton bonded to N of the pyrazolyl ring; after a while, a
white precipitate appears which is characterized as NaR
(R = Pz, PzMe3, Indz or Imz). We note that NaR can be
easily protonated by moisture of air or solvent and the
reaction must be under dry N2 atmosphere.
Table 1 Crystallographic data for compounds 1 and 2
Complex
1
2
Empirical formula
Formula mass
C12H16CuN6S2
371.97
C24H24CuN6S2
524.15
Crystal size (mm)
Crystal system
Space group
0.02 9 0.05 9 0.35 0.08 9 0.14 9 0.68
Triclinic
P-1
Orthorhombic
Pbca
hmax(ꢁ)
27.5
26.4
˚
a (A)
3.9951 (11)
7.837 (2)
12.497 (3)
77.021 (4)
83.235 (4)
85.923 (4)
378.22 (17)
1
13.0671 (4)
15.2567 (5)
24.1348 (8)
90
˚
b (A)
The synthetic procedure for all of the mentioned ligands
is similar but for [EtNCSPz]-, we brought into play EtNCS
instead of PhNCS.
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
The ligands were formed in high yield (68–88 %) as
white to bright-yellow powders and are soluble in common
solvents such as tetrahydrofuran, dichloromethane, and
acetone. Their appearance, physical properties, and IR
spectra do not change after storing in dry air for a few
months. Their formation can be easily monitored by IR
spectroscopy: removal of the strong band of SCN in the
2,000–2,100 cm-1 region in conjunction with appearance
of some new bands other than those corresponding to
pyrazolates clearly verifies formation of the ligands.
Absence of the strong bands of N–H stretching vibrations
of free pyrazoles in the 3,200 50 cm-1 region is further
evidence for their formation. The C–C, C–N, and N–N
stretching vibrations of the pyrazole rings show peaks at
1,697, 1,648, 1,606, and 1,481 cm-1 [21, 22].
90
90
3
˚
V (A )
4811.5 (3)
8
Z
Dcalc (Mg/m3)
l (mm-1)F (000)
Index ranges
1.633
1.447
1.721
1.106
1941
2168
-5 B h B 5
-9 B k B 10
-14 B h B 16
-19 B k B 17
-30 B l B 30
25662
No. of measured reflns. -16 B l B 15
No. of independent
reflns/Rint
3137
No. of observed reflns
I [ 2r(I)
No. of parameters
1651/0.094
4924/0.102
1217
98
3398
302
Goodness-of-fit (GOF)
R1 [(F2), observed
data)]
Syntheses of complexes 1–5
0.96
1.06
wR2 (all data)a
0.0391
0.0989
0.06
The complexes were prepared by direct reaction of the
reactants, and copper(II) chloride was used as a common
salt. While the NaR is not stable in protic solvents such as
methanol, synthesis of complexes can take place in
CH3CN/MeOH (2:1) mixture, even though acetone is a
risk-free alternative. All of the complexes 1–5 are com-
pletely air stable and soluble in common laboratory sol-
vents such as acetone, tetrahydrofuran, dichloromethane,
and acetonitrile. The complexes were characterized by a
combination of analytical and spectroscopic techniques,
including IR and CHN elemental analysis.
0.1160
a
w = 1/[r2(F2o) ? (0.0468P)2] for 1, w = 1/[r2(F2o) ? (0.0466P)2 ?
3.2574P] for 2
The crystals were mounted on a cryoloop using Paratone
N-Exxon oil and placed under a stream of nitrogen at
100 K. The detector was placed at a distance of 5.009 cm
from the crystals. The data were corrected for absorption
with the SADABS program. The structures were refined
using the Bruker SHELXTL Software Package (Version
6.1) and were solved using direct methods until the final
anisotropic full-matrix, least squares refinement of F2
converged [20]. Crystal data are summarized in Table 1.
Crystal structures
The ORTEP drawings of 1 and 2 with the atom numbering
are shown in Figs. 1 and 2. Selected bond lengths and
angles are given in Table 2. A view of the molecular
packing in the crystal 2 is given in Fig. 3. Both copper ions
are in an N2S2 environment such that complex 1 has s4
value of 0.00, which fits with a square planar description,
and complex 2, which is closer to a seesaw description, has
a s4 value of 0.40, supporting an assignment of distorted
Results and discussion
Synthesis of the ligands
The ligands are simply synthesized through nucleophilic
addition of pyrazolate anion to the C=S bond of PhNCS or
123

Transition Met Chem (2012) 37:611–617
615
Fig. 1 The ORTEP plot of 1
showing 40 % probability
displacement ellipsoids and the
atomic numbering scheme
Fig. 2 The ORTEP plot of 2
showing 40 % probability
displacement ellipsoids and the
atomic numbering scheme
tetrahedral geometry [23]. In complex 1, the asymmetric
unit of the complex comprises half of the compound which
means the complex lies on center of symmetry (i) and this
emphasizes the space group is P-1. Due to the 1-bar sym-
metry located at the central copper(II) atom, structure 1
will be perfectly planar about this atom by definition and
also there is not any distortion from planarity for donors in
the square planar structure. The copper with a square
planar N2S2 coordination sphere has two equivalent Cu–N
˚
˚
bonds [1.952 (2) A] and two Cu–S bonds [2.3110(8) A],
which has features in common with trans-CuN2S2,
[Cu(PhNCSPz)2] [2]. These bond distances are comparable
to those reported in other Cu(II) complexes with negatively
charged nitrogen atoms, [Cu(H2B(3,5-Me2Pz)2)2] [12] or
[Cu(H2B(3,5-(CF3)2-Pz)2)2] [24]. Both of the Cu–S (2.281
˚
A) distances in 1 are equal and are similar to those found
123

616
Transition Met Chem (2012) 37:611–617
˚
values for other Cu(II) structures such as [Cu{(3,5-
R2Pz)2BH2}2] (R = H, CH3, CF3, Ph) [28]. The Cu–N
distances in 1 and 2 are similar to complexes with 3,5-
dihydro [29], 3,5-dimethyl [16], and 3,5-bis(trifluoro-
methyl) [30] substituents in the pyrazole rings. Compound
2 shows a planar distortion of 42ꢁ between the planes as
defined by the central copper atom and N–N–C–S frag-
ments forming the square planar center of the compound.
In fact, as the size of the 3,5-substituents increase, S–Cu–S
angle decreases and S–Cu–N angle increases causing the
adoption of a distorted tetrahedral geometry and departure
from Td symmetry. The crystal packing of 2 shows inter-
molecular C–H…S interactions which link molecules to
each other (Fig. 3).
Table 2 Selected bond lengths (A) and angles (ꢁ) of compounds 1
and 2
1
2
Cu–N
Cu–S
Cu1–N1
1.952 (2)
1.952 (2)
2.3110 (8)
2.3110 (8)
180
Cu1–N1
1.981 (3)
1.971 (3)
2.238 (1)
2.235 (1)
102.4 (1)
97.89 (4)
86.9 (1)
Cu1–N1
Cu1–N4
Cu1–S1
Cu1–S1
Cu1–S1
Cu1–S2
N–Cu–N
S–Cu–S
S–Cu–N
N1–Cu1–N1
S1–Cu1–S1
N1–Cu1–S1
N1–Cu1–S1
N1–Cu1–S1
N1–Cu1–S1
N1–Cu1–N4
S1–Cu1–S2
S1–Cu1–N1
S1–Cu1–N4
S2–Cu1–N1
S2–Cu1–N4
180
85.60 (7)
94.40 (7)
94.40 (7)
85.60 (7)
151.6 (1)
150.9 (1)
87.0 (1)
for (NEt4)2[Bp-CuMoS4Cu2(l-Bp’)2Cu2MoS4CuBp’] [25]
or (NEt4)2[MS4(CuBp’)2] (M = Mo, W; Bp’=H2B(3,5-
Me2Pz)2) [24]. The structure of 1 is also very similar to that
of the anionic cis-CuN2S2 complex, [Cu(SCH2CH(CO2Me)
NHCH2)2]-, which has been introduced as a synthetic
model for the copper proteins such as plastocyanin [25].
Even if the bonding parameters around the copper atom in
1 are somewhat different from those of the mentioned
metalloproteins, they match better than the previously
reported complexes [25–27].
Conclusion
Four Cu(II) complexes with new chelate N,S-donor ligands
have been synthesized and characterized. The ligands can be
stored for months in dry air without any significant decom-
position, as indicated by their physical properties and IR
spectroscopy. As learned from the synthesis of [EtNCSPz]-
analogue, by using EtNCS instead of PhNCS, there may be a
possibility of synthesizing new similar ligands via dis-
placement of similar pyrazole-type nucleophiles.
The crystal structure of 2 exhibits a D2d-flattened tet-
rahedral geometry with bond angles varying from 86.93ꢁ to
151.59ꢁ and average Cu–N and Cu–S distances of 1.976 (3)
We find that increasing the steric bulk on the pyrazole
ring, from compound 1 to compound 2, leads to a change
from a square planar geometry to a distorted tetrahedral
˚
˚
A and 2.237 (1) A, which are comparable to the reported
Fig. 3 The packing diagram of
2 viewed down the a axis
showing linking of molecules
through intermolecular C–H…S
interactions
123

Transition Met Chem (2012) 37:611–617
617
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which indicate that they can be models for CuA sites in
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Supplementary data
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Centre via www.ccdc.cam.ac.uk/data_request/cif.
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Acknowledgments This research has been supported by a research
fund Number 403/313 from Azarbaijan University of Tarbiat
Moallem.
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