New palladium(II) complexes bearing pyrazole-based Schiff base ligands: Synthesis, characterization and cytotoxicity

Article abstract of DOI:10.1016/j.ejmech.2009.10.029

Reactions of 5-hydrazino-1,3-dimethyl-4-nitro-1H-pyrazole (1) with substituted benzaldehydes (2-5) in methanol gave the new substituted benzaldehyde (1,3-dimethyl-4-nitro-1H-pyrazol-5-yl)hydrazone Schiff base ligands (6-9) benzaldehyde (1,3-dimethyl-4-nit

Full text of DOI:10.1016/j.ejmech.2009.10.029

European Journal of Medicinal Chemistry 45 (2010) 471–475
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
New palladium(II) complexes bearing pyrazole-based Schiff base ligands:
Synthesis, characterization and cytotoxicity
,
a
b
c
Adnan S. Abu-Surrah a , Kayed A. Abu Safieh , Iman M. Ahmad , Maher Y. Abdalla ,
*
Mikdad T. Ayoub a, Abdussalam K. Qaroush a, Ahmad M. Abu-Mahtheieh a
a Department of Chemistry, Hashemite University, P.O. Box 150459, Zarqa 13115, Jordan
b Department of Radiography, Hashemite University, Zarqa 13115, Jordan
c Department of Biology & Biotechnology, Hashemite University, Zarqa 13115, Jordan
a r t i c l e i n f o
a b s t r a c t
Article history:
Reactions of 5-hydrazino-1,3-dimethyl-4-nitro-1H-pyrazole (1) with substituted benzaldehydes (2–5) in
methanol gave the new substituted benzaldehyde (1,3-dimethyl-4-nitro-1H-pyrazol-5-yl)hydrazone Schiff
base ligands (6–9) benzaldehyde (1,3-dimethyl-4-nitro-1H-pyrazol-5-yl)hydrazone (H-BDH, 6),
2,3-dimethoxybenzaldehyde (1,3-dimethyl-4-nitro-1H-pyrazol-5-yl)hydrazone (MeO-BDH, 7), 4-chlor-
obenzaldehyde (1,3-dimethyl-4-nitro-1H-pyrazol-5-yl)hydrazone (Cl-BDH, 8), and 4-hydroxybenzaldehyde
(1,3-dimethyl-4-nitro-1H-pyrazol-5-yl)hydrazone (OH-BDH, 9) in moderate to excellent yields. Reactions of
these pyrazole-based Schiff bases with [PdCl2(NCPh)2] in acetone at room temperature gave the trans-pal-
ladium(II) complexes trans-[PdCl2(L)2] (10–13) (L [ 6–9). The isolated compounds were characterized by
their physical properties, elemental analysis, IR-, MS (EI)- and NMR-spectroscopy. The cytotoxic effect of
these complexes against the fast growing head and neck squamous carcinoma cells SQ20B and SCC-25 has
been studied. The influence was dose dependent and varies by cell type. The complexes 11, 12, and 13 had
higher clonogenic cytotoxic effect than cisplatin when tested on SQ20B cell line.
Received 23 March 2009
Received in revised form
9 October 2009
Accepted 15 October 2009
Available online 29 October 2009
Keywords:
Palladium(II) complexes
N-methylpyrazole
Schiff bases
Head and neck carcinoma
Ó 2009 Elsevier Masson SAS. All rights reserved.
1. Introduction
Due to the steric effect that results from the bulk on the donor
atoms, these ligands could minimize any possible cis-trans isom-
The significant similarity between the coordination chemistry of
palladium(II) and platinum(II) compounds has advocated studies of
Pd(II) complexes as antitumor drugs. A key factor that might explain
why platinum is most useful comes from the ligand-exchange
kinetics. The hydrolysis in palladium complexes is too rapid: 105
times faster than for their corresponding platinum analogues [1].
They dissociate readily in solution leading to very reactive species
that are unable to reach their pharmacological targets.
Compared to cisplatin, the corresponding cispalladium, cis-
[PdCl2(NH3)2] does not show antitumoral activity. It is well known
that it undergoes an inactive trans-conformation and that the two
compounds hydrolyze very fast assuming that they interact in vivo
with a lot of molecules particularly proteins preventing them to
reach the DNA, their pharmalogical target [2].
erism and insure the direct separation of the desired trans-Pd
isomers [5]. In general, research results indicated that most of the
trans-palladium complexes showed a better activity than the cis-
platinum isomers and superior activity than that of the cis-palla-
dium isomers. More importantly, they showed activities equal to
(or superior than) those of cisplatin, carboplatin, and oxaliplatin
(the anticancer drugs in clinical use) in vitro [3].
Studies of platinum and palladium compounds with biologically
active carriers have yielded promising results in the field of anti-
cancer chemistry and there is potential for varying the biological
activity of these complexes by changing the structure of the carrier
[6]. Significant advances have emerged from this methodology of
design [1,3].
Recently, we reported about the synthesis and molecular
structure of an enantiometrically pure, trans-palladium(II)
complex, trans-[PdCl2{(R)-(þ)-bornylamine}2] that bears the bulky
amine ligand R-(þ)-bornylamine (endo-(1R)-1,7,7-trimethylbicy-
clo[2-2-1]-heptan-2-amine) [5]. The complex showed similar
antitumor activity against HeLa cells when compared with the
activity of the standard references, cisplatin, carboplatin and
oxaliplatin.
The considerably higher activity of palladium complexes implies
that if an antitumor palladium drug is to be developed, it must
somehow be stabilized by a chelate or a strongly coordinated, bulky
monodentate nitrogen ligand and a suitable leaving group [3,4].
* Corresponding author. Tel.: þ962 5 390 3333x4315; fax: þ962 5 390 3349.
E-mail address: asurrah@hu.edu.jo (A.S. Abu-Surrah).
0223-5234/$ – see front matter Ó 2009 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2009.10.029

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A.S. Abu-Surrah et al. / European Journal of Medicinal Chemistry 45 (2010) 471–475
Complexes bearing naturally occurring compounds have also
ascribed to the imine protone (HC]N) [13]. In addition, a singlets at
around 2.4, 4.1, and 11.0 ppm have also been observed which can be
attributed to the methyl groups of the pyrazol ring, CeCH3 and
NeCH3, and NH, respectively. The 13C-NMR spectra of the ligands
exhibit a singlet at about 142 ppm which can be assigned to the
imine (HC]N) carbon that is close to the phenyl ring.
been utilized. The palladium complex which contains the bulky
nitrogen ligand harmine (7-methoxy-1-methyl-9H-pyrido[3,4-
b]indole), trans-[PdCl2(harmine)(DMSO)] exhibits a greatercytotoxic
activity against P388, L1210 and K562 cell lines than cisplatin [7].
Pyrazole arylhydrazones were designed as mixed-hybrid iso-
steres of two known inhibitors of prostaglandin synthase and
5-lipoxygenase enzymes, BW-755c and CBS-1108 [8]. Some deriv-
atives of these compounds inhibit the in vitro platelet aggregation
of citrated platelet-rich rabbit plasma. The compound, p-methox-
yformylbenzene-5-(1-phenyl-3-methyl-4-nitropyrazolyl)hydrazone,
which contains a methoxy group at the p-position of the aryl part,
was found to be the most active with 62% inhibition of aggregation
[9]. The antiedematogenic properties and structure-activity rela-
tionship of several 5-N-phenylpyrazole arylhydrazone derivatives
have been evaluated, the compound 5-(1-phenyl-3-methyl-4-
nitropyrazolyl)-based aryl hydrazone showed the best profile as
antiedematogenic agent [10].
Several studies of pyrazole-based complexes of palladium(II)
and platinum(II) have been reported [11]. However, as far as we
know, the coordination chemistry of pyrazole arylhydrazones with
palladium has not been investigated. As an extension of our studies
on both the coordination chemistry of heteroatom containing
ligands [12,13] and on the biological activity [5,14,15] of their metal
complexes, we describe here the synthesis and characterization of
new N-methylpyrazol-5-arylhydarazonyl-based Schiff base ligands
and their corresponding square-palnar palladium(II) complexes. To
confirm the identity of the compounds prepared in the present
study, a variety of techniques including elemental analysis, MS (EI),
IR, 1H- and 13C-NMR spectroscopy have been used. The aim of our
study was to investigate the influence of those bulky carriers on the
initial cytotoxic properties of the trans-palladium(II) complexes
against human head and neck sqamous carcinoma cells.
The mass spectra of the Schiff base ligands showed the base
peaks at m/z 259, 319, 293, and 275 which correspond to the
original molecular weight of the ligands 6, 7, 8, and 9, respectively.
The palladium(II) complexes (10–13) were prepared by treating
the starting material, [PdCl2(NCPh)2] with two equivalents of the
corresponding ligand in acetone at room temperature (Scheme 2).
The reaction with one equivalent of the ligand led also to the
formation of the palladium complexes but with lower yields. The
isolated compounds are microcrystalline or powder-like and stable
at atmospheric conditions. A variety of techniques including
elemental analysis, IR-, 1H- and 13C-NMR-spectroscopy have been
used to characterize the new complexes. Attempts to analyze the
complexes by mass spectroscopy (EI) were not successful. This may
be due to the non-volatility of the palladium(II) complexes. They
showed a decomposition behavior at around 290 ꢀC.
Elemental analyses of the complexes (10–13) showed that the
metal to the pyrazole ligand ratio in the dichloro complexes is 1:2.
The presence of the ligands in the complexes was confirmed by
IR-analyses. An insignificant shift of the peak due to the imine bond
(y(C]N)) was observed indicating complexation of the ligands with
palladium. Due to geometrical reasons and the bulkiness of the
ligand, we believe that the trans geometrical isomer is more
favorable than the cis. This was indicated by the presence of the IR-
band at 628 cmꢁ1 which can be assigned to
y(PdeN) [16,17]. If they
were cis complexes, two well defined bands should appear. The
self-arrangement of such bulky monodentate ligands towards the
trans isomer has also been observed in many palladium(II)
complexes containing bulky monodentate ligands [5,7].
The solution behavior of the complexes was determined by NMR
spectroscopy in DMSO-d6 at room temperature (Table 1). The
coordination of the bulky Schiff base ligands in the complexes most
probably takes place via N-pyrazole, as this lone pair of electrons is
more available for coordination than that of N]CH or NH due to
geometrical and steric reasons [7a]. The 1H-NMR experiments
2. Results and discussion
2.1. Chemistry
Reaction of 5-hydrazino-1,3-dimethyl-4-nitro-1H-pyrazole (1)
with one equivalent of the desired arylaldehyde (2–5) in EtOH at
25 ꢀC readily yields the hydrazone Schiff base ligands 6–9 in
a moderate to high yield (Scheme 1). IR- and 1H-NMR spectral
features agree with the formula assignments. The IR spectra of these
ligands (6–9) indicate the formation of the Schiff base product by
the absence of the carbonyl group (1700 cmꢁ1) band and the
appearance of a strong band in the region of 1614–1622 cmꢁ1,
showed that the d (HC]N) and d (NeH) of the free ligands (8.5 and
11.0, respectively) remains almost unchanged upon coordination
with palladium. Furthermore, only a minor shift for the singlet due
to methyl group of the pyrazole ring (4.0 ppm) could be observed
compared with the free ligand. This was also confirmed by
13C-NMR; no change in the chemical shift for the carbon atom in
the imine HC]N (w142.5–142.9 ppm) for free ligand was observed
upon complexation (Table 1), which indicate that the imine
nitrogen is not involved in coordination. On the contrary, a slight
assignable to the n(C]N)imine group [13].
The 1H-NMR spectra (Table 1) of the ligands in DMSO-d6 showed
a singlet in the range between 8.30 and 8.50 ppm which can be
R
CHO
CH3
N
NO2
N
CH3
N
NO2
N
EtOH
R2
R1
NH2
R1
+
N
N
N
R2
H
CH3
H
R
CH3
(6-9)
(1)
(2-5)
2, 6 : R, R1, R2 = H
3, 7 : R = H, R1, R2 = OCH3
4, 8 : R = Cl, R1, R2 = H
5, 9 : R = OH, R1, R2 = H
Scheme 1. Synthesis of the hydrazino pyrazole ligands (6–9).

A.S. Abu-Surrah et al. / European Journal of Medicinal Chemistry 45 (2010) 471–475
473
Table 1
NMR data of compounds 6–13.
Compound
1H-NMRa
13C-NMRa
6
2.38 (s, 3H CeCH3), 4.13 (s, 3H, NeCH3), 8.44 (s, 1H, N]CH), 11.1
14.6 (N]CeCH3), 142.9 (N]CH), 145.9 (NeCeNH)
(s, 1H, NH)
7
2.38 (s, 3H, CeCH3), 4.14 (s, 3H, NeCH3), 8.50 (s, 1H, N]CH), 11.0
(s, 1H, NH)
14.4 (N]CeCH3), 142.4 (N]CH), 143.5 (N]CeCH3), 145.4 (NeCeNH),
153.1 (CeOCH3)
8
2.35 (s, 3H CeCH3), 4.0 (s, 3H, NeCH3), 8.49 (s, 1H, N]CH), 11.04
14.4 (N]CeCH3), 142.7 (N]CH), 143.6 (N]CeCH3), 145.6 (NeCeNH)
(s, 1H, NH)
9
2.37 (s, 3H CeCH3), 4.11 (s, 3H, NeCH3), 8.33 (s, 1H, N]CH), 11.05
14.4 (N]CeCH3), 142.7 (N]CH), 143.6 (N]CeCH3), 147.3 (N]CeNH),
(s, 1H, NH)
159.7 (CeOH)
10
11
12
13
2.35 (s, 3H CeCH3), 4.02 (s, 3H, NeCH3), 8.51 (s, 1H, N]CH), 11.03
n.d.b
(s, 1H, NH)
2.35 (s, 3H CeCH3), 4.0 (s, 3H, NeCH3), 8.50 (s, 1H, N]CH), 11.1
(s, 1H, NH)
2.35 (s, 3H CeCH3), 4.0 (s, 3H, NeCH3), 8.50 (s, 1H, N]CH), 11.1
(s, 1H, NH)
2.37 (s, 3H CeCH3), 4.11 (s, 3H, NeCH3), 8.47 (s, 1H, N]CH), 11.1
(s, 1H, NH)
14.6 (N]CeCH3), 142.9 (N]CH), 143.8 (N]CeCH3), 145.6 (NeCeNH),
153.3 (CeOCH3)
14.4 (N]CeCH3), 142.5 (N]CH), 143.9 (N]CeCH3), 145.6 (NeCeNH)
14.5 (N]CeCH3), 142.9 (N]CH), 143.8 (N]CeCH3), 147.5 (NeCeNH),
159.8 (CeOH)
a
25 ꢀC, in DMSO-d6,
n.d. not determined due to low solubility of the Pd(II) complex.
d [ppm].
b
shift to the signal due to the imin carbon of the pyrazole ring
palladium(II) complexes. Only slight difference was observed in the
(N]CeCH3) was observed (143.8 ppm).
shift for the peak due to the imine bond (y(C]N) in the complexes.
2.2. Biological investigations
3. Experimental
The effect of palladium(II) complexes on human head and neck
squamous carcinoma cell survival, SQ20B and SCC has been studied
and compared with commercial drug, cisplatin. The cells were
3.1. Chemistry
3.1.1. Materials and physical measurements
treated with two different doses (0.2, 0.5
for clonogenic survival. The results showed that at 0.2
dium(II) complexes (11, 12, and 13) or cisplatin did not significantly
alter SCC cell survival compared to control (Fig. 1A). The maximum
cell killing was observed with complex (11). Further increasing the
dose of cisplatin to 0.5 mM caused significant cell killing compared
to control or palladium(II) complexes (Fig. 1B).
SQ20B cells were more sensitive to palladium(II) complexes
treatment compared to SCC, with significant cell killing observed at
m
M) for 24 h and analyzed
Reagent grade chemicals were used as received unless other-
wise stated. [PdCl2(PhCN)2] was prepared according to a literature
procedure [19].
mM, palla-
Elemental analyses were performed using a (EURO EA 3000
instrument). 1H-NMR spectra were recorded on a Bruker spec-
trometer operating at 300 MHz using DMSO-d6 as a solvent with
TMS as an internal standard. 13C-NMR spectra were obtained on
a Bruker spectrometer operating at 75 MHz using DMSO-d6 as
a solvent. Infrared spectra (KBr discs) were measured on a Nicolet-
Magna-IR 560 Spectrophotometer. Mass spectra (EI) were acquired
using a Shimadzu-QP5050A. Melting points were measured by
a Stuart Scientific melting Apparatus (uncorrected ꢂ0.1 ꢀC).
the dose of 0.2 and 0.5
compared to either control or cisplatin (Figs. 2A,B). Furthermore,
SQ20B cells were more sensitive to cisplatin treatment at 0.5
mM with 20 and 60% killing respectively as
mM
consistent with previous results [18]. At this concentration, the
palladium(II) complexes 11 and 12 showed similar cytotoxic effect
but fairly higher than that observed for 13.
3.1.2. General procedure for the synthesis of ligands
To a solution of 5-hydrazino-1,3-dimethyl-4-nitro-1H-pyrazole
(1) (0.34 g, 2.0 mmol) in absolute ethanol (100 ml), arylaldehydes
(2–5) (2.0 mmol) was added. The solution was refluxed for 3 h.
Ethanol was evaporated, and the solid product was collected to
afford the desired products (6–9) as yellowish to orange solids.
These results showed that the cytotoxic effect of the palladiu-
m(II) complexes (11, 12, and 13) on SQ20B head and neck cancer
cells is dose dependent and varies by cell type. The slight differ-
ences among the cytotoxic influence of the complexes under
investigation indicate that different substituents on the ligands
(OMe (7), Cl (8), and OH (9)) had insignificant influence on the
coordinated nitrogen donor atom and consequently on the elec-
tronic properties of the palladium metal center. This observation is
coincide with the results observed in the IR-analysis of the
3.1.2.1. H-BDH (6). Yield, 0.52 g (83%). M.p. (dec.) 246 ꢀC. Found: C,
55.36; H, 5.21; N, 27.50. Anal. Calc. for C12H13N5O2: C, 55.59; H,
5.05; N, 27.01. IR (KBr, cmꢁ1):
n
¼ 3421 (m), 3255 (m), 1619 (s). 1H-
NMR (DMSO-d6, ppm):
d
¼ 11.1 (s, NH), 8.44 (s, HC]N), 7.94–7.74
R2
H
N
CH3
CH3
R 1
NO2
Cl
Pd
Cl
N
R
N
[Pd(NCPh)2Cl2]
N
N
N
R
L (6-9)
N
N
H
O2N
R1
CH3
CH3
R2
10 : R, R1, R2 = H
11 : R = H, R1, R2 = OCH3
12 : R = Cl, R1, R2 = H
13 : R = OH, R1, R2 = H
(10-13)
Scheme 2. Synthesis and suggested structure of the palladium(II) complexes (10–13).

474
A.S. Abu-Surrah et al. / European Journal of Medicinal Chemistry 45 (2010) 471–475
SQ20B
SCC-25
A
[0.2 uM]
1.1
1.0
0.9
0.8
0.7
0.6
0.5
0.4
1.1
1.0
0.9
0.8
0.7
0.6
0.5
0.4
A
[0.2 uM]
ψ
*
ψ
*
ψ
*
B
1.1
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
B
[0.5 uM)
1.1
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
[0.5 uM)
*
ψ
*
ψ
*
ψ
*
*
11
12
13
11
12
13
Control
Cisplatin
Control
Cisplatin
Fig. 1. Effect of palladium(II) complexes (11–13) compared to cisplatin on survival of
SCC-25 cells. The cells were treated with 0.2 (A) and 0.5 (B) M of the palladium(II)
complexes and cisplatin for 24 h and then plated for clonogenic survival. Clonogenic
cell survival data were normalized to control. Error bars represent ꢂ standard error of
the mean of N ¼ 3 experiments performed with at least three cloning dishes taken
from one treatment dish. *p < 0.05 versus respective control.
Fig. 2. Effect of palladium(II) complexes (11–13) compared to cisplatin on survival of
SQ20B cells. The cells were treated with 0.2 (A) and 0.5 (B) M palladium(II) complexes
m
m
and cisplatin for 24 h and then plated for clonogenic survival. Clonogenic cell survival
data were normalized to control. Error bars represent ꢂ standard error of the mean of
N ¼ 3 experiments performed with at least three cloning dishes taken from one
treatment dish. *p < 0.05 versus respective control;
j
p < 0.05 versus cisplatin.
(m, Harom), 4.13 (s, NeCH3), 2.38 (s, CeCH3). 13C-NMR (DMSO-d6,
3.1.3. General procedure for the synthesis of complexes
ppm):
d
¼ 14.6, 40.6, 127.4, 128.9, 129.1, 129.3, 130.8, 145.9, 154.7,
A filtered solution of the desired ligand (6–9) (0.72 mmol) in
acetone (30 ml) was added to a solution of [PdCl2(NCPh)2] (0.25 g,
0.65 mmol) in acetone (50 ml) with continuous stirring. Upon
addition, a yellow solid was formed. After 5 h stirring, the precip-
itate (10–13) was filtered, washed with acetone (2 ꢃ 5 ml), Et2O
(2 ꢃ 10 ml) and dried in vacuum.
MS (EI) (%): 259 (Mþ, 38), 207 (40), 180 (32), 131 (100).
3.1.2.2. MeO-BDH (7). Yield, 0.58 g (92%). M.p. (dec.) 234 ꢀC.
Found: C, 52.41; H, 5.76; N, 21.96. Anal. Calc. for C14H17N5O4: C,
52.66; H, 5.37; N, 21.93. IR (KBr, cmꢁ1):
n
¼ 3422 (m), 3240 (m),
¼ 11.03 (s, NH), 8.50 (s, HC]N), 7.50–
7.13 (m, Harom), 4.14 (s, NeCH3), 2.38 (s, CeCH3). 13C-NMR (ppm):
1614 (s). 1H-NMR (ppm):
d
3.1.3.1. PdCl2(HeBDH)2$ H2O (10 $ H2O). Yield of 0.16 g (35%). M.p.
(dec.) 278 ꢀC. Found: C, 40.64; H, 4.23; N, 20.05. Anal. Calc. for
C24H26N10O4PdCl2 $ H2O: C, 40.38; H, 3.95; N, 19.62. IR (KBr,
d
¼ 14.4, 41.1, 56.1, 61.6, 114.3, 117.1, 124.8, 142.4, 153.1, MS (EI) (%):
319 (Mþ, 78), 307 (46), 289 (35).
cmꢁ1):
n
¼ 3442 (mbr), 3252 (m), 1629 (s), 1547 (m), 1455 (m), 1373
(s),1230 (m), 1142 (w), 1086 (w), 758 (m), 628 (w), 513 (w). 1H-NMR
(ppm):
3.1.2.3. Cl-BDH (8). Yield, 0.28 g (48%). M.p. (dec.) 266 ꢀC. Found: C,
49.15; H, 4.26; N, 24.38. Anal. Calc. for C12H12ClN5O2: C, 49.07; H,
d
¼ 11.03 (s, NH), 8.51 (s, HC]N), 7.70–7.45 (m, Harom),
4.12; N, 23.84. IR (KBr, cmꢁ1):
n
¼ 3423 (m), 3252 (w), 1623 (s). 1H-
4.02 (s, N]CH3), 2.35 (s, CeCH3).
NMR (ppm):
d
¼ 11.04 (s, NH), 8.49 (s, HC]N), 7.69–7.50 (m,
Harom), 4.00 (s, NeCH3), 2.35 (s, CeCH3). 13C-NMR (ppm):
d
¼ 14.4,
3.1.3.2. PdCl2(MeO-BDH)2$ H2O (11 $ H2O). Yield of 0.08 g (15%).
M.p. (dec.) 269 ꢀC. Found: C, 40.23; H, 4.24; N, 16.82. Anal. Calc. for
C28H34N10O8PdCl2$H2O: C, 40.33; H, 4.35; N, 16.8. IR (KBr, cmꢁ1):
39.8, 116.1, 116.6, 125.3, 128.9, 133.4, 134.8, 142.7, 143.6, 145.6. MS
(EI) (%): 293 (Mþ, 64), 153 (71), 111 (37), 67 (100).
n
¼ 3423 (mbr), 3270 (m), 1618 (s), 1532 (m), 1447 (m), 1373 (s),
1265 (m), 1241 (m), 1228 (m), 1142 (w), 1085 (w), 756 (m), 628 (w),
585 (w). 1H-NMR (ppm):
¼ 11.1 (s, NH), 8.50 (s, HC]N), 7.69–7.50
(m, Harom), 4.00 (s, NeCH3), 2.35 (s, CeCH3). 13C-NMR (ppm):
¼ 14.6, 99.9, 128.9, 129.5, 133.5, 142.9, 143.8, 145.6, 153.3.
3.1.2.4. OH-BDH (9). Yield, 0.28 g (76%). M.p. (dec.) 265 ꢀC. Found:
C, 52.80; H, 4.81; N, 25.82. Anal. Calc. for C12H13N5O3: C, 52.36; H,
d
4.76; N, 25.44. IR (KBr, cmꢁ1):
n
¼ 3247 (m), 1619 (s). 1H-NMR
(ppm):
d
¼ 11.05 (s, NH), 8.33 (s, HC]N), 7.63–6.93 (m, Harom),
d
4.11 (s, N]CH3), 2.37 (s, CeCH3). 13C-NMR (ppm):
d
¼ 14.4, 39.8,
116.1, 116.6, 125.3, 128.9, 142.7, 143.6, 147.3, 159.7. MS (EI) (%): 275
3.1.3.3. PdCl2(Cl-BDH)2$ 3H2O (12 $ 3H2O). Yield of 0.21 g (39%).
M.p. (dec.) 300 ꢀC. Found: C, 34.55; H, 3.39; N, 17.30. Anal. Calc. for
(Mþ, 20), 176 (100).

A.S. Abu-Surrah et al. / European Journal of Medicinal Chemistry 45 (2010) 471–475
475
C24H24Cl2N10O4PdCl2 $ 3H2O: C, 35.21; H, 3.69; N, 17.11. IR (KBr,
cmꢁ1):
¼ 3416 (mbr), 3250 (m), 1629 (s), 1541 (m), 1455 (m), 1373
(s), 1235 (m),1148 (w), 1086 (w), 753 (m), 622 (w), 518 (w). 1H-NMR
Acknowledgements
n
Financial support by the Hashemite University is gratefully
acknowledged. The authors would like to thank Mr. Mohanad
Masad for carrying out the NMR measurements.
(ppm):
d
¼ 11.1 (s, NH), 8.50 (s, HC]N), 7.95–7.51 (m, Harom), 4.00
(s, NeCH3), 2.35 (s, CeCH3). 13C-NMR (ppm):
d
¼ 14.5, 98.0, 128.9,
129.5, 133.5, 134.7, 142.5, 143.9, 145.6.
3.1.3.4. PdCl2(OHeBDH)2 (13). Yield of 0.27 g (57%). M.p. (dec.)
290 ꢀC. Found: C, 39.94; H, 3.94; N, 19.55%. Anal. Calc. for
C24H26N10O6PdCl2: C, 39.60; H, 3.60; N, 19.24. IR (KBr, cmꢁ1):
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6 (2008)
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