Palladium(II) complexes of 4-formylantipyrine N(3)-substituted thiosemicarbazones: First example of X-ray crystal structure and description of bonding properties

Article abstract of DOI:10.1016/S0020-1693(03)00087-2

Reaction of 4-formylantipyrine with thiosemicarbazide, N(3)-methylthiosemicarbazide and N(3)-ethylthiosemicarbazide produced the expected thiosemicarbazones, 1, 2 and 3. The three thiosemicarbazones were then reacted with K₂PdCl₄ to produce [Pd(NS)₂] complexes, 4, 5, and 6, respectively, with coordination by the imine nitrogen and thiolate sulfur of the anionic thiosemicarbazone moiety. The thiosemicarbazones and their palladium complexes have been characterized by spectral IR, UV-Vis and ¹H, ¹³C NMR and electrochemical techniques. The crystal structure of 6 has been obtained and found to be highly symmetrical with a trans arrangement of the two bidentate ligands.

Full text of DOI:10.1016/S0020-1693(03)00087-2

Inorganica Chimica Acta 349 (2003) 30Á36
/
www.elsevier.com/locate/ica
Palladium(II) complexes of 4-formylantipyrine N(3)-substituted
thiosemicarbazones: first example of X-ray crystal structure and
description of bonding properties
Paras Nath Yadav a, Mavroudis A. Demertzis a,*, Dimitra Kovala-Demertzi a,*,
Stavroula Skoulika a, Douglas X. West b
a Department of Chemistry, University of Ioannina, GR-45110 Ioannina, Greece
b Department of Chemistry 351700, University of Washington, Seattle, WA 98195-1700, USA
Received 17 August 2002; accepted 7 January 2003
Abstract
Reaction of 4-formylantipyrine with thiosemicarbazide, N(3)-methylthiosemicarbazide and N(3)-ethylthiosemicarbazide
produced the expected thiosemicarbazones, 1, 2 and 3. The three thiosemicarbazones were then reacted with K2PdCl4 to produce
[Pd(NS)2] complexes, 4, 5, and 6, respectively, with coordination by the imine nitrogen and thiolate sulfur of the anionic
thiosemicarbazone moiety. The thiosemicarbazones and their palladium complexes have been characterized by spectral IR, UVÁVis
/
and 1H, 13C NMR and electrochemical techniques. The crystal structure of 6 has been obtained and found to be highly symmetrical
with a trans arrangement of the two bidentate ligands.
# 2003 Elsevier Science B.V. All rights reserved.
Keywords: Antipyrine; Thiosemicarbazone; Palladium; Crystal structure; Spectral study; Electrochemistry
1. Introduction
formylpyridine and 2-acetylpyridine N(3)-substituted
thiosemicarbazones have been studied with regard to
their structural and biological properties, and some of
Antipyrine (2,3-dimethyl-1-phenyl-5-pyrazolone) and
its derivatives possess a wide variety of potentially useful
biological properties. Antipyrine is a molecule with
minimal protein binding, which is rapidly and com-
pletely absorbed from the gastrointestinal tract and
extensively metabolized by the cytochrome P-450 liver
enzymes [1]. Estimates of half-life and systemic clear-
ance of antipyrine have been used for the in vivo
assessment of hepatic drug oxidation in different species
[2]. Owing to its low pKa value and its small degree of
plasma protein binding, antipyrine is distributed in total
body water.
them have shown remarkable antitumor activity [11Á
/
13]. This work is an extension of previously studied
palladium(II) complexes of 2-acetylpyridine TSC with
potentially interesting biological activity [11,12]. Here,
we report on the palladium(II) complexes of 4-formy-
lantipyrine N(4)-substituted thiosemicarbazones. To
our knowledge, this is the first report of a structure of
a metal complex of a 4-formylantipyrine N(3)-substi-
tuted thiosemicarbazone.
Thiosemicarbazones have demonstrated significant
biological activity and new examples are being tested
for their antitumor, antimicrobial, and antiviral activity
2. Experimental
Solvents were purified and dried according to stan-
dard procedures. Infrared and far-infrared spectra were
recorded on a Nicolet 55XC Fourier transform spectro-
photometer using KBr pellets (4000Á
nujol mulls dispersed between polyethylene disks (400Á
40 cmꢀ1). UV spectra were acquired with a JASCO V-
[2Á13]. Palladium(II) and platinum(II) complexes of 2-
/
/
400 cmꢀ1) and
/
* Corresponding authors. Tel.: ꢁ
/
30-6-514 4825.
E-mail address: dkovala@cc.uoi.gr (D. Kovala-Demertzi).
0020-1693/03/$ - see front matter # 2003 Elsevier Science B.V. All rights reserved.
doi:10.1016/S0020-1693(03)00087-2

P. Yadav et al. / Inorganica Chimica Acta 349 (2003) 30Á
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31
570 spectrophotometer UV/VIS/NIR. The 1H (250.13
MHz) and 13C (62.90 MHz) spectra were obtained on a
Bruker AMX-400 spectrometer at room temperature
with the signal of free DMSO or CHCl3 (at 2.49 and
7.24 ppm, respectively) as reference. The complexes were
analyzed for C, H, N and S in a Carlo-Erba EA 1108 at
the University of Ioannina. Analyses of palladium and
chlorine were performed in our laboratory by gravi-
metric and potentiometric techniques, respectively.
Electrochemical measurements were made using an
Autolab PGSTAT30 potentiostat with a platinum
microsphere as working electrode, a platinum wire
auxiliary electrode and an Ag/AgCl reference electrode
in a three electrode configuration. Ferrocene was added
at the end of each experiment and used as an internal
standard. All potentials are reported relative to a Ag/
AgCl reference electrode and ferrocinium/ferrocene
of 6, which was mounted on a glass fiber and used for
data collection. Cell constants and an orientation matrix
for data collection were obtained by least-squares
refinement of the diffraction data from 25 reflections
in the range 2.12B
/
u B
/
25.008 on a Bruker-P4 diffract-
ometer. Data were collected at 293 K using Mo Ka
˚
radiation (lꢂ0.71073 A) and the v-scan technique, and
/
corrected for Lorentz and polarization effects [19]. A
semi-empirical absorption correction (C-scans) was
made. The structure was solved by Patterson and
Fourier methods [20] and refined on F2 by a full-matrix
least-squares procedure using anisotropic displacement
parameters [19]. All hydrogen atoms were located in
˚
H 0.93Á0.97 A) and
their calculated positions (Cꢀ
/
/
refined using a riding model. Atomic scattering factors
are from the ‘International Tables for X-ray Crystal-
lography’ [19] and molecular graphics from PLA-
TON2001 [20]. A summary of the crystal data,
experimental details and refinement results are listed in
Table 1.
(Feꢁ/Fc, E1/2
ꢂ0.173 V in DMF); under the experi-
/
mental conditions used (scan rate 100 mV sꢀ1). Et4N-
ClO4 (0.1 M) was used as supporting electrolyte, the
solutions were 1ꢃ
10ꢀ3 M in complex, and all experi-
ments were carried out under a dinitrogen atmosphere.
/
2.1. Preparation of the complexes and ligands
The ligands HFoATP4DH, 1, HFoATP4Me, 2,
HFoATP4Et, 3, were prepared according to the method
described previously [15]. The yields and melting points
Table 1
Crystallographic data for the X-ray diffraction studies for
[Pd(FoATP4NEt)2]
are as follows: 1, 40.5%, m.p.ꢂ
m.p.ꢂ216 8C; 3, 67.7%, m.p.ꢂ212 8C.
[Pd(FoATP4DH)2], 4, [Pd(FoATP4Me)2],
[Pd(FoATP4Et)2], 6, were prepared as follows: to a
solution of 1.5 mmol K2PdCl4 in 10 ml of distilled water
was added 3.2 mmol of a thiosemicarbazone (i.e., 1, 2,
/
219 8C; 2, 42.5%,
Empirical formula
Formula weight
Temperature (K)
C30H36N10O2PdS2
739.25
293(2)
/
/
5,
˚
Radiation (A)
Mo Ka, lꢂ0.71073
/
Crystal system
Space group
Monoclinic
P21/n
or 3). The pH of the solution was adjusted to 8.0Á9.0 by
the addition of aqueous 1.0 M NH3, and the reaction
mixture was stirred for 5 h at room temperature. The
/
Unit cell dimensions
˚
a (A)
˚
11.0670(10)
14.0970(10)
11.690(3)
115.350(10)
1648.2(5)
4
b (A)
˚
c (A)
resulting orangeÁred powder was filtered off, washed
/
b
with cold methanol and ether, dried in vacuo over silica
gel, and finally redried at 70 8C in vacuo over P4O10.
Melting points, percentage yields and elemental analyses
are as follows: 4, m.p., 234 8C; yield 95%; %Found: C,
45.7; H, 4.1; N, 20.5; S, 9.4; Pd, 15.6; Cl, 0.0;%Calcd. for
C28H35N10O2S2Pd: C, 45.6; H, 4.2; N, 20.5; S, 9.6; Pd,
15.3; Cl, 0.0%; 5, m.p., 235 8C; yield 92%; %Found: C,
47.3; H, 5.6; N, 19.7; S, 9.0; Pd, 15.6; Cl, 0.0;%Calcd. for
C29H34N10O2S2Pd: C, 47.2; H, 5.2; N, 19.7; S, 9.1; Pd,
15.6; Cl, 0.0%; 6, m.p., 230 8C; yield 77%; %Found: C,
48.8; H, 4.9; N, 18.9; S, 8.7; Pd, 14.4; Cl, 0.0;%Calcd. for
C30H36N10O2Pd: C, 48.8; H, 5.0; N, 19.0; S, 9.6; Pd,
14.4; Cl, 0.0.
3
˚
V (A )
Z
Dcalc (mg mꢀ3
)
0.427
0.316
214
Absorption coefficient (mmꢀ1
F(0 0 0)
)
Crystal size (mm)
u range for data collection
Limiting indices
0.20ꢃ
2.12Á25.00
00h 013,
10k 014,
130l 012
/
0.20ꢃ
/
0.30
/
/
/
ꢀ
ꢀ/
/
/
/
/
/
Reflections collected/unique
3230/2817 [Rint
97.10%
ꢂ/0.0555]
Completeness to uꢂ
Refinement method
/25.00
Full-matrix least-squares on
F2
Data/restraints/parameters
Final R indices [I ꢀ2s(I)]
R indices (all data)
Goodness-of-fit on F2
2817/0/213
/
R1ꢂ
R1ꢂ
1.009
0.395 and ꢀ0.437
/
0.0639, wR2ꢂ
/
0.1074
0.1334
/
0.1404, wR2ꢂ
/
2.2. X-ray crystallography
Largest difference peak and hole
ꢀ3
/
Slow evaporation of a dilute 1:1 by volume CH3CN/
CH3OH solution provided an orange prismatic crystal
˚
(eA
)

32
P. Yadav et al. / Inorganica Chimica Acta 349 (2003) 30Á36
/
Table 2
Main IR absorptions (cmꢀ1) for 4-formylantipyrine N(4)-substituted thiosemicarbazones and their palladium(II) complexes
nas,s(N3H)
nas,s(N2H)
n(Cꢁ/O)
n(Cꢁ/N)
d(N3H)
d(N2H)
n(NN)
n(Cꢁ
/
S)
n(PdN)
n(PdS)
1
3431s
3252s
3371s
3356s
3444w
3307s
3382mb
3135mb
1634s
1614m
1541b
1489m
1053m
829s
2
3
4
3213s
3057m
1635s
1635s
1618s
1606w
1603m
1589w
1582w
1619m
1589m
1593s
1529vb
1515vb
1493b
1529vb
1515vb
1068s
1059s
1082m
847w
887s
740m
432m
448s
397s
342m
356m
357s
5
6
1653s
1648s
1503b
1497b
1085m
1083m
773s
766s
3356sh
3292b
3. Results and discussion
primarily as the Z isomer with respect to the imine bond
(i.e., CꢁN1) in solution based on the appearance of the
N(2)H resonance at Â13.00 ppm, which is indicative of
intramolecular hydrogen bonding. The resonance at
10.70Á11.10 ppm in the spectrum of the thiosemicarba-
/
/
3.1. Spectroscopic and electrochemical studies
/
The IR spectral bands most useful for determining a
thiosemicarbazone’s mode of coordination are given in
zones is also assigned to N(2)H, which is hydrogen
bonded to the d6-DMSO solvent; it and the resonance at
Table 2. Decreases in the n(Cꢁ
cmꢀ1 on complexation are consistent with coordination
of the imine nitrogen, as is the presence of a band at Â
450Á N). Coordi-
/
N) energy by 20Á35
/
7.88Á/7.92 ppm disappear in the presence of D2O,
confirming the assignment of the latter as N(3)H [14Á
/
/
500 cmꢀ1, which is assigned to n(Pdꢀ
/
18]. The resonances at 13 and 11 ppm are absent in the
spectra of the complexes indicating the loss of N(3)H
and the presence of the anionic thiosemicarbazone
moiety in the complexes. The two signals in the range
/
nation of the thiolato sulfur is indicated by a decrease in
energy of thioamide IV band, as well as by the presence
of a band at 340Á
/
380 cmꢀ1 that is assignable to n(Pdꢀ
S). As expected, greater energy decreases in the thioa-
mide IV band occur for the anionic form of the ligand
/
of 6.89Á/8.09 ppm are assigned to the formyl hydrogen
HꢀCꢁN. This signal and the signal at 7.88Á
/
/
/7.92 ppm
(N4H) are shifted upfield indicating increased electron
density at these sites in the palladium(II) complexes. On
coordination of the sulfur and imine nitrogen atoms the
electron density would be expected to be lost from the
owing to the Cꢀ
bond. A band in the 1634Á
spectra of the 1, 2, and 3 is assigned to n(Cꢁ
band is shifted to 1648Á
1654 cmꢀ1 in the spectra of 4, 5,
and 6 which, indicates that coordination of the carbonyl
oxygen does not occur. The relatively low energy for
/
S entity formally becoming a single
1642 cmꢀ1 region of the
O). This
/
/
/
Hꢀ
/
Cꢁ/N and N3H functions, as has been observed for
zinc(II) complexes of 4-formylantipyrine N(4)-substi-
tuted thiosemicarbazones [15] However, p-back bonding
from the palladium(II) to the thiolato and imine
functions occurs causing an upfield shift of these
n(Cꢁ
/
O) bond in the spectra of 4-formylantipyrine
thiosemicarbazones and their complexes is indicative
that the carbonyl oxygen is involved in hydrogen
resonances. The signals owing to Cꢀ
/
CH3 and Nꢀ
/
CH3
bonding, i.e., Nꢀ
/
H
/
Á Á Á
/
O [14Á18].
/
The H and 13C NMR assignments for thiosemicar-
bazones and their palladium(II) complexes in d6-DMSO
are shown in Tables 3a, 3b and 4 is not sufficiently
soluble in DMSO to obtain an 13C NMR spectrum. The
1H NMR spectra of 1, 2, and 3 indicate that they exist
1
groups (i.e., pyrazolone ring) are unshifted in the
palladium(II) complexes indicating that the carbonyl
oxygen is not involved in coordination in solution. The
thiosemicarbazone moiety’s thione carbon is found in
the dꢂ
/
175.0Á180.0 ppm range and the imine carbon in
/
Table 3a
1H NMR spectra of 4-formylantipyrine N(4)-substituted thiosemicarbazones and their palladium(II) complexes
Compound
Cꢀ
/
CH3
Nꢀ/CH3
C6H5
Hꢀ
/
Cꢁ/N
N2H
N3H
1
2
3
4
5
6
2.44
2.57s
3.33
7.30Á
7.31Á
7.27Á
7.30Á
7.15Á
7.14Á
/
7.60
7.60
7.58
7.63
7.56
7.60
7.58, 6.92
7.77
11.15, 13.09
11.16, 13.09
11.14, 13.04
7.88, 7.92s
7.92s
7.92s
3.24s
3.24, 3.51
3.33
/
2.44, 2.56
2.42
/
7.76, 6.89
7.11
/
6.75
2.57
3.25
/
7.66
8.01s
2.56, 2.62
3.25
/
6.89
7.63

P. Yadav et al. / Inorganica Chimica Acta 349 (2003) 30Á
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33
Table 3b
13C NMR spectra of 4-formylantipirine N(5)-substituted thiosemicarbazones and itspalladium(II) complexes in d6-DMSO
Compound
Cꢀ/CH3
Nꢀ/CH3
Hꢀ
/
Cꢁ
/
N
Cꢁ/O
CꢁS
/
1
2
3
5
6
9.7
9.7
33.7, 33.5
30.4, 30.0
34.3, 34.0
32.2, 32.1
34.9, 34.2
152.0, 151.8
152.0, 151.7
163.1
176.3
163.1, 160.9
163.5, 161.3
163.2
177.0, 176.5
176.4, 175.9
174.5
10.2
10.5
10.6
152.2, 152.5, 151.7
152.9, 152. 5
153.1, 152.4
163.6, 163.4, 161.6
176.5, 170.6
Table 4
˚
Selected bond lengths [A] and angles [8] for 6
Pd(1)ꢀ
Pd(1)ꢀ
Pd(1)ꢀ
Pd(1)ꢀ
Sꢀ
N(1)ꢀ
N(1)ꢀ
N(4)ꢀ
N(4)ꢀ
N(4)ꢀ
N(2)ꢀ
N(5)ꢀ
N(5)ꢀ
C(4)ꢀ
C(4)ꢀ
C(1)ꢀ
N(3)ꢀ
/
N(1a)
N(1)
S
2.028(5)
2.028(5)
2.285(2)
2.285(2)
1.761(8)
1.315(9)
1.378(8)
1.361(9)
1.382(8)
1.472(9)
1.316(9)
1.393(8)
1.429(9)
1.316(9)
1.323(10)
1.229(9)
1.457(10)
/
/
/Sa
/
C(4)
/
C(3)
/
N(2)
C(7)
/
/
N(5)
C(9)
/
/
C(4a) 1
C(1)
/
/
C(10)
/
N(2a)
N(3)
O(1)
/
/
/
C(5)
N(1a)ꢀ
N(1a)ꢀ
N(1)ꢀPd(1)ꢀ
N(1a)ꢀPd(1)ꢀ
N(1)ꢀPd(1)ꢀSa
SꢀPd(1)ꢀSa
C(4)ꢀSꢀPd(1)
C(3)ꢀN(1)ꢀ
C(3)ꢀN(1)ꢀ
N(2)ꢀN(1)ꢀ
C(7)ꢀN(4)ꢀ
C(7)ꢀN(4)ꢀ
N(5)ꢀN(4)ꢀ
C(4a)ꢀN(2)ꢀ
N(2a)ꢀC(4)ꢀ
N(2a)ꢀC(4)ꢀ
N(3)ꢀC(4)ꢀ
O(1)ꢀC(1)ꢀ
O(1)ꢀC(1)ꢀ
C(4)ꢀN(3)ꢀ
N(3)ꢀC(5)ꢀ
/
Pd(1)ꢀ
/
N(1)
180.00(13)
82.42(19)
97.58(19)
97.58(19)
82.42(19)
180.00(13)
96.6(3)
/
Pd(1)ꢀ
/S
/
/
S
/
/
Sa
/
/
/
/
/
/
/
/N(2)
114.8(6)
121.9(5)
123.3(5)
108.3(6)
126.1(7)
117.6(6)
112.5(6)
120.5(7)
124.6(6)
114.9(6)
123.5(8)
130.7(7)
124.3(8)
110.7(7)
Fig. 1. Electronic absorption spectra of ligands 1
palladium(II) complexes 4
/
3 (a) and its
10ꢀ5 M).
/
/Pd(1)
Á
/
6 (b) in DMF solution (5ꢃ
/
/
/Pd(1)
Á
/
/N(5)
/
/C(9)
density and may indicate stronger hydrogen bonding
in the complexes compared to the ligands.
/
/C(9)
/
/
N(1)
N(3)
S
The bands of 1
/
3 at :310 and 330 nm are due to
/
/
/
Á
p0
/
p* and n 0
/
p* transitions of the phenyl and
/
/
/
/S
pyrazolone rings and the imine portion of the thiosemi-
carbazone moiety. The energies of these two bands are
affected by changes in organic solvents due to differ-
ences in the extent and type of hydrogen bonding. The
electronic spectra of the ligands and complexes are
/
/N(5)
/
/C(2)
/
/C(5)
/
/C(6)
shown in Fig. 1. The broad band at :
/
380Á
/
400 cmꢀ1
for 4
/
6 is assignable to HomoÁ
/
Lumo transition. The
Á
the 152.0 ppm region. The signal at 161.0Á
assigned to the carbonyl carbon, which is in agreement
with values found for amide functions [14Á18]. In the
complexes upfield shifts are observed for CꢁS indicating
increased electron density and p-back bonding from
palladium(II) to the thiolato carbon. Downfield shifts
are observed for CO indicating decreased electron
/
163.0 ppm is
Homo orbital is mainly centered on pyrazolone rings
and the imine portion of the thiosemicarbazone moi-
eties, while the Lumo orbital is a mixed orbital centered
on the metal center and the four donor atoms, d(Pd)/
/
/
p(S)/p(N). The strong bands at :
340 cmꢀ1 is assign-
able to intraligand and charge transfer transitions
[18,21,22]. The UV spectrum of 6 was computed by
/

34
P. Yadav et al. / Inorganica Chimica Acta 349 (2003) 30Á36
/
Oxidation waves for 4 and 6 are observed at 0.496 and
0.488 V, respectively, and might be regarded as being
more or less centered on the ligand system [23,24].
However, in the range from ꢁ
/
1 to ꢀ2.52 V additional
/
peaks are observed, Fig. 2.
3.2. Crystal structure of [Pd(FoATP4Et)2]
Fig. 2. Cyclic voltammograms (100 mV sꢀ1) of complex 6 in DMF
A perspective view of [Pd(FoATP4Et)2], 6, with the
atomic numbering scheme is shown in Fig. 3. The
crystallographic data are summarized in Table 1 and
selected bond distances and angles are listed in Table 4.
The equivalent, anionic FoATP4Et ligands coordinate
in a bidentate manner by the imine nitrogen and thiolato
sulfur atoms. The trans-S2 and trans-N2 coordination
environment is strictly coplanar in this symmetrical
complex with N(1)PdN(1a) and SPdSa angles equal to
(1.0 mM) in the range ꢁ
ferrocene/ferrocenium.
/
1.0Á2.0 V. The quoted potentials are vs
/
using single point calculations at the ZINDO/S singly
excited interaction configuration level on the molecule 6
[24]. The molecular geometry of 6 was established by
using the crystallographic coordinates of the complex.
The cyclic voltammogram of 1, 2, and 3 in DMF
solution exhibits an irreversible cathodic wave in the
180.08. These two five-member rings exhibit a value of
negative margin at ꢀ
/
1.41, ꢀ
/
1.38 and ꢀ1.43 V,
/
˚
Q(2)ꢂ
/
0.096 A and of Fꢂ
/
352.788 and the closest
respectively. This results from the reduction of the imine
and thioamide groups present in the thiosemicarbazone
moiety, and its value is comparable to that observed for
other thiosemicarbazones [23,24]. The cyclic voltammo-
grams of the complexes 4, 5, and 6 show irreversible
pucker descriptor is envelope on Pd. The torsion angle
between the two chelated rings PdSC(4)N(2)N(1) and
PdSaC(4a)N(2a)N(1a) is 0.08. The torsion angle be-
tween the five-membered chelate ring PdSC(4)N(2)N(1)
and the two thiosemicarbazone moieties is 1.598, while
the dihedral angles between the five-membered chelate
ring PdSC(4)N(2)N(1) and the pyrazolone and phenyl
rings are 37.3 and 69.458, respectively. The negative
charge of the ligand is delocalized over the thiosemi-
reductions at ꢀ
/
1.39, ꢀ
/
1.35, ꢀ1.38 V, respectively.
/
These values indicate that the reduction process in the
complexes is more easily accomplished than the reduc-
tion of the free thiosemicarbazones. The electrochemical
data suggest that the reduction of 4
/
6 might be
carbazone moiety and the Sꢀ
consistent with increased single bond character, while
the imine CꢀN distances and both thioamide Cꢀ
distances indicate considerable double bond character.
This is indicative of the coordinated thiosemicarbazo-
ne’s greater conjugation and more delocalized electron
/
C bond distances are
Á
regarded as being more or less centered on the metal
center. The electron transfers from the platinum cathode
and is directed to the p* Lumo orbital. The Lumo
orbital of 6 is a mixed orbital centered on the metal
center and the four donor atoms, d(Pd)/p(S)/p(N) [24].
/
/N
Fig. 3. Perspective view of 6.

P. Yadav et al. / Inorganica Chimica Acta 349 (2003) 30Á
/36
35
Fig. 4. A view of the extended network of 6 (a) along the a axis and (b) along the b axis.
˚
density. The Pdꢀ
/
N bond distance, 2.028(7) A, and Pdꢀ
/S
Acknowledgements
˚
distance, 2.286(2) A, are similar to those found in other
We thank the NMR centrum of the University of
Ioannina. PNY thanks IKY for a scholarship. MAD
thanks the Research Committee of the University of
Ioannina, Project S. Dakaris, for partial funding of this
research.
palladium thiosemicarbazone complexes [22].
The polar hydrogen atom on the thioamide nitrogen
participates in an intermolecular hydrogen bond, Nꢀ
Á Á ÁO, resulting in hydrogen-bonded polymers linked by
two of these hydrogen bonds (1/2ꢀx, ꢀ1/2ꢁy, 1/2ꢀz).
/
H/
/
/
/
/
/
These two intermolecular hydrogen bonds connect the
monomers, which results in an infinite two-dimensional
network. Weak intramolecular hydrogen bonding (i.e.,
References
C8ꢀ
/
H
/
Á Á Á
/
N4) helps to stabilize the structure, while the
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