Synthesis, characterization and X-ray structures of [α- diphenylethanedione bis(4-ethylthiosemicarbazonato)]palladium(II) and 1,2,4-triazine-3-thione-zinc(II) complexes obtained by metal-induced cyclization

Article abstract of DOI:10.1002/ejic.200700619

The new cyclic 5-ethoxy-4-ethyl-5,6-diphenyl-4,5-dihydro-2H-[1,2,4]- triazine-3-thione ligand (HTa3T-Et) has been obtained by an intramolecular cyclization reaction of α-diphenylethanedione bis(4- ethylthiosemicarbazone) (H₂BbTSC-Et). The cyclization may be promoted either by hydroxylic solvents or by Zn^II ions. Thus, the reaction of H₂BbTSC-Et with ZnCl₂ led to the formation of [Zn(HTa3T-Et)₂Cl₂] containing not the ligand H ₂BbTSC-Et but the cyclic HTa3T-Et ligand that forms during the reaction. On the other hand, crystallization of H₂BbTSC-Et from DMSO/EtOH produces a cocrystal containing the open-chain H₂BbTSC-Et ligand together with the cyclic HTa3T-Et molecules, which are linked to a DMSO molecule by hydrogen bonds. However, reaction of the cocrystal with Pd ^II ions yields a planar tetracoordinate complex in which only the H₂BbTSC-Et ligand, in the deprotonated form, is present. The preparation and molecular structures of these compounds are discussed. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.

Full text of DOI:10.1002/ejic.200700619

FULL PAPER
DOI: 10.1002/ejic.200700619
Synthesis, Characterization and X-ray Structures of [α-Diphenylethanedione
bis(4-ethylthiosemicarbazonato)]palladium(II) and 1,2,4-Triazine-3-thione–
Zinc(II) Complexes Obtained by Metal-Induced Cyclization
Ana I. Matesanz,[a] Cesar Pastor,[b] and Pilar Souza*[a]
Keywords: Thiosemicarbazones / Cocrystals / Palladium(II) / Zinc(II) / X-ray diffraction
The new cyclic 5-ethoxy-4-ethyl-5,6-diphenyl-4,5-dihydro-
tal containing the open-chain H2BbTSC-Et ligand together
2H-[1,2,4]-triazine-3-thione ligand (HTa3T-Et) has been ob- with the cyclic HTa3T-Et molecules, which are linked to a
tained by an intramolecular cyclization reaction of α-diphen-
ylethanedione bis(4-ethylthiosemicarbazone) (H2BbTSC-Et).
The cyclization may be promoted either by hydroxylic sol-
vents or by ZnII ions. Thus, the reaction of H2BbTSC-Et with
ZnCl2 led to the formation of [Zn(HTa3T-Et)2Cl2] containing
not the ligand H2BbTSC-Et but the cyclic HTa3T-Et ligand
that forms during the reaction. On the other hand, crystalli-
zation of H2BbTSC-Et from DMSO/EtOH produces a cocrys-
DMSO molecule by hydrogen bonds. However, reaction of
the cocrystal with PdII ions yields a planar tetracoordinate
complex in which only the H2BbTSC-Et ligand, in the depro-
tonated form, is present. The preparation and molecular
structures of these compounds are discussed.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2007)
Introduction
Thiosemicarbazones (TSCs) are a versatile type of ligand
because of the number of donor atoms they possess, among
which sulfur is of paramount importance in the metal–li-
gand linkage; moreover, their configurational flexibility cre-
ates the possibility of a variety of coordination modes.[1–3]
Thiosemicarbazone derivatives have raised considerable
interest in chemistry and biology because of the antibacte-
rial, antiviral and antitumor activity that many of them
have shown.[4,5] In some cases, the highest activity is associ-
ated with a metal complex rather than the free thiosemi-
carbazone.[6]
It is well known that thiosemicarbazones derived from
1,2-dicarbonyl compounds easily cyclize during the synthe-
sis process, especially when hydroxylic solvents are used or
when solutions in such solvents are allowed to crystallize
over several days.[7] In all cases, this cyclization leads to
1,2,4-triazine-3-thione ligands (Scheme 1); these ligands are
very versatile and are able to form mono-, di- and polynu-
clear metal complexes as a result of two different coordina-
tion modes: as a monodentate, neutral ligand with coordi-
nation through the sulfur atom or as an anionic bidentate
ligand with coordination through the sulfur and nitrogen
atoms.[8]
Scheme 1. Structures for the open-chain H2BbTSC-ET and the cy-
clic HTa3T-Et ligands.
Compounds containing the 1,2,4-triazine moiety have
been found in natural products and some of these have im-
portant applications in various fields. For example, 1,2,4-
triazine-3,5-diones represent aza analogues of pyrimidine
nucleic acid bases, some neutral antibiotics are derivatives
of pyrimido[5,4-e]-1,2,4-triazine, and 4-amino-6-tert-butyl-
3-methylthio-1,2,4-triazine-5-one and 4-amino-3-methyl-6-
phenyl-1,2,4-triazine-5-one are used as agricultural chemi-
cals.[9]
As part of our systematic investigation on the coordina-
tion chemistry of thiosemicarbazone derivatives,[10,11] we re-
cently reported a paper that focuses on the structure–antitu-
mor activity relationships of a series of palladium and plati-
num α-diphenylethanedione bis(thiosemicarbazone) deriva-
tives. In all compounds studied there, the ligands unambig-
uously show the bis(thiosemicarbazone) form.[12] To extend
[a] Departamento de Química Inorgánica, Facultad de Ciencias,
Universidad Autónoma de Madrid,
C/ Francisco Tomás y Valiente 7, 28049 Madrid, Spain
Fax: +34-914974833
E-mail: pilar.souza@uam.es
[b] Servicio Interdepartamental de Apoyo a la Investigación,
Facultad de Ciencias, Universidad Autónoma de Madrid,
C/ Francisco Tomás y Valiente, 7, 28049 Madrid, Spain
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A. I. Matesanz, C. Pastor, P. Souza
FULL PAPER
our studies, particularly with respect to the coordination
properties of H2BbTSC-Et and the stereochemistry and
molecular structure of the complexes, we planned to synthe-
size new metal derivatives. It was possible, after numerous
attempts at crystallization of the H2BbTSC-Et ligand, to
obtain good quality crystals suitable for X-ray analysis
from DMSO/EtOH solution. These proved to be cocrystals
containing, together with H2BbTSC-Et, the cyclic deriva-
tive formed by an intramolecular cyclization reaction. To
the best of our knowledge, this is the first report of the
isolation of a bis(thiosemicarbazone) molecule and the cy-
clized form as single crystals. Interestingly, the reaction of
the new cocrystal isolated with palladium(II) ions gave the
mononuclear N2S2-tetracoordinate bis(thiosemicarbazone)
complex instead the binuclear CNS2-tetracoordinate com-
plex recently reported by us.[12]
Some of the different routes published that undergo the
Figure 1. Structure of the cocrystal H2BbTSC-Et/HTa3T-Et.
cyclization of thiosemicarbazones use a metallic salt (Zn2+
,
Cu2+ and Fe3+). On this basis and in order to search for
novel cyclized compounds, we also report here the reaction
of H2BbTSC-Et with ZnCl2. The reaction yields a new
zinc(II) compound containing, in neutral form, the cyclic
ligand 5-ethoxy-4-ethyl-5,6-diphenyl-4,5-dihydro-2H-[1,2,4]-
triazine-3-thione (HTa3T-Et, see Scheme 1).
Table 1. Selected bond lengths [Å] for H2BbTSC-Et and H2BbTSC-
Et/HTa3T-Et.
H2BbTSC-Et
H2BbTSC-Et/HTa3T-Et
S1–C3
S2–C6
N1–C2
N1–C3
N2–N3
N2–C3
N3–C4
N4–C5
N4–N5
N5–C6
N6–C6
N6–C7
1.678(2)
S1–C3
S2–C6
1.681(3)
1.689(3)
1.467(4)
1.313(4)
1.362(4)
1.371(4)
1.290(3)
1.294(4)
1.360(3)
1.375(4)
1.325(4)
1.460(4)
1.679(3)
1.470(4)
1.344(4)
1.490(4)
1.359(4)
1.354(4)
1.281(4)
1.676(2)
1.459(3)
1.317(3)
1.356(2)
1.369(3)
1.286(3)
1.291(3)
1.360(2)
1.368(3)
1.317(3)
1.456(3)
N1–C2
N1–C3
N2–N3
N2–C3
N3–C4
N4–C5
N4–N5
N5–C6
N6–C6
N6–C7
S3–C23
N7–C22
N7–C23
N7–C25
N8–N9
N8–C23
N9–C24
Results and Discussion
Synthesis of the Ligands
The preparation of crude H2BbTSC-Et was carried out
according to ref.[12] Analytical and spectroscopic properties
are consistent with those reported.
Attempted slow recrystallization of H2BbTSC-Et from
DMSO/EtOH resulted in the isolation of a cocrystal
H2BbTSC-Et/HTa3T-Et in a 1:1 ratio that also contains
DMSO molecules. The structural data suggests that some
H2BbTSC-Et molecules may be transformed into the final
1,2,4-triazine-3-thione ligand by an intramolecular cycliza-
tion reaction, similar to that described by Alsop et al.[13]
The cyclization with concomitant insertion of ethanol and
elimination of 4-ethylthiosemicarbazide seems to be fa-
voured when hydroxylic solvents are used or when solutions
in such solvents are allowed to crystallize over several days.
The crystal and molecular structures with the numbering
schemes of the H2BbTSC-Et and HTa3T-Et molecules are
shown in Figure 2.
The H2BbTSC-Et molecule consists of two distinct es-
sentially planar sections, which are pivoted about the C5–
C4 “backbone” of the ligand, with a C15–C5–C4–C9 tor-
sion angle of 79.4(3)°. Within each planar section, the C–
N and N–N bond lengths, intermediate between the ideal
values of corresponding single and double bonds, are in-
dicative of a delocalized system. The existence of the thio-
semicarbazone groups in the thione form, in the solid state,
is evidenced by the C–S bond lengths of 1.681(3) and
1.689(3) Å, which are close to a formal C=S bond length.[13]
The HTa3T-Et molecule is a triazine–thione formed from
Structures of the Ligands
The structure of the cocrystal H2BbTSC-Et/HTa3T-Et
consists of one H2BbTSC-Et molecule and one cyclic tri- an intramolecular reaction during the recrystallization pro-
azine molecule HTa3T-Et together with one dimethylsulfox- cess. This six-membered heterocyclic C3N3 ring is close to
ide molecule of crystallization (Figure 1). Selected bond planar [torsional angles: C25–N7–C23–N8 10.0(4)°, N9–
lengths and angles are given in Table 1.
N8–C23–N7 1.5(4)°, N8–N9–C24–C25 –0.4(4)°]. Although
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Synthesis of Thiosemicarbazone Complexes by Metal-Induced Cyclization
of 1.359(4) Å is significantly shorter than the predicted N–
N bond length of 1.45 Å. On the other hand, the N7–C25
bond [1.490(4) Å] is slightly longer than the predicted C–N
bond, and the C24–C25 bond [1.523(4) Å] is slightly shorter
than the predicted length 1.54 Å for a C–C bond.[14]
Within the crystal, the two independent molecules are
linked to a DMSO molecule by N–H···O bonds. The crystal
packing along the b axis (Figure 3) shows parallel alternat-
ing lines of H2BbTSC-Et and HTa3T-Et molecules.
Synthesis and Structure of the Complex [Pd(BbTSC)]
We have recently verified that the reaction of crude
H2BbTSC-Et with Li2PdCl4 in methanol undergoes ortho-
metallation to give a dinuclear bis(thiosemicarbazone) com-
plex.[12] Thus, we decided to investigate the coordinating
properties of the cocrystal H2BbTSC-Et/HTa3T-Et to pal-
ladium(II). The analytical and spectroscopic data of the iso-
lated compound are in agreement with the formula
[Pd(BbTSC)], in which the H2BbTSC ligand is in the dou-
bly deprotonated form. Green single crystals were obtained
on recrystallization from DMSO, and the X-ray diffraction
study confirmed the proposed formulae.
An ORTEP representation of [Pd(BbTSC)] together with
the atom labelling scheme is shown in Figure 4, and selected
bond lengths and angles are given in Table 2. This neutral
PdII complex crystallizes in the monoclinic C2/c space
group with Z = 4 as discrete C20H22N6S2Pd·DMSO mole-
cules.
Figure 2. Molecular structure of the H2BbTSC-Et (top) and
HTa3T-Et (below) molecules, which shows the atom numbering
scheme.
the C–S bond length of 1.679(3) Å is in the range of a C=S
bond, some electronic delocalization occurs in the ring
formed. Thus, while the bond length for N9–C24 of
1.281(4) Å is consistent with a C=N bond, both N8–C23
and N7–C23 bonds [1.354(4) and 1.344(4) Å, respectively]
are considerably shorter than the predicted length of 1.47 Å
for a C–N bond. Further, the N8–N9 bond with a length
Figure 4. Molecular structure of [Pd(BbTSC)].
On the basis of other α-diketone bis(thiosemicarb-
azones),[15] the mode of coordination for this complex is as
expected; two iminic nitrogen atoms and two thiolato sulfur
atoms bond to palladium on the loss of the hydrogen atoms
of N2 and N2A from both thiosemicarbazone moieties to
give an approximately planar, four-coordinate complex.
Thus, the coordination of the bis(thiosemicarbazone) re-
sults in the formation of three five-membered chelate rings
(PdSCNN, PdNCCN and PdNNCS).
A careful examination of the bond length data shows
that the Pd–Niminic and Pd–S distances are comparable with
those reported for other thiosemicarbazone palladium(II)
complexes with strong Pd–N coordination.[10] Since the Pd–
S bonds are significantly longer than the Pd–N bonds, the
coordination geometry around the metal ion is more trape-
Figure 3. View of cocrystal H2BbTSC-Et/HTa3T-Et along the b
axis.
Eur. J. Inorg. Chem. 2007, 5433–5438
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A. I. Matesanz, C. Pastor, P. Souza
FULL PAPER
Table 2. Selected bond lenghs [Å] and angles [°] for [Zn(HTa3T-
Et)2Cl2] and [Pd(BbTSC)].
The crystal packing (Figure 5) shows parallel pseu-
dochains of molecules, and the absence of any solvent of
crystallization indicates possible existence of noncovalent
interactions between the individual bis(thiosemicarbazone)
molecules. A closer look reveals π–π stacking interactions
between successive thiosemicarbazone moieties (3.62 Å).
These extended intermolecular interactions are responsible
for holding the crystal together.
[Zn(HTa3T-Et)2Cl2]
[Pd(BbTSC)]
S1–C1
N1–C1
N1–C2
N2–C1
N3–C3
N2–N3
Zn1–Cl1
Zn1–Cl1A
Zn1–S1
Zn1–S1A
Cl1A–Zn1–Cl1
Cl1A–Zn1–S1A
Cl1A–Zn1–S1
Cl1–Zn1–S1
Cl1–Zn1–S1A
S1A–Zn1–S1
1.7113(19)
1.329(2)
1.490(2)
1.342(2)
1.281(3)
1.376(2)
2.2380(5)
2.2379(5)
2.3694(5)
2.3693(5)
124.74(3)
S1–C1
N1–C4
N2–C1
N3–C1
N3–C2
N1–N2
Pd1–N1
Pd1–N1A
Pd1–S1
Pd1–S1A
N1A–Pd1–N1
1.771(3)
1.325(4)
1.332(4)
1.334(4)
1.462(4)
1.351(4)
1.982(3)
1.982(3)
2.2792(8)
2.2792(8)
82.38(15)
166.84(8)
84.47(8)
84.46(8)
166.84(8)
108.69(4)
111.374(17) N1–Pd1–S1A
102.003(17) N1–Pd1–S1
111.376(17) N1A–Pd1–S1A
102.000(17) N1A–Pd1–S1
103.79(3)
S1A–Pd1–S1
zoid than square. The overall impression from the values of
the bond lengths and angles in the vicinity of the palladium
atom is that the ligand cavity is too small to accommodate
the Pd2+ ion ideally. Thus, the N–Pd–N bond angles are
less than 90°, and the sulfur ends of the ligand arms are
pushed outwards beyond the natural position that would be
adopted by the planar ligand, with S–Pd–S bond angles of
ca. 109°.
Figure 5. Side view of H2BbTSC-Et, which shows the parallel dis-
position of the molecules as a result of π–π stacking.
The loss of the protons originally bonded to N2 and
N2A atoms produces a negative charge delocalized in the
ligand system, which is consistent with the C–N distances
(intermediate between formal single and double bonds) and
C–S distances (see Table 2). This substantiates the displace-
ment of the tautomeric equilibrium to the thiol form in the
ligand.
An ORTEP representation of [Zn(HTa3T-Et)2Cl2] to-
gether with the atom labelling scheme is shown in Figure 6,
and selected bond lengths and angles are given in Table 2.
The terminal uncoordinated nitrogen atoms are involved
in intermolecular hydrogen bonds with the oxygen atoms of
the solvent molecules; the contact distances and angles are
N3···O1 2.897(4) Å and N–H–O 162(4)°.
Synthesis and Structure of the Complex [Zn(HTa3T-Et)2Cl2]
The reaction of crude H2BbTSC-Et ligand with ZnCl2 in
ethanol led to the formation of the crystalline yellow
[Zn(HTa3T-Et)2Cl2] complex. The analytical, spectroscopic,
and X-ray diffraction data (see Experimental Section) re-
vealed that H2BbTSC-Et is transformed into cyclic 5-
ethoxy-4-ethyl-5,6-diphenyl-4,5-dihydro-2H-[1,2,4]-triazine-
3-thione (HTa3T-Et) during the complexation reaction. An
analogous cyclization of 2-pyridinformamide 4-ethylthio-
semicarbazone that is promoted by the presence of silver(I)
ions was reported recently by Castiñeiras et al.[16]
Figure 6. Molecular structure of [Zn(HTa3T-Et)2Cl2] (H atoms
were omitted for clarity).
This neutral complex crystallizes in the orthorhombic
The mother liquor was allowed to stand at 4 °C. After Fdd2 space group with Z = 8. The zinc atom is tetracoordi-
several days, crystalline pale yellow needles were isolated, nated by two chlorido ligands and two sulfur atoms from
which were identified as the free ligand H2BbTSC-Et by X- the neutral monodentate ligands HTa3T-Et. The largest
ray diffraction analysis. Its molecular structure essentially angular distortion from ideal tetrahedral geometry is shown
shows the same structural characteristics as that of the by Cl1A–Zn–Cl1 [124.74(3)°]. Although the chlorido li-
open-chain molecule in the cocrystal H2BbTSC-Et/HTa3T- gands participate in the hydrogen bonding, the distances
Et. Selected bond lengths and angles are given in Table 1.
Zn–Cl [2.238 Å] fall in the range of the shortest lengths for
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Synthesis of Thiosemicarbazone Complexes by Metal-Induced Cyclization
terminal Zn–Cl bonds.[17] The Zn–S and C–S distances in this case, the presence of either the phenyl rings, which
4
[2.369 and 1.711 Å, respectively] are similar to those found allow extensive delocalization, or the N substitution ap-
in other complexes with thiocarbonyl sulfur atoms.[18] The pears to facilitate the cyclization of the H2BbTSC-Et li-
4-ethyl substituent on the N1 atom reduces the possibilities gand.
for hydrogen bonding. Thus, only two intramolecular N2–
H···Cl bonds are present in the complex.
Experimental Section
An analysis of the relative disposition of the complex
molecules in the crystal structure highlights the importance
of aromatic–aromatic edge-to-face interactions in the pack-
ing that takes place when the crystal is formed.[19,20] The
perpendicular (ca. 96°) distance between C–H and the plane
of π system is ca. 2.88 Å.
Materials: Solvents were purified and dried according to standard
procedures. 4-Ethylthiosemicarbazide, 1,2-diphenylethanedione,
lithium chloride, palladium(II) chloride and zinc chloride were
commercially available from Aldrich.
Preparation of the Ligands: H2BbTSC-Et was synthesized accord-
ing to ref.[11]. Yield: 0.35 g (77%). Analytical and spectroscopic
properties are consistent with those reported. Attempted slow
recrystallization of H2BbTSC-Et from DMSO/EtOH resulted in
the isolation of a cocrystal, which is composed of a 1:1 ratio of
H2BbTSC-Et and cyclic HTa3T-Et according to its crystal and mo-
lecular structure.
Conclusions
The investigations show that the synthesis of bis(thio-
semicarbazone) derivatives from α-diketones with alkyl sub-
stituents can be complicated by the formation of cyclized
[Zn(HTa3T-Et)2Cl2]: The reaction of ZnCl2 (0.3 mmol) in ethanol
products. Typically, the α-bis(thiosemicarbazones) are made (40 mL) with H2BbTSC-Et (0.3 mmol), over 5 h whilst stirring and
refluxing, led to the formation of a yellow solution, which was fil-
tered and allowed to evaporate at room temperature overnight to
give a yellow crystalline solid. The product was identified as the
[Zn(HTa3T-Et)2Cl2] complex, which does not contain the
H2BbTSC-Et ligand but the cyclic HTa3T-Et molecule. Single pris-
matic crystals suitable for X-ray diffraction were selected directly
from the reaction vessel. Yield: 0.17 g (71%). MS (FAB+ with
mNBA matrix): m/z (%) = 816.1 [M + H]+, 340.1 (100) [HTa3T –
by heating a thiosemicarbazide under reflux with an α-dike-
tone in an alcoholic solvent with an acid catalyst. Although
it is well known that such solvents favour cyclization, we
have not found the cyclic 1,2,4-triazine-3-thione form in our
previous studies. However, slow recrystallization of the
H2BbTSC-Et from DMSO/EtOH affords a cocrystal com-
posed of a 1:1 ratio of open-chain H2BbTSC-Et and cyclic
1,2,4-triazine-3-thione. The formation of the cocrystal
could be favoured by the presence of DMSO molecules
Et + H]+. IR (KBr): ν = 3252 (s, NH), 1574 (s, CN), 854 (w, CS-
˜
thioamide IV band). 1H NMR ([D6]DMSO): δ = 9.72 (s, 1 H,
since they each form two hydrogen bonds with the terminal 2NH), 7.72–7.20 (m, 6 H, Ph), 3.64–3.59 (m, 3 H, CH2CH3), 3.35–
3.33 (m, 3 H, OCH2CH3), 1.30–1.25 (t, J = 3.0 Hz, 2 H, CH2CH3),
1.20–1.15 (t, J = 2.0 Hz, 2 H, OCH2CH3) ppm. After filtering the
ZnII complex, the mother liquor was allowed to stand at 4 °C, and
after several days, pale yellow needles of the free ligand H2BbTSC-
Et suitable for X-ray analysis were obtained. Analytical and spec-
troscopic properties are consistent with those previously re-
ported.[11]
nitrogen atom of one thiosemicarbazone moiety (hindering
the cyclization) and with the hydrazinic nitrogen atom of
the other thiosemicarbazone moiety (favouring the cycliza-
tion).
The intramolecular cyclization reaction may also be pro-
moted by the presence of the salt ZnCl2. Thus, we have
achieved the isolation of a ZnII–1,2,4-triazine-3-thione
complex in which the zinc atom is tetracoordinated by two
chlorido ligands and two sulfur atoms from the neutral
monodentate cyclic ligands. Although the different steps in-
volved in this process are not completely understood, it has
been assumed that the metal ion plays an important role in
this process, probably because of both inductive and stereo-
[Pd(BbTSC-Et)]: The reaction of cocrystal H2BbTSC-Et/HTa3T-Et
(1 mmol) with a methanol solution of lithium tetrachloropalladate
prepared in situ from palladium(II) chloride (1.2 mmol) and lith-
ium chloride (4.4 mmol), over 5 h at room temperature while stir-
ring, led to a dark green solution, which was filtered. From the
solution, a dark green solid was isolated by slow evaporation of
the solvent, which could then be recrystallized from DMSO to give
chemical effects, as do the solvent and the counterion of green crystals suitable for X-ray analysis. On the basis of the molec-
ular structure of [Pd(BbTSC-Et)], the coordinated doubly depro-
tonated ligand was unambiguously identified as H2BbTSC-Et.
Yield: 0.15 g (30%). C20H22N6S2Pd·DMSO (595.08): calcd. C
44.40, H 4.70, N 14.10, S 16.15; found C 44.00, H 5.00, N 13.50,
the metal.
However, reaction of the cocrystal with Li2PdCl4 yields
a planar tetracoordinate complex in which the bis(4-ethyl-
thiosemicarbazone) ligand in the deprotonated form is pres-
ent. In this case, the clear preference for a planar environ-
ment of the PdII ion assists the stabilization of the bis-
(thiosemicarbazone) form.
S 15.40%. IR (KBr): ν = 3237, 3187 (s, NH), 1547 (s, CN), 842 (w,
˜
1
CS-thioamide IV band) cm–1. H NMR ([D6]DMSO): δ = 8.10 (t,
J = 4.0 Hz, 1 H, 4NH), 7.17–7.11 (m, 6 H, Ph), 3.26 (m, 2 H,
CH2CH3), 1.23 (m, 3 H, CH2CH3).
In summary, the conversion of H2BbTSC-Et to the cyclic
1,2,4-triazine-3-thione form is relatively rapid in hydroxylic
solvents, and when a metallic salt is present, the formation
of the metal complex stabilizes one of the forms according
to its structural preferences. Thus, the cyclization of the
H2BbTSC-Et ligand can be controlled by selection of the
Physical Measurements: Elemental analyses were performed on a
LECO CHNS-932 microanalyzer. Fast atom bombardment (FAB)
mass spectra were performed with a VG AutoSpec spectrometer
(nitrobenzyl alcohol matrix). H NMR spectra ([D6]DMSO) were
recorded with BRUKER AMX-300 spectrometer. All cited physical
measurements were obtained from the Servicio Interdepartamental
1
appropriate metal salt and reaction conditions. Moreover, de Investigación (SIDI) of the Universidad Autónoma de Madrid.
Eur. J. Inorg. Chem. 2007, 5433–5438
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
5437

A. I. Matesanz, C. Pastor, P. Souza
Table 3. Crystal data and structure refinement for H2BbTSC-Et, H2BbTSC-Et/HTa3T-Et, [Zn(HTa3T-Et)2Cl2] and [Pd(BbTSC)].
FULL PAPER
H2BbTSC-Et
H2BbTSC-Et /HTa3T-Et [Zn(HTa3T-Et)2Cl2]
[Pd(BbTSC)]
Formula
M
System
Space group
a [Å]
b [Å]
c [Å]
C20H24N6S2
412.57
C41H51N9O2S4
830.15
monoclinic
P21/c
19.1014(9)
11.3471(5)
20.9504(10)
90
105.820(3)
90
4368.9(4)
1.54178
100(2)
C38H42Cl2N6O2S2Zn
815.17
orthorhombic
Fdd2
22.1376(5)
28.2782(8)
12.6602(2)
90
90
90
7925.4(3)
1.54178
100(2)
C22H28N6OPdS3
595.08
monoclinic
C2/c
12.3451(6)
22.2996(11)
9.1162(5)
90
95.758(3)
90
2496.9(2)
1.54178
100(2)
triclinic
¯
P1
9.5938(11)
9.8145(12)
12.0817(15)
98.752(4)
106.338(4)
96.281(4)
1065.0(2)
1.54178
100(2)
α [°]
β [°]
γ [°]
V [Å3]
λ [Å]
T [K]
Z
2
4
8
4
Dc [gcm–3]
F(000)
1.287
436
2.402
0.0535
0.0425
0.1215
0.1104
1.036
1.262
1760
2.359
0.0829
0.0503
0.1327
0.1166
1.019
1.366
3392
3.412
0.0254
0.0251
0.0645
0.0642
1.122
1.583
1216
8.562
0.0401
0.0315
0.0806
0.0760
1.023
µ [mm–1]
R1 (all data)
R1 [IϾ2σ(I)]
wR2(all data)
wR2[IϾ2σ(I)]
GOF
[4] Y. Yu, J. Wong, D. B. Lovejoy, D. S. Kalinowski, D. R. Rich-
ardson, Clin. Cancer Res. 2006, 12, 6876–6883.
[5] P. Genova, T. Varadinova, A. I. Matesanz, D. Marinova, P.
Souza, Toxicol. Appl. Pharmacol. 2004, 197, 107–112.
[6] D. X. West, A. E. Liberta, S. B. Padhye, P. B. Chikate, P. B.
Sonawane, A. S. Kumbhar, R. G. Yerande, Coord. Chem. Rev.
1993, 123, 49–71.
Infrared spectra (KBr discs) were recorded with a Bomen–Michel-
son spectrophotometer (4000–400 cm–1).
X-ray Crystallographic Studies: A summary of the crystal data, ex-
perimental details and refinement results is listed in Table 3. The
X-ray measurement was performed on a Bruker SMART 6 K CCD
area-detector three-circle diffractometer with a rotating anode gen-
erator (Cu-Kα radiation, λ = 1.54178 Å) equipped with Goebel mir-
rors at settings of 50 kV and 110 mA. X-ray data were collected at
100 K. The software package SHELXTL version 6.10 was used for
space group determination, structure solution and refinement. The
structures were solved by direct methods, completed with difference
Fourier syntheses, and refined with full-matrix least-squares tech-
niques against F2 by using SHELXL-97.
[7] M. Christlieb, J. R. Dilworth, Chem. Eur. J. 2006, 12, 6194–
6206.
[8] E. Lopez-Torres, M. Mendiola, Polyhedron 2005, 24, 1435–
1444.
[9] J. G. Haasnoot, Coord. Chem. Rev. 2000, 200–202, 131–185.
[10] A. I. Matesanz, J. M. Pérez, P. Navarro, J. M. Moreno, E. Col-
acio, P. Souza, J. Inorg. Biochem. 1999, 76, 29–37.
[11] A. I. Matesanz, P. Souza, J. Inorg. Biochem. 2007, 101, 245–
253.
CCDC-649679 (ligand H2BbTSC-Et), -649677 (cocrystal
H2BbTSC-Et/HTa3T-Et), -649678 {compound [Zn(HTa3T-Et)2-
Cl2]} and -634275 {compound [Pd(BbTSC-Et)]} contain the sup-
plementary crystallographic data for this paper. These data can be
obtained free of charge from The Cambridge Crystallographic
Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
[12] A. I. Matesanz, P. Souza, J. Inorg. Biochem. 2007, 101, 1354–
1361.
[13] L. Aslop, A. R. Cowley, J. R. Dilworth, P. S. Donnelly, J. M.
Peach, J. T. Rider, Inorg. Chim. Acta 2005, 358, 2770–2780.
[14] P. Souza, A. Arquero, A. Garcia-Onrubia, V. Fernández, A. M.
Leiva, U. Müller, Z. Naturforsch., Teil B 1989, 44, 946–950.
[15] P. J. Blower, T. C. Castle, A. R. Cowley, J. R. Dilworth, P. S.
Donnelly, E. Labisbal, F. E. Sowrey, S. J. Teat, M. Went, Dal-
ton Trans. 2005, 4416–4425.
[16] A. Castiñeiras, I. García-Santos, S. Dehnen, P. Sevillano, Poly-
hedron 2006, 25, 3653–3660.
[17] N. C. Kasuga, K. Sekino, M. Ishikawa, A. Honda, M. Yokoy-
ama, S. Nakano, N. Shimada, C. Koumo, K. Nomiya, J. Inorg.
Biochem. 2003, 96, 298–310.
Acknowledgments
We are grateful to Ministerio de Sanidad y Consumo, Instituto de
Salud Carlos III (PI040354) of Spain for financial support.
[1] D. X. West, A. E. Liberta, S. B. Padhye, R. C. Chikate, P. B.
Sonawane, A. S. Kumbhar, R. G. Yerande, Coord. Chem. Rev.
1993, 123, 49–71.
[2] J. S. Casas, M. S. García-Tasende, J. Sordo, Coord. Chem. Rev.
2000, 209, 197–261.
[3] A. Amoedo, L. A. Adrio, J. M. Antelo, J. Martínez, M. T. Per-
eira, A. Fernández, J. M. Vila, Eur. J. Inorg. Chem. 2006, 15,
3016–3021.
[18] P. Souza, L. Sanz, V. Fernández, A. Arquero, E. Gutierrez, A.
Monge, Z. Naturforsch., Teil B 1991, 46, 767–774.
[19] J. W. Steed, D. R. Turner, K. Wallace, Core Concepts in Supra-
molecular Chemistry and Nanochemistry, VCH, Weinheim,
2007, p. 23.
[20] P. Gamez, J. Reedijk, Eur. J. Inorg. Chem. 2006, 1, 29–42.
Received: June 14, 2007
Published Online: October 16, 2007
5438
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© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2007, 5433–5438