Synthesis and structure of the dimeric copper(II) complex tetrakis[N-thiazol-2-yl-(4-methylphenyl)sulfonamidate]dicopper(II)

Article abstract of DOI:10.1007/s10870-007-9303-9

The coordination chemistry of the ligand N-thiazol-2-yl- toluenesulfonamidate towards the copper(II) ion has been investigated using an electrochemical synthesis method. The X-ray structure of this complex was elucidated and is discussed. The compound cry

Full text of DOI:10.1007/s10870-007-9303-9

J Chem Crystallogr (2008) 38:71–75
DOI 10.1007/s10870-007-9303-9
COMMUNICATION
Synthesis and Structure of the Dimeric Copper(II) Complex
Tetrakis[N-thiazol-2-yl-(4-methylphenyl)
sulfonamidate]dicopper(II)
´
´
´
Santiago Cabaleiro Æ Rafael Calvo Æ Jesus Castro Æ J. Arturo Garcıa-Vazquez Æ
´
Lia M. B. Napolitano Æ Otaciro R. Nascimento Æ Paulo Perez-Lourido Æ
Jaime Romero Æ Antonio Sousa
Received: 27 July 2007 / Accepted: 5 November 2007 / Published online: 28 November 2007
Ó Springer Science+Business Media, LLC 2007
Abstract The coordination chemistry of the ligand
N-thiazol-2-yl-toluenesulfonamidate towards the copper(II)
ion has been investigated using an electrochemical syn-
thesis method. The X-ray structure of this complex was
elucidated and is discussed. The compound crystallised in
the monoclinic crystal system, P21/c space group with
field of medicine [1]. In particular, copper(II) [2] and
zinc(II) [3] complexes have been used in the treatment of
numerous diseases, silver(I) [4] complexes have been used
for the treatment of burns, the carbonic anhydrase inhibi-
tory properties were studied for nickel(II) complexes [5]
and copper(II) complexes have been investigated as
superoxide dismutase (SOD) imitators [6].
˚
a = 17.3888(9), b = 16.3003(9), c = 18.3679(9) A and
b = 114.3640(10)°. Four bidentate sulfathiazolato anions
bridge two metal centers in a paddle-wheel fashion, with
the nitrogen atoms as donors to give a dimeric species with
Moreover, metal complexes containing amide ligands
are easily made and variation of the substituents is facile,
providing the possibility of changing almost at will the
ligand bite angle and steric hindrance. It is believed that the
presence of bulky substituents on these ligands stabilises
the metal complexes. One possibility is the introduction of
a sulfonyl group as a substituent on the nitrogen atom,
because this group also has an electron-withdrawing effect
that increases the acid character of the NH group and
makes the ligand deprotonation process easier. In addition,
the presence of a heterocyclic ring with potential donor
atoms would increase the coordination ability. In this
respect the most widely explored system is the pyridine
ring [7–14].
˚
a CuꢀꢀꢀCu distance of 2.7859(5) A.
Keywords Copper(II) complexes ꢀ X-ray structure ꢀ
N,N0-bidentate ligands
Introduction
Amide ligands and their metal complexes have been widely
investigated due to their use as antibacterial drugs in the
In the search for new systems on different sulfonamide
ligands several other heterocyclic rings with potential
donor atoms were investigated [5, 15] and this paper deals
with the N-thiazol-2-yl-toluenesulfonamidatecopper(II)
complex.
´
S. Cabaleiro ꢀ J. Castro (&) ꢀ P. Perez-Lourido
´
Departamento de Quımica Inorganica, Universidade de Vigo,
36310 Vigo, Galicia, Spain
´
e-mail: jesusc@uvigo.es
R. Calvo ꢀ L. M. B. Napolitano ꢀ O. R. Nascimento
´
Departamento de Fısica e Informatica, Universidade de Sa˜o
Paulo, CP 369, Sao Carlos 13560-970, Brazil
´
´
´
J. A. Garcıa-Vazquez ꢀ J. Romero ꢀ A. Sousa
Experimental
´
Departamento de Quımica Inorganica, Universidade de Santiago
de Compostela, Santiago 15782, Galicia, Spain
´
Acetonitrile, dichloromethane, 2-aminothiazole, tosyl
chloride, and all other reagents were commercial products
and were used as supplied. Copper (Aldrich Chemie) was
used as 2 9 2 cm plates.
R. Calvo
´
´
Facultad de Bioquımica y Ciencias Biologicas, Universidad
Nacional del Litoral, INTEC (CONICETUNL),
3000 Santa Fe, Argentina
123

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J Chem Crystallogr (2008) 38:71–75
Crystal Structure Determination
HTzTs: The proligand was prepared by reaction of
the corresponding amine and the tosyl chloride. Tosyl-
chloride (0.96 g, 5.0 mmol) and 2-aminothiazole (0.50 g,
5.0 mmol) were reacted together in pyridine. Evaporation
of the solvent gave a white solid, which was indentified as
HTzTs. Anal. C, 46.9; H, 4.5; N, 10.9; S, 24.1% Calc for
C10H10N2O2S2 C, 47.2; H, 4.0; N, 11.0; S, 25.0%. 1H NMR
(CDCl3, ppm) 2.4 (–CH3); 12.9 (N–H). IR (KBr, cm-1):
3136(w), 3092(w), 3062(w), 3030(w), 2904(w), 2800(w),
1566(s), 1540(s), 1329(m), 1286(m), 1147(s), 1090(s),
937(s), 851(s), 814(m), 731(m), 701(m), 670(s), 630(m),
598(w), 567(m), 547(m). The product was recrystallized
from CH3CN/(CH3)2CO prior to use.
The data collection was taken on a SIEMENS Smart CCD
area-detector diffractometer with graphite-monochromated
Mo–Ka radiation. Absorption correction was carried out
using SADABS [17].
The structure was solved by direct methods and refined
by a full-matrix least-squares based on F2 [18]. Non-
hydrogen atoms were refined with anisotropic displace-
ment parameters. Hydrogen atoms were included in
idealised positions and refined with isotropic displacement
parameters. Atomic scattering factors and anomalous
dispersion corrections for all atoms were taken from
International Tables for X-ray Crystallography [19].
Details of crystal data and structural refinement are given
in Table 1.
Synthesis of the Complex [Cu2(TzTs)4]
CCDC 654012 contains the supplementary crystallo-
graphic data for this paper. These data can be obtained free
of charge via http://www.ccdc.cam.ac.uk/data_request/cif,
by e-mail.
The complex was obtained by following an electrochemi-
cal procedure [16]. Electrolysis of an acetonitrile/
dichloromethane (25 + 25 mL) solution containing HTzTs
(0.240 g, 0.93 mmol) and tetraethylammonium perchlorate
(ca. 20 mg) as a current carrier using a platinum wire as the
cathode and a copper plate as the sacrificial anode at
10 mA and 11 V for 2 h dissolved 49.8 mg of copper from
the anode (Ef = 1.05 mol F-1). During the experiment
hydrogen gas was evolved at the cathode. At the end of the
experiment the dark-green solid was filtered off, washed
with hot acetonitrile and ether and dried in vacuo. The
compound was characterised as [Cu2(TzTs)4]: Anal.
Found: C, 42.5; H, 2.9; N, 9.1; S, 21.7% Calc. for
C20H18N4O4S4Cu C, 42.2; H, 3.2; N, 9.8; S, 22.5%. IR
(KBr, cm-1): 1140(vs), 1322(s), 1598(s), 1473(s),
2921(m). Crystals suitable for X-ray diffraction studies
were obtained by crystallisation from (CH3)2CO/CH3CN.
Table 1 Summary of crystal data and structure refinement
Identification code
CCDC deposit no.
Empirical formula
Formula weight
Cu2(TzTs)2
654012
C
40H36Cu2N8O8S8
1140.33
Temperature
293(2) K
˚
0.71073 A
Wavelength
Crystal system, space group
Unit cell dimensions
Monoclinic, P21/c
˚
a = 17.3888(9) A
˚
b = 16.3003(9) A
˚
c = 18.3679(9) A
b = 114.3640(10)°
4742.6(4) A
Physical Measurements
3
˚
Volume
Z, Calculated density
Absorption coefficient
F(000)
4, 1.597 mg/m3
1.309 mm-1
The C, N, H and S contents of the compounds were
determined on a Carlo-Erba EA 1108 microanalyser. IR
spectra were recorded as KBr mulls on a Bruker Vector-22
2328
Crystal size
0.47 9 0.44 9 0.36 mm
1.74–29.86°
-14 B h B 24; -21 B k B 21;
-22 B l B 13
1
spectrophotometer. The H NMR spectrum of the ligand
h range for data collection
Index ranges
was recorded on a Bruker ARX-400 MHz spectrometer
using CDCl3 as solvent. X- (9.5 GHz) and Q-band
(35 GHz) EPR measurements were carried out on poly-
crystalline samples using a Varian E109 spectrometer and
cavities with 100-kHz field modulation. The measurements
were performed at room temperature and a Cr(III)
(g = 1.9797) sample was used for field calibration. The
g-values and zero-field splitting (D and E terms) of the spin
Hamiltonian were obtained from the simultaneous spectral
simulation of the X- and Q-band spectra using the Easy-
Spin program.
Reflections collected/unique
Completeness to 2h = 48.0°
Max. and min. transmission
Data/restraints/parameters
Goodness-of-fit on F2
26,319/10,521 [R(int) = 0.0304]
96.3%
1.00 and 0.87
10521/0/599
0.875
Final R indices [I [ 2r(I)]
R indices (all data)
R1 = 0.0370, wR2 = 0.0751
R1 = 0.0800, wR2 = 0.0841
-3
˚
0.277 and -0.320 e.A
Largest diff. peak and hole
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J Chem Crystallogr (2008) 38:71–75
73
Results and Discussion
Nsulfonamide atom. The copper atom labeled as Cu(1) is
bonded to N(21) and N(31) thiazole nitrogen atoms from
two molecules of sulfathiazolato ligands and N(12) and
N(42) from the other two sulfathiazolato anions; the Cu(2)
enviroment is similar, with bonding to N(11) and N(41) of
the thiazole rings and N(22) and N(32) of the sulfonamido
groups, in such a way that the disposition is trans in both
cases. The internal geometry of the sulfathiazole ligand is
normal and is consistent with the results from numerous
studies performed previously. A selection of bond dis-
tances and angles are included in Table 2. A representation
of the molecule is illustrated in Fig. 1.
Anodic oxidation of copper metal in a non-aqueous
solution containing the weakly acidic ligand [(4-methyl-
phenyl)sulfonyl]imino-1H-2-thiazole (HTzTs) yielded
crystalline products of formulae [Cu2(TzTs)4]. The value
of the electrochemical efficiency, defined as the amount of
metal dissolved per number of Faradays, was close to
1.0 mol F-1. This fact, together with the formation of
hydrogen gas at the cathode, is compatible with a reaction
mechanism involving the anodic oxidation to copper(I) and
deprotonation of the ligand at the cathode.
´
It is noteworthy than Borras et al. have already obtained
Anode : Cu þ TzTsꢁ ! ½CuðTzTsÞꢂ þ eꢁ
another polymorph of the compound and determined its
crystal structure [6], but in this case different synthetic and
re-crystallization methods gave different space groups and
small differences in the geometrical parameters. Firstly, the
aforementioned polymorph crystallized in the monoclinic
C2/c space group, with a = 27.174(3), b = 10.1931(10),
ꢁ
ꢁ
1
Cathode : HTzTs þ e ! TzTs þ = H
2
2
1
½CuðTzTsÞꢂ þ HTzTs ! ½CuðTzTsÞ ꢂ þ = H
2
2
2
The oxidation of copper(I) by another HL molecule to
copper(II) has been observed in another electrochemical
processes involving copper as the anode [20]. The species
[Cu(TzTs)2] contains two anionic ligands, but the
coordination polyhedron is probably incomplete due the
difficulty in the ligands acting in a chelating manner [13].
As a result, the species is dimeric. This kind of dimer has
been obtained previously by us (unpublished results) and
by other research groups [6, 14, 15]. It is interesting to
note that the clinically used sulfanilamides show similar
behavior to the tosylamides, and the deprotonated form of
the sulfanilamides can act in a monodentate or bidentate
fashion [21].
˚
c = 20.025(2) A, b = 122.025(2)°. This compound has a
˚
Table 2 Selected bond lengths [A] and angles [°] for [Cu2(TzTs)4]
Cu(1)–N(31)
1.912(2)
1.921(2)
1.998(2)
2.003(2)
2.7859(5)
95.74(9)
84.24(9)
84.29(9)
93.60(9)
Cu(2)–N(11)
Cu(2)–N(41)
Cu(2)–N(32)
Cu(2)–N(22)
1.964(2)
1.964(2)
1.960(2)
1.932(2)
Cu(1)–N(21)
Cu(1)–N(12)
Cu(1)–N(42)
Cu(1)–Cu(2)
N(31)–Cu(1)–N(12)
N(31)–Cu(1)–N(42)
N(21)–Cu(1)–N(12)
N(21)–Cu(1)–N(42)
N(22)–Cu(2)–N(41)
N(32)–Cu(2)–N(41)
N(22)–Cu(2)–N(11)
N(32)–Cu(2)–N(11)
93.12(9)
86.31(9)
86.16(9)
92.45(9)
The structure consists of dimeric units in which each
copper atom is four-coordinated with a slightly distorted
square-planar environment. The sulfathiazolato anions act
as bridges linking to one copper(II) ion through the Nthiazole
atom and to the other copper(II) ion by means of the
N(12)–Cu(1)–N(42) 162.82(9)
N(22)–Cu(2)–N(32) 162.11(9)
N(31)–Cu(1)–N(21) 172.79(10) N(41)–Cu(2)–N(11) 173.69(9)
Fig. 1 Molecular structure of
the compound. Thermal
ellipsoids have been drawn with
20% probability. Hydrogen
atoms have been omitted for
clarity
123

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J Chem Crystallogr (2008) 38:71–75
˚
environment, with the Cu(2) atom displaced 0.205(1) A
symmetry center in the middle of the Cu–Cu bond and,
consequently, both copper atoms are identical and the
asymmetric unit contains only two ligands. Our polymorph
is much more irregular, crystallized in the monoclinic
P21/c space group, and the asymmetric unit contains one
whole dimeric molecule. The Cu–Nthiazole bond lengths are
from the best plane defined by the Cu(2)N4 chromophore.
The torsion angles Namido–Cu–Cu–Nthiazole of 17.78(9)° are
higher than those previously published, as one would
expect for a more distorted structure.
˚
in the range 1.912(2)–1.964(2) A, and the Cu–Nsulfonamido
˚
bond lengths are in the range 1.932(2)–2.003(2) A, and a
Spectroscopic Properties
clear trend depending on the kinds of atoms involved in the
bond is not observed—in contrast to the previously pub-
lished compound. For the copper atom labeled as Cu(1) the
The IR spectrum of the complex does not contain the band
observed in the ligand at 3,136 cm-1, which is attributed to
m(N–H) stretching. This difference in the spectra indicates
that the ligand is in the anionic amidate form in the com-
plex. The spectrum also shows weak bands in the aromatic
˚
Cu–Nthiazole bond lengths are about 0.08 A shorter than the
Cu–Nsulfonamido bond lengths, but for the copper atom
labeled as Cu(2) the opposite trend is found. The cis bond
angles in both CuN4 chromophores are almost regular. The
trans bond angles range from 162.11(9)° to 173.69(9)°, i.e.
different to that found previously, with one trans angle
virtually linear (178°) and the other clearly bent (155.7°)
due the small bite of the bridging ligand. The distance
region and these are due to m(C=N) (1,608–1,587 cm-1
)
and m(C=C) (1,580–1,555 cm-1). These bands are shifted
to lower frequencies with respect to those in the free ligand
as a result of coordination through the sulfonamide nitro-
gen atom. The band at 1,322 cm-1, which is attributed to
mas(S=O), and band at 1,140 cm-1, attributed to the
˚
between the two Cu centers, Cu(1)–Cu(2), is 2.7859(5) A
and this is slightly longer than that found previously.
The two CuN4 planes are almost parallel, with a dihedral
angle between the two CuN4 mean planes of 0.4(1)°. The
planes are slightly distorted, with the Nsulfonamido atoms
˚
0.089(1) A above the theoretical best plane and the Nthiazole
˚
atoms 0.089(1) A below it. The Cu(1) atom is displaced
msym(S=O) vibration, are also present in the spectrum along
with a band at 2,921 cm-1, corresponding to m(CH3).
The next step in our work was to study the spectroscopic
properties of the complex by applying the Electron Para-
magnetic Resonance (EPR) technique at the X- and Q-
bands. The complex has a total electronic spin S = 1, and
the zero-field splitting parameters, D and E, are close to
2,127 and 14 Gauss, respectively. Analysis of the EPR
measurements of a crystalline sample are currently under-
way through the investigation of the spectral lines obtained
on changing the relative angle of crystal orientation with
the direction of the magnetic field.
˚
0.209(1) A below, in the opposite direction to the other
Cu(2)N4 plane, in such a way than the distorted prism
formed by the donor atoms is capped by the copper atoms
(see Fig. 2). Similar values are found for the Cu(2)
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