Reaction of copper(II) with 1-carboxamide-3,5-dimethylpyrazole, 1-carboxamidine-3,5-dimethylpyrazole, 4-acetyl-3-amino-5-methylpyrazole and 5-amino-4-carboxamide-1-phenylpyrazole

Article abstract of DOI:10.1016/S0020-1693(03)00231-7

Complex formation of copper(II) bromide and acetate with 1-carboxamide-3,5-dimethylpyrazole (HL³) and copper(II) bromide with 5-amino-4-carboxamide-1-phenylpyrazole (L²), 4-acetyl-3-amino-5-methylpyrazole (HL⁴) and 1-carboxamidine-3,5-dimethylpyrazole (HL⁵), was studied. The obtained compounds, CuBr₂(L²)₂, Cu(L ³)₂, CuBr₂(HL⁴)₂, CuBr₂(HL⁵)₂ and [CuBr(HL¹)(L ³)]₂ (HL¹ denotes the 3,5-dimethylpyrazole), are characterized by elemental analysis, FT-IR spectrometry, molar conductivity, TG-MS and DSC. The X-ray structure of [CuBr(HL¹)(L ³)]₂ and Cu(L³)₂ is discussed. For [CuBr(HL¹)(L³)]₂ a dimeric penta-co-ordinated structure has been found; the co-ordination around the metal in Cu(L ³)₂ is trans-square planar. To CuBr₂(L ²)₂ and CuBr₂(HL⁴)₂ a nearly tetrahedral, while for CuBr₂(HL⁵)₂ an octahedral geometry may be assumed. It means that the geometry of the compounds in the first place depends on the ligand substituents. The course of the complex formation reaction is anion-dependent and may be explained on the basis of Pearson's theory, taking into account the steric factors. A low stability intermediate formation was observed in the thermal decomposition of Cu(L ³)₂.

Full text of DOI:10.1016/S0020-1693(03)00231-7

Inorganica Chimica Acta 353 (2003) 253ꢀ262
/
www.elsevier.com/locate/ica
Reaction of copper(II) with 1-carboxamide-3,5-dimethylpyrazole, 1-
carboxamidine-3,5-dimethylpyrazole, 4-acetyl-3-amino-5-
methylpyrazole and 5-amino-4-carboxamide-1-phenylpyrazoleꢀ
a,
K. Me´sza´ros Sze´cse´nyi *, V.M. Leovac , V.I. Cesˇljevic´ , A. Kova´cs , G. Pokol ,
a
a
b
c
ˇ
d
Gy. Argay , A. Ka´lma´n , G.A. Bogdanovic´ , Z.K. Jac´imovic´ , A. Spasojevic´-de Bire´
d
e
f
g
ˇ
a Department of Chemistry, University of Novi Sad, Faculty of Sciences, 21000 Novi Sad, Trg D. Obradovic´a 3, Serbia and Montenegro
b Research Group of Technical Analytical Chemistry of the Hungarian Academy of Sciences at the Institute of General and Analytical Chemistry,
Budapest University of Technology and Economics, H-1521 Budapest, Hungary
c Institute of General and Analytical Chemistry, Budapest University of Technology and Economics, H-1521 Budapest, Hungary
d Institute of Chemistry, Chemical Research Center, Hungarian Academy of Sciences, P.O. Box 17, H-1525 Budapest, Hungary
ˇ
Laboratory of Theoretical Physics and Condensed Matter Physics, VINCA Institute of Nuclear Sciences, P.O. Box 522, 11001 Belgrade, Serbia and
e
Montenegro
f Faculty of Metallurgy and Technology, University of Montenegro Podgorica, Serbia and Montenegro
g Laboratoire de Structures, Properie´te´s et Mode´lisation des Solides (SPMS), UMR 8580 du CNRS, Ecole Centrale Paris, Grande Voie des Vignes,
92295 Chaatenay-Malabry Cedex, France
Received 19 December 2002; accepted 28 February 2003
Abstract
Complex formation of copper(II) bromide and acetate with 1-carboxamide-3,5-dimethylpyrazole (HL3) and copper(II) bromide
with 5-amino-4-carboxamide-1-phenylpyrazole (L2), 4-acetyl-3-amino-5-methylpyrazole (HL4) and 1-carboxamidine-3,5-dimethyl-
pyrazole (HL5), was studied. The obtained compounds, CuBr2(L2)2, Cu(L3)2, CuBr2(HL4)2, CuBr2(HL5)2 and [CuBr(HL1)(L3)]2
(HL1 denotes the 3,5-dimethylpyrazole), are characterized by elemental analysis, FT-IR spectrometry, molar conductivity, TG-MS
and DSC. The X-ray structure of [CuBr(HL1)(L3)]2 and Cu(L3)2 is discussed. For [CuBr(HL1)(L3)]2 a dimeric penta-co-ordinated
structure has been found; the co-ordination around the metal in Cu(L3)2 is trans-square planar. To CuBr2(L2)2 and CuBr2(HL4)2 a
nearly tetrahedral, while for CuBr2(HL5)2 an octahedral geometry may be assumed. It means that the geometry of the compounds in
the first place depends on the ligand substituents. The course of the complex formation reaction is anion-dependent and may be
explained on the basis of Pearson’s theory, taking into account the steric factors. A low stability intermediate formation was
observed in the thermal decomposition of Cu(L3)2.
# 2003 Elsevier B.V. All rights reserved.
Keywords: Pyrazole-complexes; Copper(II)-complexes; Pearson theory
1. Introduction
structure and the activity of the active site of metallo-
proteins. Namely, the metal ion in biological systems is
often co-ordinated to one or more imidazole groups
which are part of histidine fragments of the proteins [2].
On the other hand, the aromatic ring systems of
imidazoles and pyrazoles are very much alike in the
electronic and steric sense, but the latter ones more
readily synthesized compared to the former ligands.
Hence, there are excellent review articles on the pyra-
Complexes with pyrazole-based ligands are a frequent
subject of chemical investigations giving an opportunity
for a better understanding the relationship between the
ꢀ This paper is Part 14 in the series of our studies on Transition
Metal Complexes with pyrazole-based ligands. Part 13 [1].
zole-based co-ordination compounds [3ꢀ5]. Nowadays,
attention is paid to the design of various pyrazole
ligands with special structural properties to fulfill the
/
* Corresponding author. Tel.: ꢁ
54-065.
E-mail address: mszk@eunet.yu (K. Me´sza´ros Sze´cse´nyi).
/
381-21-35-0122x832; fax: ꢁ381-21-
/
0020-1693/03/$ - see front matter # 2003 Elsevier B.V. All rights reserved.
doi:10.1016/S0020-1693(03)00231-7

254
K. Me´sza´ros Sze´cse´nyi et al. / Inorganica Chimica Acta 353 (2003) 253ꢀ262
/
specific stereochemical requirements of a particular
metal-binding site [6]. The review [6] deals with the co-
ordination chemistry of transition metal complexes with
bi- and polydentate pyrazole derivatives.
In our systematic studies on transition metal com-
plexes the pyrazole derivatives take part in co-ordina-
tions of the compounds in DMF was measured at room
temperature using a Jenway 4010 conductivity meter.
Magnetic susceptibility measurements were conducted
at room temperature by means of a magnetic suscept-
ibility balance MSB-MKI, Sherwood Scientific Ltd,
Cambridge. The data were corrected for diamagnetic
susceptibilities.
tion mostly as monodentate ligands [7ꢀ9]. However,
/
during thermal treatment of the compounds, depending
on the pyrazole substituents, relatively stable intermedi-
ates with a stoichiometric composition are formed,
whereby the co-ordination mode of the ligand changes.
This points to a possibility of a solid phase synthesis of
new compounds. The goal of our systematic studies on
pyrazole complexes with transition metal ions is to
examine how the substituents of the pyrazole ring, as
well as various cations and anions, influence the course
of the complex formation reaction. Additionally, our
aim is to gain information on the structural dependence
of the thermal properties within the investigated series.
In this part we report the synthesis, physico-chemical
characteristics and structure of copper(II) complexes
formed with 5-amino-4-carboxamide-1-phenylpyrazole,
(L2), 1-carboxamide-3,5-dimethylpyrazole, (HL3), 4-ace-
tyl-3-amino-5-methylpyrazole (HL4) and 1-carboxami-
dine-3,5-dimethylpyrazole, (HL5) ligands. Compounds
with the following compositions are obtained:
CuBr2(L2)2, Cu(L3)2, CuBr2(HL4)2, CuBr2(HL5)2 and
[CuBr(HL1)(L3)]2, where HL1 denotes the 3,5-dimethyl-
pyrazole ligand.
2.2. Synthesis
All the compounds were synthesized by mixing warm
ethanolic solutions of the ligand (2 mmol) and cop-
per(II) bromide (1 mmol) except for Cu(L3)2, where
copper(II) acetate monohydrate was used instead, and
both the ligand (2 mmol) and the metal salt (1 mmol)
were dissolved in methanol. The total volume of the
mixture was about 10 cm3. The coloured precipitates
were obtained at room temperature. The formed com-
pounds were washed with cold EtOH and Et2O and
dried at room temperature.
2.2.1. [CuBr(HL1)(L3)]2
Reaction time: 24 h. Colour: green. Yield: 64.7%. meff,
mB: 1.72. lM, S cm2 molꢂ1: 31.5. Elemental analysis data
(Found (Required)%): C, 33.10 (34.98); H, 3.94 (4.27);
N, 18.80 (18.54).
2.2.2. CuBr2(L2)2
Reaction time: 0.5 h. Colour: black. Yield: 74.2%. meff,
mB: 2.19. lM, S cm2 molꢂ1: 55.0. Elemental analysis data
(Found (Required)%): C, 38.60 (38.26); H, 3.78 (3.21);
N, 18.22 (17.85).
2. Experimental
2.1. General procedures
2.2.3. Cu(L3)2
Reaction time: 3 h. Colour: blue. Yield: 76.5%. meff,
mB: 1.80. lM, S cm2 molꢂ1: 14.6. Elemental analysis data
(Found (Required)%): C, 42.62 (42.40); H, 5.21 (4.75);
N, 24.50 (24.73).
All pyrazole derivatives were reagent grade, commer-
cial products of Aldrich Company, except of HL4. Its
synthesis was described previously [10]. The copper(II)
salts were analytical reagent grade. The IR-spectra were
recorded in the range of 4000ꢀ
/
150 cmꢂ1 on a Perkinꢀ
/
2.2.4. CuBr2(HL4)2
Elmer System 2000 FT-IR spectrometer at room tem-
perature using KBr pellets in the mid-IR range and
polyethylene pellets in the far-IR range. The spectra
were obtained with a resolution of 4 cmꢂ1 and with a
co-addition of 16 scans. The thermal analysis was
carried out using a DuPont 2000 TA system with a
thermobalance DuPont 951 TGA. At the thermogravi-
metric measurements the samples were heated in a
platinum crucible with a heating rate of 10 K minꢂ1
up to 1000 K. With the same heating rate the DSC
curves were registered up to 600 K using an open
aluminium pan as sample holder and an empty alumi-
nium pan as reference. For the TG-MS measurements a
TA Instruments SDT 2960 was employed, coupled with
Balzers Termostar GSD 300 T capillary MS. The molar
conductivity of freshly prepared 10ꢂ3 mol dmꢂ3 solu-
Reaction time: 15 h. Colour: black. Yield: 83.3%. meff,
mB: 1.85. lM, S cm2 molꢂ1: 48.4. Elemental analysis data
(Found (Required)%): C, 28.67 (28.73); H, 3.77 (3. 62);
N, 16.90 (16.75).
2.2.5. CuBr2(HL4)2
Reaction time: 24 h. Colour: blue. Yield: 75.0%. meff,
mB: 1.83. lM, S cm2 molꢂ1: 95.1. Elemental analysis data
(Found (Required)%): C, 29.31 (28.84); H, 3.79 (4.03);
N, 23.38 (22.73).
All the compounds were characterized by FT-IR
spectrometry. Compounds [CuBr(HL1)(L3)]2 and
Cu(L3)2 were also studied by single crystal X-ray
structure analysis. The structure of the compounds is
presented in ORTEP projection [11]. For the compounds

K. Me´sza´ros Sze´cse´nyi et al. / Inorganica Chimica Acta 353 (2003) 253ꢀ
/262
255
Table 1
IR assignments
CuBr2(L2)
CuBr2(HL4)2
CuBr2(HL5)2
Assignment
3439 s
3305 s a
3146 s
3312 s
NH stretch
NH stretch
3427 s
3341 s
3262 sh
3104 s
NH2 asymmetric stretch
NH2 asymmetric stretch
NH2 symmetric stretch
NH2 symmetric stretch
aryl CH stretch
2962 m a
3050 s
2852 m a
3090 vw
3067 vw
3050 vw
2967 vw
2931 vw
aryl CH stretch
aryl CH stretch
CH3 asymmetric stretch
CH3 symmetric stretch
2924 vw
1665 vs
imine Cꢀ
/
N stretch
1648 vs
1625 vs
1610 sh
1596 sh
1587 sh
1552 s
1623 vs
CO stretch
pyr skeleton stretchꢁCN stretch
aryl skeleton stretch
/
1563 w
1536 s
1480 s
1591 m
1565 m
pyr skeleton stretch (ꢁ
aryl skeleton stretch
/
NH2 scissoring) b
NH2 scissoring) b
pyr skeleton stretch
pyr skeleton stretch (ꢁ
aryl skeleton stretch
/
1516 w
1497 m
1494 s
1468 m
CH3 asymmetric defꢁ
CH3 asymmetric def
aryl skeleton stretch
CH3 asymmetric def
/
1458 m
1441 s
1450 m
1414 w
1386 m
1372 sh
1448 w
1411 s
1384 m
1373 sh
1356 s
CH3 asymmetric defꢁ
CH3 symmetric defꢁ
CH3 symmetric defꢁ
CH3 symmetric def
NH bendꢁpyr skeleton stretch
pyr skeleton stretchꢁdef
CꢁN stretch
/
pyr skeleton stretch
/
pyr skeleton stretch
/
pyr skeleton stretch
1353 m
1315 w
1320 s
/
1310 sh
1312 m
1249 m
/
/
1296 m
1287 m
1230 m
1175 w
1131 w
1092 w
1077 w
1046 w
1019 w
962 m
aryl in-plane CH bend
aryl in-plane CH bend
aryl in-plane CH bend
aryl in-plane CH bend
pyr skeleton stretch
1147 m
1095 m
1071 w
1037 w
1025 w
960 m
1134 m
1078 w
1058 m
1030 w
CC stretchꢀ
NH2 rockꢁpyr skeleton stretch
CH3 rock
pyr skeleton stretchꢀ
CC stretchꢁCH3 rock
aryl CH wag
imine NH wag
/pyr skeleton def
/
/
NH2 rock
994 m
/
916 m
843 m
806 w
801 m
742 m
pyr skeleton defꢀCN stretch
/
777 m
754 m
734 m
697 m
aryl CH wag
769 m
Cꢁ
/
NH2 bendꢁpyr skeleton torsion
/
aryl skeleton bend
aryl CH wag
NCN bend
714 w
665 w
648 w
664 w
631 w
591 w
680 m
CC stretchꢁ
pyr skeleton torsion
CO wagꢁCH3 rock
pyr skeleton defꢀCC stretch
NH2 torsionꢁNH2 wag
aryl ring torsion
NH2 wag ꢁNH2 torsion
NH wagꢁCꢁCH3 wag
CuꢁBr stretch
pyr skeleton torsion
CꢁCH3 wagꢁCꢁNH2 wag
CuꢁN stretch
CH3 torsion
/
Cꢁ
/
CH3 bend
592 m
583 sh
562 w
/
/
582 w
516 s
/
537 w
500 m
451 s
470 s
367 w
323 m
/
/
/
423 w
369 w
408 w
343 m
313 w
285 w
210 w
/
/
/
/
251 w
212 w
245 w
/
a
Observed also in the IR spectrum of the ligand [12]; may be attributed to different pattern of intermolecular interactions in the crystal.
NH2 scissoring may contribute to these fundamentals in derivatives with an NH2 group.
b

256
K. Me´sza´ros Sze´cse´nyi et al. / Inorganica Chimica Acta 353 (2003) 253ꢀ262
/
with no X-ray data the IR assignments [12ꢀ14] are given
in Table 1.
/
Table 2
Crystal data and structure refinement for [CuBr(HL1)(L3)]2 and
Cu(L3)2
[CuBr(HL1)(L3)]2
Cu(L3)2
2.3. Crystal structure determination
Crystal data for [CuBr(HL1)(L3)]2 and Cu(L3)2 were
collected at room temperature on Enraf-Nonius CAD-4
Empirical formu- C22H32Br2Cu2N10O2
la
C12H16CuN6O2
Formula mass
Temperature (K) 293(2)
755.5
339.85
293(2)
diffractometers [15] in different laboratories (Paris,
˚
0.71073 A)
˚
Wavelength (A)
0.710730
triclinic
0.710730
triclinic
Budapest), using Mo Ka radiation (lꢃ
/
Crystal system
Space group
Unit cell dimen-
sions
and v/2u scans. Data correction [16] and absorption
correction was applied: psi-scan type [17] for Cu(L3)2
and Gaussian-type [18], based on the crystal morphol-
¯
¯
P1
P/
1
/
ꢃ
0.735) for [CuBr(HL1)(L3)]2.
/
˚
ogy (Tmin
ꢃ/0.335, Tmax
a (A)
9.277(4)
9.287(5)
10.734(5)
91.11(4)
106.53(4)
122.25(4)
732.9(6)
1
8.461(1)
8.631(1)
10.745(2)
68.72(1)
70.29(1)
77.64(1)
684.57(17)
2
˚
b (A)
The structures were solved by heavy atom [19] and
difference Fourier methods and refined on F2 by full-
matrix least-squares method [20]. The weighting
˚
c (A)
a (8)
b (8)
g (8)
schemes were wꢃ
[s2(Fo2)ꢁ(0.1000P)2]
Cu(L3)2, respectively; Pꢃ
/
1/[s2(Fo2)ꢁ
for
[CuBr(HL1)(L3)]2
(Fo2ꢁ2Fc2)/3. In both crystal
/
(0.1731P)2] and wꢃ
/1/
3
˚
/
and
Volume (A )
Z
/
/
Density (calcu-
1.712
1.649
structures non-hydrogen atoms were refined with aniso-
tropic displacement parameters. In refinement of
Cu(L3)2 some least-squares restraints (ISOR, DELU
lated) (Mg mꢂ3
Absorption coef- 4.215
)
1.610
ficient (mmꢂ1
F(0 0 0)
)
for all non-hydrogen atoms, DFIX and SADI for Nꢁ
/
H
378
350
Crystal size (mm) 0.25ꢄ/0.21ꢄ/0.08
0.50ꢄ/0.25ꢄ/0.20
distances) were used. H atoms (except H7 and H17 in
Cu(L3)2, they were located in difference map) were
placed in calculated positions and refined with isotropic
u range for data 2.025
/
u 527.99
/
2.555
/
u 538.47
/
collection (8)
Index ranges
ꢂ
/
125
/
h 5
/
11; ꢂ
/
125
/
ꢂ
/
145
/
h 5
/
13; ꢂ
/
155
/
/
displacement
parameters.
In
the
case
of
k 512; 05
/
/
l 514
/
k 514; ꢂ
/
/
185/l 58
[CuBr(HL1)(L3)]2 all H atoms were placed in calculated
positions (for the purpose of decreasing the number of
refined parameters) and they are in good agreement with
positions located in difference maps. Details and final R
values are given in Table 2, together with other
experimental data relevant to the X-ray analyses.
Reflections col-
lected
3723
8193
Independent re-
flections
3533 [Rint
ꢃ/0.0235]
7666 [Rint
ꢃ/0.0137]
Refinement
method
Full-matrix least-squares Full-matrix least-
squares on F2
7666/193/196
on F2
3533/0/172
Data/restraints/
parameters
Goodness-of-fit
on F2
Note: unit cell dimensions for [CuBr(HL1)(L3)]2 can be
˚
1.031
0.907
transformed to the next values: aꢃ
/
8.965 A, bꢃ
/
9.277
˚
˚
A, cꢃ
/
10.734 A, aꢃ
/
73.478, bꢃ
/
71.678, gꢃ
/
61.188.
Final R indices
R1ꢃ
/
0.0869, wR2ꢃ
/
R1ꢃ
/
0.0449, wR2ꢃ
/
[I ꢀ2s(I)]
/
0.2247
0.1315
3. Results and discussion
where (L) denotes (L2) and (HL4). The same is valid for
the [CuBr(HL1)(L3)]2 complex with mixed ligands.
Nonetheless, for these compounds the co-ordination of
the anion may be regarded as non-ionic, even in
solution.
The complexes are coloured and stable in air. They
are soluble in DMF and MeOH, slightly soluble in
EtOH, but insoluble in H2O and Et2O. The molar
conductivity for all of the compounds was measured in
DMF. A low molar conductivity is characteristic for the
Cu(L3)2 referring to its non-electrolytic character, while
in the case of the CuBr2(HL5)2 the value of the molar
conductivity corresponds to an electrolyte of 1:1 type
[21]. The molar conductivity of the other complexes
suggests only a partial replacement of the bromide ion
by the solvent molecule:
3.1. Description of the structures
3.1.1. [CuBr(HL1)(L3)]2
The compound has a dimeric centrosymmetric struc-
˚
ture (Fig. 1) with a Cu
ordination around the Cu atom is a square pyramid,
formed by co-ordination of the N1 atom of the
/
Á Á Á
/
Cu? distance of 3.72 A. The co-
CuBr2(L)2 ꢁDMFXCuBr(L)2DMFꢁ ꢁBrꢂ

K. Me´sza´ros Sze´cse´nyi et al. / Inorganica Chimica Acta 353 (2003) 253ꢀ
/262
257
octahedral surrounding around the copper atom. The
bridging Br? and H( Cu) atoms are displaced from the
Á Á Á
N1ꢁN3ꢁN5ꢁBr equatorial plane for 2.98 and 2.24 A,
respectively, and to the opposite direction forming a
Br?ꢁCuꢁH angle of 1538.
The angle between the mean planes of the two
pyrazole rings is 788. There is a short HL1 L3
Á Á Á
interligand contact of 3.26 A between the C10 methyl
group and the N1 atom, enabling a short Cꢁ Á Á Á
interaction between a hydrogen atom of C10 and the
N1ꢁN2 bond centroid (Cg) with a HÁ Á ÁCg distance of
about 2.6 A.
In the crystal lattice, the binuclear molecules are
mutually connected by intermolecular N2ꢁ Á Á ÁO, N5ꢁ
Á Á ÁO and C4ꢁ Á Á ÁO hydrogen bonds forming 3D
supramolecular structure. The geometrical parameters
/
/
˚
/
/
/
/
/
/
/
˚
/
H
/
/
p
/
/
/
˚
/
H/
/
/
Fig. 1. ORTEP drawing of complex [CuBr(HL1)(L3)]2 with atom
numbering scheme.
H/
/
/
H
/
/
˚
of the H-bonds are: N2ꢁ
/
H2Nꢃ
/
0.86A, N2
2.43 A, N2ꢁH2NÁ Á ÁO(i)ꢃ
O(ii)ꢃ3.01 A, H5N
Á Á ÁO(ii)ꢃ1728; C4ꢁH4Aꢃ
3.24 A, H4A O(i)ꢃ
Á Á Á
1518; symmetry code: (i) xꢂ
1,ꢂyꢁ1,ꢂz. The packing diagram for the
/
Á Á Á
/
O(i)ꢃ
1728;
Á Á Á
/
monodentate HL1 and N3 and N5 of the bidentate L3 as
˚
˚
3.16A, H2N
N5ꢁH5Nꢃ0.86 A, N5
O(ii)ꢃ
/
Á Á Á
/
O(i)ꢃ
/
/
/
/
/
well as the bridging bromine atoms*
ial plane and Br? in the apical position. As the ligand L3
is approximately planar with C9ꢁ Á Á ÁO, an intramole-
cular hydrogen-bond formation takes place, yielding a
six-membered C9ꢁ Á Á ÁOꢁC11ꢁN4ꢁC6 ring. The cop-
per atoms are displaced from the equatorial N1ꢁN3ꢁ
N5ꢁBr co-ordination plane to the apical Br? atom for an
/Br in the equator-
˚
˚
/
/
/
Á Á Á
/
/
/
/
˚
/
2.16 A, N5ꢁ
/
H5N
/
/
/
/
/
/
H
/
/
˚
˚
˚
0.96 A, C4
H4A O(i) ꢃ
Á Á Á
z; (ii) ꢂxꢁ
/
Á Á Á
/
O(i)ꢃ
/
/
/
/
2.36 A, C4ꢁ
1,ꢁyꢂ1,ꢁ
/
/
/
/
/
/
/
/
/
H/
/
/
/
/
/
/
/
/
/
/
/
compound is presented in Fig. 3, while the interatomic
bond lengths and selected bond angles in the complex
are given in Table 3.
/
˚
expectable value of 0.24 A. However, the arrangement
of the atoms in the equatorial plane is quite irregular.
Namely, the N3, N5 and Br atoms together with the two
Cu atoms are almost ideally coplanar (root-mean-square
3.1.2. Cu(L3)2
The a-modification of this compound was synthesized
by Valach et al. [22] by the reaction of freshly obtained
[Cu(NCO)2(2,4-Me2py)] with 3,5-dimethylpyrazole li-
gand in a methanolic solution at 278 K. The crystal
structure of this modification was determined by X-ray
structure analysis. By similar method, at higher tem-
perature the former authors obtained the b-modification
of the same compound also, in form of blue flakes.
In our case, the compound was prepared by the
reaction of copper(II) acetate with 1-carboxamide-3,5-
˚
deviation of N3, N5, Br, Cu atoms is 0.006 A) what is an
unusual position for a square-pyramidal co-ordination.
This geometry may be explained by the interaction
between the metal atom and the C5 methyl group’s
hydrogen that is supported by the short Cu
/
Á Á Á
C5 angle is much smaller
C5 one. It means that the C5 methyl
group is shifted towards Cu. Although the rotation of
HL1 around the Cuꢁ
N1 bond is possible, it is oriented
in such a way as to enable the Cu H contact in the
Á Á Á
CuꢁN1ꢁC3ꢁC5 plane with a torsion angle of nearly 08.
As a consequence, N1 is displaced from the N3ꢁN5ꢁ
/
H distance
˚
(2.67 A). Besides, the N1ꢁ
/
C3ꢁ
/
than the C2ꢁC3ꢁ
/
/
/
/
/
/
/
/
/
/
1
˚
Cu plane for 0.82 A (Fig. 2), because the whole HL
Brꢁ
is shifted out of the equatorial plane to obtain the best
position for the Cu H interaction, resulting a pseudo-
Á Á Á
/
/
/
Fig. 2. The equatorial plane of complex [CuBr(HL1)(L3)]2 with
displaced position of N1 atom to the BrꢁCuꢁN3ꢁN5 plane.
Fig. 3. Projection of the crystal packing along crystallographic ‘c’ axis
for [CuBr(HL1)(L3)]2 (the dashed lines show the hydrogen bonds).
/
/
/

258
K. Me´sza´ros Sze´cse´nyi et al. / Inorganica Chimica Acta 353 (2003) 253ꢀ262
/
Table 3
˚
Interatomic bond lengths (A) and selected bond angles (8) for
[CuBr(HL1)(L3)]2
Bond lengths
Cuꢁ
Cuꢁ
Cuꢁ
Cuꢁ
Cuꢁ
N1ꢁ
N1ꢁ
N2ꢁ
C1ꢁ
C1ꢁ
C2ꢁ
/
N5
N1
N3
Br
1.909(8)
1.988(8)
2.019(8)
C3ꢁ
N3ꢁ
N3ꢁ
N4ꢁ
N4ꢁ
N5ꢁ
C6ꢁ
C6ꢁ
C7ꢁ
C8ꢁ
Oꢁ
/
C5
1.501(15)
1.328(12)
1.341(11)
1.344(13)
1.455(13)
1.290(13)
1.343(17)
1.504(17)
1.437(16)
1.468(15)
1.246(12)
/
/
C8
N4
C6
/
/
/
2.4786(19)
2.770(2)
/
/Br?
/
C11
C11
C7
/
C3
N2
C1
C2
C4
C3
1.342(12)
1.357(10)
1.318(12)
1.370(14)
1.503(15)
1.392(15)
/
/
/
/
/
C9
/
/
C8
/
/
C10
/
/
C11
Bond angles
Fig. 4. ORTEP drawing of complex Cu(L3)2 with atom numbering
scheme.
N5ꢁ
N5ꢁ
N1ꢁ
N5ꢁ
N1ꢁ
N3ꢁ
/
Cuꢁ
Cuꢁ
Cuꢁ
Cuꢁ
Cuꢁ
Cuꢁ
/
N1
N3
N3
Br
154.3(4)
79.9(4)
93.9(3)
91.7(3)
93.4(2)
171.5(2)
N5ꢁ
N1ꢁ
N3ꢁ
BrꢁCuꢁ
CuꢁBrꢁ
/
Cuꢁ
Cuꢁ
Cuꢁ
/
Br?
Br?
Br?
110.5(3)
94.6(2)
93.6(3)
/
/
/
/
/
/
/
/
˚
˚
/
/
/
/
Br?
90.08(7)
89.92(7)
O8(iii)ꢃ
O8(iii)ꢃ
The magnetic moment of the Cu(L3)2 and
[CuBr(HL1)(L3)]2 complexes (meff
1.80 and 1.72 mB,
1/2 systems.
/
3.206(2) A, H7
/
Á Á Á
/
O8(iii)ꢃ
/
2.43 A, N7ꢁ
/
H7
/
Á Á Á
/
/
/Br
/
/Cu?
/
176.78; symmetry code (iii) ꢂ
/
x, ꢂyꢁ1, ꢂ
/
/
/z.
/
/Br
ꢃ
/
respectively) is characteristic for the Sꢃ
/
The lower meff value for [CuBr(HL1)(L3)]2 is in agree-
ment with its bridged structure.
dimethylpyrazole. By the deprotonation of the ligand
the blue b-modification of Cu(L3)2 was obtained in a
single crystalline form, suitable for an X-ray structure
analysis. The deprotonation of the NH2-group (leading
to L3 in the complex) is well reflected also by the IR
spectrum of the complex, where the respective NH
stretching band has vanished. Additional information
provided by IR spectrometry is the unchanged position
In complexes with L2 and HL4, Cu(L2)2Br2 and
Cu(HL4)2Br2, the pyrazole derivative acts as monoden-
tate ligand through the pyridine ring nitrogen atom. In
principle, most of the copper(II) complexes should have
a tetrahedral geometry with a magnetic susceptibility of
about 2.2 [24]. On this basis (meff
ꢃ2.19) for the
/
Cu(L2)2Br2 complex a tetrahedral geometry may be
assumed, also. For the bis(ligand) complexes of CuCl2
with HL4 a distorted tetrahedral geometry was found by
X-ray analysis [10]. As the space requirement of the
bromine atoms is larger, for the bromide complex,
Cu(HL4)2Br2, with the same ligand, a tetrahedral
geometry may be proposed.
of the n(Cꢀ
/
O) vibrational band upon complex forma-
tion indicating that the oxygen atom is not involved in a
coordinative bonding with Cu. The IR-spectral data are
in accordance with the X-ray analysis. Namely, the
oxygen atoms are not involved in co-ordination with the
central atom because the Cuꢁ
/
O distances for the
˚
adjacent molecules are greater than 3.3 A [23]. The co-
ordination is established through the nitrogen atom of
the deprotonated carboxamide group and the pyridine
nitrogen atom from two ligand molecules.
Both crystalline modifications have a distorted trans
square-planar arrangement around the central atom.
The ORTEP drawing for the b-modification is presented
in Fig. 4. The main difference between the two
structures is that the a-modification belongs to mono-
Copper(II) bromide with HL5 also forms a bis(ligand)
complex. Its structure seems to have similar geometry as
the analogous copper(II) nitrate complex whose struc-
ture was determined by X-ray analysis [25]. In this
compound the copper(II) is co-ordinated endobidentate
to the pyridine-type and the ꢀ/NH nitrogen atoms of the
ring and the carboxamidine group, respectively. The
nitrate groups are bonded as monodentate species in the
axial positions providing thus an octahedral environ-
ment around the metal atom. As the complexing ability
of the nitrate is low, it is not co-ordinated in solution.
Bromides form more readily complexes than nitrates.
However, the molar conductivity of the corresponding
bromide complex is also high and corresponds to an 1:1
electrolyte. Based on this, for the CuBr2(HL5)2 a similar
octahedral geometry could be proposed.
clinic P21/c space group with Zꢃ
modification to triclinic P
/
4, while the b-
¯
/
1 space group with Zꢃ2.
/
The interatomic distances and bond angles are given in
Table 4 for both a- and b-modifications. The differences
are not significant.
In the crystal lattice of the b-modification molecules
form N7ꢁ
/
H7
/
Á Á Á
/
O8(iii) dimers (Fig. 5), with the follow-
˚
0.78 A, N7
ing geometrical parameters: N7ꢁ
/
H7ꢃ
/
/
Á Á Á
/

K. Me´sza´ros Sze´cse´nyi et al. / Inorganica Chimica Acta 353 (2003) 253ꢀ
/262
259
Table 4
Interatomic bond lengths (A) and selected bond angles (8) for b-Cu(L )2 compared to those found in a-modification [22]
3
˚
Bond lengths
b
a
Bond lengths
b
a
Cu1ꢁ
Cu1ꢁ
/
N2
1.999(1)
1.924(1)
1.372(2)
1.356(2)
1.328(2)
1.405(3)
1.376(2)
1.494(2)
1.488(2)
1.450(2)
1.315(2)
1.228(2)
1.985(8)
1.926(8)
Cu1ꢁ
Cu1ꢁ
N11ꢁ
N11ꢁ
N12ꢁ
C13ꢁ
C14ꢁ
C13ꢁ
C15ꢁ
N11ꢁ
C16ꢁ
C16ꢁ
/
N12
N17
1.996(1)
1.924(2)
1.367(2)
1.357(2)
1.335(2)
1.409(2)
1.379(2)
1.494(2)
1.484(2)
1.450(2)
1.311(2)
1.229(2)
1.990(8)
/N7
/
1.908(10)
1.363(11)
1.368(13)
1.316(12)
1.367(15)
1.358(13)
1.493(14)
1.481(16)
1.432(12)
1.306(16)
1.218(14)
N1ꢁ
N1ꢁ
N2ꢁ
C3ꢁ
C4ꢁ
C3ꢁ
C5ꢁ
N1ꢁ
C6ꢁ
C6ꢁ
/
N2
C5
C3
1.363(11)
1.345(13)
1.352(11)
1.370(16)
1.388(14)
1.461(14)
1.487(15)
1.465(11)
1.313(14)
1.220(13)
/
N12
C15
C13
C14
C15
C19
C20
/
/
/
/
/
C4
/
/
C5
/
/
C9
/
/
C10
/
/
C6
N7
O8
/
C16
/
/N17
/
/O18
N2ꢁ
N2ꢁ
N2ꢁ
N1ꢁ
C3ꢁN2ꢁ
C5ꢁN1ꢁ
N2ꢁN1ꢁ
C3ꢁN2ꢁ
N7ꢁC6ꢁ
O8ꢁC6ꢁ
C6ꢁN7ꢁ
N2ꢁC3ꢁ
N2ꢁC3ꢁ
N1ꢁC5ꢁ
N1ꢁC5ꢁ
C3ꢁC4ꢁ
/
Cu1ꢁ
Cu1ꢁ
Cu1ꢁ
N2ꢁ
/
N7
81.98(6)
100.66(6)
157.21(6)
109.78(9)
141.9(1)
111.1(1)
117.6(1)
106.2(1)
111.4(1)
117.6(2)
118.3(1)
109.7(1)
123.5(2)
106.3(2)
124.9(2)
106.7(2)
81.5(3)
99.8(3)
N12ꢁ
N12ꢁ
N7ꢁCu1ꢁ
N11ꢁN12ꢁ
C13ꢁN12ꢁCu1
C15ꢁN11ꢁN12
N12ꢁN11ꢁ
C13ꢁN12ꢁ
N17ꢁC16ꢁ
O18ꢁC16ꢁ
C16ꢁN17ꢁ
N12ꢁC13ꢁ
N12ꢁC13ꢁ
N11ꢁC15ꢁ
N11ꢁC15ꢁ
C13ꢁC14ꢁ
/
Cu1ꢁ
/
N17
81.16(6)
102.46(6)
164.32(8)
110.6(1)
142.4(1)
111.4(1)
117.5(1)
106.4(1)
110.8(1)
117.9(2)
119.4(1)
109.4(1)
122.2(2)
106.1(1)
124.6(2)
106.8(2)
81.0(3)
99.0(3)
/
/N17
/
Cu1ꢁ
/N17
/
/N12
173.5(3)
111.0(5)
143.1(6)
112.4(7)
117.6(7)
105.8(7)
110.0(8)
117.6(8)
119.2(6)
108.6(8)
121.6(8)
104.3(8)
121.1(8)
108.9(9)
/
/
N17
Cu1
168.9(3)
110.4(5)
143.4(7)
110.2(7)
118.0(7)
106.2(7)
110.5(9)
117.9(9)
119.8(7)
110.3(8)
122.0(8)
105.6(8)
124.0(9)
107.7(9)
/
/
Cu1
/
/
/
/
Cu1
/
/
/
/
N2
/
/
/
/
C6
N1
N1
/
/
C16
N11
N11
/
/
/
/
/
/
/
/
/
/N1
/
/N11
/
/
Cu1
C4
/
/
Cu1
C14
C19
C14
C20
/
/
/
/
/
/
C9
/
/
/
/
C4
/
/
/
/
C10
/
/
/
/C5
/
/C15
the acetate ion in methanol is high enough for the
deprotonation of the ligand, replacing thus the volumi-
nous acetate ion and yielding the Cu(L3)2 complex. On
the other hand, the complex formation with copper(II)
chloride leads to a complete decarboxamidation of the
ligand [26]. As the Brønsted basicity of both the chloride
and bromide ions is too low for the deprotonation of the
carboxamide group, the explanation of the complex
formation with copper(II) bromide and chloride may be
based on Pearson’s theory [27ꢀ29], taking also into
/
account the structural rearrangements and steric factors.
In the presence of the hard chloride base a complete
decarboxamidation of 1-carboxamide-3,5-dimethylpyr-
azole takes place, transforming the ligand to 3,5-
dimethylpyrazole, which allows an intermediate hardꢀ
/
Fig. 5. Projections of the crystal packing along crystallographic ‘a’
axis for Cu(L3)2.
hard interaction between the copper(II) and the newly
formed ligand. On the other hand, between the relatively
small chloride ions and the ligand’s methyl substituents
the steric repulsion is weak. At the same time the
elimination of isocyanic acid is probably promoted by
ethanol, forming ethylcarbamate. With copper(II) bro-
mide, decarboxamidation of the ligand occurs, too.
However, only one ligand is transformed to 3,5-
dimethylpyrazole, while the carboxamide group of the
other ligand molecule is deprotonated, replacing thus
one voluminous bromide ion. Two such molecules are
3.2. Complex formation reactions
The influence of the anion on the complex formation
was investigated using different copper(II) salts in
conjunction with 1-carboxamide-3,5-dimethylpyrazole
(HL3) ligand. We have found that in the reaction of
HL3 with CuBr2 a partial decarboxamidation of the
ligand takes place, while with Cu(OAc)2 no degradation
was observed. In the latter case the Brønsted basicity of

260
K. Me´sza´ros Sze´cse´nyi et al. / Inorganica Chimica Acta 353 (2003) 253ꢀ262
/
coupled through bromide bridges forming the dimeric
[CuBr(HL1)(L3)]2 complex with mixed ligands.
3.3. Thermal decomposition of the compounds
The thermal decomposition of all the compounds was
followed in an air and argon atmosphere with sample
masses of about 5 mg. The thermal decomposition data
in air are given in Table 5. As an example, the TG- and
DTG-curves of the decomposition of [CuBr(HL1)(L3)]2
and CuBr2(HL5)2 in air and argon are presented in Fig.
6.
All the samples begin to decompose in the tempera-
ture range of 400ꢀ470 K. The lowest thermal stability
/
exhibits the compound with the mixed 3,5-dimethylpyr-
azole and 1-carboxamide-3,5-dimethylpyrazole ligands,
[CuBr(HL1)(L3)]2, which in the context of the mixed
softꢀhard interaction can be understandable. The most
/
stable complex is that with 5-amino-4-carboxamide-1-
phenylpyrazole, CuBr2(L2)2, presumably because of the
n 0p transition between the unshared electrons of the
/
pyrazole nitrogen and phenyl nucleus.
The decomposition of Cu(L3)2 in air results in an
unstable intermediate around 470 K. In the mass
spectrum recorded at the beginning of the decomposi-
tion, the molecular peak of 3,5-dimethylpyrazole, ac-
companied by the peaks of its fragments, was observed.
This was followed by the peak of H2 evolution. The
intermediate was isolated and investigated by IR
spectrometry. The characteristic changes in the IR
spectrum include the disappearance of the n(NH)
vibrational band at 3302 cmꢂ1 and the rise of new
bands at 2241 and 2170 cmꢂ1. These latter bands can be
assigned to coupled stretching vibrations of two isocy-
anate groups within a molecule. Another characteristic
Fig. 6. TG-DTG curves for the CuBr2(HL5)2 and [CuBr(HL1)L3]2 in
air and in argon.
stretching vibrations. The spectrum contains addition-
ally the bands of the methylpyrazole ligand, too. This is
the consequence of the low stability of the intermediate,
viz., the decomposition of the starting compound was
new band appears at 3122 cmꢂ1 assigned to ꢀ
/CH2
Table 5
Thermal decomposition data in air
Compound
Temperature Range in K
Mass loss in %
Temperature in K
Residue (%)
Found
Found Calc.
(departing group)
Calc.
[CuBr(HL1)(L3)]2
CuBr2(L2)2
400ꢀ
470ꢀ
425ꢀ
430ꢀ
530ꢀ
465 ꢀ
/
467
680
485
530
725
12.6
(-3,5-DMP)
26.7
12.72
830
CuOꢁ
920
29.3
(1:1)
27.5
29.52
/CuBr
/
24.57
28.88
8.57
(-2Ph)
30.0
?
Cu(L3)2
/
690
CuO
930
21.8
23.40
22.22
(ꢁ
8.0
(ꢁCH3CO)
/C5H10N2)
CuBr2(HL4)2
/
19.6
(1:1)
/
CuOꢁ
/
CuBr
/
14.5
15.97
38.48
(-5-MP-H)
41.8
-2(3,5-DMP)
CuBr2(HL5)2
/610
800
27.0
28.71
CuBr
3,5-DMPꢃ
/
3,5-dimethylpyrazole; Phꢃ
/
phenyl group; 5-MPꢀ
/
Hꢃ5-methylpyrazole-H. The presence of the bromide in the end product was
/
determined by a qualitative analysis.

K. Me´sza´ros Sze´cse´nyi et al. / Inorganica Chimica Acta 353 (2003) 253ꢀ
/262
261
not finished yet when the next decomposition step
started. The elemental analysis (Found (%) C, 36.55;
H, 3.7; N, 20.04, Required (%): C, 34.78; H. 2,50; N.
23,18) and mass loss data up to 500 K (Found (%) 30.0;
Required (%): 28.88) as well as the IR results indicate an
elimination process presented in Scheme 1. We note that
an analogous isothiocyanate intermediate has been
suggested for the formation mechanism of
[CuCl2(HL1)]2 and CuCl2(HL1)2 complexes from 1-
carboxamide-3,5-dimethylpyrazole [26].
and [CuBr(HL1)(L3)]2, respectively. Copies of this
information may be obtained free of charge from The
Director, CCDC, 12 Union Road, Cambridge, CB2
1EZ, UK (fax: ꢁ44-1223-336-033; e-mail: depos-
/
it@ccdc.cam.ac.uk or www: http://www.ccdc.cam.a-
c.uk).
Acknowledgements
The thermal decomposition of the pyrazole complexes
The authors (K. Me´sza´ros Sze´cse´nyi) would like to
thank the Domus Hungarica Scientiarum Artiumque
Foundation for their support and the Hungarian Na-
tional Scientific Research Foundation (OTKA, T-
038189, A. Kova´cs). The work was financed in part by
the Ministry for Science and Technology of the Republic
of Serbia.
is usually independent of purge gas up to 500ꢀ600 K.
/
Above this temperature the degradation in argon slows
down and in most cases is not finished up to 1100 K, as
is the case with CuBr2(L2)2, Cu(L3)2 and CuBr2(HL4)2
complexes. However, an interesting phenomenon was
observed at the decomposition of the [CuBr(HL1)(L3)]2
and CuBr2(HL5)2 complexes: in argon above 900 K no
residue was obtained. Unfortunately, at the end of the
decomposition, by mass spectrometry we could not
detect the evolved fragments, due to too high decom-
position temperature. The different thermal decomposi-
tion pattern of the compounds in air and argon
atmospheres may be explained by the increased basicity
and acidity of the remaining components with increasing
temperature [30]. Thus, in the CuBr2(HL5)2 and
[CuBr(HL1)(L3)]2 complexes the covalency of the bonds
is strengthened to the extent which allows a complete
evaporation of the remaining parts of the molecule in
argon.
References
[1] S.R. Lukic´, V.M. Leovac, A.F. Petrovic´, S.J. Skuban, V.I.
ˇ
.Cesˇljevic´, M.M Garic´, Synth. React. Inorg. Met.ꢀ
/
Org. Chem.
32 (2002) 873.
[2] (a) W.G. Haanstra, Ph.D. Thesis, Leiden University, Leiden, The
Netherlands, 1991;
(b) W.G. Haanstra, W.A.J.W. van der Donk, W.L. Driessen, J.
Reedijk, J.S. Wood, M.G.B. Drew, J. Chem. Soc., Dalton (1990)
3123.
[3] S. Trofimenko, in: S.J. Lippard (Ed.), Progress in Inorganic
Chemistry, vol. 34, Wiley, New York, 1986, p. 115.
[4] N.T. Sorrel, Tetrahedron 45 (1989) 3.
The decomposition of the compounds starts with an
endothermic reaction which is usually accompanied by
the melting of the sample. The next step is an exothermic
process except for CuBr2(HL5)2 and [CuBr(HL1)(L3)]2
complexes which is in agreement with the different
thermal behavior of these compounds in argon.
[5] S. Trofimenko, Chem. Rev. 93 (1993) 943.
[6] R. Mukherjee, Coord. Chem. Rev. 203 (2000) 151.
[7] K. Me´sza´ros Sze´cse´nyi, E.Z. Ivegesˇ, V.M. Leovac, L.S. Vojinovic,
ˇ
A. Kova´cs, G. Pokol, J. Madara´sz, Z.K. Jacimovic, Thermochim.
Acta 316 (1998) 79.
[8] K. Me´sza´ros Sze´cse´nyi, E.Z. Ivegesˇ, V.M. Leovac, A. Kova´cs, G.
ˇ
Pokol, Z.K Jac´imovic´, J. Therm. Anal. Cal. 56 (1999) 493.
[9] K. Me´sza´ros Sze´cse´nyi, V.M. Leovac, Z.K. Jacimovic, V.I.
ˇ
.Cesˇljevic, A. Kova´cs, G. Pokol, J. Therm. Anal. Cal. 63 (2001)
723.
4. Supplementary material
[10] A. Hergold-Brundic´, B. Kaitner, B. Kamenar, V.M. Leovac, E.Z.
Ivegesˇ, N. Juranic´, Inorg. Chim. Acta 188 (1991) 151.
[11] M.N. Burnett, C.K. Johnson, ORTEPIII, Report ORNL-6895. Oak
Ridge National Laboratory, Oak Ridge, TN, 1996.
A full list of crystal data and refinement have been
deposited at the Cambridge Crystallographic Data
Centre, CCDC Nos. 179602 and 179603 for Cu(L3)2
ˇ
[12] A. Szabo´, V.I. .Cesˇljevic´, A. Kova´cs, Chem. Phys. 270 (2001) 67.
Scheme 1.

262
K. Me´sza´ros Sze´cse´nyi et al. / Inorganica Chimica Acta 353 (2003) 253ꢀ262
/
[13] G. Socrates, Infrared Characteristic Group Frequencies. Tables
and Charts, 2nd ed., Wiley, New York, 1994.
[21] W.J. Geary, Coord. Chem. Rev. 7 (1971) 81.
[22] F. Valach, J. Kohout, M. Dunaj-Jurco, M. Hvastijova´, J. Gazo, J.
Chem. Soc., Dalton (1979) 1867.
[14] K. Nakamoto, Infrared and Raman Spectra of Inorganic and Co-
ordination Compounds, in: Applications in Co-ordination, Orga-
nometallic and Bioinorganic Chemistry, Part B, 5th ed., Wiley,
New York, 1997.
[23] J. Gazo, I.B. Bersuker, J. Garaj, M. Kabesova´, J. Kohout, H.
Langfelderova´, M. Melnik, M. Sera´tor, F. Valach, Coord. Chem.
Rev. 19 (1976) 253.
[15] Enraf-Nonius. CAD-4 Software. Version 5. Enraf-Nonius, Delft,
The Netherlands, 1989.
[24] A.B. Neinding, Magnetochemistry of Transition Metal Com-
plexes, Results in Sciences (Series Chemistry), Moscow (1970) 205
(in Russian).
[16] C.K. Fair, MolEN, An Interactive Intelligent System for Crystal
Structure Analysis, Enraf-Nonius, Delft, The Netherlands, 1990.
[17] A.C. North, D.C. Philips, F. Mathews, Acta Crystallogr., A 24
(1968) 350.
[25] Z.K. Jacimovic, Ph.D. Thesis, University of Novi Sad, Faculty of
Sciences and Mathematics, Yugoslavia (1998) 76.
[26] K. Me´sza´rossze´cse´nyi, Z.K. Jacimovic, V.M. Leovac, V.I.
[18] (a) A.L. Spek, Acta Crystallogr., A 46 (1990) C34;
(b) A.L. Spek, PLATON, A Multipurpose Crystallographic Tool,
Utrecht University, Utrecht, The Netherlands,, 1998.
[19] G.M. Sheldrick, SHELXS86, Program for the Solution of Crystal
ˇ
.Cesˇljevic, A. Kova´cs, G. Pokol, J. Therm. Anal. Cal. 66 (2001)
573.
[27] R.G. Pearson, J. Am. Chem. Soc. 85 (1963) 3533.
[28] R.G. Pearson, Science 151 (1966) 172.
[29] R.G. Pearson, J. Songstad, J. Am. Chem. Soc. 89 (1967) 1827.
[30] (a) L. Erdey, Period Politech Chem. 1 (1957) 91;
(b) L. Erdey, S. Gal, Talanta 10 (1963) 23.
Structures, University of Gottingen, Gottingen, Germany, 1985.
¨ ¨
[20] G.M. Sheldrick, SHELXL97, Program for the Refinement of
Crystal Structures, University of Gottingen, Gottingen, Germany,
1997.
¨
¨