Syntheses and spectrothermal studies of triethanolamine complexes of Co(II), Ni(II), Cu(II) and Cd(II) squarates

Article abstract of DOI:10.1007/s10973-005-7477-y

The triethanolamine complexes, [M(tea)₂]sq?nH₂O, (n=2 for Co(II), n=0 for Ni(II), Cu(II) and n=1 for Cd(II), tea=triethanolamine, sq^2-=squarate), have been synthesized and characterized by elemental analyses, magnetic susceptibility and conductivity measurements, UV-Vis and IR spectra, and thermal analyses techniques (TG, DTG and DTA). The Co(II), Ni(II) and Cu(II) complexes possess octahedral geometry, while the Cd(II) complex is monocapped trigonal prismatic geometry. Dianionic squarate behaves as a counter ion in the complexes. The thermal decomposition of these complexes takes place in three stages: (i) dehydration, (ii) release of the tea ligands and (iii) burning of organic residue. On the basis of the first DTG_max of the decomposition, the thermal stability of the anhydrous complexes follows the order: Ni(II), 289°C>Co(II), 230°C>Cu(II), 226°C>Cu(II), 170°C in static air atmosphere. The final decomposition products - the respective metal oxides - were identified by FTIR spectroscopy.

Full text of DOI:10.1007/s10973-005-7477-y

Journal of Thermal Analysis and Calorimetry, Vol. 89 (2007) 1, 261–265
SYNTHESES AND SPECTROTHERMAL STUDIES OF TRIETHANOLAMINE
COMPLEXES OF Co(II), Ni(II), Cu(II) AND Cd(II) SQUARATES
O. Z. Yeêilel1* and H. Ölmez2
1Department of Chemistry, Faculty of Arts and Sciences Eskiêehir Osmangazi University, 26480 Eskiêehir, Turkey
2Department of Chemistry, Faculty of Arts and Sciences Ondokuz MayÏs University, 55139 Kurupelit-Samsun, Turkey
The triethanolamine complexes, [M(tea)2]sq×nH2O, (n=2 for Co(II), n=0 for Ni(II), Cu(II) and n=1 for Cd(II), tea=triethanolamine,
sq2–=squarate), have been synthesized and characterized by elemental analyses, magnetic susceptibility and conductivity measure-
ments, UV-Vis and IR spectra, and thermal analyses techniques (TG, DTG and DTA). The Co(II), Ni(II) and Cu(II) complexes pos-
sess octahedral geometry, while the Cd(II) complex is monocapped trigonal prismatic geometry. Dianionic squarate behaves as a
counter ion in the complexes. The thermal decomposition of these complexes takes place in three stages: (i) dehydration, (ii) release
of the tea ligands and (iii) burning of organic residue. On the basis of the first DTGmax of the decomposition, the thermal stability of
the anhydrous complexes follows the order: Ni(II), 289ºC>Co(II), 230ºC>Cd(II), 226ºC>Cu(II), 170ºC in static air atmosphere. The
final decomposition products – the respective metal oxides – were identified by FTIR spectroscopy.
Keywords: squaric acid, thermal decomposition, triethanolamine complexes
Introduction
The triethanolamine ligand, (tris(2-hydoxy-
ethyl)amine, N(CH2CH2OH)3, Fig. 1b) has a number
of potential donor sites which are high in electro-
negativity, and a diversity of coordination modes. Al-
though, tea usually acts as a N,O,O’-tridentate ligand
Squaric acid, (3,4-dihydroxycyclobut-3-ene-1,2-di-
one, H2C4O4, H2sq, Fig. 1a), synthesized for the first
time by Cohen et al. in 1959 [1], has been of much in-
terest because of its cyclic structure and possible aro-
maticity. The behavior of the squarate dianion has
been thoroughly investigated in the last years both in
solution [2–4] and in the solid-state [5–27]. The
squarate anion does not behave like a chelating ligand
but rather like a bridge between two or more metal at-
oms as mono- or bidentate ligand. The squarato
mononuclear complexes with first-row transition
metal ions are isolated when squarate acts as a
monodentate ligand [16, 18] whereas dinuclear and
chain compounds result when the squarato ligand is
coordinated in m-1,2- [14, 15, 25–27] and m-1,3-bis-
monodentate [4–8, 13, 16, 28, 29] fashions. Diaqua
and tetraaqua complexes of sq with transition metals
were reported [5–8]. Synthesis and structural charac-
terization of mixed-ligand transition metal complexes
of sq with mono- and bidentate N-donor ligands such
as pyridine [12], imidazole [13], 2,2’-bipyridine
[13–17] and 1,10-phenanthroline [15–18] appear in
recent literature. In some transition metal complexes,
the squaric acid acts as a counter ion [19–24].
Solid-state thermal studies of several metal squarate
and mixed ligand of the metal squarate complexes
have been reported, indicating a high thermal stability
of the squarate moiety [30–34].
in transition metal complexes [35–37],
a
N,O,O’,O’’-tetradentate ligand behavior has also
been observed, especially towards metal ions having
large ionic radii [38–40]. YÏlmaz et al. has stud-
ied [41] the thermal decomposition of the tea com-
plexes of metal saccharinates, while the decomposi-
tion behaviours of the aqua complexes of the
metal(II) squarates were studied by Bailey et al. [42].
We reported earlier the crystal structure determi-
nations of the [Ni(tea)2]sq, [Cu(tea)2]sq and
[Cd(tea)2]sq×H2O complexes [20–22]. The Ni(II),
Cu(II) and Cd(II) complexes crystallize in the
triclinic, monoclinic and triclinic system with space
group P1, P21/c, P1, respectively. Two tea ligands
coordinate to the Ni(II) and Cu(II) ions through four
O atoms and two N atoms acting as N,O,O’-tridentate
ligands, resulting in a distorted octahedral environ-
ment. In the complex cation, in which the Cd(II) ion is
Fig. 1 a – Squaric acid and b – triethanolamine
*
Author for correspondence: yesilel@ogu.edu.tr
1388–6150/$20.00
Akadémiai Kiadó, Budapest, Hungary
Springer, Dordrecht, The Netherlands
© 2007 Akadémiai Kiadó, Budapest

YEŸILEL, ÖLMEZ
coordinated by two tea ligands and seven-coordi-
7, 2 and 0, respectively) in distilled water (20 mL).
The mixture was stirred for 4 h at 60°C and then
cooled to room temperature. The Msq×2H2O crystals
formed were filtered and washed with 10 mL of cold
distilled water and dried in air.
A solution of triethanolamine (0.596 g, 4 mmol)
in methanol (20 mL) was added dropwise with stirring
to a suspension of Msq×2H2O (2 mmol; M=Co(II),
0.414 g; Ni(II), 0.414 g; Cu(II), 0.423 g; Cd(II),
0.520 g) in water (30 mL). The mixture was stirred
at 60ºC for 12 h and then cooled to room temperature.
The crystals formed were filtered and washed with
10 mL of water and methanol and dried in air.
nated, both tri- and tetradentate tea molecules are
present. One of the tea ligands acts as an
N,O,O’-tridentate ligand, whereas the other behaves
as an N,O,O’,O’’-tetradentate donor. The squarate an-
ions and [M(tea)2]2– cations are linked to each other
by hydrogen bonding between coordinated hydroxyl
H atoms of tea and squarate O atoms, forming layers.
In the present paper, syntheses, spectroscopic
properties and thermal decomposition of the Co(II),
Ni(II), Cu(II) and Cd(II) complexes with squaric acid
and triethanolamine are reported.
Experimental
Results and discussion
Materials and instrumentation
Structures of the complexes
All chemicals used were analytical reagent products.
Elemental analyses for C, H and N were carried out at
the Tübitak Marmara Research Centre in Turkey.
Magnetic susceptibility measurements at room tem-
peratures were performed using a Sherwood Scien-
tific MXI model Gouy magnetic balance. UV-Vis
spectra were obtained for the aqueous solutions
(10–3 M) of the complexes with a Unicam UV2 spec-
trometer in the range 900–190 nm. IR spectra were re-
corded in the 4000–500 cm–1 region with a
Mattson 1000 FT-IR spectrometer using KBr pellets.
Thermal analysis curves (TG, DTG and DTA) were
recorded simultaneously in a static air atmosphere
with a Rigaku TG8110 thermal analyzer. The heating
rate was 10ºC min–1 and the DTG sensitivity
was 0.05 mg s–1. The conductance values were
measured on 522 Crison conductimeter.
Analytical results, molar conductivity values and com-
positions of the complexes are listed in Table 1. The
complexes were synthesized in good yields and with
high purity. The Ni(II), Cu(II) and Cd(II) complexes of
sq with tea were also structurally characterized [20–22].
The elemental analyses conformed to their given for-
mula (Table 1). The molar ratio M:tea:sq in all the com-
plexes are 1:2:1. In the Co(II), Ni(II) and Cu(II) com-
plexes, tea acts as a tridentate ligand (N,O,O’), while in
the Cd(II) complex, which is seven coordination, tea
ligand behaves both tridentate (N,O,O’) and tetradentate
(N,O,O’,O’’) [20–22]. Dianionic squarate behaves as a
counter ion in all the complexes. These results were sup-
ported by conductivity measurements. The molar con-
ductance values (L) of the complexes are 167, 206, 151
and 187 S cm2 mol–1 for the Co(II), Ni(II), Cu(II) and
Cd(II), respectively, indicating that all the complexes
are a 1:2 electrolyte in water.
Synthesis of the complexes
A solution of squaric acid (0.57 g, 5 mmol) in distilled
water (20 mL) was neutralized with NaOH (0.40 g,
10 mmol) and added dropwise with stirring at 60°C to
a solution of MCl2·xH2O (5 mmol; M=Co(II), 1.185 g;
Ni(II), 1.185 g; Cu(II), 0.850 g, Cd(II), 0.917 g; x=7,
UV-Vis spectra and magnetic moments of the complexes
The lmax, e, 10 Dq and effective magnetic moment val-
ues and assignment of d–d transitions of the complexes
are given in Table 2. The Co(II), Ni(II) and Cu(II)
Table 1 Analytical data and conductance values of the complexes
Found (calc.)/%
Complexes
F.W./g mol–1
Yield/%
Colour
L/S cm2 mol–1
C
H
N
[Co(tea)2]sq×2H2O
C16H34N2O12Co
37.78
(38.03)
7.02
(6.78)
5.55
(5.54)
505.38
469.11
473.98
540.85
65
60
63
55
brown
blue
167
206
151
187
[Ni(tea)2]sq
C16H30N2O10Ni
40.98
(40.97)
6.53
(6.45)
5.98
(5.97)
[Cu(tea)2]sq
C16H30N2O10Cu
40.16
(40.55)
6.52
(6.38)
5.83
(5.91)
green
[Cd(tea)2]sq×H2O
C16H32N2O11Cd
35.43
(35.53)
6.00
(5.96)
4.98
(5.18)
colourless
262
J. Therm. Anal. Cal., 89, 2007

TRIETHANOLAMINE COMPLEXES OF Co(II), Ni(II), Cu(II) AND Cd(II) SQUARATES
Table 2 Absorption spectra and magnetic moment values of the complexes
Assignment of
d–d transitions
e/L cm–1 mol–1
10 Dq/cm–1
–
lmax/nm
meff/BM
Complexes
[Co(tea)2]sq×2H2
O
4T1g®4T1g (P)
530
48
4.21
388
641
890
81
35
23
3A2g®3T1g (P)
3A2g®3T1g
[Ni(tea)2]sq
[Cu(tea)2]sq
11236
13495
2.61
1.84
3A2g®3T2g
741
119
2Eg®2T2g
3
3
3
complexes exhibit the magnetic moment values of
4.21, 2.61 and 1.84 BM, which correspond to three,
two and one unpaired electrons, respectively, which
are consistent with a weak field octahedral geometry.
The Cd(II) complex is diamagnetic as expected.
assigned to A2g®3T1g (P), A2g®3T1g and A2g®3T2g,
respectively. The 10 Dq value for the Ni(II) complex
was calculated as 11236 cm–1.
The single band observed for the complex of
copper(II) at 741 nm (e=119 L mol–1 cm–1) that all
The tea ligand and sq2– anion exhibit two bands in
the UV region at 211 and 229 nm, which are assigned
to p®p* and n®p* transitions and the bands with low
intensity between 350 and 800 nm are due to d–d tran-
sitions. The assignments of d-d transitions corre-
sponded to an octahedral coordination geometry of the
metal ions and the values of the 10 Dq parameter were
found using Tanabe and Sugano diagrams [43].
three transitions, i.e. B1g®2Eg, B1g®2B2g and
2B1g®2A1g lie within one broad envelope. The 10 Dq
value for the complex was calculated as 13495 cm–1.
The colourless Cd(II) complex do not show any
d–d bands as expected but only exhibits the intra-
ligand transitions.
2
2
IR spectra
The lmax value of the absorption band in the
spectrum of the Co(II) complex is 530 nm and the cor-
responding e value is 48 L mol–1 cm–1. The lmax value
The main IR group frequencies of the metal com-
plexes are presented in Table 3. The strong bands
at 3357, 3385, 3356 and 3391 cm–1 in the spectra of
the Co(II), Ni(II), Cu(II) and Cd(II) complexes, re-
spectively, are assigned to nOH stretching of the etha-
nol groups of the tea ligand. nOH stretching of water
molecule appears at 3462 and 3496 cm–1 of the Co(II)
and Cd(II) complexes, respectively. The weak peaks
in the 3081–2803 cm–1 range are due to nCH stretching
of tea. A very strong and broad absorption centered at
1497, 1424; 1499, 1433; 1501, 1413 and 1511,
1437 cm–1 of the Co(II), Ni(II), Cu(II) and Cd(II)
complexes, respectively, are assigned to the combina-
tion of squarato C–O and C–C band stretching vibra-
tions, respectively. In addition to that only one weak
peak at around 1715 cm–1 assigned to C=O is ob-
4
was assigned to the T1g®4T1g (P) d–d transition,
which is characteristic of octahedral geometry around
4
4
the metal ion [44]. The T1g®4T2g and T1g®4A2g
transition was not observed which is of low and high
4
energy, respectively, and the T1g®4T2g shifts to the
4
IR region, while T1g®4A2g shifts to the UV region
and hidden under the intraligand transitions in the
spectrum. Therefore, the 10 Dq value for Co(II) com-
plex could not be calculated.
The UV-Vis spectrum for [Ni(tea)2]sq exhibits
three weak d–d absorption transitions centered at
388 nm (e=81
L
mol–1 cm–1), 641 nm
(e=35 L mol–1 cm–1) and 890 nm (e=23 L mol–1 cm–1)
and supported octahedral geometry. These values were
Table 3 IR group frequencies (cm–1)
Complexes
nOH
nOH
nCH
nC=O
nC=C
nC–C+nC–O
tea
2
1530vs,b
1516s
Squaric acid
3462s
–
–
1818w
1618m
3023m
2859m
1497vs,b
1424s
[Co(tea)2]sq×2H2O
[Ni(tea)2]sq
3462s
3357s
3385s
3356s
3391m
1725w
1737w
1705w
1712w
–
–
–
–
3031m
2981m
1499vs,b
1433s
–
–
3081m
2982m
1501vs,b
1413s
[Cu(tea)2]sq
2943w
2803w
1511vs,b
1437s
[Cd(tea)2]sq×H2O
3496m
w – weak, m – medium, s – strong, vs – very strong and b – broad.
J. Therm. Anal. Cal., 89, 2007
263

YEŸILEL, ÖLMEZ
served due to C4O24– ion acts as a counter anion in the
melting at 223ºC. In the temperature range
of 225–353ºC, the first and second stages of the Ni(II)
complex are related to the successive decomposition
of the neutral tea ligands, by giving initially endother-
mic, and then an exothermic contribution is also ob-
served in the DTA curve of the complex
(DTGmax=289, 308ºC). The following stage involves
the exothermic decomposition of squarate by released
CO2 and the extremely burning of organic residue,
leading finally to NiO (found 83.32, calcd. 84.07%).
This type of behaviour of oxalate complexes has been
reported earlier [46].
Thermal decomposition of the [Cu(tea)2]sq com-
plex proceeds in the three stages (Fig. 4). The com-
plex is thermally stable up to about 162ºC and under-
goes complete exothermic decompositions after melt-
ing at 154ºC. In the temperature range of 162–434ºC,
the exothermic peaks (DTGmax=170, 278ºC) are re-
lated to the release of the tea ligands. In the third
stage, the strong exothermic mass loss processes oc-
curs in the temperature range of 434–542ºC. During
this stage, the remaining organic part and squarate is
abruptly burnt (DTGmax=ca. 500ºC). The final solid
product of the thermal decomposition was identified
as CuO (found 82.11, calcd. 83.22%).
complexes [30–34]. These stretching vibrations are
found at 1822 cm–1 in the IR spectrum of free squaric
acid [45]. This type of absorption is characteristic of
salts ofCn O2n– ion and it was found at 1500 cm–1 in the
IR spectrum of K2C4O4 [11]. The weak bands in the
region of 400–500 and 500–600 cm–1 are due to M–N
and M–O stretching vibrations, respectively.
Thermal analysis
The thermoanalytical curves of the complexes are
shown in Figs 2–5.
The [Co(tea)2]sq×2H2O complex exhibits three de-
composition stages (Fig. 2). In the first stage, endother-
mic removal of two moles of crystal water molecule oc-
curs in the temperature range of 65–104ºC (DTGmax
=
85ºC). The complex melts at 196ºC and then in the tem-
perature range of 168–342ºC, the anhydrous Co(II)
complex involves the decomposition of neutral tea
ligand by the endothermic effects (DTGmax=230,
309ºC). The following stage involves the burning of or-
ganic residue by the exothermic effect (DTGmax
=
374ºC), leading finally to Co3O4. The endothermic peak
at 898ºC (DTGmax) is related to the conversion of Co3O4
to CoO. The overall mass loss of 83.04%
(calcd. 85.12%) agrees with the proposed structure well.
The [Ni(tea)2]sq complex has a high thermal sta-
bility (Fig. 3). Its decomposition begins at 225ºC after
The thermal behavior of the Cd(II) complex is dif-
ferent from the Co(II), Ni(II) and Cu(II) complexes
(Fig. 5), because of the Cd(II) complex has different
structure from the other complexes. The first stage
Fig. 2 TG, DTG and DTA curves of [Co(tea)2]sq×2H2O
Fig. 4 TG, DTG and DTA curves of [Cu(tea)2]sq
Fig. 3 TG, DTG and DTA curves of [Ni(tea)2]sq
Fig. 5 TG, DTG and DTA curves of [Cd(tea)2]sq×H2O complex
264
J. Therm. Anal. Cal., 89, 2007

TRIETHANOLAMINE COMPLEXES OF Co(II), Ni(II), Cu(II) AND Cd(II) SQUARATES
21 I. Ucar, O. Z. Yeêilel, A. Bulut, H. Icbudak, H. Ölmez and
(56–136ºC) is related to the dehydration of the complex.
C. Kazak, Acta Cryst., C60 (2004) m392.
22 I. Ucar, O. Z. Yeêilel, A. Bulut, H. Icbudak, H. Ölmez and
C. Kazak, Acta Cryst., E60 (2004) m322.
23 I. Ucar, O. Z. Yeêilel, A. Bulut, H. Ölmez and
O. Büyükgüngör, Acta Cryst., E60 (2004) m1025.
24 I. Ucar, A. Bulut and O. Büyükgüngör, Acta Cryst.,
C61 (2005) m218.
25 I. Catro, M. L. Calatayud, J. Sletten, F. Lloret and
M. Julve, J. Chem. Soc., Dalton Trans., (1997) 811.
26 I. Catro, M. L. Calatayud, J. Sletten, F. Lloret and
M. Julve, Inorg. Chim. Acta, 287 (1999) 173.
27 C. E. Xanthopoulos, M. P. Sigalas, G. A. Katsoulos,
C. A. Tsipis, C. C. Hadjikostas, A. Terzis and M. Mentzafos,
Inorg. Chem., 32 (1993) 3743.
28 A. Crispini, D. Pucci, I. Aiello and M. Ghedini,
Inorg. Chim. Acta, 304 (2000) 219.
29 I. Castro, M. L. Calatayud, J. Sletten, M. Julve and F. Lloret,
C. R. Acad. Sci. Paris, Chimie/Chemistry, 4 (2001) 235.
30 A. Mondal, D. Das and N. R. Chaudhuri, J. Therm. Anal. Cal.,
55 (1999) 165.
The anhydrous Cd(II) complex starts to decompose with
melting at 184ºC (DTA). The second stage of
[Cd(tea)2]sq is related to the decomposition of the neu-
tral tea ligand in the temperature range of 184–314ºC
(DTGmax=226ºC). The following exothermic stages be-
tween 315–470ºC (DTGmax=352 and 407ºC) are related
to decomposition of the sq2– and the extremely burning
of organic residue. The final decomposition product is
CdO (found 75.30, calcd. 76.35%).
The final decomposition products, namely CoO,
NiO, CuO and CdO, were identified by IR spectros-
copy. On the basis of the first DTGmax of the decompo-
sitions, the thermal stability of the anhydrous com-
plexes follows the order: Ni(II), 251ºC>Cd(II), 226ºC>
Co(II), 203ºC>Cu(II), 170ºC in static air atmosphere.
References
31 T. K. Maji, D. Das and N. R. Chaudhuri, J. Therm. Anal. Cal.,
63 (2001) 617.
32 D. Das, A. Ghosh and N. R. Chaudhuri, Bull. Chem. Soc.,
Jpn., 70 (1997) 789.
33 T. K. Maji, D. Das and N. R. Chaudhuri, J. Therm. Anal. Cal.,
68 (2002) 319.
34 O. Z. Yeêilel, H. Ölmez and S. Soylu, Trans. Met. Chem.,
31 (2006) 396.
35 B. Sen and R. L. Dotson, J. Inorg. Nucl. Chem.,
32 (1970) 2707.
36 H. Içbudak, V. Y. YÏlmaz and H. Ölmez, J. Thermal Anal.,
44 (1995) 605.
37 I. Ucar, O. Z. Yeêilel, A. Bulut, H. Icbudak, H. Ölmez and
C. Kazak, Acta Cryst., E60 (2004) m322.
38 B. Chiswell, E. D. McKenzie and L. F. Lindoy, Compre-
hensive Coordination Chemistry, Vol. 4, Ed. G. Wilkinson,
R. D. Gillard and J. A. McCleverty, Pergamon Press,
Oxford 1997, pp. 1–122.
39 . Ucar, O. Z. Yeêilel, A. Bulut, H. Icbudak, H. Ölmez and
C. Kazak, Acta Cryst., C60 (2004) m392.
40 H. Ölmez, H. Icbudak, O. Z. Yeêilel, C. ArÏcÏ and D. Ülkü,
Z. Kristallogr., 219 (2004) 300.
41 V. T. YÏlmaz, Y. Topcu and A. Karadag, Thermochim. Acta,
383 (2002) 129.
42 R. A. Bailey, W. N. Mills and W. J. Tangredi,
J. Inorg. Nucl. Chem., 33 (1971) 2387.
43 D. Sutton, Electronic Spectra of Transition Metal Complexes,
McGraw-Hill, London 1968, p. 208.
44 T. Premkumar and S. Govindarajan, J. Therm. Anal. Cal.,
84 (2006) 395.
1 S. Cohen, J. R. Lacher and J. D. Park, J. Am. Chem. Soc.,
81 (1959) 3480.
2 H. P. Tedosco and H. F. Walton, Inorg. Chem., 8 (1969) 932.
3 I. Castro, J. Faus and M. Julve, Trans. Met. Chem.,
13 (1988) 455.
4 I. Castro, J. Faus, M. Julve, Y. Journaux and J. Sletten,
J. Chem. Soc., Dalton Trans., (1991) 2533.
5 A. Weiss, E. Riegler, I. Alt, H. Böhme and C. Robl,
Z. Naturforsch., B: Chem. Sci., 41 (1986) 18.
6 B. D. Alleyne, L. A. Hall, H. A. Hosein, H. Jaggernauth,
A. J. P. White and D. J. Williams, J. Chem. Soc.,
Dalton Trans., (1998) 3845.
7 G. M. Frankenbach, M. A. Beno, A. M. Kini,
J. M. Williams, U. Welp, J. E. Thompson and
M. H. Whangbo, Inorg. Chim. Acta, 192 (1992) 195.
8 C. Robl and A. Weiss, Z. Naturforsch., B: Chem. Sci.,
41 (1986) 1341.
9 A. Weiss, E. Riegler and C. Robl, Z. Naturforsch.,
B: Chem. Sci., 41 (1986) 1329.
10 A. Weiss, E. Riegler and C. Robl, Z. Naturforsch.,
B: Chem. Sci., 41 (1986) 1333.
11 R. West and H. Y. Niu, J. Chem. Soc., 85 (1963) 2589.
12 R. Kirchmaier, E. Altin and A. Lentz, Z. Kristallogr. NCS,
218 (2003) 1.
13 G. Bernardinelli, D. Deguenon, R. Soules and P. Castan,
Can. J. Chem., 67 (1998) 1158.
14 R. Soules, F. Dahan, J. P. Laurent and P. Castan,
J. Chem. Soc., Dalton Trans., (1998) 587.
15 J. M. Reinprecht, J. M. Miller, G. C. Vogel, M. S. Haddad
and D. N. Hendrickson, Inorg. Chem., 19 (1980) 927.
16 X. Solons, M. Aguilõ, A. Gleizes, J. Faus, M. Julve and
M. Verdaguer, Inorg. Chem., 29 (1990) 775.
17 I. Catro, M. L. Calatayud, J. Sletten, F. Lloret and M. Julve,
Inorg. Chim. Acta, 287 (1999) 173.
45 F. G. Baglin and C. B. Rose, Spectrochim. Acta, Part A,
26 (1970) 2293.
46 A. Ubaldini, C. Artini, G. A. Costa, M. M. Carnasciali and
R. Masini, J. Therm. Anal. Cal., 84 (2006) 207.
18 A. Bulut, I. Ucar, O. Z. Yeêilel, H. Icbudak, H. Ölmez and
O. Büyükgüngör, Acta Cryst., C60 (2004) m526.
19 I. Ucar, O. Z. Yeêilel, A. Bulut, H. Ölmez and
O. Büyükgüngör, Acta Cryst., E61 (2005) m947.
20 O. Z. Yeêilel, A. Bulut, I. Ucar, H. Icbudak, H. Ölmez and
O. Büyükgüngör, Acta Cryst., E60 (2004) m228.
Received: December 15, 2005
Accepted: June 14, 2006
OnlineFirst: October 20, 2006
DOI: 10.1007/s10973-005-7477-y
J. Therm. Anal. Cal., 89, 2007
265