Synthesis, characterization and molecular structures of barium(II) trichloroacetate DME/1,4-dioxane compounds

Article abstract of DOI:10.1016/j.poly.2011.09.018

Two new barium(II) trichloroacetate compounds, [Ba(H₂O)(DME) (μ-O₂CCCl₃)₂]_n (1) and [{Ba(H₂O)₂(diox)_0.5(μ-O₂CCCl ₃)₂}(diox)]_n (2) were synthesized and characterized by elemental analyses, physiochemical studies, FT-IR, ¹H NMR, thermogravimetric analyses (TG/DTG/DSC) and single crystal X-ray studies. The reaction of hydrated barium(II) trichloroacetate monohydrate with excess DME (1,2-dimethoxyethane) and diox (1,4-dioxane) in methanol at room temperature led to the isolation of the novel compounds 1 and 2, respectively. Bridging trichloroacetate groups are anticipated on the basis of FT-IR studies and this was confirmed by the X-ray studies. Both compounds dissociate to produce ions in water, as shown by molar conductance values. ¹H NMR spectroscopy confirms that DME and 1,4-dioxane are coordinated to the metal ion in these compounds. Single crystal X-ray diffraction studies reveal that the barium cation is coordinated to nine O atoms in a deformed coordination polyhedron in both compounds. Structural data of barium(II) trichloroacetates compounds have been obtained for the first time in the present investigation.

Full text of DOI:10.1016/j.poly.2011.09.018

Polyhedron 31 (2012) 202–209
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Polyhedron
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Synthesis, characterization and molecular structures of barium(II) trichloroacetate
DME/1,4-dioxane compounds
a
a
a
b,
Sukhjinder Singh a, , Deepika Saini , S.K. Mehta , Ravneet Kaur , Valeria Ferretti
⇑
⇑
a Department of Chemistry and Centre of Advanced Studies in Chemistry, Panjab University, Chandigarh 160 014, India
b Centro di Strutturistica Diffrattometrica and Dipartimento di Chimica, University of Ferrara, Via L. Borsari 46, I-44121 Ferrara, Italy
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 26 May 2011
Accepted 11 September 2011
Available online 21 September 2011
Two new barium(II) trichloroacetate compounds, [Ba(H2O)(DME)(
l-O2CCCl3)2]n (1) and [{Ba(H2O)2
(diox)0.5 -O2CCCl3)2}(diox)]n (2) were synthesized and characterized by elemental analyses, physio-
(
l
chemical studies, FT-IR, 1H NMR, thermogravimetric analyses (TG/DTG/DSC) and single crystal X-ray
studies. The reaction of hydrated barium(II) trichloroacetate monohydrate with excess DME (1,2-dime-
thoxyethane) and diox (1,4-dioxane) in methanol at room temperature led to the isolation of the novel
compounds 1 and 2, respectively. Bridging trichloroacetate groups are anticipated on the basis of FT-IR
studies and this was confirmed by the X-ray studies. Both compounds dissociate to produce ions in water,
as shown by molar conductance values. 1H NMR spectroscopy confirms that DME and 1,4-dioxane are
coordinated to the metal ion in these compounds. Single crystal X-ray diffraction studies reveal that
the barium cation is coordinated to nine O atoms in a deformed coordination polyhedron in both com-
pounds. Structural data of barium(II) trichloroacetates compounds have been obtained for the first time
in the present investigation.
Keywords:
Trichloroacetates
DME
1,4-Dioxane
Barium
X-ray structure
Ó 2011 Elsevier Ltd. All rights reserved.
1. Introduction
[10,11,35–37]. The high volatility of soluble acetylacetonate pre-
cursors often results in a change in the stoichiometry of the final
Supramolecular and coordination chemistry have provided
important advances in developing strategies for the synthesis of
complex molecular architectures and novel assemblies [1–3]. Alka-
line earth metal compounds [4–9] have attracted a lot of attention
because of their widespread use in a number of advanced material
applications [10–13]. Increasing interest in the search for alkaline
earth molecular precursors for the generation of high temperature
superconductors, ceramics and nano materials have led to the iso-
lation of a variety of alkaline earth metal zero-dimensional, low-
dimensional, three dimensional coordination polymer networks
and heterometallic compounds [14–22]. Especially, barium precur-
sors have played a significant role in the development of property
controlled thin films for ceramic YBa2Cu3O7ꢀd (YBCO) supercon-
ductor materials [10,11]. Alkaline earth metal alkoxides [23,24]
and b-diketonates [25–28] are very promising as Metal Organic
Chemical Vapor Deposition (MOCVD) precursors for metal oxide
superconductors. In general, metal alkoxides M(OR)x are excellent
precursors for the production of ceramic materials [12,29–34],
however the low solubility and high crystallization temperature
of Ba(OR)2 deters its use for the development of YBCO materials
films [10,11,35–37] which restricts their use. The use of simple car-
boxylates also suffers from decomposition pathways that proceed
via carbonate intermediates during processing [10,11,35–37]. In
this context, highly halogenated derivatives of carboxylic acid
(e.g. trifluoroacetates/trichloroacetates) may prove extremely
useful because of the solubility, volatility and carbonate problems
[38,39]. The preferential decomposition of barium fluoroacetates
into barium fluoride [40] represents a means to avoid the forma-
tion of the highly stable carbonate, which is detrimental to the
superconducting properties.
On the other hand, large numbers of crystallographic structural
reports of various metal trichloroacetates are available in the liter-
ature, with the trichloroacetate ligand (TCLA) adopting numerous
binding modes such as unidentate, bidentate chelating and biden-
tate bridging. However, only few hetero-metallic alkaline earth
metal trichloroacetates have been structurally characterized
[41,42]. Therefore, we undertook the synthesis of new barium(II)
trichloroacetate compounds, viz [Ba(H2O)(DME)(l-O2CCCl3)2]n (1)
and [{Ba(H2O)2(diox)0.5 -O2CCCl3)2}(diox)]n (2) [DME = 1,2-dime-
(l
thoxyethane and diox = 1,4-dioxane] and their characterization by
elemental analysis, molar conductance, IR, 1H NMR and thermo-
gravimetric analysis (TG/DTG/DSC). To the best of our knowledge
we are reporting the single crystal structures of barium TCLA com-
pounds 1 and 2 for the first time.
⇑
Corresponding authors. Tel.: +91 0172 2534429; fax: +91 0172 2545074
(S. Singh), tel.: +39 0532 455132/455144; fax: +39 0532 240709 (V. Ferretti).
E-mail addresses: sukhis@pu.ac.in (S. Singh), frt@unife.it (V. Ferretti).
0277-5387/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2011.09.018

S. Singh et al. / Polyhedron 31 (2012) 202–209
203
appeared. The precipitates were redissolved by adding methanol
and the resulting clear solution was stirred at room temperature
for 1 h. About 1.56 g (2.48 mmol) of 2 as white shining transparent
needle-shaped crystals, suitable for X-ray diffraction, were ob-
tained in 68.9% yield over a period of 4 days via slow evaporation
of solvent at room temperature. Anal. calc. for C10H16BaCl6O9: C,
19.05; H, 2.54; Cl, 33.81; Ba, 21.74. Found: C, 18.83; H, 2.51; Cl,
32.94; Ba, 21.25%. FT-IR (KBr pellets, cmꢀ1): 3505 mw, 3422 m
(O–H stretch.); 2968 w, 2923 mw, 2865 w (C–H stretch.); 1661
vsb (COO asym. stretch.); 1378 m, 1347 s (COO sym. stretch.);
942 vw (C–C stretch.); 874 ms, 833 sb (CCl3 asym. stretch.); 614
mw (M–O vib.); 1454 w; 1293 w; 1256 m; 1115 ms; 1080 mw;
1045 vw; 890 mw; 751 ms; 684 ms; 428 wb. 1H NMR (400 MHz,
D2O) d (ppm): 3.63 (s, 8H, 4CH2). M.Pt. >85 °C (decomp.).
2. Experimental
2.1. Materials
Commercially available analytical grade reagents [1,4-dioxane
(diox), 1,2-dimethoxyethane (DME), methanol] were used through-
out this work without further purification. Trichloroacetic acid
(Merck) and barium(II) carbonate (BDH) were used as received.
2.2. Physical measurements
Carbon and hydrogen were determined microanalytically using
an automatic Perkin-Elmer 2400 CHN/Analytischer Funktionstest
vario EL II Fab. Nr. 11975059 elemental analyzer. Barium and
chlorine were determined gravimetrically by standard literature
methods [43]. Infrared spectra were recorded as KBr pellets on a
Perkin-Elmer RXFT-IR spectrophotometer in the region 4000–
400 cmꢀ1. Conductance measurements were performed on a Pico
conductivity meter (Model CNO4091201, Lab India) at 25 °C. The
thermogravimetric analyses were carried out in a dynamic nitro-
gen atmosphere (100 mL minꢀ1) at the heating rate of 10 °C minꢀ1
using a Universal V4 SDT Q-600 V20.9 thermal analyzer. Simulta-
neous TG–DTG–DSC curves as well as separate TG curves were
obtained. 1H NMR spectra were recorded in D2O at ambient tem-
perature on a Bruker Avance II 400 MHz NMR spectrometer. Tetra-
methylsilane (TMS) was used as an external standard for the 1H
NMR spectra.
2.3.4. X-ray crystal structure information
The crystallographic data for 1 and 2 were collected on a Nonius
Kappa CCD diffractometer at room temperature using graphite-
monochromated MoKa radiation (k = 0.71073 Å). Data sets were
integrated with the Denzo-SMN package [44] and corrected for
Lorentz-polarization and absorption effects [45]. The crystal
parameters and other experimental details of the data collections
are summarized in Table 1. The structures were solved by direct
methods (SIR97) [46] and refined by full-matrix least-squares
methods with all non-hydrogen atoms as anisotropic. Hydrogens
were included in calculated positions, riding on their carrier atoms,
apart from those belonging to water molecules that were located in
the difference-fourier map. Cl2–Cl6 atoms in 1 were found to be
disordered over two equivalent positions. All calculations were
performed using SHELXL-97 [47] implemented in the WINGX system
of programs [48]. Selected bond distances and angles are given in
Table 2.
2.3. Synthesis
2.3.1. Ba(O2CCCl3)2ꢁH2O
Excess BaCO3 (4.54 g, 23.05 mmol) was added to a solution of
trichloroacetic acid (5.98 g, 36.57 mmol) in 30 mL of water. The
contents were stirred at room temperature until the evolution of
CO2 ceased. Excess BaCO3 was then filtered off. Removal of solvent
from the filtrate under vacuum gave 8.69 g (18.10 mmol) of white
shining crystalline Ba(O2CCCl3)2ꢁH2O in nearly quantitative yield
(99%). Anal. Calc. for C4H2BaCl6O5: C, 10.00; H, 0.42; Cl, 44.37; Ba,
28.54. Found: C, 10.15; H, 0.43; Cl, 43.95; Ba, 28.12%. FT-IR (KBr
pellets, cmꢀ1): 3393 sbr (OH stretch.); 1642 s (COO asym. stretch.);
1351 ms (COO sym. stretch.); 952 w (C–C stretch.); 844 s (CCl3
asym. stretch.); 756 ms; 745 m; 681 s (where br = broad; m = med-
ium; s = strong; v = very; w = weak; sh = shoulder). M.pt. >54 °C
(decomp.).
3. Results and discussion
3.1. Synthesis and characterization
The reaction between trichloroacetic acid and excess BaCO3 in
aqueous medium at room temperature resulted in the formation
of Ba(O2CCCl3)2ꢁH2O as is given below:
O
BaCO3 þ 2CCl3COOH H!2 BaðO2CCCl3Þ2 ꢁ H2O þ CO2
R:T:
Table 1
Experimental details.
2.3.2. [Ba(H2O)(DME)(
The present compound was prepared by the slow addition of
5 mL of DME (1,2-dimethoxyethane) to solution of
l-O2CCCl3)2]n (1)
Compound 1
Compound 2
a
Mr
561.21
630.27
Ba(O2CCCl3)2ꢁH2O (2.04 g, 4.25 mmol) in 25 mL of methanol with
constant stirring. The white shining crystals of 1 1.67 g (2.93 mmol)
suitable for X-ray diffraction were obtained in 68.9% yield over a
period of 3 days by slow evaporation of solvent at room tempera-
ture. Anal. Calc. for C8H12BaCl6O7: C, 16.83; H, 2.10; Cl, 37.35; Ba,
24.08. Found: C, 16.81; H, 1.98; Cl, 37.02; Ba, 24.11%. FT-IR (KBr pel-
lets, cmꢀ1): 3672 w, 3391 mbr (OH stretch.); 3008 vw, 2937 vw,
2832 vw (C–H stretch.); 1678 m, 1648 s (COO asym. stretch.);
1380 sh, 1355 s (COO sym. stretch.); 951 vw (C–C asym. stretch.);
875 sh, 841 vs (CCl3 asym. stretch.); 567 wb (M–O vib.); 1617 sh;
1452 vw; 1329 mw; 1248 vw; 1193 vw; 1119 w; 1069 ms; 1028
vw; 749 s; 681 vs; 452 w (cmꢀ1). 1H NMR (400 MHz, D2O) d
(ppm): 3.28 (s, 6H, 2-OCH3), 3.51 (s, 4H, 2CH2). M.pt. >62 °C
(decomp.).
Crystal system
Space group
a (Å)
b (Å)
c (Å)
monoclinic
C2/c
21.3473 (6)
12.3488 (4)
15.0432 (5)
90
97.7510 (11)
90
3929.4 (2)
8
triclinic
P1
ꢀ
8.8379 (1)
10.8247 (2)
12.3044 (3)
99.2990 (8)
99.4480 (8)
104.3970 (9)
1099.17 (4)
2
a
(°)
b (°)
c
(°)
V (Å3)
Z
l
(mmꢀ1
)
2.86
2.57
Crystal size (mm)
No. of measured, independent and 13736, 4695,
observed [I > 2
0.43 ꢂ 0.17 ꢂ 0.14 0.29 ꢂ 0.17 ꢂ 0.12
22038, 6363,
5051
0.074
0.042
0.105
r(I)] reflections
3896
Rint
0.047
0.045
0.121
1.10
R[F2 > 2
wR(F2)
S
r
(F2)]
1.08
No. of reflections
No. of parameters
qmin (e Åꢀ3
4695
245
1.40, ꢀ2.12
6363
241
0.74, ꢀ1.70
2.3.3. [{Ba(H2O)2(diox)0.5(l-O2CCCl3)2}(diox)]n (2)
Dioxane was added slowly to a solution of Ba(O2CCCl3)2ꢁH2O
D
qmax
,
D
)
(1.73 g, 3.6 mmol) in 20 mL of methanol until white precipitates

204
S. Singh et al. / Polyhedron 31 (2012) 202–209
Table 2
in the IR spectrum of hydrated barium(II) trichloroacetate [50].
The bands at 1642 and 1351 cmꢀ1 in the starting compound
Ba(O2CCCl3)2ꢁH2O are assigned to the asymmetric and symmetric
COO stretching vibrations, respectively, similar to the bands at
1670 (COO asymmetric stretch.) and 1379 (COO symmetric stretch.)
cmꢀ1 in hydrated barium(II) trichloroacetate [50]. The bands at
3672, 3391 and 3505, 3422 cmꢀ1 in 1 and 2, respectively, may be
attributed to OH stretching vibrations of water. The C–H stretching
vibrations are observed as weak absorptions in the 2830–3008 cmꢀ1
region in both compounds. A very strong absorption at 1648 cmꢀ1
and a weak peak at 1678 cmꢀ1 in 1 may be attributed to COO
asymmetric stretching vibrations of the unsymmetrical trichloro-
acetate ligands. The strong band at 1355 cmꢀ1 with a shoulder at
1380 cmꢀ1 in 1 may be assigned to the corresponding COO symmet-
ric stretching vibrations of the respective CCl3CO2 groups. Thus, the
Selected bond distances and angles (Å, °).
Compound 1
Ba1–O1
Ba1–O2
Ba1–O3
Ba1–O20 (ꢀx, y, 1/2 ꢀ z)
Ba1–O100 (ꢀx, ꢀy, ꢀz)
Ba1–O400 (ꢀx, ꢀy, ꢀz)
O1–Ba1–O3
O1–Ba1–O5
O1–Ba1–O6
2.952(3)
2.872(4)
2.719(3)
2.802(3)
2.734(3)
2.729(4)
70.0(1)
150.5(1)
148.6(1)
98.9(1)
Ba1–O5
Ba1–O6
Ba1–O7
2.867(5)
2.835(4)
2.902(3)
O2–Ba1–O6
O3–Ba1–O5
O3–Ba1–O6
O3–Ba1–O7
O5–Ba1–O6
O5–Ba1–O7
O6–Ba1–O7
146.6(1)
134.2(1)
78.6(1)
156.2(1)
57.7(1)
O1–Ba1–O7
O2–Ba1–O5
O2–Ba1–O3
O2–Ba1–O7
127.5(1)
96.2(1)
63.48(7)
64.1(1)
111.1(1)
Compound 2
Ba1–O1
Ba1–O2
Ba1–O3
Ba1–O4
Ba1–O50 (ꢀx, 1 ꢀ y, ꢀz)
Ba1–O300 (1 ꢀ x, 1 ꢀ y, ꢀz)
O1–Ba1–O2
O1–Ba1–O4
O1–Ba1–O5
O1–Ba1–O1W
O1–Ba1–O2W
O2–Ba1–O4
O2–Ba1–O1W
O2–Ba1–O2W
2.874(3)
2.775(3)
3.136(3)
2.817(3)
2.760(3)
2.729(3)
143.08(9)
131.91(9)
143.73(8)
71.3(1)
Ba1–O5
Ba1–O1W
Ba1–O2W
3.018(3)
2.784(3)
2.768(3)
magnitude of
D (COO asymmetric stretch – COO symmetric stretch),
of the order of 293 (=1648–1355) cmꢀ1, suggests bidentate bridging
trichloroacetate groups in 1. Similar results have also been observed
in the case of metal trichloroacetates [51–53] and other metal car-
boxylates [54,55]. A very strong band at 841 cmꢀ1 with a shoulder
at 875 cmꢀ1 in 1 is assigned to the C–Cl stretching vibrations of
the CCl3COO groups. A very strong broad absorption band at
1661 cmꢀ1 in 2 may be attributed to the COO asymmetric stretching
vibrations of the trichloroacetate ligands, and two bands at 1378
and 1347 cmꢀ1 in 2 may be attributed to COO symmetric stretching
vibrations of unsymmetrical CCl3COO groups. Again, the magnitude
O3–Ba1–O4
O3–Ba1–O5
71.38(8)
89.58(8)
153.60(8)
133.33(9)
82.22(9)
142.31(9)
141.55(9)
O3–Ba1–O2W
O4–Ba1–O1W
O4–Ba1–O2W
O5–Ba1–O1W
O1W–Ba1–O2W
72.91(9)
82.3(1)
74.1(1)
134.59(9)
of
D (COO asymmetric stretch – COO symmetric stretch), of the
order of 283 (=1661–1378) cmꢀ1, indicates bidentate bridging tri-
chloroacetate ligands in 2. The splitting of the COO stretching modes
in compounds 1 and 2, as compared to the respective single peaks in
the starting compound Ba(O2CCCl3)2ꢁH2O, suggests a different envi-
ronment of the CCl3COO ligands around the metal ion in compounds
1 and 2, in contrast to Ba(O2CCCl3)2ꢁH2O. The bands at 874 and
833 cmꢀ1 in 2 may be ascribed to C–Cl stretching vibrations of the
trichloroacetate ligands. The weak absorption at 567 cmꢀ1 in 1
and at 614 cmꢀ1 in 2 may be attributed to M–O vibrations.
1H NMR spectra of 1 and 2 were recorded in D2O. Two sharp
singlets were observed at 3.28 and 3.51 ppm relative to TMS due
to two –OCH3 and two –CH2– groups, respectively, of DME
(CH3OCH2CH2OCH3) in compound 1. The downfield values
observed in compound 1 relative to that of pure DME (3.16 and
3.35 ppm) indicate chelation of DME to the metal. In compound
2, a sharp singlet at 3.63 ppm was observed due to the CH2 groups
of 1,4-dioxane.
The use of excess BaCO3 helps in the complete consumption of
trichloroacetic acid. The white crystalline Ba(O2CCCl3)2ꢁH2O is solu-
ble in water and alcohols. Anhydrous barium(II) trichloroacetate
and hydrated barium(II) trichloroacetate (the number of water mol-
ecules is not defined) are known [49,50]. However, barium(II) tri-
chloroacetate monohydrate is not known. Further reaction of DME
or 1,4-dioxane with Ba(O2CCCl3)2ꢁH2O in methanol led to the isola-
tion of novel compounds 1 and 2, respectively, as outlined below:
[Ba(H2O)(DME)(µ-O2CCCl3)2]n
(1)
Ba(O2CCCl3)2.H2O
[{Ba(H2O)2(diox)0.5(µ-O2CCCl3)2}(diox)]n
(2)
3.3. Molar conductance
Conductance measurements of 1 and 2 were carried out at 25 °C
p
in water. The extrapolation of C to zero for both the compounds
gave values of Km of the order of 190.2 for 1 and 203 S cm2 molꢀ1
for 2. These values are fairly close to the expected range for a 1:2
electrolyte [56]. Conductance measurements, therefore, reveal that
the complexes dissociate to produce ions in aqueous media.
The isolated white crystalline new compounds 1 and 2 are sol-
uble in a number of solvents, e.g. THF, alcohols, H2O, nitromethane,
DMSO/DMF etc. The composition of compound 2, i.e. [{Ba(H2O)2
(diox)0.5(l-O2CCCl3)2}(diox)]n having two moles of water, has been
accomplished by absorbing water from the solvent (CH3OH as well
as 1,4-dioxane) since both solvents were not dried before use.
3.4. X-ray studies
3.2. Spectroscopic characterization
ORTEPIII [57] views of compounds 1 and 2 are shown in Fig. 1a
and b, respectively. In both structures, the Ba2+ cation is coordi-
nated to nine O atoms with bond distances ranging from 2.719(3)
to 2.952(3) Å and from 2.729(3) to 3.136(3) Å in 1 and 2, respec-
tively, to give the deformed coordination polyhedra shown in
Fig. 2a and b. The cation coordination can be rationalized in terms
of the concept of Bond Valence [58] which assumes that the total
The FT-IR spectral data of the starting compound
Ba(O2CCCl3)2ꢁH2O and both compounds 1 and 2, recorded as KBr pel-
lets, are given in Section 2. The crystal structures of anhydrous and
hydrated barium(II) trichloroacetates are unknown. However, IR
spectral data of hydrated barium(II) trichloroacetate has been
reported in the literature [50]. The band at 3393 cmꢀ1 in
Ba(O2CCCl3)2ꢁH2O is assigned to O–H stretching vibrations of the
water of crystallization, similar to the reported band at 3540 cmꢀ1
charge of the cation has to be saturated by
Rsi, i.e. the summation
of the separate bond valence (si) of each coordinated atom i. The
value of s can be calculated by the expression s = exp[(r0 ꢀ r)/B]

S. Singh et al. / Polyhedron 31 (2012) 202–209
205
Fig. 1. ORTEP views and atom numbering scheme for 1 (a) and 2 (b). Thermal ellipsoids are drawn at the 40% probability level. Hydrogen bonds are drawn as dashed lines.
[59] where r is the actual Ba–O distances, while r0 and B are empir-
ical parameters with values r0 = 2.15998 and B = 0.437 [60]. The s
value obtained for the Ba2+ cation is 1.99 in 1 and 1.93 in 2.
To compare the present crystal architectures with those exhibited
by similar molecules, searches in the Cambridge Structural Data-
base have been made of crystals containing alkaline earth metals/
acetate (16 hits), alkaline earth metals/haloacetate (15 hits) and
Ba/COOꢀ (140 hits) fragments, with the exclusion of entries in
which Mg and transition metals are present. The formation of poly-
mers turns out to be a very common situation for all alkaline earth
metal, mainly due to the ability of the COOꢀ group to bridge adja-
cent metal atoms. In crystals, simple chains are found in the major-
ity of cases with monocarboxylate ligands, giving origin to packing
patterns similar to the one in Fig. 3a; as an example, the cell content
for DEGJUV [61] is shown in Fig. 4a. In the case of polycarboxylate
ligands, such as, for instance, oxalate, the chains are linked to give
In both structures, the oxygens of the trichloroacetate ligand
bridge two adjacent Ba cations, giving rise to infinite polymers. In
1, the polymeric chains run along the c direction and the coordi-
nated water molecule does not form hydrogen bonds. In 2, the poly-
meric chains are extended along the a direction and are linked by
the coordinated dioxane ligands to form a two dimensional network
in the ab plane. The free dioxane molecules are located between
these planes, linking them by the formation of O–Hꢁ ꢁ ꢁO hydrogen
bonds whose structural parameters are listed in Table 3. The final
packing patterns for 1 and 2 are shown in Fig. 3a and b, respectively.

206
S. Singh et al. / Polyhedron 31 (2012) 202–209
samples, compound 2, is shown in Fig. 5. The TG/DTG/DSC super-
imposed curves for compound 1 indicate that the decomposition
process takes place as a multistep process:
BaðH2OÞðDMEÞðO2CCCl3Þ2 ! BaðDMEÞðO2CCCl3Þ2 þ H2O
BaðDMEÞðO2CCCl3Þ2 ! BaðO2CCCl3Þ2 þ DME
BaðO2CCCl3Þ2 ! BaCl2 þ CCl3COCl þ CO þ CO2
Primarily, three major mass loss regions have been observed:
the first region is associated with breakdown of the compound
and release of one water molecule. The subsequent steps involve
the loss of DME and finally the decomposition of Ba(O2CCCl3)2 to
barium chloride as the final product. The proposed decomposition
of Ba(O2CCCl3)2 to BaCl2 as a residue and CCl3COCl, CO, CO2 as vol-
atiles is similar to the reported [64] decomposition of Cu(O2CCCl3)2
{CuCl2, CCl3COCl, CO, CO2} and certain other metal trichloroacetates
[65]. The TG results obtained experimentally are in good agreement
with the calculated values, as summarized in Table 4. Transition
temperatures are indicated by the DTG curves (not shown in
Fig. 5 for the sake of clarity). The total observed weight loss of
63.13% in 1 and 66.55% in 2 is in excellent agreement with the cal-
culated weight loss of 63.46% in 1 and 66.99% in 2, for the formation
of BaCl2 as the final residue. For compound 2, again a multistep
decomposition takes place in a similar fashion, the first step being
the removal of one dioxane molecule. In the following steps, diox-
ane and water are removed, followed by decomposition of
Ba(O2CCCl3)2. Barium chloride remains as the final residual product.
fBaðH2OÞ2ðdioxÞ0:5ðO2CCCl3Þ2gðdioxÞ
! BaðH2OÞ2ðdioxÞ0:5ðO2CCCl3Þ2 þ ðdioxÞ
BaðH2OÞ2ðdioxÞ0:5ðO2CCCl3Þ2 ! BaðO2CCCl3Þ2 þ 0:5ðdioxÞ þ 2H2O
BaðO2CCCl3Þ2 ! BaCl2 þ CCl3COCl þ CO þ CO2
Separate heating of compounds 1 and 2 at 290 °C under a N2
atmosphere gave BaCl2 as the final residue, as confirmed from ele-
mental analysis. The formation of BaCl2 as the final residue is sup-
ported by the observed endothermic peaks in the DSC curves in the
region 940–960 °C in both 1 and 2 (Fig. 5 shows a representative
TG/DSC curve of compound 2). These peaks in the DSC curves are
related to the melting point of BaCl2 as the final residue (the re-
ported melting point of BaCl2 is 961 °C) [66].
Fig. 2. Coordination around the Ba cation in compound 1 (a). Symmetry operations:
O20 (ꢀx, y, 1/2 ꢀ z); O100, O400: (ꢀx, ꢀy, ꢀz); compound 2 (b). Symmetry operations:
O50 (ꢀx, 1 ꢀ y, ꢀz); O300: (1 ꢀ x, 1 ꢀ y, ꢀz).
Table 3
Hydrogen bonding parameters for compound 2 (Å, °).
D–H
Dꢁ ꢁ ꢁA
Hꢁ ꢁ ꢁA
D–Hꢁ ꢁ ꢁA
The DSC curves for the compounds prepared exhibit an endo-
thermic process initially. The area of the endothermic peak corre-
sponds to the heat of fusion and the peak temperature
corresponds to the melting point.
O2W–H4Wꢁ ꢁ ꢁO7
O1W–H1Wꢁ ꢁ ꢁO4i
O1W–H2Wꢁ ꢁ ꢁO6ii
O2W–H3Wꢁ ꢁ ꢁO2iii
0.92
2.840(4)
2.830(5)
2.881(5)
2.775(4)
2.00
150
0.86(6)
0.84(3)
0.86
1.99(5)
2.14(5)
2.00
163(4)
146(2)
148
Symmetry codes: (i) 1 ꢀ x, 1 ꢀ y, ꢀz; (ii) x, y, z ꢀ 1; (iii) ꢀx, 1 ꢀ y, ꢀz.
3.5.2. Kinetic consideration and calculation procedure
In the present study, analysis of non-isothermal data has been
performed by using the approximate computational approaches
due to Coats and Redfern [67], Horowitz–Metzger [68], Madhusu-
danan–Krishnan–Ninan [69], van Krevelen [70] and Wanjun–Yu-
wen–Hen–Cunxin [71]. Integral methods are often more reliable
and are generally preferred to the imprecise differential methods
of kinetic analysis.
planes or 3-D networks, as shown in Fig. 4b for BAOXAL02 [62]. On
the contrary, the presence of cumbersome ligands prevents any
aggregations, the complexes existing therefore as discrete entities
as shown in Fig. 4c [63].
3.5. Thermogravimetric analysis
In the Coats–Redfern method, the equation has been written in
the form:
TGA was employed to follow the thermal behavior of the com-
pounds and to determine various kinetic parameters of thermal
decomposition, such as activation energy (E), frequency factor
ꢀ
ꢁ
gð
a
Þ
AR
bE
2RT
E
E
RT
ꢀ ln
¼ ꢀ ln
1 ꢀ
þ
T2
(A), enthalpy (DH), Gibbs free energy (DG), entropy (DS) etc.
"
#
ꢀ
ꢁ
1ꢀn
3.5.1. Thermal behavior
The thermal behavior of both samples has been evaluated and
representative TG/DSC superimposed curves for one of the
1 ꢀ ð1 ꢀ
a
Þ
AR
bE
2RT
E
E
log
¼ log
1 ꢀ
ꢀ
for n–1
T2ð1 ꢀ nÞ
2:303RT

S. Singh et al. / Polyhedron 31 (2012) 202–209
207
Fig. 3. Packing architectures for (a) 1 and (b) 2. For the sake of clarity, hydrogen atoms have been omitted.
Fig. 4. (a) Cell content for DEGJUV; (b) cell content for BAOXAL02 and (c) atomic arrangement around the Ba atom in BIWBAK. For the sake of clarity, hydrogen atoms have
been omitted.
Table 4
1.0
110
100
90
TGA analysis for different decomposition steps of compounds 1 and 2.
Compound
Transition temperature (°C)
Weight loss (%)
Calculated
0.5
Observed
DME (1)
87.64
164.95
198.27
3.15
15.78
44.53
2.81
17.17
43.20
0.0
80
70
-0.5
-1.0
-1.5
-2.0
Dioxane (2)
111.90
162.82
193.74
13.97
12.70
40.32
12.94
12.98
40.63
60
50
40
energy, n the order of the reaction and T is the temperature in K.
A graphical representation of the left hand side of the above equa-
tions against 1/T gives a straight line with an inclination of ꢀ2.303E/
R and the intercept yields the value of A. In the Madhusudanan
method, the equation used has the form:
30
0
200
400
600
800
1000
T (°C)
Fig. 5. Representative TG/DSC superimposed curves of sample 2 at 10 °C minꢀ1
.
gð
a
Þ
AR
bE
E
RT
ꢀ ln
¼ ꢀ ln
þ 3:7678 ꢀ 1:9206 ln E ꢀ 0:12040
T1:9206
ꢀ
ꢁ
ꢀ
ꢁ
ꢀlogð1 ꢀ
aÞ
AR
bE
2RT
E
E
log
¼ log
1 ꢀ
ꢀ
for n ¼ 1
T2
where the symbols have their usual significance, as described
above. Similar equations were obtained using methods of Wan-
jun–Yuwen–Hen–Cunxin and van Krevelen with different approxi-
mations. For the Wanjun–Yuwen–Hen–Cunxin method
2:303RT
where is A is the Arrhenius constant, b the heating rate in °C minꢀ1
the fraction of mass loss, R the gas constant, E the activation
,
a

208
S. Singh et al. / Polyhedron 31 (2012) 202–209
Table 5
Calculation of activation energy using different methods.
Compound
Horowitz–Metzger
Coats–Redfern
Madhusudanan–Krishnan–Ninan
Wanjun–Yuwen–Hen–Cunxin
van Krevelen
E (kJ/mol)
1
2
169.708
149.555
161.587
140.564
161.890
140.872
161.591
140.596
165.714
145.103
coordinated water molecules is higher than that of hydrogen
bonded water molecules in the second coordination sphere.
Table 6
Thermodynamic decomposition parameters for compounds 1 and 2.
Compound
E
A
D
G
D
H
DS
(J/mol/K)
(kJ/mol)
(minꢀ1
)
(kJ/mol)
(kJ/mol)
4. Conclusion
1
2
161.587
140.564
1.25 ꢂ 1018
120.82
119.82
157.69
136.66
78.61
35.90
7.35 ꢂ 1015
The present synthesis has resulted in the isolation of two new
polymeric barium(II) trichloroacetate compounds 1 and 2. FT-IR
studies reveal bridging trichloroacetate groups in these com-
pounds. Compounds 1 and 2 provide new examples of barium
coordinated to nine oxygen atoms in polymeric chains. These com-
pounds thus may be explored as potential precursors in advanced
material applications because of the preferential decomposition of
1 and 2 into BaCl2.
gð
a
Þ
AR
bE
E
RT
ꢀ ln
¼ ꢀ ln
þ 3:6350 ꢀ 1:8946 ln E ꢀ 1:0014
T1:8946
and for the van Krevelen method
0
@
1
A
E
m
ꢄ
ꢅ
RT
Að0:368=TmÞ
E
RTm
ꢂ
ꢃ
ln gð
a
Þ ¼ ln
þ
þ 1 ln T
E
RTm
Acknowledgements
b
þ 1
Ms. Deepika Saini gratefully acknowledges the meritorious fel-
lowship as a financial assistance from U.G.C., New Delhi, India.
In Horowitz–Metzger method, the expression is:
E
H
RT2m
ln ln gð Þ ¼
a
Appendix A. Supplementary data
where Tm is the peak temperature. The thermodynamic results of
the TG and DTG evaluations employing different methods for the
compounds synthesized are presented in Table 5. The results indi-
cate that the values of all the methods are comparable and the ther-
modynamic data obtained by different methods agree with each
other.
CCDC 819381 and 819382 contain the supplementary crystal-
lographic data for 1 and 2. These data can be obtained free of
charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or
from the Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail:
deposit@ccdc.cam.ac.uk.
The various thermodynamic parameters of decomposition
DH,
enthalpy, S, entropy and G, Gibbs free energy of the compounds
D
D
can be calculated using the following equations once E has been
determined
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