Trimellitate complexes of divalent transition metals with hydrazinium cation thermal and spectroscopic studies

Article abstract of DOI:10.1007/s10973-009-0459-8

New dihydrazinium divalent transition metal trimellitate hydrates of empirical formula (N₂H₅)₂M(Html) ₂· nH₂O, where n - 1 for M - Co or Ni, and n - 2 for M - Mn, Zn, or Cd (H₃tml - trimell

Full text of DOI:10.1007/s10973-009-0459-8

J Therm Anal Calorim (2010) 100:955–960
DOI 10.1007/s10973-009-0459-8
Trimellitate complexes of divalent transition metals
with hydrazinium cation
Thermal and spectroscopic studies
S. Vairam Æ T. Premkumar Æ S. Govindarajan
Received: 19 May 2009 / Accepted: 2 September 2009 / Published online: 19 September 2009
´
´
Ó Akademiai Kiado, Budapest, Hungary 2009
Abstract New dihydrazinium divalent transition metal
trimellitate hydrates of empirical formula (N2H5)2M(Html)2Á
nH2O, where n = 1 for M = Co or Ni, and n = 2 for
M = Mn, Zn, or Cd (H3tml = trimellitic acid), and mono-
Introduction
Benzene-1,2,4-tricarboxylic acid, commonly referred to as
trimellitic acid, due to the presence of a pair of adjacent
carboxylic acid groups as in phthalic acid with an additional
carboxylic acid group in it, possesses a good ligating ability.
Its dianionic behavior seems to resemble the coordinating
nature of phthalates and terephthalates. The complexation
of lanthanides with trimellitic acid has been studied po-
tentiometrically and calorimetrically [1] and in terms of
basicity, the statistical effect of unbound carboxylate groups
and steric factors [2]. The stereochemistry of the trimellitate
anion shows that it functions as a bidentate ligand with
adjacent carboxylate groups in lanthanide complexes.
Trimellitates of Sc(III) and Cu(II) have also been prepared
and characterized by thermal studies [3, 4]. Scandium
trimellitate, Sc(tml)Á4H2O, undergoes decomposition to
give Sc2O3 and C as final products. Copper trimellitate
pentahydrate, Cu3(tml)2Á5H2O, decomposes in two steps
giving CuO as the final product. The burning of organic
anion is accompanied by a strong exothermic effect.
hydrazinium cadmium trimellitate, [(N2H5)Cd(Html)1.5
Á
2H2O] have been prepared and characterized by physico-
chemical methods. Electronic spectroscopic, and magnetic
moment data suggest that Co and Ni complexes adopt an
octahedral geometry. The IR spectra confirm the presence
of monodentate carboxylate anion (Dm = masy(COO-) -
m
sym(COO-) [ 190 cm-1) and coordinated N2H5 ion
?
(mN–N 1015 - 990 cm-1) in all the complexes. All the
complexes undergo endothermic decomposition eliminating
CO2 in the temperature region 200–250 °C, followed by
exothermic decomposition (in the range of 500–570 °C) of
organic moiety to give the respective metal carbonate as the
end products except nickel and cobalt complexes, which
leave respective metal oxides. X-ray powder diffraction
patterns reveal that Ni and Co complexes are isomorphous as
are those of, Zn(II) and Cd(II) of the type, (N2H5)2M(Html)2Á
2H2O.
Hydrazine, the simplest diamine even after getting
?
protonated as N2H5 evinces its coordinating ability. A
Keywords Chemical synthesis Á Inorganic compounds Á
Thermogravimetric analysis (TGA) Á X-ray diffraction
variety of complexes containing coordinated and uncoor-
dinated hydrazinium moieties, such as hydrazinium metal
oxalate [5, 6], malonate [7], and phthalate [8] have been
studied. Thermal reactivity of metal carboxylates with
hydrazine is of increasing interest, since they serve as
precursors to fine-particle oxide materials and metal car-
bonates [5–16]. Though a very few simple metal com-
plexes of trimellitate have been reported, yet, a detailed
study of trimellitic acid complexes of transition metals with
hydrazinium cation with special emphasis on its thermal
reactivity has not been attempted so far. In this paper, we
report for the first time the synthesis, spectroscopic, and
S. Vairam Á T. Premkumar Á S. Govindarajan (&)
Department of Chemistry, Bharathiar University,
Coimbatore 641046, India
e-mail: drsgovind@yahoo.co.in
Present Address:
T. Premkumar
Department of Materials Science and Engineering,
Gwangju Institute of Science and Technology, 1 Oryong-dong,
Buk-gu, Gwangju 500-712, South Korea
123

956
S. Vairam et al.
thermal studies on divalent transition metal complexes of
trimellitic acid with hydrazine.
titrating against standard KIO3 (0.025 mol dm-3) under
Andrews conditions. Metal contents were determined by
titrating with EDTA (0.01 mol dm-3) after decomposing
the complexes with conc. HNO3. The elements were
determined by microelemental analysis. Electronic spectra
in the UV–visible region were obtained using a Hitachi
Perkin Elmer 20/200 recording spectrophotometer by dis-
persing the solid samples in Nujol. IR spectral data of the
complexes were recorded as KBr pellets using a Perkin
Elmer 597 spectrometer. The magnetic susceptibility of the
complexes was measured (298 K) using a vibrating sample
magnetometer (VSM E.G&G model 155) in the magnetic
field from 2 to 10 KG and appropriate corrections were
also made. The X-ray diffractograms of the complexes
were recorded using a Philips X ray diffractometer (model
p N 1050/70) employing Cu Ka radiation with a nickel
filter. The simultaneous TG–DTA experiments were car-
ried out in air, using STA 1500 thermal analyzer at the
heating rate of 10 °C per min. Platinum cups were
employed as sample holders and alumina as reference. The
temperature was ambient to 700 °C.
Experimental
Preparation of (N2H5)2M(Html)2ÁnH2O where
M = Mn, Co, Ni, Zn, and Cd
To an aqueous solution of trimellitic acid (0.428 g, 2 mmol
in 40 mL distilled water), hydrazine hydrate of 99–100%
purity (0.2 g, 4 mmol) was added and heated over hot water
bath at 80 °C, for about 15 min. Then to the clear solution
obtained at pH 3.5, was added with vigorous stirring, the
respective metal nitrate hydrate (1 mmol, e.g., 0.292 g of
Co(NO3)2Á6H2O). The solution was then reduced to half of
its volume by heating over boiling water bath and allowed
to stand at room temperature. Slowly flake like crystals of
the complex appeared after a couple of days and settled
down. They were filtered, washed with alcohol and ether,
and air-dried. The same final product was obtained when the
above experimental procedure was pursued at room tem-
perature; however, the products were obtained after 4 days.
Results and discussion
Preparation of (N2H5)Cd(Html)1.5Á2H2O
The results of chemical analysis of the complexes are given
in Table 1 and are best fit with the proposed compositions
viz., (N2H5)2M(Html)2ÁnH2O, where M = Co and Ni,
The above procedure was followed taking trimellitic acid,
hydrazine hydrate (99–100% pure), and cadmium nitrate in
the molar ratio, 2:4:1 at room temperature. The solution
was left undisturbed without heating. Slowly a crystalline
precipitate was formed after 1 day and settled down. It was
filtered, washed with alcohol and ether, and air-dried.
n = 1; M = Mn, Zn or Cd, n = 2, and (N2H5)Cd(Html)1.5
Á
2H2O. The complexes are isolated as solids, air stable and
are insensitive to light. All the complexes are insoluble in
water and most of the organic solvents like alcohol, chlo-
roform, and acetone. While Co and Ni complexes are
monohydrated, rest of the complexes are dihydrated. Cad-
mium forms two different products with trimellitic acid in
the same ratio, but with different experimental condition.
The dihydrazinium compound of cadmium was obtained
Physicochemical techniques
The stoichiometry of the complexes was fixed by chemical
analysis [17]. Hydrazine content was determined by
Table 1 Analytical, elemental and IR data of trimellitate complexes
Complex (color)
Found (calculated)/%
Carbon Hydrogen Nitrogen
IR data/cm-1
Hydrazine Metal
mCOO
(asym)
mCOO
(sym)
mCO (free
COOH)
mN–N
(N2H5)2Co(Html)2ÁH2O (pink) 38.56 (38.64) 3.48 (3.58) 9.90 (10.02) 11.5 (11.40) 10.3 (10.54) 1607
(N2H5)2Ni(Html)2ÁH2O (green) 38.42 (38.66) 3.79 (3.58) 9.98 (10.02) 11.6 (11.5) 10.4 (10.50) 1607
1373
1373
1371
1685
1685
1697
1008
1016
993
(N2H5)2Zn(Html)2Á2H2O (dirty 36.93 (37.03) 3.81 (3.77) 9.21 (9.60) 10.6 (10.97) 11.3 (11.20) 1607
white)
(N2H5)2Cd(Html)2Á2H2O (dull
34.01 (34.26) 3.62 (3.48) 8.75 (8.89)
9.9 (10.15) 17.6 (17.83) 1620
1373
1369
1369
1697
1695
1694
987
989
987
white)
(N2H5)2Mn(Html)2Á2H2O (pale 37.52 (37.70) 3.81 (3.84) 9.72 (9.77) 10.9 (11.17) 9.8 (9.59). 1560
brown)
(N2H5)Cd(Html)1.5Á2H2O (dull 32.54 (32.83) 3.01 (3.04) 5.59 (5.67)
6.5 (6.49) 23.5 (2278) 1607
white)
123

Trimellitate complexes of divalent transition metals with hydrazinium cation
957
from the hot concentrated solution, whereas monohydrazi-
nium compound isolated without concentrating the solution.
1697–1685 cm-1 in their spectra, which are characteristic
of free carboxyl groups [23].
Thermal analysis
Electronic spectra and magnetic moment
Simultaneous TG–DTA data have been presented in
Table 2. The compositions of the intermediates and the
final products are those, which best fit with the observed
mass losses in the TG studies. Thermogravimetric results
are in good agreement with the corresponding DTA data.
The TG–DTA curves of prepared complexes are given in
Fig. 1.
The electronic spectrum shows absorptions at 14985 cm-1
29410 cm-1 for nickel complex which are assigned to the
,
3
3
3
3
transitions, A2g ? T1g(F); A2g(F) ? T1g(P) and that
for cobalt complex, shows kmax at 14490 cm-1
,
4
4
22220 cm-1 which are assigned to T1g(F) ? A2g(P);
4
4T1g(F) ? T1g(P). The absorption maxima at 37040 cm-1
for nickel and 34480 cm-1 for cobalt are charge transfer
bands. These are characteristic of octahedral coordination
around Ni(II) and Co(II) [18]. The magnetic moments of
cobalt and nickel complexes were found to be 5.1 and
3.1 BM, respectively, which corresponds to high spin
octahedral geometry [19].
(N2H5)2M(Html)2ÁH2O where M = Ni or Co
The DTA curves of these complexes show two peaks
corresponding to a two step decomposition of the com-
plexes as shown by TG. The first endothermic peak at
235 °C (Ni) and 230 °C (Co) is assigned to simultaneous
decarboxylation of two free COOH groups and dehydration
in the complexes. The second peak is an exothermic peak
at 480 °C (Ni) and 500 °C (Co) indicating the complete
decomposition of the complexes leading to the formation
of metal oxides.
IR spectra
The IR spectra of all complexes are summarized in
Table 1. The absorption bands in the range 1015–
990 cm-1 for N–N stretching establish the presence of
coordinated N2H5?. They also show the absorption bands
at 3300–3280 cm-1 owing to N–H stretching [20, 21]. The
presence of bands at 1607 cm-1 and at 1370 cm-1 in the
spectra assigned to asymmetric and symmetric stretching
of C=O of carboxylates and the difference between the
above two, 200 cm-1, supports the monodentate [22]
coordination of the carboxylate groups. The acid behaves
as dianion in the complexes showing strong absorptions at
(N2H5)2M(Html)2Á2H2O where M = Mn, Zn, or Cd
The DTA curves of these complexes exhibit an endother-
mic peak at 213, 217, and 220 °C, and exothermic peak at
573, 501, and 504 °C for Mn, Zn, and Cd complexes,
respectively. Endothermic peaks are assigned to simulta-
neous decarboxylation of the free COOH groups and
Table 2 Thermal data of trimellitate complexes
Complex
DTA peak Temp/°C
Thermogravimetry
Decomposition products
Temp. range/°C
Mass loss/%
Obsd.
Calcd.
(N2H5)2Co(Html)2ÁH2O
(N2H5)2Ni(Html)2ÁH2O
(N2H5)2Zn(Html)2Á2H2O
(N2H5)2Cd(Html)2Á2H2O
(N2H5)2Mn(Html)2Á2H2O
N2H5Cd(Html)1.5Á2H2O
230 (?)
500 (-)
235 (?)
480 (-)
210 (?)
570 (-)
220 (?)
505 (-)
215 (?)
501(-)
200–285
285–740
200–335
335–715
190–325
325–750
175–240
240–750
200–285
285–750
236–305
305–750
18.9
84.3
19.0
86.0
21.0
80.0
16.7
70.0
18.5
76.7
15.50
72.00
18.90
85.60
18.90
86.60
21.26
78.50
16.80
72.65
18.50
79.94
17.00
69.52
(N2H5)2Co(p-C6H4(COO)2)2
Co3O4
(N2H5)2Ni(p-C6H4(COO)2)2
NiO
(N2H5)2Zn(p-C6H4(COO)2)2
ZnCO3
(N2H5)2Cd(p-C6H4(COO)2)2 H2O
CdCO3
(N2H5)2Mn(p-C6H4(COO)2)2H2O
MnCO3
249 (?)
522 (-)
N2H5Cd(p-C6H4(COO)2)1.5 H2O
1/2(CdO ? CdCO3)
123

958
S. Vairam et al.
Exo
Exo 160
140
Fig. 1 TG-DTA curves of
a (N2H5)2Co(Html)2ÁH2O,
b (N2H5)2Ni(Html)2ÁH2O,
c (N2H5)2Mn(Html)2Á2H2O,
d (N2H5)2Zn(Html)2Á2H2O,
e (N2H5)2Cd(Html)2Á2H2O, and
f (N2H5)Cd(Html)1.5Á2H2O
TG
TG
100
80
60
40
20
100
120
80
60
Endo
80
Endo
80
60
40
0
40
20
DTA
DTA
0
(a)
(b)
800
0
200
400
600
800
0
200
400
600
Temperature/°C
Temperature/°C
120
100
Exo 120
80
Exo
160
120
80
40
0
TG
TG
100
80
Endo
80
Endo
60
40
20
60
40
20
40
20
DTA
DTA
(c)
800
(d)
0
200
400
600
0
200
400
600
800
Temperature/°C
Temperature/°C
Exo
120
80
40
0
Exo
TG
120
100
80
60
40
20
0
100
80
TG
Endo
Endo
80
60
40
60
40
20
DTA
DTA
(f)
(e)
800
0
200
400
600
0
200
400
600
800
Temperature/°C
Temperature/°C
800
Fig. 2 XRD patterns of
trimellitate complexes
250
200
150
100
50
700
600
500
400
300
200
100
0
a (N2H5)2Co(Html)2ÁH2O,
b (N2H5)2Ni(Html)2ÁH2O,
c (N2H5)2Mn(Html)2Á2H2O,
d (N2H5)2Zn(Html)2Á2H2O,
e (N2H5)2Cd(Html)2Á2H2O, and
f (N2H5)Cd(Html)1.5Á2H2O
(a)
(b)
0
20
30
40
50
60
70
80
90
20
30
40
50
60
70
80
90
2θ/deg
2θ/deg
900
800
700
400
600
500
300
200
400
300
200
100
0
100
0
(c)
90
(d)
90
20
30
40
50
60
70
80
20
30
40
50
60
70
80
2θ/deg
2θ/deg
350
500
400
300
250
200
150
300
200
100
0
100
50
0
(e)
(f)
20
30
40
50
60
70
80
90
20
30
40
50
60
70
80
90
2θ/deg
2θ/deg
(N2H5)Cd(Html)1.5Á2H2O
dehydration of the complexes. In the case of Mn and Cd
complexes, one water molecule is removed first and the
other subsequently. Exothermic peaks depict the decom-
position of the complexes leading to the formation of
carbonates in the temperature range 500–573 °C.
This complex also shows two peaks in its DTA curve, an
endothermic at 215 °C revealing the decomposition of the
complex liberating carbon dioxide and water molecules
123

Trimellitate complexes of divalent transition metals with hydrazinium cation
959
simultaneously and an exothermic peak at 522 °C corre-
sponding to the decomposition of the complex leading to
the formation of mixture of metal oxide and carbonate.
Our attempt to separate the intermediates was failed due
to their continuous decomposition as evident from the TG.
Hence, we have tried to assign the possible intermediates
as observed from the TG mass losses, which are in accord
with the calculated mass losses. Though the anion is the
same in all the complexes, the thermal decomposition
temperatures and the end product of the individual com-
plexes vary depending upon the composition and the metal
ion.
also isomorphic with each other and the other two, Mn(II)
and Cd (II) complexes are of different crystalline pattern.
Conclusions
The reaction between the transition metal nitrates with the
mixture of hydrazine and trimellitic acid at pH 3.5 yielded
complexes of the formulae, (N2H5)2M(Html)2ÁnH2O where
M = Mn, Co, Ni, Zn, and Cd and n = 1 or 2 and
(N2H5)Cd(Html)1.5Á2H2O. The analytical, IR spectro-
scopic, and thermal data substantiate the formulation of the
complexes. All the complexes undergo endothermic
decomposition eliminating CO2 in the temperature region
200–250 °C, and an exothermic decomposition in the range
of 500–570 °C. It is interesting to note that trimellitic acid
behaves as a dianion with one free carboxylic group in all
the complexes which manifest the carbonyl stretching
frequency in the range of 1697–1685 cm-1 in their IR
spectra and decarboxylation during its thermal decompo-
sition. The electronic spectroscopic data and magnetic
moment value confirm their geometry and coordination
number. Dihydrazinium metal trimellitate complexes have
octahedral geometry and monohydrazinium cadmium
trimellitate, the tetrahedral geometry. The insoluble nature
in any solvent indicates their polymeric nature.
X-ray powder diffraction
X-ray powder diffraction pattern of the complexes are
shown in Fig. 2. A comparison of the above indicates that
the Ni and Co complexes are isomorphic with each other,
Zn (II) and Cd (II) of the type, (N2H5)2M(Html)2Á2H2O are
(a)
O
O
O
O
O
O
+
N2H5
The structure of trimellitic acid is comparable with the
structures of the phthalic acids (all isomers) while con-
sidering the positions of any two carboxyl groups. While
extending the comparison to their complexation behavior
with transition metal ions, it is observed that it resembles
terephthalic acid complexes [8]. The involvement of car-
boxylic groups in ortho positions in complexation to metal
leading to polymeric structures cannot be obviated. Even
then, it is more probable and justifiable that only para
carboxylic groups of trimellitic acid participate in com-
plexation due to steric constraints. The structures of the
complexes are proposed as given in Fig. 3. It is worth
mentioning here that other isomers of the trimellitic acids
at the same pH do not yield hydrazinium complexes,
probably due to the substituent effects of carboxyl groups.
O
O
HO
OH
O
O
M
O
O
OH
HO
O
O
+
N2H5
O
O
O
O
O
O
+
N2H5
(b)
O
Cd
OH
O
O
O
O
HO
O
O
O
O
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O
O
OH
O
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