Cobalt(II), nickel(II) and zinc(II) dicarboxylate complexes with hydrazine as bridged ligand: Characterization and thermal degradation

Article abstract of DOI:10.1007/s10973-005-7403-3

Cobalt, nickel and zinc dicarboxylate complexes containing neutral hydrazine as bridged bidentate ligand of the type MX(N₂H ₄)_n where n=1 for X=OOCCH₂COO and n=2 for X=OOCCH₂COO, OOCCH₂CH

Full text of DOI:10.1007/s10973-005-7403-3

Journal of Thermal Analysis and Calorimetry, Vol. 86 (2006) 2, 385–392
COBALT(II), NICKEL(II) AND ZINC(II) DICARBOXYLATE
COMPLEXES WITH HYDRAZINE AS BRIDGED LIGAND
Characterization and thermal degradation
B. N. Sivasankar*
Department of Chemistry, Government Arts College, Uadhagamandalam, The Nilgiris 643 002, India
Cobalt, nickel and zinc dicarboxylate complexes containing neutral hydrazine as bridged bidentate ligand of the type MX(N2H4)n
where n=1 for X=OOCCH2COO and n=2 for X=OOCCH2COO, OOCCH2CH2COO and OOCC(CH2)CH2COO have been prepared
by aqueous reactions. These complexes have been characterized by analytical, spectral and thermal studies. The electronic spectra
coupled with magnetic moments of cobalt and nickel complexes suggest these complexes are of high-spin variety with octahedral
geometry. Infrared spectra indicate the bridging bidentate nature of hydrazine moieties present in both mono-hydrazine and
bis-hydrazine complexes and the dicarboxylate ions coordinate to the metal as bidentate ligand through the monodentate coordina-
tion of each carboxylate ion. However, in the mono-hydrazine metal malonates both carboxylate ions act as bridged ligands.
Simultaneous TG-DTA curves of all the complexes in air resulted in the formation of respective metal oxide as final residue at
low temperatures (300–400°C). These complexes decompose either in single step or decompose through respective metal
carboxylate intermediates. In most of the cases the decompositions are exothermic while in some cases they are violently exother-
mic. The thermal degradation of these complexes in nitrogen atmosphere also gives the respective metal oxide as the final residue.
Keywords: hydrazine metal carboxylates, metal oxides, thermal decomposition
Introduction
Succinate and methylene succinate (itaconate) ions
are known to coordinate with metal ions in a bridged
bidentate fashion. Hence, metal succinate and metal
methylene succinate complexes containing hydrazine
are expected to have three dimensional bridged structure
and hence result in the polymeric complexes.
Hydrazine complexes with carboxylate and di-
carboxylate anions, besides their interesting structure,
provide access to the preparation of metal oxides at
low temperatures. Neutral hydrazine coordinates to the
metal ions in various fashions as either monodentate or
bidentate bridging ligand. In the presence of mono-
and dicarboxylic acids, hydrazine may exist as
hydrazinium cation, N2H+5 which is also capable of co-
ordination with metal ions. The concentration of
hydrazine, pH of the reaction mixture and property of
the metal ion decide the nature of complex formed.
Though mono-protonated hydrazine, hydrazinium
complexes are structurally interesting thermally they
are less effective than neutral hydrazine complexes.
Further, the dicarboxylate ion like malonate
dianion, although simple, exhibit a rather flexible
stereochemistry and variable mode of binding with
metal ions in the crystalline state. It can act as chelat-
ing as well as bridging ligand at the same time. In
many complexes the malonate ion coordinates to the
metal ion as bidentate ligand through COO– coordina-
tion without involving COO– chelation. The versatil-
ity [1] of malonate ion binding of metal ions in the
solid state is shown in Fig. 1.
As a part of our research work we have reported
several bis-hydrazine, tris-hydrazine and hydrazinium
metal carboxylates and hydrazinium metal sulphites
[2–10]. Though, the bis-hydrazine metal malonates and
succinates have been studied and their thermal decom-
positions are mentioned, detailed thermal behavior and
their kinetics have not been reported. Further, mono-
hydrazine complexes are scarce [11] due to the precipi-
tation of bis-hydrazine complexes in basic medium
which are highly stable. Though in many cases the
mono-hydrazine complexes were reported as the inter-
mediates during the thermal degradation of bis-
hydrazine complexes, their instability at that tempera-
ture and their continuous decomposition make them
very difficult to isolate though in the case of bis-
hydrazine nickel glycinate the corresponding mono-
hydrazine complex has been removed during thermal
degradation and studied further [12]. Also bis-hydrazine
metal itaconates which may have similar structure and
thermal behavior to that of bis-hydrazine metal
succinate complexes have not been reported so far.
*
sivabickol@yahoo.com
1388–6150/$20.00
Akadémiai Kiadó, Budapest, Hungary
Springer, Dordrecht, The Netherlands
© 2006 Akadémiai Kiadó, Budapest

SIVASANKAR
Preparation of bis-hydrazine zinc itaconates
dihydrate Zn(OOCC(CH2)CH2COO)(N2H4)2(H2O)2
To an aqueous solution (25 mL) containing zinc nitrate
hexahydrate (2.97 g, 0.01 mol), an aqueous solution of
itaconic acid (1.3 g, 0.01 mol) in 25 mL of deionised wa-
ter was added, the resultant solution was filtered and the
clear solution was evaporated on a water bath to
about 20 mL. To this hot concentrated solution,
hydrazine hydrate was added in excess (2 mL, 0.04 mol).
The crystalline precipitate formed was filtered, washed
first with water then with alcohol and dried in air.
Methods
Fig. 1 Malonate ion bonding with metal ions
The composition of all the complexes were deter-
mined by hydrazine and metal analyses. The
hydrazine content in the complexes were determined
by titrating against 0.025 mol potassium iodate solu-
tion under Andrew’s condition [13]. The metal con-
tents were determined volumetrically using standard
disodium ethylenediaminetetraacetic acid after con-
verting a known amount of the complex into the metal
nitrate hydrate by decomposing the complex with
concentrated nitric acid and evaporating the resultant
solution. This process was repeated for three times for
the complete decomposition so as to destroy the
organic part of the complex.
The magnetic studies of the complex at room tem-
perature were determined by Gouy’s method using
Hg[Co(CNS)4] as calibrant. The solid state electronic
absorption spectra of the complexes in nujol mull were
recorded on a Shimadzu 160A UV-visible spectro-
photometer in the range 200–800 nm. The infrared
spectra of the complexes were recorded on a Perkin-
Elmer 597 spectrophotometer using KBr discs in the
range 200–4000 cm–1. Simultaneous TG-DTA of the
complexes were recorded in static air/nitrogen using a
General V2-2A DuPont 9900 thermal analyzer using
platinum cups as sample holders. About 5–10 mg of
the samples were used for the thermal studies and the
heating rate employed was 10°C min–1. The X-ray
powder diffraction patterns of the thermal residues
were recorded with a Philips pw 1050/70 diffracto-
meter using CuKa and CoKa radiations.
We have thoroughly investigated the structural and
thermal behavior of mono-hydrazine metal malonates
and bis-hydrazine metal malonates, succinates and
methylene succinates and studied the thermal kinetics of
the above complexes. The results of the above investi-
gations are presented in this paper.
Experimental
All the chemicals used were of analar grade
and 99–100% hydrazine hydrate was used in all the
reactions. The solvents were distilled before use.
Bis-hydrazine metal malonates and succinates were
prepared by the methods reported earlier [5].
Preparation of mono-hydrazine metal malonates
M(OOCCH2COO)(N2H4) where M=Co, Ni or Zn
An aqueous solution (50 mL) containing a mixture of
malonic acid (1.04 g, 0.01 mol) and hydrazine hy-
drate (1.5 mL, 0.03 mol) was added slowly with con-
stant stirring to an aqueous solution (50 mL) of re-
spective metal nitrate hydrates (0.01 mol). The
resultant solution was filtered and kept aside at room
temperature. The crystalline complexes settled was
collected after 24 h, washed with water and alcohol
and then dried in air.
Preparation of bis-hydrazine cobalt and nickel
itaconates M(OOCC(CH2)CH2COO)(N2H4)2 where
M=Co and Ni
Results and discussion
The above complexes were prepared by adding an aque-
ous solution (25 mL) containing itaconic acid (1.3 g,
0.01 mol) and hydrazine hydrate (2 mL, 0.04 mol) to an
aqueous solution (25 mL) of cobalt nitrate hexahydrate
or nickel nitrate hexahydrate (2.91 g, 0.01 mol). The
complexes precipitated immediately in the form of pow-
ders were allowed to settle down then filtered, washed
with water and alcohol and dried in air.
Mono-hydrazine and bis-hydrazine metal di-
carboxylates were prepared in basic conditions by
the reaction of respective metal nitrate hydrates with
the aqueous mixture containing hydrazine hydrate
and the respective dicarboxylic acid in appropriate
ratio. The chemical reaction may be represented by
the following general equation.
386
J. Therm. Anal. Cal., 86, 2006

Co(II), Ni(II) AND Zn(II) DICARBOXYLATE COMPLEXES WITH HYDRAZINE AS BRIDGED LIGAND
Magnetic moments and electronic spectra
M(NO3)2×6H2O+H2X+yN2H4×H2O®
MX(N2H4)n+2HNO3+(y–n)N2H4+(y+6)H2O
The magnetic moments of all the cobalt complexes
are in the range 4.5–4.6 BM and for the nickel com-
plexes the magnetic moments are in the
range 3.2–3.3 BM indicate the spin-free octahedral
geometry. The electronic spectrum of cobalt com-
plexes show bands in the region 20950–20980 cm–1
where M=Co, Ni or Zn, y=3 or 4 for X=OOCCH2COO
X=OOC(CH2)2COO
and
OOCC(CH2)CH2COO.
y=4
for
or
Our attempt to prepare bis-hydrazine zinc
itaconate by the above method resulted in the forma-
tion of zinc itaconate. Hence, though in most of the
cases aqueous mixture containing hydrazine hydrate
and respective acid was used as ligands the
bis-hydrazine zinc itaconate dihydrate was prepared
by adding hydrazine hydrate to a hot concentrated so-
lution containing a mixture of zinc nitrate hexa-
hydrate and itaconic acid in 1:1 ratio.
4
which are assigned to the T1g(F)®4T1g(P) transition
which usually split due to spin orbit coupling in the
4T1g(P) state. All the nickel complexes show two
bands at 26300–27700 and 17240–17500 cm–1 which
are attributed to 3A2g®3T1g(F) and 3A2g®3T1g(P) tran-
sitions, respectively. These transitions are character-
istic of octahedral metal(II) complexes [15].
We were also interested in mono-hydrazine com-
plexes of Co(II), Ni(II) and Zn(II) ions with succinate
and itaconate dianions. However, in these cases
when 0.03 mol of hydrazine hydrate was used similar to
the malonic acid always deposited the bis-hydrazine
complexes and incomplete conversion of metal ions to
the complexes was observed. Hence the formation of
mono-hydrazine metal carboxylates and dicarboxylates
are rare except very few cases [14].
Infrared spectra
The infrared spectra of the complexes show two or
three bands in the region 3200–3400 cm–1 which are
ascribable for the N–H stretching frequencies. The
N–N stretching frequency in both mono- and
bis-hydrazine complexes are observed in the re-
gion 960–970 cm–1 which are typical for bidentate
bridging nature of neutral hydrazine molecules [16].
All the bis-hydrazine complexes show two bands in
The composition of the complexes were deter-
mined by hydrazine and metal analyses and the results
of these analyses are summarized in Table 1.
Table 1 Analytical data
Hydrazine/%
Metal/%
calculated
Complex
Colour
Yield/%
found
calculated
16.60
found
30.20
Co(mal)(N2H4)
[C3H6O4N2Co]
rosy red
light blue
colourless
rosy red
violet
90
95
85
90
90
80
95
95
90
85
90
75
16.50
16.50
16.00
28.00
28.20
27.90
26.50
26.40
26.30
25.50
25.50
22.00
30.53
30.45
32.77
26.18
26.12
28.24
24.65
24.58
26.62
23.47
23.40
22.27
Ni(mal)(N2H4)
[C3H6O4N2Ni]
16.62
16.07
28.48
28.51
27.69
26.81
26.83
26.11
25.53
25.55
21.83
30.00
32.00
25.80
25.60
27.80
24.00
24.10
26.20
22.60
23.80
22.00
Zn(mal)(N2H4)
[C3H6O4N2Zn]
Co(mal)(N2H4)2
[C3H10O4N4Co]
Ni(mal)(N2H4)2
[C3H10O4N4Ni]
Zn(mal)(N2H4)2
[C3H10O4N4Zn]
colourless
rosy red
violet
Co(suc)(N2H4)2
[C4H12O4N4Co]
Ni(suc)(N2H4)2
[C4H12O4N4Ni]
Zn(suc)(N2H4)2
[C4H12O4N4Zn]
colourless
rosy red
violet
Co(ita)(N2H4)2
[C5H12O4N4Co]
Ni(ita)(N2H4)2
[C5H12O4N4Ni]
Zn(ita)(N2H4)2(H2O)2
[C5H16O6N4Zn]
colourless
mal – malonate , suc – succinate and ita – itaconate
J. Therm. Anal. Cal., 86, 2006
387

SIVASANKAR
the region 1610–1620 and 1380–1410 cm–1 for nasy
Thermal degradation studies
and nsym stretching of carboxylate ions, respectively,
with Dn separation of 210–240 cm–1 indicating the
monodentate coordination of both carboxylate groups
in the dicarboxylate ion [17]. However, in the
mono-hydrazine complexes these bands are observed
at higher frequencies and splitting is observed in both
the bands. This may be due to the bridging of both
carbonyl oxygen with other metal ions. These obser-
vations along with electronic spectra of mono-
hydrazine complexes suggest the octahedral structure
of these complexes with both bridged hydrazine and
bridged carboxylate ions. In addition bis-hydrazine
zinc complexes shows a band at 3400 cm–1 due to the
presence of O–H stretching of water molecules.
The magnetic, electronic and infrared spectral
data of the complexes are summarized in Table 2.
Based on the analytical, magnetic and spectral studies
the following structures have been assigned for the
mono-hydrazine metal malonate (Fig. 2), bis-hydrazine
metal malonate (Fig. 3) and bis-hydrazine metal
succinate/itaconate (Fig. 4) complexes.
These complexes decompose in different fashion to
give respective metal oxides as end residues. In most
of the cases the intermediate formed undergo continu-
ous degradation and hence the intermediates could
not be isolated for further studies. However, the final
products have been analysed for their metal contents
Fig. 3 Suggested structure of bis-hydrazine metal malonates
Fig. 2 Suggested structure of mono-hydrazine metal malonates
Fig. 4 Suggested structure of bis-hydrazine metal
succinates/itaconates
Table 2 Magnetic, electronic and infrared spectral data
Infrared spectral data
Electronic
Absorption
Assigned
transitions
meff/BM
Complex
spectra/cm–1 maxima/cm–1
nasy(COO) nsym(COO) Dn
nN–N
Co(mal)(N2H4)
Ni(mal)(N2H4)
4.65
3.15
21050
19100
19230
19610
4T1g(F)®4T1g(P)
3A2g®3T1g(F)
3A2g®3T1g(P)
1640
1640
1400
1400
240
240
960
26300
17300
960
Zn(mal)(N2H4)
Co(mal)(N2H4)2
diamagnetic
4.60
–
–
–
–
–
1640
1600
1400
1380
240
220
960
960
20960
4T1g(F)®4T1g(P)
3A2g®3T1g(F)
3A2g®3T1g(P)
26950
17240
Ni(mal)(N2H4)2
3.25
1600
1380
220
960
Zn(mal)(N2H4)2
Co(suc)(N2H4)2
diamagnetic
4.60
–
1600
1610
1380
1380
220
230
970
970
20880
4T1g(F)®4T1g(P)
3A2g®3T1g(F)
3A2g®3T1g(P)
27700
17240
Ni(suc)(N2H4)2
3.35
1600
1380
220
970
Zn(suc)(N2H4)2
Co(ita)(N2H4)2
diamagnetic
4.80
–
1610
1610
1410
1400
200
210
980
970
20500
4T1g(F)®4T1g(P)
3A2g®3T1g(F)
3A2g®3T1g(P)
26680
17500
Ni(ita)(N2H4)2
3.30
1620
1620
1390
1410
230
210
980
975
Zn(ita)(N2H4)2(H2O)2 diamagnetic
–
388
J. Therm. Anal. Cal., 86, 2006

Co(II), Ni(II) AND Zn(II) DICARBOXYLATE COMPLEXES WITH HYDRAZINE AS BRIDGED LIGAND
Bis-hydrazine cobalt malonate
to confirm their composition. The intermediates have
been assigned on the basis of TG mass loss and earlier
studies on hydrazine metal carboxylates [18–20].
One step decomposition of this complex in air in the
temperature range 180–280°C results in the formation
of Co2O3 as the final residue (Fig. 5). DTA shows an
exotherm at 220°C corresponding to this step.
Mono-hydrazine cobalt malonate
This complex undergoes two-step decomposition in air
and gives cobaltic oxide as end product. The first stage
in TG curve corresponds to the loss of one hydrazine
molecule in the temperature range 240–280°C to give
cobalt malonate as intermediate which further decom-
poses at higher temperatures.
Mono-hydrazine nickel malonate
This complex decomposes in three stages to give
nickel oxide The first stage is endothermic as shown
by DTA curve and TG shows the loss of hydrazine
molecule corresponding to this stage. The nickel
malonate further decomposes to give nickel oxalate as
another intermediate which finally gives nickel oxide.
These two stages are exothermic. DTA shows one
endotherm at 220°C and two exotherms at 285
and 340°C. The total mass loss in TG is 60% which is
in accordance with the calculated loss of 61.25%.
Fig. 5 TG and DTA curves of Co(C3H2O4) (N2H4)2
Bis-hydrazine nickel malonate
This complex decomposes in three stages (Fig. 6). The
first stage is endothermic with the peak temperature
at 90°C and in this step 1/2N2H4 is lost in the tempera-
ture range 50–130°C. The intermediate undergoes exo-
thermic degradation to give nickel oxalate, which fur-
ther decomposes exothermically at higher temperatures
(310–350°C) to give nickel oxide. It is interesting to
note that both mono- and bis-hydrazine metal malonate
complexes decompose via nickel oxalate intermediate
and the temperature range corresponding to this stage in
these two cases are almost similar.
Mono-hydrazine zinc malonate
Unlike cobalt and nickel complexes, the zinc complex
shows two distinct endotherms at 190 and 245°C
showing the loss of one hydrazine molecule in two
stages. In the first stage 1/2N2H4 is lost followed by
another 1/2N2H4 molecule to give zinc malonate. Zinc
malonate decomposes in the broad temperature range
(250–450°C) to give zinc oxide. The DTA corre-
sponding to this stage is also broad with a doublet at
the narrow temperature range (410–430°C). How-
ever, TG shows only a continuous decomposition
without any break. The formation of intermediate,
Zn(OOCCH2COO)(N2H4)1/2 is not surprising because
hydrazine complexes with 1/2N2H4 have been pre-
pared and characterised with many metals [21]. The
thermal degradation data of the above three
complexes are summarized in Table 3.
Bis-hydrazine zinc malonate
Zinc complex is found to decompose in two stages,
both exothermic with the DTA peak temperatures 210
and 280°C. These two exotherms are very sharp. The
first step corresponds to the loss of one hydrazine
molecule to give mono-hydrazine zinc malonate inter-
mediate which further decomposes in the temperature
range 260–300°C to give zinc oxide (Fig. 7).
Table 3 Thermal degradation data of M(mal)(N2H4) in air
TG mass loss/%
M
Stage
DTA peak temperature/°C
TG temperature range/°C
Residue
found
calcd
I
II
265(+)
320(–)
240–280
280–340
15.00
56.00
16.60
57.04
Co(mal)
Co2O3
Co
I
II
III
220(+)
285(–)
340(–)
180–280
280–290
290–360
17.00
23.00
60.00
16.62
23.90
61.25
Ni(mal)
Ni(oxa)
NiO
Ni
I
II
III
190(+)
245(+)
410(–)
180–200
200–250
250–440
8.00
16.00
58.00
8.03
16.07
59.21
Zn(mal)(N2H4)1/2
Zn(mal)
ZnO
Zn
(+) – endotherm and (–) – exotherm, mal – malonate (C3H2O4) and oxa – oxalate (C2O4)
J. Therm. Anal. Cal., 86, 2006
389

SIVASANKAR
Fig. 8 TG and DTA curves of Co(C5H4O4) (N2H4)2
Fig. 6 TG and DTA curves of Ni(C3H2O4) (N2H4)2
Fig. 7 TG and DTA curves of Zn(C3H2O4) (N2H4)2
Fig. 9 TG and DTA curves of Ni(C5H4O4) (N2H4)2
Though in the case of mono-hydrazine zinc
malonate the decomposition is multi-step, in the pres-
ent case, since the first step is exothermic the heat gen-
erated in that step decomposes the intermediate in one
step. The observed mass losses are well coincident
with the calculated values.
Bis-hydrazine cobalt itaconate
Thermal traces for this complex shows two-step de-
composition (Fig. 8). In the first stage one hydrazine
molecule is lost to give mono-hydrazine intermediate
which in the temperature range 332–365°C decom-
poses to give Co2O3 as the final residue. Both the
stages are exothermic.
Bis-hydrazine cobalt succinate
Single step decomposition of this complex resulted in
the formation of cobalt oxide. DTA shows an exotherm
at 330°C. The TG mass loss is observed in the tempera-
ture range 275–390°C. The observed mass loss is very
well in agreement with the calculated value.
Bis-hydrazine nickel itaconate
The thermal degradation of this complex is almost
similar to that of cobalt complex showing two-step
decomposition to give nickel oxide as the final resi-
due (Fig. 9). Both the stages are exothermic with the
peak temperatures 303 and 360°C, respectively, for
the first and second stages.
Bis-hydrazine nickel succinate
Nickel complex also decompose in single stage in the
temperature range 190–310°C with an exotherm
at 290°C in DTA.
Bis-hydrazine zinc itaconate dihydrate
The formation of hydrates are not common in the case
of aliphatic mono- and dicarboxylic acids though it is
observed with aromatic carboxylic acids [21, 22] and
hydrazine uranyl carboxylates [23]. However, in the
present case there are clear evidences for the presence
of water molecules. This complex shows an endo-
therm at 251°C with the TG mass loss of 14% clearly
indicates the dehydration. The anhydrous complex
further decomposes exothermically in two stages sim-
Bis-hydrazine zinc succinate
In the first stage this complex liberates one molecule
of hydrazine to give mono-hydrazine derivative. This
stage is very sharp and the degradation takes place be-
tween 290–295°C with an exotherm at 292°C in
DTA. The intermediate further decomposes at higher
temperature (295–370°C) to give zinc oxide.
390
J. Therm. Anal. Cal., 86, 2006

Co(II), Ni(II) AND Zn(II) DICARBOXYLATE COMPLEXES WITH HYDRAZINE AS BRIDGED LIGAND
Table 4 Thermal degradation data of M(mal)(N2H4)2 in air
TG mass loss/%
M
Stage
I
DTA peak temperature/°C
220(–)
TG temperature range/°C
180–280
Residue
Co2O3
found
64.00
calcd
63.11
Co
I
II
III
90(+)
280(–)
330(–)
50–130
265–315
310–350
21.41
34.75
68.00
20.00
33.00
66.78
Ni(mal)(N2H4)1/2
Ni(oxa)
NiO
Ni
I
II
210(–)
280(–)
180–230
260–300
14.00
65.00
13.87
64.85
Zn(mal)(N2H4)
ZnO
Zn
(+) – endotherm and (–) – exotherm, mal – malonate (C3H2O4) and oxa – oxalate (C2O4)
Table 5 Thermal degradation data of M(suc)(N2H4)2 in air
TG mass loss/%
M
Stage
DTA peak temperature/°C
TG temperature range/°C
Residue
found
calcd
68.73
68.73
Co
Ni
I
I
330(–)
290(–)
275–390
190–310
70.00
70.00
CoO
NiO
I
II
292(+)
360(–)
290–295
295–370
14.00
66.00
13.05
66.86
Zn(suc)(N2H4)
ZnO
Zn
(+) – endotherm and (–) – exotherm, suc – succinate (C4H4O4)
Table 6 Thermal degradation data of bis-hydrazine metal itaconates and bis-hydrazine zinc itaconate dehydrate in air
TG mass loss/%
M
Stage
DTA peak temperature/°C
TG temperature range/°C
Residue
found
calcd
I
II
290(–)
361(–)
250–332
332–365
24.00
64.00
25.43
65.79
Co(ita)
Co2O3
Co
Ni
I
II
303(–)
360(–)
270–342
342–372
27.00
70.00
25.53
70.34
Ni(ita)
NiO
I
II
III
251(+)
306(–)
470(–)
183–262
262–433
433–513
14.00
32.00
57.00
12.23
33.99
57.45
Zn(ita)(N2H4)2
Zn(ita)
ZnCO3
Zn
(+) – endotherm and (–) – exotherm, ita – itaconate (C5H4O4)
ilar to the cobalt and nickel complexes to give zinc
carbonate as the final residue and zinc itaconate being
the intermediate.
The intermediates formed during the thermal
degradation of the complexes were isolated by sub-
jecting the samples to controlled heating and remov-
ing the different intermediates expected from the ther-
mal analyses at the particular temperatures as shown
by the TG-DTA traces (Fig. 10). The metal and
hydrazine contents were determined for the interme-
diates containing hydrazine are in good agreement
with the expected values. In the case of simple metal
carboxylate intermediates viz., metal malonates,
metal succinates and metal itaconates, their metal
contents were determined which are in accordance
with the theoretical values. Further, the infrared spec-
tra of these intermediates, the metal carboxylates are
also found to be superimposable to that of the authen-
tic samples. The final degradation residues were also
identified by X-ray powder diffraction patterns.
Fig. 10 TG and DTA curves of Zn(C5H4O4) (N2H4)2
Thermal degradation data of bis-hydrazine metal
malonates, bis-hydrazine metal succinates and bis-
hydrazine metal itaconates are summarized in Ta-
bles 4–6, respectively.
The X-ray powder diffraction patterns of NiO
obtained as a TG residue with malonate, succinate
and itaconate complexes are shown in Fig. 11 as the
representative example.
J. Therm. Anal. Cal., 86, 2006
391

SIVASANKAR
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Received: October 19, 2005
Accepted: November 18, 2005
OnlineFirst: June 27, 2006
DOI: 10.1007/s10973-005-7403-3
392
J. Therm. Anal. Cal., 86, 2006