Spectral, thermal and X-ray studies on some new bis-hydrazine metal glyoxylates and bis-hydrazine mixed metal glyoxylates

Article abstract of DOI:10.1016/j.tca.2006.10.001

Bis-hydrazine complexes of metal glyoxylates and mixed metal glyoxylates of 3d-metal ions of the formula M(OOCCHO)₂(N₂H₄)₂, where M = Mg, Mn, Co, Ni, Cu, Zn or Cd and M_1/3Co_2/3(OOCCHO)₂(N₂H₄)₂, where M = Mg, Mn, Ni, Zn or Cd, respectively, have been prepared and studied. The compositions of the complexes have been determined by chemical analyses. The magnetic moments and electronic spectra suggest a high-spin octahedral geometry for the metal complexes. Infrared spectral data indicate the bidentate bridging by hydrazine molecules and monodentate coordination by glyoxylate ions in both the metal and mixed metal compounds. Thermogravimetry and differential thermal analyses in air have been used to study the thermal behaviour of the complexes. The simultaneous TG-DTA traces of all the complexes show multi-step degradation and the final products are found to be the respective metal oxides in the case of metal complexes and metal cobaltites in the case of mixed metal complexes. The final residues were identified by their X-ray powder diffraction patterns. X-ray powder diffraction patterns of the complexes including mixed metal complexes are almost superimposable with in each of the series indicating isomorphism. The metal cobaltites MCo₂O₄, where M = Mg, Mn, Ni, Zn or Cd were also prepared by decomposing the respective mixed metal complex in a pre-heated silica crucible at about 300 °C, and their identities were confirmed by chemical analyses, infrared spectra and X-ray powder diffraction.

Full text of DOI:10.1016/j.tca.2006.10.001

Thermochimica Acta 452 (2007) 20–27
Spectral, thermal and X-ray studies on some new bis-hydrazine metal
glyoxylates and bis-hydrazine mixed metal glyoxylates
L. Vikram, B.N. Sivasankar∗
Department of Chemistry, Government Arts College, Ooty, The Nilgiris, Udhagamandalam 643002, India
Received 21 November 2005; received in revised form 29 September 2006; accepted 1 October 2006
Available online 10 October 2006
Abstract
Bis-hydrazine complexes of metal glyoxylates and mixed metal glyoxylates of 3d-metal ions of the formula M(OOCCHO)2(N2H4)2, where
M = Mg, Mn, Co, Ni, Cu, Zn or Cd and M1/3Co2/3(OOCCHO)2(N2H4)2, where M = Mg, Mn, Ni, Zn or Cd, respectively, have been prepared and
studied. The compositions of the complexes have been determined by chemical analyses. The magnetic moments and electronic spectra suggest
a high-spin octahedral geometry for the metal complexes. Infrared spectral data indicate the bidentate bridging by hydrazine molecules and
monodentate coordination by glyoxylate ions in both the metal and mixed metal compounds. Thermogravimetry and differential thermal analyses
in air have been used to study the thermal behaviour of the complexes. The simultaneous TG-DTA traces of all the complexes show multi-step
degradation and the final products are found to be the respective metal oxides in the case of metal complexes and metal cobaltites in the case of
mixed metal complexes. The final residues were identified by their X-ray powder diffraction patterns. X-ray powder diffraction patterns of the
complexes including mixed metal complexes are almost superimposable with in each of the series indicating isomorphism. The metal cobaltites
MCo2O4, where M = Mg, Mn, Ni, Zn or Cd were also prepared by decomposing the respective mixed metal complex in a pre-heated silica crucible
at about 300 ◦C, and their identities were confirmed by chemical analyses, infrared spectra and X-ray powder diffraction.
© 2006 Elsevier B.V. All rights reserved.
Keywords: Bis-hydrazine metal glyoxylates; Mixed metal complexes; Metal oxides; Metal cobaltites; TG-DTA; X-ray powder diffraction
1. Introduction
plexesarewidelyusedinthepreparationofmetalpowders, metal
oxides and mixed metal oxides [5,7,20–22] due to their ther-
mal instability. Inspite of many bis-hydrazine and hydrazinium
metal carboxylates and mixed metal carboxylates being known
and used as precursors for metal oxides and mixed metal oxides
such as ferrites, cobaltites, manganites, chromites, etc., only a
few complexes like hydrazinium and bis-hydrazine metal and
mixed metal hydrazine carboxylates are known to undergo auto
catalytic decomposition once ignited [23,24]. Such precursors
result in the formation of voluminous, foamy and fine particle
oxide materials with high surface area which are the essential
characteristics of a metal oxide to be an effective catalyst.
In continuation of our earlier work on hydrazine metal car-
boxylates, in this paper we wish to report several, hitherto
unknown bis-hydrazine metal glyoxylates and similar mixed
metal complexes, which show self-sustaining auto decompo-
sition behaviour. This paper describes the preparation, char-
acterization, thermal and X-ray powder studies on the above
mentioned complexes and also the preparation and characteri-
zation of metal cobaltites.
Hydrazine complexes of the first row transition metal ions
with a variety of carboxylic acids have been reported in the
literature [1]. These include simple aliphatic mono-carboxylic
acids [2–5], aliphatic dicarboxylic acids [6–10], aromatic mono-
and dicarboxylic acids [11,12], aliphatic and aromatic hydroxy
acids [13,14], halo acids [15], amino acids [16–18] and hete-
rocylic carboxylic acids [19]. Among these a few carboxylic
acids are capable of forming tris-hydrazine complexes besides
the bis-hydrazine complexes [17]. While the hydrazinium metal
carboxylates and their hydrates are crystalline solids and many
of them are water soluble, the bis- and tris-hydrazine complexes
are either microcrystalline or amorphous powders and are insol-
uble in water.
Though hydrazinium complexes are gaining attention due to
their interesting structures and scarcity, the bis-hydrazine com-
∗
Corresponding author.
E-mail address: sivabickol@yahoo.com (B.N. Sivasankar).
0040-6031/$ – see front matter © 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.tca.2006.10.001

L. Vikram, B.N. Sivasankar / Thermochimica Acta 452 (2007) 20–27
21
2. Experimental
water bath to about 20 ml. To this hot concentrated solution
hydrazine hydrate (6 ml, 0.12 mol) in 10 ml of water was added
with stirring. After the addition, the clear solution was allowed to
stand at room temperature. Highly crystalline mixed metal com-
plexes formed slowly after 30 min was filtered using a vacuum
pump after 1 h, washed twice with water and then with alco-
hol and finally dried inside a vacuum desiccator. With Co–Cu
mixture a dirty brown complex was obtained with indefinite
composition.
The solvents were distilled prior to use and double distilled
water was used for the preparation and chemical analyses. All
the chemicals used were of AR grade received from SD Fine
Chemicals. The hydrazine hydrate, 99–100% was used as such
as received.
2.1. Preparation of M(OOCCHO)2(N2H4)2
An aqueous solution (30 ml) containing a mixture of gly-
oxylic acid monohydrate (1.84 g, 0.02 mol) and hydrazine
hydrate (2 ml, 0.04 mol) was added slowly with constant stirring
to an aqueous solution (30 ml) of the respective metal nitrate
hydrate (0.01 mol). The resulting clear solution was filtered
through a Whatman filter paper and left aside at room tempera-
ture. After 24 h the complex settling as crystalline powder was
filtered under suction in a vacuum pump, washed several times
first with water and then with alcohol and finally dried in air.
The above procedure was also repeated with 0.02 mol of
hydrazine hydrate instead of 0.04 mol. This method also resulted
in the formation of the same complexes. However, with the other
carboxylic acids reported so far this method did not yield the
complexes.
2.3. Preparation of metal cobaltites
The mixed metal complexes were heated at 300 ◦C in a pre-
heated silica crucible for about 5 min to yield the respective
metal cobaltites.
Alternatively the mixed metal complexes were ignited and
allowed to undergo autocatalytic decomposition. This decompo-
sition was complete within 2 min. The resulting residue, metal
cobaltites were collected.
2.4. Physico-chemical techniques
The metal contents in the complexes were determined by
EDTA titration [25] after decomposing a known weight of
the complex with nitric acid for atleast three times to destroy
the organic matter. In the case of mixed metal complexes
after decomposing a known amount of the complex with nitric
acid, the residue was dissolved in water and the cobalt con-
tent in the solution was determined by separating cobalt as
Co(C10H6ONO)3 complex using ␣-nitroso ␤-napthol [26]. The
divalent metal ion contained in the filtrate of this separation
was estimated by titration with standard EDTA solution. The
hydrazine content in the complex was determined volumetri-
cally using a standard KIO3 solution (0.025 mol dm−3) under
Andrew’s conditions [25]. The cobalt and metal contents present
in the metal cobaltites also were determined by the above method
after dissolving the respective cobaltites in a minimum amount
of nitric acid.
The above glyoxylate complexes were also prepared by
adding excess hydrazine hydrate (2 ml, 0.04 mol) in 10 ml of
water to an aqueous solution of the respective metal glyoxy-
lates.
In the latter method, the respective metal nitrate hydrate
(0.01 mol) and glyoxylic acid monohydrate (1.84 g, 0.02 mol)
were separately dissolved in 25 ml of water each and the solu-
tions were mixed. The resulting solution after filtration was
slowly evaporated on a water bath to about 20 ml. To this
hot solution hydrazine hydrate (2 ml, 0.04 mol) in 10 ml water
was added with constant stirring. The clear viscous liquid was
allowed to stand at room temperature. The crystalline complexes
settling down after 30–45 min were filtered, washed several
times with water and then with alcohol and dried in air.
The room temperature magnetic moment measurements were
carried out in a Gouy’s balance using Hg[Co(SCN)4] as the
calibrant. Diamagnetic corrections were applied using Pascal’s
constants. The solid-state absorption spectra of the complexes
in nujol mull were recorded on a Shimadzu UV–visible 240 A
spectrophotometer. The infrared spectra of the complexes were
recorded on a Perkin-Elmer 597 spectrophotometer in the range
4000–400 cm−1 using KBr discs of the samples. The simulta-
neous TG-DTA of the samples in air were recorded using a
Netzsch STA 1500 simultaneous thermal analysis system, ver-
sion V4.30, PL thermal sciences Division, UK using 2.5 mg of
the samples with platinum cups as sample holders. The heating
rate was 10 ◦C/min. The X-ray powder diffraction patterns of the
complexes were recorded using a Philips X-ray diffractometer
model PW 1050/70 employing Cu K␣ radiation ◦of wavelength
2.2. Preparation of M1/3Co2/3(OOCCHO)2(N2H4)2
Among the above three methods described for the prepara-
tion of bis-hydrazine metal glyoxylates the third method was
followed for the preparation of mixed metal complexes. Though
in all the three methods the complexes got precipitated from the
clear solutions, the last method was preferred due to the high
yield of the complexes.
Initially all the metal nitrate hydrate solutions were prepared
separately in standard flasks. The concentrations of metal ions
were determined by complexometric titrations and gravimetric
analysis [25].
The mixed metal solutions were prepared by mixing respec-
tive metal nitrate (0.01 mol) and cobalt nitrate hexahydrate
(5.94 g, 0.02 mol) by pipetting out the required volumes of the
standard metal nitrate solutions. To the resulting solution gly-
oxylic acid monohydrate (5.52 g, 0.06 mol) in 20 ml of water
was added. This solution after filtration was evaporated on a
◦
˚
λ = 1.5406 A and recorded between the 80 and 10 , 2Θ values at
a scan rate of 2◦ min−1.The X-ray patterns of the cobaltites were
˚
recorded with the Co K␣C radiation of wavelength 1.7902 A
using Philips X-ray diffractometer (model PW 1050/70).

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L. Vikram, B.N. Sivasankar / Thermochimica Acta 452 (2007) 20–27
3. Results and discussion
Though in many cases the aqueous reaction of the metal
nitrate hydrate, the respective mono-carboxylic acid and
hydrazine hydrate in 1:2:2 ratio did not yield the complex, due
to the solution being almost neutral and the adducts being pre-
cipitated only from the basic solution, we were able to isolate
the bis-hydrazine metal glyoxylates with the above ratio of the
reagents. However, the yields were found to be very low. The
chemical reaction may be represented as follows:
Hydrazine hydrate in aqueous solution is expected to undergo
neutralization reaction with glyoxylic acid to give hydrazinium
glyoxylate, OHCCOON2H5. However, our attempt to isolate
this ligand in solid state was not successful and only a dark
brown viscous liquid was obtained.
Hence an aqueous mixture of glyoxylic acid and hydrazine
hydrate in appropriate ratio was used as the ligand in the prepa-
ration of complexes. The thermal instability of bis-hydrazine
complexeshavebeenexploitedinthepreparationofmetaloxides
and metal cobaltites at low temperatures (250–300 ◦C) using
bis-hydrazine metal glyoxylates and bis-hydrazine mixed metal
glyoxylates, respectively as precursors. Similar hydrazinium
complexes are expected to undergo degradation at higher tem-
peratures.
M(NO3)2·xH2O + 2HOOCCHO · H2O + 4N2H4·H2O
→ M(OOCCHO)2(N2H4)2 + 2HNO3 + 2N2H4·H2O
+ (x + 4)H2O
where M = Mg, Mn, Co, Ni, Cu, Zn, or Cd.
Bis-hydrazine metal glyoxylates and mixed metal com-
plexes were prepared by the aqueous reaction of the respective
metal nitrates or mixture of metal nitrates, glyoxylic acid and
hydrazine hydrate in an appropriate ratio. The hydrazine hydrate
was used in excess to maintain the solution at pH 9–10. The
bis-hydrazine adducts separated form the basic solution as crys-
talline powder.
It has been reported in literature that these types of com-
plexes may be prepared by the heterogeneous reaction between
the respective solid metal carboxylates and hydrazine hydrate.
However, the purities of the compounds obtained were low.
Hence, we have prepared the present set of complexes by adding
hydrazine hydrate to a concentrated solution containing metal
nitrate hydrate (or mixture of metal nitrate hydrates) and gly-
oxylic acid in a proper ratio. A clear solution was first obtained
from which the complexes slowly got precipitated. The yields
were found to be high.
M(NO3)2·xH2O + 2Co(NO3)2·6H2O + 6HOOCCHO · H2O
+ 12N2H4·H2O → MCo2(OOCCHO)6(N2H4)6 + 6HNO3
+ 6N2H4·H2O + (x + 24)H2O
where M = Mg, Mn, Ni, Zn or Cd.
In the present case, we were able to isolate copper complex
also. However, on long standing it underwent decomposition.
With most of the carboxylic acids in the presence of excess
hydrazine, copper undergoes reduction. Hence copper com-
plexes could not be prepared. Due to the formation of hydroxide
in basic condition our attempt to prepare iron complex was also
not successful.
The compositions of the complexes were assigned on the
basis of the hydrazine and metal contents (Tables 1 and 2). All
the complexes were insoluble in water, alcohol and other organic
solvents.
Table 1
Analytical data of the complexes
Compound
Color
Yield (%)
Hydrazine (%)
Found
Metal (%)
Found
μeff (BM)
Calculated
Calculated
Mg(OOCCHO)2(N2H4)2
Mn(OOCCHO)2(N2H4)2
Co(OOCCHO)2(N2H4)2
Ni(OOCCHO)2(N2H4)2
Cu(OOCCHO)2(N2H4)2
Zn(OOCCHO)2(N2H4)2
Cd(OOCCHO)2(N2H4)2
Colorless
Colorless
Rosy red
Green
Light blue
Colorless
Colorless
95
90
95
95
80
90
90
26.60
25.20
24.00
24.50
23.00
23.60
20.00
27.34
24.18
23.82
23.84
23.42
23.26
19.87
10.00
20.00
21.10
20.80
22.50
23.80
34.00
10.37
20.72
21.90
21.83
23.22
23.73
34.85
–
5.75
4.82
3.38
1.78
–
–
Table 2
Analytical data of the mixed metal complexes
Compound
Color
Yield (%)
Hydrazine
Cobalt (%)
Found
Metal (%)
Co/M ratio Found
Found
Calculated
Calculated
Found
Calculated
Mg1/3Co2/3(OOCCHO)2(N2H4)2
Mn1/3Co2/3(OOCCHO)2(N2H4)2
Ni1/3Co2/3(OOCCHO)2(N2H4)2
Zn1/3Co2/3(OOCCHO)2(N2H4)2
Cd1/3Co2/3(OOCCHO)2(N2H4)2
Rose
90
90
95
90
90
24.10
23.20
24.70
23.00
22.00
24.89
23.94
23.83
23.63
22.34
14.60
13.90
14.10
13.90
13.00
15.26
14.67
14.61
14.49
13.69
2.95
6.60
6.90
7.70
12.60
3.15
6.84
7.27
8.04
13.06
2.04
1.96
2.03
2.00
1.97
Rosy red
Greenish red
Red
Red

L. Vikram, B.N. Sivasankar / Thermochimica Acta 452 (2007) 20–27
23
3.1. Magnetic moments
The magnetic moments of the bis-hydrazine metal glyoxy-
lates (Table 1) are in accordance with the high-spin octahedral
nature of the complexes [27]. As expected the magnesium, zinc
and cadmium complexes are diamagnetic.
3.2. Electronic spectra
The electronic spectrum of cobalt complex shows strong
bands at 20,300 and 19,250 cm−1 which are assigned to the
4
4T1g(F) → T1g(P) transition which usually splits due to spin-
orbit coupling in the 4T1g(P) state.
Fig. 2. IR spectrum of Ni1/3Co2/3(OHCCOO)2(N2H4)2.
The bis-hydrazine nickel glyoxylate shows two bands at
26,700 and 17,300 cm−1 which are attributed to 3A2g → T1g(F)
3
3
and 3A2g → T1g(P) transitions, respectively. The copper com-
all the complexes are seen at 985–990 cm−1. This shows the
bridged bidentate nature of hydrazine moieties. Though it is
below 990 cm−1 a bit higher frequency (5–10 cm−1) than the
bands observed normally for various bis-hydrazine complexes
[30] may be due to the strong interaction between metal ion and
nitrogen.
plex shows a band at 16,500 cm−1, which is assigned to the
2
2Eg → T2g transition. These electronic transitions are com-
parable with the spectra of the respective octahedral metal(II)
complexes as reported earlier [28].
3.3. Infrared spectra
3.4. Thermal decomposition
Both the bis-hydrazine metal glyoxylates and bis-hydrazine
mixed metal glyoxylate complexes show almost superimpos-
able IR spectra. The infrared spectra of Ni(OOCCHO)2(N2H4)2
and Ni1/3Co2/3(OOCCHO)2(N2H4)2 are shown in Figs. 1 and 2
respectively as representative examples. All the complexes
show two sharp and strong band in the regions 3390–3400
and 3140–3150 cm−1 which are due to the N–H stretching of
hydrazine molecules. A sharp band at 1670 cm−1 in all the
cases is attributed to the carbonyl stretching of aldehyde group.
The presence of aldehydic group was also confirmed by heat-
ing the complexes with dilute silver nitrate solutions, which
gave silver mirror. There is no shift in this band in the com-
plexes when compared to the glyoxylic acid which indicates
that there is no interaction between metal ion and aldehydic
oxygen. The νasy and νsym stretching of carboxylate ions are
observed at 1580–1590 and 1350–1360 cm−1 with the ꢀν sepa-
ration of about 220–240 cm−1 which indicates the monodentate
coordination of carboxylate ion [29]. The N–N stretching in
3.4.1. Bis-hydrazine metal glyoxylates
The magnesium complex after endothermic dehydrazination
undergoes sharp exothermic decomposition to give magnesium
carbonate which further decomposed in the broad temperature
range (280–570 ◦C) to give MgO. Cobalt, nickel and cadmium
complexes show similar decomposition behaviour. The TG and
DTA traces are almost the same except for the temperature
range. In the first stage one molecule of hydrazine is elimi-
nated to give the respective mono-hydrazine metal glyoxylate
as the intermediate. This process is endothermic in all the cases.
The intermediate then undergoes sharp and highly exothermic
degradation to give the respective metal oxide as the final prod-
uct. The hydrazine molecule is eliminated in the temperature
range of 125–220 ◦C. Further decomposition completes before
330 ◦C. The mass losses observed in TG are well in accordance
with the theoretical values.
The manganese and zinc complexes show similar decom-
position trend. In both the complexes after endothermic dehy-
drazination, the intermediates namely mono-hydrazine deriva-
tives undergo decomposition at a broad temperature range
of 180–450 ◦C to give MnO2 and ZnO respectively as the
end residue. The DTA of manganese complex shows only
one sharp exotherm for the second stage whereas zinc com-
plex shows two exotherms at 220 and 430 ◦C for the second
stage.
The copper complex undergoes one-step decomposition in
the temperature range of 180–220 ◦C to give the copper oxide.
The DTA shows an exotherm as doublet at 195 and 215 ◦C. The
cadmium complex after dehydrazination undergoes explosive
degradation at 330 ◦C to give CdO.
The final products in all the cases were identified by the TG
mass loss and X-ray powder diffraction patterns.
Fig. 1. IR spectrum of Ni(OHCCOO)2(N2H4)2.

24
L. Vikram, B.N. Sivasankar / Thermochimica Acta 452 (2007) 20–27
3.4.2. Bis-hydrazine mixed metal glyoxylates
All these complexes undergo similar type of decomposition
and the decomposition behaviour is almost similar to the degra-
dation of cobalt complex. Since these mixed metal complexes
have cobalt metal as the major component, their properties are
expected to be the same as that of simple cobalt complex.
All the mixed metal complexes show autocatalytic behaviour.
As expected these complexes show two-step degradations to
give the respective metal cobaltites as the final products and
respective mono-hydrazine derivative as the intermediate. The
first stage is endothermic and the second stage is exothermic.
The intermediates decompose in a narrow temperature range of
185–285 ◦C. Due to their continuous decomposition we were
not able to isolate the intermediates.
Fig. 6. Simultaneous TG-DTA of Zn(OHCCOO)2(N2H4)2.
The simultaneous TG-DTA of magnesium, manganese,
cobalt and zinc complexes are shown in Figs. 3–6 respectively.
The simultaneous TG-DTA of Ni1/3Co2/3(OOCCHO)2(N2H4)2
is given in Fig. 7 as typical example. The thermal data of all the
complexes are summarized in Table 3.
3.5. X-ray diffraction
The X-ray powder diffraction patterns of the complexes were
recorded to support the similarity in the structures of these
compounds. The powder patterns are almost superimposable
indicating the isomorphism among the series of compounds.
The X-ray powder diffraction data of the mixed metal com-
plexes also have been recorded and are found to be similar to
thecorrespondingsimplebis-hydrazinemetalcomplexesandthe
peaks observed are almost superimposable and sharp indicating
the solid solution formation
Fig. 3. Simultaneous TG-DTA of Mg(OHCCOO)2(N2H4)2.
The d-spacings and relative intensities of the complexes are
given in Table 4. The X-ray patterns of bis-hydrazine cad-
mium glyoxylate and cobalt–cadmium precursor are given in
Figs. 8 and 9 respectively.
3.6. Metal cobaltites
The mixed metal complexes on heating to about 300 ◦C in a
silicacrucibleorignitedonceandallowedtodecomposeautocat-
alytically yield the respective metal cobaltites, MCo2O4, where
M = Mg, Mn, Ni, Zn or Cd. While heating in a silica crucible the
complexes should be added in small portions to avoid sudden
decomposition and explosions.
Fig. 4. Simultaneous TG-DTA of Mn(OHCCOO)2(N2H4)2.
Fig. 5. Simultaneous TG-DTA of Co(OHCCOO)2(N2H4)2.
Fig. 7. Simultaneous TG-DTA of Ni1/3Co2/3(OHCCOO)2(N2H4)2.

L. Vikram, B.N. Sivasankar / Thermochimica Acta 452 (2007) 20–27
25
Table 3
Thermal decomposition data
Compound
DTA peak temperature
(◦C)
TG temperature
range (◦C)
TG mass loss (%)
Residue
Found
Calculated
Mg(OOCCHO)2(N2H4)2
179(+)
153–210
210–280
280–570
12.50
65.00
82.60
13.67
64.04
82.81
Mg(OOCCHO)2(N2H4)
MgCO3
MgO
223(−, s)
457(−), 519(−)
Mn(OOCCHO)2(N2H4)2
Co(OOCCHO)2(N2H4)2
Ni(OOCCHO)2(N2H4)2
Cu(OOCCHO)2(N2H4)2
Zn(OOCCHO)2(N2H4)2
155(+)
333(−, s)
198(+)
236(−, s)
212(+)
252(−, s)
125–198
198–355
11.00
66.00
12.09
67.18
Mn(OOCCHO)2(N2H4)
MnO2
158–203
203–239
13.00
69.20
11.91
69.18
Co(OOCCHO)2(N2H4)
Co2O3
180–218
218–329
13.40
71.50
11.92
72.22
Ni(OOCCHO)2(N2H4)
NiO
195(−, s)
215(−, s)/d
180–220
69.50
70.94
CuO
160(+)
133–193
193–444
11.00
69.00
11.63
70.46
Zn(OOCCHO)2(N2H4)
ZnO
220(−, s)
430(−, s)
Cd(OOCCHO)2(N2H4)2
174(+)
320(−, s)
150–185
285–330
10.00
62.00
9.94
60.19
Cd(OOCCHO)2(N2H4)
CdO
Mg1/3Co2/3(OOCCHO)2(N2H4)2
Mn1/3Co2/3(OOCCHO)2(N2H4)2
Ni1/3Co2/3(OOCCHO)2(N2H4)2
Zn1/3Co2/3(OOCCHO)2(N2H4)2
Cd1/3Co2/3(OOCCHO)2(N2H4)2
206(+)
234(−, s)
192(+)
216(−, s)
197(+)
229(−, s)
175(+)
252(−, s)
160–210
210–255
11.50
72.00
12.44
73.32
Mg1/3Co2/3(OOCCHO)2(N2H4)
MgCo2O4
160–195
195–225
12.00
69.50
11.97
70.52
Mn1/3Co2/3(OOCCHO)2(N2H4)
MnCo2O4
155–204
204–242
14.00
68.00
11.91
70.19
Ni1/3Co2/3(OOCCHO)2(N2H4)
NiCo2O4
140–185
185–280
11.50
71.00
11.82
69.62
Zn1/3Co2/3(OOCCHO)2(N2H4)
ZnCo2O4
182(+)
260(−, s)
140–190
90–285
11.00
67.00
11.17
65.81
Cd1/3Co2/3(OOCCHO)2(N2H4)
CdCo2O4
(+): Endotherm; (−): exotherm; d: doublet; s: sharp.
It was observed that during heating, the manganese, cobalt,
nickel and copper complexes undergo autocatalytic decompo-
sition, i.e. if ignited they undergo self sustained degradation.
However, magnesium, zinc and cadmium complexes did not
show this behaviour. Further, the nickel complex decomposes
with spurting while cadmium complex undergoes sudden and
explosive decomposition.
The metal and cobalt contents in these cobaltites deter-
mined by chemical analyses, shows a cobalt to metal
ratio of 1.97–2.02. The formation of cobaltites was con-
Table 4
˚
X-ray powder diffraction data (d-values in A)
Mg
Mn
Co
Ni
Cu
Zn
Cd
Co–Mg
Co–Ni
Co–Cd
7.80
5.75
5.34
4.46
4.27
3.90
3.21
3.12
3.03
2.95
2.59
2.40
2.24
2.13
1.70
7.76
5.88
5.31
4.46
4.38
3.88
3.19
3.13
–
2.94
2.59
2.40
2.23
2.13
1.70
7.38
5.72
5.33
4.43
4.25
3.88
–
3.12
3.02
2.94
2.59
2.40
2.24
2.13
1.70
7.43
5.83
5.30
4.42
4.39
3.90
3.18
3.16
3.01
2.95
2.58
2.38
2.24
2.13
1.70
7.69
7.64
5.41
4.42
4.33
3.86
3.19
3.15
3.02
2.96
2.59
2.38
2.24
2.13
1.70
7.76
5.83
5.38
4.51
4.42
3.86
3.19
3.13
3.01
2.97
2.58
2.38
2.24
2.13
1.70
7.80
5.88
5.38
4.50
4.44
3.88
3.19
3.16
–
2.97
2.58
2.38
2.24
2.13
1.70
7.76
5.72
5.31
4.43
4.33
3.88
–
3.13
3.01
2.96
2.59
2.40
2.24
2.13
1.70
7.56
5.83
5.33
4.43
4.38
3.90
3.18
3.13
3.02
2.96
2.59
2.38
2.23
2.13
1.70
7.50
5.83
5.34
4.42
4.38
3.88
–
3.15
3.03
2.97
2.58
2.40
2.24
2.13
1.70

26
L. Vikram, B.N. Sivasankar / Thermochimica Acta 452 (2007) 20–27
Table 5
Analytical and spectral data of metal cobaltites
˚
Oxide
Cobalt (%)
Found
Metal (%)
Found
Co/M ratio Found
IR spectra (cm−1
)
XRD (A)
Calculated
Calculated
ν1
ν2
MgCo2O4
MnCo2O4
NiCo2O4
ZnCo2O4
CdCo2O4
56.80
49.40
48.60
47.30
39.20
57.17
49.78
49.00
47.67
40.08
11.60
23.40
24.10
26.15
37.60
11.79
23.20
24.40
26.45
38.22
2.02
1.97
2.01
2.01
1.99
660
660
665
660
665
555
560
560
555
560
8.211
8.191
8.123
8.165
8.105
Fig. 10. X-ray powder pattern of NiCo2O4.
Fig. 8. X-ray powder pattern of Cd(OHCCOO)2(N2H4).
4. Conclusions
Transition metal ions such as Mg2+, Mn2+, Co2+, Ni2+, Cu2+,
Zn2+ and Cd2+ react with glyoxylic acid in the presence of excess
hydrazine hydrate to yield bis-hydrazine metal glyoxylates.
These complexes were found to be isomorphous and also
these were obtained as crystalline solids from a homogeneous
solution. Hence the above method was exploited for the prepa-
ration of bis-hydrazine mixed metal glyoxylates.
The magnetic moment and electronic spectra suggest the
high-spin octahedral nature of the complexes. Infrared spectra
indicate the monodentate nature of carboxylate ions and biden-
tate bridged nature of hydrazine moities.
During the thermal degradation all the complexes under-
went two-step decomposition to give the respective metal
oxidesthroughmono-hydrazineintermediates. Manycomplexes
showed autocatalytic behaviour. The mixed metal complexes
gave the respective metal cobaltites below 290 ◦C.
firmed by the infrared spectra and XRD patterns of the
residues.
The infrared spectra of the residues show two bands at
660–665 and 555–560 cm−1 which correspond to the metal
oxygen stretching from tetrahedral and octahedral sites, respec-
tively, which are characteristics of cobaltites. The X-ray powder
diffraction patterns of the residues are in good agreement with
those reported in the literature [31]. The line broadening indi-
cates the fine particle nature of these oxides. The analytical and
spectral data and the cell parameters, ‘a’ for the cobaltites with
cubic symmetry calculated from XRD data are given in Table 5.
The X-ray powder pattern of NiCo2O4 is given in Fig. 10.
The X-ray powder patterns of the complexes were super-
imposable and the d-values suggested isomorphism among the
complexes. The metal cobalites formed as the residues during
the decomposition of mixed metal complexes were confirmed
by their IR spectra and XRD patterns.
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