Thermal decomposition of manganese(II)bis(oxalato)nickelate(II)tetrahydrate

Article abstract of DOI:10.1007/s10973-005-0746-y

A mixed metal oxalate, manganese(II)bis(oxalato)nickelate(II)tetrahydrate, has been synthesized and characterized by elemental analysis, IR spectral and X-ray powder diffraction (XRD) studies. Thermal decomposition studies (TG, DTG and DTA) in air showed that the compound decomposed mainly to Mn ₂O₃, MnO₂ and NiO at ca.1000°C, via. the formation of several intermediates. DSC study in nitrogen upto 500°C showed the endothermic decomposition. The tentative mechanism for the thermal decomposition in air is proposed.

Full text of DOI:10.1007/s10973-005-0746-y

Journal of Thermal Analysis and Calorimetry, Vol. 81 (2005) 61–65
THERMAL DECOMPOSITION OF
MANGANESE(II)BIS(OXALATO)NICKELATE(II)TETRAHYDRATE
*
N. Deb
Department of Chemistry, North Eastern Regional Institute of Science and Technology, Nirjuli 791109, Itanagar, Arunachal
Pradesh, India
A mixed metal oxalate, manganese(II)bis(oxalato)nickelate(II)tetrahydrate, has been synthesized and characterized by elemental
analysis, IR spectral and X-ray powder diffraction (XRD) studies. Thermal decomposition studies (TG, DTG and DTA) in air
2 3 2
showed that the compound decomposed mainly to Mn O , MnO and NiO at ca.1000°C, via. the formation of several intermediates.
DSC study in nitrogen upto 500°C showed the endothermic decomposition. The tentative mechanism for the thermal decomposition
in air is proposed.
Keywords: IR, oxalato, thermal decomposition, X-ray powder diffraction
Introduction
room temperature. Recently, we reported the thermal in-
vestigation of the compounds, M[Ni(C O ) ]·xH O
2
4 2
2
Thermal decomposition of co-precipitated zinc-copper
oxalates in nitrogen indicated [1] the formation of mixed
oxide and copper metal as end product. The structure and
magnetic properties of NiCu(C O ) ·4H O have been stud-
(M=Co(II) or Cd(II)) [12], M[La(C O ) ]·xH O
2 4 3 2
(M=Cr(III) or Co(III) [13], Zn[Co(C O ) ]·5H O [14]
2
4 2
2
and Cd[Co(C O ) ]·5H O [15]. Although, there have
2
4 2
2
2
4 2
2
been quite a few reports on the mixed metal oxalate, so
far oxalate of manganese with nickel of the type
M[M(C O ) ]·xH O (where, M=different metal) has not
ied [2]. The oxalates of mixed metal of barium [3] and lead
[4] with titanium of the type BaTiO(C O4)2 and
PbTiO(C O ) ·4H O are reported. We have synthesized
2
2
4 2
2
2
4 2
2
been reported. As an extension of our work on mixed
metal oxalate, and, keeping in view of the possibility of
formation of different types of metal oxide and mixed
metal oxides and their possible applicability as prospec-
tive materials for superior technical ceramics, magnetic
recording materials, electronic components, catalysts as
well as high-temperature superconductors, this paper
describes the synthesis, characterization and thermal de-
and investigated [5, 6] the thermal decomposition of the
compounds, M[M(C O ) ]·xH O (where, M = same metal)
2
4 2
2
with Mn and Ni in air and nitrogen. The alkali metal uranyl
oxalate of the type, M UO (C O ) ·xH O (M=Li, Na) [7]
2
2
2
4 2
2
were found to decompose to monouranates around 800°C
through the formation of alkali metal carbonates and UO2
o
as intermediates at ~400 C. Mixed metal oxalates of
lanthanides
(
and
NH )Ln U (C O ) ·8H O (Ln=La, Ce, Pr, Nd, Tb) [8]
uranium
of
the
type
composition
behaviour
in
solid
state
Mn[Ni(C O ) ]·4H O in air. A tentative route of the de-
of
III IV
4
2
4 4
2
2
4 2
2
were indexed on an orthorhombic unit cell. The com-
pounds were decomposed to Ln O CO and UO as in-
termediate products in the range 625 to 655 K. Further
composition in air is also proposed.
2
2
3
2+x
above 975 K the intermediates formed solid solutions of Experimental
mixed oxides with fluorite structure in air, argon and
N
2
/H . The thermal decomposition behaviour of thal-
2
The preparative method is similar to the method
adopted earlier [12–15]. The chloride free nickel hy-
droxide prepared from nickel chloride was dissolved
in glacial acetic acid and heated on a steam bath. A
light blue precipitate was separated on adding a solu-
tion of manganese chloride followed by dropwise ad-
dition of saturated solution of oxalic acid. The precip-
itate was filtered off, washed several times with
distilled water and stored in a desiccator over calcium
lium(I)bis-oxalatodiaquaindate(III)-monohydrate and
barium dioxodiaquaperoxyoxalatouranate was studied
and their structural formulas were proposed as
Tl[In(C
2
O
4
)
2
(H O) ]·H O
2 2 2
[9]
Ba[UO (O )(C O )(H O) ]·H O [10]. The dehydra-
and
2
2
2
4
2
2
2
tion/rehydration tris-oxalato
aluminate(III), (NH ) Al(C O ) ·3H O was studied [11]
in flowing dinitrogen saturated with water vapour at
of
ammonium
4
3
2
4 3
2
*
nidhubandeb@yahoo.com
1
388–6150/$20.00
Akadémiai Kiadó, Budapest, Hungary
Springer, Dordrecht, The Netherlands
©
2005 Akadémiai Kiadó, Budapest

DEB
Table 2 X-ray powder diffraction data of Mn[Ni(C
2 4 2 2
O ) ]·4H O
chloride. The water content was determined
gravimetrically and thermogravimetrically. The manga-
nese and nickel content were estimated gravimetrically
by precipitating as MnNH PO ·H O and bis(dimethyl-
Mn[Ni(C
2
O
4
)
2
2
]⋅4H O
d/
I/Rel
4
4
2
8
.013
49.38
100.00
65.37
71.86
68.71
58.63
62.72
63.33
59.64
61.97
63.93
66.62
64.94
69.91
75.75
76.27
78.01
75.38
glyoximato)nickel(II) respectively. Carbon and hydro-
gen contents were analyzed using a Carlo Erba 1108 el-
emental analyser. Analysis as calculated for
Mn[Ni(C O ) ]·4H O: Mn 14.47%; Ni 15.46%;
4.772
3
2
2
.632
.986
.656
2
4 2
2
C 12.65%; H 2.65%; H O 23.72%; found: Mn 14.23%;
2
Ni 15.06%; C 12.17%; H 2.60%; H O 22.65%
2
–
1
2.262
.914
1.626
IR spectra (200–4000 cm ) and powder X-ray
diffraction (XRD) pattern were carried out as de-
scribed earlier [12, 16, 17]. TG, DTG and DTA
curves were recorded in static air up to 1000°C at a
1
1
1
1
1
1
.475
.363
.264
.175
.103
–
1
heating rate of 10°C min using a Shimadzu DT 30B
thermal analyser. The intermediate phases and end
products were isolated by independent pyrolysis in air
upto the required temperature in furnace. Sometimes
these were isolated by temperature arrest technique
(
ture in TG. DSC curve was recorded with a TA instru-
stopping of the TG scan) upto the required tempera-
1.006
0
0
0
0
.961
.939
.902
.875
o
ment DSC-2010 at a heating rate of 10 C min in ni-
–1
–
1
trogen atmosphere with a flow rate of 50 mL min .
The instrument was calibrated with indium (purity
9
through universal V2.3C TA software in J g and
9.9%). The enthalpy (∆H) values are obtained
–1
0.820
.809
81.69
80.53
–
1
converted into kJ mol using molecular mass, and
entropies (∆S) are calculated using simple well
known thermodynamic relation incorporating the
temperature of peak maxima.
0
posed formula of the compound. Selected bands (Ta-
ble 1) in the IR spectrum of the compound suggested
[
12–18] the chelating character of the oxalato groups
Results and discussion
and the XRD patterns (Table 2) suggest the crystal-
line nature.
The complex, Mn[Ni(C O ) ]·4H O was insoluble in
2
The thermal profiles (TG, DTG and DTA) of
Mn[Ni(C O ) ]·4H O in air is seen in Fig. 1. An in-
4 2
2
water and common organic solvents, but it decom-
poses in the presence of strong acid and alkali. Ana-
lytical and microanalytical results suggest the pro-
2
4 2
2
clined slope in TG profile between 147 and 225°C
with mass loss of 19% (calculated, 19.92%) indicates
the formation of anhydrous species. A sharp change
in DTG between 138 and 238°C, and an endothermic
peak in DTA between 130 and 232°C (∆Tmin=182°C)
correspond to the dehydration step. The pyrolysed
product in air at 272°C shows the IR bands at
Table 1 Selected bands in the IR spectrum of
2 4 2 2
Mn[Ni(C O ) ]·4H O
a
IR bands /cm
–1
Assignments
sy(O–H)+νasy(O–H) or hydrogen
bonding
ν
3000–3800 Sb
1
2
420–1900, 1360, 1310, 820, 720, 460 and ca.
–
80 cm indicates the presence of chelating oxalato
1
1
1
1
1
630 S
δ
sy(H–O–H)
groups; however, the XRD data (Table 3) are not sim-
ilar to the parent compound. The removal of water at
higher temperature suggests the presence of coordi-
nated water. The anhydrous species is stable upto
305°C. Further, a steep slope in TG curve upto 354°C
with mass loss of 54% apparently indicates the forma-
500–1800 Sb
370 m
ν
ν
ν
asy(C=O)
sy(C–O) and / or ν(C–C)
sy(C–O) and / or δ(O–C=O)
320 m
ν(M–O) and / or δ(O–C=O) or
coordinated water
730 s, 820 m
6
4
2
10 s
water of crystallization
tion of NiMnO (calculated mass loss, 55.32%)
3
which is an intimate mixture of NiO and MnO . But
2
60 m
δ(O–C=O) and / or ring deformation
π (out-of-plane bending)
there is less possibility of formation of NiMnO at this
3
90 s
temperature, because solid-solid reaction of molten
a
s=small, m =medium, S=strong, b=broad
62
J. Therm. Anal. Cal., 81, 2005

THERMAL DECOMPOSITION OF MANGANESE(II)BIS(OXALATO)NICKELATE(II)TETRAHYDRATE
Table 3 X-ray powder diffraction data of the pyrolysed products of Mn[Ni(C
2
O
4
)
2
]·4H
2
O at 272, 380, 770 and 1000°C
1000°C
Pyrolysed product at
272°C
380°C
770°C
d/
I/Rel
37.26
54.36
48.15
47.92
53.26
54.49
52.39
58.44
64.33
65.32
69.98
75.44
75.28
80.78
78.14
90.49
92.91
93.33
100.00
d/
I/Rel
79.68
79.32
84.97
82.92
100.00
83.15
83.17
84.98
79.26
79.67
82.12
80.80
77.21
75.10
75.03
73.76
78.26
80.09
82.28
75.60
79.78
80.83
75.96
79.55
78.76
79.61
d/
I/Rel
d/
I/Rel
77.63
82.52
100.00
66.48
59.68
63.52
61.97
57.69
56.58
50.79
55.25
52.03
54.98
58.25
58.37
56.11
61.08
60.16
8
.453
.779
.382
.071
.591
.849
.353
.186
.058
.984
.948
.916
.895
.880
.862
.833
.816
.799
.793
6.365
3.385
3.026
7.942
4.544
3.767
3.094
66.62
71.22
68.94
78.32
80.12
100.00
75.67
75.23
73.03
80.68
70.76
73.70
73.89
80.37
78.93
76.83
77.93
75.41
77.92
80.17
83.41
78.54
79.02
6.041
3.902
4
3
3
2
1
1
1
1
0
0
0
0
0
0
0
0
0
0
§
2.724
1.666
⊗
♦
#ꢀ§
2.973
ꢀ
2.540
ꢀ
1.352
3.035
∗
r£
ꢀ∗ •
⊗ꢀ
2.079
2.565
1.273
ꢀ
1.626
ꢀ
1.548
ꢀ
1.361
ꢀ
1.213
§
§
2.113
1.851
1.177
1.048
1.013
∗
§
⊗£
ꢀ∗
1.703
⊗
♦§
£
0.958
1.495
1.406
∗
ο
£
0.929
1.160
r
ꢀ♦
∇
1.152
1.291
§
1.184
0.886
0.853
⊗
r
r
£ •
1.090
1.082
1.017
0.966
∗
§♦ο
1.105
0.834
0.819
0.806
0.800
0.786
∗
•
1.010
0.963
0.934
0.917
0.887
0.858
0.833
0.812
0.796
r
£
£
∇£
£
0.958
•
0.939
£
0.934
∇
•
•
0
.908
∇
0
.885
•
∇
0
.862
.829
£
0
∇
0
.814
£
0
.799
•
0
.786
♦– Mn
3
O
4
; § – Mn
2
O
3
; ꢀ– MnO
2
; • – ΜnΟ; r – NiCO
3
; £ – NiO; o – Ni
2
O
3
; ∇ – NiC; ∗ – C; # – NiMnO
3
2 4
; ⊗NiMn O
NiO and MnO only at high temperature produces the
2
mixed metal oxides. A strong exotherm in the range
2
55–378°C (∆Tmax = 285°C) with a shoulder at 326°C
in DTA and a sharp DTG change between 297 to
95°C are accounted for this decomposition step. The
3
black pyrolysed species in air at 380°C shows the IR
bands at 1380, 1350, 610, 550, 460, 400, 330, 310 and
–
1,
2
40 cm which indicated the presence of MnO and
2
NiO [19]. The XRD data (Table 3) of the species con-
firmed [20] the compound to be a mixture of NiO and
MnO . Although, the peaks for NiMnO are not ob-
2
3
tained, however, the presence of a trace of MnO is
confirmed from XRD data. A few d-values are coin-
cides with NiMn O , indicates its presence which is
2
4
simply a mixture of NiO and Mn O . So in this study
2
3
o
it is apparently indicated that at 354 C, a part of
Fig. 1 TG, DTG and DTA curves of Mn[Ni(C
–
air at 10°C min
2
O
4
)
2
]·4H
2
O in
1
MnO and MnO combined, which, inturn formed
2
Mn O (which immediately reacted with a part of
2
3
J. Therm. Anal. Cal., 81, 2005
63

DEB
II III
NiO, forming Ni Mn2 O ) with the change of the ox-
4
IV
idation state from Mn and Mn to Mn . A shoulder
II
III
o
at 326 C in DTA may be due to these changes of state
in manganese or combination of NiO and Mn O . The
2
3
IV
evolved CO (g) is responsible to reduce Mn to Mn
III
II
III
and simultaneous air oxidation of Mn to Mn can-
not be ruled out. The presence of NiCO C (carbon)
3
,
and trace of NiC are confirmed from the XRD data
Table 3); the formation of NiC is possible at this tem-
perature as a part of NiO reacts with C which formed
through disproportionation of CO (g) to CO (g). The
(
2
extra band in the IR spectrum of the species isolated
o
at 380 C may be due to the presence of trace of the
carbides, carbonates and mixed metal oxides. The TG
o
curve is stable upto 418 C and then slow increase of
2 4 2 2
Fig. 2 DSC profile of Mn[Ni(C O ) ]·4H O in nitrogen at
o
mass of 6% upto 770 C (mass loss, calcd., 48%) and
–1
10°C min
o
then again decreases slowly upto 1000 C with a mass
loss of 54% indicates the formation of compound
between 325 and 460°C manifests to the decomposi-
o
similar to the species formed at 354 C in TG. The
XRD data (Table 3) of the black pyrolysed product at
tion and the respective values of ∆H and ∆S are calcu-
–1
–1
–1
lated to be 146.43 kJ mol and 208.95 J K mol .
The foregoing results suggest the following ten-
tative decomposition scheme in air.
o
70 C in air confirmed the presence of Mn O ,
7
Mn O , MnO , MnO (trace), NiO/Ni O and NiC
3
4
2
3
2
2
3
(
trace). A very small exothermal hump in DTA at
o
44 C may corresponds to the oxidation of MnO to
ca.225°C
Mn[Ni(C
4
O
)
]·4H
O   → Mn[Ni(C
O ) ] (s) +
2 4 2
2
4
2
3
2
4
Mn O and Mn O (the later also might have gener-
05–354°C
H O (v) →MnO (s) + MnO (s)(trace) +
2
2
2
3
3
4
NiO (s) + NiCO (s) + NiC (s)(trace) + C (s) +
ca.770°C
3
ated from the interaction of MnO & Mn O3 at this
2
lCO(g) + mCO (g)  → Mn O (s) +
2
3
4
temperature), NiO to Ni O or may be due to the slow
2
3
Mn O (s) + MnO (s)(unreacted) +
MnO (s)(trace) +[NiO + Ni O ] (s)(trace) +
2
3
2
decomposition of NiMn O (trace) at high tempera-
2
4
2
3
ture again to NiO and Mn O . In TG the 6% weight
2
3
o
ca.1000°C
o
gain in the range 418 to 770 C supports these oxida-
NiC (s)(trace) + xCO
MnO
2
(g) →Mn
(s) + NiO (s) + MnO (s)(trace) +
NiC (s)(trace)
O (s) +
2 3
o
tion. The black pyrolysed product at 770 C in air
shows the IR bands at 1380, 1350, 600, 540, 440, 400,
2
–
1
10 and 240 cm that shows the presence of the ox-
3
ides of manganese and nickel. Further, a slight
exothermal nature of DTA curve in the range
7
formed at 770 C in TG. The pyrolysed grey species at
Acknowledgements
o
55-889 C may be due to the changes of the products
The author is thankful to Dr.S.D.Baruah, Regional Research
Laboratory, Jorhat for the DSC profile and Director, RSIC,
CDRI, Lucknow for elemental analysis.
o
o
1
MnO and NiO as confirmed [20] from the XRD data
000 C in air is found to be a mixture of Mn O ,
2 3
2
(
Table 3). A trace of NiMnO3 and again NiMn O4
2
are also detected from XRD which may be formed
from the solid-solid reaction of a part of molten NiO
with MnO (molten) and Mn O (molten) respectively
Reference
1 B. D. Dalvi and A. M. Chavan, J. Thermal Anal.,
2
2
3
1
4 (1978) 331.
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o
DTA (755 – 889 C) may be due to change of Mn O
2
3
4
5
M. Verdaguer, M. Julve, A. Michalowicz and O. Kahn,
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3
4
to Mn O The presence of trace of MnO and NiC can-
2
3.
H. S. G. Murthy, M. Subba Rao and T. R. N. Kutty,
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bands of the species isolated at 1000°C supports the
presence of the oxides of manganese and nickel.
The DSC profile (Fig. 2) in nitrogen upto 500°C
shows two sharp endothermic changes. The first
endotherm in the range 125–257°C corresponds to the
dehydration. The enthalpy (∆H) and entropy changes
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4
∆S) of the step are found to be 216.83 kJ mol and
–1
–1
61.53 J K mol respectively. The second endotherm
64
J. Therm. Anal. Cal., 81, 2005

THERMAL DECOMPOSITION OF MANGANESE(II)BIS(OXALATO)NICKELATE(II)TETRAHYDRATE
8
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Received: September 18, 2004
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DOI: 10.1007/s10973-005-6493-2
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J. Therm. Anal. Cal., 81, 2005
65