Preparation, X-ray crystallography, and thermal decomposition of some transition metal perchlorate complexes of hexamethylenetetramine

Article abstract of DOI:10.1021/jp077278z

The Perchlorate complexes of manganese, nickel, and zinc with hexamethylenetetramine (HMTA) of the general formula [M(H₂O-HMTA- H₂O)₂(H₂O-ClO₄)₂(H ₂O)₂] (where M = Mn,

Full text of DOI:10.1021/jp077278z

12972
J. Phys. Chem. A 2007, 111, 12972-12976
Preparation, X-ray Crystallography, and Thermal Decomposition of Some Transition Metal
Perchlorate Complexes of Hexamethylenetetramine†
Gurdip Singh,* B. P. Baranwal, I. P. S. Kapoor, and Dinesh Kumar
Department of Chemistry, DDU Gorakhpur UniVersity, Gorakhpur 273009, India
Roland Fro1hlich
Organisch-Chemisches Institut, UniVersita¨t Mu¨nster, D-48149 Mu¨nster, Germany
ReceiVed: September 11, 2007; In Final Form: October 4, 2007
The perchlorate complexes of manganese, nickel, and zinc with hexamethylenetetramine (HMTA) of the
general formula [M(H2O-HMTA-H2O)2(H2O-ClO4)2(H2O)2] (where M ) Mn, Ni, and Zn) have been
prepared and characterized by X-ray crystallography. Thermal studies were undertaken using thermogravimetry
(TG), differential thermal analysis (DTA), and explosion delay (DE) measurements. The kinetics of thermal
decomposition of these complexes was investigated using isothermal TG data by applying isoconversional
method. The decomposition pathways of the complexes have also been proposed. These were found to explode
when subjected to higher temperatures.
Introduction
Hexamethylenetetramine (HMTA) known as urotropine or
tetraazaadamantane (taad) in which four nitrogen atoms are
situated at the corners of a tetrahedron, is a ligand of polycy-
clicpolydentate type. In many complexes, it acts as a mono-
dentate1 or bidentate ligands2,3 and shows nonchelating behavior4
(in low valent organometallic complexes). It is used for
preparing RDX. Studies on the thermolysis and kinetics of some
of the transition metal nitrate and perchlorate complexes with
1,4-diaminobutane,5,6 propylenediamine,7,8 ethylenediamine9,10
and 1,6-diaminohexane as ligand11 have already been reported.
Figure 1. Crystal structure of the Mn complex.
We have previously investigated the thermal decomposition and
ignition characteristics of metal nitrate complexes having
baker), nickel carbonate, silica gel TLC grade (Qualigens), 70%
perchloric acid (Merck), and HMTA (Lancaster) were used as
received.
intermolecular hydrogen-bonded HMTA.12
-
The metal amine complexes having ClO4 as counterion
undergoes self-propagative decomposition reactions due to
presence of both oxidizing (ClO4-) and reducing groups in the
same molecules.6,8,10 On the basis of their sensitivity, amine
perchlorate complexes lie in between primary and secondary
explosives.13 These complexes at higher temperature decompose
to form metal oxide with evolution of gaseous products. These
ultrafine metal oxides have interesting electrical, magnetic and
catalytic properties.14 Hence, transition metal complexes have
been found to be potential burning rate modifier for HTPB-AP
propellants.15,16 In this paper, we report the preparation, crystal
structure, thermal decomposition, and explosion characteristic
of the transition metal perchlorate complexes having hydrogen-
bonded HMTA moiety.
Preparation of the Complexes. Hexahydrate metal perchlo-
rate salts were crystallized by treating corresponding metal
carbonates with 70% perchloric acid. After being washed with
petroleum ether, these salts were recrystallized from distilled
water and finally dried under vacuum over fused calcium
chloride. The metal perchlorate complexes were prepared by
treating the aqueous solution of metal perchlorate hexahydrate
salts with HMTA in appropriate stoichiometric ratio. These
complexes were recrystallized from water and dried. The molar
conductances of the complexes have been measured on Century
CC 601 in water as well as dimethylsulphoxide (DMSO).
X-ray Crystallographic Study. Crystals of the complexes
were obtained by the recrystallization from aqueous solutions.
The data collection of the crystals were performed at low
temperature (198 K) using a Nonius Kappa CCD diffractometer,
equipped with a rotating anode generator Nonius FR591.
Programs used: involves data collection Collect (Nonius B.V.;
1998), data reduction and absorption correction Denzo-SMN.17
The structures were solved by direct methods SHELXS-9718
and refined by full-matrix least-squares method on all F2 data
using SHELXL-97.19 Hydrogen atoms were placed on calculated
Experimental Section
Materials. All commercially available chemicals are of AR
grade, zinc carbonate (s.d. fine), manganese carbonate (Thomas
* Corresponding author. E-mail: gsingh4us@yahoo.com. Phone: 91-
551-2200745 (R) 2202856 (O). Fax: 91-551-2340459.
† Part 57.
10.1021/jp077278z CCC: $37.00 © 2007 American Chemical Society
Published on Web 11/22/2007

Transition Metal Perchlorate Complexes of HMTA
J. Phys. Chem. A, Vol. 111, No. 50, 2007 12973
Figure 3. Crystal structure of the Zn complex.
Figure 2. Crystal structure of the Ni complex.
tube furnace technique22 (mass 20 mg, 100-200 mesh) in the
temperature range 280-360 °C. The accuracy of the temperature
of the tube furnace was (1 °C. Each run was repeated five
times, and mean DE values are reported in Table 4. The DE
data were found to fit in the following equation:23-25
positions and refined riding; at the water molecules they were
located from a difference Fourier map and refined independently.
Refinement with anisotropic thermal parameters for non-
hydrogen atoms led to the R values of 0.049 (Mn), 0.051 (Ni),
and 0.045 (Zn). The crystal structures (graphics done with
Schakal20) of the complexes are shown in the Figures 1-3. The
crystal data, structure refinement, bond lengths, and bond angles
for complexes are summarized in Tables 1 and 2.
Thermal Analysis of the Complexes. TG was taken at 5 °C/
min in a static air atmosphere (sample mass 20 mg, 100-200
mesh) on indigenously fabricated TG apparatus21 (Figure 4).
DTA was done in a static air atmosphere on a Universal Thermal
Analysis instrumentt(sample mass ∼20 mg, heating rate 10 °C/
min) (Figure 5). TG and DTA phenomenological data are
summarized in Table 3. Isothermal TG was performed at
appropriate temperatures in static air (mass ∼20 mg) using a
gold crucible as the sample holder, and thermograms are shown
in Figure 6. The explosion delay (DE) data were recorded using
DE ) AeE*/RT
where E* is the activation energy for explosion and T is the
absolute temperature. A plot of ln DE vs 1/T is shown in
Figure 7.
Kinetic Analysis of Isothermal TG Data. Isothermal TG
data were used to evaluate kinetics of thermolysis by model
fitting26 as well as the model free isoconversional method given
by Vyazovkin and Wight.27 The following equation was found
to fit the isothermal TG data
-ln tR,i ) ln[A/g(R)] - E/RTi
TABLE 1: Crystal and Structure Refinement Data
complex designation
empirical formula
color
formula weight
temp/K
Mn complex
C12H40Cl2MnN8O16
colorless
678.36
198(2)
Ni complex
C12H40Cl2N8NiO16
light green
682.13
198(2)
Zn complex
C12H40Cl2N8O16Zn
colorless
688.79
198(2)
λ/Å
0.71073
triclinic
P1h (No. 2)
0.71073
triclinic
P1h (No. 2)
0.71073
triclinic
P1h (No. 2)
crystal system
space group
cell constants
a ) 8.3050(2) Å
R ) 93.921(1)°
b ) 9.1845(2) Å
â ) 104.338(1)°
c ) 10.7325(2) Å
γ ) 113.913(1)°
711.78(3) Å3
1
a ) 8.1778(1) Å
R ) 93.955(1)°
b ) 9.1073(1) Å
â ) 104.417(1)°
c ) 10.6844(2) Å
γ ) 113.892(2)°
691.57(2) Å3
1
a ) 8.2148(1) Å
R ) 93.856(1)°
b ) 9.1318(2) Å
â ) 104.497(1)°
c ) 10.7006(2) Å
γ ) 113.859(1)°
697.75(2) Å3
1
volume
molecules per unit cell, Z
calculated density
absorption coefficient
F(000)
1.583 Mg/m3
0.733 mm-1
355
1.638 Mg/m3
0.978 mm-1
358
1.639 Mg/m3
1.155 mm-1
360
crystal size/nm
θ range for data collection
limiting indices
0.35 × 0.20 × 0.15
2.47 to 28.28°
-11 e h e 11
-12 e k e 11
-14 e l < 13
6631/3427
0.40 × 0.30 × 0.15
2.49 to 27.64°
-10 e h e 9
-10 e k e 11
-13 e l e 14
7503/3212
0.65 × 0.60 × 0.10
2.00to 28.24°
-7 e h e 10
-11 e k e 10
-14 e l e 13
6824/3317
reflections collected/unique
[R(int) ) 0.031]
[R(int) ) 0.049]
[R(int) ) 0.040]
reflections observed [I > 2σ(I)]
data/restraints/parameters
goodness-off-fit on F2
3003
3022
3158
3427/0/210
1.073
3212/0/210
1.056
3317/0/211
1.075
final R indices [I > 2σ(I)]
R1 ) 0.0489
wR2 ) 0.120
R1 ) 0.056
wR2 ) 0.126
none
R1 ) 0.051
wR2 ) 0.129
R1 ) 0.054
wR2 ) 0.131
none
R1 ) 0.045
wR2 ) 0.118
R1 ) 0.047
wR2 ) 0.120
0.183(11)
R indices (all data)
extinction coefficient
largest diff. peak and hole/e Å-3
CCDC no.
+1.17 and -1.07
658325
+1.21 and -1.20
658324
+1.16 and -1.12
658326

12974 J. Phys. Chem. A, Vol. 111, No. 50, 2007
Singh et al.
TABLE 2: Bond Lengths (Å) and Angles (deg) for Complexesa
Mn complex
Ni complex
Zn complex
bond
bond length
bond
bond length
bond
bond length
Mn-O(3)#1
Mn-O(3)
Mn-O(1)#1
Mn-O(1)
Mn-O(2)
Mn-O(2)#1
2.1540(18)
2.1540(18)
2.1666(18)
2.1666(18)
2.1947(17)
2.1947(17)
1.388(3)
1.399(3)
1.399(3)
1.439(2)
1.472(3)
1.474(3)
1.474(3)
1.478(3)
1.474(3)
1.476(3)
1.476(3)
1.474(3)
1.479(3)
1.474(3)
1.474(3)
1.480(3)
Ni-O(3)#1
Ni-O(3)
Ni-O(1)#1
Ni-O(1)
Ni-O(2)
2.0390(19)
2.0390(19)
2.0469(18)
2.0469(18)
2.0712(18)
2.0712(18)
1.389(3)
1.392(4)
1.395(3)
1.439(2)
1.472(3)
1.475(3)
1.477(3)
1.478(3)
1.473(3)
1.473(3)
1.477(3)
1.473(3)
1.478(3)
1.474(3)
1.475(3)
1.480(3)
Zn-O(3)#1
Zn-O(3)
Zn-O(1)#1
Zn-O(1)
Zn-O(2)#1
Zn-O(2)
2.0704(18)
2.0704(18)
2.0729(17)
2.0729(17)
2.1174(17)
2.1174(17)
1.389(3)
1.396(3)
1.397(3)
1.444(2)
1.474(3)
1.475(3)
1.478(3)
1.476(3)
1.473(3)
1.478(3)
1.478(3)
1.473(3)
1.477(3)
1.476(3)
1.476(3)
1.482(3)
Ni-O(2)#1
Cl(1)-O(14)
Cl(1)-O(13)
Cl(1)-O(12)
Cl(1)-O(11)
N(1)-C(8)
N(1)-C(2)
N(1)-C(9)
C(2)-N(3)
N(3)-C(10)
N(3)-C(4)
C(4)-N(5)
N(5)-C(6)
N(5)-C(9)
C(6)-N(7)
N(7)-C(10)
N(7)-C(8)
Cl(1)-O(14)
Cl(1)-O(12)
Cl(1)-O(13)
Cl(1)-O(11)
N(1)-C(8)
N(1)-C(2)
N(1)-C(9)
C(2)-N(3)
N(3)-C(4)
N(3)-C(10)
C(4)-N(5)
N(5)-C(6)
N(5)-C(9)
C(6)-N(7)
N(7)-C(10)
N(7)-C(8)
Cl(1)-O(14)
Cl(1)-O(12)
Cl(1)-O(13)
Cl(1)-O(11)
N(1)-C(8)
N(1)-C(2)
N(1)-C(9)
C(2)-N(3)
N(3)-C(10)
N(3)-C(4)
C(4)-N(5)
N(5)-C(6)
N(5)-C(9)
C(6)-N(7)
N(7)-C(10)
N(7)-C(8)
Mn complex
Ni complex
Zn complex
bond
bond angle
bond
bond angle
bond
bond angle
O(3)#1-Mn-O(3)
O(3)-Mn-O(1)#1
O(3)#1-Mn-O(1)
O(3)-Mn-O(1)
O(1)#1-Mn-O(1)
O(3)#1-Mn-O(2)
O(3)-Mn-O(2)
180.00(11)
91.49(7)
91.49(7)
88.51(7)
180.0
91.09(8)
88.91(8)
91.31(7)
88.69(7)
88.91(8)
91.09(8)
88.69(7)
91.31(7)
180.00(9)
109.4(3)
110.5(4)
O(3)#1-Ni-O(3)
O(3)-Ni-O(1)#1
O(3)#1-Ni-O(1)
O(3)-Ni-O(1)
O(1)#1-Ni-O(1)
O(3)#1-Ni-O(2)
O(3)-Ni-O(2)
180.00(18)
90.04(8)
90.04(8)
89.96(8)
180.00(12)
89.75(9)
90.25(9)
89.60(8)
90.40(8)
90.25(9)
89.75(9)
90.40(8)
89.60(8)
180.00(10)
110.9(5)
109.1(3)
108.7(3)
109.3(2)
108.0(2)
110.78(17)
108.1(2)
108.8(2)
108.3(2)
111.8(2)
108.2(2)
108.3(2)
108.0(2)
112.1(2)
108.4(2)
107.8(2)
108.1(2)
112.3(2)
108.3(2)
108.2(2)
107.8(2)
111.7(2)
111.7(2)
112.1(2)
O(3)#1-Zn-O(3)
O(3)-Zn-O(1)#1
O(3)#1-Zn-O(1)
O(3)-Zn-O(1)
O(1)#1-Zn-O(1)
O(3)#1-Zn-O(2)#1
O(3)-Zn-O(2)#1
O(1)#1-Zn-O(2)#1
O(1)-Zn-O(2)#1
O(3)#1-Zn-O(2)
O(3)-Zn-O(2)
180.00(17)
90.23(8)
90.23(8)
89.77(8)
180.00(11)
89.77(8)
90.23(8)
90.01(7)
89.99(7)
90.23(8)
89.77(8)
89.99(7)
90.01(7)
180.00(10)
109.5(3)
O(1)#1-Mn-O(2)
O(1)-Mn-O(2)
O(1)#1-Ni-O(2)
O(1)-Ni-O(2)
O(3)#1-Mn-O(2)#1
O(3)-Mn-O(2)#1
O(1)#1-Mn-O(2)#1
O(1)-Mn-O(2)#1
O(2)-Mn-O(2)#1
O(14)-Cl(1)-O(12)
O(14)-Cl(1)-O(13)
O(12)-Cl(1)-O(13)
O(14)-Cl(1)-O(11)
O(12)-Cl(1)-O(11)
O(13)-Cl(1)-O(11)
C(8)-N(1)-C(2)
C(8)-N(1)-C(9)
C(2)-N(1)-C(9)
N(1)-C(2)-N(3)
C(4)-N(3)-C(10)
C(4)-N(3)-C(2)
C(10)-N(3)-C(2)
N(3)-C(4)-N(5)
C(6)-N(5)-C(4)
C(6)-N(5)-C(9)
C(4)-N(5)-C(9)
N(5)-C(6)-N(7)
C(10)-N(7)-C(6)
C(10)-N(7)-C(8)
C(6)-N(7)-C(8)
N(1)-C(8)-N(7)
N(1)-C(9)-N(5)
N(7)-C(10)-N(3)
O(3)#1-Ni-O(2)#1
O(3)-Ni-O(2)#1
O(1)#1-Ni-O(2)#1
O(1)-Ni-O(2)#1
O(2)-Ni-O(2)#1
O(14)-Cl(1)-O(13)
O(14)-Cl(1)-O(12)
O(13)-Cl(1)-O(12)
O(14)-Cl(1)-O(11)
O(13)-Cl(1)-O(11)
O(12)-Cl(1)-O(11)
C(8)-N(1)-C(2)
C(8)-N(1)-C(9)
C(2)-N(1)-C(9)
N(1)-C(2)-N(3)
C(10)-N(3)-C(4)
C(10)-N(3)-C(2)
C(4)-N(3)-C(2)
N(3)-C(4)-N(5)
C(6)-N(5)-C(4)
C(6)-N(5)-C(9)
C(4)-N(5)-C(9)
N(5)-C(6)-N(7)
C(6)-N(7)-C(10)
C(6)-N(7)-C(8)
C(10)-N(7)-C(8)
N(1)-C(8)-N(7)
N(1)-C(9)-N(5)
N(3)-C(10)-N(7)
O(1)#1-Zn-O(2)
O(1)-Zn-O(2)
O(2)#1-Zn-O(2)
O(14)-Cl(1)-O(12)
O(14)-Cl(1)-O(13)
O(12)-Cl(1)-O(13)
O(14)-Cl(1)-O(11)
O(12)-Cl(1)-O(11)
O(13)-Cl(1)-O(11)
C(8)-N(1)-C(2)
C(8)-N(1)-C(9)
C(2)-N(1)-C(9)
N(1)-C(2)-N(3)
C(10)-N(3)-C(2)
C(10)-N(3)-C(4)
C(2)-N(3)-C(4)
N(3)-C(4)-N(5)
C(6)-N(5)-C(9)
C(6)-N(5)-C(4)
C(9)-N(5)-C(4)
N(5)-C(6)-N(7)
C(6)-N(7)-C(10)
C(6)-N(7)-C(8)
C(10)-N(7)-C(8)
N(1)-C(8)-N(7)
N(5)-C(9)-N(1)
N(3)-C(10)-N(7)
110.7(4)
108.4(3)
108.5(3)
109.83(18)
110.32(16)
108.17(17)
108.31(19)
108.72(19)
108.31(19)
111.76(18)
108.24(19)
107.97(19)
108.31(19)
112.03(18)
108.52(19)
107.65(19)
108.21(19)
112.18(18)
108.44(19)
107.86(19)
108.15(19)
111.70(19)
111.76(19)
112.05(19)
109.43(19)
110.70(16)
108.12(18)
108.17(19)
108.76(19)
108.48(19)
111.79(18)
108.29(19)
108.19(19)
108.13(19)
111.88(18)
107.88(19)
108.46(19)
108.30(19)
112.14(18)
108.40(19)
108.21(19)
107.83(19)
111.55(19)
111.60(19)
112.11(19)
a Symmetry transformations used to generate equivalent atoms #1: -x, -y, -z.
where R is the extent of conversion, E is the activation of energy
at a particular R, R is the gas constant, and Ti is the absolute
temperature. E is evaluated from the slope of the plot of -ln
tR,i against 1/Ti. Thus, E was evaluated at various extent of
conversion, R. The dependencies of E on the extent of
conversion are shown in Figure 8.

Transition Metal Perchlorate Complexes of HMTA
J. Phys. Chem. A, Vol. 111, No. 50, 2007 12975
Figure 4. Nonisothermal TG of complexes in air at standard
atmospheric conditions.
Figure 6. Isothermal TG of complexes.
TABLE 3: TG-DTA Phenomenological Data of the
Complexes under Air Atmosphere
TGA
DTA
decomposition
peak
complex
step T range/°C
(%)
temp./°C nature
Mn complex
I
II
I
II
I
II
85-135
258-315
90-135
259-280
95-123
291-331
10.61
78.94
10.55
78.20
10.45
67.88
140
325
135
260
120
310
endo
exo
endo
exo
endo
exo
Ni complex
Zn complex
TABLE 4: Explosion Delay (DE/s), Activation Energy for
Thermal Explosion (E*/kJ mol-1), and Correlation
Coefficient (r) for the Complexes
temp/°C
280 300 320 340 360
complex
( 1 ( 1 ( 1 ( 1 ( 1
E*
r
Mn complex
Ni complex
Zn complex
85
72
107
68
63
90
61
57
85
50
48
60
40
39
45
26.5 0.9984
23.8 0.9953
27.8 0.9997
ion through water molecules. The bonding between the HMTA
and the water is clearly shown to be hydrogen bonding. Each
HMTA is attached by hydrogen bonds between the nitrogen of
HMTA and the hydrogen of the water molecule. The perchlorate
ion is also attached to the water molecule via hydrogen bonding.
Their crystal data, structure refinement, bond lengths, and bond
angles, shown in Tables 1 and 2, clearly confirm the molecular
formula of a single molecule [M(H2O-HMTA-H2O)2(H2O-
ClO4)2(H2O)2] (where M ) Mn, Ni, and Zn).
Figure 5. DTA thermogram of complexes in air at standard atmo-
spheric conditions.
The molar conductance (80-112 Ω-1 cm2 mol-1) of the
complexes in water and DMSO at 10-2 to 10-4 molar
concentrations proves their 1:2 electrolyte nature28 and also
support the structures given by X-ray crystallography.
Results and Discussion
The crystal structures of the complexes are shown in Figures
1-3. The two HMTA molecules are attached with the metal

12976 J. Phys. Chem. A, Vol. 111, No. 50, 2007
Singh et al.
for all R, E for the Zn complex is generally higher than it is for
Mn and Ni. The DE data reported in Table 4 indicate that the
time required for thermal explosion at a fixed temperature
decreases in the order
[Zn(H2O-HMTA-H2O)2(H2O-ClO4)2(H2O)2] >
[Mn(H2O-HMTA-H2O)2(H2O-ClO4)2(H2O)2] >
[Ni(H2O-HMTA-H2O)2(H2O-ClO4)2(H2O)2]
All these complexes are stable at room temperature, but they
explode when subjected to higher temperatures. The highest
value of DE and E* for the Zn complex suggests that it is the
most stable and the Ni complex is the least stable (Table 4 and
Figure 7). The contributing factor for this trend may be due to
a lower stability of the Ni (d8 system) complex as compared to
the Mn (half-filled d5 system) complex.
Figure 7. Plot of ln DE vs 1/T for the complexes.
Conclusions
The X-ray crystallography of the complexes shows that the
HMTA is coordinated with a water molecule through the N atom
of HMTA and the H atom of the water molecule. The
perchlorate ion is also attached to metal through water. The
thermal studies indicate that all these complexes undergo
decomposition in two steps.
Figure 8. Dependence of activation energy (E) on the extent of
conversion (R) for the complexes.
It is clear from TG and DTA data that all these complexes
decompose in two steps (Table 3, Figure 4). The first step is
the mass loss in the temperature range 85-139 °C, which
corresponds to the loss of four water molecules, and the second
step corresponds to the loss of two HMTA molecules and further
interaction between the metal and perchlorate ion at higher
temperatures to give finally the respective metal oxides with
evolution of gaseous products. The rate of the thermolysis
reaction is fast and highly exothermic in the second step, which
is evident from by sharp DTA peaks presented in Table 3 and
Figure 5. The endotherm in the first step of the decomposition
is due to removal of four water molecules. Such findings have
also been reported5,6,7,11 during thermal decomposition of metal
amine complexes. The decomposition pathways may be specu-
lated as
Acknowledgment. Thanks to the Head of the Chemistry
Department of DDU Gorakhpur University for Lab facility use.
References and Notes
(1) Strohmeier, W.; Guttenberger, J. F. Chem. Ber. 1963, 96, 2112.
(2) Ahuja, I. S.; Tripathi, Shailendra. Chem. Educ. 1990, Oct-Dec,
56.
(3) Ahuja, I. S.; Yadava, C. L.; Tripathi, S. Indian. J. Chem. 1989,
167.
(4) Luttringhaus; A.; Kullick, W. Tetrahedron Lett. 1959, 10, 13.
(5) Singh, G.; Singh, C. P.; Mannan, S. M. J. Hazarad. Mater. 2005,
122, 111.
(6) Singh, G.; Singh, C. P.; Mannan, S. M. Thermochim. Acta 2005,
21, 437.
(7) Singh, G.; Pandey, D. K. Combust. Flame 2003, 135, 135.
(8) Singh, G.; Pandey, D. K. J. Therm. Anal. Cal. 2005, 82, 353.
(9) Singh, G.; Pandey, D. K. Propellants Explos. Pyro. 2003, 28, 5.
(10) Singh, G.; Prem Felix, S.; Pandey, D. K. Thermochim. Acta 2004,
411, 61.
(11) Singh, G.; Singh, C. P.; Mannan, S. M. J. Hazarad. Mater. 2006,
A135, 10.
(12) Singh, G; Baranwal, B. P.; Kapoor, I. P. S.; Kumar, D.; Singh, C.
P.; Frohlich, Roland, J. Therm. Anal. Cal., in press.
(13) Patil, K. C.; Pai, V. R.; Verneker, V. M. S. Combust. Flame 1975,
25, 387.
(14) Sawant, S. Y.; Kannan, K. R.; Verneker, V. M. S. In Thirteenth
National Symposium on Thermal Analysis BARC, Mumbai, India, 2002.
(15) Singh, G.; Kapoor, I. P. S.; Pandey, D. K. J. Energ. Mater. 2002,
20, 223.
[M(H2O-HMTA-H2O)2(H2O-ClO4)2(H2O)2] -4H O8
2
[M(H2O-HMTA)2(H2O-ClO4)2]
[M(H2O-HMTA)2(H2O-ClO4)2] f
metal oxide + gaseous products
However, such a dissociation occurring in these complexes is
difficult to detect by TG and DTA at atmospheric pressure. The
reason for this is the the metal perchlorate is unstable at higher
temperatures and would decompose with an instantaneously
explosion. As shown in DTA, the expected endotherm corre-
sponding to dissociation process may thus be completely
overshadowed by exothermic process resulting in an overall
exothermic effect.
(16) Singh, G.; Pandey, D. K. Propellants Explo. Pyro. 2003, 28, 5.
(17) Otwinowski, Z.; Minor, W. Methods Enzymol. 1997, 276, 307.
(18) Sheldrick, G. M. Acta Crystallogr. A 1990, 46, 467.
(19) Sheldrick, G. M. SHELXL-97, Program for Crystal Structure
Refinement, University of Gottingen, Germany, 1997.
(20) Keller, E. SCHAKAL - A Computer program for the Graphic
Representation of Molecular and Crystallographic Models, University of
Freiburg, Germany, 1997.
In the analysis of kinetics from the isothermal TG data using
the model fitting method, values of E obtained from different
models for a particular sample are nearly equal but in the case
of the Mn complex there is a larger deviation. It is difficult to
assign a single value of E to a particular process taking place
in such a complex solid-state decomposition. The isoconver-
sional method shows that the thermolysis of these complexes
is not as simple, as indicated by the model fitting method. As
can be seen from Figure 8, the value of E changes with R but
(21) Singh, G.; Singh, R. R. Res. Ind. 1978, 23, 92.
(22) Singh, G.; Kapoor, I. P. S.; Vasudeva, S. K. Indian J. Technol.
1991, 29, 589.
(23) Semenov, N. Chemical Kinetics and Chain Reactions; Clarendon
Press: Oxford, U.K., 1935; Chapter 18.
(24) Freeman, E. S.; Gordon, S. J. Phys. Chem. 1956, 60, 867.
(25) Zinn, J.; Rogers, R. N. J. Phys. Chem. 1962, 66, 2646.
(26) Singh, G.; Felix, Prem, S.; Pandey, D. K. Thermochim. Acta 2004,
411, 61.
(27) Vyazovkin, S.; Wight, C. A. J. Phy. Chem. A 1997, 101, 8279.
(28) Geary, W. J. Coord. Chem. ReV. 1971, 7, 81.