Thermal behavior of organotin(IV) triazolates: Molecular precursors for pure-phase, nanosized SnS/SnO2

Article abstract of DOI:10.1016/j.tca.2009.01.019

The thermal behavior of organotin(IV) triazolates of general formula, R_nSnL_m (n = 3, m = 1; R = Me and Ph; n = 2, m = 2; R = Me and n-Bu; for HL = 4-amino-3-methyl-1,2,4-triazole-2-thiol (HL-1) and 4-amino-3-ethyl-1,2,4-triazole-2-th

Full text of DOI:10.1016/j.tca.2009.01.019

Thermochimica Acta 489 (2009) 27–36
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Thermochimica Acta
journal homepage: www.elsevier.com/locate/tca
Thermal behavior of organotin(IV) triazolates: Molecular precursors for
pure-phase, nanosized SnS/SnO2
Mala Nath∗, Sulaxna
Department of Chemistry, Indian Institute of Technology, Roorkee 247 667, India
a r t i c l e i n f o
a b s t r a c t
Article history:
The thermal behavior of organotin(IV) triazolates of general formula, RnSnLm (n = 3, m = 1; R = Me
and Ph; n = 2, m = 2; R = Me and n-Bu; for HL = 4-amino-3-methyl-1,2,4-triazole-2-thiol (HL-1) and 4-
amino-3-ethyl-1,2,4-triazole-2-thiol (HL-2); n = 2, m = 2, R = Ph for HL-1), has been investigated by
thermogravimetry–differential thermal analysis–derivative thermogravimetric (TG–DTA–DTG) tech-
niques. The thermal decomposition studies under air and nitrogen indicated different thermal behavior
modes. This method provides a simple route to prepare nanosized (∼6 to 60 nm) semiconductors SnS and
SnO2 in nitrogen and air atmosphere, respectively, at low temperature ∼550 to 700 ◦C. The X-ray diffrac-
tion studies of the residues along with SEM and TEM measurements show that Ph2Sn(L-1)2 is the best
precursor for pure-phase nanoscale SnO2 and n-Bu2Sn(L-2)2 for SnS among the studied precursors, how-
ever, n-Bu2Sn(L-1)2 is a better precursor for the production of both nanoscale pure-phase SnO2 and SnS.
© 2009 Elsevier B.V. All rights reserved.
Received 24 July 2008
Received in revised form
26 December 2008
Accepted 1 January 2009
Available online 23 February 2009
Keywords:
Organotin(IV) triazolates
Thermogravimetric analysis
X-ray diffraction
Scanning electron microscopy
Transmission electron microscopy
1. Introduction
for the production of semiconducting nanoscale SnS [1,18–23] and
SnO2 [2,3,5,24–27]. In recent years, organotin–sulfur compounds
Thermal methods (TG/DTA/DTG) attracted a considerable atten-
tion of researchers during the last decade because of their wide
spread practical application, especially, in the field of the produc-
tion of nanoscale metallic particles/semiconducting metallic oxides
or sulfides [1–5]. Moreover, thermogravimetric method provides a
simple and cost effective route to prepare these nanoscale materi-
als. Thermogravimetry and differential thermal analyses (TG/DTA)
are not only the important tools in research and routine analysis,
but also are valuable techniques for the study of the thermal prop-
erties of various compounds [1–9]. Organometallic compounds as
single source precursors have attracted a great attention because
they decompose at low temperatures producing pure metallic
oxides/sulfides and metallic particles.
Semiconducting nanoparticles such as SnO2 and SnS have been
studied extensively owing to their potential applications in solar
cells as transparent electrodes, photocatalysis and in optoelectronic
industry [10–13], and used as gas sensors, heat mirrors, and varis-
tors [14–17]. Especially, SnO2 nanoparticles have been intensively
studied for gas sensing applications not only because of their rela-
tively low operating temperature, but also due to the fact that they
can be used to detect both reducing and oxidizing gases. A variety of
chemical and physical methods have been reported in the literature
have been explored as single source precursors for the preparation
of semiconducting nanoscale SnO2 and SnS [1–3,5]. Therefore, it is
worth mentioning to explore further the best precursors, which can
produce pure-phase, nanoscale SnS and SnO2 on their pyrolysis.
In our research group, earlier studies relating to thermal behav-
ior of a number of organotin compounds, and the preparation
of tin(II) sulfide and tin(IV) oxide by pyrolysis of single source
precursors have been reported [3,5,28–30] in order to explore
the best precursors for the production of nanosized SnS and
SnO2, and also to improve the yield and the quality of tin-based
materials. In continuation to our research interest, herein we
report thermal decomposition of di-/triorganotin(IV) derivatives
of 4-amino-3-methyl-1,2,4-triazole-2-thiol (HL-1) and 4-amino-3-
ethyl-1,2,4-triazole-2-thiol (HL-2) in air and nitrogen by using TG
and DTA techniques yielding semiconducting nanoscale SnO2 and
SnS. The particle size of the residues (SnO2/SnS) obtained has been
determined by X-ray diffraction analysis, SEM and TEM studies.
2. Experimental
2.1. Synthesis of di-/triorganotin(IV) derivatives of
4-amino-3-methyl-1,2,4-triazole-2-thiol (HL-1) and
4-amino-3-ethyl-1,2,4-triazole-2-thiol (HL-2)
∗
Di-/triorganotin(IV) derivatives of 4-amino-3-methyl-1,2,4-
triazole-2-thiol (HL-1) and 4-amino-3-ethyl-1,2,4-triazole-2-thiol
Corresponding author. Tel.: +91 1332 285797; fax: +91 1332 273560.
E-mail address: malanfcy@iitr.ernet.in (M. Nath).
0040-6031/$ – see front matter © 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.tca.2009.01.019

28
M. Nath, Sulaxna / Thermochimica Acta 489 (2009) 27–36
(HL-2) have been synthesized according to previously reported
method [31]. methanolic solution (30 ml) of HL-1/HL-2
A
(4.0 mmol) was added to sodium methoxide (prepared by dissolv-
ing sodium (4.2 mmol) in dry methanol (5 ml) under dry nitrogen.
The reaction mixture was immediately turned to orange–red color,
which was stirred for another 8 h at room temperature. To this, a
methanol (30 ml) solution of R2SnCl2 (2.0 mmol)/R3SnL (4.0 mmol)
was added dropwise with constant stirring, and stirred for 30–35 h
at room temperature. The reaction mixture was centrifuged and
filtered in order to remove sodium chloride, and the volatiles
were removed in vacuo. The solid obtained was recrystallized from
methanol.
2.2. Measurements and characterizations
Thermogravimetric (TG) with simultaneous derivative thermo-
gravimetric (DTG) and differential thermal analysis (DTA) of the
organotin(IV) triazolates were performed on a PerkinElmer Pyris
Diamond thermal analyzer. For TG analysis the weighed amount of
the compound and reference (alumina powder) were placed in plat-
inum crucibles of the pan sealed in a dry box. Samples of 10–15 mg
were heated up to 1000 ◦C at a heating rate of 10 ◦C/min. Dry air and
nitrogen gas were used as purge gases at a flow rate of 400 ml/min.
The residues were prepared by the thermal decomposition of organ-
otin(IV) precursors in a tube furnace under similar experimental
conditions up to the formation temperature of SnS/SnO2 as deter-
mined by TG. X-ray diffraction pattern (XRD) of the residues was
recorded on the same instruments and under similar experimental
conditions as reported previously [3,5]. The surface morphology of
the residues was studied by using a scanning electron microscope
(SEM) as reported previously [3,5] and by a transmission electron
microscope (TEM). The TEM image of the residue obtained from
pyrolysis of n-Bu2Sn(L-2)2 in air was recorded on a TEM model
Philips, EM 400 at Institute Instrumentation Center, Indian Institute
of Technology Roorkee, Roorkee and that obtained from n-Bu2Sn(L-
1) 2 in nitrogen was recorded on a TEM model Philips, Morgagni 268
D at Electron Microscopic Section, All India Institute of Medical Sci-
ences, New Delhi. To record the SEM and TEM images of the residues
the specimens were prepared according to the previously reported
methods [3,5].
Fig. 1. Structure of R2SnL2 (where R = Me, n-Bu, n-Oct and Ph; HL = HL-1 and HL-2)
(a); and for R3SnL (where R = Me, n-Pr, n-Bu and Ph; Rꢀ = Me and Et; HL = HL-1 and
HL-2) (b).
3.1. Thermal decomposition of the ligands (HL-1 and HL-2) under
air
In air, HL-1 and HL-2 follow almost similar three steps decom-
position pattern. Though the first decomposition step is not very
clear from the TG profile of HL-1, but it is clearly defined by its DTG
curve. This step corresponds to the loss of NH2 (Tables 1 and 3) for
both the ligands. However, the observed aggregate mass loss (for
HL-1: 89.59%; for HL-2: 84.57%) in the second and third steps, cor-
responds to complete decomposition of the rest of organic moiety
(Tables 1 and 3). The decomposition steps of the ligands under nitro-
gen are similar to those observed in air with only 1–2 ◦C difference
in their weight loss step tangents.
3.2. Thermal decomposition of diorganotin(IV) triazolates under
air and nitrogen
The TG plots of Me2Sn(L-1)2 exhibit complex and overlapping
consecutive decomposition steps both in air and nitrogen. The mass
loss observed in the first step corresponds to the loss of N2H4 in
both air and nitrogen (Tables 1 and 2). Further, in air, the mass loss
observed (obsd. 52.60%; calcd. 47.20%) in the second step corre-
sponds to the loss of C8H12N6 along with partial oxidation of tin,
which is evidenced by the exothermic peaks observed at 468 and
590 ◦C in its DTA curve (Fig. 3). Thereafter, a very slow decomposi-
tion is continued up to 743 ◦C followed by rapid sublimation of the
residue up to ∼1000 ◦C (10.87% residue). The residue left at 1000 ◦C
has been analyzed by powder XRD. The observed d values indicated
a mixture of SnO2 and SnO [32] (Table 5). However, in nitrogen, the
second and third steps are overlapped; therefore, tentative tem-
perature ranges have been assigned for these steps (Table 2). The
weight loss observed in the second step corresponds to the loss of
C6H6N6 (obsd. 38.0%; calcd. 39.83%). The loss of C2H6S took place
in the third step giving SnS which was completely sublimed up to
1000 ◦C. The XRD spectrum of the intermediate species formed at
∼750 ◦C is not good, and the observed d values correspond mainly
to those of SnS [32].
3. Results and discussion
The structure and stoichiometry of the single source pre-
cursors, organotin(IV) triazolates of general formula RnSnLm
(n = 3, m = 1; R = Me and Ph; n = 2, m = 2; R = Me and n-Bu; for
HL = 4-amino-3-methyl-1,2,4-triazole-2-thiol (HL-1) and 4-amino-
3-ethyl-1,2,4-triazole-2-thiol (HL-2); n = 2, m = 2, R = Ph for HL-1),
have been established by various physicochemical and spectral
studies as reported in our previous communication [21], and are
presented in Fig. 1(a) and (b).
The TG and DTA curves, respectively, of HL-1 and HL-2 in air, and
their organotin(IV) derivatives in air and nitrogen, respectively, are
presented in Figs. 2(a) and 3 and the results are given in Tables 1–4.
DTG curves of a few compounds are also presented in Fig. 2(b).
The XRD profiles of the residues obtained by thermal decompo-
sition of organotin(IV) derivatives of HL-1 and HL-2 in both air
and nitrogen atmosphere are presented in Figs. 4 and 5, respec-
tively, and the main diffraction lines have been summarized in
Table 5. The SEM images of the residue obtained from the pyrol-
ysis of Ph3Sn(L-1) in air, n-Bu2Sn(L-1)2 in nitrogen, n-Bu2Sn(L-2)2
in air and Ph3Sn(L-2) in nitrogen are given in Fig. 6(a)–(d), and
TEM images of the residues obtained by the pyrolysis of n-Bu2Sn(L-
1)2 in nitrogen and n-Bu2Sn(L-2)2 in air are given in Fig. 7(a)
and (b).
The first two steps of decomposition of Me2Sn(L-2)2 are same
in both air and nitrogen (Tables 3 and 4) which correspond to the
loss of N2H4 and C8H10N6, respectively. The third weight loss step
occurs in the temperature range 450–610 ◦C in air and 440–755 ◦C
in nitrogen, and the observed mass losses are 12.60% and 11.14%,

M. Nath, Sulaxna / Thermochimica Acta 489 (2009) 27–36
29
Fig. 2. (a) TGA plots of HL-1, HL-2 in air, and their diorganotin(IV) triazolates and triorganotin(IV) triazolates under air and nitrogen. (b) DTG plots of n-Bu2Sn(L-1)2 and
Me2Sn(L-2)2 under air and n-Bu2Sn(L-2)2 and Ph3Sn(L-1) under nitrogen.

30
M. Nath, Sulaxna / Thermochimica Acta 489 (2009) 27–36
Fig. 3. DTA plots of HL-1, HL-2 in air, and their diorganotin(IV) and triorganotin(IV) triazolates under air and nitrogen.
Fig. 4. XRD patterns of the residues obtained by the thermal decomposition of di- and triorganotin(IV) derivatives of HL-1 under air and nitrogen.

M. Nath, Sulaxna / Thermochimica Acta 489 (2009) 27–36
31
Table 1
Thermal analysis data of 4-amino-3-methyl-1,2,4-triazole-2-thione (HL-1) and its organotin(IV) derivatives in air.
Ligand/compound
Step
Trange TG (◦C)
Tpeak DTG (◦C)
Tpeak DTA (◦C) (enthalpy mJ/mg)
Loss of mass%
Obsd. (calcd.)
Species lost
NH2
HL-1
I
II
188–205
205–333
203
277
209
10.41 (12.31)
63.46
238 (−1094)
Rest of the ring moiety
272
(87.69)
III
333–725
443a
670a
447 (−69)
672 (−566)
26.13
Me2Sn(L-1)2
n-Bu2Sn(L-1)2
Ph2Sn(L-1)2
I
80–177
114
174
269
461
588
830
117 (136)
10.46 (7.88)
N2H4
II
177–618
197 (14)
46.69 (47.21)
C8H12 N6
468 (−222)
590 (−648)
785 (−60)
III
618–1000
31.98 (15.76)
2S and Sublimation
I
II
III
IV
V
82–115
115–150
150–299
299–405
405–608
608–979
108
135
274
378
566
947
110 (87)
5.66 (6.52)
5.58 (6.12)
26.26 (26.88)
9.12 (11.63)
9.45 (11.63)
13.47 (13.06)
N2H4
C2H6
C4N6
C4H9
C4H9
2S
140 (−82)
Broad exotherm
Broad exotherm
561 (−784)
VI
Broad exotherm
I
II
III
IV
88–132
132–155
155–255
255–605
109
147
209
259
278
583
110 (171)
8.80 (6.04)
6.51 (5.66)
11.46 (12.43)
51.35 (53.53)
N2H4
C2H6
C2N3
C14 H10 N3S2
151 (−102)
Broad exotherm
455 (−235)
600 (−504)
Me3Sn(L-1)
Ph3Sn(L-1)
I
71–134
107
118
209
251
408
110 (139)
33.21 (33.14)
37.95 (26.34)
C3H5N4
123 (−63)
II
134–299
Broad exotherm
C3H9S
III
I
299–455
85–539
413 (−369)
7.94 (−)
Sublimation
130
117 (81)
76.24 (75.22)
All organic moieties
attached to tin
313
343
168 (−40)
365 (−113)
512 (−602)
a
Very small peak.
respectively (calcd. 14.28% for loss of C2H6S), yielding an inter-
mediate. This intermediate sublimed in the temperature range
717–907 ◦C in air and 755–970 ◦C in nitrogen. Only 4.4% residue was
left at 984 ◦C in air. The XRD analysis (Table 5) of the residue formed
at 610 ◦C in air indicated the formation of SnO2, whereas the main
diffraction lines obtained in the XRD pattern of the intermediate
species formed at 755 ◦C in nitrogen indicated the formation of SnS
[32].
Table 2
Thermal analysis data of organotin(IV) derivatives of 4-amino-3-methyl-1,2,4-triazole-2-thione (HL-1) in nitrogen.
Compound
Step
Trange TG (◦C)
Tpeak DTG (◦C)
Tpeak DTA (◦C) (enthalpy mJ/mg)
Loss of mass%
Obsd. (calcd.)
Species lost
Me2Sn(L-1)2
I
II
III
IV
92–163
163–637
637–828
828–1000
116, 154
275, 454
–
118 (120)
–
–
9.0 (7.88)
N2H4
C6H6N6
C2H6S
38.0 (39.83)
14.0 (15.26)
39.0 (37.03)
894
888 (591)
Sublimation
n-Bu2Sn(L-1)2
I
II
III
IV
V
90–118
118–150
150–583
583–750
750–995
110
136
187, 272
–
835
111 (79)
6.0 (6.52)
6.0 (6.12)
44.0 (50.14)
8.0 (6.53)
29.0 (−)
N2H4
C2H6
C8H18 N6
Oxidation of S
Sublimation
139 (−75)
Broad exotherm
Broad exotherm
Broad exotherm
Ph2Sn(L-1)2
Me3Sn(L-1)
I
133–439
175, 282 311, 371
111 (14)a
212 (17)a
460 (−78)b
65.0 (65.58)
All organic moieties
II
I
439–725
85–125
680
8.0 (6.04)
Oxidation of S
C3H5N4
109, 118
112 (48)a
34.0 (33.14)
123 (−74)b
II
III
125–276
276–819
170, 219 248
–
Broad exotherm
Broad exotherm
38.0 (15.39)
3CH3 + sublimation
Sublimation
26.0 (−)b
Ph3Sn(L-1)
I
160–370
370–760
175, 270
Broad exotherm
Broad exotherm
85.0 (75.23)
All organic moieties
attached to tin
Sublimation
II
439a, 636a
15.0 (−)b
a
Very small peak.
Unidentified mass loss.
b

32
M. Nath, Sulaxna / Thermochimica Acta 489 (2009) 27–36
Fig. 5. XRD patterns of the residues obtained by thermal decomposition of di- and triorganotin(IV) derivatives of HL-2 under air and nitrogen.
Fig. 6. SEM image of residues obtained by thermal decomposition of Ph3Sn(L-1) in air (a); n-Bu2Sn(L-1)2 in nitrogen (b); n-Bu2Sn(L-2)2 in air (c); and Ph3Sn(L-2) in nitrogen (d).

M. Nath, Sulaxna / Thermochimica Acta 489 (2009) 27–36
33
Table 3
Thermal analysis data of 4-amino-3-ethyl-1,2,4-triazole-2-thione (HL-2) and its organotin(IV) derivatives in air.
Compound
Step
Trange TG (◦C)
Tpeak DTG (◦C)
Tpeak DTA (◦C) (enthalpy mJ/mg)
Loss of mass%
Obsd. (calcd.)
15.43 (11.11)
Species lost
NH2
HL-2
I
145–226
218
150 (153)
223(−331)
279 (101)
635 (−262)
744 (−56)
II
III
226–342
342–771
280
58.53
Rest of the organic moiety
650a
26.04
(88.89)
Me2Sn(L-2)2
I
II
140–155
155–450
150
256
140 (80)
8.30 (7.36)
42.80 (43.73)
N2H4
C8H10 N6
155 (−50)
209 (−70)
581 (−514)
773 (13)
III
IV
450–610
717–907
559, 581
858
12.60 (14.28)
C2H6S
Sublimation
31.90 (−)b
864 (39)
n-Bu2Sn(L-2)2
Me3Sn(L-2)
I
120–142
142–560
134
130 (74)
139 (−96)
226 (−64)
362 (−1164)
474
8.50 (6.17)
N2H4
II
272
353
65.70 (71.0)
Rest of the organic groups attached to tin
I
113–130
130–291
124
243
121 (28)
127 (−69)
235 (−12)
260 (−25)
378 (−108)
593 (−332)
10.50 (5.22)
43.10 (45.68)
NH2
C7H14 N3
II
III
IV
291–548
548–993
385
597
9.40 (10.45)
18.90 (–)b
Oxidation
Oxidation and sublimation
Ph3Sn(L-2)
I
59–90
80
84 (68)
8.0 (9.14)
C2H7N
II
90–418
195, 303
117 (10)
58.60 (60.28)
C20H15 N3
200 (−35)
254 (−56)
308 (−5)
346 (−71)
617 (−169)
III
418–660
585a
5.0 (6.50)
Oxidation
a
Small and broad peak.
Unidentified mass loss.
b
n-Bu2Sn(L-1)2 exhibited a complex decomposition profiles both
in air and C8H18 N6 in nitrogen. The third step in air is overlapped
by fourth and fifth steps, followed by oxidation, leaving a residue
of 30.46% (calcd. for SnO2: 30.26%) at 979 ◦C, which is confirmed as
SnO2 by its XRD spectrum (Table 5). Whereas, in nitrogen, the fourth
mass loss step in the temperature range 583–750 ◦C is overlapped
in air and nitrogen (Tables 1 and 2). The first two steps are similar
in both atmospheres and the observed mass losses in these steps
correspond to the loss of N2H4 and C2H6, respectively. However, the
mass loss observed in the third step corresponds to the loss of C4N6
Table 4
Thermal analysis data of organotin(IV) derivatives of 4-amino-3-ethyl-1,2,4-triazole-2-thione (HL-2) in nitrogen.
Compound
Step
Trange TG (◦C)
Tpeak DTG (◦C)
Tpeak DTA (◦C) (enthalpy mJ/mg)
Loss of mass%
Obsd. (calcd.)
8.02 (7.36)
Species lost
N2H4
Me2Sn(L-2)2
I
135–157
151
140 (56)
155 (−68)
210 (−82)
Broad exotherm
768 (9)
II
III
IV
157–440
440–755
755–970
267
–
–
43.98 (43.73)
11.14 (14.28)
36.80 (−)a
(C8H10 N6)
C2H6S
Sublimation
n-Bu2Sn(L-2)2
Me3Sn(L-2)
I
115–136
136–490
490–830
132
125 (60)
134 (−103)
–
8.20 (6.17)
62.70 (64.82)
25.20 (−)a
N2H4
II
III
272
473b
802
Rest of the organic moiety
Sublimation
–
I
II
123–131
131–295
127
242
123 (42)
131 (−92)
235 (−16)
247 (11)
9.10 (5.22)
48.1 (45.68)
NH2
C7H14 N3
III
295–880
861
871 (250)
39.40 (−)a
Sublimation
C2H7N
Ph3Sn(L-2)
I
57–98
82
85 (76)
9.0 (9.14)
II
98–452
197
306
116 (10)
200 (−31)
62.50 (60.28)
C20H15 N3
III
452–993
–
–
20.20 (−)a
Sublimation
a
Unidentified mass loss.
Very small peak.
b

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M. Nath, Sulaxna / Thermochimica Acta 489 (2009) 27–36
Table 5
The main diffraction lines (intensity) and crystal average size calculated by Scherrer equation for the residue obtained in air and nitrogen atmosphere.
Residue of precursors
Main diffraction lines d, Å (intensity %) (h k l)
Average size D (nm)
1
2
3
4
5
Sna
2.92 (100)
(2 0 0)
2.79 (90)
(1 0 1)
2.06 (34)
(2 2 0)
2.02 (74)
(2 1 1)
1.48 (23)
(1 1 2)
SnOa
3.39 (100)
3.00 (50)
2.89 (90)
2.67 (90)
1.77 (80)
a
SnO2
3.35 (100)
(1 1 0)
2.64 (80)
(1 0 1)
2.37 (25)
(2 0 0)
1.77 (65)
(2 1 1)
1.68 (18)
(2 2 0)
SnSa
3.24 (15)
(0 2 1)
2.83 (25)
(1 1 1)
2.79 (100)
(0 4 0)
2.31 (15)
(1 3 1)
1.40 (70)
(1 7 1)
a
SnS2
3.15 (40)
(1 0 0)
2.78 (100)
(1 0 1)
2.14 (50)
(1 0 2)
1.82 (50)
(1 1 0)
1.74 (32)
(1 0 0)
In air atmosphere
Me2Sn(L-1)2
n-Bu2Sn(L-1)2
Ph2Sn(L-1)2
Me3Sn(L-1)
Ph3Sn(L-1)
2.81 (100)
3.35 (100)
3.34 (100)
3.34 (100)
3.34 (100)
2.64 (12)
2.64 (90)
2.63 (81)
2.63 (72)
2.64 (78)
–
1.76 (7)
1.63 (15)
1.67 (55)
1.63 (34)
–
49.95
23.45
18.28
15.26
12.27
2.37 (37)
2.33 (45)
2.35 (48)
2.31 (36)
1.76 (55)
1.76 (38)
1.76 (46)
1.76 (60)
1.67 (33)
Me2Sn(L-2)2
3.34 (9)
–
2.64 (12)
3.11 (7)
–
1.76 (5)
–
1.62 (19)
35.41
2.81 (100)
n-Bu2Sn(L-2)2
Me3Sn(L-2)
Ph3Sn(L-2)
3.33 (100)
3.35 (100)
3.34 (97)
2.64 (68)
2.64 (95)
2.64 (100)
2.37 (33)
2.37 (31)
2.37 (38)
1.76 (34)
1.76 (74)
1.76 (77)
1.68 (24)
1.67 (24)
1.67 (29)
44.45
19.64
23.46
In nitrogen atmosphere
Me2Sn(L-1)2
n-Bu2Sn(L-1)2
Ph2Sn(L-1)2
Me3Sn(L-1)
Ph3Sn(L-1)
3.27 (92)
3.16 (44)
3.26 (27)
–
2.87 (73)
2.83 (47)
2.83 (100)
2.89 (−)
–
2.81 (83)
–
–
2.16 (73)
2.17 (34)
2.31 (28)
2.06 (−)
2.31 (56)
1.44 (77)
1.47 (18)
1.41 (12)
1.46 (−)
1.47 (33)
–
35.40
29.30
15.84
27.65
2.48 (−)
3.20 (88)
2.75 (81)
Me2Sn(L-2)2
3.25 (11)
2.91 (3)
2.81 (100)
–
–
–
1.99 (59)
–
1.41 (9)
26.54
n-Bu2Sn(L-2)2
Me3Sn(L-2)
Ph3Sn(L-2)
3.17 (36)
3.26 (29)
3.23 (45)
–
2.78 (44)
–
–
2.36 (27)
2.31 (10)
2.24 (16)
1.41 (21)
1.41 (11)
1.41 (13)
22.40
29.29
29.30
2.82 (100)
2.82 (100)
a
Ref. [32].
and followed by the continuous sublimation of the residue up to
995 ◦C leaving only 7% residue at 995 ◦C. The observed d values in
the XRD spectrum of the residue obtained at ∼995 ◦C indicated the
formation of SnS (Table 5).
analysis of the residue left (27.0%) at 725 ◦C suggests SnS as end
product.
3.3. Thermal decomposition of triorganotin(IV) triazolates under
air and nitrogen
In air and nitrogen, n-Bu2Sn(L-2)2 decomposed in two and
three steps, respectively. In both air and nitrogen, the loss of N2H4
occurred in the first step. Further, in air atmosphere, all the organic
moieties are lost along with oxidation of tin in the second step, leav-
ing a residue of 25.80% (calcd. for SnO2: 29.02%) at 560 ◦C, which
has been confirmed as SnO2 by its XRD data (Table 5). In nitrogen,
the mass loss observed (62.70%) in the second step corresponds
to the loss of rest of organic moiety (calcd.: 64.82%). The residue
obtained at 490 ◦C has been confirmed as SnS by its XRD spec-
trum, which sublimed on further heating up to 995 ◦C leaving 3.9%
residue.
In air, a four step decomposition mechanism is proposed for
Ph2Sn(L-1)2 on the basis of its DTG curve. For the first two decom-
position steps, the loss of N2H4 and C2H6 are tentatively proposed.
The mass loss observed in the third step corresponds to the loss
of one triazole ring moiety, which is followed by the loss of rest of
the organic moieties with simultaneous oxidation of tin (Table 1).
The residue left (obsd. 24.09%; calcd. for SnO2: 28.01%) at ∼600 ◦C
has been confirmed as SnO2 by its XRD spectrum. However, in
nitrogen, the decomposition of Ph2Sn(L-1)2 occurred in two steps.
In the first step, all organic moieties are lost, followed by a slow
decomposition step in the temperature range 323–725 ◦C. The XRD
Both in air and nitrogen, the thermal decomposition of Me3Sn(L-
1) occurred in three steps. The weight loss observed in first step
corresponds to the loss of ligand moiety in both the atmospheres.
Thereafter, a loss of 3CH3 + S (i.e. C3H9S) and 3CH3 occurred in
air and nitrogen, respectively. The XRD analyses of the residues
obtained at 300 ◦C suggested the formation of a mixture of SnO2
and Sn in air, and of SnS + Sn in nitrogen [32]. On further heating,
up to ∼1000 ◦C an unexpected mass loss step was observed in both
the atmospheres, which might be due to the sublimation of the
residue.
In air and nitrogen, the decomposition of Me3Sn(L-2) occurred
in four and three steps, respectively, with unexpectedly high aggre-
gate mass loss (obsd.: 81.60% in air, 96.60% in nitrogen; calculated
mass loss on considering Sn as final residue: 61.33%). The mass
losses observed for the first two steps correspond to the loss of NH2
and rest of the ligand moiety along with methyl groups attached to
tin, respectively, in both air and nitrogen. Further, in air the inter-
mediate is oxidized which is evidenced by an exothermic peak at
593 ◦C in DTA curve (Table 3). Thereafter, in air and nitrogen an
unexpected mass loss was observed (Tables 3 and 4) which might

M. Nath, Sulaxna / Thermochimica Acta 489 (2009) 27–36
35
Fig. 7. TEM image of residues obtained by thermal decomposition of n-Bu2Sn(L-1)2 in nitrogen (a); n-Bu2Sn(L-2)2 in air (b).
be due to the sublimation of the residue. The main diffraction lines
observed in the XRD pattern of the residues, obtained at ∼600 ◦C
are found to correspond to those of SnO2 in air and a mixture of
SnS + Sn in nitrogen [32].
value, it is very difficult to measure the smallest particles present
in the sample.
The size of the grains of the residues obtained by pyrolysis of n-
Bu2Sn(L-1) 2 in nitrogen, and n-Bu2Sn(L-2)2 in air, is also measured
by TEM (Fig. 7(a) and (b), respectively). The size determined by TEM
is in the range of ∼6.0 to 60.0 nm.
In air, the decomposition of Ph3Sn(L-1) occurred in a single step
and the experimental mass loss corresponds to the loss of all organic
moieties along with oxidation of tin, which is evidenced by exother-
mic peaks at 365 and 512 ◦C observed in its DTA curve. The XRD
pattern of the residue obtained at ∼540 ◦C is indicative of the forma-
tion of SnO2 [32]. Whereas, in nitrogen, it decomposes in two steps,
and the first mass loss step corresponds to the loss of most of organic
moieties. The XRD analysis of the residue suggested the formation
of a mixture of SnS + Sn at 370 ◦C which sublimed continuously up
to 760 ◦C without leaving any residue.
Ph3Sn(L-2) decomposed in three steps in both air and nitro-
gen. The first two steps are identical in both atmospheres and
correspond to the loss of C2H7N and C20H15N3, respectively. The
simultaneous oxidation also occurred in air which was evidenced
by some additional peaks in DTA at 254, 308 and 346 ◦C. Further, in
air, the third weight loss step occurred in the temperature range
418–660 ◦C, which corresponds to oxidation (Table 3) leaving a
residue of 28.0% (calcd. for SnO2: 30.40%). The XRD analysis of the
white powder showed the formation of SnO2. However, the XRD
analysis of the black–grey powder obtained at 452 ◦C in nitrogen
confirmed it as SnS, which sublimed continuously up to 993 ◦C
(Fig. 2).
4. Conclusions
Di- and triorganotin(IV) triazolates pyrolyzed under different
modes yielding SnO2 and SnS (or SnS + Sn) in air and nitrogen
atmospheres, respectively, as final residue. Thermal decomposi-
tion behavior along with SEM, TEM and XRD studies indicated
that Ph2Sn(L-1)2 is the best precursor for production of pure-phase
nanoscale SnO2 and n-Bu2Sn(L-2)2 for SnS among the studied pre-
cursors, however, n-Bu2Sn(L-1)2 is found to be a better precursor
for the production of both nanoscale pure-phase SnO2 and SnS.
Acknowledgements
The authors are thankful to the Heads, Department of Metal-
lurgy and Material Science and Institute Instrumentation Center,
Indian Institute of Technology Roorkee, Roorkee, and to the Head,
Electron Microscopic Section, All India Institute of Medical Science,
New Delhi. Ms. Sulaxna is also grateful to the Council of Scientific
and Industrial Research, New Delhi, for awarding Senior Research
Fellowship.
3.4. Surface morphology and size determination of the residue
(SnO2/SnS)
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