THERMOLYSIS SPECIFICS OF TIN(IV) AND TIN(II) COMPLEX DERIVATIVES
1111
Q, mW
(Acac)2SnCl(N3)
0.625Sn + 0.250SnCl2
+ 0.125SnCl4↑ + 1.5N2↑ + 2CH2CO↑
+ CH3COCH3↑ + C2H4↑ + CO↑.
1
–1
–3
–5
–7
We were interested in the comparison of thermolysis
data for complex 1, with its azide fragment which
readily generates N2, and the structurally similar
(Acac)2SnCl2 (complex 2) which however contains
strongly bound apical chlorine atoms.
170
220
270
T, °C
Compound 2 is stable to 180°ë (Figs. 1c, 1d).
Above, the decomposition starts, initially accompanied
by energy absorption. Qualitatively, the energy pattern
of the thermolysis after nitrogen elimination (Fig. 1) is
similar to the pattern observed in the thermolysis of
(Acac)2SnCl(N3) after nitrogen elimination, but all pro-
cesses occur at lower temperatures and within a nar-
rower temperature range. At 205°ë , complex 2 melts
with decomposition. Above 225°ë, vigorous energy
evolution starts in the background of continuing weight
loss, which is usually observed upon the formation of a
new structure. The process is complete at 300°ë. The
weight loss is 85.2 1.0%. The X-ray powder diffrac-
tion analysis of the solid thermolysis product showed
metallic tin. The DSC study of the thermolysis product
showed Tm = 231.4 0.5°C with ∆Hm = 58.55 0.75 J/g,
which agrees with the parameters of metallic tin and
verifies the product composition. The results enable us
to suggest the following likely scenario of thermolysis
for complex 2:
Fig. 2. Thermoanalytical curve for the thermolysis product
of complex 1 in the range170–270°C.
form upon (CO)5CrSn(Acac)2 decomposition is 35.60%
of the starting weight). For complex 4, the weight loss
is 40.5 1.0%; likely, this loss corresponds to the
removal of 0.7W(CO)6 and 0.8CO (the calculated con-
tent of these products in complex 4 is 41.60 wt %).
Above 180°ë the weight loss progresses and ends at
330.0 5.0°ë for complex 3 and 360.0 5.0°ë for com-
plex 4. At the second stage, for both compounds the
process is accompanied by the evolution of a significant
amount of energy, which usually signifies the formation
of new structures. The weight loss in the range of the
temperatures studied is 72.0 2.0 and 70.0 2.0% for
complex 3 and 4, respectively.
The phase analysis of the thermolysis products
showed SnO and Cr2Sn3 for complex 3, and SnO and
tungsten for complex 4 (Table 1).
We can propose the following thermolysis scenario
for the compounds in question. At the first thermolysis
stage, whole carbonyl molecules are eliminated (i.e.,
M=Sn bonds dissociate to an appreciable degree), and
carbonyl decomposition occurs. Thermogravimetric
data prove an argument in favor of this scenario. At the
second stage, the coordination bonds are broken and
new structures are formed.
(Acac)2SnCl2
0.5Sn + 0.5SnCl4↑
+ 2CH2CO↑ + CH3COCH3↑ + C2H4↑ + CO↑.
Thus, the thermolysis of two acetylacetonatotin(IV)
complexes was studied. These compounds have rela-
tively low decomposition and melting temperatures.
Therefore, similar compounds can serve as molecular
precursors for phases of a certain composition, whose
Likely, the significant exotherm associated with
nature is determined by the substituents at the tin atom. tin(IV) reduction to tin(II) is a means for overcoming
the energy barrier to tin(II) reduction to the metal via
To compare the thermolysis routes and the com-
acetylacetonato ligands during the thermolysis of
positions of the final solid products for tin(II) and
acetylacetonatotin(IV) derivatives. It is for this reason
tin(IV) complexes, we studied the thermolysis of
that the thermolysis of complexes 1 and 2 produces
metallic tin, which is absent in the thermolysis of com-
plexes 3 and 4.
CO)5CrSn(Acac)2 (complex 3) and (CO)5WSn(Acac)2
(complex 4).
Both compounds melt upon heating (at 91.0 0.5°ë
for complex 3 and 85.2 0.5°ë for complex 4) with
simultaneous decomposition (Fig. 3). Compound 4
loses 2.3 1.0% of its weight upon melting; for com-
pound 3, the weight loss is 4.1 1.0%. The decomposi-
tion is staged. The first stage for both compounds is
accompanied by energy absorption and ends by 180.0
2.0°ë. The weight loss for compound 3 constitutes 35.3
1.0%, likely corresponding to the removal of
5/6Cr(CO)6 (the calculated amount of Cr(CO)6 that can
The intermetallic compound Cr2Sn3 is one thermol-
ysis product of complex 3. Many similar compounds
have useful physicochemical properties, in particular,
magnetic properties; synthesis from constituent ele-
ments, the conventional method for preparing interme-
tallic compounds, requires high temperatures and pres-
sures.
In this context, we were interested in studying the
thermolysis of other complexes in which tin atoms are
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 52 No. 7 2007