Thermolysis of polynuclear platinum(II) acetamidato complexes

Article abstract of DOI:10.1134/S0036023607060149

The thermolysis of five polynuclear Pt(II) acetamidato complexes with known structures (I-V) and platinum blue of the composition Pt(NHCOCH ₃)₂ ? H₂O prepared by two different procedures (VI and VIa) has been studied by di

Full text of DOI:10.1134/S0036023607060149

ISSN 0036-0236, Russian Journal of Inorganic Chemistry, 2007, Vol. 52, No. 6, pp. 906–913. © Pleiades Publishing, Inc., 2007.
Original Russian Text © T.N. Fedotova, Zh.V. Dobrokhotova, G.N. Kuznetsova, I.L. Eremenko, 2007, published in Zhurnal Neorganicheskoi Khimii, 2007, Vol. 52, No. 6,
pp. 976−983.
PHYSICAL METHODS
OF INVESTIGATION
Thermolysis of Polynuclear
Platinum(II) Acetamidato Complexes
T. N. Fedotova, Zh. V. Dobrokhotova, G. N. Kuznetsova, and I. L. Eremenko
Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences,
Leninskii pr. 31, Moscow, 119991 Russia
Received June 5, 2006
Abstract—The thermolysis of five polynuclear Pt(II) acetamidato complexes with known structures (I–V)
and platinum blue of the composition Pt(NHCOCH3)2 · H2O prepared by two different procedures (VI and VIa)
has been studied by differential scanning calorimetry and thermogravimetry. The results of studying the ther-
molysis of these complexes allows one to assume that the structures of VI and VIa are different: complex VI is
polynuclear and consists of binuclear fragments[(H2O)(NHCOCH3)Pt(µ-NHCOCH3)2Pt(NHCOCH3)(H2O)],
whereas complex VIa is built of fragments [(H2O)(NHCOCH3)Pt(µ-OH)(µ-NHCOCH3)Pt(NHCOCH3)2].
DOI: 10.1134/S0036023607060149
The structure of the known Pt(III) complexes with well as [bipyPt(µ-OH)2Ptbipy](CF3SO3)2 (V) [5] and
acetamidato ligands can be judged on the basis of
studying their analysis of the solid phase thermolysis,
since the binding energies of organic ligands depend on
their coordination modes, for example, terminal or
bridging [1]. It turns out that terminal and bridging
anionic ligands [NHCOCH3]– are eliminated from the
complex molecules in different thermal ranges in the
course of solid phase thermolysis. Our findings were
used to determine the coordination mode of acetami-
dato ligands in platinum blue with the composition
Pt(2,2'-bipy)(NHCOCH3)2NO3 and with an unknown
structure [2]. However, the change of the oxidation
state of the metal ion in complexes, as a rule, signifi-
cantly change the distribution of electronic density on
the metal–ligand bonds, which can affect the binding
energy between the organic ligand and the metal center
and the process of thermolysis of the complex, as a
whole. In this case, it is important that, at early stages,
the thermolysis of Pt(III) complexes is accompanied by
the elimination of the apical ligands and the reduction
of Pt(III) to Pt(II) [1]. Thus, the remaining acetamide
ligands are eliminated from Pt(II) complexes. This
important fact allows us to use the regularities of ther-
molysis of Pt(III) derivatives determined previously for
the interpretation of the results of the study of Pt(II)
complexes.
the simplest platinum blue Pt(NHCOCH3)2 · H2O (VI,
VI‡), synthesized by two different procedures: hydrol-
*
ysis of cis*-[Pt(CH3CN)2 Cl2] [6] and direct interac-
tion of K2PtCl4 with acetamide [7]. Since the structure
of platinum blue Pt(NHCOCH3)2 · H2O has not yet been
determined, in this work, we also tried to determine the
coordination mode of the acetamidato ligands (bridging
or terminal) in this compound prepared by two different
procedures.
EXPERIMENTAL
All operations related to the synthesis of the com-
plexes were carried out in air. Complex I was synthe-
sized as in [3]; complexes III and IV, as in [4]; and
complex V, as in [5]. The elemental analysis for C, H,
and N was carried out on a Carlo Erba CHN analyzer at
the Laboratory of Chemical Analysis of the Institute of
General and Inorganic Chemistry of the RAS. The elec-
tronic absorption spectra of aqueous solutions and the
diffuse reflectance spectra of solid samples were
recorded on a Specord-400 spectrophotometer.
Synthesis
of [dmenPt(µ-NHCOCH3)2Ptdmen](NO3)2 · H2O.
This work deals with the processes of thermolysis of
four Pt(II) acetamidato complexes with known struc-
tures [enPt(µ-NHCOCH3)2Pten](NO3)2 · H2O (I) [3]
and [dmenPt(µ-NHCOCH3)2Ptdmen](NO3)2 · H2O
(II), where dmen is N,N'-dimethylethylenediamine;
[bipyPt(µ-NHCOCH3)2Ptbipy]2(NO3)4 (III), and
[bipyPt(µ-NHCOCH3)2Ptbipy]2(CF3SO3)4 (IV) [4], as
A 0.170-g (0.48 mmol) sample of Pt(dmen)Cl2 and
0.163 g (0.96 mmol) of AgNO3 were heated in 25 mL
of H2O in a water bath under stirring for 2 h, the result-
ing precipitate of AgCl (1.131 g (0.92 mmol),
anal.calcd. 0.138 g (0.96 mmol)) was filtered off. The
volume of the yellow mother liquor was reduced to
10 mL by evaporation, and then 0.080 g (1.356 mmol)
906

THERMOLYSIS OF POLYNUCLEAR PLATINUM(II) ACETAMIDATO COMPLEXES
907
of acetamide was added. The resulting reaction mixture
was heated for 1 h in a water bath, which made it darker.
Then, the solution was concentrated to 3 mL and cooled
to room temperature to produce a brown precipitate of
II. Yield, 0.120 g (~50%).
For PtC4N2H10O3 anal. calcd. (%): C, 14.68; N,
8.50; H, 3.08.
Found (%): C, 14.15; N, 7.08; Cl, 0; S, 0; H, 2.54.
The visible region of the electronic absorption
spectrum of an aqueous solution of VI shows rather
intense absorption bands at 12120 cm–1 (sh) (ε =
301 L mol–1 cm–1); 17510 cm–1 (ε = 1593 L mol–1 cm–1);
22900 cm–1 (sh) (ε = 1159 L mol–1 cm–1). The diffuse
reflectance spectrum of a solid sample of VI shows the
bands at 11200–11980, 14980, 16660, 21690, and
26310 cm–1.
For PtC6N4O4.5H17 anal. calcd. (%): Pt, 47.35; C,
17.47; N, 13.59; H, 3.18.
Found (%): Pt, 47.94; C, 16.17; N, 14.69; H, 3.21.
Upon recrystallization from water, complex II was
isolated in the form of bright black X-ray amorphous
plates. The electronic absorption spectrum of an aqueous
solution of II shows absorption bands at 14000 cm−1 (ε =
169 L mol–1cm–1); 16000 cm–1 (ε = 389 L mol–1cm–1);
18 000 cm–1(sh) (ε = 563 L mol–1cm–1).
The thermolysis of I–VI and VIa was studied by
differential scanning calorimetry (DSC) and thermo-
gravimetry (TG) on a Mettler TA-3000 thermoanalyzer
with DSC-20 and TG-50 units [8, 9]. The experiments
were carried out at a constant heating rate of 5 K/min in
air. In the DSC experiments, the samples of compounds
were heated in aluminum containers, whereas, in the
TG experiments, samples were heated in alundum cru-
cibles. The weight of each sample was no higher than
15 mg. Weight changes upon heating were monitored
directly on the TG-50 unit (the weighing accuracy was
(2 × 10–3) mg). DSC was also used to study thermoly-
sis stages; therefore, the temperature range under study
was divided into small intervals. The value and number
of these intervals were determined on the basis of the of
full data on the weight and energy changes upon
decomposition. This experimental technique allowed
us to determine the weight loss for each temperature
interval and to compare the DSC results with the TG
data. Good agreement between these results confirmed
their reliability. The accuracy of the determination of
anomalous points and thermal effect values on the ther-
mal curves was 1° and 0.5%, respectively. For each
compound, four experiments were carried out. The final
results were obtained using the statistical treatment of
Synthesis of Pt(NHCOCH3)2 · H2O
Procedure a. A 1.000-g (2.40 mmol) sample of
K2PtCl4 and 0.708 g (12.00 mmol) of acetamide in 30 mL
of water were heated at 70°ë for 4 h. The solution
became blue, and a precipitate with a metallic luster
appeared. Upon cooling, the precipitate was filtered off,
and repeatedly extracted with small portions of metha-
nol, until the solution stopped changing its color. All
the extracts were poured together and concentrated in a
water bath to a syrup-like state. Then, diethyl ether was
added dropwise. As a result, a dark violet precipitate of
VI was formed. The precipitate was dried in air. Yield,
~15%.
For PtC4N2H10O3 anal. calcd. (%): C, 14.68; N,
8.50; H, 3.08; Cl, O.
Found (%): C, 14.09; N, 7.64; H, 2.84; Cl, 0.
Procedure b. A 1.010-g sample (2.90 mmol) of
Pt(CH3CN)2Cl2 and 0.886 g (2.86 mmol) of Ag2SO4 in
10 mL of H2O was stirred for 10 h in the dark. The reac- the data of all the experiments. The results of the study
of thermolysis of complexes I–VI and VIa are given in
the table.
tion mixture turned light blue. A 100-mL portion of
methanol was added to a rich colored mixture under
stirring, which resulted in the quantitative formation of
the AgCl precipitate. The precipitate was filtered off
and dried at 110°ë to a constant weight of 0.810 g
(5.68 mmol; anal. calcd., 0.814 g (5.72 mmol)). A
450-mL portion of diethyl ether was added to the black-
blue filtrate. The ether extract was dried over granulated
CaCl2. Within 0.5 h, a glassy black-violet precipitate
(0.47 g, the first fraction) was formed. An additional
amount of dark violet precipitate was collected from
the decanted aqueous solution. The precipitate thus
obtained was also dried over CaCl2 to give 0.27 g (sec-
ond fraction) of a similar glassy black-violet precipi-
tate. The total yield of VIa was 0.74 g (~77.5%). The
results of the elemental analysis of fractions 1 and 2
coincided.
RESULTS AND DISCUSSION
We found that, during thermolysis of Pt(III) com-
plexes with bridging and terminal (NHCOCH3)–
ligands the terminal (NHCOCH3)– ligands are elimi-
nated from the complexes in the range 150–280°ë,
whereas the bridging ones are removed in the range
280–440°ë [1]. Taking into account the fact that the
elimination of the acetamidato ligands from these
Pt(III) complexes takes place after the elimination of
the labile axial ligands and the reduction of Pt(III) to
Pt(II) [1], we can use these data for interpreting the
results of the study of thermolysis of platinum(II) acet-
amidates (I–V).
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FEDOTOVA et al.
Thermolysis parameters for complexes I–VI and VIa
Ligand content in
the complex
Solid residue, %
(Pt content in
complex, %)
T, °C and thermal
Eliminated
ligand
Σ∆m (found)
Complex
∆m, %
event type
Σ∆m (calcd.), %
(calcd.), %
I
50–140 endo
(50–90 sh)
(90–140)
48.4 1.5
(49.23)
51.6 1.5
(50.77)
2.6 1.0 H2O
8.5 1.5
2.34
NO–3
140–210 endo
7.6 1.5
16.15
210–270 endo
270–370 exo
50–150 endo
(50–92 sh)
15.0 1.5 En
15.64
15.10
14.7 1.5 (µ-NHCOCH3)–
II
53.2 1.5
(52.71)
46.8 1.5
(47.29)
2.3 1.0 H2O
11.0 1.5
2.20
(92–150)
15.04
NO–3
150–210 endo
4.7 1.5
210–340 endo
340–450 exo
20.8 1.5 dmen
21.37
14.10
14.4 1.5 (µ-NHCOCH3)–
NO–3
III
IV
110–190 endo
12.2 1.0
13.15
57.0 1.5
(58.60)
43.0 1.5
(41.40)
190–370 endo
370–500 exo
180–415 endo
(180–290)
31.8 1.0 bipy
33.14
12.31
13.0 1.5 (µ-NHCOCH3)–
64.3 2.5
(65.04)
35.7 2.5
(34.96)
24.7 2.5 (CF3SO3)–
30.3 2.5 bipy
9.3 1.5 (µ-NHCOCH3)–
29.5 1.5 (CF3SO3)–
4.1 1.5 (µ-OH)–
27.7 2.0 bipy
0
26.69
27.97
10.38
28.82
3.30
(290–415)
415–510 exo
240–270 endo
270–310 exo
310–410 endo
410–440 exo
50–130 endo
130–230 exo
230–300 endo
above 310 exo
40–130 endo
130–180
V
61.3 2.0
(62.32)
38.7 2.0
(37.68)
30.20
VI
VIa
5.5 1.0 H2O
5.47
35.24
2.74
41.6 1.5
(40.71)
58.4 1.5
(59.29)
0
36.1 1.0 (NHCOCH3)–
2.5 1.0 H2O
0
40.2 1.5
(40.56)
58.6 1.5
(59.44)
180–235 endo
235–280 endo
280–400 exo
8.4 1.0 (NHCOCH3)–
16.9 1.5 (NHCOCH3)–
8.81
17.62
12.4 1.5 (µ-OH)–
2.58
8.81
(µ-NHCOCH3)–
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THERMOLYSIS OF POLYNUCLEAR PLATINUM(II) ACETAMIDATO COMPLEXES
909
4+
O
O
O
O
N
N
N
N
L
L (NO3)2 · H2O
bipy
bipy
Pt
Pt
Pt
Pt
2
L = en (I), dmen (II)
O
=
CH3C
O
N
NH
I, II
III, IV
OH
bipy
bipy (CF3SO3)2
Pt
Pt
OH
V
Upon heating complex I in the range 50–90°C (the is 16.1% (the second endotherm) (Fig. 1a), which,
most likely, corresponds to the stepwise elimination of
two outer-sphere (NO3)– groups, whose calculated
content in complex I is 16.15%. In the temperature
range 210−270°ë, the energy absorption (the third
endotherm) is accompanied by the weight loss 15.0%,
which presumably corresponds to the elimination of
shoulder of the first endotherm), the weight loss 2.6%
most likely corresponds to the removal of the crystal
water (Figs. 1a and 1b). The calculated content of the
crystal water in I is 2.34%. The weight losses 8.5% in
the temperature range 90–140°ë and 7.6% in the tem-
perature range 140–210°ë are accompanied by energy
absorption (the total weight loss in the range 90–210°ë two molecules of coordinated ethylenediamine. It
Q, mV
m, mg
12
(‡)
6.5
5.5
4.5
3.5
2.5
(b)
8
4
0
–4
–8
0
200
400
6.0
5.5
5.0
4.5
4.0
3.5
3.0
2.5
11
7
(d)
(c)
3
–1
–5
200
600
T, °C
0
400
0
200
400
600
T, °C
Fig. 1. Plots of the heat flux and weight change vs. temperature for (a, b) I and (c, d) II.
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 52 No. 6 2007

910
FEDOTOVA et al.
m, mg
3.0
Q, mV
8
(b)
(‡)
6
4
2
0
2.5
2.0
1.5
–2
–4
1.0
3.0
(d)
(c)
10
8
2.6
2.2
6
4
1.8
1.4
1.0
2
0
–2
–4
0
200
400
600
T, °C
0
200
400
600
T, °C
Fig. 2. Plots of the heat flux and weight change vs. temperature for (a, b) III and (c, d) IV.
should be noted that, in the case of the thermolysis of thermolysis of I. However, in this case, all the parame-
the Pt(III) acetamidato complex [en(NHCOCH3)Pt(µ- ters of thermal transformations are shifted to higher
temperatures (Fig. 1b, 1c). It is probably due to the
polymeric structure of II (the electronic absorption
spectrum of the aqueous solution of II shows low-
energy charge transfer bands, see Experimental). For
complex II, the observed energy absorption below
340°ë (three endotherms at 50–150°ë (with a shoulder
at 50–92°C), 150–210, and 210–340°ë on the thermo-
grams) (Fig. 1c) probably corresponds to the stepwise
elimination of the crystal water (2.3%), outer-sphere
NHCOCH3)2Pt(NHCOCH3)en]Cl2 [1], ethylenediamine
is removed at much lower temperature (50–150°ë).
It can be due to differences in the coordination mode
of ethylenediamine. For example, in the Pt(III) ace-
tamidate, two ethylenediamine (en) molecules are
coordinated in different ways (in the equatorial and
axial position), whereas, in the complex
[enPt(µ-NHCOCH3)2Pten](NO3)2 · H2O (I), both en
molecules are in equatorial positions. Owing to the sig-
nificant lability of the axial ligands in Pt(III) dimers,
upon heating, the axial Pt–en bonds are broken and the
monodentate ethylenediamine is eliminated at lower
temperature than the bidentate ethylenediamine in I.
Upon further heating, in the range 270–370°ë, the
observed weight loss of 14.7% accompanied by energy
evolution (an exotherm) corresponds to the elimination
of the bridging (NHCOCH3)– groups and to the forma-
tion of the structure of the platinum metal. The total
weight loss upon thermolysis in the temperature range
50–400°ë is 48.4%. The solid residue weight corre-
sponds to the platinum content in the complex (table).
NO–3 groups, and N,N'-dimethylethylenediamine. The
total weight loss 38.9% corresponds the calculated con-
tent of these ligands in the complex (38.61%). Above
340°ë, the observed energy evolution (an exotherm)
accompanied by the weight loss 14.4% corresponds to
the elimination of the bridging acetamidato ligands and
the formation of the structure of the platinum metal.
The decomposition of tetranuclear acetamidate III
starts above 110°ë (Fig. 2a and 2b). The weight loss in
the temperature range 110–190°ë accompanied by
energy absorption (an endotherm) is 12.2% and is, most
likely, due to the elimination of outer-sphere NO3–
The character of thermolysis of II, which differs
from I only by the presence of a methyl group at the groups. In the range 190–370°ë, a weight loss of
nitrogen atoms of ethyelenediamine, is very similar to 31.8% is observed, which probably corresponds to the
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THERMOLYSIS OF POLYNUCLEAR PLATINUM(II) ACETAMIDATO COMPLEXES
911
elimination of 2,2'-bipy (calculated content, 33.14%).
Q, mV
8
The energy evolution in the temperature range
370−500°ë with a weight loss of 13.0% is probably due
to the elimination of the bridging acetamidato ligands
(calculated content, 12.31%) and the formation of the
structure of the platinum metal.
(‡)
6
4
2
0
Complex IV, which differs from III by the type of
the outer-sphere ion, is stable to 180°ë. In the tempera-
ture range 180–415°ë (an endothermal effect) (Figs. 2c
and 2d), the weight loss 55.0% probably corresponds to
the elimination of the outer-sphere anions (O3SCF–3 ) (in
the range 180–290°ë, calculated content, 26.69%) and
2.2'-Bipy (in the range 290–415°ë; calculated content
27.97%). Further decomposition proceeds with energy
evolution in the temperature range 415–510°ë. In this
case, the 9.3% weight loss takes place, which corre-
sponds to the elimination of the bridging acetamidato
groups and the formation of the metal structure.
–2
–4
–6
6
5
4
3
2
1
(b)
Thermolysis
of
the
binuclear
complex
[bipyPt(µ-OH)2Ptbipy](CF3SO3)2 (V), where the bridg-
ing acetamido groups are replaced by hydroxyl ions, is
significantly different from all the platinum acetami-
dates under study (Figs. 3a, 3b). Complex V remained
stable to 237°ë, whereas acetamidate IV, with the same
outer-sphere anion, is stable only to 180°ë. At 237°ë,
the complex melts, and its melting is accompanied by
decomposition. In the temperature range 240−270°ë, a
weight loss of 29.5% is observed, which corresponds to
0
100
200
300
400
500
T, °C
Fig. 3. Plots of the heat flux and weight change vs. temper-
ature for V.
It is known that in the platinum blue prepared by the
interaction of K2PtCl4 with acetamide, according to
X-ray photoelectron spectroscopy, the oxidation state
of platinum is ~+2 [10]. In the visual range of the elec-
tronic absorption spectrum of an aqueous solution of
this complex, the absorption bands at 16950, 19305,
and 24813 cm–1 are observed; and the diffuse reflec-
tance spectrum of the solid sample shows a band at
12706 cm–1 with a shoulder at 17211 cm–1 [11]. The
positions and intensities of these bands are typical of
the mixed-valence compounds characterized by low-
energy charge transfer transitions [12].
the elimination of the CF3SO–3 anions (calculated con-
tent 28.82%). When weight loss becomes less drastic,
the processes with energy evolution start. In this case,
in the range 270–310°ë, an insignificant weight loss
(4.1%) is observed, which is probably due to the
removal of the bridging éH– groups (calculated pro-
portion 3.30%), which is accompanied by structural
changes and redox processes. In the temperature range
310–410°ë, energy absorption is accompanied by a
weight loss of 27.7%, which corresponds to bipy elim-
ination (calculated content, 30.17%). At temperatures
higher than 410°C energy evolution is observed almost
without a weight change. The total weight loss in the
range 237–410°ë is 61.3% (the calculated content of
the eliminated substances is 62.30%).
The structure of the mixed-valence compound
Pt(NHCOCH3)2 · H2O can be represented in the
form of a polynuclear compound consisting of binu-
clear fragments [Pt2(µ-NHCOCH3)4(H2O)2] (Ä),
binuclear
fragments
[(H2O)(NHCOCH3)Pt(µ-
Thus, a specific feature of platinum(II) and plati- NHCOCH3)2Pt(NHCOCH3)(H2O)] (B), or binuclear
num(III) polynuclear complexes with bridging aceta-
midato ligands is the high thermal stability of interme-
diate polynuclear structures with Pt(µ-NHCOCH3)2Pt
moieties, the bridging acetamidato groups being elimi-
nated to form the structure of the platinum metal in the
range 280–510°ë. The terminal acetamidato ligands are
eliminated at lower temperatures (150–280°ë). The
bridging hydroxyl ions are eliminated in a rather nar-
row temperature range of 270–310° C. These results
were used as the main criterion of assessment of the
thermal decomposition of platinum blue of the
Pt(NHCOCH3)2 · H2O composition.
fragments
with
bridging water molecules
[(NHCOCH3)2Pt(µ-H2O)2Pt(NHCOCH3)2] (ë). How-
ever, taking into account the ease of formation of plati-
num hydroxo complexes in the course of the reaction,
one can assume that (éç)– ions can also be bridging
ligands. (The presence of hydroxo groups in the com-
plex is probably one of the reasons of the mixed-
valence state of platinum.) Taking into account the dif-
ference in the between the binding energies of acetami-
dato and aqua/hydroxo bridges with platinum atoms,
their elimination during thermolysis must take place in
different temperature ranges. The procedure of the syn-
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912
FEDOTOVA et al.
m, mg
4.0
Q, mV
8
(b)
(‡)
3.6
6
4
2
0
3.2
2.8
2.4
–2
–4
–6
2.0
10
(d)
8
6
(c)
4
8
6
4
2
0
–2
–4
–6
–8
0
200
400
T, °C
0
200
400
T, °C
Fig. 4. Plots of the heat flux and weight change vs. temperature for (a, b) VI and (c, d) VIa.
thesis of platinum blue VI from K2PtCl4 and loss is 36.1%, corresponds to the elimination of all
acetamidato ligands [1] (calculated content,
35.24%). Therefore, one can assume that VI is a
polynuclear mixed-valence Pt complex consisting
of binuclear fragments [(H O)(NHCOCH )Pt(µ-
CH3CONH2 is analogous to the synthesis of Pt(III) ace-
tamidate [Pt2(NHCOCH3)4Cl2] [13]; therefore, one can
assume that the structure of compoundVI is that of typeA.
2
3
The character of the decomposition of VI is differ-
ent from that of that of complexes I–IV. The decompo-
sition of VI proceeds in three stages (Figs. 4a and 4b).
At the first stage in the range 50–130°ë, a weight loss
of 5.5% is observed. Upon further heating in the tem-
perature range 130–230°ë, energy evolution is
observed virtually without weight change. At last, in
the temperature range 230–300°ë, a 36.1% weight loss
with energy absorption is observed (a complex endot-
herm). Above 300°ë, the processes proceed without
weight change, but with energy evolution. This is
observed upon the formation of the platinum metal
structure. The total weight loss in the range 50–300°ë
is 41.3%.
NHCOCH ) Pt(NHCOCH )(H O)] (B).
3 2
3
2
The thermolysis of VIa prepared by hydrolysis of
cis*-[PtCH3CN)2Cl2] (with the preliminary precipita-
tion of chlorine atoms with silver sulfate) is different
from the thermolysis of VI. Two fractions of the plati-
num blue obtained by this procedure were studied (see
Experimental). Figures 4c and 4d display the results of
the thermolysis of the second fraction.
The decomposition of VIa proceeds in several
stages. At the first stage in the temperature range
40−130°ë, energy absorption is accompanied by a
weight loss of 2.5%. No energy changes or weight loss
are observed in the range 130–180°ë. Then, in the
range 180–235°ë, the weight loss with energy absorp-
tion is 8.4%. In the temperature range 235–280°ë, two
steps of energy absorption are observed with a weight
loss of 16.9%. In the range 280–400°ë, another 12.4%
A weight loss 5.5% in the range 50–130°ë is
probably due to the removal of the water molecules
(calculated content, 5.47%). The exotherm at
130−230°ë without weight loss is due to the struc-
tural rearrangement of the complex, most likely,
due to the cleavage of the acetamidato bridges. The of the weight is lost with energy evolution. The total
temperature range 230−300°ë, in which the weight weight loss in the studied range is 40.2%.
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 52 No. 6 2007

THERMOLYSIS OF POLYNUCLEAR PLATINUM(II) ACETAMIDATO COMPLEXES
913
The 2.5% weight loss in the range 40–130°ë corre- the Division of Chemistry and Materials Science of the
sponds to the elimination of one water molecule (calcu- RussianAcademy of Sciences “Chemistry and Physical
lated content, 2.74%). The 8.4% weight loss with Chemistry of Supramolecular Systems and Atomic
energy absorption, most likely, corresponds to the elim- Clusters.”
ination of one (NHCOCH3)– group (calculated content,
8.81%). The 16.9% weight loss accompanied by the
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On the basis of the results of the thermolysis of VIa,
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OH
H2O
NHCOCH3
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Pt
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ACKNOWLEDGMENTS
(1999).
This study was supported by the Russian Founda-
tion for Basic Research (project nos. 05-03-32794 and
05-03-08203) and the Program for Basic Research of
13. T. N. Fedotova, G. N. Kuznetsova, L. Kh. Minacheva,
and I. B. Baranovskii, Zh. Neorg. Khim. 35 (6), 1484
(1990).
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 52 No. 6 2007