Reaction of PtCl4 with 18-crown-6 in aprotic solvents (Nitromethane, acetonitrile, and 1,2-dichloroethane)

Article abstract of DOI:10.1134/S1070363207110047

Specific features of the reaction of anhydrous PtCl₄ with 18-crown-6 in anhydrous solvents with different donor and solvating abilities, such as nitromethane, acetonitrile, and 1,2-dichloroethane, under an inert atmosphere are studied. Ionic pl

Full text of DOI:10.1134/S1070363207110047

ISSN 1070-3632, Russian Journal of General Chemistry, 2007, Vol. 77, No. 11, pp. 1864 1873.
Original Russian Text E.V. Guseva, R.A. Khasanshin, T.T. Zinkicheva, E.G. Yarkova, V.K. Polovnyak, 2007, published in Zhurnal Obshchei Khimii,
2007, Vol. 77, No. 11, pp. 1805 1815.
Pleiades Publishing, Ltd., 2007.
Reaction of PtCl4 with 18-Crown-6 in Aprotic Solvents
(Nitromethane, Acetonitrile, and 1,2-Dichloroethane)
E. V. Guseva, R. A. Khasanshin, T. T. Zinkicheva, E. G. Yarkova, and V. K. Polovnyak
Kazan State Technological University,
K. Marksa 68, Kazan, Tatarstan, 420015 Russia
e-mail: leyaha@mail.ru
Received March 15, 2007
Abstract Specific features of the reaction of anhydrous PtCl4 with 18-crown-6 in anhydrous solvents with
different donor and solvating abilities, such as nitromethane, acetonitrile, and 1,2-dichloroethane, under an
inert atmosphere are studied. Ionic platinum complexes with oligoethylene glycols or with crown ethers,
formed by macroring opening and/or fragmentation under the action of the acidic agent, were isolated. The
1H NMR, IR, and Raman spectra of the complexes were studied. To assess the coordination mode of the
crown ether cleavage product with Pt(IV), quantum-chemical calculations at the density functional theory
level were carried out.
DOI: 10.1134/S1070363207110047
Reactions in macrocylic polyether metal halide
organic solvent systems have an intricate character
and proceed ambiguously. The composition and struc-
ture of solid products depend on many factors, the
nature and type of the solvent being among the key
ones. Halides of the main and transition group III VI
metals (SnCl4, TiCl4, MoCl5, TaCl5, TeCl4, ZrCl4,
VCl5) in the oxidation states above +3 in anhydrous
aprotic solvents characteristically cleave 18-crown-6
and 15-crown-5 polyethers to form water, hydrogen
chloride, various active oxygen-containing fragments
of the crown ether, and reaction products of these
fragments with solvents. The macroring cleavage
often gives rise podand-like structures with M O
bonds or complex multicomponent mixtures of un-
known composition, and oxychlorides included both
in the cationic and anionic part of complexes [1].
methane we isolated black- (I) and mustard-colored
(II) fine crystals melting at 183 and 160 C, respec-
tively. The reaction in acetonitrile gave a finely crys-
talline yellow powder (III), mp 220 C, and orange
crystalline plates (IV), mp 152 C. The reaction in
1,2-dichloroethane gave one product as a fine brick-
colored powder. We failed to establish the composi-
tion of this product because of its multicomponent
character. The composition of the product did not
change at varied PtCl4 :crown ether ratio. The reac-
tions were carried out at temperatures no higher than
the boiling point of the solvents or below. The solub-
ilities of compounds I IV in selected solvents are
presented in Table 1.
The elemental analyses and thermoanalytical
curves (Fig. 1) point to a complex composition of the
resulting compounds.
In the present paper, continuing the cycle of pub-
lications on reactions of crown ethers with Pt(IV)
compounds [2, 3, 4], we present the results of physi-
cochemical studies of four compounds obtained by
the reaction of anhydrous PtCl4 with 18-crown-6
under an inert atmosphere. The processes were studied
in anhydrous polar (nitromethane, acetonitrile) and
low-polar (1,2-dichloroethane) aprotic solvents having
different solvating abilities, dielectric constants (
37.78, 36.02, and 10.36, respectively), and resistance
to acidic agents, such as Lewis acids [5].
Consideration of the resulting data allows the fol-
lowing conclusions. Part of complex I, soluble in
deuterated acetone, contains practically pure tri-
ethylene glycol molecules. The intensity ratio of the
CH2 and OH signals is 5.8:1 (in triethylene glycol,
6:1). Analysis of the 1H NMR spectrum of compound
III shows that it contains oligoethylene glycol mole-
cules with the mean polymerization degree equal to 5.
1
The H NMR spectral parameters of compound IV are
typical of complexes of hydroxonium salts with crown
ethers: 10.7 ppm, br.s (9H, H3O+) (published data
1
[6]:
10.36 11.0 ppm). Hence, the H NMR data
The reactions of PtCl4 with 18-crown-6 in nitro-
methane and acetonitrile gave two products. In nitro-
permit to state that part of macrocyclic polyether
1864

REACTION OF PtCl4 WITH 18-CROWN-6 IN APROTIC SOLVENTS
1865
Table 1. Solubility of compounds I IV in selected
electron effect was considered by means of the Hay
solvents
Wadt relativic pseudopotential [14]. Valence electrons
of C, O, N, and H atoms were described in terms of
the standard basic set D95V [15]. The chosen basis
sets are known to adequately describe the structure of
transition metal complexes. Geometry optimization
was performed with no symmetry constraints. The
presence of an energy minimum (stationary point) was
Conpound no.
Solvent
I
II
III
IV
Acetonitrile
1,2-Dichlro-
ethane
poor
poor
poor
poor
poor
insoluble insoluble insoluble
Acetone
DMF
DMSO
Ammonia
Nitric acid
soluble
soluble
soluble
poor
TG, %
100
T, C
poor
poor
poor
poor
poor
poor
1
800
DTG
insoluble
poor
insoluble insoluble
poor insoluble
700
600
500
400
300
200
100
0
700
90
80
70
DTA
T
molecules undergoes cleavage to form oligoethylene
glycol molecules with various polymerization degree,
close in their nature to podands, openchain derivatives
of tri- and pentaethylene glycols. The reaction results
in formation of two types of complexes: podand com-
plexes I, III and crown ether complexes II, IV.
60
50
100
2
600
90
80
70
60
50
40
500
1
DTG
The H NMR spectra of complexes I, III revealed
400
300
200
100
0
the presence of such groups as OCH2CH2O ( 3.9
3.6 ppm) and OH ( 4.4 4.7 ppm in I and 3.8
4.2 ppm in III) (Figs. 2a, 2b). The relative intensities
(irel) of the signals of these groups are listed below.
DTA
TG
30
Compound I
Group
Compound III
DTG
3
900
800
700
600
500
400
300
200
100
0
100
90
irel
Group
irel
T
OCH2CH2O
OH
5.8
1.0
OCH2CH2O
OH
17.5
1.0
80
70
DTA
The formation of analogous compounds was ob-
served by Bulychev abd Bel’skii [7] in reactions with
strong Lewis acids like PtCl4. The structure of such
compounds was established: Ethylene glycol
units combine by forming O M O bonds. As known
[8], the affinity of Pt(IV) to soft ligands is lower as
compared to Pt(II); the former is close in properties
to class a acceptors or hard acids, because it forms
sufficiently stable complexes with OH ions. Hence,
in our case complex formation with alkoxide ions
RO should be preferred. In view of the aforesaid, to
gain a deeper insight into the structure of compound I,
we performed quantum-chemical calculations at the
density functional theory (DFT) level using the hyb-
ride nonlocal B3LYP functional with gradient correc-
tions (see, for example, [9 13]). The electronic shell
of platinum (4s4p5d6s6p) was described directly
using the double zeta split-valence basis set. The inner
60
50
TG
4
100
90
80
70
60
50
40
T
800
600
400
200
0
DTG
DTA
TG
30
0 10 20 30 40 50 60 70 80
t, min
Fig. 1. Thermoanalytical curves of complexes (1) I, (2)
II, (3) III, and (4) IV.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 77 No. 11 2007

1866
GUSEVA et al.
(a)
(b)
5
4
3
2
1
0
, ppm
5
4
3
2
1
, ppm
1
Fig. 2. H NMR spectra of complexes (a) I and (b) II.
confirmed by vibrational analysis. The quantum-
chemical calculations were carried out using Gaussian
03 [16].
gauche conformation (G) with respect to C C bonds
(torsion angles 42.7 72.7 ). The energetically
favorable trans conformation (T) with respect to the
C O bond was obtained only for the C5C6O1C3 tor-
sion angle ( 164.3 ). The conformation with respect
to two of the C O bonds is intermediate between
gauche and trans: The C3C4O2C1 and C4O2C1C2
torsion angles (+104.5 and 114.2 , respectively)
relate to a skew conformation (S). For the C6O1C3C4
and PtO3C5C6 torsion angles with the C O bond, a
gauche conformation is observed. The conformation
for the C1C2O4Pt torsion angle with respect to the
C O bond comes close to gauche (+95.7 ). Note also
that the conformation of the OCH2CH3O unit is given
by a set of torsion angles with respect to the O C,
C C, and C O bonds, labeled T ( 180 ), S ( 120 ),
G ( 60 ), and C ( 0 ). Negative angles are labeled
T , G , S , and C respectively. The symbol G relates
to torsion angles ranging from 30 to 90 , etc.
The formation of a bidentate O3 Pt O4 bridge links
terminal ethylene glycol units to give a chelate-like
structure. Such rotation of the podand-like fragment
permits the platinum atom to form a chelate fragment
with the alkoxyl RO oxygens, not violating the octa-
hedral symmetry, because Pt(IV) has a clearly pro-
nounced tendency for coordinating six ligands [19].
Hence, the conformational state of the ethylene glycol
units in I is dissimilar.
Among examined variants of coordination of the
C6H12O4 ligand in the [2(PtCl3 CH3NH2 C6H12O4)2+
(Pt2Cl6)2 ] H2O complex, the structure (Fig. 3) with
an equatorial C6H12O4 ligand coordinated through
oxygen atoms proved to be the most preferred by
energy. Note that the complex with an axial C6H12O4
ligand coordinated through oxygen atoms is less
1
stable by 32.12 kcal mol compared to the that in
Fig. 3. Table 2 lists selected geometric characteristics
of the complex together with experimental data for
similar complexes containing chlorine and nitrogen
atoms, organic crown ethers, and podands [7, 17, 18].
The calculated values are in reasonable agreement
with experiment.
Quantum-chemical calculations gave torsion angles
in structure I (Table 3). The triethylene glycol chain
is characterized by the most energetically favorable
C6
C5
C13
O3
Pt1
C3
C4
C11
Evidence for our conclusions was found in the
vibration spectra of compounds I and III (Figs. 4 6).
As known, certain vibration frequences of the ethylene
glycol unit depend on its conformation. Along with
O1
C1
N1
C2
O2
C7
1
as(COC) in the range 1000 1200 cm [20], the
C12
composite stretching bending vibrations [ (CH2) +
(CO) + (CC)] vibrations in the range 800
1
1000 cm , too, are conformationally sensitive [21].
Therefore, changes in these ranges are largely con-
nected with the coordination-induced conformational
Fig. 3. Spatial arrangement of complex I.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 77 No. 11 2007

REACTION OF PtCl4 WITH 18-CROWN-6 IN APROTIC SOLVENTS
1867
Table 2. Selected characteristic interatomic distances (d, ) and bond angles (deg) in the [2(PtCl3 CH3NH2 C6H12O4)2+
(Pt2Cl6)2 ] H2O complex as compared to experimental data for similar structures
Interatomic distance,
Compound I
[133]a
[134]b
[135]c
2.344
Pt Cl1
Pt Cl2
Pt Cl3
Pt O1
Pt O2
Pt N
2.4259
2.3905
2.4330
1.9928
2.0382
2.1209
2.288 2.311
2.273 2.316
2.011 2.021
2.035
2.060
1.891
Bond angle, deg
Compound I
[133]a
[134]b
[135]c
162.23
Cl1PtCl2
Cl1PtCl3
Cl1PtN
Cl2PtN
Cl3PtN
O1PtN
91.299
86.776
177.058
87.739
96.027
78.398
85.341
92.49
88.52 178.31
174.02
89.82
O2PtN
83.53
a
b
[133] Molecular structure of cis-[PtCl (gly) on the basis of data in [19]. [134] Structure of the [PtCl (H O )] fragment in the
2
2
5
4 2
c
[H O ][PtCl (H O )] 2(18-cr-6) complex in crystal, on the basis of data in [20]. [135] Molecular structure of the [TaCl
13
6
5
4
2
2
C H 6O ][TaCl ] complex on the basis of data in [8].
8
1
5
6
rearrangement of the ethylehe glycol chain. The
conformational state of the coordinated crown ethers
and podands in the complexes can be judged about
based on vibration spectral data and spectrum con-
formation correlations [21 27]. The available pub-
lished vibration spectra of crown ethers and podands
[20 23, 25, 26, 28, 29], as well as structures with
Pt Cl, Pt N, and Pt O bonds and chelate cyclic struc-
tures with O M O bonds [17, 18, 30 32] allow us
to identify with sufficient assurance the ranges of
wave numbers, characteristic of COC, CC, CH2, CO,
Pt O, Pt Cl, and Pt N vibrations.
Table 3. Torsion angles in compound I
Torsion angle
, deg
C1C2O4Pt
O2C1C2O4
C4O2C1C2
C3C4O2C1
O1C3C4O2
C6O1C3C4
C5C6O1C3
O3C5C6O1
PtO3C5C6
95.7
70.5
114.2
104.5
72.7
64.3
164.3
42.9
58.9
The polyethylene glycol chain in compound I
consists of three OCH2CH2O units, which make it
possible to consider this compound as an analog of
the unsubstituted crown ether [25]. In the range 1080
sion can be found in the conformationally sensitive
range of the combined stretching bending vibrations
[ (CO) + (CC) + (CH2)] at 750 1000 cm . In the
1
1
1160 cm characteristic of the as(COC) frequency
of the unsubstituted crown ether, a multiplet band
IR spectrum of compound I, the corresponding bands
1
with components at 1092, 1120, and 1136 cm is
are observed at 910, 905, 890, 860, 800, 790, and
observed, the former component being the strongest
(Fig. 4). This observation can be regarded as evidence
for the conformational inhomogeneity of the OCH2
CH2O units. According to [23], the bands at 1090
1
780 cm . Considering the values of torsion angles
(Table 3), the conformation of the triethylene glycol
chain in complex I can be presented as GGS , SG ,
or T G G . Then, according to [21], the bands at 800,
1
1100 cm relate to the TGG unit, while the as(COC)
1
860, and 890 cm can be associated with vibrations
bands of the TGT unit appear in the range 1080
1
of the TGG unit. The bands at 905 910 and 780
1090 cm . From that it follows that the strongest
1
1
790 cm are probably associated with the other two
component at 1092 cm belongs to a unit whose con-
formation is close to TGG. Evidence for this conclu-
conformations of the OCH2CH2O units.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 77 No. 11 2007

1868
GUSEVA et al.
1
1
2
2
3
3
4
4
3600 3000 2000 1600 1200 800
1
, cm
1
Fig. 4. IR spectra in the range 4000 400 cm for com-
plexes (1) I, (2) II, (3) III, and (4) IV.
600
500
400
300
200
The polyethylene glycol chain in compound III
consists of five OCH2CH2O units, and it, too, can
be considered as an analog of the unsubstituted crown
ether. In this structure, the Pt(IV) chelate entity is also
formed by means of terminal alkoxyl oxygen atoms
(RO ). But the spectral pattern in the range 750
1
, cm
1
Fig. 5. IR spectra of in the range 500 200 cm for
complexes (1) I, (2) II, (3) III, and (4) IV.
1
1000 cm , characteristic of the mixed stretching
bending vibrations { (COC) + (CC) + (CH2)} and
s
{ (CH2) + (CO) + (CC)} of separate ethylene
glycol units, is slightly different (Fig. 4). The IR spec-
1
trum in the range 800 900 cm contains a strong
1
1
band at 840 cm with an inflection point at 816 cm ,
1
as well as a weak band at 860 cm . The Raman spec-
trum in this range contains only a medium-intensity
band at 865 cm (Fig. 6).
1
299 2697 1697 14971297 1097 897 697 497 297 197 97
1
, cm
However, the noticeable asymmetry of the low-
frequency branch of this band can be connected with
Fig. 6. Raman spectrum of complex III.
1
the contribution of the absorption at 840 and 816 cm .
1
The IR spectrum (900 1000 cm ) contains a complex
structure correlations in [21, 22], the observation of
bands at 950 960 cm 1 point to the presence of a TGT
1
band whose low-frequency component at 960 cm is
1
1
stronger than the high-frequency one at 984 cm .
unit. The absorption band at 840 cm is characteristic
These components can be correlated with the Raman
bands at 972 and 957 cm . The spectral pattern
suggests conformational inhomogeneity of the poly-
ethylene glycol chain. According to the spectrum
of a TGT unit, but simultaneously points to the pres-
ence of a TGT TGG fragment in the polyethylene
glycol chain. Evidence for the presence of a TGG
ethylene glycol unit is provided by the Raman band
1
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 77 No. 11 2007

REACTION OF PtCl4 WITH 18-CROWN-6 IN APROTIC SOLVENTS
1869
1
1
at 865 cm and IR band at 860 cm . The absorption
with these fragments, contains water and hydrogen
chloride formed by hydrolysis of the agent. As known
[30, 32], the IR spectra of water-containing metal
complexes of ethylene glycol and its derivatives show
1
band at 816 cm is assignable to a TGS unit. The
weak band at 984 cm probably belongs to a TTT
unit, on account of the fact that an analogous band
was found in the spectrum of the free 18-crown-6
[24].
1
1
(M O) bands at 400 500 cm , corresponding
to structures with an O M O chelate entity. The ab-
1
1
sorption bands at 448, 456 cm and 443, 436 cm
1
The spectral range 1080 1160 cm contains a
complex band with a strong high-frequency com-
ponent as(COC) at 1112 cm . According to the cor-
relations in [23], the corresponding band in unsub-
stituted crown ethers is associated with vibrations of
the OCH2CH2O unit having a TTT conformation.
in the IR spectra of compounds I, III were attributed
to (Pt O) which in chelate-like structures are ob-
served in this spectral range (Fig. 5).
1
The solvent also reacts with PtCl4 and 18-crown-6,
as well as with products of their decomposition under
the action of water and hydrogen chloride present in
the system. Therefore, these reaction products enter
the composition of the resulting complexes. Hence,
the IR spectrum of compound I obtained in nitro-
Hence, the calculated data for compound I together
with the spectral data for compounds I, III allow us
to conclude that for these structures to close at reason-
able values of the COC and CCO bond angles the
ethylene glycol fragments in the complexes should
have different conformations, which is indeed the
case. Note also that when all the OCH2CH2O units
have the trans gauche trans conformation one of the
lone electron pairs of each ethylene glycol oxygen
atom points to the center of the molecule. This
provides conditions for the most optimal interaction
between all oxygen atoms and the metal cation. Since
the calculated and spectal data showed that OCH2
CH2O units have different conformations, the Pt(IV)
ion is bound only with alkoxyl oxygen atoms to form
the O Pt O chelate entity.
1
methane contains a (NH2) band at 1568 cm , that
belongs to the reduction product of CH3NO2 to
CH3NH2 and its coordination through the nitrogen
1
atom { (Pt N) 400 cm }. As complex I contains
1
1
water { (H2O) 3200 cm , (H O H) 1632 cm }, the
(H2O) and (NH) bands overlap and cannot be
clearly identified. But the broad continuous band at
1
3600 3100 cm characteristic of strong hydrogen
bonds may include NH2 stretching vibration bands
[30, 33].
Analysis of the IR spectrum showed that complex
II contains acetonitrile molecules forming a molecular
complex with Pt(IV). Under these conditions, absorp-
tion bands should shift to higher frequencies. The
bands of the acetonitrile molecules involved in
specific interactions with the podand-like fragment
behave in the same way. For this reason, stretching
and bending vibration bands of CH3CN are difficult
to assign. However, the strong band at 2350 cm 1 may
well belong to stretching vibrations of the molecular
complex of Pt(IV) with CH3CN in the cationic part of
The IR spectra of complexes I, III have several
strong bands in the range 250 350 cm (Fig. 5). The
composite character of the broad (Pt Cl) band ( 317,
1
1
332, 340 cm ) and the intensity ratio of its com-
ponents show that compound I contains both Pt4+ and
Pt2+, which is associated with redox processes in the
PtCl4 18-crown-6 CH3NO2 system. The Raman spec-
trum of compound I contains strong bands at 155,
1
314, 338, and 347 cm related to (Pt Cl) and
(Pt Cl). The anionic part of product I is the complex
ion [Pt2Cl6], (Pt
1
compound III { (-C N: Pt) 400 cm } [34]. The
outer-sphere location of water in compound III
1
Cl) 286 cm . The IR spectrum
follows form the positions of the (H2O) and (HOH)
of compound III, too, contains a strong band with a
1
at 3150 and 1648 cm , respectively [30].
small knee, attributed to Pt4+ (Pt Cl) 340, 330 cm .
1
1
1
The (Pt
Cl) vibrations are observed at 286 cm .
In the range 600 200 cm , the (COC) and
In the Raman spectrum (Fig. 6) of complex III,
(CCO) bands of ethylene glycol units are also ob-
served. But these bands look much stronger than ex-
pected due to partial overlap with the (Pt Cl),
(Pt O), and (Pt N) bands.
(Pt Cl) is characterized by strong bands at 155, 315,
1
335, and 347 cm [17, 18, 30, 31]. On the basis of
the (Pt Cl) frequencies of complexes I, III and
published data [18] we can conclude that the octa-
hedral symmetry of Pt4+ is preserved in both cases.
Thermal analysis shows that for the major weight
loss for product I (Fig. 1) is observed at 134 217 C
(endo effect at 183 C, found 29.3%, calculated
29.51%). At 0 134 C softening and crystallization
only take place; the weight loss is insignificant (found
4.70%, calculated 3.35%) and associated evidently
with dehydration and cleavage of bridge bonds. In the
Compounds I, III comprise as ligands fragments
of the crown ether chain, specifically tri- and penta-
ethylene glycols. But the system, along with different
macroring fragments formed under the action of such
an acidic agent as PtCl4, and PtCl4 reaction products
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 77 No. 11 2007

1870
GUSEVA et al.
temperature range 217 249 C, too, an insignificant
weight loss (found 3.80%, calculated 4.1%) due to
termal transformations of Pt(IV) and Pt(II) decom-
position products is observed The thermally stable
residue is a mixture of metallic platinum and platinum
chloride. The total weight is 37.80% (calculated
37.27%) and the solid residue is 62.20% (calculated
62.73%).
complex IV is explained by the fact that this com-
pound contains ethylene glycol units in different
conformations.
Crown ether complexes can have structures in
which the hydroxonium ion is directly bound to the
crown ring and stabilized by three hydrogen bonds
between (H3O)+ and every second oxygen atom [35].
Reactions of crown ethers with metal halides can also
form (H2Cl)+. The protonated HCl is always formed
as a main product or an admixture in reactions be-
tween such components in concentrated solutions [7].
Compounds IV, II are crown ether complexes with
(H3O)+ and (H2Cl)+, respectively. Evidence for this
conclusion is provided by the following data. The
IR spectra of complexes IV, II show (H3O)+ absorp-
With product III (Fig. 1), a sharp weight loss
(found 7.7%. calculated 7.0%) occurs at 0 132 C,
associated with cleavage of hydrogen bonds, dehydra-
tion, and partial liberation of acetonitrile molecules
(exo effect at 118 C). The endo effect at 220 C arises
from melting and decomposition of the resulting com-
pound: intramolecular decomposition and oxidation
of the ligand and liberation of two acetonitrile mole-
cules. According to the calculated thermal depen-
dences, the latter molecules are included in the inner
sphere of the complex. Partial Pt Cl bond cleavage in
the cationic and anionic parts of compound III also
takes place. The calculated TG curve shows that the
1
1
tion bands at 1700, 1508 cm and 1664, 1576 cm ,
respectively. Furthermore, the spectrum of complex
1
II contains a (H Cl) band at 2312 cm . The
decreased value of this frequency, as well as of the
frequencies of skeletal stretching vibrations of the
ether units is consistent with (H2Cl)+ coordination.
The presence of the (H Cl), (H3O)+ as well as of
the bands related to the strong hydrogen bonds (2800
major weight loss (found
30.30%, calculated
29.70%) takes place in the temperature range 132
249 C. Thermally stable decomposition products of
compound III are formed at higher temperatures. Two
exo peaks at 303 C and 389 C are observed at 249
376 and 376 425 C. They are associated with further
thermal transformations of the decomposition pro-
ducts of complex III. The weight loss in these tem-
perature ranges is 10.70% (calculated 12.40%). The
thermally stable residue is a mixture of metallic
platinum and platinum chloride. The total weight loss
is 48.70% (calculated 49.10%), and the solid residue
is 51.39% (calculated 50.90%).
1
2400, 2400 1900, 1800 1600 cm ) in the IR spec-
trum of compound II suggests crystallization of
hydrated OH3Cl molecules [6, 7, 30, 36, 37].
The acetonitrile molecules included in compound
IV generally form molecular complexes with PtCl4.
Under these conditions, the (CN) bands are shifted
to higher frequencies [34], which is consistent with
the observation of of a great number of bands at
1
2260 2290 cm .
In the long-wave region of the IR spectrum, strong
1
1
(Pt Cl) bands are observed at 324 and 339 cm for
The IR and H NMR spectra of products II, IV
compounds II and IV, respectively.
(Figs. 4, 5), together with their elemental analyses and
thermoanalytical data (Fig. 1) show that these pro-
According to thermoanalytical data (Fig. 1), in the
temperature range 0 128 C compound II undergoes a
minor weight loss due to cleavage of hydrogen bonds
and loss of volatile components (found 2.90%,
calculated 2.88%). The endo peak in the DTG curve
at 160 C points to melting of the complex with de-
composition. Therewith, a significant weight loss
(found 50%) is observed, associated with thermo-
oxidative decomposition of the complex, involving
intramolecular decomposition and oxidation of the
crown ether, removal of chloride ions together with
thermolysis products, and initiation of thermal de-
composition of the [Pt2Cl10]2 ion (calculated 50.88%).
As the temperature is increased to 500 C, the thermal
decomposition and oxidation of the [Pt2Cl10]2 ion
continues in the temperature ranges 201 263, 263
403, and 403 504 C. The weight losses are 9.00, 7.00,
and 2.00%, respectively (calculated 8.25, 7.25, and
ducts are crown ether complexes. Hence, the IR ab-
1
sorption bands at 1000 1200 cm
[ as(COC),
(CCCR] become stronger and have larger areas. The
1
maxima are shifted to 1100 and 1096 cm for com-
pounds II, IV, respectively. In 18-crown-6, these
vibrations appear as a strong band with a maximum
1
at 1108 cm , having small knees at 1132 and 1008
1
1
cm and a weak splitting ( 1050 and 1030 cm ).
1
The small low-frequency shifts of 8 and 12 cm for
complexes II, IV, respectively, provide evidence for
ion dipole complex formation [28, 29]. The altera-
1
tions in the range 1000 750 cm are more specific
for each of the complexes. The [ (COC) + (CCCR) +
s
(CH2)] and [ (CH2),
+ (CO)] vibration bands
puls
1
are at 980, 960, 852, and 808 cm for II and at 996,
1
960, 888, 840, and 752 cm for IV. The presence of
a great number of absorption bands in the spectrum of
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 77 No. 11 2007

REACTION OF PtCl4 WITH 18-CROWN-6 IN APROTIC SOLVENTS
1871
1.58%). The thermally stable residue is metallic
platinum and nonstoichiometric platinum oxychlorides.
The total weight loss is 71.50% (calculated 70.84%),
and the solid residue is 28.50% (calculated 29.16%).
tion of the crown ether ring. Solvent molecules play
an active part in the formation of the composition and
structure of the final products. Isolation of stable
reaction products is favored by a solvent with a higher
dielectric constant.
The DTG curve of compound IV has two endo
peaks at 152 and 169 C in the temperature ranges
127 160 and 160 192 C, respectively. They relate to
the melting and decomposition points (Fig. 4, curve 4).
These data show that compound IV has a more com-
plex composition as compared to the above-presented
case. The weight losses in these ranges are 23.60%
(calculated 27.70%) and 23.60% (calculated 27.70%).
The weight losses in the temperature ranges 192
377 C and 377 477 C imply step degradation (found
14.10 and 8.1%; calculated 14.10 and 8.1%). The
exo effect at 429 C is associated with thermal de-
composition of platinum ions. In the temperature
range 0 128 C, the weight loss is 5.50% (calculated
5.50%). The thermally stable residue is metallic pla-
tinum. The total weight loss is 73.57% (calculated
73.57%), and the solid residue is 26.43% (calculated
26.43%).
EXPERIMENTAL
1
The IR spectra in the range 4000 400 cm were
obtained on a Perkin Elmer 16 PC FT IR spectro-
meter, and in the range 500 200 cm , on a Specord
M-80 spectrometer in dry Nujol. The Raman spectra
were registered on a Coderg PHO-82 spectrometer
1
with a helium neon laser (
632 nm) as the excita-
ex
tion source; recording conditions: aperture width
1
1
6 cm , scan rate 50 cm 1 mm . The samples were
1
places in glass capillaries. The H NMR spectra were
taken on a Tesla-567A (100 MHz) high-resolution
Fourier spectrometer in deuterated acetone against
internal TMS. The ionic conductivity measurements
of solutions of compounds I IV were carried out on
an LM-301 conductometer in acetonitrile at 25 C.
Thermal analysis was carried out on a Paulik Paulik
Erdey Q-1500D derivatograph in the temperature
range 20 500 C (platinum crucible, heating rate
The stretching and bending absorption bands of the
OCH2CH2O units in products I IV are found in
characteristic spectral ranges [28, 29, 33] (Fig. 4):
The stretching (CH2) bands are observed at 2932
1
10 C min , sample 50 60 mg). Analysis for carbon,
hydrogen, and nitrogen was performed on a Carlo
Erba automatic CHN-analyzer. Analysis for chlorine
was performed according to [39]. Analysis for pla-
tinum was performed by X-ray fluorescence spec-
troscopy on a VRA-20L spectrometer.
1
1
2856 cm , scissor (CH2) bands, at 1460 1400 cm ,
1
(CH2) bands, at 1380 1300 cm , and twist (CH2)
wag bands, at 1296 1200 cm .
1
The electrical conductivities of acetonitrile solu-
tions of compounds I, III and II, IV were found to
be 35.0 30.0 S and 26.0, 20.0 S, respectively (for
straight acetonitrile, 3.0 S). These values point to an
ionic nature of the complexes.
18-Crown-6 of analytic grade was used. PtCl4
was prepared according to [38]. 18-Crown-6 and PtCl4
were dried in a Fischer pistol at corresponding
temperatures over P3O5. The purity of 18-crown-6
was evaluated from its melting point (40 C) and IR
spectrum [2]. PtCl4 was identified by the elemental
analysis (found Pt 57.96%, Cl 10.51%, calculated Pt
57.99%, Cl 10.20%), melting point (370 C, decomp.),
and IR spectrum [30]. The solvents (acetonitrile,
1,2-dichloroethane, chloroform, ethanol, benzene, and
nitromethane) were purified and dried by conventional
procedures directly before use. All preliminary and
synthetic works were carried out using Schlenk
technique under an inert gas or in a vacuum.
Synthesis of [2(PtCl3 CH3NH2 C6H12O4)+
(Pt2Cl6)2 ] H2O (I) and [2{(H2Cl) 18-crown-6}+
(Pt2Cl10)2 ] 2(OH3Cl) (II). PtCl4, 0.6 g, was pre-
liminary evacuated at 180 C in a flask filled with dry
argon, and a solution of 0.48 g of 18-crown-6 in 10 ml
of nitromethane was added. The solution gradually
turned red, and fine black crystals formed. They were
filtered off, washed with nitromethane benzene (1:1),
and dried in a vacuum over Al2O3 until constant
Based on the results of physicochemical studies
we can assign to the stable crystalline products iso-
lated from the solutions the following formula:
[2(PtCl3 CH3NH2 C6H12O4)+ (Pt2Cl6)2 ] H2O,
[2{(H2Cl) 18-crown-6}+ (Pt2Cl10)2 ] 2(OH3Cl),
(I)
(II)
[{PtCl2 2(CH3CN) C10H20O6}2+ (Pt2Cl10)2 ]
2(CH3CN) (H2O)
(III)
[3{(OH3) 18-crown-6}+ (Pt2Cl10)2 (PtCl5 CH3CN) ]
5(CH3CN) (IV)
Thus, the reaction of anhydrous PtCl4 with 18-
crown-6 in dry aprotic solvents leads to cleavage of
the macrocyclic polyether under the action of the
acidic agent and inclusion of the decomposition pro-
ducts in the isolated complexes. Therewith, complexes
with ligands of two types are isolated: crown ether
rings and podand-like ligands formed by fragmenta-
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 77 No. 11 2007

1872
GUSEVA et al.
weight (product I), yield 0.7 g (25%). Found, %: C
10.72, H 1.98, Cl 26.98, N 0.89, Pt 37.00. C14H31
Cl12NO5Pt. Calculated, %: C 10.62, H 1.96, Cl 26.93,
N 0.99, Pt 36.97. The filtrate was placed in a vacuum
dessicator to obtain fine crystals looking like flat
mustard-colored plates (product II), yield 0.8 g (31%).
Found, %: C 19.77, H 3.98, Cl 34.11, Pt 26.77.
C24H58Cl14O8Pt2. Calculated, %: C 19.77, H 3.98,
Cl 34.11, Pt 26.77.
10. Becke, A.D., J. Chem. Phys., 1992, vol. 98, p. 1372;
Becke, A.D., J. Chem. Phys., 1992, vol. 98, p. 648.
11. Lee, C., Yang, W., and Parr, R.G., Phys. Rev. B, 1998,
vol. 37, p. 785.
12. Vosko, S.H., Wilk, L., and Nusair, M., Can. J. Phys.,
1980, vol. 58, p. 1200.
13. Blomberg, M.R.A. and Siegbahn, P.E.M., J. Phys.
Chem. B, 2001, vol. 105, p. 9375.
Synthesis of [{PtCl2 2(CH3CN) C10H20O6}2+
(Pt2Cl1))2 ] 2(CH3CN) H2O (III) and [3{(H3O)
18-crown-6}+ (Pt2Cl10)2 (PtCl5 CH3CN)]
5(CH3CN) (IV) were prepared analogously but in
acetonitrile instead of nitrobenzene. Yield of product
III 1.2 g (47%). Found, %: C 15.12, H 2.38, Cl 29.81,
N 3.92, C18H34Cl12N4O7Pt3. Calculated, %: C 15.12,
H 2.38, Cl 29.81, N 3.92; Pt 40.94. Yield of product
IV 1.3 g (33%). Found, %: C 26.03, H 4.47, Cl 24.66,
N 3.83, Pt 26.44. C48H99Cl15N6O21Pt3. Calculated,
%: C 26.03, H 4.47, Cl 24.56, N 3.80, Pt 26.44.
14. Hay, P.J. and Wadt, W.R., J. Chem. Phys., 1985,
vol. 82, p. 270.
15. Hehre, P.J., Radom, L., Schleyer, P.v.R., and
Pople, J.A., Ab initio Molecular Orbital Theory, New
York: Wiley, 1986.
16. Frisch, M.J., Trucks, G.W., Schlegel, H.B., Scu-
seria, G.E., Robb, M.A., Cheeseman, J.R., Mont-
gomery, J.A., Vreven, Jr.T., Kudin, K.N., Burant, J.C.,
Millam, J.M., Iyengar, S.S., Tomasi, J., Barone, V.,
Mennucci, B., Cossi, M., Scalmani, G., Rega, N.,
Petersson, G.A., Nakatsuji, H., Hada, M., Ehara, M.,
Toyota, K., Fukuda, R., Hasegava, J., Ishida, M.,
Nakajima, T., Honda, Y., Kitao, O., Nakai, H.,
Klene, M., Li, X., Knox, J.E., Hratchian, H.P.,
Cross, J.B., Adamo, C., Jaramillo, J., Gomperts, R.,
Stratmann, R.E., Yazyev, O., Austin, A.J., Cammi, R.,
Pomelli, C., Ochterski, J.W., Ayala, P.Y., Moro-
kuma, K., Voth, G.A., Salvador, P., Dannenberg, J.J.,
Zakrzewski, V.G., Dapprich, S., Daniels, A.D.,
Strain, M.C., Farkas, O., Malick, D.K., Rabuck, A.D.,
Raghavachari, K., Foresman, J.B., Ortiz, J.V., Cui, O.,
Baboul, A.G., Clifford, S., Cioslowski, J., Stefa-
nov, B.B., Liu, G., Liashenko, A., Piskorz, P.,
Komaromi, I., Martin, R.L., Fox, D.J., Keith, T., Al-
Laham, M.A., Peng, C.Y., Nanayakkara, A., Chal-
lacombe, M., Gill, P.M.W., Johnson, B., Chen, W.,
Wong, M.W., Consalez, C., and Pople, J.A., Gaussian
03, Rev. B.04, Pittsburgh, PA: Gaussian, 2003.
ACKNOWLEDGMENTS
The authors express their gratitude to Prof.
R.R. Nazmutdinov for useful discussions.
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