Structure and magnetic properties of trinuclear copper(II) complex [Cu3(bipy)6(μ3-CO3)][B12H12]2·4.5DMF·2H2O

Article abstract of DOI:10.1016/j.ica.2018.04.059

Trinuclear copper(II) complex [Cu^II₃(bipy)₆(μ³-CO₃)][B₁₂H₁₂]₂·4.5DMF·2H₂O is isolated as a result of the redox reaction proceeding when [Ag^I₂B₁₂H₁₂] was allowed to react with Cu^ICl in the presence of bipy. Crystal structure, magnetic properties, and EPR spectrum of the compound are studied. It has been found that in the range 300–2 K, magnetic moment decreases from 1.98 to 1.33 μ_B with decreasing the temperature. In the EPR spectrum, the transition ΔM = ±3 transition is observed indicating the existence of the S = 3/2 state. This transition is explained by the effect of fine coupling tensor which admixes the |?1/? state into the |3/2? state and the |1/2? state into the |?3/2? state. The EPR spectrum is simulated by the spin Hamiltonians for S = 3/2 and S = 1/2.

Full text of DOI:10.1016/j.ica.2018.04.059

Inorganica Chimica Acta 479 (2018) 249–253
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Research paper
Structure and magnetic properties of trinuclear copper(II) complex
[Cu3(bipy)6(
3-CO3)][B12H12]2ꢀ4.5DMFꢀ2H2O
l
⇑
Elena A. Malinina, Irina K. Kochneva, Irina N. Polyakova, Varvara V. Avdeeva , Grigorii A. Buzanov,
Nikolai N. Efimov, Elena A. Ugolkova, Vadim V. Minin, Nikolai T. Kuznetsov
Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, Leninskii Pr. 31, Moscow 119991, Russia
a r t i c l e i n f o
a b s t r a c t
Trinuclear copper(II) complex [CuI3I(bipy)6(
l
3-CO3)][B12H12]2ꢀ4.5DMFꢀ2H2O is isolated as a result of the
Article history:
redox reaction proceeding when [AgI2B12H12] was allowed to react with CuICl in the presence of bipy.
Crystal structure, magnetic properties, and EPR spectrum of the compound are studied. It has been found
that in the range 300–2 K, magnetic moment decreases from 1.98 to 1.33 mB with decreasing the tempera-
Received 23 March 2018
Received in revised form 25 April 2018
Accepted 26 April 2018
Available online 3 May 2018
ture. In the EPR spectrum, the transition
DM = 3 transition is observed indicating the existence of the
S = 3/2 state. This transition is explained by the effect of fine coupling tensor which admixes the |ꢁ1/i state
into the |3/2i state and the |1/2i state into the |ꢁ3/2i state. The EPR spectrum is simulated by the spin
Hamiltonians for S = 3/2 and S = 1/2.
Ó 2018 Elsevier B.V. All rights reserved.
1. Introduction
prepared for boron clusters and azaheterocyclic ligands 2,20-
bipyridyl, 2,20-bipyridylamine, 1,10-phenanthroline, phenanthri-
Design of substances with desired properties sets a task of syn-
thesizing coordination compounds of new structural types. Homo-
and heterometallic polynuclear transition metal complexes attract
interest as potential molecular magnets and models of magnetic
interactions between metal atoms. A great number of these com-
pounds are present in Cambridge Structural Database and mag-
netic properties are reported in many studies indicating crucial
interest in this type of compounds.
dine. Many of them are reported in our review [3]. Among them,
mononuclear, binuclear, and polynuclear copper(II) cationic
complexes were found to form with boron cluster anions usually
acting as counterions. For bipy, tetranuclear copper(II) complex
[CuI4I(bipy)4(OH)4][B10H10]2(DMSO)2 [6] and binuclear copper(II)
complex [CuI2I(phen)4(CO3)][B10H10] [7,8] as well as heterovalent
copper(I,II) complex [CuI4I(bipy)4(OH)4][CuI2[B10H10]3] [9] containing
the mentioned tetranuclear copper(II) cationic complex were
2ꢁ
Here, we have studied the reaction ability of the dodecahydro-
obtained for the [B10H10
]
anion in copper(I) complexation reac-
2ꢁ
closo-dodecaborate anion [B12H12
]
in copper complexation. In
tions including copper(I) oxidation in the [CuI2[B10H10]]/L systems
(L = bipy, phen). Mononuclear [10], binuclear [11], tetranuclear
[10], and polynuclear [10] copper(II) complexes were selectively pre-
pared and studied by X-ray diffraction for phen whereas only a bin-
uclear copper(II) complex with CO3 bridged ligands was synthesized
for bipy [CuI2I(bipy)4(CO3)][B10H10] as DMF/H2O and CH3CN solvates
[11]. The majority of copper(II) compounds were prepared starting
from copper(I) salts in air as a result of copper(I) oxidation.
coordination chemistry, boron cluster anions [BnHn]2ꢁ (n = 10, 12)
[1,2] can be regarded as soft bases; they can act as inner-sphere
ligands in copper(I), silver(I), and lead(II) complexes (with soft acid
metals) [3,4] and form anionic parts of cationic 3d metal complexes
[5]. Our long-term studies on the reaction ability of boron cluster
anions [BnHn]2ꢁ (n = 10, 12) in complexation reaction showed that
these compounds can result in interesting products because of
reactions accompanied metal complexation. In particular, redox
processes were observed in the course of iron(III) and cobalt(III)
complexation which are discussed in details in the review [5].
A great number of copper complexes in various oxidation states
(copper(I), copper(II), heterovalent copper(I,II) compounds) were
In this paper, we report the synthesis, structure, and magnetic
properties of copper(II) complex [CuI3I(bipy)6(
l3-CO3)][B12H12]2-
ꢀ4.5DMFꢀ2H2O prepared when using copper(I) chloride as starting
reagent. This compound is the first trinuclear copper(II) complex
with boron cluster anions; it contain the bridging l
3-CO3 group, ter-
minal bipy molecules, and the dodecahydro-closo-dodecaborate
anion as a counter ion.
⇑
Corresponding author.
E-mail address: avdeeva.varvara@mail.ru (V.V. Avdeeva).
https://doi.org/10.1016/j.ica.2018.04.059
0020-1693/Ó 2018 Elsevier B.V. All rights reserved.

250
E.A. Malinina et al. / Inorganica Chimica Acta 479 (2018) 249–253
software; Bruker 2008). The structure was solved by direct meth-
2. Experimental
2.1. Synthesis
ods and refined by full matrix least-squares on F2 [15] with aniso-
tropic thermal parameters for all non-hydrogen atoms except
minor components of disordered groups. Both bipy ligands around
Cu(1) atom were found to be positionally disordered over two
positions with occupancy ratio 0.75/0.25. The minor parts of these
disordered ligands were refined with restrained CAC and CAN dis-
tances. Two of five solvent DMF molecules were also disordered
over two positions. They were refined with restrained CAN and
CAO bond lengths. All hydrogen atoms were placed in calculated
positions and refined using a riding model. The crystallographic
data and experimental details are collected in Table S2; bond
lengths and bond angles are listed in Table S3 (see SI).
DMF (HPLC grade) and anhydrous Bipy and CuCl were purchased
from Aldrich. (Et3NH)2[B12H12] was synthesized from decaborane-
14 according to the known procedure [12]. [Ag2[B12H12]] was
prepared from (Et3NH)2[B12H12] as indicated in [13].
[Cu3(m-CO3)(bipy)6][B12H12]2ꢀ2H2O6DMF (1)
A solution of CuCl (0.4 mmol) in DMF (10 ml) was added to a
solution of [Ag2[B12H12]] (0.2 mmol) in DMF (10 ml) followed by
the addition of a solution of bipy (0.8 mmol) in acetonitrile (10
ml). Once bipy was added, the reaction solution became red and
changed its color to blue for seconds because of copper oxidation
in air. Metallic silver precipitated as black powder for 1–2 h, which
was filtered off. Blue crystals 1 precipitated for 72 h from the
mother solution; which were filtered off, washed with acetonitrile,
and dried in air. Yield, 30%. Anal. Calcd.,%: Cu, 12.96; C, 49.79; H,
4.93; N, 11.42; B, 17.63. Found: Cu, 12.98; C, 49.76; H, 4.92; N,
11.44; B, 17.65.
The crystallographic data for 1 has been deposited with the
Cambridge Crystallographic Data Centre as supplementary publi-
cations under the CCDC number 1559297. This information may
be obtained free of charge from the Cambridge Crystallographic
Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
The X-ray powder diffraction pattern of complex 1 was mea-
sured on a Bruker D8 Advance diffractometer (CuK 1) at RT with
a
LynxEye detector and Ge(111) monochromator, h/2h scan from 5°
to 80°, step size 0.01125° at the Shared Equipment Centre of the
Kurnakov Institute. The measurement was performed in transmis-
sion mode with the sample deposited in the single-crystal oriented
silicon cuvette. The crystals were thoroughly triturated before
measurements. The X-ray powder diffraction pattern for 1 is
shown in Fig. S2 (see SI).
2.2. Materials and methods
Elemental analysis for carbon, hydrogen, and nitrogen was car-
ried out on a Carlo Erba CHNS-3 FA 1108 automated elemental
analyzer. Determination of boron and metals was performed on
an iCAP 6300 Duo ICP emission spectrometer with inductively cou-
pled plasma. The samples were dried under vacuum at room tem-
perature to constant weight to obtain solvent-free compounds.
IR spectrum of the crystals obtained was recorded on a Lumex
Infralum FT-02 Fourier-transform spectrophotometer in the range
of 4000–600 cmꢁ1 at a resolution of 1 cmꢁ1. The sample was pre-
pared as a CCl4 mull; NaCl pellets were used. The IR spectrum of
compound 2 is present in Fig. S1 (see SI).
The electronic structure of compound 1 was studied by EPR at T
= 295 K. The EPR spectrum of the polycrystalline sample was
recorded on a Bruker ELEXSYS E680X X band (frequency, 9.8
GHz) spectrometer. The spin Hamiltonian parameters were deter-
mined by means of computer simulation through fitting the theo-
retical spectra to the experimental ones [14].
3. Results and discussion
Trinuclear copper complex [Cu3(bipy)6(l
3-CO3)][B12H12]2-
ꢀ4.5DMFꢀ2H2O (1) was isolated as the main product of the reaction
proceeding in the [Ag2B12H12]/CuCl/bipy system in a DMF/CH3CN
solution. The reduction of silver(I) to metallic silver Ag+ ? Ag0
occurs along with the oxidation of copper(I) to copper(II) Cu+ ?
Cu2+ as shown in Scheme 1.
The presence of the CO23ꢁ group in the final compound is
explained by air CO2 and its dissolution in DMF, since the reaction
was carried out in air. Previously, carbonate group was found in a
number of copper(II) complexes with phen and bipy and anions
[BnHn]2ꢁ (n = 10, 12) [7,8,11].
The DC magnetic susceptibility of polycrystalline sample 1 was
measured in the temperature range 300–2 K at 500 mT using a
Quantum Design susceptometer PPMS-9.
The composition of the complex was determined by elemental
analysis and the purity of the product was proved by X-ray powder
diffraction (Fig. S1). In the IR spectrum of a suspension of 1 in CCl4
(Fig. S2), the stretching vibrations of the BH groups m(BH) appear as
2.3. X-ray diffraction
an intense broadened band with the maximum at 2467 cmꢁ1. The
m
(C@O) band of the bridging CO3 group is observed at ꢂ1400 cmꢁ1
;
Experimental data were collected on a Bruker SMART APEX II
the sample was studied as a CCl4 suspension to reveal the presence
of the (C@O) band, which is overlyied by the d(HCH) bands when
the sample is used as Nujol mull. The set of absorption bands of
bipy molecules appears in the range 1600–800 cmꢁ1. The bands
diffractometer using graphite monochromatized MoK ꢁradiation
a
(k = 0.71073 Å) in
x-scan mode. Absorption correction based on
measurements of equivalent reflections were applied (SADABS
Scheme 1. Preparation of compound 1.

E.A. Malinina et al. / Inorganica Chimica Acta 479 (2018) 249–253
251
The Cambridge Database (CSD version 5.37, November 2015)
[16] contains data on six solvates that include trimeric
[(Cu(bipy)2)3CO3]4+ cation (Cat): Cat(BF4)4∙EtOHꢀ3H2O [17], Cat
(ClO4)4ꢀ0.5H2O [18], Cat(ClO4)4∙4EtOHꢀ2H2O [19], Cat(F3CSO3)4-
ꢀ0.5H2O [20], Cat(ClO4)4∙MeOHꢀ2H2O [19], and Cat(PF6)4ꢀH2O [19].
In the two latter compounds, the carbonate ligand is bound to cop-
per atoms by the l3- -
g2g2g2 and l3 g2g1g1 patterns, respec-
tively. In the remaining four trinuclear compounds, the
coordination pattern is the same as in 1 and the shapes of CuON4
five-vertex polyhedra are also better approximated by two square
pyramids and a trigonal bipyramid. In the square pyramids, the
CuANap are elongated in comparison with the CuANbase, whereas
in the trigonal bipyramids, both CuANap bonds are shorter than
CuANbase
.
In studies [17–20], the source of the carbonate group was cop-
per carbonate, CO2 atmosphere, or air CO2. Copper(II) trinuclear
complexes were prepared at room temperature, on heating or in
conditions of the hydrothermal synthesis starting from copper(II)
salts. Magnetic behavior was studied only for two of these com-
pounds: weak antiferromagnetic interactions were found in [Cat]
(BF4)4∙EtOHꢀ3H2O [17] and weak ferromagnetic interactions were
found in [Cat](CF3SO3)4ꢀ0.5H2O [20]. It was found that effective
magnetic moment meff [Cat](BF4)4ꢀEtOHꢀ3H2O in the 250–100 K
range was 3.3–3.4 mB, which agrees with spin values for each cop-
per atom S = 1/2. To explain the exchange interactions found in
[17], the authors used spin Hamiltonian H = ꢁJ12 (S1ꢀS2), ꢁJ13
(S1ꢀS3), ꢁJ23 (S2ꢀS3). The low value of J = 10.6 cmꢁ1 and weak anti-
ferromagnetic intercluster interactions with zj = ꢁ1.2 cmꢁ1 were
explained by large CuACu distances in the Cu3 cluster (4.64, 4.72,
and 5.00 Å). Based on the EPR spectra data for [Cu3(bipy)6
Fig. 1. Structure of the coordination nodes of the [Cu3(bipy)6(l
3-CO3)]4+ complex
cation.
with maxima at 1680 and 3450 cmꢁ1 are attributed to the
and (OH) vibrations of solvate DMF and water molecules,
m(C@O)
m
respectively.
The crystal structure of [Cu3(bipy)6(
2H2O is built of trinuclear cations, [B12H12
l
3-CO3)][B12H12]2ꢀ4.5DMFꢀ
(
l
3-CO3)](CF3SO3)4ꢀ0.5H2O [20] with the l3
-
g1g1g1-coordination
2ꢁ
]
anions, and solvate
of carbonate ions to copper atoms and the CuACu distances equal
to 4.57, 4.68 and 5.19 Å, it was assumed that the magnetic behav-
ior of the complex corresponds to weak ferromagnetic exchange
interactions.
molecules of DMF and water (Fig. S3). The bridging carbonate
anion is bound to Cu atoms by the l3
-
g1g1g1 pattern (Fig. 1).
The Cu3(CO3) core of the cation is flattened (Fig. S4): the Cu(1)
and Cu(2) atoms deviate unidirectionally from the plane of the
CO3 group by 0.293 and 0.111 Å, and the Cu(3) atom deviates to
the opposite direction by 0.105 Å. The cation has the syn-anti con-
figuration in relation to all CAO bonds. The Cu. . .Cu distances in the
trinuclear cation are 4.663, 4.666, and 4.888 Å.
The temperature dependence of magnetic susceptibility of a
crystalline sample of 1 was measured in the range of 300–2 K.
Magnetic moment decreased from 1.98 to 1.33 mB with the
lowering of the temperature. The magnetic moment of three
non-interacting copper atoms is 3.4 0.3 mB.
The five-coordinate environment of the Cu(1), Cu(2), and Cu(3)
atoms in the cation consists of four N atoms of bipy molecules and
an O atom of the carbonate group (Fig. S5). The ranges of inter-
atomic distances are as follows: CuAO, 2.015(8)–2.119(9) Å; Cu
(1)AN, 2.009(1)–2.126(8); Cu(2)AN, 1.969(8)–2.104(7); and Cu
(3)AN, 1.991(7)–2.155(8) Å. The shapes of distorted polyhedra of
the Cu(1) and Cu(3) atoms are close to the elongated square pyra-
mids with the N(4) and N(12) atoms, respectively, at the apical ver-
tices. The polyhedron of the Cu(2) atom is approximated by the
slightly oblate trigonal bipyramid with the N(5) and N(8) atoms
at the apical vertices (Fig. 1).
Taking into account that the nearest environment of copper
atoms Cu(1) and Cu(3) differs from that of Cu(2), as it is found
by X-ray diffraction, the magnetic susceptibility of 1 was inter-
preted using spin Hamiltonian (Fig. 3, insert)
H ¼ ꢁ2J1ðS1S2 þ S2S3Þ ꢁ 2J2S1S3:
ð1Þ
Three interacting spin-1/2 particles can form one state with
total spin 3/2 and two states with total spin 1/2. Eigen energies
of the spin states are E(3/2) = ꢁJ1 ꢁ J2/2, E1(1/2) = 3 J2/2, and
E2(1/2) = 2 J1 ꢁ J2/2. The magnetic susceptibility of 1 was calculated
according to the equation reported in [21]:
In the crystal structure, complex cations [{Cu(bipy)2}3
(l
3-CO3)]4+ are packed into columns running along the b axis
NAg2b2
kT
(Figs. S6). Columns related by the a translation form loose layers
vM
¼
2ꢁ
separated by wide interlayer space filled by [B12H12
]
anions
ꢀ
ꢁ
ꢁ
ꢀ
ꢁ
ꢀ
ꢁ
E1ð1=2Þ
E2ð1=2Þ
Eð3=2Þ
and solvate DMF and water molecules (Figs. S7). The geometric
parameters of the CAH. . .O and OAH. . .O hydrogen bonds found
in the structure of complex 1 are listed in Table S1; fragments
1=2ꢀexp ꢁ
þ1=2ꢀexp ꢁ
þ5ꢀexp ꢁ
kT
kT
kT
ꢀ
ꢀ
ꢁ
ꢀ
ꢁ
ꢃ
:
E1ð1=2Þ
E2ð1=2Þ
Eð3=2Þ
2ꢀexp ꢁ
þ2ꢀexp ꢁ
þ4ꢀexp ꢁ
kT
kT
kT
showing the interactions are shown in Fig. S8.
2ꢁ
Two crystallographically independent [B12H12
]
anions form
The best correlation with the experimental data (Fig. 2) is
multiple weak BAH. . .HAX (XAC, O) interactions with complex
cations and solvate molecules: one of them has 12 contacts of
2.16–2.41 Å with bipy ligands and 3 contacts of 2.15–2.32 Å
with DMF molecules, and the other has 5 contacts of 2.23–2.43 Å
with bipy and 6 contacts of 2.26–2.44 Å with DMF and H2O
molecules.
achieved at 2 J1 = 9.8 0.2 cmꢁ1
g = 2.14 0.01. With these parameters of the spin Hamiltonian,
the E(3/2) spin state energy is intermediate between the E1(1/2)
and E2(1/2) energies (Fig. 3b).
,
2 J2 = ꢁ8.2 0.2 cmꢁ1
,
and
The EPR spectrum of 1 was simulated as a sum of spectra of two
spin-1/2 complexes and one spin-3/2 complex. Their concentra-

252
E.A. Malinina et al. / Inorganica Chimica Acta 479 (2018) 249–253
Fig. 2. Temperature dependence of meff vs. T (r); the solid line represents the calculated curve for complex 1.
Fig. 3. Geometric model of magnetic exchange in 1; the insert shows schematic
representation of spin state energies in
parameters.
1
for the best spin Hamiltonian (1)
Fig. 4. (1) Experimental and (2) calculated EPR spectrum of
sample of complex 1 at T = 293 K.
a polycrystalline
The complex concentrations in different spin states were
calculated from the Gibbs distribution of the corresponding levels
taking into account the spin degeneracy. Occupation probability
was estimated in accordance with the Boltzmann distribution
depending on the energy difference and temperature and spin
degeneracy.
A remarkable feature of the EPR spectrum of compound 1
(Fig. 4) is a low-intensity transition in the region of ꢂ100 mT in
addition to the ordinary ‘‘forbidden” transition in the half field
tions were calculated according to the Boltzmann occupancies of
the corresponding levels.
The spectrum of the spin-3/2 complex is described using the
spin Hamiltonian with fine coupling having a rhombic symmetry
H3=2 ¼ bðg SxHx þg SyHy þg HzSzÞþDðS2 ꢁSðSþ1Þ=3ÞþEðS2 ꢁS2Þ;
^
x
y
z
z
x
yð2Þ
where S = 3/2 is the total spin; Sz, Sx, and Sy are the projections of the
spin operator onto the coordinate axes; D and E are components of
the fine coupling tensor; gx, gy, and gz are components of the g ten-
sor; and H is the applied magnetic field. The spectra of two spin-1/2
complexes are simulated by the Zeeman spin Hamiltonian
(Fig. 5). Formally, it is a |ꢁ3/2i ? |3/2i transition with
DM = 3.
This transition indicates that there exists a state with total
spin S = 3/2 in the system. The fine coupling tensor admixes the
|ꢁ1/2i state into the |3/2i state and the |1/2i state into the
|ꢁ3/2i state making this transition possible [23].
^
In the earlier papers concerning the structural studies of trinu-
clear carbonato-bridged copper(II) complexes [17–20], the EPR
data are found only for Cat(F3CSO3)4ꢀ0.5H2O [20]. As it was indi-
cated by the authors, this spectrum contains a very broad signal
(g = 2.13) and a half-field signal (g = 4.33); the spectrum is not pre-
sent in the paper, and the reported data doesn’t allow us to com-
pare the results obtained here with those reported in [20].
H1=2 ¼ bðgxSxHx þ gySyHy þ gzHzSzÞ;
ð3Þ
where S = 1/2 is the total spin of the complex. It was accepted that
parameters of two different spin-1/2 complexes are equal.
Computer simulation of the EPR spectrum was performed using
the eigenfield method [22]. The D and E parameters and g tensor
components are listed in the Table 1.
Table 1
Parameters D and E of spin Hamiltonian (2) and components of the g tensor of spin Hamiltonians (2) and (3) for complex 1.
Spin
C,%
D, cmꢁ1
E, cmꢁ1
gx
gy
gz
1/2
3/2
50
50
2.040
2.030
2.080
2.110
2.190
2.190
0.01767
0.01280

E.A. Malinina et al. / Inorganica Chimica Acta 479 (2018) 249–253
253
Appendix A. Supplementary data
Supporting Information contains IR spectrum for 1 (Fig. S1),
X-ray powder diffraction pattern for 1 (Fig. 2), fragments of the
structure and crystal packing (Figs. S3–S8), geometric parameters
of hydrogen bonds (Table S1), crystal data and structure
refinement (Table S2), and bond lengths and angles (Table S3).
Supplementary data associated with this article can be found, in
the online version, at https://doi.org/10.1016/j.ica.2018.04.059.
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4. Conclusions
First trinuclear copper(II) complex [Cu3(bipy)6(l3-CO3)]
[B12H12]2∙4.5DMFꢀ2H2O with the dodechydro-closo-dodecaborate
anion has been synthesized and characterized by X-ray diffraction
techniques as well as EPR and IR spectroscopic methods. In addi-
tion, the DC magnetic susceptibility has been measured. The title
compound has been prepared when [Ag2[B12H12]] is allowed to
react with CuCl followed by the addition of bipy in DMF/CH3CN.
The final product is prepared because of redox reaction
Cu+ ? Cu2+ which is accompanied with the isolation of Ag0. A num-
ber of the BAH. . .HAC and BAH. . .HAO shortened contacts have
been revealed by the X-ray crystallography. Features of the elec-
tronic structure are reported for the trinuclear complex synthe-
sized. In the EPR spectrum, the
DM = 3 transition is observed
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indicating the existence of the S = 3/2 state of copper. The EPR
spectrum is simulated by the spin Hamiltonians for S = 3/2 and
S = 1/2.
Acknowledgments
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This study was supported by the Russian Science Foundation
(project no. 14-13-01115). The X-ray diffraction studies were per-
formed and described by I.N. Polyakova (deceased) at the Centre of
Shared Equipment of the Kurnakov Institute. The EPR studies were
performed within the State Assignment on Fundamental Research
(no. 0088-2014-0003) to the Kurnakov Institute. The authors thank
O.N. Belousova and Dr. L.V. Goeva for the IR spectral studies.