Synthesis and structure of 2,2′-diaminodiphenylditelluride bis-imines

Article abstract of DOI:10.1007/s11172-013-0261-4

Bis-imines of 2,2′-diaminodiphenylditelluride and 2-tosylamino (9a) and 2-hydroxybenz- Aldehyde (9b) were prepared and studied by X-ray diffraction, heteronuclear (¹H, ¹³C, ¹⁵N, and ¹²⁵Te) magnetic resonance, an

Full text of DOI:10.1007/s11172-013-0261-4

Russian Chemical Bulletin, International Edition, Vol. 62, No. 8, pp. 1809—1814, August, 2013
1809
Synthesis and structure of 2,2´ꢀdiaminodiphenylditelluride bisꢀimines*
I. S. Vasil´chenko,a I. G. Borodkina,a A. S. Burlov,a N. V. Karpova,b G. M. Abakarov,c K. A. Lyssenko,d
G. S. Borodkin,a I. E. Uflyand,b A. D. Garnovskii,a and V. I. Minkina
aInsitute of Physical and Organic Chemistry, Southern Federal University,
194/2 prosp. Stachki, 344090 RostovꢀonꢀDon, Russian Federation.
Eꢀmail: vas@ipoc.rsu.ru
bPedagogic Institute, Southern Federal University,
35 ul. Bol´shaya Sadovaya, 344010 RostovꢀonꢀDon, Russian Federation
cDagestan State Technical University,
70 ul. I. Shamilya, 367015 Makhachkala, Republic of Dagestan
dA. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences,
28 ul. Vavilova, 119991 Moscow, Russian Federation
Bisꢀimines of 2,2´ꢀdiaminodiphenylditelluride and 2ꢀtosylamino (9a) and 2ꢀhydroxybenzꢀ
aldehyde (9b) were prepared and studied by Xꢀray diffraction, heteronuclear (1H, 13C, 15N,
and 125Te) magnetic resonance, and quantum chemical calculations (Pbe1pbe/DGDZVP).
According to the Xꢀray diffraction data, compound 9b in the crystal phase has nonsymmetrical
structure: one of the tellurium atoms forms hypervalent bonding with the adjacent oxygen
atom, while the second one is not involved in such interaction. The NMR study showed the
symmetric molecular structure of imines 9a,b in DMSOꢀd6 with the tellurium atoms interꢀ
acting hypervalently with the C=N nitrogen atoms .
Key words: bisꢀimines, 2,2´ꢀdiaminodiphenylditelluride.
Tellurium azomethines are represented in the chemisꢀ
try of organotellurium compounds by few examples.1
Among these are complexes of acyclic Schiff bases 1,2 2,3
3,4 and 4,5 and their cyclic analogs: benzotellurazoles 5
and 6,6—10 oxazoline derivatives 7 (see Ref. 11), and
macrocyclic azomethines 8.12,13
The azomethines with the telluriumꢀcontaining subꢀ
stituent in the orthoꢀposition relative to the imino carbon
atom (see compounds 1 and 2) retain the N···Te intraꢀ
molecular hypervalent bond upon complexation. In this
regard, it is of interest to study the structure and complexꢀ
ation of aldimines 9 containing tellurium atoms in the
orthoꢀposition relative to the imino nitrogen atom.
We synthesized the derivatives of compound 9 and
studied their structures in solid state and in solution.
the distance between the proton donor and acceptor, viz.,
O(1´)···N(1´) (2.603(2) Å), is by 0.03 Å shorter than
O(1)···N(1) (2.639(2) Å). The observed differences are reꢀ
sponsible for some variations in the bond lengths in the
sixꢀmembered Hꢀbonded rings. Such Hꢀbond strengthenꢀ
ing in the N(1´)C(7´)C(8´)C(9´)O(1´)H(10´) ring is most
likely due to the secondary O(1´)···Te(1´) interaction,
which is absent in the second fragment. Indeed, the shortꢀ
ened contact O(1´)···Te(1´) (3.586(2) Å) is characterꢀ
ized by a sufficiently high directionality, viz., the
Te(1)Te(1´)O(1´) angle is equal to 162.8(1), which alꢀ
lows considering it as the interaction with charge transꢀ
fer from the oxygen lone pair to the antibonding orbital
of the Te(1)—Te(1´) bond. In this case, such interacꢀ
tion will result in an increase in the acidity of hydrogen
atom and, as a result, will be manifested in the Hꢀbond
strengthening.14
Results and Discussion
The crystal packing analysis revealed that, in addition
to the aboveꢀmentioned intramolecular interaction Te···O,
in the crystal of 9b there are also Te···Te interactions with
a shortened distance (4.054(1) Å) compared to the correꢀ
sponding van der Waals contact (4.4 Å). These interacꢀ
tions combine the molecules into dimers (Fig. 2).
Compounds 9 were prepared by the reaction shown in
Scheme 1.
The point of interest in the structure of compound 9b
(Fig. 1, Table 1) is the certain difference in the Hꢀbond
strengths in two O—H···Nꢀbonded rings. For example,
To estimate to what extent the observed variation in the
parameters of intramolecular hydrogen bonding N—H···O
is characteristic of the molecule or whether it is caused by
* Dedicated to the memory of the Corresponding Member of the
Russian Academy of Sciences M. Yu. Antipin (1951—2013).
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1809—1814, August, 2013.
1066ꢀ5285/13/6208ꢀ1809 © 2013 Springer Science+Business Media, Inc.

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Russ.Chem.Bull., Int.Ed., Vol. 62, No. 8, August, 2013
Vasil´chenko et al.
R = H, Alk, Ar, M is the Pearson hard acid, M´ is the Pearson soft acid; A = Hal, NO3, n = 1—5
Scheme 1
the crystal packing effects, we performed quantum chemꢀ
ical calculation (Pbe1pbe/DGDZVP) of the molecule of
9b with full geometry optimization.
Accodring to the data from quantum chemical calcuꢀ
lation, despite a slight tilting of aromatic rings, the molecꢀ
ular conformations in the isolated state and in crystal are
similar (Fig. 3). The distance Te(1)—Te(1´) is slightly
elongated to 2.730 Å (compared to 2.698 Å in crystal). It
should be noted that, although the distances Te—C (2.139 Å)
are identical in the isolated molecule, there are also differꢀ
C(5)
C(4)
C(6)
C(3)
C(1)
C(10´)
C(9´)
C(2)
O(1´)
Te(1´)
N(1)
C(7)
C(8)
C(13)
Te(1)
C(11´)
C(12´)
X = NTs (a), O (b)
H(10´)
N(1´)
H(10)
O(1)
C(1´)
C(6´)
C(13´)
C(8´)
C(7´)
ences in the Hꢀbond strength, which were observed in the
crystal. For example, the distance O(1)···N(1) (2.664 Å)
characterizing the hydrogen bond strenth is by 0.03 Å
longer than the distance O(1´)···N(1´) (2.630 Å). Takꢀ
ing into account that the C(1)C(2)N(1)C(7) and
C(1´)C(2´)N(1´)C(7´) torsion angles in the isolated molꢀ
ecule (139.4 and 140.7) are virtually the same, one can
C(2´)
C(3´)
C(9)
C(5´)
C(10)
C(11)
C(12)
C(4´)
Fig. 1. Molecular structure of compound 9b. General view showꢀ
ing atoms as thermal ellipsoids (p = 50%).

Structure of Teꢀcontaining bisꢀazomethines
Russ.Chem.Bull., Int.Ed., Vol. 62, No. 8, August, 2013
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Table 1. Selected bond lengths (d) and angles () in compound 9b
Parameter
Bond
9b
Parameter
Angle
9b
Parameter
Angle
9b
d/Å
/deg
/deg
Te(1)—C(1)
Te(1)—Te(1´)
Te(1')—C(1')
O(1)—C(9)
O(1')—C(9')
N(1')—C(7')
N(1')—C(2')
N(1)—C(7)
N(1)—C(2)
C(1)—C(2)
C(1´)—C(2´)
C(7´)—C(8´)
C(7)—C(8)
C(8´)—C(9´)
Angle
2.121(3)
2.6981(4)
2.134(4)
1.349(5)
1.354(4)
1.290(4)
1.416(5)
1.291(5)
1.419(4)
1.393(5)
1.404(5)
1.444(5)
1.454(5)
1.407(5)
/deg
C(1´)—Te(1´)—Te(1)
C(7´)—N(1´)—C(2´)
C(7)—N(1)—C(2)
C(2)—C(1)—C(6)
C(2)—C(1)—Te(1)
C(6)—C(1)—Te(1)
C(6´)—C(1´)—C(2´)
C(6´)—C(1´)—Te(1´)
C(2´)—C(1´)—Te(1´)
C(3´)—C(2´)—N(1´)
C(1´)—C(2´)—N(1´)
C(1)—C(2)—C(3)
100.31(1)
122.3(3)
120.8(3)
119.6(3)
121.4(2)
119.0(3)
119.5(3)
122.4(3)
118.1(3)
123.7(3)
117.0(3)
119.0(3)
118.2(3)
122.8(3)
119.8(4)
122.7(3)
N(1)—C(7)—C(8)
C(13)—C(8)—C(9)
C(13)—C(8)—C(7)
C(9)—C(8)—C(7)
C(13´)—C(8´)—C(9´)
C(13´)—C(8´)—C(7´)
C(9´)—C(8´)—C(7´)
O(1)—C(9)—C(10)
O(1)—C(9)—C(8)
C(10)—C(9)—C(8)
122.0(3)
119.0(3)
119.0(3)
122.0(3)
118.0(3)
120.2(3)
121.8(3)
118.6(3)
121.6(3)
119.8(3)
O(1´)—C(9´)—C(10´) 118.9(3)
O(1´)—C(9´)—C(8´)
C(10´)—C(9´)—C(8´)
120.3(3)
120.7(3)
C(1)—C(2)—N(1)
C(3)—C(2)—N(1)
C(4´)—C(3´)—C(2´)
N(1´)—C(7´)—C(8´)
C(1)—Te(1)—Te(1´) 95.48(9)
assume that the variation in the Hꢀbond strength in two
sixꢀmembered Hꢀbonded rings is caused by the intraꢀ
molecular interactions between the oxygen and telluriꢀ
um atoms.
To investigate compounds 9a,b, we used multidimenꢀ
sional and multinuclear NMR techniques, such as COSY,
NOESY, HSQC, and HMBC.15—18 The assignment of
1
signals for the H, 13C, 15N, and 125Te nuclei is given in
Experimental.
The presence of cross peak between the N(17) and
1
H(19) atoms in the HMBC H—15N NMR spectrum of
compound 9a (Fig. 4) suggests the presence of N···H
hydrogen bonding. Another point to be noted is the singlet
character of the signals for the tellurium nuclei in
the 125Te NMR spectra of compounds 9a,b, which sugꢀ
gests the symmetric structure of these molecules in soꢀ
lution.
Te(1)
Te(1´)
Te(1B)
Te(1A)
It is of interest to determine the molecular structures
of azomethines 9 in solution by NMR spectroscopy.
Taking into account that the 125Te NMR spectra disꢀ
play only one signal for the tellurium atom, which suggests
the symmetric structure of the molecules, the most probaꢀ
ble forms of compounds 9 in solution are forms 9´—9´´´.
The fact that the signals for azomethine protons
and tellurium atoms in the corresponding NMR spectra
appears as singlets and the absence of the signals in
1H—125Te HSQC NMR spectra characterizing the firstꢀ
order interaction allows excluding form 9´ from conꢀ
sideration.
Fig. 2. Te···Teꢀbonded dimer in the crystal of 9b.
The interesting feature of the twoꢀdimensional 1H—125Te
HMBC NMR spectrum (Fig. 5) of compound 9a is the
presence of intensive crossꢀpeak between the Te(18) atom
and azomethine H(10) atom. Based on the NMR spectral
data, the structure of this compound in solution can be
drawn as 9 (without hypervalent bonding), 9´´ with
H—Ntosyl···Te bonding (1H—125Te spinꢀspin coupling conꢀ
stant of the 5th order), or 9´´´ with H—Nazometh···Te bondꢀ
ing (1H—125Te spinꢀspin coupling constant of the 3rd orꢀ
Fig. 3. Conformational differences of the molecule in crystal
and isolated molecule. The isolated molecule is dashed.

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Russ.Chem.Bull., Int.Ed., Vol. 62, No. 8, August, 2013
Vasil´chenko et al.

N(19)
120
160
200
240
280
320
N(17)
360
13
12
11
10
9
8
7

Fig. 4. 1H—15N HMBC NMR spectrum of the aromatic fragment of compound 9a.
der). The intensity of the crossꢀpeak under discussion alꢀ
lows decision on structure 9´´´.
The 1H, 13C, 15N, 125Te of compound 9b are similar in
character.
Thus, we established that the molecule of organotelluꢀ
rium azomethine bisꢀhydroxy derivative 9b (X = O) has
nonꢀsymmetric structure with O···Te hypervalent bondꢀ
ing, whereas in solution aldimines 9a,b (X = NTs, O) have
symmetric structure with hypervalent bonding between the
tellurium and azomethine nitrogen atoms.
Experimental
1
H NMR spectra of solutions were recorded on Avansꢀ600
(Bruker) spectrometer (600 MHz) with internal stabilization of
the polar resonance line 2H in DMSOꢀd6. The IR spectra of
solid ligands and complexes were recorded on VarianꢀExcalibur
3100 FTꢀIR instrument by the attenuation total reflection methꢀ
od in powder.
Bisꢀ2,2´ꢀ(2ꢀhydroxybenzylideneimino)diphenylditelluride (9b)
was synthesized by the reaction between 2,2´ꢀdiaminodipheꢀ
nylditelluride (4.4 g, 10 mmol) prepared according to a known
procedure19 and salicylic aldehyde (2.44 g, 20 mmol) in a methꢀ
anol—chloroform (1 : 1) mixture under reflux for 1 h. The preꢀ
cipitate formed upon cooling was filtered off, washed with cold
methanol, dried in air, and recrystallized from toluene to afford
yellow crystals. The yield was 67%, m.p. 179 C. 1H NMR
(DMSOꢀd6), : 7.01 (t, 2 H, CH(12), J = 15.81 Hz); 7.09 (t, 2 H,
CH(6), J = 15.89 Hz); 7.02 (d, 2 H, CH(14), J = 8.16 Hz); 7.34
(t, 2 H, CH(7), J = 15.82 Hz); 7.35 (d, 2 H, CH(8), J = 8.18 Hz);

Structure of Teꢀcontaining bisꢀazomethines
Russ.Chem.Bull., Int.Ed., Vol. 62, No. 8, August, 2013
1813
H(10)

220
230
240
250
260
Te(18)
8.8
8.6
8.4
8.2
8.0
7.8
7.6
7.4
7.2
7.0

Fig. 5. 1H—125Te HMBC NMR spectrum of the aromatic fragment of compound 9a.
7.45 (t, 2 H, CH(13), J = 15.80 Hz); 7.75 (d, 2 H, CH(5),
J = 8.16 Hz); 7.80 (d, 2 H, CH(11), J = 9.07 Hz); 8.93 (s, 2 H,
HC=N); 11.79 (s, 2 H, OH). 13C NMR (DMSOꢀd6), : 108.56
C(4), 116.67 C(14), 117.3 C(8), 117.4 C(11), 119.51 C(12),
119.89 C(16), 128.30 C(6), 129.29 C(7), 133.84 C(13), 136.67
C(5), 150.19 C(9), 159.56 C(15), 161.55 C(10). 15N NMR
(DMSOꢀd6), : 303.10. 125Te NMR (DMSOꢀd6), : 208.90. IR,
/cm–1: 1624 s (C=N), 3296 br (O—H). Found (%): C, 48.27;
H, 3.14; N, 4.32. C26H20N2O2Te2. Calculated (%): C, 48.22;
H, 3.11; N, 4.30.
Bisꢀ2,2´ꢀ(2ꢀtosylaminobenzylideneimino)diphenylditelluride
(9a) was prepared analogously to compound 9b from 2,2´ꢀdiꢀ
aminodiphenylditelluride and 2ꢀtosylaminobenzaldehyde as yelꢀ
low crystals. The yield was 73%, m.p. 194 С. 1H NMR (DMSOꢀ
d6), : 2.36 (s, 2 H, CH3); 6.93 (d, 2 H, CH(8), J = 7.20 Hz);
7.06 (t, 2 H, CH(7), J = 15.21 Hz); 7.10 (t, 2 H, CH(12),
J = 19.09 Hz); 7.22 (d, 4 H, CH(21), J = 8.10 Hz); 7.28 (t, 2 H,
CH(6), J = 16.09 Hz); 7.40 (t, 2 H, CH(13), J = 16.99 Hz); 7.44
(d, 2 H, CH(11), J = 7.62 Hz); 7.73 (d, 2 H, CH(14), J = 8.34 Hz);
7.90 (d, 4 H, CH(20), J = 8.10 Hz); 7.99 (d, 2 H, CH(11), J =
= 8.28 Hz); 8.41 (s, 2 H, HC=N); 11.67 (s, 2 H, NH). 13C NMR
(DMSOꢀd6), : 20.72 C(24), 109.01 C(4), 116.92 C(8), 122.72
C(11), 125.15 C(12), 126.01 C(16), 126.84 C(20), 128.48 C(7),
129.07 C(6), 129.79 C(21), 131.21 C(5), 132.76 C(13), 136.12
C(15), 136.28 C(14), 137.86 C(22), 143.75 C(23), 150.57 C(9),
Atomic numbering for compound 9a is given in Fig. 4. The
chemical shifts for 125Te nuclei are given relative to the referꢀ
ence compound Te2Ph2.20
Xꢀray diffraction study. The crystals of compound 9b
(C26H20N2O2Te2, M = 647.64) are rhombic, space group Pbca,
at 100 K: a = 9.6237(5), b = 18.0833(10), c = 26.2120(13) Å,
V = 4561.6(4) Å3, Z = 8 (Z´ = 1), dcalc = 1.886 g cm–3, (MoꢀK)
= 25.84 cm–1, F(000) = 2480. The intensities of 19163 reflecꢀ
tions were measured on a Bruker APEX II CCD diffractometer
((MoꢀK) = 0.71072 Å, ꢀscanning, 2 < 58); among them
6053 independent reflections (Rint = 0.045) were used in the
subsequent refinement. The structure was solved by the direct
method and refined by the fullꢀmatrix leastꢀsquares method F2
in the anisotropicꢀisotropic approximation. The positions of hyꢀ
drogen atoms H(C) were calculated geometrically, the hydrogen
atoms of OH groups were localized from the difference elecꢀ
tronꢀdensity syntheses. All hydrogen atoms were refined in the
isotropic approximation by the riding model. The final values of
unreliability factors for compound 9: wR2 = 0.0977 and GOOF =
= 1.078 for all independent reflections (R1 = 0.0348 was calcuꢀ
lated over F for 4594 observed interactions with I > 2(I)). All
calculations were performed using the SHELXTL PLUS 5.0 proꢀ
gram complex.21 The structure was deposited in the Cambridge
Crystallographic Data Center (CCDC 905330).
The spectral measurements were performed on the
equipment of the "Molecular Spectroscopy" Core Facility
Center of the Southern Federal University.
This work was financially supported by the Council
for Grants at the President of the Russian Federation
160.21 C(10). 15N NMR (DMSOꢀd6), : 120.00 N(19), JNH
=
= 90.28 Hz; 318.00 N(17). 125Te (DMSOꢀd6), : 239.51. IR,
/cm–1: 1618 s (C=N), 3317 br (N—H). Found (%): C, 50.47;
H, 3.39; N, 5.88. C40H34N4O4S2Te2. Calculated (%): C, 50.36;
H, 3.59; N, 5.87.

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Vasil´chenko et al.
11. G. Mugesh, B. Singh, R. J. Butcher, J. Organomet. Chem.,
1999, 577, 243.
12. S. C. Menon, A. Panda, H. B. Singh, R. J. Butcher, Chem.
Commun., 2000, 143.
13. S. C. Menon, A. Panda, H. B. Singh, R. P. Patel, S. K.
Kulshreshtha, W. L. Darby, R. J. Butcher, J. Organomet.
Chem., 2004, 689, 1452.
(Program for Support of Young Scientists (Grants
MKꢀ170.2011.3 and MDꢀ1020.2012.3) and Leading Sciꢀ
entific Schools of the Russian Federation NSchꢀ
927.2012.3) and the Russian Foundation for Basic Reꢀ
search (Projects No. 12ꢀ03ꢀ00462 and No. 12ꢀ03ꢀ33107).
14. D. G. Golovanov, A. O. Tokareva, A. I. Uraev, Yu. I. Ryaꢀ
bukhin, A. I. Pyshchev, T. V. Kovaleva, M. Yu. Antipin,
K. A. Lysenko, Russ. Chem. Bull. (Int. Ed.), 2006, 55, 408
[Izv. Akad. Nauk, Ser. Khim., 2006, 396].
15. V. K. Voronov, R. Z. Sagdeev, Principles of Magnetic Resoꢀ
nance [Osnovy magnitnogo resonansa], Vost.ꢀSib. knizhnoe
izdꢀvo, Irkutsk, 1995, 347 pp. (in Russian).
16. P. S. Pregosin, H. R. Egger, in Comprehensive Coordination
Chemistry, Eds J. A. McCleverty, T. J. Meyer, Pergamon
Press, Amsterdam—New York—Oxford, 2003, V. 2, 1.
17. G. S. Borodkin, I. G. Borodkina, A. I. Uraev, I. S. Vasil´ꢀ
chenko, I. D. Sadekov, A. D. Garnovskii, Mendeleev Chem.
J. (Engl. Transl.), 2004, 48, 117 [Zh. Vsesoyuz. Khim. Obshch.
im. D. I. Mendeleeva, 2004, 48, 117].
18. R. R. Ernst, G. Bodenhausen, A. Wokaun, Principles of Nuꢀ
clear Magnetic Resonance in One and Two Dimensions, Clarꢀ
endon Press, Oxford, 1987, 711 pp.
19. G. M. Abakarov, A. A. Shabson, I. D. Sadekov, A. D. Garꢀ
noskii, V. I. Minkin, Chem. Heterocycl. Compd. (Engl. Transl.),
1988, 278 [Khim. Geterotsikl. Soedin., 1988, 276].
20. J. Mason, Multinuclear NMR, Plenum Press, New York,
1987, 639 p.
21. G. M. Sheldrick, SHELXTL PLUS, PC Version, System of
Computer Programs for the Determination of Crystal Structure
from Xꢀray Diffraction Data, Rev. 502, Siemens Analytical
XꢀRay Instruments Inc., Germany, 1994.
References
1. A. K. Singh, S. Sharma, Coord. Chem. Rev., 2000, 209, 49.
2. N. AlꢀSalim, T. A. Hamor, W. R. McWhinnie, J. Chem.
Soc., Chem. Commun., 1986, 453.
3. A. D. Garnovskii, A. S. Antsyshkina, I. S. Vasil´chenko,
O. Yu. Korshunov, G. G. Sadikov, A. A. Maksimenko, I. D.
Sadekov, J. Inorg. Chem. (Engl. Transl.), 1996, 41 [Zh. Neorg.
Khim., 1996, 41, 1297].
4. R. P. Kumar, A. K. Singh, J. E. Drake, M. B. Hursthouse,
M. E. Light, Inorg. Chem. Commun., 2004, 7, 502.
5. K. Badyal, W. R. McWhinnie, T. A. Hamor, H. Chen, Orgaꢀ
nometallics, 1997, 16, 3194.
6. A. D. Garnovskii, I. D. Sadekov, A. S. Antsyshkina, I. S.
Vasil´chenko, A. I. Uraev, G. G. Sadikov, A. A. Maksimenꢀ
ko, G. S. Borodkin, V. I. Minkin, Russ. J. Coord. Chem.
(Engl. Transl.), 1996, 22 [Koord. Khim., 1996, 22, 376].
7. A. D. Garnovskii, D. A. Garnovskii, I. S. Vasil´chenko, A. S.
Burlov, A. P. Sadimenko, I. D. Sadekov, Russ. Chem. Rev.
(Engl. Transl.), 1997, 66 [Usp. Khim., 1997, 66, 434].
8. A. D. Garnovskii, A. P. Sadimenko, Adv. Heterocycl. Chem.,
1998, 72, 1.
9. A. D. Garnovskii, I. D. Sadekov, A. S. Antsyshkina, G. G.
Sadikov, G. S. Borodkin, A. I. Uraev, A. A. Maksimenko,
I. S. Vasil´chenko, I. G. Borodkina, V. S. Sergienko, V. I.
Minkin, Russ. J. Coord. Chem. (Engl. Transl.), 1999, 25
[Koord. Khim., 1999, 25, 821].
10. I. D. Sadekov, V. I. Minkin, Adv. Heterocycl. Chem., 2001,
79, 1.
Received October 10, 2012;
in revised form June 24, 2013