Synthesis, structure, and properties of a new phosphorus-containing Schiff's base, a derivative of pyrazole-5-one

Article abstract of DOI:10.1134/S107036321307013X

A new Schiff's base and its salt have been prepared from 2-aminophenyl(triphenyl)phosphonium chloride and 5-hydroxy-3-methyl-1-phenyl-4- formylpyrazole. The products structures have been proved by IR, ¹H NMR, and UV spectroscopy, mass spectrometry, X-ray diffraction analysis, and quantum-chemical modeling. Possible tautomerism and some properties of the products have been studied.

Full text of DOI:10.1134/S107036321307013X

ISSN 1070-3632, Russian Journal of General Chemistry, 2013, Vol. 83, No. 7, pp. 1376–1382. © Pleiades Publishing, Ltd., 2013.
Original Russian Text © L.D. Popov, S.A. Borodkin, I.N. Scherbakov, Yu.N. Tkachenko, G.G. Aleksandrov, S.S. Beloborodov, A.A. Zubenko, V.A. Kogan,
O.V. Maevskii, 2013, published in Zhurnal Obshchei Khimii, 2013, Vol. 83, No. 7, pp. 1125–1131.
Synthesis, Structure, and Properties
of a New Phosphorus-Containing Schiff’s Base,
a Derivative of Pyrazole-5-one
L. D. Popova, S. A. Borodkina, I. N. Scherbakova, Yu. N. Tkachenkoa, G. G. Aleksandrovb,
S. S. Beloborodova, A. A. Zubenkoc, V. A. Kogana, and O. V. Maevskiia
a Southern Federal University, ul. Zorge 7, Rostov-on-Don, 344090 Russia
e-mail: saborod@list.ru
b Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
c North-Caucasian Regional Research Veterinary Institute, Novocherkassk, Russia
Received June 7, 2012
Abstract—A new Schiff’s base and its salt have been prepared from 2-aminophenyl(triphenyl)phosphonium
chloride and 5-hydroxy-3-methyl-1-phenyl-4-formylpyrazole. The products structures have been proved by IR,
1H NMR, and UV spectroscopy, mass spectrometry, X-ray diffraction analysis, and quantum-chemical
modeling. Possible tautomerism and some properties of the products have been studied.
DOI: 10.1134/S107036321307013X
Schiff’s bases (also known as azomethines) have
been subjects of intensive studies due to diverse bio-
logical activity [1] and high complex formation ability
[2–7]. Numerous phosphorus-containing azomethines
were described, for example, aminophosphines deri-
vatives [8–17]. Azomethines based on pyrazole-5-one
are also of interest [18–23], since pyrazolone fragment
is a part of many drugs structures [24].
The Schiff’s base was prepared according to
Scheme 1.
It is known that azomethines based on pyrazole-5-
one may exist in different tautomeric forms [18, 19].
Scheme 2 illustrates the most probable tautomeric
forms of III.
A-G Forms are in dynamic equilibrium, and its
state is likely to be appreciably dependent on the
nature of the R group containing positively charged
phosphonium fragment.
To estimate the relative stability of the tautomers,
we performed the quantum-chemical computation of
the III isomers in the isolated ion approximation. The
density functional approximation (DFT) was used,
with the B3LYP functional in the 6-311G(d,p) basic
This work is aimed at the synthesis and the study of
a new azomethine, product of 2-aminophenyl(tri-
phenyl)phosphonium chloride and 5-hydroxy-3-me-
thyl-1-phenyl-4-formylpyrazole condensation. Recently
we have reported on preparation and study of
azomethines based on the same amine and substituted
salicylic aldehydes [25].
Scheme 1.
3'
4'
6'
2'
1'
+ Ph3P
5'
N
H3C
CHO
OH
H3C
CH
3
4
Δ
5
+
H2N
N
2N
1
OH
n-BuOH
Cl_
N
N
Cl_
+ Ph3P
Ph
I
Ph
III
II
1376

SYNTHESIS, STRUCTURE, AND PROPERTIES OF A NEW PHOSPHORUS-CONTAINING
1377
Scheme 2.
CH3
O
R
CH3
O
H
CH3
O
N
N
N
N
N
N
N
N
N
Ph
Ph
H
H
Ph
R
R
A
B
C
R
CH3
R
H
CH3
OH
CH3
O
N
N
H
N
N
N
N
N
N
N
Ph
O
Ph
Ph
R
D
E
F
CH3
R
N
N
N
Ph
O
G
R = P+Ph3Cl–.
set. Table 1 lists the model forms and the calculated
total energies of their most stable conformations, as
well as the relative stability (ΔE) in the gaseous phase
and for the most stable isomers A, C, E, and F in
dimethylsulfoxide DMSO medium.
of the other aromatic protons signals was complicated
due to mutual overlapping and broadening. Methyl
group signal was observed at 1.96 ppm, azomethine
group proton signal appeared at 8.31 ppm, and the
acidic proton signal has a shape of very broad singlet
at 10.75 ppm, disappearing upon deuteration. The
significant broadening of the NH proton signal was
likely due to its participation in the strong intramole-
cular hydrogen bonding, or because of the tautomerism
А↔C, the latter also causing the absence of the spin-
According to the quantum-chemical simulation
results, the most probable form of the prepared
Schiff’s base in the gaseous phase was its pyrazolone
form (A), with the intramolecular hydrogen bond
between the NH group proton and pyrazolone oxygen
atom. In addition, the 5-hydroxypyrazole form C, also
containing the intramolecular bond of the OH···N type,
was relatively stable. When accounting for the medium
influence, significant stabilization of F isomer and
destabilization of B isomer were observed, the most
stable isomer being still A.
Table 1. Total energy (E, a. u.) and relative stability (ΔE,
kcal mol–1) of the isomers of III in the gaseous phase and in
DMSO solution, according to B3LYP/6-311G(d,p) computation
Gas phase
DMSO
1
Isomer
In the H NMR (DMSO-d6) spectrum of III the
E
∆E
E
∆E
aromatic protons signals were observed at 7.1–
8.1 ppm, they were somehow broadened, possibly due
to dynamic effects. The 4'-PhN proton signal was
observed at 7.10 ppm as a triplet. The 3'-PhN and 5'-
PhN protons were also observed as triplets at 7.34 ppm
(JHH 7.85 Hz). The signal of benzene ring H5' con-
nected with the P+Ph3 group appeared as a doublet at
7.22 ppm (JHP 15.20 Hz, JHH 7.74 Hz). The assignment
–1932.224049
–1932.205659
–1932.221377
–1932.202832
–1932.212802
–1932.211091
–1932.199938
0.0
11.6
1.7
13.4
7.1
–1932.296705
0.0
–
4.3
–
3.1
4.0
–
IIIА
IIIB
IIIC
IIID
IIIE
IIIF
IIIG
–
–1932.289896
–
–1932.291988
–1932.290277
–
8.2
15.2
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 83 No. 7 2013

1378
POPOV et al.
Table 2. Main crystallographic parameters and details of
structure refinement for substance IV
Table 3. Principal interatomic distances, bond, and dihedral
angles in the IV structure
Parameter
Value
Bond
d, Å
Angle
ω, deg
O1–C10
1.257(3)
1.393(3)
1.400(3)
1.312(2)
1.421(3)
1.410(3)
1.310(3)
N1C7C8
124.0(2)
119.08(18)
–177.4(2)
178.61(19)
–23.2(3)
Empirical composition
C36H33N3O2.50
Triclinic
P-1
P
N3–C10
C6N1C7
Crystal system
Space group
Unit cell parameters:
N2–N3
N1C7C8C10
C6N1C7C8
C5C6N1C7
C10N3C12C13
N2–C9
C8–C9
C7–C8
N1–C7
a, Å
b, Å
c, Å
10.2505(7)
12.9253(9)
13.5489(9)
171.1(2)
α, deg
β, deg
γ, deg
Volume, Å 3
Z
116.2160(10)
106.8270(10)
96.6690(10)
1477.95(17)
2
According to the X-ray diffraction data, compound
IV was of zwitter-ionic nature, being a product of
azomethine III dehydrohalogenation. In addition to IV
molecules, ethanol and water molecules were present
in the crystal, in the ratio of 1:0.5:1, respectively.
Ethanol molecule position was disordered between the
two crystallographic positions of equal population.
Spatial structure and atom numbering of IV are
presented in Fig. 1.
М
578.62
1.300
0.133
610
d
calc, g cm–3
Extinction coefficient, mm–1
F(000)
θ range, deg
Indices range
2.16 < θ < 30.21
–14 ≤ h ≤ 14,
–18 ≤ k ≤ 18,
–19 ≤ l ≤ 19
17513 / 8653 [R(int) 0.0312]
98.4%
All bond lengths and bond angles in the molecule
were of ordinary values for the corresponding atoms
[18, 26]. The most polar form of the zwitter-ion was
observed in the crystal, likely stabilized by polar
molecules of water and alcohol.
Reflections total/unique
Complement to θ = 27.00
Refinement method
Full-matrix PLS by F2
R1 0.0560,
Pairs of IV molecules were bound in the dimers due
R-indices values [I>2σ(I)]
to the formation of the four hydrogen bonds O1···H1WA
wR2 0.1553
R1 0.0779,
wR2 0.1729
0.999
и
H1WB···O1. The centrally symmetrical eight-
R-indices (all data)
Precision by F2
membered cycle was thus formed (Fig. 2). The
parameters of the hydrogen bonds are given below,
with the symmetry code (i): –x,–y – 1, –z.
d(D–H), d(H···A), <DHA, d(D···),
D–H
A
spin splitting of the azomethine proton signal. This fact
also gave a reason for the choice of the keto-imine A
structure as the most stable, supporting the quantum-
chemical computation results on the relative stability.
Å
Å
deg
Å
O1W−H1WA
O1W−H1WB
0.842
0.840
1.892
2.123
175.72
156.79
2.731
2.913
O1
O1
i
In order to study the complex formation ability of
III, we attempted to prepare its chelates with Hg(II),
Zn(II), Cd(II), Be(II), and Pb(II) acetates. However, in
all the reactions the only product was the same
substance containing no metal.
The formation of such strong hydrogen bonds
indirectly proved the high electron density at the O1
oxygen atom of IV.
Thus, upon addition of the phosphonium salt III to
metal acetates, deprotonation by the acetate anion
occurred instead of the complex formation. This was
The structure of the prepared substance was
determined by X-ray diffraction analysis. Crystal-
lographic data of IV and details of the X-ray
diffraction experiment are collected in Table 2, and
selected geometry parameters (bond lengths and bond
angles) are given in Table 3.
1
confirmed by the identity of the H NMR and IR
spectra of the compounds produced upon boiling
methanol solutions of III with lead, zinc, cadmium, or
beryllium acetates. In the 1H NMR (DMSO-d6) spectra
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 83 No. 7 2013

SYNTHESIS, STRUCTURE, AND PROPERTIES OF A NEW PHOSPHORUS-CONTAINING
1379
Fig. 1. Spatial structure of the IV molecules (ellipsoids of thermal vibrations are shown for the 50% probability).
of the compounds thus prepared, the acidic proton
signal was absent, as compared with the spectrum of
the compound III. The shift to the strong field was
characteristic of many of the aromatic protons signals.
For instance, the signal of benzene ring Н5' proton
(bound to the PPh3+ group) was observed at 6.79 ppm
(δ = 7.21 ppm in III), that of the PhN fragment proton
Н4' was shifted to 6.90 ppm (δ = 7.10 ppm in III), and
the H3',5' signals were observed at 7.21 ppm (δ =
7.34 ppm in III). This could result from the increased
electron density of aromatic rings due to the ap-
pearance of the negative charge. The most significant
shift to the strong field was observed in the case of the
methyl group signal; it was registered at δ = 1.02 ppm
(δ = 1.96 ppm in III). This was likely due to the fact
that the pyrazole ring CH3 protons were located in the
anisotropy focus of the two phenyl rings of the PPh3+
group that were oriented perpendicular to the molecule
plane. This was the evidence of the rigid spatial
location of the groups, and thus confirmed that the
structure similar to that established from the X-ray
diffraction analysis existed in the solution as well.
According to the quantum-chemical simulation of
IV isomers, in the gaseous phase the A form was
relatively less stable than B, by 2.4 kcal mol–1.
Gas phase
E, au
DMSO
E, au
Structure
∆E
∆E
–1931.787708
–1931.791454
2.4
0.0
–1931.830937
–1931.822667
0.0
5.2
IVА
IVB
However, the collected spectral and X-ray
diffraction data evidenced that the more polar A form
was more favorable. Indeed, when the solvent effect
Thus, basing on the experimental data it could be
stated that in the reaction of the above mentioned
metal acetates with III, a compound IV was formed,
with the azanide structure. The azanide thus produced
could exist in the form of a pair of Z,E isomers with
respect to the C=C bond (A and B, Scheme 3).
Fig. 2. Hydrogen-bonded dimers in the crystal of IV.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 83 No. 7 2013

1380
POPOV et al.
Scheme 3.
CH3
O
Ph3P+
N_
N
N
CH3
O
N_
CH3COO _
N
N
Ph
III
Ph3P+
Ph
A
B
_1931.787708 au
16.83 D
_1931.791454 au
11.10 D
IV
was taken into account in computations (in the frame
of polarized continuum model PCM), in the DMSO
medium the relative stability of the isomers was
inverted, and the B isomer was more stable than A (by
5.2 kcal mol–1), which was consistent with the
experimental data.
photometer, in methanol solution, in the 200–800 nm
range, with the optical path length of 1 cm. Mass
spectra were registered using the chromato-mass
spectrometer Agilent 6410 equipped with triplex
quadrupole tandem detector and electrospray ioniza-
tion source; acetonitrile with 0.1% of acetic acid was
used as eluent.
In the IR spectra of the products of interaction of
III with metal acetates, the absorption band at
3378 cm–1 disappeared, as compared with the initial
reagent spectrum; this band corresponded to either OH
or NH group. In addition, the C=N group band shifted
to lower wavenumber (from 1650 to 1591 cm–1) thus
also indicating significant structural changes. In
keeping with those data, acetates of the above-
mentioned metals acted as bases, eliminating the HCl
molecule from III.
Quantum-chemical computations. Electronic and
spatial structures of the studied compounds were
obtained in the frame of non-empirical approximation
of the density functional theory. The B3LYP hybrid
exchange-correlation potential [27] with the exchange
part introduced by Becke [28] and the Lee-Yang-Parr
correlation part [29] was used. The standard valence-
splitted extended Gaussian basic set 6-311G(d,p) was
used for computations. Molecules geometry was pre-
liminary optimized along all natural variables without
symmetry restrictions. For each of the studied
structures, the minimum at the potential energy surface
was identified by calculation of the force coefficients
matrix and the normal vibrations frequencies. All
computations were performed by using GAUSSIAN’03
software [30].
Significant changes in the structure of III upon
interaction with bases were also clearly revealed in the
electronic spectra. The long-wave absorption band
observed at λmax = 339 nm (log εmax = 4.82) in the
spectrum of III, was subjected to strong red shift upon
addition of triethylamine (λmax = 388 nm, log εmax
=
4.97), whereas addition of HCl excess did not
influence much the spectrum shape (λmax = 326 nm,
log εmax = 4.80). It should be noted that the spectrum of
IV in methanol solution was identical to that of III
with addition of triethylamine, which confirmed easy
elimination of HCl from the phosphonium salt
molecule.
(E)-{2-([(5-hydroxy-3-methyl-1-phenyl-1H-pyrazol-
4-yl)methylene]amino)phenyl}triphenylphosphonium
chloride (III). The solution of 0.4 g (0.002 mol) of 5-
hydroxy-3-methyl-1-phenyl-4-formylpyrazole (I) [31]
in 5 ml of butanol-1 was added to the solution of
0.76 g (0.002 mol) of 2-aminophenyl(triphenyl)phos-
phonium chloride (II) [32] in 5 ml of butanol-1. The
resulting solution was boiled for 4 hours and then left
overnight. The separated precipitate was filtered off
and twice washed with cold butanol-1. The product
was then recrystallized from the chloroform–ethyl
acetate (1:3) mixture. Yield 58%, yellow needle-
shaped crystals, mp > 260°С. IR spectrum, ν, cm–1:
EXPERIMENTAL
IR spectra were registered in the mineral oil
suspension using the Varian Scimitar 1000 FT-IR
1
spectrophotometer (400–4000 cm–1). H NMR spectra
were registered using Bruker AM-300 instrument with
TMS as the internal reference. Electron absorption
spectra were registered using Cary 5000 spectro-
1
3378 (ОН), 1650 (C=N), 1438 (+PPh4). H NMR
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SYNTHESIS, STRUCTURE, AND PROPERTIES OF A NEW PHOSPHORUS-CONTAINING
1381
vol. 21, no. 15, pp. 3203–3207.
spectrum (DMSO-d6), δ, ppm (J, Hz): 10.75 br.s (1Н,
ОН), 8.31 s (1Н, СН=N), 7.57–8.13 m (5Н, ArH and
10. Korupoju, S.R., Lai, R.-Y., Liu, Y.-H., Peng, S.-M., and
Liu, S.-T., Inorg. Chim. Acta., 2005, vol. 358, no. 11,
pp. 3003–3008.
11. Doherty, S., Knight, J.G., Scanlan, T.H., Elsegood, R.Y.,
and Clegg, W., J. Organometal. Chem., 2002, vol. 650,
nos. 1–2, pp. 231–248.
15H, РPh3), 7.34 t [2H, NPhH3',H5', J3'(5'),2'(6') = J3'(5'),4'
5'
7.85], 7.21 d.d (1Н, H , J5',4' = J5',6' 7.74, JН5'P 15.20),
Ar
7.10 t (1Н, NPhH4', J4',3' = J4',5' 7.32), 1.96 s (3H, Me).
Mass spectrum, m/z: 538.2 [M – Cl]+, 1075.4 [M – Cl +
M –– Cl – H]+. Found, %: С 73.48; Н 5.02; N 6.84; Р
5.29. С35Н29ClN3OP. Calculated, %: С 73.23; Н 5.06;
N 7.32; Р 5.41.
12. Dalili, S., Caiazzo, A., and Yudin A.K., J. Organo-
metal. Chem., 2004, vol. 689, no. 22, pp. 3604–3611.
13. Faller, J.W., Mason, G., and Parr, J., J. Organometal.
Chem., 2002, vol. 650, nos. 1–2, pp. 181–187.
14. Cameron, P.A., Gibson, V.C., Redshaw, C., Segal, J.A.,
White, J.P., and Williams, D.J., J. Chem. Soc., Dalton
Trans., 2002, vol. 2, no. 3, pp. 415–422.
15. Bhattacharyya, P., Loza, M.L., Parr, J., and Slawin, A.M.Z.,
J. Chem. Soc., Dalton Trans., 1999, no. 17, pp. 2917–
2922.
16. Dilworth, J.R., Howe, S.D., Hutson, A.J., Miller, J.R.,
Silver, J., Thompson, R.M., Harman, M., and
Hursthouse, M.B., J. Chem. Soc., Dalton Trans., 1994,
no. 24, pp. 3553–3562.
(E)-[(3-methyl-5-oxo-1-phenyl-1,5-dihydro-4H-
pyrazol-4-ylidene)methyl)(2-(triphenylphosphonio)-
phenyl]amide (IV). The solution of 0.027 g (0.0018 mol)
of Hg(CH3COO)2 in methanol was added to the boiling
solution of 0.10 g (0.0009 mol) of III in 5 ml of
methanol, and the resulting solution was boiled for
5 h. After cooling the mixture, the yellow precipitate
was formed. It was filtered off, washed with methanol,
and recrystallized from ethanol. Yield 82%, mp > 260°С.
1
IR spectrum, ν, cm–1: 1591 (C=N), 1434 (+PPh4). H
NMR spectrum (DMSO-d6), δ, ppm (J, Hz): 8.05 s
17. Bhattacharyya, P., Parr, J., and Slawin, A.M.Z., J. Chem.
(1Н, СН=N), 7.91 d [2H, NPhH2',H6', J2'(6'),3'(5') 8.00],
4'
Soc., Dalton Trans., 1998, no. 21, pp. 3609–3614.
7.60–7.87 m (1Н, HAr, 15H, РPh3), 7.51 t (1Н, Н ,
Ar
18. Amarasekara, A.S., Owereh, O.S., Lysenko, K.A., and
Timofeeva, T.V., J. Struct. Chem., 2009, vol. 50, no. 6,
pp. 1159–1165.
J4',3' = J4',5' 7.00), 7.21 t [2H, NPhH3',H5', J3'(5'),2'(6')
=
6'
J3'(5'),4' 7.90], 7.10–7.20 m (1Н, Ar , partially over-
Ar
lapping with NPhH3',H5'), 6.90 t (1Н, NPhH4', J4',3' = J4',5'
5'
19. Kvitko A.Ya. and Porai-Koshits, B.A., Russ. J. Org.
7.16), 6.79 d.d (1Н, H , J5',4' = J5',6' 7.78, JН5',P 14.45),
Ar
Chem., 1966, vol. 11, no. 1, p. 3005.
1.02 s (3H, Me). Mass spectrum, m/z: 538.2 [M + H]+,
1075.4 [M + H + M – H]+. Found, %: С 78.63; Н 5.17;
N 7.64; Р 5.49. С35Н28N3OP. Calculated, %: С 78.21;
Н 5.21; N 7.82; Р 5.77.
20. Surati, K.R., Thaker, B.T., and Shan, G.R., Synth.
React. Inorg. Metal-Org. and Nano-Metal Chem., 2008,
vol. 38, no. 3, pp. 272–279.
21. Raj, D.S., Parmar, N.J., and Shah, J.R., Synth. React.
Inorg. Metal-Org. and Nano-Metal Chem., 2004, vol. 34,
no. 4, pp. 697–711.
REFERENCES
1. Minbaev, B.U., Shiffovy osnovaniya (Schiff’s Bases),
22. Jadeja, R.N., Shah, J.R., Suresh, E., and Paul, P.,
Alma-Ata: Nauka, 1989.
Polyhedron, 2004, vol. 23, no. 18, pp. 2465–2474.
2. Garnovskii, A.D., Nivorozhkin, A.L., and Minkin, V.I.,
23. Thaker, B.T., Surati, K.R., and Modi, C.K., Russ. J.
Coord. Chem., 2008, vol. 34, no. 1, pp. 25–33.
Coord. Chem. Rev., 1993, vol. 126, nos. 1–2, pp. 1–69.
3. Garnovskii, A.D., Burlov, A.S., Vasilchenko I.G.,
Garnovskii, D.A., Uraev, A.I., and Sennikova, E.V.,
Russ. J. Coord. Chem., 2010, vol. 36, no. 2, pp. 81–96.
4. Garnovskii, A.D., Sadimenko, A.P., Vasilchenko, I.S.,
Sennikova, E.V., and Minkin, V.I., Adv. Heterocycl.
Chem., 2009, vol. 97, pp. 291–392.
24. Mashkovskii, M.D., Lekarstvennye sredstva (Pharma-
ceuticals), Мoscow: Meditsina, 1998, p. 1.
25. Popov, L.D., Borodkin, S.A., Shcherbakov, I.N., Tka-
chenko, Yu.N., and Kogan, V.A., Russ. J. Gen. Chem.,
2008, vol. 78, no. 4, pp. 567–574
26. Casas, J.S., Garcia-Tasende, M.S., Sanchez, A., Sordo, J.,
and Touceda, A., Coord. Chem. Rev., 2007, vol. 251,
nos. 11–12, pp. 1561–1589.
27. Stephens, P.J., Devlin, F.J., Chabalowski, C.F., and
Frisch, M.J., J. Phys. Chem., 1994, vol. 98, no. 45,
pp. 11623–11627.
28. Becke, A.D., J. Chem. Phys., 1993, vol. 98, no. 7,
pp. 5648–5652.
5. Garnovskii, A.D., and Vasilchenko, I.S., Russ. Chem.
Rev., 2005, vol. 74, no. 3, pp. 193–215.
6. Garnovskii, A.D., Russ. J. Coord. Chem., 1993, vol. 19,
no. 5, pp. 368–382.
7. Vigato, P.A. and Tamburini, S., Coord. Chem. Rev.,
2004, vol. 248, nos. 17–20, pp. 1717–2128.
8. Parr, J. and Slawin, A.M.Z., Inorg. Chim. Acta., 2000,
vol. 303, no. 1, pp. 116–120.
29. Lee, C., Yang, W.,and Parr, R.G., Phys. Rev. (B).,
1988, vol. 37, no. 2, pp. 785–789.
9. Shi, P.-Y. and Liu, Y.-H., Organometallics, 2002,
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 83 No. 7 2013

1382
POPOV et al.
30. Frisch, M.J., Trucks, G.W., Schlegel, H.B., Scuseria, G.E.,
Robb, M.A., Cheeseman, J.R., Montgomery, 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.,
Hasegawa, J., Ishida, M., Nakajima, T., Honda, Y.,
Kitao, O., Nakai, H., Klene, M., Li, X., Knox, J.E.,
Hratchian, H.P., Cross, J.B., Bakken, V., Adamo, C.,
Jaramillo, J., Gomperts, R., Stratmann, R.E., Yazyev, O.,
Austin, A.J., Cammi, R., Pomelli, C., Ochterski, J.W.,
Ayala, P.Y., Morokuma, 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, Q., Baboul, A.G., Clifford, S.,
Cioslowski, J., Stefanov, 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.,
Challacombe, M., Gill, P.M.W., Johnson, B., Chen, W.,
Wong, M.W., Gonzalez, C., and Pople, J.A.,
GAUSSIAN 03, Revision D.01, Gaussian, Inc.,
Wallingford CT, 2004.
31. Porai-Koshits, B.A. and Kvitko, I.Ya., Russ. J. Org.
Chem., 1962, vol. 32, no. 12, p. 4050.
32. Cooper, M.K., Downes, J.M., Duckworth, P.A., and
Tiekins, E.R.T., Austral. J. Chem., 1992, vol. 45, no. 3,
pp. 595–609.
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