New magnetoactive copper complexes with Schiff's bases

Article abstract of DOI:10.1134/S0036023606070096

Tridentate azomethine ligands with N₂O and N₃ donor atoms and their copper complexes have been synthesized and characterized. Magnetochemical measurements in the temperature range of 5-300 K show that the change in the coordination e

Full text of DOI:10.1134/S0036023606070096

ISSN 0036-0236, Russian Journal of Inorganic Chemistry, 2006, Vol. 51, No. 7, pp. 1065–1070. © Pleiades Publishing, Inc., 2006.
Original Russian Text © A.S. Burlov, Yu.V. Koshchienko, V.N. Ikorskii, V.G. Vlasenko, I.A. Zarubin, A.I. Uraev, I.S. Vasil’chenko, D.A. Garnovskii, G.S. Borodkin, S.A. Nikola-
evskii, A.D. Garnovskii, 2006, published in Zhurnal Neorganicheskoi Khimii, 2006, Vol. 51, No. 7, pp. 1143–1148.
COORDINATION
COMPOUNDS
New Magnetoactive Copper Complexes
with Schiff’s Bases
a
a
b
c
A. S. Burlov , Yu. V. Koshchienko , V. N. Ikorskii , V. G. Vlasenko ,
c
a
a
a
I. A. Zarubin , A. I. Uraev , I. S. Vasil’chenko , D. A. Garnovskii ,
a
a
a
G. S. Borodkin , S. A. Nikolaevskii , and A. D. Garnovskii
a
Research Institute of Physical and Organic Chemistry, Rostov State University, South Scientific Center,
Russian Academy of Sciences, pr. Stachki 194/3, Rostov-on-Don, 344104 Russia
b
International Tomography Center, Siberian Division, Russian Academy of Sciences,
Institutskaya ul. 3a, Novosibirsk, 630090 Russia
Research Institute of Physics, Rostov State University, pr. Stachki 194, Rostov-on-Don, 344104 Russia
Received June 20, 2005
c
Abstract—Tridentate azomethine ligands with N2O and N3 donor atoms and their copper complexes have been
synthesized and characterized. Magnetochemical measurements in the temperature range of 5–300 K show that
the change in the coordination environment induces the change in the sign of exchange coupling in the mole-
cules of complexes.
DOI: 10.1134/S0036023606070096
Among molecular ferromagnets, an important place thine ligand of type I, which served as the base for prep-
is occupied by ferromagnetic complexes of Schiff’s aration of various homo- and heteronuclear complexes II
bases. In the late 1970s, O. Kahn designed the azome- with ferro- and antiferromagnetic exchange [1].
O
O
O
O
L L
M
O
O
N
O
O
N
OH HO
OH HO
Cu
N
N
I
II:
M = Cr, Fe, VO; L = H2O, MeOH
Cu–VO J = +118 cm–1
Cu–Cr J = +115 cm–1
Cu–Fe J = –105 cm–1
It was shown that the magnetic characteristics of nide complexes [13–15], by using free-radical azome-
binuclear chelates II obtained from I depend on the elec-
tronic configuration and different combinations of com-
plexing metals [1–3]. The Kahn model is still success-
fully used to prepare ferromagnetic complexes [3–8].
thine ligand systems [15–17], and by using chelates of
Schiff’s bases as metal ligands [18–21].
Recently, we proposed a new approach to the search
for and design of ferromagnetic complexes of azome-
thine ligands. According to this approach, binuclear
complexes with different magnetic properties can be
obtained by varying the fine structure of the considered
ligand system (rational design of azomethines and their
analogues [29, 30]). Both ferro- and antiferromagnetic
Another approach to the design of molecular mag-
nets based on chelates of azomethine ligands involves
incorporation of diverse bridging fragments between
the metal ions in binuclear complexes, for example,
azides [9, 10], chlorides [11], or carboxylates [12]. Fer-
romagnetic complexes have also been prepared by
introducing salicylaliminate fragments into hexacya- structures were prepared in this way.
1065

1066
BURLOV et al.
As a development of this approach, this publication X, and their copper complexes IV and on the magnetic
presents data on the synthesis and properties of new
ligand systems III (LH2), differing by the donor atom
properties of these complexes in the temperature range
of 5–300 K.
NO2
XH
H
C2H5
N
X
N
N
X
N
N C2H5
Cu
Cu
N
C2H5
O2N
O2N
III
(a) X = O, (b) NTs
IV
(a) X = O, (b) NTs
EXPERIMENTAL
nonlinear fitting of the calculated values χcalcd to exper-
imental ones χexp carried out using the IFFEFIT-1.2.5
software [32]. The phases and amplitudes of photoelec-
tronic wave scattering needed to simulate the spectrum
were calculated with the FEFF7 software [33]. Copper
complexes with related structures that had been deter-
mined by X-ray diffraction were taken as model com-
pounds.
1H NMR spectra were recorded on a Varian Unity
300 (300 MHz) spectrometer using an internal deute-
rium lock (CDCl3). IR spectra were recorded on a Nico-
let Impact 400 spectrophotometer in KBr pellets.
The magnetic measurements of complexes IVa and
IVb were carried out on a Quantum Design SQUID
magnetometer in the temperature range of 5–300 K in a
magnetic field of 5 kOe. In calculations of the paramag-
netic component of the magnetic susceptibility χ, the
additive diamagnetic contributions of ions were taken
according to the Pascal constants to be 340 × 10–6 and
509 × 10–6 cm3/mol for IVa and IVb, respectively. The
effective magnetic moment as a function of temperature
was calculated by the formula
The quality function of fitting Q, which was mini-
mized when determining the structure parameters of
the local environment, was calculated by the formula
[kχexp(k) – kχcalcd(k)]2
2
∑
--------------------------------------------------------------
Q(%) =
× 10 .
[kχexp(k)]2
∑
2χT 1/2 ≈ (8χT)1/2,
3k
⎛
⎝
⎞
---------
Synthesis of Ligands
µeff(T) =
⎠
Nβ
2,4-Dinitro-N-ethylaniline. Ethylamine hydro-
where N, k, and β are the Avogadro number, the Boltz- chloride (8.97 g, 0.11 mol) was added to a suspension
mann constant, and the Bohr magneton, respectively.
of 2,4-dinitrochlorobenzene (20.26 g, 0.1 mol) and
sodium acetate trihydrate CH3COONa · 3H2O (29.94 g,
0.22 mol) in ethanol (50 ml). The mixture was refluxed
for 2 h and cooled, and the precipitate was filtered off
and washed with water and ethanol. Yield, 15.2 g
(72%); mp 113–114°C (from ethanol), which is consis-
tent with the published data [34].
2-Ethylamino-5-nitroaniline. A suspension of
N-ethyl-2,4-dinitroaniline (21.1 g, 0.1 mol) in ethanol
(40 ml) was added to a warm solution of sodium sulfide
nonahydrate (Na2S · 9H2O) (48.01 g, 0.2 mol) and crys-
talline sulfur (6.41, 0.2 mol) in water (63 ml). The mix-
ture was refluxed for 2 h, diluted with water (30 ml),
and cooled. The precipitate was filtered off and washed
The Cuä-edge X-ray EXAFS spectra of the com-
pounds under study were recorded on a laboratory
EXAFS spectrometer based on a DRON-3 diffractome-
ter. A BSV-21-Mo tube at U = 17 kV and I = 30 mA was
used as the X-radiation source. X-radiation was
expanded in the spectrum by means of a quartz mono-
chromator crystal (1340). After standard background
isolation, normalization to the K-edge step, and isola-
tion of the atomic absorption µ0 [31], the recorded
EXAFS (χ) spectra were subjected to Fourier transform
in the range of photoelectron wave vectors k from 3.0 to
13 Å–1 with the weight function n = 2. The threshold
ionization energy E0 was chosen from the maximum of
the first derivative of the K-edge and was subsequently with warm water. The yield of dark red crystals was
varied during a fitting procedure. The parameters of the 12.5 g (69%), mp = 138–139°C (from ethanol), which
local environment of copper atoms were found by the is consistent with the published data [34].
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 51 No. 7 2006

NEW MAGNETOACTIVE COPPER COMPLEXES WITH SCHIFF’S BASES
1067
Synthesis of Azomethines III
RESULTS AND DISCUSSION
Like other azomethine systems [30], compounds III
used as ligands tend to undergo enol–imine (IIIa) and
amine–imine (IIIb) tautomerism, as follows from the
IR and 1H NMR spectra. This is indicated by the C=N
stretching vibration frequencies (1615 and 1618 cm–1)
and the OH (12.31 ppm) and NH (12.45 ppm) proton
signals for fragments IIa and IIIb, respectively.
A solution of 2-ethylamino-5-nitroaniline (1.81 g,
0.01 mol) in ethanol (100 ml) was added to a solution
of salicylaldehyde (1.22 g, 0.01 mol) or 2-(N-tosyl-
amino)benzaldehyde [35] in ethanol (30 ml), and the
mixture was refluxed for 3 h. The precipitates formed
after cooling were filtered off and recrystallized from
ethanol.
The elemental analysis data of the complexes
obtained by direct reaction of the ligands and metal
salts [36, 37] attest to L : M = 1 : 1, i.e., to the formation
of binuclear chelates M2L2.
IIIa, X = O. Yield, 78%. Light yellow crystals, mp
194–195°C.
For C15H15N3O3 anal. calcd. (%): C, 63.15; H, 5.30;
N, 14.73. Found (%): C, 63.25; H, 5.15; N, 14.83.
The chelate structure of the complexes is also indi-
cated by characteristic changes in their IR spectra with
respect to the spectra of the ligands, namely, the OH
and NH stretches disappear, the C=N stretching fre-
quencies and symmetric and antisymmetric SO2 vibra-
3
1H NMR, δ, ppm: 1.34 (t, 3H, J = 7.2 Hz, CH2–
3
3
CH3), 3.31–3.40 (t, 2H, J
= 7.2 Hz, JCH –NH
=
CH2–CH3
2
4.9 Hz, CH2–CH3), 5.07 (t, 1H, 3J = 4.9 Hz, NH–C2H5),
6.62–8.15 (t, 7H, CAr–H), 8.71 (s, 1H, CH=N), 12.31
(s, 1H, OH). IR (cm–1): 3400 w (NH), 1615 s (C=N),
1275 m (Ph–O).
IIIb, X = NTs. Yield, 84%. Orange needles, mp
141–142°C.
For C22H22N4O4S anal. calcd. (%): C, 60.26; H,
5.06; N, 12.78, S, 7.31.
tion frequencies decrease by 10–15 cm–1, and the Ph–O
vibration frequency increases by 50 cm–1 [38].
The dimeric structure and the type of ligand envi-
ronment are confirmed by analysis of the EXAFS spec-
tra of complexes IVa and IVb.
Figure 1 shows the Fourier transform modules
(FTM) of the ä-edge EXAFS spectra of copper com-
plexes IVa and IVb. Table 1 summarizes the parame-
ters of the local environment of the copper atom in these
compounds determined by fitting the theoretical χ(k) of
Found (%): C, 60.16; H, 5.16; N, 12.88, S, 7.42.
3
1H NMR, δ, ppm: 1.42 (t, 3H, J = 7.2 Hz, CH2–
CH3), 2.38 (s, 3H, CH3), 3.39–3.43 (t, 2H, 3J = 7.2 Hz,
CH2–CH3), 5.51 (t, 1H, 3J = 4.9 Hz, NH–C2H5), 6.67–
8.17 (t, 11H, CAr–H), 8.68 (s, 1H, CH=N), 12.45 (s, 1H,
the chosen model to the experimental EXAFS spectra.
.
The complex [C36H59Cu2N4O2]+[CF3O3S]– C5H12
·
C4H8O, bis(µ2-oxo)(N,N'-bis(2,6-diisopropylphenyl)-
2,5-pentanediiminato)(N,N,N',N'-tetramethylpropane-
1,3-diamino)dicopper(II)]trifluoromethanesulfonate pen-
tane tetrahydrofuran solvate) [39], containing oxygen
NH). IR (cm–1): 3446 w (NH), 1618 s (C=N), 1349 vs
(νasSO2), 1168 vs (νsSO2).
Synthesis of Copper Complexes IV
A solution of copper acetate monohydrate (0.199 g,
0.001 mol) in ethanol (10 ml) was added to a solution of
azomethine IIIa (0.283 g, 0.001 mol) or azomethine IIIb
(0.438 g, 0.001 mol) in ethanol (50 ml). The mixture
was refluxed for 4 h. The crystals of the complexes that
precipitated on cooling were filtered off, washed with
boiling ethanol (3 × 5 ml), and dried in a vacuum drying
chamber at 100°C.
IVa. Yield, 63%. Dark brown crystals, mp 234–
235°C, dec.
For C30H26N6O6Cu2 anal. calcd. (%): C, 51.95; H,
3.78; N, 12.12; Cu, 18.32. Found (%): C, 52.01; H,
3.72; N, 12.32; Cu, 18.42.
Table 1. Structural data found from the multisphere fitting
of the EXAFS data (R are interatomic distances, CN is the
coordination number, σ2 is the Debye–Waller factor, Q is the
quality function of fitting)
Complex CN*
R**, Å σ2, Å2
Atom
0.0027 O/N
0.0055
Q, %
IVa
IVb
2
2
4
1
4
1
6
1.99
2.02
2.81
2.99
1.93
2.78
3.24
6.5
N
0.0062 C/N
0.0038 Cu
0.0035
0.0049 Cu
0.0066
N
11.3
IR (cm–1): 1604 s (C=N), 1327 w (Ph–O).
IVb. Yield, 78%. Dark brown crystals, mp > 260°C.
C
For C44H40N8O2S2Cu2 anal. calcd. (%): C, 52.84; H,
4.03; N, 11.20; S, 6.41; Cu, 12.71. Found (%): C,
52.75; H, 4.13; N, 11.32; S, 6.51; Cu, 12.92.
IR (KBr, cm–1): 1603 vs (C=N), 1283 vs, (νasSO2),
1136 vs (νsSO2).
Notes: * CN is determined to a accuracy of 10% for the first coor-
dination sphere and 20% for the subsequent coordination
spheres.
** The accuracy of determination of the distances is 0.02 Å
for the first coordination sphere and 0.04 Å for the subse-
quent coordination spheres.
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 51 No. 7 2006

1068
BURLOV et al.
FTM
0.028
Cu–N/O
0.024
Cu–Cu
IVa
0.020
0.016
0.012
0.008
0.004
IVb
0
2
4
6
r, Å
Fig. 1. FTMs of the CuK-edge EXAFS spectra for complexes IVa and IVb. The solid line shows the experimental results and the
circles correspond to theoretical FTMs. The phase correction was not applied.
bridges with R = 1.818 Å for Cu–O distances and R = correspond to two unpaired electrons per molecule. The
2.849 Å for Cu–Cu distances was used as the model.
decrease in µeff with decreasing temperature and the
It can be seen from Fig. 1 that the FTM of both sam- magnetic susceptibility maximum at ~20 K for IVa
ples consist of the major peak with r = 1.59 Å (FTM
for IVa) and r = 1.63 Å (FTM for IVb) and a minor
µeff(β)
peak with r = 2.75 Å (FTM for IVa) and r = 2.61 Å
(FTM for IVb). The major peak corresponds to photo-
2.5
electron wave scattering on the nearest coordination
spheres of nitrogen (or nitrogen and oxygen for IVa)
χ, cm3/mol
0.020
2.0
whose radii were found from fitting and are summa-
rized in Table 1. The radii for the first coordination
spheres of the compounds are typical of copper com-
plexes. The second peak in the FTM may be due to the
Cu···Cu distance, which is in line with the proposed
dimeric model for the structure of the complexes. Note
that the Cu···Cu distance in IVb is 0.2 Å shorter than
that in IVa.
1.5
1.0
0.5
0.015
0.010
0.005
Thus, EXAFS studies of two copper complexes con-
firm the proposed dimeric structure of these com-
pounds.
The results of magnetic measurements for com-
plexes IVa and IVb are presented in Figs. 2 and 3,
respectively. As can be seen, the effective magnetic
moments µeff of the complexes at room temperature
0
50 100 150 200 250 300
T, ä
0
50
100
150
200
250
300
T, ä
Fig. 2. Temperature dependences of the effective magnetic
moment µ (T) and magnetic susceptibility χ(T) (inset) for
eff
complex IVa.
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 51 No. 7 2006

NEW MAGNETOACTIVE COPPER COMPLEXES WITH SCHIFF’S BASES
1069
plots by solid lines. The optimal parameters of the
model are presented in Table 2.
Attention is attracted by the positive ferromagnetic
exchange between the dimers in complex IVb, which
creates the possibility for ferromagnetic ordering of the
complex at lower temperatures.
Thus, variation of the coordination core of binuclear
copper azomethine complexes (IV) by changing the
donor atoms in their aldehyde fragments gives rise to
two types of magnetically anomalous structures,
namely, antiferromagnetic (X = O) and ferromagnetic
(X = NTs) coordination compounds.
µeff(β)
3.0
2.9
2.8
2.7
2.6
2.5
0
ACKNOWLEDGMENTS
50
100
150
200
250
300
T, ä
This work was supported by the Program of Presid-
ium of the RAS “Targeted Synthesis of Compounds
with Desired Properties and Development of Func-
tional Materials Based on Them” (theme 00-04-17), the
Russian Foundation for Basic Research (project
no. 04-03-32366), and the BRHE (grant NO-008-X1).
Fig. 3. Temperature dependence of the effective magnetic
moment µ (T) for complex IVb.
eff
point to antiferromagnetic exchange interactions in the
dimeric complex molecules. Conversely, µeff of com-
plex IVb increases with a decrease in temperature to
reach a value of 2.97β at 5 K, which exceeds the ferro-
magnetic limit of the dimer (2.83β at g = 2).
The theoretical simulation of the experimental
curves was carried out using the known Bleaney–Bow-
ers equation for the magnetic susceptibility of a dimeric
cluster with the spins 1/2 [40]:
REFERENCES
1. O. Kahn, P. Tola, P. Galy, and H. Condanne, J. Am.
Chem. Soc. 100 (12), 3931 (1978).
2. O. Kahn, P. Galy, Y. Journaux, et al., J. Am. Chem. Soc.
104 (8), 2165 (1982).
3. M. Verdaguer, Polyhedron 20, 1115 (2001).
4. F. Tuna, L. Patron, Y. Journaux, et al., J. Chem. Soc.,
Dalton Trans., 539 (1999).
Nβ2g2
---------------
3kT
1
–2J
---------
kT
–1
5. J.-P. Costes, F. Dahan, A. Dupies, et al., Inorg. Chem. 39
⎛
⎝
⎞
⎠
--
1 + exp
χCuCu
=
+ Nα,
(1), 169 (2000).
3
6. J.-P. Costes, F. Dahan, F. Demeste, et al., J. Chem. Soc.,
Dalton Trans., 464 (2003).
7. Gattechi, R. Sessoli, and A. Cornia, in Comprehensive
Coordination Chemistry II, Ed. by H. A. McClevertry
and T. J. Meyer (Elsevier/Pergamon Press, Amster-
dam/New York, 2003), p. 393.
where N is the Avogadro number, g is the g-value of the
Cu(II) ion, J is the exchange coupling parameter of the
paramagnetic ions in the dimer, and Nα is a tempera-
ture-independent constant term. The dimer–dimer
exchange interactions were considered in the molecular
field approximation using the relation [40]
8. J. S. Miller and M. Drillon, Magnetism. From Molecules
to Materials (Elsevier, Amsterdam, 2005).
9. P. S. Mukherjee, T. K. Maij, A. Escuer, et al., Eur. J.
Inorg. Chem., No. 4, 943 (2002).
χCuCu
------------------------------------------------------
χ =
,
1 – (2zJ'/Ng2β2)χCuCu
10. Y. Song, C. Massera, O. Roubeau, et al., Inorg. Chem.
43, 6842 (2004).
11. M. Rodriguez, A. Liobet, and M. Corbella, Inorg. Chem.
where χCuCu is the magnetic susceptibility of the iso-
lated dimer, z is the number of the nearest neighbors of
the dimers, and J' is the exchange parameter between
the dimers. The results of simulation are shown in the
38 (10), 2328 (1999).
12. Z. Zou, W.-L. Liu, S. Gao, et al., Polyhedron 23 (14),
2253 (2004).
13. V. V. Pavlishchuk, Teor. Eksp. Khim. 33 (6), 341 (1997).
14. H. Miyazaka, H. Ieda, N. Matsumoto, et al., Inorg.
Table 2. Model parameters
Chem. 37 (2), 255 (1998).
15. V. I. Ovcharenko and R. Z. Sagdeev, Usp. Khim. 68 (5),
Nα,
Complex
g
J, cm–1
zJ', cm–1
381 (1999).
cm3/mol
16. F. Thomas, O. Yarjayes, C. Duboc, et al., J. Chem. Soc.,
Dalton Trans., 2662 (2004).
17. A. Burdukov,Yu. Shvedenkov, N. Pervukhina, et al., Eur.
J. Inorg. Chem., No. 9, 1776 (2005).
IVa
IVb
2.05
2.02
–10.1
4.0
–2.6
0.27
–
0.00029
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 51 No. 7 2006

1070
BURLOV et al.
18. I. Romade, O. Kahn, Y. Jeannin, et al., Inorg. Chem. 36
on Coordination Chemistry, Chisinau, 2005 (Chisinau,
2005), p. 274.
(5), 930 (1997).
28. A. I. Uraev and V. N. Ikorskii, M.P. Bubnov, et al. Koord.
19. M. L. Kahn, T. M. Rajendiran, Y. Yennin, et al., C. R.
Khim. 32 (4), 299 (2006).
Acad. Sci., Ser. LLC: Chem. 3, 131 (2000).
29. A. D. Garnovskii and I. S. Vasil’chenko, Usp. Khim. 71
20. S. Mohanta, H.-H. Lin, C. J. Lee, et al., Inorg. Chem.
(11), 943 (2002).
Commun. 5, 585 (2000).
30. A. D. Garnovskii and I. S. Vasil’chenko, Usp. Khim. 74
21. C. Brewer, G. Brewer, W. P. Scheid, et al., Inorg. Chim.
(3), 193 (2005).
Acta 313 (1), 65 (2001).
31. D. I. Kochubei, Yu. A. Babanov, K. I. Zamaraev, et al.,
EXAFS as an X-ray Spectroscopic Method for the Inves-
tigation of Structures of Amorphous Solids (Nauka,
Novosibirsk, 1988) [in Russian].
22. A. D. Garnovskii, Proceedings of the III International
Conference on Advanced Technologies and Applications
of Advanced Physicochemical Techniques in Environ-
mental Research, Rostov-on-Don, 2005 (Rostov-on-
Don, 2005), p. 24.
32. M. Newville, J. Synchrotron Rad. 8, 96 (2001).
33. S. I. Zabinski, J. J. Rehr, A. Ankudinov, and R. C. Alber,
23. A. I. Uraev, I. S. Vasil’chenko, V. N. Ikorskii, et al., Pro-
ceedings of the III International Conference on
Advanced Technologies and Applications of Advanced
Physicochemical Techniques in Environmental
Research, Rostov-on-Don, 2005 (Rostov-on-Don, 2005),
p. 222.
Phys. Rev. B: Condens. Matter 52 (4), 2995 (1995).
34. R. Foster, J. Chem. Soc., No. 11, 4687 (1957).
35. N. I. Chernova, Yu. S. Ryabokobylko, V. G. Brudz’, and
B. M. Bolotin, Zh. Org. Khim. 7 (8), 1680 (1971).
36. A. D. Garnovskii, I. S. Vasil’chenko, and D. A. Gar-
novskii, Contemporary Aspects of Metal Complex Syn-
thesis. Basic Ligands and Methods (Izd. Lab. Persp.
Obr., Rostov-on-Don, 2000) [in Russian].
37. Synthetic Coordination and Organometallic Chemistry,
Ed. by A. D. Garnovskii and B. I. Kharisov (Marcell
Dekker, New-York/Basel, 2003).
24. A. I. Uraev, V. N. Ikorskii, M. P. Bubnov, et al., Proceed-
ings of the III International Conference on Advanced
Technologies and Applications of Advanced Physico-
chemical Techniques in Environmental Research, Ros-
tov-on-Don, 2005 (Rostov-on-Don, 2005), p. 227.
25. A. I. Uraev, I. S. Vasilchenko, V. N. Ikorskii, et al., Men-
38. A. D. Garnovskii, V. A. Alekseenko, A. S. Burlov, and
deleev Commun. 15 (4), 133 (2005).
V. S. Nedzvetskii, Zh. Neorg. Khim. 36 (34), 886 (1991).
26. A. D. Garnovskii, Proceedings of the XXII International
Chugaev Conference on Coordination Chemistry, Chi-
sinau, 2005 (Chisinau, 2005), p. 117.
39. N. W. Aboelella, E. A. Lewis, A. M. Reynolds, et al.,
J. Am. Chem. Soc. 124 (36), 10660 (2002).
40. V. T. Kalinnikov andYu. V. Rakitin, Introduction to Mag-
netochemistry. Static Magnetic Susceptibility Method
(Nauka, Moscow, 1980) [in Russian].
27. A. I. Uraev, I. S. Vasilchenko, V. N. Ikorskii, et al., Pro-
ceedings of the XXII International Chugaev Conference
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 51 No. 7 2006