Complex compounds of azomethines with an MN2S2 five-membered coordination unit: Metal chelates of 2-{[4-(3,5-diphenyl-4,5- dihydropyrazol-1-yl)benzylidene]amino}benzenethiol

Article abstract of DOI:10.1023/B:RUGC.0000039093.42205.e6

Chelate complexes of 2-{[4-(3,5-diphenyl-4,5-dihydropyrazol-1-yl) benzylidene]amino}benzenethiol (LH) of the ML₂ composition and with an M₂N₂S₂ five-membered coordination unit were obtained. The syntheses were c

Full text of DOI:10.1023/B:RUGC.0000039093.42205.e6

Russian Journal of General Chemistry, Vol. 74, No. 5, 2004, pp. 772 775. Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 5, 2004,
pp. 840 843.
Original Russian Text Copyright
Garnovskii.
2004 by Burlov, Borodkina, Kuznetsova, Uraev, Makarova, Vasil’chenko, Borodkin, Altun, Feiizoglu (Abdullaev),
Complex Compounds of Azomethines with an MN2S2
Five-membered Coordination Unit:
Metal Chelates of 2-{[4-(3,5-Diphenyl-4,5-dihydropyrazol-1-yl)-
benzylidene]amino}benzenethiol
A. S. Burlov, I. G. Borodkina, L. I. Kuznetsova, A. I. Uraev, N. I. Makarova,
I. S. Vasil’chenko, G. S. Borodkin, O. Altun, A. Feiizoglu (Abdullaev), and A. D. Garnovskii
Rostov State University, Rostov-on-Don, Russia
Trakai University, Turkey
Received May 27, 2002
Abstract Chelate complexes of 2-{[4-(3,5-diphenyl-4,5-dihydropyrazol-1-yl)benzylidene]amino}benzene-
thiol (LH) of the ML2 composition and with an M2N2S2 five-membered coordination unit were obtained. The
syntheses were carried out by chemical (from LH and metal acetates) and electrochemical (from LH and zero-
valent metals) methods in methanol. The chelate compounds were assigned cis-planar (M = Ni) and tetra-
hedral (M = Co, Zn, Cd) configurations.
Complexes of Schiff bases with an MN2S2 coor-
dination unit occupy an important place in the
S
H
chemistry of azomethine metal chelates in view their
N
peculiar stereochemistry (preferential formation of
cis-planar and distorted tetrahedral structures) [1 3]
and the possibility of creation of models of active
centers of nonheme metal proteins [4 8]. Whereas
most emphasis in the development of this field of
coordination chemistry has been placed on six-
membered metal chelates I [1 , 5 8], five-membered
chelates II are equally interesting objects [1 3, 9 25].
H
N
N
Ph
Ph
IIIA
S
H
R3
N
S
S
R2
M/2
R
M/2
N
N
N
R1
N
Ph
I
II
Ph
IIIB
I, R1, R2, R3 = Alk, Ar, Ht; II, R = Ar, Ht.
The IR spectrum of compound III contains a well-
defined band at 3346 cm , which relates to stretching
1
Proceeding with the research initiated in [9, 10],
we synthesized for the first time and studied ligand
III (LH) and metal complexes IV, Va Vc derived
from it.
vibrations of the secondary amino group, and bands
in the region of 1580 cm characteristic of the endo-
1
cyclic C=N bond of the pyrazoline ring [29]. Vibra-
1
tions of the open form B in the region 1620 1660 cm
(exocyclic azomethine C=N bond) and 2500
2600 cm [ (SH)] are absent from the spectrum.
As would be expected [26 28], ligands III in
1
crystal and in solutions exist mainly in the closed
1
benzothiazoline form A, which is proved by the H
The presence of a chiral center in the pyrazoline
NMR and IR spectra.
fragment of ligand III results in the observation in the
1070-3632/04/7405-0772 2004 MAIK Nauka/Interperiodica

..
COMPLEX COMPOUNDS OF AZOMETHINES WITH AN MN2S2
773
IR spectra, magnetic characteristics, and elemental analyses of azometine III and complexes IV, Va Vc
Found, %
Calculated, %
IR
Mef, spectrum,
mp,
C
Color
Formula
BM
(C=N),
C
H
N
S
M
C
H
N
S
M
1
cm
a
a
b
III
IV
Light
yellow
Red-
170 171 77.16 5.54 9.89 7.39
>250
C28H23N3S
77.56 5.34 9.69 7.40
1620 m
72.99 4.70 9.95 6.91 6.55 C56H44N6NiS2 72.80 4.80 9.10 6.94 6.35
72.75 4.82 8.70 7.15 6.58 C56H44CoN6S2 72.78 4.80 9.10 6.94 6.38
72.30 4.74 9.00 6.93 7.12 C56H44N6S2Zn 72.26 4.77 9.04 6.98 7.03
68.30 4.65 8.74 6.71 11.64 C56H44CdN6S2 68.79 4.54 8.60 6.56 11.50
brown (decomp.)
Va 4.35 1624 m Brown
>250
(decomp.)
>250
(decomp.)
>250
a
Vb
Vc
1625 m Orange
1620 m
a
(decomp.)
a
b
Diamagnetic.
(NH) 3346s.
1H NMR spectra (CDCl3) of anisochronous CH2
proton signals at (ppm) 3.17 d.d (JHH 17.2, JHH
7.0 Hz) and 3.83 d.d (JHH 17.2, JHH 12.3 Hz) The
pyrazoline CHPh proton signal is observed at
5.22 d.d (JHH 12.3, JHH 7.0 Hz). The thiazoline CH
and NH proton signals are observed at 6.29 s and
4.22 s, respectively. Aromatic protons appear as
the chelates contain well-defined absorption bands at
1620 1625 cm , corresponding to stretching vibra-
tions of coordinated C=N bond [10].
1
1
The H NMR spectra of the Ni(II), Zn(II), and
Cd(II) complexes preserve the general pattern charac-
teristic of the ligand, but the NH signal at 4.22 dis-
appears and the signal of the HC=N proton ( 8 9)
appears.
multiplets at
6.50 7.80 m (18H).
Chelates IV, Va Vc of the ML2 composition [M =
Co(II), Ni(II), Zn(II), and Cd(II)] (see table) were
synthesized chemically and electrochemically from
compound III (see Experimental). The IR spectra of
Together the above evidence allows us to assign
structures IV and V to the complexes described for
the first time. In these structures, the azomethine
ligand system is stabilized by coordination (cf. [28]).
S
S
S
S
.
.
Ni
M
N
N
N
N
R
R
N
R
R
IV
Va Vc
Ph
; M = Co (a), Zn (b), Cd (c).
R =
N
Ph
The 1H NMR evidence allows the diamagnetic
nickel complex to be assigned a slightly tetrahedrally
distorted planar configuration in solution, which is
evidenced by the fact that the chemical shifts of
aromatic proton signals span an extended range (
6.0 9.0). This result is consistent with the diamag-
netism of the nickel chelate in the crystal phase, we
revealed by Faraday’s method, as well as published
data based on X-ray diffraction data for complexes II
(M = Ni) [13, 18, 23, 30, 31]. Similar complexes
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 74 No. 5 2004

774
BURLOV et al.
Va Vc were assigned a tetrahedral configuration,
based on the magnetic moment (Mef 4.35 BM) for the
cobalt chelate and published data for the zinc and
cadmium complexes [32, 33].
ACKNOWLEDGMENTS
The work was financially supported by the Rus-
sian Foundation for Basic Research (project nos. 00-
03-32538 and 00-15-97320).
Thus, the example of new azometine chelates with
account for published data [9 28] was used to show
that the character of polyhedra that are realized in
complexes with MN2S2 five-membered coordination
unit is determined by the electronic configuration of
the metal and does not depend on the nature of the
substituent in the aldehyde fragment of the ligand
system.
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