New ambidentate ligands-azomethin derivatives of 1-amino-3- methylbenzimidazoline-2-thion

Article abstract of DOI:10.1007/s11173-005-0163-6

Metal chelates ML₂ (M = Co²⁺, Ni²⁺, Cu²⁺, Cd²⁺) are synthesized from azomethin derivative of amino-3-methyl-benzimidazoline-2-thion and 2-N-tosylaminobenzaldehyde (HL) and their compositions and struc

Full text of DOI:10.1007/s11173-005-0163-6

Russian Journal of Coordination Chemistry, Vol. 31, No. 10, 2005, pp. 747–751. Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 10, 2005, pp. 786–790.
Original Russian Text Copyright © 2005 by Vasil’chenko, Kuz’menko, Shestakova, R. Borisenko, Divaeva, Burlov, N. Borisenko, Uflyand, Garnovskii.
New Ambidentate Ligands—Azomethin Derivatives
of 1-Amino-3-methylbenzimidazoline-2-thion
I. S. Vasil’chenko*, T. A. Kuz’menko*, T. E. Shestakova**, R. N. Borisenko***,
L. N. Divaeva*, A. S. Burlov*, N. I. Borisenko*,
I. E. Uflyand**, and A. D. Garnovskii*
*Research Institute of Physical and Organic Chemistry, Rostov State University, Rostov-on-Don, Russia
*Rostov State Pedagogical University, Rostov-on-Don, Russia
***South Scientific Center, Russian Academy of Sciences
Received April 16, 2004
Abstract—Metal chelates ML2 (M = Co2+, Ni2+, Cu2+, Cd2+) are synthesized from azomethin derivative of
amino-3-methyl-benzimidazoline-2-thion and 2-N-tosylaminobenzaldehyde (HL) and their compositions
and structures are determined from the electronic mass spectrometry, IR and electronic spectroscopy and
magnetochemistry data.
The complexes based on azomethin ligand systems ates (IIIa), semi- (IIIb), and thiosemicarbazonates
(IIIc) of metals.1 At the same time, metal chelates of
compounds where the exocyclic donor atomY (N, O, S,
Se) is bonded to the cyclic (including heterocyclic) sys-
tem are unknown.
containing extra coordination-active groups at the imine
nitrogen atom are the most extensively studied com-
pounds in the modern coordination chemistry [1–6].
Metal chelates of azomethins are well known that con-
tain at the N atom of the C=N group the azine fragments
with endocyclic N-donor atoms involved, for example,
in pyridyl (I) [6–9] or quinolyl (II) [10, 11] cycles.
However, chelates based on azomethin ligands with
exocyclic donor atoms in the imine substituent are rep-
With the aim to study the structures of novel com-
plexes of the Schiff bases with different exoheterocy-
clic donor fragments, we synthesized for the first time
and investigated 1-(2-tosylaminobenzylidene)amino-3-
methylbenzimidazoline-2-thion (IV, HL) containing
resented only by the thoroughly studied acylhydrazon- nucleophilic donor S atom and its metal chelates (V).
R
X
N
X
N
X
N
R1
M/2
N
M/2
M/2
N
Y
N
R
R1
I: X = NTs, O, S;
II: X = NTs, O
III: X = O, NTs, Y = O,
R = H, R1 = Alk (a);
X = O, Y = O,
Ts = –SO2C6H4CH3-p;
R, R1 = Ar, Het(heteryl).
R = H, R1 = NH2 (b);
X = O, Y = S,
R = H, R1 = NH2 (c).
M = Ni, Co, Cu, Zn, Cd
1
Cambridge Structural Database contains structures of 73 similar metal complexes.
1070-3284/05/3110-0747 © 2005 Pleiades Publishing, Inc.

748
VASIL’CHENKO et al.
Ts
H
Ts
N
N
N
N
M/2
S
S
N
N
N
N
CH3
CH3
(IV)
(V)
M = Co, Ni, Cu, Cd
EXPERIMENTAL
1H NMR (DMSO-D6); δ, ppm: 2.27 (3H, s, PhCH3);
3.80 (3H, s, NCH3); 7.20–8.00 (12H, m, Harom); 9.97
(1H, s, HC=N); 10.65 (1H, s, HNTs).
Mass spectra were obtained by the electrospray ion-
ization (ESI) method on Water/Micromass ZQ
(Manchester, Great Britain) mass spectrometer
equipped with syringe pump (Harvard Apparatus). The
solutions of the samples in methanol were injected in
electrospray ionization source by the same pump at
flow rate 40 µl/min. The potentials applied to electro-
spray ionization source were as follows: 3 kV (tube),
0.5 kV (lenses), 4 V (extractor). As in the case of a stan-
dard experiment with electrospray ionization, the cone
potential was 30 V. The source temperature was 120°ë,
the temperature of desolvation was 300°ë. Nitrogen
was used as both the sprayer gas and desolvation gas
with flow rates 100 and 300 l/h, respectively.
Bis[1-(2-tosylaminobenzylideneamino)-3-methyl-
benzimidazoline-2-thionato]nickel(II) (V(Ni)). A 1N
solution of sodium methylate (1 ml) and a hot solution
containing Ni(CH3COO)2 · 4H2O (0.05 g, 0.25 mmol)
in 5 ml of the same solvent were added to a hot solution
of azomethin IV (0.218 g, 0.5 mmol) in 20 ml of meth-
anol. The mixture was refluxed for 15 min. The precip-
itate formed after cooling was filtered off, washed with
cold methanol, and dried at 120°ë. The yield was
0.190 g (82%). The brown needle-shaped crystals were
obtained after recrystallization of precipitate V from
butanol, mp > 200°C.
IR spectra of the samples were recorded on a Nico-
let Impact-400 instrument (with essential oil mulls and
KBr pellets). The electronic absorption spectra of solu-
tions of the studied compounds in methylene chloride
were measured on a UNICAM Helyos Gamma instru-
For C44H38N8O4S4Ni
anal. calcd. (%):
Found (%):
C, 56.84;
C, 57.02;
H, 4.12;
H, 4.23;
N, 12.05.
N, 12.17.
1
The remaiming metal chelates were prepared fol-
lowing the analogous procedure and using the corre-
sponding metal acetates.
ment. The H NMR spectra of solutions of ligand IV
and its complex with Cd (V(Cd)) in DMSO-D6 were
recorded on a Bruker DPX-250 instrument.
Bis[1-(2-tosylaminobenzylidene)amino-3-meth-
The magnetic susceptibility of paramagnetic metal
chelates was measured in DMSO-D6 solution by the
Evans method.
ylbenzimidazoline-2-thionato]cobalt(II)
(V(Co)).
The brown fine needle-shaped crystals were formed in
the yield 0.175 g (75%), mp > 200°C.
1-(2-Tosylaminobenzylidene)amino-3-methylbenz-
imidazoline-2-thion (IV). A solution of 1-amino-3-
methylbenzimidazolilne-2-thion (1.79 g, 0.01 mol)
[12] and 2-tosylaminobenzaldehyde (2.75 g, 0.01 mol)
[13] in glacial acetic acid (15 ml) was refluxed for 2 h.
The precipitate formed after cooling was filtered off,
washed with ether, and dried at 120°ë. The yield was
2.35 g (83%). Colorless needle-shaped crystals were
obtained by recrystallization of the precipitate from
butanol, mp = 202–204°ë.
For C44H38N8O4S4Co
anal. calcd. (%):
Found (%):
C, 56.82;
C, 57.12;
H, 4.12;
H, 4.20;
N, 12.05.
N, 12.11.
Bis[1-(2-tosylaminobenzylidene)amino-3-methyl-
benzimidazoline-2-thionato]copper(II) (V(Cu)). The
dark brown prismatic crystals were formed with a yield
of 0.210 g (90%), mp > 200°C.
For C22H20N4O2S2
For C44H38N8O4S4Cu
anal. calcd. (%):
Found (%):
C, 60.53;
C, 60.48;
H, 4.62;
H, 4.55;
N, 12.83.
N, 12.87.
anal. calcd. (%):
Found (%):
C, 56.54;
C, 56.63;
H, 4.10;
H, 4.18;
N, 11.99.
N, 12.08.
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 31 No. 10 2005

NEW AMBIDENTATE LIGANDS—AZOMETHIN DERIVATIVES
749
Bis[1-(2-tosylaminobenzylidene)amino-3-methyl- and the signals due to the subsequent destruction of this
benzimidazoline-2thionato]cadmium(II) (V(Cd)). The
yellow finely-crystalline powder was formed, mp >
200°C.
fragment. In addition to the above signals, one more
peak is observed in mass spectrum of compound V(Cu)
that corresponds to a dimer [Cu2L2] (m/z = 998, I =
13%) formed, probably, as a result of combination of
the V(Cu) molecule and the Cu2+ ion. The spectrum of
chelate V(Cd) contains the [LNa] signals (m/z = 459,
I = 43%), [LCd] (m/z = 549, I = 58%), [L2Cd + H]
(m/z = 985, I = 30%). An attempt to record mass spec-
trum of complex V(Co) was failure, obviously, due to
its low solubility.
For C44H38N8O4S4Cd
anal. calcd. (%): C, 53.73;
Found (%): C, 53.90;
H, 3.89;
H, 3.95;
N, 11.39.
N, 11.27.
1H NMR (DMSO-D6), δ, ppm: 2.25 (6H, s,
2PhCH3); 3.8 (6H, s, 2NCH3), 6.7–7.75 (24H, m,
24Harom), 9.40 (2H, s, 2HC=N).
The analysis of the low-intensity peaks with m/z <
ML2 showed that the fragmentation of metal complexes
V mainly occurs as a result of detachment of the methyl
groups at the N atom of benzimidazole substituent and
of different fragments of the tosyl substituent C7H7SO2.
The main course of destruction of the above chelates is
the detachment of the whole deprotonated molecules of
the ligand systems.
RESULTS AND DISCUSSION
Metal chelates V were obtained by the direct reac-
tion of a ligand (HL) and metal salts according to the
following scheme [2, 3]:
2LH + M(OAc)2
ML2 + 2AcOH.
The ligand system IV is potential tridentate and con-
tains, in addition to the chelate-forming N atoms of the
tosylamine and azomethin groups (compounds V) [18–
20], the atoms that can form the donor–acceptor bonds,
namely, the S atoms of thiobenzimidazole fragment
(complexes VI) [21–24] and the O atoms of sulfamide
group (complexes VII) [25]. Moreover, one should take
into account the possibility of formation of pentacoor-
dinated structures ML2 [23, 25–27], where one of the
ligands is bidentate (as in V), while the other one is tri-
dentate ligand (as in VI or VII).
The composition of metal complexes ML2 (L is the
deprotonated ligand) was determined by the elemental
analysis, IR (lacking absorption bands of the NH frag-
ment of the HNTs group), 1H NMR (disappearing sig-
nal from a proton of the HNTs group, shifts of the
remaining signals, lacking signals of the protons of the
solvent molecules) [14], and mass spectrometry
method (the molecular peaks in mass spectra of che-
lates correspond to the indicated composition) [15].
The mass spectral data we obtained together with
the data [16, 17] made it possible to establish the com-
position of metal complexes formed and to consider the
route of fragmentation and recombination of the frag-
ments of their molecules (and of the molecules of the
initial ligand system) under the experimental condi-
tions. Thus, the spectrum of compound IV contains,
along with a peak of the protonated ligand [HL + H]
CH3
CH3
O
O
S O
M/2
S O
M/2
2
N
N
(m/z = 437, I = 15%), the following signals: [HL + Na]
(m/z = 459, I = 100%), [2HL + Na] (m/z = 895, I =
3
N
N
12%) , where HL is the ligand molecule, m/z is the ratio
S
S
N
N
of a fragment mass to its charge, I is the signal intensity.
The spectrum of complex V(Ni) contains the following
signals: the most intense signal corresponding to [NiL]
(m/z = 493, I = 100%), the [NaL] signal (m/z = 459, I =
10%), and the low-intensity molecular peak due to
[NiL2] (m/z = 928).
N
N
CH3
CH3
(VI)
(VII)
The spectrum of complex V(Cu) exhibits the low-
intensity molecular peak of [CuL2 + H] (m/z = 935, I =
8%), the intense signal [CuL] (m/z = 498, I = 100%),
This work was performed with the aim to determine
the composition and the structure of the coordination
unit of metal chelates V and to study them by IR, UV
spectroscopy, and magnetochemistry methods. IR spec-
tra of the ligand system IV contain bands due to the
stretching vibrations of the NSO2 (1158 and 1358 cm–1),
C=S (1186 cm–1), C=N (1571 cm–1, benzimidazole
ring and 1597 cm–1, azomethin fragment), and HNTs
(3350 cm–1) groups. The latter band is significantly
broadened due to the formation of the intramolecular
2
+
The appearance in all mass spectra of the [M + Na] ion can be
explained by the presence of sodium in a solvent, glass bottles,
tubes used in the experiment, and, possibly, in the spectrometer
ionization chamber itself [16].
3
The signals from the products of complex IV decomposition have
low intensity and correspond to the fragments [HL–2O–CH ]
2
(m/z = 390), [HL–C H –SO] (m/z = 295).
7
9
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 31 No. 10 2005

750
VASIL’CHENKO et al.
hydrogen bond with azomethin N atom. In IR spectra of Science (projects nos. NSh-945.2003.3, VSh no. 15402),
all metal chelates V, the band due to vibrations of the Integrated Program of Presidium of the Russian
HNTs group is lacking, which suggests the formation Academy of Sciences “The Target Synthesis of Com-
of a chelate compound. In the spectra of metal chelates, pounds with the Desired Properties and the Develop-
the band due to the stretching vibrations of the C=S ment of Functional Materials on Their Basis” (project
group is noticeably shifted (by 25–60 cm–1) toward no. 00-04-17), and by the RF Ministry of Education and
long waves, as compared to its position in the spectrum Science and the CRDF Foundation (USA) for the Rus-
of the ligand, which indicates the formation of the bond sian–American Program “Fundamental Research and
between the S atom of benzimidazolthion fragment and the Higher Education” (project RO-004-X1).
the metal atom (type VI). The bands from the SO2
group of the tosyl fragment are only slightly shifted,
which can be explained by the lacking coordination of the
O atom of this group to the central metal ion (type VI).
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