Structural and spectral studies of some coordination complexes of Ni(II) with N-benzylidene-2-mercaptoaniline derivatives

Article abstract of DOI:10.1016/S0022-2860(00)00723-7

Nickel(II) complexes of N-(4-bromobenzylidene)-2-mercaptoaniline, N-(4-methyl benzylidene)-2-mercaptoaniline and N-(4-methoxybenzylidene)-2-mercaptoaniline were prepared and investigated. The proposed structures for these complexes derived from the two-di

Full text of DOI:10.1016/S0022-2860(00)00723-7

Journal of Molecular Structure 562 (2001) 1±9
www.elsevier.nl/locate/molstruc
Structural and spectral studies of some coordination complexes of
Ni(II) with N-benzylidene-2-mercaptoaniline derivatives
a,
S. Ide , N. Ancõn , S.G. OztasË , M. TuÈzuÈn
b
b
b
Ç
È
*
aDepartment of Physics Engineering, Faculty of Engineering, University of Hacettepe, 06532 Beytepe, Ankara, Turkey
b
Ï
Department of Chemistry, Ankara University, 06100 Tandogan, Ankara, Turkey
Received 10 April 2000; accepted 21 July 2000
Abstract
Nickel(II) complexes of N-(4-bromobenzylidene)-2-mercaptoaniline, N-(4-methyl benzylidene)-2-mercaptoaniline and N-
(4-methoxybenzylidene)-2-mercaptoaniline were prepared and investigated. The proposed structures for these complexes
derived from the two-dimensional (2-D) NMR techniques and the infrared spectra are consistent with the X-ray powder
diffraction measurements and the elemental analysis results. On the other hand, energy minimization studies of the molecules
were carried out to obtain the most probable molecular conformations. q 2001 Elsevier Science B.V. All rights reserved.
Keywords: NMR techniques; IR spectroscopy; X-ray studies; Nickel(II) complexes
1. Introduction
XRD method to see if any common structural features
exist between them and similar complexes. Three-
dimensional conformations of the complexes were
also predicted by an energy minimizer program
Alchemy 2000 [3].
There has been continuous interest in the chemistry
of the metal complexes of Schiff bases containing N
and S donor atoms because of their structural features
and biological activities [1]. The title complexes were
prepared by the following reaction (Scheme 1).
Bayer reported the rearrangement of 2,20-bisbenzo-
thiazoline by mercury(II) salts to the corresponding
chelate [2]. This rearrangement should be possible
through an equilibrium in which the ring structure is
transformed into chelate-forming chain structure.
Here, the rearrangement of benzothiazoline derivatives
occurs by nickel(II) salts to the corresponding chelate.
Therefore, the structures of the title complexes
were elucidated using IR, NMR spectroscopy and
2. Experimental
2.1. Synthesis
The methods used to prepare these complexes are
the same. To an anhydrous ethanolic solution of 2-
mercapto aniline (1 mmol), ethanolic solution of
benzaldehyde derivatives (1 mmol) (4-bromo, 4-
methyl, 4-methoxy) was added. These solutions
were allowed to stand for 3 h for the formation of
Schiff bases. Then 0.5 mmol nickel(II) acetate in
ethanol was added to these solutions. The reaction
mixtures were re¯uxed and heated for 3 h and during
* Corresponding author. Tel.: 190-312-235-2551; fax: 190-312-
235-2550.
0022-2860/01/$ - see front matter q 2001 Elsevier Science B.V. All rights reserved.
PII: S0022-2860(00)00723-7

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S. Ide et al. / Journal of Molecular Structure 562 (2001) 1±9
2
Scheme 1.
this time a red±brown powder was formed. The
products were ®ltered and recrystallized from dichlor-
omethane±ethanol solution.
on a Mattson-1000 FTIR spectrometer using KBr
pellets in the range 4000±400 cm21 (Fig. 1). A
resolution of 4 cm21 was feasible and 32 pulses
were found to be suitable for a spectrum of acceptable
quality. Band locations were found by means of a
microprocessor.
The 1H NMR spectra were obtained by using
deuterated chloroform solvent on a Bruker DPX 400
FT-NMR spectrometer with TMS as internal standard
(Fig. 2).
2.2. Elemental analysis
Chemical analysis of C, H, N and S were deter-
mined by LECO CHNS-932 elemental analyzer.
Ni(C14H12NS)2: Found: C: 66.10, H: 4.217,
N: 5.386, S: 11.86%. Calc. C: 65.75, H: 4.73,
N: 5.48, S: 12.52%.
Ni(C13H9NSBr)2: Found: C: 48.90, H: 2.617, N: 4.47,
S: 9.15%. Calc. C:48.67, H:2.808, N:4.37, S: 9.98%.
Ni(C14H12NSO)2: Found: C: 62.01, H: 3.96, N: 5.20,
S: 10.91%. Calc. C: 61.88, H: 4.44, N: 5.16, S:
11.78%.
The powder X-ray diffraction patterns (Fig. 3)
were recorded using a General Electric XRD-700,
SPG-2 manual spectrogoniometer employing
Ê
CuKa (g ˆ 1.5418 A) over the range 2u
(3 # 2u # 568).
3. Results and discussion
2.3. Physical measurements
The infrared spectra of complexes were recorded
In our study, the infraredspectra and 1H NMR spectra

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S. Ide et al. / Journal of Molecular Structure 562 (2001) 1±9
3
Fig. 1. The infrared spectra of (A) Ni(C13H9NSBr)2; (B) Ni(C14H12NS)2; and (C) Ni(C14H12NSO)2.

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S. Ide et al. / Journal of Molecular Structure 562 (2001) 1±9
4
1
Fig. 2. The H NMR spectra of (A) Ni(C13H9NSBr)2; (B) Ni(C14H12NS)2; and (C) Ni(C14H12NSO)2.

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S. Ide et al. / Journal of Molecular Structure 562 (2001) 1±9
5
Fig. 3. X-ray powder diffraction patterns of (A) Ni(C14H12NSO)2; (B) Ni(C14H12NS)2; and (C) Ni(C13H9NSBr)2.

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S. Ide et al. / Journal of Molecular Structure 562 (2001) 1±9
6
vibration bands occur between 380 and 325 cm21
[5]. In our study, these bands could not be observed,
because of the inadequacy of the spectrophotometer
as it can work at 4000±400 cm21 range.
Table 1
The fundamental vibrational wavenumber (cm21
) of Ni(II)
complexes
Ni(C13H9NSBr)2 Ni(C14H12NS)2 Ni(C14H12NSO)2 Assignments
The bands due to n(Ni±N) stretching vibration are
usually found between 580 and 430 cm21 [6]. In the
metal complexes of bromo, methyl and methoxy
derivatives, these bands occurred at 494, 499 and
510 cm21, respectively.
3059
2926
2852
3055
2920
2850
3059
2926
2850
n(C±H)
n(C±H)
(CHyN)
n(CyN)
nring
1585
1574
1483
1458
1439
±
1599
1574
1510
1456
1400
1371
1603
1550
1508
1458
1425
1304
1
The H NMR spectra of these compounds were
nring
nring
recorded in CDCl3 at 400 MHz using two-dimen-
sional (2-D) NMR techniques and all proton signals
were completely assigned (Table 2).
nring
d(C±H)
(±CH3)
n(C±O)
n(C±N)
(Ar±N)
d(CCH)
dring
Although ±CHyN protons usually absorb in the 8±
9 d range, in all three of our complexes the proton
resonance of the ±CHyN± group was observed
between the 7 and 8 d range, as shown in Table 2.
These high-®eld signals are explained in terms of
complex formation through the ±CHyN± bond. H6
(H9) proton signals d values are increasing with
respect to the substituents order of ±OCH3 , ±
CH3 , ±Br. This increasing is in accordance with
the electron-donating effect in the ±OCH3 . ±
CH3 . ±Br order.
±
±
1259
1280
1281
1286
1174
1070
1011
1173
1065
1032
1171
1065
1028
n(CC)
d(CH)
d(CCH)
d(CCH)
n(C±S)
(Ar±S)
n(Ni±N)
808
748
592
802
742
590
825
750
590
494
499
510
Single crystal X-ray diffraction method could not be
used, because of poor single crystal quality, to obtain
certain crystal and molecular structures. The unit cell
of nickel(II) complexes of N-(4-bromobenzylidene)-2-
mercaptoaniline, N-(4-methylbenzylidene)-2-mercap-
toaniline and N-(4-methoxybenzylidene)-2-mercaptoa-
niline were compared with the spectra of 2-(3,4,5-
trimethoxyphenyl)-benzothiazole [4].
parameters
mercaptoanilinato(nickel(II) (I) were determined by
of
bis(N-(4-methoxybenzylidene)-2-
using the xrd calculator program [7] as follows:
Ê
a ˆ 13.665(5);
b ˆ 12.983(5);
c ˆ 15.150(9) A;
Ê 3
The important vibrational bands of these complexes
were recorded in Table 1. In the infrared spectra of
these complexes, the bands observed at about
2850 cm21 were assigned to the C±H (CHyN)
stretching vibrations. It was shown that the formation
of the benzothiazole ring did not occur. The band of
S±H stretching vibration was not observed. There-
fore, it is believed that the {S,N}-chelated complexes
of Schiff bases were formed. In the infrared spectra of
2-(3,4,5-trimethoxyphenyl)-benzothiazole [4], the
band due to n(C±S) stretching vibration disappeared
in the IR spectra of complexes. Because of complex
formation, the band of CyN stretching vibration
shifts to a lower wavenumber in all metal complexes.
This shift suggests that coordination has taken place
through the nitrogen of the azomethine group.
According to the literature, (Ni±S) stretching
b ˆ 112.58(5)8; and V ˆ 2481.7(2) A . The probable
crystal systems for bis[N-(4-methylbenzylidene)-2-
mercaptoanilinato] nickel(II) (II) and bis[N-(4-bromo-
benzylidene)-2-mercaptoanilinato] nickel(II) (III)
are also monoclinic because the interplanar distances
of bis(N-(4-chlorobenzylidene)-2-mercaptoanilinato]
nickel(II) crystals [8] are in agreement with those of II
and III. These consistences were obtained using Table 3
and unit cell knowledge of bis(N-(4-chlorobenzyli-
dene)-2-mercaptoanilinato] nickel(II) [8].
alchemy 2000 packet program was used to mini-
mize the molecular energies [9]. The lowest energy
values have been determined as 88.973(7), 148.961(6)
and 90.595(7) kcal/mol for I, II and III, respectively.
The big energy value for II shows that the structures
of I and III are more stable than the structure of II.
The effect of this unstable form of II can also be seen

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S. Ide et al. / Journal of Molecular Structure 562 (2001) 1±9
7
Table 2
Proton chemical shifts of Ni(II) complexes. All values were assigned relatively to tetramethylsilane as internal standard
Proton chemical shifts (ppm)
X
1 (d)
2 (t)
3 (t)
4 (d)
5 (s)
6,9 (d)
7,8 (d)
±CH3 (s)
±OCH3 (s)
±Br
6.33
6.23
6.32
6.78
6.64
6.67
7.10
7.00
7.00
7.45
7.38
7.38
7.79
7.72
7.71
7.36
7.00
6.67
8.75
8.75
8.85
±
±
±CH3
±OCH3
2.34
±
±
3.74
Table 3
X-ray powder diffraction analysis of the title complexes
Ni(C14H12NSO)2
Ni(C14H12NS)2
Ni(C13H9NSBr)2
Ê
d (A)
Ê
d (A)
Ê
d (A)
2u (8)
I/I0
19.3
2u (8)
I/I0
2u (8)
I/I0
89.7
7.0
12.6
11.6
11.3
7.7
7.4
6.7
6.4
5.8
5.0
4.7
4.6
4.4
4.2
3.7
3.7
3.4
3.2
2.9
2.8
2.4
2.2
9.4
10.4
12.6
13.6
14.6
18.8
20.6
21.0
26.8
27.2
29.2
33.6
37.8
40.4
9.4
8.5
7.0
6.5
6.1
4.7
4.3
4.2
3.3
3.3
3.1
2.7
2.4
2.2
68.6
6.8
13.6
16.4
27.2
34.8
38.4
40.4
42.0
43.2
44.6
47.0
49.4
13.0
6.5
5.4
3.3
2.6
2.3
2.2
2.2
2.1
2.0
1.9
1.8
7.6
100.0
92.7
19.3
69.7
25.7
59.6
11.0
48.6
70.6
22.0
35.8
24.8
85.3
20.2
22.9
11.9
11.0
16.5
43.1
39.5
55.9
73.5
67.6
100.0
96.1
28.4
30.4
29.4
28.4
17.7
18.6
17.7
17.7
100.0
19.8
32.8
11.2
25.0
27.6
35.3
15.5
23.3
13.8
25.9
7.8
11.4
12.0
13.2
13.8
15.4
17.8
19.0
19.4
20.4
21.4
23.8
24.2
26.2
28.2
30.6
32.0
38.2
40.6

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S. Ide et al. / Journal of Molecular Structure 562 (2001) 1±9
8
Fig. 4. The most probable geometries of (A) Ni(C14H12NSO)2; (B) Ni(C14H12NS)2; and (C) Ni(C13H9NSBr)2.
Table 4
Some torsion angles of Ni(II) complexes
Angles
Ni(C14H12NSO)2
Ni(C14H12NS)2
Ni(C13H9NSBr)2
C20 ±N10 ±Ni±S10
C2±N1±Ni±S1
C8±N1±Ni±S1
C80 ±N10 ±Ni±S10
C80 ±N10 ±Ni±N1
C8±N1±Ni±N10
C2±N1±Ni±N10
C20 ±N10 ±Ni±N1
222.4
222.3
151.7
151.7
282.1
282.7
103.2
103.8
224.3
224.6
149.3
149.7
286.3
286.2
99.9
224.5
224.7
149.4
149.6
286.5
286.4
99.5
99.8
99.3
in the X-ray diffraction pattern of II. In this pattern,
the area under the peaks is larger than the others. This
condition may be explained by the effect of polycrys-
talline and unstable solid form. At the end of the
energy minimization studies, the most probable
structures of these complexes in gaseous form were
predicted as seen in Fig. 4.
all of the similar complexes [8±11]. But, as a result
of our energy minimizing studies, the valance
angles around Ni atoms for I, II and III were
found in the range of 103.1±135.4, 102.5±133.9
and 102.4±133.98, respectively. These differences
may be explained by the differences of the solid
state and the gas phases. All phenyl rings in the
title complexes are planar and the ®ve-membered
rings have envelope conformation. The Ni atom is
The Ni atoms have been coordinated in square
planar or distorted square planar con®guration in

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S. Ide et al. / Journal of Molecular Structure 562 (2001) 1±9
9
[5] S.E. Livingstone, A.E. Mihkelson, Inorg. Chem. 11 (1970)
2545±2551.
located on the tip of the envelope conformation in
each complex. Some torsion angles in relation with
the molecular conformation were given in Table 4.
[6] K. Nakamato, Infrared Spectra of Inorganic and Coordination
Compounds, Wiley, New York, 1963.
[7] X-ray Diffraction Calculator Program, Window Chem.
Software, TM. Inc. at 707, 864-0845, 1994.
È
References
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[8] F. Ercan, D. UlkuÈ, N. Ancõn, S.G. Oztas, M. TuÈzuÈn, Acta
Crystallogr. C 52 (1996) 1141±1143.
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