A.V. Zaidman et al. / Inorganica Chimica Acta 367 (2011) 29–34
31
solution of 3.45 g (14.22 mmol) of 1-(benzthiazole-2-yl)-3-fur-
ylhydrazone in 50 mL of DMF. When the addition was completed,
the resulted mixture was left for 20 min. Then the vigorously
stirred mixture was alkalized to pH ꢂ9 with a 2 N solution of so-
dium hydroxide and left for half an hour. After that a concentrated
solution of acetic acid was added to reach pH about 7 and left the
mixture for 10–15 h at rt. The precipitate was filtered off, washed
with water, air dried, and recrystallized from acetone.
Bis-1-phenyl-3-thiophenyl-5-(benzthiazole-2-yl)formazane (II),
bis-1-(2-methoxyphenyl)-3-furyl-5-(benzthiazole-2-yl)formazane
(III), bis-1-(2- methoxyphenyl)-3-thiophenyl-5-(benzthiazole-2-yl)
formazane (IV) were prepared similarly to compound I. Their char-
acteristics are given in Table 1.
cm3, Z = 8. The experiment completeness at h < 26.38° was 99.4%
-scanning at 1° step and 20-s exposure per frame, crystal-detec-
(x
tor distance 50 mm). To collect and edit the experimental data and
refine the unit cell parameters, we used the CrysAlis CD program
[6]. The structure was solved and refined using the SHELX program
package [7]. The refinement was carried out by the full matrix
least-squares method by F2 with all nonhydrogen atoms taken in
the anisotropic approximation. The hydrogen atoms were placed
in calculated positions and included in refinement in the rider
model in the isotropic approximation with dependent thermal
parameters.
The formazan molecule except its benzthiazole moiety is flat;
the atoms fit into the mean-square plane with a 0.1 Å deviation.
The benzthiazole cycle plane is turned relative to the rest of the
molecule at an angle of 6.4°. The bond lengths are typical for sys-
tems of this sort. In particular, a significant equalization of the
bond lengths is observed for the formazan moiety. The molecular
package is composed of oblique piles of molecules oriented along
axis a. The interplanar distance between molecules inside the piles
1,5-Bis(10-o-chlorophenyl-30-o-oxophenyl-50-benzthiazolylfor-
mazyl)-3-oxopentane (V) was synthesized according to Ref. [5].
A diazo solution, prepared from 0.42 mL of chloroaniline in
1 mL of HCl (1:1) and 0.23 g (3.33 mmol) of sodium nitrite in
5 mL of water, was added to a cooled solution of 1.0 g (1.6 mmmol)
of 1,5-bis(benzthiazolyl-2-hydrazone of salicylic aldehyde)-
3-oxopentane in a mixture of 10 mL of isopropanol and 30 mL of
DMF, acidified with concentrated HCl. Then the stirred mixture
was alkalized to pH 8–9 with a NaOH solution and left for an hour.
After that the mixture was neutralized to pH 6–7 with acetic acid.
The solution was evaporated; the resulted precipitate was washed
with water and dried.
is about 3.2 Å that suggests the possibility of intermolecular
p–p
contacts, in particular, between the
and methoxyphenyl substitutes.
p-systems of the benzthiazole
The structure parameters, including atom coordinates, of 1-(2-
methoxyphenyl)-3-thiophenyl-5-(benzthiazole-2-yl)formazane are
registered in the Cambridge Structural Database (CCDC 764964).
1,5-Bis(10-o-methoxyphenyl-30-o-oxophenyl-50-benzthiazolyl-
formazyl)-3-oxopentane (VI) was prepared similarly to com-
pound V.
2.4. General procedure for ethylene oligomerization
Ethylene oligomerization was carried out in toluene solutions in
a 200 mL stainless steel jacketed reactor equipped with a magnetic
stirrer, manometer, and ethylene pressure control system. The
reactor jacket was supplied with thermostat-controlled water.
The cleaned and inert gas washed reactor was kept evacuated for
1–2 h at 353 K. Then the reactor, heated up to a required temper-
ature, was charged with a solvent and ethylene. Nickel formaza-
nate and alkylaluminum dichloride, the catalyst components,
were successively injected as solutions with metallic syringes from
Schlenk vessels. After an hour reaction period the reactor was
cooled and an excess of ethylene vented. The total volume (mass)
of the products was determined and the reaction quenched by
addition of 10% HCl. An aliquot of the organic phase was taken
for GC analysis.
2.2.2. 1-(2-Chlorophenyl)-3-furyl-5-(benzthiazol-2-yl)formazane
(VII)
A diazonium salt solution, prepared from 0.40 g (3.1 mmol) of
o-chloroaniline in isopropanol and 0.21 g. (3.12 mmol) of sodium
nitrite in 3 mL of water, was slowly added to a stirred and cooled
to ꢂ0 °C solution of 0.75 g (3.1 mmol) of furaldehyde benzthiazol-
yl-2-hydrazone in 30 mL of isopropanol acidified with 2 mL of con-
centrated hydrochloric acid. Then the reaction mixture was
alkalized to pH 8–9 with a 2 N NaOH, left for an hour, acidified
to pH 7 with acetic acid, and left for 3 h at rt. The resulted brown
precipitate was filtered off, washed with water, air dried, and
recrystallized from acetone.
1-(2-Chlorophenyl)-3-thiophenyl-5-(benzthiazol-2-yl)formaz-
ane (VIII), 1-(2-chlorophenyl)-3-pyridinyl-5-(benzthiazol-2-yl)
formazane
(IX),
1-(2-methoxyphenyl)-3-thiophenyl-5-(ben-
zthiazol-2-yl)formazane (X) were prepared similarly to
compound VII.
3. Results and discussion
3.1. Synthesis and characterization of nickel complexes
2.2.3. Nickel(II) bis-1-phenyl-3-furyl-5-(benzthiazol-2-yl)formazanate
(1Ni)
It was previously reported [8] that the ratios of formazane
tautomers and conformers are dependent on the character of the
substitutes and aggregate state. For example, according to the
single-crystal X-ray diffraction data formazane X has the chelate
A
hot water solution of 0.21 g (0.85 mmol) of Ni(CH3-
COO)2ꢃ4H2O was added to a warmed and stirred solution of 6 g
(0.85 mmol) of the formazane in 20 mL of acetone. After warming
during 15 min the mixture was allowed to get cooled at rt. The pre-
cipitate was filtered off, washed with warm water, and air dried.
Nickel(II) formazanates 2Ni–10Ni were synthesized similarly to
1Ni. The characteristics of the prepared metal complexes are given
in Table 1.
E1,2Z2,3 3,4-configuration (Fig. 3), with the NH group proton located
Z
at the benzthiazole nitrogen. However, when dissolved in DMSO-d6
both mono- (VII–X) and bis-formazanes I–VI exist substantially in
the forms of disclosed tautomers as evidenced by the NH proton
chemical shifts dNH = 8.2–9.0 ppm [9].
FTIR spectra of 3- thiophenylformazanes II and IV show the
band mNH at 3338 cmꢁ1 pointing to the amine-tautomeric form of
the ligand [10]. 3-Furyl-containing formazans I and III exist in
the amine-imine equilibrium that supported by the bands at
3419 and 3338 cmꢁ1 in their spectra.
It is known [11] that formazanes readily form complexes with
nickel(II) ions. When ethanol solutions of model compounds VII–
X (Fig. 4A) were studied using spectrophotometric titration, the
resulted spectral pattern had a single isosbestic point associated
2.3. Crystal structure determination
Single-crystal X-ray diffraction analysis was performed at
295(2) K with an Xcalibur 3 autodiffractometric system equipped
with a CCD detector. Crystals of 1-(2-methoxyphenyl)-3-thio-
phenyl-5-(benzthiazole-2-yl)formazan (green needles) belong to
the orthorhombic system. Unit cell parameters: a = 8.3295(5), b =
20.9193(8), c = 21.7123(10) Å, V = 3783.3(3) Å3,
q(calc.) = 1.385 g/