2
A. Erdem et al. / Journal of Molecular Structure 1220 (2020) 128556
hydrogenation [12] and the trend in these work is dedicated to
increase or alter their selectivity, stability and activity by steric and
corresponding benzyl halide derivative (11.0 mmol) (benzyl bro-
mide,1.92 g; 2-methylbenzyl chloride,1.56 g; 2,4,6-trimethylbenzyl
chloride, 1.86 g; 2,3,5,6-tetramethylbenzyl chloride, 2.01 g;
2,3,4,5,6-pentamethylbenzyl chloride, 2.16 g; 1-(chloromethyl)
naphthalene, 2.00 g) was added to the reaction mixture and the
mixture was refluxed for 8h. The solvent was removed in vacuo,
electronic properties. The
p-acceptor nitrogen-containing ligands
such as N-heteroaromatic structure like pyridine- or quinoline-
based chelating diamine bidentate ligand 2-(N-aromatic
structure)-1H-benzimidazoles on ruthenium center in complex
have enlarged the scope of TH reactions because of these NN-type
ligands can be readily derivatized and strongly bonded to metal
and the residue was filtered by adding CH
allowed to crystallize by adding hexane. For characterization data
3
L -L14, please see supporting materials.
2 2
Cl . The filtrate was
[3b,7a,13]. In such ligands, the electronic and steric properties on
the benzimidazol can be easily modified. Also, this area has
attracted increasing interest related to environmentally sustainable
processing, simple product separation, and pH dependent selec-
2.3. General procedure for the synthesis of [RuCl(L1-14)(
cymene)]Cl (C1-14
h
6- p-
)
II
tivity in aqueous medium [14]. For example, the Ru complexes [(p-
2
þ
6
þ
cymene)Ru(NLN)(OH
2
)]
,
[(h
-C
6
Me
6
)Ru(phen)Cl]
and [(p-
2 2
The ligands (1.0 mmol) and [RuCl (p-cymene)] (0.5 mmol)
þ
cymene)Ru(NLN)Cl] where NLN are pyridine-based ligands and
phen is 1,10-phenanthroline and other related complexes [3b,15]
have been shown to catalyze the reduction of ketones (such as
cyclohexanone and acetophenone) to alcohols and imines [16]. The
research for TH reactions and efficient catalysts continues to create
great interest in ruthenium catalysis. In spite of many efficient the
ruthenium complexes based benzimidazole ligands which are
biologically effective and medicinally significant compounds [17]
have been investigated [3b,7a,18], the availability of metal com-
were refluxed in ethanol for 8 h. At the end of this time, the mixture
was cooled at room temperature. The solvent was evaporated to
some extent. Then, the mixture was precipitated by addition of
diethyl ether. The precipitate was filtered off, washed and dried.
The product was recrystallized from EtOH/Et O.
2
2.4. X-ray crystallography
Intensity data of the compounds were collected with a STOE
IPDS II diffractometer at room temperature using graphite-
monochromated Mo Ka radiation by applying the u-scan method.
0
plexes containing 2-(2 -quinolyl)benzimidazoles remains limited,
and only few examples have been published [7a,19].
In this report we expand on previous work involving the use of
Data collection and cell refinement were carried out using X-AREA
[22] while data reduction was applied using X-RED32 [22]. The
structure solutions were obtained using SIR2019 [23] and SHELXL-
2018 [24] was applied for the refinements. The coordinates of the
water H atom were determined from a difference Fourier map and
refined freely [OeH ¼ 0.85(4)-0.88(3) Å]. The remaining H atoms
were inserted in idealized positions and treated using a riding
model, fixing the bond lengths at 0.86, 0.93, 0.97 and 0.96 Å for NH,
CH, CH and CH atoms, respectively. The displacement parameters
II
the half-sandwich Ru complexes that contain benzyl substituted
0
2
-(2 -quinolyl)benzimidazole ligands and illuminate structural
characterization with X-ray diffraction technique (Fig. 1) [7a], we
herein report the synthesis of ruthenium complexes, their thermal
and electrochemical properties and also their catalytic studies in
the catalytic transfer hydrogenation of acetophenone.
2
. Experimental
2
3
of the H atoms were fixed at Uiso(H) ¼ 1.2Ueq (1.5Ueq for CH
3
). The
2.1. General considerations
crystallographic data and refinement parameters are summarized
in Table 1. OLEX2 [25] was used to prepare artwork representations.
1 2 2
L , L h -p-cymene)Ru(m-Cl)] dimer were obtained ac-
and [( 6
cording to the published procedure in the literature [7a,20]. Infor-
mation about the devices and techniques used is given in the
supporting information section.
3
. Results and discussions
3.1. Synthesis and characterization of compounds
2
.2. Synthesis of ligands
2
-(1H-benzimidazol-2-yl)quinoline (L
1
, QuBim) [20] and 2-
QuDmBim)
(
[
5,6-dimethyl-1H-benzimidazol-2-yl)quinoline (L ,
26] substances also used as chelating ligands were synthesized in
2
2.2.1. General procedure for synthesis of 2-(1H-benzimidazol-2-yl)
quinoline (L
1
) and 2-(5,6-dimethyl-1H-benzimidazol-2-yl)quinoline
2
(L )
Quinaldic acid (20.0 mmol, 3.46 g) and corresponding diamine
derivative (20.0 mmol) (o-phenylenediamine, 2.163 g or 4,5-
dimethyl-o-phenylenediamine, 2.724 g) were stirred in poly-
ꢀ
phosphoric acid (PPA) (40 mL) for 4h at 200 C under argon. At the
end this time, the green-colored molten fluid was poured into iced
water. Then the ammonium hydroxide was added to make the pH:
9
and obtaining solid was filtered off. The precipitate was boiled
with EtOH for 2h with activated charcoal. Finally, the product was
recrystallized by EtOH. For characterization data L
1
and L
2
, please
see supporting materials.
2.2.2. General procedure for the synthesis of other N^N-type ligands
(
L
3-14
)
L
3
-L
8
1 9
ligands were synthesized starting from L while L -L14
ligands were synthesized starting from L
literature procedure [7a,21]. (10.0 mmol, 2.45 g) or
10.0 mmol, 0.27 g) and KOH (10.0 mmol, 0.56 g) were stirred in a
2
by modification of the
L
1
L
2
(
ꢀ
Schlenk tube at 40 C for 2h in PhMe. At the end of the time, the
Fig. 1. The quinoline based ligands synthesized in the previous study.
?zdemir, Nam?k
