The first used half sandwich ruthenium(II) complexes bearing benzimidazole moiety for N-alkylation of amines with alcohols This paper is dedicated to Professor Irina P. Beletskaya on the occasion of her contribution to catalysis.

Article abstract of DOI:10.1016/j.jorganchem.2014.01.007

Half sandwich ruthenium(II) complexes were synthesized from [RuCl ₂(η⁶-p-cymene)]₂ and N-substituted benzimidazole. All new compounds were characterized by elemental analysis, ¹H NMR, ¹³C NMR, and IR spectroscopy. Aminoarenes were readily converted into secondary amines by the reaction at 150 C with benzyl alcohol and in the presence of a catalytic amount of novel ruthenium complexes. All of [RuCl₂(η⁶-p-cymene)(N-substituted benzimidazole)] complexes were the most effective catalyst for N-alklyation reaction using borrowing hydrogen methodology.

Full text of DOI:10.1016/j.jorganchem.2014.01.007

Journal of Organometallic Chemistry 755 (2014) 134e140
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
The first used half sandwich ruthenium(II) complexes bearing
benzimidazole moiety for N-alkylation of amines with alcohols
_
*
Serpil Demir, Feyzullah Cos¸ kun, Ismail Özdemir
Inönü University, Faculty of Science and Art, Department of Chemistry, 44280 Malatya, Turkey
a r t i c l e i n f o
a b s t r a c t
Half sandwich ruthenium(II) complexes were synthesized from [RuCl2(h
6-p-cymene)]2 and N-
Article history:
substituted benzimidazole. All new compounds were characterized by elemental analysis, 1H NMR, 13
C
Received 11 November 2013
Received in revised form
16 December 2013
NMR, and IR spectroscopy. Aminoarenes were readily converted into secondary amines by the reaction at
150 ꢀC with benzyl alcohol and in the presence of a catalytic amount of novel ruthenium complexes. All
Accepted 8 January 2014
of [RuCl2(
alklyation reaction using borrowing hydrogen methodology.
h
6-p-cymene)(N-substituted benzimidazole)] complexes were the most effective catalyst for N-
This paper is dedicated to Professor Irina P.
Beletskaya on the occasion of her contribu-
tion to catalysis.
Ó 2014 Elsevier B.V. All rights reserved.
Keywords:
Half sandwich ruthenium(II) complex
N-Substituted benzimidazole
N-Alkylation
Borrowing hydrogen methodology
Secondary amine
1. Introduction
hydrogen from the alcohol 1 to form the aldehyde 2. This aldehyde
can react with an amine to form an imine 3, and the hydrogen is
then returned to give a CN bond in product 4 (Scheme 1) [4,9e11].
Regarding the fundamental principles of a green transformation,
advantageous synthetic methods avoiding mutagenic and waste-
producing reagents are of extraordinary interest in both academic
and industrial work [12,13]. Most common catalysts used for the
alkylation of amines using alcohols are based on Ru [14,15] and Ir
[16,17]. Catalysts derived from other metals, such as Au [18], Ag [19],
Cu [20], Fe [21], Ni [22], Os [23], Pd [24], and Rh [25] have also been
explored, and many of them showed very good activity and selec-
tivity under moderate to higher temperatures (typically 100e
200 ꢀC). The first examples of homogeneous catalysts for the alkyl-
ation of amines by alcohols were published independently by Grigg
[26] and Watanabe [27]. Many of these catalysts require rather
forcing conditions, although milder conditions have been employed
by Yamaguchi and co-workers with Cp*IrCl2 [28] and by Beller’s
group using Ru3(CO)12 with bulky phosphines [29] as well as a report
on the use of CpRuCl(PPh3)2 [30]. Ruthenium complexes have been
commonly used as catalysts for the N-alkylation of amines via a
hydrogen autotransfer process, particularly RuCl2(PPh3)3 and its
derivatives [31,32]. In addition, Albretch et al. just recently described
the use of ruthenium triazolylidene complexes as catalysts for
oxidative coupling of alcohols and amines [33]. On the other hand,
Alkylated amines are important chemicals for many uses such as
synthetic intermediates, pharmaceuticals, agrochemicals, and bulk
chemicals. The alkylation of amines is usually achieved by a sub-
stitution reaction with an alkyl halide, although these reactions can
lead to over alkylation, and the toxicity of many alkyl halides and
related alkylating agents can be problematic [1]. The N-alkylation of
primary amines with alcohols has been recently focused as a new
efficient method for the production of alkylated amines [2]. The use
of alcohols as direct alkylating agents for amines is appealing since
the reaction is atom economical, the alcohol is likely to be less toxic
than the corresponding alkyl halide, and the only reaction
byproduct is water. Due to the poor electrophilicity of simple al-
cohols, the direct reaction between amines and alcohols is not
readily achieved. Recently, the transition metal-catalyzed dehy-
drative N-alkylation of amines and amides using alcohols as the
greener alkylating reagents, namely the borrowing of hydrogen or
hydrogen autotransfer methodology has become a useful way to
achieve versatile amine and amide derivatives [3e8]. This strategy
typically uses ruthenium or iridium as the catalyst and takes the
* Corresponding author. Tel./fax: þ90 (422)3410212.
_
E-mail address: ismail.ozdemir@inonu.edu.tr (I. Özdemir).
0022-328X/$ e see front matter Ó 2014 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.jorganchem.2014.01.007

S. Demir et al. / Journal of Organometallic Chemistry 755 (2014) 134e140
135
possibility of using benzimidazole derivatives as ligands because
they are structurally simple, readily available, and inexpensive, and
they allow for simplistic introduction of various substituents into
their structure.
The N-substituted ligands (L1eL6) were prepared by the reac-
tion of benzimidazole and base with alkyl halides in one step re-
action (Scheme 2).
The synthesis and characterization of L2 ligand have been indi-
cated by R.W. Hartmann in 2011 [43]. All new ligands were isolated as
colorless and air-stable solids. They were characterized by 1H NMR,
13C NMR, IR, elemental analysis techniques which support the pro-
posed structures. The analytical data are in good agreement with the
compositions proposed for all the ligands are presented in Table 1.
Coordination was immediate, as a change of color from red to
orange. All the complexes were isolated as air-stable, non-hygro-
scopic solids and soluble in dimethylformamide, dimethylsulfoxide
and halogenated solvents such as chloroform, dichloromethane but
insoluble in petroleum ether, diethyl ether, and n-hexane and do
not show any signs of decomposition in solution upon exposure to
Scheme 1. Alkylation of amines with alcohols using the borrowing hydrogen strategy.
Crabtree and co-workers have also reported the use of a ruthenium
pyrimidine-NHC complex as a catalyst for the N-alkylation of amines
[17]. To the best of our knowledge, there are no previous reports of
borrowing hydrogen methodology being performed by half sand-
wich ruthenium (II) complexes bearing benzimidazole ligand.
Therefore we report the preparation of ruthenium(II) complexes
having aliphatic and chloro, dichloro and methoxy bearing benzylic
functionalized N-substituted benzimidazole ligands, and their cata-
lytic activity in the alkylation of amines with alcohols. The first ex-
amples of the use of all new complexes as catalyst for borrowing
hydrogen methodology are reported and found to be especially
beneficial for the synthesis of secondary amines.
air for days. New benzimidazole ligands and [RuCl2(h
6-p-cyme-
ne)(N-substituted benzimidazole)] complexes have been two
important advantage. The first, all compounds can be synthesized
in a single step, latter the products both in solution and in the solid
state is stable structure. The 1H and 13C NMR of L1eL6 showed that
the NCHN resonances occurred between 7.93e8.22 ppm and
143.4e144.9 ppm, respectively. The values of complexes (1e6) also
showed that the NCHN resonances occurred between 8.41e
8.45 ppm and 144.4e145.0 ppm, respectively. The 1H NMR values
showed that the C2eH signals shifted to low fieldin the ruthenium
complexes as compared to corresponding ligand due to an electron
withdrawing effect of the metal center. The presence of the eC]
2. Results and discussion
Ne group in the complexes was verified by the
between 1507 and 1522 cmꢁ1. The NMR and IR values are similar to
those found for other N-substituted benzimidazole and [RuCl2(h6
y(C]N) vibrations
2.1. Synthesis and characterization of ligands and their ruthenium
complexes
-
p-cymene)(N-substituted benzimidazole)] complexes [39e43]. The
analytical data are in good agreement with the general molecular
formula proposed for all the complexes (Table 1).
Nitrogen containing ligands have been extensively studied in
coordination chemistry, and have been shown important applica-
tions in the fields of homogeneous catalysis and organic synthesis
due to the easy manipulations and high reactivities of their tran-
sition metal complexes [34]. In contrast to phosphine type ligands,
the low toxicity and stability of nitrogen based ligands, such as
benzimidazole derivatives, have attracted the interest of synthetic
organic chemists. However, there are few reports of highly catalytic
reactive complexes bearing nitrogen ligands, although there are
many reports of nitrogen ligands [35e43]. We are interested in the
2.2. Catalytic application of ruthenium complexes for N-alkylation
reaction
An environmentally benign approach is the N-alkylation of
amines with readily available alcohols using borrowing hydrogen
methodology [3e11]. The N-alkylation has been mainly studied in
Scheme 2. Synthesis of N-substituted benzimidazole ligands.

136
S. Demir et al. / Journal of Organometallic Chemistry 755 (2014) 134e140
Scheme 3. Synthesis of half sandwich ruthenium (II) complexes.
the presence of homogeneous metal catalysts [27,44e46]. But to
the best of our knowledge, there are no previous reports of
borrowing hydrogen methodology being performed by half sand-
wich ruthenium complex bearing benzimidazole moiety. This
prompted us to test the catalytic activities of new ruthenium
complexes for N-alkylation of amines with alcohols. Initially, we
studied the reaction of aniline with benzyl alcohol as a model re-
action. The reaction was carried out using aniline (0.55 mmol) and
benzyl alcohol (0.5 mmol) in toluene in the presence of [RuCl2(p-
cymene)(L1)] (1) as catalyst (1.0 mol%) and base (0.5 mmol) at
150 ꢀC for 15 h. The results are summarized in Table 2.
When the reaction was carried out without a base, neither
amine nor imine was formed (Table 2, entry 1). The reaction was
considerably accelerated by addition of a base. When the reaction
was carried out in the presence of tKOBu, N-benzylaniline was
formed in an excellent yield (>99%), while moderate yield (67%)
was observed with KOH base (Table 2, entries 2 and 3). On the other
hand, desired product was not observed with Cs2CO3 and NaOH
bases (Table 2, entries 4 and 5). After optimization of the reaction
conditions, the N-alkylation reactions of amines with benzyl
alcohol and p-methylbenzyl alcohol were tested (Table 3).
between benzyl alcohol and primary amines. Surprisingly, the re-
action under similar conditions using potassium hydroxide at
100 ꢀC for 24 h gave only imine in good yield (Table 3, entry 2). With
higher temperatures (150 ꢀC) amine formation was observed
instead of the expected imine (Table 3, entry 4). However in similar
reaction condition there was no formation of any product at 5 h
(Table 3, entry 5). Corresponding imine was obtained as a minor
product when we used equal amounts of aniline (0.5 mmol) and
benzyl alcohol (0.5 mmol) (Table 3, entries 6e11). The temperature
of the reaction was found to have a strong impact on the reaction
rate. The temperature could be lowered, but in this case the
selectivity decreases. (130 ꢀC, 79% amine, Table 3, entry 12
compared 150 ꢀC, >99% amine, Table 3, entry 13). All catalysts have
been good activity for the synthesis of N-benzyl amine (Table 3,
entries 13e18). As previously reported for related Ru catalysts such
as pyrimidineeNHCeRu [17], the N-alkylation of benzyl alcohol
and aniline was retarded at 45h-110 ꢀC. In the present catalytic
system using [RuCl2(h
6-p-cymene)(N-substituted benzimidazole)]
complexes was particularly effective for the same reaction at 15 h-
150 ꢀC. Complex 1 was chosen for further optimization studies
(catalyst loading and temperature) due to its high reactivity. With
the best catalyst full conversion was obtained 10 h and the lower
the catalyst loading (0.25 mol%) (Table 3 entries 19,28 and 20,29,30
respectively). The reaction of aniline with p-methylbenzyl alcohol
successfully converted corresponding secondary amine (Table 3
entries 22,24,26 and 28e30). The reaction of 2,4-dimethylaniline
with benzyl alcohol/p-methylbenzyl alcohol transformed into the
corresponding N-benzyl amines (Table 3 entries 31,32). As shown in
Table 3 electronic and steric effects of benzimidazole substituents
was not caused remarkable difference on the catalytic performance.
It is interesting to explore the byproducts of the N-alkylation
reactions. By tracing the reactions by using GCMS, imine was also
observed as the major or minor byproduct in all of the reactions
Table 1
Selected analytical data for the ligand (L1eL6) and ruthenium complexes (1e6).
Compound Isolated
yield (%)
M.p. (ꢀC) y(C
]
N) (cmꢁ1
13C NMR
C(2) (ppm) H(2) (ppm)
1H NMR
)
L1
L2
L3
L4
L5
L6
1
2
3
4
5
92
63
92
88
89
81
69
72
85
78
68
75
128e129 1493
143.4
144.0
143.9
143.7
143.5
144.9
144.9
144.9
144.8
144.9
144.4
145.0
8.15
7.94 [43]
7.94
7.97
7.93
8.22
8.42
8.45
8.41
8.55
8.45
8.45
68e69
64e65
1490
1492
137e138 1450
3. Conclusion
63e64
44e45
1493
1456
232e233 1507
228e229 1509
222e223 1512
221e222 1516
235e236 1522
214e215 1513
In conclusion, inexpensive and easily prepared half sandwich
ruthenium (II) complexes bearing benzimidazole moiety have been
shown to be an active, stable, versatile, and highly selective catalyst
for the selective monoalkylation of aromatic amines. The protocol
has been applied for the first time successfully by this type com-
plexes. In future N-alkylation reaction can be improved for sec-
ondary amine and different alcohol.
6
Reaction of 1:2 ratio of [Ru(p-cymene)Cl2]2 with L in toluene at 110 ꢀC for 5 h
afforded half sandwich ruthenium (II) complexes (1e6) in good yield (Scheme 3).

S. Demir et al. / Journal of Organometallic Chemistry 755 (2014) 134e140
137
Table 2
Effects of bases on N-alkylation of aniline with benzyl alcohol catalyzed by 1.
Entry
Base
Yield (%)
A
B
1
2
3
4
5
No
e
e
tKOBu
KOH
>99
67
e
33
e
Cs2CO3
NaOH
e
e
Reaction conditions: Aniline (0.55 mmol), benzyl alcohol (0.5 mmol), cat. (1.0 mol%), base (0.5 mmol), toluene (2 mL), 150 ꢀC-15 h.
4. Experimental
under argon in flame-dried glassware using standard Schlenk
techniques. Chemicals were obtained from Sigma Aldrich and
Fluka. Melting points were determined in glass capillaries under
air with an Electrothermal-9200 melting point apparatus. FT-IR
spectra were recorded as KBr pellets in the range 400e
4000 cmꢁ1 on a Perkin Elmer Spectrum 100. 1H and 13C NMR
4.1. General procedures
All reactions for the preparation of N-substituted benzimid-
azole as ligand and their ruthenium complexes were carried out
Table 3
N-Alkylation of anilines with benzyl alcohol derivatives in the presence of [RuCl2(p-cymene)(L1eL6)].
Entry
Ru complex
Temp./time/base
R
R’
Yield (%)
A
B
1
2
3
4
1
1
4
1
1
1
2
5
3
6
4
1
1
2
3
4
5
6
1
1
1
1
2
3
4
5
6
1
1
1
1
1
100 ꢀC/24 h/tKOBu
100 ꢀC/24 h/KOH
100 ꢀC/24 h/KOH
150 ꢀC/15 h/KOH
150 ꢀC/5 h/tKOBu
150 ꢀC/15 h/tKOBu
150 ꢀC/15 h/tKOBu
150 ꢀC/15 h/tKOBu
150 ꢀC/15 h/tKOBu
150 ꢀC/15 h/tKOBu
150 ꢀC/15 h/tKOBu
130 ꢀC/15 h/tKOBu
150 ꢀC/15 h/tKOBu
150 ꢀC/15 h/tKOBu
150 ꢀC/15 h/tKOBu
150 ꢀC/15 h/tKOBu
150 ꢀC/15 h/tKOBu
150 ꢀC/15 h/tKOBu
150 ꢀC/10 h/tKOBu
150 ꢀC/15 h/tKOBu
150 ꢀC/15 h/tKOBu
150 ꢀC/15 h/tKOBu
150 ꢀC/15 h/tKOBu
150 ꢀC/15 h/tKOBu
150 ꢀC/15 h/tKOBu
150 ꢀC/15 h/tKOBu
150 ꢀC/15 h/tKOBu
150 ꢀC/10 h/tKOBu
150 ꢀC/15 h/tKOBu
150 ꢀC/15 h/tKOBu
150 ꢀC/15 h/tKOBu
150 ꢀC/15 h/tKOBu
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
50
e
50
100
71
33
e
29
67
e
5
6a
98
83
82
94
79
92
79
2
7a
17
18
6
21
8
8a
9a
10a
11a
12
13
14
15
16
17
18
19
20b
21c
22
23
24
25
26
27
28
29b
30c
31
32
21
>99
>99
>99
>99
>99
>99
>99
>99
95
>99
75
>99
97
>99
65
>99
>99
>99
83
H
H
H
H
H
25
25
3
p-CH3
p-CH3
p-CH3
p-CH3
p-CH3
p-CH3
p-CH3
p-CH3
p-CH3
H
35
2,4-(CH3)
2,4-(CH3)
17
28
p-CH3
72
Reaction conditions: Aniline (0.55 mmol), benzyl alcohol (0.5 mmol), cat. (1.0 mol%), base (0.5 mmol), toluene (2 mL), 150 ꢀC-15 h.
a
Aniline (0.5 mmol).
Cat. (0.5 mol%).
Cat. (0.25 mol%).
b
c

138
S. Demir et al. / Journal of Organometallic Chemistry 755 (2014) 134e140
spectra were recorded with a Varian AS 400 Merkur spectrometer
operating at 400 MHz (1H), 100 MHz (13C) in CDCl3 with tetra-
methylsilane as an internal reference. Coupling constants (J values)
are given in hertz. NMR multiplicities are abbreviated as follows:
4.2.1.5. N-(Methylcyclobutane)benzimidazole, L5. Yield:1.66g(89%).
FT-IR y(CN): 1493 cmꢁ1, m.p.: 63e64 ꢀC. Anal. Calc. for C12H14N2: C,
77.38; H, 7.58; N, 15.04. Found: C, 77.35; H, 7.54; N: 15.01%. 1H NMR
(399.9 MHz, CDCl3)
d
(ppm) ¼ 7.93 (s, 1H, NCHN), 7.85e7.79 (m, 1H,
s
¼
singlet,
d
¼
doublet,
t
¼
triplet, hept
¼
heptet, and
NC6H4N), 7.44e7.39 (m, 1H, NC6H4N), 7.35e7.26 (m, 2H, NC6H4N), 4.17
(d, 2H, J ¼ 7.2 Hz, CH2CH(CH2)2CH2), 2.89 (hept., 1H, J ¼ 7.5 Hz,
CH2CH(CH2)2CH2), 2.13e2.03 (m, 2H, CH2CH(CH2)2CH2), 2.00e1.76
(m, 4H, CH2CH(CH2)2CH2). 13C NMR (100.5 MHz, CDCl3)
m ¼ multiplet signal. All catalytic reactions were monitored on an
Agilent 6890N GC system by GC-FID with an HP-5 column of 30 m
length, 0.32 mm diameter and 0.25
mm film thickness. Column
chromatography was performed using silica gel 60 (70e
230 mesh). Solvent ratios are given as v/v.
d
(ppm) ¼ 144.3 (NCHN), 143.9, 134.5, 122.7, 121.8, 119.9, 110.9
(NC6H4N), 49.4 (CH2CH(CH2)2CH2), 35.4 (CH2CH(CH2)2CH2), 25.7
(CH2CH(CH2)2CH2), 18.0 (CH2CH(CH2)2CH2).
4.2. Synthesis and characterization of 1-alkylbenzimidazole ligand
(L1eL6)
4.2.1.6. N-(2-Ethylbutane)benzimidazole, L6. Yield: 1.64 g (81%). FT-
IR y(CN): 1456 cmꢁ1, m.p.: 44e45 ꢀC. Anal. Calc. for C13H18N2: C, 77.18;
H, 8.97; N, 13.85. Found: C, 77.15; H, 8.94; N: 13.81%. 1H NMR
4.2.1. General procedure for the preparation of the 1-
alkylbenzimidazole
(399.9 MHz, CDCl3)
d
(ppm) ¼ 8.22 (s, 1H, NCHN), 7.66e7.55 (m, 2H,
Benzimidazole (10 mol) was added to a solution of NaH
(10 mol) in dry THF (30 mL), the mixture was stirred for 1 h at
room temperature, and the corresponding alkyl halides (10.1 mol)
was added dropwise and heated for 8 h. The solvent was removed
in vacuum, after that dichloromethane (50 mL) was added in the
Schlenk tube. The mixture was filtered and then the salt was
separated from solution. The solution was concentrated and
diethyl ether was added. The colorless product was obtained as a
crystal.
NC6H4N), 7.27e7.17 (m, 2H, NC6H4N), 4.13 (d, 2H, J ¼ 7.25 Hz,
CH2CH(CH2CH3)2, 1.83(hept., 1H, J ¼ 6.75 Hz, CH2CH(CH2CH3)2), 1.25
(p, 4H, J ¼ 7.5 Hz, CH2CH(CH2CH3)2), 0.86 (t, 6H, J ¼ 6.9 Hz,
CH2CH(CH2CH3)2). 13C NMR (100.5 MHz, CDCl3)
d
(ppm) ¼ 144.9
(NCHN), 143.9, 134.5, 122.7, 121.8, 119.9, 110.9 (NC6H4N), 47.9
(CH2CH(CH2CH3)2), 39.2 (CH2CH(CH2CH3)2), 23.2 (CH2CH(CH2CH3)2),
10.8 (CH2CH(CH2CH3)2).
4.3. Synthesis and characterization of the half sandwich
ruthenium(II) complexes (1e6)
4.2.1.1. N-(3,4-Dichlorobenzyl)benzimidazole, L1. Yield: 2.55
(92%). FT-IR y(CN): 1493 cmꢁ1, m.p.: 128e129 ꢀC. Anal. Calc. for
14H10N2Cl2: C, 60.67; H, 3.64; N, 10.11. Found: C, 60.62; H, 3.66; N:
10.18%. 1H NMR (399.9 MHz, CDCl3)
g
4.3.1. General procedure for the preparation of the half sandwich
ruthenium(II) complexes
C
d
(ppm) ¼ 8.15 (s, 1H, NCHN),
A solution of N-alkylbenzimidazole (1.0 mol) and [RuCl2(p-
cymene)]2 (0.5 mol) in 10 mL toluene was heated under reflux for
5 h. Upon cooling to room temperature, orange crystals of 1e6 were
obtained. The crystals were filtered off, washed with diethyl ether
(3 ꢂ 15 mL) and dried under vacuum.
7.90e7.85 (m, 1H, NC6H4N), 7.48e7.25 (m, 5H, NC6H4N and
CH2C6H3Cl2-3,4), 7.03e6.99 (m, 1H, NC6H4N), 5.37 (s, 2H,
CH2C6H3Cl2-3,4). 13C NMR (100.5 MHz, CDCl3)
(NCHN), 142.9, 135.6, 133.5, 133.4, 132.6, 131.1, 128.9, 126.2, 123.6,
122.8, 120.5109.9 (NC6H4N and CH2C6H3Cl2-3,4), 47.8 (CH2C6H3Cl2-
3,4).
d
(ppm) ¼ 143.4
4.3.1.1. Dichloro-(N-(3,4-dichlorobenzyl)benzimidazole)(p-cymene)
ruthenium(II), 1. Yield: 0.40 g (69%). FT-IR y(CN): 1507 cmꢁ1, m.p.:
232e233 ꢀC. Anal. Calc. for C24H24Cl4N2Ru: C, 49.41; H, 4.15; N, 4.80.
Found: C, 49.45; H, 4.12; N:4.76%. 1H NMR (399.9 MHz, CDCl3)
4.2.1.2. N-(4-Chlorobenzyl)benzimidazole, L2. Synthesis and char-
acterization data has been given by R.W. Hartmann [43].
d
(ppm) ¼ 8.42 (s, 1H, NCHN), 8.03 (d, 1H, J ¼ 8.4 Hz, NC6H4N), 7.36e
7.14 (m, 6H, NC6H4N and CH2C6H3Cl2-3,4), 5.55 (d, 2H, J ¼ 6.0 Hz,
(CH3)2CHC6H4CH3-4), 5.42 (d, 2H, J ¼ 6.0 Hz, (CH3)2CHC6H4CH3-4),
4.2.1.3. N-(4-Methoxybenzyl)benzimidazole, L3. Yield: 2.19 g (92%).
FT-IR y(CN): 1492 cmꢁ1, m.p.: 64e65 ꢀC. Anal. Calc. for C15H14N2O: C,
75.61; H, 5.92; N, 11.76. Found: C, 75.65; H, 5.90; N: 11.77%. 1H NMR
4.97 (s, 2H, CH2C6H3Cl2-3,4), 2.77 (hept., 1H,
J
¼
6.0 Hz,
(CH3)2CHC6H4CH3-4), 2.11 (s, 3H, (CH3)2CHC6H4CH3-4), 1.24 (d, 6H,
(399.9 MHz, CDCl3)
d
(ppm) ¼ 7.94 (s, 1H, NCHN), 7.87e7.82 (m, 1H,
J ¼ 6.9 Hz, (CH3)2CHC6H4CH3-4). 13C NMR (100.5 MHz, CDCl3)
NC6H4N), 7.35e7.23 (m, 3H, NC6H4N), 7.16 (d, 2H, J ¼ 11.1 Hz,
CH2C6H4(OCH3)-4), 6.89 (d, 2H, J ¼ 11.7 Hz, CH2C6H4(OCH3)-4), 5.30
(s, 2H, CH2C6H4(OCH3)-4), 3.80 (s, 3H, CH2C6H4(OCH3)-4). 13C NMR
d
(ppm) ¼ 144.9 (NCHN), 142.3, 135.4, 133.2, 133.0, 132.6, 131.0,
128.8, 127.2, 124.8, 123.4, 111.6 (NC6H4N and CH2C6H3Cl2-3,4), 102.4,
98.0, 83.1, 81.1 ((CH3)2CHC6H4CH3-4), 48.2 (CH2C6H3Cl2-3,4),
30.7 ((CH3)2CHC6H4CH3-4), 22.3 ((CH3)2CHC6H4CH3-4), 18.5
((CH3)2CHC6H4CH3-4).
(100.5 MHz, CDCl3)
128.7, 127.4, 123.0, 122.2, 120.4, 114.4, and 110.1(NC6H4N and
d
(ppm) ¼ 143.9 (NCHN), 159.6, 143.1, 133.9,
CH2C6H4(OCH3)-4),
(CH2C6H4(OCH3)-4).
55.3 (CH2C6H4(OCH3)-4), 48.5
4.3.1.2. Dichloro-(N-(4-chlorobenzyl)benzimidazole)-(p-cymene)
ruthenium(II), 2. Yield: 0.39 g (72%). FT-IR y(CN): 1509 cmꢁ1, m.p.:
228e229 ꢀC. Anal. Calc. for C24H25CI3N2Ru: C, 52.52; H, 4.59; N,
5.10. Found: C, 52.48; H, 4.62; N: 5.15%. 1H NMR (399.9 MHz, CDCl3)
4.2.1.4. N-(3,5-Ditert-butylbenzyl)benzimidazole, L4. Yield: 2.82 g
(88%). FT-IR y(CN): 1450 cmꢁ1, m.p.: 137e138 ꢀC. Anal. Calc.
for C22H28N2: C, 82.45; H, 8.81; N, 8.74. Found: C, 82.48; H,
8.83; N: 8.72%. 1H NMR (399.9 MHz, CDCl3)
d
(ppm) ¼ 7.97 (s,
d
(ppm) ¼ 8.45 (s, 1H, NCHN), 8.03 (d, 1H, J ¼ 7.8 Hz NC6H4N), 7.38e
1H, NCHN), 7.87e7.84 (m, 1H, NC6H4N), 7.41e7.28 (m, 4H,
NC6H4N and CH2C6H3(C(CH3)3)2)-3,5), 6.88e6.74 (m, 2H,
CH2C6H3(C(CH3)3)2-3,5), 5.36 (s, 2H, CH2C6H3(C(CH3)3)2-3,5),
1.30 (s, 18H, CH2C6H3(C(CH3)3)2)-3,5). 13C NMR (100.5 MHz,
7.25 (m, 3H, NC6H4N), 7.26 and 7.12 (d, 4H, J ¼ 8.4 Hz, CH2C6H4Cl-4),
5.55 (d, 2H, J ¼ 6.0 Hz (CH3)2CHC6H4CH3-4), 5.40 (d, 2H, J ¼ 6.0 Hz
(CH3)2CHC6H4CH3-4), 5.08 (s, 2H, CH2C6H4Cl-4), 2.81 (hep. 1H,
J ¼ 6.9 Hz, (CH3)2CHC6H4CH3-4), 2.1 (s, 3H, (CH3)2CHC6H4CH3-4),
1.24 (d, 6H, J ¼ 6.9 Hz, (CH3)2CHC6H4CH3-4). 13C NMR (100.5 MHz,
CDCl3)
d
(ppm) ¼ 143.7 (NCHN), 151.8, 143.0, 134.3, 134.1, 126.9,
123.0, 122.5, 122.4, 122.3, 121.7, 120.3, and 110.1(NC6H4N and
CH2C6H3(C(CH3)3)2)-3,5), 49.5 (CH2C6H3(C(CH3)3)2)-3,5), 34.9
(CH2C6H3(C(CH3)3)2)-3,5), 31.4 (CH2C6H3(C(CH3)3)2)-3,5).
CDCl3)
d
(ppm) ¼ 144.9 (NCHN), 142.5, 134.4, 133.5, 133.4, 129.2,
128.8, 124.5, 123.6, 120.5, 111.4 (NC6H4N and CH2C6H4Cl-4), 102.5,
97.8, 83.0, 81.1 ((CH3)2CHC6H4CH3-4), 48.7 (CH2C6H4Cl-4),

S. Demir et al. / Journal of Organometallic Chemistry 755 (2014) 134e140
139
30.7 ((CH3)2CHC6H4CH3-4), 22.3 ((CH3)2CHC6H4CH3-4), 18.5
((CH3)2CHC6H4CH3-4).
CH2CH(CH2CH3)2). 13C NMR (100.5 MHz, CDCl3)
(NCHN), 142.6, 134.0, 124.0, 123.5, 120.7, 110.8 (NC6H4N),
d
(ppm) ¼ 145.0
49.3
(CH2CH(CH2CH3)2),
30.7
((CH3)2CHC6H4CH3-4),
40.8
4.3.1.3. Dichloro-(N-(4-methoxybenzyl)benzimidazole)-(p-cymene)
ruthenium(II), 3. Yield: 0.46 g (85%). FT-IR y(CN): 1512 cmꢁ1, m.p.:
222e223 ꢀC. Anal. Calc. for C25H28Cl2N2ORu: C, 55.15; H, 5.18; N, 5.14.
Found: C, 55.09; H, 5.22; N: 5.17%. 1H NMR (399.9 MHz, CDCl3)
(CH2CH(CH2CH3)2), 23.2(CH2CH(CH2CH3)2), 22.3 ((CH3)2CHC6H4CH3-
4), 18.5 ((CH3)2CHC6H4CH3-4), 10.5 (CH2CH(CH2CH3)2).
4.4. General procedure for the N-alkylation of aniline and alcohol
d
(ppm) ¼ 8.41 (s, 1H, NCHN), 8.02 (d, 1H, J ¼ 7.5 Hz, NC6H4N), 7.33e
7.28 (m, 3H, NC6H4N), 7.14 (d, 2H, J ¼ 8.1 Hz, CH2C6H4(OCH3)-4), 6.82
(d, 2H, J ¼ 8.1 Hz, CH2C6H4(OCH3)-4), 5.50 (d, 2H, J ¼ 5.4 Hz,
(CH3)2CHC6H4CH3-4), 5.37 (d, 2H, J ¼ 5.7 Hz, (CH3)2CHC6H4CH3-4),
5.10 (s, 2H, CH2C6H4(OCH3)-4), 3.76 (s, 3H, CH2C6H4(OCH3)-4), 2.77
Under an inert atmosphere, a mixture containing the complexes
[RuCl2(N-alkylbenzimidazole)(p-cymene)]
(1e6)
(1
mol%),
tKOBu (0.5 mmol), aniline (0.55 mmol), and alcohol (0.5 mmol) was
heated at 100e150 ꢀC in toluene (2 mL) for 5e24 h. After
completion, the mixture was cooled, filtered and concentrated. The
products were purified by column chromatography to give the N-
alkylation products in good yields.
(hept. 1H,
J
¼
6.9 Hz, (CH3)2CHC6H4CH3-4), 2.07 (s, 3H,
(CH3)2CHC6H4CH3-4),1.21 (d, 6H, J ¼ 6.9 Hz, (CH3)2CHC6H4CH3-4). 13
C
NMR (100.5 MHz, CDCl3)
d
(ppm) ¼ 144.8 (NCHN),159.6,144.8,142.6,
133.6, 129.1, 126.7, 124.2, 123.5, 120.4, 114.4, and 111.6 ( NC6H4N
and CH2C6H4(OCH3)-4),102.3, 97.8, 83.0 and 81.1 ((CH3)2CHC6H4CH3-
4), 55.4 (CH2C6H4(OCH3)-4), 49.2 (CH2C6H4(OCH3)-4), 30.6
Acknowledgments
_
((CH3)2CHC6H4CH3-4),
((CH3)2CHC6H4CH3-4).
22.3
((CH3)2CHC6H4CH3-4),
18.5
This work was financially supported by the Inönü University
Research Fund.
4.3.1.4. Dichloro-(N-(3,5-diter-butylbenzyl)benzimidazole)(p-cym-
ene)ruthenium(II), 4. Yield: 0.49 g(78%). FT-IR y(CN): 1516 cmꢁ1, m.p.:
221e222 ꢀC. Anal. Calc. for C32H42Cl2N2Ru: C, 61.33; H, 6.76; N, 4.47.
Found: C, 61.37; H, 6.70; N: 4.48%. 1H NMR (399.9 MHz, CDCl3)
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(s, 1H, NCHN), 8.05e6.74 (m, 4H, NC6H4N), 5.56 (d, 2H, J ¼ 5.4 Hz,
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4.01 (d, 2H, J ¼ 6.9 Hz, CH2CH(CH2CH3)2), 2.85 (hept., 1H, J ¼ 6.9 Hz,
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CH2CH(CH2CH3)2), 1.36e1.33 (m, 4H, CH2CH(CH2CH3)2), 1.27 (d, 6H,
J
¼
6.9 Hz, ((CH3)2CHC6H4CH3-4), 0.94 (t, 6H,
J
¼
7.2 Hz,

140
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