The synthesis of oligoether-substituted benzimidazolium bromides and their use as ligand precursors for the Pd-catalyzed Heck coupling in water

Article abstract of DOI:10.1016/j.jorganchem.2009.07.010

The oligoether-substituted (CH₃(OCH₂CH₂)_n-; n = 1, 2 or 3) benzimidazolium bromides (3-7) and oligoether-linked (-CH₂(CH₂OCH₂)_nCH₂-, n = 1, 2 or 3) bisbenzimidazolium dibromides (8-13) were prepared by quarternization of N-substituted benzimidazoles (1 and 2) with the bulky benzyl bromides (ArCH₂Br: Ar = C₆H₂(CH₃)₃-2,4,6 and C₆(CH₃)₅). trans-Bis(carbene) palladium(II) complexes 14 and 15 derived from 4 and 6 were synthesized by using Ag complexes as carbene-transfer agents in dichloromethane at ambient temperature. In addition, the reactions of 4 and 6 with Pd(OAc)₂ and NaBr gave the Pd(II) dimers 16 and 17 which can readily be cleaved by triphenylphosphine to afford the benzannulated monocarbene (NHC) monophosphine Pd(II) complexes [PdBr₂(NHC)(PPh₃)] (18 and 19). All compounds have been fully characterized by using elemental analysis, ¹H, ¹³C and ³¹P NMR spectroscopies. X-ray diffraction studies on single crystals of 19a and 19b confirm the cis square planar geometry. In situ formed complexes from Pd(OAc)₂ and benzimidazolium salts (3-13) and preformed Pd(II) complexes 14, 15, 18 and 19 were tested as catalyst for the Heck coupling reaction in water. The influence of the oligoether and benzyl substituents on N atoms and CH₃-substituents on the 5,6-positions of benzimidazole frame were investigated under the same conditions in the Heck coupling reaction. In situ formed catalysts showed better conversions than the isolated Pd(II) complexes. The length of the oligoether spacer significantly increases the activity. The salts with two benzimidazole moieties connected by an oligoether as the spacer 8-13 showed similar catalytic activities in the Heck coupling reaction with the mono salts 3-7 bearing corresponding oligoethers on the N atom.

Full text of DOI:10.1016/j.jorganchem.2009.07.010

Journal of Organometallic Chemistry 694 (2009) 3580–3589
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
The synthesis of oligoether-substituted benzimidazolium bromides and their use
as ligand precursors for the Pd-catalyzed Heck coupling in water
a
b
a
a
Süleyman Gülcemal a, , Sema Kahraman , Jean-Claude Daran , Engin Çetinkaya , Bekir Çetinkaya
*
a Department of Chemistry, Ege University, 35100 Bornova-Izmir, Turkey
b Laboratoire de Chimie de Coordination du CNRS, 205 Route de Narbonne, 31077 Toulouse Cedex 4, France
a r t i c l e i n f o
a b s t r a c t
Article history:
The oligoether-substituted (CH3(OCH2CH2)n–; n = 1, 2 or 3) benzimidazolium bromides (3–7) and oli-
goether-linked (–CH2(CH2OCH2)nCH2–, n = 1, 2 or 3) bisbenzimidazolium dibromides (8–13) were
prepared by quarternization of N-substituted benzimidazoles (1 and 2) with the bulky benzyl bro-
mides (ArCH2Br: Ar = C6H2(CH3)3-2,4,6 and C6(CH3)5). trans-Bis(carbene) palladium(II) complexes 14
and 15 derived from 4 and 6 were synthesized by using Ag complexes as carbene-transfer agents
in dichloromethane at ambient temperature. In addition, the reactions of 4 and 6 with Pd(OAc)2
and NaBr gave the Pd(II) dimers 16 and 17 which can readily be cleaved by triphenylphosphine to
afford the benzannulated monocarbene (NHC) monophosphine Pd(II) complexes [PdBr2(NHC)(PPh3)]
(18 and 19). All compounds have been fully characterized by using elemental analysis, 1H, 13C and
31P NMR spectroscopies. X-ray diffraction studies on single crystals of 19a and 19b confirm the cis
square planar geometry. In situ formed complexes from Pd(OAc)2 and benzimidazolium salts (3–
13) and preformed Pd(II) complexes 14, 15, 18 and 19 were tested as catalyst for the Heck coupling
reaction in water. The influence of the oligoether and benzyl substituents on N atoms and CH3-sub-
stituents on the 5,6-positions of benzimidazole frame were investigated under the same conditions in
the Heck coupling reaction. In situ formed catalysts showed better conversions than the isolated
Pd(II) complexes. The length of the oligoether spacer significantly increases the activity. The salts
with two benzimidazole moieties connected by an oligoether as the spacer 8–13 showed similar cat-
alytic activities in the Heck coupling reaction with the mono salts 3–7 bearing corresponding oligoe-
thers on the N atom.
Received 15 June 2009
Received in revised form 2 July 2009
Accepted 6 July 2009
Available online 9 July 2009
Keywords:
Benzimidazolium bromides
Oligoether substituents
Heck coupling
Palladium–NHC complexes
Ó 2009 Elsevier B.V. All rights reserved.
1. Introduction
Incorporation of alkoxyethyl substituents on N atom(s) of a
variety of the NHC rings has shown enhanced activity over their
The transition metal complexes of N-heterocyclic carbenes
(NHCs) based on imidazole, imidazoline and benzimidazole
framework have been the focus of intense research in organome-
tallic chemistry and homogeneous catalysis [1], for example, pal-
ladium–NHC complexes have been employed as catalysts for the
Mizoroki–Heck and Suzuki–Miyaura C–C coupling reactions be-
cause of their facile preparation methods and better stability
toward air and moisture [1f,2]. Even, benzannulated carbenes
derived from benzimidazolium precursors exhibit interesting
properties due to their intermediate position between saturated
and unsaturated analogues [3], only a few groups reported the
catalytic activities of Pd(II) benzimidazole-2-ylidene complexes
[4].
hydrocarbon analogues [5]. Furthermore, highly active water-solu-
ble ruthenium catalysts bearing oligoether-attached NHC ligands
for olefin metathesis have been reported [6]. Some related imi-
dazolium salts bearing oligoether substituents [7], and Hg(II)-and
Ag(I)–NHC complexes of oligoether bridged benzimidazolin-2-yli-
dene [8] were reported while this work was in progress. Tsuji
and co-workers reported that the NHC derivatives bearing hydro-
philic tetraethylene glycol (TEG) chains on both sides of NHC ring
enhance the catalytic activity considerably in the Suzuki–Miyaura
coupling reaction [9]. Inspired by these reports, we decided to
examine the influence of oligoether incorporated benzimidazolium
salts as NHC precursors for the Pd(II) catalyzed C–C coupling reac-
tions. We have also synthesized and characterized the bis(carbene)
Pd(II) and mixed NHC–phosphine–Pd(II) complexes derived from
the benzimidazolium salts. The Mizoroki–Heck reaction was used
to compare the catalytic activities of both in situ formed and pre-
formed carbene complexes of benzimidazolium salts with
Pd(OAc)2 and isolated NHC–Pd(II) complexes in water.
* Corresponding author. Tel.: +90 232 3884000/1581; fax: +90 232 3888264.
E-mail address: suleyman.gulcemal@ege.edu.tr (S. Gülcemal).
0022-328X/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2009.07.010

S. Gülcemal et al. / Journal of Organometallic Chemistry 694 (2009) 3580–3589
3581
complexes. 13C NMR spectrum of bis(carbene) Pd(II) complexes
(14 and 15) showed Ccarbene resonance between d 180.8 and
182.4 ppm, which is consistent with the range for the reported
trans-configurated benzimidazole-2-ylidene Pd(II) complexes
[4f,j,l,11,12].
2. Results and discussion
2.1. Synthesis and characterization of oligoether-substituted (5,6-
dimethyl)benzimidazolium bromides (3–7) and oligoether-linked
bis(5,6-dimethyl)benzimidazolium dibromides (8–13)
A synthetic pathway for the dimeric Pd(II) carbene complexes
by reaction of benzimidazolium salt with Pd(OAc)2 in the presence
of NaBr in DMSO has been reported by Huynh [4i]. The dimeric
Pd(II) carbene complexes of N1-oligoether-substituted (5,6-
dimethyl)benzimidazole-2-ylidenes (16 and 17) were obtained in
about 80% yield by this procedure as air-stable orange solids solu-
ble in halogenated solvents (Scheme 2). The formation of com-
plexes was confirmed by the absence of the downfield signal for
the NCHN proton in the 1H NMR spectra. 13C NMR spectrum of
the dimeric Pd(II) carbene complexes 16 and 17 showed Ccarbene
resonance between d 156.9 and 159.5 ppm, which is in a good
range for the previously reported dimeric benzimidazole-2-ylidene
Pd(II) complexes [4c,d].
The (5,6-dimethyl)benzimidazolium bromides (3–7) were ob-
tained in almost quantitative yield by quarternization of 1-oligoe-
ther-substituted (5,6-dimethyl)benzimidazole (1) in PhMe with
the alkylated benzyl bromides (Scheme 1). In a similar manner,
bis(5,6-dimethyl)benzimidazolium dibromide salts (8–13) were
obtained in a moderate yield by quarternization of oligoether
bridged (5,6-dimethyl)benzimidazole (2), in DMF with alkylated
benzyl bromides. These salts are air-stable, colorless solids. The
1H NMR spectra of these salts exhibit characteristic NCHN reso-
nance at d = 8.74–11.14 ppm. The formation of the salts was also
supported by a resonance at d = 139.5–143.4 ppm in the 13C NMR
spectrum for the NCHN carbon atom.
Dimeric Pd(II) carbene complexes are useful precursors for the
preparation of neutral and mixed NHC–phosphine complexes of
Pd(II) under mild conditions. Previously mixed NHC–phosphine
complexes of Pd(II) derived from benzimidazolin-2-ylidene by
cleavage of dimeric Pd(II) carbene complex with triphenylphos-
phine in dichloromethane have been reported [4c,i]. The dimeric
Pd(II) carbene complexes 16 and 17 and triphenylphosphine re-
acted in dichloromethane to give mixed NHC–phosphine com-
plexes of Pd(II) 18 and 19 as air-stable yellow solids soluble in
halogenated solvents in about 90% yield (Scheme 2). NMR analyses
of the complexes showed that the triphenylphosphine ligands
coordinated the palladium center. 13C NMR spectrum of the com-
plexes 18 and 19 shown Ccarbene resonance between d 173.1 and
175.6 ppm. The presence of triphenylphosphine is also demon-
2.2. Synthesis and characterization of palladium complexes, 14–19
In general, the bis(carbene) complexes of palladium(II) can be
prepared by deprotonation of two equivalent azolium salts with
Pd(OAc)2 [4n,10]. The bis(carbene) Pd(II) complexes 14 and 15
bearing one oligoether substition on N1 of (5,6-dimethyl)benz-
imidazole were synthesized by carbene-transfer reaction of
in situ formed NHC–Ag species with [PdCl2(MeCN)2] in dichloro-
methane at ambient temperature [11]. The complexes 14 and 15
were obtained in high yields as air-stable yellow solids, soluble
in halogenated solvents (Scheme 2). The characteristics downfield
signals for the NCHN proton of the benzimidazolium salts (4 and 6)
were not observed in the 1H NMR spectra of bis(carbene) Pd(II)
Y
Y
Y
Y
Y
Y
a
: Y = H
b
: Y = CH3
CH3
N
N
N
N
N
N
(
)
n
(
)
O
O
n
1
2
ArCH2-Br
DMF, 80 oC
ArCH2-Br
PhMe, reflux
Y
Y
Y
Y
Y
Y
2 Br -
O
Ar
Ar
Ar
+
N
+
Br-
+
N
CH3
n
N
N
N
N
(
)
n
(
)
O
3: n = 1; Ar = C6H2(CH3)3-2,4,6;
4: n = 2; Ar = C6H2(CH3)3-2,4,6;
5: n = 1; Ar = C6(CH3)5;
8 : n = 1; Ar = C6H2(CH3)3-2,4,6;
9 : n = 2; Ar = C6H2(CH3)3-2,4,6;
10: n = 3; Ar = C6H2(CH3)3-2,4,6;
11: n = 1; Ar = C6(CH3)5;
6: n = 2; Ar = C6(CH3)5;
7: n = 3; Ar = C6(CH3)5;
12: n = 2; Ar = C6(CH3)5;
13: n = 3; Ar = C6(CH3)5
Scheme 1. Synthesis of benzimidazolium salts.

3582
S. Gülcemal et al. / Journal of Organometallic Chemistry 694 (2009) 3580–3589
H3C
H3C
O
O
Ar
O
O
1) Ag2O
Cl
Y
Y
Y
Y
Y
N
N
N
N
N
2) [PdCl2(CH3CN)2]
Br-
Pd
Cl
2
+
N
CH2Cl2, rt
Y
O
Ar
Ar
O
CH3
14
15
4
: Ar = C6H2(CH3)3-2,4,6
: Ar = C6(CH3)5
: Ar = C6H2(CH3)3-2,4,6
: Ar = C6(CH3)5
6
Pd(OAc)2, NaBr
DMSO, 90 oC
H3C
O
H3C
Ar
O
O
Br
N
Pd
Br
Y
PPh3
O
Y
N
N
2 PPh3
CH2Cl2, rt
Y
N
Br
N
Pd
Br
2
Y
Br
Pd
Br
Y
O
N
Y
Ar
O
Ar
CH3
18
19
: Ar = C6H2(CH3)3-2,4,6
: Ar = C6(CH3)5
16
17
: Ar = C6H2(CH3)3-2,4,6
: Ar = C6(CH3)5
Scheme 2. Synthesis of NHC–Pd(II) complexes.
strated by 31P NMR spectroscopy, where one singlet between d
26.99 and 27.20 ppm for the complexes 18 and 19 was observed.
2.3. Molecular structures of complexes 19a and 19b
The molecular view of compounds 19a and 19b are represented
in Figs. 1 and 2. In both of them, the Pd atom is coordinated to two
bromine, the phosphorus atom of a triphenyl phosphine ligand and
the C atom of an N-heterocyclic carbene in a square planar geom-
etry. The geometry of the square plane is very similar for the two
compounds.
Expectedly, the Pd–Br bond lengths trans to carbene are slightly
but significantly shorter than the Pd–Br bonds trans to phosphorus
(Table 1). The heterocyclic carbene ring is oriented nearly perpen-
dicular to the Pd square plane making a dihedral angle of
77.21(11)° and 86.03(8)°, respectively, for 19a and 19b.
2.4. Catalysis
The catalytic activities of compounds (with 1.5 mol% catalyst
loading) were investigated in the Heck coupling reaction at
100 °C and Cs2CO3 was used as base. Reactions were performed
in air and without any additive and the results are summarized
in Table 2. The initial studies have been carried out using
the in situ formed complexes with Pd(OAc)2 and oligoether-substi-
tuted (5,6-dimethyl)benzimidazolium bromide salts (3–7, entries
1–10) and oligoether-linked bis(5,6-dimethyl)benzimidazolium
dibromides (8–13, entries 11–22) under identical conditions. As
Fig. 1. Molecular view of complexes 19a with the atom labeling scheme. Ellipsoids
are drawn at the 30% probability level. H atoms have been omitted for clarity. In
compound 19a only the major component of the disordered (CH2)2O(CH2)2OCH3
chain is represented.

S. Gülcemal et al. / Journal of Organometallic Chemistry 694 (2009) 3580–3589
3583
Table 2
The Heck coupling reaction of styrene with aryl bromide.
%[Pd]
O
O
Br
+
H2O, Cs2CO3
Entry
Catalyst
Yield (%)
1
2
3
4
5
6
7
8
3a
3b
4a
4b
5a
5b
6a
6b
7a
7b
8a
8b
9a
9b
10a
10b
11a
11b
12a
12b
13a
13b
14a
14b
15a
15b
18a
18b
19a
19b
71
76
84
88
86
91
92
95
93
95
73
75
83
85
89
90
87
88
90
93
92
96
56
59
61
63
73
80
77
81
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
Fig. 2. Molecular view of complexes 19b with the atom labeling scheme. Ellipsoids
are drawn at the 30% probability level. H atoms have been omitted for clarity. In
compound 19a only the major component of the disordered (CH2)2O(CH2)2OCH3
chain is represented.
Table 1
Selected bond distances (Å) and angles (°) for 19a and 19b.
19a
19b
Pd Br1
Pd Br2
Pd P
Pd C
2.4606(5)
2.4648(5)
2.2667(9)
2.001(4)
2.4627(8)
2.4726(8)
2.2620(9)
1.986(2)
Br1–Pd–Br2
Br1–Pd–P
Br1–Pd–C
Br2––Pd–P
Br2–Pd–C
P–Pd–C
91.173(18)
178.62(3)
86.57(10)
87.46(3)
177.00(10)
94.81(10)
93.50(4)
176.387(17)
87.41(7)
89.42(4)
178.81(7)
89.69(8)
Reaction conditions: 1.0 mmol p-BrC6H4COCH3, 1.5 mmol styrene, 2.0 mmol Cs2CO3,
1. 5 mmol% Pd(OAc)2, 3.0 mmol% 3–7 or 1.5 mmol% 8–13, water (3.0 mL), diethyl-
eneglycol-di-n-butyl ether as the internal standard. Purity of compound was
checked by 1H NMR and yields are based on aryl bromide, 100 °C, 4 h. GC yields.
the number of OCH2CH2 entities increase the catalytic activity
slightly increases: n = 3 > n = 2 > n = 1. We also observed that both
the pentamethylbenzyl substituent on N3 position of benzimidazo-
lium salts and the methyl groups on 5,6-position of benzimidazole
ring increase the catalytic activity. These results are comparable
with the previously reported studies [13]. Similarly, bis(carbene)
Pd(II) complexes (14 and 15, entries 23–26) and mixed NHC–phos-
phine complexes of Pd(II) (18 and 19, entries 27–30) were tested
for the same coupling reaction. The results showed that the mixed
NHC–phosphine complexes have better activities (entires 27–30)
than the classic bis(carbene) Pd(II) complexes (entries 23–26).
However, it is worthy to note that the in situ formed complexes
of the ligand by deprotonation of the (5,6-dimethyl)benzimidazo-
lium bromides led to significantly better results (entries 3, 4 and
7, 8) than the use of the both bis(carbene) Pd(II) complexes and
mixed NHC–phosphine complexes. Generally, in situ formed cata-
lyst show better conversions than the isolated Pd(II) complexes. It
is possible that the activity difference between Pd(OAc)2/4, 6 sys-
tem and preformed 14, 15 or 18, 19 is due to the additional species,
such as AcOꢀ/AcOH in the in situ generated catalyst mixtures. In
connection with this assumption, a recent report stated that
weakly coordinating acetate counterions incorporated to NHC–
Pd(II) complexes enhance the catalytic activity [14].
Table 3
Reusability of the benzimidazolium salt (6b) in Heck coupling.
Recycles
Yield (%)
1st
95
2nd
92
3rd
90
3. Conclusions
Benzimidazolium bromides (3–7) bearing oligoether side
chains –(CH2CH2O)n – (n = 1, 2 or 3) and oligoether-linked bis-
benzimidazolium dibromides (8–13) were synthesized, character-
ized and used with Pd(OAc)2 as in situ formed Heck coupling
catalyst. The former series were converted to synthesize bis, di-
meric and mixed Pd–NHC complexes 14 and 15, 16 and 17 and
18 and 19, respectively. The identity of 19a and 19b as cis-com-
plexes has been confirmed by X-ray diffraction studies. Both the
longer oligoether and bulky benzyl substituents on N atoms and
the methyl groups on 5,6-position of benzimidazole ring gave
an enhanced reaction rate. On the basis of such results, it is not
unreasonable to assume that the interactions between the O
atoms of the oligoether and the palladium center could play an
important role.
Reusability of the catalyst 6b showed only 5% difference at
three reaction cycles (Table 3).

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S. Gülcemal et al. / Journal of Organometallic Chemistry 694 (2009) 3580–3589
7.35 (d, J = 8.4 Hz, 1H, Ar–H), 7.45 (t, J = 7.2 Hz, 1H, Ar–H), 7.55 (t,
4. Experimental
J = 7.2 Hz, 1H, Ar–H), 7.92 (d, J = 8.2 Hz, 1H, Ar–H), 10.44 (s, 1H,
NCHN) ppm. 13C {1H} NMR (100.6 MHz, CDCl3, TMS, 25 °C):
d = 20.4, 21.3, 47.2, 48.1, 59.1, 68.7, 70.6, 71.9, 113.5, 114.5,
125.1, 127.2, 127.4, 130.4, 131.4, 132.4, 138.3, 140.1, 142.7 (NCN)
ppm.
Unless otherwise noted all manipulations were performed in
air. All solvents used as received. 2,4,6-Trimethylbenzyl bromide,
2,3,4,5,6-pentamethylbenzyl bromide were synthesized according
to methods previously known [15]. Substituted- or linled- oligoe-
ther functionalized (5,6-dimethyl)benzimidazoles and (5,6-
dimethyl)bisbenzimidazoles (1 and 2) were prepared according
to a slightly modified procedure from Refs. [5,16]. All reagents
were purchased from Merck, Fluka, Alfa Aesar and Acros Organics.
Melting points were recorded with Gallenkamp electrothermal
melting point apparatus. 1H NMR, 13C NMR and 31P spectra were
recorded with a Varian AS 400 Mercury instrument. As solvents
CDCl3, were employed. Chemical shifts (d) are given in ppm, cou-
pling constants (J) in Hz. Elemental analyses were performed on
a Perkin–Elmer PE 2400 elemental analyzer.
4.1.4. Synthesis of 1-[2-(2-methoxyethoxy)ethyl]-3-(2,4,6-trimethylb-
enzyl)-5,6-dimethylbenzimidazolium bromide (4b)
Yield: 91%. m.p. = 138 °C. Anal. Calc. for C24H33BrN2O2 (461.4):
C, 62.47; H, 7.21; N, 6.07. Found: C, 62.49; H, 7.24; N, 6.10%. 1H
NMR (400 MHz, CDCl3, TMS, 25 °C): d = 2.27 (s, 3H,
CH2C6H2(CH3)3-2,4,6), 2.28 (s, 6H, CH2C6H2(CH3)3-2,4,6), 2.31 (s,
3H, CH3–Ar), 2.38 (s, 3H, CH3–Ar), 3.23 (s, 3H, OCH3), 3.37 (t,
J = 4.8 Hz, 2H, CH2), 3.59 (t, J = 4.8 Hz, 2H, CH2), 3.97 (t, J = 4.8 Hz,
2H, CH2), 4.80 (t, J = 4.8 Hz, 2H, CH2), 5.72 (s, 2H, CH2C6H2(CH3)3-
2,4,6), 6.92 (s, 2H, CH2C6H2(CH3)3-2,4,6), 7.15 (s, 1H, Ar–H), 7.66
(s, 1H, Ar–H), 10.05 (s, 1H, NCHN) ppm. 13C {1H} NMR
(100.6 MHz, CDCl3, TMS, 25 °C): d = 20.2, 20.7, 20.9, 21.2, 46.7,
47.9, 59.0, 68.6, 70.5, 71.8, 113.2, 114.0, 125.2, 130.0, 130.2,
137.5, 138.2, 140.5 (NCN) ppm.
4.1. Preparation of oligoether-substituted (5,6-dimethyl)benzimidazo-
lium bromides (3–7)
1-Alkyl-(5,6-dimethyl)benzimidazole (5.0 mmol) was dissolved
in toluene (20 mL) and then 2,4,6-trimethylbenzyl bromide or
2,3,4,5,6-pentamethylbenzyl bromide (5.0 mmol) was added. The
mixture was refluxed for 6 h. The solid that separated out after
cooling was filtered off and washed with diethyl ether (20 mL).
The product was recrystallized from CH2Cl2/Et2O. The following
salts 3–7 were synthesized according to this procedure.
4.1.5. Synthesis of 1-(2-methoxyethyl)-3-(2,3,4,5,6-pentamethylbenz-
yl)benzimidazolium bromide (5a)
This salt was synthesized according to published procedure [4c]
4.1.6. Synthesis of 1-(2-methoxyethyl)-3-(2,3,4,5,6-pentamethylbenz-
yl)-5,6-dimethylbenzimidazolium bromide (5b)
Yield: 95%, m.p. = 166 °C. Anal. Calc. for C24H33BrN2O (445.4): C,
64.71; H, 7.47; N, 6.29. Found: C, 64.65; H, 7.39; N, 6.31%. 1H NMR
(400 MHz, CDCl3, TMS, 25 °C): d = 2.23 (s, 6H, CH2C6(CH3)5), 2.25 (s,
6H, CH2C6(CH3)5), 2.27 (s, 3H, CH2C6(CH3)5), 2.37 (s, 3H, CH3–Ar),
2.41 (s, 3H, CH3–Ar), 3.24 (s, 3H, OCH3), 3.80 (t, J = 4.0 Hz, 2H,
CH2), 4.84 (t, J = 4.0 Hz, 2H, CH2), 5.62 (s, 2H, CH2C6(CH3)5), 7.33
(s, 1H, Ar–H), 7.66 (s, 1H, Ar–H), 9.54 (s, 1H, NCHN) ppm. 13C
{1H} NMR (100.6 MHz, CDCl3, TMS, 25 °C): d = 17.0, 17.1, 17.4,
20.8, 20.9, 47.6, 48.0, 59.1, 70.1, 113.1, 114.0, 124.9, 129.9, 130.8,
133.7, 134.1, 137.5, 137.7, 140.2 (NCN) ppm.
4.1.1. Synthesis of 1-(2-methoxyethyl)-3-(2,4,6-trimethylbenzyl)benz-
imidazolium bromide (3a)
Yield: 97%, m.p. = 205 °C. Anal. Calc. for C20H25BrN2O (389.3): C,
61.70; H, 6.47; N, 7.20. Found: C, 61.58; H, 6.54; N, 7.12%. 1H NMR
(400 MHz, CDCl3, TMS, 25 °C): d = 2.22 (s, 3H, CH2C6H2(CH3)3-
2,4,6), 2.23 (s, 6H, CH2C6H2(CH3)3-2,4,6), 3.23 (s, 3H, OCH3), 3.82
(t, J = 4.0 Hz, 2H, CH2), 4.84 (t, J = 4.0 Hz, 2H, CH2), 5.75 (s, 2H,
CH2C6H2(CH3)3-2,4,6), 6.88 (s, 2H, CH2C6H2(CH3)3-2,4,6), 7.36 (d,
J = 8.0 Hz, 1H, Ar–H), 7.44 (t, J = 7.6 Hz, 1H, Ar–H), 7.53 (t,
J = 7.6 Hz, 1H, Ar–H), 7.53 (d, J = 8.0 Hz, 1H, Ar–H), 10.33 (s, 1H,
NCHN) ppm. 13C {1H} NMR (100.6 MHz, CDCl3, TMS, 25 °C):
d = 20.2, 21.2, 47.2, 48.0, 59.0, 69.8, 113.7, 114.4, 125.1, 127.4,
130.3, 131.3, 132.1, 138.1, 139.9, 142.1 (NCN) ppm.
4.1.7. Synthesis of 1-[2-(2-methoxyethoxy)ethyl]-3-(2,3,4,5,6-penta-
methylbenzyl)benzimidazolium bromide (6a)
Yield: 98%. m.p. = 164 °C. Anal. Calc. for C24H33BrN2O2 (461.4):
C, 62.47; H, 7.21; N, 6.07. Found: C, 62.42; H, 7.19; N, 6.11%. 1H
NMR (400 MHz, CDCl3, TMS, 25 °C): d = 2.17 (s, 3H, CH2C6(CH3)5),
2.19 (s, 6H, CH2C6(CH3)5), 2.25 (s, 6H, CH2C6(CH3)5), 3.20 (s, 3H,
OCH3), 3.36 (t, J = 4.6 Hz, 2H, CH2), 3.59 (t, J = 4.6 Hz, 2H, CH2),
3.98 (t, J = 4.4 Hz, 2H, CH2), 4.94 (t, J = 4.4 Hz, 2H, CH2), 5.73 (s,
2H, CH2C6(CH3)5), 7.54–760 (m, 3H, Ar–H), 7.99 (d, J = 8.0 Hz, 1H,
Ar–H), 9.93 (s, 1H, NCHN) ppm. 13C {1H} NMR (100.6 MHz, CDCl3,
TMS, 25 °C): d = 17.2, 17.3, 17.5, 48.0, 48.3, 59.0, 68.9, 70.6, 71.8,
113.4, 114.8, 124.8, 127.4, 127.4, 131.4, 132.5, 133.8, 134.3,
137.7, 142.0 (NCN) ppm.
4.1.2. Synthesis of 1-(2-methoxyethyl)-3-(2,4,6-trimethylbenzyl)-5,6-
dimethylbenzimidazolium bromide (3b)
Yield: 93%, m.p. = 203 °C. Anal. Calc. for C22H29BrN2O (417.4): C,
63.31; H, 7.00; N, 6.71. Found: C, 63.44; H, 7.09; N, 6.74%. 1H NMR
(400 MHz, CDCl3, TMS, 25 °C): d = 2.21 (s, 3H, CH2C6H2(CH3)3-
2,4,6), 2.23 (s, 6H, CH2C6H2(CH3)3-2,4,6), 2.27 (s, 3H, CH3–Ar),
2.34 (s, 3H, CH3–Ar), 3.21 (s, 3H, OCH3), 3.79 (t, J = 4.2 Hz, 2H,
CH2), 4.75 (t, J = 4.2 Hz, 2H, CH2), 5.64 (s, 2H, CH2C6H2(CH3)3-
2,4,6), 6.87 (s, 2H, CH2C6H2(CH3)3-2,4,6), 7.14 (s, 1 H, Ar–H), 7.61
(s, 1H, Ar–H), 9.98 (s, 1H, NCHN) ppm. 13C {1H} NMR (100.6 MHz,
CDCl3, TMS, 25 °C): d = 20.2, 20.7, 20.8, 21.2, 46.8, 47.8, 59.1,
69.8, 113.3, 113.8, 125.2, 129.9, 130.2, 130.6, 137.6, 138.1, 139.9,
140.8 (NCN) ppm.
4.1.8. Synthesis of 1-[2-(2-methoxyethoxy)ethyl]-3-(2,3,4,5,6-penta-
methylbenzyl)-5,6-dimethylbenzimidazolium bromide (6b)
Yield: 95%, m.p. = 198 °C. Anal. Calc. for C26H37BrN2O2 (489.5):
C, 63.80; H, 7.62; N, 5.72. Found: C, 63.77; H, 7.58; N, 5.74%. 1H
NMR (400 MHz, CDCl3, TMS, 25 °C): d = 2.20 (s, 6H, CH2C6(CH3)5),
2.21 (s, 6H, CH2C6(CH3)5), 2.23 (s, 3H, CH2C6(CH3)5), 2.36 (s, 3H,
CH3–Ar), 2.38 (s, 3H, CH3–Ar), 3.17 (s, 3H, OCH3), 3.31 (t,
J = 4.6 Hz, 2H, CH2), 3.52 (t, J = 4.6 Hz, 2H, CH2), 3.89 (t, J = 4.6 Hz,
2H, CH2), 4.82 (t, J = 4.6 Hz, 2H, CH2), 5.59 (s, 2H, CH2C6(CH3)5),
7.39 (s, 1H, Ar–H), 7.74 (s, 1H, Ar–H), 9.37 (s, 1H, NCHN) ppm.
13C {1H} NMR (100.6 MHz, CDCl3, TMS, 25 °C): d = 16.9, 17.0, 17.3,
20.6, 20.7, 47.0, 47.7, 58.7, 68.3, 70.3, 71.5, 113.0, 113.9, 124.7,
129.9, 130.5, 133.6, 133.9, 137.6, 139.5 (NCN) ppm.
4.1.3. Synthesis of 1-[2-(2-methoxyethoxy)ethyl]-3-(2,4,6-trimethylb-
enzyl)benzimidazolium bromide (4a)
Yield: 93%. m.p. = 147 °C. Anal. Calc. for C22H29BrN2O2 (433.4):
C, 60.97; H, 6.74; N, 6.46. Found: C, 61.01; H, 6.71; N, 6.43%. 1H
NMR (400 MHz, CDCl3, TMS, 25 °C): d = 2.26 (s, 3H,
CH2C6H2(CH3)3-2,4,6), 2.28 (s, 6H, CH2C6H2(CH3)3-2,4,6), 3.21 (s,
3H, OCH3), 3.37 (t, J = 4.4 Hz, 2H, CH2), 3.60 (t, J = 4.4 Hz, 2H,
CH2), 4.00 (t, J = 4.4 Hz, 2H, CH2), 4.87 (t, J = 4.4 Hz, 2H, CH2), 5.74
(s, 2H, CH2C6H2(CH3)3-2,4,6), 6.91 (s, 2H, CH2C6H2(CH3)3-2,4,6),

S. Gülcemal et al. / Journal of Organometallic Chemistry 694 (2009) 3580–3589
3585
4.1.9. Synthesis of 1-[2-(2-(2-methoxyethoxy)ethoxy)ethyl]-3-(2,3,4,5,
6-pentamethylbenzyl)benzimidazolium bromide (7a)
20.6, 21.3, 45.8, 47.0, 68.2, 113.9, 114.2, 126.8, 130.2, 130.5,
130.5, 136.9, 137.1, 138.8, 139.3, 141.2 (NCN) ppm.
Yield: 89%, m.p. = 118 °C. Anal. Calc. for C26H37BrN2O3 (505.5):
C, 61.78; H, 7.38; N, 5.54. Found: C, 61.75; H, 7.48; N, 5.61%. 1H
NMR (400 MHz, CDCl3, TMS, 25 °C): d = 2.26 (s, 6H, CH2C6(CH3)5),
2.28 (s, 6H, CH2C6(CH3)5), 2.29 (s, 3H, CH2C6(CH3)5), 3.30 (s, 3H,
OCH3), 3.42 (t, J = 4.2 Hz, 2H, CH2), 3.46–3.49 (m, 4H, CH2), 3.62
(t, J = 4.2 Hz, 2H, CH2), 3.99 (t, J = 4.8 Hz, 2H, CH2), 4.96 (t,
J = 4.4 Hz, 2H, CH2), 5.77 (s, 2H, CH2C6(CH3)5), 7.58–7.65 (m, 3H,
Ar–H), 8.07 (d, J = 8.8 Hz, 1H, Ar–H), 9.84 (s, 1H, NCHN) ppm. 13C
{1H} NMR (100.6 MHz, CDCl3, TMS, 25 °C): d = 17.1, 17.2, 17.4,
40.0, 48.2, 59.0, 68.8, 70.3, 70.7, 71.8, 113.6, 114.7, 124.9, 127.5,
131.4, 132.3, 133.8, 134.1, 137.5, 141.6 (NCN) ppm.
4.2.3. Synthesis of 1,10-di(2,4,6-trimethylbenzyl)-3,30-dioxaoctanebib-
enzimidazolium dibromide (9a)
Yield: 50%, m.p. = 201 °C. Anal. Calc. for C40H48Br2N4O2 (776.6):
C, 61.86; H, 6.23; N, 7.21. Found: C. 61.92; H. 6.32; N, 7.08%. 1H
NMR (400 MHz, CDCl3, TMS, 25 °C): d = 2.25 (s, 6H,
CH2C6H2(CH3)3-2,4,6), 2.27 (s, 12H, CH2C6H2(CH3)3-2,4,6), 3.57 (s,
4H, CH2), 4.00 (t, J = 4.0 Hz, 4H, CH2), 4.87 (t, J = 4.4 Hz, 4H, CH2),
5.87 (s, 4H, CH2C6H2(CH3)3-2,4,6), 6.90 (s, 4H, CH2C6H2(CH3)3-
2,4,6), 7.26 (d, J = 8.0 Hz, 2H, Ar–H), 7.43 (t, J = 8.0 Hz, 2H, Ar–H),
7.58 (t, J = 7.6 Hz, 2H, Ar–H), 8.00 (d, J = 8.4 Hz, 2H, Ar–H), 10.57
(s, 2H, NCHN) ppm. 13C {1H} NMR (100.6 MHz, CDCl3, TMS,
25 °C): d = 20.5, 21.3, 47.5, 48.1, 68.4, 70.9, 113.8, 114.4, 125.5,
127.4, 127.4, 130.4, 131.4, 132.0, 138.9, 139.7, 142.8 (NCN) ppm.
4.1.10. Synthesis of 1-[2-(2-(2-methoxyethoxy)ethoxy)ethyl]-3-(2,3,4,
5,6-pentamethylbenzyl)-5,6-dimethylbenzimidazolium bromide (7b)
Yield: 92%, m.p. = 135 °C. Anal. Calc. for C28H41BrN2O3 (533.6):
C, 63.03; H, 7.75; N, 5.25. Found: C, 63.12; H, 7.67; N, 5.17%. 1H
NMR (400 MHz, CDCl3, TMS, 25 °C): d = 2.16 (s, 3H, CH2C6(CH3)5),
2.21 (s, 6H, CH2C6(CH3)5), 2.24 (s, 6H, CH2C6(CH3)5), 2.34 (s, 3H,
CH3–Ar), 2.37 (s, 3H, CH3–Ar), 3.25 (s, 3H, OCH3), 3.35 (t,
J = 4.8 Hz, 2H, CH2), 3.40–3.46 (m, 4H, CH2), 3.56 (t, J = 4.4 Hz, 2H,
CH2), 3.93 (t, J = 4.4 Hz, 2H, CH2), 4.82 (t, J = 4.6 Hz, 2H, CH2), 5.65
(s, 2H, CH2C6(CH3)5), 7.30 (s, 1H, Ar–H), 7.77 (s, 1H, Ar–H), 9.73
(s, 1H, NCHN+) ppm. 13C {1H} NMR (100.6 MHz, CDCl3, TMS,
25 °C): d = 17.0, 17.2, 17.4, 20.7, 20.9, 47.5, 59.0, 68.9, 70.4, 70.7,
71.8, 113.0, 114.2, 124.9, 130.0, 130.8, 133.8, 134.1, 137.6, 137.7,
140.2 (NCN) ppm.
4.2.4. Synthesis of 1,10-di(2,4,6-trimethylbenzyl)-3,30-dioxaoctane-5,
6-dimethylbibenzimidazolium dibromide (9b)
Yield: 78%, m.p. = 231 °C. Anal. Calc. for C44H56Br2N4O2 (832.8):
C, 63.46; H, 6.78; N, 6.73. Found: C, 63.77; H, 6.70; N, 6.61%. 1H
NMR (400 MHz, CDCl3, TMS, 25 °C): d = 2.15 (s, 6H,
CH2C6H2(CH3)3-2,4,6), 2.23 (s, 12H, CH2C6H2(CH3)3-2,4,6), 2.26 (s,
6H, CH3–Ar), 2.41 (s, 6H, CH3–Ar), 3.55 (s, 4H, CH2), 3.98 (t,
J = 4.8 Hz, 4H, CH2), 4.78 (t, J = 4.8 Hz, 4H, CH2), 5.77 (s, 4H,
CH2C6H2(CH3)3-2,4,6), 6.90 (s, 4H, CH2C6H2(CH3)3-2,4,6), 7.02 (s,
2H, Ar–H), 7.72 (s, 2H, Ar–H), 10.30 (s, 2H, NCHN) ppm. 13C {1H}
NMR (100.6 MHz, CDCl3, TMS, 25 °C): d = 20.4, 20.7, 20.9, 21.2,
47.0, 47.9, 68.4, 70.9, 113.4, 113.8, 125.6, 129.9, 130.2, 130.4,
137.4, 137.6, 138.2, 139.7, 141.3 (NCN) ppm.
4.2. Preparation of linked-oligoether functionalized (5,6-dimethyl)be-
nzimidazolium dibromides (8–13)
4.2.5. Synthesis of 1,10-di(2,4,6-trimethylbenzyl)-3,30-trioxaundecane-
bibenzimidazolium dibromide (10a)
The linked-oligoether functionalized benzimidazole (2.5 mmol)
was dissolved in DMF (20 mL) and 2,4,6-trimethylbenzyl bromide
or 2,3,4,5,6-pentamethylbenzyl bromide was added. The mixture
was heated at 80 °C for 24 h. After completion of the reaction,
the volume of DMF was reduced to ca. 2 mL and diethyl ether
added (20 mL) then the products were obtained with crystalliza-
tion from CH2Cl2/Et2O. The following salts (8–13) were synthesized
according to this procedure.
Yield: 42%, m.p. = 91 °C. Anal. Calc. for C42H52Br2N4O3 (820.7): C,
61.47; H, 6.39; N, 6.83. Found: C, 61.19; H, 6.26; N, 7.01%. 1H NMR
(400 MHz, CDCl3, TMS, 25 °C): d 8 2.41 (s, 6H, CH2C6H2(CH3)3-
2,4,6), 2.65 (s, 12H, CH2C6H2(CH3)3-2,4,6), 3.40–3.55 (m, 8H, CH2),
3.99 (t, J = 4.4 Hz, 4H, CH2), 4.87 (t, J = 4.4 Hz, 4H, CH2), 5.79 (s,
4H, CH2C6H2(CH3)3-2,4,6), 6.88 (s, 4H, CH2C6H2(CH3)3-2,4,6), 7.30
(d, J = 8.4 Hz, 2H, Ar–H), 7.42 (t, J = 8.0 Hz, 2H, Ar–H), 7.53 (t,
J = 7.6 Hz, 2H, Ar–H), 8.02 (d, J = 8.0 Hz, 2H, Ar–H), 10.30 (s, 2H,
NCHN) ppm. 13C {1H} NMR (100.6 MHz, CDCl3, TMS, 25 °C):
d = 20.4, 21.3, 47.4, 48.2, 68.5, 70.7, 70.8, 113.7, 114.5, 125.3,
127.3, 130.4, 131.4, 132.1, 138.2, 139.9, 142.7 (NCN) ppm.
4.2.1. Synthesis of 1,10-di(2,4,6-trimethylbenzyl)-3,30-oxapentanebibe-
nzimidazolium dibromide (8a)
Yield: 51%, m.p. = 220 °C. Anal. Calc. for C38H44Br2N4O (752.6):
C, 62.30; H, 6.05; N, 7.65. Found: C, 62.58; H, 5.95; N, 7.58%. 1H
NMR (400 MHz, CDCl3, TMS, 25 °C): d = 2.25 (s, 6H,
CH2C6H2(CH3)3-2,4,6), 2.29 (s, 12H, CH2C6H2(CH3)3-2,4,6), 4.11 (t,
J = 4.8 Hz, 4H, CH2), 4.95 (t, J = 4.4 Hz, 4H, CH2), 5.99 (s, 4H,
CH2C6H2(CH3)3-2,4,6), 6.88 (s, 4H, CH2C6H2(CH3)3-2,4,6), 7.06 (d,
J = 8.8 Hz, 2H, Ar–H), 7.37 (t, J = 8.6 Hz, 2H, Ar–H), 7.53 (t,
J = 8.0 Hz, 2H, Ar–H), 8.03 (d, J = 8.4 Hz, 2H, Ar–H), 11.14 (s, 2H,
NCHN) ppm. 13C {1H} NMR (100.6 MHz, CDCl3, TMS, 25 °C):
d = 20.6, 21.2, 47.7, 48.0, 68.4, 114.0, 114.1, 125.7, 127.5, 130.4,
131.8, 138.1, 139.7, 143.4 (NCN) ppm.
4.2.6. Synthesis of 1,10-di(2,4,6-trimethylbenzyl)-3,30-trioxaundecane-
5,6-dimethylbibenzimidazolium dibromide (10b)
Yield: 65%, m.p. = 163 °C. Anal. Calc. for C46H60Br2N4O3 (876.8):
C, 63.01; H, 6.90; N, 6.39. Found: C, 63.17; H, 6.82; N, 6.34%. 1H
NMR (400 MHz, CDCl3, TMS, 25 °C): d = 2.25 (s, 6H,
CH2C6H2(CH3)3-2,4,6), 2.26 (s, 12H, CH2C6H2(CH3)3-2,4,6), 2.28 (s,
6H, CH3–Ar), 2.34 (s, 6H, CH3–Ar), 3.48 (t, J = 4.4 Hz, 4H, CH2),
3.58 (t, J = 4.8 Hz, 4H, CH2), 4.01 (t, J = 4.8 Hz, 4H, CH2), 4.84 (t,
J = 4.8 Hz, 4H, CH2), 5.76 (s, 4H, CH2C6H2(CH3)3-2,4,6), 6.86 (s, 4H,
CH2C6H2(CH3)3-2,4,6), 7.02 (s, 2H, Ar–H), 7.79 (s, 2H, Ar–H), 10.18
(s, 2H, NCHN) ppm. 13C {1H} NMR (100.6 MHz, CDCl3, TMS,
25 °C): d = 20.5, 20.7, 20.9, 21.3, 47.1, 48.1, 68.4, 70.6, 70.8, 113.3,
114.1, 125.9, 130.0, 130.2, 130.6, 136.9, 137.2, 138.3, 139.5, 141.9
(NCN) ppm.
4.2.2. Synthesis of 1,10-di(2,4,6-trimethylbenzyl)-3,30-oxapentane-5,6-
dimethylbibenzimidazolium dibromide (8b)
Yield: 73%, m.p. = 234 °C. Anal. Calc. for C42H52Br2N4O (788.7):
C, 63.96; H, 6.65; N, 7.10. Found: C, 63.74; H, 6.60; N, 7.17%. 1H
NMR (400 MHz, CDCl3, TMS, 25 °C): d = 2.26 (s, 6H,
CH2C6H2(CH3)3-2,4,6), 2.33 (s, 12H, CH2C6H2(CH3)3-2,4,6), 2.41 (s,
12H, CH3–Ar), 4.08 (t, J = 4.0 Hz, 4H, CH2), 4.84 (t, J = 4.4 Hz, 4H,
CH2), 5.92 (s, 4H, CH2C6H2(CH3)3-2,4,6), 6.85 (s, 4H,
CH2C6H2(CH3)3-2,4,6), 6.90 (s, 4H, Ar–H), 10.93 (s, 2H, NCHN)
ppm. 13C {1H} NMR (100.6 MHz, CDCl3, TMS, 25 °C): d = 20.1,
4.2.7. Synthesis of 1,10-di(2,3,4,5,6-pentamethylbenzyl)-3,30-oxapent-
anebibenzimidazolium dibromide (11a)
Yield: 53%, m.p. = 223 °C. Anal. Calc. for C42H52Br2N4O (788.7):
C, 63.96; H, 6.65; N, 7.10. Found: C, 63.91; H, 6.55; N, 7.02%. 1H
NMR (400 MHz, CDCl3, TMS, 25 °C): d = 2.19 (s, 6H, CH2C6(CH3)5),
2.23 (s, 12H, CH2C6(CH3)5), 2.28 (s, 12H, CH2C6(CH3)5), 4.12 (t,

3586
S. Gülcemal et al. / Journal of Organometallic Chemistry 694 (2009) 3580–3589
J = 4.8 Hz, 4H, CH2), 4.93 (t, J = 4.4 Hz, 4H, CH2), 6.00 (s, 4H,
CH2C6(CH3)5), 7.13 (d, J = 8.4 Hz, 2H, Ar–H), 7.40 (t, J = 8.8 Hz, 2H,
Ar–H), 7.55 (t, J = 8.4 Hz, 2H, Ar–H–), 7.99 (d, J = 8.0 Hz, 2H, Ar–
H), 10.84 (s, 2H, NCHN) ppm. 13C {1H} NMR (100.6 MHz, CDCl3,
TMS, 25 °C): d = 17.2, 17.4, 17.5, 47.6, 48.9, 68.4, 113.9, 114.1,
125.7, 127.4, 131.5, 131.9, 133.8, 134.0, 137.2, 142.9 (NCN) ppm.
12H, CH2C6(CH3)5), 2.27 (s, 12H, CH2C6(CH3)5), 2.38 (s, 6H, CH3–Ar),
2.42 (s, 6H, CH3–Ar), 3.38–3.53 (m, 8H, CH2), 3.97 (t, J 8 4.0 Hz, 4H,
CH2), 4.84 (t, J = 4.4 Hz, 4H, CH2), 5.69 (s, 4H, CH2C6(CH3)5), 7.30 (s,
2H, Ar–H), 7.75 (s, 2H, Ar–H), 9.63 (s, 2H, NCHN) ppm. 13C {1H}
NMR (100.6 MHz, CDCl3, TMS, 25 °C): d = 17.2, 17.3, 17.5, 20.8,
20.9, 47.7, 48.1, 68.7, 70.6, 70.7, 113.1, 114.1, 125.2, 130.0, 130.8,
133.8, 134.2, 137.4, 137.5, 137.6, 140.7 (NCN) ppm.
4.2.8. Synthesis of 1,10-di(2,3,4,5,6-pentamethylbenzyl)-3,30-oxapent-
ane-5,6-dimethylbibenzimidazolium dibromide (11b)
4.3. Preparation of bis(NHC)–Pd(II) complexes (14 and 15)
Yield: 75%, m.p. = 187 °C. Anal. Calc. C46H60Br2N4O (844.8): C,
65.40; H, 7.16; N, 6.63. Found: C, 65.63; H, 7.10; N, 6.68%. 1H
NMR (400 MHz, CDCl3, TMS, 25 °C): d = 2.16 (s, 6H, CH2C6(CH3)5),
2.19 (s, 12H, CH2C6(CH3)5), 2.24 (s, 12H, CH2C6(CH3)5), 2.34 (s,
6H, CH3–Ar), 2.48 (s, 6H, CH3–Ar), 4.02 (t, J = 4.8 Hz, 4H, CH2),
4.78 (t, J = 4.8 Hz, 4H, CH2), 5.84 (s, 4H, CH2C6(CH3)5), 6.95 (s, 2H,
Ar–H), 7.71 (s, 2H, Ar–H), 10.41 (s, 2H, NCHN) ppm. 13C {1H}
NMR (100.6 MHz, CDCl3, TMS, 25 °C): d = 17.1, 17.3, 17.4, 20.7,
21.0, 47.2, 48.3, 68.2, 110.0, 113.5, 125.8, 129.9, 130.3, 133.1,
133.7, 137.3, 137.7, 141.5 (NCN) ppm.
Ag2O (0.5 mmol) was added to a solution of salt 4 and 6
(1.0 mmol) in CH2Cl2 (15 mL). The suspension became clear after
stirring for 24 h at room temperature. [Pd(CH3CN)2Cl2] (0.5 mmol)
was added to the suspension. After the mixture was stirred for 2 h
at room temperature, the solid AgBr was filtered off and the vol-
ume of the clear yellow solution was reduced to 3 mL. The yellow
solid, formed after the addition of 15 mL of Et2O, was filtered and
dried under vacuum to give trans-bis(NHC)–Pd(II) complex. The
following complexes 14 and 15 were synthesized according to this
procedure.
4.2.9. Synthesis of 1,10-di(2,3,4,5,6-pentamethylbenzyl)-3,30-dioxaoc-
tanebibenzimidazolium dibromide (12a)
4.3.1. Synthesis of trans-bis{1-[2-(2-methoxyethoxy)ethyl]-3-(2,4,6-
trimethylbenzyl)benzimidazolin-2-ylidene}palladium(II) dichloride
(14a)
Yield: 55%, m.p. = 140 °C. Anal. Calc. for C44H56Br2N4O2 (832.8):
C, 63.46; H, 6.78; N, 6.73. Found: C, 63.42; H, 6.77; N, 6.42%. 1H
NMR (400 MHz, CDCl3, TMS, 25 °C): d = 2.17 (s, 6H, CH2C6(CH3)5),
2.22 (s, 12H, CH2C6(CH3)5), 2.26 (s, 12H, CH2C6(CH3)5), 3.52 (s,
4H, CH2), 3.95 (s, 4H, CH2), 4.85 (t, J = 4.8 Hz, 4H, CH2), 5.85 (s,
4H, CH2C6(CH3)5), 7.38 (d, J = 8.0 Hz, 2H, Ar–H), 7.48 (t, J = 8.4 Hz,
2H, Ar–H), 7.60 (t, J = 8.0 Hz, 2H, Ar–H), 7.90 (d, J = 7.6 Hz, 2H,
Ar–H), 10.15 (s, 2H, NCHN) ppm. 13C {1H} NMR (100.6 MHz, CDCl3,
TMS, 25 °C): d = 17.2, 17.4, 17.5, 48.4, 68.7, 70.9, 113.7, 114.5,
125.3, 127.4, 127.5, 131.5, 132.2, 133.8, 134.1, 137.4, 142.3 (NCN)
ppm.
Yield: 81%, m.p. = 213 °C. Anal. Calc. for C44H56Cl2N4O4Pd
(882.3): C, 59.90; H, 6.40; N, 6.35. Found: C, 60.13; H, 6.23; N,
6.17%. 1H NMR (400 MHz, CDCl3, TMS, 25 °C): d = 2.32 (s, 12H,
CH2C6H2(CH3)3-2,4,6), 2.39 (s, 6H, CH2C6H2(CH3)3-2,4,6), 3.22 (s,
3H, OCH3), 3.26 (t, J = 4.0 Hz, 2H, CH2), 3.33 (s, 3H, OCH3), 3.46 (t,
J = 4.0 Hz, 2H, CH2), 3.54 (t, J = 4.0 Hz, 2H, CH2), 3.63 (t, J = 4.0 Hz,
2H, CH2), 4.33 (t, J = 8.0 Hz, 4H, CH2), 5.14 (t, J = 8.0 Hz, 4H, CH2),
6.03–6.27 (m, 4H, CH2C6H2(CH3)3-2,4,6), 6.46–6.57 (m, 2H, Ar–H),
6.86 (s, 2H, CH2C6H2(CH3)3-2,4,6), 6.92 (d, J = 8.0 Hz, 2H, Ar–H),
6.95 (s, 2H, CH2C6H2(CH3)3-2,4,6), 7.14 (d, J = 8.0 Hz, 2H, Ar–H),
7.51–7.57 (m, 2H, Ar–H). 13C {1H} NMR (100.6 MHz, CDCl3, TMS,
25 °C): d = 21.2, 21.3, 48.4, 49.7, 50.1, 50.6, 59.1, 59.2, 70.6, 70.9,
71.0, 71.1, 71.9, 72.1, 111.5, 111.7, 122.7, 123.1, 128.3, 128.4,
129.8, 134.4, 134.5, 135.8, 138.5, 138.7, 138.9, 182.3 (NCN) ppm.
4.2.10. Synthesis of 1,10-di(2,3,4,5,6-pentamethylbenzyl)-3,30-dioxaoc-
tane-5,6-dimethylbibenzimidazolium dibromide (12b)
Yield: 80%, m.p. = 202 °C. Anal. Calc. for C48H64Br2N4O2 (888.9):
C, 64.86; H, 7.26; N, 6.30. Found: C, 64.93; H, 7.18; N, 6.31%. 1H
NMR (400 MHz, CDCl3, TMS, 25 °C): d = 2.11 (s, 6H, CH2C6(CH3)5),
2.17 (s, 12H, CH2C6(CH3)5), 2.34 (s, 12H, CH2C6(CH3)5), 2.41 (s,
6H, CH3–Ar), 2.45 (s, 6H, CH3–Ar), 3.23 (s, 4H, CH2), 3.62 (s, 4H,
CH2), 4.53 (s, 4H, CH2), 5.63 (s, 4H, CH2C6(CH3)5), 7.86 (s, 2H, Ar–
H), 8.00 (s, 2H, Ar–H), 8.74 (s, 2H, NCHN) ppm. 13C {1H} NMR
(100.6 MHz, CDCl3, TMS, 25 °C): d = 16.9, 17.3, 17.6, 20.7, 20.8,
46.8, 47.0, 68.2, 69.9, 114.1, 114.2, 126.4, 130.5, 130.6, 133.6,
134.4, 136.9, 137.0, 137.2, 140.7 (NCN) ppm.
4.3.2. Synthesis of trans-bis{1-[2-(2-methoxyethoxy)ethyl]-3-(2,4,6-
trimethylbenzyl)-5,6-dimethylbenzimidazolin-2-ylidene}palladium(II)
dichloride (14b)
Yield: 78%, m.p. = 223 °C. Anal. Calc. for C48H64Cl2N4O4Pd
(938.4): C, 61.44; H, 6.87; N, 5.97. Found: C, 61.31; H, 6.72; N,
6.08%. 1H NMR (400 MHz, CDCl3, TMS, 25 °C): d = 2.09, 2.26, 2.28,
2.30, 2.34, 2.39 (s, 30H, CH2C6H2(CH3)3-2,4,6, CH3–Ar), 3.24 (s,
3H, OCH3), 3.27 (t, J = 4.2 Hz, 2H, CH2), 3.35 (s, 3H, OCH3), 3.47 (t,
J = 4.2 Hz, 2H, CH2), 3.54 (t, J = 4.2 Hz, 2H, CH2), 3.64 (t, J = 4.2 Hz,
2H, CH2), 4.31 (t, J = 8.0 Hz, 4H, CH2), 5.07 (t, J = 8.0 Hz, 4H, CH2),
5.99–6.30 (m, 6H, CH2C6H2(CH3)3-2,4,6, Ar–H), 6.85, 6.94 (s, 4H,
CH2C6H2(CH3)3-2,4,6), 7.26 (s, 1H, Ar–H), 7.30 (s, 1H, Ar–H). 13C
{1H} NMR (100.6 MHz, CDCl3, TMS, 25 °C): d = 20.3, 20.5, 20.6,
21.1, 21.3, 21.4, 48.1, 48.4, 49.5, 50.3, 59.1, 59.2, 70.7, 70.9, 71.0,
71.1, 71.9, 72.2, 111.7, 111.9, 128.5, 128.7, 129.7, 131.7, 133.1,
133.2, 134.3, 134.4, 138.3, 138.7, 138.9, 180.8 (NCN) ppm.
4.2.11. Synthesis of 1,10-di(2,3,4,5,6-pentamethylbenzyl)-3,30-trioxau-
ndecanebibenzimidazolium dibromide (13a)
Yield: 45%, m.p. = 120 °C. Anal. Calc. for C46H60Br2N4O3 (876.8):
C, 63.01; H, 6.90; N, 6.39. Found: C, 62.94; H, 6.78; N, 6.15%. 1H
NMR (400 MHz, CDCl3, TMS, 25 °C): d = 2.15 (s, 6H, CH2C6(CH3)5),
2.19 (s, 12H, CH2C6(CH3)5), 2.21 (s, 12H, CH2C6(CH3)5), 3.35 (d,
J = 4.4 Hz, 4H, CH2), 3.49 (t, J = 4.0 Hz, 4H, CH2), 3.93 (t, J = 4.0 Hz,
4H, CH2), 4.89 (t, J = 4.0 Hz, 4H, CH2), 5.83 (s, 4H, CH2C6(CH3)5),
7.42 (t, J = 7.6 Hz, 4H, Ar–H), 7.48 (t, J = 7.6 Hz, 2H, Ar–H), 8.05 (d,
J = 8.0 Hz, 2H, Ar–H), 9.94 (s, 2H, NCHN) ppm. 13C {1H} NMR
(100.6 MHz, CDCl3, TMS, 25 °C): d = 17.2, 17.4, 17.5, 48.2, 48.4,
68.6, 70.5, 70.6, 113.7, 114.8, 125.7, 127.0, 127.1, 131.5, 132.2,
133.8, 133.9, 137.0, 142.5 (NCN) ppm.
4.3.3. Synthesis of trans-bis{1-[2-(2-methoxyethoxy)ethyl]-3-
(2,3,4,5,6-pentamethylbenzyl)benzimidazolin-2-ylidene}palladium(II)
dichloride (15a)
Yield: 84%, m.p. = 220 °C. Anal. Calc. for C48H64Cl2N4O4Pd
(938.4): C, 61.44; H, 6.87; N, 5.97. Found: C, 61.59; H, 6.69; N,
5.75%. 1H NMR (400 MHz, CDCl3, TMS, 25 °C): d = 2.14 (s, 6H,
CH2C6(CH3)5), 2.21 (s, 9H, CH2C6(CH3)5), 2.27 (s, 9H, CH2C6(CH3)5),
2.32 (s, 6H, CH2C6(CH3)5), 3.13 (s, 3H, OCH3), 3.18 (t, J = 4.0 Hz,
2H, CH2), 3.27 (s, 3H, OCH3), 3.41 (t, J = 4.0 Hz, 2H, CH2), 3.47 (t,
J = 4.0 Hz, 2H, CH2), 3.59 (t, J = 4.0 Hz, 2H, CH2), 4.28 (t, J = 8.0 Hz,
4.2.12. Synthesis of 1,10-di(2,3,4,5,6-pentamethylbenzyl)-3,30-trioxau-
ndecane-5,6-dimethylbibenzimidazolium dibromide (13b)
Yield: 71%, m.p. = 74 °C. Anal. Calc. for C50H68Br2N4O3 (932.9): C,
64.37; H, 7.35; N 6.01. Found: C, 64.54; H, 7.24; N, 5.87%. 1H NMR
(400 MHz, CDCl3, TMS, 25 °C): d = 2.24 (s, 6H, CH2C6(CH3)5), 2.26 (s,

S. Gülcemal et al. / Journal of Organometallic Chemistry 694 (2009) 3580–3589
3587
4H, CH2), 5.07 (t, J = 8.0 Hz, 4H, CH2), 6.14–6.35 (m, 6H,
CH2C6(CH3)5, Ar–H), 6.80 (t, J = 8.0 Hz, 2H, Ar–H), 7.05 (t,
J = 8.0 Hz, 2H, Ar–H), 7.45 (d, J = 8.4 Hz, 2H, Ar–H) ppm. 13C {1H}
NMR (100.6 MHz, CDCl3, TMS, 25 °C): d = 17.1, 17.4, 17.5, 17.9,
48.4, 51.5, 51.6, 51.9, 59.0, 59.2, 70.7, 70.8, 70.9, 71.1, 71.9, 72.1,
111.4, 112.0, 122.5, 122.9, 128.5, 133.3, 134.6, 134.7, 135.9, 182.4
(NCN) ppm.
51.0, 59.2, 70.2, 70.9, 72.0, 111.7, 112.1, 127.6, 129.7, 132.5,
133.3, 134.4, 139.1, 157.1 (NCN) ppm.
4.4.3. Synthesis of di-l-bromobis{1-[2-(2-methoxyethoxy)ethyl]-3-(2,
3,4,5,6-pentamethylbenzyl)benzimidazolin-2-ylidene}dibromodipalla-
dium(II) (17a)
Yield: 85%, m.p. = 267 °C. Anal. Calc. for C48H64Br4N4O4Pd2
(1293.5): C, 44.57; H, 4.99; N, 4.33. Found: C, 44.48; H, 5.06; N,
4.26%. 1H NMR (400 MHz, CDCl3, TMS, 25 °C): d = 2.23 (s, 24H,
CH2C6(CH3)5), 2.33 (s, 6H, CH2C6(CH3)5), 3.30 (s, 6H, OCH3), 3.42
(t, J = 4.2 Hz, 4H, CH2), 3.61 (t, J = 4.2 Hz, 4H, CH2), 4.31 (t,
J = 4.4 Hz, 4H, CH2), 5.11 (br, 4H, CH2), 6.26 (d, J = 8.0 Hz, 2H, Ar–
H), 6.33 (s, 4H, CH2C6(CH3)5), 6.90 (t, J = 8.0 Hz, 2H, Ar–H), 7.14 (t,
J = 8.0 Hz, 2H, Ar–H), 7.58 (d, J = 8.8 Hz, 2H, Ar–H) ppm. 13C {1H}
NMR (100.6 MHz, CDCl3, TMS, 25 °C): d = 17.1, 17.8, 49.4, 52.0,
59.2, 70.3, 70.9, 71.9, 111.7, 112.0, 123.0, 123.6, 127.3, 133.4,
134.8, 134.9, 135.9, 159.2 (NCN) ppm.
4.3.4. Synthesis of trans-bis{1-[2-(2-methoxyethoxy)ethyl]-3-(2,3,4,5,
6-pentamethylbenzyl)-5,6-dimethylbenzimidazolin-2-ylidene}palladi-
um(II) dichloride (15b)
Yield: 86%, m.p. = 234 °C. Anal. Calc. for C52H72Cl2N4O4Pd
(994.5): C, 62.80; H, 7.30; N, 5.63. Found: C, 63.01; H, 7.46; N,
5.69%. 1H NMR (400 MHz, CDCl3, TMS, 25 °C): d = 2.02, 2.21, 2.26,
2.28, 2.35, 2.41 (s, 42H, CH2C6(CH3)5, CH3–Ar), 3.23 (s, 3H, OCH3),
3.27 (t, J = 4.0 Hz, 2H, CH2), 3.37 (s, 3H, OCH3), 3.49 (t, J = 4.0 Hz,
2H, CH2), 3.55 (t, J = 4.0 Hz, 2H, CH2), 3.66 (t, J = 4.0 Hz, 2H, CH2),
4.32 (t, J = 8.0 Hz, 4H, CH2), 5.07 (t, J = 8.0 Hz, 4H, CH2), 6.08–6.31
(m, 6H, CH2C6(CH3)5, Ar–H), 7.26 (s, 1H, Ar–H), 7.29 (s, 1H, Ar–H).
13C {1H} NMR (100.6 MHz, CDCl3, TMS, 25 °C): d = 17.1, 17.4, 17.5,
17.9, 48.1, 48.2, 51.1, 51.3, 51.5, 51.7, 59.1, 59.3, 70.8, 70.9, 71.1,
72.0, 72.2, 111.6, 112.5, 128.9, 131.5, 133.1, 133.2, 133.4, 134.4,
134.6, 134.7, 134.8, 181.0 (NCN) ppm.
4.4.4. Synthesis of di-l-bromobis{1-[2-(2-methoxyethoxy)ethyl]-3-(2,
3,4,5,6-pentamethylbenzyl)-5,6-dimethylbenzimidazolin-2-ylidene}-
dibromodipalladium(II) (17b)
Yield: 83%, m.p. = 274 °C. Anal. Calc. for C52H72Br4N4O4Pd2
(1349.6): C, 46.28; H, 5.38; N, 4.15. Found: C, 46.17; H, 5.32; N,
4.19%. 1H NMR (400 MHz, CDCl3, TMS, 25 °C): d = 1.95, 2.08, 2.16,
2.24, 2.32 (s, 42H, CH2C6(CH3)5, CH3–Ar), 3.26 (s, 6H, OCH3), 3.41
(t, J = 4.6 Hz, 4H, CH2), 3.56 (t, J = 4.4 Hz, 4H, CH2), 4.28 (t,
J = 4.4 Hz, 4H, CH2), 4.98 (br, 4H, CH2), 5.93 (s, 2H, Ar–H), 6.14 (s,
4H, CH2C6(CH3)5), 7.25 (s, 2H, Ar–H) ppm. 13C {1H} NMR
(100.6 MHz, CDCl3, TMS, 25 °C): d = 17.1, 17.5, 17.9, 49.2, 52.2,
59.2, 70.3, 70.9, 72.0, 112.0, 112.1, 127.7, 132.3, 132.4, 133.3,
133.5, 134.4, 134.8, 136.3, 156.9 (NCN) ppm.
4.4. Preparation of dimeric NHC–Pd(II) complexes (16 and 17)
A mixture of salt 4 and 6 (0.5 mmol), Pd(OAc)2 (0.5 mmol) and
NaBr (2 mmol) in DMSO (10 mL) was stirred at 90 °C for 24 h. The
reaction mixture was filtered over CeliteÒ, and the solvent of fil-
trate was removed by vacuum distillation. The resulting residue
was suspended in CH2Cl2 (20 mL) and then extracted with H2O
(3 ꢁ 20 mL). Drying of the organic phase over MgSO4 followed by
removal of the solvent by vacuum afforded the solid as an orange
solid. The following complexes 16 and 17 were synthesized accord-
ing to this procedure.
4.5. Preparation of mixed NHC–phosphine Pd(II) complexes (18 and
19)
A mixture of complex 16 and 17 (0.2 mmol) and triphenylphos-
phine (0.4 mmol) in CH2Cl2 (5 mL) was stirred at room tempera-
ture for 1 h. Solution was reduced to 1 mL. The yellow solid,
formed after the addition of 10 mL of pentane, was filtered and
dried under vacuum to give cis-NHC–phosphine Pd(II) complexes
as yellow solid. The following complexes 18 and 19 were synthe-
sized according to this procedure. Slow evaporation of a CH2Cl2/
hexane mixture afforded the yellow crystals for the complexes
19a and 19b.
4.4.1. Synthesis of di-l-bromobis{1-[2-(2-methoxyethoxy)ethyl]-3-(2,
4,6-trimethylbenzyl)benzimidazolin-2-ylidene}dibromodipalladium-
(II) (16a)
Yield: 82%, m.p. = 230 °C. Anal. Calc. for C44H56Br4N4O4Pd2
(1237.4): C, 42.71; H, 4.56; N, 4.53. Found: C, 42.84; H, 4.47; N,
4.58%. 1H NMR (400 MHz, CDCl3, TMS, 25 °C): d = 2.29 (s, 12H,
CH2C6H2(CH3)3-2,4,6), 2.35 (s, 6H, CH2C6H2(CH3)3-2,4,6), 3.30 (s,
6H, OCH3), 3.42 (t, J = 4.0 Hz, 4H, CH2), 3.61 (t, J = 4.0 Hz, 4H,
CH2), 4.31 (t, J = 4.4 Hz, 4H, CH2), 5.13 (br, 4H, CH2), 6.21 (s, 4H,
CH2C6H2(CH3)3-2,4,6), 6.35 (d, J = 8.0 Hz, 2H, Ar–H), 6.93 (s, 4H,
CH2C6H2(CH3)3-2,4,6), 6.95 (t, J = 7.6 Hz, 2H, Ar–H), 7.16 (t,
J = 7.6 Hz, 2H, Ar–H), 7.59 (d, J = 8.0 Hz, 2H, Ar–H) ppm. 13C {1H}
NMR (100.6 MHz, CDCl3, TMS, 25 °C): d = 21.2, 21.4, 49.4, 51.4,
59.2, 70.3, 70.9, 71.9, 111.4, 112.2, 123.2, 123.7, 127.2, 129.9,
134.62, 135.9, 139.2, 159.5 (NCN) ppm.
4.5.1. Synthesis of cis-dibromo{1-[2-(2-methoxyethoxy)ethyl]-3-(2,4,6
-trimethylbenzyl)benzimidazolin-2-ylidene}(triphenylphosphine)pall-
adium(II) (18a)
Yield: 93%, m.p. = 223 °C. Anal. Calc. for C40H43Br2N2O2PPd
(881.0): C, 54.53; H, 4.92; N, 3.18. Found: C, 54.48; H, 5.01; N,
3.16%. 1H NMR (400 MHz, CDCl3, TMS, 25 °C): d = 1.99 (s, 6H,
CH2C6H2(CH3)3-2,4,6), 2.31 (s, 3H, CH2C6H2(CH3)3-2,4,6), 3.29 (s,
3H, OCH3), 3.31–3.37 (m, 1H, CH2), 3.41–3.45 (m, 3H, CH2),
3.98–4.16 (m, 3H, CH2), 4.72–4.79 (m, 1H, CH2), 4.95 (d,
J = 14.0 Hz, 1H, CH2C6H2(CH3)3-2,4,6), 5.79 (d, J = 8.0 Hz, 1H, Ar–
H), 6.42 (d, J = 14.0 Hz, 1H, CH2C6H2(CH3)3-2,4,6), 6.78 (t,
J = 8.0 Hz, 1H, Ar–H), 6.86 (s, 2H, CH2C6H2(CH3)3-2,4,6), 7.04 (t,
J = 8.0 Hz, 1H, Ar–H), 7.20 (br, 8H, Ar–H–PPh3), 7.28 (d,
J = 8.0 Hz, 1H, Ar–H) 7.35 (br, 3H, Ar–H–PPh3), 7.58 (br, 4H, Ar–
H–PPh3), ppm. 13C {1H} NMR (100.6 MHz, CDCl3, TMS, 25 °C):
d = 21.0, 21.3, 48.9, 50.5, 59.1, 69.1, 70.6, 71.8, 111.1, 111.8,
122.7, 123.3, 126.6, 128.6, 128.7, 129.7, 131.4, 134.5, 134.8,
135.6, 139.4, 175.6 (NCN) ppm. 31P {1H} NMR (161.9 MHz, CDCl3,
25 °C): d = 26.99 ppm.
4.4.2. Synthesis of di-l-bromobis{1-[2-(2-methoxyethoxy)ethyl]-3-(2,
4,6-trimethylbenzyl)-5,6-dimethylbenzimidazolin-2-ylidene}dibrom-
odipalladium(II) (16b)
Yield: 78%, m.p. = 227 °C. Anal. Calc. for C48H64Br4N4O4Pd2
(1293.5): C, 44.57; H, 4.99; N, 4.33. Found: C, 44.51; H, 4.91; N,
4.36%. 1H NMR (400 MHz, CDCl3, TMS, 25 °C): d = 2.07, 2.28,
2.30, 2.36 (s, 30H, CH2C6H2(CH3)3-2,4,6, CH3–Ar), 3.21 (s, 6H,
OCH3), 3.37 (t, J = 4.2 Hz, 4H, CH2), 3.55 (t, J = 4.4 Hz, 4H, CH2),
4.28 (t, J = 4.4 Hz, 4H, CH2), 5.06 (br, 4H, CH2), 6.12 (s, 2H, Ar–
H), 6.13 (s, 4H, CH2C6H2(CH3)3-2,4,6), 6.94 (s, 4H,
CH2C6H2(CH3)3-2,4,6), 7.35 (s, 2H, Ar–H) ppm. 13C {1H} NMR
(100.6 MHz, CDCl3, TMS, 25 °C): d = 20.1, 20.5, 21.0, 21.1, 49.1,

3588
S. Gülcemal et al. / Journal of Organometallic Chemistry 694 (2009) 3580–3589
135.6, 136.8, 175.6 (NCN) ppm. 31P {1H} NMR (161.9 MHz, CDCl3,
25 °C): d = 27.13 ppm.
Table 4
Crystal data and structure refinement.
Identification code
19a
19b
4.5.4. Synthesis of cis-dibromo{1-[2-(2-methoxyethoxy)ethyl]-3-(2,3,
4,5,6-pentamethylbenzyl)-5,6-dimethylbenzimidazolin-2-ylidene}(tri-
phenylphosphine)palladium(II) (19b)
Empirical formula
Formula weight
Temperature (K)
Wavelength (Å)
Crystal system
Space group
a (Å)
C42H47Br2N2O2PPd
909.01
110(2)
C44H51Br2N2O2PPd
937.06
180(2)
0.71073
0.71073
Yield: 91%, m.p. = 245 °C. Anal. Calc. for C44H51Br2N2O2PPd
(937.1): C, 56.39; H, 5.49; N, 2.99. Found: C, 56.42; H, 5.54; N,
2.96%. 1H NMR (400 MHz, CDCl3, TMS, 25 °C): d = 1.89, 1.92, 2.20,
2.31 (s, 21H, CH2C6(CH3)5, CH3–Ar), 3.34 (s, 3H, OCH3), 3.37–3.42
(m, 1H, CH2), 3.46–3.48 (m, 3H, CH2), 3.89–4.07 (m, 3H, CH2),
4.63–4.69 (m, 1H, CH2), 5.09 (d, J = 14.0 Hz, 1H, CH2C6(CH3)5),
5.38 (s, 1H, Ar–H), 6.37 (d, J = 14.0 Hz, 1H, CH2C6(CH3)5), 6.99 (s,
1H, Ar–H), 7.21 (br, 8H, Ar–H–PPh3), 7.36 (br, 3H, Ar–H–PPh3),
7.55 (br, 4H, Ar–H–PPh3), ppm. 13C {1H} NMR (100.6 MHz, CDCl3,
TMS, 25 °C): d = 17.0, 17.2, 20.2, 20.6, 48.6, 50.1, 59.2, 68.9, 70.6,
71.9, 111.6, 111.9, 127.0, 127.3, 128.6, 128.7, 131.3, 131.7, 131.9,
133.8, 134.1, 134.6, 136.6, 173.1 (NCN) ppm. 31P {1H} NMR
(161.9 MHz, CDCl3, 25 °C): d = 27.20 ppm.
Triclinic
Triclinic
ꢀ
ꢀ
P1
P1
11.7736(4)
12.2100(5)
14.0081(6)
94.377(4)
106.357(3)
90.343(3)
1925.81(13)
2
1.568
2.636
920
0.59 ꢁ 0.39 ꢁ 0.10
3.04–30.03°
18 046
12.043(5)
12.804(5)
15.010(5)
85.593(5)
84.969(5)
64.379(5)
2077.0(14)
2
1.498
2.447
952
0.48 ꢁ 0.36 ꢁ 0.29
3.19–30.51
29 154
b (Å)
c (Å)
a
(°)
b (°)
c
(°)
Volume (Å3)
Z
Dcalc (Mg/m3)
Absorption coefficient (mmꢀ1
F(0 0 0)
)
Crystal size (mm)
h Range (°)
Reflections collected
Independent reflections (Rint
Completeness (%)
)
10 770 (0.0438)
95.7
12 460 (0.0874)
98.3
4.6. General procedure for the Heck coupling reactions
Absorption correction
Maximum/minimum transmission
Refinement method
Multi-scan
1.0/0.513
F2
10 770/13/467
1.032
0.0509, 0.1241
0.0787, 0.1396
2.201/ꢀ2.535
Multi-scan
1.0/0.7605
F2
12 460/0/476
0.946
0.0386, 0.0881
0.0653, 0.0947
1.255/ꢀ1.051
In a typical run, a reaction vessel was charged with 4-bromo-
acetophenone (1.0 mmol), styrene (1.5 mmol), Cs2CO3 (2 mmol),
diethyleneglycol-di-n-butyl ether and catalyst (1.5 mmol%). About
3 mL water was added. The reaction mixture was vigorously stirred
at 100 °C for 4 h. At the conclusion the solution was allowed to
cool, extracted with Et2O and the organic phase separated. Yields
were determined by gas chromatography for an average of two
runs.
Data/restraints/parameters
Goodness-of-fit (GOF) on F2
R1, wR2 [I > 2
r
(I)]
R1, wR2 (all data)
Residual density (e Åꢀ3
)
4.5.2. Synthesis of cis-dibromo{1-[2-(2-methoxyethoxy)ethyl]-3-(2,4,6
-trimethylbenzyl)-5,6-dimethylbenzimidazolin-2-ylidene}(triphenylp-
hosphine)palladium(II) (18b)
4.7. X-ray diffraction studies
A single crystal of each compound was mounted under inert
perfluoropolyether at the tip of a glass fiber and cooled in the cryo-
stream of either an Oxford-Diffraction XCALIBUR or a Bruker APEX-
II CCD diffractometer. Data were collected using the
Yield: 87%, m.p. = 226 °C. Anal. Calc. for C42H47Br2N2O2PPd
(909.0): C, 55.49; H, 5.21; N, 3.08. Found: C, 55.51; H, 5.25; N,
3.04%. 1H NMR (400 MHz, CDCl3, TMS, 25 °C): d = 1.93 (s, 3H,
CH2C6H2(CH3)3-2,4,6), 1.97 (s, 6H, CH2C6H2(CH3)3-2,4,6), 2.20 (s,
3H, CH3–Ar), 2.31 (s, 3H, CH3–Ar), 3.32 (s, 3H, OCH3), 3.34–3.40
(m, 1H, CH2), 3.43–3.49 (m, 3H, CH2), 3.93–4.06 (m, 3H, CH2),
4.65–4.71 (m, 1H, CH2), 4.91 (d, J = 14.0 Hz, 1H, CH2C6H2(CH3)3-
2,4,6), 5.45 (s, 1H, Ar–H), 6.33 (d, J = 14.0 Hz, 1H, CH2C6H2(CH3)3-
2,4,6), 6.85 (s, 2H, CH2C6H2(CH3)3-2,4,6), 7.02 (s, 1H, Ar–H), 7.21
(br, 8H, Ar–H–PPh3), 7.35 (br, 3H, Ar–H–PPh3), 7.56 (br, 4H, Ar–
H–PPh3), ppm. 13C {1H} NMR (100.6 MHz, CDCl3, TMS, 25 °C):
d = 20.2, 20.6, 20.9, 21.2, 48.6, 50.3, 59.2, 69.0, 70.6, 71.9, 111.5,
111.8, 126.9, 128.6, 128.7, 129.5, 131.3, 131.9, 132.1, 133.5,
134.2, 134.5, 139.2, 173.2 (NCN) ppm. 31P {1H} NMR (161.9 MHz,
CDCl3, 25 °C): d = 27.07 ppm.
monochromatic Mo K
a radiation (k = 0.71073). The structures
were solved by direct methods (SIR97) [17] and refined by least-
squares procedures on F2 using SHELXL-97 [18]. All H atoms attached
to carbon were introduced in idealized positions and treated as rid-
ing on their parent atoms in the calculations. In the ligand struc-
ture the H atoms attached to nitrogen and oxygen atoms were
located in difference Fourier synthesis but were treated as riding
on their parent atoms. In compound 19b, some residual electron
density were difficult to modelize and therefore, the SQUEEZE
function of PLATON [19] was used to eliminate the contribution of
the electron density in the solvent region from the intensity data,
and the solvent-free model was employed for the final refinement.
There is one cavity of 39 Å3 per unit cell. PLATON estimated that the
cavity contains 14 electrons which may correspond to a 1/3 of
ether molecule as suggested by the synthetic procedure. In com-
pound 6d, the long methoxyethoxy chain is disordered over two
positions with occupancy factors in the ratio 0.53/0.47. This disor-
der was treated using the tools (PART and SAME) available in SHEL-
XL-97. The drawing of the molecules was realized with the help of
ORTEP3 [20]. Crystal data and refinement parameters are shown in
Table 4. Bond distances and angles are given in Table 1.
4.5.3. Synthesis of cis-dibromo{1-[2-(2-methoxyethoxy)ethyl]-3-(2,3,
4,5,6-pentamethylbenzyl)benzimidazolin-2-ylidene}(triphenylphosp-
hine)palladium(II) (19a)
Yield: 92%, m.p. = 232 °C. Anal. Calc. for C42H47Br2N2O2PPd
(909.0): C, 55.49; H, 5.21; N, 3.08. Found: C, 55.42; H, 5.16; N,
3.13%. 1H NMR (400 MHz, CDCl3, TMS, 25 °C): d = 1.93 (s, 6H,
CH2C6(CH3)5), 2.19 (s, 6H, CH2C6(CH3)5), 2.29 (s, 3H, CH2C6(CH3)5),
3.30 (s, 3H, OCH3), 3.34–3.39 (m, 1H, CH2), 3.43–3.48 (m, 3H,
CH2), 3.96–4.09 (m, 3H, CH2), 4.70–4.78 (m, 1H, CH2), 5.15 (d,
J = 14.0 Hz, 1H, CH2C6(CH3)5), 5.75 (d, J = 8.0 Hz, 1H, Ar–H), 6.43
(d, J = 14.0 Hz, 1H, CH2C6(CH3)5), 6.75 (t, J = 8.0 Hz, 1H, Ar–H),
7.02 (t, J = 8.0 Hz, 1H, Ar–H), 7.20 (br, 8H, Ar–H–PPh3), 7.25 (d,
J = 8.0 Hz, 1H, Ar–H) 7.34 (br, 3H, Ar–H–PPh3), 7.57 (br, 4H, Ar–
H–PPh3), ppm. 13C {1H} NMR (100.6 MHz, CDCl3, TMS, 25 °C): d
= 17.2, 17.6, 48.9, 52.2, 59.3, 69.1, 70.7, 71.9, 111.6, 111.8, 122.6,
123.4, 127.1, 128.7, 128.8, 131.5, 133.4, 134.6, 135.0, 135.3,
Supplementary material
CCDC 733626 and 733625 contain the supplementary crystallo-
graphic data for 19a and 19b. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via
http://www.ccdc.cam.ac.uk/data_request/cif.

S. Gülcemal et al. / Journal of Organometallic Chemistry 694 (2009) 3580–3589
3589
_
(n) I. Özdemir, S. Demir, Y. Gök, E. Çetinkaya, B. Çetinkaya, J. Mol. Catal. A:
Chem. 222 (2004) 97;
Acknowledgements
_
(o) I. Özdemir, Y. Gök, N. Gürbüz, E. Çetinkaya, B. Çetinkaya, Heteroatom
Chem. 15 (2004) 419;
Financial supports from Ege University (Project 07-FEN-047;
08-BIL-006) and TUBITAK (106T364) are gratefully acknowledged.
(p) C. Metallions, F.B. Barret, J.L. Chaytor, M.E.A. Heska, Org. Lett. 6 (2004)
3641.
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[5] I. Özdemir, N. Sßahin, Y. Gök, S. Demir, B. Çetinkaya, J. Mol. Catal. A: Chem. 234
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