Monomeric triphenylphosphite palladacycles with N-imidazole ligands as catalysts of Suzuki-Miyaura and Sonogashira reactions

Article abstract of DOI:10.1016/j.jorganchem.2011.08.011

Three monomeric triphenylphosphite palladacycles of the formula [PdCl(P-C)(im)], where P-C = P(OC₆H₄)(OC₆H ₅)₂, im = 1-methylimidazole, 2, 1,2-dimethylimidazole, 3, and 1-butylimidazole, 4, were obtained in reaction of [PdCl(P-C)]₂, 1, with the respective imidazoles. These complexes exhibited high catalytic activity in the Suzuki-Miyaura reaction in ethane-1,2-diol and in the Sonogashira reaction in ionic liquids, [bmim]BF₄ and [bmim]PF ₆. While the application of two imidazoles per palladium caused improvement of the reaction yield, an inhibiting effect was found in both reactions when 1-methylimidazole or 1-butylimidazole was used in 20-fold excess relative to palladium.

Full text of DOI:10.1016/j.jorganchem.2011.08.011

Journal of Organometallic Chemistry 696 (2011) 3601e3607
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Monomeric triphenylphosphite palladacycles with N-imidazole ligands as
catalysts of SuzukieMiyaura and Sonogashira reactions
*
Izabela B1aszczyk, Andrzej Gniewek, Anna M. Trzeciak
Faculty of Chemistry, University of Wrocław, 14 F. Joliot-Curie St., 50-383 Wrocław, Poland
a r t i c l e i n f o
a b s t r a c t
Article history:
Three monomeric triphenylphosphite palladacycles of the formula [PdCl(PeC)(im)], where PeC ¼
P(OC6H4)(OC6H5)2, im ¼ 1-methylimidazole, 2, 1,2-dimethylimidazole, 3, and 1-butylimidazole, 4, were
obtained in reaction of [PdCl(PeC)]2, 1, with the respective imidazoles. These complexes exhibited high
catalytic activity in the SuzukieMiyaura reaction in ethane-1,2-diol and in the Sonogashira reaction in ionic
liquids, [bmim]BF4 and [bmim]PF6. While the application of two imidazoles per palladium caused
improvement of the reaction yield, an inhibiting effect was found in both reactions when
1-methylimidazole or 1-butylimidazole was used in 20-fold excess relative to palladium.
Ó 2011 Elsevier B.V. All rights reserved.
Received 29 May 2011
Received in revised form
6 August 2011
Accepted 12 August 2011
Keywords:
Palladacycles
Imidazole ligands
SuzukieMiyaura reaction
Sonogashira reaction
Ionic liquid
1. Introduction
Inspired by the fact that palladium complexes with imidazole
ligands exhibited attractive catalytic activity in CeC cross-coupling
Dimeric triarylphosphite-based palladacycles have been
obtained in the reaction of PdCl2 with P(OR)3 or, alternatively, with
PdCl2[P(OR)3]2 [1e3]. These complexes are active catalysts of
SuzukieMiyaura [1,4,5], Hiyama [6], Stille [1], Sonogashira [6], Heck
[7] reactions and in the allylation of aldehydes with allyl tributyltin
[8]. Most catalytic reactions with triarylphosphite palladacycles
have been performed in organic solvents; however, successful
application of ionic liquids as reaction media has also been reported
[6]. Interestingly, an increase in the catalytic activity of dimeric
palladacycles has been observed after their transformation to
monomeric complexes in reaction with mono- or bi-dentate
phosphorus ligands [4,9]. Particularly high activity in the cross-
coupling of deactivated aryl chlorides has been noted for palla-
dium derivatives containing PCy3 [9].
While the presence of a phosphorus ligand in the coordination
sphere of a palladacycle complex mostly improved its catalytic
activity, less spectacular results have been found for monomeric
palladacycles containing bulky N-heterocyclic carbene ligands,
which only gave a modest yield in the SuzukieMiyaura cross-
coupling of aryl bromides [10e12]. The same complexes showed
poor activity in reactions with aryl chlorides as substrates [10].
reactions [13e15], we decided to examine whether N-imidazoles
can improve the reactivity of palladacycles. In this paper, we
report studies of reactions of triphenylphosphite palladacycles
with imidazoles resulting in the formation of monomeric palla-
dacycles. These complexes were next tested in two model reac-
tions, SuzukieMiyaura and Sonogashira, in organic solvents and in
ionic liquids.
2. Results and discussion
2.1. Formation of [PdCl(PeC)(im)] complexes
Monomeric phosphite-based palladacycles with coordinated
1-methylimidazole, 2, 1,2-dimethylimidazole, 3, and 1-butylimid-
azole, 4, were obtained in the reaction of dimeric palladacycle 1 with
a stoichiometric amount of the free imidazole according to Scheme 1.
31P NMR spectra of complexes 2e4 exhibited signals in the
region of 120e130 ppm, characteristic for the presence of
a chelating PeC ligand and slightly shifted downfield compared
with 1. The presence of two signals in the spectra of 2e4 is
consistent with the formation of two isomers with different local-
izations of the N-imidazole ligand. On the basis of literature data, it
can be proposed that the isomer with imidazole trans to phos-
phorus is dominating [2,10].
* Corresponding author. Tel.: þ48 71 3757 253; fax: þ48 71 3757 356.
E-mail address: ania@wchuwr.chem.uni.wroc.pl (A.M. Trzeciak).
0022-328X/$ e see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2011.08.011

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I. Błaszczyk et al. / Journal of Organometallic Chemistry 696 (2011) 3601e3607
O
P(OPh)
Pd
O
P(OPh)
Pd Cl
+
2
Cl
2
N
N
30oC, 1h
R'
N
R"
N
R"
1.
R'
Scheme 1. Synthesis of monomeric palladacycles with coordinated imidazole ligands.
The solid state studies also revealed that the investigated
complexes may form two different isomers. The molecular structure
of compounds 2 and 4 has been determined by single crystal X-ray
diffraction (Figs.1 and 2). Pd atoms in both the compounds are four-
coordinated in a slightly distorted square-planar environment
(Table 1). In compound 2 the metallated carbon is in cis orientation
to Cl. The PdeCl bond length in 4 is somewhat longer than in 2,
indicating the trans influence of the aryl group. All other bond
distances and angles in compounds 2 and 4 are within standard
ranges.
Fig. 2. Molecular structure and atom numbering scheme of 4. Displacement ellipsoids
are drawn at the 30% probability level and H atoms are shown as small spheres of
arbitrary radii.
Reactions of complex 1 with different N-imidazole ligands were
studied in situ using 1H and 31P NMR methods in order to get more
data about the formation and stability of the new complexes. The
completeness of the transformation of 1 to 2, 3, or 4 was observed
at the [Pd]:[im] ratio equal to 1:2. When the amount of imidazole
was smaller and the [Pd]:[im] ratio was 2:1, signals of unreacted
1 (at 122.8 and 125.1 ppm) were present in addition to those of
the monomeric products 2e4. In reactions with 20-fold excess
of N-imidazole, only peaks originating from the monomeric
complexes 2e4 were found in the 31P NMR spectrum. It is impor-
tant to note that signals of free phosphite were not observed, which
confirms the stability of PdeP and PdeC bonds even in the presence
of an excess of N-imidazole.
of signals of unreacted 1 in 31P NMR, suggesting that the formation of
monomeric complexes is slower than in the case of complexes 2e4.
Consequently, 28% of 1 was converted to the monomeric complex
during reaction with 2-phenylimidazole, and only 19% in reaction
with 4-methyl-2-phenylimidazole. The formation of these new
complexes was additionally confirmed by ESI-MS(þ), where new
signals were found at m/z 559 assigned to [Pd(PeC)(2-phenyl-
imidazole)]þ and at m/z 573 assigned to [Pd(PeC)(4-methyl-2-
phenylimidazole)]þ (where PeC is the orthometallated ring).
Similar cations of the [Pd(PeC)(im)]þ composition were also
observed in MS spectra measured for complexes 2, 3, and 4 in
dichloromethanesolution orfor suchcomplexesformedinsitufrom1
and the respective N-imidazole. Thus, for 2 a peak at m/z 497 was
found, for 3 at m/z 511, and for 4 at m/z 539.
Studies of the reaction of 1 with 2-phenylimidazole or 4-methyl-
2-phenylimidazoleatthe[Pd]:[im]ratioof1:20revealedthepresence
In 1H NMR spectra the most characteristic signal was that of the
proton of the orthometallated ring at ca. 8.26 ppm. The presence of
this signal in the spectra of palladium complexes formed in reaction
of 1 with imidazoles is additional evidence of the preservation of
the orthometallated rings.
2.2. SuzukieMiyaura reaction
The obtained monomeric phosphite-based palladacycles
with coordinated N-imidazole ligands were tested in a model
SuzukieMiyaura cross-coupling reaction of 2-bromotoluene with
phenylboronic acid (Scheme 2).
Table 1
Selected bond lengths (Å) and angles (ꢀ) for 2 and 4.
2
4
PdeP
PdeCl
PdeN41
PdeC11
2.1583 (10)
2.3652 (11)
2.1259 (17)
2.0186 (19)
2.1658 (12)
2.3872 (13)
2.092 (3)
2.026 (3)
PePdeCl
172.44 (4)
80.70 (5)
174.01 (6)
93.63 (5)
90.28 (4)
95.79 (4)
96.20 (4)
81.40 (10)
94.70 (12)
176.52 (10)
87.88 (8)
PePdeC11
C11ePdeN41
C11ePdeCl
N41ePdeCl
N41ePdeP
Fig. 1. Molecular structure and atom numbering scheme of 2. Displacement ellipsoids
are drawn at the 30% probability level and H atoms are shown as small spheres of
arbitrary radii.
174.37 (8)

I. Błaszczyk et al. / Journal of Organometallic Chemistry 696 (2011) 3601e3607
3603
OH
B
CH
H C
A
Br
[Pd], base
OH
+
ethane-1,2-diol
80 oC, 2h
Scheme 2. SuzukieMiyaura reaction.
First, the effect of the base was studied and the best results,100%
conversion, were obtained for complexes 3 and 4 with Cs2CO3 and
for 4 with K3PO4 (Table 2). Very good results, 96e97% yield, were
also obtained when NaHCO3 was used as a base. Under these
conditions, imidazole-substituted palladacycles gave the coupling
product with 96% yield, ca. 10% higher than the dimeric pallada-
cycle 1, indicating a positive effect of imidazole ligands. In all
experiments with complex 3, yields of 97e100% were achieved, and
consequently 1,2-dimethylimidazole might be considered the most
promising modifying ligand. Recycling trials showed that catalyst 3
may be reused although the yield of 2-methylbiphenyl obtained in
the second run (69%) was lower than in the first one (100%). Results
collected in Table 2 were obtained after 2 h of reaction; however,
a kinetic profile shows that the reaction is quite fast and reaches the
maximum yield already after 15 min (Fig. 3A). When lower
concentration of palladium was used (0.1 mol%), a short induction
period was found indicating the transformation of 3 to the active
species (Fig. 3B).
B
2.3. Effect of imidazole excess in SuzukieMiyaura reaction
The good results obtained in SuzukieMiyaura reactions with
complexes 2, 3, and 4 prompted us to study the activity of palla-
dacycle 1 in the presence of imidazole excess. It was expected that
catalytically active imidazole-modified complexes would be
formed in situ. Five different imidazoles were used together with
complex 1 and it was discovered that the efficiency of the reaction
depended on the [im]:[Pd] ratio (Table 3). When a small amount of
imidazole was used, at an [im]:[Pd] ratio equal to 2, conversion in
all reactions increased compared with reactions catalyzed by 1
only. Good results were also observed for dimer 5, which produced
90e97% of the cross-coupling product when a 2-fold excess of
imidazole was added. Apparently, increasing the [im]:[Pd] ratio to
20 resulted in the catalytic reaction being totally retarded when
2-methylimidazole and 2-butylimidazole were added. These two
imidazoles applied in 20-fold excess with complexes 2 or 3 also
stopped the reaction completely. In contrast, imidazoles
substituted at C2 with a methyl or phenyl group did not cause any
Fig. 3. Kinetic profile of SuzukieMiyaura reaction catalyzed by 3 at 1 mol% (A) and
0.1 mol% (B).
inhibiting effect even when used in excess, as shown for complexes
1 or 5.
It is also worth noting that the above-presented influence of
imidazoles on the SuzukieMiyaura cross-coupling reaction was
independent of the reaction procedure. In the first set of experiments
imidazoles were mixed with the catalyst for 10 min to facilitate
coordination of imidazole to palladium and then the other react-
ants were introduced. Subsequently, similar experiments were per-
formed without any pre-treatment. In both cases, practically the
sameresultswereobtained, whichsuggestfastactionofimidazoles in
the studied systems.
Table 2
Results of SuzukieMiyaura cross-coupling with catalysts 1e4.
Base
Yield [%]a
C
C
P
C
P
C
P
P
Cl
N
Cl
N
Cl
N
Cl
Cl
Pd
Pd
Pd
Pd
Pd
CH3
CH3
P
C
N
N
N
CH3
1
4
2
3
NaHCO3
Na2CO3
K3PO4
86
96
88
85
98
97
99
96
84
85
100
Cs2CO3
100
100/69b
100
Reaction conditions: [Pd] 1 mol%, [PhB(OH)2] 1.5 mmol, [2-bromotoluene] 1 mmol, [base] 2 mmol, [ethane-1,2-diol] 2.5 cm3, 80 ꢀC, 2 h.
a
Conversion to the coupled product determined by GC.
Recycled catalyst.
b

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I. Błaszczyk et al. / Journal of Organometallic Chemistry 696 (2011) 3601e3607
Table 3
Effect of imidazoles on the yield of SuzukieMiyaura cross-coupling.
Catalyst
Imidazole
None
[Pd]:[Imidazole]
Yield [%]a
86
1
e
1
1
1
2
5
1:20
1:40
1:2
1:20
1:2
1
0
94
0
N
N
H3C
90
1
1
1
3
5
1:2
93
0
0
0
96
1:20
1:40
1:20
1:2
H3C
N
N
N
1
5
5
N
1:20
1:2
1:20
95
98
92
H3C
CH3
Fig. 4. Sonogashira reaction in ionic liquids with catalysts 1e4.
N
1
5
5
1:20
1:2
1:20
93
96
95
optimized and besides catalyst deactivation some leaching of
palladium to the hexane phase during extraction cannot be
excluded.
N
H3C
1
5
5
1:20
1:2
1:20
92
97
97
In order to find a simple and efficient protocol of the Sono-
gashira cross-coupling, reactions were carried out in [bmim]PF6
using 1 and free imidazoles as additives. In all five reactions per-
formed at the [im]:[Pd] ratio equal to 2, satisfactory results were
obtained with a yield of 80e85%, which is over 20% higher than
with 1 alone (Table 4). Also, recycling was relatively good with the
best result 75% in the second run when 1-butylimidazole was
applied. Generally, the recycling experiments performed with in
situ formed imidazole palladacycles were more productive than
with isolated complexes 2, 3, and 4 (Table 4).
Similarly as in the SuzukieMiyaura reaction, the Sonogashira
cross-coupling was inhibited by an excess of free imidazoles. The
most dramatic effect was noted for 1,2-dimethylimidazole, which
afforded only 6% of the product when used in 20-fold excess. In
contrast, 20-fold excessof 1-methylimidazole and1-butylimidazole,
which stopped the SuzukieMiyaura reaction completely, only
caused some decrease in the yield of diphenylacetylene, to 29% and
20% respectively.
N
N
Reaction conditions: [Pd] 1 mol%, [PhB(OH)2] 1.5 mmol, [2-bromotoluene] 1 mmol,
[base] 2 mmol, [ethane-1,2-diol] 2.5 cm3, 80 ꢀC, 2 h.
a
Conversion to the coupled product determined by GC.
The observed inhibiting effect is not related to the formation or
decomposition of palladium complexes, because according to the
NMR results, the monomeric palladacycle complexes with imid-
azole ligands were stable in the range of concentrations used.
2.4. Sonogashira reaction
Imidazole-modified phosphite-based palladacycles 2, 3, and 4
were also tested in the Sonogashira cross-coupling of iodobenzene
with phenylacetylene (Scheme 3). On the basis of our previous
experience, ionic liquids were selected as the reaction media. The
presented results (Fig. 4) clearly show a higher yield of the reaction
obtained with complexes 2, 3, and 4 than with complex 1. In [bmim]
PF6 conversion increased from 56 to 78e84%, and in [bmim]BF4,
from 44 to 71e81%. When [emim][EtSO4] was used as solvent, the
yield of 2-methylbiphenyl was similar for all the complexes 1e4
and in this case no improvement relating to the presence of imid-
azole was observed. Moreover, complex 4 may be indicated as the
most efficient of all the investigated catalysts.
To estimate the stability of the catalysts studied, recycling tests
were undertaken with the ionic liquid phase containing the palla-
dium catalyst used for the second run. In all cases, the yield of the
product was lower than in the first reaction and in the best case ca.
50% of 2-methylbiphenyl was obtained with catalyst 4 (Fig. 5).
It should be pointed out that the recycling procedure was not
[Pd]
I
+
H
Ionic Liquid, NEt
o
80 C, 1h
Scheme 3. Sonogashira reaction.
Fig. 5. Sonogashira reaction with recycled catalysts 1e4.

I. Błaszczyk et al. / Journal of Organometallic Chemistry 696 (2011) 3601e3607
3605
Table 4
Effect of imidazoles on the yield of Sonogashira reaction catalyzed by 1.
Imidazole
None
[Pd]:
[Imidazole]
Yield [%]a
1st cycle
Yield [%]a
2nd cycle
e
56
47
1:2
1:20
85
29
66
8
N
N
N
H3C
N
1:2
1:20
81
6
54
2
H3C
CH3
1:2
1:20
81
20
75
7
H3C
N
N
N
1:2
1:20
85
82
62
48
N
H3C
N
1:2
1:20
80
80
50
35
Fig. 6. TEM of 3 after SuzukieMiyaura reaction.
N
Reaction conditions: [Pd] 1 mol%, [PhI] 1 mmol, [phenylacetylene] 1 mmol, [NEt3]
1.9 mmol, [bmim]PF6 1.5 cm3, 80 ꢀC, 1 h.
a
Conversion to the coupled product determined by GC.
While homogeneous mechanism operates in the first catalytic
run, participation of Pd(0) nanoparticles in the second run cannot
be excluded especially, when separation step was performed in the
presence of air. When palladium catalyst was recovered together
with Hg(0) and used in the next catalytic run, only 24% of product
was formed. A better result, 67% of 2-methylbiphenyl, was obtained
when extraction of organic products was performed in N2 atmo-
sphere. Similarly, even 85% of product was formed when the
catalyst was recovered after the first reaction under N2 and Hg(0)
was added to the second reaction.
Imidazoles bearing phenyl substituents at C2, 2-phenylimidazole
and 4-methyl-2-phenylimidazole, used together with 1 produce
80e85% of diphenylacetylene regardless of their concentration.
3. Mechanistic considerations
According to the present state of knowledge the CeC cross-
coupling reactions can be catalyzed by homogeneous, soluble
palladium complexes or by Pd(0) nanoparticles [16,17]. In partic-
ular, Pd(0) nanoparticles can act as heterogeneous catalysts or,
alternatively, they can be a reservoir of soluble palladium species,
the real catalytic active form [18]. Although the formation of Pd(0)
nanoparticles is not very plausible in the presence of phosphorus
ligands, we decided to perform a Hg(0) test to estimate the role of
Pd(0) nanoparticles in SuzukieMiyaura reaction catalyzed by 3.
The experimental data, obtained at 200-fold excess of Hg(0)
with respect to palladium, showed that the catalyst was unaffected
by Hg(0) and, consequently, homogeneous mechanism with
a Pd(0)/Pd(II) catalytic cycle was highly likely (Table 5). During
induction period Pd(0) complex can be formed from the pallada-
cycle precursor by reductive elimination of the orthometallated
ring with an aryl group introduced by the boronic acid [1].
The presence of Pd(0) nanoparticles in post-reaction mixture
was evidenced by TEM (Fig. 6). The obtained micrographs showed
some small Pd(0) nanoparticles of 7e9 nm diameter and domi-
nating bigger agglomerates of 40e200 nm size.
4. Conclusions
Modification of triphenylphosphite palladacycles with N-
imidazole ligands led to the formation of monomeric complexes
preserving the orthometallated ligand in the coordination sphere
of palladium. These new complexes efficiently catalyzed the
SuzukieMiyaura reaction and 100% yield was obtained with
complexes 3 and 4 when Cs2CO3 was used as a base. Attempts to
use imidazole-modified palladacycles in the Sonogashira reaction
resulted in the development of an efficient protocol for ionic
liquids, [bmim]BF4 and [bmim]PF6. In these two solvents, high
yields and good recyclability were obtained for complex 1 used
with an N-imidazole additive. However, it should be pointed out
that the amount of N-imidazole must be carefully controlled
because an excess of imidazole can stop the catalytic process
completely. This inhibiting effect is most probably related to
interactions between organic components of the reaction mixture
rather than to the formation of inactive palladium species.
Table 5
Effect of Hg(0) on the yield of SuzukieMiyaura reaction catalyzed by 3.
Catalyst
Yield [%] 1st cycle
Yield [%] 2nd cycle
in air
in N2
in air
in N2
3
100
99
99
99
99
e
88
14
11
81
67
e
3 þ Hg(0)a
3 þ Hg(0)b
As far as the influence of N-imidazole is concerned, our results
differ from those reported by Welton, who observed an inhibiting
effect of imidazoles incorporating NeH bonds in the SuzukieMiyaura
reaction in dioxane as well as in ionic liquids as solvents [13,15]. In
Reaction conditions: [Pd] 1 mol%, [PhB(OH)2] 1.5 mmol, [2-bromotoluene] 1 mmol,
[base] 2 mmol, [ethane-1,2-diol] 2.5 cm3, 80 ꢀC, 1 h; [Hg]:[Pd] ¼ 200.
a
Hg(0) added together with the catalyst.
Hg(0) added after 4 min of reaction.
b

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I. Błaszczyk et al. / Journal of Organometallic Chemistry 696 (2011) 3601e3607
Table 6
our system, the presence of an NeH bond (in 2-phenylimidazole and
4-methyl-2-phenylimidazole) did not inhibit the catalytic process.
We proposed homogeneous Pd(0)/Pd(II) mechanism as the
main pathway in CeC cross-coupling reactions catalyzed by palla-
dium complexes under studies. However, some Pd(0) nanoparticles
can be formed in the end of catalytic process or, during separation
of products from the catalyst performed in air atmosphere. Small
Pd(0) nanoparticles can take part in the catalytic reaction.
Crystallographic data for 2 and 4.
2
4
Chemical formula
Formula mass
Crystal system
a/Å
C22H20ClN2O3PPd
533.22
Monoclinic
9.624 (4)
18.381 (6)
12.168 (5)
90
99.94 (3)
90
2120.2 (14)
100 (2)
P21/n
C25H26ClN2O3PPd
575.30
Triclinic
8.378 (3)
9.488 (4)
16.360 (6)
97.45 (3)
102.29 (3)
102.43 (3)
1219.7 (8)
100 (2)
P ꢁ 1
b/Å
c/Å
ꢀ
ꢀ
ꢀ
/
a
/
b
/
5. Experimental
g
Unit cell volume/Å3
Temperature/K
Dimeric palladacycle complex 1 was obtained according to the
literature method [3].
Space group
[PdCl{k2eP,CeP(OC6H4)(OC6H5)2}{1-methylimidazole}], 2: To
the solution of complex 1 (0.20 g; 0.22 mmol) in CH2Cl2 (4 cm3)
1-methylimidazole (0.07 cm3; 0.88 mmol) was added. Reaction
mixture was stirred at room temperature for 1 h, after which the
solvent was evaporated in vacuo and the white product was
precipitated by addition of ethanol and recrystallized from
the CH2Cl2/EtOH mixture. Yield: 0.2 g, 85%; calcd (%) for
C22H20ClO3N2PPd (533.26): C 49.55, H 3.78, N 5.25; found: C 49.25,
H 3.56, N 5.21. ESI-MS(m/z): 497; 1H NMR (300.13 MHz, CDCl3):
No. of formula units per unit cell, Z
4
2
Absorption coefficient,
m
/mmꢁ1
1.104
1.566
No. of reflections measured
No. of independent reflections
No. of parameters
14,471
4813
10,391
5447
272
299
Rint
0.0204
0.0234
0.0627
0.0277
0.0641
1.076
0.0423
0.0420
0.0726
0.0694
0.0772
0.888
Final R1 values (I > 2
s
(I))
Final wR(F2) values (I > 2
Final R1 values (all data)
s
(I))
Final wR(F2) values (all data)
Goodness of fit on F2
d
¼ 8.26 (t, 1H, JHeH ¼ 6.4 Hz; orthopalladated ring), 6.69e7.79 (m,
Ph), 3.71 (s, 3H, CH3; major isomer), 3.63 (s, 3H, CH3; minor isomer)
ppm; 31P NMR (202.5 MHz, CDCl3): 129.91 (minor isomer); 126.53
(major isomer) ppm.
0.076 cm3 of dodecane as an internal standard. The products were
identified by GCeMS (Hewlett Packard 5971A).
[PdCl{k2eP,CeP(OC6H4)(OC6H5)2}{1,2-dimethylimidazole}], 3: To
the solution of complex 1 (0.30 g; 0.33 mmol) in CH2Cl2 (4 cm3) 1,2-
dimethylimidazole (0.127 g; 1.32 mmol) was added. Reaction
mixture was stirred at room temperature for 1 h, after which
the solvent was evaporated in vacuo and the white product
was precipitated by addition of ethanol and recrystallized from
the CH2Cl2/EtOH mixture. Yield: 0.35 g, 97%; calcd (%) for
C23H22ClO3N2PPd (546.29): C 50.48, H 4.05, N 5.12; found: C 50.30, H
5.2. Sonogashira reaction
The Sonogashira reaction was carried out in a Schlenk tube with
magnetic stirring. Reagents: iodobenzene (0.11 cm3, 1 mmol),
phenylacetylene (0.11 cm3, 1 mmol), NEt3 (1.9 mmol), ionic liquid
(1.5 cm3) and palladium catalyst (1 mol%), were introduced directly
to the Schlenk tube. Next, the Schlenk tube was sealed with
a rubber stopper and introduced into an oil bath pre-heated to
80 ꢀC. The reaction was carried out at 80 ꢀC for 1 h and after this
time cooled down. Organic products were separated by extraction
with hexane (4 cm3, 3 cm3 and 3 cm3). The extracts (10 cm3) were
GCeFID analyzed (Hewlett Packard 5890) with 0.05 cm3 of mesi-
tylene as an internal standard. The products were identified by
GCeMS (Hewlett Packard 5971A).
3.98, N 4.93. ESI-MS(m/z): 511; 1H NMR (300.13 MHz, CDCl3):
d
¼ 8.27
(t,1H, JHeH ¼ 6.1 Hz; orthopalladated ring), 6.30e7.60 (m, Ph), 3.54 (s,
3H, CH3; major isomer), 3.45 (s, 3H, CH3; minor isomer), 2.29 (s, 3H,
CH3; major isomer), 2.07 (s, 3H, CH3; minor isomer) ppm; 31P NMR
(202.5MHz,CDCl3): 132.17 (majorisomer),124.70(minorisomer)ppm.
[PdCl{k2eP,CeP(OC6H4)(OC6H5)2}{1-butylimidazole}], 4: To the
solution of complex 1 (0.18 g; 0.20 mmol) in CH2Cl2 (4 cm3)
1-butylimidazole (0.105 cm3; 0.80 mmol) was added. Reaction
mixture was stirred in room temperature for 1 h, after which the
solvent was evaporated in vacuo and the white product was
precipitated by addition of ethanol and recrystallized from
the CH2Cl2/EtOH mixture. Yield: 0.18 g, 78%; calcd (%) for
C25H26ClO3N2PPd (575.34): C 52.19, H 4.55, N 4.87; found: C 51.42,
H 4.88, N 5.87. ESI-MS(m/z): 539; 1H NMR (300.13 MHz, CDCl3):
5.3. X-ray studies
Single crystals of 2 and 4 suitable for X-ray measurements were
mounted on glass fibers in silicone grease, cooled to 100 K in
a nitrogen gas stream, and the diffraction data were collected on
a Kuma KM-4 CCD diffractometer with graphite monochromated
MoeK
a
radiation (
l
¼ 0.71073 Å). The structures were subse-
d
¼ 8.27 (t, 1H, JHeH ¼ 6.2 Hz; orthopalladated ring), 6.60e8.00 (m,
quently solved using direct methods and developed by full least-
squares refinement on F2. Structural solution and refinement was
carried out using SHELX suite of programs [19]. Analytical
absorption corrections were performed with CrysAlis RED [20]. C,
N, O, P, Cl, and Pd atoms were refined anisotropically. The carbon-
bonded H atoms were positioned geometrically and refined iso-
tropically using a riding model with a common fixed isotropic
thermal parameter. The molecular structure plots were prepared
using ORTEP-3 program [21]. Crystal data and selected details of
structure determination are summarized in Table 6.
Ph), 3.84e3.96 (m, 4H, CH2), 1.68e1.82 (m, 4H, CH2), 1.25e1.37 (m,
4H, CH2), 0.89e0.96 (m, 6H, CH3) ppm; 31P NMR (202.5 MHz,
CDCl3): 129.60 (minor isomer), 126.60 (major isomer) ppm.
5.1. SuzukieMiyaura reaction
The SuzukieMiyaura reaction was carried out in a Schlenk tube
with magnetic stirring. Reagents: phenylboronic acid (0.183 g,
1.5 mmol), 2-bromotoluene (0.118 cm3, 1 mmol), base (2 mmol),
ethane-1,2-diol (2.5 cm3) and palladium catalyst (1 mol%) were
introduced directly to the Schlenk tube. Next, the Schlenk tube was
sealed with a rubber stopper and introduced into an oil bath pre-
heated to 80 ꢀC. The reaction was carried out at 80 ꢀC for 2 h and
after this time cooled down. Organic products were separated by
extraction with hexane (4 cm3, 3 cm3 and 3 cm3). The extracts
(10 cm3) were GCeFID analyzed (Hewlett Packard 5890) with
Acknowledgments
Financial support of the Polish Ministry of Science and Higher
Education (N164/COST/2008) and COST D40 are gratefully
acknowledged.

I. Błaszczyk et al. / Journal of Organometallic Chemistry 696 (2011) 3601e3607
3607
[7] D.A. Albisson, R.B. Bedford, P.N. Scully, Tetrahedron Lett. 39 (1998)
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[8] R.B. Bedford, L.T. Pilarski, Tetrahedron Lett. 49 (2008) 4216e4219.
[9] R.B. Bedford, C.S.J. Cazin, S.L. Hazelwood, Angew. Chem. Int. Ed. 41 (2002)
4120e4122.
[10] R.B. Bedford, M. Betham, M.E. Blake, R.M. Frost, P.N. Horton, M.B. Hursthouse,
R.M. Lopez-Nicolas, Dalton Trans. (2005) 2774e2779.
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Authors are grateful to Mr. Marek Hojniak (Faculty of Chemistry,
University of Wroc1aw) for GC and GCeMS analyses.
Appendix A. Supplementary material
CCDC 826119 and 816415 contain the supplementary crystallo-
graphic data for this paper. These data can be obtained free of
charge from the Cambridge Crystallographic Data Centre via www.
ccdc.cam.ac.uk/data_request/cif.
[13] C.J. Mathews, P.J. Smith, T. Welton, J. Mol. Catal. A Chem. 214 (2004) 27e32.
[14] M.S. Szulmanowicz, W. Zawartka, A. Gniewek, A.M. Trzeciak, Inorg. Chim. Acta
363 (2010) 4346e4354.
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