Synthesis, structural elucidation and catalytic activity toward a model Mizoroki-Heck C-C coupling reaction of the pyrazolic Tr?ger's base Pd 4Cl8(PzTB)2 complex

Article abstract of DOI:10.1016/j.jorganchem.2011.02.016

The synthesis of a novel palladium (II) complex Pd₄Cl ₈(PzTB)₂, where PzTB is a pyrazole Tr?ger's base analogue ligand is reported. A complete structure elucidation of the complex was achieved by spectroscopic and crystallographic data, exhibiting a metallomacrocycle supramolecular structure and a planar-square geometry on each palladium atom. This complex exhibited also a high activity and selectivity toward a model Mizoroki-Heck C-C coupling reaction of styrene with some iodobenzene derivatives.

Full text of DOI:10.1016/j.jorganchem.2011.02.016

Journal of Organometallic Chemistry 696 (2011) 1834e1839
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Synthesis, structural elucidation and catalytic activity toward a model
MizorokieHeck CeC coupling reaction of the pyrazolic Tröger’s base
Pd Cl (PzTB) complex
4
8
2
Fernando Cuenú a b, Rodrigo Abonia b , Alberto Bolaños , Armando Cabrera c
,
,
b
*
a
Laboratorio de Química Inorgánica y Catálisis, Programa de Química, Universidad del Quindío, Avenida Bolívar Calle 12 Norte, Armenia, Colombia
Departamento de Química, Universidad del Valle, A.A. 25360, Cali, Colombia
Instituto de Química, Universidad Nacional Autónoma de México, 04510 México D.F., Mexico
b
c
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 11 February 2011
Accepted 14 February 2011
The synthesis of a novel palladium (II) complex Pd Cl (PzTB) , where PzTB is a pyrazole Tröger’s base
4
8
2
analogue ligand is reported. A complete structure elucidation of the complex was achieved by spec-
troscopic and crystallographic data, exhibiting a metallomacrocycle supramolecular structure and
a planar-square geometry on each palladium atom. This complex exhibited also a high activity and
selectivity toward a model MizorokieHeck CeC coupling reaction of styrene with some iodobenzene
derivatives.
Keywords:
Palladium(II) complexes
Tröger’s base
Pyrazole derivatives
Metallomacrocycles
Stilbenes
Ó 2011 Elsevier B.V. All rights reserved.
MizorokieHeck reaction
1. Introduction
palladium complexes to produce chemicals for advanced synthesis
of pharmaceuticals and natural products [11].
Tröger’s base (Fig. 1), is a compound with a bridged and rigid V-
shaped methanodiazocine skeleton and has been recognized as the
first chiral tertiary amines which could be resolved [1,2]. Tröger’s
Continuing with our current studies on the synthesis and
chemical properties of novel Tröger’s bases [12], we were interested
to evaluate the ability of complexation of a new pyrazolic Tröger’s
base (PzTB) toward the Pd(II) metal ion, on the structural elucida-
tion of the novel palladium complex that was formed and in eval-
uating its catalytic potentiality through a model MizorokieHeck
CeC coupling reaction.
base has gained importance in the study of CH-
p interactions [3],
host molecules and molecular tweezers [4], and cyclophanes [5].
Also they have been considered as potential N-based ligand for the
synthesis of transition metal complexes. In this sense, complexes
type TB$2MCl
3
2 with [(M ¼ Rh(III) and Ir(III)], previously reported
by Golberg and Alper [6], constituted the first example where a TB
2. Results and discussion
was used as a N-based ligand (Fig. 1). Some other examples like Rh
(
I) metallomacrocycles [7], Ru(II) complexes based on phenan-
Based on the stoichiometry established for complex 2 [6], the
throline [8], and Pd(II) self-assembled complexes [9] have been
reported.
treatment of PdCl
2
(CH
3
CN)
2
3 [13] (2 eq) with the pyrazolic Tröger’s
Palladium-catalyzed MizorokieHeck type reaction is the most
efficient route for the vinylation of aryl/vinyl halides or triflates
involving the formation of a new CeC bond [10]. Among various
commonly used reactions for CeC coupling (viz. MizorokieHeck,
Suzuki, Stille and Sonogashira reactions), perhaps the Mizor-
okieHeck is the most attractive organic reaction catalyzed by
MCl3
N
N
N
N
MCl3
2
1
*
Corresponding author. Fax: þ57 2 3393248.
Fig. 1. Original Tröger’s base 1 and the first transition metal complexes 2 bearing
a Tröger’s base as a N-based ligand.
E-mail address: rodrigo.abonia@correounivalle.edu.co (R. Abonia).
0
022-328X/$ e see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2011.02.016

F. Cuenú et al. / Journal of Organometallic Chemistry 696 (2011) 1834e1839
1835
Cl
Cl
Cl
N
Pd
Pd
Ph
N
Ph
Cl
N
N
9
N
tBu
tBu
8
1
2
13
6
7
N 3
N
N
2
MeOH, rt
2
PdCl (CH CN)
N
14
N
1
N
2
3
2
+
N
5
N
N
4
3
1
0
Ph
Ph
N
N
N
N
1
1
tBu
tBu
Cl
4
(PzTB)
Pd
Pd
Cl
Cl
Cl
5
4 8 2
, Pd Cl (PzTB)
Scheme 1. Synthesis of the new Pd(II) complex 5 bearing the pyrazolic Tröger’s base 4 as N-based ligand.
base, PzTB 4 [12], (1 eq), at ambient temperature and using MeOH
as solvent afforded complex 5 as a red precipitate air stable, non-
hygroscopic and soluble in CHCl , CH Cl and DMSO (Scheme 1).
3 2 2
mode whereas the last one (i.e. 308 cmꢀ1) is related to a
n
b
(MeX)
trans to (PzTB) mode since it is sensitive to the nature of the ligand
[15]. These findings suggest initially a planar geometry around each
Pd metal atom and their four ligands in complex 5, as well as, the
existence of a terminal PdeCl and two bridging PdeCl bonds in its
structure, in agreement with the literature [15]. Finally, the
The elemental analyses indicated that there are two palladium
atoms for each molecule of the PzTB 4 in the structure of complex 5,
similarly as was found for complex 2 [6].
The IR spectrum of complex 5 showed new absorption bands
and significant differences with respect to the IR of the free PzTB
ligand 4, indicating the formation of a new product. Table 1
summarizes the main absorption bands observed for both free
and Pd-complexed PzTB ligand 4.
ꢀ
1
absorption band at 258 cm is assigned to a PdeN stretching
frequency.
As expected, the NMR spectra of complex 5 showed the same
number of protons (with the same splitting pattern), and carbon
atoms as the free ligand. Table 2 summarizes the comparison of the
most relevant NMR signals observed for the both free and com-
plexed PzTB ligand.
According to the literature, halogens frequently tend to form
bridges with two metal atoms and generally bridging MeX
stretching frequencies [
stretching frequencies [
n
b
(MeX)] are lower than terminal MeX
t
(MeX)] [14]. In addition, trans-planar
The ligand 4 possesses three types of nitrogen atoms (i.e. 1-N, 2-
N and 12-N, see Scheme 1), from which 1-N and 12-N are suitable
for coordination to the metal. In contrast to that observed for
complex 2, the proton and carbon atom NMR signals of the 13- and
14-methylene groups were not significantly shifted by complexa-
tion of the metal to the PzTB ligand 4, as shown in Table 2. This
finding may indicate a different coordination place of the Pd atoms
to the PzTB ligand 4 with respect to complex 2. To confirm without
ambiguity the structure of complex 5, single crystals suitable for
n
M
2
X
4
L
2
-type complexes with C2h symmetry, exhibit three IR active
n
(MeX) absorption bands [i.e. one (MeX) and two (MeX)] in
n
t
n
b
ꢀ
1
the range of 360e294 cm [15]. In the lower-frequencies region of
the IR spectrum of complex 5 (Fig. 2), an absorption was observed at
ꢀ
1
3
69 cm which could be assigned to the
n
t
(MeX) mode, as well as,
ꢀ
1
ꢀ1
two absorption bands at 349 cm and 308 cm , respectively,
b
which could be assigned to the two n (MeX) modes. The second
ꢀ1
band (i.e. 349 cm ) is frequently related to a
n
b
(MeX) trans to X
2 2
X-ray diffraction were grown from a mixture of CH Cl /pentane.
The X-ray diffractograms (see Fig. 3), showed that the metals are
coordinated to the pyrazolic 1-N nitrogen atoms of 4 but not to the
12-N atoms in agreement with that observed by NMR.
Table 1
Since the PzTB ligand 4 possesses two pyrazolic 1-N nitrogen
atoms diametrically opposed and equivalent between them, PzTB 4
behaves as a bridged ligand, therefore, it coordinates two palladium
ions, where each ion is dimerized obeying the 18 electron rule.
Thus, generating a square-planar geometry around each palladium
atom, with each one bonded to two bridged chloride ligands, to
a terminal chloride and to a PzTB ligand 4. The four bonding angles
N1ePd1eCl2, N1ePd1eCl3, Cl1ePd1eCl3 and Cl2ePd1eCl1 with
Main IR absorption bands for the free and Pd-complexed PzTB
ligand 4.
IR absorption bands (cm 1)a
ꢀ
Free ligand
Pdecomplexed ligand
3
3
2
2
1
1
069 (s)
036 (s)
964 (b)
869 (m)
667 (b)
597 (b)
3052 (s)
e
2966 (b)
2871 (m)
1648 (b)
1587 (m)
1517 (m)
1491 (m)
1456 (b)
1387 (m)
1356 (m)
1287 (s)
1208 (m)
1149 (b)
963 (s)
ꢁ
ꢁ
ꢁ
ꢁ
comparable values of 91.16 (9) , 90.66 (9) , 86.49 (4) and 91.87 (4)
respectively, confirm the square-planar geometry of each Pd
atom in the complex 5 (see Fig. 3 and Table 4). Interestingly, the
supramolecular structure of complex 5 corresponded to a metal-
lomacrocycle conformed by four palladium atoms, eight chlorines
and two bridged PzTB ligands, as shown in (Fig. 3). According to our
knowledge there are very few examples in the literature of met-
allomacrocycles bearing a Tröger’s base as ligand [7,9,16].
e
1
1
1
1
1
499 (b)
449 (m)
376 (b)
346 (b)
300 (m)
e
1
9
7
6
144 (m)
95 (m)
54 (b)
90 (m)
748 (b)
692 (m)
2.1. Reactivity toward the CeC coupling reaction
a
In a preliminary study, complex 5 was probed as catalyst for
a CeC coupling MizorokieHeck type reaction between styrene and
(
s), (m) and (b) refers to short, medium and broad size bands
respectively.

1836
F. Cuenú et al. / Journal of Organometallic Chemistry 696 (2011) 1834e1839
1
00
9
5
0
5
0
5
0
5
0
5
0
9
8
8
7
7
6
6
5
5
4
80
460
440
420
400
380
360
340
320
300
280
260
240
Wavenumber (cm-1)
Fig. 2. Lower-frequencies region of the IR spectrum of compound 5.
three different iodobenzene derivatives (i.e. iodobenzene,
-iodoanisole and 4-iodonitrobenzene), as a model experiment to
evaluate the catalytic ability of this complex (Scheme 2, see Table 3
and experimental).
Interestingly, compound 5 presented high catalytic activity and
considerable selectivity towards the CeC coupling products, espe-
cially towards the formation of trans-stilbene derivatives, as shown
in Table 3.
The Table 3 also shows that the electron-donating OMe group
decreased the reactivity of the aryl substrate (ArI) giving only a 76%
of conversion after 3.5 h of reaction with TOF ¼ 21.8. When X ¼ H it
had a major conversion (89%, TOF ¼ 25.5) for the same giving time,
4
2
but the strong electron-withdrawing NO group increased signifi-
cantly its reactivity and consequently the conversion was 100%
with a TOF ¼ 28.6 after 3.5 h. These findings are in agreement with
previous reports about the substrate dependence [17], and with the
proposed mechanism for the MizorokieHeck reactions [17a,18].
Table 2
Main 1H and 13C NMR signals for the free and complexed PzTB ligand 4.
2.2. Effect of the complex:substrate ratio over the reactivity and
selectivity of the complex 5
1H and 13C NMR signals (ppm) in DMSO-d
6
Type of signal
Free ligand
Pdecomplexed ligand
The (Fig. 4) shows that complex 5 is highly active toward the CeC
coupling reaction between iodobenzene and styrene, reaching the
00% of conversion of iodobenzene into products during the first
1
1
1
1
1-H
1.09
3.69
4.36
4.31
156.5
33.3
29.6
47.4
67.8
1.06
3.66
4.34
4.30
156.0
32.7
29.0
48.9
67.2
3-Ha
3-Hb
4-H
1
1
00 min with a TOF ¼ 29.5, for a complex:substrate ratio 1:2950.
C-5
During the course of the reaction the selectivity toward the trans-
stilbene and 1,1-diphenylethene was 89% and 11%, respectively.
When the complex:substrate ratio was increased to 1:19600
C-10
C-11
C-13
C-14
(
Table 4, entry 2), the activity of the complex 5 increased too,
reaching the 100% of conversion of iodobenzene in 435 min, with
4 8 2
Fig. 3. ORTEP drawing of Pd Cl (PzTB) complex 5 with 50% probability ellipsoids. a) Hydrogen atoms, phenyl rings and solvent molecules have been omitted for clarity. b) Phenyl
and tert-butyl groups are shown.

F. Cuenú et al. / Journal of Organometallic Chemistry 696 (2011) 1834e1839
1837
100
PhI
trans-stilbene
8
6
4
2
0
0
0
0
0
X
I
trans-stilbenes
complex 5
+
+
DMF
X
Styrene
Iodobenzenes
X
1
,1-diarylethenes
1,1-diphenylethene
Scheme 2. General procedure for a model MizorokieHeck CeC coupling reaction.
a TOF of 45.0. The selectivity toward the trans-stilbene and
1
,1-diphenylethene remained almost the same with respect to the
0
20
40
60
80
100
above experiment (i.e. 88% and 11% respectively).
Time (min)
To determine the homogeneity of the catalyst 5, an Hg drop test
was carried out [19]. As shown in (Fig. 5), the reaction performed in
the presence of an excess of mercury had a very similar behavior
than when reaction was carried out without mercury as depicted in
Fig. 4. Kinetic behavior for the MizorokieHeck CeC coupling reaction of iodobenzene
and styrene catalyzed by complex 5. Reaction conditions: iodobenzene (1.794 mmol),
styrene (2.602 mmol), Et
20 C, solvent DMF (10 mL), catalyst:substrate ratio 1:2950, TOF ¼ 29.5.
3
N (2.152 mmol), complex 5 (0.609
m
mol), temperature
ꢁ
1
(Fig. 4). This experiment indicated that amalgamation of Pd parti-
cles and for instance poisoning of complex 5 do not proceeded in
the course of the reaction, confirming a homogeneous character of
catalyst 5.
As shown in Table 4, complex 5 worked efficiently even at
ꢁ
160 C. In contrast, it has been reported that the efficiency of
monodentate PPh -based Pd complexes used as catalyst for Miz-
3
orokieHeck CeC coupling reactions commonly decreases their
ꢁ
activities when temperature exceeds 140 C. This drawback is
2
.3. Effect of the temperature over the reactivity and selectivity of
frequently associated with oxidation processes of the phosphorous
in such ligands [20].
the complex 5
In a final experiment, we evaluated the activity of the phos-
phine-based ligand complex PdCl (PPh ) as catalyst for our model
2 3 2
From a comparative study to evaluate the effect of the variation
of the temperature of reaction over the reactivity and selectivity of
complex 5 maintaining the same catalyst:substrate ratio (i.e.
MizorokieHeck reaction, (Table 4, entry 4), in comparison with
complex 5 (Table 4, entry 2). It is observed that the selectivities
toward trans-stilbene and 1,1-diphenylethene were almost the
same for both catalysts (i.e. 88:12 and 88:11 respectively). However,
the reactivity of complex 5 was higher (100% conversion) than
1
9
:19600), we found that the increasing of the temperature from
ꢁ
ꢁ ꢁ
0
C, 120 Ce160 C (Table 4, entries 1, 2 and 3) improved the
reactivity of complex 5 showing TOF’s of 12.1, 45.0 and 490.0
respectively. Interestingly the selectivity toward trans-stilbene kept
almost the same in all three experiments (i.e. 92, 88 and 92%
respectively), see Table 4.
PdCl
even with a higher catalyst:substrate ratio (i.e. 1:19600, TOF ¼ 45.0
for complex 5 vs 1:1000, TOF ¼ 2.9 for PdCl (PPh ).
2 3 2
(PPh ) (86% of conversion) for the same giving reaction time,
2
3 2
)
Table 3
MizorokieHeck CeC coupling reaction of styrene with iodobenzene derivatives
3. Conclusions
catalyzed by the Pd
4
Cl
8
(PzTB)
2
complex 5.
Entry
We established that the reaction of the starting compound
PdCl (CH CN) with a pyrazolic Tröger’s base (PzTB) readily affor-
ded the new (2:1) Pd Cl (PzTB) complex 5. The supramolecular
I
X
2
3
2
4
8
2
Substituent
X ¼ NO
100
Yield (%)
2
X ¼ H
89
Yield (%)
X ¼ OMe
76
Yield (%)
structure of this complex interestingly corresponded to a metal-
lomacrocycle conformed by four palladium atoms, each of them
possessing a planar-square geometry, and bonded to two bridged
PzTB ligands. Complex 5 displayed high catalytic activity and
considerable selectivity towards the formation of trans-stilbenes
from a model MizorokieHeck CeC coupling reaction of styrene
with iodobenzene derivatives. The mercury drop test confirmed
that complex 5 behaved as a homogeneous catalyst during the
course of the MizorokieHeck CeC coupling reactions performed.
Further kinetic studies directed to establish the reaction mecha-
nism are currently in progress.
Total conversion (%)
Structure of products
9
7
3a
90a
10
89a
X
X
H
H
9
X
X
0
0
2
4
. Experimental section
TON
TOF
6000
28.6
5346
25.5
4580
21.8
4.1. Solvent and starting materials
Reaction conditions: 1.794 mmol of (iodobenzene, 4-iodonitrobenzene or 4-
iodoanisol), styrene (2.602 mmol), Et (2.152 mmol), palladium complex
mol). Temperature 120 oC, solvent DMF (10 mL), reaction time 3.5 h
210 min), catalyst:substrate ratio 1:6000.
3
N
5
All chemicals palladium chloride, iodobenzene, 4-iodoanisole, ;
(
(
0.299 m
4-iodo-nitrobenzene, styrene, triethylamine (Et
3
N), N,N-dime-
4,4 -dimethyl-3-
a
0
trans-stilbene isomer. TON ¼ mol of product/mol Pd. TOF ¼ TON/min.
thylformamide
(DMF), phenylhydrazine,

1838
F. Cuenú et al. / Journal of Organometallic Chemistry 696 (2011) 1834e1839
Table 4
Effect of the temperature over the reactivity and selectivity of the complex 5.
ꢁ
Entry
Temperature
C
Time min
Conversion of PhI (%)
TOF
Selectivity toward
Selectivity toward
transestilbene (%)
1,1-diphenylethene (%)
1
2
3
90
1620
435
40
93
12.1
45.0
490.0
2.9
92
88
92
88
8
11
8
120
160
120
100
100
86
a
4
300
12
3
Standard reaction conditions: iodobenzene (1.794 mmol), styrene (2.602 mmol), Et N (2.152 mmol), complex 5 (0.091 mmol), solvent DMF (10 mL), catalyst:substrate ratio
1
:19600. Time in minutes.
PdCl (PPh ) :substrate ratio 1:1000.
2 3 2
a
oxopentanenitrile, paraformaldehyde, hydrochloric acid, ammo-
nium hydroxide, acetonitrile (ACN) and dichloromethane (DCM)
were purchased from Aldrich Chemical Co, Sigma and Fluka
companies and were used as received. All solvents were distilled
and dried by standard methods just before use. A sample of the
FID’s were made by using a Jeol-GC-mate mass selective detector.
Identification of the reaction products was carried out by GCeMS
analysis (comparing with standard samples) and NMR techniques
of the pure products after column chromatography on silica gel and
DCM-AcOEt mixtures as eluent.
2 2
PdCl (ACN) salt 3 was prepared as described in the literature [13].
The pyrazolic Tröger’s base PzTB 4, was obtained when 5-amino-3-
tert-butyl-1-phenylpyrazole was treated with paraformaldehyde in
acetic acid, as described in the literature [12].
4
.3. Synthesis of the Pd
4 8 2
Cl (PzTB) complex 5
The reaction was performed under a nitrogen atmosphere using
standard Schlenk techniques and vacuum line. A sample of
4.2. Analytical and physicoechemical measurements
PdCl (CH CN) 3 (100 mg, 0.386 mmol) was added to a solution of
2
3
2
PzTB 4 (90.4 mg, 0.194 mmol) dissolved in MeOH (3 mL). The
reaction mixture was stirred for 1 h at ambient temperature. The
red precipitated formed was filtered off, washed with MeOH and
Melting points were determined on a Büchi melting point
apparatus and are uncorrected. IR spectra were recorded on a Per-
1
kin Elmer FT spectrophotometer series 2000 in KBr disks. H and
dried under reduced pressure yielding pure complex 5 148 mg, 93%
1
3
1
ꢁ
C NMR spectra were recorded on a Varian-Inova 500 MHz spec-
trometer operating at 500 MHz and 125 MHz respectively, and on
a Bruker Avance 400 spectrophotometer operating at 400 MHz and
yield. Mp 266e267 C H NMR (500 MHz, [D ] DMSO):
d
¼ 1.06 (s,
6
18H, 11-H), 3.66 (d, Jgem ¼ 16.0 Hz, 2H, 13-Ha), 4.30 (s, 2H, 14-H),
4.34 (d, Jgem ¼ 15.5 Hz, 2H, 13-Hb), 7.30 (t, J ¼ 7.5 Hz, 2H, 9-H), 7.49
13
1
00 MHz respectively, using DMSO-d
6
as solvent and tetrame-
(t, J ¼ 8.0 Hz, 4H, 8-H), 7.86 (d, J ¼ 8.5 Hz, 4H, 7-H) ppm. C NMR
thylsilane as internal standard. Microanalyses were performed on
an Agilent elemental analyzer and the values are within ꢂ0.4% of
the theoretical values. Silica gel aluminum plates (Merck 60 F254)
were used for analytical TLC. Catalytic reactions were carried out in
a 50 mL 2-necked round bottom flask fitted with a condenser
immersed into an oil bath and maintained at the desired temper-
ature. The stirring was carried out by means of a spinbarr. Analysis
of the content of the reaction mixtures were made by using an
Agilent 6890A Chromatograph, with an AT5 capillary column (5%
(125 MHz, [D ] DMSO):
d
¼ 29.0 (C-11), 32.7 (C-10), 48.9 (C-13), 67.2
6
(C-14), 102.1 (C-4), 120.6 (C-7), 125.8 (C-9), 129.2 (C-8), 139.1 (C-6),
Table 5
Crystal and structure refinement parameters for complex 5.
Parameter
Value
Empirical formula
Formula weight
Temperature
60 4
C H72Cl12N12Pd
1812.30
298(2) K
0.71073 Å
phenylmethylsiloxane) 30 m ꢃ 0.25 mm ꢃ 0.1
m
m and the GCeMS
Wavelength
Crystal system
Space group
Unit cell dimensions
Monoclinic
P2 /c
1
ꢁ
a ¼ 13.6868(10) Å,
b ¼ 20.5808(15) Å,
c ¼ 26.6607(19) Å,
a
b
g
¼ 90
1
00
ꢁ
¼ 101.3490(10)
PhI
ꢁ
¼ 90
Z
4
8
6
4
2
0
0
0
0
0
trans-stilbene
7363.1(9) Å3
Volume
3
Density (calculated)
Absorption coefficient
F(000)
1.635 Mg/m
ꢀ
1
1.442 mm
3616
Crystal size/shape/color
Theta range for data collection
Diffractometer used/Scan
Mode Bruker Smart
omega scans
0.26 ꢃ 0.24 ꢃ 0.22 mm/Prism/Red
ꢁ
1.81e25.36
APEX AXS CCD area detector/
1,1-diphenylethene
Index ranges
16< ¼ h< ¼ 16, ꢀ24< ¼ k< ¼ 24,
ꢀ
32< ¼ l < ¼ 32
Reflections collected
60385
Independent reflections
Completeness to theta ¼ 25.36
Max. and min. transmission
Refinement method
13468 [R(int) ¼ 0.0645]
ꢁ
0
20
40
60
80
100
99.7%
0.7723 and 0.6686
Time (min)
Full-matrix least-squares on F2
Data/restraints/parameters
13468/272/907
0.896
Fig. 5. Mercury drop test: Kinetic behavior for the MizorokieHeck CeC coupling
reaction of iodobenzene and styrene catalyzed by complex 5 in the presence of an
excess of mercury. Reaction conditions: iodobenzene (8.97 mmol), styrene
Goodness-of-fit on F2
Final R indices[I > 2sigma(I)]
R indices (all data)
Largest diff. peak and hole
R
R
1
¼ 0.0390, wR
2
2
¼ 0.0703
1
¼ 0.0652, wR
¼ 0.0764
(
13.01 mmol), Et
3
N
(10.76 mmol), complex
5
(3.045
mmol), Hg(0) (125.7
mmol,
ꢀ3
0.654 and ꢀ0.440 e.Å
ꢁ
25.57 mg), temperature 120 C, solvent DMF (50 mL), catalyst:substrate ratio 1:2950.

F. Cuenú et al. / Journal of Organometallic Chemistry 696 (2011) 1834e1839
1839
Table 6
de Química de la Universidad Nacional Autónoma de México, Ciudad
de México-Mexico for financial support.
ꢁ
ꢁ
Selected bonding lengths (A ) and angles ( ) for complex 5.
Bond lengths
Pd1eN1; 2.013(3)
Pd1eCl1; 2.312(11)
Pd2eN16; 2.026(3)
N1eN2; 1.364(4)
C3eN2; 1.354(5)
Pd1eCl2; 2.2582(12)
Pd2eCl1; 2.3035(12)
Pd2eCl3; 2.3496(11)
C6eN2, 1.343(5)
Pd1eCl3; 2.3462(11)
Pd2eCl4; 2.2660(12)
C5eC12; 1.519(5)
N2eC5, 1.343(5)
Appendix A. Supplementary material
CCDC 775353 contains the supplementary crystallographic data
for for complex 5. These data can be obtained free of charge from
the Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.
uk/data_request/cif.
N3eC3, 1.08(5)
C3eC4, 1.366(5)
Bonding angles
N1ePd1eCl1; 176.13(10) N1ePd1eCl2; 91.16(9)
N1ePd1eCl3; 90.66(9)
N16ePd2eCl1; 175.03(10) N16ePd2eCl4; 92.00(10) N16ePd2eCl3; 89.80(9)
Cl2ePd1eCl3; 175.60(5)
N1eN2ePd1; 119.70(2)
N1eN2eC6; 125.21(3)
Cl1ePd1eCl3; 86.49(4)
Cl2ePd1eCl1; 91.87(4)
C3eN2eC6; 125.22(3)
Cl4ePd2eCl3; 178.19(5)
Cl4ePd2eCl1; 91.58(4)
C3eN2eN1; 109.30(3)
References
[
[
[
[
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(
1
1
4
45.1 (C-3), 156.0 (C-5) ppm. C58
1.05, H 4.01, N 16.73; found C 41.16, H 4.16, N 16.68.
8 4
H68Cl N12Pd (1646.52): calcd. C
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(
(
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4
.4. Crystal structure of complex 5
4] (a) S. Goswami, K. Ghosh, Tetrahedron Lett. 38 (1997) 4503e4506;
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(
Crystals suitable for single X-ray diffraction were grown by
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N. Shimizu, T. Inazu, J. Heterocycl. Chem. 35 (1998) 209e215;
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The main crystallographic data of complex 5 are listed in (Tables 5
and 6).
[
[
[8] (a) C. Bresson, M. Luhmer, M. Demeunynck, A. Kirsch-De Mesmaeker,
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4
.5. General procedure for the model CeC coupling MizorokieHeck
(
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[
9] T. Weilandt, U. Kiehne, G. Schnakenburg, A. Lützen, Chem. Commun. (2009)
2
320e2322.
In a typical experiment according to (Scheme 2), a mixture of
iodobenzene (1.787 mmol), styrene (2.602 mmol), Et
2.152 mmol), complex 5 (1.158 mol) and DMF (8 mL) in a 50 mL 2-
[
10] (a) R.F. Heck, Pure Appl. Chem. 50 (1978) 691e701;
(b) R.F. Heck, W.A. Herrmann, Angew. Chem. Int. Ed. 41 (2002) 1290e1309.
11] S. Bräse, A. de Meijere, in: A. de Meijere, F. Diederich (Eds.), Metal-Catalyzed
Cross-Coupling Reactions, second ed.. Wiley-VCH, Weinheim, Germany, 2004,
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[12] For the synthesis of compound 4 see (a) R. Abonia, A. Albornoz, H. Larrahondo,
J. Quiroga, B. Insuasty, H. Insuasty, A. Hormaza, A. Sánchez, M. Nogueras,
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3
N
[
(
m
ꢁ
necked bottle was immersed in a pre-heated oil bath at 120 C with
magnetic stirring. Samples were removed from the reaction
mixture at regular intervals and analyzed by GCeMS until complete
ꢁ
consumption of iodobenzene. trans-Stilbene. mp 123e124 C (Lit.
(b) R. Abonia, E. Rengifo, J. Quiroga, B. Insuasty, A. Sánchez, J. Cobo, J.N. Low,
ꢁ
ꢁ
mp 122e124 C) [21]; (E)-4-nitrostilbene, mp 156e158 C, (Lit. mp
M. Nogueras, Tetrahedron Lett. 43 (2002) 5617e5620.
ꢁ
1
[13] Compound 3 was obtained following a similar procedure as described by
A.G.M. Mostafa-Hossain, T. Nagaoka, K. Ogura, Electrochim. Acta 41 (1996)
1
57 C) [22]. H NMR (400 MHz, [D
H, Ph-H), 7.41 (d, J ¼ 15.2 Hz, 1H, Htrans), 7.42 (t, J ¼ 7.4 Hz, 2H, Ph-
H), 7.53 (d, J ¼ 16.8 Hz, 1H, Htrans), 7.68 (d, J ¼ 7.2 Hz, 2H, Ph-H),
6
] DMSO):
d
¼ 7.34 (t, J ¼ 7.2 Hz,
1
2
773e2780.
[14] K. Nakamoto, in: J. Wiley, Sons (Eds.), Infrared and Raman Spectra of Inorganic
and Coordination Compounds, Part B, sixth ed.. Wiley-VCH, Weinheim,
Germany, 2009, p. 193.
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(b) T. Weilandt, U. Kiehne, J. Bunzen, G. Schnakenburg, A. Lützen, Chem. Eur. J.
13
7
.87 (d, J ¼ 8.9 Hz, 2H, AreH), 8.23 (d, J ¼ 8.8 Hz, 2H, AreH) ppm.
NMR (100 MHz, [D ] DMSO):
¼ 124.5, 126.8, 127.6, 127.8, 129.2,
29.3, 133.7, 136.7 (Cq), 144.5 (Cq), 146.7 (Cq) ppm. (E)-4-Methox-
C
6
d
[
[
1
ꢁ
ꢁ
1
ystilbene, mp 132e133 C, (Lit. mp 131e132 C) [23]. H NMR
400 MHz, [D ] DMSO): ), 6.96 (d, J ¼ 8.8 Hz,
¼ 3.78 (s, 3H, OCH
H, Ph-H), 7.09 (d, J ¼ 16.4 Hz, 1H, Htrans), 7.20 (d, J ¼ 16.4 Hz, 1H,
Htrans), 7.24 (t, J ¼ 7.6 Hz, 1H, Ph-H), 7.36 (t, J ¼ 7.6 Hz, 2H, Ph-H),
1
6 (2010) 2418e2426.
(
6
d
3
[
17] (a) M. Oestreich, in: M. Oestreich (Ed.), The Mizoroki–Heck Reaction, John
Wiley & Sons, Ltd., Chichester, United Kingdom, 2009, pp. 56e57;
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2
13
[18] C. Amatore, A. Jutand, Acc. Chem. Res. 33 (2000) 314e321.
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7
(
(
.56 (bt, 4H, AreH) ppm. C NMR (100 MHz, [D
OCH ), 114.6, 126.5, 126.6, 127.6, 128.3, 128.5, 129.1, 130.1 (Cq), 137.8
Cq), 159.5 (Cq) ppm.
6
] DMSO):
d
¼ 55.6
[
3
(
[20] (a) W.A. Herrmann, C. Brossmer, K. Öfele, C.P. Reisinger, T. Priermeier,
M. Beller, H. Fischer, Angew. Chem. Int. Ed. Engl. 34 (1995) 1844e1848;
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Acknowledgments
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22] F. Bergmann, D. Schapiro, J. Org. Chem. 12 (1947) 57e66.
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165e173.
[
[
[
Authors wish to credit the Universidad del Quindío, Armenia-
Colombia, the Universidad del Valle, Cali-Colombia, and the Instituto