Synthesis and characterization of a new zwitterionic palladium complex as an environmentally friendly catalyst for the Heck-Mizoroki coupling reaction in GVL

Article abstract of DOI:10.1016/j.mcat.2019.110406

A new zwitterionic Palladium (II) complex has been synthesized by the one-pot mixing of Pd(OAc)₂, 2-aminophenol and (3-formyl-4-hydroxy-5-methylbenzyl) triphenylphosphonium chloride, in refluxing ethanol. The metal complex formed was characterized by ¹H NMR, ¹³C NMR, ³¹P NMR and X-ray crystallographic technique and its efficiency tested as a homogeneous pre-catalyst in Heck-Mizoroki cross coupling reaction using γ-Valerolactone (GVL) as a biomass-derived green medium. All the products were obtained in good to excellent yields.

Full text of DOI:10.1016/j.mcat.2019.110406

MolecularCatalysis474(2019)110406
Contents lists available at ScienceDirect
Molecular Catalysis
journal homepage: www.elsevier.com/locate/mcat
Synthesis and characterization of a new zwitterionic palladium complex as
an environmentally friendly catalyst for the Heck-Mizoroki coupling
reaction in GVL
⁎⁎
Mojtaba Bagherzadeha, , Hamed Mahmoudia, Saeed Ataiea, Mohammad Bahjatia, Reza Kiaa,
⁎
Paul R. Raithbyb, Luigi Vaccaroc,
a Chemistry Department, Sharif University of Technology, P.O. Box 11155-3516, Tehran, Iran
b Chemistry Department, University of Bath, Bath, BA2 7AY, UK
c Green SOC – Dipartimento di Chimica Biologia e Biotecnologie, Università degli Studi di Perugia, I-06123, Perugia, Italy
A R T I C L E I N F O
A B S T R A C T
Keywords:
A new zwitterionic Palladium (II) complex has been synthesized by the one-pot mixing of Pd(OAc)2, 2-amino-
phenol and (3-formyl-4-hydroxy-5-methylbenzyl) triphenylphosphonium chloride, in refluxing ethanol. The
metal complex formed was characterized by 1H NMR, 13C NMR, 31P NMR and X-ray crystallographic technique
and its efficiency tested as a homogeneous pre-catalyst in Heck-Mizoroki cross coupling reaction using γ-
Valerolactone (GVL) as a biomass-derived green medium. All the products were obtained in good to excellent
yields.
Cross-coupling reactions
Heck-Mizoroki coupling
Zwitterionic complex
Green chemistry
1. Introduction
catalysts that do not need any co-catalyst or additives still allowing to
define a protocol operating under mild conditions.
The palladium-catalyzed coupling reactions have confirmed as one
of the most efficient synthetic tools for carbon-carbon bonds with
precision reliability [1]. Among them, Heck-Mizoroki reaction has been
widely applied and still are attracting the attention of researchers who
are aiming at finely tune their efficiency and applications [2]. Indeed,
this reaction allows the widely general preparation of valuable com-
pounds that find applications in a variety of fields such as in the
synthesis of natural products, agrochemicals, pharmaceutical inter-
mediates, and innovative materials [3] Most of the efforts for improving
the efficiency of this reaction is directed towards the identification of
effective catalytic systems that may allow defining faster milder reac-
tion conditions [4].
The natural sources, no more have enough potential to satisfy de-
mands for various types of compounds in fine chemical and drug in-
dustries, and in this cumbersome circumstance, applying effective
synthetic procedures can effectively and efficiently help the situation
[8].
Heck-Mizoroki reaction (firstly introduced by Tsutomu Mizoroki [9]
and described by Richard F. Heck [10] about half a century ago) which
introduces a palladium-catalyzed carbon-carbon bond forming reaction,
has been proved as a assorted gadget in synthetic chemistry for creation
of compounds and resourceful procedure in the procurement of fine
chemicals, natural products, agrochemicals and pharmaceutical inter-
mediates as well as for materials chemistry [3g,11].
Among the transition metals with catalytic ability in the carbon-
carbon coupling reactions, palladium is still one of the most effective
and widely employed [1f,5]. In addition, the use of adequate ligands
can strongly affect the catalytic performance of the metal [6]. Our in-
terest has been often directed towards the preparation of Schiff base
type ligands which have proven to be effective in the creation of a good
π-conjugated electron system and in addition not less importantly, can
be accessed with highly reliable synthetic procedures [7] The design
and preparation of effective ligands may lead to effective palladium
The solvent used as a reaction medium represents another para-
meter that obviously influences the efficiency of a catalytic system. In
addition, nowadays solvents play a crucial in shaping the overall che-
mical and environmental efficiency of synthetic protocols as they are
directly related to critical safety, and toxicity issues. Among these as-
pects, the EHS (Environmental, Health, and Safety aspects) are the most
important. Unfortunately, most of the organic solvents generally used
in the design and synthesis of novel catalytic systems for cross-coupling
protocols are toxic information on their behavior in safer solvents and
⁎ Corresponding author at: Green SOC – Dipartimento di Chimica Biologia e Biotecnologie, Università degli Studi di Perugia, I-06123, Perugia, Italy.
⁎⁎ Corresponding author at: Chemistry Department, Sharif University of Technology, P.O. Box 11155-3516, Tehran, Iran.
E-mail address: luigi.vaccaro@unipg.it (L. Vaccaro).
https://doi.org/10.1016/j.mcat.2019.110406
Received 22 April 2019; Received in revised form 10 May 2019; Accepted 13 May 2019
2468-8231/©2019PublishedbyElsevierB.V.

M. Bagherzadeh, et al.
MolecularCatalysis474(2019)110406
Fig. 1. Synthesis of zwitterionic complex 1.
Fig. 2. Optimized structure of zwitterionic complex 1.
Fig. 3. Contour map of the HOMO and LOMO orbitals of zwitterionic complex 1.
conditions are not accessible [12]. Since many years we have been
investigating the use of safer solvents as an alternative to classic was-
teful and toxic reaction media generally used in cross-coupling proto-
cols [1d,13]. We have found that gamma-valerolactone (GVL), is a very
effective non-toxic biomass-derived solvent alternative to replace the
use of classic polar aprotic solvents such as DMF, DMA, and NMP. It is a
valuable chemical deriving from - manipulation of lignocellulosic bio-
masses [14], possessing interesting physical properties [15].
Therefore, we have directed our investigation towards the design
and synthesis of a palladium/Shiff base catalytic system specifically
aiming at the evaluation of its efficiency in GVL. In this work, the novel
zwitterionic palladium (II) Schiff Base complex 1 was synthesized and
characterized by different techniques including its DFT computational
study. We tested the zwitterionic complex 1 as a catalyst in the Heck-
Mizoroki coupling reaction in GVL as a green medium (Fig. 1).
2

M. Bagherzadeh, et al.
MolecularCatalysis474(2019)110406
Fig. 4. The ORTEP of complex 1 with selected
atom numbering and ellipsoids with 40%
probability
[Pd1—Cl1 = 2.3283(7)
Å;
Pd1—N1 = 1.9661(19)
Å;
Pd1—O1 =
1.9666(17) Å; Pd1—O2 = 1.9929(17) Å;
O1—Pd1—O2 = 178.32(8) º; Cl1—Pd1—N1
= 176.32(6) º]. The water molecules were
omitted for clarity.
NMR 400 MHz (1H at 400 MHz, 13C at 100.6 MHz and 31P at 162 MHz)
spectrometer in CDCl3 or DMSO-d6. The progress of catalytic reactions
was performed by an Agilent Technologies 6890 N gas chromato-
graphy, equipped with a 19091J-236 HP-5, 5% phenyl methyl siloxane
capillary column.
Table 1
Crystal data and refinement parameters of complex 1.
Empirical formula
Formula mass
Crystal size (mm)
Color
C32H31NO5PClPd. 0.53 H2O
691.94
0.08 × 0.03 × 0.02
red
Crystal system
Space group
θmax (°)
a (Å)
triclinic
2.2. X-ray Crystallography
P-1
73.03
10.6165(4)
11.0509(3)
14.6958(6)
89.951(3)
76.172(3)
63.400(3)
1485.73(10)
2
Single crystals of the complex suitable for X-ray diffraction analysis
were grown by an ethanolic solution of the complex. X-ray intensity
data were collected using the full sphere routine by φ and ω scans
strategy on the Agilent SuperNova dual wavelength EoS S2 dif-
fractometer with mirror monochromated Cu Kα radiation (λ = 1.54184
Ǻ). For the data collections, the crystal was cooled to 150 K using an
Oxford diffraction Cryojet low-temperature attachment. The data re-
duction, including an empirical absorption correction using spherical
harmonics, implemented in SCALE3 ABSPACK scaling algorithm [17],
was performed using the CrysAlisPro software package [18]. The crystal
structure of the complex was solved by direct methods using the online
version of AutoChem 2.0 in conjunction with OLEX2 [19 (a)] suite of
programs implemented in the CrysAlis software, and then refined by
full-matrix least-squares (SHELXL-97) [20] on F2. The non-hydrogen
atoms were refined anisotropically. All of the hydrogen atoms were
positioned geometrically in idealized positions and refined with the
riding model approximation, with Uiso(H) = 1.2 or 1.5 Ueq(C). For the
molecular graphics, the program SHELXTL [21] was used. All geometric
calculations were carried out using the PLATON software [22]. One of
the water molecules (O1W) is not fully occupied and was disordered
over a center of inversion.
b (Å)
c (Å)
α(°)
β(°)
γ(°)
V (Å3)
Z
Dcalc (Mg/m3)
μ(mm−1)
F (000)
1.547
6.740
707
Index ranges
−10 ≤ h ≤13
−12 ≤ k ≤13
−17 ≤ l ≤18
17529
No. of measured reflns.
No. of independent reflns./Rint
No. of observed
5883/0.034
reflns. I > 2σ(I)
5510
No. of parameters
379
Goodness-of-fit (GOF)
R1 (observed data)
wR2 (all data)a
1.034
0.0269
0.0669
a
w = 1/[σ2(Fo2)+(0.0310 P)2 + 0.6995 P] where P = (Fo2+2Fc2)/3.
2. Experimental
2.3. Synthesis of zwitterionic complex 1
2.1. Materials and methods
To a refluxing and stirring solution of 1.5 mmol (3-Formyl-4-hy-
droxy-5-methylbenzyl) triphenylphosphonium chloride in 20 mL
Ethanol, a solution of 2-Aminophenol (1.5 mmol in 20 mL Ethanol) was
added dropwise. After 3 h, 1.5 mmol Pd(OAc)2 in 100 mL Ethanol was
added to the above solution. As soon as, adding the Pd precursor to the
solution, a green-brown powder was precipitated. After 1 h the pre-
cipitation has been completed and the complex was separated by fil-
tration and washed with hot ethanol to remove unreacted materials and
dry in air. (679 mg, 72% yield). Anal. Calc. for PdO2NClPC32H25: C
61.16, H 4.01, N 2.23%. found: C 61.23, H 4.01, N 2.22%., 1H NMR
5-(Chloromethyl)-2-hydroxybenzaldehyde and (3-Formyl-4-hy-
droxy-5-methylbenzyl) triphenylphosphonium chloride was synthe-
sized according to the previously published procedures [16]. All other
chemicals and solvents were purchased from Merck and Sigma-Aldrich
companies and were used without further purification. Elemental ana-
lyses for carbon, hydrogen, and nitrogen (CHN) were performed on a
leco truspec elemental analyzer. FT-IR spectra were obtained em-
ploying KBr pellets on a Bruker Tensor 27 FT-IR spectrophotometer.
The NMR spectra were recorded at room temperature with a Burker FT-
3

M. Bagherzadeh, et al.
MolecularCatalysis474(2019)110406
Table 2
3. Results and discussion
The details of the intermolecular interactions in complex 1.
3.1. Synthesis and characterization
D—H⋯A
H—A
D⋯A
D—H⋯A
O2W—H1W2⋯Cl1
O2W—H2W2⋯O1W
O2W—H2W2⋯O1W
O3W—H1W3⋯O2W
O3W—H2W3⋯Cl1
O4W—H2W4⋯O2
C14—H14B⋯O3W
C19—H19⋯O1
2.48
2.01
2.14
2.09
2.70
1.97
2.44
2.58
3.230(3)
2.804(8)
2.773(7)
2.933(4)
3.425(3)
2.731(3)
3.343(3)
3.221(3)
147
155
131
167
145
148
155
126
Zwitterionic complex 1 was synthesized by the addition of Pd(OAc)2
to a refluxing solution of (3-Formyl-4-hydroxy-5-methylbenzyl) tri-
phenylphosphonium chloride and 2-aminophenol in ethanol (Fig. 1).
A singlet resonance at δ = 8.30 ppm appears in the 1H NMR spec-
trum of zwitterionic complex 1 (Fig. S3, supporting information), which
is designated to the hydrogen of Schiff-base group (H5, Fig S3). Three
sets of multiple resonances between δ = 7.61-7.91 ppm are assigned to
hydrogens of phenyl phosphonium rings. The signal between δ = 7.87-
7.91 ppm can be allocated to para-hydrogen of phenyl phosphonium
rings, and also the pattern of this resonance looks like an incomplete
triplet, due to the long-range coupling of these hydrogens with phos-
phor and other hydrogens. The resonance of Meta and Ortho positions
of phenyl phosphonium rings are appeared at δ = 7.72-7.77 ppm and
δ = 7.65-7.70 ppm respectively, and they are also merged together. As
shown in the 1H-1H COSY NMR spectrum (Fig. S6), these three sets of
signals are correlated together. According to 1H-1H COSY NMR spec-
trum, two sets of the doublet pattern can be observed at δ = 7.79 and
δ=6.64 ppm and they are assigned to H6 and H9, respectively. Other
(400 MHz, DMSO) δ: 8.30 (s, 1 H), 7.93 – 7.85 (m, 3 H), 7.82 – 7.52 (m,
13 H), 7.33 – 7.18 (m, 1 H), 6.99 – 6.88 (m, 1 H), 6.69 (m, 3 H), 6.47
(m, 1 H), 5.16 – 4.90 (d, JPH = 14.23 Hz, 2 H). 13C NMR (101 MHz,
2
DMSO) δ: 167.67 (s), 162.42 (d, JPC = 1.91 Hz), 145.34 (s), 139.33(s),
136.79 (s), 136.73 (d, JPC = 2.53 Hz), 134.96 (d, JPC = 2.53 Hz),
134.05 (d, JPC = 9.68 Hz), 130.10 (d, JPC = 12.22 Hz), 128.79 (s),
121.41 (d, JPC = 2.32 Hz), 120.91 (s), 118.05 (d, JPC = 84.77 Hz),
118.00 (s), 115.96 (s), 113.63 (s), 111.84 (d, JPC = 8.44 Hz), 27.55 (d,
J
PC = 45.54 Hz). 31P NMR (162 MHz, DMSO) δ: 21.54 (s).
two sets of resonance with
a triplet pattern at δ = 6.46 and
δ=6.94 ppm can be assigned to H7 and H8 hydrogens, respectively.
The H6-H9 hydrogens are correlated together, as observed in the 1H-1H
COSY NMR spectrum. The resonance of H3 and H4 are appeared at
δ = 6.67 and δ=6.62 ppm respectively. These two hydrogens are
merge and correlated together and they split each other into doublet
signals. Another signal at δ = 7.29 ppm is related to H2 and this hy-
drogen is correlated with benzylic hydrogen as shown in the 1H-1H
COSY NMR spectrum. At last, the resonance of benzylic hydrogens is
2.4. General procedure for catalytic Heck cross-coupling reaction
In
a 4 mL screw-capped vial equipped with magnetic stirrer,
0.5 mmol Aryl halide, 0.75 mmol Alkene, 1.5 mmol bases, 3.2 × 10-2
mol% of catalyst 1 (using stock solution prepared by dissolving 0.002 g,
3.18 × 10-3 mmol complex 1 in 10 mL solvent) was mixed with to-
gether and temperature raised to 130 °C. After 90 min, the system was
cooled to room temperature and 2 mL of n-Hexane was added to the
system. The liquid extraction was performed by adding water
(3 × 2 mL) to extracting the GVL. Finally, the product (3 or 4) was
obtained by distillation of n-Hexane. Final purification of the catalytic
product was performed by using flash chromatography.
appeared at δ = 5.03 ppm which has
2JPH = 14.23 Hz.
a doublet pattern with
As well as, 13C NMR, 1H-13C HSQC, and 1H-13C HMBC analyses are
performed to confirm these assignments (Figs. S4, S7, S8). And also, a
Fig. 5. Part of the crystal packing viewed
down the a-axis, showing the connection of the
neighboring molecules into a one-dimensional
infinite chain through water cluster formation
along the b-axis. All H-atoms were omitted for
clarity except for water molecules. On the
other hand, intermolecular π⋯π and C―H⋯O
interactions form a one-dimensional infinite
chain of molecules along the a-axis (Fig. 6).
4

M. Bagherzadeh, et al.
MolecularCatalysis474(2019)110406
Table 4
Heck-Mizoroki coupling of aryl iodide with alkyl acrylates in the presence of
zwitterionic complex 1.a.
Entry
Ar
R
Product
Conv%b
Yield%c
TOFd
1
2
3
4
Ph
-Me
-Me
3a
3b
3c
3d
> 99
93
89
86
91
90
2062
1938
2021
2062
4-CH3-C6H4
4-OCH3-C6H4 -Me
97
4'-COCH3-
C6H4
-Me
> 99
5
6
7
8
Ph
-nBu
-nBu
3e
3f
> 99
96
88
87
93
96
2062
2000
2042
2062
4-CH3-C6H4
4-OCH3-C6H4 -nBu
3 g
3 h
98
4'-COCH3-
C6H4
-nBu
99
aReaction conditions: aryl iodide 0.5 mmol, alkyl acrylates 0.75 mmol, TEA
1.5 mmol, catalyst 1 3.2 × 10-2 mol % (500 μL of stock solution in GVL), 130 °C,
and 1.5 h.
b
c
d
Measured by GC analyses.
Isolated yield of the pure product after flash chromatography.
TOF=(mmol substrate/mmol Cat)×Conversion/Time (h).
negative frequency in the calculated vibrational spectrum showed that
complex 1 was in the minimum energy level. Optimized structure of 1 is
shown in Fig. 2. (Details of optimized bonds lengths and angles are
illustrated in Tables S3 and S4 in Supporting information).
The contour map of frontier molecular orbitals of 1 is shown in
Fig. 3, Fig. S1 and the energy and composition of them are shown in
Table S5. In general, it is very important to understand the nature of
frontier molecular orbitals, because they play a vital role in both che-
mical activity and electronic transitions of the complex. These data
confirm that zwitterionic complex 1 has a closed-shell structure. Ac-
cording to Fig. 3, and Table S5, for complex 1, the HOMO and LUMO
orbitals are distributed over the ligand and only 3% of these two
frontier molecular orbitals is located on the palladium. The large energy
gap between HOMO and LUMO (3.35 eV) illustrates the low chemical
activity and kinetic stability of this complex [24].
Fig. 6. Part of the crystal packing viewed down the b-axis, showing the con-
nection of the neighboring molecules into a one-dimensional infinite chain
through the intermolecular π…π and C―H⋯O interactions along the a-axis.
resonance at δ = 21.54 ppm in 31P NMR of complex 1 (Fig. S5) con-
firmed that just one type of phosphorus atom exists in the complex
structure and the chemical shift of this signal is in the range of phos-
phonium salt chemical shifts [22].
3.2. DFT studies
3.3. X-ray crystal structure
Full geometry optimization was performed in ethanol (CPCM
model) for zwitterionic complex 1 in DFT B3LYP level with 6-311++g
(d,p) basis set for all ligands atoms and LANL2DZ for Palladium by
using Gaussian 09 package [23]. After optimization, the absence of
The solid-state structure of complex 1 was determined by X-ray
crystallography and the ORTEP of the complex was shown with their
atom-labeling scheme in Fig. 4. Details of data collection and refine-
ment parameters are given in Table 1. Selected bond lengths and angles
are listed in Table S1. The details of the intermolecular interactions are
summarized in Table 2.
Table 3
Parameter optimization for the Heck- Mizoroki coupling reaction.
The details of the hydrogen bonding interactions are listed in
Table 2. The geometry around the Pd atom is a square-planar involving
the chlorine atom and a tridentate OON donor ligand. The Pd atom is
coplanar to the least-squares plane of O1, O2, N1, and Cl1 atoms with a
slight deviation of 0.007(1) Å. The interesting feature of the crystal
packing is the connection of the neighboring molecules through a
cluster of water molecules (Fig. 5) along the b-axis.
entry mol % cat Volume
Base
GVL
Temp. Time Convb
TOFc
1/h
of stock
Volume
h
solutiona
1
2
3
4
5
6
7
8
5.4 × 10-3 85 μL
3.2 × 10-2 500
6.4 × 10-2 1000
6.4 × 10-2 1000
6.4 × 10-2 1000
3.2 × 10-2 500
1.6 × 10-2 250
8.0 × 10-3 125
KOAc 2 mL
130 °C 24
14%
43%
51%
108
56
KOAc 1.5 m L 130 °C 24
KOAc 1 mL
130 °C 24
130 °C 1.5
130 °C 1.5
130 °C 1.5
130 °C 1.5
130 °C 1.5
33
TEA
TEA
TEA
TEA
TEA
1 mL
0 mL
0 mL
0 mL
0 mL
> 99% 1031
> 99% 1031
> 99% 2062
3.4. Catalytic efficiency of complex 1
93%
49%
3875
4083
In order to understand the catalytic potential of zwitterionic com-
plex 1, the Heck coupling was tested, and representative and iodo-
benzene (2a) and methyl acrylate (3a) were selected to optimize the
reaction conditions (Table 3). The efficiency of the process was eval-
uated by GC conversion and isolated yield of product 3a, but also by
turnover frequency (TOF).
a
The Stock solution was prepared by dissolving of 0.002 gr (3.18 × 10-
3mmol) of complex in 10 mL of solvent.
b
Reaction conditions: 0.5 mmol Iodobenzene, 0.75 mmol methyl acrylate,
1.5 mmol base.
c
TOF=(mmol substrate/mmol Cat)×Conversion/Time (h).
5

M. Bagherzadeh, et al.
MolecularCatalysis474(2019)110406
Table 5
Heck-Mizoroki coupling of aryl iodide with different styrenes in the presence of zwitterionic complex 1.a.
Entry
Ar
R
Product
Conv%b
Yield%c
4/4'/4"b
TOFd
1
2
3
4
5
6
7
8
Ph
-H
-H
-H
-H
-Cl
-Cl
-Cl
-Cl
4a
4b
4c
4d
4e
4f
> 99
94
83
78
80
85
86
84
88
77
87/13/0
85/15/0
84/16/0
89/9/2
2062
1958
2042
2062
2021
1938
2062
2062
4-CH3-C6H4
4-OCH3-C6H4
4'-COCH3-C6H4
Ph
98
> 99
97
91/9/0
4-CH3-C6H4
4-OCH3-C6H4
4'-COCH3-C6H4
93
86/14/0
89/11/0
83/10/7
4g
4h
> 99
> 99
aReaction conditions: aryl iodide 0.5 mmol, styrenes 0.75 mmol, TEA 1.5 mmol, catalyst 1 3.2 × 10-2 mol % (500 μL of stock solution in GVL), 130 °C, and 1.5 h.
b
c
d
Measured by GC analyses.
Isolated yield of the pure product after flash chromatography.
TOF=(mmol substrate/mmol Cat)×Conversion/Time (h).
At this latter purpose, a stock solution of complex 1 was prepared in
GVL at a concentration of 3.18 × 10-4 M. The system was initially
evaluated with the KOAc as a base, but after 24 hours even with an
increase in catalyst content, no acceptable conversion was obtained
(Table 3, entries 1-3). In order to solve this problem, the base was re-
placed with TEA, which increased the conversion to 99% in just
1.5 hours (entry 4). Also, to reduce the amount of waste from the re-
action, the amount of solvent was reduced and only the solvent in the
stock solution was used, which did not make a difference in the con-
version of reaction (entry 5). In the end, the amount of catalyst was
reduced and the catalytic system showed tremendous performance in a
lower amount of catalyst, which increased the TOF of reaction (entries
6-8).
and Physical Sciences Research Council (EPSRC) for continued funding
(EP/K004956/1). The Università degli Studi di Perugia and MIUR are
acknowledged for financial support to the project AMIS, through the
program “Dipartimenti di Eccellenza - 2018-2022”.
Appendix A. Supplementary data
Supplementary material related to this article can be found, in the
online version, at doi:https://doi.org/10.1016/j.mcat.2019.110406.
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4. Conclusion
In summary, a new zwitterionic Pd (II) Schiff base complex was
synthesized and fully characterized, by various technics. Also, DFT
studies were performed on this complex and the nature of frontier
molecular orbitals was obtained. Afterward, the complex was used as a
homogeneous catalyst in Heck cross-coupling reaction. The importance
of this catalytic system is related to using GVL as a green and renewable
medium. The catalytic system showed remarkable activity in GVL for
Heck coupling of various substrates and the catalyst successfully
showed high potential in the green coupling of iodobenzene to methyl
acrylate with the turnover frequency more than 4000/h.
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