Synthesis of a novel ZnO nanoplates supported hydrazone-based palladacycle as an effective and recyclable heterogeneous catalyst for the Mizoroki-Heck cross-coupling reaction

Article abstract of DOI:10.1016/j.ica.2017.11.060

A new hydrazone-based palladacycle complex was successfully prepared onto ZnO nanoplates support and was fully identified by using a variety of methods such as energy dispersive X-ray spectroscopy (EDX), Brunauer-Emmett-Teller analysis (BET), inductively coupled plasma technique (ICP), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The morphology of nanoplates support has been also confirmed by scanning electron microscopy (SEM) and powder X-ray diffraction (XRD). Furthermore, it was shown that ZnO nanoplates supported hydrazone-based palladacycle can act as a highly efficient heterogeneous catalyst for the Mizoroki-Heck cross-coupling reaction with excellent yields. The reaction was successfully carried out between aryl iodides, bromides or even aryl chlorides with a variety of olefins. Additionally, it is possible to isolate the catalyst from the reaction mixture and reused for eight sequential cycles without remarkable decrease in catalytic activity.

Full text of DOI:10.1016/j.ica.2017.11.060

Inorganica Chimica Acta 471 (2018) 664–673
Contents lists available at ScienceDirect
Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Research paper
Synthesis of a novel ZnO nanoplates supported hydrazone-based
palladacycle as an effective and recyclable heterogeneous catalyst for the
Mizoroki-Heck cross-coupling reaction
⇑
Fatemeh Nouri, Shahnaz Rostamizadeh , Mohammad Azad
Department of Chemistry, K.N. Toosi University of Technology, P.O. Box: 15875-4416, Tehran, Iran
a r t i c l e i n f o
a b s t r a c t
Article history:
A new hydrazone-based palladacycle complex was successfully prepared onto ZnO nanoplates support
and was fully identified by using a variety of methods such as energy dispersive X-ray spectroscopy
Received 27 September 2017
Received in revised form 27 November 2017
Accepted 28 November 2017
Available online 2 December 2017
(EDX), Brunauer-Emmett-Teller analysis (BET), inductively coupled plasma technique (ICP), thermogravi-
metric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spec-
troscopy (XPS). The morphology of nanoplates support has been also confirmed by scanning electron
microscopy (SEM) and powder X-ray diffraction (XRD). Furthermore, it was shown that ZnO nanoplates
supported hydrazone-based palladacycle can act as a highly efficient heterogeneous catalyst for the
Mizoroki-Heck cross-coupling reaction with excellent yields. The reaction was successfully carried out
between aryl iodides, bromides or even aryl chlorides with a variety of olefins. Additionally, it is possible
to isolate the catalyst from the reaction mixture and reused for eight sequential cycles without remark-
able decrease in catalytic activity.
Keywords:
Palladacycle
Heterogeneous catalyst
ZnO nanoplates
Mizoroki-Heck cross-coupling
Ó 2017 Elsevier B.V. All rights reserved.
1
. Introduction
Palladium-catalyzed processes facilitate the formation of CAC
However, palladacycles are known to be the most efficient cat-
alysts among the other Pd(II) complexes [22,23]; and between the
several types of palladacycle catalysts, CN-type palladacycles,
which exist typically as bridged dimers by halogen or acetate, are
one of the most effective palladium catalysts for carbon-carbon
bond formation due to having a highly energetic CAPd bond
[24,25], in which the nitrogen atom can be from amine [26,27],
imine [28,29], oxime [30], hydrazone [31] or N-heterocycle ligands
bonds between aryl halides and vinyl groups via Mizoroki-Heck
type reactions, which provide a versatile, effective and common
way for the synthesis of various substituted olefins [1–3]. There-
fore, palladium-catalyzed reactions accelerate the organic syn-
thetic routes into a large number of biological and medicinal
compounds [4–6]. However, in most of the reactions catalyzed by
palladium complexes, in addition to low catalytic efficiency, a cat-
alyst with high loading amount of Pd and an inert atmosphere are
commonly required to promote the conversion, which is costly and
not suitable from an environmental viewpoint [7]. Thus, utilization
of the new palladium complexes as catalyst has been of consider-
able interest especially regarding aryl chlorides [8–10] under aer-
obic and aqueous conditions [11–14]. In the past few years,
various Pd(II) complexes, such as N-heterocyclic carbene [15] and
phospha-containing complexes [16] have been applied as catalyst
in CAC cross-coupling reactions. In addition, YCY-type [17] and
CY-type palladacycles [18,19], in which Y could be various func-
tional groups bound to palladium through P, N, S or O atoms, have
also demonstrated their catalytic activities [20,21].
2
and etc. Also, the metalated carbon is usually an aromatic sp car-
bon. For example, Iyer reported the cyclopalladated acetylferro-
cenyl oxime as a CN-type palladacycle in the Mizoroki-Heck
coupling reaction [32]. Nowtony [33] and Wu [34] also investi-
gated the use of imino-palladacycle complexes in this type of
CAC coupling reaction in good yields.
Although, the palladacycle catalysts as Herrmann described, are
effectively able to promote many reactions, similar to Heck cou-
pling reaction [35], these catalysts suffer from some disadvantages
associated with their instability, the necessity of using toxic phos-
phine auxiliary ligands, degradation, deactivation of catalyst dur-
ing the first run as well as palladium leaching and difficult
separation [36]. However, to the extent of our knowledge, a little
research on the stability, recovery and reusability of these catalysts
has been performed in the literature. In recent years, efforts have
been made to solve the problem by immobilization of palladacy-
cles on different supports. Accordingly, Nowotny et al. immobilized
⇑
Corresponding author.
E-mail address: shrostamizadeh@yahoo.com (S. Rostamizadeh).
https://doi.org/10.1016/j.ica.2017.11.060
020-1693/Ó 2017 Elsevier B.V. All rights reserved.
0

F. Nouri et al. / Inorganica Chimica Acta 471 (2018) 664–673
665
the previously synthesized imine-based palladacycle complex onto
polystyrene to improve its reusability for the Heck reaction. How-
ever, it failed after the second run [33]. As a result, a phospha-con-
taining ligand was used for the recovery of the Pd catalysts during
the reaction [37–42]. Afterwards, Gladysz prepared an imine-type
palladacycle immobilized onto a thermomorphic fluorous polymer,
in which recyclability of the catalyst was enhanced significantly;
but this reactivity was not observed for aryl bromides [43]. More-
over, Alonso et al. used the graphene oxide supported oxime-pal-
ladacycle in the coupling reaction, in which the efficiency of the
catalyst was missed in third run [44]. In this manner, some pal-
ladacycles were immobilized onto polystyrene [45–48], chitosan
X-ray equipment. X-ray diffraction was performed using a PHILIPS
X-ray diffractometer system (PW1800-Model). The surface mor-
phology of the ZnO nanoplates supported hydrazone-based pal-
ladacycle catalyst was analysed by scanning electron microscope
(KYKY-EM3200 Digital Scanning). A 2400 series II PerkinElmer ele-
mental analyzer was employed for the CHN analysis. A twin anode
X-ray source system (XR3E2, 8025-BesTec) was applied for X-ray
photoelectron spectroscopy analysis. The specific surface area of
the nanostructure was determined by the nitrogen sorption mea-
surement, ([5.0.0.3] Belsorp, BEL Japan, INC.). The porous structural
parameter in this paper is based on Barret-Joyner-Halenda (BJH)
data. The NMR spectra of the products in Table 5 were provided
with electronic Supplementary information (ESI).
[
49], polyethylene glycol [50], Fe
3 4
O nanoparticles [51], MCM-41,
SiO , polystyrene-divinyl benzene polymer [52] and polyvinyl pyr-
2
idine [53] supports to obtain an improved heterogeneous catalyst.
But these catalysts have still been suffering from the problem of
low reusability and low catalytic activity, especially for aryl bro-
mides and chlorides. Therefore, the exploration of new stable pal-
ladacycles is still required. To the best of our knowledge, no
research dealing with immobilization of a palladacycle onto ZnO
support has been reported. ZnO is a valuable material in biomedi-
cine, ceramics, ointments, foods, etc. [54] due to its exceptional
physical and chemical properties including high chemical, thermal
and mechanical stability [55], hardness, biocompatibility and
biodegradability, antibacterial and non-toxicity [56–58]. Further-
more, ZnO nanoparticles, by having high surface area to volume
ratio and considerable stability as mentioned above, are expected
to be an efficient, suitable, and stable heterogeneous support for
organic catalytic centres [59–62]. Therefore, in continuation of
our research interest in preparing of heterogeneous nano catalysts
2.2. Synthesis of the catalyst
2.2.1. Synthesis of hydrazone ligand (1)
4-formylbenzoic acid (0.300 g, 2 mmol) was dissolved in dry
MeOH (20 mL) at room temperature and then hydrazine
hydrateÁ6H
2
O (0.1 mL, excess) was added dropwise to the solution
according to the literature procedure with slightly modification
[71]. After a few minutes yellow crystals precipitated. The product
was collected by filtration, washed with MeOH and acetonitrile,
and then dried under vacuum condition. As a result, the compound
(1E,2E)-1,2-bis(1,4-hydraziniumbenzoyl)ethylidene)
was synthesized as yellow fine powder (0.3 g, 95%). dH
(300 MHz; [D6] DMSO; Me Si): 7.07 (10H, br s, NH ), 7.57
-NH+
( J = 8.9, 4H, d, CH), 7.82 ( J = 8.9, 4H, d, CH), 8.66 (2H, s, CH = N);
hydrazine
4
2
3
3
3
dC (75 MHz; [D6] DMSO; Me
(C), 140.0 (C), 162.4 (C = N), 172.4 (COO ). Also, elemental analysis
was performed to confirm the synthesis of the ligand (Found: C,
4
Si): 129.9 (CH), 130.0 (CH), 139.0
À
[
63–66], we are intending to prepare a new hydrazone-based pal-
ladacycle which can be immobilized onto ZnO nano support to pro-
mote its stability and catalytic activity. To do so, we chose a
hydrazone ligand containing carboxylate groups; because carboxy-
late onions strongly adsorbs Zn centres and significantly adjusts
the surface morphologies by promoting or reducing the crystal
growth as well [67–70]. Although, organic additives have been
widely used to alter the crystal growth of ZnO nanoparticles, but
this strategy has not been used for immobilization of organometal-
lic catalytic centres onto ZnO nanostructure support.
Herein, for the first time, we report the synthesis of a novel ZnO
nanoplates supported hydrazone-based palladacycle which can be
applied as a highly effective and reusable palladacycle catalyst for
running Mizoroki-Heck cross-coupling reaction between aryl
halides and various olefins with high yields in short reaction times
even for aryl chlorides.
20 6 4
53.3; H, 5.1; N 22.7. Calc. for C16H N O : C, 53.3; H, 5.5; N, 23.3%).
2.2.2. Synthesis of ZnO nanoplates supported hydrazone ligand
(hydrazone@ZnO, 2)
ZnO nanoplates supported hydrazone ligand was synthesized
by reacting Zn(NO
3
)
2 2
Á6H O (1.18 g, 4 mmol) with the prepared
hydrazone ligand (1) (0.3 g) in 25 mL DMF in a sealed vessel reac-
tion. Then the yellow solution was heated at 90 °C for 18 h. As soon
as the solution temperature reached to 90 °C, ZnO nanoplates
hydrazone ligand rapidly was produced from solution. After 18 h,
the resulting pale yellow powder was collected by filtration,
washed with DMF and subsequently with chloroform and dried
under vacuum for 2 h to give ZnO nanoplates supported hydrazone
ligand (2).
2.2.3. Synthesis of ZnO nanoplates supported hydrazone-based
palladacycle catalyst (hydrazon-Pd@ZnO, 3)
2
. Experimental
To 0.3 g ZnO nanoplates supported hydrazone ligand was added
0
2
.045 g Pd(OAc) and 100 mL dry dichloromethane as solvent. The
2
.1. Materials and instruments
lemon mixture was stirred at room temperature for 1 day. Subse-
quently, the cream-green mixture was centrifuged and washed
several times with dichloromethane and allowed to dry at 80 °C.
All chemical materials were supplied from Aldrich, Merck and
Fluka. A Buchi or Heidolph rotary evaporator was employed to
remove solvents at reduced pressure. Thin layer chromatography
2.3. General procedure for Mizoroki-Heck coupling reaction of aryl
halides with olefins
plate was prepared on plates of silica gel 60 (5–40 lm mesh size
2
diameter) on glass plates (20 Â 20 cm ) using 10 g of silica gel. IR
spectroscopy was accomplished by a Shimadzu FTIR-8300 spec-
To a 25 mL round bottom flask containing aryl halide (1 mmol),
olefin (1.2 mmol), Et N (1.5 mmol), and ZnO nanoplates supported
3
1
13
trophotometer. H and C NMR of the resulting Mizoroki-Heck
products were provided with Bruker Avance spectrometer at 300
and 75 MHz, respectively. Inductively coupled plasma technique
was performed by Varian Vista-MPX instrument to determine the
amount of metal. Thermogravimetric curve was recorded under
nitrogen atmosphere by NETZSCH STA 409 PC instrument. Energy
dispersive X-ray analysis was achieved using Vega TESCAN-Model
scanning electron microscope supplied with energy dispersive
hydrazone-based palladacycle (10 mg, 0.26 mol% Pd), 3 mL DMF
was added as solvent. The resulting solution was stirred at 130
°C in an oil bath. The reaction was followed by TLC (thin layer chro-
matography) and at the end; it was allowed to cool to room tem-
perature and was centrifuged to separate the catalyst. The
residue was diluted with ethyl acetate (2 Â 5 mL), and washed
with water (2 Â 5 mL). Then the organic phase was dried with

6
66
F. Nouri et al. / Inorganica Chimica Acta 471 (2018) 664–673
anhydrous MgSO
4
, filtered, and the solvent was removed by evap-
2.3.1.10. (E)-n-butyl 3-m-tolylacrylate (6r). dH (300 MHz, CDCl
Me Si): 0.98 (3H, t, CH ), 1.45 (2H, m, CH ), 1.71 (2H, m, CH
2.38 (3H, s, CH ), 4.22 (2H, t, CH
7.20 ( J = 8.2, 1H, d, CH), 7.27 (1H, m, CH), 7.33 (2H, m, CH), 7.67
3
;
oration under vacuum conditions. Further purification was
achieved by thin layer chromatography plate, using EtOAc and
n-hexane with 2:10 ratio as eluent.
4
3
2
2
),
2
), 6.44 ( J = 17.7, 1H, d, CH),
3
3
3
3
(
3 4
J = 17.7, 1H, d, CH); dC (75 MHz; CDCl ; Me Si): 13.7, 19.2, 21.2,
3
1
0.1, 64.3, 118.0, 123.9, 125.2, 128.7, 130.9, 134.4, 138.4, 144.7,
68.0.
2
.3.1. Selected spectral data of the Mizoroki-Heck products
3
2.3.1.1. (E)-4-styrylbenzonitrile (6a, 6g). dH (300 MHz; CDCl ;
3
3
4
Me Si): 7.09 ( J = 18.25, 1H, d, CH), 7.22 ( J = 18.25, 1H, d, CH),
7
7
CDCl
3
.32 (1H, dd, CH), 7.39 (2H, dd, CH), 7.54 ( J = 8.2, 2H, d, CH),
3
3
3. Results and discussion
.57 ( J = 7.4, 2H, d, CH), 7.64 ( J = 7.4, 2H, d, CH); dC (75 MHz;
; Me Si): 110.5, 119.03, 126.7, 126.8, 126.9, 128.6, 128.8,
3
4
3.1. Preparation and characterization of the catalyst
1
32.4, 132.4, 136.2, 141.8.
All the steps involved in the preparation of the catalyst have
2
3
.3.1.2. (E)-1-methyl-4-styrylbenzene (6b, 6l). dH (300 MHz; CDCl ;
been outlined in Scheme 1. As shown in Scheme, we firstly pre-
pared a hydrazone ligand (1) and then immobilized it onto ZnO
nanoplates support (2). Finally, by insertion of palladium, the
heterogeneous ZnO nanoplates supported hydrazone-based pal-
ladacycle catalyst (3) was successfully produced.
3
3
4 3
Me Si): 2.39 (3H, s, CH ), 7.04 ( J = 18.49, 1H, d, CH), 7.17 ( J =
1
7
CH); dC (75 MHz; CDCl
1
3
8.49, 1H, d, CH), 7.22 ( J = 8.8, 2H, d, CH), 7.27 (1H, dd, CH),
3
3
.38 (2H, dd, CH), 7.44 ( J = 8.9, 2H, d, CH), 7.54 ( J = 8.8, 2H, d,
; Me Si): 21.2, 126.4, 126.4, 128.6, 128.6,
27.4, 127.7, 129.4, 134.5, 137.5, 137.5.
3
4
The presence of corresponding functional groups at different
steps was confirmed by FTIR analysis (given at ESI). In IR spectra
2
.3.1.3. (E)-1-(4-styrylphenyl)ethanone (6c). dH (300 MHz; CDCl
3
;
À1
of ligand (1), the medium peak appeared at 959 cm and two
3
Me
4 3
Si): 2.60 (3H, s, CH ), 7.12 ( J = 18.15, 1H, d, CH), 7.22
À1
sharp peaks at 1378 and 1617 cm are related to the NAN bond
3
(
(
J = 18.15, 1H, d, CH), 7.30 (1H, dd, CH), 7.39 (2H, dd, CH), 7.54
in hydrazone functional group, symmetric and asymmetric stretch-
3
3
3
J = 8.1, 2H, d, CH), 7.58 ( J = 9.2, 2H, d, CH), 7.95 ( J = 9.2, 2H, d,
; Me Si): 26.6, 126.4, 126.8, 127.4, 128.3,
28.8, 128.8, 131.4, 135.9, 136.6, 141.9, 197.4.
ing vibrations in carboxylate ions, respectively. Also, the ZnAO
CH); dC (75 MHz; CDCl
1
3
4
À1
bond stretching appeared at 431 cm and C@N vibration band
À1
was observed at 1657 cm for free ligand in IR spectra of com-
pound (2). After the cyclopalladation, in IR spectra of catalyst (3),
À1
2
2
.3.1.4. (E)-3-p-tolylacrylonitrile (6d). dH (300 MHz, CDCl
3
; Me
4
Si):
the C@N band shifted to lower frequency 1646 cm and a new
3
3
À1
.38 (3H, s, CH
3
), 5.80 ( J = 18.51, 1H, d, CH), 7.20 ( J = 9.0, 2H, d,
small peak appeared at 1412 cm
could be assigned to CAO
3
3
CH), 7.33 ( J = 9.0, 2H, d, CH), 7.34 ( J = 18.51, 1H, d, CH); dC (75
MHz; CDCl ; Me Si): 21.5, 94.9, 118.4, 127.3, 129.8, 130.8, 141.8,
1
stretching vibration of the acetate bound to Pd [72].
3
4
Moreover, in order to determine all the elements, the synthe-
sized compound (2) was characterized by energy-dispersive
X-ray spectroscopy (EDX) (Fig. 1a). The presence of palladium in
the catalyst (3) was confirmed by EDX as well (Fig. 1b). As seen
in Fig. 1, the obtained ZnO supported hydrazone-based palladacy-
cle contains all the elements in both of the organic ligand and the
ZnO nanostructure as support.
Furthermore, according to the inductively coupled plasma-
atomic emission spectroscopy (ICP-AES) and elemental analysis
shown in Table 1, about 38.18 wt% of the catalyst constructed from
Zinc as support and 28.68 wt% carbon as organic ligand. In
addition, the amount of palladium incorporated into the ZnO
50.5.
2
.3.1.5. (E)-3-(4-acetylphenyl)acrylonitrile (6e). dH (300 MHz,
3
CDCl
3
; Me
J = 18.54, 1H, d, CH), 7.31 ( J = 9.3, 2H, d, CH), 7.64 ( J = 9.3, 2H,
d, CH); dC (75 MHz; CDCl ; Me Si): 30.9, 98.7, 117.5, 127.4,
28.6, 137.3, 138.2, 148.8, 196.9.
4 3
Si): 2.64 (3H, s, CH ), 5.83 ( J = 18.54, 1H, d, CH), 7.15
3
3
3
(
3
4
1
2
Me
3
.3.1.6. (E)-1-methoxy-3-styrylbenzene (6i). dH (300 MHz; CDCl ;
3
4 3
Si): 3.86 (3H, s, CH ), 6.83 ( J = 16.7, 1H, d, CH), 7.10 (4H, m,
CH), 7.26 (1H, s, CH), 7.28 (1H, dd, CH), 7.38 (2H, dd, CH), 7.52
3
(
3 4
J = 8.1, 2H, d, CH); dC (75 MHz; CDCl ; Me Si): 55.5, 111.7,
1
1
13.2, 119.2, 126.5, 127.6, 128.5, 128.6, 129.0, 129.6, 137.2,
38.7, 159.8.
N
N
COO NH NH2 (1)
NH NH3 OOC
N
3
2
2
Me
2
7
1
6
.3.1.7. (E)-n-butyl 3-p-tolylacrylate (6j). dH (300 MHz; CDCl
Si): 0.97 (3H, t, CH ), 1.44 (2H, m, CH ), 1.69 (2H, m, CH
.37 (3H, s, CH ), 4.20 (2H, t, CH
3
;
Zn(NO ) .6H O
DMF, 18 h
4
3
2
2
),
), 6.39 ( J = 17.7, 1H, d, CH),
3 2
2
3
3
2
3
3
3
.18 ( J = 8.9, 2H, d, CH), 7.42 ( J = 8.9, 2H, d, CH), 7.66 ( J = 17.7,
H, d, CH); dC (75 MHz; CDCl ; Me Si): 13.7, 19.2, 21.4, 30.7,
3
4
O
O
(
2)
ZnO
O
N
ZnO
ZnO
4.3, 117.1, 128.0, 129.5, 131.7, 140.5, 144.5, 167.2.
O
2.3.1.8. (E)-n-butyl 3-(4-acetylphenyl)acrylate (6k). dH (300 MHz,
Pd(OAc)2
CH Cl2
CDCl
3
; Me
4
Si): 0.96 (3H, t, CH
3
), 1.44 (2H, m, CH
2
3
), 1.69 (2H, m,
2
CH ), 2.60 (3H, s, CH
2
3
), 4.22 (2H, t, CH
2
), 6.52 ( J = 17.8, 1H, d,
2
AcO
3
3
CH), 7.59 ( J = 9.2, 2H, d, CH), 7.68 ( J = 17.8, 1H, d, CH), 7.96
3
Pd
(
J = 9.2, 2H, d, CH); dC (75 MHz; CDCl
3
; Me
4
Si): 14.0, 19.1, 22.6,
O
O
O
(
3)
3
1.9, 64.6, 120.8, 128.0, 128.4, 137.9, 138.7, 142.9, 166.5, 197.1.
ZnO
O
N
N
Pd
OAc
2
2
3
.3.1.9. (E)-1,2-diphenylethene (6n, 6o). dH (300 MHz, CDCl ;
4
Me Si): 7.13 (1H, s, CH), 7.28 (1H, dd, CH), 7.38 (2H, dd, CH),
7
3 4
.54 (2H, d, CH); dC (75 MHz; CDCl ; Me Si): 126.5, 127.6, 127.9,
Scheme 1. Synthesis of ZnO nanoplates supported hydrazone-based palladacycle
1
28.6, 137.3.
catalyst.

F. Nouri et al. / Inorganica Chimica Acta 471 (2018) 664–673
667
Fig. 1. EDX data of ZnO nanoplates supported hydrazone ligand (2) (a) and ZnO nanoplates supported hydrazone-based palladacycle (3) (b).
Table 1
ICP and elemental analysis of ZnO supported composites.
Entry
Composite
C%
H%
N%
Zn%
Pd%
1
2
Hydrazone@ZnO
Hydrazone-Pd@ZnO
29.45
28.68
1.53
1.51
4.29
4.08
40.13
38.18
–
2.8
nanoplates supported hydrazone ligand was also determined by
ICP technique. According to this analysis, 2.8 wt% of the Pd was
immobilized into the ZnO nanoplates supported hydrazone-based
palladacycle, which indicates the synthesized hydrazone ligand,
has good capability of binding to the palladium (Table 1).
The XRD patterns of ZnO nanoplates supported hydrazone
ligand (2) confirm the formation of the ZnO nanoplates (Fig. 2),
in which the crystal phases pattern is remarkably in accordance
with Zincite having the wurtzite structure ZnO (JCPDS Card File
No. 36-1451). Moreover, all diffraction peaks are attributed to crys-
talline phases. The XRD characteristics appeared at 31.56°, 34.24°,
36.08°, 47.32° and 56.51° are due to the diffractions of (1 0 0), (0 0
2), (1 0 1), (1 0 2) and (1 1 0) planes, while the peaks at lower
angles 16.56°, 18.40°, 20.14°, 24.84°, 29.48° and 30.81° are related
to the organic phase which has been bound as cross-link to ZnO
nanoparticles (Fig. 2a). Also, an XRD analysis was performed on
ZnO nanoplates supported hydrazone-based palladacycle (3)
(Fig. 2b). As seen in Figure, all the peaks were unchanged, which
Fig. 2. XRD pattern of ZnO nanoplates supported hydrazone ligand (2) (a) and ZnO nanoplates supported hydrazone-based palladacycle (3) (b).

6
68
F. Nouri et al. / Inorganica Chimica Acta 471 (2018) 664–673
reveal that the crystalline structure of the compound has been
maintained well after palladation and no metallic palladium has
been involved [73]. As a result, only palladium complex has been
formed.
The morphology of the synthesized ZnO nanostructure sup-
ported hydrazone-based palladacycle was characterized from
SEM images. As seen in Fig. 3, it could clearly be observed that
ZnO nanostructures in the presence of organic ligand containing
carboxylate groups resulted in the formation of ZnO nanoplates.
The growth of nanoplates is quite typical and is clearly associated
to the role of the anionic ligand as cross-linking agent, which
restrained the longitudinal growth of nanorods but assisted the
growth of plates [67]. Furthermore, as shown in the Fig. 3, thick-
nesses of nanoplates are about 28–45 nm and their width is
between 200 nm and 1000 nm.
In order to investigate the surface area and porous properties of
the prepared catalyst (3), the nitrogen adsorption–desorption anal-
ysis was performed. The resulting nitrogen adsorption–desorption
isotherm and the corresponding BET plot are shown in Fig. 4. Also,
the physical parameters including the BET surface area and average
pore diameter and pore volume of the ZnO nanostructure sup-
ported hydrazone-based palladacycle (3) were summarized in
Table 2. The results for catalyst (3), which is a modified ZnO nanao-
plates with organic moiety, indicate an acceptable surface area in
comparison with non-modified ZnO nanoplates, which have sur-
2
face areas between 3 and 15 m /g [74–76]. This surface area could
be assigned to their small size and thickness. Furthermore, accord-
ing to the BET experiment in Fig. 4, the sample possess type-III iso-
therm with a small H3 hysteresis loop according to IUPAC
classification [77], which recommends that the pores have a slit
and sheet shape [78].
Moreover, the thermal stability of the catalyst was studied by
thermogravimetric-differential thermal analysis (TG-DTA) under
nitrogen atmosphere (Fig. 5). According to the DTG curve, a slight
mass loss occurred below 220 °C which could be related to desol-
vation or dehydration. In addition, a major mass loss was observed
between 220 °C and 550 °C, which was attributed to degradation of
the organic materials and the hydrazone-based palladacycle com-
plex. Additionally, the maximum weight loss which has occurred
at 380 °C reveals the thermal stability of the catalyst for organic
reactions with high temperature.
To investigate the formation of ZnO nanoplates hydrazone-
based palladacycle catalyst (3), X-ray photoelectron spectroscopy
(
XPS) technique was applied. According to this analysis, the pres-
ence of C, N, O, Zn and Pd atoms were recognized in the prepared
catalyst (Fig. 6). As is clear from Fig. 6b, two evident peaks at
3
37.60 eV and 343.04 eV are obviously related to 3d5/2 and 3d3/2
core-levels of Pd(II) in the ZnO nanoplates supported hydrazone-
based palladacycle catalyst. The binding energy shifts for Pd(II)
3
2
d5/2 of Pd(OAc) from 336.4 eV to 337.6 eV and Pd(II) 3d3/2 from
3
41.7 to 343.0 eV reveals the formation of hydrazone-based pal-
ladacycle complex [79]. Also, the XPS spectra of C 1s obviously
indicates the peaks at 284.7, 285.0, 286.3 and 288.5 eV, which
are related to C@C, CAC, C@N and OAC@O bonds, respectively
(Fig. 6c). In addition, the XPS spectra of N 1s in Fig. 6d, clearly exhi-
bits the presence of NAN@C and NAPd bonds at 400.5 and 402.1
eV [44]. The average peak for O 1s is located at 531.8 eV (Fig. 6e)
and the peaks at 90, 1022 and 1044 eV are also related to Zn 3p,
2
p3/2 and 2p1/2, respectively [80].
3.2. Catalytic application of ZnO nanoplates supported hydrazone-
based palladacycle (3) in Mizoroki-Heck cross-coupling reaction
In order to examine the efficiency of the ZnO nanoplates sup-
ported hydrazone-based palladacycle catalyst, it was applied in
the Mizoroki–Heck cross-coupling reaction. This reaction was cho-
sen, because this type of reactions provides a potent way for the
CAC bond formation between olefins and aryl halides in the pres-
ence of the palladium complexes. Hence, the optimization of Heck
cross-coupling reaction was carried out using 4-bromobenzonitrile
(
1 mmol) and styrene (1.2 mmol) derivatives in the presence of the
ZnO nanoplates supported hydrazone-based palladacycle catalyst
3). The reaction was studied under various conditions such as dif-
(
ferent amounts of catalyst, different bases, solvents and tempera-
tures. The experimental results are summarized in Tables 3–5. At
Fig. 3. SEM images of ZnO nanoplates supported hydrazone-based palladacycle (3)
catalyst.

F. Nouri et al. / Inorganica Chimica Acta 471 (2018) 664–673
669
Fig. 4. Nitrogen adsorption-desorption isotherm (a) and BET plot of ZnO nanoplates supported hydrazone-based palladacycle (3) catalyst (b).
Table 2
of the expected product was improved to 95% in a shorter reaction
The results of BET and BJH measurements for ZnO
nanoplates supported hydrazone-based palladacycle (3)
catalyst.
time. But there were no differences in yield and reaction time
between 0.010 g (entry 2) and 0.020 g (entry 4) of the catalyst.
Therefore, we chose 0.010 g (0.26 mol% Pd) of the catalyst for fur-
ther experiments. In order to show the unique behaviour of the
catalyst, the reaction was also separately examined in the absence
of catalyst as well as in the presence of ZnO and ZnO nanoplates
supported hydrazone ligand alone (entries 5, 6, 7) in which we
did not observed any product even on TLC. Furthermore, a control
Experiment
Results
2
À1
BET Surface area
Average pore diameter
Pore volume
38.838 (m .g
28.165 (nm)
0.2759 (cm .g
)
3
À1
)
2
À1
BJH adsorption surface area
48.652 (m .g
)
2
reaction was also performed in the presence of Pd(OAc) without
any ligand and the yield of the reaction was only 20% after 24 h
(entry 8) and all of the palladium was also leached into the solution
(palladium black), while in the presence of catalyst (3), no palla-
dium black was observed (Section 3.3). The comparison of these
the beginning, the reaction was performed using different amounts
of catalyst at 130 °C (Table 3, entries 1–4). As seen in Table, by
increasing the amount of catalyst from 0.008 g to 0.010 g, the yield
Fig. 5. TG-DTA curve for ZnO nanoplates supported hydrazone-based palladacycle (3).

6
70
F. Nouri et al. / Inorganica Chimica Acta 471 (2018) 664–673
Fig. 6. XPS spectrum: full range (a), the Pd 3d (b), C 1s (c), N 1s (d) and O 1s (e) of the catalyst (3).
results showed the stability and catalytic efficiency of the catalyst
3) and proved the formation of the hydrazone-based palladacycle
complex (3). The reaction was then carried out at various temper-
atures. The comparison of the results in Table 4, entries 6 and 10
revealed that the reaction proceeded slightly better at 130 °C
various ratios produces a by-product (homocoupling) and
(
decreases the reaction yields (Table 4, entries 2, 3). Protic polar sol-
vents, such as EtOH, which was regularly used in coupling reac-
tions catalyzed by Pd, were not operative in the present method
(Table 4, entry 7). The use of toluene was not successful and only
30% yield were observed (Table 4, entry 8). Moreover, the reaction
progressed much better in DMF (Table 4, entry 1, 4). Then, by add-
ings 0.75 eq TBAB, the reaction time was shortened (Table 4, entry
6), which is due to its ionic environment to stabilize intermediates
or transition states in the course of the reaction [81–83]. Therefore,
based upon the optimized reaction conditions, the Heck cross-cou-
pling reaction was performed in the presence of the catalyst (3)
(
entry 6). Based on the results outlined in Table 4, it is obvious that
Et N as organic base acts much better than inorganic bases such as
CO , Na CO , and K PO . Consequently, since Et N is an inexpen-
3
K
2
3
2
3
3
4
3
sive and readily available organic base, we chose it for further
investigations in the reaction. It is worth mentioning that in the
absence of the base only a trace of the product was formed (entry
1
3). To evaluate the effect of solvent, the reaction was performed in
different solvents. The use of DMF/H O mixture as solvent in
2
3
(0.26 mol% Pd), Et N and TBAB (was not required for aryl iodides)

F. Nouri et al. / Inorganica Chimica Acta 471 (2018) 664–673
671
Table 3
Optimization of the amount of the ZnO nanoplates supported hydrazone-based palladacycle catalyst (3) in the Heck reaction .
a
Entry
Catalyst (g)
mol% of Pd
Time (h)
Yield (%)b
1
2
3
4
5
6
7
0.008
0.010
0.015
0.020
No catalyst
ZnO
Hydrazone@ZnO (2)
0.21
0.26
0.39
0.52
0
0
0
0.26
2
1
1
1
24
24
24
24
90
95
95
95
0
0
0
20
c
8
Pd(OAc)
2
a
Reaction conditions: 4-bromobenzonitrile (1 mmol), styrene (1.2 mmol), Et
entries 1–4).
3
N (1.5 mmol), TBAB (0.75 mmol) in DMF (3 mL) at 130 °C, in the presence of catalyst (3) (only
b
Isolated yields.
Only Pd(OAc) was used as catalyst.
2
c
Table 4
a
Optimization of the reaction conditions for Mizoroki-Heck cross-coupling reaction .
Solvent, Base
NC
Br
NC
Cat. 0.26 mol%
4
a
5a
6a
Entry
Solvent
DMF
Base
Et
Temperature (°C)
Time (h)
Yield (%)b
1
2
3
4
5
3
N
130
130
130
130
130
130
80
110
130
120
130
130
130
12
24
24
24
36
1
1.5
12
1.5
1
65
20
30
85
65
95
40
30
20
90
65
72
Trace
DMF/H
DMF/H
DMF
2
O
O
K
2
CO
3
2
Et
Et
3
N
N
3
DMF
DMF
EtOH
Toluene
DMF
DMF
DMF
DMF
DMF
K CO
2
3
c
6
Et
Et
Et
3
N
N
N
c
7
8
3
3
c
c
9
Na
Et
Na
2
CO
N
CO
PO
3
1
1
1
1
0c
1
3
2
3
48
48
24
c
2
K
–
3
4
c
3
a
b
c
Reaction conditions: 4-bromobenzonitrile (1 mmol), styrene (1.2 mmol), base (1.5 mmol) and catalyst (3) (0.26 mol%) in solvent (3 mL) in oil bath.
Isolated yields.
0
.75 mmol TBAB was added.
in DMF at 130 °C (entry 6). Finally, in order to show the novelty
and generality of the ZnO nanoplates supported hydrazone-based
palladacycle catalyst (3), we then tried to study the Heck reaction
between a range of aryl halides (I, Br and Cl) and different olefins
Finally, we provided a table which compared the presented con-
ditions and catalytic activity of the catalyst in this study with other
CN-type palladacycles reported in literature (Table 6). The results
indicate that the prepared catalyst (3) has carried out the Heck
reaction with highest yield in shortest reaction time and excellent
recyclability relative to the other homogeneous and heterogeneous
CN-type palladacycles.
(Table 5). As revealed in Table 5, the reaction of aryl iodides con-
taining electron-rich and electron-poor substituent proceeded
easily, and the desired products were achieved with excellent
yields. The reaction of aryl bromides was also carried out with high
yields. Moreover, derivatives with electron-withdrawing sub-
stituents (Table 5, entries 1, 13) were more reactive than those
with electron-donating groups (Table 5, entries 8, 9, 17). The steric
hindrance caused by the ortho substituents on the aryl halides did
not significantly affect the reaction progress, thus 2-bromotoluene
proceeded as well as 4-bromotoluene (entries 6, 12). As seen in
Table 5, aryl halides with electron-donating substituents at para
position such as 4-bromoanisole which have resonance effect,
needed a longer reaction time than 3-bromoanisole (Table 5,
entries 8, 9). Furthermore, the reaction for styrene and t-butylacry-
late were carried out in short times, but for acrylonitrile, the reac-
tion takes longer time; because the olefins containing electron-
withdrawing groups have less reactivity (entries 4, 5). Also, with
regard to aryl chlorides, the reaction proceeded well in acceptable
yields (entries 7, 16).
3.3. Reusability of the catalyst
One of the most significant features of a heterogeneous catalyst
is the recovery of the catalyst, especially from an industrial view-
point. Hence, the recoverability of the catalyst was investigated
via running the Heck reaction for iodobenzene and styrene under
optimized conditions for several runs. At the end of the first run
(after 1 h), the catalyst was isolated by centrifuging and after
washing with dichloromethane and ethanol, it was dried at 80 °C.
Then, it was applied for subsequent cycle. In this manner, the cat-
alyst successfully carried out the reaction up to 8 cycles in high
yields and its efficiency was not significantly decreased yet after
8 runs (Fig. 7). After removing of catalyst by centrifuging, the
amount of leached palladium into the reaction solution was deter-
mined by ICP. The aforementioned investigation was performed

6
72
F. Nouri et al. / Inorganica Chimica Acta 471 (2018) 664–673
Table 5
a
Mizoroki–Heck reaction of aryl halides with various olefins .
R2
DMF, Et
3
N, 130°C
R2
X
R1
Cat. 0.26 mol%
R1
4
5
6
Entry
R1
X
R2
Product
Time (h)
Yield (%)b
1c
2
3
4-CN
4-CH
Br
I
I
I
I
Br
Cl
Br
Br
I
Ph
Ph
Ph
CN
CN
Ph
Ph
Ph
Ph
CO
CO
Ph
CO
Ph
Ph
CO
CO
CO
Ph
6a
6b
6c
6d
6e
6f
6g
6h
6i
6j
6k
6l
6m
6n
6o
6p
6q
6r
6s
1
95
90
87
85
83
90
68
82
85
98
96
91
90
98
85
65
86
93
92
3
1.5
1.5
10
10
1.5
24
4
3
2
2
1.5
12
1
1.5
24
3
4-COCH
4-CH
4-COCH
3
4
3
5
3
c
6
2-CH
4-CN
3
c
7
8
c
4-OCH
3-OCH
3
c
9
3
n
2
10
11
12
13
14
15
16
17
18
19
4-CH
4-COCH
3
Bu
Bu
n
3
I
2
c
c
4-CH
4-CN
H
3
Br
Br
I
Br
Cl
Br
I
n
2
Bu
c
c
c
H
4-CN
3-OMe
n
2
Bu
Bu
Bu
n
2
n
2
3-CH
3-CH
3
1.5
1.5
3
I
a
b
c
Reaction conditions: aryl halide (1 mmol), olefine (1.2 mmol), Et
Isolated yields.
3
N (1.5 mmol) and catalyst (3) (0.26 mol%) in DMF (3 mL) at 130 °C.
0
.75 mmol TBAB was added.
Table 6
a
Comparison of catalytic activity of various CN-type palladacycle based catalysts in the Mizoroki-Heck reaction .
Entry
Catalyst
Pd (mol%)
Temp. (°C)
Time (h)
Yield (%)
Recyclability /Yield (%)
Ref.
1
2
3
4
5
6
7
8
Imine-Pd
0.064
0.0025
0.0064
0.02
0.1
0.08
100
100
140
100
120
120
100
130
12
10
11
5
6
9
100
92
100
85
94
99
1
1
[33]
[34]
[33]
[43]
[47]
[49]
[50]
This study
b
Fe-imine -Pd
Imine-Pd@PSc
3/100–0
4/85–52
4/94–88
5/97–88
4/80–76
8/98–85
Imine-Pd@fluorous P
Oxime-Pd@PS
Fe-imine-Pd@CSd
Amine-Pd@PEG
Hydrazone-Pd@ZnO
0.0045
0.26
16
1
80
98
a
b
c
Iodobenzene and styrene have been considered as substrates.
Ferrocenyl imine.
Polystyrene.
Chitosan.
d
after the first and eight runs. The content of palladium leached into
À5
the solution was only 6.7 Â 10 wt% (0.67 ppm) during the first
reaction. Moreover, the amount of palladium in recovered catalyst
after eight reaction runs was determined, which showed 0.43 wt%
of total palladium has been released. Therefore, according to the
result of leaching test, the prepared catalyst (3) is a highly effective
heterogeneous catalyst to recover and reuse. Moreover, in order to
prove the heterogeneity of the catalyst, a reaction was also per-
formed under optimized condition in the presence of polyvinyl
pyridine (PVPy) as poison (PVP is a strong poison for the homoge-
neous Pd species). The excess amount of PVPy was added at the
beginning of reaction of iodobenzene with styrene. Then, the reac-
tion was stopped after 1 h (according to the time for model reac-
tion, Table 5, entry 14). The yield of isolated product (96%)
showed insignificant decrease in reactivity of the catalyst which
confirmed that no Pd nanoparticles was leached into the solution.
Fig. 7. Reusability of ZnO nanoplates supported hydrazone-based palladacycle as
catalyst for Heck reaction; reaction conditions: iodobenzene (0.5 mmol), styrene
(
3
0.75 mmol), Et N (0.75 mmol) and 5 mg catalyst (0.26 mol%) in DMF (2 mL), at
1
30 °C for 1 h.

F. Nouri et al. / Inorganica Chimica Acta 471 (2018) 664–673
673
[
[
[
29] I.R. Girling, D.A. Widdowson, Tetrahedron Lett. 23 (1982) 1957–1960.
30] D.A. Alonso, C. Najera, Chem. Soc. Rev. 39 (2010) 2891–2902.
31] T. Mino, Y. Shirae, M. Sakamato, J. Org. Chem. 70 (2005) 2191–2194.
4
. Conclusion
In a few words, we have been successful in preparation of a
[32] S. Iyer, A. Jayanthi, Tetrahedron Lett. 42 (2001) 7877–7878.
[33] M. Nowotny, U. Hanefeld, H. Koningsveld, T. Maschmeyer, Chem. Commun.
2000) 1877–1878.
highly efficient and reusable heterogeneous ZnO nanoplates sup-
ported hydrazone-based palladacycle catalyst. This catalyst carried
out the Mizoroki-Heck arylation of various olefins under air condi-
tions with excellent yields for aryl iodides and bromides in short
reaction times and also acceptable yields for aryl chlorides. Addi-
tionally, the catalyst is capable of being recovered and reused for
eight sequential runs without considerable decrease in catalytic
reactivity. Therefore, this approach provides a cost-effective syn-
thetic method for preparation of stable palladacycles and makes
the ZnO nanoplates supported hydrazone-based palladacycle com-
plex appropriate for cross-coupling reactions.
(
[
34] J.J. Hou, L.R. Yang, Y.J. Wu, Chin. J. Chem. 21 (2003) 717–719.
[
35] W.A. Herrmann, V.P.W. Bohm, J. Organomet. Chem. 572 (1999) 141–145.
[36] N. Miyaura, Metal-Catalyzed Cross-Coupling Reactions, second ed., Wiley-
VCH, Weinheim, 2004.
[
[
37] D. Villemin, D. Goussu, Heterocycles 29 (1989) 1255–1261.
38] S.B. Jang, Tetrahedron Lett. 38 (1997) 1793–1796.
[39] F. Benvenuti, C. Carlini, M. Marchionna, A.M.R. Galletti, G. Sbrana, J. Mol. Catal.
A 145 (1999) 221–228.
[
[
40] C.A. Parrish, S.L. Buchwald, J. Org. Chem. 66 (2001) 3820–3827.
41] K. Inada, N. Miyaura, Tetrahedron 56 (2000) 8661–8664.
[42] C.A. McNamara, M.J. Dixon, M. Bradley, Chem. Rev. 102 (2002) 3275–3300.
[43] C. Rocaboy, J.A. Gladysz, New. J. Chem. 27 (2003) 39–49.
[44] M.G. Martinez, A. Baeza, D.A. Alonso, Catalysts 7 (2017) 94–110.
[45] F.T. Luo, C.A. Lin, Tetrahedron Lett. 44 (2003) 7565–7568.
Acknowledgement
[46] E. Alacid, C. Najera, Synlett (2006) 2959–2964.
[
[
[
47] E. Alacid, C. Najera, ArKivoc 8 (2008) 50–67.
48] E. Alacid, C. Najera, Eur. J. Org. Chem. (2008) 3102–3106.
49] Y. Yang, G. Li, Z. Song, P. Liu, Lett. Org. Chem. 7 (2010) 533–538.
We appreciatively acknowledge the Research Council of K.N.
Toosi University of Technology for supporting this research.
[50] K. Karami, Z. Karami-Moghadam, M. Hosseini-Kharat, Catal. Commun. 43
2014) 25–28.
(
[
[
[
[
51] M. Gholinejad, M. Razeghi, C. Na’jera, in: RSC Adv. 5 (2015) 49568–49576.
52] C. Baleizao, A. Corma, H. Garcı’a, A. Leyva, J. Org. Chem. 69 (2004) 439–446.
53] K. Mennecke, W. Solodenko, A. Kirschning, Synthesis (2008) 1589–1599.
54] M.D. Liedekerke, UlmannˊS Encyclopdia of Industrial Chemistry, Wiley-VCH,
Weinheim, 2006.
Appendix A. Supplementary data
Supplementary data associated with this article can be found, in
the online version, at https://doi.org/10.1016/j.ica.2017.11.060.
[
[
[
55] D. Segets, J. Gradl, R.K. Taylor, V. Vassilev, W. Peukert, ACS Nano 3 (2009)
1703–1710.
56] U. Ozgur, Y.L. Alivov, C. Liu, A. Teke, M.A. Reshchikov, S. Dogan, V. Avrutin, J.
Appl. Phys. 98 (2005) 1–103.
57] S. Bhattacharyya, A. Gedanken, Microporous Mesoporous Mater. 110 (2007)
References
[
1] A. de Meijere, F. Diederich, Metal-Catalyzed Cross-Coupling Reactions, Wiley-
VCH, New York, 2004.
553–559.
[
[
[
58] B. Ludi, M. Niederberger, Dalton Trans. 42 (2013) 12554–12568.
59] C.W. Lim, S. Lee, Nano Today 5 (2010) 412–434.
60] S. Shylesh, V. Schunemann, W.R. Thiel, Angew. Chem. Int. Ed. 49 (2010) 3428–
[
2] J. Tsuji, Palladium Reagents and Catalysts: New Perspectives for the 21st
Century, Wiley-VCH, New York, 2004.
[
[
[
[
[
[
[
3] J.P. Corbet, G. Mignani, Chem. Rev. 106 (2006) 651–710.
4] L.E. Overman, D.T. Ricca, V.D. Tran, J. Am. Chem. Soc. 115 (1993) 2042–2044.
5] L.F. Tietze, W. Ruhr, Angew. Chem. Int. Ed. 34 (1995) 1366–1368.
6] G. Ren, X. Cui, E. Yang, F. Yang, Y. Wu, Tetrahedron 66 (2010) 4022–4028.
7] R.B. Bedford, Chem. Commun. (2003) 1787–1796.
3
459.
61] T. Zeng, W.W. Chen, C.M. Cirtiu, A. Moores, G. Song, C.J. Li, Green Chem. 12
2010) 570–573.
62] D. Zhang, C. Zhou, Z. Sun, L.Z. Wu, C.H. Tunga, T. Zhang, Nanoscale 4 (2012)
244–6255.
63] S. Rostamizadeh, M. Rezghi, N. Shadjou, M. Hasanzadeh, J. Chin. Chem. Soc. 60
2013) 1317–1322.
64] S. Rostamizadeh, M. Nojavan, R. Aryan, E. Isapoor, M. Azad, J. Mol. Catal. A 374
2013) 102–110.
65] S. Rostamizadeh, N. Zekri, L. Tahershamsi, Polycycl. Aromat. compd. 34 (2014)
42–560.
[
[
[
[
[
(
6
8] G.Y. Li, J. Org. Chem. 67 (2002) 3643–3650.
9] S.Y. Liu, M.J. Choi, G.C. Fu, Chem. Commun. (2001) 2408–2409.
(
[
[
10] O. Navarro, R.A. Kelly, S.P. Nolan, J. Am. Chem. Soc. 125 (2003) 16194–16195.
11] D. Badone, M. Baroni, R. Cardamone, A. Ielmini, U. Guzzi, J. Org. Chem. 62
(
(
1997) 7170–7173.
12] C. Najera, J. Gil-Molto, S. Karlstroem, L.R. Falvello, Org. Lett. 5 (2003) 1451–
454.
[
5
1
[
[
[
[
[
[
[
[
[
[
[
[
[
66] F. Nouri, S. Rostamizadeh, M. Azad, Mol. Catal. 443 (2017) 286–293.
67] Z.R. Tian, J.A. Voigt, J. Liu, Nat. Mater. 2 (2003) 821–826.
68] Q. Zhou, W. Chen, L. Xu, Sensors 13 (2013) 6171–6182.
69] A. Pramanik, S. Das, K. Dutta, CrystEngComm 15 (2013) 6349–6358.
70] M.H. Jung, M.J. Chu, J. Mater. Chem. 2 (2014) 6675–6682.
71] J. Safari, S. Gandomi-Ravandi, Synth. Commun. 41 (2011) 645–651.
72] K. Kaneko, J. Membr. Sci. 96 (1994) 59–89.
73] J. Horniakova, T. Raja, Y. Kubota, Y. Sugi, J. Mol. Catal. A 217 (2004) 73–80.
74] Z. Jing, J. Zhan, Adv. Mater. 20 (2008) 4547–4551.
75] E.S. Jang, J. Korean Chem. Soc. 54 (2017) 167–183.
[13] S. Venkatraman, C.J. Li, Org. Lett. 1 (1999) 1133–1135.
[14] J.F. Jensen, M. Johannsen, Org. Lett. 5 (2003) 3025–3028.
[15] S.P. Nolan, N-Heterocyclic Carbenes: Tools for Organometallic Synthesis,
Wiley-VCH, 2015.
[
[
[
[
[
16] J.L. Serrano, L. Garcia, I.J.S. Fairlamb, Organometallics 30 (2011) 5095–5109.
17] N. Seler, K.J. Szabo, Chem. Rev. 111 (2011) 2048–2076.
18] J. Dupont, C.S. Consorti, J. Spencer, Chem. Rev. 105 (2005) 2527–2571.
19] R. Ratti, Can. Chem. Trans. 2 (2014) 467–488.
20] W.A. Herrmann, K.O. Preysing, S.K. Schneider, J. Organomet. Chem. 687 (2003)
2
29–248.
76] S.G. Leonardi, Chemosensors 5 (2017) 17–45.
77] K.S.W. Sing, Pure Appl. Chem. 54 (1982) 2201–2218.
78] M. Brun, A. Berthet, J.C. Bertolini, J. Electron. Spectrosc. Rel. Phenom. 104
[
[
[
21] M.E. Van der Boom, D. Milstein, Chem. Rev. 103 (2003) 1759–1792.
22] G. Dyker, Chem. Ber. Recl. 130 (1997) 1567–1578.
23] W.A. Herrmann, V.P.W. Bӧhm, C.P. Reisinger, J. Organomet. Chem. 576 (1999)
(
1999) 55–60.
79] L. Huang, Y. Wang, Z. Wang, F. Chen, J. Tan, P.K. Wong, Phys. Chem. 2 (2012)
7–34.
2
3–41.
[
[
[
[
[
24] A.D. Ryabov, Synthesis (1985) 233–252.
2
25] J. Dupont, M. Pfeffer, J. Spencer, Eur. J. Inorg. Chem. (2001) 1917–1927.
26] R.D. O’Sullivan, A.W. Parkins, J. Chem. Soc, Chem. Commun. (1984) 1165–1166.
27] J. Vicente, I. Saura-LIamas, P.G. Jones, J. Chem. Soc, Dalton Trans. (1993) 3619–
[
[
[
[
80] M. Salavati-Niasari, M. Bazarganipour, Appl. Surf. Sci. 255 (2008) 2963–2970.
81] F. Bellina, C. Chiappe, Molecules 15 (2010) 2211–2245.
82] B.K. Allam, K.N. Singh, Synthesis (2011) 1125–1131.
3
624.
83] D.H. Lee, A. Taher, S. Hossain, M.J. Jin, Org. Lett. 13 (2011) 5540–5543.
[
28] R. Vanhelder, G. Verberg, Recl. Trav. Chim. Pays-Bas 84 (1965) 1263–1273.