Amidoxime modified PAN supported palladium complex: A greener and efficient heterogeneous catalyst for heck reaction

Article abstract of DOI:10.1016/j.ica.2019.119305

Development of a facile and greener approach for Heck reaction using a modified PAN supported palladium catalyst is described. The preparation of the catalyst involves a simple process through amidoxime modification of nitrile group in Polyacrylonitrile (PAN), followed by the complexation with Palladium chloride (PdCl₂). The resulting supported catalyst was characterized by spectroscopic analyses and further by computational studies. This polymer supported Palladium complex displayed excellent catalytic activity in Heck coupling reaction of a series of activated alkenes and aryl halides and afforded the corresponding coupling products upto 96% isolated yield. After the reaction, the catalyst was easily recovered by simple filtration and recycled with excellent stability and activity even after 5 runs. This is the first report on the use of amidoxime functionalized PAN- Palladium (II) complex as a heterogeneous catalyst in Heck coupling reaction.

Full text of DOI:10.1016/j.ica.2019.119305

Journal Pre-proofs
Amidoxime Modified PAN Supported Palladium Complex: A Greener and Ef-
ficient Heterogeneous Catalyst for Heck Reaction
Pambingal Rajan Sruthi, Vijayalekshmi Sarika, Arya Suku, Aravind Krishnan,
Saithalavi Anas
PII:
S0020-1693(19)31414-8
https://doi.org/10.1016/j.ica.2019.119305
ICA 119305
DOI:
Reference:
Inorganica Chimica Acta
To appear in:
Received Date:
Revised Date:
Accepted Date:
12 September 2019
12 November 2019
25 November 2019
Please cite this article as: P.R. Sruthi, V. Sarika, A. Suku, A. Krishnan, S. Anas, Amidoxime Modified PAN
Supported Palladium Complex: A Greener and Efficient Heterogeneous Catalyst for Heck Reaction, Inorganica
Chimica Acta (2019), doi: https://doi.org/10.1016/j.ica.2019.119305
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover
page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will
undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing
this version to give early visibility of the article. Please note that, during the production process, errors may be
discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
© 2019 Published by Elsevier B.V.

Amidoxime Modified PAN Supported Palladium Complex: A Greener and Efficient
Heterogeneous Catalyst for Heck Reaction
Pambingal Rajan Sruthia, Vijayalekshmi Sarikaa, Arya Sukua, Aravind Krishnanb, Saithalavi Anas*a,c
aSchool of Chemical Sciences, Mahatma Gandhi University, Kottayam,Kerala, India-686560
bDepartment of Chemistry, St. Berchmans’ College Changanassery, Kerala, India-686101
cAdvanced Molecular Materials Research Centre, Mahatma Gandhi University, Kottayam, Kerala, India-686560
E-mail:anas@mgu.ac.in, anastvr@gmail.com
Dedicated to Dr. K. V. Radhakrishnan on the occasion of his 50th Birthday
Abstract: Development of a facile and greener approach for Heck reaction using a modified
PAN supported palladium catalyst is described. The preparation of the catalyst involves a simple
process through amidoxime modification of nitrile group in Polyacrylonitrile (PAN), followed by
the complexation with Palladium chloride (PdCl2).The resulting supported catalyst was
characterized by spectroscopic analyses and further by computational studies. This polymer
supported Palladium complex displayed excellent catalytic activity in Heck coupling reaction of
a series of activated alkenes and aryl halides and afforded the corresponding coupling products
upto 96% isolated yield. After the reaction, the catalyst was easily recovered by simple filtration
and recycled with excellent stability and activity even after 5 runs. This is the first report on the
use of amidoxime functionalized PAN- Palladium (II) complex as a heterogeneous catalystin
Heck coupling reaction.
Keywords: Green Chemistry, Heck Reaction, Heterogeneous Catalysis, Palladium, Polymer
Support
1. Introduction
Transition metal catalyzed coupling reactions have been widely explored for various
important carbon-carbon and carbon-heteroatom bond forming reactions and substantial
development has been achieved in this area using different homogeneous catalysis.1However,
serious disadvantages such as difficulty in separation of the catalyst from the reaction mixture,
metal contamination in the final products and poor recyclability, extremely limits the industrial
application of homogeneous processes. Therefore, in contemporary synthetic chemistry, much
attention has been paid towards the development of greener, environmentally benign and cost-
efficient catalytic systems.2 Among those, the heterogenization of homogeneous catalysts onto
solid supports has received significant attention in recent years and various supports such as
1

mesoporous materials,3 nanoparticles,4 silica,5 zeolites and polymers6 have been well exploited.
Therefore, the development of novel polymer supported metal catalysts which are ecofriendly,
easily recoverable and recyclable without losing their catalytic performance ishighly
demanding.7 In this regard, Polymer supported palladium catalysis has considerable importance
due to their potential application in organic synthesis, especially for the construction of the C-C
and C-heteroatom bond forming reactions.8 However, identifying a suitable support having
adequate stability for heterogeneous catalysis and provides the desired product in good catalytic
activity is very challenging.
Polyacrylonitrile (PAN) has identified as an appropriate support to immobilize Palladium
catalyst and has been explored in some synthetic applications.9 Moreover, the abundant active
nitrile groups present in Polyacrylonitrile offer the prospects for introduction of various
functional groups via synthetic transformations.10One of such modification involves the reaction
of PAN with hydroxylamine hydrochloride to form amidoxime functionalized (hydroxyl
functionalized) polymerand the resulting modified polymer finds several interesting
applications.11 However, synthetic applicability of this modified polymer as support in
heterogeneous catalysis has been less investigated. Z. C. Wu et al. explored amidoxime modified
fiber-Palladium (II) complexes as heterogeneous catalysts in Suzuki cross coupling reaction.12
We, herein, report the amidoxime functionalized PAN supported palladium catalyst as an
efficient heterogeneous catalyst for Heck Coupling reaction in an environmentally friendly
manner.
2. Experimental
2.1.
Materials and Methods
Analytical grade reagents and freshly distilled solvents (using standard procedure) were
used throughout the experiment. All reactions were carried in oven dried glasswares. Fourier
transform infrared spectroscopy (FTIR) was recorded on a Shimadzu ATR-FTIR spectrometer
that was operating in the range of 4000-400 cm-1 under atmospheric conditions with a resolution
of 1 cm-1. Powdered X-ray diffraction (XRD) was conducted with a Rigaku MiniFlex600
instrument. Energy-dispersive X-ray spectroscopic (EDAX) analysis (equipped with the SEM
instrument) was done using OXFORD XMX N instrument. ICP-MS analysis was conducted
using Inductively Coupled Mass Spectrometer (ICP-MS) (Thermo Scientific). X-ray
photoelectron spectroscopy (XPS) analysis was performed on a Thermo Fisher Scientific
Instruments UK, Sr.No.-KAS2020 with a Aluminium Kα+. Reactions were monitored by thin
2

layer chromatography using silica gel 60 F254 plates (Merck) and were visualized by fluorescence
quenching under UV light. Compounds were isolated and purified by Column chromatography
1
13
with silica gel (60-120 mesh) using a mixture of ethyl acetate and hexane as eluent. H and C
NMR (400 MHz and 100 MHz respectively) spectra were recorded on a Bruker nuclear
resonance spectrometer using CDCl3 as the solvent and chemical shifts are expressed in parts per
million (ppm) downfield from TMS (δ= 0.00). In assignment of the NMR spectra, multiplicities
and abbreviations used are as follows: Ar = Aromatic, Ph = Phenyl, s = singlet d = doublet, t =
triplet, q = quartet, dd= doublet of doublets and m = multiplet. The reaction products were
analyzed by Gas chromatograph equipped with a capillary column and a flame ionization
detector.
2. 2. General Procedure for Heck Reaction
To a dried sealed tube, aryl halide (0.25 mmol), activated alkene (0.3 mmol), Na2CO3 (0.75
mmol), polymer supported palladium catalyst (2 mol%) were added followed by the addition of
DMF (2 ml). The reaction mixture was then stirred at 120 °C under N2 atmosphere and progress
of the reaction was monitored by TLC. After completion of the reaction (3 hours), the reaction
mixture was extracted with ethyl acetate and water. The organic layer was separated and dried
over anhydrous Na2CO3 and concentrated on rotary evaporator. The obtained crude product was
separated by column chromatography using appropriate Ethylacetate/Hexanemixture (85 to 95:
15 to 5) and the yields were noted. The structure of the products was characterized using
spectroscopic analyses and in comparison with literature data.
Representative data for compound (3a): Colourless Liquid. Rf = 0.47 (Hexane/EtOAc = 95:5).1H
NMR (400 MHz, CDCl3): δ 7.64 (d, J= 16 Hz, 1H), 7.45-7.43 (m, 2H), 7.31-7.29 (m, 3H), 6.38
(d, J=16Hz, 1H), 3.73 (s, 3H).13C NMR (100 MHz, CDCl3): δ.167.2, 144.8, 134.4, 130.3, 128.8,
128.1, 117.7, 51.7. FTIR (neat): 2947, 1711, 1636, 1313, 1274 cm-1. GC-MS (EI) [M]+: m/z
calculated for C10H10O2:162.1, found:162.1
3. Results and Discussions
3.1. Synthesis of modified PAN supported Palladium catalyst (m-PAN-Pd)
Our studies commenced with the preparation13 of Polyacrylonitrile (PAN) II from
acrylonitrile (I) followed by its reaction with Hydroxylamine hydrochloride in aqueous
methanolic solution under reflux condition for 20 h to generate the amidoxime modified
polymerm-PAN (III). The resulting amidoxime functionalized polymer (III) was, then subjected
3

to the metal complexation on treatment with PdCl2 solution to afford the m-PAN-Pd (IV)
complex (scheme 1).11e Successful metal loading on the modified polymer was monitored by
following the disappearance of reddish browncolor.
n
Na2S2O5, FeSO4,
K2S2O8
n
HO
NH2OH.HCl
PdCl2, NaCl
H2O,12h, rt
CN
n
N
NH2
HO
N
NH2
H2O,
20 min, N2 atm
CN
MeOH/H2O (5:1)
Reflux, 20 h
Pd
Cl
Cl
m-PAN-Pd
IV
AN
I
m-PAN
III
PAN
II
Scheme 1. Synthesis of m-PAN-Pd Catalyst
3.2. Characterization of m-PAN-Pd complex(IV)
The formation of the compounds II, III and IV are characterized using FTIR analyses and the
corresponding spectra are shown in Figure S1(Supporting information). The X-ray diffraction
(XRD) and EDX analyses also provided evidence for the synthetic modification of PAN and
subsequent metal complexation (Figure S2 and S3, supporting information). Moreover, ICP-MS
analyses of m-PAN-Pd complex exposed that the palladium loading in the sample is 0.026 g per
1 g.
Figure 1. XPS Spectra of (a) m-PAN Pd IV (b) High resolution analysis of Pd3d signal
In order to understand, the state of the active Pd species present in m-PAN Pd IV complex, we
have further carried out X-ray photoelectron spectroscopy (XPS) analysis and the corresponding
spectra is shown in figure 1. This compound exhibited only two spin-orbital splitting peaks
corresponding to the low energy band PdII(3d5/2) and high energy band PdII(3d3/2) at the binding
energy (BE) values of 338.32 eV and 343.58 eV, respectively and there were no peaks observed
4

corresponding to Pd(0). The binding energy values of N1s, O1s and Cl2p in the prepared
complex were detected at 400.29 eV, 533.02 eV and 198.77 eV respectively. These observations
in comparison with the literature values.12,14 clearly revealed the presence of Pd(II) species,
coordinated to the amidoxime group in the complex.
3.3. Computational studies
Figure 2. Structure of the monomer in (a) 2D and (b) 3D, Geometry optimized structures of (c)
PdNN and (d) PdNO (carbon = ash, hydrogen= white, nitrogen = blue, palladium= light blue,
oxygen = red, chlorine=Green)
For better understanding of the exact structure and metal complexation pattern, the
probable structure of the m-PAN-Pd complex (IV) was predicted using preliminary
computational studies. A monomer unit complexed with Palladium was selected as the input
structure. In the ligand, Methyl group was chosen as the background in the monomer unit for
computational convenience (Fig.2a and 2b). Palladium being in the +2 oxidation state is
expected to have a square planar structure,15 with two bonds connected with the Chlorine atoms.
For the remaining two co-ordination to the Palladium atoms, three possible structures, with
Palladium coordinated to the two Nitrogen atoms (PdNN), Nitrogen and Oxygen (PdNO) and
both the Nitrogen atoms and Oxygen (PdNNO), with the remaining were generated. All the
structures were geometry optimized using the Gaussian 09 package.16 B3LYP functional17 in
DFT method was used for the studies, with LanL2DZ basis set for Palladium and Chlorine atoms
and 6-31G* basis set for all the other atoms.18 The geometry optimized structures for the two
coordinated system were obtained but the three coordinated system failed to converge which can
be expected due to high strain during bonding. Out of the two structures, PdNN was found to be
more probable that PdNO as it has slightly higher stabilization energy as compared with the
latter. The energy values for the structures are -1272.18 au and -1269.18 au respectively (Fig.2c
5

and 2d). This result was promising in terms of the fact that, the corresponding complexation was
described earlier as Palladium coordinated to Nitrogen and Oxygen (PdNO) atoms by Wu et.al.12
3.4. Heck Coupling reaction using m-PAN-Pd
I
O
O
m-PAN-Pd (2 mol%)
O
O
Na2CO3, DMF
120 °C, 3h, N2
( 1.2 eq.)
74%
( 1 eq.)
1a
3a
2a
Scheme 2. Heck reaction using m-PAN-Pd
After detailed characterization of the m-PAN-Pd, we have decided to evaluate the
catalytic activity of this complex in performing Heck coupling reaction. A model reaction using
Iodobenzene 1a and Methylacrylate 2a resulted in the formation of corresponding product 3a in
74% yield (Scheme 2).The reaction was conducted with 2 mol% of m-PAN-Pd IVas catalyst, 3
eq. Na2CO3 base and DMF solvent at 120 °C for 3 h without any other ligand.
Table 1. Catalyst loading studies
Entry[a]
m-PAN-Pd(mol %)[b]
Yield(%)[c]
1
2
3
4
5
0.1
0.5
1
2
3
3
22
66
74
75
[a] Reaction conditions: 1a (1 eq.), 2a (1.2 eq.), Catalayt, Na2CO3 (3 eq.), DMF (2 ml), N2 atm, 120 °C, 3h.
[b]Mol% was calculated with reference to the actual amount of PdCl2 coordinated to a single monomer unit.
[c] Isolated yield
Subsequently, several optimization studies were conducted to improve the reaction yield.
Firstly, the effect of catalyst loading was studied under the model Heck reaction condition and
the results are tabulated in Table 1. It is clear that the amount of the catalyst is significantly
influencing the reaction outcome. Lower amounts (0.1and 0.5mol%) of the catalyst resulted in
the poor yields (Table 1, entry 1-2). 1 and 2 mol% of the catalyst gave 66 and 74% of the product
respectively (Table 1, entry 3-4) However, a further increase in the amount of catalyst from 2 to
3 mol% did not offer much increase in the conversion (Table 1, entry 5). Therefore, 2 mol% of
the catalyst was selected as the optimum catalyst loading for further studies.
In the next set of experiments, other reaction parameters such as Base, Solvent and
Temperature were optimized (Table 2). Among the various bases studied in DMF solvent, the
6

highest yield (94%) was obtained with Et3N (Table 2, entry 6).Use of inorganic bases like
Na2CO3, K2CO3and KHCO3 afforded 74, 67 and 54% yields of the product respectively (Table 2,
entry 1-3). However, in the case of NaHCO3 and Cs2CO3 very low yields were resulted (Table 2,
entry 4-5). Solvent screening studies revealed that DMF is the most suitable solvent for this
reaction and other solvents such as water, DMA, Toluene, Acetonitrile and Dioxane gave poorer
results (Table 2, entry 7-11).
Table 2. Screening of Base and Solvent
Entry[a]
Base
Solvent
Yield(%)[b]
1
2
Na2CO3
K2CO3
DMF
DMF
74
67
3
4
5
KHCO3
NaHCO3
Cs2CO3
Et3N
DMF
DMF
DMF
DMF
54
17
Trace
94
6
7
Et3N
H2O
12
8
Et3N
DMA
22
9
10
11
Et3N
Et3N
Et3N
Toluene
Acetonitrile
Dioxane
35
27
18
[
a] Reaction conditions: 1a (1eq. ), 2a (1.2 eq. ), m-PAN-Pd (2 mol%), Base (3 eq.), Solvent (2 ml),
N2atm, 120 °C, 3h.
[b] Isolated Yield
Table 3.Control experiments
Entry[a]
Catalyst
-
m-PAN-Pd
m-PAN-Pd
m-PAN-Pd
m-PAN-Pd
m-PAN-Pd
Base
Et3N
Temp(°C)
Yield(%)[b]
1
2
3
4
5
6
120
120
120
100
120
140
nd[c]
nd[c]
25[d]
57
-
Et3N
Et3N
Et3N
Et3N
86[e]
96
[a]Reaction conditions: 1a (1 eq.), 2a (1.2 eq.), m-PAN-Pd (2 mol %), Et3N (3 eq.), DMF (2 ml), N2atm, 3h.
[b]Isolated yield
[c]Product not detected
[d]Reaction carried out in Air
[e]Reaction for 4 h
Next, we have performed some control experiments and the results are presented in Table
3.The reaction was not working in the absence of the catalyst or base (Table 3, entry 1 and 2).
This proves the inevitable role of catalyst and base in the reaction. When the reaction was carried
out at in the absence of Nitrogen atmosphere the yield was significantly decreased (Table 3,
7

entry 3). Attempt to lower the reaction temperature (Table 3, entry 4) and increase in the reaction
time (4 h) also resulted in poor yields of the product (Table 3, entry 5). However, further increase
of temperature to 140 °C gave 96% yield. (Table 3, entry 6). Therefore based on the optimization
studies and control experiments, the reaction using 2 mol% catalyst, Et3N as base (3 eq.) and
DMF (2 ml) solvent at 140 °C in N2 atmosphere for 3h was chosen as the optimum condition for
this coupling reaction.
Under the optimum reaction conditions, the Heck coupling reactions were carried out
using various aryl halides and a series of activated alkenes with varying substitutions (Table 4).
Among the non-substituted aryl halides, iodobenzene 1a displayed highest reactivity with 2a to
give the product 3a in 96% yield(Table 4, entry 1).While aryl bromides 1b and aryl chloride 1c
were less reactive and afforded 3a in lower yields (Table 4, entry 2-3).The reaction of 1a with
other activated alkenes such as ethylacrylate 2b and tertiary butylacrylate2c, acrylic acid 2d,
acrylamide 2e and styrene 2g in presence of m-PAN-Pd worked well and afforded moderate
yields of the coupling products (Table 4, entry 4-7 and 9). But acrylonitrile 2f was found to be
less effective under the coupling reaction condition (Table 4, entry 8). The catalyst IV was also
found to be very effective for the cross coupling of a number para substituted aryl iodides 1c-f
with methylacrylate 2a, as evident by the entries10-12 in table 4. Excellent cross coupling yield
(96%) was obtained with 4-Iodonitrobenzene 1d (entry 11). Relatively moderate cross coupling
yields were observed when the aryl iodide containing electron releasing group such as 4-
Iodoanisole (entry 10) was used. However, 4-Iodo benzoic acid 1f failed to deliver the reaction
product (entry 13). The cross coupling reactions of 4-Iodo anisole 1c and 4-iodoTolune 1e with
styrene 2g proceeded smoothly to afford the corresponding products 3l and 3n in moderate yields
(entry 14 and 16), while reaction of 1d with styrene 2g gave product 3m in low yield (30%, entry
15). Interestingly, the reaction of 2-Iodotoluene 1g with methacrylate 2a afforded the product 3o
in 41% yield (entry 17), while no product formation was observed for the reaction of 2-
Iodotoluene 1g with styrene 2g under the same conditions (entry 18). Notably, in all coupling
reactions, complete trans selectivity was obtained19 as evidenced by NMR analyses and the
formation of cis or homo coupling products were not observed which was different from that
reported earlier.20
8

Table 4. Heck reaction of different substrates using m-PAN-Pd
Z
X
m-PAN-Pd (2 mol%)
Z
Et3N (3 eq.),DMF (2 ml)
140 °C, 3h, N2
Y
W
Y
W
1a-g
2a-g
3a-p
Product
CO2Me
Yield(%)[b]
Entry[a]
Aryl halide
Alkene
X
96
45
25
1
2
3
1a
1b
1c
X = I
3a
2a
Z = CO2Me
Z = CO2Et
X = Br
X =Cl
3b
3c
3d
3e
3f
78
2b
2c
2d
2e
2f
4
5
6
7
8
9
1a
1a
1a
1a
1a
1a
t
68
Z = CO2 Bu
Z
84
Z = CO2H
Z = CONH2
Z = CN
77
trace
51
3g
2g
Z = Ph
I
3h
3i
59
1c
1d
1e
1f
10
11
12
13
Y = OMe
Y = NO2
Y = Me
2a
2a
2a
2a
CO2Me
96
3j
30
nd[c]
Y
Y
3k
Y =COOH
Y
1c
1d
1e
Y = OMe
Y = NO2
Y = Me
3l
53
30
54
Ph
Z
2g
2g
2g
14
15
16
3m
3n
I
3o
3p
1g
1g
W = Me
W = Me
17
18
41
nd[c]
2a
2g
Z = CO2Me
Z = Ph
[a]Reaction conditions:1a-g (1 eq.), 2a-g (1.2 eq.), m-PAN-Pd (2 mol %), Et3N (3 eq.), DMF (2 ml), N2 atm, 3h.
[b]Isolated yield
[c] Product not detected
3.5. Recyclability studies
Recyclability and reusability are important parameters concerning the use of
heterogeneous catalysts, particularly for the industrial application of coupling reactions.
Therefore, the polymer supported catalyst was tested for recyclability and reusability for the
coupling reaction between 1a and 2a under the standard optimized conditions. After completion
of the reaction, the catalyst was removed by simple filtration and was reused in the next run
under the same conditions. The activity of the separated catalyst for five cycles in the Heck
coupling was summarized in Table 5. After the first, second and third cycle; the yield obtained
was almost the same. Slight decrease was observed only after the third cycle. Therefore, it is
very clear from the study that the catalyst retains excellent activity even after 5 runs.
9

Table 5.Reusability studies using m-PAN-Pd
Run
1
94
2
94
3
93
4
92
5
92
Yield (%)[a]
[a]Isolated yield
4. Conclusions
In conclusion, we have developed a greener and efficient methodology for the Heck
coupling reaction by using a modified PAN supported Palladium catalyst. This heterogeneous
catalyst can be prepared by the amidoxime modification of PAN followed by the metal
complexation with PdCl2. The structure of the complex was established based on FTIR, XRD,
XPS, EDX and ICP-MS analyses and further backed by computational studies. This supported
catalyst was successfully explored as an efficient heterogeneous catalyst for Heck coupling
reaction of a series of substrates to afford the products upto 96 % isolated yield. This supported
catalyst also showed excellent reusability up to 5 runs without significant loss of catalytic
activity. Other remarkable advantages of this catalyst include, the easy preparation, handling
stability and moisture insensitivity. This is the first study of using amidoxime functionalized
PAN supported Palladium catalysts in Heck coupling reaction and more studies to explore the
synthetic applicability are in progress and will be reported in due course.
Declaration of interest
There are no conflicts of interests to declare
Acknowledgements
PRS thank the Council of Scientific and Industrial Research (CSIR), New Delhi for
Junior Research Fellowship (Grant No. 09/499(0088)/2015-EMR-1). Authors are thankful to St.
Thomas College (Pala), SAIF (CUSAT), NCL (Pune), IIRBS and School of Environmental
Sciences (MG University, Kottayam) for Spectroscopic Analyses. Authors also thank DST-
PURSE.Govt. of India (SR/417 and 418/2017) for the financial assistance.
References
1. (a) Biffis, A.; Zecca, M.; Basato M. Mol. Catal.173, (2001),249. (b) Ruiz-Castillo,P.;
Buchwald, S. L.Chem. Rev. 116, (2016),12564.
2. (a) Lancaster, M.Green Chemistry: An Introductory Text, RSC, Cambridge. (2002),310. (b)
Sheldon, R. A.Chem. Soc. Rev. 41,(2012),1437.
3. (a) Perego, C.;Millini, R.Chem. Soc. Rev. 42, (2013),3956. (b) Parlett, C. M. A.;Bruce,
D.W.;Hondow, N.S.;Newton, M.A.;Lee, A. F.;Wilson, K.ChemCatChem. 5, (2013), 939.
10

4. (a) Wang, D.;Astruc, D.Chem. Rev. 114, (2014),6949. (b) Online, V. A, Nan, A.RSC
Advances.4, (2014), 5927.
5. Opanasenko, M.; Stepnicka, P.; Cejka, J.RSC. Adv.4, (2014), 65137.
6. (a) Lamblin, M.; Nassar-hardy, L.; Hierso, J.; Fouquet, E.;Felpin, F.Adv. Synth. Catal.352,
(2010),33. (b) Lu, J.; Toy, P. H.Chem. Rev.109, (2009),815 (c) Cho, H.;Jung, S.; Kong, S.;
Park, S.; Lee, S.; Lee Y. Adv. Synth.Catal.356, (2014),1056.
7. (a) Benaglia, M.; Puglisi, A.; Cozzi, F.Chem. Rev.103, (2003), 9. (b) Lin, K.;Song, M.; Cai,
D.; Wu, Y.Tetrahedron Lett..44, (2003), 3955. (c) Lal, J.; Gupta, S. K.; Agarwal, D. D.Catal
Commun. 27, (2012), 38. (d) Xing, G. Fibers and Polymers. 17, (2016),194. (e) Shao, L.;Qi,
C.Fibers and Polymers. 15, (2014),2233.
8. (a) Garrett, C. E.; Prasad, K.Adv. Synth.Catal.346, (2004),889. (b)Benaglia, M.;Puglisi, A.;
Cozzi, F.Chem. Rev. 103, (2004),3401. (c) Kann, N. Molecules. 15, (2010), 6306. (d ) Che
Soh, S.K.; Jusoh, S.A.; Mohd Yusof, M.S.;Khairul, W. M. Journal of Scientific Research
and Developments.4, (2016),24. (e) Qil, S.; Long Feng, Z.; Zhen Hua, S.; Xiang Ju, M.;
Feng-Shou, X.Sci China Chem. 55, (2012), 10. (f) Suzuka, T.; Nagamine, T.;Ogihara, K.;
Higa M. Transactions of the Materials Research Society of Japan.4, (2010),889.
9. Moroi, G.; Bilba, D.; Bilba, N. Polymer Degradation and Stability.84, (2004),207. (b)
Beletskaya, I. P.; Cheprakov, A.V.Chem. Rev.100, (2000),3009.
10. (a)Kiani, G.R.;Sheikhloie, H.; Arsalani,N. Desalination. 269, (2011), 266. (b) Jain,
S.;Chattopadhyay, S.; Jackeray, R.; Singh H.Anal. Chim. Acta. 654, (2009), 103. (c)
Kundu,D.; Patra, A. K; Sakamoto, J.; Uyama.; H. Reactive & Functional Polymers 79
(2014), 8.
11. (a) Kiani, G.R.; Arsalani, N.Iranian Polymer Journal. 15, (2006),727. (b) Arsalani, N.;
Ghasemi, E.; Rakh, R.; Entezami, A. A.J. Iran. Chem. Res.3, (2010),195. (c) Qingrun,
M.;Jie, B.; Shoujun, G.; Chunping, L. Chem. Res. Chin. Univ. 31, (2015),1072. (d) Islam,
M.S.; Rahman, M. L.; Yusoff, M.; Sarkar, S. M. Journal of Cleaner production. 149,
(2017), 4045. (e) Santa Maria.; L et. al. Reactive & Functional Polymers, 49, (2001) 133.
12. Wu, Z.; Huang, Y.;Lu, Y.;Tao, T.; Zhang, Z. Catal. Commun.29, (2012),158.
13. El-newehy, M. H.; Alamri, A.; Al-deyab, S. S. Arab. J. Chem. 7, (2014),235.
14. (a) Wu, Z. C.; Zhang, Y.; Tao, T. X.; Zhang, L. F. Applied Surface Science. 257, (2010),
1092. (b) Wojnicki, M.; Socha, R. P.; Pędzich, Z.; Mech, K.; Tokarski, T.; Fitzner, K. J.
Chem. Eng. Data, 63, (2018), 702.
11

15. Şahin, Ö.; Özdemir, Ü.Ö.; Seferoğlu, N.; Genc, Z.K.; Kaya, K.; Aydıner, B.; Tekin, S.;
Seferoğlu, Z.Journal of Photochemistry and Photobiology B: Biology. 178,( 2018),428.
16. Complete list of authors of Gaussian 09. (2014), 1.
17. Lee, C.;Yang, W.; Parr, R. G. Physical Review B.37, (1988),785.
18. Deschamps, B.; Le Goff,X.; Ricard, L. Heteroatom Chemistry.18, (2007), 363.
19. Lin, K.;Song, M.; Cai, D.; Hao, X.;Wu, Y. Tetrahedron Lett. 44 (2003) 3955.
20. (a) Bhanage, B. M.; Arai, M. Catal. Rev. 43, (2001), 315. (b) He,Y.; Cai.; C. Transition
Met. Chem. 36,(2011), 113.
12

Declaration of interests
The authors declare that they have no known competing financial interests or personal relationships that
could have appeared to influence the work reported in this paper.
13

Graphical Abstract
Amidoxime Modified PAN Supported Palladium Complex: A Greener and Efficient
Heterogeneous Catalyst for Heck Reaction
Pambingal Rajan Sruthi,Vijayalekshmi Sarika, Arya Suku, Aravind Krishnan,Saithalavi Anas*
n
CN
PAN
X
R2
m-PAN-Pd
(Cat.)
R2
Et3N, DMF, N2
140 °C, 3h,
R1
R1
n
upto 96 % Yield
(18 Examples)
HO
N
NH2
X = I, Br, Cl
R
R
1 = 4-H, 4-OMe, 4-NO2, 4-CO2H, 4-Me, 2-Me
2 = CO2Me, CO2Et, CO2tBu, CO2H, CONH2, CN, Ph
Pd
Cl
Cl
m-PAN-Pd
Amidoxime modified Polyacrylonitrile (PAN) supported Palladium complex is prepared and
explored as an efficient and greener catalyst for Heck reaction of a series of substrates. This
catalyst exhibited excellent recyclability (upto 5 runs) without much loss of activity.
14

Highlights
 Amidoxime modified PAN supported Palladium (m-PAN-Pd) complex is prepared and
characterized by detailed experimental and computational analyses.
 m-PAN-Pd complex displayed excellent catalytic activity in Heck reaction.
 First report on the use of amidoxime functionalized PAN as a support in heterogeneous
catalysis for Heck reaction.
 The catalyst showed good recyclability up to 5 times without significant loss of activity.
15