A new air and moisture stable robust bio-polymer based palladium catalyst for highly efficient synthesis of biaryl compounds

Article abstract of DOI:10.1002/aoc.4076

The designs of robust natural polymer based catalysts are important for catalytic systems in the view of industrial purposes and green chemistry. In this study, a new air and moisture stable robust starch-based Pd(II) catalyst was designed and characterized with different analytical techniques. Catalytic behavior of the prepared robust palladium(II) catalyst was investigated in the Suzuki coupling reactions of aryl iodides, aryl bromides and aryl chlorides with phenyl boronic acid under microwave irradiation using very short reaction time. Sustainability and reusability of the catalyst was also explored under benign conditions. As a result of the catalytic tests, the green catalyst gave excellent biphenyl yields, TONs and TOFs with very low catalyst loading. More importantly, the robust catalyst has showed that it can be reused several times without important loses from its activity in the coupling reactions. The study showed that the robust starch-based Pd(II) catalyst had more advantages than other catalysts reported in the literature due to its economic, sustainable, thermal durable, environmentally friendly and practice properties.

Full text of DOI:10.1002/aoc.4076

Received: 1 July 2017
DOI: 10.1002/aoc.4076
Revised: 12 August 2017
Accepted: 13 August 2017
F U L L P A P E R
A new air and moisture stable robust bio‐polymer based
palladium catalyst for highly efficient synthesis of biaryl
compounds
1
2
1
Talat Baran
| Nuray Yılmaz Baran
| Ayfer Menteş
1
Faculty of Science and Letters,
Department of Chemistry, Aksaray
University, 68100 Aksaray, Turkey
The designs of robust natural polymer based catalysts are important for cata-
lytic systems in the view of industrial purposes and green chemistry. In this
study, a new air and moisture stable robust starch‐based Pd(II) catalyst was
designed and characterized with different analytical techniques. Catalytic
behavior of the prepared robust palladium(II) catalyst was investigated in the
Suzuki coupling reactions of aryl iodides, aryl bromides and aryl chlorides with
phenyl boronic acid under microwave irradiation using very short reaction
time. Sustainability and reusability of the catalyst was also explored under
benign conditions. As a result of the catalytic tests, the green catalyst gave
excellent biphenyl yields, TONs and TOFs with very low catalyst loading. More
importantly, the robust catalyst has showed that it can be reused several times
without important loses from its activity in the coupling reactions. The study
showed that the robust starch‐based Pd(II) catalyst had more advantages than
other catalysts reported in the literature due to its economic, sustainable, ther-
mal durable, environmentally friendly and practice properties.
2
Technical Vocational School,
Department of Chemistry Technology,
Aksaray University, 68100 Aksaray,
Turkey
Correspondence
Nuray Yılmaz Baran, Aksaray University,
Technical Vocational School, Department
of Chemistry Technology, 68100 Aksaray,
Turkey.
Email: nybaran@aksaray.edu.tr
KEYWORDS
biphenyl, ninhydrin test, robust catalyst, starch, TOF
[
7]
1
| INTRODUCTION
in Suzuki coupling reactions. It was reported that het-
erogeneous catalysts were more beneficial than homoge-
nous catalysts because of their high catalytic activity
Transition metal‐catalyzed carbon–carbon formation
reactions are an effective process for synthesis of biaryl
compounds via coupling reaction. Suzuki C(sp )‐C(sp )
reactions among the coupling reactions such as, Stille,
Heck, Negishi, and Kumada, are one of the most
important and has been widely used in on a academic
lab scale and industrial fields. Also, Suzuki C‐C reac-
tion is advantageous over the other coupling reactions
thanks to their stability of temperature, moisture, air
as well as tolerance to broad range of functional groups
on the substrate.
developed different homogeneous and heterogeneous
catalysts and their catalytic behaviors were investigated
[
8]
and ease of separation from reaction media. However,
the biggest problems in catalytic systems are (1) low
recycle performance due to leaching from the support
(2) difficult recovery of the used catalyst (3) and expen-
siveness of synthesis of catalyst. These factors are very
important for catalysts because of economical and prac-
tical demands in industrial applications. So, for the last
few years, both robust bio‐based heterogeneous catalysts
and magnetically recoverable catalysts have been drawn
considerable attention because they retain the catalytic
activity of catalyst for a long time and prevent leaching
2
2
[
1]
[2]
[3]
[4]
[
9]
[5]
[6]
In literature, many researchers
[
10]
of the metal ions.
Besides these, to fabricate catalysts
Appl Organometal Chem. 2017;e4076.
wileyonlinelibrary.com/journal/aoc
Copyright © 2017 John Wiley & Sons, Ltd.
1 of 11
https://doi.org/10.1002/aoc.4076

2
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BARAN ET AL.
which are cheaper and easily synthesizable, researchers
have frequently tended to synthesis biopolymer based
catalysts and one‐step synthesis methods.
ethanol and ninhydrin were purchased from Sigma‐
Aldrich.
[11]
Polysaccharide‐supported heterogeneous catalysts
such as cellulose and chitosan derivatives have played
an important role in different catalyst systems and cata-
lytic reactions due to green nature, low cost, mechanical
2
.2 | Instrumentation
FT‐IR spectra of the ST, ST‐APT, ST‐Shf and catalyst were
recorded on a Perkin Elmer Spectrum 100 FT‐IR spectro-
photometer. X‐ray spectra were obtained on a Rigaku
smart lab system (at 40 kV, 30 mA, and 2θ with a scan
angle of 10–60°). Thermal and mechanical durability of
ST, ST‐APT, ST‐Shf and catalyst were studied on an
EXSTAR S11 7300 (nitrogen atmosphere; 30–650 °C
heating range). The surface properties of samples were
obtained on a QUANTA‐FEG 250 ESEM. The analyses
of Pd, Cl and Si ions on the catalyst were determined
using an EDAX‐Metek. Palladium ion content of the
robust starch based catalyst was detected by using Perkin
Elmer Optima 2100 DV Inductively Coupled Plasma (ICP)
Optical Emission Spectrometer (OES). Characterization of
biaryl compounds were done on GC–MS Agilent GC‐7890
A‐ MS 5975. A domestic microwave oven was used in the
catalytic performance tests.
[12]
stability and ease of source, in recent years.
Among
the polysaccharides, starch is versatile solid polymeric
material because of its unique properties such as the
abundance in nature, nontoxicity, biodegradability, and
[12c]
easy chemical modification.
Therefore, starch has
great potential for catalytic systems as a support material
due to its mentioned superior properties.
In the current article, to overcome leaching from the
support and improve reusability performance of the cata-
lyst, a novel heterogeneous Pd(II) catalyst was designed
using starch which is robust biopolymer for catalytic sys-
tems. Briefly, amine functionalization of starch was done
with using 3‐aminopropyl triethoxysilane (APTES). Then,
Schiff base formation of starch was performed by
refluxing with 2‐thiophenecarboxaldehyde in ethanol.
Finally, palladium catalyst was prepared by stirring with
Na PdCl in water. The chemical structure of catalyst
2
4
2
.3 | Amino functionalisation of starch
was illuminated by using FTIR, TGA, XRD, ICP‐OES,
SEM and EDAX. Catalytic behavior of high thermally sta-
ble Pd(II) catalyst was investigated in synthesis of biaryls
via microwave irradiation under benign reaction condi-
tions. Catalytic tests revealed that the bio‐based palladium
catalyst produced excellent biphenyl yields in short reac-
tion time (6 min). Noticeably, the catalyst yielded higher
TONs and TOFs. The catalyst also showed superior reus-
ability in Suzuki reactions.
(ST‐APT)
2
g of starch and 3‐aminopropyl triethoxysilane (4 ml)
were transferred into 40 mL dry toluene and refluxed at
00 °C for 48 h. After the end of the reaction, amino func-
1
tionalized precipitate of starch was filtered and dried at
room temperature (Scheme 1).
2.4 | Preparation of starch Schiff base
(
ST‐Shf)
2
2
| MATERIAL AND METHODS
.1 | Materials
Schiff base formation of starch was prepared by refluxing
NH ‐functionalized starch (1 g) with 2‐thiophene-
carboxaldehyde (3 ml) in ethanol for 96 h. Formation of
imine groups was followed by using FT‐IR ATR
technique. After the Schiff base reaction completed, the
product was filtered and rinsed hot ethanol. Then,
2
Starch from potato, APTES, 2‐thiophenecarboxaldehyde,
Na PdCl , KOH, NaHCO , NaOH, Cs CO , Na CO ,
K CO , MgSO , phenyl boronic acid, aryl halides toluene,
2
4
3
2
3
2
3
2
3
4
H
H
S
S
NH2
N
N
Pd
Cl
Cl
O
Si
O
CH3
H3C
NH2
Si
O
Si
O
Si
O
O
H
OH OH OH
O
O
S
O
O
O
O
H3C
O
Na2PdCl4
Starch Surface
Starch Surface
Starch Surface
Starch Surface
reflux, toluene
48 h
reflux, ethanol
96 h
water, 5h,
room temperature
ST
ST-APT
ST-Shf
ST-Shf-Pd
SCHEME 1 Production of robust strach based Pd(II) catalyst

BARAN ET AL.
3 of 11
yellowish Schiff base product was dried in an oven at
6
0 °C for 24 h (Scheme 1).
2
.5 | Synthesis of robust starch‐based
Pd(II)catalyst (ST‐Shf‐Pd)
ST‐Shf (0. 3 g) and Na PdCl (0.45 g) were stirred in water
2
4
(25 ml) at room temperature for 5 h. Then, brownish pre-
cipitate was filtered and washed with water. Robust
starch‐based catalyst was dried at room temperature
(Scheme 1).
2.6 | Catalytic performance experiments
To a dried Schlenk tube, the aryl iodide, aryl bromide or
aryl chloride (1.12 mmol) and phenyl boronic acid
(
1.87 mmol), K CO (3.75 mmol) and robust ST‐Shf‐Pd
2
3
3
−
catalyst (2x10 mol %) were added and irradiated in
microwave oven for 6 min at 50 °C under a solvent‐free
medium. At the end of the reaction time, the mixture
was extracted with water‐toluene (1:2). Then organic
phase, which is containing biphenyl compounds, was
send to GC/MS analysis.
3
| RESULTS AND DISCUSSION
3
.1 | Characterization studies
.1.1 | FT‐IR analysis
FIGURE 1 FT‐IR spectra of a) ST, b) ST‐APT, c) ST‐Shf, and d)
ST‐Shf‐Pd
3
FT‐IR analysis gives rapid and enough information to
illuminate chemical characterization of samples. To
determine the chemical structural changes of the sam-
ples following the chemical modifications, FTIR spectra
of ST, ST‐APT, ST‐Shf, and ST‐Shf‐Pd were recorded
and they are presented in Figure 1. The characteristic
bands were observed for ST: ‐OH stretching at 3287 cm
3.1.2 | Ninhydrin test
Ninhydrin test was performed to confirm free primer
amino groups on the surface of starch following the treat-
ment of APTES with starch (Figure 2). This test was car-
ried out by refluxing the ST‐APT with ninhydrin in
ethanol. After the test, immediately, it was observed that
the colour of the reaction solution turned into purple
(Figure 2b). This obvious color conversion showed that
APTES was attached on the starch surface. In addition,
the electronic spectrum of this solution was analyzed
and strongly transition at 580 nm was observed in the
spectrum (Figure 2b). This absorption band also revealed
−
1
−1
,
−C‐H stretching at 2923 cm , −O–H bending at
−
1
−1
1
634 cm , −CH bending at 1456 cm , and ‐C‐O
stretching at 761–1457 cm (Figure 1a).
2
−
1
[13]
In the spec-
trum of ST‐APT, −OH and ‐NH stretching bands were
−
1
observed at 3291 cm . Also, bending vibration of N‐H
−
1
was observed at 1642 cm (Figure 1b). These important
bands showed that immobilization of the APTES onto
starch were achieved. On the other hand, strong band
attributed to imine bonds (−CH = N) was observed at
[
14]
presence of –NH groups on the starch chain.
2
−
1
1
633 cm in the spectrum of ST‐Shf following condensa-
tion reaction of ST‐APT with 2‐thiophenecarboxaldehyde
Figure 1c). This important peak gave a good evidence of
(
3.1.3 | Thermal analysis (TG/DTG)
successful preparation of Schiff base of ST‐APT. In the
case of ST‐Shf‐Pd, this band was shifted lower frequency
Thermal durability is one of the most effective property
for retain catalytic performance of catalyst under harsh
reaction conditions. Thermal degradation behaviors of
−
1
(
1624 cm ) because of coordination of Pd(II) ions with
[10c]
the nitrogen of imine (Figure 1d).

4
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BARAN ET AL.
dium catalyst can be a potential candidate for catalytic
systems due to its mechanical and chemical durability
capacity.
3.1.4 | Powder X‐ray diffraction analyses
Crystalline and purity natures of ST, ST‐APT, ST‐Shf
and ST‐Shf‐Pd were explored by powder X‐ray and their
diagrams are presented in Figure 4. The characteristic
peaks of starch were observed at 5.5°, 14.84°, 17.12°,
19.14°, 22.22°, 23.68°, and 24.02° in the spectrum of ST
(
Figure 4a). After the chemical modification of ST,
peaks were widened and crystallinity structures of
ST‐APT (Figure 4b) and ST‐Shf (Figure 4c) were
decreased compared to ST. These findings can be attri-
buted to decrease of the number of OH groups of ST
following the chemical modifications. On the other
hand, after the palladium attachment to the ST‐Shf,
two new peaks are observed at 42.72° and 48.98° which
can be assigned palladium space in the spectrum of the
[
10d]
catalyst
(Figure 4d). These peaks revealed that
catalyst was successfully prepared.
3.1.5 | SEM‐EDAX analyses
Surface morphological characters of ST, ST‐APT, ST‐Shf
and ST‐Shf‐Pd were studied using SEM‐EDAX. When
SEM images showing surface structure of ST were exam-
ined, it was seen that the surface was nearly smooth and
contains different sizes granules (Figure 5a‐b). After
amino functionalisation of starch, granules were covered
with particles (Figure 5c‐d). On the other hand, we
observed that numbers of the particles on the surfaces of
granules were increased following the Schiff base forma-
tion of ST‐APT (Figure 5e‐f). These clear differences in
the images showed that the chemical modifications of
ST were achieved. In the case of the catalyst, partially reg-
ular surface structure was observed following the coordi-
nation of palladium to ST‐Shf (Figure 5g‐h). In addition,
to confirm chemical modifications of ST, the structural
compositions of the samples were examined with EDAX
analysis (Figure 6). In the EDAX spectrum of the ST‐APT,
clearly Si peak was observed, verifying that APTES was
attached on the starch surface (Figure 6a). On the other
hand, Pd and Cl peaks were obviously appeared along
with Si in the spectrum of the catalyst (Figure 6d). These
peaks indicated that catalyst was successfully prepared.
In addition, to determine amount of palladium in the cat-
alyst, ICP‐OES analysis was carried out and the palladium
content was detected as 17.5% by mass.
FIGURE 2 Ninhidrin test of a) solution of ST‐APT, b) solution of
ST‐APT containing ninhydrin
ST, ST‐APT, ST‐Shf, and ST‐Shf‐Pd were studied by TG/
DTG analysis and their curves are given in Figure 3.
When thermal stability of ST was examined, it was
detected ST had high thermal durability (303 °C). Ther-
mal degradation temperature of ST‐APT and ST‐Shf
were determined as 301 and 302 °C, respectively. These
results showed that chemical stability of the starch was
conserved after the chemical modifications. On the
other hand TGA diagram of the ST‐Shf‐Pd indicated
that it was durable up to about 357 °C. This high
decomposition temperature has shown that catalyst has
good mechanical and chemical strength. All these
obtained results showed that robust starch based palla-

BARAN ET AL.
5 of 11
FIGURE 3 TG/DTG spectra of a) ST, b) ST‐APT, c) ST‐Shf, and d) ST‐Shf‐Pd
−
4
−4
3
.2 | Investigation of catalytic
x10 mol% catalyst (15%), 5x10 mol% catalyst (45%),
−
3
−3
performance of the catalyst
1x10 mol% catalyst (%85), 2x10 mol% catalyst (99%),
−
3
3
x10 mol% catalyst (99%). We selected optimal catalyst
3.2.1 | Optimization studies
−3
loading as 2x10 mol%.
The catalytic activity studies were performed using
microwave irradiation under solvent‐free media to pro-
vide more effective, more economical and practical
advantages than conventional heating systems. Optimiza-
tion studies were carried out on the coupling reaction of
3
.2.2 | Catalytic performance of ST‐Shf‐Pd
catalyst in Suzuki coupling reaction
Catalytic activity of robust starch‐based Pd(II) catalyst
was investigated in the coupling reaction of different aryl
bromides (Table 1, entries 1–10), iodides (Table 1, entries
11–15), or chlorides (Table 1, entries 16–22) with phenyl
boronic acid under mentioned above optimum reaction
conditions. Catalytic activity tests showed that ST‐Shf‐Pd
catalyst gave excellent biphenyl product yield in the cou-
pling reaction of aryl iodide. The catalyst also produced
high reaction yields with aryl bromides using very small
catalyst loading. On the other hand, it is known that aryl
chloride is less active than aryl iodide and aryl bromides
4‐bromoanisole with phenyl boronic acid which was
selected as a represent reaction. The influence of base sys-
tem on biphenyl yield was studied using different bases
and K CO was determined to be the most effective base
2
3
system (KOH, 45%; NaHCO , 22%; NaOH, 39%; Cs CO ,
3
2
3
8
1%; Na CO , 58%; and K CO , 99% yield). The effect of
2 3 2 3
reaction time on the product yield was also investigated
and obtained biphenyl yields were recorded as follows;
1
5
min (20%), 2 min (45%), 3 min (60%), 4 min (78%),
min (89%), 6 min (99%) and 7 min (99%). From the
[
15]
results optimum reaction time was selected as 6 min. In
order to determine optimum catalyst loading in Suzuki
coupling reaction, preliminary experiments were carried
out using different catalyst loading as follows: 2.5
in the Suzuki cross coupling reaction.
Therefore, aryl
chlorides are expected to give lower yields in the coupling
reactions. However, good reaction yields were obtained
with aryl chlorides in the presence of robust starch‐based

6
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BARAN ET AL.
In addition, the catalytic activity studies showed that
electron withdrawing groups (−NO or −CN) were more
2
reactive than electron‐donor groups (−CH ) in the
3
coupling reactions. For example, the coupling reaction
of 4‐bromobenzonitrile with phenyl boronic acid pro-
duced 94% biphenyl yield (Table 1, entry 6). In addition,
TON and TOF values, which are the key parameters for
industrial applications such as pharmaceuticals and fine
[
32]
chemicals,
were calculated for all Suzuki cross
coupling reactions and the findings are given in Table 1.
As seen from the Table 1, robust starch‐based Pd(II) pro-
duced excellent TONs and TOFs.
3.2.3 | Comparison with other reported
catalyst
To show the superior catalytic performance of robust
starch‐based Pd(II) catalyst, biphenyl yields, reaction
time, TON and TOF values obtained in the present study
were compared to different catalysts in the literature and
the results are presented in Table 2. As seen from
Table 2, robust starch‐based Pd(II) catalyst gave higher
reaction yields, TON and TOF values with very small of
the catalyst and very short reaction time than other cata-
lysts. In addition, in the view of low cost, high thermal
stability, green nature, reusability and sustainability,
robust starch‐based Pd(II) catalyst are advantageous than
previously reported studies.
3
.2.4 | Sustainability and reusability of
robust starch‐based Pd(II) catalyst
The sustainability and reusability of any catalyst is one of
the most significant feature for an industrial and aca-
demic point of view. Therefore, reusability of robust
starch‐based Pd(II) catalyst was investigated on the repre-
sent coupling reaction under optimum conditions. After
each of cycle experiment, the ST‐Shf‐Pd catalyst was
removed from reaction media with filtration and regener-
ated by washing with hot methanol and water. After dry-
ing, the same ST‐Shf‐Pd catalyst was reused for the next
runs under similar conditions. As a result of the longevity
tests, robust starch‐based Pd(II) catalyst showed superior
FIGURE 4 XRD diagrams of a) ST, b) ST‐APT, c) ST‐Shf, and d)
ST‐Shf‐Pd
Pd(II) catalyst in the present study (Table 2, entries
1
6–22). These findings indicate that ST‐Shf‐Pd catalyst is
2
2
2
2
suitable for Suzuki C(sp )‐C(sp ) reactions. In addition,
the effect of the electronic properties of the substrate on
the biphenyl yields were studied in the coupling reaction
of different ‐ortho, meta‐, or para‐substituted aryl halides
with phenyl boronic acid. These tests exhibited that –para
substituent groups on the substrate gave higher reaction
yield compared to –ortho and ‐meta substitute groups.
reusability in the Suzuki C(sp )‐C(sp ) reactions. Follow-
ing the 10 cycles, biphenyl yield decreased from 99% to
80%. These tests showed that ST‐Shf‐Pd catalyst could be
reused for 10 cycles without important change in its activ-
ity. These findings reveal that robust starch‐based Pd(II)
catalyst can be used in different industrial applications
thanks to its recoverable and reusable potential.

BARAN ET AL.
7 of 11
FIGURE 5 SEM images of a‐b) ST, c‐d) ST‐APT, e‐f) ST‐Shf, and g‐h) ST‐Shf‐Pd

8
of 11
BARAN ET AL.
FIGURE 6 EDAX spectra of a) ST, b) ST‐APT, c) ST‐Shf, and d) ST‐Shf‐Pd
TABLE 1 Suzuki C‐C reactions of different aryl halides and phenyl boronic acid in the presence of robust starch based palladium(II)
catalyst
Entry
Phenyl boronic acid
Aryl halide
Product
Biphenyl Yield (%)
TON
TOF
1
99
49.500
495.000
2
3
97
86
48.500
43.000
485.000
430.000
4
5
88
85
44.000
42.500
440.000
425.000
6
7
98
91
49.000
45.500
490.000
455.000
(
Continues)

BARAN ET AL.
9 of 11
TABLE 1 (Continued)
Entry
Phenyl boronic acid
Aryl halide
Product
Biphenyl Yield (%)
TON
TOF
8
90
45.000
450.000
9
56
55
28.000
27.500
280.000
275.000
1
0
1
1
1
1
2
3
97
87
91
48.500
43.500
45.500
485.000
435.000
455.000
1
1
4
5
72
67
36.000
33.500
360.000
335.000
1
1
1
6
7
8
70
65
62
35.000
32.500
31.000
350.000
325.000
310.000
1
2
9
0
80
75
40.000
37.500
400.000
375.000
2
2
1
2
45
38
22.5000
19.000
225.000
190.000
−3
Reaction conditions: 1.12 mmol aryl halides, 1.87 mmol phenyl boronic acid, 3.75 mmol K
.1 h under MW.
TON, turnover number; TOF, turnover frequency (mol product mol
2 3
CO , 2x10 mol % robust starch based palladium(II) catalyst, 50 °C,
0
−1
−1
catalyst h ).

10 of 11
BARAN ET AL.
TABLE 2 Comparison results of robust starch‐based Pd(II) catalyst with other catalysts in the Suzuki coupling reactions
Entry Catalyst
mol % of Pd Time Temperature Yield (%) TON
TOF
Ref.
[
[
[
[
[
[
[
[
[
[
[
[
[
16]
1
2
3
4
5
6
7
8
9
1
1
1
1
Polyaniline‐anchored palladium catalyst 2.2
4 h
95
91
96
41
96
10
17]
18]
19]
20]
21]
22]
9]
PdNPs catalyst
1.0
12 h
100
8
208
4
Pd‐SMU‐MNPs catalyst
0.92
1.0
30 min 50
96
104
99
Cis‐chelated Pd(II)–NHC complex
Tridentate NHC–Pd(II) complex
24 h
12 h
100
80
99
1.0
88
88
7
Fe
CpNiBr(NHC) complexes
Fe /SiO –DTZ–Pd.
N‐heterocyclic carbene complexes
PdNP‐NMe @SiO catalyst
X‐Pd L catalyst
3
O
4
/DAG/Pd catalyst
0.2
9.6 min Room temp.
2 h 90
30 min 80
98
490
29
3062
14
3.0
87
3
O
4
2
0.5
98
198
485
196
396
40
23]
24]
25]
26]
27]
0.2
12 h
4 h
100
97
0
1
2
3
2
2
0.5
50
70
98
49
3
0.005
0.01
0.02
2 h
99
19.800
9.900
Chitosan supported Pd catalyst
4 min 50
100
100
10.000 151.515
O‐carboxymethyl chitosan Schiff bases
12 h
100
5000
417
and its Pd(II) complex.
[
[
[
[
[
[
8]
1
1
1
1
1
1
4
5
6
7
8
9
Pd@NH
CS‐g‐mPEG Pd (0) catalyst
Fe
2
‐MIL‐125 catalyst
0.9
0.5
22 h
3 h
100
150
80
86
95
95
190
990
4
63
28]
10d]
29]
30]
31]
3
O
4
/P(GMA‐AA‐MMA)‐Schiff base‐Pd. 0.1
1 h
99
990
Binuclear Pd(II) complexes
0.01
0.5
2 h
75
99
9.900
200
1.000
4.950
80
3.333
Pd(II)‐SBA‐16 catalyst
2.5 h
0.3 h
80
100
100
Silica gel‐supported N‐heterocyclic
carbene–Pd catalyst
0.1
85
−
3
2
0
Robust starch‐based Pd(II) catalyst
2x10
6 min
50
99
49.500 495.000 Present study
3
.2.5 | Leaching and mercury poisoning
remarkable catalytic activity towards the synthesis of the
biaryls in a Suzuki coupling reaction by producing excel-
lent TONs and TOFs values as high as 49.500 and
tests
We carried out leaching test by analyzing hot filtrate with
ICP‐OES following the10 run to determine amount of
Pd lost on the support. The test revealed very low leaching
495.000 after very short reaction time. In addition, sus-
th
tainability and reusability tests showed that the catalyst
could be used several times. These findings indicate that
starch is suitable as support material for Suzuki coupling
reactions and in different catalytic systems. In addition,
this paper has revealed that robust starch based palladium
catalyst can be also potential candidate for various cata-
lytic systems due to its superior catalytic performance
than other catalysts in the literature.
(
∼1%) of palladium ion from bio‐based palladium(II) cat-
alyst. Additionally, this value is consistent with biphenyl
yield decreased from 99% to 80% after the 10 cycles. On
the other hand, we performed mercury poisoning test on
the model coupling reaction according to our previous
study and the test indicates that robust starch‐based Pd(II)
[33]
catalyst has heterogeneous nature
.
ORCID
4
| CONCLUSIONS
Talat Baran http://orcid.org/0000-0003-0206-3841
Nuray Yılmaz Baran
458
http://orcid.org/0000-0001-9725-
In this paper, a new high thermally stable bio‐based
palladium(II) complex containing starch Schiff base
ligand was synthesized and its chemical structure was
illuminated with different analytical and spectral
methods. Catalytic behavior of designed robust palladium
catalyst was examined against Suzuki cross coupling reac-
tions. The starch supported palladium catalyst showed
3
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How to cite this article: Baran T, Yılmaz Baran
N, Menteş A. A new air and moisture stable robust
bio‐polymer based palladium catalyst for highly
efficient synthesis of biaryl compounds. Appl
Organometal Chem. 2017;e4076. https://doi.org/
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