Synthesis and characterization of a new Pd(II)-Schiff base complex [Pd(APD)2]: An efficient and recyclable catalyst for Heck-Mizoroki and Suzuki-Miyaura reactions

Article abstract of DOI:10.1016/j.jorganchem.2017.05.049

The synthesis of a new Schiff base ligand “4-((Z)-((Z)-3-hydroxy-1,3-diphenylallylidene)amino) -1,5-dimethyl-2-phenyl-1H-pyrazol-3(2H)-one (APD)” and its palladium complex [Pd(APD)₂] is described. The ligand and complex are characterized by FTIR, FESEM, EDX, Elemental analyses and Mass spectrometry. The structure of the ligand is also confirmed by single crystal X-ray determination and ¹H NMR data. The complex is insoluble in almost all common organic solvents. It has been used as an efficient catalyst in a series of Heck-Mizoroki and Suzuki-Miyaura coupling reactions giving good TON and TOF. The ease of synthesis, air-stability and recyclability are some of the important characteristics of the synthesized catalyst.

Full text of DOI:10.1016/j.jorganchem.2017.05.049

Accepted Manuscript
Synthesis and characterization of a new Pd(II)-Schiff base complex [Pd(APD) ]: An
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efficient and recyclable catalyst for Heck-Mizoroki and Suzuki-Miyaura reactions
Samaresh Layek Anuradha, Bhumika Agrahari, Devendra D. Pathak
PII:
S0022-328X(17)30355-8
10.1016/j.jorganchem.2017.05.049
JOM 19975
DOI:
Reference:
To appear in: Journal of Organometallic Chemistry
Received Date: 11 March 2017
Revised Date: 19 May 2017
Accepted Date: 25 May 2017
Please cite this article as: S.L. Anuradha, B. Agrahari, D.D. Pathak, Synthesis and characterization
of a new Pd(II)-Schiff base complex [Pd(APD) ]: An efficient and recyclable catalyst for Heck-
2
Mizoroki and Suzuki-Miyaura reactions, Journal of Organometallic Chemistry (2017), doi: 10.1016/
j.jorganchem.2017.05.049.
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ACCEPTED MANUSCRIPT
Graphical Abstract Synopsis:
Synthesis of a new Schiff base ligand and its palladium complex [Pd(APD)2] have been
reported. The ligand and complex are structurally characterized. Complex acts as an efficient
catalyst for Heck-Mizoroki and Suzuki-Miyaura coupling reactions with good Turnover number.

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Synthesis and Characterization of a new Pd(II)-Schiff base complex
[Pd(APD)2]: An efficient and recyclable catalyst for Heck-Mizoroki and
Suzuki-Miyaura reactions
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Samaresh Layek, Anuradha, Bhumika Agrahari, Devendra D. Pathak*
Department of Applied Chemistry, Indian Institute of Technology (Indian School of Mines), Dhanbad-826004, India
Email: ddpathak@yahoo.com
*Phone number: +91 9431126250
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Abstract:
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The synthesis of a new Schiff base ligand “4-((Z)-((Z)-3-hydroxy-1,3-diphenylallylidene)amino)
-1,5-dimethyl-2-phenyl-1H-pyrazol-3(2H)-one (APD)” and its palladium complex [Pd(APD)2] is
described. The ligand and complex are characterized by FTIR, FESEM, EDX, Elemental
analyses and Mass spectrometry. The structure of the ligand is also confirmed by single crystal
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X-ray determination and H NMR data. The complex is insoluble in almost all common organic
solvents. It has been used as an efficient catalyst in a series of Heck-Mizoroki and Suzuki-
Miyaura coupling reactions giving good TON and TOF. The ease of synthesis, air-stability and
recyclability are some of the important characteristics of the synthesized catalyst.
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Keywords: Schiff base, crystal structure, Pd(II) complex, C-C cross coupling reactions
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1. Introduction:
The C-C bond formation and functional group transformation have emerged as
exceedingly important methodologies for the preparation of organic compounds. The catalytic
emergence of C-C bond formation is one of the most powerful tool for the construction of
complex organic molecules [1-2]. Such methodologies have been successfully exploited in the
synthesis of a number of natural products, bioactive compounds and materials [3-6]. Among
numerous C-C bond formation reactions, Heck, Suzuki, Sonogashira, Tsuji-Trost, Stille, Negishi,
and Hiyama-coupling reactions occupy important places [7]. Since the Heck-Mizoroki and
Suzuki-Miyaura reactions are frequently used on a large scale for the preparation of
pharmaceuticals, agrochemicals, polymers, natural products and advanced materials in chemical
industries, we were interested to develop new efficient catalysts for these reactions [8].
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In simple words, Heck-Mizoroki and Suzuki-Miyaura may be defined as aryl olefination
/vinylation and aryl arylation, respectively [9]. A perusal of the literature reveals that these
reactions have been carried out in presence of a large number of phosphine based palladium
catalysts [10-11]. The phosphine ligands are toxic, air-sensitive, expensive and difficult to
synthesise. In order to circumvent these inherited drawbacks, a quest for the rational design of
new catalysts for C-C bond-forming reactions was realized [12]. In this direction, the
development of palladium complexes bearing N-heterocyclic carbenes (NHC) or nitrogen-donor
ligands is noteworthy [13-14]. Although spectacular success in these reactions was achieved
using Pd-NHC complexes, the multistep tedious synthesis of NHC ligands remained a synthetic
challenge, and it precluded their large scale industrial application.
The ease of synthesis of Schiff base ligands and the thermal/chemical stability of the
resultant complexes have resulted in numerous industrial applications [15-16]. Schiff base
complexes of palladium(II) have been used extensively as catalysts in a variety of organic
reactions [17], such as olefin polymerization [18], hydrogenation of olefins, and removal of toxic
metals [19].
The last decade has witnessed the application of Pd(II) Schiff base complexes, containing
no phosphine Ligands, in the Heck-Mizoroki and Suzuki-Miyaura reactions [20-23]. Therefore,
in continuation of our research interest on the synthesis, structural characterization and catalytic
applications of transition metal complexes [24-26], we herein, report a new palladium(II) Schiff
base complex as an efficient catalyst in Heck-Mizoroki and Suzuki-Miyaura reactions.
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2. Experiment:
2.1. Synthesis of Schiff base ligand “4-((Z)-((Z)-3-hydroxy-1,3-diphenylallylidene)amino)-1,5-
dimethyl-2-phenyl-1H-pyrazol-3(2H)-one” (APD)
4-Aminoantipyrene (0.204 g, 1 mmol) dissolved in 3 mL ethanol was added drop-wise to
an ethanolic solution (3 mL) of 1,3-diphenylpropane 1,3-dione(0.224 g, 1 mmol). The light
yellow solution was heated to reflux for 4 hrs and then cooled to room temperature to give
yellow crystals. The crystals were filtered, washed with ice-cold ethanol and air-dried at room
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temperature. Yield: 0.340 g (83%). H NMR (CDCl3, 25 C, 400 MHz):
δ 11.77 (s, 1H, enolic
OH), 7.94-7.96 (s, 2H, Ar H), 7.49-7.50 (s, 2H, Ar H), 7.40-7.44 (m, 5H, Ar H), 7.28-7.33 (m,
3H, Ar H), 7.26-7.28 (d, 3H, Ar H), 6.10 (s, 1H, -(C6H5)C=CH-), 2.87 (s, 3H, NCH3), 2.01 (s,
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3H, CCH3). Selected FTIR (KBr), cm-1: 3151 (ν OH), 1672 (ν C=O), 1558 (ν C=N), 1406 (ν
C=C). MS (ESI; m/z): Calculated for C26H23N3O2 409.18, Found 410.14 (M+H)+.
2.2. Synthesis of the complex “bis(((1Z,3Z)-3-((1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-
pyrazol-4-yl)imino)-1,3-diphenylprop-1-en-1-yl)oxy)palladium,” [Pd(APD)2]
Palladium(II) acetate (0.122 g, 0.5 mmol) was added to a suspension of the Schiff base
ligand APD (0.410 g, 1 mmol) in methanol (10 mL) at room temperature. The reaction mixture
was stirred for 12 h at room temperature to give a light greenish yellow precipitate which was
filtered, washed with cold methanol and dried vacuum over anhydrous CaCl2. Yield: 0.346 g
(75%), Selected FTIR (KBr), cm-1: 1672 (ν C=O), 1499 (ν C=N), 1401 (ν C=C), 580 (ν Pd-O),
498 (ν Pd-N). LC-MS (TOF ES+; m/z): Calculated for C52H44N6O4Pd 922.25, Found 923.70
(M+H)+.
3. Results and discussion:
A new Schiff base ligand (APD) was synthesized in single step by the reaction of 4-
aminoantipyrene with 1,3-diphenylpropane 1,3-dione in refluxing ethanol and isolated in high
yield ( 83%) as yellow crystalline solid. The ligand was fully characterized by FTIR, FESEM,
EDX, Elemental analyses, Mass and 1H NMR. The structure of the ligand was also confirmed by
single crystal X-ray analysis [27-28] (Fig. 1). A summary of the crystallographic and refinement
data of the APD ligand is given in Table 1 and selected bond lengths and bond angles are listed
in Table 1S. The reaction of the ligand with palladium acetate at room temperature in methanol
yielded the complex [Pd(APD)2] as a greenish yellow solid (Scheme 1). The complex was found
to be insoluble in almost all organic solvents, however, it was fully characterized by FTIR,
FESEM, EDX, Elemental analysis, and TGA-DTG and ESI-Mass spectrum. The single crystals
of the complex could not be grown by virtue of its insolubility in most organic solvents. The
ESI-Mass spectrum of the complex shows a peak at m/z 923.70 corresponding to the [M+H]+
cation (Fig. 3S).
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The FTIR spectrum of the Schiff base ligand exhibited three prominent peaks at 3194 cm-
1, 1673 cm-1 and 1558 cm-1, corresponding to ν OH, ν (C=O) and ν (C=N) of azomethine group,
respectively (Fig. 2). However, the FTIR spectrum of the complex showed peaks at 1672 cm-1
and 1499 cm-1 which were assigned to ν (C=O), and ν (C=N), respectively. The complete
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disappearance of ν OH confirmed the deprotonation of the hydroxyl group. A comparison of the
FTIR spectra of the complex and the ligand clearly indicated that on complex formation, the
ν (C=N) stretching frequency was shifted from 1558 cm-1 in free ligand to 1499 c m-1 in the
complex ( lowering by ∆ = 59 cm-1), confirming the coordination of the nitrogen atom of
azomethine group of ligand to the metal center [29]. No noticeable change in the C=O stretching
frequency of the ligand was observed upon complexation. This confirmed that the C=O group of
pyrazole ring of ligand remained intact. The appearance of a new peak in the FTIR of the
complex at 580 cm-1 assignable to ν Pd-O indicated the coordination of the enolic oxygen to the
palladium [30-31].
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The FESEM micrographs of the APD ligand (Fig. 3a) and the complex [Pd(APD)2] (Fig
3b) displayed blocked shaped smooth and irregular rough surface morphologies, respectively.
From the micrographs, it can be concluded that surface roughness had increased on complex
formation. The EDX provided the detailed chemical analysis of Schiff base ligand APD (Fig 3c)
and its palladium complex (Fig 3d). The EDX analysis of the complex confirmed the presence of
all constituent atoms, i.e. C, N, O and Pd. The palladium content, based upon EDX analysis, was
found to be 14.26 % by weight.
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The TGA of the complex was carried out in the temperature range 40-730 C with a 20
oC/min interval in nitrogen atmosphere to assess the stability and mode of decomposition of the
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synthesized complex (Fig. 4S). Above 175 C, the TGA/DTA curve exhibits three steps of
weight loss. Complex shows a very low weight loss of 2% supported by an exothermic peak at
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about 230 C, which may correspond to the loss of or decomposition of one ligand moiety and
the framework is quite stable up to 450 oC. In the temperature range 230- 450 oC, a 65% weight
loss was observed suggesting the concomitant loss of the second ligand unit from the compound.
Catalytic studies:
After synthesis and characterization of the [Pd(APD)2] complex, it was screened for its
catalytic activity in Heck-Mizoroki and Suzuki-Miyaura C-C cross coupling reactions (Scheme
2) [32]. The results obtained in Heck-Mizoroki and Suzuki-Miyaura reactions with Pd-catalyst
are given below.
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Catalyst testing for the Heck-Mizoroki reaction:
A model reaction was performed by stirring 4-methylstyrene with bromobenzene in DMF-H2O
(1:1) using 0.2 mol % of the Pd(II) Schiff base catalysts at 80oC for 4 h. The results of the
different reaction conditions such as, variation of temperature, solvent, bases, catalyst loading
etc. are summarized in Table 2. A blank reaction (without palladium complex) between 4-
methystyrene and bromobenzene in DMF-H2O (1:1) under appropriate conditions (Table 2, entry
19) yielded no product. However, the reaction in presence of 0.05 and 0.1 mol % of complex
gave 68% and 82% yield of the product (Table 2, entries 10 & 11). The best yield of the product
was obtained using 0.2 mol % of the complex (Table 2, entry 4). On the other hand, increasing
the catalyst loading from 0.2 mol % to 0.5 mol % did not improve the yield of the product (Table
2, entry 12). Therefore, 0.2 mol % of the catalyst was found to be optimal for the coupling
reaction (Table 2, entry 4). A reaction between 4-methylstyrene with bromobenzene was carried
out in presence of Pd(OAc)2 (0.2 mol %) (without any ligand) to give low yield (Table 2, entry
5). However, the same reaction with Pd(OAc)2 and Schiff base ligand (1:2 molar ratio) under the
same reaction conditions, resulted in moderate yield of the desired coupling product (Table 2,
entry 6). The presence of Schiff base ligand has resulted in enhancement of the yield [14-15].
However, the best yield (95 %) was obtained using a pre-formed, isolated complex [Pd(APD)2]
(Table 2, entry 4). After optimization of catalyst loading, solvent, base, temperature and reaction
time were optimized. The reaction was also carried out in a number of solvents such as, H2O,
CH3CN, DMF, CH3OH etc. and in presence of different bases such as Na2CO3, KOH, NaOH and
CH3COONa (Table 2, entries 1-19). The best result was obtained with 0.2 mol % of catalyst, 1
equiv. of K2CO3 at 80oC (Table 2). The DMF-H2O mixture (1:1) was found to be the best solvent
(Table 2, entry 4).
With the optimized reaction conditions in hand, the scope of the Heck reaction was
extended to a variety of substituted aryl/hetero-aryl bromides/iodides and substituted olefins. The
reactions with the aryl bromides required a longer time as compared to aryl iodide. Aryl bromide
or iodide with electron-donating methoxy group (Table 3, entries 7, 9, 11 & 13,) or an electron-
withdrawing group (Table 3, entries 12, 14 & 16), both reacted smoothly under optimized
conditions to give the desired products in almost quantitative yields. The reaction with hetero-
aryl substrate, i.e. 2-bromopyridine with styrene under optimized condition resulted in 75% yield
of the desired coupling product (Table 3, entry 15). The reaction of chloro-substrates, instead of
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bromo- and iodo-substrates, did not succeed under optimized conditions presumably owing to
less reactivity of C-Cl bond due to higher bond energy. The isolated products were fully
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characterized by H and 13C NMR. Furthermore, the catalytic activity of the complex
[Pd(APD)2] was compared with previously reported catalysts [10, 33-34] for Heck-Mizoroki
coupling reaction in terms of temperature, catalytic loading, time etc (Table 4). Our catalyst gave
better yields at low temperature using less amount of catalyst in aqueous medium.
Catalyst testing for the Suzuki-Miyaura reaction:
A model reaction between 4-methoxybromobenzene and 4-methylphenylboronic acid
was chosen for optimization of catalyst loading, solvent, base and the reaction temperature
(Table 5). When the reaction was carried out in the absence of palladium complex in DMF-H2O
(1:1), no coupling product was formed (Table 5, entry 20). When the reaction was carried out
with 0.1 mol % catalyst loading, product was isolated in 68% yield (Table 5, entry 2). It was
observed that the reaction was completed in 4.5 h using 0.2 mol % [Pd(APD)2] as a catalyst in
DMF-H2O at 80 oC (Table 5, entry 6). No significant improvement in yield of biaryl product was
noticed when the catalyst loading was increased from 0.2 mol% to 0.5 mol% under optimized
reaction conditions (Table 3, entries 7, 9, 11 & 13,). Therefore, 0.2 mol% catalyst loading was
found to be optimum. Further the reaction between 4-methoxybromobenzene and 4-
methylphenylboronic acid carried out in presence of Pd(OAc)2 alone resulted in low yield (52%)
of the product (Table 5, entry 7). However, the reaction in presence of Pd(OAc)2 and Schiff base
ligand (1:2 molar ratio) under the optimized conditions resulted in only 64% yield of the desired
coupling product (Table 5, entry 8). The best yield of the product was achieved when isolated
[Pd(APD)2] complex was used as the catalyst (Table 3, entries 6). To optimize the suitable
solvent, the reaction was performed in the presence of various solvents such as H2O, CH3CN,
DMF, DMF-H2O (1:1), CH3OH, iPrOH, CH3CH2OH, H2O/CH3CH2OH (1:1) and H2O/iPrOH
(1:1) (Table 5). Among all solvents used, the best result was obtained in a 1:1 (by volume)
mixture of DMF-H2O (Table 5, entry 6). A number of bases were used, however, K2CO3 was
found to be the most efficient base (Table 5, entries 1-20).
Subsequently, all reactions were carried out under optimized conditions with a
structurally diverse range of aryl iodide and aryl/hetero-aryl bromide with arylboronic acid to
produce the corresponding biaryls (Table 6). The electron-withdrawing and electron-releasing
substituents on both aryl halide and arylboronic acid (Table 6, entries 2-14) afforded the
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coupling products in good to excellent yields (87-95%). The substituent in the meta-position
(Table 6, entry 10) of phenylboronic acid resulted in lower yields than the para-position (Table
6, entry 2) presumably due to the steric hindrance. The reaction with hetero-aryl substrate, i.e. 2-
bromopyridine with phenylboronic acid under optimized condition resulted in 72% yield of the
desired coupling product (Table 6, entry 15). However, reactions with aryl chloride under similar
conditions were unsuccessful. All isolated products were fully characterized by 1H NMR and 13C
NMR spectroscopic methods (Supplementary Material). A plausible mechanism for Suzuki
coupling reaction, based on previous reports [35], is suggested in Scheme 3.
Recyclability test:
The heterogeneous nature of the catalyst facilitated its easy removal by simple filtration under
gravity. After filtration, the catalyst was washed with water and methanol and dried under
vacuum. The recyclability of [Pd(APD)2] complex was tested in both Heck-Mizoroki and
Suzuki-Miyaura coupling reactions. The complex could be recycled up to three times (Fig. 5S),
however, a progressive decrease in yields of product was observed. The decrease in yield of
products may be due to the physical loss of the catalyst during separation, filtration and washings
among each run. The decrease in yields may also be due to the passivation of catalyst surface
after three cycles.
4. Conclusion:
In conclusion, a new Schiff base ligand (APD) was synthesized for the first time and
characterized by single crystal structure determination. The reaction of ligand with palladium
acetate in methanol afforded the corresponding palladium complex [Pd(APD)2] which was
characterized by various physico-chemical methods. The heterogeneous nature and the catalytic
activity of the complex has been explored in Heck-Mizoroki and Suzuki-Miyaura coupling at a
low (0.2 mol %) catalyst loading. The present methodology offers good turnover numbers (TON)
in both Heck-Mizoroki and Suzuki-Miyaura cross coupling reactions.
Acknowledgments
We are thankful to the CRF IIT (ISM), STIC Cochin, SAIF Panjab University, Chandigarh and
IISER Bhopal for providing help in the analysis of the samples. Samaresh acknowledges the
receipt of IIT (ISM) fellowship.
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Supplementary data
Supplementary data related to this article.
References:
[1]
[2]
K. C. Nicolaou, P. G. Bulger, D. Sarlah, Angew. Chem. Int. Ed. 2005, 44, 4442-4489.
W. A. Herrmann, M. Elison, J. Fischer, C. Kocher, G. R. J. Artus, Angew. Chem. Int. Ed.
Engl. 1995, 34, 2371-2374.
[3]
G. B. Smith, G. C. Dezeny, D. L. Hughes, A. O. King, T. R. Verhoeven, J. Org. Chem.
59 (1994) 8151-8156.
[4]
[5]
[6]
[7]
[8]
S. Cacchi, G. Fabrizi, Chem. Rev. 105 (2005) 2873-2920.
P. Yang, R. Ma, F. Bian, ChemCatChem. 8 (2016) 3746-3754.
I. Maluenda, O. Navarro, Molecules 20 (2015) 7528-7557.
A. Dhakshinamoorthy, A. M. Asiri, H. Garcia, Chem. Soc. Rev. 44 (2015) 1922-1947.
(a) X. Liu, X. Zhao, M. Lu, J. Org. Chem. 768 (2014) 23-27;
(b) T. Begum, M. Mondal, P. K. Gogoi, U. Bora, RSC Adv. 5 (2015) 38085-38092.
C. J. Li, Chem. Rev. 105 (2005) 3095-3165.
[9]
[10] R. N. Prabhu, R. Ramesh, Tetrahedron Lett. 53 (2012) 5961-5965.
[11] V. Arumugam, W. Kaminsky, N. S. P. Bhuvaneshc, D. Nallasamy, RSC Adv. 5 (2015)
59428-59436.
[12] R. Rossi, F. Bellina, M. Lessi, Adv. Synth. Catal. 354 (2012) 1181-1255.
[13] (a) E. A. B. Kantchev, C. J. O. Brien, M. G. Organ, Angew. Chem. Int. Ed. 16 (2007)
2768-2813;
(b) T. Begum, M. Mondal, M. P. Borpuzari, R. Kar, G. Kalita, P. K. Gogoi, U. Bora ,
Dalton Trans., 46 (2017) 539-546;
(c) G. Sarmah, U. Bora, Tetrahedron Lett. 56 (2015) 2906-2909.
[14] (a) J. M. Collinson, J. D. E. T. Wilton-Ely, S. Diez-Gonzalez, Catal. Commun. 87 (2016)
78-81;
(b) M. Mondal, U. Bora, Tetrahedron Lett. 55 (2014) 3038-3040
(c) M. Mondal, U. Bora, New J. Chem., 40 (2016) 3119-3123
[15] (a) A. F. Littke, G. C. Fu, Angew. Chem. Int. Ed. 41 (2002) 4176-4211;
(b) A. Dewan, Bull. Korean Chem. Soc. 35 (2014) 1855-1858;
8

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262
263
264
265
266
267
268
269
270
271
272
273
274
275
(c) A. Dewan, U. Bora, G. Borah, Tetrahedron Lett. 55 (2014) 1689-1692.
[16] (a) J. Dupont, C. S. Consorti, J. Spencer, Chem. Rev. 105 (2005) 2527-2572;
(b) A. Gogoi, A. Dewan, G. Borah, U. Bora, New J. Chem., 39 (2015) 3341-3344.
[17] C. A. Fleckenstein, H. Plenio, Organometallics 26 (2007) 2758-2767.
[18] N. M. Chaignon, I. J. S. Farlamb, A. R. Kapdi, R. J. K. Taylor, A. C. Whitwood, J. Mol.
Catal. A: Chem. 219 (2004) 191-199.
[19] R. B. Bedford, S. L. Hazelwood, M. E. Limmert, Chem. Commun. (2002) 2610-2611.
[20] T. Mino, Y. Shirae, Y. Sasai, M. Sakamoto, T. Fujita, J. Org. Chem. 71 (2006) 6834-
6839.
[21] B. Banik, A. Tairai, P. K. Bhattacharyya, P. Das, Appl. Organometal. Chem. 30 (2016)
519-523.
[22] S. R. Borhade, S. B. Waghmode, Tetrahedron Lett. 49 (2008) 3423-3429.
[23] A. P. S. Andrade, L. M. Arantes, J. Y. Kadooca, R. L. Carvalho, A. Fatima, A. A. Sabino,
Chem. Select 5(2016) 886-890.
[24] (a) S. Layek, S. Kumari, Anuradha, B. Agrahari, R. Ganguly, D. D. Pathak, Inorg. Chim.
Acta 453 (2016) 735-741;
(b) S. Layek, B. Agrahari, A. Tarafdar, C. Kumari, Anuradha, R. Ganguly, D. D. Pathak,
J. Mol. Struct. 1141 (2017) 428-435.
[25] Anuradha, S. Kumari, S. Layek, D. D. Pathak, J. Mol. Struct. 1130 (2017) 368-373.
[26] B. Agrahari, S. Layek, S. Kumari, Anuradha, R. Ganguly, D. D. Pathak, J. Mol. Struct.
1134 (2017) 85-90.
[27] Crystal data for APD ligand were obtained at 295 K with a Bruker Kappa diffractometer
equipped with a CCD detector, employing Mo Kα radiation ( λ = 0.71073 Å), with the
SMART suite of programs using a Bruker Kappa Apex Four Circle CCD diffractometer,
C26 H23 N3 O2, monoclinic, space group P21/n, a=8.6261(3) Å, b=18.5933(6) Å,
c=13.4820(4), V = 2161.94(12) Å3, Z = 4, Dx = 1.258 g/cm3, F(000) = 864. A total of
6643 reflections were collected and the structure was refined by full-matrix least-squares
on F2. The final refinement [I > 2ns (I)] gave R1 = 0.0480, wR2 = 0.1328.
[28] Crystallographic data for APD ligand has been deposited at the Cambridge
Crystallographic Data Centre as supplementary publication number CCDC 1441973.
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This data can be obtained free of charge from the Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data_request/cif.
[29] S. Priyarega, D. S. Raja, S. G. Babu, R. Karvembu, T. Hashimoto , A. Endo, K.
Natarajan, Polyhedron 34 (2012) 143-148.
[30] M. Khorshidifard, H. A. Rudbari, B. Askari, M. Sahihi, M. R. Farsani, F. Jalilian, G.
Bruno, Polyhedron 95 (2015) 1-13.
[31] M. Shabbir, Z. Akhter, I. Ahmad, S. Ahmed, M. Shafiq, B. Mirza, V. McKee, K. S.
Munawar, A. R. Ashraf, J. Mol. Struct. 1118 (2016) 250-258.
[32] General procedure for the Heck-Mizoroki reaction: A mixture of aryl halide (1 mmol),
olefin (1 mmol), K2CO3 (1 mmol), and the Pd-Schiff base complex (2.1 mg, 0.2 mol %)
in DMF-H2O (1:1) was stirred at 80°C for 3-4 h. The reaction progress was monitored
periodically by TLC. After completion of the reaction, it was cooled to room temperature
and the product was extracted with ethyl acetate (3 x10 mL) from aqueous phase. The
combined organic fractions were dried over Na2SO4, the solvent removed under reduced
pressure to afford a crude product. The residue was purified by short column
chromatography on silica gel eluted with petroleum ether/ethyl acetate afforded the
1
13
desired coupled products up to 98 % yield. The products were confirmed by H and C
NMR.
General procedure for the Suzuki-Miyaura reaction: A mixture of aryl halide (1 mmol),
arylboronic acid (1 mmol), K2CO3 (1 mmol), and the Pd- Schiff base complex (2.1 mg,
0.2 mol %) in DMF-H2O (1:1) was stirred at 80ºC for 3-5 h. The progress of reaction was
monitored by TLC until the complete consumption of the aryl halide. After the reaction,
the mixture was cooled down to room temperature and repeatedly extracted with ethyl
acetate. The combined organic layer was separated, dried over Na2SO4 and evaporated
under reduced pressure. The residue was purified by column chromatography on silica
gel to give the corresponding coupling products in up to 95% isolated yield. The products
were confirmed by 1H and 13C NMR.
[33] S. R. Borhade, S. B. Waghmode, Tetrahedron Lett. 49 (2008) 3423-3429.
[34] M. B. Andrus, C. Song, J. Zhang, Org. Lett. 4 (2002) 2079-2082.
[35] (a) A. J. J. Lennox, G. C. L. Jones, Chem. Soc. Rev. 43 (2014) 412-443;
(b) L. M. Kumar, B. R. Bhat, J. Organomet. Chem. 827 (2017) 41-48;
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(c) A. Vignesh, W. Kaminsky, N. Dharmaraj, ChemCatChem. 8 (2016) 3207-3212;
(d) A. Vignesh, W. Kaminsky, N. Dharmaraj, Green Chem. 18 (2016) 3295-3301.
List of Scheme’s caption
Scheme 1. Synthesis of Schiff base ligand (APD) and [Pd(APD)2] complex
Scheme 2. The catalytic activity of [Pd(APD)2] complex in Heck-Mizoroki (2a) and Suzuki-
Miyaura (2b) coupling reactions
Scheme 3. Plausible mechanism for the Suzuki-Miyaura coupling reaction
List of figure’s caption
Fig. 1. ORTEP diagram of APD ligand with 50% ellipsoid probability
Fig. 2. FT-IR Spectra of APD ligand and [Pd(APD)2] complex
Fig. 3. FESEM micrographs of (a) APD ligand, (b) [Pd(APD)2] complex and EDX Analysis of
(c)APD ligand, (d) [Pd(APD)2] complex
List of Table’s caption
Table 1: Crystallographic and refinement data for APD ligand
Table 2. Optimization of the Heck-Mizoroki reaction conditions
Table 3. Heck-Mizoroki reactions with different substituents catalyzed by [Pd(APD)2] complex
under optimized reaction conditions
Table 4. A comparison study of [Pd(APD)2] complex with the previous reported catalysts in
Heck-Mizoroki reactions in terms of temperature, catalyst loading, time.
Table 5. Optimization of the Suzuki-Miyaura reaction conditions
Table 6. Suzuki-Miyaura reactions with different substituents catalyzed by [Pd(APD)2] complex
under optimized reaction conditions
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332
333
Scheme 1. Synthesis of Schiff base ligand (APD) and [Pd(APD)2] complex
334
335
Heck-Mizoroki coupling reaction (2a)
336
337
Suzuki-Miyaura coupling reaction (2b)
Scheme 2. The catalytic activity of [Pd(APD)2] complex in Heck-Mizoroki (2a) and Suzuki-
Miyaura (2b) coupling reactions
338
339
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340
341
Scheme 3. Plausible mechanism for the Suzuki-Miyaura coupling reaction
342
343
Fig. 1. ORTEP diagram of APD ligand with 50% ellipsoid probability
344
345
346
Fig. 2. FT-IR Spectra of APD ligand and [Pd(APD)2] complex
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348
Fig. 3. FESEM micrographs of (a) APD ligand, (b) [Pd(APD)2] complex and EDX Analysis of
349
350
351
(c)APD ligand, (d) [Pd(APD)2] complex
Table 1: Crystallographic and refinement data for APD ligand
CCDC No.
1441973
Space group
Volume
P 21/n
2263.8(4) Å3
Chemical formula
Formula weight
Temperature
C26H2N3O2
409.47 g/mol
295 K
Z
4
Density (calculated)
1.496 g/cm3
Wavelength
Density (gm cm-3)
0.71073 Å
1.258
Absorption coefficient 1.002 mm-1
R int
0.0567
0.0513
0.1145
Volume
2161.94 (12)
yellow block
Monoclinic
R1[I>2δ(I)]
wR2 (all data)
Crystal habit
Crystal system
Unit cell dimensions
a = 8.6261(3) Å
b = 18.5933(6) Å
c = 13.4820(4) Å
α = 90°
β = 91.111(2)°
γ = 90°
352
353
354
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356
Table 2. Optimization of the Heck-Mizoroki reaction conditions *
Entry Catalyst
loading
Solvents
Base
Temp
(oC)
Time Yield**
(h)
(%)b
(mol %)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
0.5
0.2
0.2
0.2
0.2#
0.2##
0.2
0.2
0.2
0.05
0.1
0.5
0.2
0.2
0.2
0.2
0.2
0.2
-
DMF
DMF
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
Na2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
KOH
80
80
80
80
80
80
80
80
100
80
80
80
100
RT
60
80
80
80
80
7
8
7
4
4
4
8
6
4
4
4
4
12
12
12
7
7
4
78
75
95
95
65
74
64
82
90
68
82
80
55
62
trace
65
68
78
-
DMF-H2O
DMF-H2O
DMF-H2O
DMF-H2O
CH3CN
DMF-H2O
DMF-H2O
DMF-H2O
DMF-H2O
DMF-H2O
H2O
DMF-H2O
MeOH
DMF-H2O
DMF-H2O
DMF-H2O CH3COONa
DMF-H2O K2CO3
NaOH
7
357
358
359
360
361
362
363
364
*Reaction conditions: 1a (0.5 mmol, 1.0 equiv), 2b (0.6 mmol, 1.2 equiv),
Base (0.75 mmol, 1.5 equiv).
**Yield after column chromatography
#Only Pd(OAc)2 used as catalyst
##Pd(OAc)2/Schiff base ligand (1:2 ratio) as catalyst
365
366
367
368
369
370
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372
Table 3. Heck-Mizoroki reactions with different substituents catalyzed by [Pd(APD)2] complex
under optimized reaction conditions
Entry
1
X
Br
Br
Br
Br
I
Z
R1
H
R2
Time (h) Yields (%)
TON
475
514
492
464
485
480
482
461
530
475
504
498
514
499
346
TOF
(h-1)
119
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
N
C6H5
4.0
4.0
3.5
4.0
4.0
3.5
3.5
3.5
3.0
3. 5
3. 5
3.5
3.5
3.5
4
92
95
91
90
94
93
89
85
98
92
93
92
95
92
75
2
H
CH3-C6H4
CH3-C6H4
C6H5
129
141
116
162
137
138
132
177
135
144
138
147
143
86
3
CHO
COCH3
OCH3
H
4
5
C6H5
6
I
CH3-C6H4
COOCH3
ClCH2-C6H4
CH3-C6H4
COOCH3
COOCH3
CH3-C6H4
CH3-C6H4
COOCH3
C6H5
7
Br
I
OCH3
H
8
9
I
OCH3
CHO
COCH3
CHO
OCH3
CHO
H
10
11
12
13
14
15
Br
Br
Br
Br
I
Br
373
374
Table 4. A comparison study of [Pd(APD)2] complex with the previous reported catalysts in
375
Heck-Mizoroki reactions in terms of temperature, catalyst loading, time.
Entry
Catalyst
Catalyst
loading
Temperature
Time
Yields
(%)
Reference
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1
Pd(II) bis
thiosemi
0.1 mol %
100oC
8h
60-98
10
carbazone
complex
Pd(II)- salen
complex
Pd-Imidazolium 2.0 mol %
Carbene
2
3
0.5 mol %
130oC
25oC
6h
20-97
32-91
33
34
3-5h
complex
[Pd(APD)2]
complex
4
0.2 mol %
80oC
3-4h
85-98
This work
376
377
Table 5. Optimization of the Suzuki-Miyaura reaction conditions *
378
379
380
Entry Catalyst
loading
Solvents
Base
Temp
(oC)
Time Yield**
(h)
(%)b
(mol %)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
0.2
0.1
0.2
0.2
0.2
0.2
0.2#
0.2##
0.2
0.5
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
0.2
-
DMF
DMF
DMF-H2O
DMF-H2O
CH3CN
DMF-H2O
DMF-H2O
DMF-H2O
DMF-H2O
DMF-H2O
DMF-H2O
H2O
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
Na2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
KOH
80
80
80
80
110
80
80
80
100
80
80
100
80
80
80
80
RT
80
5
5
7
3
5
67
68
90
79
70
94
52
64
90
90
81
45
55
62
48
50
60
65
68
-
4.5
4.5
4.5
4.5
4.5
5
12
4.5
4.5
4.5
4.5
18
7
iPrOH
iPrOH-H2O
CH3CH2OH
CH3CH2OH-H2O
DMF-H2O
DMF-H2O
DMF-H2O
DMF-H2O
NaOH
K2CO3 80-100
80
7
24
381
382
383
384
*Reaction conditions: Aryl halide (0.5 mmol, 1.0 equiv), Phenyl boronic acid (0.6
mmol, 1.2 equiv),
Base (0.75 mmol, 1.5 equiv).
**Yield after column chromatography.
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385
386
387
388
389
#Only Pd(OAc)2 used as catalyst
##Pd(OAc)2/Schiff base ligand (1:2 ratio) as catalyst
Table 6. Suzuki-Miyaura reactions with different substituents catalyzed by [Pd(APD)2] complex
under optimized reaction conditions.
Entry
X
Z
R1
H
R3
H
Time (h)
4.5
Yields
91
TON
470
475
514
480
477
509
464
475
504
464
459
464
476
471
332
TOF
(h-1)
105
1
2
Br
Br
Br
Br
Br
I
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
N
H
4-CH3
4-CH3
H
4.0
92
118
129
120
119
145
116
119
112
103
102
103
106
105
74
3
OCH3
COCH3
OCH3
OCH3
H
4.0
95
4
4.0
93
5
4-OCH3
4-CH3
4-CH2CH3
4-OCH3
4-CH2CH3
3-CH3
4-Cl
4.0
92
6
3.5
94
7
Br
Br
Br
Br
Br
Br
Br
Br
Br
4.0
90
8
H
4.0
92
9
OCH3
H
4.5
93
10
11
12
13
14
15
4.5
90
H
4.5
89
OCH3
H
4-Cl
4.5
90
3-CN
4-F
4.5
88
OCH3
H
4.5
87
H
4.5
72
390
18

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Highlights:
•
•
•
•
Synthesis of a new Schiff base ligand and its palladium complex [Pd(APD)2]
Ligand structure determined by single crystal X-ray study
Complex is a good catalyst for Heck-Mizoroki and Suzuki-Miyaura coupling reactions
Catalyst recyclability up to three times