Palladium(II) complexes containing sterically bulky O, N donor ligands: Synthesis, characterization and catalytic activity in the Suzuki-Miyaura and Sonogashira coupling reactions

Article abstract of DOI:10.1016/j.jorganchem.2019.121080

A new class of palladium(II)1-(arylazo)naphtholate complexes of the type [Pd(L_1-4)₂] containing sterically bulky O, N donor functionalized arylazo ligands has been synthesized. These palladium(II) complexes were characterized by elemental analysis and spectral (FT-IR, UV–Vis, ¹H NMR and ¹³C NMR) studies. The molecular structure of the Palladium(II) complexes [Pd(L₁)₂] and [Pd(L₂)₂] were established by X-ray crystallography. These complexes were found to efficiently catalyze the Suzuki-Miyaura coupling of arylboronic acids and aryl halides, and the Sonogashira reaction of aryl halides and phenylacetylene in DMF and i-PrOH media to afford the corresponding C–C coupling products in high yields.

Full text of DOI:10.1016/j.jorganchem.2019.121080

Journal Pre-proof
Palladium(II) complexes containing sterically bulky O, N donor ligands: Synthesis,
characterization and catalytic activity in the Suzuki-Miyaura and Sonogashira coupling
reactions
Raja Nandhini, Paranthaman Vijayan, Galmari Venkatachalam
PII:
S0022-328X(19)30523-6
DOI:
https://doi.org/10.1016/j.jorganchem.2019.121080
JOM 121080
Reference:
To appear in: Journal of Organometallic Chemistry
Received Date: 25 October 2019
Accepted Date: 16 December 2019
Please cite this article as: R. Nandhini, P. Vijayan, G. Venkatachalam, Palladium(II) complexes
containing sterically bulky O, N donor ligands: Synthesis, characterization and catalytic activity in the
Suzuki-Miyaura and Sonogashira coupling reactions, Journal of Organometallic Chemistry (2020), doi:
https://doi.org/10.1016/j.jorganchem.2019.121080.
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Palladium(II) Complexes Containing sterically bulky O, N Donor
Ligands: Synthesis, Characterization and Catalytic activity in the Suzuki-
Miyaura and Sonogashira Coupling Reactions
Raja Nandhinia, Paranthaman Vijayanb and Galmari Venkatachalam*a
aPG & Research Department of Chemistry, Government Arts College, Dharmapuri- 636 705,
Tamilnadu, India.
bSchool of Chemistry & Physics, University of KwaZulu-Natal, Pietermaritzburg Campus,
Scottsville 3209, South Africa.
Corresponding Author: *E-mail address: gvchem@gmail.com [G. Venkatachalam].
Abstract
A new class of palladium(II)1-(arylazo)naphtholate complexes of the type [Pd(L1-4)2]
containing sterically bulky O, N donor functionalized arylazo ligands has been synthesized.
These palladium(II) complexes were characterized by elemental analysis and spectral (FT-IR,
1
UV-Vis, H-NMR and 13C-NMR) studies. The molecular structure of the Palladium(II)
complexes [Pd(L1)2] and [Pd(L2)2] were established by X-ray crystallography. These complexes
were found to efficiently catalyze the Suzuki-Miyaura coupling of arylboronic acids and aryl
halides, and the Sonogashira reaction of aryl halides and phenylacetylene in DMF and i-PrOH
media to afford the corresponding C-C coupling products in high yields.
Keywords: Palladium(II) complexes; Bulkyazo ligands; X-ray structure; Suzuki-Miyaura
reaction; Sonogashira reaction.

1. Introduction
Arylazo ligands have important roles in coordination chemistry as they form stable
complexes with most of transition metals [1-2]. Azo containing compounds are capable of
stabilizing metals in formally low oxidation states [3, 4] and as redox non-innocent nature of the
ligands; the metal complexes with azo-ligands have tunable redox properties [5]. Azo ligand with
hard nitrogen, oxygen and soft sulphur donor atoms again have a tunable capability for
coordinating with a wide range of metal ions, to give stable and intensely colored metal
complexes [6]. Complexes of transition metals with azo ligands have interesting physical,
chemical, photophysical, photochemical, catalytic and material properties [7,8].
Arylazo ligands provide a great platform in coordination/organometallic chemistry for
development of ligand systems [9]. Most azo ligands are easily accessible using simple synthetic
procedures with selection of an amine and substituted phenol. These ligands can potentially
stabilize metals in different oxidation states which are particularly useful in catalytic reactions.
The palladium complexes have wide-spread application in syntheses and become one of
the most powerful and convenient C–C, C-N bond forming processes in pharmaceutical
chemistry, materials and synthetic chemistry [10]. Moreover, the metal complexes incorporating
ortho substituted azo benzene ligands have versatile properties such as C-H activation [11, 12],
C-C activation [13], C-C coupling [14], ‒N=N‒bond cleavage [15], electron transfer reaction
[16, 17], hydroxylation [18], isomerization [19], photoisomerization [20], cytotoxicity toward
cancer cells and application in catalytic transformations [21].
Palladium-catalyzed cross-coupling reaction for the formation of carbon–carbon bonds
has recently emerged as a powerful method in an organic synthesis. The palladium-catalyzed
coupling [22] of an aryl halide with aryl boronic acid (Suzuki coupling) or terminal alkyne

(Sonogashira coupling) is recognized as the most successful method for carbon–carbon bond
forming reactions. Many catalytic systems have been developed for the Suzuki-Miyaura and
Sonogashira cross-coupling reactions using different palladium catalysts such as Pd(PPh3)4,
Pd(OAc)2, PdCl2(PPh3)2, and PdCl2(CH3CN)2 [23]. However, phosphine ligands used in these
reactions are sensitive to air oxidation and thus require air-free conditions which pose significant
inconvenience on synthetic applications [24]. Palladium(II) complexes containing nitrogen,
oxygen donor ligands showed high catalytic activity in C-C coupling reaction than commercially
used phosphine containing metal complexes. Further, nitrogen based ligands are popular in
coordination chemistry because they are easily modified both sterically and electronically [25-
27].
In the present work, we report the synthesis of Pd(II) complexes by the reaction of bulky
ortho, para substituted 1-(arylazo)naphtholate ligands with [Pd(OAc)2]. The molecular structure
of [Pd(L1)2] 1 and [Pd(L2)2] 2 has been established using single crystal X- ray diffraction. The
1
new complexes were fully characterized by FT-IR, UV-Vis, H-NMR and 13C-NMR spectral
studies. The catalytic activity in Suzuki and Sonogashira coupling reactions of various aryl
halides by these complexes has also been examined.
2. Results and Discussion
Treatment of 2:1 molar ratio of sterically bulky 1−(arylazo)naphthol ligands with
[Pd(OAc)2] in acetonitrile at room temperature for 4h afforded the new palladium(II) complexes
of the general composition [Pd(L1−4)2] (Scheme 1) in good yields. All the palladium complexes
are air stable in both the solid and the liquid states at room temperature and are non–hygroscopic.
The synthesized complexes are readily soluble in highly polar solvents such as dichloromethane

and chloroform etc., producing intense red colored solutions. The analytical data of all the
palladium(II) complexes are in good agreement with the proposed molecular structure.
R'
R
R
OH
O
N
O
N
Pd(OAc)2
Pd
N
N
CH3CN / Stirring / 4h
N
N
R
R
R
R
R'
R'
L1; 1
CH3
H
L2; 2
CH3
L4; 4
L3; 3
Complex
R
CH(CH3)2
H
Br
Br
CH3
R'
Scheme 1. Synthesis of Palladium(II) 1-(arylazo)naphtholate complexes 1-4.
2.1. Characterization of the complexes
The FT–IR spectra of the free ligands displayed ν(N=N) strong absorptions in the region
1443–1446 cm−1 (Supporting information Fig S1-S4). The stretching frequency of ν(N=N) was
observed at a lower frequency in the complexes around the region 1357–1390 cm–1, indicating
the coordination of azo nitrogen to Pd(II) ion, due to reduction of electron density in the
naphthol-azo link. The stretching vibration of phenolic oxygen is confirmed by the increase in
ν(C–O) at higher frequencies appear at 1300–1313 cm−1 in all the complexes [28–31].
The electronic spectra of all the palladium(II) complexes were recorded in chloroform
and exhibited three bands with absorption maxima in the region 200–800 nm (Supporting
information Fig S5). The absorption spectra of palladium(II) complexes exhibited very intense
bands below 250–270 nm and 320–360 nm are assigned to ligand–centre transitions. The intense

bands with absorption maxima in the region 430–455nm are assigned to metal to ligand charge-
transfer (MLCT) transitions. A square planar geometry around palladium(II) centre has been
proposed based on the pattern of electronic spectra of other square planar palladium(II)
complexes [32–37].
1
The H–NMR spectra of all the complexes were recorded in CDCl3 to confirm the
binding of 1–(arylazo)naphthol to palladium ion. All complexes showed multiplets in the
respective region at δ = 7.0 – 7.9 ppm for the presence of all the aromatic protons of the ligands.
The methyl protons of the complex 1 observed as singlet at δ = 2.3 ppm. Additionally, the
isopropyl proton appears as doublet at δ = 1.29 ppm and methyl proton appear as septet at δ =
3.12 ppm respectively for complex 3. The 1H and 13C NMR spectra are shown in Figs. S6 –S12
(Supporting information).
2.2. X-ray structure
The solid-state structure of the palladium(II) complexes (1) and (2) was performed by
single crystal X-ray diffraction method and the partial atom numbering scheme shown in Fig. 1
& 2. X-ray data collection and structure refinement parameters for complexes were shown in
Table 1 and the selected bond lengths and bond angles were given in Table 2. Complexes 1 and
2 crystallized with monoclinic with space group P21/c, P21/n respectively. Subsequently, two
compartments of azo monodentate ligands coordinated with Pd(II) ion via phenolate oxygen and
azo nitrogen donor atoms forming six membered chelate rings. The selected bond lengths and
bond angles (Table 2) of the palladium complexes exhibited perfect square planar geometry with
N2O2 coordination environment. Nevertheless, the perfect square planar geometry identified with
the bite angles 180o for O(1)-Pd(1)-O(1) (complex 1) and N(2)-Pd(1)-N(2) (complex 2). In both

complexes, Pd(1)-O(1) bond length (1.981-1.967 Å) is shorter than Pd(1)-N(2) (2.000-2.003 Å)
bond length, which were in the expected range for the previously reported [38].
Figure 1. The ORTEP diagram of the complex (1).

Figure 2. The ORTEP diagram of the complex (2).

Table 1. Selected crystal data and structure refinement summary of complexes 1 and 2.
1
2
Empirical formula
Formula weight
C36 H30 N4 O2 Pd
657.04
C38 H34 N4 O2 Pd
685.09
Temperature
296(2)
296(2)
Wavelength/ Å
Crystal system
Space group
a/ Å
b/ Å
0.71073 Å
monoclinic
P 21/c
11.4362(9) Å
17.4698(13) Å
16.6423(13) Å
90
0.71073 Å
monoclinic
P 21/n
11.3334(5) Å
12.3600(6) Å
12.2210(5) Å
90
c/ Å
α/°
β/°
107.094(2)
90
107.5880 (10)
90
γ/°
3
Volume/ Å
Z
3178.1(4)
4
1631.90(13)
2
3
Density (calculated)/ Mg/m
1.373
1.394
-1
Absorption coefficient/ mm
F(000)
0.621
1344
0.22 x 0.17 x 0.11
1.166 to 29.213°
40759
0.608
704
0.24 x 0.17 x 0.09
2.708 to 29.218
35090
Crystal size/mm3
Theta range of data collection/°
Reflections collected
Independent reflections
Data / restraints / parameters
17251 [R(int) = 0.0301]
14068 / 2 / 775
4424 [R(int) = 0.0462]
4410 / 0 / 205
2
Goodness-of-fit on F
0.848
0.806
Final R indices [I>2sigma(I)]
R indices (all data)
R1 = 0.0381, wR2 = 0.1172 R1 = 0.0466, wR2 = 0.1655
R1 = 0.0766, wR2 = 0.1704 R1 = 0.0621, wR2 = 0.1967
-3
Largest diff. peak / hole/ e.Å
0.282 and -0.359
1.213 and -0.489

Table 2. Selected bond lengths (Å) and angles (°) in complexes 1 and 2.
________________________________________________________________
Distances/ angles
1
2
________________________________________________________________
Pd(1)-O(1)
Pd(1)-N(2)
O(1)-C(1)
N(2)-N(1)
N(2)-C(11)
N(1)-C(10)
C(11)-C(12)
1.981(3)
2.000(3)
1.288(4)
1.275(4)
1.456(5)
1.366(4)
1.396(6)
1.967(2)
2.003(2)
1.283(3)
1.281(3)
1.452(4)
1.369(3)
1.387(4)
O(1)-Pd(1)-O(1)
O(1)-Pd(1)-N(2)
N(2)-Pd(1)-N(2)
C(1)-O(1)-Pd(1)
N(1)-N(2)-C(11)
N(1)-N(2)-Pd(1)
C(11)-N(2)-Pd(1)
N(2)-N(1)-C(10)
180.0
180.0
90.29(11)
180.0
88.52(9)
180.00(5)
125.21(18)
111.6(2)
127.71(17)
120.49(19)
122.8(2)
124.1(2)
111.7(3)
128.1(2)
120.2(2)
123.1(3)
________________________________________________________________

2.3. Catalytic Suzuki-Miyaura coupling reaction
Table 3. Optimization of the reaction conditiona
Catalyst 1
NO2
Br
NO2
+
B(OH)2
base/ reflux/ 5h
Entry
Catalyst (mol%)
Solvent
Base
Yieldb(%)
1
1.0
DMF
DMF
DMF
DMF
DMF
DMF
DMF
Methanol
Toluene
THF
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
NaOH
KOH
99
90
88
65
50
43
32
84
68
40
36
NRc
80
88
90
60
2
0.5
3
0.2
4
0.1
5
0.01
0.001
0.0001
1.0
6
7
8
9
1.0
10
11
12
13
14
15
16
1.0
1.0
DCM
H2O
1.0
1.0
DMF
DMF
DMF
DMF
1.0
1.0
Na2CO3
Et3N
1.0
aReaction conditions: 4-bromonitrobenzene (1mmol), phenylboronic acid (1.2mmol), base
(1mmol), catalyst, solvent (5mL). bIsolated yields. cNo reaction.

Initially, a brief screening of the base, catalyst loading and solvent was conducted by
running a carbon-carbon coupling reaction of 4-bromonitrobenzene and phenylboronic acid
(Table 3). After optimization, we found that 1mol% catalyst, 1mmol K2CO3, DMF as solvent and
a reaction time 5h furnished a good yield of expected product.
Upon lowering the catalyst loading, the yield of the reaction also decreased significantly.
Different bases were tested and the coupling products were obtained in good yields when K2CO3
was used. Moderate yields were obtained in the cases of Na2CO3, KOH and NaOH and very low
yield was obtained with Et3N. Using K2CO3 as a base, different solvent were tested and the
product were obtained in good yield in DMF.
A general catalytic cycle for the cross-coupling reaction of organoboron reagents with
aryl halides involves an oxidative-addition of the aryl halide, transmetalation, and reductive-
elimination steps [39, 40]. Aryl bromides with various functional groups efficiently reacted with
boronic acids (entries 1-9) using K2CO3 and 5 mL of DMF at reflux temperature in presence of
palladium(II) complex 1 for 5 h to yield Suzuki-Miyaura products in good to excellent
conversions. The conversion of 4‒bromotoluene and 4‒bromoanisole (entries 3 and 4) in to their
corresponding biaryls compounds are 95% and 92% respectively. Substrate with electron
withdrawing substituents such as NO2 and CN (entries 2 and 5) gave excellent conversions of
99% and 85% respectively. In addition, the complex efficiently catalyzes the 4-chloro phenol
and 4-bromo benzaldehyde (entries 6 and 8) into corresponding C-C coupling products of 88%
and 80% respectively.

Table 4. Suzuki-Miyaura coupling of aryl halide with phenylboronic acid using complex (1)a
Entry
Substrate
Product
Yieldb (%)
Br
Br
Br
1
2
96
99
NO2
CH3
OCH3
CN
O2N
H3C
3
4
5
95
92
85
H3CO
NC
Br
Cl
HO
Cl
OH
6
80
Br
H3C
CH3
7
8
9
82
88
68
OHC
Br
CHO
Cl
aReaction conditions: aryl halides (1 mmol), phenylboronic acid (1.2 mmol), K2CO3 (1 mmol),
catalyst (1 mol%), DMF solvent (5mL).
bIsolated yield after column chromatography.
2.4. Catalytic Sonogashira coupling reactions
To extend the scope of our work, we next investigated the coupling of various aryl
bromides with terminal alkynes. The results are summarised in Table 5. The electron donating

groups such as –Me, –OMe, at the para position of aryl bromide couple smoothly with phenyl
acetylene to give good to excellent yield of isolated cross coupling products (Table 5, entries 3 &
4). The p-chlorobenzonitrile having electron-deficient aromatic rings, also underwent the
Sonogashira coupling with terminal alkynes under similar conditions to afford the corresponding
products in good yields (entries 5). Bromobenzene could be smoothly coupled with phenyl
acetylene resulting in a high yield of diphenyl acetylene (95%, entry 1). 2-Bromotoluene (entry
7), gave the corresponding product in a slightly lower yield (73–87%), which may be due to
steric effects compare with p-bromotoluene (entry 3). The reaction of chlorophenol (entry 6)
found to be moderate yield 85%.

Table 5 Sonogashira reaction of aryl halides with phenylacetylenea.
Pd catalyst (1-4)
Br +
Base/ 5 hr/ Solvent
Entry
Substrate
Product
Yieldb (%)
Complexes
1
2
3
4
Br
Cl
1
2
95
82
86
95
89
92
85
O2N
H3C
H3CO
NC
NO2
92
90
97
90
85
Br
Br
CH3
OCH3
CN
3
4
5
6
79
90
89
80
92
95
80
75
89
90
92
79
Cl
Cl
Br
HO
OH
CH3
H3C
Br
7
8
87
89
83
85
80
91
73
79
CHO
OHC
aReaction condition: aryl halides (1 mmol), phenyacetylene (1.5 mmol), K2CO3 (2 mmol),
catalyst (1 mol%), solvent 5mL.
bIsolated yield after column chromatography.
3. Conclusion
The present study shows that the steric bulky 1-(arylazo)naphthol ligands can readily
bind to palladium(II) metal ion. The characterization of all the complexes was accomplished by
1
analytical and spectral (IR, UV-Vis, H NMR and 13C-NMR) methods. Single crystal X-ray

diffraction studies evidenced the coordination mode of ligands to the metal through O, N donors
and reveal the presence of a square-planar geometry. Our catalyst showed good catalytic
activities toward Suzuki and Sonogashira cross-coupling reactions of aryl halides with
phenylboronic acid and phenylacetylene.
4. Experimental Section
4.1. Materials and physical measurements
Commercial Pd(OAc)2 was purchased from Himedia. All the used reagents were
chemically pure or analytical reagent grade. Solvents were purified and dried according to
standard procedures. The 1‒(aryllazo)naphthol ligands [31] were prepared by diazotization
reaction of ortho, para-substituted amines with β-naphthol. The substrates used in the catalytic
studies, were purchased from Merck and Aldrich. The IR spectra of the complexes were recorded
on an agilent resolution pro model in 4000–400 cm‒1 range. Electronic spectra of the complexes
were recorded in CHCl3 solution in a Cary 300 Bio UV–Vis Varian spectrophotometer in the
1
range 800‒200 nm. The H-NMR spectra were recorded in CDCl3 with Bruker 300MHz
instrument using TMS as internal reference.
4.2. Synthesis of Palladium (II) 1-(arylazo)naphtholate complexes
To a solution of (1-arylazo)naphthols (HL1–HL4) (2 mmol, 0.1229-0.2160 g), Pd(OAc)2
(1 mmol, 0.224 g) and triethylamine were mixed in acetonitrile with constant stirring for 4h. The
precipitate of the resulting product was filtered and dried in vacuo.
o
[Pd(L1)2] (1): Red solid, M.p. 230 C. Anal. Calc. for C36H30O2N4Pd: C, 65.85; H, 4.57;
N, 8.53. Found: C, 65.84; H, 4.58; N, 8.52. IR (cm‒1):1370 υ(N=N), 1303 υ(C-O). UV–Vis λmax
1
(nm): 455, 345, 250. H‒NMR (300 MHz, CDCl3): δ (ppm) = 7.1–7.6 (m, Ar-H), 6.4 (dd, CH),
2.3 (s, CH3). 13C‒NMR (CDCl
) δ (ppm): 128-132 (m, Ar-H), 18.0 (s, CH3).
3

o
[Pd(L2)2] (2): Orange solid, M.p. 210 C. Anal. Calc. for C38H34O2N4Pd: C, 66.47; H,
5.24; N, 8.16. Found: C, 66.47; H, 5.23; N, 8.17. IR (cm‒1): 1367 υ(N=N), 1304 υ(C-O). UV–Vis
1
λmax (nm): 440, 360, 260. H‒NMR (300 MHz, CDCl3): δ (ppm) =7.0–7.6 (m, Ar-H), 6.4 (dd,
CH), 2.4 (s, 3CH3). 13C‒NMR (CDCl
3
) δ (ppm): 120-136 (m, Ar-H), 24.0 (2CH3), 44.0 (CH3, s).
o
[Pd(L3)2] (3): Brown solid, M.p. 200 C. Anal. Calc. for C44H48O2N4Pd: C, 68.57; H,
6.23; N, 7.27. Found: C, 68.56; H, 6.24; N, 7.26. IR (cm‒1): 1387 υ(N=N), 1313υ(C-O). UV–Vis
1
λmax (nm): 450, 350, 270. H‒NMR (300 MHz, CDCl3): δ (ppm) =7.1–7.9 (m, Ar-H), 3.12 (m,
CH), 1.29 (d, 2(CH3)2C).
[Pd(L4)2] (4): Brown solid, M.p. 240 oC. Anal. Calc. for C32H18O2N4Br6Pd: C, 35.88; H,
1.68; N, 5.23. Found: C, 35.90; H, 1.67; N, 5.24. IR (cm‒1): 1354 υ(N=N), 1313 υ(C-O). UV–Vis
λmax (nm): 450, 320, 260. 1H‒NMR (300 MHz, CDCl3): δ (ppm) = 7.0–7.7 (m, Ar-H). 13C‒NMR
(CDCl
4.3. X-ray crystallography
Single crystals of the complexes [Pd(L1)2] (1) and [Pd(L2)2] (2) were grown in
3
) δ (ppm): 120-134 (m, Ar-H).
dichloromethane–pentane mixture at room temperature. A single crystal of suitable size was
covered with Paratone oil, mounted on the top of a glass fiber, and transferred to a Bruker
SMART APEX II single crystal X-ray diffractometer using monochromated Mo-Kα radiation (kI
= 0.71073 Å). Data were collected at 293 K. The structure was refined by full matrix least
squares method on F2 with SHELXL-18. Non-hydrogen atoms were refined with anisotropy
thermal parameters. All hydrogen atoms were geometrically fixed and allowed to refine using a
riding model. Frame integration and data reduction were performed using the Bruker SAINT-
Plus (Version 7.06a) software. The multi scan absorption correction was applied to the data using
SADABS software.

4.4. General procedure for Suzuki-Miyaura cross coupling reactions
A mixture of the appropriate aryl halide (1 mmol), phenylboronic acid (1.2 mmol),
palladium catalyst (1 mmol%), K2CO3 (1 mmol) was added to DMF (2 mL) in round-bottom
flask equipped with condenser and placed into the oil bath. Then the reaction mixture was heated
for the desired time at 110 ºC. After the reaction was completed (monitored by TLC), the
mixture was cooled to room temperature and the reaction mixture was poured into a separating
funnel and water (30 mL) and n-hexane (30 mL) were added. The organic phase was dried over
CaCl2, filtered, and the solvent was evaporated. The residue was purified by silica gel column
chromatography.
4.5. General procedure for the Sonogashira coupling reactions
A mixture of aryl halides (1mmol), alkyne (1.5 mmol), base (2 mmol), i-PrOH (2 mL),
and the catalyst (1 mol%) was stirred at 82 °C under aerial conditions. The progress of the
reaction was monitored by TLC. After the completion of the reaction, the mixture was diluted
with 20 mL of water and extracted with diethyl ether (3 ×20 mL). The combined organic layer
were washed with brine and dried over anhydrous Na2SO4 and evaporated in a rotary evaporator
under reduced pressure. The crude compound was purified by column chromatography on silica
gel using hexane as eluent to afford the desired products.
Acknowledgments
The authors express sincere thanks to Single Crystal X‒ray Diffraction Facility, SAIF
Guwahati University, for providing X‒ray data collection.

Appendix A. Supplementary data
1
FT-IR, UV-Vis, H-NMR and 13C-NMR spectra of representative complexes. CCDC
1957026 and CCDC 1938588 contain the supplementary crystallographic data for complex 1 and
2. These data can be obtained free of charge from The Director, CCDC, 12 Union Road,
Cambridge, CB2 1EZ, UK (fax: +44 1223 336033; email: deposit@ccdc.cam.ac.uk or
http://www.ccdc.cam.ac.uk).
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Highlights
‹ The new family of Palladium(II) 1-(arylazo)naphtholate complexes have been
synthesized.
‹ Characterizations of the complexes were performed by spectral and SC-XRD.
‹ Palladium(II) 1-(arylazo)naphtholate complexes were used as catalysts for the Suzuki-
Miyaura and Sonogashira coupling reactions.

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.
☐The authors declare the following financial interests/personal relationships which may be considered
as potential competing interests:
No conflict of interest.