Palladium(II) complexes with salicylideneimine based tridentate ligand and triphenylphosphine: Synthesis, structure and catalytic activity in Suzuki-Miyaura cross coupling reactions

Article abstract of DOI:10.1016/j.ica.2012.08.024

Square planar palladium(II) complexes of the type [Pd(L)(PPh₃)] (1-6) (where L is the dianion of N-(2-mercaptophenyl)salicylideneimine or 5-substituted-N-(2-mercaptophenyl)salicylideneimine or N-(2-mercaptophenyl) naphthylideneimine) have been synthesised from the reactions between [Pd(PPh₃)₄] and H₂L in dichloromethane-ethanol mixture. The new complexes have been characterized by analytical and spectral (electronic, IR, ¹H, ¹³C{¹H} and ³¹P{¹H} NMR spectroscopy) techniques. The structures of three complexes (1, 2 and 6) have been solved by single-crystal X-ray diffraction experiments which indicate square planar coordination geometries around palladium(II) by O, N, S and P donor atoms. The palladium(II) complexes (1-6) exhibited good catalytic activity in Suzuki-Miyaura cross-coupling reaction between phenylboronic acid and 4-bromotoluene in N,N-dimethylacetamide at 100 °C. Complex 3 (1 mol%) was found to be the most active and hence was used for probing the scope of possible substrates. Heterocyclic boronic acid and heterocyclic aryl bromides have also been used as substrates to provide heterocyclic biaryls.

Full text of DOI:10.1016/j.ica.2012.08.024

Inorganica Chimica Acta 394 (2013) 391–400
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Palladium(II) complexes with salicylideneimine based tridentate ligand
and triphenylphosphine: Synthesis, structure and catalytic activity
in Suzuki–Miyaura cross coupling reactions
Manoharan Muthu Tamizh a, Benjamin F.T. Cooper b, Charles L.B. Macdonald b, Ramasamy Karvembu a,
⇑
a Department of Chemistry, National Institute of Technology, Tiruchirappalli 620 015, India
b Department of Chemistry & Biochemistry, University of Windsor, Windsor, Ontario, Canada N9B 3P4
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 1 May 2012
Received in revised form 16 August 2012
Accepted 18 August 2012
Available online 10 September 2012
Square planar palladium(II) complexes of the type [Pd(L)(PPh3)] (1–6) (where L is the dianion of N-(2-
mercaptophenyl)salicylideneimine or 5-substituted-N-(2-mercaptophenyl)salicylideneimine or N-(2-
mercaptophenyl)naphthylideneimine) have been synthesised from the reactions between [Pd(PPh3)4]
and H2L in dichloromethane–ethanol mixture. The new complexes have been characterized by analytical
and spectral (electronic, IR, 1H, 13C{1H} and 31P{1H} NMR spectroscopy) techniques. The structures of
three complexes (1, 2 and 6) have been solved by single-crystal X-ray diffraction experiments which indi-
cate square planar coordination geometries around palladium(II) by O, N, S and P donor atoms. The pal-
ladium(II) complexes (1–6) exhibited good catalytic activity in Suzuki–Miyaura cross-coupling reaction
between phenylboronic acid and 4-bromotoluene in N,N-dimethylacetamide at 100 °C. Complex 3
(1 mol%) was found to be the most active and hence was used for probing the scope of possible sub-
strates. Heterocyclic boronic acid and heterocyclic aryl bromides have also been used as substrates to
provide heterocyclic biaryls.
Keywords:
Salicylideneimine ligand
Triphenylphosphine
Palladium(II)
Crystal structure
Suzuki–Miyaura coupling
Ó 2012 Elsevier B.V. All rights reserved.
1. Introduction
[12]. Subsequently, many catalytic systems have been developed
for Suzuki cross-coupling reactions using different palladium cata-
Carbon–carbon coupling reactions particularly with aryl halides
are some of the important processes in chemical industry that con-
stitute a key step in the synthesis of more complex molecules from
simple precursors. In the 1970’s, several such coupling reactions be-
tween aryl halides and aryl magnesium/zinc in the presence of pal-
ladium/nickel complexes have been reported for the synthesis of
biaryls [1–5]. In the later part of the same decade, Suzuki and Miya-
ura reported cross-coupling reactions between alkenylboranes and
various organic halides [6–8], that are effectively catalyzed by a
catalytic amount of [Pd(PPh3)4] in the presence of bases. In 1981,
Suzuki and co-workers disclosed the palladium-catalyzed cross-
coupling reaction of phenylboronic acid with aryl halides in the
presence of bases to produce biaryls [9] and this has proven to be
a quite general technique for carbon–carbon bond formation. The
importance of these powerful cross-coupling synthetic methods
was recognized by the 2010 Nobel Prize for Chemistry being
awarded to Suzuki, Negishi and Heck [10,11]. Many organometallic
reagents undergo similar cross-coupling reactions, but much atten-
tion has recently been focused on the use of organoboronic acids
since they are thermally stable and inert to water and oxygen
lysts such as [Pd(PPh3)4] [13], [Pd(OAc)2] [14], [PdCl2(dppb)] [15],
Pd(0) [16], [Pd(dba)2] [17], [PdCl2(PCy3)2] [18], [PdCl2(PPh3)2]
[19], [PdCl2(dppf)] [20], Pd2(dba)3 [21], Pd nanoparticles [22], Pd-
doped KF/Al2O3 [23], Pd(OAc)2/guanidine [24], Pd/imidazolium salt
[25], etc. Most of these catalysts contain phosphine ligands. Palla-
dium(II) complexes of salicylideneimine ligands have also been
found to be useful as catalysts for Suzuki coupling reactions [26–
30]. But palladium(II) complexes containing both salicylideneimine
and phosphine ligands have rarely been used as catalysts in Suzuki
coupling reactions. At the same time, phosphine-functionalized
Schiff base complexes are known to be efficient catalysts for this
reaction [31]. We disclose herein the synthesis of novel palla-
dium(II) complexes containing both salicylideneimine based tri-
dentate ligand and triphenylphosphine and its catalytic activity in
Suzuki–Miyaura cross coupling reactions. Salicylideneimine based
tridentate ligands employed in this study are shown in Fig. 1. The
same ligands have already been used by us for the synthesis of
Ni(II), Ru(II) and Cu(II) complexes [32–35]. The analogous ONS do-
nor Schiff base ligands formed from 2-oxoquinoline-3-carbalde-
hyde were used for making Pd(II) complexes [36]. All these Schiff
base complexes were found to be good catalysts for various organic
transformations.
⇑
Corresponding author. Tel.: +91 431 2503636; fax: +91 431 2500133.
E-mail address: kar@nitt.edu (R. Karvembu).
0020-1693/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.ica.2012.08.024

392
M. Muthu Tamizh et al. / Inorganica Chimica Acta 394 (2013) 391–400
displacement parameters for the heavy atoms using SHELXL-97 [45]
and the WINGX [46] software package, the solutions were assessed
using tools in PLATON, and thermal ellipsoid plots were produced
using SHELXTL [47]. All H atoms were placed in calculated positions
with a C–H distance of 0.95 Å for the atoms attached to carbon
atoms in the phenyl or imine groups or a C–H distance of 0.96 Å
for the atoms attached to the methyl carbon atom. These atoms
were included in the refinement using the riding model approxi-
mation with Uiso(H) = 1.2Ueq(C) for the H atoms in the phenyl
groups or Uiso(H) = 1.5Ueq(C) for the H atoms in the methyl groups.
For complex 2, the SQUEEZE [48] routine in PLATON was employed to
remove a disordered and partial occupancy CH2Cl2 solvent mole-
cule proximate to an inversion center; the process improved the
R1(obs) value from ca. 0.067 to 0.046.
Fig. 1. Structure of ligands.
2. Experimental
2.4. Synthesis of Pd(II) complexes of type [Pd(L)(PPh3)]
2.1. Materials
Ligand (0.433 mmol) dissolved in CH2Cl2 (10 ml) was added to
the suspension of [Pd(PPh3)4] (0.433 mmol) in ethanol (10 ml),
yielding a dark red solution after stirring at 27 °C for 30 min. The
resulting solutions were evaporated to approximately 3 ml and
cooled. Hexane (20 ml) was then added whereupon the product
complex separated. The reddish brown colored complex was iso-
lated by filtration in air, washed with small amounts of ethanol
and hexane, and dried in vacuo.
Solvents were purified and dried by standard procedures [37].
PdCl2 and salicylaldehyde were purchased from Loba Chemie, India
and later was used after double distillation. 2-Hydroxy-5-methyl-
benzaldehyde, 2-hydroxy-5-methoxybenzaldehyde and 5-chloro-
salicylaldehyde were purchased from Sigma–Aldrich and were
used without further purification. 5-Bromo-2-hydroxybenzalde-
hyde and 2-hydroxy-1-naphthaldehyde were purchased from
Merck and Alfa-Aesar, respectively. o-Aminothiophenol was pur-
chased from S.D. Fine Chemicals, India. The metal precursor
[Pd(PPh3)4] was prepared according to the literature method
[38]. Schiff base ligands were prepared by the condensation be-
tween salicylaldehyde or its derivatives or 2-hydroxy-1-naphthal-
dehyde and o-aminothiophenol in ethanol [39,40].
2.4.1. [Pd(LS)(PPh3)] (1)
[Pd(LS)(PPh3)] (1) is prepared from [Pd(PPh3)4] (0.5 g;
0.433 mmol) and H2LS (0.099 g; 0.433 mmol). Yield: 170 mg
(66%). M.p. 242 °C (dec.). Anal. Calc. for C31H24NPdOPS: C, 62.5;
H, 4.1; N, 2.4; S, 5.4. Found: C, 62.1; H, 4.0; N, 2.5; S, 5.6%. UV–
Vis (CH2Cl2), kmax/nm
(54205), 299 (21060), 314 (16580), 328 (10195), 433 (11120).
FT-IR (KBr disk), cmꢀ1
(C@N) 1605, (C–O) 1332, (C–S) 750,
(Pd–O) 531, (Pd–N) 464, bands due to PPh3 1434, 1098, 694.
(e
/dm3 molꢀ1 cmꢀ1): 231 (48225), 246
2.2. Physical measurements
:
m
m
m
Elemental analyses for C, H, N and S were carried out on Ther-
moflash EA1112 series elemental analyzer. Electronic spectra were
recorded on a PerkinElmer Lambda 25 UV–Vis double beam spec-
trophotometer in CH2Cl2 solvent in the 200–800 nm range. FT-IR
spectra were obtained on a PerkinElmer Spectrum 100 FT-IR spec-
trophotometer as KBr pellet in the frequency range of 400–
4000 cmꢀ1. The 1H and 13C{1H} NMR spectra were recorded in
CDCl3 or CD2Cl2 solution on Bruker Avance 500 spectrometer at
500.13 (1H) and 125.76 (13C) MHz using TMS as internal standard.
31P{1H} NMR spectra were recorded in CDCl3 solution on Bruker
Avance 500 spectrometer at 202.46 (31P) MHz using H3PO4 as
external standard. The 1H–1H COSY 500.13 (1H), 1H–13C HSQC
500.13 (1H) and 1H–31P HMBC 400.13 (1H) spectra were obtained
by using the standard Bruker pulse programs. Gas chromatography
m
m
1H NMR (500 MHz, CDCl3): d = 6.64–6.71 (m, 2H, H2 and H4),
7.00–7.09 (m, 2H, H10 and H11), 7.30 (t, J = 8.5 Hz, 1H, H3),
7.42–7.53 (m, 11H, Hm, Hp and H5), 7.71–7.84 (m, 7H, Ho and
H9), 8.95 (d, J = 15.5 Hz, 1H, H7) ppm. 13C{1H} NMR (125.76 MHz,
CDCl3): d = 114.91 (C4), 115.32 (C9), 119.44 (C6), 122.10 (C2),
122.29 (C10), 127.11 (C11), 128.28 (d, J = 11 Hz, Cm), 129.06 (d,
J = 52 Hz, Cq), 129.26 (C12), 130.99 (d, J = 2.5 Hz, Cp), 134.90 (d,
J = 11 Hz, Co), 135.14 (C5), 135.81 (C3), 143.95 (d, J = 8 Hz, C13),
148.40 (d, J = 2.5 Hz, C8), 153.65 (C7), 165.11 (C1) ppm. 1P{1H}
NMR (202.46 MHz, CDCl3): d = 28.23 (s, 1P) ppm.
2.4.2. [Pd(LM)(PPh3)] (2)
[Pd(LM)(PPh3)] (2) is prepared from [Pd(PPh3)4] (0.25 g;
0.216 mmol) and H2LM (0.0526 g; 0. 0.216 mmol). Yield: 60 mg
(46%). M.p. 239 °C (dec.). Anal. Calc. for C32H26NPdOPS: C, 63.0;
H, 4.3; N, 2.3; S, 5.3. Found: C, 62.9; H, 4.4; N, 2.3; S, 5.3%. UV–
was undertaken using
a
Shimadzu GC-2010 with
a
60 m ꢁ 0.32 mm Restek RtxÒ-5 column.
2.3. X-ray crystallography
Vis (CH2Cl2) kmax/nm
(48855), 300 (18605), 317 (14025), 332 (8265), 442 (8950). FT-IR
(KBr disk), cmꢀ1
(C@N) 1589, (C–O) 1324, (C–S) 750, (Pd–O)
531,
(Pd–N) 467, bands due to PPh3 1433, 1096, 694. 1H NMR
(e
/dm3 molꢀ1 cmꢀ1): 231 (43925), 247
Slow crystallization from CH2Cl2/Et2O yielded red crystals of 1,
2 and 6. Each subject crystal was covered in NujolÒ, mounted on a
goniometer head and rapidly placed in the dry N2 cold-stream of
the low-temperature apparatus (Kryoflex) attached to the diffrac-
tometer. The data were collected using the SMART software [41] on
a Bruker APEX CCD diffractometer using a graphite monochroma-
:
m
m
m
m
m
(500 MHz, CDCl3): d = 2.28 (s, 3H, H40), 6.61 (d, J = 9 Hz, 1H, H2),
6.99–7.08 (m, 2H, H10 and H11), 7.14 (dd, J = 8.7, 2.4 Hz, 1H, H3),
7.25 (d, J = 1.6 Hz, 1H, H5), 7.39–7.47 (m, 7H, Hm and H12),
7.47–7.53 (m, 3H, Hp), 7.71 (dd, J = 7.8, 1.9 Hz, 1H, H9), 7.73–
7.80 (m, 6H, Ho), 8.90 (d, J = 15.5 Hz, 1H, H7) ppm. 13C{1H} NMR
(125.76 MHz, CDCl3): d = 20.14 (C40), 115.23 (C9), 118.91 (C6),
121.84 (C2), 122.24 (C10), 123.62 (C4), 126.94 (C11), 128.26 (d,
J = 12 Hz, Cm), 129.19 (d, J = 51 Hz, Cq), 129.30 (C12), 130.95 (d,
J = 2 Hz, Cp), 134.52 (C5), 134.91 (d, J = 11 Hz, Co), 137.06 (C3),
143.84 (d, J = 7.5 Hz, C13), 148.57 (d, J = 2 Hz, C8), 153.42 (C7),
tor with Mo K
a radiation (k = 0.71073 Å). A hemisphere of data
was collected using a counting time of 10 or 30 s per frame at
ꢀ100 °C. Data reductions were performed using the SAINT-PLUS soft-
ware [42] and the data were corrected for absorption using SADABS
[43]. Each structure was solved by direct methods using SIR97
[44] and refined by full-matrix least-squares on F2 with anisotropic

M. Muthu Tamizh et al. / Inorganica Chimica Acta 394 (2013) 391–400
393
163.61 (C1) ppm. 31P{1H} NMR (202.46 MHz, CDCl3): d = 28.14 (s,
1P) ppm.
(d, J = 2 Hz, C8), 152.52 (C7), 163.95 (C1) ppm. 1P{1H} NMR
(202.46 MHz, CDCl3): d = 28.06 (s, 1H) ppm.
2.4.3. [Pd(LO)(PPh3)] (3)
2.4.6. [Pd(LN)(PPh3)] (6)
[Pd(LO)(PPh3)] (3) is prepared from [Pd(PPh3)4] (0.25 g;
0.216 mmol) and H2LO (0.0561 g; 0. 0.216 mmol). Yield: 65 mg
(48%). M.p. 242 °C (dec.). Anal. Calc. for C31H24NPd2OPS: C, 61.4;
H, 4.2; N, 2.2; S, 5.1. Found: C, 61.4; H, 4.2; N, 2.3; S, 5.2%. UV–
[Pd(LN)(PPh3)] (6) is prepared from [Pd(PPh3)4] (0.5 g;
0.433 mmol) and H2LN (0.121 g; 0.433 mmol). Yield: 173 mg
(62%). M.p. 247 °C. Anal. Calc. for C35H26NPdOPS: C, 65.1; H, 4.1;
N, 2.2; S, 5.0. Found: C, 65.0; H, 4.1; N, 2.2; S, 5.0%. UV–Vis (CH2Cl2)
(e
/dm3 molꢀ1 cmꢀ1): 229 (44380), 247
kmax/nm
(36630), 324 (14370), 340 (10455), 451 (12065), 472 (9900). FT-
IR (KBr disk), cmꢀ1
(C@N) 1614, (C–O) 1339, (C–S) 742,
(Pd–O) 532, (Pd–N) 457, bands due to PPh3 1435, 1095, 692.
(e
/dm3 molꢀ1 cmꢀ1): 232 (54300), 248 (56085), 271
Vis (CH2Cl2) kmax/nm
(47085), 302 (18110), 321 (11950), 338 (6420), 465 (8350). FT-IR
(KBr disk), cmꢀ1
(C@N) 1591, (C–O) 1315, (C–S) 746, (Pd–O)
530,
(Pd–N) 457, bands due to PPh3 1433, 1098, 693. 1H NMR
:
m
m
m
m
:
m
m
m
m
m
m
(500 MHz, CDCl3): d = 3.79 (s, 3H, H40), 6.63 (d, J = 9.5 Hz, 1H,
H2), 6.87 (d, J = 3.2 Hz, 1H, H5), 6.99–7.08 (m, 3H, H3, H10 and
H11), 7.40–7.47 (m, 7H, Hm and H12), 7.47–7.53 (m, 3H, Hp),
7.71–7.80 (m, 7H, Ho and H9), 8.92 (d, J = 15.5 Hz, 1H, H7) ppm.
13C{1H} NMR (125.76 MHz, CDCl3): d = 56.07 (C40), 114.17 (C5),
115.23 (C9), 117.73 (C6), 122.23 (C10), 123.12 (C2), 126.49 (C3),
128.25 (d, J = 11 Hz, Cm), 129.14 (d, J = 51 Hz, Cq), 129.35 (C12),
130.97 (d, J = 2 Hz, Cp), 134.91 (d, J = 11 Hz, Co), 143.90 (d,
J = 8 Hz, C13), 148.48 (d, J = 2 Hz, C8), 149.14 (C4), 152.77 (C7),
161.24 (C1) ppm. 31P{1H} NMR (202.46 MHz, CDCl3): d = 29.50 (s,
1P) ppm.
1H NMR (500 MHz, CDCl3): d = 6.80 (d, J = 9.1 Hz, 1H, H2), 7.06–
7.13 (m, 2H, H10 and H11), 7. 30 (t, J = 6.9 Hz, 1H, H30), 7.42–
7.60 (m, 11H, Hm, Hp, H60 and H12), 7.62–7.73 (m, 2H, H3, H40),
7.75–7.89 (m, 7H, Ho and H9), 8.23 (d, J = 8.5 Hz, 1H, H50), 9.95
(d, J = 15.7 Hz, 1H, H7) ppm. 13C{1H} NMR (125.76 MHz, CDCl3):
d = 109.74 (C6), 115.38 (C9), 119.56 (C50), 122.42 (C10), 122.48
(C30), 125.15 (C2), 126.46 (C11), 127.14 (C40), 127.67 (C60),
128.34 (d, J = 11 Hz, Cm), 129.12 (C12), 129.17 (d, J = 51 Hz, Cq),
129.21 (C40), 131.01 (d, J = 2.5 Hz, Cp), 134.86 (d, J = 11 Hz, Co),
135.35 (C5), 135.77 (C3), 143.06 (d, J = 7.5 Hz, C13), 147.26 (C7),
149.86 (d, J = 2 Hz, C8), 165.87 (C1) ppm. 1P{1H} NMR
(202.46 MHz, CDCl3): d = 28.06 (s, 1P) ppm.
2.4.4. [Pd(LC)(PPh3)] (4)
[Pd(LC)(PPh3)] (4) is prepared from [Pd(PPh3)4] (0.5 g;
0.433 mmol) and H2LC (0.114 g; 0.433 mmol). Yield: 145 mg
(53%). M.p. 246 °C (dec.). Anal. Calc. for C31H23ClNPdOPS: C, 59.1;
H, 3.7; N, 2.2; S, 5.1. Found: C, 59.0; H, 3.7; N, 2.3; S, 5.1%. UV–
2.5. General procedure for the Suzuki–Miyaura cross coupling reaction
To the catalyst (1.0 mol%) dissolved in 1 ml DMAc, aryl bromide
(1.0 mmol), phenyl boronic acid (1.5 mmol) in 1 ml ethanol, K2CO3
(2.0 mmol) in 1 ml water and DMAc (5 ml) were all added. The
mixture was heated at 100 °C for 12 h. Then, the mixture was
cooled, water was added and the product was extracted with
ethylacetate. The organic layer was washed with brine, dried over
Na2SO4, filtered, passed through celite, and analyzed by GC. Yields
were based on corresponding aryl bromides.
Vis (CH2Cl2) kmax/nm
(56675), 299 (21775), 317 (16595), 331 (11580), 442 (11875).
FT-IR (KBr disk), cmꢀ1
(C@N) 1602, (C–O) 1320, (C–S) 741,
(Pd–O) 530, (Pd–N) 468, bands due to PPh3 1434, 1096, 693.
(e
/dm3 molꢀ1 cmꢀ1): 230 (50590), 248
:
m
m
m
m
m
1H NMR (500 MHz, CDCl3, 25 °C): d = 6.60 (d, J = 9.1 Hz, 1H, H2),
6.99–7.09 (m, 2H, H10 and H11), 7.19 (dd, J = 9.1, 2.8 Hz, 1H, H3),
7.40–7.47 (m, 8H, Hm, H5 and H12), 7.48–7.54 (m, 3H, Hp), 7.69
(d, J = 8.2 Hz, 1H, H9), 7.71–7.79 (m, 6H, Ho), 8.85 (d, J = 15.1 Hz,
1H, H7) ppm. 13C{1H} NMR (125.76 MHz, CDCl3): d = 115.41 (C9),
118.79 (C6), 119.96 (C4), 122.43 (C10), 123.64 (C2), 127.44 (C11),
128.32 (d, J = 12 Hz, Cm), 128.90 (d, J = 52 Hz, Cq), 129.30 (C12),
131.09 (d, J = 2 Hz, Cp), 133.49 (C5), 134.86 (d, J = 12 Hz, Co),
134.98 (C3), 144.38 (d, J = 7.5 Hz, C13), 148.04 (d, J = 2.5 Hz, C8),
152.59 (C7), 163.67 (C1) ppm. 13C-DEPT 135 NMR (125.76 MHz,
CDCl3): d = 115.41 (C9), 122.43 (C10), 123.62 (C2), 127.44 (C11),
128.33 (d, J = 12 Hz, Cm), 129.30 (C12), 131.09 (d, J = 2 Hz, Cp),
133.49 (C5), 134.85 (d, J = 12 Hz, Co), 152.59 (C7) ppm. 1P{1H}
NMR (202.46 MHz, CDCl3, 25 °C): d = 29.48 (s, 1P) ppm.
3. Results and discussion
3.1. Synthesis
The syntheses of palladium(II) complexes are summarized in
Scheme 1. The desired complexes of the type [Pd(L)(PPh3)] (1-6)
(L = dianion of tridentate ONS donor Schiff base ligand) have been
prepared from the reactions between [Pd(PPh3)4] and the
respective ligand (H2LS, H2LM, H2LO, H2LC, H2LB or H2LN) in etha-
nol–dichloromethane mixture at 25–27 °C. The palladium(II) com-
plexes were characterized by elemental analysis and spectroscopic
methods (FT-IR, UV–Vis and 1H, 13C{1H}, and 31P{1H} NMR). Struc-
tures of representative complexes 1, 2 and 6 were examined by X-
ray crystallography. The data show that a single Schiff base ligand
displaces three triphenylphosphine ligands in the precursor. The
coordination behavior of Schiff base ligands towards palladium(II)
is very similar to that observed in nickel(II), copper(II) and ruthe-
nium(II) complexes [32–35]. All the palladium(II) complexes are
red in color and soluble in common organic solvents.
2.4.5. [Pd(LB)(PPh3)] (5)
[Pd(LB)(PPh3)] (5) is prepared from [Pd(PPh3)4] (0.5 g;
0.433 mmol) and H2LB (0.133 g; 0.433 mmol). Yield: 143 mg
(49%). M.p. 252 °C (dec.). Anal. Calc. for C31H23BrNPdOPS: C, 55.2;
H, 3.4; N, 2.1; S, 4.8. Found: C, 55.1; H, 3.5; N, 2.1; S, 4.6%. UV–
Vis (CH2Cl2) kmax/nm (
(49930), 300 (17900), 316 (12885), 332 (6885), 443 (9555). FT-IR
(KBr disk), cmꢀ1
(C@N) 1597, (C–O) 1317, (C–S) 747, (Pd–O)
531,
(Pd–N) 467, bands due to PPh3 1434, 1098, 694. 1H NMR
e
/dm3 molꢀ1 cmꢀ1): 230 (41880), 248
:
m
m
m
m
m
(500 MHz, CDCl3): d = 6.55 (d, J = 9.1 Hz, 1H, H2), 6.99–7.10 (m,
2H, H10 and H11), 7.30 (dd, J = 9.1, 2.5 Hz, 1H, H3), 7.41–7.48 (m,
7H, Hm and H12), 7.49–7.55 (m, 3H, Hp), 7.58 (d, J = 2.8 Hz, 1H,
H5), 7.70 (d, J = 7.9 Hz, 1H, H9), 7.72–7.78 (m, 6H, Ho), 8.85 (d,
J = 15.1 Hz, 1H, H7) ppm. 13C{1H} NMR (125.76 MHz, CDCl3):
d = 105.43 (C4), 115.41 (C9), 120.88 (C6), 122.44 (C10), 124.04
(C2), 127.47 (C11), 128.33 (d, J = 11 Hz, Cm), 128.83 (d, J = 52 Hz,
Cq), 129.29 (C12), 131.10 (d, J = 2 Hz, Cp), 134.85 (d, J = 12 Hz,
Co), 136.71 (C5), 137.51 (C3), 144.34 (d, J = 7.5 Hz, C13), 147.99
3.2. FT-IR spectra
A strong band around 1615 cmꢀ1 due to
m(C@N) of the ligands
shifts to 1589–1614 cmꢀ1 in the complexes, indicating the azome-
thine coordination to palladium through nitrogen [49]. The coordi-
nation of azomethine nitrogen atom is further supported by the
presence of a new band in the range 457–468 cmꢀ1, assignable to
m
(Pd–N) [50]. All the ligands exhibited a medium intensity band
in the region 1304–1320 cmꢀ1 due to phenolic
m
(C–O). This band

394
M. Muthu Tamizh et al. / Inorganica Chimica Acta 394 (2013) 391–400
Scheme 1. Synthesis of the palladium(II) complexes [R = H (1), CH3 (2), OCH3 (3), Cl (4) or Br (5)].
became shifted to higher wave number and appeared in the region
1315–1339 cmꢀ1 in palladium complexes, suggesting the coordi-
nation of phenolic oxygen atom to palladium. Further evidence
for oxygen coordination arises from the appearance of a new band
around 530 cmꢀ1 in all the palladium complexes, which are assign-
229–472 nm and the spectra are given in Fig. S1 (Online Supple-
mentary material). The bands appeared in the region 229–
302 nm have been assigned to intra-ligand transitions [32]. More-
over, a set of less intense bands in the region 314–340 nm have
been ascribed to metal-to-ligand charge transfer (MLCT) transi-
tions [54,55]. The electronic spectra of palladium complexes also
showed bands attributable to d–d spin allowed transitions in the
region 442–465 nm [56].
able to
m(Pd–O) [51]. A weak band observed in the region 750–
757 cmꢀ1 corresponding to
m(C–S) in the ligands, shifts to lower
wave number (741–750 cmꢀ1) which supports coordination of
thiolato sulfur atom with the palladium center [52]. Three bands
are observed around 1434, 1096 and 693 cmꢀ1 for the coordinated
triphenylphosphine molecule [53].
3.4. NMR spectra
In their 1H NMR spectra, each of the palladium(II) complexes
(1–6) exhibited multiplets in the region 6.61–7.89 ppm for the aro-
matic protons of the coordinated Schiff base and for those of tri-
phenylphosphine. An assignment to individual aromatic protons
has been made based on 1H–1H COSY spectrum of 4 and is given
3.3. Electronic spectra
Electronic spectra of each of the palladium complexes recorded
in dichloromethane solution showed six bands in the region
Fig. 2. Molecular structure of [Pd(LS)(PPh3)] (1) showing 50% displacement ellipsoids.

M. Muthu Tamizh et al. / Inorganica Chimica Acta 394 (2013) 391–400
395
Fig. 3. Molecular structure of [Pd(LM)(PPh3)] (2) showing 50% displacement ellipsoids.
in Online Supplementary material (Fig. S2). The absence of reso-
nances due to phenolic and thiolato hydrogen atoms indicates
the deprotonation of these groups and the Schiff base behaves as
dianionic ligands. A doublet (4J = 15.13–15.78 Hz) observed in the
1H NMR spectra of all the complexes in the region 8.85–
9.95 ppm has been assigned to the HC@N resonance. 1H–31P HMBC
spectrum of 1 (Fig. S3) revealed that this doublet is due to the four
bond coupling of phosphorus in triphenylphosphine with the azo-
methine proton [57]. The coupling between the phosphorus atom
and the aromatic protons of the phenyl rings attached to it is also
identified by the 1H–31P HMBC spectrum. Complexes 2 and 3 each
exhibit a singlet at 2.28 and 3.79 ppm that corresponds to methyl
and methoxy protons respectively. In the 13C NMR spectra of all the
complexes, azomethine carbon resonances are observed in the
148.08–149.08 ppm range [58]. The resonances for the C–S, C–N,
C–O and C–P carbon atoms are observed in the regions 143.03–
144.41, 147.99–149.86, 161.24–165.87 and 128.20–134.95 ppm,
respectively [59,60]. The methyl and methoxy carbon atoms pres-
ent in complexes 2 and 3 exhibited signals at 20.14 and 56.07 ppm,
respectively. The assignment of all the aromatic carbon resonances
is made with the help of 1H–13C HSQC. 31P NMR spectra of all the
complexes exhibited a singlet around 28 ppm suggesting the pres-
ence of one coordinated triphenylphosphine in each of these palla-
dium(II) complexes [61].
monoclinic and crystallizes in the space group P21/c with Z = 4. The
palladium ion in each complex is coordinated by one Schiff base
anion via the O, N and S atoms, producing a six membered chelate
ring with the O and N atoms and a five membered ring with the S
and N atoms. The fourth coordination site of the palladium in the
complexes is occupied by the P atom of the triphenylphosphine li-
gand. The angles between adjacent atoms in the coordination
sphere of palladium in 1, 2 and 6 are close to the ideal value of
90°, with most notable deviation being the O(1)–Pd(1)–P(1) angle
of 83.67(8)° in complex 1. The structures of 1, 2 and 6 adopt a near
square planar geometry with O(1)–Pd(1)–S(1) and N(1)–Pd(1)–
P(1) bond angles in the ranges 175.72(4)–179.03(9)° and
176.44(8)–177.57(5)°, respectively. The Pd(1)–O(1), Pd(1)–N(1),
Pd(1)–S(1) and Pd(1)–P(1) bond lengths in 1, 2 and 6 are in the
ranges 2.019(2)–2.046(3), 2.0359(17)–2.078(3), 2.2502(10)–
2.2771(10) and 2.2794(9)–2.3056(9) Å, respectively, which are in
agreement with the reported values for such distances [31,57]. It
should be noted, however, that the Pd(1)–N(1) bond length in each
of the complexes is longer than the value of 2.01 Å predicted on the
basis of the covalent radii of N (sp2) and palladium (0.70 and
1.30 Å, respectively) [62], reflecting the strong trans influence of
the phosphine ligand [63]. Conversely, the Pd(1)–P(1) bond length
in each of these complexes is shorter than the sum of the single
bond radii for palladium and phosphorus (2.41 Å), suggesting some
partial multiple bond character between the palladium and phos-
phorus atom [64]. The sum of the bond angles around N(1) (ca.
359°) in these complexes is in accordance with sp2 hybridization
[65].
3.5. X-ray crystallography
The structures of 1, 2 and 6 were determined by single crystal
X-ray diffraction method. Thermal ellipsoid plots of complexes 1,
2 and 6 are shown in Figs. 2–4 respectively. The crystallographic
and measurement data are shown in Table 1. Selected bond lengths
and bond angles are listed in Table 2. Compounds 1 and 2 are tri-
3.6. Catalytic activity
All the palladium complexes (1–6) can be stored for prolonged
periods and are air, light and moisture stable. Given these
ꢀ
clinic and crystallize in the space group P1 with Z = 2, whereas 6 is

396
M. Muthu Tamizh et al. / Inorganica Chimica Acta 394 (2013) 391–400
Fig. 4. Molecular structure of [Pd(LN)(PPh3)] (6) showing 50% displacement ellipsoids.
Table 1
Crystal data, data collection and structure refinement parameters for [Pd(LS)(PPh3)] (1), [Pd(LM)(PPh3)] (2) and [Pd(LN)(PPh3)] (6).
Parameters
[Pd(LS)(PPh3)] (1)
31H24NPdOPS
595.98
dark red
block
[Pd(LM)(PPh3)] (2)
[Pd(LN)(PPh3)] (6)
Empirical formula
Formula weight
Color
C
C32H26NPdOPS
610.01
dark red
C35H26NPdOPS
646.06
dark red
block
Habit
block
Crystal dimension (mm)
Crystal system
Space group
a (Å)
b (Å)
c (Å)
0.20 ꢁ 0.20 ꢁ 0.20
0.20 ꢁ 0.10 ꢁ 0.10
0.60 ꢁ 0.40 ꢁ 0.30
monoclinic
P21/c
10.7831(12)
29.070(3)
9.0339(10)
90
104.2240(10)
90
2745.0(5)
4
triclinic
triclinic
ꢀ
ꢀ
P1
P1
9.0411(15)
10.1247(17)
14.7840(2)
101.249(2)
92.357(2)
96.148(2)
1317.0(4)
2
9.0028(7)
12.1482(9)
14.1443(11)
73.7480(10)
84.5460(10)
70.2210(10)
1397.5
a
(°)
b (°)
c
(°)
V (Å3)
Z
2
T (K)
173(2)
1.503
0.869
604
173(2)
1.450
0.821
620
173(2)
1.421
0.841
1312
Dcalc (Mg/m3)
Absorption coefficient (mmꢀ1
F(000)
)
k (Mo K
h Range (°)
a
) (Å)
0.71073
1.41–27.43
0.71073
1.50–27.49
0.71073
1.40–27.50
Scan type
x
, /
x
, /
x, /
Index ranges
Reflections collected/unique
Rint
Refinement method
Diffractometer
Absorption correction
ꢀ11 6 h 6 11, ꢀ12 6 k 6 12, ꢀ18 6 l 6 18 ꢀ11 6 h 6 11, ꢀ15 6 k 6 15, ꢀ18 6 l 6 18 ꢀ13 6 h 6 13, ꢀ37 6 k 6 37, ꢀ11 6 l 6 11
13594/5497
0.0331
15750/6191
0.0418
30517/6209
0.0210
full-matrix least-squares on F2
Bruker SMART APEX CCD
multi-scan SADABS
Final R indices R1/wR2 [I > 2
R1/wR2 (all data)
r
(I)] 0.0359/0.0928
0.0490/0.1200
1.085
0.0458/0.1101
0.0591/0.1160
1.035
0.0257/0.0721
0.0308/0.0876
1.240
Goodness-of-fit on F2
D
qmax and
D
qmin (e Åꢀ3
)
0.654 and ꢀ0.837
0.781 and ꢀ0.583
0.898 and ꢀ0.515
Data/restraints/parameters
5497/0/325
6191/0/334
6209/0/365
favorable properties, the catalytic activity of each of these com-
plexes in the Suzuki–Miyaura coupling reaction of 4-bromotoluene
with phenylboronic acid was investigated in DMAc–H2O mixture
at 100 °C with 1 mol% of catalyst and results are summarized in
Table 3. It was found that the use of complex 3 as a catalyst pro-
vided good yield of biaryl (92%) after 12 h without requiring the
use of an inert atmosphere. Hence, complex 3 was selected as
the catalyst in order to assess the scope of substrates that may

M. Muthu Tamizh et al. / Inorganica Chimica Acta 394 (2013) 391–400
397
Table 2
Selected bond lengths (Å) and angles (°).
[Pd(LS)(PPh3)] (1)
[Pd(LM)(PPh3)] (2)
[Pd(LN)(PPh3)] (6)
Pd(1)–O(1)
Pd(1)–N(1)
Pd(1)–S(1)
Pd(1)–P(1)
O(1)–C(1)
N(1)–C(7)
N(1)–C(8)
S(1)–C(13)
P(1)–C(14)
P(1)–C(20)
P(1)–C(26)
C(1)–C(6)
C(6)–C(7)
C(8)–C(13)
C(4)–X
2.046(3)
2.078(3)
2.2771(10)
2.3056(9)
1.326(4)
1.317(5)
1.447(5)
1.789(4)
1.845(3)
1.848(4)
1.853(4)
1.431(5)
1.448(5)
1.424(5)
0.95 (X = H)
2.019(2)
2.053(3)
2.2502(10)
2.2794(9)
1.301(4)
1.302(4)
1.429(5)
1.754(4)
1.817(4)
1.826(4)
1.836(4)
1.415(5)
1.422(5)
1.394(5)
1.517(5) (X = C(40)
2.0193(14)
2.0359(17)
2.2530(6)
2.2815(6)
1.293(2)
1.306(3)
1.430(3)
1.755(2)
1.820(2)
1.828(2)
1.820(2)
1.419(3)
1.418(3)
1.398(3)
1.409(3) (X = C(40)
O(1)–Pd(1)–S(1)
N(1)–Pd(1)–P(1)
O(1)–Pd(1)–N(1)
N(1)–Pd(1)–S(1)
O(1)–Pd(1)–P(1)
S(1)–Pd(1)–P(1)
Pd(1)–O(1)–C(1)
Pd(1)–N(1)–C(7)
Pd(1)–N(1)–C(8)
Pd(1)–S(1)–C(13)
Pd(1)–P(1)–C(14)
Pd(1)–P(1)–C(20)
Pd(1)–P(1)–C(26)
C(14)–P(1)–C(20)
C(20)–P(1)–C(26)
C(20)–P(1)–C26)
C(1)–C(6)–C(7)
C(6)–C(7)–N(1)
C(7)–N(1)–C(8)
C(8)–C(9)–S(1)
179.03(9)
176.44(8)
93.55(11)
86.47(8)
83.67(8)
96.35(4)
125.5(2)
121.3(2)
117.9(2)
98.73(13)
120.46(12)
106.57(11)
112.77(11)
105.78(16)
104.83(16)
105.31(16)
125.5(3)
177.98(8)
176.84(8)
92.87(11)
86.37(8)
90.07(7)
90.72(4)
126.1(2)
122.0(2)
117.4(2)
98.48(13)
114.47(12)
113.93(12)
115.07(12)
103.42(16)
103.92(17)
104.70(16)
125.4(3)
175.72(4)
177.57(5)
91.33(6)
86.15(5)
91.08(4)
91.43(2)
125.73(13)
122.39(14)
117.24(13)
98.46(7)
111.67(7)
113.96(7)
114.51(7)
105.57(10)
104.66(9)
105.63(9)
122.86(18)
128.72(19)
119.84(18)
120.27(16)
129.0(3)
120.8(3)
120.5(3)
128.6(3)
120.6(3)
121.2(3)
Table 3
Evaluation of complexes 1–6 as catalysts for the Suzuki–Miyaura cross-coupling of 4-bromotoluene with phenylboronic acid.a
Complex
Yield (%)b
1
2
3
4
5
6
[Pd(PPh3)4]
83
87
86
92
85
87
86
a
Reaction conditions: 4-bromotoluene (1 mmol), phenylboronic acid (1.5 mmol) in 1 ml of ethanol, K2CO3 (2 mmol) in 1 ml of H2O, catalyst (1 mol%) in 1 ml of DMAc,
additional DMAc (5 ml), stirring for 12 h, 100 °C.
b
Yield is determined by GC with area normalization.
be coupled using this system and the cross-coupling reactions be-
tween various aryl bromides and arylboronic acids were investi-
gated. Interestingly, the new palladium(II) complexes exhibited
better catalytic activity compared to its precursor, [Pd(PPh3)4] (Ta-
ble 3). The reaction between 4-bromobenzene and phenylboronic
acid proceeded smoothly to yield 96% of biphenyl (Table 4, entry
1). Of course, other reported palladium complexes for this reaction
are more efficient or comparable with the complexes presented in
this paper [31,66,67]. The coupling reaction of aryl bromides bear-
ing an electron donating group, such as CH3 and OCH3, with phen-
ylboronic acid produced biaryls in good yields (92% and 87%)
(Table 4, entries 2 and 3). But, 3,5-dimethyl-1-bromobenzene gen-
erated the substituted biphenyl in only 65% yield (Table 4, entry 4).
Electron deficient aryl bromides, such as 4-bromoacetophenone, 4-
bromobenzaldehyde, 4-bromobenzoinc acid, 4-trifluoromethyl-1-
bromobenzene, 4-nitro-1-bromobenzene and 2-bromonaphtha-
lene, reacted with phenylboronic acid to produce biaryls in high
yield, ranging from 84% to 98% (Table 4, entries 5–10) under the
same reaction conditions. Using this methodology, the coupling
between aryl bromides and phenylboronic acid that contain elec-
tron-donating as well as electron-withdrawing groups, proceeded
efficiently to afford the corresponding products. However there
are some systems in which the electronic effect of substituents
had a great influence on the efficacy of the coupling reaction
[28,68], which hinders synthetic applicability of those approaches.
When heterocyclic aryl halides were used for cross coupling with
phenyl boronic acid using catalyst 3, a decrease in the yield of
product (to between 69% and 84%) was observed; although these

398
M. Muthu Tamizh et al. / Inorganica Chimica Acta 394 (2013) 391–400
Table 4
Yields from Suzuki–Miyaura cross-coupling reactions catalyzed by complex 3.a
Entry
1
ArB(OH)2
Ar–X
Product
Yieldb (%)
96
2
3
4
92 (86)c
87 (78)
65 (55)
5
6
7
97 (95)
98 (90)
93 (92)
8
9
84 (68)
98 (95)
10
11
94 (89)
80
12
13
84 (75)
72d
14
15
69d
58

M. Muthu Tamizh et al. / Inorganica Chimica Acta 394 (2013) 391–400
399
Table 4 (continued)
Entry
16
ArB(OH)2
Ar–X
Product
Yieldb (%)
78d
a
Reaction conditions: 4-bromoarene (1 mmol), arylboronic acid (1.5 mmol), catalyst 3 (1 mol%), additional DMAc (5 ml), stirring for 12 h, 100 °C.
b
c
Yield is determined by GC with area normalization.
Isolated yields are given in parenthesis.
Yield is determined by GC–MS.
d
[3] K.M. Tamao, A.N. Miyake, T. Matsuda, Y. Kiso, M. Kumada, Chem. Lett. 4 (1975)
133.
yields are lower than those presented above, they are still reason-
ably good (Table 4, entries 12–14). In fact, the lowest yield was
found in the reaction of 2-bromopyridine with pyridine-3-boronic
acid to produce isonicoteine in 58% yield (Table 4, entry 15); we
postulate that the low yield may be due to chelating ability of
isonicoteine with the metal which has the capacity to alter the nat-
ure of catalyst. Reaction of 2-bromo naphthalene with pyridine-3-
boronic acid gave product in 78% yield (Table 4, entry 16). Palla-
dium black was observed in all the present coupling reactions.
Hence, the catalysis may not be true homogeneous [69].
[4] A. Sekiya, N. Ishikawa, J. Organomet. Chem. 118 (1976) 349.
[5] E. Negishi, A.O. King, N. Okukado, J. Org. Chem. 42 (1977) 1821.
[6] N. Miyaura, K. Yamada, A. Suzuki, Tetrahedron Lett. 20 (1979) 3437.
[7] N. Miyaura, A. Suzuki, Chem. Commun. (1979) 866.
[8] N. Miyaura, T. Yano, A. Suzuki, Tetrahedron Lett. 21 (1980) 2865.
[9] N. Miyaura, T. Yanagi, A. Suzuki, Synth. Commun. 11 (1981) 513.
[10] A. Suzuki, Angew. Chem., Int. Ed. Engl. 50 (2011) 6722.
[11] T.J. Colacot, Platinum Met. Rev. 55 (2011) 84.
[12] N. Miyaura, A. Suzuki, Chem. Rev. 95 (1995) 2457.
[13] A. Bahl, W. Grahn, S. Stadler, F. Feiner, G. Bourhill, C. Bräuchle, A. Reisner, P.G.
Jones, Angew. Chem., Int. Ed. Engl. 34 (1995) 1485.
[14] M. Beller, J.G.E. Krauter, A. Zapf, Angew. Chem., Int. Ed. Engl. 36 (1997) 772.
[15] K. Jones, M. Keenan, F. Hibbert, Synlett 1996 (1996) 509.
[16] R. Dalessio, A. Rossi, Synlett 1996 (1996) 513.
[17] M.B. Goldfinger, K.B. Crawford, T.M. Swager, J. Org. Chem. 63 (1998) 1676.
[18] F. Firooznia, C. Gude, K. Chan, Y. Satoh, Tetrahedron Lett. 39 (1998) 3985.
[19] M.B. Goldfinger, K.B. Crawford, T.M. Swager, J. Am. Chem. Soc. 119 (1997)
4578.
[20] T. Ishiyama, Y. Itoh, T. Kitano, N. Miyaura, Tetrahedron Lett. 38 (1997) 3447.
[21] C. Zhang, J. Huang, M.L. Trudell, S.P. Nolan, J. Org. Chem. 64 (1999) 3804.
[22] M. Perez-Lorenzo, J. Phys. Chem. Lett. 3 (2012) 167.
[23] G.W. Kabalka, R.M. Pagni, C.M. Hair, Org. Lett. 1 (1999) 1423.
[24] S. Li, Y. Lin, J. Cao, S. Zhang, J. Org. Chem. 72 (2007) 4067.
[25] G.A. Grasa, M.S. Viciu, J. Huang, C. Zhang, M.L. Trudell, S.P. Nolan,
Organometallics 21 (2002) 2866.
[26] E. Tas, A. Kilic, M. Durgun, I. Yilmaz, I. Ozdemir, N. Gurbuz, J. Organomet. Chem.
694 (2009) 446.
[27] I.D. Kostas, B.R. Steele, A. Terzis, S.V. Amosova, A.V. Martynov, N.A. Makhaeva,
Eur. J. Inorg. Chem. 2006 (2006) 2642.
[28] J. Cui, M. Zhang, Y. Zhang, Inorg. Chem. Commun. 13 (2010) 81.
[29] E.G. Bowes, G.M. Lee, C.M. Vogels, A. Decken, S.A. Westcott, Inorg. Chim. Acta
377 (2011) 84.
[30] B.J. Tardiff, J.C. Smith, S.J. Duffy, C.M. Vogels, A. Decken, S.A. Westcott, Can. J.
Chem. 85 (2007) 392.
[31] P.R. Kumar, S. Upreti, A.K. Singh, Polyhedron 27 (2008) 1610.
[32] M. Muthu Tamizh, K. Mereiter, K. Kirchner, B.R. Bhat, R. Karvembu, Polyhedron
28 (2009) 2157.
[33] M. Muthu Tamizh, B. Varghese, A. Endo, R. Karvembu, Spectrochim. Acta 77A
(2010) 411.
4. Conclusions
In conclusion, we have reported convenient syntheses and com-
prehensive characterization of six new palladium(II) complexes
(1–6) containing salicylideneimine based tridentate ligand and tri-
phenylphosphine. The solid state structures of complexes 1, 2 and
6 were determined by X-ray crystallography. The complexes
showed the expected square planar geometry about the metal cen-
ter. The complexes were applied to the Suzuki–Miyaura cross-cou-
pling reaction between 4-bromobenzene and phenylboronic acid
and found that 3 was the most active and was suitable for use
without an inert atmosphere. Complex 3 was further used to assess
the efficacy of cross-coupling reactions between various aryl ha-
lides and boronic acids. The coupling reactions were effective with
electron-donating as well as electron-withdrawing substituents on
the aryl halide. Heterocyclic boronic acid and aryl halides were also
used successfully in Suzuki–Miyaura cross-coupling reactions with
this catalyst. The palladium(II) complexes reported in this paper
are air and light stable compared to its precursor, [Pd(PPh3)4].
[34] M. Muthu Tamizh, K. Mereiter, K. Kirchner, R. Karvembu, J. Organomet. Chem.
700 (2012) 194.
Acknowledgements
[35] S. Priyarega, M. Muthu Tamizh, S. Ganesh Babu, R. Karvembu, K. Natarajan,
Indian J. Chem. 51A (2012) 453.
[36] S. Priyarega, D. Senthil Raja, S. Ganesh Babu, R. Karvembu, T. Hashimoto, A.
Endo, K. Natarajan, Polyhedron 34 (2012) 143.
[37] D.D. Perrin, W.L.F. Armarego, Purification of Laboratory Chemicals, Fourth ed.,
Buttrewort-Heinemann, Oxford, 1996.
[38] J.J. Levison, S.D. Robinson, Inorg. Synth. 13 (1972) 121.
[39] F. Tisato, F. Refosco, U. Mazzi, G. Bandoli, M. Nicolini, J. Chem. Soc., Dalton
Trans. (1987) 1693.
R.K. and M.M. gratefully acknowledge CSIR [01(2137)/07/EMR-
II] for financial support. We thank SAIF, IIT-Madras, Chennai and
NRC, SIF, IISc, Bangalore for NMR measurements. Funding from
DST through FIST Programme is acknowledged. C.L.B.M. acknowl-
edges NSERC for financial support. We also thank the reviewers
for useful suggestions.
[40] L.D. Albin, M. Jacobson, D.B. Olson, US Patent 5,426,085, 1995.
[41] SMART, Bruker AXS Inc., Madison, WI, 2001.
[42] SAINT PLUS, Bruker AXS Inc., Madison, WI, 2001.
Appendix A. Supplementary material
[43] SADABS, Bruker AXS Inc., Madison, WI, 2001.
[44] A. Altomare, M.C. Burla, M. Camalli, G.L. Cascarano, C. Giacovazzo, A. Guagliardi,
A.G.G. Moliterni, G. Polidori, R. Spagna, J. Appl. Crystallogr. 32 (1999) 115.
[45] G. Sheldrick, Acta Crystallogr. 64A (2008) 112.
CCDC 853722, 853723 and 727007 contain the supplementary
crystallographic data for complexes 1, 2 and 6, respectively. These
data can be obtained free of charge from The Cambridge Crystallo-
graphic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.ica.2012.08.024.
[46] L. Farrugia, J. Appl. Crystallogr. 32 (1999) 837.
[47] G.M. Sheldrick, Bruker AXS Inc., Madison, WI, 2001.
[48] P. van der Sluis, A.L. Spek, Acta Crystallogr. 46A (1990) 194.
[49] J.E. Kovic, Spectrochim. Acta 23 (1967) 183.
[50] B.J. Hathaway, A.E. Underhill, J. Chem. Soc. (1961) 3091.
[51] R. Karvembu, K. Natarajan, Polyhedron 21 (2002) 219.
[52] K. Nakamoto, Infrared and Raman Spectra of Inorganic and Coordination
Compounds, Fourth ed., Wiley, New York, 1986.
References
[53] V. Philip, V. Suni, M.R.P. Kurup, M. Nethaji, Polyhedron 23 (2004) 1225.
[54] J. Fornies, S. Fuertes, J.A. Lopez, A. Martin, V. Sicilia, Inorg. Chem. 47 (2008)
7166.
[1] R.J.P. Corriu, J.P. Masse, Chem. Commun. (1972) 144a.
[2] K. Tamao, K. Sumitani, M. Kumada, J. Am. Chem. Soc. 94 (1972) 4374.

400
M. Muthu Tamizh et al. / Inorganica Chimica Acta 394 (2013) 391–400
[55] S. Fernandez, J. Fornies, B. Gil, J. Gomez, E. Lalinde, Dalton Trans. (2003) 822.
[56] I.P. Romm, A.A. Malkov, S.A. Lebedev, V.V. Levashova, T.M. Buslaeva, Russ. J.
Phys. Chem. A 85 (2011) 248.
[57] M. López-Torres, A. Fernández, J.J. Fernández, A. Suárez, S. Castro-Juiz, M.T.
Pereira, J.M. Vila, J. Organomet. Chem. 655 (2002) 127.
[58] R. Karvembu, S. Hemalatha, R. Prabhakaran, K. Natarajan, Inorg. Chem.
Commun. 6 (2003) 486.
[62] L. Pauling, The Nature of Chemical Bond, Third ed., Cornell University Press,
New York, 1960.
[63] J. Vila, M. Gayoso, M. López Torres, J.J. Fernandez, A. Fernández, J.M. Ortigueira,
N.A. Bailey, H. Adams, J. Organomet. Chem. 511 (1996) 129.
[64] R. Bosque, C. López, X. Solans, M. Font-Bardia, Organometallics 18 (1999) 1267.
[65] R.L. Beddoes, L. Dalton, J.A. Joule, O.S. Mills, J.D. Street, C.I.F. Watt, J. Chem. Soc.,
Perkin Trans. 2 (1986) 787.
[59] J. Gradinaru, A. Forni, V. Druta, S. Quici, A. Britchi, C. Deleanu, N. Gerbeleu,
Inorg. Chim. Acta 338 (2002) 169.
[66] Z.-Z. Zhou, F.-S. Liu, D.-S. Shen, C. Tan, L.-Y. Luo, Inorg. Chem. Commun. 14
(2011) 659.
[60] S.K. Gupta, P.B. Hitchcock, Y.S. Kushwah, G.S. Argal, Inorg. Chim. Acta 360
(2007) 2145.
[61] P. Chellan, N. Shunmoogam-Gounden, D.T. Hendricks, J. Gut, P.J. Rosenthal, C.
Lategan, P.J. Smith, K. Chibale, G.S. Smith, Eur. J. Inorg. Chem. 2010 (2010)
3520.
[67] Y. He, C. Cai, Catal. Commun. 12 (2011) 678.
[68] P. Paul, S. Datta, S. Halder, R. Acharyya, F. Basuli, R.J. Butcher, S.-M. Peng, G.-H.
Lee, A. Castineiras, M.G.B. Drew, S. Bhattacharya, J. Mol. Catal. A: Chem. 344
(2011) 62.
[69] J.A. Widegren, R.G. Finke, J. Mol. Catal. A: Chem. 198 (2003) 317.