Novel binuclear palladium(II) complexes of 2-oxoquinoline-3-carbaldehyde Schiff bases: Synthesis, structure and catalytic applications

Article abstract of DOI:10.1016/j.poly.2011.12.017

A series of novel binuclear Pd(II) complexes of the type [(PPh ₃)₂ClPd(L)PdCl] [where L = dianionic bridged ligands derived from 2-oxo-1,2-dihydroquinoline-3-carbaldehyde or its derivatives with o-aminophenol/o-aminothiophenol] have been reported. The new complexes have been characterized by elemental analysis, FT-IR, UV-Vis and NMR (¹H and ³¹P) spectroscopic techniques. The coordination mode of the ligands and the geometry of the complexes were confirmed by single crystal X-ray crystallography of one of the complexes. The catalytic efficiency of one of the binuclear Pd(II) complexes was tested for N-arylation of imidazole.

Full text of DOI:10.1016/j.poly.2011.12.017

Polyhedron 34 (2012) 143–148
Contents lists available at SciVerse ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Novel binuclear palladium(II) complexes of 2-oxoquinoline-3-carbaldehyde
Schiff bases: Synthesis, structure and catalytic applications
Sivakumar Priyarega a, Duraisamy Senthil Raja a, Sundaram Ganesh Babu b, Ramasamy Karvembu b,
Takeshi Hashimoto c, Akira Endo c, Karuppannan Natarajan a,
⇑
a Department of Chemistry, Bharathiar University, Coimbatore 641 046, India
b Department of Chemistry, National Institute of Technology, Tiruchirappalli 620 015, India
c Department of Chemistry, Faculty of Science and Technology, Sophia University, 7-1 Kioicho, Chiyoda-ku, Tokyo 102-8554, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of novel binuclear Pd(II) complexes of the type [(PPh3)2ClPd(L)PdCl] [where L = dianionic bridged
ligands derived from 2-oxo-1,2-dihydroquinoline-3-carbaldehyde or its derivatives with o-aminophenol/o-
aminothiophenol] have been reported. The new complexes have been characterized by elemental analysis,
FT-IR, UV–Vis and NMR (1H and 31P) spectroscopic techniques. The coordination mode of the ligands and the
geometry of the complexes were confirmed by single crystal X-ray crystallography of one of the complexes.
The catalytic efficiency of one of the binuclear Pd(II) complexes was tested for N-arylation of imidazole.
Ó 2011 Elsevier Ltd. All rights reserved.
Received 28 September 2011
Accepted 19 December 2011
Available online 28 December 2011
Keywords:
Binuclear palladium(II) complexes
Schiff base
Crystal structure
N-arylation
1. Introduction
palladium-catalyzed cross-coupling reactions may also be applied
to the formation of C–heteroatom such as C–N, C–O, C–S bonds
Heterocyclic compounds containing nitrogen atom attract a
great deal of attention in coordination chemistry and homoge-
neous catalysis [1–3]. The combination of heterocyclic ring and
azomethine moiety exerts potential biological and catalytic activi-
ties [4–6]. Although extensive studies have been made on the tran-
sition metal complexes of various nitrogen heterocyclic Schiff base
ligands, comparatively less is reported on transition metal com-
plexes derived from 2-oxo-1,2-dihydroquinoline-3-carbaldehyde
[7–9]. The incorporation of phosphine ligands into the platinum
group metal complexes brings remarkable changes in structural
and electronic rearrangements, chemical reactivity and physical
[13]. On the other hand, Buchwald–Hartwig amination has been
widely used for the preparation of aryl amines by the reactions of
aryl halides with primary or secondary amines, amides, sulfona-
mides, imines, and heterocyclic compounds containing N–H bonds
[14]. N-arylation reactions catalyzed by the palladium complexes
are performed under mild conditions [15]. Though many reports
are available on the palladium complexes as catalysts for C–N cross
coupling reactions [16–18], palladium(II) complexes containing tri-
phenylphosphine as well as Schiff base are rarely explored. So here-
in, we report the synthesis and characterization of novel binuclear
Pd(II) complexes containing Schiff base ligands derived from
2-oxo-1,2-dihydroquinoline-3-carbaldehyde or its derivatives and
o-aminophenol/o-aminothiophenol. The novel binuclearPd(II) com-
plexes have been tested as catalysts for N-arylationof imidazole. The
general structure of quinoline based Schiff base ligands is given in
Fig. 1.
properties because of their large steric demands as well as
and -acceptor properties [10].
r-donor
p
Metal-catalyzed Ullmann-type C–N coupling reaction represents
one of the most efficient methods to form various C–N bond contain-
ing compounds that have important biological, pharmaceutical, or
material properties [11]. Traditional Cu-catalyzed Ullmann reac-
tions require the use of stoichiometric amounts of copper, harsh
reaction conditions, strong bases and often use of toxic polar sol-
vents such as hexamethylphosphoramide (HMPA), and thus limited
their large scale applications in industries. One of the most signifi-
cant achievements in this field is the development of palladium-
catalyzed cross-coupling reactions that became a major synthetic
protocol for the construction of aryl–carbon bonds [12]. The
2. Experimental
2.1. Materials
All the reagents were purchased from Merck or Sigma–Aldrich
and used as received. Solvents were freshly distilled and dried over
the appropriate drying agents. 2-Oxo-1,2-dihydroquinoline-3-carb-
aldehyde, its derivatives or 2-oxo-1,2-dihydrobenzo[h]quinoline-
3-carbaldehyde and the starting complex [PdCl2(PPh3)2] were
prepared according to the reported literature procedures [19–21].
⇑
Corresponding author. Tel.: +91 422 2428319; fax: +91 422 2422387.
E-mail address: k_natraj6@yahoo.com (K. Natarajan).
0277-5387/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2011.12.017

144
S. Priyarega et al. / Polyhedron 34 (2012) 143–148
Table 1
R
R
Y Abbreviation
Crystal data and structure refinement parameters for [(PPh3)2ClPd(L1)PdCl]
Á1.5CH3CN.
H
O
S
H2L1
HN
H
H2L2
H2L3
H2L4
O
N
Empirical formula
Formula weight
Color
C55H44.50N3.50O2P2Pd2Cl2
1132.13
red
CH3
CH3
O
S
HY
Habit
black
Crystal dimensions (mm)
Wavelength (Å)
Crystal system
Lattice type
Space group
Detector position (mm)
Pixel size (mm)
Lattice parameters
a (Å)
0.20 Â 0.10 Â 0.04
0.71070
orthorhombic
primitive
Pna21(#33)
44.92
HN
Y Abbreviation
O
N
0.137
O
S
H2L5
H2L6
HY
16.8400(10)
27.7902(18)
b (Å)
c (Å)
10.4866(8)
4907.6(6)
V (Å3)
Fig. 1. Structure of quinoline based Schiff base ligands.
Z
4
Dcalc (g/cm3)
F(000)
1.532
2284
9.532
2.2. Physical measurements
l
(MoKa
) (cmÀ1
)
Absorption correction
Refinement method
No. of reflections measured
Rint
Lorentz-polarization
full-matrix least squares on F2
total: 37292, unique: 5935
0.062
9.01
0.951
IR spectra of the ligands and complexes were recorded on a
Nicolet FT-IR spectrophotometer using KBr pellets. Electronic spec-
tra of the complexes were recorded in dichloromethane using Sys-
tronics 119 spectrophotometer in the 200–800 nm range.
Magnetic susceptibility measurements were made with the EG &
G-Parc vibrating sample magnetometer. Nuclear Magnetic Reso-
nance spectra were recorded on Bruker Avance 500 MHz spectrom-
eter. 1H NMR chemical shifts were reported using tetramethylsilane
(TMS) as the internal standard. 31P NMR spectra were measured rel-
ative to H3PO4 as the external standard. Elemental analysis of the
complexes was performed by Vario EL III elemental analyser. Melt-
ing points were determined with Raaga melting point apparatus.
Reflection/parameter ratio
Goodness-of-fit (GOF) on F2
R indices [I > 2
r
(I)]
R1 = 0.0436, wR2 = 0.1189
1.93, À1.29
D
qmax
,
D
qmin (e ÅÀ3
)
were refined anisotropically, using full-matrix least squares refine-
ments on F2 with crystal structure crystallographic software
package [24]. Table 1 gives further details of data collection, refine-
ment, and the structural details of [(PPh3)2ClPd(L1)PdCl]Á 1.5CH3CN.
2.3. General preparation of 2-oxo-1,2-dihydroquinoline-3-
carbaldehyde or 2-oxo-1,2-dihydrobenzo[h]quinoline-3-carbaldehyde
Schiff bases
2.6. Catalytic N-arylation of imidazole by binuclear Pd(II) complexes
A methanol (20 cm3) solution of either o-aminophenol or
o-aminothiophenol (0.44/0.50 g; 4.00 mmol) was added to 2-oxo-1,
2-dihydroquinoline-3-carbaldehyde or its derivatives or 2-oxo-1,2-
dihydrobenzo[h]quinoline-3-carbaldehyde (4.00 mmol) dissolved
in the same solvent (20 cm3) and refluxed for 6 h. The yellow precip-
itate that separated out was filtered and washed with methanol and
dried in vacuo. Yield: 73–77%.
In a typical N-arylation reaction, [(PPh3)2ClPd(L1)PdCl] (0.01 g,
0.01 mmol) was added to a mixture of 4-chlorobenzonitrile (0.137
g, 1 mmol), imidazole (0.088 g, 1.2 mmol) and K2CO3 (0.276 g,
2 m mol) in N,N-dimethyl acetamide (DMAc) (4 cm3) and stirred at
120 °C. After completion of the reaction (as monitored by TLC), the
reaction mixture was extracted with ethyl acetate and quenched
with aqueous sodium hydrogen carbonate. The organic layer was
separated, dried over anhydrous sodium sulfate and filtered. The
filtrate was concentrated and the residue was purified by column
chromatography on silica gel (hexane/ethyl acetate, 70/30) to afford
pure 4-(1H-imidazol-1-yl)benzonitrile. Melting point: 142–144 °C;
MS (GC): m/z 169.06 (M+).
2.4. Preparation of binuclear Pd(II) complexes of the type
[(PPh3)2ClPd(L1)PdCl] (L = binucleating 2-oxoquinoline-3-
carbaldehyde Schiff base ligand)
To a solution of [PdCl2(PPh3)2] (0.14 g; 0.20 mmol) in dichloro-
methane (20 cm3), the appropriate quinoline Schiff base ligands
(0.10 mmol) in methanol (25 cm3) and two drops of triethylamine
were added. The mixture was refluxed for 5 h. An orange colored
precipitate that formed was separated from the solution by suction
filtration. The complex was washed with ethanol and dried under
vacuum. Yield: 66–72%.
3. Results and discussion
Binuclear Pd(II) complexes were obtained from the reactions of
[PdCl2(PPh3)2] with 2-oxoquinoline-3-carbaldehyde Schiff base li-
gands (H2L1–H2L6) in presence of a base, triethylamine (Scheme
1). The complexes are pure and air stable. They are quite soluble
in CHCl3, CH2Cl2, DMSO and DMF, and insoluble in MeOH and
EtOH. The elemental analyses data and melting points of the com-
pounds have been tabulated (Table 2). The results of elemental
analyses for the ligands and complexes are in good agreement with
the proposed molecular formula. As expected, the ligands are coor-
dinated in a tridentate fashion (ONO/ONS) to palladium ion. In
addition to that, the presence of triethylamine promoted deproto-
nation of the NH of quinoline moiety followed by coordination to
another palladium ion resulting in the formation of binuclear Pd(II)
complexes.
2.5. X-ray crystallography
Crystals of [(PPh3)2ClPd(L1)PdCl]Á1.5CH3CN suitable for X-ray
diffraction study were grown from dichloromethane/acetonitrile
solution. A red block crystal having approximate dimensions of
0.20 Â 0.10 Â 0.04 mm was mounted on a Rigaku Mercury CCD
diffractometer with graphite monochromated MoK
a radiation
(k = 0.71070 Å). The structure was solved by direct methods and
expanded using Fourier techniques [22,23]. All non-hydrogen atoms

S. Priyarega et al. / Polyhedron 34 (2012) 143–148
145
Cl
PPh3
R
Pd
Ph3P
R
N
Cl
Pd
Y
O
N
HN
O
N
[PdCl2(PPh3)2]
+
(or)
Cl
(or)
HN
(C2H5)3N
CH3OH / CH2Cl2
Reflux, 5 h
PPh3
N
HY
O
N
Pd
Ph3P
HY
Cl
O
N
Pd
Y
(Y = O or S; R = H or CH3)
Scheme 1. Synthesis of binuclear palladium(II) complexes.
Table 2
Analytical data of ligands and palladium(II) complexes.
Table 3
IR and UV–Vis spectral data of ligands and palladium(II) complexes.a
Compound
Melting point (°C) Elemental analysis
Found (calc.)%
Compound
m(C@N)
m
O)
(C–
m
S)
(C–
m
(C@O) Bands kmax (emax)
due to
PPh3
C
H
N
S
H2L1
H2L2
H2L3
H2L4
H2L5
H2L6
1
1600
1592
1613
1595
1585
1598
1542
1339
1347
1331
1373
1649
1269 1656
1659
1256 1647
1637
1258 1643
1590
H2L1
H2L2
H2L3
H2L4
H2L5
H2L6
208
211
221
226
206
213
72.31 4.56 10.59
(72.72) (4.58) (10.60)
68.71 4.30 10.05 11.39
(68.55) (4.31) (9.99) (11.44)
73.36 5.09 10.07
(73.37) (5.07) (10.07)
69.35 4.79 9.55
(69.36) (4.79) (9.52) (10.89)
76.47 4.45 8.94
(76.42) (4.49) (8.91)
72.76 4.26 8.48
(72.70) (4.27) (8.48) (9.70)
58.56 3.60 2.54
(58.30) (3.76) (2.61)
57.79 3.67 2.59
(57.45) (3.70) (2.57) (2.94)
58.34 4.07 2.34
(58.66) (3.90) (2.58)
57.96 3.91 2.41
(57.80) (3.80) (2.54) (2.91)
60.14 3.61 2.39
1419,
1097,
694
1424,
1095,
696
1405,
1099,
696
1428,
1094,
695
1436,
1098,
695
1425,
1095,
694
238 (14803), 337 (8552),
353 (4821), 414 (3738), 471
(2181)
262 (12462), 341 (6231),
362 (4497), 400 (2306), 423
(2172)
267 (14683), 345 (7880),
402 (4649), 425 (3343), 465
(2103)
250 (13680), 347 (8230),
405 (4212), 425 (2385), 465
(2045)
230 (14068), 340 (9100),
355 (4350), 445 (2452), 480
(2185)
235 (13865), 342 (8336),
357 (4290), 434 (2562), 470
(2175)
10.95
2
3
4
5
6
1569
1553
1550
1549
1545
1304 1622
1593
9.71
1371
1371
[(PPh3)2ClPd(L1)PdCl] (1) 248
[(PPh3)2ClPd(L2)PdCl] (2) 265
[(PPh3)2ClPd(L3)PdCl] (3) >300
[(PPh3)2ClPd(L4)PdCl] (4) >300
[(PPh3)2ClPd(L5)PdCl] (5) 217
[(PPh3)2ClPd(L6)PdCl] (6) 256
3.01
1319 1589
1590
2.96
1310 1582
(59.99) (3.77) (2.49)
59.27 3.67 2.30
(59.14) (3.72) (2.46) (2.81)
2.71
a
m
in cmÀ1; k in nm; emax in dm3 molÀ1 cmÀ1
.
3.1. Electronic spectra
which is shifted to 1582–1622 cmÀ1 in the corresponding Pd(II)
complexes, indicating the coordination of metal through carbonyl
oxygen in all the complexes [28]. The infrared spectra of the free
All the complexes are diamagnetic (leff = 0) indicating +2 oxida-
tion state of Pd ions. The electronic spectra of all the Pd(II) com-
plexes were recorded in dichloromethane solution. Five bands
were observed in the region 230–480 nm (Table 3). The bands in
the region 230–347 nm have been assigned to charge transfer tran-
sitions. The electronic spectra of complexes also showed three d–d
spin allowed transitions from the three low lying d levels to the
ligands (H2L1, H2L3 and H2L5) showed
a
band around
3375–3396 cmÀ1 due to the stretching of phenolic OH. This band
is absent in the spectra of all the complexes, indicating the depro-
tonation of phenolic OH followed by coordination to metal ion.
This is further supported by the shift of the band around 1331–
1347 cmÀ1 due to phenolic C–O to higher wave number (1371–
1373 cmÀ1) [29]. In the complexes formed from H2L2, H2L4 and
empty dx2
orbital. The bands are attributed to 1A1g ? 1A2g
,
Ày2
1A1g ? 1B1g and to 1A1g ? 1Eg transitions in accordance with the
electronic spectra of other square planar Pd(II) complexes [25,26].
H2L6, the band (2515–2590 cmÀ1) corresponding to
free ligands disappeared and absorption due to (C–S) of free li-
m(S–H) in the
m
gands around 1256–1269 cmÀ1 is shifted to 1304–1319 cmÀ1 in
the complexes, indicating that the other coordination site is thio-
phenolic sulfur atom. However, the characteristic absorption band
around 3150–3169 cmÀ1 due to quinoline NH has disappeared on
complexation [29]. This shows the involvement of quinoline nitro-
gen in the coordination with the palladium ion. In addition to
these, three strong bands observed around 1405–1436, 1094–
1099 and 694–696 cmÀ1 in all the complexes are attributed to
coordinated PPh3 ligand [27].
3.2. IR spectra
The IR spectra of Pd(II) complexes exhibited characteristic
absorption bands around 1542–1569 cmÀ1 attributed to
m(C@N).
A shift observed in the absorption due to the imine in the free li-
gands (1585–1613 cmÀ1) to lower wave numbers in the metal
complexes, is indicative of the coordination of Pd to imine nitrogen
[27]. The intense band around 1637–1659 cmÀ1 in the IR spectra
(Table 3) of free ligands is associated with C@O stretching vibration

146
S. Priyarega et al. / Polyhedron 34 (2012) 143–148
Table 4
Table 5
1H NMR spectral data of ligands and palladium(II) complexes.
Selected bond lengths (Å) and bond angles (°) of [(PPh3)2ClPd(L1)PdCl]Á1.5CH3CN.
Compound 1H NMR (d in ppm)
31P NMR (d in ppm)
Pd(1)–Cl(1)
Pd(1)–O(1)
Pd(1)–O(2)
Pd(1)–N(1)
Pd(2)–Cl(2)
Pd(2)–P(1)
Pd(2)–P(2)
Pd(2)–N(2)
O(1)–C(1)
O(2)–C(9)
N(1)–C(2)
N(1)–C(7)
N(2)–C(9)
N(2)–C(10)
2.304(2)
1.993(5)
2.002(5)
1.974(6)
2.311(2)
2.3220(19)
2.3278(19)
2.041(6)
1.335(10)
1.293(8)
1.426(10)
1.276(11)
1.329(9)
1.383(9)
Cl(1)–Pd(1)–O(1)
Cl(1)–Pd(1)–O(2)
Cl(1)–Pd(1)–N(1)
O(1)–Pd(1)–O(2)
O(1)–Pd(1)–N(1)
O(2)–Pd(1)–N(1)
Cl(2)–Pd(2)–P(1)
Cl(2)–Pd(2)–P(2)
Cl(2)–Pd(2)–N(2)
P(1)–Pd(2)–P(2)
P(1)–Pd(2)–N(2)
P(2)–Pd(2)–N(2)
Pd(1)–O(1)–C(1)
Pd(1)–O(2)–C(9)
Pd(1)–N(1)–C(2)
Pd(1)–N(1)–C(7)
89.49(17)
91.20(15)
173.2(2)
177.7(2)
84.2(2)
H2L1
H2L2
H2L3
12.07 (s, 1H, OH); 10.35 (s, 1H,
NH(quinoline)); 8.41 (s, 1H, CH@N);
6.63–7.84 (m, 39H, aromatic)
11.93 (s, 1H, SH); 10.29 (s, 1H,
NH(quinoline)); 8.13 (s, 1H, CH@N);
6.63–7.85 (m, 39H, aromatic)
11.97 (s, 1H, OH); 10.39 (s, 1H,
NH(quinoline)); 8.37 (s, 1H, CH@N);
6.62–7.83 (m, 38H, aromatic); 1.72 (s,
3H, CH3)
95.2(2)
89.69(7)
88.69(6)
176.96(17)
174.48(8)
92.00(16)
89.86(16)
109.7(4)
124.4(4)
110.8(5)
124.2(5)
H2L4
12.04 (s, 1H, SH); 10.33 (s, 1H,
NH(quinoline)); 8.48 (s, 1H, CH@N);
6.60–7.89 (m, 38H, aromatic); 1.72 (s,
3H, CH3)
H2L5
H2L6
11.88 (s, 1H, OH); 10.26 (s, 1H,
NH(quinoline)); 8.29 (s, 1H, CH@N);
6.67–7.88 (m, 41H, aromatic)
11.93 (s, 1H, SH); 10.31 (s, 1H,
NH(quinoline)); 8.23 (s, 1H, CH@N);
6.75–7.92 (m, 41H, aromatic)
8.35 (s, 1H, CH@N), 6.62–7.83 (m, 39H,
aromatic)
results in the formation of five member chelate ring. Complexes
3 and 4 showed a signal corresponding to methyl group at 1.61
and 1.66 ppm, respectively. Resonances due to aromatic protons
of the ligands and triphenylphosphine are observed as multiplets
around 6.62–7.89 ppm. The absence of NH signal in all the com-
plexes suggests that the NH in the quinoline moiety underwent
deprotonation and nitrogen is coordinated to another Pd ion. 31P
NMR spectra of the complexes exhibited only one signal at around
20.0–30.0 ppm indicating identical environment for both the phos-
phorus atoms and hence, trans positions were assigned to triphen-
ylphosphine groups around one of the Pd centers.
1
2
3
4
5
6
24.5 (s)
25.7 (s)
28.5 (s)
28.7 (s)
27.4 (s)
26.7 (s)
8.39 (s, 1H, CH@N), 6.96–7.84 (m, 39H,
aromatic)
8.30 (s, 1H, CH@N), 6.62–7.85 (m, 38H,
aromatic), 1.61 (s, 3H, CH3)
9.17 (s, 1H, CH@N), 7.01–7.89 (m, 38H,
aromatic), 1.66 (s, 3H, CH3)
8.30 (s, 1H, CH@N), 6.66–7.87 (m, 41H,
aromatic)
8.35 (s, 1H, CH@N), 6.95–7.89 (m, 41H,
aromatic)
3.4. X-ray crystallography
3.3. NMR spectra
The molecular structure of [(PPh3)2ClPd(L1)PdCl]Á1.5CH3CN
studied by single crystal X-ray diffraction analysis supported the
spectroscopic results of Pd(II) complexes. The ORTEP diagram of
[(PPh3)2ClPd(L1)PdCl]Á1.5CH3CN with atom numbering scheme is
shown in Fig. 2. Selected bond lengths and bond angles are given
in Table 5. The ligand is coordinated to two Pd(II) ions forming
NO2Cl and NP2Cl coordination spheres. The Pd(II) ions adopt a
square planar geometry as reflected from all the bond parameters
The 1H NMR spectral data of all the ligands and their Pd(II) com-
plexes are given in Table 4. The 1H NMR spectra of all the Pd(II)
complexes exhibited a singlet in the region 8.30–9.17 ppm due to
imine proton. Disappearance of the signal for OH/SH proton in
the complexes confirmed deprotonation followed by coordination
of phenolic oxygen or thiophenolic sulfur to the Pd ion which
Fig. 2. ORTEP drawing of [(PPh3)2ClPd(L1)PdCl]Á1.5CH3CN showing thermal ellipsoids at the 30% probability level. The hydrogen atoms and CH3CN molecules have been
omitted for clarity.

S. Priyarega et al. / Polyhedron 34 (2012) 143–148
147
Table 6
Catalytic N-arylation of imidazole using [(PPh3)2ClPd(L1)PdCl].
Entry
1
Aryl halide
Product
Reaction time (h)
28
Isolated yield (%)
83
85
78
81
89
82
84
CN
Cl
N
N
N
N
N
N
N
CN
N
N
N
N
N
N
N
2
3
4
5
6
7
28
24
24
24
24
24
CN
Br
Cl
Br
Cl
Cl
Br
CN
COOH
COOH
NO2
CF3
COOH
COOH
NO2
CF3
CF3
CF3
around Pd(II) centers [Cl(1)–Pd(1)–N(1) 173.2(2)°, O(1)–Pd(1)–
O(2) 177.7(2)°, Cl(2)–Pd(2)–N(2) 176.96(17)°, P(1)–Pd(2)–P(2)
174.48(8)°]. The Pd–N, Pd–O, Pd–Cl and Pd–P distances are all
quite normal and so are phenolic C–O, carbonyl C@O and azome-
thine C@N distances of the coordinated ligand [30,31]. Around
Pd(2), triphenylphosphine ligands are trans to each other. This
complex contains 1.5 acetonitrile molecules in the lattice.
The results obtained from various spectroscopic techniques and
single crystal X-ray crystallography of one of the complexes re-
vealed that the ligands act as tridentate donor to one metal center
and monodentate donor to another metal center yielding binuclear
Pd(II) complexes.
Appendix A. Supplementary data
CCDC 845753 contains the supplementary crystallographic data
for the complex [(PPh3)2ClPd(L1)PdCl]Á1.5CH3CN. These data can
be obtained free of charge via http://www.ccdc.cam.ac.uk/conts/
retrieving.html, or from the Cambridge Crystallographic Data
Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-
336-033; or e-mail: deposit@ccdc.cam.ac.uk.
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Acknowledgments
Financial assistance received from the Council of Scientific and
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