Palladium(II) complexes containing 2,6-bis(imino)pyridines: Synthesis, characterization, thermal study, and catalytic activity in suzuki reactions

Article abstract of DOI:10.1080/15533174.2010.486822

A series of palladium complexes: [(Pydim)PdCl](PdCl3) (Pydim (1): pyridine-2,6-diimine) have been synthesized from palladium dichloride and the corresponding pydim. The Pd (II) complexes have been used as catalyst in the Suzuki reaction of aryl halides. Moreover, thermal behaviors of palladium complexes have been studied in nitrogen atmosphere using TG/DTG and DTA techniques. The values of activation energy Ea, and reaction order n, the entropy change δSz.ast;, enthalpy change δH#, and Gibbs free energy change δG# of the thermal decomposition were calculated by means of several methods based on the single heating rate. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/15533174.2010.486822

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Palladium(II) Complexes Containing 2,6-
Bis(Imino)Pyridines: Synthesis, Characterization,
Thermal Study, and Catalytic Activity in Suzuki
Reactions
Osman Dayan a , Fatih Doĝan a , İsmet Kaya a & Bekir Çetinkaya b
a Department of Chemistry , Çanakkale Onsekiz Mart University , Çanakkale, Turkey
b Ege University, Department of Chemistry , Izmir, Turkey
Published online: 27 May 2010.
To cite this article: Osman Dayan , Fatih Doĝan , İsmet Kaya & Bekir Çetinkaya (2010) Palladium(II) Complexes Containing
2,6-Bis(Imino)Pyridines: Synthesis, Characterization, Thermal Study, and Catalytic Activity in Suzuki Reactions, Synthesis
and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 40:5, 337-344
To link to this article: http://dx.doi.org/10.1080/15533174.2010.486822
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Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 40:337–344, 2010
Copyright © Taylor & Francis Group, LLC
ISSN: 1553-3174 print / 1553-3182 online
DOI: 10.1080/15533174.2010.486822
Palladium(II) Complexes Containing
2,6-Bis(Imino)Pyridines: Synthesis, Characterization,
Thermal Study, and Catalytic Activity in Suzuki Reactions
1
1
1
2
˙
Osman Dayan, Fatih Dogˇan, Ismet Kaya, and Bekir C¸ etinkaya
1Department of Chemistry, C¸ anakkale Onsekiz Mart University, C¸ anakkale, Turkey
2Ege University, Department of Chemistry, Izmir, Turkey
A series of palladium complexes: [(Pydim)PdCl](PdCl3) (Pydim
(1): pyridine-2,6-diimine) have been synthesized from palladium
dichloride and the corresponding pydim. The Pd (II) complexes
have been used as catalyst in the Suzuki reaction of aryl halides.
Moreover, thermal behaviors of palladium complexes have been
studied in nitrogen atmosphere using TG/DTG and DTA tech-
niques. The values of activation energy Ea, and reaction order n,
the entropy change ꢀS*, enthalpy change ꢀH#, and Gibbs free
energy change ꢀG# of the thermal decomposition were calculated
by means of several methods based on the single heating rate.
Keywords activation energy, Pd(II) complexes, pyridine-2,6-
diimines, Suzuki reaction, thermal behavior
INTRODUCTION
Transition metal complexes with tridentate nitrogen donor
ligands containing pyridine-ring (I-IV) have been extensively
synthesized and studied for many potential applications.[1−4] For
example, these complexes as catalysts have been widely used
in various organic transformation reactions, especially polymer-
ization, epoxidation, and hydrogenation reactions.[5−7]
ligands are rare in literature. More recently, two related papers
on the catalytic activity of pyridine-2,6-dimines (IV)/Palladium
complexes in the Suzuki reactions of aryl halides and phenyl-
boronic acid were published.[12,13]
On the other hand, the non-isothermal thermogravimetry
(TG) with a linear temperature growth is a method frequently
used to characterize materials from their thermal behavior
standpoint. In addition, it enables us to determine apparent
kinetic parameters of heterogeneous reactions (the reaction
order n, the activation energy E, and the frequency factor A).
For instance, Dogˇan et al.[14−16] investigated using thermo
gravimetric technique on the effect of the calculation methods
on the solid state decomposition kinetic of semiconducting
polymeric materials. Also, Dogˇan et al.[17] have investigated
the thermal behavior, kinetic and thermodynamic parameters of
imidazolinium and benzimidazolium bromide salts with
pentafluorobenzyl substitutients in a nitrogen atmosphere with
TG/DTG and DTA. Kok [18] estimated the thermal analysis and
kinetics of several coal and oil shale samples by using the same
method based on the single heating rate. A similar study using
isothermal function by various methods on Ruthenium (II)
On the other hand, the most powerful method for the prepa-
ration of biaryl compounds is Suzuki reactions involving cross-
coupling of aryl halides with aryl boronic acids.[8−11] Suzuki
reactions involve the use of various Pd complexes as catalyst in
various solvents. These complexes include many different kinds
of nitrogene-based palladium complexes. However, palladium
complexes containing planar tridentate pyridine-bridged N,Nꢀ,N
Received 13 November 2009; accepted 16 April 2010.
This research has been supported by The Scientific and Technical
˙
Research Council of Turkey (TUBITAK) (Project No: 107T808) and
C¸ anakkale Onsekiz Mart University Scientific Research Projects Com-
mission (Project No: 2009-16).
Address correspondence to Osman Dayan, Department of Chem-
istry, C¸ anakkale Onsekiz Mart University, 17020, Canakkale, Turkey.
E-mail: osmandayan@comu.edu.tr
337

338
O. DAYAN ET AL.
pyridine-2,6-diimines[19]
and
Synthesis of Complex 2a
complexes
containing
rhodium(III)-pentamethylcyclopentadienyl and ruthenium(II)-
Yield: 0.29 g, % 86. Anal. calcd. for C21H19Cl4N3Pd2: C:
arene has been reported.[20]
37.76; H: 2.87; N: 6.29; found: C: 40.91; H: 3.41; N: 6.59. 1H-
In this work, we prepare well-defined Pd(II) catalyst pre- NMR (δ, d6-DMSO): 2.54 (s, 6 H, N C-Me), 7.20 (t, J = 8.0
cursors incorporating pydim ligands for the Suzuki reactions, Hz, 2 H, Ph-Hp), 7.32 (m, 4 H, Ph-Hm), 7.51 (d, J = 8.0 Hz, 4 H,
described the thermal behaviors of those, and determined the Ph-Ho), 8.57 (d, J = 7.8 Hz, 2 H, Py-Hm), 8.75 (t, J = 8.0 Hz, 1
kinetic and thermodynamic parameters such as the reaction or- H, Py-Hp). 13C-NMR (δ, d6-DMSO): 26.1, 123.5, 125.3, 129.6,
der n, activation energy Ea, the entropy change ꢀS#, enthalpy 139.7, 142.8, 152.9, 155.9, 184.6. IR (cm−1): 1634 (νC N).
change ꢀH#, and Gibbs free energy change ꢀG# of the ther-
mal decomposition by means of MC, vK, MKN and WYHC
methods.
Synthesis of Complex 2b
Yield: 0.318 g, % 90. Anal. calcd. for C21H17Cl4F2N3Pd2:
C: 35.83; H: 2.43; N: 5.97; found: C: 38.80; H: 4.00; N: 6,63%.
1H-NMR (δ, d6-DMSO): 2.50 (s, 6 H, N C-Me), 7.26–7.34
(m, 8 H, Ph-H), 8.50 (d, J = 8.0 Hz, 2 H, Py-Hm), 8.69(t, J =
8.0 Hz, 1 H, Py-Hp). 13C-NMR (δ, d6-DMSO): 23.3, 123.8,
126.1, 130.6, 133.5, 140.6, 156.7, 163.9, 172.4. IR (cm−1):
1614 (νC N).
EXPERIMENTAL
All manipulations were performed under argon atmosphere
using standard Schlenk techniques. All reagents were obtained
from commercial suppliers and used without further purifica-
tion. Solvents were dried by standard methods and distilled un-
der argon before use. 1a,[21] 1b,[22] 1c,[23] 1d and 1e[6] and 1f[24]
were synthesized according to published procedures. NMR
spectra were recorded at 297 K on a Varian Mercury AS 400
NMR spectrometer at 400 MHz (1H), 100,56 MHz (13C). The C,
H and N analyses were performed using a CHNS-932 (LECO)
instrument at Inonu University Scientific and Technological Re-
search Center, IBTAM. Infrared spectra were measured with a
Perkin Elmer SpectrumOne FTIR system and recorded using a
universal ATR sampling accessory within the range 550–4000
cm−1. GC measurements for catalytic experiments were per-
formed using an Agillent 6890N GC instrument with a HP5
capillary column. The DTA and TG curves were obtained with
TG-DTA Perkin Elmer Diamond system apparatus. The mea-
surements were performed by using a dynamic nitrogen at-
mosphere at a flow rate of 200 mL.min−1 up to 1000◦C. The
heating rate was 10◦C min−1, and the sample sizes ranged
in mass from 8 to 10 mg contained in platinum crucible. All
the experiments were performed twice for repeatability and
the results showed good reproducibility with the smaller varia-
tions in the kinetic parameters. α-Al2O3 is used as a reference
material.
Synthesis of Complex 2c
Yield: 0.306 g, % 81. Anal. calcd. for C25H29Cl4N5Pd2: C:
39.81; H: 3.88; N: 9.29; found: C: 43.97; H: 4.59; N: 9.81%.
1H-NMR (δ, d6-DMSO): 2.47 (s, 6 H, N C-Me), 2.93 (m, 12
H, 4-N(Me)2-Ph), 6.67 (d, J = 7.8 Hz, 4 H, Ph-Ho), 7.05 (d,
J = 7.8 Hz, 4 H, Ph-Hm), 8.33 (d, J = 8.0 Hz, 2 H, Py-Hm),
8.53 (t, J = 8.0 Hz, 1 H, Py-Hp). 13C-NMR (δ, DMSO): 21.3,
43.2, 122.6, 123.3, 131.1, 134.6, 138.8, 146.5, 154.1, 160.4. IR
(cm−1): 1603 (νC N).
Synthesis of Complex 2d
Yield: 0.313 g, %80. Anal. calcd. for C29H35Cl4N3Pd2: C:
44.64; H: 4.52; N: 5.39; found: C: 46.17; H: 5.66; N: 5.58%.
1H-NMR (δ, d6-DMSO): 1.27 (s, 18 H, -C(CH3)3), 2.44 (s, 6
H, N C-Me), 7.13 (d, J = 8.6 Hz, 4 H, Ph-Ho), 7.45 (d, J =
8.6 Hz, 4 H, Ph-Hm), 8.46 (d, J = 8.2 Hz, 2 H, Py-Hm), 8.65
(t, J = 8.2 Hz, 1 H, Py-Hp). 13C-NMR (δ, d6-DMSO): 19.2,
25.3, 31.1, 34.2, 122.3, 125.5, 138.9, 142.2, 147.0, 150.5, 152.2,
163.6. IR (cm−1): 1626 (νC N).
Ligands and Complexes, General Synthesis Procedures
(1a-F and 2a-F)
1a-f were synthesized according to published procedu-
res.[6,21−24] 2a was described in another publication.[13]
2a-f were prepared a modification of literature method:[12] An
Synthesis of Complex 2e
Yield: 0.337 g, % 93. Anal. calcd. for C25H27Cl4N3Pd2: C:
ethanolic solution (20 mL) of 1.10 eq. of 1 was mixed with 43.46; H: 3.76; N: 5.80; found: C: 45.87; H: 4.73; N: 6.55%.
PdCl2 (0.177 g, 1 mmol). The reaction mixture was heated un- 1H-NMR (δ, d6-DMSO): 2.31 (s, 12 H, 3,5-(Me)2-Ph), 2.44
der reflux for 10 h. The precipitate occurred in reaction mixture. (s, 6H, N C-Me), 7.14 (s, 2H, Ph-Hp), 7.81 (m, 4 H, Ph-
The reaction mixture was cooled and filtered. The precipitate Ho), 8.64 (d, J = 8.0 Hz, 2H, Py-Hm), 8.81 (t, J = 8.0
was washed with diethyl ether (3 × 10 mL) and pentane (3 × Hz, 1 H, Py-Hp). 13C-NMR (δ, d6-DMSO): 16.8, 22.9, 120.5,
10 mL), respectively. The desired products were dried under 124.3, 128.1, 131.2, 144.3, 153.1, 156.9, 161.4. IR (cm−1):
reduced pressure at 50◦C for 1 h.
1627 (νC N).

PD(II) COMPLEXES
339
SCH. 1. Synthesis of Pydim ligands.
complexes can be isolated (Scheme 2). All of the complexes
were soluble in dimethylsulfoxide and were fully characterized
by elemental analysis and spectroscopic methods.
Synthesis of Complex 2f
Yield: 0.354 g, % 80. Anal. calcd. for C27H31Cl4N3Pd2: C:
43.11; H: 4.15; N: 5.59; found: C: 45.63; H: 5.49; N: 5.98%.
1H-NMR (δ, d6-DMSO): 2.21 (s, 12 H, 2,6-(Me)2,4-Me-Ph),
2.22 (s, 6 H, 2,6-(Me)2,4-Me-Ph), 3.36 (s, 6 H, N C-Me), 6.93
(s, 4 H, Ph-H), 8.59 (d, J = 8.2 Hz, 2 H, Py-Hm), 8.77 (t,
J = 8.2 Hz, 1 H, Py-Hp). 13C-NMR (δ, d6-DMSO): 17.6, 20.9,
23.5, 126.4, 29.8, 133.6, 138.7, 141.4, 142.3, 153.15, 164.9. IR
(cm−1): 1631 (νC N).
The 1H-NMR spectra of these complexes showed some dif-
ferences from their respective ligands, especially in the pyridine
backbone. Py-Hp and Py–Hm protons for all Pydim-Pd(II) (2a-
f) complexes were observed as triplets and doublets in a 1: 2
ratio, which had shifted towards downfield when compared to
their respective free ligands (1a-f) (Table 1).
The IR spectra of 1a-f showed peaks ν(C N) around 1655–
1621 cm−1 given in Table 2. Upon the coordination of Pd(II),
C N peaks are shifted significantly to lower frequency.
Suzuki Cross-Coupling Reactions: General Procedure
In a typical reaction, the catalyst (1 mmol % of Pd com-
plexes), aryl halides (1.0 mmol), phenyl boronic acid (1.5
mmol), Cs2CO3 (2.0 mmol), diethyleneglycol-di-n-buthylether
as internal standard (30 mg), 2-propanol (3 mL) were all added
to a small Schlenk tube and the mixture was heated at 80◦C for
1 h under argon. At the end, the mixture was cooled, filtrated
and concentrated. The purity of the compounds was checked by
GC and yields were based on aryl halides.
Catalytic Studies
Studies of the Suzuki reaction in 2-propanol catalyzed by the
2a-f complexes were carried out under identical conditions to
allow comparison of results.
Preliminary studies were performed using 2a as a catalyst as
this complex was reported in Suzuki reaction in H2O at 80◦C.[13]
As a result, all complexes were found to be active catalysts in
Suzuki reaction, leading to the formation of biaryl compounds
with moderate to good conversions (21–97%) after 1h. The
results are summarized in Table 3.
RESULTS AND DISCUSSION
Synthesis of Ligands and Complexes
Pydim ligands (1a-f) were prepared in good yields by a
The most remarkable features are (i) very rapid reactions
Schiff-base condensation reaction (Scheme 1). The prepara- achieved at 80◦C. The reactions become notably slower as the
tions of Pydims have been described elsewhere.[6,21−24] All temperature decreases. (ii) Reaction rate strongly depended on
compounds were characterized by NMR and FT-IR techniques. the amount of catalyst, which should not be lower than 1%.
Py-Hp and Py–Hm protons for these compounds were observed Otherwise, the reaction becomes slower. (iii) The efficiency of
as doublets and triplets in a 2:1 ratio at 7.82–8.48 ppm. On the the catalyst seems to depend on the imine fragment of the pydim
other hand, PdCl2 reacts with 1.0 equiv. of pydim ligands (1) ligands. And (iv) although all of the Pydim-Pd(II) complexes
in refluxing EtOH and the resulting air-stable four coordinated are active catalysts, 2f is much more efficient. Catalytic activity
N
EtOH
+
N
PdCl3-
Ar
PdCl2
N
N
Ar
Pd
+
Ar
N
N
Ar
Cl
2a-f
SCH. 2. Synthesis of Pd(II) complexes.

340
O. DAYAN ET AL.
TABLE 1
Selected 1H-NMR resonances of the synthesized compounds 1 and 2
1H-NMR (δ, ppm)
Compounds
Py-Hp
Py-Hm
Py-Hp
1a
2a
1b
2b
1c
2c
1d
2d
1e
2e
1f
7.91
8.75
7.87
8.69
7.82
8.53
7.86
8.65
7.84
8.81
7.90
8.77
8.40
8.57
8.34
8.50
8.32
8.33
8.36
8.46
8.31
8.64
8.48
8.59
Py-Hm
N
PdCl3
Pd+
N
N
Ar
Ar
Cl
Ar :
a)
b)
F
2f
c)
e)
d)
f)
N
increases when electron donating groups are introduced at the Kinetic Parameters
aryl ring.
The four methods investigated in this paper are those by vK,
MC, MKN and WHYC.
The Madhusudanan-Krishnan-Ninan method[25]
Thermal Stability
ꢀ
ꢁ
ꢂ
ꢃ
Pydim-Palladium(II) complexes (2a-f) were studied by ther-
mogravimetric analysis from ambient temperature to 1000◦C
in nitrogen atmosphere. Typical TG/DTG and DTA curves for
compounds in the nitrogen atmosphere are present in Figures
1, 2 and 3. The initial and final temperatures and total mass
loses for each decomposition step in the thermal decomposition
of complexes are given Table 4, together with temperatures of
greatest rate of decomposition (DTGmax), evolved moiety and
the theoretical percentage mass losses.
g(α)
T1.9206
AE
E
ln
=ln
+3.7678 − 1.9206 ln E − 0.12040( )
βR
T
[1]
The MacCallum-Tanner method[26]
ꢂ
ꢃ
ꢂ
ꢃ
AE
0.449 + 0.217E
log g(α) = log
− 0.4828E0.4351
−
βR
10−3T
[2]
Wanjun-Yuwen-Hen-Cunxin method[27]
ꢀ
ꢁ
ꢀ
ꢁ
ꢂ
ꢃ
g(α)
T1.8946
AR
E
ln
= ln
+ 3.6350 − 1.8946lnE − 1.0014
TABLE 2
βE
RT
[3]
Selected IR bands (νC N cm−1) of the synthesized
compounds 1 and 2
The van Krevelen method[28]
Compounds
⎡
⎤
⎦
E
RT
ꢂ
ꢃ
a
m
a
b
c
d
e
f
A(0.368/Tm)
Ea
⎣
ꢄ
ꢅ
ln g(α) = ln
+
+ 1 lnT [4]
Ea
RTm
1
2
1655
1634
1621
1614
1622
1603
1633
1626
1636
1627
1643
1631
β
+ 1
RTm

PD(II) COMPLEXES
341
TABLE 3
Suzuki reaction of phenylboronic acid with aryl halidesa
cat.
1 h
B(OH)2
X
COMe
+
COMe
Entry
Complex
X
Yield
1
2
3
4
5
6
7
8
9
2a
2b
2c
2d
2e
2f
2a
2b
2c
2d
2e
2f
Br
Br
Br
Br
Br
Br
Cl
Cl
Cl
Cl
Cl
Cl
65
59
78
72
67
97 (23)b (34)c
35
21
46
43
39
56
10
11
12
aReaction conditions: 1 mmol of halide substrate, 1.5 mmol of PhB(OH)2, 2.0 mmol of Cs2CO3
◦
b
as base, 1 mol % of catalyst, 3 mL of 2-propanol, 80 C, GC yield. Reaction conditions: 1
mmol of halide substrate, 1.5 mmol of PhB(OH)2, 2.0 mmol of Cs2CO3 as base, 0.1 mol % of
catalyst, 3 mL of 2-propanol, 80◦C, GC yield. c Reaction conditions: 1 mmol of halide substrate,
1.5 mmol of PhB(OH)2, 2.0 mmol of Cs2CO3 as base, 1 mol % of catalyst, 3 mL of 2-propanol,
25◦C, GC yield.
In the equations above, α, g(α), β, Tm, E, A, R are the degree obtained using the least squares method. From the TG/DTG and
of reaction, integral function of conversion, heating rate, DTG DTA curves, the reaction order, n and activation energy, E of
peak temperature, activation energy (kJ.mol−1), pre-exponential the decomposition have been elucidated by the first one of the
factor (min−1) and gas constant (8.314 J.mol−1K−1), respec- methods mentioned above which has higher linear regression
tively.
coefficient obtained for Arrhenius plots (Table 5). The kinetic
In this study, the several methods based on a single heat- and thermodynamic parameters related to the complexes were
ing rate were used in the thermal analysis. The linearization calculated by the software developed in our laboratory using
curves of the each decomposition step of the complexes were PHP Web programming language.[29]
FIG. 1. Typical TG curves for 2a-f in the nitrogen atmosphere.

342
O. DAYAN ET AL.
FIG. 2. Typical DTG curves for 2a-f in the nitrogen atmosphere.
The decomposition processes of Pd(II)-pydim complexes are molecule C6H4F2 from the 2b. The reaction order and activation
similar for 2a-b, 2c-e and 2f. However the thermal decomposi- energies for the first and second decomposition steps of 2b were
tion pattern of each complex shows a different decomposition found to be 1.6 and 218.8 kJ.mol−1, and 2.6 and 97.87 kJ.mol−1
,
pattern due to the different aryl groups.
respectively, according to vK method and MKN method. 2f ex-
From the TG curve for complex 2a, it appears that the sample hibited two step decomposition processes. In the first step, 1/2
decomposes in two stages over the temperature range 30–579◦C. molecule Cl2 was eliminated in the temperature range 120–
The first decomposition occurs between 30 and 106◦C with a 195◦C with a 6.44% mass loss. This reaction was in an order
mass loss 6.99% in mass due to the loss of 1/2 molecule Cl2. of 1.5 with an activation energy of 165.5 kJ.mol−1according
This step required activation energy of 39.87 kJ.mol−1with the to vK method. The second decomposition step occurs in the
order of 0.7 according to MC method. In the second decom- temperature range 195–565◦C with 42.6% mass loss and corre-
position step, a mass loss of 45.98% with the order of 1.5 and sponds to the formation of 2 molecules C9H11on the complex.
46.26 kJ.mol−1activation energy according to MC involved the As seen in Figure3, from the DTA profile two exothermic peaks
elimination of 3 molecules C6H5on the complex in temperature for 2a and 2f are noted. The maximas of these peaks, which
range 106–579◦C. 2b is more stable than 2a and decompose are due to the formation of intermediate, are found to be 75
at 101 and 193◦C, respectively, to give 1/2 molecule Cl2 and 2 and 257, 149 and 244◦C, respectively. One exothermic peak
FIG. 3. Typical DTA curves for 2a-f.

PD(II) COMPLEXES
343
TABLE 4
TG/DTG and DTA data for the 2a-f
Complexes Step DTAmax/◦C DTGmax/◦C Temperature range /◦C DTA Weight loss /%, found (calc.)
Assignment
2a
I
II
75
257
65
247
30–106
106–579
Exo
Exo
6.99 (7.24)
45.98 (45.03)
1/2 Cl2
3 C6H5
residue
>579
2b
I
II
146
235
101–182
193–625
7.14 (6.74)
36.28 (36.12)
1/2 Cl2
2C6H4F2
219
>625
261
>489
269
>699
286
>336
149
Exo
Exo
Exo
Exo
residue
2c
2d
2e
2f
I
245
263
270
109–498
134–699
234–336
41.03 (41.66)
51.12 (49.33)
56.97 (57.60)
2C8H10N
1/2 Cl2, 2C10H13
3C8H9
residue
I
residue
I
residue
I
159
261
120–195
195–565
Exo
Exo
6.44 (6.18)
42.62 (41.46)
1/2 Cl2
2C9H11
II
244
residue
>565
for 2b is noted. The maximum of this peak is found to be activation energies for 2c-e complexes were found to be 1.30
219◦C.
and 47.35 kJ.mol−1according to vK method, and 1.60 and 59.38
From TG curves (Figure 1), 2c-e exhibited one step decom- kJ.mol−1, 2.5 and 317.3 kJ.mol−1according to MC method, re-
position process. Also, exothermic thermal effect at 261, 269, spectively.
and 286◦C in DTA profiles correspond to the decomposition of
The kinetic data obtained by different methods agree with
2c, 2d, and 2e complexes, respectively. The reaction orders and each other. The thermal stabilities of complexes increase in the
TABLE 5
Kinetic data on complexesa
Complexes Step Methods
n
Ea
lnA
ꢀS#
ꢀH#
ꢀG#
r
2a
I
MC
vK
MC
vK
vK
MC
MKN
0.7
0.7
1.5
1.9
1.6 218.8
1.5 217.6
39.87 17.82 −97.760 37.05
70.103 0.99904
69.152 0.99902
36.81 17.07 −104.00
46.26 15.47 −120.88
41.94 14.86 −125.93
33.99
43.98
II
I
106.84
113.12
0.99962
0.99952
47.66
2b
88.27
65.76
486.28 225.37
299.07 214.20
21.627 0.99905
88.894 0.99885
II
I
2.6
97.87 20.77 −76.62
97.77 20.69 −77.26
47.35 13.01 −141.35
47.07 14.58 −128.30
59.38 15.39 −121.85
56.77 15.68 −119.39
93.54
93.54
43.04
42.76
44.92
52.31
132.47
132.79
116.26
109.22
110.23
116.31
110.65
153.32
0.99962
0.99962
0.99948
0.99890
0.99681
0.99645
0.99972
0.99972
WHYC 2.6
2c
2d
2e
2f
vK
MC
MC
vK
MC
vK
1.3
1.1
1.6
2.2
I
I
2.5 317.3
2.7 319.4
1.5 165.56 67.02
1.4 169.52 75.94
2.1
2.2
74.83
68.06
372.38 312.85
316.06 324.94
309.29 171.964
383.46 165.924
I
vK
38.350 0.99813
0.2697 0.99745
MC
MC
MKN
II
65.34 18.91 −92.515 60.900 110.30
0.99825
0.99735
58.52 10.85 −159.53 54.080 139.27
aUnit of parameters: E /kJ mol−1, A /s−1, ꢀS#/kJ mol−1, ꢀH#/kJ mol−1, ꢀG#/kJ mol−1, r-correlation
coefficient of the linear plot, n-order of reaction

344
O. DAYAN ET AL.
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CONCLUSIONS
In summary, we synthesized a series of novel cationic
Pd(II) complexes with appropriate ligand precursors. A sys-
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reactions afforded the following order of catalytic activities:
bis(imino)pyridine palladium(II) complexes as efficient catalysts for Suzuki
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about the influence of several structural factors, including the
steric bulkiness around the Pd(II) center and the presence of
electron-withdrawing groups on the aromatic ring of the imine
fragment of the pydim ligands: when an electron withdrawing
group was introduced into the the imine fragment, catalytic yield
decreased. However, if an electron donating group was intro-
duced into the imine fragment, catalytic yield was increased. A
study on the thermal decomposition of the Pd(II) complexes was
also carried out by using several kinetic methods. The decom-
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