Synthesis, structural and theoretical studies of Pd(II) complexes containing an orthometallated C, C-chelating phosphorus ylide

Article abstract of DOI:10.1016/j.poly.2013.05.051

The phosphorus ylide [Ph₃PCHC(O)C₆H ₄-NO₂-4] (1) reacted with Pd(OAc)₂ to give the C, C-orthometallated complexes [Pd{K²(C, C)-C₆H ₄PPh2C(H)CO(C₆H₄-NO₂-4)}(μ-X)] ₂ (X = Cl (2); X = Br (3)) as a mixture of isomers, which underwent bridge cleavage reactions with monodentate ligands to afford the monomeric, neutral Pd(II) complexes [Pd{κ²(C, C)-C₆H ₄PPh₂C(H)CO(C₆H₄-NO ₂-4)}X(L)] (X = Cl, L=Me₃Py (4), PPh₃ (5); X = Br, L = Me₃Py (6), 4-MePy (7), PPh₃ (8). The complexes were identified and characterized by spectroscopic studies (IR and NMR). The X-ray single crystal analysis of 6 and 7 revealed the presence of an orthometallated C6H₄-2-PPh2 unit and a C-linked ylide, Pd-C(H). In the crystal structure of 6, the location of the Me₃Py ligand is trans to the Pd-C_ylide, according to the anti-symbiotic effect, whereas in 7 the 4-MePy ligand is preferentially cis to the Pd-C_ylide. Density functional theory (DFT) calculations in the reaction solvent (dichloromethane) indicated that the trans isomers of 6 and 7 are 3.03 and 0.70 kcal/mol more stable than their cis isomers, respectively.

Full text of DOI:10.1016/j.poly.2013.05.051

Polyhedron 61 (2013) 143–150
Contents lists available at SciVerse ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Synthesis, structural and theoretical studies of Pd(II) complexes
containing an orthometallated C,C-chelating phosphorus ylide
a
a
b
Kazem Karami a, , Mina Salimian , Mahboubeh Hosseini-Kharat , Giuseppe Bruno ,
⇑
Hadi Amiri Rudbari b, Hossein Tavakol a
a Department of Chemistry, Isfahan University of Technology, Isfahan 84156/83111, Iran
b Dipartimento di Chimica Inorganica, Università di Messina, Vill. S. Agata, Salita Sperone 31, 98166 Messina, Italy
a r t i c l e i n f o
a b s t r a c t
Article history:
The phosphorus ylide [Ph3PCHC(O)C6H4–NO2-4] (1) reacted with Pd(OAc)2 to give the C,C-orthometallat-
ed complexes [Pd{
isomers, which underwent bridge cleavage reactions with monodentate ligands to afford the monomeric,
neutral Pd(II) complexes [Pd{
2(C,C)–C6H4PPh2C(H)CO(C6H4–NO2-4)}X(L)] (X = Cl, L = Me3Py (4), PPh3
j l-X)]2 (X = Cl (2); X = Br (3)) as a mixture of
2(C,C)–C6H4PPh2C(H)CO(C6H4–NO2-4)}(
Received 6 April 2013
Accepted 23 May 2013
Available online 7 June 2013
j
(5); X = Br, L = Me3Py (6), 4-MePy (7), PPh3 (8). The complexes were identified and characterized by spec-
troscopic studies (IR and NMR). The X-ray single crystal analysis of 6 and 7 revealed the presence of an
orthometallated C6H4-2-PPh2 unit and a C-linked ylide, PdꢀC(H). In the crystal structure of 6, the location
of the Me3Py ligand is trans to the PdꢀCylide, according to the anti-symbiotic effect, whereas in 7 the 4-
MePy ligand is preferentially cis to the PdꢀCylide. Density functional theory (DFT) calculations in the reac-
tion solvent (dichloromethane) indicated that the trans isomers of 6 and 7 are 3.03 and 0.70 kcal/mol
more stable than their cis isomers, respectively.
Keywords:
Cyclopalladated
CH bond activation
Phosphorus ylide
Anti-symbiotic effect
Theoretical study
Ó 2013 Elsevier Ltd. All rights reserved.
1. Introduction
2. Results and discussion
Phosphorous ylides have been shown to be very versatile li-
gands due to their ambidentate character. Their coordination oc-
curs with notable selectivity, which has been explained in terms
of the anti-symbiotic effect and the nature of the donor atoms
bonded to the metal center [1–3]. The utility of metallated phos-
phorus ylides in synthetic chemistry has been well documented
[4,5]. We have recently reported some aspects of the chemistry
2.1. Spectral characterization
Ylide 1 can undergo a CꢀH activation process at two different
positions: (i) the phenyl ring of the phosphine group (Site A) and
(ii) the phenyl ring of the benzoyl moeity (Site B) (Scheme 1).
We have recently reported that the exclusive position for pallada-
tion on the related ylides Ph3P = CHC(O)R [6,8] is the phenyl ring
bonded to the P atom.
of
a-stabilized keto ylides, which can behave as monodentate
and chelate bidentate ligands towards Pd(II), Ag(I) and Hg(II) com-
plexes using different donor atoms [6–10]. Although many bond-
ing modes are possible for keto ylides [11], coordination through
carbon is more predominant and is observed with soft metal ions.
The orthometallation of phosphorous ylides R3P = C(R0)(R00) (R = al-
kyl, aryl; R0 and R00 = H, alkyl, aryl, acyl, etc.) [12–21] occurs in the
vast majority of cases, regioselectively at the Ph rings of the phos-
phine unit. With the aim of expanding the scope of this type of
orthometallated derivative, and also to gain more insight into their
chemical behavior, we have studied the C–H bond activation pro-
cess, induced by a Pd(II) salt, in ylide 1 (Scheme 1). In addition,
we have also studied the reactivity of the resulting orthopalladated
complexes towards different neutral ligands.
The IR spectrum of 3 shows a strong absorption due to the car-
bonyl stretching, shifted to higher frequency with respect to the
corresponding absorption in the parent ylide 1, this fact indicating
that the ylide is C-bonded to the Pd center [6,8,20–23]. Complex 3
is dinuclear and it is obtained as a mixture of geometric isomers, cis
(minor) and trans (major). This behavior has already been seen for
other dinuclear C-coordinated phosphorus ylide complexes [6,20].
In the 1H and 31P{1H} NMR spectra of 3, two sets of signals are ob-
served for each of the isomers.
The reactivity of complexes 2 and 3 was examined in order to
check the stability of the metallated chelating ligand. Thus, the
dinuclear complexes 2 and 3 were reacted with neutral monoden-
tate ligands L (L = Me3Py, 4-MePy and PPh3) to give the corre-
sponding
mononuclear
derivatives,
[Pd{j
2(C,C)–C6H4PPh2
C(H)CO(C6H4–NO2-4)}X(L)] (X = Cl, L = Me3Py (4), PPh3 (5); X = Br,
L = Me3Py (6), 4-MePy (7), PPh3 (8) (Scheme 1). The spectroscopic
⇑
Corresponding author. Tel.: +98 3113913239; fax: +98 3113912350.
E-mail address: karami@cc.iut.ac.ir (K. Karami).
0277-5387/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.poly.2013.05.051

144
K. Karami et al. / Polyhedron 61 (2013) 143–150
5
Ph
4
6
P
Ph
3
O
Site A
X
2
1
H
(i), (ii)
2
Pd
H
Site B
Ph2P
O
C
(1)
X = Cl (2)
Br (3)
C6H4-NO2
NO2
(iii)
(iv)
L
Pd
Br
Cl
Ph2P
O
H
Pd
C
X
H
Ph2P
O
C6H4-NO2
C
L = Me3Py (4)
PPh3 (5)
L = Me3Py (6)
4-MePy (7)
C6H4-NO2
PPh3
(8)
Scheme 1. (i) Pd(OAc)2, CH2Cl2,
D; (ii) KCl or KBr in MeOH; (iii) (complex 2, CH2Cl2, r.t), Me3Py, PPh3; (iv) (complex 3, CH2Cl2, r.t), Me3Py, 4-MePy, PPh3.
data of 4–8 are in accordance with the proposed structure in
Scheme 1. In their IR spectra, the band corresponding to (CO) ap-
singlets at 19.24 and 21.07 ppm, respectively. The appearance of
single signals for the P = C(H) group in each of the 1H and 31P{1H}
NMR spectra indicates the presence of only one isomer [8]. In the
1H NMR spectra, the signals due to the H6 proton (ortho to the met-
allated position) in 4 and 6 appear at 6.20 and 6.15 ppm, respec-
tively. These signals are clearly shifted to high field with respect
to the position in the starting dinuclear derivatives 2 and 3 (d
ꢁ7.12 ppm), and this high-field shift must be due to the aniso-
tropic shielding [27] produced by the pyridine ring of the Me3Py
group, which is non-planar to the phenyl ring. This fact implies a
cis arrangement of the C6H4 fragment of the metallated ligand
and the Me3Py, in accord with the anti-symbiotic behavior of the
Pd(II) centre [28].
m
pears in the range 1622–1633 cmꢀ1, which is higher than the par-
ent ylide 1. This high-frequency is a well-established effect in
complexes containing other carbonyl-stabilized phosphorus ylides
[6,8,20–23] and shows that the ligand coordinates through the
carbon atom and not through the oxygen; this has been confirmed
for complexes 6 and 7 by X-ray diffraction studies.
2
In the 1H NMR spectra of 4–8, the JPH values are smaller than
that in the parent ylide; this behavior has already been observed
for other C-coordinated carbonyl-stabilized phosphorus ylide com-
plexes [24–26], because the hybridization changes in the ylidic car-
bon (sp2 to sp3) in the C-coordination mode. Moreover, the NMR
spectroscopic data show that the mononuclear complexes 4, 5, 6
and 8 were obtained as a single isomer, while 7 was obtained as
a mixture of the geometric isomers, (a) and (b) depicted in Fig. 1.
The 1H NMR spectra of 4 and 6 show signals for the P = C(H) group
at 5.23 and 5.34 ppm, whilst the 31P{1H} NMR spectra show sharp
The 1H, 13C{1H} and 31P{1H} NMR spectra of 5 and 8 display a
single set of signals in each case, which shows that these com-
plexes are obtained as a single isomer. In the 13C{1H} NMR spectra
of 5 and 8, the ylidic carbon atoms appear as doublet of doublets at
38.42 and 40.02 ppm, respectively, meaning that each carbon is
O
O
Ph2
P
Ph2
P
C
C
CH
Pd
CH
Pd
NO2
NO2
N
Br
N
Br
Me
Me
(a)
(b)
Fig. 1. Possible isomers for complex 7.

K. Karami et al. / Polyhedron 61 (2013) 143–150
145
coupled with two different P nuclei (PPh3 and P = C(H)). Also, the
the anti-symbiotic effect [28], while in 7 the 4-MePy ligand is cis
to the PdꢀCylide. A similar behavior was observed earlier in the case
of ylide complexes of palladium (II) containing the 4-MePy ligand
[8].
orthometallated carbon atoms (C1) in 5 and 8 appear at 126.23
2
2
(d, JPC = 11.6 Hz) and 126.33 ppm (d, JPC = 11.4 Hz), respectively,
coupling with the P atom in the ring, while a coupling with a trans
phosphine should give a coupling constant of about 110–130 Hz
[29,30]. Moreover, in the 1H NMR spectra, the H6 proton of the
orthometallated C6H4 group is shifted to lower frequencies for 5
(6.58 ppm) and 8 (6.60 ppm) because of the anisotropic shielding
from the phenyl ring [27,31]. These data support the structure
shown in Scheme 1 for 5 and 8, in which the PPh3 ligand is trans
to the ylidic C atom, in good agreement with the transphobia be-
tween the PPh3 group and the arylic carbon [20,29,32].
2.3. Theoretical studies
2.3.1. Optimized structures
We have attempted to study important aspects of the prepared
molecules by computational methods. In this part, two complexes
(6 and 7) have been investigated. The X-ray structures of these two
complexes were also obtained. Therefore, we have optimized the
structures of both the cis and trans (CylideꢀPdꢀN) isomers of com-
plexes 6 and 7. The optimized structures of these four molecules
are shown in Fig. 4.
According to the the X-ray structures, complexes 6 and 7 have a
trans and cis geometry, respectively. The calculation of the Gibbs
free energies of both complexes showed that the trans isomers
The 1H NMR spectrum of 7 shows two signals for the P = C(H)
group that are assigned to a fast equilibrium between the cis and
trans isomers or a dynamic activity for exchange of 4-MePy and
Cl groups in solution [1] (Fig. 1).
The major isomer 7a has been characterized as that containing
the 4-MePy ligand cis with respect to the ylidic carbon. This assign-
ment of the structures 7a and 7b has been carried out by compar-
ison of the chemical shifts of the H6 proton of the C6H4 group (ortho
to the metallated position) in the two isomers. Thus, the major iso-
mer 7a shows the signal corresponding to H6 at d = 7.02 ppm, while
the minor isomer 7b shows the corresponding signal at
d = 6.52 ppm. This clear upfield shift can be due to the anisotropic
shielding undergone by H6, which is promoted by the cis pyridine
ligand in 7b. We have also observed the cis structure of complex 7,
with a cis-configuration of the coordinated 4-MePy to the carbon
(C1) of ylide, in the solid state.
are more stable than the cis isomers. The calculated
DGcis–trans val-
ues for 6 and 7 are 5.96 and 1.54 kcal/mol in the gas phase and 3.03
and 0.70 kcal/mol in the solvent (CH2Cl2), respectively. Therefore,
since
DGcis–trans for complex 7 is very low, its cis isomer might be
prepared. In addition, we have calculated the dipole moment of
these complexes. The calculated dipole moments of complexes
6trans, 6cis, 7trans and 7cis are respectively 11.58, 12.29, 13.01 and
12.08 Debye. Interestingly, in each complex, the isomer with a les-
ser dipole moment is the major isomer (trans in complex 6 and cis
in complex 7). We have not found any reasonable evidence for this
observation.
2.2. Crystal structures
From the optimized structures, molecular parameters can be
obtained. The most important parameters for the optimized
structures, in comparison with the X-ray parameters, are listed in
Table 2. A comparison between the calculated parameters of 6cis
and 7trans with those of the X-ray structures confirms that these
structures are close to the real structures. In addition, according
to the data, in both complexes, the PdꢀBr bond length in the cis
isomer is less than that in the trans isomer, and the PdꢀN bond
length in the trans isomer is less than that in the cis isomer. This
observation shows that the phenyl substituent increases the bond
length between the central metal and the opposite ligand, in agree-
Single crystals suitable for structure determinations were ob-
tained by slow evaporation of a concentrated CH2Cl2ꢀhexane solu-
tion of 6 and 7, respectively. Crystallographic data and parameters
concerning data collection and structure solution and refinement
are summarized in Table 1. Figs. 2 and 3 show the ORTEP plot of com-
plexes 6 and 7, and selected bond distances and angles, respec-
tively. The square planar coordination geometry of the Pd atoms
is slightly but not negligibly tetrahedrally distorted, with the metal
atoms protruding from the plane of the C2NBr core by 0.065 and
0.006 Å in 6 and 7, respectively. The distortion from the regular
square planar geometry is indicated by the values of the bond an-
gles subtended at the Pd centers (Figs. 2 and 3).
The P1–C1 bond lengths in 6 and 7 are significantly longer than
that observed in the related free ylide (1.711 Å) of the formula
PPh3C(H)COPh [33]. The PdꢀC bond distances involving the ortho-
metallated carbon and the ylide carbon atoms in 6 and 7 are not
significantly different from those found in related ortho-palladated
complexes (1.991(3), 2.017(5) and 2.115 (3), 2.117(5) Å [6]),
respectively.
The stabilized resonance structure for the parent ylide is de-
stroyed due to the complexation, thus the C19ꢀC20 and C1ꢀC2
bond lengths (1.435(9) and 1.470(3) Å) in 6 and 7, respectively,
are significantly longer than the corresponding distances found
in the similar uncomplexed phosphoranes (1.407(8) Å [34]), mean-
ing that this bond has been relaxed, while the C20ꢀO1 and C2ꢀO1
bond lengths (1.241(8) and 1.221(3) Å in 6 and 7, respectively) are
shorter than that observed in a similar ligand (1.256(2) Å) [34],
which indicates that the C-bonding of the ligand fixes the density
charge at the C atom and breaks the conjugation.
ment with a greater trans influence of Caryl in relation to Cylide
.
Moreover, the BrꢀPdꢀN bond angles in the cis isomer of both com-
plexes are smaller than in the trans isomers.
2.3.2. NBO and population analyses: frontier orbitals and partial
charges
We employed population analyses for all the geometric isomers
to extract the energies of the frontier molecular orbitals (FMOs).
Graphical presentations of the HOMO and LUMO of all the isomers
and their energies (eV) are shown in Fig. 5.
Fig. 5 shows noticeable different electron density distributions
in the frontier orbitals of the cis and trans isomers of each complex
and the electron density in both the LUMO and HOMO orbitals are
different from each other. These differences are related to the loca-
tion of the electron density and its quantity. Therefore, it is obvious
that the reactivity of these complexes is different and the energy
values of the frontier orbitals confirm these differences. By com-
paring the energies of the frontier orbitals, the LUMO–HOMO en-
ergy gap in the cis isomers are less than that in the trans isomers
in both complexes, which shows maybe the cis isomers are more
reactive than trans isomers for these two complexes.
In the crystal structure of 7, the PdC3P five-membered metalla-
cycle assumes an envelope conformation, with the atoms Pd1 and
C1 displaced from the mean plane of the remaining four atoms by
0.3995(2) and 0.2556(3) Å.
Comparing 6 and 7, the crystal structure of 6 shows that the
Me3Py ligand and PdꢀCylide are trans to each other, according to
NBO calculations are used as a useful method for the determi-
nation of many properties, especially for the reproduction of more
exact partial atomic charges. The results of these calculations for
both isomers of complexes 6 and 7 showed that the carbon atoms

146
K. Karami et al. / Polyhedron 61 (2013) 143–150
Table 1
X-ray crystallography data.
6
7
Empirical formula
Formula weight
T/K
C
34H30N2O3PPdBr
C32H26N2O3PPdBr
703.86
296
731.91
293
Crystal system
Space group
a (Å)
monoclinic
P21/n
13.0280(2)
monoclinic
P21/c
10.0671(2)
b (Å)
16.5210(3)
23.2805(5)
c (Å)
15.3470(2)
13.8637(3)
a
(°)
90
90
b (°)
108.30(3)
106.782(1)
c
(°)
90
3136.22
90
V (Å3)
3110.81(11)
Z
l
4
4
1.97
1.563
1432
(mmꢀ1
)
1.9538
1.5586
1487
Dcalc (Mg mꢀ3
F (000)
)
h Range (°)
2.4–20.12
2.3–26.5
Independent reflections
Data/restraints/parameters
Goodness-of-fit (GOF) on F2
Final R indices
6236
6236/0/379
1.03
R1 = 0.0641, wR2 = 0.1498
R1 = 0.1162, wR2 = 0.1755
6789
6789/0/389
0.88
R1 = 0.0286, wR2 = 0.0877
R1 = 0.0347, wR2 = 0.0953
R indices (all data)
Fig. 2. ORTEP diagram for complex 6 with ellipsoids drawn at the 50% probability level. The hydrogen atoms have been omitted for clarity. Selected bond lengths (Å), and angles
(°), Pd1–Br1 2.5345(10), Pd1–N1 2.089(5), P1–C19 1.766(6), P1–C7 1.819(7), P1–C13 1.789(6), P1–C1 1.796(6), C18–Pd1–C19 85.9(3), N1–Pd1–Br1 88.63(15), N1–Pd1–C19
176.0(2), C18–Pd1–Br1 172.72(18), C19–Pd1–Br1 95.38(18), N1–Pd1–Br1 88.63(15).
connected to Pd have different charges in the cis and trans isomers,
while for the other atoms, smaller differences can be observed.
such as Me3Py, 4-MePy and PPh3, split the halide bridging system
in 2 and 3 to give mono-nuclear complexes 4–8, in which the five-
membered metallacycle remains stable. The reaction is selective in
the case of P-ligands, while in the case of N-donors, two isomers
were detected in only one case. The crystal structures of 6 and 7
show that the Me3Py ligand is in a trans position to the ylidic car-
bon, while the 4-MePy ligand is in a cis position to this atom. The-
oretical calculations in the reaction solvent (dichloromethane)
3. Conclusion
New cyclopalladated complexes have been prepared through a
CꢀH bond activation process of the ylide ligand 1. The palladation
is formed selectively at the phenyl ring of the PPh3 unit (A posi-
tion), giving dinuclear halide-bridge palladacycles 2 and 3, which
are obtained as mixtures of isomers. Neutral monodentate ligands,
indicate that
DGcis–trans in complexes 6 and 7 is 3.03 and
0.70 kcal/mol, respectively.

K. Karami et al. / Polyhedron 61 (2013) 143–150
147
Fig. 3. ORTEP diagram for complex 7 with ellipsoids drawn at the 50% probability level. The hydrogen atoms have been omitted for clarity. Selected bond lengths (Å), and angles
(°): Pd1–C12 1.994(2), Pd1–C1 2.116(2), Pd1–Br1 2.4716(4), Pd1–N1 2.126(2), P1–C1 1.775(2), P1–C17 1.807(3), P1–C11 1.781(3), P1–C23 1.800(3), C12–Pd1–C1 83.66(10),
N1–Pd1–Br1 88.41(6), C1–Pd1–Br1 174.82(7), C12–Pd1–N1 174.29(10), C1–Pd1–N1 94.66(9), N1–Pd1–Br1 88.41(6).
19.51 (s, CHP, min.), 20.08 (s, CHP, maj.). Anal. Calc. for C52H38O6-
Br2P2N2Pd2: C, 51.13; H, 3.13; N, 2.29. Found: C, 51.20; H, 3.11;
N, 2.31%.
4. Experimental
4.1. General
4.3. General procedure for the synthesis of [Pd{j
2(C,C)–
C6H4PPh2C(H)CO(C6H4–NO2-4)}Cl(L)] (L = Me3Py (4), PPh3 (5))
The starting materials and solvents were purchased from Merck
and were used without further purification. Infrared spectra were
recorded on a FT-IR JASCO 680 spectrophotometer in the spectral
range 4000–400 cmꢀ1 using the KBr pellet technique. NMR spectra
were measured on a Bruker spectrometer at 400.13 MHz (1H),
100.61 MHz (13C) and 161.97 MHz (31P) using standard pulse se-
quences at 298 K. Melting points were measured on a Gallenhamp
9B 3707 F apparatus. Elemental analysis was performed on a Leco,
CHNS-932 apparatus. Ylide 1 and complex 2 were obtained using
procedures described earlier [6,35].
To a suspension of 2 (0.113 g, 0.1 mmol) in dichloromethane
(15 mL) was added Me3Py (0.026 mL, 0.2 mmol) or PPh3 (0.052 g,
0.2 mmol). The resulting solution was stirred at room temperature
for 8 h and then filtered through a plug of MgSO4. The filtrate was
concentrated to ca. 2 mL, and n-hexane (15 mL) was added to pre-
cipitate a deep yellow (4) or white (5) solid, which was collected
and air-dried.
(4): Yield: 0.097 g, 71%. Mp: 157 °C. IR (KBr, cmꢀ1): 1622
m(CO).
4.2. Synthesis of [Pd{
j
2(C,C)–C6H4PPh2C(H)CO(C6H4–NO2-4)}(
l-Br)]2
1H NMR (CDCl3, ppm) d: 2.09 (s, 3H, Me), 2.28 (s, 3H, Me), 2.87 (s,
2
(3)
3H, Me), 5.23 (d, 1H, CHP, JPH = 5.5 Hz), 6.20 (d, H6, C6H4,
3JHH = 7.3 Hz), 6.71 (br s, H5, C6H4), 6.93–6.96 (m, 2H, C6H4),
7.01–7.18 (m, 1H, Me3Py), 7.52–7.56 (m, 2H, Hp, PPh2), 7.62–7.68
(m, 1H, Me3Py), 7.66–7.71 (m, 4H, Hm, PPh2), 7.89–7.9 (m, 2H,
Ho, PPh2), 8.21–8.23 (m, 2H, Ho, PPh2), 8.26–8.28 (d, 2H, Hm,
C6H4C(O), 3JHH = 8.7 Hz), 8.60–8.61 (d, 2H, Ho, C6H4C(O), 3JHH = 8.7 -
Hz). 31P{1H} NMR (CDCl3, ppm) d: 19.24 (s, CHP). Anal. Calc. for C34-
H30O3ClPN2Pd: C, 59.40; H, 4.39; N, 4.07. Found: C, 59.38; H, 4.25;
N, 4.12%.
Pd(OAc)2 (0.0673 g, 0.3 mmol) was added to a solution of 1
(0.1275 g, 0.3 mmol) in CH2Cl2 (15 mL) and the resulting mixture
was refluxed overnight. The solvent was then evaporated and the
resulting deep yellow solid residue was dissolved in MeOH
(10 mL) and anhydrous KBr (0.0710 g, 0.6 mmol) was added. A pale
yellow solid immediately precipitated. The mixture was stirred for
12 h at room temperature and the resulting suspension was fil-
tered. The pale yellow solid thus obtained was washed with H2O
(5 mL) and Et2O (15 mL) and air dried to give (3). Yield: 0.230 g,
(5): Yield: 0.117 g, 70.6%. Mp: 167 °C. IR (KBr, cmꢀ1): 1623
m
(CO). 1H NMR (CDCl3, ppm) d: 5.53 (br s, 1H, CHP), 6.58 (d, H6,
3
62%. Mp: 208 °C. IR (KBr, cmꢀ1): 1627
m
(CO). 1H NMR (CDCl3,
C6H4, JHH = 3.2 Hz), 6.94–6.97 (m, 2H, C6H4), 7.19–7.23 (m, 6H,
Hm, PPh3), 7.29–7.35 (m, 7H, 6Ho (PPh3) + 1H (C6H4)), 7.49–7.52
(m, 3H, Hp, PPh3),7.64–7.64 (m, 2H, Hm, PPh2), 7.65–7.71 (m, 2H,
ppm) d: 4.96 (br s, 1H, CHP, min.), 5.13 (br s, 1H, CHP, maj.),
7.22–8.11 (m, 36H, HAr, both); 31P{1H} NMR (CDCl3, ppm) d:

148
K. Karami et al. / Polyhedron 61 (2013) 143–150
Fig. 4. Graphical presentation of the optimized structures of the cis (top) and trans (bottom) isomers of complexes 6 (left) and 7 (right).
2
Hm, PPh2), 7.71–7.72 (m, 2H, Hp, PPh2), 7.78–7.91 (m, 2H, Ho, PPh2),
8.0–8.02 (m, 2H, Ho, PPh2), 8.21–8.23 (d, 2H, Hm, C6H4C(O),
(s, 3H, Me), 5.33 (d, 1H, CHP, JPH = 5.4 Hz), 6.15 (d, H6, C6H4,
3JHH = 7.6 Hz), 6.73 (s, H5, C6H4), 6.95–6.98 (m, 2H, C6H4), 7.17–
7.19 (m, 1H, Me3Py), 7.52–7.56 (m, 2H, Hp, PPh2), 7.62–7.64 (m,
1H, Me3Py), 7.67–7.71 (m, 4H, Hm, PPh2), 7.89–7.93 (m, 2H, Ho,
PPh2), 8.21–8.23 (m, 2H, Ho, PPh2), 8.26 (dd, 2H, Hm, C6H4C(O),
3
3JHH = 9.2 Hz), 8.56 (d, 2H, Ho, C6H4C(O), JHH = 8.1 Hz). 13C{1H}
NMR d: 38.42 (dd, CHP, 1JPC = 67.7 Hz, 2JPC = 19.5 Hz),
1
2
C
aromatic{123.72 (d, JPC = 13.2 Hz), 126.23 (d, C1, JPC = 11.6 Hz),
3
2
3
129.08 (d, Cm, PPh2, JPC = 7.1 Hz), 129.68 (d, Ci, PPh2, JPC = 11.3
3JHH = 8.8 Hz), 8.25 (dd, 2H, Ho, C6H4C(O), JHH = 8.8 Hz). 13C{1H}
Hz), 130.26, 130.98, 131.50, 132.84, 134.44, 135.06, 138.14,
NMR d: 23.92 (Me), 24.81 (Me), 25.00 (Me), 29.94 (CHP), Caromatic
3
140.8, 144.2}, 132.11 (d, PPh3, JPC = 7.3 Hz), 133.76 (d, Ci PPh3,
{126.19, 128.30, 129.15, 129.9, 130.25, 130.34, 132.21 (d,
2JPC = 12.3 Hz), 200.21 (CO). 31P{1H} NMR (CDCl3, ppm) d: 15.09
(s, CHP), 32.64 (s, PdꢀPPh3). Anal. Calc. for C44H34O3ClP2NPd: C,
63.78; H, 4.13; N, 1.69. Found: C, 63.81; H, 4.05; N, 1.65%.
1JPC = 9.6 Hz), 132.82, 133.38 (d, JPC = 8.8 Hz), 136.25, 136.76,
2
141.32}, 198.13 (CO). 31P{1H} NMR (CDCl3, ppm) d: 21.07 (s,
CHP). Anal. Calc. for C34H30O3BrPN2Pd: C, 55.79; H, 4.13; N, 3.82.
Found: C, 55.71; H, 4.14; N, 3.80%.
4.4. General procedure for the synthesis of [Pd{
j
2(C,C)–
7: Yield: 0.095 g, 68%. Mp: 185 °C. IR (KBr, cmꢀ1): 1633
m(CO);
C6H4PPh2C(H)CO(C6H4–NO2-4)}Br(L)] (L = Me3Py (6), 4-MePy (7),
PPh3 (8)
1H NMR (CDCl3, ppm) d: 2.25 (s, 3H, Me, min), 2.45 (s, 3H, Me,
maj.), 5.01 (br s, 1H, CHP, min), 5.30 (br s, 1H,CHP, maj.), 6.52
(m, H6, C6H4, min.), 6.64–6.66 (m, 2H, C6H4, min), 6.91–6.97 (m,
2H, C6H4, maj.), 7.02 (m, H6, C6H4, maj.), 7.04–7.20 (m, 2H, C6H4,
both), 7.38–8.62 (m, 36H, PPh2 + 4-MePy + C6H4C(O), both).
13C{1H} NMR d: 20.75, 21.24 (Me, both), 29.94, 32,54 (CHP, both),
Caromatic both {125.48, 126.3, 127.9, 128.1, 129.05, 129.6, 129.8,
To a suspension of 3 (0.122 g, 0.1 mmol) in dichloromethane
(15 mL) was added Me3Py (0.026 mL, 0.2 mmol), 4-MePy
(0.019 mL, 0.2 mmol) or PPh3 (0.052 g, 0.2 mmol). The resulting
solution was stirred at room temperature for 8 h and then filtered
through a plug of MgSO4. The filtrate was concentrated to ca. 2 mL,
and n-hexane (15 mL) was added to precipitate a deep yellow (6),
yellow (7) or white (8) solid, which was collected and air-dried.
3
129.9, 130.05, 130.74, 133.11 (d, JPC = 9.6 Hz), 133.12, 133.38 (d,
3JPC = 8.8 Hz), 136.5, 136.6,141.32}, 199.4, 201.1 (CO, both).
31P{1H} NMR (CDCl3, ppm) d: 17.25 (s, CHP), 20.43(s, CHP). Anal.
Calc. for C32H26O3BrPN2Pd: C, 54.60; H, 3.72; N, 3.98. Found: C,
54.71; H, 3.66; N, 3.92%.
6: Yield: 0.107 g, 73%. Mp: 159 °C. IR (KBr, cmꢀ1): 1622
1H NMR (CDCl3, ppm) d: 2.11 (s, 3H, Me), 2.28 (s, 3H, Me), 2.87
m(CO).

K. Karami et al. / Polyhedron 61 (2013) 143–150
149
Table 2
7.91–7.98 (m, 2H, Hp, PPh2), 8.04 (m, 2H, Hm, C6H4C(O)), 8.21–
3
8.23 (d, 2H, Ho, C6H4C(O), JHH = 8.7 Hz). 13C{1H} NMR d: 40.02
Important molecular parameters for the calculated isomers (trans and cis) in
comparison with those from the X-ray structures of 6 and 7. Bond lengths are in
angstroms and bond angles are in degrees.
(dd, CHP, 1JPC = 63.1 Hz, 2JPC = 21.0 Hz), Caromatic{122.32 (d,
2
1JPC = 13.4 Hz), 126.33 (d, C1, JPC = 11.4 Hz), 128.12 (d, Cm, PPh2,
2
3JPC = 6.8 Hz), 129.78 (d, Ci, PPh2, JPC = 11.6 Hz), 130.06, 130.58,
Trans
Cis
X-ray
Complex 6
Bond lengths (Å)
Pd1–C18
Pd1–C19
Pd1–Br1
Pd1–N1
P1–C19
P1–C7
P1–C13
131.20, 132.74, 134.43, 136.02, 139.12, 140.58, 143.24}, 133.11
3
2
(d, PPh3, JPC = 8.2 Hz), 135.14 (d, Ci PPh3, JPC = 11.8 Hz), 197.4
(CO). 31P{1H} NMR (CDCl3, ppm) d: 16.41(s, CHP), 32.74 (s,
PdꢀPPh3). Anal. Calc. for C44H34O3BrP2NPd: C, 60.53; H, 3.92; N,
1.60. Found: C, 60.53; H, 4.13; N, 1.60%.
2.06
2.05
2.044(7)
2.109(7)
2.5345(10)
2.089(5)
1.766(6)
1.819(7)
1.789(6)
2.087
2.759
2.153
2.005
1.971
1.921
2.116
2.719
2.197
2.003
1.967
1.909
4.5. X-ray structure determinations
Bond angles (°)
C18–Pd1–C19
N1–Pd1–Br1
N1–Pd1–C19
N1–Pd1–C18
C18–Pd1–Br1
87.16
86.84
176.71
94.86
172.07
87.65
84.01
94.64
176.98
93.90
85.9(3)
Diffraction data for 6 and 7 were measured on a Bruker-Nonius
X8 ApexII diffractometer equipped with a CCD area detector by
88.63(15)
176.0(2)
90.2(2)
using graphite-monochromated Mo K
a radiation (k = 0.71073 Å)
generated from a sealed tube source. Data were collected and re-
duced by SMART and SAINT software [36] in the Bruker package. The
structures were solved by direct methods [37] and then developed
by least squares refinement on F2 [38,39]. All non-H atoms were
placed in calculated positions and refined as isotropic with the
‘‘riding-model technique’’.
172.72(18)
Complex 7
Bond lengths (Å)
Pd1–C12
Pd1–C1
Pd1–Br1
Pd1–N1
P1–C1
P1–C17
2.062
2.086
2.733
2.127
2.002
1.961
2.049
2.114
2.699
2.169
1.99
1.994(2)
2.116(2)
2.4716(4)
2.126(2)
1.775(2)
1.807(3)
1.962
4.6. Computational methods
Bond angles (°)
C12–Pd1–C1
N1–Pd1–Br1
C1–Pd1–Br1
C12–Pd1–N1
C1–Pd1–N1
N1–Pd1–Br1
85.365
85.506
95.07
94.145
178.728
85.506
84.725
85.144
178.769
177.697
96.06
83.66(10)
88.41(6)
174.82(7)
174.29(10)
94.66(9)
88.41(6)
The DFT method was applied to optimize all the structures and
to calculate molecular and spectral parameters of the prepared
compounds in the gas phase. The energy values in the solvent
(dichloromethane) were calculated using SCRF keyword with Tom-
asi’s polarized continuum (PCM) model [40]. The GAUSSIAN 09 pro-
gram package [41] was employed for optimizing the structures
and for the calculation of the molecular properties. To perform
DFT calculations, Becke0s three-parameter exchange functional
[42] was used in combination with the Lee–Yang–Parr correlation
functional (B3LYP) with the LANL2DZ basis set [43]. All molecules
have been used without any symmetry restriction and C1
85.144
8: Yield: 0.122 g, 69.6%. Mp: 165 °C. IR (KBr, cmꢀ1): 1623
m(CO);
1H NMR (CDCl3, ppm) d: 5.60 (br s, 1H, CHP), 6.60 (m, H6, C6H4,
3JHH = 4.6 Hz), 6.96–6.97 (m, 2H, C6H4), 7.06–7.08 (m, 1H, C6H4),
7.18–7.23 (m, 6H, Hm, PPh3), 7.29–7.35 (m, 9H, Hp + Ho,
PPh3),7.49–7.53 (m, 4H, Hm, PPh2), 7.63–7.76 (m, 4H, Ho, PPh2),
6-cis
6-trans
7-cis
7-trans
LUMO
E = 0.017
Eg= 0.026
E = 0.005
Eg= 0.145
E = −0.012
Eg= 0.132
E = 0.009
Eg = 0.146
HOMO
E = −0.140
E = −0.144
E = −0.137
E = −0.009
Fig. 5. Graphical presentation of the LUMO and HOMO for the optimized structures of the cis and trans isomers of complexes 6 and 7, and their energies (eV).

150
K. Karami et al. / Polyhedron 61 (2013) 143–150
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We are grateful for financial support from the Department of
Chemistry, Isfahan University of Technology (IUT).
Appendix A. Supplementary data
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