2,6-Dibenzhydryl-N-(2-aryliminoacenaphthylenylidene)-4-chlorobenzenamino- palladium dichlorides: Synthesis, characterization, and use as catalysts in the Heck-reaction

Article abstract of DOI:10.1016/j.jorganchem.2012.05.015

A series of 2,6-dibenzhydryl-N-(2-aryliminoacenaphthylenylidene)-4- chlorobenzenaminopalladium(II) chloride complexes (C1-C6) were prepared and fully characterized by FT-IR and NMR spectroscopy, and by elemental analysis. The molecular structures of repre

Full text of DOI:10.1016/j.jorganchem.2012.05.015

Journal of Organometallic Chemistry 713 (2012) 151e156
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Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
2,6-Dibenzhydryl-N-(2-aryliminoacenaphthylenylidene)-4-chlorobenzenamino-
palladium dichlorides: Synthesis, characterization, and use as catalysts
in the Heck-reaction
,
a
,
,
b,
Qing Ban a , Jun Zhang b, Tongling Liang b, Carl Redshaw c , Wen-Hua Sun
**
*
***
a Shandong Provincial Key Laboratory of Fine Chemicals, Shandong Polytechnic University, Jinan 250353, China
b Key laboratory of Engineering Plastics and Beijing National Laboratory for Molecular Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
c School of Chemistry, University of East Anglia, Norwich NR4 7TJ, UK
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of 2,6-dibenzhydryl-N-(2-aryliminoacenaphthylenylidene)-4- chlorobenzenaminopalladium(II)
chloride complexes (C1eC6) were prepared and fully characterized by FT-IR and NMR spectroscopy, and
by elemental analysis. The molecular structures of representative complexes C2 and C6 were confirmed
as square planar at the palladium center by single crystal X-Ray diffraction. All palladium complexes
exhibited good activity in the Heck cross-coupling reaction with conversions greater than 90%. Catalytic
activity trends were attributed to differences in the solubility of the pre-catalysts; palladium complexes
bearing more soluble alkyl-substituents performed with higher catalytic activities.
Received 16 March 2012
Received in revised form
26 April 2012
Accepted 8 May 2012
Keywords:
Palladium
Heck reaction
Cross-coupling
X-ray diffraction
Ó 2012 Elsevier B.V. All rights reserved.
1. Introduction
which showed good capability in Heck coupling [32]. In our previous
work employing benzhydryl-substituted anilines as ligand precur-
The carbonecarbon cross-coupling reaction has played a key role
in organic synthesis, and has been utilized in synthetic methodol-
ogies or the targeting of natural products, pharmaceuticals, and
other useful materials [1e6]. The Heck reaction [7e10] has attracted
attention ever since its discovery in the early 1970s [11,12], and has
provided an efficient coupling methodology (haloarenes and olefin
derivatives) [3,13]. The advantages of this type of reaction are that it
only requires mild reaction conditions and can tolerate a variety of
functional groups [14e16]. In comparison with palladium-mediated
reactions such as the SonogashiraeHagihara [17,18], and
SuzukieMiyaura [19e22], the catalytic behavior of palladium
complexes in the Heck reaction are hugely affected by the nature of
the ligands employed due to electronic and steric influences of
substituents [23e25]. More recently, organophosphine ligands have
been studied in order to develop new palladium catalysts for Heck
coupling [26e31]. However, to overcome issues of sensitivity and
toxicity associated with organophosphines (P3þ), palladium
complexes bearing sp3-N-bidentate chelates have been developed,
sors for metal pre-catalysts for ethylene polymerization [33e39],
nickel pre-catalysts bearing unsymmetrical benzhydryl-substituted
diimine ligands showed not only high activities but also enhanced
thermal stabilities [37e39]. However, palladium complexes ligated
by
2,6-dibenzhydryl-N-(2-aryliminoacenaphthylenylidene)-4-
chlorobenzenamines polymerized ethylene with relatively low
activity. To broaden the scope for potential application, these
palladium complexes were exploredfor theirability tocatalyze Heck
coupling. Herein, the synthesis and characterization of the title
palladium complexes and their catalytic behavior in the Heck reac-
tion are reported.
2. Results and discussion
2.1. Synthesis and characterization of ligands and complexes
The unsymmetrical 2,6-dibenzhydryl-N-(2-aryliminoacenaphthyl-
enylidene)-4-chloro- benzenamines (L1eL5) were prepared according
to the reported method [38], and the symmetrical 2,6-dibenzhydryl-N-
(2-(2,6-dibenzhydryl-4-chlorophenylimino)-acenaphthylenylidene)-4-
chlorobenzenamine (L6) was isolated as a by-product from the
condensation reaction of 2,6-dibenzhydryl-4-chlorobenzenamine and
acenaphthylene-1,2-dione [38].
* Corresponding author. Tel.: þ44 (0) 1603 593137; fax: þ44 (0) 1603 592003.
** Corresponding author. Tel.: þ86 531 89631208; fax: þ86 10 531 89631212.
*** Corresponding author. Tel.: þ86 10 62557955; fax: þ86 10 62618239.
E-mail addresses: banqing70619@yahoo.com.cn (Q. Ban), carl.redshaw@
uea.ac.uk (C. Redshaw), whsun@iccas.ac.cn (W.-H. Sun).
0022-328X/$ e see front matter Ó 2012 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2012.05.015

152
Q. Ban et al. / Journal of Organometallic Chemistry 713 (2012) 151e156
The stoichiometric reaction of PdCl2(CH3CN)2 with the
a-dii-
mino ligands (L1eL6) in dichloromethane afforded the corre-
sponding palladium chloride complexes (C1eC6) in reasonable
isolated yields (Scheme 1), and these palladium complexes could be
purified by column chromatography. The elemental analysis data
confirmed their composition as LPdCl2, which were further iden-
tified by FT-IR spectra and NMR measurements. Due to the efficient
coordination of Nimino to Pd, the absorption of the C]N vibration
became quite weak in the IR spectra of the palladium complexes,
which is consistent with the observation of the infrared inactive
C]N vibration in the palladium complexes [40]. The 13C NMR peaks
for the C]N groups in the palladium complexes were shifted to
lower field, for example 177.5 ppm for C6 vs 163.8 ppm for L6, and
were indicative of strong coordination between the Nimino atom
and the Pd center [41].
2.2. Crystal and molecular structures
Single crystals of representative complexes C2 and C6 were
obtained by slow diffusion of hexane into dichloromethane
solutions at ambient temperature. The molecular structures of C2
and C6 revealed a similar square planar geometry at palladium
(Figs. 1 and 2); selected bond lengths and angles are tabulated in
Table 1.
Fig. 1. The molecular structure of the complex C2; thermal ellipsoids are shown at 30%
probability. Hydrogen atoms are omitted for clarity.
As shown in Fig. 1 (C2), the palladium center is coordinated by
two nitrogen of the chelate ligand and two chloride ligands. The
coordination plane containing the Pd1, N1, and N2 atoms is almost
coplanar with the phenyl ring with a dihedral angle of 7.61ꢀ;
meanwhile the coordination plane containing the Pd1, N1, N2
atoms forms a dihedral angle of 9.02ꢀ with the phenyl plane in
complex C6 (Fig. 2). On comparison with literature data [41,42], the
PdeCl distances in complexes C2 and C6 are within the normal
range, as are the PdeN bond lengths.
Heck reaction required an activation temperature, for example at
150 ꢀC (entry 2) the conversion was dramatically increased (to 92%)
compared with only trace product formation at 130 ꢀC (entry 1). To
confirm the solution stability of the palladium complex (C5) at the
reaction temperature (150 ꢀC), noting that it has a decomposition
temperature above 250 ꢀC, its N,N-dimethylacetamide (DMA)
solution was refluxed for 12 h, and the palladium complex was
recovered in more than 95% yield. Thus, this palladium complex can
be considered a highly thermally stable catalyst for the Heck
reaction. On prolonging the reaction time, the reaction was almost
quantitative with only trace bromobenzene remaining (entry 3).
Using DMA as the solvent, and employing Na2CO3 (entry 2) as base
produced a higher yield than the system using NaOAc (entry 4) or
2.3. Catalytic behavior
Given the poor performance of complexes C1eC6 in ethylene
polymerization, (catalytic activities were in the range 103
gPE$molꢁ1(Pd)$hꢁ1), the focus of our screening program switched
to Heck coupling.
The synergic effect of solvent and base employed is commonly
considered in the Heck reaction, and complex C5 was used to
optimize the reaction conditions for the typical coupling reaction of
bromobenzene and styrene (affording 1,2-diphenylethene). By
employing a slight excess (1.2 equivalent) of styrene and 1.1
equivalent of base to bromobenzene in the presence of a catalytic
amount ([Pd]/[bromobenzene] ¼ 2 ꢂ 10ꢁ5) of C5 and different
solvents, the conversion of bromobenzene were observed and
results are tabulated in Table 2. As shown by the entries 1 and 2, the
PdCl2(CH3CN)2
R1
R1
N
N
N
Cl
N
CH2Cl2
Pd
DBCPh
DBCPh
Cl
R1
L1-L6
DBCPh- as
2,6-dibenzhydryl-4-chlorophenyl
R1
R2
R2
C1-C6
1
2
3
4
5
6
i
R1
R2
Me Et Pr Me Et CH(Ph)2
H
H H Me Me Cl
Fig. 2. The molecular structure of the complex C6; thermal ellipsoids are shown at 30%
probability. Hydrogen atoms are omitted for clarity.
Scheme 1. Synthetic procedure for the palladium complexes (C1eC6).

Q. Ban et al. / Journal of Organometallic Chemistry 713 (2012) 151e156
153
Table 1
Table 3
Selected bond lengths (Å) and angles (ꢀ) for complexes C2 and C6.
Heck reaction of bromobenzene and styrene by C1eC6.a
2×10-3 mol% [Pd]
1.1 mol% Na2CO3
DMA
C2
C6
2.041(3)
2.063(3)
2.274(2)
2.267(1)
1.288(5)
1.431(5)
1.303(5)
1.436(5)
Br
Bond Lengths (Å)
Pd(1)eN(1)
Pd(1)eN(2)
Pd(1)eCl(1)
Pd(1)eCl(2)
N(1)eC(11)
N(1)eC(13)
N(2)eC(12)
2.051(3)
2.052(3)
2.277(1)
2.265(1)
1.291(4)
1.428(4)
1.280(4)
1.429(4)
c
Entry
Complex
Conversion (%)b
TOF (hꢁ1
)
1
2
3
4
5
6
C1
C2
C3
C4
C5
C6
82
83
87
85
92
83
3400
3500
3700
3600
3800
3500
N(2)eC(45)
Bond Angles (ꢀ)
N(1)ePd(1)eN(2)
N(1)ePd(1)eCl(1)
N(2)ePd(1)eCl(1)
N(1)ePd(1)eCl(2)
N(2)ePd(1)eCl(2)
Cl(1)ePd(1)eCl(2)
81.10(11)
92.68(8)
173.31(8)
174.43(8)
94.32(9)
92.03(4)
80.79(14)
173.31(11)
94.32(11)
93.42(10)
173.71(11)
91.64(5)
a
Reaction conditions: 2.0 mmol bromobenzene, 2.4 mmol styrene, 2.2 mmol
Na2CO3, 4.0 mL DMA, 150 ꢀC, 12 h.
b
Determined by GC.
c
TOF: mol bromobenzene/mol Pd h.
K2CO3 (entry 5). Considering the influence of solvent, the perfor-
mance in DMA (entry 2) was better than that of observed in other
solvents such as N,N-dimethylformamide (DMF, entry 6) or toluene
(entry 7).
species. All products were isolated and confirmed by 1H NMR and
13C NMR spectroscopy and by comparison with literature data
[44e46].
According to the above results, the solvent DMA and 1.1 equiv-
alents of Na2CO3 at 150 ꢀC for 12 h was chosen to further explore
this coupling reaction using the other palladium complexes
(Table 3). In general, catalytic activities were quite similar, with
only slight differences that could be attributed to the substituents
present on the ligands, which in turn can affect the solubility of
each complex. Given the solubility tendency is i-Pr (for C3) > Et (for
C2 and C5 with an additional methyl group) > Me (for C1 and C4
with an additional methyl group), the catalytic activities were thus
observed as C5 > C3 > C4 > C2 > C1.
To understand the scope of the Heck coupling reaction, different
aryl substituted bromides were used to react with styrene (Table 4).
In all cases, the coupling reactions achieved high activities. Alter-
native aryl bromides showed relative lower activities than did
bromobenzene, which is consistent with previous literature
observations [43] reflecting the bulk of the substituents. In addi-
tion, the position of substituents also influenced the results due to
electronic effects. Moreover, the lower activities observed for 2-
bromothiophene (entry 4) and 4-bromoaniline (entry 7) were
tentatively attributed to the potential coordination between the
functional groups (amine and sulfur atom) and the palladium
3. Conclusion
A series of 2,6-dibenzhydryl-N-(2-phenyliminoacenaphthyleny
lidene)-4-chlorobenzenamine Pd(II) complexes were prepared
and fully characterized. These Pd(II) complexes exhibited high
Table 4
Heck reaction of aryl bromides and styrene using complex C5.a
2 × 10-3 mol% C5
1.1 mol % Na2CO3
Ar
Ph
ArBr
Ph
DMA
c
Entry
1
ArBr
Conversion(%)b
92
TOF (hꢁ1
)
3800
Br
2
3
84
78
3500
3300
H3C
Br
Br
CH3
Table 2
Optimization of bromobenzene and styrene using complex C5.a
2×10-3 mol% C5
1.1 mol% base
Br
S
4
76
82
3200
3400
Br
Solvent
5
6
MeO
MeO
Br
c
Entry Base
Solvent Temp. (ꢀC) Time (h) Conversion (%)b TOF (hꢁ1
)
1
2
3
4
5
6
7
Na2CO3 DMA
130
150
150
150
150
150
12
12
24
12
12
12
12
trace
92
99
82
44
e
Na2CO3 DMA
Na2CO3 DMA
NaOAc DMA
K2CO3
Na2CO3 DMF
3800
2100
3400
1800
3300
1400
87
82
3600
3400
Br
Br
DMA
7
79
34
H2N
Na2CO3 Toluene 110
a
a
Reaction conditions: 2.0 mmol bromobenzene, 2.4 mmol styrene, 2.2 mmol
Reaction conditions: 2.0 mmol ArBr, 2.4 mmol styrene, 2.2 mmol Na2CO3, 4.0 mL
DMA, 150 ꢀC, 12 h.
base, 4.0 mL solvent.
b
b
Determined by GC.
TOF ¼ mol bromobenzene/mol Pd h.
Determined by GC.
TOF: mol ArBr/mol Pd h.
c
c

154
Q. Ban et al. / Journal of Organometallic Chemistry 713 (2012) 151e156
activities towards the Heck coupling reaction, exhibiting high
thermal stability.
(d, J ¼ 7.32 Hz, 1H), 2.59 (s, 6H) ppm. 13C NMR (100 MHz, CDCl3,
TMS):
d 178.3, 176.2, 146.4, 143.2, 141.5, 140.9, 139.7, 139.6, 134.2,
132.5, 131.2, 129.9, 129.8, 129.6, 129.2, 128.9, 128.5, 128.4, 127.8,
127.3, 127.1, 126.2, 124.3, 123.4, 123.1, 52.9, 21.2, 19.0 ppm. Anal. Calc
for C52H39Cl3N2Pd (902): C, 69.04; H, 4.35; N, 3.10%. Found: C,
68.75; H, 4.43; N, 3.00%.
4. Experimental section
4.1. General considerations and materials
4.2.3. 2,6-Dibenzhydryl-N-(2-(2,6-diethylphenylimino)
acenaphthylenylidene)-4-chlorobenzenaminopalladium
dichloride (C2)
Using the same procedure as for the synthesis of C1, C2 was
obtained as a red powder in 62.7% yield (82 mg). M.p.>250 ꢀC
(dec.). FT-IR (KBr; cmꢁ1): 3061, 2966, 2927, 2875, 1622, 1600, 1576,
1494, 1445, 1299, 1178, 1099, 765, 741, 700. 1H NMR (400 MHz,
All manipulations of moisture-sensitive compounds were
carried out under an atmosphere of nitrogen using standard
Schlenk techniques. All organic compounds used as ligands were
prepared according to our previous procedure [38]. Melting points
were determined using a digital electrothermal apparatus without
calibration. NMR spectra were recorded on a Bruker DMX 400 MHz
instrument at ambient temperature using TMS as an internal
CDCl3, TMS):
d
7.87 (d, J ¼ 8.20 Hz, 1H), 7.66 (d, J ¼ 8.27 Hz, 1H), 7.49
standard;
spectra were obtained on a PerkineElmer FT-IR 2000 spectropho-
tometer by using the KBr disc in the range of 4000-400 cmꢁ1
d values are given in ppm and J values in Hz. The IR
(t, J ¼ 7.82 Hz, 1H), 7.36e7.22 (m, 13H), 7.13 (d, J ¼ 7.60 Hz, 4H), 7.04
(s, 2H), 6.98 (t, J ¼ 7.44 Hz, 1H), 6.47 (t, J ¼ 7.48 Hz, 6H), 6.38 (d,
J ¼ 7.24 Hz, 1H), 6.19 (t, J ¼ 7.46 Hz, 2H), 5.71 (d, J ¼ 7.03 Hz, 1H),
3.23 (m, 2H), 2.82 (m, 2H), 1.40 (t, J ¼ 7.52 Hz, 6H) ppm. 13C NMR
.
Elemental analysis was carried out using a Flash EA 1112 micro-
analyzer. Conversions were determined by CP-3800 GC.
(100 MHz, CDCl3, TMS):
d 178.1, 176.4, 146.3, 142.1, 141.6, 140.9,
139.8, 139.7, 135.1, 134.2, 132.3, 129.9, 129.6, 129.2, 129.0, 128.5,
128.4, 127.8, 127.3, 127.1, 126.6, 126.3, 123.7, 123.1, 53.0, 25.1,
14.2 ppm. Anal. Calc for C54H43Cl3N2Pd (930): C, 69.54; H, 4.65; N,
3.00%. Found: C, 69.37; H, 4.62; N, 2.76%.
4.2. Syntheses and characterization
4.2.1. 2,6-Dibenzhydryl-N-(2-(2,6-dibenzhydryl-4-
chlorophenylimino)acenaphthylenylidene)-4-chlorobenzenamine
(L6)
4.2.4. 2,6-Dibenzhydryl-N-(2-(2,6-diisopropylphenylimino)
acenaphthylenylidene)-4-chlorobenzenaminopalladium
dichloride (C3)
Using the same procedure as for the synthesis of C1, C3 was
obtained as a red powder in 59.9% yield (80 mg). M.p. >250 ꢀC (dec.).
FT-IR (KBr; cmꢁ1): 3060, 2964, 2870, 1622, 1600, 1577, 1494, 1442,
1300, 1181, 1079, 768, 744, 700. 1H NMR (400 MHz, CDCl3, TMS):
A solution of 2,6-dibenzhydryl-4-chlorobenzenamine (2.12 g,
4.6 mmol), acenaphthylene-1,2-dione (0.84 g, 4.6 mmol), and
a catalytic amount of p-toluenesulfonic acid in toluene (100 mL)
was refluxed for 6 h. After solvent evaporation at reduced pressure,
the crude product was purified by silica column chromatography
(Vpetroleum
: Vdichloromethane ¼ 2 : 1) to afford yellow 2-(2,6-
ether
dibenzhydryl-4-chlorophenylimino)-acenaphthylenone (1.48 g,
51.5% isolated yield), and further elution gave yellow 2,6-
dibenzhydryl-N-(2-(2,6-dibenzhydryl -4-chlorophenylimino)ace-
naphthylenylidene)-4-chlorobenzenamine (L6) in 0.47 g (10.1%).
M.p.: 257e258 ꢀC. FT-IR (KBr; cmꢁ1): 3061, 3029, 2894, 1655, 1592,
1493, 1423, 1180, 1034, 890, 765, 728, 696. 1H NMR (400 MHz,
d
7.87 (d, J ¼ 8.30 Hz,1H), 7.63 (d, J ¼ 8.38 Hz,1H), 7.54 (t, J ¼ 7.81 Hz,
1H), 7.37 (m, 7H), 7.30e7.22 (m, 6H), 7.09 (d, J ¼ 7.59 Hz, 4H), 7.04 (s,
2H), 6.93 ( t, J ¼ 7.83 Hz, 2H), 6.48 (t, J ¼ 7.43 Hz, 4H), 6.42 (s, 2H), 6.34
(d, J ¼ 7.26 Hz, 1H), 6.21 (t, J ¼ 7.44 Hz, 2H), 5.67 (d, J ¼ 7.28 Hz, 1H),
3.66 (m, 2H),1.60 (d, J ¼ 6.63 Hz, 6H),1.11 (d, J ¼ 6.78 Hz, 6H) ppm.13C
NMR (100 MHz, CDCl3, TMS): d 177.7,176.3,141.0,139.9,139.8, 139.5,
CDCl3, TMS):
d
7.56 (d, J ¼ 8.25 Hz, 2H), 7.18e7.13 (m, 12H), 7.09 (s,
139.2,138.6,133.4,132.3,130.7,129.0,128.8,128.1,127.8,127.7,127.3,
126.7, 126.5, 125.9, 124.6, 123.9, 122.8, 121.9, 52.3, 29.2, 23.9,
23.4 ppm. Anal. Calc for C56H47Cl3N2Pd (958): C, 70.01; H, 4.93; N,
2.92%. Found: C, 69.69; H, 5.14; N, 2.84%.
4H), 7.03 (m, 8H), 6.92 (t, J ¼ 7.55 Hz, 2H), 6.83 (m, 8H), 6.67 (t,
J ¼ 8.64 Hz, 12H), 6.16 (d, J ¼ 7.15 Hz, 2H), 5.65 (s, 4H) ppm. 13C NMR
(100 MHz, CDCl3, TMS):
d 163.8, 147.5, 142.9, 141.8, 134.0, 129.8,
129.5, 129.2, 129.0, 128.4, 128.2, 126.9, 126.5, 126.3, 124.4, 51.6 ppm.
Anal. Calc for C76H54Cl2N2 (1064): C, 85.62; H, 5.11; N, 2.63%. Found:
C, 85.77; H, 5.01; N, 2.84%.
4.2.5. 2,6-Dibenzhydryl-N-(2-(2,4,6-trimethylphenylimino)
acenaphthylenylidene)-4-chlorobenzenaminopalladium
dichloride (C4)
4.2.2. 2,6-Dibenzhydryl-N-(2-(2,6-dimethylphenylimino)
acenaphthylenylidene)-4-chlorobenzenaminopalladium(II)
dichloride (C1)
Using the same procedure as for the synthesis of C1, C4 was
obtained as a red powder in 52.7% yield (68 mg). M.p. >250 ꢀC
(dec.).FT-IR (KBr; cmꢁ1): 3056, 2961, 2871, 1623, 1600, 1576, 1490,
1442, 1299, 1182, 1076, 768, 742, 698. 1H NMR (400 MHz, CDCl3,
The syntheses of C1eC6 were conducted by a similar procedure,
thus only the synthesis of C1 is described here in detail. The ligand
2,6-dibenzhydryl-N-(2-(2,6-dimethylphenylimino)acenaph-
thylenylidene)-4-chloro- benzenamine L1 (0.11 g, 0.14 mmol) and
PdCl2(CH3CN)2 (0.04 g, 0.14 mmol) were added to a Schlenk tube
together with 10 mL of dried dichloromethane. The reaction
mixture was then stirred for 12 h at room temperature, the
resulting solutions were concentrated under vacuum, the residual
solids were further purified by silica column chromatography
(Vpetroleum ether : Vethyl acetate ¼ 5:1) to afford a red powder of C1 in
62.3% yield (80 mg). M.p.>250 ꢀC (dec.). FT-IR (KBr; cmꢁ1): 3058,
2965, 2875, 1624, 1600, 1581, 1494, 1443, 1302, 1185, 1075, 768, 743,
TMS):
d
7.89 (d, J ¼ 8.31 Hz, 1H), 7.68 (d, J ¼ 8.30 Hz, 1H), 7.35 (m,
5H), 7.29e7.21 (m, 6H), 7.14 (d, J ¼ 7.48 Hz, 4H), 7.03 (s, 2H), 7.01 (s,
2H), 6.99 (d, J ¼ 7.73 Hz, 1H), 6.45 (t, J ¼ 9.88 Hz, 7H), 6.16 (t,
J ¼ 7.40 Hz, 2H), 5.69 (d, J ¼ 7.22 Hz, 1H), 2.55 (s, 6H), 2.40 (s, 3H)
ppm. 13C NMR (100 MHz, CDCl3, TMS):
d 178.2, 176.3, 146.3, 141.5,
141.0, 139.7, 138.7, 143.2, 132.3, 130.0, 129.9, 129.6, 129.3, 128.9,
128.6, 128.5, 128.4, 127.7, 127.3, 127.1, 126.1, 124.3, 123.6, 123.2, 53.0,
21.4, 18.9 ppm. Anal. Calc for C53H41Cl3N2Pd (916): C, 69.29; H, 4.50;
N, 3.05%. Found: C, 69.04; H, 4.64; N, 2.97%.
4.2.6. 2,6-Dibenzhydryl-N-(2-(2,6-diethyl-4-methylphenylimino)
acenaphthylenylidene)-4-chlorobenzenaminopalladium dichloride
(C5)
698. 1H NMR (400 MHz, CDCl3, TMS):
d
7.89 (d, J ¼ 8.30 Hz, 1H), 7.68
(d, J ¼ 8.92 Hz, 1H), 7.36 (m, 6H), 7.30e7.21 (m, 8H), 7.15 (d,
J ¼ 9.80 Hz, 4H), 7.04 (s, 2H), 6.99 (t, J ¼ 7.89 Hz, 1H), 6.45 (t,
J ¼ 7.67 Hz, 6H), 6.37 (d, J ¼ 7.21 Hz,1H), 6.17 (t, J ¼ 7.33 Hz, 2H), 5.70
Using the same procedure as for the synthesis of C1, C5 was
obtained as a red powder in 62.1% yield (82 mg). M.p. >250 ꢀC (dec.).

Q. Ban et al. / Journal of Organometallic Chemistry 713 (2012) 151e156
155
FT-IR (KBr; cmꢁ1): 3060, 2965, 2933, 2871, 1625, 1603, 1581, 1489,
1442,1301,1182,1069, 767, 745, 699.1HNMR (400 MHz, CDCl3, TMS):
procedure, the example uses C5 as in entry 2 of Table 2. A 50 mL
oven-dried Schlenk flask was charged under nitrogen with
d
7.88 (d, J ¼ 8.30 Hz,1H), 7.66 (d, J ¼ 8.32 Hz,1H), 7.35 (d, J ¼ 7.27 Hz,
2.0 mmol bromobenzene (210
(280 L, 254 mg), anhydrous 2.2 mmol Na2CO3 (233 mg) and 4.0 mL
DMA. A 50 L solution of 4 mol complex C5 in 5 mL DMA, was
mL, 313 mg), 2.4 mmol styrene
4H), 7.30e7.18 (m, 8H), 7.13 (d, J ¼ 5.57 Hz, 6H), 7.03 (s, 2H), 6.97 (t,
J ¼ 7.90 Hz,1H), 6.46 (t, J ¼ 6.80 Hz, 6H), 6.18 (t, J ¼ 7.34 Hz, 2H), 5.69
(d, J ¼ 7.10 Hz, 1H), 3.15 (m, 2H), 2.80 (m,2H), 2.44 (s, 3H), 1.38 (t,
m
m
m
added via syringe to the above solution, and then the reactor was
sealed and placed in a 150 ꢀC oil bath, and the mixture was stirred
for 12 h. After cooling to room temperature, the reaction mixture
was poured into water (50 mL) and extracted with EtOAc
(3 ꢂ 40 mL). The combined organic extracts were washed with
brine, dried over MgSO4 and concentrated. Purification by flash
chromatography on silica gel (Vhexanes : VCH2Cl2 ¼ 1:1) gave pure 1,2-
diphenylethene (331 mg, 92%).
J ¼ 7.50 Hz, 6H) ppm. 13C NMR (100 MHz, CDCl3, TMS):
d 177.8,176.3,
145.8, 141.1, 140.2, 139.1, 138.7, 138.4, 134.1, 133.5, 132.1, 129.1, 129.0,
128.9,128.2,128.0,127.9,127.2,126.8,126.5,125.8,124.2,122.8,122.1,
53.0, 24.3, 21.1, 13.7 ppm. Anal. Calc for C55H45Cl3N2Pd (944): C,
69.78; H, 4.79; N, 2.96%. Found: C, 69.39; H, 4.97; N, 2.75%.
4.2.7. 2,6-Dibenzhydryl-N-(2-(2,6-dibenzhydryl-4-
chlorophenylimino)acenaphthylenylidene)-4-
chlorobenzenaminopalladium dichloride (C6)
4.4. X-ray crystallographic studies
Using the same procedure as for the synthesis of C1, C6 was
obtained as a red powder in 51.3% yield (89 mg). M.p. > 250 ꢀC
(dec.). FT-IR (KBr; cmꢁ1): 3057, 2905, 1726, 1602, 1574, 1494, 1445,
1241, 1178, 1078, 767, 736, 694. 1H NMR (400 MHz, CDCl3, TMS):
Single crystals of complexes C2 and C6 suitable for X-ray
diffraction were grown by slow diffusion of hexane into
dichloromethane (v/v ¼ 1:1) solutions at room temperature. X-
ray studies were carried out on a Rigaku Saturn724 þ CCD with
d
7.67 (d, J ¼ 8.29 Hz, 2H), 7.35e7.33 (m, 8H), 7.21e7.17 (m, 16H),
6.92e6.86 (m, 10H), 6.67e6.59 (m, 12H), 6.20 (s, 4H), 6.03 (d,
graphite-monochromatic Mo K
a
radiation (
l
¼ 0.71073 Ǻ) at
J ¼ 7.22 Hz, 2H) ppm. 13C NMR (100 MHz, CDCl3, TMS):
d 177.5,141.4,
173(2) K; cell parameters were obtained by global refinement of
the positions of all collected reflections. Intensities were cor-
rected for Lorentz and polarization effects and empirical
absorption. The structures were solved by direct methods and
refined by full-matrix least squares on F2. All hydrogen atoms
were placed in calculated positions. Structure solution and
refinement were performed by using the SHELXL-97 package [47].
Details of the X-ray structure determinations and refinements are
provided in Table 5.
140.0, 139.9, 138.7, 133.6, 129.4, 129.0, 128.7, 128.0, 127.9, 127.4,
126.6, 126.4, 122.3, 51.6 ppm. Anal. Calc for C76H54Cl4N2Pd (1240):
C, 73.41; H, 4.38; N, 2.25%. Found: C, 73.21; H, 4.74; N, 1.98%.
4.3. Heck reaction
General procedure for the Heck reaction of bromobenzene with
styrene in the presence of palladium complex. As a typical
Acknowledgments
Table 5
Crystal data and structure refinements for C2 and C6.
CR wishes to thank the EPSRC for an overseas travel grant (EP/
H031855/1).
C2
C6
Empirical formula
Formula weight
Temperature (K)
Wavelength (Å)
Crystal system
Space group
a (Å)
C54H43Cl3N2Pd
932.65
446(2)
0.71073
Monoclinic
P2(1)/n
15.961(3)
16.080(3)
18.015(4)
90.00
102.58(3)
90.00
4512.6(16)
4
1.373
C76H54Cl4N2Pd
1243.41
173(2)
0.71073
Monoclinic
P2(1)
11.913(2)
22.787(5)
12.387(3)
90.00
103.04(3)
90.00
3275.9(12)
2
1.261
Appendix A. Supplementary material
CCDC 865687(C2) and 865688(C6); contain the supplementary
crystallographic data for this paper. These data can be obtained free
of charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
b (Å)
c (Å)
a
b
g
(ꢀ)
(ꢀ)
(ꢀ)
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