Synthesis and characterizations of arsine- and stibine-ligated Schiff base palladacycles and their applications in Suzuki-Miyaura cross-coupling reactions

Article abstract of DOI:10.1002/aoc.3426

A series of arsine- and stibine-ligated Schiff base palladacycles were synthesized by the reaction of μ-Cl-bridged Schiff base palladacycles [Pd(C₆H₄CH]NC₆H₂R)(μ-Cl)]₂ (R = 2,4,6-trimethyl or 2,6-diis

Full text of DOI:10.1002/aoc.3426

Full paper
Received: 11 October 2015
Revised: 15 November 2015
Accepted: 8 December 2015
Published online in Wiley Online Library: 29 January 2016
(wileyonlinelibrary.com) DOI 10.1002/aoc.3426
Synthesis and characterizations of arsine– and
stibine–ligated Schiff base palladacycles and
their applications in Suzuki–Miyaura
cross-coupling reactions
Haozhen Wang and Jin Yang*
A series of arsine- and stibine-ligated Schiff base palladacycles were synthesized by the reaction of μ-Cl-bridged Schiff base
palladacycles [Pd(C H CH]NC H R)(μ-Cl)] (R = 2,4,6-trimethyl or 2,6-diisopropyl) with AsPh or SbPh The new arsine- and
6
4
6
2
2
3
3.
1
13
stibine-ligated palladacycles were fully characterized using H NMR, C NMR and infrared spectroscopies, high-resolution
mass spectrometry, elemental analysis and single-crystal X-ray diffraction. Further exploration of the catalytic application
of the palladacycles for Suzuki–Miyaura cross-coupling reactions of aryl bromides with arylboronic acids was carried out. It
was found that the new palladacycles are considerably active for these coupling reactions. Copyright © 2016 John Wiley &
Sons, Ltd.
Additional supporting information may be found in the online version of this article at the publisher’s web site.
Keywords: Palladacycles; AsPh ; SbPh ; Suzuki–Miyaura cross-coupling
3
3
reported that the phosphine adducts of imine-based
palladacycles exhibited higher catalytic activities than dinuclear
phosphine-free palladacycles in Suzuki coupling and further de-
Introduction
Since the first cyclopalladacycles were initially isolated and char-
acterized from the cyclopalladation of azobenzene derivatives in
scribed the role played by the phosphine and the anionic ligand
[
1]
[6a–c]
1
965, cyclopalladacycles have attracted increasing attention
in terms of both catalyst activity and lifetime.
Serrano and
and have been much explored in coordination and organometal-
co-workers reported that phosphine adducts of the imine-based
palladacycles with imidate anions also exhibit greater activity than
phosphine-free palladacycles.
[
2]
lic chemistry. The applications of cyclopalladacycles in organic
synthesis, organometallic catalysis and new molecular materials
[
6g]
[
3]
have been fully investigated. In particular, palladacycles are en-
countered as the intermediate species in many palladium-
The original idea of our work came from the interesting reports
of Bedford et al. Serrano et al. We thought that changing the ancil-
lary ligand by replacing the P-donor with As-donor and Sb-donor
may provide an opportunity to systematically study the catalytic
activities of palladacycles since some derivatives of triarylarsine
have been reported as more efficient ligands than their phosphorus
analogues in transition-metal-catalyzed reactions. For example,
Farina and co-workers have reported that in Stille reactions there
[
4]
catalyzed reactions. Many groups have focused their research
on the modification of palladacycles in order to tune and improve
their catalytic properties. The electronic and steric properties of
palladacycles are influenced by various factors, such as the size
of the metallocyclic ring, the type of the donor atoms and the na-
[
2a]
ture of the ancillary ligand. Recently, there has been a growing
interest in the use of ancillary ligands for modification of
palladacycles. In this regard, various functional ligands, such as
is a large rate acceleration with AsPh as palladium ligand, of two
3
[
10a–c]
and three orders of magnitude, relative to PPh3.
Pringle and
[
5]
[6]
N-heterocyclic carbene ligands, phosphine derivatives and
co-workers have reported that AsPh is a more effective ligand for
3
[
7]
[10d]
nitrogen-donor compounds, have been involved in coordina-
tion with palladacycles. The combination of palladacycles with
N-heterocyclic carbenes and phosphine derivatives can effectively
promote the catalytic performance, due to the inherent hybrid
character of the mixed-ligand complexes which would be elec-
tronically more sensitive and tunable to the needs of the sub-
strates. Among them, phosphine derivatives have attracted
more attention since the phosphine compounds exhibit high effi-
palladium-catalyzed Heck olefination than PPh3.
In sharp contrast
to phosphines, reports of palladacycle fragments coordinated to
arsine or stibine ligands are much rarer. As part of our program of
exploring ligand synergism in catalysis, herein we report the synthe-
sis and full characterization of well-defined mixed palladacycle/AsPh3
[
8]
* Correspondence to: Jin Yang, Department of Chemistry, Huaibei Normal
University, Huaibei, Anhui 235000, PR China. E-mail: yangjinlz@163.com
ciency in C–C bond forming reactions catalyzed by palladium.
With regard to imine-based palladacycles, Weissman and Milstein
first reported the use of a dinuclear phosphine-free complex in the
Department of Chemistry, Huaibei Normal University, Huaibei, Anhui, 235000,
People’s Republic of China
[
9]
Suzuki coupling of aryl bromides. Bedford and co-workers then
Appl. Organometal. Chem. 2016, 30, 262–267
Copyright © 2016 John Wiley & Sons, Ltd.

Arsine, Stibine-ligated Schiff-base Palladacycles
are shifted downfield compared to the corresponding Cl-
1
3
bridged palladacycle 2 (7.72 ppm). The C NMR spectra show
the expected signals in the appropriate regions. The chemical
shifts of the Cimine atoms (HC¼N) which appear in the range
1
3
1
55.5–157.5 ppm in the C NMR spectra are comparable with
1
3
the C NMR signals of the C
atom in palladacycle 2 (155.4
imine
1
3
ppm). In addition, the C NMR spectra reveal the appearance
of diagnostic Pd–C peaks (177.0–178.1 ppm) for 3–6. These
values are shifted slightly upfield when compared with
palladacycle 2 (176.2 ppm) and the PCy -ligated palladacycle
3
[
6f]
[
Pd(C H CH¼NC H -2,6-iPr)(PCy )(Cl)] (176.1 ppm). Further-
6
4
6
3
3
more, the formation is further confirmed from the HRMS
analysis where exclusive signals are observed for their respec-
tive [M ꢀ Cl ] fragments.
Scheme 1. Overview of preparation of AsPh - and SbPh -ligated Schiff
3
3
ꢀ
+
base palladacycles.
Crystal structures
or palladacycle/SbPh systems and their catalytic performance in
Suzuki–Miyaura cross-coupling reactions.
Single crystals of 3–6 suitable for X-ray diffraction analysis were
obtained from a chloroform–hexane solution, and the structures
were unambiguously determined using X-ray crystallography.
Complexes 3 and 4 crystallize as CHCl3 solvates 3ꢁCHCl3 and
3
Results and discussion
4
ꢁCHCl , respectively. Figure 1 displays ORTEP plots of 3–6, and
3
Table 1 summarizes selected bond distances and bond angles. As
shown in Fig. 1, in all structures, the coordination of the Pd atom
is essentially square-planar, containing a cyclometallated Schiff
base ligand, a chloride moiety and an As or Sb donor with angles
between adjacent ligands ranging from 80.50(16)° to 101.15(17)°.
As expected, the As or Sb donor is located at a trans-position of
the nitrogen atom. The five-membered chelate ring that contains
the imine functionality defined by Pd1, N1, C1, C2 and C3, which
are quasi-coplanar with the coordination planes defined by As1
(Sb1), C3, N1, Cl1 and Pd1, is oriented roughly perpendicular to
the trimethylphenyl or diisopropylphenyl rings with the smallest
dihedral angle of 76.05°, in accordance with a previous study. The
Pd1–C1 (1.992(4) Å for 3, 2.011(6) Å for 4, 1.984(3) Å for 5 and
1.987(3) Å for 6) and the Pd1–N1 (2.052(3) Å for 3, 2.098(5) Å for
4, 2.079(3) Å for 5 and 2.096(2) Å for 6) bond lengths are within
Synthesis and characterization of palladacycles
The cleavages of Cl-bridged palladacycles by phosphines giving
[
6a,f,g]
neutral or ionic complexes have been reported.
we examined the reactions of μ-Cl-bridged palladacycles [Pd
C H CH¼NC H R)(μ-Cl)] (R = 2,4,6-trimethyl or 2,6-diisopropyl)
Consequently,
(
6
4
6
2
2
with AsPh or SbPh , as shown in 1. Treatment of Cl-bridged
3
3
palladacycles 1 or 2 with 2 equiv. of AsPh or SbPh in CHCl at
3
3
3
ambient temperature produces yellow mononuclear palladacycles
Pd(C H CH¼NC H R)(L)(Cl)] (3–6; AsPh3, SbPh3).
Palladacycles 3–6 were both air- and moisture-stable, and
[
L
=
6
4
6 2
1
13
were fully characterized using H NMR, C NMR and Fourier
transform infrared (FT-IR) spectroscopies, high-resolution mass
spectrometry (HRMS), elemental analysis and X-ray crystallog-
raphy. As evident from Table 1, the FT-IR spectra of 3–6 show
strengthened stretching for ν ¼ in the range 1602–1613
the expected range, relative to the corresponding palladacycle 2
C
N
ꢀ
1
[11]
cm , which are similar to that of the Cl-bridged palladacycle
(Pd–C bond: 1.965(2) Å; Pd–N bond: 2.022(1) Å) and the PCy -li-
3
ꢀ
1
[11]
1
2
(1603 cm ).
The H NMR spectra of 3–6 display the reso-
gated palladacycle [Pd(C H CH¼NC H -2,6-iPr)(PCy )(Cl)] (Pd–C
6
4
6
3
3
[
6f]
nances for HC¼N protons in the range 8.07–8.15 ppm, which
bond: 2.016(2) Å; Pd–N bond: 2.109(2) Å). The Pd–As bond
1
13
Table 1. Selected FT-IR, H NMR and C NMR spectral data, bond lengths and angles for complexes 3–6
3
4
5
6
ꢀ
1
FT-IR ν
(cm
)
1612
8.07
1613
8.10
1602
8.13
1602
8.15
C¼N
1
a
H NMR δ
(ppm)
(ppm)
CH¼N
1
1
3
a
C NMR δ
157.3
178.1
1.992(4)
155.5
177.7
2.011(6)
157.5
177.4
1.984(3)
155.7
177.0
1.987(3)
CH¼N
3
a
C NMR δ
(ppm)
Pd–C
Pd1–C3 (Å)
Pd1–N1 (Å)
2.052(3)
2.3587(9)
2.3668(14)
80.50(16)
101.02(12)
85.72(5)
2.098(5)
2.3904(17)
2.5195(7)
80.9(2)
2.079(3)
2.3606(10)
2.3533(7)
80.74(11)
94.94(9)
2.096(2)
2.3648(8)
2.5007(3)
81.18(11)
95.11(8)
89.21(2)
94.46(7)
Pd1–Cl1 (Å)
b
Pd1–E (Å)
C1–Pd1–N1 (°)
b
C1–Pd1–E (°)
101.15(17)
82.91(5)
b
E –Pd1–Cl1 (°)
91.39(3)
N1–Pd1–Cl1 (°)
92.95(11)
95.17(15)
92.83(7)
a1
b
13
H and C NMR spectra were recorded in CDCl at 298 K.
3
E represents As or Sb donor.
Appl. Organometal. Chem. 2016, 30, 262–267
Copyright © 2016 John Wiley & Sons, Ltd.
wileyonlinelibrary.com/journal/aoc

H. Wang and J. Yang
lengths in complexes 3 and 5 (2.3668(14) and 2.3533(7) Å) are lon-
ger than the Pd–P bond lengths in the related complexes, but are
somewhat shorter than that in the arsine-stabilized N-heterocyclic
[
12]
carbene palladium complexes (2.4103(7) and 2.4676(7) Å). A sim-
ilar disparity can be observed when the SbPh -bearing complexes 4
3
and 6 are compared.
Catalytic study
Suzuki–Miyaura cross-coupling catalyzed by palladacycles has been
researched extensively since the first well-known phosphine-derived
palladacycles were developed by Herrmann and co-workers in
[
13]
1995.
After that a variety of modified palladacycles containing
functional groups have shown their efficiency in these coupling
[
14]
reactions. Herein, the catalytic activities of the AsPh - and SbPh -
3
3
ligated palladacycles (3–6) as catalysts in Suzuki–Miyaura
cross-coupling were investigated. According to the general
[
6f]
reaction conditions reported in the literature, the reactions
were directly performed in EtOH in the presence of K CO3
2
as base. The focus of the study was essentially to demonstrate
the potential of AsPh and SbPh as ancillary ligands; the re-
3
3
action conditions were not further optimized. In all instances
the solvent was used as obtained commercially without
further purification. The organic products were isolated by
1
flash column chromatography and then analyzed using
H
1
3
NMR and C NMR spectroscopy. The activities of 3–6 were
investigated in the Suzuki–Miyaura cross-coupling reactions
of various aryl bromides with arylboronic acids yielding the
corresponding biphenyl products. The results are summarized
in Table 2. At the beginning of the determination of the aryl
bromide substrate scope, phenylboronic acid was used as a
model substrate, and several substituted aryl bromides were
examined. Aryl bromides with both electron-drawing groups
(
4-OMe and 4-NO ) and electron-donating group (4-Me) are
2
able to effectively react with phenylboronic acid. The most
facile reaction is that between 4-nitrobromobenzene and
phenylboronic acid with yields of 93–98% (Table 2, entries
5
–8). Also, the cross-coupling of arylboronic acids with 4-
bromoanisole was evaluated. Under the given conditions, 4-
chlorophenylboronic acid and 4-trifluoromethylphenylboronic
acid are able to undergo the coupling reactions smoothly
with 4-bromoanisole and generate the corresponding
products in good yields. Meanwhile, it should be noted that
the reaction can tolerate ortho-substituted groups, the reac-
tion of 2,4-dimethoxyphenylboronic acid with 4-bromoanisole
under identical reaction conditions giving good yields of the corre-
sponding product (Table 2, entries 21–24). Unfortunately, the
coupling reaction of aryl chlorides, such as 4-choloroanisole and
4-choloronitrobenzene, with phenylboronic acid gives poor results
(Table 2, entries 25–28). Furthermore, the Suzuki–Miyaura cross-
coupling reactions of 4-bromoanisole with phenylboronic acid con-
ducted in aqueous media were carried out. The reactions using cat-
alysts 3 and 4 were carried out in pure water (Table 2, entries 29
and 30). The rapid formation of palladium black was observed
under these conditions, leading to limited conversions. When the
catalytic activity results from the palladacycles are analyzed, it is
found that the arsine and stibine adducts are very similar to each
other and are both efficient precatalysts for the cross-coupling re-
actions tested. Small differences can be attributed to the chemical
functions present on the substrate. Generally, electron-deficient
aryl bromides react more easily than electron-rich ones and give
products in good yields.
Figure 1. ORTEP diagrams of 3–6 with thermal displacement parameters
drawn at 30% probability. The hydrogen atoms and solvent molecules
(
CHCl for 3 and 4) have been omitted for clarity.
3
wileyonlinelibrary.com/journal/aoc
Copyright © 2016 John Wiley & Sons, Ltd.
Appl. Organometal. Chem. 2016, 30, 262–267

Arsine, Stibine-ligated Schiff-base Palladacycles
a
Table 2. Suzuki–Miyaura cross-coupling of aryl bromides with arylboronic acids catalyzed by 3–6
b
Entry
Catalyst
Aryl bromide
Arylboronic acid
Yield (%)
1
2
1
2
3
4
5
6
7
8
9
3
4
5
6
3
4
5
6
3
4
5
6
3
4
5
6
3
4
5
6
3
4
5
6
3
4
5
6
3
4
R = 4-MeO
R = H
91
92
96
94
93
95
98
98
80
82
85
86
92
90
94
92
91
93
90
94
92
90
93
95
22
25
30
32
Trace
Trace
1
2
R = 4-NO
R = H
2
1
2
R = 4-Me
R = H
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
1
2
R = 4-MeO
R = 4-Cl
1
2
R = 4-MeO
R = 4-CF
3
1
2
R = 4-MeO
R = 2,4-di-MeO
c
1
2
R = 4-MeO
R = H
c
d
d
e
e
1
2
R = 4-NO
R = H
2
1
2
R = 4-MeO
R = H
a
Reaction conditions: aryl bromide (0.50 mmol), arylboronic acid (0.60 mmol), catalyst (0.0025 mmol), K CO (1.0 mmol) in EtOH (2.0 ml) at 70°C for 6 h.
2
3
b
c
Isolated yield.
Suzuki–Miyaura cross-coupling of 4-choloroanisole with phenylboronic acid.
d
Suzuki–Miyaura cross-coupling of 4-choloronitrobenzene with phenylboronic acid.
e
Reaction performed in aqueous media.
1
indicated. NMR spectra were recorded at 400 MHz (for H NMR)
Conclusions
13
and 100 MHz (for C NMR) with a Bruker Avance 400 NMR spec-
trometer. H NMR and C NMR spectroscopy was performed in
CDCl with tetramethylsilane as an internal standard. C, H and N
1
13
A series of arsine- and stibine-ligated Schiff base palladacycles
have been synthesized and fully characterized using H NMR,
1
13
C
3
NMR and FT-IR spectroscopies, HRMS and elemental analysis. The
solid-state structures have been further confirmed using single-
crystal X-ray diffraction. The catalytic behavior of the palladacycles
in Suzuki–Miyaura cross-coupling reactions was investigated and
good yields of the corresponding products were achieved. The
results demonstrate that these complexes show high catalytic
activity and good tolerance to various chemical functions.
analyses were performed with a Vario El III Elementar. High-
resolution mass spectra were recorded with an Agilent 6550
iFunnel Q-TOF MS system. FT-IR spectra were recorded with a
Bruker IFS 120HR spectrometer using KBr discs. Flash column chro-
matography was carried out using 300–400 mesh silica gel. The μ-
Cl-bridged palladacycles 1 and 2 were prepared according to the
[
11]
literature.
Synthesis of complexes 3–6
Experimental
A mixture of the μ-Cl-bridged palladacycles (0.10 mmol) 1 or 2 and
General remarks
the arsine or stibine ligand (0.20 mmol) was dissolved in CHCl (5.0
3
The chemicals were purchased from commercial suppliers and
were used without purification prior to use unless otherwise
ml). After stirring for 12 h at ambient temperature, the reaction mix-
ture was reduced under vacuum and the resulting residue was
Appl. Organometal. Chem. 2016, 30, 262–267
Copyright © 2016 John Wiley & Sons, Ltd.
wileyonlinelibrary.com/journal/aoc

H. Wang and J. Yang
washed with ether to afford a yellow solid. Single crystals of com-
2,6-iPr )(SbPh )(Cl)] (C H ClNPdSb) (%): C, 58.52; H, 4.91; N,
2
3
37 37
plexes 3–6 suitable for X-ray diffraction analysis were obtained
1.84. Found (%): C, 58.77; H, 5.16; N, 1.63.
from the evaporation of CHCl –n-hexane solutions of the
3
complexes.
General procedure for Suzuki–Miyaura cross-coupling reaction
[
Pd(C H CH¼NC H -2,4,6-Me )(AsPh )(Cl)] (3)
6
4
6
2
3
3
A sealable reaction tube equipped with a magnetic stir bar was
charged with aryl bromide (0.50 mmol), arylboronic acid (0.60
The procedure yielded 115 mg (86%) of pure product 3 as yellow
1
mmol), K CO3 (1.0 mmol), palladacycle catalyst (0.0025 mmol)
2
crystals. H NMR (CDCl , 400 MHz, δ, ppm): 8.07 (s, 1H, CH¼N),
3
and EtOH (2.0 ml). The mixture was heated in an oil bath at
7
2
3
(
1
.71–7.69 (m, 6H), 7.45–7.36 (m, 10H), 7.04–7.01 (m, 1H), 6.91 (s,
70°C and stirred for 6 h. After the reaction the mixture was
H, NC H -2,4,6-Me ), 6.70–6.62 (m, 2H), 2.41(s, 6H, o-CH ), 2.29 (s,
6
2
3
3
1
3
cooled to room temperature, the filtrate was concentrated with
a rotary evaporator and the residue was then subjected to purifi-
cation via flash column chromatography with petroleum ether–
EtOAc as eluent to give the corresponding pure products.
H, p-CH3). C NMR (CDCl , 100 MHz, δ, ppm): 178.1 (Pd–C), 157.3
3
CH¼N), 148.3 (N C), 145.1 (As C), 138.4, 135.8, 134.5, 133.4, 130.8,
30.4, 130.1, 128.9, 128.6, 128.3, 124.3, 21.0 (p-CH ), 19.1 (o-CH ).
3
3
ꢀ
1
FT-IR (KBr, cm ): 3046, 2987, 2915, 1612 (ν ¼ ), 1577, 1481,
C
N
ꢀ
+
1
6
2
4
436, 1199, 733. HRMS (ESI): calcd for C H AsNPd [M ꢀ Cl ]
3
4 31
34.0707; found 634.0741. Anal. Calcd for [Pd(C H CH¼NC H -
X-Ray crystallography
6
4
6 2
,4,6-Me )(AsPh )(Cl)]ꢁCHCl (C H AsCl NPd) (%): C, 53.23; H,
3
3
3
35 32
4
Data collection was performed with a Bruker-AXS SMART CCD
area detector diffractometer at 296 K using ω rotation scans
with a scan width of 0.3° and Mo Kα radiation (λ = 0.71073
.08; N, 1.77. Found (%): C, 53.48; H, 4.14; N, 1.93.
[Pd(C H CH¼NC H -2,4,6-Me )(SbPh )(Cl)] (4)
6
4
6
2
3
3
[
15]
Å). Multi-scan corrections were applied using SADABS.
The procedure yielded 132 mg (92%) of pure product 4 as yellow
Structure solutions and refinements were performed with the
1
[
16]
crystals. H NMR (CDCl , 400 MHz, δ, ppm): 8.10 (s, 1H, CH¼N),
3
SHELX-97 package.
All non-hydrogen atoms were refined
2
7
(
.79–7.77 (m, 6H), 7.47–7.40 (m, 10H), 7.08–6.92 (m, 4H), 6.72–6.69
anisotropically by full-matrix least-squares on F . The hydro-
gen atoms to carbon were included in idealized geometric po-
sitions with thermal parameters equivalent to 1.2 times those
of carbon atoms. A summary of the crystallographic data, data
collection and refinement parameters for complexes 3–6 is
provided in Table S1. CCDC 1427408, 1427409, 1427410 and
1427411 contain the supplementary crystallographic data for
this paper. These data can be obtained free of charge from
the Cambridge Crystallographic Data Centre via http://www.
ccdc.cam.ac.uk/data_request/cif.
13
m, 1H), 2.47(s, 6H, o-CH ), 2.35 (s, 3H, p-CH ). C NMR (CDCl , 100
3 3 3
MHz, δ, ppm): 177.7 (Pd–C), 155.5 (CH¼N), 148.4 (N–C), 144.3 (Sb–
C), 139.9, 136.7, 136.0, 131.4, 131.3, 130.5, 130.2, 129.6, 129.1, 128.6,
ꢀ
1
1
(
24.6, 21.1 (p-CH ), 19.1 (o-CH ). FT-IR (KBr, cm ): 3046, 2977, 1613
3 3
ν ¼ ), 1575, 1555, 1479, 1433, 1199, 997, 730. HRMS (ESI):
C
N
ꢀ +
calcd for C H NPdSb [M ꢀ Cl ] 680.0529; found 680.0557.
34 31
Anal. Calcd for [Pd(C H CH¼NC H -2,4,6-Me )(SbPh )(Cl)]ꢁCHCl
6
4
6
2
3
3
3
(
5
C H Cl NPdSb) (%): C, 50.25; H, 3.86; N, 1.67. Found (%): C,
35 32 4
0.37; H, 4.03; N, 1.75.
[
Pd(C H CH¼NC H -2,6-iPr )(AsPh )(Cl)] (5)
6
4
6
3
2
3
The procedure yielded 124 mg (87%) of pure product 5 as yellow
Acknowledgments/Acknowledgements according to UK/US
spelling of paper
1
crystals. H NMR (CDCl , 400 MHz, δ, ppm): 8.13 (s, 1H, CH¼N),
3
7.73–7.71 (m, 7H), 7.47–7.38 (m, 10H), 7.24–7.22 (m, 2H), 7.08–7.04
Financial support from the National Natural Science Foundation of
China (no. 21301061) and the Anhui Provincial Natural Science
Foundation (no. 1408085QB36) is gratefully acknowledged.
(
2
m, 1H), 6.74–6.70 (m, 1H), 6.64–6.62 (m, 1H), 3.57(sept, J = 6.8 Hz,
13
H, CH(CH ) ), 1.37 (br, 12H, CH(CH ) ). C NMR (CDCl , 100 MHz,
3 2 3 2 3
δ, ppm): 177.4 (Pd–C), 157.5 (CH¼N), 148.1 (N–C), 144.8 (As–C),
1
1
2
1
6
2
41.1, 138.0, 134.5, 133.9, 131.0, 130.0, 129.0, 128.6, 127.2, 124.4,
ꢀ
1
22.9, 28.7 (CH(CH ) ), 23.8 (CH(CH ) ). FT-IR (KBr, cm ): 3045,
3
2
3 2
References
961, 2868, 1602 (ν ¼ ), 1589, 1575, 1550, 1480, 1465, 1436,
C
N
ꢀ
+
225, 1179, 737. HRMS (ESI): calcd for C H AsNPd [M ꢀ Cl ]
37
37
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6
4
3
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2
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37 37
Found (%): C, 62.51; H, 5.44; N, 2.31.
4
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6
4
6
3
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2
006, 250, 1373.
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yellow crystals. H NMR (CDCl , 400 MHz, δ, ppm): 8.15 (s,
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R. B. Bedford, Chem. Commun. 1787, 2003; c) M. E. van der Boom,
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(
H, CH¼N), 7.81–7.77 (m, 7H), 7.50–7.41 (m, 10H), 7.37–7.35
m, 1H), 7.26–7.24 (m, 1H), 7.11–7.07 (m, 1H), 6.93–6.91 (m,
H), 6.74–6.71 (m, 1H), 3.60 (sept, J = 6.8 Hz, 2H, CH(CH ) ),
1
1
1
1
1
3
1
7
3
2
1
3
.41 (br, 12H CH(CH ) ). C NMR (CDCl , 100 MHz, δ, ppm):
3
2
3
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23.0, 28.7 (CH(CH ) ), 23.8 (CH(CH ) ). FT-IR (KBr, cm ):
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22.0999; found 722.1027. Anal. Calcd for [Pd(C H CH¼NC H -
6
4
6 3
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