The highly efficient Suzuki-Miyaura cross-coupling reaction using cyclopalladated N-alkylferrocenylimine as a catalyst in aqueous medium at room temperature under ambient atmosphere

Article abstract of DOI:10.1016/j.jorganchem.2008.01.012

A series of N-alkyl-substituted cyclopalladated ferrocenylimines were used in palladium-catalyzed Suzuki-Miyaura cross-coupling reactions of aryl halides in room temperature and CH₃OH/H₂O media under aerobic conditions. As for the ca

Full text of DOI:10.1016/j.jorganchem.2008.01.012

Available online at www.sciencedirect.com
Journal of Organometallic Chemistry 693 (2008) 1243–1251
www.elsevier.com/locate/jorganchem
The highly efficient Suzuki–Miyaura cross-coupling reaction using
cyclopalladated N-alkylferrocenylimine as a catalyst in aqueous
medium at room temperature under ambient atmosphere
Bing Mu, Tiesheng Li *, Jingya Li, Yangjie Wu *
Department of Chemistry, Key Lab of Chemical Biology and Organic Chemistry of Henan Province, Key Lab of Advanced Nano-information
Materials of Zhengzhou, Zhengzhou University, Zhengzhou 450052, PR China
Received 2 November 2007; received in revised form 7 January 2008; accepted 8 January 2008
Available online 12 January 2008
Abstract
A series of N-alkyl-substituted cyclopalladated ferrocenylimines were used in palladium-catalyzed Suzuki–Miyaura cross-coupling
reactions of aryl halides in room temperature and CH3OH/H2O media under aerobic conditions. As for the catalysts, the length of
N-alkyl chains has no significant effect on the catalytic activity. Using 0.01 mol% of dimer 3a in the presence of K2CO3 as base offered
excellent yields in the reaction of activated and non-activated aryl bromides with phenylboronic acid.
Ó 2008 Published by Elsevier B.V.
Keywords: Cyclopalladated ferrocenylimines; N-alkyl chains; Suzuki–Miyaura cross-coupling reactions; Room temperature; Aqueous media
1. Introduction
and hazardous organic solvents, an inert atmosphere, and
to proceed the reactions under mild conditions (e.g., room
temperature) [5]. To satisfy these concerns, water or aque-
ous solution represents a very attractive medium for
Suzuki couplings of aryl halides [6], especially in large-
scale industrial synthesis, and the development of milder
reaction conditions would also be a significant advance
[7]. There has recently been considerable interest in the
synthesis of new, high activity, air-stable palladium-based
catalyst that can be used in room-temperature Suzuki
cross-coupling reaction in aqueous solvents since such cat-
alysts have the potential to be used in industrial systems
[8]. However, the low solubility of the majority of organic
compounds in water and stability of the metal catalysts in
water are great problems [9]. In order to circumvent this
crucial problem, the applications of water soluble ligands
[10], phase-transfer catalysts [11], or the use of microwaves
[12] had been described. Recently, inverse phase-transfer
catalysts such as cyclodextrins or calix-arenes [13,14],
and surfactants [10d,15] have also proved to be good addi-
tives for Suzuki–Miyaura reactions in aqueous media. For
example, catalytic species derived from calix-arene based
The Suzuki–Miyaura cross-coupling reaction has
become a common transformation for the formation of
carbon–carbon bonds because their products [1], in partic-
ular biaryls, are recurring functional groups in many natu-
ral products and biologically active compounds as well as
useful blocks in organic synthesis [2]. This coupling is also
especially useful because of the broad tolerance to different
functional groups, the ability to couple sterically demand-
ing substrates, mild reaction conditions, non-toxic and
easy to handle reagents [3]. Consequently, considerable
effort has been dedicated to develop efficient and active
catalytic systems for Suzuki–Miyaura cross-coupling reac-
tion in the past years [2d,2e,2f,4]. Most of these reactions
were performed in traditional organic solvents and usually
required elevated reaction temperatures to function effi-
ciently. From an economic, environmental and safe stand-
point, however, it is desirable to avoid any use of expensive
*
Corresponding authors. Tel./fax: +86 371 67766667.
E-mail addresses: lts34@zzu.edu.cn (T. Li), wyj@zzu.edu.cn (Y. Wu).
0022-328X/$ - see front matter Ó 2008 Published by Elsevier B.V.
doi:10.1016/j.jorganchem.2008.01.012

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B. Mu et al. / Journal of Organometallic Chemistry 693 (2008) 1243–1251
imidazolium salts as ligand precursors and inverse phase-
transfer catalysts showed high activity in the Suzuki–Miya-
ura cross-coupling of aryl chlorides at 80 °C [14]. Also,
fewer catalytic systems could perform the cross-coupling
reaction of aryl bromides or aryl chlorides at room temper-
ature in aqueous solvent under air conditions [10a].
In previous studies [16], we found that cyclopalladated
ferrocenylimines with long alkyl chains were highly efficient
catalysts in the Suzuki–Miyaura cross-coupling reaction.
Although there are high activities obtained in the amphi-
philic catalysts, a high reaction temperature (110 °C) was
still required to afford high yield of the product. In view
of the observations that the surfactants could accelerate
Suzuki–Miyaura cross-coupling reactions because the sur-
factants could form microemulsions and had the function
as phase transfer reagent [10d], we are especially interested
in the possibility of using cyclopalladated ferrocenylimines
with long-chain hydrocarbon as catalysts and surfactants
for Suzuki–Miyaura cross-coupling reactions in room tem-
perature and aqueous solvents under air. Further research
by using cyclopalladated ferrocenylimines with short alkyl
chains was also studied.
dichloromethane, benzene, toluene, ethyl acetate, etc.),
slightly soluble in petroleum ether, hexane and insoluble
in water.
The new compounds 3a, 3b were characterized by IR,
1H NMR, 13C NMR, 31P NMR spectra, MS, and elemen-
tal analysis. For compound 3b, the appearance of only one
signal around 38 ppm in 31P NMR spectra suggested the
formation of a single isomer [18].
2.2. Suzuki–Miyaura cross-coupling reactions
We have previously shown that complexes 1a–d, 2a–d
(Scheme 1) were efficient catalysts for the coupling of a
range of aryl halides with phenylboronic acid in toluene
at 110 °C [16]. In the present study, complexes 1a–d, 2a–d
still showed high activity in the room-temperature
Suzuki–Miyaura cross-coupling reactions in CH3OH/H2O
media under air.
The coupling reaction of the relatively unactivated
4-bromotoluene with phenylboronic acid, catalyzed by pal-
ladacycle 2c, was selected as a model reaction. As shown in
Table 1, K2CO3 were found to be the most effective base
although KOH, NaOH can be also used, giving slightly
lower yields. Among the tested aqueous-organic solvents,
CH3OH/H2O system afforded the highest yield (Table 1,
entry 1). When the loading of H2O was increased (Table
1, entry 13), the system also gave the desired products in
high yield.
2. Results and discussion
2.1. Synthesis and characterization of complexes 3a and 3b
The ferrocenylimine was synthesized by the condensa-
tion of acetylferrocene with n-butylamine in the presence
of active Al2O3 at 75 °C for 1–2 days and the progress of
the condensation reaction was controlled by recording
the infrared spectra of the solution. The ferrocenylimine
obtained without further purification was used for the
cyclopalladation. Compounds 3a, 3b were prepared
according to the general procedure [17]. They are highly
soluble in most of the common solvents (chloroform,
With the appropriate solvent (CH3OH/H2O = 1:1) and
base (K2CO3) in hand, the relative activities of several
palladacycles (Table 2) for the same model reaction were
studied. When the reaction was carried out at room tem-
perature, dimeric complexes exhibited higher activity than
monomeric complexes.
A variety of electronically and structurally diverse aryl
bromides could be coupled efficiently with phenylboronic
R1
R1
R1
H
H
CH3
CH3
R2
C NR2
C NR2
a
b
c
d
n-C12H25
n-C16H33
n-C12 25
n-C16 33
Fe
Fe
H
Pd Cl
Pd Cl
H
PPh3
2a-d
2
1a-d
H
H
CH3
CH3
C N
C N
C N
C
N
Fe
Pd Cl
Pd Cl
Pd Cl
Fe
Fe
Fe
Pd Cl
PPh3
4b
2
2
PPh3
3b
3a
4a
CH3
CH3
C N
CH3
C
N
CH3
Fe
Fe
Pd Cl
PPh3
5b
Pd Cl
2
5a
Scheme 1.

B. Mu et al. / Journal of Organometallic Chemistry 693 (2008) 1243–1251
1245
Table 1
Investigation of the Suzuki–Miyaura reaction conditionsa
Cat. 2c, base
+
Br
H3C
H3C
B(OH)2
Solvent, rt
Entry
Base
Solvent
Yieldb (%)
1
2
3
4
5
6
7
8
K2CO3
NaOH
CH3OH/H2O
CH3OH/H2O
CH3OH/H2O
CH3OH/H2O
CH3OH/H2O
CH3OH/H2O
DMF/H2O
94
87
Trace
77
26
83
37
8
87
KF Á 2H2O
K3PO4 Á 7H2O
Na2CO3
KOH
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
THF/H2O
9
1,4-Dioxane/H2O
CH3CN/H2O
Toluene/ethanol/H2O
CH3OH
10
11c
12d
13e
a
Trace
43
94
CH3OH/H2O
98
Reaction condition: 4-Bromotoluene 0.5 mmol, PhB(OH)2 0.6 mmol, base 1.0 mmol, n-Bu4NBr 0.5 mmol, solvent 3 mL (v/v = 2:1), 0.5% mol of
catalyst 2c, at room temperature under air for 7 h.
b
Isolated yields based on 4-bromotoluene in two runs.
Toluene/ethanol/H2O 3 mL (v/v/v = 1:1:1).
c
d
CH3OH 3 mL.
CH3OH/H2O 3 mL (v/v = 1:1).
e
Table 2
Suzuki–Miyaura reaction: catalyst studya
Catalysts
K2CO3
+
Br
H3C
H3C
B(OH)2
CH3OH/H2O=1:1
rt
Entry
Catalyst
Yieldb (%)
1
2
3
4
5
6
7
8
a
1a
1b
1c
1d
2a
2b
2c
2d
99
81
99
99
38
89
98
88
Reaction condition: 4-bromotoluene 0.5 mmol, PhB(OH)2 0.6 mmol, K2CO3 1.0 mmol, n-Bu4NBr 0.5 mmol, CH3OH/H2O 3 mL (v/v = 1:1), 0.5 mol%
of catalyst, at room temperature under air for 7 h.
b
Isolated yields based on 4-bromotoluene in two runs.
acid by using 0.1 mol% of complex 1c under the optimized
reaction conditions (K2CO3, CH3OH/H2O = 1:1, rt)
(Table 3). However, using sterically hindered aryl bro-
mides, such as 2-bromonitrobenzene, 2-bromo-m-xylene
as substrates, the cross-coupled products were obtained
in modest yields even by increasing catalyst loading and
prolonging the reaction time (Table 3, entries 14, 16). Fur-
thermore, 2-bromofluorene and 4-bromoaniline also only
gave the cross-coupled products in modest yields (Table
3, entries 15, 17). When the reaction temperature was
increased from room temperature to 60 °C, for 3-bromo-
pyridine and 4-chloronitrobenzene, the coupling reactions
proceeded well. When the catalyst loading of 1c was low-
ered to 0.01 mol% for 4-bromotoluene reacted with phenyl-
boronic acid, 70% isolated yield could be obtained (Table
3, entry 7). As for non-activated chlorobenzene, complex
1c was nearly inactive under the similar reaction condi-
tions. Moreover, the coupling reaction of 4-bromotoluene
with phenylboronic acid carried out in the absence of n-
Bu4NBr is in a very low yield (Table 3, entry 8). This could
be accredited with two reasons: one was that n-Bu4NBr
probably stabilized colloidal palladium nanoparticles that
act as catalysts in the Suzuki coupling [19], the other was
that the ammonium salts may accelerate the coupling reac-
tion in virtue of activating the arylboronic acid to react by
the formation of [ArB(OH)3]À[R4N]+ [11a].
We thought that it was interesting to study whether the
high activity of palladacycles required long N-alkyl chains

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B. Mu et al. / Journal of Organometallic Chemistry 693 (2008) 1243–1251
Table 3
Suzuki coupling of aryl halides with phenylboronic acida
Cat. 1c
K2CO3
+
ArBr
Ar
B(OH)2
CH3OH/H2O
rt
Entry
1
ArBr
mol%
0.1
t (h)
T (°C)
Product
Product no.
Yieldb (%)
96
1.5
rt
rt
rt
rt
rt
6a
O2N
Br
O2N
H3COC
Cl
2
3
4
5
0.1
0.1
0.1
0.1
1.5
1.5
1.5
1.5
6b
6c
6d
6e
99
97
98
99
H3COC
Cl
Br
Br
Br
Br
6
0.1
0.01
0.1
0.1
0.1
1.5
2
rt
rt
rt
rt
rt
6f
6f
6f
6g
6h
94
70
37
97
50
Br
7
Br
Br
8c
9
1.5
2
H3CO
Br
H3CO
10
2
Br
Br
11
12
0.1
0.1
5
5
rt
rt
6h
6i
99
99
CHO
Br
CHO
13
14
0.1
0.1
18
18
rt
rt
6j
99
68
N
Br
N
6k
NO2
Br
NO2
15
16
0.1
0.5
18
12
rt
rt
6l
56
51
H2N
Br
H2N
6m
Br
17
0.5
18
rt
6n
49
Br

B. Mu et al. / Journal of Organometallic Chemistry 693 (2008) 1243–1251
1247
Table 3 (continued)
Entry
18
ArBr
mol%
0.5
t (h)
T (°C)
Product
Product no.
Yieldb (%)
89
12
60
6o
Br
Cl
N
N
19
20
a
1
1
12
12
60
60
6a
6d
77
O2N
Cl
O2N
Trace
Reaction condition: aryl halides 0.5 mmol, PhB(OH)2 0.6 mmol, K2CO3 1.0 mmol, n-Bu4NBr 0.5 mmol, CH3OH/H2O 3 mL (v/v = 1:1), 0.1 mol% of
catalyst 1c, at room temperature under air.
b
Isolated yields based on aryl halids in two runs.
n-Bu4NBr was not added.
c
Table 4
Screening of catalysts with different N-alkyl chains and N-aryl groups for Suzuki–Miyaura cross-coupling reactiona
Catalysts
K2CO3
+
Ar
ArBr
B(OH)2
CH3OH/H2O=1:1
rt
Entry
1
ArBr
Catalysts
t (h)
T (°C)
Product
Product no.
Yieldb (%)
91
1c
2
rt
rt
rt
6d
Br
Br
Br
2
3
3a
3b
2
2
6d
6d
95
Trace
4
5
6
7
8
9
a
4a
4b
5a
5b
3a
5a
2
2
2
2
3
3
rt
rt
rt
rt
rt
rt
6d
6d
6d
6d
6f
95
Br
Br
Br
Br
Trace
66
Trace
77
Br
Br
6f
25
Reaction condition: Aryl bromides 0.5 mmol, PhB(OH)2 0.6 mmol, K2CO3 1.0 mmol, n-Bu4NBr 0.5 mmol, CH3OH/H2O 3 mL (v/v = 1:1), 0.01 mol%
of catalyst, at room temperature under air.
b
Isolated yields based on aryl halides in two runs.
for the room-temperature Suzuki–Miyaura cross-coupling
reactions in aqueous media. So we synthesized cyclopalla-
dated ferrocenylimines 3a, 3b and undertook a broader
investigation into Suzuki–Miyaura cross-coupling reac-
tions. Initially, the relative catalytic activity of 1c with n-
C12H25 group at nitrogen, 3a and 3b with n-butyl group
at nitrogen, 4a and 4b with i-propyl substituent at nitrogen,
5a and 5b with N-aryl substituent (Scheme 1) was examined
by the coupling reaction of aryl bromides with phenylbo-
ronic acid in the presence of K2CO3 as base in aqueous
media (CH3OH/H2O = 1:1). Dimers 3a, 4a were slightly
more active than 1c (Table 4, entries 1, 2, 4, 8), while com-
plex 5a was low active under the same reaction conditions
(Table 4, entries 6, 9). The results revealed that N-alkyl-
substituted cyclopalladated ferrocenylimines were higher
activity than those with N-aryl groups for the room-tem-
perature Suzuki–Miyaura cross-coupling reactions in aque-
ous media, and that the length of N-alkyl chains has no
significant influence on the catalytic activity. The possible
reason for the results was that alkyl substituents at nitro-

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B. Mu et al. / Journal of Organometallic Chemistry 693 (2008) 1243–1251
gen promoted oxidative addition of aryl halides to the Pd
intermediate by making palladium more electron rich and
increased the activity consequently [16], and electronic
effects of N-alkyl chains with different length to palladium
could be nearly the same. Moreover, monomers 3b, 4b, 5b
were almost inactive under similar reaction conditions
(Table 4, entries 3, 5, 7), also suggesting that monomeric
complexes containing phosphines are sensitive to moisture
[20].
products in good to excellent yields by prolonging the reac-
tion time (entries 5–7). However, 2-bromo-m-xylene only
gave the cross-coupled product in 63% yield even by
increasing catalyst loading to 0.1 mol% and prolonging
the reaction time for 12 h (entry 8). For 4-chloronitroben-
zene, the yield was improved to 83% in the presence of
1 mol% 3a at 60 °C (entry 9), but chlorobenzene was found
to be a poor coupling partner in the same reaction condi-
tions, giving only 19% yield (entry 10).
With the optimized reaction conditions above, the cou-
plings of a number of other aryl bromides were conducted
in the presence of 0.01 mol% complex 3a (Table 5, entries
1–8). The reactions of electro-deficient aryl bromides and
bromobenzene, 1-bromonaphthalene proceeded smoothly
to give the coupling products with excellent yield after
2 h (Table 5, entries 1–4). Aryl bromides with electro-rich
groups or containing ortho-substituents also provided the
3. Conclusion
In summary, a series of cyclopalladated ferrocenyli-
mines with N-alkyl substituents were efficient catalysts for
room-temperature Suzuki–Miyaura cross-coupling reac-
tion of aryl halides with phenylboronic acid in CH3OH/
H2O system under aerobic conditions. Results from these
Table 5
Suzuki coupling of aryl halides with phenylboronic acida
Cat. 3a
K2CO3
+
ArBr
Ar
B(OH)2
CH3OH/H2O
rt
Entry
1
ArBr
mol%
0.01
t (h)
T (°C)
Product
Product no.
Yieldb (%)
96
2
rt
rt
rt
rt
6a
O2N
Br
O2N
2
3
4
0.01
0.01
0.01
2
2
2
6b
6c
6e
99
90
99
H3COC
Cl
Br
H3COC
Cl
Br
Br
5
6
0.01
0.01
3
6
rt
rt
6g
6h
91
76
H3CO
Br
H3CO
Br
7
8
0.01
0.1
6
rt
rt
6i
99
63
CHO
Br
CHO
12
6m
Br
9
1
1
12
24
60
60
6a
6d
83
19
O2N
Cl
O2N
10
Cl
a
Reaction condition: aryl halides 0.5 mmol, PhB(OH)2 0.6 mmol, K2CO3 1.0 mmol, n-Bu4NBr 0.5 mmol, CH3OH/H2O 3 mL (v/v = 1:1), 0.01 mol% of
catalyst 3a, at room temperature under air.
b
Isolated yields based on aryl halides in two runs.

B. Mu et al. / Journal of Organometallic Chemistry 693 (2008) 1243–1251
1249
studies indicated that for N-alkyl substituted cyclopalladat-
ed ferrocenylimines as catalysts for room-temperature
Suzuki–Miyaura cross-coupling reaction in CH3OH/H2O
media, the long N-alkyl groups is not the necessary condi-
tion for the catalytic activity.
The solution of the complex 3a (0.1 mmol) and PPh3
(0.3 mmol) in 10 mL of CH2Cl2 was stirred at room tem-
perature for 1 h. The solution was concentrated in vacuo
and was purified via column chromatography (CH2Cl2 as
eluent). The red oil was recrystallized from CH2Cl2–petro-
leum ether to yield cyclopalladated monomer 3b. Yield
92%, red solid, m.p. 209–211 °C; IR (KBr): 2954, 2867,
4. Experimental
1
1097, 999, 1589, 816, 745, 696 cmÀ1; H NMR (400 MHz,
4.1. General
CDCl3): d 7.79–7.74 (6H, m, PPh3), 7.43–7.37 (9H, m,
PPh3), 4.32 (1H, d, J = 2.1 Hz, C5H3), 4.06–3.98 (2H, m,
C5H3, CH2), 3.81 (5H, s, C5H5), 3.65–3.58 (1H, m, CH2),
3.26 (1H, s, C5H3), 2.20 (3H, s, CH3–C@N), 1.88–1.84
(1H, m, CH2), 1.56–1.43 (3H, m, CH2–CH2), 0.98 (3H, t,
J = 7.2 Hz, CH3); 13C NMR (100 MHz, CDCl3): d 179.4,
135.0, 132.4, 131.9, 130.3, 128.0, 101.3, 92.0, 76.2, 70.3,
67.8, 66.2, 51.0, 32.2, 30.9, 20.4, 14.5, 14.1; 31P {1H}
NMR (162 MHz, CDCl3): d 37.79; Anal. Calc. for
C34H35ClFeNPPd: C, 59.50; H, 5.14; N, 2.04. Found: C,
59.32; H, 5.13; N, 2.12%; MS: 650.2 [MÀCl]+.
All solvents were obtained from commercial sources
and used without purification. The cyclopalladated ferr-
ocenylimines 1a–d and 2a–d [16], 4a and 4b [21], 5a and
5b [17] were prepared according to the published proce-
dures. All other chemicals were used as purchased. Melt-
ing points were measured using a WC-1 microscopic
apparatus and were uncorrected. Infrared spectra were
recorded on a Bruker VECTOR22 spectrophotometer in
KBr pellets. 1H, 13C and 31P {1H} NMR spectra were
recorded on a Bruker DPX-400 spectrometer in CDCl3
with TMS as an internal standard for 1H NMR, 13C
NMR and 85% H3PO4 as external standard for 31P
{1H} NMR. Elemental analyses were determined with
Elementar Analysensystem GmbH (varioEL III). Mass
spectra were measured on a LC-MSD-Trap-XCT instru-
ment. All the Suzuki reactions were accomplished without
the protection of inert gas.
4.3. General procedure for the Suzuki–Miyaura cross-
coupling reaction of aryl halide with phenylboronic acid
General procedure A: A mixture of aryl halides
(0.5 mmol), phenylboronic acid (0.6 mmol), K2CO3
(1 mmol), TBAB (0.5 mmol), catalyst 1c (0.1%), and
CH3OH/H2O (1.5 mL/1.5 mL) was stirred at room temper-
ature under air. The reaction mixture was stirred for 1.5 h,
and then quenched with water. The mixture was diluted
with CH2Cl2. The organic layer was separated and the
aqueous layer was extracted with CH2Cl2 for three times.
The combined organic phase was dried with MgSO4, fil-
trate, solvent was removed on a rotary evaporator, and
the product was isolated by thin layer chromatography.
The purified products were identified by 1H NMR, 13C
NMR spectroscopy and melting points with the literature
data.
4.2. Preparation of complexes 3a, 3b
A mixture of acetylferrocene (1.5 mmol) and n-butyl-
amine (50 mL) was refluxed on an oil bath under nitrogen
atmosphere in the presence of active Al2O3 at 75 °C for 1–2
days. In order to control the progress of the condensation
reaction, the infrared spectra of the solution was recorded.
When the infrared spectra of the samples did not exhibit
the absorption band due to the asymmetrical stretching
of the C@O group of the acetylferrocene [t(C@O)
1661 cmÀ1], the reaction mixture was carefully filtered
and the filtrate was reduced to dryness. The oil obtained
was used without further purification. A solution of lithium
tetrachloropalladated (II) in 10 mL of methanol (Li2PdCl4,
1 mmol) and mole equivalents of NaOAc were added to the
oil, and the resulting red solution was stirred for about
24 h. The solution was carefully filtered, and then the deep
red solid obtained was purified via column chromatogra-
phy (CH2Cl2 as eluent) to yield cyclopalladated dimer 3a.
Yield 61%, red solid, m.p. >220 °C; IR (KBr): 2956,
General procedure B: Catalyst 3a of 100 ll was intro-
duced to a small round-bottom flask as a CHCl3 solution
(0.0005 mmol/mL). After CHCl3 evaporated, aryl halides
(0.5 mmol), phenylboronic acid (0.6 mmol), K2CO3
(1 mmol), TBAB (0.5 mmol), and CH3OH/H2O (1.5 mL/
1.5 mL) were added into the small round-bottom flask.
The reaction mixture was stirred at room temperature
under air for 2 h and then quenched with water. The mix-
ture was diluted with CH2Cl2. The organic layer was sepa-
rated and the aqueous layer was extracted with CH2Cl2 for
three times. The combined organic phase was dried with
MgSO4, filtrate, solvent was removed on a rotary evapora-
tor, and the product was isolated by thin layer chromatog-
2862, 1105, 1001, 1581, 813 cmÀ1; H NMR (400 MHz,
1
CDCl3): d 4.74–4.72 (1H, m, C5H3), 4.34–4.23 (7H, m,
C5H5, C5H3), 3.45–3.36 (2H, m, CH2), 2.13 (3H, s, CH3–
C@N), 1.82–1.63 (2H, m, CH2), 1.45–1.41 (2H, m, CH2),
0.99 (3H, t, J = 7.0 Hz, CH3); 13C NMR (100 MHz,
CDCl3): d 180.6, 100.2, 91.3, 73.4, 73.3, 70.8, 70.7, 66.2,
65.6, 52.9, 52.0, 31.8, 20.4, 20.3, 14.2, 14.0; Anal. Calc.
for C32H40Cl2Fe2N2Pd2: C, 45.32; H, 4.75; N, 3.30. Found:
C, 45.69; H, 4.78; N, 3.39%.
1
raphy. The purified products were identified by H NMR,
13C NMR spectroscopy and melting points with the litera-
ture data.
4.3.1. Compound 6a [23]
Light yellow solid; m.p. 111–113 °C (lit. 111–112 °C). 1H
NMR (400 MHz, CDCl3): d 8.30 (2H, d, J = 8.8 Hz), 7.74

1250
B. Mu et al. / Journal of Organometallic Chemistry 693 (2008) 1243–1251
(2H, d, J = 8.8 Hz), 7.63 (2H, d, J = 7.0 Hz), 7.52–7.45
(3H, m). 13C NMR (100 MHz, CDCl3): d 147.6, 147.1,
138.8, 129.2, 128.9, 127.8, 127.4, 124.1.
137.8, 133.7, 133.6, 130.8, 130.1, 128.5, 128.1, 127.8,
127.6.
4.3.10. Compound 6j [24]
4.3.2. Compound 6b [24]
White solid; m.p. 117–119 °C (lit. 118–120 °C). 1H
NMR (400 MHz, CDCl3): d 7.57–7.49 (4H, m), 7.41–7.37
(2H, m), 7.27–7.23 (1H, m), 6.83 (2H, d, J = 8.4 Hz),
2.99 (6H, s). 13C NMR (100 MHz, CDCl3): d 149.9,
141.2, 129.2, 128.6, 127.7, 126.3, 126.0, 113.0, 40.7.
White solid; m.p. 117–118 °C (lit. 116–118 °C). 1H
NMR (400 MHz, CDCl3): d 8.04 (2H, d, J = 8.3 Hz),
7.69–7.62 (4H, m), 7.49–7.40 (3H, m), 2.64 (3H, s). 13C
NMR (100 MHz, CDCl3): d 197.8, 145.8, 139.8, 135.8,
128.9, 128.89, 128.21, 127.25, 127.20, 26.7.
4.3.11. Compound 6k [28]
1
4.3.3. Compound 6c [27]
White solid; m.p. 74–76 °C (lit. 74–76 °C). 1H NMR
(400 MHz, CDCl3): d 7.56–7.49 (4H, m), 7.45–7.38
(4H, m), 7.37–7.33 (1H, m). 13C NMR (100 MHz,
CDCl3): d 140.0, 139.7, 133.4, 128.9, 128.89, 128.4, 127.6,
127.0.
Yellow oil. H NMR (400 MHz, CDCl3): d 7.84 (1H,
d, J = 8.1 Hz), 7.62 –7.58 (1H, m), 7.49–7.39 (5H, m),
7.33–7.30 (2H, m). 13C NMR (100 MHz, CDCl3): d
149.3, 137.4, 136.3, 132.3, 132.0, 128.7, 128.2, 128.18,
127.9, 124.1.
4.3.4. Compound 6d [22]
4.3.12. Compound 6l [29]
White solid; m.p. 69–70 °C (lit. 68–71 °C). 1H NMR
(400 MHz, CDCl3): d 7.60–7.58 (4H, m), 7.45–7.42 (4H,
m), 7.36–7.32 (2H, m). 13C NMR (100 MHz, CDCl3): d
141.3, 128.8, 127.3, 127.2.
Yellow solid; m.p. 51–52 °C (lit. 51 °C). 1H NMR
(400 MHz, CDCl3): d 7.53 (2H, d, J = 8.1 Hz), 7.42–7.37
(4H, m), 7.26 (1H, t, J = 8.8 Hz), 6.74 (2H, d,
J = 8.6 Hz), 3.70 (2H, s). 13C NMR (100 MHz, CDCl3):
d 145.9, 141.2, 131.6, 128.7, 128.0, 126.4, 126.3, 115.4.
4.3.5. Compound 6e [25]
Light yellow liquid. 1H NMR (400 MHz, CDCl3): d
7.90–7.80 (3H, m), 7.50–7.36 (9H, m). 13C NMR (100
MHz, CDCl3): d 140.7, 140.2, 133.8, 131.6, 130.0, 128.2,
127.6, 127.2, 126.9, 126.0, 125.7, 125.3.
4.3.13. Compound 6m [30]
1
Light-yellow oil. H NMR (400 MHz, CDCl3): d 7.44–
7.40 (2H, m), 7.35–7.31 (1H, m), 7.18–7.09 (5H, m), 2.03
(6H, s). 13C NMR (100 MHz, CDCl3): d 141.9, 141.1,
136.1, 129.0, 128.4, 127.3, 127.0, 126.6, 20.9.
4.3.6. Compound 6f [23]
White solid; m.p. 43–44 °C (lit. 43–44 °C). 1H NMR
(400 MHz, CDCl3): d 7.58–7.56 (2H, m), 7.49 (2H, d,
J = 8.1 Hz), 7.42 (2H, t, J = 7.5 Hz), 7.33–7.30 (1H, m),
7.24 (2H, d, J = 7.9 Hz), 2.39 (3H, s). 13C NMR
(100 MHz, CDCl3): d 141.1, 138.3, 137.0, 129.4, 128.7,
126.9, 21.1.
4.3.14. Compound 6n [31]
White solid; m.p. >190 °C. 1H NMR (400 MHz,
CDCl3): d 7.84 (1H, d, J = 7.9 Hz), 7.81 (1H, d,
J = 7.5 Hz), 7.77 (1H, s), 7.67–7.61 (3H, m), 7.56 (1H, d,
J = 7.5 Hz), 7.46 (2H, t, J = 7.6 Hz), 7.41–7.29 (3H, m),
3.96 (2H, s). 13C NMR (100 MHz, CDCl3): d 143.9,
143.5, 141.5, 141.4, 140.9, 139.9, 128.8, 127.2, 127.1,
126.8, 126.7, 126.0, 125.1, 123.8, 120.1, 120.0, 37.0.
4.3.7. Compound 6g [27]
White solid; m.p. 86–87 °C (lit. 85–87 °C). 1H NMR
(400 MHz, CDCl3): d 7.56–7.52 (4H, m), 7.41 (2H, t,
J = 7.7 Hz), 7.30–7.25 (1H, m), 6.98 (2H, d, J = 8.8 Hz),
3.85 (3H, s). 13C NMR (100 MHz, CDCl3): d 159.1,
140.8, 133.8, 128.7, 128.2, 126.7, 126.65, 114.2, 55.3.
4.3.15. Compound 6o [30]
1
Light-yellow oil. H NMR (400 MHz, CDCl3): d 8.85
(1H, s), 8.58 (1H, d, J = 4.1 Hz), 7.87 (1H, d, J =
7.9 Hz), 7.57 (2H, d, J = 7.3 Hz), 7.49–7.33 (4H, m). 13C
NMR (100 MHz, CDCl3): d 148.4, 148.2, 137.8, 136.7,
134.4, 129.1, 128.1, 127.1, 123.6.
4.3.8. Compound 6h [26]
Light yellow liquid. 1H NMR (400 MHz, CDCl3): d
7.41–7.39 (2H, m), 7.35–7.31 (3H, m), 7.26–7.23 (4H, m),
2.27 (3H, s). 13C NMR (100 MHz, CDCl3): d 142.0,
135.4, 130.3, 129.8, 129.2, 128.1, 127.3, 126.8, 125.8,
20.5.
Acknowledgements
We are grateful to the National Natural Science Foun-
dation of China (No. 20472074), the Innovation Found
for Outstanding Scholar of Henan Province (No.
0621001100), the Fund for Outstanding Younger Scholar
of Henan Province (074100510015) and the National Nat-
ural Science Foundation of Henan Province (0611020100,
2007150042) for their financial support.
4.3.9. Compound 6i [28]
1
Colorless oil. H NMR (400 MHz, CDCl3): d 9.98 (1H,
s), 8.02 (1H, d, J = 9.1 Hz), 7.62–7.60 (1H, m), 7.48–7.35
(7H, m). 13C NMR (100 MHz, CDCl3): d 192.5, 146.0,

B. Mu et al. / Journal of Organometallic Chemistry 693 (2008) 1243–1251
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