Preparation of a palladium dimer with a cobalt-containing bulky phosphine ligand: Its application in palladium catalyzed Suzuki reactions

Article abstract of DOI:10.1016/j.poly.2006.07.005

A palladium dimer with a cobalt-containing phosphine ligand, {(μ-PPh₂CH₂PPh₂)Co₂(CO)₄(μ,η-(tBu)₂PC{triple bond, long}CC₆H₄-κC¹)Pd(μ-Cl)}₂ (3), was prepared from the reaction of its monomer precursor, (μ-PPh₂CH₂PPh₂)Co₂(CO)₄(μ,η-(tBu)₂PC{triple bond, long}CC₆H₄-κC¹)Pd(μ-OAc) (2), with LiCl. The crystal structure of 3, determined by X-ray diffraction methods, revealed a doubly chloride-bridged palladium dimeric conformation. Suzuki coupling reactions of bromobenzene with phenylboronic acid were carried out catalytically using these two novel palladium complexes 2 and 3 as catalyst precursors. Factors such as the molar ratio of substrate/catalyst, reaction temperature, base and solvent that might affect the catalytic efficiencies were investigated. As a general rule, the performance is much better by employing 3 than 2 as the catalyst precursor.

Full text of DOI:10.1016/j.poly.2006.07.005

Polyhedron 25 (2006) 3555–3561
www.elsevier.com/locate/poly
Preparation of a palladium dimer with a cobalt-containing
bulky phosphine ligand: Its application in palladium
catalyzed Suzuki reactions
*
Ya-Huei Gan, Jian-Cheng Lee, Fung-E. Hong
Department of Chemistry, National Chung Hsing University, Taichung 40227, Taiwan
Received 3 June 2006; accepted 5 July 2006
Available online 15 July 2006
Abstract
A palladium dimer with a cobalt-containing phosphine ligand, {(l-PPh2CH2PPh2)Co2(CO)4(l,g-(tBu)2PC„CC6H4-jC1)Pd(l-Cl)}2
(3), was prepared from the reaction of its monomer precursor, (l-PPh2CH2PPh2)Co2(CO)4(l,g-(tBu)2PC„CC6H4-jC1)Pd(l-OAc) (2),
with LiCl. The crystal structure of 3, determined by X-ray diffraction methods, revealed a doubly chloride-bridged palladium dimeric
conformation. Suzuki coupling reactions of bromobenzene with phenylboronic acid were carried out catalytically using these two novel
palladium complexes 2 and 3 as catalyst precursors. Factors such as the molar ratio of substrate/catalyst, reaction temperature, base and
solvent that might affect the catalytic efficiencies were investigated. As a general rule, the performance is much better by employing 3 than
2 as the catalyst precursor.
ꢀ 2006 Elsevier Ltd. All rights reserved.
Keywords: Palladium dimer; Suzuki reaction; Transition-metal containing phosphine ligand; Orthometallation
1. Introduction
having bulky and hopefully electron-rich character. Their
efficiencies as assisting ligands in palladium-catalyzed
Suzuki and amination reactions have been carefully evalu-
ated [4,5]. Generally speaking, the catalytic efficiencies with
monodentate phosphines are higher than with bidentate
ones.
Our previous work had demonstrated that amination
reactions of arylbromides and morpholine could be carried
out by employing (l-PPh2CH2PPh2)Co2(CO)4(l,g-
(tBu)2PC„CPh) (1)-modified Pd(OAc)2 complex as cata-
lyst precursor. The reactions were carried out at various
conditions and with satisfactory results. Meanwhile, a
unique palladium complex 2, (l-PPh2CH2PPh2)Co2(CO)4-
(l,g-(tBu)2PC„CC6H4-jC1)Pd(l-OAc), was prepared
from the reaction of the cobalt-containing bulky phosphine
1 with Pd(OAc)2 (Scheme 2) [5]. As disclosed by its crystal
structure, during the formation of 2 a process of orthomet-
allation occurred accompanied by the release of one
equivalent of acetic acid. For comparison, amination reac-
tions of aryl bromides and morpholine employing in situ
For the past few decades, phosphines have been proven
to be the most versatile and commonly employed ligands
in transition metal-catalyzed reactions [1]. Lately, due to
their bulkiness, metal-containing phosphines, rather than
the conventional organic phosphines, have received increas-
ing interest from experimentalists [2]. Among all the
metal-containing bidentate phosphine ligands, bis(diph-
enylphosphino)ferrocene (dppf) and its derivatives are
probably the most well known [3]. Recently, the authors
have been involved in developing a new category of
metal-containing phosphine ligands. A series of cobalt-con-
taining (mono- or bidentate) phosphine ligands (l-PPh2-
CH2PPh2)Co2(CO)4(l,g-R1C„CR2) {R1, R2: P(t-Bu)2,
P(i-Pr)2, PCy2, PPh2, Ph, py} were prepared (Scheme 1).
These types of ligands lead directly to a class of phosphines
*
Corresponding author.
E-mail address: fehong@dragon.nchu.edu.tw (Fung-E. Hong).
0277-5387/$ - see front matter ꢀ 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2006.07.005

3556
Y.-H. Gan et al. / Polyhedron 25 (2006) 3555–3561
(CO)2
Co
R1
R2
P
+ R1C CR2
- 2CO
R1, R2: P(t-Bu)2, P(i-Pr)2, PCy2, PPh2, Ph, py
(CO)
C
C
(CO)
3 Co
Co
Ph
3
Ph2
Ph2 P
P
2
P
Co
(CO)2
Ph2
Scheme 1.
(tBu)2
P(tBu)2
P
(CO)2
Co
O
P
C
C
C
C
C
C
+ Pd(OAc)2
C
C
Pd
C CH3
Ph2
O
P
Co
(CO)2
Ph2
1
2
Scheme 2.
prepared 1/Pd(OAc)2 and 2 were carried out. In general,
complex 2 results in lower efficiency compared with that
of in situ prepared 1/Pd(OAc)2.
Table 1
Crystal data of 3
Compound
3
Formula
C
45H44ClCo2O4P3Pd
It is well-known that halide-coordinated palladium com-
plexes such as [(g4-C4Ph4)PdBr2]2 are always present in
dimeric form with two bridging halides [6]. The bonding
of the chelating acetate toward palladium atom in 2 is seem-
ingly weak resulting in replacement by a stronger ligand
such as halide. It leads naturally to an energetically favor-
able form, a dimeric complex. Herein, we report the prepa-
ration of a new unusually large sized palladium dimeric
compound and its catalytic activity in Suzuki reactions.
Formula weight
Crystal system
Space group
1001.42
monoclinic
C2/c
28.1956(18)
26.0181(16)
18.2245(11)
˚
a (A)
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
128.0030(10)
3
˚
V (A )
10534.8(11)
8
1.263
0.71073
1.136
1.36–26.05
10370
485
Z
Dc (Mg/m3)
2. Results and discussion
˚
k (Mo Ka, A)
l (mmꢀ1
h Range (ꢁ)
)
2.1. Preparation and characterization of a palladium dimer 3
Observed reflections (F > 4r(F))
A new and unusually large-sized palladium dimeric
compound, {(l-PPh2CH2PPh2)Co2(CO)4(l,g-(tBu)2PC„
CC6H4-jC1)Pd(l-Cl)}2 (3), was obtained in good yield
from the treatment of 2 with LiCl in toluene at 25 ꢁC for
72 h (Scheme 3).
Number of refined parameters
a
R1 for significant reflections
0.0526
0.1624
0.997
b
wR2 for significant reflections
Goodness-of-fitc
P
P
a
b
c
R1 = j (jFoj ꢀ jFcj)/j Foi.
P
P
wR2 ¼ f ½wðF 2o ꢀ F 2cÞ = ½wðF 2oÞ gg1=2; w = 0.1015 for 3.
2
2
The identity of 3 was confirmed by spectroscopic means
as well as X-ray diffraction methods (Table 1). Interestingly,
the spectroscopic data of 3 exhibit two distinct sets of sig-
nals for its constructed units, (l-PPh2CH2PPh2)Co2-
(CO)4(l,g-(tBu)2PC„CC6H4-jC1). These two components
P
2
1=2
Goodness-of-fit ¼ ½ wðF 2o ꢀ F 2c Þ =ðNreflections ꢀ NparametersÞꢁ
.
and 3.50 ppm are assigned to two distinct sets of methylene
protons of 3. The 31P NMR spectrum displays two sets of
singlets at 82.87 and 84.40 ppm assigned to two phospho-
rous atoms coordinated to Pd. In addition, two sets of
multiplets at 38.00 and 41.43 ppm correspond to the coordi-
nated dppm ligand. The 13C NMR data also support the
account that the two constructed components of 3 are not
in the same magnetical environment. The ORTEP diagram
for 3 is depicted in Fig. 1. As shown, it is a doubly chloride-
bridged palladium dimer. The original chelating acetate
ligand was removed from 2. The four atoms, Pd2Cl2, are
arranged in a diamond shape and almost coplanar. The
conformation of the rest of the dimer is almost unaltered
from its counterpart in 2. Two isomeric forms of 3 might
1
are not magnetically equivalent. In H NMR, two sets of
doublets appear at 8.52 and 8.69 ppm, which correspond
to the adjacent protons of the orthomatallated arene.
Another two sets of multiplets signals observed at 3.34
(tBu)2
P
C
C
Cl
Cl
C
C
Pd
Pd
LiCl
+
2
P
(tBu)2
3
Scheme 3.

Y.-H. Gan et al. / Polyhedron 25 (2006) 3555–3561
3557
˚
Fig. 1. ORTEP drawing of 3. Hydrogen atoms are omitted for clarity. Selected bond lengths (A) and angles (ꢁ): Pd(1)–C(3) 2.013(7); Pd(1)–P(1)
2.2690(19); Pd(1)–Cl(1) 2.4329(18); Pd(1)–Cl(1)#1 2.4512(19); Co(1)–C(2) 1.960(6); Co(1)–C(1) 1.998(7); Co(1)–P(2) 2.239(2); Co(1)–Co(2) 2.4770(13);
Co(2)–C(2) 1.956(7); Co(2)–C(1) 1.959(7); Co(2)–P(3) 2.208(2); P(1)–C(1) 1.793(8); P(2)–C(45) 1.827(7); P(3)–C(45) 1.831(7); Cl(1)–Pd(1)#1 2.4512(19);
C(1)–C(2) 1.362(9); C(2)–C(4) 1.461(10); C(3)–Pd(1)–P(1) 89.41(19); C(3)–Pd(1)–Cl(1) 90.42(19); P(1)–Pd(1)–Cl(1) 170.10(8); C(3)–Pd(1)–Cl(1)#1
164.9(2); P(1)–Pd(1)–Cl(1)#1 100.45(7); Cl(1)–Pd(1)–Cl(1)#1 81.83(7) and C(2)–Co(1)–C(1) 40.3(3); C(2)–Co(2)–C(1) 40.7(3); C(1)–P(1)–Pd(1) 104.3(2);
Pd(1)–Cl(1)–Pd(1)#1 96.60(7); C(2)–C(1)–P(1) 123.2(5); C(2)–C(1)–Co(2) 69.5(4); C(2)–C(1)–Co(1) 68.4(4); Co(2)–C(1)–Co(1) 77.5(3); C(1)–C(2)–C(4)
128.8(7); Co(2)–C(2)–Co(1) 78.5(3); P(2)–C(45)–P(3) 110.8(4).
be presented in solution. Crystal structure of 3 only repre-
sents one of the two isomeric forms.
2.2. Suzuki reactions using 2
The authors have previously reported the preparation of a
novel palladium complex cis-dichloride(1,2-bis(diphenyl-
phosphino)vinyl-P,P0,C)palladium(II)–(bis(diphenyl phos-
phino)methane-P,P0)cobaltacarbonyl (5). It was obtained
from the treatment of (l-Ph2PCH2PPh2)Co2(CO)4-
((l,g-Ph2PC„CPPh2)-j2P,P0)PdCl2 (4) with hydrochloric
acid (Scheme 4) [7]. This complex can be regarded as an
unique derivative of the well known compound, PdCl2(dppe)
[8]. Nevertheless, there was no sign of forming a doubly
chloride-bridged palladium dimer 6 from the reaction of 4
with LiCl.
Palladium-catalyzed Suzuki reactions of bromobenz-
enes with phenylboronic acid were carried out by
employing 2 as a catalyst precursor (Scheme 5). The gen-
eral procedures for the catalytic reactions under investi-
gation are described as follows. A suitable Schlenk tube
was charged with 1.0 mmol of bromobenzene, 1.5 mmol
of phenylboronic acid, 1.0 ml THF, 3.0 mmol KF and
1.0 mol% of 2. The reaction mixture was stirred at
60 ꢁC for 3–19 h followed by a work-up (Diagram 1).
A satisfactory result was obtained only when the reaction
time was 19 h.
Ph2
(CO)2
Co
Ph2
P
P
Cl
Cl
C
C
Pd
+ HCl
P
Ph2
L
L
Cl
Cl
P
Ph2
H
5
Pd
L
L
L
Cl
4
+ HCl or LiCl
Pd
Pd
Cl
6
L
Ph2
P
(CO)2
Co
L
P
Ph2
C
C
L
P
Ph2
P
Co
(CO)2
Ph2
Scheme 4.

3558
Y.-H. Gan et al. / Polyhedron 25 (2006) 3555–3561
Table 3
[Pd]
Suzuki coupling reactions employing 2 with various basesa
B(OH)2
Br
+
Entry
Base
Yield (%)b
Scheme 5.
1
2
3
4
5
6
7
8
9
a
KF
CsF
93.7
99.7
75.9
99.2
82.7
96.7
3.1
NaOH
NaOtBu
K2CO3
K3PO4
morpholine
NEt3
100
80
31.5
7.2
60
40
piperidine
Condition: 1.0 mmol bromobenzene, 1.5 mmol phenylboronic acid,
1.0 mol% 2, 1.0 ml 1,4-dioxane, 3.0 mmol base, 60 ꢁC, 19 h.
b
Isolated yield; average of two runs.
20
2.3. Suzuki reactions using 3
3
5
7
9
11 13 15 17 19
Time (hrs)
For comparison, the same Suzuki reactions were carried
out by employing 3 as the catalyst precursor. The general
procedures for the catalytic reactions under investigation
are described as follows. A suitable Schlenk tube was
charged with 1.0 mmol of bromobenzene, 1.5 mmol of
phenylboronic acid, 1.0 ml THF, 3.0 mmol KF and
0.5 mol% of 3. The reaction mixture was stirred at 60 ꢁC
for 3–9 h followed by a work-up. As shown in Diagram
1, the catalytic efficiencies were much better than in the
Diagram 1. The dependence of yield of the Suzuki coupling reactions
employing 2 (in d) and 3 (in h) on reaction hours.
Subsequently, the impact of various solvents used in
the reaction was evaluated. As shown, the reaction rate
is greatly affected by the kind of solvent used (Table 2).
For instance, the coupling reaction was ineffective when
DMF was used (entry 4). However, the yield was greatly
improved when 1,4-dioxane was employed as solvent
(entry 5).
It is well-known that the choice of a base is crucial to
the success of a palladium-catalyzed Suzuki reaction [9].
Therefore, the influences of the bases used on the reac-
tions were examined (Table 3). As shown, excellent yields
were observed when alkaline metal fluorides such as KF
and CsF (entries 1and 2) as well as NaOtBu and K3PO4
(entries 4 and 6) were used as bases. The yields were lower
when NaOH and K2CO3 were employed as bases under
the same reaction condition (entries 3 and 5). Amine
derived bases such as morpholine, NEt3 and piperidine
failed to promote the reactions resulting in very low yields
(entries 7–9).
Table 4
Suzuki coupling reactions employing 3 in various solventsa
Entry
Solvent
Yield (%)d
1
2
3
4
5
6
7
a
THF
toluene
DME
85.1b
62.5c
16.2c
31.0c
94.8c
38.9c
52.9c,e
DMF
1,4-dioxane
CH3CN
H2O
Condition: 1.0 mmol bromobenzene, 1.5 mmol phenylboronic acid,
0.5 mol% 3, 3.0 mmol KF, 60 ꢁC, 1.0 ml solvent, 6 h.
b
Determined by GC.
Isolated yield.
Average of two runs.
0.2 mmol TBAB added.
c
d
e
Table 2
Suzuki coupling reactions employing 2 in various solventsa
Table 5
Suzuki coupling reaction employing 3 with various basesa
Entry
Solvent
Yield (%)d
82.7c
43.1b
78.2b
25.9b
93.7b
68.4b
48.3b,e
Entry
Base
Yieldb
1
2
3
4
5
6
7
a
THF
toluene
DME
1
2
3
4
5
6
7
8
9
a
KF
CsF
94.8
99.1
25.9
30.1
36.6
55.9
23.3
19.8
4.1
DMF
K3PO4
K2CO3
NaOH
NaOt-Bu
morpholine
NEt3
1,4-dioxane
CH3CN
H2O
Condition: 1.0 mmol bromobenzene, 1.5 mmol phenylboronic acid,
1.0 mol% 2, 1.0 ml solvent, 3.0 mmol KF, 60 ꢁC, 19 h.
b
piperidine
Isolated yield.
Determined by GC.
Average of two runs.
0.2 mmol TBAB added.
c
Condition: 1.0 mmol bromobenzene, 1.5 mmol phenylboronic acid,
0.5 mol% 3, 3.0 mmol base, 60 ꢁC, 1.0 ml 1,4-dioxane, 6 h.
d
e
b
Isolated yield; average of two runs.

Y.-H. Gan et al. / Polyhedron 25 (2006) 3555–3561
3559
Table 6
same as previously mentioned. Again, the best yield was
observed using 1,4-dioxane as a solvent (entry 5). It is in
accord with the previous case (Table 2).
Suzuki coupling reactions under various substrate/3 ratiosa
Entry
3 (mmol%)
Yield (%)b
The influences of the bases used on the reactions were
examined next (Table 5). As shown, excellent yields were
observed when alkaline metal fluorides KF and CsF were
used as bases (entries 1 and 2). Other bases, especially
amines, were much less effective (entries 3–9).
The Suzuki coupling reactions with various substrate/
catalyst loading ratios (0.5–0.05 mol% 3) were also exam-
ined (Table 6). A reasonable yield was achieved even when
0.05 mol% 3 was employed.
The following table shows the results from the 3-assisted
Suzuki cross-coupling reactions (Table 7). The catalytic
performance was good for the substrate with electron-with-
drawing group (entries 6–8). Nevertheless, the efficiency
was low for the substrate with electron-donating group
(entries 2 and 3). It is consistent with the general observa-
tion for the palladium-catalyzed Suzuki reaction.
1
2
3
4
a
0.5
0.25
0.1
99.1
97.3
91.2
85.9
0.05
Condition: 1.0 mmol bromobenzene, 1.5 mmol phenylboronic acid,
3.0 mmol CsF, 60 ꢁC, 1.0 ml 1,4-dioxane, 6 h.
b
Isolated yield; average of two runs.
previous case when 2 was employed. With 3 it takes a
shorter reaction time to reach the same conversion. As
known, the halide bridging bond is intrinsically weak in
dimer. It is ready to break and form an unsaturated palla-
dium monomer. The latter is presumably an active species
that promptly accepts the oncoming substrate(s) for further
catalytic reaction.
The effect of the solvent used was evaluated as well
(Table 4). The procedures for Suzuki reactions were the
3. Concluding remarks
Table 7
Suzuki coupling reactions employing 3 under various substratea
We have demonstrated that the Suzuki reactions of aryl
bromides with phenylboronic acid could be carried out cat-
alytically with two novel palladium complexes 2 and 3. The
catalytic performance is better with 3 probably due to its
readiness to form the unsaturated active monomer.
Entry Subtract
1
Temperatue (ꢁC) Yield (%)b
50
60
83.9
89.7
Br
2
50
60
14.7
62.8
H3CO
Br
Br
4. Experimental
4.1. General
3
50
60
17.7
71.5
H3C
All manipulations were carried out under a dry nitrogen
atmosphere. All solvents including deuterated solvents were
purified before use. All separations of the products were
performed by Centrifugal Thin Layer Chromatography
4
5
50
60
2.5
50.3
CH3
Br
1
(CTLC, Chromatotron, Harrison model 8924). H NMR
spectra were recorded (Varian VXR-300S spectrometer) at
300.00 MHz; chemical shifts are reported in ppm relative
to internal CHCl3 or CH2Cl2. 31P and 13C NMR spectra
were recorded at 121.44 and 75.46 MHz, respectively. Some
50
60
4.4
40.1
N
Br
1
other routine H NMR spectra were recorded on Gemini-
6
50
60
83.1
91.2
O
200 spectrometer at 200.00 MHz or Varian-400 spectrome-
ter at 400.00 MHz. Mass spectra were recorded on JOEL
JMS-SX/SX 102A GC/MS/MS spectrometer. Elemental
analyses were obtained on Heraeus CHN-O-S-Rapid.
Br
Br
7
50
60
87.3
95.1
O
4.2. Synthesis of 3
A 100 cm3 round-bottomed flask was charged with
O
8
50
60
87.9
96.8
1.00 mmol (1.025 g) (l-PPh2CH2PPh2)Co2(CO)4(l,g-
(tBu)2PC„CC6H4-jC1)Pd(l-OAc)
2
and one molar
equivalent of LiCl (0.0424 g) as well as 15 ml of toluene.
The mixture was stirred at 25 ꢁC for 72 h. Subsequently,
purification of products using centrifugal thin-layer
chromatography (CTLC) was carried out. The first band,
brown in color, was eluted out by a mixture solvent of
Br
a
Conditions: 1.00 mmol phenylbromide, 1.50 mmol phenylboronic acid,
3.00 equiv. CsF, 0.05 mol% 3, 1.0 mL 1,4-dioxane, 5 h, 50 ꢁC.
b
Averaged by two runs; isolated yield.

3560
Y.-H. Gan et al. / Polyhedron 25 (2006) 3555–3561
CH2Cl2/ethyl acetate (10/1). It was identified as the title
Acknowledgement
compound
{(l-PPh2CH2PPh2)Co2(CO)4(l,g-(tBu)2PC
„CC6H4-jC1)Pd(l-Cl)}2 (3). The yield of 3 is 75%
We thank the National Science Council of the ROC
(Grant NSC-94-2113-M-005-011) for the financial support.
(0.1503 g, 0.750 mmol).
1
3: H NMR (C6D6, d/ppm): 1.37 (t, JP–H = 30.0, 36H,
–C(CH3)3), 3.34, 3.50 (m, 2H, dppm), 6.71–7.46 (m, 46H,
arene), 8.52 (d, JH–H = 6.8, 1H, o-hydrogen of the ortho-
metallated arene), 8.69 (d, JH–H = 7.2, 1H, o-hydrogen of
the orthometallated arene); 13C NMR (C6D6, d/ppm):
30.5 (d, 12C, C(CH3)3), 39.0 (d, 4C, C(CH3)3), 40.8 (s,
2C, CH2), 73.8 (d, 4C, PhC„CP(t-Bu)2), 124.6–146.9
(m, 56C, arene), 146.0 (s, 2C, ipso of arene), 158.4 (d,
2C, ipso of arene), 202.8–207.0 (m, 8C, CO); 31P NMR
(C6D6, d/ppm): 38.0 (dd, JP–P = 109.9, 2P, dppm), 41.4
(t, JP–P = 86.1, 2P, dppm), 82.9 (s, 1P, P(t-Bu)2), 84.4
(s, 1P, P(t-Bu)2). Anal. Calc. for 3: C, 41.60; H, 4.07.
Found: C, 41.59; H, 4.04%. M.S.: m/z 696 (M+).
Appendix A. Supplementary data
Crystallographic data for the structural analysis of
compound 3 have been deposited with the Cambridge Crys-
tallographic Data Center, CCDC no. 293127. Copies of this
information may be obtained free of charge from the Direc-
tor, CCDC, 12 Union Road, Cambridge CB2 1EZ, UK,
fax: +44 1223 336 033, e-mail: deposit@ccdc.cam.ac.uk
or www:http://www.ccdc.cam.ac.uk. Supplementary data
associated with this article can be found, in the online ver-
sion, at doi:10.1016/j.poly.2006.07.005.
References
4.3. General procedures for the Suzuki cross-coupling
reactions
[1] (a) T.E. Barder, S.D. Walker, J.R. Martinelli, S.L. Buchwald, J. Am.
Chem. Soc. 127 (2005) 4685;
(b) S.D. Walker, T.E. Barder, J.R. Martinelli, S.L. Buchwald, Angew.
Chem., Int. Ed. 43 (2004) 1871;
(c) W. Tang, X. Zhang, Chem. Rev. 103 (2003) 3029;
(d) Q.-S. Hu, Y. Lu, Z.-Y. Tang, H.-B. Yu, J. Am. Chem. Soc. 125
(2003) 2856;
(e) T.E. Pickett, F.X. Roca, C.J. Richards, J. Org. Chem. 68 (2003)
2592;
(f) Z.-Y. Tang, Y. Lu, Q.-S. Hu, Org. Lett. 5 (2003) 297;
Suzuki cross-coupling reactions were performed accord-
ing to the following procedures. Complex 3 (10.02 mg,
0.005 mmol), boronic acid (0.183 g, 1.500 mmol) and
potassium fluoride (0.174 g, 3.0 mmol) were placed into a
20 ml Schlenk flask. The flask was evacuated and backfilled
with nitrogen before adding THF (1 ml) and bromoben-
zene (0.11 ml, 1.000 mmol). The solution was stirred at
60 ꢁC for 6 h. Subsequently, excess amount of water was
added and the product was extracted with ether
(2 · 30 ml). The combined organic extracts were dried over
anhydrous MgSO4 and concentrated under vacuum. The
crude residue was purified by flash chromatography on
silica gel or gas chromatography.
´
(g) J. Hassan, M. Sevingnon, C. Gozzi, E. Schulz, M. Lemaire, Chem.
Rev. 102 (2002) 1359;
(h) N. Kataoka, Q. Shelby, J.P. Stambuli, J.F. Hartwig, J. Org.
Chem. 67 (2002) 5553;
(i) J.G. Planas, J.A. Gladysz, Inorg. Chem. 41 (2002) 6947;
(j) N.G. Andersen, B.A. Keay, Chem. Rev. 101 (2001) 997;
(k) C.A. Bessel, P. Aggarwal, A.C. Marschilok, K.J. Takeuchi, Chem.
Rev. 101 (2001) 1031;
(l) A.F. Littke, C. Dai, G.C. Fu, J. Am. Chem. Soc. 122 (2000) 4020;
(m) J.F. Hartwig, Angew. Chem., Int. Ed. 37 (1998) 2046;
(n) G. Mann, J.F. Hartwig, J. Am. Chem. Soc. 118 (1996) 13109.
[2] (a) S. Eichenseher, O. Delacroix, K. Kromm, F. Hampel, J.A.
Gladysz, Organometallics 24 (2005) 245;
4.4. X-ray crystallographic studies
Suitable crystals of 3 were sealed in thin-walled glass cap-
illaries under nitrogen atmosphere and mounted on a Bru-
ker AXS SMART 1000 diffractometer. Intensity data were
collected in 1350 frames with increasing x (width of 0.3ꢁ
per frame). The absorption correction was based on the
symmetry equivalent reflections using SADABS program.
The space group determination was based on a check of
the Laue symmetry and systematic absences, and was con-
firmed using the structure solution. The structure was solved
by direct methods using a SHELXTL package [10]. All non-H
atoms were located from successive Fourier maps and the
hydrogen atoms were refined using a riding model. Aniso-
tropic thermal parameters were used for all non-H atoms
and fixed isotropic parameters were used for H atoms.1
Crystallographic data of 3 are summarized in Table 1.
(b) O. Delacroix, J.A. Gladysz, Chem. Commun. (2003) 665;
(c) K. Kromm, F. Hampel, J.A. Gladysz, Organometallics 21 (2002)
4264.
[3] (a) R.C.J. Atkinson, V.C. Gibson, N.J. Long, Chem. Soc. Rev. 33
(2004) 313;
(b) T.J. Colacot, Chem. Rev. 103 (2003) 3101.
[4] (a) F.-E. Hong, Y.-J. Ho, Y.-C. Chang, Y.-L. Huang, J. Organomet.
Chem. 690 (2005) 1249;
(b) C.-P. Chang, Y.-L. Huang, F.-E. Hong, Tetrahedron 61 (2005)
3835;
(c) Y.-C. Chang, F.-E. Hong, Organometallics 24 (2005) 5686;
(d) F.-E. Hong, Y.-C. Chang, C.-P. Chang, Y.-L. Huang, Dalton
Trans. (2004) 157;
(e) F.-E. Hong, Y.-J. Ho, Y.-C. Chang, Y.-C. Lai, Tetrahedron 60
(2004) 2639;
(f) F.-E. Hong, C.-P. Chang, Y.-C. Chang, Dalton Trans. (2003)
3892;
(g) F.-E. Hong, Y.-C. Lai, Y.-J. Ho, Y.-C. Chang, J. Organomet.
Chem. 688 (2003) 161;
(h) F.-E. Hong, Y.-C. Chang, R.-E. Chang, S.-C. Chen, B.-T. Ko,
Organometallics 21 (2002) 961.
[5] J.-C. Lee, M.-G. Wang, F.-E. Hong, Eur. J. Inorg. Chem. (2005) 5011.
1
The hydrogen atoms were ride on carbons or oxygen atoms in their
˚
idealized positions and held fixed with the C–H distances of 0.96 A.

Y.-H. Gan et al. / Polyhedron 25 (2006) 3555–3561
3561
[6] (a) A.T. Blomquist, P.M. Maitlis, J. Am. Chem. Soc. 84 (1962) 2329;
Science Books, Mill Valley, CA, 1987 (Chapter 3);
(b) R.J. Puddephatt, Chem. Soc. Rev. 12 (1983) 99.
[9] (a) N. Miyaura, K. Yamada, H. Suginome, A. Suzuki, J. Am. Chem.
Soc. 107 (1985) 972;
(b) G.A. Grasa, A.C. Hillier, S.P. Nolan, Org. Lett. 3 (2001)
1077;
(c) S.R. Dubbaka, P. Vogel, Org. Lett. 6 (2004) 95.
[10] G.M. Sheldrick, SHELXTL PLUS User’s Manual. Revision 4.1 Nicolet
XRD Corporation, Madison, WI, USA, 1991.
(b) P.M. Maitlis, M.L. Games, Can. J. Chem. 42 (1964) 183;
(c) J. Dupont, C.S. Consorti, J. Spencer, J. Chem. Rev. 105 (2005) 2527;
(d) M. Prashad, X.Y. Mak, Y. Liu, O. Repic, J. Org. Chem. 68 (2003)
1163;
(e) K. Yuan, T.K. Zhang, X.L. Hou, J. Org. Chem. 70 (2005) 6085.
[7] C.-P. Chang, F.-E. Hong, J. Chin. Chem. Soc. 52 (2005) 1105.
[8] (a) P. Collman, L.S. Hegedus, J.R. Norton, R.G. Finke, Principles
and Applications of Organotransition Metal Chemistry, University