Water as an activator for palladium(II)-catalyzed olefin polymerization

Article abstract of DOI:10.1002/chem.201300890

By a reasonable combination of the Wacker reaction and olefin polymerization processes, water proves to be an excellent activator for the palladium(II)-catalyzed polymerization of ethylene and it provides a safe, environmental-friendly and handy initiator for olefin polymerization. The activity of the olefin polymerization is comparable to reactions catalyzed by the corresponding alkylated cationic palladium complexes. Just a drop! By careful combination of the Wacker reaction and olefin polymerization processes, water proves to be an excellent activator for the Pd^II-catalyzed polymerization of ethylene and it provides a safe, environmentally friendly and handy initiator for olefin polymerization (see scheme). The activity of the olefin polymerization is comparable to reactions catalyzed by the corresponding alkylated cationic palladium complexes (Tf = triflate). Copyright

Full text of DOI:10.1002/chem.201300890

DOI: 10.1002/chem.201300890
Water as an Activator for Palladium(II)-Catalyzed Olefin ACHUTNRGNENUGP olymerization
Wen-Jie Tao, Jun-Fang Li, Ai-Qing Peng, Xiu-Li Sun,* Xiao-Hong Yang, and
[
a]
Yong Tang*
Abstract: By a reasonable combination of the Wacker reaction and olefin polymer-
ization processes, water proves to be an excellent activator for the palladium(II)-
catalyzed polymerization of ethylene and it provides a safe, environmental-friendly
and handy initiator for olefin polymerization. The activity of the olefin polymeri-
zation is comparable to reactions catalyzed by the corresponding alkylated cationic
palladium complexes.
Keywords: olefins
polymerization · Wacker reaction ·
water chemistry
· palladium ·
Introduction
[
1–7]
II
Since Brookhartꢀs pioneering works in the 1990s,
imine complexes have been widely employed as precatalysts
for olefin polymerization, producing various polyolefins
Pd –di-
ACHTUNGTRENNUNG
[1–3]
with attractive structures and properties.
For example, in
the polymerization of ethylene and copolymerization of eth-
[1]
ylene with polar olefins reported by Brookhart, in the con-
trol of polyethylene (PE) topology through chain walking
[2]
reported by Guan, and in Meckingꢀs aqueous coordination
polymerizations of ethylene based on the water-insolubility
[3]
of catalyst precursors and the encapsulation effect, the
Pd –diimine complexes exhibited unique reactivity.
II
Scheme 1. Strategy for H
2
O-initiated polymerization of ethylene.
However, in all of the aforementioned polymerizations,
either presynthesized cationic alkyl–palladium(II)–diimine
complexes were employed or methylaluminoxane (MAO)
was used as a cocatalyst. Feldman and co-workers report-
ed an elegant ethylene polymerization that took place at
pressures above 300 psi with [ArN=C(Me)C(Me)=NArPd-
[
1f]
+
initial catalytic species. Combined with the fact that [Pd
[10]
–H] can be generated by the Wacker reaction of ethylene
and water (Scheme 1, left side), we envisioned that the
Wacker process may be integrated into ethylene polymeriza-
[3a]
+
tion to provide [Pd –H] species to initiate olefin polymeri-
[
11]
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
(MeCN) ]
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
[BF ] (Ar=2,6-(iPr) C H ) without activator, in
zation. The challenge is the control of the conflict associ-
ated with b-H elimination in two processes, in which fast b-
H elimination is desired in the Wacker reaction to generate
2
4
2
2
6
3
which they found that activity was reduced by the presence
of more than trace amounts of water, but the mechanism
[8]
[9]
+
was unclear.
Recently, Labinger and Bercaw et al.
[Pd –H] whereas it has to be inhibited in the olefin poly-
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
documented that, in the presence of the desired amount
merization. Very recently, we developed a water-initiated
facile and efficient palladium(II) ethylene polymerization
system in which the Wacker process was successfully inte-
grated into the polymerization system to provide the key
palladium–hydride species, without the need to prepare al-
kylated palladium precursors or organometallic activators.
The role of water is clarified. In this paper, we wish to
report the results in details.
2
+
of water,
a
[(ArN=C(Me)C(Me)=NAr)Pd ACHTUNGERTNNUNG( m-OH)]
2
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
(Ar=3,5-(CMe ) C H /trifluoroethanol (TFE) system can
ACHTUNGTRENNUNG
3
2
6
3
promote the oligomerization of ethylene and propylene, as
well as the isomerization/oligomerization of 1-hexene. The
aforementioned reports and mechanistic studies on the
Brookhart catalyst system have revealed that [LnPd –H]
species, formed by b-H elimination of [LnPd –alkyl], is the
+
+
[
a] W.-J. Tao, Dr. J.-F. Li, A.-Q. Peng, Dr. X.-L. Sun, X.-H. Yang,
Prof. Dr. Y. Tang
Results and Discussion
State Key Laboratory of Organometallic Chemistry
Shanghai Institute of Organic Chemistry
Synthesis of a-diimine–palladium(II) complexes: The proce-
dures for the preparation of palladium(II) complexes 1, 2,
and 3 are shown in Scheme 2. L1–L4 were synthesized ac-
3
45 Lingling Lu, Shanghai 200032 (P.R. China)
Fax : (+86)21-54925078
E-mail: tangy@sioc.ac.cn
[1h]
cording to known procedures.
13956
ꢁ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2013, 19, 13956 – 13961

FULL PAPER
Figure 1. Molecular structure of 3. Selected bond lengths [ꢂ] and angles
[
8]: Pd(1)ꢀO(1) 2.040(3), Pd(1)ꢀO(2) 2.039(3), Pd(1)ꢀN(1) 2.001(3),
Pd(1)ꢀN(2) 1.993(3), N(1)ꢀC(13) 1.444(4), N(2)ꢀC(25) 1.434(4), N(1)ꢀ
N(2) 2.625(4); O(1)-Pd(1)-N(1) 93.51(12), O(1)-Pd(1)-O(2) 91.66(12),
N(1)-Pd(1)-N(2) 82.18(11), O(2)-Pd(1)-N(2) 92.64(11), C(1)-N(1)-C(13)-
C(14) 93.4(4), C(5)-N(2)-C(25)-C(30) 79.3(4).
Scheme 2. Synthesis of a-diimine–palladium(II) complexes.
All of the palladium complexes were characterized by
NMR and elemental analyses. Fortunately, single crystals of
[
a]
Table 1. Water-initiated polymerization.
Entry Cat. Water Activity
[
12]
ꢀ
3
(X= OTf) that were suitable for X-ray diffraction anal-
[
c,d]
[c]
[d,e]
M
w,GPC
M
w
/M
n
M
w, LLS
ysis were formed from CH Cl solution. As shown in
2
2
AHCTUNGERTNNUNG[ equiv] [g per mmol·Pd·h]
Figure 1, the crystal structure of 3 displays a square-planar
geometry. Similar to the structure of [ArN=C(Me)C(Me)=
[
b]
1
2
3
4
5
6
7
8
9
0
1
2
3
3
3
3
3
3
3
3
2.0
2.0
2.0
0
5.0
10.0
50.0
100.0
200.0
500.0
–
–
–
–
–
–
–
–
[b]
[1f]
NAr]Pd
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
(CH ) , (Ar=2,6-(iPr) C H ), the aryl rings on the
1.2
0.8
1.1
2.0
8.7
7.4
2.5
0.6
0.84
0.84
0.87
0.74
0.59
0.54
0.53
0.44
3.13
1.49
2.65
3.62
1.65
1.90
2.52
3.72
1.91
1.85
1.94
1.63
1.22
1.05
1.17
0.93
3
2
2
6
3
aniline moieties are oriented approximately perpendicular
to the chelated ring.
Ethylene polymerization: Initially, we used diimine–PdCl 1
2
to test the water-initiated polymerization of ethylene be-
cause PdCl2 is the most commonly used catalyst for the
Wacker reaction. Unfortunately, it failed to promote the
1
[a] Reaction conditions: catalyst (50 mmol), CH
1 atm), 6 h, 258C. [b] No product was observed. [c] Determined by GPC
analysis. [d] 104 gmol . [e] Determined by LLS analysis.
2 2
Cl (50 mL), ethylene
II
(
polymerization. Considering cationic Pd should be more ef-
ꢀ
1
ficient for the activation of ethylene and speed up the
Wacker reaction to generate palladium–hydride for the
II
polymerization, we synthesized and evaluated Pd com-
of magnitude in comparison to the reaction without addi-
plexes 2 and 3 for comparison. As shown in Table 1, dii-
tional water (entry 4 vs. entry 7). Thus, H O successfully ini-
2
mine–Pd
zation. However, when Pd
ACHTUNGTRENNUNG( OTf) ·2H O, we are pleased to find that the desired poly-
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
(OAc) 2 also failed to promote ethylene polymeri-
tiated ethylene polymerization catalyzed by complex 3.
The molecular weight of the polyethylene decreased as
the amount of water was increased (Table 1, entries 3–10),
suggesting that by changing the amount of water the molec-
ular weight of the polymer in our system could be adjusted.
The reason behind this phenomenon is probably chain trans-
2
AHCTUNGTRNENUG( OAc) was replaced by Pd-
2
2
2
merization worked well at 258C under 1 atm ethylene in the
presence of 2.0 equivalents of water (entry 3). Indeed, water
proved to be essential to activate the Pd complexes for the
polymerization. Although we cannot make the solvent com-
pletely free of water (2.5–4.0 ppm), as expected, without ad-
ditional water, decreased activity was observed (entry 4). In-
creasing the amount of water revealed a maximum polymer-
ization activity (entries 4–10), and when 50 equivalents of
water was added the reactivity increased by nearly an order
[15]
fer to water. When a low amount of water is present (en-
tries 3–5), the molecular weight of the polyethylene was sim-
ilar to that achieved by the cationic alkylated palladium
[2a]
complex.
[13]
Because it has been documented that the Wacker reac-
ꢀ
tion with pyridine-coordinated [PdCl3] is much slower (by
Chem. Eur. J. 2013, 19, 13956 – 13961
ꢁ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
13957

X.-L. Sun, Y. Tang et al.
2ꢀ
ca. 750-fold) relative to [PdCl ] , we supposed that the
4
polymerization might be hampered by the retarded Wacker
reaction initiated by 3. When one-pot polymerization was
tried, to our delight, much higher activity was observed by
using mixed ligand L1 generated in situ with
Pd ACHTUNGTRENNUNG( OTf) ·2H O rather than complex 3 (Table 2, entry 1 vs.
2 2
[
a]
Table 2. Ligand effects on the one-pot ethylene polymerization.
[
b]
[c,d]
w,GPC
[c]
[d,e]
Entry
Complex
Yield
g]
Act.
M
M
w
/M
n
M
w,LLS
[
+
[
f]
Scheme 3. New strategy for the generation of [LnPd –H].
1
2
3
4
5
3
0.32
1.69
0.90
6.34
2.25
1.07
5.63
2.98
21.13
7.50
0.82
0.72
0.25
0.46
0.68
1.41
1.41
2.20
1.25
1.46
9.19
7.50
2.46
4.23
6.95
L1/[Pd]
L2/[Pd]
L3/[Pd]
L4/[Pd]
ture of the polymers, which are very useful as lubricants and
[16]
plastic additives.
[
2 2
a] Reaction conditions: ligand (75 mmol), Pd ACHTUNGTRNENUG( OTf) ·2H O (50 mmol),
DCE (50 mL), ethylene (1 atm), 6 h. [b] g per mmol·Pd·h. [c] Determined
Mechanistic study: As was initially proposed in Scheme 1,
acetaldehyde should be formed as a byproduct during the
polymerization reaction. After carefully adjusting the pa-
rameters, GC-MS was employed as a convenient method to
monitor acetaldehyde formation. As shown in Scheme 4,
4
ꢀ1
by GPC analysis. [d] 10 gmol
. [e] Determined by LLS analysis.
[
f] Complex 3: 50 mmol.
2). This may be ascribed to the fact that the coordination of
the diimine ligand to Pd
ACHTUNGTRENNUNG
(OTf) decreases the Lewis acidity
2
of the palladium and slows down the hydroxyl-palladation
step (Scheme 1), which is the rate-determining step in the
[13]
Wacker reaction. In the one-pot system, part of the Pd-
(OTf) ·2H O was supposed to promote the Wacker reaction
ACHTUNGTRENNUNG
2
2
to generate palladium–hydride, followed by coordination of
[14]
the diimine ligand (Scheme 3). As a result, both the effi-
ciency of the generation of the active species INTI and the
polymerization activity are increased. Using this protocol,
several diimine ligands (L1–L4) were examined and L3/Pd-
Scheme 4. Detection of acetaldehyde and 2-hexanone.
ACHTUNGTRENNUNG( OTf) ·2H O was found to give the highest activity (21.13 g
2 2
per mmol·Pd·h) under 1 atm ethylene pressure at 258C
Table 2, entry 4), which was comparable to that obtained
with the corresponding alkylated Pd catalyst.
The influences of solvent, catalyst concentration, and tem-
perature were examined. As shown in Table 3, 1,2-dichloro-
ethane (DCE) was found to be more suitable than PhCl and
toluene (entries 2, 10, and 11). The activity was
acetaldehyde was detected in the cases of both L1/Pd
ACHTUNGTRENNUNG( OTf) /
2
(
H O and 3/H O (Scheme 4a). Under similar conditions, 1-
2
2
II
[1h]
hexene also underwent polymerization and, as expected, 2-
hexanone was also detected by GC-MS analysis (Sche-
[17]
me 4b).
nearly doubled when Pd ACHTUNGRETNN(UNG OTf) concentration was
2
increased from 0.5 to 1.0 mm (entries 1 and 2),
whereas further increasing its concentration to
[a]
Table 3. Olefin polymerization of Pd(II) initiated by water.
[
b]
[c,d]
[c]
[d,e]
Entry Pd
A
H
U
G
R
N
N
(OTf)
2
·2H
2
O
t
T
Yield Act.
M
w,GPC
M
w
/M
n
M
w,LLS
AHCTUNGTR[ENNUNG mmol]
[h] [8C] [g]
2.0 mm did not enhance the activity further
1
2
3
4
5
6
7
8
9
25
50
6
6
6
6
6
1
2
4
2
6
6
6
25
25
25
0
40
25
25
25
25
25
25
25
1.85 12.33
6.34 21.13
0.52
0.46
0.42
2.29
0.55
0.51
0.49
0.47
0.43
0.04
0.01
0.40
1.16
1.25
1.27
3.12
1.23
1.24
1.23
1.21
1.33
3.32
2.51
3.06
5.28
4.23
5.20
8.44
5.53
6.04
5.27
4.86
3.70
–
(
entry 3). Under the optimized conditions, the best
result was achieved when polymerization was per-
formed at 258C (entry 2). The catalyst system is
quite stable and ethylene polymerization continued
for at least 6 h (entries 2, and 6–8). Higher ethylene
pressure could further increase the yield of polymer
formation (entry 7 vs. 9). Under the same condi-
100
50
50
50
50
50
50
50
50
50
10.0
1.27
2.86
16.67
4.23
9.53
2.80 56.0
3.80 38.0
5.13 25.7
9.64 96.39
[
[
[
[
f]
g]
h]
i]
tions, 1-hexene also polymerized to give polyhexene 10
2.30
1.38
0.11
7.67
4.60
0.40
1
1
12
–
0.47
(
entry 12). All polymers generated were colorless
1
13
oils. H and C NMR spectroscopic studies showed
that the polymers were highly branched, similar
to those obtained with the corresponding cationic
[15]
[a] Reaction conditions: L3 (1.5 equiv), Pd
2 2
ACHTUNGTNRENUNG( OTf) ·2H O (1.0 equiv), DCE (50 mL),
ethylene (1 atm), 6 h. [b] g per mmol·Pd·h. [c] Determined by GPC analysis.
d] 10 gmol . [e] Determined by LLS analysis. [f] ethylene (8 atm). [g] Solvent: PhCl
(50 mL). [h] Solvent: toluene (50 mL). [i] 1-Hexene (10.0 mL), L1 (75 mmol), no ethyl-
4
ꢀ1
[
[1h]
palladium methyl complexes.
The ratios of Mw,LLS
to Mw,GPC also indicated the highly branched struc- ene.
13958
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Chem. Eur. J. 2013, 19, 13956 – 13961

Water-Initiated Olefin Polymerization
FULL PAPER
To investigate further the Wacker process involved in the
polymerization initiation, we determined the GC yield of
acetaldehyde produced during the one-pot polymerization.
Heptane was chosen as an internal standard, and the aver-
age correction factor between acetaldehyde and heptane
that polymerization activity depends on the Wacker process.
This result further proved that the polymerization is initiat-
ed, at least mainly, by the Wacker reaction, and differs from
Bercawꢀs system, in which oligomerization of the olefin
became very slow (on the order of days) in the absence of
TFE and when Ar is 2,6-(CHMe ) C H , the dimer complex
[15b]
was determined to be 2.80.
polymerization conditions, consistently more than 80% GC
Under the standard ethylene
2
2
6
3
is completely inert.
[18]
yield of acetaldehyde (based on Pd) was detected,
sug-
gesting that the Wacker process is truly involved in the poly-
merization.
Conclusion
To further confirm the proposed mechanism, we attempt-
ed to correlate the amount of polyethylene and acetalde-
hyde produced during the one-pot polymerization. As
shown in Figure 2, the amount of the polyethylene is nicely
In the transition-metal-catalyzed coordination polymeriza-
[19]
tion of olefins, the activator plays an important role.
Although a variety of activators have been developed for
[1–7]
different precatalysts
in the past decades, most involve
metal alkyl compounds such as triethylaluminane and MAO,
[19]
which are usually air- and moisture-sensitive. In the cur-
rent work, water was identified as an excellent activator for
the cationic palladium(II)-catalyzed ethylene polymeriza-
tion, providing a safe, environment-friendly and handy ini-
tiator for olefin polymerization. Under the optimal condi-
tions, the activity of the polymerization is comparable to
that catalyzed by alkylated cationic palladium complexes.
The presynthesis of alkylpalladium complexes or the use of
metal alkyl compounds such as triethylaluminum and MAO,
is not necessary, making the palladium(II)-catalyzed olefin
polymerization very simple. The success of the integration
of the Wacker reaction into the olefin polymerization proc-
ess should pave the way for the development of new activa-
II
tors for Pd -catalyzed olefin polymerization.
Figure 2. Relationship between acetaldehyde and polyethylene. The poly-
merizations were performed with L1/Pd ACHTUNGTRENNNU(G OTf) ·2H O.
2 2
Experimental Section
[
a]
Table 4. Relationship between acetaldehyde and polyethylene.
General remarks: All air- or moisture-sensitive manipulations were car-
Entry
Pd
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
(OTf)
2
·2H
2
O
Heptane
[mg]
CH
[mg]
3
CHO
Polymer
[mg]
ried out under a nitrogen atmosphere either by using Schlenk techniques
[mg]
1
13
or in a glove box. H and C NMR spectra were recorded on a Varian
Mercury 300 or Varian 400 MR spectrometer. Mass spectra were carried
out with a HP5989A spectrometer. Elemental analysis was performed by
the Analytical Laboratory, Shanghai Institute of Organic Chemistry. GC-
MS analysis was performed by the Analytical Laboratory of Shanghai In-
1
2
3
4
5
6
7
8
9
8.4
7.1
6.0
5.8
4.4
3.6
3.6
2.7
2.8
1.4
5.3
7.5
9.9
4.1
8.0
5.1
8.3
5.6
7.5
5.5
0.40
0.33
0.26
0.25
0.18
0.15
0.19
0.088
0.12
0.08
143
128
101
100
72
66
64
43
39
n w w n
stitute of Organic Chemistry (CAS). M , M , and M /M values of poly-
mers were determined with an Agilent Technologies PL-GPC 220 High
Temperature Chromatograph at 1508C (polystyrene calibration, 1,2,4-tri-
ꢀ1
1
chlorobenzene as a solvent at a flow rate of 1.0 mLmin ). H and
1
3
4
C NMR data of polymers were obtained by using [D ]-o-dichloroben-
zene as solvent at 1108C. X-ray crystallographic data were collected with
a Bruker AXSD8 X-ray diffractometer. Gas chromatography (GC) was
performed with an Agilent 7890A instrument with a flame ionization de-
tector (FID). Routine runs were performed with an Agilent 19091S-001
HP-PONA Methyl Siloxane chromatographic column (50 m length,
1
0
29
ꢀ1
[
a] Pd
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
(OTf)
2
·2H
2 2 2
O (1.0 equiv), L1 (1.5 equiv, 18.5 mmolmL ), CH Cl
(
10 mL), H
2
O(mL)/Pd(mg)=1, 0.5 h, 258C.
0
1
.2 mm diameter, 0.5 mm film) with the following program: 508C for
0 min, 108Cmin to 1508C then 10 min. Response factors (or named
proportional to the amount of acetaldehyde when different
amounts of L1/Pd(OTf) ·2H O was used (Table 4). More-
ꢀ
1
ACHTUNGTRENNUNG
2
2
correction factor) for acetaldehyde was calculated versus heptane. A
known mass of acetaldehyde and heptane were added to a volumetric
flask, then dissolved in CH Cl (10 mL). The solution (0.1–0.2 mL) was
then injected into the GC instrument for analysis. The correction factor
for acetaldehyde was calculated by using the following equation:
II
over, by varying the amount of water at a fixed Pd concen-
tration, the amount of polyethylene was also found to be di-
2
2
[15b]
rectly proportional to the amount of acetaldehyde.
Be-
cause acetaldehyde can only be produced by the Wacker
process, the nearly linear correlation between the amount of
polyethylene and acetaldehyde supports well the fact that
water is essential in the activation of the precatalysts and
correction factor K ¼ ½ðmass of acetaldehydeÞ ꢁ ðarea of heptaneÞꢂ=
½
ðmass of heptaneÞ ꢁ ðarea of acetaldehydeÞꢂ
Chem. Eur. J. 2013, 19, 13956 – 13961
ꢁ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
13959

X.-L. Sun, Y. Tang et al.
Materials: Toluene, hexane, CH
2
Cl
2
, and THF solutions were purified by
heptane (5.3 mg) and the solution was stirred for ca. 5 min at ꢀ788C.
Acetaldehyde yields were determined based on GC analysis. After re-
moval of the solvent, the yields of polyethylene were obtained.
using a MB SPS-800 system. Unless otherwise stated, all solvents and re-
agents were purchased from commercial suppliers and used as received.
[
1h]
[20]
Ligands L1–L4
known procedures.
General procedure for synthesis of palladium(II) complexes 1–3 and Pd-
(OTf) ·2H O:
Complex 1:
(COD)PdCl
for one week. The solution was filtered and concentrated, and the solid
was washed with CH Cl twice and dried under vacuum to afford com-
pound 1 (1.4 g, 40%) as a yellow solid. H NMR (300 MHz, CDCl
and Pd
A
H
U
G
E
N
N
(OTf)
2
·2H
2
O
were synthesized according to
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
2
2
Acknowledgements
A
solution of diimine L1 (2.7 g, 5.44 mmol) and
[
2
] (1.48 g, 5.18 mmol) in CH Cl (30 mL) was stirred at RT
2
2
We are grateful for the financial support from the National Natural Sci-
ences Foundation of China (Grant Nos. 21174159 and 21121062), the
Major State Basic Research Development Program (Grant No.
2009CB825300) and the Chinese Academy of Sciences.
2
2
1
3
): d=
.12 (d, J=8.4 Hz, 2H), 7.49 (t, J=6.3 Hz, 4H), 7.36 (d, J=7.5 Hz, 4H),
.53 (d, J=7.2 Hz, 2H), 3.58–3.42 (m, 4H), 1.52 (d, J=6.6 Hz, 12H),
.98 ppm (d, J=6.9 Hz, 12H); elemental analysis calcd (%) for
8
6
0
[1] a) M. D. Leatherman, S. A. Svejda, L. K. Johnson, M. Brookhart, J.
Am. Chem. Soc. 2003, 125, 3068–3081; b) A. C. Gottfried, M. Broo-
khart, Macromolecules 2003, 36, 3085–3100; c) S. Mecking, L. K.
Johnson, L. Wang, M. Brookhart, J. Am. Chem. Soc. 1998, 120, 888–
36 2 2
C H40Cl N Pd (677.64): C 63.77, H 5.95, N 4.13; found: C 63.56, H 5.86,
N 4.04.
Complex 2: A solution of Pd
0.50 g, 1.0 mmol) in CH Cl (15 mL) was stirred at RT for 17 h. The sol-
ution was filtered and concentrated. The solid was washed with cold
CH Cl and dried under vacuum to give the desired compound (0.51 g,
0.3%) as a yellow solid. H NMR (300 MHz, CDCl
2
AHCTUNGTNERUNG( OAc) (0.224 g,1.0 mmol) and diimine L1
8
2
99; d) L. H. Shultz, D. J. Tempel, M. Brookhart, J. Am. Chem. Soc.
001, 123, 11539–11555; e) D. P. Gates, S. A. Svejda, E. OÇate,
(
2
2
C. M. Killian, L. K. Johnson, P. S. White, M. Brookhart, Macromole-
cules 2000, 33, 2320–2334; f) D. J. Tempel, L. K. Johnson, R. L.
Huff, P. S. White, M. Brookhart, J. Am. Chem. Soc. 2000, 122, 6686–
2
2
1
7
8
4
1
1
3
): d=8.12 (d, J=
.4 Hz, 2H), 7.47–7.31 (m, 8H), 6.63 (d, J=7.2 Hz, 2H), 3.68–3.64 (m,
H), 1.56 (d, J=6.6 Hz, 12H), 1.49 (s, 6H), 0.92 ppm (d, J=6.6 Hz,
2H); C NMR (100 MHz, CDCl
32.7, 131.4, 129.1, 129.0, 125.8, 124.7, 124.3, 29.4, 24.4, 23.7, 22.4 ppm; el-
Pd (724.76): C 66.25, H 6.39,
6
700; g) L. K. Johnson, S. Mecking, M. Brookhart, J. Am. Chem.
1
3
Soc. 1996, 118, 267–268; h) L. K. Johnson, C. M. Killian, M. Broo-
khart, J. Am. Chem. Soc. 1995, 117, 6414–6415.
3
): d=176.5, 174.0, 146.8, 140.6, 140.3,
[
2] a) C. S. Popeney, Z. Guan, Macromolecules 2010, 43, 4091–4097;
b) C. S. Popeney, Z. Guan, J. Am. Chem. Soc. 2009, 131, 12384–
emental analysis calcd (%) for C40
N 3.86; found: C 66.11, H 6.50, N 3.70.
Complex 3: A solution of AgOTf (3.8 g, 14.8 mmol) and complex 1
4.8 g, 7.08 mmol) in CH Cl (100 mL) was stirred in the dark at RT for
h. The solution was filtered and concentrated, and the solid was washed
with CH Cl twice and dried under vacuum to give the desired compound
4.84 g, 73.8%) as a yellow solid. H NMR (300 MHz, CDCl
d, J=8.7 Hz, 2H), 7.70–7.52 (m, 4H), 7.39 (d, J=7.5 Hz, 4H), 6.56 (d,
46 2 4
H N O
1
2
2393; c) D. H. Leung, J. W. Ziller, Z. Guan, J. Am. Chem. Soc.
008, 130, 7538–7539; d) C. S. Popeney, D. H. Camacho, Z. Guan, J.
(
3
2
2
Am. Chem. Soc. 2007, 129, 10062–10063; e) D. H. Camacho, E. V.
Salo, J. W. Ziller, Z. Guan, Angew. Chem. 2004, 116, 1857–1861;
Angew. Chem. Int. Ed. 2004, 43, 1821–1825; f) Z. Guan, Chem. Eur.
J. 2002, 8, 3086–3092; g) Z. Guan, P. M. Cotts, E. F. McCord, S. J.
McLain, Science 1999, 283, 2059–2062.
2
2
1
(
(
3
): d=8.26
J=7.5 Hz, 2H), 3.70–3.56 (m, 4H), 1.61 (d, J=6.6 Hz, 12H), 0.98 ppm
[
[
3] a) G. Noꢃl, J. C. Roder, S. Dechert, H. Pritzkow, L. Bolk, S. Meck-
ing, F. Meyer, Adv. Synth. Catal. 2006, 348, 887–897; b) A. Held,
F. M. Bauers, S. Mecking, Chem. Commun. 2000, 301–302; c) A.
Held, S. Mecking, Chem. Eur. J. 2000, 6, 4623–4629.
1
3
(
1
1
d, J=6.9 Hz, 12H); C NMR (100 MHz, [D
6
]DMSO): d=179.9, 148.3,
41.0, 138.4, 134.4, 131.1, 131.0, 129.7, 126.1, 125.4, 123.5, 122.2, 119.0,
15.8, 28.8, 23.9, 23.6 ppm; elemental analysis calcd (%) for
PdS (940.66): C 48.49, H 4.71, N 2.98; found: C 48.53, H
C
38
H
44
F
6
N
2
O
8
2
II
II
4] For other selected examples of diimine-derived Ni and Pd com-
plexes for olefin polymerization, see a) L. Guo, H. Gao, Q. Guan,
H. Hu, J. Deng, J. Liu, F. Liu, Q. Wu, Organometallics 2012, 31,
6054–6062; b) Z. Zhang, Z. Ye, Chem. Commun. 2012, 48, 7940–
7942; c) D. Takeuchi, J. Am. Chem. Soc. 2011, 133, 11106–11109;
d) C. S. Popeney, C. M. Levins, Z. Guan, Organometallics 2011, 30,
2432–2452; e) M. M. Wegner, A. K. Ott, B. Rieger, Macromolecules
2010, 43, 3624–3633; f) C. Chen, R. F. Jordan, J. Am. Chem. Soc.
2010, 132, 10254–10255; g) G. Sun, Z. Guan, Macromolecules 2010,
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Green, I. C. Vei, J. E. Warren, C. Windsor, Inorg. Chim. Acta 2010,
363, 1157–1172; i) F.-S. Liu, H.-B. Hu, Y. Xu, L.-H. Guo, S.-B. Zai,
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M. Leskela, B. Rieger, Organometallics 2001, 20, 2321–2330; k) D.
Pappalardo, M. Mazzeo, S. Antinucci, C. Pellecchia, Macromolecules
4
.86, N 2.97.
Pd(OTf) ·2H
7.8 mmol) were added to a solution of PdCl
220 mL). Pd sponge was precipitated after stirring for 30 min at RT. The
solid was collected and washed with acetone to afford Pd sponge.
CF SO H (42.74 mL) was added at 08C to a solution of Pd(NO , pre-
pared by dissolving Pd sponge in conc. HNO (3.19 mL). The solution
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
2
2
O: NaOH (4.47 g, 111.8 mmol) and HCOONa (3.93 g,
(2.24 g, 12.7 mmol) in H
5
(
2
2
O
3
3
A
H
U
G
R
N
U
G
3 2
)
3
was stirred for 2 h, and the solid was separated by centrifugation and
dried under reduced pressure at 1108C for 18 h to give the desired com-
pound (3.8 g, 59%) as light-purple powder. Elemental analysis calcd (%)
2 6 4 8 2
for C F H O PdS (440.35): C 5.45; found: C 5.74.
General procedure for olefin polymerization:
2 2
One-pot process: Ligand (1.5 equiv, 75 mmol) and Pd ACHTUNGRTENN(NUG OTf) ·2H O
(
1.0 equiv, 50 mmol) were dissolved in DCE (50 mL) and the solution was
stirred for ca. 15 min, then ethylene was bubbled into the solution for 6 h
at 258C. The resulting mixture was diluted with petroleum ether, filtered,
and concentrated to give polyethylene as a colorless oil.
2
000, 33, 9483–9487.
[
5] For other selected examples of late-transition-metal complexes for
olefin polymerization, see a) A. Nakamura, T. Kageyama, H. Goto,
B. P. Carrow, S. Ito, K. Nozaki, J. Am. Chem. Soc. 2012, 134, 12366–
Typical procedure for water-initiated ethylene polymerization (Table 1,
entry 7): H
CH Cl (50 mL), and ethylene was bubbled into the solution for 6 h at
58C. The resulting mixture was diluted with petroleum ether, filtered,
2
O (45 mL) was added to a solution of complex 3 (50 mmol) in
1
2369; b) B. Neuwald, F. Oelscher, I. Goettker-Schnetmann, S.
2
2
Mecking, Organometallics 2012, 31, 3128–3137; c) M. P. Weber-
ski Jr., C. Chen, M. Delferro, T. J. Marks, Chem. Eur. J. 2012, 18,
2
and concentrated to give polyethylene as a colorless oil.
1
0715–10732; d) M. R. Radlauer, M. W. Day, T. Agapie, J. Am.
Typical procedure to correlate acetaldehyde and polyethylene (Table 4,
entry 1): Pd ACHTUNGTRENNUNG( OTf) ·2H O (8.4 mg) under an ethylene atmosphere was
2 2
Chem. Soc. 2012, 134, 1478–1481; e) S. Ito, M. Kanazawa, K. Muna-
kata, J.-i. Kuroda, Y. Okumura, K. Nozaki, J. Am. Chem. Soc. 2011,
133, 1232–1235; f) A. Nakamura, K. Munakata, S. Ito, T. Kochi,
L. W. Chung, K. Morokuma, K. Nozaki, J. Am. Chem. Soc. 2011,
133, 6761–6779; g) T. Rꢄnzi, D. Froehlich, S. Mecking, J. Am.
Chem. Soc. 2010, 132, 17690–17691; h) T. Rꢄnzi, D. Guironnet, I.
cooled to ꢀ788C, and CH
2
Cl
2
(5.0 mL), H
2
O (8.4 mL), and CH
2
Cl
Cl
2
(
(
5.0 mL) were injected sequentially. Ligand L1 (31 mmol) in CH
2
2
1.68 mL) was injected and the tube was sealed. The mixture was stirred
for 0.5 h at 258C, then cooled to ꢀ788C. To this solution was added to
13960
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ꢁ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2013, 19, 13956 – 13961

Water-Initiated Olefin Polymerization
FULL PAPER
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[11] Another difficulty is the immediate decomposition of Pd -based
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8
49–850.
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3
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[14] The reaction of L1 with Pd AHCTUNGTRNEUNG( OTf) proceeded sluggishly and only ca.
31% of L1 was converted even after 4 h at room temperature. The
Pd–hydride formation or the coordination of ethylene increased the
solubility of Pd
used diimine–Pd
A
H
U
G
R
N
U
G
2
and might favor the coordination. When we
2
as precatalyst, the acetaldehyde yield was
A
H
U
G
R
N
U
G
approximately 30% whereas in the one-pot reaction the acetalde-
hyde yield could be improved to 60–84%. These results support
5
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2 2
speculation that some Pd ACHNUTGTRNNEUG( OTf) ·2H O promotes the Wacker reac-
tion to generate palladium–hydride before the coordination of the
diimine ligand in the one-pot system.
1
1
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Me
2 4 2
ported that [( DABMe)Pd(OH)] ACHTUNRTGNNEG[U BF ] could promote the oligome-
[
9]
1
rization and isomerization of 1-hexene. In this work, we obtained
n) M. R. Salata, T. J. Marks, Macromolecules 2009, 42, 1920–1933;
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p) L. Zhang, Y. Luo, Z. Hou, J. Am. Chem. Soc. 2005, 127, 14562–
the homopolymer of 1-hexene (Table 3, entry 12;
w,GPC
M =
ꢀ
1
ꢀ1
3988 gmol , M
w
/M
n
=3.06, Mw,LLS =4692 gmol ).
[18] Average yield for five repeated runs; for details, see the Supporting
Information.
1
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Received: March 8, 2013
Revised: July 7, 2013
Published online: September 3, 2013
Chem. Eur. J. 2013, 19, 13956 – 13961
ꢁ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
13961