Synthesis, structures, and norbornene ROMP behavior of o-aryloxide-N- heterocyclic carbene p-cymene ruthenium complexes

Article abstract of DOI:10.1021/om300474n

Treatment of the o-hydroxyaryl imidazolium proligands (2-OH-3,5- ^tBu₂C₆H₂)(R)(C₃H ₃N₂)⁺Br^- (R = ⁱPr (1a), ^tBu (1b), Ph (1c), Mes (1d))

Full text of DOI:10.1021/om300474n

Article
pubs.acs.org/Organometallics
Synthesis, Structures, and Norbornene ROMP Behavior of o-
Aryloxide-N-Heterocyclic Carbene p-Cymene Ruthenium Complexes
Yong Kong,† Shansheng Xu,† Haibin Song,† and Baiquan Wang*,†,‡
†State Key Laboratory of Elemento-Organic Chemistry, College of Chemistry, Nankai University, Tianjin 300071, People’s Republic
of China
‡State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences,
Shanghai 200032, People’s Republic of China
S
* Supporting Information
ABSTRACT: Treatment of the o-hydroxyaryl imidazolium
i
proligands (2-OH-3,5-tBu2C6H2)(R)(C3H3N2)+Br− (R = Pr
t
(1a), Bu (1b), Ph (1c), Mes (1d)) with 3 equiv of Ag2O
afforded the corresponding silver complexes 2a−d. The
subsequent metal-exchange reactions with [(p-cymene)-
RuCl2]2 at room temperature yielded the desired o-aryloxide-
N-heterocyclic carbene p-cymene ruthenium complexes 3a−d
in nearly quantitative yields. All the complexes were
characterized by 1H and 13C NMR, high-resolution mass
spectrometry (HRMS), and elemental analysis. The molecular
structure of complex 3b was determined by single-crystal X-ray
diffraction analysis. The ring-opening metathesis polymer-
ization (ROMP) of norbornene (NBE) with 3a−d was studied. Among them, complex 3d showed high activity and efficiency
toward ROMP of NBE at 85 °C without the need for any cocatalyst, and polymers with very high molecular weight (>106) and
narrow molecular weight distributions were obtained. This complex can also catalyze the alternating copolymerization of NBE
and cyclooctene (COE).
In these catalyst systems the active alkylidenes are generally
formed in situ by the addition of a carbene source or by
coordination of the substrate to the coordinatively unsaturated
complex and a subsequent 1,2-H shift. The ill-defined
ruthenium catalysts are generally readily commercially available
or are easily prepared from commercially available compounds
and sometimes exhibit performance comparable to or even
better than that of the well-defined catalysts and allow for
straightforward synthetic procedures.4 After the first highly
efficient arene ruthenium ring-opening metathesis polymer-
ization (ROMP) catalyst (p-cymene)RuCl2(PCy3) was pio-
neered by the Noels group in 1992,5 p-cymene-based catalytic
systems involving different types of ligands such as phosphine
ligands,6,7 bidentate Schiff base ligands,8,9 and NHC ligands10,11
have been extensively investigated by different groups.
Recently, a great deal of research effort has been made
toward the study of transition-metal complexes with anion-
tethered NHC ligands.12 As an anchor, the introduced anion
groups can reduce the tendency of ligand dissociation, via
enhancing the bond between the NHCs and metal centers. In
our previous work we developed the o-hydroxyaryl imidazolium
proligands and synthesized a series of o-aryloxide-N-hetero-
cyclic carbene palladium and nickel complexes, which showed
INTRODUCTION
■
The discovery of the ruthenium benzylidene catalyst (Grubbs I,
Chart 1) by Grubbs and co-workers in the mid-1990s1 was a
Chart 1
solid milestone in the transformation of olefin metathesis to a
versatile and powerful tool for the construction of a variety of
small molecules and macromolecules. Later the introduction of
a N-heterocyclic carbene (NHC) ligand into Grubbs I led to
the development of the second-generation Grubbs catalyst
(Grubbs II, Chart 1),2 which generally gives rise to higher
activities, increased thermal stability, and high tolerance to
broad functional groups. A large number of well-defined Ru
benzylidene catalysts have been subsequently developed.3
In comparison to the well-defined ruthenium catalysts
featuring a ruthenium−carbon double bond, the ill-defined
ones do not contain an alkylidene fragment in their molecules.
Received: June 6, 2012
Published: July 16, 2012
© 2012 American Chemical Society
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high activities for the addition polymerization of norbornene
(NBE) in the presence of MAO.13 As a part of the systematic
study of metal complexes bearing o-aryloxide-N-heterocyclic
carbene ligands, in this work, we report the synthesis and
structures of a series of o-aryloxide-N-heterocyclic carbene p-
cymene ruthenium complexes. The ROMP of NBE with these
complexes was also studied. It is interesting to note that one of
the complexes exhibits almost the same high activity and
efficiency toward ROMP of NBE at 85 °C as Grubbs I, without
the need for any cocatalyst, whereas the resultant polymer has a
much higher molecular weight (>106) than that generated using
Grubbs I. This catalyst is also effective at catalyzing the
copolymerization of NBE and cyclooctene (COE), producing
alternating copolymers possessing high molecular weights and
narrow molecular weight distributions.
RESULTS AND DISCUSSION
■
Synthesis of o-Aryloxide-N-Heterocyclic Carbene p-
Cymene Ruthenium Complexes. The synthesis of 3,
derived from the proligands 1, is slightly different from the
well-established approach to other transition-metal complexes
in our laboratory.13 Treatment of 1a−d with 3 equiv of Ag2O
afforded the corresponding silver complexes 2a−d. The
subsequent metal-exchange reactions with [(p-cymene)RuCl2]2
at room temperature yielded the desired o-aryloxide-N-
heterocyclic carbene p-cymene ruthenium complexes 3a−d in
nearly quantitative yields (Scheme 1).
Figure 1. ORTEP diagram of 3b. Thermal ellipsoids are shown at the
30% probability level. Hydrogen atoms are omitted for clarity.
the imidazolylidene). The Ru−C(carbene) (2.022(2) Å) and
Ru−O (2.0964(12) Å) bond lengths are analogous to those in
the o-aryloxide-NHC ligated Ru complexes.10 The Ru−Cl, Ru−
centroid (arene), and average Ru−C (arene) bond lengths are
2.4069(9), 1.697, and 2.2088 Å, respectively. The angles
C(15)−Ru(1)−O(1), C(15)−Ru(1)−Cl(2), C(15)−Ru(1)−
centroid (arene), O(1)−Ru(1)−centroid (arene), and Cl(2)−
Ru(1)−centroid (arene) are 81.43(6), 86.74(6), 130.42,
130.38, and 127.02°, respectively. The isopropyl group on the
arene ligand is slightly distorted away from the metal center as a
result of steric repulsion, analogous to the previously reported
results.11
Scheme 1
Norbornene Polymerization. ROMP has become a
powerful methodology for the synthesis of linear or branched
polymers with narrow molecular weight distributions.3a We
have tested the catalytic activity of complexes 3a−d toward
ROMP of NBE at 85 °C with and without the presence of
TMSD, and the polymerization results are summarized in Table
1. 3a,b both showed moderate activity with and without TMSD
Table 1. ROMP of NBE with Ruthenium Catalysts with and
a
without the Presence of TMSD
yield
(%)
Mn
cis
(%)
entry
cat.
t
(×103)
PDI
1
3a
3 h
3 h
3 h
3 h
3 h
3 h
3 min
1 h
1 h
3 h
3 h
29
902
98
2.02
3.59
1.97
3.21
39
42
40
45
2
3a + TMSD
29
3
3b
43
1314
276
4
3b + TMSD
47
Complexes 2a−d and 3a−d are all air and moisture stable. In
their 1H NMR spectra, the signals of the phenol proton and the
imidazole proton at the C-2 position, appearing for compound
1, completely disappear. The characteristic signals of the
carbene carbons in their 13C NMR spectra (161.8 (2a), 161.6
(2b), 161.7 (2c), 161.6 (2d); 174.5 (3a), 174.0 (3b), and 173.0
ppm (3d)) are comparable to those of the previously reported
silver and ruthenium NHC complexes.14,15
5
3c
trace
30
6
3c + TMSD
25
1522
1202
294
5.26
1.95
1.96
1.96
64
42
43
44
b
7
3d
80
c
8
3d
>99
9
3d + TMSD
[(p-cymene)RuCl2]2
86
10
11
trace
40
[(p-cymene)RuCl2]2 +
TMSD
53
6.11
1.93
45
11
We could easily grow single crystals of 3b from a CH2Cl2/
ether solution. The molecular structure of 3b was confirmed by
single-crystal X-ray diffraction analysis (Figure 1). Its molecule
consists of an η6-bonding p-cymene ligand, an anionic chloride,
and a bidentate o-aryloxide-NHC ligand. The ligand retains the
characteristic bond angle for a singlet carbene (104.87(16)° for
12
Grubbs I
3 min
99
217
a
General polymerization conditions: 30 mL of toluene; 1.0 g (10.62
mmol) of NBE; [cat.] = 0.167 mmol L−1; 85 °C; GPC versus
polystyrene standards. The reaction mixture quickly turned into a gel-
like substance. 0.378 g (4.0 mmol) of NBE, [NBE]/[cat.] = 800.
b
c
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(entries 1−4). In contrast, 3c itself exhibited no activity (entry
5), while the addition of TMSD to the reaction mixture gave a
moderate yield (entry 6). It is clear that the polymers obtained
in the presence of TMSD have much lower molecular weights
and higher PDIs. Much to our surprise, the mesityl complex 3d
exhibited quickly increasing activity at elevated temperatures
and remarkably high activity was achieved at 85 °C (Table 2).
NHC ligand exhibited very low efficiency toward ROMP of
NBE, even in the presence of cocatalysts such as
trimethylsilyldiazomethane (TMSD) and phenylacetylene.11
In general, the ruthenium catalysts with saturated NHC are
far more reactive than the corresponding unsaturated NHC-
derived catalysts.10d,16 Thus, the reasons for the high activity of
3d are still unclear. The steric effect of the bulky tert-butyl
group at the ortho position of the aryloxide may be helpful for
increasing the activity.
a
Table 2. ROMP of NBE with 3d at Different Temperatures
NBE and COE Copolymerization. We next turned our
attention to the homopolymerization of other olefins. Different
from the case for most Noels-type4−11 and all Grubbs-type
initiators,1−4 complexes 3a−d were inactive toward ROMP of
COE, even in the presence of TMSD, indicating that the active
ruthenium carbene species cannot be formed from 3 and COE
(Table 3, entry 2). This interesting behavior allowed us to
study the copolymerization of NBE and COE. A great deal of
research effort has been recently devoted to the synthesis and
study of alternating copolymers by the metathesis copoly-
merization of two different monomers.17
T
conversn
(%)
Mn
cis
entry cat.
(°C)
t
(×103)
PDI
(%)
1
2
3
4
3d
3d
3d
3d
25
45
65
85
3 h
16.3
62.8
70.6
80.0
1543
1607
1765
1522
2.02
1.84
1.90
1.95
0.42
0.42
0.42
0.42
b
b
b
50 min
12 min
3 min
a
Polymerization conditions: 30 mL of toluene; norbornene 1.0 g;
b
[cat.] = 5 μmol. The reaction mixture turned into a gel-like
substance; the yield increased (nearly 100%) with a longer reaction
time.
To explore the copolymerization potential of complex 3d,
various ratios of NBE and COE were used for copolymerization
(Table 3). As shown in Table 3, the percentage of the
alternating diads poly(NBE-alt-COE) in the obtained copoly-
mers (2.7 × 105 < Mw < 12 × 105, 1.4 < PDI < 2.1) gradually
increases as the NBE/COE ratio decreases. GPC investigations
showed a single, smooth, monomodal peak (see the Supporting
Information), indicating that the polymer is not a physical
mixture of the homopolymers of NBE and COE. The 13C
NMR spectra of the copolymers derived from various ratios of
NBE and COE further support the alternate incorporation of
the two monomers in the ROMP. A representative 13C NMR
spectrum of a copolymer is shown in Figure 2. The signals for
the alternating diads were observed around δ 134.2−134.6 and
128.1 ppm on the basis of the literature data.17d−h,j The signals
for the poly(COE) block were also detected at δ 129.4 and
129.8 ppm. The signals around δ 132−134 ppm were assigned
to the poly(NBE) block. Not all ruthenium metathesis catalysts
are suitable for the catalytic synthesis of alternating copolymers.
It was reported that the copolymerization of a 1/1 NBE/COE
mixture using Grubbs I catalyst afforded a copolymer consisting
of a poly(NBE) block and a poly(COE) block.17d,e
Gelation of the reaction mixture occurred within 3 min at 85
°C, and a polymer with a high molecular weight (>106) was
obtained in 80% yield (entry 7). A quantitative yield was
obtained upon reducing the concentration of NBE (entry 8).
These catalytic systems worked well even in the dark, indicating
that the formation of the active species does not require light
irradiation.
Complex 3d exhibited high activity and efficiency almost
identical with those of Grubbs I under the same conditions, but
the polymers obtained using 3d have much higher molecular
weights than that obtained using Grubbs I (Table 1, entries 7,
8, and 12). Since 3a−d are stable 18-electron complexes, the
formation of the active species might follow the same
mechanism that has been widely accepted for the p-cymene
ruthenium system.3e,8a,9 The release of a p-cymene ligand from
3, followed by the coordination of NBE and a subsequent 2,3-
hydrogen shift, generates an active ruthenium carbene species
which propagates the ROMP in the same way as the well-
defined ruthenium catalysts do (Scheme 2).
It should be noted that the p-cymene ruthenium complex
incorporating a bidentate o-aryloxide-substituted saturated
Controlling the composition of polymers is a very important
issue, since polymers with different compositions often exhibit
different properties. For the alternating copolymers produced
by ROMP using complex 3d, the percentages of the alternating
diads were roughly controlled from 0% to 53% by changing the
relative ratios of the two monomers.
Scheme 2
CONCLUSION
■
In summary, we have successfully developed a series of o-
aryloxide-NHC ligated Ru arene complexes which can be used
as single-component catalysts to initiate the ROMP of NBE.
What is remarkable is that complex 3d exhibits very high
activity and efficiency toward the ROMP of NBE at 85 °C. The
catalytic performance for 3d is comparable to that for Grubbs I,
but the generated polymers have much higher molecular
weights (>106). Complex 3d was also found to efficiently
catalyze the copolymerization of NBE and COE, generating the
alternating copolymers with high molecular weights and narrow
molecular weight distributions. The degree of alternation can
be controlled by changing the relative stoichiometry of NBE
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a
Table 3. Alternating Copolymerization of NBE and COE using the Initiator 3d
b
b
b
entry
cat./NBE/COE
t (h)
Mn (×10−3
)
PDI
1.96
poly(NBE) (%)
100
poly(NBE-alt-COE) (%)
poly(COE) (%)
c
1
1/800/0
1
24
2
1202
0
0
2
1/0/1000
3
1/800/200
1/500/500
1/500/1000
1/500/1500
1/500/2000
1/500/3000
1/500/4000
1/500/5000
1164
377
347
379
330
383
351
269
2.05
1.50
1.61
1.52
1.67
1.46
1.53
1.71
97
82
68
64
44
33
35
38
3
18
32
34
42
49
51
0
0
4
12
12
12
12
12
12
12
5
0
6
2
7
14
18
14
9
8
9
10
53
a
b
Polymerization conditions: 10 mL of toluene; [cat.] = 0.5 mmol L−1; 85 °C; GPC versus polystyrene standards. Calculated from the 13C NMR
c
spectra. Polymerization conditions: 30 mL of toluene (also see Table 1, entry 8).
Figure 2. 13C NMR spectrum of a copolymer obtained via the copolymerization of NBE and COE triggered by 3d (Table 3, entry 10).
were added to a round-bottom flask equipped with a cooler. Dried
CH2Cl2 (20.0 mL) was added to the flask. The reaction mixture was
stirred at reflux for 4 h, cooled to room temperature, and diluted with
CH2Cl2 (20 mL). The mixture was then filtered through a pad of
Celite (2/5 cm, w/l), that successively was washed with CH2Cl2 (3 ×
5 mL). The solvent was removed under reduced pressure to provide
the silver complex as a yellow solid in a yield of ∼99% (based on the
proligands 1a−d).
and COE. Further investigations into the alternating copoly-
merization of other olefins are still in progress.
EXPERIMENTAL SECTION
■
General Considerations. All experimental manipulations were
carried out under an atmosphere of dry argon using standard Schlenk
techniques. All solvents were distilled from appropriate drying agents
under argon before use. 1H and 13C NMR spectra were recorded on a
Bruker AV400, Bruker AV300, or Varian 300 spectrometer, while ESI
mass spectra and HRMS measurements were carried out on Thermo
Finnigan LCQ Advantag and Varian 7.0 T FTICR mass spectrometers,
respectively. Elemental analyses were performed on a Perkin-Elmer
240C analyzer. The molecular weights and molecular weight
distribution were obtained on Polymer Laboratories PL-GPC 50 and
GPC (Waters 510 liquid chromatograph connected with four styragel
GPC columns (guard, 103 Å, 104 Å, 105 Å), and a Waters 410
differential refractometer. All of the o-aryloxide-NHC proligands were
prepared according to the literature procedures.13
Compound 2a (R = Me). Yield: 99%. 1H NMR (CDCl3): δ 7.22 (d,
1H, J = 2.51 Hz, im-H), 7.07 (s, 1H, Ar-H), 7.03 (s, 1H, Ar-H), 6.77
(d, 1H, J = 2.37 Hz, im-H), 3.76 (s, 3H, NCH3), 1.25 (s, 9H,
C(CH3)3), 1.24 (s, 9H, C(CH3)3) ppm. 13C NMR (100 MHz,
CDCl3): δ 161.8, 140.4, 134.5, 129.8, 124.6, 121.7, 120.8, 120.7, 38.0,
35.8, 33.8, 31.7, 31.3, 29.9, 29.7 ppm.
Compound 2b (R = iPr). Yield: 99%. 1H NMR (CDCl3): δ 7.22 (d,
1H, J = 2.54 Hz, im-H), 7.05 (s, 2H, Ar-H), 6.76 (s, 1H, J = 2.50 Hz,
im-H), 4.62 (m, 1H, CH(CH3)2), 1.47 (d, 3H, J = 6.71 Hz, CHCH3),
1.46 (d, 3H, J = 6.61 Hz, CHCH3), 1.26 (br s, 18H, C(CH3)3) ppm.
13C NMR (100 MHz, CDCl3): δ 161.6, 140.5, 134.4, 130.0, 124.4,
121.8, 115.4, 53.2, 35.8, 33.8, 31.6, 30.0, 24.1, 23.4 ppm.
General Procedures for Preparation of the o-Aryloxide-NHC
Ligated Silver Complexes 2a−d. The o-hydroxyaryl imidazolium
proligands (2-OH-3,5-tBu2C6H2)(R)(C3H3N2)+ Br− (R = Me (1a), iPr
(1b), Ph (1c), Mes (1d); 1.0 mmol) and Ag2O (0.696 g, 3 mmol)
Compound 2c (R = Ph). Yield: 99%. 1H NMR (CDCl3): δ 7.40 (s,
3H, Ar-H), 7.35 (s, 1H, Ar-H), 7.33 (s, 1H, Ar-H), 7.24 (d, 1H, J =
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2.04 Hz, im-H), 7.22 (s, 1H, Ar-H), 7.12 (s, 1H, Ar-H), 6.82 (d, 1H, J
= 2.02 Hz, im-H), 1.29 (s, 9H, C(CH3)3), 1.26 (s, 9H, C(CH3)3) ppm.
13C NMR (100 MHz, CDCl3): δ 161.7, 140.6, 139.9, 134.4, 129.9,
129.7, 128.0, 125.1, 124.6, 123.7, 121.5, 120.4, 120.3, 35.8, 33.8, 31.7,
30.0, 29.6 ppm.
Crystallographic Studies. Single crystals suitable for X-ray
diffraction were obtained from CH2Cl2/ether for 3b. Data collections
were performed on a Rigaku Saturn 70 diffractometer equipped with a
rotating anode system at 113(2) K by using graphite-monochromated
Mo Kα radiation (ω−2θ scans, λ = 0.710 73 Å). Semiempirical
absorption corrections were applied for all complexes. The structures
were solved by direct methods and refined by full-matrix least squares.
All calculations were performed by using the SHELXL-97 program
system. All non-hydrogen atoms were refined anisotropically. Hydro-
gen atoms were assigned idealized positions and were included in
structure factor calculations.
NBE Polymerization. In a typical procedure, 1.0 g of NBE in 30.0
mL of toluene was added into a flask (100 mL) with stirring under an
Ar atmosphere. After the mixture was kept at the desired temperature
for 3−5 min, the catalyst (5 μmol) in CH2Cl2 (1 mL) was injected
into the flask via syringe, and the reaction was started. To stop the
polymerization, a 2-ethyl vinyl ether/BHT (2,6-di-tert-butyl-4-
methylphenol) solution in CHCl3 was added. The reaction mixture
was then poured into MeOH (50 mL) to precipitate the polymer. The
polymer was isolated upon filtration and analyzed gravimetrically by
1H NMR and 13C NMR spectroscopy and GPC (gel permeation
chromatography).
NBE and COE Copolymerization. In a typical procedure, the
NBE/COE mixture with different ratios in 10.0 mL of toluene was
added into a flask (100 mL) with stirring under an Ar atmosphere.
After the mixture was kept at the desired temperature for 3−5 min,
initiator 3d (3.3 mg, 5 μmol) dissolved in 1.0 mL of CH2Cl2 was
injected into the flask via syringe, and the reaction was started. The
reaction mixture was stirred for 12 h. Then the reaction was stopped
by the addition of a 2-ethyl vinyl ether/BHT (2,6-di-tert-butyl-4-
methylphenol) solution in CHCl3. The polymer was precipitated by
the dropwise addition of the reaction mixture into ethanol. The
polymer was collected by filtration and analyzed gravimetrically by 13C
NMR spectroscopy and GPC (gel permeation chromatography).
1
Compound 2d (R = Mes). Yield: 99%. H NMR (CDCl3): δ 7.21
(d, 1H, J = 2.30 Hz, im-H), 7.12 (s, 1H, Ar-H), 7.02 (s, 1H, Ar-H),
6.95 (s, 1H, Ar-H), 6.85 (s, 1H, Ar-H), 6.73 (d, 1H, J = 2.28 Hz, im-
H), 2.40 (s, 3H, Ar-CH3), 2.08 (s, 3H, Ar-CH3), 1.80 (s, 3H, Ar-CH3),
1.30 (s, 9H, C(CH3)3), 1.29 (s, 9H, C(CH3)3) ppm. 13C NMR (100
MHz, CDCl3): δ 161.6, 140.6, 138.7, 135.9, 135.3, 135.1, 134.3, 129.3,
129.0, 124.6, 121.8, 35.8, 33.8, 31.6, 30.4, 21.0, 19.0, 18.0 ppm.
General Procedures for Preparation of the o-Aryloxide-NHC
Ligated p-Cymene Ruthenium Complexes 3a−d. To a solution
of [(p-cymene)RuCl2]2 (0.304 g, 0.5 mmol) in CH2Cl2 (10 mL) was
added a solution of AgL (1 mmol) in CH2Cl2, and the resultant red
solution was stirred at room temperature for 20 h. The mixture was
subsequently filtered through Celite, and the red filtrate was
evaporated to dryness under reduced pressure. After recrystallization
from CH2Cl2/Et2O, complex 3 was obtained in a yield of ∼99%.
Compound 3a (R = Me). Yield: 99%. Mp: 180 °C dec. Anal. Calcd
for C28H39ClN2ORu: C, 60.47; H, 7.07; N, 5.04. Found: C, 60.36; H,
1
7.17; N, 5.03. H NMR (CDCl3): δ 7.27 (s, 1H, im-H), 7.02 (s, 2H,
Ar-H), 6.89 (d, 1H, J = 1.80 Hz, im-H), 5.54 (d, 1H, J = 5.61 Hz, p-
cymene-CH), 5.42 (d, 1H, J = 5.60 Hz, p-cymene-CH), 4.90 (d, 1H, J
= 5.65 Hz, p-cymene-CH), 4.56 (d, 1H, J = 5.59 Hz, p-cymene-CH),
3.90 (s, 3H, NCH3), 2.16 (m, 1H, CH(CH3)2), 1.97 (s, 3H, Ar-CH3),
1.50 (s, 9H, C(CH3)3), 1.25 (s, 9H, C(CH3)3), 0.94 (d, 3H, J = 6.75
Hz, CHCH3), 0.82 (d, 3H, J = 6.91 Hz, CHCH3) ppm. 13C NMR (100
MHz, CDCl3): δ 174.5, 159.3, 140.8, 135.4, 129.7, 123.4, 120.9, 118.7,
113.9, 86.4, 82.1, 78.3, 37.9, 35.7, 33.9, 31.6, 30.2, 30.1, 30.0, 20.8, 18.7
ppm. HRMS (MALDI, m/z): calcd for C28H39ClN2ORu (M − Cl)
521.2107, found 521.2115.
i
Compound 3b (R = Pr). Yield 99%. Mp: 200 °C dec. Anal. Calcd
for C30H43ClN2ORu: C, 61.68; H, 7.42; N, 4.80. Found: C, 61.46; H,
7.37; N, 5.03. H NMR (CDCl3): δ 7.38 (d, 1H, J = 1.98 Hz, im-H),
ASSOCIATED CONTENT
* Supporting Information
A CIF file giving X-ray structural information for 3b and figures
giving 1H and 13C NMR spectra for complexes 2a−d and 3a−d
and GPC curves and NMR spectra for the obtained polymers.
This material is available free of charge via the Internet at
http://pubs.acs.org.
1
■
S
7.15 (d, 1H, J = 2.03 Hz, im-H), 7.04 (d, 1H, J = 2.43 Hz, Ar-H), 6.90
(d, 1H, J = 2.43 Hz, Ar-H), 5.59 (d, 1H, J = 5.65 Hz, p-cymene-CH),
5.43 (d, 1H, J = 5.68 Hz, p-cymene-CH), 5.13(m, 1H, CH(CH3)2),
4.92 (d, 1H, J = 5.70 Hz, p-cymene-CH), 4.57 (d, 1H, J = 5.73 Hz, p-
cymene-CH), 2.12 (m, 1H, CH(CH3)2), 2.02 (s, 3H, Ar-CH3), 1.58
(d, 3H, J = 6.86 Hz, CHCH3), 1.52 (d, 3H, J = 6.08 Hz, CHCH3), 1.51
(s, 9H, C(CH3)3), 1.26 (s, 9H, C(CH3)3), 0.93 (d, 3H, J = 6.81 Hz,
CHCH3), 0.85 (d, 3H, J = 6.96 Hz, CHCH3) ppm. 13C NMR (100
MHz, CDCl3): δ 174.0, 160.0, 140.8, 135.6, 130.1, 121.0, 119.4, 118.2,
114.1, 86.4, 82.8, 81.7, 78.0, 52.5, 35.7, 34.0, 31.7, 30.3, 24.5, 24.2,
23.6, 20.6, 18.8 ppm. HRMS (MALDI, m/z): calcd for
C30H43ClN2ORu (M − Cl) 549.2420, found 549.2426.
AUTHOR INFORMATION
Corresponding Author
*Tel and fax: +86-22-23504781. E-mail: bqwang@nankai.edu.
■
cn.
Compound 3c (R = Ph). Yield: 99%. Mp: 185 °C dec. Anal. Calcd
for C33H41ClN2ORu: C, 64.11; H, 6.68; N, 4.53. Found: C, 64.06; H,
Notes
1
The authors declare no competing financial interest.
6.56; N, 4.73. H NMR (CDCl3): δ 8.03 (d, 1H, J = 7.34 Hz, Ar-H),
7.50 (m, 4H, Ar-H), 7.25 (s, 1H, Ar-H), 7.06 (d, 1H, J = 1.90 Hz, im-
H), 6.95 (d, 1H, J = 1.98 Hz, im-H), 5.47−3.86 (m, 4H, p-cymene-
CH), 2.14 (m, 1H, CH(CH3)2), 1.89 (s, 3H, Ar-CH3), 1.52 (s, 9H,
C(CH3)3), 1.28 (s, 9H, C(CH3)3), 0.89 (d, 3H, J = 6.71 Hz, CHCH3),
0.78 (d, 3H, J = 6.90 Hz, CHCH3) ppm. HRMS (MALDI, m/z): calcd
for C33H41ClN2ORu (M − Cl) 583.2265, found 583.2268.
ACKNOWLEDGMENTS
■
We are grateful to the National Natural Science Foundation of
China (No. 21174068), the Specialized Research Fund for the
Doctoral Program of Higher Education of China
(20110031110009), and the Fundamental Research Funds for
the Central Universities for financial support.
Compound 3d (R = Mes). Yield: 99%. Mp: 165 °C dec. Anal. Calcd
for C36H47ClN2ORu: C, 65.48; H, 7.17; N, 4.24. Found: C, 65.40; H,
1
7.11; N, 4.33. H NMR (CDCl3): δ 7.56 (d, 1H, J = 1.68 Hz, Ar-H),
REFERENCES
7.17 (s, 1H, Ar-H), 7.07 (s, 1H, im-H), 7.03 (d, 1H, J = 2.18 Hz, im-
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z): calcd for C36H47ClN2ORu (M − Cl) 625.2735, found 625.2736.
■
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