O -aryloxide-N-heterocyclic carbenes: Efficient synthesis of the proligands and their p -cymene ruthenium complexes

Article abstract of DOI:10.1021/acs.organomet.5b00256

An efficient method to synthesize o-hydroxyaryl-substituted imidazoles (2-OH-3-R-5-^tBuC₆H₂)(C₃H₃N₂) [R = ^tBu (1a), H (1b)] was developed through copper-catalyzed C-N bond formation. Treatment of 1a or 1b with a halohydrocarbon in refluxing toluene afforded a series of o-hydroxyaryl imidazolinium proligands 2a-h in high yields. Reactions of proligands 2a-h with Ag₂O and [(p-cymene)RuCl₂]₂ gave the corresponding o-aryloxide-N-heterocyclic carbene ligated p-cymene ruthenium complexes 3a-h. All the imidazolium salts and ruthenium complexes were fully characterized by ¹H and ¹³C NMR spectra, elemental analysis, and high-resolution mass spectrometry. Without the cocatalyst or irradiation, these complexes can efficiently catalyze norbornene ring-opening metathesis polymerization. Notably, the structures of the catalysts were found to have significant effects on the catalytic activity and the properties of obtained polymers.

Full text of DOI:10.1021/acs.organomet.5b00256

Article
pubs.acs.org/Organometallics
o‑Aryloxide-N-heterocyclic Carbenes: Efficient Synthesis of the
Proligands and Their p‑Cymene Ruthenium Complexes
Dandan Yang,† Yungang Tang,† Haibin Song,† and Baiquan Wang*,†,‡,§
‡
†State Key Laboratory of Elemento-Organic Chemistry, College of Chemistry, and Collaborative Innovation Center of Chemical
Science and Engineering, 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: An efficient method to synthesize o-hydroxyaryl-
t
substituted imidazoles (2-OH-3-R-5-tBuC6H2)(C3H3N2) [R = Bu
(1a), H (1b)] was developed through copper-catalyzed C−N bond
formation. Treatment of 1a or 1b with a halohydrocarbon in refluxing
toluene afforded a series of o-hydroxyaryl imidazolinium proligands
2a−h in high yields. Reactions of proligands 2a−h with Ag2O and [(p-
cymene)RuCl2]2 gave the corresponding o-aryloxide-N-heterocyclic
carbene ligated p-cymene ruthenium complexes 3a−h. All the
imidazolium salts and ruthenium complexes were fully characterized
1
by H and 13C NMR spectra, elemental analysis, and high-resolution
mass spectrometry. Without the cocatalyst or irradiation, these
complexes can efficiently catalyze norbornene ring-opening metathesis
polymerization. Notably, the structures of the catalysts were found to
have significant effects on the catalytic activity and the properties of obtained polymers.
metal complexes.13 Among them, the cymene or benzene Ru
complexes can efficiently catalyze the ROMP of norbornene
INTRODUCTION
■
In the past decades, the chemistry of N-heterocyclic carbenes
(NHCs) as well as their metal complexes has received much
and alternating copolymerization of norbornene and cyclo-
octene without any cocatalyst or irradiation conditions.13e,f
attention in the field of organometallics and catalysis since the
precursory work of Arduengo.1 By introducing an NHC ligand
However, the synthetic methods for the proligands of catalysts
are not very efficient (Scheme 1).13a,b It may limit their further
into a Grubbs I catalyst, the resulting Grubbs II catalyst shows
higher activities for olefin metathesis reaction, excellent
functional group tolerance, and better thermal stability.2
These NHC-Ru complexes as well as Ru-benzylidene catalysts
lead to excellent olefin metathesis catalysts. They are widely
applied in constructing a variety of molecules.3 Different from
the well-defined ruthenium catalysts containing a ruthenium−
carbon double bond, the ill-defined ruthenium catalysts do not
have an alkylidene fragment. They are generally commercially
available and exhibit comparable performance to the well-
defined catalysts or even better results.4 Since Noels and co-
workers first reported that (p-cymene)RuCl2(PCy3) can
efficiently catalyze the ring-opening metathesis polymerization
(ROMP) of norbornene,5 p-cymene-based catalysts with
various types of ligands including phosphines,6,7 bidentate
Schiff bases,8,9 and NHC ligands10,11 have been widely
investigated so far.
application. Hence, it is vitally important to look for a new way
to synthesize the proligands and in turn develop various
transition-metal catalysts bearing this ligand framework. In this
work, we report an efficient method to synthesize the o-
Scheme 1. Synthetic Routes of the Proligands
Recently, transition-metal complexes with anion-tethered
NHC ligands have received much attention.12 As an anchor, the
featured anion groups can enhance the bond between the NHC
ligands and metal atoms and inhibit the possibility of ligand
dissociation. In the previous work, we designed and synthesized
a series of o-hydroxyaryl NHC proligands and their transition-
Received: March 25, 2015
© XXXX American Chemical Society
A
DOI: 10.1021/acs.organomet.5b00256
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Article
Scheme 2. Synthesis of o-Hydroxyaryl Imidazolium Proligands 2a−h
hydroxyaryl imidazolium proligands through copper-catalyzed
C−N bond formation and nucleophilic substitution with
halohydrocarbon (Scheme 1). The corresponding p-cymene
ruthenium complexes featuring these o-aryloxide-NHC ligands
were also prepared and used to catalyze the ROMP of
norbornene (NBE) without any cocatalyst or irradiation
conditions.
Scheme 3. Synthesis of o-Aryloxide-NHC Ruthenium
Complexes 3a−h
RESULTS AND DISCUSSION
■
Synthesis of o-Hydroxyaryl Imidazolium Proligands.
In 2007, we reported the synthesis of the o-hydroxyaryl
imidazolium proligand;13a,b however, the reactions were
relatively complicated and the yields were very low, which
extremely discouraged their wide research and usage. Thus, we
herein develop a new, simple, and efficient method, which is
different from the well-established approach in our laboratory.
As shown in Scheme 2, upon dropwise addition of a
methanolic iodine solution to a solution of 2,4-di-tert-
butylphenol in methanol containing KOH at room temper-
ature,14a the reaction mixture became light yellow. It should be
noted that if the reactant is 4-tert-butylphenol, the iodine was
added at 0 °C. Then the mixture was washed with an aqueous
Na2SO3 solution, followed by acidification, extraction, and
eventually evaporation to leave an iodophenol compound as a
yellow solid. This process is very simple, and the yield is nearly
quantitative. The product can be directly used without further
purification in the next step. The second step is a common C−
N coupling reaction catalyzed by CuI. In short, materials of the
reaction are cheap, and the yield is high (51−55%). So it can be
synthesized in large scale. Then o-hydroxyaryl imidazolium salts
2a−h were synthesized by the reactions of 1a or 1b with a
halohydrocarbon in refluxing toluene in 80−97% yields.14b
Proligands 2a−h are soluble in CH2Cl2, CHCl3, and
CH3OH, but insoluble in diethyl ether and hexane. They
diethyl ether and other hydrocarbon solvents. All of them have
1
been fully characterized by H and 13C NMR, HRMS, and
1
elemental analysis. In their H NMR spectra the characteristic
signals of the phenol and imidazole protons for the proligands
disappeared completely. The signals of the cymene protons in
the 1H NMR spectra and the carbene carbons in the 13C NMR
spectra appeared at 4.50−5.50 ppm and about 175.0 ppm,
respectively. They are similar to those of the Ru-cymene NHC
complexes reported previously.13,15 HRMS and elemental
analysis results supported their structures. Single-crystal X-ray
diffraction analysis further confirmed the structures of 3b. The
unit cell contains two crystallographically independent
molecules, and the structure description is for one of them
(Figure 1). The Ru−C(carbene) and Ru−O bond lengths are
2.036(2) and 2.0946(14) Å, respectively. They are similar to
those in other o-aryloxide-N-heterocyclic ruthenium com-
plexes.13
ROMP of NBE. ROMP is a very powerful method for the
preparation of polymers with narrow polydispersities.3a,16,17 To
study the structure−property relationship of catalysts, the
ROMP of NBE with 3a−g was studied, while the polymer data
of 3h were reported by our group previously.13e The
polymerization results are shown in Table 1. It is clear that
without any cocatalyst all the ruthenium complexes 3a−g
exhibit moderate or high activity toward the ROMP of
norbornene at 85 °C. Much to our surprise, the introduction
of tert-butyl at the ortho position of the aryloxide could decrease
the activity, but results in a significant increase in the molecular
weight of the obtained polymer (entries 2, 4, 6, 8). The
substituents of imidazole also have an effect on the catalytic
1
have been fully characterized by H and 13C NMR spectra and
1
high-resolution mass spectrometry (HRMS). All the H NMR
spectra of 2a−h display a characteristic singlet at 9−10 ppm for
the imidazolium proton, as reported in the previous literature
for similar imidazolium salts.
Synthesis of o-Aryloxide-NHC Ruthenium Complexes.
Following the procedures as described previously by our
group,13 3a−h were synthesized by the reactions of proligands
2a−h with 3 equiv of Ag2O and 1 equiv of [(p-cymene)RuCl2]2
in high yields (Scheme 3).
The ruthenium complexes 3b, 3d, 3f, and 3h are very stable
in air, but 3a, 3c, 3e, and 3g turn dark when exposed to air for a
few hours. They are all soluble in 1,2-dimethoxyethane,
CH2Cl2, THF, acetone, dioxane, and toluene, but insoluble in
B
DOI: 10.1021/acs.organomet.5b00256
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Article
decrease the stability of active species 4 and suppress its
formation, which leads to the low yield of the resultant
polymer.
CONCLUSION
■
In conclusion, we have successfully developed an efficient route
to synthesize o-hydroxyaryl imidazolinium proligands and
synthesized a series of corresponding o-aryloxide-N-hetero-
cyclic carbene p-cymene-Ru complexes. These complexes can
efficiently catalyze the ROMP of NBE without any cocatalyst.
Notably, introduction of a tert-butyl at the ortho position of the
aryloxide could decrease the activity, but results in a significant
increase in the molecular weight (up to 1.57 × 106) of the
obtained polymer. The steric effect of the substituting group at
imidazole may improve the activity. The bulkier the N-bonded
alkyl substituent, the higher the yield the resultant polymer.
Figure 1. ORTEP diagram of 3b (one of two independent molecules
in the unit cell is shown). Thermal ellipsoids are shown at the 30%
probability level. Hydrogen atoms are omitted for clarity. Selected
bond lengths (Å) and angle (deg): Ru(1)−C(17) 2.036(2), Ru(1)−
O(1) 2.0946(14), Ru(1)−Cl(1) 2.4184(7), C(17)−Ru(1)−O(1)
82.06(7), C(17)−Ru(1)−Cl(1) 86.33(6), O(1)−Ru(1)−Cl(1)
85.50(4), N(1)−C(17)−N(2) 104.66(18).
EXPERIMENTAL SECTION
■
General Considerations. All experiments were carried out under
an atmosphere of dry argon using standard Schlenk techniques. All
solvents were distilled from appropriate drying agents under argon
1
before using. H and 13C NMR spectra were recorded on a Bruker
a
Table 1. ROMP of NBE with 3a−h
AV400 spectrometer. HRMS were carried out on Agilent 6520 Q-TOF
mass spectrometers. Elemental analyses were performed on a
PerkinElmer 240C analyzer. The molecular weights and molecular
weight distribution of entries 1 and 5 in Table 1 were obtained on
GPC [Waters 1525 liquid chromatography connected with styragel
GPC columns (HT 2, 3, 4 THF) and a Waters 2414 differential
refractometer], while the others were obtained on GPC [Waters 510
liquid chromatography connected with four styragel GPC columns
(guard, 103 Å, 104 Å, 105 Å) and a Waters 410 differential
refractometer]. The eluent of all polymers is THF.
entry
cat.
yield (%)
Mn (×103)
PDI
cis (%)
1
2
3
4
5
6
7
3a
3b
3c
3d
3e
3f
85
44
70
57
68
30
30
29
372
476
424
1571
470
572
454
902
1.94
2.88
3.33
1.81
1.63
3.05
2.56
2.02
27
20
34
25
21
28
26
39
3g
3h
Synthesis of 2,4-Di-tert-butyl-6-(1H-imidazol-1-yl)phenol
(1b). To a stirred solution of 2,4-di-tert-butylphenol (6.18 g, 30.0
mmol) and KOH (6.72 g, 120.0 mmol) in methanol (60 mL) at room
temperature was dropwisely added a solution of I2 (7.61 g, 30.0 mmol)
in methanol (50 mL) over a period of ca. 1 h. After stirring for 30 min,
a solution of Na2SO3 (3.78 g, 30.0 mmol) in 30 mL of water was
added to quench unreacted I2. The reaction mixture was acidified with
HCl until pH = 5 and extracted with CH2Cl2. Removal of solvent
under reduced pressure gave the crude product 2,4-di-tert-butyl-6-
iodophenol. A mixture of the above crude product (30 mmol),
imidazole (2.50 g, 36 mmol), Cs2CO3 (19.5 g, 60 mmol), and CuI
(570 mg, 3 mmol) in 120 mL of DMSO was stirred under an argon
atmosphere at 120 °C for 36 h. After cooling to room temperature, the
reaction mixture was poured into water and extracted with ethyl
acetate. The organic layer was separated, and the aqueous layer was
extracted with ethyl acetate. The combined organic layers were washed
with water again, dried over anhydrous Na2SO4, and concentrated
under reduced pressure to get the crude product. Purification by
column chromatography afforded 1b as a white solid. Yield: 51%. Mp:
162−163 °C. 1H NMR (400 MHz, CDCl3): δ 7.46 (s, 1H, im-H), 7.41
(d, 1H, J = 2.36 Hz, im-H), 7.10 (s, 1H, Ar-H), 7.05 (s, 1H, im-H),
6.96 (d, 1H, J = 2.35 Hz, im-H), 1.48 (s, 9H, C(CH3)3), 1.30 (s, 9H,
C(CH3)3) ppm. 13C NMR (100 MHz, CDCl3): δ 148.3, 142.2, 139.2,
128.6, 125.4, 124.7, 121.4, 35.5, 34.3, 31.4, 29.7 ppm. HRMS (ESI, m/
z): calcd for C17H24N2O [M + H]+ 273.1967, found 273.1969.
Synthesis of 4-tert-Butyl-2-(1H-imidazol-1-yl)phenol (1a).
This compound was prepared in a similar manner to that described
for 1b, except that a solution of I2 in methanol was dropped into the
b
8
a
Polymerization conditions: In 30 mL of toluene; 1.0 g of NBE; [cat.]
= 0.167 mmol L−1; 85 °C; 3 h; GPC versus polystyrene standards.
b
The data are from our previous work.13e
activity. The rough rule is that the bulkier the N-bonded alkyl
substituent, the higher the yield the resultant polymer.
Following a similar mechanism for the p-cymene-Ru system
reported previously,3e,8a,9,13 the active ruthenium carbene
species might be generated by the release of a p-cymene ligand
from 3, the coordination of NBE to ruthenium, and then a 2,3-
hydrogen shift (Scheme 4). The bulky steric effect of the N-
bonded alkyl substituent may increase the interaction with the
p-cymene group and promote the release of a p-cymene ligand
and the formation of the active ruthenium species 5, which lead
to the high yield of the resultant polymer. When R is tert-butyl,
the interaction between tert-butyl and the NBE ligand may
Scheme 4. Proposed Catalytic Mechanism
1
mixture in an ice water bath. Yield: 55%. Mp: 189−190 °C. H NMR
(400 MHz, CDCl3): δ 7.80 (s, 1H, im-H), 7.28 (d, 1H, J = 8.80 Hz,
Ar-H), 7.21 (s, 1H, Ar-H), 7.18 (d, 1H, J = 1.60 Hz, Ar-H), 7.08−7.12
(m, 2H, im-H), 1.30 (s, 9H, C(CH3)3) ppm. 13C NMR (100 MHz,
CDCl3): δ 148.8, 137.3, 126.8, 125.9, 123.9, 121.9, 120.1, 117.2, 33.8,
31.1 ppm. HRMS (ESI, m/z): calcd for C13H16N2O [M + H]+
217.1341, found 217.1340.
C
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General Procedures for Synthesis of Proligands 2a−h. A
mixture of o-hydroxyarylimidazole and 1.5 equiv of halohydrocarbon
was refluxed for 15 h in toluene. Recrystallization from CH2Cl2/Et2O
gave the product as a white solid.
29.4 ppm. HRMS (ESI, m/z): calcd for C18H27IN2O [M − I]+
287.2123, found 287.2126.
General Procedures for Synthesis of Complexes 3a−g. A
solution of 2 and 3 equiv of Ag2O in CH2Cl2 was stirred at room
temperature in the dark for 12 h and then filtered over a pad of Celite.
The filtrate was added to a solution of 1 equiv of [(p-cymene)RuCl2]2
in CH2Cl2. The resultant red solution was stirred for 48 h under
exclusion of light. After filtration over a pad of Celite and removal of
the solvent under reduced pressure the crude product was obtained.
Recrystallization from CH2Cl2/hexane gave compounds 3 as brown
crystals.
Compound 2a. Yield: 87%. Mp: 190−191 °C. 1H NMR (400
MHz, CDCl3): δ 9.57 (s, 1H, NCHN), 7.65−7.48 (m, 4H, Ar-H), 7.41
(m, 4H, Ar-H), 7.28 (d, 1H, J = 5.2 Hz, im-H), 7.15 (d, 1H, J = 2.08
Hz, im-H), 6.10−6.13 (m, 1H, NCH), 2.01 (m, 3H, CHCH3), 1.26 (s,
9H, C(CH3)3) ppm. 13C NMR (100 MHz, CDCl3): δ 147.7, 144.1,
137.6, 134.2, 129.7, 128.6, 127.3, 123.7, 121.4, 120.3, 119.0, 60.2, 34.4,
31.5, 21.3 ppm. HRMS (ESI, m/z): calcd for C21H25BrN2O [M − Br]+
321.1967, found 321.1966.
Compound 3a. Yield: 71%. Mp: >300 °C. Anal. Calcd for
C31H37ClN2ORu: C, 63.09; H, 6.32; N, 4.75. Found: C, 62.95; H,
6.50; N, 4.83. 1H NMR (400 MHz, CDCl3): δ 7.58 (s, 2H, Ar-H), 7.42
(d, J = 7.0 Hz, 2H, Ar-H), 7.35 (s, 2H, Ar-H), 7.26−7.22 (m, 2H, Ar-
H), 7.12 (s, 1H, Ar-H), 7.05 (s, 2H, im-H), 6.43−6.44 (m, 1H, NCH),
5.38 (s, 1H, p-cymene-CH), 4.83 (s, 1H, p-cymene-CH), 4.73 (s, 1H,
p-cymene-CH), 4.40 (s, 1H, p-cymene-CH), 1.94 (s, 3H, CH-CH3),
1.91−1.93 (m, 1H, CH(CH3)2), 1.85 (d, J = 6.5 Hz, CH-CH3), 1.29
(s, 9H, C(CH3)3), 0.75 (d, J = 6.2 Hz, 6H, CH(CH3)2) ppm. 13C
NMR (100 MHz, CDCl3): δ 178.0, 144.2, 138.0, 129.9, 129.1, 127.4,
125.1, 121.2, 120.4, 118.6, 116.3, 88.0, 84.4, 80.7, 77.4, 76.7, 59.6, 33.9,
31.7, 30.3, 23.7, 23.1, 22.7, 21.1, 18.4, 14.1 ppm. HRMS (ESI, m/z):
calcd for C31H37ClN2ORu [M − Cl]+ 555.1949, found 555.1952.
Compound 3b. Yield: 95%. Mp: >300 °C. Anal. Calcd for
C35H45ClN2ORu: C, 65.05; H, 7.02; N, 4.33. Found: C, 65.03; H,
Compound 2b. Yield: 81%. Mp: 136−137 °C. 1H NMR (400
MHz, CDCl3): δ 9.52 (s, 1H, NCHN), 8.24 (s, 1H, Ar-H), 7.54 (s,
1H, Ar-H), 7.53 (s, 1H, Ar-H), 7.40−7.43 (m, 4H, Ar-H), 7.29 (s, 1H,
im-H), 7.01 (d, 1H, J = 2.08 Hz, im-H), 5.78−5.83 (m, 1H, NCH),
2.03−2.06 (m, 3H, CHCH3), 1.41 (s, 9H, C(CH3)3), 1.27 (s, 9H,
C(CH3)3) ppm. 13C NMR (100 MHz, CDCl3): δ 147.0, 144.4, 143.1,
137.7, 136.5, 129.5, 127.5, 126.3, 126.0, 123.8, 121.0, 119.8, 60.6, 35.7,
34.6, 31.4, 30.0, 21.1 ppm. HRMS (ESI, m/z): calcd for C25H33BrN2O
[M − Br]+ 377.2593, found 377.2595.
Compound 2c. Yield: 82%. Mp: 200−201 °C. 1H NMR (400 MHz,
CDCl3): δ 9.55 (s, 1H, NCHN), 9.46 (s, 1H, Ar-OH), 7.53 (dd, 1H,
Ar-H), 7.43 (s, 1H, Ar-H), 7.24 (s, 1H, Ar-H), 7.22 (s, 1H, Ar-H), 7.15
(d, 1H, J = 7.30 Hz, Ar-H), 6.90 (s, 2H, im-H), 5.67 (s, 2H, NCH2),
2.27 (s, 9H, ArCH3), 1.24 (s, 9H, C(CH3)3) ppm. 13C NMR (100
MHz, CDCl3): δ 147.9, 143.8, 140.0, 138.3, 135.8, 130.0, 129.0, 128.5,
128.2, 125.3, 125.2, 123.2, 121.4, 121.0, 121.0, 118.8, 48.5, 34.3, 31.4,
21.1, 19.9 ppm. HRMS (ESI, m/z): calcd for C23H29BrN2O [M − Br]+
349.2280, found 349.2284.
1
7.08; N, 4.35. H NMR (400 MHz, CDCl3): δ 7.50 (d, 1H, J = 1.53
Hz, Ar-H), 7.42−7.45 (m, 2H, Ar-H), 7.39 (d, 1H, J = 1.45 Hz, Ar-H),
7.32−7.36 (m, 1H, Ar-H), 7.30 (s, 1H, Ar-H), 7.28 (s, 1H, Ar-H), 7.06
(d, 1H, J = 2.13 Hz, im-H), 6.99 (d, 1H, J = 2.02 Hz, im-H), 6.47−6.52
(m, 1H, NCH), 5.30 (d, 1H, J = 1.93 Hz, p-cymene-CH), 4.84 (d, 1H,
J = 3.65 Hz, p-cymene-CH), 4.77 (s, 1H, p-cymene-CH), 4.30 (d, 1H,
J = 4.45 Hz, p-cymene-CH), 1.99 (s, 3H, Ar-CH3), 1.98 (m, 1H,
CH(CH3)2), 1.85 (d, 3H, J = 7.08 Hz, CH-CH3), 1.52 (s, 9H,
C(CH3)3), 1.29 (s, 9H, C(CH3)3), 0.81 (d, 3H, J = 4.80 Hz, CH-
CH3), 0.70 (d, 3H, J = 5.90 Hz, CH-CH3) ppm. 13C NMR (100 MHz,
CDCl3): δ 175.7, 159.2, 143.5, 134.0, 134.7, 129.2, 128.1, 126.4, 124.1,
120.3, 119.3, 118.4, 113.3, 58.5, 34.8, 33.1, 30.7, 29.3, 29.2, 23.0, 21.9,
20.2, 17.8 ppm. HRMS (MALDI, m/z): calcd for C35H45ClN2ORu [M
− Cl]+ 611.2575, found 611.2573.
Compound 3c. Yield: 96%. Mp: >300 °C. Anal. Calcd for
C33H41ClN2ORu: C, 64.11; H, 6.68; N, 4.53. Found: C, 64.23; H,
6.88; N, 4.35. 1H NMR (400 MHz, CDCl3): δ 7.48 (s, 1H, Ar-H), 7.30
(s, 1H, Ar-H), 7.24 (s, 1H, im-H), 7.18 (s, 1H, Ar-H), 6.67 (s, 1H, im-
H), 6.20 (dd, 1H, NCH), 5.94 (d, 1H, J = 5.50 Hz, p-cymene-CH),
5.69 (d, 1H, J = 5.60 Hz, p-cymene-CH), 5.35 (dd, 1H, NCH), 5.30
(d, 1H, J = 5.74 Hz, p-cymene-CH), 5.02 (d, 1H, J = 5.64 Hz, p-
cymene-CH), 2.55 (d, 9H, J = 3.95 Hz, ArCH3), 2.39 (s, 1H,
CH(CH3)2), 2.28 (s, 3H, Ar-CH3), 1.48 (s, 9H, C(CH3)3), 1.15 (d,
3H, J = 6.92 Hz, CH-CH3), 1.11 (d, 3H, J = 6.77 Hz, CH-CH3) ppm.
13C NMR (100 MHz, CDCl3): δ 174.7, 137.8, 128.7, 128.5, 126.7,
123.3, 120.3, 119.5, 116.0, 115.1, 102.1, 101.9, 87.6, 83.7, 79.5, 78.7,
52.8, 48.0, 32.9, 30.7, 30.6, 29.5, 28.3, 22.8, 20.1, 19.6, 19.0, 17.5 ppm.
HRMS (MALDI, m/z): calcd for C33H41ClN2ORu [M − Cl]+
583.2262, found 583.2260.
Compound 3d. Yield: 97%. Mp: >300 °C. Anal. Calcd for
C37H49ClN2ORu: C, 65.90; H, 7.32; N, 4.15. Found: C, 65.83; H,
7.48; N, 4.35. 1H NMR (400 MHz, CDCl3): δ 7.19 (s, 1H, Ar-H), 7.19
(s, 1H, Ar-H), 6.97 (s, 2H, Ar-H), 6.89 (s, 1H, im-H), 6.43 (s, 1H, im-
H), 5.96 (dd, 1H, NCH), 5.72 (d, 1H, J = 5.46 Hz, p-cymene-CH),
5.57 (d, 1H, J = 5.55 Hz, p-cymene-CH), 5.17 (dd, 1H, NCH), 5.04
(d, 1H, J = 5.61 Hz, p-cymene-CH), 4.64 (d, 1H, J = 5.61 Hz, p-
cymene-CH), 2.35 (s, 6H, Ar-CH3), 2.33 (s, 3H, Ar-CH3), 2.17 (s, 1H,
CH(CH3)2), 2.12 (s, 3H, Ar-CH3), 1.54 (s, 9H, C(CH3)3), 1.26 (s,
9H, C(CH3)3), 0.95 (d, 3H, J = 6.71 Hz, CH-CH3), 0.86 (d, 3H, J =
6.88 Hz, CH-CH3) ppm. 13C NMR (100 MHz, CDCl3): δ 173.5,
158.8, 139.9, 137.7, 134.7, 129.2, 128.5, 126.8, 120.3, 119.3, 116.7,
113.2, 85.8, 82.5, 80.5, 47.8, 34.8, 33.0, 30.7, 29.4, 22.7, 20.1, 19.7,
19.0, 17.9 ppm. HRMS (MALDI, m/z): calcd for C37H49ClN2ORu [M
− Cl]+ 639.2888, found 639.2890.
Compound 2d. Yield: 83%. Mp: 237−238 °C. 1H NMR (400
MHz, CDCl3): δ 9.14 (s, 1H, NCHN), 7.42 (s, 1H, Ar-H), 7.33 (s,
1H, Ar-H), 7.29 (s, 1H, Ar-H), 6.94 (s, 1H, Ar-H), 6.93 (s, 2H, im-H),
5.59 (s, 2H, NCH2), 2.38 (s, 6H, ArCH3), 2.29 (s, 3H, ArCH3), 1.38
(s, 9H, C(CH3)3), 1.27 (s, 9H, C(CH3)3) ppm. 13C NMR (100 MHz,
CDCl3): δ 147.3, 143.9, 142.4, 139.9, 138.7, 136.7, 129.9, 126.3, 125.3,
125.2, 123.6, 121.8, 119.7, 48.5, 35.7, 34.5, 31.4, 29.8, 21.1, 20.3 ppm.
HRMS (ESI, m/z): calcd for C27H37BrN2O [M − Br]+ 405.2906,
found 405.2912.
Compound 2e. Yield: 97%. Mp: 125−126 °C. 1H NMR (400 MHz,
CDCl3): δ 9.76 (s, 1H, NCHN), 7.53 (d, 1H, J = 3.19 Hz, Ar-H), 7.47
(d, 4H, J = 8.50 Hz, Ar-H), 7.26 (s, 1H, Ar-H), 7.26 (s, 1H, Ar-H),
7.18−7.22 (m, 3H, Ar-H), 7.12 (d, 2H, J = 4.49 Hz, im-H), 5.61 (s,
2H, NCH2), 1.17 (s, 9H, C(CH3)3) ppm. 13C NMR (100 MHz,
CDCl3): δ 147.6, 143.9, 135.9, 135.8, 133.0, 129.5, 129.4, 129.0, 128.4,
128.2, 125.3, 123.2, 121.8, 121.2, 118.5, 65.8, 34.3, 31.4 ppm. HRMS
(ESI, m/z): calcd for C20H23BrN2O [M − Br]+ 307.1810, found
307.1815.
Compound 2f. Yield: 83%. Mp: 219−220 °C. 1H NMR (400 MHz,
CDCl3): δ 9.50 (s, 1H, NCHN), 8.17 (s, 1H, Ar-OH), 7.53 (s, 3H, Ar-
H), 7.40 (d, 4H, J = 8.09 Hz, Ar-H), 7.29 (s, 1H, im-H), 7.00 (s, 1H,
im-H), 5.55 (s, 2H, NCH2), 1.37 (s, 9H, C(CH3)3), 1.26 (s, 9H,
C(CH3)3) ppm. 13C NMR (100 MHz, CDCl3): δ 147.9, 147.2, 144.0,
142.5, 142.1, 139.9, 137.2, 133.1, 132.4, 132.4, 129.7, 129.6, 129.5,
126.4, 125.6, 125.1, 124.3, 123.8, 122.3, 122.3, 120.1, 115.2, 53.8, 35.7,
34.5, 31.4, 39.8 ppm. HRMS (ESI, m/z): calcd for C24H31BrN2O [M
− Br]+ 363.2436, found 363.2440.
Compound 2g. Yield: 97%. Mp: 292−295 °C. 1H NMR (400
MHz, CDCl3): δ 9.45 (s, 1H, NCHN), 8.30 (s, 1H, Ar-H), 7.67 (s, 1H,
Ar-H), 7.53 (d, 1H, J = 8.58 Hz, Ar-H), 7.43 (s, 1H, im-H), 7.32 (s,
1H, im-H), 4.14 (s, 3H, NCH3), 1.24 (s, 9H, C(CH3)3) ppm. 13C
NMR (100 MHz, CDCl3): δ 147.2, 144.5, 136.3, 128.6, 125.7, 123.2,
121.7, 121.4, 118.5, 37.8, 34.4, 31.4 ppm. HRMS (ESI, m/z): calcd for
C14H19IN2O [M − I]+ 231.1497, found 231.1499.
1
Compound 2h. Yield: 94%. Mp: >300 °C. H NMR (400 MHz,
DMSO): δ 9.43 (s, 1H, Ar-OH), 9.14 (s, 1H, NCHN), 7.91 (m, 1H,
Ar-H), 7.88 (m, 1H, Ar-H),7.42 (d, 1H, J = 2.40 Hz, im-H), 7.86 (d,
1H, J = 2.40 Hz, im-H), 3.91 (s, 3H, NCH3), 1.41 (s, 9H, C(CH3)3),
1.28 (s, 9H, C(CH3)3) ppm. 13C NMR (100 MHz, DMSO): δ 147.2,
142.2, 138.1, 125.1, 124.3, 124.0, 123.4, 121.5, 35.7, 35.0, 34.0, 30.1,
D
DOI: 10.1021/acs.organomet.5b00256
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
Compound 3e. Yield: 44%. Mp: >300 °C. Anal. Calcd for
AUTHOR INFORMATION
■
C30H35ClN2ORu: C, 62.54; H, 6.12; N, 4.86. Found: C, 62.43; H,
Corresponding Author
*E-mail: bqwang@nankai.edu.cn. Tel/fax: +86-22-23504781.
1
6.18; N, 4.75. H NMR (400 MHz, CDCl3): δ 7.47 (s, 1H, Ar-H),
7.39−7.43 (m, 2H, Ar-H), 7.33−7.36 (m, 3H, Ar-H), 7.08 (s, 2H, im-
H), 7.04 (s, 1H, Ar-H), 7.00 (s, 1H, Ar-H), 5.71 (d, 1H, J = 15.87 Hz,
NCH), 5.51 (d, 1H, J = 5.19 Hz, p-cymene-CH), 5.43 (d, 1H, J =
15.86 Hz, NCH), 5.05 (d, 1H, J = 5.71 Hz, p-cymene-CH), 4.95 (d,
1H, J = 5.68 Hz, p-cymene-CH), 4.55 (d, 1H, J = 5.68 Hz, p-cymene-
CH), 2.04−2.10 (m, 1H, CH(CH3)2), 1.97 (s, 3H, ArCH3), 1.28 (s,
9H, C(CH3)3), 0.83 (d, 6H, J = 6.88 Hz, CH-CH3) ppm. 13C NMR
(100 MHz, CDCl3): δ 176.4, 136.4, 128.0, 127.0, 126.1, 123.4, 122.1,
120.3, 117.6, 115.2, 101.4, 87.5, 83.4, 79.7, 78.6, 53.4, 32.9, 30.6, 29.4,
22.2, 20.0, 17.4 ppm. HRMS (MALDI, m/z): calcd for
C30H35ClN2ORu [M − Cl]+ 541.1793, found 541.1791.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work is financially supported by the National Natural
Science Foundation of China (Grants 21174068 and
21421062) and Specialized Research Fund for the Doctoral
Program of Higher Education of China (Grant
20110031110009).
Compound 3f. Yield: 98%. Mp: >300 °C. Anal. Calcd for
C34H43ClN2ORu: C, 64.59; H, 6.88; N, 4.43. Found: C, 64.43; H,
6.88; N, 4.35. 1H NMR (400 MHz, CDCl3): δ 7.37−7.42 (m, 6H, Ar-
H), 7.07 (s, 1H, Ar-H), 7.00 (s, 1H, im-H), 6.96 (s, 1H, imH), 5.80
(dd, 1H, NCH), 5.45 (s, 1H, NCH), 5.43 (d, 1H, J = 6.10 Hz, p-
cymene-CH), 5.16 (d, 1H, J = 4.12 Hz, p-cymene-CH), 4.90 (d, 1H, J
= 4.91 Hz, p-cymene-CH), 4.84 (d, 1H, J = 5.73 Hz, p-cymene-CH),
2.15 (s, 1H, CH(CH3)2), 2.00 (s, 3H, ArCH3), 1.52 (s, 9H, C(CH3)3),
1.29 (s, 9H, C(CH3)3), 0.94 (d, 3H, J = 6.42 Hz, CH-CH3), 0.79 (d,
3H, J = 6.19 Hz, CH-CH3) ppm. 13C NMR (100 MHz, CDCl3): δ
176.2, 159.9, 141.1, 137.5, 135.7, 130.0, 129.0, 128.0, 127.2, 122.9,
121.3, 119.4, 114.2, 86.4, 82.8, 82.2, 78.1, 54.3, 35.9, 34.1, 31.8, 30.4,
30.3, 23.0, 21.2, 18.8 ppm. HRMS (MALDI, m/z): calcd for
C34H43ClN2ORu [M − Cl]+ 597.2419, found 597.2429.
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1
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ASSOCIATED CONTENT
■
S
* Supporting Information
A CIF file for 3b, figures of NMR spectra for 1a,b, 2a−h, and
3a−h, NMR spectra, and GPC curves for the obtained
polymers. The Supporting Information is available free of
charge on the ACS Publications website at DOI: 10.1021/
acs.organomet.5b00256.
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DOI: 10.1021/acs.organomet.5b00256
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