Robust bulky [P,O] neutral nickel catalysts for copolymerization of ethylene with polar vinyl monomers

Article abstract of DOI:10.1021/acscatal.8b01088

Several nickel complexes bearing sterically bulky phosphino-phenolate ([P,O]) ligands were synthesized and explored as catalysts for olefin (co)polymerization. In the absence of an activator, the complexes showed very high catalytic activities (up to 10

Full text of DOI:10.1021/acscatal.8b01088

Subscriber access provided by Kaohsiung Medical University
Article
Robust Bulky [P,O] Neutral Nickel Catalysts for
Copolymerization of Ethylene with Polar Vinyl Monomers
Yanping Zhang, Hongliang Mu, Li Pan, Xuling Wang, and Yuesheng Li
ACS Catal., Just Accepted Manuscript • DOI: 10.1021/acscatal.8b01088 • Publication Date (Web): 21 May 2018
Downloaded from http://pubs.acs.org on May 21, 2018
Just Accepted
“Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted
online prior to technical editing, formatting for publication and author proofing. The American Chemical
Society provides “Just Accepted” as a service to the research community to expedite the dissemination
of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in
full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully
peer reviewed, but should not be considered the official version of record. They are citable by the
Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore,
the “Just Accepted” Web site may not include all articles that will be published in the journal. After
a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web
site and published as an ASAP article. Note that technical editing may introduce minor changes
to the manuscript text and/or graphics which could affect content, and all legal disclaimers and
ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or
consequences arising from the use of information contained in these “Just Accepted” manuscripts.
is published by the American Chemical Society. 1155 Sixteenth Street N.W.,
Washington, DC 20036
Published by American Chemical Society. Copyright © American Chemical Society.
However, no copyright claim is made to original U.S. Government works, or works
produced by employees of any Commonwealth realm Crown government in the course
of their duties.

Page 1 of 35
1
2
3
ACS Catalysis
Robust Bulky [P,O] Neutral Nickel Catalysts for Copolymerization of
Ethylene with Polar Vinyl Monomers
4
5
6
7
Yanping Zhang,† Hongliang Mu,‡ Li Pan,*,† Xuling Wang, Yuesheng Li*,†,#
†Tianjin Key Lab of Composite & Functional Materials, School of Materials Science and Engineering, Tianjin
University, Tianjin 300072, China
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
‡Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China
#Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin 300072, China
Abstract: Several nickel complexes bearing sterically bulky phosphinoꢀphenolate ([P,O]) ligands were
synthesized and explored as catalysts for olefin (co)polymerization. In the absence of an activator, the
complexes showed very high catalytic activities (up to 107 g·molNi−1·h−1) for ethylene polymerization
even at 90 °C or with the addition of a large amount of a polar additive (such as ethyl alcohol, diethyl
ether, acetone, or even water), affording linear polymers with high molecular weights (up to 6.53 × 105).
In contrast, most of the previously reported nickel catalysts suffer from severe activity suppression at
elevated temperature. It is rare that a catalyst owns so many good performances simultaneously, such as
high catalytic activity, good tolerance for polar group, strong thermal stability, and yielding linear
polyethylene with highꢀmolecularꢀweight. Most importantly, these bulky nickel complexes used in this
study also effectively copolymerized of ethylene with challenging polar vinyl monomers, including
commercially available acrylates and an acrylamide. As we expected, introducing a bulky substituent
group on the phosphorus atom of the complex was vital for enhanced catalytic activity and the
formation of highꢀmolecularꢀweight linear copolymers. Microstructure analyses revealed that the polar
functional units were mainly incorporated into the polymer main chain and also located at the chain end,
with insertion percentages of up to 7.4 mol %. The bulky [P,O] neutral nickel complexes reported herein
are promising alternatives to the wellꢀestablished palladium catalysts for direct copolymerization of
olefins with commercially available polar vinyl comonomers.
Keywords: neutral nickel catalyst, bulky substituent, ethylene polymerization, copolymerization, polar
vinyl monomer.
ACS Paragon Plus Environment

ACS Catalysis
Page 2 of 35
1. Introduction
1
2
3
4
5
6
7
8
9
Introducing polar groups into the polymer chain of polyolefins is an effective strategy for improving
their surface properties, such as wettability, adhesion, printability, and compatibility.1,2 The most
straightforward method for this purpose is the direct coordination–insertion copolymerization of olefins
with polar monomers by means of singleꢀsite organometallic catalysts.2 Because earlyꢀtransitionꢀmetal
catalysts are highly oxophilic and easily deactivated by polar functional groups, lateꢀtransitionꢀmetal
catalysts, especially palladium catalysts, are extensively used for copolymerization of ethylene with
industrially relevant polar monomers, including acrylates,3 acrylonitrile,4 vinyl acetate,5 vinyl fluoride,6
and vinyl ethers,7 as well as others.8,9 Nevertheless, the high cost and relatively low activity of
palladium catalysts limit their practical utility; and their replacement with less expensive catalysts, such
as nickel catalysts, would therefore be highly desirable. In fact, numerous nickel complexes have been
developed to catalyze (co)polymerization reactions, but these complexes are active mainly toward
ethylene and norbornene (co)polymerization.10,11 In addition to their relatively poor thermal stability,11
most of the nickel catalysts reported to date suffer from severe activity suppression by polar monomers
and can produce only copolymers with low molecular weights (MWs) or with negligible polar
comonomer incorporation.12,13 Although some nickel complexes have been reported to copolymerize
ethylene with vinyl polar comonomers that have a relatively long spacer between the C=C bond and the
polar functional group,12 attempts at nickelꢀcatalyzed copolymerization of olefins with commercially
available polar vinyl monomers to yield semiꢀcrystalline highꢀMW polymers with wellꢀcontrolled
composition have met with only limited success.13
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
The reasons for this limited success have been explored. For example, a mechanistic investigation
about ethylene/methyl acrylate copolymerization achieved by neutral nickel salicylaldimine ([N,O])
catalysts revealed that 2,1ꢀinsertion of methyl acrylate (MA) into the Ni–C bond does occur, but the
insertion products readily undergo bimolecular deactivation with nickel hydride complexes derived from
βꢀH elimination.13b In addition, the formation of a carbonyl chelate complex (the O atom of the carbonyl
group interaction with the Ni center) leads to difficulty in chain initiation and propagation (Scheme 1).
ACS Paragon Plus Environment

Page 3 of 35
ACS Catalysis
Similar to [N,O] (e.g., salicylaldimine) neutral nickel catalysts, Shell Higher Olefin Process (SHOP)
catalysts and some [P,O] (e.g., phosphineꢀsulfonate) neutral nickel catalysts generated in situ have been
found to be inactive for ethylene/MA copolymerization.12a,d In addition to showing poor tolerance to
polar comonomers, nickel catalysts such as SHOP catalysts and αꢀdiimine nickel catalysts usually
produce higher αꢀolefins or highly branched polyethylenes (PEs) because of incidental βꢀH elimination
reactions and ‘‘chain walking’’ processes.2c Recently, making use of interactions between nickel centers
and other atoms such as nitrogen atom or oxygen atom via transient interaction with metal center has
been proved to be an effective strategy for the ethylene/MA copolymerization by the Mitsubishi team
and the Chen group,13g,h a strategy that is likely to retard βꢀH elimination reactions. Moreover, as shown
in Scheme 2, introduction of a sterically bulky group oriented axially with respect to the nickel center
also suppresses associative chain transfer or chain transfer to monomer, because the resting and
terminating states are sharply destabilized, whereas the insertion state is stabilized.9f,11a,14
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Scheme 1. Deactivation of [N,O] Nickel Complexes in the Case of Methyl Acrylate (MA).
Scheme 2. Suppression of Chain Transfer by Introduction of an Axially Oriented Bulky Group.
Recently, we have been developing several wellꢀdefined phosphinoꢀphenolate ([P,O]) neutral nickel
catalysts based on SHOP catalysts because of their good tolerance for polar functional groups.
Encouraged by the effect of an axial bulky group, we expected that the introduction of bulky
substituents to shield the vacant pz orbital would effectively suppress the chelating interaction and βꢀH
elimination, as well as would hinder the coordination of a monomer approaching from the direction
ACS Paragon Plus Environment

ACS Catalysis
Page 4 of 35
perpendicular to the nickel coordination plane to produce highꢀMW polymers. In addition, a sterically
hindered environment around the nickel center would help to reduce the possibility of bimolecular
deactivation reactions. In this study, we strategically tune the steric hindrance at the axial direction of
the nickel active site and evaluated the effects of bulky substituent group on the phosphorus atom.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
2. Results and Discussion
2.1 Synthesis and Characterization of [P,O] Neutral Nickel Complexes
To evaluate the effects of steric hindrance at the axial position, we used commercially available
chlorodiphenylphosphine (P1) as a small phosphine chloride, and we also designed and synthesized
three
additional
diaromatic
phosphine
chlorides
of
different
sizes:
(2′,6′ꢀdimethoxybiphenylꢀ2ꢀyl)phenylphosphine chloride (P2), (biphenylꢀ2ꢀyl)phenylphosphine chloride
(P3), and bis(biphenylꢀ2ꢀyl)phosphine chloride (P4). P2–P4 were synthesized as described in
Supporting Information, and were used for ligand synthesis without purification. Ligands 1a–1d, which
bear substituents with different steric bulk, were synthesized as shown in Scheme 3. Briefly,
2ꢀ(2ꢀ(tertꢀbutyl)phenoxy)tetrahydroꢀ2Hꢀpyran was lithiated with nꢀBuLi, and the prepared lithium salt
was allowed to react with P1, P2, P3, or P4. The tetrahydroꢀ2Hꢀpyran protecting group was easily
removed by reaction with hydrochloric acid and quenching with aqueous NaHCO3 to afford ligands
1a–1d. [P,O] neutral nickel complexes 2a–2d were obtained in high yields (>76%) by addition of the
corresponding ligands (1a–1d, respectively) to a stirred solution of Py2NiMe2 in dry toluene. In order to
explore the difference between Mitsubishi catalysts and these bulky [P,O] neutral catalysts, we also
synthesized complex 2e according the literature for comparision.13g It was found that complex 2e was
not very stable in toluene or benzene, as nickel black could be obviously observed in about 5 hours,
while no nickel black was not detectable for complexes 2aꢀ2d even after 48 hours. This difference might
be ascribed to the weaker coordination of labile ligand 1,5ꢀCyclooctadiene (COD).
ACS Paragon Plus Environment

Page 5 of 35
ACS Catalysis
1
2
3
4
5
O
O
O
O
P
OH
Ar1
Ar1
Ar2
t-Bu
t-Bu
HCl/H2O t-Bu
n-BuLi
P1-P4
P
Ar2
NaHCO3
6
7
8
9
1a-1d
2a: Ar1 = Ar2 = Ph
2b: Ar1 = Ph, Ar2 =
O
O
t-Bu
O
P
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
N
Py2NiMe2
toluene, rt.
2c: Ar1 = Ph, Ar2 =
2d: Ar1 = Ar2 =
Ni
Me
Ar1
Ar2
2a-2d
Cl
strong -donor
weak -donor
Cl
O
P
Cl
P
O
P
P
Cl
P1
P3
P2
P4
axial steric control
t-Bu
t-Bu
OH
P
O
Ni(COD)2
Ni
P
Ar
2e: Ar = 2,6-(MeO)2C6H3
Ar
Ar
Ar
Scheme 3. Synthesis of [P,O] Neutral Nickel Complexes 2a–2d.
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
For Xꢀray diffraction analysis, we obtained single crystals of 2b–2d by slowly diffusing nꢀhexane into
solutions of the complexes in dry toluene. Xꢀray diffraction analysis for all single crystals revealed that
these nickel complexes exhibited a square planar geometry around the nickel center, and labile ligand
pyridine located trans to the phosphorus atom (Figures 1, 2, S97, and S98). The differences in Ni–N
bond length between the complexes were negligible. Inspection of spaceꢀfilling diagrams of 2b–2d
clearly indicates that the bulky 2ꢀ(2,6ꢀ(OCH3)2C6H3)C6H4– or 2ꢀ(C6H5)C6H4– group effectively shielded
the vacant pz orbital of the dsp2ꢀhybridized nickel center (Figure 2). The C(1)–P(1)–C(3) angle in 2a
was 108.71°,12i and the corresponding angles were slightly smaller in the other three complexes: 107.67°
in 2b (C(6)–P(1)–C(17)), 107.21° in 2c (C(2)–P(1)–C(17)), and 105.08° in 2d (C(30)–P(1)–C(18)),
respectively. This difference suggests a more sterically crowded environment in 2b–2d than in 2a.
Moreover, the dihedral angles between the bulky phenylꢀsubstituted planar group at the axial direction
and the nickel coordination plane (21.22, 24.43, and 18.76° in 2b–2d, respectively), as well as the
distances from the nickel center to the axial phenyl ring (3.221, 3.238, and 2.824 Å in complexes 2b–2d,
ACS Paragon Plus Environment

ACS Catalysis
Page 6 of 35
respectively), reflected greater steric hindrance. Notably, the spaceꢀfilling diagram of 2d shows two
pseudoꢀaxial phenyl rings perpendicular to the coordination plane, and these rings jointly shield the
vacant pz orbital from above and below. The steric bulk of these complexes clearly increased in the order
2a < 2c < 2b < 2d. Note also that the Ni(1)–O(3) and Ni(1)–O(2) distances in 2b were 3.556 and 4.557
Å, respectively, both of which are longer than the sum of the van der Waals radii between Ni atom and
O atom (3.15 Å).13b This distance indicates that the interaction between the –OMe group and the nickel
center was negligible.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Figure 1. ORTEP plot of complex 2b. Ellipsoids are shown with 30% probability. Hydrogen atoms are omitted
for clarity. Selected bond lengths (Å) and angles (°): Ni(1)–C(36) 1.931(3), Ni(1)–O(1) 1.9330(19), Ni(1)–N(1)
1.950(2), Ni(1)–P(1) 2.0981(7), Ni(1)–O(3) 3.556 ， Ni(1)–O(2) 4.557; C(36)–Ni(1)–O(1) 174.64(11),
C(36)–Ni(1)–N(1) 92.86(12), O(1)–Ni(1)–N(1) 89.18(9), C(36)–Ni(1)–P(1) 90.85(9), O(1)–Ni(1)–P(1) 87.08(6),
N(1)–Ni(1)–P(1) 176.25(8), C(6 )–P(1)–C(17) 107.67(11).
Figure 2. Spaceꢀfilling diagrams of complexes 2a–2d, respectively. Hydrogen atoms are omitted for clarity.
Selected bond lengths (Å) and angles (°) for complex 2c: Ni(1)–C(34) 1.943(3), Ni(1)–O(1) 1.9358(18),
Ni(1)–N(1) 1.956(2), Ni(1)–P(1) 2.1090(7); O(1)–Ni(1)–C(34) 177.57(11), O(1)–Ni(1)–N(1) 90.03(8),
C(34)–Ni(1)–N(1) 91.48(11), O(1)–Ni(1)–P(1) 86.78(5), C(34)–Ni(1)–P(1) 91.84(9), N(1)–Ni(1)–P(1) 174.87(6).
ACS Paragon Plus Environment

Page 7 of 35
ACS Catalysis
C(2)–P(1)–C(17) 107.21(11). Selected bond lengths (Å) and angles (°) for complex 2d: Ni(1)–C(40) 1.927(3),
Ni(1)–O(1) 1.9227(15), Ni(1)–N(1) 1.9507(18), Ni(1)–P(1) 2.1015(6); O(1)–Ni(1)–C(40) 177.75(10),
O(1)–Ni(1)–N(1) 89.30(7), C(40)–Ni(1)–N(1) 91.74(10), O(1)–Ni(1)–P(1) 87.36(5), C(40)–Ni(1)–P(1) 91.35(8),
N(1)–Ni(1)–P(1) 171.88(6), C(30)–P(1)–C(18) 105.08(10).
1
2
3
4
5
6
7
8
9
2.2 Ethylene Polymerization
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
We began by investigating the catalytic performances of neutral nickel complexes 2a–2d in ethylene
polymerization; representative results are listed in Table 1. Without an activator, all four complexes
were highly active for ethylene polymerization. Complex 2a, which has the smallest phosphorus ligand
(–PPh2), displayed a catalytic activity of 210 × 103 g·molNi−1·h−1 at 70 °C (entry 1); whereas at a lower
reaction temperature, this complex did not initiate ethylene polymerization (data of 30 and 50 °C was
not shown). When the catalyst concentration and the reaction temperature were increased, the catalytic
activity increased remarkably (up to ca. 107 g·molNi−1·h−1; entry 2).11,14a
In sharp contrast, complexes 2b and 2c, which have bulkier phosphorus ligands perpendicular to the
coordination plane, produced PEs with higher MWs (up to 653 × 103 for 2b and up to 613 × 103 for 2c).
Additionally, the catalytic activities of 2b and 2c were nearly 2 orders of magnitude higher than that of
2a under the same conditions (compare entries 6 and 10 with entry 1). These results are consistent with
our initial hypothesis that the axially oriented bulky phosphinoꢀphenolate ligands would prevent chain
transfer to an incoming monomer, leading to the formation of highꢀMW polymers. Note that although
the difference between the catalytic activities of 2b and 2c for ethylene polymerization was not large,
the activity of 2b was slightly higher. Such slight difference indicates that there was no transient
coordination of the apical –OMe group with Ni center in complex 2b, a result that differs from
previously reported results.3c,13g Unexpectedly, the performance of the complex with two bulky
substituents on the phosphorus atom (2d) was inferior to that of the nickel complex with a single bulky
substituent (2c), in terms of both catalytic activity and polymer MW (Table 1, compare entries 8 and 11).
This result suggests that steric hindrance around the active site of 2d may have slowed ethylene
coordination or insertion. Besides, there was no big difference between 2a and Mitsubishi catalyst 2e in
catalytic activity, and MW of polymer synthesized by these two complex is also very similar.
ACS Paragon Plus Environment

ACS Catalysis
Page 8 of 35
Table 1. Ethylene Polymerization Catalyzed by Complexes 2a–2d.a
1
2
3
4
5
6
7
8
9
d
d
e
Temp
(°C)
70
Yield
(g)
Mn
Mw
Tm
d
Entry
Cat.
TOFb
Activityc
Mw/Mn
(103)
(103)
11.5
7.8
(°C)
130
126
136
136
136
131
129
137
136
134
136
126
125
1
2f
3
0.35
32.6
0.34
4.9
7.5
350
7.3
210
9780
204
5.6
2.0
2.0
1.4
1.4
1.9
1.5
2.7
1.5
1.9
2.1
1.3
2.2
2.5
2a
2a
2b
2b
2b
2b
2b
2c
2c
2c
2d
2a
2e
90
3.9
10
90
124
653
458
219
25.5
613
390
126
238
8.4
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
4
30
105
233
396
359
75
2940
6540
11100
10020
2100
5280
8400
660
480
241
146
9.4
5
50
10.9
18.5
16.7
3.5
6
70
7
90
8
30
398
206
59
9
50
8.8
189
300
24
10
11
12g
13g
70
14
30
1.1
183
3.8
70
9.6
206
245
5760
6840
70
11.4
3.1
7.7
a
Reaction conditions, unless otherwise noted: 5 ꢁmol of catalyst; 100 mL of toluene; ethylene pressure, 10 bar;
20 min. TOF, turnover frequency. In units of 103 molE·molNi−1·h−1, E, ethylene. c In units of 103 g·molNi−1·h−1. d
b
Determined by gel permeation chromatography (GPC) at 150 °C vs narrow polystyrene standard in
1,2,4ꢀtrichlorobenzene. Determined by differential scanning calorimetry (DSC), 20 °C·min−1, second heating
e
f
g
curve. Reaction carried out with 10 ꢁmol of catalyst. Reaction carried out with 5 ꢁmol of catalyst, 50 mL of
toluene.
To our delight, the yields and MW of PE obtained with catalyst 2b at 30 °C increased with increasing
reaction time, and the catalytic activity ( 4860 × 103 g·molNi−1·h−1) was still very high even after one
hour (Table S1, entries S10–S13). In addition, 2a and 2b also showed strong thermal stability, retaining
very high catalytic activity (up to 107 g·molNi−1·h−1), and produced highꢀmolecularꢀweight PE even at
90 °C (Table 1). As we know, it is a very good example that the catalytic activity value is among the
highest activities of neutral nickel systems (e.g., SHOP catalyst, salicylaldiminato nickel systems, and
phosphine sulfonate nickel system).15 The catalytic activities of catalyst 2b and 2c clearly increased as
the temperature was raised from 30 to 70 °C, but the MWs of the resulting PEs decreased owing to
acceleration of chain transfer reactions.
ACS Paragon Plus Environment

Page 9 of 35
ACS Catalysis
As we have mentioned, tolerance to polar reagents is essential for copolymerization of olefins with
1
2
polar monomers. In order to explore the polar additives effects on catalytic activity, we carried out
ethylene polymerization by using complex 2c in the presence of the following saturated polar additives
(Table 2): acetonitrile, dimethyl formamide, ethyl alcohol, diethyl ether, ethyl acetate, acetone,
dichloromethane, and water. We found that although the inhibitory effects of acetonitrile and dimethyl
formamide on the catalyst activity were relatively strong because these compounds can coordinate
readily with the nickel center, the catalytic activity of 2c still remained as high as approximately 106
g·molNi−1·h−1 even in the presence of these additives (Table 2, entries 8 and 9). To our surprise, 2c still
showed good tolerance to ethyl alcohol and diethyl ether; the catalytic activity of 2c barely decreased in
the presence of either of these polar solvents at a concentration of 2 M (40,000 equiv relative to the
catalyst, entries 2 and 3). In addition, only a slight decrease in catalytic activity was observed after
addition of ethyl acetate or acetone, indicating that the carbonyl group of these compounds coordinated
only weakly, if at all, to the nickel center. Complex 2c also exhibited high activity (3480 kg·molNi−1·h−1)
with the addition of alkyl halide dichloromethane. We were surprised to find that the activity of 2c was
only moderately decreased with addition of 40,000 equiv of water. To our knowledge, this complex is
one of the most robust catalysts reported to date for ethylene polymerization in the presence of water.16
As shown in Figure 3, the catalytic activities of ethylene polymerization decreased in the order ethanol
< diethyl ether < acetone < ethyl acetate < water < dichloromethane < acetonitrile < dimethyl
formamide. Taken together, these results indicate that 2c shows good tolerance to various polar additives,
retaining remarkably high catalytic activity for ethylene polymerization with the addition of the tested
additives; whereas most of the previously reported catalysts show severely decreased activity under
similar conditions, especially in the presence of water.8h,16c–e More interestingly, although abundant
polar additives has been added, the MW and polydispersity index (PDI) of the obtained PE was not
affected a lot, except for that when large amount of acetonitrile (MW decreased to 120000 and PDI is
about 3.9) or dimethyl formamide (MW decreased to 307000) was added.
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
ACS Paragon Plus Environment

ACS Catalysis
Page 10 of 35
Table 2. Representative Data for Ethylene Polymerization with the Addition of Polar Additives
using complex 2c.a
1
2
3
4
5
6
7
8
9
d
c
Tm
Catalyst
(ꢁmol)
Additive
(mol Lꢀ1)
Yiled
(g)
Mw
Entry
Activityb
PDIc
(103)
(°C)
1
2
3
4
5
6e
7
8
9
2c(2.5)
2c(2.5)
2c(2.5)
2c(2.5)
2c(2.5)
2c(2.5)
2c(2.5)
2c(2.5)
No additive
Ethanol (2)
4.5
4.3
4.2
3.9
3.7
3.1
2.9
0.9
0.6
5400
5160
5040
3900
4440
3720
3480
960
467
437
502
456
478
552
698
120
307
1.9
2.0
2.0
1.9
1.9
1.9
1.8
3.9
1.8
138
137
137
138
136
136
138
135
134
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Diethyl ether (2)
Acetone (2)
Ethyl acetate (2)
Water (2)
Dichloromethane (2)
Acetonitrile (2)
2c(2.5) Dimethyl formamide (2)
720
a
b
Reaction conditions, unless otherwise noted: ethylene 10 atm, toluene, 50 mL.
In 103 g·molNi−1·h−1.
cDetermined by GPC at 150 °C vs narrow polystyrene standard in 1,2,4ꢀtrichlorobenzene. d Measured by DSC, 20
°C minꢀ1. e Addition of 0.3 g SDS (sodium dodecyl sulfate).
Figure 3. Ethylene polymerization with the addition of various polar additives. Reaction conditions: 2.5 ꢁmol of
catalyst 2c, 50 °C, 20 min, 10 bar, total volume 50 mL, 2 M additive. Control, no additive; DMF, dimethyl
formamide; AcN, acetonitrile; DCM, dichloromethane; EA, ethyl acetate; ACE, acetone; DE, diethyl ether.
2.3 Copolymerization of Ethylene with Polar Vinyl Monomers
As shown in Figure 2, the bulky group 2,6ꢀ(OCH3)2C6H3C6H4– and C6H5C6H4– of complexes 2b–2d
effectively shielded the vacant pz orbital of the dsp2ꢀhybridized nickel center. Furthermore, these groups
prevented monomer access to the metal center from the axial direction relative to the coordination plane,
ACS Paragon Plus Environment

Page 11 of 35
ACS Catalysis
thus reducing the chain transfer rate and favoring the formation of highꢀMW polymers. Because these
nickel complexes displayed impressive catalytic performance for ethylene polymerization and good
tolerance to various polar additives, we expected that introduction of a bulky axial substituent could
facilitate copolymerization of ethylene with challenging polar vinyl monomers. Therefore, we
conducted a detailed investigation of the catalytic performance of 2a–2d in the copolymerizations of
ethylene with MA, a commercially available polar monomer (Table 3). We found that 2a gave
unsatisfactory results under mild conditions: only tiny amounts of solid products were obtained even at
a high catalyst loading (entry 1). In sharp contrast, 2b and 2c, which have bulkier phosphorus
substituents, exhibited much higher catalytic activity and afforded much higherꢀMW copolymers
(entries 3 and 4, respectively), suggesting that the bulky axial substituents not only retarded associative
chain transfer and chain transfer to monomer but also prevented deactivation reactions such as
bimolecular deactivation by means of chelating interaction between the ester group (−C(O)OMe) and
the nickel center. Among the four complexes, 2d, which has the bulkiest substituents, displayed the
highest catalytic activity (up to 105 g·molNi−1·h−1) under similar conditions (entry 5). All in all, these
neutral nickel catalysts displayed impressive catalytic activity for the copolymerization and produced
highꢀMW copolymers (MW up to 108.0 × 103); MA incorporation percentages as high as 5.4 mol %
could be easily achieved under mild conditions without requiring a large amount of MA.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Notably, all the copolymerizations described in this study were carried out with singleꢀcomponent
nickel catalysts in the absence of any activators or additives that might generate radicals.17 In order to
understand the catalytic copolymerization thoroughly, we also conducted the ethylene/MA
copolymerization in the presence of butylated hydroxytoluene, a radical trap (Table 3, entry 7).
Although the productivity decreased slightly (compare entries 6 and 7)—as was observed for ethylene
polymerization in the presence of butylated hydroxytoluene (Table S1, compare entries S4 and
S5)—similar MA incorporation was achieved. This result confirmed that all the copolymerizations
catalyzed by 2a–2d via a coordination–insertion mechanism.
ACS Paragon Plus Environment

ACS Catalysis
Page 12 of 35
Table 3. Representative Copolymerization of Ethylene and Polar Vinyl Monomers Using
1
2
Complexes 2a–2d.a
3
4
5
6
7
8
9
e
f
Cat.
Temp. [Comon.] Yield
TOFc
Incorp.d
Mw
Tm
Comon.
Act.b
PDIe
Entry
(°C)
70
(mol L−1) (mg)
(E/Comon.) (mol %) (103)
(°C)
92
(ꢁmol)
2a (20)
2b (10)
2b (10)
2c (10)
1
2
3
4
5
6g
7h
8g
9
MA
MA
MA
MA
MA
0.1
0.2
0.2
0.2
0.2
64
3.2
100/6
823/30
882/20
1547/69
3517/17
5.4
3.7
2.2
4.3
0.5
1.2
9.4
1.3
2.0
2.0
2.1
1.8
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
70
257
263
493
25.7
26.3
49.3
112
117
108
126
50
22.6
21.7
72.4
50
2d (10)
2b (10)
2b (10)
2a (30)
2b (10)
2c (10)
50
1000 100.0
MA
MA
BA
BA
BA
30
30
70
50
50
0.1
0.1
0.2
0.2
0.2
370
240
84
37.0
24.0
2.8
1301/7
844/4
0.5
0.5
7.7
1.9
4.0
108.0 1.6
131
129
1.3 n.d.j
64.4
1.6
1.7
73/6
500
402
50.2
40.2
1646/32
1221/47
45.3
30.3
2.6
2.1
120
111
10
11
12g
13
14
15
2d (10)
BA
50
70
50
50
50
0.2
0.1
0.2
0.2
0.2
536
3.6
89
53.6
1.2
1947/14
37/2
0.7
3.3
95.8
3.2
1.8
2.7
1.7
1.8
2.2
125
113
126
127
129
2a (30) DMAA
2b (10) DMAA
2c (10) DMAA
2d (10) DMAA
8.9
301/4
1.2
16.3
23.4
63.2
111
202
11.1
20.2
386/3
0.7
710/(<4)
<0.5
16
17
18i
2e (10)
2e (10)
2e (20)
MA
MA
MA
50
70
70
0.1
0.1
0.1
trace
trace
46
–
–
–
–
–
–
–
–
–
–
–
–
–
–
2.3
55/9
13.6
n.d.
a
Reaction conditions, unless otherwise noted: 50 mL of toluene, ethylene pressure 10 bar, copolymerization for
60 min. MA, methyl acrylate; BA, nꢀbutyl acrylate; DMAA, N,Nꢀdimethylacrylamide. In units of 103
g·molNi−1·h−1. In units of molE·molNi−1·h−1/molComon. molNi−1·h−1. E, ethylene. Determined by H NMR
b
c
d
1
e
spectroscopy at 120 °C. PDI, polydispersity index; determined by gel permeation chromatography (GPC) in
f
1,2,4ꢀtrichlorobenzene at 150 °C vs narrow polystyrene standard. Determined by differential scanning
calorimetry. g Reaction carried out in 100 mL of toluene. Reaction conducted in 100 mL of toluene in the
h
presence of 200 mg of butylated hydroxytoluene. i Ethylene pressure 18 bar. j Not detected.
Moreover, these bulky nickel catalysts can be used to efficiently incorporate not only MA but also
other polar vinyl monomers, specifically nꢀbutyl acrylate (BA; Table 3, entries 8–11) and
N,Nꢀdimethylacrylamide (DMAA; entries 12–15, the first successful example via neutral nickel catalyst)
into polymer chains. Specifically, 2a afforded ethylene/BA copolymers containing up to 7.7 mol % BA
ACS Paragon Plus Environment

Page 13 of 35
ACS Catalysis
and ethylene/DMAA copolymers containing up to 3.3 mol % DMAA, whereas 2d afforded copolymers
with high MWs (BA, Mw up to 95.8 × 103; DMAA, Mw up to 63.2 × 103). The data in Table 3 indicates
that the activities of the catalysts and the MWs of the copolymers increased upon introduction of bulky
substituent group on the phosphorus atom of the nickel complexes. All the nickel catalysts showed
better tolerance to a –C(O)OR group than to a –C(O)NMe group; that is, both catalytic activity for
ethylene/acrylate copolymerization and –C(O)OR content in the ethylene/MA copolymer were much
higher than the corresponding values in ethylene/acrylamide copolymerization.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Mitsubishi catalysts has only been reported to achieve the copolymerization of ethylene and MA
under harsh reaction conditions (e.g., much higher ethylene pressure, 30 bar; a large amount of catalysts,
80 ꢁmol).13g In this study, copolymerization of ethylene and MA promoted by Mitsubishi catalyst 2e was
also tried under milder reaction conditions. Unfortunately, there was hardly any polymers at 10 bar of
ethylene pressure (Table 3, entries 16 and 17), or only discernible amount of polymers could be obtained
even under 18 bar of ethylene pressure and larger dosage of 2e was added (Table 3, entry 18).
The MWs of copolymers and the incorporation percentage of polar units in the copolymers could be
controlled by tuning ethylene pressure, the concentration of polar comonomer in feed, and reaction
temperature. In order to study the effect of different reaction parameter, we conducted the tunable
ethylene/MA copolymerization by means of 2c, and the results are summarized in Table 4. As ethylene
pressure was increased from 5 to 20 bar, the catalytic activities (11.4–185 kg·molNi−1·h−1) and MWs
(10–79 × 103) of the resulting copolymers dramatically increased, while the MA content (7.4–2.6 mol %)
gradually decreased. In addition, reaction temperature was also intimately correlated with catalytic
activity and copolymer structure. As the temperature was increased from 30 to 90 °C (Table 4, entries
1–4), catalytic activities and MWs of the copolymers decreased, whereas MA insertion percentage
gradually increased, from 1.4 to 4.8 mol % (the data for reactions catalyzed by 2b and 2d at 70 °C are
shown in Supporting Information). This observation is reasonable because the possible chain transfer
reactions, like βꢀhydride elimination, were accelerated relative to chain propagation as reaction
temperature increased. Compared with the palladium catalysts bearing classical phosphinoꢀsulfonate
ACS Paragon Plus Environment

ACS Catalysis
Page 14 of 35
ligands, which work only at elevated temperature (>80 °C),3 the nickel complexes described herein can
achieve the copolymerization of ethylene with MA in a wide temperature range (30–90 °C).
Furthermore, 2c exhibited impressive copolymerization ability: high MA incorporation percentages (up
to 7.4 mol %) can be easily achieved without the need for a large amount of MA in feed.
1
2
3
4
5
6
7
8
9
Table 4. Tunable Copolymerization of Ethylene and Methyl Acrylate by Using Complex 2c.a
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
e
f
Temp
(°C)
30
Comon.
(mol L−1) (bar) (mg)
P
Yield
TOFc
Incorp.d
(mol %)
1.4
Mw
Tm
Entry
Act.b
PDIe
(E/MA)
1858/26
1546/70
1379/68
(103)
107.4
21.7
13.5
6.7
(°C)
127
108
108
101
96
1
2
3
4
5
6
7
0.2
0.2
0.2
0.2
0.2
0.2
0.4
10
10
10
10
5
543
493
444
271
114
54.3
49.3
44.4
27.1
11.4
2.0
2.1
2.0
2.1
1.7
1.8
50
4.3
70
4.7
90
50
50
50
843/35
329/26
4.8
7.4
2.6
5.8
10.0
78.9
12.3
20
10
1850 185.0 6107/163
137 13.7 411/25
108
97
1.9
b
a
Reaction conditions, unless otherwise noted: 50 mL of toluene, copolymerization for 60 min. In units of
kg·molNi−1·h−1.
E, ethylene; in units of molE·molNi−1·h−1/molMA·molNi−1·h−1.
Determined by H NMR
c
d
1
e
spectroscopy at 120 °C.
PDI, polydispersity index; determined by gel permeation chromatography in
f
1,2,4ꢀtrichlorobenzene at 150 °C vs narrow polystyrene standard. Determined by differential scanning
calorimetry.
2.4 Characterization of Copolymers and Analysis of Their Microstructure
Differential scanning calorimetry (DSC) and gel permeation chromatography (GPC) experiments
showed that all the copolymers had relatively high MWs, unimodal MW distributions (Mw/Mn =
1.3–2.7), and high melting temperatures (92–131 °C), indicating their suitability for applications
1
13
requiring functional semiꢀcrystalline polymeric materials with homogeneous compositions. H and C
NMR analyses of the resultant copolymer microstructures (Supporting Information, Figures S23–S41)
unambiguously confirmed successful insertion of polar units into the polymer backbone. All the
collected characterization data (NMR, GPC and DSC) suggested that the comonomers were inserted
both into the main chain and located at the chain end, as shown in Chart 1. The structure of the terminal
polar unit of the copolymer indicates that the terminal polar monomer was inserted in a 2,1ꢀfashion.
ACS Paragon Plus Environment

Page 15 of 35
ACS Catalysis
1
2
3
4
5
6
7
Chart 1. Microstructures of Copolymers and ChainꢀEnd Structure.
13
8
To shed some light on the microstructure of the produced copolymers, we measured the C NMR
spectra of three lowerꢀMW copolymer samples that were produced with catalyst 2a and that contained
5.4 mol % MA, 7.7 mol % BA, or 3.3 mol % DMAA (Table 3, entries 1, 8 and 12, respectively). In the
13C NMR spectrum of the ethylene/MA copolymer (Figure 4), the resonances at 176.3, 166.9, and 50.3
ppm were ascribed to the –C=O group of inꢀchain MA (2.0 mol %), the –C=O group of terminal MA
(3.4 mol %), and the –OCH3 group of MA units, respectively. Note that signals corresponding to
MAꢀinitiated structure were negligible. In addition to the unimodal MW distribution (as indicated by
GPC, Figures S72–S78) and the single melting point (as indicated by DSC, Figures S50–S56) for
ethylene/MA copolymers, the presence of resonances for –CH(COOCH3)CH2CH2– and
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
13
–CH(COOCH3)CH2CH2– moieties at 32.1 and 27.4 ppm in the C NMR spectrum of the 5.4 mol %
MA copolymer confirmed that true copolymers rather than a simple mixture of PE and a MA
13
homopolymer had been produced. Quantitative analysis of the C NMR spectrum of the 7.7 mol % BA
copolymer revealed that BA had been incorporated both into the polymer main chain and at the chain
1
end (Figure S38). In the H NMR spectra of the ethylene/DMAA copolymers (Figures S35–S37), we
observed two resonances of –N–(CH3)2 at around 3.08 ppm, which resulted from the presence of
13
inꢀchain DMAA and chainꢀend DMAA structure. In the C NMR spectrum of the 3.3 mol % DMAA
copolymer (Figure 5), a broad signal at around 35.7 ppm, corresponding to –N–(CH3)2, was clearly
observed. The carbonyl resonance at 166.0 ppm was ascribed to C=O carbon linked to a C=C bond. This
C=C double bond was generated via βꢀH elimination process after 2,1ꢀinsertion of DMAA. The other
two lowerꢀfield carbonyl signals, at 175.5 and 176.8 ppm, were ascribed to inꢀchain DMAA units and
DMAAꢀinitiated end groups, respectively.
ACS Paragon Plus Environment

ACS Catalysis
Page 16 of 35
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
13
Figure 4. The C NMR spectrum of an ethylene/methyl acrylate (MA) copolymer containing 5.4 mol % MA
produced via catalyst 2a at 70 °C (Entry 1 in Table 3).
13
Figure 5. The C NMR spectrum of an ethylene/N,Nꢀdimethylacrylamide (DMAA) copolymer containing 3.3
mol % DMAA produced via catalyst 2a at 70 °C (Table 3, entry 12).
Finally, we carried out H–1H correlation spectroscopy (COSY) to obtain additional information
1
about the microstructure of the copolymers. In the H–1H COSY spectrum of the ethylene/MA
1
copolymer containing 5.4 mol % MA (Figure 6), we observed a crossꢀpeak (B, C; 7.04, 2.28 ppm)
corresponding to correlation between the two protons of the C=C bond (CH3OOCCH2=CH–) of a
terminal MA unit, along with crossꢀpeaks (D, E) and (C, D), which we ascribed to correlation between
the protons of the C=C of the terminal MA unit (CH3OOCCH2=CH–) and the protons of the adjacent
methylene group (PEꢀCH2). In addition, crossꢀpeaks (3,4) and (4,5) illustrate the correlation between the
protons of the inꢀchain MA unit (CH3OOCCHCH2–) and the protons of the methylene group (PEꢀCH2).
ACS Paragon Plus Environment

Page 17 of 35
ACS Catalysis
The correlation between the vinyl chainꢀend proton and the protons of the PEꢀCH2 group in the PE
1
2
3
skeleton was too weak to be observed, whereas correlation between the methyl chainꢀend proton and the
4
5
6
7
8
9
13
1
PEꢀCH2 protons could be observed as crossꢀpeak (a′, b′). Taken together, the C NMR, H–1H COSY,
FTꢀIR (Figures S88 and S89), and DSC data indicate definitively that the material was a true copolymer
rather than a mixture of PE and poly(methyl acrylate).
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Figure 6. 1H–1H correlation spectrum of an ethylene/methyl acrylate (MA) copolymer containing 5.4 mol % MA
obtained via catalyst 2a at 70 °C (Table 3, entry 1).
All the NMR data of the copolymers produced by the new neutral nickel catalysts indicate that (1) the
polar monomer can be inserted both into the polymer main chain and at the chain end in isolation and (2)
the copolymers were highly linear structures without side branches. To investigate how the bulky nickel
catalysts influenced the microstructure of the copolymers, we also carried out an inꢀdepth analysis of the
1H NMR spectra of four ethylene/MA copolymers, which were designated copolymer a–d, and which
were obtained with complexes 2a–2d, respectively (Table 5 and Figure 7). We found that the percentage
of terminal MA structure (signal A in Figure 7) considerably decreased from 3.4 mol % in copolymer a
(obtained with 2a) to <0.1 mol % in copolymer d (obtained with 2d), and the proportion of inꢀchain
MA structure in total MA structure (signal 1 in Figure 7) dramatically increased from 37% in
copolymer a to > 93% in copolymer d. That is, a βꢀH elimination reaction after 2,1ꢀinsertion of MA
was effectively inhibited. In addition, the vinyl end (CH2=CH–) signal (signal a in Figure 7), which
ACS Paragon Plus Environment

ACS Catalysis
Page 18 of 35
originates from the product of βꢀH elimination after ethylene insertion, was observed only in the
copolymer produced with 2a at 70 °C, confirming the hypothesis that the βꢀH elimination reaction was
inhibited by the bulky axial group.
1
2
3
4
5
6
7
8
Table 5. Structures of Ethylene/Methyl Acrylate (MA) Copolymers a–d Obtained with Catalysts
9
2a–2d at 70 °C, respectively.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Copolymer a
Copolymer b
Copolymer c
Copolymer d
1.4
Total MA (mol %)
Inꢀchain MA (mol %)
Terminal MA (mol %)
Inꢀchain/total (%)
5.4
2.0
3.4
37
3.7
2.8
4.7
4.0
>1.3
0.9
0.8
<0.1
76
85
>93
Vinyl end (mol %)
0.8
n.d.a
n.d.a
n.d.a
a Not detected. The copolymerization data of copolymer a-d were found in Table 3, entry 1, Table 3, entry 2,
Table 4, entry 3, and Table S2, entry 6, respectively.
1
Figure 7. H NMR spectra of ethylene/methyl acrylate (MA) copolymers (copolymer a–d) produced with
complexes 2a–2d, respectively, at 70 °C. The copolymers contained 5.4 mol %, 3.7 mol %, 4.7 mol %, and 1.4
mol % MA, respectively.
In addition to the MW and the percentage incorporation of MA, the manner that MA was incorporated
into polymer chain was also strongly influenced by the reaction temperature. Since the temperature was
elevated from 30 to 90 °C, the proportion of inꢀchain MA structure decreased from 100% to 85%
(Figure 8), owing to the acceleration of the βꢀhydride elimination reaction; nevertheless, the vinylꢀend
ACS Paragon Plus Environment

Page 19 of 35
ACS Catalysis
structure (signal a in Figure 8) could not be clearly observed even at 90 °C because the structure
corresponding to vinylꢀend incorporation accounted for only 0.2 mol % of the obtained copolymer. In
the 13C NMR spectrum of a copolymer obtained by complex 2c at low temperature 30 °C (Figure 9), the
signals of terminal MA (signal F in Figure 4) were very weak, and the isolated MA units (signal 6 in
Figures 4 and 9) were present mainly in the polymer main chain.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
1
Figure 8. Temperature dependence of the H NMR spectra of ethylene/methyl acrylate (MA) copolymers
produced by means of complex 2c (Table 4, entry 1ꢀ4). The copolymers produced at 30, 50, 70, and 90 °C
contained 1.4 mol %, 4.3 mol %, 4.7 mol %, and 4.8 mol % MA, respectively.
13
Figure 9. The C NMR spectrum of an ethylene/methyl acrylate (MA) copolymer produced by catalyst 2c at
30 °C (Table 3, entry 1, 1.4 mol % of MA incorporation).
2.5 Possible Deactivation Pathways for Reaction of Methyl Acrylate with [P,O] Nickel Catalysts
ACS Paragon Plus Environment

ACS Catalysis
Page 20 of 35
According to previous studies of ethylene/MA copolymerization,3c,2d the desired chain propagation
reaction may be accompanied by undesirable side reactions leading to the formation of an inactive metal
center via the three pathways shown in Scheme 4: (a) formation of a stable σꢀcoordination complex by
direct coordination of the ester group of free MA with the nickel center, resulting in loss of catalytic
activity or even catalyst poisoning; (b) formation of a stable metalꢀcarbonyl chelate after MA insertion
through backꢀbiting reaction of the carbonyl group; and (c) formation of a carbonyl chelate complex via
coordination of the carbonyl group with the nickel center at the axial direction, which results in
bimolecular deactivation.13b These side reactions must be suppressed if effective chain propagation is to
be achieved. The experimental results in this current study demonstrate that nickel catalysts with high
activity for ethylene/MA copolymerization can be achieved by introducing a bulky group in the axial
position relative to the nickel center. Compared with a small complex (2a), the nickel catalysts bearing
bulkier axial groups exhibited much higher activities and produced copolymers with higher MWs.
Therefore, we speculate that steric bulk in the axial position plays a vital role in the distinct differences
between small complex 2a and bulkier complexes 2b–2d; that is, introduction of a bulky group in the
axial position may partially or completely inhibit the abovementioned side reactions.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Scheme 4. Reaction Pathways during Ethylene/Methyl Acrylate Copolymerization in the Presence of
[P,O] Neutral Nickel Catalysts.
ACS Paragon Plus Environment

Page 21 of 35
ACS Catalysis
To further explore the effect of the bulky groups of these nickel complexes on the polymerization
1
2
characteristics and the microstructure of the resultant polymers and, more importantly, to elucidate the
possible mechanism of ethylene and MA copolymerization by these catalysts, we conducted realꢀtime
1H NMR spectroscopic monitoring of separate reactions of complex 2a and 2b with MA in the absence
of ethylene in NMR tubes at ambient temperature (Supporting Information, Figures S92–S94). We
observed that immediately upon addition of MA (60 equiv relative to the nickel complex) to a
benzeneꢀd6 solution of complex 2a or 2b, the C=C double bond of MA inserted into the Ni(II)–CH3
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
1
bond to afford a shortꢀlived nickel species (not observed by H NMR). Specifically, the resonance for
Ni(II)–CH3 decreased while the characteristic signals for MA insertion increased. The characteristic
resonances of methyl butyrate, which forms readily via a bimolecular deactivation mechanism after
3
2,1ꢀinsertion of MA (Scheme 5, pathway a),13b were clearly observed at 2.02 (t, JHꢀH = 7.3 Hz),
3
1.63–1.26 (m), and 0.76 (t, JHꢀH = 7.4 Hz) ppm. In addition, we observed the formation of methyl
crotonate, a deactivation product generated by βꢀH elimination reaction after MA insertion into
Ni(II)–CH3 bond by 2,1ꢀfashion (Scheme 5, pathway b; 1.37 and 3.44 ppm for CH3CH=CH– and
–C(O)OCH3, respectively). Meanwhile, no distinct signal for the ultimate product formed via
1
1,2ꢀinsertion of MA was found in the H NMR spectra, indicating that MA inserted into Ni(II)–C bond
mainly via 2,1ꢀfashion under these conditions. As revealed in Figures S95 and S96, the residual Ni–CH3
content relative to the initial Ni–CH3 content decreased over time, following firstꢀorder kinetics, and the
rate for the reaction between MA and complex 2a (2.36 × 10−4 s−1, Figure S95) was faster than the rate
for complex 2b (9.97 × 10−5 s−1, Figure S96).
ACS Paragon Plus Environment

ACS Catalysis
Page 22 of 35
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Scheme 5. Possible Pathways for Reaction of Methyl Acrylate with [P,O] Neutral Nickel Catalysts As
Indicated by the NMR Monitoring at Ambient Temperature.
3. Summary and Conclusions
In conclusion, phosphinoꢀphenolate nickel complexes with steric bulk were highly active for ethylene
polymerization in a wide temperature window (10–90 °C); and produced highly linear, highꢀMW (Mw
up to 6.53 × 105) PEs. Furthermore, these nickel complexes displayed unexpectedly high catalytic
activities for ethylene polymerization (up to ca. 107 g·molNi−1·h−1) even in the presence of large amounts
of polar additives; and these values of catalytic activity among the highest catalytic activities by using
neutral nickel catalysts. Moreover, highly efficient copolymerization between ethylene and
commercially available polar vinyl monomers (MA, BA, and DMAA) was readily achieved with these
complexes under mild conditions. Highꢀmolecularꢀweight (Mw up to 1.08 × 105) copolymers, greatly
improved catalytic activity, and good tolerance to polar solvents were simultaneously achieved by
introducing bulky phosphorus substituents in the axial position. This paper describes a serious of unique
singleꢀcomponent neutral nickel catalysts that showed unprecedentedly high catalytic activity and robust
thermal stability to yield linear (co)polymers with high molecular weight, and also have potential utility
for efficiently incorporating various challenging polar monomers (acrylates or an acrylamide) into linear
polymer backbones. These phosphinoꢀphenolate nickel catalysts may serve as economical alternatives to
ACS Paragon Plus Environment

Page 23 of 35
ACS Catalysis
palladium catalysts for copolymerizing ethylene with challenging polar vinyl monomers. Future work
will focus on exploring the effects of various bulky substituents on catalytic activity and copolymer MW,
as well as on broadening the scope to other commercially available polar comonomers.
1
2
3
4
5
6
7
8
9
4. Experimental Section
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Methods and Materials. All experiments and manipulations sensitive to moisture or air were
performed in an MBraun glovebox or by means of standard Schlenk techniques, unless otherwise noted.
Diethyl ether, nꢀhexane, dichloromethane, and toluene were purified by an MBraun solvent purification
systems. Ethylene (99.9%) was purchased from BF Special Gas Limited Company without any
purification.
Compound
2ꢀ(diphenyphosphanyl)ꢀ6ꢀtertꢀbutylphenol
(1a),
complex
[6ꢀtBuꢀ2ꢀPPh2ꢀC6H3O]Ni(Me)(Py) (2a), Py2Ni(CH3)2, and Py4NiCl2 were synthesized by literature
procedure.12i NiCl2·6H2O was purchased from Chinese Medicine. Polar comonomers methyl acrylate
(MA), nꢀbutyl acrylate (BA), N,Nꢀdimethylacrylamide (DMAA), and nꢀbutyl acrylate (BA) were
distillated over calcium hydride (CaH2) prior to use.
Physical and Analytical measurements. The NMR spectra of obtained (co)polymers and
complexes were recorded on a Bruker 400 MHz spectrometer at room temperature or 120 °C (1H NMR:
31
13
400Hz, P NMR: 162 Hz, C NMR: 101 Hz). Chemical shift values for protons in all spectra are
referenced to the residual proton resonance of chloroformꢀd (δ: 7.26), benzeneꢀd6 (δ: 7.16),
1,1,2,2ꢀtetrachloroethaneꢀd2 (δ: 6.00) and oꢀdichlorobenzeneꢀd4 (δ: 7.14, 7.28, 7.41). Chemical shift
values for carbons in all spectra are also referenced (δ: 77.16 for chloroformꢀd, δ: 128.62 for benzeneꢀd6,
δ: 73.80 for 1,1,2,2ꢀtetrachloroethaneꢀd2, (δ: 132.45, 129.86 (t), 126.86 (t) for oꢀdichlorobenzeneꢀd4).
Gel permeation chromatography (GPC) analyses were performed at 150 °C on a highꢀtemperature
chromatograph (PLꢀGPC 220 type) equipped with three PLgel columns (10 ꢁm MixedꢀB LS type) using
1,2,4ꢀtrichlorobenzene as mobile phase at a rate of 1.0 mL·min−1. Molecular weights were calculated
according the calibration by the polystyrene standard EasiCal PSꢀ1 (PL). DSC measurements were
carried out with a differential scanning calorimeter (Q2000 V24.11 Build 124) under N2 at a heating rate
ACS Paragon Plus Environment

ACS Catalysis
Page 24 of 35
of 20 °C·minꢀ1 from the second scan. Xꢀray data of crystals were collected on a Bruker Smart APEX
diffractometer (Mo Kα radiation, λ = 0.71073Å) with CCD detector at 186 K with the ω scan mode.
Elemental analyses were proceeded on an elemental Vario EL spectrometer. FTꢀIR data of polymer
samples were collected on a BioꢀRad FTSꢀ135 spectrometer (KBr pellet).
1
2
3
4
5
6
7
8
9
Preparation and characterization of ligands and nickel complexes. The ligand 1a and nickel
complex 2a were synthesized as our previous work,12i and all the other ligands (1b–1d) as well as nickel
complexes (2b–2d) were prepared as following similar procedures:
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Synthesis of 2-[(2′,6′-dimethoxybiphenyl-2-yl)phenylphosphanyl]-6-tert-butylphenol (1b). A 100
mL vial was charged with 2ꢀ(2ꢀtertꢀbutylphenoxy)ꢀtetrahydroꢀ2Hꢀpyran (2.34 g, 10 mmol) and 25 mL of
diethyl ether. nꢀBuLi (4.6 mL, 11 mmol, 2.4 M in hexane) was slowly injected dropwise, and the
reaction mixture was stirred for 6 h at 25 °C, yielding suspension A. Meanwhile, another vial was
charged with of 2ꢀbromoꢀ2′,6′ꢀdimethoxybiphenyl (2.9 g, 10 mmol) and 30 mL of THF, and 1.1 equiv of
nꢀBuLi (11 mmol, 2.4 M in nꢀhexane) was added under an ice bath. After stirring for 3 h, the resulting
reaction mixture was slowly transferred to a solution of PPhCl2 (10 mmol, 1.35 mL) in 10 mL of THF
cooled in an ice bath, and then the suspension was stirred for 7 h at 25 °C, yielding reaction mixture B.
Hereafter the suspension A was slowly transferred into B. After reaction for overnight, the solvent was
removed under vacuum by means of a rotary evaporator, and the residue was purified by column
chromatography. The resultant white solid was dissolved in degassed ethyl acetate and mixed with
aqueous HCl. The solution was stirred at room temperature for 5 h before addition of aqueous NaHCO3,
and then extracted with ether. The pure target compound was obtained by column chromatography as a
1
white solid (2.5 g, 53%). H NMR (400 MHz, C6D6): δ 7.49 (dd, J = 7.6, 4.5 Hz, 1H), 7.32 (m, 3H),
7.25 (d, J = 7.7 Hz, 1H), 7.14–6.92 (m, 7H), 6.74 (t, J = 7.6 Hz, 1H), 6.32 (dd, J = 15.2, 8.4 Hz, 2H),
3.14 (d, J = 5.3 Hz, 6H, –OCH3), 1.50 (s, 9H, tꢀBu). 13C NMR (101 MHz, C6D6): δ 158.8, 158.6, 158.3
(d, J = 10.9 Hz), 142.4, 142.1, 136.3 (d, J = 5.5 Hz), 136.1, 135.8, 134.0, 133.9, 133.8, 133.0, 131.7 (d,
J = 6.6 Hz), 129.6, 128.7, 122.5 (d, J = 2.7 Hz), 120.5, 119.5 (d, J = 8.0 Hz), 104.1 (d, J = 4.7 Hz), 55.2
(d, J = 12.1 Hz, –OCH3), 35.1 (d, J = 19 Hz, –C(CH3)3), 30.0 (–C(CH3)3). 31P NMR (162 MHz, C6D6): δ
ACS Paragon Plus Environment

Page 25 of 35
ACS Catalysis
–26.53. Anal. Calcd for C30H31O3P: C, 76.58; H, 6.64. Found: C, 76.79; H, 6.43.
1
2
3
4
5
6
7
8
9
Synthesis of 2-[(biphenyl-2-yl)phenylphosphanyl]-6-tert-butylphenol (1c). Into a 250 mL flask
equipped with PPhCl2 (1.85 g, 10 mmol) and 20 mL of dry THF, a solution of
2ꢀbiphenylmagnesiumbromide (0.5 M, 10 mmol, 20 mL) in diethyl ether was slowly transferred over
0.5 h at –78 °C. After stirring for 2 h at 25 °C, the resulting white suspension was slowly transferred
into the suspension A (10 mmol, the same synthesis as that for compound 1b) at 0 °C, and then the
mixture quickly became clear. After reaction for 6 h, all the solvents of resulting mixture were removed
under vacuum, and the residue were dissolved in 40 mL of degassed ethyl acetate. After the addition of
several drops aqueous HCl, the mixture was reaction for 5 h at room temperature until saturated aqueous
NaHCO3 added, and then extracted with ether. The organic phase was dried over Na2SO4, filtered, and
concentrated under vacuum via a rotary evaporator. The ultimate pure target compound was obtained by
column chromatography as a white solid (1.84 g, 45%). 1H NMR (400 MHz, C6D6): δ 7.34 (dd, J = 6.8,
5.4 Hz, 1H), 7.30–7.22 (m, 3H), 7.18 (m, 3H), 7.14–7.03 (m, 5H), 6.95 (m, 5H), 6.72 (t, J = 7.6 Hz, 1H),
1.46 (s, 9H, –C(CH3)3). 13C NMR (101 MHz, C6D6): δ 158.8 (d, J = 15.1 Hz), 148.5, 148.3, 142.1 (d, J
= 6.3 Hz), 136.4 (d, J = 0.9 Hz), 135.6 (d, J = 3.0 Hz), 135.3 (d, J = 4.9 Hz), 134.0, 133.9 (d, J = 1.5
Hz), 133.5, 130.6, 130.5, 129.8 (d, J = 3.3 Hz), 129.3 (d, J = 5.3 Hz), 128.9, 128.8, 128.1, 127.7, 121.5,
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
31
120.9 (d, J = 1.8 Hz), 35.2 (d, J = 1.8 Hz, –C(CH3)3), 29.8 (–C(CH3)3). P NMR (162 MHz, C6D6): δ
–29.03. Anal. Calcd for C28H27OP: C, 81.93; H, 6.63. Found: C, 81.83; H, 6.82.
Synthesis of 2-[bis(biphenyl-2-yl)phosphanyl]-6-tert-butylphenol (1d). In a 100 mL vial,
2ꢀbromobiphenyl (4.66 g, 20 mmol) was dissolved in 40 mL of diethyl ether, and then nꢀBuLi (4.6 mL,
2.4 M in nꢀhexane, 11 mmol) was slowly added under a dry iceꢀacetone bathing. After reaction for
further 2 h at room temperature, (Et2N)PCl2 (1.74 g, 10 mmol, 0.5 equiv) was added dropwise at that
temperature, and then the reaction mixture was stirred for 5 h at –20 °C (slowly warm to –20 °C).
Ethereal HCl (10 mL, 20 mmol, 2 M in diethyl ether) was slowly added, and the reaction mixture stirred
for 6 h, and then the resulting precipitate was filtered off over Celite under N2 atmosphere. The filtrate
used as obtained as purification was slowly transferred into another vial charged with suspension A (10
ACS Paragon Plus Environment

ACS Catalysis
Page 26 of 35
mmol, the same synthesis as that for compound 1b) at an ice bath, and then the resulting mixture was
warm to 25 °C. After stirring for 10 h, all the solvents were removed under vacuum and the residue was
redissolved in 50 mL of degassed ethyl acetate. After addition of 2 mL of aqueous HCl (5 M in diethyl
ether), the mixture was stirred at ambient temperature for 6 h before aqueous NaHCO3 added, and then
extracted with ether. The organic phase was dried over Na2SO4, filtered and concentrated. Finally, the
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
1
pure target compound was prepared by column chromatography as a white solid (2.08 g, 43%). H
NMR (400 MHz, C6D6): δ 7.38–7.32 (m, 2H), 7.25 (dd, J = 7.7, 1.4 Hz, 1H), 7.10–6.98 (m, 14H), 6.95
(td, J = 7.4, 1.5 Hz, 2H), 6.90 (d, J = 12.1 Hz, 1H), 6.75 (t, J = 7.6 Hz, 1H), 1.47 (s, 9H). 13C NMR (101
MHz, C6D6): δ 159.1, 158.9, 148.3, 148.0, 142.1 (d, J = 6.0 Hz), 136.4 (d, J = 1.0 Hz), 135.0 (d, J = 3.7
Hz), 134.3, 134.3, 130.4 (d, J = 5.2 Hz, 1H), 129.9, 129.8, 129.3, 129.2, 128.0, 121.3, 120.9, 35.2 (d, J
= 2.1 Hz, –C(CH3)3), 29.9 (–C(CH3)3). 31P NMR (162 MHz, C6D6): δ –50.14. Anal. Calcd for C34H31OP:
C, 83.92; H, 6.42. Found: C, 84.01; H, 6.50.
Synthesis of [6-tert-Bu-2-(2-(2’,6’-(MeO)2-C6H3)-C6H4)(Ph)P-C6H3O]Ni(Me)(Py) (2b). To a
stirred solution of Py2NiMe2 (0.15 g, 0.6 mmol) in 10 mL of dry toluene, a solution of ligand 1b (0.24 g,
0.5 mmol) in toluene (10 mL) at room temperature was added over 5 min. After reaction for 5 h, the
resultant nickel black was filtered off through Celite and washed with 3 mL of toluene by two times.
The filtrate was concentrated to about 2 mL, and crystallization by diffusion of nꢀhexane (15 mL) into
1
the clear solution afforded yellowish brown crystals 2b (0.24 g, 76%). H NMR (400 MHz, C6D6): δ
8.50–8.12 (m, 2H), 7.76–7.54 (m, 3H), 7.48 (m, 1H), 7.30 (d, J = 6.5 Hz, 1H), 7.29–7.18 (m, 3H),
7.13–6.88 (m, 4H), 6.80 (m, 1H), 6.68–6.46 (m, 4H), 6.37 (d, J = 8.2 Hz, 1H), 3.37 (s, 3H, (–OCH3),
2.97 (s, 3H, –OCH3), 1.55 (s, 9H, –C(CH3)3), –0.71 (d, J = 4.9 Hz, 3H, Ni–CH3). 13C NMR (101 MHz,
C6D6): δ 174.9 (d, J = 20.8 Hz), 159.7, 158.2, 150.6, 137.4 (d, J = 8.8 Hz), 137.1, 136.6, 136.0, 134.9,
133.3 (d, J = 9.3 Hz), 132.4 (d, J = 9.6 Hz), 130.4, 130.4, 129.9, 129.19, 128.8, 128.6 (d, J = 1.7 Hz),
126.5 (d, J = 6.8 Hz), 122.7 (d, J = 1.5 Hz), 120.2, 119.9 (d, J = 5.1 Hz), 119.7, 113.2 (d, J = 7.7 Hz),
103.0 (d, J = 6.6 Hz), 54.6 (–OCH3), 54.0 (–OCH3), 35.0 (d, J = 1.7 Hz, –C(CH3)3), 29.5 (–C(CH3)3),
ACS Paragon Plus Environment

Page 27 of 35
ACS Catalysis
–14.6 (d, J = 40.0 Hz, Ni–CH3). 31P NMR (162 MHz, C6D6): δ 21.47. Anal. Calcd for C36H38NNiO3P: C,
69.59; H, 6.00; N, 2.25. Found: C, 69.43; H, 6.13; N, 2.19.
1
2
3
4
5
6
7
8
9
Synthesis of [6-tert-Bu-2-(2-C6H5-C6H4)(Ph)P-C6H3O]Ni(Me)(Py) (2c). Complex 2c was prepared
in 86% yield analogously to the synthesis of complex 2b using ligand 1c instead of ligand 1b. 1H NMR
(400 MHz, C6D6): δ 8.43 – 8.29 (m, 2H), 7.78–7.65 (m, 4H), 7.62–7.49 (m, 1H), 7.43 (dd, J = 7.3, 1.0
Hz, 1H), 7.38 (t, J = 7.6 Hz, 2H), 7.28 (m, 2H), 7.20 (t, J = 7.4 Hz, 1H), 7.12 (ddd, J = 7.6, 4.5, 1.4 Hz,
1H), 7.08–6.98 (m, 3H), 6.95 (t, J = 7.6 Hz, 1H), 6.73 (ddd, J = 9.2, 3.2, 1.6 Hz, 1H), 6.64 (td, J = 7.4,
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
13
2.1 Hz, 1H), 6.46–6.40 (m, 2H), 1.61 (s, 9H, –C(CH3)3), –0.84 (d, J = 4.9 Hz, 3H, Ni–CH3). C NMR
(101 MHz, C6D6): δ 175.0, 174.8, 150.9, 148.6, 148.5, 142.9 (d, J = 5.2 Hz), 139.1 (d, J = 8.8 Hz),
136.4, 135.7, 135.2, 135.0 (d, J = 1.2 Hz), 132.8, 132.7, 132.1, 132.0, 131.8, 131.3, 131.1, 131.0, 130.97,
130.4 (d, J = 2.2 Hz), 129.7 (d, J = 1.2 Hz), 129.3 (d, J = 2.1 Hz), 128.9, 128.8, 128.2, 126.9 (d, J = 6.6
Hz), 123.1, 120.6, 120.1, 114.1 (d, J = 7.7 Hz), 35.4 (d, J = 1.9 Hz, –C(CH3)3), 29.9 (–C(CH3)3), –14.28
(d, J = 37.4 Hz, Ni–CH3). 31P NMR (162 MHz, C6D6): δ 25.02. Anal. Calcd for C34H36NNiOP: C, 72.62;
H, 6.09; N, 2.49. Found: C, 72.51; H, 5.97; N, 2.54.
Synthesis of [6-tert-Bu-2-(2-C6H5-C6H4)2P-C6H3O]Ni(Me)(Py) (2d). Complex 2d was prepared in
84% yield analogously to the synthesis of complex 2b using ligand 1d instead of ligand 1b. 1H NMR
(400 MHz, C6D6): δ 8.59–8.49 (m, 2H), 7.87 (broad, 4H), 7.67–7.55 (m, 1H), 7.25–7.17 (m, 6H),
7.14–6.93 (m, 7H), 6.88–6.80 (m, 1H), 6.59–6.54 (m, 2H), 6.38 (td, J = 7.5, 2.2 Hz, 1H), 1.53 (s, 9H,
13
–C(CH3)3), C1.04 (d, J = 5.2 Hz, 3H, Ni–CH3). C NMR (101 MHz, C6D6): δ 172.6, 172.4, 150.6,
147.7, 147.5, 142.3 (d, J = 3.0 Hz), 137.5, 137.4, 136.1, 134.7 (d, J = 3.3 Hz), 133.4, 132.9, 131.9 (d, J
= 7.8 Hz), 129.9, 129.7, 129.0, 126.7, 126.0 (d, J = 7.1 Hz), 122.7 (d, J = 1.4 Hz), 121.6, 121.1, 113.4 (d,
J = 7.8 Hz), 34.8 (d, J = 1.9 Hz, –C(CH3)3), 29.5 (–C(CH3)3), –13.2 (d, J = 37.3 Hz, Ni–CH3). 31P NMR
(162 MHz, C6D6): δ 22.39. Anal. Calcd for C40H38NNiOP: C, 75.25; H, 6.00; N, 2.19. Found: C, 75.51;
H, 5.87; N, 2.24.
Polymerization using well-defined neutral nickel catalysts. Polymerizations was performed in a
200 mL autoclave, which was heated under vacuum at 150 °C for 5 h, and then was cooled to the
ACS Paragon Plus Environment

ACS Catalysis
Page 28 of 35
required temperature. Into the autoclave equipped with a vigorous mechanical stirring motor, toluene
was added under vacuum. A fresh toluene solution of certain amount of catalyst was injected into the
autoclave by a dry syringe. The total volume of the polymerization medium was fixed at 100 mL or 50
mL. The polymerization apparatus was filled with ethylene rapidly to the prescribed pressure, and
maintain at the desired constant pressure. For copolymerization trials, polymerization medium was
preꢀsaturated with ethylene before catalysts added. Then, the comonomer solution was quickly injected
into the autoclave, followed by quickly pressuring of ethylene. After a specified reaction time, the
mechanical stirring motor was quickly stopped, and the remaining ethylene was evacuated. The solid
polymer or copolymer was collected by filtration after precipitation from ethanol, except for
ethylene/MA copolymer precipitation from methanol, washed with acetone, and dried in a vacuum
drying oven at 60 °C.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
ASSOCIATED CONTENT
Supporting Information
In the Supporting Information, details for the characterization of the compounds, representative NMR
spectra, DSC traces, FTꢀIR spectra, and GPC traces of the polymers, and Xꢀray crystallography data are
all supplied. It is available free of charge via the Internet at http://pubs.acs.org.
Corresponding Author
lilypan@tju.edu.cn, ysli@tju.edu.cn.
ACKNOWLEDGMENT
The authors are grateful for subsidy supported by the National Natural Science Foundation of China (No.
21690071).
ACS Paragon Plus Environment

Page 29 of 35
ACS Catalysis
REFERENCES
1
2
3
4
5
6
7
8
(1) (a) Chung, T. C. Functionalization of Polyolefins; Academic Press: London, 2002. (b) Dong, J. Y.;
Hu, Y. L. Design and Synthesis of Structurally Wellꢀdefined Functional Polyolefins via Transition
Metalꢀmediated Olefin Polymerization Chemistry. Coord. Chem. Rev. 2006, 250, 47ꢀ65.
9
(2) (a) Boffa, L. S.; Novak, B. M. Copolymerization of Polar Monomers with Olefins Using
Transitionꢀmetal Complexes. Chem. Rev. 2000, 100, 1479ꢀ1493. (b) Nakamura, A.; Ito, S.; Nozaki, K.
Coordinationꢀinsertion Copolymerization of Fundamental Polar Monomers. Chem. Rev. 2009, 109,
5215ꢀ5244. (c) Mecking, S. Olefin Polymerization by Late Transition Metal Complexes–A Root of
Ziegler Catalysts Gains New Ground. Angew. Chem. Int. Ed. 2001, 40, 534ꢀ540. (d) Nakamura, A.;
Anselment, T. M. J.; Claverie, J.; Goodall, B.; Jordan, R. F.; Mecking, S.; Rieger, B.; Sen, A.; Van
Leeuwen, P.; Nozaki, K. Orthoꢀphosphinobenzenesulfonate: A Superb Ligand for Palladiumꢀcatalyzed
Coordinationꢀinsertion Copolymerization of Polar Vinyl Monomers. Acc. Chem. Res. 2013, 46, 1438ꢀ
1449.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
(3) (a) Drent, E.; van Dijk, R.; van Ginkel, R.; van Oort, B.; Pugh, R. I. Palladium Catalysed
Copolymerisation of Ethene with Alkylacrylates: Polar Comonomer Built into the Linear Polymer Chain.
Chem. Commun. 2002, 744ꢀ745. (b) Kochi, T.; Yoshimura, K.; Nozaki, K. Synthesis of Anionic
Methylpalladium Complexes with Phosphineꢀsulfonate Ligands and Their Activities for Olefin
Polymerization. Dalton Trans. 2006, 25ꢀ27. (c) Skupov, K. M.; Marella, P. R.; Simard, M.; Yap, G. P. A.;
Allen, N.; Conner, D.; Goodall, B. L.; Claverie, J. P. Palladium Aryl Sulfonate Phosphine Catalysts for
the Copolymerization of Acrylates with Ethene. Macromol. Rapid. Commun. 2007, 28, 2033ꢀ2038. (d)
Guironnet, D.; Roesle, P.; Rünzi, T.; GöttkerꢀSchnetmann, I.; Mecking, S. Insertion Polymerization of
Acrylate. J. Am. Chem. Soc. 2009, 131, 422ꢀ423; (e) Skupov, K. M.; Hobbs, J.; Marella, P.; Conner, D.;
Golisz, S.; Goodall, B. L.; Claverie, J. P. Kinetic and Mechanistic Aspects of Ethylene and Acrylates
Catalytic Copolymerization in Solution and in Emulsion. Macromolecules 2009, 42, 6953ꢀ6963. (f)
Neuwald, B.; Ölscher, F.; GöttkerꢀSchnetmann, I.; Mecking, S. Limits of Activity: Weakly Coordinating
Ligands in Arylphosphinesulfonato Palladium(II) Polymerization Catalysts. Organometallics 2012, 31,
3128ꢀ3137. (g) Piche, L.; Daigle, J. C.; Rehse, G.; Claverie, J. P. Structureꢀactivity Relationship of
Palladium Phosphanesulfonates: Toward Highly Active Palladiumꢀbased Polymerization Catalysts.
Chem.-Eur. J. 2012, 18, 3277ꢀ3285.
ACS Paragon Plus Environment