Bimetallic coordination insertion polymerization of unprotected polar monomers: Copolymerization of amino olefins and ethylene by dinickel bisphenoxyiminato catalysts

Article abstract of DOI:10.1021/ja4004816

Dinickel bisphenoxyiminato complexes based on highly substituted p- and m-terphenyl backbones were synthesized, and the corresponding atropisomers were isolated. In the presence of a phosphine scavenger, Ni(COD)₂, the phosphine-ligated syn-dinickel complexes copolymerized α-olefins and ethylene in the presence of amines to afford 0.2-1.3% α-olefin incorporation and copolymerized amino olefins and ethylene with a similar range of incorporation (0.1-0.8%). The present rigid catalysts provide a bimetallic strategy for insertion polymerization of polar monomers without masking of the heteroatom group. The effects of the catalyst structure on the reactivity were studied by comparisons of the syn and anti atropisomers and the p- and m-terphenyl systems.

Full text of DOI:10.1021/ja4004816

Communication
pubs.acs.org/JACS
Bimetallic Coordination Insertion Polymerization of Unprotected
Polar Monomers: Copolymerization of Amino Olefins and Ethylene
by Dinickel Bisphenoxyiminato Catalysts
Madalyn R. Radlauer, Aya K. Buckley, Lawrence M. Henling, and Theodor Agapie*
Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 East California Boulevard, MC 127-72,
Pasadena, California 91125, United States
S
* Supporting Information
We recently reported dinickel bisphenoxyiminato catalysts
ABSTRACT: Dinickel bisphenoxyiminato complexes
based on highly substituted p- and m-terphenyl backbones
were synthesized, and the corresponding atropisomers
were isolated. In the presence of a phosphine scavenger,
Ni(COD)2, the phosphine-ligated syn-dinickel complexes
copolymerized α-olefins and ethylene in the presence of
amines to afford 0.2−1.3% α-olefin incorporation and
copolymerized amino olefins and ethylene with a similar
range of incorporation (0.1−0.8%). The present rigid
catalysts provide a bimetallic strategy for insertion
polymerization of polar monomers without masking of
the heteroatom group. The effects of the catalyst structure
on the reactivity were studied by comparisons of the syn
and anti atropisomers and the p- and m-terphenyl systems.
with pyridine (Py) auxiliary ligands for the copolymerization of
ethylene and α-olefins.8a Permethylation of the central arene of
the p-terphenyl (p-TPh) backbone allowed for the isolation of
syn and anti atropisomers.8a The syn atropisomer 1-s-Py (Figure
1) successfully polymerized ethylene in the presence of up to 500
unctionalized polyolefins have desirable physical properties,
F
including improved adhesion to substrates, response to
stimuli, and increased compatibility with other materials for use
in polymer blends and composites.1 While numerous function-
alized polymers have been synthesized, even on industrial scales,
their synthesis is primarily achieved through radical polymer-
ization or postpolymerization modification, which often provide
only limited control over the polymer microstructure (e.g.,
tacticity, branching, functionality incorporation).1d,f,2 Polymers
generated by coordination polymerization and having polar
groups, including ester,3 amine,3c,i,4 alcohol,2e,3c,f,i,4a,b,d,f,5a,b and
acid3c,f functionalities, have been reported. For insertion
polymerization (IP) of amino olefins (AOs), protection of the
amine or masking with a Lewis acid is common.3c,i,4f,5c IP of α-
olefins functionalized with tertiary amines catalyzed by
zirconocene complexes favors bulky subtituents on the amine
to discourage base coordination to Zr and afford olefin
coordination.4d,e,l,m Herein we present a strategy for AO
copolymerization employing an alternate mechanism in which
inhibitory binding of base to the metal is disfavored by the
proximity of two catalytic sites.
Figure 1. Dinickel bisphenoxyiminato complexes used in this study.
equiv of tertiary amine per Ni center.8b This is notable in view of
reports that related neutral Ni catalysts are more inhibited by
tertiary amines than by water, alcohols, and ethers.9 We attribute
the increased tolerance to a steric effect wherein the binding of an
amine to one Ni center of the syn atropisomer disfavors the
binding of an amine to the other Ni, allowing the polymerization
to continue.8b We expected this effect to allow for the
incorporation of polar monomers, but the inherently low
turnover and low levels of α-olefin incorporation of these
catalysts precluded AO polymerization.
Multinuclear late-transition-metal catalysts have recently been
used to incorporate polar olefins by coordination IP.6 Such
catalysts are generally more tolerant of polar groups because of
their reduced oxophilicity.3b,f−h,7 In addition, their multinuclear
nature has been proposed to disfavor the formation of stable
chelates that can slow polymerization after polar olefin
insertion.6a Bimetallic Ni complexes have thus been studied for
the polymerization of olefins, including polar monomers.6b
A variant of our bimetallic complex with a different auxiliary
ligand was targeted because the stability of the Py-ligated
complexes causes lower activity.10 A variety of mono- and
Received: January 15, 2013
Published: February 20, 2013
© 2013 American Chemical Society
3784
dx.doi.org/10.1021/ja4004816 | J. Am. Chem. Soc. 2013, 135, 3784−3787

Journal of the American Chemical Society
Communication
dinickel alkyl phenoxyiminato complexes with Py, amine, nitrile,
and phosphine auxiliary ligands have been employed as catalyst
precursors.6c,9a,10 No activator or scavenger is needed for Py,
amine, or nitrile auxiliary ligands, and the precursor behaves as a
single-component catalyst.8a,9a,10,11 For phosphine-ligated com-
plexes, Ni(COD)2 and B(C6F5)3 were used as phosphine
scavengers.6c,9a,12 The PMe3-ligated complexes 1-s and 1-a
(Figure 1) were synthesized by deprotonation of the syn and anti
p-terphenyl bisphenoxyimines, respectively, and subsequent
metalation with NiClMe(PMe3)2. In ethylene/1-hexene copoly-
merization, 1-s displayed a significant increase in activity (>2
orders of magnitude) relative to 1-s-Py (Table 1, entries 1−3).
Figure 2. Solid-state structure of 1-s with thermal ellipsoids at the 50%
probability level. H atoms have been omitted for clarity.
a
Table 1. Ethylene/1-Hexene Copolymerizations
b
c
d
complex
additive
yield (g)
a
R
%I
longer in 1-s (8.9 Å) than in 1-s-Py (7.1 Å).8b This likely occurs
because the PMe3 ligands have a relatively conical steric profile,
whereas the planar Py ligands of 1-s-Py can avoid steric
repulsion. The structural distortion of the ligand framework
supports our proposal that the decreased inhibition by amines
with the syn isomer versus the anti isomer is due to steric
repulsion that hinders binding of amines at both Ni centers.
The five PMe3-ligated dinickel complexes displayed similar
activities and 1-hexene incorporation in ethylene/1-hexene
copolymerizations (Table 1, entries 3−7). The generated
polymer contains primarily methyl and butyl branches, similar
to the Py-ligated analogues, and up to 1.2% incorporation of 1-
hexene (as calculated from 1H and 13C NMR data).8a
Polymerizations run over different time periods indicated that
the catalysts continued to produce polymer over the course of the
trial (Tables S3 and S4 in the SI).14 Ethylene/1-hexene
copolymerizations in the presence of tertiary amines revealed
distinct inhibition trends. As expected from our previous studies
of the Py-ligated catalysts,8b the anti atropisomers were much
more inhibited than the syn isomers but their incorporation of 1-
hexene was not significantly affected (e.g., entries 13−16). 2-s
and 2-s-OMe, which experienced the least inhibition of activity,
produced polymers with the lowest levels of 1-hexene
incorporation (e.g., entries 15 and 17). The relative activities
can be rationalized by the mechanistic proposal that steric
interactions disfavor the binding of amines to both Ni centers in
the syn complex.8b Thus, a shorter Ni−Ni distance should
disfavor the binding of a second amine, as observed for 2-s.
For 2-s, where the metal centers are closest, the presence of
amines cause the greatest decrease in 1-hexene incorporation
(from 1.1 to 0.2−0.3%; Table 1, entries 5, 10, 15, 20, and 25). For
1-s, the 1-hexene incorporation dropped only from 1.2 to 0.8−
1.0% (entries 3, 8, 13, and 18), but there was a greater activity
decrease than for 2-s. The steric considerations for simultaneous
binding of two amines also apply to the relative binding of
ethylene and 1-hexene when one amine is coordinated. For the
closely spaced metal centers in 2-s, amine coordination more
strongly affects binding at the second metal site, resulting in less
favorable 1-hexene coordination than for 1-s. Variation in 1-
hexene incorporation is expected to affect the catalyst activity, as
previous reports indicated that the overall activity of the catalyst
decreased significantly when an α-olefin was copolymerized with
ethylene relative to the homopolymerization of ethylene.8a,11a,15
Ethylene/1-hexene copolymerizations with 2-s and 2-s-OMe in
the presence of amines resulted in different levels of
incorporation of 1-hexene and a divergent trend in the activity
(2-s-OMe produced more polymer in the presence of NnPr3 than
in the presence of NMenPr2, opposite to what was seen with 2-s;
e
1
2
1-s-Py
1-s-Py
1-s
none
0.003
0.033
1.266
1.590
1.444
1.469
1.095
0.187
0.106
0.199
0.087
0.142
0.073
0.011
0.447
0.006
0.457
0.094
0.005
0.783
1
−
f
none
1
1.0
1.2
1.1
1.1
1.0
0.9
0.8
0.5
0.3
0.9
0.7
1.0
1.3
0.3
−
e
3
none
317
397
361
367
274
23
13
25
11
18
9
e
4
1-a
none
e
5
2-s
none
e
6
2-a
none
e
7
2-s-OMe
1-s
none
8
NMeEt2
NMeEt2
NMeEt2
NMeEt2
NMeEt2
NEt3
13
30
15
34
17
33
290
7
9
1-a
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
2-s
2-a
2-s-OMe
1-s
1-a
NEt3
1
2-s
NEt3
56
1
2-a
NEt3
515
5
2-s-OMe
1-s
NEt3
57
12
1
0.7
0.9
1.2
0.2
−
NMenPr2
NMenPr2
NMenPr2
NMenPr2
NMenPr2
NnPr3
26
639
4
1-a
2-s
98
−
21
g
2-a
−
−
14
2-s-OMe
1-s
0.165
0.7
g
−
−
−
−
56
−
−
6
−
−
g
1-a
NnPr3
2-s
NnPr3
0.447
0.2
g
2-a
NnPr3
−
−
49
−
6
−
2-s-OMe
NnPr3
0.390
0.5
a
Polymerizations were run for 1 h at 25 °C under ethylene (100 psig)
in toluene with 4 μmol of dinickel complex, 4 equiv of Ni(COD)2, and
500 equiv of 1-hexene and additive per Ni. Solution volume = 5 mL.
Activity, defined as mass of polymer (in g) per mmol of Ni per hour.
b
c
d
R = (activity without additive)/(activity with additive). Mole percent
incorporation of 1-hexene as determined from 1H and 13C NMR
e
f
spectroscopy. Polymerization was run for 0.5 h. Polymerization was
run for 3 h to get enough polymer for H and 13C NMR spectra.
1
g
Insufficient product for accurate mass determination (<1 mg).
Complexes 2 (Figure 1), the m-TPh analogues of 1, were
synthesized to examine the effects of changing the Ni−Ni
distance and the relative orientation of the Ni coordination
planes. The orientation of 2-s-OMe was verified by nuclear
Overhauser effect spectroscopy [Figure S45 in the Supporting
Information (SI)]. The solid-state structures of 1-s and 2-s
confirmed the syn orientation relative to the central ring and the
coordination of the PMe3 groups trans to the imines (Figures 2
and S76).13 The Ni−Ni distances are >8 Å, and the TPh
backbones are bowed (average TPh backbone angle of 171° for
1-s vs 177° for 1-s-Py).8b The Ni−Ni distance is significantly
3785
dx.doi.org/10.1021/ja4004816 | J. Am. Chem. Soc. 2013, 135, 3784−3787

Journal of the American Chemical Society
Communication
Table 1, entries 20, 22, 25, and 27). These dissimilarities between
the two syn complexes with m-TPh backbones suggest that
subtle differences in the sterics affect the polymerization behavior
and that tuning of the ligand framework may allow for
optimization of the polymerization.
The ability of the reported complexes to incorporate 1-hexene
in the presence of amines suggested that these complexes might
be effective for the polymerization of AOs. AO substrates were
selected to have ethyl or propyl substituents on the basis of the
ability of the syn catalysts to perform ethylene/1-hexene
copolymerizations in the presence of such tertiary amines
(Table 1). Indeed, the use of a variety of tertiary AOs (500 equiv)
in copolymerizations with ethylene resulted in incorporation
levels similar to those for 1-hexene (0.4−0.8 and 0.3−0.4% with
1-s and 2-s, respectively; Table 2, entries 3−14). Incorporation
same range as for 1-hexene. The possibility that the
incorporation of amines could lead to the formation of chelates
that would inhibit polymerization or lead to termination was
considered. The AO monomers were examined by 1D total
correlation NMR spectroscopy (TOCSY) and compared with
the polymers. The TOCSY spectra of the AO precursors showed
correlations between the NCH2 peak and the olefinic peaks that
were not observed for the polymers, indicating that the polymers
were not terminated by the amine monomers (Figure S74).
The similar levels of incorporation of AO and 1-hexene (in the
presence of tertiary amines) and the activity profiles in
copolymerizations with various catalysts support a related
mechanism of polymerization for the two cases (Scheme 1).
Scheme 1. Mechanism for Ethylene/AO Copolymerization
a
Table 2. Ethylene/Amino Olefin Copolymerizations
b
c
complex
comonomer
yield (g)
a
%I
1
2
1-s
N(allyl)nPr2
0.034
0.083
0.019
0.044
0.064
0.178
0.063
0.217
0.059
0.310
0.050
0.398
0.034
0.151
8
0.0
0.1
0.4
0.4
0.5
0.3
0.7
0.3
0.8
0.3
0.7
0.3
0.5
0.3
2-s
N(allyl)nPr2
21
5
3
1-s
N(butenyl)nPr2
N(butenyl)nPr2
N(pentenyl)nPr2
N(pentenyl)nPr2
N(hexenyl)nPr2
N(hexenyl)nPr2
N(heptenyl)nPr2
N(heptenyl)nPr2
N(octenyl)nPr2
N(octenyl)nPr2
N(pentenyl)Et2
N(pentenyl)Et2
N(pentenyl)nPr2
N(pentenyl)nPr2
N(pentenyl)nPr2
4
2-s
11
16
45
16
54
15
78
13
100
8
5
1-s
6
2-s
7
1-s
8
2-s
9
1-s
10
11
12
13
14
15
16
17
2-s
1-s
2-s
1-s
2-s
38
d
d
d
1-a
2-a
2-s-OMe
−
0.032
−
−
0.7
Coordination of the amine moiety to Ni sterically hinders
binding of an amine to the second Ni center for the syn
complexes. Ethylene or the olefin moiety of the polar monomer
have a lower steric profile than the amine and hence can
coordinate to the second Ni and afford chain growth.
8
0.176
44
0.3
a
Polymerizations were run for 0.5 h at 25 °C under ethylene (100
psig) in toluene with 4 μmol of dinickel complex, 4 equiv of
Ni(COD)2, and 500 equiv of comonomer per Ni. Solution volume = 5
b
c
The incorporation of AOs with the present catalysts is notable
for several reasons. Monometallic neutral Ni catalysts are greatly
inhibited by amines, as reported previously9a and also observed
for 1-a-Py,8b 1-a, and 2-a relative to the syn analogues. The
proposed mechanism for polymerization and polar olefin
incorporation relies on two Ni centers but is distinct from
previous proposals.6 Other dinickel complexes have been
claimed to incorporate polar monomers by a mechanism in
which insertion of the monomer into the polymer growing at one
Ni center is followed by coordination of the polar moiety to the
second Ni center, thereby avoiding chelation that would slow the
polymerization.6a Also, greater incorporation of various mono-
mers was explained by concomitant coordination of a CH bond
or polar group to one Ni center and an olefin to the other, thus
favoring comonomer coordination and insertion.6a,c The
mechanism at work with the present catalysts is not consistent
with those proposals because the Ni centers are likely too distant
for a single monomer to coordinate to both. Moreover, for those
proposed mechanisms, varying the number of CH2 groups
between the amine and olefin functionalities should have a
significant effect on the degree of polar monomer incorporation,
which was not observed here (Table 2).
mL. Mass of polymer (in g) per mmol of Ni per hour. Mole percent
incorporation of comonomer as determined by 1H NMR spectroscopy.
d
Insufficient product for accurate mass determination (<1 mg).
of N(allyl)nPr2 was not successful with 1-s, but 0.1%
incorporation was achieved using 2-s. The proximity of the
large NnPr2 moiety at the allylic position likely hinders binding of
olefin to the metal and insertion. All of the longer-chain olefins
were incorporated by both 1-s and 2-s. The number of CH2 units
between the olefin and amine moieties (beyond allylamine) did
not significantly affect the level of polar monomer incorporation.
Copolymerizations of ethylene and N(pentenyl)nPr2 performed
with 1-a, 2-a, and 2-s-OMe yielded no polymer, 6 times less
polymer than with 2-s with 0.7% incorporation, and results
similar to those for 2-s, respectively (entries 15−17).
Diffusion-ordered NMR spectroscopy confirmed that the
amines were incorporated into the polymers (see Figures S72
and S73). The diffusion constant for the CH2 peak of the
polymer chain (at 1.4 ppm in C2Cl4D2) matched the diffusion
constant for the NCH2 peaks (at 3.0 ppm). AO incorporation
levels were lower and the activities higher with 2-s than with 1-s
for all of the polar monomers investigated, mirroring the
copolymerizations with 1-hexene in the presence of amines (vide
supra). The levels of polar monomer incorporation were in the
The proposed mechanism (Scheme 1) is expected to extend to
other classes of polar monomers. Binding of polar olefins
through the heteroatom instead of the olefin typically leads to
3786
dx.doi.org/10.1021/ja4004816 | J. Am. Chem. Soc. 2013, 135, 3784−3787

Journal of the American Chemical Society
Communication
Commun. 2002, 744. (e) Szuromi, E.; Shen, H.; Goodall, B. L.; Jordan, R.
F. Organometallics 2008, 27, 402. (f) Nakamura, A.; Ito, S.; Nozaki, K.
Chem. Rev. 2009, 109, 5215. (g) Chen, E. Y. X. Chem. Rev. 2009, 109,
5157. (h) Guironnet, D.; Roesle, P.; Runzi, T.; Gottker-Schnetmann, I.;
Mecking, S. J. Am. Chem. Soc. 2009, 131, 422. (i) Ito, S.; Kanazawa, M.;
Munakata, K.; Kuroda, J.-i.; Okumura, Y.; Nozaki, K. J. Am. Chem. Soc.
2011, 133, 1232.
different steric profiles around the metal center. In the present
design, binding of the olefin orients the substituents in the plane
perpendicular to the metal−olefin interaction and away from the
second metal center. Conversely, coordination of the amine (or
other polar) moiety would be expected to direct the steric bulk
toward the second metal center. Hence, judicious design of the
metal−metal distance and ligand steric properties could be
employed for the copolymerization of other polar olefins.
In summary, we have synthesized a series of rigid terphenyl
dinickel bisphenoxyiminato complexes with phosphine auxiliary
ligands that exhibit activity for copolymerization of ethylene and
amino olefins. The syn complexes are more active than the anti
analogues because of a bimetallic effect arising from the
proximity of the Ni centers. The polar monomers and 1-hexene
are incorporated at similar levels. Comparisons between the m-
and p-TPh catalyst systems support a mechanism in which
inhibitory coordination of amines at both Ni centers is disfavored
because of steric repulsion. Thus, coordination of olefin moieties
with smaller steric profiles is favored, allowing for polymer
formation and polar monomer incorporation. Future efforts will
focus on extending the present approach for polar olefin
polymerization to other monomers and catalyst types in order
to increase the level of functional group incorporation, catalyst
activity, and tolerance of other polar groups.
(4) (a) Giannini, U.; Bruckner, G.; Pellino, E.; Cassata, A. J. Polym. Sci.,
Part B: Polym. Lett. 1967, 5, 527. (b) Giannini, U.; Bruckner, G.; Pellino,
E.; Cassata, A. J. Polym. Sci., Part C: Polym. Symp. 1968, 22, 157.
(c) Giannini, U.; Bruckner, G. U.S. Patent 3,476,726, 1969. (d) Kesti, M.
R.; Coates, G. W.; Waymouth, R. M. J. Am. Chem. Soc. 1992, 114, 9679.
(e) Stehling, U. M.; Stein, K. M.; Kesti, M. R.; Waymouth, R. M.
Macromolecules 1998, 31, 2019. (f) Hagihara, H.; Tsuchihara, K.;
Sugiyama, J.; Takeuchi, K.; Shiono, T. Macromolecules 2004, 37, 5145.
(g) Hakala, K.; Helaja, T.; Lofgren, B. Polym. Bull. 2001, 46, 123.
(h) Mustonen, I.; Hukka, T.; Pakkanen, T. Macromol. Rapid Commun.
2000, 21, 1286. (i) Naga, N.; Toyota, A.; Ogino, K. J. Polym. Sci., Part A:
Polym. Chem. 2005, 43, 911. (j) Park, M. H.; Huh, J. O.; Do, Y.; Lee, M.
H. J. Polym. Sci., Part A: Polym. Chem. 2008, 46, 5816. (k) Schneider, M.
J.; Schafer, R.; Mulhaupt, R. Polymer 1997, 38, 2455. (l) Stehling, U. M.;
Malmstrom, E. E.; Waymouth, R. M.; Hawker, C. J. Macromolecules
1998, 31, 4396. (m) Stehling, U. M.; Stein, K. M.; Fischer, D.;
Waymouth, R. M. Macromolecules 1999, 32, 14. (n) Wilen, C. E.; Auer,
M.; Stranden, J.; Nasman, J. H.; Rotzinger, B.; Steinmann, A.; King, R.
E.; Zweifel, H.; Drewes, R. Macromolecules 2000, 33, 5011.
(5) (a) Hagihara, H.; Tsuchihara, K.; Sugiyama, J.; Takeuchi, K.;
Shiono, T. J. Polym. Sci., Part A: Polym. Chem. 2004, 42, 5600.
(b) Hagihara, H.; Tsuchihara, K.; Takeuchi, K.; Murata, M.; Ozaki, H.;
Shiono, T. J. Polym. Sci., Part A: Polym. Chem. 2004, 42, 52. (c) Dong, J.
Y.; Wang, Z. M.; Hong, H.; Chung, T. C. Macromolecules 2002, 35, 9352.
(6) (a) Rodriguez, B. A.; Delferro, M.; Marks, T. J. J. Am. Chem. Soc.
2009, 131, 5902. (b) Delferro, M.; Marks, T. J. Chem. Rev. 2011, 111,
2450. (c) Rodriguez, B. A.; Delferro, M.; Marks, T. J. Organometallics
2008, 27, 2166.
(7) (a) Ittel, S. D.; Johnson, L. K.; Brookhart, M. Chem. Rev. 2000, 100,
1169. (b) Stockland, R. A.; Foley, S. R.; Jordan, R. F. J. Am. Chem. Soc.
2003, 125, 796. (c) Heyndrickx, W.; Occhipinti, G.; Bultinck, P.; Jensen,
V. R. Organometallics 2012, 31, 6022.
(8) (a) Radlauer, M. R.; Day, M. W.; Agapie, T. Organometallics 2012,
31, 2231. (b) Radlauer, M. R.; Day, M. W.; Agapie, T. J. Am. Chem. Soc.
2012, 134, 1478.
(9) (a) Younkin, T. R.; Conner, E. F.; Henderson, J. I.; Friedrich, S. K.;
Grubbs, R. H.; Bansleben, D. A. Science 2000, 287, 460. (b) Bauers, F.
M.; Mecking, S. Macromolecules 2001, 34, 1165.
(10) Wehrmann, P.; Mecking, S. Organometallics 2008, 27, 1399.
(11) (a) Connor, E. F.; Younkin, T. R.; Henderson, J. I.; Hwang, S. J.;
Grubbs, R. H.; Roberts, W. P.; Litzau, J. J. J. Polym. Sci., Part A: Polym.
Chem. 2002, 40, 2842. (b) Zuideveld, M. A.; Wehrmann, P.; Rohr, C.;
Mecking, S. Angew. Chem., Int. Ed. 2004, 43, 869.
ASSOCIATED CONTENT
* Supporting Information
■
S
Experimental procedures and additional data. This material is
available free of charge via the Internet at http://pubs.acs.org.
AUTHOR INFORMATION
Corresponding Author
agapie@caltech.edu
■
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
We thank Caltech and Dow Chemical for funding.
■
REFERENCES
■
(1) (a) Koning, C.; van Duin, M.; Pagnoulle, C.; Jerome, R. Prog.
Polym. Sci. 1998, 23, 707. (b) Ren, Y.; Jiang, X.; Liu, R.; Yin, J. J. Polym.
Sci., Part A: Polym. Chem. 2009, 47, 6353. (c) Ren, Y.; Jiang, X.; Yin, J. J.
Polym. Sci., Part A: Polym. Chem. 2009, 47, 1292. (d) Meyer, J.; Keul, H.;
Moeller, M. Macromolecules 2011, 44, 4082. (e) Dhende, V. P.; Samanta,
S.; Jones, D. M.; Hardin, I. R.; Locklin, J. ACS Appl. Mater. Interfaces
2011, 3, 2830. (f) Jones, E. R.; Semsarilar, M.; Blanazs, A.; Armes, S. P.
Macromolecules 2012, 45, 5091. (g) Zhang, C.; Maric, M. J. Polym. Sci.,
Part A: Polym. Chem. 2012, 50, 4341. (h) Yang, Y.; Mijalis, A. J.; Fu, H.;
Agosto, C.; Tan, K. J.; Batteas, J. D.; Bergbreiter, D. E. J. Am. Chem. Soc.
2012, 134, 7378.
(12) (a) Connor, E. F.; Younkin, T. R.; Henderson, J. I.; Waltman, A.
W.; Grubbs, R. H. Chem. Commun. 2003, 2272. (b) Sujith, S.; Joe, D. J.;
Na, S. J.; Park, Y. W.; Chow, C. H.; Lee, B. Y. Macromolecules 2005, 38,
10027.
(13) The quality of the data set for 2-s precluded the determination of
anisotropic structural parameters.
(14) The one exception to this behavior was ethylene/AO
copolymerizations with 1-s, for reasons that are unclear at this time.
(15) Wehrmann, P.; Zuideveld, M.; Thomann, R.; Mecking, S.
Macromolecules 2006, 39, 5995.
(2) (a) Imuta, J.; Kashiwa, N.; Toda, Y. J. Am. Chem. Soc. 2002, 124,
1176. (b) Amin, S. B.; Marks, T. J. Angew. Chem., Int. Ed. 2008, 47, 2006.
(c) Itagaki, K.; Nomura, K. Macromolecules 2009, 42, 5097.
(d) Alidedeoglu, A. H.; York, A. W.; McCormick, C. L.; Morgan, S. E.
J. Polym. Sci., Part A: Polym. Chem. 2009, 47, 5405. (e) Nomura, K. J.
Synth. Org. Chem., Jpn. 2010, 68, 1150. (f) Hibi, Y.; Ouchi, M.;
Sawamoto, M. Angew. Chem., Int. Ed. 2011, 50, 7434. (g) Janoschka, T.;
Teichler, A.; Krieg, A.; Hager, M. D.; Schubert, U. S. J. Polym. Sci., Part A:
Polym. Chem. 2012, 50, 1394.
(3) (a) Holler, H. V.; Youngman, E. A. U.S. Patent 3,761,458, 1973.
(b) Johnson, L. K.; Mecking, S.; Brookhart, M. J. Am. Chem. Soc. 1996,
118, 267. (c) Boffa, L. S.; Novak, B. M. Chem. Rev. 2000, 100, 1479.
(d) Drent, E.; van Dijk, R.; van Ginkel, R.; van Oort, B.; Pugh, R. I. Chem.
3787
dx.doi.org/10.1021/ja4004816 | J. Am. Chem. Soc. 2013, 135, 3784−3787