Polyethylene as a Cosolvent and Catalyst Support in Ring-Opening Metathesis Polymerization

Article abstract of DOI:10.1021/acs.macromol.5b01141

Polyethylene oligomers (PE_Olig) can be used as cosolvents and sometimes soluble catalyst supports in ring-opening metathesis polymerization (ROMP) reactions. As a catalyst support, this polyolefin serves as an N-heterocyclic carbene ligand for a ROMP catalyst, making it soluble at 70 °C and insoluble at room temperature. As a cosolvent, unfunctionalized PE oligomers facilitate quantitative separation of PE_Olig-bound Ru-catalyst residues from polymer products. In these cases, the insolubility of the unfunctionalized polyethylene (Polywax) and its entrapment of the PE_Olig-supported Ru residue in the product phase at room temperature afford ROMP products with Ru contamination lower than other procedures that use soluble catalysts. These separations require only physical processes to separate the product and catalyst residues - no additional solvents are necessary. Control experiments suggest that most (ca. 90%) of the Ru leaching that is seen results from Ru byproducts formed in the vinyl ether quenching step and not from the polymerization processes involving the PE_Olig-supported Ru complex. (Chemical Equation Presented).

Full text of DOI:10.1021/acs.macromol.5b01141

Article
pubs.acs.org/Macromolecules
Polyethylene as a Cosolvent and Catalyst Support in Ring-Opening
Metathesis Polymerization
Jakkrit Suriboot,† Christopher E. Hobbs,‡ William Guzman,† Hassan S. Bazzi,*,§
and David E. Bergbreiter*,†
†Department of Chemistry, Texas A&M University, College Station, Texas 77840, United States
‡Department of Chemistry, Texas A&M University, Kingsville, Texas 78363-8202, United States
§Department of Chemistry, Texas A&M University at Qatar, P.O. Box 23874, Doha, Qatar
S
* Supporting Information
ABSTRACT: Polyethylene oligomers (PEOlig) can be used as
cosolvents and sometimes soluble catalyst supports in ring-
opening metathesis polymerization (ROMP) reactions. As a
catalyst support, this polyolefin serves as an N-heterocyclic
carbene ligand for a ROMP catalyst, making it soluble at 70 °C
and insoluble at room temperature. As a cosolvent,
unfunctionalized PE oligomers facilitate quantitative separation
of PEOlig-bound Ru-catalyst residues from polymer products.
In these cases, the insolubility of the unfunctionalized
polyethylene (Polywax) and its entrapment of the PEOlig
-
supported Ru residue in the product phase at room
temperature afford ROMP products with Ru contamination
lower than other procedures that use soluble catalysts. These
separations require only physical processes to separate the product and catalyst residuesno additional solvents are necessary.
Control experiments suggest that most (ca. 90%) of the Ru leaching that is seen results from Ru byproducts formed in the vinyl
ether quenching step and not from the polymerization processes involving the PEOlig-supported Ru complex.
leaching that was reported to be 2.8%.11 Another alternative
INTRODUCTION
■
approach for CM and RCM reactions is to design more and
more active catalysts. This approach addresses this issue best
since highly active catalysts with catalyst loadings of <0.01 mol
% used in a reaction of a 0.2 M substrate lead to less than 1
ppm Ru contamination. However, a more active catalyst does
not address this problem in polymerization chemistry. The
situation is especially different in polymerization reactions when
the polymer products have modest degrees of polymerization.
In the absence of chain transfer reactions, ROMP chemistry
with a living Ru catalyst will produce 1 mmol of Ru/mmol of
product. Thus, a polymerization reaction often leads to higher
levels of Ru contamination.
Our groups and others have been interested in the
development of recyclable/reusable ring-closing metathesis
(RCM) catalysts7,8 as well as in developing procedures for
ROMP that eliminate Ru contamination in products while
minimizing the use of additional solvents or processing steps.12
We recently showed that a polyisobutylene-supported
Hoveyda−Grubbs catalyst can be used in ROMP reactions of
various monomers.12 This soluble PIB-phase anchored NHC-
Olefin metathesis is ubiquitous both as a methodology for the
synthesis of low molecular weight fine chemicals and for the
synthesis of designer macromolecules using cross metathesis
(CM), ring-closing metathesis (RCM), and polymerization
chemistry including both ring-opening metathesis polymer-
ization (ROMP) and acyclic diene metathesis polymerization
(ADMET).1 However, the presence of Ru residues in the
products remains a challenge.2 In the case of products from
RCM and CM, Ru contamination is a problem because of the
undesirability of heavy metals especially in drug candidates.2 Ru
catalyst residues can also lead to undesirable postsynthesis
reactions like alkene isomerization.3 This problem has been
addressed in several ways. Sequestration of Ru residues by a
postreaction cleanup step is one approach to reduce Ru
contamination in products.4 We and others have also described
using supported catalysts that separate catalysts from products
either by solid−liquid or liquid−liquid separations.5−11 For
example, Balcar and Skowerski described using mesoporous
molecular sieves in both RCM with Ru leaching that ranged
from 0.3 to 3% of the charged Ru catalyst, and Grubbs has
reported Ru leaching as low as 0.01% of the charged catalyst
(<5 ppb Ru content in the product solution for catalysis with
0.4 mol % of Ru) for a silica-supported RCM catalyst. Similar
approaches for ROMP chemistry were less successful with Ru
Received: May 27, 2015
Revised: July 22, 2015
© XXXX American Chemical Society
A
DOI: 10.1021/acs.macromol.5b01141
Macromolecules XXXX, XXX, XXX−XXX

Macromolecules
Article
Scheme 1. Synthesis of PEOlig-Supported Hoveyda−Grubbs Second-Generation Catalyst 7
ligated catalyst allows for polymerizations to proceed normally.
It then facilitates the sequestration and separation of nonpolar
PIB-NHC-ligated Ru contaminants from the more polar
ROMP polymers using a biphasic solvent extraction method.12
Here we describe a significantly improved thermomorphic
separation system that separates >99.5% of catalyst residues
from products without using excess solvent by using
unfunctionalized polyethylene oligomers (Polywax) as a
cosolvent with a polyethylene (PEOlig)-NHC ligated metathesis
catalyst previously described by our lab.8 While this system
requires elevated temperatures to dissolve the PE oligomers
which could be a problem for some catalysts, it overall leads to
polymer products with lower Ru contamination.
Scheme 2. Synthesis Route to Monomers 10−14
RESULTS AND DISCUSSION
■
The PEOlig-supported Hoveyda−Grubbs second generation
catalyst 7 that we used in this paper for ROMP reactions was
synthesized from the commercially available PEOlig-alcohol (1)
and N-Boc-4-amino-3,5-xylenol (2) using a Mitsunobu reaction
to form the PEOlig-aniline (3). After formation of the protected
arylamine, deprotection led to the aniline 3 which was used to
form PEOlig-bisimine (4). The bright yellow powder so formed
was then reduced using excess BH3·SMe2 in THF to form the
PEOlig-bisamine (5). Treatment of 5 with CH(OEt)3, NH4BF4,
was suspended in ca. 5 g of THF, and the resulting suspension
was heated to 80 °C until a solution formed. This solution was
then stirred for 1 h, at which point it was cooled. This led to
precipitation of 7. We initially hoped to simply separate this
precipitate of 7 from the solution, but the precipitate that
formed contained very fine particles that were difficult to
separate. Filtration of these solutions followed by inductively
coupled plasma mass spectrometry (ICP-MS) analyses of the
residue showed Ru contamination at levels that seemingly
randomly varied from 4 to 16 ppm (ca. 2−8% Ru leaching).
While this is only a modest amount of leaching, the variability
from experiment to experiment was problematic. To alleviate
this problem, we added a small amount of narrow dispersity
polyethylene (PE) oligomer as a cosolvent (Polywax-400, PDI
1.08). We and others had previously used this strategy of
adding unfunctionalized polyethylene to increase the mass of
the recovered catalyst which facilitates catalyst recycling and
separation. We had also shown that this type of unfunction-
alized PE was itself an alternative to heptane as a hydrocarbon
solvent in recycling similar Ru catalysts in RCM chemistry.17−19
In this second experiment, 0.01 mmol of the Ru complex 7 (ca.
1 mg of Ru) and 100 mg of Polywax 400 were suspended in ca.
and a catalytic amount of formic acid formed the PEOlig
-
imidazolinium salt 6. The catalyst 7 was then synthesized by the
addition of KHMDS and Hoveyda−Grubbs first-generation
catalyst to PEOlig-imidazolinium salt, as shown in Scheme 1.8
The ROMP monomers used in this study were synthesized
as shown in Scheme 2 using known reactions. Diels−Alder
reactions of maleic anhydride with cyclopentadiene or furan
afforded anhydrides 8 or 910,11 that were in turn used to
prepare monomers 10, 11, and 12 by reactions with MeOH or
PhCH2NH2.12−14 Monomer 13 was prepared using SN2
chemistry from furan−maleimide Diels−Alder adduct, and
monomer 14 was prepared by a Diels−Alder reaction of N-
phenylmaleimide with furan in toluene.15,16
To test whether a thermomorphic PEOlig-bound Ru alkylidine
complex could be effectively quenched with vinyl ether and to
determine if the Ru residues could be easily separated from
products, we carried out two control reactions. In the first
experiment, 0.01 mmol of the Ru complex 7 (ca. 1 mg of Ru)
B
DOI: 10.1021/acs.macromol.5b01141
Macromolecules XXXX, XXX, XXX−XXX

Macromolecules
Article
Scheme 3. Scheme To Examine Ru Leaching from 7, from Residues of 7 Formed in a Butyl Vinyl Ether (BVE) Quenching Step,
and from a Polymerization Using 7
5 g of THF, and the resulting suspension was heated to 80 °C
until a solution formed. This solution was also stirred for 2 h, at
which point it was cooled, and the resulting coprecipitate of 7/
Polywax proved much easier to filter through Celite and a 0.2
μm filter. The resulting THF solution contained only 0.08 ppm
Ru (0.04% of the starting Ru). A second control experiment
was also carried out. Since the ROMP experiments below
require reaction of the terminal Ru vinylidene on the polymer
with alkyl vinyl ether, we carried out a second control
experiment that was identical to the first experiment but that
included a step where the solution of the hot Ru complex 7 was
allowed to react with excess butyl vinyl ether. This simulating
the step where vinyl ether cleaves the Ru from the polymer
chain at 80 °C. As was the case in the first control experiment
above, this solution was cooled to form a coprecipitate of the
residues of Ru complex 7 and Polywax. Filtration of these
residues through Celite and a 0.2 μm filter yielded a THF
filtrate that contained 0.84 ppm Ru (0.42% of the starting Ru).
This ca. 10-fold increase in Ru residues still yields a solution
with minimal Ru leaching. We presume some soluble Ru
byproduct or byproducts formed in this quenching reaction but
did not attempt to determine the structure of the ca. 0.5% of
this soluble Ru byproduct.
Our initial studies of the utility of PEOlig supports in
minimizing Ru leaching in ROMP used the PEOlig-supported
Hoveyda−Grubbs second-generation catalyst 7 and monomer
10. The polymerization was carried out using unfunctionalized
polyethylene (Polywax) as a cosolvent in the reaction mixture
as shown in Scheme 3 since the experiments above showed that
this added cosolvent facilitated filtration and Ru recovery.
Polymer 15 was prepared on 1 mmol scale in THF with using
2.5% (w/w) of Polywax-400 as a cosolvent. The polymerization
was carried out at 80 °C for 1 h using 1 mol % of 7. The
reaction was then terminated by the addition of butyl vinyl
ether and stirred for an additional hour. At this point, cooling
led to coprecipitation of the Polywax cosolvent phase, and the
Ru species derived from 7. That Polywax phase containing
PEOlig-NHC-ligated residue was removed from product solution
by filtration through Celite and a 0.2 μm filter. The
homopolymer was then isolated by precipitation in MeOH.
The amount of Ru residues in product polymer was analyzed by
ICP-MS. The result showed that the Ru content in polymer 15
is 26 ppm. This Ru leaching of 0.5% is comparable to the
leaching seen in the absence of a polymerization using only a
hot butyl vinyl ether quench of 7 (vide infra).
The experiments described above used a modest amount of
the linear polyethylene oligomer cosolvent. In the case of
monomers 11−14, increasing the amount of this Polywax
cosolvent led to problems in that the polymer products
precipitated. However, in the case of monomer 10, we were
able to increase the amount of Polywax 10-fold in reactions
forming polymer 15. In this case, the amount of Ru leaching
with 1 g of the Polywax cosolvent was 25 ppma result that is
essentially the same as the 26 ppm seen with 0.1 g of the
Polywax cosolvent.
To compare the PEOlig-bound catalyst with its low molecular
weight counterpart, polymers 15 were made using 1 mol % of
the low molecular weight Hoveyda−Grubbs catalyst second-
generation 20 on 1 mmol scale. In this case, the product
solution was concentrated, and the homopolymer product was
isolated as solid by precipitation from THF using MeOH.
Unlike the experiment above, the polymer 15 prepared from 20
was reprecipitated twice more from THF using MeOH. These
experiments and precipitations used the same amount of
polymer, THF, and MeOH as was used in isolating polymer 15
prepared using 7. Polymer samples after each precipitation were
collected and analyzed by ICP-MS. The analysis showed that
the Ru content in the polymer samples was 768, 478, and 349
ppm for the first, second, and third precipitation, respectively.
While these results suggest that the Ru content in polymer
product can be reduced by solvent precipitation, the results
with even with three precipitations and are still inferior to the
much lower contamination seen for the polymer prepared with
PEOlig-supported catalyst 7. The colors of the solutions of
polymers prepared from 7 versus 20 were also different and
indicative of the different levels of Ru contamination. We also
noted that the isolated polymer 15 prepared with catalyst 20
after two precipitations appeared white. However, a solution of
this polymer in CH2Cl2 was colored. This is in contrast to a
CH2Cl2 solution of polymer 15 prepared with the PEOlig
-
supported catalyst 7, which was a colorless as shown in Figure
1.
To further establish the utility of 7 and to show that 7 was
equivalent to 20 as a catalyst for ROMP chemistry, we explored
polymerization of a series of monomers using this PEOlig
-
supported Ru catalyst (Scheme 4). Polymerizations of 11 and
13 were carried out in THF, and polymerization of 12 and 14
was carried out in 1,2-dichloroethane (1,2-DCE) on 1 mmol
scales. After the termination and isolation process, the resulting
polymers 16−19 were analyzed by GPC and ICP-MS for Mn,
PDI, E/Z ratios in the product polymers, and Ru leaching in
C
DOI: 10.1021/acs.macromol.5b01141
Macromolecules XXXX, XXX, XXX−XXX

Macromolecules
Article
Table 1. Results for the ROMP of Various Monomers Using
Ru Complexes 7 and 20
a
b
c
polymers yield (%)
Mn
PDI E:Z ratio Ru content (ppm)
d
e
e
e
e
c
15
80
87
85
89
76
80
80
98
95
85
30 400
33 300
62 000
26 000
197 500
23 600
26 400
58 700
28 000
147 200
1.48
1.55
1.23
1.51
1.84
1.35
1.34
1.65
1.71
1.53
−
26 (0.51)
23 (0.45)
19 (0.37)
25 (0.49)
26 (0.51)
349 (6.84)
461 (9.04)
263 (5.16)
348 (6.83)
300 (5.88)
16
36:64
d
17
−
18
48:52
19
53:47
d
f
f
f
f
f
eg
,
15a
16a
17a
18a
19a
−
eg
,
38:62
d
eg
,
−
eg
,
47:53
eg
,
52:48
Figure 1. Solutions of polymer 15 in CH2Cl2 prepared either with 20
(left) or with 7 (right).
a
Yield of polymer isolated after one precipitation from THF (or DCE)
b
into the poor solvent MeOH. Polymers 16, 18, and 19 had
distinguishable E and Z isomers (chemical shifts are noted in the
Experimental Section). The E/Z ratio was determined by integrating
c
1H NMR signals for these isomers. Ru analysis based on ICP-MS
d
e
analysis. The E and Z isomers had overlapping 1H NMR signals. The
percent of the original Ru that was present as a contaminant in the
f
g
polymer product. This polymer was prepared using catalyst 20. This
polymer was precipitated three times from MeOH.
oligomers (Polywax 400) with a nominal Mn of 400 and a PDI of 1.08
are commercial products and were gifts from Baker Hughes.20 All
other reagents were purchased from commercial sources and used
without further purification unless otherwise stated. Tetrahydrofuran
(THF) was freshly distilled from CaH2 and sodium/benzophenone
under nitrogen. 1,2-Dichloroethane (DCE) was dried with molecular
sieves (3 Å) and degassed by three freeze−pump−thaw cycles.
Compounds 7,8 10,12 11,13 12,14 13,15 and 1416 were all prepared
Scheme 4. Ring-Opening Metathesis Polymerization of 10−
14 Using 7
1
according to literature procedures. The H and 13C NMR spectral
assignments of the ROMP polymers 15,21 16,22 17,23 18,9 and 1924
were consistent with literature reports. Chemical shifts were reported
in parts per million (δ) relative to residual proton resonances in
deuterated chloroform (CDCl3).
Procedure for Control Experiment 1. To a 50 mL centrifuge
tube, 25 mg (0.01 mmol) of PEOlig-[Ru] 7 and 0.1 g of Polywax were
charged with a magnetic stir bar and sealed with a rubber septum and
copper wire. After this tube was evacuated and filled with N2 three
times, 5 mL of THF was added to the mixture. The initial suspension
was stirred and heated to 80 °C for 2 h. The solution that formed was
then cooled to room temperature to form a precipitate of 7/Polywax.
At this point, the solid/liquid biphasic mixture was filtered through
Celite and 0.2 μm filter to yield a clear solution. This entire was
transferred to a 20 mL vial. The solvent was removed at reduced
pressure. Any residue left in the vial was digested and prepared for
ICP-MS analysis. This analysis showed that the residue contained 0.08
ppm of Ru (0.04% of the Ru) in the catalyst 7.
Procedure for Control Experiment 2. To a 50 mL centrifuge
tube, 25 mg (0.01 mmol) of PEOlig-[Ru] 7 and 0.1 g of Polywax were
charged with a magnetic stir bar and sealed with a rubber septum and
copper wire. After this tube was evacuated and filled with N2 three
times, 5 mL of THF was added to the mixture. The initial suspension
was stirred and heated to 80 °C for 2 h. The solution that formed was
then allowed to react with 0.05 mL of butyl vinyl ether (BVE). Stirring
was continued for an additional 2 h, at which point the solution was
cooled to room temperature to form a precipitate of a Ru-complex/
Polywax. At this point, the solid/liquid biphasic mixture was filtered
through Celite and 0.2 μm filter to yield a clear solution. This entire
was transferred to a 20 mL vial. The solvent was removed at reduced
pressure. Any residue left in the vial was digested and prepared for
ICP-MS analysis. This analysis showed that the residue contained 0.84
ppm of Ru (0.42% of the Ru in 7 used initially).
the polymer products (Table 1). The analysis showed that Ru
contaminant contents in polymers prepared from 7 were in the
range 19−26 ppm as shown in when the insoluble PE
precipitates were carefully filtered the product polymer
solutions. In these cases, the Ru leaching was quite similar to
that seen in a control reaction where the only chemistry was
treatment of the starting Ru complex 7 with butyl vinyl ether.
In all cases, Ru leaching was much lower than that seen with the
conventional catalyst 20. The data in Table 1 include
polymerizations using both 7 and 20. They show that the use
of a PEOlig-bound Ru complex has no significant effect on Mn,
PDI, or E/Z ratios in the products in polymerizations that use
similar conditions and similar catalyst loadings. Our results also
showed that the PEOlig-bound precatalyst 7 works with a variety
of monomers. The only significant difference between
polymerizations using 7 versus 20 is the lower Ru leaching
with the PEOlig-bound catalyst.
EXPERIMENTAL SECTION
■
General Procedure for ROMP Reactions Catalyzed by PEOlig
-
Materials. Hydroxyl-terminated PE oligomers (Unilin 550) with a
nominal Mn of 550 and a PDI of 1.10 and unfunctionalized PE
[Ru] 7. To a 50 mL centrifuge tube, 25 mg (0.01 mmol) of PEOlig
-
[Ru] 7 and 0.1 g of Polywax were charged with magnetic stir bar and
D
DOI: 10.1021/acs.macromol.5b01141
Macromolecules XXXX, XXX, XXX−XXX

Macromolecules
Article
sealed with a rubber septum and copper wire. After this tube was
evacuated and filled with N2 three times, 2 mL of solvent (THF in the
case of monomers 10, 11, and 14 or 1,2-dichloroethane (DCE) in the
case of monomers 12 and 14) was added to the mixture and stirred at
80 °C until the solution became homogeneous. At this point, the
solution of 1 mmol monomer in an additional 2 mL of THF or DCE
was added to the reaction mixture. The polymerization was allowed to
continue at 80 °C for 1 h. After that 0.05 mL of butyl vinyl ether
(BVE) was added to quench the reaction. After 1 h the reaction
mixture was allowed to cool to room temperature, inducing phase
separation of the PEOlig-ligated Ru/Polywax matrix and polymer
product solution. This solid/liquid biphasic mixture was filtered
through 0.2 μm filter to yield a clear solution. Then the product
polymer solution was concentrated using reduced pressure to
approximately 1 mL, and this solution was added to 10 mL of
MeOH to precipitate the ROMP polymer product. The product was
with unfunctionalized polyethylene (Polywax) as a cosolvent
does not change the nature of the polymer products in any
significant way other than to significantly decrease Ru
contamination of the polymer products. While this linear
polyolefin cosolvent can affect solubility of the polymer
products if its concentration is too high, its use at modest
concentrations simplifies catalyst separations. Control experi-
ments suggested that most of the leaching of Ru species that is
seen results not from the polymerization process but rather
from byproducts formed during a terminating step that uses
butyl vinyl ether.
ASSOCIATED CONTENT
* Supporting Information
■
S
1
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.macro-
mol.5b01141.
then characterized by gel permeation chromatography, H NMR and
13C NMR spectroscopy, and by ICP-MS analysis for Ru contami-
nation.
1
1H and 13C NMR spectra of catalyst 7, monomers 10−
14, and polymer products 15−19 (Figures S1−S21)
(PDF)
Polymer 15. H NMR (300 MHz, CDCl3): δ 5.55 (2H, br), 3.62
(6H, br), 3.12 (2H, br), 2.81 (2H, br), 1.90 (2H,br) ppm. 13C NMR
(75 MHz, CDCl3): δ 174.4, 131.5, 51.3, 44.6, 39.5, 38.0 ppm.
1
Polymer 16. H NMR (300 MHz, CDCl3): δ 5.90 (1H, br, trans),
5.60 (1H, br, cis), 5.08 (1H, br, cis), 4.69 (1H, br, trans), 3.65 (6H, br),
3.09 (2H, br) ppm. 13C NMR (75 MHz, CDCl3): δ 171.0, 132.5,
131.0, 80.5, 80.2, 53.3, 52.9, 52.6 ppm.
AUTHOR INFORMATION
Corresponding Authors
*(H.S.B.) E-mail: bazzi@tamu.edu.
*(D.E.B.) E-mail: bergbreiter@tamu.edu.
Author Contributions
■
1
Polymer 17. H NMR (300 MHz, CDCl3): δ 7.25 (5H, br), 5.58
(2H, br), 4.60 (2H, br), 3.22 (2H, br), 2.90 (2H, br), 1.83 (2H, br)
ppm. 13C NMR (75 MHz, CDCl3): δ 178.1, 136.3, 129.3, 128.9, 128.1,
49.2, 45.2, 42.3, 40.3, 37.8 ppm.
1
Polymer 18. H NMR (300 MHz, CDCl3): δ 6.09 (1H, br; trans),
J.S. and C.E.H. contributed equally.
5.80 (1H, br, cis), 5.04 (1H, br, cis), 4.48 (1H, br, trans), 3.48 (2H, br),
3.33 (2H, br), 1.56 (2H, br), 1.29 (2H, br), 0.90 (3H, br) ppm. 13C
NMR (75 MHz, CDCl3): δ 175.7, 131.0, 81.1, 53.3, 52.2, 38.8, 29.7,
20.0, 13.6 ppm.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
1
■
Polymer 19. H NMR (300 MHz, CDCl3): δ 7.40−7.00 (5H, br),
Support of this research by the National Science Foundation
(Grant CHE-1362735), the Robert A. Welch Foundation
(Grant A-0639), and the Qatar National Research Fund project
number: 4-081-1-016 is acknowledged as is the generous gift of
Polywax and end-functionalized polyethylene oligomers by Dr.
Paul K. Hanna of Baker-Hughes.
5.93 (1H, br, trans), 5.62 (1H, br, cis), 5.05 (1H, br, cis), 4.50 (1H, br,
trans), 3.22 (2H, br) ppm. 13C NMR (75 MHz, CDCl3): δ 175.1,
133.8, 131.8, 129.3, 128.8, 126.6, 81.2, 53.6, 53.4 ppm.
General Procedure for ROMP Reactions Catalyzed by 20.
This procedure was identical to that used with 7 except that the
MeOH precipitation process was repeated three times to yield ROMP
polymer product for characterization by gel permeation chromatog-
1
raphy, H NMR and 13C NMR spectroscopy, and ICP-MS analysis.
REFERENCES
Digestion Procedure for ICP-MS Analyses. The sample that
was to be analyzed and 2 g of concentrated nitric acid were added to a
glass vial. The mixture was heated to 120 °C for 24 h. At this point, 2 g
of concentrated sulfuric acid was added to the solution at room
temperature, and the system was again heated to 120 °C for 24 h. The
clear solution that formed was then allowed to cool to room
temperature and was diluted with 1% nitric acid aqueous solution as
necessary to produce an ICP-MS analysis sample. The diluted sample
solution was then analyzed by ICP-MS which allowed us to determine
the ppm of metal in the diluted ICP-MS sample which could be
converted by simple math into the μg of metal/g of analysis sample
(ppm).
■
(1) (a) Vougioukalakis, G. C.; Grubbs, R. H. Chem. Rev. 2010, 110,
1746. (b) Bielawski, C. W.; Grubbs, R. H. Prog. Polym. Sci. 2007, 32,
1−29. (c) Handbook of Metathesis; Grubbs, R. H., Ed.; Wiley-VCH:
Weinheim, Germany, 2003. (d) Allen, D. P.; Van Wingerden, M. M.;
Grubbs, R. H. Org. Lett. 2009, 11, 1261−1264. (e) Leitgeb, A.;
Wappel, J.; Slugovc, C. Polymer 2010, 51, 2927−2946. (f) Sutthasupa,
S.; Shiotsuki, M.; Sanda, F. Polym. J. 2010, 42, 905−915. (g) Bunz, U.
H. F.; Maker, D.; Porz, M. Macromol. Rapid Commun. 2012, 33, 886−
910. (h) Hemelaere, R.; Carreaux, F.; Carboni, B. J. Org. Chem. 2013,
78, 6786−6792. (i) Peng, Y.; Decatur, J.; Meier, M. A. R.; Gross, R. A.
Macromolecules 2013, 46, 3293−3300. (j) Schulz, M. D.; Wagener, K.
B. Macromol. Chem. Phys. 2014, 215, 1936−1945. (k) Reimann, S.;
Baumeister, U.; Binder, W. H. Macromol. Chem. Phys. 2014, 215,
1963−1972.
Instruments. The molecular weight of polymers was determined
using a Viscotek gel permeation chromatograph equipped with UV, RI,
1
and RALS detectors using polystyrene standards. H NMR spectra
were obtained using a 300 MHz spectrometer operating at 299.91
MHz. 13C NMR spectra were obtained using a 300 MHz spectrometer
operating at 75.41 MHz. ICP-MS analyses were performed using
PerkinElmer’s NexION 350 ICP-MS spectrometer.
(2) (a) Vougioukalakis, G. C. Chem. - Eur. J. 2012, 18, 8868−8880.
(b) Chu, D. S. H.; Schellinger, J. G.; Shi, J.; Convertine, A. J.; Stayton,
P. S.; Pun, S. H. Acc. Chem. Res. 2012, 45, 1089−1099.
(3) (a) Courchay, F. C.; Sworen, J. C.; Ghiviriga, I.; Abboud, K. A.;
Wagener, K. B. Organometallics 2006, 25, 6074−6086. (b) Alcaide, B.;
Almendros, P.; Luna, A. Chem. Rev. 2009, 109, 3817−3858. (b) Hong,
S. H.; Day, M. W.; Grubbs, R. H. J. Am. Chem. Soc. 2004, 126, 7414−
7415. (c) Schmidt, B. Eur. J. Org. Chem. 2004, 9, 1865−1880.
(4) (a) Deraedt, C.; d’Halluin, M.; Astruc, D. Eur. J. Inorg. Chem.
2013, 28, 4881−4908. (b) Rosen, E. L.; Varnado, C. D., Jr.;
Arumugam, K.; Bielawski, C. W. J. Organomet. Chem. 2013, 745−
CONCLUSIONS
■
In summary, we have shown that a PEOlig-supported Hoveyda−
Grubbs second-generation Ru complex is a competent catalyst
in ROMP with a variety of furan- and cyclopentadiene-derived
monomers in dichloroethane or THF at 80 °C. Using 7 along
E
DOI: 10.1021/acs.macromol.5b01141
Macromolecules XXXX, XXX, XXX−XXX

Macromolecules
Article
746, 201−205. (c) Lambeth, R. H.; Pederson, S. J.; Baranoski, M.;
Rawlett, A. M. J. Polym. Sci., Part A: Polym. Chem. 2010, 48, 5752−
5757. (d) Maynard, H. D.; Grubbs, R. H. Tetrahedron Lett. 1999, 40,
4137−4140.
(5) (a) Szczepaniak, G.; Kosinski, K.; Grela, K. Green Chem. 2014,
16, 4474−4492. (b) Skowerski, K.; Wierzbicka, C.; Szczepaniak, G.;
Gulajski, L.; Bieniek, M.; Grela, K. Green Chem. 2012, 14, 3264−3268.
(c) Ferraz, C.; Autenrieth, B.; Frey, W.; Buchmeiser, M. R.
ChemCatChem 2014, 6, 191−198.
(6) Buchmeiser, M. R. Chem. Rev. 2009, 109, 303−321.
(7) Hongfa, C.; Su, H. L.; Bazzi, H. S.; Bergbreiter, D. E. Org. Lett.
2009, 11, 665−667.
(8) Hobbs, C.; Yang, Y. C.; Ling, J.; Nicola, S.; Su, H. L.; Bazzi, H. S.;
Bergbreiter, D. E. Org. Lett. 2011, 13, 3904−3907.
̌
̌
(9) Pastva, J.; Skowerski, K.; Czarnocki, S. J.; Zilkova, N.; Cejka, J.;
́
Bastl, Z.; Balcar, H. ACS Catal. 2014, 4, 3227−3236.
(10) Balcar, H.; Bek, D.; Sediacek, J.; Dedecek, J.; Bastl, Z.; Lamac,
́ ̌ ̆ ̌ ̌
M. J. Mol. Catal. A: Chem. 2010, 332, 19−24.
(11) Allen, D. P.; Van Wingerden, M. M.; Grubbs, R. H. Org. Lett.
2009, 11, 1261−1264.
(12) Al-Hashimi, M.; Hongfa, C.; George, B.; Bazzi, H. S.;
Bergbreiter, D. E. J. Polym. Sci., Part A: Polym. Chem. 2012, 50,
3954−3959.
(13) Goll, J. M.; Fillion, E. Organometallics 2008, 27, 3622−3625.
(14) Heath, W. H.; Palmieri, F.; Adams, J. R.; Long, B. K.; Chute, J.;
Holcombe, T. W.; Zieren, S.; Truitt, M. J.; White, J. L.; Willson, C. G.
Macromolecules 2008, 41, 719−726.
(15) Wilson, G. O.; Caruso, M. M.; Schelkopf, S. R.; Sottos, N. R.;
White, S. R.; Moore, J. S. ACS Appl. Mater. Interfaces 2011, 3, 3072−
3077.
(16) Musa, O. M. US. Patent 20,110,065,880, March 17, 2011.
(17) Camm, K. D.; Martinez Castro, N.; Liu, Y.; Czechura, P.;
Snelgrove, J. L.; Fogg, D. E. J. Am. Chem. Soc. 2007, 129, 4168−4169.
(18) Clevenger, R. C.; Turnbull, K. D. Synth. Commun. 2000, 30,
1379−1388.
(19) (a) Olson, C. L.; Caserio, M. C.; Roberts, J. D. Org. Synth. 1973,
5, 944. (b) Anderson, W. K.; Milowsky, A. S. J. Org. Chem. 1985, 50,
5423−5424.
(20) Older, C. M.; Kristjansdottir, S.; Ritter, J. C.; Tam, W.; Grady,
M. C. Chem. Ind. 2009, 123, 319−328.
(21) Yang, Y.; Priyadarshani, N.; Khamatnurova, T.; Suriboot, J.;
Bergbreiter, D. E. J. Am. Chem. Soc. 2012, 134, 14714−14717.
(22) Priyadarshani, N.; Suriboot, J.; Bergbreiter, D. E. Green Chem.
2013, 15, 1361−1367.
(23) (a) Unilin 550, Baker Hughes Web site: http://www.
bakerhughes.com/news-and-media/resources/technical-data-sheet/
unilin-alcohols (accessed July 21, 2015). (b) Polywax 400, Baker
Hughes Web site: http://www.bakerhughes.com/news-and-media/
resources/technical-data-sheet/polywax-polyethylenes (accessed July
21, 2015).
(24) Flook, M. M.; Borner, J.; Kilyanek, S. M.; Gerber, L. C. H.;
Schrock, R. R. Organometallics 2012, 31, 6231−6243.
(25) Keitz, B. K.; Fedorov, A.; Grubbs, R. H. J. Am. Chem. Soc. 2012,
134, 2040−2043.
(26) Thomas, R. M.; Fedorov, A.; Keitz, B. K.; Grubbs, R. H.
Organometallics 2011, 30, 6713−6717.
(27) Yoon, K.-H.; Kim, K. O.; Wang, C.; Park, I.; Yoon, D. Y. J.
Polym. Sci., Part A: Polym. Chem. 2012, 50, 3914−3921.
F
DOI: 10.1021/acs.macromol.5b01141
Macromolecules XXXX, XXX, XXX−XXX