Living and block copolymerization of ethylene and α-olefins using palladium(II)-α-diimine catalysts

Article abstract of DOI:10.1021/ma025902u

Living polymerization of ethylene with palladium(II) diimine complexes coupled with use of a functionalized initiator and/or cleavage of the palladium-polymer bond with various reagents provides a protocol for synthesis of mono- and di-end-functionalized, branched, amorphous polyethylenes. The functional initiator used is the chelate complex [(ArN=C(Me)-C(Me)=NAr)Pd(CH₂)₃C(O)OMe] [(Bar′₄)] (Ar = 2,6-(iPr)₂C₆ H₃) (3). The alkylchain is cleaved by insertion of alkyl acrylates or methyl vinyl ketone, followed by cleavage with Et₃SiH to generate alkyl ester or methyl ketone end groups, respectively. Insertion of 5-hexen-1-ol, followed by chain running and β-elimination, results in formation of aldehyde end groups. Conditions for living polymerization of propylene, 1-hexene, and 1-octadecene have also been established. Rates of first monomer insertion and subsequent chain growth are shown to be a sensitive function of the palladium complex used for initiation and the nature and concentration of auxiliary nitrile ligands. Block copolymers of ethylene and 1-octadecene were prepared under living conditions. The copolymers microstructure differed depending on the order of introduction of the blocks.

Full text of DOI:10.1021/ma025902u

Macromolecules 2003, 36, 3085-3100
3085
Living and Block Copolymerization of Ethylene and R-Olefins Using
Palladium(II)-R-Diimine Catalysts
Am y C. Gottfr ied a n d M. Br ook h a r t*,†
Department of Chemistry, University of North Carolina at Chapel Hill,
Chapel Hill, North Carolina 27599-3290
Received December 2, 2002; Revised Manuscript Received February 13, 2003
ABSTRACT: Living polymerizations of ethylene with palladium(II) diimine complexes coupled with use
of a functionalized initiator and/or cleavage of the palladium-polymer bond with various reagents provides
a protocol for synthesis of mono- and di-end-functionalized, branched, amorphous polyethylenes. The
functional initiator used is the chelate complex [(ArNdC(Me)-C(Me)dNAr)Pd(CH
Ar ) 2,6-(iPr) ) (3). The alkyl chain is cleaved by insertion of alkyl acrylates or methyl vinyl ketone,
followed by cleavage with Et SiH to generate alkyl ester or methyl ketone end groups, respectively.
2 3 4
) C(O)OMe][(BAr′ )]
(
2 6 3
C H
3
Insertion of 5-hexen-1-ol, followed by chain running and â-elimination, results in formation of aldehyde
end groups. Conditions for living polymerization of propylene, 1-hexene, and 1-octadecene have also been
established. Rates of first monomer insertion and subsequent chain growth are shown to be a sensitive
function of the palladium complex used for initiation and the nature and concentration of auxiliary nitrile
ligands. Block copolymers of ethylene and 1-octadecene were prepared under living conditions. The
copolymer microstructure differed depending on the order of introduction of the blocks.
In tr od u ction
The key feature of living polymerization is that chain
growth occurs without significant chain transfer or
termination. Living polymerization techniques allow the
synthesis of polymers with control of the average Mn
and narrow molecular weight distributions as well as
block copolymers and end-functionalized materials.
Transition-metal-catalyzed polymerization of olefins in
a living fashion via a coordination-insertion mechanism
is frequently frustrated by facile chain transfer pro-
cesses, especially â-elimination and chain transfer to
aluminum activators. The past few years have wit-
nessed a growing number of reports of transition metal
catalysts which have achieved living polymerizations of
F igu r e 1. Ni and Pd R-diimine catalysts.
with those studies we have probed the possible use of
these systems for living polymerization. Attractive
features of these late metal systems include production
of polymers with quite different microstructures relative
to early metal systems, compatibility with polar solvents
and certain functionalized olefins, and facile incorpora-
tion of chain-end functionality. The first system exam-
ined, the cobalt(III) catalyst [C5Me5P(OMe)3CoCH2CHR-
1
ethylene and R-olefins. In this regard, more progress
has been reported for R-olefins than for ethylene.
Much of the groundwork in this area was laid by Doi
who described living polymerization of propylene using
2
derivatives of V(acac)3 activated with aluminum alkyls.
These catalysts exhibit living character only at low
temperatures (-78 °C) which favor a high ratio of the
propagation rate to the chain transfer rate. Doi also
showed that these systems could be used to prepare end-
+
µ-H] (R ) H, alkyl), polymerizes ethylene in a living
fashion at 25 °C (Mw/Mn ∼1.1-1.2 up to Mn ) 20 000)
and, using functionalized initiators, produces end-
3
functionalized polypropylene as well as polypropylene/
1
6
capped polyethylene.
4
polyethylene block and copolymers. More recent ex-
More recently, our focus has shifted to Ni and Pd
R-diimine catalysts. The Ni complexes 1a ,b (Figure 1)
polymerize R-olefins in a living fashion at -10 °C in
amples of early metal catalysts which carry out living
polymerizations of R-olefins at much higher tempera-
5
6
tures have been reported by McConville (Ti), Kim (Zr),
1
7
dilute monomer solutions. High molecular weight
polymers with quite narrow molecular weight distribu-
tions can be obtained (for example, polypropylene Mn
7
8
9
10
Schrock (Zr, Hf), Sita (Zr), Shino (Ti), Fukui (Zr, Hf),
Kol (Zr, Ti),11 Coates (Ti), and Fujita (Ti). Examples
of early transition metal complexes which have been
shown to polymerize ethylene in a living fashion include
Mashima’s C5Me5M(butadiene)X2/MAO (M ) Nb, Ta)
12
13
)
161 000, Mw/Mn ) 1.13; poly(1-hexene) Mn ) 44 000,
Mw/Mn ) 1.09.) Block polymers of various R-olefins were
also prepared and exhibit unusual properties since, due
to a chain-straightening mechanism, long chain R-ole-
fins such as 1-octadecene are crystalline in contrast to
polypropylene and poly(1-hexene) which are amorphous
materials.
1
4
systems, which operate at -20 °C, and Fujita’s highly
active bis(salicylaldiminato)titanium-based catalysts.
1
5
Our interests have centered on developing late metal
catalysts for olefin polymerizations, and in connection
The Pd R-diimine catalysts 2b and 3 have been shown
to carry out living polymerization of ethylene at 5 °C
†
E-mail: mbrookhart@unc.edu.
1
0.1021/ma025902u CCC: $25.00 © 2003 American Chemical Society
Published on Web 04/10/2003

3
086 Gottfried and Brookhart
Macromolecules, Vol. 36, No. 9, 2003
Sch em e 1. En d -ca p p in g of P olyeth ylen e w ith F u n ction a lized Olefin s
under 400 psi ethylene.18 Quenching the polymerization
reaction with silane, which cleaves the Pd-C bond to
generate a saturated end group, proved to be critical in
obtaining monomodal polymers with narrow molecular
weight distributions. Without the silane quench, some
chain coupling occurs which results in polymers with
bimodal distributions. Amorphous, highly branched
polyethylene (∼100 branches per 1000 Cs) with Mn
values greater than 100K and Mw/Mn’s less than 1.1
could readily be prepared. This system was also used
to prepare polyethylene macromonomers with functional
end groups that were copolymerized with n-butyl acry-
late via ATRP.19
end-functionalized with a methyl ester group as shown
in eq 1.
Taking advantage of the ability of alkyl acrylates to
insert into a Pd-C bond and form chelates which do
not exhibit further insertion chemistry with acrylates
(as shown in eq 2), we have developed a method for end-
In this manuscript, we describe extension of our
studies of Pd R-diimine-catalyzed living polymerization
of ethylene to include the following: (1) use of this
catalyst system to prepare mono- and di-end-function-
alized amorphous polyethylene; (2) demonstration of
living polymerization of R-olefins; (3) preparation of
1
-octadecene/ethylene diblock polymers with unusual
microstructures.
Resu lts a n d Discu ssion
A. En d -Ca p p ed P olyeth ylen e. A number of meth-
ods have been previously described for end-functional-
izing polyolefins prepared through a coordination/
insertion mechanism. A common method involves
cleavage of the metal-carbon bond with various re-
agents following chain growth. For example, in the Doi
vanadium systems, cleavage of the vanadium-carbon
capping the polymer following chain growth. This
procedure is outlined in Scheme 1.
3
a
bond with I2 results in production of an iodo end group,
Ethylene was polymerized with catalyst 2c for 1 h at
5 °C and 400 psi ethylene (high pressures are generally
required to ensure rapid initiation.) After 1 h, all of the
ethylene was purged from the reactor and 200 equiv of
methyl acrylate were added. After 1 h, the time required
for complete acrylate insertion, the catalyst was quenched
+
3d
reaction with CO/H results in a terminal aldehyde,
+
propylene oxide/H yields predominantly a secondary
alcohol, and styrene/H provides an aryl end group.
3
e
+
3e
Numerous chain transfer agents have been used to end
cap polymers and oligomers. The advantage of this
method is that many chains per metal center can be
generated but this high productivity comes at the
expense of broader molecular weight distributions,
typically about 2. Examples of molecules successfully
by addition of Et SiH. A turnover frequency of 216/h
3
was calculated on the basis on moles of catalyst em-
1
ployed per weight of polymer produced. The H NMR
spectrum of the isolated polymer showed the presence
of the ester end group and was without olefinic reso-
nances. The polymer prepared by this method was
identical in all respects (including integral ratios and
yield) to the material prepared from chelate initiator 3
2
0
used as chain transfer agents include silanes, bo-
ranes,21 thiophene, and allyl alcohol. A less common
method of end-capping has been the use of functional-
ized initiators, which introduce a functional group at
22
23
1
6
the start of the chain rather than after chain growth.
(1 h, 5 °C, 400 psi ethylene) followed by silane quench
As reported in our earlier communication, polymer-
ization of ethylene with catalyst 2b (Figure 1) followed
by quenching with Et3SiH results in a fully saturated,
unfunctionalized, amorphous polyethyelene.1 However,
reaction of ethylene with the functionalized initiator
generated from methyl acrylate insertion into the Pd-
CH3 bond of 2a (the chelate complex 3,24 Figure 1)
followed by silane quench yields saturated polyethylene
which introduces the ester end cap at the beginning of
the chain. Similar terminal end-capping procedures
employing ethyl acrylate and methyl vinyl ketone
produced polyethylene end-functionalized with ethyl
ester and methyl vinyl ketone end groups, respectively.
In the case of methyl vinyl ketone, longer times and
higher temperatures (18 h, 25 °C) were used to ensure
complete insertion.
8

Macromolecules, Vol. 36, No. 9, 2003
Palladium(II)-R-Diimine Catalysts 3087
Sch em e 2. Syn th esis of Telech elic P olyeth ylen e
F igu r e 3. 1H NMR (CDCl
, 400 MHz, 25 °C) of telechelic
3
polyethylene end capped with both a methyl ketone and a
F igu r e 2. 1H NMR (CDCl
3
, 400 MHz, 25 °C) of telechelic
polyethylene end-capped with both a methyl ester and an ethyl
ester end group. (The inset shows a blowup of the 4.5-2.0 ppm
region to reveal end groups.)
methyl ester end group. (The inset shows a blowup of the 4.0-
2
.0 ppm region to reveal end groups.)
dride elimination to yield an aldehyde (eq 3).
By a combination of the functionalized initiator 3 and
the end-capping procedure described above, difunctional
(telechelic) polyethylene could be prepared. The general
method is outlined in Scheme 2.
To prepare the polyethylene bearing one methyl ester
and one ethyl ester group, the following procedure was
used. Chelate complex 3 was exposed to ethylene for 1
h (5 °C, 400 psi) after which ethylene was purged from
the solution and 200 equiv of ethyl acrylate were added.
After 2 h, Et3SiH was added, and the polymer was
1
isolated in the usual way. The H NMR spectrum of the
This reaction can be used to end-cap polyethylene
following chain growth. The polymerization method
using the chelate initiator 3 and quenching with 4-pent-
polymer is shown in Figure 2. Again, no olefinic reso-
nances are present, and the 3:2 integral ratio of the
methyl group of the methyl ester at 3.68 ppm to the
methylene quartet of the ethyl ester at 4.1 ppm indi-
cates a molar ratio of ester groups of 1:1. This ratio
firmly establishes that the introduction of the ester
functional group following chain growth is highly ef-
ficient; otherwise, the molar ratio of ethyl ester to
methyl ester would have been less than 1. Figure 3
1
en-1-ol is outlined in Scheme 3. The H NMR spectrum
of the polyethylene prepared using this procedure
exhibits an aldehyde CH resonance at 9.78 ppm and a
methyl ester resonance at 3.68 ppm in a 1:3 intensity
ratio confirming successful quantitative end function-
alization.
B. Livin g P r op ylen e P olym er iza tion . After eth-
ylene was successfully polymerized in a living manner
with the Pd(II) R-diimine catalysts, efforts turned to
living polymerization of R-olefins. Initial attempts to
polymerize propylene were carried out with the chelate
catalyst 3. The results obtained using 1 atm of propylene
at 0 °C were inconsistent and often reflected very little
catalyst activation for polymerization. To initiate pro-
pylene polymerization, the alkyl propylene complex
must be generated through palladium chelate opening
and propylene coordination. Since the bulkier propylene
1
shows the H NMR spectrum of the telechelic polymer
containing one methyl ester group and one methyl
ketone group prepared from initiation with 3 and
quenching with methyl vinyl ketone. Again, an integral
ratio of functionalities of 1:1 is established.
One other telechelic technique was developed to end-
cap polymers with an aldehyde group. In unpublished
2
5
work, we have shown that 4-penten-1-ol will insert
into the Pd-CH3 bond of 4 and, following Pd migration
down the chain, the alkyl complex will undergo â-hy-

3
088 Gottfried and Brookhart
Macromolecules, Vol. 36, No. 9, 2003
Sch em e 3. Syn th esis of Telech elic P olyeth ylen e w ith a n Ald eh yd e En d Ca p
F igu r e 6. Plot of M
n w n
and M /M as a function of reaction time
F igu r e 4. Initiation of propylene polymerization using Pd(II)
R-diimine catalysts
for the polymerization of 1-hexene (0.8 M, 2 mL) [0 °C; catalyst
-
6
3
(15 × 10 mol) in chlorobenzene, 20 mL of total solution;
Et SiH quench].
3
per hour. At Mn values above ca. 40K, there was a
broadening of the polypropylene molecular weight dis-
tribution accompanied by the appearance of a low
molecular weight tail in the GPC traces, indicating
catalyst decomposition. These systems are thus not as
long-lived as the ethylene polymerization systems where
polymers with Mn's of up to 200K can be achieved with
molecular weight dispersities of less than 1.1.
J ust as nonliving behavior was exhibited in the
ethylene polymerizations at room temperature, the
molecular weight of propylene increased in a nonlinear
fashion with time at 25 °C. A low molecular weight tail
in the GPC traces of these polymers indicates that
catalyst decomposition is taking place, preventing a
living polymerization. As has been previously observed,
the polypropylenes generated under living conditions
exhibit branching numbers of ∼253 branches per 1000
carbons. This low branching number is indicative of
some chain straightening occurring via a 2,1-insertion
followed by chain-walking of the Pd, which results in
F igu r e 5. Plot of M
n w n
and M /M as a function of reaction time
for the polymerization of propylene (1 atm) [0 °C; catalyst 2c
-
6
(
5 × 10 mol) in 20 mL of chlorobenzene; Et
3
SiH quench].
has a lower binding affinity than ethylene and since the
carbonyl oxygen of the chelate is fairly strongly bound
to palladium, the propylene concentration at 1 atm is
not sufficient to shift the equilibrium appreciably to the
palladium propylene complex as shown in Figure 4a.
Quantitative aspects of this equilibrium have been
studied and support this contention.24 This unfavorable
equilibrium results in extremely slow initiation.
To circumvent the chelate problem, catalyst 2c (Fig-
ure 1) which features the weakly bound, electron-
deficient 3,5-bis(trifluoromethyl)benzonitrile ligand was
employed. Using this ligand, the equilibrium shown in
Figure 4b apparently lies sufficiently far to the right to
provide an initiation rate comparable to the propagation
rate since living behavior is observed. The results of
polymerization of propylene in chlorobenzene at 0 °C
under 1 atm of propylene are summarized in Figure 5.
As with ethylene polymerizations, solutions are quenched
with Et3SiH prior to work up.
2
6
1,3-enchainment of propylene.
C. Livin g 1-Hexen e P olym er iza tion . The pal-
ladium chelate complex 3 was found to initiate polym-
erization of 1-hexene (0.8 M) at 0 °C at rates comparable
to chain growth. The success of the chelate complex here
is clearly due to high concentrations of 1-hexene which
produce a significant equilibrium concentration of the
+
(diimine)Pd(alkyl)(1-hexene) complex, the species re-
quired for initiation. By taking aliquots of the polym-
erization solution and quenching with Et SiH, the Mn
3
and molecular weight dispersity of the poly(1-hexene)
could be monitored as a function of time. Results are
presented graphically in Figure 6. Mn grows linearly
with time in the early stages of polymerization (up to
ca. 100 min) but then, the slope begins to decrease. The
dispersity remains low (<1.08) through 100 min and
then begins to increase, reaching 1.15 at a 3 h polym-
erization time. These results suggest that either some
catalyst decay is occurring or that chain transfer is
The plots in Figure 5 show a linear increase in
polypropylene molecular weight with time accompanied
by a narrow molecular weight distribution. The average
turnover frequency based on the weight of polymer
produced vs moles of catalyst employed at 0 °C in 20
-4
mL of chlorobenzene under 1 atm of propylene (5 × 10
M in 2c) was constant at approximately 100 turnovers

Macromolecules, Vol. 36, No. 9, 2003
Palladium(II)-R-Diimine Catalysts 3089
Sch em e 4. Com p etition of Nitr ile a n d 1-Hexen e for th e Op en Coor d in a tion Site a t P d
beginning to limit Mn and broaden the molecular weight
distribution.
zene and adding 1 equiv of various nitriles. The reaction
protocol is outlined in eq 4.
Catalysts 2b and 2c were also used to polymerize
-hexene under the same reaction conditions. The
1
polymers made with these catalysts showed nearly
linear molecular weight growth over time with corre-
sponding narrow molecular weight distributions over
polymerization times of 3 h. The chelate catalyst 3
produces poly(1-hexene) with an Mn of 35 000 after 3
h, whereas the 3,5-bis(trifluoromethyl)benzonitrile li-
gated catalyst 2c and the acetonitrile ligated catalyst,
2
b, yield lower molecular weight poly(1-hexene), 30 000
and 14 000, respectively. The lower molecular weights
of the polymers made with nitrile catalysts are at-
tributed to the ability of the nitrile to compete with
1
-hexene for the open coordination site at palladium
throughout the polymerization reaction as illustrated
in Scheme 4a.
Under these conditions, some fraction of the Pd
species exists as the dormant nitrile complex. As
expected, the more basic, sterically less bulky acetoni-
trile ligand has a higher binding affinity than (CF3)2C6H3-
CN and thus when catalyst 2b is used, a greater fraction
of the Pd species exists as the dormant nitrile complex
leading to slower chain growth and a lower Mn of poly-
The results are summarized in Table 1. As expected,
the Mn values and turnover frequencies decrease as a
function of the coordinating ability of the nitrile. For
the most basic nitrile, p-methoxybenzonitrile, the TOF
falls to 19 TO per hour and the Mn falls to ca. 3300
relative to 234 TO/h and Mn ) 31 000 for catalyst 2c
with no added nitrile.
(
1-hexene) after a given polymerization time. In the case
of the chelate complex, following a relatively few mono-
mer insertions, formation of a chelate will no longer be
favorable and no other ligand is present to compete with
1
-hexene for the vacant site. This feature is illustrated
The data in Table 1 illustrates two additional points.
First, added nitrile ligands do not induce chain transfer
as is evident from the very narrow molecular weight
distributions observed, generally significantly less than
1.1. Second, the TOF’s are not consistent with the Mn
in Scheme 4b.
To further illustrate the effect of the equilibrium
between dormant and active Pd complexes, polymeriza-
tions were carried out using catalyst 2c in chloroben-

3
090 Gottfried and Brookhart
Macromolecules, Vol. 36, No. 9, 2003
Ta ble 1. P olym er iza tion of 1-Hexen e by 2c w ith 1 equ iv
a
of Nitr ile Ad d ed
these catalysts polymerize the internal olefins, the
products of isomerization? And second, was isomeriza-
tion a factor at the lower temperatures used for the
living polymerizations? As eq 6 illustrates, the polym-
a
Polymerizations at 0 °C; 3 h; 0.8 M 1-hexene (2 mL); catalyst
-6
2
c (15 × 10 mol) in chlorobenzene; 20 mL total solution; 1 equiv
b
of nitrile to catalyst added; Et3SiH quench. Molecular weight
c
data determined by GPC vs polystyrene standards. TOF (turn-
over frequency ) “moles of monomer/moles of catalyst”)
Ta ble 2. Effect of 3,5-Bis(tr iflu or om eth yl)ben zon itr ile
Con cen tr a tion on th e P olym er iza tion of 1-Hexen ea
added nitrile
-
4
Mn (×10-3)b
Mw/Mnb
entry
(×10 M)
1
2
3
4
0
31.0
24.4
23.4
19.7
1.03
1.05
1.04
1.06
2.5
5.0
7.5
a
-6
1
-hexene (0.8 M, 2 mL); 0 °C; 3 h; catalyst 2c, (15 × 10 mol)
in chlorobenzene for a total solution volume of 20 mL; Et3SiH
quench. Molecular weight determined by GPC vs polystyrene
erization of internal olefins (trans-2-hexene and trans-
b
3
-hexene) by the Pd(II) R-diimines does take place, but
at a very slow rate, yielding only 11 mg of polymer in a
h run, well below the 296 mg of poly(1-hexene)
standards.
3
values measured by GPC. For example, for entry 1, the
TOF is 234/h which would lead to a Mn of 60 400 in a
living polymerization [1-hexene (234/h × 3 h × 86 g/mol
obtained under the same conditions. The dramatic
decrease in the rate of polymerization of internal
hexenes is attributable to their increased steric bulk
which leads to both decreased coordination and a slower
rate of insertion. Given the very slow rate of polymer-
ization of the internal hexenes, complete isomerization
of 1-hexene would lead to a dramatically decreased rate
of polymerization in the living systems.
1
-hexene).] The measured Mn using polystyrene stan-
dards is 30 000. This molecular weight discrepancy can
be attributed to the polystyrene standards used to
calibrate the results. For the same Mn values, the
hydrodynamic volume for a branched poly(1-hexene) in
THF will differ from that of polystyrene in THF. Thus,
the GPC data collected are useful for comparing relative
molecular weights of branched poly(1-hexenes) but are
not accurate for determining absolute molecular weights.
A study similar to the one shown in eq 5, utilizing
the reaction conditions that achieved living polymeri-
-
6
zation (0 °C, 0.8 M 1-hexene, 2c (15 × 10 mol) in
chlorobenzene, total solution volume 20 mL) was then
undertaken in order to determine whether 1-hexene
isomerization was occurring during the polymerization.
Aliquots were removed from the polymerization solution
at various times. The volatiles were separated from any
polymer that had formed and then examined by GC to
assess the ratios of hexene isomers. Figure 7 sum-
marizes the data obtained over the course of the
experiment. After 3 h polymerization at 0 °C, 71% of
all hexenes in solution remained as 1-hexene, while 29%
of the 1-hexene had been isomerized to internal olefins.
The binding affinity of 2- and 3-hexenes is far less than
that of 1-hexene, thus these isomers neither inhibit the
binding and insertion of 1-hexene nor undergo insertion
competitive with 1-hexene.
In the second experiment designed to establish a
nitrile concentration dependence on the rate of polym-
erization, increasing numbers of equivalents of 3,5-bis-
(
trifluoromethyl)benzonitrile were added to polymer-
izations of 1-hexene catalyzed by 2c. The results in
Table 2 show that as the concentration of 3,5-bis-
(
trifluoromethyl)benzonitrile increases, the molecular
weight of the polymer made over a 3 h time period
decreases. The increased nitrile concentration shifts the
equilibrium toward the dormant palladium-nitrile com-
plex and thus decreases the rate of chain growth,
resulting in lower Mn’s (Scheme 4). Again, the molecular
weight distribution is not affected by excess nitrile.
One final aspect of 1-hexene polymerization with the
Pd(II) R-diimine systems was examined. Previous re-
Under living conditions, the poly(1-hexene) is chain
2
7
sults showed that at room temperature, using catalyst
17,28
straightened as has been previously observed.
The
2
a , isomerization of 1-hexene to internal hexenes is
branching in these polymers ranges from 75 to 85
branches per thousand carbons and, as observed in the
ethylene polymerizations, the branching numbers at 0
°C are unaffected by catalyst or monomer concentration
and are the same for catalysts 2a -c and 3.
competitive with polymerization. A typical result is
shown in eq 5.
Two questions were raised about the effect of isomer-
ization in the Pd(II) R-diimine systems. First, could

Macromolecules, Vol. 36, No. 9, 2003
Palladium(II)-R-Diimine Catalysts 3091
while at 3 h the distribution has broadened to 1.34.
Visual observation of the polymerization reveals that a
white, flaky solid begins to precipitate from the cold
chlorobenzene after approximately 1.5 h. We suggest
this precipitation process is responsible for the broaden-
ing dispersities.
The turnover frequency at 0 °C for 1-octadecene is
very low (9-12 TO/h) at this monomer concentration,
and unfortunately, the turnover rate limits the molec-
ular weight of the polymer that can be achieved. The
turnover frequency does not decrease significantly over
1
F igu r e 7. Distribution of hexenes in solution over time during
a 4 /2 h polymerization time, indicating that the catalyst
-
6
polymerization (0 °C, 0.8 M 1-hexene, catalyst 2c (15 × 10
is not decomposing. This claim is also supported by a
lack of a low molecular weight tail in the GPC traces
as observed when decomposition of catalyst occurs
during the polymerization of other monomers. Solubility
of the polymer at low temperatures seems to be the only
impediment to sustaining molecular weight distribu-
tions of <1.1. The growth in Mn with time and the lack
of appreciable catalyst decay over 4 h implies that this
monomer can be successfully used in the formation of
block polymers, and these experiments are reported in
the next section.
mol) in chlorobenzene, determined by GC).
E. Block Cop olym er s. Given the differing properties
of polyethylene vs poly(1-octadecene) it was of interest
to attempt to prepare block copolymers. This section
describes preparation of polyethylene-b-poly(1-octa-
decene) copolymers and, as will be illustrated, the
microstructure of the block polymers differs substan-
tially depending on the order of growth of the blocks
from the palladium center.
F igu r e 8. Plot of M
n w n
and M /M as a function of reaction time
for the polymerization of 1-octadecene (0.3 M, 1.0 mL) [0 °C;
-
6
catalyst 2c (8 × 10 mol) in chlorobenzene, 10 mL of total
solution; Et SiH quench].
3
D. 1-Octa d ecen e P olym er iza tion . One of the at-
tractive features of living polymerization is the ability
to make block copolymers. Such polymers are of par-
ticular interest when the blocks have different physical
properties. The polyethylene, polypropylene, and poly-
1
. Block Cop olym er Syn th esis. Careful attention
to experimental protocol is necessary to ensure that each
block of the diblock is a homopolymer block and not a
copolymer block. In cases where ethylene is introduced
as the first block, it is relatively easy to remove excess
ethylene from the polymerization solution through a
series of cycles involving application of vacuum to the
reaction mixture followed by purging with argon at 0
(
1-hexene) made under living conditions with the Pd-
(
II) R-diimine catalysts are all highly branched, amor-
phous polymers. Using the Pd(II) R-diimine catalysts
for polymerization of very long chain R-olefins (e.g.,
1
7
-octadecene) leads to a semicrystalline polymer (Tm )
1.7 °C, 86.1 °C) as a result of lower branching numbers
°
C. This process is described in detail in the Experi-
mental Section. Control experiments have established
that no chain transfer or termination occurs during this
procedure and that all ethylene is removed prior to
introduction of the 1-octadecene for growth of the second
block.
due to enchainment of the long chain R-olefin in 1,ω-
“
chain straightened” fashion.29 Thus, it was of interest
to screen a long chain R-olefin, 1-octadecene, for living
polymerization with the intent of incorporating it in
formation of a diblock R-olefin polymer.
In cases where the R-olefin block is grown first, the
removal of excess monomer becomes more difficult since
all of the 1-octadecene cannot be consumed during
polymerization and the 1-octadecene is not sufficiently
volatile to be removed under reduced pressure at low
temperatures. A successful procedure was developed
which involved running the 1-octadecene polymerization
at 0-5 °C in concentrated solutions (0.353 M, 7 mL
solution volume) then diluting these solutions to 100-
1
-Octadecene polymerizations were carried out using
catalyst 2c at low temperatures (0 °C) and monomer
concentrations of 0.3 M, and were quenched in the usual
way with Et3SiH. The polymer produced was a solid,
semicrystalline material containing a modest 34 branches
per thousand carbons30 (eq 7). Like the other R-olefins
1
50 mL followed by introduction of ethylene at 400 psi.
Since the binding affinity of ethylene is so much greater
2
8
than R-olefins, under these conditions of dilute 1-oc-
tadecene and high ethylene pressure, only ethylene is
incorporated. A control experiments was conducted in
which ethylene was polymerized at 400 psi in the
presence of 0.015 M 1-octadecene. The polyethylene
produced had physical and spectral properties es-
sentially identical to homopolyethylene indicating in-
significant incorporation of 1-octadecene.
polymerized by 2c, the poly(1-octadecene) is chain
straightened (from an anticipated 55-56 branches per
thousand carbons).
A plot of Mn vs Mw/Mn for the polymerizations
described in eq 7 is shown in Figure 8. While the Mn
values clearly increase with polymerization time, the
Mw/Mn values, in contrast to similar polymerizations
with propylene and 1-hexene, broaden quite substan-
tially over 4.5 h. For example, at 1 h, Mw/Mn ) 1.13
Table 3 summarizes the molecular weight data and
branching numbers for a series of diblock polymers
made using the above protocols. Examining the data in

3
092 Gottfried and Brookhart
Macromolecules, Vol. 36, No. 9, 2003
Ta ble 3. P olyeth ylen e-b-p oly(1-octa d ecen e)a a n d P oly(1-octa d ecen e)-b-p olyeth ylen eb
c
C18d (h)
Mn (×10-3)
e
Mw/Mne
branches/1000 Cf
C-18d (h)
c
Mne (×10-3
Mw/Mne
branches/1000 Cf
PE (h)
PE (h)
)
2
2
2
1
2
3
1
2
3
2
2
2
30
34
50
1.10
1.18
1.22
64
59
53
55
59
58
1
2
3
2
2
2
2
2
2
1
2
3
18
25
23
1.15
1.06
1.10
43
74
66
75
74
67
34
46
1.18
1.17
a
-6
Catalyst 2c (8 × 10 mol), ethylene (400 psig, 5-6 °C, 80 mL chlorobenzene); ethylene removal; 1-octadecene (10 mL in 10 mL
b
-6
chlorobenzene) added (0.32 M, 4 °C). Catalyst 2c (8 × 10 mol), 1-octadecene (0.7 mL, 0.32 M, 7.0 mL solution, 2 °C); ethylene (400
psig, 5-6 °C, 143 mL of chlorobenzene). PE ) polyethylene. d C-18 ) poly(1-octadecene). e By GPC vs polystyrene standards (k ) 4.34
c
-
4
1
×
10 ; R ) 0.724). f By H NMR.
F igu r e 9. 13C NMR (C
D Br 0.5 M Cr(acac) , 100 MHz, 120 °C) of polyethylene.
6 5 , 3
Table 3, the left half contains data on polyethylene (PE)-
b-poly(1-octadecene) (C18) polymers in which the poly-
ethylene block is made first, while the right half
summarizes data for blocks grown in the reverse order.
As shown in Table 3, all copolymers have fairly narrow
molecular weight distributions (1.06-1.22) and the
overall branching numbers of the copolymers (43-75)
fall between the 90-110 branches per 1000 C of
polyethylene and the 39-40 branches/1000 C of poly-
lower than anticipated polymer molecular weight is
likely due to the precipitation of the polymer from the
cold polymerization solution as observed in the homo-
polymerization of 1-octadecene.
. Ch a r a cter iza tion of Block Cop olym er s by 13
2
C
NMR Sp ectr oscop y. The most intriguing feature of
these block copolymers is that there are differences in
microstructures as a function of the order of growth of
1
3
the blocks, as indicated by C NMR analysis and DSC
data. To analyze these differences we first must consider
(
1-octadecene.) The copolymers are clear, rubbery solids
as opposed to amorphous gels (polyethylene) or white
1
3
(
the C analyses of the homopolymers themselves.
1
3
solids (poly(1-octadecene)), with the stiffness of the
material increasing with increasing 1-octadecene incor-
poration. Polymer molecular weights of the polyethylene-
b-poly(1-octadecene) polymers increase with increasing
polyethylene or poly(1-octadecene) block time. Contrary
to this trend, the molecular weights of the poly(1-
octadecene)-b-polyethylene copolymers increase from
the one to 2 h polymerization time of 1-octadecene but
do not increase beyond this point. The reason for the
Resonances in the C spectrum of the hyperbranched
polyethylenes produced from Pd(II) R-diimine catalysts
have been previously assigned, and it has been shown
that branches can be quantitated by running spectra
in deuterated bromobenzene at 120 °C, using Cr(acac)3
1
as a T relaxation agent and employing a 5 s delay
3
1,32
13
time.
Figure 9 shows a typical C spectrum of
polyethylene with the key methyl resonance from meth-
+
yl, ethyl, propyl, and butyl or longer (C4 ) branches

Macromolecules, Vol. 36, No. 9, 2003
Palladium(II)-R-Diimine Catalysts 3093
F igu r e 10. 13C NMR (C
D Br 0.5 M Cr(acac) , 100 MHz, 120 °C) of poly(1-octadecene).
6 5 , 3
Ta ble 4. Br a n ch es p er 1000 C in
microstructures as a function of the order of introduction
of the blocks is the comparison of the ethyl and propyl
branches per 1000 C’s in block polymers which differ
only in the order of block growth. While integration of
the weak resonances of sparsely populated branches in
P olyeth ylen e-b-p oly(1-octa d ecen e) Cop olym er sa
PE(2)
PE(2)
PE(2)
PE(3)
PE
28
16
5.2
41
C18(1)
C18(2)
C18(3)
C18(2)
C18
Me
Et
25
24
27
25
16
0
0
1
3
9.4
1.6
24
8.5
1.6
24
7.2
1.1
21
8.4
3.2
19
the C spectra can be imprecise, comparison of data in
Tables 4 and 5 reveal a clear trend in these copolymers.
The polymers in which the C-18 olefin is introduced
second (Table 4) consistently exhibit lower fractions of
ethyl and propyl branches compared to diblocks in which
the C-18 olefin is made first (Table 5.) For example in
comparing the P(C-18)(3 h)-b-PE(2 h) with the PE(2 h)-
b-P(C-18)(3 h), the ethyl and propyl branching numbers
decrease from 11 and 3.6, respectively, to 7.2 and 1.1.
Pr
C4
+
9
a
By 13C NMR (C6D5Br, 0.05 M Cr(acac)3, 100 MHz, 120 °C)
branches per 1000 C in polymer; Me ) methyl; Et ) ethyl; Pr )
+
propyl; C4 ) butyl or longer chain; PE ) polyethylene; C18 )
poly(1-octadecene); PE(2)C18(3) ) polyethylene (2 h)-b-poly(1-
octadecene) (3 h).
Ta ble 5. Br a n ch es p er 1000 C in
P oly(1-octa d ecen e)-b-p olyeth ylen e Cop olym er sa
13
The C NMR spectra of these polymers are shown in
Figure 11. Similarly, comparing P(C-18)(2 h)-b-PE(3 h)
with PE(3 h)-b-PC-18(2 h), branches decrease from 13
and 5.1 per thousand to 8.5 and 1.6, per thousand,
respectively. These data clearly suggest that when
C18(1)
PE (2)
C18(2)
PE(2)
C18(3)
PE(2)
C18(2)
PE(3)
PE
28
16
5.2
41
C18
Me
Et
23
14
3.3
30
26
13
5.1
26
25
11
3.6
28
28
13
5.4
36
16
0
0
1
-octadecene is introduced as the second block, ethyl and
Pr
C4
+
9
propyl branches are converted to other types of branches.
A mechanistic rationale is proposed below.
a
By 13C NMR (C6D5Br, 0.05 M Cr(acac)3, 100 MHz, 120 °C)
branches per 1000 C in polymer; Me ) methyl; Et ) ethyl; Pr )
3. Mech a n istic Ra tion a le. Previous mechanistic
studies provide an explanation for the dependence of
the microstructure of the diblock polymers on the order
of block introduction. Mechanistic studies of polyethyl-
ene formation show that dissociation of ethylene from
+
propyl; C4 ) butyl or longer chain; PE ) polyethylene; C18 )
poly(1-octadecene); C18(3)PE(2) ) poly(1-octadecene) (3 h)-b-
polyethylene (2 h).
marked on the spectrum. The signal marked with an
asterisk (/) is due to CH2 groups in the chain flanked
by at least four methylene groups on each side.
+
an alkyl ethylene complex (diimine)Pd(R)(ethylene)
(e.g., 5 in Scheme 5) at 25 °C is anywhere from 10 to
1
00 times faster than insertion, depending on the nature
1
3
The C spectra of poly(1-octadecene) is shown in
Figure 10. As previously established, R-olefins insert
only into primary Pd-carbon bonds and 1,2- and 2,1-
33
of R (the alkyl group) (kdissoc > kins). Furthermore, once
dissociation occurs, Pd migration along the chain via
1
,2-shifts takes place significantly faster than retrap-
2
6
insertions occur with about equal probability. This
feature, coupled with rapid chain running in the Pd-
alkyl intermediates, results in “chain-straightened”
polymers with fewer branches than expected. In the case
of poly(1-octadecene), the polymer exhibits approxi-
mately 34-39 branches per 1000 carbons and only
methyl and longer branches (most are no doubt C16
branches) occur. Even though palladium migrates down
the chain following a 2,1-insertion, no insertion into
secondary alkyl bonds occur and thus no propyl or ethyl
branches are observed in these polymers (compare
Figure 10 with Figure 9.)
ping with ethylene (kmig > ktrap[d]), (see Scheme 5)
where obviously the trapping rate is dependent on
ethylene concentration. Note also that we have estab-
lished that metal migration through a tertiary center
poses no barrier to chain walking. Thus, from the alkyl
resting state (e.g., 5), Pd migrates over tens to hundreds
of carbons prior to insertion. Guan has shown that the
overall architecture of the PE's produced depends on the
30,33
ethylene pressure.
At low pressures, the polyethyl-
ene is hyperbranched with branches-on-branches while
at higher pressures, the polyethylene is still highly
branched, but the architecture is more linear and less
hyperbranched with fewer branches-on-branches. This
change in structure is a direct result of higher trapping
rates of the alkyl complex at high ethylene pressures
Tables 4 and 5 summarize similar branching data for
polyethylene/poly(1-octadecene) block polymers. The
feature that is most diagnostic of the differences in

3
094 Gottfried and Brookhart
Macromolecules, Vol. 36, No. 9, 2003
F igu r e 11. 13C NMR (C
octadecene) (3 h)-b-polyethylene (2 h).
D
Br
0.5 M Cr(acac)
, 100 MHz, 120 °C): (a) polyethylene (2 h)-b-poly(1-octadecene) (3 h); (b) poly(1-
6
5
,
3
Sch em e 5. P d Ch a in -Wa lk in g d u r in g Eth ylen e P olym er iza tion
and thus fewer 1,2-Pd migrations on average before
insertion.
fin insertion into primary Pd-R bonds is somewhat
slower than analogous ethylene insertions. Faster dis-
sociation, slower trapping, and slower insertion into only
primary Pd-R bonds, implies in this case that Pd will
chain walk over far more carbons, probably 1000’s of
carbons, prior to R-olefin insertion. When insertion does
Consider how this picture will change when using an
R-olefin monomer such as 1-octadecene in place of
ethylene. Because of the increased bulk of the 1-octa-
decene relative to ethylene, the dissociation rate from
an alkyl olefin complex will be faster while the trapping
rate of a Pd alkyl complex will be slower relative to
ethylene. Previous work has established that R-olefins
do not insert into Pd secondary alkyl bonds which is a
result of very low equilibrium concentrations of the Pd-
+
occur, it will be into a Pd(n-alkyl) bond. Thus, consid-
ering block polymer formation, if the initial block is
hyperbranched polyethylene, then growth of an R-olefin
block will occur from the ends of the branches of the
hyperbranched polyethylene by virtue of the Pd chain
walking extensively through the hyperbranched struc-
+
28b-d
(
R-olefin)(sec-alkyl) complexes.
Furthermore, R-ole-

Macromolecules, Vol. 36, No. 9, 2003
Palladium(II)-R-Diimine Catalysts 3095
Sch em e 6. Mod el for Gr ow th of a P olyeth ylen e-b-p oly(1-octa d ecen e) Cop olym er .
ture prior to each insertion. In the case of 1-octadecene,
insertion at the ends of ethyl branches will result in
disappearance of the ethyl branch and formation of
either a methyl branch following a 1,2-insertion or a
long chain branch following a 2,1-insertion. Likewise,
insertion at the end of a propyl branch will eliminate
that branch and reduce the overall density of the
branching in the polymer. Some typical possibilities are
illustrated in Scheme 6. The net result of such a process
is that the block polymer will form a “core” of polyeth-
ylene surrounded by a shell of 1-octadecene.
On the other hand, when the 1-octadecene block is
grown first, it forms a polymer with methyl and C16 or
longer branches. The high pressure of ethylene used to
make the second block allows much less time for the
palladium catalyst center to chain walk between inser-
tions. This results in ethylene being added in a more
linear fashion, working away from the first polymer
block. These types of copolymers have branching data
that correspond closely with what is expected from a
mix of polyethylene and poly(1-octadecene). They appear
to contain two distinct blocks, although some chain
walking of the palladium into the first block while
inserting ethylene may occur, and thus the blocks will
not be “cleanly” separated.
F igu r e 12. DSC trace of poly(1-octadecene) (2 h)-b-polyeth-
ylene (2 h).
show only two high melt transitions at 60 and 84 °C as
shown in Figure 13. The two high-temperature melting
transitions in both types of polymers are similar to those
observed in the homo poly(1-octadecene) prepared from
catalyst 2c with Tm ) 67 and 81 °C.
For the block copolymer with the poly(1-octadecene)
grown first, the two high melt transitions are attributed
to the moderately linear main chain and the C16 side
chains. The assignment of the -24 °C transition in the
poly(octadecene)-b-polyethylene diblock materials is
speculative at this point. As ethylene is enchained to
form a second block, the catalyst walks back to some
extent into the 1-octadecene block creating a few short
branches on the primarily linear chain. As more ethyl-
ene is added, a block of highly branched PE with no Tm
is grown. The “fuzzy” junction point between the two
The thermal data on the diblock polymers support the
contention of differing microstructures depending on the
order of monomer enchainments. All of the diblock
polymers in which the poly(1-octadecene) was intro-
duced first exhibit two high-temperature melting tran-
sitions (ca. 66 and 83 °C) and a broad low-temperature
melt transition at ca -24 °C as shown in Figure 12. The
diblock polymers in which polyethylene is made first

3
096 Gottfried and Brookhart
Macromolecules, Vol. 36, No. 9, 2003
purchased from Aldrich, dried over sodium, and distilled under
argon before storing over sieves. Acetonitrile (99.5%), 3,5-bis-
(
(
trifluoromethyl)benzonitrile (97%), and 4-methoxybenzonitrile
99%) were purchased from Aldrich and added as received to
chlorobenzene to form a 0.1 M solutions that were degassed
and stored over sieves. cis-2-Hexene (97%, Fluka), trans-2-
hexene (97%, Lancaster), cis-3-hexene (95%, Fluka), and trans-
3
-hexene (99+%, Aldrich) were used as received for polymer-
ization and as GC standards. The Pd(II) R-diimine complexes
+
-
[
2
(Ar-NdC(Me)-C(Me)dN-Ar)Pd(Me)(NCMe)] BAr′
4
(Ar )
i
,6- Pr
2
C
6
H
3
; Ar ) 3,5-(CF
3
)
3
2
C
6
H
3
) (2b), [(Ar-NdC(Me)-C-
+
-
(
Me)dN-Ar)Pd(Me)(3,5-(CF
)
2
C
6
H
3
CN)] BAr′
4
(Ar ) 2,6-
i
Pr
C(Me)dN-Ar)Pd((CH C(O)OCH
3 2 6 3
; Ar ) 3,5-(C ) C H ) (3) were prepared according to the
2
C
6
H
3
; Ar ) 3,5-(CF ) C H ) (2c), and [(Ar-NdC(Me)-
3 2 6 3
+
-
i
2
)
3
3
)] BAr′
4
(Ar ) 2,6- Pr
2 6
C -
H
3
2
4
literature.
P r ep a r a tion of Ester En d -Ca p p ed P olyeth ylen e. A
mechanically stirred 300 mL Parr reactor equipped with an
electric heating mantle controlled by a thermocouple was
heated overnight to 150 °C under vacuum and then cooled to
27 °C. The autoclave was pressurized to 100 psig ethylene and
vented three times, then charged with 90 mL of chlorobenzene
and sealed. Ethylene (100 psig) was added to the stirring
solvent and released twice. The ethylene pressure was then
raised to 400 psig. The Parr reactor was placed in an ice bath
and the chlorobenzene polymerization solvent stirred under
F igu r e 13. DSC trace of polyethylene (3 h)-b-poly(1-octa-
decene) (2 h).
blocks may account for the -24 °C Tm. Despite the lack
of definitive assignment of this Tm, it is clear from the
DSC traces in Figures 12 and 13 that the materials
must possess somewhat different microstructures.
Exp er im en ta l Section
4
00 psig ethylene until the system cooled to 5-6 °C. The
Gen er a l Meth od s. All manipulations of air and/or water
sensitive compounds were performed using standard high
vacuum or Schlenk techniques. Argon was purified by passage
through columns of BASF R3-11 catalyst (Chemalog) and 4
Å molecular sieves. Solid organometallic compounds were
ethylene pressure was vented and a solution of 0.0132 g (8.11
-6
× 10 mol) of catalyst 2c dissolved in 10 mL of chlorobenzene
was transferred via cannula into the reactor. The system was
pressurized to 400 psig ethylene to begin the polymerization.
After the allotted polymerization time, ethylene was vented.
Excess ethylene was then removed at 5 °C: vacuum was
applied to the reactor for 3 min, the reactor was then back-
filled with argon, and the polymerization solution was purged
with argon for 3 min. The vacuum/backfill/purge cycle was
repeated three times. Then, 200 equiv of methyl acrylate were
added. The solution was stirred for 1 h. Finally, 0.2 mL of
triethylsilane was added to quench the catalyst. The polym-
erization solution and two chlorobenzene rinses of the reactor
were combined in a tared round-bottom flask from which all
volatiles were removed via rotary evaporation. The light
brown, highly viscous polymer was dissolved in hexanes and
filtered through a plug of silica gel and alumina to remove
1
transferred in an argon-filled MBraun drybox. H NMR spectra
were recorded on a Bruker DRX400 or a Bruker AMX-300
1
13
spectrometer. H and C chemical shifts are reported in ppm
1
downfield of TMS and were referenced to residual H NMR
and C NMR signals of the deuterated solvents. 1H NMR
13
spectra of polyethylene, polypropylene, and poly(1-hexene)
1
were taken at 25 °C in CDCl
3
.
H NMR spectra of poly(1-
octadecene) and ethylene/1-octadecene copolymers were taken
1
3
6 5
at 120 °C in C D Br. C spectra of polymers were taken as
described below. GPC traces of polyethylene, polypropylene,
and poly(1-hexene) were performed at UNC (35 °C, 1.0 mL/
min) on a Waters Alliance HPLC Separations Module equipped
with Waters Styragel HR2 (molecular weight range 500-
1
the catalyst. The polymer was precipitated in methanol. H
2
00K), HR4 (molecular weight range 5K-600K), and HR5
NMR (CDCl
(t, 2H, CH OC(O)CH
(polyethylene CH ). The H integrals of the polymer showed
3
, 300 MHz, 25 °C, δ 3.65 (s, 3H, CH
3
OC(O)), 2.41
(molecular weight range 50K-4M) columns all packed with 5
3
2
), 1.45-1.0 (polyethylene CH
2
, CH), 0.8
1
µm spherical particles in series and a Waters 2410 differential
refractometer RI (refractive index) detector relative to poly-
styrene standards. Samples consisted of ∼1 mg of polymer in
3
∼750 ethylene insertions per OMe end group. The number of
insertions is in the range of insertions obtained while polymer-
izing ethylene with catalyst 3 under identical conditions with
no end cap introduced.
1
mL of degassed THF. GPC traces of poly(1-octadecene) and
ethylene/1-octadecene copolymers were performed at DuPont
Wilmington, DE) in 1,2,4-trichlorobenzene at 135 °C with a
(
P r ep a r a tion of Telech elic P olyeth ylen e. A procedure
-
6
flow rate of 1.0 mL/min using a Waters HPLC 150C equipped
with dual Shodex columns (Shodex AT-806MS columns with
an exclusion limit of 20 000 000 Da.) A calibration curve was
established with polystyrene standards and universal calibra-
tion was applied using Mark-Houwink constants for polyeth-
similar to that describred above using 0.0118 g (8.0 × 10
mol) of catalyst 3 dissolved in 10 mL of chlorobenzene to
initiate the polymerization was used to polymerize ethylene.
At the end of the polymerization time, the excess ethylene was
vented and the reactor purged as described above. Then the
functionalized monomer (methyl acrylate, ethyl acrylate,
methyl vinyl ketone, or 4-penten-1-ol) (200 equiv) was added.
The solution was stirred for the noted reaction time, allowing
the system to warm to room temperature. Finally, 0.2 mL of
triethylsilane was added to quench the catalyst except when
4-penten-1-ol was used as an end cap. The polymerization
solution and two chlorobenzene rinses of the reactor were
combined in a tared round-bottom flask from which all
volatiles were removed via rotary evaporation. The light
brown, highly viscous polymer was dissolved in hexanes and
filtered through a plug of silica gel and alumina to remove
-
4
ylene (k ) 4.34 × 10 ; R ) 0.724). Thermal analysis was
preformed on a Seiko Instruments DSC220C differential
scanning calorimeter. To standardize thermal measurements,
every DSC sample was heated above the melting point of the
polymer followed by rapid cooling and then data was collected
at a heating rate of 10 °C/min (second heat). Isomerization of
1
-hexene was analyzed on a Hewlett-Packard 5890 A gas
chromatograph using a Supelco Petrocol DH 50.2 capillary
column (50m, 0.20 i.d., 0.50 µm film thickness) and flame
ionization detector.
Ma ter ia ls. Chlorobenzene (99.5+%, Aldrich) was dried over
Å molecular sieves and degassed with argon. Polymer grade
1
4
the catalyst. The polymer was precipitated in methanol. H
ethylene and propylene were purchased from Matheson and
used without further purification. Et
SiH (97%), methyl acry-
late (99%), ethyl acrylate (99%), methyl vinyl ketone (99%),
-penten-1-ol (99%), and 1-octadecene (90%) were purchased
from Aldrich and used as received. 1-Hexene (99+%) was
NMR (CDCl
methyl ester group using methyl acrylate (1 h)): δ 3.65 (s, 3H,
CH OC(O)), 2.41 (t, 2H, CH OC(O)CH ), 1.45-1.0 (polyethyl-
ene CH , CH), 0.8 (polyethylene CH ). The integrals of the
polymer protons indicated ∼375 ethylene insertions per OMe
3
, 300 MHz, 25 °C; polymer end-capped with a
3
3
3
2
4
2
3

Macromolecules, Vol. 36, No. 9, 2003
Palladium(II)-R-Diimine Catalysts 3097
group as expected based on the singly end-capped polyethylene
present). The polymer was then dissolved in hexanes, filtered
through silica gel and alumina to remove the catalyst, and
precipitated in methanol. The methanol was decanted and the
polymer rinsed in acetone. Finally, the polymer was dried in
a vacuum oven at 60 °C overnight. No added nitrile: 0.296 g
1
chains. H NMR (CDCl
3
, 300 MHz, 25 °C; polymer end-capped
with an ethyl ester end group using ethyl acrylate (2 h)): δ
4
4
.13 (q, 2H, CH
H, CH OC(O)CH
, CH), 0.8 (polyethylene CH
3
CH
2
2
OC(O)), 3.65 (s, 3H, CH
and CH CH OC(O)CH ), 1.45-1.0 (poly-
), (CH CH OC(O))
, 300 MHz, 25 °C; polymer end-
capped with a methyl ketone group using methyl vinyl ketone
3
OC(O)), 2.35 (m,
3
3
2
2
ethylene CH
not visible. H NMR (CDCl
2
3
3
2
of polymer; M
methyl)benzonitrile (0.15 mL of a 0.1 M solution in chloroben-
zene): 0.219 g of polymer; M ) 19,700, M /M ) 1.06.
Acetonitrile (0.15 mL of a 0.1 M solution in chlorobenzene):
0.061 g of polymer; M ) 8300, M /M ) 1.05. 4-Methoxyben-
zonitrile (0.15 mL of a 0.1 M solution in chlorobenzene): 0.024
g of polymer; M ) 3000, M /M ) 1.11.
P olym er iza tion of In ter n a l Hexen es. Catalyst 1c (0.0123
n
) 30 700, M
w n
/M ) 1.03. 3,5-Bis(trifluoro-
1
3
n
w
n
(
(
1
overnight)): δ 3.65 (s, 3H, CH
O)CH ), 2.31 (t, 2H, CH C(O)CH
.45-1.0 (polyethylene CH , CH), 0.8 (polyethylene CH
NMR (CDCl , 300 MHz, 25 °C; polymer end-capped with an
aldehyde group using 4-penten-1-ol (3 h)): δ 9.78 (s, 1H, HC-
O)CH ), 3.65 (s, 3H, CH OC(O)), 2.41 (t, 2H, CH OC(O)CH ),
.30 (t, 2H, HC(O)CH ), 1.45-1.0 (polyethylene CH , CH), 0.8
polyethylene CH ). The functionalities at the terminal end of
3
OC(O)), 2.41 (t, 2H, CH
3
OC-
2
3
2
), 2.15 (s, 3H, CH C(O)),
3
n
w
n
1
2
3
). H
3
n
w
n
-
6
(
2
(
2
3
3
2
g, 7.56 × 10 mol) was weighed into a flame-dried Schlenk
flask in the drybox. Chlorobenzene (9.0 mL) was added to the
flask, dissolving the solid to form a yellow solution which was
stirred in an ice bath for 30 min to cool to 0 °C. trans-2-Hexene
(0.5 mL) and trans-3-hexene (0.5 mL) were combined in a vial.
The hexenes were then added to the polymerization solution
to begin the polymerization. After 3 h at 0 °C, the polymeri-
2
2
3
the polymer chains integrated in a 1:1 molar ratio with the
methyl ester introduced by initiation of the polymer chain with
3
.
Gen er a l P olym er iza tion of P r op ylen e (1 a tm ). Catalyst
-
6
3
zation was quenched by adding 0.2 mL of Et SiH. The
2
c (0.0065 g, 3.99 × 10 mol) was weighed into a flame-dried
polymerization solution and two rinses of the polymer flask
with chlorobenzene were combined in a tared flask and
volatiles were removed via rotary evaporation. The final
product was dried in vacuo and weighed to determine polymer
yield. An 1H NMR spectrum of the product showed traces of
the catalyst as well as a very small amount of polymer.
Isom er iza tion of 1-Hexen e d u r in g P olym er iza tion
Schlenk flask in the drybox. Chlorobenzene (20 mL) was added
to this flask to dissolve the catalyst, forming a bright orange-
yellow solution. The polymerization solution was stirred in an
ice bath at 0 °C for 30 min to cool to the polymerization
temperature. Propylene (1 atm) was introduced to the flask
to begin the polymerization by evacuating the flask and back-
filling it with propylene three times. After the allotted polym-
erization time, triethylsilane (0.2 mL) was added to the
polymerization to quench the catalyst. The polymerization
solution and two rinses of the polymerization flask with
chlorobenzene were combined in a tared flask and the solvent
removed via rotary evaporation. The brown to orange, gooey
polymer was dried overnight in vacuo. After weighing, hexanes
were added to dissolve the polymer. The polymer solution was
filtered through a plug of silica gel and alumina to remove
the catalyst and the polymer precipitated in methanol. The
methanol was decanted, the polymer washed in acetone and
dried in a vacuum oven at ∼60 °C overnight. Gel permeation
-
5
w ith 1c. Catalyst 1c (0.0246 g, 1.5 × 10 mol) was weighed
into a flame-dried Schlenk flask. Chlorobenzene (20 mL) was
added, dissolving the catalyst to form a light orange-yellow
solution. Benzene (0.125 mL) was also added as an internal
standard. The catalyst solution was stirred in an ice bath for
3
0 min to cool it to the polymerization temperature. 1-Hexene
(2.2 mL) was added to begin polymerization. Immediately, an
aliquot (0.5 mL) was removed from the polymerization and
quenched by adding 2-3 mL of acetone. Every 30 min for 3 h,
an additional aliquot (0.5-1.0 mL) was removed and quenched
by adding acetone (2-3 mL). Volatiles of the aliquot were
vacuum transferred for analysis by GC. GC conditions: injec-
tor temperature 220 °C; detector temperature 250 °C; oven
temperature program 30 °C/18 min; 20 °C/min ramp, 150 °C/
chromatography (THF, 35 °C, polystyrene reference): (1 h) M
9000, M /M
7 400, M ) 1.04; (3 h) M
) 1.06; (4 h) M ) 26 800, M
) 33 900, M ) 36 700, M
) 47 200, M /M ) 1.11.
n
)
w
) 9500, M
/M
w
n
) 1.03; (2 h) M
) 23 000, M
) 28 700, M
/M ) 1.08; (6 h) M
n
) 16 800, M
w
w
)
1
w
n
n
) 24 300, M /
w
2
5 min. Retention times for hexene isomers under analytical
M
h) M
M
n
n
w
w
/M
n
) 1.07; (5
) 42 400,
conditions used are as follows: 1-hexene, 14.45 min; trans-3-
hexene, 15.75 min; cis-3-hexene, 15.82 min; trans-2-hexene,
n
w
w
n
n
w
w
n
1
6.14 min; cis-2-hexene, 17.15 min. The percentage of hexene
Aliq u ot Sa m p lin g of t h e Livin g P olym er iza t ion of
isomer in solution was determined by taking its peak area and
dividing by the sum of the areas of all hexene isomers present.
Gen er a l P r oced u r es for 1-Octa d ecen e P olym er iza tion .
-5
1
-Hexen e. Catalyst 2b, 2c, or 3 (1.5 × 10 mol) was weighed
into a flame-dried Schlenk flask in a drybox. Chlorobenzene
10 mL) was added, dissolving the catalyst to form a light
orange/yellow solution. 1-Hexene (15.0 mL) and chlorobenezne
125 mL) were added under argon to a second flame-dried
(
-6
The catalyst 1c (0.0065 g, 4 × 10 mol) was weighed into a
flame-dried Schlenk flask under argon in a drybox. Chloroben-
zene (1.5 mL) was added to the flask to dissolve the catalyst.
A second flame-dried Schlenk flask was prepared with the
desired amount of 1-octadecene and chlorobenzene to make a
total of 8.5 mL. The 1-octadecene solution was stirred in an
ice bath for 30 min to cool it to the polymerization temperature.
The catalyst solution was vac-cannulaed into the flask con-
taining the 1-octadecene solution to begin the polymerization.
After the polymerization time (usually 1.5, 3, or 4.5 h), 0.2
mL of triethylsilane was added to quench the catalyst. The
polymerization solution was poured into 150 mL of methanol
and a white precipitate formed immediately. The solid was
allowed to settle out and then collected on a B u¨ chner funnel,
rinsing copiously with hexanes and acetone to rid the polymer
of any remaining monomer. The solid was collect and dried in
a vacuum oven at 60 °C overnight. Gel permeation chroma-
tography (1,2,4-trichlorobenzene, 135 °C, polystyrene stan-
(
Schlenk flask. The resulting solution of 1-hexene in chloroben-
zene was stirred in an ice bath for 30 min to cool to the
polymerization temperature. The catalyst solution was then
cannulaed into the flask containing the 1-hexene solution to
begin the polymerization. Every 20 min for 3 h, a 5.0 mL
aliquot of the polymerization solution was removed and
quenched by addition of 0.1 mL of triethylsilane. Solvent was
removed from each aliquot via rotary evaporation, leaving a
sticky brown polymer residue. Gel permeation chromatography
(THF, 35 °C, polystyrene reference) was used to obtain the
molecular weight and dispersity of each polymer aliquot.
P olym er iza tion of 1-Hexen e w ith Ad d ed Nitr ile. Cata-
-
5
lyst 2c (1.5 × 10 mol) was weighed into a flame-dried
Schlenk flask under argon in the drybox. Chlorobenzene (18
mL) was added to the flask to dissolve the catalyst. Any excess
nitrile was added. The resulting solution was stirred in an ice
bath for 30 min to cool it to the polymerization temperature.
Polymerization was initiated upon addition of 2 mL of 1-hex-
ene. After the 3 h polymerization time, 0.2 mL of triethylsilane
was added to quench the catalyst. Solvent was then removed
by rotory evaporation leaving a brown/orange sticky film of
polymer. The polymer was dried overnight in vacuo and
weighed to determine yield (accounting for the catalyst
-
4
dards, correction factors k ) 4.34 × 10 . R ) 0.724): (1 h) M
) 5600, M ) 6300, M /M ) 1.13; (1.5 h) M ) 8200, M
9900, M /M ) 1.20; (3 h) M ) 13 600, M ) 18 000, M
) 1.34; (4.5 h) M ) 17 600, M ) 26 500, M /M ) 1.51.
n
w
w
n
n
w
)
/M
w n
w
n
n
w
n
w
w
n
Con t r ol E xp er im en t s for Block Cop olym er iza t ion .
1-Octa d ecen e P olym er iza tion a fter Eth ylen e Rem ova l.
This experiment was designed to determine the effectiveness
of ethylene removal from the polymerization solution. Ethylene

3
098 Gottfried and Brookhart
Macromolecules, Vol. 36, No. 9, 2003
would be declared effectively removed if there was no change
in 1-octadecene polymerization run after ethylene had been
removed from solution as compared to a 1-octadecene polym-
erization run in solution where no ethylene was ever present.
A mechanically stirred 300 mL Parr reactor equipped with
an electric heating mantle controlled by a thermocouple
dipping into the reaction mixture was heated overnight to 150
dipping into the reaction mixture was heated overnight to 150
°C under vacuum and then cooled to 27 °C. The autoclave was
pressurized to 100 psig of ethylene and vented three times.
The autoclave was then charged with 75 mL of chlorobenzene
and sealed. Ethylene to 100 psig was added and released twice.
Then, the reactor was pressurized to 400 psig of ethylene and
the solution cooled to 5-6 °C. The ethylene pressure was
vented, and a solution of catalyst (2c) (0.013 g, 8 × 10 mol)
weighed into a Schlenk tube under argon and dissolved in 5
mL of chlorobenzene was added to the reactor via cannula.
The reactor was sealed and pressurized with ethylene to 400
psig. The reaction mixture was stirred under constant ethylene
pressure for the given ethylene block time, after which time
the ethylene pressure was vented.
Ethylene was removed: vacuum was applied to the reactor
for 3 min, the reactor was back-filled with argon, and the
polymerization solution was purged with argon for 3 min. The
vacuum, backfill, and purge cycle was repeated three times.
A solution of 1-octadecene (10 mL) in chlorobenzene (10.0 mL)
that had been stirring in an ice bath was added to the reactor
via cannula. The polymerization solution was stirred for the
allotted block time. The catalyst was quenched by addition of
0.2 mL of triethylsilane. The polymerization solution and two
rinses of the reactor with chlorobenzene were poured into 300
mL of stirring methanol. The polymer was collected via
filtration, rinsed with methanol and acetone, and dried in a
vacuum oven at 60 °C.
-
6
°
C under vacuum and then cooled to 27 °C. The reactor was
pressurized to 100 psig of ethylene and vented three times.
The reactor was then charged with 80 mL of chlorobenzene
and sealed. Ethylene at 100 psig was added and released twice.
Then, the reactor was pressurized to 400 psig and the solution
cooled to 5-6 °C. Ethylene was vented, the reactor was placed
under vacuum for 3 min, the reactor was back-filled with
argon, and the polymerization solution was purged with argon
for 3 min. The vacuum, backfill, and purge cycle was repeated
three times.
-
6
Meanwhile catalyst (2c) (0.0129 g, 7.92 × 10 mol) was
weighed into a flame-dried Schlenk flask in the drybox.
Chlorobenzene (10.0 mL) was added to dissolve the catalyst,
forming a bright yellow solution. A solution of 10.0 mL of
chlorobenzene and 10.0 mL of 1-octadecene was also prepared
in a flame-dried Schlenk flask. The monomer solution was
stirred in an ice bath for 20 min in order to cool it to the
polymerization temperature.
After the ethylene removal, the catalyst solution was added
to the reactor via cannula. This addition was followed closely
by the addition of the 1-octadecene solution to the reactor via
cannula to begin the polymerization. The polymerization was
carried out for 2 h and then quenched by adding 2.0 mL of
triethylsilane. The polymerization solution and two chloroben-
zene rinses of the reactor were poured into ∼300 mL of stirring
methanol, immediately forming a white precipitate. The
polymer was collected as a fluffy, light gray solid. The solid
was washed with both methanol and acetone and dried in the
Gen er a l P r oced u r e for P oly(1-octa d ecen e)-b-p olyeth -
-
6
ylen e. The catalyst (2c) (0.0130 g, 8 × 10 mol) was weighed
into a flame-dried Schlenk flask under argon in the drybox.
Chlorobenzene (1.0 mL) was added to the catalyst, dissolving
the solid to form a bright yellow solution. 1-Octadecene (0.7
mL) and chlorobenzene (5.1 mL) were combined in a second
flame-dried Schlenk flask and stirred in an ice bath to cool to
the polymerization temperature. The catalyst solution was
cannula transferred to the 1-octadecene solution to initiate
polymerization of the first block.
1
vacuum oven. Polymer characterization was performed by H
NMR (400 MHz, C
6
D
5
Br, 120 °C). Poly(1-octadecene) run with
) 67.1 °C,
1.2 °C; by H NMR 43 branches/1000 C. Poly(1-octadecene)
after ethylene removal from chlorobenzene: 36 TO/h by
no ethylene: 41 TO/h by polymer weight; DSC, T
m
Meanwhile, a mechanically stirred 300 mL Parr reactor
equipped with an electric heating mantle controlled by a
thermocouple dipping into the reaction mixture was heated
to 150 °C under vacuum and then cooled to 27 °C. The
autoclave was pressurized to 100 psig of ethylene and vented
three times. The autoclave was then charged with 100 mL of
chlorobenzene and sealed. Ethylene at 100 psig was added and
released twice. Then, the reactor was pressurized to 400 psig
of ethylene and the solution cooled to 5-6 °C. The reactor was
vented after the noted 1-octadecene block time and the
polymerization solution containing the poly(1-octadecene) block
was added via cannula. The reactor was then pressurized to
400 psig of ethylene and the solution stirred for the allotted
polyethylene block time. The polymerization was quenched by
adding 0.2 mL of triethylsilane.
The polymerization solution and two chlorobenzene rinses
of the reactor were poured into 300 mL of stirring methanol.
The polymer was collected via filtration, washed with methanol
and acetone and dried in the vacuum oven at 60 °C.
P olym er Ch a r a cter iza tion . The block copolymers were
characterized by three methods. First GPC traces (as described
above) were taken of the ethylene/1-octadecene block copoly-
mers at DuPont. DSC traces of all polymers were obtained by
heating polymer samples from 25 to 175 °C at 10 °/min and
holding for 5 min. The samples were cooled to -100 °C at 10°/
min and held for 15 min. The temperature was then raised at
1
8
1
polymer weight; DSC T
branches/1000 C.
m
) 73.8 °C, 85.3 °C; by H NMR 39
P olym er izin g Eth ylen e in th e P r esen ce of Dilu te
1
-octa d ecen e. The purpose of this experiment was to deter-
mine whether polyethylene made in the presence of diluted
1
1
-octadecene was different from polyethylene made with no
-octadecene present.
A mechanically stirred 300 mL Parr reactor equipped with
an electric heating mantle controlled by a thermocouple was
heated overnight to 150 °C under vacuum and then cooled to
2
7 °C. The autoclave was pressurized to 100 psig of ethylene
and vented three times. The autoclave was then charged with
0 mL of chlorobenzene and sealed. Ethylene at 100 psig was
8
added and released twice. Then, the reactor was pressurized
to 400 psig and the solution cooled to 5-6 °C.
-
6
Meanwhile catalyst (2c) (0.0130 g, 8.0 × 10 mol) was
weighed into a flame-dried Schlenk flask in the drybox.
Chlorobenzene (10.0 mL) was added to dissolve the catalyst,
forming a bright yellow solution.
Ethylene was vented from the reactor, and 0.1 mL of
1
-octadecene was added followed by addition of the catalyst
solution via cannula. The reactor was re-pressurized to 400
psig of ethylene and the polymerization begun. After 2 h of
polymerization in 1-octadecene solution, the reactor was
vented, and 0.2 mL of triethylsilane was added to quench the
catalyst. The polymer was isolated using the procedure for
poly(1-octadecene) workup described above. Polyethylene made
in the absence of 1-octadecene as described in the literature:
10°/min to 175 °C to obtain the reported data. The T of most
g
of the polymers was broad and tended to run into the Tm curves
so they were not reported. Polymer Tm values are reported as
the endothermic maximum. Finally, the polymers were char-
1
H and 13C NMR spectroscopy. The ethylene/1-
acterized by
1
8
1
2
16 TO/h by weight; T
Polyethylene made in the presence of 0.034 M 1-octadecene:
70 TO/h; T -61 °C; 90 branches/1000 C.
Gen er a l P r oced u r e for P olyeth ylen e-b-p oly(1-octa -
g
-67 °C; 90-110 branches/1000 C.
octadecene copolymers were characterized by H NMR spec-
1
3
troscopy in C D Br at 120 °C (393 K). C NMR (100 MHz)
6
5
2
g
6 5 3
was carried out in C D Br containing 0.05 M Cr(acac) at 120
°C (393 K) using a 90° pulse of 17.8 µs, a spectral width of 35
d ecen e). A mechanically stirred 300 mL Parr reactor equipped
with an electric heating mantle controlled by a thermocouple
kHz, a relaxation delay of 5 s, an acquisition time of 0.64 s,
3
1 1
and inverse gated decoupling to allow for integration.
H

Macromolecules, Vol. 36, No. 9, 2003
Palladium(II)-R-Diimine Catalysts 3099
NMR spectroscopy was used to determine overall branching
in the polymer, using the following formula:
Goldberg, I.; Kol, M. J . Am. Chem. Soc. 2000, 122, 10706-
10707. (c) Tshuva, E. Y.; Goldberg, I.; Kol, M.; Goldschmidt,
Z. Chem. Commun. 2001, 2120-2121.
(
12) Tian, J .; Hustad, P. D.; Coates, C. W. J . Am. Chem. Soc. 2001,
CH integral
3
2
1
23, 5134-5135.
branches/1000 C )
× 3 × 1000
total integral
(13) (a) Saito, J .; Mitani, M.; Onada, M.; Mohri, J . T.; Ishii, S.;
Yoshida, Y.; Nakano, T.; Tanaka, H.; Matsugi, T.; Kojoh, S.;
Kashiwa, N.; Fujita, T. Macromol. Rapid Commun. 2001, 22,
13C NMR was used to examine the types of branches in the
polymers and block copolymers. Of the peaks identified in
Figure 9, the CH * represents the methylenes in the middle
2
1
072-1075. (b) Saito, J .; Mitani, M.; Matsui, S.; Kashiwa,
N.; Fujita, T. Macromol. Rapid Commun. 2000, 21, 1333-
336. (c) Matsui, S.; Mitani, M.; Saito, J .; Tohi, Y.; Makio,
1
of long, straight chains. Other carbons in the polymer chain
such as the methine carbons at branch points and carbons in
the main chain that are R-, â-, or γ- to a branch have been
H.; Matsukawa, N.; Takagi, Y.; Tsuru, K.; Nitabaru, M.;
Nakano, T.; Tanaka, H.; Kashiwa, N.; Fujita, T. J . Am. Chem.
Soc. 2001, 123, 6847-6856. (d) Fujita, T.; Mitani, M.;
Ypshida, Y.; Matsugi, T.; Suzuki, Y.; Ishii, S.; Tohi, Y.; Makio,
H.; Inoue, Y.; Saito, J .; Kojoh, S.; Kashiwa, N. Polym. Mater.
Sci. Eng. 2002, 86, 299-300.
2
8c,d,31,34
identified in the literature.
The branches that were
included in our polymer analysis all have peaks which are
unique and easily separated from the other peaks in the
(
14) (a) Mashima, K.; Fujikawa, S.; Tanaka, Y.; Urata, H.; Oshiki,
spectrum to ensure more accurate integration. To calculate
T.; Tanaka, E.; Nakamura, A. Organometallics 1995, 14,
+
the number of methyl, ethyl, propyl, and C
4
branches, or the
2
633-2640. (b) Mashima, K.; Fujikawa, S.; Urata, H.;
Tanaka, E.; Nakamura, A. J . Chem. Soc., Chem. Commun.
994, 1623-1624.
straight chain methylenes per 1000 carbons in the polymer
chain, the integrals of all peaks from 10 to 42 ppm were
summed. The integral of the peak representing the desired
branch or methylene was then divided by the sum of all the
carbons in the polymer chain and multiplied by 1000.
1
(
15) Mitani, M.; Mohri, J .; Yoshida, Y.; Saito, J .; Ishii, S.; Tsuru,
K.; Matsui, S.; Furuyama, R.; Nakano, T.; Tanaka, H.; Kojoh,
S.; Matsugi, T.; Kashiwa, N.; Fujita, T. J . Am. Chem. Soc.
2
002, 124, 3327-3336 and references therein.
(
16) (a) Brookhart, M.; DeSimone, J . D.; Grant, B. E.; Tanner, M.
J . Macromolecules 1995, 28, 5375-5380. (b) Schmidt, G. F.;
Brookhart, M. J . Am. Chem. Soc. 1985, 107, 1443-1444. (c)
Brookhart, M.; Volpe, A. F., J r.; Lincoln, D. M.; Horvath, I.
T.; Millar, J . M. J . Am. Chem. Soc. 1990, 112, 5634-5636.
Ack n ow led gm en t. We thank DuPont and the Na-
tional Science Foundation (CHE0107810) for support
and DuPont analytical services for GPC data on semi-
crystalline polymers. A.C.G. was supported by a UNC
Board of Governors Fellowship.
(d) Brookhart, M.; Volpe, A. F., J r.; DeSimone, J . D.; La-
manna, W. M. Polym. Prepr. (Am. Chem. Soc., Div. Polym.
Chem.) 1991, 32, 461. (e) The living nature of the polymer-
ization has been confirmed by spectroscopic characterization
of initiating and propagating species and by linear plots of
Mn versus conversion: Volpe, A. F., J r. Ph.D. Thesis, Uni-
versity of North Carolina at Chapel Hill, 1991.
Refer en ces a n d Notes
(
1) Coates, G. W.; Hustad, P. D.; Reinartz, S. Angew. Chem., Int.
Ed. Engl. 2002, 41, 2237-2257.
(2) (a) Doi Y.; Ueki, S.; Keii, T. Macromolecules 1979, 12, 814-
(
(
(
17) Killian, C. M.; Tempel, D. J .; J ohnson, L. K.; Brookhart, M.
J . Am. Chem. Soc. 1996, 118, 11664-11665.
18) Gottfried, A. C.; Brookhart, M. Macromolecules 2001, 34,
8
1
19. (b) Doi Y.; Ueki, S.; Keii, T. Makromol. Chem. 1979, 180,
359-1361. (c) Doi, Y.; Tokuhiro, N.; Soga, K. Makromol.
Chem. 1989, 190, 643-651.
1
140-1142.
(3) (a) Doi, Y.; Keii, T. Adv. Polym. Sci. 1986, 73/ 74, 201-248.
19) Hong, S. C.; J ia, S.; Teodorescu, M.; Kowalewski, T.; Maty-
jaszewski, K.; Gottfried, A. C.; Brookhart, M. J . Polym. Sci.,
Part A: Polym. Chem. 2002, 40, 2736-2749.
(b) Doi, Y.; Watanabe, Y.; Ueki, S.; Soga, K. Makromol.
Chem., Rapid Commun. 1983, 4, 533-537. (c) Doi, Y.;
Nozawa, F.; Murata, M.; Suzuki, S.; Soga, K. Makromol.
Chem. 1985, 186, 1825-1834. (d) Doi, Y.; Murata, M.; Soga,
K. Makromol. Chem., Rapid Commun. 1984, 5, 811-814. (e)
Doi, Y.; Hizal, G.; Soga, K. Makromol. Chem. 1987, 188,
(
20) (a) Fu, P. F.; Marks, T. J . J . Am. Chem. Soc. 1995, 117,
1
0747-10748. (b) Koo, K.; Fu, P. F.; Marks, T. J . Macromol-
ecules 1999, 32, 981-988. (c) Koo, K M.; Marks, T. J . J . Am.
Chem. Soc. 1998, 120, 4019-4020. (d) Koo, K.; Marks, T. J .
J . Am. Chem. Soc. 1999, 121, 8791-8802.
1
273-1279.
(
(
4) (a) Doi, Y.; Suzuki, S.; Soga, K. Macromolecules 1986, 19,
(
21) (a) Xu, G. X.; Chung, T. C. J . Am. Chem. Soc. 1999, 121,
2
896-2900. (b) Doi, Y.; Ueki, S.; Keii, T. Makromol. Chem.,
6
2
763-6764. (b) Xu, G.; Dong, J . Y.; Ching, T. C. Polym. Prepr.
000, 41, 1926. (c) Chung, T. C.; Xu, G.; Lu, Y.; Hu, Y.
Rapid Commun. 1982, 3, 225-229. (c) Doi, Y.; Kayama, T.;
Soga, K.; Asakura, T. Makromol. Chem. 1984, 185, 1827-
Macromolecules 2001, 33, 8040-8050.
1
1
833. (d) Doi, Y.; Koyama, T.; Soga, K. Makromol. Chem.
985, 186, 11-15.
(
(
(
22) Hessen, B.; Ringelberg, S. N.; Meppelder, G.; Teuben, J . H.
Polym. Prepr. 2000, 41, 397-398.
23) Imuta, J .; Kashiwa, N.; Toda, Y. J . Am. Chem. Soc. 2002,
5) (a) Scollard, J . D.; McConville, D. H. J . Am. Chem. Soc. 1996,
1
18, 10008-10009. (b) Scollard, J . D.; McConville, D. H.;
Vittal, J . J .; Payne, N. C. J . Mol. Catal. A 1998, 128, 201-
14.
6) J eon, Y. M.; Park, S. J .; Heo, J .; Kim, K. Organometallics
1
24, 1176-1177.
24) Mecking, S.; J ohnson, L. K.; Wang, L.; Brookhart, M. J . Am.
2
Chem. Soc. 1998, 120, 888-899.
(25) Huff, R. L.; Brookhart, M. University of North Carolina at
Chapel Hill. Unpublished results, 2000.
(
(
1
998, 17, 3161-3163.
7) (a) Schrock, R. R.; Baumann, R.; Reid, S. M.; Goodman, J .
T.; Stumpf, R.; Davis, W. M. Organometallics 1999, 18, 3649-
(26) McCord, E. F.; McLain, S. J .; Nelson, L. T. J .; Arthur, S. D.;
Coughlin, E. B.; Ittel, S. D.; J ohnson, L. K.; Tempel, D.;
Killian, C. M.; Brookhart, M. Macromolecules 2001, 34, 362-
371.
3
670. (b) Baumann, R.; Davis, W. M.; Schrock, R. R. J . Am.
Chem. Soc. 1997, 119, 3830-3831. (c) Baumann, R.; Schrock,
R. R. J . Organomet. Chem. 1998, 557, 69-75. (d) Schrodi,
Y.; Schrock, R. R.; Bonitatebus, P. J ., J r. Organometallics
(27) Tempel, D. Mechanistic Studies of Pd(II)- and Ni(II)-
Catalyzed Olefin Polymerization. Ph.D. Thesis, University
of North Carolina at Chapel Hill, Chapel Hill, NC, 1998.
(28) (a) J ohnson, L. K.; Killian, C. M.; Brookhart, M. J . Am. Chem.
Soc. 1995, 117, 6414-6415. (b) Ittel, S. D.; J ohnson, L. K.;
Brookhart, M. Chem. Rev. 1999, 1169-1203. (c) McLain, S.
J .; McCord, E. F.; J ohnson, L. K.; Ittel, S. D.; Nelson, L. T.
J .; Arthur, S. D.; Halfhill, M. J .; Teasley, M. F.; Tempel, D.
J .; Killian, C.; Brookhart, M. S. Polym. Prepr. (Am. Chem.
Soc. Div. Polym. Chem.) 1997, 38, 772-773. (d) Nelson, L.
T. J .; McCord, E. F.; J ohnson, L. K.; McLain, S. J .; Ittel, S.
D.; Killan, C. M.; Brookhart, M. Polym. Prepr. (Am. Chem.
Soc. Div. Polym. Chem.) 1997, 38, 133-134.
2
001, 21, 3560-3573. (e) Mehrkhodavandi, P.; Bonitatebus,
P. J ., J r.; Schrock, R. R. J . Am. Chem. Soc. 2001, 122, 7841-
842. (f) Mehrkhodavandi, P.; Schrock, R. R. J . Am. Chem.
7
Soc. 2001, 123, 10746-10747.
(
8) (a) Keaton, R. J .; J ayaratne, K. C.; Henningsen, D. A.;
Koterwas, L. A.; Sita, L. R. J . Am. Chem. Soc. 2001, 123,
6
197-6198. (b) J ayaratne, K. C.; Keaton, R. J .; Henningsen,
D. A.; Sita, L. R. J . Am. Chem. Soc. 2000, 122, 10490-10491.
c) J ayaratne, K. C.; Sita, L. R. J . Am. Chem. Soc. 2000, 122,
58-959.
9) Hagimoto, H.; Shiono, T.; Ikeda, T. Macromolecules 1998, 31,
184-3188.
10) Fukui, Y.; Murata, M.; Soga, K. Macromol. Rapid Commun.
(
9
(
3
(
(
(29) (a) M o¨ hring, V. M.; Fink, G. Angew. Chem., Int. Ed. Engl.
1985, 24, 1001-1003. (b) Schubbe, R.; Angermund, K.; Fink,
G.; Goddard, R. Makromol. Chem. Phys. 1995, 196, 467-478.
(c) Fink, G.; M o¨ hring, V. M.; Heinrichs, A.; Denger, C.;
1
999, 20, 637-640.
11) (a) Tshuva, E. Y.; Goldberg, I.; Kol, M.; Goldschmidt, Z. Inorg.
Chem. Commun. 2000, 3, 611-614. (b) Tshuva, E. Y.;

3
100 Gottfried and Brookhart
Macromolecules, Vol. 36, No. 9, 2003
Schubbe, R. H.; M u¨ hlenbrock, P. H. In Polymeric Materials
Encyclopedia; Salamone, J . C., Ed.; CRC Press: New York,
also are highly branched, correction for end-of-chain methyl
groups makes no significant change in the calculated branch-
ing numbers.
1
996; Vol. 6, pp 4720-4727.
(
30) The number of branches in the polymer was calculated by
(31) Guan, Z.; Cotts, P. M.; McCord, E. F.; McLain, S. J . Science
1999, 283, 2059-2062.
(32) Prasad, J . V.; Rao, P. V. C.; Garg, V. N. Eur. Polym. J . 1991,
27, 251-254.
integrating the methylene/methine and methyl regions of the
1
H NMR. The multiplet at 1.2 ppm, including the small peak
at 1.0 ppm represents the protons of the methylene and
methine polymer carbons. The smaller multiplet centered at
(
33) Shultz, L. H.; Tempel, D. J .; Brookhart, M. J . Am. Chem. Soc.
001, 123, 11539-11555.
0
.8 ppm represents the methyl protons of the polymer. Every
2
branch ends in a methyl group. Making no corrections for
end-of-chain methyl groups, the number of branches per 1000
(
34) Cotts, P. M.; Guan, Z.; McCord, E.; McLain, S. Macromol-
ecules 2000, 33, 6945-6952.
2
C is given by: (CH3 integral)/(total integral) × /3 × 1000.
Since the polymers are of quite high molecular weight and
MA025902U