Syndiospecific living catalysts for propylene polymerization: Effect of fluorination on activity, stereoselectivity, and termination

Article abstract of DOI:10.1560/XKLD-HWTH-Q45E-1V9G

The polymerization of propylene using a variety of fluorinated bis(phenoxyimine)titanium complexes is reported. The synthesis of ten complexes containing varying fluorinated N-aryl substituents is described. X-ray structural and solution NMR data indicate that these complexes are C ₂-symmetric in the solid state, although in some cases C ₁-symmetric isomers are observed in solution. When activated with methylalumoxane, all complexes formed syndiotactic polypropylene. Catalysts with ortho-fluorine substituents formed polymers with very narrow molecular weight distributions, indicative of a living polymerization. Catalysts with fluorine in at least the ortho and para positions exhibited the highest syndiospecificities. Catalysts with meta- or para-fluorine-containing substituents were more active for propylene polymerization than the corresponding non-fluorinated catalyst.

Full text of DOI:10.1560/XKLD-HWTH-Q45E-1V9G

Syndiospecific Living Catalysts for Propylene Polymerization:
Effect of Fluorination on Activity, Stereoselectivity, and Termination
ANDREW F. MASON, JUN TIAN, PHILIP D. HUSTAD, EMIL B. LOBKOVSKY, AND GEOFFREY W. COATES*
Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, USA
(Received 2 November 2002)
Abstract. The polymerization of propylene using a variety of fluorinated
bis(phenoxyimine)titanium complexes is reported. The synthesis of ten complexes
containing varying fluorinated N-aryl substituents is described. X-ray structural and
solution NMR data indicate that these complexes are C2-symmetric in the solid state,
although in some cases C1-symmetric isomers are observed in solution. When
activated with methylalumoxane, all complexes formed syndiotactic polypropylene.
Catalysts with ortho-fluorine substituents formed polymers with very narrow mo-
lecular weight distributions, indicative of a living polymerization. Catalysts with
fluorine in at least the ortho and para positions exhibited the highest syndio-
specificities. Catalysts with meta- or para-fluorine-containing substituents were
more active for propylene polymerization than the corresponding non-fluorinated
catalyst.
INTRODUCTION
catalyst precursors, prompted us to investigate these
The last two decades have witnessed a tremendous compounds as catalysts for stereospecific polymeriza-
amount of research in the area of metallocene-based tion of propylene. Utilizing a pooled combinatorial
catalysts for olefin polymerization,1,2 which led to the methodology, we quickly identified compound 1 as a
development of catalysts with unprecedented control promising catalyst for syndiospecific propylene poly-
over polymer stereochemistry.3 In more recent years, merization (Scheme 1).8 This study revealed the impor-
non-metallocene catalysts have further expanded the tant influence of ligand architecture on polymerization
realm of possibilities for polyolefin-based materials.4,5 behavior, as only one of the many compounds screened
Perhaps the most important advance from these new showed promising catalytic behavior. We then em-
catalysts is the ability to polymerize olefins in a con- ployed a more traditional approach to optimize selectiv-
trolled or living fashion.6 Utilizing a combination of ity and activity of this interesting class of catalysts.
creativity, molecular modeling, and serendipity, judi- From this work, the perfluorinated compound 10 was
cious combinations of ligand, metal, and activator have found to give marked improvement over 1/methyl-
produced catalysts capable of forming olefin-based alumoxane (MAO) in activity and gave highly syndio-
block copolymers previously unavailable by other tactic polypropylenes ([rrrr] = 0.96).9 Furthermore, we
methods.
found that this catalyst system also polymerized propy-
Utilizing these principles, researchers at Mitsui lene in a living fashion, allowing the synthesis of new
Chemical Co. reported a new family of catalysts that polyolefin-based materials. Scientists at Mitsui have
displayed remarkable potential for olefin polymer- independently discovered similar catalysts for living
ization.7 These Group IV compounds bearing two ethylene and syndiospecific propylene polymeriza-
phenoxyimine ligands, named FI catalysts, displayed tion.10–14 During the work that led to the discovery of 10
extremely high activities for ethylene polymerization for the living, syndiospecific polymerization of propy-
upon activation with an appropriate cocatalyst. These
results, coupled with the C2-symmetric nature of these
*Authortowhomcorrespondenceshouldbeaddressed. E-mail:
gc39@cornell.edu
Israel Journal of Chemistry
Vol. 42
2002 pp. 301–306

302
lene, we screened a variety of bis(phenoxyimine)-based
catalysts. Herein we report the effect of these modifica-
tions with regard to catalyst activity, selectivity, and
living nature of propylene polymerization. These ex-
periments demonstrate the profound effects of ligand
substitution patterns on polymerization behavior for this
interesting class of catalysts.
RESULTS AND DISCUSSION
Synthesis and Structure of Titanium Complexes
In an effort to better understand the various factors
influencing the propylene polymerization behavior of
bis(phenoxyimine) titanium catalysts, we decided to in-
vestigate the effects of electron-withdrawing substitu-
ents on the N-aryl ring of the phenoxyimine ligand.
Since a wide variety of fluorinated anilines are commer-
cially available, and we have shown that complex 10 is
an exceptional catalyst precursor for the formation of
living, highly syndiospecific polypropylene,9 we have
synthesized a number of titanium complexes containing
fluorinated phenoxyimine ligands. Complexes 1–10
(Scheme 1) were formed by deprotonation of the appro-
priate ligand with n-butyllithium, followed by reaction
with titanium tetrachloride. The desired products were
recrystallized from a mixture of toluene and hexanes,
and were isolated in moderate to good yields.
We have previously reported the molecular structure
of 10, which was determined using single-crystal X-ray
diffraction.9 Suitable crystals of 1 and 4 have also been
obtained; their molecular structures are shown in
Fig. 1. Molecular structure of 1 (non-hydrogen atoms) with
Figs. 1 and 2, respectively. In the solid state, com- thermal ellipsoids drawn at the 40% probability level.
pounds 1, 4, and 10 are C2-symmetric, with slightly
distorted octahedral geometries. The two oxygen atoms
are trans to each other, while the nitrogen donors are cis.
Selected bond distances and angles are listed in Table 1.
Although these complexes appear to be completely C2-
symmetric in the solid state, NMR studies indicate that
in some cases there is a mixture of C1- and C2-symmetric
1
isomers in solution. Based on integrations of H NMR
spectra, C1-symmetric isomers account for 37–39% of
the molecules in solution for compounds 1, 3, 4, 6, and
7. For compound 8, the C1 isomer accounts for only
19%. The presence of a C1-symmetric isomer cannot be
detected for compounds with fluorine in at least one of
the ortho positions (2, 5, 9, and 10). The factors influ-
encing this C1/C2 ratio are still unclear, but it appears
that the C1 isomer can be severely disfavored or elimi-
nated by placing fluorine substituents at the ortho posi-
tions of the N-aryl ring.
Scheme 1. Catalysts for syndiospecific propylene polymeri-
zation.
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303
Polymerization Results
Table 2 lists propylene polymerization data for com-
pounds 1–10 under a set of standard conditions. When
activated with MAO, all complexes were found to be
active for the syndiospecific polymerization of propy-
lene. It is interesting to note that complexes 2, 5, 9, and
10 all produce polypropylene with very low molecular
weight distributions (Mw/Mn ~ 1.1), which is indicative
of a living polymerization. Increasing the number of N-
aryl fluorine substituents from 2-fluoro (2) to 2,6-
difluoro (5) to 2,4,6-trifluoro (9) increases catalyst
activity as well as polymer syndiotacticity. These three
catalysts all have fluorine groups at the ortho positions,
and they all exhibit extremely low activities, especially
when compared to catalyst 10, which is also living, but
an order of magnitude more active. Comparison with
non-fluorinated 1 indicates that for catalysts 2 and 5,
ortho fluorine groups significantly reduce catalyst activ-
ity. Catalyst 9, containing an additional fluorine group
in the para position, is closer in activity to 1.
While catalysts with ortho-fluorine groups appear to
be poor catalysts, fluorine-containing groups in the meta
or para positions appear to improve catalyst perfor-
mance. Compounds 3, 4, and 6–8 are all more active
than non-fluorinated 1 (but less active than perfluorin-
ated 10). Increasing the number of fluorinated substitu-
ents increases catalyst activity (compare 4 with 8 and 6
with 7). These catalysts form polypropylene with a
much broader molecular weight distribution (Mw/Mn =
1.75–2.19) and lower tacticity than 9 and 10. Catalysts
Fig. 2. Molecular structure of 4 (non-hydrogen atoms) with
thermal ellipsoids drawn at the 40% probability level.
Table 2. Polymerization of propylene using bis(phenoxyimine)
catalysts 1–10
complex
yield (g)
TOFb
Mnc
Mw/Mnc [rrrr]d
1
2
3
4
5
6
7
8
9
4.20
0.38
7.20
6.40
0.56
14.30
23.40
12.10
2.48
5.34e
16.20
41.7
3.8
71.4
63.6
5.5
142
232
120
24.5
245
161
9 910
3 220
18 600
19 280
16 410
9 150
13 580
14 090
43 420
95 900
216 610
2.14
1.07
1.75
2.19
1.06
2.03
1.91
2.17
1.08
1.11
1.26
0.78
0.52
0.78
0.81
0.83
0.83
0.81
0.51
0.95
0.96
0.96
Table 1. Selected bond distances and angles for complexes 1,
4, and 10
complex
1
4
10
bond distances (Å)
Ti-O(1)
Ti-O(2)
Ti-N(1)
Ti-N(2)
Ti-Cl(1)
Ti-Cl(2)
1.8478(11)
1.8402(11)
2.2267(14)
2.2536(14)
2.3040(5)
2.3070(5)
1.853(4)
1.842(5)
2.245(5)
2.215(6)
2.299(2)
1.855(3)
1.844(3)
2.216(4)
2.245(4)
2.2744(14)
10
10
aGeneral conditions: 0.1 mmol catalyst in toluene (5 mL)
added to a propylene-saturated (40 psi) MAO solution (150 mL
toluene; [Al]/[Ti] = 150) at 0 ºC for 24 h. bTurnover frequency:
2.2936(19) 2.2808(14)
bond angles (deg)
c
mol propylene/(mol Ti·h). Determined by GPC in 1,2,4-
O(1)-Ti-O(2)
N(1)-Ti-N(2)
Cl(1)-Ti-Cl(2)
166.19(5)
80.01(5)
98.63(2)
171.04(19) 165.29(14)
trichlorobenzene at 140 ºC vs. polystyrene standards.
dDetermined by integration of the methyl region of the 13C NMR
spectrum. eReaction time = 5.2 h.
75.35(18)
103.63(8)
88.33(13)
97.79(5)
Mason et al. / Effect of Fluorination on Propylene Polymerization

304
collected using a SMART CCD Area Detector System
(Mo Kα, λ = 0.71073 Å), and frames were integrated with the
Siemens SAINT program.
with fluorine in at least the 2, 4, and 6 positions exhib-
ited the highest stereoselectivities. The relationship ob-
served between the living behavior of a catalyst and
ortho electron-withdrawing groups is in agreement with
work done at Mitsui, where a similar relationship was
observed for ethylene polymerizations with similar
ligands.13 It is also interesting to note that the four
compounds exhibiting living behavior upon activation
(2, 5, 9, and 10) do not have any minor C1-symmetric
isomers present in solution.
Materials
Toluene and hexanes were purified over columns of alu-
mina and copper. Methylene chloride was purified over an
alumina column and degassed by freeze-pump-thaw cycles
prior to use. Diethyl ether and benzene-d6 were distilled from
sodium benzophenone ketyl under nitrogen. Propylene
(Matheson, polymer grade) was purified through a mixed-bed
column (R & D Separations, BOT-4). Methylalumoxane
(PMAO-IP, 12.9 wt% Al in toluene, Akzo Nobel) was concen-
trated in vacuo to dryness (10–3 mmHg) to remove residual
trimethylaluminum, providing a solid white powder. (H5-
PHI)2TiCl2 1 and (F5-PHI)2TiCl2 10 were synthesized accord-
ing to published procedures.8,9 All other chemicals were used
as received from commercial sources.
CONCLUSION
In summary, we report the synthesis of a variety of
fluorinated bis(phenoxyimine) titanium complexes that
are active for the syndiospecific polymerization of
propylene in the presence of MAO cocatalyst. Place-
ment of fluorine groups at the ortho positions of the N-
aryl ring of the ligand results in living catalysts that
produce polymer with narrow molecular weight distri-
butions. Placement of fluorine-containing groups at the
meta or para positions greatly increases catalyst activity,
but does not impart any living behavior. For these non-
living catalyst precursors, there is a significant amount
of a C1-symmetric isomer in solution that may influence
their potential for living polymerization behavior. Fur-
ther mechanistic investigations involving this important
class of catalysts are currently underway.15
Ligand Synthesis
General Procedure for Fluorinated Phenoxyimine Ligand
Synthesis
A round-bottom flask was charged with 3,5-di-tert-butyl-
2-hydroxybenzaldehyde (2.34 g, 10 mmol), the desired aniline
(10 mmol), dry phosphorous pentoxide (4.32 g, 30 mmol), and
a few crystals of p-toluenesulfonic acid. The reaction mixture
was heated to 120 ºC and stirred for six h. After cooling,
organic materials were extracted into methylene chloride and
filtered through Celite. The solvent was removed in vacuo,
and the solid residue was recrystallized from methanol at
–20 ºC to give the desired product.
EXPERIMENTAL SECTION
N-(3,5-di-t-butylsalicylidene)-2-fluoroaniline (2-F-PHI)H
3,5-Di-tert-butyl-2-hydroxybenzaldehyde (1.5 g, 6.4
mmol) and 2-fluoroaniline (0.71 g, 6.4 mmol) were reacted to
General Methods
All manipulations of air- and/or water-sensitive com-
pounds were carried out under dry nitrogen using a Braun
Labmaster drybox or standard Schlenk line techniques. Rou-
tine small-molecule 1H and 13C NMR spectra were recorded on
a Varian Inova (1H, 400 MHz, 13C, 100 MHz) spectrometer
and referenced vs. residual non-deuterated solvent shifts.
19F NMR was recorded on a Varian Inova (376 MHz) and
referenced vs. internal CCl3F. 13C NMR spectra of the poly-
mers were recorded on a Varian VXR-400 (100 MHz) spec-
trometer and referenced vs. residual non-deuterated solvent
shifts. The polymer samples were dissolved in 1,1,2,2-tetra-
chloroethane-d2 in a 5-mm O.D. tube by heating to 120 ºC in
an oil bath. For quantitative analysis, an inverse gated
decoupling sequence was employed with a 30º pulse width
over a 160-ppm spectral width at a 2.0-s acquisition.
1
give the desired ligand as orange crystals (1.74 g, 83%). H
NMR (400 MHz, CDCl3): δ 1.31 (s, 9H, tBu), 1.47 (s, 9H, tBu),
7.12–7.27 (m, 5H, Ar), 7.46 (d, 2H, J = 2.4 Hz, Ar), 8.69 (s,
1H, HC = N), 13.55 (s, 1H, ArOH). 19F NMR (376 MHz,
CDCl3): δ –6.11 (s).
N-(3,5-di-t-butylsalicylidene)-4-fluoroaniline (4-F-PHI)H
3,5-Di-tert-butyl-2-hydroxybenzaldehyde (1.6 g, 6.7 mmol)
and 4-fluoroaniline (0.75 g, 6.7 mmol) were reacted to give the
1
desired ligand as orange crystals (1.71 g, 78%). H NMR
(400 MHz, CDCl3): δ 1.31 (s, 9H, tBu), 1.44 (s, 9H, tBu), 7.07
(t, 2H, J = 2.6 Hz, ArF), 7.20–7.30 (m, 3H, Ar), 7.45 (d, 2H,
J = 2.4 Hz, Ar), 8.70 (s, 1H, HC = N), 13.57 (s, 1H, ArOH).
19F NMR (376 MHz, CDCl3): δ –16.21 (s).
Molecular weights (Mn and Mw) and polydispersities (Mw/ N-(3,5-di-t-butylsalicylidene)-4-(trifluoromethyl)aniline
Mn) were determined by high-temperature gel-permeation (4-CF3-PHI)H
chromatography (GPC). All analyses were performed with a
3,5-Di-tert-butyl-2-hydroxybenzaldehyde (1.6 g, 6.7 mmol)
Waters Alliance 2000 liquid chromatograph equipped with a and 4-trifluoromethylaniline (1.1 g, 6.7 mmol) were dissolved
Waters DRI detector and a Jordi styrene–divinylbenzene linear in methanol (20 mL) and heated at reflux for 12 h. Concentra-
mixed-bed column. The GPC columns were eluted with 1,2,4- tion of the solvent and crystallization at –20 ºC produced the
trichlorobenzene (TCB) containing 0.1 wt% Irganox 1010 at desired ligand as orange crystals (2.26 g, 89%). 1H NMR (400
140 ºC at 1.0 mL/min and were calibrated using 23 monodis- MHz, CDCl3): δ 1.35 (s, 9H, tBu), 1.45 (s, 9H, tBu), 7.24 (d,
perse polystyrene standards. X-Ray crystallographic data were 1H, J = 2.4 Hz, Ar), 7.34 (d, 2H, J = 8.4 Hz, ArF), 7.50 (d, 1H,
Israel Journal of Chemistry
42
2002

305
J = 2.4 Hz, Ar), 7.66 (d, 2H, J = 8.4 Hz, ArF), 8.61 (s, 1H, HC phenoxyimine ligand (2.0 mmol) in diethyl ether (20 mL) at
= N), 13.34 (s, 1H, ArOH). 19F NMR (376 MHz, CDCl3): –78 ºC. After warming to room temperature, this solution was
δ –70.28 (s).
stirred for 30 min before being added via cannula to a solution
of titanium tetrachloride (1.0 M in toluene, 1.0 mmol) in
diethyl ether (20 mL) at –78 ºC. The resulting solution was
warmed to room temperature and stirred under nitrogen for
12 h. The solvent was removed in vacuo; residues were taken
up in methylene chloride and filtered through Celite to give a
clear dark red solution. The solvent was removed in vacuo,
and the resulting solid was recrystallized from a toluene/
hexane mixture to give the desired complex.
N-(3,5-di-t-butylsalicylidene)-2,6-difluoroaniline
(2,6-F2-PHI)H
3,5-Di-tert-butyl-2-hydroxybenzaldehyde (1.6 g, 6.7 mmol)
and 2,6-difluoroaniline (0.86 g, 6.7 mmol) were reacted to
1
give the desired ligand as yellow crystals (1.78 g, 76%). H
NMR (400 MHz CDCl3): δ 1.33 (s, 9H, tBu), 1.45 (s, 9H, tBu),
6.97 (m, 2H, ArF), 7.10 (m, 1H, ArF), 7.18 (d, 1H, J = 2.4 Hz,
Ar), 7.47 (d, 1H, J = 2.4 Hz, Ar), 8.84 (s, 1H, HC = N), 13.40
(s, 1H, ArOH). 19F NMR (376 MHz, CDCl3): δ 9.14 (t).
(2-F-PHI)2TiCl2 (2)
(2-F-PHI)H (0.85 g, 2.6 mmol) was reacted as described
N-(3,5-di-t-butylsalicylidene)-3,4,5-trifluoroaniline
(3,4,5-F3-PHI)H
above, producing red-brown crystals (0.39 g, 39%). 1H NMR
t
t
(400 MHz, CDCl3): δ 1.26 (s, 18H, Bu), 1.29 (s, 18H, Bu),
6.90 (m, 4H, ArF), 7.08 (d, 2H, J = 2.4 Hz, Ar), 7.30 (m, 4H,
ArF), 7.43 (d, 2H, J = 2.4 Hz, Ar), 8.10 (s, 2H, HC = N).
3,5-Di-tert-butyl-2-hydroxybenzaldehyde (1.6 g, 6.7 mmol)
and 3,4,5-trifluoroaniline (0.98 g, 6.7 mmol) were reacted to
give the desired ligand as orange crystals (2.25 g, 93%).
t
1H NMR (400 MHz, CDCl3): δ 1.31 (s, 9H, Bu), 1.45 (s, 9H,
(4-F-PHI)2TiCl2 (3)
tBu), 6.92 (m, 2H, ArF), 7.21 (d, 1H, J = 2.4 Hz, Ar), 7.48 (d, 1H,
J = 2.4 Hz, Ar), 8.54 (s, 1H, HC = N), 13.02 (s, 1H, ArOH).
19F NMR (376 MHz, CDCl3): δ –30.50 (m), –0.76 (m).
(4-F-PHI)H (0.98 g, 3.0 mmol) was reacted as described
above, producing red-brown crystals (0.51 g, 44%). 1H NMR
(400 MHz, CDCl3, isomeric mixture in solution, 63% C2-
t
t
symmetric isomer): δ 1.25 (s, 18H, Bu), 1.30 (s, 18H, Bu),
N-(3,5-di-t-butylsalicylidene)-3,5-difluoroaniline
(3,5-F2-PHI)H
t
1.31, 1.33, 1.59 (s, Bu, C1 isomer), 7.05 (d, 2H, J = 2.4 Hz,
Ar), 7.08 (d, Ar, C1isomer), 7.12 (d, 4H, J = 7.6 Hz, ArF), 7.27
(d, 4H, J = 8.4 Hz, ArF), 7.46, 7.48 (d, ArF, C1 isomer), 7.49 (d,
2H, J = 2.4 Hz, Ar), 7.62, 7.69 (d, Ar, C1 isomer), 7.92, 8.04 (s,
HC = N, C1 isomer), 8.06 (s, 2H, HC = N).
3,5-Di-tert-butyl-2-hydroxybenzaldehyde (1.7 g, 7.2 mmol)
and 3,5-difluoroaniline (0.92 g, 7.2 mmol) were reacted to
give the desired ligand as yellow-brown crystals (1.99 g,
80%). 1H NMR (400 MHz, CDCl3): δ 1.31 (s, 9H, tBu), 1.46 (s,
9H, tBu), 6.71 (m, 1H, ArF), 6.80 (m, 2H, ArF), 7.22 (d, 1H, J =
2.4 Hz, Ar), 7.48 (d, 1H, J = 2.4 Hz, Ar), 8.60 (s, 1H, HC = N),
13.14 (s, 1H, ArOH). 19F NMR (376 MHz, CDCl3): δ –23.40 (t).
(4-CF3-PHI)2TiCl2 (4)
(4-CF3-PHI)H (1.16 g, 3.1 mmol) was reacted as described
1
above, producing dark red crystals (0.94 g, 70%). H NMR
(400 MHz, CDCl3, isomeric mixture in solution, 63% C2-
N-(3,5-di-t-butylsalicylidene)-3,5-bis(trifluoromethyl)aniline
(3,5-CF3-PHI)H
t
t
symmetric isomer): δ 1.24 (s, 18H, Bu), 1.30 (s, 18H, Bu),
t
1.31, 1.32, 1.34, 1.59 (s, Bu, C1 isomer), 6.80 (d, ArF, C1
3,5-Di-tert-butyl-2-hydroxybenzaldehyde (1.6 g, 6.7 mmol)
and 3,5-bis(trifluoromethyl)aniline (1.5 g, 6.7 mmol) were dis-
solved in methanol (20 mL) and heated at reflux for 12 h.
Concentration of the solvent and crystallization at –20 ºC
produced the desired ligand as orange crystals (1.98 g, 64%).
isomer), 7.06 (d, 2H, J = 2.4 Hz, Ar), 7.08 (d, Ar, C1 isomer),
7.12 (d, 4H, J = 8.0 Hz, ArF), 7.27 (d, 4H, J = 8.0 Hz, ArF),
7.45, 7.47 (d, ArF, C1 isomer), 7.49 (d, 2H, J = 2.4 Hz, Ar),
7.63, 7.69 (d, Ar, C1 isomer), 7.91, 8.04 (s, HC = N, C1
isomer), 8.07 (s, 2H, HC = N).
t
1H NMR (400 MHz, CDCl3): δ 1.33 (s, 9H, Bu), 1.44 (s, 9H,
tBu), 7.27 (m, 1H, ArF), 7.52 (d, 1H, J = 2.4 Hz, Ar), 7.68 (m, 2H,
ArF), 7.77 (d, 1H, J = 2.4 Hz, Ar), 8.64 (s, 1H, HC = N), 13.28 (s,
1H, ArOH). 19F NMR (376 MHz, CDCl3): δ –69.50 (s).
(2,6-F2-PHI)2TiCl2 (5)
(2,6-F2-PHI)H (0.96 g, 2.8 mmol) was reacted as described
above, producing red-brown crystals (0.72 g, 64%). 1H NMR
t
t
(400 MHz, CDCl3): δ 1.26 (s, 18H, Bu), 1.30 (s, 18H, Bu),
6.43 (m, 2H, ArF), 6.87 (m, 2H, ArF), 6.95 (m, 2H, ArF), 7.15
(d, 2H, J = 2.4 Hz, Ar), 7.51 (d, 2H, J = 2.4 Hz, Ar), 8.19 (s,
2H, HC = N).
N-(3,5-di-t-butylsalicylidene)-2,4,6-trifluoroaniline
(2,4,6-F3-PHI)H
3,5-Di-tert-butyl-2-hydroxybenzaldehyde (1.4 g, 5.9 mmol)
and 2,4,6-trifluoroaniline (0.87 g, 5.9 mmol) were reacted to
give the desired ligand as yellow crystals (1.42 g, 66%).
(3,4,5-F3-PHI)2TiCl2 (6)
t
1H NMR (400 MHz, CDCl3): δ 1.31 (s, 9H, Bu), 1.45 (s, 9H,
(3,4,5-F3-PHI)H (1.13 g, 3.1 mmol) was reacted as described
tBu), 6.76 (m, 2H, ArF), 7.16 (d, 1H, J = 2.4 Hz, Ar), 7.47 (d, 1H,
J = 2.4 Hz, Ar), 8.81 (s, 1H, HC = N), 13.17 (s, 1H, ArOH).
19F NMR (376 MHz, CDCl3): δ –12.63 (t), 8.72 (m).
1
above, producing red-brown crystals (0.54 g, 41%). H NMR
(400 MHz, CDCl3, isomeric mixture in solution, 61% C2-sym-
t
t
metric isomer): δ 1.27 (s, 18H, Bu), 1.30, 1.31 (s, Bu, C1
isomer), 1.38 (s, 18H, tBu), 1.58 (s, tBu, C1 isomer), 6.39 (m, ArF,
C1 isomer), 6.62 (m, 4H, ArF), 6.72 (m, ArF, C1 isomer), 7.11 (d,
2H, J = 2.4 Hz, Ar), 7.22 (d, Ar, C1 isomer), 7.58 (d, 2H, J = 2.4
Complex Synthesis
General Procedure for Titanium Complex Synthesis
A gastight syringe was used to dropwise add n-butyl- Hz, Ar), 7.64, 7.70 (d, Ar, C1 isomer), 8.00, 8.01 (s, HC = N, C1
lithium (1.6 M in hexanes, 2.1 mmol) to a stirred solution of isomer), 8.07 (s, 2H, HC = N).
Mason et al. / Effect of Fluorination on Propylene Polymerization

306
(3,5-F2-PHI)2TiCl2 (7)
Teacher-Scholar Award, a Beckman Foundation Young
(3,5-F2-PHI)H (1.14 g, 3.3 mmol) was reacted as described Investigator Award, and financial support from the Cornell
above, producing red-brown crystals (0.74 g, 55%). 1H NMR Center for Materials Research and Mitsubishi Chemical.
(400 MHz, CDCl3, isomeric mixture in solution, 63% C2-
symmetric isomer): δ 1.26 (s, 18H, tBu), 1.29,1.30 (s, tBu, C1
isomer), 1.36 (s, 18H, tBu), 1.59 (s, tBu, C1 isomer), 6.29 (m,
2H, ArF), 6.42 (m, 2H, ArF), 6.53 (m, 2H, ArF), 6.67 (m, ArF, C1
isomer), 6.75 (m, ArF, C1 isomer), 7.11 (d, 2H, J = 2.4 Hz, Ar),
7.15 (d, Ar, C1 isomer), 7.53 (d, 2H, J = 2.4 Hz, Ar), 7.62, 7.68
(d, Ar, C1 isomer), 7.99, 8.03 (s, HC = N, C1 isomer), 8.08 (s,
2H, HC = N).
REFERENCES AND NOTES
(1) Brintzinger, H.H.; Fischer, D.; Mülhaupt, R.; Rieger,
B.; Waymouth, R.M. Angew. Chem. Int. Ed. 1995, 34,
1143–1170.
(2) Resconi, L.; Cavallo, L.; Fait, A.; Piemontesi, F. Chem.
Rev. 2000, 100, 1253–1345.
(3) Coates, G.W. Chem. Rev. 2000, 100, 1223–1252.
(4) Britovsek, G.J.P.; Gibson, V.C.; Wass, D.F. Angew.
Chem. Int. Ed. 1999, 38, 429–447.
(5) Gibson, V.C.; Spitzmesser, S.K. Chem. Rev. 2003, 103,
283–315.
(6) Coates, G.W.; Hustad, P.D.; Reinartz, S. Angew. Chem.
Int. Ed. 2002, 41, 2236–2257.
(7) Makio, H.; Kashiwa, N.; Fujita, T. Adv. Synth. Cat.
2002, 344, 477–493.
(8) Tian, J.; Coates, G. W. Angew. Chem. Int. Ed. 2000, 39,
3626–3629.
(9) Tian, J.; Hustad, P.D.; Coates, G.W. J. Am. Chem. Soc.
2001, 123, 5134–5135.
(3,5-CF3-PHI)2TiCl2 (8)
(3,5-CF3-PHI)H (1.15 g, 2.6 mmol) was reacted as described
above, producing dark red crystals (0.76 g, 58%). H NMR
(400 MHz, CDCl3, isomeric mixture in solution, 81% C2-
symmetric isomer): δ 1.11 (s, 18H, Bu), 1.29 (s, 18H, Bu),
1.31, 1.32, 1.33, 1.59 (s, Bu, C1 isomer), 7.16 (m, 2H, ArF),
7.22 (m, 2H, ArF), 7.26 (d, 2H, J = 2.4 Hz, Ar), 7.30 (d, Ar, C1
isomer), 7.59 (d, 2H, J = 2.4 Hz, Ar), 7.60 (m, 2H, ArF), 7.66
(m, ArF, C1 isomer), 7.71, 7.76 (d, Ar, C1 isomer), 7.84 (m, ArF,
C1 isomer), 8.06, 8.09 (s, HC = N, C1 isomer), 8.26 (s, 2H,
HC = N).
1
t
t
t
(2,4,6-F3-PHI)2TiCl2 (9)
(2,4,6-F3-PHI)H (0.81 g, 2.2 mmol) was reacted as de-
scribed above, producing red-brown crystals (0.76 g, 80%). 1H
NMR (400 MHz, CDCl3,): δ 1.29 (s, 18H, tBu), 1.30 (s, 18H,
tBu), 6.21 (m, 2H, ArF), 6.65 (m, 2H, ArF), 7.14 (d, 2H, J = 2.4
Hz, Ar), 7.56 (d, 2H, J = 2.4 Hz, Ar), 8.15 (s, 2H, HC = N).
(10) Kojoh, S.; Matsugi, T.; Saito, J.; Mitani, M.; Fujita, T.;
Kashiwa, N. Chem. Lett. 2001, 822–823.
(11) Saito, J.; Mitani, M.; Mohri, J.; Yoshida, Y.; Matsui, S.;
Ishii, S.; Kojoh, S.; Kashiwa, N.; Fujita, T. Angew.
Chem. Int. Ed. 2001, 40, 2918–2920.
(12) Saito, J.; Mitani, M.; Mohri, J.; Ishii, S.; Yoshida, Y.;
Matsugi, T.; Kojoh, S.; Kashiwa, N.; Fujita, T. Chem.
Lett. 2001, 576–577.
(13) 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. 2002, 124, 3327–3336.
(14) Mitani, M.; Furuyama, R.; Mohri, J.; Saito, J.; Ishii, S.;
Terao, H.; Kashiwa, N.; Fujita, T. J. Am. Chem. Soc.
2002, 124, 7888–7889.
(15) For some recent mechanistic studies, see: (a) Milano,
G.; Cavallo, L.; Guerra, G. J. Am. Chem. Soc. 2002,
124, 13368–13369. (b) Hustad, P.D.; Coates, G.W. J.
Am. Chem. Soc. 2002, 124, 11578–11579. (c) Milano,
G.; Fiorello, G.; Guerra, G.; Cavallo, L. Macromol.
Chem. Phys. 2002, 203, 1564–1572. (d) Hustad, P.D.;
Tian, J.; Coates, G.W. J. Am. Chem. Soc. 2002, 124,
3614–3621. (e) Lamberti, M.; Pappalardo, D.;
Zambelli, A.; Pellecchia, C. Macromolecules 2002, 35,
658–663.
General Procedure for Polypropylene Synthesis
A 6-ounce Lab-Crest pressure reaction vessel (Andrews
Glass) equipped with a magnetic stir bar was first conditioned
under dynamic vacuum and high temperature and then
charged with a desired amount of dry PMAO-IP and toluene.
The reactor was then equilibrated at 0 ºC, the atmosphere was
exchanged three times with propylene, and the solution was
saturated under pressure (40 psi). The titanium catalyst was
dissolved in toluene (5 mL) and added to the reactor via
gastight syringe to initiate the polymerization. After the de-
sired period of time, the reaction was quenched with methanol
(10 mL) and the reactor was vented. The polymer was precipi-
tated in copious methanol/HCl, filtered, washed with metha-
nol, and then dried in vacuo to constant weight.
Acknowledgments. This work made use of Cornell Center for
Materials Research Shared Experimental Facilities, supported
through the NSF MRSEC program (DMR-0079992). G.W.C.
gratefully acknowledges a Packard Foundation Fellowship in
Science and Engineering, a Sloan Fellowship, a Dreyfus
Israel Journal of Chemistry
42
2002