Diverse structure-activity trends in amine bis(phenolate) titanium polymerization catalysts

Article abstract of DOI:10.1021/om049630q

The activity of amine bis(phenolate) Ti dibenzyl complexes in 1-hexene polymerization catalysis as a function of the phenolate substituents was investigated. Two series of Ti complexes carrying either a dimethylamino or a methoxy sidearm donor were prepared and characterized. In each series, the substituents on the phenolate rings were either alkyl groups of varying bulk or electron-withdrawing chloro groups. When activated with a suitable Lewis acid, all precatalysts have shown reactivity toward 1-hexene. Different structure-activity trends were observed in the two series: The activity of the catalysts of the OMe series was low to moderate and was almost independent of the phenolate substituents. In contrast, the activity of the NMe₂ catalysts had a strong dependence on both the steric and electronic character of the phenolate substituents, ranging from mild to highly active. The difference in polymerization activity trends between the two series may be traced back to their different tendency toward misinsertions. A NMe₂ -Ti complex having Cl groups in the ortho, para positions of the phenolate rings led to the most active catalyst and to a remarkably high-M_w polymer (>4 000 000) obtained within 1 h of polymerization at RT. The characterization of this ultrahigh-M_w atactic poly(1-hexene) by means of oscillatory rheometry and stress relaxation experiments indicated typical elastomeric behavior at RT.

Full text of DOI:10.1021/om049630q

Organometallics 2004, 23, 5291-5299
5291
Diver se Str u ctu r e-Activity Tr en d s in Am in e
Bis(p h en ola te) Tita n iu m P olym er iza tion Ca ta lysts
Stanislav Groysman,† Edit Y. Tshuva,† Israel Goldberg,† Moshe Kol,*,†
Zeev Goldschmidt,*,‡ and Michael Shuster§
School of Chemistry, Raymond and Beverly Sackler Faculty of Exact Sciences,
Tel Aviv University, Tel Aviv 69978, Israel, Department of Chemistry, Bar-Ilan University,
Ramat Gan 52900, Israel, and Research and Development Division, Carmel Olefins Ltd.,
P.O.B. 1468, Haifa 31014, Israel
Received May 24, 2004
The activity of amine bis(phenolate) Ti dibenzyl complexes in 1-hexene polymerization
catalysis as a function of the phenolate substituents was investigated. Two series of Ti
complexes carrying either a dimethylamino or a methoxy sidearm donor were prepared and
characterized. In each series, the substituents on the phenolate rings were either alkyl groups
of varying bulk or electron-withdrawing chloro groups. When activated with a suitable Lewis
acid, all precatalysts have shown reactivity toward 1-hexene. Different structure-activity
trends were observed in the two series: The activity of the catalysts of the “OMe” series
was low to moderate and was almost independent of the phenolate substituents. In contrast,
the activity of the “NMe2” catalysts had a strong dependence on both the steric and electronic
character of the phenolate substituents, ranging from mild to highly active. The difference
in polymerization activity trends between the two series may be traced back to their different
tendency toward misinsertions. A “NMe2”-Ti complex having Cl groups in the ortho, para
positions of the phenolate rings led to the most active catalyst and to a remarkably high-Mw
polymer (>4 000 000) obtained within 1 h of polymerization at RT. The characterization of
this ultrahigh-Mw atactic poly(1-hexene) by means of oscillatory rheometry and stress
relaxation experiments indicated typical elastomeric behavior at RT.
In tr od u ction
siderably less established. Deciphering of these param-
eters can lead to development of catalysts exhibiting
new activity modes and consequently to polymeric
materials exhibiting desired physical characteristics.
Recently, we introduced the family of amine bis-
(phenolate) ligands to group IV metals and studied the
potential of the resulting complexes as precatalysts for
polymerization of R-olefins.7 The general structure of
the ligand precursors LigH2 (including a sidearm donor
that was found essential for the formation of active
catalysts) is depicted in Figure 1. These tetradentate
ligands wrap around group IV metals forming Cs-
symmetrical octahedral complexes in which the two
labile groups (most commonly alkyl groups) are forced
into a cis relationship, as required from an olefin
polymerization precatalyst. All the ligands employed in
group IV chemistry carried bulky (t-Bu) ortho substit-
uents on the phenolate rings.8
The recent exploration of group IV cyclopentadienyl-
free R-olefin polymerization catalysts has yielded several
systems that exhibited polymerization modes and ac-
tivities unmatched by the traditional metallocene-type
catalysts.1 Some noteworthy examples include the living
polymerization of high olefins at ambient tempera-
tures,2,3 the extremely active ethylene polymerization
catalysts,4 the living and isotactic polymerization of high
olefins at RT,5 and the living and syndiotactic poly-
merization of propylene.6 Yet, due to their wide-ranging
structures, the parameters responsible for the unique
polymerization modes of the Cp-free systems are con-
* To whom correspondence should be addressed. E-mail: moshekol@
post.tau.ac.il; goldz@mail.biu.ac.il.
† Tel Aviv University.
‡ Bar-Ilan University.
§ Carmel Olefins Ltd.
Following activation with a strong Lewis acid such
as tris(pentafluorophenyl)borane, the amine bis(pheno-
(1) (a) Britovsek, G. J . P.; Gibson, V. C.; Wass, D. F. Angew. Chem.,
Int Ed. 1999, 38, 428. (b) Gibson, V. C.; Spitzmesser, S. K. Chem. Rev.
2000, 103, 283.
(2) Scollard, J . D.; McConville, D. H. J . Am. Chem. Soc. 1996, 118,
10008.
(3) Baumann, R.; Davis, W. M.; Schrock, R. R. J . Am. Chem. Soc.
1997, 119, 3830.
(4) Matsui, S.; Mitani, M.; Saito, J .; Tohi, Y.; Makio, H.; Matsukawa,
N.; Takagi, Y.; Tsuru, K.; Nitabaru, M.; Nakano, T.; Tanaka, T.;
Kashiwa, T.; Fujita, T. J . Am. Chem. Soc. 2001, 123, 6847.
(5) Tshuva, E.; Goldberg, I.; Kol, M. J . Am. Chem. Soc. 2000, 122,
10706.
(6) (a) Tian, J .; Hustad, P. D.; Coates, G. W. J . Am. Chem. Soc. 2001,
123, 5134. (b) Mitani, M.; Furuyama, R.; Mohri, J .; Saito, J .; Ishi, S.;
Terao, H.; Nakano, T.; Tanaka, H.; Fujita, T. J . Am. Chem. Soc. 2003,
125, 4293.
(7) (a) Tshuva, E. Y.; Versano, M.; Goldberg, I.; Kol, M.; Weitman,
H.; Goldschmidt, Z. Inorg. Chem. Commun. 1999, 2, 371. (b) Tshuva,
E. Y.; Goldberg, I.; Kol, M.; Goldschmidt, Z. Inorg. Chem. Commun.
2000, 3, 611. (c) Tshuva, E. Y.; Goldberg, I.; Kol, M.; Goldschmidt, Z.
Organometallics 2001, 20, 3017. (d) Tshuva, E. Y.; Groysman, S.;
Goldberg, I.; Kol, M.; Goldschmidt, Z. Organometallics 2002, 21, 662.
(e) Tshuva, E. Y.; Goldberg, I.; Kol, M.; Goldschmidt, Z. Chem.
Commun. 2001, 2120. (f) Groysman, S.; Goldberg, I.; Kol, M.; Genizi,
E.; Goldschmidt, Z. Inorg. Chim. Acta 2003, 345, 137. (g) Groysman,
S.; Goldberg, I.; Kol, M.; Goldschmidt, Z. Organometallics 2003, 22,
3013. (h) Groysman, S.; Tshuva, E. Y.; Reshef, D.; Gendler, S.;
Goldberg, I.; Kol, M.; Goldschmidt, Z. Shuster, M.; Lidor, G. Isr. J .
Chem. 2002, 42, 373.
10.1021/om049630q CCC: $27.50 © 2004 American Chemical Society
Publication on Web 09/21/2004

5292 Organometallics, Vol. 23, No. 22, 2004
Groysman et al.
activity of titanium catalysts, namely, those expected
to be affected mostly by steric influence. The effect of
electron-withdrawing substituents on the polymeriza-
tion activity was explored as well. Herein we describe
two series of tetradentate amine bis(phenolate) ligand
precursors (each having a specific sidearm donor), their
respective dibenzyltitanium complexes, and their activ-
ity in polymerization of 1-hexene. We show that, unex-
pectedly, the activity of the complexes belonging to one
of the series is almost uniform, whereas the activity of
the complexes of the second series varies dramatically
as a function of phenolate substituents. One such
catalyst led to unprecedented high molecular weight
polymer (under ambient conditions) that exhibited
elastomeric properties.
F igu r e 1. Amine bis(phenolate) ligand precursors carrying
t-Bu substituents on the phenolate rings and varying
sidearm donors D.
late) dialkyl complexes led to R-olefin polymerization
catalysts whose activity, revealed thus far, depended
mostly on the nature of the metal atom, with the
following general order: Zr g Hf . Ti.9 The most active
Zr-based catalysts were derived from ligands bearing
“strong” sidearm donors, such as OMe (ca. 50 000 gpol
Resu lts
mmolcat-1 h-1), NMe2, and THF (ca. 20 000 gpol mmolcat
-1
h-1 each).7d,f Typically, the molecular weight of the
resulting poly(1-hexene) samples was around 100 000
g mol-1, and the PDI was around 2.0.7c,d,f Employing
the same ligands in titanium chemistry led to moder-
Syn t h esis a n d St r u ct u r e. The dibenzyl titanium
complexes of the ligands employed in this study are
outlined in Figure 2. They are divided into two series,
each featuring a different “strong” sidearm donor, i.e.,
either a dimethylamino or a methoxy group. Each series
allows the estimation of steric effects on the resulting
catalyst’s reactivity, through a gradual decrease in the
phenolate (ortho) substituents’ size, and of electronic
effects by the introduction of electron-withdrawing
chloro groups. The synthesis and reactivity of the most
sterically congested members of each series (1 and 4)
that led to living polymerization catalysts at room
temperature were described previously.7b,c All ligand
-1
ately active catalysts (10-35 gpol mmolcat h-1),7b,e,f
which exhibited, however, a living character for pro-
longed periods of time (up to several days)7e,f at room
temperature, leading, in certain cases, to very high
molecular weight polymers (up to 1 000 000 g mol-1) and
block copolymers. Looking for new structure-activity
relationships and, possibly, discovering catalysts that
would exhibit new activity modes, we turned to explore
the influence of the phenolate substituents on the
F igu r e 2. Dibenzylamine bis(phenolate) Ti(IV) complexes 1-7.

Amine Bis(phenolate) Ti Polymerization Catalysts
Organometallics, Vol. 23, No. 22, 2004 5293
Sch em e 1
precursors were prepared by a Mannich condensation
between the corresponding phenol, amine, and formalde-
hyde.7b,e,8b
The dibenzyl titanium complexes 1-7 were prepared
by a straightforward toluene-elimination reaction of the
ligand precursors with tetrabenzyltitanium as shown
in Scheme 1. This reaction is of high yield and takes
place readily when both reagents are mixed in toluene
at RT. Employing this route generally eliminates the
need for recrystallization and leads to sufficiently pure
complexes following pentane washings of the crude
products. All complexes were found to possess Cs-
symmetry on the NMR time scale, according to the
symmetry-related phenolate rings, distinct benzyl ligands,
and AB pattern for the ligand benzyl protons.
The X-ray structures of complexes 1 and 4 were
previously described.7b,e We carried out X-ray structure
determinations for complexes 2, 3, 6, and 7 (see Figures
3-6, and Supporting Information for the crystal struc-
ture data). These structures are closely related to each
other and to previous structures of this family of ligands
with group IV metals.7 All complexes feature hexaco-
ordinate titanium centers with the sidearm donor firmly
attached. The phenolate oxygens are located mutually
trans. The Ti-OPh bond lengths and the corresponding
Ti-O-C(Ph) bond angles are common for the amine bis-
(phenolate) Ti complexes, lying in the narrow ranges of
1.851-1.875 Å and 143-146°, respectively. All benzyl
ligands are coordinated to the metal in the usual η1
fashion (105-117°), with the narrowest angle (105°)
found for the “axial” benzyl group in the least sterically
hindered complex 6 (ortho-H phenolate substituents).
In complex 2 the “axial” benzyl ligand twists sideways
and seems to undergo a CH-π interaction with the ortho-
Me group on one of the phenolate rings.
The Ti-D bonds (D ) sidearm donor) deserve special
attention since their presence and strength were shown
to be essential for olefin polymerization catalysis in the
amine bis(phenolate) series. We have previously re-
ported the solid-state structures of the dibenzyl com-
plexes of the entire group IV triad with Lig1 (OMe) and
Lig4 (NMe2) ligands (the Ti structure with Lig4 was of
low quality).7b-e Very narrow ranges of M-D bond
distances were observed in both series: M-O bond
distances of 2.43-2.46 Å for the “OMe”-type complexes
and M-N bond distances of 2.54-2.59 Å for the “NMe2”-
type complexes. The reduction of steric repulsion by
replacement of the bulky t-Bu groups with smaller Me
or H groups causes the Ti-NMe2 bond lengths to
contract (2.451 and 2.466 Å in 6 and 7, respectively).
Notably, the complexes of the “OMe” set present a dual
behavior. No bond contraction is detected in 3 vs 1
(2.457 Å in 3 vs 2.433 Å for 1), possibly due to the
already low steric congestion in 1: a methoxy group
bears a single methyl substituent that experiences a
small steric interaction with the t-Bu groups in 1 (and
in the analogous Zr and Hf complexes). In contrast, 2
features a significantly shorter Ti-OMe bond length,
which may result from the different arrangement of the
“axial” benzyl ligand (see Figure 3 for details).
F igu r e 3. ORTEP representation of 2 (50% probability
ellipsoids). Selected bond lengths (Å) and angles (deg):
Ti1-O2 1.856(3), Ti1-O3 1.854(3), Ti1-N4 2.385(3), Ti1-
O5 2.339(3), Ti1-C6 2.129(4), Ti1-C7 2.128(4), O2-Ti1-
O3 162.14(11), C6-Ti1-O5 173.46(13), C20-O2-Ti1
144.5(2), C36-O3-Ti1 145.4(2), C8-C6-Ti1 120.3(3),
C14-C7-Ti1 120.7(3).
Rea ctivity in 1-Hexen e P olym er iza tion : “OMe”
Ser ies. Activation of 1 with B(C6F5)3 at RT led to
polymerization of 1-hexene that remained living for
more than 24 h.7e The activity of this catalyst was
moderate: 20-35 gpol mmolcat h-1. Activation of deep
-1
red 2 in neat 1-hexene led to a similar low to moderate
-1
activity of 15-20 gpol mmolcat h-1. In common with 1,
the less sterically congested 2 was active for a long
period of time. However, in contrast to 1, 2 does not
promote a prolonged living polymerization, as revealed
from the PDI values that are narrow (1.1-1.2) only in
the first hour of the reaction (Table 1). Activation of the
yellow-orange 3 with B(C6F5)3 resulted in only slightly
more active 1-hexene polymerization catalyst (34-44 g
polymer mmolcat-1 h-1). After 60 min the polymerization
reaction yields poly(1-hexene) of Mw ) 38 000 and PDI
) 1.4 (Table 1). Thus, it appears that, surprisingly,
neither steric nor electronic modification of the “OMe”-
type ligands leads to any pronounced activity enhance-
ment of the resulting polymerization catalysts, while the
living character is lost, apparently due to an increase
in the termination/propagation ratio.
The 13C NMR spectra of the resulting polymers
indicated that they are atactic, as expected to result
from these Cs-symmetrical catalysts. The regioregularity
aspect was more revealing. All the poly(1-hexene)
samples derived from the catalysts of this series exhib-
ited additional peaks at the ranges of 34.9-38.1 and
30.2-30.7 ppm that were previously reported to be
indicative of regioirregular poly(1-hexene).10 According
to a DEPT-135 spectrum, the peaks at 34.9-35.9 and
at 36.6-38.1 are CH-type carbons, while the peak at
30.2-30.7 ppm represents a CH2-type carbon. An ad-
ditional CH2 peak, of relatively low intensity (ca. 20%
(8) (a) A ligand bearing ortho Me groups led to a mixture of a bis-
(homoleptic) complex alongside the desired complex, see ref 7c. (b) The
bulky t-Bu groups inhibited the reaction of the ligand precursors with
pentabenzyltantalum, see: Groysman, S.; Goldberg, I.; Kol, M.; Genizi,
E.; Goldschmidt, Z. Organometallics 2004, 23, 1880.
(9) Exceptionally, a hafnium catalyst based on a ligand bearing an
-SMe sidearm donor was more active than its zirconium analogue;
see ref 7d.

5294 Organometallics, Vol. 23, No. 22, 2004
Ta ble 1. Selected P olym er iza tion Da ta for 2 a n d 3
Groysman et al.
precat.
(µmol)
B(C6F5)3,
µmol
1-hexene,
g
polym.
polymer
obtained, g
conversion,
%
no.
1
time, mina
activityb
Mw
PDI
2 (17)
28
3.37
20
60
120
48
177
240
1522
20
0.081
0.261
0.524
c
0.806
1.448
6.860
0.160
0.572
1.236
14
15
15
c
16
21
16
34
41
44
2
8
17
c
3
5
26
5
17
37
7400
17 300
29 800
20 300
46 600
43 700
54 000
17 200
38 200
77 800
1.13
1.18
1.24
1.09
1.41
1.62
1.98
1.13
1.36
1.52
2
2 (17)
17
26.92
3
3 (14)
25
3.37
60
120
Values represent aliquots taken out at the specified time in polymerization runs 1-3. gpol mmolcat-1 h-1
.
c The weight of the resulting
a
b
polymer was too low to be determined precisely.
Ta ble 2. Selected P olym er iza tion Da ta in th e “NMe2” Ser ies
precat.
(µmol)
B(C6F5)3,
µmol
1-hexene,
g/ClPh, g
polym. time,
min
polymer
obtained, g
conversion,
%
no.
activitya
Mw
PDI
1b
2
5 (14)
5 (10)
19
15
neat, 3.36
4.04/26.57
7.0
12.5c
26.5c
52.3c
6.2
2.35
1.34
2.86
4.1
1.84
0.82
1.15
1.64
1.18
4.20
1,400
620
630
470
1,500
190
140
110
5,900
6,200
70
33
71
37,000
45,000
35,000
26,000
24,000
40,000
52,000
51,000
10.3
1.3
2.3
3.2
2.5
1.4
1.5
1.8
2.0
1.8e
∼100
3b
4
6 (12)
6 (17)
29
17
neat, 3.36
4.04/26.57
55
15.0d
28.0d
52.0d
1.0
2
28
41
35
5b
6b
7 (12)
7 (15)
29
23
neat, 3.40
neat, 13.60
330,000
1,140,000
2.7
31
gpol mmolcat h-1
.
A typical polymerization out of at least 3 runs. c Aliquots taken in run 2. Aliquots taken in run 4. e Bimodal
a
-1
b
d
MWD.
compared to the peak at 30.2-30.7), is found at 35.9-
36.6 ppm. On the basis of these data and the previous
reports, we assigned the absorptions at 34.9-35.9 and
at 36.6-38.1 to misinserted C2 carbons of H-H and
T-T linkages (H ) Head ) C2; T ) Tail ) C1), while
the large peak at ca. 30.2-30.7 was assigned as a
regioirregular C1 carbon of a T-T linkage type. The
degree of misinsertions could be estimated by integra-
tion of the irregular C1 peak relative to the “normal”
(H-T) C1 peak (ca. 40.6 ppm).10 Significantly, the extent
of regioregularity was found to decrease as the bulk of
the phenolate substituents decreased. The bulkiest
precatalyst of this series, 1, led to an almost regioregular
poly(1-hexene), exhibiting ca. 4% misinsertions. How-
ever, the less bulky 2 and 3 led to a significantly higher
number of regioerrors, with ca. 16% and 20% misinser-
tions, respectively.
The fast polymerization caused the monomer to boil in
the reaction vessel while being almost completely
consumed. This is the first time a titanium catalyst of
this family showed such a high activity, previously
observed only for the Zr/Hf catalysts. In contrast to the
Zr catalysts, 5/B(C6F5)3 yielded poly(1-hexene) of broad
molecular weight distribution (PDI values of ca. 10; Mw
) 30 000-40 000), possibly due to its lower thermal
stability under these harsh conditions. Dilution of the
monomer with chlorobenzene slowed the temperature
rise, and consequently the PDI values narrowed to
around 2, while the catalyst’s activity decreased to ca.
600 gpol mmolcat h-1
.
-1
Interestingly, a further drop in steric congestion (Me
to H ortho-substituents on the phenolate rings) caused
only a minor increase in activity of the catalyst. Thus,
following activation with B(C6F5)3, red-brown 6 led to a
highly active 1-hexene polymerization catalyst, with an
Rea ctivity in 1-Hexen e P olym er iza tion : “NMe2”
Ser ies. As previously described, activation of the steri-
activity of 1400-1900 gpol mmolcat h-1. The resulting
-1
cally congested precatalyst 4 with B(C6F5)3 led to a
polymer had a Mw of 40 000-50 000 and a broad
molecular weight distribution. When the polymerization
is performed in chlorobenzene, the polymer obtained has
narrower PDI values (1.7-2.0), thereby supporting the
single-site nature of the catalyst.
-1
moderate activity of 30 gpol mmolcat h-1 7b
A 30 min
.
polymerization run led to poly(1-hexene) having Mw of
several tens of thousands and a narrow PDI consistent
with living polymerization. However, in a stark diver-
sion from the almost uniform activity of the “OMe”-type
catalysts, the less sterically congested complex 5 exhib-
its a dramatically higher activity. Following activation
As a second diversion from the “OMe”-type catalysts,
electronic factors were found to affect the reactivity of
the “NMe2”-type catalysts even more dramatically. Upon
by B(C6F5)3 its polymerization activity approached 1400
-1
h-1, namely, an almost 2 orders of
activation, purple-brown 7 led to a polymerization
gpol mmolcat
-1
magnitude higher activity in comparison to 4 (Table 2).
catalyst, whose activity (6000-8000 gpol mmolcat h-1
)
approaches that of the Zr catalysts of this family.7c,d As
a matter of fact, this is one of the highest activities
reported for 1-hexene polymerization by Cp-free Ti
catalysts and is comparable to the activities of ti-
tanocenes11 and constrained-geometry titanium cata-
lysts.12
(10) (a) Saito, J .; Mitani, M.; Matsui, S.; Kashiwa, N.; Fujita, T.
Macromol. Rapid. Commun. 2000, 21, 1333. (b) Makio, H.; Kashiwa,
N.; Fujita, T. Adv. Synth. Catal. 2002, 344, 477. (c) Zhao, X.; Odian,
G.; Rossi, A. J . Polym. Sci. 2000, 38, 3802. (d) Presumably, the
irregular peak at ca. 30.2-30.7 ppm corresponds to C1 of a misinserted
unit as well as to C1 of the following unit. The degree of misinsertions
was calculated accordingly.

Amine Bis(phenolate) Ti Polymerization Catalysts
Organometallics, Vol. 23, No. 22, 2004 5295
Ta ble 3. La r ge-Sca le P olym er iza tion w ith 7/
B(C6F 5)3 (7, 4 µm ol; B(C6F 5)3, 10 µm ol; 1-h exen e, 104
m L)
time (min) polymer weight (g) activitya
Mw
PDI
5
10
15
20
30
40
60
80
120
0.405
0.693
1.086
1.857
2.161
2.572
n.d.
1200
1000
1100
1400
1100
1000
n.d.
660 000
1 330 000
1 930 000
2 670 000
3 200 000
3 560 000
4 170 000
4 340 000
4 340 000
1.5
1.5
1.6
2.1
2.7
1.8
1.9
2.0
2.5
6.000
8.748
1100
1100
a
-1
gpol mmolcat h-1
.
F igu r e 5. ORTEP representation of 6 (50% probability
ellipsoids). Selected bond lengths (Å) and angles (deg):
Ti1-O2 1.851(2), Ti1-O3 1.852(2), Ti1-N4 2.451(3), Ti1-
N5 2.437(2), Ti1-C6 2.153(3), Ti1-C7 2.174(3), O2-Ti1-
O3 162.56(10), C6-Ti1-N4 166.32(11), C20-O2-Ti1
143.2(2), C37-O3-Ti1 146.17(19), C8-C6-Ti1 104.56(19),
C14-C7-Ti1 120.5(2).
F igu r e 4. ORTEP representation of 3 (50% probability
ellipsoids). Selected bond lengths (Å) and angles (deg): Ti-
O2 1.856(2), Ti1-O3 1.875(2), Ti1-N4 2.374(3), Ti1-O5
2.457(2), Ti1-C6 2.120(3), Ti1-C7 2.149(3), O2-Ti1-O3
162.8(1), C6-Ti1-O5 167.5(1), C20-O2-Ti1 144.5(2),
C36-O3-Ti1 144.9(2), C8-C6-Ti1 108.7(2), C14-C7-Ti1
117.0(2).
Yet, the most unique feature of this catalytic system
is the very high propagation-to-termination ratio, af-
fording poly(1-hexene) of unusually high molecular
weight. Relatively small-scale experiments (molar ratio
ca. 3000/1 1-hexene/7) led to polymers having Mw values
of several hundreds of thousands within 1 min and
higher than 1 000 000 within 2.7 min. In larger-scale
polymerization experiments, even though some reduc-
tion in catalytic activity was observed (to ca. 1000-2500
F igu r e 6. ORTEP representation of 7 (50% probability
ellipsoids). Selected bond lengths (Å) and angles (deg):
Ti1-O2 1.857(2), Ti1-O3 1.864(2), Ti1-N4 2.414(2), Ti1-
N5 2.466(2), Ti1-C6 2.154(3), Ti1-C7 2.175(3), O2-Ti1-
O3 162.26(8), C6-Ti1-N5 170.08(9), C20-O2-Ti1 145.7
(2), C37-O3-Ti1 143.47(18), C8-C6-Ti1 109.1(2), C14-
C7-Ti1 117.3(2).
g
pol mmolcat-1 h-1), polymers with even higher molecular
weights of several millions were obtained. Thus, the
combination of high activity and negligible termination
resulted in an ultrahigh molecular weight polymer with
a Mw value of more than 4 000 000, within less than 1
h (Table 3, Figure 7). To our knowledge, this is the
highest Mw poly(1-hexene) ever prepared at RT under
atmospheric pressure. It is also the highest Mw atactic
poly(1-hexene) ever prepared under any conditions.
The 13C NMR spectra of the polymer samples result-
ing from this series of catalysts revealed valuable
information, especially when compared to the spectra
of the polymers resulting from the “OMe”-type catalysts.
As expected, all polymers were atactic. On the other
hand, the degree of regioregularity induction was much
higher for the “NMe2”-type catalysts. Bulky 4 yielded
F igu r e 7. Mw evolution in the large-scale polymerization
with 7/B(C6F5)3.
essentially regioregular poly(1-hexene) (misinsertions <
1%). The reduction in steric bulk led to some regioir-
regularity; however, its extent was much lower than
that observed for the “OMe”-type catalysts. Thus the
(11) Qian, Y.; Huang, J ., Bala, M. D., Lian, B., Zhang, H.; Zhang,
H. Chem. Rev. 2003, 103, 2633.
(12) McKnight, A. L.; Waymouth, R. M. Chem. Rev. 1998, 98, 2587.

5296 Organometallics, Vol. 23, No. 22, 2004
Groysman et al.
F igu r e 8. Stress relaxation plot for the p-HEX1, p-HEX2, and p-HEX3 samples.
polymer samples produced by catalysts 5-7 exhibited
rather similar microstructures, with only 4-5% misin-
sertions, giving rise to a highly regioregular poly(1-
hexene).
the Me value obtained for both polymers was ca. 27 000,
which is markedly different from the predicted value
of 12 100 recently reported.15,16 The full characterization
of this material will be published elsewhere.
Ch a r a cter iza tion of th e Ultr a h igh Mw P olym er .
The ultrahigh Mw polymer samples produced by complex
7 have the appearance of a solid elastomer rather than
that of a sticky oil, typical of lower Mw atactic poly(1-
hexene). The viscoelastic properties of two high-Mw
samples (p-HEX1, Mw ) 4 300 000, PDI ) 2.5; p-HEX2,
Mw ) 1 500 000, PDI ) 2.0) were characterized and
compared with those of a low-Mw sample (p-HEX3 Mw
) 50 000), produced by a Zr catalyst of this family.7c
The loss modulus G′′(ω) dependence (going through the
minimum) and the storage modulus G′(ω) dependence
(going through the plateau) of p-HEX1 and p-HEX2,
measured in oscillatory tests, are typical of rubbery
polymers having high-Mw and low PDI.13 For both
materials in the temperature range 296-463 K, G′′(ω)
was found to be lower than G′(ω), indicating that the
elasticity dominates the rheological behavior of these
polymers. For p-HEX3, on the contrary, G′(ω) is lower
than G′′(ω) even at room temperature, indicating a
typical liquidlike behavior. To directly compare the
viscoelastic properties of the high molecular weight
p-HEX1 and p-HEX2 with those of the regular p-HEX3,
stress relaxation experiments were performed at 296 K.
Since the concept of a relaxation modulus G(t) applies
to liquids as well as to solids, it is well suited for this
comparison. Figure 8 displays the normalized G(t)
curves for all three polymer samples. The relaxation
modulus of p-HEX3 drops very fast to zero, showing a
behavior typical of non-crosslinked and nonentangled
polymer melts. For the high molecular weight samples
p-HEX1 and p-HEX2, an initial fast relaxation is
followed by a plateau zone in which the modulus
decrease is very slow, and then the second drop occurs
at substantially long times. The existence of a plateau
for p-HEX1 and p-HEX2 is characteristic of polymers
in the rubbery state and implies the presence of
entanglements. The plateau moduli Gp and Gp(t) were
determined for p-HEX1 and p-HEX2 from both oscilla-
tory and relaxation experiments,14 and the entangle-
ment molecular weights Me were calculated. Notably,
Discu ssion
This work further establishes that amine bis(pheno-
late) ligands bind in a uniform and rigid manner to early
transition metals as apparent from spectroscopic and
solid-state data. Variation of structural parameters such
as phenolate ring substituents does not alter the overall
binding of the ligand core to the metal and has only a
minor effect on bond lengths and angles. Yet, as this
and previous studies on these systems have shown,
these minor structural changes have a major effect on
reactivity, leading to a broad variety of olefin polymer-
ization catalysts.
Contrary to our initial expectations, the dependence
of activity on steric and electronic factors obeys a
different trend for the two series of complexes: a strong
dependence for the “NMe2”-type catalysts and an almost
negligible dependence for the “OMe”-type catalysts. The
behavior of the “NMe2”-type catalysts is more in line
with our predictions. Comparing the low activity of 4
to the high activity of its zirconium analogue, we may
assume that it is caused by steric congestion. Thus, the
reduction of steric bulk by replacement of t-Bu groups
with Me groups (4 to 5) indeed leads to a dramatic
activity enhancement. An observed Ti-NMe2 bond
contraction supports the notion of strain relief at the
metal center. Notably, the polymerization modes of
5/B(C6F5)3 and 6/B(C6F5)3 are very similar, indicating
that “opening” the catalytic site beyond a certain value
does not have a considerable effect on reactivity. How-
ever, 7/B(C6F5)3, carrying Cl substituents, exhibits a
different behavior in terms of propagation vs termina-
tion rates and stability of the catalyst. In addition, the
Cl substituents lead to a further increase in activity
relative to the catalysts bearing small alkyl groups.
Thus, the “positive” effect of the Cl substituents in the
ortho and para positions of the phenolate rings should
be assigned to their electron-withdrawing nature. A
similar activity enhancement following introduction of

Amine Bis(phenolate) Ti Polymerization Catalysts
Organometallics, Vol. 23, No. 22, 2004 5297
electron-withdrawing F groups was reported for the
phenoxyimine Ti catalysts.17 In contrast, electron-
withdrawing Cl or F substituents in the diamido/donor
Zr/Hf complexes had a negative effect on the polymer-
ization behavior by decreasing polymerization rate and
increasing termination (â-hydride elimination), thus
producing shorter polymeric chains.18
currently exploring other types of polymerization em-
ploying these catalysts.
Exp er im en ta l Section
Gen er a l P r oced u r es. All experiments were performed
under an atmosphere of dry nitrogen in a nitrogen-filled
glovebox. Ether was purified by reflux and distillation under
dry argon atmosphere from Na/benzophenone. Pentane was
washed with HNO3/H2SO4 prior to distillation from Na/
benzophenone/tetraglyme. Toluene was refluxed over Na and
distilled. Benzylmagnesium chloride, 1-hexene, and chloroben-
zene were purchased from Aldrich Inc. Tris(pentafluorophen-
yl)borane was obtained from Strem Chemicals Inc. 1-Hexene
and chlorobenzene were passed through activated alumina
prior to use. Titanium tetrabenzyl was synthesized according
to published procedures20 and used shortly after its synthesis.
The ligand precursors Lig1H2, Lig2H2, and Lig4H2-Lig7H2were
prepared as previously described.7c,8b The preparation of
complexes 1 and 4 was previously described.7b,c
NMR data of metal complexes were recorded on Bruker AC-
200 and Bruker Avance AC-400 spectrometers and referenced
to protio impurities in benzene-d6 (δ 7.15) and to the 13C
chemical shift of benzene (δ 128.70). 13C NMR data of poly(1-
hexene) samples were recorded on a Bruker AM-500B spec-
trometer in CDCl3 at 300 K and referenced to CDCl3 (77.16
ppm). Scanned copies of all (7) 13C NMR spectra discussed in
the text may be found in the Supporting Information.
Elemental analyses were performed in the microanalytical
laboratory of the Hebrew University in J erusalem. The metal
complexes were analyzed within a few hours of being taken
out of the freezer of the glovebox. Though showing good H/N
percentage, the analyzed complexes consistently showed low
carbon percentage. This may stem from their extreme air-
sensitivity, leading to an immediate hydrolysis upon contact
with air.
The molecular weight of the poly(1-hexene) samples was
determined by gel permeation chromatography (GPC) relative
to polystyrene standards using tetrahydrofuran (HPLC grade,
distilled and filtered under vacuum prior to use) as the eluting
solvent and TSKgel GMHHR-M, TSKgel G 5000 HHR, and
PSS SDV 108 Å columns set on a J asco instrument equipped
with a refractive index detector.
The X-ray diffraction measurements were performed on a
Nonius Kappa CCD diffractometer system, using Mo KR (λ )
0.7107 Å radiation). The analyzed crystals were embedded
within a drop of viscous oil and freeze-cooled to ca. 110 K. The
structures were solved by a combination of direct methods and
Fourier techniques using SIR-92 software21 and were refined
by full-matrix least squares with SHELXL-97.22 The crystal
and experimental data are summarized in Table 4.
With the trend of the “NMe2”-type catalysts in mind,
the source of the indifference of the “OMe”-type catalysts
to electronic and steric effects is at first glance unclear.
Especially, the low activity of all the titanium catalysts
of the “OMe”-type stands in sharp contrast to the
extremely high activity of the zirconium and hafnium
catalysts of this series. A possible explanation for this
unexpected behavior is the unusually high ratio of
regioerrors occurring in this series of catalysts, as
observed in the 13C NMR spectra. A misinsertion is
expected to lower the rate of the following insertion step,
by blocking the metal center.19 Thus, the expected
increase in insertion rate as the bulk of the phenolate
substituents is reduced is compensated by the increased
degree of regioerrors reducing the insertion rate. Alto-
gether, a uniform behavior is observed along this series.
A further outcome of the current work is the insight
into the requirements for living polymerization in this
system. In both series of catalysts, only the members
bearing t-Bu groups, namely, 4/B(C6F5)3 and 1/B(C6F5)3,
led to living polymerization. Providing a more open
metal center in both series led to acceleration of the
termination processes even when the polymerization
was run under conditions wherein the heat release was
quenched. Thus, as previously observed for other sys-
tems,2,5,7 steric crowding at the metal center seems to
be an important requirement for living polymerization
catalysis.
Con clu sion s
This work demonstrates that although the effects of
structural parameters on reactivity are difficult to
predict, highly successful catalysts of the amine bis-
(phenolate) family may be obtained. Such a catalyst
featuring high activity and low termination allowed the
preparation of ultrahigh-Mw poly(1-hexene) within a
short time under ambient conditions. This work gives
further evidence for the potential of Cp-free catalysts
for production of specialty polymers not accessible by
classical Ziegler-Natta or metallocene catalysts. We are
Polymer densities were measured at 296 K by means of
hydrostatic weighing in ethanol. Storage G′(ω), loss G′′( ω) and
relaxation G(t) shear moduli were measured using an ARES
mechanical spectrometer (ex Rheometric) with a parallel plate
geometry 25 mm in diameter. All poly(1-hexene) samples were
studied under nitrogen atmosphere to prevent possible ther-
mooxidative destruction of these unstabilized polymers.
Syn th esis of Lig3H2 (2,2′-[[(2-Meth oxyeth yll)im in o]bis-
(m eth ylen e)]bis(4,6-d ich lor op h en ol)). A solution of 2,4-
dichlorophenol (6.0 g, 36.7 mmol), (2-methoxy)ethylamine
(0.901 g, 12 mmol), and 36% aqueous formaldehyde (2.1 mL,
24.4 mmol) in methanol (10 mL) was stirred and refluxed for
48 h. Upon cooling, the reaction mixture separated into two
(13) Ferry, J . Viscoelastic Properties of Polymers, 3rd ed.; J ohn Wiley
& Sons: New York, 1980.
(14) (a) Eckstein, A.; Suhm, J .; Friedrich, C.; Maier, R.-D.; Sass-
mannshausen, J .; Bochmann, M.; Mu¨lhaupt, R. Macromolecules 1998,
31, 1335. (b) Barnes, H. A Handbook of Elementary Rheology; Institute
of Non-Newtonian Fluid Mechanics, University of Wales, 2000.
(15) (a) Entanglement molecular weights Me were estimated from
the measured plateau modulus values using the equation Me ) FRT/
Gp; see ref 13. (b) In addition, Me can be estimated from the absolute
value of G(t) in the plateau zone Gp(t) using a similar equation: Me
)
FRT/Gp(t); see: Dealy, J .; Wissbrun, K. Melt Rheology And Its Role in
Plastics Processing; Van Nostrand Reinhold: New York, 1990.
(16) Fetters, L. J .; Lohse, D. J .; Garsia-Franko, C. A.; Brant, P.;
Richter, D. Macromolecules 2002, 35, 10096.
(17) (a) Makio, H.; Kashiwa, N.; Fujita, T. Adv. Synth. Catal. 2002,
344, 477. (b) Mason, A. F.; Tian, J .; Hustad, F. D.; Lobkovsky, E. B.;
Coates, G. W. Isr. J . Chem. 2002, 42, 301.
(18) Schrock, R. R.; Adamchuk, J .; Ruhland, K.; Lopez, L. P. H.
Organometallics 2003, 22, 5079.
(20) Van der Linden, A.; Schaverien, C. J .; Neijboom, N.; Orpen, G.
J . Am. Chem. Soc. 1996, 117, 3088.
(21) Altomare, A.; Cascarano, G.; Giacovazzo, C.; Guagliardi, A.;
Burla, M. C.; Polidori, G.; Camali, M. J . Appl. Crystallogr. 1994, 27,
435.
(19) Resconi, L.; Cavallo, L.; Fait, A.; Piemontesi, F. Chem. Rev.
2000, 100, 1253.
(22) Sheldrick, G. M. SHELXL-97 Program; University of Go¨ttin-
gen: Go¨ttingen, Germany, 1997.

5298 Organometallics, Vol. 23, No. 22, 2004
Ta ble 4. Cr ysta llogr a p h ic Da ta for 2, 3, 6, a n d 7
Groysman et al.
2
3
6
7
formula
fw
a (Å)
b (Å)
c (Å)
C
35H41NO3Ti
C31H29Cl4NO3Ti
653.25
13.9020(8)
12.2160(8)
17.3030(8)
90.00
95.005(4)
90.00
monoclinic
P21/c
C36H44N2O2Ti
584.63
C32H32N2O2Ti‚C4H8O
571.59
11.1230(4)
13.5580(4)
19.8870(7)
90.00
90.00
90.00
orthorombic
P212121
2999.1(2)
1.266
740.42
10.3640(2)
17.5590(6)
20.3320(6)
90.00
93.738(2)
90.00
monoclinic
P21/c
8.8780(2)
11.5040(3)
16.2040(6)
90.050(1)
96.651(1)
105.940(2)
triclinic
P1h
R (deg)
â (deg)
γ (deg)
cryst syst
space group
V (Å3)
2927.3(3)
1.482
0.692
1579.69(8)
1.229
0.305
3692.2(2)
1.332
0.558
Dc (g cm-1
)
µ (cm-1
Z
)
0.321
4
4
2
4
no. of measd reflns
no. of reflns [I>2σ(I)]
R1 [I>2σ(I)]
wR2 [I>2σ(I)]
GOF
5257
4010
0.0567
0.1016
1.012
6947
4273
0.0613
1.1199
6985
4688
0.0657
0.1601
8858
5623
0.0541
0.1253
1.018
1.016
1.025
phases. The upper phase was decanted, and the remaining
heavy oil containing the product, excess phenol, and the
corresponding benzoxazine was triturated with cold methanol
to give colorless crystals of the product (1.2 g, 28% yield). The
filtrate was concentrated and left at room temperature for ca.
2 months, during which further crystals of the product had
formed, increasing the reaction yield to a total of 60%. Mp:
115-116 °C (methanol). Anal. Calc for C17H17NO3 (425.13): C,
48.03; H, 4.03; N, 3.29; Cl, 33.36. Found: C, 48.13; H, 4.02;
P r ep a r a tion of Com p lex 5. To a stirring dark red solution
of Ti(CH2Ph)4 (58 mg, 0.141 mmol) in toluene (ca. 1 mL) was
added dropwise Lig5H2 (49 mg, 0.138 mmol) in toluene (1 mL)
at RT. After 2 h the solvent was evaporated, and the resulting
dark red solid was washed with pentane (ca. 2 mL) and dried
under vacuum. The final yield of 5 was 86% (69 mg, 0.118
mmol). Anal. Calc for C36H44N2O2Ti (584.61): C, 73.96; H, 7.59;
N, 4.79. Found: C, 69.58; H, 7.50; N, 4.90. 1H NMR (C6D6,
200 MHz): δ 7.58 (d, J ) 7.9 Hz, 2H), 7.35 (t, J ) 7.8 Hz, 2H),
7.03 (br s, 2H), 6.95 (m, 3H), 6.86 (t, J ) 7.3 Hz, 2H), 6.62 (t,
J ) 7.1 Hz, 1H), 6.62 (t, J ) 1.7 Hz, 2H), 3.21 (s, 2H), ca. 3.13
and 3.09 (d and s, 4H), 2.71 (s, 6H), 2.38 (d, J ) 13.6 Hz, 2H),
2.23 (s, 6H), 1.69 (br s, 2H), 1.40 (s, 6H), 1.18 (m, 2H). 13C
NMR (C6D6, 50.29 MHz): δ 160.36 (C-O), 154.01 (C), 150.95
(C), 132.66 (CH), 129.01 (CH), 129.82 (CH), 128.65 (CH),
128.15 (CH), 127.81 (CH), 126.53 (C), 125.74 (C), 122.66 (CH),
122.29 (CH), 95.44 (CH2), 89.46 (CH2), 64.80 (CH2), 60.18
(CH2), 52.29 (CH2), 46.95 (CH3), 21.50 (CH3), 17.97 (CH3).
P r ep a r a tion of Com p lex 6. To a stirring dark red solution
of Ti(CH2Ph)4 (54 mg, 0.131 mmol) in toluene (1 mL) was
added dropwise Lig6H2 (45 mg, 0.126 mmol) in toluene (1 mL)
at RT. After 2 h the solvent was evaporated, and the resulting
red-brown solid was washed once with pentane (ca. 3 mL) and
dried under vacuum. The final yield of 6 was 98% (72 mg, 0.123
mmol). Anal. Calc for C36H44N2O2Ti (584.61): C, 73.96; H, 7.59;
N, 4.79. Found: C, 70.07; H, 7.52; N, 4.80. 1H NMR (C6D6,
200 MHz) δ 7.70 (d, J ) 7.5 Hz, 2H), 7.40 (t, J ) 7.5 Hz, 2H),
7.25(s, 2H), 6.86 (t, J ) 7.6 Hz, 2H), 6.61 (s and m, 3H), 3.27
(s, 2H), 3.10 (d, J ) 13.4 Hz, 2H), 3.09 (s, 2H), 2.35 (d, J )
13.6 Hz, 2H), 2.18 (s, 6H), 2.11 (s, 6H), 1.65 (m, 2H), 1.49 (s,
6H), 1.22 (m, 2H). 13C NMR (C6D6, 50.29 MHz): δ 162.29 (C-
O), 154.16 (C), 150.34 (C), 138.74 (C), 131.69 (CH), 129.01
(CH), 128.69 (CH), 128.55 (CH), 128.04 (CH), 127.92 (C),
124.81 (C), 122.76 (CH), 122.33 (CH), 118.71 (CH), 95.33 (CH2),
90.86 (CH2), 64.39 (CH2), 60.32 (CH2), 52.17 (CH2), 47.31 (CH3),
20.62 (CH3), 19.74 (CH3).
P r ep a r a tion of Com p lex 7. To a stirring dark red solution
of Ti(CH2Ph)4 (57 mg, 0.138 mmol) in toluene (ca. 1 mL) was
added dropwise Lig7H2 (55 mg, 0.125 mmol) in toluene (1 mL)
at RT. After 1 h the solvent was evaporated, and the resulting
purple-brown solid was washed with pentane (ca. 2 mL) and
dried under vacuum. The final yield of 7 was 93% (77 mg, 0.116
mmol). Anal. Calc for C32H32Cl4N2O2Ti (666.29): C, 57.68; H,
4.84; N, 4.20. Found: C, 58.89; H, 4.96; N, 4.17. 1H NMR (C6D6,
200 MHz): δ 7.94 (d, J ) 7.3 Hz, 2H), 7.42 (d, J ) 2.1 Hz,
2H), 7.35 (t, J ) 7.3 Hz, 2H), 7.00 (m, 1H), 6.7-6.5 (Ar-H,
6H), 3.21 (s, 2H), 3.14 (s, 2H), 2.65 (d, J ) 13.9, 2H), 1.87 (d,
J ) 13.7, 2H), 1.35 (s, 6H), 1.21 (m, 2H), 0.90 (m, 2H). 13C
NMR (C6D6, 50.29 MHz): δ 158.27 (C-O), 154.06 (C), 150.03
(C), 130.89 (CH), 130.00 (CH), 128.99 (CH), 128.92 (CH),
128.60 (CH), 127.98 (CH), 124.57 (C), 123.76 (CH), 123.60 (C),
1
N, 3.19; Cl, 33.13. H NMR (CDCl3): δ 8.09 (2H, bs), 7.27 (d,
J ) 2.5 Hz, 2H), 6.98 (d, J ) 2.5 Hz, 2H); 3.81 (s, 4H), 3.61 (t,
J ) 5.0 Hz, 2H), 3.41 (s, 3H), 2.76 (t, J ) 5.0 Hz, 2H). 13C
NMR (CDCl3): δ 150.83 (2C), 128.82 (2CH), 128.46 (2CH),
124.49 (2C), 124.13 (2C), 121.58 (2C), 70.18 (2CH2), 58.94
(CH3), 55.78 (CH2), 55.54, (CH2). HRMS (DCI-CH4): 424.0060
(C17H18Cl4NO3)(MH+) (35Cl).
P r ep a r a tion of Com p lex 2. To a stirring dark red solution
of Ti(CH2Ph)4 (35 mg, 0.085 mmol) in 1 mL of toluene was
added dropwise Lig2H2 (26 mg, 0.076 mmol) in toluene (1 mL)
at RT. After 2 h the solvent was evaporated, and the resulting
red-orange solid was washed with a small amount of pentane
and dried under vacuum. The final yield of 2 was 71% (31 mg,
0.054 mmol). Anal. Calc for C35H41NO3Ti (571.57): C, 73.55;
1
H, 7.23; N, 2.45. Found: C, 71.23; H, 7.25; N, 2.42. H NMR
(C6D6, 200 MHz): δ 7.48 (d, J ) 7.4, 2H), 7.21 (t, J ) 7.6 Hz,
2H), 7.01-6.77 (Ar-H, 7H), 6.59 (m, 1H), 6.52 (br s, 2H), 3.49
(s, 2H), 3.35 (s, 2H), 2.95 (d, J ) 13.2 Hz, 2H), 2.74 (s, 6H),
2.57 (d, J ) 13.6, 2H), 2.34 (s, 3H), 2.26 (m, 2H), 2.22 (s, 6H),
1.57 (m, 2H). 13C NMR (C6D6, 50.29 MHz): δ 160.54 (C-O),
150.56 (C), 147.53 (C), 132.58 (CH), 129.72 (CH), 129.45 (C),
129.14 (CH), 128.99 (C), 128.88 (C), 128.84 (CH), 125.39 (CH),
125.69 (CH), 122.98 (CH), 122.92 (CH), 91.17 (CH2), 86.00
(CH2), 71.01 (CH2), 63.46 (CH2), 58.62 (CH3), 49.24 (CH2), 21.50
(CH3), 17.83 (CH3).
P r ep a r a tion of Com p lex 3. To a stirring dark red solution
of Ti(CH2Ph)4 (70 mg, 0.169 mmol) in 2 mL of toluene was
added dropwise 65 mg (0.153 mmol) of Lig3H2 in toluene (1
mL) at RT. After 1 h the toluene was evaporated, and the
resulting orange solid was washed with pentane (2 mL) and
dried under vacuum. The final yield of 3 was 82% (82 mg, 0.126
mmol). 3 can be recrystallized from cold ether (-30 °C). 1H
NMR (C6D6, 200 MHz): δ 7.83 (d, J ) 7.2 Hz, 2H), 7.39 (d, J
) 2.5 Hz, 2H), 7.12 (m, 2H), 6.81 (t, J ) 7.3 Hz, 2H), 6.74-
6.66 (m, 4H), 6.62-6.56 (d, J ) 2.5 Hz, and m, 3H), 3.53 (s,
2H), 3.24 (s, 2H), 2.58 (d, J ) 13.7 Hz, 2H), 2.40 (d, J ) 13.8
Hz, 2H), 2.32 (s, 3H), 2.07 (t, 5.1 Hz, 2H), 1.14 (br s, 2H). 13C
NMR (C6D6, 50.29 MHz): δ 157.86 (C-O), 14579 (C), 144.93
(C), 131.93 (CH), 130.79 (CH), 130.46 (CH), 129.64 (CH),
129.08 (CH), 124.79 (CH), 124.68 (C), 123.95 (CH), 123.23 (C),
92.36 (CH2), 90.20 (CH2), 69.36 (CH2), 61.14 (CH2), 58.99 (CH3),
47.29 (CH2).

Amine Bis(phenolate) Ti Polymerization Catalysts
Organometallics, Vol. 23, No. 22, 2004 5299
122.96 (CH), 101.68 (CH2), 94.92 (CH2), 63.34 (CH2), 59.78
(CH2), 52.18 (CH2), 47.01 (CH3).
P olym er Ch a r a cter iza tion . Specimens for density deter-
mination and viscoelastic parameter measurements (storage,
loss, and relaxation shear moduli) were prepared by compres-
sion molding of the high molecular weight samples p-HEX1
and p-HEX2 into plates of about 1.8 mm thickness at 170 and
150 °C, respectively. Disks of 25 mm in diameter were cut from
the plates and used in the viscoelasticity studies; small
specimens having no sharp edges were also cut out of the
plates and used in the density measurements. A sample of
p-HEX3 (Mw ) 50 000, PDI ) 3.0), previously prepared by a
Zr catalyst,7c required no specific preparation for the rheologi-
cal testing.
P olym er iza tion of Nea t 1-Hexen e w ith 2/B(C6F 5)3 a n d
w ith 3/B(C6F 5)3. B(C6F5)3 (17-28 µmol) was dissolved in ca.
1 mL of 1-hexene and added to a stirred solution of 2 (or 3)
(14-17 µmol) in 1-hexene. The resulting mixture was allowed
to stir at RT. The polymerization was monitored by taking out
a measured volume of the solution, evaporating to dryness,
weighing, and analyzing by GPC.
P olym er iza tion of Nea t 1-Hexen e w ith 5-7/B(C6F 5)3.
B(C6F5)3 (15-29 µmol) was dissolved in ca. 1 mL of 1-hexene
and added to a stirred solution of 5 (or 6 or 7) (10-17 µmol)
in 1-hexene. The total volume of the solution was 5-15 mL.
The resulting mixture was stirred for 1-9 min (until 1-hexene
had started to boil). The remaining olefin was evaporated in
vacuo, yielding poly(1-hexene) as a colorless sticky oil. The
polymer was weighted and subjected to GPC analysis.
P olym er iza t ion in ClP h w it h 5/B(C6F 5)3 a n d w it h
6/B(C6F 5)3. 1-Hexene (6 mL, 4.04 g) was dissolved in 24 mL
(26.57 g) of ClPh. B(C6F5)3 (15-17 µmol) was dissolved in ca.
1 mL of the resulting mixture and added in one portion to the
5 (or 6) (10-17 µmol) predissolved in the remaining solution.
The polymerization process was monitored by taking out
measured volumes, evaporating to dryness, weighing, and
subjecting to GPC analysis.
La r ge-Sca le P olym er iza tion w ith 7/B(C6F 5)3. B(C6F5)3
(9 µmol) was dissolved in ca. 1 mL of 1-hexene and added in
one portion to a stirred solution of 7 (4 µmol) in 100-140 mL
of 1-hexene. The polymerization process was monitored by
taking out measured aliqouts, evaporating to dryness, weigh-
ing, and subjecting to GPC analysis.
To prepare p-HEX1, the polymerization process was allowed
to proceed for at least 2 h, after which time methanol/HClaq
was added. The organic phase was separated, and the solvent
(1-hexene) was removed under vacuum. The resulting white
rubber-like solid was dried under vacuum for 3 h. According
to GPC, the final polymer had Mw ) 4 300 000, PDI ) 2.5. To
prepare p-HEX2, the polymerization was allowed to proceed
for ca. 30 min (only a slight increase in the polymer weight
was detected after 30 min). The resulting polymer was worked
up as above. According to GPC, the final had Mw ) 1 500 000,
PDI ) 2.0
Frequency sweeps were made at 2% strain (well below the
linear viscoelasticity limit of more than 10%) in the frequency
window from 5 × 10-2 to 16 Hz. The temperature ranged from
296 to 463 K for p-HEX1, from 296 to 443 K for p-HEX2, and
from 296 to 323 K for p-HEX3. The isotherms of the high
molecular weight poly(1-hexene) samples were shifted to
obtain master curves at the reference temperature T0 ) 403
K using the Time-Temperature Superposition (TTS) module
of the Orchestrator Software. A master curve for p-HEX3 was
constructed for the reference temperature 323 K. The dynamic
frequency sweep data were converted into relaxation time
spectra using the Orchestrator Molecular Weight Distribution
(MWD) module. Shear stress relaxation tests were made at
5% strain at 296 K.
Ack n ow led gm en t. This research was supported by
the Israel Science Foundation, founded by the Israel
Academy of Sciences and Humanities. We thank Eli-
sheva Genizi (BIU) and Dalia Gut-Regev (TAU) for
technical assistance.
Su p p or tin g In for m a tion Ava ila ble: Crystallographic
information files for compounds 2, 3, 6, and 7. 13C NMR spectra
of the polymers prepared by catalysts 1-7. This material is
available free of charge via the Internet at http://pubs.acs.org.
OM049630Q