Olefin Polymerization by Dinuclear Zirconium Catalysts Based on Rigid Teraryl Frameworks: Effects on Tacticity and Copolymerization Behavior

Article abstract of DOI:10.1021/acs.organomet.7b00015

Toward gaining insight into the behavior of bimetallic catalysts for olefin polymerization, a series of structurally related binuclear zirconium catalysts with bisamine bisphenolate and pyridine bisphenolate ligands connected by rigid teraryl units were synthesized. Anthracene-9,10-diyl and 2,3,5,6-tetramethylbenzene-1,4-diyl were employed as linkers. Bulky SiⁱPr₃ and SiPh₃ substituents were used in the position ortho to the phenolate oxygen. Pseudo-C_s and C₂ symmetric isomers are observed for the binuclear complexes of bisamine bisphenolate ligands. In general, binuclear catalysts show higher isotacticity compared to the monozirconium analogues, with some differences between isomers. Amine bisphenolate-supported dizirconium complexes were found to be moderately active (up to 1.5 kg mmol_Zr^-1 h^-1) for the polymerization of 1-hexene to isotactically enriched poly-1-hexene (up to 45% mmmm) in the presence of stoichiometric trityl or anilinium borate activators. Moderate activity was observed for the production of isotactically enriched polypropylene (up to 2.8 kg mmol_Zr^-1 h^-1 and up to 25.4% mmmm). The previously proposed model for tacticity control based on distal steric effects from the second metal site is consistent with the observed behavior. Both bisamine bisphenolate and pyridine bisphenolate supported complexes are active for the production of polyethylene in the presence of MAO with activities in the range of 1.1-1.6 kg mmol_Zr^-1 h^-1 and copolymerize ethylene with α-olefins. Little difference in the level of α-olefin incorporation is observed between mono- and dinuclear catalysts supported with the pyridine bisphenolate catalysts. In contrast, the size of the olefin affects the level of incorporation differently between monometallic and bimetallic catalysts for the bisamine bisphenolate system. The ratio of the incorporation levels with dinuclear vs mononuclear catalysts decreases with increasing comonomer size. This effect is attributed to steric pressure provided by the distal metal center on the larger olefin in dinuclear catalysts.

Full text of DOI:10.1021/acs.organomet.7b00015

Article
pubs.acs.org/Organometallics
Olefin Polymerization by Dinuclear Zirconium Catalysts Based on
Rigid Teraryl Frameworks: Effects on Tacticity and Copolymerization
Behavior
Jessica Sampson,† Gyeongshin Choi,† Muhammed Naseem Akhtar,‡ E. A. Jaseer,‡ Rajesh Theravalappil,‡
Hassan Ali Al-Muallem,§ and Theodor Agapie*,†
†Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
‡Center for Refining and Petrochemicals and §Department of Chemistry, King Fahd University of Petroleum and Minerals, Dhahran,
31261, Saudi Arabia
S
* Supporting Information
ABSTRACT: Toward gaining insight into the behavior of bimetallic catalysts for olefin polymerization, a series of structurally
related binuclear zirconium catalysts with bisamine bisphenolate and pyridine bisphenolate ligands connected by rigid teraryl
units were synthesized. Anthracene-9,10-diyl and 2,3,5,6-tetramethylbenzene-1,4-diyl were employed as linkers. Bulky SiiPr3 and
SiPh3 substituents were used in the position ortho to the phenolate oxygen. Pseudo-Cs and C2 symmetric isomers are observed
for the binuclear complexes of bisamine bisphenolate ligands. In general, binuclear catalysts show higher isotacticity compared to
the monozirconium analogues, with some differences between isomers. Amine bisphenolate-supported dizirconium complexes
were found to be moderately active (up to 1.5 kg mmolZr−1 h−1) for the polymerization of 1-hexene to isotactically enriched poly-
1-hexene (up to 45% mmmm) in the presence of stoichiometric trityl or anilinium borate activators. Moderate activity was
observed for the production of isotactically enriched polypropylene (up to 2.8 kg mmolZr−1 h−1 and up to 25.4% mmmm). The
previously proposed model for tacticity control based on distal steric effects from the second metal site is consistent with the
observed behavior. Both bisamine bisphenolate and pyridine bisphenolate supported complexes are active for the production of
polyethylene in the presence of MAO with activities in the range of 1.1−1.6 kg mmolZr−1 h−1 and copolymerize ethylene with α-
olefins. Little difference in the level of α-olefin incorporation is observed between mono- and dinuclear catalysts supported with
the pyridine bisphenolate catalysts. In contrast, the size of the olefin affects the level of incorporation differently between
monometallic and bimetallic catalysts for the bisamine bisphenolate system. The ratio of the incorporation levels with dinuclear
vs mononuclear catalysts decreases with increasing comonomer size. This effect is attributed to steric pressure provided by the
distal metal center on the larger olefin in dinuclear catalysts.
higher molecular weights, and increased incorporation of the
comonomer (C).4 Enhanced α-olefin incorporation by double-
decker-type dinickel phenoxy-imine catalysts (D)5 and
enhanced activity for 1-hexene polymerization with enhanced
chain straightening by related double-decker α-diimine
dipalladium catalysts have been reported (E).6 We have
reported enhanced incorporation of unprotected amino olefins
and enhanced amine tolerance with dinickel phenoxy-imine
catalysts linked via para- and meta-terphenyl moieties (F).7
Multinuclear catalysts have also been explored for tacticity
control, in particular with early metals, though to a much lesser
INTRODUCTION
■
Dinuclear early and late transition metal catalysts have been
studied for improved performance in polyolefin synthesis.1
Enhanced activity, incorporation of α-olefins, tolerance to
functional groups, and tacticity control are among the benefits
demonstrated for dinuclear catalysts compared to related
mononuclear catalysts. Enhanced activity and 1-hexene
incorporation were reported for dizirconium catalysts sup-
ported by dimethylsilyl-linked cyclopentadienyl-amide ligands
linked via an alkane-diyl chain (A, Figure 1).2 Increased 1-
hexene incorporation was reported with dizirconium complexes
supported by fused phenoxy-imine ligands (B).3 Pyridine-amide
dihafnium complexes with naphthalene-based linkers show
enhanced activity for polymerization of ethylene with 1-octene,
Received: January 9, 2017
© XXXX American Chemical Society
A
DOI: 10.1021/acs.organomet.7b00015
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Figure 1. Selected example of previously reported dinuclear polymerization catalysts.
Figure 2. Compounds prepared and evaluated in this study.
extent than mononuclear systems.8,9 Dizirconium bis-propa-
gators supported by amidinate ligands (G) exhibit similar
stereoselectivity in the presence of ZnEt2 to that in its absence,
in contrast with monometallic catalysts, which typically exhibit
lower selectivity in the presence of the chain transfer reagent.10
Dinuclear titanocene complexes (H) show enhanced syndio-
tacticity in styrene polymerization relative to the corresponding
monotitanium catalysts.11
complexes are attributed to both the ligand environment
around each isolated metal center and the interactions of the
growing polymer chain with the sterics of the distal metal
center. For comparison, the original Cs symmetric bisamine
bisphenolate system reported by Kol and co-workers has
−1
activities of up to 102 kg mmolZr h−1 and produces atactic
poly-1-hexene.13 Related C2 symmetric catalysts produce >95%
isotactic poly-1-hexene, but with significantly lower activity,
although C1 symmetric versions show enhanced activity with
lower isoselectivity.14
Our previous report demonstrated that dizirconium bisamine
bisphenolate complexes with bulkier tert-butyl substituents
were less active and produced poly-1-hexene and polypropylene
with lower tacticity control compared to complexes with
smaller chloride substituents. A combination of steric effects,
We have previously reported that bimetallic zirconium amine
bisphenolate complexes supported by a rigid para-terphenyl
linker polymerize propylene and 1-hexene with enhanced
activity and tacticity control.12 Dinuclear Zr2Cl4-NMe2 and
Zr2Cl4-OMe have activities of up to 103 kg mmolZr h−1 in 1-
−1
hexene polymerization and produce poly-1-hexene with >75%
mmmm. The greater activities and isoselectivities of these
B
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a
Scheme 1. Preparation of Phenols and Dinuclear Complexes Zr2SiiPr3-NMe2 and anthZr2SiiPr3-NMe2 Complexes
a
Inset: top view of the coordination environment and linker for the Cs and C2 isomers.
including the distal pressure of the second metal and the
difference in size between the small chloride substituent and the
large aryl substituent that also serves as linker, was proposed to
account for the observed changes in activity and tacticity
between mono- and dinuclear catalysts. Variations in the
electronic properties of the substituents likely contribute to
differences in behavior among the various monometallic or
bimetallic catalysts. As options to replace the chloride
substituent with a smaller one are very limited, the opposite
strategy of significantly increasing the steric bulk is appealing.
To gain further insight into structure−function correlations of
these dinuclear catalysts, determining the effect of the type of
linker employed is desirable. Further related to the steric
constraints generated within the coordination sphere of
dizirconium complexes, the role of denticity of supporting
ligand is of interest. In this context, pyridine bisphenolate
systems provide a more open, tridentate ligand framework, to
compare to the tetradentate bisamine bisphenolate complexes.
Monometallic pyridine bisphenolate complexes have previously
been shown to be active catalysts for ethylene and propylene
homopolymerization and ethylene−α-olefin copolymeriza-
tion.15 Herein we report the synthesis and characterization of
the dizirconium bisamine bisphenolate and pyridine bi-
sphenolate complexes (Figure 2) and their ethylene, propylene,
1-hexene, and 1-tetradecene homo- and copolymerization
behavior.
previously reported catalysts12 (Scheme 1). Double Negishi
coupling of 2-bromo-4-tert-butylanisole with 1,4-dibromo-
2,3,5,6-tetramethylbenzene or 9,10-dibromoanthracene affords
the corresponding terphenyl compounds 2 and anth-2 with
tetramethylphenyl and anthracenyl linkers. Upon removal of
protecting groups with boron tribromide, the syn and anti
atropisomers of the resulting phenols (3 and anth-3) were
separated by column chromatography. The syn atropisomers
were further treated with paraformaldehyde and gaseous
hydrogen bromide to afford ligand precursors 4 and anth-4.
Ligand precursor 7 was synthesized starting with the silylation
of 2,6-dibromo-4-tert-butyphenol (Scheme 2). Subsequent
retro-Brook rearrangement and quenching with dimethylforma-
mide affords tri-isopropyl-substituted salicylaldehyde 6. Reduc-
tive amination of this species with N,N-dimethylethylenedi-
Scheme 2. Synthesis of Phenol Ligand Precursors Featuring
i
ortho-SiR3 Substituents (R = Pr, Ph)
RESULTS AND DISCUSSION
■
Dinuclear amine bisphenolate complexes based on a para-
terphenyl framework were synthesized analogously to the
C
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Figure 3. Solid-state structures of Zr1ArSiiPr3-NMe2 (top), C2 Zr2SiiPr3-NMe2 (center), and C2 anthZr2SiiPr3-NMe2 (bottom). Views perpendicular to the
plane of the linker (D and F) or aryl substituent ortho to phenoxide oxygen (B) are shown on the right. Ellipsoids are drawn at the 50% probability
level, and H atoms are omitted for clarity.
amine affords 7. Reaction of 4 and anth-4 with 7 in the
the two metal centers of the previously reported dinuclear
complexes linked by terphenyl frameworks. The slightly longer
distance between the metal centers may be due to the bulky
substituents applying steric pressure on the benzyl ligands.
Metalation of anthH4SiiPr3-NMe2 afforded the C2 symmetric
complex in 85% purity based on 1H NMR analysis of the crude
reaction mixture. Low-temperature metalation improved this to
95%. Recrystallization of this mixture affords analytically pure
C2 isomer. The identity of the isolated complex was confirmed
by XRD (Figure 3). The two Zr centers again adopt similar
coordination environments to those in previously reported Zr
complexes of bisamine bisphenolate ligands. The overall
geometry of the dinuclear species is similar to that of the C2
Zr2SiiPr3-NMe2 complex. The Zr−Zr distance (7.604 Å) is
shorter by more than 0.1 Å compared to the tetramethylphenyl-
linked complex. The slightly shorter metal−metal distance may
be a consequence of the anthracene linker being flatter than
tetramethylbenzene and alleviating some steric constraints in
the cavity between the two metal centers. Related meta-
terphenyl-linked complexes, triphenylsilyl-substituted, and
presence of NEtiPr2 produces the desired proligands H4
-
SiiPr3
NMe2 and anth-H4SiiPr3-NMe2, which were purified by column
chromatography and isolated in moderate yields (∼55%).
Dizirconium complexes supported by these new binucleating
ligands were prepared by protonolysis of the phenolic
proligands with two equivalents of tetrabenzylzirconium,
resulting in a mixture of Cs and C2 symmetric metalation
isomers. Metalation of H4SiiPr3-NMe2 affords that mixture in a
roughly one to one ratio. Solubility differences between the two
isomers allowed isolation of the Cs complex (in up to 95%
purity) and the C2 complex (analytically pure) following
recrystallization, each in roughly 25% overall yield. The
structure of C2 Zr2SiiPr3-NMe2 was confirmed by single-crystal
X-ray diffraction (XRD) analysis (Figure 3). The two Zr centers
adopt similar geometries to those seen in previously reported
mono- and bimetallic complexes with bisamine bisphenolate
ligands. The distance between the two metal centers is 7.74 Å,
longer by more than 0.1 Å than in the solid-state structure of
Zr2Cl4-NMe2 (7.62 Å), which has the longest distance between
D
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Scheme 3. Synthesis of Monozirconium Bisamine Bisphenolate Complexes Featuring ortho-SiiPr3 Substituents
Scheme 4. Preparation of pyZr2SiiPr3 and pyZr2SiPh3 via Protonolysis of the Corresponding Binucleating Proligands pyH4SiiPr3 and
SiPh3
pyH4
with Two Equivalents of ZrBn4
a
Table 1. 1-Hexene and Propylene Homopolymerizations
b
activity (kg mmolZr h−1
)
% mmmm
−1
entry
catalyst
monomer
activator
yield (g)
1
Zr1ArSiiPr3-NMe2
1-hexene
1-hexene
1-hexene
1-hexene
1-hexene
1-hexene
1-hexene
1-hexene
1-hexene
1-hexene
1-hexene
1-hexene
1-hexene
1-hexene
1-hexene
propylene
propylene
propylene
propylene
propylene
[CPh3][B(C6F5)4]
[HNMe2Ph][B(C6F5)4]
MAO
0.076
0.046
0.116
0.067
0.238
0.613
0.513
0.596
0.676
0.036
0.046
0.204
0.870
0.980
0.860
5.5
0.11
0.069
0.17
0.10
0.36
0.92
0.77
0.89
1.0
34
37
40
45
45
10
34
34
15
5
2
Zr1ArSiiPr3-NMe2
3
Zr1ArSiiPr3-NMe2
4
CS Zr2SiiPr3-NMe2
CS Zr2SiiPr3-NMe2
CS Zr2SiiPr3-NMe2
C2 Zr2SiiPr3-NMe2
C2 Zr2SiiPr3-NMe2
C2 Zr2SiiPr3-NMe2
anthZr1ArSiiPr3-NMe2
anthZr1ArSiiPr3-NMe2
anthZr1ArSiiPr3-NMe2
C2 anthZr2SiiPr3-NMe2
C2 anthZr2SiiPr3-NMe2
C2 anthZr2SiiPr3-NMe2
Zr1ArSiiPr3-NMe2
[CPh3][B(C6F5)4]
[HNMe2Ph][B(C6F5)4]
MAO
5
6
7
[CPh3][B(C6F5)4]
[HNMe2Ph][B(C6F5)4]
MAO
8
9
10
11
12
13
14
15
16
17
18
19
20
[CPh3][B(C6F5)4]
[HNMe2Ph][B(C6F5)4]
MAO
0.054
0.069
0.31
1.3
3
4
[CPh3][B(C6F5)4]
[HNMe2Ph][B(C6F5)4]
MAO
28
33
42
14
19
25
15
24
1.5
1.3
MAO
0.55
1.9
Cs Zr2SiiPr3-NMe2
C2 Zr2SiiPr3-NMe2
anthZr1ArSiiPr3-NMe2
C2 anthZr2SiiPr3-NMe2
MAO
19
MAO
22
2.2
MAO
9.6
0.96
2.8
MAO
28
a
1-Hexene polymerizations were run with 4.0 μmol of Zr, 1 equiv of [B(C6F5)4] activator or 250 equiv of dried MAO, and 5000 equiv (2.5 mL) of 1-
hexene in 2.5 mL of PhCl for 10 min, and propylene polymerizations were run with 10 μmol of Zr, 1000 equiv (2.5 mL) of MAO, and 5 bar of
b
propylene in 85 mL of toluene for 60 min in a 250 mL reactor. From integration of the 13C{1H} NMR spectra.
E
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Figure 4. Comparison of tacticity control by dinuclear catalysts with substituents ortho to phenoxide oxygens shown in blue and pendant donors, L,
in green and by monometallic catalysts with either ortho-aryl substituents (Ar = C6Me5 or 9-methylanthracenyl) or ortho-tert-butyl substituents. 1-
Hexene polymerizations were run with [CPh3][B(C6F5)4], and propylene polymerizations were run with excess MAO as activators. Legend at
bottom provides graphical representations of catalysts and abbreviations under each class of compounds.
Zr2SiiPr3-OMe were also targeted, but single metalation isomers
of these complexes could not be isolated. The monometallic
complexes Zr1ArSiiPr3-NMe2, anthZr1ArSiiPr3-NMe2, and
Zr1tBuSiiPr3-NMe2 were synthesized by protonolysis of the
corresponding proligand with 1 equiv of ZrBn4 (Scheme 3).
The structure of Zr1ArSiiPr3-NMe2 was also confirmed by XRD
(Figure 3).
analogously and also feature only two CH2 benzylic resonances,
indicating Cs symmetry on the H NMR time scale.
1
1-Hexene and Propylene Homopolymerization. The
precatalyst performance in 1-hexene polymerization was tested
under three sets of conditions: upon activation with
stoichiometric amounts of [CPh3][B(C6F5)4] or [HNMe2Ph]-
[B(C6F5)4] and with excess MAO. The bimetallic bisamine
bisphenolate complexes show moderate activity and produce
isotactically enriched poly-1-hexene in the presence of
stoichiometric [CPh3][B(C6F5)4] and [HNMe2Ph][B(C6F5)4]
activators. C2 Zr2SiiPr3-NMe2 and C2 anthZr2SiiPr3-NMe2 generate
poly-1-hexene with ca. 30% mmmm content with activities in
Dizirconium complexes supported by binucleating pyridine
bisphenolate ligands were synthesized according to Scheme 4.
Ortho-lithiation of the syn atropisomer of 12 followed by
treatment with trimethylborate and subsequent in situ
deprotection affords boronic acid 13. Suzuki coupling with 2-
bromo-6-chloropyridine provides access to ligand precursor 14.
Species 15R (R = SiiPr3 and SiPh3) were synthesized through
retro-Brook rearrangement of the corresponding silyl ethers 5R
and quenched with trimethylborate (Scheme 2). Suzuki
coupling of two equivalents of 15R with 14 affords the final
−1
the range of 0.77−1.5 kg mmolZr h−1 (Table 1, entries 7, 8,
13, and 14). In the presence of MAO as a cocatalyst the activity
of both C2 and Cs Zr2SiiPr3-NMe2 is improved, but the tacticity
control is lowered to only 10 and 15% mmmm, respectively
(Table 1, entries 6 and 9). Cs Zr2SiiPr3-NMe2 has improved
tacticity control, producing poly-1-hexene with 45% mmmm
content in the presence of [CPh3][B(C6F5)4] and
[HNMe2Ph][B(C6F5)4] (Table 1, entries 4 and 5). In contrast,
C2 Zr2SiiPr3-NMe2 has overall lower isotacticity (34% mmmm)
for 1-hexene homopolymerization in the presence of the borate
counteranion as compared to the Cs isomer, although with
improved activity (Table 1, entries 4 and 5 vs 7 and 8). All
dinuclear catalysts show a slight improvement in activity in the
presence of [HNMe2Ph][B(C6F5)4] compared to [CPh3][B-
(C6F5)4]. Monometallic Zr1ArSiiPr3-NMe2 shows lower activities
and similar tacticities to the dinuclear catalysts, except in the
SiiPr3
SiPh3
binucleating proligands pyH4
and pyH4
in moderate
and pyH2
SiiPr3
SiPh3
overall yields. Mononucleating ligands pyH2
were synthesized analogously.
Reaction of phenol proligands with two equivalents of ZrBn4
afforded in quantitative yields single species that display NMR
spectroscopic characteristics consistent with the desired
SiiPr3
products, pyZr2
and pyZr2SiPh3. Only two resonances
corresponding to the benzylic CH2 moiety are observed in
the 1H NMR spectra of pyZr2SiiPr3 and pyZr2SiPh3, indicating that
the complexes are C2v symmetric on the NMR time scale.
Mononuclear Zr dibenzyl complexes were synthesized
F
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a
Table 2. Ethylene Homopolymerizations and Ethylene−Propylene Copolymerizations
b
c
activity (kg mmolZr h−1
)
MN (kDa)
PDI
TM (°C)
% I (C3)
−1
catalyst
% C2 feed
% C3 feed
yield (g)
1
Zr1ArSiiPr3-NMe2
100
100
100
100
100
100
100
100
100
25
0
0
16
11
14
15
14
14
12
13
12
15
21
20
24
24
4.8
7.2
10
6.4
1.6
1.1
1.4
1.5
1.4
1.4
1.2
1.3
1.2
1.5
2.1
2.0
2.4
2.4
0.48
0.72
1.0
0.64
4.7
17
47
23
29
15
32
40
30
34
44
133
134
133
132
134
135
133
132
132
76
2
Cs Zr2SiiPr3-NMe2
C2 Zr2SiiPr3-NMe2
anthZr1SiiPr3-NMe2
C2 anthZr2SiiPr3-NMe2
3
0
27
4
0
8.6
21
5
0
ArSiiPr3
6
pyZr1
0
9.9
4.6
4.9
4.7
3.6
12
SiiPr3
7
pyZr2
0
ArSiPh3
8
pyZr1
0
SiPh3
9
pyZr2
0
10
11
12
13
14
15
16
17
18
Zr1ArSiiPr3-NMe2
75
75
75
75
75
75
75
75
75
6.0
6.6
6.7
4.6
6.3
25
52
40
36
49
12
8
Cs Zr2SiiPr3-NMe2
C2 Zr2SiiPr3-NMe2
anthZr1SiiPr3-NMe2
C2 anthZr2SiiPr3-NMe2
25
108
25
11
111
e
25
7.8
12
25
110
118
117
115
110
ArSiiPr3
pyZr1
25
15
10
SiiPr3
pyZr2
25
5.1
5.3
8.5
28
23
13
ArSiPh3
pyZr1
25
9
SiPh3
pyZr2
25
14
a
Polymerizations were run with 10 μmol of Zr in 85 mL of toluene in the presence of 1000 equiv (2.5 mL) of MAO and 5 bar of ethylene at 60 °C.
b
c
d
PDI determined from GPC measurements, where PDI is defined as Mw/Mn. Calculated from DSC measurements. Percentage incorporation of
e
propylene from 13C{1H} NMR integration. Not measured.
presence of the MAO cocatalyst, where the monometallic
catalyst shows higher tacticity control. Comparing anthZ-
r1ArSiiPr3-NMe2 and anthZr2SiiPr3-NMe2 for 1-hexene polymer-
ization, the dinuclear precatalyst shows significantly greater
tacticity control (between 28% and 42% mmmm vs between 3%
with MAO, however, Zr1ArSiiPr3-NMe2 and anthZr1ArSiiPr3-NMe2
show similar tacticity control, both lower than Zr1ArCl2-NMe2.
The Bu-substituted catalysts generally show very low tacticity
t
control. The lower activity of the new catalysts is consistent
with the previous observation of higher 1-hexene polymer-
ization activities from complexes bearing ligands with electron-
withdrawing substituents.12,21 The lack of significant improve-
ments in tacticity control for Zr1ArSiiPr3-NMe2 and anthZ-
r1ArSiiPr3-NMe2 could result from one or several features of the
previously proposed mechanism, including site epimerization
and selectivity of monomer insertion based on steric control of
polymer orientation by the bulk of the aryl substituent. With
the more bulky SiiPr3 substituents, the difference between the
two phenolates is less pronounced, potentially leading to less
and 5% mmmm for anthZr1ArSiiPr3-NMe2). C2 anthZr2SiiPr3-NMe2
SiiPr3
has similar activity and isotacticity compared to C2 Zr2
-
NMe2 in the presence of the stoichiometric activators.
Zr2SiiPr3-NMe2 and anthZr2−Si1iPr3-NMe2 both show moderate
activity (1.9−2.8 kg mmolZr h−1) for propylene polymer-
ization at 60 °C in toluene in the presence of excess MAO at 5
bar propylene pressure (Table 1, entries 17, 18, and 20). These
catalysts produce low-tacticity polypropylene. Cs Zr2SiiPr3-NMe2
shows slightly lower tacticity control with 19% mmmm as
compared to 25% and 24% for C2 Zr2SiiPr3-NMe2 and
anthZr2SiiPr3-NMe2 (Table 1, entries 17, 18, and 20). Both
Zr1ArSiiPr3-NMe2 and anthZr1A−r1SiiPr3-NMe2 have lower activity
(0.55 and 0.96 kg mmolZr h−1, respectively) than the
dinuclear catalysts and show lower tacticity control (ca. 14%
mmmm) (Table 1, entries 16 and 19).
t
control of polymer chain orientation. The more spherical Bu
substituent does not provide efficient tacticity control likely
because it is less expansive compared to the pentamethylphenyl
and anthracenyl substituents.
In comparison with the previously reported bimetallic
catalysts supported by amine bisphenolate ligands bearing the
bulky ortho-tert-butyl substituent (Zr2tBu2-OMe), the new C2
symmetric complexes have similar activities for 1-hexene
polymerization (∼1 kg mmolZr−1 h−1) but produce significantly
more isotactic poly-1-hexene in the presence of the
stoichiometric activators (19% mmmm for Zr2tBu2-OMe, Figure
4). C2 anthZr2SiiPr3-NMe2 shows similar tacticity control (28%
mmmm) to the previously reported Cs and C2 Zr2Me4-OMe and
to C2 Zr2Br4-NMe2 (28−30% mmmm). C2 and Cs Zr2SiiPr3-NMe2
produce similarly isotactically enriched polymer (34% and 45%
mmmm) to that seen for the more sterically open Zr2Cl4-NMe2,
Zr2Cl4-OMe, and Zr2Br4-OMe catalysts at room temperature
(35% to 50% mmmm), albeit with lower activity. Both C2
anthZr2SiiPr3-NMe2 and C2 Zr2SiiPr3-NMe2 have similar activity
for propylene homopolymerization to C2 Zr2tBu2-OMe (ca. 2 kg
Generally, the mononuclear catalysts show significantly lower
activity and tacticity control compared to the dinuclear
analogues. These differences may be explained in terms of
the distal steric effect of the second metal, limiting anion
association and degrees of freedom for olefin insertion.12 The
observed differences between the C2 and Cs Zr2SiiPr3-NMe2
isomers suggest that the particular coordination environment of
the distal metal center affects reactivity, despite being remote.
The shape of the cavity between the two metal centers has
consequences on both tacticity and activity.
In comparison with the previously reported complexes
bearing ortho-pentamethylphenyl substituents, Zr1ArSiiPr3-NMe2
shows a decrease in activity relative to Zr1ArCl2-NMe2 (1.5−1.9
kg mmolZr h−1) with fairly similar tacticity control in 1-
−1
hexene polymerization (24−25% mmmm for Zr1ArCl2-OMe and
mmolZr h−1) but with improved tacticity control (24−25%
−1
12
31−32% mmmm for Zr1ArCl2-NMe2, Figure 4). anthZr1
-
mmmm vs 6−8% mmmm). The new complexes with SiiPr3
substituents show similar tacticity control in propylene
polymerization to Zr2Br4-OMe, Zr2Br4-NMe2, and Zr2Me4-OMe.
ArSiiPr3
NMe2 shows significantly lower tacticity control as compared to
these catalysts. For propylene polymerization upon activation
G
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a
Table 3. Copolymerizations of Ethylene with 1-Hexene and 1-Tetradecene
b
c
activity (kg mmolZr h−1
)
Mn (kDa)
PDI
TM (°C)
% I
−1
catalyst
comonomer
yield (g)
1
Zr1ArSiiPr3-NMe2
1-hexene
15
19
20
24
19
20
14
29
19
9.7
20
20
25
23
1.5
1.9
2.0
2.4
1.9
2.0
1.4
2.9
1.9
0.97
2.0
2.0
2.5
2.3
2.2
5.9
8.8
7.1
11
3.6
3.7
12
104
99
19
12
22
28
30
7
2
Cs Zr2SiiPr3-NMe2
C2 Zr2SiiPr3-NMe2
anthZr1SiiPr3-NMe2
C2 anthZr2SiiPr3-NMe2
1-hexene
3
1-hexene
105
g
4
1-hexene
3.4
8.8
7.2
19
5
1-hexene
104
115
125
112
121
ArSiiPr3
6
pyZr1
1-hexene
1.6
3.5
0.8
1.9
17
SiiPr3
7
pyZr2
1-hexene
4
ArSiPh3
8
pyZr1
1-hexene
11
7
SiPh3
9
pyZr2
1-hexene
35
5
10
11
12
13
14
Zr1ArSiiPr3-NMe2
1-tetradecene
1-tetradecene
1-tetradecene
1-tetradecene
1-tetradecene
8.8
g
61
g
7
Cs Zr2SiiPr3-NMe2
C2 Zr2SiiPr3-NMe2
anthZr1SiiPr3-NMe2
C2 anthZr2SiiPr3-NMe2
41
6
39
26
2.7
6.6
104
110
105
3
12
10
7
22
a
Polymerizations were run with 10 μmol of Zr in 65 mL of toluene in the presence of 1000 equiv (2.5 mL) of MAO and 3 bar of ethylene and 20 mL
b
c
d
(1.6 × 104 equiv) of 1-hexene or 20 mL (7900 equiv) of 1-tetradecene at 60 °C. Yield in g. Activity reported in kg mmolZr−1 h−1. Mn and PDI
e
f
determined from GPC measurements, where Mn is reported in kDa and PDI is defined as Mw/Mn. Reported in °C, from DSC measurements. %
g
incorporation of the comonomer determined from 13C{1H} NMR integration. Not measured.
Importantly, an extensive set of dinuclear catalysts was
compared to mononuclear versions, and in all cases, the
dinuclear catalysts show improvement in tacticity control
(Figure 4). This suggests that the steric pressure provided by
the coordination environment of the second metal restricts the
orientation of the polymeryl chain and incoming olefin better
than that possible in analogous mononuclear systems. Overall,
within the series of dinuclear catalysts, increasing steric bulk
ortho to the phenolate oxygen away from the linker does not
benefit control of tacticity. The smallest substituent, chloride,
displays the highest degree of tacticity control. This behavior is
consistent with the highest mmmm content resulting from
maximizing the difference in steric profile relative to the linker,
with the smaller chloride substituents ortho to the phenolate
oxygen having the largest impact. The much larger silyl
substituents likely make the two phenolate sides more similar
and less discriminating with respect to interaction with the
polymeryl chain and the incoming monomer and, therefore,
decrease tacticity control.
4.7 and 8.6 kDa). The high TM values support the formation of
linear polymers under these conditions with all catalysts.22
Ethylene−propylene copolymerization behavior was tested in
the presence of excess MAO under 5 bar total pressure with a
1:3 C2:C3 flow ratio (Table 2). Initial optimization with
Zr1tBuSiiPr3-NMe2 indicated that under these conditions
propylene was incorporated well with relatively high overall
activity (Supporting Information Table S1). Under these
SiPh3
conditions pyZr1ArSiiPr3, pyZr2SiiPr3, pyZr1ArSiPh3, and pyZr2
have lower activities than for ethylene homopolymerization
(0.48−1.0 kg mmolZr h−1, Table 2, entries 15−18). Both
−1
pyZr2 and pyZr1 catalysts incorporate low levels of propylene,
and while pyZr2SiPh3 shows a slight enhancement in comonomer
SiPh3
incorporation over pyZr1
(14% C3 vs 9% C3) (Table 2,
entries 18 vs 17), pyZr2SiiPr3 and pyZr1SiiPr3 are very similar (8%
C3 vs 9% C3) (Table 2, entries 16 vs 15). The low levels of
comonomer incorporation lead to relatively high melting
temperatures (110−119 °C). Similar Mn and PDI values were
observed between the catalysts.
Zr2SiiPr3-NMe2 and C2 anthZr2SiiPr3-NMe2 more effectively
incorporate propylene than the corresponding monometallic
complexes under these conditions. While Zr1ArSiiPr3-NMe2
incorporates only 25% propylene, Cs and C2 Zr2SiiPr3-NMe2
incorporate 52% and 40%, respectively, and show slightly
enhanced activity (2.1 and 2.0 kg mmolZr−1 h−1, respectively, vs
1.5 kg mmolzr−1 h−1 for Zr1ArSiiPr3-NMe2) (Table 2, entries 10−
12). Similarly, anthZr1ArSiiPr3-NMe2 incorporates 36% propy-
lene, while anthZr2SiiPr3-NMe2 incorporates 49% propylene
(Table 2, entries 13, 14). Both anthracene-substituted
complexes show enhanced activity and propylene incorporation
compared with the phenyl-substituted complexes (36% C3 for
anthZr1SiiPr3-NMe2 vs 25% C3 for Zr1SiiPr3-NMe2 (Table 2, entry
13 vs entry 10) and 49% C3 for C2 anthZr2SiiPr3-NMe2 vs 40%
C3 for C2 Zr2SiiPr3-NMe2 (Table 2, entry 14 vs entry 12)). In the
presence of propylene, lower PDI values were observed for
these bisamine bisphenolate complexes (between 4.6 and 6.7),
and the MN values were higher for the bimetallic catalysts
(between 10.6 and 12.2 kDa for the bimetallics and between 3.6
and 7.8 kDa for the monometallics), although the effect is less
dramatic than in the ethylene homopolymerizations.
Ethylene Homopolymerization and Ethylene-α-Olefin
Copolymerization. The ethylene homopolymerization of all
complexes was investigated in the presence of excess MAO
tBuSiiPr3
(Table 2). Initial optimization with monometallic Zr1
-
NMe2 indicated that addition of AlMe3 resulted in loss of
activity. Improved yield was obtained at 60 °C in the presence
of MAO alone (Supporting Information Table S1). Under
optimized conditions pyZr1ArSiiPr3, pyZr2SiiPr3, pyZr1ArSiPh3, and
pyZr2SiPh3 all show moderate activity for polyethylene formation
(1.2−1.4 kg mmolZr h−1) and produce polymers with similar
−1
Mn and PDI values (between 4.7 and 9.9 kDa for MN and 30.9
ArSiiPr3
and 44.4 for the PDI values) (Table 2, entries 6−9). Zr1
-
NMe2 and anthZr1ArSiiPr3-NMe2 both have slightly improved
activities (1.6 and 1.5 kg mmolZr h−1, respectively) (Table 2,
−1
entries 1 and 4) although not very different from Zr2SiiPr3-NMe2
and anthZr2SiiPr3-NMe2 (1.1−1.4 kg mmolZr h−1) (Table 2,
−1
entries 2, 3, and 5). Under these conditions, although high
PDIs (between 15 and 47, with multimodal distributions in
some instances) were observed for all catalysts, the MN values
were higher for the bimetallic catalysts (between 17.2 and 26.7
kDa) as compared with the monometallic catalysts (between
H
DOI: 10.1021/acs.organomet.7b00015
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Ethylene−1-hexene copolymerization was investigated in the
presence of excess MAO, 3 bar of ethylene, and 1.6 × 104 equiv
C2 dinuclear vs mononuclear catalysts reveals a systematic
trend. The dizirconium catalysts incorporate 1.4−2.1 times the
small propylene comonomer compared to the mononuclear
versions, but incorporate the larger 1-hexene comonomer
similarly. With 1-tetradecene, however, both the dinuclear C2
catalysts incorporate less of the comonomer than the
corresponding monozirconium catalysts (Figure 5). The Cs
SiPh3
of 1-hexene. pyZr1ArSiiPr3, pyZr2SiiPr3, pyZr1ArSiPh3, and pyZr2
are more active under these conditions than in the presence of
propylene as a comonomer or under ethylene homopolyme-
rization conditions, although incorporation of the comonomer
is overall low. On the basis of the 13C NMR spectra of the
resulting polymers (Supporting Information, Figures S24 and
SiiPr3
SiPh3
S25), both pyZr1
and pyZr1
randomly incorporate ca.
SiiPr3
7% 1-hexene (Table 3, entries 6 and 8), while pyZr2
and
pyZr2SiiPh3 randomly incorporate only 4−5% (Table 3, entries 7
and 9). The resulting polymers have fairly high melting
temperatures, consistent with the low, random incorporation.
SiiPr3
The monometallic catalysts Zr1ArSiiPr3-NMe2 and anthZr1
-
NMe2 both incorporate 1-hexene well (19% and 28%,
respectively) with similar activity as in the presence of the
propylene comonomer (Table 3, entries 1 and 4). While the C2
symmetric Zr2SiiPr3-NMe2 and anthZr2SiiPr3-NMe2 show modest
increases (to 22% and 30%, Table 3, entries 3 and 5) in
comonomer incorporation relative to the monometallic
analogues, Cs Zr2SiiPr3-NMe2 incorporates less of this como-
nomer than either the C2 dizirconium complexes or the
monozirconium complexes (12% 1-hexene incorporation,
Table 3, entry 2). PDI values for these catalysts are large
under these conditions, with the Mn values for the polymers
obtained from the bimetallic catalysts generally higher
compared with the Mn values from the monometallic catalysts.
To evaluate the effect of comonomer size on incorporation
level between mono- and dinuclear catalysts, ethylene−1-
tetradecene copolymerizations were also performed using the
bisamine bisphenolate catalysts in the presence of MAO, 3 bar
of ethylene, and 7900 equiv of 1-tetradecene. Zr1ArSiiPr3-NMe2
has lower activity under these conditions than in the presence
of propylene or 1-hexene comonomers and incorporates 1-
tetradecene at the 7% level (Table 3, entry 10). Both Cs and C2
Zr2SiiPr3-NMe2 have similar activities under these conditions,
although the incorporation of the comonomer is lower with the
dinuclear catalysts than with the mononuclear catalysts (ca. 6%
for Cs Zr2SiiPr3-NMe2 and ca. 3% for C2SiiPr3-NMe2). Similarly,
anthZr2SiiPr3-NMe2 incorporates around 7% of 1-tetradecene
(Table 3, entries 11 and 12), while anthZr1ArSiiPr3-NMe2
incorporates more (9%, Table 3, entry 13). Again, higher Mn
values are obtained with the bimetallic catalysts as compared to
the monometallic, although the PDI values remain fairly high
for all catalysts under these conditions.
Figure 5. Plot of the ratio of comonomer incorporation by the
bimetallic catalyst to monometallic catalyst according to the length of
the comonomer.
Zr2SiiPr3-NMe2 catalyst does not show a similar behavior.
Overall, the C2 dinuclear catalysts relative to the mononuclear
analogues show a decrease in comonomer incorporation with
increasing size of the olefin (Figure 5). This is consistent with
the distal steric bulk of the second metal disfavoring larger
comonomer incorporation. This trend is inconsistent with the
α-olefin having an agostic interaction with the second metal
center as previously proposed for dinuclear catalysts A (Figure
1).2 The longer chain olefins are expected to be able to better
accommodate such distal agostic interactions and incorporate
in higher levels with dinuclear compared to mononuclear
catalysts, which is not observed. The proposed steric effect is
further supported by the difference in the magnitude of the
effects between anthracene and tetramethylbenzene linkers.
Plotting the ratio of α-olefin incorporation with dinuclear vs
mononuclear analogues, the tetramethylbenzene linker shows a
more pronounced effect with the increasing size of the olefin,
which correlates with a higher steric pressure on the incoming
olefin from the methyl-substituted linker compared to flatter
anthracene (Figure 5).
The lack of substantial difference in activity between the
mono- and dizirconium catalysts supported by pyridine
bisphenolate ligands likely results from the more open
coordination environment afforded by the tridentate ligand
environment. As the metal centers have an additional
coordination site available for polymeryl or olefin coordination
compared to the bisamine bisphenolate systems, the distal
steric effect of the second metal is not consequential.
Association of the anion(s) may be relatively facile, leading to
attenuation of activity. The lower activity and α-olefin
incorporation may also be related to differences in ligand
denticity.13c,d
SUMMARY
■
Mono- and dinuclear Zr benzyl complexes supported by
pyridine bisphenolate and bisamine bisphenolate ligands
featuring bulky SiR3 (R = Pr, Ph) substituents were prepared
i
and studied for olefin polymerization catalysis. With these
compounds, an extensive series of dinuclear olefin polymer-
ization catalysts and their mononuclear analogues is available
for structure function studies. Generally, the dinuclear systems
show better control of tacticity, although only modest levels of
isotacticity were achieved. The distal steric effect caused by the
second metal is proposed to lead to improved tacticity control
for dinuclear complexes. Of the ligands studied, the largest
steric difference between the substituents on the two phenolate
Both C2 anthZr2SiiPr3-NMe2 and anthZr1SiiPr3-NMe2 incorpo-
rate more of all of the α-olefin comonomers than the
corresponding C2 Zr2SiiPr3-NMe2 and Zr1SiiPr3-NMe2, suggesting
that the anthracene substituents are not as sterically bulky to
the zirconium centers compared to methylated aryl sub-
stituents. Comparison of comonomer incorporation levels with
I
DOI: 10.1021/acs.organomet.7b00015
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The ether fraction afforded primarily the Cs symmetric isomer with ca.
12% of the C2 symmetric isomer (80.0 mg, 0.0442 mmol, 28%). The
benzene fraction afforded primarily the C2 symmetric isomer, which
was cleanly isolated following recrystallization from toluene−pentane
(81.8 mg, 0.0452 mmol, 28%). X-ray quality crystals of the C2 isomer
were grown by vapor diffusion of pentane into toluene at −35 °C. Cs
Zr2SiiPr3-NMe2: 1H NMR (400 MHz, C6D6) δ 7.73 (d, J = 2.6 Hz, 2H,
Ar-H), 7.45 (d, J = 2.6 Hz, 2H Ar-H), 7.27 (m, 4H, Ar-H), 7.17 (d, J =
2.5 Hz, 2H, Ar-H), 7.12 (d, J = 2.2 Hz, 2H, Ar-H), 7.03 (m, 4H, Ar-
H), 6.93 (m, 4H, Ar-H), 6.81 (t, J = 7.4 Hz, 2H, Ar-H), 6.69 (t, J = 7.4
Hz, 2H, Ar-H), 3.90 (d, J = 13.4 Hz, 2H, CH2), 3.74 (d, J = 13.4 Hz,
2H, CH2), 2.93 (s, 6H, ArCH3), 2.75 (d, J = 13.4 Hz, 2H, ArCH2),
2.65 (d, J = 13.4 Hz, 2H, ArCH2), 2.56 (s, 6H, ArCH3), 2.40 (m, 4H),
2.29 (m, 4H), 2.07−1.99 (m, 6H), 1.78 (m, 4H), 1.54−1.34 (m, 84H),
0.99 (br m, 2H). 13C NMR (101 MHz, CDCl3): δ 165.43 (Ar), 157.36
(Ar), 152.14 (Ar), 146.00 (Ar), 141.56 (Ar), 140.42 (Ar), 140.18 (Ar),
135.38 (Ar), 134.67 (Ar), 132.06 (Ar), 131.06 (Ar), 130.76 (Ar),
129.11 (Ar), 129.04 (Ar), 126.38 (Ar), 126.06 (Ar), 125.57 (Ar),
125.14 (Ar), 122.24 (Ar), 121.69 (Ar), 119.88 (Ar), 70.82 (CH2),
65.10 (CH2), 64.83 (CH2), 64.05 (CH2), 60.39 (CH2), 51.50 (CH2),
34.28 (C(CH3)3), 34.16 (C(CH3)3), 31.90 (C(CH3)3), 20.30, 19.99,
19.89, 19.83, 19.39, 13.15 (SiCH(CH3)2). Anal. Calcd for
C108H154N4O4Si2Zr2: C, 71.63; H, 8.57, N, 3.09. Found: C, 71.65;
ligands bound to the same metal correlates with best tacticity
control. This results from a small rather than very large
substituent on the phenoxide that is not connected to the
linker. Ethylene−α-olefin copolymerization studies revealed
that the longer chain olefins are incorporated at lower levels by
dinuclear compared to mononuclear catalysts relative to shorter
chain olefins. This effect is also consistent with steric effects
caused by the second metal and not with a distal agostic
interaction. Overall, the reported studies provide fundamental
insight into the advantages of dinuclear vs mononuclear
catalysts for olefin polymerization, in particular related to
control of tacticity and comonomer incorporation.
EXPERIMENTAL SECTION
■
General Notes. All air- and water-sensitive compounds were
manipulated under N2 or Ar using standard Schlenk or glovebox
techniques. Solvents for air- and moisture-sensitive reactions were
dried by the method of Grubbs.16 Chlorobenzene and 1-hexene for
polymerization with stoichiometric activators were refluxed over CaH2
for greater than 72 h, vacuum transferred, and run over activated
alumina plugs prior to use. [CPh3][B(C6F5)4] and [HNMe2Ph][B-
(C6F5)4] were purchased from Strem and used without further
purification. Ethylene (99.999%) and propylene (99.999%) were
passed through purification columns containing molecular sieves and
oxygen scavenger. Toluene, 1-hexene, and 1-tetradecene for polymer-
izations were purchased from Sigma-Aldrich and dried over 4 Å
molecular sieves prior to use. MAO (30 wt % in toluene) was
purchased from Chemtura. Deuterated solvents were purchased from
Cambridge Isotopes Lab, Inc.; CDCl3 and 1,1,2,2-tetrachloroethane-d2
were used without further purification; C6D6 was distilled from purple
Na/benzophenone ketyl and filtered over activated alumina prior to
use. 1H and 13C spectra were recorded on Varian Mercury 300, Varian
INOVA-300, 400, or 500, or Bruker Cryoprobe 400 spectrometers. 1H
and 13C chemical shifts are reported relative to residual solvent
resonances. Elemental analysis was performed on a PerkinElmer 2400
CHNS/O analyzer, and samples were taken from representative
batches prepared in an N2-filled glovebox.
H, 8.81; N, 3.41. C2 Zr2SiiPr3-NMe2: H NMR (500 MHz, CD2Cl2) δ
1
7.42 (d, J = 2.2 Hz, 2H, Ar-H), 7.18 (d, J = 2.3 Hz, 2H, Ar-H), 7.08
(m, 4H, Ar-H), 7.02 (m, 6H, Ar-H), 6.99 (d, J = 2.2 Hz, 2H, Ar-H),
6.83−6.77 (m, 6H, Ar-H), 6.63 (m, 6H, Ar-H), 3.62 (d, J = 13.5 Hz,
2H, CH2), 3.42 (d, J = 13.5 Hz, 2H, CH2), 2.85 (d, J = 13.9 Hz, 2H,
CH2), 2.77 (d, J = 13.7 Hz, 2H, CH2), 2.66 (br m, 2H, CH2), 2.58 (s,
6H, ArCH3), 2.30 (br s, 2H, CH2) 2.25 (s, 6H, ArCH3), 2.04−1.99
(m, 4H, CH2), 1.89−1.84 (m, 6H), 1.78 (br m, 2H), 1.52 (m, 8H),
1.41 (m, 4H, CH2), 1.35 (m, 24H), 1.27 (m, 42H), 1.16 (d, J = 7.5 Hz,
18H). 13C NMR (101 MHz, C6D6): δ 165.46 (Ar), 157.04 (Ar),
152.93 (Ar), 144.27 (Ar), 141.30 (Ar), 140.60 (Ar), 139.50 (Ar),
135.33 (Ar), 134.84 (Ar), 132.23 (Ar), 131.40 (Ar), 130.15 (Ar),
129.46 (Ar), 129.33 (Ar), 126.15 (Ar), 125.79 (Ar), 125.70 (Ar),
124.75 (Ar), 122.71 (Ar), 121.58 (Ar), 119.86 (Ar), 67.61 (CH2),
64.79 (CH2), 64.07 (CH2), 63.87 (CH2), 60.00 (CH2), 51.37 (CH2),
34.32 (C(CH3)3), 34.16 (C(CH3)3), 31.93 (C(CH3)3), 31.88
(C(CH3)3), 22.75, 21.45, 20.33, 20.24, 19.83, 19.54, 14.31, 13.11
(SiCH(CH3)2). Anal. Calcd for C108H154N4O4Si2Zr2: C, 71.63; H,
8.57, N, 3.09. Found: C, 72.01; H, 8.74; N, 3.12.
Preparation of H4SiiPr3-NMe2. To a solution of 4 (613.4 mg, 1.508
mmol, 2.5 mmol) and NEtiPr2 (0.21 mL, 1.506 mmol, 2.5 equiv) in
THF (15 mL) at 0 °C was added 7 (375.8 mmol, 0.6096 mmol, 1
equiv) in THF (21 mL) over the course of several minutes. The
reaction was stirred 3 h, with warming; then volatiles were removed
under reduced pressure. The residue was dissolved in dichloromethane
(DCM) and washed with K2CO3 (2×), water, and brine. The
combined organics were dried with MgSO4, filtered, and evaporated.
Purification by column chromatography (3:2 EtOAC−hexanes (v/v),
Rf ∼0.2) and lyophilization from benzene afforded H4SiiPr3-NMe2 as a
Preparation of H2ArSiiPr3-NMe2. To a solution of 10 (1.21 g, 2.965
mmol, 1.25 equiv) and NEtiPr2 (0.52 mL, 3.0 mmol, 1.25 equiv) in
THF (45 mL) was added 7 (0.927 g, 2.38 mmol, 1 equiv) in THF (50
mL) over the course of several minutes. The reaction was stirred 3 h,
with warming; then volatiles were removed under reduced pressure.
The residue was dissolved in DCM and washed with K2CO3 (2×),
water, and brine, then dried with MgSO4, filtered, and evaporated.
Purification by column chromatography (5:1 EtOAc−hexanes (v/v))
and lyophilization from benzene afforded the proligand as a white solid
1
white solid (434.8 mg, 56.2%). H NMR (400 MHz, CDCl3): δ 9.53
(br s, 4H, OH), 7.34 (d, J = 2.9 Hz, 2H, Ar-H), 7.15 (d, J = 2.2 Hz,
2H, Ar-H), 7.08 (d, J = 2.2 Hz, 2H, Ar-H), 7.05 (d, J = 2.4 Hz, 2H, Ar-
H), 3.78 (s, 4H, ArCH2), 3.74 (s, 4H, ArCH2), 2.66 (m, 4H, CH2),
2.57 (m, 4H, CH2), 2.24 (s, 12H, ArCH3), 2.00 (s, 12H, N(CH3)2),
1.50 (m, 6H, SiCH(CH3)2), 1.32 (s, 18H, C(CH3)3), 1.31 (s, 18H,
C(CH3)3), 1.07 (d, J = 7.5 Hz, 36H, SiCH(CH3)2). 13C NMR (101
MHz, CDCl3): δ 160.47 (Ar), 151.31 (Ar), 141.62 (Ar), 140.25 (Ar),
137.48 (Ar), 133.73 (Ar), 133.06 (Ar), 129.40 (Ar), 128.16 (Ar),
127.63 (Ar), 126.48 (Ar), 121.90 (Ar), 120.63 (Ar), 120.41 (Ar),
58.16 (CH2), 56.95 (CH2), 55.57 (CH2), 49.81 (CH2), 45.32
(N(CH3)2), 34.24 (ArC(CH3)3), 34.08 (ArC(CH3)3), 31.88 (ArC-
(CH3)3), 19.27 (SiCH(CH3)2), 17.99(ArCH3), 11.94 (SiCH(CH3)2).
HRMS (FAB+): calcd for C80H131O4N4Si2 (M + H)+ 1267.971, found
1267.970.
1
(1.1 g, 1.5 mmol, 65%). H NMR (400 MHz, CDCl3): δ 9.08 (br s,
2H, OH), 7.31 (d, J = 2.4 Hz, 1H, Ar-H), 7.08 (d, J = 2.5 Hz, 1H, Ar-
H), 7.03 (d, J = 2.4 Hz, 1H, Ar-H), 6.94 (d, J = 2.5 Hz, 1H, Ar-H),
3.74 (s, 2H, CH2), 3.69 (s, 2H, CH2), 2.62 (m, 2H, CH2), 2.53 (m,
2H, CH2), 2.32 (s, 3H, ArCH3), 2.28 (s, 6H, ArCH3), 2.20 (s, 6H,
ArCH3), 1.97 (s, 6H, N(CH3)2), 1.48 (sept, J = 7.59 Hz, 3H,
CH(CH3)2), 1.30 (s, 9H, C(CH3)3), 1.28 (s, 9H, C(CH3)3), 1.05 (d, J
= 7.5 Hz, 18H, CH(CH3)2). 13C NMR (101 MHz, CDCl3): δ 160.27
(Ar), 151.71 (Ar), 141.40 (Ar), 140.32 (Ar), 136.72 (Ar), 133.88 (Ar),
133.82 (Ar), 132.84 (Ar), 132.16 (Ar), 129.81 (Ar), 127.73 (Ar),
126.34 (Ar), 121.65 (Ar), 120.69 (Ar), 120.29 (Ar), 58.16 (CH2),
56.95 (CH2), 55.99 (CH2), 49.66 (CH2), 45.36 (N(CH3)2), 34.16
(C(CH3)3), 34.07 (C(CH3)3), 31.86 (C(CH3)3), 19.27 (SiCH-
(CH3)2), 18.27 (ArCH3), 17.13 (ArCH3), 16.85 (ArCH3), 11.96
(SiCH(CH3)2). HRMS (FAB+): calcd for C46H75N2O2Si (M + H)+
715.5598, found 715.5579.
Preparation of Zr2SiiPr3-NMe2 (Cs and C2 Symmetric). Proligand
H4SiiPr3-NMe2 (201.4 mg, 0.1588 mmol, 1 equiv) in toluene (2.5 mL)
was added to a stirred solution of ZrBn4 (144.7 mg, 0.3175 mmol, 2
equiv) in toluene (3 mL), and the reaction stirred in the dark at room
temperature for 3 h. Volatiles were removed in vacuo, and the crude
material was fractionated between pentane, diethyl ether, and benzene.
Preparation of Zr1ArSiiPr3-NMe2. Proligand H2ArSiiPr3-NMe2 (137
mg, 0.191 mmol, 1.0 equiv) in toluene (3 mL) was added to a stirring
solution of ZrBn4 (87.3 mg, 0.192 mmol, 1.0 equiv) in toluene (2 mL).
J
DOI: 10.1021/acs.organomet.7b00015
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
The reaction was stirred 3 h, in the dark; then volatiles removed in
vacuo to afford a yellow solid. This was washed with 6 mL each of
pentane and diethyl ether to afford the desired product (145 mg, 0.147
mmol, 76.7%). X-ray quality crystals were grown by slow evaporation
(Ar), 141.53 (Ar), 140.60 (Ar), 136.22 (Ar), 135.40 (Ar), 133.09 (Ar),
131.69 (Ar), 131.12 (Ar), 130.29 (Ar), 129.88 (Ar), 129.34 (Ar),
128.60 (Ar), 127.23 (Ar), 126.67 (Ar), 126.33 (Ar), 126.25 (Ar),
125.71 (Ar), 125.58 (Ar), 124.71 (Ar), 122.41 (Ar), 121.59 (Ar),
119.85 (Ar), 68.12 (CH2), 64.86 (CH2), 63.92 (CH2), 63.73 (CH2),
60.15 (CH2), 51.37, 34.36 (C(CH3)3), 34.19 (C(CH3)3), 31.90
(C(CH3)3), 31.83, 22.75, 20.25, 19.76, 14.31, 13.02. Anal. Calcd for
C112H150N4O4Si2Zr2: C, 72.52; H, 8.15; N, 3.02. Found: C, 72.18; H,
8.35; N, 3.05.
1
of benzene at room temperature. H NMR (500 MHz, C6D6): δ 7.72
(s, 1H, Ar-H), 7.31 (s, 1H, Ar-H), 7.24 (t, J = 7.2 Hz, 2H, Ar-H), 7.07
(d, J = 6.6 Hz, 2H, Ar-H), 7.01−6.6.95 (m, 5H, Ar-H), 6.85 (t, J = 7.2
Hz, 2H, Ar-H), 6.64 (t, J = 7.2 Hz, 1H, Ar-H), 3.82 (d, J = 13.5 Hz,
1H, CH2), 3.59 (d, J = 13.5 Hz, 1H, CH2), 2.66 (d, J = 13.5 Hz, 1H,
CH2), 2.62 (s, 3H, ArCH3), 2.61 (d, 1H, CH2), 2.45 (s, 3H, ArCH3),
2.43 (d, 1H, CH2), 2.39 (d, J = 10.1 Hz, 1H, CH2), 2.30 (s, 6H,
ArCH3), 2.26 (d, J = 9.8 Hz, 1H, CH2), 2.19 (d, J = 9.8 Hz, 1H, CH2),
2.14−2.07 (m, 7H), 1.90 (br m, 1H), 1.51−1.41 (m, 16H), 1.36−1.33
(m, 27H), 1.25 (br m, 1H). 13C NMR (126 MHz, C6D6): δ 165.19
(Ar), 156.80 (Ar), 151.20 (Ar), 145.79 (Ar), 141.54 (Ar), 140.75 (Ar),
137.11 (Ar), 135.45 (Ar), 133.96 (Ar), 133.73 (Ar), 132.85 (Ar),
132.34 (Ar), 130.79 (Ar), 130.67 (Ar), 129.02 (Ar), 128.76 (Ar),
127.30 (Ar), 127.10 (Ar), 126.91 (Ar), 126.60 (Ar), 125.47 (Ar),
125.35 (Ar), 124.78 (Ar), 122.36 (Ar), 122.00 (Ar), 120.18 (Ar),
67.38 (CH2), 66.03 (CH2), 64.98 (CH2), 64.43 (CH2), 60.08 (CH2),
51.30 (CH2), 47.14 (CH2), 34.24 (C(CH3)3), 34.19 (C(CH3)3), 31.88
(C(CH3)3), 20.33, 19.84, 19.40, 17.40, 16.98, 13.22 (SiCH(CH3)2).
Anal. Calcd for C60H86N2O2SiZr: C, 73.04; H, 8.79; N, 2.84. Found:
C, 73.22; H, 8.96; N, 3.14.
Preparation of anthH2ArSiiPr3-NMe2. To a solution of anth10
(2.384 g, 5.861 mmol, 1.25 equiv) and NEtiPr2 (1.02 mL, 5.86 mmol,
1.25 equiv) in THF (150 mL) at 0 °C was added 7 (2.035 g, 4.695
mmol, 1 equiv) in THF (100 mL) over the course of several minutes.
The resulting red solution was stirred 3 h, with warming; then volatiles
were removed under reduced pressure. The residue was taken up in
DCM and washed with K2CO3 (2×), water, and brine, then dried with
MgSO4, filtered, and evaporated. Purification by column chromatog-
raphy (3:1 EtOAc−hexanes (v/v)) and lyophilization from benzene
afforded the desired proligand as a tan solid (1.233 g, 1.624 mmol,
35%). 1H NMR (500 MHz, CDCl3): δ 9.81 (br s, 2H, OH), 8.36 (d, J
= 8.7 Hz, 2H, anth-H), 7.66 (d, J = 8.7 Hz, 2H, anth-H), 7.50 (dd, 2H,
anth-H), 7.31 (m, 4H, anth-H and Ar-H), 7.20 (d, J = 2.4 Hz, 1H, Ar-
H), 7.06 (d, J = 2.5 Hz, 1H, Ar-H), 3.84 (s, 2H, ArCH2), 3.76 (s, 2H,
ArCH2), 3.19 (s, 3H, anthCH3), 2.70 (m, 2H, CH2), 2.55 (m, 2H,
CH2), 2.07 (s, 6H, N(CH3)2), 1.37 (m, 3H, SiCH(CH3)2), 1.33 (s,
9H, C(CH3)3), 1.31 (s, 9H, C(CH3)3), 0.93 (d, 18H, J = 7.5 Hz,
SiCH(CH3)2). 13C NMR (126 MHz, CDCl3): δ 160.29 (Ar), 153.04
(Ar), 141.54 (Ar), 140.20 (Ar), 134.00 (Ar), 133.37 (Ar), 130.49 (Ar),
130.09 (Ar), 129.84 (Ar), 129.76 (Ar), 128.54 (Ar), 128.13 (Ar),
128.03 (Ar), 126.99 (Ar), 126.01 (Ar), 124.96 (Ar), 124.77 (Ar),
124.57 (Ar), 122.22 (Ar), 121.31 (Ar), 120.19 (Ar), 57.28 (CH2),
56.74 (CH2), 56.26 (CH2), 49.44 (CH2), 45.16 (N(CH3)2), 34.28
(C(CH3)3), 34.06 (C(CH3)3), 31.89 (C(CH3)3), 19.09 (SiCH-
(CH3)2), 14.41 (anthCH3), 11.85 (SiCH(CH3)2). HRMS (FAB+):
Preparation of anthH4SiiPr3-NMe2. To a solution of 7 (1.539 g,
3.785 mmol, 2.5 equiv) were added NEtiPr2 (0.658 mL, 3.78 mmol,
2.5 equiv) in THF (75 mL) at 0 °C and anth4 (1.008 g, 1.523 mmol, 1
equiv) in THF (40 mL) over the course of several minutes. The
resulting red solution was stirred for 3 h, with warming; then volatiles
were removed under reduced pressure. The residue was dissolved in
DCM, washed with K2CO3 (2×), water, and brine, dried with MgSO4,
filtered, and evaporated. Purification by column chromatography
(3:2:1 EtOAc−hexanes−benzene (v/v/v)) afforded the desired
1
proligand as a tan solid (1.16 g, 0.886 mmol, 58%). H NMR (400
MHz, CDCl3): δ 9.73 (br s, 4H, OH), 7.71−7.69 (m, 4H, anth-H),
7.36 (d, J = 2.8 Hz, 2H, Ar-H), 7.35 (d, J = 2.8 Hz, 2H, Ar-H), 7.32−
7.30 (m, 4H, anth-H), 7.26 (d, J = 2.3 Hz, 2H, Ar-H), 7.08 (d, J = 2.8
Hz, 2H, Ar-H), 3.89 (s, 4H, Ar-CH2), 3.83 (s, 4H, Ar-CH2), 2.74 (m,
4H, CH2), 2.59 (m, 4H, CH2), 2.13 (s, 12H, N(CH3)2), 1.42 (m, 6H,
SiCH(CH3)2), 1.35 (s, 18H, C(CH3)3), 1.33 (s, 18H, C(CH3)3, 1.00
(d, J = 7.5 Hz, 36 H, SiCH(CH3)2). 13C NMR (101 MHz, CDCl3): δ
160.51 (Ar), 152.66 (Ar), 141.79 (Ar), 140.25 (Ar), 134.17 (Ar),
133.87 (Ar), 130.61 (Ar), 129.80 (Ar), 127.85 (Ar), 127.32 (Ar),
127.27 (Ar), 125.82 (Ar), 124.96 (Ar), 122.41 (Ar), 121.03 (Ar),
120.31 (Ar), 57.72 (CH2), 56.82 (CH2), 55.47 (CH2), 49.60 (CH2),
45.27 (N(CH3)2), 34.34 (C(CH3)3), 34.09 (C(CH3)3), 31.89
(C(CH3)3), 19.16 (SiCH(CH3)2), 11.90 (SiCH(CH3)2). HRMS
(FAB+): calcd for C84H127N4O4Si2 1311.94, found 1311.9396.
calcd for C50H71SiN2O2 (M + H)+ 759.5285, found 759.5264.
ArSiiPr3
Preparation of anthZr1ArSiiPr3-NMe2. Proligand anthH2
-
NMe2 (200.0 mg, 0.2634 mmol, 1 equiv) in 4 mL of toluene was
added to the top of a stirred solution of ZrBn4 (119.9 mg, 0.2631
mmol, 1 equiv) in 3 mL of toluene and stirred for 3 h in the dark.
Volatiles were removed in vacuo, and the resulting yellow solid was
washed with pentane and ether to afford the desired complex (140 mg,
0.136 mmol, 52%). 1H NMR (500 MHz, C6D6): δ 8.44 (d, J = 9.1 Hz,
1H, anth-H), 8.41 (d, J = 9.1 Hz, 1H, anth-H), 8.33 (d, J = 9.1 Hz, 1H,
anth-H), 8.00 (d, J = 9.0 Hz, 1H, anth-H), 7.69 (d, J = 2.4 Hz, 1H, Ar-
H), 7.57 (d, J = 2.2 Hz, 1H, Ar-H), 7.51 (m, 2H, anth-H), 7.38 (m,
1H, anth-H), 7.22 (m, 2H, Ar-H), 7.12 (d, J = 2.2 Hz, 1H, Ar-H),
6.97−6.93 (m, 4H, Ar-H), 6.89−6.83 (m, 3H, Ar-H), 6.70 (m, 1H,
anth-H), 6.13 (d, J = 6.9 Hz, 2H, Ar-H), 4.01 (d, J = 13.3 Hz, 1H,
CH2), 3.46 (d, J = 13.3 Hz, 1H, CH2), 2.99 (s, 3H, anthCH3), 2.70
(2d, J = 13.3 Hz, 2H, CH2), 2.30 (br m, 1H, CH2), 2.11 (d, J = 10.2
Hz, 1H, CH2), 2.00−1.89 (m, 5H), 1.53 (m, 1H, CH2), 1.49 (d, J = 9.3
Hz, 1H, CH2), 1.46 (d, J = 9.3 Hz, 1H, CH2), 1.41−1.36 (m, 18 H),
1.32−1.26 (m, 25H). 13C NMR (126 MHz, C6D6): δ 165.30 (Ar),
157.86 (Ar), 151.74 (Ar), 143.57 (Ar), 141.82 (Ar), 140.66 (Ar),
135.41 (Ar), 134.20 (Ar), 131.49 (Ar), 131.41 (Ar), 130.95 (Ar),
130.75 (Ar), 130.58 (Ar), 129.01 (Ar), 126.96 (Ar), 126.77 (Ar),
126.50 (Ar), 126.21 (Ar), 125.98 (Ar), 125.91 (Ar), 125.79 (Ar),
125.37 (Ar), 124.77 (Ar), 124.68 (Ar), 124.08 (Ar), 122.64 (Ar),
121.86 (Ar), 120.00 (Ar), 66.14 (CH2), 65.07 (CH2), 64.61 (CH2),
64.19 (CH2), 60.09 (CH2), 51.64, 47.47, 34.33, 34.18, 31.86, 20.19,
19.70, 14.31, 13.06. Anal. Calcd for C64H82N2O2SiZr: C, 74.58; H,
8.02; N, 2.72. Found: C, 74.25; H, 8.17; N, 2.64.
Preparation of anthZr2SiiPr3-NMe2. A 20 mL scintillation vial was
charged in the dark with a stirbar, ZrBn4 (113 mg, 0.248 mmol, 2
equiv), and 3 mL of toluene, and the solution was frozen in the
glovebox cold well. A separate vial was charged with anthH4SiiPr3-NMe2
(163 mg, 0.124 mmol, 1 equiv) dissolved in toluene (4 mL), and the
solution frozen in the cold well. The thawing proligand solution was
added to the top of the thawing ZrBn4 solution and then stirred, in the
dark, with warming, for 3 h. Volatiles were removed, and the resulting
yellow solid was recrystallized by pentane−benzene layering at room
temperature to give the C2 symmetric complex as a yellow, crystalline
solid (116 mg, 0.0626 mmol, 51%). X-ray quality crystals were grown
by toluene−hexanes layering at −35 °C. 1H NMR (400 MHz, C6D6):
δ 8.84 (d, J = 8.5 Hz, 2H, anthH), 8.12 (d, J = 9.1 Hz, 2H, anthH),
7.70−7.63 (m, 4H, Ar-H), 7.59 (t, J = 7.1 Hz, 2 H, Ar-H) 7.41 (t, J =
7.1 Hz, 2H, Ar-H), 7.25 (d, J = 2.3 Hz, 2H, Ar-H), 7.12 (d, J = 2.3 Hz,
2H, Ar-H), 6.99 (m, 10H), 6.83 (br m, 4H), 6.70 (m, 4H), 6.43 (br m,
2H), 4.07 (d, J = 13.6 Hz, 2H, CH2), 3.75 (d, J = 12.4 Hz, 2H, CH2),
2.75 (d, J = 12.4 Hz, 2H, CH2), 2.70 (d, J = 13.2 Hz, 2H, CH2), 2.39
(br m, 2H), 2.04−1.91 (m, 10H), 1.80 (br m, 2H), 1.67 (d, J = 10.2
Hz, 4H, CH2), 1.60 (br m, 2H) 1.46 (d, J = 7.52 Hz, 18H), 1.36 (s,
18H), 1.31 (m, 42H) 1.19 (br s, 6H), 1.08 (br m, 2H). 13C{1H} NMR
(101 MHz, C6D6): δ 165.50 (Ar), 157.91 (Ar), 153.07 (Ar), 143.63
Preparation of 11. Bis-syn-13-MOM (6.12 g, 11.8 mmol),
N,N,′N,′N′-tetramethylethylenediamine (1.77 mL, 11.8 mmol), and
THF (80 mL) were added to a Schlenk tube under inert atmosphere
and cooled to −78 °C using a dry ice−acetone cooling bath. n-
Butyllithium (2.5 M solution in hexane, 10.4 mL, 26.0 mmol) was
added dropwise to the reaction solution and stirred while it warmed to
room temperature for 4 h. The resulting orange-red solution was
recooled at −78 °C, and trimethyl borate (3.95 mL, 35.4 mmol) was
K
DOI: 10.1021/acs.organomet.7b00015
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added dropwise to the reaction mixture. After 30 min of stirring at −78
°C, the reaction mixture was allowed to warm to room temperature
and stirred for 15 h. A saturated aqueous solution of NH4Cl (30 mL)
was added to quench the reaction. The crude product was extracted
with diethyl ether (3 times), washed with brine (2 times), dried over
anhydrous MgSO4, and filtered, and volatiles were evaporated to
dryness. The residue was dissolved in THF (80 mL), and NaI (5.31 g,
35.4 mmol) and trimethylsilyl chloride (4.49 mL, 35.4 mmol) were
added to the solution. The resulting mixture was stirred at room
temperature for 15 h. The product was extracted with diethyl ether (3
times), washed with water and brine, dried over MgSO4, filtered, and
concentrated in vacuo. The crude product was precipitated from
MeOH and dried under vacuum. This crude slightly yellow powder
(3.2 g, 6.2 mmol, 52% yield) was used for the subsequent Suzuki
coupling reaction without further purification.
J = 7.7 Hz, 2H, pyH), 6.87−6.81 (m, 16H, BnH), 6.66 (m, 4H, BnH),
2.56 (s, 12H, ArCH3), 2.39 (d, J = 9.2 Hz, 4H, CH2Ph), 2.27 (d, J =
9.2 Hz, 4H, CH2Ph), 2.04 (sept, J = 7.6 Hz, 6H, SiCH(CH3)2), 1.42
(d, J = 7.6 Hz, 36H, SiCH(CH3)2), 1.40 (s, 18H, C(CH3)3), 1.33 (s,
18H, C(CH3)3). 13C NMR (101 MHz, C6D6, 25 °C): δ 161.0, 160.6,
159.6, 153.6, 142.0, 141.0, 140.7, 139.8, 137.9, 137.1, 133.6, 132.7,
131.1, 130.2, 129.6, 128.8, 128.6, 126.8, 126.2, 124.4, 123.5, 122.9,
t
122.6, 62.4 (CH2 of Bn), 34.5 (C(CH3)3 of Bu), 34.3(C(CH3)3 of
t
t
i
tBu), 31.8 (CH3 of Bu), 31.8 (CH3 of Bu), 19.9 (CH3 of Pr), 19.4
(CH3 of Ar), 13.2 (CH of iPr). Anal. Calcd for C106H132N2O4Si2Zr2: C,
73.30; H, 7.66; N, 1.61. Found: C, 72.21; H, 7.51; N, 1.76.
Preparation of pyH2ArSiiPr3. Synthesis of pyH2SiiPr3 was identical to
that of pyH4SiPh3except that boronic acid 15iPr was used as a coupling
1
partner for the Suzuki coupling reaction (55% yield). H NMR (400
MHz, CDCl3, 25 °C): δ 13.10 (s, 1H, OH), 7.95−7.88 (m, 2H), 7.84
(d, J = 2.5 Hz, 1H), 7.79 (dd, J = 7.3, 1.8 Hz, 1H), 7.75 (d, J = 2.4 Hz,
1H), 7.53 (d, J = 2.4 Hz, 1H), 7.16 (d, J = 2.5 Hz, 1H), 6.89 (s, 1H,
OH), 2.33 (s, 3H, CH3 of Ar), 2.30 (s, 6H, CH3 of Ar), 2.07 (s, 6H,
Preparation of 12. A mixture of boronic acid 14 (2 g, 3.9 mmol),
2-bromo-6-chloropyridine (1.47 g, 7.72 mmol), and potassium
carbonate (3.20 g, 23.2 mmol) was dissolved in a mixture of toluene
(40 mL), ethanol (13 mL), and water (13 mL). The reaction mixture
was degassed via three freeze−pump−thaw cycles; then tetrakis-
(triphenylphosphine)palladium(0) (0.223 g, 0.193 mmol) was added,
and the resulting yellow solution was stirred at 75 °C for 24 h. The
organic layer was separated, and the aqueous layer was extracted with
ethyl acetate. The combined organic layers were washed with brine,
dried over anhydrous MgSO4, filtered, and concentrated to dryness.
Purification by flash column chromatography on silica gel using
CH2Cl2−hexanes as the eluent (v/v = 1:1) gave a slightly yellow solid
i
CH3 of Ar), 1.58 (sept, J = 14.8, 7.4 Hz, 3H, CH of Pr), 1.38 (s, 9H,
CH3 of tBu), 1.37 (s, 9H, CH3 of tBu), 1.15 (d, J = 7.5 Hz, 18H, CH3
i
of Pr). 13C NMR (101 MHz, CDCl3, 25 °C): δ 161.7, 158.1, 154.5,
149.5, 143.3, 140.4, 138.5 (CH), 136.8 (CH), 135.3, 133.6, 133.2,
133.2, 129.9, 129.5 (CH), 125.4 (CH), 124.5 (CH), 123.2, 123.0,
t
121.3 (CH), 118.3, 118.2 (CH), 34.5, 34.3, 31.71 (CH3 of Bu), 31.65
(CH3 of tBu), 19.2 (CH3 of iPr), 18.2 (CH3 of Ar), 17.0 (CH3 of Ar),
16.9 (CH3 of Ar), 12.0. HRMS (EI+): calcd for C45H64NO2Si (M +
H)+ 678.4706, found 678.4712.
1
in 85% yield (2.15 g, 3.29 mmol). H NMR (400 MHz, CDCl3, 25
ArSiiPr3
Preparation of pyZr1ArSiiPr3. pyH2
(676 mg, 0.998 mmol)
°C): δ 12.43 (s, 2H, OH), 7.91 (d, J = 8.0 Hz, 2H, CH of py), 7.80 (t,
J = 7.9 Hz, 2H, CH of py), 7.78 (d, J = 2.5 Hz, 2H, CH of a phenol
ring), 7.31 (d, J = 2.4 Hz, 2H, CH of a phenol ring), 7.24 (d, J = 7.7
Hz, 2H, CH of py), 2.08 (s, 12H, CH3 of Ar), 1.39 (s, 18H, CH3 of
tBu). 13C NMR (101 MHz, CDCl3, 25 °C): δ 159.3 (py), 154.4
(phenol ring), 148.5 (py), 141.4 (phenol ring), 139.9 (CH of py),
137.6 (Ar), 132.5 (Ar), 131.8 (phenol ring), 131.7 (CH of phenol
ring), 121.8 (CH of a phenol ring), 121.5 (CH of py), 118.0 (phenol
and ZrBn4 (453 mg, 0.998 mmol) were used for the reaction in
1
benzene (quantitative yield). H NMR (400 MHz, C6D6, 25 °C): δ
7.87 (d, J = 2.5 Hz, 1H), 7.40 (d, J = 2.4 Hz, 1H), 7.29 (dd, J = 2.5, 1.6
Hz, 2H, CH of Bn), 7.26 (dd, J = 7.8, 1.1 Hz, 1H, CH of py), 7.23 (dd,
J = 7.9, 1.0 Hz, 1H, CH of py), 6.95 (t, J = 7.9 Hz, 1H, CH of py), 6.82
(t, J = 7.4 Hz, 4H, CH of Bn), 6.73 (t, J = 7.2 Hz, 2H), 6.53 (d, J = 7.3
Hz, 4H, CH of Bn), 2.29 (br s, 15H, CH3 of Ar), 2.19 (d, J = 8.9 Hz,
2H, CH2 of Bn), 2.02 (sept, J = 7.5 Hz, 3H, CH of iPr), 1.91 (d, J = 9.0
t
t
ring), 117.5 (CH of py), 34.4 (C(CH)3 of Bu), 31.7 (CH3 of Bu),
18.0 (CH3 of Ar). HRMS (EI+): calcd for C40H43Cl2N2O2 (M + H)+
653.2702, found 653.2715.
t
Hz, 2H, CH2 of Bn), 1.39 (s, 9H, CH3 of Bu), 1.39 (d, J = 7.7 Hz,
i
t
18H, CH3 of Pr), 1.33 (s, 9H, CH3 of Bu). 13C NMR (101 MHz,
C6D6, 25 °C): δ 161.2, 161.1, 159.9, 153.0, 142.3, 141.4, 140.3, 140.2
(CH of py), 137.5, 137.0 (CH), 134.2, 132.7, 132.6, 131.5, 131.2
(CH), 130.6, 129.9 (CH of Bn), 129.5 (CH of Bn), 128.6, 127.1, 126.9
(CH of Bn), 126.7, 124.4 (CH of py), 123.7 (CH of py), 123.2, 123.0
Preparation of pyH4SiiPr3. A mixture of 15 (1.3 g, 2.0 mmol),
boronic acid 11 (2.25 g, 4.98 mmol), and potassium carbonate (1.65 g,
11.9 mmol) was dissolved in a mixture of toluene (40 mL), ethanol
(13 mL), and water (13 mL). The reaction mixture was degassed via
three freeze−pump−thaw cycles, and then, tetrakis-
(triphenylphosphine)palladium(0) (0.12 g, 0.10 mmol) was added.
The resulting yellow solution was stirred at 75 °C for 24 h. The
organic layer was separated, and the aqueous layer was extracted with
ethyl acetate. The combined organic layers were washed with brine,
dried over anhydrous MgSO4, filtered, and concentrated to dryness.
Purification by flash column chromatography on silica gel using
CH2Cl2−hexanes as the eluent (v/v = 1:1) gave a slightly yellow solid
t
(CH), 59.2 (CH2 of Bn), 34.4 (C(CH3)3 of Bu), 34.3 (C(CH3)3 of
t
i
tBu), 31.8 (two set of CH3 of Bu), 19.8 (CH3 of Pr), 18.9 (CH3 of
Ar), 17.0 (CH3 of Ar), 16.9 (CH3 of Ar), 13.4 (CH of iPr). Anal. Calcd
for C59H75NO2SiZr: C, 74.63; H, 7.96; N, 1.48. Found: C, 75.15; H,
8.00; N, 1.65.
Preparation of pyH4SiPh3. A mixture of 12 (1.3 g, 2.0 mmol),
11SiPh3 (2.25 g, 4.98 mmol), and potassium carbonate (1.65 g, 11.9
mmol) was dissolved in a mixture of toluene (40 mL), ethanol (13
mL), and water (13 mL). The reaction mixture was degassed via three
freeze−pump−thaw cycles. Then tetrakis(triphenylphosphine)-
palladium(0) (0.12 g, 99.7 μmol) was added, and the resulting yellow
solution was stirred at 75 °C for 24 h. The organic layer was separated,
and the aqueous layer was extracted with ethyl acetate. The combined
organic layers were washed with brine, dried over anhydrous MgSO4,
filtered, and concentrated to dryness. Purification by flash column
chromatography on silica gel using CH2Cl2−hexanes as the eluent (v/
v = 1:1) gave a slightly yellow solid in 45% yield (1.25 g, 0.895 mmol).
1H NMR (400 MHz, CDCl3, 25 °C): δ 12.26 (s, 2H, OH), 7.87−7.79
(m, 4H), 7.73 (d, J = 2.5 Hz, 2H), 7.69 (dd, J = 7.7, 1.4 Hz, 2H), 7.65
(d, J = 2.5 Hz, 2H), 7.61−7.56 (m, 14H), 7.29−7.26 (m, 4H), 7.25−
7.20 (m, 14H), 7.16 (s, 2H, OH), 7.09 (d, J = 2.5 Hz, 2H, py), 1.94 (s,
1
in 27% yield. H NMR (400 MHz, CDCl3, 25 °C): δ 12.84 (s, 2H,
OH), 7.95−7.92 (m, 4H, py and a phenol ring), 7.88 (d, J = 2.5 Hz,
2H, a phenol ring), 7.81−7.76 (m, 2H, py), 7.73 (d, J = 2.4 Hz, 2H, a
phenol ring), 7.52 (d, J = 2.4 Hz, 2H, a phenol ring), 7.36 (s, 2H,
OH), 7.22 (d, J = 2.4 Hz, 2H, py), 2.11 (s, 12H, CH3t of Ar), 1.56
i
(sept, J = 7.5 Hz, 6H, CH of Pr), 1.39 (s, 18H, CH3 of Bu), 1.37 (s,
t
i
18H, CH3 of Bu), 1.13 (d, J = 7.5 Hz, 36H, CH3 of Pr). 13C NMR
(101 MHz, CDCl3, 25 °C): δ 161.4, 158.1, 154.6, 149.7, 143.4, 140.5,
138.7 (CH), 136.8 (CH), 136.4, 134.1, 129.4 (py), 125.5 (CH), 124.7
(CH), 123.2, 122.9, 121.3 (CH), 118.6, 118.4 (CH), 34.6 (C(CH)3 or
tBu), 34.3 (C(CH)3 or Bu), 31.7 (CH3 of Bu), 31.7 (CH3 of Bu),
t
t
t
19.2 (CH3 of iPr), 18.0 (CH3 of Ar), 12.0 (CH of iPr). HRMS (EI+):
calcd for C78H109N2O4Si2 (M + H)+ 1193.7926, found 1193.7931.
t
Preparation of pyZr2SiiPr3. pyH4
(100 mg, 83.8 μmol) and
SiiPr3
12H, CH3 of Ar), 1.21 (s, 18H, CH3 of Bu), 1.12 (s, 18H, CH3 of
tBu). 13C NMR (101 MHz, CDCl3, 25 °C): δ 160.9, 157.5, 155.2,
149.9, 143.2, 141.4, 138.6 (CH), 138.0 (CH), 136.6 (CH), 136.5
(CH), 135.2 (CH), 134.0, 129.6 (CH), 129.5, 129.3 (CH), 127.7
(CH), 126.6 (CH), 125.2 (CH), 122.6, 122.0, 121.5 (CH), 119.7,
ZrBn4 (76.1 mg, 168 μmol) were used for the reaction in benzene
(quantitative yield). 1H NMR (300 MHz, C6D6): δ 7.84 (d, J = 2.6 Hz,
2H, ArH of phenol), 7.47 (d, J = 2.3 Hz, 2H, ArH of phenol), 7.37 (d,
J = 2.6 Hz, 2H, ArH of phenol), 7.30 (d, J = 7.3 Hz, 2H, pyH), 7.23 (d,
J = 2.4 Hz, 2H, ArH of phenol), 7.13 (d, J = 7.5 Hz, 2H, pyH), 6.96 (t,
t
t
118.7 (CH), 34.5 (C(CH3)3 of Bu), 34.3 (C(CH3)3 of Bu), 31.7
L
DOI: 10.1021/acs.organomet.7b00015
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
t
t
(CH3 of Bu), 31.6 (CH3 of Bu), 18.1 (CH3 of Ar). HRMS (EI+):
General Procedure for 1-Hexene Polymerization. In the
glovebox, a Schlenk tube was charged with a stirbar, 1-hexene (2.5 mL,
20.0 mmol, 5000 equiv), 1.5 mL of PhCl, and Zr catalyst (4.0 μmol, 1
equiv) in 0.5 mL of PhCl. [CPh3][B(C6F5)4] (3.7 mg, 4.0 μmol) in 0.5
mL of PhCl was added, and the reaction stirred 10 min then quenched
by addition of 0.5 mL of MeOH in 5 mL of hexanes. In the case of
dried MAO and the anilinium activator, a Schlenk tube was charged
with a stirbar, 1-hexene (2.5 mL, 20.0 mmol, 5000 equiv), 2.0 mL of
PhCl, and dried MAO (58.0 mg, 1.00 mmol, 250 equiv) or
[HNMe2Ph][B(C6F5)] (3.2 mg, 4.0 μmol). Then the Zr catalyst
(4.0 μmol, 1 equiv) in 0.5 mL of PhCl was added, and the reaction
stirred for 10 min before quenching by addition of 0.5 mL of MeOH
in 5 mL of hexanes. (Note: MAO was purchased from Albemarle, and
volatiles were removed first at room temperature and then under high
vacuum at 110 °C for 12 h.) Volatiles were removed under reduced
pressure, and the resulting highly viscous oil was dried in a vacuum
oven at 150 °C for 10 h. 13C{1H} NMR were acquired in CDCl3 on a
500 MHz instrument, and samples were prepared using ca. 50 mg of
isolated polymer. Integration of the C3 signal was used to determine
the % mmmm, where the region of δ 35.1−34.58 was assigned to the
mmmm pentad and the region of δ 34.58−33.1 was assigned to the
remaining pentads.17
calcd for C96H97N2O4Si2 (M + H)+ 1397.6987, found 1397.7026.
Preparation of pyZr2SiPh3. pyH4
(100 mg, 71.6 μmol) in
SiPh3
benzene (3 mL) was slowly added to a solution of ZrBn4 (65.0 mg,
143 μmol) in benzene (2 mL) under dark conditions. The resulting
solution was stirred for 5 h at room temperature. All volatiles were
removed under vacuum to give a yellow powder (quantitative yield).
1H NMR (300 MHz, C6D6): δ 8.01−7.97 (m, 12H, SiPh3), 7.71 (d, J =
2.4 Hz, 2H, ArH of phenol), 7.46 (d, J = 2.6 Hz, 2H, ArH of phenol),
7.39 (d, J = 2.5 Hz, 2H, ArH of phenol), 7.32 (d, J = 2.5 Hz, 2H, ArH
of phenol), 7.29−7.21 (m, 22H, SiPh3 and pyH), 6.99 (t, J = 8.3 Hz,
2H, pyH), 6.73−6.63 (m, 12H, BnH), 6.37 (m, 8H, BnH), 2.48 (s,
12H, ArCH3), 1.78 (d, J = 8.9 Hz, 4H, CH2Ph), 1.29 (s, 18H,
C(CH3)3), 1.25 (s, 18H, C(CH3)3), 1.15 (d, J = 8.9 Hz, 4H, ArCH2).
13C NMR (101 MHz, C6D6, 25 °C): δ 161.4, 160.2, 160.0, 153.5,
142.0, 141.9, 141.7, 140.3, 139.6, 139.5, 137.2, 137.1, 135.7, 133.6,
133.2, 131.8, 130.5, 130.1, 129.8, 128.8, 128.6, 127.0, 126.2, 124.2,
124.0, 122.4, 121.8, 60.5 (CH2 of Bn), 38.2 (two sets of C(CH3)3 of
tBu), 31.7 (CH3 of tBu), 31.6 (CH3 of tBu), 19.4 (CH3 of Ar).). Anal.
Calcd for C124H120N2O4Si2Zr2: C, 76.73; H, 6.23; N, 1.44. Found: C,
76.67; H, 6.62; N, 1.39.
Preparation of pyH2ArSiPh3. A mixture of 18 (2.63 g, 6.46 mmol),
11 (2.92 g, 6.45 mmol), and potassium carbonate (2.68 g, 19.4 mmol)
was dissolved in a mixture of toluene (40 mL), ethanol (13 mL), and
water (13 mL). The reaction mixture was degassed via three freeze−
pump−thaw cycles. Then tetrakis(triphenylphosphine)palladium(0)
(0.370 g, 0.320 mmol) was added, and the resulting yellow solution
was stirred at 75 °C for 24 h. The organic layer was separated, and the
aqueous layer was extracted with ethyl acetate. The combined organic
layers were washed with brine, dried over anhydrous MgSO4, filtered,
and concentrated to dryness. Purification by flash column chromatog-
raphy on silica gel using CH2Cl2−hexanes as the eluent (v/v = 1:5)
gave a slightly yellow solid in 48% yield (2.42 g, 3.10 mmol). 1H NMR
(400 MHz, CDCl3, 25 °C): δ 7.92 (t, J = 7.9 Hz, 1H), 7.85 (dd, J =
7.9, 0.8 Hz, 1H), 7.82 (d, J = 2.5 Hz, 1H), 7.77 (d, J = 7.3 Hz, 1H),
7.70−7.67 (m, 7H), 7.39−7.35 (m, 3H), 7.33 (dd, J = 6.9, 1.2 Hz,
5H), 7.31−7.29 (m, 2H), 7.10 (d, J = 2.5 Hz, 1H), 2.34 (s, 3H, CH3 of
Ar), 2.29 (s, 6H, CH3 of Ar), 1.99 (s, 6H, CH3 of Ar), 1.26 (s, 9H,
General Procedure for Ethylene and Propylene Homo- and
Copolymerizations. Ethylene and propylene homopolymerizations
were carried out in a 250 mL Buchi glass autoclave using an Imtech
̈
(The Netherlands) laboratory-scale reactor system. The reactor was
heated to 120 °C and was purged several times with Ar to remove air
and moisture. It was then cooled to 60 °C under Ar and charged with
85 mL of toluene, 2.5 mL (10.0 mmol, 1000 equiv) of MAO, and 0.01
mmol of Zr catalyst in 2 mL of toluene. The reactor was pressurized to
5 bar with ethylene or propylene and maintained at that pressure for 1
h. For ethylene−propylene copolymerizations the pressure was
maintained at 5 bar using an ethylene−propylene feed with a 2:3
flow ratio. Gas consumption was measured by a mass flow controller
(Brooks Instrument). After 1 h the reactor was degassed and quenched
by addition of 30 mL of 5% HCl−MeOH. The polymer was isolated
by filtration, washed with fresh methanol, and dried under high
vacuum.
CH3 of Bu), 1.21 (s, 9H, CH3 of Bu). 13C NMR (101 MHz, CDCl3,
25 °C): δ 161.1, 157.5, 155.1, 149.7, 143.2, 141.3, 138.4 (CH), 138.0
(CH), 136.6 (CH), 135.3, 135.1, 133.7, 133.2, 133.0, 130.0, 129.6,
129.2 (CH), 127.7 (CH), 126.5 (CH), 125.1 (f H), 122.6, 122.0, 121.4
t
t
General Procedure for the Copolymerization of Ethylene
with 1-Hexene and 1-Tetradecene. The polymerizations were
carried out in a 250 mL Buchi glass autoclave using an Imtech (The
̈
Netherlands) laboratory-scale reactor system. The reactor was
prepared in the same manner as for homopolymerizations; however,
it was charged with 65 mL of toluene, 20 mL of comonomer, 2.5 mL
of MAO (10.0 mmol, 1000 equiv), and 0.01 of mmol Zr catalyst in 2
mL of toluene and run at 3 bar of ethylene pressure.
t
(CH), 119.6, 118.4 (CH), 34.4 (C(CH3t)3 of Bu), 34.3 (C(CH3)3 of
tBu), 31.7 (CH3 of Bu), 31.6 (CH3 of Bu), 18.2 (CH3 of Ar), 17.0
t
(CH3 of Ar), 16.9 (CH3 of Ar).
Preparation of pyZr1ArSiPh3. pyH2ArSiPh3 (100 mg, 0.128 mmol) in
benzene (3 mL) was slowly added to a solution of ZrBn4 (58.2 mg,
0.128 mmol) in benzene (2 mL) under dark conditions. The resulting
solution was stirred for 5 h at room temperature. All volatiles were
removed under vacuum to give a yellow powder (quantitative yield).
1H NMR (400 MHz, C6D6, 25 °C): δ 7.96−7.90 (m, 6H, CH of
SiPh3), 7.64 (d, J = 2.5 Hz, 1H, a phenol ring), 7.52 (d, J = 2.5 Hz, 1H,
a phenol ring), 7.38−7.35 (m, 2H, CH of py and a phenol ring), 7.28−
7.25 (m, 2H, CH of py and a phenol ring), 7.22−7.19 (m, 9H, CH of
SiPh3), 7.00 (t, J = 7.9 Hz, 1H, CH of py), 6.70−6.64 (m, 2H, CH of
Bn), 6.61 (t, J = 7.3 Hz, 4H, CH of Bn), 6.11 (d, J = 6.4 Hz, 4H, CH of
Bn), 2.23 (s, 3H, CH3 of Ar), 2.21 (s, 6H, CH3 of Ar), 2.18 (s, 6H,
CH3 of Ar), 1.82 (d, J = 8.5 Hz, 2H, CH2 of Bn), 1.32 (s, 9H, CH3 of
GPC Analysis. Gel permeation chromatographic analyses of
ethylene and propylene homo- and copolymers were performed at
160 °C using a PL-GPC 220 (Agilent Technologies) equipped with
two PLgel Olexis 300 × 7.5 mm columns. BHT (0.0125 wt %) was
added to 1,2,4-trichlorobenzene to prevent polymer sample degrada-
tion. A sample solution of 5 mg/1.5 mL (w/v) was prepared at 140 °C
in the prepared solvent, and 100 μL was injected into the GPC
columns. Chromatogram data were analyzed using the Cirrus software,
which was calibrated using polystyrene standards. The polystyrene-
based calibration curve was converted into the universal one using the
Mark−Houwink constants of polystyrene (K = 0.000 121 dL/g and α
= 0.707) and polyethylene (K = 0.000 406 dL/g and α = 0.725).17
Differential Scanning Calorimetry Analysis. Differential
scanning calorimetric (DSC) analysis was performed using a DSC
Q2000 (TA Instruments). The temperature and heat flow of the
apparatus were calibrated with an indium standard. Polymer samples
were first equilibrated at 25 °C, followed by heating from 25 to 200 °C
at a rate of 10 °C/min under N2 flow (5 mL/min). This temperature
was maintained for 5 min. Then samples were cooled to 25 °C at a rate
of 10 °C/min. This temperature was maintained for 5 min; then
samples were reheated to 200 °C at a rate of 10 °C/min. The melting
temperature (Tm) was determined from the second heating scan. The
percent crystallinity was calculated from ΔHf(J/g)/ΔHstd(J/g), where
tBu), 1.23 (s, 9H, CH3 of Bu), 0.96 (d, J = 8.3 Hz, 2H, CH2 of Bn).
t
13C NMR (101 MHz, C6D6, 25 °C): δ 161.3, 160.8, 160.4, 152.7,
142.2, 142.1, 140.6 (CH of py), 139.7 (CH of a phenol ring), 137.2,
137.1, 137.0 (CH of a phenyl ring), 135.8, 133.9, 132.50, 132.48 (CH
of a phenol ring), 132.3, 131.4, 131.2, 130.0 (CH), 129.8 (CH of Bn),
129.5 (CH of Bn), 128.6 (CH of a phenyl ring), 127.1, 127.1, 126.7
(CH), 124.2 (CH), 124.1 (CH), 122.7 (CH of Bn), 122.0, 58.2 (CH2
of Bn), 34.4 (C(CH3)3 of tBu), 31.8 (CH3 of tBu), 31.6 (CH3 of tBu),
18.9 (CH3 of Ar), 16.9 (CH3 of Ar), 16.8 (CH3 of Ar). Anal. Calcd for
C68H69NO2SiZr: C, 77.67; H, 6.61; N, 1.33. Found: C, 77.29; H, 6.66;
N, 1.44.
M
DOI: 10.1021/acs.organomet.7b00015
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
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ASSOCIATED CONTENT
* Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.organo-
met.7b00015.
■
S
Detailed experimental procedures for ligand precursors,
full polymerization tables, and spectroscopic data (PDF)
ArSiiPr3
X-ray crystallographic data for compounds Zr1
-
NMe2, Zr2SiiPr3-NMe2, and anthZr2SiiPr3-NMe2 (CIF)
AUTHOR INFORMATION
Corresponding Author
*E-mail: agapie@caltech.edu.
ORCID
Theodor Agapie: 0000-0002-9692-7614
Notes
The authors declare no competing financial interest.
■
ACKNOWLEDGMENTS
■
Mike Takase, Larry Henling, and Heui Beom Lee are
acknowledged for crystallographic assistance. We thank Prof.
Grubbs for allowing access to a GPC instrument in his
laboratory at Caltech for measurements of 1-hexene homopol-
ymers. The authors are grateful for the support provided by
King Fahd University of Petroleum and Minerals, Dhahran,
Saudi Arabia, offered under the KFUPM-Caltech Research
Collaboration.
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DOI: 10.1021/acs.organomet.7b00015
Organometallics XXXX, XXX, XXX−XXX