Pyridylamido hafnium complexes with a silylene bridge: Synthesis and olefin polymerization

Article abstract of DOI:10.1039/d0dt01031f

The synthesis and characterisation of six novel C_s-symmetric pyridylamido hafnium complexes with a silylene bridge of the type [ArPy(R₂Si)NAr′]HfAlk₂ are reported. Four complexes have been structurally characterised using single crystal X-ray diffraction. Appreciable differences between the solid state structures of these complexes and the pyridylamido hafnium complexes with a CRR′ bridge were noted. Reactions with B(C₆F₅)₃, [Ph₃C][B(C₆F₅)₄] and [HMe₂NPh][B(C₆F₅)₄] yielded active catalysts for the homopolymerisations of propene and 1-hexene and ethene/1-octene copolymerization. In spite of the C_s-symmetry of the precatalysts, isotactically enriched polypropylene and poly(1-hexene) were obtained. The fact that the mechanism of the catalyst activation includes the insertion of alkene into the Hf-C_Ar bond was demonstrated. It was found that the structures of Ar and the R₂Si bridge influence the activity, molecular weight capability and 1-octene affinity of the catalysts.

Full text of DOI:10.1039/d0dt01031f

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DOI: 10.1039/D0DT01031F
ARTICLE
Pyridylamido Hafnium Complexes with the Silylene Bridge:
Synthesis and Olefin Polymerization†
Pavel S. Kulyabina, Dmitry V. Uborskya, Alexander Z. Voskoboynikov*a, Jo Ann M. Canichb, John R. Hagadorn*b
Received 00th January 20xx,
Accepted 00th January 20xx
The synthesis and characterisation of six novel Cs-symmetric pyridylamido hafnium complexes with silylene bridge of the
type [ArPy(R2Si)NAr’]HfAlk2 is reported. Four complexes have been structurally characterised using single crystal X-ray
diffraction. Appreciable diffirences between solid state structures of these complexes and the pyridylamido hafnium
complexes with CRR’ bridge were noted. Reactions with [Ph3C][B(C6F5)4] and [HMe2NPh][ B(C6F5)4] yielded catalysts active
for the homopolymerisations of propene and 1-hexene and ethene/1-octene copolymerization. In spite of Cs-symmetry of
the precatalysts, isotactically enriched polypropylene and poly(1-hexene) were obtained. The fact that mechanism of the
catalyst activation includes insertion of alkene into the Hf-CAr bond was demonstrated. It was found that the structure of Ar
and R2Si bridge influence, activity, molecular weight capability and 1-hexene affinity of the catalyst.
DOI: 10.1039/x0xx00000x
Introduction
R1
R3
R4
Polyolefins are among the most important products of chemical
industry with production of 178 million tons in 2015.1 Free-
radical processes are used to produce less than 20% of these
polyolefins, with the bulk being produced in processes using
coordinative olefin polymerization catalysts. Traditional Ziegler-
Natta catalysts dominate polyolefin production in terms of
volume, but the use of single-site catalysts continues to be of
great interest due to the ability of such catalysts to control the
molecular architecture (e.g. molecular weight distribution
(MWD), compositional distribution, long chain branching,
sequence distribution) of a polymer chain.2
R2
N
N
Si
R5
Ar
Ar
N
N
Hf
Hf
Me Me
X
X
R5
I
II
, R1 = R2 = H, Ar = Ph
Ia
, R1 = 2-iPrPh, R2 = H, Ar = 1-Napht
, R1 = R2 = Me, Ar = 1-Napht
, R1 = R2 = Me, Ar = Ph
Ib
Ic
Id
Figure
1. Pyridylamido hafnium precatalysts with C-bridge (I) and Si-bridge (II)
A
critical structural feature of pyridylamido hafnium
One of the notable examples of success in the field of single-site
olefin polymerization catalysis are the Symyx-Dow pyridylamido
hafnium catalysts of type I (Fig. 1), which were discovered and
developed using high throughput screening technologies.3,4
These catalysts were reported to produce high MW isotactic
polypropylene with Tm≈150 °C at process temperatures above
100 °C. It should be noted that the two ortho-isopropyl
substituents of the aniline moiety are necessary to achieve the
combination of high activity and MW capability at a high
process temperature.4 Additionally, pyridylamido hafnium
catalysts have been shown to be excellent incorporators of
higher α-olefins in ethylene/1-hexene and ethylene/1-octene
copolymerizations in solution at high temperature.5 These
catalysts have also been used to produce olefin block
copolymers through chain shuttling polymerization.6
precatalysts I is ortho-metalation of the aryl moiety at the
pyridyl ring. Based on computational and experimental studies,
it was found, that, upon activation of I, the resulting cation
inserts one molecule of an olefin into the Hf-aryl bond.7,8,9 Due
to this modification of the ligand in situ, even initially Cs-
symmetrical complexes of structure I, where R1=R2, upon
activation with B(C6F5)3 are able to produce isoenriched poly(1-
hexene) and polypropylene.10 The in situ ligand modification,
however, can form a mixture of active catalysts, which generally
leads to a broadening of MWD and compositional distribution
in the (co)polymer produced.
The performance of pyridylamido hafnium catalysts in
polymerization significantly depends on the substitution at the
C-bridge (R1 and R2 in I) between the pyridine and the aniline
fragments. For example, catalyst derived from complex Ia (Fig.
1) produced polypropylene with [mmmm]=56%, Mw=72 kDa
and PDI=1.05 in solution polymerization at 20 °C,10 whereas
catalyst Ib (Fig. 1) gives polypropylene with [mmmm]=94%,
Mw=198 kDa and PDI=3.0 in solution polymerization even at
90 °C.5 The bulky substituent at the C-bridge seems to be
necessary for high stereoselectivity. It also appears to improve
a. Department of Chemistry, M. V. Lomonosov Moscow State University, Leninskie
Gory, 1/3, Moscow 119991, Russian Federation.
b. Baytown Technology and Engineering Complex, ExxonMobil Chemical Company,
Baytown, TX, 77520, United States.
†Electronic Supplementary Information (ESI) available: 1-Hexene polymerization
details, depiction of spectra, crystal structure analysis details. CCDC 1987153-
1987156. See DOI: 10.1039/x0xx00000x
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DOI: 10.1039/D0DT01031F
, Ar = Ph, R' = Me, R'' = iPr
NHLi
1
2
3
4
5
6
R''
R''
, Ar = 1-Napht, R' = Me, R'' = iPr
, Ar = Ph, SiR'2 = cyclo-(CH2)4Si, R'' = iPr
, Ar = Ph, R' = Et, R'' = iPr
1. nBuLi, THF, -78°C
Ar
N
SiR'2 R''
HN
2. R'2SiCl2
C6H6–THF
Ar
N
Br
Ar
N
SiR'2Cl
, Ar = Ph, R' = Ph, R''= iPr
, Ar = Ph, R' = Ph, R''= Me
R''
Scheme 1. Synthesis of pro-ligands 1-6 for pyridylamido hafnium precatalysts
catalyst activity and MW capability in high temperature pyridylamine pro-ligands were prepared from the lithium salt of
polymerization.4c Recently, it was reported that Cs-symmetric 2,6-diisopropylaniline and one from lithium 2,6-
complex Ic (Fig. 1) upon activation with B(C6F5)3 produces dimethylanilide. The latter was used for synthesis of
polypropylene with [mmmm]=91%, Mw=319 kDa and PDI=1.2 in pyridylamine pro-ligand 6 to test whether isopropyl groups in
solution polymerization at 20 °C.11 It was found that the C- ortho positions of the aniline moiety are still necessary to
bridge substituents R1 and R2 affect the C(Py)-C(bridge)- achieve high activity and molecular weight capability if the
N(aniline) angle thereby pushing the ortho substituents at the corresponding catalyst contains the bulky Ph2Si bridge. The two-
aniline moiety closer to the metal, and thus influencing the step sequence we used is shorter than the method used to
stereoselectivity and living behavior of the catalyst.11 Since the synthesize C-bridged pro-ligands for hafnium complexes (such
development of pyridylamido hafnium catalysts, many as I) from 6-aryl-2-bromopyridines.4 Moreover, this synthetic
analogous complexes have been synthesized and tested in route led to excellent yields of the desired pro-ligands without
olefin polymerization. The examples of variation of the any purification, which is not generally the case in the synthesis
structure include installation of different alkyl or aryl groups at of the related carbon-bridged pyridylamine pro-ligands.
the C-bridge and ortho-positions of the aniline moiety, or Syntheses of complexes 7–9 were performed by reaction of pro-
replacement of phenyl or naphtyl groups at the pyridine with ligands 1–3 with tetrabenzylhafnium in benzene overnight at
heteroaryls.4,10–13 We assumed that change of the C-bridge in I 80 °C (Scheme 2). All three products were crystallized from
to the Si-bridge also might significantly modifies the geometry toluene/hexane mixture and were isolated in good yields (44–
of the pyridylamido hafnium complexes and, consequently, 56%). The 13C NMR spectra for each of these complexes
change the polymerization performance of the respective contained a downfield resonance at 201.2–204.2 ppm which is
catalysts. Herein, we report synthesis of novel pyridylamido consistent with ortho-metalation of the aryl group at pyridine.8
hafnium complexes of type II (Fig. 1) and the results of their Surprisingly, this synthetic method did not work in case of pro-
tests as olefin polymerization precatalysts. The effects of ligands 4–6, and only starting compounds were observed in the
substituents R3, R4 and R5 as well as aryl group at the pyridyl ring reaction mixture. Perhaps, the aminogroups in 4–6 are less
on activity, molecular weight capability and comonomer affinity reactive toward tetrabenzylhafnium due to the relatively large
of the generated catalysts were studied.
Et2Si and Ph2Si bridges in these ligands. Interestingly, the
cyclo(CH2)4Si bridge in 3 did not hinder reaction of the pro-
ligand with HfBn4, whereas the Et2Si-bridge in 4 suppressed the
reaction completely.
Results and Discussions
Synthesis of complexes
HfBn4, C6H6
Synthesis of pro-ligands for the desired Si-bridged pyridylamido
hafnium complexes was achieved using a simple two-step
method from readily available 6-phenyl- and 2-bromo-6-(1-
naphtyl)pyridines (Scheme 1). The first step of the technique
was reaction of the lithiated pyridines with various
dichlorodialkylsilanes or dichlorodiphenylsilane. The reactions
proceeded in almost quantitative yields, and the resultant
chlorosilanes were used in the next step without any additional
purification. The choice of substitution on the dichlorosilanes
was dictated by our desire to explore the influence of sterics at
the Si-bridge on the polymerization performance of the
respective catalysts. In the second step of the ligand synthesis
the (2-pyridyl)chlorosilanes were combined with lithium
anilides in benzene. A drop of tetrahydrofuran (THF) was added
to the stirring mixtures to aid the dissolution of the lithium
reagents. The reactions produced the desired pyridylamines in
almost quantitative yields and good purity, which allowed the
skipping of purification before synthesis of complexes. Five
Ar
N
SiR'2
HN
N
SiR'2
N
80°C
Ar
Hf
Bn Bn
7, Ar = Ph, R' = Me, 56%
1–3
8, Ar = 1-Napht, R' = Me, 48%
9, Ar = Ph, SiR'2= cyclo-(CH2)4Si, 44%
Scheme 2. Synthesis of pyridylamido hafnium precatalysts 7–9.
For synthesis of Si-bridged pyridylamido hafnium precatalysts
from pyridylamines 4–6, an alternative approach was applied.
First, pro-ligands 4–6 were reacted with dibenzylhafnium
dichloride etherate (Hf2Bn2Cl2(Et2O)2) in benzene overnight at
80 °C followed by methylation of the resultant dichloride
complexes with MeMgBr in toluene at 70 °C (Scheme 3). The
target complexes 10-12 were obtained in 19-52% isolated
yields; the lower isolated yields are attributed to the higher
solubility of the products in hydrocarbon solvents. Formation of
2 | J. Name., 2012, 00, 1-3
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1. HfBn2Cl2(Et2O)2, C6H6, 80°C
2. MeMgBr, PhMe, 70°C, 3 h
Ph
N
SiR'2 R''
HN
N
SiR'2 R''
N
Hf
Me Me
R''
4–6
R''
10, R' = Et, R'' = iPr, 28%
11, R' = Ph, R'' = iPr, 19%
12, R' = Ph, R'' = Me, 52%
Scheme 3. Synthesis of pyridylamido hafnium precatalysts 10–12.
the Hf-phenyl bond in 10–12 was confirmed by the presence of
resonances at 202.0–202.4 ppm in the 13C NMR spectra of 10–
12.8
Figure 3. Molecular structure for 8. Hydrogen atoms were removed for clarity. Thermal
ellipsoids are shown at the 50% probability level. Selected bond distances (Å) and angles
(°): Hf1−N1 = 2.307(2), Hf1-N2 = 2.096(2), Hf1-C15 = 2.312(3), Hf1-C28 = 2.224(3), Hf1-
C35 = 2.257(2), Si1-N2 =1.736(2), Si1-C1 = 1.892(3), Si1-C42 = 1.865(3), Si1-C43 =
1.852(3); N1-Hf1-N2 = 77.44(7), C15-Hf1-N1 = 70.37(8), C28-Hf1-N1 = 106.48(9), C28-
Hf1-C35 = 101.36(10), C1-Si1-N2 = 99.78(11), C42-Si1-C43 = 108.75(14).
Single-crystal X-ray structures
Solid-state structures were obtained for four complexes (7, 8, 9
and 11) via single crystal X-ray analysis. Thermal ellipsoid
diagrams and selected metrical parameters are presented in
Figures 2–5. Although these complexes exhibit Cs symmetry in
1
solution as evidenced by H NMR spectroscopy, in the solid
symmetric pyridylamido hafnium complexes with C-bridge.11
The longer bonds in the silicon bridge make the C-Si-N angle
remarkably smaller (99.18–100.15°) than the respective C-C-N
angle in the C-bridged complexes (106.50–111.48°)11 and the
angle in a perfect tetrahedron 109.47°. The smaller angle in Si-
bridge leads to the strain in molecules of complexes which
results in the longer Hf-N(Py) and Hf-N(aniline) (vide supra)
bond distances compared to those for C-bridged analogues (for
complexes I Hf-N(Py): 2.280–2.308 Å and Hf-N(aniline): 2.067–
2.089 Å).11 Also it is interesting to compare complexes 8 and Ic
(Fig. 1). In the solid state, 8 exhibits a torsion angle between
ortho-metalated naphtalene and pyridine of 27.7° (Figure 3)
which is significantly larger than the respective torsion angle in
Ic (16.5°).11
state all of them adopt distorted square-pyramidal geometry
with one benzyl or methyl group situated in the apical position.
Bond distances associated with the chelate ligand skeleton
showed little variation throughout the series. For example, the
Hf-N(Py) bond distance only varied from 2.307 to 2.349 Å, and
the Hf-N(aniline) distances appear in the similarly small range
2.094–2.119 Å. The Hf-C(phenyl/naphthyl) distances range
within 2.266-2.312 Å, with the shortest and longest distances
observed for 11 and 8, respectively. Interestingly, hafnium atom
does not lie in the (C,N,N)-plane of the chelate ligands while in
the described complexes of type I it does.5,11 The distance
between Hf and (C,N,N)-plane varies from 0.474 Å for 11 to
0.726 Å for 8. Bond distances in Si- bridge of complexes-7–9 and
11 Si-C(Py) (1.884–1.892 Å) and Si-N(aniline) (1.7203–1.736 Å)
are significantly longer compared to the C(bridge)-C(Py) (1.469–
1.518 Å) and C(bridge)-C(aniline) (1.438–1.489 Å) in Cs-
For complexes 7–9 the Hf-C(Bna) bond distance (2.222–2.228 Å)
between hafnium and carbon atom of the apical benzyl is
slightly shorter than the Hf-C(Bnb) distance between the metal
Figure 4. Molecular structure for 9. Hydrogen atoms were removed for clarity. Thermal
ellipsoids are shown at the 50% probability level. Selected bond distances (Å) and angles
(°): Hf1−N1 = 2.323(2), Hf1-N2 = 2.119(2), Hf1-C11 = 2.277(3), Hf1-C31 = 2.228(3), Hf1-
C24 = 2.254(3), Hf1-C32 = 2.710(3), Si1-N2 = 1.728(2), Si1-C1 = 1.884(3), Si1-C38 =
1.890(3), Si1-C41 = 1.892(3); N1-Hf1-N2 = 77.46(8), C11-Hf1-N1 = 70.93(9), C31-Hf1-N1
= 115.99(9), C31-Hf1-C24 = 98.13(11), Hf1-C31-C32 = 91.58(17), C1-Si1-N2 = 100.15(11),
C38-Si1-C41 = 95.25(13).
Figure 2. Molecular structure for 7. Hydrogen atoms were removed for clarity. Thermal
ellipsoids are shown at the 50% probability level. Selected bond distances (Å) and angles
(°): Hf1-N2 = 2.3333(18), Hf1−N1 = 2.0946(17), Hf1-C19 = 2.294(2), Hf1-C24 = 2.222(2),
Hf1-C31 = 2.253(2), Si1-N1 = 1.7285(18), Si1-C13 = 1.888(2), Si1-C38 = 1.873(2), Si1-C39
= 1.860(2); N1-Hf1-N2 = 77.17(6), C19-Hf1-N2 = 70.71(7), C24-Hf1-N2 = 94.26(8), C24-Hf-
C31 = 110.33(9), C13-Si1-N1 = 99.18(9), C38-Si1-C39 = 107.45(12).
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Upon activation with B(C6F5)3, [HMe2NPhD][OBI(:C106F.150)34]9/(D“0aDnTil0in10iu3m1F
borate”, AB), or [Ph3C][B(C6F5)4] (“trityl borate”, TTB) complexes
7 and 8 formed active catalysts of 1-hexene polymerization at
room temperature and at 60 °C (Table 1).
Catalyst 7/TTB (Table 1, entry 6) appeared to behave similarly
to its Me2C-bridged analogue Id10/TTB (Table 1, entry 8), in
terms of the activity and MWD as both produced bimodal
polyhexene. Increase of the polymerization temperature to 60
°C narrowed down MWD of the polymer produced by 7/TTB
(Table 1, entry 11), and the shape of the GPC curve changed
from clearly bimodal to the peak with a shoulder.
Replacement of TTB with B(C6F5)3 also resulted in a narrowing
of the MWD observed for the polyhexene produced with both
Id- and 7-based catalysts (Table 1, entries 5 and 3, respectively).
The substantially lower activity of the latter in comparison with
Id/B(C6F5)3may be due the difference of alkyl ligands (HfBn2 in 7
and HfMe2 in Id) at the metal in the precatalysts.17
Figure 5. Molecular structure for 11. Hydrogen atoms were removed for clarity. Thermal
ellipsoids are shown at the 50% probability level. Selected bond distances (Å) and angles
(°): Hf1−N1 = 2.3490(15), Hf1-N2 = 2.0995(15), Hf1-C1 = 2.266(2), Hf1-C24 = 2.226(2),
Hf1-C25 = 2.216(2), Si1-N2 = 1.7203(16), Si1-C11 = 1.8876(18), Si1-C26 = 1.8684(19), Si1-
C32 = 1.8818(19); C1-Hf1-N1 = 70.55(6), N2-Hf1-N1 = 76.82(5), N1-Hf1-C25 = 110.50(8),
C25-Hf1-C24 = 102.02(10), C11-Si1-N2 = 99.66(8), C26-Si1-C32 = 105.41(8).
Activation of 7 with AB resulted in unimodal MWD of the
polymer (Table 1, entries 1, 9). Interestingly, catalysts derived
and the benzyl carbon in the base of the square pyramid (2.253– from 8 gave unimodal polymers with narrow MWD (Mw/Mn =
2.257 Å). In complex 8 bond angle Hf1-C28-C29 = 101.58° (Fig. 1.3–1.7) under all the activation and polymerization conditions
3) which is significantly smaller than the corresponding angle in studied.
the second benzyl group in the complex (123.97°) and in the Comparing the 1-hexene homopolymerization data, we can
benzyl groups in 7 (119.06°, 122.59°). The reduced bond angle conclude that silicon bridged pyridylamide catalysts might be a
and a relatively short Hf1-C29 bond distance 2.915 Å suggests good alternative to the carbon-bridged prototypes.
the presence of η2 bonding of benzyl group in the crystal of 8 Complexes 7 and 8 yielded isotactically enriched polyhexene
which is a common thing for benzylic complexes of hafnium.14– (Fig. S7 and S8, Supporting Information). It was previously
16 Moreover, an even smaller bond angle Hf1-C31-C32 = 91.58° described by Domski et. al.10 that Cs-symmetric pyridylamido
and shorter bond distance Hf1-C32 = 2.710 Å in 9 is observed hafnium catalysts are able to give isotactic polyolefins due to
(Fig. 4), and η2 bonding of one of the benzyl group is even more desymmetrization of the catalytic species in situ via α-olefin
obvious. Furthermore, for the latter complex π-π interactions insertion into the Hf-CAr bond. To test a hypothesis that the
between the η2-benzyl group and the pyridine ring of the ligand studied complexes undergo similar post-activation alkene
are present; the distance between the C6H5 group centroid and insertion into the Hf-CAr bond, we performed 4-methyl-1-
the plane of the pyridine ring is 3.268 Å, and an angle of 10.33° pentene polymerizations catalyzed by 7/TTB and 8/TTB. After
is formed between the benzyl and pyridine planes.16
quenching the polymerizations with methanol, the obtained
mixtures containing the products of decomposition of the
catalyst were analysed with GC-MS. The mixtures were
Table 1. 1-Hexene polymerization data for complexes 7-12 and Ica
Tpol
°C
,
Yield,
mg
370
107
267
1305
1212
1267
1341
1145
987
Conversion,
Mn,b
kDa
18
14
14
17
20
9
10
10
6
11
6
Mw,b
kDa
48
18
32
27
43
119
17
38
8
Entry
Complex
Activator
Đb
%
27
8
1
2
3
4
5
6
7
8
9
7
8
7
8
Id
7
8
Id
7
8
7
AB
AB
B(C6F5)
B(C6F5)
B(C6F5)
TTB
TTB
TTB
AB
AB
25
25
33
33
33
33
33
33
60(±2)
60(±2)
60(±2)
60(±2)
2.6
1.3
2.3e
1.6
2.1
14e
1.7
3.8e
1.4
1.3
1.8e
1.4
20
96
89
93
99
84
73
38
49
64
10
11
12
522
662
865
15
11
10
TTB
TTB
8
7
aPolymerization conditions: 7, 8,or 1d, 10 μmol, [B]/[Hf] = 1.0, 8.0 mL toluene, 2.0 mL 1-hexene, 30 min. bDetermined using gel permeation chromatography in THF
at 35 °C vs polystyrene standards. eBimodal molecular weight distribution.
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Table 2. Propylene polymerization data for complexes 7-12 and Ib at 70 °Ca
c
c
d
Activity,
g·mmol-1·h-1
7220
270
5060
2280
2820
3320
48200
Mw ,
Mn ,
Tm
,
Entry
Complex
Đc
kDa
31
n.d.
37
22
21
kDa
18
n.d.
22
10
12
°C
1
2
7
8
1.7
n.d.
1.7
2.3
2.4
1.9
1.8
131
n.d.
135
138
134
n.d.
148
3
9
4
5
6
7e
10
11
12
Ib
54
1469
28
812
aPolymerization conditions: 0.04 μmol complexes; 0.044 μmol AB activator; propylene = 1 mL; total volume: 5.1 mL; 3.8 mL isohexane; 0.5 μmol of (nOct)3Al;
temperature: 70 °C; 800 rpm stirring speed. bReactor quenched at 12 psig uptake (quench value, see Supporting Information for details) or at a maximum time of 45
minutes. cDetermined using gel permeation chromatography in 1,2,4-C6H3Cl3 at 135 °C vs polystyrene standards. dDetermined via differential scanning calorimetry.
e0.06 μmol of complex used.
found to contain significant amounts of 2-(2-(1,3- Every complex except 8 gave active catalyst for propylene
dimethylbutyl)phenyl)pyridine or 2-(2-(4-methylpentan-2- homopolymerization, although the activities for the Si-bridged
yl)naphthalen-1-yl)pyridine (Fig. S2 and S5, Supporting catalysts were lower than that observed for the well-optimized
Information), which could only be formed via decomposition of catalyst Ib. In the most active Si-bridged catalyst 7/AB (ca. 1/7
the products of insertion of 4-methyl-1-pentene into Hf-CAr of activity of Ib/AB), the silylene bridge is the least sterically
bonds of the catalysts. This observation, together with the fact hindered. Interestingly, replacement of the phenylene moiety
that the catalysts based on 7 and 8 give isotacticaly enriched in 7 with 1,2-naphtalenediyl in 8 resulted in a dramatic drop in
poly(α-olefins), proves that the insertion of alkene does occur activity in propylene polymerization although the same change
during the activation of the silicon-bridged precatalysts.
in the structure of Me2C-bridged catalyst resulted in a 5-fold
Since 7 and 8 were active in 1-hexene and 4-methylpentene increase of activity.10
Catalysts derived from 7 and 9-11 gave crystalline polypropyl
polymerization and, moreover, gave isotactically enriched
polymers, propylene homopolymerization and ethylene/1-
octene copolymerization experiments were carried out in
parallel pressure reactors, as generally described
elsewhere.3,18–21 The industrially relevant catalyst Ib5 was used
for comparison.
Propylene homopolymerization. Propylene polymerizations
were carried out using complexes 7-12 as catalyst components.
Run details and characterization data are presented in Table 2.
The propylene polymerizations were performed at 70 °C under
identical conditions. For each run, the reactor was loaded with
liquid propylene, trioctylaluminum scavenger, and isohexane
solvent. Lastly, separate toluene solutions of AB and the
hafnium complex were sequentially added to begin the
polymerization. The polymerization was quenched by the
addition of compressed air to the reactor.
ene (Tm = 131–138 °C) which is an evidence in favor of the
formation of isotactically enriched polymer, similar to what was
observed for Me2C-bridged pyridylamido hafnium catalysts Ic
and Id.11 Ic gave polypropylene with Tm = 133 °C when the
polymerization was conducted at 20 °C (B(C6F5)3 activation) and
Tm = 127 °C when performed at 50 °C.11 Comparison of these
values with Tm = 131 °C of polypropylene produced by 7/AB at
even higher polymerization temperature (70 °C) indicates that
catalysts derived from Cs-symmetric silicon-bridged
pyridylamido hafnium complexes can be more stereoselective
than carbon-bridged analogues such as Ic and Id.
The only catalyst that gave amorphous polypropylene was
12/AB. This result can be considered as an additional proof that
isopropyl groups in the aniline moiety of pyridylamide ligands
Table 3. Ethylene/1-octene copolymerization data for complexes 7-12 and Ib at 80 °Ca
c
c
d
Activity,
Mw ,
kDa
384
n.d.
87
Mn ,
Tm
,
Octene content,
Entry Complex
Đc
g·mmol-1·h-1·bar[C2H4]-1
kDa
110
n.d.
64
84
80
°C
116
n.d.
120
110
108
119
76
wt %
7
n.d.
8
10
12
8
1
2
7
8
3580
160
990
2350
2770
390
3.5
n.d.
1.4
1.3
1.4
1.3
1.5
3
9
4
5
6
7e
10
11
12
Ib
110
112
71
54
263
15600
402
22
aPolymerization conditions: 0.04 μmol complexes; 0.04 μmol AB activator; 3.8 mL isohexane; ethylene pressure 75 psi, 0.1 mL 1-octene; 0.3 μmol of (nOct)3Al;
temperature: 80 °C; 800 rpm stirring speed. bReactor quenched at 10 psig ethylene (quench value, see Supporting Information for details) uptake or at a maximum
time limit of 30 minutes. cDetermined using gel permeation chromatography in 1,2,4-C6H3Cl3 at 135 °C vs polystyrene standards. dDetermined via differential scanning
calorimetry. e0.02 μmol of complex used.
This journal is © The Royal Society of Chemistry 20xx
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are essential for stereo-induction in the pyridylamido hafnium
catalysts.11
the best C-bridged pyridylamido hafnium catalysts for olefin
copolymerization. Catalysts 10 and 11 also gave copolymers
View Article Online
DOI: 10.1039/D0DT01031F
with the highest content of incorporated 1-octene units in the
series of newly prepared catalysts.
Relatively low molecular weights of the resulting polymers (Mw
~ 22–54 kDa) can be in part associated with the presence of
trioctylaluminum (added as a scavenger) also acting as a chain-
transfer agent, which impact can be more pronounced at lower
rate of chain propagation.6,22
Using polymerization of 4-methylpentene as a model, it was
demonstrated that alkene insertion into the Hf-CAr bond occurs
during catalyst activation, resulting in in situ formation of the
C1-symmetric active species (from the initially Cs-symmetric
precatalyst), which is consistent with the observed isoselective
1-hexene polymerization and formation of crystalline rather
than amorphous polypropylene.
Ethylene/1-octene copolymerization. Ethylene/1-octene
copolymerizations were carried out using complexes 7-12 as
catalyst components. Run details and characterization data are
presented in Table 3. Each of the copolymerizations were
performed at 80 °C under identical conditions. For each run, the
reactor was pressurized with ethylene to 75 psi, loaded with 1-
octene, trioctylaluminum scavenger, and isohexane solvent.
Lastly, separate toluene solutions of AB and the hafnium
complex were sequentially added to begin the polymerization.
The polymerization was quenched by the addition of
compressed air to the reactor.
Similar to what was observed for the propylene polymerization,
8/AB was the least and 7/AB was the most active silicon-bridged
catalyst, the latter being 4.4 times less active than the reference
Ib. Catalyst 7/AB also displayed the highest molecular weight
capability among the Si-bridged catalysts approaching that of
Ib, but produced the polymer with comparatively broad
molecular weight distribution (Table 3, entry 1). The rest of the
catalysts gave copolymers with narrow molecular weight
distributions. Replacement of the Me2Si bridge in 7 with cyclo-
(CH2)4Si in 9 (Entry 3, Table 3) or isopropyl groups in aniline
moiety in 11 with methyls in 12 (Table 3, entry 6) thus lowering
steric hindrance around hafnium lead to the lower activity of
the respective catalysts and lower molecular weights of the
obtained copolymers. Combination of high activity and high
comonomer insertion is demonstrated by catalysts 10/AB and
11/AB with the bulkiest ligands.23
Experimental part
All syntheses involving air- and moisture sensitive compounds
were carried out using standard Schlenk-type glassware or in a
nitrogen-filled Vacuum Atmospheres glove box (<1 ppm O2).
Toluene, CH2Cl2, hexane, pentane, chloroform-d1 and
dichloromethane-d2 were dried using 4Å molecular sieves
activated for 24 h at 200-230 °C under dynamic vacuum. Diethyl
ether
and
tetrahydrofuran
were
refluxed
over
Na/benzophenone and distilled prior to use. All dry solvents
were stored under an argon atmosphere. MeMgBr, (3.0 M
solution in Et2O), nBuLi (2.5 M solution in hexanes),
dichlorodimethylsilane,
dichlorodiethylsilane,
1,1-
dichlorosilolane, dichlorodiphenylsilane, 2,6-dimethylaniline,
2,6-diisopropylaniline and HfBn4 were purchased from
commercial supplier and used as received. HfBn2Cl2(Et2O)2 was
prepared by reaction of one equivalent of HfBn4 with HfCl4 in
diethyl ether for 5 h followed by filtration and crystallization of
the product from the mother liquor at -30 °C.24 2-Bromo-6-
phenylpyridine and 2-bromo-6-(1-naphtyl)pyridine were
synthesized following the literature methods.25,26 Referral
complexes Ib and Id were prepared following the literature
methods.5,11 NMR spectra were recorded on Bruker Avance 400
MHz spectrometer at ambient temperature (external standard
1
TMS for H, 13C). Elemental analysis (C,H,N) was performed on
Conclusions
Elementar Vario MICRO cube analyser. Mass spectra were
collected with an Agilent Technologies 6530A Q-TOF using
manual injection regime. Single-crystal X-ray diffraction
experiments were carried out with a Bruker SMART APEX II
diffractometer (graphite monochromated Mo-K radiation,  =
0.71073 Å, -scan technique).
Six new R2Si-bridged pyridylamido hafnium post-metallocene
complexes were synthesized, four of which were characterized
by X-ray structure analysis. The ligands were prepared in a
simple two-step procedure from easily available 2-bromo-6-
phenylpyridine and 2-bromo-6-(napht-1-yl)pyridine. The
complexes were synthesized either by reaction of the ligands
with tetrabenzylhafnium or via a two-step procedure including
reaction of the ligands with Hf2Bn2Cl2(Et2O)2 followed by
methylation of the dichloride complexes formed. In 1-hexene
polymerization, Me2Si-bridged catalysts 7 and 8 appeared to
behave similarly to the Me2C-bridged analogue Id and produced
isotactically enriched polymer.
Propylene homopolymerization and ethylene/1-octene
copolymerization experiments revealed that catalytic
performance of the prepared complexes depended on the
structure of the ligand. Catalysts 7 and 9–11 containing 2,6-
diisopropylaniline fragment upon activation give crystalline
polypropylene. In ethylene/1-octene copolymerization catalyst
7 was approached the molecular weight capability of Ib, one of
General procedure A for preparation of (2-chlorodialkylsilyl)-
6-arylpyridines and (2-chlorodiphenylsilyl)-6-phenylpyridine.
To a solution of a 2-bromo-6-arylpyridine (7.91 mmol) in
tetrahydrofuran (35 mL) a 2.5 M hexane solution of nBuLi (3.16
o
mL, 7.91 mmol) was added dropwise at -78 C to form a clear
orange solution. After 20 min, a dialkyldichlorosilane or
diphenyldichlorosilane (31.6 mmol) was added in one portion.
The mixture was warmed up to ambient temperature and the
volatiles were removed under reduced pressure to afford a
white solid or a turbid oil. The solid was extracted into Et2O (15
mL) and filtered. Removal of the volatiles afforded the product
as a white solid or a colorless oil of suitable purity, which was
used in the next step without additional purification.
This journal is © The Royal Society of Chemistry 20xx
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(2-Chlorodimethylsilyl)-6-phenylpyridine. General procedure A chlorodimethylsilyl)-6-phenylpyridine (1.24 g, 5.0 mmol) and
View Article Online
DOI: 10.1039/D0DT01031F
was applied using 2-bromo-6-phenylpyridine (1.85 g, 7.91 lithium 2,6-diisopropylanilide (0.92 g, 5.0 mmol). Yield: 1.69 g
mmol) and dichlorodimethylsilane (3.85 mL, 31.6 mmol). Yield: (87%) were isolated. 1H NMR (CD2Cl2, 400 MHz): δ 8.12 (m, 2H),
1.86 g (95%) were isolated as a white solid. 1H NMR (CD2Cl2, 400 7.72–7.76 (m, 2H), 7.43–7.57 (m, 4H), 7.07–7.09 (m, 2H), 6.99–
MHz): δ 8.09 (m, 2H), 7.76–7.78 (m, 1H), 7.70 (m, 1H), 7.44–7.52 7.05 (m, 1H), 3.67 (br.s, 1H), 3.49 (m, 2H), 1.14 (d, J = 6.9 Hz,
(m, 4H), 0.78 (s, 6H). 13C NMR (CD2Cl2, 100 MHz): δ 163.6, 157.2, 12H), 0.47 (s, 6H). 13C NMR (CD2Cl2, 100 MHz): δ 167.2, 157.1,
139.6, 135.8, 129.5, 129.1, 127.7, 127.2, 121.0, 1.6.
143.5, 140.3, 140.2, 135.3, 129.2, 129.0, 127.5, 127.3, 123.3,
(2-Chlorodimethylsilyl)-6-(1-naphtyl)pyridine.
General 123.1, 123.0, 120.2, 28.6, 23.7, -0.88. HRMS (APPI) m/z calcd for
procedure A was applied using 2-bromo-6-(1-naphtyl)pyridine C25H33N2Si [M+H]+: 389.2408; found: 389.2413.
(2.25 g, 7.91 mmol) and dichlorodimethylsilane (3.85 mL, 31.6 N-(2,6-Diisopropylphenyl)-1,1-dimethyl-1-(6-(1-
1
mmol). Yield: 2.31 g (98%) were isolated as a yellowish oil. H naphtyl)pyridin-2-yl)silanamine (2). General procedure B was
NMR (CD2Cl2, 400 MHz): δ 8.25 (d, J = 8.1 Hz, 1H), 8.01 (m, 2H), applied using (2-chlorodimethylsilyl)-6-(1-naphtyl)pyridine
7.86 (m, 2H), 7.67-7.69 (m, 1H), 7.63 (m, 2H), 7.56 (m, 2H), 0.84 (1.49 g, 5.0 mmol) and lithium 2,6-diisopropylanilide (0.92 g, 5.0
1
(s, 6H). 13C NMR (CD2Cl2, 100 MHz): δ 163.4, 159.6, 139.3, 135.6, mmol). Yield: 1.95 g (89%) were isolated. H NMR (CDCl3, 400
134.4, 131.6, 129.3, 128.7, 128.0, 127.6, 126.7, 126.3, 126.2, MHz): δ 8.38 (m, 1H), 8.10 (m, 2H), 7.84–7.90 (m, 2H), 7.77 (m,
125.72, 125.70, 1.7.
2H), 7.63–7.69 (m, 3H), 7.26–7.30 (m, 2H), 7.19–7.23 (m, 1H),
2-(1-Chlorosilolan-1-yl)-6-phenylpyridine. General procedure 4.06 (s, 1H), 3.65 (sep, J = 6.9 Hz, 2H), 1.28 (d, J = 6.9 Hz, 12H),
A was applied using 2-bromo-6-phenylpyridine (1.85 g, 7.91 0.70 (s, 6H). 13C NMR (CDCl3, 100 MHz): δ 166.7, 158.9, 142.7,
mmol) and 1,1-dichlorosilolane (4.9 g, 31.6 mmol). Yield: 1.73 g 139.9, 139.2, 134.3, 133.9, 131.3, 128.6, 128.2, 127.3, 126.7,
(80%) were isolated as a colorless oil. 1H NMR (CDCl3, 400 MHz): 126.1, 125.8, 125.7, 125.2, 124.3, 122.8, 122.4, 28.1, 3.4, -0.9.
δ 8.06 (m, 2H), 7.74 (m, 3H), 7.48 (m, 2H), 7.42 (m, 1H), 1.91 (m, HRMS (APPI) m/z calcd for C29H35N2Si [M+H]+: 439.2564; found:
4H), 1.31 (m, 2H), 1.08 (m, 2H). 13C NMR (CDCl3, 100 MHz): δ 439.2566.
162.2, 156.8, 139.1, 135.2, 129.1, 128.7, 128.1, 126.8, 120.3, N-(2,6-Diisopropylphenyl)-1-(6-phenylpyridin-2-yl)silolan-1-
26.6, 15.1.
amine (3). General procedure B was applied using (2-(1-
(2-Chlorodiethylsilyl)-6-phenylpyridine. General procedure A chlorosilolan-1-yl)-6-phenylpyridine (1.37 g, 5.0 mmol) and
was applied using 2-bromo-6-phenylpyridine (1.85 g, 7.91 lithium 2,6-diisopropylanilide (0.92 g, 5.0 mmol). Yield: 1.70 g
mmol) and dichlorodiethylsilane (4.73 mL, 31.6 mmol). Yield: (82%) were isolated. 1H NMR (CDCl3, 400 MHz): δ 8.17 (m, 2H),
1
2.14 g (98%) were isolated as a colorless oil. H NMR (CD2Cl2, 7.71–7.78 (m, 2H), 7.48–7.58 (m, 5H), 7.18 (m, 1H), 7.13 (m, 1H),
400 MHz): δ 8.09 (m, 2H), 7.77 (m, 1H), 7.72 (m, 2H), 7.43–7.53 3.95 (s, 1H), 3.59 (sep, J = 6.9 Hz, 2H), 1.86 (m, 4H), 1.27 (d, J =
(m, 3H), 1.18-1.25 (m, 4H), 1.08–1.14 (m, 6H). 13C NMR (CD2Cl2, 6.9 Hz, 12H), 0.95–1.16 (m, 4H). 13C NMR (CDCl3, 100 MHz): δ
100 MHz): δ 162.6, 157.2, 139.7, 135.7, 129.4, 129.1, 128.7, 165.6, 156.7, 142.7, 139.64, 139.63, 134.8, 128.8, 128.6, 127.7,
127.2, 120.8, 8.1, 6.9.
126.9, 123.0, 122.7, 119.8, 28.4, 26.7, 23.5, 12.2. HRMS (APPI)
(2-Chlorodiphenylsilyl)-6-phenylpyridine. General procedure A m/z calcd for C27H35N2Si [M+H]+: 415.2564; found: 415.2560.
was applied using 2-bromo-6-phenylpyridine (1.85 g, 7.91 N-(2,6-Diisopropylphenyl)-1,1-diethyl-1-(6-phenylpyridin-2-
mmol) and dichlorodiphenylsilane (6.65 mL, 31.6 mmol). The yl)silanamine (4). General procedure B was applied using (2-
excess of dichlorodiphenylsilane was distilled off at 190°С/0.01 chlorodiethylsilyl)-6-phenylpyridine (1.38 g, 5.0 mmol) and
mbar using Kugelrohr short-path distillation apparatus. Yield: lithium 2,6-diisopropylanilide (0.92 g, 5.0 mmol). Yield: 1.85 g
2.56 g (87%) were isolated as a grey solid. 1H NMR (CDCl3, 400 (89%) were isolated. 1H NMR (CD2Cl2, 400 MHz): δ 8.13 (m, 2H),
MHz): δ 8.10 (m, 2H), 7.91 (m, 4H), 7.86 (dd, J = 6.6 Hz, 2.0 Hz, 7.72–7.75 (m, 2H), 7.43–7.55 (m, 4H), 7.07-7.09 (m, 2H), 6.98
1H), 7.75–7.81 (m, 2H), 7.42-7.52 (m, 9H). 13C NMR (CDCl3, 100 (m, 1H), 4.01 (br.s, 1H), 3.48 (m, 2H), 1.16 (d, J = 6.9 Hz, 12H),
MHz): δ 160.6, 156.9, 139.0, 135.5, 135.2, 132.7, 130.6, 129.1, 0.94-1.05 (m, 10H). 13C NMR (CD2Cl2, 100 MHz): δ 165.7, 165.6,
129.0, 128.7, 128.0, 126.8, 120.5.
157.22, 157.21, 142.6, 142.4, 140.9, 140.3, 135.2, 129.2, 129.0,
General procedure B for preparation of pro-ligands 1–6. 128.1, 127.3, 123.3, 122.5, 122.4, 120.2, 120.1, 28.7, 23.7, 7.3,
Benzene (20 mL) was added to a mixture of a (2- 6.39. HRMS (APPI) m/z calcd for C27H37N2Si [M+H]+: 417.2721;
chlorodialkylsilyl)-6-arylpyridines or (2-chlorodiphenylsilyl)-6- found: 417.2727.
phenylpyridine (5.0 mmol) with a substituted lithium anilide N-(2,6-Diisopropylphenyl)-1,1-diphenyl-1-(6-phenylpyridin-2-
(5.0 mmol) previously prepared by reaction of 2,6- yl)silanamine (5). General procedure B was applied using (2-
diisopropylaniline or 2,6-dimethylbenzene with one equivalent chlorodiphenylsilyl)-6-phenylpyridine (1.86 g, 5.0 mmol) and
of n-butyllithium in hexane. To the stirred slurry thus obtained lithium 2,6-diisopropylanilide (0.92 g, 5.0 mmol). Yield: 2.0 g
tetrahydrofuran was added (1 mL). The mixture was stirred for (78%) were isolated. 1H NMR (CDCl3, 400 MHz): δ 8.11 (m, 2H),
1 h, the volatiles were then removed and the oily residue was 7.73 (m, 1H), 7.66–7.69 (m, 4H), 7.64 (m, 1H), 7.34–7.54 (m,
redissolved in benzene (20 mL). The extract was filtered through 10H), 7.00–7.04 (m, 2H), 6.93–6.96 (m, 1H), 5.14 (s, 1H), 3.48
Celite® and then evaporated to give the product as yellowish oil. (sep, J = 6.8 Hz, 2H), 0.91 (d, J = 6.8 Hz, 12H). 13C NMR (CDCl3,
The compound was used in the next step without additional 100 MHz): δ 164.3, 156.9, 140.8, 139.9, 139.7, 135.7, 135.0,
purification.
134.4, 129.8, 129.3, 128.8, 128.6, 127.7, 127.1, 123.1, 121.6,
N-(2,6-Diisopropylphenyl)-1,1-dimethyl-1-(6-phenylpyridin-2- 120.2, 28.7, 23.3. HRMS (APPI) m/z calcd for C35H37N2Si [M+H]+:
yl)silanamine (1). General procedure B was applied using (2- 513.2721; found: 513.2718.
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N-(2,6-Dimethylphenyl)-1,1-diphenyl-1-(6-phenylpyridin-2-
Journal Name
3.1 mmol) was added and the mixture was stirred at 80 oC in the
View Article Online
yl)silanamine (6). General procedure B was applied using (2- dark for 12 h. After that, the mixture DwOaI:s10f.i1lt0e3r9e/Dd0DthT0ro10u3g1hF
chlorodiphenylsilyl)-6-phenylpyridine (1.86 g, 5.0 mmol) and Celite® and the volatiles were removed. The residue was
lithium 2,6-diisopropylanilide (0.64 g, 5.0 mmol). Yield: 1.94 g triturated with hexane, filtered off and dried in vacuum. This
(85%) were isolated. 1H NMR (CDCl3, 400 MHz): δ 8.15 (m, 2H), gave a pyridylamido hafnium dichloride complex of appropriate
7.80 (m, 4H), 7.73 (m, 1H), 7.64 (t, J = 7.7 Hz, 1H), 7.37–7.56 (m, purity which was then methylated without any additional
10H), 6.95 (d, J = 7.4 Hz, 2H), 6.76 (m, 1H), 5.27 (s, 1H), 2.25 (s, purification. Pyridylamido hafnium dimethyl complexes. A 3.0 M
6H). 13C NMR (CDCl3, 100 MHz): δ 164.3, 156.8, 143.6, 139.6, solution of MeMgBr in diethyl ether (2.5 mL, 7.5 mmol) was
135.5, 135.19, 135.15, 129.8, 129.2, 128.9, 128.6, 128.54, added to a solution of pyridylamido hafnium dichloride complex
128.48, 127.8, 127.0, 120.2, 120.1, 20.8. HRMS (APPI) m/z calcd (1.5 mmol) in toluene (50 mL). The mixture was then stirred for
o
for C31H29N2Si [M+H]+: 457.2095; found: 457.2094.
3 h at 70 C. After that, the volatiles were removed under
General procedure C for preparation of complexes 7–9. To a reduced pressure, and the residue was extracted with boiling
solution of pro-ligand 1–3 (2.3 mmol) in benzene (50 mL) solid hexane (3×30 mL). The volatiles were removed under reduced
tetrabenzylhafnium (1.25 g, 2.3 mmol) was added and the pressure, and the residue was washed with cold pentane and
o
mixture was stirred overnight at 80 C in the dark. After that, dried in vaccum to give a crude product as a white powdery
the mixture was filtered through Celite® and the volatiles were solid. Recrystallization of the crude product from toluene-
removed. Crystallization of the solid residue from toluene- hexane mixture afforded the pure dimethylated complex.
hexane mixture afforded the product as an orange crystalline Complex 10. General procedure D was applied using 4 (1.29 g,
solid.
3.1 mmol). Yield: 1.40 g (68%) of pyridylamido hafnium
Complex 7. General procedure C was applied using 1 (0.894 g, dichloride as a brown powder. 1H NMR (CDCl3, 400 MHz): δ 8.23
2.3 mmol). Yield: 963 mg (56%) were isolated. Сalcd for (m, 1H), 7.93–7.98 (m, 2H), 7.83 (m, 1H), 7.58 (dd, J = 6.4, 2.0
C39H44HfN2Si: C, 62.68; H, 5.93; N, 3.75; found: C, 62.75; H, 6.01; Hz, 2H), 7.34–7.39 (m, 2H), 7.08–7.16 (m, 3H), 3.41 (m, 2H), 1.29
N, 3.68. 1H NMR (CDCl3, 400 MHz): δ 7.77–7.84 (m, 2H), 7.71 (d, (d, J = 6.7 Hz, 6H), 1.19 (d, J = 6.9 Hz, 6H), 1.00–1.09 (m, 2H),
1H), 7.62 (d, J = 7.5 Hz, 1H), 7.45 (m, 2H), 7.14-7.27 (m, 4H), 0.89-0.93 (m, 8H). 13C NMR (CDCl3, 100 MHz): δ 199.5, 168.5,
7.05–7.09 (m, 1H), 6.87 (t, J = 7.6 Hz, 4H), 6.66 (t, J = 7.4 Hz, 2H), 164.1, 145.4, 143.9, 143.5, 143.4, 140.0, 130.7, 129.8, 128.4,
6.39 (d, J = 7.3 Hz, 4H), 3.44 (m, 2H), 2.11 (d, J = 11.6 Hz, 2H) 124.5, 123.8, 123.1, 119.0, 28.2, 26.1, 24.1, 7.5, 6.2. Yield of 10
1.79 (d, J = 11.7 Hz, 2H), 1.17 (d, J = 6.9 Hz, 6H), 1.09 (d, J = 6.9 on methylation step: 383 mg (41%) as a white solid. Сalcd for
Hz, 6H), 0.31 (s, 6H). 13C NMR (CDCl3, 100 MHz): δ 201.2, 170.3, C29H40HfN2Si: C, 55.89; H, 6.47; N, 4.49; found: C, 56.02; H, 6.64;
164.0, 146.0, 144.7, 144.0, 143.8, 139.4, 129.7, 129.0, 128.2, N, 4.21. 1H NMR (CDCl3, 400 MHz): δ 8.15 (m, 1H), 7.87–7.92 (m,
127.8, 127.1, 126.6, 124.1, 123.4, 123.0, 122.0, 118.4, 86.6, 2H), 7.83 (d, J = 7.8 Hz, 1H), 7.52 (dd, J1 = 5.6 Hz, J2 = 2.8 Hz, 1H),
28.5, 25.3, 25.0, 0.9.
7.42 (m, 1H), 7.33 (m, 1H), 7.10–7.13 (m, 2H), 7.03–7.07 (m, 1H),
Complex 8. General procedure C was applied using 2 (1.01 g, 2.3 3.55 (m, 2H), 1.19 (d, J = 6.8 Hz, 6H), 1.17 (d, J = 6.8 Hz, 6H),
mmol). Yield: 880 mg (48%) were isolated. Сalcd for 0.87–0.93 (m, 10H), 0.28 (s, 6H). 13C NMR (CDCl3, 100 MHz): δ
C43H46HfN2Si: C, 64.77; H, 5.81; N, 3.51; found: C, 64.92; H, 6.06; 202.2, 169.8, 165.1, 146.4, 144.5, 142.0, 139.8, 139.0, 130.1,
N, 3.40. 1H NMR (CDCl3, 400 MHz) δ 8.35 (d, J = 8.43, 1H), 8.06 128.4, 128.1, 123.7, 123.5, 122.9, 118.3, 64.3, 27.9, 25.8, 24.4,
(d, J = 8.2 Hz, 1H), 7.82–7.93 (m, 3H), 7.66 (d, J = 7.8 Hz, 1H), 7.6, 7.4.
7.42–7.52 (m, 3H), 7.18–7.20 (m, 2H), 7.09–7.13 (m, 1H), 6.86 Complex 11. General procedure D was applied using 5 (1.59 g,
(m, 4H), 6.63 (m, 2H), 6.42 (m, 4H), 3.56 (m, 2H), 2.18 (d, J = 11.9 3.1 mmol). Yield: 1.34 g (57%) of pyridylamido hafnium
1
Hz, 2H) 1.96 (d, J = 11.9 Hz, 2H), 1.18 (d, J = 6.9 Hz, 6H), 1.15 (d, dichloride as a brown powder. H NMR (CD2Cl2, 400 MHz): δ
J = 6.9 Hz, 6H), 0.38 (s, 6H). 13C NMR (CDCl3, 100 MHz): δ 204.2, 8.21 (m, 1H), 8.09–8.11 (m, 2H), 7.96 (m, 1H), 7.63 (dd, J = 6.5,
170.8, 164.9, 144.5, 144.0, 143.9, 143.4, 138.8, 135.4, 134.6, 2.2 Hz, 1H), 7.43 (m, 8H), 7.29 (m, 4H), 7.08–7.12 (m, 1H), 7.03
129.8, 129.0, 128.1, 127.1, 126.2, 126.1, 125.1, 124.1, 124.1, (s, 1H), 7.01 (d, J = 1.4 Hz, 1H) 3.18 (m, 2H), 1.16 (d, J = 6.9 Hz,
123.5, 123.3, 122.0, 87.7, 28.4, 25.3, 25.1, 0.9.
6H), 0.25 (d, J = 6.7 Hz, 6H). 13C NMR (CD2Cl2, 100 MHz): δ 199.7,
Complex 9. General procedure C was applied using 3 (0.954 g, 166.5, 164.6, 146.0, 145.0, 143.6, 141.3, 136.3, 135.6, 133.6,
2.3 mmol). Yield: 783 mg (44%) were isolated. Сalcd for 131.3, 130.8, 130.7, 130.4, 128.6, 128.3, 124.4, 123.8, 120.1,
C41H46HfN2Si: C, 63.67; H, 6.00; N, 3.62; found: C, 63.85; H, 6.18; 29.0, 26.5, 23.0. Yield of complex 11 on methylation step: 367
1
N, 3.48. H NMR (CDCl3, 400 MHz): δ 7.73–7.82 (m, 4H), 7.15– mg (34%) as a white solid. Сalcd for C37H40HfN2Si: C, 61.78; H,
7.36 (m, 6H), 6.92 (t, J = 7.6 Hz, 4H), 6.68 (t, J = 7.4 Hz, 2H), 6.56 5.61; N, 3.89; found: C, 61.99; H, 5.87; N, 3.72. 1H NMR (CDCl3,
(d, J = 7.2 Hz, 4H), 3.54 (m, 2H), 2.40 (d, J = 11.8 Hz, 2H) 2.10 (d, 400 MHz): δ 8.21 (m, 1H), 7.88–8.02 (m, 3H), 7.58 (m, 1H), 7.34–
J = 11.8 Hz, 2H), 1.68 (m, 4H), 1.25 (d, J = 6.8 Hz, 6H), 1.21 (d, J 7.42 (m, 8H), 7.25–7.30 (m, 4H), 8.98–7.07 (m, 3H), 3.33 (m, 2H),
= 6.8 Hz, 6H), 0.70-0.89 (m, 4H). 13C NMR (CDCl3, 100 MHz): δ 1.08 (d, J = 6.9 Hz, 6H), 0.41 (s, 6H), 0.32 (d, J = 6.9 Hz, 6H). 13C
201.8, 170.5, 164.1, 146.1, 144.0, 143.3, 139.7, 139.0, 129.8, NMR (CDCl3, 100 MHz): δ 202.0, 167.1, 165.0, 146.4, 145.4,
129.0, 128.2, 128.1, 127.9, 127.4, 126.7, 125.3, 124.2, 123.7, 140.0, 139.7, 139.4, 136.4, 135.7, 135.4, 135.1, 134.9, 130.3,
122.8, 122.1, 118.4, 89.1, 28.3, 26.6, 25.4, 24.9, 13.4.
130.1, 129.7, 128.5, 127.8, 125.4, 124.1, 123.8, 123.6, 123.0,
General procedure D for preparation of complexes 10–12. 118.8, 65.6, 64.6, 64.3, 34.7, 28.3, 27.8, 25.7, 25.5, 23.9, 23.4,
Pyridylamido hafnium dichlorides. To a solution of pro-ligand 4– 22.2, 14.2.
6 (3.1 mmol) in benzene (60 mL) solid HfBn2Cl2(Et2O)2 (1.80 g,
8 | J. Name., 2012, 00, 1-3
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Journal Name
ARTICLE
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R. D. J. Froese, P. D. Hustad, R. L. Kuhlman, T. T. Wenzel, J. Am.
Complex 12. General procedure D was applied using 6 (1.42 g,
3.1 mmol). Yield: 1.83 g (84%) of pyridylamido hafnium
dichloride as a white powder. 1H NMR (CDCl3, 400 MHz): δ 8.30
(m, 1H), 8.03–8.08 (m, 2H), 7.90 (m, 1H), 7.63 (dd, J = 6.4 Hz, 1.9
Hz, 1H), 7.43 (m, 8H), 7.30 (m, 4H), 6.89–6.97 (m, 3H), 1.91 (s,
6H). 13C NMR (CDCl3, 100 MHz): δ 199.5, 167.1, 165.1, 145.2,
145.1, 142.6, 140.7, 135.4, 134.6, 133.5, 131.1, 130.3, 130.1,
130.0, 128.6, 127.9, 124.2, 123.2, 119.6, 20.5. Yield of complex
12 on methylation step: 617 mg (62%) as a white powder. Сalcd
for C33H32HfN2Si: C, 59.76; H, 4.86; N, 4.22; found: C, 59.85; H,
5.02; N, 4.11. 1H NMR (CDCl3, 400 MHz): δ 8.27 (m, 1H), 8.01 (m,
1H), 7.87–7.95 (m, 2H), 7.56 (m, 1H), 7.50 (m, 1H), 7.35–7.42
(m, 7H), 7.27 (m, 4H), 6.85–6.92 (m, 3H), 1.83 (s, 6H), 0.43 (s,
6H). 13C NMR (CDCl3, 100 MHz): δ 202.4, 168.5, 166.2, 145.7,
142.8, 139.6, 139.4, 136.1, 135.3, 135.2, 130.5, 130.1, 129.8,
128.6, 128.4, 127.8, 123.2, 123.0, 119.0, 66.0, 20.5.
View Article Online
Chem. Soc., 2007, 129, 7831.
DOI: 10.1039/D0DT01031F
C. Zuccaccia, A. Macchioni, V. Busico, R. Cipullo; G. Talarico, F.
Alfano, H. W. Boone, K. A. Frazier, P. D. Hustad, J. C. Stevens,
P. C. Vosejpka, K. A. Abboud, J. Am. Chem. Soc., 2008, 130,
10354.
C. Zuccaccia, V. Busico, R. Cipullo, G. Talarico, R. D. J. Froese,
P. C. Vosejpka, P. D. Hustad, A. Macchioni, Organometallics,
2009, 28, 5445.
9
10 G. J. Domski, E. B. Lobkovsky, G. W. Coates, Macromolecules,
2007, 40, 3510.
11 G. J. Domski, J. M. Eagan, C. De Rosa, R. Di Girolamo, Dr. A. M.
LaPointe, E. B Lobkovsky, G. Talarico, G. W. Coates, ACS Catal.,
2017, 7, 6930.
12 L. Luconi, A. Rossin, G. Tuci, I. Tritto, L. Boggioni, J. J. Klosin, C.
N. Theriault and G. Giambastiani, Chem. Eur. J., 2012, 18, 671.
13 G. Li, C. Zuccaccia, C. Tedesco, I. D'Auria, A. Macchioni and C.
Pellecchia, Chem. Eur. J., 2014, 20, 232.
14 G. R. Davies, J. A. J. Jarvis and B. T. Kilbourn, J. Chem. Soc. D,
1971, 1511.
15 L. J. Irwin, J. H. Reibenspies, S. A. Miller, Polyhedron, 2005, 24,
1314.
16 L. Luconi, A. Rossin, G. Tuci, S. Germain, E. Schulz, J.
Hannedouche and G. Giambastiani, ChemCatChem, 2013, 5,
1142.
17 Low activity of dibenzyl catalyst precursors when activated
with B(C6F5)3 was noticed previously in reference [12]. See
also: A. Noor, W. P. Kretschmer, G. Glatz, A. Meetsma, R.
Kempe, Eur. J. Inorg. Chem., 2008, 32, 5088.
18 H. W. Turner, G. C. Dales, L. VanErden, J. A. M. van Beek, US
6306658 B1 (for Symyx Technologies, Inc.), 2001.
19 H. W. Turner, G. C. Dales, L. VanErden, J. A. M. van Beek, D. A.
Hajduk, R. B. Nielsen, P. Mansky, L. Matsiev, P. Wang, E.
McFarland, US 6455316 B1 (for Symyx Technologies, Inc.),
2002.
Propylene homopolymerization and ethylene/1-octene
copolymerization – general procedure.
Polymerizations were carried out in 48-cell parallel, pressure
reactors (PPR) developed by Symyx Technologies.3,18 The
detailed procedure may be found in Supporting Information.
Conflicts of interest
There are no conflicts to declare.
Acknowledgements
20 P. Wang, G. C. Dales, US 6489168 B1 (for Symyx Technologies,
Inc.), 2002.
21 H. W. Turner, G. C. Dales, L. VanErden, J. A. M. van Beek, D. A.
Hajduk, R. B. Nielsen, P. Mansky, L. Matsiev, P. Wang, E.
McFarland, WO 00/09255 A2 (for Symyx Technologies, Inc.),
2000.
We thank ExxonMobil Chemical Company for financial support
and assistance in publication of this work. Also authors are
grateful to M. V. Lomonosov Moscow State University (Russia)
for the opportunity to use the NMR facilities of the Center for
Magnetic Tomography and Spectroscopy.
22 Organozinc and organoaluminum reagents are known to
function as facile, sometimes reversible, chain-transfer agents
in olefin polymerizations catalyzed by group 4 pyridylamide
and related systems. See for example: (a) R. Kempe, Chem.
Eur. J., 2007, 13, 2764; (b) A. Valente, A. Mortreux, M.
Visseaux, P. Zinck, Chem. Rev., 2013, 113, 3836.
23 The increase of copolymer incorporation with the size of the
substituent on the bridge was previously found for
pyridylamido zirconium catalysts, where the change of the
linker from CH2 to CH(iPrC6H4) led to the increase in content
of octene units in polymer from 4.2 to 8.4 mol%, see ref. [12].
24 J. R. Hagadorn, J. A. M. Canich, A. Z. Voskoboynikov, P. S.
Kulyabin, G. P. Goryunov, D. V. Uborsky, WO 2018/022249 A1
(for ExxonMobil), 2018.
Notes and references
1
D. W. Sauter, M. Taoufik and C. Boisson, Polymers, 2017, 9,
185.
N. Friederichs, N. Ghalit and W. Xu, in Tailor-Made Polymers,
ed. J.R. Severn, and J.C. Chadwick, Wiley-VCH, Weinheim,
2008, ch. 8, pp. 211–237.
2
3
4
T. R. Boussie, G. M. Diamond, C. Goh, K. A. Hall, A. M. LaPointe,
M. Leclerc, C. Lund, V. Murphy, J. A. W. Shoemaker, U. Tracht,
H. Turner, J. Zhang, T. Uno, R. K. Rosen and J. C. Stevens, J. Am.
Chem. Soc., 2003, 125, 4306.
(a) T. R. Boussie, G. M. Diamond, C. Goh, K. A. Hall, A. M.
LaPointe; M. K. Leclerc, C. Lund, V. Murphy, WO 02/38628 A2
(for Symyx Technologies, Inc.), 2002; (b) T. R. Boussie, G. M.
Diamond, C. Goh, K. A. Hall, A. M. LaPointe, M. K. Leclerc; C.
Lund, V. Murphy, WO 02/46249 A2 (for Symyx Technologies,
Inc.), 2002; (c) T. R. Boussie, G. M. Diamond, C. Goh, K. A. Hall,
A. M. LaPointe, M. K. Leclerc, C. Lund, V. Murphy, J. A. W.
Shoemaker, H. Turner, R. K. Rosen, J. C. Stevens, F. Alfano, V.
Busico, R. Cipullo, G. Talarico, Angew. Chem., Int. Ed., 2006,
45, 3278.
25 P. Gros, Y. Fort, J. Org. Chem., 2003, 68, 2028.
26 R.-Z. Jin, Z. Bian, C.-Q. Kang, H.-Q. Guo, L.-X. Gao, Synth.
Commun., 2005, 35, 1897.
5
6
K. A. Frazier, R. D. Froese, Y. He, J. Klosin, C. N. Theriault, P. C.
Vosejpka, Z. Zhou, Organometallics, 2011, 30, 3318.
J. Arriola, E. M. Carnahan, P. D. Hustad, R. L. Kuhlman, T. T
Wenzel, Science, 2006, 312, 714.
This journal is © The Royal Society of Chemistry 20xx
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Page 10 of 10
View Article Online
DOI: 10.1039/D0DT01031F
Pyridylamido Hafnium Complexes with the Silylene Bridge: Synthesis and
Olefin Polymerization
Pavel S. Kulyabin, Dmitry V. Uborsky, Alexander Z. Voskoboynikov, Jo Ann M. Canich, John R. Hagadorn
Pyridylamido hafnium complexes with silylene bridge were synthesized, characterized with X-ray
structure determination analysis and shown to polymerize 1-hexene, propene and copolymerize
ethylene and 1-octene.
Polypropylene
R'
R'
N
Si
nBu
R''
Polyhexene
Hf
N
X
X
nHex
R''
Poly(ethylene-co-
octene) (LLDPE)
[HNMe2Ph][B(C6F5)4]
+