Synthesis and structural analysis of (imido)vanadium(V) dichloride complexes containing imidazolin-2-iminato- and imidazolidin-2-iminato ligands, and their use as catalyst precursors for ethylene (Co)polymerization

Article abstract of DOI:10.1021/ic402747d

A series of (imido)vanadium(V) dichloride complexes containing 1,3-imidazolin-2-iminato or 1,3-imidazolidin-2-iminato ligands of the type, V(NR′)Cl₂(L) [R′ = 2,6-Me₂C₆H ₃, L = 1,3-R₂(CHN)₂C

Full text of DOI:10.1021/ic402747d

Article
pubs.acs.org/IC
Synthesis and Structural Analysis of (Imido)vanadium(V) Dichloride
Complexes Containing Imidazolin-2-iminato- and Imidazolidin-2-
iminato Ligands, and their Use as Catalyst Precursors for Ethylene
(Co)polymerization
Kotohiro Nomura,*,†,‡ Bijal Kottukkal Bahuleyan,† Shu Zhang,†,‡ Prabhuodeyara M. Veeresha Sharma,‡
Shohei Katao,‡ Atsushi Igarashi,† Akiko Inagaki,‡ and Matthias Tamm*,§
†Department of Chemistry, Tokyo Metropolitan University, Minami-Osawa 1-1, Hachioji, Tokyo 192-0397, Japan
‡Graduate School of Materials Science, Nara Institute of Science and Technology, Ikoma, Nara 630-0101, Japan
§Institut fur Anorganische und Analytische Chemie, Technische Universitat Braunschweig, Hagenring 30, 38106 Braunschweig,
̈
̈
Germany
S
* Supporting Information
ABSTRACT: A series of (imido)vanadium(V) dichloride com-
plexes containing 1,3-imidazolin-2-iminato or 1,3-imidazolidin-
2-iminato ligands of the type, V(NR′)Cl2(L) [R′ = 2,6-Me2C6H3,
L = 1,3-R2(CHN)2CN (1a−c,e) or 1,3-R2(CH2N)2CN
t
(2a−d), R = Bu (a), 2,6-Me2C6H3 (b), 2,6-iPr2C6H3 (c),
C6H5 (d), 2,6-(Ph2CH)2-4-MeC6H2 (e); L = 1,3-
(2,6-iPr2C6H3)2(CHN)2CN, R′ = 1-adamantyl (Ad, 3c), C6H5
(4c); L = 1,3-(2,6-iPr2C6H3)2(CH2N)2CN, R′ = Ad (5c)], were
prepared and characterized. The molecular structures of 1a, 2a,c,d,
3c, 4c, and 5c were determined by X-ray crystallography. All
complexes showed high catalytic activity for ethylene polymerization especially in the presence of Et2AlCl cocatalyst; the 2,6-
i
t
R2C6H3 analogues (R = Me, Pr; 1b,c, 2b,c) exhibited higher catalytic activities than the Bu analogues (1a, 2a), which display
rather unique (small) VNC(imido) bond angles in the solid state. A good correlation between the activity and the 51V NMR
chemical shift was found for the (arylimido)vanadium precatalysts (1a−c,e, 2a−d, and 4c). These complexes showed high
catalytic activity for the copolymerization of ethylene with norbornene (NBE), affording ultrahigh molecular weight copolymers
with uniform molecular weight distributions. The activities were affected by the imido ligand as well as by the substituents in the
anionic ligand, and the 2,6-iPr2C6H3 analogues (especially 2c and 4c) showed the higher activities. The complexes 2c and 4c also
showed high activities with efficient comonomer incorporation for the ethylene copolymerization with 5-ethylidene-2-
norbornene (ENB) in the presence of Et2AlCl; both the comonomer incorporation and the molecular weight in the resulting
polymers were affected by the comonomer employed (NBE vs ENB).
that (2-anilidomethyl)pyridine-supported (imido)vanadium(V)
complexes of the type, V(NR′)Cl2[2-ArNCH2(C5H4N)] [Ar =
2,6-Me2C6H3, etc.; R′ = 1-adamantyl (Ad), cyclohexyl, o-tolyl,
phenyl, etc.], efficiently dimerize ethylene with both notable
catalytic activity and high selectivity in the presence of
methylaluminoxane (MAO),8 whereas the resulting products
were polyethylene with ultrahigh molecular weight when the
reactions were conducted in the presence of Et2AlCl or
Me2AlCl.8b,d
Half-titanocenes containing imidazolin-2-iminato ligands as
an anionic donor ligand (Y) were also introduced as promising
catalyst precursors for olefin polymerization, and complexes
of this type, exemplified by CpTiCl2[1,3-tBu2(CHN)2N] (B
in Scheme 1), exhibit high catalytic activities for ethylene
INTRODUCTION
■
The classical Ziegler-type vanadium catalyst systems [e.g., con-
sisting of V(acac)3, VOCl3, etc. and Et2AlCl, EtAlCl2, BuLi,
n
etc.] are known to display uniquely high reactivity toward
olefins in olefin coordination/insertion polymerization.1−5 The
design and synthesis of efficient vanadium precatalysts for
olefin coordination insertion polymerization has thus attracted
considerable attention in the fields of catalysis, organometallic
chemistry, and polymer chemistry.5−7 Our group has focused
on (imido)vanadium(V) complexes containing anionic donor
ligands of the type, VCl2(Y)(NR) (Y = aryloxo, ketimide,
phenoxyimine, etc.),5c,e,6,8 and has demonstrated that these
complexes, exemplified by V(N-2,6-Me2C6H3)Cl2(O-2,6-
Me2C6H3) (A in Scheme 1),6a−d exhibit remarkable catalytic
activities not only for ethylene polymerization but also for
ethylene copolymerization with norbonene (NBE) in the
presence of aluminum cocatalysts.6a−d Moreover, we also reported
Received: November 1, 2013
Published: December 20, 2013
© 2013 American Chemical Society
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Scheme 1. Recently Reported Complexes as Effective
Precatalysts for Ethylene/Norbornene Copolymerization
RESULTS AND DISCUSSION
■
1. Synthesis and Structural Characterization of (Imido)-
vanadium(V) Dichloride Complexes Containing Imidazolin-
2-iminato, and Imidazolidin-2-iminato Ligands. A series of
(arylimido)vanadium(V) dichloride complexes containing
imidazolin-2-iminato ligands of type V(NAr)Cl2(L1) [Ar =
t
2,6-Me2C6H3; L1 = 1,3-R2(CHN)2CN, R = Bu (1a), 2,6-
Me2C6H3 (1b), 2,6-(Ph2CH)24-MeC6H2 (1e)] were prepared
according to a published procedure12n for the synthesis of
V(NAr)Cl2[1,3-(2,6-iPr2C6H3)2(CHN)2CN] (1c) by react-
14
ing V(NAr)Cl3 with L1-SiMe3 in toluene (Scheme 3); this
protocol is also similar to that for the preparation of the cor-
responding CpTiCl2(L1) complexes.9b Complexes 1a,b,e were
identified by 1H, 13C, and 51V NMR spectroscopy and
elemental analysis, and the molecular structure of 1a was
determined by X-ray diffraction analysis (described below, see
Figure 1). Similarly, the reactions of V(NAd)Cl3 (Ad = 1-
adamantyl)15 or V(NPh)Cl38a with L1-SiMe3 (R = 2,6-iPr2C6H3)
in toluene afforded the corresponding V(NR′)Cl2[1,3-
(2,6-iPr2C6H3)2(CHN)2CN] [R′ = Ad (3c), Ph (4c)], and
both compounds were fully characterized by NMR spectros-
copy and elemental analyses, and their molecular structures
were determined by X-ray diffraction analysis (described below,
see Figure 1).
polymerization in the presence of MAO,9 affording ultrahigh
molecular weight polymers.9b Furthermore, these complexes
show notable catalytic activities for copolymerization of
ethylene with α-olefins (1-hexene, 1-dodecene) and superior
catalyst performance in the (living) copolymerization of
ethylene with styrene.9d More recently, an efficient synthesis
of high molecular weight poly(ethylene-co-NBE)s with high
NBE contents (affording high Tg values) was achieved by use of
complex B for ethylene/NBE copolymerization (Scheme 1).9e
Certain cyclic olefin copolymers (COCs) are amorphous
materials with a promising combination of high transparency
in the UV−vis region along with humidity- and heat-resistance
(high glass transition temperature, Tg),10 and these polymers
have been commercialized (as TOPAS) by using metallocene
catalysts as ultrapure (applicable to advanced pharma pack-
aging, food contact films), crystal-clear (glass clear, amor-
phous), high barrier (resistant to moisture, alcohols, acids)
materials.11 Similar to imidazolin-2-iminato ligands, which have
been extensively used for the preparation of early transition
metal complexes,12 their 4,5-dihydro congeners are also suitable
ancillary ligands, and thus, the corresponding half-titanocenes
containing imidazolidin-2-iminato ligands also exhibit unique
characteristics for ethylene (co)polymerization.13 For both li-
gand systems, a similar stabilization by the zwitterionic
resonance structures shown in Scheme 2 can be considered,
A related series of (arylimido)vanadium(V) dichloride com-
plexes containing imidazolidin-2-iminato ligands of the type,
t
V(NAr)Cl2(L2) [L2 = 1,3-R2(CH2N)2CN, R = Bu (2a),
2,6-Me2C6H3 (2b), 2,6-iPr2C6H3 (2c), Ph (2d)], were prepared
by reacting V(NAr)Cl314 with L2-Li in toluene, with the lithium
reagents obtained by treatment of L2-H13,16 with n-BuLi (1
equiv) in THF; it should be noted that the corresponding
CpTiCl2(L2) complexes had been prepared in a similar
fashion.13 The analogous reaction of V(NAd)Cl3 with L2c-Li
(R = 2,6-iPr2C6H3) in toluene afforded V(NAd)Cl2[1,3-
(2,6-iPr2C6H3)2(CH2N)2CN] (5c). Complexes 2a−d and
1
5c were identified by H, 13C, and 51V NMR spectroscopy and
elemental analysis, and the molecular structure of each
complexes except for 2b were determined by X-ray diffraction
analysis (described below, see Figure 2).
Figure 1 shows structures for V(NAr)Cl2[1,3-tBu2(CHN)2CN]
(1a), V(NAd)Cl2[1,3-(2,6-iPr2C6H3)2(CHN)2CN] (3c),
and V(NPh)Cl2[1,3-(2,6-iPr2C6H3)2(CHN)2CN] (4c), and
selected bond distances and angles are summarized in Table 1.17
As expected from the previously reported structure of 1c12n and
from that of the ketimide analogue, V(NAr)Cl2(NCtBu2),18
these complexes display distorted tetrahedral geometries
around the vanadium atoms. The VCl bond distances in
1a [2.2462(8), 2.2514(7) Å] are longer than those in the
2,6-iPr2C6H3 analogues (1c,12n 3c, 4c) [2.2120(10)−2.2386(7)
Å] but somewhat shorter than that in V(NAr)Cl2(NCtBu2)
[2.2710(5), 2.2338(5) Å].18 The VN(1) imido bond length
in 3c [1.638(2) Å] is apparently shorter than those in the other
imidazolin-2-iminato analogues [1.664(3)−1.6689(15) Å]. The
Cl(1)VCl(2) angles in 3c and 4c [112.66(3), 112.66(4)°]
are just slightly smaller than that in 1a [113.00(3)°] but are
slightly larger than that in 1c [111.45(2)°];12n however, these
angles are smaller than that in V(NAr)Cl2(NCtBu2)
[118.87(2)°],18 which might be ascribed to the presence of
the sterically more demanding imidaozolin-2-iminato ligands.
Moreover, the imidazolin-2-iminato VNC bond angle in
3c [158.07(15)°] is apparently smaller than those in the other
complexes [163.92(10)−164.58(18)°], which corresponds to
Scheme 2. Resonance Structures for Imidazolin-2-iminato
(top) and Imidazolidin-2-iminato (bottom) Ligands
affording strong basic nitrogen donor ligands with a high
π-electron release capability toward early transition metals
and/or metals in a higher oxidation state.9,12,13
In this paper, we report the synthesis of (imido)vanadium-
(V) dichloride complexes containing both imidazolin-2-iminato
and imidazolidin-2-iminato ligands (Chart 1) and their use as
catalyst precursors for ethylene polymerization and ethylene
copolymerization with the cyclic olefins [norbornene (NBE),
ethylidene-2-norbornene (ENB)]. In particular, we wish to
demonstrate that these complexes are promising candidates as
catalyst precursors for the efficient synthesis of high molecular
weight poly(ethylene-co-NBE)s.
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Chart 1
in the same range as found for the imidazolin-2-iminato
analogues (1a,c, 3c, 4c) [2.2120(10)−2.2514(7) Å]. The
VN(1) imido bond length in 2a [1.620(13) Å] is shorter
than those in the other complexes [1.645(3)−1.6635(12) Å],
whereas the VN(1)C angle [157.3(11)°] in 2a is smaller
than the others [167.96(11)179.20(11)°]: the angle in 2c
[167.96(11)°] is smaller than those in 2d and 5c [179.20(11),
174.5(2)°, respectively]. Moreover, the imidazolidin-2-iminato
VNC bond angle is affected by the ligand substituents, and
accordingly, the bond angles in V(N-2,6-Me2C6H3)Cl2[1,3-
R2(CH2N)2CN] [R = tBu (2a), 2,6-iPr2C6H3 (2c), Ph (2d)]
increase in the order: 150.06(12)° (2d) < 157.9(4)° (2a) <
174.79(11)° (2c). In contrast, the corresponding vanadium−
nitrogen bond distance in 2d [1.7538(13) Å] is longer than
those in 2a [1.736(5) Å] and 2c [1.7383(13) Å]. The Cl(1)
VCl(2) bond angle in 2a [111.71(9)°] is smaller than those
in 2c and 2d [113.006(15), 113.164(15)°, respectively] but
close to that in 5c [111.23(4)°].
Scheme 3. Synthesis of (Imido)vanadium Dichloride
Complexes Containing Imidazolin-2-iminato and
Imidazolidin-2-iminato Ligands
Overall, all complexes display the expected tetrahedral
geometry around vanadium atom, and the structural parameters
along the VNC axes of the anionic donor ligands (imidazolin-
2-iminato or imidazolidin-2-iminato) are clearly affected by the
substituents of the respective N-heterocycle. In particular, the
complexes containing tert-butyl substituents (1a, 2a) possess rather
unique VNC bond angles in both arylimido and the anionic
donor ligands, probably due to a steric bulk of the tert-butyl groups.
2. Ethylene Polymerization Using (Imido)vanadium(V)
Dichloride Complexes Containing Imidazolin-2-iminato
and Imidazolidin-2-iminato Ligands in the Presence of
Al Cocatalysts. Table 2 summarizes the results for ethylene
polymerization using the imidazolin-2-iminato precatalysts,
t
V(N-2,6-Me2C6H3)Cl2[1,3-R2(CHN)2CN] [R = Bu (1a),
2,6-Me2C6H3 (1b), 2,6-iPr2C6H3 (1c), 2,6-(Ph2CH)2-4-MeC6H2
(1e)] and V(NR′)Cl2[1,3-(2,6-iPr2C6H3)2(CHN)2CN] [R′ =
1-adamantyl (3c), C6H5 (4c)], in the presence of Al cocatalysts
(in toluene, ethylene 8 atm, 10 min). As additionally illustrated by
Figure 3 (left), the catalytic activity, on the basis of polymer yield,
was affected by the Al/V molar ratio and by the nature of the Al
cocatalyst; the activities in the presence of methylaluminoxane
(MAO) cocatalyst were lower than those in the presence of
EtAlCl2. Moreover, the activity in ethylene polymerization in the
presence of Et2AlCl cocatalyst at 25 °C became low compared
to that conducted at 0 °C. The observed trends are similar to
those found for ethylene polymerization using the aryloxo
substituted (arylimido)vanadium dichloride complexes, Al
cocatalyst systems.6b−d The resulting polymers are linear
polyethylene that are not sufficiently soluble in hot o-
dichlorobenzene (140 °C) required for a GPC analysis.
Because the poly(ethylene-co-norbornene)s obtained below
possessed uniform molecular weight distributions, it is highly
the fact that the VN(2) bond distance in 3c [1.7466(18) Å]
is longer than those in the other systems [1.7256(15)−
1.7308(11) Å]. It might be interesting to note that the
VN(1)C in the imido ligand [163.45(13)°] angle in 1a is
smaller than the others [171.14(17)−171.25(18)°], whereas
the corresponding VN(1) distance in 1a [1.6689(15) Å] is
close to those in the others [1.664(3)−1.6684(13) Å], except
3c [1.638(2) Å].
Figure 2 shows molecular structures of V(N-2,6-Me2C6H3)-
t
Cl2[1,3-R2(CH2N)2CN] [R = Bu (2a), 2,6-iPr2C6H3 (2c),
Ph (2d)], and V(NAd)Cl2[1,3-(2,6-iPr2C6H3)2(CH2N)2CN]
(5c), and their selected bond distances and angles are sum-
marized in Table 1.17 Likewise, these complexes display distorted
tetrahedral geometries around the vanadium atoms. The VCl
bond distances in these complexes [2.2222(4)−2.248(3) Å] fall
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Figure 1. ORTEP drawings for V(N-2,6-Me2C6H3)Cl2[1,3-tBu2(CHN)2CN] (1a, left), V(NAd)Cl2[1,3-(2,6-iPr2C6H3)2(CHN)2CN]
(3c, middle), and V(NPh)Cl2[1,3-(2,6-iPr2C6H3)2(CHN)2CN] (4c, right). Thermal ellipsoids are drawn at the 30% probability level, and H
atoms are omitted for clarity. Details are given in the Supporting Information.17
assumed that ultrahigh molecular weight polyethylene has
formed in this catalysis as previously reported for the
polymerization in the presence of the aryloxo modified
(arylimido)vanadium catalysts (exemplified as complex A in
Scheme 1).6b−d
found for the imidazolin-2-iminato catalyst systems. The
arylimido complexes with aryl substituents in 1,3-positions of
the imidazolidin-2-iminato ligand (N-heterocycle 2b,c) showed
higher activity than the tert-butyl analogue (2a), suggesting
again that the electronic nature of the substituent affects the
activity. The observed trend was similar to that described above
for ethylene polymerization using the imidazolin-2-iminato
(imido)vanadium complexes.
Table 4 summarizes the selected results for ethylene
polymerization using the imidazolin-2-iminato (1a−c,e, 3c,
4c) and the imidazolidin-2-iminato (2a−d, 5c) complexes
under the optimized conditions. In both cases, the 2,6-
dimethylphenyl (1b, 2b) and the 2,6-diisopropylphenyl
analogues (1c, 2c) exhibited higher catalytic activities than
the tert-butyl analogues (1a, 2a). The low activities displayed by
1a and 2a containing tert-butyl substituents may be ascribed to
the fact that these complexes (1a, 2a) possess rather unique
VNC bond angles within the arylimido as well as within
the anionic ancillary donor ligands. The adamantylimido com-
plexes (3c, 5c) showed low activities, suggesting that an elec-
tronic nature of the imido ligand might play a role. Moreover,
the imidazolin-2-iminato analogues exhibited higher activities
than the imidazolidin-2-iminato analogues in the ethylene
polymerization using the (arylimido)vanadium(V) dichloride
complexes Et2AlCl systems.
Figure 4 shows plots of catalytic activity against the chemical
shifts (δ in ppm) in the 51V NMR spectra in CDCl3 (at 25 °C).
It might be interesting to note that a good relationship between
the activity and the chemical shift was observed for the
(arylimido)vanadium complexes (1a−c,e, 2a−d, 4c), this fact
might suggest that a certain degree of electron donation
through the imidazolin-2-iminato or imidazolidin-2-iminato
ligands plays a role toward the catalytic activity. One simple
assumption that one might take into consideration for an
explanation based on the results reported for the half-
metallocenes such as Cp′Ti(OMe)3 in the syndiospecific
styrene polymerization19 or Cp′TiCl2(O-2,6-iPr2C6H3) in
ethylene polymerization20 could be that a stabilization of the
The activity of the imidazolin-2-iminato analogues (with
optimized Al/V molar ratio) in the presence of the Et2AlCl
cocatalyst increased in the order (in toluene, ethylene 8 atm,
0 °C, 10 min): 6300 kg-PE/mol-V·h (1a) < 8220 (3c) < 26 700
(1e) < 34 700 (1c) < 38 300 (1b) < 42 900 (4c). Among the
arylimido congeners (1a−c,e), the complexes with aryl
substituents (1b,c,e) in the imidazolin-2-iminato ligand showed
higher activity than the tert-butyl analogue (1a), suggesting that
the electronic nature of the substituent has an impact on the
activity. Further increase of steric bulk in the 1,3-position upon
going from 1b to 1c and 1e led to a decrease in activity,
suggesting that the activity is also influenced by the steric bulk
requirements of the ancillary ligands. Moreover, the activity of
V(NR′)Cl2[1,3-(2,6-iPr2C6H3)2(CHN)2CN] [R′ = 2,6-
Me2C6H3 (2c), 1-adamantyl (3c), C6H5 (4c)] increased in
the order: 8220 (3c) ≪ 34 700 (1c) < 42 900 (4c).
Table 3 summarizes the results for ethylene polymerization
using the imidazolidin-2-iminato precatalysts, V(N-2,6-
t
Me2C6H3)Cl2[1,3-R2(CH2N)2CN] [R = Bu (2a), 2,6-
Me2C6H3 (2b), 2,6-iPr2C6H3 (2c), C6H5 (2d)], and V(NAd)-
Cl2[1,3-(2,6-iPr2C6H3)2(CHN)2CN] (5c), in the presence of
Al cocatalysts (in toluene, ethylene 8 atm, 10 min). As also
shown in Figure 3 (right), the catalytic activity was affected by
the Al/V molar ratio employed, and similar trends with regard
to the effect of the Al cocatalyst and the temperature were
observed as described above for the polymerization in the
presence of the imidazolin-2-iminato analogues. The activity
(with the optimized Al/V molar ratio) in the presence of
Et2AlCl cocatalyst increased in the order (in toluene, ethylene 8
atm, 0 °C, 10 min): 9420 kg-PE/mol-V·h (5c) < 13 200 (2a) <
26 700 (2d) < 29 000 (2c) < 32 000 (2b). The catalytic activity
of the arylimido derivatives (2a−d) was higher than the
adamantylimido analogue (5c), in agreement with the findings
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Figure 2. ORTEP drawings for V(N-2,6-Me2C6H3)Cl2[1,3-tBu2(CH2N)2CN] (2a, top left), V(N-2,6-Me2C6H3)Cl2[1,3-
(2,6-iPr2C6H3)2(CH2N)2CN] (2c, top right), V(N-2,6-Me2C6H3)Cl2[1,3-Ph2(CH2N)2CN] (2d, bottom left), and V(NAd)Cl2[1,3-
(2,6-iPr2C6H3)2(CH2N)2CN] (5c, bottom right). Thermal ellipsoids are drawn at the 30% probability level, and H atoms are omitted for
clarity. Details are given in the Supporting Information.17
active site by more electron-donating substituents is important
for the observation of high activity.21
ethylene with norbornene (NBE) using the imidazolin-2-
iminato derivatives, V(N-2,6-Me2C6H3)Cl2[1,3-R2(CHN)2-
t
3. Copolymerization of Ethylene with Norbornene
(NBE) Using (Imido)vanadium(V) Dichloride Complexes
Containing Imidazolin-2-iminato and Imidazolidin-2-
iminato Ligands in the Presence of Al Cocatalysts.
Table 5 summarizes the results for the copolymerization of
CN] [R = Bu (1a), 2,6-Me2C6H3 (1b), 2,6-iPr2C6H3 (1c),
2,6-(Ph2CH)2-4-MeC6H2 (1e)] or V(NR′)Cl2[1,3-
(2,6-iPr2C6H3)2(CHN)2CN] [R′ = 1-adamantyl (3c), C6H5
(4c)], in the presence of Al cocatalysts (in toluene, ethylene 8
atm, 10 min).22
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Table 2. Ethylene Polymerization by V(N-2,6-
t
Me2C6H3)Cl2[1,3-R2(CHN)2CN] [R = Bu (1a), 2,6-
Me2C6H3 (1b), 2,6-iPr2C6H3 (1c), 2,6-(Ph2CH)2-4-MeC6H2
(1e)], V(NR′)Cl2[1,3-(2,6-iPr2C6H3)2(CHN)2CN] [R′ =
a
1-adamantyl (Ad, 3c), C6H5 (4c)] Cocatalyst Systems
complex
(μmol)
Al
temperature
yield
(mg)
b
c
cocatalyst Al/V
(°C)
activity
1a (0.04)
1a (0.04)
1a (0.04)
1b (0.04)
1b (0.04)
1b(0.04)
1b (0.04)
1b (0.04)
1b (0.04)
1b (2.0)
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
MAO
500
0
0
23
42
3450
6300
1000
1500
500
0
33
4950
0
67
10100
22500
27300
38300
17400
7650
1000
1500
2000
2500
2000
500
0
150
182
255
116
51
0
0
0
25
25
25
0
142
169
62
426
1b (2.0)
MAO
1000
200
507
1c (0.04)
1c (0.04)
1c (0.04)
1c (0.04)
1e (0.04)
1e (0.04)
1e (0.04)
1e (0.04)
1e (0.02)
3c (0.10)
3c (0.10)
3c (0.10)
3c (0.10)
4c (0.04)
4c (0.04)
4c (0.04)
4c (0.04)
4c (0.04)
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
9300
500
0
231
126
62
34700
18900
9300
1000
1500
100
0
0
0
trace
178
159
102
111
120
131
137
122
48
200
0
26700
23900
15300
33300
7200
500
0
1000
500
0
0
500
0
1000
1500
2000
250
0
7860
0
8220
0
7320
0
7200
500
0
286
205
171
118
42900
30800
25600
17700
1000
1500
2000
0
0
0
a
Conditions: toluene 30 mL, ethylene 8 atm, 10 min, Et2AlCl or
d-MAO (prepared by removing toluene and AlMe3 from ordinary
b
c
MAO). Molar ratio of Al/V. Activity in kg-PE/mol-V·h.
Although the activities observed for 1a−c were lower than
those found in ethylene homopolymerization, the copolymer-
ization proceeded with moderate catalytic activities, affording
ultrahigh molecular weight polymers with uniform molecular
weight distributions (runs 1−14). The activities of the 2,6-
dimethylphenylimido analogues (1a−c) Et2AlCl catalyst
systems under the same conditions (ethylene 8 atm, NBE
0.50 mmol/mL, under optimized A/V molar ratio) increased in
the order: 1a (102 kg-polymer/mol-V·h) < 1b (1920) < 1c (4830).
The activity of the 1c Et2AlCl catalyst system decreased upon
increasing the NBE concentrations (0.50 M → 0.90M), and the
activity also decreased upon increasing the polymerization temper-
ature (run 9 vs run 6). In contrast, the activity in the presence of
MAO cocatalyst increased at 25 °C (runs 11−12), although these
values were low even under the optimized conditions.
The activity in the copolymerization by V(NR′)Cl2[1,3-
(2,6-iPr2C6H3)2(CHN)2CN] [R′ = 2,6-Me2C6H3 (1c), 1-
adamantyl (3c), C6H5 (4c)] Et2AlCl catalyst systems under
optimized Al/V molar ratios (ethylene 8 atm, NBE 0.50 mmol/mL)
increased in the order: 3c (R′ = Ad, activity =2850 kg-polymer/
mol-V·h, run 16) < 1c (R′ = 2,6-Me2C6H3, 4830, run 6) < 4c (R′ =
Ph, 7080, run 24). The same order was observed, when these
612
dx.doi.org/10.1021/ic402747d | Inorg. Chem. 2014, 53, 607−623

Inorganic Chemistry
Article
Figure 3. Plots of catalytic activity (kg-PE/mol-V·h) vs Al/V molar ratios in ethylene polymerization using (imido)vanadium complexes containing
⧫
◊
●
○
imidazolin-2-iminato and imidazolidin-2-iminato ligands (on the basis of data in Tables 2 and 3). Left: complexes 1a ( ), 1b ( ), 1c ( ), 1e ( ), 3c
⧫
◊
□
■
□
●
○
( ), and 4c ( ). Right: complexes 2a ( ), 2b ( ), 2c ( ), 2d ( ), and 5c ( ). V(NR′)Cl2[1,3-R2(CHN)2CN] [R′ = 2,6-Me2C6H3 (1a,c,e), Ad
t
(3c), Ph (4c), shown left]; V(NR′)Cl2[1,3-R2(CH2N)2CN] [R′ = 2,6-Me2C6H3 (2a-d), Ad (5c), shown right]; R = Bu (a), 2,6-Me2C6H3 (b),
2,6-iPr2C6H3 (c), 2,6-Ph2C6H3 (d), 2,6-(Ph2CH)2-4-MeC6H2 (e).
Table 3. Ethylene Polymerization by V(N-2,6-
Table 4. Selected Data for Ethylene Polymerization by V(N-
t
t
Me2C6H3)Cl2[1,3-R2(CH2N)2CN] [R = Bu (2a), 2,6-
2,6-Me2C6H3)Cl2[1,3-R2(CHN)2CN] [R = Bu (1a), 2,6-
Me2C6H3 (2b), 2,6-iPr2C6H3 (2c), C6H5 (2d)], and
Me2C6H3 (1b), 2,6-iPr2C6H3 (1c), 2,6-(Ph2CH)2-4-MeC6H2
(1e)], V(N-2,6-Me2C6H3)Cl2[1,3-R2(CH2N)2CN] [R =
tBu (2a), 2,6-Me2C6H3 (2b), 2,6-iPr2C6H3 (2c), C6H5 (2d)],
V(NR′)Cl2[1,3-(2,6-iPr2C6H3)2(CHN)2CN] [R′ = Ad (3c),
C6H5 (4c)], V(NAd)Cl2[1,3-(2,6-iPr2C6H3)2(CH2N)2CN]
V(NAd)Cl2[1,3-(2,6-iPr2C6H3)2(CH2N)2CN] (5c)
a
Cocatalyst Systems
complex
(μmol)
Al
temperature
yield
b
c
cocatalyst Al/V
(°C)
(mg)
activity
a
(5c) Et2AlCl Catalyst Systems
2a (0.04)
2a (0.04)
2a (0.04)
2b (0.04)
2b (0.04)
2b (0.04)
2b (0.04)
2b (0.04)
2b (2.0)
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
MAO
500
0
0
58
88
8700
13200
9000
1000
1500
500
δ (ppm)
0
60
51V
NMR
complex
(μmol)
Al
cocatalyst Al/V activity
b
c
d
R′; R
0
163
213
195
190
40
24500
32000
29300
28500
6000
imidazolin-2-iminato
1a (0.04) Et2AlCl
1b (0.04) Et2AlCl
1000
1500
2000
1000
500
0
t
2,6-Me2C6H3; Bu
1000
2000
6300
−85
−148
0
2,6-Me2C6H3; 2,6-
Me2C6H3
38300
0
25
25
25
0
2,6-Me2C6H3;
2,6-iPr2C6H3
1c (0.04)
1e (0.04)
Et2AlCl
Et2AlCl
500
200
34700
26700
−147
−107
167
209
106
193
153
126
151
133
178
127
104
27
501
2b (2.0)
MAO
1000
500
627
2,6-Me2C6H3; 2,6-
(Ph2CH)2-4-
MeC6H2
2c (0.04)
2c (0.04)
2c (0.04)
2c (0.04)
2c (2.0)
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
MAO
15900
29000
23000
18900
453
1000
1500
2000
1000
200
0
1-adamantyl (Ad);
3c (0.10)
4c (0.04)
Et2AlCl
Et2AlCl
1500
500
8220
−257
−180
0
2,6-iPr2C6H3
0
C6H5; 2,6-iPr2C6H3
42900
25
0
imidazolidin-2-iminato
2d (0.04)
2d (0.04)
2d (0.04)
2d (0.04)
5c (0.10)
5c (0.10)
5c (0.10)
5c (0.10)
5c (0.10)
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
20000
26700
19100
15600
1620
t
2,6-Me2C6H3; Bu
2a (0.04)
Et2AlCl
1000
13200
32000
−77
−158
500
0
2,6-Me2C6H3; 2,6-
Me2C6H3
2b (0.04) Et2AlCl
1000
1000
500
1000
1500
250
0
0
2,6-Me2C6H3;
2,6-iPr2C6H3
2c (0.04)
2d (0.04) Et2AlCl
5c (0.10) Et2AlCl
Et2AlCl
29000
26700
9420
−140
−99
0
500
0
136
143
157
141
8160
2,6-Me2C6H3; 2,6-
C6H5
1000
1500
2000
0
8580
1-adamantyl (Ad);
2,6-iPr2C6H3
1500
−251
0
9420
0
8460
a
Conditions: toluene 30 mL, ethylene 8 atm, 0 °C, 10 min, Et2AlCl
a
Conditions: toluene 30 mL, ethylene 8 atm, 10 min, Et2AlCl or
d-MAO (prepared by removing toluene and AlMe3 from ordinary
b
c
d
cocatalyst. Molar ratio of Al/V. Activity in kg-PE/mol-V·h. In
CDCl3 at 25 °C.
b
c
MAO). Molar ratio of Al/V. Activity in kg-PE/mol-V·h.
copolymerizations were conducted at rather higher NBE
concentrations (0.50 M → 0.90M), although the activities of
3c (run 19) and 4c (run 27) became low as observed for 1c
(run 10). The resulting polymers were poly(ethylene-co-NBE)s
with ultrahigh molecular weights with uniform molecular
weight distributions. These results suggest that the copoly-
merization proceeded with uniform catalytically active species.
The NBE contents in the resulting copolymers prepared by
1c, 3c, and 4c Et2AlCl catalyst systems increased upon
increasing the NBE concentration from 0.50 to 0.90 M [1c,
15.3 mol % (run 6) → 23.2 mol % (run 10); 3c, 14.9 mol %
(run 16) → 19.4 mol % (run 19); 4c, 14.5 mol % (run 24) →
21.9 mol % (run 27)]. Significant differences were not observed
in terms of NBE incorporation by 1c, 3c, and 4c under these
613
dx.doi.org/10.1021/ic402747d | Inorg. Chem. 2014, 53, 607−623

Inorganic Chemistry
Article
cocatalyst on the activities. The observed facts are in interesting
contrast to what had been observed for the copolymerization
using V(N-2,6-Me2C6H3)Cl2(O-2,6-Me2C6H3) Al cocatalyst
systems in which both the activity and the NBE incorporations
were affected by the Al cocatalyst and the solvent employed.6c,d
Table 6 summarizes the results of the copolymerization of
ethylene with norbornene (NBE) using the imidazolidin-2-iminato
derivatives, V(NR′)Cl2[1,3-(2,6-iPr2C6H3)2(CH2N)2CN] [R′ =
2,6-Me2C6H3 (2c), 1-adamantyl (Ad, 5c)], in the presence of
Al cocatalysts (in toluene, 10 min).22
The activities of the arylimido complex 2c were generally
higher than those of its adamantylimido congener 5c, and the
activities decreased upon increasing the NBE concentration
charged: the activities were low when these copolymerizations
were conducted at 60 °C (runs 35, 43), probably because of
deactivation of the catalytically active species. The resulting
polymers were poly(ethylene-co-NBE)s possessing ultrahigh
molecular weights with uniform molecular weight distributions.
These results also suggest that the copolymerizations proceed
with uniform catalytically active species. The NBE contents in
the resultant copolymers prepared by 2c, 5c Et2AlCl catalyst
systems increased upon increasing the NBE concentration from
0.50 to 0.90 M, but the NBE contents did not increase upon
further increase of the NBE concentration (0.90 → 2.50 M),
Figure 4. Plots of catalytic activity (kg-PE/mol-V·h) vs chemical shifts
(δ in ppm) of the vanadium complexes (based on data in Table 4).
conditions, although, as described above, the activities were
affected by the nature of the imido ligand employed. Moreover,
it is interesting to note that the NBE contents (in the
copolymers by 1c, 3c, 4c Et2AlCl catalyst systems) did not
increase upon further increasing of the NBE concentration
(0.90 M → 2.50M), although the observed activities became
low under high NBE concentration conditions. It might also
be interesting to note that the NBE content in the resulting
copolymers was not affected by the Al cocatalyst employed
(Et2AlCl, d-MAO, Me2AlCl), despite a rather strong impact Al
Table 5. Copolymerization of Ethylene with Norbornene (NBE) by V(N-2,6-Me2C6H3)Cl2[1,3-R2(CHN)2CN] [R = tBu (1a),
2,6-Me2C6H3 (1b), 2,6-iPr2C6H3 (1c), 2,6-(Ph2CH)2-4-MeC6H2 (1e)], V(NR′)Cl2[1,3-(2,6-iPr2C6H3)2(CHN)2CN] [R′ =
a
1-adamantyl (Ad, 3c), C6H5 (4c)] Cocatalyst Systems
b
c
d
e
e
f
run
complex(μmol) Al cocatalyst Al/V
500
NBE (mol/L)
temperature (°C) yield (mg) activity
Mn × 10−5
Mw/Mn
NBE (mol %)
16.5
1
1a (2.0)
1a (2.0)
1b (0.2)
1b (0.2)
1c (0.2)
1c (0.2)
1c (0.2)
1c (0.2)
1c (0.4)
1c (0.2)
1c (2.0)
1c (2.0)
1c (1.2)
1c (1.2)
3c (0.2)
3c (0.2)
3c (0.2)
3c (0.2)
3c (0.2)
3c (0.2)
3c (1.2)
4c(0.2)
4c(0.2)
4c(0.1)
4c(0.2)
4c(0.2)
4c(0.2)
4c(1.2)
4c(1.2)
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
d-MAO
d-MAO
Et2AlCl
Me2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Me2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Me2AlCl
0.50
0.50
0.50
0.50
0.50
0.50
0.50
0.50
0.50
0.90
0.90
0.90
2.50
2.50
0.50
0.50
0.50
0.50
0.90
0.90
2.50
0.50
0.50
0.50
0.50
0.50
0.90
2.50
2.50
0
0
34
14
102
42
18.1
19.5
27.1
25.8
23.1
22.5
19.4
16.7
17.2
18.5
10.4
16.2
10.1
9.6
1.8
2.2
1.7
2.0
2.1
1.9
1.8
2.3
2.4
2.4
1.7
1.9
2.0
2.3
2.3
2.6
2.5
2.8
2.1
2.3
2.5
1.8
2.1
2.4
2.0
2.5
2.1
2.2
2.5
2
1000
500
1000
250
500
1000
1500
500
500
500
1000
500
500
250
500
1000
500
500
500
500
250
500
500
1000
1500
500
500
500
3
0
64
1920
1080
600
13.4
4
0
36
5
0
20
6
0
161
72
4830
2160
2040
720
15.3
14.8
7
0
8
0
68
9
25
0
48
10
11
12
75
2250
129
23.2
34.1
26.1
24.5
26.3
25
0
43
31
93
g
13
0
53
265
g
14
0
61
305
15
16
17
18
19
20
0
27
810
17.1
16.5
13.8
12.4
10.7
12.2
4.8
0
95
2850
2340
1100
1710
3600
160
14.9
0
78
25
0
37
57
19.4
20.8
26.2
14.2
0
120
32
g
21
0
22
23
24
25
26
27
0
59
1770
6510
7080
4920
3960
4710
420
19.8
19.1
18.8
16.9
13.3
12.8
7.8
0
217
118
164
132
157
84
0
14.5
0
0
0
21.9
24.8
25.2
g
28
0
g
29
0
97
485
6.4
a
Conditions: toluene 30 mL, ethylene 8 atm, 10 min, Et2AlCl, Me2AlCl or d-MAO (prepared by removing toluene and AlMe3 from ordinary MAO) cocatalyst.
b
c
d
e
Molar ratio of Al/V. Norbornene (NBE) concentration charged (mol/L). Activity in kg-polymer/mol-V·h. GPC data in o-dichlorobenzene vs
f
g
polystyrene standards. Comonomer content estimated by 13C NMR spectra. Toluene 10 mL.
614
dx.doi.org/10.1021/ic402747d | Inorg. Chem. 2014, 53, 607−623

Inorganic Chemistry
Article
t
Table 6. Copolymerization of Ethylene with Norbornene (NBE) by V(N-2,6-Me2C6H3)Cl2[1,3-R2(CH2N)2CN] [R = Bu
(2a), 2,6-Me2C6H3 (2b), 2,6-iPr2C6H3 (2c), C6H5 (2d)] and V(NAd)Cl2[1,3-(2,6-iPr2C6H3)2(CH2N)2CN] (5c) Cocatalyst
a
Systems
complex
(μmol)
Al
temperature
ethylene
(atm)
yield
(mg)
b
c
d
e
e
f
run
cocatalyst Al/V
NBE (mol/L)
(°C)
activity Mn × 10−5 Mw/Mn NBE (mol %)
30
31
32
33
34
35
2c (0.2)
2c (0.2)
2c (0.2)
2c (0.2)
2c (0.2)
2c (1.2)
2c (0.2)
2c (0.2)
2c (1.2)
5c (0.2)
5c (0.2)
5c (0.2)
5c (0.2)
5c (1.2)
5c (1.2)
5c (1.2)
5c (2.0)
5c (2).0
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Me2AlCl
Me2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Me2AlCl
Me2AlCl
Me2AlCl
125
0.50
0.50
0.50
0.50
0.90
0.90
2.50
2.50
2.50
0.50
0.50
0.50
0.90
0.90
2.50
2.50
2.50
2.50
0
0
8
8
8
8
8
8
8
8
4
8
8
8
8
8
8
8
4
2
98
173
157
112
102
10
2940
5190
4710
3360
3060
50
25.1
24.4
23.9
19.8
17.5
11.4
10.2
11.8
7.6
1.8
1.9
2.1
2.0
2.4
3.5
2.6
2.4
2.3
1.9
2.0
2.3
2.5
2.7
2.4
2.2
2.6
3.2
250
500
1000
250
250
250
250
250
250
500
1000
500
500
500
500
500
0
11.3
24.0
0
0
60
0
g
36
29
870
26.1
27.0
32.8
g
37
g
0
59
1770
265
38
0
53
39
40
41
42
43
0
74
2220
3450
2880
1920
145
17.4
15.9
13.7
9.6
0
115
96
10.0
11.3
17.7
0
0
64
60
0
29
5.4
g
44
44
220
5.7
23.1
24.7
29.6
g
45
0
69
345
6.1
g
46
0
63
189
2.8
g
47
500
0
27
81
1.3
37.3
a
b
c
d
e
Conditions: toluene 30 mL, 10 min. Molar ratio of Al/V. Norbornene concentration charged (mol/L). Activity in kg-polymer/mol-V·h. GPC
f
g
data in o-dichlorobenzene vs polystyrene standards. Comonomer content estimated by 13C NMR spectra. Toluene 10 mL.
Table 7. Selected Data for Copolymerization of Ethylene with Norbornene (NBE) by V(N-2,6-Me2C6H3)Cl2[1,3-R2(CHN)2CN]
t
[R = Bu (1a), 2,6-Me2C6H3 (1b), 2,6-iPr2C6H3 (1c)], V(NR′)Cl2[1,3-(2,6-iPr2C6H3)2(CHN)2CN] [R′ = Ad (3c), C6H5 (4c)],
a
V(NR′)Cl2[1,3-(2,6-iPr2C6H3)2(CH2N)2CN] [R′ = 2,6-Me2C6H3 (2c), Ad (5c)] Et2AlCl Catalyst Systems
b
c
d
e
e
f
run
complex V(NR′)Cl2(L)
Al/V
NBE (mol/L)
activity
Mn × 10−5
Mw/Mn
NBE (mol %)
R′
R
(μmol)
1
2,6-Me2C6H3
2,6-Me2C6H3
2,6-Me2C6H3
2,6-Me2C6H3
1-adamantyl
C6H5
tBu
1a (2.0)
1b (0.2)
1c (0.2)
2c (0.2)
3c (0.2)
4c (0.1)
5c (0.2)
1c (0.2)
2c (0.2)
3c (0.2)
4c (0.2)
5c (0.2)
500
500
500
250
500
500
500
500
250
500
500
500
0.50
0.50
0.50
0.50
0.50
0.50
0.50
0.90
0.90
0.90
0.90
102
1920
4830
5190
2850
7080
3450
2250
3060
1710
4710
1920
18.1
27.1
22.5
24.4
16.5
18.8
15.9
18.5
17.5
10.7
12.8
9.6
1.8
1.7
1.9
1.9
2.6
2.4
2.0
2.4
2.4
2.1
2.1
2.5
16.5
13.4
15.3
3
2,6-Me2C6H3
2,6-iPr2C6H3
2,6-iPr2C6H3
2,6-iPr2C6H3
2,6-iPr2C6H3
2,6-iPr2C6H3
2,6-iPr2C6H3
2,6-iPr2C6H3
2,6-iPr2C6H3
2,6-iPr2C6H3
2,6-iPr2C6H3
6
31
16
24
40
10
34
19
27
42
14.9
14.5
10.0
23.2
24.0
19.4
21.9
17.7
1-adamantyl
2,6-Me2C6H3
2,6-Me2C6H3
1-adamantyl
C6H5
1-adamantyl
0.90
a
b
c
Conditions: toluene 30 mL, ethylene 8 atm, 10 min, 0 °C, Et2AlCl cocatalyst. Molar ratio of Al/V. Norbornene (NBE) concentration charged
d
e
f
(mol/L). Activity in kg-polymer/mol-V·h. GPC data in o-dichlorobenzene vs polystyrene standards. Estimated by 13C NMR spectra.
although the activities decreased under high NBE concen-
trations. Significant differences were not observed in terms of
NBE incorporation by 2c and 5c under these conditions,
although, as described above, the activities were affected by the
nature of the imido ligand. It might also be interesting to note
that the NBE content in the resulting copolymers was not
affected by the Al cocatalyst employed (Et2AlCl, Me2AlCl),
although the activities were indeed.
It is interesting to note that the NBE contents in the
resulting copolymer increased upon conducting these copoly-
merizations at low ethylene pressure (ethylene 2 or 4 atm, runs
38, 46, 47), although the NBE contents did not exceeded values
of ca. 25−27 mol % if these copolymerizations were conducted
even under high NBE concentration (ethylene 8 atm). It is an
interesting observation that the NBE content in the copolymer
can be increased to rather high values by varying the ethylene
pressure (and the reaction temperature for the 1c Et2AlCl
catalyst system).
Table 7 summarizes the selected results for the copoly-
merization using the imidazolin-2-iminato and the imidazolidin-
2-iminato analogues employed in this study for comparison. It
is clear that the activities were affected by the imido ligand
employed. The activity was also affected by the substituents
present in the imidazolin-2-iminato ligands (see 1a−c). No
significant differences were observed between the imidazolin-2-
iminato and imidazolidin-2-iminato precatalysts in terms of
both activity and NBE incorporation. Moreover, no significant
ligand effects were observed with respect to the NBE content in
the copolymers, although it seems justified to state that the
adamantylimido complexes (3c, 5c) showed rather less efficient
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Figure 5. 13C NMR spectra (in 1,2,4-trichlorobenzene/C6D6 at 120 °C) for poly(ethylene-co-norbornene)s prepared by (a) V(N-2,6-
Me2C6H3)Cl2[1,3-(2,6-iPr2C6H3)2(CHN)2CN] (1c) Et2AlCl catalyst system (NBE 0.90 M, run 10), (b) V(N-2,6-Me2C6H3)Cl2[1,3-
(2,6-iPr2C6H3)2(CH2N)2CN] (2c) Et2AlCl catalyst system (NBE 0.90 M, run 34), (c) 1c d-MAO catalyst system (NBE 0.90 M, run 12), d)
1c Et2AlCl catalyst system (NBE 2.50 M, run 13).
NBE incorporation under these conditions (especially under
NBE 0.90 M conditions, runs 19, 42).
Figure 5 shows selected 13C NMR spectra in the resultant
poly(ethylene-co-NBE)s prepared by 1c, 2c Al cocatalyst
systems.22 Resonances ascribed to carbon atoms corresponding
to isolated and alternating NBE insertions were observed in the
spectra in all cases,22 and integration ratio revealed that the
ratio of the peaks corresponding to isolated and alternating
NBE units were not changed even under high NBE con-
centration conditions (Figures 5a,d; NBE 0.90 vs 2.50 M),
although the activity decreased remarkably upon increasing the
NBE concentration charged (runs 10 vs 13). Moreover, no
significant differences were observed in the spectra of the
polymers obtained from imidazolin-2-iminato (1c) or imida-
zolidin-2-iminato (2c) derivatives. It might be interesting to
note that the ratio of peaks corresponding to isolated and
alternating NBE units in the copolymer prepared by the 1c
MAO catalyst system was somewhat different from that
obtained from the 1c Et2AlCl catalyst system conducted
under the same conditions, although the NBE content in the
resulting copolymers was similar (Figures 5a,c; runs 10, 12).
Because the resonances ascribed to NBE repeated insertions
were not observed in these NMR spectra,22 we assume that
these spectra might explain why the synthesis of copolymer
with high NBE contents is difficult by use of these catalysts.
Figure 6 shows selected 13C NMR spectra of the resulting
poly(ethylene-co-NBE)s prepared by the 5c Me2AlCl catalyst
system conducted under high NBE concentrations (NBE
Figure 6. 13C NMR spectra (in 1,2,4-trichlorobenzene/C6D6 at
2.50 M), and under various ethylene pressures (ethylene 2−8
120 °C) for poly(ethylene-co-norbornene)s prepared by V(NAd)-
atm, runs 45−47).22 As described above, resonances ascribed to
Cl2[1,3-(2,6-iPr2C6H3)2(CH2N)2CN] (5c) Me2AlCl catalyst
carbon atoms corresponding to isolated and alternating NBE
system (a) NBE content 24.7 mol % (NBE 2.50 M, ethylene
insertions were observed in the spectra,22 and a small amount
of the resonances ascribed to the NBE repeat units was
also observed in the copolymer obtained under low ethylene
8 atm, run 45), (b) NBE content 29.6 mol % (NBE 2.50 M,
ethylene 4 atm, run 46), (c) NBE content 37.3 mol % (NBE
2.50 M, ethylene 2 atm, run 47).
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a
Scheme 4. Possible Insertion Modes after Norbornene (NBE) or Ethylene Insertion in the Ethylene/NBE Copolymerization
a
kNE denotes a rate of ethylene insertion after NBE incorporation, and kNN denotes a rate of NBE insertion after NBE incorporation (NBE repeated
insertion). kNEE denotes a rate of ethylene insertion (isolated NBE incorporation), and kNEN denotes a rate of NBE insertion (alternative NBE
incorporation).
pressure conditions (Figure 6c, ethylene 2 atm, run 47).
Although the activity dropped upon decreasing the ethylene
pressure (runs 45−47), these results clearly indicate that the
NBE contents in the copolymer can be modified even under
high NBE concentration conditions by varying the ethylene
pressure. This fact is interesting with regard to the observation
that the NBE content did not increase even under high NBE
concentration conditions, as described above.
On the basis of the above facts that (i) the NBE content as
well as the microstructures of the copolymer can be modified
by ethylene pressure under high NBE concentration conditions
and that (ii) significant changes in the NBE content and the
microstructure of the copolymers were not observed when the
copolymerizations were conducted under rather high NBE
concentration (NBE 0.90−2.50 M) under the same ethylene
pressure, we may consider an assumption shown in Scheme 4.
There might be equilibrium of coordination and dissociation of
two olefins to the metal center, and it seems clear (from the 13C
NMR spectra) that repeated NBE incorporation would be
difficult (probably) due to a steric bulk. This suggests that the
rate of NBE incorporation after NBE insertion (denoted as
these facts, it seems likely that the NBE contents as well as
the microstructures in the copolymers are controlled by the
ethylene concentration charge and, therefore, by the degree of
ethylene insertion but not by the [NBE]/[E] molar ratio in the
solution under these conditions. Although it seems difficult to
obtain copolymers with high NBE contents, the present
catalysts are suited for the synthesis of ultrahigh molecular
weight copolymers with high catalytic activities; they might also
be suited for synthesis of the end-functionalized copolymers in
the presence of certain chain transfer reagents.
4. Copolymerization of Ethylene with 5-Ethylidene-2-
norbornene (ENB) Using (Imido)vanadium(V) Dichloride
Complexes Containing Imidazolin-2-iminato and Imida-
zolidin-2-iminato Ligands in the Presence of Al
Cocatalysts. Table 8 summarizes results in copolymerization
of ethylene with 5-ethylidene-2-norbornene (ENB) using V(N-
2,6-Me2C6H3)Cl2[1,3-(2,6-iPr2C6H3)(CH2N)2CN] (2c) and
V(NPh)Cl2[1,3-(2,6-iPr2C6H3)2-(CHN)2CN] (4c) cocata-
lyst systems.24 Complexes 2c and 4c have been chosen because
these complexes showed high catalytic activities in the ethylene
copolymerization with norbornene (NBE), as shown above.
1
kNN) should be much smaller than that of ethylene in-
The ENB contents were estimated on the basis of H NMR
corporation after NBE insertion (denoted as kNE, Scheme 4a).
A decrease in the activity by increasing the NBE concentration
(without increase in the NBE content) may be due to a favored
NBE coordination without incorporation (formation of certain
dormant species that suppress ethylene coordination).6d,23
Moreover, it may be assumed that the rate of NBE alternating
incorporation (NBE incorporation after insertion of NBE
followed by ethylene, denoted as kNEN) would be smaller than
that of ethylene incorporation after NBE insertion (ethylene
incorporation after insertion of NBE followed by ethylene,
denoted as kNEE). This fact may also explain that use of the 1c
d-MAO catalyst system (probably forming isolated cationic
alkyl species because of the bulky, delocalized MAO anion)
showed better NBE incorporation than the 1c Et2AlCl catalyst
system (formation of associated cationic alkyl species through
interaction with halogenated Al alkyls).5e,6c,d,8b Based on
spectra according to the previous reports.24
The catalytic activities in the copolymerization with ENB
displayed by the 2c Et2AlCl catalyst system were higher than
those in the copolymerization with NBE [e.g., NBE or ENB 0.50
M: activity 5190 kg-polymer/mol-V·h (NBE, run 31) vs 7620
(ENB, run 50)], although the activity of 4c was similar in these
copolymerizations [e.g., activity 7080 kg-polymer/mol-V·h (NBE,
run 24) vs 7020 (ENB, run 60)]. The activity of 2c decreased
upon increasing the ENB concentration (runs 50, 52, 53).
The resulting copolymers possessed uniform molecular
weight distributions but rather low molecular weights (Mn =
7000−128 000, Mw/Mn = 2.4−2.8). Interestingly, this is in
contrast to the characteristics of the resulting poly(ethylene-co-
NBE)s obtained under the similar conditions [Mn = 1.02−2.51
× 106 (with 2c), 6.4−19.8 × 105 (with 4c)]. It should be noted
that the ENB contents in the resulting copolymers were higher
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Table 8. Copolymerization Results of Ethylene with 5-Ethylidene-2-norbornene (ENB) by V(N-2,6-Me2C6H3)Cl2[1,3-
a
(2,6-iPr2C6H3)(CH2N)2CN] (2c), V(NPh)Cl2[1,3-(2,6-iPr2C6H3)2(CHN)2CN] (4c) Cocatalyst Systems
b
c
d
e
run
complex (μmol)
Al cocatalyst
Al/V
ENB (mol/L)
yield (mg)
activity
Mn × 10−3
Mw/Mn
ENB (mol %)
48
49
50
51
52
53
54
55
56
57
58
59
60
2c (0.1)
2c (0.1)
2c (0.1)
2c (0.1)
2c (0.1)
2c (0.1)
2c (1.0)
2c (1.0)
2c (1.0)
4c (0.1)
4c (0.1)
4c (0.1)
4c (0.1)
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
d-MAO
d-MAO
d-MAO
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
500
1000
1500
2000
1500
1500
1000
1500
2000
500
0.50
0.50
0.50
0.50
1.50
2.50
0.50
0.50
0.50
0.50
0.50
0.50
0.50
98
110
127
123
93
5880
6600
7620
7380
5580
3480
336
7.0
7.4
2.8
2.7
2.8
2.7
2.7
2.8
2.5
2.6
2.5
2.5
2.4
2.5
2.7
38.7
38.2
39.7
8.5
7.8
6.4
44.6
53.5
18.3
19.5
58
6.2
56
9.2
68
408
10.1
9.6
64
384
86
5160
5700
6900
7020
9.4
36.5
37.1
35.9
1000
1500
2000
95
10.7
12.8
11.5
115
117
a
Conditions: toluene 30 mL, ethylene 8 atm, 10 min, 0 °C, Et2AlCl or d-MAO (prepared by removing toluene and AlMe3 from ordinary MAO)
b
c
d
cocatalyst. Initial monomer concentration charged (mol/L). Activity in kg-polymer/mol-V·h. GPC data in o-dichlorobenzene vs polystyrene
standards. Estimated by H NMR spectra.
e
1
than the NBE contents under similar comonomer (NBE or
ENB) concentration [e.g., by 2c, NBE 11.3 mol % (run 32) vs
ENB 39.7 mol % (run 50); 4c, NBE 14.5 mol % (run 24) vs
ENB 35.9 mol % (run 59); ethylene 8 atm, NBE or ENB 0.50 M].
Moreover, synthesis of the copolymer with ENB content
higher than 50 mol % has been attained upon increasing the
ENB concentration. This can be regarded as unique contrast
between these two types of copolymerizations, although the
reasons for the observed difference are not clear at this
moment. It might also be interesting to note that the ENB
content in the resulting copolymers prepared with the 2c MAO
catalyst system were lower than those prepared with the 2c
Et2AlCl catalyst system, despite the observation of significant
differences in the copolymerization with NBE.
Although the molecular weights of the resulting copolymers
were lower than those obtained in the copolymerization with
NBE, the observation described above are interesting to the
effect that the norbornene substituent does not only affect the
catalytic activity but also the comonomer incorporation and the
molecular weights of the resulting copolymers.
(2) These complexes showed high catalytic activity for
ethylene polymerization especially in the presence of Et2AlCl
cocatalyst. Both the 2,6-Me2C6H3 (1b, 2b) and the
2,6-iPr2C6H3 (1c, 2c) derivatives showed higher catalytic activ-
t
ities than the Bu analogues (1a, 2a): a reason for the low
activities displayed by 1a and 2a may be tentatively related to
rather small VNC(imido) bond angles (as described
above). Among the (arylimido)vanadium(V) dichloride com-
plexes, the imidazolin-2-iminato analogues exhibited higher
activities than their imidazolidin-2-iminato congeners. A
relatively good relationship between the activity and the
chemical shift [51V NMR spectra in CDCl3 (δ in ppm, at
25 °C)] was observed for the (arylimido)vanadium complexes
(1a−c,e, 2a−d, 4c), indicating that a certain degree of electron
donation through the anionic ligands play a role toward the
high activity probably by a stabilization of the active site by
more electron-donating substituents.
(3) The copolymerization of ethylene with norbornene
(NBE) proceeded with high catalytic activities, affording
ultrahigh molecular weight polymers with uniform molecular
weight distributions. The activities of the 2,6-iPr2C6H3 ana-
logues (1c) showed higher than those by the others (1a,b), and
the activity of V(NR′)Cl2[1,3-(2,6-iPr2C6H3)2(CHN)2 CN]
increased in the order: 3c (R′ = Ad) < 1c (R′ = 2,6-Me2C6H3)
< 4c (R′ = Ph). No significant differences were observed
between the imidazolin-2-iminato and imidazolidin-2-iminato
complexes in terms of both activity and NBE incorporation.
Although it seems difficult to obtain copolymers with high NBE
contents, the present catalysts are promising candidates for the
efficient synthesis of ultrahigh molecular weight copolymers
with high catalytic activities.
CONCLUSION
■
We have prepared a series of (imido)vanadium complexes
containing imidazolin-2-iminato and imidazolidin-2-iminato
ligands and reported their use as catalyst precursors for ethylene
polymerization and copolymerization with cyclic olefins. The
results of this study can be summarized as follows:
(1) A series of (imido)vanadium(V) dichloride complexes
containing 1,3-imidazolin-2-iminato or 1,3-imidazolidin-2-imina-
to ligands of the type, V(N-2,6-Me2C6H3)Cl2[1,3-R2(CHN)2-
t
CN] [R = Bu (1a), 2,6-Me2C6H3 (1b), 2,6-iPr2C6H3 (1c),
2,6-(C6H5)2CH-4-MeC6H2 (1e)], V(N-2,6-Me2C6H3)Cl2[1,3-
(4) The complexes 2c and 4c showed high catalytic activities
for the ethylene copolymerization with 5-ethylidene-2-norbor-
nene (ENB) in the presence of Et2AlCl cocatalyst. Notable
improvement in the comonomer (ENB) incorporations can be
achieved, although the resulting polymers possessed rather low
molecular weights compared to those obtained from the
copolymerization with NBE. This constitutes another interest-
ing feature of this type of catalysis.
t
R2(CH2N)2CN] [R = Bu (2a), 2,6-Me2C6H3 (2b), 2,6-
i Pr2 C6 H3 (2c ), C6 H5 (2d )], V(NR′)Cl2 [1, 3-
(2,6-iPr2C6H3)2(CHN)2CN] [R′ = 1-adamantyl (Ad, 3c),
C6H5 (4c)], or V(NAd)Cl2[1,3-(2,6-iPr2C6H3)2(CH2N)2CN]
(5c)] have been prepared and identified. The crystal structures
of 1a, 2a,c,d, 3c, 4c, and 5c were determined by X-ray crystallo-
graphy, revealing in all cases a distorted tetrahedral geometry
around the vanadium atom. The tert-butyl analogues (1a, 2a)
possess rather unique (small) VNC bond angles, especially
in the arylimido ligands, probably because of a steric reason.
We are currently exploring the possibility of synthesizing
polymers containing reactive functionalities by using comonomers
(cyclic olefins) containing reactive functional groups on the
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was removed under vacuum and the resulting residue was extracted
with n-hexane. After n-hexane was removed, the product was dissolved
in a small amount of n-hexane (about 1.5 mL). The solution was kept
at −30 °C. The brown solid (983 mg, 2.70 mmol) was obtained in
basis of the above facts through this study. We highly believe
that the results presented herein are highly promising for
further design of the catalysts for this purpose, and we hope to
be able to introduce more details in the near future.
1
53% yield. H NMR (CDCl3): δ 7.02 (t, 2H, ArH), 6.96 (d, 4H,
ArH), 5.70 (s, 4H, =CH), 2.20 (s, 12H, CH3), −0.11 (s, 9H,
Si(CH3)3). 13C NMR (CDCl3): δ 137.6, 137.2, 128.5, 128.4, 112.2,
18.3, 3.3.
EXPERIMENTAL SECTION
■
General Procedure. All experiments were carried out under a
nitrogen atmosphere in a Vacuum Atmospheres drybox unless
otherwise specified. All chemicals used were of reagent grade and
were purified by the standard purification procedures. Anhydrous
grade toluene, n-hexane, and 1,2-dichloromethane (Kanto Chemical
Co., Inc.) were transferred into bottles containing molecular sieves
(mixture of 3 Å 1/16 and 4 Å 1/8, and 13X 1/16) under a nitrogen
stream in the drybox and passed through a short alumina column
under N2 prior to use. Imidazolin-2-iminato ligands, 1,3-R2(CHN)2
CN(R = tBu,9a 2,6-iPr2C6H39b), and imidazolidin-2-iminato ligands,
The synthetic procedure of 1b is similar to that for 1a, except that
1,3-(2,6-Me2C6H3)2(CHN)2CNSiMe3 (545 mg, 1.50 mmol) was
used in place of 1,3-tBu2(CHN)2CNSiMe3. Green microcrystals
1
were collected in a yield of 79% (630 mg, 1.19 mmol). H NMR
(CDCl3): δ 7.23 (t, 2H, J = 7.40, ArH), 7.06 (d, 4H, J = 7.60, Ar
H), 6.76−6.71 (m, 5H, CH = and ArH), 2.09 (s, 12H, ArCH3), 2.05
(s, 6H, ArCH3). 13C NMR (CDCl3): δ 135.8, 134.8, 133.2, 130.1,
128.8, 126.9, 125.0, 116.7, 19.1, 17.9. 51V NMR (CDCl3): δ −148
(Δν1/2 = 1038 Hz). Anal. Calcd for C27H29Cl2N4V: C, 61.03 (58.77 +
VC, vanadium carbide); H, 5.50; N, 10.54. Found: C, 60.41; H, 5.68;
N, 10.28. The observed C values were somewhat low because of the
incomplete combustion (by production of vanadium carbide), whereas
both H and N observed values were close to the calculated values.
Synthesis of V(N-2,6-Me2C6H3)Cl2[1,3-(2,6-(Ph2CH)2-4-Me-
C6H2)2(CHN)2 CN] (1e). The ligand 1,3-(2,6-(Ph2CH)2-4-Me-
C6H2)2(CHN)2CNSiMe3 was prepared according to the literature
procedure.9b To a toluene solution (30 mL) containing 1,3-bis{2,6-
bis(diphenylmethyl)-4-methylphenyl}-imidazolin-2-ylidene,26 [1,3-
(2,6-(Ph2CH)2-4′-Me-C6H2)2(CHN)2C] (1.30 g, 1.42 mmol) in a
sealed Schlenk tube was added N3SiMe3 (0.23 g, 2 mmol) dropwise at
room temperature. The reaction mixture was stirred at 110 °C for
72 h. The solution was filtered through a Celite pad, and the filtercake
was washed with toluene. The combined filtrate and the wash were
placed in a rotary evaporator to remove all volatiles. A pale yellow
13b
1,3-R2(CH2N)2 CN(R = Bu,
2,6-Me2C6H3,13a 2,6-iPr2C6H3,16
t
C6H513a), and V(N-2,6-Me2C6H3)Cl3,14 V(NAd)Cl3,15 V(NPh)Cl3,
V(N-2,6-Me2C6H3)Cl2[1,3-(2,6-iPr2C6H3)2(CHN)2 CN](1c)12n
were prepared according to previous reports. Toluene and AlMe3 in
the commercially available methylaluminoxane (PMAO-S, 9.5 wt %
(Al) toluene solution, Tosoh Finechem Co.) were removed under
reduced pressure (at ca. 50 °C for removing toluene and AlMe3 and at
>100 °C for 1 h for completion) in the drybox to give white solids.
Et2AlCl and Me2AlCl in n-hexane (Kanto Chemical Co., Inc.) were
used as received under N2 stream in the drybox. Polymerization grade
ethylene (purity >99.9%, Sumitomo Seika Co., Ltd.) was used as
received.
8a
Elemental analyses were performed by using EAI CE-440 CHN/O/S
Elemental Analyzer (Exeter Analytical, Inc.). All 1H, 13C, and 51V NMR
spectra were recorded on a Bruker AV500 spectrometer (500.13 MHz
1
1
for H, 125.77 MHz for 13C, and 131.55 MHz for 51V). All spectra
precipitate was obtained (0.65 g, 0.65 mmol) in 46% yield. H NMR
(CDCl3): δ 7.22−7.17 (br, 20H, ArH), 7.07−7.05 (m, 12H, Ar
H), 6.87−6.85 (m, 12H, ArH), 5.57 (s, 4H, Ph2CH), 4.58 (s, 2H,
CH=), 2.20 (s, 6H, CH3), −0.43 (s, 9H, Si(CH3)3). 13C NMR
(CDCl3): δ 144.0, 143.5, 142.9, 137.8, 133.6, 130.1, 129.4, 129.2,
128.9, 128.4, 128.1, 128.0, 127.8, 126.1, 126.0, 125.9, 125.1, 112.8,
51.7, 21.6, 3.7.
were obtained in the solvent indicated at 25 °C unless otherwise
noted. Chemical shifts are given in ppm and are referenced to SiMe4
1
(δ 0.00 ppm, H, 13C) and VOCl3 (δ 0.00, 51V). Coupling constants
and half-width values, Δν1/2, are given in Hz. Molecular weights and
molecular weight distributions for the resultant polymers were
measured by gel permeation chromatography (Tosoh HLC-
8121GPC/HT) using a RI-8022 detector (for high temperature,
Tosoh Co.) with a polystyrene gel column (TSK gel GMHHR-H
HT × 2, 30 cm × 7.8 mm i.d.), ranging from <102 to <2.8 × 108 MW)
at 140 °C using o-dichlorobenzene containing 0.05 wt/v% 2,6-di-tert-
butyl-p-cresol as the solvent. The molecular weight was calculated by a
standard procedure based on the calibration with standard polystyrene
amples.
The synthetic procedure of 1e is similar to that for 1a, except that
1,3-(2,6-(Ph2CH)2-4-Me-C6H2)2(CHN)2CNSiMe3 (250 mg, 0.25
mmol) was used in place of 1,3-tBu2(CHN)2CNSiMe3. Green
microcrystals were collected in a yield of 82% (241 mg, 0.206 mmol).
1H NMR (CDCl3): δ 7.19 (br, 8H, ArH), 7.14−7.12 (m, 12H, Ar
H), 7.07−7.06 (m, 12H, ArH), 6.82 (s, 4H, ArH), 6.77 (br, 8H,
Ar), 6.68 (m, 3H, VNArH), 5.41 (s, 4H, Ph2CH), 4.62 (s, 2H,
CH=), 2.21 (s, 6H, CH3), 2.08 (s, 6H, CH3). 13C NMR (CDCl3): δ
143.3, 142.0, 141.8, 140.1, 135.5, 130.3, 130.1, 130.0, 129.1, 129.0,
128.9, 128.6, 128.2, 128.1, 128.0, 127.0, 126.9, 126.4, 125.1, 124.5,
115.9, 52.0, 31.4, 22.5, 21.9, 21.7, 18.8, 14.0. 51V NMR (CDCl3):
δ −107 (Δν1/2 = 2794 Hz). Anal. Calcd for C77H65Cl2N4V: C, 79.17
(78.14 + VC, vanadium carbide); H, 5.61; N, 4.80. Found: C, 78.13;
H, 5.95; N, 4.52.
Synthesis of V(N-2,6-Me2C6H3)Cl2[1,3-tBu2(CHN)2 CN] (1a).
To a toluene solution containing V(N-2,6-Me2C6H3)Cl3 (420 mg,
1.50 mmol) was added 1,3-tBu2(CHN)2CNSiMe3 at −30 °C. The
reaction mixture was warmed slowly to room temperature, and was
then stirred for 6 h. The solution was filtered through a Celite pad, and
the filtercake was washed with hot toluene. The combined filtrate and
the wash were placed in a rotary evaporator to remove volatiles. The
resultant solids were dissolved in a minimum amount of toluene and
placed in the freezer (cooled at −30 °C). The green crystals were
grown from the chilled solution. Yield: 463 mg (1.06 mmol, 71%). 1H
NMR (CDCl3): δ 6.83 (d, 2H, J = 7.60, CH=), 6.75−6.70 (m, 3H,
ArH), 2.52 (s, 6H, ArCH3), 1.62 (s, 18H, C(CH3)3). 13C NMR
(CDCl3): δ 135.3, 126.8, 125.1, 111.7, 59.5, 28.9, 18.8. 51V NMR
(CDCl3): δ −85 (Δ ν1/2 = 862 Hz) Anal. Calcd for C19H29Cl2N4V: C,
52.42; H, 6.71; N, 12.87. Found: C, 52.58; H, 6.51; N, 12.53.
Synthesis of V(N-2,6-Me2C6H3)Cl2[1,3-(2,6-Me2C6H3)2(CHN)2
CN] (1b). The ligand precursor, 1,3-(2,6-Me2C6H3)2(CHN)2C
NSiMe3 was prepared according to the literature procedure.9a,b To a
toluene solution containing 1,3-bis(2,6-dimethylphenyl)-imidazolin-2-
ylidene [1,3-(2,6-Me2C6H2)2(CHN)2C] (1.0 g, 3.62 mmol), which
was prepared from 1,3-bis-(2,6-dimethylphenyl)-1H-imidazol-3-ium
chloride25 by treatment of KOtBu in THF followed by extraction with
hot toluene,9a,b was added N3SiMe3 (583 mg, 5.07 mmol) in a sealed
tube. The mixture was refluxed for 72 h. After the solvent cooled, it
Synthesis of V(N-2,6-Me2C6H3)Cl2[1,3-tBu2(CH2N)2 CN]
(2a). To a THF solution (20 mL) containing 1,3-tBu(CH2N)2C
NH (0.197 g,1.0 mmol) was added n-BuLi (0.65 mL, 1.0 mmol,
n-hexane solution) at −30 °C. The reaction mixture was slowly
warmed to room temperature, and was stirred for 3 h. The solvent was
removed in vacuo, and the white solid was dissolved in 20 mL of
toluene. The solution was cooled to −30 °C, and V(N-2,6-
Me2C6H3)Cl3 (0.276 g, 1.0 mmol) was then added. The reaction
mixture was warmed slowly to room temperature and then stirred for
12 h. The solvent was removed in vacuo, and the resulting green solid
was extracted with hot toluene. The solution was then placed in a
rotary evaporator to remove volatiles. The solid was then dissolved in a
minimum amount of CH2Cl2 and layered with n-hexane. Dark green
crystals (0.240 g, 0.55 mmol) were grown from the chilled solution
1
(−30 °C). Yield of 55%. H NMR (CDCl3): δ 6.89 (d, 2H, J = 7.50,
ArH), 6.80 (t, 1H, J = 7.50, ArH), 3.52 (s, 4H, CH2), 2.71 (s, 6H,
ArCH3), 1.41 (s, 18H, C(CH3)3). 13C NMR (CDCl3): δ 136.3, 127.1,
619
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Article
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Inorganic Chemistry
Article
126.1, 56.1, 43.5, 28.7, 19.1. 51V NMR (CDCl3): δ −77 (Δν1/2 = 597
Hz) Anal. Calcd for C19H31Cl2N4V: C, 52.18 (49.43 + VC, vanadium
carbide); H, 7.14; N, 12.81. Found: C, 50.72; H, 6.90; N, 12.34.
Synthesis of V(N-2,6-Me2C6H3)Cl2[1,3-(2,6-Me2C6H3)2(CH2N)2
CN] (2b). The synthetic procedure for 2b is similar to that for 2a,
except that 1,3-(2,6-Me2C6H3)2(CH2N)2CNH (2.0 g, 6.8 mmol)
was used in place of 1,3-tBu(CH2N)2CNH. Green microcrystals
were collected in a yield of 97% (3.50 g, 6.6 mmol). 1H NMR
(CDCl3): δ 7.15 (t, 2H, J = 7.60, ArH), 7.02 (d, 4H, J = 7.20, Ar
H), 6.81−6.74 (m, 3H, NarH), 4.00 (s, 4H, CH2), 2.28 (s, 12H,
ArCH3), 2.10 (s, 6H, ArCH3). 13C NMR (CDCl3): δ 136.8, 134.8,
134.0, 129.0, 128.7, 126.7, 125.5, 46.8, 18.8, 17.8. 51V NMR (CDCl3):
δ −158 (Δν1/2 = 964 Hz). Anal. Calcd for C27H31Cl2N4(0.4 CH2Cl2):
C, 58.00; H, 5.65; N, 9.87. Found: C, 57.90; H, 5.58; N, 9.88.
Synthesis of V(N-2,6-Me2C6H3)Cl2[1,3-(2,6-iPr2C6H3)2(CH2N)2
CN] (2c). The synthetic procedure for 2c is similar to that for 2a,
except that 1,3-(2,6-iPr2C6H3)2(CH2N)2CNH (1.24 g, 6.0 mmol)
was used in place of 1,3-tBu(CH2N)2CNH. Green microcrystals
Synthesis of V(NAd)Cl2[1,3-(2,6-iPr2C6H3)2(CH2N)2 CN] (5c).
To a THF solution (20 mL) containing 1,3-(2,6-iPr2C6H3)2(CH2N)2
CN(0.649 g,1.60 mmol) was added n-BuLi (1.01 mL, 1.60 mmol, n-
hexane solution) at −30 °C. The reaction mixture was slowly warmed
to room temperature and stirred for 3 h. All volatiles were removed in
vacuo, and the resulting white solid was dissolved in 20 mL of toluene.
The solution was cooled to −30 °C, and V(NAd)Cl3 (0.49 g,
1.60 mmol) was added. The reaction mixture was allowed to slowly
warm up to room temperature and stirred for 12 h. The solvent was
then removed in vacuo, and the green solid was extracted with hot
toluene. The solution was placed under vacuum to remove all volatiles.
The remaining solid was dissolved in a minimum amount of CH2Cl2
and layered with n-hexane. Purple microcrystals were grown from the
chilled solution (−30 °C) and collected in a yield of 79.6% (0.86 g,
1.27 mmol). 1H NMR (CDCl3): δ 7.33 (t, 2H, J = 7.70, ArH), 7.19
(d, 4H, J = 7.70, ArH), 4.03 (s, 4H, CH2), 3.21−3.14 (m, 4H,
CH(CH3)2), 1.95(s, 3H, AdH), 1.82(s, 6H, AdH), 1.50 (d, 12H,
CH(CH3)2), 1.48 (s, 6H, AdH) 1.33 (d, 12H, CH(CH3)2). 13C
NMR (CDCl3): δ 147.4, 132.4, 129.4, 124.1, 49.2, 42.7, 35.7, 29.5,
29.1, 25.1, 24.6. 51V NMR (CDCl3): δ −251 (Δv1/2 = 801 Hz). Anal.
Calcd for C37H53Cl2N4V: C, 65.77; H, 7.91; N, 8.29. Found: C, 65.73;
H, 7.89; N, 8.00.
Ethylene Polymerization. Ethylene polymerizations were con-
ducted in toluene by using a 100 mL scale autoclave. The solvent and
the prescribed amount of cocatalyst (total solvent volume = 30 mL)
were charged into the autoclave in the drybox, and the apparatus was
placed under ethylene atmosphere (1 atm). After the addition of a
toluene solution (1.0 mL) containing a prescribed amount of the
vanadium precatalyst via a syringe, the reaction apparatus was
immediately pressurized to 8, 4, or 2 atm and the mixture was stirred
magnetically for 10 min. After the above procedure, ethylene was
purged, and the mixture was then poured into MeOH (150 mL)
containing HCl (10 mL). The resulting polymer was collected on a
filter paper by filtration and was adequately washed with MeOH and
then dried in vacuo.
1
were collected in a yield of 46% (0.894 g, 1.38 mmol). H NMR
(CDCl3): δ 7.36 (t, 2H, J = 7.60, ArH), 7.18 (d, 4H, J = 8.00, Ar
H), 6.68−6.60 (m, 3H, ArH), 4.04 (s, 4H, CH2), 3.21−3.14 (m, 4H,
CH(CH3)2), 1.98 (s, 6H, ArCH3), 1.30−1.27 (m, 24H, CH(CH3)2).
13C NMR (CDCl3): δ 147.4, 135.1, 132.2, 129.7, 126.5, 125.1, 124.4,
49.2, 29.2, 24.9, 23.9, 18.5. 51V NMR (CDCl3): δ −140 (Δν1/2 = 816
Hz). Anal. Calcd for C35H47Cl2N4V: C, 65.11(63.25 + VC, vanadium
carbide); H, 7.34; N, 8.68. Found: C, 64.08; H, 7.38; N, 8.52.
Synthesis of V(N-2,6-Me2C6H3)Cl2[1,3-Ph2(CH2N)2 CN] (2d).
The synthetic procedure of 2d is similar to that for 2a, expect that 1,3-
Ph2(CH2N)2CNH (0.948 g, 4 mmol) was used in place of
1,3-tBu2(CH2N)2CNH. Green microcrystals were collected in a
1
yield of 93% (1.782 g, 3.74 mmol). H NMR (CDCl3): δ 7.31−7.26
(m, 8H, PhH), 7.17 (t, 2H, J = 6.60, PhH), 6.81−6.74 (m, 3H,
NArH), 4.19 (s, 4H, CH2), 2.23 (s, 6H, ArCH3). 13C NMR
(CDCl3): δ 137.1, 135.8, 128.9, 126.8, 125.9, 125.8, 122.7, 46.6, 18.1,
18.0. 51V NMR (CDCl3): δ −99 (Δν1/2 = 723 Hz). Anal. Calcd for
C23H23Cl2N4V: C, 57.88 (55.36 + VC, vanadium carbide); H, 4.86; N,
11.74. Found: C, 57.28; H, 5.04; N, 11.47.
Copolymerization of Ethylene with Norbornene (NBE), 5-
Ethylidene-2-norbornene (ENB). Experimental procedures for the
copolymerization of ethylene with NBE and ENB were the same as
those for the ethylene polymerization described above except that
prescribed amounts of NBE or ENB were added into an autoclave and
the total volume of toluene and ENB was set to 30 mL.
Synthesis of V(NAd)Cl2[1,3-(2,6-iPr2C6H3)2(CHN)2 CN] (3c).
To a toluene solution containing V(NAd)Cl3 (193 mg, 0.63 mmol)
was added 1,3-(2,6-iPr2C6H3)2(CHN)2CNSiMe3 (300 mg,
0.63 mmol) at −30 °C. The reaction mixture was slowly warmed to
room temperature and stirred for 6 h. The solution was then filtered
through a Celite pad, and the filtercake was washed with hot toluene.
The combined filtrate and the wash were placed in a rotary evaporator
to remove volatiles. Bluish green crystals were grown from a chilled
solution (dissolution in a minimum amount of CH2Cl2/toluene and
Crystallographic Details. The X-ray diffraction analyses of 2c,d,
3c, and 4c were performed on a Rigaku RAXIS-RAPID Imaging Plate
diffractometer with graphite monochromated Mo Kα radiation. The
analyses of 1a, 2a, and 5c were carried out on a Rigaku XtaLAB mini
diffractometer with graphite-monochromated Mo Kα radiation. The
structures were solved by direct methods27 and expanded using
Fourier techniques. The non-hydrogen atoms for were refined aniso-
tropically: some non-hydrogen atoms for 2a were refined anisotropi-
cally, whereas the rest were refined isotropically. Hydrogen atoms were
refined isotropically. The crystal collection parameters are listed below
(Table 9). All calculations were performed using the CrystalStruc-
ture28,29 crystallographic software package except for refinement,
which was performed using SHELXL-97.30 All calculations for 2d were
performed using the CrystalStructure28,29 crystallographic software
package. Detailed structure reports including CIF files are shown in
the Supporting Information.17
1
placed in drybox freezer) at −30 °C. Yield: 362 mg (85%). H NMR
(C6D6): δ 7.21 (t, 2H, J = 7.70, ArH), 7.19 (d, 4H, J = 7.70, Ar
H), 5.91 (s, 4H, CH2), 2.98−2.95 (m, 4H, CH(CH3)2), 1.77 (s, 3H,
AdH), 1.54 (d, 12H, CH(CH3)2), 1.34 (s, 6H, AdH), 1.21 (s, 6H,
AdH) 1.11 (d, 12H, CH(CH3)2). 13C NMR (C6D6): δ 146.2, 131.7,
130.5, 124.1, 116.3, 42.9, 35.7, 29.5, 28.9, 24.1, 23.6. 51V NMR
(C6D6): δ −268 (Δv1/2 = 1415 Hz). 51V NMR (CDCl3): δ −257
(Δv1/2 = 1087 Hz). Anal. Calcd for C37H51Cl2N4V: C, 65.97 (64.18 +
VC, vanadium carbide); H, 7.63; N, 8.32. Found (1): C, 64.82; H,
7.41; N, 8.12. Found (2): C, 64.64; H, 7.54; N, 8.05. Found (3): C,
64.52; H, 7.64; N, 8.07.
Synthesis of V(NPh)Cl2[1,3-(2,6-iPr2C6H3)2(CHN)2 CN] (4c).
The synthetic procedure for 4c is similar to that for 3c, except that
V(NPh)Cl3 (132 mg, 0.53 mmol) was used in place of V(NAd)Cl3.
Greenish brown microcrystals were grown from a chilled CH2Cl2/n-
hexane solution (−30 °C) and collected in 79% yield (257 mg, 0.42
ASSOCIATED CONTENT
■
S
* Supporting Information
1
mmol). H NMR (CDCl3): δ 7.41 (t, 2H, J = 7.67, PhH), 7.24 (d,
Selected NMR spectra for poly(ethylene-co-norbonene)s, poly-
(ethylene-co-ethylidene-2-norbonene) and structural reports includ-
ing CIF files for V(N-2,6-Me2C6H3)Cl2[1,3-tBu2(CHN)2CN]
4H, J = 7.86, ArH), 7.02 (t, 2H, J = 7.67, PhH), 6.89 (t, 1H, J =
7.32, PhH), 6.77 (s, 2H, CH=) 6.62 (d, 2H, J = 7.86, ArH),
2.83−2.75 (m, 4H, CH(CH3)2), 1.26−1.18 (m, 24H, CH(CH3)2. 13C
NMR (CDCl3): δ 145.9, 130.8, 130.7, 127.5, 125.1, 124.4, 124.0,
117.4, 29.2, 24.4, 23.2. 51V NMR (CDCl3): δ −180 (Δv1/2 = 951 Hz).
Anal. Calcd for C33H41Cl2N4V: C, 64.39; H, 6.71; N, 9.10. Found: C,
64.27; H, 6.72; N, 9.01.
t
(1a), V(N-2,6-Me2C6H3)Cl2[1,3-R2(CH2N)2CN] [R = Bu
(2a), 2,6-iPr2C6H3 (2c), Ph (2d)], V(NR′)Cl2[1,3-
(2,6-iPr2C6H3)2(CHN)2CN] [R′ = Ad (3c), Ph (4c)],
V(NAd)Cl2[1,3-(2,6-iPr2C6H3)2(CH2N)2CN] (5c). This
621
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Inorganic Chemistry
Article
Chem. 2001, 640, 21. (n) Gibson, V.; Redshaw, C.; Elsegood, M. R. J.
J. Chem. Soc., Dalton Trans. 2001, 767. (o) Milione, S.; Cavallo, G.;
Tedesco, C.; Grassi, A. J. Chem. Soc., Dalton Trans. 2002, 1839.
(p) Feghali, K.; Harding, D. J.; Reardon, D.; Gambarotta, S.; Yap, G.;
Wang, Q. Organometallics 2002, 21, 968. (q) Ruther, T.; Cavell, K. J.;
Braussaud, N. C.; Skelton, B. W.; White, A. H. J. Chem. Soc., Dalton
Trans. 2002, 4684. (r) Reardon, D.; Guan, J.; Gambarotta, S.; Yap, G.
P. A.; Wilson, D. R. Organometallics 2002, 21, 4390.
material is available free of charge via the Internet at http://
pubs.acs.org.
AUTHOR INFORMATION
■
Corresponding Authors
*K. Nomura. Tel.: +81-42-677-2547. Fax: +81-42-677-2547.
E-mail: ktnomura@tmu.ac.jp.
(8) (a) Zhang, S.; Nomura, K. J. Am. Chem. Soc. 2010, 132, 4960.
(b) Igarashi, A.; Zhang, S.; Nomura, K. Organometallics 2012, 31,
3575. (c) Nomura, K.; Igarashi, A.; Katao, S.; Zhang, W.; Sun, W.-H.
Inorg. Chem. 2013, 52, 2607. (d) Igarashi, A.; Zhang, W.; Sun, W.-H.;
Nomura, K. Catalysts 2013, 3, 148.
*M. Tamm. Tel.: +49 (0)531 391-5309. Fax: +49 (0)531 391-5387.
E-mail: m.tamm@tu-bs.de.
Notes
The authors declare no competing financial interest.
(9) (a) Tamm, M.; Randoll, S.; Bannenberg, T.; Herdtweck, E. Chem.
Commun. 2004, 876. (b) Tamm, M.; Randoll, S.; Herdtweck, E.;
Kleigrewe, N.; Kehr, G.; Erker, G.; Rieger, B. Dalton Trans. 2006, 459.
(c) Stelzig, S. H.; Tamm, M.; Waymouth, R. M. J. Polym. Sci., Part A:
Polym. Chem. 2008, 46, 6064. (d) Nomura, K.; Fukuda, H.; Apisuk,
W.; Trambitas, A. G.; Kitiyanan, B.; Tamm, M. J. Mol. Catal. A: Chem.
2012, 363−364, 501. (e) Apisuk, W.; Trambitas, A. G.; Kitiyanan, B.;
Tamm, M.; Nomura, K. J. Polym. Sci., Part A: Polym. Chem. 2013, 51,
2575.
(10) (a) Kaminsky, W.; Beulich, I.; Arndt-Rosenau, M. Macromol.
Symp. 2001, 173, 211. (b) Kaminsky, W. Angew. Makromol. Chem.
1994, 223, 101. (c) Cherdron, H.; Brekner, M.-J.; Osan, F. Angew.
Makromol. Chem. 1994, 223, 121. (d) Dragutan, V.; Streck, R. Catalytic
Polymerisation of Cycloolefins (Studies in Surface Science and Catalysis),
Vol. 131; Elsevier: Amsterdam, 2000. (e) Nomura, K. Chin. J. Polym.
Sci. 2008, 26, 513 References are cited therein.
ACKNOWLEDGMENTS
■
S.Z. and B.K.B. express their sincere thanks to Japan Society for
the Promotion of Science (JSPS) for postdoctoral fellowships
(P08361 for S.Z., P11072 for B.K.B.). M.T. acknowledges
support by the Deutsche Forschungsgemeinschaft through
grant TA 189/6. K.N., S.Z., and B.K.B. express their thanks to
Tosoh Finechem Co. for donating MAO, and K.N. expresses
his heartfelt thanks to Dr. Bart Hessen (formerly University of
Groningen, Netherlands) for fruitful discussion.
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Et
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