Synthesis and structural analysis of (imido)vanadium(V) complexes containing chelate (anilido)methyl-imine ligands: Ligand effect in ethylene dimerization

Article abstract of DOI:10.1021/ic302633y

A series of (imido)vanadium dichlorido complexes containing chelate anionic donor ligands of the type, VCl₂(L)(NR) [R = 1-adamantyl (Ad), L = 2-(2,6-Me₂C₆H₃)NCH₂(C ₉H₆N) (2), 8-(2,6-Me₂C₆H ₃)NCH₂(C₉H₆N) (3); L = 2-(2,6-R′₂C₆H₃)NCH₂(C ₅H₄N), R = 2-MeC₆H₄, R′ = Me (4a), ⁱPr (4b); L = 2-(2,6-Me₂C₆H ₃)NCH₂(C₅H₄N), R = 4-MeC ₆H₄ (5), 3,5-Me₂C₆H₃ (6)], have been prepared and identified. The reactions with ethylene by 2,3 in the presence of methylaluminoxane (MAO) afforded a mixture of high molecular weight polyethylene and oligomers. Reactions with ethylene by VCl ₂[2-(2,6-R′₂C₆H₃)NCH ₂(C₅H₄N)](NAd) (1a,b), 4-6 afforded 1-butene with high selectivities (>92%), and the activities by 4a,b are at the same level as those in 1a,b. The activities by 5,6 were lower than 4a,b and were at the same level of that by VCl₂[2-(2,6-Me₂C ₆H₃)NCH₂(C₅H₄N)](NPh). These results thus suggest that both the chelate anionic donor and the imido ligands play a role for both the activity and the selectivity.

Full text of DOI:10.1021/ic302633y

Article
pubs.acs.org/IC
Synthesis and Structural Analysis of (Imido)Vanadium(V) Complexes
Containing Chelate (Anilido)Methyl-imine Ligands: Ligand Effect in
Ethylene Dimerization
Kotohiro Nomura,*,† Atsushi Igarashi,† Shohei Katao,‡ Wenjuan Zhang,§ and Wen-Hua Sun§
†Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University, 1-1 Minami Osawa,
Hachioji, Tokyo 192-0397, Japan
‡Graduate School of Materials Science, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0101, Japan
§Key Laboratory of Engineering Plastics, Institute of Chemistry, Chinese Academy of Sciences, Zhongguancun, Beijing 100190,
People’s Republic of China
S
* Supporting Information
ABSTRACT: A series of (imido)vanadium dichlorido complexes contain-
ing chelate anionic donor ligands of the type, VCl2(L)(NR) [R = 1-
adamantyl (Ad), L = 2-(2,6-Me2C6H3)NCH2(C9H6N) (2), 8-(2,6-
Me2C6H3)NCH2(C9H6N) (3); L = 2-(2,6-R′2C6H3)NCH2(C5H4N), R =
2-MeC6H4, R′ = Me (4a), iPr (4b); L = 2-(2,6-Me2C6H3)NCH2(C5H4N), R
= 4-MeC6H4 (5), 3,5-Me2C6H3 (6)], have been prepared and identified. The
reactions with ethylene by 2,3 in the presence of methylaluminoxane
(MAO) afforded a mixture of high molecular weight polyethylene and
oligomers. Reactions with ethylene by VCl2[2-(2,6-R′2C6H3)-
NCH2(C5H4N)](NAd) (1a,b), 4−6 afforded 1-butene with high
selectivities (>92%), and the activities by 4a,b are at the same level as
those in 1a,b. The activities by 5,6 were lower than 4a,b and were at the
same level of that by VCl2[2-(2,6-Me2C6H3)NCH2(C5H4N)](NPh). These
results thus suggest that both the chelate anionic donor and the imido ligands play a role for both the activity and the selectivity.
Scheme 1
INTRODUCTION
■
Since the classical Ziegler-type vanadium catalyst systems
[V(acac)3, VOCl3, etc. and Et2AlCl, EtAlCl2, nBuLi, etc.]
display unique high reactivity toward olefins in olefin
coordination/insertion polymerization,1−5 the design and
synthesis of efficient vanadium complex catalysts for olefin
coordination insertion polymerization/oligomerization thus
attract considerable attention in the field of catalysis, organo-
metallic chemistry, as well as of polymer chemistry.5 Our group
focuses on (imido)vanadium(V) complexes containing anionic
donor ligands of the type, VCl2(Y)(NR) [Y = aryloxo, ketimide,
phenoxyimine, etc.],6,7 and demonstrated that these complexes,
exemplified as VCl2(O-2,6-Me2C6H3)(N-2,6-Me2C6H3), ex-
hibited remarkable catalytic activities for ethylene (co)-
polymerization in the presence of aluminum cocatalysts.5c−e,6
More recently, we demonstrated that the (imido)vanadium(V)
complexes containing (2-anilidomethyl)pyridine ligand,
VCl2[2-ArNCH2(C5H4N)](NR) [Ar = 2,6-Me2C6H3,
2,6-iPr2C6H3; R = 1-adamantyl (Ad, 1), cyclohexyl, phenyl],
efficiently dimerize ethylene with both notable catalytic
activities and high selectivities in the presence of methyl-
aluminoxane (MAO) cocatalyst (Scheme 1),5e,7,8 whereas the
2 , 6 - d i m e t h y l p h e n y l i m i d o a n a l o g u e , V C l 2 [ 2 -
ArNCH2(C5H4N)](N-2,6-Me2C6H3), showed moderate cata-
lytic activity for ethylene polymerization.6e Through these facts,
we thus assumed that (i) steric bulk of the imido ligand directly
affects the reactivity (dimerization vs polymerization), and that
(ii) the electronic factor also plays a role toward the activity (in
dimerization).7a Moreover, on the basis of both the electron
spin resonance (ESR) spectra and the 51V NMR spectra, it was
suggested that the chelate anionic donor ligand plays an
important role for stabilization of the oxidation state in the
catalyst solution even containing aluminum alkyls in excess
amount.7b
Received: December 1, 2012
Published: February 18, 2013
© 2013 American Chemical Society
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To explore the ligand effect toward both the activity and the
selectivity in detail, we thus prepared a series of (imido)-
vanadium(V) dichlorido complexes containing chelate anionic
donor ligands (shown in Scheme 2) of the type, VCl2(L)(NR)
= Me (1a), iPr (1b)],7a VCl2[2-(2,6-R′2C6H3)NCH2(C5H4N)]-
(N-2,6-Me2C6H3),6e reported previously. The resultant com-
plexes were identified by NMR spectra (1H, 13C, 51V) and
elemental analyses, and their structures were determined by X-
ray crystallography (Figure 1, shown below).11
In contrast, attempted reactions of VCl3(N-2-MeC6H4)12
with Li[2-(2,6-R′2C6H3)NCH2(C5H4N)] afforded the desired
complexes, VCl2[2-(2,6-R′2C6H3)NCH2(C5H4N)](N-2-
Scheme 2
i
MeC6H4) [R′ = Me (4a), Pr (4b)], in extremely low or
negligible yields (described in the Supporting Information).
The dichlorido complexes (4a,b) could be isolated in moderate
yields, if the reactions of VCl3(N-2-MeC6H4) with (2-
anilidomethyl)pyridine, 2-(2,6-R′2C6H3)N(H)CH2(C5H4N),
were conducted in toluene in the presence of NEt3 (Scheme
4). The other (arylimido)vanadium(V) dichlorido complexes
containing (2-anilidomethyl)pyridine ligand, VCl2[2-(2,6-
Me2C6H3)NCH2(C5H4N)](NR) [R = 4-MeC6H4 (5), 3,5-
Me2C6H3 (6)] could also be prepared similarly from VCl3(N-4-
MeC6H4) or VCl3(N-3,5-Me2C6H3), prepared from VOCl3 by
treating with the corresponding isocyanate (Scheme 4).12 The
resultant complexes were identified by NMR spectra (1H, 13C,
51V) and elemental analyses, and the structures of 4a,b were
determined by X-ray crystallography (Figure 2, shown below).
2. Structural Analysis of VCl2(L)(NAd) [L = 2-(2,6-
Me2C6H3)NCH2(C9H6N) (2), 8-(2,6-Me2C6H3)NCH2-(C9H6N)
(3)], and VCl2[2-(2,6-R′2C6H3)NCH2(C5H4N)](N-2-MeC6H4)
[R′ = Me (4a), iPr (4b)]. Structures of VCl2(L)(NAd) [L = 2-
(2,6-Me2C6H3)NCH2(C9H6N) (2), 8-(2,6-Me2C6H3)-
NCH2(C9H6N) (3)] determined by X-ray crystallographic
analysis are shown in Figure 1, and selected bond distances and
angles are summarized in Table 1.11 The structures indicate
that these complexes fold a distorted trigonal bipyramidal
geometry around vanadium consisting of two nitrogen atoms in
the quinoline, and the imido ligands axis and an equatorial
plane consisted of two chlorine atoms and the nitrogen in the
anilide ligand, as observed in 1a,7a reported previously [N(1)−
V−N(2): 173.09(6)° in 2, 173.35(9)° in 3; total bond angles of
Cl(1)−V−Cl(2), Cl(1)−V−N(3), Cl(2)−V−N(3) = 356.822°
in 2, 356.272° in 3]. The nitrogen atom in the quinoline is
located trans to the imido ligand. The bond distances in V−
N(1) and V−N(2) are similar to those in 1a, and bond angles
in Cl(1)−V−Cl(2), Cl(1)−V−N(3), Cl(2)−V−N(3) are
slightly larger than those in 1a. A V−Cl bond distance in 3
[2.3054(6) Å] is longer than the others [2.2630(5)−2.2792(5)
Å] probably because of steric bulk [forms 6 membered ring in 3
vs 5 membered ring in 1a and 2]. It might be interesting to
note that the bond distances between vanadium and nitrogen in
the imino ligand in 2,3 [2.2911(14) Å, 2.3338(18) Å, in 2,3,
respectively] are apparently longer than that in 1a [2.2241(11)
Å]. These bond distances are also longer than those in VCl2[2-
(2,6-iPr2C6H3)NCH2(C5H4N)](NAd) [1b, 2.225(2) Å],7a
VCl2[2-(2,6-iPr2C6H3)NCH2(C5H4N)](NCy) [2.221(2) Å],7a
and VCl2[2-(2,6-iPr2C6H3)NCH2(C5H4N)](N-2,6-Me2C6H3)
[2.211(2) Å].6e Moreover, these bond distances are also longer
than those between vanadium and nitrogen in the phenoxy-
imine ligand of VCl2[O-2-R′′-6-{(2,6-iPr2C6H3)N=CH}C6H3]-
[R = Ad, L = 2-(2,6-Me2C6H3)NCH2(C9H6N) (2), 8-(2,6-
Me2C6H3)NCH2(C9H6N) (3); L = 2-(2,6-R′2C6H3)-
i
NCH2(C5H4N), R = 2-MeC6H4 {R′ = Me (4a), Pr (4b)}; L
= 2-(2,6-Me2C6H3)NCH2(C5H4N), R = 4-MeC6H4 (5), 3,5-
Me2C6H3 (6)], and conducted the reaction with ethylene in the
presence of MAO cocatalyst. Through this study, we wish to
present that the ligand modifications (both the imido and the
chelate anionic donor ligands) play an important role for
exhibiting both high activity and selectivity.9
RESULTS AND DISCUSSION
■
1. Synthesis and Structural Analysis of VCl2(L)(NR) [R
= 1-adamantyl (Ad), 2-MeC6H4, 4-MeC6H4, 3,5-Me2C6H3;
L = 2-(2,6-Me2C6H3)NCH2(C9H6N), 8-(2,6-Me2C6H3)-
NCH2(C9H6N), 2-(2,6-R′2C6H3)NCH2(C5H4N)]. (1-
Adamantlyimido)vanadium(V) dichlorido complexes contain-
ing 2- or 8-(anilidomethyl)quinoline ligands, VCl2(L)(NAd) [L
= 2-(2,6-Me2C6H3)NCH2(C9H6N) (2), 8-(2,6-Me2C6H3)-
NCH2(C9H6N) (3); Ad = 1-adamantyl], were prepared in
Et2O by reacting the trichlorido analogue, VCl3(NAd), with the
lithium salts that were prepared in situ by treating 2- or 8-(2,6-
Me2C6H3)N(H)CH2(C9H6N)10 with 1 equiv of BuLi in hexane
at −30 °C (Scheme 3). These are analogous procedures for
synthesis of VCl2[2-(2,6-R′2C6H3)NCH2(C5H4N)](NAd) [R′
Scheme 3
t
(N-2,6-Me2C6H3) [2.216(4)-2.203(2) Å; R′′ = H, Me, Bu],
reported previously.6d It thus seems likely that these (rather
long bond distances) might be due to the use of the
(anilidomethyl)quinoline ligand in place of the
(anilidomethyl)pyridine ligand.
The structures of VCl2[2-(2,6-R′2C6H3)NCH2(C5H4N)](N-
i
2-MeC6H4) [R′ = Me (4a), Pr (4b)] are shown in Figure 2,
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Figure 1. ORTEP drawings for VCl2[2-(2,6-Me2C6H3)NCH2(C9H6N)](N-1-adamantyl) (2), and VCl2[8-(2,6-Me2C6H3)NCH2(C9H6N)](N-1-
adamantyl) (3). Thermal ellipsoids are drawn at 50% probability level, and H atoms were omitted for clarity.11.
Scheme 4
and selected bond distances and angles are summarized in
Table 1. Similarly to 2,3, the structures indicate that these
complexes fold a distorted trigonal bipyramidal geometry
around vanadium consisting of two nitrogen atoms in the
pyridine, and the imido ligands axis and an equatorial plane
consisted of two chlorine atoms and the nitrogen in the anilide
ligand [N(1)−V−N(2) = 173.65(7)° in 4a, 173.26(16)° in 4b;
total bond angles of Cl(1)−V−Cl(2), Cl(1)−V−N(3), Cl(2)−
V−N(3): 354.98° in 4a, 355.17° in 4b]. The nitrogen atom in
the pyridine locates at the trans-position of the imido ligand.
The vanadium−nitrogen bond distances in the imido and the
anilido ligands as well as the V−Cl bond distances are close to
those in 1a: the bond angles in Cl(1)−V−Cl(2), Cl(1)−V−
N(3), Cl(2)−V−N(3) are slight larger than those in 1a, but are
similar to those in 2,3. The vanadium−nitrogen bond distances
in the pyridine ligand are 2.1790(19) Å (4a), 2.1976(17) Å
(4b), respectively, which are rather shorter than those in 1a,b
[2.2241(11), 2.225(2) Å, respectively]7a and VCl2[2-
(2,6-iPr2C6H3)NCH2(C5H4N)](N-2,6-Me2C6H3) [2.211(2)
Å].6e
NCH2(C5H4N)](NR) [R = 2-MeC6H4 (4a,b), 4-MeC6H4 (5),
3,5-Me2C6H3 (6)]−MAO Catalyst Systems. Reactions with
ethylene in the presence of VCl2[2-(2,6-Me2C6H3)-
NCH2(C9H6N)](NAd) (2), VCl2[8-(2,6-Me2C6H3)-
NCH2(C9H6N)](NAd) (3) in the presence of MAO
(methylaluminoxane) were conducted in toluene, and the
results are summarized in Table 2. The results using VCl2[2-
i
(2,6-R′2C6H3)NCH2(C5H4N)](NAd) [R′ = Me (1a), Pr
(1b)], and VCl2[2-(2,6-iPr2C6H3)NCH2-6-Me(C5H3N)]-
(NAd) (7b) are also shown for comparison.7a We recently
demonstrated that 1a,b showed the significant catalytic
activities affording 1-butene exclusively in the presence of
MAO (runs 1,2):7a the activity was affected by the aluminum/
vanadium molar ratios and ethylene pressure without significant
changes in the selectivity of 1-butene.7b In contrast, we also
demonstrated that attempts at using the complex containing
methyl group in the ortho position (7b) in place of 1b showed
low activities affording a mixture of 1-butene and high
molecular weight polyethylene (runs 8,9).7a
Unfortunately, the catalytic activities by 2,3 were apparently
lower than 1a,b: the activities by 2,3 under the optimized
aluminum/vanadium molar ratios (runs 5, 7) were lower than
that by 7b (run 9). Moreover, the resultant products by the
3. Reaction with Ethylene by VCl2[2-(2,6-Me2C6H3)-
NCH2(C9H6N)(NAd)] (2), VCl2[8-(2,6-Me2C6H3)-
NCH2(C9H6N)](NAd) (3), and VCl2[2-(2,6-R′2C6H3)-
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Figure 2. ORTEP drawings for VCl2[2-(2,6-Me2C6H3)NCH2(C5H4N)](N-2-MeC6H4) (4a), and VCl2[2-(2,6-iPr2C6H3)NCH2(C5H4N)(N-2-
MeC6H4)] (4b). Thermal ellipsoids are drawn at 50% probability level, and H atoms were omitted for clarity.11.
Table 1. Selected Bond Distances and Angles for VCl2[2-(2,6-Me2C6H3)NCH2(C9H6N)](NAd) (2), VCl2[8-(2,6-
Me2C6H3)NCH2(C9H6N)](NAd) (3), VCl2[2-(2,6-Me2C6H3)NCH2(C5H4N)](N-2-MeC6H4) (4a), and VCl2[2-
(2,6-iPr2C6H3)NCH2(C5H4N)(N-2-MeC6H4)] (4b)
a
b
1a
2
3
4a
4b
VCl2(L)(N-2,6-Me2C6H3)
Bond Distances (Å)
1.6503(18)
2.3338(18)
1.844(3)
V−N(1)
V−N(2)
V−N(3)
V−Cl(1)
V−Cl(2)
1.6517(12)
2.2241(11)
1.8580(12)
2.2677(3)
2.2709(4)
1.6502(14)
2.2911(14)
1.8567(12)
2.2792(5)
2.2630(5)
1.6697(19)
2.1790(19)
1.8524(18)
2.2776(7)
2.2695(7)
1.640(18)
2.1976(17)
1.8526(17)
2.2645(8)
2.2642(7)
1.679(2)
2.211(2)
1.850(2)
2.2645(10)
2.2868(9)
2.3054(6)
2.2752(7)
Bond Angles (deg)
126.02(3)
Cl(1)−V−Cl(2)
N(1)−V−N(2)
V−N(1)−C(1)
Cl(1)−V−N(3)
Cl(2)−V−N(3)
119.953(16)
174.90(4)
170.94(10)
98.90(3)
121.512(17)
173.09(6)
172.15(11)
119.12(5)
115.64(5)
125.45(3)
173.47(9)
176.42(17)
115.31(6)
114.22(6)
122.42(3)
175.65(7)
173.26(19)
118.12(7)
114.63(7)
121.87(3)
175.93(10)
176.2(2)
173.35(9)
172.2(2)
114.50(6)
114.55(7)
116.98(8)
96.02(4)
b
115.81(6)
a
Cited from reference 7a. VCl2[2-(2,6-iPr2C6H3)NCH2(C5H4N)](N-2,6-Me2C6H3) cited from reference 6e.
(anilidomethyl)quinoline analogues (2,3) were a mixture of
oligomer (1-butene as the major product) and polyethylene for
which the molecular weight (and the distribution) could not be
measured by ordinary GPC analysis (in o-dichlorobenzene at
140 °C, suggesting formation of ultrahigh molecular weight
polymers6c,7b). The facts observed here might suggest that
there are several (at least two) catalytically active species
generated in the reaction mixture from 2,3 in the presence of
MAO under these conditions. One probable speculation we
may consider is that these might be because complexes 2 and 3
possess rather long vanadium−nitrogen bond distances in the
imine ligand [expressed as V−N(2)] compared to those in
1a,4a and the others, and these might lead a partial dissociation
of the vanadium−nitrogen bond in the reaction mixture upon
addition of MAO in excess amount.
summarized in Table 3. The results using the adamantylimido
analogues (R = Ad; 1a,b) and the phenylimido analogue,
VCl2[2-(2,6-Me2C6H3)NCH2(C5H4N)](NPh) (8),7a are also
shown for comparison.
It should be noted that the 2-methylphenylimido analogues
(4a,b) exhibited remarkable catalytic activities affording 1-
butene as the major product. Moreover, the observed activities
by 4a,b are the same level as those in 1a,b [ex. TOF 1760000
h−1 (run 14) by 4a vs 2060000 (run 1) by 1a; 1450000 (run
17) by 4b vs 1280000 (run 2) by 1b]. The activity by the 2-
methylphenyl analogue (4a) under the optimized conditions
was much higher than that by the phenylimido analogue (8, run
31). As reported previously by 1a,b,7a the activities were
dependent upon the aluminum/vanadium molar ratios
employed, whereas the selectivity in 1-butene were not affected
by the ratio because the initial product was 1-butene, and 1-
hexene was formed from 1-butene that accumulated in the
mixture.7a
The results in ethylene dimerization using VCl2[2-(2,6-
R′2C6H3)NCH2(C5H4N)](NR) [R = 2-MeC6H4 (4a,b), 4-
MeC6H4 (5), 3,5-Me2C6H3 (6)] in the presence of MAO are
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Table 2. Reactions with Ethylene by VCl2(L)(NAd) [L = 2-
Table 3. Ethylene Dimerization by VCl2[2-(2,6-
i
(2,6-R′2C6H3)NCH2(C5H4N) {R′ = Me (1a), Pr (1b)}, 2-
R′2C6H3)NCH2(C5H4N)](NR) [R = 2-MeC6H4, R′ = Me
i
(2,6-Me2C6H3)NCH2(C9H6N) (2), 8-(2,6-
(4a), Pr (4b); R′ = Me, R = 4-MeC6H4 (5), 3,5-Me2C6H3
Me2C6H3)NCH2(C9H6N) (3), 2-(2,6-iPr2C6H3)NCH2-6-
(6), Ph (8)]−MAO Catalyst Systems (Ethylene 8 atm in
a
a
MeC5H3N (7b)]−MAO Catalyst Systems
Toluene at 25 °C for 10 min)
b
c
d
e
e
polyethylene
run complex (μmol) Al/V
activity
TOF
C4′/% C6′/%
d
oligomer / %
(PE)
f
10
1a (0.5)
1a (0.2)
1b (0.5)
500
51100
57800
35700
1830000
2060000
1280000
92.5
96.8
92.1
7.5
3.2
7.9
f
complex
yield/
mg
1
500
b
c
e
(μmol)
Al/V
activity
C4′
C6′
activity
f
2
1000
f
1
2
3
4
5
6
7
8
9
1a (0.2)
1b (0.5)
2 (2.0)
2 (2.0)
2 (2.0)
3 (5.0)
3 (5.0)
7b (0.5)
7b (0.5)
500
1000
200
57800
35700
103
96.8
92.1
90.2
92.4
92.0
3.2
7.9
9.8
7.6
8.0
none
none
f
11
12
13
14
15
4a (0.2)
4a (0.2)
4a (0.2)
4a (0.2)
4a (0.2)
200
400
20500
44400
41400
50300
34000
718000
1560000
1450000
1760000
1190000
98.6
97.5
94.7
95.2
96.0
1.4
2.5
5.3
4.8
4.0
g
16
47
30
45
16
53
g
1000
1500
200
201
10
500
g
249
15
600
g
trace
43
13
1000
g
1000
1000
2000
71.6
28.4
trace
4.1
44
h
f
f
h
510
>99
95.9
16
17
18
4b (0.2)
4b (0.2)
4b (0.2)
500
700
27000
41500
28000
946000
1450000
980000
97.4
97.1
95.6
2.6
2.9
4.4
h
h
2100
a
b
Conditions: toluene 30 mL, ethylene 8 atm, 25 °C, 10 min. Molar
ratio of aluminum/vanadium. Activity in kg-ethylene reacted/mol-
V·h. Determined by GC. Activity in kg-PE/mol-V·h. Data cited
from reference 7a. Insoluble for ordinary GPC measurement (in o-
1000
c
d
e
f
19
20
21
22
23
24
5 (0.5)
5 (0.5)
5 (0.5)
5 (0.5)
5 (0.5)
5 (0.5)
100
200
13800
15100
14000
8680
483000
529000
490000
304000
393000
71600
93.1
94.0
95.3
96.4
94.5
96.6
6.9
6.0
4.7
3.6
5.5
3.4
g
h
dichlorobenzene at 140 °C). Small amount of PE was obtained, [Mw
500
= 2.55 × 106, Mw/Mn = 1.9 (run 8); Mw = 2.93 × 106, Mw/Mn = 2.6
750
(run 9)].7a
1000
1500
11200
2040
The 4-methylphenylimido analogue (5) also showed high
catalytic activities affording 1-butene as the major product (runs
19−24), but the activities were apparently lower that those the
2-methylphenyl analogue (4a), suggesting that the placement
of the methyl group in the ortho position plays a role for
exhibiting high activity. Moreover, the 3,5-dimethylphenylimido
analogue (6) also showed high catalytic activities affording 1-
butene as the major product (runs 25−30). These results are,
we believe, a unique contrast to those by the 2,6-
dimethylphenylimido analogue, VCl2[2-(2,6-Me2C6H3)-
NCH2(C5H4N)](N-2,6-Me2C6H3),6e which afforded ultrahigh
molecular weight polyethylene with moderate (rather low)
catalytic activity under the same conditions [activity 78 kg-PE/
mol-V·h, Mw = 2.98 × 106, Mw/Mn = 2.0].6e
25
26
27
28
29
30
31
6 (0.5)
6 (0.5)
6 (0.5)
6 (0.5)
6 (0.5)
6 (0.2)
8 (0.5)
200
500
5800
13400
14200
2710
203000
470000
497000
95000
95.6
95.0
94.6
95.4
97.2
96.7
95.1
4.4
5.0
5.4
4.6
2.8
3.3
4.9
750
1000
1500
1250
500
1300
45700
14200
18300
499000
654000
f
a
Conditions: toluene 30 mL, d-MAO white solid [methylaluminoxane
prepared by removing AlMe3, toluene from PMAO-S], 25 °C.
Aluminum/vanadium molar ratio. Activity in kg-ethylene reacted/
mol-V·h. TOF (turnover frequency) = (molar amount of ethylene
reacted)/mol-V·h. By GC analysis vs internal standard. Cited from
reference 7a.
b
c
d
e
f
We previously demonstrated that the activities by VCl2[2-
(2,6-Me2C6H3)NCH2(C5H4N)](NR) increased in the order: R
= 1-adamantyl (1a) > cyclohexyl > phenyl, and assumed that
the activities are affected by an electronic nature of the imido
ligand employed.7a As described above, the results by 4a,b also
suggest that the ortho substituent in the phenyl imido ligand
plays an important role toward the activity, although we do not
have clear explanation of the observed unique ligand effect.
Taking into account the facts summarized above, we can at
least say it is clear that fine-tuning of substituents in both the
imido ligand and the chelate anionic donor ligand plays an
essential key role for the remarkable activity with high
selectivity. We highly believe that such information is
potentially important for designing efficient molecular catalysis
with vanadium for precise olefin polymerization as well as
oligomerization.
passed through an alumina short column under N2 stream prior to use.
VCl3(NAd)13 (Ad = 1-adamantyl), VCl2[2-(2,6-R′2C6H3)-
NCH2(C5H4N)](NAd) [R′ = Me (1a), iPr (1b)], Li[2-(2,6-
Me2C6H3)NCH2(C5H4N)], Li[2-(2,6-iPr2C6H3)NCH2(C5H4N)]
were prepared according to our previous reports.6e,7a o-Tolyl
isocyanate, 3,5-dimethylphenylisocyanate, triethylamine (TCI Co.,
Ltd.), and VOCl3 (Sigma-Aldrich Co.) were used as received.
Polymerization grade ethylene (purity >99.9%, Sumitomo Seika Co.
Ltd.) was used as received. 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, AlMe3, and then heated at >100 °C
for 1 h for completion) in the drybox to give white solids. GC analysis
was performed with a SHIMADZU GC-2025AF gas chromatograph
(Shimadzu Co. Ltd.) equipped with a flame ionization detector.
Elemental analyses were performed by using EAI CE-440 CHN/O/
1
S Elemental Analyzer (Exeter Analytical, Inc.). All H, 13C and 51V
NMR spectra were recorded on a Bruker AV500 spectrometer (500.13
MHz for 1H, 125.77 MHz for 13C and 131.55 MHz for 51V). All
spectra were obtained in the solvent indicated at 25 °C unless
otherwise noted. Chemical shifts are given in parts per million (ppm)
and are referenced to SiMe4 (δ 0.00 ppm, 1H, 13C) and VOCl3 (δ 0.00,
51V). Coupling constants and half-width values, Δν1/2, are given in
hertz (Hz).
EXPERIMENTAL SECTION
■
General Procedures. All experiments were carried out under a
nitrogen atmosphere in a Vacuum Atmospheres drybox. Anhydrous
grade toluene, n-hexane (Kanto Kagaku Co., Ltd.) were transferred
into a bottle containing molecular sieves (a mixture of 3A 1/16, 4A 1/
8, and 13X 1/16) in the drybox under nitrogen stream, and were
2611
dx.doi.org/10.1021/ic302633y | Inorg. Chem. 2013, 52, 2607−2614

Inorganic Chemistry
Article
Synthesis of VCl2[2-(2,6-Me2C6H3)NCH2(C9H6N)](N-1-ada-
mantyl) (2). Into a toluene solution (15.0 mL) containing 2-(2,6-
Me2C6H3)NHCH2(C9H6N) (300 mg, 1.15 mmol) was added n-BuLi
(0.75 mL, 1.18 mmol, n-hexane solution) at −30 °C. The reaction
mixture was warmed slowly to room temperature, and the mixture was
then stirred for 3 h. The resultant solid (lithium salt) was collected on
a glass filter and was washed with n-hexane. The solid was then dried
in vacuo to yield green solid (266 mg). Into a Et2O solution (15.0 mL)
containing VCl3(NAd) (304 mg, 0.992 mmol) was added the above
green solid (266 mg) at −30 °C. The reaction mixture was then
warmed slowly to room temperature, and the solution was then stirred
overnight. The resultant solution was passed 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 the volatiles.
The resultant solid was dissolved in a minimum amount of CH2Cl2,
and was then layered with n-hexane. The chilled solution placed in the
freezer (−30 °C) afforded orange crystals (216 mg, 0.406 mmol).
hexane several times to extract VCl3(N-2-MeC6H4). The combined
filtrate and the wash were added toluene and were placed to dry under
reduced pressure to remove solvent (octane, n-hexane and toluene).
The resultant solid was dissolved in a minimum amount of CH2Cl2,
and a deep brown solid (7.80 g, 29.7 mmol) was obtained at room
temperature. Yield: 77.1% (based on o-tolyl isocyanate). 1H NMR
(CDCl3): δ 7.61 (d, 1H, J = 7.85, Ar-H), 7.21 (m, 3H, Ar-H), 2.85 (s,
3H, ArCH3). 13C NMR (CDCl3): δ 138.3, 132.3, 130.2, 128.8, 126.2,
18.5. 51V NMR (CDCl3): δ 296.7 (Δν1/2 = 349 Hz).
Synthesis of VCl2[2-(2,6-Me2C6H3)NCH2(C5H4N)](N-2-MeC6H4)
(4a). Into a toluene solution (60.0 mL) containing VCl3(N-2-
MeC6H4) (524 mg, 2.00 mmol) was added a toluene solution (20.0
mL) containing 2-(2,6-Me2C6H3)NHCH2(C5H4N) (427 mg, 2.01
mmol) and triethylamine (223 mg, 2.20 mmol) at −30 °C. The
reaction mixture was then warmed slowly to room temperature, and
the mixture was then stirred overnight. The solution was passed
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 the volatiles. The resultant solid was dissolved in a
minimum amount of hot toluene. The chilled solution placed in the
freezer (−30 °C) afforded red microcrystals (589 mg, 1.34 mmol).
Yield: 67.3%. 1H NMR (CDCl3): δ 9.04 (d, 1H, J = 5.50, Py-H), 7.99
(dt, 1H, J = 7.73 and 1.20, Py-H), 7.60 (t, 1H, J = 6.48, Py-H), 7.53 (d,
1H, J = 7.90, Py-H), 6.98 (d, 2H, J = 7.50, Ar-H), 6.93−6.89 (m, 2H,
Ar-H), 6.87−6.83 (m, 3H, Ar-H), 5.32 (s, 2H, NCH2), 2.62 (s, 3H,
ArCH3), 2.20 (s, 6H, ArCH3). 13C NMR (CDCl3): δ 161.6, 157.4,
149.7, 139.8, 138.4, 131.0, 129.5, 129.2, 128.3, 128.3, 127.8, 127.0,
125.4, 123.8, 120.3, 72.0, 18.6, 18.3. 51V NMR (CDCl3): δ 35.4 (Δν1/2
= 1380 Hz). Anal. Calcd. for C21H22Cl2N3V: C, 57.55; H, 5.06; N,
9.59. Found: C, 57.51; H, 5.06; N, 9.45. The attempted synthesis of 4a
by treatment with Li[2-(2,6-Me2C6H3)NCH2(C5H4N)] is shown in
the Supporting Information.
1
Yield: 40.9% [based on VCl3(NAd)]. H NMR (CDCl3): δ 8.67 (d,
1H, J = 8.75, quino-H), 8.34 (d, 1H, J = 8.50, quino-H), 7.90 (d, 1H, J
= 7.95, quino -H), 7.81−7.78 (m, 1H, quino-H), 7.63 (t, 1H, J = 7.33,
quino-H), 7.46 (d, 1H, J = 8.45, quino-H), 7.18−7.13 (m,3H, Ar-H),
5.31 (s, 2H, NCH2) 2.30 (s, 6H, ArCH3), 1.92 (s, 3H, Ad-H), 1.81 (d,
6H, Ad-H), 1.47 (t, 6H, Ad-H). 13C NMR (CDCl3): δ 163.5, 158.2,
144.7, 139.3, 130.2, 129.2, 129.0, 128.5, 128.4, 128.1, 127.3, 127.1,
117.6, 70.9, 41.1, 35.7, 35.7, 28.8, 18.5. 51V NMR (CDCl3): δ −119.3
(Δν1/2 = 1973 Hz). Anal. Calcd. for C28H32Cl2N3V: C, 63.16
(60.91+VC, vanadium carbide); H, 6.06; N, 7.89. Found (1): C, 61.52;
H, 5.97; N, 7.58. Found (2): C, 61.90; H, 6.00; N, 7.66. Found (3): C,
61.81; H, 5.84; N, 7.66. In spite of several independent analysis runs
(with different samples), the observed C values were somewhat low
because of incomplete combustion (by production of vanadium
carbide), whereas both H and N observed values were close to the
calculated values. NMR spectra for 2 are shown in the Supporting
Information.
Synthesis of VCl2[8-(2,6-Me2C6H3)NCH2(C9H6N)](N-1-ada-
mantyl) (3). Into a toluene solution (15.0 mL) containing 8-(2,6-
Me2C6H3)N(H)CH2(C9H6N) (300 mg, 1.15 mmol) was added n-
BuLi (0.75 mL, 1.18 mmol, n-hexane solution) at −30 °C. The
reaction mixture was then warmed slowly to room temperature, and
the mixture was stirred for 3 h. The resultant solid (lithium salt) was
collected on a glass filter and was washed with n-hexane. The solid was
then dried in vacuo to yield yellow powder (296 mg). Into a Et2O
solution (15.0 mL) containing VCl3(NAd) (332 mg, 1.10 mmol) was
added the above yellow powder (296 mg) at −30 °C. The reaction
mixture was then warmed slowly to room temperature, and the
mixture was then stirred overnight. The resultant solution was passed
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 the volatiles. The solid was then dissolved in a minimum
amount of CH2Cl2, and was layered with n-hexane. The chilled
solution placed in the freezer (−30 °C) afforded red microcrystals
(145 mg, 0.272 mmol). Yield: 25.1% [based on VCl3(NAd)]. 1H
NMR (CDCl3): δ 9.48−9.47 (m, 1H, quino-H), 8.45−8.43 (m, 1H,
quino-H), 7.94−7.92 (m, 1H, quino-H), 7.71−7.68 (m, 1H, quino-H),
7.57−7.24 (m, 2H, quino-H), 7.18−7.08 (m, 3H, Ar-H), 5.29 (s, 2H,
NCH2), 2.21 (s, 6H, ArCH3), 1.88 (s, 3H, Ad-H), 1.74−1.73 (d, 6H,
Ad-H), 1.46−1.41 (m, 6H, Ad-H). 13C NMR (CDCl3): δ 168.8, 153.8,
145.7, 139.7, 135.7, 129.5, 128.8, 128.8, 128.6, 128.5, 127.3, 126.8,
122.2, 67.3, 53.6, 41.2, 35.8, 29.0, 19.5. 51V NMR (CDCl3): δ −106.4
(Δν1/2 = 1776 Hz). Anal. Calcd. for C28H32Cl2N3V CH2Cl2: C, 56.42;
H, 5.55; N, 6.81. Found: C, 56.40; H, 5.49; N, 6.73.
Synthesis of VCl2[2-(2,6-iPr2C6H3)NCH2(C5H4N)](N-2-MeC6H4)
(4b). Into a toluene solution (12.0 mL) containing VCl3(N-2-
MeC6H4) (782 mg, 2.98 mmol) was added a toluene solution (2.0
mL) containing 2-(2,6-iPr2C6H3)NHCH2(C5H4N) (800 mg, 2.98
mmol) and triethylamine (336 mg, 3.32 mmol) at −30 °C. The
reaction mixture was then warmed slowly to room temperature, and
the mixture was then stirred overnight. The solution was passed
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 the volatiles. The resultant solid was dissolved in minimum
amount of hot toluene. The chilled solution placed in the freezer (−30
°C) afforded dark yellow microcrystals (432 mg, 0.874 mmol). Yield:
1
29.3%. H NMR (CDCl3): δ 8.99 (d, 1H, J = 5.35, Py-H), 7.99 (dt,
1H, J = 7.70 and 1.28, Py-H), 7.60 (t, 1H, J = 6.48, Py-H), 7.53 (d, 1H,
J = 7.90, Py-H), 7.37 (t, 1H, J = 7.70, Ar-H), 7.27 (d, 2H, Ar-H), 7.02
(d, 1H, J = 7.55, Ar-H), 6.83 (t, 1H, J = 7.45, Ar-H), 6.67 (t, 1H, J =
7.62, Ar-H), 5.46 (d, 1H, J = 8.00, Ar-H), 5.33 (s, 2H, NCH2), 2.93−
2.88 (m, 5H, ArCH3 and −CH(CH3)2), 1.17 (d, 6H, J = 6.95,
−CH(CH3)2), 1.12 (d, 6H, J = 6.65, −CH(CH3)2). 13C NMR
(CDCl3): δ160.2, 157.2, 149.7, 141.3, 139.2, 138.5, 129.8, 128.3, 127.8,
125.1, 124.7, 123.9, 120.2, 74.4, 28.2, 25.2, 24.4, 19.6. 51V NMR
(CDCl3): δ 79.7 (Δν1/2 = 2049.5 Hz). Anal. Calcd. for C25H30Cl2N3V:
C, 60.73 (58.31+VC, vanadium carbide); H, 6.13; N, 8.50. Found: C,
59.50; H, 6.22; N, 8.37. Attempted synthesis of 4b by treatment with
Li[2-(2,6-iPr2C6H3)NCH2(C5H4N)] is shown in the Supporting
Information.
Synthesis of VCl2[2-(2,6-Me2C6H3)NCH2(C5H4N)(N-4-MeC6H4)]
(5). Into a toluene solution (60.0 mL) containing VCl3(N-4-MeC6H4)
(525 mg, 2.00 mmol) was added a toluene solution (20.0 mL)
containing 2-(2,6-Me2C6H3)NHCH2(C5H4N) (425 mg, 2.00 mmol)
and triethylamine (226 mg, 2.23 mmol) at −30 °C. The reaction
mixture was then warmed slowly to room temperature, and the
mixture was then stirred overnight. The solution was passed 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 the volatiles. The solid was dissolved in a minimum amount of
CH2Cl2 and was layered with n-hexane. The chilled solution placed in
the freezer (−30 °C) afforded red microcrystals (387 mg, 0.833
Synthesis of VCl3(N-2-MeC6H4). Into a sealed Schlenk glass tube,
n-octane (50 mL) and o-tolyl isocyanate (5.13 g, 38.5 mmol) were
added sequentially in the drybox, and VOCl3 (11.1 g, 64.6 mmol) was
then added to the mixture. The wall of the tube was washed with n-
octane (5 mL), and the mixture was placed in an oil bath that had been
preheated at 140 °C, and was stirred overnight (17 h). The tube was
connected to a nitrogen line, and evolved CO2 was carefully removed
several times from the mixture. After the reaction, the cooled mixture
was filtered through a Celite pad, and the filtercake was washed with n-
2612
dx.doi.org/10.1021/ic302633y | Inorg. Chem. 2013, 52, 2607−2614

Inorganic Chemistry
Article
Table 4. Crystal Data and Collection Parameters of VCl2[2-(2,6-Me2C6H3)NCH2(C9H6N)](NAd) (2), VCl2[8-(2,6-
Me2C6H3)NCH2(C9H6N)](NAd) (3), VCl2[2-(2,6-Me2C6H3)NCH2(C5H4N)](N-2-MeC6H4) (4a), and VCl2[2-
a
(2,6-iPr2C6H3)NCH2(C5H4N)](N-2-MeC6H4) (4b)
b
c
2
3
4a
4b
formula
C28H32Cl2N3V
532.43
C29H34Cl4N3V
617.36
C21H22Cl2N3V
438.27
C51H62Cl6N6V2
1073.69
formula weight
crystal color, habit
crystal size (mm)
crystal system
space group
a (Å)
yellow, platelet
0.210 × 0.180 × 0.030
monoclinic
orange, platelet
0.200 × 0.180 × 0.070
triclinic
orange, platelet
0.240 × 0.170 × 0.010
orthorhombic
Pbca (#61)
yellow, platelet
0.120 × 0.080 × 0.020
triclinic
P21/c (#14)
16.4655(3)
P1 (#2)
P1 (#2)
̅
̅
8.9224(2)
10.1100(3)
16.7358(5)
77.7248(7)
85.5932(7)
74.3597(7)
1420.22(6)
2
7.7648(2)
9.4747(2)
17.3921(4)
17.9733(4)
68.8893(7)
74.8665(7)
80.4037(7)
2658.4(1)
2
b (Å)
14.5364(2)
14.4294(3)
c (Å)
10.7782(1
36.7708(8)
α (deg)
β (deg)
99.4194
γ (deg)
V (Å3)
2544.96(7)
4119.9(2)
Z value
Dcalcd (g/cm3)
4
8
1.389
1.444
1.413
1.341
F000
1112.00
640.00
1808.00
1116.00
123
temp (K)
μ (MoKα) (cm−1
123
123
123
)
6.214
7.492
7.509
6.923
no. of reflections measured (Rint)
total: 25020
total: 14238
unique: 6483 (0.0169)
54.9
total: 66707
total: 26683
unique: 12147 (0.0379)
55.0
unique: 5821 (0.0296)
unique: 4720 (0.0585)
2θmax (deg)
54.9
55.0
no. of observations [I > 2.00σ(I)]
no. of variables
5821
309
6483
4720
247
12147
336
596
R1 [I > 2.00σ(I)]
wR2 [I > 2.00σ(I)]
goodness of fit
0.0334
0.0901
1.137
0.0529
0.0412
0.1220
0.0407
0.1554
0.0969
1.096
1.082
1.046
a
b
c
Detailed structural data are shown in the Supporting Information. Complex 3 contains CH2Cl2 in the crystal. Structure for 4b was solved as two
crystals containing CH2Cl2.
1
mmol). Yield: 44.2%. H NMR (CDCl3): δ 9.02 (d, 1H, J = 5.35, Py-
VCl3(N-3,5-Me2C6H3) (631 mg, 2.28 mmol) was added a toluene
solution (20.0 mL) containing 2-(2,6-Me2C6H3)NHCH2(C5H4N)
(484 mg, 2.28 mmol) and triethylamine (253 mg, 2.51 mmol) at −30
°C. The reaction mixture was then warmed slowly to room
temperature, and the mixture was then stirred overnight. The solution
was passed 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 the volatiles. The solid was dissolved in a
minimum amount of CH2Cl2 and was layered with n-hexane. The
chilled solution placed in the freezer (−30 °C) afforded red
microcrystals (400 mg, 0.884 mmol). Yield: 38.8%. 1H NMR
(CDCl3): δ 9.02 (d, 1H, J = 5.40, Py-H), 8.00−7.96 (m, 1H, Py-H),
7.60 (t, 1H, J = 6.43, Py-H), 7.52 (d, 1H, J = 7.90, Py-H), 7.06 (d, 2H,
J = 7.35, Ar-H), 7.02−6.99 (m, 1H, Ar-H), 6.65 (s, 1H, Ar-H), 6.47 (s,
2H, Ar-H), 5.31 (s, 2H, NCH2), 2.17 (s, 6H, ArCH3), 2.09 (s, 6H,
ArCH3). 13C NMR (CDCl3): δ 162.4, 157.6, 149.7, 138.5, 137.4,
130.5, 128.7, 128.3, 127.0, 125.4, 123.9, 120.3, 71.8, 21.1, 18.4. 51V
NMR (CDCl3): δ 24.9 (Δν1/2 = 1973 Hz). Anal. Calcd. for
C22H24Cl2N3V: C, 58.42; H, 5.35; N, 9.29. Found: C, 58.40; H,
5.35; N, 9.55.
Oligomerization/Polymerization of Ethylene. Ethylene oligo-
merizations were conducted in a 100 mL scale stainless steel autoclave.
The typical reaction procedure is as follows. Toluene (29 mL) and
prescribed amount of MAO were added into the autoclave in the
drybox. The reaction apparatus was then filled with ethylene (1 atm),
and the prescribed amount of complexes in toluene (1.0 mL) was then
added into the autoclave, the reaction apparatus was then immediately
pressurized to 7 atm (total 8 atm), and the mixture was magnetically
stirred for 10 min. After the above procedure, the remaining ethylene
was purged at −30 °C, and 0.5 g of heptane was added as an internal
standard. The solution was then analyzed by GC to determinate the
activity and the product distribution. Ethylene polymerizations were
H), 7.99−7.96 (m, 1H, Py-H), 7.59 (t, 1H, J = 6.43, Py-H), 7.52 (d,
1H, J = 7.90, Py-H), 7.03 (d, 2H, J = 7.40, Ar-H), 6.98−6.95 (m, 1H,
Ar-H), 6.84−6.80 (m, 4H, Ar-H), 5.30 (s, 2H, NCH2), 2.31 (s, 3H,
ArCH3), 2.17 (s, 6H, ArCH3). 13C NMR (CDCl3): δ 162.1, 157.6,
149.6, 138.7, 138.5, 128.5, 128.5, 128.3, 128.0, 127.0, 123.8, 71.8, 21.7,
18.3. 51V NMR (CDCl3): δ 31.3 (Δν1/2 = 1868 Hz). Anal. Calcd. for
C21H22Cl2N3V: C, 57.55; H, 5.06; N, 9.59. Found: C, 57.52; H, 5.07;
N, 9.72.
Synthesis of VCl3(N-3,5-Me2C6H3). Into a sealed Schlenk glass
tube, n-octane (20 mL) and 3,5-dimethylphenylisocyanate (2.5 g, 17.0
mmol) were added sequentially in the drybox, and VOCl3 (4.98 g, 28.8
mmol) was then added to the mixture. The wall of the reactor was
washed with n-octane (5 mL), and the mixture was placed in an oil
bath that had been preheated at 140 °C, and was stirred overnight (24
h). The tube was connected to a nitrogen line, and CO2 evolved was
carefully released several times from the mixture. After the reaction,
the cooled mixture was filtered through a Celite pad, and the filtercake
was washed with n-hexane and toluene several times to extract
VCl3(N-3,5-Me2C6H3). The combined filtrate and the wash were
placed into dryness under reduced pressure to remove solvent (octane,
n-hexane, and toluene). The resultant residue was dissolved in a
minimum amount of hot toluene. A black solid (2.79 g, 10.1 mmol)
was collected from the chilled solution (placed in the freezer at −30
°C). Yield: 59.3% (based on 3,5-dimethylphenylisocyanate). VCl3(N-
1
3,5-Me2C6H3), yield 2.79 g, 10.1 mmol, 59.3% H NMR (CDCl3): δ
7.19 (2, 2H, Ar-H), 6.98 (s, 1H, Ar-H), 2.32 (s, 6H, ArCH3). 13C
NMR (CDCl3): δ 138.6, 134.7, 124.0, 21.2. 51V NMR (CDCl3): δ
280.3 (Δν1/2 = 506 Hz). Anal. Calcd for C8H9Cl3NV: C, 34.76; H,
3.28; N, 5.07. Found: C, 34.82; H, 3.29; N, 4.79.
Synthesis of VCl2[2-(2,6-Me2C6H3)NCH2(C5H4N)](N-3,5-
Me2C6H3) (6). Into a toluene solution (70.0 mL) containing
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dx.doi.org/10.1021/ic302633y | Inorg. Chem. 2013, 52, 2607−2614

Inorganic Chemistry
Article
also conducted similarly. After oligomerization, the chilled remaining
mixture in the autoclave was then poured into MeOH containing HCl.
The resultant polymer (white precipitate) was collected on a filter
paper by filtration and was adequately washed with MeOH. The
resultant polymer was then dried in vacuo at 60 °C for 2 h.
Crystallographic Analysis. All measurements were made on a
Rigaku RAXIS-RAPID Imaging Plate diffractometer with graphite
monochromated Mo−Kα radiation. The crystal collection parameters
are listed below (Table 4). All structures were solved by direct
methods and expanded using Fourier techniques,14 and the non-
hydrogen atoms were refined anisotropically. Hydrogen atoms were
refined using the riding model. All calculations were performed using
the Crystal Structure15 crystallographic software package except for
refinement, which was performed using SHELXL-97.16
K.; Zhang, W. Chem. Sci. 2010, 1, 161. (d) Redshaw, C. Dalton Trans.
2010, 39, 5595. (e) Nomura, K.; Zhang, S. Chem. Rev. 2011, 111, 2342
; related references are cited therein.
(6) (a) Nomura, K.; Sagara, A.; Imanishi, Y. Macromolecules 2002, 35,
1583. (b) Wang, W.; Nomura, K. Macromolecules 2005, 38, 5905.
(c) Wang, W.; Nomura, K. Adv. Synth. Catal. 2006, 348, 743.
(d) Onishi, Y.; Katao, S.; Fujiki, M.; Nomura, K. Organometallics 2008,
27, 2590. (e) Zhang, S.; Katao, S.; Sun, W,-H.; Nomura, K.
Organometallics 2009, 28, 5925.
(7) (a) Zhang, S.; Nomura, K. J. Am. Chem. Soc. 2010, 132, 4960.
(b) Igarashi, A.; Zhang, S.; Nomura, K. Organometallics 2012, 31,
3575.
(8) V complex catalysts, see: (a) Brussee, E. A. C.; Meetsma, A.;
Hessen, B.; Teuben, J. H. Chem. Commun. 2000, 497. (b) Schmidt, R.;
Welch, M. B.; Knudsen, R. D.; Gottfried, S.; Alt, H. G. J. Mol. Catal. A
2004, 222, 17. (c) Hanton, M. J.; Tenza, K. Organometallics 2008, 27,
5712. ; Vanadium complexes containing chelate bis(imino)pyridine
ligands yielded polymers/oligomers with Schultz−Flory distribu-
tion.8b,c
ASSOCIATED CONTENT
* Supporting Information
■
S
Experimental procedures for syntheses of 2-ArN(H)-
CH2(C9H6N) and 8-ArN(H)CH2(C9H6N) (Ar = 2,6-
Me2C6H3). Attempted syntheses of VCl2[2-(2,6-Me2C6H3)-
NCH2(C5H4N)](N-2-MeC6H4) (4a), and VCl2[2-
(2,6-iPr2C6H3)NCH2(C5H4N)](N-2-MeC6H4) (4b) by anoth-
er method via treatment of VCl3(N-2-MeC6H4) with the
lithium salts, Li[2-(2,6-R′2C6H3)NCH2(C5H4N)]. 1H NMR
spectra for V(NAd)Cl2[2-(2,6-Me2C6H3)NCH2(C9H6N)] (2),
V(NAd)Cl2[8-(2,6-Me2C6H3)NCH2(C9H6N)] (3), and V(N-
2-MeC6H4)Cl2[2-(2,6-iPr2C6H3)NCH2(C5H4N)] (4b). Struc-
tural reports including CIF files for VCl2[2-(2,6-Me2C6H3)-
NCH2(C9H6N)](NAd) (2), VCl2[8-(2,6-Me2C6H3)-
NCH2(C9H6N)](NAd) (3), VCl2[2-(2,6-Me2C6H3)-
NCH2(C5H4N)](N-2-MeC6H4) (4a), and VCl2[2-
(2,6-iPr2C6H3)NCH2(C5H4N)](N-2-MeC6H4) (4b). This ma-
terial is available free of charge via the Internet at http://pubs.
acs.org.
(9) These results were partly introduced by K.N. at the Chemelot
International Polyolefins Symposium 2012 (CIPS2012), Maastricht, The
Netherlands, October, 2012.
(10) Syntheses of 2-(2,6-Me2C6H3)N(H)CH2(C9H6N), 8-(2,6-
Me2C6H3)N(H)CH2(C9H6N) are described in the Supporting
Information.
(11) Structural reports including CIF files for VCl2[2-(2,6-Me2C6H3)
NCH2(C9H6N)](NAd) (2), VCl2[8-(2,6-Me2C6H3)NCH2(C9H6N)]
(NAd) (3), VCl2[2-(2,6-Me2C6H3)NCH2(C5H4N)](N-2-MeC6H4)
(4a), and VCl2[2-(2,6-iPr2C6H3)NCH2(C5H4N)](N-2-MeC6H4)
(4b) are provided in the Supporting Information.
(12) Syntheses of VCl3(N-2-MeC6H4) and VCl3(N-3,5-Me2C6H3)
were performed under the same conditions for that in V(N-4-
MeC6H4)Cl3, reported previously, as described in the Experimental
Section. (a) Devore, D. D.; Lichtenhan, J. D.; Takusagawa, F.; Maata,
E. A. J. Am. Chem. Soc. 1987, 109, 7408. Analogous synthesis of the
THF adduct of VCl3(THF)(N-3,5-Me2C6H3) (b) Nomura, K.;
Schrock, R. R.; Davis, W. M. Inorg. Chem. 1996, 35, 3695.
(13) Zhang, W.; Nomura, K. Inorg. Chem. 2008, 47, 6482.
(14) SIR2008: Burla, M. C.; Calandro, R.; Camalli, M.; Carrozzini,
B.; Cascarano, G. L.; De Caro, L.; Giacovazzo, C.; Polidori, G.; Siliqi,
D.; Spagna, R. J. Appl. Crystallogr. 2007, 40, 609.
AUTHOR INFORMATION
Corresponding Author
*Phone: +81-42-677-2547. Fax: +81-42-677-2547. E-mail:
ktnomura@tmu.ac.jp.
■
(15) Crystal Structure 4.0, Crystal Structure Analysis Package; Rigaku
and Rigaku Americas: Tokyo, Japan, 2000−2010; pp 196−8666.
(16) SHELX97: Sheldrick, G. M. Acta Crystallogr., Sect. A 2008, 64,
112.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This project was partly supported by Bilateral Joint Projects
between Japan Society of Promotion of Sciences (JSPS) and
National Natural Science Foundation of China (NSFC). K.N.
and A.I. express their heartfelt thanks to Tosoh Finechem Co.
for donating MAO. This project by W.Z. and W.S. was also
supported partly by NSFC (No. 21011140068).
REFERENCES
■
(1) (a) Carrick, W. L. J. Am. Chem. Soc. 1958, 80, 6455. (b) Carrick,
W. L.; Kluiber, R. W.; Bonner, E. F.; Wartman, L. H.; Rugg, F. M.;
Smyth, J. J. J. Am. Chem. Soc. 1960, 82, 3883. (c) Phillips, G. W.;
Carrick, W. L. J. Polym. Sci. 1962, 59, 401.
(2) (a) Junghanns, E.; Gumboldt, O.; Bier, G. Makromol. Chem.
1962, 58, 18. (b) Natta, G.; Mazzanti, G.; Valvassori, A.; Sartori, G.;
Fiumani, D. J. Polym. Sci. 1961, 51, 411.
(3) For example Christman, D. L.; Keim, G. I. Macromolecules 1968,
1, 358.
(4) (a) Doi, Y.; Ueki, S.; Keii, T. Macromolecules 1978, 12, 814.
(b) Doi, Y.; Koyama, T.; Soga, K. Makromol. Chem. 1985, 186, 11.
(5) For recent reviews (vanadium catalysts), see: (a) Hagen, H.;
Boersma, J.; van Koten, G. Chem. Soc. Rev. 2002, 31, 357.
(b) Gambarotta, S. Coord. Chem. Rev. 2003, 237, 229. (c) Nomura,
2614
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