Synthesis of (arylimido)vanadium(V) complexes containing (2-anilidomethyl)pyridine ligands and their use as the catalyst precursors for olefin polymerization

Article abstract of DOI:10.1021/om900633u

A series of (arylimido)vanadium(V) dichloride complexes containing (2-anilidomethyl)pyridine ligands of the type V(NAr)Cl₂[2- ′NCH₂(C₅H4N)] [Ar′ = 2,6-Me₂C ₆H₃; Ar′ = 2,6-Me₂C

Full text of DOI:10.1021/om900633u

Organometallics 2009, 28, 5925–5933 5925
DOI: 10.1021/om900633u
Synthesis of (Arylimido)vanadium(V) Complexes Containing
(2-Anilidomethyl)pyridine Ligands and Their Use as the Catalyst
Precursors for Olefin Polymerization
Shu Zhang,† Shohei Katao,† Wen-Hua Sun,‡ and Kotohiro Nomura*,†
†Graduate School of Materials Science, Nara Institute of Science and Technology (NAIST), 8916-5
Takayama, Ikoma, Nara 630-0101, Japan, and ‡Key Laboratory of Engineering Plastics, Institute of
Chemistry, Chinese Academy of Sciences, Beijing 100190, People’s Republic of China
Received July 19, 2009
A series of (arylimido)vanadium(V) dichloride complexes containing (2-anilidomethyl)pyridine
ligands of the type V(NAr)Cl2[2-Ar0NCH2(C5H4N)] [Ar=2,6-Me2C6H3; Ar0 =2,6-Me2C6H3 (1a),
2,6-iPr2C6H3 (1b), 2,6-F2C6H3 (1c)] have been prepared from V(NAr)Cl3 by treating with Li-
[2-Ar0NCH2(C5H4N)], and the structures of 1b,c have been determined by X-ray crystallography.
These complexes are effective catalyst precursors for ethylene polymerization in the presence of Al
cocatalysts: 1b showed the highest catalytic activities in the presence of Et2AlCl (6000 kg PE/mol
V h), and the observed activities of 1a,b in the presence of Et2AlCl were much higher than those in the
3
presence of MAO. V(NAr)(CH2SiMe3)2[2-Ar0NCH2(C5H4N)] (2a,b) have been prepared by treating
1a,b with 2.0 equiv of LiCH2SiMe3, and their structures have been determined by X-ray crystallo-
graphy. The dialkyl complex 2b cleanly reacted with 2.0 equiv of (CF3)2CHOH in C6D6 at 25 °C to
afford V(NAr)(CH2SiMe3)[OCH(CF3)2][2-Ar0NCH2(C5H4N)] (3), and the reaction with 3.0 equiv
of (CF3)2CHOH eventually afforded V(NAr)[OCH(CF3)2]2[2-Ar0NCH2(C5H4N)] (4) from 3 after
3 days. The dialkyl complexes 2a,b showed catalytic activities for ring-opening metathesis poly-
merization (ROMP) of norbornene in benzene at 80 °C in the presence of PMe3. The ROMP did not
occur in the absence of PMe3 under the same conditions, suggesting that an additional coordination
of PMe3 may be required to induce the R-hydrogen elimination.
Introduction
and polymer chemistry.1-6 Classical Ziegler-type vanadium
catalyst systems [consisting of vanadium compounds
{V(acac)3, VOCl3, etc.} and organometallic reagents (Et2-
Designing efficient transition metal complex catalysts for
olefin coordination polymerization attracts considerable
attention in the field of catalysis, organometallic chemistry,
n
AlCl, Et2AlCl EtAlCl2, BuLi, etc.)] are known to display
3
unique characteristics6,7 due to the high reactivity toward
olefins in olefin coordination polymerization, and the synth-
esis of new efficient vanadium complex catalysts for con-
trolled olefin polymerization has thus been one of the most
attractive targets.2f,2h,2i,6,8-10
*Corresponding author. Tel: þ81-743-72-6041. Fax: þ81-743-72-
6049. E-mail: nomurak@ms.naist.jp.
(1) Mason, A. F.; Coates, G. W. In Macromolecular Engineering;
Matyjaszewski, K.; Gnanou, Y.; Leibler, L., Eds.; Wiley-VCH: Weinheim,
Germany, 2007; Vol. 1, p 217.
Although there have been many reports especially with
vanadium(III) and vanadium(IV) complexes for the above
purpose,6c,7,8c-8q we focused on high oxidation state
(imido)vanadium(V) complexes containing an anionic ancil-
lary donor ligand.6c,8b,8c,9 We recently reported that
(arylimido)vanadium(V) complexes containing anionic donor
ligands of the type V(NAr)Cl2(L) (Ar = 2,6-Me2C6H3, L =
aryloxo, ketimide, phenoxyimine, Chart 1) exhibited moder-
ate/remarkable catalytic activities in ethylene polymerization
€
(2) (a) Brintzinger, H. H.; Fischer, D.; Mulhaupt, R.; Rieger, B.;
Waymouth, R. M. Angew. Chem., Int. Ed. Engl. 1995, 34, 1143. (b)
Kaminsky, W. Macromol. Chem. Phys. 1996, 197, 3903. (c) Kaminsky, W.;
Arndt, M. Adv. Polym. Sci. 1997, 127, 143. (d) Suhm, J.; Heinemann, J.;
€
Worner, C.; M€uller, P.; Stricker, F.; Kressler, J.; Okuda, J.; M€ulhaupt, R.
Macromol. Symp. 1998, 129, 1. (e) McKnight, A. L.; Waymouth, R. M.
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€
L. K.; Brookhart, M. Chem. Rev. 2000, 100, 1169. (b) Alt, H. G.; Koppl, A.
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r
2009 American Chemical Society
Published on Web 09/23/2009
pubs.acs.org/Organometallics

5926 Organometallics, Vol. 28, No. 20, 2009
Zhang et al.
in the presence of methylaluminoxane (MAO), affording
(ultra) high molecular weight polyethylene with uniform
molecular weight distributioins.9a-9c,9f,9h It also turned out
that the catalytic activities by the aryloxo analogue V(NAr)-
V(NAr)Cl2[O-2-R3-6-{(2,6-iPr2C6H3)NdCH}C6H3] (R3
H, Me, tBu) exhibited notable catalytic activities for ethylene
polymerization in the presence of MAO,9h and we assumed
that a coordination of the imino nitrogen to the vanadium
(with a distorted square-pyramidal or trigonal-bipyramidal
geometry) should lead to better stabilization than the above
aryloxo ligands. In this paper, we thus focused on using a (2-
anilidomethyl)pyridine ligand, [2-Ar0NCH2(C5H4N)]-, that
can be simply derived from 2-iminopyridine (used as efficient
ligands for ethylene polymerization by late transition metal
catalysis)11 and that can be used as promising ligands for olefin
polymerization by group 4 transition metal catalysis.12 We herein
present the synthesis, structural analysis for (arylimido)-
vanadium(V) dichloride complexes containing (anilidomethyl)-
pyridine ligands, V(NAr)Cl2[2-Ar0CH2(C5H4N)] [Ar0 = 2,6-
R2C6H3, R=Me (1a), iPr (1b), F (1c), Chart 1], and their use
as catalyst precursors for ethylene polymerization in the presence
of Al cocatalysts (MAO, Et2AlCl). Moreover, we have recently
reported syntheses of various vanadium(V)-alkyl complexes and
the reaction with alcohol13,14b as well as the successful isolations
of “olefin metathesis active” vanadium(V)-alkylidenes by sub-
sequent R-hydrogen elimination;14-16 therefore, we herein pre-
sent the synthesis of vanadium(V)-dialkyl complexes and ring-
opening metathesis polymerization (ROMP) of norbornene with
the dialkyl complexes including attempted isolation of the
vanadium(V)-alkylidene.
=
Cl2(O-2,6-R1 C6H3) (R1 = Me, iPr, Ph, etc.) in the presence of
2
halogenated aluminum alkyls (such as Et2AlCl, EtAlCl2,
EtAlCl2 Et2AlCl, etc.) were higher than those in the presence
3
of MAO,9b,9d,9e,9g whereas the remarkable enhancement in the
activities by the ketimide analogue V(NAr)Cl2[NdC(R2)tBu]
(R2=tBu, CH2SiMe3) was not seen in the presence of Et2AlCl.9f
We reported more recently that (arylimido)vanadium(V)
complexes containing phenoxy-imine ligands of the type
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Results and Discussions
1. Synthesis and Structural Analysis of (Arylimido)-
vanadium(V) Dichloride Complexes Containing (2-Anilido-
methyl)pyridine Ligands of Type V(NAr)Cl2[2-Ar0NCH2-
(C5H3N)] [Ar0 = 2,6-Me2C6H3 (1a), 2,6-iPr2C6H3 (1b), 2,6-
F2C6H3 (1c)]. The ligands, 2-Ar0N(H)CH2(C5H3N) [Ar0 =
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Article
Organometallics, Vol. 28, No. 20, 2009 5927
˚
0.275 A for 1c. This would be explained as due to the steric
Chart 1
i
bulk of the Pr substituent in 1b compared to the fluorine
substituent in 1c.
˚
The V-N(pyridine) bond distances [2.211(2), 2.208(2) A]
are close to those in V(NAr)Cl2[O-2-R3-6-{(2,6-iPr2-
9h
˚
C6H3)NdCH}C6H3] [2.216(4)-2.203(2) A]. The V-N-
˚
(anilido) [V(1)-N(1)] bond distances [1.850(2), 1.877(2) A]
are longer than that in V(NAr)Cl2(NdCtBu2) [1.787-
14a
˚
(1) A],
but apparently shorter than the V-N(pyridine)
bond distances. The distances are, however, shorter than the
˚
covalent radii (1.964 A) for a vanadium-nitrogen single
bond according to Pauling’s covalent radii.19 It is thus clear
that the vanadium and nitrogen form a σ bond in addition to
π donation from the nitrogen, although the π donation from
nitrogen to vanadium may be weak compared to the keti-
mide complexes.14a
2,6-R2C6H3; R=Me, iPr, F] were prepared by condensation
reactions between pyridinecarboxaldehyde and the corre-
sponding anilines, followed by the reduction of imine by
NaBH4.12b Reactions of V(NAr)Cl3, prepared from VOCl3
by treatment with ArNCO in n-octane,17 with LiN(2,6-
R2C6H3)CH2(C5H3N) (R = Me, iPr, F) [prepared by treat-
ing 2-Ar0N(H)CH2(C5H3N) with 1 equiv of nBuLi in
n-hexane at -30 °C] in Et2O afforded V(NAr)Cl2[2-(2,6-
2. Ethylene Polymerization by V(NAr)Cl2[2-Ar0NCH2-
(C5H3N)]-Cocatalyst Systems. Ethylene polymerizations
by V(NAr)Cl2[2-Ar0NCH2(C5H3N)] [Ar0 = 2,6-R2C6H3;
R = Me (1a), iPr (1b), F (1c)] were conducted in toluene in
the presence of d-MAO [white solid prepared by removing
toluene and AlMe3 from commercial PMAO-S (Tosoh
Finechem Co.), as described in the Experimental Section]
or Et2AlCl (1 M in n-hexane). The results are summarized in
Tables 2 and 3.
The catalytic activities at 25 °C in the presence of MAO
were affected by the Al/V molar ratio, and the ratio of 3000
seems favored for 1a,b (and the ratio of 1000 for 1c) under
these conditions. The activity increased in the order (Al/V =
i
R2C6H3)NCH2(C5H3N)] [R = Me (1a), Pr (1b), F (1c)] in
yields of 29-58% (Scheme 1). Analytically pure complexes
1b and 1c were collected as deep red microcrystals from
a concentrated toluene solution layered with n-hexane
at -30 °C, whereas pure 1a was collected as red precipitates
according to the same procedure. These complexes were
1
identified on the basis of H, 51V, and 13C NMR spectra
and elemental analyses. The structures of 1b and 1c were
determined by X-ray crystallography (Figure 1), and selected
bond lengths and the angles are summarized in Table 1.18
The structures of 1b and 1c indicate that these complexes
have a distorted trigonal-bipyramidal geometry around
vanadium consisting of two nitrogen atoms in the pyridine
and the imido ligands axis and an equatorial plane consisting
of two chlorine atoms and the nitrogen in the anilide ligand
[total bond angles of Cl(1)-V(1)-Cl(2), N(1)-V(1)-Cl(1),
N(1)-V(1)-Cl(2) are 353.4° (1b), 354.94° (1c), respectively;
N(2)-V(1)-N(3): 175.93(10)° for 1b, 170.71(10)° for 1c].
Two chlorine atoms are positioned in a cis form.
3000 at 25 °C) 78 kg PE/mol V h (1a, R = Me) < 189 (1b,
3
R = iPr) < 594 (1c, R = F). Both the activity and the Mw
value in the resultant polymer increased if the polymeriza-
tion by 1c was conducted at 0 °C, but the activity decreased at
50 °C probably due to a partial decomposition of the
catalytically active species as seen in the aryloxo analogue.9c
The resultant polymers possessed high molecular weights
(Mw = (1.06-2.98) ꢀ 106) with unimodal molecular weight
distributions, suggesting that these polymerizations pro-
ceeded with uniform catalytically active species under these
conditions. The Mw values in the resultant polymers pre-
pared by 1c were not strongly affected by the Al/V molar
ratios (runs 5-8, Table 2), but the Mw values seemed to
˚
The V-Cl bond distances [2.2449(9)-2.2868(9) A] are
similar to those in V(NAr)Cl2(NdCtBu2) [2.2338(5),
14a
˚
2.2710(5) A]
and V(NAr)Cl2[O-2-R3-6-{(2,6-iPr2C6H3)-
t
NdCH}C6H3] (R3 = H, Me, Bu) [2.2452(18)-2.2828(7)
A],9h but shorter than those in V(NAr)Cl2(NdCtBu2)(PMe3)
be affected by the substituent in the anilide moiety [Mw
=
˚
(1.06-1.67) ꢀ 106 (R = F, 1c) vs (1.84-2.98) ꢀ 106 (R =
t
[2.298(2), 2.314(2) A] and V(NAr)Cl2(NdC Bu2)(dmpe)
˚
Me, iPr, 1a,b)].
˚
[2.3652(7), 2.3751(9) A, dmpe = 1,2-(dimethylphosphino)-
methane].14a The V-N bond distances in the arylimido
In contrast, as shown in Table 3, the catalytic activity of 1c
in the presence of Et2AlCl in place of MAO at 0 °C was much
lower than those of 1a,b [activity under the same conditions,
complex 1.0 μmol, Al/V = 100 (molar ratio): 156 kg PE/mol
˚
ligand in 1b,c [V(1)-N(3)=1.679(3), 1.676(2) A, respecti-
vely] are somewhat longer than those in V(NAr)Cl2-
t
(NdC Bu2) [1.669(2) A],
14a
V(NAr)Cl2(NdCtBu2)(PMe3)
˚
and V(NAr)Cl2[O-2-R3-6-{(2,6-iPr2C6-
14a
V h (run 23, 1c) vs 840 (runs 12, 1a), 3780 (run 17, 1b)]. The
3
˚
[1.652(3) A],
iPr analogue (1b) showed remarkable catalytic activities, and
the activity of 6000 kg PE/mol V h was attained under the
H3)NdCH}C6H3] [1.6376(18)-1.654(4) A],9h but similar to
˚
t
that in V(NAr)Cl2(NdC Bu2)(dmpe) [1.677(2) A].
14a
˚
3
This
optimized conditions (run 21). The observed catalytic activ-
ities of 1a,b in the presence of Et2AlCl were much higher than
those in the presence of MAO, and the facts are somewhat
analogous to those observed in the ethylene polymerization
using (arylimido)vanadium(V) complexes containing ary-
loxo ligands.9b,9d The activity decreased at 25 °C, as seen
previously for ethylene polymerization using the aryloxo
analogues.9d The resultant polymers prepared by 1a-c
possessed high molecular weights (Mw = (1.72-3.52) ꢀ
106, prepared at 0 °C) with unimodal distributions, as
would be thus explained as due to a trans influence of the
pyridine ligand.
The bond angle of N(imido)-V-N(pyridine) [N(2)-
V(1)-N(3)] in 1b is larger than that in 1c [175.93(10)° vs
170.71(10)°], the Cl(1)-V-Cl(2) in 1b is also larger than that
in 1c [121.87(3)° vs 114.03(3)°], and the vanadium atom
˚
deviates from the equatorial plane by 0.317 A for 1b and
(17) Buijink, J.-K. F.; Teubin, J. H.; Kooijman, H.; Spek, A. L.
Organometallics 1994, 13, 2922.
(18) Structural analysis reports (including crystal data and collection
parameters) and CIF files are shown in the Supporting Information.
(19) Pauling, L. J. Am. Chem. Soc. 1947, 69, 542.

5928 Organometallics, Vol. 28, No. 20, 2009
Zhang et al.
i
Figure 1. ORTEP drawings of V(N-2,6-Me2C6H3)Cl2[(2,6-R2C6H3)NCH2(C5H3N)] [R = Pr (1b, left), F (1c, right)]. Thermal
ellipsoids are drawn at the 50% probability level, and hydrogen atoms are omitted for clarity.18
Table 1. Selected Bond Lengths and Angles for V(N-2,6-Me2-
C6H3)Cl2[(2,6-R2C6H3)NCH2(C5H3N)] [R = iPr (1b), F (1c)]a
Table 2. Ethylene Polymerization by V(N-2,6-Me2C6H3)Cl2-
[(2,6-R2C6H3)NCH2(C5H3N)] [R = Me (1a), iPr (1b), F
(1c)]-MAO Catalyst Systemsa
complex (R)
1b (iPr)
1c (F)
d
complex
(R)
Mw
Al/Vb temp/°C yield/mg activityc 10-6 Mw/Mn
ꢀ
d
˚
Bond Distances (A)
run
V(1)-N(1)
1.850(2)
2.211(2)
1.679(2)
2.2645(10)
2.2868(9)
1.877(2)
2.208(2)
1.676(2)
2.2661(9)
2.2449(9)
1
2
3
4
5
6
7
8
9
1a (Me)
1000
3000
1000
3000
100
25
25
25
25
25
25
25
25
0
24
26
72
78
1.84
2.98
2.55
2.93
2.6
2.0
1.9
2.6
V(1)-N(2)
V(1)-N(3)
V(1)-Cl(1)
V(1)-Cl(2)
1a (Me)
1b (iPr)
1b (iPr)
1c (F)
1c (F)
1c (F)
1c (F)
1c (F)
22
63
66
189
198
555
618
594
822
327
66
Bond Angles (deg)
500
185
206
198
274
109
1.38
1.06
1.67
2.42
1.10
2.8
2.3
2.9
2.6
2.6
1000
3000
1000
1000
N(1)-V(1)-N(2)
N(1)-V(1)-N(3)
N(1)-V(1)-Cl(1)
N(1)-V(1)-Cl(2)
N(2)-V(1)-N(3)
N(2)-V(1)-Cl(1)
N(2)-V(1)-Cl(2)
N(3)-V(1)-Cl(1)
N(3)-V(1)-Cl(2)
Cl(1)-V(1)-Cl(2)
77.66(9)
76.93(9)
98.52(11)
114.55(7)
116.98(8)
175.93(10)
82.45(7)
94.10(10)
120.40(8)
120.51(8)
170.71(10)
85.09(6)
85.86(7)
97.67(8)
100.97(8)
114.03(3)
169.3(2),
10 1c (F)
50
a Conditions: complex 2.0 μmol, toluene 30 mL, ethylene 8 atm, 10 min,
MAO (prepared by removing toluene and AlMe3 from the commercially
83.87(6)
available MAO). b Molar ratio of Al/V. c Activity in kg polymer/mol V h.
3
100.56(9)
96.74(8)
121.87(3)
d GPC data in o-dichlorobenzene versus polystyrene standards.
V(1)-N(imido)-C(Ar)176.2(2),
V(1)-N(3)-C(19)
a Detailed analysis results are shown in the Supporting Information.18
V(NAr)Cl3 without isolation of 1b. A similar attempt for the
synthesis of 2a failed because of the difficulty in isolating 2a from
the reaction mixture. Attempts to isolate V(NAr)(CH2SiMe3)2-
[2-(2,6-F2C6H3)NCH2(C5H3N)] by adopting the above two
approaches were not successful. Analytically pure 2a,b were
collected as red microcrystals from a concentrated n-hexane
solution at -30 °C, and these complexes were identified by 1H,
13C, and 51V NMR spectra and elemental analyses. The struc-
tures of 2a,b were also determined by X-ray crystallography
(Figure 2), and selected bond lengths and angles are summarized
in Table 4.18
The structures of 2a and 2b indicate that the coordination
geometry around vanadium is a distorted trigonal bipyra-
midal consisting of an axis with two nitrogen atoms (in the
pyridine and the imido ligands) and an equatorial plane (with
two carbon atoms in the CH2SiMe3 ligand and the nitrogen in
the anilide ligand) [total bond angles of C(23)-V(1)-C(27),
V(1)-N(3)-C(13)
exemplified in Figure 3. The results also suggest that these
polymerizations proceeded with uniform catalytically active
species under these conditions. As also shown in Figure 3, the
Mw values were dependent upon the polymerization tem-
perature as well as the substituent in the anilide moiety.
3. Synthesis and Structural Analysis of the (Aryli-
mido)vanadium(V) Dialkyl Complexes V(NAr)(CH2SiMe3)2-
[2-Ar0NCH2(C5H3N)] [Ar0 = 2,6-Me2C6H3 (2a), 2,6-iPr2-
C6H3 (2b)]. The vanadium(V)-dialkyl complexes of the type
V(NAr)(CH2SiMe3)2[2-Ar’NCH2(C5H3N)] [Ar0=2,6-R2C6H3,
R = Me (2a), iPr (2b)] were prepared by treating the dichloride
analogues (1a,b) with 2.0 equiv of LiCH2SiMe3 in toluene
(Scheme 1). Alternatively, 2b can also be prepared directly from

Article
Organometallics, Vol. 28, No. 20, 2009 5929
Scheme 1
the monoalkoxo complex V(NAr)(CH2SiMe3)[OCH-
(CF3)2][2-(2,6-iPr2C6H3)NCH2(C5H3N)] (3), and the 51V
NMR spectrum in the mixture showed a resonance of 3 in
addition to a resonance ascribed to 2b as a tiny trace
(Scheme 2). A resonance ascribed to the bis(alkoxo) complex
V(NAr)[OCH(CF3)2]2[2-(2,6-iPr2C6H3)NCH2(C5H3N)] (4)
was seen in addition to the monoalkoxide (3) when 2b was
treated with 3.0 equiv of (CF3)2CHOH in C6D6 at 25 °C.20
The percentage of 4 increased at prolonged reaction times,
and a resonance ascribed to 4 became the major product in
the 51V NMR spectrum after 3 days; 4 could thus be isolated
in 63% yield as red microcrystals from the chilled n-hexane
solution (-30 °C).20 The complexes 3 and 4 were identified
by NMR spectra and elemental analyses. The reaction
proceeded slowly even upon addition of an excess amount
of (CF3)2CHOH, probably because, as we recently pro-
posed, the reactions proceeded via intermediates formed by
coordination of ROH.13c,20
Table 3. Ethylene Polymerization by V(N-2,6-Me2C6H3)Cl2-
[(2,6-R2C6H3)NCH2(C5H3N)] [R = Me (1a), iPr (1b),
F (1c)]-Et2AlCl Catalyst Systemsa
d
complex
run ( μmol) Al/Vb temp/°C yield/mg activityc
Mw
ꢀ
Mwd/
Mn
10-6
11 1a (1.0)
50
0
0
0
25
0
0
0
0
25
0
0
104
140
102
86
194
440
630
418
97
124
200
141
26
624
840
612
516
1164
2640
3780
2508
582
3720
6000
4230
156
12 1a (1.0) 100
13 1a (1.0) 200
14 1a (1.0) 100
15 1b (1.0)
16 1b (1.0)
17 1b (1.0) 100
18 1b (1.0) 200
19 1b (1.0) 100
20 1b (0.2) 100
21 1b (0.2) 200
22 1b (0.2) 300
23 1c (1.0) 100
3.12
4.1
4.1
6.04
25
50
2.57
1.72
0.97
3.42
2.18
3.36
3.52
3.1
3.0
3.2
3.4
2.7
3.4
3.7
0
0
a Conditions: toluene 30 mL, ethylene 8 atm, 10 min, Et2AlCl (1 M in
n-hexane). b Molar ratio of Al/V. c Activity in kg polymer/mol V h.
Ring-Opening Metathesis Polymerization of Norbornene
by 2a,b in the Presence of PMe3: Attempt for Isolation of
Vanadium(V)-Alkylidene. We previously reported that V-
(NAr)(CH2SiMe3)2(NdCtBu2) and V(NAr)(CH2SiMe3)2-
3
d GPC data in o-dichlorobenzene versus polystyrene standards.
N(1)-V(1)-C(23), N(1)-V(1)-C(27) are 353.4° (2a), 352.97°
(2b), respectively; N(2)-V(1)-N(3): 173.78(5)° for 2a,
175.60(17)° for 2b]. Two carbon atoms in the CH2-
SiMe3 ligands are positioned in a cis form, and the bond
angles for N(1)-V(1)-N(2) are small [76.37(5)° for 2a,
75.88(17)° for 2b] due to the two nitrogen atoms coordinating
to vanadium as a chelate bidentate ligand. Both the
N(imido)-V-N(pyridine) and the N(imido)-V-N(anilide)
bond angles in 2b are larger than those in 2a, probably due to an
(O-2,6-R1 C6H3) (R1=Me, iPr) initiated ring-opening meta-
2
thesis polymerization (ROMP) of norbornene at 50-80 °C
in the presence of PMe3.14a,14b These results clearly indicated
formation of the vanadium(V)-aklylidene species via
R-hydrogen elimination.14,15 We thus explored possibilities
of 2a,b as the catalyst precursors for the ROMP of norbor-
nene, and the results are summarized in Table 5. Ring-
opened poly(norbornene)s, confirmed by 1H NMR spctra,21
were collected when the reactions of 2a,b were conducted in
the presence of PMe3, and the polymer yields were dependent
upon the molar ratios of PMe3/V (Scheme 3). The ROMP
did not take place or afforded negligible amounts of poly-
mers if the reactions were conducted in the absence of PMe3.
It is thus assumed that a certain amount of vanadium(V)-
alkylidene was formed especially in the presence of PMe3, as
seen in the previous reports.14a,14b Although the resultant
polymers possessed ring-opened structures (which possessed
a mixture of cis- and trans-olefinic double bonds) confirmed
i
increased steric bulk of the Pr substituent in 2b compared
to the Me substituent in 2a [N(2)-V(1)-N(3) = 173.78(5)°
(2a), 175.60(17)° (2b); N(1)-V(1)-N(3) = 97.60(6)° (2a),
99.74(19)° (2b)].
4. Some Reactions with the Vanadium(V)-Dialkyl Com-
i
plexes (2a,b). The reaction of the Pr analogue (2b) with
2.0 equiv of (CF3)2CHOH in C6D6 at 25 °C cleanly afforded
(20) 1H and 51V NMR spectra for monitoring the reaction of V(N-
2,6-Me2C6H3)(CH2SiMe3)2[2-(2,6-iPr2C6H3)NCH2(C5H3N)] (2b) with
3.0 equiv of (CF3)2CHOH in C6D6 at 25 °C are shown in the Supporting
Information. Although resonances ascribed to an intermediate
were seen (in the 1H, 19F, 51V NMR spectra) in the reaction of the
(adamantyl)vanadium(V)-dialkyl complex containing a chelate alkoxo-
(imino)pyridine ligand, V(1-adamantyl)(CH2SiMe3)2(L0) [L0 = 6-OC-
(Me)2-2-{(2,6-iPr2C6H3)NdCMe}C5H3N], with (CF3)2CHOH,13c other
resonances (in addition to 3 and 4) were not seen in the 51V NMNR
spectra during the course of the reaction.
(21) 1H NMR spectra for the resultant ring-opened poly-
(norbornene)s are shown in the Supporting Information. As described
in the text, however, attempts to measure the molecular weights and their
distributions by GPC (in THF at 50 °C as well as in o-dichlorobenzene at
140 °C) failed due to their poor solubility.

5930 Organometallics, Vol. 28, No. 20, 2009
Zhang et al.
i
Figure 2. ORTEP drawings of V(N-2,6-Me2C6H3)(CH2SiMe3)2[(2,6-R2C6H3)NCH2(C5H3N)] [R = Me (2a, left), Pr (2b, right)].
Thermal ellipsoids are drawn at the 50% probability level, and hydrogen atoms are omitted for clarity.18
Table 4. Selected Bond Lengths and Angles for V(N-2,
6-Me2C6H3)(CH2SiMe3)2[(2,6-R2C6H3)NCH2(C5H3N)] [R =
Me (2a), iPr (2b)]a
complex (R)
2a (Me)
2b (iPr)
˚
Bond Distances (A)
V(1)-N(1)
1.9006(13)
2.2752(13)
1.6807(14)
2.0758(19)
2.0864(18)
1.900(3)
2.259(4)
1.659(4)
2.101(5)
2.093(5)
V(1)-N(2)
V(1)-N(3)
V(1)-C(23)
V(1)-C(27)
Bond Angles (deg)
N(1)-V(1)-N(2)
N(1)-V(1)-N(3)
N(1)-V(1)-C(23)
N(1)-V(1)-C(27)
N(2)-V(1)-N(3)
N(2)-V(1)-C(23)
N(2)-V(1)-C(27)
N(3)-V(1)-C(23)
N(3)-V(1)-C(27)
C(23)-V(1)-C(27)
V(1)-N(3)-C(15)
76.37(5)
97.60(6)
125.11(6)
114.21(6)
173.78(5)
82.32(6)
86.23(6)
100.24(7)
97.78(7)
114.08(6)
176.96(11)
75.88(17)
99.74(19)
125.0(2)
113.17(19)
175.60(17)
82.61(18)
85.45(18)
100.4(2)
96.1(2)
Figure 3. GPC traces for resultant polyethylene prepared
by V(N-2,6-Me2C6H3)Cl2[(2,6-R2C6H3)NCH2(C5H3N)] [R =
iPr (1b), F (1c)]-Et2AlCl catalyst systems (Table 3).
1
by H NMR spectra, attempts for measurements of their
molecular weights and their distributions by GPC measure-
ment (in THF at 50 °C as well as in o-dichlorobenzene at
140 °C) failed due to their poor solubility probably owing to
ultra high molecular weights.21
114.8(2)
179.0(3)
a Detailed analysis results are shown in the SupportingInformation.18
Scheme 2
A C6D6 solution containing 2b in the presence of PMe3
(excess, 7 equiv) was heated at 80 °C on the basis of the above
polymerization results.22 Resonances probably ascribed to
alkylidene protons were observed at 16.7 and 17.1 ppm in the
1H NMR spectrum after 6 h, and at least three resonances
including 2b were seen in the 51V NMR spectrum.22 However,
the observed resonances (assumed to be ascribed to the alky-
lidenes) disappeared after 24 h, probably due to decomposition.
(22) 1H and 51V NMR spectra for monitoring the reaction of
V(N-2,6-Me2C6H3)(CH2SiMe3)2[2-(2,6-iPr2C6H3)NCH2(C5H3N)] (2b)
in C6D6 in the presence or absence of PMe3 at 80 °C are shown in the
Supporting Information.

Article
Table 5. Ring-Opening Metathesis Polymerization (ROMP)
Organometallics, Vol. 28, No. 20, 2009 5931
V(NAr)(CH2SiMe3)[OCH(CF3)2][2-Ar0NCH2(C5H4N)] (3)
in high isolated yield. The reaction with 3.0 equiv of
(CF3)2CHOH at 25 °C initially gave 3 (major) in addition
to V(NAr)[OCH(CF3)2]2[2-Ar0NCH2(C5H4N)] (4), and 4
became the major product after 3 days: a unique reacti-
vity of these vanadium(V)-alkyls with alcohol was thus ob-
served.13,14b
The dialkyl complexes 2a,b showed catalytic activities for
ring-opening metathesis polymerization (ROMP) of norbor-
nene in benzene in the presence of PMe3, but the polymer
yields were low and the reaction did not occur in the absence
of PMe3. The facts are in good agreement with those in the
NMR experiments, in which resonances assumed to be
ascribed to the vanadium(V)-alkylidene(s) were initially ob-
served if a C6D6 solution of 2b was heated at 80 °C in the
presence of PMe3, but these resonances were not seen in
the absence of PMe3. The facts also clearly indicate that the
presence of a pyridine moiety in the chelate ligand in 2a,b
could not initiate the R-hydrogen elimination, and it is thus
assumed that an octahedral geometry formed by coordina-
tion of an additional donor ligand may be required to induce
R-hydrogen elimination.
of Norbornene by V(N-2,6-Me2C6H3)(CH2SiMe3)2-
[(2,6-R2C6H3)NCH2(C5H3N)] [R = Me (2a), iPr (2b)]a
complex
PMe3/Vb
time/min
yield/mg
TONc
2a
2a
2a
2b
2b
2b
2b
0
30
30
30
30
30
30
30
trace
10.2
20.8
trace
6.0
3.0
5.0
0
3.0
5.0
10.0
55
112
32
158
16
29.1
3.0
a Reaction conditions: complex 2.0 μmol, benzene 2.5 mL, norbor-
nene 2.12 mmol (0.85 mmol/mL), 80 °C. b Molar ratio. c TON=nor-
bornene consumed (mmol)/V (mmol).
Scheme 3
Experimental Section
General Procedures. All experiments were carried out under
a nitrogen atmosphere in a Vacuum Atmospheres drybox. An-
hydrous grade toluene, n-hexane, diethyl ether, and benzene
(Kanto Kagaku Co., Ltd.) were transferred into a bottle con-
taining molecular sieves (a mixture of 3A 1/16, 4A 1/8, and 13X
1/16) in the drybox under N2 and were passed through an short
alumina column under a N2 stream before use. Polymerization
grade ethylene (purity >99.9%, Sumitomo Seika Co. Ltd.) was
used as received. Toluene and AlMe3 in commercially available
methylaluminoxane [PMAO-S, 9.5 wt % (Al) toluene solution,
Tosoh Finechem Co.] were removed under reduced pressure (at
ca. 50 °C to remove toluene and AlMe3, and then at >100 °C for
1 h for completion) in the drybox to give white solids (d-MAO).
Et2AlCl (1 M in n-hexane) was used as received. V(N-2,6-Me2-
C6H3)Cl2 was prepared according to a published method.17
Molecular weights and molecular weight distributions for
polyethylene (shown in Table 2) were measured by gel permea-
tion chromatography (Tosoh HLC- 8121GPC/HT) with a poly-
styrene gel column (TSK gel GMHHR-H HT ꢀ 2, 30 cm ꢀ 7.8
mm j), ranging from <102 to <2.8 ꢀ 108 MW) at 140 °C using
o-dichlorobenzene containing 0.05 w/v % 2,6-di-tert-butyl-p-
cresol as eluent. The molecular weight was calculated by a
standard procedure based on the calibration with standard
polystyrene samples. The molecular weights and molecular
weight distributions of the polyethylene in Table 3 were mea-
sured at 145 °C by gel permeation chromatography (Waters
150 CV) using o-dichlorobenzene as the solvent and calibration
with standard polystyrene samples (measured at Sumitomo
Chemical Co., Ltd.).
Although we initially expected that the pyridine moiety in the
ligand [2-Ar0NCH2(C5H3N)]- might be used as the neutral
donor ligand like PMe3 to induce R-hydrogen elimination, a
C6D6 solution containing 2b caused only decomposition of 2b
after 18 h.22 The result thus clearly explains the fact that we could
not collect the ROMP polymer if the polymerization by 2b was
conducted in the absence of PMe3. The low polymer yields by 2a,
b would also be explained by the fact that the percentage of the
vanadium(V)-alkylidene formed in situ was low under these
conditions. We have thus not yet isolated the targeted vanadium-
(V)-alkylidene presumably due to the difficulty in isolating it
from the mixture.
Concluding Remarks
We have prepared a series of (arylimido)vanadium(V)
complexes containing (2-anilidomethyl)pyridine ligands of
the type V(N-2,6-Me2C6H3)Cl2[2-Ar0NCH2(C5H4N)] [Ar0=
2,6-Me2C6H3 (1a), 2,6-iPr2C6H3 (1b), 2,6-F2C6H3 (1c)], and
the structures of 1b,c have been determined as having a
distorted trigonal-bipyramidal geometry around vanadium
by X-ray crystallography. These complexes are effective
catalyst precursors for ethylene polymerization in the pre-
sence of Al cocatalysts, and 1c showed the highest catalytic
activities among 1a-c in the presence of MAO cocatalyst,
whereas 1b showed much higher catalytic activities in the
presence of Et2AlCl cocatalyst (6000 kg PE/mol V h). The
Elemental analyses were performed by using a PE2400II
3
1
Series (Perkin-Elmer Co.). All H, 13C, and 51V NMR spectra
resultant polymers are linear polyethylene and possessed
high molecular weights with unimodal molecular weight
distributions in most cases, suggesting that the polymeriza-
tions proceeded with uniform catalytically active species.
The activity by 1b was much higher than that by V(NAr)Cl2-
(NdCtBu2)9f but lower than that by V(NAr)Cl2(O-2,
6-Me2C6H3)9d under similar conditions (Et2AlCl cocatalyst,
ethylene 8 atm, 0 °C). The dialkyl complexes (2a,b) have been
prepared by treating 1a,b with 2.0 equiv of LiCH2SiMe3, and
the structures have been determined by X-ray crystallo-
graphy. Complex 2b cleanly reacted with 2.0 equiv of
(CF3)2CHOH in C6D6 at 25 °C to afford the mono(alkoxide)
were recorded on a JEOL JNM-LA400 spectrometer (399.65
MHz for 1H, 100.40 MHz for 13C, and 105.31 MHz for 51V). All
spectra were obtained in the solvent indicated at 25 °C unless
otherwise noted. Chemical shifts are given in ppm and are
1
referenced to SiMe4 (δ 0.00, H, 13C) and VOCl3 (δ 0.00, 51V).
Coupling constants and half-width values, Δν1/2, are given in Hz.
Synthesis of V(N-2,6-Me2C6H3)Cl2[2-(2,6-Me2C6H3)NCH2-
(C5H3N)] (1a). Into an Et2O solution containing V(N-2,6-
Me2C6H3)Cl3 (277 mg, 1.0 mmol) was added Li[2-(2,6-
Me2C6H3)NCH2(C5H3N)] (218 mg, 1.0 mmol) at -30 °C. The
reaction mixture was warmed slowly to room temperature, and
the mixture was stirred overnight. The solvent was then removed

5932 Organometallics, Vol. 28, No. 20, 2009
Zhang et al.
in vacuo, and the resultant deep red-tan residue was extracted
with hot toluene. The solution was concentrated in vacuo and
was layered with n-hexane. A red powder was obtained upon
standing at -30 °C. Yield: 289 mg (58%). 1H NMR (CDCl3): δ
9.04 (d, 1H, J = 5.20, Py-H), 7.95 (t, 1H, J = 7.70, Py-H), 7.57
(t, 1H, J = 6.40, Py-H), 7.49 (d, 1H, J=7.60, Py-H), 6.90 (d, 2H,
J = 7.20, Ar-H), 6.83 (t, 1H, J = 8.80, Ar-H), 6.69 (s, 3H, VdN-
Ar-H), 5.31 (s, 2H, NCH2), 2.60 (s, 6H, ArCH3), 2.17 (s, 6H,
ArCH3). 13C NMR (CDCl3): δ 160.7, 157.0, 149.8, 142.9, 138.1,
128.0, 127.9, 127.4, 127.2, 126.8, 123.6, 119.9, 71.9, 19.3, 18.2.
51V NMR (CDCl3): δ 76.7 (Δν1/2=1424 Hz). Anal. Calcd for
C22H24Cl2N3V(0.5 toluene): C, 58.42; H, 5.35; N, 9.29. Found:
C, 58.31; H, 5.44; N, 8.94.
the red solid was washed by n-hexane (20 mL). The solid was dried
in vacuo and then dissolved in toluene (40 mL). LiCH2SiMe3
(0.330 g, 3.52 mmol) was added into the solution at -30 °C, and
the reaction mixture was warmed slowly to room temperature and
was stirred overnight. The solvent was then removed in vacuo to
remove volatiles, and the resultant residue was extracted with
n-hexane. The n-hexane was replaced in vacuo, and the resultant
sticky brown oil was then dissolved with a small amount of
n-hexane. The solution was placed in the freezer (-30 °C), afford-
ing a red solid (0.603 g, 0.985 mmol) in 56% yield. (ii) Method 2
from 1b. Complex 2b can also be prepared from 1b. Into a toluene
solution (10 mL) containing V(N-2,6-Me2Ar)Cl2[2-(2,6-iPr2-
C6H3)NCH2(C5H3N)] (0.102 g, 0.20 mmol) was added LiCH2-
SiMe3 (0.038 g, 0.40 mmol) at -30 °C. The reaction mixture was
warmed slowly to room temperature and was stirred for 6 h. The
solvent was then removed in vacuo, and the resultant residue was
extracted with n-hexane. The n-hexane extract was placed in vacuo
to remove volatiles, and the resultant red solid was dissolved in a
small amount of n-hexane (ca. 0.5 mL). The chilled solution placed
in the freezer (-30 °C) gave red microcrtystals (0.089 g, 0.146
mmol) in a yield of 73%. 1H NMR (C6D6): δ 9.05 (d, 1H, J =5.12,
Py-H), 7.08-7.01 (m, 4H, Py-H and Ar-H), 6.83 (t, J = 5.12, Py-
H), 6.84-6.81 (m, 3H, Ar-H), 6.70-6.66 (m, 2H, Ar-H), 5.00 (s,
2H, NCH2), 3.29-3.22 (m, 2H, CH(CH3)2), 3.06 (d, 2H, J=10.24,
CH2SiMe3), 2.61 (s, 6H, ArCH3), 1.08-1.00 (m, 14H, CH(CH3)2
and CH2SiMe3), 0.04 (s, 18H, Si(CH3)3). 13C NMR (C6D6): δ
161.8, 157.9, 148.6, 141.9, 140.0, 137.2, 125.7, 124.4, 124.2, 123.3,
120.2, 70.1, 27.6, 27.5, 23.0, 21.0, 2.8, 1.5. 51V NMR (C6D6): δ
435.7 (Δν1/2 =1141 Hz). Anal. Calcd for C34H54N3Si2V: C, 66.73;
H, 8.89; N, 6.87. Found: C, 66.03; H, 8.97;N, 7.06.
Synthesis of V(N-2,6-Me2C6H3)Cl2[2-(2,6-iPr2C6H3)NCH2-
(C5H3N)] (1b). Synthesis of 1b was similar to that of 1a, except
that Li[2-(2,6-iPr2C6H3)NCH2(C5H3N)] (330 mg, 1.2 mmol)
was used in place of Li[2-(2,6-Me2C6H3)NCH2(C5H3N)]. Red
microcrystals of 1b were collected in a yield of 30% (yield:
190 mg). 1H NMR (CDCl3): δ 8.96 (b, 1H, Py-H), 7.95 (t, 1H,
J =7.00, Py-H), 7.56 (d, 1H, J = 5.60, Py-H), 7.48 (d, 1H, J =
6.40, Py-H), 7.23 (m, 1H, Ar-H), 7.14 (m, 2H, Ar-H), 6.76 (s, 3H,
VdN-Ar-H), 5.38 (s, 2H, NCH2), 3.02 (m, 2H, CH(CH3)2), 2.36
(s, 6H, ArCH3), 1.11 (m, 12H, CH(CH3)2). 13C NMR (CDCl3):
δ 158.9, 156.4, 142.8, 139.4, 138.2, 128.1, 128.1, 127.6, 127.4,
124.2, 123.7, 119.9, 74.4, 27.8, 25.9, 23.3, 19.8. 51V NMR
(CDCl3): δ 142.0 (Δν1/2 =3587 Hz). Anal. Calcd for C26H32-
Cl2N3V(0.25 toluene): C, 62.72; H, 6.45; N, 7.91. Found: C,
62.62; H, 6.46; N, 7.87.
Synthesis of V(N-2,6-Me2C6H3)Cl2[2-(2,6-F2C6H3)NCH2-
(C5H3N)] (1c). Synthesis of 1c was similar to that in 1a except
that Li[2-(2,6-F2C6H3)NCH2(C5H3N)] (415 mg, 1.5 mmol) was
used in place of Li[2-(2,6-Me2C6H3)NCH2(C5H3N)]. Red mi-
crocrystals of 1c were collected in a yield of 29% (yield: 222 mg).
1H NMR (CDCl3): δ 9.09 (d, 1H, J = 5.60, Py-H), 7.95 (t, 1H,
J = 7.70, Py-H), 7.56 (t, 1H, J = 6.40, Py-H), 7.49 (d, 1H, J =
8.00, Py-H), 7.17 (toluene), 6.82 (m, 1H, Ar-H), 6.70 (s, 3H, Ar-
H), 6.67 (m, 2H, Ar-H), 5.46 (s, 2H, NCH2), 2.62 (s, 6H,
ArCH3), 2.34 (tolenen). 13C NMR (CDCl3): δ 157.3, 154.8,
152.2, 150.0, 143.2, 138.3, 129.0, 128.2, 128.0, 127.1, 126.9,
123.4, 119.9, 111.2, 111.0, 72.6, 18.8. 51V NMR (CDCl3): δ
55.0 (Δν1/2 =1988 Hz). Anal. Calcd for C20H18Cl2F2N3V(0.5
toluene): C, 55.75; H, 4.38; N, 8.33. Found: C, 55.71; H, 4.30;
N, 8.33.
Synthesis of V(N-2,6-Me2C6H3)(CH2SiMe3)[OCH(CF3)2]-
[2-(2,6-iPr2C6H3)NCH2(C5H3N)] (3). A C6D6 solution of
(CF3)2CHOH (17 mg, 0.10 mmol) was added to a C6D6 solution
containing 2b (0.031 g 0.05 mmol). The mixture was stirred for 1
h, and the solvent was then removed in vacuo. The resultant solid
was dissolved with a small amount of n-hexane, and the chilled
solution (-30 °C) afforded red microcrystals (0.027 g, 0.039
1
mmol) in a yield of 78%. H NMR (C6D6): δ 9.02 (d, 1H, J=
5.20, Py-H), 7.06-6.93 (m, 4H, Py-H and Ar-H), 6.69-6.52 (m,
5H, Ar-H), 5.20 (m, 1H, CH(CF3)2), 5.10 (d, 1H, J = 20.80,
NCH2), 4.83 (d, 1H, J = 20.40, NCH2), 3.50 (m, 1H, CH-
(CH3)2), 3.09 (m, 1H, CH(CH3)2), 2.56 (d, 1H, J = 10.80,
CH2SiMe3), 2.43 (s, 6H, ArCH3), 2.35 (d, 1H, J=10.80, CH2-
SiMe3), 1.09-1.02 (m, 12H, CH(CH3)2), 0.11 (s, 9H, Si(CH3)3).
13C NMR (CDCl3): δ 160.3, 158.6, 148.1, 141.5, 141.4, 140.4,
137.9, 126.6, 125.9, 124.6, 124.3, 123.0, 120.0, 71.3, 28.0,
27.8, 27.3, 27.0, 23.2, 22.9, 19.8, 2.7. 51V NMR (CDCl3): δ
75.7 (Δν1/2 =716 Hz). Anal. Calcd for C33H44F6N3OSiV: C,
57.30; H, 6.41; N, 6.07. Found: C, 56.32; H, 6.31; N, 5.96.
Synthesis of V(N-2,6-Me2C6H3)[OCH(CF3)2]2[2-(2,6-iPr2-
C6H3)NCH2(C5H3N)] (4). A C6D6 solution of (CF3)2CHOH
(0.102 g, 0.60 mmol) was added to a C6D6 solution containing 2b
(0.124 g, 0.20 mmol). The mixture was stirred for 3 days, and the
solvent was removed in vacuo. The resultant oil was dissolved
with a small amount of n-hexane (ca. 0.5 mL), and the chilled
solution (-30 °C) afforded red microcrystals (0.097 g, 0.126
mmol) in a yield of 63%. 1H NMR (C6D6): δ 8.79 (d, 1H, J =
5.48, Py-H), 7.09-7.02 (m, 3H, Py-H), 6.74 (t, 1H, J = 7.60, Ar-
H), 6.52 (d, 2H, J = 7.60, Ar-H), 6.46-6.40 (m, 2H, Ar-H), 6.32
(d, 1H, J = 7.60, Ar-H), 4.99-4.95 (m, 4H, NCH2 and CH-
(CF3)2), 3.38 (m, 2H, CH(CH3)2), 2.36 (s, 6H, ArCH3),
1.10-1.08 (m, 12H, CH(CH3)2). 13C NMR (CDCl3): δ 159.3,
159.0, 147.7, 142.3, 141.2, 138.7, 124.7, 123.4, 121.9, 119.9,
80.7 (m), 71.5, 28.0, 27.2, 23.0, 18.8. 51V NMR (C6D6): δ
214.7 (Δν1/2 = 1353 Hz). Anal. Calcd for C32H34F12N3O2V:
C, 49.81; H, 4.44; N, 5.45. Found: C, 50.07; H, 4.61; N, 5.33. 1H
and 51V NMR spectra for monitoring the reaction are shown in
the Supporting Information.20
Synthesis of V(N-2,6-Me2C6H3)(CH2SiMe3)2[2-(2,6-Me2C6-
H3)NCH2(C5H3N)] (2a). Into a toluene solution (20 mL) con-
taining V(N-2,6-Me2Ar)(L)Cl2 (0.114 g, 0.25 mmol) was added
LiCH2SiMe3 (0.047 g, 0.50 mmol) at -30 °C. The reaction
mixture was warmed slowly to room temperature and was
stirred for 6 h. The solvent was then removed in vacuo, and the
resulting residue was extracted with n-hexane. The n-hexane
extracts were placed in vacuo, and the resultant red solid was
dissolved in a small amount of n-hexane (ca. 1 mL). The solution
was placed in a freezer (-30 °C), and red microcrystals were
grown from the chilled solution (0.083 g, 0.15 mmol) in a yield
of 60%. 1H NMR (C6D6): δ 9.06 (d, 1H, J = 5.60, Py-H), 7.03 (t,
1H, J = 7.70, Py-H), 6.84-6.65 (m, 8H, Py-H and Ar-H), 4.56
(s, 2H, NCH2), 3.00 (d, 2H, J = 10.00, CH2SiMe3), 2.74 (s, 6H,
ArCH3), 2.10 (s, 6H, ArCH3), 0.75 (d, 2H, J = 10.40, CH2-
SiMe3), 0.07 (s, 18H, Si(CH3)3). 13C NMR (C6D6): δ162.3,
159.1, 148.2, 139.0, 136.9, 130.7, 124.5, 124.3, 122.9, 120.6,
67.1, 20.5, 18.9, 2.8, 1.5. 51V NMR (C6D6): δ 386.7 (Δν1/2
=
622 Hz). Anal. Calcd for C30H46N3Si2V: C, 64.83; H, 8.34; N,
7.56. Found: C, 64.81; H, 8.73; N, 7.53.
One-Pot Synthesis of V(N-2,6-Me2C6H3)(CH2SiMe3)2-
[2-(2,6-iPr2C6H3)NCH2(C5H3N)] (2b). (i) Method 1 from
V(NAr)Cl3. Into a Et2O solution (40 mL) containing Li-
[2-(2,6-iPr2C6H3)NCH2(C5H3N)] (0.482 g, 1.76 mmol) was added
V(N-2,6-Me2C6H3)Cl3 (0.490 g, 1.76 mmol) at -30 °C. The
reaction mixture was warmed slowly to room temperature and
was stirred for 12 h. The solvent was then removed in vacuo, and
Crystallographic Analysis. All measurements were made on
a Rigaku RAXIS-RAPID imaging plate diffractometer with

Article
Organometallics, Vol. 28, No. 20, 2009 5933
graphite-monochromated Mo KR radiation. Selected crystal
collection parameters and the detailed results are described in
the Supporting Informatioin.18 All structures were solved by
direct methods and expanded using Fourier techniques,23 and
the non-hydrogen atoms were refined anisotropically. Hydro-
gen atoms were included but not refined. All calculations were
performed using the CrystalStructure24,25 crystallographic soft-
ware package, except for refinement for 1c as well as 2b, which
was performed using SHELXL-97.26
benzene solution containing 2b (or 2a, 2.0 μmol) and a benzene
solution (1.0 mL) containing a prescribed amount of PMe3 in the
drybox at room temperature. Then the mixture was magneti-
cally stirred for a prescribed time at a prescribed temperature.
The polymerization was then quenched by the addition of excess
PhCHO, and the solution was stirred for an additional 1 h at
room temperature for completion. The mixture was then poured
into MeOH (ca. 100 mL). The resultant polymer was collected
on filter paper and was adequately washed with MeOH. The
1
Polymerization of Ethylene. Ethylene polymerizations were
conducted in a 100 mL scale stainless steel autoclave, and the
typical reaction procedure is as follows. Toluene (29 mL) and
MAO solid (prepared from ordinary MAO by removing toluene
and AlMe3) or Et2AlCl (1 M in n-hexane) were added into the
autoclave in the drybox. The reaction apparatus was then filled
with ethylene (1 atm), and a toluene solution (1.0 mL) contain-
ing the dichloride complex 1 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, remaining ethylene was
purged upon cooling, and the mixture was then poured into
MeOH containing HCl. The resultant polymer (white pre-
cipitate) 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.
polymer was then dried in vacuo for several hours. H NMR
(CDCl3) of the PNBE: δ 5.31 (m), 5.19 (m), 2.76 (b), 2.40 (b),
1.85-1.74 (m), 1.33 (m), 1.07-0.99 (m).21
Acknowledgment. This work was partly supported by a
Grant-in-Aid for Scientific Research on Priority Areas
(No. 19028047, “Chemistry of Concerto Catalysis”) from
the Ministry of Education, Culture, Sports, Science and
Technology, Japan. This project is also partly supported
by Bilateral Joint Projects between the Japan Society for
the Promotion of Science (JSPS) and National Natural
Science Foundation of China (NSFC). S.Z. expresses his
sincere thanks to JSPS for a postdoctoral fellowship
(P08361). K.N. and Z.S. express their thanks to Sumitomo
Chemical Co., Ltd. (Petrochemicals Research Laboratory)
for GPC analysis.
Ring-Opening Metathesis Polymerization of Norbornene. Into
a sealed Schlenk tube containing a benzene solution (0.5 mL)
containing norbornene (2.12 mmol, 200 mg) were added a
Supporting Information Available: 1H and 51V NMR spectra
for monitoring reactions of V(N-2,6-Me2C6H3)(CH2SiMe3)2-
[2-(2,6-iPr2C6H3)NCH2(C5H3N)] (2b) in C6D6 at 80 °C in the
presence/absence of PMe3, reaction of 2b with 3.0 equiv of
(CF3)2CHOH in C6D6 at 25 °C, affording V(N-2,6-Me2C6H3)-
[OCH(CF3)2]2[2-(2,6-iPr2C6H3)NCH2(C5H3N)] (2b), and 1H
NMR spectra of poly(norbornene)s prepared by 2b in benzene
in the presence of PMe3. Text giving crystal structure reports
(including crystal data and collection parameters) and CIF files
for 1b, 1c, 2a, and 2b. These materials are available free of charge
via the Internet at http://pubs.acs.org.
(23) DIRDIF94: Beurskens, P. T.; Admiraal, G.; Beurskens, G.;
Bosman, W. P.; de Delder, R.; Israel, R.; Smits, J. M. M. The DIRDIF94
Program System, Technical Report of the Crystallography Laboratory;
University of Nijmegen: The Netherlands, 1994.
(24) CrystalStructure 3.6.0: Crystal Structure Analysis Package;
Rigaku and Rigaku/MSC: The Woodlands, TX, 2000-2004 .
(25) Watkin, D. J., Prout, C. K. Carruthers, J. R.; Betteridge, P. W.
CRYSTALS Issue 10; Chemical Crystallography Laboratory: Oxford, UK,
1996.
(26) Sheldrick, G. M. SHELX97; Program for Crystal Structure
€
€
€
Determination; Institut fur Anorganische Chemie der Universitat:
€
Gottingen, Germany, 1997.