Synthesis, structural characterization, and olefin polymerization behavior of vanadium(iii) complexes bearing tridentate schiff base ligands

Article abstract of DOI:10.1021/om801028g

Vanadium(III) complexes bearing tridentate salicylaldiminato ligands (2a - f) [OC₆H₄CH=NL]-VC1₂(THF) (L = CH ₂CH₂OMe, 2a; CH₂CH₂NMe₂, 2b; CH₉C₅H<

Full text of DOI:10.1021/om801028g

Organometallics 2009, 28, 1817–1825
1817
Synthesis, Structural Characterization, and Olefin Polymerization
Behavior of Vanadium(III) Complexes Bearing Tridentate Schiff
Base Ligands
Ji-Qian Wu,†,‡ Li Pan,† Yan-Guo Li,† San-Rong Liu,† and Yue-Sheng Li*,†
State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry,
Chinese Academy of Sciences, Changchun 130022, People’s Republic of China, and Graduate School of
the Chinese Academy of Sciences, Changchun Branch, People’s Republic of China
ReceiVed October 26, 2008
Vanadium(III) complexes bearing tridentate salicylaldiminato ligands (2a-f) [OC6H4CHdNL]-
VCl2(THF) (L ) CH2CH2OMe, 2a; CH2CH2NMe2, 2b; CH2C5H4N, 2c; 8-C9H6N (quinoline), 2d;
2-MeSC6H4, 2e; 2-Ph2PC6H4, 2f) and tridentate ꢀ-enaminoketonato ligands [OC6H8CHdN-2-
Ph2PC6H4]VCl2(THF) (2g) and [O(Ph)CdCHCHdN-2-Ph2PC6H4]VCl2(THF) (2h) were prepared from
VCl3(THF)3 by treating with 1.0 equiv of the deprotonated ligands in tetrahydrofuran (THF). These
complexes were characterized by FTIR and mass spectrometry as well as elemental analysis. Structures
of complexes 2e, 2f, and 2h were further confirmed by X-ray crystallographic analysis. These complexes
were investigated as catalysts for olefin polymerization in the presence of organoaluminum compounds.
On activation with Et2AlCl, complexes 2a-h exhibited high catalytic activities toward ethylene
polymerization (up to 20.64 kg PE/mmolV · h · bar) even at high temperature, suggesting these catalysts
possess high thermal stability. Moreover, high molecular weight polymers with unimodal molecular weight
distribution can be obtained, indicating the single site behavior of these catalysts. The copolymerizations
of ethylene and norbornene or 1-hexene with catalysts 2a-h were also explored in the presence of Et2AlCl,
which led to high molecular weight poly(ethylene-co-1-hexene)s (Mw up to 138 000) and poly(ethylene-
co-norbornene)s (Mw up to 164 000). Catalytic activity, comonomer incorporation, and polymer molecular
weight can be controlled in a wide range by the variation of catalyst structure and the reaction parameters
such as Al/V molar ratio, comonomer feed concentration, and polymerization reaction temperature.
been employed in “non-metallocene” catalysts for olefin
polymerization.1b,3a,b,20 In several cases, the enhancements of
catalytic activity and/or selectivity engendered by the introduc-
tion of pendant donor groups in N, O ligands have been proposed
to arise from both steric hindrance and electronic effects.21 In other
cases, it was proposed that ligand denticity plays an important role
Introduction
The development of homogeneous, single-site transition metal
catalysts for olefin polymerization has attracted considerable
attention.1 Among the transition metals, vanadium catalysts have
played a critically important role in producing high molecular
weight polyethylene with narrow molecular weight distribution
as well as ethylene/R-olefin or cycloolefin copolymers with high
comonomer incorporations.2 However, catalyst deactivation is
an issue in polymerization with vanadium complexes in general,
especially at high polymerization temperatures, due to reduction
of catalytically active vanadium species to low-valent, less
active, or inactive species. Nonetheless, there has been consider-
able and growing interest in designing and synthesizing ancillary
ligands to stabilize the active vanadium species in recent
years.3-19 The bidentate, tridentate, or polydentate ligands can
be used to provide protective shields for catalytically active
metal centers. This protection strategy is one that has recently
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* To whom correspondence should be addressed. Fax: +86-431-
85262039. E-mail: ysli@ciac.jl.cn.
† Changchun Institute of Applied Chemistry.
‡ Graduate School of the Chinese Academy of Sciences.
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10.1021/om801028g CCC: $40.75
2009 American Chemical Society
Publication on Web 02/18/2009

1818 Organometallics, Vol. 28, No. 6, 2009
Wu et al.
Scheme 1. Previously Reported Salicylaldiminato Vanadium-
(III) Complexes
Scheme 2. General Synthetic Route of the Vanadium
Complexes Used in This Study
in influencing the stability of vanadium complexes.22 Many
tridentate or polydentate ligands have been applied to stabilize the
active vanadium complexes.4c,6b,7b,13,16c,f,22–25 For example, va-
nadium complexes bearing tridentate bis(benzimidazole) amine
ligands reported by Gibson’s group showed high activity toward
olefin polymerization.4c Vanadium complexes with calixarene
ligands were also applied to ethylene polymerization by Redshaw
and co-workers.16c,f Lorber and his colleagues found the amine
bis(phenolate) ligand can stabilize vanadium complexes that
exhibited high activity for ethylene polymerization.25 However,
complexes with high thermal stability in olefin polymerizations
were scarce.19a,b
especially for the mono chelate vanadium(III) complexes I.26
Thus, this work was initially aimed at stabilizing vanadium(III)
complexes and exploring their olefin polymerization behavior
by introducing π donation from pendant heteroatoms such as
O, N, S, P in the Schiff base ligands.
Previously, vanadium complexes I and II (Scheme 1) bearing
one or two bidentate N, O ligands have been shown to be
efficient catalysts for ethylene polymerization;18 however, fast
deactivation took place at high polymerization temperatures,
Results and Discussion
1. Synthesis and Characterization of Tridentate Schiff
Base Containing Vanadium(III) Complexes. The general
synthetic routes of new vanadium complexes adopted in this
study are shown in Schemes 2 and 3. The tridentate salicyla-
ldiminato ligands 1a-f were prepared by the known proce-
dure,27 and tridentate ꢀ-enaminoketonato ligands 1g and 1h were
readily obtained in 62% and 85% yields by Schiff base
condensation of the corresponding diketones with o-(diphe-
nylphosphino)aniline. The tridentate ligands were deprotonated
by 1.0 equiv of NaH, followed by treating with 1.0 equiv of
VCl3(THF)3 in THF at room temperature. The reaction products
were isolated by recrystallization from a mixture of THF and
n-hexane at room temperature. These complexes were identified
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Y.; Katao, S.; Fujiki, M.; Nomura, K. Organometallics 2008, 27, 2590. (h)
Nomura, K.; Onishi, Y.; Fujiki, M.; Yamada, J. Organometallics 2008, 27,
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A. R.; Kranenburg, M.; McInnes, E.; Mountford, P. Inorg. Chem. 2006,
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1
by FTIR and mass spectra as well as elemental analysis. H
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Commun. 2004, 1954. (b) Redshaw, C.; Rowan, M. A.; Homden, D. M.;
Dale, S. H.; Elsegood, M.; Matsui, S.; Matsuura, S. Chem. Commun. 2006,
3329. (c) Redshaw, C.; Rowan, M. A.; Warford, L.; Homden, D. M.;
Arbaoui, A.; Elsegood, M.; Dale, S. H.; Yamato, T.; Casas, C. P.; Matsui,
S.; Matsuura, S. Chem.-Eur. J. 2007, 13, 1090. (d) Homden, D. M.;
Redshaw, C.; Hughes, D. L. Inorg. Chem. 2007, 46, 10827. (e) Homden,
D.; Redshaw, C.; Wright, J. A.; Hughes, D. L.; Elsegood, M. Inorg. Chem.
2008, 47, 5799. (f) Homden, D.; Redshaw, C. Chem. ReV. 2008, 108, 5086.
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Commun. 1999, 1015. (b) Janas, Z.; Jerzykiewicz, L. B.; Przybylak, S.;
Richards, R. L.; Sobota, P. Organometallics 2000, 19, 4252. (c) Janas, Z.;
Wisniewska, D.; Jerzykiewicz, L. B.; Sobota, P.; Drabent, K.; Szczegot,
K. Dalton Trans. 2007, 2065.
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J. Polym. Sci., Part A: Polym. Chem. 2008, 46, 2038.
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Chem. Lett. 2003, 32, 766. (b) Nakayama, Y.; Bando, H.; Sonobe, Y.; Fujita,
T. J. Mol. Catal. A: Chem. 2004, 213, 141. (c) Bialek, M.; Czaja, K. J.
Polym. Sci., Part A: Polym. Chem. 2008, 46, 6940.
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(21) (a) Tshuva, E. Y.; Goldberg, I.; Kol, M. J. Am. Chem. Soc. 2000,
122, 10706. (b) Tshuva, E. Y.; Goldberg, I.; Kol, M.; Weitman, H.;
Goldschmidt, Z. Chem. Commun. 2000, 379. (c) Hu, W. Q.; Sun, X. L.;
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NMR spectra indicated that these complexes are paramagnetic
species, which is similar to the case of bidentate Schiff base
vanadium(III) complexes.18,26
Crystals suitable for crystallographic analysis were grown
from the THF-hexane mixture solution containing compounds
2e, 2f, 2h, respectively, and their molecular structures were
further confirmed by X-ray crystallographic analyses. As shown
in Figures 1 and 2, the molecular structures of 2e and 2f display
meridional binding of the tridentate ligand, with the two chloride
ligands occupying mutually trans positions. Crystals of 2e
consist of two crystallographically independent molecules in
the unit cell, with only minor differences from each other (e.g.,
bond angles Cl(1)-V(1)-Cl(2) and Cl(3)-V(2)-Cl(4) are
166.41° and 167.94°, respectively). The V-S distances (2.539
and 2.546 Å) in complex 2e are similar to those in the
thiofunctional vanadium complexes containing neutral tetraden-
tate ligand 1,6-bis(2′-pyridyl)-2,5-dithiahexane (N2S2)28a or
[O, S, O] ligand28b (2.433-2.597 Å). The bond length V-P
2.5698 Å in complex 2f is slightly longer than those in the
(26) Wu, J. Q.; Pan, L.; Hu, N. H.; Li, Y. S. Organometallics 2008, 27,
3840.
(27) Cameron, P. A.; Gibson, V. C.; Redshaw, C.; Segal, J. A.; Bruce,
M. D.; White, A.; Williams, D. J. Chem. Commun. 1999, 1883.
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Rehder, D. Inorg. Chem. 2002, 41, 2379. (b) Paine, T. K.; Weyhermuller,
T.; Slep, L. D.; Neese, F.; Bill, E.; Bothe, E.; Wieghardt, K.; Chaudhuri, P.
Inorg. Chem. 2004, 43, 7324.
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2002, 1839.
(24) Matsunaga, P. T., WO 99/57159.
(25) Lorber, C.; Wolff, F.; Choukroun, R.; Vendier, L. Eur. J. Inorg.
Chem. 2005, 2850.

Vanadium(III) Complexes Bearing Schiff Base Ligands
Organometallics, Vol. 28, No. 6, 2009 1819
Scheme 3. General Synthetic Route of the Vanadium Complexes Used in This Study
reported vanadium complexes (2.367-2.500 Å),29 indicating
that the interaction between V and P is not so strong, probably
due to the steric crowding of the bulky group around the P atom.
With the introduction of pendant donor, the bond distances of
V-N (2.077 and 2.075 Å in 2e, 2.091 Å in 2f) and V-O(THF)
(2.106 and 2.126 Å in 2e, 2.094 Å in 2f) slightly shorten, and
the bond angles of Cl(1)-V-Cl(2) (166.41° in 2e, 169.48° in
2f) are also smaller than those of complex I.26 Complex 2h
(Figure 3) exhibits the same configuration as complex 2f, just
with slightly wider bond angles of Cl(1)-V-Cl(2) (169.48° in
2f, 171.78° in 2h).
2. Ethylene Polymerization Screening Results. Complexes
2a-h have been investigated as effective catalysts for ethylene
polymerization in the presence of the cocatalyst Et2AlCl and
the reactivating agent ethyl trichloroacetate. As shown in Figure
4, both pendant donor atom and the reaction temperature
considerably influence catalytic activities. With the introduction
of a nitrogen, phosphine, or sulfur donor, catalysts 2b-h display
higher activity than does catalyst 2a bearing an oxygen donor
under the same conditions. Among three complexes bearing a
nitrogen donor, the pyridylmethyl derivative 2c exhibited the
highest activity of 15.6 kg PE/mmolV · h · bar, followed by 2b
(9.6 kg PE/mmolV · h · bar) and 2d (9.1 kg PE/mmolV · h · bar)
under the optimal conditions. The known tetradentate complex
III30 also displayed good activities under analogous polymer-
ization conditions.
Note that all catalysts are highly active toward ethylene
polymerization even at high reaction temperatures, and the
highest activity (20.64 kg PE/mmolV · h · bar) was obtained by
catalyst 2h at 50 °C. Although the molecular weights of
polymers produced by catalysts 2a-h were decreased sharply
with the increase of reaction temperature, the molecular weight
distributions hardly broaden, and the polydispersity indexes
remained in the range of 1.9-3.0, suggesting 2a-h are single-
site catalysts even at high polymerization temperature.16d By
contrast, the molecular weight distributions obviously broaden
under similar conditions when the vanadium(III) catalysts
bearing bidentate Schiff base ligand were used.26 This result
indicates that the pendant donors help to stabilize the active
species, although we do not know the exact nature of the active
species up to now. Ethylene polymerization lifetime studies of
catalysts 2a-h at 50 °C during 5-30 min were conducted for
verifying their deactivation process (Figure 5) and found that
there was a remarkable decrease in catalytic activities of 2a-d
(at 30 min more than 70% of activity was reduced in contrast
with at 5 min), whereas catalysts 2e-h bearing softer second-
row donors (S, P) showed less decrease (ca. 30%), indicating
the latter four catalysts possess higher thermal stability.31
As shown in Figure 6 and Table S1 (see Supporting
Information), catalytic activity and the molecular weight of the
polyethylene proved to be sensitive to the concentration of
cocatalyst (Et2AlCl). The catalytic activity of 2c first rapidly
Figure 1. Molecular structure of complex 2e. Thermal ellipsoids are drawn at the 50% probability level, and H atoms are omitted for
clarity. Selected bond lengths (Å) and bond angles (deg): V(1)-N(1), 2.077(7); V(1)-O(1), 1.875(6); V(1)-O(2), 2.106(6); V(1)-S(1),
2.539(3); V(1)-Cl(1), 2.355(3); V(1)-Cl(2), 2.330(3); O(1)-V(1)-N(1), 91.4(3); O(1)-V(1)-O(2), 90.0(3); O(1)-V(1)-S(1), 171.6(2);
N(1)-V(1)-O(2), 178.5(3); N(1)-V(1)-S(1), 81.3(2); O(2)-V(1)-S(1), 97.2(2); O(1)-V(1)-Cl(1), 97.2(2); N(1)-V(1)-Cl(1), 92.7(2);
Cl(1)-V(1)-S(1), 79.05(9); O(2)-V(1)-Cl(1), 87.5(2); O(1)-V(1)-Cl(2), 95.4(2); N(1)-V(1)-Cl(2), 92.0(2); Cl(2)-V(1)-S(1), 91.8(3);
O(2)-V(1)-Cl(2), 87.5(2); Cl(1)-V(1)-Cl(2), 166.42(11); V(2)-N(2), 2.075(7); V(2)-O(3), 1.867(6); V(2)-O(4), 2.126(6); V(2)-S(2),
2.545(3); V(2)-Cl(3), 2.326(3); V(2)-Cl(4), 2.346(3); O(3)-V(2)-N(2), 91.8(3); O(3)-V(2)-O(4), 90.3(3); O(3)-V(2)-S(2), 172.0(2);
N(2)-V(2)-O(4), 177.7(3); N(2)-V(2)-S(2), 81.1(2); O(4)-V(2)-S(2), 96.9(2); O(3)-V(2)-Cl(3), 94.3(2); N(2)-V(2)-Cl(3), 91.0(2);
Cl(3)-V(2)-S(2), 89.47(10); O(4)-V(2)-Cl(3), 87.84(19); O(3)-V(2)-Cl(4), 97.2(2); N(2)-V(2)-Cl(4), 92.3(2); Cl(4)-V(2)-S(2),
79.59(10); O(4)-V(2)-Cl(4), 88.49(19); Cl(3)-V(2)-Cl(4), 167.96(12).

1820 Organometallics, Vol. 28, No. 6, 2009
Wu et al.
Figure 4. Catalytic activities of complexes 2a-h and III toward
ethylene polymerization at different temperatures. Reaction condi-
tions: 0.5 µmol of vanadium complex, Cl3CCO2Et 0.15 mmol,
Et2AlCl 2 mmol, ethylene 1 bar, toluene 50 mL, polymerization
for 5 min.
Figure 2. Molecular structure of complex 2f. Thermal ellipsoids
are drawn at the 50% probability level, and H atoms are omitted
for clarity. Selected bond lengths (Å) and bond angles (deg):
V-N(1), 2.091(3); V-O(1), 1.887(3); V-O(2), 2.094(3); V-P,
2.5698(14);V-Cl(1),2.3447(13);V-Cl(2),2.3305(13);O(1)-V-N(1),
92.05(14); O(1)-V-O(2), 90.22(13); O(1)-V-P, 172.32(10);
N(1)-V-O(2), 175.82(13); N(1)-V-P, 80.30(10); O(2)-V-P,
97.36(9); O(1)-V-Cl(1), 92.19(10); N(1)-V-Cl(1), 87.47(10);
Cl(1)-V-P, 86.76(4); O(2)-V-Cl(1), 88.94(9); O(1)-V-Cl(2),
98.31(10); N(1)-V-Cl(2), 92.69(10); Cl(2)-V-P, 82.90(4);
O(2)-V-Cl(2), 90.44(9); Cl(1)-V-Cl(2), 169.48(5).
Figure 5. Lifetime graph of ethylene polymerization for catalysts
2a-h and I. Conditions: 50 mL of toluene at 50 °C, ethylene 1
bar, 30 µmol of ETA, 0.4 mmol of DEAC, 0.2 µmol of catalyst.
Figure 3. Molecular structure of complex 2h. Thermal ellipsoids
are drawn at the 50% probability level, and H atoms are omitted
for clarity. Selected bond lengths (Å) and bond angles (deg):
V-N(1), 2.029(3); V-O(1), 1.964(2); V-O(2), 2.088(2); V-P,
2.5647(10);V-Cl(1),2.3414(10);V-Cl(2),2.3272(10);O(1)-V-N(1),
88.79(10); O(1)-V-O(2), 91.07(10); O(1)-V-P, 166.41(8);
N(1)-V-O(2), 179.80(10); N(1)-V-P, 77.88(8); O(2)-V-P,
102.27(7); O(1)-V-Cl(1), 96.12(8); N(1)-V-Cl(1), 92.74(8);
Cl(1)-V-P, 87.26(4); O(2)-V-Cl(1), 87.14(7); O(1)-V-Cl(2),
88.86(8);N(1)-V-Cl(2),93.90(8);Cl(2)-V-P,89.41(4);O(2)-V-
Cl(2), 86.23(7); Cl(1)-V-Cl(2), 171.78(4).
Figure 6. Plot of catalytic activity of vanadium complexes and
molecular weight of the polymers obtained vs Al/V (molar ratio)
in ethylene polymerization. Reaction conditions: 0.5 µmol of
catalyst 2c, Cl3CCO2Et 0.15 mmol, ethylene 1 bar, toluene 50 mL,
at 50 °C polymerization for 5 min.
enhanced and then gradually declined with the increase of Al/V
molar ratio, and the maximal catalytic activity of 2c (15.6 kg
PE/mmolV · h · bar) was obtained when the Al/V ratio equals
4000. The molecular weight of the resultant polymer produced
by 2c monotonously decreased with increased Al/V molar ratio.
Similar to the behavior of catalyst 2c, a reduction in molecular
weight of the resultant polymer produced by all of the other
tridentate vanadium(III) catalysts is observed as the Al/V ratio
is raised, suggesting that chain transfers to aluminum compounds
existed in these systems during the ethylene polymerization.
Other organoaluminum compounds such as MMAO, DMAO,

Vanadium(III) Complexes Bearing Schiff Base Ligands
Organometallics, Vol. 28, No. 6, 2009 1821
Table 1. Effect of Catalyst Concentration and Cocatalyst in
Ethylene Polymerization Catalyzed by 2ca
(entry 3, 3.18 kg/mmolV · h · bar; entry 4, 4.32 kg/mmolV · h · bar)
and hexene incorporation (from 3.0% to 6.0%), but a decrease
in the molecular weight of the resultant copolymer, while the
molecular weight distribution of the copolymers almost remained
constant. As shown in Figure 7, the molecular weight decreased
with the increase of Al/V molar ratio; however, the polydis-
persity index (PDI) of the resultant polymers was independent
of cocatalyst concentration. These results indicate that chain
transfers to aluminum also happened in the copolymerization.
The data listed in Table 2 (entries 3 and 6-10) indicated that
catalytic activity, the melting point, and the Mw of the resultant
polymers gradually decreased with the increase of initial hexene
concentration, although the hexene incorpoaration steadily
increased. When polymerization was conducted at 4 bar ethylene
pressure (entry 4 in Table 2), productivity rapidly increased and
the catalytic activity was comparable to that under atmospheric
pressure, but much higher molecular weight copolymer (Mw )
13.8 × 104) was produced.
c
catalyst
entry (µmol) cocatalyst
polymer
(g)
Mw
activityb (×104) Mw/Mn
c
1
2
3
0.1
0.5
1.0
2.0
0.5
0.5
1.5
0.5
0.5
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
Et2AlCl
MMAO
DMAOf
AlMe3
0.12
0.65
0.95
1.36
1.22
0.86
0.05
trace
trace
14.4
15.6
11.4
8.04
6.20
3.59
1.88
7.40
1.58
2.2
2.2
2.5
2.6
3.4
3.0
4
8.16
5d
6e
7
7.32
5.16
0.40
8
9
a Conditions: toluene 50 mL, ethylene 1 bar, catalyst 2c 0.5 µmol,
Al/V ) 4000 (mol/mol), ETA/V ) 300 (molar ratio), 50 °C. b Activity
in kg of polymer/(mmolV · h · bar). c GPC data in 1,2,4-trichlorobenzene
versus polystyrene standard. d Ethylene 4 bar. e Ethylene 4 bar, 70 °C.
f Prepared by removing AlMe3 and toluene from MMAO.
and AlMe3 were also tested as cocatalyst in combination with
complex 2c; however, only 2c/MMAO system displayed moder-
ate activity (0.40 kg PE/mmolV · h · bar). Trace or even no
polymer was obtained using DMAO or AlMe3 as the cocatalyst.
These results indicate that the cocatalyst significantly affects
the catalytic behavior of these vanadium(III) catalysts.3a Yet it
should be noted that the cocatalyst alone produced only
negligible polymer. The data listed in Table 1 also indicate that
the catalytic activity was influenced by catalyst concentration;
the highest activity appeared when 0.5 µmol catalyst was used.
Moreover, the molecular weight decreased with the increase of
catalyst concentration, while the molecular weight distributions
of the resultant PEs were independent of the catalyst concentra-
tion employed. An increase in ethylene pressure results in
enhancing productivity but decreasing catalytic activity, while
slightly enhancing the molecular weight of the resultant polymer
(entries 2, 5 in Table 1). The activity at 70 °C at 4 bar is also
slightly lower than that at 50 °C (entries 5, 6 in Table 1). This
result indicates that the effects of monomer depletion may exist
while elevating polymerization temperature at 1 bar, but the
main reason of reduction in activity at 70 °C of these
vanadium(III) catalysts probably is that some active species
deactivated, which commonly occurred in the vanadium olefin
polymerization catalysis.3a
3. Ethylene/1-Hexene Copolymerization by Complexes
2a-h. The representative results of ethylene/1-hexene copo-
lymerization catalyzed by 2a-h are summarized in Table 2.
All of the catalysts show high activities toward copolymerization
and produce the high molecular weight copolymers with
unimodal molecular weight distributions. Both the pendant donor
and the electronic effect of the backbone of ligands show
influences on the catalytic activity. Complex 2a bearing an
oxygen donor and complex 2g containing weak conjugated
backbone ligand exhibit low activities. The poly(ethylene-co-
1-hexene)s produced by complexes bearing a nitrogen donor
displayed higher molecular weight (entries 2, 3, 11 in Table 2).
For catalyst 2c, an enhancement in polymerization temperature
from 25 to 50 °C led to an increase in the catalytic activity
The microstructure of the copolymer was established by 13
C
NMR in o-C6D4Cl2 at 135 °C, with the assignment of the
microstructure following previous work reported by Hsieh and
Randall.32 As shown in Figure 8, the hexene units are usually
isolated between the ethylene units, but when the comonomer
incorporation increased up to 12.9 mol % a block-type sequence
of hexene appeared (the peak assigned as RR). Triad distribution
data arising from 13C NMR analysis of poly(ethylene-co-1-
hexene)s produced by 2c were summarized in Table S2 (see
Supporting Information). We found that HHH and HEH triads
appeared (0.3 and 0.7 mol %) in poly(ethylene-co-1-hexene)
with 12.9 mol % hexene incorporation, and EHH sequence also
increased (from 1.7 to 8.2 mol %) as compared to that of 3.0
mol % hexene incorporation. The behavior is different from
the resultant polymers obtained by the corresponding mono(ꢀ-
enaminoketonato) vanadium(III) catalysts or VCl3(THF)3,18
which only contained isolated hexene units even with high
hexene incorporation (16.0 mol %).
4. Ethylene/Norbornene Copolymerization by Complexes
2a-h. Cyclic olefin copolymers like poly(ethylene-co-nor-
bornene) not only display promising processibility, but also
could show desirable thermal, optical, and mechanical properties
toward resistance to heat and chemicals, transparency, refractive
index, and stiffness or softness.33 Vanadium(III) complexes
bearing mono(ꢀ-enaminoketonato) ligand have been found to
show excellent ability to copolymerize ethylene with nor-
bornene.18 Because complexes 2a-h display unique character-
istics in ethylene/1-hexene polymerization, we are interested in
exploring their catalytic behaviors for ethylene/norbornene
copolymerization. The typical experimental results are sum-
marized in Table 3. The data show that ligand structure
considerably influences catalytic activity toward ethylene/
norbornene copolymerization. Under the same conditions,
complex 2f containing the phosphorus donor exhibits the highest
catalytic activity (17.28 kg/mmolV · h · bar), while complex 2a
shows the lowest catalytic activity (2.88 kg/mmolV · h · bar). All
of the copolymers obtained by complexes 2a-h displayed high
Mw with unimodal molecular weight distribution. Moreover, the
copolymers obtained by the soft donor bearing complexes 2e-h
show higher molecular weight than do those of 2a-d bearing
hard donor. Nonetheless, no obvious difference in NBE
incorporations of the resultant copolymers was observed among
(29) (a) Hsu, H. F.; Su, C. L.; Gopal, N. O.; Wu, C. C.; Chu, W. C.;
Tsai, Y. F.; Chang, Y. H.; Liu, Y. H.; Kuo, T. S.; Ke, S. C. Eur. J. Inorg.
Chem. 2006, 1161. (b) Chu, W. C.; Wu, C. C.; Hsu, H. F. Inorg. Chem.
2006, 45, 3164.
(30) Mazzanti, M.; Gambarotta, S.; Floriani, C.; Chiesi-Villa, A.;
Guastini, C. Inorg. Chem. 1986, 2308.
(31) Examples for soft donors stabilizing group 4 olefin polymerization
catalysts: (a) Wang, C.; Ma, Z.; Sun, X.-L.; Gao, Y.; Guo, Y.-H.; Tang,
Y.; Shi, L.-P. Organometallics 2006, 25, 3259. (b) Long, R. J.; Gibson,
V. C.; White, A.; Williams, D. J. Inorg. Chem. 2006, 45, 511. (c) Long,
R. J.; Gibson, V. C.; White, A. Organometallics 2008, 27, 235.
(32) Hsieh, E. T.; Randall, J. C. Macromolecules 1982, 15, 1402.
(33) Li, X.; Hou, Z. Coord. Chem. ReV. 2008, 252, 1842.
(34) Li, X. F.; Dai, K.; Ye, W. P.; Pan, L.; Li, Y. S. Organometallics
2004, 23, 1223.

1822 Organometallics, Vol. 28, No. 6, 2009
Wu et al.
Table 2. Copolymerization of Ethylene and 1-Hexene by 2a-ha
d
d
e
entry
catalyst
T (°C)
1-hexene (mol/L)
polymer (g)
activityb
hexane contentc
Mw (×103)
Mw/Mn
Tm (°C)
1
2
2a
2b
2c
2c
2c
2c
2c
2c
2c
2c
2d
2e
2f
25
25
25
25
50
25
25
25
25
25
25
25
25
25
25
0.27
0.27
0.27
0.27
0.27
0.13
0.54
0.81
1.08
1.35
0.27
0.27
0.27
0.27
0.27
0.15
0.32
0.53
2.42
0.72
0.77
0.40
0.27
0.21
0.15
0.35
0.30
0.48
0.05
0.41
0.90
1.92
3.18
3.61
4.32
4.62
2.40
1.62
1.26
0.90
2.10
1.80
2.88
0.30
2.46
2.78
3.20
3.00
0.76
5.96
1.21
5.08
7.90
9.60
12.9
3.16
2.33
3.28
n.d.
47.7
77.5
56.4
138
2.4
2.8
2.0
2.8
2.1
1.9
2.0
1.9
2.0
1.9
2.9
1.9
2.0
2.0
2.1
110
109
108
120
101
115
102
94
3
4f
5
13.3
57.1
47.8
39.6
30.9
24.5
93.8
49.4
41.8
59.2
45.5
6
7
8
9
10
11
12
13
14
15
85
75
109
112
107
107
108
2g
2h
3.29
a Conditions: toluene + comonomer ) 30 mL, ethylene 1 bar, catalyst 1.0 µmol, cocatalyst Et2AlCl 4.0 mmol, ETA/V ) 300 (molar ratio), 10 min.
b Activity in kg of polymer/(mmolV · h · bar). c Comonomer content (mol %) estimated by 13C NMR spectra. d GPC data in 1,2,4-trichlorobenzene versus
polystyrene standard. e Determined by DSC. f Ethylene 4 bar.
a considerable influence on the catalytic activity, the comonomer
incorporation, and molecular weight of the resultant copolymers,
but no remarkable effect on the molecular weight distributions
of copolymers (entries 3, 5 in Table 3). It is interesting to note
that higher catalytic activity (16.2 kg/mmolV · h · bar, entry 6 in
Table 3) was observed when the ethylene pressure was increased
to 4 bar, and a much higher molecular weight (Mw ) 16.4 ×
104) copolymer was produced, although the NBE incorporation
decreased to 15.0 mol %. This result differs from the homo-
polymerization of ethylene under similar condidtions.
Conclusions
In summary, we have prepared and characterized a series of
vanadium(III) complexes bearing tridentate Schiff base ligands
(2a-h), which were highly air and moisture sensitive. These
complexes displayed high activity toward catalyzing ethylene
Figure 7. Plot of Mw and PDI of copolymers obtained by precatalyst
2c/Et2AlCl versus Al/V molar ratio in ethylene and 1-hexene
copolymerization (2c 1.0 µmol, 1-hexene 1.0 mL, Vtotal ) 30 mL,
25 °C, polymerization for 10 min).
polymerization in the presence of Et2AlCl as a cocatalyst and
Cl3CCOOEt as a reactivating agent and produced high molecular
weight polyethylenes with unimodal molecular weight distribu-
tion even at high polymerization temperature, especially the
complexes bearing soft donor containing ligands showed high
thermal stability. In contrast to the bidentate Schiff base ligands,
tridentate Schiff base ligands with pendant donors are beneficial
to stabilize vanadium(III) catalysts. The cocatalyst type also
significantly affected the catalytic behavior of these vana-
dium(III) catalysts, and the increase of cocatalyst concentration
resulting in decreasing the molecular weight of the resultant
polymer is suggestive of chain transfer to aluminum. The
reaction parameters such as catalyst concentration, ethylene
pressure, and polymerization reaction temperature also play an
important role in ethylene polymerization. In addition, these
complexes exhibited high catalytic activity for ethylene and
1-hexene or NBE copolymerization and produced copolymers
with high molecular weights, unimodal molecular weight
distribution, and high comonomer incorporations.
2a-h. The copolymers displayed glass transition temperatures
in the range of 28.8-94.0 °C, which were determined by means
of DSC techniques at a heating rate of 10 °C/min. The
microstructures of the copolymers have been investigated using
13C NMR techniques (Figure S5). It was found that NBE was
incorporated in an isolated or alternating manner and no NBE
dyads were observed, which is similar to our previous results.18,34
The effect of reaction conditions on the ethylene/NBE
copolymerization was also investigated using catalyst 2c. As
shown in Figure 9, with the increase of comonomer in feed,
the catalytic activity toward copolymerization decreases rapidly,
while NBE incorporation first increases almost linearly then
tardily. The molecular weights of the copolymers were also
decreasing with the increase of NBE concentration (entries 5,
8, 9 in Table 3), which is similar to bidentate ꢀ-enaminoketonato
vanadium(III) catalysts,18 but it is different from bidentate
ꢀ-enaminoketonato titanium(IV) catalysts.34 No remarkable
effect of Al/V molar ratio on catalytic activity and comonomer
incorporation was observed (entries 4, 5, and 7 in Table 3).
However, the molecular weight of copolymers decreased with
the increase of Al/V molar ratio, indicating chain transfer to
Al. Combined with the results described above and previous
conclusions,18,26 we suppose this is one of the unique charac-
teristics of using Schiff base ligand chelated vanadium(III) type
catalyst for olefin polymerization. The reaction temperature has
Experimental Section
General Procedures and Materials. All manipulation of air-
and/or moisture-sensitive compounds was carried out under a dry
argon atmosphere by using standard Schlenk techniques or under
a dry argon atmosphere in an MBraun glovebox unless otherwise
noted. All solvents were purified from an MBraun SPS system.
1
The H NMR spectra of the vanadium complexes were obtained
on a Bruker 300 MHz spectrometer at ambient temperature, with
CD2Cl2 as a solvent. The IR spectra were recorded on a Bio-Rad

Vanadium(III) Complexes Bearing Schiff Base Ligands
Organometallics, Vol. 28, No. 6, 2009 1823
Figure 8. 13C NMR of ethylene/1-hexene copolymer using catalyst 2c: (a) 3.00 mol % (entry 3); (b) 12.9 mol % (entry 10) in Table 2.
Table 3. Copolymerization of Ethylene and Norbornene (NBE) by
The weight-average molecular weights (Mw’s) and the polydispersity
indexes (PDIs) of polymer samples were determined at 150 °C by
a PL-GPC 220 type high-temperature chromatograph equipped with
three Plgel 10 µm Mixed-B LS type columns. 1,2,4-Trichloroben-
zene (TCB) was employed as the solvent at a flow rate of 1.0 mL/
min. The calibration was made by polystyrene standard EasiCal
PS-1 (PL Ltd.).
2a-ha
d
e
T
NBE polymer
NBE
Mw
Tg
d
entry catalyst (°C) (mol/L)
(g)
activityb contentc (×104) Mw/Mn (°C)
1
2a
2b
2c
2c
2c
2c
2c
2c
2c
2d
2e
2f
50
50
25
50
50
50
50
50
50
50
50
50
50
50
0.50
0.50
0.50
0.50
0.50
0.50
0.50
0.10
0.90
0.50
0.50
0.50
0.50
0.50
0.12
0.21
0.35
0.46
0.57
2.70
0.57
0.66
0.32
0.19
0.31
0.72
0.23
0.65
2.88
5.04
8.40
37.8
37.6
33.5
39.4
39.1
15.0
39.3
16.6
42.8
37.5
37.3
37.7
36.2
38.9
3.05
3.21
5.58
3.45
2.97
2.4
2.4
2.0
2.0
2.0
3.0
2.3
2.0
2.1
2.3
2.2
2.0
2.0
2.1
71
71
51
75
69
47
63
29
94
71
78
73
68
76
2
3
4f
5
11.0
13.7
16.2
13.7
15.8
Ethyl trichloroacetate (ETA) was purchased from Aldrich, dried
over calcium hydride at room temperature, and then distilled.
VCl3(THF)3 was purchased from Aldrich. Et2AlCl and AlMe3 were
obtained from Albemarle Corp. Modified methylaluminoxane
(MMAO, 7% aluminum in heptane solution) was purchased from
Akzo Nobel Chemical Inc. Literature procedures were used to
synthesize tridentate salicylaldiminato ligands (1a-f)27 and com-
plexes I, II,26 and III.30
6g
7h
8
16.4
2.40
3.61
2.20
3.15
3.70
5.72
5.60
5.98
9
7.68
4.56
7.44
17.3
5.52
15.6
10
11
12
13
14
2g
2h
Synthesis of Tridentate ꢀ-Enaminoketonato Ligands.
C6H8(2-OH)CHdN-2-C6H4PPh2 (1g). To a stirred solution of
2-hydroxymethylene-cyclohexanone (2.52 g, 20 mmol) in dried
methanol (25 mL) were added 2-(diphenylphosphino)aniline (5.54
g, 20 mmol) and formic acid (1 mL) as a catalyst. The mixture
was refluxed and stirred for 4 h. During the stirring period, a yellow
solution was formed. The product was purified by recrystallization
from ethanol, and the yellow crystals were collected. Yield: 5.20 g
(62%). Ligand 1h was prepared via the same procedure. 1H NMR
(300 MHz, d6-DMSO): δ 12.16 (m, 1H, O-H), 7.66-6.94 (m, 14H,
Ph-H), 6.72 (m, 1H, NdCH), 2.38 (t, 2H, CH2), 2.20 (t, 2H, CH2),
1.61 (m, 4H, CH2CH2). 13C NMR (300 MHz, CDCl3): δ 200.1,
145.2, 141.9, 135.7, 135.6, 135.1, 134.6, 134.5, 134.1, 130.9, 129.4,
129.0, 128.9, 128.7, 127.9, 126.8, 126.0, 123.3, 114.7, 110.9, 106.9,
38.7, 28.9, 24.3, 23.1. Anal. Calcd for C25H24NOP: C, 77.90; H,
6.28; N, 3.63. Found: C, 77.68; H, 6.21; N, 3.68.
a Conditions: toluene + comonomer ) 30 mL, ethylene 1 bar,
catalyst 0.5 µmol, cocatalyst Et2AlCl, Al/V ) 4000 (molar ratio), ETA/
V ) 300 (molar ratio), 5 min. b Activity in kg polymer/(mmolV · h · bar).
c Comonomer content (mol %) estimated by 13C NMR spectra. d GPC
data in 1,2,4-trichlorobenzene versus polystyrene standard. e Determined
by DSC. f Al/V ) 2000 (molar ratio). g Ethylene 4 bar. h Al/V ) 6000
(molar ratio).
C6H5(OH)CdCHCHdN-2-PPh2C6H4 (1h). Yield: 85%. 1H
NMR (300 MHz, d6-DMSO): δ 12.59 (m, 1H, O-H), 7.91-7.88
(m, 3H, Ph-H), 7.53-7.5 (m, 16H, Ph-H), 6.81 (d, 1H, NdCH),
6.09 (d, 1H, CdCH). 13C NMR (300 MHz, CDCl3): δ 190.5, 144.9,
144.8, 144.5, 139.7, 135.7, 135.6, 135.1, 134.6, 134.3, 131.8, 130.9,
129.4, 129.0, 128.9, 128.7, 127.9, 127.0, 126.8, 124.1, 115.4, 95.1.
Anal. Calcd for C27H22NOP: C, 79.59; H, 5.44; N, 3.44. Found: C,
79.68; H, 5.49; N, 3.38.
Synthesis of Vanadium Complexes. [OC6H4CHdNCH2CH2-
OMe]VCl2(THF) (2a). To a slurry of NaH (40 mg, 1.67 mmol) in
THF (10 mL) was added a solution of ligand 1a (269 mg, 1.50
mmol) in THF (10 mL) at -30 °C. The resulting suspension was
warmed to room temperature and stirred for 4 h. Next, the yellow
mixture was slowly transferred to a solution of VCl3(THF)3 (561
mg, 1.50 mmol) in THF (20 mL), and the red brown solution was
stirred for 12 h. The reaction mixture was condensed and filtered
to remove NaCl and the excess NaH. The filtrate was concentrated
Figure 9. Plots of the activity of precatalyst 2c/Et2AlCl and the
NBE incorporation versus comonomer content in the feed (2c 0.5
µmol, 300 equiv of Cl3CCO2Et, 4000 equiv of Et2AlCl, ethylene 1
bar, Vtotal ) 30 mL, 50 °C, polymerization for 5 min).
FTS-135 spectrophotometer. Elemental analyses were recorded on
an elemental Vario EL spectrometer. Mass spectra were obtained
using electron impact (EI-MS) and LDI-1700 (Linear Scientific
Inc.). Magnetic moments were recorded following the Evans’ NMR
method.35 DSC measurements were performed on a Perkin-Elmer
Pyris 1 differential scanning calorimeter at a rate of 10 °C/min.
(35) Evans, D. F. J. Chem. Soc. 1959, 2003.

1824 Organometallics, Vol. 28, No. 6, 2009
Wu et al.
Table 4. Crystallographic Data, Collection Parameters, and Refinement Parameters
2×2e
C36H40Cl4N2O4S2V2
872.50
2f · THF
2h
formula
fw
C33H34Cl2NO3PV
645.45
C31H29Cl2NO2PV
600.36
crystal system
space group
a (Å)
b (Å)
c (Å)
R (deg)
ꢀ (deg)
γ (deg)
V (Å3)
triclinic
P-1
triclinic
P-1
triclinic
P-1
10.2611(16)
12.6840(19)
14.834(2)
96.249(3)
91.485(3)
92.038(3)
1917.1(5)
2
11.2970(14)
11.4125(14)
12.4665(16)
98.476(2)
91.255(2)
106.202(2)
1523.2(3)
3
10.2321(13)
10.3502(13)
15.6136(19)
79.189(2)
78.476(2)
60.655(2)
1404.5(3)
2
Z
Dcalcd (Mg/m3)
1.511
0.916
896
1.409
0.589
672
1.420
0.630
620
absorption coeff (mm-1
F (000)
)
cryst size (mm)
θ range (deg)
no. of reflns collected
no. of indep reflns
0.17 × 0.12 × 0.09
1.62-26.07
10 745
7388 (Rint ) 0.0579)
7388/0/453
0.988
0.26 × 0.16 × 0.05
1.66-25.25
8123
5426 (Rint ) 0.0373)
5426/0/370
0.989
0.15 × 0.09 × 0.05
2.27-23.78
7927
5403 (Rint ) 0.0297)
5403/0/343
1.005
no. of data/restraints/params
GOF on F2
R1
0.0953
0.0998
0.0875
wR2
0.1934
0.612 and -0.457
0.1605
0.530 and -0.404
0.1270
0.490 and -0.330
largest diff. peak/hole (e · Å-3
)
and recrystallized in THF/n-hexane and yielded 421 mg of the pure
complex as a brown solid (75%). Compounds 2b-h were prepared
analogously. IR (KBr pellets): ν 2943, 1624, 1600, 1548, 1449,
1281, 1157, 1043, 1007, 918, 867, 777, 633, 534, 437 cm-1. EI-
MS (70 eV): m/z 371 [M+]. Anal. Calcd for C14H19Cl2NO3V: C,
[O(Ph)CdCHCHdN-2-PPh2C6H4]VCl2(THF) (2h). Yield: 60%.
IR (KBr pellets): ν 3058, 2979, 2883, 1544, 1513, 1460, 1374,
1274, 1258, 1186, 1021, 970, 864, 835, 758, 698, 514, 500 cm-1
.
EI-MS (70 eV): m/z 598 [M+]. Anal. Calcd for C31H28Cl2NO2PV:
C, 62.12; H, 4.71; N, 2.34. Found: C, 62.23; H, 4.66, N, 2.38. µeff
) 2.80 µB.
45.30; H, 5.16; N, 3.77. Found: C, 45.80; H, 5.23, N, 3.71. µeff
2.83 µB.
)
Ethylene Polymerization. olymerization was carried out in
toluene in a 150 mL glass reactor equipped with a mechanical
stirrer. Toluene (25 mL) was introduced into the nitrogen-purged
reactor and stirred vigorously (600 rpm). The toluene was kept at
a prescribed polymerization temperature, and then ethylene gas feed
was started. After 15 min, a solution of organoaluminum in toluene
and a solution of ETA in toluene were added and stirred for 5 min.
Next, a toluene solution of one of the four complexes was added
into the reactor with vigorous stirring (900 rpm) to initiate
polymerization. After a prescribed time, ethanol (10 mL) was added
to terminate the polymerization reaction, and the ethylene gas feed
was stopped. The resulting mixture was added to acidic ethanol.
The solid polyethylene was isolated by filtration, washed with
ethanol, and dried at 60 °C for 12 h in a vacuum oven.
[OC6H4CHdNCH2CH2NMe2]VCl2(THF) (2b). Yield: 65%. IR
(KBr pellets): ν 3204, 2980, 1616, 1546, 1471, 1445, 1297, 1151,
997, 907, 763, 625, 476 cm-1. EI-MS (70 eV): m/z 385 [M+]. Anal.
Calcd for C15H22Cl2N2O2V: C, 46.89; H, 5.77; N, 7.29. Found: C,
47.01; H, 5.71, N, 7.33. µeff ) 2.79 µB.
[OC6H4CHdNCH2C5H4N]VCl2(THF) (2c). Yield: 35%. IR
(KBr pellets): ν 3067, 2955, 2874, 1610, 1542, 1480, 1447, 1284,
1247, 1150, 1054, 1028, 999, 868, 762, 651, 627, 493, 453 cm-1
.
EI-MS (70 eV): m/z 403 [M+]. Anal. Calcd for C17H18Cl2N2O2V:
C, 50.52; H, 4.49; N, 6.93. Found: C, 50.43; H, 4.52, N, 6.96. µeff
) 2.87 µB.
[OC6H4CHdN-8-C9H6N]VCl2(THF) (2d). Yield: 58%. IR (KBr
pellets): ν 3057, 2973, 1603, 1539, 1508, 1435, 1401, 1313, 1216,
1149, 1090, 834, 759, 569, 515 cm-1. EI-MS (70 eV): m/z 440
[M+]. Anal. Calcd for C20H18Cl2N2O2V: C, 54.57; H, 4.12; N, 6.36.
Found: C, 54.43; H, 4.05, N, 6.41. µeff ) 2.86 µB.
[OC6H4CHdN-2-SMeC6H4]VCl2(THF) (2e). Yield: 38%. IR
(KBr pellets): ν 3060, 2958, 2901, 1601, 1572, 1531, 1463, 1428,
1386, 1300, 1183, 1147, 1124, 1030, 925, 878, 857, 808, 767, 629,
562, 509, 486, 452, 423 cm-1. EI-MS (70 eV): m/z 434 [M+]. Anal.
Calcd for C18H19Cl2NO2SV: C, 49.67; H, 4.40; N, 3.22. Found: C,
49.73; H, 4.44, N, 3.16. µeff ) 2.88 µB.
Ethylene/1-Hexene or Norbornene (NBE) Polymerization.
Polymerization was carried out in toluene in a 150 mL glass reactor
equipped with a mechanical stirrer. The reactor was charged with
20 mL of toluene and the prescribed amount of olefins (NBE or
1-hexene). Next, the ethylene gas feed was started followed by
equilibration at the desired polymerization temperature. After 15
min, a solution of Et2AlCl in toluene and a solution of ETA in
toluene were added and stirred for 5 min. Subsequently, a toluene
solution of vanadium complexes was added into the reactor with
vigorous stirring (900 rpm) to initiate polymerization. After a
prescribed time, ethanol (10 mL) was added to terminate the
polymerization reaction, and the ethylene gas feed was stopped.
The resulting mixture was added to acidic ethanol. The polymer
was isolated by filtration, washed with ethanol, and dried at 60 °C
for 12 h in a vacuum oven.
Crystallographic Studies. Crystals for X-ray analysis were
obtained as described in the preparations. The crystallographic data,
collection parameters, and refinement parameters are listed in Table
4. The crystals were manipulated in a glovebox. The intensity data
were collected with the ω scan mode (186 K) on a Bruker Smart
APEX diffractometer with CCD detector using Mo KR radiation
(λ ) 0.71073 Å). Lorentz, polarization factors were made for the
intensity data, and absorption corrections were performed using the
[OC6H4CHdN-2-PPh2C6H4]VCl2(THF) (2f). Yield: 88%. IR
(KBr pellets): ν 3060, 2973, 2868, 1603, 1576, 1535, 1482, 1460,
1434, 1389, 1309, 1180, 1151, 1092, 1061, 1019, 869, 851, 807,
772, 756, 743, 694, 623, 564, 552, 510, 497, 485, 448, 413 cm-1
.
EI-MS (70 eV): m/z 572 [M+]. Anal. Calcd for C29H26Cl2NO2PV:
C, 60.75; H, 4.57; N, 2.44. Found: C, 61.25; H, 4.50, N, 2.49. µeff
) 2.85 µB.
[OC6H8CHdN-2-PPh2C6H4]VCl2(THF) (2g). Yield: 65%. IR
(KBr pellets): ν 3058, 2930, 2867, 1572, 1560, 1482, 1456, 1437,
1389, 1321, 1271, 1253, 1148, 1064, 857, 743, 695, 518, 490 cm-1
.
EI-MS (70 eV): m/z 576 [M+]. Anal. Calcd for C29H30Cl2NO2PV:
C, 60.33; H, 5.24; N, 2.43. Found: C, 60.44; H, 5.17, N, 2.41. µeff
) 2.84 µB.

Vanadium(III) Complexes Bearing Schiff Base Ligands
Organometallics, Vol. 28, No. 6, 2009 1825
SADABS program. The crystal structures were solved using the
SHELXTL program and refined using full matrix least-squares. The
positions of hydrogen atoms were calculated theoretically and
included in the final cycles of refinement in a riding model along
with attached carbons.
Major State Basis Research Projects (no. 2005CB623800)
from the Ministry of Science and Technology of China.
Supporting Information Available: X-ray diffraction data for
2e, 2f, and 2h (as CIF). DSC thermograms and 13C NMR spectra
of polymers. This material is available free of charge via the Internet
at http://pubs.acs.org.
Acknowledgment. We are grateful for subsidy provided
by the National Natural Science Foundation of China (nos.
20734002 and 50525312), and by the Special Funds for
OM801028G