Vinyl Polymerization of Norbornene with Neutral Salicylaldiminato Nickel(II) Complexes

Article abstract of DOI:10.1021/om030018t

A study on the vinyl polymerization of norbornene with neutral salicylaldiminato nickel(II) complexes was presented. The structures of the salicylaldiminato complexes were confirmed by infrared radiation (IR) and nuclear magnetic resonance (NMR) spectra. The ligands of salicylaldimines were efficiently synthesized via the condensation reaction of substituted salicylaldehydes and anilines.

Full text of DOI:10.1021/om030018t

3678
Organometallics 2003, 22, 3678-3683
Vin yl P olym er iza tion of Nor bor n en e w ith Neu tr a l
Sa licyla ld im in a to Nick el(II) Com p lexes
Wen-Hua Sun,*,† Haijian Yang,† Zilong Li,‡ and Yan Li†
State Key Laboratory of Engineering Plastics and The Center for Molecular Science,
Institute of Chemistry, The Chinese Academy of Sciences, Beijing 100080, China, and
State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of
Matter, Chinese Academy of Sciences, Fuzhou 350002, China
Received J anuary 10, 2003
A series of neutral salicylaldiminato Ni(II) complexes have been synthesized and
characterized, and complexes a and e have been confirmed by X-ray single-crystal analyses.
These compounds show highly catalytic activities for the vinyl polymerization of norbornene
with MAO cocatalyst, which could be up to 2.86 × 108 g PNB/(mol Ni‚h), and also lead to
various activities, molecular weights, and distributions of polynorbornenes under different
reaction conditions.
In tr od u ction
polymer with constrained rings in each unit, possesses
interesting and unique properties such as high chemical
resistance, good UV resistance, low dielectric constant,
high glass transition temperature, excellent transpar-
ency, large refractive index, and low birefringence.1,7
Such a polymerization akin to the classical olefin
polymerization is termed vinyl polymerization,1a,e in
which the polymerization opens the double bond and
leaves the bicyclic structural unit intact. V-PNB ap-
peared with a TiCl4/AliBu3 catalyst back in the early
1960s.1a,e,8 Subsequently various complexes of nickel,
cobalt, chromium, titanium, zirconium, and palladium
Bicyclo[2.2.1]hept-2-ene, better known by its trivial
name norbornene, can be homo-polymerized via three
pathways, which lead to their corresponding polymers
with different structures and properties.1 The first
report by Andersen and Merckling2 in the 1950s, ring-
opening metathesis polymerization (ROMP) of nor-
bornene, was well investigated with a variety of cata-
lysts containing transition metals (e.g., Ti, Zr, Hf, V,
Nb, Ta, Cr, Mo, W, Re, Ru, Os, Co, or Ir in high
oxidation state).3 Those ROMP poly(norbornene)s con-
taining double bonds in their backbones have been
commercialized with further modification through vul-
canization or hydrogenation.4 The second type of poly-
(norbornene) is a cationic or free-radical polymerization
product of norbornene through 2,7-linkage, which is,
however, usually formed with low molecular weights
(molecular weight <1000) and low yield because of the
rearrangements and transfer reactions.1a,b,e,5 Driven by
industrial application, the vinyl polymerization of nor-
bornene inspired the interest of chemists and chemical
engineers.6 V-PNB (vinylic polynorbornene), a special
(6) (a) Maezawa, H.; Matsumoto, J .; Aiura, H.; Asahi, S. (Idemitsu
Kosan) EP 445,755, 1991; Chem. Abstr. 1991, 115, 256943g. (b) Goodall,
B. L.; Benedikt, G. M.; McIntosh, L. H., III; Barnes, D. A.; Rhodes, L.
F. (B.F. Goodrich) U.S. Patent 5468819, 1995; Chem. Abstr. 1995, 125,
329750k. (c) Goodall, B. L.; Risse, W.; Mathew, J . P. (B.F. Goodrich)
U.S. Patent 5705503, 1996; Chem. Abstr. 1996, 126, 104553u.
(7) (a) Grove, N. R.; Kohl, P. A.; Allen, S. A. B.; J ayaraman, S.; Shick,
R. J . Polym. Sci., Part B: Polym. Phys. 1999, 37, 3003-3010. (b)
Ahmed, S.; Bidstrup, S. A.; Kohl, P. A.; Ludovices, P. J . J . Phys. Chem.
B 1998, 102, 9783-9790. (c) Haselwander, Th. F. A.; Heitz, W.; Kru¨gel,
St. A.; Wendorff, J . H. Macromolecules 1997, 30, 5345-5351. (d)
Kru¨gel, S. A.; Raubacher, F.; Wendorff, J . H. Macromol. Chem. Phys.
1998, 199, 757-762.
(8) (a) Haselwander, T. F. A.; Heitz, W.; Krgu¨el, S. A.; Wendorff, J .
H. Macromol. Chem. Phys. 1996, 197, 3435-3453. (b) Sartori, G.;
Ciampelli, F. C.; Cameli, N. Chim. Ind. (Milan) 1963, 45, 1478. (c)
Seehof, N.; Mehler, C.; Breuning, S.; Risse, W. J . Mol. Catal. 1992,
76, 219-228.
* To whom correspondence should be addressed. Fax: +86-10-
62559373. E-mail: whsun@iccas.ac.cn.
† Institute of Chemistry.
‡ Fujian Institute of Research on the Structure of Matter.
(1) (a) J aniak, C.; Lassahn, P. G. J . Mol. Catal. A: Chem. 2001,
166, 193-209. (b) Heinz, B. S.; Alt, F. P.; Heiz, W. Macromol. Rapid
Commun. 1998, 19, 251-256. (c) Alt, F. P.; Heiz, W. Macromol. Chem.
Phys. 1998, 199, 1951-1956. (d) J aniak, C.; Lassahn, P. G. Polym.
Bull. 2002, 47, 539-546. (e) J aniak, C.; Lassahn, P. G. Macromol.
Rapid Commun. 2001, 22, 479-492.
(2) Andersen, A. W.; Merkling, N. G. ( DuPont) U.S. Patent 2721189,
1954; Chem. Abstr. 1954, 50, 3008i.
(3) (a) Ivin, K. J .; Mo, J . C. Olefin Metathesis and Metathesis
Polymerization; Academic Press: San Diego, 1977; pp 407-410. (b)
Goodall, B. L.; McIntosh, L. H., III; Rhodes, L. F. Macromol. Symp.
1995, 89, 421-432.
(4) (a) Ohm, R.; Stein, C. Encyclopedia of Chemical Technology;
Wiley: New York, 1982; Vol. 18, pp 436-442. (b) Steinha¨usler, T.;
Koros, W. J . J . Polym. Sci. (Part B) 1997, 35, 91-99.
(5) (a) Kennedy, J . P.; Makowski, H. S. J . Macromol. Sci. Chem.
1967, A1, 345-370. (b) Gaylord, N. G.; Mandal, B. M.; Martan, M. J .
Polym. Sci., Polym. Lett. Ed. 1976, 14, 555-559. (c) Gaylord, N. G.;
Deshpande, A. B.; Mandal, B. M.; Martan, M. J . Macromol. Sci.-Chem.
1977, A11, 1053-1070. (d) Gaylord, N. G.; Deshpande, A. B. J . Polym.
Sci., Polym. Lett. Ed. 1976, 14, 613-617.
(9) (a)Rush, S.; Reinmuth, A.; Risse, W. Macromolecules 1997, 30,
7375-7385. (b) Tsujino, T.; Saegusa, T.; Furukawa, J . Makromol.
Chem. 1965, 85, 71. (c) Mehler, C., Risse, W. Makromol. Chem., Rapid
Commun. 1991, 12, 255-259. (d) Melia, J .; Connor, E.; Rush, S.;
Mehler, C.; Risse, W. Macromol. Symp. 1995, 89, 433-442. (e) Sen,
A.; Lai, T.-W. Organometallics 1982, 1, 415-417. (f) Abu-Surrah, A.
S.; Thewalt, U.; Rieger, B. J . Organomet. Chem. 1999, 587, 58-66. (g)
Mehler, C.; Risse, W. Macromolecules 1992, 25, 4226-4228. (h)
Deming, T. J .; Novak, B. M. Macromolecules 1993, 26, 7089-7091. (i)
Reinmuth, A.; Mathew, J . P.; Melia, J .; Risse, W. Macromol. Rapid
Commun. 1996, 17, 173-180. (j) Haselwander, T. F. A.; Heitz, W.
Macromol. Rapid Commun. 1997, 18, 689-697. (k) Peucker, U.; Heitz,
W. Macromol. Rapid Commun. 1998, 19, 159-162. (l) Mast, C.;
Krieger, M.; Dehnicke, K.; Greiner, A. Macromol. Rapid Commun.
1999, 20, 232-235. (m) Lassahn, P.-G.; J aniak, C.; Oh, J .-S. Macromol.
Rapid Commun. 2002, 23, 16-20. (n) Sacchi, M. C.; Sonzogoni, M.;
Losio, S.; Forlini, F.; Locatelli, P.; Tritto, I.; Licchelli, M. Macromol.
Chem. Phys. 2001, 202, 2052-2058. (o) Younkin, T. R.; Connor, E. F.;
Henderson, J . I.; Friedrich, S. K.; Grubbs, R. H.; Bansleben, D. A.
Sciences 2000, 287, 460-463. (p) Li, X.-F.; Li, Y.-S. J . Polym. Sci., Part
A: Polym. Chem. 2002, 40, 2680-2685.
10.1021/om030018t CCC: $25.00 © 2003 American Chemical Society
Publication on Web 07/18/2003

Vinyl Polymerization of Norbornene
Organometallics, Vol. 22, No. 18, 2003 3679
Ta ble 1. Su m m a r y of Cr ysta llogr a p h ic Da ta for
Com p lexes a a n d e
Sch em e 1. Syn th esis of Com p lexes
a
e
formula
fw
temp (K)
cryst syst
space group
a (Å)
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V, Å3
C
51H52I2NNiO2P
C43H34I2NNiOP
924.19
293(2)
monoclinic
P2(1)/c
15.599(2)
14.173(3)
17.799(3)
90
100.622(6)
90
3867.8(11)
4
21.73
1.587
1054.42
293(2)
triclinic
P1h
11.4427(8)
13.0579(7)
18.0665(15)
109.15(4)
96.460(2)
105.9380(10)
2390.2(3)
2
Z
µ(Mo KR), cm-1
17.69
1.465
Fcalcd (g cm-3
)
cryst size (mm)
θ range (deg)
total no. of reflns
no. of unique data
no. of params
F000
0.51 × 0.19 × 0.08
1.22-27.45
17 071
10 555
507
0.63 × 0.45 × 0.10
1.33-27.48
13 922
8513
392
1060
1824
R1
0.0355
0.0544
wR2
0.0880
0.1174
goodness of fit
0.944
0.758
confirmation, crystals of complexes a and e suitable for
X-ray structure determination were grown from diethyl
ether solution. The data collection and refinement data
of the analyses are summarized in Table 1, and the
ORTEP diagrams are shown in Figure 1 and Figure 2.
In the solid state, complex a is in the triclinic form and
complex e is in the monoclinic geometry. Both molecules
adopt a nearly ideal square-planar coordination geom-
etry with the Ni approximately 0.0315 and 0.0611 Å,
respectively, from the planes of the complexes.
have been used as catalysts for norbornene vinyl po-
lymerization and strained cyclic olefins in general.1,9 It
was reported that the nickel(II) complexes bearing
phosphoraniminato ligands had high catalytic activity
for the vinyl polymerization of norbornene to produce
high polymer.9l In addition, single-site neutral salicy-
laldiminato Ni(II) catalysts were used to copolymerize
ethylene and norbornene derivatives.9o More recently,
the neutral nickel complexes were reported for vinyl
homopolymerization of norbornene.9p With those trail-
blazing studies of neutral nickel complexes as catalysts
for vinyl polymerization of norbornene, their significant
importance is further investigated to clarify catalytic
activities of the nickel catalysts with their ligands for
electronic and steric considerations as well as the
reaction parameters. The scope of this contribution is
designing a series of (1-naphthyl)(triphenylphosphine)-
{N-[1-(2,6-dihalophenyl)]-(3,5-dialkylsalicylaldiminate)}-
nickel(II) complexes and investigating their catalytic
activities for vinyl polymerization of norbornene. Those
complexes showed promising characteristics with good
to extremely high activities up to 2.86 × 108 g PNB/
(mol Ni‚h) by varying their reaction conditions.
In complex a , the bulky 2,6-diisopropylbenbzimine
occupies the position trans to the triphenylphosphine
ligand with a nearly linear N1-Ni1-P1 angle (176.88-
(9)°). The naphthyl group attached to Ni1 lies in a
position trans to O1 with an O1-Ni1-C1 angle of
174.64(13)°. Moreover, the naphthalene unit swings out
of the coordination mean plane defined by P1-N1-
Ni1-O1-C1, forming an 84.3° angle. A similar struc-
ture is also obtained in its analogue complex e, in which
the N1-Ni1-P1 angle of 174.60(17)° and the C16-Ni1-
O1 angle of 173.6(3)° were observed. Compared to the
angle in complex a , a wider angle of 94.5° was found
between the naphthalene plane and the coordination
plane defined by P1-N1-Ni1-O1-C16 in complex e.
Additionally, the angle C16-Ni1-P1 (88.6(2)°) in com-
plex e is wider than the C1-Ni1-P1 (86.77(11)°) angle
of complex a ; a plausible reason is the bulky isopropyl
Resu lts a n d Discu ssion
The syntheses of the nickel complexes as catalytic
precursors are shown in Scheme 1. The ligands of
salicylaldimines were efficiently synthesized via the
condensation reaction of substituted salicylaldehydes
and anilines.10 Similar to the procedure reported by
Grubbs,11e the obtained salicylaldimines were treated
with NaH in THF and then reacted with trans-chloro-
(1-naphthyl)bis(triphenylphosphine)nickel(II) to give
their corresponding complexes.
(11) (a) Feldman, J .; McLain, S. J .; Parthasarathy, A.; Marshall W.
J .; Calabrese, J . C.; Arthur, S. D. Organometallics 1997, 16, 1514-
1516. (b) Keim, W.; Kowaldt F. H.; Goddard R.; Kru¨ger, C. Angew.
Chem., Int. Ed. Engl. 1978, 17, 466-467. (c) Klabunde, U.; Ittel S. D.
J . Mol. Catal. 1987, 41, 123-134. (d) Desjardins, S. Y.; Cavell, K. J .;
Hoare, J . L.; Skelton, B. W.; Sobolev, A. N.; White, A. H.; Keim, W. J .
Organomet. Chem. 1997, 544, 163-174. (e) Wang, C.; Friedrich, S.;
Younkin, T. R.; Li R. T.; Grubbs, R. H.; Bansleben, D. A.; Day, M. W.
Organometallics 1998, 17, 3149-3151. (f) Bauers, F. M.; Mecking, S.
Macromolecules 2001, 34, 1165-1171. (g) Zhang, D.; J in, G.-X.; Hu,
N. Chem. Commun. 2002, 574-575. (h) J ohnson, L. K.; Bennett, A.
M. A.; Ittel, S. D.; Wang, L.; Parthasarathy, A.; Hauptman, E.;
Simpson, R. D.; Feldman, J .; Coughlin, E. B. (DuPont) WO98 30,609,
1998; Chem. Abstr. 1998, 129, 149362j. (i) Carlini, C.; Martinelli, M.;
Galletti, A. M. R.; Sbrana, G. Macromol. Chem. Phys. 2002, 203, 1606-
1613.
The structures of the salicylaldiminato complexes
1
were confirmed by IR and H NMR spectra. For further
(10) (a) Ismail, M. M. Indian J . Pharm. Sci. 1986, 48, 121-124. (b)
Yang, H.; Sun, W.-H.; Li, Z.; Wang, L. Synth. Commun. 2002, 32,
2395-2402. (c) Darensbourg, D. J .; Rainey, P.; Yarbrough, J . Inorg.
Chem. 2001, 40, 986-993.

3680 Organometallics, Vol. 22, No. 18, 2003
Sun et al.
Ta ble 2. Activity of Com p lexes a -f for
Nor bor n en e P olym er iza tion
b
cat.
yield (%)
activitya
Mw
Mw/Mn
TGA (°C)
a
b
c
d
e
f
78
81
80
85
75
79
265.20
271.49
271.33
286.60
253.69
267.07
19.54
7.11
5.45
9.51
5.01
7.47
4.51
6.90
5.08
9.08
6.86
8.76
458
461
456
458
457
457
a
b
(× 10-6 g PNB/(mol Ni‚h)). (× 10-5 g/mol). Conditions:
solvent, toluene; total volume, 20 mL; temperature, 25 °C; reaction
time, 20 s; M/Ni ) 20 000; complex, 5 µmol; Al/Ni ) 2000; MAO,
7.20 mL.
activities greatly relied on the molar ratio of norbornene
monomer to nickel catalytic precursor.9m In a combina-
tion of 20 000:1 norbornene monomer to nickel precur-
sors (expressed as M/Ni) in toluene, 2000 equiv of MAO
compared with the amount of the nickel precursors (Al/
Ni ) 2000) was added. The mixed solution resulted in
a white solid mass that could no longer be stirred within
20 s. Therefore the resulting reaction mixture was
quenched with acidic ethanol at 20 s, and the PNB was
filtered and washed prior to drying to constant weight
under vacuum at 100 °C. The norbornene polymeriza-
tion results are collected in Table 2. Accordingly the
complexes with more electron-withdrawing chloro sub-
stituents on the ligand segments showed a little higher
activities than the ones with iodo substituents. The
polymer molecular weight distribution exhibited a
similar tendency as the activity, suggesting that the
higher activity results in different chain growth and
termination of polymerization. Unlike late-transition
metal complexes as catalysts for ethylene polymeriza-
tion,12 the steric hindrance of individual ligands does
not clearly affect their catalytic activities. The aryl
group directly coordinated on the nickel center, however,
made a significant difference in the catalytic activity.
Compared to previous nickel phenyl complexes [with the
highest activity as 7.08 × 107 g PNB/(mol Ni‚h)],9p
herein the nickel naphthyl complexes had higher activi-
ties. Plausible reasons could be attributed to the intro-
duction of bigger naphthyl and the more electron-
withdrawing substituents in the complexes. Furthermore,
the volatile trimethylaluminum in MAO might affect
the performance of this kind of catalyst.
To investigate the reaction parameters affecting vinyl
polymerization of norbornene, the catalyst precursor a
was typically investigated by changing the ratios of
MAO, the reaction temperature, and the molar ratios
of norbornene monomer to the precursor (M/Ni). Al-
though neutral salicylaldiminato nickel catalysts did not
require activators in their ethylene polymerization,9o,12c
the activator MAO was essential to the polymerization
of norbornene here. The role of MAO is to initiate the
polymerization and probably create an empty site for
the insertion of the norbornene monomer. Moreover, it
is necessary to use an excessive amount of MAO for good
to high activities. In a combination of 5000:1 M/Ni,
variation of the ratio of MAO:a (expressed as Al:Ni)
showed considerable effects on polymer yield (Table 3).
There is a remarkable difference from 500 to 1000 Al:
F igu r e 1. ORTEP of complex a . Selected bond distances
(Å) and angles (deg): Ni(1)-C(1), 1.903(3); Ni(1)-O(1),
1.903(2); Ni(1)-N(1), 1.941(3); Ni(1)-P(1), 2.2002(10);
C(1)-Ni(1)-O(1), 174.64(13); C(1)-Ni(1)-N(1), 93.01(13);
O(1)-Ni(1)-N(1), 92.30(11); C(1)-Ni(1)-P(1), 86.77(11);
O(1)-Ni(1)-P(1), 87.97(8); N(1)-Ni(1)-P(1), 176.88(9).
One ethyl ether molecule was omitted for clarity.
F igu r e 2. ORTEP of complex e. Selected bond distances
(Å) and angles (deg): Ni(1)-O(1), 1.894(4); Ni(1)-N(1),
1.922(5); Ni(1)-C(16), 1.958(9); Ni(1)-P(1), 2.1979(17);
O(1)-Ni(1)-C(16), 173.6(3); N(1)-Ni(1)-C(16), 92.9(3);
O(1)-Ni(1)-N(1), 92.9(2); C(16)-Ni(1)-P(1), 88.6(2); O(1)-
Ni(1)-P(1), 85.93(13); N(1)-Ni(1)-P(1), 174.60(17).
group of the 2,6-diisopropylbenzimine unit in complex
a has a steric influence on the naphthalene and Ph3P
segments.
The Ni1-O1, Ni1-N1, Ni1-C1, and Ni1-C16 bond
distances in complexes a and e are similar to those in
known nickel complexes.11 The Ni1-P bonds of com-
plexes a and e (2.2002(10) Å for a and 2.1979(17) Å for
e) are more than 0.02 Å longer than those in Grubbs’
neutral nickel-based complex (2.172(2) Å) and in Cavell’s
[Ni(PPh3)(o-tolyl)(N-O)] complexes with N-O bidentate
pyridinecarboxylate ligands (d(Ni-P) ) 2.1653(2) Å),11d
which suggests that in the solid state there is steric
interaction, although not significant, between the naph-
thalene moiety and the triphenylphosphine ligand.
The active catalysts were produced in situ in toluene
solution by activating the catalytic precursors with the
cocatalyst methylaluminoxane (MAO) in the presence
of norbornene. Polymerization of norbornene in the
presence of complexes and MAO resulted in the forma-
tion of vinyl-type PNB. It was realized that the catalytic
(12) (a) Small, B. L.; Brookhart, M.; Bennett, A. M. A. J . Am. Chem.
Soc. 1998, 120, 4049-4050. (b) Bruce M.; Gibson V. C.; Redshaw C.;
Solan G. A.; White A. J . P.; Williams D. J ., Chem. Commun. 1998,
2523-2524. (c) Mecking, S. Coord. Chem. Rev. 2000, 203, 325-351.

Vinyl Polymerization of Norbornene
Organometallics, Vol. 22, No. 18, 2003 3681
Ta ble 3. In flu en ce of th e MAO Am ou n t on th e
Activity of Com p lex a
tion periods; shorter reaction periods were chosen for
higher concentrations of norbornene. So the transforma-
tion of norbornene (yield) was not comparable in Table
5.
b
run no. Al/Ni yield (%) activitya Mw
Mw/Mn TGA (°C)
1
2
3
4
5
500
1000
1500
2000
2500
38
71
72
81
80
359.12
671.20
675.16
761.60
760.40
5.73
2.72
6.23
8.40
7.15
3.38
3.20
2.95
3.81
6.86
463
459
461
456
456
All the polymers obtained showed very similar IR and
1H NMR spectra. The IR spectra proved the absence of
a double bond, which often appear at 1620-1680 cm-1
,
ensuring the occurrence of vinyl-type polymerization
rather than ring-opening metathesis polymerization
(ROMP).9j 1H NMR spectra also proved no trace of any
double bond, which is typical for ROMP polynorbornene.
TGA investigation for all obtained polymers showed that
all of the polymer samples were very stable up to 450
°C. The determination of the glass transition temper-
ature (Tg) of vinyl homo-polynorbornene has been
described as being difficult, since it is apparently located
close to the temperature where decomposition tends to
set in.8b,9m Our attempts to determine the Tg of the
obtained vinyl polymers also failed, and the DSC studies
did not show an endothermic signal upon heating to the
decomposition temperature. All the polymer samples
obtained here are soluble in chlorobenzene at room
temperature. No indication of stereoregularity was
observed, which was verified by the amorphous mor-
phology of the products.
a
b
(× 10-3 g PNB/(mol Ni‚h)). (× 10-5 g/mol). Conditions:
temperature, 25 °C; solvent, toluene; total volume, 20 mL; reaction
time, 30 min; complex a , 5 µmol; M/Ni ) 5000.
Ta ble 4. In flu en ce of th e Rea ction Tem p er a tu r e
(T) on th e Activity of Com p lex a
run no. T (°C) yield (%) activitya Mw
Mw/Mn TGA (°C)
b
1
2
3
4
5
0
25
50
75
100
80
81
83
94
90
757.48
761.60
783.36
882.28
844.76
8.05
8.40
4.51
3.25
2.72
5.26
3.81
2.72
3.01
3.03
453
456
457
455
453
a
b
(× 10-3 g PNB/(mol Ni‚h)). (× 10-5 g/mol). Conditions:
solvent, toluene; total volume, 20 mL; reaction time, 30 min; M/Ni
) 5000; complex a , 5 µmol; Al/Ni ) 2000; MAO, 7.20 mL
Ta ble 5. In flu en ce of th e Nor bor n en e
Con cen tr a tion on th e Activity of Com p lex a
b
run no. M/Ni yield (%) activitya Mw
Mw/Mn TGA (°C)
1
2
3
4
2500
5000
10 000
20 000
98
81
79
78
0.47
0.76
14.19
2.92
8.40
7.85
5.17
3.81
2.85
4.51
458
456
459
458
Con clu sion
In summary, the nickel complexes a -f and MAO
systems showed extremely high activities in the vinyl-
type polymerization of norbornene. The complexes with
more electron-withdrawing chloro substituents on the
ligands exhibited higher activity than those with less
electron-withdrawing iodo substituents. The polymers
obtained here are amorphous and soluble in halo-
benzene and stable up to 450 °C. Catalytic activity,
conversion yield, polymer molecular weight, and mo-
lecular weight dispersion could be controlled over a wide
range.
265.20 19.54
a
b
(× 10-6 g PNB/(mol Ni‚h)). (× 10-5 g/mol). Conditions:
temperature, 25 °C; solvent, toluene; total volume, 20 mL; complex
a , 5 µmol; Al/Ni ) 2000; MAO, 7.20 mL; reaction time, (1) 30 min;
(2) 30 min; (3) 3 min; (4) 20 s.
Ni. However, the difference of yield for varying Al:Ni
between 1000 and 2500 is not impressive. In addition,
an Al:Ni ratio higher than 2000 will decrease the
activity for the catalytic system.
Table 4 shows the results with respect to reaction
temperature. The catalytic system shows good activity
over a large range of reaction temperatures. The tem-
perature was obtained with an external oil bath except
for entry 1, in which 0 °C was maintained with an ice-
water bath. Accordingly, the reaction showed better
activity with increasing reaction temperature, but not
higher than 75 °C. While the molecular weight disper-
sion varied with temperature, the molecular weight
decreased with an increase in temperature.
Increasing the monomer concentration, with fixed
amount of nickel precursor (5 µmol) and the same
solution volume, resulted in a dramatic increase of
activity with a higher ratio of M:Ni. High catalytic
activity of complex a up to 2.65 × 108 g PNB/(mol Ni‚h)
was observed with the M:Ni ratio of 20000:1 compared
to the activity [4.70 × 105 g PNB/(mol Ni‚h)] with the
M:Ni ratio of 2500:1. In addition, the higher concentra-
tion of norbornene produced a higher molecular weight
and a wider molecular weight distribution of PNB.
These results are listed in Table 5. That could be easily
Exp er im en ta l Section
Gen er a l Con sid er a tion s. All procedures were carried out
by using standard Schlenk techniques. Toluene and THF were
dried over sodium metal and distilled under nitrogen. Methy-
laluminoxane (MAO) was purchased from Albemarle as a 1.4
M toluene solution and used without further treating. 3,5-
Dichlorosalicylaldehyde, 3,5-diiodosalicylaldehyde, 2,6-diiso-
propylaniline, 2,6-diethylaniline, and 2,6-dimethylaniline were
bought from Aldrich Chem. Co. and used without further
purification. NaH obtained from Beijing Chemical Regents
Company was treated with petroleum ether to get rid of the
outside wrapped oil before use. trans-Chloro(1-naphthyl)bis-
(triphenylphosphine)nickel was synthesized according to the
procedure reported in the literature.13 Norbornene (bicyclo-
[2.2.1]hept-2-ene; Acros) was purified by distillation over
potassium and used as a solution in toluene.
Mea su r em en t. NMR spectra were recorded on a J EOL AL-
300 or
a Bruker BMX-300 MHz instrument at ambient
temperature using TMS as internal standard, and NMR data
for polynorbornene were obtained on a J EOL AL-300 instru-
ment using o-dichlorobenzene-d4 as solvent. The 31P NMR
spectra were obtained on a Varian-200 MHz with phosphoric
acid as internal standard. The melting points (mp) of ligands
and complexes were measured with an electrical apparatus.
explained like the regular olefin polymerization:
a
higher pressure of monomer gives a higher catalytic
activity and high-order polyolefins. However, since the
reaction became very exothermic under these conditions,
the control of reaction temperature became critical.
Therefore the reaction was quenched in different reac-
(13) Soolingen, J . V.; Verkruijsse, H. D.; Keegstra, M. A.; Brandsma,
L. Synth. Commun. 1990, 20, 3153-3156.

3682 Organometallics, Vol. 22, No. 18, 2003
Sun et al.
IR spectra were recorded on a Perkin-Elmer 2000 FT-IR
spectrometer. Elemental analyses were carried out using a HP-
MOD 1106 microanalyzer. Molecular weights of polymers were
determined by a Waters Alliance GPCV 2000 system at 135
°C in 1,2,4-trichlorobenzene with polystyrene narrow distribu-
tion standards. TGA data were measured with a Perkin-Elmer
7 Series thermal analysis system instrument.
to that for complex a in a yield of 37%. Mp: 187-189 °C. IR
(KBr pellet): 3049.55 (m), 2967.43 (m), 2930.36 (w), 2873.81
(w), 1897.82 (w), 1581.45 (vs), 1545.59 (w), 1484.63 (m),
1438.66 (vs), 1393.77 (w), 1372.57 (m), 1323.50 (s), 1242.40
(w), 1222.16 (m), 1178.51 (w), 1150.08 (s), 1096.25 (s), 1028.26
(w), 999.84 (w), 954.45 (w), 892.39 (w), 863.88 (w), 843.45 (w),
810.53 (w), 784.86 (w), 772.36 (w), 748.28 (m), 722.96 (w),
693.05 (s), 620.01 (w), 543.49 (w), 527.27 (w), 510.74 (m),
Syn th eses of Liga n d s a n d Com p lexes. Dihalosalicylal-
dehyde and aniline were refluxed in ethanol for 5-10 h to
afford the corresponding yellow or orange phenoxyimine
products via a Schiff-base condensation reaction. The crude
products were purified by recrystallization in ethanol, except
for 4,6-dichloro-2-[[(4,6-diethylphenyl)imino]methyl]phenol,
which was purified by column chromatography on silica gel
using Et2O-petroleum (volume ratio ) 1:10) as eluent. All the
ligands are known compounds,14 and their structures were
confirmed with 1H NMR.
493.10 (w), 422.56 (w) cm-1 1H NMR (CDCl3, 300 MHz): δ
.
0.62 (t, J ) 7.4 Hz, 3H, CH3), 1.19 (t, J ) 7.4 Hz, 3H, CH3),
1.89-1.98 (m, H, CH2), 2.36-2.45 (m, H, CH2), 3.01-3.21 (m,
2H, CH2), 6.20-7.96 (m, 27H, aromatic-H), 9.46 (d, J ) 7.5
Hz, 1H, CHdN). 31P NMR (CDCl3, 300 MHz): δ. 24.56. Anal.
Calcd for C45H38I2NNiOP‚Et2O: C, 57.34; H, 4.71; N, 1.36.
Found: C, 57.18; H, 4.66; N, 1.41.
(1-Naph th yl)(tr iph en ylph osph in e){N-[1-(2,6-dieth ylph e-
n yl)]-(3,5-d ich lor osa licyla ld im in a te)}n ick el(II) (com p lex
d ). A dark brown powder was obtained in a manner similar
to that for complex a in a yield of 54%. Mp: 167-169 °C. IR
(KBr pellet): 3052.06 (m), 2956.12 (w), 2914.21 (m), 2876.52
(w), 1897.45 (w), 1585.88 (s), 1544.53 (m), 1482.37 (s), 1434.78
(vs), 1371.27 (m), 1311.37 (m), 1243.65 (m), 1188.14 (m),
1158.47 (m), 1094.65 (s), 1028.03 (w), 999.58 (w), 954.01 (w),
848.97 (w), 785.67 (m), 744.19 (s), 693.88 (vs), 645.69 (w),
540.36 (m), 513.19 (vs), 494.54 (w) cm-1. 1H NMR (CDCl3, 300
MHz): δ 1.07 (t, J ) 7.5 Hz, 3H, CH3), 1.69 (t, J ) 7.5 Hz, 3H,
CH3), 2.38 (m, H, CH2), 2.84 (m, H, CH2), 4.58-4.72 (m, 2H,
CH2), 7.71-9.30 (m, 27H, aromatic-H), 10.06 (d, J ) 8.0 Hz,
1H, CHdN). 31P NMR (CDCl3, 300 MHz): δ 22.08. Anal. Calcd
for C45H38Cl2NNiOP‚Et2O: C, 69.77; H, 5.74; N, 1.66. Found:
C, 70.01; H, 5.71; N, 1.63.
(1-Na p h th yl)(tr ip h en ylp h osp h in e){N-[1-(2,6-d iisop r o-
pylph en yl)]-(3,5-diiodosalicylaldim in ate)}n ickel(II) (com -
p lex a ). To a stirred solution of 4,6-diiodo-2-[[(2,6-diisopropy-
lphenyl)imino]methyl]phenol (5.0 mmol) in THF (100 mL) at
room temperature was added NaH (5.0 mmol) at once. The
reaction was allowed to stir for 1 h. Then trans-chloro(1-
naphthyl)bis(triphenylphosphine)nickel (5.0 mmol) was added
quickly. After being stirred at room temperature for 10 h, the
mixture was filtered through a glass filter, and the filtrate
was evaporated in vacuo to yield a dark brown solid. The
brown solid was again dissolved in diethyl ether and concen-
trated to 1/5 volume. After filtration and drying in vacuo,
complex a was obtained as a reddish brown powder (75%).
Mp: 209-211 °C. IR (KBr pellet): 3050.98 (m), 2959.88 (s),
2927.76 (w), 2867.43 (w), 1893.46 (w), 1732.38(w), 1583.11 (vs),
1546.96 (w), 1487.02 (m), 1437.40 (vs), 1372.23 (m), 1323.53
(m), 1245.03 (w), 1223.68(m), 1151.26 (s), 1094.70 (m), 1026.96
(w), 954.59(w), 871.48 (w), 841.86 (w), 746.05 (m), 694.12 (s),
(1-Na p h t h yl)(t r ip h en ylp h osp h in e){N-[1-(2,6-d im et h -
ylp h en yl)]-(3,5-d iiod osa licyla ld im in a te)}n ick el(II) (com -
p lex e). A reddish brown powder was obtained in a manner
similar to that for complex a in good yield (63%). Mp: 199-
201 °C. IR (KBr pellet): 3050.34 (m), 2978.34 (w), 2914.97 (m),
2878.21 (w), 1897.36 (w), 1776.09 (w), 1581.82 (vs), 1545.39
(m), 1483.23 (s), 1439.23 (vs), 1372.73 (m), 1324.00 (s), 1241.68
(w), 1227.86 (w), 1181.07 (m), 1151.06 (s), 1096.12 (s), 1028.89
(w), 999.70 (w), 954.49 (w), 891.98 (w), 861.06 (w), 844.11 (w),
784.27 (m), 771.00 (m), 744.38 (m), 722.86 (w), 692.75 (s),
646.17 (w), 610.96 (w), 543.94 (m), 527.66 (w), 512.35 (s),
1
620.06 (w), 542.13 (m), 527.71 (s), 509.86 (m) cm-1. H NMR
(CDCl3, 300 MHz): δ -0.38 (d, J ) 6.6 Hz, 3H, CH3), 0.82 (d,
J ) 6.9 Hz, 3H, CH3), 1.08 (d, J ) 6.6 Hz, 3H, CH3), 1.70 (d,
J ) 6.9 Hz, 3H, CH3), 2.50-2.59 (m, 1H, CH), 4.71-4.81 (m,
1H, CH), 6.04-7.96 (m, 27H, aromatic-H), 10.01 (d, J ) 8.4
Hz, 1H, CHdN, Hz). 31P NMR (CDCl3, 300 MHz): δ. 24.41.
Anal. Calcd for C47H42I2NNiOP‚Et2O: C, 58.09; H, 4.97; N,
1.33. Found: C, 58.10; H, 4.91; N, 1.31.
421.02 (w) cm-1 1H NMR (CDCl3, 300 MHz): δ 1.62 (s, 3H,
.
CH3), 2.59 (s, 3H, CH3), 6.19-7.98 (m, 27H, aromatic-H), 9.56
(d, J ) 6.9 Hz, 1H, CHdN). 31P NMR (CDCl3, 300 MHz): δ
24.51. Anal. Calcd for C43H34I2NNiOP‚Et2O: C, 56.54; H, 4.44;
N, 1.40. Found: C, 56.61; H, 4.41; N, 1.39.
(1-Na p h th yl)(tr ip h en ylp h osp h in e){N-[1-(2,6-d iisop r o-
p ylp h en yl)]-(3,5-d ich lor osa licyla ld im in a t e)}n ick el(II)
(com p lex b). A dark brown powder was obtained in a manner
similar to that for complex a in good yield (68%). Red crystals
were obtained from CH3CN. Mp: 174-176 °C. IR (KBr
pellet): 3054.36 (s), 2961.20 (vs), 2926.83 (m), 2867.28 (w),
1956.70 (w), 1895.09 (w), 1816.82 (w), 1602.27 (vs), 1545.94
(w), 1512.31 (m), 1479.56 (w), 1449.76 (vs), 1437.20 (vs),
1373.57 (m), 1328.16 (s), 1260.53 (m), 1212.92 (w), 1166.03 (vs),
1118.92 (m), 1095.45 (s), 1071.22 (w), 1026.84 (m), 999.24 (w),
954.21 (w), 933.68 (w), 862.76 (m), 755.03 (s), 745.46 (s), 722.32
(m), 694.68 (vs), 630.54 (w), 541.77 (vs), 509.92 (s), 454.97 (w),
(1-Na p h t h yl)(t r ip h en ylp h osp h in e){N-[1-(2,6-d im et h -
ylp h en yl)]-(3,5- d ich lor osa licyla ld im in a t e)}n ick el(II)
(com p lex f). A reddish brown powder was obtained in a
manner similar to that for complex a in a yield of 52%. Mp:
178-180 °C. IR (KBr pellet): 3052.77 (m), 2974.14 (w), 2935.83
(w), 2969.51 (w), 1933.49 (w), 1736.71 (w), 1604.97 (vs), 1589.23
(w), 1518.79 (s), 1470.31 (w), 1444.29 (vs), 1372.84 (m), 1328.59
(w), 1315.46 (s), 1242.74 (w), 1221.25 (m), 1171.62 (vs), 1093.62
(m), 1030.10 (w), 998.40 (w), 970.76 (w), 862.65 (m), 779.69
(vs), 763.66 (w), 749.53 (w), 693.88 (s), 625.04 (m), 588.14 (w),
1
422.10 (w) cm-1. H NMR (CDCl3, 300 MHz): δ -0.33 (d, J )
6.6 Hz, 3H, CH3), 0.86 (d, J ) 6.6 Hz, 3H, CH3), 1.11 (d, J )
6.6 Hz, 3H, CH3), 1.74 (d, J ) 6.6 Hz, 3H, CH3), 2.59-2.68
(m, 1H, CH), 4.70-4.79 (m, 1H, CH), 6.19-7.92 (m, 27H,
aromatic-H), 10.12 (d, J ) 8.2 Hz, 1H, CHdN). 31P NMR
(CDCl3, 300 MHz): δ 24.24. Anal. Calcd for C47H42Cl2NNiOP‚
CH3CN: C, 70.19; H, 5.41; N, 3.34. Found: C, 70.03; H, 5.50;
N, 3.38.
539.84 (w), 520.71 (s), 455.88 (w), 419.84 (w) cm-1 1H NMR
.
(CDCl3, 300 MHz): δ 1.63 (s, 3H, CH3), 2.63 (s, 3H, CH3), 6.25-
7.83 (m, 27H, aromatic-H), 9.69 (d, J ) 7.9 Hz, 1H, CHdN).
31P NMR (CDCl3, 300 MHz): δ 22.15. Anal. Calcd for C43H34
-
Cl2NNiOP‚Et2O: C, 69.23; H, 5.44; N, 1.72. Found: C, 69.31;
H, 5.41; N, 1.75.
X-r a y Cr ysta llogr a p h y. Indensity data of crystal a and e
were collected on a Rigaku R-Axis Rapid IP CCD area detector
at 293(2) K with graphite-monochromated Mo KR radiation
(λ ) 0.71073 Å). Cell parameters were obtained by global
refinement of the positions of all collected reflections. Intensi-
ties were corrected for Lorentz and polarization effects and
empirical absorption. The structures were solved by direct
methods and refined by full-matrix least-squares on F2. Each
(1-Naph th yl)(tr iph en ylph osph in e){N-[1-(2,6-dieth ylph e-
n yl)]-(3,5-d iiod osa licyla ld im in a te)}n ick el(II) (com p lex
c). A reddish brown powder was obtained in a manner similar
(14) Darensbourg, Donald J .; Rainey, P.; Yarbrough, J . Inorg. Chem.
2001, 40, 986-993; Chem. Abstr. 2001, 134, 260482r. (b) Ismail, M.
M. Indian J . Pharm. Sci. 1986, 48, 121-124; Chem. Abstr. 1986, 107,
175589d.

Vinyl Polymerization of Norbornene
Organometallics, Vol. 22, No. 18, 2003 3683
H atom was placed in a calculated position and refined
anisotropically. Structure solution and refinement were per-
formed using the SHELXL-97 package. Crystallographic data
(excluding structure factors) for the structure reported in this
paper have been deposited with the Cambridge Crystal-
lographic Data Center as CCDC-199518 for complex a and
CCDC-199519 for complex e. Copies of the data can be
obtained on application to CCDC, 12 Union Road, Cambridge
CB21EZ, UK (fax: (+44)1223-336-033; e-mail: deposit@
ccdc.cam.ac.uk).
above-mentioned typical procedure. IR (KBr): 2947.55 (vs),
2869.30 (vs), 1473.45 (s), 1452.69 (s), 1374.89 (m), 1295.35 (m),
1258.08 (m), 1222.49 (m), 1147.57 (m), 1108.43 (m), 1041.40
(w), 942.69 (m), 892.91 (m), 756.45 (w) cm-1 1H NMR (o-
.
dichlorobenzene-d4, 300 MHz): δ 0.86-2.30 (m, maxima at
0.86, 1.22, 1.58, 2.21). 13C NMR (o-dichlorobenzene-d4, 300
MHz): δ 29.65-50.18 (m, maxima at 29.65, 30.02, 31.79, 32.14,
37.31, 38.63, 47.47, 50.18).
P olym er iza tion of Nor bor n en e. In a typical procedure
(entry 4, Table 2), the catalyst (5 µmol) was dissolved in 9.50
mL of toluene under nitrogen, and 3.30 mL of a toluene
solution of norbornene (7.80 M, 25 mmol of norbornene) was
added via syringe. The polymerization was initiated by addi-
tion of methylaluminoxane (MAO) (7.2 mL, 10.00 mmol) in
toluene via syringe. After 30 min, the polymerization was
terminated by injecting 200 mL of acidic ethanol (ethanol-
HClconc, 95:5). The polymer was isolated by filtration, washed
with ethanol, and dried in a vacuum at 100 °C for 100 h.
Unless otherwise stated, the total reaction volume was 20 mL,
which was achieved by variation of the amount of toluene when
necessary.
Ack n ow led gm en t. We are grateful to the Chinese
Academy of Sciences for financial support under the
“One Hundred Young Talents”, Core Research for
Engineering Innovation KGCX203-2 and National Natu-
ral Science Foundation of China Grant No. 20272062.
Su p p or tin g In for m a tion Ava ila ble: Text giving experi-
mental details and analysis data for the compounds prepared
in this work, and tables of crystals and intensity collection
data, positional and thermal parameters, and all bond dis-
tances and angles for complexes a and e. This material is
available free of charge via the Internet at http://pubs.acs.org.
All the polymer samples exhibited similar IR and NMR
spectral absorption. The following are the spectral data of the
OM030018T