Nickel and cationic palladium complexes bearing (imino)pyridyl alcohol ligands: Synthesis, characterization and vinyl polymerization of norbornene

Article abstract of DOI:10.1016/j.jorganchem.2011.01.024

A series of nickel and palladium complexes bearing (imino)pyridyl alcohol tridentate [N,N,O] ligands, 2-(ArNCMe)-6-{(HO)CR₂}C₅H ₃N (L1-L4), were synthesized and sufficiently characterized by elemental and spectroscopic ana

Full text of DOI:10.1016/j.jorganchem.2011.01.024

Journal of Organometallic Chemistry 696 (2011) 1465e1473
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Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Nickel and cationic palladium complexes bearing (imino)pyridyl alcohol ligands:
Synthesis, characterization and vinyl polymerization of norbornene
*
Suyun Jie , Pengfei Ai, Qimeng Zhou, Bo-Geng Li
State Key Laboratory of Chemical Engineering, Department of Chemical and Biological Engineering, Zhejiang University, 38 Zheda Road, Hangzhou 310027, China
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of nickel and palladium complexes bearing (imino)pyridyl alcohol tridentate [N,N,O] ligands,
2-(ArN]CMe)-6-{(HO)CR2}C5H3N (L1eL4), were synthesized and sufficiently characterized by elemental
and spectroscopic analysis along with X-ray diffraction analysis. The X-ray diffraction demonstrated that
five-coordinated nickel halide complexes (1ae4a and 1b) and six-coordinated nickel acetate complex
(1c) were prepared, and cationic palladium complexes (1d and 2d) formed with the [PdCl4]2ꢀ counterion.
All these complexes displayed high catalytic activities up to 1.883 ꢁ 107 g(PNB) molꢀ1(cat) hꢀ1 (2d) for
the vinyl polymerization of norbornene on treatment with excess methylaluminoxane (MAO), affording
the vinyl-type PNBs with high molecular weights and relatively narrow molecular weight distributions.
The parameters of reaction conditions, the type of metals and steric effects of coordinative ligands had
influences on the catalytic properties.
Received 10 December 2010
Received in revised form
14 January 2011
Accepted 18 January 2011
Keywords:
Nickel
Palladium
Norbornene
Vinyl polymerization
Ó 2011 Elsevier B.V. All rights reserved.
1. Introduction
drawn much attention since the discovery of the
complexes of Ni and Pd for the polymerization of ethylene and
-olefins by Brookhart and coworkers [6]. Novak reported the first
a-diimine
Norbornene (bicyclo[2.2.1]hept-2-ene, NB) and its derivatives
can be polymerized in three different pathways: ring-opening
metathesis polymerization (ROMP) [1], cationic or radical poly-
merization [2], and vinyl/addition polymerization [3]. Each route
produces its own polymer type with different structures and
properties and can be differentiated through various transition
metal containing catalysts. Vinyl-type polymerization was first
described in the early 1960s and cycloaliphatic polymers contain-
ing bicyclic structural units intact without any double bond were
produced by using classical TiCl4-based Ziegler catalyst [4]. With
constrained rings in each unit, the vinyl-type norbornene polymers
(PNBs) possess interesting and unique properties [5], such as high
chemical resistance, good UV resistance, low dielectric constant,
excellent transparency, low water uptake, large refractive index,
small optical birefringence and dielectric loss, high glass transition
and decomposition temperatures.
a
example of nickel complexes for the vinyl polymerization of nor-
bornene in 1993 [7], and recently some of nickel and palladium
complexes were also found to be highly active for the vinyl poly-
merizationof norbornene, affording vinyl-typePNBswith molecular
weights higher than 106 g/mol [3e]. Among the Ni and Pd pre-
catalysts developed, most contained bidentate ligands, such as [N,O]
[8], [N,N] [9], [P,N] [10], [P,P] [11]. However, only a few nickel and
palladium complexes bearing tridentate [12] or multidentate
[12a,13] ligands were reported for the vinyl polymerization of nor-
bornene, of which tridentate phenoxy-imine ligands with an
hydroxyl group or an alkoxyl group sidearms ([O,N,O]) [12a,b] and
phenoxy-imine(quinoline) framework ([N,N,O]) [12f] were of
interest for us. In order to develop new late-metal catalysts with
tridentate ligands and confirm the function of phenoxy-O group, we
synthesized the nickel and palladium complexes ligated by tri-
dentate (imino)pyridyl alcohol tridentate [N,N,O] ligands, some of
which had been used in an (1-adamantylimido)vanadium(V)
complex [14] and iron(II) complexes showing moderate activities in
ethylene polymerization [15]. In this paper, we will describe the
synthesis and structures of nickel and cationic palladium complexes
Catalysts containing the metals titanium, zirconium, chromium,
and currently the late-transition metals cobalt, nickel and palladium
are described in the literatures for the vinyl homo-polymerization of
norbornene [3]. Nickel and palladium complexes especially have
bearing
a series of tridentate 2-arylimino-6-(alcohol)pyridine
ligands and the evaluation of their catalytic properties for the vinyl
polymerization of norbornene.
* Corresponding author. Tel.: þ86 571 87952631; fax: þ86 571 87951612.
E-mail address: jiesy@zju.edu.cn (S. Jie).
0022-328X/$ e see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2011.01.024

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S. Jie et al. / Journal of Organometallic Chemistry 696 (2011) 1465e1473
R1
N
1) 2 eq MeLi
2) H2O
N
OH
OEt
N
L1: R1 = i-Pr, R2 = H
L2: R1 = Et, R2 = H
L3: R1 = R2 = Me
R1
R2
O
O
OEt
R1
N
p-TsOH
toluene
R2
+
N
O
NH2
R1
R1
R1
N
1) NaBH4/CaCl2
2) H2O
1: R1 = i-Pr, R2 = H
2: R1 = Et, R2 = H
3: R1 = R2 = Me
N
OH
R2
L4
Scheme 1. Synthesis of (imino)pyridyl alcohol ligands L1eL4.
2. Results and discussion
complexes 1d and 2d was requisite to be carried out at 60 ꢂC for 3 h
(Scheme 4). All the complexes were well characterized by FT-IR
spectra and elemental analysis. In the IR spectra, the stretching
vibration bands of C]N double bonds of these nickel and palladium
complexes (1616e1620 cmꢀ1) apparently shifted to lower wave
number and the peak intensity greatly reduced, as compared to the
corresponding ligands (1642e1645 cmꢀ1), indicating the coordi-
nation interaction between the imino nitrogen atom and the metal
center; and so did the hydroxyl group. The 1H NMR spectra of
palladium complexes 1d and 2d exhibited two sets of protons with
slightly different chemical shifts. The molecular structures of
complexes 1a, 1c and 2d were further confirmed by the single-
crystal X-ray diffraction analysis (Figs. 1e3).
2.1. Synthesis of (imino)pyridyl alcohol ligands and their complexes
The starting materials, 2-carboxylate-6-iminopyridine compo
unds, 2-COOEt-6-(ArN]CMe)C5H3N (Ar ¼ 2,6-i-Pr2C6H3, 1; 2,6-
Et2C6H3, 2; 2,4,6-Me3C6H2, 3) [16], were readily accessible by the
condensation reaction of 6-acetylpyridine-2-carboxylate and the
corresponding substituted anilines. Those compounds had been
developed by the group of Sun [16] and were proven to be
effective as ligands for iron, cobalt, nickel, palladium and
chromium complexes in catalytic ethylene polymerization/
oligomerization [17]. The desired (imino)pyridyl alcohol ligands,
2-(ArN]CMe)-6-{(HO)CMe2}C5H3N (Ar ¼ 2,6-i-Pr2C6H3, L1; 2,6-
Et2C6H3, L2; 2,4,6-Me3C6H2, L3), were prepared by the slow
addition of MeLi solution in THF into a solution of 2-carbox-
ylate-6-iminopyridines (1e3) in THF at 0 ꢂC, stirring at room
temperature and subsequent hydrolysis (Scheme 1), which were
obtained in high purity after separation by using column chro-
matography. The ligand L4, 2-(2,6-i-Pr2C6H3N¼CMe)-6-(CH2OH)
C5H3N, was prepared via the reduction of compound 1 by
sodium borohydride with the assistance of calcium chloride in
methanol in good yield (Scheme 1). All the ligands were iden-
tified on the basis of FT-IR, 1H and 13C NMR spectra as well as
elemental analysis and some of them were compared with the
reference data [14,15].
2.2. Crystal structures
Single crystals of complex 1a suitable for X-ray diffraction
analysis were obtained by slow diffusion of diethyl ether into its
methanol solution. The molecular structure is shown in Fig. 1, and
the selected bond lengths and angles are listed in Table 1. According
to its structure, the coordination geometry around the nickel center
can be described as a distorted trigonal bipyramidal, in which the
nitrogen of pyridyl group (N1) and two chlorides (Cl1 and Cl2)
compose an equatorial plane and the nickel atom slightly deviates
by 0.0774 Å from this triangular plane. The three equatorial angles
N1eNieCl1, Cl1eNieCl2 and N1eNieCl2 are respectively 95.42
(8)ꢂ, 109.46(5)ꢂ and 154.59(9)ꢂ with the larger distortion of
N1eNieCl2 and the axial NieN2 and NieO1 bonds subtend an
angle of 150.10(10)ꢂ (O1eNieN2). The equatorial plane is nearly
perpendicular to the pyridyl plane with a dihedral angle of 90.7ꢂ.
The dihedral angle between the phenyl ring and the pyridyl plane is
126.4ꢂ. The NieN1 (pyridyl) bond (1.995(3) Å) in the equatorial
The nickel complexes 1ae4a,1b and 1c were readily prepared by
mixing the corresponding ligand and one equivalent of NiCl2$6H2O,
NiBr2 or Ni(OAc)2$4H2O in ethanol at room temperature and were
isolated as orange or brown air-stable powders (Schemes 2 and 3).
The reaction of ligands and PdCl2 in ethanol at room temperature
proceeded relatively slowly; therefore the preparation of palladium
R
R
R1
N
R
R1
N
R
NiCl2·6H2O or NiBr2
EtOH, r.t.
N
O
N
OH
Ni
H
X
X
R2
R1
R1
R2
L1–L4
1a: R1 = i-Pr, R2 = H, R = Me, X = Cl
1b: R1 = i-Pr, R2 = H, R = Me, X = Br
2a: R1 = Et, R2 = H, R = Me, X = Cl
3a: R1 = R2 = R = Me, X = Cl
4a: R1 = i-Pr, R2 = R = H, X = Cl
Scheme 2. Synthesis of nickel complexes 1ae4a and 1b.

S. Jie et al. / Journal of Organometallic Chemistry 696 (2011) 1465e1473
1467
N
N
N
O
EtOH
r.t.
H
O
N
OH
Ni
+
Ni(OAc)2·4H2O
O
O
O
L1
1c
Scheme 3. Synthesis of nickel complex 1c.
plane is shorter by about 0.124 Å than the axial NieN2(imino) (2.119
(3) Å). The two NieCl bond lengths show a slight difference
between the Ni-Cl2 (2.2284(11) Å) and NieCl1 (2.3095(11) Å) and
the bond length of NieO1 is 2.105(3) Å. The imino N2eC6 bond
length is 1.292(4) Å with the typical character of C]N double bond.
Single crystals of complex 1c suitable for X-ray diffraction
analysis were obtained by slow diffusion of n-hexane into its
dichloromethane solution. Analysis of X-ray crystallography reveals
that complex 1c displays a distorted octahedral geometry as shown
in Fig. 2, in which the nickel center is coordinated to the tridentate
ligand (NNO in a meridional manner) and two acetate anions in
monodentate and bidentate modes, respectively. In its molecular
structure, the O1, O2, O4, N2 atoms could be located in an equatorial
plane and the two axial bonds nearly form a straight angle
(N1eNieO3, 173.09(7)ꢂ). All the bond angles in the equatorial plane
are very close to a right angle (O1eNieO2, 93.22(6)ꢂ; O1eNieO4,
91.48(7)ꢂ; O2eNieN2, 91.60(6)ꢂ; O4eNieN2, 92.43(7)ꢂ). The
dihedral angles between the phenyl ring and the equatorial plane,
the pyridyl plane are 113.0ꢂ and 85.5ꢂ, respectively. The axial
NieN1(pyridyl) bond length (1.9925(17) Å) is shorter by about
0.135 Å than the NieN2(imino) (2.1277(16) Å) in the equatorial
plane. The NieO1(alcohol group) bond (2.1841(15) Å) is obviously
longer than the NieO(acetate groups) distances (2.1231(16), 2.0514
(17), and 2.0315(16) Å). The imino N2eC6 bond length is 1.285(3) Å
with the typical character of C]N double bond. Intramolecular
hydrogen bonding interaction is observed in the structure of
complex 1c between the hydrogen atom (H1) of hydroxyl group
and O atom (O5) of acetate group: O1eH1/O5 (dH1/O5 ¼ 1.717 Å
and dO1/O5 ¼ 2.559 Å with :O1eH1/O5 ¼ 173.86ꢂ).
pyridyl plane are almost coplanar with the dihedral angle of 7.3ꢂ
and the phenyl ring is nearly perpendicular to the square plane
with the dihedral angle of 95.6ꢂ. The two PdeN distances were
measured as PdeN(py) (1.927(3) Å) and PdeN(imino) (2.006(3) Å)
and the PdeCl distance is 2.2940(1) Å within the normal range of
PdeCl bonds, which are all similar to the other pyridyl-imine
palladium complexes [17b,18]. The imino N2eC6 bond length
(1.295(5) Å) is in the range of typical C]N double bond. The
counterion [PdCl4]2ꢀ forms another square planar in the unit cell
with the similar PdeCl distances (Pd2eCl2, 2.3080(2) Å; Pd2eCl3,
2.2971(2) Å) and nearly perpendicular bond angles (Cl3ePd2eCl2,
88.69(7)ꢂ).
In the solid state, complex 2d displays intermolecular hydrogen
bonding interactions between the hydrogen atom of hydroxyl group
(H1) and the oxygen atom (O2) of H2O, the hydrogen atoms of H2O
and the chlorine atoms of counterion [PdCl4]2ꢀ as shown in Fig. 4. The
hydrogen bond angle of O1eH1/O2 is 160.80ꢂ and the distances of
H1/O2 and O1/O2 are 1.718 Å and 2.513 Å, respectively. The two
types of hydrogen bonding between hydrogen atoms of H2O and
chlorine atoms of [PdCl4]2ꢀ are slightly different: dH201/Cl3 ¼ 2.394 Å,
dO2/Cl3 ¼ 3.210 Å, :O2eH201/Cl3 ¼ 141.88ꢂ and dH202/Cl2
¼
2.184 Å, dO2/Cl2 ¼ 3.058 Å, :O2eH202/Cl2 ¼ 150.31ꢂ, respectively.
2.3. Vinyl polymerization of norbornene
All the synthesized nickel and palladium complexes were
evaluated for the vinyl polymerization of norbornene. The detailed
results were summarized in Table 2. To investigate the influences of
reaction parameters, nickel complex 1a was typically studied as
a model catalyst precursor by varying polymerization conditions.
Almost no catalytic activities were observed with triethyl
aluminum or triisobutylaluminum (Al/Ni ¼ 200) as a co-catalyst at
30 ꢂC, whereas in the presence of methylaluminoxane (MAO) the
catalytic activity increased remarkably with the production of
vinyl-type PNBs by using toluene as the solvent. According to the
literatures, for other nickel and palladium complexes with tri-
dentate ligands, high catalytic activities were obtained in the
chlorinated alkanes, such as dichloromethane, 1,2-dichloroethane,
1,1,2,2-tetrachloroethane, but only trace of PNBs could be obtained
in toluene [12c,f]. The polymerization solution resulted in a white
solid mass that was difficult to be stirred around 10 min and the
Single crystals of complex 2d suitable for X-ray diffraction
analysis were obtained by slow diffusion of n-hexane into its
dichloromethane solution. Analysis of X-ray crystallography reveals
that the cationic palladium complex formed with [PdCl4]2ꢀ as the
counterion (Fig. 3). In the cationic complex moieties, a slightly
distorted square planar geometry around the metal center is
observed, in which the central palladium atom is coordinated to the
tridentate ligand (NNO) and one chloride. The O1, N1, N2 and Cl1
atoms could be located in the square plane and the palladium atom
slightly deviates by 0.0252 Å from this plane. The N2ePd1eO1
(160.43(1)ꢂ) and N1ePd1eCl1 (177.84(1)ꢂ) bond angles in the
square plane are close to a straight angle. The square plane and the
R1
N
R1
N
EtOH
60 ºC
2
N
OH
[PdCl4]
+ 3 PdCl2
N
O
Pd
Cl
H
R1
R1
L1–L2
2
1d: R1 = i-Pr
2d: R1 = Et
Scheme 4. Synthesis of palladium complex 1d and 2d.

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S. Jie et al. / Journal of Organometallic Chemistry 696 (2011) 1465e1473
Fig. 3. Molecular structure of complex 2d with thermal ellipsoids at the 30% proba-
bility level. Hydrogen atoms (apart from H1) and H2O molecules have been omitted for
clarity.
were carried out under the similar conditions with the Al/cat molar
ratio of 1000 and at 30 ꢂC. The anion of nickel complexes had a great
effect on the catalytic properties. For instance, nickel complex
1ae1c bearing the same ligand (L1) showed large differences in the
conversions of norbornene and catalytic activities. Nickel chloride
1a (51.92% conversion, 2.93 ꢁ 106 g(PNB) molꢀ1(cat) hꢀ1, entry 4)
proved to be more active than the corresponding bromide 1b
(48.21% conversion, 2.72 ꢁ 106 g(PNB) molꢀ1(cat) hꢀ1, entry 12).
When chloride or bromide was replaced by acetate, higher
conversion and activity were obtained by complex 1c (62.28%
conversion, 3.52 ꢁ 106 g(PNB) molꢀ1(cat) hꢀ1, entry 13). The
substituents (R1 and R2) on the imino-N aryl ring also affected the
catalytic performances of nickel complexes. The bulkier substitu-
ents led to the lower conversion of norbornene and lower catalytic
activity. The greater bulkiness of the isopropyl groups at the ortho-
positions of imino-N aryl ring of complex 1a may to some extent
prevent the access of monomer to the active center in the catalytic
system, therefore resulting in the decrease of catalytic activity.
However, the substituents (R) on the HOeC atom had more
important influence on the catalytic performance. Instead of the
two methyl groups on the HOeC atom with two hydrogen atoms,
complex 4a gained much higher conversion of norbornene and
activity (85.38% conversion, 4.82 ꢁ 106 g(PNB) molꢀ1(cat) hꢀ1, entry
16). Despite the different conversions and activities obtained by
different nickel complexes, all the PNBs produced had high
molecular weight (>106 g/mol) and relatively narrow molecular
weight distributions around 2.0.
Fig. 1. Molecular structure of complex 1a with thermal ellipsoids at the 30% proba-
bility level. Hydrogen atoms (apart from H1) and one methanol molecule have been
omitted for clarity.
conversion of norbornene increased by 7.33% in the next 10 min
(entry 4 and 5 in Table 2). Therefore the resulting reaction mixture
for the following cases was quenched with HCl-acidic ethanol at
10 min. The polymerization behaviors were influenced strongly by
the Al/Ni molar ratios. For example, with the increase of the Al/Ni
ratio from 200 to 2000, the conversion of norbornene and the
catalytic activity were both enhanced gradually. Nevertheless, the
molecular weight of obtained PNBs decreased slightly without
great difference of their molecular weight distribution (1.84e2.01).
With the Al/Ni molar ratio of 1000, the catalytic systems showed
good catalytic activities over a large range of polymerization
temperatures. The highest conversion and catalytic activity were
obtained at 0 ꢂC, which was maintained with an ice-water bath.
When the reaction temperature increased from 0 ꢂC to 90 ꢂC, the
conversion of norbornene and catalytic activity declined from
66.52% (3.76 ꢁ 106 g(PNB) molꢀ1(cat) hꢀ1) to 37.94% (2.14 ꢁ 106
g
(PNB) molꢀ1(cat) hꢀ1) along with the decrease of molecular weight
(2.14e0.60 ꢁ 106 g/mol), although the molecular weight distribu-
tion didn’t change remarkably.
In order to explore the effects of anion, ligand environment and
metal center on the catalytic performance, the polymerization
reactions for all other nickel complexes and palladium complexes
In general, the type of metal had a decisive influence on the
catalytic activity for norbornene polymerization. For palladium
complexes 1d and 2d, 100% conversion of norbornene and much
higher activity were obtained under the employed reaction
conditions. In other cases, nickel and palladium complexes bearing
different tridentate ligands, such as, [N,N,O] (comparable for Ni and
Pd) [12f], [N,N,P] (nearly inert for Pd) [12c], [N,N,S] (much higher
for Pd than Ni) [12d], showed respective activity trends although
they all had similar distorted square planar geometry. Whereas for
the (imino)pyridyl alcohol ligands, nickel and palladium complexes
possessed very different structures; cationic palladium complexes
were possibly more favorable for the formation of active species
than the neutral five- or six-coordinated nickel complexes. The
polymerization reaction catalyzed by complex 2d was so rapid that
the stirring was stopped within less than 3 min with the 100%
conversion of norbornene and high activity (18.83 ꢁ 106
g
(PNB) molꢀ1(cat) hꢀ1, entry 19). The PNBs generated from palla-
dium catalytic systems were not fully soluble in 1,2,4-tri-
chlorobenzene and the corresponding values of molecular weight
and molecular weight distribution in Table 2 only represented the
soluble portion. The PNBs obtained by complex 2d showed bimodal
Fig. 2. Molecular structure of complex 1c with thermal ellipsoids at the 30% proba-
bility level. Hydrogen atoms (apart from H1) have been omitted for clarity.

S. Jie et al. / Journal of Organometallic Chemistry 696 (2011) 1465e1473
1469
Table 1
Selected bond lengths (Å) and bond angles (ꢂ).
Bond lengths
1a
1c
2d
NieN1
NieN2
NieCl1
NieCl2
NieO1
C20eO1
C6eN2
C8eN2
1.995 (3)
2.119 (3)
2.3095 (11)
2.2284 (11)
2.105 (3)
1.434 (4)
1.292 (4)
1.449 (4)
NieN1
NieN2
NieO1
NieO2
NieO3
NieO4
C6eN2
C2eO1
C23eO2 (O3)
C25eO4
C25eO5
1.9925 (17)
2.1277 (16)
2.1841 (15)
2.1231 (16)
2.0514 (17)
2.0315 (16)
1.285 (3)
1.445 (2)
1.260 (3)
1.256 (3)
1.253 (3)
Pd1eN1
Pd1eN2
Pd1eO1
Pd1eCl1
Pd2eCl2
Pd2eCl3
C18eO1
C6eN2
C8eN2
1.927 (3)
2.006 (3)
2.051 (3)
2.2940 (1)
2.3080 (2)
2.2971 (2)
1.465 (5)
1.295 (5)
1.450 (5)
Bond angles
O1eNieN1
O1eNieN2
O1eNieCl1
O1eNieCl2
N2eNieCl1
N2eNieCl2
N1eNieCl1
N1eNieCl2
N1eNieN2
Cl1eNieCl2
75.25 (10)
150.10 (10)
97.05 (10)
96.08 (8)
98.93 (8)
102.13 (8)
95.42 (8)
154.59 (9)
78.21 (10)
109.46 (5)
O1eNieN1
O1eNieN2
O1eNieO2
O1eNieO3
O1eNieO4
N1eNieO2
N1eNieO3
N1eNieO4
N1eNieN2
O2eNieN2
O3eNieN2
O4eNieN2
O3eNieO2
O4eNieO2
O4eNieO3
O3eC23eO2
O5eC25eO4
77.60 (6)
155.49 (6)
93.22 (6)
101.95 (6)
91.48 (7)
110.17(6)
173.09 (7)
90.52 (7)
78.18 (6)
91.60 (6)
101.64 (7)
92.43 (7)
62.92 (7)
159.31 (6)
96.39 (7)
119.7 (2)
124.9 (2)
N1ePd1eN2
N1ePd1eO1
N2ePd1eO1
N1ePd1eCl1
N2ePd1eCl1
O1ePd1eCl1
Cl3ePd2eCl2
Cl3ePd2eCl2A
80.69 (1)
79.77 (1)
160.43 (1)
177.84 (1)
100.93 (1)
98.57(9)
88.69 (7)
91.31 (7)
molecular weight distribution in GPC traces, which probably
attributed to the formation of two different active species in the
catalytic system. One of them formed from the cationic complex
moiety in charge of the production of high molecular weight PNBs;
the other possibly formed from the [PdCl4]2ꢀ counterion contrib-
uted to the formation of norbornene oligomers. According to the
literatures, palladium chloride could be used for the vinyl-type
oligomerization of norbornene [19] and palladium(II) salts con-
taining [PdCl4]2ꢀ or [Pd2Cl6]2ꢀ anions and the organic cations [K
(18-crown-6)]þ or [imidazolium]þ could be activated with MAO or
B(C6F5)3/AlEt3 and showed high activities for the vinyl polymeri-
zation of norbornene [20].
The PNBs obtained by nickel and palladium complexes showed
similar FT-IR and 1H NMR spectra. The FT-IR and 1H NMR spectra
proved no existence of double bonds, which confirmed the occur-
rence of vinyl-type polymerization rather than ring-opening
metathesis polymerization (ROMP) [21]. TGA studies indicated that
the PNB samples were stable up to 450 ꢂC under an atmosphere of
nitrogen. The determination of glass transition temperature (Tg) of
vinyl-type PNBs has been described as being difficult, since it is
apparently close to the temperature where decomposition tends to
set in [3e]. Therefore, the attempts to determine the Tg of obtained
PNBs were unsuccessful, and the DSC curves did not show an
endothermic signal upon heating the samples up to the decom-
position temperature.
3. Conclusions
Nickel(II) and cationic palladium(II) complexes with the
[PdCl4]2ꢀ counterion bearing (imino)pyridyl alcohol tridentate
ligands have been synthesized and characterized. The X-ray
diffraction studies revealed that the N, N and O atoms of ligand
coordinated to the metal center with a distorted trigonal bipyra-
midal for nickel chloride complex 1a, a distorted octahedron for
nickel acetate complex 1c, and a square planar for the cation moiety
of palladium complex 2d. Upon activation with methylaluminoxane
(MAO), these nickel and palladium complexes showed high
conversions of norbornene and catalytic activities for the vinyl
Fig. 4. The hydrogen bonding interactions in complex 2d.

1470
S. Jie et al. / Journal of Organometallic Chemistry 696 (2011) 1465e1473
Table 2
Nobel Corp. Triethylaluminum, triisobutylaluminum (1.41 M in
toluene) and all the anilines were purchased from Acros Chemicals.
Methyl lithium (1.0 M inTHF)and palladium chloridewere purchased
from Jingyan Chemicals (Shanghai) co., Ltd. NiC12$6H2O, NiBr2 and Ni
(OAc)2$4H2O were obtained from Beijing Chemical Regents Co. and
directly used without further purification. Norbornene (from Acros)
was purified by distillation over sodium and used as a solution in
toluene. All other chemicals were obtained commercially and used
withoutfurtherpurificationunlessotherwisestated.Thecompounds,
2-COOEt-6-(ArN]CMe)C5H3N (Ar ¼ 2,6-i-Pr2C6H3,1; 2,6-Et2C6H3, 2)
[16] and the ligand, 2-(2,6-i-Pr2C6H3N]CMe)-6-{(HO)CMe2}C5H3N
(L1) [14] were prepared according to the literatures.
Polymerization of norbornene with complexes 1ae1c, 2ae4a, 1d and 2d/MAOa.
Activityb Mw
(105 g/mol)c
Mw/Mn
c
Entry Cat. Al/
cat
1d
2
T
Conv.
(ꢂC) (%)
1a
1a
1a
1a
1a
1a
1a
1a
1a
1a
1a
1b
1c
2a
3a
4a
1d
2d
200
200
500
30
30
30
30
30
30
30
0
50
70
90
30
30
30
30
30
30
30
e
e
e
e
35.14
46.20
51.92
59.25
58.05
60.38
66.52
49.72
38.48
37.94
48.21
62.28
58.43
60.87
85.38
100
1.98
2.61
2.93
1.57
3.28
3.41
3.76
2.81
2.17
2.14
2.72
3.52
3.30
3.44
4.82
5.65
5.65
15.97
17.01
16.53
e
1.84
1.84
1.94
e
3
4
1000
1000
1500
2000
1000
1000
1000
1000
1000
1000
1000
1000
1000
1000
1000
5e
6
13.71
13.59
21.38
13.36
11.22
5.96
14.53
10.56
12.93
11.23
13.42
5.10g
0.0067,
6.37g
0.0065,
5.07g
2.01
1.91
2.04
1.92
1.79
1.98
2.12
2.19
1.99
2.18
2.25
1.95g
1.20,
2.86g
1.24,
2.24g
7
8
9
10
11
12
13
14
15
16
17
18
4.2. Synthesis of 2-COOEt-6-(2,4,6-Me3C6H2N]CMe)C5H3N (3)
A solution of ethyl 6-acetylpyridine-2-carboxylate (0.985 g,
5.10 mmol), 2,4,6-trimethylaniline (0.920 g, 6.61 mmol), and
a catalytic amount of p-toluenesulfonic acid in toluene (100 mL)
were refluxed for 24 h. The volatiles were removed under reduced
pressure to give the crude product, which was purified by column
chromatography on silica gel with petroleum ether/ethyl acetate
(15/1) as eluents to afford compound 3 as a yellow solid (yield:
100
19f
2d
1000
30
100
18.83
a
General conditions: 5
mmol of complex; NB: 50 mmol; co-catalyst: MAO;
1.002 g, 63.3%). FT-IR (KBr disk, cmꢀ1): 1714 (
1584, 1570, 1477, 1453, 1370, 1324, 1301, 1251, 1216, 1157, 1136, 1112,
1077, 1024, 993, 858, 768. 1H NMR (400 MHz, CDCl3),
(ppm): 8.57
nC]O), 1643 (nC]N),
solvent: toluene; total volume: 20 mL; reaction time: 10 min.
b
In units of 106 g(PNB) molꢀ1(cat) hꢀ1
Determined by GPC.
Co-catalyst: Al(Et)3 or Al(i-Bu)3.
Reaction time: 20 min.
Reaction time: 3 min.
The values only represent the soluble portion.
.
c
d
e
f
d
(dd, 1 H, J1 ¼ 8.0 Hz, J2 ¼ 0.8 Hz, py-H), 8.19 (dd, 1 H, J1 ¼ 8.0 Hz,
J2 ¼ 0.8 Hz, py-H), 7.93 (t,1 H, J ¼ 8.0 Hz, py-H), 6.89 (s, 2 H, Ar-H), 4.49
(q, 2 H, J ¼ 7.2 Hz, OCH2CH3), 2.29 (s, 3 H, CH3C]N), 2.26 (s, 3 H, p-Ar-
g
CH3); 1.99 (s, 6 H, o-Ar-CH3), 1.46 (t, 3 H, J ¼ 7.2 Hz, OCH2CH3). 13
C
NMR (100 MHz, CDCl3), d (ppm): 167.2 (COOEt), 165.2 (C]N), 156.6,
polymerization of norbornene. The catalytic activities relied on the
type of metal and the ligand environment; and decrease of the steric
bulkiness resulted in the higher activities. The activities of up to
4.82 ꢁ 106 g(PNB) molꢀ1(cat) hꢀ1 (85.38% conversion) and
1.883 ꢁ 107 g(PNB) molꢀ1(cat) hꢀ1 (100% conversion) have been
achieved by nickel complex 4a and palladium complex 2d, respec-
tively. The molecular weights of PNBs obtained by nickel complexes
were more than 106 g/mol (except for those at 90 ꢂC) and molecular
weight distributions (in the range of 1.79e2.25) indicated the
presence of a single active species in the polymerizationprocess. The
PNBs obtained by palladium complex 2d displayed bimodal
molecular weight distribution due to the two different active species
formed by the cation moiety and the counterion, respectively.
147.3, 146.0, 137.2, 132.2, 128.6, 126.0, 125.1, and 124.3 (aromatic-C
and py-C), 61.8 (OCH2CH3), 20.7 (p-Ar-CH3), 17.8 (CH3C]N), 16.4 (o-
Ar-CH3), 14.3 (OCH2CH3). Anal. Calcd for C19H22N2O2 (310.39): C,
73.52; H, 7.14; N, 9.03. Found: C, 73.48; H, 7.28; N, 8.95.
4.3. Synthesis of ligands (L2eL4)
4.3.1. Synthesis of 2-(2,6-Et2C6H3N]CMe)-6-{(HO)CMe2}C5H3N
(L2)
Into a THF solution (80 mL) containing compound 2 (1.3551 g,
4.18 mmol), was added 2 equiv of MeLi (1.0 M in THF, 8.40 mL,
8.40 mmol) at 0 ꢂC. The reaction mixture was thenwarmed slowly to
room temperature and was stirred for 24 h. The mixture was then
added water and extracted with CHCl3 (50 mL ꢁ 3). The combined
organic extracts were dried over anhydrous Na2SO4 and filtered.
After all the volatiles were removed under reduced pressure, the
resultant yellow oil was purified on a silica column (petroleum
ether/ethyl acetate ¼ 8:1) to give L2 as a yellowsolid (yield: 0.7434 g,
57.3%). FT-IR (KBr disk, cmꢀ1): 3380 (nOeH), 3068, 2971, 2925, 2871,
4. Experimental
4.1. General considerations
All manipulations of air- or moisture-sensitive compounds were
carried out under an atmosphere of nitrogen using standard Schlenk
techniques. FT-IR spectra were recorded on a PerkineElmer FT-IR
1642 (
n
C]N),1586,1572,1455,1371,1355,1310,1170,1160,1083, 962,
(ppm): 8.27 (d, 1 H,
280, 194, 765. 1H NMR (400 MHz, CDCl3),
d
2000 spectrometer by using KBr disks in the range 4000e400 cmꢀ1
.
J ¼ 7.8 Hz, py-H), 7.82 (t,1 H, J ¼ 7.8 Hz, py-H), 7.45 (d,1 H, J ¼ 8.0 Hz,
py-H), 7.10 (d, 2 H, J ¼ 7.6 Hz, Ar-H), 7.02 (t,1 H, J ¼ 7.6 Hz, Ar-H), 5.13
(b,1 H, OH), 2.35 (m, 4 H, CH2CH3), 2.19 (s, 3 H, CH3C]N),1.59 (s, 6 H,
(CH3)2COH), 1.12 (t, 6 H, J ¼ 7.2 Hz, CH2CH3). 13C NMR (100 MHz,
1H NMR and 13C NMR spectra were recorded on a Bruker DMX-400
instrument with TMS as the internal standard. Splitting patterns are
designated as follows: s, singlet; d, doublet; dd, double doublet; t,
triplet; q, quadruplet; sept, septet; m, multiplet. Elemental analysis
was performed on a Flash EA1112 microanalyzer. The molecular
weight and molecular weight distribution of PNBs were measured at
150 ꢂC in 1,2,4-trichlorobenzene using a PL-GPC220 coupled with an
in-line capillary viscometer. TGA data were collected with a Per-
kineElmer Pyris 1 TGA instrument under a nitrogen atmosphere up
to 600 ꢂC at heating rate of 10 ꢂC/min.
CDCl3),
d (ppm): 168.3 (C]N), 164.9 (py-CCOH), 154.0 (py-CC]N),
147.6 (aromatic-Cipso), 137.6, 131.1, 125.9, 123.4, 119.9, and 119.3
(aromatic-C and py-C), 71.7 (Me2COH), 30.7 ((CH3)2COH), 24.5
(CH2Me), 16.9 (CH3C]N), 13.7 (CH2CH3). Anal. Calcd for C20H26N2O
(310.43): C, 77.38; H, 8.44; N, 9.02. Found: C, 77.68; H, 8.62; N, 8.57.
4.3.2. Synthesis of 2-(2,4,6-Me3C6H2N]CMe)-6-{(HO)CMe2}C5H3N
(L3) [15]
Toluene and tetrahydrofuran were refluxed over sodiume
benzophenone and distilled under nitrogen prior to use. Methyl-
aluminoxane (MAO, 1.46 M in toluene) was purchased from Akzo
By using the same procedure described for L2, compound L3
was obtained as a yellow solid in 44.0% yield. 1H NMR (400 MHz,

S. Jie et al. / Journal of Organometallic Chemistry 696 (2011) 1465e1473
1471
CDCl3),
d
(ppm): 8.29 (dd, 1 H, J1 ¼7.6 Hz, J2 ¼ 0.8 Hz, py-H), 7.84 (t,
4.4.4. Synthesis of [2-(2,6-Et2C6H3N]CMe)-6-{(HO)CMe2}C5H3N]
NiCl2 (2a)
1 H, J ¼ 8.0 Hz, py-H), 7.47 (dd, 1 H, J1 ¼ 7.6 Hz, J2 ¼ 0.8 Hz, py-H),
6.90 (s, 2 H, Ar-H), 5.19 (s, 1 H, OH), 2.31 (s, 3 H, CH3C]N), 2.21 (s,
3 H, p-Ar-CH3); 2.01 (s, 6 H, o-Ar-CH3), 1.61 (s, 6 H, (CH3)2COH).
By using the similar procedure described for 1a, complex 2a was
obtained as an orange powder in 53.3% yield. FT-IR (KBr disk,
cmꢀ1): 3415, 3273, 2935, 2870, 1620, 1591, 1459, 1375, 1342, 1288,
1258, 1411, 1128, 1098, 1030, 818. Anal. Calcd for C20H26Cl2N2NiO
(440.03): C, 54.59; H, 5.96; N, 6.37. Found: C, 54.96; H, 5.82; N, 5.97.
4.3.3. Synthesis of 2-(2,6-i-Pr2C6H3N]CMe)-6-(CH2OH)C5H3N (L4)
To a methanol solution (50 mL) containing compound 1
(0.1673 g, 0.47 mmol) and anhydrous calcium chloride (0.1346 g,
1.21 mmol), was slowly added sodium borohydride (0.0400 g,
1.06 mmol) at 0 ꢂC. The reaction solution was slowly warmed to
room temperature and then refluxed for 5 h. After the solution
was cooled to room temperature, distilled water was added and
methanol was removed on the rotatory evaporator. The resulting
solution was then extracted with chloroform (30 mL ꢁ 3), and the
combined organic extracts were dried over anhydrous Na2SO4 and
filtered. After all the volatiles were removed under reduced
pressure, the resultant yellow oil was purified on a silica column
(petroleum ether/ethyl acetate ¼ 8:1) to give L4 as a yellow solid
(yield: 0.0833 g, 56.5%). FT-IR (KBr disk, cmꢀ1): 3483 (nOeH), 3061,
4.4.5. Synthesis of [2-(2,4,6-Me3C6H2N]CMe)-6-{(HO)CMe2}
C5H3N]NiCl2 (3a)
By using the similar procedure described for 1a, complex 3a was
obtained as a yellow powder in 65.0% yield. FT-IR (KBr disk, cmꢀ1):
3384, 2972, 2920, 1617, 1590, 1476, 1370, 1283, 1217, 1127, 1096,
1032, 853, 813, 749. Anal. Calcd for C19H24Cl2N2NiO (426.01): C,
53.57; H, 5.68; N, 6.58. Found: C, 53.56; H, 5.65; N, 6.61.
4.4.6. Synthesis of [2-(2,6-i-Pr2C6H3N]CMe)-6-(CH2OH)C5H3N]
NiCl2 (4a)
By using the similar procedure described for 1a, complex 4a was
obtained as a brick red powder in 91.2% yield. FT-IR (KBr disk,
cmꢀ1): 3216, 2964, 2924, 2867, 1616, 1592, 1464, 1445, 1418, 1384,
1373, 1323, 1300, 1198, 1099, 1051, 804. Anal. Calcd for
C20H26Cl2N2NiO (440.03): C, 54.59; H, 5.96; N, 6.37. Found: C, 54.31;
H, 6.27; N, 5.80.
2962, 2926, 2868, 1645 (
nC]N), 1586, 1574, 1457, 1437, 1363, 1310,
1239, 1192, 1155, 1116, 1057, 798, 765. 1H NMR (400 MHz, CDCl3),
d
(ppm): 8.32 (d, 1 H, J ¼ 7.6 Hz, py-H), 7.87 (t, 1 H, J ¼ 7.6 Hz, py-
H), 7.38 (d, 1 H, J ¼ 7.6 Hz, py-H), 7.20e7.13 (m, 3 H, Ar-H), 4.87 (s,
2 H, CH2OH), 4.03 (b, 1 H, OH), 2.74 (sept, 2 H, J ¼ 6.8 Hz, CHMe2),
2.28 (s, 3 H, CH3C]N), 1.17 (d, 6 H, J ¼ 6.8 Hz, CHMe2), 1.16 (d, 6 H,
J ¼ 6.8 Hz, CHMe2). 13C NMR (100 MHz, CDCl3),
d
(ppm): 166.8 (C]
4.4.7. Synthesis of {[2-(2,6-i-Pr2C6H3N]CMe)-6-{(HO)CMe2}
C5H3N]PdCl}2[PdCl4] (1d)
N), 157.8, 137.5, 136.0, 123.9, 123.3, 123.1, 121.7, 120.4, and 120.2
(aromatic-C and py-C), 63.7 (CH2OH), 29.7, and 28.3 (CHMe2),
23.2, and 22.8 (CHMe2), 17.4 (CH3C]N). Anal. Calcd for C20H26N2O
(310.43): C, 77.38; H, 8.44; N, 9.02. Found: C, 77.16; H, 8.70;
N, 8.53.
To a stirred solution of L1 (0.0684 g, 0.20 mmol) in anhydrous
ethanol (20 mL), PdCl2 (0.0364 g, 0.20 mmol) was added, and the
reaction mixture was stirred at room temperature overnight;
however, amounts of PdCl2 were still unreacted obviously. The
mixture was then brought to 60 ꢂC and stirred for 3 h to give a clear
brown solution. The resultant solution was concentrated to ca.
2 mL. Diethyl ether was added to precipitate the product. The
brown solid was filtered, washed repeatedly with diethyl ether and
dried in vacuum (yield: 0.0461 g, 55.7%). FT-IR (KBr disk, cmꢀ1):
3433, 2965, 2928, 2869, 1629, 1561, 1464, 1369, 1292, 1100, 1051,
4.4. Synthesis of nickel and palladium complexes
4.4.1. Synthesis of [2-(2,6-i-Pr2C6H3N]CMe)-6-{(HO)CMe2}C5H3N]
NiCl2 (1a)
To a stirred solution of L1 (0.1684 g, 0.50 mmol) in anhydrous
ethanol (20 mL), NiCl2$6H2O (0.1180 g, 0.50 mmol) was added, and
the reaction mixture was stirred at room temperature overnight.
The resultant clear yellow solution was concentrated to ca. 3 mL.
Diethyl ether was added to precipitate the product. The orange
precipitate was filtered, washed repeatedly with diethyl ether and
dried under vacuum (yield: 0.2035 g, 87.0%). FT-IR (KBr disk, cmꢀ1):
3394, 3065, 2962, 2928, 2867, 1618, 1591, 1459, 1443, 1384, 1371,
1321, 1283, 1208, 1093, 1044, 1028, 961, 827, 800, 765. Anal. Calcd
for C22H30Cl2N2NiO (468.09): C, 56.45; H, 6.46; N, 5.98. Found: C,
55.88; H, 6.93; N, 5.32.
802, 757. 1H NMR (400 MHz, d6-DMSO),
d (ppm): 8.55 (t, 1 H,
J ¼ 8.0 Hz, py-H), 8.29 (d, 1 H, J ¼ 7.6 Hz, py-H), 8.04 (d, 1 H,
J ¼ 8.0 Hz, py-H), 7.38 (t,1 H, J ¼ 7.8 Hz, Ar-H), 7.26 (d, 2 H, J ¼ 7.6 Hz,
Ar-H), 3.19 (sept, 2 H, J ¼ 6.8 Hz, CHMe2), 2.34 (s, 3 H, CH3C]N),1.78
(s, 6 H, (CH3)2COH), 1.35 (d, 6 H, J ¼ 6.8 Hz, CHMe2), 1.14 (d, 6 H,
J ¼ 6.8 Hz, CHMe2); 8.11 (d, 1 H, J ¼ 8.0 Hz, py-H), 7.93 (t, 1 H,
J ¼ 7.8 Hz, py-H), 7.80 (d,1 H, J ¼ 7.6 Hz, py-H), 7.15 (d, 2 H, J ¼ 7.2 Hz,
Ar-H), 7.06 (d, 1 H, J ¼ 7.8 Hz, Ar-H), 2.65 (sept, 2 H, J ¼ 6.8 Hz,
CHMe2), 2.12 (s, 3 H, CH3C]N), 1.51 (s, 6 H, (CH3)2COH), 1.10 (d, 6 H,
J ¼ 6.8 Hz, CHMe2), 1.07 (d, 6 H, J ¼ 6.8 Hz, CHMe2). Anal. Calcd for
C44H60Cl6N4O2Pd3 (1208.95): C, 43.71; H, 5.00; N, 4.63. Found: C,
44.18; H, 5.10; N, 4.31.
4.4.2. Synthesis of [2-(2,6-i-Pr2C6H3N]CMe)-6-{(HO)CMe2}C5H3N]
NiBr2 (1b)
By using the similar procedure described for 1a, complex 1b was
obtained as a yellowish orange powder in 71.1% yield. FT-IR (KBr
disk, cmꢀ1): 3386, 3069, 2968, 2868, 1618, 1592, 1460, 1371, 1321,
1284, 1260, 1097, 1038, 896, 818, 796, 761. Anal. Calcd for
C22H30Br2N2NiO (556.99): C, 47.44; H, 5.43; N, 5.03. Found: C, 47.68;
H, 5.53; N, 4.78.
4.4.8. Synthesis of {[2-(2,6-Et2C6H3N]CMe)-6-{(HO)CMe2}C5H3N]
PdCl}2[PdCl4] (2d)
By using the similar procedure described for 1d, complex 2d was
obtained as a brown powder in 84.9% yield. The samples for char-
acterization were prepared by slow diffusion of n-hexane to the
CH2Cl2 solution of 2d. FT-IR (KBr disk, cmꢀ1): 3439, 2968, 2931,
1621, 1562, 1456, 1372, 1291, 1218, 1135, 1100, 1052, 807. 1H NMR
4.4.3. Synthesis of [2-(2,6-i-Pr2C6H3N]CMe)-6-{(HO)CMe2}C5H3N]
Ni(OAc)2 (1c)
(400 MHz, d6-DMSO),
d
(ppm): 8.47 (t,1 H, J ¼ 8.0 Hz, py-H), 8.25 (d,
1 H, J ¼ 7.6 Hz, py-H), 7.98 (d, 1 H, J ¼ 8.0 Hz, py-H), 7.31 (t, 1 H,
J ¼ 7.6 Hz, Ar-H), 7.18 (d, 2 H, J ¼ 7.6 Hz, Ar-H), 2.72 (m, 4 H, CH2CH3),
2.27 (s, 3 H, CH3C]N), 1.71 (s, 6 H, (CH3)2COH), 1.26 (t, 6 H,
J ¼ 7.6 Hz, CH2CH3); 8.25 (d, 1 H, J ¼ 7.6 Hz, py-H), 7.92 (t, 1 H,
J ¼ 7.8 Hz, py-H), 7.79 (d, 1 H, J ¼ 7.6 Hz, py-H), 7.09 (d, 2 H,
J ¼ 7.8 Hz, Ar-H), 6.98 (t,1 H, J ¼ 7.8 Hz, Ar-H), 2.54 (m, 4 H, CH2CH3),
2.10 (s, 3 H, CH3C]N), 1.50 (s, 6 H, (CH3)2COH), 1.05 (t, 6 H,
By using the similar procedure described for 1a, complex 1c was
obtained as a yellowish brown powder in 51.2% yield. FT-IR (KBr
disk, cmꢀ1): 3422, 3082, 2984, 2962, 2945, 2927, 2866, 1618, 1591,
1578, 1544, 1457, 1420, 1385, 1365, 1255, 1217, 1167, 1098, 1059, 823,
816, 802, 765, 685, 662. Anal. Calcd for C26H36N2NiO5 (515.26): C,
60.61; H, 7.04; N, 5.44. Found: C, 60.56; H, 6.97; N, 4.90.

1472
S. Jie et al. / Journal of Organometallic Chemistry 696 (2011) 1465e1473
Table 3
Crystallographic data and refinement parameters for complexes 1a, 1c and 2d.
Data
1a
1c
2d
Formula
C22H30Cl2N2NiO$CH3OH
500.13
293 (2)
0.71073
Monoclinic
P2(1)/n
14.224 (3)
12.520 (3)
15.386 (3)
90.00
109.58 (3)
90.00
2581.6 (9)
4
1.287
C26H36N2NiO5
515.26
293 (2)
0.71073
Monoclinic
P21/c
11.962 (2)
15.161 (3)
15.648 (3)
90.00
106.73 (3)
90.00
2717.7 (9)
4
1.259
C20H26Cl3N2OPd1.5ꢃH2O
594.20
293 (2)
0.71073
Triclinic
Formula weight
Temperature (K)
Wavelength (Å)
Crystal system
Space group
a (Å)
P-1
8.9311 (18)
10.035 (2)
13.794 (3)
85.69 (3)
81.90 (3)
74.88 (3)
1180.6 (4)
2
b (Å)
c (Å)
a
b
g
(ꢂ)
(ꢂ)
(ꢂ)
Volume (Å3)
Z
Dcalc (Mg mꢀ3
)
1.671
1.512
m
(mmꢀ1
)
0.979
0.750
F(000)
Crystal size(mm)
range (ꢂ)
1056
1096
596
0.31 ꢁ 0.19 ꢁ 0.10
3.04e27.45
ꢀ18 ꢄ h ꢄ 18,
ꢀ16 ꢄ k ꢄ 16,
ꢀ19 ꢄ l ꢄ 19
24285
5826
3500
98.7 (
272
1.100
0.52 ꢁ 0.28 ꢁ 0.10
3.01e27.43
ꢀ15 ꢄ h ꢄ 13,
ꢀ19 ꢄ k ꢄ 19,
ꢀ18 ꢄ l ꢄ 20
25111
6072
4351
98.0 (
311
1.066
0.36 ꢁ 0.32 ꢁ 0.22
3.31e27.44
ꢀ10 ꢄ h ꢄ 11,
ꢀ12 ꢄ k ꢄ 13,
ꢀ17 ꢄ l ꢄ 17
11605
5330
4483
98.0 (
254
1.075
q
Limiting indices
No. of rflns collected
No. of unique rflns
No. of obsd rflns(I > 2
Completeness to
No. of parameters
Goodness-of-fit on F2
s
(I))
q
(%)
q
¼ 27.45ꢂ)
q
¼ 27.43ꢂ)
q
¼ 27.44ꢂ)
Final R indices [I > 2
R indices (all data)
s
(I)]
R1 ¼ 0.0430, wR2 ¼ 0.0831
R1 ¼ 0.0367, wR2 ¼ 0.0838
R1 ¼ 0.0433, wR2 ¼ 0.1072
R1 ¼ 0.0963, wR2 ¼ 0.1180
R1 ¼ 0.0625, wR2 ¼ 0.0985
R1 ¼ 0.0518, wR2 ¼ 0.1137
J ¼ 7.6 Hz, CH2CH3). C40H52Cl6N4O2Pd3$2H2O (1188.88): C, 40.41; H,
non-hydrogen atoms were refined anisotropically. All hydrogen
atoms were placed in calculated positions. Structure solution and
refinement were performed by using the SHELXL-97 Package [22].
Crystallographic data and processing parameters for complexes 1a,
1c and 2d are summarized in Table 3.
4.75; N, 4.71. Found: C, 40.63; H, 4.72; N, 4.36.
4.5. Polymerization of norbornene
In the typical procedure, the complex (5 mmo1) was dissolved in
Acknowledgments
toluene in a Schlenk tube under nitrogen and a solution of nor-
bornene in toluene was added with a syringe through a rubber
septum, and the reaction temperature was controlled by oil bath.
The polymerization was initiated by adding the desired amount of
This work was supported by the National Natural Science
Foundation of China (NSFC 21006085, 20936006) and the Program
for Changjiang Scholars and Innovative Research Team in Univer-
sity (PCSIRT).
methylaluminoxane (MAO, 1.46
M in toluene) by means of
a syringe. After the desired period of time, the polymerization was
terminated by adding HCl-acidic ethanol (5%). The precipitated
polynorbornenes were isolated by filtration, washed with ethanol,
and dried under vacuum at 100 ꢂC until constant weight, weighed
and finally characterized. Unless otherwise stated, the total reaction
volume of vinyl polymerization of norbornene was kept at 20 mL,
which was achieved by variation of the amount of toluene when
necessary. All the PNB samples exhibited similar FT-IR and 1H NMR
spectra. The following are the spectral data of entry 4 in Table 2. FT-
IR (KBr disk, cmꢀ1): 2947 (vs), 2869 (vs), 1474 (s), 1452 (s), 1373 (m),
1295 (m),1258 (m),1221 (m),1148 (m),1108 (m),1043 (m), 943 (m),
Appendix A. Supplementary material
CCDC 801807, 801808 and 801809 contain the supplementary
crystallographic data for complexes 1a,1c and 2d. These data can be
obtained free of charge from The Cambridge Crystallographic Data
Center via www.ccdc.cam.ac.uk/data_request/cif.
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