Synthesis and characterization of nickel(II) and palladium(II) complexes based on tridentate [N-NP] and [N-NS] ligands and their applications in norbornene polymerization

Article abstract of DOI:10.1021/om3003202

The series of anilido-imine N^-NP and N^-NS tridentate nickel and palladium complexes [(ArNHC₆H₄CH=NPh-2-XPh)MCl] (X = PPh, Ar = 2,6-Me₂C₆H₃, M = Ni (2a), X = PPh, Ar = 2,6-Et

Full text of DOI:10.1021/om3003202

Article
pubs.acs.org/Organometallics
Synthesis and Characterization of Nickel(II) and Palladium(II)
Complexes based on Tridentate [N−NP] and [N−NS] Ligands and
Their Applications in Norbornene Polymerization
Xiao-Chao Shi and Guo-Xin Jin*
Shanghai Key Laboratory of Molecular Catalysis and Innovative Material, Department of Chemistry, Fudan University, 200433
Shanghai, People's Republic of China
S
* Supporting Information
ABSTRACT: The series of anilido-imine N−NP and N−NS
tridentate nickel and palladium complexes [(ArNHC6H4CH
NPh-2-XPh)MCl] (X = PPh, Ar = 2,6-Me2C6H3, M = Ni (2a),
X = PPh, Ar = 2,6-Et2C6H3, M = Ni (2b); X = PPh, Ar = 2,6-i-
Pr2C6H3, M = Ni (2c); X = S, Ar = Ph, M = Ni (2d); X = S, Ar
= 2,6-Me2C6H3, M = Ni (2e); X = S, Ar = 2,6-i-Pr2C6H3, M =
Ni (2f); X = PPh, Ar = 2,6-Me2C6H3, M = Pd (3a); X = PPh,
Ar = 2,6-Et2C6H3, M = Pd (3b); X = PPh, Ar = 2,6-i-Pr2C6H3,
M = Pd (3c)) were synthesized. All the complexes were fully characterized by IR, NMR and elemental analyses. X-ray diffraction
analyses on complexes 2a,c and 3a revealed an almost square-planar coordination of the central metal. After activation with
methylaluminoxane (MAO), the nickel(II) complexes 2a−f can be used as catalysts for norbornene polymerization to produce
vinyl addition type polynorbornene (PNB) with high catalytic activities, up to 5.82 × 107 g of PNB (mol of Ni)−1 h−1, while poor
catalytic activities are found for the palladium complexes 3a−c.
The metal complexes coordinated by hard atoms (N, O) and
soft atoms (P, S) atoms in the side arm were mainly studied.
Gibson reported that group 4 metal complexes containing
phenoxy-amide ligands bearing soft pendant donors exhibited
ethylene polymerization catalysts more highly active than those
of counterparts containing hard donors or systems without a
pendant donor.12a A series of titanium complexes reported by
the Tang research group having extra pendant S and P donors
on salicylaldiminato ligands showed high abilities toward
ethylene polymerization and copolymerization with 1-hex-
ane.12b,c Modification of the anilido-imine ligands by the side
arm approach has also been reported.7,8c,d,9,10 Rare-earth-metal
complexes bearing quinolinyl group modified anilido-imine
ligands were demonstrated to create a single active site to
initiate the polymerization of ε-caprolactone (ε-CL).7 Anilido-
imine ligands containing an S atom which attach via the amido
nitrogen have been reported, and their nickel and palladium
complexes showed higher catalytic activity than [N,N]
bidentate anilido-imino nickel complexes toward norbornene
polymerization.8c Magnesium and zinc complexes supported by
an NNN-tridentate anilido-aldimine ligand which was modified
via the imido nitrogen have also shown high performance for
the ROP of ε-caprolactone (CL) and L-lactide (LA).9,10
INTRODUCTION
■
Increasing attraction has been paid to the late-transition-metal
catalysts for olefin polymerization in academic and industrial
fields over the past few decades.1 Among these numerous
catalysts, the nickel and palladium complexes have been the
focus of extensive studies, especially complexes based on the α-
diimine and salicylaldiminato ligands.2,3 The bulky α-diimine
nickel(II) and palladium(II) complexes showed high catalytic
abilities for olefin polymerization and produced linear to highly
branched polymers.2a−f Single-component neutral nickel
catalysts based on salicylaldiminato ligands showed excellent
performance in ethylene polymerization and exhibited good
tolerance to functional groups.3 The phosphine-sulfonate
palladium(II) complexes have also been the target of intense
research in recent years for their high tolerance toward polar
functional groups, even those containing active protons.4
Recently, complexes containing chelating anilido-imine ligands
have attracted much attention due to their ease of preparation
as well as versatile modification of the steric and electronic
demands.5−10 Nickel and palladium complexes bearing anilido-
imine ligands have been prepared and tested for the vinyl
addition polymerization of norbornene.8 For example, Wu
reported cationic nickel complexes bearing anilido-imine
ligands, which showed high activity toward the polymerization
of norbornene.8a Jin reported unique three-coordinate nickel
(I) complexes bearing an anilido-imine ligand which exhibited
high activity to norbornene polymerization, up to 2.82 × 107 g
of PNB (mol of Ni)−1 h−1, with high molecular weight.8b
It has been demonstrated that the side-arm effect of an extra
donor has a strong influence on catalytic polymerization.11−14
Previously, our group have reported Ni and Ir complexes
containing anilido-imine ligands for ethylene and norbornene
polymerization.8b,15 Moreover, we have successfully obtained
the group IV metal complexes bearing the ligands which
Received: April 19, 2012
Published: June 15, 2012
© 2012 American Chemical Society
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Scheme 1. Synthesis of Ligands
providing a soft atom coordinated to the metal center and
demonstrated the positive effect of the soft atom in the ligands
for ethylene polymerization.12d,16,17 Despite the fact that the
introduction of a soft S atom to anilido-imine ligands on the
amido nitrogen has been reported,8c there have been no
examples of modifying the anilido-imine liands on the imine
nitrogen side with soft atoms. Following our interest in
modifying anilido-imine ligands by the side arm using soft
atoms and exploring the effect of a pendant arm on the imine
nitrogen, a series of novel tridentate anilido-imine [N−NS] and
[N−NP] ligands and their nickel(II) and palladium(II)
complexes have been synthesized. After activation with MAO,
these nickel(II) complexes can be used as catalysts for the
polymerization of norbornene and show high activity up to 5.82
× 107 g of PNB (mol of Ni−1) h−1.
Figure 1. Molecular structure of 1c (thermal ellipsoids at the 30%
probability level). Hydrogen atoms have been omitted for clarity.
Selected bond lengths (Å) and angles (deg): P1−C26, 1.832(2); P1−
C9, 1.834(2); P1−C32, 1.836(2); N1−C1, 1.363(3); N1−C14,
1.424(2); N2−C7, 1.276(3); N2−C8, 1.420(3); C26−P1−C9,
103.42(9); C9−P1−C32, 102.81(9); C1−N1−C14, 126.30(18);
C7−N2−C8, 120.75(17); N2−C7−C6, 125.15(19); N1−C1−C6,
120.15(18).
RESULTS AND DISCUSSION
■
N−NP and N−NS tridentate ligands with various sterically
hindered substituents were synthesized as described in Scheme
1. Condensation of 2-fluorobenzaldehyde with 1 molar equiv of
2-(diphenylphosphino)benzenamine and 2-aminophenyl phe-
nyl sulfide in hexane gave A1 and A2 in high yields,
respectively. The N−NP and N−NS tridentate ligands were
obtained by nucleophilic aromatic displacement of fluorine in
A1 and A2 by salt elimination in THF. Pure products of 1a−f
were obtained as yellow crystals by initially chromatography
and then crystallization from ethanol. All of these new ligands
elemental analyses. The disappearance of the −NH signals
1
around 10−11 ppm in the H NMR spectra and the variety in
elemental analyses indicated the formation of the nickel and
palladium complexes. To further confirm the structures of these
complexes, crystals of 2a,c and 3c were obtained from CH2Cl2/
hexane solutions and analyzed by single-crystal X-ray diffraction
(Figures 3−5, respectively). Single crystals of nickel complexes
2d−f suitable for X-ray structure determination were not
obtained, but other analysis results testified to the purity of
these complexes.
1
were characterized by H NMR and 13C NMR spectra and
elemental analyses. In 1a, for example, new signals at 9.87 and
1
2.06 ppm in H NMR spectra, which were identified as −NH
and −CH3, indicated the displacement of fluorine. The
structures of 1c,f were further confirmed by single-crystal X-
ray diffraction analysis (Figures 1 and 2). In 1c, the C7−N2
bond distance is 1.276(3) Å, while for 1f, the C7−N2 bond
distance is 1.288(3) Å, which is typical of a carbon−nitrogen
double bond. The C1−N1 bond lengths in 1c,f are 1.363(3)
and 1.367(3) Å, respectively. The C6−C7−N2 and C6−C1−
N1 angles in 1c are 125.15(19) and 120.15(18)°, respectively,
and there are nearly no differences from those same angles in
1f.
Molecular structure analyses of complexes 2a,c reveal that
these complexes adopt an almost square-planar geometry
around the metal center, which is quite different from the case
for their corresponding anilido-imino nickel complexes with
tetrahedral geometries, due to the coordination of the P-donor
side arm.8a,c The coordinated atoms of N1, N2, P1, and Cl1
around the nickel centers in 2a,c are almost coplanar, and the
distances from the metal centers to the planes are 0.031(1) and
0.025(1) Å, respectively. The Ni1−N1 bond lengths (2a,
1.919(2) Å; 2c, 1.9215(18) Å) are slightly longer than those of
Ni1−N2 (2a, 1.890(2) Å; 2c, 1.8894(17) Å) and the C7−N2
bond lengths (2a, 1.314(3) Å; 2c, 1.318(3) Å) are obviously
shorter than those of C1−N1 (2a, 1.354(3) Å; 2c, 1.350(3) Å).
Treatments of lithium salts of corresponding anilido-imino
ligands with (DME)NiCl2 and (COD)PdCl2 in toluene at 80
°C afforded the desired nickel and palladium complexes as dark
red powders (Scheme 2). In the solid state, all of the complexes
were stable in dry air but the nickel complexes slowly
decomposed in solution. The nickel and palladium complexes
were well characterized by 1H NMR and IR spectra and
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Figure 2. Molecular structure of 1f (thermal ellipsoids at the 30%
probability level). Hydrogen atoms have been omitted for clarity.
Selected bond lengths (Å) and angles (deg): S1−C25, 1.776(2); N1−
C1, 1.367(3); N1−C8, 1.430(3); N2−C7, 1.288(3); N2−C20,
1.411(3); C25−S1−C26, 102.30(11); C1−N1−C8, 123.77(19);
C7−N2−C20, 119.3(2); N1−C1−C6, 120.4(2); N(2)−C(7)−C(6),
124.5(2).
Figure 3. Molecular structure of 2a (thermal ellipsoids at the 30%
probability level). Hydrogen atoms have been omitted for clarity.
Selected bond lengths (Å) and angles (deg): Ni1−N2, 1.890(2); Ni1−
N1, 1.919(2); Ni1−P1, 2.1452(9); Ni1−Cl1, 2.1889(10); P1−C13,
1.791(2); N1−C1, 1.354(3); N(2)−C(7), 1.314(3); N(2)−C(8),
1.448(3); N2−Ni1−N1, 94.86(8); N2−Ni1−P1, 86.12(6) ; N1−
Ni1−P1, 175.80(6); N2−Ni1−Cl1, 170.47(7) ; N1−Ni1−Cl1,
94.66(6); P1−Ni1−Cl1, 84.39(3); C13−P1−Ni1, 101.46(9); N2−
C7−C6, 127.8(2).
All of these data suggested that 2a,c are more localized than β-
diketiminato complexes and the imino CN bonds in 2a,c
retain double-bond character. The P1−Ni1 bond lengths in
2a,c are 2.1452(9) and 2.1449(8) Å, respectively, similar to that
of reported pyrrole-imine nickel(II) complexes (P−Ni =
2.1458(2) Å).14,18 Despite the different steric effects of the
N-aryl groups in complexes 2a,c, the bite angles N1−Ni1−N2
(2a, 94.86(8)°; 2c, 94.94(7)°) of the complexes are nearly the
same. The variations in the imine and amine bonds between
complex 2c (C7−N2 = 1.318(3) Å, C1−N1 = 1.350(3) Å) and
the ligand 1c (C7−N2 = 1.276(3) Å, C1−N1 = 1.363(3) Å)
are attributed to the coordination of the nitrogen atoms to the
metal center.
and the coordinated atoms. The Pd1−P1 bond length is
2.2140(9) Å, which is normal in comparison with other Pd−P
bonds.18
Norbornene Polymerization. With methylaluminoxane
(MAO) as cocatalyst, complexes 2a−f and 3a−c were not able
to catalyze ethylene polymerization at 1 atm, and no solid
polymer was observed even at high pressures of ethylene.
However, nickel complexes 2a−f could polymerize norbornene
to afford vinyl addition type polynorbornene (PNB) with high
activities (107 g of PNB (mol of Ni)−1 h−1) after activation with
MAO and produced high-molecular-weight polymers (105 g
mol−1).
The molecular structure of complex 3a (Figure 5) is similar
to that of complex 2a, which also has an almost square-planar
geometry, with a deviation of the palladium atom from the
plane constructed by the coordinated atoms of 0.027(1) Å. In
contrast to 2a, longer bond distances are observed between Pd
To investigate the reaction parameters affecting the polymer-
ization of norbornene, the catalytic precursor 2c was studied
Scheme 2. Synthesis of Nickel and Palladium Complexes
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Table 1. Results of Norbornene Polymerization with 2c/
a
MAO
b
c
entry
Al/Ni
temp (°C) NB (g) yield (g) activity
Mv
1
1000
3000
5000
7000
10000
5000
5000
5000
5000
5000
25
25
25
25
25
0
2
2
2
2
2
2
2
2
1
3
2
2
2
0.531
0.550
0.636
0.350
0.168
0.480
0.445
0.293
0.254
0.7163
0.233
0.349
0.886
1.25
1.32
1.53
0.84
0.40
1.15
1.07
0.71
0.61
1.72
2.80
2.09
1.06
7.01
6.91
6.08
6.48
6.43
7.12
6.52
6.02
6.24
6.44
6.17
6.76
6.53
2
3
4
5
6
7
50
75
25
25
25
25
25
8
9
10
11
12
13
d
5000
e
5000
f
5000
a
Polymerization conditions: complex, 0.5 μmol; time, 5 min; Vtotal, 10
b
mL; solvent, chlorobenzene. In units of 107 g of PNB (mol of Ni)−1
c
d
e
f
h−1. In units of 105 g mol−1. 1 min. 2 min. 10 min.
Figure 4. Molecular structure of 2c (thermal ellipsoids at the 30%
probability level). Hydrogen atoms have been omitted for clarity.
Selected bond lengths (Å) and angles (deg): Ni1−N2, 1.8894(17);
Ni1−N1, 1.9215(18); Ni1−P1, 2.1449(8); Ni1−Cl1, 2.1831(8); P1−
C13, 1.801(2); N1−C1, 1.350(3); N1−C14, 1.442(2); N2−C7,
1.318(3); N2−C8, 1.436(3); N2−Ni1−N1, 94.94(7); N2−Ni1−P1,
86.52(6); N1−Ni1−P1, 172.95(5); N2−Ni1−Cl1, 169.28(6); N1−
Ni1−Cl1, 95.18(5); P1−Ni1−Cl1, 83.86(3); C13−P1−Ni1,
101.24(8); N2−C7−C6, 128.42(19).
increased, the catalytic ability of 2c first increased and then
decreased sharply, while the molecular weights of the polymers
varied irregularly. The highest catalytic capacity, 1.53 × 107 g of
PNB (mol of Ni)−1 h−1 ,was observed when the Al/Ni ratio was
5000 with a molecular weight of 6.08 × 105 g mol−1 (run 3 in
Table 1). A similar tendency of the catalytic abilities was also
noted when the reaction temperature was increased from 0 to
75 °C, but the molecular weights of the obtained polymers
decreased monotonously. Increasing the monomer concen-
tration resulted in an improvement of polymerization rate and
catalytic activity from 0.61 × 107 to 1.72 × 107 g of PNB (mol
of Ni)−1 h−1, which is in agreement with other reports.8c,18,19 As
seen in Table 1, with prolongation of the polymerization time,
the activities monotonically decreased over the whole process.
This observation suggested that the active species could be
formed rapidly at the initial stage of the reaction on activation
with MAO.
The norbornene polymerization results of 2a−f are collected
in Table 2. Under the same conditions, the nickel catalysts 2a−f
Table 2. Results of Norbornene Polymerization with Ni
a
Catalysts
temp
(°C)
NB
(g)
yield
(g)
conversn
(%)
b
c
entry cat.
activity
Mv
1
2
3
4
5
6
2a
2b
2c
2d
2e
2f
25
25
25
25
25
25
2
2
2
2
2
2
0.457
0.396
0.349
0.716
0.970
0.632
22.8
19.8
17.5
35.8
48.5
31.6
2.72
2.37
2.08
4.30
5.82
3.79
6.46
7.64
6.76
7.67
6.95
7.36
Figure 5. Molecular structure of 3a (thermal ellipsoids at the 30%
probability level). Hydrogen atoms have been omitted for clarity.
Selected bond lengths (Å) and angles (deg): Pd1−N2, 2.018(3);
Pd1−N1, 2.070(3); Pd1−P1, 2.2140(9); Pd1−Cl1, 2.3143(9); P1−
C13, 1.803(3); P1−C22, 1.814(3); P1−C28, 1.816(4); N1−C1,
1.348(4); N1−C14, 1.433(4); N2−C7, 1.314(5); N2−C8, 1.447(4);
N2−Pd1−N1, 92.04(11); N2−Pd1−P1, 85.09(9); N1−Pd1−P1,
176.27(8); N2−Pd1−Cl1, 173.11(9); N1−Pd1−Cl1, 94.81(8); P1−
Pd1−Cl1, 88.03(3); N2−C7−C6, 128.3(3).
a
Polymerization conditions: complex, 0.5 μmol; time, 2 min; Vtotal, 10
b
mL; solvent, chlorobenzene. In units of 107 g of PNB (mol of Ni)−1
c
h−1. In units of 105 g mol−1.
showed high catalytic abilities toward norbornene polymer-
ization, while the palladium catalysts 3a−c only produced traces
of polymer. Complexes 2d−f, which have an S atom on the side
arm, had higher catalytic abilities than their corresponding
analogues that contain a P atom as the third coordinated atom.
In comparison to the nickel complexes reported by Wu, which
also have an S atom attached to the anilido-imine ligands but
via the amido nitrogen, complexes 2d−f displayed much higher
under different reaction conditions, and the results are collected
in Table 1. For Ni(II) catalysts, an organoaluminum
compound, such as MAO, has been determined to be an
essential ingredient for high catalytic activity.19 Variation of the
ratio of MAO to 2c, which is expressed here as Al/Ni ratio, had
a considerable effect on the catalytic activities and the molecular
weights of the obtained polymers. When the Al/Ni ratio was
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1
catalytic abilities under similar conditions.8c The reason might
be that the structures of complexes 2d−f are nearly coplanar
and could provid more space in the axial direction for the
coordination and insertion of norbornene in the procedure of
polymerization. The steric structures of the ligands substituted
on the amine had a great effect on their catalytic activities.
When R = CH3, the highest catalytic abilities, 2.72 × 107 g of
PNB (mol of Ni)−1 h−1 for 2a−c and 5.82 × 107 g of PNB (mol
of Ni)−1 h−1 for 2d−f, were observed.
78.04; H, 4.91; N, 3.72. X = S: yield 89%; H NMR (500 MHz,
CDCl3, ppm) δ 8.87 (s, 1H, CHN-Ph), 8.17 (t, 1H, Ph H), 7.23(s,
1H, Ph H), 7.18 (t, 1H, Ph H), 6.98−7.08 (m, 3H, Ph H), 6.93 (t, 2H,
Ph H), 6.76 (t, 3H, Ph H), 6.70 (m, 2H, Ph H); 13C NMR (125 MHz,
CDCl3, ppm) δ 164.2, 153.6, 149.9, 133.9, 133.5, 133.3, 133.2, 132.8,
129.4, 129.0, 128.3, 127.9, 127.2, 126.7, 124.6, 126.0, 118.3, 116.0,
115.8. Anal. Calcd for C19H14FNS: C, 74.24; H, 4.59; N, 4.56. Found:
C, 73.98; H, 4.58; N, 4.67.
Synthesis of Ligand 1a. A solution of nBuLi (6.87 mL, 11 mmol)
in hexane was added to a solution of 2,6-dimethylaniline (1.21 g, 10
mmol) in THF (30 mL) at −78 °C. The mixture was warmed to room
temperature and stirred overnight. The resulting solution of LiNHAr
(Ar = C6H3Me2-2,6) was transferred dropwise into a solution of o-
C6H4F(CHNC6H4-2-PPh2) (3.83 g, 10 mmol) in THF (40 mL) at
room temperature. After the reaction mixture was stirred for 12 h at 40
°C, it was quenched with H2O (25 mL) and extracted with n-hexane.
The organic phase was dried over MgSO4 and evaporated to dryness in
vacuo to give the crude product as a yellow-red solid. The solid was
chromatographed on aluminum oxide with hexane/EtOAc 30/1 to
1
All of the obtained polymers showed very similar IR and H
NMR spectra. The absence of signals at 1620−1680, 966, and
735 cm−1 in the IR spectra revealed that there were no traces of
double bonds, and signals only in the 0.9−3.0 ppm range
observed in the 1H NMR spectra also supplied the same
information.20 These data indicated that the polymers were
vinyl addition type PNB. Attempts to determine the glass
transition temperature (Tg) of PNB failed, and the DSC studies
did not give an endothermic signal upon heating to the
decomposition temperature (above 450 °C).
1
obtain the pure product 1a (1.74 g, 36%) as a yellow powder. H
NMR (500 MHz, CDCl3, ppm): δ 9.87 (s, 1H, Ph NH), 8.66 (s, 1H,
NCH), 7.45 (t, 1H, Ph H), 7.38 (d, 1H, Ph H), 7.25 (m, 1H, Ph H),
7.08−7.16 (m, 15H, Ph H), 6.76 (m, 1H, Ph H), 6.66 (t, 1H, Ph H),
6.15 (d, 1H, Ph H), 2.06 (s, 6H, Ph CH3). 13C NMR (125 MHz,
CDCl3, ppm): δ 162.3, 154.2, 148.5, 137.5, 137.2, 136.6, 136.5, 134.9,
133.8, 133.6, 133.0, 132.8, 132.4, 129.9, 128.3, 128.2, 128.1, 128.0,
126.2, 126.0, 117.0, 116.9, 115.1, 111.7, 18.4. Anal. Calcd for
C33H29N2P: C, 81.79; H, 6.03; N, 5.78. Found: C, 81.68; H, 6.11;
N, 5.62.
CONCLUSION
■
A series of nickel and palladium complexes bearing new
tridentate anilido-imine N−NP and N−NS legands were
synthesized and characterized. A combination of spectroscopic
and X-ray crystallographic studies confirmed the molecular
structures of these nickel and palladium complexes. By
introduction of such a side arm, the nickel(II) complexes
were demonstrated to be efficient catalytic precursors for the
addition polymerization of norbornene. After being activated
with methylaluminoxane (MAO), the nickel(II) complexes 2a−
f could polymerize norbornene with high catalytic activities up
to 5.82 × 107 g of PNB (mol of Ni)−1 h−1, while the palladium
complexes 3a−c only produced traces of polymer.
Synthesis of Ligand 1b. A procedure similar to that used for the
preparation of 1a was employed: BuLi (6.87 mL, 11 mmol), 2,6-
n
diethylaniline (1.50 g, 10 mmol), and o-C6H4F(CHNC6H4-2-PPh2)
(3.83 g, 10 mmol). Yield: 1.84 g (38%). 1H NMR (500 MHz, CDCl3,
ppm): δ 10.05 (s, 1H, Ph NH), 8.67 (s, 1H, NCH), 7.48 (t, 1H, Ph
H), 7.41 (d, 1H, Ph H), 7.10−7.32 (m, 16H, Ph H), 6.84 (m, 1H, Ph
H), 6.69 (t, 1H, Ph H), 6.23 (d, 1H, Ph H), 2.54 (q, 4H, −CH2CH3),
2.06 (t, 6H, −CH2CH3). 13C NMR (125 MHz, CDCl3, ppm): δ 162.8,
154.6, 149.5, 142.9, 136.9, 136.5, 135.1, 134.0, 133.8, 133.3, 132.8,
132.7, 132.5, 130.2, 128.4, 126.9, 126.1, 126.0, 127.3, 117.0, 115.2,
112.2, 24.6, 14.5. Anal. Calcd for C35H33N2P: C, 82.00; H, 6.49; N,
5.46. Found: C, 82.08; H, 6.45; N, 5.50.
EXPERIMENTAL SECTION
■
General Considerations. All the operations were carried out
under a pure argon atmosphere using standard Schlenk techniques.
Tetrahydrofuran (THF), hexane, and toluene were distilled from
sodium−benzophenone. Dichloromethane was distilled from calcium
hydride. Commercial reagents, namely nBuLi, methylaluminoxane
(MAO), 2-fluorobenzaldenyde (97%), 2,6-diisopropylaniline (92%),
2,6-diethylaniline (98%), 2,6-dimethylniline (95%), 2-aminophenyl
phenyl sulfide (98%), and 2-(diphenylphosphino)benzenamine, were
purchased from Acros Co. and used without further purification.
Norbornene (bicyclo[2.2.1]hept-2-ene, Acros) was purified by
distillation over sodium and used as a chlorobenzene solution. The
Synthesis of Ligand 1c. A procedure similar to that used for the
preparation of 1a was employed: BuLi (6.87 mL, 11 mmol), 2,6-
n
diisopropylaniline (1.77 g, 10 mmol), and o-C61H4F(CHNC6H4-2-
PPh2) (3.83 g, 10 mmol). Yield: 2.32 g (43%). H NMR (500 MHz,
CDCl3, ppm): δ 10.30 (s, 1H, Ph NH), 8.47 (s, 1H, NCH), 7.40 (t,
1H, Ph H), 7.04−7.32 (m, 17H, Ph H), 6.83 (m, 1H, Ph H), 6.60 (t,
1H, Ph H), 6.20 (d, 1H, Ph H), 3.16 (m, 2H, −CHCH3), 1.11(d, 6H,
−CHCH3), 1.05 (d, 6H, −CHCH3). 13C NMR (125 MHz, CDCl3,
ppm): δ 163.3, 155.1, 150.0, 147.6, 137.2, 137.1, 135.0, 134.8, 133.9,
133.8, 133.3, 132.2, 130.1, 128.4, 128.3, 128.2, 127.3, 125.7, 123.7,
117.6, 116.8, 115.0, 112.5, 28.4, 24.5, 23.6. Anal. Calcd for C37H37N2P:
C, 82.19; H, 6.90; N, 5.18. Found: C, 82.08; H, 7.01; N, 5.23.
Synthesis of Ligand 1d. A procedure similar to that used for the
20a
20b
complexes (DME)NiCl2
and (COD)PdCl2
complexes were
synthesized according to the literature. Other commercially available
reagents were purchased and used without purification. 1H (500 MHz)
and 13C NMR (125 MHz) measurements were obtained on a Bruker
AC500 spectrometer in CDCl3 solution. Elemental analyses for C, H,
and N were carried out on an Elementar III Vario EI analyzer.
Synthesis of Compound A. A solution of 2-fluorobenzaldehyde
(1.86 g, 20 mmol), 2-substituted aniline (20 mmol), and 2 g of MgSO4
in n-hexane (50 mL) was stirred for 12 h at room temperature. The
mixture was then filtered and washed with CH2Cl2. The combined
bright yellow solution was concentrated to dryness and to give a
yellow powder. Pure products were obtained as yellow crystals by
n
preparation of 1a was employed: BuLi (6.87 mL, 11 mmol), aniline
(0.93 g, 10 mmol), and o-C6H4F(CHNC6H4-2-SPh) (3.07 g, 10
1
mmol). Yield: 1.18 g (31%). H NMR (500 MHz, CDCl3, ppm): δ
11.44 (s, 1H, Ph NH), 8.52 (s, 1H, NCH), 7.60 (d, 1H, Ph H),
7.11−7.41 (m, 14H, Ph H), 7.05 (d, 1H, Ph H), 6.98 (t, 1H, Ph H),
6.80 (t, 1H, Ph H). 13C NMR (125 MHz, CDCl3, ppm): δ 161.8,
150.8, 145.3, 142.3, 136.0, 134.9, 134.8, 131.6, 129.5, 129.1, 129.0,
128.8, 126.6, 126.4, 125.9, 123.4, 121.4, 121.2, 119.9, 118.0, 113.6.
Anal. Calcd for C25H20N2S: C, 78.91; H, 5.30; N, 7.36. Found: C,
78.82; H, 5.39; N, 7.31.
Synthesis of Ligand 1e. A procedure similar to that used for the
preparation of 1a was employed: BuLi (6.87 mL, 11 mmol), 2,6-
diethylaniline (1.50 g, 10 mmol), and o-C6H4F(CHNC6H4-2-SPh)
(3.07 g, 10 mmol). Yield: 1.22 g (30%). 1H NMR (500 MHz, CDCl3,
ppm): δ 10.45 (s, 1H, Ph NH), 8.64 (s, 1H, NCH), 7.40 (d, 1H, Ph
H), 7.10−7.31 (m, 13H, Ph H), 6.67 (t, 1H, Ph H), 6.22 (d, 1H, Ph
1
recrystallization from ethanol in high yield. X = PPh: yield 92%; H
NMR (500 MHz, CDCl3, ppm) δ 8.50 (s, 1H, CHN-Ph), 7.93 (t,
1H, Ph H), 7.69(m, 3H, Ph H), 7.46 (m, 6H, Ph H), 7.35 (m, 3H, Ph
H), 7.13 (t, 3H, Ph H), 6.60 (t, 1H, Ph H), 6.91 (m, 1H, Ph H); 13C
NMR (125 MHz, CDCl3, ppm) δ 161.9, 152.8, 136.9, 134.4, 134.2,
133.8, 133.6, 133.0, 132.9, 132.7, 132.3, 132.2, 132.1, 126.4, 126.1,
125.9, 124.4, 124.2, 117.2, 115.7, 115.5, 115.2, 114.9, 112.5, 111.5.
Anal. Calcd for C25H19FNP: C, 78.32; H, 5.00; N, 3.65. Found: C,
n
4752
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Article
H), 2.18 (s, 6H, Ph CH3). 13C NMR (125 MHz, CDCl3, ppm): δ
162.7, 150.0, 148.6, 137.5, 134.9, 134.3, 132.6, 131.6, 131.5, 130.6,
129.1, 128.3, 127.9, 127.1, 126.3, 117.9, 117.1, 115.4, 111.9, 18.5. Anal.
Calcd for C27H24N2S: C, 79.37; H, 5.92; N, 6.86. Found: C, 79.45; H,
5.99; N, 6.85.
14H, Ph H and NCH overlap), 6.71 (t, 1H, Ph H), 6.50 (d, 1H, Ph
H), 6.22 (m, 1H, Ph H). 2.19 (s, 6H, Ph CH3). IR (KBr): ν 1610,
1576, 1560, 1507, 1466, 1452, 1323, 1185, 1156, 1110, 752, 740, 690
cm−1. Anal. Calcd for C27H23ClN2NiS: C, 64.64; H, 4.62; N, 5.58.
Found: C, 64.51; H, 4.51; N, 5.69.
Synthesis of Ligand 1f. A procedure similar to that used for the
Synthesis of Complex 2f. A procedure similar to that used for the
preparation of 2a was employed: nBuLi (0.68 mL, 1.1 mmol),
(DME)NiCl2 (0.219 g, 1.0 mmol), and 1f (0.46 g, 1.0 mmol). Yield:
n
preparation of 1a was employed: BuLi (6.87 mL, 11 mmol), 2,6-
diisopropylaniline (1.77 g, 10 mmol) and o-C61H4F(CHNC6H4-2-
SPh) (3.07 g, 10 mmol). Yield: 1.22 g (30%). H NMR (500 MHz,
CDCl3, ppm): δ 10.66 (s, 1H, Ph NH), 8.68 (s, 1H, NCH), 7.19−
7.41 (m, 11H, Ph H), 6.26 (d, 1H, Ph H), 3.26 (m, 2H, −CHCH3),
1.14 (d, 6H, −CHCH3), 1.09 (d, 6H, −CHCH3). 13C NMR (125
MHz, CDCl3, ppm): δ 162.6, 150.2, 147.7, 138.8, 134.7, 133.6, 133.5,
132.4, 129.4, 128.3, 128.0, 127.5, 126.7, 126.3, 123.8, 117.5, 116.8,
115.2, 112.3, 28.5, 24.8, 23.3. Anal. Calcd for C31H32N2S: C, 80.13; H,
6.94; N, 6.03. Found: C, 80.05; H, 7.09; N, 6.05.
1
0.101 g (18%). H NMR (500 MHz, CDCl3, ppm): δ 7.08−7.30 (m,
14H, Ph H and NCH overlap), 6.90 (t, 1H, Ph H), 6.72 (t, 1H, Ph
H), 6.12 (d, 1H, Ph H). 3.26 (m, 2H, −CHCH3), 1.12 (q, 12H,
−CHCH3). IR (KBr): ν 1611, 1578, 1558, 1503, 1451, 1436, 1262,
1181, 1097, 1022, 801, 746, 688 cm−1. Anal. Calcd for
C31H31ClN2NiS: C, 66.75; H, 5.60; N, 5.02. Found: C, 66.51; H,
5.51; N, 5.11.
Synthesis of Complex 3a. A procedure similar to that used for
n
n
Synthesis of Complex 2a. A solution of BuLi (0.68 mL, 1.1
the preparation of 2a was employed: BuLi (0.68 mL, 1.1 mmol),
mmol) in hexane was added to a solution of 1a (0.48 g, 1.0 mmol) in
dried toluene (10 mL) at −78 °C. The mixture was warmed to room
temperature and stirred for 2 h. The resulting red solution was
transferred dropwise into a suspension of (DME)NiCl2 (0.219 g, 1.0
mmol) in dried toluene (10 mL) at −78 °C, and the resulting mixture
was slowly warmed to room temperature and stirred overnight at 80
°C. The crude reaction mixture was filtered under nitrogen and
washed with toluene. The combined organic filtrates were
concentrated under reduced pressure to ca. 2 mL, and then dry
hexane (20 mL) was added. Solvent was removed from the precipitate
via cannula filtration, and the residual red solid was washed with n-
hexane. Drying in vacuo produces the desired nickel complex in 45%
(COD)PdCl2 (0.300 g, 1.0 mmol), and 1a (0.48 g, 1.0 mmol). Yield:
0.406 g (65%). H NMR (500 MHz, DMSO, ppm): δ 8.96 (s, 1H,
1
NCH), 8.13 (m, 1H, Ph H), 7.48−7.71 (m, 14H, Ph H), 7.28 (t,
1H, Ph H), 6.98 (m, 3H, Ph H), 6.86 (t, 1H, Ph H), 6.30 (t, 1H, Ph
H), 5.89 (d, 1H, Ph H), 2.00 (s, 6H, Ph CH3). IR (KBr): ν 1612, 1581,
1566, 1508, 1455, 1436, 1261, 1159, 1099, 745, 692 cm−1. Anal. Calcd
for C33H28ClN2PdP: C, 63.37; H, 4.51; N, 4.48. Found: C, 63.48; H,
4.59; N, 4.42.
Synthesis of Complex 3b. A procedure similar to that used for
n
the preparation of 2a was employed: BuLi (0.68 mL, 1.1 mmol),
(COD)PdCl2 (0.300 g, 1.0 mmol), and 1b (0.51 g, 1.0 mmol). Yield:
1
0.496 g (76%). H NMR (500 MHz, DMSO, ppm): δ 8.95 (s, 1H,
1
yield (0.262 g). H NMR (500 MHz, CDCl3, ppm): δ 8.21 (s, 1H,
NCH), 8.13 (t, 1H, Ph H), 7.45−7.70 (m, 15H, Ph H), 7.27 (t, 1H,
Ph H), 7.01 (m, 3H, Ph H), 6.27 (t, 1H, Ph H), 5.87 (d, 1H, Ph H),
2.53 (m, 2H, −CH2CH3), 2.37 (m, 2H, −CH2CH3), 1.02 (t, 6H,
−CH2CH3). IR (KBr): ν 1610, 1566, 1509, 1459, 1437, 1399, 1351,
1265, 1159, 1100, 1033, 748, 691 cm−1. Anal. Calcd for
C35H32ClN2PdP: C, 64.33; H, 4.94; N, 4.29. Found: C, 64.58; H,
4.99; N, 4.41.
NCH), 7.85 (t, 1H, Ph H), 7.24−7.46 (m, 12H, Ph H), 7.10 (d, 1H,
Ph H), 7.02 (m, 3H, Ph H), 6.93 (m, 2H, Ph H), 6.34 (t, 1H, Ph H),
6.15 (d, 1H, Ph H), 2.32 (s, 6H, Ph CH3). IR (KBr): ν 1614, 1561,
1510, 1455, 1433, 1369, 1268, 1206, 1182, 1156, 1096, 1026, 752, 696
cm−1. Anal. Calcd for C33H28ClN2NiP: C, 68.61; H, 4.89; N, 4.85.
Found: C, 68.88; H, 4.91; N, 4.72.
Synthesis of Complex 2b. A procedure similar to that used for
Synthesis of Complex 3c. A procedure similar to that used for
n
the preparation of 2a was employed: BuLi (0.68 mL, 1.1 mmol),
n
the preparation of 2a was employed: BuLi (0.68 mL, 1.1 mmol),
(DME)NiCl2 (0.219 g, 1.0 mmol), and 1b (0.51 g, 1.0 mmol). Yield:
(COD)PdCl2 (0.300 g, 1.0 mmol), and 1b (0.54 g, 1.0 mmol). Yield:
1
0.215 g (35%). H NMR (500 MHz, CDCl3, ppm): δ 8.18 (s, 1H,
1
0.497 g (73%). H NMR (500 MHz, DMSO, ppm): δ 8.99 (s, 1H,
NCH), 7.83 (t, 1H, Ph H), 7.08−7.44 (m, 17H, Ph H), 6.87 (m,
1H, Ph H), 6.31 (d, 1H, Ph H), 6.13 (d, 1H, Ph H), 2.68 (q, 4H,
−CH2CH3), 1.22 (t, 6H, −CH2CH3). IR (KBr): ν 1613, 1564, 1514,
1457, 1434, 1340, 1255, 1178, 1160, 1097, 1028, 750, 693 cm−1. Anal.
Calcd for C35H32ClN2NiP: C, 69.40; H, 5.32; N, 4.62. Found: C,
69.28; H, 5.31; N, 4.70.
NCH), 8.16 (m, 1H, Ph H), 7.44−7.72 (m, 13H, Ph H), 6.94−7.30
(m, 5H, Ph H), 6.28 (t, 1H, Ph H), 5.95 (d, 1H, Ph H), 3.14 (m, 2H,
−CHCH3), 1.11 (d, 6H, −CHCH3), 0.88 (d, 6H, −CHCH3). IR
(KBr): ν 1614, 1585, 1564, 1510, 1455, 1435, 1347, 1270, 1186, 1160,
1100, 1029, 749, 692 cm−1. Anal. Calcd for C37H36ClN2PdP: C, 65.20;
H, 5.32; N, 4.11. Found: C, 65.31; H, 5.26; N, 4.15.
X-ray Crystallography. Single crystals of complexes 1c,f, 2a,c, and
3a suitable for X-ray analysis were obtained from CH2Cl2/n-hexane
solutions. The intensity data of the single crystals were collected on
the CCD-Bruker Smart APEX system. All determinations of the unit
cell and intensity data were performed with graphite-monochromated
Mo Ka radiation (λ = 0.710 73 Å). All data were collected at room
temperature or −100 °C using the ω scan technique. These structures
were solved by direct methods using Fourier techniques and refined on
F2 by a full-matrix least-squares method. All the non-hydrogen atoms
were refined anisotropically, and all the hydrogen atoms were included
but not refined.
Polymerization of Norbornene. In a typical procedure (entry 3,
Table 1), 0.5 μmol of nickel complex 2c in 1.0 mL of chlorobenzene, 2
g of norbornene in 4.0 mL of chlorobenzene, and another 3.4 mL of
fresh chlorobenzene were placed in a special polymerization bottle (50
mL) with a strong stirrer under a nitrogen atmosphere. After the
mixture was kept at 30 °C for 10 min, 1.66 mL of MAO was charged
into the polymerization system via syringe and the reaction was
initiated. Five minutes later, acidic ethanol (Vethanol/Vconcd HCl = 20/1)
was added to terminate the reaction. The PNB was isolated by
filtration, washed with ethanol, and dried at 80 °C for 48 h under
vacuum. For all polymerization procedures, the total reaction volume
was 10.0 mL, which can be achieved by varying the amount of
Synthesis of Complex 2c. A procedure similar to that used for
n
the preparation of 2a was employed: BuLi (0.68 mL, 1.1 mmol),
(DME)NiCl2 (0.219 g, 1.0 mmol), and 1c (0.54 g, 1.0 mmol). Yield:
1
0.291 g (47%). H NMR (500 MHz, CDCl3, ppm): δ 8.27 (s, 1H,
NCH), 7.84 (t, 1H, Ph H), 7.46 (m, 2H,Ph H), 7.36 (m, 3H, Ph H),
7.10−7.24 (m, 12H, Ph H), 6.82 (m, 1H, Ph H), 6.60 (t, 1H, Ph H),
6.32 (t, 1H, Ph H), 3.58 (m, 2H, −CHCH3), 1.04 (d, 6H, −CH−
CH3), 0.99 (d, 6H, −CHCH3). IR (KBr): ν 1610, 1565, 1515, 1462,
1437, 1344, 1265, 1178, 1160, 1099, 1033, 748, 690 cm−1. Anal. Calcd
for C37H36ClN2NiP: C, 70.11; H, 5.72; N, 4.42. Found: C, 69.99; H,
5.67; N, 4.59.
Synthesis of Complex 2d. A procedure similar to that used for
n
the preparation of 2a was employed: BuLi (0.68 mL, 1.1 mmol),
(DME)NiCl2 (0.219 g, 1.0 mmol), and 1d (0.383 g, 1.0 mmol). Yield:
1
0.073 g (15%). H NMR (500 MHz, CDCl3, ppm): δ 7.11−7.65 (m,
16H, Ph H and NCH overlap), 6.81 (t, 1H, Ph H), 6.66 (t, 1H, Ph
H), 6.42 (d, 1H, Ph H). IR (KBr): ν 1604, 1577, 1524, 1450, 1426,
1323, 1154, 1125, 1024, 742, 690 cm−1. Anal. Calcd for
C25H19ClN2NiS: C, 63.40; H, 4.04; N, 5.91. Found: C, 63.59; H,
4.11; N, 5.89.
Synthesis of Complex 2e. A procedure similar to that used for
n
the preparation of 2a was employed: BuLi (0.68 mL, 1.1 mmol),
(DME)NiCl2 (0.219 g, 1.0 mmol), and 1e (0.41 g, 1.0 mmol). Yield:
1
0.095 g (19%). H NMR (500 MHz, CDCl3, ppm): δ 7.11−7.83 (m,
4753
dx.doi.org/10.1021/om3003202 | Organometallics 2012, 31, 4748−4754

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Article
chlorobenzene when necessary. IR (KBr): ν 2947, 2867, 1475, 1453,
(7) (a) Shang, X.; Liu, X.; Cui, D. J. Polym. Sci., Part A: Polym. Chem.
2007, 45, 5662. (b) Gao, W.; Cui, D.; Liu, X.; Zhang, Y.; Mu, Y.
Organometallics 2008, 27, 5889.
1375, 1294, 1258, 1146, 1107, 1040, 941, 891 cm−1.
(8) (a) Gao, H. Y.; Guo, W. J.; Bao, F.; Gui, G. Q.; Zhang, J. K.; Zhu,
F. M.; Wu, Q. Organometallics 2004, 23, 6273. (b) Wang, H. Y.; Meng,
X.; Jin, G. X. Dalton Trans. 2006, 2579. (c) Long, J. M.; Gao, H. Y.;
Song, K. M.; Liu, F. S.; Hu, H.; Zhang, L.; Zhu, F. M.; Wu, Q. Eur. J.
Inorg. Chem. 2008, 4296. (d) Long, J. M.; Gao, H. Y.; Liu, F. S.; Song,
K. M.; Hu, H.; Zhu, F. M.; Wu, Q. Inorg. Chim. Acta 2009, 362, 3035.
(9) Tsai, Y. H.; Lin, C. H.; Lin, C. C.; Ko, B. T. J. Polym. Sci., Part A:
Polym. Chem. 2009, 47, 4927.
ASSOCIATED CONTENT
* Supporting Information
A table giving a summary of crystallographic data and CIF files
giving crystal data for 1c,f, 2a,c, and 3a. This material is
available free of charge via the Internet at http://pubs.acs.org.
■
S
AUTHOR INFORMATION
Corresponding Author
*E-mail: gxjin@fudan.edu.cn. Fax: +86-21-65641740. Tel: +86-
21-65643776.
■
(10) Liu, Y. C.; Lin, C. H.; Ko, B. T.; Ho, R. M. J. Polym. Sci., Part A:
Polym. Chem. 2010, 48, 5339.
(11) Jone, D. J.; Gibson, V. C.; Green, S.; Maddox, P. Chem.
Commun. 2002, 1038.
Notes
(12) (a) Oakes, D. C. H.; Kimberley, B. S.; Gibson, V. C.; Jones, D.
J.; White, A. J. P.; Williams, D. Chem. Commun. 2004, 2174. (b) Hu,
W. Q.; Sun, X. L.; Wang, C.; Gao, Y.; Tang, Y.; Shi, L. P.; Xia, W.; Sun,
J.; Dai, H. L.; Li, X. Q.; Yao, X. L.; Wang, X. R. Organometallics 2004,
23, 1684. (c) Wang, C.; Ma, Z.; Sun, X. L.; Gao, Y.; Guo, Y. H.; Tang,
Y.; Shi, L. P. Organometallics 2006, 25, 3259. (d) Jia, A. Q.; Wang, J.
Q.; Hu, P.; Jin, G. X. Dalton Trans. 2011, 40, 7730.
(13) Tshuva, E. Y.; Groysman, S.; Godbeg, I.; Kol, M. Organometallics
2002, 21, 662.
(14) Siedle, G.; Lassabn, P. G.; Lozan, V.; Janiak, C.; Kersting, B.
Dalton Trans. 2007, 52.
(15) Meng, X.; Jin, G. X. J. Organomet. Chem. 2008, 693, 2597.
(16) Zhang, J.; Lin, Y. J.; Jin, G. X. Organometallics 2007, 26, 4042.
(17) Jia, A. Q.; Jin, G. X. Organometallics 2009, 28, 1872.
(18) Han, F. B.; Zhang, Y. L.; Sun, X. L.; Li, B. G.; Guo, Y. H.; Tang,
Y. Organometallics 2008, 27, 1924.
(19) (a) Tang, G. R.; Lin, Y. J.; Jin, G. X. J. Polym. Sci., Part A: Polym.
Chem. 2008, 46, 489. (b) Janiak, C.; Lassahn, P.-G. Polym. Bull. 2002,
47, 539. (c) Berchtold, B.; Lozan, V.; Lassahn, P.-G.; Janiak, C. J.
Polym. Sci., Part A: Polym. Chem. 2002, 40, 3604. (d) Lassahn, P.-G.;
Lozan, V.; Timco, G. A.; Christian, P.; Janiak, C.; Winpenny, R. E. P. J.
Catal. 2004, 222, 260. (e) Lozan, V.; Lassahn, P.-G.; Zhang, C. G.;
Wu, B.; Janiak, C.; Rheinwald, G.; Lang, H. Z. Naturforsch., B 2003, 58,
1152. (f) Blank, F.; Scherer, H.; Janiak, C. J. Mol. Catal. A: Chem.
2010, 330, 1.
The authors declare no competing financial interest.
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