New neutral nickel(II) complexes bearing pyrrole-imine chelate ligands: Synthesis, structure and norbornene polymerization behavior

Article abstract of DOI:10.1016/S0022-328X(02)02181-2

New neutral nickel(II) complexes bearing nonsymmetric bidentate pyrrole-imine chelate ligands (4a-d), [2-(ArNCH)C₄H₃N]Ni(PPh₃)Ph [Ar=2,6-diisopropylphenyl (a), 2-methyl-6-isopropylphenyl (b), 2,6-diethylphenyl (c), 2-tert-butylphenyl (d)], have been prepared in good yields from the sodium salts of the corresponding ligands and trans-Ni(PPh₃)₂(Ph)Cl, and the structure of complex 4a has been confirmed by X-ray crystallographic analysis. These neutral Ni(II) complexes were investigated as catalysts for the vinylic polymerization of norbornene. Using modified methylaluminoxane (MMAO) as a cocatalyst, these complexes display very high activities and produce great mass polymers. Catalyst activity of up to 4.2 × 10⁷ g (mol Ni h)^-1 and the viscosity-average molecular weight of polymer of up to 9.2 × 10⁵ g mol^-1 were observed. Catalyst activity, polymer yield, and polymer molecular weight can be controlled over a wide range by the variation of reaction parameters such as Al-Ni ratio, norbornene-catalyst ratio, monomer concentration, polymerization reaction temperature and time.

Full text of DOI:10.1016/S0022-328X(02)02181-2

Journal of Organometallic Chemistry 667 (2003) 185Á191
/
www.elsevier.com/locate/jorganchem
New neutral nickel(II) complexes bearing pyrrole-imine chelate
ligands: synthesis, structure and norbornene polymerization behavior
Yue-Sheng Li *, Yan-Rong Li, Xiao-Fang Li
State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022,
PR China
Received 11 June 2002; received in revised form 9 September 2002; accepted 5 November 2002
Abstract
New neutral nickel(II) complexes bearing nonsymmetric bidentate pyrrole-imine chelate ligands (4aÁ
/
d), [2-
(ArNCH)C4H3N]Ni(PPh3)Ph [ArÄ2,6-diisopropylphenyl (a), 2-methyl-6-isopropylphenyl (b), 2,6-diethylphenyl (c), 2-tert-butyl-
/
phenyl (d)], have been prepared in good yields from the sodium salts of the corresponding ligands and trans-Ni(PPh3)2(Ph)Cl, and
the structure of complex 4a has been confirmed by X-ray crystallographic analysis. These neutral Ni(II) complexes were investigated
as catalysts for the vinylic polymerization of norbornene. Using modified methylaluminoxane (MMAO) as a cocatalyst, these
complexes display very high activities and produce great mass polymers. Catalyst activity of up to 4.2ꢀ
viscosity-average molecular weight of polymer of up to 9.2ꢀ
105 g molꢁ1 were observed. Catalyst activity, polymer yield, and
polymer molecular weight can be controlled over a wide range by the variation of reaction parameters such as AlÁNi ratio,
norborneneÁcatalyst ratio, monomer concentration, polymerization reaction temperature and time.
/
107 g (mol Ni h)ꢁ1 and the
/
/
/
# 2003 Elsevier Science B.V. All rights reserved.
Keywords: Neutral Ni(II) complexes; Catalysts; Norbornene; Vinylic polymerization
1. Introduction
dium complexes, such as [Pd(CH3CN)4][BF4]2, display
extremely high catalytic activity and produce high
polymers that are soluble in organic solvents such as
chlorobenzene and o-dichlorobenzene, and exhibit high
Norbornene is known to polymerize by ring-opening
metathesis, cationic or vinylic polymerization [1Á4].
/
Recently, the vinylic polymerization of norbornene has
been considerably attracted because of the vinyl-type
polynorbornene having unique physical properties, such
as high glass transition temperature, optical transpar-
ency, and low birefringence [5]. The vinyl-type poly-
norbornene can be prepared using metal complexes
glass transition temperature (Tgꢀ350 8C). However,
/
palladium is very expensive. Recently, Greiner reported
the nickel(II) complexes bearing phosphoraneiminato
ligands exhibiting high catalytic activity for the vinyl
addition polymerization of norbornene and producing
great mass polymer [9]. More recently, Grubbs reported
that the neutral Ni(II) complexes bearing salicylaldimi-
nato ligands can catalyze copolymerization of ethylene
with norbornene derivatives and produce high copoly-
mers [26]. We found Grubbs’ neutral nickel complexes
activated with methylaluminoxane (MMAO) display
extreme activity for the vinylic polymerization of
norbornene [27]. This urges us to investigate if other
neutral Ni(II) complexes have high catalytic activity.
Here, we would like to report the synthesis of novel
neutral Ni(II) complexes bearing pyrrole-imine ligands
and the catalysis properties for the vinylic polymeriza-
tion of norbornene.
based on nickel [6Á
/
10], chromium [11], zirconium [12Á
/
15], cobalt [16,17], and palladium [18Á/25] as catalyst.
Zirconocenes and cationic palladium complexes are two
types of important catalysts for the vinylic polymeriza-
tion of norbornene. Zirconocenes exhibit only low
catalytic activity and afford high polymers that decom-
pose in air at high temperatures before they melt and are
insoluble in organic solvents [12Á15]. Cationic palla-
/
* Corresponding author. Fax: ꢂ
/
86-431-5685653.
E-mail address: ysli@ciac.jl.cn (Y.-S. Li).
0022-328X/02/$ - see front matter # 2003 Elsevier Science B.V. All rights reserved.
doi:10.1016/S0022-328X(02)02181-2

186
Y.-S. Li et al. / Journal of Organometallic Chemistry 667 (2003) 185Á191
/
2. Results and discussion
Crystals of 4a suitable for X-ray structure determina-
tion were grown from a benzeneÁpentane (1:1) solution.
/
The data collection and refinement data of the analysis
are summarized in Table 1, and the molecule structure is
shown in Fig. 1. In the solid state, the molecule adopts
nearly ideal square-planar coordination geometry. The
bulky 2,6-diisopropylbenzimine occupies the position
2.1. Synthesis and characterization complexes
Grubbs and coworkers recently developed a family of
neutral [N,O]Ni complexes capable of polymerizing
ethylene and copolymerizing ethylene with norbornene
derivatives [26]. Furthermore, we found Grubbs’ neutral
nickel complexes display extreme activity for the vinylic
polymerization of norbornene [27]. This impels us to
synthesize new neutral nickel complexes by modifying
the structure of ligands. We report here the neutral
Ni(II) complexes bearing pyrrole-imine ligands.
trans to the triphenylphosphine ligand with a PÃ
angle of 168.53(7)8. The phenyl group attached to Ni lies
trans to N1 with a N1ÃNiÃC1 angle of 167.05(12)8. The
N2ÃNiÃN1, N2ÃNiÃC1, PÃNiÃN1, and PÃNiÃC1
/
NiÃ/N2
/
/
/
/
/
/
/
/
/
/
bond angles are 82.70(10), 93.92(11), 100.09(7) and
85.69(9)8, respectively. The torsion angle of the plan
(N1, C7, C11, N2, Ni) and the plan (Ni, P, C1) is 17.88.
The NiÃ
/
C1, NiÃ
/
N1, and NiÃ
/
N2 bond distances are
˚
General synthetic route for the neutral Ni(II) com-
1.910(3), 1.952(2), and 1.982(2) A, respectively. The NiÃ
/
plexes bearing pyrrole-imine ligands 2aÁd used in this
/
˚
P bond of 4a (2.148(1) A) is shorter than that of the
study is shown in Scheme 1. The pyrrolide-imine ligands
were prepared (yields: 2a, 75; 2b, 70; 2c, 72; 2d, 67%) by
the condensation of the corresponding aniline deriva-
˚
neutral salicylaldiminato Ni(II) complex (2.172(2) A)
[29] (Table 2).
tives 1aÁ
salts 3aÁ
NaH in THF. The neutral Ni(II) complexes 4aÁ
obtained as yellow powers (yields: 4a, 76; 4b, 79; 4c, 73;
4d, 69%) by the reaction of 3aÁ with trans-
[NiCl(Ph)(PPh3)2]. According to NMR spectra, these
neutral Ni(II) complexes with pyrrole-imine ligands,
similar to those neutral salicylaldiminato Ni(II) com-
/
d and pyrrole-2-carboxaldehyde. The sodium
d were obtained by treatment of 2aÁd with
d were
2.2. Polymerization
/
/
/
The structure of the neutral nickel complexes 4aÁd is
/
similar to that of Grubbs’ catalysts that can catalyze the
polymerization of ethylene and produce great mass
polymers [26]. However, attempt to polymerize ethylene
/
d
with complexes 4aÁd did not success whether phosphine
/
scavengers or cocatalysts such as MMAO were used or
not, which is similar to the case of the neutral palladium
complexes reported by Novak and coworkers [30]. It is
plexes [29], are diamagnetic and adopt a square-planar
1
geometry. In the H-NMR spectra of 4aÁ
/d the imine
protons show a characteristic 31P coupling, which
corresponds to PPh3 bound in a trans relationship to
ketimine. The signals for the triphenylphosphine ligand
very interesting, nevertheless, that complexes 4aÁd, like
/
the neutral salicylaldiminato Ni(II) complexes [27],
exhibit extremely high catalytic activity for the vinylic
in the 31P-NMR spectra of complexes 4aÁ
between 28.0 and 28.6 ppm.
/d are observed
Table 1
Crystal data and structure refinements for 4a
Empirical formula
Formula weight
Crystal system
Space group
C41H41N2NiP
651.44
Monoclinic
P21/n
˚
a (A)
11.177(4)
17.857(6)
18.059(4)
104.79(3)
3485(2)
4
˚
b (A)
˚
c (A)
b (8)
3
V (A )
˚
Z
rcalc (g cmꢁ3
)
1.242
0.71073
1376
m(MoÁ
F(000)
u Range (8)
/
Ka) (cmꢁ1
)
1.63Á25.03
/
Independent reflections
Absorption correction
Max. and min. transmission
Parameters
6133 (Rint
c-scan
ꢃ0.0269)
/
0.4188 and 0.3786
410
Final R indices [I ꢀ
/
2s(I)]
R1ꢃ
0.812
0.235/ꢁ0.294
/
0.0380, wR2ꢃ0.0583
/
Goodness-of-fit on F2
Largest peak/hole in final difference map
ꢁ3
ꢂ/
/
˚
(e A
)
Scheme 1.

Y.-S. Li et al. / Journal of Organometallic Chemistry 667 (2003) 185Á
/191
187
Fig. 1. Molecular structure of complex 4a. Thermal ellipsoids at the 50% level are shown. Hydrogen atoms are omitted for clarity.
polymerization of norbornene and produce great mass
polynorbornene, in the presence of MAO or modified
MAO (MMAO) under moderate conditions.
conditions. MMAO was essential for the polymerization
of norbornene catalyzed by the neutral Ni(II) com-
plexes. Variation of the molar ratio of MMAOÁ
/
4a,
Polymer yields and molecular weights as well as
catalyst activities depended significantly on the reaction
which is expressed here as AlÁNi ratio, showed con-
/
siderable effects on the polymer yields, molecular
weights and catalyst activities. When the mole ratio of
AlÁ
polym (mol Ni h)ꢁ1, and a significant increase of the
activity of up to 8.8ꢀ
106 g polym (mol Ni h)ꢁ1 was
observed by increase of the ratio of AlÁNi to 2000/1 as
shown in Fig. 2. In contrast, the viscosity-average
/
Ni was 1000/1, the catalytic activity is 3.6ꢀ
106 g
/
Table 2
˚
Selected bond lengths (A) and angles (8) for complex 4a
/
Bond lengths
NiÃ
NiÃ
NiÃ
NiÃ
N(1)Ã
N(2)Ã
N(1)Ã
/
C(1)
N(1)
N(2)
P
1.910(3)
1.952(2)
1.982(2)
2.148(1)
1.346(3)
1.295(3)
1.392(3)
1.832(3)
1.829(3)
1.837(3)
/
/
/
¯
molecule weights (/Mv) of the polymers decrease with
/
increase of the AlÁ/Ni ratio.
/
C(10)
C(11)
C(7)
/
As shown in Fig. 3, the reaction temperature also
affects considerably on the catalytic activity of 4a and
molecular weights of the polymers. With increase of the
reaction temperature, the catalytic activities and viscos-
/
PÃ
PÃ
PÃ
/
C(24)
C(30)
C(36)
/
/
¯
ity-average molecule weights (Mv) of the polymers
/
Bond angles
increase first and then decrease. As for the catalytic
activity, the optimum reaction temperature is ca. 30 8C.
As shown in Fig. 4, the concentration of norbornene
also considerably affects the polymerization reaction.
An increase of the monomer concentration caused a
linear increase of the catalyst activity of 4a. Viscosity-
C(1)Ã
C(1)Ã
N(1)Ã
C(1)ÃNiÃ
N(1)ÃNiÃ
N(2)ÃNiÃ
C(30)ÃPÃ
C(30)ÃPÃ
C(30)ÃPÃ
C(24)ÃPÃ
/
NiÃ
NiÃ
NiÃ
/
N(1)
167.05(12)
93.92(11)
82.70(10)
85.69(9)
/
/N(2)
/
/
N(2)
/
/P
/
/
P
P
100.09(7)
168.53(7)
113.38(10)
102.83(13)
106.45(14)
100.44(13)
/
/
/
/Ni
/
/
C(24)
C(36)
C(36)
¯
average molecule weights (Mv) increase first and then
/
/
/
keep steady with increase of the monomer concentra-
tion.
/
/

188
Y.-S. Li et al. / Journal of Organometallic Chemistry 667 (2003) 185Á191
/
The polymerization results using complexes 4aÁd
/
activated with MMAO are summarized in Table 3.
The structures of the neutral Ni(II) complexes affect on
the polymer yields and activities under the same experi-
mental conditions. Bulky substituents in the ortho
position of nitrogen atom hinder the insertion of
norbornene. The decrease of steric hindrance is favor-
able to the insertion reaction of norbornene. Hence, 4a
with two big substituents displays the lowest catalytic
activity and produces the smallest mass polymers, and
4c with only one substituents displays the highest
catalytic activity and produces the greatest mass poly-
mers among the four catalysts. All polymers display
106 g molꢁ1). It
¯
Mv up to 1.3ꢀ
high molecular weights (
/
/
is worthy to notice that the viscosity-average molecule
¯
weights (Mv) of the polymers are almost independent of
the structure of catalyst used. The glass transition
temperatures (Tg) of the polymers are in the range of
¯
Fig. 2. Plot of activity (j) and Mv (k) vs. AlÁ
/
Ni (molar ratio). 0.5
/
mmol 4a, [norbornene]Á
/
[Ni]ꢃ
/
47 800, Vtotal
ꢃ/30 ml, polymerization
reaction at 30 8C for 30 min.
395.0Á410.0 8C as shown in Fig. 5.
/
1
IR, H- (Fig. 6) and 13C-NMR spectra (Fig. 7) are
characteristic for polynorbornene and reveal no traces
of double bonds, which are typical for metathesis-type
polynorbornene. All polymers are soluble at room
temperature in chlorobenzene, o-dichlorobenzene, and
dichloroethylene, which indicate low stereoregularity. It
is confirmed by 1H- and 13C-NMR spectra. Indeed,
analysis by wide-angle X-ray diffractometry shows no
indication of crystallinity.
3. Experimental
3.1. General procedures and materials
All work involving air and moisture sensitive com-
pounds was carried out using standard Schlenk techni-
ques. NMR analyses of polymers were performed on a
Varian Unity 400 MHz spectrometer at 135 8C, using o-
C6D4Cl2 as solvent. Other NMR data of ligands and
complexes were obtained on a Varian Unity 400 MHz
spectrometer at ambient temperature, C6D6 or CDCl3 as
solvent. IR spectra were recorded on a Bio-Rad FTS-
135 spectrophotometer. DSC measurements were per-
¯
Fig. 3. Plot of activity (j) and Mv (k) vs. reaction temperature. 0.5
mmol 4a, AlÁ
/
Niꢃ
/
2000, [norbornene]Á
polymerization reaction for 15 min.
/
[Ni]ꢃ
/
47 800, Vtotal
ꢃ/30 ml,
formed with a PerkinÁElmer Pyris 1 Differential Scan-
/
ning Calorimeter. Viscosity-average molecular weights
were calculated from the intrinsic viscosity by using the
MarkÁ
/
Houwink coefficients: aꢃ
/
0.56, Kꢃ
/
5.97ꢀ
10ꢁ4
/
dl gꢁ1 [28].
2,6-Dimethylaniline, 2,6-diethylaniline, 2,6-diisopro-
pylaniline and 2-tert-butylaniline were obtained from
Acros and purified by distillation before use. Pyrrole-2-
carboxaldehyde and triphenylphosphine were obtained
from Aldrich and used without purification. Norbor-
nene was dried over Na, vacuum-transferred, and
¯
Fig. 4. Plot of activity (j) and Mv (k) vs. norbornene concentration.
degassed by repeated freezeÁ
/
pumpÁthaw cycles. Ben-
/
0.5 mmol 4a, AlÁNiꢃ2000, Vtotal 30 ml, polymerization reaction at
/
/
ꢃ/
30 8C for 30 min.
zene-d6 was dried over CaH2, vacuum-transferred,

Y.-S. Li et al. / Journal of Organometallic Chemistry 667 (2003) 185Á
/191
189
Table 3
The results of the vinylic polymerization of norbornene
a
Entry Catalyst AlÁ/Ni (mol ratio)
Norbornene (g)
Polymer (g) Yield (%) Activity (107 g (mol Ni h)ꢁ1
)
/
Mv (104 g molꢁ1
¯
)
1
2
3
4
5
6
7
8
4a
4b
4c
4d
4a
4b
4c
4d
1200
2.40
2.40
2.40
2.40
2.40
2.40
2.40
2.40
1.39
1.49
1.58
1.68
1.61
1.68
1.78
1.85
58
62
66
70
67
70
74
77
3.3
3.6
3.8
4.0
3.9
4.0
4.3
4.4
85
87
90
92
65
67
69
71
1200
1200
1200
2000
2000
2000
2000
a
0.5 mmol catalyst, Vtotal
ꢃ/30 ml, polymerization reaction for 5 min at 30 8C.
was obtained from Aldrich and used without further
purification.
3.2. Synthesis of ligands 2aÁd
/
To a stirred solution of pyrrole-2-carboxyaldehyde
(1.90 g, 20 mmol) in dried MeOH (30 ml), 2,6-
diisopropylaniline (3.6 g, 20 mmol) and formic acid
(0.5 ml), as a catalyst, were added. The reaction mixture
was stirred for 24 h at room temperature (r.t.). Subse-
quently, the white precipitate was separated by filtra-
tion, and then recrystallized from MeOH to yield 2a as
white crystals in 75% yield (3.81 g). The other ligands
2bÁ
yields.
/
d were prepared by the same procedure with similar
Fig. 5. The glass transition temperature (Tg) of polymers by DSC with
a heating rate of 20 8C minꢁ1. 1, 2, 3, and 4 correspond to entries 5, 6,
7, and 8 in Table 3, respectively.
1
2a: H-NMR (CDCl3): d 10.8Á
7.91 (s, 1H, NÄCÃH), 7.17 (m, 3H, PhÃ
pyrrole-H), 6.25 (s, 1H, pyrrole-H), 3.07 (m, 1H, CÃ
1.15 (d, 12H, i-PrÃ
27.9, 109.8, 116.7, 123.2, 124.1, 124.5, 129.8, 138.9,
/
10.2 (br, 1H, NÃ
/
H),
/
/
/
H), 6.67 (d, 1H,
/H),
CH3). 13C-NMR (CDCl3): d 23.6,
degassed by repeated freezeÁ
/
pumpÁ
/
thaw cycles, and
stored over 4A molecular sieves. o-Dichlorobenzene-d4
/
˚
Fig. 6. 1H-NMR spectra of polynorbornene recorded in o-C6D4Cl2 at 135 8C.

190
Y.-S. Li et al. / Journal of Organometallic Chemistry 667 (2003) 185Á191
/
Fig. 7. 13C-NMR spectra of polynorbornene recorded in o-C6D4Cl2 at 135 8C.
148.4, 152.7. Anal. Calc. for C17H22N2: C, 80.27; H,
8.72; N, 11.01. Found: C, 80.35; H, 8.69; N, 10.96%.
(20 ml) and dried in vacuum. The Na salt 3a (0.28 g, 1.0
mmol) and trans-[NiCl(Ph)(PPh3)2] (0.67 g, 0.97 mmol)
were in a Schlenk flask dissolved in C6H6 (20 ml) and
stirred at r.t. for 8 h. The resulting mixture was filtered
by cannula filtration, and the filtrate was concentrated
in vacuo to ca. 5 ml. Pentane (30 ml) was added.
1
2b (70%): H-NMR (CDCl3): d 10.3Á
/
10.1 (br, 1H,
H), 7.17 (s, 1H, PhÃH),
H), 6.68 (s, 1H, pyrrole-H), 6.62
(d, 1H, pyrrole-H), 6.25 (d, 1H, pyrrole-H), 3.07 (m,
NÃ
/
H), 7.96 (s, 1H, NÄ
/
CÃ
/
/
7.08Á
/
7.02 (m, 2H, PhÃ
/
1H, CÃ
/
H), 2.15 (s, 3H, CH3), 1.13 (d, 6H, i-PrÃ
/
CH3).
Subsequently, a yellowÁorange solid precipitated from
solution and was isolated by cannula filtration, and was
washed several times by cold C5H12 to yield 0.51 g (76%)
/
13C-NMR (CDCl3): d 18.7, 23.4, 27.8, 109.9, 116.6,
123.4, 123.9, 124.2, 127.8, 127.9, 129.9, 139.3, 149.5,
153.0. Anal. Calc. for C15H18N2: C, 79.61; H, 8.02; N,
of 4a. The other complexes 4bÁ
same procedure with similar yields.
4a: 1H-NMR (C6D6): d 7.78 (s, 5H, NiPhÃ
1H, NÄCÃH), 7.16 (s, 1H, PhÃH), 6.99 (m, 15H, PPhÃ
H), 6.46 (s, 3H, 2PhÃHꢂpyrrole-H), 6.31 (s, 1H,
pyrrole-H), 6.12 (s, 1H, pyrrole-H), 4.11 (s, 2H, CÃ
CH3).
/d were prepared by the
12.38. Found: C, 79.70; H, 7.98; N, 12.32%.
1
2c (72%): H-NMR (CDCl3): d 10.5Á
/10.3 (br, 1H,
/
H), 7.68 (s,
NÃ
/
H), 7.97 (s, 1H, NÄ
/
CÃ
/
H), 7.13Á
/
7.07 (s, 3H, PhÃH),
/
/
/
/
/
6.59 (m, 1H, pyrrole-H), 6.44 (s, 1H, pyrrole-H), 6.19
(m, 1H, pyrrole-H), 2.54 (m, 4H, CH2), 2.10 (m, 6H,
CH3). 13C-NMR (400 MHz, C6D6): d 15.4, 26.0, 109.9,
116.7, 123.3, 124.2, 124.5, 129.9, 139.0, 148.6, 152.9.
Anal. Calc. for C15H18N2: C, 79.61; H, 8.02; N, 12.38.
/
/
/
H), 1.46 (s, 6H, i-PrÃ
/
CH3), 1.28 (s, 6H, i-PrÃ
/
13C-NMR (C6D6): 23.0, 26.4, 29.2, 113.5, 113.7, 118.3,
122.0, 123.0, 124.4, 126.2, 126.4, 129.1, 130.1, 130.5,
132.2, 132.6, 132.7, 132.8, 133.0, 135.2, 135.3, 137.2,
140.7, 141.6, 142.8, 144.2, 146.9, 152.4, 152.9, 162.7. 31P-
NMR (C6D6): d 28.6. Anal. Calc. for C41H41N2NiP: C,
75.59; H, 6.34; N, 4.30. Found: C, 75.31; H, 6.36; N,
Found: C, 79.60; H, 8.00; N, 12.40%.
1
2d (67%): H-NMR (CDCl3): d 9.18Á
/
9.08 (br, 1H,
H), 7.37 (dd, 1H, PhÃH),
H), 7.14 (m, 1H, PhÃH), 6.82 (dd, 1H,
pyrrole-H), 6.66 (d, 1H, pyrrole-H), 6.32 (m, 1H,
pyrrole-H), 1.43 (s, 9H, t-BuÃ
CH3). 13C-NMR
NÃ
/
H), 8.10 (s, 1H, NÄ
/
CÃ
/
/
7.21 (m, 1H, PhÃ
/
/
4.32%.
/
1
4b (79%): H-NMR (C6D6): d 7.89 (s, 1H, NÄ
/
CÃ
H), 7.12 (s, 1H,
H), 6.48 (s, 1H, pyrrole-H), 6.38 (s, 1H, PhÃH),
6.32 (s, 1H, pyrrole-H), 6.08 (s, 1H, pyrrole-H), 3.81 (s,
1H, CÃH), 2.72 (s, 3H, PhCH3), 1.34 (d, 3H, i-PrÃ
CH3), 1.18 (s, 3H, i-PrÃ
CH3). 13C-NMR (C6D6): d
/
H),
(CDCl3): d 30.6, 35.6, 110.4, 116.1, 120.3, 125.2, 126.1,
127.1, 131.0, 142.8, 148.6, 151.4. Anal. Calc. for
C15H18N2: C, 79.61; H, 8.02; N, 12.38. Found: C,
79.59; H, 8.06; N, 12.35%.
7.77 (s, 5H, NiPhÃ
/
H), 7.49 (s, 1H, PhÃ
/
PhÃ
/
/
/
/
/
20.5, 22.6, 26.4, 29.0, 113.5, 116.6, 118.3, 122.0, 123.1,
124.7, 125.9, 127.6, 129.0, 129.2, 130.1, 130.5, 132.1,
132.7, 132.8, 133.1, 135.3, 135.4, 136.8, 140.5, 141.9,
142.7, 148.2, 162.9. 31P-NMR (C6D6): d 28.0. Anal.
Calc. for C39H37N2NiP: C, 75.14; H, 5.98; N, 4.49.
Found: C, 75.34; H, 6.01; N, 4.47%.
3.3. Synthesis of neutral Ni(II) complexes 4aÁd
/
A solution of ligand 2a (0.51 g, 2.0 mmol) in THF (20
ml) was added to NaH (120 mg, 5 mmol). The resulting
mixture was stirred at r.t. for 5 h, filtered, and
evaporated. The solid residue was washed with C5H12

Y.-S. Li et al. / Journal of Organometallic Chemistry 667 (2003) 185Á
/191
191
1
4c (73%): H-NMR (C6D6): d 7.79 (m, 6H, 5 NiPhÃ
Hꢂ1 NÄCÃH), 7.38 (d, 1H, PhÃH), 7.19 (d, 1H, PhÃ
H), 7.09Á6.85 (m, 15H, PPhÃH), 6.52 (m, 1H, pyrrole-
H), 6.41 (m, 1H, PhÃH), 6.18 (s, 1H, pyrrole-H), 6.09
/
Acknowledgements
/
/
/
/
/
The authors are grateful for the financial supported
by Special Funds for Major State Basis Research
Projects (No. G1999064801) from Ministry of Science
and Technology of China.
/
/
/
(s, 1H, pyrrole-H), 3.20 (m, 2H, CH2), 2.98 (m, 2H,
CH2), 1.35 (d, 6H, CH3). 13C-NMR (C6D6): d 15.3,
26.0, 113.5, 118.3, 122.1, 125.5, 125.8, 130.5, 132.7,
133.1,135.3, 135.4, 136.9, 137.8, 140.4, 162.7. 31P-NMR
(C6D6): d 28.5. Anal. Calc. for C39H37N2NiP: C, 75.14;
References
H, 5.98; N, 4.49. Found: C, 75.02; H, 5.95; N, 4.47%.
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1
4d (69%): H-NMR (C6D6): d 7.89 (s, 5H, NiPhÃ
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7.84 (s, 1H, NÄ
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Hꢂ
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/
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ꢃ
/
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