Synthesis, structure and ethylene oligomerization behavior of non-symmetric bidentate neutral arylnickel(II) phosphine complexes

Article abstract of DOI:10.1016/j.ica.2005.08.001

A series of new neutral arylnickel(II) phosphine complexes bearing non-symmetric bidentate chelate ligands, 3-aryliminomethyl-5-chloro-2- hydroxybenzaldehyde, have been synthesized, and the structure of representative complexes (2b and 2d) has been confirmed by X-ray crystallographic analysis. These neutral arylnickel(II) phosphine complexes have been investigated as catalysts for ethylene oligomerization. Using methylaluminoxane (MAO) as a cocatalyst, these complexes display high ethylene oligomerization activities. A catalytic activity of up to 4.6 × 10⁶ g mol^-1 h ^-1 has been observed. The influence of Al/Ni molar ratio, reaction temperature, reaction period and pressure on catalytic activity was investigated.

Full text of DOI:10.1016/j.ica.2005.08.001

Inorganica Chimica Acta 358 (2005) 4423–4430
www.elsevier.com/locate/ica
Synthesis, structure and ethylene oligomerization behavior
of non-symmetric bidentate neutral arylnickel(II) phosphine complexes
a,
a
a
b
b
You-Ming Zhang *, Qi Lin , Tai-Bao Wei , Dong-Heng Zhang , Su-Yun Jie
a
College of Chemistry and Chemical Engineering, Gansu Key Laboratory of Polymer Materials, Northwest Normal University, Lanzhou,
Gansu 730070, PR China
b
Institute of Chemistry, The Center for Molecular Sciences, The Chinese Academy of Sciences, Beijing 100080, PR China
Received 28 January 2005; received in revised form 20 July 2005; accepted 6 August 2005
Available online 21 September 2005
Abstract
A series of new neutral arylnickel(II) phosphine complexes bearing non-symmetric bidentate chelate ligands, 3-aryliminomethyl-5-
chloro-2-hydroxybenzaldehyde, have been synthesized, and the structure of representative complexes (2b and 2d) has been confirmed
by X-ray crystallographic analysis. These neutral arylnickel(II) phosphine complexes have been investigated as catalysts for ethylene olig-
omerization. Using methylaluminoxane (MAO) as a cocatalyst, these complexes display high ethylene oligomerization activities. A cat-
alytic activity of up to 4.6 · 106 g molÀ1 hÀ1 has been observed. The influence of Al/Ni molar ratio, reaction temperature, reaction period
and pressure on catalytic activity was investigated.
ꢀ 2005 Elsevier B.V. All rights reserved.
Keywords: Neutral nickel(II) complex; X-ray crystallography; Catalyst; Methylaluminoxane; Ethylene oligomerization
1. Introduction
fins and polymers. Neutral nickel(II) catalystscontaining an-
ionic [N,O] chelate ring were also largely reported in recent
years [5]. The most notable example is the neutral salicylal-
diminato nickel(II) complexes described by Grubbs and
co-workers [5g,5h], which exhibited high catalytic activity
and good tolerance of polar functional group in ethylene
polymerization. In addition, other ligands such as phosphi-
nooxazoline [6], dithio-b-diketonate [7], iminophosphine
[8], monoiminopyridine [9], bis(pyrazolyl)methane [10],
a-nitroketonate [11], and bis(2-diphenylphosphinoethyl)
methylamine [12] have also been employed with late-metals
as homogeneous catalysts.
Owing to the fact that linear ethylene oligomers in C4 to
C20 range are very useful materials for the preparation of
detergents, plasticizers, linear low-density polyethlene and
other fine chemicals [13], the research on ethylene oligo-
merization is receiving increased attention in ethylene
chemistry. There are tremendous amounts of literatures
which documented the achievement in this area. Among
them, SHOP catalytic systems of a-keto-ylid nickel
catalysts [4a,14] and Brookhartꢀs Ni(II) and Fe(II) bearing
Over the past decade, olefin oligomerization and poly-
merization based on late transition metal catalysts has been
one of the most exciting developments in the area of cataly-
sis, organometallic chemistry, and polymer science [1]. For
instance, a-diimine Ni(II) or Pd(II) complexes and
bis(imino)pyridyl Fe(II) or Co(II) complexes are two kinds
of representative catalysts in this field which could not only
polymerize ethylene to high branched polymers but could
also copolymerize ethylene and polar-functionalized a-ole-
fins [2,3]. Recently, neutral nickel(II) complexes have at-
tracted much attention because they are less sensitive to
protonic solvents and polar monomers than cationic nickel
analogs [4]. The most famous example of neutral nickel(II)
catalysts is the SHOP-type [4]. These nickel complexes con-
tain an anionic [P,O] chelate ring and show high activity
and selectivity for the conversion of ethylene to linear a-ole-
*
Corresponding author. Tel.: +8613359415896; fax: +869317971216.
E-mail address: zhangnwnu@126.com (Y.-M. Zhang).
0020-1693/$ - see front matter ꢀ 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2005.08.001

4424
Y.-M. Zhang et al. / Inorganica Chimica Acta 358 (2005) 4423–4430
diimine ligands [3a,3b,3c] systems are the two famous
examples. Being interested in obtaining short-chain a-
olefins, our group carried out a series of works to develop
the ethylene oligomerization catalysts. As a part of these
works, a series of nickel complexes containing 8-amino-
quinoline, 2-(2-pyridyl)quinoxaline, 2,6-bis(imino)phenol,
2,9-bis(imino)-1,10-phenanthroline, pyridylcarboxamide
and hydrazone derivatives were investigated [15]. Almost
all of them have moderate to high ethylene oligomerization
activity. To investgate the effect of introducing an aldehyde
group in neutral salicylaldiminato nickel(II) system, in this
contribution, a series of neutral arylnickel(II) phosphine
complexes bearing non-symmetric bidentate chelate
ligands, 3-aryliminomethyl-5-chloro-2-hydroxybenzalde-
hyde, have been synthesized. The structure of them (2b
and 2d) has been confirmed by X-ray crystallographic anal-
ysis and the catalytic properties of these complexes for eth-
ylene oligomerization are reported.
fore, it is very easy to separate and purify them. The
target complexes were obtained from good to excellent
yields. All of the complexes were characterized by elemen-
1
tal analyses, IR, H NMR, 13C NMR and 31P NMR.
In IR spectra of ligands 1a–1f, the C@N stretching
vibration is distributed in the range from 1620.7 to
1629.6 cmÀ1, while in the corresponding complexes 2a–2f
the C@N stretching vibration is distributed in the range
from 1605.4 to 1608.8 cmÀ1; these shifts are contributed
to the formation of N–Ni complex bonds. Owing to the
fact that C@O groups do not form complex bonds with
Ni, the shifts of stretching vibration of C@O in IR spectra
are very slight between ligands 1a–1f and complexes 2a–2f.
1
The H NMR spectra of the complexes show the peaks in
the range 9.25–9.94 ppm, confirming the existence of the
hydrogen of formyl and the peaks in the range 8.45–8.52
according to the hydrogen on carbon in imino groups. In
the 13C NMR spectra of these complexes, the chemical
shifts of C atoms in formyl groups are distributed in the
range from 189.2 to 190.3 ppm, while the C atoms in imino
groups are distributed in the range from 163.7 to
167.7 ppm. In the 31P NMR spectra of these complexes,
the chemical shifts of P atoms are distributed in the range
from 25.15 to 26.39 ppm.
2. Results and discussion
2.1. Synthesis and spectroscopic characterization
The
3-aryliminomethyl-5-chloro-2-hydroxybenzalde-
hyde ligands 1a–1f were prepared as yellow or orange sol-
ids in moderate yields through the condensation reaction of
1 equivalent of 4-chloro-2, 6-diformylphenol with 1 equiv-
alent of the appropriate aniline (Scheme 1). Compounds
1a–1f were characterized by elemental analyses, IR and
1H NMR.
In view of the high acidity of the hydroxyl proton on the
ligands, the target complexes 2a–2f were synthesized from
reacting 3-aryliminomethyl-5-chloro-2-hydroxybenzalde-
hyde ligands with trans-[NiCl(Naph)(PPh3)2] in THF in
the presence of NEt3 (Scheme 1). Owing to the low polarity
of the target complexes, the solubility of them in diethyl
ether is very good and the target complexes can be ex-
tracted from the reaction mixture by diethyl ether; there-
2.2. Crystal structure
Single crystals of 2b and 2d, suitable for X-ray analysis,
were obtained by slow evaporation of diethyl ether from
their diethyl ether and ethanol mixed solutions. The crystal
data are listed in Table 1 and the selected bond lengths and
angles are listed in Table 2. As depicted in Fig. 1, complex
2d contains a chelating [N,O] ligand, a triphenylphosphine
group (PPh3) and a naphthyl group. The formyl [2,4,6-
Me3(C6H2)–N] moiety occupies the position trans to PPh3
with a nearly linear N(1)–Ni(1)–P(1) angle [177.42(7)ꢁ],
and the naphthyl group bonded to Ni(1) also lies in a posi-
tion trans to O(1) with an O(1)–Ni(1)–C(21) angle of
Cl
Cl
Cl
O
OH
+
O
O
R1
EtOH/p-TsOH
reflux 24h
R1
NEt3/THF
O
N
Ni R1
O
OH
N
trans-[NiCl(Naph)(PPh3)2]
r.t./24h
P
R2
NH2
R1
R2
R1
R1
1a-1f
2a-2f
1a 1b 1c 1d 1e 1f
2a 2b 2c 2d 2e 2f
R2
R1
R2
Me Et i-Pr Me Br
Me Me
F
H
H
H
H
Scheme 1.

Y.-M. Zhang et al. / Inorganica Chimica Acta 358 (2005) 4423–4430
4425
Table 1
Crystal data and structure refinement for 2b and 2d
Complexes
2b
2d
Formula
C46H39ClNNiO2P
748.90
0.38 · 0.16 · 0.12
monoclinic
C2/c
37.94190(10)
9.5483(2)
23.7550(5)
90.00
99.1790(10)
90.00
C45H37ClNNiO2P
762.93
0.40 · 0.20 · 0.15
triclinic
Formula weight
Crystal size (mm)
Crystal system
Space group
ꢀ
P1
˚
a (A)
9.7914(5)
15.1311(11)
18.3347(13)
104.630(2)
103.790(2)
95.413(2)
2517.8(3)
2
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
3
˚
V (A )
8495.8(3)
8
1.224
Z
Dcalc (g cmÀ3
)
1.293
Diffractometer
Siemens Smart CCD Mercury70
l (mmÀ1
F(000)
T (K)
)
0.595
0.516
3276
1026
293(2)
293(2)
Fig. 1. Molecular structure of 2d, showing 30% probability displacement
h Range (ꢁ)
1.74–22.00
10263
5180 (0.0475)
490
0.0880
0.2229
3.1005–27.4835
19594
11375 (0.0161)
631
0.0608
0.1509
1.030
1.831 and À1.421
ellipsoids with hydrogen atoms omitted for clarity.
Total number of reflections
Number of unique data (Rint
Number of parameters
R
)
167.68(12)ꢁ. Due to the repulsion among the naphthyl ring,
phenyl ring on chelating [N,O] ligand and the PPh3 ligand,
the cis angles at nickel are in the range from 84.08(9)ꢁ to
93.45(11)ꢁ. Thus, the four coordinate atoms [P(1), O(1),
N(1), and C(21)] have an almost exact square-planar geom-
Rw
Goodness-of-fit on F2
Dqmin and Dqmax (e A
1.33
À3
˚
)
0.992 and À0.301
˚
etry with the Ni(1) approximately 0.0776 A from the plane
in complex 1. Because of the obvious structural similarity,
complex 2b has a molecular structure (Fig. 2) similar to
complex 2d. The four-coordinate atoms [N(1), O(1), P(1),
and C(51)] and the central Ni atom are also almost in the
Table 2
˚
Selected bond lengths (A) and angles (ꢁ) for complexes 2b and 2d
Complex 2b
Ni(1)–O(1)
Ni(1)–C(51)
Ni(1)–N(1)
Ni(1)–P(1)
O(1)–C(4)
O(2)–C(7)
N(1)–C(8)
N(1)–C(9)
1.893(5)
˚
same planar; the mean deviation from plane is 0.022 A.
1.903(9)
1.934(7)
2.188(2)
1.286(10)
1.198(11)
1.300(10)
1.443(11)
The trans N(1)–Ni(1)–P(1) [C(51)–Ni(1)–O(1)] angle and
cis O(1)–Ni(1)–N(1) [C(51)–Ni(1)–N(1)] angle are 176.5
(2)ꢁ [174.1(3)ꢁ] and 86.07(19)ꢁ [93.2(3)ꢁ].
O(1)–Ni(1)–C(51)
O(1)–Ni(1)–N(1)
C(51)–Ni(1)–N(1)
O(1)–Ni(1)–P(1)
C(51)–Ni(1)–P(1)
N(1)–Ni(1)–P(1)
174.1(3)
92.6(3)
93.2(3)
86.07(19)
88.1(3)
176.5(2)
Complex 2d
Ni(1)–O(1)
Ni(1)–C(21)
Ni(1)–N(1)
Ni(1)–P(1)
O(1)–C(1)
O(2)–C(8)
N(1)–C(7)
N(1)–C(9)
1.9017(19)
1.922(3)
1.947(2)
2.1768(7)
1.288(3)
1.212(4)
1.287(4)
1.449(3)
O(1)–Ni(1)–C(21)
O(1)–Ni(1)–N(1)
C(21)–Ni(1)–N(1)
O(1)–Ni(1)–P(1)
C(21)–Ni(1)–P(1)
N(1)–Ni(1)–P(1)
167.68(12)
93.00(9)
93.45(11)
89.29(6)
84.08(9)
177.42(7)
Fig. 2. Molecular structure of 2b, showing 15% probability displacement
ellipsoids with hydrogen atoms omitted for clarity.

4426
Y.-M. Zhang et al. / Inorganica Chimica Acta 358 (2005) 4423–4430
Table 5
2.3. Ethylene oligomerization
Influence of reaction time on 2d/MAO catalytic systems and their
oligomersꢀ distribution
Upon treatment with methylaluminoxane (MAO), all of
the complexes 2a–2f are active for ethylene oligomeriza-
tion. Table 3 lists their activity and molecular weight distri-
bution of the oligomers produced by these neutral nickel
catalysts. From these data, we can find that the electronic
factor of ligands has more influence on catalystsꢀ activity
than the steric factor: the catalytic activity of complexes
2a–2d is very similar, but the catalytic activity of 2e–2f is
much lower than 2a–2d.
Entry Time (min) Activity
Distribution of oligomers (%)
(·105 g molÀ1 hÀ1
)
C4
C6
2.77
1
2
3
4
5
15
30
45
60
75
1.47
97.23
76.7
78.3
72.1
70.9
3.96
4.99
5.73
3.42
23.3
21.7
27.9
29.1
Reaction conditions: 5 lmol catalyst, 30 ml toluene, Al/Ni 1250, 25 ꢁC,
1 atm ethylene.
Owing to the fact that 2d has the highest activity in the
same conditions among these complexes, we selected 2d as
the precatalyst and carefully investigated its catalytic activ-
ity. The influence of cocatalyst MAO on catalytic activities
and the distribution of resulting oligomers are summarized
in Table 4. The best Al/Ni molar ratio for this catalytic
system is 1250. The influence of reaction temperature and
time on catalytic activities and the distribution of resulting
oligomers are listed in Tables 5 and 6. The best reaction
temperature is 25 ꢁC and the best reaction time is 1 h. After
investigating the catalytic conditions, the highest catalytic
activity in 1 atm was obtained as 5.73 · 105 g molÀ1 hÀ1
under the conditions of 5 lmol catalyst (2d), 30 ml toluene,
Al/Ni 1250, 1 h, 25 ꢁC and the distribution of C4 is 72.1%
(2-butene >98%), C6 is 27.9%. When the reaction pressure
raised to 10 atm (conditions: 10 lmol catalyst (2d), 1000 ml
toluene, Al/Ni 1250, 1 h, 20 ꢁC), the catalytic activity im-
Table 6
Influence of temperature on 2d/MAO catalytic systems and their
oligomersꢀ distribution
Entry T (ꢁC) Activity
(·104 g molÀ1 hÀ1
Distribution of oligomers (%)
)
C4
C6
1
2
3
4
0
25
50
75
8.37
49.9
32.3
74.9
78.3
66.6
60.0
25.1
21.7
33.4
40.0
7.11
Reaction conditions: 5 lmol catalyst, 30 ml toluene, Al/Ni 1250, 45 min,
1 atm ethylene.
proved to 4.6 · 106 g molÀ1 hÀ1. In the resulting oligomers,
the distribution of C4 is 92.5% (the distribution of 1-butene
is 57.3% and that of 2-butene is 42.7%) and that of C6 is
7.5%.
Table 3
Ethylene oligomerization using 2a–2f/MAO systems and their oligomersꢀ
3. Experimental
distribution
Entry Complexes Activity
(·105 g molÀ1 hÀ1
Distribution of oligomers (%)
3.1. General procedures and materials
)
C4
C6
All manipulations for air- or moisture-sensitive com-
pounds were carried out under an atmosphere of nitrogen
using standard Schlenk techniques. Melting points (m.p.)
were determined with a digital electrothermal apparatus
without calibration. The IR spectra were recorded on a
Perkin–Elmer FT-IR 2000 spectrophotometer using KBr
disc in the range of 4000–400 cmÀ1. The NMR spectra were
recorded on a Bruker DMX-300 instrument with TMS as
the internal standard. The 31P NMR spectra were recorded
on a Varian XL-200 instrument with H3PO4 (85%) as the
external standard. The elemental analyses were performed
on a Flash EA 1112 microanalyzer. Distribution of oligo-
mers obtained was measured on a Varian VISTA 6000
GC spectrometer and a HP 5971A GC–MS detector.
THF, diethyl ether and toluene were refluxed over so-
dium-benzophenone until purple color appeared and were
distilled under nitrogen atmosphere prior to use. EtOH
was purified according to literature methods. 4-Chloro-
2, 6-diformylphenol [16] and trans-[NiCl(Naph)(PPh3)2]
[17] were prepared according to the literature method.
Methylaluminoxane (MAO, 1.4 mol lÀ1 in toluene) was
purchased from Albemarle Corp. (USA). All of the ani-
1
2
3
4
6
7
2a
2b
2c
2d
2e
2f
2.92
81.4
80.1
82.5
79.0
80.0
81.5
18.6
19.9
17.5
21.0
20.0
18.5
3.00
2.78
3.70
1.92
1.12
Reaction conditions: 5 lmol catalyst, 30 ml toluene, Al/Ni 1000, 0.5 h,
25 ꢁC, 1 atm ethylene.
Table 4
Influence of Al/Ni molar ratio on 2d/MAO catalytic systems and their
oligomersꢀ distribution
Entry Al/Ni Activity
(·104 g molÀ1 hÀ1
Distribution of oligomers (%)
)
C4
C6
1
2
3
4
5
6
250
500
750
1000
1250
1500
7.01
8.74
12.5
86.3
91.2
81.2
79.0
76.6
97.9
13.7
8.8
18.8
21.0
27.9
2.1
37.0
39.6
23.6
Reaction conditions: 5 lmol catalyst, 30 ml toluene, 0.5 h, 25 ꢁC, 1 atm
ethylene.

Y.-M. Zhang et al. / Inorganica Chimica Acta 358 (2005) 4423–4430
4427
lines were purchased from Aldrich Chemical Co or Acros
3.2.4. 3-(2,4,6-Trimethylphenylimino)methyl-5-chloro-2-
hydroxybenzaldehyde (1d)
Chemical Co. All other chemicals were obtained commer-
cially and used without further purification unless stated
otherwise.
Orange crystal, Yield: 61.0%; m.p. 174–176 ꢁC. 1H
NMR: d 10.53 (s, 1H, O@CH), 8.34 (s, 1H, N@CH),
7.91 (d, J = 3.0 Hz, 1H, Ar–H), 7.55 (d, J = 2.1 Hz, 1H,
Ar–H), 6.95 (s, 2H, Ar–H), 2.31 (s, 3H, CH3), 2.19 (s,
6H, CH3). IR (KBr): 3442.3 (b, O–H), 3337.5 (w, O–H),
1676.9 (s, C@O), 1620.7 (s, C@N), 1574.2 (s, C@C),
1456.1 (s, C@C), 1265.9 (m, Ar–O) cmÀ1. Anal. Calc. for
C17H16ClNO2: C, 67.66; H, 5.34; N, 4.64. Found: C,
67.45; H, 5.40; N, 2.97%.
3.2. Synthesis of ligands (1a–1f)
2,6-Dimethyl aniline (2.0 mmol) in 10 ml dried ethanol
was added dropwise to a stirred solution of 4-chloro-2,
6-diformylphenol (2.1 mmol) and catalytic amount of p-
toluenesulfonic acid in dried ethanol (20 ml) for 1 h. The
reaction mixture was stirred and refluxed for 24 h under
N2, and then cooled. After the evaporation of ethanol,
the resulting mixture was purified by column chromatogra-
phy on silica gel using light petroleum/ethyl acetate (50/1)
as an eluent. 1a was obtained as orange crystal in 46.9%
yield. The other ligands 1b–1f were prepared via the same
procedure.
3.2.5. 3-(2,6-Dibromo-4-methylphenylimino)methyl-5-
chloro-2-hydroxybenzaldehyde (1e)
Yellow crystal, Yield: 45.2%; m.p. 234–235 ꢁC. 1H
NMR: d = 13.20 (s, 1H, Ar–OH), 10.51 (s, 1H, O@CH),
8.51 (s, 1H, N@CH), 7.94 (d, J = 2.8, Hz, 1H, Ar–H),
7.65 (s, 1H, Ar–H), 7.45 (s, 2H, Ar–H), 2.35 (s, 3H,
CH3); IR: 3448.8 (wb, O–H), 1680.4 (s, C@O), 1623.3 (s,
C@N), 1579.1 (s, C@C), 1452.0 (m, C@C) cmÀ1. Anal.
Calc. for C15H10Br2ClNO2: C, 41.75; H, 2.34; N, 3.25.
Found: C, 41.74; H, 2.41; N, 3.25%.
3.2.1. 3-(2,6-Dimethylphenylimino)methyl-5-chloro-2-
hydroxybenzaldehyde (1a)
1
Yield: 46.9%; m.p. 184–186 ꢁC. H NMR: d = 10.53 (s,
3.2.6. 3-(2,6-Difluorophenylimino)methyl-5-chloro-2-
hydroxybenzaldehyde (1f)
1H, O@CH), 8.36 (s, 1H, N@CH), 7.91 (d, J = 2.7 Hz,
1H, Ar–H), 7.57 (s, 1H, Ar–H), 7.06–7.09 (m, 3H, Ar–
H), 2.22 (s, 6H, CH3). IR (KBr): 3429.8 (wb, O–H),
3067.8 (w, Ar–H), 1677.7 (s, C@O), 1625.9 (s, C@N),
1579.2 (s, C@C), 1455.4 (s, C@C), 1259.9 (m, Ar–O)
cmÀ1. Anal. Calc. for C16H14ClNO2: C, 66.79; H, 4.90;
N, 4.87. Found: C, 66.58; H, 4.96; N, 4.64%.
Orange crystal, Yield: 55.7%; m.p. 232–233 ꢁC. 1H
NMR: d = 10.51 (s, 1H, O@CH), 8.95 (s, 1H, N@CH),
7.92 (d, J = 2.8 Hz, 1H, Ar–H), 7.65 (s, 1H, Ar–H), 7.07–
7.01 (m, 3H, Ar–H); IR: 3440.4 (w, O–H), 3080.4 (w,
Ar–H), 1679.6 (s, C@O), 1622.7 (s, C@N), 1574.8 (s,
C@C), 1456.3 (m, C@C), 1267.7 (m, Ar–O) cmÀ1. Anal.
Calc. for C14H8ClF2NO2: C, 56.87; H, 2.73; N, 4.74.
Found: C, 56.81; H, 2.83; N, 4.72%.
3.2.2. 3-(2,6-Diethylphenylimino)methyl-5-chloro-2-
hydroxybenzaldehyde (1b)
Yellow crystal, Yield: 30.6%; m.p. 116–118 ꢁC. 1H
NMR: d = 10.53 (s, 1H, O@CH), 8.36 (s, 1H, N@CH),
7.91 (d, J = 2.7 Hz, 1H, Ar–H), 7.57 (s, 1H, Ar–H), 7.16
(s, 3H, Ar–H), 2.56 (q, J = 7.6 Hz, 4H, CH2), 1.17
(t, J = 7.6 Hz, CH3). IR (KBr): 3427.4 (wb, O–H), 3068.2
(w, Ar–H), 1680.5 (s, C@O), 1629.6 (s, C@N), 1579.8 (s,
C@C), 1450.6 (s, C@C), 1251.6 (m, Ar–O) cmÀ1. Anal.
Calc. for C18H18ClNO2: C, 68.46; H, 5.84; N, 4.44. Found:
C, 68.35; H, 5.84; N, 4.34%.
3.3. Synthesis of complexes
To a stirred solution of 3-(2,6-dimethylphenylimino)
methyl-5-chloro-2-hydroxybenzaldehyde (1.00 mmol) and
Et3N (1.5 mmol) in THF (10 ml) at room temperature,
trans-[NiCl(Naph)(PPh3)2] (0.95 mmol) was added; the
reaction mixture was stirred at room temperature for
24 h. After the evaporation of the THF in vacuum, the
resulting mixture was extracted by diethyl ether
(10 ml · 3). Then, 10 ml ethanol was added to the diethyl
ether solution and the solution was evaporated in vacuum
to remove the excess diethyl ether; after keeping the
solution for several hours at room temperature, rufous
crystal of 2a was obtained in 82.8% yield. The other ligands
2b–2f were prepared via the same procedure.
3.2.3. 3-(2,6-Diisopropylphenylimino)methyl-5-chloro-2-
hydroxybenzaldehyde (1c)
Yellow crystal, Yield: 44.1%; m.p. 180–181 ꢁC. 1H
NMR: d 14.10 (s, 1H, Ar–OH), 10.53 (s, 1H, O@CH),
8.32 (s, 1H, N@CH), 7.93 (d, J = 2.8 Hz, 1H, Ar–H),
7.58 (s, 1H, Ar–H), 7.22 (s, 3H, Ar–H), 2.94 (q,
J = 6.9 Hz, 2H, CH), 1.2 (d, J = 6.9 Hz, 12H, CH3). IR
(KBr): 3434.7 (wb, O–H), 3065.0 (w, Ar–H), 1680.2
(s, C@O), 1629.5 (s, C@N), 1580.2 (s, C@C), 1454.5
(s, C@C), 1250.7 (m, Ar–O) cmÀ1. Anal. Calc. for
C20H22ClNO2: C, 69.86; H, 6.45; N, 4.07. Found: C,
69.50; H, 6.46; N, 3.85%.
3.3.1. (1-Naphthyl){[3-(2,6-dimethylphenylimino)methyl]-
5-chloro-2-hydroxybenzaldehyde}(triphenylphosphine)
nickel(II) (2a)
1
Yield: 82.8%; m.p. 177–178 ꢁC. H NMR (CDCl3): d
9.54 (d, J = 9.0 Hz, 1H, O@CH), 8.49 (s, 1H, N@CH),
7.81 (d, J = 9.0 Hz, 1H, Ar–H), 7.70 (s, 1H, Ar–H), 7.42
(t, J = 9.0, 6H, Ar–H), 7.24–7.29 (m, 6H, Ar–H),

4428
Y.-M. Zhang et al. / Inorganica Chimica Acta 358 (2005) 4423–4430
7.02–7.15 (m, 7H, Ar–H), 6.91 (d, J = 6.0 Hz, 1H, Ar–H),
6.71 (q, J = 6.0, 2H, Ar–H), 6.50 (t, J = 6.0 Hz, 1H, Ar–
H), 6.21–6.29 (m, 2H, Ar–H), 1.21 (s, 6H, CH3). 13C
NMR (CDCl3): d 190.2, 164.7, 150.8, 148.2, 147.7, 139.7,
139.3, 134.2, 133.8, 133.7, 133.0, 132.4, 130.1, 130.0
129.7, 129.4, 128.7, 127.8, 127.7, 127.3, 126.8, 124.8,
124.4, 123.6, 133.7, 118.7, 19.8, 17.9, 15.2. 31P NMR
(H3PO4 as external standard, CDCl3/ppm): 25.69. IR
(KBr): 3427.3 (wb, O–H), 3051.5 (m, Ar–H), 1674.0 (s,
C@O), 1608.7 (s, C@N), 1530.4 (s, C@C), 1439.5 (s,
Ar–O) cmÀ1. Anal. Calc. for C48H43ClNNiO2P Æ EtOH:
C, 71.74; H, 5.90; N, 1.67. Found: C, 71.78; H, 5.49; N,
1.97%.
3.3.4. (1-Naphthyl){[3-(2,4,6-trimethylphenylimino)
methyl]-5-chloro-2-hydroxybenzaldehyde}
(triphenylphosphine) nickel(II) (2d)
Rufous crystal, Yield: 94.3%; m.p. 153–154 ꢁC. 1H
NMR (CDCl3): d 9.50 (d, J = 6.0 Hz, 1H, O@CH), 8.52
(s, 1H, N@CH), 7.82 (d, J = 6.0 Hz, 1H, Ar–H), 7.72 (d,
J = 6.0 Hz, 1H, Ar–H), 7.43 (t, J = 6.1 Hz, 6H, Ar–H),
7.34 (s, 6H, Ar–H), 7.11–7.23 (m, 6H, Ar–H), 6.94 (d,
J = 4.7 Hz, 2H, Ar–H), 6.76 (d, J = 5.6, 1H, Ar–H), 6.45
(s, 1H, Ar–H), 6.31 (s, 1H, Ar–H), 6.00 (s, 1H, Ar–H),
2.54 (s, 3H, CH3), 1.93 (s, 3H, CH3), 1.58 (s, 3H, CH3).
13C NMR (CDCl3): d 189.2, 163.7, 147.2, 138.6, 138.2,
136.2, 136.0, 133.2, 133.1, 132.8, 132.7, 132.5, 131.8,
131.3, 128.9, 127.6, 127.4, 127.3, 127.1, 126.8, 126.4,
126.2, 122.5, 120.7, 19.2, 18.6, 16.9. 31P NMR (H3PO4 as
external standard, CDCl3/ppm): 25.64. IR (KBr): 3449.9
(wb, O–H), 3051.9 (m, Ar–H), 1665.9 (s, C@O), 1605.4
(s, C@N), 1530.9 (s, C@C), 1479.5 (m, C@C), 1442.6 (s,
C@C), 1243.3 (m, Ar–O) cmÀ1
.
Anal. Calc. for
C44H35NO2ClPNi Æ CH2CH3OH: C, 70.75; H, 5.29; N,
1.91. Found: C, 70.39; H, 5.40; N, 2.03%.
3.3.2. (1-Naphthyl){[3-(2,6-diethylphenylimino)methyl]-
5-chloro-2-hydroxybenzaldehyde}(triphenylphosphine)
nickel(II) (2b)
Rufous crystal, Yield: 89.7%; m.p. 181–182 ꢁC. 1H
NMR (CDCl3): d 9.50 (d, J = 6.0 Hz, 1H, O@CH), 8.49
(s, 1H, N@CH), 7.86 (d, J = 9.0 Hz, 1H, Ar–H), 7.73 (d,
J = 3, 1H, Ar–H), 7.43 (t, J = 9.0, 6H, Ar–H), 7.30–7.33
(m, 5H, Ar–H), 7.28–7.32 (m, 7H, Ar–H), 7.13–7.15 (m,
1H, Ar–H), 6.83 (d, J = 6.0, 1H, Ar–H), 6.72 (q,
J = 3.0 Hz, 2H, Ar–H), 6.64 (t, J = 7.5, 1H, Ar–H), 6.25–
6.29 (m, 2H, Ar–H), 3.24 (7, J = 9.0, 6.0, 3.0 Hz, 2H,
CH2), 2.37 (q, J = 9.0, 6.0 Hz, 1H, CH2), 1.90 (q,
J = 9.0, 3.0 Hz, 1H, CH2), 1.28 (t, J = 6.0 Hz, 3H, CH3),
0.60 (t, J = 6.0 Hz, 3H, CH3). 13C NMR (CDCl3): d
190.3, 164.6, 149.6, 139.3, 134.3, 133.9, 133.8, 133.1,
130.2, 130.0, 129.8, 128.7, 127.7, 127.3, 125.3, 125.2,
124.5, 123.6, 123.1, 122.8, 121.8, 118.7, 25.9, 24.4, 14.6,
14.1. 31P NMR (H3PO4 as external standard, CDCl3/
ppm): 25.46. IR (KBr): 3450.0 (wb, O–H), 3051.0 (m,
Ar–H), 1673.9 (s, C@O), 1608.2 (s, C@N), 1530.9 (s,
C@C), 1440.9 (s, C@C), 1242.3 (w, Ar–O) cmÀ1. Anal.
Calc. for C46H39ClNNiO2P Æ 1/2EtOH: C, 71.82; H, 5.39;
N, 1.78. Found: C, 71.67; H, 5.16; N, 1.43%.
C@C), 1298.3 (m, Ar–O) cmÀ1
.
Anal. Calc. for
C45H37NO2ClPNi: C, 72.17; H, 4.98; N, 1.87. Found: C,
72.17; H, 5.16; N, 1.61%.
3.3.5. (1-Naphthyl){[3-(2,6-dibromo-4-methylphenylimino)
methyl]-5-chloro-2-hydroxybenzaldehyde} (triphenyl-
phosphine) nickel(II) (2e)
Rufous crystal, Yield: 89.0%; m.p. 158–159 ꢁC. 1H
NMR (CDCl3): d 9.46 (d, J = 8.4 Hz, 1H, O@CH), 8.49
(s, 1H, N@CH), 7.74–7.81 (m, 1H, Ar–H), 7.74 (d,
J = 3.0 Hz, 1H, Ar–H), 7.37–7.52 (m, 9H, ArH), 7.28–
7.35 (m, 6H, Ar–H), 7.06–7.15 (m, 5H, Ar–H), 6.78–6.83
(m, 2H, Ar–H), 6.40–6.47 (q, J = 7.5, 2H, Ar–H), 1.92 (s,
3H, CH3). 13C NMR (CDCl3): d 190.3, 167.1, 147.3,
146.7, 139.8, 139.7, 137.3, 137.2, 137.1, 134.8, 133.9,
133.8, 133.7, 132.4, 132.1, 132.0, 131.7, 131.1, 130.2,
130.0, 129.7, 129.0, 128.7, 128.5, 128.4, 127.8, 127.7,
126.9, 123.7, 123.8, 123.0, 122.8, 121.9, 118.9, 118.2,
117.6, 19.81. 31P NMR (H3PO4 as external standard,
CDCl3/ppm): 25.15. IR (KBr): 3439.9 (wb, O–H), 3052.5
(m, Ar–H), 1667.5 (s, C@O), 1608.3 (s, C@N), 1581.7 (m,
C@C), 1527.4 (s, C@C), 1480.0 (m, C@C), 1247.3 (m,
3.3.3. (1-Naphthyl){[3-(2,6-diisopropylphenylimino)
methyl]-5-chloro-2-hydroxybenzaldehyde}
(triphenylphosphine) nickel(II) (2c)
Rufous crystal, Yield: 75.1%; m.p. 180–181 ꢁC. 1H
NMR (CDCl3): d 9.94 (d, J = 6.0 Hz, 1H, O@CH), 8.45
(s, 1H, N@CH), 7.94 (d, J = 9.0 Hz, 1H, Ar–H), 7.33–
7.49 (m, 6H, Ar–H), 7.29–7.23 (m, 6H, Ar–H), 7.05–7.18
(m, 7H, Ar–H), 6.88 (q, 6.1 Hz, 2H, Ar–H), 6.69 (d,
J = 9.0 Hz, 1H, Ar–H), 6.27 (t, J = 9.0, 1H, Ar–H), 1.77
(d, J = 9.0 Hz, 3H, CH3), 1.45 (d, J = 6.0 Hz, 2H, CH),
1.32 (d, J = 6.0 Hz, 3H, CH3), 1.13 (d, J = 6.0 Hz, 3H,
CH3), 0.89 (d, J = 6.0 Hz, 3H, CH3). 13C NMR (CDCl3):
d 190.2, 164.7, 148.9, 146.8, 140.4, 139.2, 135.1, 133.8,
133.6, 133.1, 131.8, 130.1, 129.9, 129.5, 127.8, 127.7,
125.9, 123.8, 123.5, 123.4, 123.2, 122.1, 118.7, 29.5, 28.1,
26.1, 25.6, 22.7, 20.3. 31P NMR (H3PO4 as external
standard, CDCl3/ppm): 26.22. IR (KBr): 3427.4 (wb,
O–H), 3054.2 (m, Ar–H), 1677.3 (s, C@O), 1608.8 (s,
C@N), 1531.1 (s, C@C), 1438.9 (s, C@C), 1216.1 (m,
Ar–O)
cmÀ1
.
Anal.
Calc.
for
C43H31Br2ClN-
NiO2P Æ C2H5OH Æ PPh3: C, 63.75; H, 4.42; N, 1.18. Found:
C, 63.67; H, 3.98; N, 0.92%.
3.3.6. (1-Naphthyl){[3-(2,6-difluorophenylimino)methyl]-
5-chloro-2-hydroxybenzaldehyde}(triphenylphosphine)
nickel(II) (2f)
1
Yield: 67.5%; m.p. 135–136 ꢁC. H NMR (CDCl3): d
9.25 (dd, J = 8.7, 2.1 Hz, 1H, O@CH), 8.49 (s, 1H,
N@CH), 8.05 (d, J = 7.8 Hz, 1H, Ar–H), 7.72 (d, J = 3.0,
1H, Ar–H), 7.48–7.57 (m, 6H, Ar–H), 7.28–7.40 (m, 6H,
Ar–H), 7.16–7.19 (m, 3H, Ar–H), 7.02–7.14 (m, 3H, Ar–
H), 7.03 (d, J = 6.9, 1H, Ar–H), 6.77 (d, J = 7.1 Hz, 1H

Y.-M. Zhang et al. / Inorganica Chimica Acta 358 (2005) 4423–4430
4429
Ar–H), 6.53 (t, J = 7.5, 1H, Ar–H), 6.38–6.48 (m, 1H, Ar–
H), 6.20 (t, J = 5.7 Hz, 1H, Ar–H), 5.94 (t, J = 9.0 Hz, 1H,
Ar–H), 5.52 (t, J = 9.0 Hz, 1H, Ar–H). 13C NMR (CDCl3):
d 190.2, 167.7, 166.2, 156.0, 152.6, 149.7, 149.0, 139.8,
139.5, 137.3, 137.1, 134.3, 134.0, 133.9, 133.6, 132.5,
131.8, 130.1, 130.0, 129.9, 129.7, 129.5, 128.9, 128.7,
128.5, 128.4, 127.9, 127.8, 127.1, 125.6, 125.4, 123.8,
123.5, 123.1, 122.3, 119.0, 110.3, 110.0. 31P NMR (H3PO4
as external standard, CDCl3/ppm): 26.39. IR (KBr):
3434.2 (wb, O–H), 3052.3 (m, Ar–H), 1671.3 (s, C@O),
1605.9 (s, C@N), 1527.8 (s, C@C), 1475.0 (m, C@C),
1442.4 (s, C@C), 1242.9 (m, Ar–O) cmÀ1. Anal. Calc. for
C42H29ClF2NNiO2P Æ PPh3: C, 71.70; H, 4.41; N, 1.39.
Found: C, 71.84; H, 4.54; N, 1.21%.
atmosphere. Then, the required amount of cocatalyst
(MAO) was injected into the reactor using a syringe. As
the prescribed temperature was reached, the reactor was
pressurized to 10 atm. After stirring for the desired reaction
time, the reaction was quenched and treated using the sim-
ilar method described above for 1 atm reaction.
4. Conclusion
In this contribution, a series of new neutral aryl-
nickel(II) phosphine complexes bearing non-symmetric
bidentate chelate ligands, 3-aryliminomethyl-5-chloro-2-
hydroxybenzaldehyde, have been synthesized in a simple
route and acceptable yields and the structure of representa-
tive complexes (2b and 2d) has been confirmed by X-ray
crystallographic analysis. Moreover, using methylalumi-
noxane (MAO) as a cocatalyst, these complexes display
high ethylene oligomerization activities. After investigating
the catalytic conditions, the highest catalytic activity
was obtained as 5.73 · 105 g molÀ1 hÀ1 at 1 atm and 4.6 ·
106 g molÀ1 hÀ1 at 10 atm.
3.4. X-ray crystal structure determination of 2b and 2d
Intensity data of 2b were collected at 293(2) K on a Sie-
mens Smart CCD diffractometer with graphite-monochro-
˚
mated Mo Ka (k = 0.71073 A) radiation, using the /–x
scan mode. Data collection and reduction were performed
using the SMART and SAINT softwares [18]. Empirical absorp-
tion correction was applied to the raw intensities by using
the SADABS program [19]. The structure was solved by direct
methods and full-matrix least-squares method based on F2
using the SHELXTL program package [20]. Non-hydrogen
atoms were subjected to anisotropic refinement.
5. Supplementary material
Details of crystallographic data for the structures re-
ported in this paper have been deposited at the Cambridge
Crystallographic Data Centre and allocated the deposition
numbers CCDC 250442 for 2d and 250421 for 2b. Copies
of the information may be obtained free of charge from
The Director, CCDC, 12 Union Road, Cambridge CB2
1EZ, UK (fax: +44 1223 336 033; e-mail: deposit@ccdc.
cam.ac.uk or http://www.ccdc.ac.uk), upon request.
Intensity data of 2d were collected at 293(2) K on a Mer-
cury70 diffractometer with graphite-monochromated
˚
Molybdenumꢀ (k = 0.71073 A) radiation. Cell parameters
were obtained by the global refinement of the positions
of all collected reflections. Intensity data were corrected
by Lorentz and polarization effects and empirical absorp-
tions were applied by using the CRYSTALCLEAR program.
The structure was solved by direct methods. The final
refinement was done by full-matrix least-squares on F2
methods, with anisotropic thermal parameters for non-
hydrogen atoms and isotropic thermal parameters for geo-
metric hydrogen atoms by using the SHELXTL-97 package
[21].
Acknowledgments
This work was supported by Natural Science
Foundation (No. 20371040) of China, the Key Project of
Chinese Ministry of Education (No. 205161) and the
Youth Science and Technology Foundation of Gansu
province (3ZS041-A25-007). We thank Professor W.-H.
Sun for valuable help.
3.5. General procedure for ethylene oligomerization
References
A flame dried three-neck round flask was loaded with
the complex (2a–2f) and vacuum-filled three times by nitro-
gen and then two times by ethylene. Then, the freshly dis-
tilled toluene was charged with ethylene and stirred for
10 min. MAO was added by a syringe. The reaction mix-
ture was stirred under 1 atm ethylene pressure for a limited
time and the catalytic reaction was terminated with acidi-
fied water. An aliquot of the reaction mixture was analyzed
by GC and GC–MS. High-pressure ethylene polymeriza-
tion was performed in a stainless steel autoclave (2000 ml
capacity) equipped with gas ballast through a solenoid
clave for continuous feeding of ethylene at constant pres-
sure. 1000 ml toluene containing the catalyst precursor
was transferred to the fully dried reactor under nitrogen
[1] (a) W. Keim, Angew. Chem., Int. Ed. Engl. 29 (1990) 235;
´
(b) J. Skupinska, Chem. Rev. 91 (1991) 613;
(c) G.J.P. Britovsek, V.C. Gibson, D.F. Wass, Angew. Chem., Int.
Ed. Engl. 38 (1999) 429;
(d) S.D. Ittel, L.K. Johnson, M. Brookhart, Chem. Rev. 100 (2000)
1169;
(e) S. Mecking, Angew. Chem., Int. Ed. Engl. 40 (2001) 534;
(f) V.C. Gibson, S.K. Spitzmesser, Chem. Rev. 103 (2003) 283.
[2] (a) L.K. Johnson, C.M. Killian, M. Brookhart, J. Am. Chem. Soc.
117 (1995) 6414;
(b) B.L. Small, M. Brookhart, A.M.A. Bennett, J. Am. Chem. Soc.
120 (1998) 4049;
(c) G.J.P. Britovsek, V.C. Gibson, B.S. Kimberley, P.J. Maddox,
S.J. McTavish, G.A. Solan, A.J.P. White, D.J. Williams, Chem.
Commun. (1998) 849;

4430
Y.-M. Zhang et al. / Inorganica Chimica Acta 358 (2005) 4423–4430
(d) G.J.P. Britovsek, M. Bruce, V.C. Gibson, B.S. Kimberley, P.J.
(f) S.Y. Desjardins, K.J. Cavell, J.L. Hoare, B.W. Skelton, A.N.
Sobolev, A.W. White, W. Keim, J. Organomet. Chem. 544 (1997)
163;
(g) C. Wang, S. Friedrich, T.R. Younkin, R.T. Li, R.H. Grubbs,
D.A. Bansleben, M.W. Day, Organometallics 17 (1998) 3149;
(h) T.R. Younkin, E.F. Connor, J.I. Henderson, S.K. Friedrich,
R.H. Grubbs, D.A. Bansleben, Science 287 (2000) 460;
(i) M.J. Rachita, R.L. Hu, J.L. Bennett, M. Brookhart, J. Polym. Sci.
Polym. Chem. 38 (2000) 4627;
Maddox, S. Mastroianni, S.J. McTavish, C. Redshaw, G.A. Solan,
S. Stromberg, A.J.P. White, D.J. Williams, J. Am. Chem. Soc. 121
(1999) 8728;
(e) C.M. Killian, D.J. Tempel, L.K. Johnson, M. Brookhart, J. Am.
Chem. Soc. 118 (1996) 11664;
(f) D.P. Gates, S.A. Svejda, E. Onate, C.M. Killian, L.K. Johnson,
P.S. White, M. Brookhart, Macromolecules 33 (2000) 2320;
(g) L.K. Johnson, S. Mecking, M. Brookhart, J. Am. Chem. Soc. 118
(1996) 267;
(h) S. Mecking, L.K. Johnson, L. Wang, M. Brookhart, J. Am.
Chem. Soc. 120 (1998) 888;
(j) D.L. Schroder, W. Keim, M.A. Zuideveld, S. Mecking, Macro-
molecules 35 (2002) 6071;
(k) F.A. Hicks, M. Brookhart, Organometallics 20 (2001) 3217;
(l) J.C. Jenkins, M. Brookhart, Organometallics 22 (2003) 250.
[6] P. Braunstein, G. Clerc, X. Morise, R. Welter, G. Mantovani,
Dalton Trans. (2003) 1601.
[7] R. Abeywickrema, M.A. Bennett, K.J. Cavell, M. Kony, A.F.
Masters, A.G. Webb, J. Chem. Soc., Dalton Trans. (1993) 59.
[8] E.K. van den Beuken, W.J.J. Smeets, A.L. Spek, B.L. Feringa,
Chem. Commun. (1998) 223.
[9] S.P. Meneghetti, P.J. Lutz, J. Kress, Organometallics 18 (1999) 2734.
[10] S. Tsuji, D.C. Swenson, R.F. Jordan, Organometallics 18 (1999)
4758.
[11] C. Carlini, M. Marchionna, A.M.R. Galletti, G. Sbrana, Appl.
Catal. A 206 (2001) 1.
(i) M.D. Leatherman, M. Brookhart, Macromolecules 34 (2001)
2748;
(j) M. Helldo¨rfer, J. Backhaus, H.G. Alt, Inorg. Chim. Acta 351
(2003) 34.
[3] (a) C.M. Killian, L.K. Johnson, M. Brookhart, Organometallics 16
(1997) 2005;
(b) S.A. Svejda, M. Brookhart, Organometallics 18 (1999) 65;
(c) B.L. Small, M. Brookhart, J. Am. Chem. Soc. 120 (1998) 7143;
(d) G.J.P. Britovsek, S. Mastroianni, G.A. Solan, S.P.D. Baugh, C.
Redshaw, V.C. Gibson, A.J.D. White, D.J. Williams, M.R.J. Else-
good, Chem. Eur. J. 6 (2000) 2221.
[4] (a) W. Keim, F.H. Kowaldt, R. Goddard, C. Kruger, Angew. Chem.,
¨
Int. Ed. Engl. 17 (1978) 466;
(b) M. Peuckert, W. Keim, Organometallics 2 (1983) 594;
(c) W. Keim, A. Behr, B. Gruber, B. Hoffmann, F.H. Kowaldt, U.
[12] M. Wang, X.M. Yu, Z. Shi, M.X. Qian, K. Jin, J.S. Chen, R. He, J.
Organomet. Chem. 645 (2002) 127.
[13] B.L. Small, Organometallics 22 (2003) 3178.
[14] W. Keim, J. Mol. Catal. 52 (1989) 19.
Kurschner, B. Limba¨cker, F.P. Sisting, Organometallics 5 (1986)
¨
2356;
[15] (a) Z. Li, W.-H. Sun, Z. Ma, Y. Hu, C. Shao, Chin. Chem. Lett. 12
(2001) 691;
(d) W. Keim, R.P. Schulz, J. Mol. Catal. 92 (1994) 21;
(e) M.C. Bonnet, F. Dahan, A. Ecke, W. Keim, R.P. Schulz, I.
Tkatchenko, Chem. Commun. (1994) 615;
(b) C. Shao, W.-H. Sun, Z. Li, Y. Hu, L. Han, Catal. Commun. 3
(2002) 405;
(f) J. Pietsch, P. Braunstein, Y. Chauvin, New J. Chem. 22 (1998)
467;
(c) L. Wang, W.-H. Sun, L. Han, Z. Li, Y. Hu, C. He, C. Yan, J.
Organomet. Chem. 650 (2002) 59;
(g) J. Heinicke, M. He, A. Dal, H.F. Klein, O. Hetche, W. Keim, U.
Flo¨rke, H.J. Haupt, Eur. J. Inorg. Chem. (2000) 431;
(h) K.A. Ostoja-Starzewski, J. Witte, Angew. Chem., Int. Ed. Engl.
24 (1985) 599;
(i) K.A. Ostoja-Starzewski, J. Witte, Angew. Chem., Int. Ed. Engl. 26
(1987) 63;
(j) U. Klabunde, S.D. Ittel, J. Mol. Catal. 41 (1987) 123;
(k) D. Matt, M. Huhn, J. Fischer, A. DeCian, W. Kla¨ui, I.
Tkatchenko, M.C. Bonnet, J. Chem. Soc., Dalton Trans. (1993)
1173;
(d) L. Wang, W.-H. Sun, L. Han, H. Yang, Y. Hu, X. Jin, J.
Organomet. Chem. 658 (2002) 62;
(e) L. Chen, J. Hou, W.-H. Sun, Appl. Catal. A 246 (2003) 11;
(f) W.-H. Sun, W. Zhang, T. Gao, X. Tang, L. Chen, Y. Li, X. Jin,
J. Organomet. Chem. 689 (2004) 917;
(g) F. Chang, D. Zhang, G. Xu, H. Yang, J. Li, H. Song, W.-H.
Sun, J. Organomet. Chem. 689 (2004) 936.
[16] (a) A. Zinke, F. Hanus, Z. Ziegler, J. Prakt. Chem. 152 (1939) 126;
(b) Z.-T. Cheng, L.-Q. Tian, G.-Q. Wu, Acta Chim. Sinica 40 (1982)
135 (in Chinese);
(l) V.C. Gibson, A. Tomov, A.J.P. White, D.J. Williams, Chem.
Commun. (2001) 719;
(m) R. Soula, J.P. Broyer, M.F. Llauro, A. Tomov, R. Spitz, J.
Claverie, X. Drujon, J. Malinge, T. Saudemont, Macromolecules
34 (2001) 2438.
(c) S. Taniguchi, Bull. Chem. Soc. Jpn. 57 (1984) 2683;
(d) H. Fironzabadi, Z. Mostafavipoor, Bull. Chem. Soc. Jpn. 56
(1983) 914.
[17] J. van Soolingen, H.D. Verkruijsse, M.A. Keegstra, L. Brandsma,
Synth. Commun. 20 (1990) 3153.
[5] (a) Z.J.A. Komon, X. Bu, G.C. Bazan, J. Am. Chem. Soc. 122 (2000)
12379;
[18] SMART 5.0 and SAINT 4.0 for windows NT: area detector control and
integration software, Bruker Analytical X-ray System, Inc., Madison,
WI, 1998.
[19] G.M. Sheldrick, SADABS: Program for Empirical Absorption Correc-
tion of Area Detector Data, University of Go¨ttingen, Germany, 1996.
[20] G.M. Sheldrick, SHELXTL: Structure Determination Software Pro-
gram, Bruker Analytical X-ray System, Inc., Madison, WI, 1997.
[21] G.M. Sheldrick, SHELXTL-97, Program for the Refinement of Crystal
Structures, University of Go¨ttingen, Germany, 1997.
(b) B.Y. Lee, X. Bu, G.C. Bazan, Organometallics 20 (2001) 5425;
(c) B.Y. Lee, G.C. Bazan, J. Vela, Z.J.A. Komon, X. Bu, J. Am.
Chem. Soc. 123 (2001) 5352;
(d) Y.H. Kim, T.H. Kim, B.Y. Lee, D. Woodmansee, X. Bu, G.C.
Bazan, Organometallics 21 (2002) 3082;
(e) S.Y. Desjardins, K.J. Cavell, H. Jin, B.W. Skelton, A.H. White,
J. Organomet. Chem. 515 (1996) 233;