Synthesis, structural characterization and catalysis of ethyl-substituted indenylnickel(II) halides

Article abstract of DOI:10.1016/j.poly.2004.03.001

The reaction of (1-Et-Ind)Li (1-Et-Ind=1-ethylindenyl) with 1.81 equivalent of Ni(PPh₃)₂Cl₂ in ether, followed by crystallization from CH₂Cl₂/hexane, affords (1-Et-Ind)Ni(PPh₃)Cl (1) in 58%

Full text of DOI:10.1016/j.poly.2004.03.001

Polyhedron 23 (2004) 1473–1478
www.elsevier.com/locate/poly
Synthesis, structural characterization and catalysis of
ethyl-substituted indenylnickel(II) halides
a,b,
a
c
Wan-Fei Li a,b, Hong-Mei Sun a,b, Qi Shen
*, Yong Zhang , Kai-Bei Yu
a
College of Chemistry and Chemical Engineering, Suzhou University, Suzhou 215006, PR China
b
The Key Laboratory of Organic Synthesis of Jiangsu Province, Suzhou University, Suzhou 215006, PR China
c
Chengdu Institute of Organic Chemistry, Chinese Academy of Sciences, Chengdu 610043, PR China
Received 11 February 2004; accepted 5 March 2004
Available online 9 April 2004
Abstract
The reaction of (1-Et-Ind)Li (1-Et-Ind ¼ 1-ethylindenyl) with 1.81 equivalent of Ni(PPh3)2Cl2 in ether, followed by crystallization
from CH2Cl2/hexane, affords (1-Et-Ind)Ni(PPh3)Cl (1) in 58% yield. Similar reaction of (1-Et-Ind)Li with 1.81 equivalent of
Ni(PPh3)2Br2 in 1,2-dimethoxyethane (DME) affords (1-Et-Ind)Ni(PPh3)Br (2) in 60% yield. The reaction of complex 1 with KI in
THF/acetone affords (1-Et-Ind)Ni(PPh3)I (3) quantitatively. Crystal structure analysis revealed that 2 and 3 are isomorphous. The
hapticities of the indenyl ligand in these complexes are very similar and significantly distorted from an idealized g5 mode to an
unsymmetrical g3 mode. The complexes are inert toward the insertion of styrene, but are able to catalyze the polymerization of
styrene effectively in the presence of PPh3 and NaBPh4.
ꢀ 2004 Elsevier Ltd. All rights reserved.
Keywords: Synthesis; Crystal structures; Indenyl ligand; Nickel complex; Catalysis
1. Introduction
kynyl, imidate, thiolate) [10] could act as effective pre-
catalysts in a number of reactions, such as the
oligomerization or polymerization of ethylene [11–15],
styrene [16] and phenylacetylene [17]. Preliminary stud-
ies have implied that the in situ generated cationic spe-
cies [Ind(PPh3)Ni]þ might be the active centers for these
reactions, which is in evidence by styrene reactions
catalyzed by in situ generated cations from (g3; g0-Ind–
CH2CH2NMe2)(PPh3)Ni–Cl [16]. However, detailed
knowledge about the structure–activity relationships of
indenyl nickel complexes seems still insufficient.
Recently, we have found that simple alkyl-substituted
indenylnickel complexes [(1-R-Ind)Ni(PPh3)Cl, R ¼ cy-
clopentyl, and benzyl] can efficiently initiate the poly-
merization of styrene in the presence of PPh3 and
NaBPh4, and the alkyl substituent has a manifest effect
on the catalytic activity of these complexes [18]. As an
extension, we report herein the synthesis and charac-
terization of a series of indenylnickel complexes con-
taining different halogen atom with the general formula
(1-Et-Ind)Ni(PPh3)X [1-Et-Ind ¼ 1-ethylindenyl; X ¼
Cl (1), Br (2) and I (3)], together with the initial
In recent years, the use of Ind (Ind ¼ indenyl anion
and its substituted derivatives) as supporting ligand
systems in transition metal coordination chemistry has
attracted considerable attention [1–5]. In comparison to
their Cp analogues (Cp ¼ cyclopentadienyl anion and its
substituted derivatives), many transition metal Ind
complexes possess greater reactivity owing to the so-
called ‘‘indenyl effect’’. The Ind ligands can be tuned
spontaneously to coordinated to the center metal from
g1 to g5 via relatively facile ‘‘ring slippage’’, thus lead-
ing to better stabilization of transition states or reaction
intermediates. However, their application in regard to
group 10 metal complexes remains relatively poorly
explored [6–9]. Recently, Zargarian reported that (In-
d)(PR3)Ni–X (Ind ¼ indenyl anion and its substituted
derivatives; R ¼ Ph, Me, Cy, Bu; X ¼ halide, alkyl, al-
* Corresponding author. Tel.: +86-512-65112513; fax: +86-512-
65112371.
E-mail address: qshen@suda.edu.cn (Q. Shen).
0277-5387/$ - see front matter ꢀ 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2004.03.001

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W.-F. Li et al. / Polyhedron 23 (2004) 1473–1478
investigation of their catalytic activities in the
polymerization of styrene.
their solubility in organic solvents is evidently better
than that of bis(triphenylphosphine)halides, e.g.,
Ni(PPh3)2Cl2.
As expected, among these complexes, 1 has the best
thermal stability, while 3 has the relatively lower thermal
stability. For example, the color of complex 1 remains
unchanged at 301–302 ꢁC (its melt point); however, the
decomposition of complex 3 is observed at 165–167 ꢁC.
Furthermore, complex 1 is slightly sensitive to air and
moisture, while both 2 and 3 are sensitive, especially the
later one, and can be kept for only a few minutes in open
air. However, all of them are relatively more sensitive to
air and moisture as compared to the corresponding
bis(triphenylphosphine)halides.
2. Results and discussion
2.1. Synthesis
The indenylnickel complexes 1 and 2 were synthesized
by the reaction of the corresponding Ni(PPh3)2Cl2 or
Ni(PPh3)2Br2 with (1-Et-Ind)Li (1-Et-Ind ¼ 1-ethylin-
denyl), respectively (Scheme 1). Because the reaction of
1-Et-Ind with an equimolar amount of n-BuLi in Et2O
gave a quantitative yield of (1-Et-Ind)Li, so freshly
prepared solution of indenyl lithium was directly used in
the following metathesis reaction. Thus, 1-Et-Ind re-
acted with n-BuLi in Et2O for half an hour at 0 ꢁC, and
the resultant solution was added dropwise into a stirring
suspension of Ni(PPh3)2Cl2 in Et2O, or a solution of
Ni(PPh3)2Br2 in 1,2-dimethoxyethane (DME), in 1:1.8
molar ratio at 0 ꢁC. After workup, the expected com-
plexes (1-Et-Ind)Ni(PPh3)X [X ¼ Cl (1), Br (2)] were
isolated as dark red crystals in 58% (1) or 60% (2) yield,
as substantiated by elemental analysis and 1H NMR
spectroscopy. Suitable crystals of 1 and 2 for X-ray
diffraction studies were grown from Et2O/hexane at
0 ꢁC. It is noteworthy that the reaction conditions, such
as concentration, temperature, and especially the rate of
the addition of (1-Et-Ind)Li, have an obvious effect on
the formation of indenylnickel complexes. It is of benefit
to prepare these complexes by the dropwise addition of
a dilute solution of (1-Et-Ind)Li to a dilute suspension
of Ni(PPh3)2Cl2 in Et2O, or a dilute solution of
Ni(PPh3)2Br2 in DME, at 0 ꢁC, since such conditions
could efficiently suppress the formation of the byprod-
ucts, i.e., the Ni(I) species and 1,10-biindene [19].
2.2. Crystal structures of (1-Et-Ind)Ni(PPh3)X [X ¼ Cl
(1), Br (2) and I (3)]
Since structural data for indenylnickel halides (1-R-
Ind)Ni(PPh3)X have seldom been reported [10], the
crystal structures of 1, 2 and 3 were determined in order
to assess the influence of the halogen on the structures of
these complexes. Complex 2 and 3 are isomorphous, and
the molecular structures of 1 and 2 are presented in Figs.
1 and 2, respectively. The crystallographic data and se-
lected bond lengths and angles for 1, 2 and 3 are listed in
Tables 1 and 2, respectively. The coordination geome-
tries around nickel atoms in 1, 2 and 3 are similar, i.e.,
each Ni in these complexes is bound to X, P, C1, C2,
and C9 based on the bond distances of Ni to these at-
oms, while the bond distances of the other two carbon
atoms of the five-membered ring, i.e., C3 and C8, to Ni
are significantly longer. Inspection of the C–C and Ni–C
bond distances for these complexes revealed that the
geometry of these complexes around Ni can be described
as a distorted square planar with C1@C9 occupying a
single coordination site (reflected by a shorter C1–C9
bond relative to C1–C2 bond) (Table 2). In all of these
structures, the Ind ligand is significantly distorted away
from an idealized g5 mode toward a fairly unsymmetric
g3 coordination, which is common in this family of
complexes [10]. Such distortions can be mainly attrib-
uted to the tendency of Ni(II) to avoid forming an 18-
electron configuration and the unequal trans influences
of the PPh3 and X (Cl, Br and I) groups [20]. Somewhat
to our surprise, except for the Ni–X bond distance, the
halogen atom has little effect on the structures of these
complexes. For instance, almost the same Ni–Ind in-
teraction occurred in present case. According to the
literature [20], the Ni–Ind interaction can be compared
The reaction of complex 1 with KI in THF/acetone at
50 ꢁC afforded the product (1-Et-Ind)Ni(PPh3)I (3)
quantitatively. After workup, the red microcrystals were
obtained in high yield as identified by elemental analysis
1
and H NMR spectroscopy. Suitable crystals of 3 for
X-ray diffraction studies were grown from Et2O/hexane
at 0 ꢁC.
Complexes 1, 2, and 3 are soluble in dichlorome-
thane, toluene, DME, THF and diethyl ether. However,
complex 1 is completely insoluble in hexane, while
complex 2 and 3 have a little solubility in hexane. Due to
their good solubility in CH2Cl2 or Et2O and sparing
solubility in hexane, they can be crystallized from
CH2Cl2/hexane (or Et2O/hexane) in high yield. Notably,
Ni(PPh3)2X2
Et2O
0 oC
1-Et-Ind + n-BuLi
1-Et-IndLi
(1-Et-Ind)Ni(PPh3)X
Et2O or DME, 0 oC/ r.t.
X = Cl (1), Br (2)
Scheme 1.

W.-F. Li et al. / Polyhedron 23 (2004) 1473–1478
1475
Ind interaction and Ni–P interaction are very similar
among these complexes, indicating that the halogen
atom play a slight role on these interactions in the in-
denylnickel halide, which is quite different from the role
of the alkyl substituent on indenyl ring [18]. On the
other hand, as expected, apparent difference among the
Ni–X bond distance in these complexes is observed, i.e.,
Ni–I > Ni–Br > Ni–Cl (Table 2).
Since the nature of the Ni–Ind interaction in solution
is believed to be able to influence substantially the re-
activity of Ind complexes, it is important to understand
Ind hapticity in solution. Zargarian’s group [20] had
reported that, for (1-Me-Ind)Ni(PPh3)Cl (4) and its
methyl derivative, the 1H NMR resonances for the
symmetry-related pairs of protons (H2/H9, H4/H7, and
H5/H6) could be used as a convenient indicator of Ind
hapticity. Accordingly, they concluded that the solid
state structures of these complexes were maintained in
the solution. Herein, the same conclusion could also be
1
reached from the paired comparisons of the H NMR
spectra of these complexes (i.e., 1/4, 2/4, and 3/4), as
their 1H NMR spectra are very similar in pairs. For
example, the H2 resonance in 1 (3.37 ppm) or in 2 (3.61
ppm) is very close to the corresponding resonance for 4
(3.37 ppm).
Fig. 1. Molecular structure of complex 1.
2.3. The catalysis of (1-Et-Ind)Ni(PPh3)X [X ¼ Cl (1),
Br (2) and I (3)] in styrene polymerization
To the best of our knowledge, the catalytic activity of
indenyl nickel complexes for styrene reactions has been
reported only by Zargarian’s group, a chelating amino-
indenyl cationic nickel complex in situ generated from
the reaction of (g3; g0-Ind–CH2CH2NMe2)Ni(PPh3)Cl
and AgBPh4 (or AgBF4) for styrene polymerization or
a [(1-Me-Ind)Ni(PPh3)Cl/AgBF4 system for oligomeri-
zation of styrene[16]. Recently, we have found that
simple alkyl-substituted indenylnickel complexes [(1-R-
Ind)Ni(PPh3)Cl, R ¼ cyclopentyl and benzyl] could also
efficiently initiate the polymerization of styrene in the
presence of PPh3 and NaBPh4, and the alkyl substituent
has a manifest effect on the catalytic activity of these
complexes [18]. The purpose of NaBPh4 is to abstract
the Clꢀ ligand from these complexes and facilitate the
formation of cationic species [16], while the addition of
moderate PPh3 is of benefit to suppress the decompo-
sition of the cationic species [18]. In the present case, the
catalytic activity of (1-Et-Ind)Ni(PPh3)X [X ¼ Cl (1), Br
(2), I(3)] in styrene polymerization has been prelimi-
narily investigated. It is observed that complex 1 or 2 or
3 without NaBPh4 is inert toward the insertion of sty-
rene, however, together with NaBPh4 and PPh3, they
show highly catalytic activity for the polymerization of
styrene, and the halogen atom of (1-R-Ind)Ni(PPh3)X
possess an significantly effect on their catalytic activity.
For example, when styrene polymerization was carried
Fig. 2. Molecular structure of complex 2.
quantitatively by calculating geometrical parameters
such as the slip value (DM–C) ¼ [M–Cav (for C1,
C5)] ) [M–Cav (for C2, C4)]. In 1, DM–C ¼ 0.256,
meanwhile the values of 2 and 3 are 0.250 and 0.246,
respectively (Table 2), indicating almost the same slip-
fold distortion of the Ind ligand in these complexes.
Furthermore, as the observed values of the C1–C9, C1–
C2, Ni–C2 and Ni–C9 bond lengths reflect the delocal-
ization of the allyl moiety of Ind ligand, so the local
symmetry in the coordination of the allyl moiety are also
very similar in 1, 2 and 3, and indicate an unsymmetrical
g3 mode Ni–Ind interaction in these complexes. Addi-
tionally, the difference among the Ni–P bond distance in
these complexes is rather small, and just a bit longer
bond distance is observed in 3 [2.1805(9)] as compared
to that of in 1 [2.179(1)] or 2 [2.178(1)]. Thus, both Ni–

1476
W.-F. Li et al. / Polyhedron 23 (2004) 1473–1478
Table 1
Crystal data and experimental parameters for 1, 2 and 3
1
2
3
Empirical formula
Formular weight
T (K)
C29H26ClNiP
499.63
291(2)
C29H26BrNiP
544.10
193(2)
C29H26INiP
591.10
193(2)
ꢀ
k (Mo Ka) (A)
0.71073
monoclinic
P2ð1Þ=n
0.71070
triclinic
0.71070
triclinic
Crystal system
Space group
Unit cell dimensions
ꢁ
ꢁ
P1
P1
ꢀ
a (A)
9.731 (2)
28.572(8)
9.750(2)
90
9.011(4)
10.339(5)
14.583(7)
83.31(1)
86.94(1)
64.598(7)
1219(1)
2
9.145(1)
10.613(1)
14.227(3)
85.00(1)
89.08(1)
64.821(7)
1244.5(3)
2
ꢀ
b (A)
ꢀ
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
113.42(2)
90
3
ꢀ
V (A )
2487.5(10)
4
1.334
Z
Dcalc (g/cm3)
1.482
2.520
1.577
2.099
Absorption cofficent (mmꢀ1
F ð000Þ
)
0.966
1040
556
0.60 · 0.30 · 0.11
55.0
592
0.09 · 0.49 · 0.35
55.0
Crystal size (mm)
2hmax (ꢁ)
0.50 · 0.32 · 0.22
50.0
4199
Reflections collected
Independent reflections
Goodness-of-fit on F 2
Final R indices [I > 2rðIÞ]
Parameters refined
Rw
12 108
5447
1.02
28 068
5604
1.004
4381
0.845
0.0740
291
0.074
0.035
382
0.100
0.030
316
0.076
Table 2
Selected bond distances (A) and angles (ꢁ) in 1, 2 and 3
(Mw=Mn ¼ 2:1) for 1, Mn ¼ 12000 (Mw=Mn ¼ 2:6) for 2,
and Mn ¼ 9000 (Mw=Mn ¼ 1:8) for 3. The differences
among their catalytic activities are probably due to the
different Ni–X distance together with the different
thermal stability of these complexes at the polymeriza-
tion temperature. By the way, some experimental results
are in the negative of a radical pathway. Careful ex-
periments showed that the addition of varying amounts
of 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO), a
strong and efficient radical scavenger, only partly re-
duced the speed of the present styrene polymerization.
For instance, when 1% or 2% (referred to monomer
weight) amounts of TEMPO were added into NaBPh4/1/
PPh3 (in large excess to 1 mol) at the beginning of the
polymerization, the polymer yield still remained at 75%
(no adding TEMPO, yield is 100%). Meanwhile, styrene
polymerization initiated by azobis(isobutyronitrile)
(AIBN; conditions are the same as 1), which is a clas-
sical radical initiator, was completely hindered by add-
ing the same amount of TEMPO. Thus, combination
with the reported results [16,18] indicate that the pres-
ent styrene polymerization mainly also be catalyzed
by the in situ generated cationic species [1-Et-
Ind(PPh3)Ni(PPh3)]þ, which produced from the reaction
of (1-Et-Ind)Ni(PPh3)X and NaBPh4 in the presence of
PPh3. Further investigations focusing on the detailed
structure–activity relationships and mechanistic aspects
of the polymerization using these complexes are now in
progress.
ꢀ
1
2
3
Bond distances
Ni–P
Ni–X
2.179(1)
2.185(1)
2.048(4)
2.022(4)
2.303(4)
2.373(4)
2.142(4)
1.418(5)
1.398(5)
1.440(5)
1.417(5)
1.469(5)
1.837(4)
1.820(4)
1.814(4)
2.178(1)
2.319(1)
2.072(5)
2.032(5)
2.315(5)
2.351(5)
2.135(6)
1.424(5)
1.401(4)
1.454(5)
1.425(4)
1.462(4)
1.828(5)
1.828(5)
1.823(5)
2.1805(9)
2.4971(6)
2.064(4)
2.031(5)
2.310(4)
2.340(4)
2.126(3)
1.411(6)
1.402(4)
1.463(5)
1.415(4)
1.462(5)
1.823(4)
1.833(4)
1.818(3)
Ni–C1
Ni–C2
Ni–C3
Ni–C8
Ni–C9
C1–C2
C1–C9
C2–C3
C3–C8
C8–C9
P–C12
P–C18
P–C24
Bond angles
C2–Ni–C9
C2–Ni–P
C9–Ni–P
X–Ni–P
66.58(15)
66.64(2)
66.5(1)
99.7(1)
100.11(12)
166.42(10)
97.70(4)
0.256
100.10(2)
166.40(2)
95.33(5)
0.250
166.1(1)
99.27(3)
0.246
ꢀ
DM–C (A)
out in toluene at 80 ꢁC with NaBPh4/1/PPh3 ¼ 7:1:4
(mole ratio), [styrene]/[1] ¼ 300 (mole ratio), the polymer
yield could reached 100% after 24 h, but only 84% for 2
and 41% for 3 under the same conditions. The obtained
polystyrene is soluble in THF with Mn ¼ 18000

W.-F. Li et al. / Polyhedron 23 (2004) 1473–1478
1477
3. Experimental
of Ni(PPh3)2Cl2 (3.53 g, 5.4 mmol) in Et2O. The dark
red product was obtained by recrystallization from
CH2Cl2/hexane at )30 ꢁC (979 mg, 60%), m.p. 285–287
ꢁC. Anal. Calc. for C29H26BrNiP: C, 63.31; H, 4.68.
Found: C, 64.02; H, 4.82%. 1H NMR (400 MHz, C6D6):
7.68 (m, 5H, PPh3), 7.40 (t, 1H, H6), 7.14 (m, 1H, H7),
7.02 (m, 10H, PPh3), 6.90 (t, 1H, H5), 6.35 (br s 1H,
H2), 6.17 (d, 1H, H4), 3.61 (br s, 1H, H1), 2.01 (m, 1H,
CH2), 2.47 (m, 1H, CH2), 1.37(t, 3H, CH3). Crystals
suitable for X-ray diffraction studies were obtained by
recrystallization from Et2O/hexane at 0 ꢁC.
All manipulations were performed under pure argon
with rigorous exclusion of air and moisture using stan-
dard Schlenk techniques. Solvents were distilled from
Na/benzophenone ketyl prior to use. 2,2,6,6-Tetra-
methyl-1-piperidinyloxy (TEMPO) (Aldrich) was used
as received. Azobis(isobutyronitrile) (AIBN) were re-
crystallized from 95% ethanol. Indene (Fluka) (dried
ꢀ
over 4 A molecular sieves) and styrene (dried over
CaH2) were distilled before use. (PPh3)2NiCl2 [21] and
(PPh3)2NiBr2 [22] were prepared by published methods.
1-Ethylindene was prepared according to the literature
method [23]. Melting points were determined in sealed
Ar-filled capillaries and are uncorrected. Carbon and
hydrogen analyses were performed by direct combustion
on a Carlo Erba-1110 instrument; quoted data are the
3.3. Synthesis of (Et-Ind)Ni(PPh3)I (3)
A Schlenk flask was charged with a solution of 1 (499
mg, 1 mmol) in THF (20 ml) and a stir bar. To this
solution, a solution of KI (200 mg, 1.2 mmol) in acetone
(10 ml) was added. The resultant mixture was stirred for
12 h at 50 ꢁC, evaporated to dryness and extracted with
Et2O. The product was obtained by evaporization of the
solvent as a red solid (ca. quantitative yield), m.p. 165–
167 ꢁC (dec.). Anal. Calc. for C29H26INiP: C, 58.92; H,
1
average of at least two independent determinations. H
NMR (C6D6) spectra were measured on a Unity Inova-
400 spectrometer. Molecular weight and molecular
weight distributions were determined against polysty-
rene standard by gel permeation chromatography
(GPC) on a Waters 1515 apparatus with three HR col-
umns (HR-1, HR-3 and HR-4); THF was used as an
eluent at 30 ꢁC.
1
4.43. Found: C, 58.54; H, 4.53%. H NMR(400 MHz,
C6D6): 7.66 (m, 5H, PPh3), 7.41 (t, 1H, H6), 7.14 (m,
1H, H7), 7.03 (m, 10H, PPh3), 6.94 (t, 1H, H5), 6.35 (br
s 1H, H2), 6.17 (d, 1H, H4), 3.93 (br s, 1H, H1), 2.87 (m,
1H, CH2), 2.46 (m, 1H, CH2), 1.37 (t, 3H, CH3).
Crystals suitable for X-ray diffraction studies were ob-
tained by recrystallization from Et2O/hexane at 0 ꢁC.
3.1. Synthesis of (1-Et-Ind)Ni(PPh3)Cl (1)
A Schlenk flask was charged with 1-Et-Ind (0.43 g, 3
mmol), Et2O (30 ml) and a stir bar. To this solution was
added a solution of n-BuLi in hexane (2.3 ml, 3 mmol)
dropwise via syringe at 0 ꢁC. The solution was stirred for
30 min and then added slowly to a stirring suspension of
Ni(PPh3)2Cl2 (3.53 g, 5.4 mmol) in Et2O (60 ml) at 0 ꢁC.
The color of the solution immediately changed to red.
The resultant solution was then stirred for another 40
min at room temperature, filtered, and evaporated to
dryness. The residue was washed with hexane (3· ca. 20
ml) to remove PPh3 and other byproducts and recrys-
talized from CH2Cl2/hexane at )30 ꢁC to give the
product as a dark red needle crystals (869 mg, 58%)
suitable for elemental analysis, m.p. 301–302 ꢁC. Anal.
Calc. for C29H26 ClNiP: C, 69.74; H, 5.21. Found: C,
3.4. A typical procedure for polymerization of styrene
A typical polymerization reaction is as follows. Un-
der dry argon, the solid initiator 1 (10 mg, 0.02 mmol),
PPh3 (21 mg, 0.08 mmol), NaBPh4 (48 mg, 0.14 mmol),
toluene (0.2 ml) and styrene (1.2 ml, 0.01 mol) were
added into a dry glass ampule in turn. Then, the sealed
ampule was placed in a water bath held at 80 ꢁC. After a
definite reaction time, the polymerization was stopped
by adding 1 ml of 5% HCl/ethanol. After evaporation of
solvent and unreacted monomer, the resulted polymer
was dissolved in THF, followed by precipitation in 95%
ethanol. After filtration, the white polymer was dried in
vacuum at room temperature overnight. The polymer
yield was determined gravimetrically.
1
69.65; H, 5.25%. H NMR (400 MHz, C6D6): 7.80 (t,
1H, H6), 7.69 (m, 5H, PPh3), 7.40 (m, 1H, H7), 7.02 (m,
10H, PPh3), 6.89 (t, 1H, H5), 6.42 (br s, 1H, H2), 6.16
(d, 1H, H4), 3.37 (br s, 1H, H1), 1.80 (m, 2H, CH2), 1.39
(d, 3H, CH3). Crystals suitable for X-ray diffraction
studies were obtained by recrystallization from Et2O/
hexane at 0 ꢁC.
3.5. X-ray structural determination of 1, 2 and 3
Suitable single crystals of complex 1, 2 and 3 were
each sealed in a thin-walled glass capillary for X-ray
structural analysis. Diffraction data were collected on a
Siemens SMART CCD area detector using theta scans
for 1, or a Rigaku Mercury CCD area detector using
omega scans for 2 and 3. The crystal structures of 1 and
3 were solved by direct methods using the SHELXS-97
program, and the crystal structures of 2 was solved by
3.2. Synthesis of (1-Et-Ind)Ni(PPh3)Br (2)
The synthesis of compound 2 was carried out as de-
scribed for 1, but a solution of Ni(PPh3)2Br2 (4.01 g, 5.4
mmol) in DME (60 ml) was used in place of the solution

1478
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Patterson methods using the CRYSTALSTRUCTURE
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CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (fax:
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We thank the Chinese National Natural Science
Foundation (20272040), the Department of Education
of Jiangsu Province (02KJB150002) and the Key Lab-
oratory of Organic Chemistry of Jiangsu Province for
the financial support.
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