Highly active 8-benzoxazolyl- or 8-benzothiazolyl-2- alkylquinolinylnickel(II) complexes for ethylene dimerization and vinyl polymerization of norbornene

Article abstract of DOI:10.1016/j.poly.2012.06.056

The series of nickel halide complexes LNiX₂ (C1-C6, X = Cl; C7-C12, X = Br), where L represents one of 8-benzoxazolyl-2-alkylquinoline or 8-benzothiazolyl-2-alkylquinoline derivatives, have been prepared. The molecular structures of the representative complexes C1, C3, C6 and C11 were determined by single crystal X-ray diffraction. Upon activation with ethylaluminium sesquichloride (EASC), all nickel complex pre-catalysts exhibited good activities for ethylene dimerization. Furthermore, such nickel pre-catalysts, in the presence of methylaluminoxane (MAO), were capable of the vinyl polymerization norbornene.

Full text of DOI:10.1016/j.poly.2012.06.056

Polyhedron 52 (2013) 1138–1144
Contents lists available at SciVerse ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Highly active 8-benzoxazolyl- or 8-benzothiazolyl-2-alkylquinolinylnickel(II)
complexes for ethylene dimerization and vinyl polymerization of norbornene
Peng Hao , Shengju Song , Tianpengfei Xiao , Yan Li , Carl Redshaw , Wen-Hua Sun a,
a,c
a
a
a
b,
⇑
⇑
a
Key Laboratory of Engineering Plastics and Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Science, Beijing 100190, China
Energy Materials Laboratory, School of Chemistry, University of East Anglia, Norwich NR4 7TJ, UK
Patent Examination Cooperation Center of The Patent Office, SIPO, Beijing 100081, China
b
c
a r t i c l e i n f o
a b s t r a c t
Article history:
Available online 30 June 2012
The series of nickel halide complexes LNiX2 (C1–C6, X = Cl; C7–C12, X = Br), where L represents one of 8-
benzoxazolyl-2-alkylquinoline or 8-benzothiazolyl-2-alkylquinoline derivatives, have been prepared. The
molecular structures of the representative complexes C1, C3, C6 and C11 were determined by single crys-
tal X-ray diffraction. Upon activation with ethylaluminium sesquichloride (EASC), all nickel complex pre-
catalysts exhibited good activities for ethylene dimerization. Furthermore, such nickel pre-catalysts, in
the presence of methylaluminoxane (MAO), were capable of the vinyl polymerization norbornene.
Ó 2012 Elsevier Ltd. All rights reserved.
Dedicated to Prof. Alfred Werner on the
1
00th Anniversary of his Nobel prize in
Chemistry in 1913.
Keywords:
Nickel complex
8
8
-Benzoxazolyl-2-alkylquinoline
-Benzothiazolyl-2-alkylquinoline
Ethylene dimerization
Norbornene polymerization
1
. Introduction
2-yl)quinoline derivatives were employed, and the resulting sys-
tems were found to maintain high activity during ethylene poly-
With the ever increasing demand for more
a
-olefins to meet the
merization conducted at high reaction temperature (100 °C)
[90,91]. Herein, 2-(2-alkylquinolin-8-yl)benzoxazole and 2-(2-
alkylquinolin-8-yl)benzothiazole derivatives were synthesized and
used to form their nickel complexes. Upon activation with ethylal-
need for synthetic lubricants, plasticizers and surfactants [1], new
complex pre-catalysts capable of ethylene dimerization and oligo-
merization have been explored both in academia and industry [2].
Additionally, interest in the area was resurrected both by the Shell
higher olefin process (SHOP), which employed nickel complex
3 2 3
uminium sesquichloride (Et Al Cl , EASC), these nickel complexes
performed with high activities for ethylene dimerization. More-
over, they show good activities for the vinyl polymerization of nor-
bornene in presence of methylaluminoxane (MAO). The catalytic
performance of the title nickel complexes in ethylene dimerization
and vinyl polymerization of norbornene is discussed.
pre-catalysts [1,3,4], and by the discovery that
a-diiminonickel
complex pre-catalysts were highly active for ethylene polymeriza-
tion [5]. Subsequently, nickel complexes have been extensively ex-
plored, and various different ligand sets have been employed,
which can be classified as bidentate ligands such as N^N [6–30],
N^O [31–39], N^P [40–44], P^O [45–48], P^P [49,50] or tridentate
ligands such as N^N^N [51–64], N^N^O [65–68], N^N^P [69–71],
and N^P^N [72,73]. Pre-catalysts have also been explored based
on other transition metals in ethylene oligomerization and poly-
merization, and have recently been reviewed [74–83]. In addition,
nickel complex pre-catalysts have shown high activity in the vinyl
polymerization of norbornene [39,84–89], producing soluble
polynorbornenes. N,N-bidentate Ni(II) complexes have attracted
particular attention, and recently substituted 8-(benzoimidazol-
2. Experimental
2.1. General considerations
All manipulations involving air and moisture-sensitive com-
pounds were carried out under an atmosphere of dried and puri-
fied nitrogen using standard Schlenk and vacuum-line
techniques. Toluene was dried over sodium metal and distilled un-
der nitrogen. Methylaluminoxane (MAO, 1.46 M solution in tolu-
ene) and modified ethylaluminoxane (MMAO, 1.93 M in heptane)
were purchased from Akzo Nobel Corp. Diethylaluminium chloride
⇑
Corresponding authors. Tel.: +44 1603 593137; fax: +44 1603 592003 (C.
Redshaw), tel.: +86 10 62557955; fax: +86 10 62618239 (W.-H. Sun).
(
2
Et AlCl, 1.70 M in toluene), ethylaluminium sesquichloride (EASC,
E-mail addresses: carl.redshaw@uea.ac.uk (C. Redshaw), whsun@iccas.ac.cn
(
W.-H. Sun).
0.87 M in toluene) were freely donated from Yande Chemicals
0
277-5387/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.poly.2012.06.056

P. Hao et al. / Polyhedron 52 (2013) 1138–1144
1139
À1
(
4
Yantai). 1H and 13C NMR spectra were recorded on Bruker DMX
00 MHz instruments at ambient temperature using TMS as an
H, 4.44; N, 10.10%. FT–IR (Diamond; cm ): 3063, 2915, 1691,
1611, 1596, 1502, 1417, 1328, 1255, 956, 837, 751, 685, 660.
2-(2-Ethylquinolin-8-yl)benzothiazole (L5). In a manner similar
internal standard. FT-IR spectra were recorded on a Perkin–Elmer
System 2000 FT-IR spectrometer. Elemental analysis was carried
out using a Flash EA 1112 microanalyzer. GC analyses were per-
formed with a Varian CP-3800 gas chromatograph equipped with
a flame ionization detector and a 30 m (0.2 mm i.d., 0.25
thickness) CP-Sil 5 CB column.
to that described for L4, L5 was prepared as a yellow solid in 75%
1
yield. H NMR (400 MHz; CDCl
3
; Me
4
Si) 9.07 (1H, d, J = 7.6 Hz),
8.14 (1H, d, J = 8.4 Hz), 8.02 (1H, d, J = 8.0 Hz), 7.90 (1H, d,
J = 8.8 Hz), 7.65 (1H, t, J = 10.3 Hz), 7.50 (1H, t, J = 10.2 Hz), 7.39
lm film
13
(1H, t, J = 10.0 Hz), 3.21 (2H, m, –CH
NMR (100 MHz; CDCl ; Me Si) 163.9, 163.8, 152.1, 144.2, 138.4,
36.7, 130.4, 130.2, 129.8, 126.7, 125.9, 125.6, 124.7, 123.0,
121.5, 121.4, 32.13, 13.98. Anal. Calc. for C18 S (290.38): C,
4.45; H, 4.86; N, 9.65. Found: C, 74.35; H, 4.90; N, 9.59%. FT-IR
2
–) 1.58 (3H, m, –CH
3
).
C
3
4
1
2
.2. Syntheses and characterization
14 2
H N
7
À1
2
-(2-Methylquinolin-8-yl)benzoxazole (L1). A reaction mixture
(Diamond; cm ): 3052, 2931, 1612, 1597, 1501, 1426, 1318,
1250, 1048, 953, 840, 755, 728, 685, 659.
of 2-methylquinoline-8-carboxylic acid (1.87 g, 10.0 mmol), 2-
aminophenol (1.09 g, 10.0 mmol), and polyphosphoric acid (PPA,
2-(2-Propylquinolin-8-yl)benzothiazole (L6). In a manner simi-
9
.00 g) was refluxed for 6 h at 170 °C. The solvent was removed
lar to that described for L4, L6 was prepared as a yellow solid in
1
(
rotary evaporator) and the resulting solid was eluted with petro-
73% yield.
3 4
H NMR (400 MHz; CDCl ; Me Si) 9.07 (1H, d,
leum ether on a silica gel column. The second eluting part was col-
J = 8.2 Hz), 8.14 (1H, t, J = 10.3 Hz), 8.03 (1H, d, J = 8.4 Hz), 7.91
(1H, d, J = 8.8 Hz), 7.65 (1H, t, J = 10.3 Hz), 7.50 (1H, t, J = 10.1 Hz),
7.41–7.38 (2H, m), 3.14 (2H, t, J = 10.2 Hz), 2.12–2.03 (2H, m),
lected, concentrated to give a yellow solid and L1 was obtained in
1
5
8
7% yield. H NMR (400 MHz; CDCl
3
; Me
4
Si) 8.43 (1H, d, J = 8.6 Hz),
1
3
.12 (1H, d, J = 8.4 Hz), 7.97 (1H, d, J = 8.8 Hz), 7.88 (1H, m), 7.68
3 3 4
1.10 (3H, t, J = 10.0 Hz, –CH ). C NMR (100 MHz; CDCl ; Me Si)
(
CH
1H, m), 7.61 (1H, t, J = 10.3 Hz), 7.41–7.37 (3H, m), 2.82 (3H, s, –
163.9, 162.8, 152.0, 144.3, 138.4, 136.7, 130.5, 130.1, 129.8,
126.8, 125.8, 125.6, 124.6, 123.0, 121.9, 121.5, 40.94, 22.97,
1
3
3
).
3 4
C NMR (100 MHz; CDCl ; Me Si) 163.0, 160.8, 151.3,
1
1
45.7, 142.3, 136.5, 132.6, 131.4, 127.0, 125.9, 125.2, 125.1,
24.4, 122.7, 120.5, 110.8, 26.13. Anal. Calc. for
14.18. Anal. Calc. for C19
H
16
N
2
S (304.41): C, 74.97; H, 5.30; N,
À1
C
17
H
12
N
2
O
9.20. Found: C, 74.85; H, 5.43; N, 9.09%. FT-IR (Diamond; cm ):
3053, 2960, 1611, 1598, 1500, 1416, 1319, 1256, 960, 835, 753,
729, 670.
(
260.29): C, 78.44; H, 4.65; N, 10.76. Found: C, 78.15; H, 4.74; N,
À1
1
1
0.59%. FT-IR (Diamond; cm ): 3057, 2916, 1622, 1609, 1585,
497, 1452, 1431, 1238, 1124, 836, 763, 750, 664.
Preparation of C1. To a solution of the ligand 2-(2-methylquin-
2
-(2-Ethylquinolin-8-yl)benzoxazole (L2). In a manner similar
2 2
olin-8-yl)benzoxazole (L1, 0.260, 1.0 mmol) in CH Cl (10 mL),
to that described for L1, L2 was prepared as a yellow solid in 74%
NiCl O (0.237 g, 1.0 mmol) was added. The reaction mixture
was stirred at room temperature for 12 h to afford a yellow
precipitate from the reaction mixture (C1, 0.491 g, 88% yield). Anal.
2
Á6H
2
1
yield. H NMR (400 MHz; CDCl
3
; Me
.14 (1H, d, J = 8.5 Hz), 7.97 (1H, d, J = 8.1 Hz), 7.89–7.85 (1H, m),
.69–7.66 (1H, m), 7.61 (1H, t, J = 10.2 Hz), 7.41–7.38 (3H, m),
4
Si) 8.42 (1H, d, J = 8.0 Hz),
8
7
3
Calc. for C17
H
12Cl
2
N
2
NiO (389.89): C, 52.37; H, 3.10; N, 7.18.
1
3
À1
.11–3.05 (2H, m), 1.43 (3H, t, J = 10.1 Hz, –CH
; Me Si) 165.1, 163.5, 151.5, 145.7, 142.1, 136.4,
32.5, 131.4, 127.2, 126.1, 125.1, 124.4, 121.6, 120.3, 110.8,
0.43, 32.31, 12.98. Anal. Calc. for C18 O (274.32): C, 78.81;
3
).
C NMR
Found: C, 52.25; H, 3.20; N, 7.10%. FT-IR (Diamond; cm ): 3261,
3050, 1620, 1600, 1574, 1554, 1454, 1290, 1152, 1023, 849, 754,
700.
(
100 MHz; CDCl
3
4
1
5
H
14
N
2
Preparation of C2. Using the same procedure as for the synthesis
H, 5.14; N, 10.21. Found: C, 78.79; H, 5.24; N, 10.39%. FT-IR (Dia-
mond; cm ): 3043, 2928, 1610, 1565, 1532, 1445, 1348, 1249,
of C1, L2 was used in the reaction with NiCl O to form C2 (yel-
2
Á6H
2
À1
low powder, 91% yield). Anal. Calc. for C18H14Cl N NiO (403.92): C,
2 2
1
172, 1122, 840, 761, 734, 662.
-(2-Propylquinolin-8-yl)benzoxazole (L3). In a manner similar
to that described for L1, L3 was prepared as a yellow solid in 64%
53.52; H, 3.49; N, 6.94. Found: C, 53.45; H, 3.60; N, 6.86%. FT-IR
(Diamond; cm ): 3051, 1617, 1600, 1569, 1547, 1515, 1352,
1291, 1248, 1152, 1034, 853, 758, 724, 684.
À1
2
1
yield. H NMR (400 MHz; CDCl
.12 (1H, d, J = 8.4 Hz), 7.96 (1H, d, J = 8.8 Hz), 7.88 (1H, m), 7.68
1H, m), 7.60 (1H, t, J = 10.1 Hz), 7.42–7.37 (3H, m), 3.01 (2H, t,
3
; Me
4
Si) 8.41 (1H, d, J = 8.0 Hz),
Preparation of C3. Using the same procedure as for the synthesis
8
(
of C1, L3 was used in the reaction with NiCl O to form C3 (red
2
Á6H
2
powder, 87% yield). Anal. Calc. for C19H16Cl N NiO (417.94): C,
2 2
1
3
J = 10.2 Hz), 1.95–1.86 (2H, m), 1.04 (3H, t, J = 9.8 Hz, –CH
NMR (100 MHz; CDCl
1
1
3
).
C
54.60; H, 3.86; N, 6.70. Found: C, 54.39; H, 3.91; N, 6.61%. FT-IR
À1
3
; Me
36.3, 132.5, 131.3, 127.2, 126.4, 125.1, 125.0, 124.3, 122.1,
20.4, 110.9, 41.32, 22.25, 14.17. Anal. Calc. for
4
Si) 164.2, 163.6, 151.6, 145.9, 142.2,
(Diamond; cm ): 3052, 2923, 1618, 1602, 1575, 1567, 1454,
1299, 1258, 1030, 852, 719, 687.
C
19
H
16
N
2
O
Preparation of C4. Using the same procedure as for the synthesis
(
9
1
288.34): C, 79.14; H, 5.59; N, 9.72. Found: C, 79.15; H, 5.64; N,
.65%. FT-IR (Diamond; cm ): 3042, 2911, 1612, 1558, 1446,
348, 1249, 1182, 1112, 840, 761, 732, 660.
of C1, L4 was used in the reaction with NiCl O to form C4 (red
2
Á6H
2
À1
powder, 93% yield). Anal. Calc. for C17H12Cl N NiS (405.95): C,
2 2
50.30; H, 2.98; N, 6.90. Found: C, 50.25; H, 3.10; N, 6.82%. FT-IR
À1
2
-(2-Methylquinolin-8-yl)benzothiazole (L4). A reaction mix-
ture of 2-methylquinoline-8-carboxylic acid (1.87 g, 10.0 mmol),
-aminobenzenethiol (1.25 g, 10.0 mmol), PPA (9.00 g) was re-
(Diamond; cm ): 3052, 2163, 1602, 1562, 1511, 1427, 1181,
970, 757, 680.
2
Preparation of C5. Using the same procedure as for the synthesis
fluxed for 6 h at 170 °C. The solvent was removed (rotary evapora-
tor) and the resulting solid was eluted with petroleum ether on a
silica gel column. The second eluting part was collected, concen-
of C1, L5 was used in the reaction with NiCl
2
Á6H
2
O to form C5 (red
powder, 91% yield). Anal. Calc. for C18
H14Cl N NiS (419.98): C,
2 2
51.48; H, 3.36; N, 6.67. Found: C, 51.25; H, 3.40; N, 6.57%. FT-IR
À1
trated to give a yellow solid and L4 was obtained in 78% yield.
(Diamond; cm ): 3069, 1612, 1600, 1561, 1514, 1440, 1252,
1
H NMR (400 MHz; CDCl
3
4
; Me Si) 9.05 (1H, d, J = 7.6 Hz), 8.14
1130, 965, 851, 726, 679.
(
1H, d, J = 8.4 Hz), 8.01 (1H, d, J = 8.0 Hz), 7.91 (1H, d, J = 8.8 Hz),
Preparation of C6. Using the same procedure as for the synthesis
7
.65 (1H, t, J = 10.3 Hz), 7.50 (1H, t, J = 10.3 Hz), 7.41–7.37 (2H,
of C1, L6 was used in the reaction with NiCl O to form C6 (red
2
Á6H
2
13
m), 2.92 (3H, s, –CH
3
3 4
). C NMR (100 MHz; CDCl ; Me Si) 163.9,
powder, 91% yield). Anal. Calc. for C19H16Cl N NiS (434.01): C,
2 2
1
1
C
58.9, 152.1, 144.2, 138.3, 136.7, 130.4, 130.1, 129.8, 126.6,
25.8, 125.7, 124.7, 123.0, 122.4, 121.5, 25.06. Anal. Calc. for
S(276.36): C, 73.88; H, 4.38; N, 10.14. Found: C, 73.79;
52.58; H, 3.72; N, 6.45. Found: C, 52.65; H, 3.80; N, 6.30%. FT-IR
(Diamond; cm ): 3073, 1614, 1603, 1564, 1516, 1431, 1187,
971, 839, 756, 678.
À1
17
H
12
N
2

1
140
P. Hao et al. / Polyhedron 52 (2013) 1138–1144
Preparation of C7. To a solution of the ligand 2-(2-methylquin-
olin-8-yl)benzoxazole (L1, 0.260, 1.0 mmol) in CH Cl (10 mL),
DME)NiBr (0.308 g, 1.0 mmol) was added. The reaction mixture
Preparation of C12. Using the same procedure as for the synthe-
sis of C7, L6 was used in the reaction with (DME)NiBr to form C12
(red powder, 91% yield). Anal. Calc. for C19 NiS (519.88): C,
2
2
2
(
2
2 2
H16Br N
was stirred at room temperature for 12 h to afford a red precipitate
from the reaction mixture (C1, 0.491 g, 88% yield). Anal. Calc. for
43.64; H, 3.08; N, 5.36. Found: C, 43.55; H, 3.20; N, 5.15%. FT-IR
(Diamond; cm ): 3070, 2960, 1614, 1601, 1562, 1514, 1431,
À1
C
17
H
12Br
2
N
2
NiO (475.87): C, 42.65; H, 2.53; Br, 33.38; N, 5.85.
1188, 970, 838, 754, 679.
À1
Found: C, 42.55; H, 2.63; N, 5.70%. FT–IR (Diamond; cm ): 3055,
2
6
951, 1617, 1601, 1570, 1548, 1512, 1434, 1295, 1148, 884, 719,
87.
2.3. Crystal structure determinations
Preparation of C8. Using the same procedure as for the synthesis
Single crystals of complexes C1, C3, C6 and C11 suitable for X–
ray diffraction studies were obtained by slow diffusion of diethyl
ether into the methanol solutions of the individual nickel com-
of C7, L2 was used in the reaction with (DME)NiBr
low powder, 90% yield). Anal. Calc. for C18
2
to form C8 (yel-
NiO (489.88): C,
H
14Br
2
N
2
4
(
1
3.87; H, 2.86; N, 5.68. Found: C, 43.99; H, 2.91; N, 5.57%. FT-IR
plexes. Diffraction data for complexes C1ÁCH
were collected on a Rigaku Saturn724+ CCD with graphite mono-
chromated Mo K radiation (k = 0.71073 Å), and cell parameters
3
OH, C3, C6 and C11
À1
Diamond; cm ): 3041, 1618, 1602, 1572, 1512, 1455, 1289,
026, 846, 750, 670.
Preparation of C9. Using the same procedure as for the synthesis
a
were obtained by global refinement of the positions of all collected
reflections. Intensities were corrected for Lorentz and polarization
effects and empirical absorption. Data were collected using phi-
scans and the structures were solved by direct methods (SIR97)
using the SHELX97 software [92] and the refinement was by full-ma-
trix least squares on F2. All non–hydrogen atoms were refined
anisotropically. Crystal data and processing parameters for
of C7, L3 was used in the reaction with (DME)NiBr
powder, 92% yield). Anal. Calc. for C19
5.02; H, 3.18; N, 5.53. Found: C, 45.25; H, 3.20; N, 5.41%. FT-IR
2
to form C9 (red
H
16Br N NiO(503.90): C,
2 2
4
(
1
À1
Diamond; cm ): 3033, 1616, 1600, 1570, 1512, 1475, 1289,
022, 846, 755, 670.
Preparation of C10. Using the same procedure as for the synthe-
sis of C7, L4 was used in the reaction with (DME)NiBr
red powder, 93% yield). Anal. Calc. for C19 NiS (434.01): C,
2.58; H, 3.72; N, 6.45. Found: C, 52.45; H, 3.70; N, 6.40%. FT-IR
2
to form C10
C1ÁCH
.4. General procedure for ethylene dimerization
Ethylene dimerization at 10 bar ethylene pressure was per-
3
OH, C3, C6 and C11 are summarized in Table 1.
(
5
(
9
2 2
H16Cl N
2
À1
Diamond; cm ): 3051, 3012, 1602, 1562, 1511, 1440, 1179,
70, 846, 755, 679.
Preparation of C11. Using the same procedure as for the synthe-
formed in a stainless steel autoclave (0.25 L capacity) equipped
with a mechanical stirrer, a temperature controller and gas ballast
through a solenoid clave for continuous feeding of ethylene at con-
stant pressure. The catalyst precursor was dissolved in 50 ml tolu-
ene in a Schlenk tube stirred with a magnetic stirrer and injected
into the reactor under an ethylene flux. The co-catalyst and
sis of C7, L5 was used in the reaction with (DME)NiBr
red powder, 89% yield). Anal. Calc. for C17 NiS (491.84): C,
1.26; H, 2.44; N, 5.66. Found: C, 41.10; H, 2.20; N, 5.49%. FT-IR
2
to form C11
(
4
(
9
2 2
H12Br N
À1
Diamond; cm ): 3057, 2980, 1611, 1601, 1560, 1451, 1130,
66, 849, 760, 680.
Table 1
3
Crystal data and structure refinement for complexes C1ÁCH OH, C3, C6 and C11.
C1ÁCH3OH
C3
C6
C11
Cryst color
colorless
yellow
brown
red
Empirical formula
Formula weight
T (K)
Wavelength (Å)
Crystal system
Space group
a (Å)
C
18
H
16Cl
2
N
2
NiO
2
C
19
H
16Cl
2
2
N NiO
C
19
H
16Cl
2
N
2
NiS
18 2 2
C H14Br N NiS
421.94
293(2) K
0.71073
monoclinic
C2/c
26.654(5)
6.6793(13
19.813(4)
90
101.08(3)
90
3461.5(12)
8
1.619
1.444
417.95
173(2)
0.71073
monoclinic
P2(1)/c
13.351(3)
11.967(2)
10.837(2)
90
95.69(3)
90
1723.0(6)
4
434.01
173(2)
0.71073
monoclinic
P2(1)/c
8.9572(18)
16.117(3)
12.515(3)
90
92.13(3)
90
1805.4(6)
4
508.90
446(2)
0.71073
monoclinic
P2(1)/c
10.869(2)
8.5381(17)
19.641(4)
90
102.92
90
1776.5(6)
4
b (Å)
c (Å)
a
(°)
b (°)
(°)
c
3
V (Å )
Z
D
l
À3
calc (mg m
)
1.611
1.445
1.597
1.490
1.903
5.709
À1
(mm
)
F(000)
1728
856
888
1000
Crystal size (mm)
h range (°)
Limiting indices
0.34 Â 0.28 Â 0.25
0.30 Â 0.30 Â 0.10
3.06–27.48
À15 6 h 6 17
–15 6 k 6 7
–13 6 l 6 13
9928
0.15 Â 0.12 Â 0.05
2.06–25.50
À10 6 h 6 10
–17 6 k 6 19
–12 6 l 6 15
13717
0.32 Â 0.26 Â 0.22
1.92–27.48
À14 6 h 6 14
–10 6 k 6 11
–25 6 l 6 25
12655
1.56–27.49
À32 6 h 6 33
–
–
8 6 k 6 8
20 6 l 6 25
No. of reflections collected
No. unique reflections (Rint
Completeness to h (%)
13544
)
3941(0.0324)
99.0%
3908 (0.0367)
98.9%
3355(0.0641)
99.9%
4057(0.0615)
99.7%
Absorption correction
none
none
none
none
Data/restraints/parameters
3941/0/230
1.163
3908/0/226
1.057
3355/41/245
1.270
4057/0/212
1.247
Goodness of fit on F2
Final R indices [I > 2
R indices (all data)
r
(I)]
R1 = 0.0438
wR2 = 0.1215
R1 = 0.0473,
wR2 = 0.1340
1.394 and À0.538
R1 = 0.0446
wR2 = 0.1015
R1 = 0.0487,
wR2 = 0.1045
0.387 and À0.347
R1 = 0.0794
wR2 = 0.1830
R1 = 0.0915,
wR2 = 0.1981
0.904 and À0.549
R1 = 0.0541
wR2 = 0.1334
R1 = 0.0634
wR2 = 0.1548
1.011 and À0.1548
À3
Largest difference in peak and hole (e Å
)

P. Hao et al. / Polyhedron 52 (2013) 1138–1144
1141
5
0 mL toluene were added. When the required reaction tempera-
ture had been reached, ethylene at the desired pressure was intro-
duced to start the reaction. After the reaction mixture had been
stirred for the desired period of time, the reaction was stopped
and about 1 ml of the reaction solution was collected, terminated
by the addition of 10% aqueous hydrogen chloride. The organic
layer was analyzed by gas chromatography (GC) for determining
the composition and mass distribution of the oligomers obtained.
2.5. General procedure for norbornene polymerization
In a typical procedure, 2.5 mol nickel complex was dissolved
l
in a Schlenk tube with 15.0 mL distilled toluene under nitrogen
and 14.3 mL toluene solution of norbornene (3.50 M, 50.0 mmol
of norbornene) was added via a syringe. The polymerization was
initiated by adding 1.72 mL of toluene solution containing
À1
1
.46 mol L MAO (2.5 mmol). After 20 min, the polymerization
was terminated by injecting 200 mL of acidic ethanol (ethanol:HCl
conc.) = 95:5) into the reactor. The polynorbornene was isolated
by filtration, washed with ethanol and dried in vacuum at 60 °C
Fig. 1. ORTEP structure of C1ÁCH
3
OH with thermal ellipsoids at the 30% probability
level. Hydrogen atoms omitted for clarity.
(
for 12 h.
Table 2
3
. Results and discussion
Selected bond lengths (Å) and angles (°) for C1ÁCH
3
OH, C3 and C6 and C11.
3.1. Preparation and characterization of the nickel complexes
3
C1ÁCH OH
C3
C6
C11
Bond lengths (Å)
Ni(1)ÀN(1)
Ni(1)ÀN(2)
Ni(1)ÀCl(1)
Ni(1)ÀBr(1)
Ni(1)ÀCl(2)
Ni(1)ÀBr(2)
N(1)ÀC(10)
N(1)ÀC(16)
N(2)ÀC(1)
The series of 8-benzooxazolylquinoline and 8-benzothiazolyl-
quinoline derivatives (L1–L6) were prepared according to the syn-
1.983(3)
2.040(2)
2.2721(8)
–
2.3939(8)
–
1.298(4)
1.408(4)
1.335(3)
1.373(3)
1.952(2)
2.022(2)
2.2538(10)
–
2.2072(9)
–
1.297(3)
1.408(3)
1.331(3)
1.381(3)
1.967(5)
2.002(5)
2.2313(19)
–
2.223(2)
–
1.304(7)
1.405(8)
1.337(8)
1.376(8)
1.954(4)
1.996(5)
–
thetic procedure shown in Scheme 1, and were characterized by
2.3839(10)
1
13
FT-IR, H and C NMR spectroscopic measurements as well by ele-
mental analysis. The stoichiometric reaction of the organic com-
pounds formed the corresponding nickel chloride complexes (C1–
2.3614(11)
1.308(7)
1.381(7)
1.347(7)
1.386(7)
C6) with NiCl
2
Á6H
2
O and nickel bromide complexes (C7–C12) with
Cl (Scheme 1) in good yield. All nickel com-
(
DME)NiBr in CH
2
2
2
N(2)ÀC(9)
plexes were found to be stable in air both in the solid-state and
solution, and were characterized by FT-IR spectroscopic and ele-
mental analyses. The molecular structures of the representative
nickel complexes C1, C3, C6 and C11 were confirmed by single
crystal X-ray diffraction studies.
Bond angles (°)
N(2)ÀNi(1)ÀN(1)
N(2)ÀNi(1)ÀCl(1)
N(2)ÀNi(1)ÀBr(1)
N(2)ÀNi(1)ÀCl(2)
N(2)ÀNi(1)ÀBr(2)
N(1)ÀNi(1)ÀCl(1)
N(1)ÀNi(1)ÀBr(1)
N(1)ÀNi(1)ÀCl(2)
N(1)ÀNi(1)ÀBr(2)
Cl(2)ÀNi(1)ÀCl(1)
Br(2)ÀNi(1)ÀBr(1)
92.58(9)
153.79(7)
–
88.98(7)
–
113.11(8)
–
96.18(7)
–
93.14(3)
–
94.05(8)
102.03(7)
–
115.71(7)
–
105.83(7)
–
100.67(7)
–
131.66(3)
–
95.2(2)
115.30(15)
–
108.27(15)
–
104.29(15)
–
108.70(16)
–
121.45(8)
–
96.22(18)
106.36(13)
108.96(13)
99.05(14)
101.45(14)
136.54(4)
3
.2. Crystal structures
Single crystals of the nickel complexes C1, C3, C6 and C11 suit-
able for X-ray diffraction studies were obtained by slow diffusion
of diethyl ether into their methanol solutions. The molecular struc-
ture of C1ÁCH
3
OH revealed a distorted square-pyramidal geometry
at the nickel center (Fig. 1), whilst in the molecular structures of
to possess a distorted tetrahedral geometry at nickel. Selected
bond lengths and angles are tabulated in Table 2.
the other nickel complexes C3, C6 and C11, the metal was found
In the distorted square-pyramidal (tau = 0.29) [93] geometry of
C1ÁCH3OH, the nickel atom is surrounded by two nitrogen atoms of
the bidentate ligand, two chlorides and one oxygen of the coordi-
Z
N
R
3
nated CH OH molecule. The square plane is occupied by Cl1, Cl2,
PPA
N
COOH
N2 and O2. In the solid state, the benzoxazolyl rings of nearby mol-
ecules interact in a ‘‘face-to-face’’ fashion with a plane-to-plane
distance of 3.225 Å (Fig. 2); the center-to-center distance is
3.509 Å. The ‘‘face-to-face’’ interaction between two quinolinyl
rings of two adjacent nickel moieties has a plane-to-plane distance
of 3.304 Å (Fig. 2) with a center-to-center distance of 3.859 Å. In
addition, there is OAHÁ Á ÁCl hydrogen bonding between adjacent
molecules (bond distance of 2.397 Å). The molecules form one-
dimensional chain polymer by H-bonds and a three-dimensional
ZH
N
R
NiCl2 6H O
2
NH2
or (DME)NiBr2 CH Cl
2
2
R
Z
Me Et Pr Me Et Pr
O
N
R
O
O
S
S
S
Ni
X
L1 L2 L3 L4 L5 L6
X=Cl C1 C2 C3 C4 C5 C6
Z
N
X
parallel supra-molecular architecture was obtained through
interactions [94–98].
p–p
X=Br
C7 C8 C9 C10 C11 C12
The molecular structure of complex C3 is shown in the Fig. 3,
Scheme 1. Synthetic procedure.
and the distorted tetrahedral geometry at nickel atom is comprised

1
142
P. Hao et al. / Polyhedron 52 (2013) 1138–1144
Fig. 2. The
p–p
stacking of molecular structure of C1ÁCH
3
OH.
Fig. 4. ORTEP structure of C6 with thermal ellipsoids at the 30% probability level.
Hydrogen atoms omitted for clarity.
Fig. 3. ORTEP structure of C3 with thermal ellipsoids at the 30% probability level.
Hydrogen atoms omitted for clarity.
In order to find the optimum conditions, the Al/Ni molar ratio
used was varied (entries 4–9, Table 3), and the highest activity
was observed at the Al/Ni molar ratio of 600. Regarding the influ-
ence of the reaction temperature (entries 7, 10–12 in Table 3), the
of two nitrogen atoms of the chelate ligand and two chlorides. The
Ni1ÀN1 bond length is 1.952(2) Å, which is shorter than that of
Ni1ÀN2 bond. Similar structures were found for complexes C6
6
À1 À1
optimum catalytic activity of 3.62 Â 10 g mol
h
was observed
(
Fig. 4) and C11 (Fig. 5), the latter involving bromides rather than
at 40 °C. Such phenomena have been commonly observed in cata-
chlorides.
lytic systems using other late-transition metal pre-catalysts
[
16,62]. In general, the main products are butenes with good selec-
3.3. Ethylene dimerization
tivity for -butene. Given this, the other nickel complexes were
a
investigated using the Al/Ni molar ratio at 600 and a temperature
The catalytic behavior of nickel complex C4 towards ethylene
of 40 °C; results are tabulated in Table 4.
was evaluated in the presence of various alkylaluminium reagents
such as MAO, Et AlCl, EASC and MMAO (entries 1–4, Table 3). On
considering the catalytic activities, EASC is considered to be the
most efficient co-catalyst.
According to the data in Table 4, the ligand substituents affected
the catalytic behavior of the corresponding nickel complexes. For
complexes C1–C3 (entries 1–3 in Table 4), the less bulky the R
group used, the higher activity of the corresponding nickel pre-cat-
2

P. Hao et al. / Polyhedron 52 (2013) 1138–1144
1143
Table 5
a
Nobornene polymerization with C1–C12/MAO.
Run
Cat.
Yield (g)
Activityb
Conversion (%)
1
2
3
4
5
6
7
8
9
C1
C2
C3
C4
C5
C6
C7
C8
2.45
2.63
2.03
2.40
1.64
2.18
1.79
2.51
1.98
2.32
2.40
3.09
2.94
3.15
2.43
2.87
1.96
2.62
2.15
3.01
2.39
2.79
2.87
3.71
50.0
53.6
41.4
48.9
33.5
44.6
36.5
51.2
40.6
47.5
48.9
63.2
C9
1
1
1
0
1
2
C10
C11
C12
a
Conditions: 2.5
lmol Ni, MAO, Al:Ni:NB = 1000:1:20000, total volume 30 mL,
2
0 °C, 20 min, toluene as solvent.
b
6
À1
À1
10 g mol (Ni) h .
Fig. 5. ORTEP structure of C11 with thermal ellipsoids at the 30% probability level.
Hydrogen atoms omitted for clarity.
complexes [55,58]. In a similar manner to the chloride analogs
C1–C6), the bromide analogues (C7–C12) revealed relatively bet-
(
ter activities. In short, it is noteworthy that the title nickel pre-cat-
alysts showed high activities for ethylene dimerization.
Table 3
a
Dimerization of ethylene with C4.
Entry
T (°C)
Co-cat.
Al/Ni
Activityb
a
-C c
4
C
4
C
6
3.4. Vinyl polymerization of norbornene
1
2
3
4
5
6
7
8
9
25
25
25
25
25
25
25
25
25
40
50
60
MAO
MMAO
Et AlCl
2
1000
1000
200
200
400
500
600
700
800
600
600
600
0.201
0.310
1.02
1.20
2.72
3.10
3.56
3.26
2.48
3.62
3.38
1.93
73.9
74.2
60.3
64.3
61.0
56.4
50.7
54.7
65.6
52.3
41.2
33.3
95.8
95.3
94.3
93.9
93.1
98.6
96.1
96.3
96.4
94.7
95.2
94.7
4.2
4.7
5.7
6.1
6.9
1.4
3.9
3.7
3.6
5.3
4.8
5.3
Although specific applications of polynorbornene remain scarce,
there is still interest in the use of nickel pre-catalysts for norborn-
ene polymerization [84–87]. Thus, the title nickel complexes
(C1–C12) were investigated for the catalytic behavior in norborn-
ene polymerization using toluene as solvent, and the results
are collected in Table 5. On fixing the Al:Ni:NB molar ratio at
EASC
EASC
EASC
EASC
EASC
EASC
EASC
EASC
EASC
1
2
000/1/20000, all nickel pre-catalysts showed high activities at
1
1
1
0
1
2
0 °C, with the pre-catalyst C12 exhibiting the activity of
6
À1
À1
3.71 Â 10 g mol (Ni) h with a conversion 63.2%.
a
b
c
Conditions: 5
l
mol Ni, 10 atm C
2
4
H , 20 min, 100 mL toluene.
Activity, 106 g mol (Ni) h
À1
À1
.
4. Conclusions
Determined by GC.
A series of nickel(II) halide complexes bearing 2-(2-alkylquino-
lin-8-yl)benzoxazole or 2-(2-alkylquinolin-8-yl)benzothiazole have
been synthesized and characterized. Upon activation with EASC, all
the nickelcomplexes showed high activityfor ethylene dimerization
with enhanced thermal stability at 40 °C. Furthermore, the nickel
complexes displayed high activities for the vinyl polymerization of
norbornene on activation with MAO.
Table 4
Dimerization of ethylene by nickel halide pre-catalyst C1–C12.
a
Activityb
A-C c
Entry
Pre-catalyst
4
C
4
C
6
1
2
3
4
5
6
7
8
9
C1
C2
C3
C4
C5
C6
C7
C8
3.86
2.66
2.15
3.62
3.60
3.10
3.89
3.51
2.35
3.70
3.61
3.27
40.0
77.6
45.6
52.3
51.5
46.5
49.3
56.3
57.2
48.9
39.8
32.4
94.4
99.0
93.5
94.7
96.4
96.9
95.4
93.4
95.9
96.0
96.6
95.0
5.6
1.0
6.5
5.3
3.6
3.1
4.6
6.6
4.1
4.0
3.4
5.0
Acknowledgments
This work is supported by MOST 863 program No.
2
009AA033601. The EPSRC are thanked for the award of a travel
C9
grant (to CR).
1
1
1
0
1
2
C10
C11
C12
Appendix A. Supplementary data
a
2 4
Conditions: 5 lmol Ni, EASC, Al/Ni = 600, 40 °C, 10 atm C H , 20 min, 100 mL of
CCDC 878226 and 878229 contains the supplementary crystal-
toluene.
b
c
Activity, 106 g mol (Ni) h
À1
À1
3
lographic data for nickel complexes C1ÁCH OH, C3, C6 and C11.
.
Determined by GC.
These data can be obtained free of charge via http://www.ccdc.
cam.ac.uk/conts/retrieving.html, or from the Cambridge Crystallo-
graphic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax:
(+44) 1223-336-033; or e-mail: deposit@ccdc.cam.ac.uk.
alyst. The activity trends were as follows: C1(R = Me) > C2
R = Et) > C3 (R = Pr), C4 > C5 > C6, C7 > C8 > C9 and
(
C10 > C11 > C12. This is caused by the bulky substituents occupy-
ing the space around the nickel center thereby hindering/slowing
the coordination of ethylene. Comparisons between pre-catalysts
C1–C3 with C4–C6, revealed that the ligands with a benzothiazolyl
group enhanced the catalytic activities of the corresponding nickel
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