T. Sun et al. / Polymer 51 (2010) 3091e3098
3093
and 3(1.1 g, 4.3 mmol) were dissolved in 50 ml benzene. Para-tolue-
3. Results and discussion
nesulfonic acid (50 mg, 0.3 mmol) was added and the solution was
refluxed for 48 h. After evaporation of solvent, the crude product was
purified by column chromatography (silica, petroleum ether/ethyl
acetate 40/1). 2.4 gofcompound N5 wasobtained (yield60%).1H NMR
3.1. Synthesis of heterobinuclear cobalt and nickel complex
We designed the hybrid ligand containing a-diimine and pyri-
(400 MHz, CDCl3,
d
in ppm): 1.12e1.20(m, 48H, ArCH(CH3)2), 2.07
dine diimine moieties according to common Brookhart [1] and
Gibson [2,3] catalyst. The synthetic route of heterobinuclear cobalt
and nickel complex N5CoNi is described in Scheme 2. The 4,40-
methylene-bis(2,6-diisopropylaniline) was used as bridge to
connect two monoketones. It was condensed with mono-(imino)
pyridyl ketone catalyzed by para-toluenesulfonic acid, which
produced compound 2. Similar condensation reaction between
compound 2 and ketimine 3 catalyzed by para-toluenesulfonic acid
gave ligand N5. The ligand N5 was characterized by 1H NMR spec-
trum (see Fig. S1), element analysis and mass spectrum. All results
proved the successful synthesis of target ligand containing both
(d, 6H, AreN]C(CH3)e(CH3)C]NeAr), 2.27(s, 6H, Pye(CH3)C]N),
2.75(m, 8H, ArCH(CH3)2), 4.03(s, 2H, AreH2eAr), 7.01(s, 4H, AreH),
7.07e7.19(m, 6H, AreH), 7.93(t, 1H, PyeHp), 8.47(dd, 2H, PyeHm).
Anal. Calcd for C62H83N5 (898.36): C, 82.89; H, 9.31; N,7.80. Found: C,
82.49; H, 9.39; N, 7.84. ESI-MS: m/z 898.7[M
þ
H]þ. m.p.:
255.3e257.8 ꢀC. IR (KBr): 1641 cmꢁ1 (C]N).
n
2.3.3. {2-[2,6-R2eC6H3N]C(CH3)e(CH3)C]N-(3,5-R2)C6H2eCH2-
(30,50-R2)C6H2N]C(CH3)]-6-[2,6-R2eC6H3N]C(CH3)]pyridine}
CoCl2 (R]i-Pr) (N5Co)
A solution of CoCl2 (0.137 g, 1.057 mmol) in 15 ml n-butanol
was added dropwisely to a yellow solution of N5 (1.000 g,
1.113 mmol) in 20 ml n-butanol. After heated at 80 ꢀC for 30 min,
the mixture was cooled to room temperature. The reaction
mixture was concentrated and 30 ml diethyl ether was added.
The yellowish brown precipitate was isolated by decantation,
washed with Et2O (3 ꢂ 5 ml), and dried under vacuum to afford
1.025 g of complex N5Co (yield 89%). 1H NMR (400 MHz, CD2Cl2,
pyridine imine and a-diimine moieties.
As reported by Bianchini and Kim [25,31], when the CoCl2 or
FeCl2 was coordinated to a ligand which has both pyridine diimine
and
a-diimine moieties, the pyridine diimine was favored to be
coordinated predominately. To confirm the selective coordination
of CoCl2 to pyridine diimine part of N5, the reaction of 0.95 equiv-
alent CoCl2 with the mixture of 1 equivalent ligand of N3Co and 1
equivalent ligand of N2Ni was conducted. Only cobalt complex
N3Co was obtained as product. The result indicates that in the
d
in ppm): ꢁ82.73(d, 4H, Pye(CH3)C]NeArCH(CH3)2), ꢁ17.75(d,
12H, Pye(CH3)C]NeAr(CH(CH3)2)eCH2), ꢁ16.93(d, 12H, Pye
(CH3)C]NeArCH(CH3)2), ꢁ8.36(s, 1H, Pye(CH3)C]NeAreHp),
0.94, 1.01(dd, 12H, ArCH(CH3)2N]C(CH3)e(CH3)C]N), 1.23, 1.48
(s, 12H, AreN]C(CH3)e(CH3)C]NeAr(CH(CH3)2)eCH2), 1.63, 1.79
(s, 6H, N]C(CH3)e(CH3)C]N), 2.50, 2.63 (s, 4H, ArCH(CH3)2eN]
C(CH3)e(CH3)C]N), 4.78, 5.39 (s, 6H, Pye(CH3)C]N), 7.02(m, 5H,
presence of both pyridine diimine and a-diimine moieties, cobalt is
predominantly coordinated to pyridine diimine.
The monometallic N5Cowas prepared byslowlyaddition of CoCl2
in n-butanol to the l.05 equivalent ligand N5 in n-butanol. The 1H
NMR spectrum of N5Co is shown in Fig. 1, which is quite different
from the spectrum of ligand N5 (see Fig. S1). The comparison of
chemical shifts of all protons of ligand N5 with complex N5Co is given
in Table 1. It is evident that the chemical shifts of protons of pyridine
diimine part of complex N5Co are quite different from the ligand N5.
HeAreN]C(CH3)e(CH3)C]N),
NeAreHm), 19.89(s, 2H, CH2),
10.32(d,
4H,
Pye(CH3)C]
d
¼ 49.94(s, 1H, Hp), 117.18(d, 2H,
Hm). Anal. Calcd for C62H83N5Cl2Co (1028.20): C, 72.42; H, 8.14; N,
6.81; Co, 5.73. Found: C, 72.02; H, 8.16; N, 6.59; Co, 5.69. ESI-MS:
m/z 1027.4[M þ H]þ, 991.7[MeCl]þ, 898.7[MeCoCl2 þ H]þ. IR
On the other side, chemical shifts of protons of a-diimine part of
N5Co do not change so much compared with ligand N5. The peaks at
49.94 ppm (proton a in Scheme 2) and 117.18 ppm (proton b in
Scheme 2) can be assigned to the signals of proton of pyridine ring,
which is close to corresponding chemical shifts of mononuclear
complex N3Co [31]. The 1H NMR result indicates that cobalt is
selectively coordinated to the pyridine imine, and the N5Co still
(KBr):
n
1618, 1637 cmꢁ1 (C]N).
2.3.4. {2-[2,6-R2eC6H3N]C(CH3)e(CH3)C]Ne(3,5-R2)
C6H2eCH2e(30,50-R2)C6H2N]C(CH3)]-6-[2,6-R2eC6H3N]C(CH3)]
pyridine}FeCl2NiBr2 (R ¼ i-Pr) (N5CoNi)
A suspension of NiBr2(DME) (0.180 g, 0.584 mmol) in CH2Cl2
(15 ml) was added to a solution of N5Co (0.500 g, 0.486 mmol)
in CH2Cl2 (20 ml) at room temperature. After 24 h, the mixture
was filtered and the solvent was evaporated. The reddish-brown
solid was washed with Et2O (3 ꢂ 5 ml) and dried under vacuum
keeps one free a-diimine moiety. In the ESI-MS of N5Co (see Fig. S3),
the peaks related to [M þ H]þ, [MeCl]þ and [MeCoCl2þH]þ were
found, no peak corresponding to [M þ CoCl2]þ (1157.40) was found.
This demonstrates no homobimetallic complexes N5Co2 is formed
during the reaction. Furthermore, The IR spectra of N5Co (see Fig. S3)
to afford 0.496
g
of product (yield 81%). Anal. Calcd for
contained two n(C]N) bands. Compared with one single n(C]N)
C62H83N5Br2Cl2CoNi (1246.70): C, 59.73; H, 6.71; N, 5.62; Co,
4.73 Ni, 4.71. Found: C, 59.79; H, 6.85; N, 5.50; Co, 5.05; Ni, 4.01.
band at 1641 cmꢁ1 assigned to free imine group of ligand N5 (see
Fig. S3), the weak band at 1618 cmꢁ1 was assigned for the coordi-
nated pyridine imine groups, and more intense one at 1637 cmꢁ1 for
ESI MS: m/z 1239.8[2MeClþNa]2þ
,
1210.8[MeCl]þ, 1075.7
[MeCoCl2Br þ K]þ, 1034.5[MeCoCl2Br]þ, 990.8[MeNiBr2Cl]þ. IR
the free a-diimine group. This indicates that not all of the nitrogen
(KBr):
n
1618, 1637 cmꢁ1 (C]N).
atoms of the potentially pentadentate ligand involved in the coor-
dination to the cobalt center. The element analysis data and cobalt
content measured by ICP confirm that only one equivalent cobalt
coordinates to each ligand N5. The polydispersity indexes of poly-
mers prepared by N5Co were around 2.0 (see Table 2), which also
suggests only one kind of cobalt center exists in the structure of
complex. Base on above characterizations, the N5Cowas successfully
synthesized.
2.4. Ethylene polymerization
The polymerization of ethylene was conducted in a 100-mL,
three-necked flask. Toluene (50 mL) and required amount of
cocatalyst were injected into the flask with vigorous stirring, and
the system was saturated by ethylene. The polymerization was
initiated by the addition of methylene dichloride solution of the
catalyst. After 30 min, the polymerization was terminated by
addition of the acidified ethanol. The resulting polymer was
separated by filtration and dried in vacuum at 50 ꢀC to constant
weight.
TheheterobinuclearcomplexN5CoNiwas prepared by adding 1.20
equivalent of NiBr2(DME) to the N5Co in CH2Cl2. The 1H NMR spec-
trum of final product is hardly to analyze due to the poor resolution of
the spectra derived from the paramagnetic property of the complex.
Attempt to obtain its crystal was failed. In the ESI-MS of N5CoNi (see
Fig. S4), the peaks related to [MeCl]þ, [MeCoCl2Br
þ
K]þ,