Chromium(III) complexes with chelating anilido-imine ligands: Synthesis, structures, and catalytic properties for ethylene polymerization

Article abstract of DOI:10.1002/ejic.201000150

A series of novel chromium complexes that bear anilidoimine ligands, [{oriho-C₆H₄(NAr")(CH=NAr")}CrCl ₂(thf)₂] [Ar' = Ar" = C₆H₅ (1); Ar' = Ar" = P-MeC₆H₄ (2); Ar' = Ar" = 2,6-Me₂C₆H₃ (3); Ar' = 2,6-iPr ₂C₆H₃, Ar" = 2,6-Me₂C ₆H₃ (4); Ar' = Ar" = 2,6-iPr₂C ₆H₃ (5)], have been synthesized and characterized by elemental analysis, IR spectroscopy, and ESI-MS. The molecular structures of complexes 1 and 2 have been confirmed by single-crystal X-ray diffraction analysis. When activated with methylaluminoxane (MAO), these complexes exhibit reasonable to good catalytic activity for ethylene polymerization and produce polyethylene with moderate molecular weights.

Full text of DOI:10.1002/ejic.201000150

FULL PAPER
DOI: 10.1002/ejic.201000150
Chromium(III) Complexes with Chelating Anilido–Imine Ligands: Synthesis,
Structures, and Catalytic Properties for Ethylene Polymerization
Tieqi Xu,*[a] Haiyan An,[a] Wei Gao,[b] and Ying Mu*[b]
Keywords: Chromium / Polymerization / Homogeneous catalysis / Ligand effects
A series of novel chromium complexes that bear anilido–
imine ligands, [{ortho-C6H4(NArЈ)(CH=NArЈЈ)}CrCl2(thf)2]
[ArЈ = ArЈЈ = C6H5 (1); ArЈ = ArЈЈ = p-MeC6H4 (2); ArЈ = ArЈЈ
= 2,6-Me2C6H3 (3); ArЈ = 2,6-iPr2C6H3, ArЈЈ = 2,6-Me2C6H3
(4); ArЈ = ArЈЈ = 2,6-iPr2C6H3 (5)], have been synthesized and
characterized by elemental analysis, IR spectroscopy, and
ESI-MS. The molecular structures of complexes 1 and 2 have
been confirmed by single-crystal X-ray diffraction analysis.
When activated with methylaluminoxane (MAO), these com-
plexes exhibit reasonable to good catalytic activity for ethyl-
ene polymerization and produce polyethylene with moderate
molecular weights.
ethylene polymerization.[3d,8] But these β-diketiminate li-
gands are not easily modified and the corresponding chro-
mium catalysts show only moderate activity for ethylene
polymerization. The bidentate salicylaldiminate chelate li-
gands possess easily modified features and have been ap-
plied in olefin polymerization chemistry. Gibson et al. re-
ported mononuclear salicylaldiminate chromium com-
plexes, which showed good catalytic activity and can tune
catalytic activity and molecular weight by easily modified
ligands.[9]
Taking these into account, our current research interest
is to choose the anilido–imine ligands that combine the
steric effect of the β-diketiminate ligand framework and the
more easily modified features of the salicylaldiminate ligand
framework to construct chromium metal catalysts for mod-
eling the Phillips catalyst. To date, only a few complexes
based on anilido–imine ligands are known. The successful
examples include the yttrium(III),[10] nickel(II),[11] and
nickel(I)[12] complexes that the groups of Piers, Wu, and Jin,
respectively, synthesized with these ligands. Recently, we
have also addressed some anilido–imine aluminum com-
plexes.[13] Herein we report the first chromium(III) com-
plexes based on anilido–imine ligands (Scheme 1) and ex-
plore their catalytic activity for ethylene homopolymeriza-
tion. These complexes exhibit much higher catalytic activity
and more easily modified features than analogue β-diket-
iminate chromium complexes.[6a,7]
Introduction
The chromium-based heterogeneous Phillips catalyst
(CrO3/SiO2)[1] and the Union Carbide Unipol catalyst
(Cp2Cr/SiO2; Cp = cyclopentadienyl)[2] play an important
role in the global production of polyolefins. However, as
heterogeneous catalysts they have not proven amenable to
intimate study on account of the relatively ill-defined nature
of these catalysts with respect to coordination environment
and oxidation state.[3] Consequently, there is a great need to
develop well-defined homogeneous chromium-based cata-
lysts that can offer the potential for understanding the
modus operandi of heterogeneous chromium catalysts.[3d]
Over the past decades, significant advances have been made
in the synthesis of homogeneous metallocene chromium
catalysts that contain cyclopentadienyl ligands as a model
system for the Union Carbide Unipol family.[4,5] However,
only a few nonmetallocene chromium complexes for model-
ing the Phillips catalyst have been reported. Recently, chro-
mium complexes with bidentate β-diketiminate ligands for
modeling the Phillips catalyst have received attention be-
cause these ligands approximate the hard coordination envi-
ronment of the silica surface and the N-substituents allow
for steric protection of the active site. Theopold and co-
workers first used the mononuclear β-diketiminate chro-
mium complexes for ethylene polymerization[6] and found a
reasonable candidate for the active surface species of the
heterogeneous Phillips catalyst.[7] Subsequently, Gibson et
al. reported chromium complexes with similar ligands for
Results and Discussion
[a] Department of Chemistry, Dalian University of Technology,
Dalian 116023, P. R. China
Synthesis of Chromium Complexes
E-mail: tqxu@dlut.edu.cn
The syntheses of five chromium complexes as catalytic
precursors are shown in Scheme 1. The free ligands L1–L5
were prepared according to the literature procedure.[10–12] It
was noteworthy that the steric bulkiness of the ligands
[b] State Key Laboratory of Supramolecular Structure and
Materials,
School of Chemistry, Jilin University,
Changchun 130012, P. R. China
E-mail: ymu@jlu.edu.cn
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Eur. J. Inorg. Chem. 2010, 3360–3364

Chromium(III) Complexes with Chelating Anilido–Imine Ligands
Scheme 1. Synthesis of chromium complexes 1–5.
could be easily adjusted by changing various arylamines.
1
These five ligands were characterized by H NMR and IR
spectroscopy. The infrared absorption bands of the imine
C=N stretch occur in the region 1621–1624 cm–1. After the
anilido–imine ligands were treated with nBuLi in THF,
[CrCl3(thf)3] (0.95 equiv.) was added to give a dark brown
solution. The chromium(III) complexes 1–5 were obtained
as brown crystals in high yields by recrystallization from
a solution of CH2Cl2/n-hexane. The complexes were well
characterized by ESI-MS and IR spectroscopy as well as
elemental analysis. The IR spectra of these complexes show
absorption bands of the imine C=N at 1606–1608 cm–1,
which are clearly blueshifted in comparison with the free
ligands.
Figure 1. Structure of complex 1 (thermal ellipsoids are drawn at
the 30% probability level).
Crystal Structures
Crystals of complexes 1 and 2 for single-crystal X-ray
diffraction analysis were grown from a solution of CH2Cl2/
n-hexane at room temperature or 0 °C. The ORTEP draw-
ings of the molecular structures of complexes 1 and 2 are
shown in Figure 1 and Figure 2, respectively. Selected bond
lengths and bond angles for complexes 1 and 2 are depicted
in Table 1. Single-crystal X-ray analysis reveals that com-
plexes 1 and 2 adopt an octahedral geometry with the metal
center chelated by the bidentate ligand by means of the
amido and imine nitrogen atoms. The Cr–N (amido) dis-
tances [1.990(2) Å for 1 and 1.985(4) Å for 2] are much
shorter than the Cr–N (imine) distances [2.033(2) Å for 1
and 2.024(4) Å for 2], because the anionic amido nitrogen
Figure 2. Structure of complex 2 (thermal ellipsoids are drawn at
the 30% probability level).
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T. Xu, H. An, W. Gao, Y. Mu
FULL PAPER
can also donate π electrons to the chromium, whereas the Ethylene Polymerization Studies
neutral imine nitrogen has no available lone pair for π do-
The experimental results of ethylene polymerization with
complexes 1–5 as precatalysts are summarized in Table 2.
Upon activation with methylaluminoxane (MAO), com-
plexes 1–5 show good catalytic activity [up to 1.37ϫ106 g
PE(molCr)–1 h–1] for ethylene polymerization, producing
polyethylene with moderate molecular weight. The influ-
ences of the Al/Cr molar ratio and reaction temperature
on ethylene reactivity were studied with a 3/MAO system.
Increasing the Al/Cr molar ratio from 300 to 500 greatly
enhanced its productivity of ethylene polymerization
(Table 2, entries 3 and 4). However, further increasing the
Al/Cr molar ratio to 1000 resulted in a lower activity of
ethylene polymerization (Table 2, entry 5). Elevation of the
reaction temperature from 20 to 60 °C resulted in a sharp
decrease of polymerization activity, which can be explained
as catalyst decomposition and lower ethylene solubility at
higher temperature (Table 2, entries 4, 6, and 7). In view of
these observations, further experiments were performed at
an Al/Cr molar ratio of 500 and at 20 °C. The order of
catalyst activity for ethylene polymerization under similar
conditions (Table 2, entries 1, 2, 4, 8, and 9) is 3 Ͼ 4 Ͼ 5
Ͼ 2 Ͼ 1, which implies that the ligand environment, with
regards to their substituents on the aryl ring linked to the
imino-N atom and amido-N atom, has a significant influ-
ence on the catalytic behavior of chromium complexes on
ethylene reactivity. Increasing the size of ortho substituents
from R1 = R3 = H to R1 = R3 = Me greatly enhanced
ethylene polymerization activity (Table 2, entries 1, 2, and
4). The higher catalytic activity is believed to arise from
improved cation···anion separation in the active species as
well as increased protection of active species. However, fur-
ther increasing the size of ortho substituents to R1 = R3 =
iPr resulted in lower catalytic activities (Table 2, entry 9).
This might be explained by the fact that bulkier substituents
slow down ethylene coordination and hinder chain propa-
gation. Complex 1, which bears para-methyl substituents on
the ligands, exhibited greater activity than the unsubstituted
complex 2. It indicates that the remote electron-donating
electronic effect also increased activity for polymerization.
13C NMR spectroscopic analysis of the typical polymer
nation. The Cr–N (imine) distances are close to the values
[2.032(6), 2.033(5) Å] previously reported for [{N(Ph)-
C(Me)2CH}2CrCl2(thf)2],[6a] but shorter than those values
[2.073(4) Å]
of
[(2-{CH=N(2,6-iPr2C6H3)}-C4H3N)2-
CrMe][3d] and [2.098(3) Å] of [Cr{3,5-(tBu)2-2-(O)-
C6H2CH2NH(2,6-Me2C6H3)}(η1-NCCH3)2Cl2].[9a] The N–
Cr–N angles (90.83(10)° for 1 and 89.38(17)° for 2) in these
complexes are less than that [91.7(2)°] of a similar complex
[({N(Ph)C(Me)}2CH)2CrCl2(thf)2], whereas they are larger
than those in the five-membered chelating ring [80.9(2)°]
of [Cr{3,5-(tBu)2-2-(O)C6H2CH2NH(2,6-Me2C6H3)}(η1-
NCCH3)2Cl2]. The values of four Cr–Cl bond lengths are
close to each other and close to those observed in some
reported chromium complexes ligated by β-diketiminate,[6]
imino–pyrrolide,[3d] salicylaldiminato,[9] and cyclopenta-
dienyl.[4] In these two complexes, the six-membered chelat-
ing ring is nearly planar, with the chromium atom lying
0.1336 and 0.2260 Å out of the plane, respectively. The di-
hedral angles between the six-membered chelating ring and
aromatic ring attached to the amido nitrogen atom are 90.9
and 91.7°, and the dihedral angles between the six-mem-
bered chelating ring and aromatic ring attached to the imine
nitrogen atom are 56.3 and 61.5°, respectively. The imino
C=N bonds in these complexes retain their double-bond
character, being 1.301(3) and 1.306(6) Å for complexes 1
and 2, respectively.
Table 1. Selected bond lengths [Å] and angles [°] for complexes 1
and 2.
Complex 1
Cr1–N1
Cr1–O1
Cr1–Cl1
N1–C1
1.990(2)
2.117(2)
2.3338(12)
1.358(3)
1.431(4)
90.83(10)
173.74(8)
91.26(9)
89.55(7)
91.57(6)
92.57(7)
88.84(6)
177.80(3)
Cr1–N2
Cr1–O2
Cr1–Cl2
C14–N2
2.033(2)
2.122(2)
2.3138(12)
1.444(3)
1.301(3)
95.43(9)
176.77(8)
82.50(9)
88.67(7)
88.04(6)
90.69(7)
89.87(6)
N1–C8
C7–N2
N1–Cr1–N2
N2–Cr1–O1
N2–Cr1–O2
N1–Cr1–Cl2
O1–Cr1–Cl2
N1–Cr1–Cl1
O1–Cr1–Cl1
Cl2–Cr1–Cl1
N1–Cr1–O1
N1–Cr1–O2
O1–Cr1–O2
N2–Cr1–Cl2
O2–Cr1–Cl2
N2–Cr1–Cl1
O2–Cr1–Cl1
Table 2. Results of ethylene polymerization using procatalysts
1–5.[a]
Complex 2
Cat. Al/Cr T [°C] Yield [g]
Activity[b]
Mn
[c]
ϫ10–6
ϫ10–5
Cr1–N1
Cr1–O1
Cr1–Cl1
N1–C1
1.985(4)
2.093(3)
2.3229(17)
1.367(6)
1.438(6)
89.38(17)
174.92(16)
92.09(15)
90.22(13)
90.54(10)
91.25(13)
89.99(11)
178.39(7)
Cr1–N2
2.024(4)
Cr1–O2
Cr1–Cl2
C14–N2
C7–N2
N1–Cr1–O1
N1–Cr1–O2
O1–Cr1–O2
N2–Cr1–Cl2
O2–Cr1–Cl2
N2–Cr1–Cl1
O2–Cr1–Cl1
2.126(3)
2.3233(17)
1.437(7)
1
2
3
4
5
6
7
8
9
1
2
3
3
3
3
3
4
5
500
500
300
500
1000
500
500
500
500
20
20
20
20
20
40
60
20
20
trace
0.08
5.12
6.87
3.96
3.45
2.66
1.68
1.45
–
–
0.02
1.02
1.37
0.79
0.69
0.53
0.34
0.29
1.56
1.54
1.38
0.67
0.96
0.89
1.06
0.61
N1–C8
1.306(6)
N1–Cr1–N2
N2–Cr1–O1
N2–Cr1–O2
N1–Cr1–Cl2
O1–Cr1–Cl2
N1–Cr1–Cl1
O1–Cr1–Cl1
Cl2–Cr1–Cl1
95.07(15)
178.21(15)
83.42(13)
86.97(12)
88.83(10)
92.38(12)
89.72(10)
[a] Polymerization conditions: 60 mL toluene, 10 µmol catalyst,
5 bar ethylene pressure, 30 min. [b] g of PE(mol Cr)–1 h–1. [c] Mea-
sured in decahydronaphthalene at 135 °C.
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Chromium(III) Complexes with Chelating Anilido–Imine Ligands
(m), 1503 (s), 1466 (w), 1465 (m), 1439 (s), 1389 (m), 1337 (m),
1266 (w), 1225 (w), 1208 (m), 1181 (m), 1163 (m), 1129 (m), 1042
(m), 1020 (m), 926 (w), 882 (m), 820 (w), 796 (w), 746 (m) cm–1.
ESI-MS: m/z = 421.2 [M – 2THF]+, 386.2 [M – 2THF – Cl]+.
C27H31Cl2CrN2O2 (566.50): calcd. C 61.48, H 6.23, N 4.94; found
C 60.99, H 6.24, N 4.85.
sample (Table 2, entry 5) reveals that the polyethylene con-
tains long-chain branches; the degree of branching is 5
branches per 1000 C atoms. The molecular weight distribu-
tion (Mw/Mn) of this polymer sample was 23.8, which was
measured by gel permeation chromatography at 150 °C.
[{ortho-C6H4N(C6H4Me2-2,6)(CH=NC6H4Me2-2,6)}CrCl2(thf)2]
(3): Complex 3 was synthesized in the same way as described above
for the synthesis of 1 with ortho-C6 H4 NH(C6 H4 Me2 -
2,6)(CH=NC6H4Me2-2,6) (0.82 g, 2.50 mmol) as starting material.
Conclusion
Five new anilido–imine chromium complexes have been
synthesized and characterized. They displayed high cata- Pure 3 (1.13 g, 1.90 mmol, 76%) was obtained as brown crystals.
lytic activity up to 1.37ϫ106 g PE(mol Cr)–1 h–1 for ethyl-
ene polymerization upon treatment with MAO. The cata-
lytic activity of these complexes and the molecular weight
of the produced polyethylenes can be tuned in a broad
range by changing the substituents on the aryl ring linked
to the imino-N atom and amido-N atom. These new cata-
lysts represent a remarkable addition to the limited list of
nonmetallocene-type chromium ethylene polymerization
catalysts.
IR (KBr): ν = 3018 (m), 2975 (m), 2870 (m), 1607 (s), 1581 (s),
˜
1523 (m), 1464 (m), 1435 (w), 1381 (m), 1327 (m), 1262 (w), 1215
(m), 1160 (s), 1129 (m), 1095 (m), 1049 (m), 969 (m), 871 (w), 768
(m), 747 (m) cm–1. ESI-MS: m/z = 449.2 [M – 2THF]+, 414.2 [M –
2THF – Cl]+. C31H39Cl2CrN2O2 (594.56): calcd. C 62.62, H 6.61,
N 4.71; found C 62.94, H 6.49, N 4.74.
[{ortho-C6H4N(C6H4iPr2-2,6)(CH=NC6H4Me2-2,6)}CrCl2(thf)2]
(4): Complex 4 was synthesized in the same way as described above
for the synthesis of 1 with ortho-C6H4NH(C6H4iPr2-2,6)-
(CH=NC6H4Me2-2,6) (0.96 g, 2.50 mmol) as starting material.
Pure 4 (1.01 g, 1.55 mmol, 62%) was obtained as brown crystals.
IR (KBr): ν = 3023 (m), 2972 (m), 2870 (m), 1608 (s), 1582 (s),
˜
Experimental Section
1522 (m), 1465 (m), 1432 (m), 1382 (m), 1320 (m), 1262 (w), 1210
(m), 1160 (s), 1129 (m), 1095 (m), 1049 (m), 969 (m), 873 (w), 796
(m), 745 (m) cm–1. ESI-MS: m/z = 505.2 [M – 2THF]+, 470.3 [M –
2THF – Cl]+. C35H47Cl2CrN2O2 (650.66): calcd. C 64.61, H 7.28,
N 4.31; found C 64.38, H 7.23, N 4.40.
General: Reactions with organometallic reagents were carried out
under a nitrogen atmosphere (ultrahigh purity) using standard
Schlenk techniques or in an inert atmosphere glove box. Solvents
were dried by means of the appropriate drying agent, distilled, de-
gassed, and stored over molecular sieves (4 Å). Polymerization-
grade ethylene was further purified by passage through columns of
molecular sieves (3 Å) and MnO. MAO and nBuLi were purchased
from Aldrich. [CrCl3(thf)3][14] was prepared according to literature
procedures. Elemental analyses were performed with a Vario EL
microanalyzer. Mass spectra were measured with a Micromass Q-
TOF mass spectrometer instrument using electrospray ionization
(ESI). IR spectra were recorded with a Nicolet NEXUS FTIR
spectrometer.
[{ortho-C6H4N(C6H4iPr2-2,6)(CH=NC6H4iPr2-2,6)}CrCl2(thf)2]
(5): Complex 5 was synthesized in the same way as described above
for the synthesis of 1 with ortho-C6H4NH(C6H4iPr2-2,6)-
(CH=NC6H4iPr2-2,6) (1.10 g, 2.50 mmol) as starting material. Pure
5 (0.90 g, 1.27 mmol, 51 %) was obtained as brown crystals. IR
(KBr): ν = 3057 (m), 2970 (s), 2867 (m), 1608 (s), 1581 (s), 1523
˜
(m), 1464 (w), (m), 1432 (m), 1383 (m), 1360 (m), 1319 (m), 1236
(w), 1204 (w), 1158 (s), 1093 (m), 1043 (m), 929 (w), 868 (w), 795
(m), 745 (m) cm–1. ESI-MS: m/z = 561.3 [M – 2THF]+, 526.4 [M –
2THF – Cl]+. C39H55Cl2CrN2O2 (706.77): calcd. C 66.28, H 7.84,
N 3.96; found C 65.99, H 7.67, N 3.96.
[{ortho-C6H4N(C6H5)(CH=NC6H5)}CrCl2(thf)2] (1): Under nitro-
gen, a solution of ortho-C6H4NLi(C6H5)(CH=NC6H5) was pre-
pared at –78 °C by the addition of nBuLi (2.55 mmol) to ortho-
C6H4NH(C6H5)(CH=NC6H5) (0.68 g, 2.50 mmol) in THF
(10 mL). The solution was warmed to room temperature and
stirred for 2h and then was added dropwise to [CrCl3(thf)3] (0.94 g,
2.50 mmol) in THF (20 mL). The resulting mixture was warmed to
room temperature and stirred for 15 h, during which time the color
changed from purple to brown. The solvents were removed under
vacuum, and the residue was extracted with CH2Cl2 (20 mL) and
filtered. The filtrate was concentrated to 5 mL and mixed with hex-
ane (50 mL). Cooling to room temperature afforded brown crystals
of complex 1 after several days (1.10 g, 2.05 mmol, 82%). IR (KBr):
Crystal Structure Determination: Single crystals of complexes 1 and
2 were obtained from a solution of CH2Cl2/n-hexane. Diffraction
data were collected at 293 K with a Bruker SMART-CCD dif-
fractometer using graphite-monochromated Mo-Kα radiation (λ =
0.71073 Å). Details of the crystal data, data collections, and struc-
ture refinements are summarized in Table 3. The structures were
solved by direct methods[15] and refined by full-matrix least-squares
on F2. All non-hydrogen atoms were refined anisotropically, and
the hydrogen atoms were included in idealized position. All calcula-
tions were performed with the SHELXTL[16] crystallographic soft-
ware packages.
ν = 3059 (m), 2976 (m), 2876 (m), 1609 (s), 1586 (s), 1527 (m),
˜
CCDC-764274 (for 1) and -764275 (for 2) contain the supplemen-
tary crystallographic data for this paper. These data can be ob-
tained free of charge from The Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data_request/cif.
1487 (w), (m), 1465 (m), 1438 (m), 1392 (m), 1334 (m), 1267 (w),
1204 (w), 1180 (m), 1163 (m), 1129 (w), 1043 (m), 1028 (w), 937
(w), 859 (m), 697 (s) cm–1. ESI-MS: m/z = 393.1 [M – 2THF]+,
358.2 [M – 2THF – Cl]+. C27H31Cl2CrN2O2 (538.45): calcd. C
60.23, H 5.80, N 5.20; found C 59.98, H 5.71, N 5.24.
General Procedure of Polymerization Reactions: A dry 200 mL steel
[{ortho-C6H4N(C6H4Me-p)(CH=NC6H4Me-p)}CrCl2(thf)2] (2): autoclave was charged with a solution of MAO in toluene (60 mL),
Complex 2 was synthesized in the same way as described above
for the synthesis of 1 with ortho-C6 H4 NH(C6 H4 Me-p)-
(CH=NC6H4Me-p) (0.75 g, 2.50 mmol) as starting material. Pure
2 (1.07 g, 1.90 mmol, 76 %) was obtained as brown crystals. IR
thermostatted at the desired temperature, and saturated with ethyl-
ene (1.0 bar). The system was maintained by continuously stirring
for 30 min, and then the polymerization reaction was started by
injection of the chromium catalyst solution (3 m). The vessel was
(KBr): ν = 3020 (m), 2975 (m), 2872 (m), 1611 (s), 1587 (s), 1526 repressurized to the necessary pressure with ethylene immediately
˜
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T. Xu, H. An, W. Gao, Y. Mu
FULL PAPER
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Table 3. Crystal data and structural refinement details for com-
plexes 1 and 2.
1
2
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Formula
Molecular weight
Crystal system
Space group
a [Å]
b [Å]
c [Å]
α [°]
β [°]
C27H31Cl2CrN2O2 C29H35Cl2CrN2O2
538.44
566.49
triclinic
P1
monoclinic
P21/c
¯
8.125(4)
12.036(8)
13.618(7)
80.27(2)
82.357(18)
82.76(2)
1293.6(12)
2
13.478(4)
8.746(3)
25.916(9)
90
113.552(18)
90
γ [°]
V [Å3]
2800.5(16)
4
Z
Dcalcd. [gcm–3
F(000)
]
1.382
1.344
562
1188
Absorption coeff. [mm–1
Collection range [°]
Independent reflections
Rint
]
0.676
0.628
3.02ՅθՅ27.48
5889
3.05ՅθՅ25.00
4930
0.0254
0.1281
Data / restraints / parameters 5889 / 18 / 307
R1 (IϾ2σ)
wR2 (IϾ2σ)
Goodness of fit
Largest difference peak
Largest hole [eÅ–3]
4930 / 12 / 327
0.0638
0.1273
0.0473
0.1246
1.092
1.003
0.778
0.293
–0.343
–0.390
and the pressure was maintained by a continuous feed of the mono-
mer. After 30 min, the polymerization was quenched by injecting
acidified methanol [HCl (3 )/methanol, 1:1]. The mixture was
stirred and the polymer was collected by filtration, washed with
water, methanol, and dried in vacuo.
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2585.
Acknowledgments
This work was supported by the National Natural Science Founda-
tion of China (grant 20804006) and Specialized Research Fund for
the Doctoral Program of Higher Education (grant 200801411015).
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Received: February 6, 2010
Published Online: June 2, 2010
3364
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Eur. J. Inorg. Chem. 2010, 3360–3364