Binuclear half-metallocene chromium(III) complexes mediated ethylene polymerization with alkylaluminium as cocatalyst

Article abstract of DOI:10.1039/c1dt10803d

Binuclear half-metallocene chromium complexes {Cp*[3-(CHNR)-2-O- C₁₀H₅]CrCl}₂ [Cp* = C₅Me ₅; R = ⁱPr (1), Ph (2), 2,6-ⁱPr ₂C₆H₃ (3)] based on 1,1′-binaphthyl ligands, as well as their mononuclear analogues Cp*[3-(CHNR)-2′- R′-2-O-C₂₀H₁₁]CrCl [R = ⁱPr, R′ = ⁿBuO (4), R = Ph, R′ = ⁿBuO (5), R = 2,6- ⁱPr₂C₆H₃, R′ = ⁿBuO (6), R = ⁱPr, R′ = H (7)], were synthesized and characterized by mass spectrometry, elemental analysis, magnetic measurement, and UV-vis spectroscopy. The molecular structures of complexes 1, 3, 5 and 6 were further confirmed by single-crystal X-ray crystallographic analysis. When activated with a small amount of AlMe₃, these binuclear complexes exhibited higher activities in catalyzing ethylene polymerization in comparison with their mononuclear analogues, affording high molecular weight polymers with unimodal molecular weight distributions. The highest activity up to 2.87 × 10 ⁶ g PE (mol Cr)^-1 h^-1 was achieved in the catalyst system of complex 3 bearing a bulky 2,6-ⁱPr ₂C₆H₃ group on the imine nitrogen atom in the presence of 25 equiv. AlMe₃ as activator at 20 °C. ¹³C NMR analysis indicates the resultant polymers are linear and no evidence on branch was found. The Royal Society of Chemistry 2011.

Full text of DOI:10.1039/c1dt10803d

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PAPER
Binuclear half-metallocene chromium(III) complexes mediated ethylene
polymerization with alkylaluminium as cocatalyst†
Tieqi Xu,* Yu Pan and Xiao-Bing Lu*
Received 30th April 2011, Accepted 21st June 2011
DOI: 10.1039/c1dt10803d
Binuclear half-metallocene chromium complexes {Cp*[3-(CH NR)-2-O-C10H5]CrCl}2 [Cp* = C5Me5;
i
R = Pr (1), Ph (2), 2,6-iPr2C6H3 (3)] based on 1,1¢-binaphthyl ligands, as well as their mononuclear
i
n
n
analogues Cp*[3-(CH NR)-2¢-R¢-2-O-C20H11]CrCl [R = Pr, R¢ = BuO (4), R = Ph, R¢ = BuO (5), R =
n
i
2,6-iPr2C6H3, R¢ = BuO (6), R = Pr, R¢ = H (7)], were synthesized and characterized by mass
spectrometry, elemental analysis, magnetic measurement, and UV-vis spectroscopy. The molecular
structures of complexes 1, 3, 5 and 6 were further confirmed by single-crystal X-ray crystallographic
analysis. When activated with a small amount of AlMe3, these binuclear complexes exhibited higher
activities in catalyzing ethylene polymerization in comparison with their mononuclear analogues,
affording high molecular weight polymers with unimodal molecular weight distributions. The highest
activity up to 2.87 ¥ 106 g PE (mol Cr)-1 h-1 was achieved in the catalyst system of complex 3 bearing a
bulky 2,6-iPr2C6H3 group on the imine nitrogen atom in the presence of 25 equiv. AlMe3 as activator at
20 ◦C. 13C NMR analysis indicates the resultant polymers are linear and no evidence on branch was
found.
alkylaluminium activated half-metallocene chromium complexes
Introduction
are Cp*Cr(acac)Cl/Et3Al (Chart 1, B) with a catalytic activity of
4.2 ¥ 104 g PE (mol Cr)-1 h-1,6a as well as chromium(III) complexes
bearing b-ketoiminato6b (Chart 1, C), b-diketiminato6b (Chart 1,
D) and hydroxyindanimine6c ligands (Chart 1, E) with relatively
high activities (1.5 ¥ 105 g PE (mol Cr-1) h-1). Interestingly, with
Over the past few decades, metallocene type catalysts for
olefin polymerization have attracted considerable attention,
since they can provide a variety of polyolefin products with
high performance, such as isotactic polypropylene,1 syndiotac-
tic polypropylene,2 linear low-density polyethylene,3 syndiotac-
tic polystyrene.4 One of the most important catalysts is half-
metallocene chromium(III) complexes, which are considered to
be very promising catalysts for olefin polymerization.5–7 Par-
ticularly, these half-metallocene chromium(III) catalysts usually
exhibit good activity with no need for large amounts of MAO
(methylaluminoxane) or expensive fluorinated borate such as
[Ph3C]+[B(C6F5)4]- as cocatalyst or activator. It is beneficial to
significantly lower the ash content (Al2O3) of the polymers.
Unfortunately, only very limited half-metallocene chromium(III)
complexes have been synthesized, possibly owing to their poor
characteristics with regard to the paramagnetism. Complexes
[Cp*CrL2R]+A- (L = py, 1/2dppe, MeCN, THF; R = Me, Et;
A = PF6, BPh4) (Chart 1, A), were first applied to ethylene
polymerization in the absence of any cocatalyst, but the catalytic
activity was not satisfied.5 The representative catalysts based on
3
Cp*Cr(C6F5)(h -Bz)/Et3Al (Bz = benzyl) (Chart 1, F) as catalyst,
oligomers rather than polymers were predominantly produced
with an activity of 2.1 ¥ 105 g PE (mol Cr)-1 h-1.7 Recently,
we reported a highly efficient catalyst system based on half-
metallocene type chromium(III) catalyst, Cp*Cr[2,4-tBu2-6-(CH
t
NR)-C6H2O]Cl/AlR¢3 [R = Bu, Ph, 2,6-iPr2C6H3; R¢ = Me, Et,
iBu] (Chart 1, G), for ethylene polymerization with activity up
to 4.0 ¥ 106 g PE (mol Cr)-1 h-1.8 Indeed, only very limited
alkylaluminium activated half-metallocene chromium(III) catalyst
systems8 have reached the activity level of cationic metallocene
complexes of titanium and zirconium or constrained geometry
chromium complexes.
Recent developments of binuclear group 4 and late transition
metal complexes with MAO or fluorinated borate as activa-
tor have acted as guidelines for catalyst design in ethylene
polymerization.9,10 Binuclear metal complexes consisting of two
linked active centers in a catalyst molecule usually exhibit remark-
able enhancement in activity by a cooperative effect, compared
with their mononuclear counterparts. For example, in a MAO
activated phenoxyiminato zirconium catalyst system, the activity
of a binuclear phenoxyiminato zirconium catalyst is about 8
times that of the mononuclear analogue.9f Herein we report the
first binuclear half-metallocene chromium(III) complexes based on
State Key Laboratory of Fine Chemicals, College of Chemistry, Dalian
University of Technology, Dalian, 116024, China. E-mail: tqxu@
dlut.edu.cn, lxb-1999@163.com
† Electronic supplementary information (ESI) available. CCDC reference
numbers 757579 and 821440–821442 for compounds 1, 3, 5 and 6,
respectively. For ESI and crystallographic data in CIF or other electronic
format see DOI: 10.1039/c1dt10803d
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Chart 1
1,1¢-binaphthyl ligands and explore their catalytic activity in the
presence of a small amount of AlMe3 as activator for ethylene
homopolymerization.
with various amines in the presence of activated molecular
sieves. The binuclear chromium complexes 1–3 were synthesized
in 30–35% yield via the reaction of Cp*CrCl2(THF) (THF:
tetrahydrofuran) with the sodium salt of the corresponding shiff-
base ligands in THF at -78 ◦C (Scheme 1). For a comparative
purpose, mononuclear analogue complexes 4–7 were prepared
through a similar procedure.
Results and discussion
Synthesis and structural analysis
The molecular structures of complexes 1, 3, 5, and 6 have
been determined by a single-crystal X-ray diffraction method.
X-ray structures of complexes 1, 3, 5, and 6 and selected bond
The schiff-base pro-ligands L1–7H were synthesized in high yields
by the condensation reaction of the corresponding salicylaldehyde
Scheme 1
8644 | Dalton Trans., 2011, 40, 8643–8650
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Fig.
1
Molecular structure of complex 1 (two CH2Cl2 solvent
˚
molecules of crystallization are omitted). Selected bond distances (A)
and angles (◦): Cr(1)–O(1) 1.894(4), Cr(1)–N(1) 2.049(5), Cr(1)–Cl(1)
2.302(2), C21–N(1) 1.290(7), O(1)–C(1) 1.310(6), Cr(2)–O(2) 1.887(4),
Cr(2)–N(2) 2.036(5), Cr(2)–Cl(2) 2.315(2), C22–N(2) 1.291(7), O(2)–C(11)
1.316(7); O(1)–Cr(1)–N(1) 89.13(19), O(1)–Cr(1)–Cl(1) 99.06(14),
N(1)–Cr(1)–Cl(1) 89.98(15), O(2)–Cr(2)–N(2) 90.6(2), O(2)–Cr(2)–Cl(2)
98.18(14), N(2)–Cr(2)–Cl(2) 92.49(15).
˚
Fig. 3 Molecular structure of complex 5. Selected bond distances (A)
and angles (◦): Cr(1)–O(1) 1.9157(19), Cr(1)–N(1) 2.066(2), Cr(1)–Cl(1)
2.3147(9), C21–N(1) 1.293(3), O(1)–C(1) 1.313(3); O(1)–Cr(1)–N(1)
89.33(8), O(1)–Cr(1)–Cl(1) 96.59(7), N(1)–Cr(1)–Cl(1) 92.41(7).
˚
Fig. 2 Molecular structure of complex 3. Selected bond distances (A) and
angles (◦): Cr(1)–O(1) 1.905(5), Cr(1)–N(1) 2.106(6), Cr(1)–Cl(1) 2.312(3),
C21–N(1) 1.288(9), O(1)–C(1) 1.299(8), Cr(2)–O(2) 1.902(5), Cr(2)–N(2)
2.102(6), Cr(2)–Cl(2) 2.292(2), C22–N(2) 1.279(8), O(2)–C(11) 1.318(7);
O(1)–Cr(1)–N(1) 87.1(2), O(1)–Cr(1)–Cl(1) 96.17(17), N(1)–Cr(1)–Cl(1)
91.86(19), O(2)–Cr(2)–N(2) 85.5(2), O(2)–Cr(2)–Cl(2) 97.60(16),
N(2)–Cr(2)–Cl(2) 91.61(17).
˚
Fig. 4 Molecular structure of complex 6. Selected bond distances (A)
and angles (◦): Cr(1)–O(1) 1.915(3), Cr(1)–N(1) 2.111(4), Cr(1)–Cl(1)
2.3157(15), C21–N(1) 1.285(6), O(1)–C(1) 1.311(5); O(1)–Cr(1)–N(1)
87.72(14), O(1)–Cr(1)–Cl(1) 95.68(11), N(1)–Cr(1)–Cl(1) 91.72(11).
deviations of two Cr atoms from the plane of their ligands are
˚
˚
0.0279 A (Cr(1)) and 0.0015 A (Cr(2)), respectively.
distances and angles are depicted in Fig. 1–4, respectively. In
complexes 1 and 3, two unique Cr(III) cations are joined up
by binaphthol ligand to form the binuclear half-metallocene
chromium molecule. Both Cr(III) cations have a pseudo-octahedral
coordination environment of a three-legged piano stool. The Cr–
Cp*, Cr–O, Cr–N, and Cr–Cl bond lengths in both complexes
are close to those observed in some salicylaldiminato chromium
complexes11 and cyclopentadienyl chromium complexes.5–7 Com-
plex 1 approximates C2 symmetry (Fig. 1). The Cr–Cl bond faces to
the naphthyl ring regarding the other Cr atom. Although the two
Cr sections have almost the same Cr–O, Cr–N, Cr–Cl, and Cr–C
bond lengths and seemingly identical chemical environments, the
coordination geometries of the two Cr atoms are slightly different.
The dihedral angles between the Cp* ring and the phenoxide ring
are 53.8◦ (Cr(1)) and 51.7◦(Cr(2)). The dihedral angle between
the Cp* ring and the plane through the Cr, O, and N atoms is
52.6◦ (Cr(1)) and 51.5◦(Cr(2)). The coplanarity of the Cr(1) atom
and the atoms around it is not identical with that of Cr(2). The
Interestingly, the complex 3 molecule has C1 symmetry (Fig.
2). Similar to complex 1, the Cr(1)–Cl(1) bond in complex 3 also
faces the naphthyl ring regarding the Cr(2) atom. Whereas, the
Cr(2)–Cl(2) bond faces the ring containing Cr(1), O(1), N(1),
C(1), and C(21), leading to the bulky ortho-substituted steric group
around Cr(2). The coordination geometries of the two Cr atoms
are obviously different. The dihedral angles between the Cp* ring
and the phenoxide ring are 84.5◦ (Cr(1)) and 90.6◦(Cr(2)). The
dihedral angles between the Cp* ring and the plane through Cr, O,
and N atoms are 54.8◦ (Cr(1)) and 54.2◦(Cr(2)). The coplanarity
of the Cr(1) atom and the atoms around it is not identical to that
of Cr(2). The deviations of two Cr atoms from the plane of their
˚
˚
ligands are 0.7544 A (Cr(1)) and 0.9116 A (Cr(2)), respectively.
Comparatively, both dihedral angles of 1 are smaller than those
of 3. The smaller dihedral angle results in more sterically opening
degree around the Cr atoms of 1,8 which is responsible for its
high activity in catalyzing ethylene polymerization (vide infra).
The naphthol–naphthol dihedral angle of 61.9◦ in 1 is smaller
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Table 1 Results of ethylene polymerization using precatalysts 1–7a
T/◦C
Yield (g)
Activityb
Mw ¥ 10-4
Mw/Mn
Tmd (◦C)
c
c
Run
Precatalyst (mmol)
Al/Cr
AlR3
1
2
3
4
5
6
7
8
1(1)
2(1)
3(1)
3(1)
3(1)
3(1)
3(1)
3(1)
3(1)
3(1)
4(2)
4(2)
4(2)
5(2)
6(2)
7(2)
25
25
10
25
50
100
25
25
25
25
25
50
100
25
25
25
AlMe3
AlMe3
AlMe3
AlMe3
AlMe3
AlMe3
AlMe3
AlMe3
AlEt3
20
20
20
20
20
20
40
60
20
20
20
20
20
20
20
20
1.57
0.65
trace
2.87
2.34
2.02
2.12
1.56
1.85
1.46
0.09
0.08
0.07
0.06
0.04
0.08
1570
650
—
17.4
29.7
—
2.71
2.78
—
137.6
141.4
—
2870
2340
2020
2120
1560
1850
1460
90
80
70
60
40
27.6
22.8
24.1
19.6
20.2
20.2
19.9
18.3
17.9
17.0
19.1
20.0
—
3.35
3.30
3.13
3.37
3.58
3.16
2.99
2.69
2.72
2.85
2.66
2.69
—
140.8
139.8
138.9
138.7
137.9
138.6
138.0
137.5
138.5
137.8
137.2
138.7
—
9
10
11
12
13
14
15
16
AliBu3
AlMe3
AlMe3
AlMe3
AlMe3
AlMe3
AlMe3
80
a Polymerization conditions: solvent, 80 mL◦of toluene; ethylene pressure, 5 bar; time, 30 min. b kg PE (mol Cr)-1 h-1. c Measured by GPC analysis.
d Determined by DSC at a heating rate of 10 C min-1.
◦
˚
than that of 74.0 in 3. The Cr ◊ ◊ ◊ Cr distance of 7.504 A in 1 is
When the Al/Cr ratio was 10, only trace PE was found in the
30 min. The highest catalytic activity was observed in the system
with an Al/Cr ratio of 25. Interestingly, a further increase in
AlMe3 content in the range of 25–100 equiv. has a negative
influence on catalytic activity (Table 1, runs 4–6). Similar results
were also observed in the catalyst systems of 4/AlMe3 (Table
˚
longer than that of 6.827 A in 3.
In the mononuclear complexes 5 and 6, one crystallographically
unique Cr(III) cation has a pseudo-octahedral coordination envi-
ronment of a three-legged piano stool (Fig. 3 and 4). Both dihedral
angles between the Cp* ring and the phenoxide ring and dihedral
angles between the Cp* ring and the plane through Cr, O, and N
atoms are 27.8◦ and 30.6◦ in complex 5. The corresponding angles
are relatively wider 53.3◦ and 83.2◦ in complex 6. Comparatively,
the dihedral angles in 6 are similar to those in Cr(1) of 3, due to
their similar coordination geometries.
3
1, runs 11–13), Cp*Cr(C6F5)(h -Bz)/Et3Al6b and Cp*Cr[2,4-tBu-
2,6-(CH NR)-C6H2O]Cl/AlR3.8 This was tentatively explained
based on the formation of a bridged heterobimetallic chromium–
aluminum complex. The catalytic activities decrease with the
increase of reaction temperature from 20 to 60 ◦C, indicating
that the system was unstable at high temperature (Table 1, runs
4, 7, and 8). A similar result was also observed in the catalyst
system based on the half-sandwich b-ketoiminato chromium(III)
complex.6b The activities of these catalysts are also dependent
Ethylene polymerization
The experimental results of ethylene polymerization with com-
plexes 1–7 as precatalysts are summarized in Table 1. In the pres-
ence of 25 equiv. AlMe3 as activator, ethylene homopolymerization
using binuclear complexes 1–3 affords a high molecular weight of
1.74–2.97 ¥ 105 g mol-1 linear polyethylene with highly catalytic
activities of 0.65–2.87 ¥ 106 g PE (mol Cr)-1 h-1, which are about
10–70 times that of the corresponding mononuclear analogous
complexes 4–6 at the same conditions (Table 1, runs 1, 2, 4, 11, 14,
and 15). To investigate if pendant ether functionality of mononu-
clear complexes might coordinate to the chromium center in the
activated species, complex 7 without any pendant ether group was
also synthesized and tested in ethylene polymerization. No distinct
difference in catalytic activity for complexes 4 and 7 was observed
at the same conditions (Table 1, runs 11 and 16). Indeed, the single-
crystal X-ray crystallographic analyses of mononuclear complexes
5 and 6 also do not suggest the coordination of the pendant ether
group to the metal ion. These results rule out the effect of the
possible coordination of the pendant ether group to the chromium
center during the polymerization. Thus, the superior reactivity of
binuclear complexes is tentatively attributed to high local active
site concentrations9a and good stability of the catalytically active
species.9e
on the AlR3 cocatalysts and decreases in the order AlMe3
>
AlEt3> AliBu3 under the same conditions (Table 1, runs 4, 9, and
10). This may result from either a slower initiation process with
the larger AlR3 or a weak interaction between the catalyst and
cocatalyst molecules, as previously reported catalyst systems.6b,6c,8
For mononuclear chromium complexes, the catalytic activity for
ethylene polymerization under similar conditions (runs 11, 14, and
15 in Table 1) is in the order of 4 > 5 > 6. The catalytic activity of
5 with R = Ph is much higher than that of 6 with R = 2,6-iPr2C6H3
group, which is in agreement with the order of the sterically
opening degree around the chromium atom. This result is similar
to the Cp*Cr[2,4-tBu-2,6-(CH NR)-C6H2O]Cl/AlR3 system.8
On the contrary, in the catalyst systems based on binuclear
chromium complexes, the enhanced steric hindrance of the R
group is beneficial to improving the catalytic activity (Table 1,
runs 1, 2, and 4). The highest activity of 2.87 ¥ 106 g PE (mol Cr)-1
h-1 was found in the catalyst system based on complex 3 with R =
2,6-iPr2C6H3 group. We tentatively suggest that the bulky ortho-
substituted steric groups around Cr(2) in 3 can stabilize active
species during polymerization, thereby leading to an increased
concentration of active species to initiate this reaction.
The optimal polymerization conditions were obtained for the
most active complex 3 as precatalyst by varying the Al/Cr molar
ratio, reaction temperature, and the kind of alkylaluminium.
The gel permeation chromatography (GPC) shows that
the molecular weight distributions (Mw/Mn) of the obtained
polyethylenes are unimodal. The molecular weight distribution
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(Mw/Mn) of polyethylenes produced by binuclear complexes 1
or 2 is close to that of the corresponding mononuclear analogue.
This suggests that the two chromium centers in 1 or 2 are identical.
Six typical GPC diagrams of the polyethylene samples prepared
with precatalyst 1–6 are shown in Fig. 5. However, the polymers
resulting from binuclear precatalyst 3 display broader molecular
weight distributions (3.35) than that from its mononuclear pre-
catalyst (2.69) under the same conditions. A possible reason is
that due to the unsymmetric structure of binuclear precatalyst
3 (Fig. 2), the two Cr units are not identical. It will cause a
slight difference in activity of the two active sites during the
polymerization, which make a contribution to broadening the
molecular weight distribution, in comparison with the scenario
where there is only one active species present.10e 13C NMR analysis
on the polymer samples indicates that the polyethylenes produced
by these catalysts are linear and no evidence on branch nature was
observed. The melt transition temperatures (Tm) of these polymers
are in the range of 137.2–141.4 ◦C.
Fig. 6 The temperature dependence of reciprocal magnetic susceptibility
cM (square) and the product cMT (circle) for complex 3.
-1
plots of 3 with Curie–Weiss law in the range of 2.0–300.0 K get
results with C = 3.692 emu cm3 K mol-1 and q = -0.84 K. The
negative Weiss constant of complex 3 confirms the presence of
weak antiferromagnetic interactions between spin carriers. Similar
trends had also been observed in other Cr(III) complexes.12 In
˚
dinuclear complex 3, owing to the Cr ◊ ◊ ◊ Cr distance (6.827 A), only
weak antiferromagnetic interactions exist between Cr(III) ions.
For complex 6, the cMT value at 300.0 K is 1.281 emu K mol-1
(3.201 mB), which is lower than the expected spin-only value (g =
2.0) of 1.875 emu K mol-1 (3.873 mB) for one Cr(III) ion (S =
3/2). When the temperature is lowered, the cMT product steadily
decreases to reach a minimum of 0.865 emu K mol-1 at 2.0 K.
The experimental data have been well fitted by the Curie–Weiss
law above 2.0 K with the following Curie and Weiss constants:
1.289 emu K mol-1 and -0.72 K, respectively (see ESI Fig.
S1†). The negative Weiss constant also confirms the presence of
weak antiferromagnetic interactions between spin carriers, as was
already mentioned above. In complex 6, the interactions between
Cr(III) centers are weaker than those in binuclear complex 3
according to the Weiss constant, because the Cr ◊ ◊ ◊ Cr distance (the
Fig. 5 The GPC traces of the polyethylene samples prepared with (a)
binuclear precatalyst 3 (run 4 in Table 1), (b) binuclear precatalyst 2 (run 2
in Table 1), (c) binuclear precatalyst 1 (run 1 in Table 1), (d) mononuclear
precatalyst 4 (run 11 in Table 1), (e) mononuclear precatalyst 5 (run 14 in
Table 1), (f) mononuclear precatalyst 6 (run 15 in Table 1).
˚
shortest is 8.541 A) is significantly longer than that in complex 3.
Conclusions
In summary, we have developed highly active binuclear half-
metallocene chromium(III) catalysts for ethylene polymerization.
When activated with a small amount of AlMe3, these binuclear
catalysts give good activities in catalyzing ethylene polymerization
in comparison with their mononuclear analogues and afforded
high molecular weight polymers with unimodal molecular weight
distributions. The catalytic activity can be tuned by changing the
R group on the imine nitrogen atom. These novel complexes
represent a remarkable contribution to the limited list of half-
metallocene type chromium catalysts for ethylene polymerization.
Magnetic properties
The solution magnetic susceptibilities of 1–7 were investigated
at 300 K. Furthermore, the temperature dependence of the
magnetic susceptibility of complex 3 and mononuclear analogue
6 has been investigated on crystalline samples. The magnetic
susceptibilities of complexes 3 and 6 were measured in the 2.0–
300.0 K temperature range under a 10 000 Oe applied field and
are shown as cMT and 1/cM versus T plots in Fig. 6 and S1.†
For complex 3, the cMT value at 300.0 K is 3.674 emu K mol-1
(5.421 mB), which is slightly lower than the expected value 3.75
emu K mol-1 (5.477 mB, considering g = 2) of two Cr(III) ions (S =
3/2). When decreasing the temperature, cMT value of 3 decreases
gradually to a minimum of 2.386 emu K mol-1 at 2.0 K. This
characteristic thermal behavior is indicative of antiferromagnetic
interactions between metal spins, which also explained the low
cMT product at room temperature. Curve fits for 1/cM versus T
Experimental
All manipulations involving air- and/or water-sensitive com-
pounds were carried out in a standard glove box or under dry
nitrogen using standard Schlenk techniques. Toluene, terahydrofu-
ran (THF) and hexane were distilled from sodium/benzophenone
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under nitrogen. Methylene chloride was distilled from CaH2 under
nitrogen.
120.6, 119.6, 118.2, 116.2, 69.7, 31.5, 28.2, 23.8, 23.7, 18.8, 13.7.
HRMS (m/z) Calcd. for [C37H40NO2]+: 530.3059, found: 530.3045.
1H and 13C NMR spectra were recorded on Varian INOVA-
400 MHz type (1H, 400 MHz) (13C, 100 MHz) spectrometer.
1H and 13C NMR chemical shifts were referred to the solvent
signal. A Micromass Q-Tof (Micromass, Wythenshawe, UK) mass
spectrometer equipped with an orthogonal electrospray source
(Zspray) operated in positive ion mode (Capillary = 2000 V, Sample
cone = 20 V). Thermo-gravimetric analyses of all resulted polymers
were measured on a Mettler-Toledo TGA/SDTA851e. Elemental
analyses were performed on a Vario EL microanalyzer. Pro-ligands
L1H13 L2H13 and L3H14 were synthesized according to the literature
method.
Synthesis of 2-methoxymethoxy-1,1¢-binaphthyl
To a 100 mL three-necked flask equipped with a pressure-funnel,
a rubber-stopper and a magnetic stir bar, THF (30 mL) and NaH
(0.12 g) were added. When the mixture was cooled down to 0 ◦C, a
solution of 2-hydroxy-1,1¢-binaphthyl16 (1.35 g, 5 mmol) in 10 mL
THF was added dropwise. After 1 h, 1.2 mL methoxymethyl
chloride (MOMCl) was added by a syringe. The reaction was
then continued for another 4 h at room temperature and then
quenched with 100 mL water. This mixture was extracted three
times with 50 mL ethyl acetate. The combined organic phase was
washed with water and brine, and dried over MgSO4. Then the
solvent was removed in vacuo. The residue was purified by column
chromatography on silica gel using petrol ether/ethyl acetate (1 : 1,
v/v) as the mobile phase to give the afforded compound as a white
solid (1.34 g, 85%). 1H NMR (400 MHz, CDCl3) d 7.93–7.96 (m,
3H), 7.87 (d, 1H, J = 8.4 Hz), 7.61 (t, J = 7.2 Hz, 1H), 7.56 (d, J =
7.2 Hz 1H), 7.44–7.48 (m, 2H), 7.34–7.37 (m, 2H), 7.28 (d, J = 6.8
Hz, 1H), 7.22 (d, J = 4.0 Hz, 1H), 7.17 (d, J = 4.0 Hz, 1H), 5.02
(s, 2H), 3.14 (s, 3H).
Synthesis of 3-(CH NiPr)-2¢-nBuO-2-OH-C20H11 (L4H)
˚
Under nitrogen, activated 4 A molecular sieves (1.00 g),
dichloromethane (10 mL) and 3-formyl-2-hydroxy-2¢-butoxy-1,1¢-
binaphthyl15 (1.85 g, 5 mmol) were added into a 50 mL Schlenk
tube. Isopropylamine (0.29 g, 5 mmol) was added, and the mixture
was stirred at room temperature. After stirring for 24 h, the
reaction mixture was filtered through a pad of Celite on a medium
glass fritted funnel. Then the solvent was removed in vacuo. The
residue was purified by column chromatography on silica gel using
petrol ether/ethyl acetate (5 : 1) as the mobile phase to give the
Synthesis of 3-formyl-2-methoxymethoxy-1,1¢-binaphthyl
1
afforded complex L4H as a bright yellow solid (1.64 g, 80%). H
To a solution of 2-methoxymethoxy-1,1¢-binaphthyl (0.79 g,
2.5 mmol) and TMEDA (0.58 g, 5 mmol) in THF (20 mL), 1.6 mL
nBuLi (1.6 M in hexane) was add◦ed at -78 ◦C under nitrogen.
The mixture was warmed up to 0 C and stirred for 30 min and
then cooled down to -78 ◦C. A solution of DMF (0.37 g, 5 mmol)
in THF (5 mL) was added dropwise. This reaction solution was
warmed up to 0 ◦C and stirred for 2 h. The obtained solution was
quenched with 50 mL saturated NH4Cl solution. After separating
the organic layer, the water layer was extracted with ethyl ether.
The combined organic layer was washed with brine, and dried
over MgSO4. After removing the organic solvent, the residue was
treated with a flash chromatography using the petroleum ether and
ethyl acetate as eluent (5 : 1, v/v) to give the afforded compound as
a white solid (0.64 g, 75%). 1H NMR (400 MHz, CDCl3) d 10.57
(s, 1H), 8.57 (s, 1H), 8.04 (d, J = 8.0 Hz, 1H), 7.95–8.01 (m, 3H),
7.63 (t, J = 8.0 Hz, 1H), 7.46–7.53 (m, 3H), 7.33–7.39 (m, 3H),
4.64 (d, J = 1.6 Hz, 2H), 2.92 (s, 3H).
NMR (400 MHz, CDCl3) d 13.33 (s, 1H), 8.62 (s, 1H), 7.94 (d, J =
9.2 Hz, 1H), 7.90 (s, 1H), 7.86 (d, J = 2.8 Hz, 1H), 7.84 (s,1H), 7.44
(d, J = 8.8 Hz, 1H), 7.25–7.33 (m, 6H), 7.12 (d, J = 8.0 Hz, 2H),
3.93–4.04 (m, 2H), 3.60 (hept, 1H), 1.35–1.43 (m, 2H), 1.27 (d, J =
4.0 Hz, 6H), 0.93–1.00 (m, 2H), 0.61 (t, 3H). 13C NMR (100 MHz,
CDCl3) d 162.3, 154.8, 154.7, 135.5, 134.0, 132.6, 129.6, 129.5,
128.6, 128.1, 127.9, 127.4, 126.4, 125.4, 125.1, 123.7, 123.1, 121.0,
120.0, 117.5, 116.2, 69.6, 60.5, 31.4, 24.2, 18.8, 13.7. HRMS (m/z)
Calcd. for [C28H30NO2]+: 412.2277, found: 412.2293.
Synthesis of 3-(CH NPh)-2¢-nBuO-2-OH-C20H11 (L5H)
The pro-ligand L5H was prepared as a similar procedure of L4H.
1H NMR (400 MHz, CDCl3) d 13.03 (s, 1H), 8.92 (s, 1H), 8.10
(s, 1H), 7.98 (d, J = 8.8 Hz, 1H), 7.87–7.91 (m, 2H), 7.47 (d,
J = 8.8 Hz, 1H), 7.24–7.35 (m, 9H), 7.17 (d, J = 7.6 Hz, 4H),
4.01–4.09 (m, 2H), 1.37–1.45 (m, 2H), 0.94–1.01 (m, 2H), 0.61 (t,
J = 7.2 Hz, 3H). 13C NMR (100 MHz, CDCl3) d 162.6, 154.8,
154.4, 148.3, 136.1, 134.4, 134.0, 129.7, 129.6, 129.5, 128.8, 128.4,
128.2, 127.6, 127.2, 126.5, 125.3, 125.2, 123.7, 123.4, 121.2, 121.1,
119.7, 118.0, 116.1, 69.6, 31.4, 18.8, 13.6. HRMS (m/z) Calcd. for
[C31H28NO2]+: 446.2120, found: 446.2141.
Synthesis of 3-formyl-2-hydroxy-1,1¢-binaphthyl
To a solution of 3-formyl-2-methoxymethoxy-1,1¢-binaphthyl
(0.51 g, 1.50 mmol) in THF (10 mL), 10 mL concentrated HCl
◦
was added dropwise at 0 C. This mixture was then stirred for 3
Synthesis of 3-(CH N-2,6-iPr2-C6H3)-2¢-nBuO-2-OH-C20H11
(L6H)
h at room temperature and then extracted with ethyl acetate. The
obtained solution was washed with water, and dried with Na2SO4.
After evaporating the solvent, the product was obtained as a yellow
solid (0.43 g, 96%). 1H NMR (400 MHz, CDCl3) d 10.49 (s, 1H),
10.19 (s, 1H), 8.31 (s, 1H), 7.95–8.00 (m, 3H), 7.64 (d, J = 8.0 Hz,
1H), 7.46–7.53 (m, 3H), 7.25–7.38 (m, 4H), 7.20–7.22 (m, 1H).
The pro-ligand L6H was prepared as a similar procedure of L4H.
1H NMR (400 MHz, CDCl3) d 12.56 (s, 1H), 8.56 (s, 1H), 8.02 (s,
1H), 8.01 (d, J = 1.2 Hz, 1H), 7.87–7.91 (m, 2H), 7.48 (d, J = 8.8
Hz, 1H), 7.28–7.36 (m, 5H), 7.17–7.20 (m, 4H), 4.01–4.09 (m, 2H),
3.04 (hept, 2H), 1.43–1.51 (m, 2H), 1.18 (d, J = 4.0 Hz, 12H), 1.03–
1.11 (m, 2H), 0.65 (t, 3H). 13C NMR (100 MHz, CDCl3) d 167.0,
154.9, 154.6, 146.6, 138.8, 136.2, 134.4, 134.0, 129.8, 129.6, 128.8,
128.6, 128.2, 127.5, 126.5, 125.6, 125.4, 125.3, 123.7, 123.5, 123.4,
Synthesis of 3-(CH NiPr)-2-OH-C20H11 (L7H)
˚
Under nitrogen, activated molecular sieves (4 A, 0.5 g),
dichloromethane (10 mL) and 3-formyl-2-hydroxy-1,1¢-binaphthyl
8648 | Dalton Trans., 2011, 40, 8643–8650
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(0.29 g, 1 mmol) were added into a 50 mL Schlenk tube.
Isopropylamine (0.12 g, 2 mmol) was added, and the mixture was
stirred at room temperature. After stirring for 10 h, the reaction
mixture was filtered through a pad of Celite on a medium glass
fritted funnel. The solvent was removed in vacuo. The residue
was purified by column chromatography on silica gel using petrol
ether/ethyl acetate (5 : 1, v/v) as the mobile phase to give the
C 71.70; H 7.02; N 2.49. UV/vis (dichloromethane): 243, 315,
487 nm. Magnetic measurement: meff (solution in benzene, 300 K) =
5.42 mB.
Synthesis of Cp*[3-(CH NiPr)-2¢-nBuO-2-O-C20H11]CrCl (4)
Complex 4 was synthesized in the same way as described above
for the synthesis of complex 1 with pro-ligand L4H (1.03 g,
2.50 mmol) as starting material. Pure complex 4 (0.81 g,
1.28 mmol, 51%) was obtained as purple crystals. HRMS (m/z)
Calcd. for [C38H43NO2Cr]+: 597.2699, found: 597.2678. Anal.
Calcd. for C38H43NO2ClCr (%): C 72.08; H 6.84; N 2.21. Found:
C 72.14; H 6.85; N 2.25. UV/vis (dichloromethane): 244, 315,
466 nm. Magnetic measurement: meff (solution in benzene, 300 K) =
3.32 mB.
1
afforded complex L7H as a pale yellow solid (0.31 g, 91%). H
NMR (400 MHz, CDCl3) d 13.51 (s, 1H), 8.62 (s, 1H), 7.92–7.97
(m, 3H), 7.86 (d, 1H), 7.63 (t, J = 7.6 Hz, 1H), 7.40–7.50 (m,
3H), 7.26–7.30 (m, 3H), 7.15 (d, J = 4.0 Hz, 1H), 3.60 (hept,
1H), 1.35–1.43 (m, 2H), 1.27 (d, J = 4.0 Hz, 6H). 13C NMR (100
MHz, CDCl3) d 162.1, 154.6, 154.5, 135.4, 134.1, 134.0, 132.8,
132.7, 128.6, 128.4, 128.1, 128.0, 127.2, 126.1, 126.0, 125.8, 125.7,
125.2, 123.3, 121.0, 120.9, 60.5, 24.2. HRMS (m/z) Calcd. for
[C24H22NO]+: 340.1701, found: 340.1686.
Synthesis of Cp*[3-(CH NPh)-2¢-nBuO-2-O-C20H11]CrCl (5)
Synthesis of {Cp*[3-(CH NiPr)-2-O-C10H5]CrCl}2 (1)
Complex 5 was synthesized in the same way as described above
for the synthesis of complex 1 with pro-ligand L5H (1.11 g,
2.50 mmol) as starting material. Pure complex 5 (0.75 g,
1.13 mmol, 45%) was obtained as purple crystals. HRMS (m/z)
Calcd. for [C41H41NO2Cr]+: 631.2542, found: 631.2518. Anal.
Calcd. for C41H41NO2ClCr (%): C 73.80; H 6.19; N 2.10. Found:
C 73.82; H 7.23; N 2.04. UV/vis (dichloromethane): 243, 314,
469 nm. Magnetic measurement: meff (solution in benzene, 300 K) =
3.36 mB.
Under nitrogen, a solution of pro-ligand L1H (0.53 g, 1.25 mmol)
in THF was added to a mixture NaH (0.07 g, 2.92 mmol) in
THF (10 mL) at -78 ◦C. The reaction mixture was allowed
to warm to room temperature and stirred for 2 h, and then
the reaction mixture was filtered through a pad of Celite on a
medium glass fritted funnel. The filtrate was added at -78 ◦C to a
solution of Cp*CrCl2(THF) which was prepared by the reaction of
CrCl3(THF)3 (0.94 g, 2.50 mmol) with Cp*Li (0.36 g, 2.50 mmol)
in THF (30 mL). The resulting mixture was allowed to warm
to room temperature and stirred for 15 h, during which time the
color changed from blue to purple. The solvent was removed under
vacuum, and the residue was extracted with CH2Cl2 (20 mL) and
filtered. The filtrate was concentrated to 5 mL and mixed with
hexane (50 mL). Cooling to –30 ◦C afforded purple crystals of
complex 1 after several days (0.37 g, 0.43 mmol, 34%). HRMS
(m/z) Calcd. for [C48H56N2O2ClCr2]+: 831.2841, found: 831.2809.
Anal. Calcd. for C48H56N2O2Cl2Cr2 (%): C 66.43; H 6.50; N 3.23.
Found: C 66.51; H 6.40; N 3.27. UV/vis (dichloromethane): 243,
316 487 nm. Magnetic measurement: meff (solution in benzene,
300 K) = 5.39 mB.
Synthesis of Cp*[3-(CH N-2,6-iPr2-C6H3)-2¢-nBuO-2-O-C20H11]-
CrCl (6)
Complex 6 was synthesized in the same way as described above
for the synthesis of complex 1 with pro-ligand L6H (1.32 g,
2.50 mmol) as starting material. Pure complex 6 (0.56 g,
0.75 mmol, 30%) was obtained as purple crystals. HRMS (m/z)
Calcd. for [C47H53NO2Cr]+: 715.3481, found: 715.3457. Anal.
Calcd. for C47H53NO2ClCr (%): C 75.13; H 7.11; N 1.86. Found:
C 75.19; H 7.19; N 1.80. UV/vis (dichloromethane): 244, 315,
467 nm. Magnetic measurement: meff (solution in benzene, 300 K) =
3.20 mB.
Synthesis of Cp*[3-(CH N-2,6-iPr2-C6H3)-2-O-C20H11]CrCl (7)
Synthesis of {Cp*[3-(CH NPh)-2-O-C10H5]CrCl}2 (2)
Complex 2 was synthesized in the same way as described above for
the synthesis of complex 1 with proligand L2H (0.62 g, 1.25 mmol)
as starting material. Pure complex 2 (0.35 g, 0.37 mmol,
30%) was obtained as purple crystals. HRMS (m/z) Calcd. for
[C54H52N2O2ClCr2]+: 899.2528, found: 899.2551. Anal. Calcd. for
C54H52N2O2Cl2Cr2 (%): C 69.30; H 5.60; N 2.99. Found: C 69.38;
H 5.71; N 3.05. UV/vis (dichloromethane): 244, 315, 487 nm.
Magnetic measurement: meff (solution in benzene, 300 K) = 5.41 mB.
Complex 7 was synthesized in the same way as described above for
the synthesis of complex 1 with pro-ligand L7H (0.85 g, 2.50 mmol)
as starting material. Pure complex 7 (0.61 g, 1.15 mmol,
46%) was obtained as purple crystals. HRMS (m/z) Calcd.
for [C34H35NOCr]+: 525.2124, found: 525.2132. Anal. Calcd. for
C34H35NOClCr (%): C 72.78; H 6.29; N 2.50. Found: C 72.83;
H 6.23; N 2.54. UV/vis (dichloromethane): 249, 315, 469 nm.
Magnetic measurement: meff (solution in benzene, 300 K) = 3.38 mB.
Synthesis of {Cp*[3-(CH N-2,6-iPr2-C6H3)-2-O-C10H5]CrCl}2
Ethylene polymerizations
(3)
A dry 250 mL steel autoclave with a magnetic stirrer was charged
with 80 mL of toluene, and saturated with ethylene (1.0 bar) at
20 ◦C. The polymerization reaction was started by injection of a
mixture of AlMe3 and a catalyst in toluene (10 mL). The vessel was
immediately repressurized to the required pressure with ethylene
and the pressure was kept by continuous feeding of ethylene. After
30 min, the polymerization was quenched by injecting acidified
Complex 3 was synthesized in the same way as described above for
the synthesis of complex 1 with pro-ligand L3H (0.83 g, 1.25 mmol)
as starting material. Pure complex 3 (0.48 g, 0.44 mmol,
35%) was obtained as purple crystals. HRMS (m/z) Calcd. for
[C66H76N2O2ClCr2]+: 1067.4406, found: 1067.4385. Anal. Calcd.
for C66H76N2O2Cl2Cr2 (%): C 71.79; H 6.94; N 2.54. Found:
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Table 2 Crystal data and structural refinement details for complexes 1, 3, 5, and 6
1
3
5
6
Mol formula
Mol wt
Cryst system
C50H60Cl6Cr2N2O2
1037.70
Monoclinic
P21/c
16.312(4)
12.288(4)
29.792(6)
90
120.392(10)
90
5151(2)
4
2160
1.338
0.772
0.1294
0.0715
0.1480
0.995
C66H76Cl2Cr2N2O2
1104.19
Monoclinic
P21/c
18.076(5)
18.047(5)
23.103(4)
90.00
125.714(14)
90.00
6119(3)
4
2336
1.199
0.485
0.1491
0.0940
0.1695
1.024
C41H41ClCrNO2
667.20
C47H53ClCrNO2
751.35
Monoclinic
Triclinic
¯
Space group
P1
P21/c
˚
a/A
8.6023(7)
12.9253(11)
16.4342(14)
69.8440(10)
83.356(2)
79.470(2)
1683.7(2)
2
11.6666(16)
20.495(3)
17.050(2)
90.00
˚
b/A
˚
c/A
a (◦)
b (◦)
g (◦)
92.581(2)
90.00
4072.6(9)
4
1596
1.225
0.385
0.0712
0.0731
0.1623
3
˚
V/A
Z
F(000)
702
1.316
0.456
0.0229
0.0513
0.1202
1.021
Dc (g cm-3)
m/mm-1
Rint
R1(I > 2d)
WR2 (I>2d)
GOF
1.056
methanol [HCl (3 M)/methanol = 1 : 1], and the polymer was
collected by filtration, washed with water, methanol, and dried at
60 ◦C in vacuo to a constant weight.
4 (a) N. Ishihara, T. Seimiya, M. Kuramoto and M. Uoi, Macromolecules,
1986, 19, 2464; (b) G. Xu and D. Chien, Macromolecules, 2000, 33,
2825; (c) Y. Luo, J. Baldamus and Z. Hou, J. Am. Chem. Soc., 2004,
126, 13910; (d) K. Nomura, N. Naga, M. Miki, K. Yanagi and A. Imai,
Organometallics, 1998, 17, 2152.
5 (a) B. J. Thomas and K. H. Theopold, J. Am. Chem. Soc., 1988, 110,
5902; (b) B. J. Thomas, S. K. Noh, G. K. Schulte, S. C. Sendlinger and
K. H. Theopold, J. Am. Chem. Soc., 1991, 113, 893.
6 (a) O. Heinemann, P. W. Jolly, C. Kruger and G. P. J. Verhovnik,
J. Organomet. Chem., 1998, 553, 477; (b) Y. Huang, W. Yu and
G. Jin, Dalton Trans., 2009, 767; (c) Y. Huang, W. Yu and G. Jin,
Organometallics, 2009, 28, 4170.
7 G. Mani and F. P. Gabbai, Angew. Chem., Int. Ed., 2004, 43, 2263.
8 T. Xu, Y. Mu, W. Gao, J. Ni, L. Ye and Y. Tao, J. Am. Chem. Soc., 2007,
129, 2236.
9 (a) L. Li, M. V. Metz, H. Li, M. Chen, T. J. Marks, L. Liable-Sands
and A. L. Rheingold, J. Am. Chem. Soc., 2002, 124, 12725; (b) H. Li,
L. Li, T. J. Marks, L. Liable-Sands and A. L. Rheingold, J. Am. Chem.
Soc., 2003, 125, 10788; (c) N. Guo, L. Li and T. J. Marks, J. Am. Chem.
Soc., 2004, 126, 6542; (d) A. Motta, I. L. Fragala and T. J. Marks, J.
Am. Chem. Soc., 2007, 129, 7327; (e) N. Guo, C. Stern and T. J. Marks,
J. Am. Chem. Soc., 2008, 130, 2246; (f) M. R. Salata and T. J. Marks, J.
Am. Chem. Soc., 2008, 130, 12; (g) H. Li, C. L. Stern and T. J. Marks,
Macromolecules, 2005, 38, 9015; (h) M. H. Lee, S. K. Kim and Y. Do,
Organometallics, 2005, 24, 3618; (i) S. K. Noh, W. Jung, H. Oh, Y. R.
Lee and W. S. Lyoo, J. Organomet. Chem., 2006, 691, 5000.
10 (a) M. R. Salata and T. J. Marks, J. Am. Chem. Soc., 2008, 130, 12;
(b) B. A. Rodriguez, M. Delferro and T. J. Marks, J. Am. Chem. Soc.,
2009, 131, 5902; (c) M. R. Salata and T. J. Marks, Macromolecules,
2009, 42, 1920; (d) T. Hu, Y. Li, J Liu and Y. Li, Organometallics, 2007,
26, 2609; (e) T. Hu, L. Tang, X. Li, Y. Li and N. Hu, Organometallics,
2005, 24, 2628.
Crystal structure determination
Single crystals of complexes 1, 3, 5, and 6 for X-ray structural
analysis were obtained from a solution of CH2Cl2/nhexane.
Diffraction data was collected at 293 K (for 1 and 5) or 200 K
(for 3 and 6) on a Bruker SMART-CCD diffractometer using
˚
graphite-monochromated Mo-Ka radiation (l = 0.71073 A).
The structure was solved by direct methods17 and refined by
full-matrix least-squares on F2. All non-hydrogen atoms were
refined anisotropically, and the hydrogen atoms were included
in an idealized position. All calculations were performed using
the SHELXTL18 crystallographic software packages. Details of
the crystal data, data collections, and structure refinements are
summarized in Table 2.
Acknowledgements
This work was supported by the National Natural Science Founda-
tion of China (No. 20804006) and Specialized Research Fund for
the Doctoral Program of Higher Education (No. 200801411015),
and the Fundamental Research Funds for the Central Universities
(DUT11LK24). X.-B. Lu gratefully acknowledges the Outstand-
ing Yong Scientist Foundation of NSFC (Grant 20625414). The
authors also thank Dr Haiyan An for her great help in describing
magnetic properties of various chromium complexes and single-
crystal X-ray crystallographic analysis.
11 V. C. Gibson, S. Mastroianni, C. Newton, C. Redshaw, G. A. Solan, A.
J. P. White and D. J. Williams, J. Chem. Soc., Dalton Trans., 2000, 1969.
12 (a) S. Y. Jie, R. Pattacini, G. Rogez, C. Loose, J. Kortusd and P.
Braunstein, Dalton Trans., 2009, 97–105; (b) M. Salidu, F. Artizzu,
P. Deplano, M. L. Mercuri, L. Pilia, A. Serpe, L. Marchio`, G. Concasc
and F. Congiuc, Dalton Trans., 2009, 557.
13 H. Brunner and J. Goldbrunner, Chem. Ber., 1989, 122, 2005.
14 T. Hu, Y. Li, Y. Li and N. Hu, J. Mol. Catal. A: Chem., 2006, 253,
155.
References
1 (a) W. Kaminsky, K. Kulper and H. H. Brintzinger, Angew. Chem., Int.
Ed. Engl., 1985, 24, 507; (b) J. A. Ewen, J. Am. Chem. Soc., 1984, 106,
6355.
2 (a) J. A. Ewen, R. L. Jones, A. Razavi and J. D. Ferrara, J. Am. Chem.
Soc., 1988, 110, 6255; (b) H. G. Alt and E. Samuel, Chem. Soc. Rev.,
1998, 27, 323.
3 (a) C. Bae, J. F. Hartwig, H. Chung, N. K. Harris, K. A. Switek and M.
A. Hillmyer, Angew. Chem., Int. Ed., 2005, 44, 6410; (b) A. L. Mckniht
and R. M. Waymouth, Chem. Rev., 1998, 98, 2587.
15 L. Jin, Y. Huang, H. Jing, T. Chang and P. Yan, Tetrahedron:
Asymmetry, 2008, 19, 1947.
16 P. Wawrzyniak and J. Heinicke, Tetrahedron Lett., 2006, 47, 8921.
17 SHELXTLPC Siemens Analytical X-ray Instruments: Madison, WI,
1993.
18 G. M. Sheldrick, SHELXTL Structure Determination Programs,
Version 6.12; PC Siemens Analytical Systems: Madison, WI,
1994.
8650 | Dalton Trans., 2011, 40, 8643–8650
This journal is
The Royal Society of Chemistry 2011
©