Synthesis of nickel complexes with bidentate N,O-type ligands and application in the catalytic oligomerization of ethylene

Article abstract of DOI:10.1039/b716111e

The dinuclear complexes [Ni(μ-Cl){(4,5-dihydro-4,4-dimethyloxazol-2-yl) methanol}]₂Cl₂14 and [Ni(μ-Cl){(pyridin-2-yl)methanol}] ₂Cl₂16 have been synthesized in high yields by reaction of NiCl₂ with 2 mol. equiv. of the ligands 4,5-dihydro-4,4- dimethyloxazol-2-yl)methanol 13 or (pyridin-2-yl)methanol 15, respectively. The reaction of NiCl₂ with 3 mol. equiv. of 15 afforded in high yield the mononuclear, octahedral mer-[Ni{(pyridin-2-yl)methanol}₃Cl ₂] complex 18. The reaction of 16 with NaH led to the deprotonation of one of the pyridine alcohol ligands to form [Ni{(pyridin-2-yl)methanol} {(pyridin-2-yl)methanolate}Cl] 21 in which the metal is coordinated by one pyridine alcohol and one pyridine alcoholate ligand. The crystal structures of the dinuclear, chloride-bridged octahedral complexes in 14?C ₆H₁₂ and in 16?3CH₂Cl₂ and of the mononuclear, octahedral complex 18 in 18?CH₂Cl₂ have been determined by X-ray diffraction. In the latter case, intermolecular OH...Cl bonding interactions generate a centrosymmetric pseudo-dimer. Complexes 14, 16 and 21 have been tested in ethylene oligomerization with AlEtCl ₂ (Al/Ni ratios of 2, 4 or 6) or MAO (50, 100 or 200 equiv.) as co-catalysts under 10 bar of ethylene and yielded mostly dimers and trimers. Complex 16 in the presence of 6 equiv. of AlEtCl₂ proved to be the most active system with a turnover frequency (TOF) up to 187-500 C ₂H₄ (mol Ni h)^-1. Complex 16 with 200 equiv. of MAO was also the most active, with TOF up to 104-300 C₂H₄ (mol Ni h)^-1 under 30 bar of ethylene. The Royal Society of Chemistry.

Full text of DOI:10.1039/b716111e

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Synthesis of nickel complexes with bidentate N,O-type ligands and
application in the catalytic oligomerization of ethylene†‡§¶
Anthony Kermagoret and Pierre Braunstein*
Received 18th October 2007, Accepted 17th January 2008
First published as an Advance Article on the web 19th February 2008
DOI: 10.1039/b716111e
The dinuclear complexes [Ni(l-Cl){(4,5-dihydro-4,4-dimethyloxazol-2-yl)methanol}]
Ni(l-Cl){(pyridin-2-yl)methanol}] Cl 16 have been synthesized in high yields by reaction of NiCl
with 2 mol. equiv. of the ligands 4,5-dihydro-4,4-dimethyloxazol-2-yl)methanol 13 or
pyridin-2-yl)methanol 15, respectively. The reaction of NiCl with 3 mol. equiv. of 15 afforded in high
yield the mononuclear, octahedral mer-[Ni{(pyridin-2-yl)methanol} Cl ] complex 18. The reaction of
6 with NaH led to the deprotonation of one of the pyridine alcohol ligands to form
Ni{(pyridin-2-yl)methanol}{(pyridin-2-yl)methanolate}Cl] 21 in which the metal is coordinated by
one pyridine alcohol and one pyridine alcoholate ligand. The crystal structures of the dinuclear,
chloride-bridged octahedral complexes in 14·C 12 and in 16·3CH Cl and of the mononuclear,
octahedral complex 18 in 18·CH Cl have been determined by X-ray diffraction. In the latter case,
intermolecular OH · · · Cl bonding interactions generate a centrosymmetric pseudo-dimer. Complexes
4, 16 and 21 have been tested in ethylene oligomerization with AlEtCl (Al/Ni ratios of 2, 4 or 6) or
MAO (50, 100 or 200 equiv.) as co-catalysts under 10 bar of ethylene and yielded mostly dimers and
2
Cl
2
14 and
[
2
2
2
(
2
3
2
1
[
6
H
2
2
2
2
1
2
trimers. Complex 16 in the presence of 6 equiv. of AlEtCl
2
proved to be the most active system with a
−
1
turnover frequency (TOF) up to 187 500 C
2
H
4
(mol Ni h) . Complex 16 with 200 equiv. of MAO was
−
1
also the most active, with TOF up to 104 300 C
2
4
H (mol Ni h) under 30 bar of ethylene.
Introduction
Neutral nickel catalysts with N,O-type ligands proved to be active
for ethylene polymerization without cocatalyst and these include
Olefin polymerization catalyzed by late transition metal complexes
has been intensively developed for the production of low-density
polyethylene (LDPE) and high-density polyethylene (HDPE).
However, the discovery of the ’nickel effect” in catalytic olefin
chemistry highlighted the oligomerizing character of nickel cata-
lysts which favour chain transfer over chain growth. The high
14,15,29
complexes described by the groups of Grubbs (type 1),
30–32
33–37
Mecking
(type 2) and others
with salicylaldimine ligands
1–5
or by Brookhart and co-workers with anilinotropone ligands (type
38–40
3) or anilinoperinaphthenone ligands (type 4).
6,7
industrial demand for linear a-olefins (LAO), particularly in the
C –C20 range, has emphasized the key role of nickel complexes as
4
8–10
catalysts. The use of heteroditopic ligands, including bidentate
11,12
13
14,15
P,O,
P,N and N,O
-type ligands, allows a fine tuning
of the catalytic properties of their Ni(II) complexes in olefin
oligomerization.
16–18
The high activity and selectivity in LAO of the SHOP process
has generated a considerable interest for nickel complexes with a
11,19–24
P,O-type ligands in catalytic ethylene oligomerization.
Based
on a neutral phenyl nickel complex, it produces a Schulz–Flory
mass distribution of the a-olefins and has inspired the synthesis
25–27
28
of numerous nickel catalysts with P,N
and N,O -type ligands.
Laboratoire de Chimie de Coordination, Institut de Chimie (UMR 7177
CNRS), Universit e´ Louis Pasteur, 4 rue Blaise Pascal, F-67070 Strasbourg
C e´ dex, France. E-mail: braunstein@chimie.u-strasbg.fr
†
‡
§
Dedicated to Professor Ken Wade on the occasion of his 75th birthday.
The HTML version of this article has been enhanced with colour images.
CCDC reference numbers 664564–664567. For crystallographic data in
CIF or other electronic format see DOI: 10.1039/b716111e
¶
Electronic supplementary information (ESI) available: Selected hydrogen
bonding interactions in the structures of 14·C 12, 16·3CH Cl and
8·CH Cl (Tables S1–S3). See DOI: 10.1039/b716111e
6
H
2
2
1
2
2
1
564 | Dalton Trans., 2008, 1564–1573
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−
Other neutral nickel complexes with anionic N,O ligands, such
41
as the imidazole-alcoholate complexes 5, iminocarboxamide
42
43
complexes 6 and 2-(alkylideamino)benzoate complexes 7, form
active catalysts for the oligomerization or polymerization of
ethylene without any cocatalyst. In these cases, ethylene insertion
in the Ni–aryl or Ni–alkyl bond represents the first step of the
reaction and is followed by b-H migration, leading to olefin
elimination and formation of a nickel–hydride complex, which
is the active species.
Even in the presence of small amounts of AlEtCl or MAO as
2
a co-catalyst, these complexes showed high activities in ethylene
oligomerization (turnover frequencies (TOF) up to 174 300 mol
−
1
C
2
H
4
(mol Ni h) for 11 with only 6 equiv. of AlEtCl
2
), giving
mostly C olefins and 1-butene. Since relatively small changes in the
4
substitution pattern of the chelating ligand may have significant
consequences on the structure and the catalytic properties of their
13
Ni(II) complexes, we wished to evaluate the possible influence of
the gem-dimethyl substituents of the alcohol ligands and prepared
the new Ni(II) complexes 14 and 16 to evaluate them for the
catalytic oligomerization of ethylene, with MAO or AlEtCl
co-catalyst.
2
as
However, many nickel precatalysts with N,O-type ligands have
to be activated with a co-catalyst, such as alkylaluminiums or
44–49
B(C
2-pyridyl)benzamides (in 8), 2-oxazolinylphenolates (in 9),
or b-ketiminates (in 10).
6
F
5
)
3
. This is the case with the ligands salicylaldimines,
N-
50
51,52
Results and discussion
(
The (4,5-dihydro-4,4-dimethyloxazol-2-yl)methanol ligand 13 was
55
prepared according to the literature by double condensation of
glycolic acid with 2-amino-2-methyl-1-propanol in xylene at reflux
1
during 24 h [eqn (1)]. Additional characterizations by H NMR
1
3
1
and C{ H} NMR spectroscopy are reported in the Experimental
section.
(
1)
Complexes 14 and 16 were synthesized at room temperature
by reaction of a methanol solution of NiCl with 2 mol. equiv.
2
of ligand 13 or of (pyridin-2-yl)methanol 15, respectively, and
after work-up, they were isolated as green powders in almost
quantitative yields [eqn (2) and (3)].
We reported recently the synthesis of Ni(II) precatalysts with
zwitterionic N,O-benzoquinonemonoimine-type ligands which
presented good activities for ethylene oligomerization with
AlEtCl
and trimerization of ethylene and the formation of the C
resulted from chain growth and/or reinsertion of 1-butene or
2
or MAO as a co-catalyst. They favoured the dimerization
6
olefins
53
2
-butene. We have also used oxazoline alcohols and pyridine
alcohols to synthesise the Ni(II) complexes 11 and 12, respectively,
of which the dinuclear structures were established by X-ray
54
diffraction.
(2)
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◦
a
Table 1 Selected bond lengths ( A˚ ) and angles ( ) in 14·C
H
12 and
6
b
1
6·3CH
2 2
Cl
1
4·C
6
H
12
2 2
16·3CH Cl
ꢀ
Ni1–Cl1
2.397(2)
2.404(2)
2.108(4)
2.117(4)
2.062(4)
2.063(4)
1.420(6)
1.489(7)
1.337(6)
1.271(6)
1.421(6)
1.486(7)
1.339(6)
1.269(6)
4.713(3)
4.702(3)
2.409(2)
2.419(2)
2.063(4)
2.059(4)
2.062(5)
2.064(5)
1.432(8)
1.507(9)
—
1.330(8)
1.433(9)
1.50(1)
—
Ni1–Cl1
Ni1–O1
Ni1–O3
Ni1–N1
Ni1–N2
O1–C1
C1–C2
C2–O2
C2–N1
O3–C7
C7–C8
C8–O4
C8–N2
(
3)
These two dicationic complexes are paramagnetic and have been
characterized by IR spectroscopy, elemental analysis and X-ray
diffraction. The dinuclear centrosymmetric structures of 14·C
and 16·3CH Cl are shown in Fig. 1 and 2 and selected bond
distances and bond angles are given in Table 1.
6
H
12
2
2
1.333(9)
4.535(2)
4.552(2)
Ni1 · · · Cl2
Ni1 · · · Cl2ꢀ
O1–Ni1–N1
O1–Ni1–Cl1
O1–Ni1–Cl1
O1–Ni1–O3
O1–Ni1–N2
N1–Ni1–Cl1
N1–Ni1–Cl1
N1–Ni1–N2
N1–Ni1–O3
N2–Ni1–Cl1
N2–Ni1–Cl1
77.5(2)
93.8(1)
92.5(1)
171.5(2)
96.5(2)
91.5(2)
169.8(1)
92.9(2)
96.6(2)
169.4(1)
90.5(2)
92.6(2)
93.5(2)
86.84(8)
93.16(8)
77.4(2)
106.3(4)
123.1(4)
114.0(3)
113.8(4)
106.4(4)
123.3(5)
113.7(3)
77.8(2)
95.4(2)
93.4(2)
167.6(2)
94.1(2)
88.5(2)
168.8(2)
98.0(2)
93.8(2)
89.3(2)
169.4(2)
93.4(2)
95.9(2)
85.48(5)
93.52(5)
77.9(2)
109.2(5)
116.7(5)
115.8(4)
113.7(4)
109.7(6)
115.9(6)
116.2(4)
ꢀ
ꢀ
ꢀ
ꢀ
O3–Ni1–Cl1
O3–Ni1–Cl1
Cl1–Ni1–Cl1
ꢀ
ꢀ
Ni1–Cl1–Ni1
N2–Ni1–O3
O1–C1–C2
C1–C2–N1
C2–N1–Ni1
Ni1–O3–C7
O3–C7–C8
C7–C8–N2
C8–N2–Ni1
Fig. 1 ORTEP view of the structure of the oxazoline alcohol complex
12 with thermal ellipsoids drawn at the 50% probability level,
1
4 in 14·C
6
H
symmetry operation generating equivalent atoms: −x, −y, −z + 1.
a
b
Symmetry operation generating equivalent atoms: −x, −y, −z + 1.
Symmetry operation generating equivalent atoms: −x, −y + 1, −z.
and OH donor groups are cis and trans to each other, respectively,
and by two bridging chlorides which are trans to the nitrogen
atoms. The unit cell 16·3CH
2
Cl contains two independent but
almost identical molecules. In both 14 and 16, the two chloride
2
counter anions do not interact with the metal centres and are at
˚ ˚
4.702(3) and 4.713(3) A for 14 and 4.535(2) and 4.552(2) A for 16
from a Ni(II) centre. However, interactions between the chloride
counter-anions and the hydrogen atoms of the OH functions are
ꢀ
ꢀ
observed, with O1–H1 · · · Cl2 and O3 –H3 · · · Cl2 distances of
˚
2
2
.984(4) and 2.994(4) A (ESI, Table S1¶), for 14 and 2.993(4) and
˚
.972(5) A (ESI, Table S2¶), for 16, respectively (calculated O1–
Fig. 2 ORTEP view of the structure of the pyridine alcohol complex 16
ꢀ
ꢀ
◦
H1 · · · Cl2 and O3 –H3 · · · Cl2 angles of 158 and 158 for 14 (ESI,
in 16·3CH
2 2
Cl with thermal ellipsoids drawn at the 50% probability level,
symmetry operation generating equivalent atoms: −x, −y + 1, −z.
◦
Table S1¶) and 157 and 162 , for 16, respectively (ESI, Table S2¶).
◦
As shown by the O1–Ni–O3 angle of 171.5(2) for 14·C
6
H12 against
◦
The dications in 14·C
6
H
12 and in 16·3CH
2
Cl form centrosym-
2
168.2(2) for 11, the metal centre in 14·C
6
H12 has a coordination
metric dimers and their Ni(II) centres adopt a distorted octahedral
coordination geometry, very similar to those of 11 and 12 which
contained gem-dimethyl substituents in a-position to the OH
geometry less distorted than in 11. The Ni–N and Ni–Cl distances
12 than in 11.
are slightly shorter in 14·C
6
H
Complex 16 has similar structural characteristics to 12 and these
54
donor. Each Ni(II) is surrounded by two N,O chelates, whose N
will therefore not be discussed in detail. The O1–C1–C2 angles in
1
566 | Dalton Trans., 2008, 1564–1573
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◦
◦
Table 2 Selected bond lengths ( A˚ ) and angles ( ) in 18·CH Cl
a
1
4 and 16 are ca. 3 larger than the corresponding O–CMe
2
–C
2
2
angles in 11 and 12, which is consistent with the gem-effect in the
latter complexes. The structure of a nickel complex coordinated
by two (pyridin-2-yl)methanol ligands has been described recently
but the coordination of two water molecules led instead to a
mononuclear structure with an octahedral nickel centre.
Complex 16 has been obtained recently in a less convenient way
by reaction of the phosphinitopyridine ligand 17 with NiCl in
MeOH. This reaction led to the cleavage of the P–O bond and
Ni–O1
Ni–O2
Ni–O3
Ni–N1
Ni–N2
Ni–N3
Ni · · · Cl1
Ni · · · Cl2
2.043(2)
2.078(2)
2.044(2)
2.055(2)
2.083(2)
2.075(2)
4.488(1)
4.328(1)
O1–C1
O2–C7
O3–C13
N1–C2
N2–C8
N3–C14
C1–C2
C7–C8
C13–C14
1.421(3)
1.434(3)
1.423(3)
1.340(4)
1.339(3)
1.433(4)
1.499(4)
1.510(4)
1.495(4)
56
2
57
formation of 16 and [NiCl
2
(PPh
2
OMe) ] [eqn (4)].
2
O1–Ni–O2
O1–Ni–O3
O1–Ni–N1
O1–Ni–N2
O1–Ni–N3
O2–Ni–O3
O2–Ni–N1
O2–Ni–N2
89.03(8)
175.07(8)
79.17(8)
94.93(9)
96.66(9)
91.63(8)
167.31(8)
79.85(9)
O3–Ni–N1
O3–Ni–N2
O3–Ni–N3
N1–Ni–N2
N1–Ni–N3
N2–Ni–N3
O2–Ni–N3
100.53(8)
89.99(9)
78.45(8)
96.41(8)
95.63(8)
164.7(1)
90.31(8)
(
4)
a
Symmetry operation generating equivalent atoms: −x + 1, −y + 2, −z +
When NiCl
2
was reacted with more than 3 mol. equiv. of
1
.
(
pyridin-2-yl)methanol 15, the octahedral nickel complex 18 was
formed quantitatively and isolated as a blue powder. The reaction
of complex 16 with 15 in methanol in a 1 : 2 ratio also led to the
formation of this complex, as indicated by a colour change of the
solution from green to blue [eqn (5)].
with a meridional coordination of the three nitrogen atoms and
of the three oxygens. The Ni1–N2 and Ni1–N3 bonds are in
˚
trans position and of similar length (2.083(2) and 2.075(2) A,
respectively). The trans influence of the nitrogen N1 trans to
˚
oxygen O2 makes the Ni1–O2 distance slightly longer (2.078(2) A)
˚
than Ni1–O1 and Ni1–O3 (2.043(2) and 2.044(2) A, respectively).
˚
˚
The Ni1–Cl1 (4.488(1) A) and Ni1–Cl2 (4.328(1) A) distances
are too long to represent any significant bonding interaction.
The counter anions Cl1 and Cl2 form hydrogen bonds with the
hydrogen atoms H1 and H3, respectively (Fig. 3), as indicated
by the O1–H1 · · · Cl1 and O3–H3 · · · Cl2 distances of 2.922(3)
(
5)
˚
and 2.934(3) A, respectively (calculated distances H1 · · · Cl1 and
˚
H3 · · · Cl2: 2.08 and 2.10 A and calculated angles O1–H1 · · · Cl1
◦
and O3–H3 · · · Cl2: 176 and 169 , respectively, ESI,¶ Table S3).
Interestingly, the atom Cl2 connects two cations by hydrogen
The crystal structure of 18·CH
2
Cl has been determined by X-
2
ꢀ
ꢀ
bonding, as depicted in Fig. 3 (O2 –H2 · · · Cl2 distance: 2.986(2)
ray diffraction. An ORTEP view of the molecular structure is
shown in Fig. 3 and selected bond distances and bond angles are
given in Table 2.
ꢀ
ꢀ
◦
˚
A, calculated O2 –H2 · · · Cl2 angle: 172 , ESI,¶Table S3).
We also considered converting the neutral donor ligand of
complex 16 (dative HO→Ni bond) into a anionic ligand by
deprotonation of at least one of the pyridine alcohol ligands with
NaH, in order to study the catalytic properties of the resulting
complex. Heinicke et al. have shown that whereas the neutral
methallylnickel(II) phosphanylphenolate complexes 19 catalyze
the polymerization of ethylene, the corresponding, protonated
cationic methallylnickel phosphinophenol complexes 20 catalyze
In the crystals of 18·CH
2
Cl , three molecules of (pyridin-2-
yl)methanol 15 chelate the metal centre in a distorted octahedral
2
geometry (Table 2) and form a mononuclear asymmetric molecule
20,58
its oligomerization.
The reaction of complex 16 with NaH in THF formed 21 which
has been characterized by elemental analysis and IR spectroscopy
[
eqn (6)].
Fig. 3 ORTEP view of the structure of the oxazoline alcohol complex 18
in 18·CH
2
Cl
2
with thermal ellipsoids drawn at the 50% probability level,
ꢀ
symmetry operation generating equivalent atoms ( ): −x + 1, −y + 2, −z +
(6)
1
.
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a
2
Table 3 Comparative catalytic data for complexes 14, 16 and 21 in the oligomerization of ethylene with AlEtCl as co-catalyst
b
Selectivity (%)
Amount/
10 mol
Al/Ni
ratio
Productivity/g
TOF/mol C
(mol Ni h)
2
H
4
1-Butene
c
−
5
−1
−1
d
Complex
t/min
C
4
C
6
C
8
C
2
H
4
(g Ni h)
(% mol)
k
a
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
4
4
4
4
6
6
6
6
6
1
1
1
1
1
1
1.05
1.05
1.05
4
4
4
1.05
1.05
1.05
4
4
4
1.05
1.05
1.05
4
4
4
2
4
6
2
4
6
2
4
6
2
4
6
2
4
6
2
4
6
35
35
35
35
35
35
35
35
35
35
35
35
35
35
35
35
35
35
92
63
64
97
68
69
95
81
70
78
68
69
77
72
62
83
60
61
8
31
29
3
30
27
5
17
25
21
29
28
19
23
32
15
35
34
0
6
7
<1
2
4
<1
2
5
1
3
3
4
5
6
2
5
5
9900
20700
97400
155000
<1000
35200
52300
<1000
42900
187500
20700
33700
40500
25300
75300
99800
8400
62
20
16
79
11
6
87
39
10
16
9
<0.10
0.33
0.30
<0.10
0.29
0.27
<0.10
0.14
0.23
0.18
0.29
0.27
0.19
0.21
0.34
0.12
0.39
0.37
46400
73900
<500
16700
24900
<1000
20500
89400
9900
16100
19300
12100
35900
47600
4000
6
43
32
29
13
3
d
ref
ref
ref
35300
35000
74100
73600
3
a
◦
b
c
d
Conditions: T = 25–30 C, 10 bar C
2
H
4
, reaction time 35 min. No C10 oligomers were detected. Selectivity within the C
} ].
3 2
4
fraction.
k
a
= Hexenes
e
[
mol]/butenes [mol]. ref: [NiCl
2
{P(n-Bu)
Complex 21 proved to be paramagnetic in solution and its mag-
59–62
netic moment, determined by the Evans method in CD
2
2
Cl ,
was 2.7 l
B
. This value is similar to those recently reported for other
Ni(II) complexes with P,N-type ligands and suggests a distorted
63,64
tetrahedral geometry in solution.
Catalytic oligomerization of ethylene
The complexes 14, 16 and 21 have been evaluated in the catalytic
oligomerization of ethylene with different amounts of AlEtCl
or MAO as co-catalyst and the complex [NiCl ] was
2
2
{P(n-Bu)
3 2
}
used as a reference catalyst (ref). This is convenient since it is
easier to check its purity by NMR techniques, in contrast to the
case of paramagnetic [NiCl
2
(PCy
3
)
2
]. Furthermore, [NiCl
2
{P(n-
Fig. 4 Catalytic activities of the complexes 14, 16, and 21 (quantity of
65
Bu) ] has well-established catalytic properties for this reaction.
3
}
2
−2
complex: 1.05 × 10 mmol) in the oligomerization of ethylene using
A comparison of the catalytic results between 14 and 16 will show
the influence of the basicity of the nitrogen and that between 16
and 21 the impact of an anionic ligand vs. a neutral ligand on
the oligomerization of ethylene. In order to study the influence
of the concentration of the precatalysts and to compare the data
with previous results obtained with Ni(II) complexes coordinated
AlEtCl
2
as co-catalyst.
mol Ni h) with 4 × 10−2 mmol and 1.05 × 10−2 of precatalyst,
−1
(
respectively.
In contrast to 16, complexes 14 and 21 were soluble in
chlorobenzene and showed high activities with 2, 4 or 6 equiv.
13
−2
−2
by P,N-type ligands, we used 1.05 × 10 or 4 × 10 mmol of
precatalyst dissolved in a total volume of 15 mL of chlorobenzene
and toluene.
of AlEtCl
2
(Table 3). The highest activities were always observed
−2
with 1.05 × 10 mmol of precatalyst and 6 equiv. of AlEtCl
2
:
−
1
1
55 000, 187 500 and 99 800 mol C
and 21, respectively. The selectivities for C
with complexes 14, 16 and 21 decreased with increasing catalytic
activity (Table 3). Complex 16 presented selectivities for C olefins
up to 95% and for 1-butene up to 87% with 2 equiv. of AlEtCl
2
H
4
(mol Ni h) for 14, 16
4
olefins and 1-butene
Use of AlEtCl as co-catalyst
2
The precatalysts 14, 16 and 21 were evaluated with 2, 4 or 6 equiv.
of AlEtCl as co-catalyst (Al/Ni ratios of 2, 4 or 6, respectively)
Table 3, Fig. 4). The low solubility of 16 in chlorobenzene could
explain its very low activity with 2 equiv. of co-catalyst (less than
4
2
2
(
(Fig. 5). The isomerization of 1-butene to 2-butene became more
important with increasing activities. However, a decrease of the
−
1
−2
−2
1
000 mol C
AlEtCl are needed to form sufficiently soluble, active species in
the catalytic solution and with 6 equiv. of AlEtCl 16 afforded
the highest turnover frequencies: 52 300 and 187 500 mol C
2
H
4
(mol Ni h) ). Indeed, more than 2 equiv. of
concentration of catalyst from 4 × 10 to 1.05 × 10 mmol had
a beneficial impact on the selectivity for 1-butene, as shown with
21 where the selectivity increased from 6 to 29% when 6 equiv. of
2
2
2
H
4
AlEtCl
2
were used.
1
568 | Dalton Trans., 2008, 1564–1573
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a
Table 4 Catalytic data and distribution of the C
6
2
oligomers for complexes 14, 16 and 21 in the oligomerization of ethylene with AlEtCl as co-catalyst
Selectivity (mass%)
c
d
Amount/
10 mol
C
6
from
6
C from
−
5
b
Complex
Al/Ni ratio
1-Hexene
2- and 3-Hexene
1-butene
2-butene
1
1
1
1
1
1
1
2
2
2
2
2
2
4
4
4
6
6
6
6
1
1
1
1
1
1
1.05
1.05
1.05
4
2
4
6
4
6
4
6
2
4
6
2
4
6
16
3
3
2
<1
8
3
3
<1
1
14
3
76
54
44
43
32
63
50
48
33
40
74
53
44
<1
12
3
7
4
9
2
8
5
6
2
11
5
7
31
50
48
63
20
45
41
61
53
10
33
48
4
1.05
1.05
4
4
4
1.05
1.05
1.05
3
a
◦
b
c
Conditions: T = 25–30 C, 10 bar C
2
H
4
, reaction time 35 min. Sum of 2-cis-hexene, 2-trans-hexene, 3-cis-hexene and 3-trans-hexene. Corresponding
d
to 2-ethyl-1-butene. Sum of 3-methyl-1-pentene, 3-methyl-2-cis-pentene and 3-methyl-2-trans-pentene.
a
Table 5 Comparative catalytic data for complexes 14, 16 and 21 in the oligomerization of ethylene with MAO as co-catalyst
Selectivity
Amount/
10 mol
MAO
(equiv.)
Productivity/g
TOF/mol C
(mol Ni h)
2
H
4
1-Butene
(% mol)
−
5
−1
−1
b
c
Complex
C
4
C
6
C
8
>C
8
C
2
H
4
(g Ni h)
k
a
1
1
1
1
1
1
1
1
1
1
1
2
2
2
4
4
4
4
6
6
6
6
6
6
6
1
1
1
1.05
1.05
1.05
1.05
4
4
4
1.05
1.05
1.05
1.05
1.05
1.05
1.05
4
50
100
200
200
50
100
200
50
100
200
200
50
100
200
50
85
70
75
92
94
74
66
91
79
75
85
92
81
80
43
25
26
41
11
24
20
7
3
5
4
1
<1
4
5
1
3
4
2
1
2
3
0
<1
1
0
0
<1
<1
0
5300
12900
17300
26400
1000
4700
6700
11100
27000
36300
55300
2200
57
36
35
61
64
28
23
61
40
34
51
61
45
42
3
<0.10
0.23
0.18
<0.10
<0.10
0.20
0.29
<0.10
0.15
0.18
0.11
<0.10
0.14
0.14
0.72
1.47
1.31
0.72
d
6
22
29
8
18
20
13
7
17
17
46
54
52
45
9800
14100
12000
24200
37100
104300
5900
20700
23000
40000
41300
36900
39600
5700
0
11600
17700
49700
2800
<1
<1
0
0
<1
3
7
6
4
d
9900
11000
18600
19200
17600
18900
e
ref
ref
ref
ref
8
4
4
4
100
200
400
14
16
10
3
3
4
a
e
◦
b
c
d
Conditions: T = 25–30 C, 10 bar C
2
H
4
, reaction time 35 min. Selectivity within the C
4
fraction. k
a
= Hexenes [mol]/butenes [mol]. Pressure: 30 bar.
ref: [NiCl
2
{P(n-Bu)
3 2
].
}
The low selectivity for C
systems could be explained by the competing reinsertion of
-butene to form 2-hexene, 3-hexene and 2-ethyl-1-butene and
the reinsertion of 2-butene, although more difficult, to form
4
olefins with very active catalytic
the complexes were active (Tables 5 and 6, Fig. 6–8). Complexes
14 and 16 have similar activities, between 11 100 and 12 000 mol
−
1
1
C
2
H (mol Ni h) with 50 equiv. of MAO, between 24 200 and
4
−
1
27 000 mol C
2
H
4
(mol Ni h) with 100 equiv. and between 36 300
53
−1
3
-methyl-1-pentene and 3-methyl-2-pentene. Table 3 shows that
and 37 100 mol C
2
H
4
(mol Ni h) with 200 equiv. MAO. These
−
2
with 1.05 × 10 mmol of precatalyst, less branched oligomers are
complexes presented similar selectivities for C olefins (up to 91%)
4
−
2
formed than with 4 × 10 mmol of precatalyst, suggesting that a
lower catalyst concentration disfavored the re-insertion of olefins.
Accordingly, increasing the amount of co-catalyst favored the
and for 1-butene (up to 61%) (Fig. 7). Complex 21 was less active
than 14 and 16 (Fig. 8) with 200 equiv. of MAO but it was more
selective for C oligomers (up to 92%) and for 1-butene (up to 61%).
4
re-insertion of olefins and resulted in an increase of the C
6
fraction
A pressure increase from 10 to 30 bar led to a very high increase
(
(
Table 4), in particular of the C
Table 4).
6
oligomers formed from 2-butene
of catalytic activity for complexes 14 and 16 (Table 5). Whereas 16
−
1
displayed the highest activity of 104 300 mol C
presented the best selectivities for C olefins (92%) and for 1-butene
61%). A pressure increase had a beneficial but modest impact on
2
H
4
(mol Ni h) , 14
4
(
Use of MAO as co-catalyst
the selectivity for 1-hexene, which increased from 7 to 11% with
14 and from 6 to 9% with 16 in the presence of 200 equiv. of MAO
(Table 6).
The precatalysts 14, 16 and 21 (1.05 × 10− mmol) have been
2
evaluated in the presence of MAO (50, 100 or 200 equiv.) and all
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a
Table 6 Catalytic data and distribution of the C
6
oligomers for complexes 14, 16 and 21 in the oligomerization of ethylene with MAO as co-catalyst
Selectivity (mass%)
−
5
c
d
e
Complex
Amount/10 mol
MAO (equiv.)
1-Hexene
2- and 3-Hexene
C
6
from 1-butene
6
C from 2-butene
1
1
1
1
1
1
1
1
1
1
1
2
2
2
4
4
4
4
6
6
6
6
6
6
6
1
1
1
1.05
1.05
1.05
1.05
4
4
4
1.05
1.05
1.05
1.05
1.05
1.05
1.05
50
100
200
200
50
100
200
50
100
200
200
50
100
200
13
7
7
11
15
5
4
16
8
6
9
60
56
54
63
59
53
53
59
58
54
58
58
58
60
12
12
12
13
13
12
12
13
12
12
12
12
12
12
15
25
27
14
13
30
31
12
22
28
21
13
20
20
e
e
17
10
8
a
◦
b
c
Conditions: T = 25–30 C, 10 bar C
2
H
4
, 35 min. Sum of 2-cis-hexene, 2-trans-hexene, 3-cis-hexene and 3-trans-hexene. Corresponding to 2-ethyl-1-
d
e
butene. Sum of 3-methyl-1-pentene, 3-methyl-2-cis-pentene and 3-methyl-2-trans-pentene. Pressure 30 bar.
Fig. 7 Selectivity in C olefins for the complexes 14, 16 and 21 (quantity
4
−
2
of complex: 1.05 × 10 mmol) in the oligomerization of ethylene using
MAO as co-catalyst.
Fig. 5 Selectivity for 1-butene in the C fraction for the complexes 14, 16,
4
−
2
and 21 (quantity of complex: 1.05 × 10 mmol) in the oligomerization of
ethylene using AlEtCl as co-catalyst.
2
Fig. 8 Selectivity for 1-butene in the C fraction with complexes 14, 16
4
−
2
and 21 (quantity of complex: 1.05 × 10 mmol) in the oligomerization of
Fig. 6 Catalytic activities of the complexes 14, 16 and 21 (quantity of
ethylene using MAO as co-catalyst.
−
2
complex: 1.05 × 10 mmol) in the oligomerization of ethylene using MAO
as co-catalyst.
of solution). Higher activities and better selectivities for 1-butene
(40% with 100 equiv. of MAO and 34% with 200 equiv.) were
obtained with 1.05 × 10 mmol of precatalyst (Table 5).
Two different concentrations were used for precatalyst 16
−
2
−2
−2
(
1.05 × 10 and 4 × 10 mmol in a total volume of 10 mL
570 | Dalton Trans., 2008, 1564–1573
1
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◦
Conclusion
distilled at 115 C. Gas chromatographic analyses were performed
on a Thermoquest GC8000 Top series gas chromatograph using a
HP Pona column (50 m, 0.2 mm diameter, 0.5 lm film thickness).
The high yield reaction of NiCl with 2 mol. equiv. of the
2
oxazoline alcohol 13 or of (pyridin-2-yl)methanol 15 yielded the
corresponding dinuclear complexes 14 or 16 with octahedral metal
coordination. They are very similar to the dinuclear complexes
Synthesis of (4,5-dihydro-4,4-dimethyloxazol-2-yl)methanol (13)
To a solution of glycolic acid (4.08 g, 53.7 mmol) in 100 mL
of xylene, was added 5 mL of 2-amino-2-methyl-1-propanol
(53.7 mmol) and the mixture was stirred at reflux for 24 h. After
evaporation of the solvent under reduced pressure, the resulting
11 and 12 with oxazoline alcohol or pyridine alcohol ligands
bearing gem-dimethyl substituents in a position to the donor
54
oxygen atom. The reaction of NiCl with 3 mol equiv. of 15
2
led to the octahedral, mononuclear complex 18 which can also be
formed by reaction of 16 with the pyridine alcohol in a 1 : 2 ratio.
Deprotonation of one of the two pyridine alcohol ligands of 16
with NaH afforded complex 21.
The complexes 14, 16 and 21 have been evaluated in the
catalytic oligomerization of ethylene with 50, 100 and 200 equiv.
◦
yellow oil was distilled under reduced pressure (160 C, 0.8 mbar)
and 13 was obtained as a white powder by placing the oil in a
◦
1
refrigerator (mp of 13 is around 15 C). Yield: 4.24 g (62%). H
NMR (CDCl
3
): d 1.30 (s, 6H, CH
3
), 4.05 (s, 2H, CH
OH). C{ H} NMR (CDCl ): d 28.2 (s, CH
OH), 66.6 (s, CCH ), 79.7 (s, CH
2
), 4.26 (s,
), 56.9 (s,
), 166.9 (s, NCO).
1
3
1
2
H, CH
2
3
3
CH
2
3
2
of MAO or with 2, 4 and 6 equiv. of AlEtCl
2
as co-catalyst.
When 1.05 × 10 mmol of complex was used, 16 presented the
best activities, up to 187 500 mol C (mol Ni h) with only
and the best selectivities for C olefins (up to
5%) and for 1-butene (up to 87%) with 2 equiv. of AlEtCl . A
−
2
−
1
Synthesis of [Ni(l-Cl){(4,5-dihydro-4,4-dimethyloxazol-2-yl)-
methanol}] Cl (14)
2
H
4
2
2
6
9
equiv. of AlEtCl
2
4
2
A solution of 2 mol. equiv. of (4,5-dihydro-4,4-dimethyloxazol-
-yl)methanol (13) (1.22 g, 9.6 mmol) in 20 mL of methanol was
added to a solution of anhydrous NiCl (0.61 g, 4.8 mmol) in 50 mL
comparison between precatalysts containing the pyridine alcohol
or the oxazoline alcohol ligands shows that it remains difficult to
2
2
54
generalise the observations made with one system. When 4 ×
mmol of precatalysts was used in the presence of AlEtCl , 16
and 21 showed similar activities compared to those obtained with
of methanol and the reaction mixture was stirred for 2 h at room
temperature. After reaction, the methanol was removed under
reduced pressure, the residue was washed with diethylether, dried
under reduced pressure and 14 was isolated as a green powder.
Yield: 1.65 g (90%). Single crystals suitable for X-ray diffraction
−
2
10
2
13
Ni(II) complexes bearing P,N type ligands.
With MAO, precatalysts 14, 16 and 21 were very active and 16
−
1
presented the highest activities up to 37100 mol C
with 200 equiv. of MAO and selectivities for C olefins (up to 94%)
and 1-butene (up to 64%) with 50 equiv. of MAO. Precatalysts 14,
6 and 21 in the presence of MAO showed higher activities than 11
2
H
4
(mol Ni h)
were obtained by slow diffusion of petroleum ether into a CH
solution of 14. Anal. Calc. for C24 Ni : C, 37.15; H,
.72; N, 7.22. Found: C, 36.97; H, 6.13; N, 6.68%. IR (KBr): 1674
2
Cl
2
4
H
44Cl
N
O
8
4
4
2
5
1
(
1
s), 1637 (vs), 1508 (w), 1467 (m), 1450 (m sh), 1406 (m), 1371 (m),
281 (s), 1209 (m), 1185 (w sh), 1063 (vs), 952 (s), 843 (w) cm .
−
2
and 12 (with 1.05 × 10 mmol of complex) and Ni(II) complexes
−1
−
2
bearing P,N type ligands (with 4 × 10 mmol of complex). The
increase of the ethylene pressure to 30 bar resulted in more active
Synthesis of [Ni(l-Cl){(pyridin-2-yl)methanol}] Cl (16)
2
2
complexes 14 and 16 (the TOF of 16 increased to 104 300 mol C
2
H
4
−
1
Complex 16 was prepared by reaction of NiCl (0.86 g, 6.6 mmol)
2
(
mol Ni h) ) and more selective for C
for 14 from 75 to 92%) and for 1-butene (selectivity increase for
4 from 35 to 61%). The fact that the catalytic properties of 14
and 16 are rather similar to those of 11 and 12 may be related
to their structural similarities. If the gem-Me groups in 11 and
2 makes the donor OH function in a-position more electron-rich
4
olefins (selectivity increase
and (pyridin-2-yl)methanol (15) (1.44 g, 13.2 mmol) by following
the same procedure described for 14 and it was isolated as a green
powder. Yield: 2.18 g (95%). Single crystals suitable for X-ray
diffraction were obtained by slow diffusion of petroleum ether
1
2
into a CH
2
Cl
2
solution of 16. Anal. Calc. for C24
H
28Cl
4
N
4
Ni
2
O
4
:
1
C, 41.43; H, 4.06; N, 8.05. Found: C, 41.25; H, 4.48; N, 7.61%.
and a better donor, the variation in the C–CH
angles is limited.
2
–O vs. C–CMe –O
2
HRMS: Mass Calcd for C12
H
14ClN
2
NiO : 311.0092. Found:
2
+
3
11.0099 (Ni(N,O)
2
Cl) . IR (KBr): 1608 (vs), 1571 (s), 1483 (s),
1
444 (s), 1440 (s sh), 1349 (w), 1286 (s), 1237 (m), 1156 (s), 1065
Experimental
(
s sh), 1050 (s sh), 1033 (vs), 778 (s sh), 765 (s), 727 (m), 648 (m),
−
1
626 (w) cm .
1
13
1
The H and C{ H} NMR spectra were recorded at 300.13 and
7
5.5 MHz on a Bruker AC300 instrument. Elemental analyses
Synthesis of [Ni{(pyridin-2-yl)methanol}
3
Cl
2
] (18)
were performed by the “Service de Microanalyse, Universite´
Louis Pasteur (Strasbourg, France)”. IR spectra in the range
of 4000–400 cm were recorded on a Bruker IFS28FT. Mass
spectra were recorded with a Bruker Daltonics microTOF (ESI;
positive mode; capillary voltage: 4.8 kV; nebulizer pressure: 0.2
To a solution of NiCl (0.70 g, 5.4 mmol) in 30 mL of methanol
2
−
1
was added a solution of 4 equiv. of (pyridin-2-yl)methanol (2.00 g,
21.6 mmol) in 5 mL of methanol and the reaction mixture was
stirred for 2 h at room temperature. At the end of the reaction, the
methanol was removed under reduced pressure and the residue
was washed with diethyl ether (3 × 20 mL) to eliminate unreacted
(pyridin-2-yl)methanol and dried under reduced pressure. The
product was isolated as a blue powder. Yield: 2.05 g (93%). Single
◦
bar; desolvation temperature: 180 C; desolvation gas flow rate:
−
1
4
.5 L min ). Commercial NiCl
2
·6H
2
O was dried by heating
◦
at 160 C overnight under vacuum to give anhydrous NiCl
2
.
Magnetic moments were determined by the Evans method in
CD Cl using a solution of CH NO in CD Cl (20 : 80, v/v)
as reference. The commercial (pyridin-2-yl)methanol (15) was
2
2
3
2
2
2
crystals of 18·CH
2
Cl
2
suitable for X-ray diffraction were obtained
Cl solution. Anal. Calc.
59–62
by slow diffusion of pentane into a CH
2
2
This journal is © The Royal Society of Chemistry 2008
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for C18
H
21Cl
2
N
3
NiO
H, 4.96; N, 8.51%. IR (KBr): 1608 (vs), 1571 (s), 1483 (s), 1444 (s),
440 (s sh), 1349 (w), 1286 (s), 1237 (m), 1156 (s), 1065 (s sh), 1050
3
: C, 47.31; H, 4.63; N, 9.20. Found: C, 47.10;
to 2, 4 or 6 equiv. respectively, is added to form a total volume
−
2
of 15 mL with the precatalyst solution. When 1.05 × 10 mmol
of precatalyst was used, a solution of the complex in 14 mL of
chlorobenzene was injected into the reactor, followed by 0.26, 0.52
or 0.75 mL of a solution of the co-catalyst corresponding to 2, 4
2
1
−
1
(
s sh), 1033 (vs), 778 (s sh), 765 (s), 727 (m), 648 (m), 626 (w) cm .
Synthesis of [Ni{(pyridin-2-yl)methanol}{(pyridin-2-yl)-
methanolate}Cl] (21)
or 6 equiv. of AlEtCl , respectively.
−
2
−2
With MAO, 1.05 × 10 or 4 × 10 mmol of Ni complex was
dissolved in 10 mL in chlorobenzene and injected into the reactor
under an ethylene flux. Then 2, 4 or 8 mL (for a complex amount
To a suspension of 16 (1.50 g, 4.3 mmol) in THF was added excess
NaH (1.00 g, 41.7 mmol) and the mixture was stirred for 24 h
at room temperature. At the end of the reaction, the solvent was
removed under reduced pressure and 20 mL of CH
The green solution obtained was filtered to eliminate unreacted
−
2
of 4 × 10 mmol) or 0.51, 1.05 or 2.10 mL (for a complex amount
of 1.05 × 10 mmol) of a co-catalyst solution, corresponding to
0, 100 or 200 equiv. of MAO respectively, was added.
−
2
2
2
Cl was added.
5
◦
All catalytic tests were started between 25 and 30 C, and no
NaH and 16. After removing the solvent under reduced pressure,
cooling of the reactor was done during the reaction. After injection
of the catalytic solution and of the co-catalyst under a constant
low flow of ethylene, the reactor was pressurized to 10 or 30 bar. A
temperature increase was observed which resulted solely from the
exothermicity of the reaction. The 10 or 30 bar working pressure
was maintained during the experiments through a continuous feed
of ethylene from a reserve bottle placed on a balance to allow
continuous monitoring of the ethylene uptake. At the end of each
test (35 min) a dry-ice bath, and in the more exothermic cases also
2
1 was washed with diethylether, dried under vacuum and isolated
as a dark green powder. Yield: 0.97 g (72%). Anal. Calc. for
NiO : C, 46.29; H, 4.21; N, 9.00. Found: C, 45.92;
H, 4.57; N, 8.64%. IR (KBr): 1632 (vs), 1597 (vs), 1569 (s sh),
479 (w), 1438 (s), 1371 (vs), 1282 (m), 1244 (w), 1153 (w), 1077
C
12
H
13ClN
2
2
1
−
1
(
s), 1049 (s), 848 (m), 761 (vs), 729 (w), 704 (m), 643 (w) cm .
Oligomerization of ethylene
All catalytic reactions were carried out in a magnetically stirred
liquid N
2
, was used to rapidly cool down the reactor, thus stopping
◦
(
900 rpm) 145 mL stainless steel autoclave. A 125 mL glass
the reaction. When the inner temperature reached 0 C the ice-bath
was removed allowing the temperature to slowly rise to 10 C. The
◦
container was used to protect the inner walls of the autoclave from
corrosion. The preparation of the catalytic solution of the precata-
lyst is dependent on the nature and the amount of the co-catalyst.
gaseous phase was then transferred into a 10 L polyethylene tank
filled with water. An aliquot of this gaseous phase was transferred
into a Schlenk flask, previously evacuated, for GC analysis. The
products in the reactor were hydrolyzed in situ by the addition of
ethanol (1 mL), transferred into a Schlenk flask, and separated
−
2
With AlEtCl
2
, 4 × 10 mmol of Ni complex were dissolved
in 14, 13 or 12 mL of chlorobenzene depending on the amount
of the co-catalyst and injected into the reactor under an ethylene
flux. Then 1, 2 or 3 mL of a co-catalyst solution, corresponding
◦
from the metal complexes by trap-to-trap evaporation (20 C,
Table 7 Crystallographic details and data collection
1
4·C
6
H
12
16·3CH
2
Cl
2
18·CH
2
Cl
2
Formula
C
860.01
Triclinic
P1
173(2)
9.519(2)
10.696(2)
10.759(3)
79.71(5)
66.07(5)
72.39(5)
952.4(4)
1
1.499
452
Mo-Ka
1.32
24
H
50Cl
4
N
4
Ni
2
O
8
·C
6
H
12
C
950.50
Triclinic
P1
173(2)
10.2260(2)
11.5260(2)
17.0800(5)
89.150(1)
77.950(1)
74.300(1)
1893.47(7)
2
1.667
964
Mo-Ka
1.74
24
H
28Cl
4
N
4
Ni
2
O
4
·3CH
2
Cl
2
C
541.91
Triclinic
P1
173(2)
10.9430(4)
11.3560(4)
12.321(5)
91.790(1)
113.320(2)
118.250(2)
1192.48(8)
2
1.509
556
Mo-Ka
1.29
18
H
21Cl
2
N
3
NiO
3
·CH
2 2
Cl
M
r
Crystal system
¯
¯
¯
Space group
T/K
a/A˚
b/A˚
c/A˚
◦
a/
b/
◦
◦
c /
V/A˚
3
Z
−
3
D
c
/g cm
F(000)
Radiation type
−
1
l/mm
Crystal shape, colour
Crystal size/mm
Measd reflect.
Prism, green
Prism, green
Prism, blue
0.10 × 0.10 × 0.10
0.10 × 0.10 × 0.10
0.10 × 0.10 × 0.10
14833
25759
15347
Indep. reflect.
5561
10998
6929
Obsd reflect.
Criter. obs. refl.
4446
I > 2r(I)
0.051
30.1
0.071
0.201, 1.07
217
6976
I > 2r(I)
0.064
30.0
0.086
0.230, 0.93
424
4133
I > 2r(I)
0.056
30.0
0.049
0.145, 0.96
271
R
max
int
◦
2
h
/
2
R [F > 2r(F )]
wR(F ), S
No. param.
2
1
572 | Dalton Trans., 2008, 1564–1573
This journal is © The Royal Society of Chemistry 2008

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0
.8 mbar) into a second Schlenk flask previously immersed in
24 P. Kuhn, D. Semeril, D. Matt, M. J. Chetcuti and P. Lutz, Dalton Trans.,
2
007, 515.
liquid nitrogen in order to avoid any loss of product.
2
2
2
5 P. Braunstein, J. Pietsch, Y. Chauvin, S. Mercier, L. Saussine, A. DeCian
and J. Fischer, J. Chem. Soc., Dalton Trans., 1996, 3571.
6 P. Braunstein, J. Pietsch, Y. Chauvin, A. DeCian and J. Fischer,
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7 M. J. Rachita, R. L. Huff, J. L. Bennett and M. Brookhart, J. Polym.
Sci., Part A: Polym. Chem., 2000, 38, 4627.
Crystal structure determinations
Diffraction data were collected on a Kappa CCD diffractometer
˚
using graphite-monochromated Mo-Karadiation (k = 0.71073 A)
(
Table 7). Data were collected using phi-scans and the structures
28 F. A. Hicks and M. Brookhart, Organometallics, 2001, 20, 3217.
2
9 T. R. Younkin, E. F. Connor, J. I. Henderson, S. K. Friedrich, R. H.
Grubbs and D. A. Bansleben, Science, 2000, 288, 1750.
0 M. A. Zuideveld, P. Wehrmann, C. R o¨ hr and S. Mecking, Angew.
Chem., Int. Ed., 2004, 43, 869.
were solved by direct methods (SIR97) using the SHELX97
software,
on F . No absorption correction was used. All non-hydrogen
66,67
and the refinement was by full-matrix least squares
3
2
atoms were refined anisotropically with H atoms introduced as
31 I. Goettker-Schnetmann, B. Korthals and S. Mecking, J. Am. Chem.
Soc., 2006, 128, 7708.
˚
fixed contributors (dC–H = 0.95 A, U11 = 0.04). All non-hydrogen
3
2 B. Korthals, I. G o¨ ttker-Schnetmann and S. Mecking, Organometallics,
007, 26, 1311.
33 X.-F. Li and Y.-S. Li, J. Polym. Sci., Part A: Polym. Chem., 2002, 40,
680.
atoms were refined anisotropically.
2
CCDC reference numbers 664564–664567.
For crystallographic data in CIF or other electronic format see
DOI: 10.1039/b716111e
2
3
3
4 D. Zhang, G.-X. Jin and N.-H. Hu, Eur. J. Inorg. Chem., 2003, 1570.
5 D. J. Darensbourg, C. G. Ortiz and J. C. Yarbrough, Inorg. Chem., 2003,
4
2, 6915.
36 T. Hu, L.-M. Tang, X.-F. Li, Y.-S. Li and N.-H. Hu, Organometallics,
005, 24, 2628.
37 Q. Chen, J. Yu and J. Huang, Organometallics, 2007, 26, 617.
Acknowledgements
2
We thank the Centre National de la Recherche Scientifique
3
8 F. A. Hicks, J. C. Jenkins and M. Brookhart, Organometallics, 2003,
2, 3533.
9 J. C. Jenkins and M. Brookhart, Organometallics, 2003, 22, 250.
(
CNRS), the Minist e` re de l’Education Nationale et de la
2
Recherche (Paris) and the Institut Fran c¸ ais du P e´ trole (IFP)
for support. We also thank Dr A. DeCian and Prof. R. Wel-
ter (ULP Strasbourg) for the crystal structure determinations
and M. Mermillon-Fournier (LCC Strasbourg) for technical
assistance.
3
40 J. C. Jenkins and M. Brookhart, J. Am. Chem. Soc., 2004, 126, 5827.
4
4
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Dalton Trans., 2008, 1564–1573 | 1573