SHOP-type nickel complexes with alkyl substituents on phosphorus, synthesis and catalytic ethylene oligomerization

Article abstract of DOI:10.1039/b713451g

The β-keto phosphorus ylides (n-Bu)₃P=CHC(O)Ph 6, (t-Bu)₂PhP=CHC(O)Ph 7, (t-Bu)Ph₂P=CHC(O)Ph 8, (n-Bu) ₂PhP=CHC(O)Ph 9, (n-Bu)Ph₂P=CHC(O)Ph 10, Me ₂PhP=CHC(O)Ph 11 and Ph₃P=CHC(O)(o-OMe-C₆H ₄) 12 have been synthesized in 80-96% yields. The Ni(ii) complexes [N=iPh{Ph₂PCHC(O=)(o-OMeC₆H₄)}(PPh ₃)] 13, [N=iPh{Ph(t-Bu)PCHC(O=)Ph}(PPh₃)] 15, [N=iPh{(n-Bu)₂PCHC(O=)Ph}(PPh₃)] 16 and [N=iPh{Ph(n-Bu)PCHC(O=)Ph}(PPh₃)] 17 have been prepared by reaction of equimolar amounts of [Ni(COD)₂] and PPh₃ with the β-keto phosphorus ylides 12 or 8-10, respectively, and characterized by ¹H and ³¹P{¹H} NMR spectroscopy. NMR studies and the crystal structure determination of 13 indicated an interaction between the hydrogen atom of the C-H group α to phosphorus and the ether function. The complexes [N=iPh{Ph₂PCHC(O=)Ph}(Py)] 18, [N=iPh{Ph(t-Bu)PCHC(O=) Ph}(Py)] 19, [N=iPh{(n-Bu)₂PCHC(O=)Ph}(Py)] 20, [N=iPh{Ph(n-Bu) PCHC(O=)Ph}(Py)] 21 and [N=iPh{Me₂PCHC(O=)Ph}(Py)] 22 have been isolated from the reactions of [Ni(COD)₂] and an excess of pyridine with the β-keto phosphorus ylides Ph₃PCH=C(O)Ph 3 or 8-11, respectively, and characterized by ¹H and ³¹P{ ¹H} NMR spectroscopy. Ligands 3, 8, 10 and 12 have been used to prepare in situ oligomerization catalysts by reaction with one equiv. of [Ni(COD)₂] and PPh₃ under an ethylene pressure of 30 or 60 bar. The catalyst prepared in situ from 12, [Ni(COD)₂] and PPh ₃ was the most active of the series with a TON of 12 700 mol C ₂H₄ (mol Ni)^-1 under 30 bar ethylene. When the β-keto phosphorus ylide 8 was reacted in situ with three equiv. of [Ni(COD)₂] and one equiv. of PPh₃ under 30 bar of ethylene, ethylene polymerization was observed with a TON of 5500 mol C ₂H₄ (mol Ni)^-1. The Royal Society of Chemistry.

Full text of DOI:10.1039/b713451g

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www.rsc.org/dalton | Dalton Transactions
SHOP-type nickel complexes with alkyl substituents on phosphorus, synthesis
and catalytic ethylene oligomerization†‡
Anthony Kermagoret and Pierre Braunstein*
Received 31st August 2007, Accepted 15th November 2007
First published as an Advance Article on the web 6th December 2007
DOI: 10.1039/b713451g
=
=
The b-keto phosphorus ylides (n-Bu)3P CHC(O)Ph 6, (t-Bu)2PhP CHC(O)Ph 7,
=
=
=
(t-Bu)Ph2P CHC(O)Ph 8, (n-Bu)2PhP CHC(O)Ph 9, (n-Bu)Ph2P CHC(O)Ph 10,
=
=
Me2PhP CHC(O)Ph 11 and Ph3P CHC(O)(o-OMe-C6H4) 12 have been synthesized in 80–96% yields.
... ...
The Ni(II) complexes [NiPh{Ph2PCH C( O)(o-OMeC6H4)}(PPh3)] 13,
−
−
... ...
... ...
[NiPh{Ph(t-Bu)PCH C( O)Ph}(PPh3)] 15, [NiPh{(n-Bu)2PCH C( O)Ph}(PPh3)] 16 and
−
−
−
−
... ...
[NiPh{Ph(n-Bu)PCH C( O)Ph}(PPh3)] 17 have been prepared by reaction of equimolar amounts of
−
−
[Ni(COD)2] and PPh3 with the b-keto phosphorus ylides 12 or 8–10, respectively, and characterized by
1H and 31P{ H} NMR spectroscopy. NMR studies and the crystal structure determination of 13
1
indicated an interaction between the hydrogen atom of the C–H group a to phosphorus and the ether
... ...
... ...
function. The complexes [NiPh{Ph2PCH C( O)Ph}(Py)] 18, [NiPh{Ph(t-Bu)PCH C( O)Ph}(Py)]
−
−
−
−
... ... ... ...
19, [NiPh{(n-Bu)2PCH C( O)Ph}(Py)] 20, [NiPh{Ph(n-Bu)PCH C( O)Ph}(Py)] 21 and
−
−
−
−
... ...
[NiPh{Me2PCH C( O)Ph}(Py)] 22 have been isolated from the reactions of [Ni(COD)2] and an
−
−
=
excess of pyridine with the b-keto phosphorus ylides Ph3PCH C(O)Ph 3 or 8–11, respectively, and
characterized by 1H and 31P{ H} NMR spectroscopy. Ligands 3, 8, 10 and 12 have been used to prepare
1
in situ oligomerization catalysts by reaction with one equiv. of [Ni(COD)2] and PPh3 under an ethylene
pressure of 30 or 60 bar. The catalyst prepared in situ from 12, [Ni(COD)2] and PPh3 was the most
active of the series with a TON of 12 700 mol C2H4 (mol Ni)−1 under 30 bar ethylene. When the b-keto
phosphorus ylide 8 was reacted in situ with three equiv. of [Ni(COD)2] and one equiv. of PPh3 under 30
bar of ethylene, ethylene polymerization was observed with a TON of 5500 mol C2H4 (mol Ni)−1.
Introduction
The commercial interest for high-density polyethylene (HDPE),
linear low-density polyethylene (LLDPE) and linear a-olefins
triggers research in ethylene polymerization and oligomerization.
Since the works of Ziegler and Natta, alkylation of the metal centre
with aluminum alkyls became the key for the formation of active
catalysts in polymerization and oligomerization.1–3 This activation
process applies well to nickel precatalysts4–6 and Brookhart and co-
workers have described a-diimines nickel complexes 1 which are
activated by various alkylaluminium derivatives such as MAO,
highly active in ethylene polymerization in the presence of MAO
(methylaluminoxane) as cocatalyst.7–10
MMAO (modified MAO), AlEtCl2, AlEt3, AlMe3, etc. With the
N,O chelating ligands salicylaldimines,13,19–22 anilinotropones23–25
or anilinoperinaphthenones,26 it was observed that very bulky
groups retard chain transfer and lead to high molecular weight
polyethylenes.27–30
Nickel catalysts for ethylene oligomerization are applied in the
Shell Higher Olefin Process (SHOP) without any cocatalyst,31 and
lead to linear a-olefins with remarkable selectivity. The known
SHOP-type catalyst 2 is synthesized by oxidative-addition of the
b-keto phosphorus ylide 3 on a zerovalent nickel compound,
such as [Ni(COD)2] (COD = 1,5-cyclooctadiene), in the presence
of a two-electron donor ligand, in general a phosphine such as
PPh3, to stabilize the resulting neutral Ni(II) complex [eqn (1)]32,33
The nature of the chelating ligand is crucial for the cata-
lyst performances and the use of a-diimine ligands with less
bulky substituents turned their nickel complexes into ethylene
oligomerization rather than polymerization catalysts. In this
case, they showed a high selectivity for linear a-olefins with
a Schulz–Flory mass distribution of the oligomers.11,12 These
results have inspired the synthesis of many nickel precatalysts
coordinated by N,N-,10–12 N,O-,13–16 or P,N-17,18 type ligands and
Laboratoire de Chimie de Coordination, Institut de Chimie (UMR 7177
CNRS), Universite´ Louis Pasteur, 4 rue Blaise Pascal, F-67070, Strasbourg
Ce´dex, France. E-mail: braunstein@chimie.u-strasbg.fr
† The HTML version of this article has been enhanced with a colour image.
‡ CCDC reference number 659315. For crystallographic data in CIF or
other electronic format see DOI: 10.1039/b713451g
=
(throughout this paper, the drawings will indicate a localized C C
bond for the enolate moiety but electronic delocalization involves
the C–O bond).18
822 | Dalton Trans., 2008, 822–831
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(1)
The stabilizing donor ligand plays a crucial role in the catalyst
behaviour34 and the use of more weakly bound ligands, such as
pyridine, or of a catalyst promoter in excess, such as [Ni(COD)2]
or [Rh(acac)(C2H4)2], which can scavenge the donor ligand, turns
these nickel complexes from oligomerization into polymerization
catalysts.35 In the absence of a coligand, a dinuclear complex 4
forms as a result of the stabilization by coordination of the oxygen
atom to another metal centre.35,36
Scheme 2 Cationic phosphino-phenol and keto-phosphine catalysts.
on the phosphorus atom and to evaluate their corresponding nickel
complexes in the catalytic oligomerization of ethylene.
Results and discussion
Synthesis of the b-keto phosphorus ylides
The ylides were prepared in two steps: synthesis of the phos-
phonium salt followed by its deprotonation.53 The reaction of
tri(n-butyl)phosphine with a-bromoacetophenone in toluene at
room temperature afforded the phosphonium salt which, after
dissolution in a mixture of MeOH–H2O (1 : 1) containing NaOH,
afforded the corresponding b-keto phosphorus ylide 6, which was
1
1
1
characterized by H, 13C{ H} and 31P{ H} NMR spectroscopy
Various substituents have been incorporated into the P,O chelate
to modify its stereo-electronic properties and the electrophilicity
of the metal centre and examine their impact on the catalyst
properties and the nature of the products formed.37–42
[eqn (2)].
Neutral phosphino-phenolate nickel complexes are known
to form ethylene oligomerization and polymerization catalysts
(Scheme 1).43–48 Heinicke, Keim et al. have observed that an
increase of the basicity of the phosphorus donor atom improves
the catalytic activity, modifies the mass distribution of the products
and favors the formation of long-chain polyethylenes.44–47
(2)
However, the reaction of 6 with [Ni(COD)2] in the presence of
PPh3 did not yield the expected complex and only decomposition
to nickel metal was observed. There was no indication for the
migration of a n-butyl substituent from the phosphorus atom to
the metal centre.54
Scheme 1 Phosphino-phenolate nickel catalysts.
The synthesis of b-keto phosphorus ylides from mixed
alkyl/phenyl phosphonium salts could provide an access to
SHOP-type nickel complexes having alkyl or mixed alkyl/phenyl
substituents on the P atom of the P,O chelate. Such mixed salts were
prepared by reaction of PPh2Cl with one equiv. of n-BuLi or t-BuLi
or by reaction of PPhCl2 with two equiv. of n-BuLi or t-BuLi at low
temperature,55 followed by reaction with a-bromoacetophenone
and deprotonation. The b-keto phosphorus ylides 7 and 8, with
tert-butyl substituents, precipitated as white powders but 9 and 10,
with n-butyl substituents, formed a pale red oil.
Cationic nickel complexes derived from this ligand family have
also been studied (Scheme 2) and it was found that the effect of an
increased P-basicity on the molecular weight of the oligomers was
much lower than in the case of the neutral, phosphino-phenolate
systems.49 Furthermore, cationic Ni(II) or Pd(II) complexes 5 with
(phenacyl)di-tert-butylphosphine or (phenacyl)diarylphosphine
ligands catalyze ethylene polymerization and bulky phosphorus
substituents tend to retard chain transfer and produce high
molecular weight polyethylenes.50,51
Since fewer studies have appeared on the influence of electron-
donating and steric properties of the phosphorus substituents in
neutral SHOP-type catalysts on the oligomer distribution,52 and
encouraged by the positive effect on catalytic activity of donor
substituents in the phosphino-phenolate systems,44–47 we decided
to synthesize new b-keto phosphorus ylides with alkyl substituents
We did not succeed in deprotonating methyl-substituted phos-
phonium salts using a MeOH–H2O (1 : 1) solution of NaOH but
the b-keto phosphorus ylide 11 was obtained in toluene using
NaH.
The intermediate 2-bromo-1-(2-methoxyphenyl)ethanone was
synthesized by reaction of 1-(2-methoxyphenyl)ethanone with Br2
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◦
˚
in CCl4 and used to prepare the b-keto phosphorus ylide 12 by
Table 1 Selected bond distances (A) and bond angles ( ) in 13
reaction with PPh3 and deprotonation with Na2CO3 [eqn (3)].56
Ni–P1
Ni–C10
Ni–P2
Ni–O1
P2–C1
2.2167(4)
1.887(2)
2.1665(4)
1.905(1)
1.768(2)
C1–C2
C2–O1
C2–C3
O2–H1
1.363(2)
1.318(2)
1.497(2)
2.283(2)
C10–Ni–P1
C10–Ni–P2
93.67(5)
92.36(5)
O1–Ni–P2
O1–Ni–P1
85.78(3)
87.88(3)
(3)
◦
˚
Table 2 Hydrogen bonding in 13 (A and
)
Donor–H · · · Acceptor
D–H H · · · A D · · · A
D–H · · · A
C1–H1 · · · O2
C4–H4 · · · O1
0.95 2.28
0.95 2.34
C4–H4 · · · (centroid C28–C33) 0.95 2.74
2.813(2) 114
2.676(2) 100
3.670(2) 167
Synthesis of the complexes
... ...
The nickel complex [NiPh{Ph PCH C( O)(o-OMeC H )}-
−
−
2
6
4
(PPh3)] 13 has been briefly described earlier56 and was obtained
in high yield by reaction of the b-keto phosphorus ylide 12 with
equimolar amounts of [Ni(COD)2] and PPh3 in toluene at room
angles of 172.90(2) and 174.58(6)◦, respectively. The metal–ligand
distances (Table 1) are comparable with those found in SHOP-type
complexes such as 2 or 14 (see below).31,32,58–60 The structure of 13
revealed that the orientation of the oxygen atom O(2) of the ether
group allows a non-classical interaction with the hydrogen atom
of the C(1)H(1) group a to the phosphorus atom (Fig. 1) and the
temperature (see Experimental). The 31P{ H} NMR spectrum of
1
this complex should display a typical AB pattern for the trans coor-
dinated phosphorus atoms but the small chemical shift difference
between the two P resonances resulted in two intense signals at 23.6
and 23.4 ppm instead of the two doublets expected. The hydrogen
atom of the C–H group ato the phosphine moiety is characterized
in 1H NMR spectroscopy by a chemical shift of 5.97 ppm,
at significantly higher value than in similar complexes.57,58 This
suggested an intramolecular bonding interaction between this
hydrogen atom and the ether function in ortho position to the
phenyl group. A 2D NOESY spectrum confirmed this hypothesis
by showing a spatial interaction between the hydrogen atom and
the methyl hydrogens of the ether function.
˚
calculated distance H(1) · · · O(2) is 2.28 A (Table 2). The resulting
steric effects may be responsible for the angle of 20.8(1)◦ between
the C(3)–C(8) ring and the NiP(2)C(1)C(2)O(1) plane since in the
parent complex 2, these two cycles are coplanar. According to
Platon software,61 the hydrogen atom H(4) is involved in another
non-classical intramolecular hydrogen bonding interaction, with
˚
O(1), at a calculated H(4) · · · O(1) distance of 2.34 A (Table 2)
and in a C–H–p interaction with the phenyl ring C(28)–C(33) at
˚
P(1), at a calculated distance of 2.74 A from its centroid (Table 2).
Consistently, the phenyl groups C(3)–C(8) and C(28)–C(33) are
almost orthogonal to each other and form an angle of 88.0(1)◦.
We have described previously the nickel complexes 14 which
display an intramolecular bonding interaction between the oxygen
atom coordinated to the metal centre and an hydrogen atom of an
ortho-substituent on the aromatic ring of the P,O ligand.58,60 This
interaction modifies sufficiently the electronic density at the metal
to shift the mass distribution of the oligomers formed toward the
desired, shorter chain a-olefins.
Single crystals of 13 suitable for X-ray diffraction have been
obtained by slow diffusion of heptane into a toluene solution.
An ORTEP view of the molecular structure of 13 is shown in
Fig. 1 and selected bond distances and bond angles are given in
Table 1. The metal centre adopts a slightly distorted square-planar
geometry as shown by the P(2)–Ni–P(1) and O(1)–Ni–C(10) bond
Noteworthy are the contrasting orientations of the o-C6H4OMe
and o-C6H4XH cycles in 13 and 14, respectively, and the associated
H-bonding behaviour of the P,O ligand which functions as both
a donor and an acceptor in the former and acceptor in the latter.
˚
However, the Ni–O(1) distance in 13 (1.905(1) A) is similar to that
58
˚
in 14 (X = NMe, 1.908(4) A) but both are shorter than in 14
60
˚
(X = NPh, 1.923(2) A).
The reaction of ylides 8–10 with equimolar amounts of
[Ni(COD)2] and PPh3 at room temperature only afforded the
desired complexes 15–17 in low yield [eqn (4)].
Fig. 1 ORTEP view of the molecular structure of 13 with ellipsoids drawn
at the 50% probability level.
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Catalytic oligomerization of ethylene
The catalytic tests have been performed with in situ-prepared
catalysts by stirring equimolar amounts of the b-keto phosphorus
ylides, [Ni(COD)2] and PPh3 under ethylene pressure (30 or 60
bar) and the results are given in Table 3.
(4)
Ylides 3, 8, 10 and 12 formed active species for ethylene
oligomerization whereas catalytic tests with 7 and 9 were unsuc-
cessful. The catalytic results with the mass distributions for the
C4–C8 olefins are given in Table 3. Catalytic tests with 8 and 10
showed low activities, with TON of 1500 and 800 mol C2H4 (mol
Ni)−1 after consumption of 8.4 and 4.5 g of ethylene in 24 h,
respectively, but very high selectivities for 1-hexene, 99% with 10
and 99% with 8 (Table 3). The b-keto phosphorus ylides 3 and 12
formed more active catalysts than 8 and 10 with TON of 11 000
and 12 700 mol C2H4 (mol Ni)−1, respectively, and both showed a
similar selectivity of 98% for 1-hexene.
Catalysis with 3 and 12 have also been performed under an
ethylene pressure of 60 bar during a period of 1.5 and 2 h
and at 50 and 82 ◦C, respectively. Under these conditions, 3
and 12 consumed 15.9 g of ethylene (TON of 5700) in 1.5 h
and 12.9 g (TON of 4600) in 2 h, respectively.56 Comparing
the results obtained under similar catalytic conditions between
isolated complexes 12 and 14 shows that the former presents higher
activities and K values.56
A significant fraction of the PPh3 reacted with the nickel
precursor to form [Ni(PPh3)4], which gave rise in 31P NMR
spectroscopy to a broad peak around 26.1 ppm, and it was
therefore not available to form the desired product. This led to
only partial reaction and the low yield was evaluated by 1H NMR
monitoring of the chemical shifts of the C–H proton a to the
phosphorus in the ligand and in the complex, or by evaluating
1
unreacted [Ni(COD)2].38 In 31P{ H} NMR spectroscopy, the two
trans-coordinated phosphorus atoms of complexes 15–17 form
the expected AB pattern with 2JPP coupling constants of 278, 280
and 282 Hz, respectively. All attempts made to isolate these nickel
complexes led to increased decomposition. In the case of the b-
keto phosphorus ylides 7 and 11, the formation of the complexes
was not observed. Performing the complexation reactions at 60 ◦C
with the hope to increase the yield resulted only in decomposition
of [Ni(COD)2].
Catalytic polymerization conditions were applied to 8 by using
three equiv. of [Ni(COD)2] for one equiv. of b-keto phosphorus
ylide and of PPh3 under an ethylene pressure of 30 bar. After
a reaction time of 70 h, 31.2 g of polyethylene was obtained,
corresponding to a TON of 5500 mol C2H4 (mol Ni)−1, higher
than under oligomerization conditions (Table 3).
To avoid the competition between the formation of [Ni(PPh3)4]
and of the desired complexes by oxidative addition of the ylide, we
used a pyridine ligand which is less nucleophilic than a phosphine.
However, pyridine was not as reactive as PPh3 and a large excess
had to be used. The reaction of the ylides 3 and 8–11 with
one equiv. of [Ni(COD)2] and an excess of pyridine at room
temperature led to the formation of the desired complexes 18–22,
Conclusion
The b-keto phosphorus ylides 6–12 with alkyl substituents on the
phosphorus atom have been synthesized in high yield. The reaction
of 8–10 and 12 with equimolar amounts of [Ni(COD)2] and PPh3
yielded the complexes 13 and 15–17 in which an aryl substituent
of the ylide phosphorus atom has migrated to the metal centre.
Migration of an alkyl group to zerovalent nickel is much less
favourable than that of an aryl group and was never observed.
Thus, the presence of three alkyl groups on the P atom of b-
keto phosphorus ylides did not allow the formation of the desired
Ni(II) complexes. In such cases, alternative synthetic approaches to
such SHOP-type catalyst are necessary (e.g. reaction of a sodium
phosphinoenolate with a aryl, halide Ni(II) complex).54 Such an
approach has been used in the case of Pd(II) analogues to the
SHOP-type catalysts since the b-keto phosphorus ylide route does
not apply to other metals but nickel.62
1
which have been characterised in 1H and 31P{ H} NMR [eqn (5)].
(5)
1H NMR studies on 13 indicated an intramolecular bonding
interaction between the H atom of the C–H group ato phosphorus
and the ether function, which was confirmed by X-ray diffraction
˚
(calculated O–H distance of 2.28 A). Complexes 18–22 have been
However, the reactions were not quantitative and unreacted
synthesized by reaction of b-keto phosphorus ylides 3 and 8–
11 with an equimolar amount of [Ni(COD)2] and an excess of
[Ni(COD)2] and b-keto phosphorus ylides were detected in the
1
1
1
1H and 31P{ H} NMR spectra. Moreover 7, remained unreactive
pyridine and have been characterized by H and 31P{ H} NMR
toward [Ni(COD)2] and an excess of pyridine, in contrast to 11.
Here too, an increase of the reaction temperature to 60 ◦C led to
decomposition of the products and formation of nickel metal.
spectroscopy.
Active catalysts for ethylene oligomerization were prepared
in situ by stirring equimolar amounts of b-keto phosphorus ylides
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Table 3 Catalytic results with b-keto phosphorus ylides 3, 8, 10 and 12a
Ligand
3
3b
8
8c
10
12
12d
C2H4 consumed/g
61.7
5300
11000
24
13 (93)
9 (98)
6
15.9
2700
5700
1.5
14
15 (98)
15
8.4
700
1500
24
21 (81)
13 (99)
9
31.2
2600
5500
70
—
—
—
100
—
4.5
70.8
6000
12700
24
19 (95)
11 (98)
8
12.9
2200
4600
2
14
17 (96)
15
Activity/g C2H4 (g Ni)−1
TON/mol C2H4 (mol Ni)−1
Reaction time/h
400
800
24
13 (84)
5 (99)
3
e
% C4 (% 1-olefin)
e
% C6 (% 1-olefin)
e
% C8
e
% <C8
72
0.44
56
0.69
57
0.41
79
0.25
62
0.40
54
0.81
K [C6 (mol)/C4 (mol)]
a Conditions: T = 25 ◦C; 30 bar of C2H4; 24 h; 0.2 mmol of ylide, [Ni(COD)2] and PPh3; solvent 20 mL toluene. b Conditions: T = 50 ◦C; 60 bar of C2H4;
0.1 mmol of ylide; [Ni(COD)2] and PPh3; solvent: 20 mL toluene.56,58 c Conditions: T = 25 ◦C; 70 h; 0.2 mmol of ylide and PPh3; 0.6 mmol of [Ni(COD)2].
d Conditions: T = 82 ◦C; 60 bar of C2H4; 0.1 mmol of ylide; [Ni(COD)2] and PPh3; solvent: 20 mL toluene.56,58 e Mass%.
3, 8, 10 or 12, [Ni(COD)2] and PPh3 under 30 or 60 bar of
ethylene. TON up to 12 700 mol C2H4 (mol Ni)−1 were obtained
with 12 under 30 bar of ethylene and the selectivity for linear a-
olefins was between 95 and 98%. The influence of the o-methoxy
group on the enolate-bound aryl appears beneficial for catalyst
activity. Catalysis with one equiv. of 8 and PPh3 and three equiv.
of [Ni(COD)2] under 30 bar of ethylene led only to the formation
of polyethylene with a TON of 5500 mol C2H4 (mol Ni)−1.
We also noted that the presence of two alkyl groups on the P
atom of the P,O chelate in the complexes was detrimental with
regard to catalytic activity and that the presence of at least one
phenyl group was beneficial for the stability of the complex. It
is difficult at this stage to conclude whether a decreased catalytic
activity is due to electronic reasons, whereas Heinicke, Keim et al.
have observed that an increased basicity of the phosphorus donor
atom improved the catalytic activity,44–47 or to a shorter lifetime of
the catalyst because of its poorer stability. Clearly, a subtle balance
has to be found which involves the nature of the P-substituents, the
aryl group on the phosphino-enolate and the monodentate two-
electron donor ligand coordinated to nickel in order to optimize
the properties of these catalysts.
Synthesis of diphenyl(tert-butyl)phosphine64
3.05 mL (17.00 mmol) of PPh2Cl were dissolved in 40 mL of a
mixture of pentane–THF (3 : 1) and cooled to −78 ◦C. 10 mL
of a t-BuLi solution in pentane (1.7 mol L−1, 17.00 mmol) were
slowly added and the solution was stirred overnight from −78 ◦C
to room temperature. The white precipitate of LiCl was eliminated
by filtration with a cannula and the solvents were removed under
reduced pressure. The brown oil obtained was distilled under
reduced pressure (140 ◦C, 0.8 mbar). The phosphine was isolated
1
as a colorless liquid. Yield: 2.630 g, 64%. H NMR (300 MHz,
CDCl3): d 1.22 (9H, d, 3JPH = 12.6 Hz, CH3), 7.36 (3H, m, aromatic
1
H) and 7.60 (2H, m, aromatic H); 31P{ H} NMR (CDCl3, 121.5
MHz): d 19.1 (s)
Synthesis of diphenyl(n-butyl)phosphine65
4.60 mL (25.60 mmol) of PPh2Cl were dissolved in 30 mL of diethyl
ether and cooled to −78 ◦C. 16 mL of a t-BuLi solution in pentane
(1.6 mol L−1, 25.60 mmol) were slowly added and the solution was
stirred overnight from −78 ◦C to room temperature. The white
precipitate of LiCl was eliminated by filtration with a cannula and
the solvents were removed under reduced pressure. The yellow oil
obtained was distilled under reduced pressure (135 ◦C, 0.8 mbar).
The phosphine was isolated as a colorless liquid. Yield: 4.270 g,
73%. 1H NMR (300 MHz, CDCl3): d 0.90 (3H, d, 3JPH = 7.7 Hz,
CH3), 1.44 (4H, m, CH2CH2), 2.04 (2H, m, PCH2), 7.31–7.46 (10H,
Experimental
General considerations
1
m, aromatic H); 31P{ H} NMR (CDCl3, 121.5 MHz): d −14.8 (s).
All solvents were dried and freshly distilled under nitrogen and
degassed under argon prior to use using common techniques. All
manipulations were carried out using Schlenk techniques under
1
1
1
argon atmosphere. The H, 31P{ H} and 13C{ H} NMR spectra
were recorded at 300.13, 121.5 and 75.5 MHz, respectively, on
a Bruker AC300 instrument. IR spectra were recorded in the
solid state on a Nicolet 380 instrument. 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 compounds [Ni(COD)2]63 and ylide
353 were prepared according to the literature. Some details of the
synthesis and analytical data for known compounds are given
below because of slight modifications or new data introduced.
Elemental analyses of air-sensitive liquids or oily products and
on nickel complexes were generally not satisfactory and their
spectroscopic data were used as purity criteria.
Synthesis of phenyldi(tert-butyl)phosphine66
2.28 mL (17.00 mmol) of PPhCl2 were dissolved in 40 mL of
pentane and cooled to −78 ◦C. 20 mL of a t-BuLi solution in
pentane (1.7 mol L−1, 34.00 mmol) were slowly added and the
solution was stirred for 3 h from −78 ◦C to room temperature.
The white precipitate of LiCl was eliminated by filtration with a
cannula and the pentane was removed under reduced pressure. The
white oil obtained was distilled under reduced pressure (110 C,
0.8 mbar). The phosphine was isolated as a colorless liquid. Yield:
1.560 g, 40%. 1H NMR (300 MHz, CDCl3): d 1.20 (18H, d, 3JPH
◦
=
11.7 Hz, CH3), 7.34–7.38 (3H, m, aromatic H) and 7.64–7.72 (2H,
1
m, aromatic H); 31P{ H} NMR (CDCl3, 121.5 MHz): d 40.5 (s)
826 | Dalton Trans., 2008, 822–831
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1
Synthesis of phenyldi(n-butyl)phosphine55
(CDCl3, 75.5 MHz): d 29.0 (s, CH3), 35.7 (d, JPC = 45.8 Hz,
PCCH3), 48.1 (d, 1JPC = 97.9 Hz, P CH), 123.7 (d, JPC = 72.3 Hz,
1
=
4.34 mL (32.00 mmol) of PPhCl2 were dissolved in 60 mL of
pentane and cooled to −78 ◦C. 40 mL of a n-BuLi solution in
pentane (1.6 mol L−1, 64.00 mmol) were slowly added and the
solution was stirred for 3 h from −78 ◦C to room temperature.
The white precipitate of LiCl was eliminated by filtration with a
cannula and the pentane was removed under reduced pressure. The
white oil obtained was distilled under reduced pressure (120 C,
0.8 mbar). The phosphine was isolated as a colorless liquid. Yield:
5.180 g, 73%. 1H NMR (300 MHz, CD2Cl2): d 0.91 (6H, t, 3JHH
CP of PPh), 126.7 (s, CH of OCPh), 127.7 (s, CH of OCPh), 128.3
(d, 2JPC = 10.8 Hz, o-C of PPh), 128.7 (s, p-C of OCPh) 131.7 (d,
4JPC = 2.6 Hz, p-C of PPh), 134.4 (d, 3JPC = 7.9 Hz, m-C of PPh),
143.5 (d, 3JPC = 15.9 Hz, ipso-C of OCPh), 183.4 (s, CO); 31P{ H}
1
NMR (CDCl3, 121.5 MHz): d 42.4. IR: 1609m, 1585w, 1569w,
1523vs, 1480mw, 1459m, 1433s cm−1. Anal. Found: C, 77.5; H,
8.45. Calc. for C22H29OP: C, 77.62; H, 8.59%.
◦
=
Synthesis of (benzoylmethylene)diphenyl(tert-butyl)phosphorane 8
6.9 Hz, CH3), 1.41 (8H, m, CH2CH2), 1.79 (4H, br m, PCH2), 7.40
(3H, m, aromatic H) and 7.55 (2H, m, aromatic H); 31P{ H} NMR
1
This compound was prepared using a method similar to that
described for 7 by reaction of 1.350 g (6.70 mmol) of a-
bromoacetophenone with 1.60 g (6.70 mmol) of diphenyl(tert-
butyl)phosphine (the phosphonium salt has not been character-
ized by 31P or 1H NMR). Yield: 2.300 g, 96%. 1H NMR (300 MHz,
(CD2Cl2, 121.5 MHz): d −20.0 (br s).
Synthesis of (benzoylmethylene)tri(n-butyl)phosphorane 6
3.700 g (18.60 mmol) of a-bromoacetophenone were added to
a solution of 3.760 g (18.60 mmol) of tri(n-butyl)phosphine in
30 mL of toluene and stirred for 24 h at room temperature. The
phosphonium salt was then filtered with a cannula, washed with
toluene (40 mL) and dried under vacuum (the phosphonium salt
CDCl3): d 1.35 (9H, d, 3JPH = 15.0 Hz, CH3), 4.22 (1H, d, 2JPH
=
23.1 Hz, PCH), 7.36 (3H, m, aromatic H), 7.46–7.58 (6H, m, aro-
matic H), 7.91–7.99 (6H, m, aromatic H); 13C{ H} NMR (CDCl3,
1
1
75.5 MHz): d 27.1 (s, CH3), 32.3 (d, JPC = 54.5 Hz, PCCH3),
1
1
=
47.4 (d, JPC = 107.4 Hz, P CH), 124.6 (d, JPC = 83.1 Hz, CP
of PPh), 126.9 (s, C of OCPh), 127.7 (s, C of OCPh), 128.7 (d,
2JPC = 11.6 Hz, o-C of PPh), 129.1 (s, p-C of OCPh), 131.8 (s, p-C
1
1
has not been characterized by 31P{ H} NMR or H NMR). The
dried salt was dissolved in a mixture of 60 mL of distilled water
and 60 mL of MeOH and, an aqueous solution of NaOH (2.0 M)
was added to the solution until pH 8 was reached. The solution
became cloudy and the phosphorane 6 settled overnight as a red
oil and the solution was eliminated with a cannula. 6 was washed
with water and dried under vacuum overnight. Yield: 5.400 g, 91%.
1H NMR (300 MHz, CDCl3): d 0.92 (9H, t, 3JHH = 7.2 Hz, CH3),
3
3
of PPh), 133.6 (d, JPC = 8.9 Hz, m-C of PPh), 142.0 (d, JPC
=
14.0 Hz, ipso-C of OCPh), 184.4 (s, CO); 31P{ H} NMR (CDCl3,
1
121.5 MHz): d 30.9. IR: 1585m, 1523vs, 1481w, 1436s cm−1.
Synthesis of (benzoylmethylene)phenyldi(n-butyl)phosphorane 9
1.45 (12H, m, CH2CH2), 2.04 (6H, m, PCH2), 3.72 (1H, d, 2JPH
=
4.300 g (21.60 mmol) of a-bromoacetophenone were added to a
solution of 4.800 g (21.60 mmol) of phenyldi(n-butyl)phosphine
in 30 mL of toluene and stirred for 24 h at room temperature. The
solvent was then removed with a cannula and the phosphonium
salt was washed with toluene (40 mL) and dried under vacuum
(the phosphonium salt has not been characterized by 31P NMR or
1H NMR). The dried salt was dissolved in a mixture of 100 mL of
distilled water and 50 mL of MeOH and an aqueous solution of
NaOH (2.0 M) was added to the solution until pH 8 was reached.
The solution became cloudy and 9 settled overnight as a red oil, it
was washed with water and dried under vacuum overnight. Yield:
=
22.8 Hz, P CH), 7.31 (3H, m, aromatic H), 7.85 (2H, m, aromatic
1
H); 13C{ H} NMR (CDCl3, 75.5 MHz): d 13.7 (s, CH3), 21.5 (d,
1JPC = 55.1 Hz, PCH2), 24.1 (d, 2JPC = 15.0 Hz, PCH2CH2), 24.3
3
1
(d, JPC = 3.9 Hz, CH2CH3), 47.8 (d, JPC = 104.3 Hz, PCH),
126.5 (s, aromatic CH), 127.7 (s, aromatic CH), 128.9 (s, p-C of
Ph), 141.4 (d, 3JPC = 13.6 Hz, C-CO of Ph), 185.1 (d, 2JPC = 3.3 Hz,
1
CO); 31P{ H} NMR (CDCl3, 121.5 MHz): d 21.2.
Synthesis of (benzoylmethylene)phenyldi(tert-butyl)phosphorane 7
1.340 g (6.70 mmol) of a-bromoacetophenone were added to a
solution of 1.50 g (6.70 mmol) of phenyldi(tert-butyl)phosphine
in 20 mL of toluene and stirred for 24 h at room temperature. The
solution was removed with a cannula and the phosphonium salt
was then washed with toluene (20 mL) and dried under vacuum.
6.900 g, 94%. 1H NMR (300 MHz, CDCl3): d 0.87 (6H, t, 3JHH
=
6.9 Hz, CH3), 1.43 (8H, m, CH2CH2), 1.32 (4H, m, PCH2), 3.99
(1H, d, 2JPH = 22.6 Hz, P CH), 7.36 (2H, m, aromatic H), 7.49–
=
7.55 (3H, m, aromatic H), 7.70–7.77 (3H, m, aromatic H), 7.91–
7.95 (2H, m, aromatic H); 13C{ H} NMR (CDCl3, 75.5 MHz):
1
1H NMR (300 MHz, MeOD): d 1.51 (18H, d, JPH = 14.7 Hz,
3
1
2
d 13.7 (s, CH3), 23.6 (d, JPC = 57.0 Hz, PCH2), 24.0 (d, JPC
=
CH3) 3.31 (2H, qnt, J = 1.5 Hz, CH2), 7.36 (3H, m, aromatic H),
3
15.6 Hz, PCH2CH2), 24.4 (d, JPC = 3.6 Hz, CH2CH3), 46.0 (d,
7.55–7.64 (3H, m, aromatic H), 7.80 (2H, m, aromatic H), 7.90–
1
1
=
JPC = 108.1 Hz, P CH), 126.5 (d, JPC = 82.0 Hz, ipso-C of
1
7.98 (2H, m, aromatic H); 31P{ H} NMR (MeOD, 121.5 MHz): d
PPh), 126.6 (s, CH of OCPh), 127.8 (s, CH of OCPh), 129.1–129.3
(overlapping s of CH of OCPh and d of o-C of PPh), 131.2 (d,
3JPC = 8.7 Hz, m-C of PPh), 131.9 (d, 4JPC = 2.6 Hz, p-C of PPh),
41.8.
The dried salt was dissolved in a mixture of 20 mL of distilled
water and 20 mL of MeOH and an aqueous solution of NaOH
(2.0 M) was added to the solution until pH 8 was reached. The
phosphorane 7 precipitated as a white powder and the solvent
was removed with a cannula. 7 was washed with water and dried
under vacuum overnight. Yield: 2.120 g, 93%. 1H NMR (300 MHz,
3
4
141.5 (d, JPC = 13.7 Hz, ipso-C of OCPh), 185.15 (d, JPC
=
3.5 Hz, CO); 31P{ H} NMR (CDCl3, 121.5 MHz): d 19.5. IR:
1
1681w, 1583m, 1512vs, 1487sh, 1463m, 1436s cm−1.
Synthesis of (benzoylmethylene)diphenyl(n-butyl)phosphorane 10
3
CDCl3): d 1.50 (18H, d, JPH = 14.7 Hz, CH3), 3.93 (1H, d,
2
=
JPH = 17.7 Hz, P CH), 7.36 (3H, m, aromatic H), 7.44–7.57 (3H,
This compound was prepared using a method similar to
that described for 9 by reaction of 1.680 g (8.40 mmol) of
m, aromatic H), 7.86–7.96 (4H, m, aromatic H); 13C{ H} NMR
1
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a-bromoacetophenone with 2.040 g (8.40 mmol) of diphenyl(n-
butyl)phosphine (the phosphonium salt has not been character-
ized by 31P or 1H NMR). Yield: 2.800 g, 92%. 1H NMR (300 MHz,
pale green solid product proved to be air-sensitive and was used
immediately (yield: 60%).
To a solution of 13.000 g (57.00 mmol) of 2-bromo-1-(2-
methoxyphenyl)ethanone in 100 mL of toluene, was added a
solution of triphenylphosphine (14.900 g, 57.00 mmol) in 100 mL
of toluene and the solution was stirred for 2 h at reflux. The
white phosphonium salt precipitated rapidly. After reaction, it
was filtered off and dried under vacuum. Yield: 26.600 g, 95%.
1H NMR (300 MHz, CD2Cl2): d 3.99 (3H, s, OCH3), 5.83 (2H,
d, PCH2), 6.95–7.10 (2H, m, aromatic H), 7.50–8.00 (17H, m,
aromatic H). This phosphonium salt (13.500 g, 27.50 mmol) was
dissolved in a saturated water solution of Na2CO3 and the solution
was stirred for a few minutes. 12 was extracted with chloroform
(3 × 50 mL) and, after elimination of the solvents, dried under
vacuum to afford an orange oil which was dissolved in 30 mL
of toluene and precipitated to form a pale yellow powder. Yield:
9.000 g, 80%. 1H NMR (300 MHz, CDCl3): d 3.93 (3H, s, OCH3),
3
CDCl3): d 0.88 (3H, t, JHH = 7.2 Hz, CH3), 1.40–1.60 (4H, m,
2
CH2CH2), 1.78 (2H, m, PCH2), 4.23 (1H, d, JPH = 23.4 Hz,
=
P CH), 7.35 (3H, m, aromatic H), 7.45–7.56 (6H, m, aromatic
H), 7.70–7.78 (4H, m, aromatic H) and 7.95 (2H, m, aromatic
1
H); 13C{ H} NMR (CDCl3, 75.5 MHz): d 13.7 (s, CH3), 24.1 (d,
1JPC = 110.9 Hz, PCH2), 24.2 (d, 2JPC = 16.7 Hz, PCH2CH2), 24.7
3
1
=
(d, JPC = 3.1 Hz, CH2CH3), 47.9 (d, JPC = 47.9 Hz, P CH),
126.9 (s, CH of OCPh), 127.8 (s, p-C of OCPh), 128.6 (d, 1JPC
=
2
88.0 Hz, ipso-C of PPh), 129.0 (d, JPC = 11.6 Hz, m-C of PPh),
129.3 (s, CH of OCPh), 131.9–132.1 (overlapping s and d, p-C and
3
o-C of PPh), 141.2 (d, JPC = 11.3 Hz, ipso-C of OCPh), 185.2
(s, CO); 31P{ H} NMR (CDCl3, 121.5 MHz): d 17.0. IR: 1677w,
1
1584m, 1520vs, 1480m, 1465w, 1436s cm−1.
4.55 (1H, d, 2JPH = 28.3 Hz, P CH), 6.96–7.01 (2H, m, aromatic
=
Synthesis of (benzoylmethylene)phenyldimethylphosphorane 11
H), 7.32 (1H, m, aromatic H), 7.53 (6H, m, aromatic H), 7.62 (3H,
1
m, aromatic H) and 7.78 (7H, m, aromatic H); 13C{ H} NMR
3.200 g (16.10 mmol) of a-bromoacetophenone were added to a
solution of 2.200 g (16.10 mmol) of phenyldimethylphosphine in
20 mL of toluene and stirred for 24 h at room temperature. The
solvent was removed with a cannula and the phosphonium salt
washed with toluene (20 mL) and dried under vacuum. 1H NMR
(300 MHz, MeOD): d 2.38 (6H, d, 2JPH = 14.7 Hz, CH3), 3.31 (2H,
qnt, J = 1.5 Hz, CH2), 7.52–7.57 (2H, m, aromatic H), 7.67–7.72
(3H, m, aromatic H), 7.75–7.81 (1H, m, aromatic H), 7.96–8.05
(CDCl3, 75.5 MHz): d 55.3 (d, 1JPC = 106.6 Hz, P CH), 55.9 (s,
=
OCH3), 111.5 (s, CH of OCPh), 120.3 (s, CH of OCPh), 126.7 (s,
CH of OCPh), 128.0 (s, CH of OCPh), 128.8 (d, 3JPC = 12.2 Hz,
m-C of PPh), 129.7 (d, 1JPC = 13.0 Hz, ipso-C of PPh), 131.9 (d,
3
4JPC = 2.6 Hz, p-C of PPh), 132.0 (d, JPC = 14.2 Hz, ipso-C of
2
OCPh), 133.2 (d, JPC = 10.0 Hz, o-C of PPh), 157.4 (s, OCH3),
1
184.0 (s, CO); 31P{ H} NMR (CDCl3, 121.5 MHz): d 16.0.
1
(4H, m, aromatic H); 31P{ H} NMR (MeOD, 121.5 MHz): d 23.3.
NaH was added to a suspension of the phosphonium salt in
toluene and the mixture was stirred overnight at room temperature.
The solution was transferred with a cannula to eliminate NaBr and
unreacted NaH. The solvent was removed under reduced pressure
and a pale yellow powder was obtained which dried under vacuum
... ...
[NiPh{Ph PCH C( O)(o-OMeC H )}(PPh )] 13
−
−
2
6
4
3
A solution of 0.170 g (0.62 mmol) of [Ni(COD)2] in 30 mL of
toluene was added to a solution of 0.160 g (0.62 mmol) of PPh3
and 0.250 g (0.62 mmol) of 12 in 50 mL of toluene and the mixture
was stirred for 24 h at room temperature. The red solution was
evaporated under reduced pressure to afford complex 13 as a
yellow powder. The 1H NMR spectrum indicated a yield of 90%
1
overnight. Yield: 3.800 g, 92%. H NMR (300 MHz, CDCl3): d
2
2
2.03 (6H, t, JPH = 13.5 Hz, CH3), 4.23 (1H, d, JPH = 25.8 Hz,
=
P CH), 7.35 (3H, m, aromatic H), 7.52 (3H, m, aromatic H),
7.77 (2H, m, aromatic H) and 7.91 (2H, m, aromatic H); 13C{ H}
1
1
based on 12. H NMR (300 MHz, C6D6): d 3.42 (3H, s, OCH3),
NMR (CDCl3, 75.5 MHz): d 12.4 (d, 1JPC = 62.1 Hz, CH3), 51.0 (d,
5.97 (1H, s, PCH), 6.50–6.77 (5H, m, aromatic H), 6.91–7.15 (18H,
br m, aromatic H), 7.45 (1H, m, aromatic H), 7.59 (5H, br m,
1
=
JPC = 111.7 Hz, P CH), 126.6 (s, CH of OCPh), 127.8 (s, CH of
OCPh), 128.9 (d, 1JPC = 87.0 Hz, ipso-C of PPh), 129.2 (d, 2JPC
=
=
1
aromatic H), 7.75 (5H, br m, aromatic H); 31P{ H} NMR (C6D6,
3
11.9 Hz, o-C of PPh), 129.5 (s, p-C of OCPh), 130.4 (d, JPC
121.5 MHz): AB spin system with the appearance of two singlets
at d 23.6 and 23.4 ppm. Anal. Found: C, 73.4; H, 4.9. Calc. for
C45H38NiO2P2: C, 73.89; H, 5.24%.
10.2 Hz, m-C of PPh), 132.0 (d, 4JPC = 2.7 Hz, p-C of PPh), 140.8
(d, 3JPC = 13.4 Hz, ipso-C of OCPh), 185.2 (d, 2JPC = 2.9 Hz, CO);
31P{ H} NMR (CDCl3, 121.5 MHz): d 7.4. IR: 1680m, 1584m,
1
1556mw, 1505vs, 1485m cm−1. Anal. Found: C, 74.5; H, 6.3. Calc.
for C16H17OP: C, 74.99, H, 6.69%.
... ...
[NiPh{Ph(t-Bu)PCH C( O)Ph}(PPh )] 15
−
−
3
A solution of 0.073 g (0.27 mmol) of [Ni(COD)2] in 5 mL of
toluene was added to a solution of 0.071 g (0.27 mmol) of PPh3
and 0.098 g (0.27 mmol) of 8 in 5 mL of toluene and the mixture
was stirred overnight at room temperature. After reaction, the red
solution was evaporated under reduced pressure to afford the pale
Synthesis of ortho-(methoxy)phenylcarbonylmethylene-
(triphenylphosphorane) 1256
Synthesis of 2-bromo-1-(2-methoxyphenyl)ethanone67. To a so-
lution of 15.000 g (100.00 mol) of 1-(2-methoxyphenyl)ethanone
in 200 mL of CCl4 at reflux, was added a solution of Br2 (5.5 mL,
100.00 mol) over a period of 50 min. After reaction, the solvents
were removed under reduced pressure and the solid residue was
dissolved in 100 mL of a mixture of diethyl ether–pentane (1 :
1
yellow complex 15. The H NMR spectrum indicated a yield of
1
83% based on [Ni(COD)2]. H NMR (300 MHz, C6D6): d 1.22
3
(9H, br d, JPC = 13.5 Hz, CH3), 5.11 (1H, br s, PCH), 6.7–7.8
1
(30H, br m, aromatic H); 31P{ H} NMR (C6D6, 121.5 MHz): AB
◦
2
1). The solution was cooled at 0 C to precipitate 2-bromo-1-(2-
spin system dA 31.4 (d, PPh(t-Bu), JAB = 278 Hz), dB 22.4 (d,
methoxyphenyl)ethanone which was filtered off and dried. The
PPh3, 2JAB = 278 Hz).
828 | Dalton Trans., 2008, 822–831
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©

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... ...
[NiPh{(n-Bu) PCH C( O)Ph}(PPh )] 16
... ...
[NiPh{(n-Bu) PCH C( O)Ph}(Py)] 20
−
−
−
−
2
3
2
A solution of 0.890 g (3.24 mmol) of [Ni(COD)2] in 50 mL of
toluene was added to a solution of 0.850 g (3.24 mmol) of PPh3 and
1.102 g (3.24 mmol) of 9 in 50 mL of toluene at 0 ◦C and the mixture
was stirred for 3 days at room temperature. After reaction, the
brown solution was evaporated under reduced pressure to afford
A solution of 0.092 g (0.33 mmol) of [Ni(COD)2] in 5 mL of
toluene was added to a solution of 0.114 g (0.33 mmol) of 9 and
1 mL of pyridine (12.66 mmol) in 5 mL of toluene and the mixture
was stirred overnight at room temperature. After reaction, the
complex 20 was isolated as pale yellow powder after elimination
1
1
complex 16 as a brown oil. The H NMR spectrum indicated a
of the solvents under reduced pressure. The H NMR spectrum
1
1
yield of 84% based on [Ni(COD)2]. H NMR (300 MHz, C6D6):
showed a yield of 24% based on 9. H NMR (300 MHz, C6D6):
3
d 0.86 (6H, t, JHH = 7.2 Hz, CH3), 1.67 (12H, br m, CH2), 4.60
d 0.81 (6H, br s, CH3), 1.52–1.75 (12H, br m, CH2), 4.81 (1H,
1
(1H, s, PCH), 6.78–7.83 (25H, br m, aromatic H); 31P{ H} NMR
br s, PCH), 6.51–7.68 (10H, br m, aromatic H), 8.00–8.41 (5H,
(C6D6, 121.5 MHz): AB spin system dA 22.6 (d, PPh(n-Bu), 2JAB
280 Hz), dB 21.4 (d, PPh3, 2JAB = 280 Hz).
=
br s, aromatic H); 31P{ H} NMR (C6D6, 121.5 MHz): d 23.2 (s,
1
P(n-Bu)2).
... ...
... ...
[NiPh{Ph(n-Bu)PCH C( O)Ph}(Py)] 21
− −
[NiPh{Ph(n-Bu)PCH C( O)Ph}(PPh )] 17
−
−
3
A solution of 0.119 g (0.43 mmol) of [Ni(COD)2] in 5 mL of toluene
was added to a solution of 0.156 g (0.43 mmol) of 10 and 1 mL
of pyridine (12.66 mmol) in 5 mL of toluene and the mixture was
stirred overnight at room temperature. After reaction, complex
21 was isolated as a pale yellow powder after elimination of the
solvents under reduced pressure. The 1H NMR spectrum indicated
a yield of 81% based on [Ni(COD)2]. 1H NMR (300 MHz, C6D6):
d 0.79 (3H, br s, CH3), 1.45–1.67 (6H, br m, CH2), 4.81 (1H, br s,
PCH), 6.28 (2H, br s, aromatic H), 6.71 (1H, br s, aromatic H),
6.93–7.35 (12H, br m, aromatic H), 8.06 (2H, br s, aromatic H),
8.37 (1H, br s, aromatic H), 8.55 (2H, br s, JPH = 7.2 Hz, aromatic
A solution of 0.078 g (0.28 mmol) of [Ni(COD)2] in 5 mL of toluene
was added to a solution of 0.073 g (0.28 mmol) of PPh3 and 0.104 g
(0.28 mmol) of 10 in 5 mL of toluene at 0 ◦C and the mixture was
stirred overnight at room temperature. After reaction, the yellow
solution was evaporated under reduced pressure to afford complex
1
17 as a pale yellow powder. The H NMR spectrum indicated a
yield of 43% based on 10. 1H NMR (300 MHz, C6D6): d 0.70–1.75
(9H, broad signals corresponding of the n-butyl substituents), 4.90
(1H, s, PCH), 6.78–7.99 (25H, br m, aromatic H), 8.39 (5H, br s,
1
aromatic H); 31P{ H} NMR (C6D6, 121.5 MHz): AB spin system
2
2
dA 22.3 (d, PPh(n-Bu), JAB = 282 Hz), dB 20.4 (d, PPh3, JAB
=
1
H); 31P{ H} NMR (C6D6, 121.5 MHz): d 22.0 (s, PPh(n-Bu)).
282 Hz).
... ...
[NiPh{Me PCH C( O)Ph}(Py)] 22
−
−
2
... ...
[NiPh{Ph PCH C( O)Ph}(Py)] 1836
−
−
2
A solution of 0.072 g (0.26 mmol) of [Ni(COD)2] in 5 mL of toluene
was added to a solution of 0.067 g (0.26 mmol) of 11 and 1 mL
of pyridine (12.66 mmol) in 5 mL of toluene and the mixture was
stirred overnight at room temperature. After reaction, complex
22 was isolated as a pale yellow powder after elimination of the
solvents under reduced pressure. The 1H NMR spectrum indicated
a yield of 83% based on [Ni(COD)2]. 1H NMR (300 MHz, C6D6):
A solution of 0.092 g (0.33 mmol) of [Ni(COD)2] in 5 mL of
toluene was added to a solution of 0.127 g (0.33 mmol) of 3 and
1 mL of pyridine (12.66 mmol) in 5 mL of toluene and the mixture
was stirred overnight at room temperature. After reaction, the
complex 18 was isolated as a pale yellow powder after filtration of
the dark suspension and elimination of the solvents under reduced
pressure. The 1H NMR spectrum indicated a yield of 77% based
on 3. 1H NMR (300 MHz, C6D6): d 5.04 (1H, s, PCH), 6.32 (2H,
br s, aromatic H), 6.61 (1H, br s, aromatic H), 6.78–7.36 (11H,
br m, aromatic H), 7.52 (2H, br s, aromatic H), 7.71 (5H, br s,
aromatic H), 8.13 (2H, br d, JPH = 6.3 Hz aromatic H), 8.45 (2H,
3
d 0.87 (6H, d, JPH = 8.4 Hz, CH3), 4.63 (1H, br s, PCH), 6.41
(2H, br s, aromatic H), 6.72 (1H, br s, aromatic H), 6.93–7.33 (7H,
br m, aromatic H), 7.56 (2H, br s, aromatic H), 8.11 (1H, br s,
1
aromatic H), 8.66 (2H, br s, aromatic H); 31P{ H} NMR (C6D6,
121.5 MHz): d 4.0 (s, P(Me)2).
1
br s, aromatic H); 31P{ H} NMR (C6D6, 121.5 MHz): d 24.4 (s,
PPh2).
Oligomerization of ethylene
All catalytic reactions were carried out in a magnetically stirred
(900 rpm) 145 mL stainless steel autoclave. A 125 mL glass
container was used to protect the inner walls of the autoclave
from corrosion. 0.20 mmol of [Ni(COD)2] (0.055 g) was dissolved
in 10 mL of toluene and the solution was added to a 10 mL toluene
solution containing 0.20 mmol (0.052 g) of PPh3 and 0.20 mmol of
ylide. The mixture was immediately injected into the reactor under
a constant low flow of ethylene and the reactor was pressurized to
30 bar. The 30 bar working pressure were maintained during the
experiments through a continuous feed of ethylene from a reserve
bottle. At the end of each test, the gaseous phase was 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
... ...
[NiPh{Ph(t-Bu)PCH C( O)Ph}(Py)] 19
−
−
A solution of 0.093 g (0.34 mmol) of [Ni(COD)2] in 5 mL of toluene
was added to a solution of 0.096 g (0.34 mmol) of 8 and 1 mL of
pyridine (12.66 mmol) in 5 mL of toluene and the mixture was
stirred overnight at room temperature. After reaction, complex
19 was isolated as pale a yellow powder after elimination of the
solvents under reduced pressure. The 1H NMR spectrum indicated
a yield of 94% based on 8. 1H NMR (300 MHz, C6D6): d 1.28 (9H,
d, 3JHH = 14.7 Hz, CH3), 4.94 (1H, s, PCH), 6.3 (1H, br s, aromatic
H), 6.6 (1H, br s, aromatic H), 6.9–7.3 (13H, br m, aromatic H),
7.6 (2H, br s, aromatic H), 7.7 (1H, br s, aromatic H), 8.06 (2H, d,
1
JPH = 7.2, aromatic H); 31P{ H} NMR (C6D6, 121.5 MHz): d 35.5
(s, PPh(t-Bu)).
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Dalton Trans., 2008, 822–831 | 829
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Table 4 Summary of crystallographic data for 13
7 L. K. Johnson, C. M. Killian and M. Brookhart, J. Am. Chem. Soc.,
1995, 117, 6414.
8 C. M. Killian, D. J. Tempel, L. K. Johnson and M. Brookhart, J. Am.
Chem. Soc., 1996, 118, 11664.
Formula
Mr
C45H38NiO2P2
731.40
Triclinic
¯
P1
10.6130(1), 13.4690(2), 14.0310(3)
76.3300(8), 82.2130(8), 74.847(1)
1875.29(5)
2
1.295
0.64
15910, 10885, 8098
9 S. D. Ittel, L. K. Johnson and M. Brookhart, Chem. Rev., 2000, 100,
Crystal system
Space group
1169.
10 V. C. Gibson and S. K. Spitzmesser, Chem. Rev., 2003, 103, 283.
11 C. M. Killian, L. K. Johnson and M. Brookhart, Organometallics, 1997,
16, 2005.
12 S. A. Svejda and M. Brookhart, Organometallics, 1999, 18, 65.
13 T. R. Younkin, E. F. Connor, J. I. Henderson, S. K. Friedrich, R. H.
Grubbs and D. A. Bansleben, Science, 2000, 287, 460.
14 D. J. Darensbourg, C. G. Ortiz and J. C. Yarbrough, Inorg. Chem., 2003,
42, 6915.
15 Q.-Z. Yang, A. Kermagoret, M. Agostinho, O. Siri and P. Braunstein,
Organometallics, 2006, 25, 5518.
16 W.-H. Sun, W. Zhang, T. Gao, X. Tang, L. Chen, Y. Li and X. Jin,
J. Organomet. Chem., 2004, 689, 917.
˚
a, b, c/A
a, b, c /◦
3
˚
V/A
Z
Dc/g cm−3
l(Mo-Ka) (mm−1
)
Measd, indep., obs.
reflections
Rint
0.021
0.039, 0.099, 1.04
10885
451
0.0392
R [F2 > 2r(F2)], wR(F2), S
No. reflections
No. parameters
R1 [I > 2r(I)]
wR2
17 F. Speiser, P. Braunstein and L. Saussine, Acc. Chem. Res., 2005, 38,
784.
18 P. Braunstein, Chem. Rev., 2006, 106, 134.
0.0895
19 C. Wang, S. Friedrich, T. R. Younkin, R. T. Li, R. H. Grubbs, D. A.
Bansleben and M. W. Day, Organometallics, 1998, 17, 3149.
20 T. R. Younkin, E. F. Connor, J. I. Henderson, S. K. Friedrich, R. H.
Grubbs and D. A. Bansleben, Science, 2000, 288, 1750.
21 M. A. Zuideveld, P. Wehrmann, C. Ro¨hr and S. Mecking, Angew.
Chem., Int. Ed., 2004, 43, 869.
22 I. Goettker-Schnetmann, B. Korthals and S. Mecking, J. Am. Chem.
Soc., 2006, 128, 7708.
23 F. A. Hicks and M. Brookhart, Organometallics, 2001, 20, 3217.
24 F. A. Hicks, J. C. Jenkins and M. Brookhart, Organometallics, 2003,
22, 3533.
transferred into a Schlenk flask, and all volatiles were separated
from high weight oligomers or polymers and the metal complexes
before GC analysis by trap-to-trap evaporation (20 ◦C, 0.3 mm Hg)
into a second Schlenk flask previously immersed in liquid nitrogen
in order to avoid any loss of product. Ethylene consumption was
calculated by addition of the mass of oligomers from the gas layer,
the mass of oligomers from the volatile liquid layer and the mass
non-volatile products minus the mass of complex.
25 J. C. Jenkins and M. Brookhart, J. Am. Chem. Soc., 2004, 126, 5827.
26 J. C. Jenkins and M. Brookhart, Organometallics, 2003, 22, 250.
27 T. Hu, L.-M. Tang, X.-F. Li, Y.-S. Li and N.-H. Hu, Organometallics,
2005, 24, 2628.
Crystal structure determination
28 R. S. Rojas, J.-C. Wasilke, G. Wu, J. W. Ziller and G. C. Bazan,
Organometallics, 2005, 24, 5644.
29 M. P. Batten, A. J. Canty, K. J. Cavell, T. Ru¨ther, B. W. Skelton and
A. H. White, Inorg. Chim. Acta, 2006, 359, 1710.
30 M. S. W. Chan, L. Deng and T. Ziegler, Organometallics, 2000, 19,
2741.
31 W. Keim, Angew. Chem., Int. Ed., 1990, 29, 235.
32 W. Keim, F. H. Kowaldt, R. Goddard and C. Kru¨ger, Angew. Chem.,
Int. Ed., 1978, 17, 466.
33 W. Keim, A. Behr, B. Gruber, B. Hoffmann, F. H. Kowaldt, U.
Ku¨rschner, B. Limba¨cker and F. P. Sistig, Organometallics, 1986, 5,
2356.
Diffraction data were collected on a Kappa CCD diffractometer
˚
using graphite-monochromated Mo-Karadiation (k = 0.71073 A)
(Table 4). Data were collected using phi-scans and the structures
were solved by direct methods using the SHELX 97 software,68,69
and the refinement was by full-matrix least squares on F2.
No absorption correction was used. All non-hydrogen atoms
were refined anisotropically with H atoms introduced as fixed
˚
contributors (dC–H = 0.95 A, U11 = 0.04).
34 J. Pietsch, P. Braunstein and Y. Chauvin, New J. Chem., 1998, 22, 467.
35 U. Klabunde and S. D. Ittel, J. Mol. Catal., 1987, 41, 123.
36 U. Klabunde, R. Mu¨hlhaupt, T. Herskowitz, A. H. Janowicz, J.
Calabrese and S. D. Ittel, J. Polym. Sci., Polym. Chem., 1987, 25, 1989.
37 W. Keim, New J. Chem., 1987, 11, 531.
38 R. Soula, J. P. Broyer, M. F. Llauro, A. Tomov, R. Spitz, J. Claverie, X.
Drujon, J. Malinge and T. Saudemont, Macromolecules, 2001, 8, 2438.
39 W. Keim, J. Mol. Catal., 1989, 52, 19.
40 P. Kuhn, D. Semeril, C. Jeunesse, D. Matt, P. Lutz and R. Welter,
Eur. J. Inorg. Chem., 2005, 1477.
41 P. Kuhn, D. Semeril, C. Jeunesse, D. Matt, M. Neuburger and A. Mota,
Chem.–Eur. J., 2006, 12, 5210.
Acknowledgements
We thank the Centre National de la Recherche Scientifique
(CNRS), the Ministe`re de lꢀEducation Nationale et de la
Recherche (Paris) (PhD grant to A. K.) and the Institut Franc¸ais
du Pe´trole (IFP) for support. We also thank Dr A. DeCian and
Prof. R. Welter (ULP Strasbourg) for the crystal structure deter-
mination, L. Saussine (IFP) and Dr R. Pattacini for discussions
and Anne Degre´mont, Jonathan Kirsch and Marc Mermillon-
Fournier (LCC Strasbourg) for experimental assistance.
42 P. Kuhn, D. Semeril, D. Matt, M. J. Chetcuti and P. Lutz, Dalton Trans.,
2007, 515.
43 J. Pietsch, P. Braunstein and Y. Chauvin, New J. Chem, 1998, 467.
44 J. Heinicke, M. Koesling, R. Bru¨ll, W. Keim and H. Pritzkow,
Eur. J. Inorg. Chem., 2000, 299.
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