Catalytic ethylene polymerisation in carbon dioxide as a reaction medium with soluble nickel(II) catalysts

Article abstract of DOI:10.1002/chem.200600499

A series of neutral Ni^II-salicylaldiminato complexes substituted with perfluorooctyl- and trifluoromethyl groups, [Ni{K²-N,O-6-C(H)= NAr-2,4-R′₂C₆H₂}(Me)(pyridine)] (6a: Ar = 2,6-{4-(F₁₇C

Full text of DOI:10.1002/chem.200600499

DOI: 10.1002/chem.200600499
Catalytic Ethylene Polymerisation in Carbon Dioxide as a Reaction Medium
with Soluble Nickel(II) Catalysts
Amaia Bastero,[a] Giancarlo Franciò,[b] Walter Leitner,*[b] and Stefan Mecking*[a]
Abstract: A series of neutral NiII–sali-
cylaldiminato complexes substituted
with perfluorooctyl- and trifluorometh-
yl groups, [Ni{k2-N,O-6-C(H)=NAr-2,4-
C
yields,
corresponding
to
2”
103 turnovers.Semicrystalline polyethy-
lene (Mn typically 104 gmolÀ1) is ob-
tained with variable degrees of branch-
ing (11 to 24 branches per 1000 carbon
atoms, predominantly Me branches)
and crystallinities (54 to 21%), de-
pending on the substitution pattern of
the catalyst.
R’2C6H2O}(Me)
2,6-{4-(F17C8)C6H4}2C6H3, R’=I; 6b:
Ar=2,6-{4-(F3C)C6H4}2C6H3, R’=I;
Ar=2,6-{3,5-(F3C)2C6H3}2C6H3,
3,5-(F3C)2C6H3; 6d: Ar=2,6-{4-
A
6c:
R’=
ACHTREUNG
(F17C8)
A
R’=3,5-(F3C)2-
A
Introduction
can be of interest, for example, to eliminate emissions of
volatile organic compounds.The aforementioned unique
properties of CO2 can be employed to control polymer mor-
phologies.In some cases, the elimination of energy-intensive
drying procedures may be environmentally and economical-
ly beneficial, though the effort for compression of CO2 must
also be considered.[2]
Most studies of polymerisation in CO2 dealt with free-rad-
ical polymerisation, although an early example of cationic
polymerization was reported in the 1960s.[3] Interest in-
creased considerably with the report of homogeneous poly-
merisation in scCO2 to afford soluble amorphous fluoropoly-
mers in the 1990s.[4] Free-radical polymerisation in scCO2
under heterogeneous conditions, either as precipitation, dis-
persion or emulsion polymerisations, has also been studied
recently.Typical monomers investigated are methylmetha-
crylate,[5] styrene,[6] vinyl acetate and acrylamide.[2]
Dense carbon dioxide, that is liquid or supercritical carbon
dioxide (scCO2), offers unique properties as a reaction
medium, such as variation of the solvent properties through
the density; volatility at ambient conditions, thus enabling
facile removal of the solvent; environmental friendliness
and non-toxicity.[1] In reactions of gaseous substrates, the
high miscibility of scCO2 with some gases can additionally
help to avoid mass transport limitations, which are frequent-
ly encountered in such reactions.In polymerisation process-
es and polymer processing, the CO2 solvent or suspension
medium, respectively, can be removed conveniently by re-
ducing the pressure, resulting in a dry polymer product.This
[a] Dr.A.Bastero, Prof.Dr.S.Mecking
Universität Konstanz
Lehrstuhl für Chemische Materialwissenschaft
Fachbereich Chemie, Universitätsstr.10
78457 Konstanz (Germany)
Fax : (+49)7531-88-5152
E-mail: stefan.mecking@uni-konstanz.de
By contrast to free-radical polymerisations, catalytic poly-
merisation offers control of polymer microstructures in gen-
eral terms.[7,8] Traditional Ziegler and metallocene catalysts
are based on early transition metals.Due to their high oxo-
philicity, early-transition-metal complexes are likely to react
with CO2.Late-transition-metal complexes are much less
oxophilic, as demonstrated by the possibility of copolymeri-
sation of polar monomers like acrylates[9] and polymerisa-
tion in aqueous emulsions.[10,11,12] Ring-opening metathesis
polymerisation (ROMP) of norbornene and derivatives,[13,14]
polycarbonate synthesis from CO2 and epoxides[15,16] and
[b] Dr.G.Franciò, Prof.Dr.W.Leitner
Institut für Technische und Makromolekulare Chemie
RWTH Aachen, Worringer Weg 1
52074 Aachen (Germany)
Fax : (+49)241-80-22177
E-mail: leitner@itmc.rwth-aachen.de
Supporting information for this article is available on the WWW
under http://www.chemeurj.org/ or from the author.
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Chem. Eur. J. 2006, 12, 6110 – 6116

FULL PAPER
phenylacetylene polymerisation[17] have been reported in
scCO2 as a reaction medium.Ethylene polymerisation has
been studied in scCO2 with Brookhartꢁs palladium catalyst,
with an emphasis on the analysis of the microstructure of
the highly branched, amorphous polyethylenes formed.[18,19]
Also, the synthesis of polyketones by olefin/CO copolymeri-
sation has been investigated.[20]
substituted aryl groups in the 2,6-positions.Condensation of
3 with 3,5-diiodosalicylaldehyde yielded salicylaldimine 5a
in 70% yield (Scheme 2).
Using a similar synthetic approach, aniline 3’ bearing
para-CF3-substituted aryl groups in the 2,6-positions was
prepared, starting from 1-bromo-4-(trifluoromethyl)benzene,
and converted to the corresponding imine 5b (Scheme 3).
Employing aldehyde 4’[26] substituted with 3,5-(CF3)2-
Ethylene polymerisation with neutral NiII complexes has
received renewed interest, as these catalysts are more func-
tional-group tolerant than their cationic NiII counter-
parts.[10,11,21] k2-N,O-salicylaldiminato–NiII complexes are
very active for ethylene polymerisation, and afford high mo-
lecular weight polyethylene (Mn >105 gmolÀ1) at the same
time.[21] Remote substituents of the salicylaldiminato ligand
can strongly influence the degree of branching and polymer
molecular weight, by promoting or retarding b-hydride
transfer.Thus, ethylene homopolymerisation affords poly-
ethylenes ranging from semicrystalline, nearly linear to
amorphous, highly branched.[22] The unique combination of
versatility and functional group tolerance prompted us to
study polymerisation in CO2 as a reaction medium with
these complexes.Nickel(II) complexes with perfluoroalkyl-
substituted salicylaldimine ligands, which render them
“CO2-philic”,[23] were prepared for this purpose.
(C6H3) groups introduces a higher number of fluorinated
groups to the ligand backbone,[27] and can also render the
salicylaldimine ligand more electron withdrawing.Conden-
sation with different anilines afforded salicylaldimines 5c
and 5d.Efforts to prepare a ligand containing para-RF-sub-
stituted aryl groups in the aldehyde moiety, through Suzuki
coupling of 1 and 4, failed.[28]
The aforementioned synthesis afforded a set of salicylaldi-
mines (5a–5d) with systematically varied substitution pat-
terns and a fluorine content ranging from 16–54 wt.%. This
degree of fluorination is well in the range required for CO2
solubility with catalytic species.[29] Indeed, preliminary solu-
bility experiments carried out with ligands 5a and 5c
showed a sufficient solubility in supercritical CO2 at concen-
trations required for the use as a catalyst precursor.[30]
Reaction of [Ni
(tmeda)(Me)2][31] (tmeda: N,N,N,N-tetra-
U
methylethylenediamine) with the corresponding fluorinated
Results and Discussion
Complex synthesis and properties: As outlined, remote sub-
stituents of N-terphenylsalicylaldiminato–NiII complexes
have a strong impact on their polymerisation properties,
namely molecular weight and degree of branching of ethyl-
ene homopolymers (Scheme 1).[22] For example, whereas for
R=CF3 high molecular weight, nearly linear semicrystalline
polyethylene is obtained (Mw =105 gmolÀ1; 10 branches per
1000 C atoms), a catalyst precursor with R=CH3 affords
highly branched, entirely amorphous low molecular-weight
polymer (Mw =2.3”103 gmolÀ1; 76 branches per 1000 C
atoms).
Scheme 1.Effect of remote substituents in ethylene polymerisation (*:
monosubstitution only of the aryl groups for NO2).[22]
Based on these insights,
complexes were targeted with
long-chain perfluoroalkyl sub-
stituents (RF), which should
enhance solubility in scCO2,[23]
but without insulating -CH2-
spacers.Perfluorinated octyl
groups (RF =C8F17) were intro-
duced by copper-catalysed cou-
pling, affording the aryl bro-
mide 1.[24] In analogy to the
synthesis of the aforemen-
tioned
terphenyl-substituted
salicylaldimines,[22,25] transfor-
mation of bromide 1 into a
boronic acid (2) followed by
Suzuki coupling afforded ani-
line 3, which bears para-RF- Scheme 2.Synthesis of perfluorinated salicylaldimine 5a.
Chem. Eur. J. 2006, 12, 6110 – 6116
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6111

S.Mecking, W.Leitner et al.
À
Ni Me signal, nor variation of
the pyridine signals were ob-
served (see Figure S1 in Sup-
porting Information).Under
the conditions investigated,
there is no evidence of any re-
action of 6b with CO2.
Polymerisation
experiments:
Complexes 6a–6d, and for
comparison also the known[22]
complex 6e (Scheme 4), were
studied as catalyst precursors
for ethylene polymerisation in
Scheme 3.Fluorinated salicylaldimines prepared.
supercritical carbon dioxide.
The complexes were introduced
ligands in the presence of pyridine (py) afforded the neutral
as solids in a 10 mL stainless-steel high-pressure reactor
equipped with thick-walled borosilicate windows.The vessel
was pressurised with ethylene to 40 bar at room tempera-
ture, and CO2 was condensed in at 08C.Complexes 6c and
6d instantaneously dissolved affording a bright orange-red
solution, which shows the high solubility of these precursors
in compressed CO2.Complex 6a was completely soluble
upon warming to 108C, whereas 6e was dissolved complete-
nickel methyl complexes [Ni
(k2-N^O)(Me)(py)] 6a–6d.The
A
complexes were isolated as air-stable orange or red solids.
1
Characterisation in solution by H and 13C NMR spectrosco-
py shows the presence of a single isomer at room tempera-
ture for all compounds.The nickel-bound methyl group and
the O donor atom are arranged in a trans position, as previ-
ously found for similar nickel–salicylaldiminato complexes
(Scheme 4).[22,32]
ly only at 208C (1
(CO2)=0.96 gmLÀ1).For complex 6b
G
almost no solubility was ob-
served even at 508C in neat CO2
(p(CO2)=126 bar), and there-
N
fore catalysis with this com-
pound was not further studied.
Ethylene polymerisation with
the different catalyst precursors
was studied at 508C (Table 1).
The reaction could be followed
visually through the windows of
the pressure reactor.Upon
warming to the reaction temper-
ature, the orange solution
became turbid already at 358C,
indicating that polyethylene pre-
cipitated.After 1 h of reaction,
significant amounts of polymer
had precipitated and the reactor
was carefully vented, extracting
at the same time unreacted mon-
omer or any low-molecular-
weight oligomers of ethylene.
The polyethylene formed was
obtained as a dry powder.
Scheme 4.Synthesis and structure of Ni II complexes (py=pyridine).
It has been documented that nickel complexes can react
with CO2, which would result in catalyst deactivation.[33] For
example, insertion of carbon dioxide into a Ni–ethyl bond of
True catalyst activities cannot be derived from the present
data, as no conversion/time profiles are available.From the
observation of immediate onset of turbidity it appears that
there is no significant induction period.Furthermore, the
[Ni(Et)2(bipy)], to afford diethylketone and the nickel pro-
pionate complex [Ni(Et)
C
(bipy)], has been report-
total turnover numbers (TON=mol(ethylene)/mol(Ni)) at
H
identical reaction times provide evidence for the relative
catalyst performance.Overall productivities are highest with
6a and 6c, approaching 2”103 TONs within one hour.Note
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Ethylene Polymerisation
FULL PAPER
Table 1.Ethylene polymerisation in scCO 2 with various complexes as catalyst precurors.[a]
branches (C4+) is also detecta-
ble in some spectra (Figure S2
in the Supporting Information).
Based on these results, poly-
merisation with 6c was studied
in more detail (Table 2).The
effect of reaction temperature
was studied (entries 1 to 3).At
308C, polymerisation is slug-
gish.At 70 8C, overall produc-
tivity is increased twofold
versus polymerisation at 508C.
This demonstrates that the cata-
[d]
[g]
Catalyst
precursor
1
G
Initial pressure[b] TON[c] Tm
Crystallinity Branches[f] Mw (Mw/Mn)
A
]
[bar]
[8C]
[%][d,e]
1
2
3
4
6a
6c
6d
6e
1.00
0.99
0.94
0.96
300
282
292
253
2079
2015
125
102–116
125
74
39
52
21
54
24
17
2.0”104 (4.4)
6.5”104 (3.1)
2.9”103 (3.7)[h]
6.7”104 (2.7)
n.d.[i]
11
1566
125
[a] Reaction conditions: 4 mmol catalyst precursor; initial ethylene pressure: 40 bar; temperature: 508C; reac-
tion time: 1 h.[b] Measured at 50 8C after loading the 10 mL reactor with 40 bar ethylene at room temperature
and with CO2.[c] Average turnover number (mol
C
13C NMR; predominantly Me branches, but also Et and C4+ higher branches, see Figure S2 in Supporting In-
formation.[g] Determined by GPC at 160 8C in trichlorobenzene versus linear polyethylene standards.[h] Bi-
modal.[i] nd. . =not determined.
that these productivities are not limited by a complete con-
Table 2.Polymerisation of ethylene in scCO with catalyst 6c: effect of
2
density, temperature and surfactants.[a]
sumption of ethylene, as the initial amount of ethylene in
the reactor is 0.8–1 g, corresponding to a substrate to nickel
ratio of approximately 8”103.Catalyst precursor 6e, which
previously showed high activity in toluene and water,[22,36] is
also active in supercritical carbon dioxide as solvent.Com-
plex 6d, which contains the largest number of CO2-philic
groups, was found to be the least active probably due to fast
decomposition of the catalyst, as evidenced by the yellowish
colour of the reaction mixture, a typical indication for de-
composition for these salicylaldimine complexes.The initial
pressure of 40 bar ethylene at room temperature corre-
sponds to an ethylene concentration of approximately
2.3 molLÀ1.[37] This concentration corresponds to polymerisa-
tion experiments in toluene solution at about 27 atm (calcu-
lating the ethylene concentration with the data of Prausnitz
et al.).[38] Activities found for 6e in toluene at 508C are 8”
103 TONhÀ1 at 5 bar and 4”104 TONhÀ1 at 40 bar.[22] This
indicates that productivities are somewhat lower in scCO2
by comparison to toluene at the same monomer concentra-
tion, but within the same order of magnitude.The lower
productivity may be due to the lower solubility of the poly-
mer in scCO2 as compared with toluene, resulting in precipi-
tation of polymer and possible enclosure of catalyst at an
early point, which can reduce catalyst activity.Another im-
portant difference is that the polymer will be less swollen
with CO2 than with toluene, which may also contribute to a
reduced overall rate.
1
A
T
[8C]
Surfactant
[mg]
TON[b]
Tm
[8C]
Mw (Mw/Mn)
[gmolÀ1
A
]
G
]
1
2
3
4
5
6
7
8
9
1.02
0.94
0.99
0.73
0.43
0.99
1.03
1.00
1.04
30
70
50
50
50
50
50
50
50
–
–
–
–
–
446
4706
2015
88[c]
114–124
119
125
9.0”103 (1.3)
1.9”104 (16)[g]
6.5”104 (3.1)
4.1”104 (2.5)
n.d.[h]
108
179[c]
670
n.d.[h]
107–119
122
25[d]
25[e]
90[f]
190[f]
3.0”104 (4.8)
6.9”104 (3.2)
1.7”104 (2.5)
6.6”104 (3.0)
4914
2059
846
107
113
[a] Reaction conditions: 4 mmol catalyst precursor 6c; 10 mL reactor; ini-
tial ethylene pressure: 40 bar; reaction time: 1 h.[b] Calculated from
mass of polymer isolated, mass of surfactant is subtracted (mol[E]/
mol[Ni]).[c] Precipitation of the catalysts was observed.[d] Fluowet
NMQ.[e] Fluowet PL80.[f] CF
modal.[h] nd. . =not determined.
3-(CF2)2-CO2-(CH2)11-CH3.[g] Multi-
lyst is quite temperature stable in scCO2.The narrow molec-
ular weight distribution of the polymer obtained at 308C
(entry 1) indicates that the chain transfer rate is on the same
order as the reaction time of 1 h at this temperature, and
that living ethylene polymerisation in CO2 may be possible.
Increased branching occurs with increasing temperature,
as expected, resulting in a lower melting temperature of the
semicrystalline polyethylene (compare entry 2 with 3).A
similar behaviour was found for catalyst precursor 6e in tol-
uene.[22]
The effect of carbon dioxide density on activity was also
studied (entries 3–5).For this purpose, the 10 mL reactor
used was charged with different amounts of CO2 (4.3–9.9 g,
corresponding to a density of 0.43–0.99 gmLÀ1).As an over-
all trend, productivities decreased with decreasing density.
This results at least partly from insufficient solubility of the
catalyst precursor in the reaction medium at lower densities,
which could be confirmed visually through the reactor win-
dows (Table 2).
For 6c and 6e, which have also been studied in toluene as
a reaction medium, the overall properties of the polyethy-
lenes obtained in scCO2 and in toluene are similar (toluene;
40 bar ethylene pressure; 508C polymerisation temperature;
6c: Mw =4.6”104 gmolÀ1; Mw/Mn =2.3; Tm =1118C; 45%
crystallinity;[26] 6e: Mw =1.0”105 gmolÀ1; Mw/Mn =5.1; Tm =
1238C; 50% crystallinity[22]).Comparing the polymers pre-
pared in scCO2 with the different catalyst precursors,
branching and thus crystallinity can be varied over a sub-
stantial range through the substitution pattern of the salicy-
laldimine ligand (Table 1).
Precipitation of polyethylene in carbon dioxide occurs
from the very beginning of the reaction, already at 358C, as
seen through the reactor windows.It was therefore investi-
gated whether appropriate surfactants with a CO2-philic and
a CO2-phobic moiety that can interact with the polyethylene
Analysis of polymer microstructures by 13C NMR spectro-
scopy reveals that the polymers predominantly contain
methyl branches; a small amount of ethyl and higher
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6113

S.Mecking, W.Leitner et al.
particles may influence polymer particle formation and pol-
ymer morphologies.[5] To this end, preliminary experiments
were carried out in the presence of Fluowet NMQ (cationic
fluorinated quaternary ammonium salt, see Figure S4 in the
Supporting Information), Fluowet PL80 (mixture of per-
fluorinated phosphinic and phosphonic acid), and perfluoro-
butyric acid dodecyl ester.All compounds were found to be
compatible with the catalyst and no significant deactivation
occurred.The presence of the surfactants affects the out-
come of the polymerisation reaction in terms of polymer
molecular weight, yield and crystallinity (Table 2, entries 6–
9), but no general trends can be derived from the data so
far.
The surface morphology of the polyethylene particles
formed was studied by transmission electron microscopy
(TEM).In the absence of surfactants, large irregular-shaped
polyethylene particles are obtained (Figure 1, left).The
presence of the cationic surfactant Fluowet NMQ and the
neutral perfluorobutyric acid dodecyl ester appears to result
in somewhat smaller and more compact particles with
needle-like structures on their surface (Figure 1 middle and
right).
eight trifluoromethyl groups, is well soluble in scCO2. A
comparison with toluene as a reaction medium indicates
that catalyst productivities are slightly lower in scCO2 under
comparable conditions.The presence of surfactants appears
to alter polymer morphologies on a micron scale.
Experimental Section
General procedures and materials: All reactions were carried out by
using standard Schlenk techniques under an argon atmosphere.Solvents
were distilled and deoxygenated prior to use.Ethylene (25. grade) and
carbon dioxide (5.5 grade) supplied by Praxair were used without further
purification.[Ni
fluoromethyl)phenylboronic
(F3C)2C6H3}2C6H2OH (4’),[26] and 6-C(H)=N
ACHTREUNG
N
A
ACHTREUNG
2,4-{3,5-(F3C)2C6H3}2C6H2OH (5c),[26] and complexes 6c[26] and 6e[22] were
prepared according to known procedures.Perfluorinated surfactants
FLUOWET NMQ and Fluowet PL80 were provided by Clariant GmbH.
1H and 13C NMR spectra were recorded on either a Bruker ARX 300, a
Bruker Avance DRX 600 or a Varian Inova 400 spectrometer. 1H and 13C
chemical shifts were referenced to solvent signals.Assignments were
made from NOE, gCOSY and gHMQC experiments (for numbering of
atoms see Scheme 4).High-temperature NMR spectroscopy for polyethy-
lene characterisation was performed in [D2]1,1,2,2-tetrachloroethane at
1008C.Elemental analyses were carried out on a Elementar Vario EL In-
strument at Freiburg University.Mass spectra were obtained with a Ther-
moelectron TSQ-7000 mass spectrometer at Freiburg University.Differ-
ential scanning calorimetry (DSC) was performed on a Netzsch DSC 204
F1 at a heating rate of 10 KminÀ1.DSC data reported are from second
heating cycles.Molecular weight determination was carried out with a PL
GPC-220 instrument using a Mixed B column in trichlorobenzene at
1608C versus polyethylene standards.
Summary and Conclusions
Ethylene can be polymerised in a precipitation polymerisa-
tion process by using scCO2 as a reaction medium with neu-
tral NiII complexes as catalysts.Semicrystalline polyethylene
is obtained.The branching structure, and thus the crystallini-
ty of the polymer can be altered through variation of the
catalyst and the reaction conditions employed.This differs
from a previous report on ethylene polymerisation with a
cationic Pd–diimine complex, which invariably affords
highly branched amorphous polyethylene with a given over-
all degree of branching.[19b] Catalyst precursors soluble in
the reaction medium are required for high catalyst activities.
A series of nickel(II)–salicylaldiminato complexes with vari-
ous substitution patterns of perfluorooctyl and trifluorome-
1-Bromo-4-(perfluorooctyl)benzene (1): 4-Bromophenyliodide was treat-
ed with C8F17I in the presence of copper following a reported proce-
dure.[24] Yield: 79%. 1H NMR (300 MHz, CDCl3, RT): d=7.66 (d, 3J=
9 Hz, 2H; CH), 7.46 ppm (d, 3J=9 Hz, 2H; CH); 13C NMR (75.4 MHz,
CDCl3, RT): d=132.3 (CH), 128.7 (CH), 128.4 (C-RF), 127.3 (C-Br),
119.4–106.9 ppm (overlapped RF signals); 19F NMR (376.5 MHz, CDCl3,
RT): d=À81.3 (CF3), À111.5 (CF2), À121.7 (CF2), À122.4 (3 CF2),
À123.3 (CF2), À126.7 ppm (CF2); MS (EI): m/z: 574 [M]+, 205
[MÀC7F15]+.
4-(Perfluorooctyl)phenylboronic acid (2): BuLi (9.6 mmol) was added
dropwise at À788C to a solution of 1 (5 g, 8.7 mmol) in Et2O (25 mL)
and stirred for an hour.After this time B (OEt)3 (9.6 mmol) was added
G
thylgroups was prepared.Solubility in scCO increases not
2
dropwise at À788C and the mixture stirred for 1.5 h. Acidic hydrolysis of
the boronic ester, and extraction from the aqueous mixture with Et2O
yielded the product as a white solid.Yield: 85%. 1H NMR (300 MHz,
only with increasing fluorine content, but also with the
number of fluorine-containing moieties.Complex 6c, with
Figure 1.TEM micrographs of polyethylene obtained with precursor 6c at 508C; in the absence of surfactant (left), in the presence of FLUOWET NMQ
(middle), and in the presence of CF3-(CF2)2-CO2-(CH2)11-CH3 (right).
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Ethylene Polymerisation
FULL PAPER
[D6]acetone, RT): d=8.40 (d, 3J=8.3 Hz, 2H), 8.20 ppm (d, 3J=8.3 Hz,
2H); 13C NMR (75.4 MHz, [D6]acetone, RT): d=136.7 (CH), 131.8, 127.9
(CH), 113.7 ppm; 19F NMR (282.4 MHz, [D6]acetone, RT): d=À80.9
(CF3), À110.8 (CF2), À121.0 (CF2), À121.7 (3CF2), À122.6 (CF2),
À126.1 ppm (CF2).
Synthesis of 2,6-disubstituted anilines: The corresponding aryl boronic
acid (3.16 mmol) in EtOH (3 mL) and an aqueous Na2CO3 solution (2m,
5 mL) were added to 2,6-dibromoaniline (0.38 g, 1.5 mmol) in toluene
Synthesis of complexes 6a, 6b and 6d: The corresponding salicylaldimine
(0.49 mmol) followed by pyridine (0.5 mL) were added to a solution of
[Ni
(tmeda)(Me)2][31] (100 mg, 0.49 mmol) in diethyl ether (10 mL) at
G
À308C.Instantaneously, an orange-red solution formed and an orange-
red precipitate appeared.The reaction mixture was stirred for 2 h at
À308C.The solvent was removed at reduced pressure, and the solid ob-
tained was washed with cold pentane affording the neutral methylnicke-
l(II) complexes.
Data for 6a: Yield: 68%; 1H NMR (400 MHz, C6D6, RT): d=8.15 (br,
2H; py), 7.95 (d, 4J=2 Hz, 1H; CH-CI), 7.59 (d, 3J=8.2 Hz, 4H; H9 or
H8), 7.45 (d, 3J=8.2 Hz, 4H; H8 or H9), 7.14 (overlapped with solvent,
H3, H5), 7.05 (m, 1H; H4), 6.80 (s, 1H; N=CH), 6.77 (d, 4J=2 Hz, 1H;
CH-CI), 6.69 (br, 1H; py), 6.41 (br, 2H; py), À0.72 ppm (s, 3H; Ni-Me);
13C NMR (100.5 MHz, CDCl3, RT): 168.0 (s, C=N), 163.9 (s, CO-Ni),
151.5 (br, CHpy), 150.1, 149.9 (s, CH-CI), 143.8, 141.7 (s, CH-CI), 136.3
(br, CHpy), 134.9, 131.0 (s, C3 +C5 +C8 or C9), 128 (C4 overlapped with
solvent), 127.4 (s, C9 or C8), 126.8, 123.2 (br, CHpy), 120.7 (s, C12), 97.5 (s,
CI), 72.5 (s, CI), À7.9 ppm (s, Ni-CH3); 19F NMR (282.4 MHz, C6D6, RT):
À81.1 (CF3), À110.9 (CF2), À121.6 (CF2), À122.2 (3CF2), À123.1 (CF2),
À126.5 ppm (CF2); no satisfactory elemental analysis was obtained as the
high fluorine content disturbed the analysis.
(15 mL), and the mixture was degassed.[Pd (PPh3)4] (0.15 mmol) was
G
added and the reaction mixture was heated to 968C and stirred for 24 h.
The aqueous phase was separated and extracted with Et2O.The solvent
was removed from the organic phases by evaporation under reduced
pressure, and the product was purified by chromatography on silica.
2,6-Di-(4-perfluorooctyl)phenylaniline (3): Yield: 85%. Rf =0.47
(hexane); 1H NMR (300 MHz, CDCl3, RT): d=7.68 (m, 8H; H8, H9),
7.16 (d, 3J=7.7 Hz, 2H; H3, H5), 6.93 (t, 3J=7.7 Hz, 1H; H4), 3.80 ppm
(br, 2H; NH2); 13C NMR (75.4 MHz, CDCl3, RT): d=143.7 (s, C1), 140.7
(s, C10), 130.6 (s, C3, C5), 129.8 (s, C8 or C9), 127.7 (s, C2, C6, C7), 126.8 (s,
C9 or C8), 118.9 (s, C4), 116.1 (m, CF), 111.7 (m, CF), 107.1 ppm (m, CF);
19F NMR (282.4 MHz, CDCl3, RT): d=À80.8 (CF3), À110.6 (CF2),
À121.3 (CF2), À121.7 (CF2), À121.9 (2CF2), À122.7 (CF2), À126.5 ppm
(CF2); MS (CI): m/z: 1082 [M]+.
Data for 6b: Yield: 88%; 1H NMR (400 MHz, C6D6, RT): d=8.13 (br,
2H; py), 7.92 (d, 4J=2.4 Hz, 1H; CH-CI), 7.54 (d, 3J=8.2 Hz, 4H; H8),
7.43 (d, 3J=8.2 Hz, 4H; H9), 7.13 (d, 3J=7.6 Hz, 2H; H3, H5), 7.06 (t,
3J=7.6 Hz, 1H; H4), 6.82 (s, 1H; N=CH), 6.79 (d, 4J=2.4 Hz, 1H; CH-
CI), 6.63 (br, 1H; py), 6.39 (br, 2H; py), À0.73 ppm (s, 3H; Ni-Me);
13C NMR (100.5 MHz, C6D6, RT): 167.9 (s, C=N), 163.8 (s, CO-Ni), 151.4
2,6-Di-(4-trifluoromethyl)phenylaniline (3’): Yield: 56%. Rf =0.93 (tol-
uene); 1H NMR (300 MHz, CDCl3, RT): d=7.74 (m, 4H; H9), 7.65 (m,
4H; H8), 7.15 (d, 3J=7.5 Hz, 2H; H3, H5), 6.93 (t, 3J=7.5 Hz, 1H; H4),
3.79 ppm (br, 2H; NH2); 13C NMR (75.4 MHz, CDCl3, RT): d=143.4 (s,
C1), 140.7 (s, C10), 130.7 (s, C3, C5), 129.6 (s, C8), 129.2 (m, CF3), 126.9 (s,
C7), 126.1 (s, C2, C6), 125.7 (s, C9), 118.8 ppm (s, C4); 19F NMR
(282.4 MHz, CDCl3, RT): d=À63.0 ppm (CF3); MS (EI): m/z: 381 [M]+,
(br, CHpy), 150.2, 149.9 (s, CH-CI), 143.5, 141.8
(s, CH-CI), 136.2 (br,
A
CHpy), 135.1, 131.0 (C8, C9), 130.3, 129.9, 129.7 (q, 2JC-F =33 Hz, C10),
129.6 (s, C4), 126.7 (s, C3 +C5), 126.3, 125.7 (m, CF3), 123.6, 123.2 (br,
CHpy), 120.7 (s, C12), 97.7 (s, CI), 72.7 (s, CI), À7.87 ppm (s, Ni-Me); ele-
mental analysis calcd (%) for NiC33H22F6I2N2O (889.0): C 44.59, H 2.49,
N 3.15; found: C 43.98, H 2.71, N 3.39.
235 [MÀC7H4F3]2+, 167 [MÀC7H4F3ÀCF3]2+
.
Synthesis of salicylaldimines: The corresponding aniline (1.16 mmol) (for
aniline 3 dissolved in (trifluoromethyl)undecafluorocyclohexane (3 mL))
and a catalytic amount of formic acid were added to a solution of 3,5-
diiodosalicylaldehyde (4) or aldehyde 4’ (1.27 mmol) in MeOH (4 mL),
and the mixture heated overnight at reflux.The precipitated imine was
isolated by filtration and washed with cold methanol.
Data for 6d: Yield: 71%; 1H NMR (400 MHz, C6D6, RT): d=7.78 (br,
3
4H; CH, py), 7.73 (br, 1H; CH), 7.67 (d, J=8.4 Hz, 4H; H9 or H8), 7.60
(br, 1H; CH), 7.54 (m, 6H; H9 or H8 and CH), 7.16 (N=CH and H15 or
H17 overlapped with solvent signal), 7.13 (m, 3H; H3, H4, H5), 6.70 (d,
4J=2.4 Hz, 1H; H15 or H17), 6.68 (m, 1H; py), 6.24 (m, 2H; py),
À0.76 ppm (s, 3H; Ni-Me); 13C NMR (100.5 MHz, C6D6, RT): d=169.9
(s, C=N), 165.0 (s, CO-Ni), 150.5, 150.1, 143.9, 143.8 (s, C1), 142.6, 141.5,
140.8 (s, C10), 136.5, 134.9, 133.0 (s, CH), 131.0 (s, C8 or C9), 130.8, 127.4,
126.9 (s, C9 or C8), 126.6 (s, CH), 125.8 (s, CH), 123.8, 123.3, 121.2, 119.9
(s, CH), 118.8 (s, C4), À7.3 ppm (s, Ni-Me); 19F NMR (282.4 MHz, C6D6,
RT): d=À63.8 (CF3), À82.0 (CF2-CF3), À111.1 (CF2), À111.5 (CF2),
À122.2 (CF2), À122.4 (CF2), À122.9 (CF2), À123.7 (CF2), À127.2 ppm
(CF2); no satisfactory elemental analysis was obtained, as the high fluo-
rine content disturbed the analysis.
Data for 5a: Yield: 70%; 1H NMR (300 MHz, CDCl3, RT): d=8.00 (d,
4J=2.1 Hz, 1H; CH-CI), 7.71 (s, 1H; N=CH), 7.60 (d, 3J=8.4 Hz, 4H;
4
H8), 7.47 (m, 7H; H3, H4, H5, H9), 7.04 ppm (d, J=2.1 Hz, 1H; CH-CI);
13C NMR (75.4 MHz, CDCl3, RT): d=167.2 (s, N=C), 159.8 (s, C-OH),
150.0 (s, CH-CI), 144.3 (s, C1), 143.0, 140.4 (s, CH-CI), 134.0 (s, C8 or C9),
131.2, 130.1 (s, C9 or C8), 129.8–127.0 (m, C10, C4, C-F), 119.9, 87.0 (s, C-
I), 80.1 ppm (s, C-I); 19F NMR (282.4 MHz, CDCl3, RT): d=À81.1 (CF3),
À111.2 (CF2), À121.6 (CF2), À122.0 (br, 2CF2), À123.1 (CF2),
À126.5 ppm (CF2); MS (EI): m/z: 1437 [M]+.
Data for 5b: Yield: 61%; 1H NMR (300 MHz, C6D6, RT): d=13.6 (s,
1H; OH), 7.87 (d, 4J=2.1 Hz, 1H; CH-CI), 7.44 (d, 3J=8.1 Hz, 4H; H9
or H8), 7.35 (s, 1H; N=CH), 7.23 (m, 7H; H3, H4, H5, and H9 or H8),
6.78 ppm (d, 4J=2.1 Hz, 1H; CH-CI); 13C NMR (75.4 MHz, C6D6, RT):
d=167.5 (s, N=C), 160.1 (s, C-OH), 150.2 (s, CH-CI), 144.6 (s, C1), 142.8,
140.3 (s, CH-CI), 134.0 (s, C2, C6), 131.1, 130.2 (s, C8, C9), 126.7 (s, C4),
125.8 (m, C10), 120.0 (s, C12), 87.7 (s, C-I), 80.5 ppm (s, C-I); 19F NMR
(282.4 MHz, C6D6, RT): d=À62.6 ppm (CF3); MS (EI): m/z: 737 [M]+,
392.2 [MÀC6H3OI2]+; elemental analysis calcd (%) for C27H15F6I2NO
(737.2): C 43.99, H 2.05, N 1.90; found: C 43.98, H 1.80, N 1.73.
Ethylene polymerisation in scCO2: The reactions were performed in a
stainless steel high-pressure reactor (10 mL) equipped with glass win-
dows.In a typical experiment, the catalyst (4 mmol) was placed in the re-
actor under inert atmosphere, followed by pressurizing with ethylene to
about 40 bar.CO was condensed into the reactor from a central high-
2
pressure supply at 08C.The amount of ethylene and CO were deter-
2
mined by weighing the reactor before and after these steps.The reactor
was warmed to 508C and stirred (1000 rpm) at this temperature for 1 h.
After carefully venting, polyethylene was collected, weighed and subject-
ed directly to further analysis.
Data for 5d: Yield: 76%; 1H NMR (400 MHz, CDCl3, RT): d=13.2 (br,
OH), 8.05 (s, 1H; N=CH), 8.01 (br, 2H; CH), 7.89 (br, 1H; CH), 7.81
3
(br, 3H; CH), 7.62 (d, 3J=8.2 Hz, 4H; H8), 7.56 (d, J=8.2 Hz, 4H; H9),
7.57 (d, 4J=2.0 Hz, 1H; H15 or H17), 7.51 (m, 3H; H3, H4, H5), 7.05 ppm
(d, 4J=2.0 Hz, 1H; H15 or H17); 13C NMR (100.5 MHz, CDCl3, RT): d=
168.8 (s, C=N), 158.8 (s, C-OH), 144.5 (s, C1), 144.5, 143.2, 141.6, 140.7,
Acknowledgements
A.B. is grateful for a research stipend by the Alexander von Humboldt
Foundation.SM. .acknowledges financial support by the BMBF (project
03X5505).We thank Ralf Thomann (Freiburg) for TEM analyses, Georg
Mçrber (Freiburg) for technical assistance, Lars Bolk for GPC and DSC
analyses and Anke Friemel for high-temperature NMR measurements
(both Konstanz).Technical support by the staff at the high-pressure labo-
138.6, 134.1 (s, C2, C6), 132.9, 132.8, 132.3 (q, 1J
(C,F)=142 Hz, CF3),
A
131.1, 130.6, 130.2 (s, C8 or C9), 130.0, 129.8 (s, C9 or C8), 129.7 (br, CF),
128.3, 128.2, 127.7 (m, CF), 127.4 (m, CF), 127.1 (s, C4), 126.9, 124.9,
124.7, 122.2, 122.0, 121.6 (m, CF), 121.2 (m, CF), 119.3 (s, C12),
118.9 ppm; MS (EI): m/z: 1608.5 [M]+.
Chem. Eur. J. 2006, 12, 6110 – 6116
ꢀ 2006 Wiley-VCH Verlag GmbH & Co.KGaA, Weinheim
www.chemeurj.org
6115

S.Mecking, W.Leitner et al.
ratories (Markus Kaever) and the mechanical workshop (Ralf Thelen) at
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der Chemischen Industrie for support, and to the Hermann–Schnell
Foundation (S.M.). Clariant GmbH is acknowledged for a gift of per-
fluorinated surfactants.
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Received: April 7, 2006
Published online: June 28, 2006
6116
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Chem. Eur. J. 2006, 12, 6110 – 6116