2-Phosphanylphenolate Nickel Catalysts for the Polymerization of Ethylene

Article abstract of DOI:10.1002/chem.200304888

The previously unknown methallylnickel 2-diorganophosphanylphenolates (R=Ph, cHex) were synthesized and found to catalyze the polymerization of ethylene. To explore the potential for ligand-tuning, a variety of P-alkyl- and P-phenyl-2-phosphanylphenols wa

Full text of DOI:10.1002/chem.200304888

FULL PAPER
2-Phosphanylphenolate Nickel Catalysts for the Polymerization of Ethylene
Joachim Heinicke,*[a] Martin Kˆhler,[a, b] Normen Peulecke,[a] Mengzhen He,[a]
Markus K. Kindermann,[a] Wilhelm Keim,[b] and Gerhard Fink[c]
Abstract: The previously unknown
methallylnickel 2-diorganophosphanyl-
phenolates (R=Ph, cHex) were synthe-
sized and found to catalyze the poly-
merization of ethylene. To explore the
potential for ligand-tuning, a variety of
P-alkyl- and P-phenyl-2-phosphanyl-
phenols was synthesized and allowed
to react with [Ni(cod)2] (cod=1,5-cy-
clooctadiene) or with NiBr2¥DME and
NaH. The complexes formed in situ
with [Ni(cod)2] are generally active as
ethylene polymerization catalysts with
all the ligands tested, whereas the
latter systems are inactive when 2-dia-
lkylphosphanylphenols are applied. Mw
values, ranging from about 1000 to
about 100000 gmolꢀ1, increase for vari-
ous R2P groups in the order R=Ph<
EtꢁtBu<iPr<cHex, while aryloxy
substituents usually diminish the mo-
lecular weights. Increasing basicity of
P- or aryloxy substituents usually leads
to increasing turnover numbers. The
polymers are high density polyethylene
(HDPE) with low methyl and some-
times low long-chain branching. Inves-
tigation of the influence of the solvent
shows that the catalysts are stabilized
by some oxygen-containing Lewis
bases as well as by olefins. The cata-
lysts are tolerant to water, in particular
the 2-dicyclohexylphosphanylphenolate
nickel catalyst, which in THF water
(1:1) gives HDPE with Mw =39000,
Mn =14500 gmolꢀ1. Additives of tetra-
hydrothiophene or pyridine do not in-
hibit the catalyst, but decrease the re-
action rate and the molecular weight of
the polymers.
Keywords: chelates
¥
homo-
geneous catalysis
¥
nickel
¥
O,P ligands ¥ polymerization
Introduction
gler Natta and metallocene catalysts with the exception of a
recently reported encapsulation of the catalytic centers by
prepolymerization.[6] 2-Diphenylphosphanylenolate nickel
complexes [Ni(Ph2P\O)(R)(PR3)], which usually oligomer-
ize ethylene[1] are known to give polymers in nonpolar sol-
vents such as hexane[7,8] or in the presence of phosphane
scavengers.[8] Similarly, high molecular weight polyethylene
is formed with phenylnickel Ph2P\Oꢀ P-ylide catalysts in cy-
clohexane.[9] Recently it was found that bulky substituents at
the enolate group[10] or use of cationic phosphanylacetophe-
none P\O nickel catalysts[11] increase the activity as poly-
merization catalysts, and that sulfonated phenylnickel diphe-
nylphosphanylenolate phosphane catalysts allow the forma-
tion of low molecular weight polyethylene in water/toluene
(95:5).[12,13] In a preliminary study we found that catalysts
formed in situ from 2-(alkylphenylphosphanyl)phenols and
[Ni(cod)2][14] (cod=1,5-cyclooctadiene) give linear polyethy-
lenes with higher yields and molecular weights than 2-diphe-
nylphosphanylphenolate catalysts.[9a,15] Similar effects were
observed in the oligomerization of ethylene with various P-
substituted 2-phosphanylphenolate methylnickel phosphane
complexes[16] and might be attributed to the higher basicity
at phosphorus. Considering the superior catalytic properties
of the recently reported N-basic salicylaldimine nickel cata-
lysts,[4] related with phosphanylphenolate catalysts by a C=N
Late transition-metal chelate catalysts, initially applied in
the Shell higher olefin process (SHOP),[1] are presently ex-
periencing a renaissance through the use of modified phos-
phanylenolate, iminophenolate, bulky diimine, or tridentate
5]
diimine chelate ligands.[2 A particular advantage of some
of these catalysts is their tolerance of polar and functional
groups and even water, which poison the traditional Zie-
[a] Prof. Dr. J. Heinicke, Dr. M. Kˆhler, Dr. N. Peulecke, Dr. M. He,
Dr. M. K. Kindermann
Institut f¸r Chemie und Biochemie, Ernst-Moritz-Arndt-Universit‰t
Greifswald
Soldmannstrasse 16, 17487 Greifswald (Germany)
Fax : (+49)3834/86-4319
E-mail: heinicke@uni-greifswald.de
[b] Dr. M. Kˆhler, Prof. Dr. Dr. h.c. W. Keim
Institut f¸r Technische Chemie und Petrolchemie, Rheinisch-Westf‰li-
sche Technische Hochschule Aachen
Worringer Weg 1, 52056 Aachen (Germany)
[c] Prof. Dr. G. Fink
Max-Planck-Institut f¸r Kohleforschung
Kaiser-Wilhelm-Platz 1, 45470 M¸lheim an der Ruhr (Germany)
Supporting information for this article is available on the WWW
under http://www.chemeuj.org or from the author.
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Chem. Eur. J. 2003, 9, 6093 6107
DOI: 10.1002/chem.200304888
¹ 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

FULL PAPER
fragment instead of phosphorus, we synthesized a variety of
2-phosphanylphenols with different substituents at phospho-
rus and the phenol backbone and investigated the polymeri-
zation of ethylene under varied conditions, with single-com-
ponent and with in situ generated nickel 2-phosphanylphe-
nolate catalysts.[17] We present here the results obtained with
neutral P-tertiary phosphanylphenolate nickel catalysts in-
cluding the influence of polar additives or solvents.
Scheme 1. Synthesis of 2-phosphanylphenols 2 via MOM ethers 1. (The
substitution pattern is assigned by a four-letter code index, representing
the substituents at the phosphorus center followed by the substituents in
4- and in 6-position of the phenoxy group: H hydrogen, M methyl, E
ethyl, I isopropyl, B tert-butyl, C cyclohexyl, P phenyl, O methoxy, F
fluoro.).
Results and Discussion
Synthesis of new ligands: 2-Phosphanylphenols are accessi-
ble by various routes such as nickel-catalyzed arylation of
triarylphosphanes and subsequent cleavage of an aryl
group,[18,19] reaction of 2-lithio-lithiumphenolates with chloro-
phosphanes,[20] metalation of 2-bromophenylphosphinites
with sodium,[21] or orthometalation of phenylmethoxymethyl-
ethers and coupling with chlorophosphanes, followed by
acidic cleavage of the methoxymethyl (MOM) protecting
group. The latter procedure, introduced by Rauchfuss,[22]
was used to synthesize several novel representatives
(Scheme 1) with various substituents at phosphorus and the
phenol backbone. However, limitations of this widely appli-
cable procedure arose from insufficient selectivity of the or-
thometallation in 2- or 3-methoxy or in dimethoxyphenyl-
methoxymethyl ethers,[17a] from acid-mediated PꢀC bond
cleavage of PH derivatives during deprotection[17a] and from
steric hindrance of substitution by tBu2PCl.[17b] Prolonged
heating with the latter furnished exclusively (tBu2P)2 instead
of the substitution product which is available by coupling
with 2-lithioanisol and subsequent ether cleavage.[23]
The novel phosphanylphenols were characterized by ele-
mental analyses, and NMR data confirmed their structure.
The general properties of 2-phosphanylphenols have been
described recently.[20]
Synthesis of methallylnickel phosphanylphenolate com-
plexes: h3-Allyl- or h5-cyclopentadienylnickel diphenylphos-
phanylenolate P\O-chelate complexes are known to cata-
lyze the oligomerization of ethylene. The reaction starts at
40 or 1308C, when the unsaturated hydrocarbon ligand is
cleaved off.[1,24] h5-Cyclopentadienylnickel 2-phosphanylphe-
nolate P\O-chelate complexes, however, do not catalyze
this reaction up to 1408C. As shown by differential thermal
analysis (DTA), they are thermally more stable and lose cy-
clopentadiene only at 180 2008C.[14a] This prompted us to
study representatives of the hitherto unknown h3-allylic
nickel phosphanylphenolates. The methallyl complexes
3PPHH and 3CCHH were obtained from 2PPHH and 2CCHH, re-
spectively, by metallation with thallium ethanolate and sub-
sequent reaction of the sparingly soluble thallium salts with
methallyl nickel bromide in THF (Scheme 2).
Abstract in German: Die bislang unbekannten Methallyl-
nickel 2-diorganophosphanylphenolate (R=Ph, cHex)
wurden dargestellt und als Einkomponentenkatalysatoren der
Ethylenpolymerisation charakterisiert. Um Mˆglichkeiten des
Ligand Tuning zu erkunden wurden eine Reihe von P-Alkyl-
und P-Phenyl-2-phosphanylphenolen synthetisiert und mit
[Ni(1,5-cod)2] oder NiBr2¥DME und NaH umgesetzt. Die mit
[Ni(cod)2] in situ gebildeten Komplexe sind generell als Poly-
merisationskatalysatoren f¸r Ethylen aktiv w‰hrend die Sys-
teme mit NiBr2¥DME und NaH im Falle von 2-Dialkylphos-
phanylphenolen inaktiv sind. Die Mw-Werte reichen von ca.
1000 bis 100000 gmolꢀ1 und steigen bei unterschiedlichen
R2P-Resten in der Reihenfolge R=Ph < EtꢁtBu < iPr <
cHex w‰hrend Aroxy-Substituenten die Molekulargewichte
zumeist vermindern. Zunehmende Basizit‰t von P- oder
Aroxy-Substituenten f¸hrt im allgemeinen zu grˆ˚eren Um-
satzzahlen. Bei den Polymeren handelt es sich um HDPE mit
niedrigem Gehalt an Methyl- oder Langkettenverzweigungen.
Die Untersuchung des Lˆsungsmitteleinflusses zeigt eine Sta-
bilisierung der Katalysatoren durch einige sauerstoffhaltige
Lewis-Basen sowie durch Olefine. Die Katalysatoren sind ge-
gen¸ber Wasser tolerant, insbesondere der 2-Dicyclohexyl-
phosphanylphenolat Nickelkatalysator, der in THF-Wasser
(1:1) HDPE mit Mw =39000, Mn =14500 gmolꢀ1 liefert. Zu-
gaben von Tetrahydrothiophen oder Pyridin f¸hren nicht zur
Inhibierung des Katalysators, sondern bewirken Abnahme
der Reaktionsgeschwindigkeit und der Molekulargewichte der
Polymeren.
Scheme 2. Synthesis of h3-methylallynickel 2-phosphanylphenolates 3PPHH
and 3CCHH
.
The diphenylphosphanyl species 3PPHH starts to decom-
pose above 408C without a sharp decomposition tempera-
ture and is sensitive to air. The dicyclohexylphosphanyl
complex 3CCHH is more stable to thermal degradation and
air. It melts at 135 1388C, displays small mass loss in the
region 60 1408C, and decomposes rapidly only above
1608C. The NMR spectra are not altered after exposure of
solid 3CCHH to air. The structure of the complexes was eluci-
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Chem. Eur. J. 2003, 9, 6093 6107

Nickel Catalysts for the Polymerization of Ethylene
6093 6107
dated by 1H, 13C, and 31P NMR spectroscopy. Chemical
shifts and coupling constants are in accordance with P\O-
chelate and h3- methallyl coordination at nickel. The chelate
nature of 3PPHH and 3CCHH can be seen from the 13C coordi-
nation chemical shifts of C1 (Dd=22.8, 17.8) and the in-
creased PꢀC coupling constants of C2 (1J=50.6, 42.4 Hz) as
well as from the 31P coordination chemical shifts (Dd=58.2,
78.1) characteristic for 2-phosphanylphenolate nickel chelate
complexes.[14,16,17,25,26] The methallyl carbon nuclei Ca (da =
43.9 (s), 38.6 ppm (d, JP, C =6.0 Hz)) of the NiꢀC bond locat-
ed trans to the oxygen atom and the protons H-1’ and H-2’
at Ca (CH-COSY) display considerable upfield shifts in
comparison to the signals of Cc (dc =70.6 (d, JP, C =22.6 Hz),
71.2 ppm (d, JP,C =20.7 Hz)) located trans to the phosphorus
atom and H-3’ and H-4’ at this carbon atom. The assign-
ments are based on comparison with the analogous Pd com-
plexes,[17b] in particular upon the line broadening and coales-
cence of the upfield proton signals (H-1’ and H-2’) upon ad-
dition of acetic acid. The hydrogen bridging bond to oxygen
weakens the coordination at the palladium center (but not
the chelate ring) and influences mainly the bond in the trans
position. The downfield signals of H-3’ and H-4’ like the 31P
resonances remain rather unaffected. The greater upfield
shift of Ca as compared to Cc in the Ni complexes, which is
found closer to the C=C(Ni) resonance in [Ni(1,5-cod)2]
(d(13C)=90 ppm), indicates some s-character of the NiꢀCa
bond. The resonances to much higher field in related meth-
ylnickel phosphanylphenolates (i.e.d(13C1H3)=ꢀ19.9/ꢀ0.82)
in [Ni(Me)(2-Ph2P-4,6-tBu2C6H2O)(PMe3)]),[16] however,
provide evidence that the bonding mode corresponds rather
to a h3-allyl than a fictive bidentate h-alkyl-p-olefin com-
plex. The greater upfield chemical shift of 13Ca and the
greater 31P coordination chemical shift in 3CCHH as compared
to 3PPHH indicates an increase of the basicity at the oxygen
and phosphorus centers which in turn diminishes the accept-
or strength of the dicyclohexylphosphanyl versus the diphe-
nylphosphanyl group. This electronic and steric impact of
the phosphanyl substituents on the NiꢀP and the adjacent
NiꢀC bonds implies different properties of dialkyl- and di-
phenyl-substituted phosphanylphenolate nickel catalysts for
the ethylene polymerization which, as shown below, causes
considerable differences in the average molecular weights
and, to a low degree, differences in the branching of the re-
sulting polymers.
Comparison of various types of phosphanylphenolate nickel
catalysts for the polymerization of ethylene: Heating a solu-
tion of catalytic amounts of 3PPHH and ethylene in toluene in
an autoclave (batch mode, pstart ꢁ50 bar) to 1008C furnishes
linear low molecular weight polyethylene PE3PPHH. The
higher molecular weights as compared to the oligomers
formed with the related methallylnickel diphenylphospha-
nylcarboxylate or 2-diphenylphosphanylbenzoate catalysts[27]
show that the more O-basic phosphanylphenolate ligands di-
minish the chain transfer relative to the chain propagation
rate. The turnover numbers, however, are comparable under
equal conditions. Replacing 3PPHH by a solution of equimolar
amounts of 2PPHH and [Ni(cod)2] in toluene, mixed at 0 to
208C, affords almost the same results, equal conditions pro-
vided. The conversion of ethylene and the properties of the
polyethylene PEPPHH obtained with the in situ formed
brown precatalyst 4PPHH are very similar (Table 1) and sug-
gest nearly identical catalysts. A defined product allowing
unambiguous identification could not be isolated, but some
information on the nature of the complexes in this solution
is furnished by NMR data. The 31P NMR spectrum in
[D8]toluene reveals the disappearance of the signals for
2PPHH and the occurrence of two new signals, a strong reso-
nance at d=16.3 ppm and a weak one at d=29.2 ppm. The
former, close to d(31P)=13.1 of [Ni0(2-Ph2P-4,6-tBu2-
C6H2OH)(PMe3)3],[26] suggests formation of a Ni0 phospha-
nylphenol precursor complex, whereas the weak signal is
very close to that of 3PPHH (d=29.7 ppm) and is indicative of
a h3-allyl-type organonickel complex. This fits with the pres-
ence of 1,3-COD, formed quantitatively by isomerization of
the 1,5-COD ligand and unambiguously identified by its typ-
ical 1H and 13C chemical shifts. Furthermore, the proton
NMR spectrum displays two sets of broad signals for strong-
ly acidic hydroxy and for agostic protons, respectively, the
more intensive at d=12.55 and ꢀ2.09 ppm, the less intensive
at d=11.1 and ꢀ5.53 ppm. Typical upfield NiH resonances
like the one in [(Ph2PCH2C(CF3)2OꢀP,O)NiH(PCy3)] (d=
ꢀ24.1[28]) are absent, while broad signals for side-on-coordi-
nated olefinic groups are detected (d=3.1 and 3.6 ppm).
Based on the NMR spectra it is supposed that two forms of
a primary Ni0 complex I with acidic OH and with agostic
protons (the nature of the COD ligand remains unclear) are
formed rapidly and undergo slow formal oxidative addition
of the OH group to give an organonickel complex II, which
Table 1. Polymerization of ethylene with single component and various in situ generated 2-phosphanylphenolate nickel catalysts.[a]
[h]
[h]
Product
Yield PE [%]
TON
M.p.
[8C]
1
Mw
Mn
Mw/Mn 1H NMR:M a/internal[i] Me/C=C[i]
(conditions)[a]
(from C2H4 [g]) [molmolꢀ1
]
[gcmꢀ3
]
[gmolꢀ1
]
[gmolꢀ1
]
[gmolꢀ1
]
olefins [%] (Me/1000 C)
[i]
[b]
PE3PPHH
PEPPHH
53 (12.6)
50 66 (12.6)
83 (11.5)
72 (13.8)
91 (11.4)
64 (13.3)
51 (14.5)
1190
2250 2960
3400
3530
3710
3030
2640
320 740
2070
118 122[g] n. d.
n. d.
5510
3760
8900
5900
4370
2180
n.d.
n. d.
4430
1230
3050
2100
1800
1560
n.d.
n. d.
1.2
3.1
2.9
2.8
2.4
1.4
n.d.
2.5
n. d.
n. d.
93:7
93:7
96:4
98:2
81:19
92:8
96:4
90:10
n. d.
[b,c]
124 126
122 124
126 128
128 130
122 124
124 126
131 133
131 133
(0.96)
2000
1360
3370
2600
1860
1420
29400
35000
1.5 (11)
1.4 (14)
1.3 (5.3)
1.5 (8)
1.6 (13)
1.3 (13)
2.1 (1)
PEPPHH (808C)[c]
(0.96)
(0.95)
(0.95)
(0.96)
(0.96)
(0.95)
(0.94)
[d]
PE5PPHH
PE2PPHH
PE2PPOH
[e]
[e]
[e]
PE2BPHH
PE3CCHH (1008C)[c] 7 16 (13.0)
PE3CCHH (1208C)[f] 95 (6.1)
40300
16300
ꢁ3 (1.2)
[a] Catalyst subscript without number means formed in situ with [Ni(cod)2]; conditions: pstart =50 bar C2H4, catalyst in toluene (20 mL), 15 h, 1008C
unless indicated otherwise; n.d. not determined. [b] 0.2 mmol 3PPHH or 2/[Ni(cod)2]. [c] 0.1 mmol 2/[Ni(cod)2] or 3CCHH. [d] 0.1 mmol 2, 0.2 mmol
NiBr2¥DME, 0.3 mmol NaH. [e] 0.1 mmol 2, 0.3 mmol NiBr2¥DME, 0.3 mmol NaH. [f] pstart =30 bar C2H4, else like [c]. [g] Without extraction of oligom-
1
ers by CH2Cl2. [h] Mw and Mn by SEC. [i] Average molecular weight/olefin and Me/olefin ratio based on H NMR analysis.
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J. Heinicke et al.
FULL PAPER
less selectively than with the
analogous 2PPHH catalyst and
gives lower conversion, whereas
the catalyst 4PPOH obtained with
[Ni(cod)2] is highly active. Simi-
larly, polymerization of ethyl-
ene with the catalyst formed
from the more P-basic 2BPHH
and NiBr2¥DME/NaH (Table 1)
led to lower conversion and
molecular weights than with the
diphenylphosphanyl analogue,
whereas the opposite is ob-
served when [Ni(cod)2] was
used as nickel source (Table 2).
The divergent properties of the
two catalyst systems become
even more evident for the
strongly P-basic 2-dialkylphos-
phanylphenols. Mixtures of
2EEHH
, 2IIHH, or 2CCHH with
NiBr2¥DME and NaH in tolu-
ene are completely inactive.
Scheme 3. Proposed formation of 2-phosphanylphenolatonickel hydride catalysts.
The yellow solutions of 4EEHH
,
4
IIHH, and 4CCHH formed with
is similar to 3 and may eliminate 1,3-COD with formation
of the proposed NiꢀH polymerization catalyst III
(Scheme 3). The isomerization of COD is probably caused
by the intermediate phosphanylphenol nickel complexes.
Neutral 2-diphenylphosphanylphenolate complexes of the
type 3PPHH do not catalyze the isomerization of olefins.
To establish the role of NiH species, attempts were made
to generate nickel hydride complex catalysts directly. For
this purpose ethylene was heated under pressure with a stir-
red mixture of 2PPHH (0.1 mmol), excess NiBr2¥DME, and
sodium hydride (each 0.3 mmol) and, in a further experi-
Figure 1. Pressure time plots for batch polymerization of ethylene with
catalysts formed in situ from 2PPHH and [Ni(1,5-cod)2] (solid), 2PPHH and
NiBr2¥DME and NaH (dash), 2CCHH and [Ni(1,5-cod)2] (dot) (pstart 50 bar,
1008C each) and with 3CCHH (pstart 30 bar, 1208C, dash dot).
ment, with the nickel bis(P\O- chelate) complex 5PPHH
,
excess NiBr2¥DME, and sodium hydride (0.1, 0.2, and
0.3 mmol), each in toluene. In both procedures, linear a-
polyethylenes (PE2PPHH and PE5PPHH, respectively) were
formed efficiently (Table 1). It is assumed that an intermedi-
ate nickel phosphanylphenolate bromide is formed and acti-
vated by NaH. The slow polymerization rate as compared to
[Ni(cod)2] in toluene, however, proved to be highly active
polymerization catalysts and give much higher molecular
weights than 4PPHH (Table 2). Even the bulky 2BBHH, which
does not display a color change on combining with the
[Ni(cod)2] solution at 0 208C, forms an active catalyst
that with 4PPHH
, illustrated by the pressure time plot
(Figure 1), suggests that the concentration of the catalyst is
low, while the higher total conversion of ethylene accounts
for a continuous generation of the catalyst, for example at
the NaH surface. The higher weight-average molecular
weight of PE5PPHH as compared to that of PE4PPHH and the
higher polydispersity may be attributed to the higher initial
ratio of the ethylene to catalyst concentration and its final
decrease, respectively. The selectivity for linear a-olefins,
however, is preserved and supports a close similarity of the
catalytically active species.
4BBHH. It is assumed that nickel hydride complexes, if gener-
ated at all with NiBr2¥DME/NaH, are more rapidly deacti-
vated, whereas the olefins eliminated from the organonickel
precursors in 4 provide sufficiently stable resting states, for
example of the type II(4). Thus, the conversion of ethylene
and TON with 4CCHH are similar to those with the analogous
diphenylphosphanyl catalyst (Figure 1). The h3-methallyl
complex 3CCHH, as mentioned above, is more stable than
3PPHH and exhibits remarkable catalytic activity only above
1008C (Table 1). Even at 1208C the reaction rate is lower,
the conversion of ethylene, however, is nearly quantitative
(Figure 1). This may be due to a slower degradation of
3CCHH and formation of catalyst species over a longer period
but also gives evidence of sufficient stable resting states.
Considerable changes are observed if substituents are in-
troduced that increase the basicity of the phenolate oxygen
atom or the phosphanyl group. The polymerization of ethyl-
ene with 2PPOH-NiBr2¥DME/NaH proceeds much slower and
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Chem. Eur. J. 2003, 9, 6093 6107

Nickel Catalysts for the Polymerization of Ethylene
6093 6107
Table 2. Polymerization of ethylene with in situ prepared 2-dialkylphosphanylphenolate nickel catalysts 4 (without substitutents in 4- or 6-position).
[d]
[d]
Product
Yield PE [%]
(from C2H4 [g])
TON
M.p.
[8C]
1
Mw
Mn
Mw/Mn
1H NMR:M
a/internal[h]
olefins [%]
Me/C=C[h]
(Me/1000 C)
(conditions)[a]
[molmolꢀ1
]
[gcmꢀ3
]
[gmolꢀ1
31350
]
[gmolꢀ1
]
[gmolꢀ1
11000
]
[h]
[c]
PEEEHH
98 (5.6)
1960
129 131
133 136
134 136
132 134
133 135
128 130
129 131
128 130
135 137
134 136
0.96
9300
3.4
94:6
1.3 (1.7)
(708C, 30 bar)
[b]
PEEEHH
64 (12.8)
84 (12.3)
40 (12.7)
60 (13.5)
25 (12.8)
94 (12.6)
51 (12.0)
72 (15.3)
2923
3673
1818
2887
1140
4207
2176
3920
0.935
0.955
0.93
0.955
0.94
0.96
0.935
0.95
n.d.
n.d.
n.d.
2.7
2.9
12000
9930
>97:3
>97:3
>97:3
88:12
90:10
77:23
1.1 (1.2)
2.0 (2.8)
2.6 (2.0)
2.3 (4.9)
2.2 (2.0)
1.8 (6.0)
(ꢁ0.7)
PEEEHH
21800
38400
25800
30000
14000
97500
59000
7940
13100
6230
7300
2330
32100
26500
[b]
PEIIHH
19460
6490
[e]
PEIIHH
PEBBHH
4.2
4.1
6.0
[b]
[f]
[f]
15000
[g]
[g]
PEBBHH
PECCHH
4230
[b]
3.0
2.2
uncertain
uncertain
>97:3
87:13
PECCHH
1.4 2 (2 3)
[a] 0.1 mmol catalyst in toluene (20 mL), 15 h, 50 bar, 1008C, else given. [b] Like [a] but 808C. [c] Before extraction of soluble oligomers with CH2Cl2.
[d] Mw and Mn by SEC. [e] Bimodal, maximum 2.5î104, sh 6î103. [f] Bimodal, maximum 2î104, sh 6î103. [g] Bimodal, maximum 1.2î104, sh
1
600 gmolꢀ1. [h] Results from H NMR analysis.
Ligand screening and investigation of substituent and sol-
vent effects with catalysts of type 4: The easy preparation of
the polymerization catalysts
4 from 2 and [Ni(cod)2]
prompted us to screen several ligand types and to study the
effects of reaction conditions, substituents, solvents, and ad-
ditives on polymerization and some properties of the poly-
mers.
Ligand screening: In the screening tests all tertiary 2-phos-
phanylphenols 2, 2-phosphanyl-1-naphthols, and even the
secondary and some primary 2-phosphanylphenols were
found to react with [Ni(cod)2] to give catalysts for the poly-
merization of ethylene. O-Trimethylsilyl ethers of 2 behave
similarly except that their reactivity is lowered by steric hin-
drance and low basicity of phosphorus as in the trimethylsil-
yl ether of 2PPBB. The MOM ethers 1, so far tested, have all
been unable to form catalysts with [Ni(cod)2]. This indicates
that hydroxy or similar functional groups are required that
allow the generation of a phosphanylphenolate ligand under
neutral or slightly basic conditions. 2-Hydroxy-2’-diphenyl-
phosphanyl-1,1’-diphenyl and -dinaphthyl were also found to
be inactive. Since the electronic situation at the OH group
and the phosphorus atom is similar to that in 2PPHH, the fail-
ure in this case hints at the necessity of a sufficiently stable
P\O chelate backbone which seems not to be the case for
more flexible seven-membered P\O chelates. Finally it
should be mentioned that also 2-phosphanylanilines did not
form polymerization catalysts with [Ni(cod)2].
Figure 2. Temperature dependence of the TON for the polymerization of
ethylene with 4PPHH in toluene, a) pstart =30 bar, C2H4 150 200 mmol,
4PPHH 0.24 mmol (dash), b)
pstart =50 bar, C2H4 460 480 mmol, 4PPHH
0.1 mmol (solid).
of the catalyst and decreasing TON at high temperature
which at low ethylene loading is overcompensated by an ex-
cessive amount of the precatalyst. Furthermore Figure 2
shows that for a given temperature the TON increases with
the ethylene-to-catalyst ratio and pressure, suggesting that
the stability of the catalyst increases with the ethylene con-
centration and should allow much higher TON in flow sys-
tems with constant high pressure of ethylene. Figure 3 illus-
trates the growing rates of the polymerization with increas-
ing temperature and the rapid catalyst deactivation at high
temperature.
Influence and selection of reaction conditions: The catalyst
system 4PPHH formed in situ from 2PPHH and [Ni(cod)2] in tol-
uene was chosen as a reference to determine suitable reac-
tion conditions for comparison with related catalysts. Initial-
ly the temperature, pressure, and ethylene-to-catalyst ratio
were varied. The conversion of ethylene was found to be
slow at 408C and to increase strongly on raising the temper-
ature to 708C. The effect of higher temperatures up to
1208C depends on the ethylene-to-catalyst ratio (TONlim). A
small molar ratio of roughly 600 800 causes a further in-
crease, a higher ratio (4600 4800) a decrease of the conver-
sion (Figure 2). This indicates growing thermal deactivation
Figure 3. Pressure time plots for batch polymerization of ethylene with
4PPHH at bath temperatures of 408C (solid), 708C (dash), 808C (dot),
1008C (dash dot), 1208C (dash dot dot); yields of isolated HDPE 7, 84,
83, 63, 35%.
6097
Chem. Eur. J. 2003, 9, 6093 6107
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¹ 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

J. Heinicke et al.
FULL PAPER
Catalysts prepared from 2-alkylphenylphosphanyl- and
2-dialkylphosphanylphenols and [Ni(cod)2] in toluene usual-
ly become active around 708C and cause a slightly slower
reaction rate. The maximum pressure decrease within
10 min was ꢀ26 and ꢀ18.5 bar for catalysis with 4PPHH and
4CCHH (each 12 g C2H4, 0.1 mmol 4 in 20 mL toluene), re-
spectively, corresponding activities of roughly 360 and
270 g(PE) mmolꢀ1 hꢀ1. In the case of moderate steric hin-
drance the 2-dialkylphosphanylphenolate catalysts display a
stronger increase of the TON and ethylene conversion on
raising the temperature from 80 to 1008C. Steric congestion
b y twotert-butyl groups at the phosphorus center demands
higher temperature for the catalyst formation so that 4BBHH
needs 1208C for high activity (Table 2). In contrast to the
effect at phosphorus, tert-butyl groups in ortho and para po-
sition to the oxygen atom lower the formation temperature.
In the case of 4BPBB the exothermic reaction begins during
the addition of ethylene at room temperature. Similarly,
4IIBB induces a rapid start but then reacts much slower. The
pressure time plot with this catalyst (Figure 4) displays an
atypical ™starting needle∫ which was observed also for other
4,6-di-tert-butyl-substituted catalysts and suggests a different
initial mechanism, for example by formation of di-tert-butyl-
phenoxy radicals, but then returns to the usual reaction
mode. p-Methoxy groups, which like 4,6-tert-butyl groups in-
crease the basicity at the oxygen center, also cause slow re-
actions and high conversions. To compare phosphanylpheno-
late nickel catalysts with different substituents, most experi-
ments were run at 1008C and at an ethylene pressure of
about 50 bar (pstart) using toluene as solvent.
Effects on catalyst stability: The pressure time plot for the
ethylene polymerization with 4PPHH in toluene at 1008C re-
veals the maximum pressure roughly after the time necessa-
ry to heat up the reaction mixture to ꢁ708C (inside). Then,
the reaction proceeds with rapid consumption of ethylene.
4CCHH behaves similarly with a slightly slower reaction rate
(Figure 1). Addition of 4CCHH to a solution of ethylene in tol-
uene (50 bar) preheated to 808C led to immediate polymeri-
zation, but strongly reduced the lifetime of the catalyst and
gave low TON. The effect is even stronger with the solution
formed from the secondary phosphanylphenol 2HIOH and
[Ni(cod)2]. In the usual batch procedure this catalyst[17a]
causes high productivity and molecular weights of HDPE
(Table 3), whereas the addition to a preheated solution of
ethylene in toluene leads to deposition of inactive black
nickel. These observations provide evidence that the use of
high temperature in the initial phase favors the production
of nickel at the expense of catalyst formation. Catalysts
formed by slower heating in the presence of ethylene are
more stable and display higher productivity. Since additives
of a-olefins and also internal olefins increase the catalyst
lifetime and conversion of ethylene considerably (see
below), this effect may be attributed to resting states in
which the catalyst is attached to the C=C bond of oligomers
or polymers. The deactivation is then slow and depends also
on the substitution pattern. Thus, using a larger amount of
Figure 4. Pressure time plots for the polymerization of ethylene with
4PPHH (solid), 4CCHH (dash dot), 4IIBB (dash) and 4PPOH (dot); bath temper-
ature 1008C.
4
EEHH, the inactive bis(chelate) 5EEHH, for comparison syn-
Table 3. Polymerization of ethylene with 2-phosphanylphenolate nickel catalysts 4, substituted in 4- or 4,6-position.
[f]
[f]
Product
Yield PE [%]
(from C2H4 [g])
TON
M.p.
[8C]
1
Mw
Mn
Mw/Mn
1H NMR:M
a/internal[j]
olefins [%]
Me/C=C[j]
(Me/1000 C)
(conditions)[a]
[molmolꢀ1
]
[gcmꢀ3
]
[gmolꢀ1
]
[gmolꢀ1
]
[gmolꢀ1
]
[j]
PEPPMH
PEPPOH
68 (13.0)
53 (13.6)
99 (13.2)
83 (10.0)
54 (11.8)
74 (11.9)
68 (14.2)
48 (8.7)
97 (15.2)
98 (14.9)
41 (12.4)
79 (15.9)
54 (11.5)
80 (17.6)
97 (15.2)
93 (9.0)
3140
2567
4670
2960
2285
3125
3430
700
5250
5200
1818
4493
2216
5030
5250
2994
4123
125 127
125 127
124 126
127 129
124 126
117 119
127 129
121 124
120 122
126 128
130 132
129 131
122 124
130 132
125 127
116 118
129 131
0.96
0.95
0.95
0.95
0.95
0.93
0.96
n.d.
0.95
0.945
0.95
0.96
0.95
0.95
0.955
0.955
0.97
n.d.
n.d.
n.d.
2.5
n. d.
2.5
n.d.
n.d.
n.d.
1.5
n.d.
2.0
1560
1850
2340
2840
2200
1200
3500
n.d.
1700
2240
5330
9000
n.d.
94:6
95:5
1.4 (12.2)
1.5 (11.4)
1.6 (9.7)
1.4 (6.8)
1.6 (12)
1.5 (20)
1.4 (5.8)
n.d.
1.6 (13)
1.6 (13.7)
1.6 (4.2)
1.4 (2.2)
n.d.
[b]
3600
n. d.
6600
n.d.
n.d.
n.d.
1400
n. d.
2700
n.d.
n.d.
n.d.
PEPPOH
PEPPFH
PEPPBB
89:10:1[k]
92:8
88:12
88:12
97:3
n.d.
94:6
87:13
93:7
92:8
n.d.
73:27
92:8
[c]
[e]
[e]
PEPPNA
PEMPMH
[d][15a]
PEIPMH
9300
n.d.
6100
n.d.
PEBPMH
PEBPBB
5700
17380
25690
23200
30200
6710
2800
2800
4000
4340
1810
3630
2200
1800
9.5î103
[b]
PEIIFH
4.3
5.9
[g]
PEIIFH
PEIIBB
[b]
[e]
[h]
12.8
8.3
3.1
PEIIBB
5300
1900
1300
n.d.
2.6 (6.9)
1.4 (10.4)
1.3 (14)
n.d.
PECCOH
PECCBB
1.6
93:7
n.d.
[b][17a]
PEHIOH
94 (12.3)
8.13î105
86 [i]
[a] Conditions: 0.1 mmol catalyst in toluene (20 mL), pstart =50 bar C2H4, 1008C, 15 h, else indicated. [b] as [a] but 808C. [c] PPNA means 1-diphenyl-
phosphanylnaphth-2-ol[20b]. [d] 0.22 mmol 4IPMH, C2H4 pstart =40 bar, T=1408C. [e] Without extraction of soluble oligomers with CH2Cl2. [f] Mw and Mn by
SEC. [g] Bimodal, maximum 1.2î104, sh 1000. [h] Bimodal, maxima 4î103 and 5î104. [i] Maxima 3î103 and 1.6î105 gmolꢀ1. [j] Results from 1H NMR
analysis. [k] CH2=CRR’ end groups.
6098
¹ 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Chem. Eur. J. 2003, 9, 6093 6107

Nickel Catalysts for the Polymerization of Ethylene
6093 6107
thesized independently,[17b] could be detected in the solution
(d(31P)=39.0 ppm). Catalysts with bulky substituents at the
phosphorus atom or in position 6, form less favored trans-
or distorted cis-bis(P\O-chelates),[17,26] the majority of
which display increased lifetimes and cause high conversion
of ethylene (e.g. 4BBHH 94%, 4BPBB 99%, 4CCBB 93%, 4IIBB
80% HDPE) with turnover numbers limited by the molar
ratio of C2H4 to 4 in the batch procedure. Thus, further addi-
tion of ethylene to the polymer catalyst (4PPOH) mixture at
1008C led to continued polymerization.
ferent and cause a strong increase of the weight average mo-
lecular weights. The high polydispersity and bimodal molec-
ular weight distribution in this case might be due to insuffi-
cient mixing.[17a]
Influence of solvents and additives: The above investigations
were all conducted in toluene. To explore the influence of
the medium other solvents and additives have been tested,
mainly with 4PPHH and 4CCHH as representatives of diphenyl-
and dialkylphosphanylphenolate precatalysts. It was found
that toluene, hexene, THF, DME, acetone, or DMF allow
the ethylene polymerization (Figure 5, Table 4), while chlor-
Influence of the substituents at phosphorus: Substituents at
P-phenyl groups have been considered only marginally. In-
troduction of one o-methoxy group on each phenyl ring
causes similar conversion (56%) and TON (2300) as 4PPHH
under analogous conditions but lower molecular weights
(Mw 2000, Mn 1120).[29] Replacement of the phenyl group by
alkyl substituents at the phosphanyl group of 4 usually leads
to increased TON and conversion of ethylene and in partic-
ular to higher molecular weights. The latter effect is strong
for dialkylphosphanyl catalysts if there are no interfering
substituents in the 4- or 6-positions (Table 2). The weight
average molecular weights of the polyethylenes obtained
with catalysts 4 of the type 2-R2PꢀC6H4Oꢀ increase roughly
in the order R=Ph<EtꢁtBu<iPr<cHex. This indicates a
superposition of two opposing effects, an increase of Mw
with growing basicity of the phosphanyl group but decrease
with increasing steric demand of the P-alkyl groups. The
polydispersity Mw/Mn rises in the order R=EtꢁcHex<
iPr<tBu and in case of PEIIHH and PEBBHH also with the
temperature. With the exception of the cHex2P catalyst this
corresponds to increasing Tolman angles (Et2PPh, iPr2PPh,
cHex2PPh, tBu2PPh #=136, 155, 162, 1708[30]). The drop of
the molecular weights with increasing polymerization tem-
perature (80 versus 1008C) agrees with the usual behavior
of polymerization catalysts. The effect of one alkyl besides a
phenyl group at phosphorus is quite low but shows the same
trend as illustrated by the molecular weights observed for
PEMPMH, PEIPMH, and PEBPMH (Table 3) as compared to
Figure 5. Polymerization of ethylene with 4PPHH in various solvents (con-
ditions: C2H4 0.4 0.6 mol, pstart 50 bar, 4PPHH 0.1 mmol, 1008C).
obenzene leads to decomposition of [Ni(cod)2]. Nonpolar
solvents like n-hexane and strongly polar solvents like etha-
nol or ethyl acetate prevent a catalytic reaction by insuffi-
cient solubility or by favoring the formation of inactive
bis(P\O-chelate) nickel complexes,[14a] respectively. The
suitability of the solvents depends also on the formation of
sufficiently stable resting states to prevent deactivation,
while coordination and subsequent insertion of ethylene
into the NiꢀH or NiꢀC bond should not be seriously hin-
dered in any of the solvents. The pressure time plots for
ethylene polymerization with 4PPHH or 4PPMH (Figure 6) and
PEPPHH and PEPPMH
.
Influence of the substituents at the aryloxy group: The influ-
ence of a 4-methyl group in phosphanylphenolate nickel cat-
alysts on the conversion of ethylene and the molecular
weights of PE is low. tert-Butyl (+I effect), 4-methoxy and
4-flourine substituents (ꢀI, +M effects) cause usually in-
creased conversion of ethylene (temperature each 1008C).
The influence on the molecular weight distribution, howev-
er, is distinct and depends on the nature of the PR2 group.
4,6-Di-tert-butyl, 4-methoxy and 4-fluorine combined with a
2-diphenylphosphanyl group cause slightly increased molec-
ular weights of PEPPFH, PEPPOH and PEPPBB as compared to
PEPPHH (each prepared at 1008C) while the combination
with a 2-diisopropyl or dicyclohexylphosphanyl group leads
to considerably lower molecular weights (PEIIFH and PEIIBB
versus PEIIHH, each prepared at 808C). The effect is most
pronounced for PECCBB and PECCOH versus PECCHH (1008C,
Table 2 and Table 3). Interestingly, 4-methoxy groups in sec-
ondary phosphanylphenolate ligands behave completely dif-
Figure 6. Pressure time plots for batch polymerization of ethylene with
4PPHH in toluene (solid), THF (dash), DME (dash dot), hexene-1 (dash
dot dot) and with 4PPMH in DMF (dot); bath temperature 1008C.
4CCHH (Figure 7) in various solvents give an impression of
the relative rates of ethylene consumption. They are lower
for O-donor solvents like DME, THF, acetone (similar as
6099
Chem. Eur. J. 2003, 9, 6093 6107
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¹ 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

J. Heinicke et al.
FULL PAPER
Table 4. Polymerization of ethylene with 2PPHH or 2CCHH and [Ni(cod)2] in various solvents systems
Product
Ligand Solvents
[mL]
Yield PE [%]
TON
M.p.
[8C]
1
Mw/Mn
1H NMR:M a/internal[h] Me/C=C[h]
[f]
[h]
(conditions)[a]
(from C2H4 [g]) [molmolꢀ1
]
[gcmꢀ3
]
[gmolꢀ1
]
[gmolꢀ1
1600
]
olefins [%] (Me/1000 C)
95% HDPE
5% oil, wax
HDPE
HDPE
HDPE
2PPHH
DME (20)
96 (11.3)
3850
125 127
0.955
3400
1600
n.d.
n.d.
n.d.
3160
1630
8700
6400[g]
4940
2470
3840
1900
2260
1340
n.d.
91:9
1.4 (12)
2PPHH
2PPMH
2PPHH
2CCHH
acetone (20)
DMF (20)
THF (20)
THF (20)
87 (13.7)
94 (9.0)
66 (14.5)
57 (13.2)
4230
3020
3420
2680
125 127
123 125
122 124
120 122[e]
0.955
0.95
0.95
0.96
2140
2000
1700
2180
88:12
86:14
95:5
2.0 (13)
1.8 (12)
1.3 (11)
1.1 (7)
HDPE
95:5
[b]
[i]
copolymer
2PPHH
2PPHH
toluene (10)
hexene-1 (10)
toluene (20)
isoprene (2)
toluene (15)
ethyl oleate (5 g)
toluene (19)
H2O (1)
toluene (19)
H2O (1)
toluene (2)
H2O (18)
THF (19)
99 (15.9)
57 (10.0)
87 (12.7)
30 (13.1)
28 (13.7)
20 (7.4)
5700
2040
3960
1400
1360
540
112 114[e]
n.d.
0.94
n.d.
65:35[i]
3.3 (7)[i]
[i]
sticky PE
90:10[i]
1.4 (8)[i]
0.7 (4)[j]
ꢁ3
[k]
PE, contamin. 2PPHH
by oleate
PE
117 119
123 125
128 129
n.d.
n.d.
n.d.
1320
n.d.
n.d.
2PPHH
2CCHH
2CCHH
2CCHH
2CCHH
2PPHH
2PPHH
2PPHH
2PPHH
0.945
0.94
n.d.
96:4
1.5 (17)
PE
PE
n.d.
[c]
HDPE
HDPE
HDPE
HDPE
69 (6.1)
1500
1530
3490
3100
3670
3000
129 131
131 133
123 125
117 119[e]
0.955
0.96
0.96
0.95
34000
12600
39000
14500
n. d.
uncertain
uncertain
2000
>97:3
97:3
ꢁ1.6 (2.5)
ꢁ1.3 (1.9)
1.5 (11)
2.1 (23)
1.2
H2O (1)
THF (10)
H2O (10)
40 (10.7)
88 (11.2)
60 (14.5)
84 (12.3)
63 (13.4)
toluene (15)
nC5H11Br (5)
toluene (18)
CH3CN (2)
toluene (18)
pyridine (2)
toluene (18)
THT (2)[d]
73:27
97:3
n. d.
n.d.
1850
80% wax
20% oil
hard wax
wax 75 77[e] n.d.
110 112[e]
325
95:5
0.94
n. d.
780
97:3
1.2
[a] Conditions: 0.1 mmol catalyst, pstart =50 bar C2H4, 1008C, 15 h. [b] Co-hexene content about 3% of C atoms. [c] In the presence of C16H33SO3Na
(131 mg). [d] THT=tetrahydrothiophene. [e] Without extraction of soluble oligomers with CH2Cl2 [f] Mw and Mn by SEC. [g] Small maximum at 3.7î
1
105 gmolꢀ1. [h] Results from H NMR analysis, unless indicated otherwise measured at 1008C after swelling. [i] Measured at 808C without swelling, inte-
gral ratio towards CH2 not reliable. [j] Separate Me signal d=0.90. [k] E/Z-CH=CH signal superimposed by oleate contamination.
up and the NMR spectra of the polymer show formation of
copolymers and thus the solvent no longer acts as a mere ac-
cessory. Copolymerizations of ethylene with olefins in pres-
ence of 4PPHH and 4CCHH will be reported separately.[17c] Ad-
ditions of ethyl oleate, which does not react with but stabil-
izes 4PPHH, lead to increased conversion of ethylene with
slightly decreased molecular weights of the polymer. Addi-
tion of the conjugated diene isoprene lowers the yield and
gives a sticky polymer, whereas additions (2 mL each) of bu-
tadiene-1,3 and of conjugatedly unsaturated hard soft che-
late ligands such as ethyl methacrylate, ethyl vinylacetate,
Figure 7. Pressure time plots for batch polymerization of ethylene with
acrylonitrile or vinylpyridine deactivate the catalyst in tolu-
ene. Vinyltrimethoxysilane and vinylbromide also suppress
the polymerization of ethylene by 4PPHH. As shown by the
activity in presence of O- or N-donor solvents or auxiliaries
as well as in presence of bromopentane (5 mL) (Table 4),
the deactivation is not due to simple Lewis base properties
but to the neighborhood of the C=C bond and a Lewis base
center.
It should be emphasized that 2-phosphanylphenolate
nickel catalysts not only tolerate ethers or some carbonyl
compounds but like the related P\O-enolate SHOP-cata-
4CCHH in THF (dash) and in THF/water (19:1 mL, dot, and 10:10 mL,
dash dot) versus 4CCHH in toluene (solid); bath temperature 1008C.
THF) or DMF and for hexene-1 compared to toluene due to
stronger solvent catalysts interactions. In the case of O-
donor solvents this is accompanied by lower molecular
weights indicating that the olefin elimination step is effected
to a lesser extend by weak coordination of solvents in com-
petition with ethylene than the chain growth step. Hexene
causes higher molecular weights, but some hexene is taken
6100
¹ 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Chem. Eur. J. 2003, 9, 6093 6107

Nickel Catalysts for the Polymerization of Ethylene
6093 6107
1
lysts[12,13] also permit to work in presence of moisture or
even higher amounts of water. The effects depend on the
solvent. Additions of 5% water decrease the conversion of
ethylene in toluene to about 30%, with 4PPHH as well as with
4CCHH as precatalyst, whereas the same amount of water in
THF induces an increased conversion. The pressure time
plot of the latter shows that the reaction becomes faster
than in dry THF (Figure 7). Increase of the water content to
50% has no further effect on the rate and lowers the con-
version to 40% but the molecular weight of the polymer is
higher than in the presence of only 10% of water. Further
increase of the water content leads to precipitation of the
ligand or catalyst and low activity. Attempts with the bipha-
sic system water/toluene (18:2 mL) using sodium 1-hexade-
canesulphonate (131 mg) as phase-transfer reagent gave
only slightly higher conversions (20%) than reaction in
water/THF (19:1 mL).
Finally, it should be mentioned that phosphanylpheno-
late nickel catalysts tolerate acetonitrile and even amine or
thioether additives. The effect of acetonitrile (2 mL) is rela-
tively low while tetrahydrothiophene (2 mL, 226 molar
excess relative to 4PPHH) and pyridine (2 mL, 246 molar
excess), which are softer and known to strongly coordinate
to nickel(ii), cause a significant drop of the reaction rate
(Figure 8) and molecular weights but stabilize the catalysts
and increase the conversion of ethylene. The presence of
tetrahydrothiophene leads to linear low-molecular weight
polyethylene (hard wax a-olefins), that of pyridine to liquid
olefin and per 1000 carbon atoms based on H NMR inte-
gration are given in Table 1 Table 2 Table 3 Table 4. To get
reliable data, the measurements were conducted in C6D5Br
at 1008C after swelling at 1208C for one day. Under these
conditions the average molecular weights calculated per
olefin agree sufficiently with the Mn values determined by
GPC except for high molecular weight polymers (Mn >
20000 gmolꢀ1). The highest contents of internal olefins are
observed for polyethylenes obtained with branched 2-di-
alkylphosphanylphenolate nickel catalysts at 1008C (PEBBHH
23%, PECCHH 13%, PEIIHH 12%) or with catalysts combin-
ing 4-methoxy or 4,6-di-tert-butyl with diphenyl- or diisopro-
pylphosphanyl groups (up to 27%). The characteristic dou-
blets for the E/Z methyl groups adjacent to the double bond
in b-olefins (d=1.56, 1.58) are usually superimposed by sat-
ellites of the intensive CH2 signals allowing no closer separa-
tion of b- and internal olefins while both are easily distin-
guished from a-olefins (vinyl multiplets at d=5.77, 5.00,
4.96 ppm) by the different chemical shifts of the CH=CH
protons at d=5.40 ppm. The degree of branching is low,
ranging from 1.1 to 1.6 methyl groups per olefin in the poly-
ethylenes obtained with diphenyl- and about 1.8 to 2.6
methyl per olefin in the polymers formed with dialkylphos-
phanylphenolate nickel catalysts. The higher values are ob-
served with catalysts containing diisopropylphosphanyl, 4-
methoxy or 4,6-di-tert-butyl substituents (except for 4CCME or
4
CCBB) while 4-fluorine gives rise to less branching. The cata-
lyst type seems to have no significance, PEPPHH, PE2PPHH
,
and PE5PPHH as well as PEPPOH and PE2PPOH each display the
same degree of branching. Also additions of pyridine or tet-
rahydrothiophene to 4PPHH did not effect the branching de-
spite its strong influence on the rate and molecular weights.
13C NMR spectra of selected polymers, measured under sim-
ilar conditions as the proton spectra but in the presence of
chromium acetylacetonate, give evidence that the excess
methyl groups derive from methyl and long-chain branching.
Based on the relative intensities of the aB1 to aBn and bB1
to bBn signals (assignment as described in[32]), the ratio in
most cases is about 2:1 to 3:1 (PEPPHH, PEPPMH, PEIIBB
;
PECCHH, PE5PPHH, PE2PPOH) or higher (PEBBHH, PEIIFH). Pre-
ferred long-chain branching was observed only for PE2PPOH
(ca. 1:2).
Figure 8. Pressure time plots for batch polymerization of ethylene with
4PPHH in toluene (18 mL) in the presence of an additive (2 mL): acetoni-
trile (dash), pyridine (dot), tetrahydrothiophene (dash dot); 4PPHH in tolu-
ene (solid) as reference; bath temperature 1008C.
Discussion: Based on the experiments with different types
of phosphanylphenolate catalysts, the structural require-
ments observed in the screening tests, and the effects of sub-
stituents and solvents, a mechanism is proposed for the poly-
merization of ethylene by the title catalysts (Scheme 4).
Nickel hydride complexes formed from organonickel
complexes by olefin elimination or by reaction with sodium
hydride initiate the polymerization by coordination and in-
sertion of ethylene. The polymerization is maintained by
continuous insertion of ethylene into the C(alkyl)ꢀNi bond.
Termination occurs through b-hydride elimination and re-
generation of the nickel hydride species. Chain transfer is
possible, but its relative rate is low and causes only minor
methyl and long-chain branching, slightly higher in the case
of dialkylphosphanyl- than diphenylphosphanylphenolate
catalysts.
and waxy oligomers with an increased content of b- and in-
ternal olefins. The effects resemble that of phosphane addi-
tives which, depending on the basicity and Tolman angle,
give hard or soft waxes, lower linear a-olefins or isoolefines
(C4-20), or suppress the conversion.[17b,31]
Polymer structure: Density, NMR and IR spectra as well as
X-ray powder diffraction measurements of representative
samples give evidence that the polyethylenes obtained with
2-phosphanylphenolate catalysts are mainly linear a-olefins
with a high degree of crystallinity. Smaller amounts of b-
and further internal olefins and low methyl and long-chain
branching were detected by NMR studies. The ratio of a to
internal olefins and the average content of methyl group per
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J. Heinicke et al.
FULL PAPER
tive to allow rapid coordination
of ethylene. The stronger the
coordination of the solvent or
an additive to nickel the slower
the polymerization (ethylene
consumption). Except in the
case of copolymerization with
a-olefins this leads to a de-
crease in molecular weights and
thus indicates that the termina-
tion by b-hydrogen transfer is
less strongly influenced by the
solvents than chain growth.
Scheme 4. Proposed mechanism of the polymerization of ethylene by phosphanylphenolate nickel catalysts.
The strong increase in molecular weight of the polyethy-
lenes by the use of dialkyl- instead of alkylphenyl- and di-
phenylphosphanylphenolate nickel catalysts is attributed to
Conclusion
the weaker trans influence of dialkylphosphanyl as com-
pared to alkylphenyl- and diphenylphosphanyl groups, that
is the weaker back donation indicated by the larger 31P coor-
dination chemical shift. The weaker back donation diminish-
es the positive charge at the nickel center as compared to
that in diphenylphosphanylphenolate catalysts and weakens
the bonding of ligands in trans position to the phosphorus
atom. This is illustrated by the lower coalescence tempera-
ture in the 31P NMR spectra of the kinetically unstable
square-planar diisopropyl- as compared to diphenylphospha-
nylphenolato-methylnickel(trimethylphosphane) complexes
(ꢀ70 versus ꢀ258C)[16] and suggests less efficient interaction
with hydrogen at the b-C atom of the growing polymer
chain. This impedes olefin elimination and results in higher
average molecular weights when dialkylphosphanylpheno-
late catalysts are used.
Ethylene is polymerized by a variety of 2-phosphanylpheno-
late nickel catalysts. The molecular weights can be tuned
from Mw <1000 up to 105 gmolꢀ1 by selection of suitable
substituents at the phosphorus atom or the aroxy group, or
by choice of solvent and additives. The catalyst lifetime and
TON can be increased by suitable reaction conditions, sub-
stituents, and solvents or additives stabilizing the catalyst.
As the turnover number in many examples with conversion
above 90% was limited by the ethylene-to-catalyst ratio,
flow reactors will allow much higher TON than reported
here. The low sensitivity of the 2-dialkylphosphanylpheno-
late nickel catalysts towards water allows the expectation
that water-soluble phosphanylphenolate nickel catalysts can
be found for polymerization of ethylene in an aqueous cata-
lyst solution or in biphasic systems.
The influence of 4,6-tert-butyl, 4-fluorine, and 4-methoxy
substituents is probably due to the enhanced electron densi-
ty at C1 and the increase of the basicity of the phenolate
oxygen atom. This may lead to a (kinetic) stabilization of
the NiꢀC bond and be the reason for the slower ethylene
consumption in 4PPMH and 4PPBB than in 4PPHH (Figure 4). Be-
cause of the large excess of ethylene and the rapid ligand
exchange in trans position to the phosphorus atom (ref.[16]
and below) the insertion of C2H4 into the NiꢀC bond, that is
the chain growth, is regarded as the rate-limiting step of eth-
ylene consumption (Scheme 4). A plausible explanation of
the different effects of 4-methoxy groups on dialkylphos-
phanyl- and secondary phosphanylphenolate catalysts is that
an increased steric demand of the P-substituents favors con-
formations of the polymer chain with the b-CH closer to the
trans position of the phosphanyl group. This facilitates b-hy-
dride elimination and thus leads to termination of the chain
growth reaction and to shorter polymers. It also accounts for
the steric effects observed for diisopropyl- and di-tert-butyl-
phosphanyl groups. The much smaller influence in diphenyl-
phosphanylphenolate catalysts may be attributed to the gen-
eral higher relative rates of b-hydride eliminations.
Experimental Section
General remarks: The reactions were carried out under carefully dried,
oxygen-free argon, using Schlenk techniques and freshly distilled dry sol-
vents. For work in aqueous mixtures, degassed water was used. PhO-
CH2OMe,[33] cHex2PCl,[34] tBuPhPCl,[35] tBu2PCl,[36] known 2-phosphanyl-
phenols,[18 and [Ni(cod)2][37] were synthesized as reported, other chemi-
21]
cals were purchased. Ethylene (99.5%, Air Liquide) was used without
further treatment. NMR spectra were recorded on a multinuclear FT-
NMR spectrometer ARX300 (Bruker) at 300.1 (1H), 75.5 (13C), and 121.5
(31P) MHz. Shift references are tetramethylsilane for 1H and 13C and
H3PO4 (85%) for 31P. Assignment numbers are given in Scheme 2.
Proton or carbon nuclei of phenyl or cyclohexyl groups are denoted i, o,
m, p and a, b, g, d, respectively. Coupling constants refer to JH,H in 1H
and JP, C in 13C NMR data unless stated otherwise. Assignments are sup-
ported by DEPT and in part by CH-COSY experiments. IR spectra were
measured on a FTIR-spectrometer System 2000 (Perkin Elmer), mass
spectra on a single-focussing mass spectrometer AMD40 (Intectra). Melt-
ing points were determined with a Sanyo Gallenkamp melting point ap-
paratus. TG/DTA were carried out with SETARAM TGDTA 92 16
(5 Kminꢀ1, 3 was heated under argon) and elemental analyses with a
CHNS-932 analyzer from LECO using standard conditions.
Aryl methoxymethyl ethers:
General procedure A: The corresponding phenols, the 4 5-fold molar
amount of dimethoxymethane (100 mL, 1.13 mol), and p-toluenesulfonic
acid (300 mg) were dissolved in dry dichloromethane (500 mL) and re-
fluxed for 8 12 h in a Soxhlett apparatus charged with freshly dried mo-
lecular sieves (4ä, 200 g) to bind the methanol formed. If the reaction
was incomplete (NMR control), the molecular sieves were replaced by a
The solvents influence the catalytic process by compet-
ing with ethylene for interactions with or coordination at
the catalyst. Suitable solvents provide resting states suffi-
ciently stable to prevent deactivation and sufficiently reac-
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Nickel Catalysts for the Polymerization of Ethylene
6093 6107
freshly dried charge and refluxing was continued. Then, the mixture was
cooled to 08C and, after addition of triethylamine (4 mL), was washed
twice with 1n aqueous sodium hydroxide solution (200 mL) and with
water. After drying over sodium sulfate and removal of the solvent, the
product was distilled. Product data are given in Table 5.
(10 mL) was added dropwise, and the suspension was stirred overnight at
room temperature. The precipitate was removed, the solvent was re-
placed by dichloromethane (10 mL), and methanol (100 mL) was added.
At 08C white crystals separated and were dried at 10ꢀ4 Torr, yield 7.1 g
1
(47%), m.p. 768C. H NMR (C6D6): d=2.94 (s, 3H; OCH3), 4.65 (s, 2H;
OCH2O), 6.70 6.78 (m, 2H; H-3, H-5), 6.84 6.91 (m, 1H; H-6), 7.00 7.05
General procedure B: The phenol (0.1 mol) was added to a suspension of
NaH (2.4 g, 0.1 mol) in toluene (500 mL) and heated for 2 h to 808C.
After the mixture had been cooled to 08C, a solution of chloromethyl-
methyl ether (7.6 mL, 0.1 mol) in toluene (10 mL) was added dropwise.
The suspension was refluxed for 2 h, cooled to 0 58C, and stirred for 1 h
with cold 1n NaOH (200 mL). Then the organic layer was separated,
washed with cold 1n NaOH, dried on sodium sulfate, and distilled in
vacuum. Product data are given in Table 5.
(m, 6H; ArH), 7.32 7.40 ppm (m, 4H; ArH); 13C NMR (C6D6): d=55.7
2
(OCH3), 94.7 (OCO), 115.3 (d, 3JF,C =8.5 Hz; C-6), 116.5 (d, JF,C
=
23.3 Hz; C-5), 120.4 (d, 2JF,C =23.4 Hz; C-3), 128.8 (d, 3J=7.1 Hz; C-m),
1
3
2
129.1 (C-p), 130.3 (dd, J=5.0, JF,C =17.6 Hz; C-2), 134.4 (d, J=21.1 Hz;
C-o), 136.8 (d, 1J=11.8 Hz; C-i), 155.4 (dd, 2J=15.3, 4JF,C =2.2 Hz; C-1),
158.5 ppm (d, JF,C =241.7 Hz; C-4); 31P{1H} NMR (C6D6): d=ꢀ14.6 ppm;
1
MS (EI, 2008C): m/z (%): 341 (2) [M+], 322 (35), 308 (21), 307 (100),
279 (48), 262 (43), 201 (31), 199 (65),
183 (86), 152 (33), 121 (31), 77 (12), 45
(32); elemental analysis calcd (%) for
C20H18FO2P (341.33): C 70.58, H 5.33;
found: C 70.76, H 5.20.
Table 5. Yields, boiling points, and 1H NMR data (CDCl3, d, J in Hz) of substituted aryl methoxymethyl
ethers.
substituents R
4-OMe
4-F
2,4-tBu2
2-OMe
3-OMe
2-(Diethylphosphanyl)phenyl methoxy-
methyl ether (1EEHH): A solution of
C6H5OCH2OCH3 (5.6 g, 40.5 mmol) in
diethyl ether (80 mL) was allowed to
react with nBuLi in hexane (26.3 mL,
1.6m, 42.1 mmol) and subsequently
with chlorodiethylphosphane (5.0 g,
40.2 mmol) in diethyl ether (10 mL)
under the conditions described for
method A
arOH g (mmol)
yield in g (%)
method B
yield in g (%)
b.p. in 8C/Torr
OCH3
OCH2O
R
Aryl
30.8 (248)
21.8 (52)
12.2 (109)
9.2 (54)
51.6 (250)
6.9 (11)
27.2 (219)
10.7 (29)
24.4 (197)
10.6 (32)
13.4 (80)
101/1
10.1 (65)
113/10
3.47 (s, 3H)
5.12 (s, 2H)
13.5 (54)
130/0.02
3.49 (s, 3H)
5.21 (s, 2H)
1.29/1.42 (2s, 18H)
7.03 (d, 1H-6)
7.16 (dd, 1H-5)
7.33 (d, 1H-3)
(JH,H =8.5, 2.5)
97/1
77 80/1
3.46 (s, 3H)
5.09 (s, 2H)
3.74 (s, 3H)
6.81 (d, 2H)
6.97 (d, 2H)
(JH,H =9.2)
3.52 (s, 3H)
5.23 (s, 2H)
3.88 (s, 3H)
6.87 (m, 1H)
6.91 (m, 1H)
6.99 (m, 1H)
7.16 (m, 1H)
3.48 (s, 3H)
5.16 (s, 2H)
3.79 (s, 3H)
6.56 (m, 1H)
6.61 (m, 1H)
6.64 m, 1H)
7.18 (m, 1H)
1
PPFH. After filtration and removal of
6.97 (ddd, 2H)[a]
6.98 (ddd, 2H)[b]
(3JF,H =7.4,
the solvent an oily yellow residue was
obtained which was distilled at 55
578C/2.4î10ꢀ4 Torr, to yield 1EEHH as
a colorless oil (7.3 g; 80%). 1H NMR
(C6D6): d=1.02 (dt, 3JP, H =14.2, 3J=
7.6 Hz, 6H; CH3), 1.70, 1.72 (m, 2Jꢁ
15, 3J(A) =7.5, 3J(B) =7.7, 2JP, H (A) =2.0,
2JP,H(B) =1.6 Hz, 2H; PCHAHB), 3.18 (s,
3H; OCH3), 4.89 (s, 2H; OCH2O),
4JF,H =5.3,
J
HH =9.3, 0.6)
[a] H-3, H-5. [b] H-2, H-6 (A2B2X type).
3
4
6.90 (m, J=7.6, 7, J=1.7 Hz, 1H; H-
4), 7.06 (m, 3J=8.3, 4JP, H =3.1, 4J=
1.7 Hz, 1H; H-6), 7.11 (m, 3J=8.2, 7,
4J=1.5 Hz, 1H; H-5), 7.30 ppm (m, 3J=7.6, 3JP, H =4.7, 4J=1.5 Hz, 1H;
H-3); 13C NMR (CDCl3): d=9.6 (d, 2J=12.9 Hz; CH3), 17.4 (d, 1J=
11.6 Hz; CH2), 56.0 (OCH3), 94.3 (OCO), 113.5 (d, 3J=1.6 Hz; C-6),
121.7 (d, 3J=2.1 Hz; C-4), 126.9 (d, 1J=18.8 Hz; C-2), 129.4 (C-5), 131.4
(d, 2J=5.4 Hz; C-3), 159.2 ppm (d, 2J=12.1 Hz; C-1); 31P{1H} NMR:
d(C6D6)=ꢀ23.5 ppm; d(CDCl3)=ꢀ24.5 ppm; MS (EI, 1508C): m/z (%):
226 (42) [M+], 211 (100), 183 (93), 138 (90), 125(46), 121 (22), 110 (42),
109 (53),107 (36), 91 (35), 77 (40), 61 (32), 47 (69), 45 (99); elemental
analysis calcd (%) for C12H19O2P (226.26): C 63.70, H 8.46; found: C
63.90, H 8.60.
2-Phosphanylphenyl methoxymethyl ethers:
2-(Diphenylphosphanyl)-4-methoxyphenyl methoxymethyl ether (1PPOH):
A solution of nBuLi (39.0 mL, 1.6m in hexane, 62.4 mmol) and TMEDA
(7.0 g, 60.2 mmol) in diethyl ether (30 ml) was added dropwise at 08C to
a solution of 4-CH3OC6H4OCH2OCH3 (10.0 g, 59.5 mmol) in the same
solvent and stirred overnight. Subsequently, a solution of Ph2PCl (13.1 g,
59.4 mmol) in petroleum ether (15 mL) was added dropwise at 08C, stir-
ring was continued for 15 h at ambient temperature and the solvent re-
moved in vacuum. The orange residue was extracted with CH2Cl2
(20 mL), and the extract was washed with aqueous NaH2PO4 solution
(1m) followed by water. Drying with Na2SO4, addition of methanol
(80 mL), and storage at 08C for one day furnished white crystals which
2-(Diisopropylphosphanyl)phenyl methoxymethyl ether (1IIHH): By using
the procedure reported for 1EEHH, a solution of C6H5OCH2OCH3 (6.4 g,
46.3 mmol) in diethyl ether (80 mL) was allowed to react with nBuLi in
hexane (29 mL, 1.6m, 46.4 mmol) and with chlorodiisopropylphosphane
(7.0 g, 45.9 mmol) in diethyl ether (10 mL) to give 1IIHH as a colorless
liquid (5.1 g; 44%), b.p. 62 638C/4î10ꢀ4 Torr. 1H NMR (C6D6): d=0.97
(dd, 3JP, H =11.5, 3J=6.9 Hz, 6H; CH3), 1.17 (dd, 3JP, H =14.8, 3J=7.0 Hz,
6H; CH3), 2.20 (sept d, 3Jꢁ7.0, 2JP, H =1.8 Hz, 2H; PCH), 3.20 (s, 3H;
OCH3), 4.90 (s, 2H; OCH2O), 6.88 (m, 1H; H-4), 7.09 7.15 (m, 2H; H-5,
were dried at 10ꢀ4 Torr to yield 1PPOH (12.8 g; 61%), m.p. 868C. H NMR
1
(C6D6): d=3.04 (s, 3H; OCH3), 3.18 (s, 3H; 4-OCH3), 4.78 (s, 2H;
OCH2O), 6.60 (dd, 4J=3.1, 3JP,H =4.5 Hz, 1H; H-3), 6.71 (ddd, 3J=8.9,
4J=3.1, 5JP, H =0.7 Hz, 1H; H-5), 7.01 7.07 (m, 6H; ArH), 7.10 (dd, 3J=
8.9, 4JP, H =4.8 Hz, 1H; H-6), 7.40 7.50 ppm (m, 4H; ArH); 13C NMR
(C6D6): d=55.6 (OCH3), 56.3 (OCH3), 95.7 (OCO), 115.7 (C-5), 116.2 (d,
3J=1.8 Hz; C-6), 120.3 (C-3), 129.4 (d, 3J=7.0 Hz; C-m), 129.5 (C-p),
129.6 (d, 1J=16.4 Hz; C-2), 135.1 (d, 2J=21.0 Hz; C-o), 138.3 (d, 1J=
H-6), 7.42 (m, 3Jꢁ7.4, JP, H ꢁ5.8, 4Jꢁ1.1 1.3, 5Jꢁ0.7 Hz, 1H; H-3); 13C
3
11.7 Hz; C-i), 154.4 (d, J=15.0 Hz; C-1), 156.0 ppm (C-4); 31P{1H} NMR
2
NMR (C6D6): d=20.6 (d, 2J=10.7 Hz; CH3), 21.4 (d, 2J=20.6 Hz; CH3),
24.2 (d, 1J=14.1 Hz; PCH), 56.6 (OCH3), 95.5 (OCH2O), 115.4 (d, 3J=
(C6D6): d=ꢀ14.1 ppm; MS (EI, 2008C): m/z (%): 352 (75) [M+], 338
(22), 337 (100), 321(11), 309 (72), 308 (17), 292 (27), 231 (30), 229 (25),
183 (61), 121 (44), 45 (85); elemental analysis calcd (%) for C21H21O3P
(352.37): C 71.58, H 6.01; found: C 71.18, H 6.24.
3
1
2.0 Hz; C-6), 122.4 (d, J=4.7 Hz; C-4), 125.9 (d, J=24.9 Hz, C-2), 131.1
(C-5), 136.3 (d, 2J=13.1 Hz, C-3), 161.9 ppm (d, 2J=10.0 Hz; C-1);
31P{1H} NMR (C6D6): d=2.7 ppm; MS (EI): m/z (%): 254 (19) [M+], 240
(14), 239 (100), 211 (37), 169 (14), 152 (40), 110 (28), 45 (52), 43 (21); ele-
mental analysis calcd (%) for C14H23O2P (254.31): C 66.12, H 9.12;
found: C 66.02, H 9.22.
2-(Diphenylphosphanyl)-4-fluorophenyl methoxymethyl ether (1PPFH): A
solution of nBuLi in hexane (29.4 mL, 1.6m, 47.0 mmol) was added drop-
wise with stirring to a solution of 4-FC6H4OCH2OCH3 (7.0 g, 44.8 mmol)
in diethyl ether (80 mL) at ꢀ508C and then allowed to warm to room
temperature. After 3 h the solution was cooled again to ꢀ508C, a solu-
tion of chlorodiphenylphosphane (9.9 g, 44.8 mmol) in diethyl ether
2-(Diisopropylphosphanyl)-4-fluorophenyl methoxymethyl ether (1IIFH):
By using the procedure reported for 1EEHH, a solution of 4-FC6H4O-
CH2OCH3 (7.0 g, 44.8 mmol) in diethyl ether (80 mL) was allowed to
6103
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J. Heinicke et al.
FULL PAPER
react with nBuLi in hexane (29.0 mL, 1.6m, 46.4 mmol) and iPr2PCl
(6.7 g, 43.9 mmol) in diethyl ether (10 mL) to give 1IIFH as a colorless oil
(10.3 g; 86%), b.p. 68 708C/4î10ꢀ4 Torr. 1H NMR (C6D6): d=0.89 (dd,
3JP, H =11.7, 3J=6.9 Hz, 6H; CH3), 1.08 (dd, 3JP, H =14.7, 3J=7.0 Hz, 6H;
2-(tert-Butylphenylphosphanyl)phenyl methoxymethyl ether (1BPHH): By
using the procedure reported for1PPFH, a solution of C6H5OCH2OCH3
(10.0 g, 72.4 mmol) in diethyl ether (100 mL) was reacted with nBuLi in
hexane (45.5 mL, 1.6m, 72.8 mmol) and tert-butylchlorophenylphosphane
(14.5 g, 72.3 mmol) in diethyl ether (10 mL) to give 1PPFH as white crystals
(9.8 g; 45%), m.p. 888C. 1H NMR (CDCl3): d=1.24 (d, 3JP, H =12.6 Hz,
9H; tBu), 3.18 (s, 3H; OCH3), 4.96 (d, 2J=6.9 Hz, 1H; OꢀCHAO), 5.07
(d, 2J=6.9 Hz, 1H; OꢀCHBO), 6.99 (™t∫d, 3Jꢁ7.5, 7.3, 4J=0.9 Hz, 1H;
H-4), 7.11 (ddd, 3J=8.0, 4JP, H =4.1, 4J=0.9 Hz, 1H; H-6), 7.22 7.32 (m,
4H; ArH), 7.43 7.53 ppm (m, 3H; ArH); 13C NMR (C6D6): d=29.7 (d,
2J=15.2 Hz; CMe3), 31.2 (d, 1J=16.9 Hz; CMe3), 56.4 (d, 6J=
0.9 Hz;OCH3), 95.2 (d, 4J=1.0 Hz; OCH2O), 115.5 (d, 3J=1.3 Hz; C-6),
3
2
CH3), 1.99 (sept d, J=7.0, JP,H =1.2 Hz, 2H; PCH), 3.17 (s, 3H; OCH3),
3
3
4
4.81 (s, 2H; OCH2O), 6.76 (ddd, J=9.0, JF,H =7.7, J=3.2 Hz, 1H; H-5),
6.92 (ddd, 3J=9.0, 4JF,H =4.6, 4JP,H =3.3 Hz, 1H; H-6), 7.18 ppm (ddd,
3JF,H =8.6, 3JP, H =4.0, 4JH =3.1 Hz, 1H; H-3); 13C NMR (CDCl3): d=19.2
(d, 2J=10.1 Hz; CH3), 20.0 (d, 2J=19.0 Hz; CH3), 22.9 (d, 1J=12.7 Hz;
CH), 56.0 (OCH3), 95.2 (OCO), 115.5 (d, 3JF,C =6.2, 3J=1.7 Hz; C-6),
116.2 (d, 2JF,C =23.1 Hz; C-5), 120.1 (dd, 2JF,C =21.8, 4J=6.5 Hz; C-3),
126.5 (dd, 3JF,C =25.3, 1Jꢁ4.4 Hz; C-2), 156.8 (dd, 2J=10.4, 4JF,C =2.2 Hz;
C-1), 157.3 ppm (dd, 1JF,C =241.8, 3J=2.3 Hz; C-4); 31P{1H} NMR (C6D6,
258C): d=0.5 ppm.
1
3
122.4 (C-4), 128.1 (d, J=24.3 Hz; C-2), 128.7 (d, J=6.4 Hz; C-m), 128.8
1
2
(C-p), 130.7 (C-5), 135.3 (d, J=2.6 Hz; C-3), 135.4 (d, J=20.0 Hz; C-o),
139.6 (d, 2J=20.0 Hz; C-i), 160.9 ppm (d, 2J=14.7 Hz; C1); 31P{1H}
NMR: d(C6D6)=5.0 ppm, d(CDCl3)=3.4 ppm; MS (EI, 1508C): m/z
(%):302 (40) [M+], 287 (100), 231 (40), 216 (22), 186 (22), 183 (27), 109
(31), 108 (33), 91 (59), 57 (69), 45 (93), 41 (36); elemental analysis calcd
(%) for C18H23O2P (302.35): C 71.51, H 7.67; found: C 70.95, H 7.94.
2-(Dicyclohexylphosphanyl)phenyl methoxymethyl ether (1CCHH): By
using the procedure reported for 1EEHH, a solution of C6H5OCH2OCH3
(15.0 g, 108.6 mmol) in diethyl ether (80 mL) was allowed to react with
nBuLi in hexane (68.0 mL, 1.6m, 108.8 mmol) and with chlorodicyclohex-
ylphosphane (25.2 g, 108.3 mmol) in diethyl ether (10 mL) to give 1CCHH
as a viscous colorless oil (21.0 g; 58%), b.p. 140 1508C/2î10ꢀ4 Torr. 1H
NMR (CDCl3): d=0.85 0.95 (m, 2H; Cy), 1.10 2.05 (m, 20H; Cy), 3.49
(s, 3H; OCH3), 5.21 (s, 2H; OCH2O), 6.98 (td, 3J=7.4, 4J=1.1 Hz, 1H;
H-4), 7.12 (ddd, 3J=8.3, 4JP, H =3.2, 4J=1.1 Hz, 1H; H-6), 7.28 (ddd, 3J=
8.3, 7.4, 4J=1.7 Hz, 1H; H-5), 7.38 ppm (ddd, 3J=7.4, 3JP, H =5.5, 4J=
1.7 Hz, 1H; H-3); 13C NMR (CDCl3): d=26.3 (C-d), 27.0 (d, 3J=8.1 Hz;
C-g), 27.2 (d, 3J=12.8 Hz; C-g’), 29.2 (d, 2J=8.2 Hz; C-b), 30.5 (d, 2J=
17.6 Hz; C-b’), 32.9 (d, 1J=12.1 Hz; C-a), 56.1 (OCH3), 94.5 (OCH2O),
114.0 (d, 3J=1.7 Hz; C-6 ), 121.2 (d, 3J=3.8 Hz; C-4), 123.5 (d, 1J=
2-Phosphanylphenols:
2-(Diphenylphosphanyl)-4-methoxyphenol (2PPOH): A suspension of 1PPOH
(5.0 g, 14.2 mmol) in methanol (100 mL) was saturated with gaseous HCl
at room temperature. After 15 h the mixture was refluxed for 1 h to com-
plete the cleavage. Then the volatiles were evaporated in vacuum, the
residue was dissolved in methanol (20 mL) and water was added until the
solution became turbid. The product was allowed to crystallize at 08C,
separated and dried at 10ꢀ4 Torr to give 2PPOH as white crystals (2.5 g;
57%), m.p. 868C. 1H NMR (CDCl3): d=3.61 (s, 3H; OCH3), 5.9 (s vbr,
1H; OH) 6.50 (dd, 3JP, H =7.5, 4J=3.0 Hz, 1H; H-3), 6.88 (dd, 3J=8.9,
4J=3.0 Hz, 1H; H-5), 7.03 (dd, 3J=8.9, 4JP, H =5.8 Hz, 1H; H-6), 7.40
7.72 ppm (m, 10H; ArH); 13C NMR (CDCl3): d=55.7 (OCH3), 116.9 (d,
3J=2.7 Hz; C-6), 118.2 (C5), 118.8 (d, 2J=5.5 Hz; C-3), 128.3 (d, 3J=
13.0 Hz; C-2), 128.9 (d, 1J=8.2 Hz; C- m), 130.0 (C-p), 132.0 (d, 1J=
10.5 Hz; C-i), 133.5 (d, 2J=17.6 Hz; C-o), 153.5 (d, 3J=4.7 Hz; C-4),
153.7 ppm (d, 2J=14.4 Hz; C-1); 31P{1H} NMR: d(CDCl3)=ꢀ21.0 ppm
(contaminated by hydrochloride); MS (EI, 1508C): m/z (%): 308 (100)
[M+], 293 (26), 230 (22), 229 (31), 215 (37), 212 (13), 199 (13), 187 (29),
183 (15), 159 (17), 133 (25); IR (nujol): n˜ =3293 v brcmꢀ1 (s); elemental
analysis calcd (%) for C19H17O2P (308.32): C 74.02, H 5.56; found: C
73.71, H 5.60.
2
2
20.8 Hz; C-2), 130.0 (C-5), 135.0 (d, J=10.5 Hz; C-3), 160.8 ppm (d, J=
10.7 Hz; C-1); 31P{1H} NMR (CDCl3): d=ꢀ8.4 ppm; MS (EI, 2008C): m/
z (%): 334 (14) [M+], 320 (22), 319 (100), 291 (8), 192 (11), 83 (25), 81
(13), 55 (39), 45 (25); elemental analysis calcd (%) for C20H31O2P
(334.44): C 71.83, H 9.34; found: C 71.77, H 9.42.
2-(Dicyclohexylphosphanyl)-4,6-di-tert-butylphenyl methoxymethyl ether
(1CCBB): By using the procedure reported for 1PPFH, a solution of 2,4-tBu2-
C6H3OCH2OCH3 (8.3 g, 33.1 mmol) in ether (80 mL) was allowed to
react with nBuLi in hexane (21.0 mL, 1.6m, 33.6 mmol) and with chloro-
dicyclohexylphosphane (7.7 g, 33.1 mmol) in diethyl ether (10 mL) to
give 1CCBB as white crystals (6.0 g; 41%), m.p. 968C. 1H NMR (C6D6):
d=1.34 (s, 9H; tBu), 1.61 (s, 9H; tBu), 1.00 1.45 (m, 10H; Cy), 1.50 1.80
5
(m, 8H; Cy), 1.90 2.08 (m, 4H; Cy), 3.61 (s, 3H; OCH3), 5.57 (d, JP, H
=
2-(Diphenylphosphanyl)-4-fluorophenol (2PPFH): A suspension of 1PPFH
(5.1 g, 15.0 mmol) was allowed to react with gaseous HCl in methanol
(100 mL) and worked up as reported for 2PPOH to yield 2PPFH as white
crystals (2.9 g; 65%), m.p. 928C. 1H NMR (C6D6): d=6.1 (s br, 1H;
3
4
2.1 Hz, 2H; OCH2O), 7.46 (™t∫, JP, H ꢁ J=2.5 Hz, 1H; H-3), 7.56 ppm (d,
4J=2.5 Hz, 1H; H-5); 13C NMR (C6D6, CH-COSY): d=27.5 (C-d), 28.2
3
3
2
(d, J=7.0 Hz; C-g), 28.3 (d, J=12.2 Hz; C-g’), 30.2 (d, J=8.1 Hz; C-b),
31.6 (d, 2J=18.2 Hz; C-b’), 31.7 (CMe3), 32.4 (CMe3), 35.1 (d, 1J=
15.4 Hz; C-a), 35.4 (CMe3), 36.4 (d, 4J=1.0 Hz; CMe3), 58.0 (d, 6J=
1.5 Hz; OCH3), 101.2 (d, 4J=23.5 Hz; OCH2O), 126.1 (C-5), 129.5 (d,
1J=23.2 Hz; C-2), 129.5 (d, 2J=2.9 Hz; C-3), 143.5 (d, 3J=3.5 Hz; C-6),
145.7 (C-4), 159.9 ppm (d, 2JP, C =20.3 Hz; C-1); 31P{1H} NMR(C6D6): d=
ꢀ10.4 ppm; MS (EI, 1508C): m/z (%): 446 (7) [M+], 432 (35), 431 (100),
404 (8), 304 (16), 57 (36), 55 (18), 41 (23); elemental analysis calcd (%)
for C28H47O2P (446.65): C 75.29, H 10.61; found: C 75.22, H 11.07.
3
4
3
OH), 6.51 (ddd, J=8.9, JP, H, F, H =5.1, 4.6 Hz, 1H; H-6), 6.66 (dd, J=8.9,
3JF,H =7.9, 4J=3.1 Hz, 1H; H-5), 6.83 (ddd, 3JF,H =8.2, 3JP, H =4.4, 4J=
3.1 Hz, 1H; H-3), 6.93 7.03 (m, 6H; ArH), 7.21 7.30 ppm (m, 4H;
ArH); 13C NMR (C6D6): d=116.9 (dd, 3JF,C =8.7, 3J=1.7 Hz; C-6), 118.1
2
2
4
(d, JF,C =23.5 Hz; C-5), 120.1 (dd, JF,C =22.9, J=3.4 Hz; C-3), 124.3 (dd,
1J=11.3, 3JF,C =4.8 Hz; C-2), 129.0 (d, 3J=7.3 Hz; C-m), 129.3 (C-p),
133.9 (d, 2J=19.4 Hz; C-o), 135.4 (d, 1J=7.5 Hz; C-i), 155.7 (d, 2J=
16.1 Hz; C-1), 157.6 ppm (d, 1JF,C =239 Hz; C-4); 31P{1H} NMR (C6D6):
d=ꢀ24.8 ppm; MS (EI, 1508C): m/z (%): 296 (100) [M+], 295 (44), 218
(23), 217 (87), 183 (16), 32 (30), 31 (45); IR (nujol): n˜ =3165 cmꢀ1 (s br);
elemental analysis calcd (%) for C18H14FOP (296.28): C 72.97, H 4.76;
found: C 73.09, H 5.07.
2-(Dicyclohexylphosphanyl)-4-methoxyphenyl
methoxymethyl
ether
(1CCOH): By using the procedure reported for 1EEHH, a solution of 4-MeO-
C6H4OCH2OCH3 (7.2 g, 42.8 mmol) in diethyl ether (80 mL) was allowed
to react with nBuLi in hexane (27.0 mL, 1.6m, 43.2 mmol) and with chloro-
dicyclohexylphosphane (10.0 g, 43.0 mmol) in diethyl ether (10 mL) to
give 1CCOH as viscous colorless oil (5.1 g; 33%), b.p. 165 1708C/4î
10ꢀ4 Torr. 1H NMR (C6D6): d=1.00 1.47 (m, 10H; Cy), 1.52 1.80 (m,
8H; Cy), 1.95 2.20 (m, 4H; Cy), 3.30, 3.36 (2s, 6H; OCH3), 4.96 (s, 2H;
OCH2O), 6.69 (dd, 3J=8.9, 4J=3.1 Hz, 1H; 5-H), 7.10 (dd, 3J=8.9,
4JP, H =3.0 Hz, 1H; 6-H), 7.29 ppm (dd, 3JP,H =6.3, 4J=3.1 Hz, 1H; 3-H);
13C NMR (C6D6, CH-COSY): d=27.5 (C-d), 28.2 (d, 3J=7.3 Hz; C-g),
2-(Diethylphosphanyl)phenol (2EEHH):
A mixture of 1EEHH (5.0 g,
22.1 mmol) and methanol (100 mL) was saturated with gaseous HCl, stir-
red for 15 h and refluxed for 1 h. Water (10 mL) was added followed by
small portions of saturated aqueous sodium carbonate until the pH was
5 6. The product was extracted with diethyl ether, the solution was dried
with anhydrous sodium sulfate, and the solvent was removed at 10ꢀ4 Torr
to give 2EEHH as an oil (2.8 g; 70%) which becomes solid at 48C, m.p. 31
358C. (The compound is easily oxidized by air yielding the phosphane
oxide, d(31P)=59.8 ppm.) 1H NMR (C6D6): d=0.83 (dt, 3JP, H =16.7, 3J=
7.6 Hz, 6H; CH3), 1.40 (m, 4H; CH2), 6.80 (td, J=7.3, 1.5 Hz, 1H; H-6
3
2
2
28.2 (d, J=12.5 Hz; C-g’), 30.8 (d, J=9.3 Hz; C-b), 32.0 (d, J=18.7 Hz;
C-˚’), 34.6 (d, 1J=14.3 Hz; C-a), 55.8, 56.6 (2 OCH3), 96.5 (OCH2O),
3
2
115.3 (C-5), 117.1 (d, J=1.6 Hz; C-6 ), 122.5 (d, J=16.4 Hz; C-3), 127.4
(d, 1J=25.7 Hz; C-2), 155.4 (d, 3J=5.8 Hz; C-4), 156.2 ppm (d, 2J=
9.9 Hz; C-1); 31P{1H} NMR: d(C6D6)=ꢀ4.3 ppm; d(CDCl3)=ꢀ7.6 ppm;
MS (EI, 1508C): m/z (%): 364 (12) [M+], 334 (27), 320 (44), 252 (41),
238 (100), 197 (24), 170 (74), 156 (70), 55 (71); elemental analysis calcd
(%) for C21H33O3P (364.47): C 69.21, H 9.13; found: C 69.01, H 8.91.
2
or H-5), 6.97 7.13 ppm (m, 3H; ArH); 13C NMR (C6D6): d=10.6 (d, J=
13.7 Hz; CH3), 20.3 (d, 1J=6.8 Hz; PCH), 116.1 (d, 3J=2 Hz; C-6), 121.5
(C-4), 122.1 (d, 1J=7 Hz, C-2), 131.6/132.0 (2s, C-3, C-5), 162.0 ppm (d,
2J=20 Hz; C-1); 31P{1H} NMR (C6D6): d=ꢀ46.6 ppm; MS (EI, 1208C):
m/z (%): 182 (71) [M+], 154 (96), 126 (67), 125 (61), 124 (20), 94 (48), 77
6104
¹ 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
Chem. Eur. J. 2003, 9, 6093 6107

Nickel Catalysts for the Polymerization of Ethylene
6093 6107
(31), 47 (100); IR (nujol): n˜ ꢁ3100 cmꢀ1 (s br); elemental analysis calcd
2EEHH to give 2CCOH as a white solid (1.5 g; 43%), m.p. 508C. 1H NMR
(CDCl3): d=1.00 1.38 (m, 10H; Cy), 1.50 2.00 (m, 12H; Cy), 3.77 (s,
3H; OCH3), 6.80 6.87 ppm (m, 3H; ArH); 13C NMR (CDCl3): d=26.0
(C-d), 26.6 (d, 3J=8.1 Hz; C-g), 26.8 (d, 3J=13.6 Hz; C-g’), 28.4 (d, 2J=
6.1 Hz; C-b), 30.0 (d, 2J=15.8 Hz; C-b’), 32.3 (d, 1J=7.5 Hz; C-a), 55.4
(%) for C10H15OP (182.20): C 65.92, H 8.30; found: C 65.71, H 8.33.
2-(Diisopropylphosphanyl)phenol (2IIHH):
A mixture of 1IIHH (4.3 g,
16.9 mmol) and methanol (100 mL) was allowed to react with gaseous
HCl and worked up as reported for 2EEHH to give 2IIHH as a colorless oil
which was distilled at 1008C/0.1 Torr, yield 2.1 g; 59%. 1H NMR (C6D6):
1
(OCH3), 115.1 (C-5), 115.9 (C-6), 117.9 (C-3), 118.5 (d, J=11.2 Hz, C-2),
152.3 (C-4), 155.1 ppm (d, 2J=18.3 Hz; C-1); 31P{1H} NMR (C6D6): d=
ꢀ30.8 ppm; IR (nujol): n˜ ꢁ3200 cmꢀ1 (s sh); elemental analysis calcd (%)
for C19H29O2P (320.40): C 71.23, H 9.12; found: C 71.36, H 8.98.
3
3
3
3
d=0.81 (dd, JP,H =12.3, J=6.9 Hz, 6H; CH3A), 0.99 (dd, JP, H =16.4, J=
7.0 Hz, 6H; CH3B), 1.90 (sept d, 3J=7.0, 2JP, H =3.5 Hz, 2H; PCH), 6.77
(m, 1H; H-6 or H-5), 7.03 7.13 (m, 3H; ArH), 7.37 ppm (s br, 1H; OH);
13C NMR (C6D6): d=19.4 (d, 2J=7.3 Hz; CH3A), 20.8 (d, 2J=18.1 Hz;
CH3B), 23.8 (d, 1J=7.0 Hz; PCH), 116.3 (C-6), 119.2 (d, 1J=9 Hz, C-2),
2-(tert-Butylphenylphosphanyl)phenol (2BPHH): A mixture of 1BPHH (5.0 g,
16.5 mmol) and methanol (100 mL) was treated with gaseous HCl (208C
for 15 h, 1 h reflux) and worked up as described for 2EEHH to give 2BPHH
as a white solid (2.6 g; 61%), m.p. 868C. 13C NMR (CDCl3): d=28.5 (d,
2J=13.4 Hz; CCH3), 31.4 (d, 1J=8.1 Hz, CCH3), 115.3 (C-6), 119.1 (d,
1J=6.0 Hz; C-2), 120.0 (C-4), 128.2 (d, 3J=7.0 Hz; C-m), 128.4 (C-p),
131.7 (C-5), 133.6 (d, 2J=17.1 Hz; C-o), 134.5 (d, 1J=9.5 Hz; C-i), 134.8
(C-3), 160.9 ppm (d, 2J=21.3 Hz; C-1); 31P{1H} NMR (CDCl3): d=
ꢀ19.7 ppm; MS (EI): m/z (%): 259 (4), 258 (21) [M+], 202 (36), 183 (7),
124 (100), 108 (50), 107 (13), 77 (24), 57 (44), 41 (21); IR (nujol): n˜ =
2
120.8 (C-4), 132.1 (C-5), 133.7 (br, C-3), 162.7 ppm (d, J=18.2 Hz; C-1);
31P{1H} NMR (C6D6): d=ꢀ23.1 ppm; elemental analysis calcd (%) for
C12H19OP (210.26): C 68.55, H 9.11; found: C 68.44, H 9.26.
2-(Diisopropylphosphanyl)-4-fluorophenol (2IIFH):
A mixture of 1IIFH
(3.2 g, 11.7 mmol) and methanol (100 mL) was allowed to react with gas-
eous HCl (15 h, 208C, 1 h reflux) and worked up as reported for 2EEHH to
give a solid which was sublimed at 60 708C/2î10ꢀ2 Torr to afford 2IIFH as
white crystals (1.2 g; 45%), m.p. 658C. 1H NMR (C6D6): d=0.70 (dd,
3JP, H =12.5, 3J=6.9 Hz, 6H; CH3), 0.88 (dd, 3JP, H =16.5, 3J=7.0 Hz, 6H;
CH3), 1.66 (sept d, 3J=7.0, 2JP, H =3.5 Hz, 2H; CH), 6.72 (ddd, 3J=8.9,
1
3296 cmꢀ1 (s). H NMR data are as given in ref [23].
Methallyl complexes:
4
4
3JF,H =8.0, 5JP, H =3.1 Hz, 1H; H-5), 6.82 (d™t∫, 3J=8.9, JF,H ꢁ JP, H
ꢁ
2-(Diphenylphosphanyl)phenolate(2-methylallyl)nickel(ii) (3PPHH): a)
Thallium ethylate (71 mL, 1.0 mmol) was added with stirring to a solution
of 2PPHH (278 mg, 1.0 mmol) in THF (10 mL). White crystals, precipitated
after some minutes and cooling, were separated, dried at 10ꢀ4 Torr (yield
450 mg, 93%) and stored at ꢀ208C until use. b) The thallium phospha-
nylphenolate (450 mg, 0.934 mmol) was suspended in THF (20 mL),
cooled to ꢀ108C, and a solution of (methallylNiBr)2 (95 mg, 0.245 mmol)
in THF (20 mL) was added. Then the suspension was allowed to warm to
room temperature. The voluminous precipitation of TlBr formed after
5 min was filtered off (after stirring for 4 h) and washed carefully with
small portions of THF. The solvent of the orange filtrate was removed in
vacuum and replaced by pentane (5 mL). The insoluble part was separat-
ed and dried in vacuum to give air-sensitive orange 3PPHH (275 mg; 71%).
The product starts to decompose below 508C and was stored at ꢀ208C.
1H NMR (C6D6): d=1.34 (s br, 1H; H-1’), 1.64 (s, 3H; CH3), 2.16 (s br,
1H; H-2’), 2.98 (d, 3JP, H =5.4 Hz, 1H; H-3’), 4.08 (s br, 1H; H-4’), 6.51
(™tt∫, 3J=8.4, 6.9, 4JP, H =1.3, 4J=1 Hz, 1H; H-4), 6.90 7.08 (m, 6H; Ph),
5.0 Hz, 1H; H-6), 6.91 (d™t∫, 3JF,H =8.4, 4Jꢁ JP,H ꢁ2.7 3.1 Hz, 1H; H-3),
6.96 ppm (d br, 4JP, H =10 Hz, 1H; OH); 13C NMR (C6D6): d=19.2 (d,
2J=7.5 Hz; CH3), 20.5 (d, 2J=18.0 Hz; CH3), 23.8 (d, 1J=7.7 Hz; CH),
117.2 (dd, 3JF,C =6.8, 3J=1.6 Hz; C-6), 118.9 (dd, 2JF,C =21.1, 2J=1.7 Hz;
C-3), 119.1 (d, 2JF,C =23.1 Hz; C-5), 120.8 (dd, 3JF,C =12.4, 1J=4.5 Hz; C-
2), 157.6 (d, 1JF,C =239.7 Hz; C-4), 158.7 ppm (dd, 2J=18.7, 4JF,C =1.7 Hz;
C-1); 31P{1H} NMR (C6D6): d=ꢀ22.2 ppm; 19F NMR ([D8]THF, CFCl3):
d=127.0 ppm (m); MS (EI, 1308C): m/z (%): 228 (78) [M+], 186 (100),
144 (76), 143 (42), 77 (25), 43(23), 41 (18); IR (nujol): n˜ =3296 cmꢀ1 (vs
br); elemental analysis calcd (%) for C12H18FOP (228.24): C 63.15, H
7.95; found: C 62.99, H 8.12.
3
2-(Dicyclohexylphosphanyl)phenol (2CCHH): A mixture of 1CCHH (5.0 g,
15.0 mmol) and methanol (100 mL) was treated with gaseous HCl (208C
for 15 h, 1 h reflux) and worked up as described for 2EEHH to give 2CCHH
as a white solid (3.5 g; 81%), which was recrystallized from diethyl ether/
methanol, m.p. 868C. 1H NMR (CDCl3): d=0.90 1.25 (m, 10H; Cy),
4
4
7.15 7.22 (m, 2H; H-3, H-5), 7.32 (ddd, 3J=8.8, JP, H =5.9, J=1 Hz, 1H;
H-6), 7.40 7.60 ppm (m br, 4H; Ph); 13C NMR (C6D6): d=24.0 (C-d),
43.9 (C-a), 70.6 (d, J=22.6 Hz; C-c), 115.7 (d, 3J=6.4 Hz; C-4), 117.8 (d,
1J=50.6 Hz; C-2), 120.9 (d, 3J=8.0 Hz; C-6), 125.7 (C-b), 128.9 (d, 1J=
51 Hz, uncertain by superimposition; C-i), 129.5 (d, 3J=9.3 Hz; C-m),
129.7 (d, 3J=8.6 Hz; C-m’), 130.8 (C-p), 133.2 (C-3), 133.5 (d, 2J=
1.45 1.65 (m, 8H; Cy), 1.70 1.90 (m, 4H; Cy), 6.76 6.84 (m, 1H; ArH),
4
7.05 7.12 (m, 2H; ArH), 7.15 7.20 (m, 1H; ArH), 7.41 ppm (d br, JP, H
=
10.5 Hz, 1H; OH); 13C NMR (C6D6): d=27.2 (C-d), 27.7 (d, 3J=8.2 Hz;
C-g), 27.9 (d, 3J=13.1 Hz; C-g’), 29.5 (d, 2J=5.9 Hz; C-b), 31.2 (d, 2J=
16.1 Hz; C-˚’), 33.6 (d, 1J=7.1 Hz; C-a), 116.3 (C-6), 118.9 (d, 1J=
8.2 Hz; C-2), 120.8 (C-4), 132.1 (C-5), 133.8 (C-3), 163.0 ppm (d, 2J=
19.8 Hz; C-1); 31P{1H} NMR (CDCl3): d=ꢀ33.7 ppm; MS (EI, 1508C):
m/z (%): 290 (26) [M+], 273 (9), 235 (7), 209 (12), 208 (63), 127 (39), 126
(100), 125 (26), 83 (28), 55 (55), 47 (39); IR (nujol): n˜ =3371 cmꢀ1 (s); el-
emental analysis calcd (%) for C18H27OP (290.39): C 74.45, H 9.37;
found: C 73.91, H 9.56.
2
13.0 Hz; C-o), 133.8 (d, J=11.4 Hz; C-o’), 134.9 (C-5), 180.4 ppm (d, J=
25.0 Hz, C-1), 1H and 13C assignments except of Ph signals follow those
in the Pd analogue of 3CCHH [17b], studied by CH-COSY; 31P{1H} NMR
(C6D6): d=29.7 ppm; elemental analysis calcd (%) for C22H21NiOP
(391.07): C 67.57, H 5.41; found: C 67.12, H 5.39.
2-(Dicyclohexylphosphanyl)phenolate(2-methylallyl)nickel(ii)
(3CCHH):
2-(Dicyclohexylphosphanyl)-4,6-di-tert-butylphenol (2CCBB): A mixture of
1CCBB (4.8 g, 10.7 mmol) and methanol (100 mL) was treated with gaseous
HCl (208C for 15 h, 1 h reflux) and worked up as described for 2EEHH to
give 2CCBB as a white solid (2.1 g; 49%), m.p. 1108C. 1H NMR (C6D6):
d=1.36 (s, 9H; CH3), 1.63 (s, 9H; CH3), 0.90 1.30 (m, 10H; Cy), 1.40
Thallium ethylate (77 mL, 1.0 mmol) was added to a stirred solution of
2CCHH (317 mg, 1.1 mmol) in THF (5 mL). White crystals, precipitated
after cooling to ꢀ788C (one day), were separated, dried at 10ꢀ1 Torr, sus-
pended in fresh THF (5 mL) and added to a cold (ꢀ208C) solution of
methallyl nickel bromide (194 mg, 0.5 mmol) in THF (12 mL). The solu-
tion was stirred for 2 h at room temperature, the precipitate was filtered
off and hexane was added cautiously to form a layer on the mother
liquor slowly mixing in. Storage at ꢀ788C furnished orange crystals (with
a second portion 280 mg, 70%), m.p. 135 1388C, in solid state air-stable.
1H NMR (CDCl3): d=0.85 2.05 (m, 23H; Cy, H-1’), 1.83 (s, 3H; CH3),
2.09 (m, Jꢁ2 Hz, 1H; H-2’), 3.90 (d, JP, H =5.1 Hz, 1H; H-3’), 4.51 (m, Jꢁ
3 Hz, 1H; H-4’), 6.55 6.63 (m, 1H; ArH), 7.12 (t br, 3J=7.4 Hz, 1H;
ArH), 7.18 7.23 ppm (m, 2H; ArH); 13C NMR (C6D6): d=24.3 (C-d),
3
4
1.70 (m, 8H; Cy), 1.80 2.05 (m, 4H; Cy), 7.34 (™t∫, JP, H =3.2, J=2.2 Hz,
4
4
1H; H-3), 7.56 (d, J=2.2 Hz, 1H; 5-H), 7.88 ppm (d, JP, H =12.4 Hz, 1H;
OH); 13C NMR (C6D6, CH-COSY): d=27.2 (C-d), 27.8 (d, 3J=7.8 Hz;
C-g), 27.9 (d, 3J=13.1 Hz; C-g’), 29.6 (d, 2J=5.7 Hz; C-b), 30.6 (CCH3),
31.3 (d, 2J=16.0 Hz; C-b’), 32.6 (CCH3), 33.8 (d, 1J=6.9 Hz; C-a), 35.2
4
1
(CCH3), 36.1 (d, J=1.6 Hz; CCH3), 118.5 (d, J=4.6 Hz; C-2), 126.3 (C-
5 ), 128.1 (d, 2J=1.7 Hz; C-3), 135.9 (d, 3J=1.8 Hz; C-6), 141.9 (C-4),
159.0 ppm (d, 2J=19.2 Hz; C-1); 31P{1H} NMR: d(C6D6)=ꢀ33.4;
d(CDCl3)=ꢀ32.5 ppm; MS (EI, 1508C): m/z (%): 403 (16), 402 (61) [M+
], 387 (22), 321 (25), 320 (100), 305 (14), 278 (14), 238 (25), 224 (13), 57
(53), 55 (31), 41 (18); IR (nujol): n˜ =3322 cmꢀ1 (s); elemental analysis
calcd (%) for C26H43OP (402.60): C 77.57, H 10.77; found: C 77.74, H
10.89.
3
3
27.1 (C-d), 27.68 (d, J=10.5 Hz; C-g), 26.74, 27.9 (2 d, J=11.5, 12.0 Hz;
2 C-g’), 29.3 (d, 2J=7.8 Hz; C-b), 30.17, 30.23 (2 d, 2J=4.4, 4.9 Hz; 2 C-
b’), 34.3 (d, 1J=24.6 Hz; C-a), 34.6 (d, 1J=24.2 Hz; C-a’), 38.6 (d, J=
6.0 Hz; C-a), 71.2 (d, J=20.7 Hz; C-c), 115.6 (d, 1J=42.4 Hz; C-2), 114.6
(d, 3J=5.4 Hz; C-4), 120.3 (d, 3J=7.1 Hz; C-6), 123.3 (C-b), 131.9, 134.0
2
(2s, C-3, C-5), 180.8 ppm (d, J=21.3 Hz; C-1); 31P{1H} NMR (C6D6): d=
2-(Dicyclohexylphosphanyl)-4-methoxyphenol (2CCOH):
A mixture of
1CCOH (4.0 g, 11.0 mmol) and methanol (100 mL) was treated with gas-
eous HCl (208C for 15 h, 1 h reflux) and worked up as described for
44.4 ppm; DTA/TG: endothermic mass loss at 60 1408C (3.5%, calc. for
C4H7 13.7%), maximum 1208C, >1608C stronger decay; elemental anal-
6105
Chem. Eur. J. 2003, 9, 6093 6107
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¹ 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

J. Heinicke et al.
FULL PAPER
ysis calcd (%) for C22H33OPNi (403.17): C 65.54, H 8.25; found: C 64.91,
H 8.60.
Witt (Greifswald) for NMR measurements, S. Babik, K. Hauschild (MPI
M¸lheim), P. Montag (PPS Mainz), and D. Lilge (BASELL, Ludwigsha-
fen) for determination of the molar mass distribution by GPC.
Ethylene polymerization: a) Equipment and general remarks: The poly-
merization of ethylene was carried out as batch reaction in a stainless
steel autoclave (75 mL), equipped with a manometer, two valves, a safety
diaphragm, Teflon-coated magnetic stirrer, heating (temperature-control-
led silicon bath). Reaction temperatures refer to the bath temperature.
After placing the autoclave into the bath, mostly 100ꢂ58C, the inside
temperature increased to 708C within 13 15 min (calibration without
pressure).
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Initial tests established that no reaction of ethylene occurs in absence of
either 2-phosphanylphenols or [Ni(cod)2] and that products obtained in
glass beakers and directly in the autoclave are almost identical. To limit
wall effects, a relatively high amount of the catalyst, 0.1 mmol (initially
0.22 mmol), was used. The reproducibility within series with similar cata-
lysts is sufficient.
b) Preparation of catalysts: The methallylnickel complexes 3 (0.1 mmol)
were dissolved in toluene (20 mL) and used immediately. Catalysts 4 and
2: Unless indicated otherwise, 0.1 mmol of the respective 2-phosphanyl-
phenol 2 was dissolved in toluene or the given solvent (10 mL), cooled to
08C and added to a solution of [Ni(cod)2] (27.5 mg, 0.1 mmol) in toluene
or the given solvent (10 mL) at 08C or, for catalysts 2, to a suspension of
NiBr2¥DME (0.2 or 0.3 mmol) in toluene (10 mL) to which finally NaH
(7.2 mg, 0.3 mmol) was added. Catalysts 5 were prepared like catalysts 2
but using the bis(chelate) complex 5 instead of the protonated ligands 2.
The catalyst solution or suspension was stirred for 30 min at 208C, usual-
ly forming a brown (PhRP catalyst) or yellow-orange (Alk2P-catalysts)
solution or suspension (with 2BBHH no color change). In experiments with
additives, the amount of toluene or the given solvent was reduced (each
50% for 2 and for [Ni(cod)2]) by the amount of the additive, and the
latter was added to the preformed catalyst solution.
c) Polymerization: The autoclave was charged with argon and the catalyst
solution (Teflon syringe). Then, ethylene was added (30 to 50 bar), the
amount of ethylene determined by weight difference and the autoclave
heated to the given temperature overnight (15 h). After cooling to room
temperature and weight control, the autoclave was connected to a cool-
ing trap (ꢀ788C, usually ꢃ 0.1 g butenes condensed) and unreacted eth-
ylene was allowed to escape. The content of the autoclave was separated
by flash distillation at 808C/10ꢀ2 Torr. The residual polymer was stirred
for 1 d with methanol/hydrochloric acid (1:1), thoroughly washed with
methanol and dried in vacuum. For melting point, density and NMR
measurements soluble oligomers were removed (usually <10 mg/g) by
extraction with CH2Cl2 (10 mLgꢀ1 PE, 15 h). Conversion and characteris-
tic polymer data are given in Tables 1 4.
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107 gmolꢀ1; software WIN-GPC; ii) PSS-WIN-GPC v4.01. NMR spectra
were measured at 1008C using concentrated solutions of the polyethylene
samples in C6D5Br, prepared by swelling for 1 d at 1208C under argon.
1
Further conditions: H NMR, acquisition time 4.9 5.4 s, delay 1.0 s, refer-
ence p-CH of the solvent d=7.23; 13C NMR, addition of [Cr(acac)3], ac-
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Acknowledgment
We thank the Deutsche Forschungsgemeinschaft for the support of this
study and grants for M. K. and M. H. and the Fonds der Chemischen In-
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6106
¹ 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Chem. Eur. J. 2003, 9, 6093 6107

Nickel Catalysts for the Polymerization of Ethylene
6093 6107
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Received: February 26, 2003
Revised: May 15, 2003 [F4888]
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Chem. Eur. J. 2003, 9, 6093 6107
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¹ 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim