Methyl(2-phosphanylphenolato[P,O])nickel(II) complexes - Synthesis, structure, and activity as ethene oligomerization catalysts

Article abstract of DOI:10.1002/(SICI)1099-0682(200003)2000:3<431::AID-EJIC431>3.0.CO;2-Q

Reactions of various substituted 2-phosphanylphenols 1a-f with half- molar amounts of cis-[MeNi(μ-OMe)(PMe₃)]₂ have been found to yield square- planar methyl(2-phosphanylphenolato)(trimethylphosphane)nickel(II) complexes 2a-f. ²J(PP) coupling constants of 305-316 Hz at low temperature indicate a trans-configuration for the products, while broad ³¹P-NMR signals at room temperature can be attributed to rapid dissociation of PMe₃. Reaction with excess 1 gave rigid bis(2-phosphanylphenolato)nickel(II) complexes as exemplified by 3e, whereas addition of PMe₃ to 2a led to the penta- coordinate methyl(2-phosphanylphenolato)bis(trimethylphosphane)nickel(II) complex 4a. Higher yields of 4a and 4d were obtained by reactions of 1a and 1d with Me₂Ni(PMe₃)₃. Single-crystal X-ray diffraction analyses of 3e and 4a have revealed the structures as square-planar trans-bis- and trigonal- bipyramidal mono(2-phosphanylphenolato)nickel(II) P(intersection set)O- chelate complexes, respectively. The methylnickel complexes 2 and 4 have been found to be effective one-component catalysts for the oligomerization of ethene. High conversions (> 96%) were achieved with the P-basic derivatives 2e, 2f, and 4d bearing one or two branched alkyl groups (isopropyl, tert- butyl), whereas the diphenylphosphanyl derivatives were less active; 4d gave shorter oligomers than 2e or 2f.

Full text of DOI:10.1002/(SICI)1099-0682(200003)2000:3<431::AID-EJIC431>3.0.CO;2-Q

FULL PAPER
Methyl(2-phosphanylphenolato[P,O])nickel(II) Complexes – Synthesis,
Structure, and Activity as Ethene Oligomerization Catalysts
Joachim Heinicke,*[a] Mengzhen He,[a] Attila Dal,[a,b] Hans-Friedrich Klein,*[b]
Olaf Hetche,[b] Wilhelm Keim,*[c] Ulrich Flörke,[d] and Hans-Jürgen Haupt[d]
Keywords: Methylnickel complexes / 2-Phosphanylphenolate / Chelates / Homogeneous catalysis / Oligomerization
Reactions of various substituted 2-phosphanylphenols 1a–f
with half-molar amounts of cis-[MeNi(µ-OMe)(PMe3)]2 have
been found to yield square-planar methyl(2-phosphanyl-
phenolato)(trimethylphosphane)nickel(II) complexes 2a–f.
2JPP coupling constants of 305–316 Hz at low temperature in-
dicate a trans-configuration for the products, while broad
31P-NMR signals at room temperature can be attributed to
rapid dissociation of PMe3. Reaction with excess 1 gave rigid
were obtained by reactions of 1a and 1d with Me2Ni(PMe3)3.
Single-crystal X-ray diffraction analyses of 3e and 4a have
revealed the structures as square-planar trans-bis- and tri-
gonal-bipyramidal mono(2-phosphanylphenolato)nickel(II)
PʝO-chelate complexes, respectively. The methylnickel com-
plexes 2 and 4 have been found to be effective one-compon-
ent catalysts for the oligomerization of ethene. High conver-
sions (Ͼ 96%) were achieved with the P-basic derivatives 2e,
bis(2-phosphanylphenolato)nickel(II) complexes as exempli- 2f, and 4d bearing one or two branched alkyl groups (isopro-
fied by 3e, whereas addition of PMe3 to 2a led to the penta-
coordinate methyl(2-phosphanylphenolato)bis(trimethyl-
pyl, tert-butyl), whereas the diphenylphosphanyl derivatives
were less active; 4d gave shorter oligomers than 2e or 2f.
phosphane)nickel(II) complex 4a. Higher yields of 4a and 4d
Introduction
seen with PPh3, P(4-X–C6H4)3 (X ϭ Cl Ͼ Me Ͼ F), and
PPh2Me, whereas PCy3 (Cy ϭ cyclohexyl), which has a
strong enhancing effect on the activity of the related
phenyl(2-diphenylphosphanyl-1-phenylenolato)(phos-
phane)nickel(II) catalysts, induces only moderate activity.
Generally, a marked tendency to produce higher oligomers,
from C10ϭ to C90ϭ, and only minor amounts of the desired
C4ϭ to C10ϭ oligomers is observed. Exceptions are com-
plexes with PMe3 and PPhMe2 ligands, which give α-
PʝO-chelate complexes are of crucial importance in the
oligomerization of ethene to give linear α-olefins by the
Shell Higher Olefins Process.[1] In order to tune the catalyst
properties, various PʝO-nickel complexes of varying ring
sizes and bearing different functional groups have been in-
vestigated.[2,5] In early studies of the oligomerization of
ethene, using in situ generated catalysts obtained from 2-
diphenylphosphanylphenol and bis(1,5-cyclooctadiene)n-
ickel or nickel salts in the presence of NaBH4, mainly poly-
mers were obtained.[6] Oligomers of ethene were, however,
formed using phenyl(2-diphenylphosphanyl-4-hydroxy-
phenolato)(triphenylphosphane)nickel(II), obtained by
olefins
of
low
molecular
weight
(C4ϭ
to
C24ϭ), although with lower catalytic activity.[3d] In view of
the recently reported access to variously substituted 2-phos-
phanylphenols[8,9] and their high tendency to form PʝO-
chelates,[8,10,11] we turned our attention to the synthesis of
catalytically active (2-phosphanylphenolato[P,O])nickel(II)
complexes and the tuning of their activity and selectivity by
variation of substituents at the phosphorus and the
phenolate group. We report here on methyl(2-phosphanyl-
phenyl migration from α-benzoyl phosphorus ylides.[2b,7]
recent study of the influence of various auxiliary phosphane
ligands on the activity and selectivity of analogously
A
prepared
phenyl(2-diphenylphosphanylphenolato)(phos-
phenolato)nickel
complexes,
which
differ
from
phane)nickel(II) catalysts established that high activity is
cyclopentadienyl(2-phosphanylphenolato)nickel(II) com-
plexes[8b,11] in that they are active oligomerization catalysts.
[a]
Institut für Chemie und Biochemie, Universität Greifswald,
Soldmannstraße 16, D-17487 Greifswald, Germany
Fax: (internat.) ϩ 49(0)3834/864337
E-mail: heinicke@mail.uni-greifswald.de
[b]
Institut für Anorganische Chemie, Technische Universität
Results and Discussion
Darmstadt,
Petersenstraße 18, D-64285 Darmstadt, Germany
Fax: (internat.) ϩ 49(0)6151/164173
E-mail: hfklein@hrz2.hrz.tu-darmstadt.de
Synthesis
[c]
Institut für Technische Chemie und Petrolchemie, Rheinisch-
Selected 2-phosphanylphenols 1a–f were synthesized
either by dilithiation of 2-bromophenols, reaction with the
respective chlorophosphane and acid workup,[9c,10i] or, in
analogy to the procedure of Rauchfuß,[8b] by ortho-
metallation of the corresponding phenolmethoxymethyl
Westfälische Technische Hochschule Aachen,
Worringer Weg 1, D-52056 Aachen, Germany
[d]
Anorganische und Analytische Chemie, Universität-GH
Paderborn,
Warburger Straße 100, D-33098 Paderborn, Germany
Fax: (internat.) ϩ 49(0)5251/603423
Eur. J. Inorg. Chem. 2000, 431Ϫ440
WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2000
1434Ϫ1948/00/0303Ϫ0431 $ 17.50ϩ.50/0
431

J. Heinicke, H.-F. Klein, W. Keim et al.
FULL PAPER
ether with butyllithium, substitution with chlorophosphane,
and subsequent acid ether cleavage (Scheme 1).
Figure 1. ORTEP plot of the molecular structure of 1e; selected
˚
distances [A] and angles [°]: P1–C2 1.847(9), P1–C7 1.877(10), P1–
C10 1.838(10); P1–C1–C2 118.7(8), P1–C1–C6 122.1(8), O1–C2–
C1 119.9(9), O1–C2–C3 116.9(10)
Scheme 1. Synthesis of 2-phosphanylphenols
When the reaction was carried out in the presence of one
equivalent of PMe3, 2e was isolated (Scheme 2). The com-
plexes 2 were purified by fractional extraction of the crude
products with pentane.
The chosen substitution pattern, i.e. diphenyl, al-
kylphenyl, and dialkyl groups at phosphorus, 4,6-di-tert-bu-
tyl-, 4-methyl-6-tert-butyl-, and 4-fluoro-substituents at the
phenoxy group, provided ligands with widely differing basi-
cities at phosphorus and oxygen, allowing a qualitative ap-
praisal of electronic effects on the oligomerization of ethene
by the corresponding nickel PʝO-chelate complexes.
Branched alkyl groups were selected since 2-isopropyl-
phenylphosphanyl- and, in particular, 2-tert-butyl-
phenylphosphanylcresol have been found to exhibit a lower
tendency to form the thermodynamically preferred bis-
(PʝO-chelates) than 2-methylphenylphosphanyl- or 2-di-
phenylphosphanyl derivatives[11b] upon reaction with equi-
molar amounts of nickelocene in toluene. The 6-tert-butyl
group stabilizes the PʝO-chelate complexes through its
steric effect on the periphery, but does not significantly shi-
eld the metal center. The steric effect causes a bending of
the substituents at oxygen towards the phosphorus, as is
Scheme 2. Synthesis of the nickel complexes 2a–f and 3e
Whereas the room-temperature NMR spectra of cis- and
evident from the unusual formation of a 2-phosphanylphen- trans-bis(2-phosphanylphenolato[P,O])nickel(II)
chelate
olate PʝO-chelate complex with the hard titanium cat- complexes 3 feature sharp signals and multiplets showing
4
ion,[10h] an extremely increased JPSn in a 2-phosphanyl- couplings to both phosphorus atoms for a number of 1H as
phenolstannyl ether, and the presence of P H–O hydrogen well as 13C nuclei,[11,12] the room-temperature spectra of 2a–
1
bonds in 1c and 1d.[9c] In 1e, the presence of a P H–O f reveal couplings of the corresponding H and 13C nuclei
4
hydrogen bond is evident from a large JPH coupling con- to only one phosphorus atom, and in the 31P-NMR spectra
stant of 12.4 Hz for the hydroxyl proton, whereas in 1f this broad doublets or singlets are observed. At low temperature
proton gives rise to a broad singlet. An X-ray structure ana- (–25 to –70 °C), the phosphorus signals of 2a–f appear as
2
lysis of single crystals of 1e, performed at –100 °C, reveals sharp doublets with JPP couplings in the range 305–
a trans-eclipsed conformation (Figure 1), which means that 316 Hz, indicating a trans configuration. These values are
2
the lone electron pair is also directed towards the hydroxyl similar to the JPP values of 245–290 Hz recently observed
group in the solid state. The lack of evidence for any such in phenylnickel-o-diphenylphosphanylphenolate phosphane
1
P H–O hydrogen bond in 1f underlines the role of the complexes.[3d] The H and 13C signals of the NiMe groups
bulky 6-substituent in inducing such interactions.
in 2a–f are split by couplings with both the phosphorus
Reactions of 1a–c and 1f with half-molar and of 1d with atoms, whereas the multiplicity of the H and 13C signals
equimolar amounts of [NiMe(PMe3)(µ-MeO)]2 in diethyl of the PʝO-ligand (at –25 to –30 °C) arises from coupling
ether, THF, or pentane solution proceeded via red interme- with the o-phosphorus nucleus only when PH or PC coup-
diates and led to the yellow or red-brown methyl(2-phos- ling is observed. These observations are indicative of rapid
phanylphenolato)(trimethylphosphane)nickel(II) complexes dissociation of the monodentate phosphane at room tem-
2a–d and 2f. However, when the P-basic 1e was used in perature, whereas exchange reactions of the PʝO-ligands, as
slight excess relative to the half-molar amount of [Ni- indicated, e.g., by the different configurations of a bulky
Me(PMe3)(µ-MeO)]2, the air-stable trans-bis(PʝO-chelate) substituted bis(2-phosphanylphenolato)nickel complex in
complex 3e was formed in high yield. This can be mainly solution and in the solid state,[12] are slow on the NMR
attributed to the more facile dissociation of PMe3 from 2e. time scale. The decreased line-widths of the room-temper-
1
432
Eur. J. Inorg. Chem. 2000, 431Ϫ440

Methyl(2-phosphanylphenolato[P,O])nickel(II) Complexes
FULL PAPER
Scheme 3. Dissociation equilibria of 2
Scheme 4. Syntheses of the nickel complexes 4a, d
ature phosphorus resonances of the diisopropylphosphanyl single-crystal X-ray structure analyses of 3e and 4a. In this
complexes 2e and 2f and the lower temperature necessary regard, we will now discuss some trends by comparison of
for obtaining sharp doublets (–70 °C) indicate enhanced selected data (Table 1). The coordination chemical shifts of
dissociation in the case of PʝO-ligands with increased the ortho-phosphorus atoms (o-P) in complexes of types 4,
donor and diminished acceptor strengths. The dissociation cis-3, and trans-3 reveal a greater deshielding in the more
products, the tricoordinate 14-electron nickel intermediates highly alkylated P–alkylnPh2–n derivative in each case, due
I, undergo a rapid back-reaction with PMe3 (Scheme 3). to the lower acceptor strength. The same trend is observed
The presence of excess 1 disrupts this equilibrium by trap- for 2a to 2d, but the more P-basic diisopropylphosphanyl
ping I, thereby yielding the more stable bis(PʝO-chelates) complexes 2e and 2f show smaller than expected values for
3. The high reactivity of I prevents the observation of equi- ∆δ(o-P). Similarly, the coordination chemical shifts of PMe3
librium concentrations. The concentrations of free trime- in 2e and 2f, which approach those in 4a and 4d, are mark-
thylphosphane and of dimers of I also fall below the limit edly lower than ∆δ(PMe3) in 2a–d. This indicates a higher
of detection by NMR, suggesting a rapid association–disso- electron density at nickel(II) and an increased electron-re-
ciation equilibrium of PMe3 with a small equilibrium con- pelling effect due to the lack of back bonding, which is also
stant. Dissociation of PMe3 also seems to be responsible responsible for the noticeable high-field shifts of the NiMe
for the rapid aerial oxidation of solutions of 2a since the carbon resonances in 2e and 2f as compared with those in
solid material is stable in air for several hours.
2a–d, the lower 1JPC2 and slightly lower 2JPC1 coupling con-
In order to ascertain whether trimethylphosphane may stants, and the aforementioned higher rate of dissociation
be scavenged by the 16-electron complexes 2, generation of in 2e and 2f. Comparison of the phosphorus coordination
the pentacoordinate complex 4a was attempted by adding shifts of PʝO,P nickel complexes 2 with those of bis(PʝO-
excess trimethylphosphane to 2a. However, this method chelates) 3 having similar substitution patterns at phos-
gave only a low yield (ca. 30%) of the red product. It was phorus reveals smaller or slightly smaller ∆δ values for the
found that 4a and 4d could be obtained much more readily trans isomers of 3, but significantly larger deshielding in cis-
by reaction of 1a and 1d, respectively, with dimethyl tris(tri- 3. An even more clear-cut distinction of cis and trans iso-
1
methylphosphane)nickel(II) in diethyl ether (Scheme 4). mers follows from the different JPC2 (Jcis Ͼ Jtrans) and
Complexes 4a and 4d were found to be stable under ambi- 2JPC1 (Jcis Ͻ Jtrans) values, which indicate different elec-
ent conditions but lose trimethylphosphane on heating and tronic situations. The latter observation would suggest that
decompose at around 106–109 °C. As expected for penta- substituent effects influence the configuration. Whereas this
coordinate nickel complexes, 4a and 4d are highly fluxional is true for the rigid bis(PʝO-chelates) 3,[8a,11,12] mono-
and exhibit two broad phosphorus singlets in their 31P- chelate PʝO,P nickel complexes 2 such as acyclic bis(phos-
NMR spectra, even at –30 °C, indicating rapid pseudo-rota- phane)bis(phenolate)nickel complexes[13] always preferen-
1
tion and dissociation of PMe3. The H and 13C nuclei of tially adopt a trans configuration. cis-Isomers of 2 would
2
the PʝO-ligand and the Ni methyl group only show coup- be expected to exhibit JPNiP coupling constants in the
ling with the rigid chelate-bound phosphorus. As in the case range 60–90 Hz.[11b,14,15] Such signals could not be de-
of 2, the dissociation equilibria account for the fact that tected, neither for P(R)–aryl nor for dialkylphosphanyl de-
solutions of 4 are rapidly oxidized, whereas the isolated rivatives. Traces of impurities giving rise to sharp phos-
complexes can be exposed to air for a short time.
phorus doublets (JPP ϭ 14–16 Hz) were detected in the
spectra of 2a,b,d, the nature of which has not yet been es-
tablished.
Structural Aspects
In addition to the dynamic effects, the 1H-, 13C-, and 31P-
A single-crystal X-ray structure analysis of 3e (Figure 2)
NMR chemical shifts and coupling constants of the rigid confirmed the trans configuration and provided the first
phosphanylphenolate ligands confirmed the configurations such data for trans-bis(phosphanylphenolato[P,O])-
of 2–4. Further structural information was provided by nickel(II) complex. Like acyclic trans-bis(phosphane)bis-
a
Eur. J. Inorg. Chem. 2000, 431Ϫ440
433

J. Heinicke, H.-F. Klein, W. Keim et al.
FULL PAPER
Table 1. Selected 31P- and 13C-NMR data of 2–4 (nr ϭ not resolved; N ϭ |J ϩ J’|)
Compound
∆δ(o-31P)
∆δ(31PMe3) at 25 °C (at T °C)
δ(Ni13CH3) at 25 °C (2JCP-2 [Hz])
1JPC1 [Hz]
2JPC2 [Hz]
2a
2b
2c
62.6
52.6
55.9
55.3
57.1 (–50)
57.7 (–50)
–19.9 (25)
–20.3 (25.1)
–22.2 (nr)
49.1
48.6
(nr)
25.1
25.8
23.4
61.9
69.8[a]
2d
2e
2f
66.8
63.9
60.5
56.7
63.3
71.1
77.5
54.0
62.0
55.3
47.9
48.7
34.8
35.3
–
56.8 (–28)
50.1 (–70)
–21.1 (25)
44.5
23.4
–24.9 (28.1)
41.2
22.0
–26.1 (26.8)
38.3
21.6
4a
4d
–18.8 (br)[b]
45.8
28.1
–20.7 (22.7)
43.0
24.9
[12]
cis-3a
–
–
–
–
–
–
–
–
N ϭ 61.2
N ϭ 55.8
N ϭ 46.8
N ϭ 42.6
N ϭ 18.9
N ϭ 17.7
N ϭ 28.7
N ϭ 30.5
[12]
cis-3c
–
[12]
trans-3d
–
–
trans-3e
[a]
[b]
Referred to δ(1c) at –15 °C, other peaks to 1 at 25 °C. – At –30 °C, δ ϭ –16.4 (19.6 Hz).
Figure 2. ORTEP plot of the molecular structure of 3e; selected
˚
distances [A] and angles [°]: Ni1–P1 ϭ Ni1–P1A 2.1997(8), Ni1–
O1 ϭ Ni1–O1A 1.857(2), P1–C2 1.794(3), P1–C15 1.841(4), P1–
C19 1.819(4), O1–C1 1.338(4), C1–C6 1.424(4); O1–Ni1–O1A
180.0, P1–Ni1–P1A 180.00(4), O1–Ni1–P1A
ϭ O1A–Ni1–P1
93.04(7), O1–Ni1–P1 ϭ O1A–Ni1–P1A 86.96(7), C1–O1–Ni1
121.30(19), C2–C1–O1 120.8(3), P1–C2–C1 111.9(2), Ni1–P1–C2
98.80(11), P1–C2–C3 126.7(3), O1–C1–C6 120.4(3)
Figure 3. ORTEP plot of the molecular structure of 4a; selected
˚
distances [A] and angles [°]: Ni1–C41 1.981(5), Ni1–P1 2.191(2),
Ni1–P2 2.245(2), Ni1–P3 2.224(2), Ni1–O1 1.984(3), P1–C6
1.797(5), O1–C1 1.332(5), C1–C6 1.411(6); C41–Ni1–O1 177.7(2),
C41–Ni1–P1 92.6(2), C41–Ni1–P2 88.9(2), C41–Ni1–P3 91.7(2),
P1–Ni1–P2 114.02(6), P1–Ni1–P3 125.16(6), P2–Ni1–P3 120.71(7),
O1–Ni1–P1 86.35(10), C1–O1–Ni1 118.9(3), C6–C1–O1 120.1(4),
P1–C6–C1 114.3(4), Ni1–P1–C6 99.2(2), P1–C6–C5 124.3(4), O1–
C1–C2 122.1(4)
(phenolato)nickel(II) complexes,[13] 3e possesses an almost
ideal square-planar geometry about the nickel center, with
O–Ni–O and P–Ni–P angles of 180°. This is in marked con-
trast to the distorted structures of cis-3, where O–Ni–O
angles of 85.0 to 87.5° and P–Ni–P angles of 97.9 to 107.1°
are found.[11b,12] The latter value relates to 3d, which occurs
in the cis form in the solid state, but in the kinetically pre-
ferred (trans effect) trans configuration in solution[12] and
may thus represent the degree of steric congestion at the
borderline of cis- and trans-bis(2-phosphanylphenolato)n-
ickel(II) complexes. The Ni–P bond lengths in 3e are some-
ideal trigonal-bipyramidal geometry with the three phos-
phorus atoms in equatorial positions and the oxygen and
the methyl group in axial positions (Figure 3). The Ni–P(1)
distance is markedly longer than the Ni–P bond lengths in
cis-3, but is comparable to the corresponding distances in
3e and phenyl(2-phosphanylenolato)(phosphane)nickel(II)
complexes. The axial Ni–O bond is longer than Ni–O bonds
in cis- and trans-3, but is comparable to the longer distances
found in the (2-phosphanylenolato)(phosphane)nickel or
pentacoordinate o-benzoyl(trimethylphosphane)nickel com-
plexes.[16] The Ni–C(Me) and Ni–P(2) or Ni–P(3) distances
fall in the usual ranges of bond lengths in methylnickel-
trimethylphosphane complexes.[17]
˚
˚
what longer [2.1997(8) A] while the Ni–O [1.857(2) A] dis-
tances are a little shorter as compared to the values in cis-
bis(2-phosphanylphenolato)nickel(II)
moieties,
i.e.
˚
2.1432(13) to 2.172(2) A (the latter in cis-3d) and 1.869(10)
˚
to 1.889(3) A, respectively. The angles within the chelate
ring are as those in cis-3 and underline the rigidity of the
five-membered Ni–PʝO-chelate ring.
Although single crystals of trans-2a–f suitable for struc-
ture determinations could not be obtained, their structures
are believed to be similar to those of phenyl(2-diphenylpho-
Ethene Oligomerization
sphanylenolato)(triphenylphosphane)nickel(II)
com-
Toluene solutions of the methylnickel phosphane com-
plexes.[2a,3b] X-ray structure analysis of 4a reveals an almost plexes 2c,e,f and 4a,d (ca. 0.1 mmol) were treated with
434
Eur. J. Inorg. Chem. 2000, 431Ϫ440

Methyl(2-phosphanylphenolato[P,O])nickel(II) Complexes
FULL PAPER
Table 2. Oligomerization of ethene (at 80 °C, 35 bar in 12 mL of toluene)
Oligomerization no.
I
II
III
IV
V
Catalyst, mg
(mmol)
2c, 56.0
(0.11)
2e, 58.0
(0.12)
2f, 47.9
(0.13)
4a, 67.7
(0.11)
7.5 (267)
10
4d, 70.8
(0.12)
7.7 (274)
10
Ethene, g (mmol)
Time [h]
7.7 (274)
10
7.6 (271)
6
7.8 (278)
6
Conv. of ethene g (%)
TON [mol/mol]
Products[a]
0.8 (10.4)
257
C4–C24
7.5 (98.7)
2174
C4–C60
7.7 (98.7)
2161
C4–C52
2.2 (29.3)
713
7.4 (96.1)
2218
oligomers[b]
C4–C14
[c]
[c]
% 1-olefins
99.0
0.84
95.1
0.78
93.2
0.73
95.9
0.58
K-value[c]
[a]
[b]
[c]
Based on MS data. – Oligomer mixture not analyzed. – Calculated for oligomers Ͼ C4.
Figure 4. Conversion of ethene at 80 °C in the presence of 2e, 2f,
and 4d
ethene (ca. 7.7 g) at 80 °C in a 75 mL autoclave (Table 2).
After an initial increase of the starting pressure (35 bar) to
45–50 bar during the induction period (about 30–45 min),
the pressure fell at a rate that depended on the one-com-
ponent catalyst (Figure 4). The bulk of the ethene reacted
Scheme 5. Proposed mechanism of oligomerization of ethene cata-
lyzed by 2 or 4
within ca. 4 h, whereas an almost quantitative conversion found in the range C10 to C14 by GC and C12 to C18 by
required 6 h in the case of 2e and 2f, and 10 h in the case mass spectrometry (based on abundance of [Mϩ] using dir-
of 4d. The less P-basic diphenylphosphanyl- and alkyl- ect inlet). The most abundant oligomers (by GC) in experi-
phenylphosphanyl representatives of 2 and 4 were much less ments II and III using the diisopropylphosphanylphenolate
active. This has a parallel in the low oligomerization activity catalysts 2e and 2f were 1-hexene and 1-octene, followed by
of phenyl(2-diphenylphosphanylphenolato)(trimethylphos- either 1-decene (II/2e) or 1-butene (III/2f). Besides these,
phane)nickel(II) as compared to phenylnickel complexes of greater amounts of C14ϩ oligomers (n Ͼ 7) (33 and 51
this type with other, mainly P-arylated monodentate phos- mass%) were observed. Interestingly, the mass spectrum of
phane ligands.[3d] This is believed to be due to the greater the oligomer mixture of II revealed low abundance maxima
stability of ‘‘push-pull’’ trans-diphosphane nickel complexes due to the molecular ions of oligomers n ϭ 10–12 and n ϭ
with a good donor on one side and a good acceptor ligand 23–25. The higher conversion and the occurrence of longer
on the other as compared with the easily dissociating P- olefins using the diisopropylphosphanylphenolate catalysts
basic complexes 2e, 2f, and 4d or phenyl(2-diphenylphos- 2e and 2f may be explained by the higher degree of dissoci-
phanylphenolato)(triarylphosphane)nickel(II)
with similar phosphane ligands on either side.
species[3d] ation allowing, over time, a proportionally faster uptake of
ethene. Since diisopropylphosphanylphenolate catalysts,
The products of the catalytic conversion of ethene were prepared in situ from 1e or 1f and Ni(COD)2 and free of
oligomers (Scheme 5), mainly linear α-olefins (Table 3). The monodentate phosphanes, give higher polyethenes than di-
selectivity decreased somewhat with increasing chain phenyl- or alkylphenyl-substituted species,[19] the lower-oli-
length, from C4 to C12, as detected by GC. The unusually gomer maxima seen in the catalysis using 2e and 2f might
high content of a hexene isomer in II (11.5%) may be attrib- be induced by stronger promotion of β-hydride elimination
uted to a competing reaction with 1-butene. With 4d, lower in the alkyl(2-diisopropylphosphanylphenolato)(phos-
oligomers with a Schultz–Flory distribution[18] and large phane)nickel(II) intermediates than in intermediates formed
amounts of 1-butene, 1-hexene, and octenes were observed. using 2c. This is in line with the higher electron density at
The mono-PMe3 complexes form longer chain oligomers nickel in 2e and 2f as compared with that in 2a–d, which is
with broad, flat maxima in their molar weight distributions. reflected in a high-field shift of the methyl group 13C reson-
In experiment I using the catalyst 2c, the maximum was ance by ca. 4 ppm (Table 1). Coordination of an alkylphos-
Eur. J. Inorg. Chem. 2000, 431Ϫ440
435

J. Heinicke, H.-F. Klein, W. Keim et al.
FULL PAPER
Table 3. Composition of ethene oligomers obtained with 2c,e,f and 4d
Oligomerization (catalyst)
I (2c)
II (2e)
III (2f)
V (4d)
% C4 (% 1-olefin)
% C6 (% 1-olefin)
[% most abund. isoolefin]
% C8 (% 1-olefin)
[% most abund. isoolefin]
% C10 (% 1-olefin)
[% most abund. isoolefin]
% C12
3.0
8.0 (100)
19.2 (99)
[1]
11.2 (100)
16.1 (87)
[11.5]
44.1 (100)
38.3 (99)
8.2 (90)
[10]
10.3
19.5 (99)
15.7 (94.4)
[4]
12.0 (85)
2.7 (79)
2.1 (69)
0.7
11.2
11.6
15.1 (85)
[6]
5.1 (91)
[4.5]
0.42
3.9 (79)
[8]
[% most abund. isoolefin]
% C14
11.6
0.9
33.3
0.48
51
[a]
% C14ϩ
[a]
C16 10.9%, C18 9.6%, C20 8.8%, C22 7.8%, C24 7%.
phane ligand will accelerate β-hydride transfer in the case
of C2n-alkyl chains at nickel. A small proportion of active
centers, depending on the equilibrium concentration of
PMe3, may produce somewhat longer chains, promoted by
a decreasing association of PMe3 with increasing chain
length.
Experimental Section
General Procedures and Materials: All procedures were carried out
under an atmosphere of purified argon using standard vacuum line
or Schlenk techniques. Solvents (THF, diethyl ether, pentane) were
dried with sodium (ketyls) and freshly distilled prior to use.
[NiMe(PMe3)(µ-OMe)]2,[16,17] trans-Me2Ni(PMe3)3,[20] and the 2-
phosphanylphenols 1a,[9c] 1b,[10i] and 1c[9c] were prepared according
to known procedures; iPr2PCl was purchased from Aldrich and
used without further purification. – IR spectra were recorded on a
Nicolet Impact 400 FT-IR spectrometer. – NMR spectra were re-
corded on Bruker AM 200, WM 300, or ARX 300 multinuclear
Fourier transform spectrometers and are referenced to tetramethyl-
Conclusions
1
silane for H and 13C and to H3PO4 (85%) for 31P. The measuring
Tertiary 2-phosphanylphenols 1 bearing phenyl and alkyl
groups at phosphorus react with [MeNi(µ-OMe)(PMe3)]2 to
give 16-electron methyl(2-phosphanylphenolato)(trimethyl-
phosphane)nickel(II) complexes 2 with trans-square-planar
structures. Complex 2 reacts with excess 1 to give nickelbi-
s(PʝO-chelates) 3 or adds PMe3 to form 18-electron tri-
gonal-bipyramidal methyl(2-phosphanylphenolato)bis(tri-
methylphosphane)nickel(II) complexes 4. Higher yields of 4
are obtained from 1 and Me2Ni(PMe3)3. Both 2 and 4 are
temperature was 298 K unless otherwise stated. For resonances that
are part of an AXX’ spin system (X,X’ ϭ 31P), vc and τ denote
‘‘virtual coupling’’ and the triplet appearance of the A resonance,
respectively. – Melting points were determined in sealed capillaries
(Büchi type 510) and are uncorrected. – Elemental analyses were
carried out using CHN 240 A (Perkin–Elmer) or CHNS-932
(LECO) analyzers.
Ligand Preparation
fluxional molecules, particularly their dialkylphosphanyl 4,6-Di-tert-butyl-2-(diisopropylphosphanyl)phenol (1e): At –40 °C, a
hexane solution of nBuLi (21.0 mL, 1.6 , 33.6 mmol) was slowly
added to 2,4-di-tert-butylphenyl methoxymethyl ether (8.3 g,
33.2 mmol) in Et2O (60 mL). After stirring for 4 h at 20 °C, chloro-
diisopropylphosphane (5.0 g, 32.8 mmol) was rapidly added at 0
°C, the suspension was stirred for 1 h at room temperature, and
then filtered. The filtrate was concentrated to dryness and the res-
idue was treated with degassed 2  HCl (200 mL) at 60 °C. After
heating for 5 h, the volatiles were removed in vacuo and the residue
was crystallized from methanol. Yield 7.8 g (73%) of 1e as white
crystals; m.p. 67–68 °C. – IR (Nujol): ν˜OH ϭ 3322 cm–1 s. – 1H
derivatives. This is attributed to rapid dissociation–associ-
ation equilibria; 4 may additionally undergo rapid pseudo-
rotation. Both the expected unsaturated 14-electron species
I (or dimers thereof) and free PMe3 escape detection by
NMR because of their low concentrations (low equilibrium
constants). Nevertheless, alkylphenyl- or dialkylphosphanyl
derivatives of 2 and 4 have proved to be effective one-com-
ponent catalysts in the oligomerization of ethene. Since ad-
dition of ethene to 2 will be much less favorable than addi-
3
3
tion to I, and since electron-rich 2-dialkylphosphanylphen- NMR (C6D6): δ ϭ 0.86 (dd, JPH ϭ 12.2, JHH ϭ 6.9 Hz, 6 H,
3
3
CHMe), 1.00 (dd, JPH ϭ 16.5, JHH ϭ 7.0 Hz, 6 H, CHMe), 1.34
olates 2, which bind trimethylphosphane in a trans fashion
less tightly than 2-diphenylphosphanyl derivatives, form the
more efficient catalysts, I can be regarded as the active spe-
cies, which may even be formed by dissociation of 4. The
short chain lengths of the oligomers obtained with 2 as
compared to those of the polymers produced with catalysts
prepared in situ from 1 and Ni(COD)2[6a,11b,19] and the even
lower molecular weights of the oligomers formed with 4
suggest that β-hydride elimination is favored by coordina-
tion of PMe3 at a free coordination site of the catalyst.
3
2
(s, 9 H, CMe3), 1.60 (s, 9 H, CMe3), 1.94 (m, JHH ϭ 7, JPH
ca. 3.5 Hz, 2 H, CH), 7.22 (ps. t, JHH ϭ 2.4, JPH ϭ ca. 2.6 Hz, 1
ϭ
4
3
4
4
H, 3-H), 7.55 (d, JHH ϭ 2.4 Hz, 1 H, 5-H), 7.76 (d, JPH
ϭ
12.4 Hz, 1 H, OH). – 13C NMR (75.5 MHz, C6D6): δ ϭ 18.6 (d,
2JPC ϭ 7.0 Hz, CHMe), 20.0 (d, JPC ϭ 17.9 Hz, CHMe), 23.1 (d,
2
1JPC ϭ 6.9 Hz, CHMe), 29.8 (CMe3), 31.8 (CMe3), 34.5 (CMe3),
35.4 (d, 4JPC ϭ 2.0 Hz, CMe3), 117.8 (d, 1JPC ϭ 5.2 Hz, C-2), 125.6
2
3
(C-5), 127.1 (d, JPC ϭ 1.1 Hz, C-3), 135.2 (d, JPC ϭ 1.7 Hz, C-
6), 141.2 (C-4), 158.1 (d, JPC ϭ 18.8 Hz, C-1). – 31P{1H} NMR
2
(121.5 MHz, C6D6): δ ϭ –24.3. – MS (EI, 70 eV): m/z: 323 [Mϩ],
436
Eur. J. Inorg. Chem. 2000, 431Ϫ440

Methyl(2-phosphanylphenolato[P,O])nickel(II) Complexes
FULL PAPER
307 [Mϩ – CH3], 281 [Mϩ – C3H6], 266 [Mϩ – tBu], 239 [Mϩ
2 C3H6], 57 [tBu]. – C20H35OP (322.47): calcd. C 74.49, H 10.94;
found C 74.19, H 10.97.
–
(900 mg, 2.49 mmol) in Et2O (80 mL), resulting in a color change
to orange. After stirring for 3 h, the solvent was evaporated in va-
cuo and the residue was extracted with warm pentane. On cooling
of the combined extracts, yellow crystals of 2b were deposited.
Yield 2.05 g (83%); dec. at 129 °C. – IR (Nujol): ν˜ ϭ 1166 s (NiMe),
956 cm–1 s (ρ1 PMe3). – 1H NMR (300 MHz, [D8]THF): δ ϭ –0.82
(d, 3JPH ϭ 7.4 Hz, 3 H, NiMe), 1.34 (s, 9 H, CMe3), 1.37 (d, 2JPH ϭ
4-Fluoro-2-(diisopropylphosphanyl)phenol (1f): At –40 °C, nBuLi
(38.5 mL 1.6
 in hexane, 61.5 mmol) was added to 9.6 g
(61.5 mmol) of 4-fluorophenyl methoxymethyl ether in Et2O
(100 mL) and the mixture was allowed to warm to room temper-
ature. After 2 h, chlorodiisopropylphosphane (9.4 g, 61.6 mmol)
was added. The resulting suspension was stirred for 1 h at 20 °C
and then filtered. The filtrate was concentrated to dryness and the
residue was treated with degassed aqueous 2  HCl solution as
above. After 5 h at 60 °C, the volatiles were removed in vacuo. The
residue was crystallized from methanol to give 4.9 g (35%) of 1f as
white needles; m.p. 61–64 °C. – IR (Nujol): ν˜OH ϭ 3302 cm–1 s. –
3
8.6 Hz, 9 H, PMe3), 2.07 (s, 3 H, 4-Me), 6.75 (d, JPH ϭ 7.4 Hz, 1
H, 3-H), 6.85 (d, 5JPH ϭ 1.7 Hz, 1 H, 5-H), 7.39 (m, 6 H, Ph), 7.65
(m, 4 H, Ph). – 13C NMR (75.5 MHz, [D8]THF): δ ϭ –20.3 (d,
1
2JPC ϭ 25.1 Hz, NiMe), 12.7 (d, JPC ϭ 22.2 Hz, PMe3), 20.7 (s,
1
4-Me), 29.7 (CMe3), 35.4 (CMe3), 118.3 (d, JPC ϭ 48.6 Hz, C-2),
122.0 (d, 3JPC ϭ 7.0 Hz, C-4), 129.1 (d, 3JPC ϭ 9.2 Hz, m-C), 130.2
2
(C-5), 130.4 (p-C), 131.2 (C-3), 134.1 (d, JPC ϭ 11.2 Hz, o-C),
134.5 (d, 1JPC ϭ 47.0 Hz, i-C), 138.4 (d, 3JPC ϭ 9.1 Hz, C-6), 173.8
3
3
1H NMR (300.1 MHz, C6D6): δ ϭ 0.70 (dd, JPH ϭ 12.5, JHH
ϭ
2
(d, JPC ϭ 25.8 Hz, C-1). – 31P NMR (81 MHz, [D8]THF): δ ϭ
3
3
6.9 Hz, 6 H, CHMe), 0.89 (dd, JPH ϭ 16.5, JHH ϭ 7.0 Hz, 6 H,
CHMe), 1.68 (m, 3JHH ϭ 7, 2JPH ϭ ca. 3.5 Hz, 2 H, CH), 6.73 (m,
3JHH ϭ 9.0, 3JFH ϭ 8.1, 4JHH ϭ 3.1 Hz, 1 H, 5-H), 6.82 (m, 3JHH ϭ
2
2
–7.4 (br. d, JPP ϭ 286 Hz, PMe), 32 (br. d, JPP ϭ 259 Hz, o-P);
trace impurity: δ ϭ 0.5 (d, JPP ϭ 14.9 Hz, PMe), 32.3 (d, JPP
ϭ
14.7 Hz, o-P). – Low-temperature NMR: 31P NMR (81 MHz,
4
4
3
9.0, JFH ϭ 5.1, JPH ϭ 3.9 Hz, 1 H, 6-H), 6.91 (m, JFH ϭ 8.3,
2
4JHH JPH 2.8 Hz, 1 H, 3-H), 7.02 (br. s, 1 H, OH). – 13C NMR
3
[D8]THF, 223 K): δ ϭ –5.6 (d, JPP ϭ 316 Hz, PMe), 32.1 (d,
2JPP ϭ 316 Hz, o-P); trace impurity: δ ϭ 2.0 (d, JPP ϭ 14.6 Hz,
PMe), 32.0 (d, JPP ϭ 14.8 Hz, o-P). – C27H36NiOP2 (497.22): calcd.
C 65.22, H 7.30, P 12.46; found C 64.83, H 7.78, P 12.31.
2
(75.5 MHz, C6D6): δ ϭ 19.3 (d, JPC ϭ 7.6 Hz, CHMe), 20.5 (d,
2JPC ϭ 18.0 Hz, CHMe), 23.8 (d, JPC ϭ 7.7 Hz, CHMe), 117.2
1
3
3
2
(dd, JFC ϭ 7.2, JPC ϭ 1.7 Hz, C-6), 119.0 (dd, JFC ϭ 21.1,
2JPC ϭ 1.7 Hz, C-3), 119.0 (d, JFC ϭ 23.1 Hz, C-5), 120.8 (dd,
2
{4,6-Di-tert-butyl-2-(isopropylphenylphosphanyl)phenolato[P,O]}-
methyl(trimethylphosphane)nickel(II) (2c): At –78 °C, THF (80 mL)
was condensed into a mixture of 1c (0.90 g 2.52 mmol) and cis-
[NiMe(PMe3)(µ-OMe)]2 (0.46 g, 1.27 mmol). On warming to room
temperature the mixture became orange in color. The solvent was
then replaced by pentane (60 mL). Crystallization furnished 0.28 g
(22%) of yellow microcrystalline 2c; m.p. 88–90 °C (dec.). An addi-
tional portion of orange, powdery 2c was obtained by removal of
the solvent from the mother liquor to give a total yield of 0.94 g
(74%) of 2c. – IR (Nujol): ν˜ ϭ 1138 m (NiMe), 953 cm–1 s (ρ1
PMe3). – 1H NMR (200 MHz, [D8]THF, 296 K): δ ϭ –0.93 (d,
3JPH ϭ 1.8 Hz, 3 H, NiMe), 0.98–1.24 (m, 12 H, CHMeA, CMe3),
1.30–1.45 (m, 21 H, CHMeB, CMe3, PMe3), 2.67 (m, 1 H, CH),
3
1
1JPC ϭ 4.5, JFC ϭ 12.4 Hz, C-2), 157.6 (d, JFC ϭ –239.7 Hz, C-
4), 158.7 (dd, JPC ϭ 18.7, JFC ϭ 1.7 Hz, C-1). – 31P{1H} NMR
(121.5 MHz, C6D6): δ ϭ –21.8. – MS (EI, 70 eV): m/z: 228 [Mϩ],
186 [Mϩ – C3H6], 144 [Mϩ – 2 C3H6], 111 [Mϩ – PiPr2]. –
C12H18FOP (228.25): calcd. C 63.15, H 7.95; found C 63.01, H
7.91.
2
4
Preparation of Complexes
{4,6-Di-tert-butyl-2-(diphenylphosphanyl)phenolato[P,O]}methyl-
(trimethylphosphane)nickel(II) (2a): At –78 °C, 1a (649 mg,
1.66 mmol) was added to a solution of cis-[NiMe(PMe3)(µ-OMe)]2
(300 mg, 0.83 mmol) in Et2O (60 mL). A rapid color change from
yellow-brown to red was observed and after 3 h the mixture became
orange. The solvent was then removed in vacuo and the residue
was extracted with warm pentane, from which 580 mg (65%) of 2a
was obtained as yellow crystals; dec. at 162–163 °C. 2a was found
2
6.93 (m, 1 H, 3-H), 7.13 (d, JPH ϭ 2.4 Hz, 1 H, 5-H), 7.39 (m, 3
H, Ph), 7.64 (m, 2 H, Ph). – 13C NMR (75.5 MHz, [D8]THF): δ ϭ –
1
22.2 (m, NiMe), 10.8 (d, JPC ϭ 22.2 Hz, PMe3), 16.0 (br., Me),
1
17.6 (br., Me), 24.2 (d, JPC ϭ 37.2 Hz, CH), 27.8 (CMe3), 30.3
to be slightly contaminated with 3a. – IR (Nujol): ν˜ ϭ 955 cm–1
s
(CMe3), 32.6 (CMe3), 33.8 (CMe3), 113.6 (m, C-2), 124.9 (C-5),
2
(ρ1 PMe3). – 1H NMR (300 MHz, [D8]THF): δ ϭ –0.82 (d, 3JPH ϭ
125.2 (C-3), 127.2 (d, 9.0 Hz, m-C), 128.1 (p-C), 131.2 (d, JPC
ϭ
4
9.0 Hz, o-C), 131.9 (C-4), ca. 133 (i-C), 135.6 (d, JPC ϭ 9.0 Hz,
7.4 Hz, 3 H, NiMe), 1.15 (s, 9 H, PMe3), 1.34, 1.38 (2 s, 18 H, 2
C-6), 174.3 (d, JPC ϭ 23.4 Hz, C-1). – 31P NMR (81 MHz,
2
3
CMe3), 6.95 (d, JPH ϭ 8.0 Hz, 1 H, 3-H), 7.12 (s, 1 H, 5-H), 7.39
2
2
(m, 6 H, Ph), 7.65 (m, 4 H, Ph). – 13C NMR (75.5 MHz, [D8]THF):
[D8]THF): δ ϭ –8.0 (d, JPP ϭ 310 Hz, PMe), 40.0 (d, JPP
ϭ
2
1
308 Hz, 2-P). – C27H44NiOP2 (505.29): calcd. C 64.18, H 8.78, P
12.26; found C 63.64, H 8.55, P 12.56.
δ ϭ –19.9 (d, JPC ϭ 25 Hz, NiMe), 10.8 (d, JPC ϭ 22.5 Hz,
PMe3), 27.9 (CMe3), 30.3 (CMe3), 32.6 (CMe3), 33.9 (CMe3), 115.9
(d, 1JPC ϭ 49.1 Hz, C-2), 124.7 (C-5), 125.5 (C-3), 127.3 (d, 3JPC ϭ
{4,6-Di-tert-butyl-2-(tert-butylphenylphosphanyl)phenolato[P,O]}-
methyl(trimethylphosphane)nickel(II) (2d): At –78 °C, 1d (1.13 g,
3.05 mmol) was added to a solution of [NiMe(PMe3)(µ-OMe)]2
(1.10 g, 3.04 mmol) in diethyl ether (80 mL). After stirring for 3 h
at room temperature, the solvent was removed in vacuo from the
dark-red solution and the residue was extracted with pentane. On
cooling of the combined extracts, 1.15 g (73%) of 2d was deposited
as red-brown crystals; m.p. 78–79 °C. – IR (Nujol): ν˜ ϭ 1138 m
2
9.5 Hz, m-C), 128.6 (p-C), 132.2 (d, JPC ϭ 11.4 Hz, o-C), 132.6
(C-4), 133.5 (d, 1JPC ϭ 47.7 Hz, i-C), 135.9 (C-6), 173.6 (d, 2JPC
ϭ
25.1 Hz, C-1). – 31P NMR (81 MHz, [D8]THF): δ ϭ –10.7 (br. s,
PMe), 32.9 (br. s, 2-P). – Low-temperature NMR: 1H NMR
(200 MHz, [D8]THF, 208 K): δ ϭ –0.83 (m, 3 H, NiMe), 1.15 (s, 9
H, PMe3), 1.35 (s, 9 H, CMe3), 1.39 (s, 9 H, CMe3), 7.00 (d, 3JPH ϭ
8.6 Hz, 1 H, 3-H), 7.09 (s, 1 H, 5-H), 7.46 (m, 6 H, Ph), 7.64 (m,
4 H, Ph). – 31P NMR (81 MHz, [D8]THF, 223 K): 2a: δ ϭ –6.1 (d,
1
(NiMe), 952 cm–1 s (ρ1 PMe3). – H NMR (300 MHz, [D8]THF):
2
2JPP ϭ 316 Hz, PMe), 32.7 (d, JPP ϭ 316 Hz, 2-P); trace impurit-
δ ϭ –0.88 (d, 3JPH ϭ 7.5 Hz, 3 H, NiMe), 1.24 (s, 9 H, CMe3), 1.30
3
ies: δ ϭ 1.4 (d, JPP ϭ 15.9 Hz), 32.9 (d, JPP ϭ 15.9 Hz), 42.1 (3a). –
C30H42NiOP2 (539.30): calcd. C 66.81, H 7.85, P 11.49; found C
66.24, H 7.68, P 11.76.
(br. s, 9 H, PMe3), 1.39 (s, 9 H, CMe3), 1.44 (d, JPH ϭ 13.7 Hz, 9
3
4
H, PCMe3), 7.01 (dd, JPH ϭ 7.8, JHH ϭ 2.5 Hz, 1 H, 3-H), 7.17
4
(d, JHH ϭ 2.5 Hz, 1 H, 5-H), 7.43 (m, 3 H, Ph), 7.88 (m, 2 H,
{6-tert-Butyl-4-methyl-2-(diphenylphosphanyl)phenolato[P,O]}- Ph). – 13C NMR (75.5 MHz, [D8]THF): δ ϭ –21.1 (br. d, JPC
ϭ
2
1
2
methyl(trimethylphosphane)nickel(II) (2b): At –78 °C, 1b (1.73 g, 25 Hz, NiMe), 12.8 (d, JPC ϭ 20.4 Hz, PMe3), 28.9 (d, JPC
ϭ
4.97 mmol) was added to a solution of cis-[NiMe(PMe3)(µ-OMe)]2
Eur. J. Inorg. Chem. 2000, 431Ϫ440
5.3 Hz, PCMe3), 29.7 (CMe3), 32.2 (CMe3), 34.4 (CMe3), 35.4 (d,
437

J. Heinicke, H.-F. Klein, W. Keim et al.
FULL PAPER
1
1JPC ϭ 21.1 Hz, PCMe3), 35.7 (CMe3), 117.2 (d, JPC ϭ 44.5 Hz,
trans-Bis{4,6-di-tert-butyl-2-(diisopropylphosphanyl)phenolato-
3
C-2), 126.8 (C-5), 127.4 (C-3), 128.9 (d, JPC ϭ 9 Hz, m-C), 129.9 [O,P]}nickel(II)
(p-C), 133.0 (d, JPC ϭ 33.2 Hz, i-C), 134.1 (d, JPC ϭ 8.3 Hz, o-
(3e):
cis-[NiMe(PMe3)(µ-OMe)]2
(0.43 g,
1
2
1.19 mmol) was dissolved in THF (60 mL) and the solution was
cooled to –50 °C. 1e (0.98 g, 3.04 mmol) was then added, resulting
in a color change from brown through orange to yellow-green.
After stirring for 1 h at room temperature, the solvent was removed
in vacuo. The residue was extracted with pentane (40 mL) and crys-
3
3
C), 134.6 (d, JPC ϭ 6.1 Hz, C-4), 137.5 (d, JPC ϭ 8.3 Hz, C-6),
175.3 (d, JPC ϭ 23.4 Hz, C-1). – 31P NMR (81 MHz, [D8]THF):
2
2
2
δ ϭ –8.0 (br. d, JPP ϭ 293.7 Hz, PMe), 47.8 (br. d, JPP
307.7 Hz, 2-P); trace impurities: δ ϭ –0.9 (d, JPP ϭ 13.9 Hz), 52.6
(d, JPP ϭ 13.6 Hz), 35.2 (3d). – Low-temperature NMR: H NMR tallized from this solvent yielding 0.84 g (79%) of 3e as green crys-
(200 MHz, [D8]THF, 248 K): δ ϭ –0.93 (dd, JPH ϭ 11.2, JP’H
ϭ
1
3
3
ϭ
tals; m.p. 228–230 °C (with color change to brown), dec. at 234
1
7.6 Hz, 3 H, NiMe), 1.20 (s, 9 H, CMe3), 1.31 (s, 9 H, PMe3), 1.34
°C. – H NMR (300 MHz, C6D6): δ ϭ 1.38 (s, 18 H, CMe3), 1.35
3
3
(s, 9 H, CMe3), 1.38 (d, JPH ϭ 13.8 Hz, 9 H, PCMe3), 6.97 (dd,
(τd, N ϭ 14.2, JHH ϭ 7.0 Hz, 12 H, MeA), 1.49 (s, 18 H, CMe3),
4JHH ϭ 2, JPH ϭ 7.7 Hz, 1 H, 3-H), 7.11 (d, JHH ϭ 2 Hz, 1 H, 1.64 (τd, N ϭ 16.8, 3JHH ϭ 7.4 Hz, 12 H, MeB), 2.36 (m, 4 H, CH),
3
4
5-H), 7.42 (m, 3 H, Ph), 7.83 (m, 2 H, Ph). – 31P NMR (81 MHz, 7.18 (τd, N 8, JHH ϭ 2.3 Hz, 2 H, 3-H), 7.39 (d, JHH ϭ 2.3 Hz,
4
4
[D8]THF, 245 K): δ ϭ –6.5 (d, JPP ϭ 308.3 Hz, PMe), 47.9 (d, 2 H, 5-H). – 13C NMR (75.5 MHz, C6D6): δ ϭ 18.2 (s, CMeA),
2
2JPP ϭ 308.5 Hz, o-P); trace impurities: δ ϭ 0.5 (d), 52.3 (d), 34.9 19.5 (τ, N ϭ 6.0 Hz, CMeB), 24.8 (τ, N ϭ 22.0 Hz, CH), 29.8
(3d). – C28H46NiOP2 (519.31): calcd. C 64.76, H 8.93, P 11.93; (CMe3), 32.1 (CMe3), 34.0 (CMe3), 35.3 (CMe3), 113.1 (τ, N ϭ
found C 64.75, H 7.83, P 11.85.
42.6 Hz, C-2), 125.3 (C-5), 126.9 (C-3), 136.2 (τ, N ϭ 6.4 Hz, C-
4), 138.5 (τ, N ϭ 7.4 Hz, C-6), 175.2 (τ, N ϭ 30.5 Hz, C-1). – 31P
NMR (121.5 MHz, C6D6): δ ϭ 37.7. – MS (70 eV): m/z (%) ϭ 701
(100) [Mϩ], 336 (24) [M – Lig – iPrϩ], 321 (31) [Lig – Hϩ], 280 (22)
[Lig – iPrϩ] (Lig ϭ 1e-Hϩ). – C40H68NiO2P2 (701.62): calcd. C
68.48, H 9.77; found C 68.48, H 9.86.
{4,6-Di-tert-butyl-2-(diisopropylphosphanyl)phenolato[O,P]}-
methyl(trimethylphosphane)nickel(II) (2e): At –78 °C, 1e (1.42 g,
4.4 mmol) and PMe3 (0.34 g, 4.4 mmol) were added to a solution
of cis-[NiMe(PMe3)(µ-OMe)]2 (0.80 g, 2.2 mmol) in diethyl ether
(50 mL). After stirring for 3 h at room temperature (color change
through red to brown), the solvent was evaporated in vacuo and
the residue was treated with a small volume of pentane, yielding
1.78 g (86%) of 2e as red-brown crystals; m.p. 79–81 °C. – 1H NMR
(300.1 MHz, C6D6): δ ϭ –0.66 (d, 3JPH ϭ 7.4 Hz, 3 H, NiMe), 1.01
{4,6-Di-tert-butyl-2-(diphenylphosphanyl)phenolato[O,P]}-
methylbis(trimethylphosphane)nickel(II) (4a): At –78 °C, 1a
(945 mg, 2.42 mmol) was added to a solution of NiMe2(PMe3)3
(800 mg, 2.52 mmol) in Et2O (60 mL). On warming to room tem-
perature and stirring for 3 h, the color of the mixture turned from
yellow-brown to dark-red. Crystallization from diethyl ether con-
taining PMe3 furnished 1.06 g (71%) of 4a as red crystals; m.p. 109
°C. – IR (Nujol): ν˜ ϭ 1159 m (NiCH3), 937 cm–1 s (ρ1 PMe3). –
1H NMR (300 MHz, [D8]THF): δ ϭ –0.69 (d, 3JPH ϭ 8.8 Hz, 3 H,
2
3
3
(d, 9 H, JPH ϭ 8.1 Hz, PMe3), 1.21 (dd, JPH ϭ 13.7, JHH
ϭ
3
3
7.0 Hz, CHMea), 1.30 (dd, JPH ϭ 15.6, JHH ϭ 7.1 Hz, CHMeb),
1.43 (s, 9 H, CMe3), 1.65 (s, 9 H, CMe3), 2.21 (m, 2 H, CHMe2),
7.19 (d, 4JHH ϭ 2.5 Hz, partly superimposed, 3-H), 7.54 (d, 4JHH ϭ
2.5 Hz, 1 H, 5-H). – 13C NMR (75.5 MHz, C6D6): δ ϭ –24.9 (d,
2JPC ϭ 28.1 Hz, 3 H, NiMe), 13.0 (d, 1JPC ϭ 21.2 Hz, PMe3), 18.8
2
NiMe), 1.12 (s, 9 H, CMe3), 1.15 (d, JPH ϭ 3.3 Hz, 18 H, PMe3),
1.34 (s, 9 H, CMe3), 7.03 (br. d, 3JPH ϭ 8.4 Hz, 1 H, 3-H), 7.09 (d,
5JPH ϭ 2.3 Hz, 1 H, 5-H), 7.35 (m, 6 H, Ph), 7.62 (m, 4 H, Ph). –
13C NMR (75.5 MHz, [D8]THF, 293 K): δ ϭ –18.8 (br., NiMe),
2
1
(CMea), 19.7 (d, JPC ϭ 4.8 Hz, CMeb), 24.8 (d, JPC ϭ 22.8 Hz,
CH), 30.4 (CMe3), 32.9 (CMe3), 34.8 (CMe3), 36.2 (CMe3), 115.8
(d, 1JPC ϭ 41.2 Hz, C-2), 125.4 (C-5), 127.4 (C-3), 135.2 (d, 3JPC ϭ
1
12.5 (d, JPC ϭ 6.5 Hz, PMe3), 28.1 (CMe3), 30.3 (CMe3), 32.6
3
2
5.3 Hz, C-4), 137.9 (d, JPC ϭ 8.3 Hz, C-6), 176.2 (d, JPC
ϭ
1
(CMe3), 34.0 (CMe3), 117.1 (d, JPC ϭ 45.8 Hz, C-2), 125.0 (C-5),
22.0 Hz, C-1). – 31P NMR (121.5 MHz, C6D6, 298 K): δ ϭ –15.4
3
125.3 (C-3), 127.1 (d, JPC ϭ 9.3 Hz, m-C), 128.0 (p-C), 132.0 (d,
(br. s, PMe), 39.6 (br. s, 2-P); trace impurity: δ ϭ 31.4 (br. s). – 31P
3
2JPC ϭ 11.7 Hz, o-C), 133.3 (d, JPC ϭ 5.0 Hz, C-4), 134.5 (d,
2
NMR (121.5 MHz, [D8]toluene, 203 K): δ ϭ –13.2 (d, JPP
ϭ
3
1JPC ϭ 36.5 Hz, i-C), 136.1 (d, JPC ϭ 8.9 Hz, C-6), 173.3 (d,
305 Hz, PMe), 39.6 (d, 2JPP ϭ 305 Hz, 2-P). – MS (EI, 70 eV): m/z
(%) ϭ 470 (10) [Mϩ]. – C24H46NiOP2 (471.27): calcd. C 61.17, H
9.84; found C 60.34, H 9.65.
2JPC ϭ 28.1 Hz, C-1). – 31P NMR (81 MHz, [D8]THF): δ ϭ –28.5
(br. s, PMe3), 27.0 (br. s, o-P); trace impurity: δ ϭ –15.9 (s), 41.4
(s). – Low-temperature NMR: 13C NMR (75.5 MHz, [D8]THF,
2
1
243 K): δ ϭ –16.4 (d, JPC ϭ 19.6 Hz, NiMe), 15.4 (d, JPC
ϭ
{4-Fluoro-2-(diisopropylphosphanyl)phenolato[O,P]}-
methyl(trimethylphosphane)nickel(II) (2f): At –78 °C, 1f (0.23 g,
1.01 mmol) was added to a solution of cis-[NiMe(PMe3)(µ-OMe)]2
(0.21 g, 0.58 mmol) in pentane (30 mL) and the resulting mixture
was stirred for 1 h at room temperature (color change through red
to yellow). The solvent was then evaporated in vacuo and the res-
9.8 Hz, PMe3), 30.2 (CMe3), 32.2 (CMe3), 34.5 (CMe3), 35.9
1
(CMe3), 120.4 (d, JPC ϭ 43.0 Hz, C-2), 126.0 (C-5), 127.8 (C-3),
3
2
128.9 (d, JPC ϭ 8.1 Hz, m-C), 129.3 (p-C), 133.5 (d, JPC
ϭ
11.9 Hz, o-C), 134.0 (br., C-4), 138.0 (d, 3JPC ϭ 8.9 Hz, C-6), 138.6
(d, JPC ϭ 30.0 Hz, i-C), 174.8 (d, JPC ϭ 31.1 Hz, C-1). –
C33H51NiOP3 (615.38): calcd. C 64.41, H 8.35, P 15.10; found C
64.67, H 8.06, P 15.18.
1
2
idue was extracted with diethyl ether to afford 228 mg (60%) of
yellow 2f. – 1H NMR (300.1 MHz, C6D6): δ ϭ –0.73 (d, JPH
ϭ
3
7.9 Hz, 3 H, NiMe), 0.93 (d, 2JPH ϭ 8.4 Hz, 9 H, PMe3), 1.06 (dd,
{4,6-Di-tert-butyl-2-(tert-butylphenylphosphanyl)phenolato-
3
3
3JPH ϭ 13.8, JHH ϭ 7.1 Hz, 6 H, CHMea), 1.21 (dd, JPH ϭ 15.8, [O,P]}methylbis(trimethylphosphane)nickel(II) (4d): At –78 °C, 1d
3JHH ϭ 7.1 Hz, 6 H, CHMeb), 1.96 (m, 2 H, CHMe2), 6.75 (dτ, (945 mg, 2.55 mmol) was added to a solution of NiMe2(PMe3)3
3JHH ϭ 8.9, JPH and JFH ϭ ca. 4.5–4.7 Hz, 1 H, 6-H), 6.87–6.98
(800 mg, 2.52 mmol) in Et2O (60 mL) and the mixture was stirred
(m, 2 H, 3-H, 5-H). – 13C NMR (75.5 MHz, C6D6): δ ϭ –26.1 (d, for 3 h at room temperature. The bulk of the solvent was then re-
2JPC ϭ 26.8 Hz, 3 H, NiMe), 11.3 (d, 1JPC ϭ 22.4 Hz, PMe3), 17.9 moved. Crystallization of the residue from diethyl ether containing
(Mea), 18.8 (d, 2JPC ϭ 5.2 Hz, Meb), 23.9 (d, 1JPC ϭ 21.9 Hz, CH),
PMe3 furnished 1.07 g (71%) of 4d as dark-red crystals; m.p. 106–
1
2
115.4 (d, JPC ϭ 38.3 Hz, C-2), 115.8 (d, JFC ϭ 21.7 Hz, C-5), 109 °C. – IR (Nujol): ν˜ ϭ 1157 m (NiCH3), 937 cm–1 s (ρ1 PMe3). –
3
3
2
118.8 (ps. t, JPC and JFC ϭ ca. 8 Hz, C-6), 120.0 (d, JFC
ϭ
1H NMR (300 MHz, [D8]THF): δ ϭ –0.87 (d, 3JPH ϭ 8.1 Hz, 3 H,
1
3
23.4 Hz, C-3), 153.3 (dd, JFC ϭ 230.8, JPC ϭ 6.4 Hz, C-4), 176.0
NiMe), 1.22 (s, 9 H, CMe3), 1.25 (br. s, 18 H, PMe3), 1.34 (s, 9 H,
(d, JPC ϭ 21.6 Hz, C-1). – 31P NMR (121.5 MHz, C6D6, 298 K): CMe3), 1.36 (d, JPH ϭ 12.8 Hz, 9 H, PCMe3), 7.06 (dd, JPH
ϭ
2
3
3
4
4
δ ϭ –14.6 (s, PMe), 38.7 (s, 2-P). – C16H29FNiOP2 (377.04).
7.4, JHH ϭ 2.5 Hz, 1 H, 3-H), 7.12 (d, JHH ϭ 2.5 Hz, 1 H, 5-H),
438
Eur. J. Inorg. Chem. 2000, 431Ϫ440

Methyl(2-phosphanylphenolato[P,O])nickel(II) Complexes
FULL PAPER
7.37 (m, 3 H, Ph), 7.81 (m, 2 H, Ph). – 13C NMR (75.5 MHz,
3e: A green crystal of 3e was sealed under argon in a capillary;
[D8]THF): δ ϭ –20.7 (d, 2JPC ϭ 22.7 Hz, NiMe), 15.1 (br. s, PMe3), data were collected as above on a Bruker P4 diffractometer. Lattice
2
28.5 (d, JPC ϭ 5.3 Hz, PCMe3), 29.3 (CMe3), 31.7 (CMe3), 33.9 parameters were refined from 28 reflections in the range 15 Յ 2Θ Յ
1
(CMe3), 35.0 (d, JPC ϭ 20.4 Hz, PCMe3), 35.2 (CMe3), 117.3 (d,
40°. During data collection, 3 standard reflections were checked
every 397 intensities and were found to show only random devi-
3
1JPC ϭ 43.0 Hz, C2), 125.9 (C-5), 127.2 (C-3), 128.3 (d, JPC
ϭ
2
8.3 Hz, m-C), 128.9 (p-C), 133.2 (d, JPC ϭ 8.3 Hz, o-C), 133.6 (d, ations. Lorentz and polarization corrections were applied, as well
1
3JPC ϭ 5.3 Hz, C-4), 133.8 (d, JPC ϭ 29.4 Hz, i-C), 137.1 (d, as an absorption correction based on psi-scans. The structure was
2
3JPC ϭ 9.1 Hz, C-6), 174.7 (d, JPC ϭ 24.9 Hz, C-1). – 31P NMR
solved by direct and conventional Fourier methods, with full-mat-
(81 MHz, [D8]THF): δ ϭ –28.0 (v br. s, PMe3), 44.4 (br. s, o-P). – rix least-squares refinement based on F2. All atoms other than the
C31H55NiOP3 (595.39): calcd. C 62.54, H 9.31, P 15.61; found C
62.06, H 9.11, P 15.31.
H-atoms and disordered C-atoms were refined anisotropically. The
tert-butyl group C7–C102 and the isopropyl group C19–C21 were
each found to be disordered over two sites and were refined with a
split model. Site occupancy factors were refined to 0.43(1) and
0.57(1) for the tert-butyl group and to 0.29(1) and 0.71(1) for the
isopropyl group, respectively. Hydrogen atoms were refined at
idealized positions with a riding model. Further crystallographic
and refinement data are given in Table 4; selected bond lengths and
angles are indicated in Figure 2.
Complex-Catalyzed Oligomerization of Ethene. – General Proced-
ure: A solution of the appropriate nickel complex 2 or 4 (ca.
0.1 mmol) in toluene (12 mL) was transferred at room temperature
into an argon-filled stainless steel autoclave (75 mL) equipped with
a magnetic stirrer. Ethene was introduced with stirring until the
pressure remained constant at 35 bar (7.5–7.8 g by weight differ-
ence), then the valve was closed and the autoclave was heated at
80 °C for 6–10 h. After cooling to ca. 20 °C and weight control,
the valve was opened and the gases were passed through a cooling
trap (–60 °C) to condense gaseous butenes. The remaining material
4a: A red crystal of 4a was sealed under argon in a glass capillary.
Data collection was performed as described for 3e. Lattice para-
was flash distilled at 25–30 °C/10–2 Torr to separate volatile oligo- meters were refined from 25 reflections in the range 17 Յ
mers (condensed at –60 °C) and waxes. The former were analyzed
by GC and in some cases by GC/MS. The results are summarized
in Table 2 and 3.
2Θ Յ 34°. Standard reflections showed a decrease of 7%. Lorentz,
polarization, and absorption corrections were applied as above.
Structure solution and refinement and the positioning of the hydro-
gen atoms was as described above. Further crystallographic and
refinement data are given in Table 4; selected bond lengths and
angles are indicated in Figure 3.
Crystal Structure Analysis
1e: A crystal of 1e was sealed under argon in a glass capillary,
mounted on a Siemens R3m/V diffractometer, and examined using
α
˚
graphite-monochromated Mo-K radiation, λ ϭ 0.71073 A. Lattice
Crystallographic data (excluding structure factors) have been de-
posited with the Cambridge Crystallographic Data Centre. Copies
parameters were determined from 25 selected reflections. The struc-
ture was solved by
a full-matrix least-squares refinement of the data [CCDC-136785 (1e)], [CCDC-135904 (3e)], [CCDC-
(SHELXL-97). Non-hydrogen atoms were treated anisotropically,
hydrogen atoms were fixed in idealized positions. Crystal data are
presented in Table 4; selected bond lengths and angles are indicated
in Figure 1.
135905 (4a)] can be obtained free of charge on application
to the CCDC, 12 Union Road, Cambridge CB2 1EZ,
U.K.
[Fax:
(internat.)
ϩ44
(0)1223/336033;
E-mail:
deposit@chemcrys.cam.ac.uk].
Table 4. Crystallographic data of compounds 1e, 3e, and 4a
1e
3e
4a
Empirical formula
Molecular mass
Crystal size [mm3]
Crystal system
C20H35OP
322.47
0.49 ϫ 0.56 ϫ 0.39
Monoclinic
P21/c
C40H68NiO2P2
701.59
0.58 ϫ 0.55 ϫ 0.50
Orthorhombic
Pbca
C33H51NiOP3
615.36
0.35 ϫ 0.21 ϫ 0.10
Triclinic
Space group
P-1
Unit cell dimensions
˚
a [A]; α [°]
11.2190(4); 90
10.0580(6); 90.8(3)
18.9040(8); 90
2132.93(17); 4
1.004
10.425(2); 90
18.611(2); 90
21.529(6); 90
4177.0(15); 4
1.116
9.646(2); 98.90(2)
10.236(2); 95.86(2)
18.837(4); 107.24(2)
1733.2(6); 2
1.179
˚
b [A]; β [°]
˚
c [A]; γ [°]
3
˚
V [A ]; Z
Density (calcd.) [Mg/m3]
Temperature [K]
193
298(2)
293(2)
Absorption coefficient [mm–1]
F(000)
0.097
0.570
0.720
712
1528
660
θ range for data collection [°]
Limiting indices
2.00 to 17.50
–9 h 9
0 k 8
2.38 to 27.50
–1 h 13
2.22 to 25.00
–12 h 12
–13 k 13
0 l 24
–1 k 24
0 l 15
–27 l 1
Reflections collected
3384
5889
6289
Independent reflections
Absorption correction
Max./min. transmission
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I Ͼ 2σ(I) ]
R indices (all data)
1357
4788 (Rint ϭ 0.0176)
Psi-scan
6094 (Rint ϭ 0.0564)
Psi-scan
–
0.779/0.748
4788/332/203
1.023
0.883/0.805
3122/11/356
1.034
1357/3/111
1.144
R1 ϭ 0.077; wR2 ϭ 0.2364
R1 ϭ 0.1018; wR2 ϭ 0.2795
R1 ϭ 0.0599, wR2 ϭ 0.1491
R1 ϭ 0.1016, wR2 ϭ 0.1732
0.566/–0.355 eA
R1 ϭ 0.0540, wR2 ϭ 0.1093
R1 ϭ 0.1423, wR2 ϭ 0.1434
0.321/–0.348 eA
–3
–3
–3
˚
˚
˚
Largest diff. peak and hole
0.39/–0.41 eA
Eur. J. Inorg. Chem. 2000, 431Ϫ440
439

J. Heinicke, H.-F. Klein, W. Keim et al.
FULL PAPER
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Heiden, Institut für Chemie und Biochemie, Universität Greifs-
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