Nickel chelate complexes of 2-alkylphenylphosphanylphenolates: Synthesis, structural investigation and use in ethylene polymerization

Article abstract of DOI:10.1002/(sici)1099-0682(200002)2000:2<299::aid-ejic299>3.0.co;2-j

2-Diphenylphosphanyl- and 2-alkylphenylphosphanyl-4-methylphenols 1 or their silyl ethers 2 and equimolar amounts of nickelocene react in benzene preferably to give orange-brown diamagnetic cyclopentadienylnickel chelate complexes [η-CpNi(P(intersection set)O)] (3). Addition of a second equivalent of 1 or 2 affords (RR) and (SS) diastereoisomers of cis- bis(P(intersection set)O-chelates) 4a-c (R = Ph, Me, iPr) or the unsymmetrical cis-bis(P(intersection set)O-chelate) 5, whereas with bulkier substituted derivatives 1d or 2d (R = tBu) the second step is hindered or retarded. The reactivity of 1d remains high towards nickel salts in polar solvents, but in contrast to 1a-c, yielding 4, a sparingly soluble green trans-bis(P-O-chelate) nickel complex 6d is formed. Complexes formed in situ from 1 or 2 and Ni(COD)₂ in toluene catalyze the polymerization of ethylene. The cyclopentadienyl (P(intersection set)O) complexes 3, however, are too stable to be active in this process. The crystal and molecular structure of 3c and 4c are described.

Full text of DOI:10.1002/(sici)1099-0682(200002)2000:2<299::aid-ejic299>3.0.co;2-j

FULL PAPER
Nickel Chelate Complexes of 2-Alkylphenylphosphanylphenolates: Synthesis,
Structural Investigation and Use in Ethylene Polymerization
Joachim Heinicke,*[a] Manuela Koesling,[a] Robert Brüll,[b] Wilhelm Keim,[b]
and Hans Pritzkow[c]
Keywords: Phosphanylphenolate / Cyclopentadienylnickel complexes / Chelates / Ethylene polymerization / Crystal
structure / Polymerizations
2-Diphenylphosphanyl- and 2-alkylphenylphosphanyl-4-
methylphenols or their silyl ethers and equimolar
hindered or retarded. The reactivity of 1d remains high
towards nickel salts in polar solvents, but in contrast to 1a–c,
yielding 4, a sparingly soluble green trans-bis(P–O-chelate)
nickel complex 6d is formed. Complexes formed in situ from
1 or 2 and Ni(COD)2 in toluene catalyze the polymerization of
ethylene. The cyclopentadienyl (PʝO) complexes 3, however,
are too stable to be active in this process. The crystal and
molecular structure of 3c and 4c are described.
1
2
amounts of nickelocene react in benzene preferably to give
orange-brown diamagnetic cyclopentadienylnickel chelate
complexes [η-CpNi(PʝO)] (3). Addition of
a
second
equivalent of 1 or 2 affords (RR) and (SS) diastereoisomers of
cis-bis(PʝO-chelates) 4a–c (R
= Ph, Me, iPr) or the
unsymmetrical cis-bis(PʝO-chelate) 5, whereas with bulkier
substituted derivatives 1d or 2d (R = tBu) the second step is
phenols and Ni(COD)2. The influence of substituents on
the polymerization will be reported separately.
Introduction
Functionalized phosphanes containing hard and soft do-
nor centers allow various coordination modes with tran-
sition metals in high or low oxidation states and thus have
attracted considerable interest in complex chemistry and
homogenous catalysis. Tertiary 2-phosphanylphenol-
ates[1Ϫ3] prefer bis(P∩O-chelate) transition-metal com-
plexes;[2,4] these are remarkably stabilized, are formed even
by dealkylation of 2-phosphanylphenyl-alkyl ether com-
plexes[5] and are able to undergo O,OЈ-coordination with a
second hard metal ion.[6] Furthermore, monophosphanyl-
phenolate chelate complexes bearing an additional phos-
phane molecule,[7] a solely P-coordinate 2-phosphanyl-
phenol or a cyclopentadienyl ligand[2,8,9] are known. Very
recently, phenylnickel diphenylphosphanylphenolate phos-
phane complexes were reported.[10] In view of the crucial
role of mono(P∩O-chelate) species in the industrially im-
portant homogenous nickel-catalyzed oligomerization of
ethene (Shell Higher Olefin Process, SHOP),[11] we investi-
gated complex chemical reactions of various P-substituted
2-phenylphosphanyl-4-methylphenols 1a؊d and their O-tri-
methylsilyl ethers 2a؊d with nickelocene in toluene, some
nickel salts or complexes in more polar solvents and the
polymerization with catalysts obtained from phosphanyl-
Results and Discussion
Reactions
2-Diphenylphosphanyl-4-methylphenol (1a) and an equi-
molar amount of nickelocene in benzene afford the cyclo-
pentadienyl(P∩O-chelate)nickel complex 3a (δ31P ϭ 37.8;
∆δ ϭ 65 ppm) and a small amount of cis-(P-O)2Ni (4a) (δ
31P ϭ 34.4; ∆δ ϭ 61.6 ppm) (Scheme 1). 2-Isopropylphe-
nylphosphanyl-4-methylphenol (1c) exhibits a higher selec-
tivity for monosubstitution and is isolated as pure orange-
brown 3c (δ 31P ϭ 50.5; ∆δ ϭ 80.3 ppm) from a benzene
solution at 20°C. Contamination by 4c is observed if the
complex is precipitated by ether or, markedly increased, on
heating solutions of 1c or 2c with nickelocene. The silyl
ethers 2 are less reactive than 1 and the higher temperatures
required favor contamination by 4. Reactions of the methyl-
(1b, 2b) or tert-butyl derivatives (1d, 2d) with nickelocene
(1:1) in benzene furnish brown diamagnetic substances,
which are highly soluble in benzene, THF, CH2Cl2 or
chloroform. NMR spectra of the products give evidence of
monosubstitution of the tert-butyl derivatives, whereas di-
[a]
Institut für Chemie und Biochemie, Ernst-Moritz-Arndt-Uni- substitution to 4b is preferred for the sterically less de-
1
versität Greifswald,
manding methyl species. This is seen in the H-NMR spec-
Soldmannstr. 16, D-17487 Greifswald, Germany
tra by pseudotriplets for the P-methyl protons. A side prod-
uct with δ31P ϭ 26.4 (ca. 15%) in the reaction with 2b,
which could not be isolated, is tentatively assigned to 3b.
Like the other η5-cyclopentadienyl(P∩O-chelate)nickel
complexes, it exhibits modest larger values of the typical
downfield coordination shift of five-membered chelate com-
plexes[12] than the cis-bis(phosphanylphenolato)nickel com-
Fax: (internat.) ϩ 49(0)3834/86-4319
E-mail: heinicke@mail.uni-greifswald.de
[b]
[c]
Institut für Technische Chemie und Petrolchemie, Rheinisch-
Westfälische Technische Hochschule Aachen,
Worringer Weg 1, D-52056 Aachen, Germany
Anorganisch-Chemisches Institut, Universität Heidelberg,
Im Neuenheimer Feld 270, D-69120 Heidelberg, Germany
Supporting information for this article is available on the WWW
under http://www.wiley-vch.de/home/eurjic or from the author.
Eur. J. Inorg. Chem. 2000, 299Ϫ305
WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2000
1434Ϫ1948/00/0202Ϫ299 $ 17.50ϩ.50/0
299

J. Heinicke, M. Koesling, R. Brüll, W. Keim, H. Pritzkow
FULL PAPER
plexes 4 with OϪ donors trans to the phosphorus atoms 2). The bulkier tert-butyl derivatives react differently to the
(Table 1).
others, forming brown solutions of 4a؊c, by precipitation
Scheme 1. Reactions of 1 or 2 with nickelocene
Table 1. 31P chemical shifts of 1a؊d, 3a؊d, 4a؊c[a] and 6d and coordination chemical shifts ∆δ
R
δ (1)
δ (3)
∆δ (3؊1)
δ (4a؊c) [δ (6d)]
∆δ (4؊1) [∆δ (6dϪ1d)]
a Ph
b Me
c iPr
d tBu
Ϫ27.2
Ϫ50.9
Ϫ29.8
Ϫ18.7
37.8
65
34.4
61.6
26.4[b]
50.5
77.3
80.3
75.8
21.9[c]
45.3
72.8
75.1
57.1[b]
[24.4][d]
[43.1][d]
[a]
[b]
[d]
Spectra in CDCl3. Ϫ Substance not isolated, tentative assignment. Ϫ [c] 31P resonance of a minor isomer at δ ϭ 20.0. Ϫ Solid-
state NMR data.[19]
The reaction of nickelocene with two equivalents of 1a؊c of a diamagnetic green trans-bis(P∩O-chelate)nickel com-
or 2a؊c in benzene smoothly gives cis-bis(PϪO-che- plex 6d which is insoluble or sparingly soluble in all com-
late)nickel complexes 4a؊c, indicating an easy replacement mon organic solvents.
of the second cyclopentadienyl ligand in the 18-valence-
electron complexes 3. Similarly, addition of 1b to 3c yields
the unsymmetrical cis-[Ni(P∩O)(PЈ∩O)] chelate complex 5.
Contamination by 4c and to a smaller amount by 4b (ratio
Catalysis
roughly 60:30:10) provides evidence that ligand substitution
The organonickel phosphanylphenolates 3 are structur-
is not limited to the cyclopentadienyl anion but involves ally related to organonickel phosphanylenolates,[9,13-15]
also the (P∩O-chelate) group. The reaction of nickelocene which form the catalytically active species in the Shell
with two equivalents of the tert-butyl-substituted 2-phos- Higher Olefin Process.[10] Attempts to oligomerize ethylene
phanylphenol derivatives 1d or 2d in benzene does not pro- by using the cyclopentadienylnickel complex 3c at 40 bar
ceed completely. Neither 4d nor 6d can be detected. It is and 140°C failed, however. The reason is, that despite the
assumed that the conversion in benzene is hindered or easy replacement of the cyclopentadienyl group by 1 or 2,
slowed for steric reasons. In polar solvents, however, the the semisandwich complexes 3 are thermally very stable and
ligand exchange is much faster, and bis(P∩O)nickel com- are unable to form catalytically active η1-CpNi- or NiH-
plexes are formed with 1a؊c or 2a؊c as well as with 1d or (PO-chelate) complexes. DTA of 3c indicates loss of cyclo-
2d. The reason is the high driving force for the bis(phos- pentadiene only at 190Ϫ210°C (endothermic). Complete
phanylphenolato)nickel complexes which are also the usual decomposition of the Ni(P∩O-chelate) structure occurs at
products in reactions with nickel acetylacetonate, with 280Ϫ340°C. For comparison, the thermal degradation of
aqueous nickel salts in methanol, or anhydrous nickel salts 4c proceeds in the same temperature range (280Ϫ340°C)
in THF if a sufficient amount of base or buffer is added. after an exothermic process at 271°C, whereas 5d starts to
Similarly, attempts to prepare [(PhtBuP∩O)NiBr(PPh3)n] by decompose at even higher temperature (310Ϫ340°C). The
reacting 1d(Li) with NiBr2·2PPh3 in ether in an equimolar importance of the loss of the cyclopentadienyl group for
ratio failed in favor of the bis(P∩O)nickel complex (Scheme catalytic activity was demonstrated for the less stable related
Scheme 2. Reactions of 1 or 2 with nickel salts
300
Eur. J. Inorg. Chem. 2000, 299Ϫ305

Nickel Chelate Complexes of 2-Alkylphenylphosphanylphenolates
FULL PAPER
phosphanylenolate
complex
[Ni(η5-Cp){Ph2PCHϭ tra. 6d, obtained as powder or microcrystals, was not suffic-
C(Ph)O}] (decomp. at 130°C) which like other nickel enol- iently soluble for solution-NMR studies, and therefore was
ate complexes becomes active at the decomposition tem- structurally characterized in comparison with 4c by a solid-
perature and thus gives evidence that the remaining (phos- state 31P-NMR investigation which is reported separ-
phanylenolato)nickel hydride represents the starting cata- ately.[19] The solid-state structures of 3c and 4c were deter-
lyst.[11,13b] That less stable organonickel complexes obtained mined by single-crystal X-ray structure analysis.
from phosphanylphenols and Ni(COD)2 catalyze the poly-
13C-NMR data of 3c indicate unambiguously the semi-
sandwich arrangement by a doublet for the cyclopen-
merization or oligomerization of ethylene was first claimed
by Singleton.[16] A catalyst prepared from o-diphenylphos-
tadienyl group and typical doublet or singlet signals for the
phanylphenol and Ni(COD)2 was found to convert ethylene
in high yield (95%) to linear polyethylene and a lower
amount of linear oligomers whereas a catalyst prepared
with 2-diethylphosphanylphenol was found to be much less
active (conversion 3.5%) and shows high preference for
lower oligomers (C4 68%, C6 24%, C8 4.3%). The recently
phosphanylphenolate ligand with J(31P13C), depending on
the position towards the phosphorus atom. Proton, CH-
COSY and phosphorus-NMR data of 3c support the pro-
posed structure. The assignment of the proton signals of 3a,
3b and 3d was done by comparison with those of 3c. In the
solid state, 3c crystallizes in the centrosymmetric space
group PϪ1 with two independent molecules in the asym-
metric unit, which show no significant deviations. The mo-
reported phenylnickel phosphanylphenolate phosphane
complexes[10] and an immobilized [PhNi(PPh3)(2-Ph2P-6-
HO-C6H3OϪ)] (P∩O-chelate) complex[17] were found to oli-
lecular structure of 3c (Figure 1) shows a perpendicular ar-
rangement of the CpϪ moiety and the planar (P∩O) chelate
gomerize ethylene. We observed that complex solutions pre-
pared from the alkylarylphosphanylphenol 1c or its silyl
ring (89.1 and 88.5°), with the Ni atom only slightly dis-
ether 2c and equimolar amounts of Ni(1,5-COD)2 form
torted from this plane. The distance from Ni to the cyclo-
pentadienyl carbon atom (C21 and C39, respectively)
placed in the trans position to the oxygen atom, are signifi-
cantly shorter than are the NiϪC distances to the remain-
catalysts for the formation of polymers and smaller
amounts of oligomers of ethylene with high selectivity for
linear structures (Scheme 3). Toluene was used as the sol-
vent to avoid conversion into the catalytically inactive bi-
ing cyclopentadienyl carbon atoms. This indicates a stabiliz-
s(phosphanylphenolato)nickel complex 4c, which as seen
ation of the NiϪC bond by the phenolate trans coordi-
above, is strongly favored in more polar solvents. Indeed,
nation which for related catalytically active organonickel
no catalytic activity was observed if the reaction was run in
phosphanylphenolate species is important for the chain
ethanol. In toluene, at 50 bar/160°C, the oligomer-to-poly-
growth in the polymerization or oligomerization of ethyl-
ene. The CϪPϪC angles are typical for tetracoordination
at the phosphorus atom, whereas the small PϪNiϪO and
aroxyϪPϪNi angles result from geometric factors of the
rigid five-membered ring and the bond lengths. The slight
increase of the PϪNiϪO angle (by 2Ϫ3°) in comparison to
(diphenylphosphanylenolato)-[13Ϫ15] and (diphenylphos-
phanylalkoxido)nickel complexes[20,21] is consistent with a
shorter PϪNi bond length (ca. 5 pm) within the ring.
mer ratio was 15%:85%. The oligomer portion consisted of
linear olefins, mainly from C6 to C26 with a flat maximum
at C16/C18. The polymer exhibits sharp absorptions for vinyl
C
end groups at 909 and 991 cmϪ1 (ν˜CϭC 1641 cmϪ1) and a
small band for CH3 at 1368 cmϪ1 but only weak bands for
the trans-CHϭCH or CϭCH2 groups and no indications of
branching.[18] X-ray powder diffraction revealed high crys-
tallinity. A molar mass distribution with Mw ϭ 9310
gmolϪ1 (corresponding to n ϭ 330) and Mn ϭ 6087 gmolϪ1
was determined. The results with 1c and 2c are similar and
can be attributed to the easy formation of (P∩O-chelates)
in both cases, as was also found in the reaction with nickel-
ocene.
1
In solution H- and 13C-NMR spectra of 4, various nu-
clei show “triplets” or other multiplets representing the An
or AnAnЈ part of AnXXЈ or AnAЈnXXЈ spin systems by
coupling with two 31P nuclei (X, XЈ) and hence, reveal the
bis(P∩O-chelate) nature of 4. The appearance depends on
the relative magnitudes and signs of all coupling constants
in the spin system.[22,23] Whereas the cis geometry of 5 is
Structure Investigations
2
deduced from JPP ϭ 80 Hz, which is much smaller than
Compounds 3؊5 are sparingly soluble in hexane or ether 2JPP in trans-methylnickel(phosphanylphenolato)PMe3
but easily soluble in benzene, CH2Cl2, chloroform or THF, complexes (ca. 316 Hz),[24] the geometry of 4 cannot easily
allowing structure elucidation by multinuclear NMR spec- be derived from the NMR data. In the proton spectrum
Scheme 3
Eur. J. Inorg. Chem. 2000, 299Ϫ305
301

J. Heinicke, M. Koesling, R. Brüll, W. Keim, H. Pritzkow
FULL PAPER
lings and should display the most intensive external lines.
As mentioned above, the geometry of 4c was determined by
solid-state investigations.[19] From the 31P-CP/MAS NMR
2
study, a two-bond coupling constant JPP of ca. 75 Hz was
determined, thus indicating cis geometry. Detailed struc-
tural information is provided by the single-crystal X-ray
structure analysis indicating a slightly distorted square-
planar cis configuration of 4c (Figure 2). The molecule has
a crystallographic two-fold axis through the Ni atom yield-
ing the (RR) or (SS) configuration. The PϪNiϪO and
PЈϪNiϪOЈ planes are twisted by 7.1°. The distances and
angles within the five-membered rings are similar to those
in 3c (PϪNiϪO less by 2°). The OϪNiϪOЈ angle (87.5°) is
somewhat smaller than 90° whereas the PϪNiϪPЈ angle is
considerably widened in order to reduce steric repulsion of
the P substituents. For the sterically less hindered methyl
derivative 4a, we observe characteristic 31P- and H-NMR
1
signals of a second nickel atom bis(P∩O-chelate) (B) (about
15%), which gives evidence of the existence of rac and meso
isomers of 4a.
˚
Figure 1. ORTEP plot of 3c; selected bond lengths [A] and angles
[°], corresponding data for the second independent molecule are
given in brackets: Ni1ϪP1 2.126(2) [2.132(2)], Ni1ϪO1 1.889 (3)
[1.885(3)], Ni1ϪC21 2.048(4) [2.048(4)], Ni1Ϫ(C17Ϫ20)
2.144(4)Ϫ2.155(4) [2.146Ϫ2.162(4)], P1ϪC1 1.807(4) [1.807(4)],
P1ϪC11 1.819(4) [1.823(4)], P1ϪC8 1.840(3) [1.850(3)];
O1ϪNi1ϪP1 89.49(11) [89.56(12)], Ni1ϪP1ϪC1 98.90(13)
[98.48(14)], C2ϪC1ϪP 111.9(2) [112.3(2)], C2ϪO1ϪNi1 118.3(1)
[118.1(2)], O1ϪC2ϪC1 121.5(3) [121.5(3)], C1ϪP1ϪC11 105.7 (2)
[107.4(2)], C1ϪP1ϪC8 107.0(2) [106.2(2)]
The bulkier nickel bis(2-tert-butylphenylphosphanyl-4-
methylphenolate) (6d), resembling trans-[Ni(tBu2PϪ
C6H4O)2][2a] and trans-[Ni(Ph2PCH2R2O)2] (R ϭ CF3)[20]
in its unusual green color and low solubility, prefers an
(RS)/(SR)-trans configuration with an inversion center at
the nickel atom, as established by the high symmetry found
in the solid-state 31P-NMR investigation.[19] The low coor-
dination shift of ∆δ(31P) ϭ 43 ppm for 6d as compared to
∆δ(31P) ϭ 61Ϫ75 ppm for 4a؊c may be indicative for the
different geometry but the lack of data for comparison
needs further investigations to establish such a dependence.
Conclusion
(P∩O-chelate)nickel(II) complexes 3؊6 containing phos-
phanylphenolato ligands may be obtained by reaction of
phosphanylphenols 1 or their silyl ethers 2 with nickelocene
or nickel salts. Monochelates are formed with nickelocene
in benzene. Small substituents, addition of polar solvents
or increased temperature favor formation of bis(P∩O-che-
late)nickel complexes. Complexes formed in situ from 1c or
2c and equimolar amounts of Ni(COD)2 in toluene were
found to catalyze the formation of linear polymers and a
smaller amount of oligomers of ethylene. From the slower
˚
Figure 2. ORTEP plot of 4c; selected bond lengths [A] and angles
[°]: Ni1ϪP1 2.1423 (13), Ni1ϪO1 1.885 (2), P1ϪC1 1.800 (2),
P1ϪC11 1.814 (3), P1ϪC8 1.844 (3); P1ϪNi1ϪP£1 97.93 (7),
O1ϪNi1ϪO£1 87.50 (11), O1ϪNi1ϪP1 87.50 (8), Ni1ϪP1ϪC1
99.22 (10), C2ϪC1ϪP1 110.9 (2), C2ϪO1ϪNi1 118.7 (2),
O1ϪC2ϪC1 121.6 (2), C1ϪP1ϪC11 107.16 (12), C1ϪP1ϪC8
109.55 (12); symmetry transformation used to generate equivalent
atoms: £1: Ϫx, y, Ϫz ϩ 1/2)
of 4c multiplets are observed for the diastereotopic methyl formation of catalytically inactive 6d from 1d and nickelo-
groups of PCHMe2 resembling a “doublet of a doublet” cene in benzene or toluene, it may be concluded that bulkier
and a “filled-in doublet” with doublet splitting of the exter- organonickel 2-phosphanylphenolate (P∩O-chelate) com-
nal lines. Pseudotriplets by coupling with two 31P nuclei plexes form interesting catalysts for olefin oligomerization
(ԽJXXЈԽ > ԽJAX Ϫ JAXЈԽ) are observed in the proton spectra or polymerization. The strengthening of the NiϪC bond in
of 4b (PMe) or 6d (PCMe3) as well as in the 13C-NMR the trans position to the oxygen atom, as observed in 3c,
spectra of 4b,c. The two external lines in the five-line pat- suggests a strong influence of donor properties at the OϪ
2
tern in the A part (13C) depend significantly on JPP and site on the chain length of polyethylene. A more detailed
should allow an assignment of the geometry. However, the study on the influence of steric and electronic effects of sub-
intensity of these lines is too low, even for the resonances stituents at the phosphorus atom and the aroxy group on
of C2 or Ci(Ph), which exhibit the largest 31PϪ13C coup- polymerization or oligomerization of ethylene is in progress.
302
Eur. J. Inorg. Chem. 2000, 299Ϫ305

Nickel Chelate Complexes of 2-Alkylphenylphosphanylphenolates
FULL PAPER
solvent, the suspension was filtered, 4c was washed with a little
benzene and dried at 10Ϫ2 Torr (8 h) affording 1.65 g (65%) of an
orange powder, m.p. 278Ϫ280°C. Ϫ 1H NMR and CH COSY: δ ϭ
Experimental Section
General: All reactions were carried out under argon, using Schlenk
techniques and freshly distilled dry solvents. Synthesis, properties
and structures of the P-tertiary o-phosphanylphenols have been de-
scribed elsewhere.[3b] Thermal analyses were carried out with a
TGDTA92 (SETARAM) instrument. UV-Vis spectra were re-
corded with a Lambda19 spectrometer (PerkinϪElmer), mass spec-
tra with a single-focussing mass spectrometer AMD40 (Intectra).
NMR spectra were measured in CDCl3 (unless indicated other-
3
3
0.98 (dd, JPH ϭ 12.7, JHH ϭ 6.8 Hz, 6 H, MeA), 1.24 (m, 2 H,
3
CHMe2), 1.41 (vc, JHH ഠ 7 Hz, 6 H, MeB) 2.08 (s, 6 H, 4-Me),
3
6.42 (vc, 2 H, 3-H), 6.88 (dτ, JHH ϭ 8.6, N ϭ 5.2 Hz, 2 H, 6-H),
7.02 (br. d, 3JHH ϭ 8.6 Hz, 2 H, 5-H), 7.40 (m, 4 H, o-H), 7.51 (m,
4 H, m-H), 7.60 (m, 2 H, p-H). Ϫ 13C NMR: δ (NPC) ϭ 16.6 (τ,
N ϭ 8.2 Hz, MeB), 19.4 (τ, N ϭ 6.8 Hz, MeA), 20.0 (s, Me-4), 23.0
(τ, N ϭ 28.1 Hz, CH), 112.9 (τ, N ϭ 54 Hz, Cq-2), 118.2 (τ, N ϭ
13.8 Hz, C-6), 123.5 (τ, N ϭ 6.9 Hz, Cq-4), 128.8 (τ, N ϭ 10.0 Hz,
C-m), 129.2 (τ, N ϭ 46.3 Hz, C-i), 131.0 (s, C-p), 131.4 (s, C-3),
132.1 (τ, N ϭ 8.3 Hz, C-o), 135.2 (s, C-5), 175.1 (τ, N ϭ 16.6 Hz,
Cq-1). Ϫ 31P {1H} NMR: δ ϭ 45.3. Ϫ C32H36NiO2P2 (573.27):
calcd. C 67.05 H 6.33 Ni 10.24 P 10.81; found C 66.76 H 6.66 Ni
10.56 P 10.27. (b) A solution of nickelocene (493 mg, 2.6 mmol)
and 2c (1.73 g, 5.2 mmol) in benzene (30 mL) was refluxed for 3 d
wise), using
a multinuclear FT-NMR spectrometer ARX300
(Bruker) at 300.13 (1H), 75.47 (13C), and 121.49 (31P) MHz. Shift
references are tetramethylsilane for H and 13C, and H3PO4 (85%)
1
for 31P. For resonances which are part of a AnX2 spin system (X ϭ
31P) vc denotes “virtual coupling”, τ the usual triplet appearance
of the A resonance (n ϭ 1) and N ϭ ԽJ ϩ JЈԽ.
Reactions of 1 and 2 with Nickelocene in Equimolar Ratio. ؊ Cyclo-
pentadienyl(2-diphenylphosphanyl-4-methylphenolato)nickel (3a): A to afford a brown solution. Most of the benzene was removed by
solution of 1a (900 mg, 3.08 mmol) in benzene (10 mL) was added
to a solution of nickelocene (580 mg, 3.07 mmol) in benzene
(10 mL) and stirred for 2 h. Most of the solvent (ca. 18 mL) was
removed in vacuo and ether (5 mL) was added to give 1.15 g of an
orange-brown precipitate, consisting of 3a and 4a (ca. 70%:30%,
d31P ϭ 37.8, 34.5). Column chromatography on silica gel yielded
distillation. From the residual suspension (ca. 3 mL) the solid was
separated by filtration and washed with cold benzene (1 mL) yield-
ing 319 mg (21%) of 4c, m.p. 285°C. Ϫ 31P NMR: δ ϭ 45.3.
Reaction of 1b with 3c: A solution of 3c (0.95 g, 2.5 mmol) in ben-
zene (10 mL) was added to 1b (0.57 g, 8.8 mmol) in benzene. About
12 mL of benzene was distilled off. 1.1 g of a brown precipitate was
separated from the resulting viscous solution and analyzed by 31P
NMR (CDCl3). The precipitate was found to be a mixture of the
unsymmetrical cis-bis(P∩O-chelate) 5 and the symmetrical cis-bis-
(P∩O-chelates) 4c and 4b (intensity ratio roughly 60:30:10). Ϫ
0.7 g (55%) of pure 3a by elution with CHCl3/acetone (10:1). Ϫ 1H
3
NMR: δ ϭ 2.13 (s, 3 H, 4-Me), 5.31 (s, 5 H, Cp), 6.63 (d, JHH
ϭ
4
3
7Ϫ8, JPH ϭ 5.5 Hz, 1 H, 6-H), 6.87 (d, JHH ϭ 7Ϫ8 Hz, 1 H, 5-
H), 6.87 (d, JPH ϭ 10 Hz, 1 H, 3-H), 7.35Ϫ7.55 (m, 6 H, m,p-H),
3
7.65Ϫ7.8 (m, 4 H, o-H). Ϫ C24H21NiOP (415.10): calcd. C 69.44,
H 4.80; found C 69.62, H 4.95.
2
31P{1H} NMR of 5: δ ϭ 46.4 (d), 21.7 (d), JPP ϭ 80 Hz.
Reactions of 1 or 2 with Nickel Salts or Complexes. ؊ cis-Bis(2-
diphenylphosphanyl-4-methylphenolato)nickel (4a): NiCl2·6H2O
(650 mg, 2.74 mmol) was dissolved in hot methanol (20 mL), and
a solution of 1a (1.6 g, 5.48 mmol) in methanol (5 mL) was added.
A rapid color change to orange started on addition of Et3N of
which a total of 1.1 g (10.9 mmol, ca. 100% excess) was added.
After removing the solvent, the solid residue was crystallized from
MeOH/CH2Cl2 (1:1) and dried for 2 h at 10Ϫ2 Torr to yield 1.4 g
(80%) of orange-brown 4a containing a small amount of water. Ϫ
1H NMR: δ ϭ 2.04 (s, 6 H, 4-Me), 3.50 (s, 2 H, H2O), 6.47 (vc to
br. τ, 2 H, 3-H), 6.89 (dτ, 3JHH ϭ 8.7, N ϭ 5.5 Hz, 2 H, 6-H), 7.02
Cyclopentadienyl(2-isopropylphenylphosphanyl-4-methylphenolato)-
nickel (3c): (a) A solution of 1c (274 mg, 1.06 mmol) in benzene
(10 mL) was added to nickelocene (200 mg, 1.06 mmol) in benzene
(10 mL). After 1 d, about 80% of the solvent was removed. Within
3 d, 216 mg (53%) of orange-brown 3c crystallized, m.p. 184°C. Ϫ
UV/Vis [MeOH; λmax/nm (ε/Ϫ1cmϪ1)]: 454 (880), 301 (1700), 267
(1500), 226 (sh, 2600). Ϫ 1H NMR and CH COSY (C6D6): δ ϭ
0.99 (dd, 3JPH ϭ 18.5, 3JHH ϭ 7.0 Hz, 3 H, MeA), 1.17 (dd, 3JPH ϭ
3
16.8, JHH ϭ 6.9 Hz, 3 H, MeB), 2.04 (m, 1 H, CH), 2.07 (s, 3 H,
3
4-Me), 5.18 (s, 5 H, Cp), 6.81 (d, JHH ϭ 8.5, 1 H, 5-H), 6.97 (dd,
4
3JHH ϭ 8.5, JPH ϭ 5.5 Hz, 1 H, 6-H), 7.07 (s, 1 H, 3-H), 6.94 (m,
3
3
1 H, p-H), 7.06 (m, 2 H, m-H), 7.66 (m, o-H). Ϫ 13C NMR (C6D6):
δ (JPC) ϭ 18.2 (d, 1.9 Hz, MeB), 18.8 (d, 5.6 Hz, MeA), 20.4 (s, Me-
4), 27.4 (d, 31.0 Hz, CH), 91.4 (d, 1.8 Hz, Cp), 117.9 (d, 51.1 Hz,
Cq-2), 119.3 (d, 9.9 Hz, C-6), 121.9 (d, 7.0 Hz, Cq-4), 128.9 (d,
10.4 Hz, 2 C-m), 129.9 (d, 2.6 Hz, C-3), 130.5 (s, C-p), 131.9 (d,
10.3 Hz, 2 C-o), 134.1 (d, 1.7 Hz, C-5), 134.2 (d, 43.3 Hz, i-C),
176.1 (d, Hz, Cq-1). Ϫ 31P {1H} NMR: δ ϭ 50.4. Ϫ C21H23NiOP
(381.1): calcd. C 66.19 H 6.08 P 8.13; found C 66.26 H 6.48 P 7.76.
Ϫ (b) 965 mg of 2c (2.9 mmol) in benzene (10 mL) was added to
nickelocene (545 mg, 2.9 mmol) in benzene (10 mL). No visible re-
action took place within 5 d at 20°C, but on reflux (24 h) a dark
brown solution was formed. Work up as above afforded 750 mg
(70%) of 3c, m.p. 185°C. A trace of 4c was formed besides 3c. The
proportion increased up to 1:3 in larger runs and on precipitation
with ether from the benzene solution. Single crystals of 3c and of
4c were grown from benzene/nitromethane (ca. 1:1) solution.
(br. d, JHH ϭ 8.7 Hz, 2 H, 5-H), 7.42 (m, 4 H, o-H), 7.10 (τ, J ഠ
7.4Ϫ7.6 Hz, 4 H, m-H), 7.32 (τ, J ഠ 7.3Ϫ7.5 Hz, 2 H, p-H). Ϫ
31P{1H} NMR: δ ϭ 34.4. Ϫ C38H32NiO2P2·H2O (659.32): calcd.
Ni 8.90; found Ni 8.85.
cis-Bis(2-methylphenylphosphanyl-4-methylphenolato)nickel (4b): (a)
A solution of 1b (103 mg, 0.45 mmol) in ethanol (5 mL) was added
to a warm solution of nickel acetate · 4 H2O (57 mg, 0.23 mmol)
in ethanol (10 mL), affording a yellow solution which slowly turned
brown. The solvent was removed in vacuo (after 3 d), the remainder
was extracted with CH2Cl2 and dried with Na2SO4. Hexane was
added and a part of the solvent (mainly CH2Cl2) was evaporated
in vacuo to yield a brown precipitate which was dried for 2 h at
10Ϫ2 Torr. 70 mg (59%) of two isomers of 4b were obtained, isomer
1
ratio (A)/(B) ca. 85%:15% with δ(31P) ϭ 21.9, 20.0. Ϫ H NMR:
(A): δ ϭ 1.09 (τ, N ϭ 11.7 Hz, 6 H, PMe), 2.06 (s, 6 H, 4-Me),
6.43 (br. τ, N ϭ 8Ϫ9 Hz, 2 H, 3-H), 6.87 (m, 2 H), 6.98 (m, 2 H),
7.4Ϫ7.6 (m, 10 H, Ph); (B): δ ϭ 1.87 (τ, N ϭ 11.1 Hz, PMe), other
Reactions of Nickelocene with Two Equivalents of 1 or 2. ؊ cis-
Bis(2-isopropylphenylphosphanyl-4-methylphenolato)nickel (4c): (a) signals superimposed. Ϫ 13C NMR: δ (NPC) ϭ 9.1 (τ, N ϭ 32 Hz,
Nickelocene (831 mg, 4.4 mmol) in benzene (10 mL) was added to
PMe), 20.0 (Me-4), 118.3 (τ, C-6), 124.6 (τ, C-4), 128.9 (C-p), 129.1
1c (2.27 g, 8.8 mmol) in benzene (10 mL). The color turned from (τ, N ϭ 10.6 Hz, C-m), 131.4 (τ, N ϭ 10.6 Hz, C-o), 135.3 (C-5);
green to brown within 1 h, and an orange-brown precipitate was
formed after refluxing for 30 min. After removing a part of the
weak intensities of C-1, C-2, C-i signals. Ϫ C28H28NiO2P2 (517.17):
calcd. Ni 11.35; found Ni 11.08. Ϫ (b) An equimolar mixture of
Eur. J. Inorg. Chem. 2000, 299Ϫ305
303

J. Heinicke, M. Koesling, R. Brüll, W. Keim, H. Pritzkow
FULL PAPER
2b (647 mg, 2.14 mmol) and nickel acetylacetonate (550 mg,
branching of the PE. Use of a catalyst prepared from 1c and
2.14 mmol) was refluxed for 8 h in benzene (30 mL) to give, after Ni(COD)2 and 8.7 g of C2H4 at 140°C led similarly to PE (TON ϭ
removal of 2/3 of the solvent, 188 mg (34%) of the bis(phosphanyl- 698; 3.64 g of HDPE, 85% of converted ethylene), m.p. 121°C;
phenolate) 4b, m.p. 216Ϫ218°C. Ϫ UV/Vis [MeOH, λmax/nm (ε/ DTA (5 K/min): 131.8°C (up), 117.2°C (down). Mw ϭ 9310

Ϫ1cmϪ1)]: 403(400), 347 (1.300), 293 (sh), 281 (14.000), 220 (sh,
gmolϪ1, Mn ϭ 6087 gmolϪ1. Ethylene (40 bar) heated with a solu-
tion of 3c (37.3 mg) in toluene (20 mL) for 12 h at 140°C was not
converted. A more detailed study of ethylene polymerization and
oligomerization with varied phosphanylphenols is in progress and
will be described elsewhere.
17.000). Ϫ 31P{1H} NMR: δ ϭ 21.8.
cis-Bis(2-isopropylphenylphosphanyl-4-methylphenolato)nickel
(4c): 2c (193 mg, 0.59 mmol) and nickel acetylacetonate (54 mg,
0.21 mmol) were refluxed for 8 h in benzene (20 mL) to give, after
removal of the bulk of the solvent, 88 mg (73%) of 4c, NMR data
as above.
Crystal Structure Analysis: Crystal data are presented in Table 2,
selected bond angles and bond lengths are given in the captions of
Figures 1 and 2. Ϫ Data collection: The crystals were mounted on
a glass fiber in inert oil and transferred to the cold gas stream
(Ϫ55°C) of the diffractometer (Siemens-Stoe AED2). Data were
collected in the ω-scan mode using monochromated Mo-Kα radi-
trans-Bis(2-isopropylphenylphosphanyl-4-methylphenolato)nickel
(6d): (a) 160.8 mg (0.735 mmol) of NiBr2 and 170 µL of HBr (48%,
1.51 mmol) were dissolved in warm methanol and two equivalents
of 1d (400 mg, 1.47 mmol) in methanol (7 mL) were added. A tran-
sient brown color was observed in the mixing area, indicating an
equilibrium with dominance of octahedral Ni2ϩ complexes in solu-
tion [λmax/nm: 398 (st), 730 (w), 660 (sh)]. On buffering with excess
sodium acetate the solution turned brown and 265 mg (60%) of
green 6d precipitated. Ϫ (b) A solution of 1d (588 mg, 2.16 mmol)
in THF (15 mL) was added to a suspension of NiBr2·1.1DME
(337 mg, 1.09 mmol) in 15 mL of THF. On addition of LiOiPr
(2.3 mmol) the solution turned brown and a total of 415 mg (63%)
of green 6d precipitated. The reaction of NiBr2·1.1DME with 2d
proceeded similarly. Ϫ (c) The best variant yielding microcristalline
6d was the following: Butyllithium in hexane (9.6 mmol) was added
at Ϫ5°C to 3.26 g (9.46 mmol) of 2d in THF (20 mL). A solution
of NiBr2·2Ph3P (3.52 g, 4.73 mmol) in THF (40 mL) was added
dropwise, forming a brown solution and, after 5Ϫ10 min, a green
precipitate. The reaction was complete within 20Ϫ30 min and gave
2.06 g (73%) of microcrystalline, diamagnetic 6d, m.p. 312Ϫ317°C
(DTA 327.5°C with dec.). Above 120°C 6d exhibited a reversible
gradual color change via olive-green to yellow. The solubility in
acetonitrile, nitromethane, methanol, acetone, benzene or hexane
was very low and in THF, CHCl3 or CH2Cl2 was just sufficient for
UV/Vis spectra. Ϫ UV/Vis [THF; λmax/nm, (relative intensities in
satd. soln.)]: 611 (10), 434 (100), 391 (500), 320 st, 284 st, 275 st. Ϫ
Solid-state NMR investigation see ref.[19] Ϫ C34H40NiO2P2 (601.3):
calcd. C 67.92, H 6.70, Ni 9.76, P 10.30; found C 67.36, H 6.83,
Ni 9.63, P 10.26. Ϫ X-ray powder diffraction data and density (in
ethanol) ϭ 0.89Ϫ0.95 gcmϪ3 fit best with a triclinic crystal system
˚
ation (0.71073 A). Ϫ Solution and refinement: The structures were
solved by direct methods (G.M. Sheldrick, SHELXS-86, Univ.
Göttingen, 1986) and were refined by the least-squares method
based on F2 with all measured reflections (G. M. Sheldrick,
SHELXL-93, Univ. Göttingen, 1993) using anisotropic tempera-
ture factors for all non-hydrogen atoms. Hydrogen atoms were in-
cluded in calculated positions or as part of a rigid group (methyl).
Only an isotropic temperature factor for each type of hydrogen
atom was refined. Ϫ Crystallographic data (excluding structure fac-
tors) for the structure reported in this paper have been deposited
with the Cambridge Crystallographic Data Centre as supplemen-
tary publication no. CCDC-114167 (3c) and -114168 (4c). Copies
of the data can be obtained free of charge on application to CCDC,
12 Union Road, Cambridge CB2 1EZ, UK [Fax: (internat.) ϩ 44-
1223/336-033; E-mail: deposit@ccdc.cam.ac.uk].
Acknowledgments
Financial support by the Deutsche Forschungsgemeinschaft and
the Fond der Chemischen Industrie is gratefully acknowledged. We
thank Dr. M. K. Kindermann and B. Witt for NMR experiments,
P. Engler for thermal analyses, Prof. Dr. Fink (Mülheim) for deter-
mination of the molar mass distribution and Dr. H. Wulff for pow-
der X-ray diffraction measurements.
˚
˚
with unit cell dimensions of ao ϭ 10.126 A, bo ϭ 17.630 A, co
12.184 A, α ϭ 89.44°, β ϭ 90.55°, γ ϭ 89.98°, Z ϭ 2.
ϭ
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