Nickel and palladium complexes of pyridine-phosphine ligands bearing aromatic substituents and their behavior as catalysts in ethene oligomerization

Article abstract of DOI:10.1021/om9000378

Bidentate pyridine-phosphine ligands 1 of general structure 2-aryl-6-[2-(diphenylphosphino)ethyl]pyridine were developed, in which the aryl group is phenyl (a), 1-naphthyl (b), 9-phenanthryl (c), 9-anthracyl (d), and ferrocenyl (e). The influence of these

Full text of DOI:10.1021/om9000378

3264
Organometallics 2009, 28, 3264–3271
Nickel and Palladium Complexes of Pyridine-Phosphine Ligands
Bearing Aromatic Substituents and Their Behavior as Catalysts in
Ethene Oligomerization
Jitte Flapper,†,‡ Piet W. N. M. van Leeuwen,† Cornelis J. Elsevier,† and
Paul C. J. Kamer*,†,§
Van ’t Hoff Institute for Molecular Sciences, UniVersity of Amsterdam, Nieuwe Achtergracht 166, 1018WV
Amsterdam, The Netherlands, Dutch Polymer Institute, PO Box 902, 5600 AX EindhoVen, The Netherlands,
and School of Chemistry, UniVersity of St. Andrews, St. Andrews, Fife, Scotland KY16 9ST, U.K.
ReceiVed January 16, 2009
Bidentate pyridine-phosphine ligands 1 of general structure 2-aryl-6-[2-(diphenylphosphino)ethyl]py-
ridine were developed, in which the aryl group is phenyl (a), 1-naphthyl (b), 9-phenanthryl (c), 9-anthracyl
(d), and ferrocenyl (e). The influence of these substituents on the nickel and palladium complexes of the
ligands and their ethene oligomerization behavior was studied. The largest influence was observed in
species with a square-planar surrounded metal center, whereas the nickel dichloride complexes 5 appeared
as monometallic species with a tetrahedrally surrounded metal center. A classical binding mode of the
ligand was not possible for the methylpalladium chloride complexes coordinated in a square-planar fashion.
Instead, binuclear species in which two ligands span two metal centers were observed for 6a-d, and an
undefined mixture of complexes was obtained for 6e. In contrast to these neutral palladium complexes,
the cationic methylpalladium complexes 7, lacking the chloride anion, appear as well-defined, monomeric
complexes. When the nickel complexes 5a-d were activated with MAO, they catalyzed the oligomerization
of ethene with a maximum turnover frequency of 11 × 103 mol ethene per mol nickel per hour, whereas
5e showed no activity. Selectivities for butenes were between 93 and 97 mol %, with a maximum 1-butene
content of 93%. The catalytic behavior is different from that of the nickel complex lacking an aromatic
group at the ligand, again showing the influence of these substituents. The palladium complexes 7 were
hardly active in ethene oligomerization, giving very small amounts of oligomers.
have been applied in nickel- or palladium-catalyzed ethene
oligomerization and polymerization.2,4 In a search to tune the
performance of ethene oligomerization catalysts, different types
of P,N-based catalysts have been tested. Among them are nickel
and palladium complexes of pyridine-phosphines and -phos-
phinites,5-8 oxazoline-phosphines and -phosphinites,8–10 imino-
phosphoranes,11 amido- and imino-phosphines,12-14 imino-pyr-
rolylphosphines,15pyrazole-phosphines,16quinoline-phosphines,17,18
and pyridine-phospholes.19
Introduction
Industrially, R-olefins are produced on a scale of megatons
per year. Oligomerization of ethene is the most important
reaction for their production. Depending on their chain length,
R-olefins find their most important applications in the production
of linear low-density polyethylene (LLDPE) (C4-C10), poly-
R-olefins (C4, C10), plasticizers (C6-C10), lubricants (C8-C10),
lube oil additives (C12-C18), and surfactants (C12-C20).1,2
Bidentate ligands with a nitrogen and a phosphorus donor
atom (P,N ligands) have found considerable attention in the field
of transition metal catalysis.3 Next to many other reactions, they
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100, 1169–1203. (b) Gibson, V. C.; Spitzmesser, S. K. Chem. ReV. 2003,
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* To whom correspondence should be addressed. E-mail: pcjk@
st-andrews.ac.uk. Fax: +44-(0)1334463808. Tel: +44-(0)1334467285.
† University of Amsterdam.
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A: Chem. 2005, 229, 177–181. (b) Bonnet, M. C.; Dahan, F.; Ecke, A.;
Keim, W.; Schulz, R. P.; Tkatchenko, I. J. Chem. Soc., Chem. Commun.
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2003, 22, 4893–4899.
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metallics 2004, 23, 2613–2624. (b) Tang, X.; Zhang, D.; Jie, S.; Sun, W.-
H.; Chen, J. J. Organomet. Chem. 2005, 690, 3918–3928.
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‡ Dutch Polymer Institute.
§ University of St. Andrews.
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10.1021/om9000378 CCC: $40.75
2009 American Chemical Society
Publication on Web 04/28/2009

Ni and Pd Complexes Bearing Aromatic Substituents
Organometallics, Vol. 28, No. 11, 2009 3265
Scheme 1. Synthesis of Ligands 1a
Herein, we present the development of new pyridine-phosphine
ligands and nickel and palladium complexes thereof. Also, their
behavior as catalyst precursors in ethene oligomerization was
studied. The nickel dichloride complexes form active catalysts in
this reaction, giving mainly butenes as the product, whereas the
palladium complexes were inactive. The used ligands differ in the
steric bulk of the aromatic substituent at the pyridine 6-position.
We have shown that modification of 1,1′-bis(diarylphosphino)f-
errocene ligands with large aromatic groups induces an increased
enantioselectivity in palladium-catalyzed allylic substitution and
rhodium-catalyzed hydrogenation.20,21 Furthermore, bulky aro-
matic substituents have a beneficial effect on the performance
of nickel-salicylaldiminato-based ethene polymerization cata-
lysts.22
Recently, we showed the unique coordination behavior of
methylpalladium chloride complexes 6a-d of ligands 1a-d,
which are modified with large aromatic substituents.23 In this
article, we also report on the corresponding complex 6e of ligand
1e, the cationic methylpalladium acetonitrile complexes 7
obtained from the neutral palladium complexes, and the neutral
nickel dichloride complexes 5 of the ligands. Also, complexes
5 (using MAO activation) and 7 were evaluated as catalyst
precursors for ethene oligomerization.
a
i: (1) HPPh2, KOtBu, THF, 60 °C, 16 h; (2) NaClO4, H2O, CH2Cl2,
rt, 1 h; ii (for a, b, and c): RB(OH)2, Pd(PPh3)4, K2CO3, toluene, water,
reflux, 16 h; iii (for d and e): RZnCl, Pd(PPh3)4, THF, 60 °C, 24h.; iV:
PhSiH3, reflux, 16 h.
Scheme 2. Synthesis of Nickel Complexes 5
Results and Discussion
We prepared the ligands 1 as depicted in Scheme 1. They
are all bidentate, with a pyridine and a diphenylphosphine
donor group, which are connected through an 1,2-ethanediyl
bridge. The ligands differ in the bulky substituents at the
6-position of the pyridine group. The substituents are phenyl
(for a), 1-naphthyl (b), 9-phenanthryl (c), 9-anthracyl (d),
and ferrocenyl (e).
Ligand Synthesis. The ligands were synthesized according
to Scheme 1. Hydrophosphination of 2-bromo-6-vinylpyridine
(2) with diphenylphosphine and subsequent oxidation using
household bleach gave 2-bromo-6-[2-(diphenylphosphinoyl)-
ethyl]pyridine (3), which is a suitable precursor for differently
substituted phosphine oxides 4. These were obtained via
palladium-catalyzed Suzuki coupling with arylboronic acids (for
a, b, and c) or Negishi-Takahashi coupling with arylzinc
chlorides (for d and e). The thus obtained phosphine oxides 4
were reduced using phenylsilane to give the free phosphines 1
in good yields.
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Sarkar, A. Eur. J. Inorg. Chem. 2005, 125, 4–1263.
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Van Leeuwen, P. W. N. M.; Lutz, M.; Spek, A. L. J. Org. Chem. 2001, 66,
759–770.
Synthesis and Characterization of Nickel Complexes. The
nickel dichloride complexes 5 were obtained by reaction of the
ligands with the precursor (DME)NiCl2 [DME ) 1,2-dimethoxy-
ethane]; see Scheme 2. The reaction mixture was stirred at room
temperature and then filtered through a pad of Celite to remove
residual (DME)NiCl2. After evaporation of the solvent, the solid
was washed with diethyl ether to remove remaining free ligand.
The complexes were paramagnetic species, as evidenced by
their magnetic moment in solution. They were further character-
ized by elemental analyses, which were in agreement with the
proposed structures, and high-resolution mass spectrometry.
Using fast atom bombardment (FAB) ionization, the [(ligand)-
NiCl]+ species were observed in the mass spectrum for all
complexes. The loss of one chlorine atom is a consequence of
the ionization technique employed, as the ionization of the
complex by proton addition is immediately followed by loss of
HCl. The magnetic moments in CD2Cl2 were 2.50 (5a), 2.24
(5b), 2.62 (5c), 2.75 (5d), and 2.28 µB (5e). These values are
indicative for a distorted tetrahedral geometry of the nickel
center.24 No useful NMR signals were observed, and all
complexes were EPR-silent, as can be expected for this type of
complexes.25
(21) Nettekoven, U.; Kamer, P. C. J.; Van Leeuwen, P. W. N. M.;
Widhalm, M.; Spek, A. L.; Lutz, M. J. Org. Chem. 1999, 64, 3996–4004.
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R. H.; Bansleben, D. A.; Day, M. W. Organometallics 1998, 17, 3149–
3151. (b) Younkin, T. R.; Connor, E. F.; Henderson, J. I.; Friedrich, S. K.;
Grubbs, R. H.; Bansleben, D. A. Science 2000, 287, 460–462.
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P. W. N. M.; Elsevier, C. J.; Kamer, P. C. J. Eur. J. Inorg. Chem. 2008,
4968–4976.
Synthesis and Characterization of Neutral Palladium
Complexes. We recently reported on the methylpalladium
chloride complexes 6a-d of ligands 1a-d.23 They appear as

3266 Organometallics, Vol. 28, No. 11, 2009
Flapper et al.
Scheme 3. Synthesis of Dimeric Palladium Complexes 6a-d
Scheme 5. Synthesis of Cationic Palladium Complexes 7
dimeric species, with two ligands spanning two palladium
centers, as shown in Scheme 3. The complexes are insoluble
and were characterized by different solid state techniques. This
revealed that the methyl and chloride anions can be in the trans
or cis configuration at both metal centers, but also complexes
were obtained in which one palladium center has a cis and one
a trans configuration of the anions within one complex, like
the structure depicted in Figure 1.
In contrast to their precursors (the dimeric complexes 6a-d
and the undefined mixture 6e), all complexes 7 are well-defined,
1
monometallic, soluble complexes. The H, 13C, and 31P NMR
spectra showed that in all cases one species was present, and
the possibility of an unsymmetrical dimer was excluded. The
presence of the coordinated acetonitrile molecule was evidenced
by a singlet in the proton spectrum. The Pd-CH3 protons gave
rise to a singlet or a doublet. For 7a-d, the methyl signals for
these two groups were at remarkably low ppm values, compared
to similar complexes lacking the bulky aryl substituents at the
ligands.26 For the methylpalladium group, this value became
lower with increasing size of the aryl substituent, and the signal
appeared at 0.36, -0.22, -0.63, and -0.67 ppm for 7a-d,
respectively. The CH3CN singlet was also observed at lower
ppm value than expected: 1.95, 1.51, 1.55, and 1.62 ppm,
respectively. These chemical shifts can be explained by an
interaction of the ring current of the aryl substituents with the
methyl protons, thus causing an increased shielding of these
nuclei. In 7e, the ferrocenyl substituent does not have an
interaction with the methylpalladium group and the signal for
the Pd-CH3 protons appears at 0.73 ppm in the 1H NMR
spectrum. The chemical shift of the CH3CN protons of 1.98
ppm does show an interaction of this group with the ferrocenyl
substituent. This is an indication of a cis orientation of the
acetonitrile with respect to the pyridine, as this places the
acetonitrile-methyl in closer proximity to the ferrocenyl than
the palladium-methyl. This configuration around palladium can
be expected on the basis of the larger trans effect of the
phosphorus donor atom compared to the nitrogen donor. Indeed,
the cis configuration of the palladium-methyl and the phosphine
was shown by the 3JPH coupling constant of the Pd-CH3 signals.
This coupling with the phosphorus nucleus is small or not
observed, indicating that the methyl group is orientated cis with
respect to the phosphorus. The 31P NMR spectra show one
singlet between 36 and 39 ppm, and the 19F signal appears at
-63.0 ppm for all complexes. The high-resolution mass spectra
show the peak for the [(ligand)PdCH3]+ species. Apparently,
acetonitrile dissociates under the conditions used for FAB
ionization, as was observed before for similar complexes.26
When the milder field desorption (FD) ionization technique is
used, the [(ligand)Pd(CH3)(CH3CN)Na]+ ions were observed
for 7a-d, but as a consequence of FD ionization, not in high
resolution. For 7e, the same species is observed as when FAB
is used. The ions observed in MS have an overall charge of
+1, as evidenced by the distance of 1 amu between the peaks
of different isotopes. This shows that the cationic complexes
We tried to obtain the methylpalladium chloride complex of
ferrocenyl-substituted ligand 1e by the same procedure we
obtained 6a-d, viz., via reaction with (COD)Pd(CH3)Cl [COD
) 1,5-cyclooctadiene] in dichloromethane; see Scheme 4. To
our surprise, this gave rise to a complicated mixture of products.
The products were soluble in dichloromethane and chloroform,
and after workup no signals corresponding to free or coordinated
1
COD were detected in the H NMR spectrum. We performed
the reaction several times, and identical 1H and 31P NMR spectra
were obtained for the products of the individual reactions,
showing that the product formation was reproducible. As a
consequence of the stoichiometry of the reactants, a 1:1 mixture
of methylpalladium chloride and the ligand was obtained. This
was confirmed by elemental analysis. The mixture was used
directly in the next step (see below).
The steric bulk of the ferrocenyl group might prevent the
ligand from acting as a classical bidentate ligand. We have
shown before that the bulk of a ferrocenyl substituent can be
more demanding than that of large aromatic substituents such
as 9-phenanthryl.20
Synthesis and Characterization of Cationic Palladium
Complexes. The cationic palladium species 7 were obtained
by reaction of their precursors with NaBAr′4 [Ar′ ) 3,5-
di(trifluoromethyl)phenyl] and acetonitrile; see Scheme 5.
Cannula filtration separated the product from the sodium
chloride precipitate, and evaporation of the solvent yielded the
pure products in high yields.
Figure 1. Structure of complex with cis- and trans-surrounded metal
centers.
Scheme 4. Synthesis of a Mixture of Palladium Complexes
6e
(24) Hayter, R. G.; Humiec, F. S. Inorg. Chem. 1965, 4, 1701–1706.
(25) Desrochers, P. J.; Telser, J.; Zvyagin, S. A.; Ozarowski, A.;
Krzystek, J.; Vicic, D. A. Inorg. Chem. 2006, 45, 8930–8941.
(26) (a) Flapper, J.; Kooijman, H.; Lutz, M.; Spek, A. L.; Van Leeuwen,
P. W. N. M.; Elsevier, C. J.; Kamer, P. C. J. Organometallics 2009, 28,
1180–1192. (b) Flapper, J.; Kooijman, H.; Lutz, M.; Spek, A. L.; Van
Leeuwen, P. W. N. M.; Elsevier, C. J.; Kamer, P. C. J. Organometallics
2009, http://dx.doi.org/10.1021/om900038u.

Ni and Pd Complexes Bearing Aromatic Substituents
Organometallics, Vol. 28, No. 11, 2009 3267
Table 1. Ethene Oligomerization Using Complexes 5 as Catalyst
Precursorsa
precursor, with MAO under identical conditions resulted in the
formation of a soluble species.26a
product distribution (%)c
The other nickel complexes form active catalysts, with
butenes as the major product of the catalytic reaction. Only small
amounts of higher oligomers are formed, and the complexes
can be regarded as dimerization catalysts. Selectivities for
dimerization are high in general and reach a maximum of 97%
(for 5d). From the amount of cooling required to maintain the
reaction temperature (against the exothermic reaction), it became
clear that the activity decreased over time. The highest activity
was observed in the first 10 min. The productivity goes up with
increasing bulk of the substituent at the pyridine of the ligand.
This might be explained by a destabilization of the ground state
caused by interaction of these substituents with the metal center.
A similar explanation was proposed for the high activity of
nickel complexes with R-diimine ligands bearing bulky sub-
stituents (the so-called Brookhart catalyst) in ethene polymer-
ization.28
productivity
(g C2H4/
complex (mol Ni · h))
1-butene
TOFb
C4 C6 C8 C10
(%)d
5a
5b
5c
5d
5e
8 × 104
18 × 104
16 × 104
30 × 104
0
2.8 × 103 93
6.5 × 103 96
5.7 × 103 93
11 × 103 97
0
6
4
7
3
1
<1
<1
<1
<1
93
88
83
82
a Conditions: 10 µmol of nickel complex, MAO activator (Al/Ni )
230), 10 bar of ethene, 1.0 mmol of heptane (internal standard), toluene
solvent, total volume: 25 mL, T: 30 °C, time: 30 min. b Turnover
frequency in (mol C2H4) · (mol Ni · h)-1 c Mol percentage of combined
.
Cn products. d As percentage of total C4 fraction.
Chart 1. Complex 8
The effect of the bulky substituents at the pyridine of the
ligand becomes clear when the results presented here are
compared with the catalytic results of complex 8 (lacking these
substituents), as reported previously.26a Under the same condi-
tions, this complex gave a higher TOF of 70 × 103 (mol
C2H4) · (mol Ni)-1 · h-1, but the selectivity for butenes in the
product (86 mol%) and 1-butene within the butenes fraction
(18%) was lower. Especially the much lower selectivity for
1-butene is notable. The large difference in catalytic behavior
between complexes 5 and complex 8 indicates that the active
species must adopt a different conformation when the ligand
bears an aromatic substituent at the 6-position of the pyridine.
After MAO activation, a cationic complex is formed with a
square-planar geometry around the nickel,29 causing a much
larger influence of the substituents than in the tetrahedrally
surrounded dichlorides. This is in line with the finding that the
substituents have a large effect on the conformation of the
(square-planar surrounded) methylpalladium chloride complexes
of these ligands.23
The high selectivity for 1-butene shows that the bulky
substituents in complexes 5 prevent isomerization. Remarkably,
this bulk should not be too large; with increasing size of the
substituent (going from 5a to 5d), the rate of isomerization
increases. ꢀ-Hydride elimination is favored over ethene insertion
with these catalysts, as indicated by the large butene fractions
in the product. From the species formed after ꢀ-hydride
elimination, reinsertion with opposite regiochemistry would lead
to 2-butenes. So apparently, this route is disfavored and chain
transfer takes place instead.
are mononuclear species. For dinuclear species, a double charged
ion would be created, and the distance between two isotope
peaks would be 1/2 amu.
On the basis of the combined analytical techniques, we have
assigned the structure as shown in Scheme 5 to complexes 7.
The reason for the difference with the neutral precursors (dimeric
complexes 6a-d or mixture of complexes 6e) is probably the
steric repulsion between the bulky pyridine substituents and the
chloride ion in 6. This prevents a chelating behavior of the ligand
with the chloride ion cis to the pyridine donor moiety. A trans
configuration of these groups is electronically disfavored, as
this would place the methyl group and the phosphine ligand,
both having a large trans effect, in mutual trans positions. A
configuration around the metal with the two donor functionalities
of the ligand trans to one another is not possible, as the ligand
cannot adopt the required conformation for this. The nickel
dichloride complexes 5 show a tetrahedral geometry around the
metal. This positions the chloride atoms further away from the
bulky substituents, as compared to square-planar complexes such
as 6, and hence a mononuclear cis coordination is possible for
these complexes.
Nickel-Catalyzed Ethene Oligomerization. Nickel com-
plexes bearing pyridine-phosphine ligands have been success-
fully applied in the oligomerization of ethene.2,5,26,27 We tested
the ability of complexes 5 to act as catalyst precursors in this
reaction after activation with MAO, and the results are sum-
marized in Table 1.
Palladium-Catalyzed Ethene Oligomerization. Palladium
complexes bearing pyridine-phosphine ligands have been em-
ployed in many catalytic reactions.3f-h For example, they have
shown very good activity and selectivity in methoxycarbony-
lation of propyne to methyl methacrylate.30 In ethene oligo-
merization, they have been applied with variable success. Active
systems have been reported,7 but other systems showed no or
very low productivity.6,26 We tested complexes 7 for their ability
to function as ethene oligomerization catalysts, and the results
are summarized in Table 2.
Complexes 5a-d formed active catalysts after activation,
whereas 5e did not show any activity. To test the stability of
the complex in the presence of MAO, in a separate experiment
5e was dissolved in a Schlenk flask in toluene in the presence
of a little 1-hexene to stabilize the complex formed after
activation. When a solution of MAO was added, the immediate
formation of solids was observed, together with a color change.
From this we concluded that the complex decomposes in the
presence of MAO, possibly as a result of reduction of the
ferrocenyl substituent by the free trimethylaluminum in MAO.
Treatment of complex 8 (see Chart 1), which is a good catalyst
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(30) (a) Drent, E.; Arnoldy, P.; Budzelaar, P. H. M. J. Organomet. Chem.
1993, 455, 247–253. (b) Drent, E.; Arnoldy, P.; Budzelaar, P. H. M. J.
Organomet. Chem. 1994, 475, 57–63.
(27) Chen, H.-P.; Liu, Y.-H.; Peng, S.-M.; Liu, S.-T. Organometallics
2003, 22, 4893–4899.

3268 Organometallics, Vol. 28, No. 11, 2009
Flapper et al.
Table 2. Ethene Oligomerization Using Complexes 7 as Catalyst
Precursora
complexes 7 are hardly active as ethene oligomerization
catalysts, giving very low turnover frequencies.
product distribution (%)c
complex
TOFb
C4
C5
C6
Experimental Section
7a
7b
7c
7d
7e
3.1
2.5
2.6
2.6
1.6
90
92
90
92
94
7
6
10
6
3
2
General Information. All reactions involving sensitive com-
pounds were carried out under an atmosphere of purified dinitrogen
using standard Schlenk and glovebox techniques. Solvents were
dried and distilled under dinitrogen; acetonitrile, CH2Cl2, CD2Cl2,
and CDCl3 from CaH2, toluene from sodium, Et2O and THF from
sodium/benzophenone, and pentane and hexanes from sodium/
benzophenone/triglyme. Toluene and heptane in toluene solution
used for nickel-catalyzed oligomerization were stored over sodium/
potassium alloy. The syntheses of 2-bromo-6-vinylpyridine (2),
2-bromo-6-[2-(diphenylphosphinoyl)ethyl]pyridine (3), 2-aryl-6-[2-
(diphenylphosphinoyl)ethyl]pyridines 4a-d, and 2-aryl-6-[2-(diphe-
nylphosphino)ethyl]pyridines 1a-d were reported recently.23
2
6
a Conditions: 100 µmol of palladium complex, 10 bar of ethene, 0.10
mmol of heptane (internal standard), toluene solvent, total volume: 25
mL, T: 30 °C, time: 120 min. b Turnover frequency in (mol C2H4) · (mol
Pd · h)-1 c Mol percentage of combined Cn products.
.
As can be seen from the table, the complexes are hardly
active in this reaction, having almost negligible TOFs. The
major products are butenes, as is the case with the nickel-
catalyzed reaction. No polymer was detected after evaporation
of the reaction mixture. The C5 fraction is a result of the
first growing olefin chain on the methylpalladium complex,
giving rise to an odd-numbered carbon chain. After chain
termination, a palladium hydride is the starting species for
the next chain growth, and from then on only even-numbered
carbon chains are formed. With such low TOFs, the percent-
age of odd-numbered chains should be higher than is observed
here. This shows that most chains eliminate after insertion
of only one molecule of ethene, thus producing propene,
which is vented off at the end of the reaction. Although active
palladium catalysts bearing P,N ligands have been reported
for ethene oligomerization,7,9,12,31 low or no activity is not
uncommon with such complexes.6,13,15,17,26,32
(DME)NiCl2,33 (COD)Pd(CH3)Cl,34 and NaBAr′4 were synthe-
35
sized according to the published procedures. Zinc chloride was dried
by refluxing in freshly distilled thionyl chloride for 16 h, removal
of all volatiles under reduced pressure, and drying in Vacuo for
24 h. Phenylsilane was distilled under dinitrogen. All other
chemicals were purchased from commercial suppliers and used as
received. Silica 60 was used for column chromatography. Elemental
analyses were carried out by Kolbe Mikroanalytisch Laboratorium,
Mu¨lheim an der Ruhr (Germany). Electron ionization (EI) mass
spectrometry (MS) was carried out on an Agilent Technologies
6890N/5973N GC-MS using an ionizing energy of 70 eV. Samples
were dissolved in Et2O or CH2Cl2. Fast atom bombardment (FAB)
high-resolution mass spectrometry (HRMS) and field desorption
(FD) mass spectrometry were carried out at the Department of Mass
Spectrometry at the University of Amsterdam using a JEOL JMS
SX/SX102A four-sector mass spectrometer, coupled to a JEOL MS-
MP9021D/UPD system program. For FAB, samples were loaded
in a matrix solution (3-nitrobenzyl alcohol) onto a stainless steel
probe and bombarded with xenon atoms with an energy of 3 keV.
During the high-resolution FAB-MS measurements a resolving
power of 10 000 (10% valley definition) was used. For FD, 10 µm
tungsten wire FD emitters containing carbon microneedles with an
average length of 30 µm were used. The samples were dissolved
in CH2Cl2 and then loaded onto the emitters with the dipping
technique. An emittercurrent of 0-30 mA was used to desorb the
samples. The ion source was generally at room temperature. NMR
spectra were recorded on a Varian Mercury 300 operating at 300.1
(1H), 75.5 (13C), 121.5 (31P), and 282.4 (19F) MHz or a Varian Inova
500 operating at 499.8 (1H) and 125.7 (13C) MHz, at ambient
temperature unless stated otherwise. Signals are referenced to TMS
(1H and 13C), 85% H3PO4 (31P), and CCl2F2 (19F) as external
standards at 0 ppm. The following abbreviations are used: py )
pyridyl, Fc ) ferrocenyl, Ar′ ) 3,5-di(trifluoromethyl)phenyl.
Magnetic moments were determined in CD2Cl2 solution with 5%
cyclohexane as reference by the Evans NMR method.36 Experi-
mental X-band EPR spectra were recorded on a Bruker EMX Plus
spectrometer with a spectrometer frequency of 9.378347 GHz in
CH2Cl2 at 20 K. The addition of ∼0.1 M [n-Bu4N]PF6 to the
solution improved the quality of the glass. Solution-phase GC
analyses were performed on an Interscience Thermo Focus GC
equipped with a flame ionization detector and a 10 m Restek RTX-5
Conclusions
We have prepared the pyridine-phosphine ligands 1, their
nickel dichloride complexes 5, their methylpalladium chloride
complexes 6, and cationic methylpalladium acetonitrile
complexes 7. The ligands have bulky substituents at the
6-position of the pyridine. These show a large influence on
the coordination chemistry and catalytic behavior of com-
plexes with a square-planar surrounded metal center. In the
neutral palladium complexes 6, with the chloride anion
coordinated to the metal, the ligands are unable to adopt a
classical bidentate coordination mode. Binuclear species are
formed for 6a-d, whereas 6e gives a mixture of products.
In the cationic complexes 7, with acetonitrile ligated to the
palladium instead of the chloride anion, homonuclear cis
coordination is possible. This is also the case with the
tetrahedrally surrounded nickel dichloride complexes 5.
After MAO activation, the nickel complexes are active in
the oligomerization of ethene. Turnover frequencies are between
2800 and 11 000 [mol C2H4] · [mol Ni · h-1], and butenes form
93 to 97 mol % of the product. Selectivity for 1-butene up to
93% was observed. A larger aromatic substituent at the ligand
results in increased productivity and decreased 1-butene forma-
tion. The influence of the ligand substituents on the active
species (with a square-planar surrounded metal center) became
evident from the different catalytic behavior of precatalysts 5
and that of the catalyst precursor 8. This complex is similar to
complexes 5, but lacks such a substituent and, as a consequence
of this, shows a different behavior in catalysis. The palladium
(33) Ward, L. G. L. Inorg. Synth. 1971, 13, 154–64.
(34) Rulke, R. E.; Ernsting, J. M.; Spek, A. L.; Elsevier, C. J.; Van
Leeuwen, P. W. N. M.; Vrieze, K. Inorg. Chem. 1993, 32, 5769–5778.
(35) Brookhart, M.; Grant, B.; Volpe, A. F. Organometallics 1992, 11,
3920–3922.
(36) (a) Evans, D. F. J. Chem. Soc. 1959, 2003–5. (b) Evans, D. F.;
Fazakerley, G. V.; Phillips, R. F. J. Chem. Soc. A 1971, 1931–4. (c)
Britovsek, G. J. P.; Gibson, V. C.; Spitzmesser, S. K.; Tellmann, K. P.;
White, A. J. P.; Williams, D. J. J. Chem. Soc., Dalton Trans. 2002, 1159–
1171. (d) Grant, D. H. J. Chem. Educ. 1995, 72, 39–40.
(31) Daugulis, O.; Brookhart, M. Organometallics 2002, 21, 5926–5934.
(32) Guan, Z. B.; Marshall, W. J. Organometallics 2002, 21, 3580–
3586.

Ni and Pd Complexes Bearing Aromatic Substituents
Organometallics, Vol. 28, No. 11, 2009 3269
column with a 0.18 mm internal diameter, using helium as carrier
gas at 0.2 mL/min. Gas-phase GC analyses were performed on an
Interscience Compact GC equipped with a thermal conductivity
detector and a 10 m Porabond Q column with a 0.32 mm internal
diameter operated isothermally at 60 °C, using helium as carrier
gas at 60 kPa. Oligomerization reactions were performed in a
stainless steel 180 mL autoclave, equipped with a glass linear, a
thermocouple, an internal cooling spiral, a magnetic stirrer, and a
gas inlet via a 40 mL injection chamber.
2.95. Found: C, 73.22; H, 5.48, N, 2.87. MS (EI) m/z (rel intensity):
475 (91) [M]+•, 410 (100) [M - Cp]+, 290 (11) [M - PPh2]+, 289
(14) [M - PPh2 - H]+, 224 (26) [M - Cp - PPh2 - H]+.
2-[2-(Diphenylphosphino)ethyl]-6-phenylpyridinenickel Dichlo-
ride (5a). A mixture of 2-[2-(diphenylphosphino)ethyl]-6-phenylpy-
ridine (1a) (100 mg, 0.27 mmol, 1.0 equiv), (DME)NiCl2 (60 mg,
0.27 mmol, 1.0 equiv), and CH2Cl2 (10 mL) was stirred for 2 days.
It was filtered through a pad of Celite, washed with CH2Cl2, and
concentrated in Vacuo. Et2O (5 mL) was added, and the mixture
was put in a sonification bath for 30 min. The solids were filtered
off, washed with Et2O, and dried in Vacuo to yield the product as
a purple solid (60 mg, 0.12 mmol, 45%, mp 130 °C dec). Anal.
Calcd for C25H22Cl2NNiP: C, 60.41; H, 4.46; N, 2.82. Found: C,
60.45; H, 4.58, N, 2.89. HRMS (FAB) m/z: calcd for C25H22ClNNiP
[M - Cl]+ 460.0532; found 460.0528. µeff ) 2.50 µB.
2-[2-(Diphenylphosphinoyl)ethyl]-6-ferrocenylpyridine (4e).
To a solution of ferrocene (3.35 g, 18.0 mmol, 6.0 equiv) in THF
(40 mL) was slowly dropped a 1.5 M solution of tert-butyllithium
in pentane (10.0 mL, 15.0 mmol, 5.0 equiv) at 0 °C, after which
the mixture was stirred at that temperature for 30 min. Then, the
mixture was cooled to -78 °C and a solution of ZnCl2 (2.04 g,
15.0 mmol, 5.0 equiv) in THF (20 mL) was added. The mixture
was stirred for 1 h at room temperature, after which a solution of
Pd(PPh3)4 (173 mg, 0.15 mmol, 0.05 equiv) in THF (10 mL) was
added. The mixture was cooled to 0 °C, a solution of 2-bromo-6-
[2-(diphenylphosphinoyl)ethyl]pyridine (3) (1.16 g, 3.00 mmol, 1.0
equiv) in THF (40 mL) was added, and the mixture was stirred at
60 °C for 24 h. After that, 5 mL of water was added, the mixture
was concentrated in Vacuo, and EtOAc (150 mL) was added. The
organic layer was washed with water, a solution of potassium
oxalate (6.0 g, 36 mmol) in water, water again, and finally brine.
After it was dried and concentrated in Vacuo, column chromatog-
raphy (eluents: CH2Cl2 f 5% MeOH/CH2Cl2) yielded the product
as an orange solid (1.40 g, 2.84 mmol, 95%, mp 166 °C). 1H NMR
δ (500 MHz, CD2Cl2) ppm: 7.84-7.79 (m, 4H, Ph-H2), 7.57-7.49
(m, 6H, Ph-H3 + -H4), 7.46 (t, J ) 7.7 Hz, 1H, py-H4), 7.25 (d,
J ) 7.7 Hz, 1H, py-H5), 6.91 (d, J ) 7.7 Hz, 1H, py-H3), 4.93 (t,
J ) 1.9 Hz, 2H, Fc-H2 or -H3), 4.93 (t, J ) 1.9 Hz, 2H, Fc-H2 or
-H3), 4.03 (s, 5H, Fc-H1′), 3.07-3.01 (m, 2H, py-CH2), 2.87-2.81
(m, 2H, P-CH2). 13C(1H) NMR δ (125 MHz, CD2Cl2) ppm: 160.1
(d, J ) 14.8 Hz, py-C2), 159.1 (s, py-C6), 136.8 (s, CH), 134.2 (d,
J ) 97.5 Hz, Ph-C1), 132.1 (d, J ) 3.0 Hz, CH), 131.3 (d, J ) 9.2
Hz, CH), 129.2 (d, J ) 11.4 Hz, CH), 120.0 (s, CH), 118.2 (s,
CH), 84.8 (s, Fc-C1), 70.3 (s, Fc-C2 or -C3), 70.1 (s, Fc-C1′), 67.9
(s, Fc-C2 or -C3), 30.2 (d, J ) 2.6 Hz, py-CH2), 29.5 (d, J ) 71.6
Hz, P-CH2). 31P(1H) NMR δ (121 MHz, CD2Cl2) ppm: 32.2. Anal.
Calcd for C29H26FeNOP: C, 70.89; H, 5.33; N, 2.85. Found: C,
70.84; H, 5.28, N, 2.76. HRMS (FAB) m/z: calcd for C29H27FeNOP
[M + H]+ 492.1180; found 492.1173.
2-[2-(Diphenylphosphino)ethyl]-6-ferrocenylpyridine (1e). 2-[2-
(Diphenylphosphinoyl)ethyl]-6-ferrocenylpyridine (4e) (1.39 g, 2.83
mmol, 1.0 equiv) was dissolved in phenylsilane (15 mL, 122 mmol,
43 equiv), and the mixture was refluxed overnight, after which
unlocked 31P NMR showed full conversion. The mixture was
concentrated in Vacuo and purified by column chromatography
(eluents: CH2Cl2 f 4% MeOH/CH2Cl2). Co-evaporation with
hexanes yielded the product as an orange solid (1.11 g, 2.33 mmol,
82%, mp 104 °C). 1H NMR δ (500 MHz, CD2Cl2) ppm: 7.54-7.50
(m, 4H, Ph-H2), 7.48 (t, J ) 7.7 Hz, 1H, py-H4), 7.39-7.33 (m,
6H, Ph-H3 + -H4), 7.25 (d, J ) 7.7 Hz, 1H, py-H5), 6.91 (d, J )
7.7 Hz, 1H, py-H3), 4.93 (t, J ) 1.7 Hz, 2H, Fc-H2 or -H3), 4.38
(t, J ) 1.7 Hz, 2H, Fc-H2 or -H3), 4.03 (s, 5H, Fc-H1′), 2.90-2.84
(m, 2H, py-CH2), 2.60-2.56 (m, 2H, P-CH2). 13C(1H) NMR δ (125
MHz, CD2Cl2) ppm: 161.6 (d, J ) 12.7 Hz, py-C2), 159.0 (s, py-
C6), 139.6 (d, J ) 14.0 Hz, Ph-C1), 136.6 (s, CH), 133.3 (d, J )
18.6 Hz, CH), 129.5 (d, J ) 7.6 Hz, CH), 129.0 (s, CH), 119.8 (s,
CH), 118.0 (s, CH), 85.0 (s, Fc-C1), 70.2 (s, Fc-C2 or -C3), 70.1
(s, Fc-C1′), 67.9 (s, Fc-C2 or -C3), 34.9 (d, J ) 17.4 Hz, py-CH2),
28.6 (d, J ) 12.3 Hz, P-CH2). 31P(1H) NMR δ (121 MHz, CD2Cl2)
ppm: -15.2. Anal. Calcd for C29H26FeNP: C, 73.28; H, 5.51; N,
2-[2-(Diphenylphosphino)ethyl]-6-(1-naphthyl)pyridinenickel
Dichloride (5b). A mixture of 2-[2-(diphenylphosphino)ethyl]-6-
(1-naphthyl)pyridine (1b) (200 mg, 0.48 mmol, 1.0 equiv), (DME)N-
iCl2 (105 mg, 0.48 mmol, 1.0 equiv), and CH2Cl2 (10 mL) was
stirred for 16 h. It was filtered through a pad of Celite, washed
with CH2Cl2, and concentrated in Vacuo. Et2O (10 mL) was added,
and the mixture was put in a sonification bath for 30 min. The
solids were filtered off, washed with Et2O, and dried in Vacuo to
yield the product as a purple solid (160 mg, 0.29 mmol, 61%, mp
110 °C dec). Anal. Calcd for C29H24Cl2NNiP: C, 63.67; H, 4.42;
N, 2.56. Found: C, 63.84; H, 4.50; N, 2.48. HRMS (FAB) m/z:
calcd for C29H24NNiP [M - 2Cl]+ 475.1000; found 475.0997. µeff
) 2.24 µB.
2-[2-(Diphenylphosphino)ethyl]-6-(9-phenanthryl)pyridinenick-
el Dichloride (5c). A mixture of 2-[2-(diphenylphosphino)ethyl]-
6-(9-phenanthryl)pyridine (1c) (227 mg, 0.49 mmol, 1.0 equiv),
(DME)NiCl2 (107 mg, 0.49 mmol, 1.0 equiv), and CH2Cl2 (15 mL)
was stirred for 16 h. It was filtered through a pad of Celite, washed
with CH2Cl2, and concentrated in Vacuo. Et2O (10 mL) was added,
and the mixture was put in a sonification bath for 30 min. The
solids were filtered off, washed with Et2O, and dried in Vacuo to
yield the product as a purple solid (266 mg, 0.45 mmol, 92%, mp
145 °C dec). Anal. Calcd for C33H26Cl2NNiP: C, 66.38; H, 4.39;
N, 2.35. Found: C, 66.47; H, 4.45; N, 2.32. HRMS (FAB) m/z:
calcd for C33H26ClNNiP [M - Cl]+ 560.0845; found 560.0859. µeff
)2.62 µB.
2-(9-Anthracyl)-6-[2-(diphenylphosphino)ethyl]pyridinenickel
Dichloride (5d). A mixture of 2-(9-anthracyl)-6-[2-(diphenylphos-
phino)ethyl]pyridine (1d) (100 mg, 0.21 mmol, 1.0 equiv),
(DME)NiCl2 (47 mg, 0.21 mmol, 1.0 equiv), and CH2Cl2 (10
mL) was stirred for 16 h. It was filtered through a pad of Celite,
washed with CH2Cl2, and concentrated in Vacuo. Et2O (5 mL)
was added, and the mixture was put in a sonification bath for
30 min. The solids were filtered off, washed with Et2O, and dried
in Vacuo to yield the product as a brown solid (93 mg, 0.16
mmol, 73%, mp 150 °C dec). Anal. Calcd for C33H26Cl2NNiP:
C, 66.38; H, 4.39; N, 2.35. Found: C, 66.18; H, 4.45; N, 2.26.
HRMS (FAB) m/z: calcd for C33H26ClNNiP [M - Cl]+ 560.0845;
found 560.0849. µeff ) 2.75 µB.
2-[2-(Diphenylphosphino)ethyl]-6-ferrocenylpyridinenickel Dichlo-
ride (5e). A mixture of 2-[2-(diphenylphosphino)ethyl]-6-ferro-
cenylpyridine (1e) (100 mg, 0.21 mmol, 1.0 equiv), (DME)NiCl2
(46 mg, 0.21 mmol, 1.0 equiv), and CH2Cl2 (10 mL) was stirred
for 16 h. It was filtered through a pad of Celite, washed with
CH2Cl2, and concentrated in Vacuo. Et2O (5 mL) was added,
and the mixture was put in a sonification bath for 30 min. The
solids were filtered off, washed with Et2O, and dried in Vacuo
to yield the product as a dark red solid (78 mg, 0.13 mmol,
61%, mp 120 °C dec). Anal. Calcd for C29H26Cl2FeNNiP: C,

3270 Organometallics, Vol. 28, No. 11, 2009
Flapper et al.
57.58; H, 4.33; N, 2.32. Found: C, 57.50; H, 4.31; N, 2.26.
HRMS (FAB) m/z: calcd for C29H26ClFeNNiP [M - Cl]+
568.0194; found 568.0197. µeff ) 2.28 µB.
38.8. 19F(1H) NMR δ (282 MHz, CD2Cl2) ppm: -63.0. Anal. Calcd
for C64H42BF24N2PPd: C, 53.26; H, 2.93; N, 1.94. Found: C, 53.21;
H, 3.05; N, 1.89. HRMS (FAB) m/z: calcd for C30H27NPPd [M -
BAr′4 - CH3CN]+ 538.0928; found 538.0929. MS (FD) m/z: 602 [M
- BAr′4 + Na]+.
2-[2-(Diphenylphosphino)ethyl]-6-ferrocenylpyridinemethylpal-
ladium Chloride (6e). 2-[2-(Diphenylphosphino)ethyl]-6-ferroce-
nylpyridine (6e) (500 mg, 1.05 mmol, 1.0 equiv) and (COD)-
Pd(CH3)Cl (279 mg, 1.05 mmol, 1.0 equiv) were dissolved in
CH2Cl2 (30 mL), and the mixture was stirred for 16 h. Then, it
was concentrated in Vacuo to approximately 3 mL, after which 40
mL of hexanes was added under vigorous stirring. The orange
precipitate was filtrated off and washed with hexanes. Drying in
Vacuo yielded the product as an orange solid (621 mg, 0.98 mmol,
94%). Anal. Calcd for C30H29ClFeNPPd: C, 56.99; H, 4.62; N, 2.22.
Found: C, 56.94; H, 4.60; N, 2.19.
2-[2-(Diphenylphosphino)ethyl]-6-(9-phenanthryl)pyridinemeth-
ylpalladium(acetonitrile) Tetrakis[3,5-bis(trifluoromethyl)phe-
nyl]borate (7c). To a mixture of 2-[2-(diphenylphosphino)ethyl]-
6-(9-phenatryl)pyridinemethylpalladium chloride (6c) (184 mg,
0.295 mmol, 1.0 equiv) and sodium tetrakis[(3,5-trifluorometh-
yl)phenyl]borate (261 mg, 0.295 mmol, 1.0 equiv) were added
CH3CN (3 mL) and CH2Cl2 (15 mL), and the mixture was stirred
for 18 h. It was cannula filtrated, evaporated to dryness, and co-
evaporated with pentane (2 times 5 mL) to yield the product as a
2-[2-(Diphenylphosphino)ethyl]-6-phenylpyridinemethylpalla-
dium(acetonitrile) Tetrakis[3,5-bis(trifluoromethyl)phenyl]borate
(7a). To a mixture of 2-[2-(diphenylphosphino)ethyl]-6-phenylpy-
ridinemethylpalladium chloride (6a) (131 mg, 0.250 mmol, 1.0
equiv) and sodium tetrakis[(3,5-trifluoromethyl)phenyl]borate (221
mg, 0.250 mmol, 1.0 equiv) were added CH3CN (4 mL) and CH2Cl2
(20 mL), and the mixture was stirred for 16 h. It was cannula
filtrated, evaporated to dryness, and co-evaporated with 5 mL of
pentane to yield the product as a white solid (321 mg, 0.230 mmol,
1
white solid (399 mg, 0.267 mmol, 91%). H NMR δ (500 MHz,
CD2Cl2) ppm: 9.06 (d, J ) 8.3 Hz, 1H), 8.81 (d, J ) 8.3 Hz, 1H),
8.12-8.07 (m, 2H), 8.04 (s, 1H), 8.01-7.97 (m, 2H), 7.91-7.85
(m, 4H), 7.83-7.79 (m, 1H), 7.76-7.72 (m, 8H, Ar′-H2), 7.60-7.48
(m, 10H), 7.46-7.40 (m, 4H), 3.39-3.26 (m, 2H, py-CH2),
2.71-2.62 (m, 1H, P-CHH), 2.39-2.31 (m, 1H, P-CHH), 1.55 (s,
3H, NCCH3), -0.63 (s, 3H, Pd-CH3). 13C(1H) NMR δ (125 MHz,
CD2Cl2) ppm: 162.4 (q, J ) 49.8 Hz, Ar′-C1), 159.6 (s, py-C2),
159.4 (s, py-C6), 141.3 (CH), 135.5 (bs, Ar′-C2), 133.6 (d, J )
11.4 Hz, CH), 133.4 (d, J ) 11.0 Hz, CH), 132.8 (d, J ) 2.5 Hz,
CH), 132.7 (d, J ) 2.5 Hz, CH), 131.5 (s, Cq), 131.2 (s, Cq), 131.0
(s, CH), 130.2-129.7 (m (consisting of 5 peaks), CH), 129.5
(quartet of multiplets, J ) 31.6 Hz, Ar′-C3), 129.2 (s, CH), 128.8
(d, J ) 55.3 Hz, Ph-C1), 128.8 (s, CH), 126.5 (s, CH), 125.9 (s,
NCCH3), 125.4 (s, CH), 125.3 (s, CH), 125.2 (q, J ) 272.4, CF3),
123.7 (s, CH), 118.1 (m, Ar′-C4), 33.3 (s, py-CH2), 25.5 (d, J )
32.1 Hz, P-CH2), 6.5 (s, NCCH3), 1.7 (s, Pd-CH3); signals for some
quaternary carbons oVerlapped with other signals. 31P(1H) NMR
δ (121 MHz, CD2Cl2) ppm: 38.9. 19F(1H) NMR δ (282 MHz,
CD2Cl2) ppm: 63.0. HRMS (FAB) m/z: calcd for C34H29NPPd [M
- BAr′4 - CH3CN]+ 588.1086; found 588.1088. MS (FD) m/z:
652 [M - BAr′4 + Na]+.
1
92%). H NMR δ (500 MHz, CD2Cl2) ppm: 7.93 (t, J ) 7.6 Hz,
1H, py-H4), 7.85-7.82 (m, 2H, Ph(P)-H4), 7.76-7.72 (m, 8H, Ar′-
H2), 7.68-7.54 (m, 18 H, py-H5 + Ph(P)-H2 + -H3 + Ph(py)-
H2 + -H3 + -H4 + Ar′-H4), 7.39 (dd, J ) 0.8 Hz, 1H, py-H3),
3.54-3.46 (m, 2H, py-CH2), 2.54-2.49 (m, 2H, P-CH2), 1.95 (s,
3H, NCCH3), 0.36 (d, J ) 1.7 Hz, 3H, Pd-CH3). 13C(1H) NMR δ
(125 MHz, CD2Cl2) ppm: 162.4 (q, J ) 49.8 Hz, Ar′-C1), 162.2
(s, py-C2), 161.2 (s, py-C6), 140.7 (s, CH), 140.1 (s, Ph(py)-C1),
135.5 (bs, Ar′-C2), 133.3 (d, J ) 13.4 Hz, CH), 132.6 (d, J ) 7.6
Hz, CH), 131.3 (s, CH), 130.4 (s, CH), 129.9 (d, J ) 11.0 Hz,
CH), 129.5 (quartet of multiplets, J ) 31.6 Hz, Ar′-C3), 127.6 (s,
CH), 125.2 (q, J ) 272.4, CF3), 124.5 (s, CH), 124.4 (s, CH), 118.1
(m, Ar′-C4), 35.2 (d, J ) 3.0 Hz, py-CH2), 25.0 (d, J ) 29.9 Hz,
P-CH2), 2.7 (s, NCCH3), 0.3 (s, Pd-CH3); signals for Ph(P)-C1 and
NCCH3 could not be obserVed due to oVerlap with other signals.
31P(1H) NMR δ (121 MHz, CD2Cl2) ppm: 38.5. 19F(1H) NMR δ
(282 MHz, CD2Cl2) ppm: -63.0. Anal. Calcd for C60H40BF24N2PPd:
C, 51.73; H, 2.89; N, 2.01. Found: C, 51.56; H, 2.94; N, 1.88.
HRMS (FAB) m/z: calcd for C26H25NPPd [M - BAr′4 - CH3CN]+
488.0770; found 488.0775. MS (FD) m/z: 552 [M - BAr′4 + Na]+.
2-(9-Anthracyl)-6-[2-(diphenylphosphino)ethyl]pyridinemethyl-
palladium(acetonitrile) Tetrakis[3,5-bis(trifluoromethyl)phenyl]bo-
rate (7d). To a mixture of 2-(9-anthracyl)-6-[2-(diphenylphosphi-
no)ethyl]pyridine methylpalladium chloride (6d) (409 mg, 0.655
mmol, 1.0 equiv) and sodium tetrakis[(3,5-trifluoromethyl)phe-
nyl]borate (580 mg, 0.655 mmol, 1.0 equiv) were added CH3CN
(2 mL) and CH2Cl2 (20 mL), and the mixture was stirred for 16 h.
It was cannula filtrated, evaporated to dryness, and co-evaporated
with hexanes and pentane to yield the product as a yellow solid
(927 mg, 0.621 mmol, 95%). 1H NMR δ (500 MHz, CD2Cl2) ppm:
8.83 (s, 1H, anth-H10), 8.27 (d, J ) 8.5 Hz, 2H), 8.18 (t, J ) 7.9
Hz, 1H), 7.81-7.73 (m, 10H), 7.70 (d, J ) 8.8 Hz, 2H), 7.67-7.63
(m, 2H), 7.60-7.52 (m, 6H), 7.46-7.36 (m, 10H), 3.37-3.28 (m,
2H, py-CH2), 2.54-2.49 (m, 2H, P-CH2), 1.62 (s, 3H, NCCH3),
-0.67 (s, 3H, Pd-CH3). 13C(1H) NMR δ (125 MHz, CD2Cl2) ppm:
162.4 (q, J ) 49.8 Hz, Ar′-C1), 160.5 (s, py-C6), 158.3 (s, py-
C2), 140 (s, CH), 135.5 (bs, Ar′-C2), 135.3 (s, Cq), 133.5 (d, J )
11.4 Hz, CH), 132.6 (d, J ) 2.5 Hz, CH), 132.4 (s, Cq), 131.0 (s,
CH), 130.3 (s, CH), 129.8 (d, J ) 11.0 Hz, CH), 129.6 (s, Cq),
129.5 (quartet of multiplets, J ) 31.6 Hz, Ar′-C3), 128.9 (d, J )
46.8 Hz, Ph-C1), 128.8 (s, CH), 128.4 (s, CH), 127.1 (s, CH), 125.5
(s, CH), 125.2 (q, J ) 272.4, CF3), 123.3 (s, CH), 118.1 (m, Ar′-
C4), 117.9 (s, NCCH3), 33.2 (s, P-CH2), 25.1 (d, J ) 32.1 Hz,
P-CH2), 3.8 (s, NCCH3), 1.9 (s, Pd-CH3). 31P(1H) NMR δ (121
MHz, CD2Cl2) ppm: 38.2. 19F(1H) NMR δ (282 MHz, CD2Cl2) ppm:
-63.0. Anal. Calcd for C68H44BF24N2PPd: C, 54.69; H, 2.97; N,
2-[2-(Diphenylphosphino)ethyl]-6-(1-naphthyl)pyridinemeth-
ylpalladium(acetonitrile) Tetrakis[3,5-bis(trifluoromethyl)phe-
nyl]borate (7b). To a mixture of 2-[2-(diphenylphosphino)ethyl]-6-
(1-naphthyl)pyridine methylpalladium chloride (6b) (76 mg, 0.132
mmol, 1.0 equiv) and sodium tetrakis[(3,5-trifluoromethyl)phenyl]bo-
rate (117 mg, 0.132 mmol, 1.0 equiv) were added CH3CN (1 mL)
and CH2Cl2 (5 mL), and the mixture was stirred for 24 h. It was cannula
filtrated, evaporated to dryness, and co-evaporated with pentane (5
mL) to yield the product as a yellow solid (189 mg, 0.131 mmol, 99%).
1H NMR δ (500 MHz, CD2Cl2) ppm: 8.17-8.15 (m, 2H), 8.04-8.00
(m, 2H), 7.81-7.79 (m, 1H, py-H4), 7.76-7.72 (m, 8H, Ar′-H2),
7.72-7.69 (m, 4H), 7.68-7.61 (m, 3H), 7.61-7.53 (m, 8H), 7.50-7.46
(m, 4H), 3.56-3.35 (m, 2H, py-CH2), 2.72 (dt, J ) 14.2, 6.6 Hz, 1H,
P-CHH), 2.32 (dt, J ) 12.7, 7.3 Hz, 1H, P-CHH), 1.51 (s, 3H,
NCCH3), -0.22 (s, 3H, Pd-CH3). 13C(1H) NMR δ (125 MHz, CD2Cl2)
ppm: 162.4 (q, J ) 49.8 Hz, Ar′-C1), 160.9 (s, py-C2), 160.0 (s, py-
C6), 140.4 (s, CH), 138.9 (s, CH), 137.8 (s, Cq), 135.5 (bs, Ar′-C2),
135.1 (s, Cq), 134.0 (d, J ) 11.4 Hz, CH), 133.0 (s, CH), 132.7 (d, J
) 10.6 Hz, CH), 132.2 (s, CH), 131.7 (s, CH), 131.1 (s, Cq), 130.6 (s,
CH), 130.0 (d, J ) 11.0 Hz, CH), 129.8 (s, CH), 129.5 (quartet of
multiplets, J ) 31.6 Hz, Ar′-C3), 127.8 (s, CH), 126.4 (s, CH), 125.2
(q, J ) 272.4, CF3), 124.9 (s, CH), 118.1 (m, Ar′-C4), 117.6 (s,
NCCH3), 34.9 (s, py-CH2), 25.7 (d, J ) 32.9 Hz, P-CH2), 4.0 (s,
NCCH3), 1.8 (s, Pd-CH3). 31P(1H) NMR δ (121 MHz, CD2Cl2) ppm:

Ni and Pd Complexes Bearing Aromatic Substituents
Organometallics, Vol. 28, No. 11, 2009 3271
1.88. Found: C, 54.84; H, 3.03; N, 1.84. HRMS (FAB) m/z: calcd
for C34H29NPPd [M - BAr′4 - CH3CN]+ 588.1086; found
588.1078. MS (FD) m/z: 652 [M - BAr′4 + Na]+.
of heptane in toluene (0.20 M, total internal standard 1.0 mmol)
were introduced under dinitrogen atmosphere. Then, it was purged
with 10 bar of ethene three times and brought to 10 bar of ethene
pressure. After 10 min, the injection chamber was closed, the
autoclave was disconnected from all lines, and the autoclave was
weighed. The autoclave was reconnected, the pressure in the
reaction chamber was lowered to ∼8 bar, and the connection
between the reaction chamber and the injection chamber was
opened, causing the immediate introduction of the MAO and
internal standard solution in the reaction chamber. During the run,
a constant ethene pressure of 10 bar was applied and the temperature
was controlled at 30 °C through the internal cooling spiral against
the exotherm of the reaction. After the run, the autoclave was closed,
disconnected from all lines, and weighed. A sample for gas-phase
GC analysis was taken, and the autoclave was vented and opened.
A 50 mL amount of ice-cold 2 M hydrochloric acid was added to
the reaction mixture, and it was stirred vigorously in an ice-bath
before samples for liquid-phase GC analysis were taken. Ethene
consumption was calculated from the increase in weight of the
autoclave. Total amount of butenes was calculated from the
difference between total ethene consumption and the amount of
other oligomers formed.
2-[2-(Diphenylphosphino)ethyl]-6-ferrocenylpyridinemethylpal-
ladium(acetonitrile) Tetrakis[3,5-bis(trifluoromethyl)phenyl]bo-
rate (7e). To a mixture of 2-[2-(diphenylphosphino)ethyl]-6-
ferrocenylpyridinemethylpalladium chloride (6e) (219 mg, 0.347
mmol, 1.0 equiv) and sodium tetrakis[(3,5-trifluoromethyl)phe-
nyl]borate (307 mg, 0.347 mmol, 1.0 equiv) were added CH3CN
(4 mL) and CH2Cl2 (20 mL), and the mixture was stirred for 18 h.
It was cannula filtrated, evaporated to dryness, and co-evaporated
two times with 5 mL of pentane to yield the product as an orange
solid (478 mg, 0.318 mmol, 92%). 1H NMR δ (500 MHz, CD2Cl2)
ppm: 7.77-7.71 (m, 13H, py-H4 + Ph-H2 + Ar′-H2), 7.67-7.62
(m, 2H, Ph-H4), 7.61-7.54 (m, 9H, py-H5 + Ph-H3 + Ar′-H4),
7.16 (d, J ) 5.6 Hz, 1H, py-H3), 5.49-5.46 (m, 2H, Fc-H2 or
-H3), 4.78-4.75 (m, 2H, Fc-H2 or -H3), 4.48 (s, 5H, Fc-H1′),
3.13-3.05 (m, 2H, py-CH2), 2.63-2.57 (m, 2H, P-CH2), 1.98 (s,
3H, NCCH3), 0.73 (d, J ) 1.2 Hz, 3H, Pd-CH3). 13C(1H) NMR δ
(125 MHz, CD2Cl2) ppm: 162.4 (q, J ) 49.8 Hz, Ar′-C1), 161.6
(s, py-C2), 159.2 (s, py-C6), 139.9 (s, CH), 135.5 (bs, Ar′-C2),
133.6 (d, J ) 11.4 Hz, CH), 132.7 (s, CH), 130.0 (d, J ) 11.4 Hz,
CH), 129.5 (quartet of multiplets, J ) 31.6 Hz, Ar′-C3), 129.2
(oVerlapping with BAr′4 signals, Ph-C1), 125.2 (q, J ) 272.4, CF3),
124.2 (s, CH), 122.5 (s, CH), 118.1 (m, Ar’-C4), 117.3 (s, NCCH3),
86.8 (s, Fc-C1), 74.1 (s, Fc-C2 or -C3), 71.3 (s, Fc-C1′), 64.5 (s,
Fc-C2 or -C3), 33.0 (s, py-CH2), 25.2 (d, J ) 33.3 Hz, P-CH2), 2.7
(s, NCCH3), 1.2 (s, Pd-CH3). 31P(1H) NMR δ (121 MHz, CD2Cl2)
ppm: 36.7. 19F(1H) NMR δ (282 MHz, CD2Cl2) ppm: -63.0. HRMS
(FAB) m/z: calcd for C30H29FeNPPd [M - BAr′4 - CH3CN]+
General Procedure for the Palladium-Catalyzed Oligomeriza-
tion. The autoclave was charged with the catalyst precursor (100
µmol), closed, brought under dinitrogen atmosphere, and warmed
to 30 °C. Then, 25 mL of a solution of heptane in toluene (0.0040
M, total internal standard 0.10 mmol) was introduced, and the
autoclave was purged with 10 bar of ethene three times and brought
under 10 bar of ethene pressure. After the run, the autoclave was
vented and opened. A 50 mL amount of ice-cold 2 M hydrochloric
acid was added to the reaction mixture, and it was stirred vigorously
in an ice-bath. A sample of the organic phase was cooled to -70
°C and evacuated three times to remove ethene before liquid-phase
GC analysis was performed.
596.0436; found 596.0428. MS (FD) m/z: 696 [M - BAr′4
-
CH3CN]+.
General Procedure for the Nickel-Catalyzed Oligomerization.
The autoclave was heated to 140 °C under vacuum for 1 h and
cooled under dinitrogen atmosphere. A solution or suspension of
the catalyst precursor (10 µmol) in toluene (18.5 mL) was
introduced in the reaction chamber, and the autoclave was purged
with 10 bar of ethene three times and brought to 10 bar of ethene
pressure. After 10 min, the reaction chamber was closed. The
injection chamber was vented, and 1.5 mL of MAO in toluene
solution (10% w/w, total Al 2.3 mmol) and 5.0 mL of a solution
Acknowledgment. This work is part of the research
program of the Dutch Polymer Institute (project 106). We
thank Jurriaan Beckers for gas-phase GC measurements and
Dr. Bas de Bruin for EPR measurements and discussions.
OM9000378