Nickel and palladium complexes of Pyridine-Phosphine ligands as ethene oligomerization catalysts

Article abstract of DOI:10.1021/om800903n

Pyridine-phosphine ligands 1-5 have been used to prepare neutral nickel dichloride complexes, neutral methylpalladium chloride complexes, and cationic methylpalladium complexes. The ligands consist of a diphenylphosphine and a pyridine moiety and differ i

Full text of DOI:10.1021/om800903n

1180
Organometallics 2009, 28, 1180–1192
Nickel and Palladium Complexes of Pyridine-Phosphine Ligands as
Ethene Oligomerization Catalysts
Jitte Flapper,†,‡ Huub Kooijman,§ Martin Lutz,§ Anthony L. Spek,§ 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, School of Chemistry, UniVersity of St. Andrews, St. Andrews, Fife,
Scotland KY16 9ST, U.K., BijVoet Center for Biomolecular Research, Crystal and Structural Chemistry,
Faculty of Science, Utrecht UniVersity, Padualaan 8, 3584 CH Utrecht, The Netherlands, and Dutch
Polymer Institute, P.O. Box 902, 5600 AX EindhoVen, The Netherlands
ReceiVed September 17, 2008
Pyridine-phosphine ligands 1-5 have been used to prepare neutral nickel dichloride complexes, neutral
methylpalladium chloride complexes, and cationic methylpalladium complexes. The ligands consist of a
diphenylphosphine and a pyridine moiety and differ in the backbone connecting those donor groups.
Nickel complexes 9-13 are paramagnetic complexes, and they were characterized by elemental analysis,
high-resolution mass spectrometry, and, for 10 and 12, single-crystal X-ray diffraction. Neutral palladium
complexes 14-18 were fully characterized. Single-crystal X-ray diffraction was performed on complexes
15 and 16, and variable-temperature NMR demonstrated that 16 exhibits slow inversion of the metallacycle.
Cationic palladium species 19-23 were obtained from the neutral complexes after chloride abstraction.
Like its neutral precursor, 21 showed slow ring inversion. The nickel species were evaluated as ethene
oligomerization catalysts after activation with MAO. All complexes were highly active, with TOFs between
24 × 103 and 85 × 103 (mol C2H4) · (mol Ni · h)-1. Butenes were the major product in all cases, forming
76 to 96 mol % of the product. Selectivities for 1-butene were between 10% and 40%. The cationic
palladium species showed a very low productivity for ethene oligomerization, with TOFs e16 (mol
C2H4) · (mol Pd · h)-1 and 38 to 88 mol % butenes as the main product.
palladium complexes with P,N ligands have been used in the
oligomerization and polymerization of ethene.4,5 An advantage
of those ligands can be the improved thermal stability in
catalysis, as nickel complexes with P,N ligands showed much
higher thermal stability than related N,N ligand complexes.6,7
This might overcome the problem of fast catalyst deactivation
at high temperatures that diimine-based catalysts suffer from.8
A drawback of P,N ligands can be the reduced activity as a
consequence of the different trans-effect of the two donor
atoms;7,9 in polyketone synthesis the symmetric P,P and N,N
ligands give much faster catalysts than P,N ligands,10 but the
SHOP catalyst for instance contains an asymmetric P,O ligand
that gives high rates.11 Among the different types of P,N ligands
tested in nickel- or palladium-catalyzed ethene oligomerization
are pyridine-phosphines and -phosphinites,12-19 oxazoline-
phosphines and -phosphinites,18-22 iminophosphoranes,23 ami-
Introduction
The development of metal complexes based on bidentate
ligands with a phosphorus and a nitrogen donor atom (P,N
ligands) is an important part of the field of transition metal
catalysis.1,2 This class of ligands is particularly interesting
because of the different trans-effect, as a result of different donor
and acceptor properties of the two coordinating groups in the
ligand. Despite extensive research, the influence of a ligand on
catalytic properties of a transition metal complex is still very
hard to predict.3 We wanted to investigate the effect of
systematic changes of the backbone in a series of closely related
ligands and study the effect of changes in chelating properties
when metal complexes bearing these ligands are used in
catalysis.
The oligomerization of ethene is one of the most important
industrial processes to obtain linear R-olefins. Nickel and
* To whom correspondence should be adressed. E-mail: pcjk@st-
andrews.ac.uk. Fax: +44-(0)1334463808. Tel: +44-(0)1334-467285.
† University of Amsterdam.
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‡ Dutch Polymer Institute.
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10.1021/om800903n CCC: $40.75
2009 American Chemical Society
Publication on Web 01/09/2009

Nickel and Palladium Complexes with P,N Ligands
Organometallics, Vol. 28, No. 4, 2009 1181
Chart 1. Ligands Used in This Study
Scheme 1. One-Pot Synthesis of Ligand 1
geometry. The ligands all consist of a diphenylphosphine moiety
and a 2-pyridyl group and differ in the backbone connecting
those parts of the molecule. Compounds 1-3 have respectively
one, two, or three methylene groups as the backbone. Ligand 4
has a two-carbon bridge between the 2-pyridyl and the phos-
phine, but integrated in a phenylene ring. The two-carbon spacer
in 5 is aliphatic as in 2, but integrated in a substituted ring
system, which makes it much more rigid.
do- and iminophosphines,24-26 iminopyrrolylphosphines,27 pyra-
zolephosphines,28
quinolinephosphines,29,30
and
pyridinephospholes.31 We are particularly interested in pyridine-
phosphine ligands.1
In this article, we present the synthesis and characterization
of neutral nickel complexes 9-13, neutral palladium compounds
14-18, and cationic palladium species 19-23. The metal
centers in these complexes are coordinated by pyridine-phosphine
ligands 1-5. The so far unreported synthesis of 4 and the
modified syntheses of 1 and 5 are presented as well. Also,
we evaluate the nickel complexes (using MAO activation) and
the cationic palladium complexes as catalyst precursors in the
oligomerization of ethene.
Ligand Synthesis. The ligands 1,32 2,33 and 332 were first
reported over three decades ago. Their original syntheses
involved the labile (2-pyridyl)-(CH2)n-Cl species, which were
made to react with diphenylphosphide. Different synthetic
procedures for 1 and 2 have appeared since, mainly to
circumvent the use of the labile intermediates. Synthesis of
2-[(diphenylphosphino)methyl]pyridine (1) has been carried out
by lithiation of picoline and subsequent reaction with chlo-
rodiphenylphosphine, either direct34 or via a more stable
intermediate in a two-step process.14 We developed a new, one-
pot procedure starting from commercial reagents for the
synthesis of the ligand; see Scheme 1. Triphenylphosphine was
added to a solution of sodium in liquid ammonia at -78 °C,
resulting in P-C cleavage to give sodium diphenylphosphide
and phenylsodium, the latter giving sodium amide and benzene.
The formation of 1 equiv of sodium amide allows the direct
use of the stable 2-(chloromethyl)pyridine hydrochloride
(6 · HCl). When this is added to the reaction mixture, it is
deprotected in situ at low temperatures. The resulting 2-(chlo-
romethyl)pyridine (6) reacts with diphenylphosphide to give the
product. After workup and purification, 1 was obtained as a
white solid in 65% isolated yield. The yield is the highest
reported for the pure product from commercial reagents.
Results and Discussion
We studied ligands 1-5 (see Chart 1) and their neutral nickel
complexes and neutral and cationic palladium complexes. They
were chosen for their similar donor groups but different
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most convenient procedure, because of the ease of multigram
preparation from commercial starting compounds.
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(3), we found that 2-(3-chloropropyl)pyridine39 was sufficiently
stable to synthesize conveniently the ligand via the original
procedure.32
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4.

1182 Organometallics, Vol. 28, No. 4, 2009
Flapper et al.
Scheme 2. Synthesis of Ligand 4
Chart 2. Complex 10′ as Reported by Braunstein et al.14
Scheme 3. Synthesis of Ligand 5
10 and 12, single-crystal X-ray diffraction was performed. All
complexes showed a characteristic purple color in dichlo-
romethane solution. In the solid state, however, only 10 and 13
were purple. The other solids were very deep purple (appearing
almost black) (9), orange (11), or light brown (12).
Very recently, the group of Braunstein also reported on
complex 9.14 They used a slightly different synthetic procedure
(NiCl2 as precursor, methanol as solvent, and 1 h reaction time)
and obtained the product as a gray powder. Also the magnetic
moment in CD2Cl2 solution of 2.2 µB differed from the value
of 2.61 µB we found. This indicates that a slightly different
species formed in our case compared to theirs.
Scheme 4. Synthesis of Nickel Complexes 9-13
The formation of a slightly different complex when using
different conditions is further illustrated when the nickel
complex of ligand 2 is considered. Braunstein et al. also reported
the formation of a related dimeric species (10′); see Chart 2.14
Although the dimeric species was not observed in the mass
spectrum, the crystal structure unambiguously proved the
binuclear nature of the complex in the solid state.
We obtained single crystals of 10 suitable for X-ray diffrac-
tion. The structure is shown in Figure 1, and selected angles
and bond lengths are given in Table 1. This shows that 10 has
a mononuclear structure. The tetracoordinated nickel center has
a distorted tetrahedral geometry, in contrast to the pentacoor-
dinated metal centers in 10′, which are distorted square-
pyramidal. Bond lengths around nickel are normal and similar
to those in a tetrahedral surrounded nickel dichloride complex
with a phosphinitopyridine ligand.14 The Cl1-Ni-Cl2 and the
P-Ni-N angles in 10 are 124.33(2)° and 98.36(4)°, respec-
tively, and the other angles around the metal are less distorted
from tetrahedral. The six-membered nickel chelate ring is in a
“twist-boat” conformation. X-ray crystal structures of nickel
dichloride complexes have been reported with the tetracoordi-
Several groups have reported the use of 2-[2-(diphenylphos-
phino)phenyl]pyridine (4),40 but, to the best of our knowledge,
full synthetic and analytical data were never reported. The
synthesis of the ligand oxide, 2-[2-(diphenylphosphinoyl)phe-
nyl]pyridine, has been reported,41 but it involved several steps
and moderate yields. We synthesized ligand 4 starting from 2-(2-
fluorophenyl)pyridine (7);42 see Scheme 2. Following a proce-
dure for a similar compound,43 we obtained 4 in 63% yield.
The ligand 2-[(1S,2R,3R,4S)-3-(diphenylphosphino)-1,7,7-
trimethylbicyclo[2.2.1]hept-2-yl]pyridine (5) was developed in
the group of Knochel.44 The synthesis involved hydrophosphi-
nation of 2-[(1R,4R)-1,7,7-trimethylbicyclo[2.2.1]hept-2-en-2-
yl]pyridine (8) with diphenylphosphine oxide to give the oxide
of the ligand, which was reduced in a second step. Use of
diphenylphosphine in the hydrophosphination led to a mixture
of 5 and its oxide, as the product is partially oxidized by DMSO,
which was used as the solvent. We found that the use of THF
as solvent prevents this oxidation. Thus, the product could be
obtained in one step from 8 in 68% yield; see Scheme 3. The
yield was somewhat lower than the reported two-step process
(76% overall yield).
nated nickel having
a
square-planar geometry with
pyridine-phosphine16 and pyridine-phosphinite19 ligands, but
these were shown to be tetrahedral in solution. The tetrahedral
geometry of nickel in the crystal structure of 10 is in agreement
with the paramagnetic nature of the complex.45
Synthesis and Characterization of Nickel Complexes. We
obtained nickel dichloride complexes of the ligands by reaction
with (DME)NiCl2 [DME ) 1,2-dimethoxyethane]; see Scheme
4. All complexes were paramagnetic, as evidenced by their
magnetic moment in solution. Satisfactory elemental analyses
were obtained for all complexes. The high-resolution mass
spectra showed the peak for the [(ligand)NiCl]+ ion. Loss of
one chlorine atom is a consequence of the ionization; proton
addition is immediately followed by loss of HCl. For complexes
The difference between 10 and 10′ is further illustrated by
the color of the solid (purple and green, respectively) and the
magnetic moment in CD2Cl2 solution (3.12 and 2.7 µB,
respectively). The difference in synthetic procedures was the
same as mentioned above for complex 9. The original report33
on complex 10 describes a red-violet complex with magnetic
moment of 3.29 µB (presumably in the solid state), obtained
after reaction of the ligand with NiCl2 in refluxing n-butanol
for 20 min.
The complexes 9 and 11-13 are EPR silent, as can be
expected for this type of complexes.45 Compound 10, however,
did give rise to a signal (the EPR spectrum is given in the
Supporting Information). When the dichloromethane solution
of the complex was cooled to liquid nitrogen temperature
(necessary for the measurement), a color change from purple
to green was observed. This color change was reversible. We
(40) (a) Gsponer, A.; Consiglio, G. HelV. Chim. Acta 2003, 86, 2170–
2172. (b) Takacs, J. M.; Schroeder, S. D.; Han, J.; Gifford, M.; Jiang, X.-
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(42) Clavier, S.; Rist, O.; Hansen, S.; Gerlach, L. O.; Hogberg, T.;
Bergman, J. Org. Biomol. Chem. 2003, 1, 4248–4253.
(43) Lyle, M. P. A.; Narine, A. A.; Wilson, P. D. J. Org. Chem. 2004,
69, 5060–5064.
(44) (a) Bunlaksananusorn, T.; Knochel, P. J. Org. Chem. 2004, 69,
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Nickel and Palladium Complexes with P,N Ligands
Organometallics, Vol. 28, No. 4, 2009 1183
Figure 1. Displacement ellipsoid plot of 10 in the crystal, drawn at the 50% probability level. Hydrogen atoms are omitted for clarity.
Table 1. Selected Angles (deg) and Bond Lengths (Å) in Complex 10
P1-Ni1-N1
P1-Ni1-Cl1
P1-Ni1-Cl2
N1-Ni1-Cl1
N1-Ni1-Cl2
Cl1-Ni1-Cl2
Ni1-P1
98.36(4)
Ni1-N1-C1
N1-C1-C6
C1-C6-C7
C6-C7-P1
C7-P1-Ni1
128.43(10)
119.64(13)
113.96(12)
110.30(10)
104.61(5)
110.81(2)
108.41(2)
100.46(4)
111.19(5)
124.33(2)
2.3018(5)
2.0240(13)
2.2301(5)
2.2196(6)
N1-C1
P1-C7
C6-C7
C1-C6
1.352(2)
1.8231(15)
1.543(2)
1.509(2)
Ni1-N1
Ni1-Cl1
Ni1-Cl2
cannot explain the EPR spectrum at present, but it is very likely
that a different conformation of the species is formed compared
to the solution structure at room temperature or the solid state
structure.
Complexes 11-13 are all new compounds. Synthesis was
straightforward, and complexes with magnetic moments (in
CD2Cl2) of 3.47 (11), 3.23 (12), and 3.11 µB (13) were obtained,
indicative of distorted tetrahedral geometry of the nickel
center.46 We obtained the crystal structure of 12. The structure
is shown in Figure 2, and selected angles and bond distances
are presented in Table 2.
Just as in 10, the nickel chelate ring in complex 12 has a
“twist-boat” conformation, with a distorted tetrahedral geometry
around the metal. The P-Ni-N angle of 89.75(4)° is relatively
small, presumably due to the inflexibility of the backbone. As
a consequence, the Cl1-Ni-Cl2 angle is relatively large
(131.542(18)°). The other angles around nickel are less distorted
from tetrahedral. The distances around nickel are normal and
comparable to those in complex 10. The torsion angle
C7-C6-C1-N1 between the phenylene backbone and the
pyridyl ring is 37.3(2)°.
Figure 2. Displacement ellipsoid plot of 12 in the crystal, drawn
at the 50% probability level. Hydrogen atoms are omitted for clarity.
Table 2. Selected Angles (deg) and Bond Lengths (Å) in Complex 12
P1-Ni1-N1
P1-Ni1-Cl1
P1-Ni1-Cl2
N1-Ni1-Cl1
N1-Ni1-Cl2
Cl1-Ni1-Cl2
Ni1-P1
89.75(4)
Ni1-N1-C1
N1-C1-C6
C1-C6-C7
C6-C7-P1
C7-P1-Ni1
127.68(10)
121.21(13)
125.53(12)
120.33(10)
102.26(5)
106.390(15)
109.788(16)
102.54(3)
108.68(3)
131.542(18)
2.2548(4)
2.0001(12)
2.2170(4)
2.2105(4)
N1-C1
P1-C7
C6-C7
C1-C6
1.3587(18)
1.8172(14)
1.414(2)
Ni1-N1
Ni1-Cl1
Ni1-Cl2
Bite Angle Calculations. We calculated the natural bite angle
(ꢀn)47,48 for complexes 1-5 when coordinated to nickel; values
are given in Table 3. As expected, ligand 1 exhibits the smallest
bite angle, and this increases on increasing the number of
methylenes in the backbone (ligands 2 and 3). The phenylene
1.497(2)
backbone in 4 results in a ꢀn between those of 1 and 2. The
anti configuration of the pyridine and the diphenylphosphine
groups in ligand 5 induces a rather large natural bite angle, being
similar to that of 3.
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The difference between the calculated value of 94.7° for
ligand 2 and the value in the crystal structure of complex 10
(98.36(4)°) can be ascribed to the electronic preference of the
metal. The dummy metal used in the bite angle calculations

1184 Organometallics, Vol. 28, No. 4, 2009
Flapper et al.
Table 3. Calculated Natural Bite angles (ꢀn) for Complexes 9-13
proton or the chemical shift of those protons in the free ligand.
This large difference can be explained by the relatively short
Pd · · · H distance of one of the protons in the crystal structure
(see below). Apparently, there is an interaction between this
proton and the metal, both in the solid state and in solution.
This phenomenon has been observed before in a similar
complex.51 At 80 °C, the ring inversion was fast on the NMR
time scale. The 13C NMR spectrum at 25 °C in CDCl3 showed
some broad signals, and the signal for the ipso carbon could
not be observed. At 80 °C in Cl2DCCDCl2, all carbon atoms
gave rise to sharp signals.
ligand
1
2
3
4
5
ꢀn (deg)
87.2
94.7
101.8
90.8
101.7
Scheme 5. Synthesis of Neutral Palladium Complexes 14-18
The other neutral palladium complexes did not give rise to
broad peaks in room-temperature NMR spectra. In complex 18,
the backbone of the ligand prohibits ring inversion, and (also
as a consequence of the chirality of the complex) the two phenyl
rings are inequivalent. In the other complexes, the phenyl rings
were equivalent in NMR spectra at ambient temperature.
Single crystals of 15 suitable for X-ray diffraction were
obtained. The crystal structure is shown in Figure 4, and selected
angles and bond lengths are summarized in Table 4. Just like
the nickel complex of this ligand, the palladium complex 15
has the metal chelate ring in a “twist-boat” conformation. The
metal has a distorted square-planar geometry. The five atoms
of the palladium coordination plane have a dihedral angle of
21.87(11)° with the pyridyl ring. In comparison with palladium
complexes of the same ligand with an alkoxycarbonyl group
instead of a methyl group coordinated to the palladium, the
P-Pd-Cl bond is a little more distorted from linear, the Pd-P
distance is slightly shorter and the Pd-Cl bond slightly longer.52
Bond lengths and angles are similar to those in Pd(CH3)Cl or
PdCl2 complexes of related pyridine-phosphine ligands.53
The X-ray crystal structure of 16 is shown in Figure 5, and
selected angles and bond lengths are shown in Table 5. The
palladium has a distorted square-planar geometry. The flexibility
of the backbone is demonstrated by the P-Pd-N bite angle of
94.86(5)°, which is not larger than that in complex 15, which
has a shorter backbone. Also, the angles around the metal are
a little less distorted from square-planar geometry. The most
notable feature in the structure is a relatively short Pd · · · H
distance: H6B is in a pseudoaxial position and has a distance
does not have a preference, and ꢀn is determined by ligand
factors only.48 The tetrahedrally surrounded d8 metal center in
10, on the other hand, prefers an angle of 109°. As a
consequence of the ligand preferred bite angle and the sterics
of the chloride anions, the Cl-Ni-Cl angle is larger than this
ideal angle, while P-Ni-N is smaller. The latter angle is still
larger than the natural bite angle of the ligand, though. We have
shown before that electronic preference of the metal can give a
deviation from the natural bite angle of the ligand.49 In complex
12, due to the inflexibility of the ligand, the P-Ni-N angle is
determined by ligand preference. The found value of 89.75(4)°
in 12 is therefore in good correlation with the calculated natural
bite angle of 90.8° of ligand 4. In ethene oligomerization, the
active species is believed to be a nickel complex with a square-
planar-surrounded metal center.50 This has an electronic prefer-
ence for a bite angle of 90°, and the deviation from the natural
bite angle will therefore be much less than in the nickel
dichloride complexes.
Synthesis and Characterization of Neutral Palladium
Complexes. Neutral methylpalladium chloride complexes were
obtained from reaction of the ligand with (COD)Pd(CH3)Cl
[COD ) 1,5-cyclooctadiene]; see Scheme 5. All compounds
were obtained as white solids and were characterized by NMR,
high-resolution mass spectrometry (showing the [(ligand)-
Pd(CH3)]+ ion), and elemental analysis. In addition, single-
crystal X-ray diffraction was performed on complexes 15 and
16.
1
of 2.81 Å to palladium. This is also reflected in the H NMR
spectrum (see above). In complex 15, the shortest Pd · · · H
distance is 3.39 Å. The structure of 16 can be compared with
the PdCl2 complex of a similar pyridine-phosphine ligand with
a backbone consisting of three aliphatic carbons.51 In this
structure, there also is a relatively short Pd · · · H distance of
2.72(3) Å.
Synthesis and Characterization of Cationic Palladium
Complexes. All neutral palladium complexes were preactivated
to give cationic complexes by reaction with NaBAr′4 [Ar′ )
3,5-di(trifluoromethyl)phenyl] and acetonitrile; see Scheme 6.
The products were obtained as white solids and characterized
by NMR, elemental analysis, and mass spectrometry.
In analogy to the neutral complex 16, complex 21 gave rise
to broad signals in room-temperature NMR spectra (the variable-
temperature 1H NMR spectra are given in the Supporting
Information). When the sample was cooled to -40 °C, the
The NMR spectra showed the formation of the desired
complexes. As a consequence of the different trans influence
of the two donor functionalities, the phosphine is expected to
coordinate trans to chloride. This coordination mode is dem-
onstrated by the coupling constant between the phosphorus and
the Pd-CH3 protons, which is small (2.5 to 3.1 Hz) for 14-17
and not observed for 18. Again, this is in agreement with the
X-ray structures (see below).
The room-temperature 13C and 1H NMR spectra in CDCl3 of
compound 16 contained broad peaks, indicative of hindered
inversion of the seven-membered palladium chelate ring.
Variable-temperature 1H NMR spectra of 16 are shown in Figure
3. Upon cooling to -20 °C, the separate signals of the
inequivalent protons are visible in the 1H NMR spectrum. One
of the signals of the two CH2-(2-pyridyl) protons is shifted by
1.0 ppm toward higher value compared to the signal of the other
(51) Stoccoro, S.; Chelucci, G.; Zucca, A.; Cinellu, M. A.; Minghetti,
G.; Manassero, M. J. Chem. Soc., Dalton Trans. 1996, 1295–9.
(52) Giannoccaro, P.; Cornacchia, D.; Doronzo, S.; Mesto, E.; Quaranta,
E.; Aresta, M. Organometallics 2006, 25, 2872–2879.
(53) (a) Durran, S. E.; Smith, M. B.; Dale, S. H.; Coles, S. J.; Hursthouse,
M. B.; Light, M. E. Inorg. Chim. Acta 2006, 359, 2980–2988. (b) Song,
H. B.; Zhang, Z. Z.; Mak, T. C. W. J. Chem. Soc., Dalton Trans. 2002,
1336–1343.
(49) (a) Kranenburg, M.; Delis, J. G. P.; Kamer, P. C. J.; Van Leeuwen,
P. W. N. M.; Vrieze, K.; Veldman, N.; Spek, A. L.; Goubitz, K.; Fraanje,
J. J. Chem. Soc., Dalton Trans. 1997, 1839–1849. (b) Delis, J. G. P.; Rep,
M.; Kranenburg, M.; Vrieze, K.; Van Leeuwen, P. W. N. M.; Veldman,
N.; Spek, A. L. J. Organomet. Chem. 1998, 564, 29–35.
(50) Britovsek, G. J. P.; Gibson, V. C.; Wass, D. F. Angew. Chem., Int.
Ed. 1999, 38, 428–447.

Nickel and Palladium Complexes with P,N Ligands
Organometallics, Vol. 28, No. 4, 2009 1185
1
Figure 3. Methylene region of the H NMR spectra of compound 16 at different temperatures (in °C), recorded in CDCl3 except spectra
marked with *, which are recorded in Cl2DCCDCl2.
Figure 4. Displacement ellipsoid plot of 15 in the crystal, drawn at the 50% probability level. Hydrogen atoms are omitted for clarity.
signals became sharp. Like in 16, one of the (2-pyridyl)-CH2
Table 4. Selected Angles (deg) and Bond Lengths (Å) in Complex 15
protons showed a difference in chemical shift (of 0.7 ppm) from
P1-Pd1-N1
P1-Pd1-Cl1
P1-Pd1-C20
N1-Pd1-Cl1
N1-Pd1-C20
Cl1-Pd1-C20
Pd1-P1
95.02(6)
172.20(3)
85.86(9)
92.35(6)
177.21(11)
86.88(9)
2.1964(8)
2.223(2)
2.3837(7)
2.041(3)
Pd1-N1-C1
N1-C1-C6
C1-C6-C7
C6-C7-P1
C7-P1-Pd1
126.85(18)
119.5(2)
114.1(2)
110.97(19)
108.94(9)
the other one and from the shift of the free ligand, indicative of
a Pd · · · H interaction. At 80 °C the ring inversion was fast on
the NMR time scale.
Nickel-Catalyzed Ethene Oligomerization. Nickel halide
complexes bearing pyridine-phosphine ligands have been used
as precursors in oligomerization of ethene.4,12-14,16,17 We tested
the ability of complexes 9-13 to act as catalyst in this reaction
after activation with MAO. Although the nickel halide com-
N1-C1
C1-C6
P1-C7
C6-C7
1.358(3)
1.505(4)
1.815(3)
1.536(4)
Pd1-N1
Pd1-Cl1
Pd1-C20

1186 Organometallics, Vol. 28, No. 4, 2009
Flapper et al.
Figure 5. Displacement ellipsoid plots of 16 in the crystal, drawn at the 50% probability level. Aromatic hydrogen atoms and disordered
solvent molecules are omitted for clarity.
Table 5. Selected Angles (deg) and Bond Lengths (Å) in Complex 16
isomerization takes place, as can be seen from the relatively
low amount of 1-butene. The other C4 products were cis- and
trans-2-butene. The GC traces contained multiple peaks for the
other fractions, showing that these fractions consist of a mixture
of isomers as well.
P1-Pd1-N1
P1-Pd1-Cl1
P1-Pd1-C21
N1-Pd1-Cl1
N1-Pd1-C21
Cl1-Pd1-C21
Pd1-P1
94.86(5)
175.96(2)
87.31(7)
89.17(5)
176.71(9)
88.65(7)
2.2204(6)
2.1746(19)
2.3923(6)
2.057(2)
1.839(2)
Pd1-N1-C1
N1-C1-C6
C1-C6-C7
C6-C7-C8
C7-C8-P1
C8-P1-Pd1
N1-C1
125.37(16)
118.3(2)
111.1(2)
114.68(19)
113.65(17)
113.50(8)
1.357(3)
1.502(3)
1.545(3)
1.536(3)
2.81
The observed trends can be rationalized by considering the
mechanism of isomerization and chain growth. Isomerization
proceeds via ꢀ-hydrogen elimination and reinsertion. From the
species formed after ꢀ-hydrogen elimination, chain transfer can
take place. Thus, a high rate of isomerization results in a higher
change of chain transfer. This chain transfer could lead to a
nickel(ethene) hydride complex or proceed via chain transfer
to monomer. For nickel complexes, theoretical studies showed
that termination is more likely to proceed via the latter
pathway.54 Migratory insertion in a hydride complex is faster
than in an alkylmetal complex (formed after every ethene
insertion). Chain transfer to monomer requires the consumption
of a molecule of ethene. So, both pathways would lead to a
higher productivity. Indeed, the catalyst precursors that give
more isomerization have a higher productivity and a lower
percentage of oligomers (as compared to dimers) formed, with
the exception of complex 9. In complex 9, ethene insertion (and
thus chain growth) is probably disfavored as a consequence of
the small ligand bite angle, which disfavors migratory
insertion.47,48
Pd1-N1
C1-C6
Pd1-Cl1
C6-C7
Pd1-C21
C7-C8
P1-C8
Pd1 · · · H6B
Scheme 6. Synthesis of Cationic Palladium Complexes
19-23
plexes are only sparingly soluble in toluene, the species formed
after activation are soluble. When a suspension of the nickel
complex in toluene (with a little 1-hexene to stabilize the species
formed) was treated with MAO in a Schlenk flask, the
immediate dissolution of the complex was observed, together
with a color change.
The results of the oligomerization are presented in Table 6.
All complexes form active species after activation, with
butenes being the major catalysis product. Activities in general
are high and among the best reported for ethene oligomerization
with nickel complexes bearing P,N ligands. From the amount
of cooling, necessary to maintain the reaction temperature
(against the exotherm of the reaction), it was clear that the
catalysts were most active in the first 5 to 10 min. In general,
oligomerization activities seem to follow the same trend as the
isomerization, with the catalysts giving most isomerization being
the most active. Selectivity for C4 products can be as high as
96%. Complexes 9, 11, and 12 all have selectivity for butenes
higher than 90% and can be considered dimerization catalysts
rather than oligomerization catalysts. A significant amount of
The catalytic behavior of complexes 9-11 shows a good
correlation with their natural bite angle (see Table 3). With
increasing value for the bite angle, both the productivity and
amount of isomerization go up. The correlation between catalytic
performance and the bite angle does not hold for complexes 12
and 13. This shows that the behavior in ethene oligomerization
is dependent not only on the natural bite angle of the ligand
but also on factors such as steric and electronic properties and
ligand flexibility. The influence of the bite angle of diphosphine
ligands on the outcome of nickel-catalyzed ethene oligomer-
ization has been studied, but the dependence on ꢀn is not
(54) Fan, L.; Krzywicki, A.; Somogyvari, A.; Ziegler, T. Inorg. Chem.
1996, 35, 4003–4006.

Nickel and Palladium Complexes with P,N Ligands
Organometallics, Vol. 28, No. 4, 2009 1187
Table 6. Ethene Oligomerization Using 9-13 as Catalyst Precursora
product distribution (%)c
productivity (g C2H4/
complex
(mol Ni · h))
TOFb
C4
C6
C8
C10
C12
1-butene (%)d
9
83 × 104
196 × 104
240 × 104
218 × 104
68 × 104
30 × 103
70 × 103
85 × 103
78 × 103
24 × 103
96
86
96
92
76
4
11
3
6
17
<1
3
<1
1
29
18
11
10
40
10
11
12
13
<1
<1
3
6
1
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,
b
total volume: 25 mL, T: 30 °C, time: 30 min. Turnover frequency in (mol C2H4) · (mol Ni · h)-1
.
c Mol percentage of combined Cn products. d As
percentage of total C4 fraction.
Table 7. Ethene Oligomerization Using 19-23 as Catalyst
uniform.55 Catalyst precursor 13, having a backbone that has a
similar bite angle to that of complex 11 but that is very rigid,
has the lowest rate of isomerization, accompanied with a
relatively low productivity. Complex 12 behaves similarly to
complex 11, with only slightly more oligomers formed and
slightly lower productivity.
Precursora
product distribution (%)c
complex TOFb C4 C5 C6 C7 C8 C9 C10 <C10
19
20
21
22
23
8
6
2.7
16
1.4
56
85
88
38
78
6
11
11
11
13
2
1
3
1
8
1
6
6
<1 <1
<1 <1
2
The aromatic backbone in 12, more flat and electronically
different from the aliphatic backbones, makes comparison with
the other catalysts tested difficult. A paper by the group of
Braunstein reports the use of a catalyst precursor similar to our
complex 12, the only difference being a methyl group on the
pyridyl-6 position of the ligand in their case.17 Surprisingly,
this complex showed no activity toward ethene after activation
with 400 or 800 equiv of MAO, presumably due to decomposi-
tion as a result of free trimethylaluminum in the MAO used.
When the complex was activated with EtAlCl2, a maximum TOF
of 56 000 was reached, with selectivities comparable to complex
12. The catalytic performance of precursor 12 can also
be compared with nickel complexes with phosphinooxazoline
ligands.22 The ligands in these complexes have the same
phenylene backbone and a diphenylphosphine donor, but the
nitrogen donor atom is part of an oxazoline group instead of a
pyridine. Under slightly different conditions than we used, these
complexes gave systems that were 2 to 4 times less active and
gave 45% to 90% butenes. Selectivity for 1-butene was higher
than for 12, reaching a maximum of 30%.
The recent paper by the group of Braunstein that describes
complexes 9 and 10′ also deals with their oligomerization
productivity.14 Although they tested more activation methods,
which sometimes gave better results, the conditions that compare
best to our conditions are the activation with 200 equiv of MAO
in chlorobenzene as solvent. Under these conditions, they found
turnover frequencies of 14 000 (9) and 17 300 (10′), being lower
than the activities we found. The selectivity for butenes was
64% for both catalyst precursors, while selectivity for 1-butene
within that fraction was 19% and 16%, respectively. The
difference in catalytic behavior can partly be explained by the
difference in geometry of the metal complexes (see above) and
the differences in solvent, concentration, reactor, quality of
MAO, and reaction time. But presumably the largest influence
is the temperature of the reaction mixture. Braunstein reports
that no cooling was applied to the reactor during the reaction,
and a temperature increase was observed as a consequence of
reaction exotherm. We used an internal cooling spiral to
14
9
1
8
17
22 <1 <1
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.
.
maintain the temperature, and a maximum temperature increase
of 5 °C was observed. The high temperature reached in the
experiments without cooling explains the lower TOF due to
catalyst deactivation and lower selectivity for 1-butene due to
enhanced isomerization. The higher amounts of hexenes are
probably a result of the higher catalyst concentration used. This
results in a higher butenes concentration, which then reinserts
to give hexenes or methylpentenes. It was reported that a
significant amount of the C6 fraction was the result of butene
reinsertion. At lower Ni/Al ratios, complexes 9 and 10′ showed
the same trends in productivity, product distribution, and
selectivity as we observed for 9 and 10.
Palladium-Catalyzed Ethene Oligomerization. Palladium
complexes bearing pyridine-phosphine ligands have only
sparingly been used as ethene oligomerization catalyst.13,15 The
group of Rieger presented an active catalyst,15 whereas Liu
reported the formation of negligible amounts of oligomers with
complexes of this kind.13 We tested our complexes for their
ability to oligomerize ethene, and results are presented in Table
7.
The table shows that the complexes have a very low
productivity. Low or no activity has been described for other
palladium complexes with P,N ligands,6,26,27,29 although turn-
over frequencies of up to several hundreds per hour have also
been reached with such systems.7,20,24 A significant amount of
oligomers with an odd number of carbons is formed. These
originate from the first chain growing at the complex, which
starts from the methylpalladium complex. After this first chain
terminates, the next chain starts from a palladium hydride
complex, producing only chains with an even number of carbons
from then on. At very low TOFs (like with complexes 21 and
23), the odd-numbered chains still do not exceed one-fifth of
the total amount of oligomers formed. This shows that a large
part of the growing chains eliminates after only one ethene
insertion. The propene thus formed was evaporated together with
the ethene at the end of the reaction and is not included in the
calculation of the turnover frequency. Complex 22 has a
relatively high percentage of chains with an odd number of
carbons, compared to the other complexes. This is consistent
(55) (a) Ledford, J.; Shultz, C. S.; Gates, D. P.; White, P. S.; DeSimone,
J. M.; Brookhart, M. Organometallics 2001, 20, 5266–5276. (b) Albers, I.;
Alvarez, E.; Campora, J.; Maya, C. M.; Palma, P.; Sanchez, L. J.; Passaglia,
E. J. Organomet. Chem. 2004, 689, 833–839. (c) Dennett, J. N. L.; Gillon,
A. L.; Heslop, K.; Hyett, D. J.; Flemming, J. S.; Lloyd-Jones, E.; Orpen,
A. G.; Pringle, P. G.; Wass, D. F.; Scutt, J. N.; Weatherhead, R. H.
Organometallics 2004, 23, 6077–6079. (d) Lejeune, M.; Semeril, D.;
Jeunesse, C.; Matt, D.; Peruch, F.; Lutz, P. J.; Ricard, L. Chem.-Eur. J.
2004, 10, 5354–5360.

1188 Organometallics, Vol. 28, No. 4, 2009
Flapper et al.
X-ray Crystal Structure Determinations. X-ray reflections
were measured with Mo KR radiation (λ ) 0.71073 Å) on a Nonius
Kappa CCD diffractometer with rotating anode at a temperature
of 150 K up to a resolution of (sin θ/λ)max ) 0.65 Å-1. The
structures were solved with direct methods (program SHELXS-
8660 for 10, 12, and 15; SIR-9761 for 16) Refinement was performed
with SHELXL-9760 against F2 of all reflections. Non hydrogen
atoms were refined with anisotropic displacement parameters. All
hydrogen atoms were introduced in calculated positions and refined
with a riding model. The crystal of 16 contained large voids (114
Å3/unit cell) filled with disordered solvent molecules. Their
contribution to the structure factors was secured by back-Fourier
transformation using the routine SQUEEZE of the program PLA-
TON,62 resulting in 31 electrons/unit cell. Geometry calculations
and checking for higher symmetry were performed with the
PLATON62 program. Further details about the crystal structure
determinations are given in Table 8.
with the lower probability of chain termination, as evidenced
by the formation of higher molecular weight products.
The difference between the very low productivity of our
complexes and of those of Liu13 and the active catalyst of
Rieger15 could be explained by the precursor used. The former
systems make use of preactivated cationic complexes, where
acetonitrile coordinates to palladium. It has been shown that
acetonitrile binds much more strongly to palladium than ethene,
and the nitrile adduct is an inactive species.56 The system of
Rieger was activated in ether just before the oligomerization,
thus circumventing the use of nitriles.
Recently, a palladium complex with a P,N ligand was reported
in which an axial Pd · · · H interaction resulted in the increased
formation of olefins of C6 and higher compared to butenes.20
In complex 21, the Pd · · · H interaction is clearly not enough to
give a similar effect, as it produces the largest fraction of dimers
of the complexes tested.
Computational Details. Natural bite angle calculations were
performed using the Cache WorkSystem (Fujitsu Ltd.) Pro Version
7.5.0.85, using the MM2 program without changing parameters.
The Ni-P distance parameter amounts to 2.20 Å, the Ni-N distance
to 1.91 Å.
Conclusions
The pyridine-phosphine ligands 1-5 were used to make
nickel and palladium complexes. The nickel dichloride com-
plexes 9-13 are monomeric, paramagnetic species with a
distorted tetrahedral structures. The difference in the structures
of 9 and 10 compared to the nickel dichloride complexes of
the same ligands recently reported14 is probably the result of
differences in the synthetic procedures. The neutral methylpal-
ladium chloride complexes 14-18 of the ligands all have a
distorted square-planar geometry, with the chloride always trans
to the phosphorus. In 16, a relatively short Pd · · · H distance is
observed in the X-ray crystal structure and the NMR spectra of
this complex.
When tested as catalyst precursors in the oligomerization of
ethene, the cationic methylpalladium complexes 19-23 show
a very low productivity to give mainly butenes as product. After
MAO activation, the nickel complexes 9-13 show a high
productivity with turnover frequencies between 24 × 103 and
85 × 103 mol ethene per mol nickel per hour, which is
competitive with earlier reported nickel catalysts. The activity
decreases over time and is highest in the first 5 to 10 min of
the reaction, showing that the catalysts do not have a prolonged
stability. Butenes are the main product, with maximum selec-
tivities of 96 mol %. The 1-butene content within this fraction
is between 10% and 40%. Comparison of the catalytic results
of the different complexes shows that within a series of highly
related backbones (ligands 1-3) the productivity and isomer-
ization increase with increasing bite angle. The results obtained
with complexes of ligands 4 and 5 do not follow this trend,
showing that other factors have a pronounced influence on the
outcome of the catalysis as well. This complicates comparison
of different catalysts.
2-[(Diphenylphosphino)methyl]pyridine (1). To a solution of
sodium (841 mg, 36.6 mmol, 2.0 equiv) in liquid ammonia (250
mL) was added triphenylphosphine (4.79 g, 18.3 mmol, 1.0 equiv)
at -78 °C. The mixture was stirred at that temperature for 4 h,
after which the deep blue solution had become yellow. Then,
2-(chloromethyl)pyridine hydrochloride (6 · HCl) (3.00 g, 18.3
mmol, 1.0 equiv) was added at -78 °C, and the mixture was stirred
at -33 °C. THF (40 mL) was added, and the ammonia was
evaporated overnight. The resulting mixture was refluxed for 1 h,
water (5 mL) was added, and the THF was evaporated. CH2Cl2
was added and the organic layer was washed with water, saturated
aqueous NaHCO3, and water again. Purification by column chro-
matography using Et2O as the eluent yielded the product as a white
solid (3.47 g, 12.5 mmol, 68%, mp 47 °C). 1H NMR δ (500 MHz,
CDCl3) ppm: 8.51 (d, J ) 4.6 Hz, 1H, py-H6), 7.49-7.43 (m, 5H,
py-H4 + Ph-H2), 7.33-7.28 (m, 4H, Ph-H3 + -H4), 7.07-7.05
(m, 1H, py-H5), 6.99 (d, J ) 7.8 Hz, 1H, py-H3), 3.65 (s, 2H,
CH2). 13C{1H} NMR δ (125 MHz, CDCl3) ppm: 158.3 (d, J ) 8.0
Hz, py-C2), 149.6 (s, py-C6), 138.4 (d, J ) 15.2 Hz, Ph-C1), 136.6
(s, CH), 133.1 (d, J ) 19.0 Hz, CH), 129.0 (s, CH), 128.7 (d, J )
6.8 Hz, CH), 123.9 (d, J ) 5.9 Hz, CH), 121.3 (d, J ) 2.1 Hz,
CH), 39.1 (d, J ) 16.5 Hz, CH2). 31P{1H} NMR δ (121 MHz,
CDCl3) ppm: -9.6. Anal. Calcd for C18H16NP: C, 77.96; H, 5.82;
N, 5.05. Found: C, 78.11; H, 5.94, N, 4.85. MS (EI) m/z (rel
intensity): 277 (85) [M]+, 200 (19) [M - Ph]+, 185 (23) [PPh2]+,
183 (100) [PPh2 - 2H]+, 168 (94).
2-[3-(Diphenylphosphino)propyl]pyridine (3). The compound
was prepared according to the published procedure.32 Full NMR
characterization was never reported. 1H NMR δ (500 MHz, CDCl3)
ppm: 8.52 (dd, J ) 5.3, 1.7 Hz, 1H, py-H6), 7.61 (dt, J ) 7.7, 1.7
Hz, 1H, py-H4), 7.44-7.38 (m, 4H, Ph-H2), 7.34-7.30 (m, 6H,
Ph-H3 + -H4), 7.15-7.12 (m, 2H, py-H3 + -H5), 2.96 (t, J ) 7.6
Hz, 2H, py-CH2), 2.14-2.09 (m, 2H, P-CH2), 1.95-1.88 (m, 2H,
P-CH2-CH2). 13C{1H} NMR δ (75 MHz, CDCl3) ppm: 161.7 (s,
py-C2), 149.5 (s, py-C6), 138.9 (d, J ) 12.2 Hz, Ph-C1), 136.6 (s,
CH), 133.0 (d, J ) 18.3 Hz, CH), 128.7 (d, J ) 3.7 Hz, CH),
128.6 (s, CH), 123.1 (s, CH), 121.3 (s, CH), 39.8 (d, J ) 12.2 Hz,
py-CH2), 27.8 (d, J ) 12.2 Hz, P-CH2-CH2), 26.4 (d, J ) 17.1 Hz,
P-CH2) 31P{1H} NMR δ (121 MHz, CDCl3) ppm: -15.4
Experimental Part
2-[2-(Diphenylphosphino)ethyl]pyridine (2),36 2-(2-fluorophe-
nyl)pyridine (7),42 2-[(1R,4R)-1,7,7-trimethylbicyclo[2.2.1]hept-2-
en-2-yl]pyridine (8),44 (DME)NiCl2,57 (COD)Pd(CH3)Cl,58 and
NaBAr′459 were synthesized according to the published procedures.
General experimental considerations are given in the Supporting
Information.
2-[2-(Diphenylphosphino)phenyl]pyridine (4). To solution of
2-(2-fluorophenyl)pyridine (7) (505 mg, 2.92 mmol, 1.0 equiv) and
(56) Mecking, S.; Johnson, L. K.; Wang, L.; Brookhart, M. J. Am. Chem.
Soc. 1998, 120, 888–899.
(57) Ward, L. G. L. Inorg. Synth. 1971, 13, 154–64.
(58) 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.
(59) Brookhart, M.; Grant, B.; Volpe, A. F. Organometallics 1992, 11,
3920–3922.
(60) Sheldrick, G. Acta Crystallogr., Sect. A 2008, 64, 112–122.
(61) Altomare, A.; Burla, M. C.; Camalli, M.; Cascarano, G. L.;
Giacovazzo, C.; Guagliardi, A.; Moliterni, A. G. G.; Polidori, G.; Spagna,
R. J. Appl. Crystallogr. 1999, 32, 115–119.
(62) Spek, A. L. J. Appl. Crystallogr. 2003, 36, 7–13.

Nickel and Palladium Complexes with P,N Ligands
Organometallics, Vol. 28, No. 4, 2009 1189
Table 8. Selected Crystallographic Data for Complexes 10, 12, 15, and 16
10
12
15
16
formula
fw
C19H18Cl2NNiP
420.92
C23H18Cl2NNiP
468.96
C20H21ClNPPd
448.20
C21H23ClNPPd + disordered solvent
462.22a
cryst color
cryst size [mm3]
cryst syst
space group
a [Å]
deep purple
0.30 × 0.10 × 0.10
triclinic
dark red
colorless
0.20 × 0.04 × 0.02
monoclinic
P21/c (no. 14)
11.7992(18)
13.940(2)
11.7544(12)
90
96.56(3)
90
1920.7(5)
4
1.550
42 054/4325
1.189
multiscan
0.86-0.97
218/0
0.0323/0.0584
0.0544/0.0647
1.027
yellowish
0.30 × 0.20 × 0.15
orthorhombic
Pbca (no. 61)
17.1048(10)
13.3897(10)
18.552(2)
90
90
90
4248.9(6)
8
1.466
99 443/4869
1.249
multiscan
0.75-0.83
253/0
0.0247/0.0584
0.0307/0.0609
1.035
0.30 × 0.09 × 0.04
triclinic
j
j
P1 (no. 2)
P1 (no. 2)
7.4772(10)
8.4117(10)
15.416(2)
97.787(12)
101.974(14)
101.194(10)
914.7(2)
9.6302(2)
10.2603(2)
11.4891(2)
110.8761(10)
95.4957(10)
95.8718(8)
1044.40(4)
2
b [Å]
c [Å]
R [deg]
ꢀ [deg]
γ [deg]
V [Å3]
Z
2
Dx [g/cm3]
reflns measd/unique
1.528
24 320/4167
1.440
multiscan
0.77-0.87
217/0
0.0236/0.0570
0.0277/0.0588
1.052
1.470a
16 860/5775
µ [mm-1
abs corr
]
1.096a
multiscan
0.62-0.96
227/0
0.0282/0.0628
0.0369/0.0657
1.074
abs corr range
params/restraints
R1/wR2 [I > 2σ(I)]
R1/wR2 [all reflns]
S
res density [e/Å3]
-0.40/0.35
-0.29/0.32
-0.63/0.44
-0.51/0.49
a Derived parameters do not contain the contribution of the disordered solvent.
18-crown-6 (1.00 g, 3.79 mmol, 1.3 equiv) in THF (25 mL) was
slowly added a 0.5 M solution of potassium diphenylphosphide
(7.0 mL, 3.50 mmol, 1.2 equiv) in THF at 0 °C. The mixture was
stirred at room temperature for 24 h, after which water (10 mL)
was added, and it was concentrated in Vacuo. Et2O (60 mL) was
added, and the organic phase was washed with water twice, dried,
and concentrated in Vacuo. Purification on a basic alumina 90
column (PE to PE:EtOAc ) 9:1 as the eluent) yielded the product
sonification bath for 30 min. The solids were filtered off, washed
with Et2O, and dried in Vacuo to yield the product as a very dark
purple solid (280 mg, 0.69 mmol, 87%, mp 208 °C dec). Anal.
Calcd for C18H16Cl2NNiP: C, 53.13; H, 3.96; N, 3.44. Found: C,
53.26; H, 4.08, N, 3.34. HRMS (FAB) m/z: calcd for C18H16ClNNiP
[M - Cl]+ 370.0062; found 370.0063. µeff ) 2.61 µB.
2-[2-(Diphenylphosphino)ethyl]pyridinenickel Dichloride (10).
A mixture of 2-[2-(diphenylphosphino)ethyl]pyridine (2) (500 mg,
1.72 mmol, 1.0 equiv), (DME)NiCl2 (377 mg, 1.72 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. Washing with hexanes four times yielded the product as a
purple solid (697 mg, 1.66 mmol, 96%, mp 203 °C dec). Crystals
suitable for X-ray diffraction were obtained by layering a CH2Cl2
solution of the product with hexanes. Anal. Calcd for
C19H18Cl2NNiP: C, 54.21; H, 4.31; N, 3.33. Found: C, 54.06; H,
4.25, N, 3.26. HRMS (FAB) m/z: calcd for C19H18ClNNiP [M -
Cl]+ 384.0219; found 384.0210. µeff ) 3.12 µB.
2-[3-(Diphenylphosphino)propyl]pyridinenickel Dichloride
(11). A mixture of 2-[3-(diphenylphosphino)propyl]pyridine (3)
(200 mg, 0.65 mmol, 1.0 equiv), (DME)NiCl2 (144 mg, 0.65 mmol,
1.0 equiv), and CH2Cl2 (20 mL) was stirred for 24 h. It was filtered
through a pad of Celite, washed with CH2Cl2, and concentrated to
a volume of 5 mL. This was slowly dropped to 75 mL of vigorously
stirred Et2O. The solids were filtered off, washed with Et2O, and
dried in Vacuo to yield the product as an orange solid (224 mg,
0.52 mmol, 79%, mp 143 °C dec). Anal. Calcd for C20H20Cl2NNiP:
C, 55.23; H, 4.63; N, 3.22. Found: C, 55.35; H, 4.61, N, 3.20.
HRMS (FAB) m/z: calcd for C20H20ClNNiP [M - Cl]+ 398.0375;
found 398.0361. µeff ) 3.47 µB.
2-(2-(Diphenylphosphino)phenyl)pyridinenickel Dichloride
(12). This was obtained following the procedure for 11 from 2-(2-
(diphenylphosphino)phenyl)pyridine (4) (100 mg, 0.29 mmol, 1.0
equiv) and (DME)NiCl2 (65 mg, 0.29 mmol, 1.0 equiv) to yield
the product as a light brown solid (104 mg, 0.22 mmol, 76%, mp
268 °C dec). Anal. Calcd for C23H18Cl2NNiP: C, 58.90; H, 3.87;
N, 2.99. Found: C, 59.08; H, 3.84, N, 2.92. HRMS (FAB) m/z:
calcd for C23H18ClNNiP [M - Cl]+ 432.0219; found 432.0200. µeff
) 3.23 µB.
1
as a light yellow solid (628 mg, 1.85 mmol, 63%, mp 86 °C). H
NMR δ (500 MHz, CDCl3) ppm: 8.55 (d, J ) 4.9 Hz, 1H, py-H6),
7.62 (dd, J ) 7.6, 0.7 Hz, 1H, phenylene-H6), 7.61-7.58 (m, 1H,
py-H4), 7.45 (dt, J ) 7.6, 1.1 Hz, 1H, phenylene-H5), 7.42 (d, J )
7.9 Hz, 1H, py-H3), 7.34-7.26 (m, 11H, phenylene-H4 + Ph-H2
+ -H3 + -H4), 7.16 (dd, J ) 7.1, 4.9 Hz, 1H, py-H5), 7.11 (ddd,
J ) 7.7, 4.0, 0.6 Hz, 1H, phenylene-H3). 13C{1H} NMR δ (125
MHz, CDCl3) ppm: 159.0 (d, J ) 2.8 Hz, py-C2), 148.8 (s, py-
C6), 146.1 (d, J ) 24.2 Hz, Cq), 138.3 (d, J ) 11.1 Hz, Cq), 136.4
(d, J ) 17.7 Hz, Ph-C1), 135.7 (s, CH), 134.7 (s, CH), 134.0 (d, J
) 20.0 Hz, CH), 129.8 (d, J ) 4.5 Hz, CH), 128.9 (s, CH), 128.5
(s, CH), 128.5 (s, CH), 128.4 (s, CH), 124.3 (d, J ) 4.8 Hz, CH),
122.0 (s, CH). 31P{1H} NMR δ (121 MHz, CDCl3) ppm: -10.1.
Anal. Calcd for C23H18NP: C, 81.40; H, 5.35; N, 4.13. Found: C,
81.35; H, 5.32, N, 4.07. MS (EI) m/z (rel intensity): 339 (9) [M]+,
262 (100) [M - Ph]+, 185 (21) [M - 2Ph]+.
2-[(1S,2S,3R,4S)-3-(Diphenylphosphino)-1,7,7-trimethylbi-
cyclo[2.2.1]hept-2-yl]pyridine (5). To a solution of 2-[(1R,4R)-
1,7,7-trimethylbicyclo[2.2.1]hept-2-en-2-yl]pyridine (8) (1.01 g,
4.74 mmol, 1.0 equiv) and diphenylphosphine (0.82 mL, 4.74 mmol,
1.0 equiv) in THF (25 mL) was added t-BuOK (106 mg, 0.95 mmol,
0.2 equiv), after which the solution turned orange. After stirring at
60 °C for 16 h, water (5 mL) was added, and the mixture was
concentrated. Et2O was added, and the organic layer was washed
with water three times and evaporated. Purification using column
chromatography (eluent PE:EtOAc ) 9:1) yielded the product as
a viscous oil (1.29 g, 3.22 mmol, 68%). Analysis was consistent
with literature data.44
2-[(Diphenylphosphino)methyl]pyridinenickel Dichloride (9).
A mixture of 2-[(diphenylphosphino)methyl]pyridine (1) (220 mg,
0.79 mmol, 1.0 equiv), (DME)NiCl2 (174 mg, 0.79 mmol, 1.0
equiv), and CH2Cl2 (15 mL) was stirred for 20 h. It was filtered
through a pad of Celite, washed with CH2Cl2, and concentrated in
2-[(1S,2R,3R,4S)-3-(Diphenylphosphino)-1,7,7-trimethylbi-
cyclo[2.2.1]hept-2-yl]pyridinenickel Dichloride (13). A mixture
Vacuo. Et2O (15 mL) was added, and the mixture was put in a
of
2-[(1S,2R,3R,4S)-3-(diphenylphosphino)-1,7,7-

1190 Organometallics, Vol. 28, No. 4, 2009
Flapper et al.
trimethylbicyclo[2.2.1]hept-2-yl]pyridine (5) (115 mg, 0.29 mmol,
1.0 equiv), (DME)NiCl2 (63 mg, 0.28 mmol, 1.0 equiv), and CH2Cl2
(6 mL) was stirred for 24 h. It was filtered through a pad of Celite,
washed with CH2Cl2, and concentrated to approximately 5 mL, after
which the product was precipitated with 30 mL of Et2O. It was
filtrated off and washed with Et2O. Drying in Vacuo yielded the
product as a purple solid (104 mg, 0.20 mmol, 68%, mp 298 °C
dec). Anal. Calcd for C27H30Cl2NNiP: C, 61.29; H, 5.71; N, 2.65.
Found: C, 61.20; H, 5.67; N, 2.49. HRMS (FAB) m/z: calcd for
C27H30ClNNiP [M - Cl]+ 492.1158; found 492.1163. µeff ) 3.11
µB.
Phb-H2 + Ph-H3 + -H4), 7.35-7.32 (m, 1H, py-H5), 7.24 (d, J )
7.5 Hz, 1H, py-H3), 3.99-3.91 (m, 1H, py-CHH), 2.93-2.90 (m,
1H, py-CHH), 2.16-2.09 (m, 1H, P-CHH), 2.00-1.85 (m, 1H,
P-CHH), 1.80-1.73 (m, 1H, P-CH2-CHH), 1.59-1.50 (m, 1H,
1
P-CH2-CHH), 0.67 (d, J ) 3.0 Hz, 3H, CH3). H NMR δ (500
MHz, Cl2DCCDCl2, 80 °C) ppm: 9.13 (d, J ) 5.3 Hz, 1H, py-H6),
7.79-7.70 (m, 5H, py-H4 + Ph-H2), 7.56-7.48 (m, 6H, Ph-H3 +
-H4), 7.35-7.31 (m, 1H, py-H5), 7.23 (d, J ) 7.7 Hz, 1H, py-
H3), 3.55-3.48 (m, 2H, py-CH2), 2.00-1.93 (m, 2H, P-CH2),
1.87-1.78 (m, 2H, P-CH2-CH2), 0.74 (d, J ) 3.0 Hz, 3H, CH3).
13C{1H} NMR δ (125 MHz, CDCl3, 25 °C) ppm: 159.8 (s, py-
C2), 152.3 (s, py-C6), 138.3 (s, CH), 135-132 (bs, CH), 131.1
(bs, CH), 129.0 (d, J ) 10.6 Hz, CH), 123.8 (s, CH), 123.1 (s,
CH), 36.6 (d, J ) 8.2 Hz, py-CH2), 26.3 (d, J ) 27.8 Hz, P-CH2),
24.5 (s, P-CH2-CH2), -0.5 (d, J ) 2.7 Hz, CH3) the signal for
the Ph-C1 carbon atom was not obserVed. 13C{1H} NMR δ (125
MHz, Cl2DCCDCl2, 80 °C) ppm: 159.5 (s, py-C2), 152.0 (s, py-
C6), 137.8 (s, CH), 133.0 (d, J ) 11.0 Hz, CH), 130.6 (d, J ) 2.5
Hz, CH), 130.3 (d, J ) 48.1 Hz, Ph-C1), 128.6 (d, J ) 10.6 Hz,
CH), 123.3 (s, CH), 122.5 (s, CH), 36.2 (d, J ) 8.4 Hz, py-CH2),
26.2 (d, J ) 27.4 Hz, P-CH2), 24.1 (s, P-CH2-CH2), -1.2 (d, J )
3.4 Hz, CH3). 31P{1H} NMR δ (121 MHz, CDCl3, 25 °C) ppm:
23.1. Anal. Calcd for C21H23ClNPPd: C, 54.56; H, 5.02; N, 3.03.
Found: C, 54.37; H, 4.96; N, 2.88. HRMS (FAB) m/z: calcd for
C21H23NPPd [M - Cl]+ 426.0612; found 426.0609.
2-[(Diphenylphosphino)methyl]pyridinemethylpalladium Chlo-
ride (14). 2-[(Diphenylphosphino)methyl]pyridine (1) (71 mg, 0.26
mmol, 1.0 equiv) and (COD)Pd(CH3)Cl (68 mg, 0.26 mmol, 1.0
equiv) were dissolved in CH2Cl2 (5 mL), and the mixture was stirred
for 16 h. Then, it was concentrated in Vacuo to approximately 0.5
mL, after which 5 mL of Et2O was added under vigorous stirring.
The white precipitate was filtrated off and washed with Et2O. Drying
in Vacuo yielded the product as a white solid (92 mg, 0.21 mmol,
83%). 1H NMR δ (500 MHz, CDCl3) ppm: 9.42 (dd, J ) 5.5, 1.5
Hz, 1H, py-H6), 7.73 (tt, J ) 7.5, 1.5 Hz, 1H, py-H4), 7.68-7.63
(m, 4H, Ph-H2), 7.52-7.48 (m, 2H, Ph-H4), 7.47-7.42 (m, 4H,
Ph-H3), 7.42-7.40 (m, 1H, py-H5), 7.30-7.27 (m, 1H, py-H3),
4.03 (d, J ) 12 Hz, 2H, CH2), 0.78 (d, J ) 2.5 Hz, 3H, CH3).
13C{1H} NMR δ (75 MHz, CDCl3) ppm: 157.3 (d, J ) 4.6 Hz,
py-C2), 151.3 (s, py-C6), 138.6 (s, CH), 133.2 (d, J ) 12.2 Hz,
CH), 131.7 (d, J ) 2.5 Hz, CH), 129.5 (d, J ) 51.0 Hz, Ph-C1),
129.3 (d, J ) 11.4 Hz, CH), 123.4 (s, CH), 123.2 (d, J ) 9.7 Hz,
CH), 43.1 (d, J ) 30.0 Hz, CH2), -5.2 (s, CH3). 31P{1H} NMR δ
(121 MHz, CDCl3) ppm: 41.6. Anal. Calcd for C19H19ClNPPd: C,
52.56; H, 4.41; N, 3.23. Found: C, 52.45; H, 4.30; N, 3.18. HRMS
(FAB) m/z: calcd for C19H19NPPd [M - Cl]+ 398.0298; found
398.0294.
2-[2-(Diphenylphosphino)phenyl]pyridinemethylpalladium
Chloride (17). This was obtained following the procedure for 14
from 2-[2-(diphenylphosphino)phenyl]pyridine (4) (128 mg, 0.377
mmol, 1.0 equiv) and (COD)Pd(CH3)Cl (100 mg, 0.377 mmol, 1.0
equiv) to yield the product as a white solid (170 mg, 0.343 mmol,
91%, mp 213 °C dec). 1H NMR δ (500 MHz, CDCl3) ppm:
9.53-9.51 (m, 1H, py-H6), 7.64 (dt, J ) 7.8, 1.7 Hz, 1H, py-H4),
7.61-7.53 (m, 2H, phenylene-H5 + -H6), 7.45-7.38 (m, 3H,
phenylene-H4 + Ph-H4), 7.37-7.32 (m, 8H, Ph-H2 + -H3), 7.27
(d, J ) 7.8 Hz, 1H, py-H3), 7.25-7.22 (m, 1H, py-H5), 7.12-7.07,
(m, 1H, phenylene-H3), 0.75 (d, J ) 2.7 Hz, 3H, CH3). 13C{1H}
NMR δ (125 MHz, CDCl3) ppm: 155.6 (d, J ) 5.5 Hz, py-C2),
152.6 (s, py-C6), 142.9 (d, J ) 13.5 Hz, phenylene-C1), 138.6 (s,
CH), 134.5 (d, J ) 11.8 Hz, CH), 132.2 (d, J ) 8.4 Hz, CH),
131.8 (d, J ) 4.2 Hz, CH), 131.5 (d, J ) 2.1 Hz, CH), 131.4 (d,
J ) 2.5 Hz, CH), 129.7 (d, J ) 7.6 Hz, CH), 128.8 (d, J ) 11.0
Hz, CH), 127.5 (d, J ) 44.3 Hz, Cq), 127.3 (d, J ) 51.9 Hz, Cq),
125.5 (s, CH), 124.1 (s, CH), 1.2 (s, CH3). 31P{1H} NMR δ (121
MHz, CDCl3) ppm: 39.2. Anal. Calcd for C24H21ClNPPd: C, 58.08;
H, 4.27; N, 2.82. Found: C, 57.89; H, 4.17; N, 2.72. HRMS (FAB)
m/z: calcd for C24H21NPPd [M - Cl]+ 460.0456; found 460.0458.
2-[2-(Diphenylphosphino)ethyl]pyridinemethylpalladium Chlo-
ride (15). This was obtained following the procedure for 14 from
2-[2-(diphenylphosphino)ethyl]pyridine (2) (300 mg, 1.03 mmol,
1.1 equiv) and (COD)Pd(CH3)Cl (273 mg, 1.03 mmol, 1.0 equiv)
to yield the product as a white solid (390 mg, 0.87 mmol, 84%,
1
mp 231 °C dec). H NMR δ (500 MHz, CDCl3) ppm: 9.54 (dd, J
) 5.5, 1.2 Hz, 1H, py-H6), 7.71-7.63 (m, 5H, py-H4 + Ph-H2),
7.48-7.38 (m, 6H, Ph-H3 + -H4), 7.25-7.22 (m, 1H, py-H5), 7.16
(d, J ) 7.6 Hz, 1H, py-H3), 3.21-3.12 (m, 2H, py-CH2), 2.33-2.27
(m, 2H, P-CH2), 0.67 (d, J ) 3.1 Hz, 3H, CH3). 13C{1H} NMR δ
(125 MHz, CDCl3) ppm: 159.5 (s, py-C2), 153.8 (d, J ) 1.7 Hz,
py-C6), 138.5 (s, CH), 133.6 (d, J ) 11.5 Hz, CH), 131.6 (d, J )
51.3 Hz, Ph-C1), 131.2 (d, J ) 2.3 Hz, CH), 129.0 (d, J ) 10.4
Hz, CH), 124.6 (s, CH), 123.2 (s, CH), 34.3 (d, J ) 5.2 Hz,
py-CH2), 26.1 (d, J ) 29.4 Hz, P-CH2), -0.7 (s, CH3). 31P{1H}
NMR δ (121 MHz, CDCl3) ppm: 36.3. Anal. Calcd for
C20H21ClNPPd: C, 53.59; H, 4.72; N, 3.12. Found: C, 53.62; H,
4.67; N, 2.98. HRMS (FAB) m/z: calcd for C20H21NPPd [M - Cl]+
412.0455; found 412.0457.
2-[(1S,2S,3R,4S)-3-(Diphenylphosphino)-1,7,7-trimethylbi-
cyclo[2.2.1]hept-2-yl]pyridinemethylpalladium Chloride (18).
Thiswasobtainedfollowingtheprocedurefor14from2-[(1S,2R,3R,4S)-
3-(diphenylphosphino)-1,7,7-trimethylbicyclo[2.2.1]hept-2-yl]pyri-
dine (5) (133 mg, 0.33 mmol, 1.0 equiv) and (COD)Pd(CH3)Cl
(88 mg, 0.33 mmol, 1.0 equiv) to yield the product as a white solid
(143 mg, 0.26 mmol, 77%, mp 181 °C dec). 1H NMR δ (500 MHz,
CDCl3) ppm: 9.53 (dd, J ) 5.6, 1.2 Hz, 1H, py-H6), 7.83-7.77
(m, 2H, Pha-H2), 7.76-7.68 (m, 3H, py-H4 + Phb-H2), 7.48-7.37
(m, 7H, py-H3 + Ph-H3 + -H4), 7.23-7.19 (m, 1H, py-H5), 3.85
(dd, J ) 24.2, 9.6 Hz, 1H, H2), 2.24 (ddd, J ) 13.9, 9.3, 5.1 Hz,
1H, H6), 2.17 (dd, J ) 6.7, 3.5 Hz, 1H, H6′), 2.07-2.02 (m, 1H,
H3), 1.97 (ddd, J ) 22.0, 11.6, 5.4 Hz, 1H, H4), 1.67-1.60 (m,
1H, H5), 1.35-1.29 (m, 1H, H5′), 1.12 (s, 3H, CH3), 0.98 (d, J )
1.2 Hz, 3H, CH3), 0.75 (s, 3H, CH3), 0.17 (s, 3H, Pd-CH3). 13C{1H}
NMR δ (125 MHz, CDCl3) ppm: 161.6 (s, py-C2), 154.8 (s, py-
C6), 137.2 (s, CH), 136.8 (bs, CH), 133.4 (d, J ) 49.4 Hz, Pha-
C1), 132.8 (d, J ) 10.6 Hz, CH), 131.4 (d, J ) 2.5 Hz, CH), 130.7
(d, J ) 2.1 Hz, CH), 129.2 (d, J ) 48.1 Hz, Phb-C1), 129.0 (d, J
) 10.1 Hz, CH), 128.1 (d, J ) 11.0 Hz, CH), 122.1 (s, CH), 122.0
(s, CH), 56.7 (d, J ) 4.7 Hz, CH), 50.2 (s, Cq), 47.7 (d, J ) 7.6
2-[3-(Diphenylphosphino)propyl]pyridinemethylpalladium
Chloride (16). This was obtained following the procedure for 14
from 2-[3-(diphenylphosphino)propyl]pyridine (3) (102 mg, 0.33
mmol, 1.0 equiv) and (COD)Pd(CH3)Cl (89 mg, 0.33 mmol, 1.0
equiv) to yield the product as a white solid (131 mg, 0.28 mmol,
85%, mp 208 °C dec). Crystals suitable for X-ray diffraction were
obtained by layering a CH2Cl2 solution of the product with Et2O.
1H NMR δ (500 MHz, CDCl3, 25 °C) ppm: 9.11 (d, J ) 5.5 Hz,
1H, py-H6), 7.80-7.58 (bs, 4H, Ph-H2) 7.72 (t, J ) 7.5 Hz, 1H,
py-H4), 7.56-7.40 (bs, 6H, Ph-H3 + -H4), 7.31-7.28 (m, 1H,
py-H5), 7.20 (d, J ) 7.5 Hz, 1H, py-H3), 4.2-2.6 (bs, 2H, py-
CH2), 2.1-1.8 (bs, 2H, P-CH2), 1.9-1.6 (bs, 2H, P-CH2-CH2), 0.73
(d, J ) 3.0 Hz, 3H, CH3). 1H NMR δ (500 MHz, CDCl3, -20 °C)
ppm: 9.08 (d, J ) 5.5 Hz, 1H, py-H6), 7.91-7.87 (m, 2H, Pha-
H2), 7.76 (dt, J ) 7.5, 1.5 Hz, 1H, py-H4), 7.61-7.38 (m, 8H,

Nickel and Palladium Complexes with P,N Ligands
Organometallics, Vol. 28, No. 4, 2009 1191
Hz, Cq), 46.7 (d, J ) 6.3 Hz, CH), 46.1 (d, J ) 24.1 Hz, C3), 32.8
(d, J ) 8.0 Hz, CH2), 28.2 (s, CH2), 20.8 (s, CH3), 19.5 (s, CH3),
14.7 (s, CH3), 0.9 (d, J ) 3.4 Hz, Pd-CH3). 31P{1H} NMR δ (121
MHz, CDCl3) ppm: 41.3. Anal. Calcd for C28H33ClNPPd: C, 60.44;
H, 5.98; N, 2.52. Found: C, 60.35; H, 5.91; N, 2.46. HRMS (FAB)
m/z: calcd for C28H33NPPd [M - Cl]+ 520.1397; found 520.1387.
0.8 Hz, 1H, py-H6), 7.89 (dt, J ) 7.7, 1.7 Hz, 1H, py-H4),
7.90-7.46 (m, 22H, Ph-H2 + -H3 + -H4 + Ar′-H2 + -H4), 7.40
(ddd, J ) 7.7, 5.5, 1.4 Hz, 1H, py-H5), 7.38 (ddd, J ) 7.7, 1.4, 0.8
Hz, 1H, py-H3), 3.9-2.8 (bs, 2H, py-CH2), 2.23 (s, 3H, NCCH3),
2.1-1.6 (bs, 4H, P-CH2-CH2), 0.59 (d, J ) 2.2 Hz, 3H, Pd-CH3).
1H NMR δ (500 MHz, CD2Cl2, -40 °C) ppm: 8.56 (d, J ) 4.9
Hz, 1H, py-H6), 7.83-7.73 (m, 11H, py-H4 + Pha-H2 + Ar′-H2),
7.65-7.61 (m, 2H, Phb-H2), 7.60-7.54 (m, 6H, Pha-H3 + Ar′-
H4), 7.51-7.46 (m, 2H, Ph-H4), 7.44-7.36 (m, 3H, py-H5 + Phb-
H3), 7.32 (d, J ) 7.8 Hz, 1H, py-H3), 3.70-3.61 (m, 1H, py-
CHH), 3.01-2.96 (m, 1H, py-CHH), 2.23 (s, 3H, NCCH3),
2.15-2.08 (m, 1H, P-CHH), 2.00-1.87 (m, 1H, P-CH2-CHH),
1.76-1.68 (m, 1H, P-CHH) 1.51-1.43 (m, 1H, P-CH2-CHH), 0.49
(d, J ) 1.9 Hz, 3H, Pd-CH3). 1H NMR δ (500 MHz, Cl2DCCDCl2,
80 °C) ppm: 8.55 (d, J ) 5.1 Hz, 1H, py-H6), 7.83 (dt, J ) 7.8,
1.5 Hz, 1H, py-H4), 7.78-7.74 (m, 8H, Ar′-H2), 7.65-7.59 (m,
6H, Ph-H2 + -H4), 7.59-7.52 (m, 8H, Ph-H3 + Ar′-H4),
7.39-7.34 (m, 1H, py-H5), 7.34 (d, J ) 7.8 Hz, 1H, py-H3),
3.48-3.42 (m, 2H, py-CH2), 2.20 (s, 3H, NCCH3), 1.97-1.92 (m,
2H, P-CH2), 1.89-1.80 (m, 2H, P-CH2-CH2), 0.68 (d, J ) 2.0 Hz,
3H, Pd-CH3). 13C{1H} NMR δ (125 MHz, CD2Cl2, 25 °C) ppm:
162.4 (q, J ) 49.8 Hz, Ar′-C1), 160.7 (s, py-C2), 150.2 (s, py-
C6), 140.1 (s, CH), 135.5 (bs, Ar′-C2), 132.6-132.1 (bs, CH), 129.8
(d, J ) 11.0 Hz, CH), 129.5 (quartet of multiplets, J ) 31.6 Hz,
Ar′-C3), 125.7 (s, CH), 125.2 (q, J ) 272.4, CF3), 124.3 (s, CH),
119.6 (s, NCCH3), 118.1 (m, Ar′-C4), 36.8 (d, J ) 8.0 Hz, py-
CH2), 26.2 (d, J ) 31.2 Hz, P-CH2), 24.4 (s, P-CH2-CH2), 3.2 (s,
NCCH3), -0.4 (s, Pd-CH3) signals for some carbons could not be
obserVed. 13C{1H} NMR δ (125 MHz, CD2Cl2, -40 °C) ppm: 161.7
(q, J ) 49.8 Hz, Ar′-C1), 159.7 (s, py-C2), 149.8 (s, py-C6), 139.4
(s, CH), 134.9-134.5 (m, CH + Ar′-C2), 132.3 (d, J ) 2.2 Hz,
CH), 131.4 (d, J ) 10.1 Hz, CH), 131.0 (d, J ) 2.2 Hz, CH),
130.4 (d, J ) 55.7 Hz, Pha-C1), 129.4 (d, J ) 11.4 Hz, CH), 129.0
(d, J ) 11.0 Hz, CH), 128.6 (quartet of multiplets, J ) 31.6 Hz,
Ar′-C3), 125.1 (s, CH), 125 (oVerlapping with other signals, Phb-
C1), 124.4 (q, J ) 272.4, CF3), 123.7 (s, CH), 119.1 (d, J ) 12.7
Hz, NCCH3), 117.5 (m, Ar′-C4), 36.1 (d J ) 8.0 Hz, py-CH2),
25.0 (d, J ) 30.8 Hz, P-CH2), 23.7 (s, P-CH2-CH2), 3.3 (s, NCCH3),
-1.1 (d, J ) 3.2 Hz, Pd-CH3). 31P{1H} NMR δ (121 MHz, CD2Cl2,
25 °C) ppm: 25.3. 19F{1H} NMR δ (282 MHz, CD2Cl2, 25 °C)
ppm: -63.0. Anal. Calcd for C55H38BF24N2PPd: C, 49.63; H, 2.88;
N, 2.10. Found: C, 49.60; H, 2.84; N, 2.06. HRMS (FAB) m/z:
calcd for C21H23NPPd [M - BAr′4 - CH3CN]+ 426.0612; found
426.0616. MS (FD) m/z: 467 [M - BAr′4]+.
2-[(Diphenylphosphino)methyl]pyridinemethylpalladium-
(acetonitrile) Tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (19).
To a mixture of 2-[(diphenylphosphino)methyl]pyridinemethylpal-
ladium chloride (14) (188 mg, 0.433 mmol, 1.0 equiv) and sodium
tetrakis[(3,5-trifluoromethyl)phenyl]borate (384 mg, 0.433 mmol,
1.0 equiv) were added CH3CN (5 mL) and CH2Cl2 (25 mL), and
the mixture was stirred for 16 h. It was cannula filtrated, evaporated
to dryness, and coevaporated with 5 mL of pentane to yield the
1
product as a white solid (529 mg, 0.406 mmol, 94%). H NMR δ
(500 MHz, CD2Cl2) ppm: 8.77 (bs, 1H, py-H6), 7.88-7.84 (m,
1H, py-H4), 7.80-7.75 (m, 8H, Ar′-H2), 7.69-7.63 (m, 4H, Ph-
H2), 7.62-7.57 (m, 6H, Ph-H4 + Ar′-H4), 7.56-7.51 (m, 5H, py-
H5 + Ph-H3), 7.39-7.36 (m, 1H, py-H3), 4.16 (d, J ) 12.5 Hz,
2H, CH2), 2.33 (s, 3H, NCCH3), 0.72 (s, 3H, Pd-CH3). 13C{1H}
NMR δ (125 MHz, CD2Cl2) ppm: 162.4 (q, J ) 49.8 Hz, Ar′-C1),
157.7 (s, py-C2), 150.2 (s, py-C6), 140.4 (s, CH), 135.5 (bs, Ar′-
C2), 135.4 (oVerlapping with BAr′4 signal, Ph-C1), 133.5 (d, J )
12.2 Hz, CH), 133.0 (s, CH), 130.1 (d, J ) 11.4 Hz, CH), 129.5
(quartet of multiplets, J ) 31.6 Hz, Ar′-C3), 125.2 (q, J ) 272.4,
CF3), 124.9 (d, J ) 8.3 Hz, CH), 124.6 (s, CH), 120.6 (s, NCCH3),
118.1 (m, Ar′-C4), 43.5 (d, J ) 88.5 Hz, CH2), 3.4 (s, NCCH3),
-3.6 (s, Pd-CH3). 31P{1H} NMR δ (121 MHz, CD2Cl2) ppm: 43.1.
19F{1H} NMR δ (282 MHz, CD2Cl2) ppm: -63.0. Anal. Calcd for
C53H34BF24N2PPd: C, 48.85; H, 2.63; N, 2.15. Found: C, 49.08; H,
2.57; N, 2.20. HRMS (FAB) m/z: calcd for C19H19NPPd [M - BAr′4
- CH3CN]+ 398.0298; found 398.0299. MS (FD) m/z: 439 [M -
BAr′4]+.
2-[2-(Diphenylphosphino)ethyl]pyridinemethylpalladium-
(acetonitrile) Tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (20).
This was obtained following the procedure for 19 from 2-[2-
(diphenylphosphino)ethyl]pyridinemethylpalladium chloride (15)
(381 mg, 0.850 mmol, 1.0 equiv) and sodium tetrakis[(3,5-
trifluoromethyl)phenyl]borate (753 mg, 0.850 mmol, 1.0 equiv) to
1
yield the product as a white solid (1.11 g, 0.845 mmol, 99%). H
NMR δ (500 MHz, CD2Cl2) ppm: 8.66-8.64 (m, 1H, py-H6), 7.83
(dt, J ) 7.6, 1.7 Hz, 2H, Ph-H4), 7.76-7.73 (m, 9H, py-H4 +
Ar′-H2), 7.69-7.64 (m, 4H, Ph-H2), 7.58 (s, 4H, Ar′-H4),
7.54-7.49 (m, 4H, Ph-H3), 7.38-7.34 (m, 2H, py-H3 + -H5),
3.27-3.18 (m, 2H, py-CH2), 2.42-2.37 (m, 2H, P-CH2), 2.31 (s,
3H, NCCH3), 0.55 (d, J ) 2.0 Hz, Pd-CH3). 13C{1H} NMR δ (125
MHz, CD2Cl2) ppm: 162.4 (q, J ) 49.8 Hz, Ar′-C1), 160.3 (s, py-
C2), 151.6 (s, py-C6), 140.3 (s, CH), 135.5 (bs, Ar′-C2), 133.8 (d,
J ) 11.8 Hz, CH), 132.5 (d, J ) 2.9 Hz, CH), 130 (oVerlapping
with other signals, Ph-C1), 129.8 (d, J ) 11.4 Hz, CH), 129.5
(quartet of multiplets, J ) 31.6 Hz, Ar′-C3), 126.5 (s, CH), 125.2
(q, J ) 272.4, CF3), 120.0 (s, NCCH3), 118.1 (m, Ar′-C4), 34.4 (d,
J ) 3.4 Hz, py-CH2), 25.9, (d, J ) 32.9 Hz, P-CH2), 3.2 (s,
NCCH3), -0.1 (s, Pd-CH3). 31P{1H} NMR δ (121 MHz, CD2Cl2)
ppm: 39.3. 19F{1H} NMR δ (282 MHz, CD2Cl2) ppm: -63.0. Anal.
Calcd for C54H36BF24N2PPd: C, 49.24; H, 2.76; N, 2.13. Found: C,
49.38; H, 2.81; N, 2.12. HRMS (FAB) m/z: calcd for C20H21NPPd
[M - BAr′4 - CH3CN]+ 412.0455; found 412.0454. MS (FD) m/z:
453 [M - BAr′4]+.
2-[2-(Diphenylphosphino)phenyl]pyridinemethylpalladium-
(acetonitrile) Tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (22).
This was obtained following the procedure for 19 from 2-[2-
(diphenylphosphino)phenyl]pyridinemethylpalladium chloride (17)
(164 mg, 0.330 mmol, 1.0 equiv) and sodium tetrakis[(3,5-
trifluoromethyl)phenyl]borate (293 mg, 0.330 mmol, 1.0 equiv) to
yield the product as a white solid (362 mg, 0.265 mmol, 80%). 1H
NMR δ (500 MHz, CD2Cl2) ppm: 8.64 (d, J ) 5.1 Hz, 1H, py-
H6), 7.80-7.72 (m, 9H, py-H4 + Ar′-H2), 7.72-7.67 (m, 2H,
phenylene-H5 + -H6), 7.59 (s, 4H, Ar′-H4), 7.56-7.50 (m, 3H,
phenylene-H4 + Ph-H4), 7.48 (d, J ) 8.1 Hz, 1H, py-H3),
7.45-7.40 (m, 4H, Ph-H3), 7.35-7.29 (m, 5H, py-H5 + Ph-H2),
7.19 (dd, J ) 10.7, 8.1 Hz, 1H, phenylene-H3), 2.30 (s, 3H,
NCCH3), 0.63 (d, J ) 1.5 Hz, 3H, Pd-CH3). 13C{1H} NMR δ (125
MHz, CD2Cl2) ppm: 162.4 (q, J ) 49.8 Hz, Ar′-C1), 156.1 (d, J )
5.0 Hz, py-C2), 150.3 (s, py-C6), 142.5 (d, J ) 12.7 Hz, phenylene-
C1), 140.5 (s, CH), 135.5 (bs, Ar′-C2), 134.7 (d, J ) 12.2 Hz,
CH), 132.9 (s, CH), 132.7 (s, CH), 131.0 (d, J ) 8.4 Hz, CH),
129.7 (d, J ) 12.2 Hz, CH), 129.5 (quartet of multiplets, J ) 31.6
Hz, Ar′-C3), 127.4 (s, CH), 125.5 (d, J ) 48.5 Hz, Cq), 125.4 (d,
J ) 57.4 Hz, Cq), 125.3 (s, CH), 125.2 (q, J ) 272.4, CF3), 119.9
(s, NCCH3), 118.1 (m, Ar′-C4), 3.3 (s, Pd-CH3), 2.0 (s, NCCH3)
signals for two aromatic CH carbons could not be obserVed due
2-[3-(Diphenylphosphino)propyl]pyridinemethylpalladium-
(acetonitrile) Tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (21).
This was obtained following the procedure for 19 from 2-[3-
(diphenylphosphino)propyl]pyridinemethylpalladium chloride (16)
(173 mg, 0.374 mmol, 1.0 equiv) and sodium tetrakis[(3,5-
trifluoromethyl)phenyl]borate (332 mg, 0.374 mmol, 1.0 equiv) to
yield the product as a white solid (481 mg, 0.363 mmol, 97%). 1H
NMR δ (500 MHz, CD2Cl2, 25 °C) ppm: 8.57 (ddd, J ) 5.5, 1.7,

1192 Organometallics, Vol. 28, No. 4, 2009
Flapper et al.
to oVerlap with other signals. 31P{1H} NMR δ (121 MHz, CD2Cl2)
ppm: 40.2. 19F{1H} NMR δ (282 MHz, CD2Cl2) ppm: -63.0. Anal.
Calcd for C58H36BF24N2PPd: C, 51.03; H, 2.66; N, 2.05. Found: C,
51.07; H, 2.69; N, 2.01. HRMS (FAB) m/z: calcd for C24H21NPPd
[M - BAr′4 - CH3CN]+ 460.0456; found 460.0454. MS (FD) m/z:
501 [M - BAr′4]+.
with 10 bar of ethene three times and brought to 10 bar 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 and the autoclave was disconnected from all
lines and weighed. A sample for gas-phase GC analysis was taken,
and the autoclave was vented and opened. Ice cold 2 M hydrochloric
acid (50 mL) 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-[(1S,2S,3R,4S)-3-(Diphenylphosphino)-1,7,7-trimethylbi-
cyclo[2.2.1]hept-2-yl]pyridinemethylpalladium(acetonitrile) Tet-
rakis[3,5-bis(trifluoromethyl)phenyl]borate (23). This was ob-
tained following the procedure for 19 from 2-[(1S,2S,3R,4S)-3-
(diphenylphosphino)-1,7,7-trimethylbicyclo[2.2.1]hept-2-
yl]pyridinemethylpalladium chloride (18) (167 mg, 0.300 mmol,
1.0 equiv) and sodium tetrakis[(3,5-trifluoromethyl)phenyl]borate
(266 mg, 0.300 mmol, 1.0 equiv) to yield the product as an off-
1
white solid (325 mg, 0.288 mmol, 76%). H NMR δ (500 MHz,
CD2Cl2) ppm: 9.24-9.18 (m, 1H, py-H6), 7.83 (dt, J ) 7.8, 1.5
Hz, 1H, py-H4), 7.78-7.68 (m, 10 H, Pha-H2 + Ar′-H2),
7.66-7.61 (m, Phb-H2), 7.58 (s, 4H, Ar′-H4), 7.56-7.45 (m, 7H,
py-H3 + Ph-H3 + -H4), 7.35-7.32 (m, 1H, py-H5), 3.62-3.57
(m, H2), 2.22-2.10 (m, 6H, H3 + H6 + NCCH3), 2.00-1.93 (m,
1H, H4), 1.70-1.64 (m, 1H, H5), 1.37-1.23 (m, 1H, H5′), 1.12
(s, 3H, CH3), 0.89 (s, 3H, CH3), 0.76 (s, 3H, CH3), 0.15 (s, 3H,
Pd-CH3). 13C{1H} NMR δ (125 MHz, CD2Cl2) ppm: 162.5 (s, py-
C2), 162.4 (q, J ) 49.8 Hz, Ar′-C1), 154.1 (s, py-C6), 138.6 (s,
CH), 137.1 (d, J ) 11.8 Hz, CH), 135.5 (bs, Ar′-C2), 133.0 (d, J
) 15.1 Hz, CH), 132.6 (s, CH), 132 (oVerlapping with other signals,
Ph-C1), 131.7 (s, CH), 129.7 (d, J ) 10.1 Hz, CH), 129.5 (quartet
of multiplets, J ) 31.6 Hz, Ar′-C3), 129.0 (d, J ) 11.4 Hz, CH),
125.2 (q, J ) 272.4, CF3), 123.5 (s, CH), 122.8 (s, CH), 118.2 (s,
NCCH3), 118.1 (m, Ar′-C4), 57.4 (s, CH), 50.8 (s, Cq), 48.3 (d, J
) 7.2 Hz, Cq), 47.1 (d, J ) 5.5 Hz, CH), 46.6 (d, J ) 25.3 Hz,
C3), 33.1 (d, J ) 8.9 Hz, CH2), 28.4 (s, CH2), 20.9 (s, CH3), 19.7
(s, CH3), 15.2 (s, CH3), 2.8 (s, NCCH3), 1.4 (s, Pd-CH3). 31P{1H}
NMR δ (121 MHz, CD2Cl2) ppm: 42.7. 19F{1H} NMR δ (282 MHz,
CD2Cl2) ppm: -63.0. Anal. Calcd for C62H48BF24N2PPd: C, 52.25;
H, 3.39; N, 1.97. Found: C, 52.38; H, 3.42; N, 1.87. HRMS (FAB)
m/z: calcd for C28H33NPPd [M - BAr′4 - CH3CN]+ 520.1397;
found 520.1391. MS (FD) m/z: 520 [M - BAr′4 - CH3CN]+.
General Procedure for the Nickel-Catalyzed Oligome-
rization. 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
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
of heptane in toluene (0.20 M, total internal standard 1.0 mmol)
were introduced under dinitrogen atmosphere. Then, it was purged
General Procedure for the Palladium-Catalyzed Oligomeri-
zation. 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 ethene pressure. After the run, the autoclave was
vented and opened. Then 50 mL 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.
Acknowledgment. The work described here is part of the
research program of the Dutch Polymer Institute (project
106). It was financially supported (M.L., A.L.S.) by the
Council for Chemical Sciences of The Netherlands Organi-
zation for Scientific Research (CW-NWO). We thank Jur-
riaan Beckers for gas-phase GC measurements and Dr. Bas
de Bruin for EPR measurements and discussions.
Supporting Information Available: A CIF file giving crystal
data for 10, 12, 15, and 16 and a file giving the EPR spectrum of
10, variable-temperature 1H NMR spectra of 21, and general
experimental considerations. This material is available free of charge
via the Internet at http://pubs.acs.org.
OM800903N