Nickel and palladium complexes of new pyridine-phosphine ligands and their use in ethene oligomerization

Article abstract of DOI:10.1021/om900038u

New pyridine-phosphine ligands of general structure 2-[2-(diarylphosphino) ethyl]pyridine were developed. The phosphorus substituents in these bidentates are 2-tolyl, 2-anisyl, and mesityl. The ligands could be conveniently synthesized in good yields. The

Full text of DOI:10.1021/om900038u

3272
Organometallics 2009, 28, 3272–3281
Nickel and Palladium Complexes of New Pyridine-Phosphine
Ligands and Their Use in Ethene Oligomerization
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, Dutch Polymer Institute, PO Box 902, 5600 AX EindhoVen,
The Netherlands, BijVoet Center for Biomolecular Research, Crystal and Structural Chemistry, Faculty of
Science, Utrecht UniVersity, Padualaan 8, 3584 CH Utrecht, The Netherlands, and School of Chemistry,
UniVersity of St. Andrews, St. Andrews, Fife, Scotland KY16 9ST, U.K.
ReceiVed January 16, 2009
New pyridine-phosphine ligands of general structure 2-[2-(diarylphosphino)ethyl]pyridine were
developed. The phosphorus substituents in these bidentates are 2-tolyl, 2-anisyl, and mesityl. The ligands
could be conveniently synthesized in good yields. The nickel dichloride complexes of the ligands are
paramagnetic. The metal centers have a distorted tetrahedral geometry, as was evident from the crystal
structures and the magnetic moments in solution. The neutral methylpalladium chloride and the cationic
methylpalladium complexes have a distorted square-planar geometry around the metal center. For the
complexes of two of the ligands, an anagostic C-H · · · Pd interaction of a ligand-proton with the palladium
atom was observed in the crystal structures and in solution. These interactions probably were related to
hindered inversion of the six-membered metallocycle, which was observed in VT-NMR measurements.
The complexes of the mesityl-substituted ligand show neither hindered inversion of the metal chelate
ring nor a sign of Pd · · · H interactions. The nickel complexes form active catalysts for the oligomerization
of ethene after MAO activation. The bulky 2-tolyl and mesityl groups suppress isomerization of the
growing chain, reflected in a high 1-butene selectivity. For the complex made from the ligand with the
most bulky (mesityl) substituents, this selectivity was 90%. The anisyl substituents induced a different
catalytic behavior of the corresponding nickel complex. Selectivity for 1-butene was lower, but the
productivity was higher, with a turnover frequency of 65 × 103 (mol C2H4) · (mol Ni · h)-1. The cationic
palladium complexes showed a very low activity in ethene oligomerization. Butenes were the major
product, but significant amounts of higher olefins were formed as well.
in this reaction. The development and application of P,N ligands
is a significant field of homogeneous catalysis, and this ligand
type has proven its value in many reactions.4,5 We were
particularly interested in pyridine-phosphine ligands. The chem-
istry of this class of ligand has been reviewed4 and has been
studied in nickel- and palladium-catalyzed ethene oligomeriza-
tion.2,6-10
Introduction
The oligomerization of ethene is an important industrial
reaction, and megatons of R-olefins are produced yearly in this
way. Depending on the chain length of the alkene, they are used
for the production of various products. The most important ones
are 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
In order to understand better the behavior of oligomerization
catalysts and possibly improve their performance, much research
is still devoted to the formation of olefins from ethene.2,3 Among
many transition metal complexes, nickel andsto a lesser
extentspalladium complexes of P,N ligands (bidentate ligands
with a phosphorus and a nitrogen donor atom) have been studied
(3) (a) Hessen, B. J. Mol. Catal. A: Chem. 2004, 213, 129–135. (b)
Dixon, J. T.; Green, M. J.; Hess, F. M.; Morgan, D. H. J. Organomet. Chem.
2004, 689, 3641–3668. (c) Wass, D. F. Dalton Trans. 2007, 816–819. (d)
Bianchini, C.; Giambastiani, G.; Rios, I. G.; Mantovani, G.; Meli, A.;
Segarra, A. M. Coord. Chem. ReV. 2006, 250, 1391–1418. (e) Kuhn, P.;
Semeril, D.; Matt, D.; Chetcuti, M. J.; Lutz, P. Dalton Trans. 2007, 515–
528. (f) Janiak, C. Coord. Chem. ReV. 2006, 250, 66–94. (g) Heinicke, J.;
Peulecke, N.; Koehler, M.; He, M.; Keim, W. J. Organomet. Chem. 2005,
690, 2449–2457.
(4) (a) Chelucci, G.; Orru, G.; Pinna, G. A. Tetrahedron 2003, 59, 9471–
9515. (b) Espinet, P.; Soulantica, K. Coord. Chem. ReV. 1999, 195, 499–
556. (c) Newkome, G. R. Chem. ReV. 1993, 93, 2067–2089.
* To whom correspondence should be addressed. E-mail: pcjk@
st-andrews.ac.uk. Fax: +44-(0)1334463808. Tel: +44-(0)1334-467285.
† University of Amsterdam.
(5) (a) Braunstein, P. J. Organomet. Chem. 2004, 689, 3953–3967. (b)
Braunstein, P.; Naud, F. Angew. Chem., Int. Ed. 2001, 40, 680–699. (c)
Guiry, P. J.; Saunders, C. P. AdV. Synth. Catal. 2004, 346, 497–537. (d)
Helmchen, G.; Pfaltz, A. Acc. Chem. Res. 2000, 33, 336–345. (e) Pfaltz,
A.; Drury, W. J. Proc. Natl. Acad. Sci. U.S.A. 2004, 101, 5723–5726.
(6) (a) Bluhm, M. E.; Folli, C.; Walter, O.; Doring, M. J. Mol. Catal.
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.
1994, 615–616. (c) Kermagoret, A.; Braunstein, P. Organometallics 2008,
27, 88–99. (d) Speiser, F.; Braunstein, P.; Saussine, L. Organometallics
2004, 23, 2625–2632. (e) Speiser, F.; Braunstein, P.; Saussine, L. Orga-
nometallics 2004, 23, 2633–2640.
‡ Dutch Polymer Institute.
Utrecht University.
§ University of St. Andrews.
(1) (a) Skupinska, J. Chem. ReV. 1991, 91, 613–648. (b) Al-Jarallah,
A. M.; Anabtawi, J. A.; Siddiqui, M. A. B.; Aitani, A. M.; Al-Sa’doun,
A. W. Catal. Today 1992, 14, 1–124. (c) Vogt, D. Oligomerization of
ethylene to higher linear R-olefins. In Applied Homogeneous Catalysis with
Organometallic Compounds; Cornils, B., Herrmann, W. A., Eds.; 1996;
Vol. 1, pp 245-258.
(2) Speiser, F.; Braunstein, P.; Saussine, L. Acc. Chem. Res. 2005, 38,
784–793.
10.1021/om900038u CCC: $40.75
2009 American Chemical Society
Publication on Web 04/28/2009

New Ni and Pd Complexes with P,N Ligands
Organometallics, Vol. 28, No. 11, 2009 3273
Scheme 1. Synthesis of Ligands 1
Scheme 2. Synthesis of Nickel Complexes 4
Figure 1. Displacement ellipsoid plot of 4a 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 4a
P1-Ni1-N1
P1-Ni1-Cl1
P1-Ni1-Cl2
N1-Ni1-Cl1
N1-Ni1-Cl2
Cl1-Ni1-Cl2
Ni1-P1
96.90(4)
Ni1-N1-C1
N1-C1-C6
C1-C6-C7
C6-C7-P1
C7-P1-Ni1
123.50(11)
118.14(14)
112.00(14)
110.53(11)
103.50(5)
103.407(17)
113.147(18)
104.18(4)
104.63(4)
129.513(19)
2.3036(4)
2.0121(14)
2.2261(5)
2.2151(5)
In this article, we present the development and study of
pyridine-phosphine ligands (1) and their neutral nickel (4),
neutral palladium (5), and cationic palladium (6) complexes.
Complexes 4 (with MAO activation) and 6 were also evaluated
for their potential as ethene oligomerization catalysts.
N1-C1
P1-C7
C6-C7
C1-C6
1.358(2)
1.8349(16)
1.549(2)
1.509(2)
Ni1-N1
Ni1-Cl1
Ni1-Cl2
Results and Discussion
In this study we used P,N ligands 1a-c, with a pyridine and
a diarylphosphine donor group, connected by a 1,2-ethanediyl
bridge. They differ in the aryl groups at the phosphine, which
are 2-tolyl, 2-anisyl, and mesityl for a, b, and c, respectively.
Ligand Synthesis. The ligands were synthesized in two steps
as depicted in Scheme 1. Base-catalyzed hydrophosphination
of 2-vinylpyridine (2) with diarylphosphine oxides gave 2-[2-
(diarylphosphinoyl)ethyl]pyridine compounds 3 in moderate to
good yields. The secondary phosphine oxides used in this
reaction can conveniently be prepared by reaction of aryllithium
or Grignard reagents with diethylphosphite.11,12 In the second
step, phosphine oxides 3 were reduced using phenylsilane, and
the 2-[2-(diarylphosphino)ethyl]pyridine ligands 1 were obtained
in excellent yields. In the solid state, they are stable in air. In
solution under aerobic conditions, they are slowly oxidized to
phosphine oxides 3.
with ether to remove any remaining free ligand, and this yielded
the complexes 4 in pure form. All complexes exhibit a
characteristic purple color in CH2Cl2 solution; in the solid state
4a and 4c are purple as well, while 4b is a brown solid.
The nickel complexes are paramagnetic, as evidenced by their
magnetic moments in CD2Cl2 solution of 3.85 (4a), 3.30 (4b),
and 3.30 µB (4c). These values are indicative of a distorted
tetrahedral geometry of the nickel.13 Using high-resolution mass
spectrometry, the [(ligand)NiCl]+ ion was observed for all
complexes. Ionization of the complexes is accomplished by
proton addition, which is immediately followed by loss of HCl,
and this results in the formation of the observed ion. Elemental
analyses for the nickel complexes were in agreement with the
proposed structures. Compounds 4 were EPR-silent, as can be
expected for this type of complexes.14 In addition to the above-
mentioned characterization, we performed single-crystal X-ray
structure determinations on complexes 4a and 4c.
The X-ray crystal structure of complex 4a is shown in Figure
1, and selected bond angles and distances are presented in Table
1. In agreement with the magnetic moment in solution, the nickel
has a distorted tetrahedral geometry. As a result of the small
bite angle of the ligand and the steric repulsion of the chlorides,
the P-Ni-N angle is somewhat smaller than the ideal value
of 109°, while the Cl-Ni-Cl angle is larger. The other angles
around nickel are less distorted from tetrahedral. The other
angles and the bond distances are in the normal range and do
not require specification. The structure is similar to the related
nickel dichloride complex 7 (see Chart 1).9
Synthesis and Characterization of Nickel Complexes. The
nickel dichloride complexes 4 were obtained from reaction of
the ligands with (DME)NiCl2 [DME ) 1,2-dimethoxyethane];
see Scheme 2. After the reaction, the products were filtered
through a pad of Celite to remove any unreacted (DME)NiCl2.
The solids obtained after evaporation of the solvent were washed
(7) Chen, H.-P.; Liu, Y.-H.; Peng, S.-M.; Liu, S.-T. Organometallics
2003, 22, 4893–4899.
(8) Muller, G.; Klinga, M.; Osswald, P.; Leskela, M.; Rieger, B. Z.
Naturforsch., B: Chem. Sci. 2002, 57, 803–809.
(9) 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.
(10) Flapper, J.; Van Leeuwen, P. W. N. M.; Elsevier, C. J.; Kamer,
P. C. J. Organometallics 2009, http://dx.doi.org/10.1021/om9000378.
(11) Busacca, C. A.; Lorenz, J. C.; Grinberg, N.; Haddad, N.; Hrapchak,
M.; Latli, B.; Lee, H.; Sabila, P.; Saha, A.; Sarvestani, M.; Shen, S.;
Varsolona, R.; Wei, X.; Senanayake, C. H. Org. Lett. 2005, 7, 4277–4280.
(12) Wife, R. L.; Van Oort, A. B.; Van Doorn, J. A.; Van Leeuwen,
P. W. N. M. Synthesis 1983, 71–73.
The X-ray crystal structure of 4c is shown in Figure 2, and
selected bond distances and angles are presented in Table 2.
(13) Hayter, R. G.; Humiec, F. S. Inorg. Chem. 1965, 4, 1701–1706.
(14) Desrochers, P. J.; Telser, J.; Zvyagin, S. A.; Ozarowski, A.;
Krzystek, J.; Vicic, D. A. Inorg. Chem. 2006, 45, 8930–8941.

3274 Organometallics, Vol. 28, No. 11, 2009
Flapper et al.
Chart 1
structure determination. On the basis of the larger trans influence
of the phosphorus compared to the nitrogen, it is expected that
the methyl coordinates cis with respect to the phosphine. This
coordination mode was indeed observed, as shown by the small
3JP-H coupling constant (3 to 4.5 Hz) between the phosphorus
nucleus and the palladium-methyl protons. These solution phase
observations are in agreement with the solid state structures of
5a and 5b obtained by single-crystal X-ray structure determina-
tions; see below.
Just as in 4a, the metal has a distorted tetrahedral geometry,
and this is in agreement with the paramagnetic nature of the
complex in solution. The structure is similar to that of 4a,
although the P-Ni-N and Cl-Ni-Cl bonds are less distorted
from perfect tetrahedral.
Synthesis and Characterization of Neutral Palladium
Complexes. The methylpalladium chloride complexes 5 were
obtained by reaction of the ligands with (COD)Pd(CH3)Cl [COD
) 1,5-cyclooctadiene]; see Scheme 3. Precipitation of the
product with diethyl ether separated the metal complexes from
free COD, and the pure complexes 5 were obtained in high
yields.
For complex 5c, only sharp peaks were observed in the NMR
spectra at ambient temperature. In the room-temperature 1H and
13C NMR spectra (recorded in CDCl3) of 5a and 5b, on the
contrary, broad peaks were observed. This is caused by hindered
inversion of the six-membered palladium chelate ring, making
the interconversion slow on the NMR time scale. When the
proton spectra were recorded at -50 °C, all peaks appeared
sharp. As a consequence of the slow ring inversion at this
temperature, several nuclei became inequivalent. Especially
notable is the large chemical shift difference for the ortho-aryl
protons. The two signals for these protons are observed at 8.84
and 6.76 ppm (5a) and 8.66 and 6.55 ppm (5b). This can be
explained by an anagostic interaction of one of these protons
with the palladium atom.15,16 This is also shown by relatively
short Pd · · · H distances in the crystal structures of the complexes
(see below). At 60 °C, the inversion of the chelate ring was
fast on the NMR time scale, and as a consequence, only sharp
peaks were visible in the NMR spectra. The aryl groups and
the protons at each methylene were equivalent. The aromatic
The products were characterized by NMR, mass spectrometry,
elemental analyses, and, for 5a and 5b, single-crystal X-ray
1
region of the variable-temperature H NMR spectra for 5a is
shown in Figure 3. The spectra of the methylene region of 5a
and the aromatic and methylene regions of 5b are given in the
Supporting Information.
We have recently reported on the palladium complexes 8-10
(see Chart 2), which are related to complexes 5.9 Complex 10
also exhibited broad signals in room-temperature NMR spectra
as a consequence of slow inversion of the metallocycle. In the
crystal structure and NMR spectra, a Pd · · · H interaction was
observed as well. Complexes 8 and 9 did not exhibit hindered
inversion of the palladium chelate ring, nor did they show
indications of short Pd · · · H distances. As the slow ring inversion
is only observed for complexes that have an anagostic interaction
of a proton with the axial position of the palladium, we believe
this could explain these phenomena. The interaction of a proton
with the axial position of the palladium atom could have a
stabilizing effect, resulting in the observed hindered ring
inversion.
We obtained the single-crystal X-ray crystal structure of
complex 5a. The structure is shown in Figure 4, and selected
bond lengths and angles are given in Table 3. The complex is
in a “boat” conformation and has a square-planar surrounded
metal center. The methyl group is coordinated cis with respect
to the phosphorus atom, which is in accordance with the NMR
studies (see above). The bond angles around palladium show
that the complex is only slightly distorted from perfect square
planar. The most notable feature of the structure is the relatively
Figure 2. Displacement ellipsoid plot of 4c 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 4c
P1-Ni1-N1
P1-Ni1-Cl1
P1-Ni1-Cl2
N1-Ni1-Cl1
N1-Ni1-Cl2
Cl1-Ni1-Cl2
Ni1-P1
98.83(16)
124.71(8)
96.89(7)
115.67(16)
98.55(16)
117.39(7)
2.305(2)
1.999(5)
2.2158(18)
2.244(2)
Ni1-N1-C1
N1-C1-C6
C1-C6-C7
C6-C7-P1
C7-P1-Ni1
130.0(5)
120.8(5)
119.0(5)
109.4(5)
97.9(2)
N1-C1
P1-C7
C6-C7
C1-C6
1.361(7)
1.837(6)
1.531(9)
1.517(9)
Ni1-N1
Ni1-Cl1
Ni1-Cl2
(15) Brookhart, M.; Green, M. L. H.; Parkin, G. Proc. Natl. Acad. Sci.
U.S.A. 2007, 104, 6908–6914.
Scheme 3. Synthesis of Neutral Palladium Complexes 5
(16) For recent examples of palladium complexes showing anagostic
(sometimes called preagostic) interactions, see: (a) Doherty, M. D.; Trudeau,
S.; White, P. S.; Morken, J. P.; Brookhart, M. Organometallics 2007, 26,
1261–1269. (b) Han, Y.; Huynh, H. V.; Koh, L. L. J. Organomet. Chem.
2007, 692, 3606–3613. (c) Han, Y.; Huynh, H. V.; Tan, G. K. Organome-
tallics 2007, 26, 6447–6452. (d) Trudeau, S.; Morken, J. P. Tetrahedron
2006, 62, 11470–11476. (e) Wurtz, S.; Glorius, F. Acc. Chem. Res. 2008,
41, 1523–1533. (f) Yen, S. K.; Koh, L. L.; Huynh, H. V.; Hor, T. S. A. J.
Organomet. Chem. 2009, 694, 332–338.

New Ni and Pd Complexes with P,N Ligands
Organometallics, Vol. 28, No. 11, 2009 3275
Figure 3. Aromatic region of the 1H NMR spectra of compound 5a at different temperatures (°C) recorded in CDCl3. The arrows indicate
the signals for the ortho-aryl protons.
Table 3. Selected Angles (deg) and Bond Lengths (Å) in Complex
5aa
Chart 2
P1-Pd1-N1
P1-Pd1-Cl1
P1-Pd1-C22
N1-Pd1-Cl1
N1-Pd1-C22
Cl1-Pd1-C22
Pd1-P1
89.77(4)
178.675(15)
88.97(6)
91.08(4)
177.57(7)
90.13(6)
2.2305(6)
2.1687(14)
2.3796(6)
2.0487(17)
2.77
Pd1-N1-C1
N1-C1-C6
C1-C6-C7
C6-C7-P1
C7-P1-Pd1
C13-H13 · · · Pd1
N1-C1
123.02(11)
117.72(15)
112.11(14)
114.02(12)
108.74(6)
123
1.352(2)
1.505(2)
1.8493(17)
1.536(2)
Pd1-N1
C1-C6
short Pd · · · H13 distance of 2.77 Å. The hydrogen atom is in a
pseudoaxial position and shows an anagostic interaction with
palladium, as was also revealed in the NMR spectra of the
complex in solution (see above). The bond length and angle
Pd1-Cl1
P1-C7
C6-C7
Pd1-C22
Pd1 · · · H13
a Hydrogen atoms were introduced in calculated positions and refined
with a riding model (see Experimental Section).
associated with this interaction are within the values usually
found for this type of interaction.15 In the solid state structure
of the related palladium complex 9 (see Chart 2) a similar
interactions was not observed; the shortest corresponding
Pd · · · H distance was 3.09 Å´.9
We have also obtained the crystal structure of 5b; it is shown
in fFigure 5, and selected bond lengths and angles are given in
Table 4. The structure is similar to that of 5a: the metallocycle
has a “boat” conformation and has a slightly distorted square-
planar geometry of the palladium atom, with a cis orientation
of the phosphorus atom and the methyl group. The oxygen atoms
have no interaction with the palladium atom, as shown by the
shortest Pd · · · O distance of 3.5845(18)Å. One ortho-aryl proton
shows an anagostic interaction with palladium: H13 is in a
pseudoaxial position of the metal, with a short Pd · · · H13
distance of 2.92 Å. These findings were corroborated by the
NMR studies in the solution phase (see above).
Figure 4. Displacement ellipsoid plot of 5a in the crystal, drawn
at the 50% probability level. Hydrogen atoms (except H13) and
disordered solvent molecules are omitted for clarity.

3276 Organometallics, Vol. 28, No. 11, 2009
Flapper et al.
Table 5. Ethene Oligomerization Using 4a-c and 7 as Catalyst
Precursorsa
product
distribution (%)c
1-butene
productivity
complex (g C2H4/(mol Ni · h)) TOFb C4 C6 C8 C10 >C10 (%)d
4a
4b
4c
7
46 × 104
182 × 104
38 × 104
16 × 103 78
7
5
4
6
76
46
90
18
65 × 103 95 4 <1
14 × 103 93 7 <1
196 × 104
70 × 103 86 11
3
<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, 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.
shows that ring inversion of this complex is fast on the NMR
time scale at ambient temperature, just like that of its precursor
5c.
Figure 5. Displacement ellipsoid plot of 5b in the crystal, drawn
at the 50% probability level. Hydrogen atoms (except H13) and
disordered solvent molecules are omitted for clarity.
Nickel-Catalyzed Ethene Oligomerization. Nickel com-
plexes of pyridine-phosphine ligands have been applied suc-
cessfully in the oligomerization of ethene.2,6,7,9,10 We studied
the behavior of nickel complexes 4 as catalyst precursors in
this reaction. The complexes were activated by MAO, and
catalytic runs were performed in toluene at 30 °C for 30 min.
The results of the catalytic studies are summarized in Table 5.
For comparison, the results we have previously obtained with
complex 7 (see Chart 1) are included as well.9
Table 4. Selected Angles (deg) and Bond Lengths (Å) in Complex
5ba
P2-Pd1-N1
P2-Pd1-Cl1
P2-Pd1-C22
N1-Pd1-Cl1
N1-Pd1-C22
Cl1-Pd1-C22
Pd1-P2
92.22(4)
175.035(17)
88.68(7)
89.45(4)
176.44(8)
89.94(7)
2.2177(6)
2.1644(17)
2.3794(6)
2.047(2)
Pd1-N1-C1
N1-C1-C6
C1-C6-C7
C6-C7-P2
C7-P2-Pd1
C13-H13 · · · Pd1
N1-C1
123.03(13)
117.86(16)
112.94(15)
113.13(13)
108.69(6)
119
1.350(2)
1.497(3)
1.8412(19)
1.544(3)
2.92
As can be seen from the table, complexes 4 form active
catalysts after MAO activation. They were most active during
the first 5 to 10 min of a run, as evident from the amount of
cooling necessary to maintain the desired temperature of the
exothermic reaction. Butenes are the main products in all cases,
with a maximum selectivity of 95% for 4b. Complex 4a
produces a significant amount of higher olefins, while 4b and
4c can be regarded as dimerization catalysts. The influence of
the different aromatic P-substituents is apparent from the
different catalytic behavior of complexes 4a-c and 7. Whereas
the selectivity for 1-butene within the butenes fraction is low
for complex 7, which has phenyl substituents at phosphorus,
the larger aromatic groups in 4 cause the formation of a higher
percentage of 1-butene. Especially 4c shows a high selectivity
of 90%. Apparently the bulky mesityl substituents prevent
isomerization of the growing oligomer chain. This can be
rationalized by considering the fact that a branched alkyl chain,
formed after isomerization, requires more space around the metal
center than a linear chain, which can bend away from this center.
The formation of branched alkyl chains is therefore disfavored
in the case of the bulky mesityl substituents at phosphorus. This
is accompanied by a decrease in activity, as compared to the
catalytic behavior of phenyl-substituted 7.
Pd1-N1
C1-C6
Pd1-Cl1
P2-C7
Pd1-C22
C6-C7
Pd1 · · · O2
3.5845(18)
Pd1 · · · H13
a Hydrogen atoms were introduced in calculated positions and refined
with a riding model (see Experimental Section).
Scheme 4. Synthesis of Cationic Palladium Complexes 6
Synthesis and Characterization of Cationic Palladium
Complexes. We obtained the cationic palladium complexes 6
from reaction of their neutral precursors with NaBAr′4 [Ar′ )
3,5-di(trifluoromethyl)phenyl]; see Scheme 4. After workup, the
pure products were obtained as white solids in high yields.
In analogy with their neutral precursors, complexes 6a and
6b exhibited slow inversion of the six-membered metallocycle,
as indicated by the appearance of broad signals in the room-
temperature 1H NMR spectra (measured in CD2Cl2). When the
samples were cooled to -40 °C, the signals became even
broader and sharp separate signals for inequivalent aromatic or
methylene protons could not be observed. Due to practical
limitations, we did not cool the samples to a temperature at
which the separate signals could be observed. When the
temperature was raised, the signals became sharper. At 80 °C
(in CDCl2CDCl2 solution), all peaks in the spectra of compounds
6a and 6b appeared sharp.
The 2-tolyl substituents in 4a cause a similar, but less strong
effect than 4c. This explains the 1-butene selectivity and activity
of this complex. Catalyst precursor 4b deviates from this trend.
The electronic properties of this complex are expected to be
similar to those of 4c, and the electronic properties cannot
explain the lower 1-butene selectivity and higher activity of 4b.
Possibly, an interaction of the methoxy oxygen atoms causes
the different catalytic behavior. No Pd · · · O interaction was
observed in the crystal structure of palladium complex 5b, but
this might be different for the catalytically active, cationic
species formed from 4b. A different behavior in ethene
oligomerization for a palladium complex of an anisyl-substituted
Complex 6c did not show broad signals at room temperature,
and the aryl groups and methylene protons were equivalent. This

New Ni and Pd Complexes with P,N Ligands
Organometallics, Vol. 28, No. 11, 2009 3277
Table 6. Ethene Oligomerization Using 6a-c as Catalyst
precursors, with square-planar surrounded metal centers, and
hindered ring inversion for 6a and 6b.
Precursorsa
product distribution (%)c
After MAO activation the nickel complexes form active
catalysts for the oligomerization of ethene. The bulky mesityl
and 2-tolyl phosphorus substituents in 4a and 4c disfavor
isomerization of the oligomer chain, as shown by a high
1-butene selectivity. This becomes evident from the comparison
with the catalytic behavior of earlier reported complex 7, in
which the corresponding substituents are phenyl groups. The
higher 1-butene selectivity is accompanied by a lower produc-
tivity. The catalytic behavior of the complex formed after
activation of 4b, containing the anisyl-substituted ligand, is
different from that of the other complexes. An interaction of
the methoxy oxygen with the nickel center might be the reason
for this. The cationic palladium complexes 6 show a very low
activity in ethene oligomerization. Selectivity for butenes is
much lower than for their nickel counterparts, and significant
amounts of higher oligomers are formed.
complex TOFb C4 C5 C6 C7 C8 C9 C10 >C10
6a
6b
6c
6
25
8
47
41
63
8
3
9
10
11
6
4
1
4
8
10
5
1
<1
2
6
9
4
15
24
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.
.
ligand, as compared to complexes of related alkyl-substituted
ligands, has been observed before.17
Palladium-Catalyzed Ethene Oligomerization. Palladium
complexes of P,N ligands have been tested for ethene oligo-
merization activity much less frequently than their nickel
counterparts. They have been reported to be active in ethene
oligomerization,8,16a,17,18 although no or very low activity in
this reaction has often been observed as well with these
complexes.7,9,10,19 Only one report describes an active catalyst
containing a pyridine-phosphine ligand,8 whereas other systems
showed no or very low activity.7,9,10 We tested complexes 6
for productivity in the oligomerization of ethene, and the results
are summarized in Table 6.
Experimental Part
General experimental information is given in the Supporting
Information. The following abbreviations are used: py ) pyridyl,
tol ) tolyl, anis ) anisyl, mes ) mesityl, Ar′ ) 3,5-di(trifluoro-
methyl)phenyl.
As can be seen from the table, the complexes all have a very
low productivity. Like their nickel counterparts, the complex
containing ligand 1b forms the most active catalyst. Next to
butenes, a significant amount of higher oligomers is formed as
well. This is in contrast to the catalytic behavior of related
complexes.9,10 The oligomers with an odd number of carbons
in the chain originate from the first chain growing from the
catalyst precursor, which starts from a methylpalladium species.
After ꢀ-hydride elimination, a palladium hydride species is
formed, and only chains with an even number of carbons are
formed henceforth. As a consequence, the catalyst with the
highest turnover number (6b) has the lowest percentage of
oligomers with an odd number of carbons.
Materials. 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. Phenylsilane and 2-vi-
nylpyridine (2) were distilled under dinitrogen. Di-2-tolylphosphine
oxide,11 di-2-anisylphosphine oxide,12 dimesitylphosphine oxide,11
(DME)NiCl2,20 (COD)Pd(CH3)Cl,21 and NaBAr′4 were synthe-
22
sized according to the published procedures. All other chemicals
were purchased from commercial suppliers and used as received.
X-ray Crystal Structure Determinations. X-ray reflections
were measured with Mo KR radiation (λ ) 0.71073 Å) on a Nonius
KappaCCD diffractometer with rotating anode. The structures were
solved with direct methods (SHELXS-9723 program for 4a;
SHELXS-8623 program for 4c and 5b) or automated Patterson
methods (DIRDIF-9924 program for 5a). Refinement was performed
with SHELXL-9723 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.
In 4a the methyl group at C14 was refined with two orientations.
The crystals of 5a and 5b contained a large void, respectively
(118 Å3/unit cell for 5a; 285 Å3/unit cell for 5b) filled with
disordered solvent molecules. Their contribution to the structure
factors was secured by back-Fourier transformation using the routine
SQUEEZE of the program PLATON,25 resulting in 34 electrons/
unit cell for 5a and 35 electrons/unit cell for 5b.
Conclusions
The new pyridine-phosphine ligands 1 were used for the
preparation of nickel and palladium complexes. The nickel
complexes 4 all have a distorted tetrahedral geometry of the
metal center and are consequently paramagnetic. The neutral
palladium complexes 5 have a distorted square-planar geometry
around the metal. In complexes 5a and 5b, the inversion of the
six-membered metallocycle is hindered. This phenomenon is
probably related to an anagostic C-H · · · Pd interaction of a
proton of the ligand with the axial position of the palladium
atom. The interaction was apparent from the crystal structures
and low-temperature NMR spectra of the complexes. Complex
5c does not exhibit hindered inversion of the palladium chelate
ring nor any Pd · · · H interactions. The cationic palladium
complexes 6 show similar coordination behavior to their neutral
Geometry calculations and checking for higher symmetry was
performed with the PLATON25 program. Further details about the
crystal structure determinations are given in Table 7.
(17) Keim, W.; Killat, S.; Nobile, C. F.; Suranna, G. P.; Englert, U.;
Wang, R. M.; Mecking, S.; Schroder, D. L. J. Organomet. Chem. 2002,
662, 150–171.
(18) (a) Daugulis, O.; Brookhart, M. Organometallics 2002, 21, 5926–
5934. (b) van den Beuken, E. K.; Smeets, W. J. J.; Spek, A. L.; Feringa,
B. L. Chem. Commun. 1998, 223–224.
(19) (a) Anderson, C. E.; Batsanov, A. S.; Dyer, P. W.; Fawcett, J.;
Howard, J. A. K. Dalton Trans. 2006, 5362–5378. (b) Guan, Z. B.; Marshall,
W. J. Organometallics 2002, 21, 3580–3586. (c) Shi, P. Y.; Liu, Y. H.;
Peng, S. M.; Liu, S. T. Organometallics 2002, 21, 3203–3207. (d) Sirbu,
D.; Consiglio, G.; Gischig, S. J. Organomet. Chem. 2006, 691, 1143–1150.
(20) Ward, L. G. L. Inorg. Synth. 1971, 13, 154–64.
(21) 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.
(22) Brookhart, M.; Grant, B.; Volpe, A. F. Organometallics 1992, 11,
3920–3922.
(23) Sheldrick, G. Acta Crystallogr., Sect. A 2008, 64, 112–122.
(24) Beurskens, P. T.; Admiraal, G.; Beurskens, G.; Bosman, W. P.;
Garcia-Granda, S.; Gould, R. O.; Smits, J. M. M.; Smykalla, C. The
DIRDIF99 Program System, Technical Report of the Crystallography
Laboratory; University of Nijmegen: The Netherlands; 1999.
(25) Spek, A. L. J. Appl. Crystallogr. 2003, 36, 7–13.

3278 Organometallics, Vol. 28, No. 11, 2009
Flapper et al.
Table 7. Selected Crystallographic Data for Complexes 4a, 4c, 5a, and 5b
4a
4c
5a
5b
formula
C21H22Cl2NNiP
C25H30Cl2NNiP
C22H25ClNPPd +
disordered solvent
476.25a
C22H25ClNO2PPd +
disordered solvent
fw
448.98
505.08
508.25a
cryst color
cryst size [mm3]
temp [K]
cryst syst
space group
a [Å]
purple
purple
colorless
colorless
0.36 × 0.21 × 0.15
0.35 × 0.03 × 0.01
0.25 × 0.10 × 0.10
0.30 × 0.15 × 0.10
150
100
150
150
monoclinic
P21/c (no. 14)
9.3096(1)
20.1793(2)
13.9525(2)
90
129.6543(4)
90
2018.03(4)
4
monoclinic
P21/c (no. 14)
16.490(2)
10.2308(12)
14.870(2)
90
101.206(12)
90
2460.8(5)
4
1.363
0.60
33 780/4445
1.083
none
triclinic
triclinic
j
j
P1 (no. 2)
P1 (no. 2)
8.6654(10)
11.1373(10)
12.839(2)
74.356(15)
73.078(15)
68.916(18)
1087.0(3)
2
8.3871(10)
12.376(2)
13.626(2)
103.680(15)
106.062(18)
99.75(2)
1278.2(4)
2
b [Å]
c [Å]
R [deg]
ꢀ [deg]
γ [deg]
V [Å3]
Z
Dx [g/cm3]
1.478
0.65
1.455a
0.65
1.321a
0.65
(sin θ/λ)max [Å-1
]
reflns measd/unique
34 570/4606
1.310
multiscan
0.56-0.82
238/0
0.0261/0.0574
0.0350/0.0610
1.026
30 812/4982
26 835/5829
µ [mm-1
abs corr
]
1.055a
0.908a
none
none
abs corr range
params/restraints
R1/wR2 [I > 2σ(I)]
R1/wR2 [all reflns]
S
277/0
238/0
257/0
0.0795/0.1477
0.1530/0.1746
1.084
0.0223/0.0562
0.0256/0.0573
1.060
0.0251/0.0731
0.0267/0.0741
1.102
resid density [e/Å3]
-0.31/0.33
-0.61/0.77
-0.86/0.49
-0.67/0.59
a Derived parameters do not contain the contribution of the disordered solvent.
2-[2-(Di-2-tolylphosphinoyl)ethyl]pyridine (3a). Di-2-tolylphos-
phine oxide (1.07 g, 4.63 mmol, 1.0 equiv) and 2-vinylpyridine
(2) (0.487 g, 4.63 mmol, 1.0 equiv) were dissolved in 25 mL of
THF. KOtBu (26 mg, 0.23 mmol, 0.05 equiv) was added, and the
mixture was stirred at 60 °C for 16 h. Water (5 mL) was added,
and the mixture was concentrated in vacuo. EtOAc (100 mL) was
added, and the solution was washed with water twice and with brine,
dried over MgSO4, and concentrated in vacuo to yield a colorless
oil. The product was precipitated by addition of Et2O (20 mL),
filtrated, washed with Et2O, and dried in vacuo to yield the product
7.09-7.05 (m, 1H, py-H5), 7.02-6.97 (m, 2H, anis-H5), 6.85 (dd,
J ) 8.3, 5.2 Hz, 2H, anis-H3), 3.70 (s, 6H, CH3), 3.12-3.05 (m,
2H, py-CH2), 3.05-2.97 (m, 2H, P-CH2). 13C{1H} NMR δ (75
MHz, CDCl3) ppm: 161.5 (d, J ) 15.3 Hz, py-C2), 160.7 (s, anis-
C2), 149.1 (s, py-C6), 136.3 (s, CH), 134.1 (d, J ) 6.5 Hz, CH),
133.5 (s, CH), 123.0 (s, CH), 121.2 (s, CH), 120.9 (d, J ) 100.6
Hz, anis-C1), 120.7 (d, J ) 11.3 Hz, CH), 110.9 (d, J ) 5.9 Hz,
CH), 55.5 (s, CH3), 30.5 (s, py-CH2), 29.2 (d, J ) 74.4 Hz, P-CH2).
31P{1H} NMR δ (121 MHz, CDCl3) ppm: 33.7. Anal. Calcd for
C21H22NO3P: C, 68.66; H, 6.04; N, 3.81. Found: C, 68.52; H, 5.94,
N, 3.72. HRMS (FAB) m/z: calcd for C21H23NO3P [M + H]+
368.1416; found 368.1417.
1
as a white solid (1.24 g, 3.69 mmol, 80%, mp 120 °C). H NMR
δ (500 MHz, CDCl3) ppm: 8.50-8.48 (m, 1H, py-H6), 7.80 (ddd,
J ) 12.8, 7.7, 1.0 Hz, 2H, tol-H6), 7.56 (dt, J ) 7.7, 1.3 Hz, 1H,
py-H4), 7.39-7.35 (m, 2H, tol-H4), 7.29-7.25 (m, 2H, tol-H5),
7.17-7.13 (m, 3H, py-H3 + tol-H3), 7.12-7.08 (m, 1H, py-H5),
3.16-3.10 (m, 2H, py-CH2), 2.92-2.86 (m, 2H, P-CH2), 2.30 (s,
6H, CH3). 13C{1H} NMR δ (125 MHz, CDCl3) ppm: 160.6 (d, J )
14.3 Hz, py-C2), 149.4 (s, py-C6), 141.7 (d, J ) 8.6 Hz, tol-C2),
136.6 (s, CH), 132.2 (d, J ) 10.4 Hz, CH), 132.0 (s, CH), 131.9
(s, CH), 131.8 (s, CH), 131.4 (d, J ) 95.5 Hz, tol-C1), 125.8 (d, J
) 11.8 Hz, CH), 123.2 (s, CH), 121.5 (s, CH), 30.0 (d, J ) 2.2
Hz, py-CH2), 28.6 (d, J ) 71.6 Hz, P-CH2), 21.4 (d, J ) 4.3 Hz,
CH3). 31P{1H} NMR δ (121 MHz, CDCl3) ppm: 34.6. Anal. Calcd
for C21H22NOP: C, 75.21; H, 6.61; N, 4.18. Found: C, 75.06; H,
6.70; N, 4.06. HRMS (FAB) m/z: calcd for C21H23NOP [M + H]+
336.1517; found 336.1505.
2-[2-(Di-2-anisylphosphinoyl)ethyl]pyridine (3b). Di-2-anis-
ylphosphine oxide (2.49 g, 9.49 mmol, 1.0 equiv) and 2-vinylpy-
ridine (2) (1.00 mL, 9.49 mmol, 1.0 equiv) were dissolved in 50
mL of THF. KOtBu (0.11 g, 0.95 mmol, 0.1 equiv) was added,
and the mixture was stirred at 60 °C for 16 h, after which unlocked
31P NMR showed full conversion. Water (10 mL) was added, and
the mixture was concentrated in vacuo. It was redissolved in EtOAc
(200 mL) and washed with water twice and with brine. After drying
over MgSO4 and concentration in vacuo, column chromatography
(eluent 5% MeOH in CH2Cl2) yielded the product as a white solid
(2.52 g, 6.87 mmol, 72%, mp 67 °C). 1H NMR δ (500 MHz, CDCl3)
ppm: 8.45 (d, J ) 4.3 Hz, 1H, py-H6), 7.64 (ddd, J ) 13.4, 7.5,
1.6 Hz, 2H, anis-H6), 7.52 (dt, J ) 7.7, 1.5 Hz, 1H, py-H4),
7.46-7.42 (m, 2H, anis-H4), 7.14 (d, J ) 7.7 Hz, 1H, py-H3),
2-[2-(Dimesitylphosphinoyl)ethyl]pyridine (3c). Dimesitylphos-
phine oxide (0.425 g, 1.48 mmol, 1.0 equiv) and 2-vinylpyridine
(2) (0.156 mL, 1.48 mmol, 1.0 equiv) were dissolved in 10 mL of
THF. KOtBu (34 mg, 0.29 mmol, 0.2 equiv) was added, and the
mixture was stirred at 60 °C for 16 h, after which unlocked 31P
NMR showed full conversion. Water (5 mL) was added, and the
mixture was concentrated in vacuo. It was redissolved in 100 mL
of EtOAc and washed with water twice and with brine. It was dried
over MgSO4 and concentrated in vacuo, after which column
chromatography (eluent 5% MeOH in CH2Cl2) yielded the product
1
as an off-white solid (0.361 g, 0.92 mmol, 62%, mp 158 °C). H
NMR δ (300 MHz, CDCl3) ppm: 8.45 (d, J ) 7.9 Hz, 1H, py-H6),
7.52 (dt, J ) 7.7, 1.8 Hz, 1H, py-H4), 7.11 (d, J ) 7.7 Hz, 1H,
py-H3), 7.06 (m, 1H, py-H5), 6.77 (d, J ) 3.4 Hz, 4H, mes-H3),
3.08-2.96 (m, 2H, py-CH2), 2.92-2.82 (m, 2H, P-CH2), 2.37 (s,
12H, mes-2-CH3), 2.22 (s, 6H, mes-4-CH3). 13C{1H} NMR δ (75
MHz, CDCl3) ppm: 161.1 (d, J ) 15.2 Hz, py-C2), 149.2 (s, py-
C6), 141.4 (d, J ) 9.8, mes-C2), 140.8 (s, mes-C4), 136.8 (s, CH),
131.3 (d, J ) 10.7 Hz, mes-C3), 130.2 (d, J ) 94.4 Hz, mes-C1),
123.3 (s, CH), 121.5 (s, CH), 35.8 (d, J ) 66.3 Hz, P-CH2), 31.2
(s, py-CH2), 23.2 (s, mes-2-CH3), 21.1 (s, mes-4-CH3). 31P{1H}
NMR δ (121 MHz, CDCl3) ppm: 41.8. Anal. Calcd for C25H30NOP:
C, 76.70; H, 7.72; N, 3.58. Found: C, 76.61; H, 7.78, N, 3.93.
HRMS (FAB) m/z: calcd for C25H31NOP [M + H]+ 392.2143;
found 392.2147.
2-[2-(Di-2-tolylphosphino)ethyl]pyridine (1a). 2-[2-(Di-2-
tolylphosphinoyl)ethyl]pyridine (3a) (1.48 g, 4.41 mmol, 1.0 equiv)
was dissolved in phenylsilane (8.0 mL, 65 mmol, 15 equiv), and

New Ni and Pd Complexes with P,N Ligands
Organometallics, Vol. 28, No. 11, 2009 3279
the mixture was refluxed overnight, after which unlocked 31P NMR
showed full conversion. The mixture was concentrated in vacuo
and co-evaporated with three times with 5 mL of toluene. The
product was purified using column chromatography using Et2O as
the eluent and a second column with CH2Cl2 as the eluent to yield
the product as a yellowish oil (1.33 g, 4.18 mmol, 95%). 1H NMR
δ (500 MHz, CDCl3) ppm: 8.50-8.48 (d, J ) 4.4 Hz, 1H, py-H6),
7.58 (dt, J ) 7.7, 1.8 Hz, 1H, py-H4), 7.29-7.26 (m, 2H, tol-H4),
7.25-7.21 (m, 2H, tol-H6), 7.19-7.14 (m, 4H, tol-H3 + -H5),
7.14-7.09 (m, 2H, py-H3 + -H5), 2.97-2.92 (m, 2H, py-CH2),
2.48-2.44 (m, 2H, P-CH2), 2.45 (s, 6H, CH3). 13C{1H} NMR δ
(125 MHz, CDCl3) ppm: 162.2 (d, J ) 13.9 Hz, py-C2), 149.5 (s,
py-C6), 142.5 (d, J ) 25.2 Hz, tol-C2), 136.9 (d, J ) 13.5 Hz,
tol-C1), 136.5 (s, CH), 131.3 (s, CH), 130.2 (d, J ) 4.6 Hz, CH),
128.6 (s, CH), 126.3 (s, CH), 122.8 (s, CH), 121.4 (s, CH), 34.7
(d, J ) 18.6 Hz, py-CH2), 27.1 (d, J ) 12.7 Hz, P-CH2), 21.4 (d,
J ) 21.1 Hz, CH3). 31P{1H} NMR δ (121 MHz, CDCl3) ppm:
-35.8. Anal. Calcd for C21H22NP: C, 78.97; H, 6.94; N, 4.39.
Found: C, 78.88; H, 6.87, N, 4.31. MS (EI) m/z (rel intensity): 319
(8) [M]+•, 228 (100) [M - tol]+, 106 (10) [M - P(tol)2]+.
2-[2-(Di-2-anisylphosphino)ethyl]pyridine (1b). 2-[2-(Di-2-
anisylphosphinoyl)ethyl]pyridine (3b) (137 mg, 0.37 mmol, 1.0
equiv) was dissolved in phenylsilane (2.0 mL, 16.2 mmol, 43 equiv),
and the mixture was refluxed overnight, after which unlocked 31P
NMR showed full conversion. The mixture was concentrated and
purified by column chromatography with CH2Cl2 f 5% MeOH/
CH2Cl2 as the eluent to yield the product as a white solid (122 mg,
0.35 mmol, 93%, mp 47 °C). 1H NMR δ (500 MHz, CDCl3) ppm:
8.53 (d, J ) 4.7 Hz, 1H, py-H6), 7.58 (t, J ) 7.6 Hz, 1H, py-H4),
7.34-7.30 (m, 2H, anis-H4), 7.21-7.16 (m, 3H, py-H3 + anis-
H6), 7.12-7.09 (m, 1H, py-H5), 6.93 (t, J ) 7.4 Hz, 2H, anis-
H5), 6.87 (dd, J ) 8.1, 4.1 Hz, 2H, anis-H3), 3.80 (s, 6H, CH3),
3.01-2.94 (m, 2H, py-CH2), 2.55-2.50 (m, 2H, P-CH2). 13C{1H}
NMR δ (125 MHz, CDCl3) ppm: 162.7 (d, J ) 13.6 Hz, py-C2),
161.7 (d, J ) 13.5 Hz, anis-C2), 149.3 (s, py-C6), 136.4 (s, CH),
132.9 (d, J ) 5.1 Hz, CH), 130.0 (s, CH), 125.7 (d, J ) 15.2 Hz,
anis-C1), 122.8 (s, CH), 121.1 (s, CH), 121.0 (d, J ) 2.1 Hz, CH),
110.4 (s, CH), 55.7 (s, CH3), 35.2 (d, J ) 18.6 Hz, py-CH2), 25.1
(d, J ) 13.1 Hz, P-CH2). 31P{1H} NMR δ (121 MHz, CDCl3) ppm:
-34.6. Anal. Calcd for C21H22NO2P: C, 71.78; H, 6.31; N, 3.99.
Found: C, 71.64; H, 6.27, N, 3.84. MS (EI) m/z (rel intensity): 351
(18) [M]+•, 244 (100) [M - anis]+, 137 (7) [M - 2anis]+, 136 (7)
[M - 2anis - H]+, 107 (13) [anis]+, 106 (12) [M - P(anis)2]+.
2-[2-(Dimesitylphosphino)ethyl]pyridine (1c). 2-[2-(Dimesit-
ylphosphinoyl)ethyl]pyridine (3c) (205 mg, 0.52 mmol, 1.0 equiv)
was dissolved in phenylsilane (4.0 mL, 32 mmol, 62 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 chromotagraphy with CH2Cl2 f 5% MeOH/
CH2Cl2 as the eluent. After co-evaporation with hexanes (5 × 5
mL), the product was obtained as a white solid (196 mg, 0.52 mmol,
100%, mp 83 °C). 1H NMR δ (500 MHz, CDCl3) ppm: 8.51 (d, J
) 4.2 Hz, 1H, py-H6), 7.56 (dt, J ) 7.7, 1.8 Hz, 1H, py-H4),
7.11-7.06 (m, 2H, py-H3 + -H5), 6.78 (d, J ) 2.1 Hz, 2H, mes-
H3), 2.94-2.89 (m, 2H, py-CH2), 2.80-2.74 (m, 2H, P-CH2), 2.31
(s, 12H, mes-2-CH3), 2.24 (s, 6H, mes-4-CH3). 13C{1H} NMR δ
(125 MHz, CDCl3) ppm: 162.5 (d, J ) 16.8 Hz, py-C2), 149.4 (s,
py-C6), 142.1 (d, J ) 13.6 Hz, mes-C2), 137.5 (s, mes-C4), 136.5
(s, CH), 133.1 (d, J ) 21.5 Hz, mes-C1), 130.1 (d, J ) 3.0 Hz,
mes-C3), 122.7 (s, CH), 121.2 (s, CH), 36.1 (d, J ) 22.7 Hz, py-
CH2), 31.2 (d, J ) 16.0 Hz, P-CH2), 23.4 (d, J ) 13.1 Hz, mes-
2-CH3), 21.0 (s, mes-4-CH3). 31P{1H} NMR δ (121 MHz, CDCl3)
ppm: -20.8. Anal. Calcd for C25H30NP: C, 79.97; H, 8.05; N, 3.73.
Found: C, 80.11; H, 7.98, N, 3.65. MS (EI) m/z (rel intensity): 375
(10) [M]+•, 360 (100) [M - CH3], 256 (89) [M - mes]+, 138 (25)
[M - 2mes + H]+, 106 (37) [M - P(mes)2]+.
2-[2-(Di-2-tolylphosphino)ethyl]pyridinenickel Dichloride (4a).
A mixture of 2-[2-(di-2-tolylphosphino)ethyl]pyridine (1a) (215 mg,
0.67 mmol, 1.0 equiv), (DME)NiCl2 (148 mg, 0.67 mmol, 1.0
equiv), and CH2Cl2 (8 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
sonication bath for 30 min. The solids were filtered off, washed
with Et2O, and dried in vacuo to yield the product as a purple solid
(175 mg, 0.39 mmol, 58%, mp 254 °C dec). Anal. Calcd for
C21H22Cl2NNiP: C, 56.18; H, 4.94; N, 3.12. Found: C, 55.99; H,
4.90, N, 2.96. HRMS (FAB) m/z: calcd for C21H22ClNNiP [M -
Cl]+ 412.0532; found 412.0536. µeff ) 3.85 µB.
2-[2-(Di-2-anisylphosphino)ethyl]pyridinenickel Dichloride
(4b). A mixture of 2-[2-(di-2-anisylphosphino)ethyl]pyridine (1b)
(114 mg, 0.32 mmol, 1.0 equiv), (DME)NiCl2 (71 mg, 0.32 mmol,
1.0 equiv), and CH2Cl2 (5 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
sonication bath for 30 min. The solids were filtered off, washed
with Et2O, and dried in vacuo to yield the product as a brown solid
(134 mg, 0.28 mmol, 86%, mp 235 °C dec). Anal. Calcd for
C21H22Cl2NNiO2P: C, 52.44; H, 4.61; N, 2.91. Found: C, 52.53;
H, 4.72, N, 2.85. HRMS (FAB) m/z: calcd for C21H22ClNNiO2P
[M - Cl]+ 444.0430; found 444.0426. µeff ) 3.30 µB.
2-[2-(Dimesitylphosphino)ethyl]pyridinenickel Dichloride (4c).
A mixture of 2-[2-(dimesitylphosphino)ethyl]pyridine (1c) (42 mg,
0.11 mmol, 1.0 equiv), (DME)NiCl2 (25 mg, 0.11 mmol, 1.0 equiv),
and CH2Cl2 (3 mL) was stirred for 16 h. It was filtered through a
pad of Celite, washed with CH2Cl2, and concentrated in vacuo. Et2O
(3 mL) was added, and the mixture was put in a sonication bath
for 30 min. The solids were filtered off, washed with Et2O, and
dried in vacuo to yield the product as a purple solid (38 mg, 0.075
mmol, 67%, mp 240 °C dec). Anal. Calcd for C25H30Cl2NNiP: C,
59.45; H, 5.99; N, 2.77. Found: C, 59.36; H, 5.91, N, 2.71. HRMS
(FAB) m/z: calcd for C25H30ClNNiP [M - Cl]+ 468.1158; found
468.1168. µeff ) 3.30 µB.
2-[2-(Di-2-tolylphosphino)ethyl]pyridine Methylpalladium Chlo-
ride (5a). 2-[2-(Di-2-tolylphosphino)ethyl]pyridine (1a) (350 mg,
1.10 mmol, 1.0 equiv) and (COD)Pd(CH3)Cl (291 mg, 1.10 mmol,
1.0 equiv) were dissolved in CH2Cl2 (20 mL), and the mixture was
stirred for 16 h. Then, it was concentrated in vacuo to approximately
2 mL, after which 20 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 (460 mg, 0.97 mmol,
88%, mp 227 °C dec). 1H NMR δ (500 MHz, CDCl3, 25 °C) ppm:
9.30 (dd, J ) 5.4, 1.0 Hz, 1H, py-H6), 7.90-7.66 (bs, 2H, tol-
H6), 7.63 (d pst, J ) 7.7, 1.7 Hz, 1H, py-H4), 7.40-7.34 (m, 2H,
tol-H4), 7.32-7.26 (m, 2H, tol-H3), 7.24-7.20 (m, 1H, py-H5),
7.20-7.14 (m, 3H, py-H3 + tol-H5), 3.50-3.42 (m, 2H, py-CH2),
2.51 (s, 6H, CH3), 2.49-2.43 (m, 2H, P-CH2), 0.39 (d, J ) 3.7
Hz, 3H, CH3). 1H NMR δ (500 MHz, CDCl3, -50 °C) ppm: 9.21
(d, J ) 5.3 Hz, 1H, py-H6), 8.86-8.82 (m, 1H, tol-H6), 7.71-7.67
(m, 1H, py-H4), 7.47-7.43 (m, 1H, tol-H4), 7.41-7.34 (m, 2H,
tol′-H3 + -H4), 7.34-7.25 (m, 3H, py-H3 + tol-H3 + -H5), 7.23
(d, J ) 7.6 Hz, 1H, py-H5), 7.11-7.04 (m, 1H, tol′-H5), 6.78-6.72
(m, 1H, tol′-H6), 3.73-3.3.65 (m, 1H, py-CHH), 3.36-3.24 (m,
1H, py-CHH), 2.84 (s, 3H, tol-CH3), 2.71-2.63 (m, 1H, P-CHH),
2.21 (s, 3H, tol′-CH3), 2.20-2.12 (m, 1H, P-CHH), 0.23 (d, J )
3.0 Hz, 3H, Pd-CH3). 1H NMR δ (500 MHz, CDCl3, 60 °C) ppm:
9.37 (d, J ) 5.5 Hz, 1H, py-H6), 7.77 (dd, J ) 13.5, 7.8 Hz, 2H,
tol-H6), 7.62 (d pst, J ) 7.6, 1.5 Hz, 1H, py-H4), 7.38-7.34 (m,
2H, tol-H4), 7.30-7.26 (m, 2H, tol-H3), 7.24-7.21 (m, 1H, py-
H5), 7.20-7.16 (m, 2H, tol-H5), 7.14 (d, J ) 7.6 Hz, 1H, py-H3),
3.50-3.41 (m, 2H, py-CH2), 2.53 (s, 6H, tol-CH3), 2.49-2.45 (m,
2H, P-CH2), 0.47 (d, J ) 3.7 Hz, 3H, Pd-CH3). 13C{1H} NMR δ
(125 MHz, CDCl3, 25 °C) ppm: 159.2 (d, J ) 3.0 Hz, py-C2),
152.7 (s, py-C6), 140.8 (d, J ) 6.3 Hz, tol-C2), 138.5 (s, CH),

3280 Organometallics, Vol. 28, No. 11, 2009
Flapper et al.
137.0-136.1 (bs, CH), 132.2 (d, J ) 7.6 Hz, CH), 131.4 (s, CH),
129.7 (d, J ) 48.5 Hz, tol-C1), 126.1 (d, J ) 12.7 Hz, CH), 124.1
(s, CH), 123.3 (s, CH), 36.7 (d, J ) 6.8 Hz, py-CH2), 25.5 (d, J )
29.1 Hz, P-CH2), 23.5 (d, J ) 5.9 Hz, tol-CH3), 0.0 (s, Pd-CH3).
31P{1H} NMR δ (121 MHz, CDCl3, 25 °C) ppm: 40.3. Anal. Calcd
for C22H25ClNPPd: C, 55.48; H, 5.29; N, 2.94. Found: C, 55.56;
H, 5.22; N, 2.82. HRMS (FAB) m/z: calcd for C22H25NPPd [M -
Cl]+ 440.0768; found 440.0756.
2.24 (s, 6H, mes-4-CH3), 0.53 (d, J ) 4.5 Hz, 3H, Pd-CH3). 13C{1H}
NMR δ (75 MHz, CDCl3) ppm: 159.7 (s, py-C2), 152.4 (s, py-
C6), 141.4 (d, J ) 8.6 Hz, mes-C2), 139.9 (s, mes-C4), 138.4 (s,
CH), 131.1 d, J ) 7.3 Hz, mes-C3), 129.9 (d, J ) 46.4 Hz, mes-
C1), 123.9 (s, CH), 123.3 (s, CH), 37.6 (d, J ) 5.2 Hz, py-CH2),
30.4 (d, J ) 31.7 Hz, P-CH2), 25.2 (d, J ) 7.3 Hz, mes-2-CH3),
21.0 (s, mes-4-CH3), 1.1 (s, Pd-CH3). 31P{1H} NMR δ (121 MHz,
CDCl3) ppm: 14.4. Anal. Calcd for C26H33ClNPPd: C, 58.66; H,
6.25; N, 2.63. Found: C, 58.60; H, 6.35; N, 2.57. HRMS (FAB)
m/z: calcd for C26H33NPPd [M - Cl]+ 496.1396; found 496.1400.
2-[2-(Di-2-anisylphosphino)ethyl]pyridine Methylpalladium
Chloride (4b). 2-[2-(Di-2-anisylphosphino)ethyl]pyridine (1b) (332
mg, 0.95 mmol, 1.0 equiv) and (COD)Pd(CH3)Cl (250 mg, 0.95
mmol, 1.0 equiv) were dissolved in CH2Cl2 (15 mL), and the
mixture was stirred for 16 h. Then, it was concentrated in vacuo to
approximately 1.5 mL, after which 15 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
(436 mg, 0.86 mmol, 91%). 1H NMR δ (500 MHz, CDCl3, 25 °C)
ppm: 9.35 (dd, J ) 5.5, 1.1 Hz, 1H, py-H6), 7.64-7.60 (m, 1H,
py-H4), 7.47-7.43 (m, 2H, anis-H4), 7.22-7.19 (m, 1H, py-H5),
7.14 (d, J ) 7.7 Hz, 1H, py-H3), 6.96-6.92 (m, 4H, anis-H3 +
-H5), 3.83 (s, 6H, anis-CH3), 3.48-3.40 (m, 2H, py-CH2),
2.41-2.38 (m, 2H, P-CH2), 0.31 (d, J ) 3.5 Hz, 3H, Pd-CH3); the
signal for anis-H6 was not obserVed. 1H NMR δ (500 MHz, CDCl3,
-50 °C) ppm: 9.22 (d, J ) 5.1 Hz, 1H, py-H6), 8.66 (dd, J )
16.5, 7.2 Hz, 1H, anis-H6), 7.68-7.64 (m, 1H, py-H4), 7.58-7.54
(m, 1H, anis-H4), 7.43-7.39 (m, 1H, anis′-H4), 7.24-7.20 (m, 2H,
py-H3 + -H5), 7.10-7.07 (m, 1H, anis-H5), 7.01-6.98 (m, 1H,
anis′-H3), 6.91 (d, J ) 7.8 Hz, 1H, anis-H3), 6.82-6.78 (m, 1H,
anis′-H5), 6.57-6.52 (dd, J ) 11.5, 8.1 Hz, 1H, anis′-H6), 4.00
(s, 3H, anis-CH3), 3.80-3.69 (m, 1H, py-CHH), 3.68 (s, 3H, anis′-
CH3), 3.25-3.12 (m, 1H, py-CHH), 2.79-2.72 (m, 1H, P-CHH),
2.01-1.92 (m, 1H, P-CHH), 0.17 (d, J ) 3.5 Hz, 3H, Pd-CH3). 1H
NMR δ (500 MHz, CDCl3, 60 °C) ppm: 9.40 (d, J ) 5.1 Hz, 1H,
py-H6), 7.69-7.61 (m, 2H, anis-H6), 7.61-7.56 (m, 1H, py-H4),
7.44-7.39 (m, 2H, anis-H4), 7.20-7.16 (m, 1H, py-H5), 7.10 (d,
J ) 7.7 Hz, 1H, py-H3), 6.95-6.90 (m, 4H, anis-H3 + -H5), 3.81
(s, 6H, anis-CH3), 3.45-3.34 (m, 2H, Py-CH2), 2.44-2.37 (m, 2H,
P-CH2), 0.35 (d, J ) 3.4 Hz, 3H, Pd-CH3). 13C{1H} NMR δ (125
MHz, CDCl3, 25 °C) ppm: 160.7 (d, J ) 2.1 Hz, py-C2), 160.1 (s,
anis-C2), 152.9 (s, py-C6), 138.1 (s, CH), 138-136 (bs, CH), 132.9
(s, CH), 123.9 (s, CH), 122.8 (s, CH), 120.7 (d, J ) 12.2 Hz, CH),
119.2 (d, J ) 51.9 Hz, anis-C1), 111.1 (d, J ) 4.2 Hz, CH), 55.8
(s, anis-CH3), 36.5 (d, J ) 7.2 Hz, py-CH2), 25.2 (d, J ) 33.3 Hz,
2-[2-(Di-2-tolylphosphino)ethyl]pyridine Methylpalladium(ac-
etonitrile) Tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (6a).
To a mixture of 2-[2-(di-2-tolylphosphino)ethyl]pyridine meth-
ylpalladium chloride (5a) (148 mg, 275 mmol, 1.0 equiv) and
sodium tetrakis[(3,5-trifluoromethyl)phenyl]borate (NaBAr′4) (275
mg, 0.311 mmol, 1.0 equiv) were added CH3CN (2 mL) and CH2Cl2
(10 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 (392 mg, 0.291 mmol,
1
94%). H NMR δ (500 MHz, CD2Cl2, 25 °C) ppm: 8.58 (bs, 1H,
py-H6), 7.80-7.73 (m, 9H, py-H4 + Ar′-H2), 7.68-7.58 (bs, 2H,
tol-H6), 7.58 (s, 4H, Ar′-H4), 7.47-7.42 (m, 2H, tol-H4), 7.38-7.29
(m, 4H, py-H3 + -H5 + tol-H5), 7.26-7.20 (m, 2H, tol-H3),
3.50-3.40 (m, 2H, py-CH2), 2.58-2.42 (m, 8H, P-CH2 + tol-CH3),
2.29 (s, 3H, NCCH3), 0.26 (s, 3H, Pd-CH3). 1H NMR δ (500 MHz,
Cl2DCCDCl2, 80 °C) ppm: 8.63-8.57 (m, 1H, py-H6), 7.78-7.74
(m, 8H, Ar′-H2), 7.72 (t, J ) 7.6 Hz, py-H4), 7.60 (dd, J ) 14.4,
7.6 Hz, 2H, tol-H6), 7.57 (s, 4H, Ar′-H4), 7.48-7.44 (m, 2H, tol-
H4), 7.37-7.33 (m, 2H, tol-H5), 7.29-7.22 (m, 4H, py-H3 + -H5
+ tol-H3), 3.44-3.36 (m, 2H, py-CH2), 2.55-2.47 (m, 2H, P-CH2),
2.48 (s, 3H, tol-CH3), 2.24 (s, 3H, NCCH3), 0.39 (s, 3H, Pd-CH3).
13C{1H} NMR δ (125 MHz, CD2Cl2, 25 °C) ppm: 162.4 (q, J )
49.8 Hz, Ar′-C1), 159.9 (s, py-C2), 150.6 (s, py-C6), 141.4 (d, J
) 6.3 Hz, tol-C2), 140.2 (s, CH), 135.5 (bs, Ar′-C2), 132.9 (d, J
) 8.0 Hz, CH), 132.5 (s, CH), 129.5 (quartet of multiplets, J )
31.6 Hz, Ar′-C3), 128.0 (d, J ) 57.3 Hz, tol-C1), 126.7 (d, J )
12.7 Hz, CH), 126.1 (bs, CH), 125.2 (q, J ) 272.4, CF3), 124.4
(bs, CH), 119.7 (s, NCCH3), 118.1 (m, Ar′-C4), 36.9 (s, Py-CH2),
25.6 (d, J ) 30.3 Hz, P-CH2), 23.6 (d, J ) 6.3 Hz, tol-CH3), 3.2
(s, Pd-CH3), 0.7 (s, NCCH3). 31P{1H} NMR δ (121 MHz, CD2Cl2)
ppm: 42.7. 19F{1H} NMR δ (282 MHz, CD2Cl2) ppm: -63.0. Anal.
Calcd for C56H40BF24N2PPd: C, 50.00; H, 3.00; N, 2.08. Found: C,
49.94; H, 3.06; N, 2.10. HRMS (FAB) m/z: calcd for C22H25NPPd
[M - BAr′4 - CH3CN]+ 440.0768; found 440.0765. MS (FD) m/z:
481 [M - BAr′4]+.
P-CH2), -1.3 (s, Pd-CH3). 13C{1H} NMR
δ (125 MHz,
Cl2DCCDCl2, 80 °C) ppm: 160.4 (d, J ) 2.5 Hz, py-C2), 159.9 (s,
anis-C2), 152.6 (s, py-C6), 137.6 (s, CH), 136.6 (d, J ) 15.2 Hz,
CH), 132.5 (s, CH), 123.5 (s, CH), 122.1 (s, CH), 120.4 (d, J )
12.2 Hz, CH), 119.2 (d, J ) 51.1 Hz, anis-C1), 111.2 (d, J ) 4.7
Hz, CH), 55.5 (s, anis-CH3), 36.0 (d, J ) 6.8 Hz, py-CH2), 24.9
(d, J ) 32.9 Hz, P-CH2), -1.9 (s, Pd-CH3). 31P{1H} NMR δ (121
MHz, CDCl3, 25 °C) ppm: 37.5. Anal. Calcd for C22H25ClNO2PPd:
C, 51.99; H, 4.96; N, 2.76. Found: C, 51.84; H, 5.08; N, 2.64.
HRMS (FAB) m/z: calcd for C22H25NO2PPd [M - Cl]+ 472.0667;
found 472.0661.
2-[2-(Di-2-anisylphosphino)ethyl]pyridine Methylpalladium-
(acetonitrile) Tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (6b).
To a mixture of 2-[2-(di-2-anisylphosphino)ethyl]pyridine meth-
ylpalladium chloride (5b) (323 mg, 0.64 mmol, 1.0 equiv) and
sodium tetrakis[(3,5-trifluoromethyl)phenyl]borate (NaBAr′4) (563
mg, 0.64 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 5 mL of
hexanes to yield the product as a white solid (762 mg, 0.55 mmol,
1
2-[2-(Dimesitylphosphino)ethyl]pyridine Methylpalladium
Chloride (5c). 2-[2-(Dimesitylphosphino)ethyl]pyridine (1c) (100
mg, 0.27 mmol, 1.0 equiv) and (COD)Pd(CH3)Cl (71 mg, 0.27
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 3 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
87%). H NMR δ (500 MHz, CD2Cl2, 25 °C) ppm: 8.58 (d, J )
4.9 Hz, 1H, py-H6), 7.79-7.73 (m, 9H, py-H4 + Ar′-H2), 7.58 (s,
4H, Ar′-H4), 7.56-7.51 (m, 2H, anis-H4), 7.54-7.46 (bs, 2H, anis-
H6), 7.33 (d, J ) 7.8 Hz, 1H, py-H3), 7.32-7.28 (m, 1H, py-H5),
7.04-6.97 (m, 4H, anis-H3 + -H5), 3.85 (s, 3H, anis-CH3),
3.46-3.39 (m, 2H, py-CH2), 2.46-2.40 (m, 2H, P-CH2), 2.29 (s,
1
3H, NCCH3), 0.15 (d, J ) 4.2 Hz, 3H, Pd-CH3). H NMR δ (500
MHz, Cl2DCCDCl2, 80 °C) ppm: 8.61-8.55 (m, 1H, py-H6),
7.78-7.74 (m, 8H, Ar′-H2), 7.73 (dt, J ) 7.7, 1.5 Hz, 1H, py-H4),
7.57 (s, 4H, Ar′-H4), 7.56-7.51 (m, 2H, anis-H4), 7.49 (dd, J )
14.8, 7.4 Hz, 2H, anis-H6), 7.29 (d, J ) 7.7 Hz, 1H, py-H3),
7.27-7.23 (m, 1H, py-H5), 7.04-6.99 (m, 4H, anis-H3 + -H5),
3.84 (s, 6H, anis-CH3), 3.43-3.34 (m, 2H, py-CH2), 2.48-2.43
1
(115 mg, 0.22 mmol, 81%). H NMR δ (500 MHz, CDCl3) ppm:
9.20 (dd, J ) 4.5, 2.0 Hz, 1H, py-H6), 7.62 (dt, J ) 7.5, 2.0 Hz,
1H, py-H4), 7.27-7.25 (m, 1H, py-H5), 7.12 (d, J ) 7.5 Hz, 1H,
py-H3), 6.82 (d, J ) 3.0 Hz, 4H, mes-H3), 3.56-3.47 (m, 2H,
py-CH2), 2.54-2.49 (m, 2H, P-CH2), 2.44 (s, 12H, mes-2-CH3),

New Ni and Pd Complexes with P,N Ligands
Organometallics, Vol. 28, No. 11, 2009 3281
(m, 2H, P-CH2), 2.24 (s, 3H, NCCH3), 0.27 (s, 3H, Pd-CH3).
13C{1H} NMR δ (125 MHz, CD2Cl2, 25 °C) ppm: 162.4 (q, J )
49.8 Hz, Ar′-C1), 161.5 (s, anis-C2), 160.6 (s, py-C2), 150.7 (s,
py-C6), 139.9 (s, CH), 137.0 (s, CH), 135.5 (bs, Ar′-C2), 134.3 (s,
CH), 129.5 (quartet of multiplets, J ) 31.6 Hz, Ar′-C3), 125.9
(s, CH), 125.2 (q, J ) 272.4, CF3), 123.9 (s, CH), 121.3 (d, J )
12.7 Hz, CH), 119.6 (s, NCCH3), 118.1 (m, Ar′-C4), 117.3 (d, J )
56.4 Hz, anis-C1), 111.9 (d, J ) 4.6 Hz, CH), 56.1 (s, anis-CH3),
36.7 (d, J ) 4.6 Hz, py-CH2), 25.5 (d, J ) 37.1 Hz, P-CH2), 3.3
(s, NCCH3), -1.0 (s, Pd-CH3). 31P{1H} NMR δ (121 MHz, CD2Cl2)
ppm: 39.7. 19F{1H} NMR δ (282 MHz, CD2Cl2) ppm: -63.0. Anal.
Calcd for C56H40BF24N2O2PPd: C, 48.84; H, 2.93; N, 2.03. Found:
C, 48.90; H, 3.01; N, 2.05. HRMS (FAB) m/z: calcd for
C22H25O2NPPd [M - BAr′4 - CH3CN]+ 472.0667; found 472.0664.
MS (FD) m/z: 513 [M - BAr′4]+.
2-[2-(Dimesitylphosphino)ethyl]pyridine Methylpalladium(ac-
etonitrile) Tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (6c).
To a mixture of 2-[2-(dimesitylphosphino)ethyl]pyridine meth-
ylpalladium chloride (5c) (161 mg, 0.302 mmol, 1.0 equiv) and
sodium tetrakis[(3,5-trifluoromethyl)phenyl]borate (NaBAr′4) (268
mg, 0.302 mmol, 1.0 equiv) were added CH3CN (1 mL) and CH2Cl2
(10 mL), and the mixture was stirred for 16 h. It was cannula
filtrated, evaporated to dryness, and co-evaporated with hexanes
and pentane (5 mL each) to yield the product as a white solid (353
mg, 0.252 mmol, 83%). 1H NMR δ (500 MHz, CD2Cl2) ppm: 8.61
(d, J ) 5.4 Hz, 1H, py-H6), 7.78-7.73 (m, 9H, py-H4 + Ar′-H2),
7.59 (s, 4H, Ar′-H4), 7.37-7.33 (m, 1H, py-H5), 7.30 (d, J ) 7.6
Hz, py-H3), 6.91 (d, J ) 3.4 Hz, 4H, mes-H3), 3.51-3.45 (m, 2H,
py-CH2), 2.57-2.54 (m, 2H, P-CH2), 2.42 (s, 12H, mes-2-CH3),
2.26 (s, 6H, mes-4-CH3), 2.22 (s, 3H, NCCH3), 0.39 (d, J ) 3.4
Hz, 3H, Pd-CH3). 13C{1H} NMR δ (125 MHz, CD2Cl2) ppm: 162.4
(q, J ) 49.8 Hz, Ar′-C1), 160.6 (s, py-C2), 150.5 (s, py-C6), 141.6
(s, mes-C2), 141.5 (s, mes-C4), 140.29 S, CH), 135.5 (bs, Ar′-
C2), 131.8 (d, J ) 8.9 Hz, mes-C3), 129.5 (quartet of multiplets,
J ) 31.6 Hz, Ar′-C3), 128.0 (d, J ) 42.5 Hz, mes-C1), 125.8 (s,
CH), 125.2 (q, J ) 272.4, CF3), 124.4 (s, CH), 120.1 (s, NCCH3),
118.1 (m, Ar′-C4), 37.9 (d, J ) 4.4 Hz, py-CH2), 30.8 (d, J ) 34.6
Hz, P-CH2), 25.2 (d, J ) 8.2 Hz, mes-2-CH3), 21.0 (s, mes-4-CH3),
3.4 (s, NCCH3), 2.1 (s, Pd-CH3). 31P{1H} NMR δ (121 MHz,
CD2Cl2) ppm: 14.7. 19F{1H} NMR δ (282 MHz, CD2Cl2) ppm:
-63.0. HRMS (FAB) m/z: calcd for C26H33NPPd [M - BAr′4 -
CH3CN]+ 496.1396; found 496.1395. MS (FD) m/z: 537 [M -
BAr′4]+.
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
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
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. 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 consump-
tion and the amount of other oligomers formed.
General Procedure for the Palladium-Catalyzed Oligomer-
ization. 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.
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.
General Procedure for the Nickel-Catalyzed Oligomeriza-
tion. The autoclave was heated to 140 °C under vacuum for 1 h
and cooled under a 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
Supporting Information Available: A CIF file giving crystal
data for 4a, 4c, 5a, and 5b and a file giving variable-temperature
1H NMR spectra for 5a and 5b and general experimental informa-
tion. This material is available free of charge via the Internet at
http://pubs.acs.org.
OM900038U