P(CH2CH2Py)nPh3-n (Py = 2-Pyridyl; n = l, 2, 3) as Chelating and as Binucleating Ligands for Palladium

Article abstract of DOI:10.1021/ic970745e

Several neutral palladium(II) complexes of the type [PdRCJ(PN_n)] with the ligands P(CH₂CH₂Py)Ph₂ (PN), P(CH₂-CH₂Py)₂Ph (PN₂), and P(CH₂CH₂Py)

Full text of DOI:10.1021/ic970745e

Inorg. Chem. 1997, 36, 5251-5256
5251
P(CH2CH2Py)nPh3-n (Py ) 2-Pyridyl; n ) 1, 2, 3) as Chelating and as Binucleating Ligands
for Palladium
Juan A. Casares, Pablo Espinet,* and Katerina Soulantica
Departamento de Qu´ımica Inorga´nica, Facultad de Ciencias, Universidad de Valladolid, E-47005
Valladolid, Spain
Isabel Pascual and A. Guy Orpen
School of Chemistry, University of Bristol, Bristol BS8 1TS, United Kingdom
ReceiVed June 17, 1997X
Several neutral palladium(II) complexes of the type [PdRCl(PNn)] with the ligands P(CH2CH2Py)Ph2 (PN), P(CH2-
CH2Py)2Ph (PN2), and P(CH2CH2Py)3 (PN3) have been prepared by reacting the corresponding phosphines with
[Pd2(µ-Cl)2R2(tht)2] (R ) C6Cl2F3, C6F5; tht ) tetrahydrothiophene). In all these complexes, the ligands act as
bidentate P,N-chelating ligands. Abstraction of the chloride with AgBF4 leads to the formation of the dimeric
compounds [Pd2R2(PN2)2](BF4)2 and [Pd2R2(PN3)2](BF4)2, in which the PNn ligands act as P,N-chelating and
P,N-bridging ligands. The bridges are labile, and exchange experiments on mixtures of the complexes with different
R groups show the equilibrium in solution between the dimeric “pure” complexes and the mixed complexes
[Pd2(C6F5)(C6Cl2F3)(PNn)2]2+. The structure of the complex [Pd2(C6Cl2F3)2{P(CH2CH2Py)2Ph}2](BF4)2 has been
studied by X-ray diffraction.
Introduction
P(CH2CH2Py)Ph2 (PN), P(CH2CH2Py)2Ph (PN2), and P(CH2-
CH2Py)3 (PN3) (Py ) 2-pyridyl), in order to study the behavior
of these multidentate ligands. The coordination properties of
PN have been previously tested with a variety of metal
centers: Mo,6 Ir,7 Ru,8 Os,9 Cu, Ag, and Au.10 The synthesis
of the complexes [PdCl2(PN)] and [Pd(PN)2](ClO4)2 has also
been reported,11 as well as the use of related secondary and
primary phosphines PH(CH2CH2Py)Ph and PH2(CH2CH2Py).12
Surprisingly little attention has been paid to the synthesis of
compounds with PN2 and PN3 ligands, although tri- or tetraden-
tate phosphines, as well as tri- or tetradentate amines, are very
often used in the stabilization of metal complexes.13 Both
ligands can potentially act as polydentate ligands on the same
metal center or as bridging ligands. Some of their possibilities
are depicted in Chart 1.
Metal complexes with ligands containing donor atoms with
different donor characteristics are of interest for their ability to
act as “hemilabile” ligands. Thus, the combination of P and O
or P and N donor atoms on a soft metal center can afford labile
M-O or M-N bonds and more inert M-P bonds.1 In this
context, pyridylphosphines, and particularly 2-pyridyl mono-
and diphosphines, have received attention in view of their
structural features, reactivity, and catalytic applications.2 They
usually behave as bridging ligands,3 but their less favored
behavior as chelating ligands forming a four-membered ring
has also been described.4 2-Pyridyl monophosphines with the
P atom separated from the Py group by one or two methylene
links, capable of forming five- and six-membered rings by
chelation, have been much less studied.
As a part of our research on complexes with pyridylphos-
phines and derivatives,3a,5 we have synthesized a group of
neutral and cationic complexes of palladium(II) with the ligands
Results and Discussion
1. Neutral Complexes. The base-catalyzed addition of P-H
bonds to 2-vinylpyridine provides an easy route to prepare (2-
* Corresponding author. E-mail: espinet@cpd.uva.es.
X Abstract published in AdVance ACS Abstracts, October 1, 1997.
(1) Bader, A.; Lindner, E. Coord. Chem. ReV. 1991, 108, 27-110.
(2) (a) Newcome, G. R. Chem. ReV. 1993, 93, 2067-2089. (b) Ru¨lke, R.
E.; Kaasjager, R. E.; Wehman, P.; Elsevier, C. J.; van Leeuwen, P.
W. N. M.; Vrieze, K.; Fraanje, J.; Goubitz, K.; Spek, A. L.
Organometallics 1996, 15, 3022-2031. (c) Yang, H.; Alvarez, M.;
Lugan, N.; Mathieu, R. J. Chem. Soc., Chem. Commun. 1995, 1721-
1722. (d) Anderson, M. P.; Casalnuovo, A. L; Johnson, B. J.; Mattson,
B. N.; Mueting, A. M.; Pignolet, L. H. Inorg. Chem. 1988, 27, 1649-
1658. (e) Kurtev, K.; Ribola, D.; Jones, R. A.; Cole-Hamilton, D. J.;
Wilkinson, G. J. Chem. Soc., Dalton Trans. 1980, 55-58.
(3) (a) Casares, J. A.; Espinet, P.; Hernando, R.; Iturbe, G.; Villafan˜e, F.;
Ellis, D. D.; Orpen, G. Inorg. Chem. 1997, 36, 44-49 and references
therein. (b) Zhang, Z. Z.; Cheng, H.; Kuang, S. M.; Zhou, Y. Q.; Liu,
Z. X.; Zhang, J. K.; Wang, H. G. J. Organomet. Chem. 1996, 516,
1-10.
(5) (a) Casares, J. C.; Coco, S.; Espinet, P.; Lin, Y. S. Organometallics
1995, 14, 3058-3067. (b) Casares, J. C.; Espinet, P.; Mart´ınez de
Ilarduya, J. M.; Lin, Y. S. Organometallics 1997, 16, 770-779.
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(7) (a) Wang, H. H.; Casalnuovo, A. L.; Johnson, B. J.; Mueting, A. M.;
Pignolet, L.H. Inorg. Chem. 1988, 27, 325-331. (b) Anderson, M.
P.; Casalnuovo, A. L.; Johnson, B. J.; Mattson, B. M.; Mueting, A.
M.; Pignolet, L. H. Inorg. Chem. 1988, 27, 1649-1658.
(8) Costella, L.; Del Zotto, A.; Mezzetti, A.; Zangrando, E.; Rigo, P. J.
Chem. Soc., Dalton Trans. 1993, 3001-3008.
(9) Del Zotto, A.; Mezzetti, A.; Rigo, P. J. Chem. Soc., Dalton Trans.
1994, 2257-2264.
(10) Del Zotto, A.; Nardin, G.; Rigo, P. J. Chem. Soc., Dalton Trans. 1995,
334-3351.
(11) Uhlig, E.; Keiser, S. Z. Anorg. Allg. Chem. 1974, 406, 1-6.
(12) Hessler, A.; Fischer, J.; Kucken, S.; Stelzer, O. Chem. Ber. 1994, 127,
481-488.
(13) (a) Reedijk, J. In ComprehensiVe Coordination Chemistry; Wilkinson,
G.; Gillard, R. D.; McCleverty, J. A., Eds.; Pergamon Press: Oxford,
U.K., 1987; Vol. 2, pp 73-98. (b) McAuliffe, C. A. Ibid., Vol. 2, pp
990-1066.
(4) (a) Ecke, A.; Keim, W.; Bonnet, M. C.; Tkatchenko, I.; Dahan, F.
Organometallics 1995, 14, 5302-5307. (b) Jain, V. K.; Jakkal, V.
S.; Bohra, R. J. Organomet. Chem. 1990, 389, 417-426. (c) Suzuki,
T.; Kita, M.; Kashiwabara, K.; Fujita, J. Bull. Chem. Soc. Jpn. 1990,
63, 3434-3442. (d) Wajda-Hermanowicz, K.; Pruchnik, F. P. Transi-
tion Met. Chem. (London) 1988, 13, 101-103.
S0020-1669(97)00745-3 CCC: $14.00 © 1997 American Chemical Society

5252 Inorganic Chemistry, Vol. 36, No. 23, 1997
Casares et al.
Chart 1
the two H atoms on each methylene group of the phosphine
also become equivalent; rotation of the aryl group would not
produce this equivalence. The question of whether the con-
formational inversion occurs with or without N decoordination
is answered by the fact that it is clearly faster than the exchange
of Py groups discussed below for 3 and 4. Hence the
conformational inversion does not involve N decoordination.
Complexes 3 and 4 show exchange between the coordinated
4
and free Py groups (Scheme 2) with preservation of the JP-F
coupling. In the static limit, the two Fortho signals, as well as
the H6 signals for the free and coordinated Py groups, should
be inequivalent. This is the situation observed at -30 °C. At
room temperature, the H6 signals in the 1H NMR spectrum and
the Fortho signals in the 19F NMR spectrum are broad but have
not yet reached coalescence. Tc for both compounds in the 1H
NMR spectrum is approximately 40 °C. At Tc, the exchange
rates (estimated as k ) π∆ν/x2) are 560 s-1 for 3 and 572 s-1
for 4. These rates are much slower than the Py exchange rates
observed for other analogous complexes such as [PdCl(C6F5)-
(OPPy3-N,N)] (for which k ) 17 500 s-1 at 6.7 °C).5b The
activation parameters for the exchange have been obtained by
NMR line shape analysis17 and are given in Table 2.
Scheme 1
As expected, the ∆Gq298 values obtained are higher than that
observed for [PdCl(C6F5)(OPPy3-N,N)], and it can be seen that
the difference arises from higher ∆Sq values for the complexes
described in this paper, although the ∆Hq values are similar for
both kinds of complexes. Since we have previously proved that
the exchange in [PdCl(C6F5)(OPPy3-N,N)] is associative, we
assume that the exchange is also associative for 3 and 4.
Although the interpretation of activation entropies is always
difficult, the main difference between compounds 3 and 4 and
[PdCl(C6F5)(OPPy3-N,N)] is that in the latter the Py group is
connected to a very rigid boatlike metallacycle in which an
associative exchange of Py groups does not produce a great
change in the geometry, while in 3 and 4 the simultaneous
coordination of both Py groups leads to a much more ordered
situation compared to that of the ground state. Thus, it is not
unreasonable that the activation entropies are more negative for
the latter.
The same fluxional behavior is observed for the compounds
with the PN3 ligand, 5 and 6. In these compounds, the exchange
has no effect on the 19F NMR, since the Fortho atoms are not
diastereotopic even in a rigid situation, but the exchange of
uncoordinated and coordinated Py groups can be observed in
1H NMR. The exchange observed is slightly faster than for
PN2 (the presence of two uncoordinated Py groups in the PN3
complexes makes higher the “concentration” of the entering Py
ligand). The activation parameters obtained, given in Table 2,
are very close to those of 3 and 4.
2. Cationic Complexes. Halide abstraction by thallium(I)
in complexes 3-6 gives the cationic complexes 7-10, in which
the position previously occupied by the halide must be filled
by the second Py group. The NMR data for 7 and 8 are not in
agreement with a simple intramolecular substitution to give the
bischelated complex (Scheme 3). First of all, the two coordi-
nated Py groups are inequivalent at room temperature in the
1H NMR. Although a different rigid conformation in the two
six-membered metallacycles formed could explain this fact, such
behavior is in disagreement with the fast conformational
inversion observed for 1 and 2. The second point is that there
is a through-space coupling of only one Fortho atom to the H6
atom of only one of the two coordinated Py groups. Selective
19F decouplings at the frequency of this Fortho signal (7, δ )
pyridylethyl)phosphines PNn, which react with the dimers [Pd2-
(µ-Cl)2(R)2(tht)2] (R: C6F5, C6Cl2F3) to generate the neutral
complexes [PdCl(R)(PNn)] (Scheme 1). Their NMR parameters
are given in the Experimental Section (1H) or in Table 1 (19F
and 31P).
In complexes 1-6, the phosphorus is coordinated “cis” to
the fluoroaryl ring and one Py group is coordinated “cis” to the
chloride, as evidenced by the deshielding of H6.5a,14 This
preference of the soft phosphorus to coordinate “cis” to the
Pd-C bond obeys the antisymbiotic effect commonly observed
for Pd15 and has been found for other palladium complexes with
P,N ligands.16 The 31P NMR spectra of all these complexes
show a triplet due to coupling with the ortho-fluorine atoms
from the fluoroaryl group.
For complexes 1 and 2, the 19F NMR spectra show the
equivalence of the two ortho-fluorine atoms from the fluoroaryl
rings, even at -60 °C. Since the rotation of these groups is
expected to have a high ∆Gq value,5b this suggests that the
equivalence is attained by means of conformational inversion
of the six-membered metallacycle formed by the chelating P,N
ligand, which is plane-averaged on the NMR time scale. This
conformational change has a very low energetic barrier, in
contrast to the case of other P,N chelating ligands.16 This
mechanism of equivalence is further supported by the fact that
(14) (a) Brown, D. G.; Byers, P. K.; Canty, A. J. Organometallics 1990,
9, 1231-1235. (b) Byers, P. K.; Canty, A. J.; Honeyman, R. T. J.
Organomet. Chem. 1990, 385, 417-427.
(15) Pearson, R. G. Inorg. Chem. 1973, 12, 712-713.
(16) Kapteijn, G. M.; Spee, M. P. R.; Grove, D. M.; Kooijman, H.; Spek,
A. L.; van Koten, G. Organometallics 1996, 15, 1405-1413.
(17) DNMR6: Quantum Chemistry Program Exchange, Program No. QCPE
633.

P(CH2CH2Py)nPh3-n Ligands for Palladium
Inorganic Chemistry, Vol. 36, No. 23, 1997 5253
Table 1. 19F NMR and 31P NMR Data (δ, ppm; J, Hz)a
no.
compound
T, K
Fo
Fp
Fm
-163.66
31P (4JP-F
)
1
2
3
4
5
6
7
8
9
[Pd(C6Cl2F3)Cl{P(C2H4Py)Ph2}]b
[Pd(C6F5)Cl{P(C2H4Py)Ph2}]b
[Pd(C6Cl2F3)Cl{P(C2H4Py)2Ph}]b
[Pd(C6F5)Cl{P(C2H4Py)2Ph}]b
[Pd(C6Cl2F3)ClP(C2H4Py)3]b
293
293
213
243
293
293
293
293
243
263
-91.35
-120.50
-161.92
-118.6
-159.96
-118.13
-159.99
-117.03
-158.93
-116.93
-159.21
31.72 (10.5)
31.89 (10.6)
28.38 (10.2)
28.80 (9.2)
31.64 (8.3)
32.29 (8.5)
27.93 (7.6)
28.11
-117.75
-90.52, -92.03
-116.72, -118.08
-90.02
-162.08, -162.54
-162.39
[Pd(C6F5)ClP(C2H4Py)3]b
-116.65
c
[Pd2(C6Cl2F3)2{P(C2H4Py)2Ph}2[(BF4)2
[Pd2(C6F5)2{P(C2H4Py)2Ph}2](BF4)2
[Pd2(C6Cl2F3)2{P(C2H4Py)3}2](BF4)2
[Pd2(C6F5)2{P(C2H4Py)3}2](BF4)2
-88.73, -89.52
-111.92, -116.60
-88.86, -88.95
-111.23, -116.18
c
-159.61, -164.45
-158.96, -161.19
d
34.64 (6.0)
34.46 (5.8)
d
10
a Reference CFCl3 or 85% H3PO4. b Solvent CDCl3. c Solvent acetone-d6. d Solvent CD3CN.
Scheme 2
Table 2. Activation Parameters for the Exchange between Py
Groups
q
∆Hq,
∆Sq,
∆G298
,
compound
kJ mol-1
J K-1 mol-1
kJ mol-1
3
4
5
6
47.9(0.9)
47.7(1.0)
52.2(1.0)
47.7(0.9)
45.6(9)
-39.0(3.0)
-39.9(3.4)
-20.6(3.6)
-35.1(3.1)
-0.3(7)
59.5(2)
59.6(2)
58.3(2)
58.1(2)
45.7(1.0)
60.8(2)
[Pd(C6F5)Cl(OPPy3)]a
[Pd(C6F5)2(OPPy3)]a
61.6(2)
2.8(1)
a Data from ref 5b.
Scheme 3
Figure 1. Molecular structure of complex 7 showing the labeling
scheme. All hydrogens have been omitted for clarity. Atoms are shown
as displacement ellipsoids enclosing 30% probability density.
Cl2F3){µ-PPh(C2H4Py)2-P,N,µ-N′}]2 together with disordered
BF4 anions and solvent acetonitrile molecules. A displacement
ellipsoid diagram is shown in Figure 1. The orientation of the
metal centers is mutually “transoid”. Each palladium atom is
in a square planar environment. The metal is coordinated to a
C6Cl2F3 group trans to a pyridyl group of the PPh(C2H4Py)2
ligand. This group forms a six-membered chelate ring with the
phenylphosphine function of the ligand. The remaining arm
of the ligand bridges the second palladium with the pyridyl
group occupying the remaining coordination site at palladium,
trans to the phosphine. A highly puckered, 12-membered ring
is created in which the two palladium coordination planes are
exactly parallel and trans-bridged by P(C2H4Py) moieties. The
Pd‚‚‚Pd nonbonding distance is 5.261(2) Å.
The Pd-C distance (2.018(8) Å) is within the range com-
monly found for other pentahalophenyl Pd(II) or Pt(II) com-
plexes.19 The internal angles at the ipso carbon atoms of the
pentahalophenyl ring are noticeably lower than 120°, as found
in related complexes.20 Other selected distances and angles are
listed in Table 3.
-89.52; 8, δ ) -116.60) simplify the signal of the correspond-
ing H6 (7, δ ) 8.45; 8, δ ) 8.35) from an apparent triplet to a
doublet. This kind of 19F-1H coupling is often observed in
complexes with fluorinated aryls, provided that the F and H
atoms are in close proximity in a rigid structure.18 Although
these data suggest an intramolecular coordination of the second
Py group, the structure of 7 was determined by X-ray diffraction
methods to obtain unambiguous and detailed information about
the geometry of the compounds.
3. Molecular Structure of [Pd(C6Cl2F3){µ-PPh(C2H4Py)2-
P,N,µ-N′}]2(BF4)2‚CH3CN (7). The crystal structure of com-
plex 7 contains centrosymmetric dimeric dications [Pd(C6-
(19) (a) Ara, I.; Berenguer, J. R.; Fornie´s, J.; Lalinde, E.; Toma´s, M.
Organometallics 1996, 15, 1014-1022. (b) Berenguer, J. R.; Fornie´s,
J.; Lalinde, E.; Mart´ınez, F.; Urriolabeitia, E.; Welch, A. J. J. Chem.
Soc., Dalton Trans. 1994, 1291-1299. (c) Falvello, L. R.; Fornie´s,
J.; Navarro, R.; Rueda, A.; Urrialobeitia, E. P. Organometallics 1996,
15, 309-316. (d) Lo´pez, G.; Ruiz, J.; Vicente, C.; Mart´ı, J. M.; Garc´ıa,
G.; Chaloner, P. A.; Hitchcock, P. B.; Harrison, R. M. Organometallics
1992, 11, 4090-4096. (e) Albe´niz, A. C.; Espinet, P.; Jeannin, Y.;
Philoche Levisalles, M.; Mann, B. E. J. Am. Chem. Soc. 1990, 112,
6594-6600.
(18) (a) Mallory, F. B.; Mallory, C. W.; Ricker, W. M. J. Org. Chem. 1985,
50, 457-461. (b) Fornie´s J.; Fortun˜o, C.; Go´mez, M. A.; Menjo´n, B.
Organometallics 1993, 12, 4368-4375. (c) Bell, T. W.; Helliwell,
M.; Perutz, R. N. Organometallics 1992, 11, 1911-1918. (d) Kane,
J. M.; Dalton, C. R.; Staeger, M. A.; Huber, E. W. J. Heterocycl.
Chem. 1995, 32, 183-187. (e) Lyga, J. W.; Henrie, R. N.; Meier, G.
A.; Creekmore, R. W.; Patera, R. M. Magn. Reson. Chem. 1993, 31,
323-328.

5254 Inorganic Chemistry, Vol. 36, No. 23, 1997
Casares et al.
Experimental Section
General Methods and NMR Techniques. Commercial 2-vinylpy-
ridine, phenylphosphine, diphenyl phosphine, diethylphosphonate, and
potassium tert-butoxide were used without further purification. Solvents
were distilled and degassed using standard methods. [Pd2(µ-Cl)2(C6F5)2-
(tht)2] was prepared as reported in the literature,21 and [Pd2(µ-Cl)2(C6-
Cl2F3)2(tht)2] was prepared similarly using 1,3,5-C6Cl3F3 instead of
BrC6F5.22 PH2(CH2CH2Py), P(O)(CH2CH2Py)(OEt)2, and 2-PyCH2CH2-
Cl were prepared by published methods.23-25
1H NMR (300.16 MHz), 19F NMR (282.4 MHz) and 31P NMR (121.4
MHz), spectra were recorded on a Bruker ARX 300 instrument
equipped with a VT-100 variable-temperature probe. Chemical shifts
are reported in ppm from tetramethylsilane (1H), CCl3F (19F), or H3-
PO4 (85%) (31P), with positive shifts downfield, and at ambient probe
temperature unless otherwise stated. 19F EXSY experiments were
carried out with a standard NOESY program operating in the phase-
sensitive mode, with a 5% random variation of the evolution time to
avoid COSY cross-peaks. Combustion CHN analyses were made on
a Perkin-Elmer 2400 CHN microanalyzer. All reactions were carried
out under nitrogen atmosphere using standard Schlenk techniques. The
phosphines prepared have varying sensitivities to oxygen, forming the
corresponding phosphine oxides. The isolated metal complexes are
air stable.
Figure 2. Phase-sensitive NOESY spectrum (Fortho region only, CD3-
CN, 273 K) showing the equilibrium between complexes 7 and 11 and
the exchange between both Fortho of each C6Cl2F3 group.
Table 3. Selected Bond Lengths (Å) and Angles (deg) for
[Pd(C6Cl2F3){P(C2H4Py)2Ph-P,N-µ-N′}]2(BF4)2‚CH3CN (7)
Pd(1)-C(51)
Pd(1)-N(1)
2.018(8)
2.140(7)
Pd(1)-N(3)
Pd(1)-P(1)
2.144(6)
2.237(2)
Synthesis of the Ligands. The ligand P(CH2CH2Py)Ph2 (PN), first
prepared by Uhlig and Maaser,26 was synthesized according to the
general method described for the preparation of polytertiary phosphines
by King et al.27 and was purified according to Wang et al.7a
Vinylpyridine (10 mmol, 1.05 g), KButO (0.6 mmol, 0.067 g), and
PHPh2 (10 mmol, 1.862 g) were dissolved in THF (30 mL) in a three-
necked flask, and the mixture was refluxed for 4 h. Evaporation of
the solvent gave the crude phosphine as a thick yellow oil. The product
was purified by passing it through a silica gel column, using diethyl
ether as eluant, and crystallized from ether. Yield: 1.6 g (55%).
C(51)-Pd(1)-N(1)
C(51)-Pd(1)-N(3)
N(1)-Pd(1)-P(3)
90.0(3)
172.9(3)
90.7(3)
C(51)-Pd(1)-P(1)
N(1)-Pd(1)-P(1)
N(3)-Pd(1)-P(1)
85.9(2)
175.6(2)
93.6(2)
The bridging Py group is nearly perpendicular to the
coordination plane of the metal (dihedral angle 86.3(2)°) whereas
the chelating Py group is more nearly parallel to it (dihedral
angle of 34.3(2)°). In spite of the very different coordination
geometries for the bridging and chelating Py groups and the
different groups trans to them, the Pd-N bond lengths are very
similar. The H6 atom of the bridging pyridyl group is only 2.62-
(7) Å from the nearest fluorine atom, consistent with the
presence of through-space F-H coupling in the NMR spectra
noted above.
The ligand P(CH2CH2Py)2Ph (PN2), previously synthesized in a
different way by Du Bois et al.,28 was prepared by the same method
used for (PN). Vinylpyridine (175 mmol, 18.96 mL), KButO (11 mmol,
1.270 g), and PH2Ph (86 mmol, 9.466 g) were dissolved in THF (200
mL) in a three-necked flask, and the mixture was refluxed for 4 h.
Evaporation of the solvent gave a yellow oil which was dissolved in
diethyl ether, washed with water, and dried over MgSO4. The solvent
was evaporated, and the product was purified by passing it through a
silica gel column, using as eluant n-hexane (only vinylpyridine is
removed) and then diethyl ether. The compound was obtained as a
colorless oil. Yield: 20.57 g (75%).
The dimeric nature of the cationic compounds raises the
question of the stability of the bridge. Although 7 and 8 show
apparently static NMR spectra at room temperature, the
complexes with PN3, 9 and 10, show very broad signals. It
must be noted that it is not possible to exchange the uncoor-
dinated Py with the chelated one unless the bridging Py also
decoordinates, thus allowing a 120° rotation of the phosphine
around the P-Pd bond. The involvement of the bridging Py
group is confirmed by the fact that 7 and 8 also show exchange,
although at a somewhat higher temperature. The bridge splitting
is definitely proved by exchange experiments: A 1:1 mixture
of 7 and 8 gives within minutes a statistical 1:1:2 mixture of 7,
8, and the mixed complex [Pd2(C6F5)(C6Cl2F3)(PN2)2]2+ (11),
which can be identified by 19F NMR spectroscopy. The
exchange between 7 and 11 can be clearly seen in the phase-
sensitive NOESY shown in Figure 2, in which cross peaks are
observed correlating (a) the two inequivalent Fortho atoms on
each C6Cl2F3 ring (exchanging as discussed before) and (b) each
Fortho atom of 7 with the two Fortho atoms of 11. Thus, the
spectrum confirms that there is an intermolecular equilibrium
between complexes 7 and 11, where obviously 8 must be
involved. Similarly, a 1:1 mixture of 9 and 10 gives a statistical
1:1:2 mixture of 9, 10, and the mixed complex [Pd2(C6F5)(C6-
Cl2F3)(PN3)2]2+ (12).
The ligand P(CH2CH2Py)3 (PN3) was prepared similarly. To a
solution of PH2(CH2CH2Py) 4.870 g (35 mmol) in 40 mL of THF were
added 8.10 mL (75.0 mmol) of vinylpyridine and 0.53 g (4.7 mmol)
of KButO. The mixture was refluxed until completion of the reaction
(about 30 h, monitored by 31P{1H} NMR of aliquots of the crude
mixture in acetone-d6). The solvent was evaporated, and the excess
vinylpyridine was removed by heating under vacuum at 80 °C. Yield:
9.137 g (74%). Anal. Calcd: C, 72.19; N, 12.08; H, 6.87. Found:
C, 72.22; N, 12.31; H, 6.92. 31P{1H} NMR (acetone-d6): δ -26.4
(s). 1H NMR (acetone-d6): δ 8.49 (m, 1H), 7.66 (m, 1H), 7.28 (m,
1H), 7.14 (m, 1H), 2.91 (m, 2H), 1.92 (m, 2H).
(21) (a) Albe´niz, A. C.; Espinet, P.; Foces-Foces, C.; Cano, F. H.
Organometallics 1990, 9, 1079-1085. (b) Uso´n, R.; Fornie´s, J.; Nalda,
J. A.; Lozano, M. J.; Espinet, P.; Albe´niz, A. C. Inorg. Chim. Acta
1989, 156, 251-256. (c) Uso´n, R.; Fornie´s, J. J. Organomet. Synth.
1986, 3, 161-185. (d) Uso´n, R.; Fornie´s, J.; Mart´ınez, F.; Toma´s, M.
J. Chem. Soc., Dalton Trans. 1980, 888-894. (e) Uso´n, R.; Fornie´s,
J.; Navarro, R.; Garc´ıa, M. P. Inorg. Chim. Acta 1979, 33, 69-75.
(22) Casado, A.; Espinet, P. Unpublised results.
(23) Spiegel, G. U.; Stelzer, O. Z. Naturforsch. 1987, 42B, 579-588.
(24) Page, P.; Mazieres, M.-R.; Bellan, J.; Sanchez, M.; Chaudret, B.
Phosphorus, Sulfur Silicon Relat. Elem. 1992, 70, 205-210.
(25) Ohki, S.; Noike, Y. J. Pharm. Soc. Jpn. 1952, 72, 490-492.
(26) Uhlig, V. E.; Maaser, M. Z. Anorg. Allg. Chem. 1966, 334, 205-213.
(27) King, R. B.; Kapoor, R. N.; Saran, M. S.; Kapoor, P. N. Inorg. Chem.
1971, 10, 1851-1860.
(20) (a) Jones, P. G. J. Organomet. Chem. 1988, 345, 405-411. (b)
Domenicano, A.; Vaciago, A.; Coulson, C. A. Acta Crystallogr., Sect.
B 1975, 31, 221-234.
(28) DuBois, D. L.; Miedaner, A.; Haltiwanger, R. C. J. Am. Chem. Soc.
1991, 113, 8753-8764.

P(CH2CH2Py)nPh3-n Ligands for Palladium
Inorganic Chemistry, Vol. 36, No. 23, 1997 5255
Synthesis of the Complexes. [PdCl(C6Cl2F3)(PN)] (1). To a
stirred solution of [Pd2(µ-Cl)2(C6Cl2F3)2(tht)2] (106.6 mg, 0.134 mmol)
in CH2Cl2 (20 mL) was added PN (78 mg, 0.268 mmol) in 10 mL of
CH2Cl2. After 30 min, the pale yellow solution was filtered, 15 mL of
ethanol was added, and the solution was concentrated to 10 mL. After
the concentrate was allowed to stand overnight at -20 °C, 1 crystallized
as a white product, which was filtered off and dried in vacuum.
Yield: 129 mg (76%). Anal. Calcd: C, 47.42; N, 2.21; H, 2.86.
Found: C, 46.85; N, 2.00; H, 3.05. 1H NMR (CDCl3): δ 9.25 (d,
1H), 7.76 (td, 1H), 7.30 (m, 12H), 3.71 (m, 2H), 2.60 (m, 2H).
Table 4. Crystal Data and Structure Refinement Details for
[Pd(C6Cl2F3){µ-P(C2H4Py)2PhP,N,µ-N′}]2(BF4)2‚CH3CN (7)
empirical formula
fw
C58H45B2Cl4F14N5P2Pd2
1516.2
crystal size, mm
crystal system
0.4 × 0.37 × 0.60
triclinic
space group
a, Å
b, Å
c, Å
P1h (No. 2)
10.972(2)
11.113(2)
12.898(3)
70.55(1)
88.39(1)
75.13(1)
1430.4(5)
1
1.76
0.960
2.39-25.09
6844
4858 [R(int) ) 0.0973]
0.0775, 0.1857
1.088
R, deg
[Pd(C6F5)Cl(PN)] (2). To a stirred solution of [Pd2(µ-Cl)2-
(C6F5)2(tht)2] (100 mg, 0.126 mmol) in CH2Cl2 (20 mL) was added
PN (74 mg, 0.254 mmol) in 10 mL of CH2Cl2. After 30 min, the
solution was filtered and evaporated to dryness. The resulting oil was
washed twice with 10 mL of n-hexane to remove the remaining tht,
and the product 2 was crystallized from CH2Cl2/ethanol. Yield: 131
mg (87%). Anal. Calcd: C, 50.05; N, 2.33; H, 3.00. Found: C, 50.12;
N, 2.41; H, 2.88. 1H NMR (CDCl3): δ 9.22 (d, 1H), 7.65 (td, 1H),
7.3 (m, 12H), 3.67 (m, 2H), 2.52 (m, 2H).
â, deg
γ, deg
V, Å3
Z
F(calcd), Mg m-3
µ, mm-1
θ range, deg
no. of collcd reflecns
no. of reflecns for calcns
final R1, wR2a
goodness-of-fit, Sa
max peak in final diff map, e Å-3
[Pd(C6Cl2F3)Cl(PN2)] (3). This compound was prepared as de-
scribed for 1, but using PN2 (85.8 mg, 0.268 mmol) instead of PN.
Yield: 142 mg (81%). Anal. Calcd: C, 47.16; N, 4.23; H, 3.20.
Found: C, 47.02; N, 4.11; H, 3.31. 1H NMR (CDCl3 at 213 K): δ
9.28 (d, coord Py, 1H), 8.48 (d, free Py, 1H), 7.83 (m, 1H) 7.63 (m,
1H), 7.28-7.60 (m, 7H), 7.17 (dd, 1H), 6.99 (d, 1H), 3.60 (broad m,
2H), 2.95 (broad m, 1H), 2.45 (broad m, 2H), 2.27 (broad m, 3H).
2.33
a Residuals calculated for reflections with I > 2σ(I); wR2 ) [∑w∆2/
4
∑wFo ]0.5; S ) [∑w∆2/(N - NV)]0.5; R1 ) ∑||Fo| - |Fc||/∑|Fo|; ∆ )
2
Fo - Fc2.
7.65 (m, 2H), 7.55 (d, 1H), 7.31 (m, 2H), 7.17 (m, 2H), 4.99 (broad
m, 1H), 3.50 (broad m, 4H), 3.37 (m, 2H), 2.60 (m, 2H), 2.58 (m,
3H).
[Pd(C6F5)Cl(PN2)] (4). This compound was prepared as described
for 2, but using PN2 (81.4 mg, 0.254 mmol) instead of PN. Yield:
105 mg (66%). Anal. Calcd: C, 47.71; N, 4.45; H, 3.33. Found: C,
47.68; N, 4.35; H, 3.41. 1H NMR (CDCl3 at 213 K): δ 9.29 (d, coord
Py, 1H), 8.45 (free Py, 1H), 7.83 (m, 1H), 7.62 (m, 1H), 7.49 (dd,
2H), 7.36 (m, 5H), 7.17 (dd, 1H), 7.00 (d, 1H), 3.58 (broad m, 2H),
2.97 (broad m, 1H), 2.40 (broad m, 3H), 2.25 (broad m, 2H).
[Pd2(C6F5)2(PN3)2](BF4)2 (10). This compound was prepared as
described for 8, but starting from 6 (110 mg, 0.18 mmol) instead of 4.
Yield: 95 mg (78%). Anal. Calcd: C, 45.71; N, 5.95; H, 3.38.
Found: C, 45.82; N, 6.01; H, 3.49. 1H NMR (243 K, CD3CN): δ
8.53 (d, 1H), 8.38 (dd, 1H), 7.95 (m, 2H), 7.82 (t, 1H), 7.65 (m, 3H),
7.35 (t, 1H), 7.24 (t, 1H), 7.17 (m, 2H), 4.94 (broad m, 1H), 3.60-3.1
(broad m, 5H), 2.65 (m, 2H), 2.48 (m, 1H), 2.07 (m, 3H).
Equilibrium between 7 and 8. Complexes 7 (10.4 mg, 0.0073
mmol) and 8 (9.9 mg, 0.0073 mmol) were dissolved in 0.5 mL of CD3-
CN in an NMR tube. The 19F NMR spectrum at room temperature
showed the signals of the complex [Pd2(C6F5)(C6Cl2F3)(PN2)2](BF4)2
(11). 19F NMR (acetone-d6): δ(C6F3Cl2 group), -88.85 (d, 3JF-P ) 8
Hz, 1F), -89.1 (t, 1F), -117.45 (s, 1F); δ(C6F5 group) -112.02 (m,
1F), -116.71 (m, 1F), -159.50 (t, 1F), -159.85 (m, 1F), -162.32
(m, 1F).
Equilibrium between 9 and 10. Complexes 9 (17.4 mg, 0.0117
mmol) and 10 (16.6 mg, 0.0117 mmol) were dissolved in 0.6 mL of
CD3CN in an NMR tube. The 19F NMR spectrum at 243 K showed
signals (1:1:2 ratio) for complexes 9 and 10 and for [Pd2(C6F5)(C6-
Cl2F3)(PN3)2](BF4)2 (12). 19F NMR (CD3CN) for 12: δ(C6F3Cl2 group)
-88.41 (broad, 1F), -88.53 (broad d, 1F), -117.12 (s, 1F); δ(C6F5
group) -111.40 (m, 1F), -116.49 (m, 1F), -158.7 (m, 1F), -159.18
(m, 1F), -161.21 (m, 1F).
X-ray Structure of [Pd2(C6Cl2F3)2{µ-PPh(C2H4Py)2-P,N,µ-N′}2]-
(BF4)2‚CH3CN (7). Crystal data and other details of the structure
analysis are presented in Table 4. Colorless crystals of 7 were
recrystallized from an acetonitrile/2-propanol/ether solution and showed
a regular blocklike habit. The mother liquors, as well as the crystals,
showed signs of decomposition, yielding metallic palladium. The
crystals showed signs of partial decomposition of the crystal, reflected
in broad diffraction peaks and high-background scattered radiation. After
checking a number of crystals, we selected one with approximate
dimensions of 0.4 × 0.37 × 0.60 mm for study and mounted it on a
glass fiber with vacuum grease.
All diffraction measurements were made at -100 °C with a Siemens
three-circle SMART29 area detector diffractometer using graphite-
monochromated Mo KR radiation. Unit cell dimensions were deter-
mined from reflections taken from three sets of 30 frames (at 0.3° steps
in ω), each at 10 s exposure. A full hemisphere of reciprocal space
(1321 frames in total, 10 s exposure per frame) was scanned by 0.3° ω
[Pd(C6Cl2F3)Cl(PN3)]‚0.5 CH2Cl2 (5). This compound was pre-
pared as described for 1, but using PN3 (93.6 mg, 0.268 mmol) instead
of PN. Yield: 149 mg (81%). Anal. Calcd: C, 45.15; N, 5.74; H,
3.42. Found: C, 45.23; N, 5.80; H, 3.52. 1H NMR (CDCl3 at -60
°C): δ 9.32 (coord Py, 1H), 8.43 (free Py, 2H), 7.78 (m, 1H), 7.62 (m,
2H), 7.2-7.4 (m, 2H), 7.11 (m, 4H), 3.35 (broad m, 2H), 3.22 (broad
m, 2H), 2.68 (broad m, 2H), 2.09 (broad m, 2H), 1.65 (broad m, 4H).
[Pd(C6F5)Cl(PN3)] (6). This compound was prepared as described
for 1, but using PN3 (88.7 mg, 0.254 mmol) instead of PN. Yield:
125 mg (75%). Anal. Calcd: C, 49.28; N, 6.41; H, 3.65. Found: C,
49.14; N, 6.33; H, 3.47. 1H NMR (-213 K, CDCl3): δ 9.40 (dd, coord
Py, 1H), 8.43 (dd, free Py, 2H), 7.87 (t, coord Py, 1H), 7.63 (t, free
Py, 2H), 7.38 (m, coord Py, 2H), 7.15 (m, free Py, 4H), 3.28 (broad
m, free CH2CH2Py, 4H), 2.71 (broad m, coord CH2CH2Py, 2H), 2.12
(broad m, coord CH2CH2Py, 2H), 1.89 (broad m, free CH2CH2Py, 4H).
[Pd2(C6Cl2F3)2(PN2)2](BF4)2 (7). To a stirred solution of 3 (111.2
mg, 0.168 mmol) in acetone (30 mL) was added AgBF4 (33 mg, 0.168
mmol). After 30 min, the AgCl formed was removed by filtration.
Addition of ethanol (15 mL) and evaporation gave a white precipitate,
which was filtered off and dried in vacuum. Yield: 97 mg (81%).
Anal. Calcd: C, 43.76; N, 3.93; H, 2.97. Found: C, 43.63; N, 3.75;
H, 3.07. 1H (acetone-d6): 8.8 (broad d, coord Py, 1H), 8.4 (t, bridging
Py, JF-H ) 4.8 Hz, 1H), 8.19 (td, 1H), 8.08 (td, 1H), 7.83 (ddd, 2H),
7.74 (dd, 2H), 7.52 (m, 3H), 7.38 (m, 2H), 5.41 (broad m, 1H), 3.98
(broad m, 3H), 3.48 (m, 1H), 3.30 (m, 1H), 2.63 (m, 2H).
[Pd2(C6F5)2(PN2)2](BF4)2 (8). This compound was prepared as
described for 7, but starting from 4 (106 mg, 0.168 mmol) instead of
3. Yield: 80 mg (70%). Anal. Calcd: C, 45.88; N, 4.16; H, 2.79.
Found: C, 45.59; N, 4.06; H, 2.58. 1H (acetone-d6): 8.92 (broad d,
coord Py, 1H), 8.35 (t, bridging Py, JF-H ) 4.1 Hz, 1H), 8.21 (td, 1H),
8.11 (td, 1H), 7.80 (ddd, 2H), 7.70 (dd, 2H), 7.49 (m, 3H), 7.35 (m,
2H), 5.40 (broad m, 1H), 3.90 (broad m, 3H), 3.47 (m, 1H), 3.30 (m,
1H), 2.58 (m, 2H).
[Pd2(C6Cl2F3)2(PN3)2](BF4)2 (9). This compound was prepared as
described for 7, but starting from 5 (110 mg, 0.168 mmol) instead of
3. Yield: 73 mg (61%). Anal. Calcd: C, 44.77; N, 5.80; H, 3.31.
Found: C, 44.63; N, 5.74; H, 3.45. 1H NMR (243 K, CD3CN): δ
8.45 (d, 1H), 8.36 (dd, 1H), 7.96 (t, 1H), 7.93 (t, 1H), 7.82 (t, 1H),
(29) SMART Siemens Molecular Analysis Research Tool V4.014, Siemens
Analytical X-ray Instruments, Madison, WI.

5256 Inorganic Chemistry, Vol. 36, No. 23, 1997
Casares et al.
steps at φ ) 0, 88, and 180° with the area detector center held at 2θ
) -27°. A final set of 50 frames collected repeated the first 50 in
order to check for signs of decay over the period of data collection.
The reflections were integrated using the SAINT30 program. No further
crystal decay over the period of data collection was observed. A total
of 6884 diffracted intensities were measured, and 4858 unique
observations remained after averaging of duplicate and equivalent
measurements (Rint ) 0.097) and deletion of the systematic absences;
of these, 3987 had I > 2σ(I). An absorption correction was applied;
transmission coefficients were in the range 0.837-0.584. Lorentz and
polarization corrections were applied.
Refinement of the 407 least-squares variables converged to the
2
residuals given in Table 4. Weights, w, were set equal to 1/[σ2(Fo ) +
2
(aP)2 + bP]-1 where P ) [Max(Fo ,0) + 2Fc2]/3 and a ) 0.1190 and
b ) 7.64 were varied to minimize the variation in S as a function of
|Fo|. Final difference electron density maps showed features in the
range +2.32 to -1.93 e Å-3, the largest being within 1 Å of the
palladium atoms. The poor residual indices and high difference
electronic density features are presumably related to the crystal quality
problems noted above and consequent difficulties with accurate
integration of the intensity data. Complex neutral-atom scattering
factors were taken from ref 32.
The structure was solved by direct and Fourier methods and refined
using full-matrix least-squares calculations on F2 with the SHELXL-
93 program31 and a Silicon Graphics IRIS computer. All non-hydrogen
atoms were assigned anisotropic displacement parameters and refined
without positional constraints. The anion shows signs of disorder, and
the fluorine atoms F(91) and F(92) are disordered over two sites (in
the ratio 0.74(2):0.26(2)); the acetonitrile is disordered about the
inversion center. All hydrogen atoms were constrained to idealized
geometries and assigned isotropic displacement parameters 1.2 times
the Uiso values of their attached carbons for the aromatic hydrogens.
The displacement parameters of the disordered fluorine atoms were
restrained to be nearly isotropic. Hydrogen atoms of the CH3CN were
not located or geometrically imposed due to the disorder of the
molecule.
Acknowledgment. The Direccio´n General de Investigacio´n
Cient´ıfica y Te´cnica (Projects PB96-0363 and SB95-BOZ-
67791015), the Junta de Castilla y Leo´n (Project VA40/96),
and the European Community (Contract CHRX-CT93-0147; DG
12 DSCS) are gratefully acknowledged for financial support
and fellowships for I.P. and K.S.
Supporting Information Available: Listings of observed rate
constants for the Py exchange in complexes 3-6 and, for the crystal
structure of 7, tables of atomic coordinates, bond distances and angles,
anisotropic thermal parameters, and hydrogen atom positions and
isotropic thermal parameters (8 pages). Ordering information is given
on any current masthead page.
IC970745E
(30) SAINT (Siemens Area detector INTegration) program, Siemens
Analytical X-ray Instruments, Madison, WI.
(31) SHELXTL Rev. 5.0, Siemens Analytical X-ray Instruments, Madison,
WI.
(32) International Tables for Crystallography; Kluwer: Dordrecht, The
Netherlands, 1992; Vol. C.