The effect of a fourth binding site on the stabilization of cationic sps pincer palladium complexes: Experimental, DFT, and mass spectrometric studies

Article abstract of DOI:10.1021/om800690t

A potentially tetradentate ligand was synthesized by the addition of α-Li-picoline to the 2,6-bis(diphenylphosphine sulfide)-3,5- diphenylphosphinine (SPS) ligand. The corresponding Pd complex (3) was obtained by the reaction with [(COD)PdCl₂].

Full text of DOI:10.1021/om800690t

2020
Organometallics 2009, 28, 2020–2027
The Effect of a Fourth Binding Site on the Stabilization of Cationic
SPS Pincer Palladium Complexes: Experimental, DFT, and Mass
Spectrometric Studies
Matthias Blug,† Marjolaine Doux,† Xavier Le Goff,† Philippe Maˆıtre,‡ Franc¸ois Ribot,§
Pascal Le Floch,†,* and Nicolas Me´zailles*,†
Laboratoire He´te´roe´le´ments et Coordination, Ecole Polytechnique, CNRS, 91128 Palaiseau, France,
Laboratoire de Chimie Physique, UniVersite´ Paris-Sud 11, CNRS, 91405 Orsay, France, and Chimie de la
Matie`re Condense´e de Paris, UPMC-UniVersite´ Paris 6, CNRS, 75252 Paris, France
ReceiVed July 21, 2008
A potentially tetradentate ligand was synthesized by the addition of R-Li-picoline to the 2,6-
bis(diphenylphosphine sulfide)-3,5-diphenylphosphinine (SPS) ligand. The corresponding Pd complex
(3) was obtained by the reaction with [(COD)PdCl2]. An air-stable cationic Pd(II) complex (4) was obtained
after abstraction of Cl- with silver salt. The role of the additional binding site in the stabilization of the
cationic complex was explored using NMR spectroscopic and tandem ESI-MS studies combined with
DFT calculations. Additionally the picoline moiety was used to tune the electronic properties of the
cationic complex 7 to modify the activity in the Lewis acid-catalyzed allylation of aldehydes.
of anionic S∼P∼S ligands based on phosphinine derivatives, the
as [(S∼P∼SR)PdCl] proved to be very robust and could efficiently
catalyze the Miyaura coupling process, which allows the synthesis
of boronic esters from halogenoarenes and pinacolborane.6
Introduction
phosphorus analogues of pyridines. We found that complexes such
After the seminal report by Shaw in the 1970s, the chemistry of
pincer ligands has evolved to maturity.1 The structures that have
been studied early on, [2,6-(LCH2)2C6H3]- (L∼C∼L), where L is
a two-electron donor and C is an anionic aryl carbon atom, have
uncovered the peculiarities of these tridentate ligands.2 Of these,
N∼C∼N, P∼C∼P, and S∼C∼S have then found numerous
applications.3 In particular, the “P∼C∼P-metal” fragments have
found applications in fundamental processes such as C-H activa-
tion as well as in several catalytic processes.4 For example, highly
efficient Pd catalysts for cross-coupling processes were developed
by the groups of Milstein, Morales-Morales, Jensen, and others.5
For a few years now, we have been involved in the development
In 2003, Szabo and co-workers reported on interesting advances
in the promotion of new allylation processes by using pincer
palladium complexes in the catalyzed conversion of aldehydes into
homoallyl alcohols through reaction with allylstannanes.7 In their
studies, these authors have tested several ligand systems and
showed that Se∼C∼Se tridentate pincer ligands have the optimal
electronic properties for the desired transformation. They proposed
the involvement of η1-allyl species based on the strong coordination
of the pincer ligand, which occupies three of the four coordination
sites of a square-planar Pd(II) complex.8 Interested by these results,
we performed a combined experimental and theoretical study on
this catalytic process, with the in-house designed S∼P∼SR and
S∼C∼S pincer ligands. In terms of reactivity, the two Pd
complexes were as efficient as the Se∼C∼Se-based system.
Notably, we could show that the activity was increased by the
addition of silver salts. The DFT study allowed us to rule out the
involvement of the η1-allyl intermediates because of much higher
energetic demand compared to the Lewis acid-promoted process.
In practice, the two in situ synthesized [(S∼X∼S)Pd]+ (X ) C or
P) systems were found to be excellent Lewis acids capable of
activating the aldehyde toward nucleophilic attack by the allyl-
stannane derivative (Scheme 1).9
* Corresponding author. E-mail: nicolas.mezailles@polytechnique.edu.
Fax: +33 169 33 44 40.
† Ecole Polytechnique, CNRS.
‡ Universite Paris-Sud 11.
§ UPMC-Univ. Paris 6.
(1) Moulton, C. J.; Shaw, B. L. J. Chem. Soc., Dalton Trans. 1976,
1020.
(2) Morales-Morales, D. J. C. M. The Chemistry of Pincer Compounds;
Elsevier: 2007.
(3) (a) Albrecht, M.; van Koten, G. Angew. Chem., Int. Ed. 2001, 40,
3750. (b) Cantat, T.; Jaroschik, F.; Nief, F.; Ricard, L.; Me´zailles, N.; Le
Floch, P. Chem. Commun. 2005, 5178. (c) Cantat, T.; Ricard, L.; Me´zailles,
N.; Le Floch, P. Organometallics 2006, 25, 6030. (d) Friggeri, A.; van
Manen, H. J.; Auletta, T.; Li, X. M.; Zapotoczny, S.; Schonherr, H.; Vancso,
G. J.; Huskens, J.; van Veggel, F.; Reinhoudt, D. N. J. Am. Chem. Soc.
2001, 123, 6388. (e) Dani, P.; Karlen, T.; Gossage, R. A.; Gladiali, S.; van
Koten, C. Angew. Chem., Int. Ed. 2000, 39, 743. (f) Rietveld, M. H. P.;
Grove, D. M.; van Koten, G. New J. Chem. 1997, 21, 751. (g) Steenwinkel,
P.; James, S. L.; Grove, D. M.; Veldman, N.; Spek, A. L.; van Koten, G.
Chem.-Eur. J. 1996, 2, 1440. (h) Gozin, M.; Weisman, A.; Bendavid, Y.;
Milstein, D. Nature 1993, 364, 699.
(4) (a) Gupta, M.; Hagen, C.; Kaska, W. C.; Cramer, R. E.; Jensen,
C. M. J. Am. Chem. Soc. 1997, 119, 840. (b) Salem, H.; Ben-David, Y.;
Shimon, L. J. W.; Milstein, D. Organometallics 2006, 25, 2292. (c) Gomez-
Benitez, V.; Baldovino-Pantaleon, O.; Herrera-Alvarez, C.; Toscano, R. A.;
Morales-Morales, D. Tetrahedron Lett. 2006, 47, 5059.
(5) (a) Ohff, M.; Ohff, A.; vanderBoom, M. E.; Milstein, D. J. Am.
Chem. Soc. 1997, 119, 11687. (b) Morales-Morales, D.; Grause, C.; Kasaoka,
K.; Redon, R.; Cramer, R. E.; Jensen, C. M. Inorg. Chim. Acta 2000, 300,
958. (c) Morales-Morales, D.; Redon, R.; Yung, C.; Jensen, C. M. Chem.
Commun. 2000, 1619.
The purpose of the present study is threefold. First we wished
to isolate cationic Pd derivatives bearing SPS-based tridentate
ligands in order to probe their reactivity in Lewis acid-catalyzed
transformations. Second, we envisioned the introduction of a
potentially fourth binding moiety, which would be able to
stabilize the highly electrophilic cationic Pd species during a
catalytic process. A geometrical requirement for this fourth
moiety is that it should be connected to the ligand backbone in
a manner that prevents the formation of a highly stable square-
planar Pd(II) complex, which would hamper any catalytic
process. Finally, it was desirable to be able to tune the Lewis
10.1021/om800690t CCC: $40.75
2009 American Chemical Society
Publication on Web 03/20/2009

Cationic SPS Pincer Palladium Complexes
Organometallics, Vol. 28, No. 7, 2009 2021
Scheme 1
acidity of the Pd center via the fourth ligand, which was
therefore selected as a pyridine moiety. The results of this study
are presented herein. In the course of these endeavors, density
functional theory (DFT) calculations combined with electrospray
ionization tandem mass spectrometry (ESI-MS/MS) techniques
were used to uncover the geometry of a cationic Pd complex.
Results and Discussion
As mentioned above, the [(S∼P∼SBu)PdCl] complex 1 can
be activated to a postulated [(S∼P∼SBu)Pd]+ cationic species
upon addition of silver salts. When this reaction was performed
stoichiometrically, in a noncoordinating solvent, the disappear-
ance of the starting complex and the formation of species that
rapidly decomposed were observed, proving again the high
Lewis acid character of the cationic complex. On the other hand,
when the reaction was performed in the presence of a coordinat-
ing species, such as a few equivalents of acetonitrile, a single
new complex was obtained (eq 1).
is clearly a better ligand than aldehydes, preventing the catalytic
process from occurring.
It was therefore highly desirable at this point to synthesize
complexes that would be (1) more electrophilic than the chloride
derivative 1, allowing the direct incorporation in the catalytic
cycle; (2) more stable than the “unstabilized” cationic Pd
derivative; (3) yet more reactive than the acetonitrile cationic
derivative 2; (4) finally, if possible, allowing fine-tuning of the
catalytic activity. Point 2 clearly requires the presence of a labile
two-electron donor, and point 3 implies a weaker two-electron
donor than a nitrile ligand. We thus envisioned the incorporation
of an R-picoline moiety on the phosphorus center of the SPS
ligand, in a way to prevent the formation of a stable square-
planar complex.
The synthesis of this ligand has been reported recently,10 and
its neutral Pd complex 3 synthesized readily (eq 2) and isolated
in 74% yield. This complex was characterized by NMR
spectroscopy, elemental analyses, and X-ray crystallography
(Figure 1).
This complex, 2, was isolated in 85% yield and characterized
by NMR spectroscopy and elemental analyses. In particular the
31P NMR spectrum shows an AX2 spin system pattern with a
doublet at δ 49.7 ppm (2JPP ) 69.6 Hz) and triplet at δ 64.6
ppm (2JPP ) 69.6 Hz), contrasting with the AB2 spin system of
2
the starting complex (δ 49.2 and 55.4 ppm with JPP ) 87.0
Hz). The activity of complex 2 was tested in the nucleophilic
allylation of aldehydes. Not surprisingly, this complex appeared
as a poor catalyst because of the high stability of the square-
planar Pd(II) complex. Indeed, as shown in our proposed
mechanism, aldehydes have to coordinate the electrophilic Pd
center prior to attack by the nucleophile. In this case, acetonitrile
In the 31P NMR spectrum, an AB2 system (δ 48.4 and 51.9
2
1
ppm with JPP ) 89.0 Hz) is seen as for 1. In the H NMR
spectrum the H4 proton is found at rather high field, δ 5.46
ppm in CDCl3, compared to the starting anion, and at a similar
chemical shift than in complex 2, and resonates as a triplet
because of the coupling with the two phosphorus atoms of the
Ph2PdS groups. As expected for a Pd(II) complex, its geometry
(6) Doux, M.; Me´zailles, N.; Melaimi, M.; Ricard, L.; Le Floch, P. Chem.
Commun. 2002, 1566.
(7) Solin, N.; Kjellgren, J.; Szabo, K. J. Angew. Chem., Int. Ed. 2003,
42, 3656.
(8) (a) Szabo, K. J. Chem.-Eur. J. 2000, 6, 4413. (b) Wallner, O. A.;
Szabo, K. J. J. Org. Chem. 2003, 68, 2934. (c) Szabo, K. J. Chem.-Eur.
J. 2004, 10, 5269. (d) Nakamura, H.; Bao, M.; Yamamoto, Y. Angew.
Chem., Int. Ed. 2001, 40, 3208.
(9) Piechaczyk, O.; Cantat, T.; Me´zailles, N.; Le Floch, P. J. Org. Chem.
2007, 72, 4228.
(10) Doux, M.; Thuery, P.; Blug, M.; Ricard, L.; Le Floch, P.; Arliguie,
T.; Me´zailles, N. Organometallics 2007, 26, 5643.

2022 Organometallics, Vol. 28, No. 7, 2009
Blug et al.
is square planar with the pyridine moiety not in interaction with
the metal center.
The chloride abstraction was then attempted on this
complex with 1 equiv of AgBF4 in methylene chloride
(Scheme 1). Instantaneous precipitation of the expected AgCl
was observed. The 31P{1H} NMR spectrum showed the
complete transformation of 3 into a new complex, 4,
characterized by a complex spin system between δ 45.4 and
49.8 ppm. These chemical shifts, similar to the ones observed
for complex 2, are in agreement with the expected formation
1
of a cationic species. In the H NMR spectrum in CD2Cl2
this complex also shows a triplet for the H4 proton at δ 6.08
ppm (4JHP(B) ) 4.7 Hz). This complex, unlike the “SPSBu”
analogue, is stable in solution for extended periods of time,
which clearly points to the coordination of the pyridine
fragment to the Pd center. Despite many efforts, we have
been unable to crystallize this species. Two possibilities have
thus to be envisaged for the geometry of this complex: either
monomeric or dimeric. In the first case, the geometry at the
Pd center would be highly distorted from square planar,
because it is obvious from the structure of 3 that the pyridine
moiety cannot reach over to be located trans to the phos-
phorus center. In the second case, the pyridine fragment of
one ligand coordinates a second metal center to form a
square-planar arrangement at the Pd center. A combined DFT
and ESI tandem MS study was then performed to shed light
on the precise nature of this complex (Vide supra). Further
experimental proof of the cationic character of complex 4
was obtained by adding a few equivalents of pyridine
(Scheme 1). The new complex is 5, characterized in the 31P
NMR spectrum in CD2Cl2 by an AB2 system at δ 45.7 and
47.6 ppm (2JPP ) 79.5 Hz). The formulation of 5 was
confirmed by elemental analyses as well as X-ray diffraction
analysis (Figure 2). The complete formation of this complex
is quite interesting in the sense that it shows that the pyridine
fragment coordinated on a Pd center in complex 4 is readily
displaced by another external pyridine ligand. This points to
a weak stabilization, yet efficient in terms of complex stability
in time, of the cationic Pd center.
Figure 2. ORTEP plot (50% thermal ellipsoids) of the X-ray crystal
structure of cation of compound 5. Ph groups and BF4 were
-
omitted for clarity. Selected bond lengths [Å] and angles [deg]:
Pd(1)-P(1) 2.2040(6), Pd(1)-S(1) 2.3126(6), Pd(1)-S(2) 2.3359(6),
S(1)-P(2) 2.0313(8), S(2)-P(3) 2.036(1), P(1)-C(1) 1.776(2),
P(1)-C(5) 1.771(2), P(1)-C(6) 1.841(2), P(1)-Pd(1)-S(1) 87.49(2),
P(1)-Pd(1)-S(2) 86.83(2), S(1)-Pd(1)-S(2), 173.78(2), P(1)-
Pd(1)-N(2) 175.43(5).
In parallel, in order to probe the possibility of tuning the
catalytic activity, quaternarization of the lone pair of pyridine
was attempted. Indeed, the overall increase of the charge of the
complex should in turn increase the Lewis acidity of the Pd
center. In practice, addition of a few equivalents of HCl to a
solution of complex 3 led to the instantaneous formation of
complex 6, which was isolated quantitatively. The electronic
influence of the protonation on the whole ligand backbone was
1
clearly observed in the H NMR spectrum. Indeed, the CH2
group of the picoline experiences a downfield shift by 0.46 ppm
(from δ 3.83 ppm in 3 to δ 4.29 ppm in 6). This effect is also
observed on the shift of H4 on the phosphinine ring (from δ
5.46 ppm in 3 to δ 5.72 ppm in 6). The ORTEP plot of complex
6 is presented in Figure 3. As for 3, the formation of a stable
cationic Pd center was then attempted.
Two equivalents of AgBF4 were added to a solution of 6 in
dichloromethane, leading to the precipitation of AgCl. In the
31P NMR spectrum, the second-order spectrum of 6 disappeared
rapidly in favor of a very broad singlet centered at δ 47.4 ppm.
The fact that this species, 7, is unique was evidenced by addition
of 10 equiv of acetonitrile. Indeed, it resulted in the clean
formation of a single complex, 8, characterized again by an AB2
spin system at δ 44.7 and 47.7 ppm (2JPP ) 80.4 Hz). This
complex was isolated in 75% yield and fully characterized by
NMR techniques. Interestingly, exhaustive drying of this
complex under vacuum resulted in the partial loss of acetonitrile
to re-form 7. This process is reversible and shows that this ligand
is more weakly bound to the Pd center than in 2, which could
be of interest for catalytic processes.
Catalytic Tests. Having in hand several complexes, prelimi-
nary tests were performed to confirm our hypotheses, namely,
the influence of pyridine as a fourth ligand, the use of isolated
cationic species, and finally the increase of the overall charge
by protonation of pyridine. The allylation of aldehydes was
chosen, as complex 1 is known to perform well in this process
and could therefore be used as benchmark. The reaction between
Figure 1. ORTEP plot (50% thermal ellipsoids) of the X-ray crystal
structure of compound 3. Ph groups were omitted for clarity.
Selected bond lengths [Å] and angles [deg]: Pd(1)-P(1) 2.1783(8),
Pd(1)-S(1) 2.3207(8), Pd(1)-S(2) 2.332(1), Pd(1)-Cl(1) 2.3894(8),
S(1)-P(2) 2.033(1), S(2)-P(3) 2.043(1), P(1)-C(1) 1.761(3),
P(1)-C(5) 1.760(3), P(1)-C(6) 1.839(3), P(1)-Pd(1)-S(1) 87.93(3),
P(1)-Pd(1)-S(2) 87.17(3), S(1)-Pd(1)-S(2), 172.76(3), P(1)-
Pd(1)-Cl(1) 170.25(3).

Cationic SPS Pincer Palladium Complexes
Organometallics, Vol. 28, No. 7, 2009 2023
in situ chloride abstraction from 6 was done, and the resulting
complex 7 directly engaged in the catalytic process (entry 6).
As in the case of 1, it resulted in doubling the activity (30.2%
vs 15.3%), but as mentioned above (activities of 1 and 6) the
overall dicationic complex does not perform better than “1 +
AgBF4” (30.2% vs 37.8%). Finally, it does not appear that
protonation of the pyridine moiety is a positive factor on the
activity of the complex. Overall, isolated cationic complex 4
provides the best compromise between catalytic performance
(50% lower), kinetic stability, and ease of handling (no need
for activation). It is obvious from these results that the pyridine
moiety indeed brings stability to a cationic Pd center, yet does
not suppress catalytic behavior.
DFT Study. The question of the precise nature of complex
4 remained: monomer or dimer? A DFT study has been
performed to investigate the possible conformations of the
cationic compound [(S∼P∼SPic)Pd]+. All calculations were
carried out using the Gaussian 03 set of programs11 with the
B3PW91 functional,12 the 6-31G* basis set for all nonmetallic
atoms (C, H, P, N, S), and the Hay-Wadt13 basis set for
palladium with an additional f-polarization function.14 A model
compound, replacing all the phenyl groups by protons, was used
for this study in order to preserve calculation time (Note: this
model has proven to be appropriate in theoretical studies
reported before15). As we are dealing here with either mono-
meric-monocationic or dimeric-dicationic species, the effect of
solvation had to be taken into account in the DFT studies. This
was achieved by using the polarized continuum model (PCM),16
considering CH2Cl2 as the solvent. However, entropic factors
are not incorporated in this PCM energy, and free energies were
therefore also calculated. In turn, these relative free energies,
∆G, are related to the gas phase systems, and the extrapolation
to the condensed phase is delicate and subject to intense
debate.17,18 In particular, Maseras and co-workers proposed the
use of a free energy ∆GPCM taking into account both the entropic
and the solvation effects, which is given by the relation ∆GPCM
) ∆G + (∆EPCM - ∆E).17
Figure 3. ORTEP plot (50% thermal ellipsoids) of the X-ray crystal
structure of compound 6. Ph groups were omitted for clarity.
Selected bond lengths [Å] and angles [deg]: Pd(1)-P(1) 2.184(1),
Pd(1)-S(1) 2.323(1), Pd(1)-S(2) 2.319(1), Pd(1)-Cl(1) 2.380(8),
S(1)-P(2) 2.023(1), S(2)-P(3) 2.041(1), P(1)-C(1) 1.777(3),
P(1)-C(5) 1.762(3), P(1)-C(6) 1.853(3), P(1)-Pd(1)-S(1) 88.39(3),
P(1)-Pd(1)-S(2) 86.55(3), S(1)-Pd(1)-S(2), 174.37(3), P(1)-
Pd(1)-Cl(1) 173.92(4).
Table 1. Catalytic Results
entry
catalyst
yield (%)
1
2
3
4
5
6
1
18.2
37.8
10.4
18.9
15.3
30.2
1 + 1 AgBF4
3
4
6
6 + 1 AgBF4
Table 2. Relative Energies of Structures I-IVa
relative energies
(kcal · mol-1
)
I
II
III
IV
4.9
-1.7
11.7
5.1
∆E
0
0
0
0
1.7
-2.4
3.1
-4.5
-10.4
5.2
∆EPCM
∆G
∆GPCM
-1.1
-0.7
Two monomeric species were envisaged: an S∼P∼S-bound
monomeric complex, I, and an S∼P∼N-bound monomeric
complex, II. Two dimeric structures were also envisaged: one
in which the pyridine fragment of one ligand is coordinated to
a second Pd center, complex III, and another in which sulfur
atoms are bridging, complex IV. This latter coordination mode
has not yet been observed in phosphinine-based SPS pincer
complexes. Pictures of the optimized structures are shown in
a With ∆GPCM ) ∆G + (∆EPCM - ∆E).
p-bromobenzaldehyde and allyltributyltin was conducted in
CHCl3 using 1% of catalyst, at 70 °C for 4 h. The results are
gathered in Table 1.
Entries 1, 3, and 5 allow the direct comparison of “PdCl”
fragments, whereas entries 2, 4, and 6 are related to the
corresponding cationic complexes. As mentioned previously,
the stoichiometric addition of a silver salt to a solution of
complex 1 led to an increase in the yield of the product, resulting
from the fast generation of the catalytically active species
(entries 1 and 2). Entry 3 allows the direct assessment of the
role of the pyridine ligand. Complex 3 is the least active
precatalyst (entry 3). Reasonably postulating a kinetically similar
formation of the active species as for 1, it is clear that the
pyridine ligand has a significantly stabilizing influence, thereby
reducing the Lewis acidity of the Pd center. Cationic complex
4 (monomer or dimer, Vide supra), obtained after chloride
abstraction from 3 followed by isolation, performs almost twice
as well as 3 (entry 4). This clearly shows that this complex is
not only stable once isolated but also more efficient than the
“PdCl” complex. Complex 6, the pyridine protonated version
of complex 3, is also more efficient, which would result from
the expected increase of the Lewis acidity of the Pd center (entry
5). However, its reactivity is similar to that of complex 1, which
would point to a negligible influence of the overall charge. This
complex also performs almost as well as complex 4. Eventually,
(11) Frisch, M. J.; et. al. Gaussian 03 (ReVision C.02); Gaussian Inc:
Wallingford, CT, 2004.
(12) (a) Becke, A. D. J. Chem. Phys. 1993, 98, 5648. (b) Perdew, J. P.;
Wang, Y. Phys. ReV. B 1992, 45, 13244.
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A.; Jonas, V.; Kohler, K. F.; Stegmann, R.; Veldkamp, A.; Frenking, G.
Chem. Phys. Lett. 1993, 208, 111.
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2006, 25, 1101. (c) Doux, M.; Le Floch, P.; Jean, Y. J Mol. Struct.
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Y. Organometallics 2005, 24, 1608.
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2024 Organometallics, Vol. 28, No. 7, 2009
Blug et al.
Figure 4. Calculated structures I-IV for the conformation of cationic compound 4. Selected bond lengths [Å] and angles [deg] for I:
Pd(31)-P(17): 2.201, Pd(31)-S(15): 2.393, Pd(31)-S(16): 2.402, Pd(31)-N(23): 3.013, P(17)-Pd(31)-S(15): 86.1, P(17)-Pd(31)-N(23):
76.7, N(23)-Pd(31)-S(15): 97.7 S(15)-P(31)-S(16): 176.0. For II: Pd(31)-P(17): 2.278, Pd(31)-S(15): 2.383, Pd(31)-S(16): 6.176,
Pd(31)-N(23): 2.086, P(17)-Pd(31)-S(15): 96.3, P(17)-Pd(31)-N(23): 83.4, N(23)-Pd(31)-S(15): 167.6. For III: Pd(31)-P(17): 2.249,
Pd(31)-S(15): 2.418, Pd(31)-S(16): 2.379, Pd(31)-N(32): 2.182, P(17)-Pd(31)-S(15): 83.6, P(17)-Pd(31)-N(32): 173.4,
N(32)-Pd(31)-S(15): 90.7. For IV: Pd(31)-P(17): 2.239, Pd(31)-S(15): 2.393, Pd(31)-S(16): 2.414, Pd(31)-N(23): 4.943, Pd(31)-Pd(62):
3.777, Pd(31)-S(60): 2.558, P(17)-Pd(31)-S(15): 84.6, P(17)-Pd(31)-S(60): 151.6, S(15)-P(31)-S(16): 170.7.
Figure 4. Note that in complex I there is a weak interaction
between the pyridine moiety and the Pd center, as shown by
the long distance between these atoms: 3.013 Å. This distance
is definitely longer than a true bond, yet the particular orientation
of the pyridine pointing toward the Pd center is unambiguous.
Structure I is used as a reference. Not considering the weak
interaction of the pyridine ligand, the overall geometry around
the Pd center is T shaped, with the two S-Pd-P angles of 86.1°.
The geometry of complex II was optimized in distorted T shape,
with the pending phosphino sulfide ligand pointing in the
opposite direction. In this complex, the peculiar arrangement
of the ligand leads to angles significantly different from the
expected 90°: P(17)-Pd(31)-S(15) ) 96.3° and P(17)-Pd(31)-
N(23) ) 83.4°.
Interestingly, this complex is lower in energy (∆EPCM) than
I, by 2.4 kcal/mol, but the free energy of this complex is slightly
higher (3.1 kcal/mol), showing that the phosphine sulfide is as
good a ligand as pyridine for this Pd(II) cationic center. The
potential energy, E, of compound III was found to be lower
than that of the monomers, whereas compound IV was found
at higher energy relative to the monomeric compounds. It should
be noted that both dimeric structures were stabilized by ca. 6
kcal/mol, when the contribution of the solvation is added to
the potential energy (∆EPCM), whereas the monomeric structures
were only slightly stabilized (0-4.1 kcal/mol). However,
dimerization is obviously entropically unfavorable, and the
Gibbs free energies, ∆G, for the dimers III and IV are found
higher than that of the monomers. Of these dimers, the sulfur-
bridged complex IV is less stable than complex III by 8.0 kcal/
mol. In complex IV, the coordination deviates significantly from
the expected square planar, as shown by the P(17)-Pd(31)-S(60)
angle of 151.6°. This probably results from geometrical
constraints. The geometry of the two “(S∼P∼S)Pd” fragments
in III is very similar to the one found in the monomeric complex
I. In the dimer, the expected more favored square-planar
geometry of Pd(II) is achieved by the coordination of a pyridine
moiety of the opposite ligand. Finally, when ∆GPCM is calcu-
lated, compounds I, II, and III all lie within 1.1 kcal/mol and
should therefore coexist in solution.
not provide a definitive answer. We thus had to rely on an
experimental technique to quantify the amount of the different
complexes in solution.
TANDEM ESI-MS Study. Electrospray ionization tandem
mass spectrometry (tandem ESI-MS) was used to further
characterize the Pd complexes present in solution. Indeed, soft
ionization tandem mass spectrometry appears to be a sensitive
and rapid technique for the determination of molecular weight
of organometallic compounds.19 Electrospray ionization allows
for a soft transfer to the gas phase of pre-existing molecules or
ions in solution. Short-lived reactive intermediates can also be
mass analyzed, thus providing a method of choice for mecha-
nistic studies.20 The present tandem ESI-MS study was per-
formed using a 7 T Fourier transform ion cyclotron resonance
(FT-ICR) mass spectrometer. The aim of this investigation was
to determine the chemical nature of the Pd complex 4,
postulating that the ionization technique would not result in the
splitting of the dimer if present in solution. The mass spectrum
of the CH2Cl2 solution of the synthesized complexes is given
in Figure 5, and a detailed view of the dominant signal at m/z
879.06 is provided in Figure 5b. The observed isotopic pattern
of the dominant peak at m/z 879.06 nicely matches the
theoretical isotopic patterns calculated for the dicationic dimer
complex, modeled by III above (Figure 5b). A numerical fit of
the experimental spectrum, however, shows that a small fraction
(∼2.5%) of the monocationic monomeric complex (isotopic
patterns given in Figure 5d) is also present under our experi-
mental conditions. When used in conjunction with chemical-
induced dissociation (CID), ESI-MS/MS can provide additional
insights. After mass selection of the ions at m/z 879.06 with an
isolation width of 10 Da, CID was performed for 100 ms. The
resulting mass spectrum suggests that the dicationic dimeric
species [(S∼P∼SPic)Pd]2 fragments into two monocationic
2+
monomers [(S∼P∼SPic)Pd]+. At the ion/argon collision energies
used (20 V), loss of C6H6N from the monomeric species was
also observed. In the end, the results of this electrospray
ionization tandem mass spectrometry study very nicely comple-
ment the results of the DFT study. Indeed, the DFT calculations
did not allow settling conclusively between monomers or dimer
complex in solution. On the grounds of the ESI-MS study and
the respective percentages of the species at room temperature,
we can conclude that the dimer (type III) is more stable than
the monomers by ca. 2 kcal/mol.
In the end, taking only ∆EPCM into account, the dimeric-
dicationic species III is predicted to be more stable and would
be the only one to be observed in solution. On the other hand,
∆G predicts the monomeric-monocationic species I to be more
stable and would be the only one to be observed in solution.
Finally, the difference in energy ∆GPCM predicted the coexist-
ence of the three complexes I, II, and III in solution. This case
is therefore a complicated one, for which DFT calculations did
(19) Chaplin, A. B.; Dyson, P. J. Organometallics 2007, 26, 2447.
(20) Chen, P. Angew. Chem., Int. Ed. 2003, 42, 2832.

Cationic SPS Pincer Palladium Complexes
Organometallics, Vol. 28, No. 7, 2009 2025
the structure of the cationic complex 4. The increase of the
calculated hydrodynamic radius (rH(4)/rH(3) ) 1.78) is in
excellent agreement with the existence of a dimeric structure
in solution. This final result clearly proves that the dimeric
complex is present in solution and not formed during the
ionization process.
Conclusions
In this study, an anionic potentially tetradentate ligand, based
on an in-house-developed S∼P∼S ligand, was coordinated to
a Pd(II) center. Several cationic complexes have been isolated
and fully characterized. In particular, complex 4, unlike other
related cationic “(S∼P∼SR)Pd” species, is kinetically stable and
isolable. Catalytic tests in the known allylation of aldehydes
were performed. The stabilization of the Pd center in complex
4 results in lower catalytic activity than in situ generated cationic
complexes from complex 1 or 6, yet this complex is easy to
handle and does not need to be activated. It is obvious from
these results that the pyridine moiety does indeed bring stability
to a cationic Pd center, without suppressing catalytic behavior,
as expected. The precise nature of complex 4 was not accessible
by usual NMR spectroscopy, which prompted us to carry out a
combined DFT and tandem ESI-MS spectroscopic study. The
DFT study, taking into account the solvation effects on a model
complex, predicts a dimeric species, III, to be more stable than
a monomeric species by ca. 8 kcal/mol, which would imply
the sole presence of the dimer in solution. Free energy
calculations on the other hand favor the monomeric form I by
ca. 5 kcal/mol. Finally, the use of a recently introduced free
energy GPCM calculation, adding solvation effects, predicted the
three complexes to lie within 1.1 kcal/mol (monomer II most
stable, and, therefore, that they would coexist in solution. A
precise quantification of the isomers in solution was obtained
by the FT-ICR technique: about 97.5% to 2.5% (dimer III to
monomers I and/or II). This corresponds to a difference in
energy of ca. 2 kcal/mol in favor of the dimer. Our study points
to an overestimation of the entropic factors by DFT calculations
and confirms the importance of carrying out PCM calculations
for charged species. In the case presented here, the recently
proposed free energy ∆GPCM calculation also overestimated the
entropic factors and did not lead to the accurate prediction of
the experimental system. Finally, our study clearly shows the
interest of using combined experimental, in this case mass
spectrometric techniques, and theoretical studies when the
precise nature of complexes cannot be solved by usual NMR
techniques or X-ray crystallography.
Figure 5. Mass spectra of a sample solution of Pd complexes in
CH2Cl2 at 10-5 mol · L-1. Full mass spectrum recorded without mass
selection (a) and detailed view of the isotopic distribution of the
dominant peak at m/z 879.06 (b). Theoretical isotopic patterns
calculated for the dicationic dimer (c) and monocationic monomer
complexes (d).
Table 3. Diffusion Constants and Hydrodynamic Radii of
Complexes 3 and 4
diffusion constant,
compound
10-10 m2 s-1
rH, Å
TMS
complex 3
complex 4
25.1
9.5
5.4
2.95
7.76
13.80
1H-DOSY-NMR Study. Nevertheless, it has been reported
in specific cases that the dimerization of monocationic transition-
metal complexes bearing halide ions, leading to halide-bridged
dimer complexes, could occur in a mass spectrometer21 using
the electrospray ionization technique. To finally prove the
dimeric structure of complex 4 in solution, a DOSY-NMR22
study using the bipolar pulse longitudinal eddy current delay
(BPPLED) pulse sequence23 was performed. This technique
allows measuring diffusion constants of molecules in solution.
In recent studies it was shown that the hydrodynamic radii of
these compounds can be estimated from the diffusion constants
via the Stokes-Einstein equation.24
D ) (kBT)/(CπηrH)
(1a)
Experimental Section
The diffusion constants of tetramethylsilane (TMS) and
complexes 3 and 4, as well as the corresponding hydrodynamic
radii, are listed in Table 3. In all cases the diffusion constant of
TMS was determined to be DTMS ) 2.51 × 10-9 m2 s-1. This
shows that the viscosity of the solutions is not influenced by
complexes 3 and 4. As the size of the observed samples is
relatively close to the size of the solvent molecules, the frictional
constant C was set to 4.24 The difference of the diffusion
constants of complexes 3 and 4 reveals an important change in
General Methods. All reactions were routinely performed under
an inert atmosphere of argon or nitrogen using Schlenk and
glovebox techniques and dry deoxygenated solvents. Dry THF,
hexanes, and diethyl ether were obtained by distillation from Na/
benzophenone and dry CH2Cl2 from P2O5. CDCl3 was dried from
P2O5 and stored on 4 Å Linde molecular sieves. CD2Cl2 was used
as purchased and stored in the glovebox. Nuclear magnetic
resonance spectra were recorded on a Bruker Avance 300 spec-
1
trometer operating at 300.0 MHz for H, 75.5 MHz for 13C, and
121.5 MHz for 31P. Solvent peaks are used as an internal reference
relative to Me4Si for 1H and 13C chemical shifts (ppm); 31P chemical
shifts are relative to a 85% H3PO4 external reference. Coupling
constants are given in hertz. The following abbreviations are used:
s, singlet; d, doublet; t, triplet; q, quadruplet; p, pentuplet; m,
multiplet; v, virtual; b, broad.
(21) (a) Hofmann, P.; Volland, M. A. O.; Hansen, S. M.; Eisentrager,
F.; Gross, J. H.; Stengel, K. J. Organomet. Chem. 2000, 606, 88. (b) Zanini,
M. L.; Meneghetti, M. R.; Ebeling, G.; Livotto, P. R.; Rominger, F.; Dupont,
J. Inorg. Chim. Acta 2003, 350, 527.
(22) (a) Pregosin, P. S.; Kumar, P. G. A.; Fernandez, I. Chem. ReV.
2005, 105, 2977. (b) Johnson, C. S. Prog. Nucl. Magn. Reson. Spectrosc.
1999, 34, 203.

2026 Organometallics, Vol. 28, No. 7, 2009
Blug et al.
Table 4. Experimental Details for X-ray Crystal Structures of 3, 5, and 6
3
5
6
cryst size (mm)
empirical formula
mol wt
space group
a (Å)
0.22 × 0.20 × 0.12
C50H40Cl10NP3PdS2
1272.76
P21/c
9.311(1)
40.894(3)
14.666(1)
90.00
103.870(1)
90.00
5421.5(8)
4
1.559
0.20 × 0.20 × 0.16
C52H42N2P3PdS2,BF4
1283.85
0.23 × 0.16 × 0.05
C47H38ClNP3PdS2, 2(CH2Cl2),Cl
1205.89
j
j
P1
P1
12.787(1)
13.547(1)
17.359(1)
111.820(1)
100.400(1)
93.630(1)
2717.6(3)
2
1.569
0.855
30.03
1296
9.618(1)
b (Å)
c (Å)
13.260(1)
22.200(1)
82.918(1)
89.160(1)
68.868(1)
2619.4(4)
2
1.529
0.970
27.48
1220
R (deg)
ꢀ (deg)
γ (deg)
V (Å3)
Z
calcd density (g cm-3
)
abs coeff (cm-1
2F max (deg)
F(000)
)
1.037
27.48
2560
index ranges
-12 to 12; -53 to 48;
-18 to 19
19 701/11 969
9526
-17 to 17; -15 to 19;
-24 to 24
23 605/15 786
12 722
-12 to 11; -17 to 17;
-28 to 28
21 984/11 290
8108
no. of collected/indep reflns
no. of reflns used
Rint
0.0216
0.0183
0.0280
abs corr
multiscan; 0.8040
min, 0.8857 max
627
multiscan; 0.8475
min, 0.8753 max
586
multiscan; 0.8077
min, 0.9531 max
562
no. of params refined
no. of reflns/params
15
21
14
final R1a/wR2 (I > 2σ(I))b
0.0479/0.1457
1.050
1.391(0.095)/
-1.030(0.095)
0.0466/0.1527
1.115
1.607(0.093)/
-1.121(0.093)
0.0479/0.1442
1.062
1.201(0.089)/
-0.918(0.089)
goodness of fit on F2
diff peak/hole (e Å-3
)
b
a R1 ) ∑|Fo| - |Fc|/∑|Fo|. wR2 ) (∑w|Fo| - |Fc|2/∑w|Fo|2)1/2
.
DOSY experiments were performed using the bipolar pulse
longitudinal eddy current delay (BPPLED) pulse sequence.23 In
all cases the lock signal was adjusted to CD2Cl2. The duration of
the magnetic field pulse gradients and the diffusion times were
optimized for each sample in order to obtain an attenuation of 95%
of the signal with the maximum gradient strength. In each PFG
NMR experiment a series of 32 spectra on 8 K data points were
acquired. The pulse gradients were incremented from 1 to 95% of
the maximum gradient strength in a linear ramp. The temperature
control unit and the tube spinning were turned off to prevent
convection. After Fourier transformation and baseline correction,
the diffusion dimension was processed with the Bruker TopSpin
software.
A hybrid 7 T Fourier transform ion cyclotron resonance (FTICR)
mass spectrometer was used for the mass spectroscopic study. High-
resolution mass spectra, recorded in the 200-2000 m/z range in
positive mode, were obtained by Fourier transformation of a time-
domain transient signal averaged over 16 scans. Sample solutions
of the Pd complexes (10-5 M in CH2Cl2) were infused via syringe
pump at a flow rate of 140 µL/h. Standard ESI conditions were
used, with a capillary voltage of 4 kV and a heater temperature of
200 °C. Our FT-ICR instrument (Bruker Apex IV Qh) features a
quadrupole mass filter followed by a hexapole cell pressurized at
∼10-3 mbar with Ar for collision-induced dissociation (CID)
experiments. CID experiments were performed at a collision energy
of 20 V after selection of precursor ions (dimer of Pd complexes,
with a small fraction of monomer) with an isolation width of 10
Da.
[SPS(CH2Py)PdCl], 3. A freshly prepared solution of R-Li-picoline
(500 µL, 0.31 mmol) was added to a stirred solution of SPS (200
mg, 0.29 mmol) in THF (5 mL) at -78 °C. The solution turned
immediately deep red and was allowed to return to room temper-
ature during 15 min. [(COD)PdCl2] (83.6 mg, 0.29 mmol) was
added as a solid, and the resulting brick-red solution was stirred
for 2 h at room temperature. The solvent was evaporated, and the
resulting solid was rinsed with hexanes (3 × 10 mL) and diethyl
ether (2 × 10 mL). The residue was dissolved in CH2Cl2 and filtered
through a pad of Celite. After evaporation of the solvent the title
compound was obtained as a brick-red powder. Single crystals
suitable for an X-ray crystal structure analysis were grown from a
concentrated solution of CHCl3. Yield: 200 mg (0.215 mmol, 74%).
Anal. Calcd for [C47H37ClNP3PdS2] (914.7): C 61.71, H 4.08.
1
2
Found: C 61.86, H 3.89. H NMR (CDCl3): δ 3.83 (d, JHP(A)
)
12.5 Hz, 2H, CH2), 5.46 (t, 4JHP(B) ) 4.3 Hz, 1H, H4), 6.74-7.52
(m, 31H, CH of Ph and CH of Py), 7.71-7.83 (m, 2H, CH of Py),
8.53 (d, JHH ) 3.9 Hz, 1H, CH of Py). 13C NMR (CDCl3): δ 47.7
(d, 1JCP ) 22.7 Hz, CH2), 72.3 (ddd, 1JCP ) 92.9, 1JCP ) 51.5, 3JCP
) 3.1 Hz, C2,6), 119.3 (pseudo q, 3JCP ) 11.3 Hz, C4H), 121.9 (d,
JCP ) 3.0 Hz, CH of Py), 126.8 (d, JCP ) 3.0 Hz, H of Py),
1
3
127.8-129.0 (m, CH of Ph), 131.5 (dd, JCP ) 83.8, JCP ) 9.1
Hz of PPh2), 132.3-132.5 (m, CH of Ph), 132.9 (m, C of PPh2),
132.9-133.2 (m, CH of Ph), 136.6 (d, JCP ) 2.3, CH of Py), 140.0
2
4
(dt, JCP ) 7.6 Hz, JCP ) 3.0 Hz, C3,5), 149.6 (d, JCP ) 2.3 Hz,
2
CH of Py), 153.4 (d, JCP ) 7.6 Hz, C of Py), 159.6 (s, C of Ph).
31P NMR (CDCl3): δ 48.4 (AB2, m, JP(A)P(B) ) 89.0 Hz, PBPh2),
2
2
51.9 (AB2, m, JP(A)P(B) ) 89.0 Hz, PA).
2,6-Bis(diphenylphosphine sulfide)-3,5-diphenylphosphinine
(SPS)25 and R-Li-picoline26 were prepared according to reported
procedures.
[SPS(CH2Py)Pd]2(BF4), 4. To a solution of complex 3 (82 mg,
0.09 mmol) in CH2Cl2 (2 mL) was added solid AgBF4 (20 mg,
0.10 mmol). The resulting orange-red solution was stirred for 2 h
at room temperature. AgCl was separated by centrifugation. After
evaporation of the solvent the title compound was obtained as a
red powder. Yield: 75 mg (0.08 mmol, 86%). Anal. Calcd for
[C47H37BF4NP3PdS2] (966.1): C 58.43, H 3.86. Found: C 58.24,
(23) (a) Wu, D. H.; Chen, A. D.; Johnson, C. S. J. Magn. Reson. A
1995, 115, 260. (b) Gibbs, S. J.; Johnson, C. S. J. Magn. Reson. 1991, 93,
395.
(24) Macchioni, A.; Ciancaleoni, G.; Zuccaccia, C.; Zuccaccia, D. Chem.
Soc. ReV. 2008, 37, 479.
(25) (a) Doux, M.; Bouet, C.; Me´zailles, N.; Ricard, L.; Le Floch, P.
Organometallics 2002, 21, 2785. (b) Avarvari, N.; LeFloch, P.; Ricard, L.;
Mathey, F. Organometallics 1997, 16, 4089.
H 3.81. 1H NMR (CD2Cl2): δ 4.08 (dd, 2JHH ) 13.6 Hz, 2JHP(A)
)
(26) Fraser, R. R.; Mansour, T. S.; Savard, S. Can. J. Chem.-ReV. Can.
Chim. 1985, 63, 3505.

Cationic SPS Pincer Palladium Complexes
Organometallics, Vol. 28, No. 7, 2009 2027
2
2
8.9 Hz, 1H, CH2), 4.39 (pseudo t, JHP(A) ) JHH ) 13.6 Hz, 1H,
Ph and PPh2), 8.15 (m, 2H, CH of Py) 8.79 (t, 3JHH ) 7.5 Hz, 1H,
CH of Py), 8.96 (br, 1H, CH of Py). 13C NMR(CD2Cl2): δ 1.39
(hep, MeCN), 42.9 (d, 1JPC ) 17.9 Hz, CH2), 70.8 (dd, 1JPC ) 57.1
4
2
CH2), 6.08 (t, JHP(B) ) 4.7 Hz, 1H, H4), 6.24 (dd, JHP(A) ) 14.0
Hz, 2JHH ) 7.3 Hz, 2H, CH of Ph) 6.77-7.79 (m, 30H, CH of Ph
and CH of Py), 7.99 (td, JHH ) 7.8 Hz, JHH ) 1.3 Hz, 1H, CH of
Py), 8.43 (d, JHH ) 5.7 Hz, 1H, CH of Py). 13C NMR (CD2Cl2): δ
44.3 (d, JCP ) 20.0 Hz, CH2), 65.6 (m, C2 or 6), 72.1 (m, C2 or
6), 119.9 (pseudo q, JCP ) 10.6 Hz, C4H), 123.3 (s, CH of Py),
1
Hz, JPC ) 93.0 Hz, C2,C6), 118.0 (br, MeCN), 120.7 (pseudo-q,
∑J ) 11.7 Hz), 126.2 (s, CH of Py), 128.1 (CH of Ph), 128.6 (CH
of Ph), 128.9 (CH of Ph), 129.1 (CH of Ph), 129.2 (CH of Ph),
129.3 (CH of Ph), 130.2 (d, 1JCP ) 4.1 Hz, C of PPh2), 130.3 (CH
of Py), 132.4 (CH of Ph), 132.5 (CH of Ph), 132.6 (CH of Ph),
133.2 (CH of Ph), 133.4 (CH of Ph), 137.8 (dt, C3,C5), 142.4 (s,
CH of Py), 147.2 (d, C of Py), 147.5 (s, CH of Py), 161.2 (s, C of
Ph). 31P NMR (CDCl3): 44.7 (m, AB2, JP(A)P(B) ) 80.4 Hz), 47.7
(m, AB2, JP(A)P(B) ) 80.4 Hz).
Palladium-Catalyzed Allylation of Aldehydes. Representative
procedure for the allylation of p-bromobenzaldehyde with allyl-
tributyltin in the presence of complex 1: A dried Schlenk was
charged with p-bromobenzaldehyde (92.5 mg, 0.5 mmol), complex
1 (4.4 mg, 0.0050 mmol, 1.0 mol %), and THF (0.5 mL) under
nitrogen. Allyltributyltin (186 µL 0.6 mmol) was then added via a
syringe. The resulting solution was stirred at the desired temperature
for 24 h. Thereafter the reaction mixture was evaporated, diluted
into water, and extracted with ether. The organic layer was
separated, washed with brine, dried (Na2SO4), and concentrated.
The crude product was then purified by flash column chromatog-
raphy (hexanes/EtOAc) to give the homoallylic alcohol as a
colorless oil. The NMR data obtained for the coupling products
are in agreement with the corresponding literature.23
X-ray Crystallographic Study. Data were collected at 150.0(1)
K on a Nonius Kappa CCD diffractometer using a Mo KR (λ )
0.71070 Å) X-ray source and a graphite monochromator. All data
were measured using phi and omega scans. Experimental details
are described in Table 4. The crystal structures were solved using
SIR 9727 and Shelxl-97.28 ORTEP drawings were made using
ORTEP III for Windows.29 CCDC 695195-695197 contain the
supplementary crystallographic data for this paper. These data can
be obtained free of charge at www.ccdc.cam.ac.uk/conts/retriev-
ing.html or from the Cambridge Crystallographic Data Centre, 12
Union Road, Cambridge CB2 1EZ, UK; fax: (int.) +44-1223/336-
033; e-mail: deposit@ccdc.cam.ac.uk.
1
3
127.0-132.8 (m, CH of Py, CH and C of Ph), 136.7 (m, ∑J )
12.8 Hz, C3 or 5), 137.3 (m, ∑J ) 13.6 Hz, C3 or 5), 138.6 (s, CH
2
of Py), 151.0 (d, JCP ) 6.0 Hz, C of Py), 153.0 (s, CH of Py),
159.7 (s, C of Ph), 160.0 (s, C of Ph). 31P NMR (CD2Cl2): δ
45.4-49.8 (ABC, m, PACH2, PBPh2, PCPh2).
[SPS(CH2Py)Pd(Pyr)]BF4, 5. Pyridine (10 µL, 0.12 mmol) was
added to a solution of complex 4 (98 mg, 0.10 mmol) in CH2Cl2
(2 mL). After evaporation of the solvent the title compound was
obtained as a red powder. Yield: 94.6 mg (0.98 mmol, 98%). Anal.
Calcd for [C52H42BF4N2P3PdS2] (1045.18): C 59.76, H 4.05.
1
2
Found: C 59.54, H 4.09. H NMR (CDCl3): δ 3.94 (d, JHP(A)
)
11.5 Hz, 2H, CH2), 5.58 (t, 4JHP(B) ) 4.4 Hz, 1H, H4), 6.82-8.74
(m, 29H, CH of Py and CH of Ph). 13C NMR(CDCl3): δ 48.5 (s,
CH2), 71.1 (s, C2, C6), 119.6 (s, C4H), 122.7 (s, CH of R-picoline),
124.2 (s, CH of Py), 126.1 (s, CH of R-picoline), 128.1-129.3 (s,
5 × CH of Ph), 130.1 (s, C of PPh2), 131.2 (s, C of PPh2),
131.9-133.4 (s, 4 × CH of Ph), 136.5 (s, CH of Py), 138.7 (s, CH
of R-picoline), 139.0 (s, C3, C5), 150.2 (s, CH of Py), 150.6 (s,
CH of R-picoline), 151.1 (s, C of R-picoline), 160.9 (s, C of Ph).
31P NMR (CDCl3): δ 45.7 (AB2, m, JP(B)P(A) ) 79.5 Hz, PBPh2),
47.6 (AB2, m, 2J(PB-PA) ) 79.5, PA).
2
[SPS(CH2PyH)PdCl]Cl, 6. A 2 M solution of HCl in diethyl ether
(120 µL, 240 mmol) was added to a solution of 3 (200 mg, 0.22
mmol) in CH2Cl2 (5 mL). The solution turned immediately from
deep red to light orange. The title compound was obtained by
evaporation of the solvents as an orange powder. Single crystals
suitable for X-ray crystal structure analysis were grown by the
diffusion of hexanes into a concentrated solution of the product in
CH2Cl2. Yield: 200 mg (0.21 mmol, 95%). Anal. Calcd for
[C47H38Cl2NP3PdS2] (951.19): C 59.35, H 4.03. Found: C 59.30,
1
2
H 4.07. H NMR (CD2Cl2): δ 4.29 (d J(P-H) ) 12.7 Hz, 2H,
CH2), 5.72 (t, JPH) 4.6 Hz), 1H, H4), 6.70-7.1 (m, 10H, CH of
4
Acknowledgment. This work was supported by the CNRS
and the Ecole Polytechnique. The authors would like to thank
IDRIS (project no. 091616) for the allowance of computer
time.
Ph), 7.20-7.65 (m, 20H, CH of PPh2) 7.69, (br, 1H, CH of Py),
8.31 (br, 1H, CH of Py) 8.60 (br, 1H, CH of Py) 8.68 (br, 1H, CH
of Py). 13C NMR (CD2Cl2): δ 42.2 (CH2), 72.3 (C2,C6) 119.9 (s,
C4), 124.5 (CH of Py), 127.1 (CH of Ph), 127.6 (CH of Ph), 128.2
(CH of Ph and PPh2), 130.2 (CH of Py), 131.1 (CH of PPh2), 131.9
(CH of PPh2), 138.7 (C3,C5), 144.1 (CH of Py), 148.5 (C of Py),
Supporting Information Available: CIF files for 3, 5, and 6,
complete ref 11, and computed Cartesian coordinates, SCF energies,
thermochemistry, PCM enrgies, and three lower frequencies of the
theoretical structures. This material is available free of charge via
the Internet at http://pubs.acs.org.
160.0 (C of Ph). 31P NMR (CD2Cl2): δ 48.2 (m, AB2, JP(A)P(B)
91.0 Hz), 51.9 (m, AB2, JP(A)P(B) ) 91.0 Hz).
)
[SPS(CH2PyH)Pd(MeCN)](BF4)2, 8. AgBF4 (8.2 mg, 0.04 mmol)
was added as a solid to a solution of 6 (20 mg, 0.02 mmol) in
CH2Cl2 (2 mL). The solution turned immediately deep red. AgCl
was eliminated by centrifugation. Acetonitrile (10 µL, 0.2 mmol)
was added via a microsyringe. Evaporation of the solvents led to
the partial re-formation of the desolvated product. The NMR
spectrum of 7 was fully restored after the addition of 1 equiv of
OM800690T
(27) Altomare, A.; Burla, M. C.; Camalli, M.; Cascarano, G.; Giaco-
vazzo, C.; Guagliardi, A.; Moliterni, A. G. G.; Polidori, G.; Spagna, R.
SIR97, an integrated package of computer programs for the solution and
refinement of crystal structures using single crystal data.
(28) Sheldrick, G. M. SHELXL-97; Universita¨t Go¨ttingen: Go¨ttingen,
Germany, 1997.
1
MeCN-d6 (∼1 µL). Yield: 16.6 mg (0.015 mmol, 75%). H NMR
2
(CD2Cl2): δ 2.03 (br, 3H, MeCN), 4.20 (d, JPH ) 12.3 Hz, 2H,
CH2), 5.93 (t, 4JPH ) 4.7 Hz, 1H, H-4), 6.80-7.70 (m, 30H, CH of
(29) Farrugia, L. J. ORTEP-3; University of Glasgow.