Oxidative addition of Sn-C bonds on palladium(0): Identification of palladium-stannyl species and a facile synthetic route to diphosphinostannylene- palladium complexes

Article abstract of DOI:10.1021/om1007067

Methyl-, phenyl-, and n-butyltin trichloride RSnCl₃ (R = Me, Ph, ⁿBu) react selectivily with palladium(0)-phosphine precursors through the unprecedented oxidative addition of the Sn-C bond. With [Pd(2-PyPPh₂)₃] (2-PyPPh₂ = 2-pyridyldiphenylphoshine), the reaction cleanly leads to stable cationic dichlorostannylene palladium complexes of the general formula trans-[PdR(SnCl₂(2-PyPPh₂)₂)][X] (X = Cl, R = Me ([5]Cl), R = Ph ([6]Cl), R = ⁿBu ([11]Cl); X = RSnCl₄, R = Me ([5][MeSnCl₄]), R = Ph ([6][PhSnCl₄]), R = ⁿBu ([11][ⁿBuSnCl₄])). The SnCl ₂(2-PyPPh₂)₂ fragment, formed by intramolecular coordination of the pyridyl groups to the dichlorostannylene moiety, can be considered as a self-assembled pincer-type ligand with a remarkable ability to suppress β-H elimination in its Pd-alkyl derivatives: [11][ ⁿBuSnCl₄], containing a Pd-ⁿBu moiety, was found to be stable up to 70 °C. Oxidative addition of SnCl₄ on [Pd(2-PyPPh₂)₃] resulted in trans-[PdCl(SnCl ₂(2-PyPPh₂)₂)]Cl ([7]Cl) and trans-[PdCl(SnCl₃(2-PyPPh₂)₂)] (8). The molecular structure of 8 was determined by single-crystal X-ray crystallography, indicating that the Sn atom of the trichlorostannyl function has an octahedral coordination geometry. In contrast, oxidative addition of the Sn-C bond of RSnCl₃ on [Pd(PPh₃)₄] resulted in palladium trichlorostannyl complexes that were not stable toward cis-trans isomerization, (partial) elimination of SnCl₂ (R = Me, Ph), or β-H elimination (R = ⁿBu). The resulting mixtures of palladium alkyl and palladium hydride species were analyzed by multinuclear NMR, resulting in the identification of novel cis-[PdMe(SnCl₃)(PPh₃) ₂] (cis-4), trans-[PdMe(SnCl₃)(PPh₃) ₂] (trans-4), and cis-[PdH(SnCl₃)(PPh₃) ₂] (cis-10) along with previously observed trans-[PdPh(Cl)(PPh ₃)₂] (1), trans-[PdMe(Cl)(PPh₃)₂] (3), trans-[PdH(SnCl₃)(PPh₃)₂] (trans-10), and trans-[PdH(Cl)(PPh₃)₂] (9).

Full text of DOI:10.1021/om1007067

5904 Organometallics 2010, 29, 5904–5911
DOI: 10.1021/om1007067
Oxidative Addition of Sn-C Bonds on Palladium(0): Identification of
Palladium-Stannyl Species and a Facile Synthetic Route to
Diphosphinostannylene-Palladium Complexes
Yves Cabon,† Irena Reboule,† Martin Lutz,§ Robertus J. M. Klein Gebbink,† and
Berth-Jan Deelman*,†,‡
†Organic Chemistry & Catalysis, Utrecht University, Faculty of Science, Debye Institute for Nanomaterial
Science, Padualaan 8, 3584 CH Utrecht, The Netherlands, §Crystal and Structural Chemistry, Utrecht
University, Faculty of Science, Bijvoet Center for Biomolecular Research, Padualaan 8, 3584 CH Utrecht,
The Netherlands, and ‡ARKEMA Vlissingen B.V., P.O. Box 70, 4380 AB Vlissingen, The Netherlands
Received July 19, 2010
n
Methyl-, phenyl-, and n-butyltin trichloride RSnCl3 (R = Me, Ph, Bu) react selectivily with
palladium(0)-phosphine precursors through the unprecedented oxidative addition of the Sn-C
bond. With [Pd(2-PyPPh2)3] (2-PyPPh2 = 2-pyridyldiphenylphoshine), the reaction cleanly leads to
stable cationic dichlorostannylene palladium complexes of the general formula trans-[PdR(SnCl2(2-
PyPPh2)2)][X] (X = Cl, R = Me ([5]Cl), R = Ph ([6]Cl), R = nBu ([11]Cl); X = RSnCl4, R = Me
([5][MeSnCl4]), R = Ph ([6][PhSnCl4]), R = nBu ([11][nBuSnCl4])). The SnCl2(2-PyPPh2)2 fragment,
formed by intramolecular coordination of the pyridyl groups to the dichlorostannylene moiety, can
be considered as a self-assembled pincer-type ligand with a remarkable ability to suppress β-H
elimination in its Pd-alkyl derivatives: [11][nBuSnCl4], containing a Pd-nBu moiety, was found to be
stable up to 70 °C. Oxidative addition of SnCl4 on [Pd(2-PyPPh2)3] resulted in trans-[PdCl(SnCl2(2-
PyPPh2)2)]Cl ([7]Cl) and trans-[PdCl(SnCl3(2-PyPPh2)2)] (8). The molecular structure of 8 was
determined by single-crystal X-ray crystallography, indicating that the Sn atom of the trichloro-
stannyl function has an octahedral coordination geometry. In contrast, oxidative addition of the
Sn-C bond of RSnCl3 on [Pd(PPh3)4] resulted in palladium trichlorostannyl complexes that were not
stable toward cis-trans isomerization, (partial) elimination of SnCl2 (R = Me, Ph), or β-H elimina-
n
tion (R = Bu). The resulting mixtures of palladium alkyl and palladium hydride species were
analyzed by multinuclear NMR, resulting in the identification of novel cis-[PdMe(SnCl3)(PPh3)2]
(cis-4), trans-[PdMe(SnCl3)(PPh3)2] (trans-4), and cis-[PdH(SnCl3)(PPh3)2] (cis-10) along with previously
observed trans-[PdPh(Cl)(PPh3)2] (1), trans-[PdMe(Cl)(PPh3)2] (3), trans-[PdH(SnCl3)(PPh3)2] (trans-10),
and trans-[PdH(Cl)(PPh3)2] (9).
Introduction
exclusively through oxidative addition of the Sn-Cl bond,
resulting in bisphosphine(monoorganodichlorostannyl)-
platinum chloride complexes [PtCl(Sn(R)Cl2)(phosphine)2].1a
It appears that this reactivity, well-described for platinum(0),
has never been extended to palladium(0) precursors despite
the interest in organotin(IV) derivatives in some important
palladium-catalyzed transformations.2
The reactivity of organotin chloride reagents on platinum(0)-
phosphine precursors has been the subject of many studies in
the last decades.1 In the case of monoorganotin trichloride
RSnCl3 (R = Me, Ph), the reaction was found to occur
We recently reported that the presence of 2-pyridyldi-
phenylphosphine ligands (2-PyPPh2) affects the coordination of
tin-containing ligands in the vicinity of a group 10 metal (eq 1).3
It was found that the reaction of SnCl2 with [M(X)(Cl)(2-
PyPPh2)2] precursors (X = Cl, Me) does not result in neutral
trichlorostannyl complexes but in cationic complexes [M(X)-
(SnCl2(2-PyPPh2)2)]þ, in which the dichlorostannylene moiety
*Corresponding author. Tel: þ31-113617225. Fax: þ31-113612984.
E-mail: berth-jan.deelman@arkema.com.
(1) (a) Butler, G.; Eaborn, C.; Pidcock, A. J. Organomet. Chem. 1979,
181, 47. (b) Al-Allaf, T. A. K. Asian J. Chem. 1999, 11, 348, and references
therein. (c) Al-Allaf, T. A. K. J. Organomet. Chem. 1999, 590, 25
(phosphines are introduced after oxidative addition on [Pt(COD)2)]).
(2) Well-known examples are hydrostannylation and Stille-type
cross-coupling. In the latter, the reaction of an activated alkynyltrial-
kyltin with a palladium(0)-iminophosphine precursor has been demon-
strated to occur through oxidative addition of the Sn-alkynyl bond,
which was claimed to be the first case of a Sn-C bond undergoing
oxidative addition on palladium. Theoretical work has also been
published on this system. (a) Shirakawa, E.; Yoshida, H.; Hiyama, T.
Tetrahedron Lett. 1997, 38, 5177. (b) Shirakawa, E.; Hiyama, T. J.
Organomet. Chem. 1999, 576, 169. (c) Matsubara, T. Organometallics
2003, 22, 4286. (d) Matsubara, T. Organometallics 2003, 22, 4297.
(3) (a) Cabon, Y.; Kleijn, H.; Siegler, M. A.; Spek, A. L.;
Klein Gebbink, R. J. M.; Deelman, B.-J. Dalton Trans. 2010, 39, 2423.
(b) These results were recently communicated at The 17th International
Symposium on Homogeneous Catalysis (ISHC-17), July 2-9, 2010, Poznan,
Poland.
r
pubs.acs.org/Organometallics
Published on Web 10/26/2010
2010 American Chemical Society

Article
Organometallics, Vol. 29, No. 22, 2010 5905
is stabilized by intramolecular coordination of the pyridyl
groups to the tin center and exerting a strong trans-influence.
Table 1. 31P and 1H NMR Data (T = -50 °C, THF-d8) of the
Products Resulting from the Reaction of MeSnCl3 with
[Pd(PPh3)4]
31P NMR
1H NMR (Me group)
2JP-P 2JP-Sn
3JH-P
(Hz)
3JH-Sn
(Hz)
compound
δ
(Hz)
(Hz)
δ
PPh3
2
3
cis-4
-5.4
þ24.4
þ31.2
þ37.2
þ26.7
þ27.9
-0.16
þ0.29
11.5
a
36
36
271
42.6
48.0
a
a
trans-4
96
þ1.00
Because the 2-PyPPh2 ligand appears to stabilize otherwise
inaccessible species, we decided to study the reactivity of [Pd-
(2-PyPPh2)3] toward RSnCl3 (R = Ph, Me, and nBu) and to
compare it to the reactivity of the more common [Pd(PPh3)4]
precursor.3b
a Coupling constant not detected.
for the known compounds PPh3, 2, and 3 was done by com-
parison with literature data.6 The remaining signals were
attributed to the new products cis-4 and trans-4. This attri-
bution was consistent with the presence of a 2JP-P coupling
constant for the cis compound and tin satellites in both the
Results
Reaction of RSnCl3 (R = Me, Ph) with [Pd(PPh3)4] and
[Pd(2-PyPPh2)3]. The equimolar reaction of [Pd(PPh3)4] with
PhSnCl3 in THF-d8 in an NMR tube at room temperature
(eq 2) led within 1 min to the formation of free PPh3 (2 equiv),
trans-[PdPh(Cl)(PPh3)2] (1, 1 equiv), and SnCl2 (detected by
119Sn NMR, 1 equiv). The NMR data were assigned to 1 by
comparison with literature values.4 High-resolution mass
spectroscopy analysis of the reaction mixture diluted with MeCN
showed the expected [PdPh(PPh3)2]þ and [PdPh(MeCN)-
(PPh3)2]þ cations along with a weak signal for [PdPh(PPh3)-
(PPh3O)]þ that was most probably due to oxidation during
sample preparation.
1
31P and H NMR spectra for both compounds. Moreover,
mass spectroscopy of the reaction mixture in the presence of
acetonitrile exhibited two major signals at m/z=645.1108
and 686.1337, corresponding to the fragments [PdMe(PPh3)2]þ
and [PdMe(PPh3)2(MeCN)]þ. This observation is consistent
with the assignment to complexes 4, as the SnCl3- ligand has
a well-established labile character7 and can easily dissociate
from the complexes during the ionization process. No attempts
were made to separate and isolate the products.
The equimolar reaction of [Pd(2-PyPPh2)3] with MeSnCl3
in THF-d8 in an NMR tube at room temperature cleanly led
within 1 min to the formation of free 2-PyPPh2 (1 equiv) and
the ionic dichlorostannylene complex trans-[PdMe(SnCl2(2-
PyPPh2)2)]Cl ([5]Cl, 1 equiv, eq 4), which was indentified on
the basis of the stoichiometry of the reaction and by compar-
ison of its 1H and 31P NMR data with the previously described
analogue [5][BF4].3a When the reaction was run with 2 equiv
of MeSnCl3, [5][MeSnCl4] was formed, as indicated by the
detection of the [MeSnCl4]- anion by 1Hand119Sn NMR (eq 4).8
[5][MeSnCl4] was isolated in good yield on a preparative
scale (67%) and characterized by multinuclear NMR (1H,
13C, 31P, and 119Sn) and high-resolution mass spectroscopy.
The reaction of [Pd(2-PyPPh2)3] with 2 equiv of PhSnCl3 in
THF-d8 in an NMR tube at room temperature also cleanly
led within 1 min to the formation of free 2-PyPPh2 (1 equiv)
and trans-[PdPh(SnCl2(2-PyPPh2)2)][PhSnCl4] ([6][PhSnCl4],
1 equiv, eq 4). On a preparative scale, complex [6][PhSnCl4]
was isolated in 72% yield and characterized by multinuclear
NMR (1H, 13C, 31P, and 119Sn) and high-resolution mass
spectroscopy. The structure of [6][PhSnCl4] was attributed to
be analogous to [5][MeSnCl4] and [5][BF4] on the basis of
similar analytical observations (downfield shifted 31P NMR
In a similar reaction where PhSnCl3 was replaced by MeSnCl3
(eq 3), the resulting product mixture after 1 min consisted of
the known compounds PPh3 (2 equiv), cis-[PdCl2(PPh3)2] (2,
10%),5 and trans-[PdMe(Cl)(PPh3)2] (3, 15%) along with the
new compounds trans- and cis-[PdMe(SnCl3)(PPh3)2] (trans-
4 and cis-4, 45% and 30%, respectively) and SnCl2 (25%,
according to the stoichoimetry). This ratio evolved after 2 h
at room temperature to PPh3 (2 equiv), 2 (10%), 3 (25%),
trans-4 (65%), and SnCl2 (35%). An experiment at -50 °C
afforded a similar product mixture within a minute after
addition of MeSnCl3 with a slightly higher cis-4/trans-4 ratio
(eq 3). The NMR spectra obtained gave no indication of any
intermediates other than 4.
(5) The small quantities of cis-[PdCl2(PPh3)2] detected as a minor
signal at δ 24.4 in the 31P NMR spectrum and m/z = 665.0547
([PdCl(PPh3)2]þ) in the HRMS spectrum for the experiments using
[Pd(PPh3)4] in combination with MeSnCl3 or nBuSnCl3 are most likely
due to some protonolysis of the generated Pd-R bond (R = Me, H) by
small quantities of HCl that are generated from hydrolysis of the starting
alkyltin trichloride reagent by moisture.
(6) Knight, L. K.; Freixa, Z.; van Leeuwen, P. W. N. M.; Reek,
J. N. H. Organometallics 2006, 25, 954.
All compounds were identified on the basis of their NMR
data at -50 °C (Table 1). The assignment of the resonances
(7) Fernandez, D.; Garcia-Seijo, M. I.; Kegl, T.; Petocz, G.; Kollar,
L.; Garcia-Fernandez, M. E. Inorg. Chem. 2002, 41, 4435.
(8) Organotin trichlorides can easily act as chloride anion acceptors
to form organotin tetrachloride anions. Dakternieks, D.; Zhu, H.
Organometallics 1992, 11, 3820.
(4) Herrmann, W. A.; Brossmer, C.; Priermeier, T.; Ofele, K. J.
Organomet. Chem. 1994, 481, 97.

5906 Organometallics, Vol. 29, No. 22, 2010
Cabon et al.
Table 2. Comparison of 31P NMR and High-Resolution MS Data for the Products [PdR(SnCl2(2-PyPPh2)2)][RSnCl4]
(R = Me, Ph, and nBu)
[5][MeSnCl4]
(R = Me)
[6][PhSnCl4]
(R = Ph)
[11][nBuSnCl4]
analytical method
31P NMR (δ)
ESI-HRMS (m/z, (calcd
(R = nBu)
63.6
836.9351
(836.9391)
64.3
898.9539
(898.9547)
62.5
878.9868
(878.9860)
for [PdR(SnCl2(2-PyPPh2)2)]þ))
signal and detection of only the [PdR(SnCl2(2-PyPPh2)2)]þ
cation in mass spectroscopy, Table 2).
To verify the nature of the products obtained from the
previous experiments, the chloride precursors trans-[PdR-
(Cl)(PPh2Ar)2] (Ar = Ph, R = Me (3), Ph (1); Ar = 2-Py,
R = Ph)4,6 were reacted with SnCl2.1a For the case Ar = Ph,
NMR analysis of the equimolar reaction of SnCl2 with 1 in
THF-d8 indicated that it does not react to form a trichloro-
stannyl species [PdPh(SnCl3)(PPh3)2] (eq 5 left). However,
the equimolar reaction of SnCl2 with 3 exhibited the forma-
tion of the same mixture of 3, cis-4, and trans-4 complexes as
the one found in the reaction of [Pd(PPh3)4] with MeSnCl3
(eq 5 right, cf. eq 3), except for the presence of free PPh3 and
the impurity of 2.5
Figure 1. Displacement ellipsoid plot (50% probability level) of
complex 8 in the crystal. Hydrogen atoms are omitted for clarity.
Selected bond lengths (A) and angles (deg): Pd1-Cl2 2.3987(14),
Pd1-P1 2.2815(14), Pd1-P2 2.2966(14), Pd1-Sn1 2.5201(6),
Sn1-Cl1 2.4819(17), Sn1-Cl3 2.5175(16), Sn1-Cl4 2.3903(16),
Sn1-N1 2.368(4), Sn1-N2 2.378(4), Cl2-Pd1-P1 90.37(5),
P1-Pd1-Sn1 88.51(4), Sn1-Pd1-P2 88.14(4), P2-Pd1-Cl2
92.91(5), Cl1-Sn1-Pd1 96.70(4), Pd1-Sn1-Cl3 88.82(4),
Cl3-Sn1-Cl4 84.53(6), Cl4-Sn1-Cl1 89.95(6), Cl1-Sn1-Cl3
174.43(6), N1-Sn1-N2 166.05(14).
˚
(eq 7) showed the quatitative formation of the previously
described cationic dichlorostannylene complex trans-[PdCl-
(SnCl2(2-PyPPh2)2)]Cl ([7]Cl),3a the crystals obtained from
the reaction mixture correspond to trans-[PdCl(SnCl3(2-
PyPPh2)2)] (8) according to a single-crystal X-ray diffraction
analysis. The molecular structure of 8 (Figure 1) exhibits a
square-planar palladium(II) complex (sum of the angles
around Pd1 is 359.93(9)°) bearing a SnCl3- ligand. However,
the trichlorostannyl ligand does not adopt the usual tetrahedral
geometry but is octahedral instead with intramolecular co-
ordination of both pyridyl groups of the phosphine ligands
tothe Sn center. Thisoctahedral geometry isslightly distorted,
as the Pd1, Cl1, Cl3, and Cl4 atoms form a plane (sum of the
angles around Sn1 is 360.00(10)°), but the N1-Sn1-N2
angle is only 166.05(14)°.
For the case Ar = 2-Py, we already reported that the equi-
molar reaction of SnCl2 with trans-[PdMe(Cl)(2-PyPPh2)2]
led to the formation of the ionic complex [5]Cl (eq 6, R =
Me).3a In a similar fashion, we determined that the equi-
molar reaction of SnCl2 with trans-[PdPh(Cl)(2-PyPPh2)2] in
THF-d8 instantaneously led to the ionic complex [6]Cl (eq 6),
confirming that [6]Cl is also the product of the reaction of
[Pd(2-PyPPh2)3] with PhSnCl3.
Although NMR analysis of a solution resulting from the
equimolar reaction of [Pd(2-PyPPh2)3] with SnCl4 in THF-d8
Reaction of nBuSnCl3 with [Pd(PPh3)4] and [Pd(2-PyPPh2)3].
The equimolar reaction of [Pd(PPh3)4] withnBuSnCl3 in THF-d8

Article
Organometallics, Vol. 29, No. 22, 2010 5907
Table 3. 31P and 1H NMR Data (T = -50 °C, THF-d8) of the
Products Resulting from the Reaction of nBuSnCl3 with
[Pd(PPh3)4] after 15 min of Reaction at Room Temperature
at room temperature cleanly led within 1 min to the formation
of free 2-PyPPh2 (1 equiv) and an ionic palladium complex
that was identified as trans-[PdnBu(SnCl2(2-PyPPh2)2)]Cl
([11]Cl, 1 equiv, eq 4) on the basis of multinuclear NMR
and mass spectroscopic analysis (Table 2). Once again, the
chloride counteranion was not formally identified, but per-
forming the reaction with 2 equiv of nBuSnCl3 led to
[11][nBuSnCl4], the anion of which could be directly observed
by 1H and 119Sn NMR (eq 4).8 Remarkably, [11][nBuSnCl4]
was stable enough to allow its isolation in 88% yield and its
complete characterization (1H, 13C, 31P, and 119Sn NMR,
high-resolution MS). Despite the presence of β-H atoms in
the Pd-nBu moiety, no decomposition of [11][nBuSnCl4] was
detected by NMR in THF-d8 at 70 °C for 6 h.
31P NMR
1H NMR (Pd-H)
relative
amount
of each species
2JP-P 2JP-Sn
compound
δ
(Hz)
(Hz)
δ
PPh3
2
9
trans-10 28.3
cis-10
-5.4
24.4
30.8
2 equiv
10%
10%
30%
50%
-12.6
-7.0
-7.0
101
38.3 36 211, 287
26.6 36
a
a Coupling constant not detected.
in an NMR tube at room temperature led to several products
(eq 8). 1H NMR analysis of the reaction mixture after 15 min
Discussion
n
showed the quantitative transformation of BuSnCl3 into
Two types of equilibria have to be considered when trying
to explain the experimental results obtained for the reactions
of RSnCl3 (R = Me, Ph, and nBu) on Pd(0)-phosphine
precursors. The first equilibrium concerns the cis/trans iso-
merization of [MR(SnCl3)(phosphine)2] complexes. For plat-
inum, Scrivanti showed that [PtEt(SnCl3)(PPh3)2], obtained
by insertion of ethene into trans-[PtH(SnCl3)(PPh3)2], exists
in solution as both its cis- and trans isomers. cis-[PtEt(SnCl3)-
(PPh3)2] was found to be the kinetic product, which evolved
to the thermodynamically more stable trans-[PtEt(SnCl3)-
(PPh3)2].12a The second equilibrium concerns the (reversible)
deinsertion of SnCl2 from a M-SnCl3 bond to form the
corresponding M-Cl species. It is known to occur for group
10 metal complexes, probably involving five-coordinate
intermediates, and has been proven to be more facile for
palladium than for platinum centers.13 With this in mind, the
results of the reactions of RSnCl3 (R=Ph, Me, nBu) can be
fully rationalized (Scheme 1). The results suggest that, in
every case, oxidative addition of the Sn-C bond of the
RSnCl3 reagent initially leads in a rapid process to the key
intermediate cis-[PdR(SnCl3)(PArPh2)2] (R = Me, Ph, nBu ;
Ar = Ph, 2-Py), which rapidly evolves depending on the
nature of the R and Ar groups.
Case of R = Me and Ph. For R = Me and Ph with the [Pd-
(PPh3)4] precursor, cis-[PdR(SnCl3)(PPh3)2] is first formed
and isomerized to give trans-[PdR(SnCl3)(PPh3)2]. Thiscomplex
can then (reversibly) eliminate SnCl2 to form trans-[PdR(Cl)-
(PPh3)2]. For R = Ph, the equilibria are completely shifted to
the side of trans-[PdPh(Cl)(PPh3)2], 1, and the fact that 1
does not insert SnCl2 suggests that the elimination of SnCl2
from [PdPh(SnCl3)(PPh3)2] is indeed highly favorable. In
contrast, for R = Me, both equilibria are observed as the
initial mixture of cis-4 and trans-4 complexes evolved to the
thermodynamically favored trans-isomer after a 2 h equilibration
butene isomers (both internal and terminal) and a palladium
hydride function (1H NMR δ -9.4 ppm, br, line width at
half-height (lwhh) = 297 Hz at 25 °C). The 31P NMR spectrum
of the reaction mixture displayed a broad signal at room
temperature (δ 9 ppm, lwhh = 470 Hz), indicating a fast
exchange between the free phosphine and phosphine-palla-
dium species. Compound 2 was also detected as an impurity
(10%).5 At -50 °C, the hydride signal is split into two broad
signals at δ -7.0 and -12.6 ppm (9:1 ratio, Table 3);
lowering the temperature to -90 °C did not significantly
improve the line width of the signals, but the relative ratio of
the hydride resonances evolved to 26:1. The broad 31P NMR
signal also decoalesced at -50 °C to give six signals, which
were assigned (Table 3) to the known compounds PPh3
(2 equiv), 2 (10%), trans-[PdH(Cl)(PPh3)2] (9, 10%),9 and
trans-[PdH(SnCl3)(PPh3)2] (trans-10, 30%)9,10 as well as to
the new complex cis-[PdH(SnCl3)(PPh3)2] (cis-10, 50%).
Involvement of an ionic [PdH(PPh3)3][SnCl3] complex, re-
sulting from the interaction of [PdH(SnCl3)(PPh3)2] com-
plexes 10 with free PPh3, cannot be completely excluded, as
such [PdH(PPh3)3]þ compounds have been reported to dis-
play hydride signals in the same region (δ -7.0 ppm)11 and as
the 31P NMR signal measured for free PPh3 remained broad
at -50 °C (δ -5.4 ppm, lwhh=271 Hz). Determination of
theactivationparametersofthe underlyingprocesses involved
proved impossible due to the simultaneous occurrence of at
least two, if not three, dynamic processes (cis/trans isomeri-
-
zation, SnCl2 insertion-elimination, and potentially SnCl3
-
PPh3 ligand exchange; see Discussion). The solution contain-
ing the three different palladium hydride species did not
show any sign of decomposition in the 1H NMR (two days at
room temperature), but attempts to isolate a product by
removing the solvent under vacuum or precipitating it with a
different solvent resulted in the loss of the palladium hydride
functionality (no longer detected in the 1H NMR spectrum),
probably because of the loss of the stabilizing excess of PPh3.
(9) (a) Kudo, K.; Hidai, M.; Murayama, T.; Uchida, Y. J. Chem. Soc.
D, Chem. Commun. 1970, 1701b. (b) Heaton, B. T.; Hebert, S. P. A.; Iggo,
J. A.; Metz, F.; Whyman, R. Dalton Trans. 1993, 3081.
(10) Nguyen, D. H.; Laurenczy, G.; Urrutigoity, M.; Kalck, P. Eur. J.
Chem. 2005, 4215.
(11) Zudin, V. N.; Chinakov, V. D.; Nekipelov, V. M.; Likholobov,
V. A.; Yermakov, Yu. I. J. Organomet. Chem. 1985, 289, 425.
(12) (a) Scrivanti, A.; Berton, A.; Toniolo, L.; Botteghi, C. J.
Organomet. Chem. 1986, 314, 369. (b) Clark, H. C.; Jablonski, C.; Halpern,
J.; Mantovani, A.; Weil, T. A. Inorg. Chem. 1974, 13, 1541. (c) Petrosyan,
V. S.; Permin, A. B.; Bogdashkina, V. I.; Krut'ko, D. P. J. Organomet. Chem.
1985, 292, 303.
(13) (a) Anderson, G. K.; Clark, H. C.; Davies, J. A. Organometallics
1982, 1, 64. (b) Anderson, G. K.; Billard, C.; Clark, H. C.; Davies, J. A.;
Wong, C. S. Inorg. Chem. 1983, 22, 439. (c) Ruegg, H. J.; Pregosin, P. S.;
Scrivanti, A.; Toniolo, L.; Botteghi, C. J. Organomet. Chem. 1986, 316, 233.
In constrast to [Pd(PPh3)4], the equimolar reaction of
nBuSnCl3 with [Pd(2-PyPPh2)3] in THF-d8 in an NMR tube

5908 Organometallics, Vol. 29, No. 22, 2010
Cabon et al.
Scheme 1. Rationalization of the Reactions of RSnCl3 Reagents
on Pd(0)-Phosphine Precursors
as in the PhSnCl3 and MeSnCl3 cases, but the end products
differ dramatically depending on which phosphine ligand is
used (Scheme 1). With [Pd(PPh3)4], we detected the formation
of butene isomers and a mixture of at least three different
palladium hydride compounds. As it is known that (i) the
oxidative addition of MeSnCl3 gives a mixture of cis-4 and
-
trans-4 complexes both containing a SnCl3 ligand, (ii) the
SnCl3- ligand has a labile character,7 and (iii) a nBu ligand on
palladium can suffer β-H elimination when a cis- vacant site
becomes available on the Pd center,14 this result is consistent
with the formation of a transient cis-[PdnBu(SnCl3)(PPh3)2]
complex that rapidly undergoes β-H elimination to form
1-butene and cis-[PdH(SnCl3)(PPh3)2] (cis-10, Scheme 1).
cis-10 then isomerizes into trans-10, which partially elimi-
nates SnCl2 to form 9, as for the R = Me case, thus
explaining the formation of all three palladium hydride
species detected in the 1H and 31P NMR spectra. As (i) the
reported 1H NMR chemical shift for trans-10 (δ -6.9 ppm)10
lies very close to the one reported for [PdH(PPh3)3][CF3-
-
COO] (δ -7.0 ppm),11 (ii) SnCl3 is known for its labile
character,7 and (iii) in our experiment the 31P NMR reso-
nance of free PPh3 is broad even at -50 °C, it is possible that
[PdH(PPh3)3][SnCl3] is also formed in solution. However,
the absence of the corresponding characteristic doublet and
triplet signals in the 31P NMR spectrum11 suggests that such
a species is only transient in nature or highly dynamic even at
low temperature. The detection of internal isomers of butene
in the reaction can be explained by a palladium-hydride-
catalyzed isomerization of the initially generated 1-butene
through a 2,1-insertion/β-H elimination sequence.14 We
-
favor a mechanism involving the dissociation of the SnCl3
ligand (Scheme 2) rather than one involving a pentacoordinated
[PdH(butene)(SnCl3)(PPh3)2] intermediate, which was, for
example, proposed in related platinum chemistry,12 because
in [11][BuSnCl4] β-H elimination and isomerization are effi-
ciently blocked (see below). This is clearly due to the reduced
lability of the Pd-Sn bond rather than lack of availability of
a fifth coordination site on the Pd center.
period along with the presence of a significant amount of 3
from the beginning of the reaction. As no cis-[PdR(Cl)-
(PPh3)2] is detected in our experiments, we suggest that the
(reversible) elimination of SnCl2 from [PdR(SnCl3)(PPh3)2]
complexes takes place only from the trans- isomer. However,
elimination of SnCl2 from cis-[PdR(SnCl3)(PPh3)2] to form
directly either trans-[PdR(Cl)(PPh3)2] or a transient cis-[PdR-
(Cl)(PPh3)2] that would rapidly evolve to its trans-isomer
cannot be completely ruled out at this stage.
The difference in behavior when nBuSnCl3 is reacted with
[Pd(2-PyPPh2)3] hardly could have been more striking. In
this case, oxidative addition of the Sn-C bond results in a
stable alkyl species [11]X (X = Cl, [BuSnCl4], Scheme 1) that
shows no tendency to undergo β-H elimination up to 70 °C
(6 h). This last observation is truly remarkable, as β-H elimi-
nation from an alkyl ligand is normally a facile process on
palladium complexes containing triarylphosphine ligands.14
To avoid β-H elimination usually requires strongly bound
and bulky monodentate phosphines or polydentate ligands.14
In that respect, strongly bound terdentate pincer ligands
have been used successfully to generate stable n-alkyl-
palladium complexes containing β-H atoms.15 The fact that
[11][X] (X = Cl, nBuSnCl4) does not undergo β-H elimination
strongly supports the potential of the SnCl2(2-PyPPh2)2
ligand to act as a terdentate diphosphinostannylene ligand
and underlines the strength of the N-Sn interaction.
For R = Me and Ph with the [Pd(2-PyPPh2)3] precursor,
we believe that cis-[PdR(SnCl3)(PPh3)2] is also initially formed
followed by isomerization to trans-[PdR(SnCl3)(2-PyPPh2)2].
However in that case, further stabilization occurs through
intramolecular coordination of the pyridyl groups of the
phosphine ligands to the tin center to lead to a trans-[PdR-
(SnCl3(2-PyPPh2)2)] complex, as exemplified in the X-ray
structure of8 (Figure1). This neutralsix-coordinate trichloro-
stannyl complex then eventually evolves further to form the
cationic five-coordinate dichlorostannylene complex trans-
[PdR(SnCl2(2-PyPPh2)2)]þ[X]- by elimination of a chloride
anion (to form [5]Cl and [6]Cl) or by transferring it to a second
RSnCl3 molecule that acts as a chloride acceptor (to form the
five-coordinate [RSnCl4]- counteranion in [5][MeSnCl4] and
[6][PhSnCl4]).8 In both cases, the SnCl2(2-PyPPh2)2 moiety
behaves as a P-Sn-P terdentate ligand that forces the result-
ing complexinto a trans-geometry in which the intramolecular
coordination of the pyridyl groups to the tin center hamper
elimination of SnCl2.
(14) (a) Crabtree, R. H. The Organometallic Chemistry of the Transi-
tion Metals, 4th ed.; Wiley-Interscience, 2005. (b) Spaniel, T.; Schmidt, H.;
Wagner, C.; Merzweiler, K.; Steinborn, D. Eur. J. Chem. 2002, 2868.
(c) Kirchhoff, J. H.; Netherton, M. R.; Hills, I. D.; Fu, G. C. J. Am. Chem.
Soc. 2002, 124, 13662. (d) Hills, I. D.; Netherton, M. R.; Fu, G. C. Angew.
Chem., Int. Ed. 2003, 42, 5749. (e) Reger, D. L.; Garza, D. G.; Baxter, J. C.
Organometallics 1990, 9, 873.
(15) (a) Fafard, C. M.; Ozerov, O. V. Inorg. Chim. Acta 2006, 360,
286. (b) Fafard, C. M.; Adhikari, D.; Foxman, B. M.; Mindiola, D. J.; Ozerov,
O. V. J. Am. Chem. Soc. 2007, 129, 10318.
n
n
Case of R = Bu. BuSnCl3 reacts with [Pd(PPh3)4] and
[Pd(2-PyPPh2)3] through oxidative addition of the Sn-C bond,

Article
Organometallics, Vol. 29, No. 22, 2010 5909
Scheme 2. Proposed Mechanism for the Formation of Internal
Butenes in the Reaction of nBuSnCl3 with [Pd(PPh3)4]
Figure 2. Representation of the transition state of the direct
activation of the Me-SnCl3 bond by the [Pd(PH3)2] fragment as
calculated by DFT (Gaussian 09, RB3LYP, H/C/P/Cl 6-31G*,
Pd/Sn LANL2DZ).
Scheme 3. Comparison of the Reactivity of RSnCl3 Reagents on Pt(0) and Pd(0) Precursors
Comparison with the Platinum Case and Mechanism of the
Sn-C Bond Oxidative Addition. With respect to studies on
the oxidative addition of alkyltin derivatives on zero oxida-
tion-state group 10 metal complexes in the literature, only
Eaborn and Pidcock reported the case of RSnCl3 reagents
(R = Me, Ph), which underwent an oxidative addition of the
Sn-Cl bond on the platinum(0) precursor [Pt(PPh3)2(C2H4)],
resulting in cis- and trans-isomers of [PtCl(SnRCl2)(PPh3)2]
(Scheme 3, left).1a From the work reported here, it can be
concluded that the reactivity of RSnCl3 (R = Ph, Me, nBu)
towards the Pd(0) precursors [Pd(PPh3)4] and [Pd(2-PyPPh2)3]
differs significantly from the structurally related Pt(0) pre-
cursor (Scheme 3, right). Oxidative addition is formally
taking place in the Sn-C bond, which results exclusively in
transient cis-[Pd(alkyl)(SnCl3)(phosphine)2] species (Scheme 1),
which can undergo cis-trans isomerization followed by, in
the case of [Pd(PPh3)4], reversible SnCl2 elimination or, in the
case of [Pd(2-PyPPh2)3], chloride elimination to form stable
palladium dichlorostannylene species.
intermediates were not detected when the reaction between
[Pd(PPh3)4] and MeSnCl3 was monitored at low temperature
(T = -50 °C, eq 3) by 1H and 31P NMR. Certainly, in the
case of [Pd(2-PyPPh2)3] as starting compound, one would
expect such intermediates to be stabilized by intramolecular
coordination of the pyridyl groups to the Sn atom. No
complexes of this type were detected, however. Moreover,
in the formation of complex [11][nBuSnCl4], such a reaction
pathway would involve [PdnBu(Cl)(2-PyPPh2)2] as an inter-
mediate that is expected to be unstable toward β-H elimina-
tion and would result in formation of butenes. The latter are
not observed. The absence of R2SnCl2 species also excludes a
redistribution of [PdCl(SnRCl2)(phosphine)2] and RSnCl3.
Another possible reaction route for the formal oxidative
addition reactions observed is an SN2-type reaction of a
[Pd(phosphine)3] fragment with RSnCl3 leading to a transient
-
ionic [PdR(phosphine)3][SnCl3] intermediate. The SnCl3
anion would then substitute one of the phosphine ligands
to give the observed complexes. Pentacoordinated [PdR(SnCl3)-
(phosphine)3] complexes could then be envisioned as inter-
mediates or transition states, which would provide a good
explaination for the cis/trans isomerization of the [PdMe-
(SnCl3)(PPh3)2] complexes via a Berry pseudorotation.
However, when the reaction by [Pd(PPh3)4] and MeSnCl3
was carried out and monitored by NMR at low temperature
(T = -50 °C), cis-[PdMe(SnCl3)(PPh3)2] is initially the major
product of the reaction, suggesting a concerted activation of
the Sn-C bond. Those observations make us favor a reac-
tion pathway involving the direct activation of the Sn-C
bond by [Pd(phosphine)2] or [Pd(phosphine)3] species. This
Several mechanisms can be envisioned for the observed
Sn-C bond activation reactions that, at least formally, lead
to the oxidative addition on Pd. The first one would involve a
preliminary oxidative addition of the Sn-Cl bond to give
[PdCl(SnRCl2)(phosphine)2] complexes, as was observed in
the analogous platinum chemistry. Those would then have to
evolve rapidly to the observed [PdR(SnCl3)(phosphine)2]
complexes, either through deinsertion of SnCl2 from the
-
SnRCl2 ligand and its reinsertion into the Pd-Cl bond
or through redistribution of the substituents on Sn with an-
other RSnCl3 molecule. However, [PdCl(SnMeCl2)(PPh3)2]

5910 Organometallics, Vol. 29, No. 22, 2010
Cabon et al.
hypothesis is further supported by DFT calculations on a
model system, which show that the activation barrier for
such a process starting from the encounter complex is indeed
δ 9.09 (d, 3JH-H = 5.3 Hz, 2H, Py), 8.17 (m, 2H, Py), 7.94 (m,
2H, Py), 7.66 (d, 3JH-H = 7.7 Hz, 2H, Py), 7.59-7.52 (m, 12H,
2
Ph), 7.48-7.44 (m, 8H, Ph), 1.55 (s, JH-Sn = 112.9 and
117.9 Hz, 3H, MeSnCl4-), 1.36 (s, 3JH-Sn = 45.1 Hz, Me-Pd).
13C NMR (CDCl3, 25 °C, 101 MHz): δ 149.6 (t, JP-C = 62 Hz),
149.3 (t, JP-C = 17 Hz), 141.8 (s), 134.2 (t, JP-C = 13 Hz),
132.5 (s), 131.5 (t, JP-C = 12 Hz), 129.6 (t, JP-C = 11 Hz), 129.2
(s), 127.3 (t, JP-C = 51 Hz), 24.3 (s), 15.2 (s). 31P NMR (CDCl3,
25 °C, 121 MHz): δ63.6 (s). 119Sn NMR (CDCl3, 25 °C, 112 MHz):
δ -244.7 (br, [MeSnCl4]-). ESI-HRMS (in CH2Cl2): found
836.9351 (calculated for [5]þ 836.9391, with the correct isotope
pattern).
low (ΔG‡ = 24 kJ mol-1, Figure 2).16
3
Conclusions
The above studies show that the reaction of alkyltin
trichlorides on Pd(0)-phosphine complexes exclusively pro-
ceeds through an oxidative addition of the Sn-C bond,
which is in sharp contrast to the related Pt(0) case. By using
[Pd(2-PyPPh2)3] as a precursor instead of [Pd(PPh3)4], it
became possible to efficiently block degradation of the
initially formed palladium-alkyl products and to synthesize
in a single step a cationic (bis(2-(diphenylphosphino)pyridine)-
dichlorostannylene)-palladium-alkyl complex that showed
no tendency to undergo β-H elimination. The unique P-
Sn(II)-P terdentate ligand, through its stannylene donor
function, can be expected to induce new interesting proper-
ties to derived metal complexes, the synthesis and reactivity of
which are currently under investigation.
Preparation of [6][PhSnCl4] and [11][nBuSnCl4]. Synthesis was
performed using the same procedure as for the synthesis of
[5][MeSnCl4] except that PhSnCl3 (74.0 μL, 0.45 mmol) or
nBuSnCl3 (75.0 μL, 0.45 mmol) was slowly introduced as the
neat compound (and, for [6][PhSnCl4], an extra washing with
2 ꢀ 5 mL of Et2O). A white solid was obtained ([6][PhSnCl4],
198.8 mg, 16 mmol, 72%; [11][nBuSnCl4], 235.1 mg, 20 mmol,
88%).
[6][PhSnCl4]: 1H NMR (CDCl3, 25 °C, 300 MHz): δ 8.52 (m,
2H), 8.25 (m, 1H), 8.08 (m, 2H), 7.91 (m, 1H), 7.77 (m, 2H),
7.68-7.35 (m, 30H). 13C NMR (CDCl3, 25 °C, 101 MHz): δ
149.2 (t, JC-P = 8.6 Hz), 149.1 (t, JC-P = 31.3 Hz), 145.9 (s),
141.5 (s), 135.7 (s), 135.4 (s), 134.2 (t, JC-P = 6.8 Hz), 132.4 (s),
Experimental Section
131.2 (s), 131.0 (s), 130.3 (s), 130.0 (s), 129.8 (s), 129.5 (t, JC-P =
5.5 Hz), 128.6 (s), 128.5 (s), 127.5 (t, JC-P = 25.5 Hz). 31P NMR
General Considerations. All operations were performed in
dry, degassed (deuterated) solvents under a dinitrogen atmo-
sphere using standard Schlenk techniques or a glovebox. PhSnCl3,
2
(CDCl3, 25 °C, 121 MHz): δ 64.3 (s, JP-Sn =145 Hz). 119Sn
NMR (CDCl3, 25 °C, 112 MHz): δ -321.7 (br, [PhSnCl4]-).
ESI-HRMS (in CH2Cl2): found 898.9539 (calculated for [6]þ
898.9547, with the correct isotope pattern).
n
MeSnCl3, and BuSnCl3 were purchased from Sigma-Aldrich.
Metal precursors [Pd(PPh3)4], trans-[PdMe(Cl)(PPh3)2], trans-
[PdPh(Cl)(PPh3)2], [Pd(2-PyPPh2)3], and trans-[PdPh(Cl)(2-Py-
PPh2)2] were prepared according to literature procedures.4,6
Toluene was distilled from sodium; THF-d8 was distilled from
sodium benzophenone. NMR data were recorded on a Varian
Oxford 300 MHz or Varian Oxford AS 400 MHz, and chemical
shifts are reported relative to SiMe4 (1H, 13C), external 85%
H3PO4 in water (31P), or SnMe4 (1 M) in benzene (119Sn). The
119Sn NMR signal of the stannylene ligand in complexes [5]-
[MeSnCl4], [6][PhSnCl4], and [11][nBuSnCl4] could not be ob-
served, which is presumably due to a very broad signal caused by
a significant chemical shift anisotropy for the tin atom.17 High-
resolution mass spectroscopy (HRMS) has been performed on a
Waters LCT Premier XE Micromass instrument using the
electrospray ionization technique.
Preparation of [5][MeSnCl4]. MeSnCl3 (108.0 mg, 0.45 mmol)
dissolved in toluene (1 mL) was slowly added to a stirred
solution of [Pd(2-PyPPh2)3] (200.0 mg, 0.22 mmol) in toluene
(10 mL) at room temperature. Within 10 min, a white precipitate
formed, which was recovered by filtration, washed with toluene
(3 ꢀ 5 mL), and dried under vacuum to lead to a white solid
(166.4 mg, 15 mmol, 67%). 1H NMR (CDCl3, 25 °C, 300 MHz):
[11][nBuSnCl4]: 1H NMR (CDCl3, 25 °C, 300 MHz): δ 9.05 (d,
3JH-H = 5.2 Hz, 2H, Py), 8.17 (m, 2H, Py), 7.94 (m, 2H, Py),
7.57 (d, 3JH-H = 7.7 Hz, 2H, Py), 7.48-7.34 (m, 20H, Ph), 2.15
(t, 3JH-H = 7.6 Hz, 2JH-Sn = 107 Hz, 2H, [nPr-CH2-SnCl4]-),
3
n
1.92 (t, JH-H = 7.6 Hz, 2H, Pr-CH2-Pd), 1.82 (m, 2H, [nEt-
CH2-CH2SnCl4]-), 1.37 (m, 2H, [Me-CH2-C2H4SnCl4]-), 0.84
(m, 2H, nEt-CH2-CH2-Pd), 0.81 (t, JH-H = 7.3 Hz, 3H,
3
[Me-C3H6SnCl4]-), 0.74 (m, 2H, Me-CH2-C2H4-Pd), 0.27 (t,
3JH-H = 7.1 Hz, 3H, Me-C3H6-Pd). 13C NMR (CDCl3, 25 °C,
101 MHz): δ 149.8 (m), 149.7 (m), 142.0 (s), 134.1 (t, JC-P = 6.7
Hz), 132.6 (s), 131.9 (t, JC-P = 6.0 Hz), 129.7 (t, JC-P = 5.5 Hz),
129.4 (s), 127.1 (t, JC-P = 25.6 Hz), 44.5 (s), 33.2 (s), 28.0 (s),
27.8 (s), 26.6 (s), 25.7 (s), 14.0 (s), 13.7 (s). 31P NMR (CDCl3,
25 °C, 121 MHz): δ62.5 (s). 119Sn NMR (CDCl3, 25 °C, 112 MHz):
δ -249.6 (br, [nBuSnCl4]-). ESI-HRMS (in CH2Cl2): found
878.9868 (calculated for [11]þ 878.9860, with the correct isotope
pattern).
Monitoring of the Reactions of [Pd(PPh3)4] with MeSnCl3,
PhSnCl3, or nBuSnCl3 by NMR. [Pd(PPh3)4] (11.5 mg, 0.01
mmol) was introduced in an NMR tube and dissolved in 0.5 mL
of THF-d8. MeSnCl3 (2.4 mg, 0.01 mmol), PhSnCl3 (1.65 μL,
0.01 mmol), or nBuSnCl3 (1.67 μL, 0.01 mmol) was then intro-
duced in the tube, and the resulting solution was shaken and
then analyzed by 31P and 1H NMR as well as by mass spectros-
copy (except for the nBuMeSnCl3 case).
(16) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.;
Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci, B.;
Petersson, G. A.; Nakatsuji, H.; Caricato, M.; Li, X.; Hratchian, H. P.;
Izmaylov, A. F.; Bloino, J.; Zheng, G.; Sonnenberg, J. L.; Hada, M.;
Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima,
T.; Honda, Y.; Kitao, O.; Nakai, H.; Vreven, T.; Montgomery, J. A., Jr.;
Peralta, J. E.; Ogliaro, F.; Bearpark, M.; Heyd, J. J.; Brothers, E.;
Kudin, K. N.; Staroverov, V. N.; Kobayashi, R.; Normand, J.;
Raghavachari, K.; Rendell, A.; Burant, J. C.; Iyengar, S. S.; Tomasi,
J.; Cossi, M.; Rega, N.; Millam, J. M.; Klene, M.; Knox, J. E.; Cross,
J. B.; Bakken, V.; Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann,
R. E.; Yazyev, O.; Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski,
J. W.; Martin, R. L.; Morokuma, K.; Zakrzewski, V. G.; Voth, G. A.;
Salvador, P.; Dannenberg, J. J.; Dapprich, S.; Daniels, A. D.; Farkas,
O.; Foresman, J. B.; Ortiz, J. V.; Cioslowski, J.; Fox, D. J. Gaussian 09,
Revision A.02; Gaussian Inc.: Wallingford CT, 2009.
[Pd(PPh3)4] and MeSnCl3. The spectra were recorded at -50 °C
because broad signals were observed at room temperature. NMR
analysis indicated the formation of the known compounds PPh3
(2 equiv), cis-[PdCl2(PPh3)2] (2, 10%), and trans-[PdMe(Cl)-
(PPh3)2]6 (3, 15% at t = 1 min, 25% at t = 2 h), as well as the
new compounds trans-[PdMe(SnCl3)(PPh3)2] (trans-4, 45% at
t = 1 min, 65% at t = 2 h) and cis-[PdMe(SnCl3)(PPh3)2] (cis-4,
30% at t = 1 min, 0% at t = 2 h). As a mixture of products was
1
present, only the methyl signals were attributed by H NMR.
P
PPh3: 31P NMR (THF-d8, -50 °C, 121 MHz): δ -5.4 (s). 2: 31
1
NMR (THF-d8, -50 °C, 121 MHz): δ 24.4 (s). 3: H NMR
(THF-d8, -50 °C, 300 MHz): δ -0.16 (t, 3JH-P = 11.6 Hz). 31
NMR (THF-d8, -50 °C, 121 MHz): δ 31.2 (s). trans-4: 1H NMR
(THF-d8, -50 °C, 300 MHz): δ 1.00 (s, 3JH-Sn = 48.0 Hz). 31
P
(17) For reviews on 119Sn NMR see for example: (a) Hani, R.;
Geanangel, R. A. Coord. Chem. Rev. 1982, 44, 229. (b) Agustin, D.; Ehses,
M. C. R. Chim. 2009, 12, 1189.
P

Article
Organometallics, Vol. 29, No. 22, 2010 5911
NMR (THF-d8, -50 °C, 121 MHz): δ 27.9 (s, 2JP-Sn = 96 Hz).
Synthesis and X-ray Crystal Structure Determination of Com-
pound 8. [Pd(2-PyPPh2)3] (10 mg, 0.011 mmol) was reacted with
SnCl4 (1.3 μL mg, 0.011 mmol) in THF-d8 (0.5 mL) in an NMR
tube. The 1H and 31P NMR spectra were recorded and indicated
the quantitative formation of free 2-PyPPh2 (1 equiv) and [7][Cl]
(1 equiv).3a The THF-d8 solution in the tube was covered with an
n-hexane layer and left at room temperature (7 days) until single
white crystals suitable for X-ray analysis were formed. C34H28-
Cl4N2P2PdSn, fw = 893.41, yellow needle, 0.24 ꢀ 0.03 ꢀ
cis-4: 1H NMR (THF-d8, -50 °C, 300 MHz): δ 0.29 (s, 3JH-Sn
=
42.6 Hz). 31P NMR (THF-d8, -50 °C, 121 MHz): δ 37.2 (d,
2JP-P = 36 Hz, 2JP-Sn = 271 Hz), 26.7 (d, 2JP-P = 36 Hz). ESI-
HRMS of the reaction mixture (in DCM/MeCN): found 645.1248
and 686.1473 corresponding respectively to [PdMe(PPh3)2]þ
(calculated 645.1087) and [PdMe(MeCN)(PPh3)2]þ (calculated
686.1352).
[Pd(PPh3)4] and PhSnCl3. Analysis of the solution by 1H and
31P NMR after 1 min indicated the complete formation of PPh3
(2 equiv) and trans-[PdPh(Cl)(PPh3)2] (1, 1 equiv) assigned by
comparison with literature data.4 PPh3: 31P NMR (THF-d8,
25 °C, 121 MHz): δ -5.4 (s). 1: 31P NMR (THF-d8, 25 °C, 121
MHz): δ 24.2 (s). ESI-HRMS of the reaction mixture (in DCM/
MeCN): found 707.1136, 723.1086, 748.1352 corresponding
respectively to [PdPh(PPh3)2]þ (calculated 707.1265), [PdPh(PPh3)-
(PPh3O)]þ (calculated 723.1198), and [PdPh(MeCN)(PPh3)2]þ
(calculated 748.1514).
3
˚
0.03 mm , monoclinic, P21/c (no. 14), a = 14.4729(6) A, b =
˚
˚
12.5944(13) A, c = 22.8027(11) A, β = 124.973(2)°, V =
3405.9(4) A , Z = 4, Dx = 1.742 g/cm , μ=1.70 mm-1. A total
of 45 500 reflections were measured on a Nonius KappaCCD
diffractometer with rotating anode (graphite monochromator,
3
3
˚
λ = 0.71073 A) up to a resolution of (sin θ/λ)max = 0.55 A-1 at a
temperature of 150(2) K. Intensity integration was performed
with Eval15 using a model for large mosaicity.18 The SADABS
program was used for absorption correction and scaling based
˚
˚
[Pd(PPh3)4] and nBuSnCl3. The NMR spectra were recorded
at -50 °C because broad signals were observed at room tem-
perature. NMR analysis of the solution indicated the formation
of the known compounds PPh3 (2 equiv), butene isomers (1 equiv,
isomer ratio evolves from initially >80% 1-butene to >95%
2-butene after 2 h), cis-[PdCl2(PPh3)2] (2, 10%), trans-[PdH-
(Cl)(PPh3)2] (9, 10%),9,10 and trans-[PdH(SnCl3)(PPh3)2] (trans-
10, 30%)10 as well as the new compound cis-[PdH(SnCl3)-
(PPh3)2] (cis-10, 50%). As a mixture of products is present, only
the hydride signals were attributed by 1H NMR. PPh3: 31P
NMR (THF-d8, -50 °C, 121 MHz): δ -5.4 (br, lwhh = 271 Hz).
on multiple measured reflections (0.61-0.75 correction range).19
A
total of 4725 reflections were unique (Rint = 0.071), of which
3581 were observed [I > 2σ(I)]. The structure was solved with
direct methods using the program SHELXS-97.20 The structure
was refined with SHELXL-97 against F2 of all reflections.20
Non-hydrogen atoms were refined with anisotropic displace-
ment parameters. Hydrogen atoms were introduced in calcu-
lated positions and refined with a riding model. A total of 397
parameters were refined with no restraints. R1/wR2 [I > 2σ(I)]:
0.0338/0.0678. R1/wR2 [all reflns]: 0.0573/0.0760. S = 1.035.
3
˚
Residual electron density was between -0.52 and 0.81 e/A .
Geometry calculations and checking for higher symmetry were
1
1-Butene: H NMR (THF-d8, -50 °C, 300 MHz): δ 5.90 (m,
1H), 5.02 (m, 1H), 4.93 (m, 1H), 2.07 (m, 2H), 1.01 (t, 3H,
J
performed with the PLATON program.21
H-H = 14.9 Hz). 2-Butenes (Z and E mixture): 1H NMR
(THF-d8, -50 °C, 300 MHz): 5.46 (m, 2H), 1.84 (m, 6H). 2:
31P NMR (THF-d8, -50 °C, 121 MHz): δ 24.4 (s). 9: 1H NMR
(THF-d8, -50 °C, 300 MHz): δ -12.6 (br). 31P NMR (THF-d8,
Acknowledgment. Y.C. thanks ARKEMA for a post-
doctoral fellowship. The authors thank Prof. Dr. Gerard
van Koten for valuable discussions and the Dutch Min-
istry of Economic Affairs/Agentschap NL for financial
support.
1
-50 °C, 121 MHz): δ 30.8 (s). trans-10: H NMR (THF-d8,
-50 °C, 300 MHz): δ -7.0 (br). 31P NMR (THF-d8, -50 °C,
121 MHz): δ 28.3 (s, 2JP-Sn = 101 Hz). cis-10: 1H NMR (THF-
d8, -50 °C, 300 MHz): δ -7.0 (br). 31P NMR (THF-d8, -50 °C,
121 MHz): δ 38.3 (d, 2JP-P = 36 Hz, 2JP-Sn = 211 and 287 Hz),
26.6 (d, 2JP-P = 36 Hz).
Supporting Information Available: For experiments with
1
[Pd(PPh3)4] in NMR tubes, 31P and H NMR spectra (at RT
Monitoring of the Reactions of trans-[PdR(Cl)(PPh3)2] (R =
Me, Ph) and trans-[PdPh(Cl)(2-PyPPh2)2] with SnCl2 by NMR.
trans-[PdMe(Cl)(PPh3)2] (3, 6.8 mg, 0.01 mmol), trans-[PdPh-
(Cl)(PPh3)2] (1, 7.4 mg, 0.01 mmol), or trans-[PdPh(Cl)(2-
PyPPh2)2] (7.5 mg, 0.01 mmol) was introduced in an NMR tube
and dissolved in 0.5 mL of THF-d8. SnCl2 (1.9 mg, 0.01 mmol)
was then introduced, and the tube was shaken. The resulting
or -50 °C) and HRMS spectra. For experiments with [Pd(2-
PyPPh2)3], full analytical data (1H, 13C, and 31P NMR, HRMS)
of complexes [5][MeSnCl4], [6][PhSnCl4], and [11][nBuSnCl4].
Crystallographic details of compound 8 in cif format. This
material is available free of charge via the Internet at http://
pubs.acs.org.
1
mixture was then analyzed by 31P and H NMR. For trans-
(18) Schreurs, A. M. M.; Xian, X.; Kroon-Batenburg, L. M. J. J.
Appl. Crystallogr. 2010, 43, 70.
(19) Sheldrick, G. M. SADABS: Area-Detector Absorption Correc-
[PdPh(Cl)(2-PyPPh2)2], quantitative formation of the cationic
dichlorostannylene cation [6]þ was observed, suggesting the for-
mation of [6]Cl. For the trans-[PdR(Cl)(PPh3)2] precursors, no
reaction was observed for 1, whereas for3 partial formation of cis-4
and trans-4 was detected. See previous sections for NMR data.
€
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tion, v2.10; Universitat Gottingen: Germany, 1999.
(20) Sheldrick, G. M. Acta Crystallogr. 2008, A64, 112.
(21) Spek, A. L. Acta Crystallogr. 2009, D65, 148.