Carbosilane dendrimers peripherally functionalized with P-stereogenic monophosphines. Catalytic behavior of their allylpalladium complexes in the asymmetric hydrovinylation of styrene

Article abstract of DOI:10.1021/om050915s

The first dendrimers containing P-stereogenic monophosphines as peripheral groups were obtained by reacting the protected BH₃-LiCH ₂PPhR (R = 2-biphenylyl, 9-phenanthryl) with zeroth- and first-generation chlorocarbosilane dendrimers

Full text of DOI:10.1021/om050915s

1368
Organometallics 2006, 25, 1368-1376
Carbosilane Dendrimers Peripherally Functionalized with
P-Stereogenic Monophosphines. Catalytic Behavior of Their
Allylpalladium Complexes in the Asymmetric Hydrovinylation of
Styrene†
Lara-Isabel Rodr´ıguez, Oriol Rossell,* Miquel Seco, Arnald Grabulosa,
Guillermo Muller,* and Merce` Rocamora
Departament de Qu´ımica Inorga`nica, UniVersitat de Barcelona, Mart´ı i Franque`s, 1-11,
08028 Barcelona, Spain
ReceiVed October 21, 2005
The first dendrimers containing P-stereogenic monophosphines as peripheral groups were obtained by
reacting the protected BH3-LiCH2PPhR (R ) 2-biphenylyl, 9-phenanthryl) with zeroth- and first-generation
chlorocarbosilane dendrimers, followed by treatment with morpholine and subsequent chromatographic
purification. The first-generation dendrimer with the 9-phenanthryl-substituted phosphine could not be
obtained, due to the incomplete functionalization of all the arms of the dendrimer. The reaction of the
chiral dendrimers with the dinuclear allyl complex [Pd(µ-Cl)(η3-2-MeC3H4)]2 allowed us to graft PdCl-
(η3-2-MeC3H4) units on their surface. Complete characterization of these species was achieved by
multinuclear NMR spectra (including 2D experiments), mass spectrometry, and optical rotation
determinations. The catalytic properties of the new palladodendrimers were tested in the asymmetric
hydrovinylation of styrene. To evaluate possible dendritic effects, two model chiral compounds, (CH3)3-
SiCH2PPhR, were prepared. The results in terms of activity, selectivity, and enantiomeric excess depend
strongly on the nature of the phosphine and the halide abstractor. The best results were achieved with the
employment of the first-generation dendrimer containing the 2-biphenylyl-substituted phosphine and
NaBARF (79% ee toward the S enantiomer). In all experiments, the major enantiomer of 3-phenyl-1-
butene had the absolute configuration S, with the exception of that catalyzed by the 9-phenanthryl-
substituted phosphine dendrimer, which afforded (R)-3-phenyl-1-butene as the predominant enantiomer.
described by Gade et al.,5 and the species reported by Togni et
al. by grafting chiral ferrocenyl diphosphines (“Josiphos”) into
the periphery of a dendrimer.6 Very recently, a third-generation
chiral phosphorus-containing dendrimer has been described and
used in Pd-catalyzed asymmetric allylic alkylation by Majoral
et al.7 In addition, a dendrimer displaying a Ru-BINAP chiral
core is also known.8 By far, chiral diphosphines have been the
most successfully used ligands in catalysis, but unfortunately,
they do not offer a straightforward method of functionalization
that allows their attachment to dendrimers, thus restricting their
use in this field. Moreover, in some catalytic reactions such as
hydrovinylation, the presence of bidentate ligands inhibits the
reaction.9 Having in mind these precedents and the lack of
dendrimers containing P-stereogenic phosphines, we undertook
Introduction
One of the most interesting aims of metallodendrimer research
is the preparation of novel and efficient catalytically active
hyperbranched macromolecules. Some of these species have
shown properties that differ significantly from those of the parent
compounds, due to the distinct environment around the metal
center created by the dendritic scaffold. Thus, a good number
of examples of dendritic effects on catalyst properties have been
reported in the literature.1 However, the number of reports on
asymmetric catalysis carried out by chiral dendritic systems is
still very limited. Relevant examples include the amino alcohol-
zinc alkyl compounds attached to PPI (phosphine-functionalized
poly(propyleneimine)) by Meijer et al.,2 the Ti-TADDOL
systems studied by Seebach,3 the chiral Salen systems reported
by Jacobsen et al.,4 the “pyrphos”-functionalized PPI dendrimers
(4) Breinbauer, R.; Jacobsen, E. Angew. Chem., Int. Ed. 2000, 39, 3604.
(5) (a) Engel, G. D.; Gade, L. H. Chem. Eur. J. 2002, 8, 4319. (b)
Riboudouille, Y.; Engel, G.; Richard-Plouet, M.; Gade, L. Chem. Commun.
2003, 1228.
(6) (a) Ko¨llner, C.; Pugin, A.; Togni, A. J. Am. Chem. Soc. 1998, 120,
10274. (b) Schneider, R.; Ko¨llner, C.; Weber, I.; Togni, A. Chem. Commun.
1999, 2415. (c) Togni, A.; Bieler, N.; Burckhardt, U.; Ko¨llner, C.; Pioda,
G.; Schneider, R.; Schnyder, A. Pure Appl. Chem. 1999, 71, 1531. (d)
Ko¨llner, C.; Togni, A. Can. J. Chem. 2001, 79, 1762.
(7) Laurent, R.; Caminade, A. M.; Majoral, J. P. Tetrahedron Lett. 2005,
46, 6503.
(8) (a) Fan, Q.; Chen, Y.; Chen, X.; Jiang, D.; Xi, F.; Chan, A. Chem.
Commun. 2000, 789. (b) Deng, G.; Fan, Q.; Chen, X.; Liu, D.; Chan, A.
Chem. Commun. 2002, 1570. (c) Deng, G.; Fan, Q.; Chen, X.; Liu, D. J.
Mol. Catal. A: Chem. 2003, 193, 21.
* To whom correspondence should be addressed. E-mail: oriol.rossell@
qi.ub.es (O.R.); guillermo.muller@qi.ub.es (G.M.).
† Dedicated to Professor Victor Riera on the occasion of his 70th birthday.
(1) For reviews of dendrimer catalysis, see: (a) Astruc, D.; Chardac, F.
Chem. ReV. 2001, 101, 2991. (b) van Heerbeeck, R.; Kamer, P. C. J.; van
Leeuwen, P. W. N. M.; Reek, J. N. H. Chem. ReV. 2002, 102, 3717. (c)
Crooks, R. M.; Zhao, M.; Sun, L.; Chechik, V.; Yueng, L. K. Acc. Chem.
Res. 2001, 34, 181. (d) Twyman, L. J.; King, A. S. H.; Martin, I. K. Chem.
Soc. ReV. 2002, 31, 69. (e) Oosterom, G. E.; Reek, J. N. H.; Kramer, P. C.
J.; van Leeuwen, P. W. N. M. Angew. Chem., Int. Ed. 2001, 40, 1828.
(2) Sanders-Hoven, M. S. T. H.; Jansen, J.; Vekemans, J.; Meijer, E.
Polym. Mater. Sci. Eng. 1995, 210, 180.
(3) (a) Seebach, D.; Marti, R.; Hintermann, T. Y. HelV. Chim. Acta 1996,
79, 1710. (b) Rheiner, P. B.; Seebach, D. Polym. Mater. Sci. Eng. 1997,
77, 130.
(9) RajanBabu, T. V. Chem. ReV. 2003, 103, 2845.
10.1021/om050915s CCC: $33.50 © 2006 American Chemical Society
Publication on Web 02/11/2006

Carbosilane Dendrimers
Organometallics, Vol. 25, No. 6, 2006 1369
Chart 1
In the first step, sec-BuLi was reacted with the protected
P-BH3 phosphines in thf at -78 °C to yield the corresponding
lithiated derivatives LiP-BH3. After 2 h, 1Cl, 2Cl, or 3Cl was
added to the solution to give nP-BH3 (n ) 1-3). In the case of
the dendrimers, a slight excess of P-BH3 with respect to sec-
BuLi is needed to prevent the potential substitution of the
chlorine atoms by sec-Bu groups. Moreover, the derivatives LiP-
BH3 formed must be in excess to complete the phosphorylation
of all the arms of the dendrimer. These considerations are not
necessary when model compounds are prepared, given that the
mononuclear 1P-BH3 can be isolated by precipitation. The
lithiated form of the phosphine and subsequent nucleophilic
attack to the chloro compounds were carried out under the BH3-
protected form in order to increase the nucleophilicity of the
deprotonated phosphine and to facilitate the workup.13 Crystals
suitable for an X-ray crystal structure determination of the
borane adduct 1P2-BH3 were grown from a CH2Cl2/hexane
solution. Figure 1 shows the molecular structure, confirming
the expected S-isomer geometry of the stereogenic center. The
distances and angles were similar to those reported for analogous
1
molecules.10 The H NMR spectrum of nP-BH3 (n ) 2, 3)
showed no traces of the external methyl groups of the starting
carbosilane, indicating that it was completely consumed. In the
phosphorylated dendrimers, these methyl groups appeared as
two distinct singlets, confirming their diastereotopic character,
as expected. In all cases, the molecules were made impure by
the slight excess of P-BH3. The second step involved the
deprotection of this mixture with morpholine, followed by
purification with column chromatography, which allowed us to
isolate the desired compounds as pure white solids. The new
compounds were characterized by multinuclear NMR spectros-
copy (including HSQC 1H-13C experiments to unambiguously
assign the aliphatic protons and the carbon signals), mass
spectrometry, elemental analyses, and optical rotation determi-
nations (Table 1).
Characteristic spectroscopic features are a unique signal for
the phosphorus nucleus and four signals for the different silicon
environments expected for 3P1 with the external silicon coupled
with the phosphorus atom (JSi-P ) 14.0 Hz). The MALDI-TOF
spectrum of the dendrimers showed the molecular peak in all
cases, with no indication of incomplete functionalization.
Attempts to obtain 3P2 were unsuccessful, probably due to
the rigidity and bulk of the phenanthryl moiety of the phosphine
P2, resulting in only a partial functionalization of the dendrimer
branches.
Allylpalladium Compounds [PdCl(η3-2-Me-C3H4)(nP1)] (n
) 1-3) and [PdCl(η3-2-Me-C3H4)(nP2)] (n ) 1, 2). The
grafting of the Pd(η3-2-MeC3H4)Cl units on the surface of the
dendrimers was achieved in good yields by reaction of the
dinuclear allyl complex [Pd(µ-Cl)(η3-2-MeC3H4)]2 with the
corresponding phosphine derivatives in CH2Cl2 at room tem-
perature (Scheme 2).14
The mononuclear model compounds 1P1 and 1P2 were
obtained similarly. The synthesis was monitored by 31P NMR
spectroscopy. The free phosphine signal of the starting com-
pounds (at about -33 ppm) completely disappeared after 20
min, and the emergence of two singlets (in the range of 2-8
ppm) was seen, indicative of the presence of the (R) and (S)-Pd
isomers, which are in equilibrium. The yellow compounds were
pure within the limits of the NMR spectroscopic detection. They
are soluble in moderately polar organic solvents (CH2Cl2,
the synthesis of these kinds of compounds. For this, we took
advantage of the clean synthesis of the chiral monodentate
phosphines P*, (S)-MePPh(2-biphenylyl), and (S)-MePPh(9-
phenanthryl), recently described by some of us.10 These ligands
are especially appropriate because of the presence of the methyl
group, which permits the easy formation of the corresponding
lithium derivatives. Thus, according to the previously developed
methodology,11 the reaction of the lithium species with the
zeroth or first generation of chlorocarbosilane dendrimers
enabled isolation of the targeted compounds. The catalytic
properties of the related palladium dendrimers were tested in
the hydrovinylation of styrene, which is an interesting process,
because it opens up easy access to building blocks for fine
chemicals.12 The excellent results obtained in terms of selectivity
and enantiomeric excess were compared with those of two
mononuclear models prepared in order to detect dendritic effects.
Results and Discussion
Preparation of Chiral Phosphine Ended Carbosilane
Dendrimers. The starting carbosilane dendrimers 2Cl and 3Cl
and the chiral phosphine ligands P1 and P2 used in this work
are represented in Chart 1, and they were obtained as described
earlier.10,11
Two model compounds, 1P1 and 1P2, and three dendrimers
peripherally functionalized with chiral phosphines, 2P1, 2P2, and
3P1, were synthesized by following the protocol shown in
Scheme 1.
(10) Grabulosa, A.; Muller, G.; Ordinas, J. I.; Mezzetti, A.; Maestro,
M.; Font-Bardia, M.; Solans, X. Organometallics 2005, 24, 4961.
(11) (a) Benito, M.; Rossell, O.; Seco, M.; Segale´s, G. Inorg. Chim. Acta
1999, 291, 247. (b) Benito, M.; Rossell, O.; Seco, M.; Segale´s, G.
Organometallics 1999, 18, 5191.
(12) Jolly, W.; Meijer, E. In Applied Homogeneous Catalysis with
Organometallic Compounds; Cornils, B., Herrmann, W. A., Eds.; Wiley-
VCH: New York, 1992.
(13) Tsuruta, H.; Imamoto, T. Synlett 2001, 999.
(14) Benito, M.; Rossell, O.; Seco, M.; Muller, G.; Ordinas, J. I.; Font-
Bardia, M.; Solans, X. Eur. J. Inorg. Chem. 2002, 2477.

1370 Organometallics, Vol. 25, No. 6, 2006
Rodr´ıguez et al.
Scheme 1
Table 1. Characteristic Features of Compounds nP1 (n ) 1-3) and nP2 (n ) 1, 2)
1H NMR (δ (ppm))a
13C NMR (δ (ppm))b
31P NMR
MS (MALDI-TOF)
mol peak (m/z)
R (CH2Cl2)
(deg)
compd
CH2P
Si(CH3)2CH2P
CH2P
(δ (ppm))c
1P1
2P1
1.21 (pq, J ) 7.5 Hz)d
1.18 (pq, J ) 15.6 Hz)
-0.20 (s)d
-0.23 (s)
-0.28 (s)
-0.24 (s)
-0.27 (s)
0.03 (s)
15.1 (d, J ) 28.4 Hz)e
13.2 (d, J ) 31.5 Hz)
-33.6 (s)
-33.5 (s)
349.1 (349.5 calcd) [M + H]+
-108.8
-74.3
1473.5 (1474.2 calcd) [M]•+
3P1
1.20 (pq, J ) 14.8 Hz)
13.3 (d, J ) 31.4 Hz)
-33.1 (s)
3549.6 (3549.8 calcd) [M]•+
-37.5
1P2
2P2
1.21 (s (br))
1.54 (s (br))
14.6 (d, J ) 29.9 Hz)
12.7 (d, J ) 30.7 Hz)
-33.2 (s)
-36.8 (s)
597.3 (598.6 calcd) [M + DTH]•+
+87.9
+65.5
0.00 (s)
1570.9 (1570.2 calcd) [M]•+
-0.02 (s)
a Conditions (except as noted): CDCl3, 400.1 MHz, 298 K. For all NMR spectra, abbreviations for multiplicity are as follows: s, singlet; d, doublet; p,
pseudo; q, quartet; br, broad. b Conditions (except as noted): CDCl3, 100.6 MHz, 298 K. c Conditions (except as noted): CDCl3, 101.3 MHz, 298 K.
d Conditions: CDCl3, 250.1 MHz, 298 K. e Conditions: CDCl3, 62.9 MHz, 298 K.
1
CHCl3, acetone, thf) and were characterized by H, 13C, and
31P NMR spectroscopy as well as by fast atom bombardment
(FAB) and electrospray mass spectrometry. The NMR data are
collected in Table 2, and Figure 2 shows the scheme used for
the assignation of the allylic fragment of the isomers.
The 1H NMR spectra contained in all cases two sets of signals
due to the presence of the two isomers. The integration revealed
isomeric ratios of 1:2 for P1 species and 1:1.2 for those
containing P2; no differences were noted between dendrimers
and model compounds of each phosphine. The higher discrimi-
nation effect of the 2-biphenylyl-substituted phosphine versus
the related 9-phenanthryl ligand indicates that the former induces
higher steric hindrance. Although no contribution of the skeleton
of the dendrimers is observed, it is worth noting that the silylated
fragments -Si(Me)2CH2- increase this discrimination effect
in comparison to the methylphosphines in the P1 compounds.10
The diastereomeric character of the methylene protons
SiCH2P was evidenced by different signals for the two nuclei
in each isomer. For example, for the compounds [PdCl(η3-2-
MeC3H4)(nP1)] one of these protons appears in the range 2.00-
1.85 ppm, overlapped with other signals, whereas the other
resonates as a multiplet at 1.70-1.50 ppm. The 13C NMR
spectra in the aliphatic region revealed two doublets (JC-P about
10 Hz) corresponding to CH2P of each isomer. The diaste-
reotopic nature of the methyl groups in the Me2Si fragments of
the dendritic skeleton in both isomers is also observed.
Confirmation of these assignations was obtained from NOESY
1H-1H and HSQC H-13C experiments. The two groups of
1
Figure 1. ORTEP view of 1P2-BH3, Hydrogen atoms have been
omitted for clarity. Thermal ellipsoids are drawn at the 50%
probability level. Selected distances (Å): P1-C21, 1.801(2); P1-
C1, 1.813(2); P1-C15, 1.813(2); P1-B1, 1.915(3); Si1-C21,
1.898(2).
signals of the allyl fragment for each pair of isomers were
assigned by taking into account the relative amounts of the major
and minor isomers, the coupling with 31P in a trans position,
1
and the two-dimensional NMR experiments (NOESY H-1H

Carbosilane Dendrimers
Organometallics, Vol. 25, No. 6, 2006 1371
Scheme 2
high regioselectivity and excellent enantioselectivity at very low
temperatures.19 On the other hand, the palladium catalysts are
generally employed under moderate reaction conditions between
0 °C and room temperature, although the concomitant isomer-
ization of the 3-aryl-1-butene to achiral 2-aryl-2-butenes
complicates their use. Despite this, the choice of a suitable chiral
ligand can surmount this drawback.20
Asymmetric hydrovinylation of vinylarenes to give 3-aryl-
1-butenes and related derivatives with palladium is achieved
by using [PdCl(allyl)L] (L ) monodentate phosphine) as the
precursor of the active species. Interestingly, the activity of the
catalyst improves with the increasing bulk of L up to a certain
point, beyond which a sharp decline is observed.21 The
preparation of dentritic precursors could be an alternative to be
used in continuous homogeneous catalysis performed in a
continuously operated membrane reactor.22 With these prece-
dents in mind, we focused our attention on the phosphine-
containing palladium complexes reported here. We were mainly
interested in determining the influence of the volume and nature
of the ligand L on the activity, codimerization-homodimer-
ization selectivity, isomerization of codimers, and enantio-
selectivity of the process. All the allylic precursors derived from
P1 and P2 are stable. It is worth noting that this is the first report
where chiral metallodendrimers have been used in catalytic
asymmetric hydrovinylation.
(a) Systems Based on P1. As the active catalysts in
hydrovinylation reactions are cationic species, we began this
study by preparing the precursors [Pd(L)(η3-2-MeC3H4)(nP1)]-
BF4 (L ) solvent, styrene) in situ from Pd-1P1, Pd-2P1, or Pd-
3P1, styrene, and AgBF4 in CH2Cl2. After the AgCl that formed
was filtered out, the solution was introduced immediately in
the reactor and was pressurized with ethylene. In none of the
cases did we try to isolate the precursors (using CH3CN as
solvent for example), given that previous work in our laboratory
with nonchiral palladodendrimers had shown that the compounds
stabilized with acetonitrile were less effective in terms of
activity.14 The results shown in Table 3 were obtained as a mean
value of at least three runs.
Gas chromatography and optical rotation measurements
showed that (S)-3-phenyl-1-butene was obtained preferably from
the (S)-phosphine-containing precursors in all experiments. No
significant differences were found in comparing the behavior
of the zeroth and first dendrimer generation. For example, at
moderate conversions, the selectivities were almost identical,
while the first generation showed a TOF that was slightly higher.
The formation of styrene dimers was in all cases very low and,
notably, the ee values found in both cases were excellent: 63%
for Pd-2P1 and 65% for Pd-3P1. The mononuclear model
compound displayed similar behavior at moderate conversion.
In this case, the ee was 68%. At higher conversions, the catalytic
properties of dendrimers were similar. With both dendritic
species a decrease of TOF was observed as a consequence of
the deactivation of the active species, since the precipitation of
1
and HSQC H-13C). 13C chemical shifts for allylic carbons
showed that the carbon atom located in a position trans to
phosphorus is more deshielded than the cis carbon. The methyl
allyl group appears in both isomers in nearly identical positions,
indicating that there is a very small discrimination between (R)-
and (S)-Pd environments produced by the chiral phosphine.
Notably, the phase-sensitive NOESY H-1H spectra of the
1
palladium derivatives at 298 K with a mixing time of 500 ms
showed the well-known η3-η1-η3 dynamic exchange in all
cases, while the pseudorotation mechanism was only detected
for the P2 compounds. Both mechanisms allow the rapid
interconversion of isomers at room temperature15 (see the
Supporting Information).
Hydrovinylation of Styrene. After the first report of a
hydrovinylation reaction using a RhCl3 catalyst,16 several metals
have been used, nickel17 and palladium18 being the most
successful ones. However, the asymmetric version of the
reaction has been much less studied.9 In general, it has been
observed that nickel-catalyzed hydrovinylation of olefins offers
(15) Trost, B. M.; Verhoeven, T. R. In ComprehensiVe Organometallic
Chemistry; Wilkinson, G., Stone, F. G. A., Abel, E. W., Eds.; Pergamon:
Oxford, U.K., 1982; Vol. 8, p 799.
(16) Alderson, T.; Jenner, E. L.; Lindsey, R. V. J. Am. Chem. Soc. 1965,
87, 5638.
(19) (a) Wegner, A.; Leitner, W. Chem. Commun. 1999, 1583. (b)
Bo¨smann, A.; Francio`, G.; Janssen, E.; Solinas, M.; Leitner, W.; Wasser-
scheid, P. Angew. Chem., Int. Ed. 2001, 40, 2697. (c) Park, H.; RajanBabu,
T. V. J. Am. Chem. Soc. 2002, 124, 734. (d) Francio`, G.; Faraone, F.; Leitner,
W. J. Am. Chem. Soc. 2002, 124, 736.
(17) See, for example: (a) Bogdanovic, B.; Henc, B.; Karmann, H.-G.;
Nu¨ssel, H.-G.; Walter, D.; Wilke, G. Ind. Eng. Chem. 1970, 62, 35. (b)
Nozima, H.; Kawata, N.; Nakamura, Y.; Maruya, K.; Mizoroki, T.; Ozaki,
A. Chem. Lett. 1973, 1163. (c) Ceder, R.; Muller, G.; Ordinas, J. I. J. Mol.
Catal. 1994, 92, 127. (d) Wilke, G. Angew. Chem., Int. Ed. Engl. 1988, 27,
185.
(18) See, for example: (a) Barlow, M. G.; Bryant, M. J.; Hazeldine, R.
N.; Mackie, A. G. J. Organomet. Chem. 1970, 21, 215. (b) Britovsek, G.
J. P.; Cavell, K. J.; Keim, W. J. Mol. Catal. 1996, 110, 77.
(20) (a) Englert, U.; Haerter, R.; Vasen, D.; Salzer, A.; Eggeling, E. B.;
Vogt, D. Organometallics 1999, 18, 4390. (b) Albert, J.; Cadena, M.;
Granell, J.; Muller, G.; Ordinas, J. I.; Panyella, D.; Puerta, C.; San˜udo, C.;
Valerga, P. Organometallics 1999, 18, 3511.
(21) Muller, G.; Ordinas, J. I. J. Mol. Catal. A: Chem. 1997, 125, 97.
(22) (a) Hovestad, N.; Eggeling, E.; Heidbu¨chel, H.; Jastrzebski, J.; Kragl,
U.; Keim, W.; Vogt, D.; van Koten, G. Angew. Chem., Int. Ed. 1999, 38,
1655. (b) Mu¨ller, C.; Nijkamp, M.; Vogt, D. Eur. J. Inorg. Chem. 2005,
4011.

1372 Organometallics, Vol. 25, No. 6, 2006
Rodr´ıguez et al.
1
Table 2. 31P and Selected H NMR (CDCl3, 298 K, 101.3 and 400.1 MHz) and 13C NMR (CDCl3, 298 K, 100.6 MHz) Data (δ
(ppm)) for the Complexes [PdCl(η3-2-Me-C3H4)(nP)]
(a) 31P and 1H NMRa
1H
complex
31P
allyl-Me
syn-tP
4.45 (m)
anti-tP
syn-cP
anti-cP
CH2P
Pd-1P1
minor
major
7.6
6.7
1.99 (s)
1.89 (s)
3.44 (d, 9.6)
3.21 (d, 10.4)
3.27 (s (br))
3.37 (s (br))
2.49 (s (br))
1.99-1.87
1.99-1.87 (m), 1.70-1.50 (m)
1.99-1.87 (m), 1.70-1.50 (m)
4.41 (m)
Pd-2P1
minor
major
7.3
6.4
1.97 (s)
1.87 (s)
4.42 (d (br), 6.4)
4.37 (d (br), 7.2)
3.41 (d, 10.0)
3.18 (d, 9.6)
3.28 (s (br))
3.33 (s (br))
2.47 (s (br))
1.96-1.87
1.96-1.87 (m), 1.67-1.53 (m)
1.96-1.87 (m), 1.67-1.53 (m)
Pd-3P1
minor
major
7.9
6.7
1.97 (s)
1.87 (s)
4.44 (d (br), 4.4)
4.39 (d (br), 4.4)
3.43 (d, 9.6)
3.19 (d, 10.0)
3.28 (s (br))
3.35 (s (br))
2.49 (s (br))
1.97-1.87
1.97-1.87 (m), 1.70-1.50 (m)
1.97-1.87 (m), 1.70-1.50 (m)
Pd-1P2
minor
major
7.9
4.0
1.82 (s)
1.53 (s)
4.41 (dd, 10.0, 2.8)
4.37 (dd, 10.0, 2.8)
3.47 (d, 10.4)
3.41 (d, 10.4)
3.24 (s)
2.83 (s)
2.53 (s)
2.54 (s)
2.10-1.92 (m)
2.17 (pt, 12.8), 2.10-1.92 (m)
Pd-2P2
minor
major
7.5
2.7
1.79 (s)
1.42 (s)
4.39-4.29 (m)
4.39-4.29 (m)
3.42 (d, 10.0)
3.38 (d, 10.0)
3.24 (s)
2.70 (s)
2.49 (s)
2.56 (s)
2.17-1.95 (m)
2.23 (pt, 12.8), 2.17-1.92 (m)
(b) 13C NMRa
complex
Callyl-Me
C-tP
C-cP
CH2P
Pd-1P1
minor
major
23.5 (s)
23.7 (s)
77.8-77.0
77.8-77.0
58.3 (s)
56.0 (s)
18.3 (d, 10.8)
16.2 (d, 10.8)
Pd-2P1
minor
major
23.5 (s)
23.8 (s)
77.8-77.0
77.8-77.0
58.4 (s)
57.0 (s)
16.9 (d (br), ∼10)
14.6 (d (br), ∼10)
Pd-3P1
minor
major
23.4 (s)
23.7 (s)
77.6-76.9
77.6-76.9
58.1 (s)
56.7 (s)
16.6 (d (br), ∼10)
14.4 (d, 11.0)
Pd-1P2
minor
major
23.4 (s)
23.0 (s)
77.7-77.0
77.7-77.0
59.3 (s)
60.3 (s)
16.7 (d, 10.8)
16.0 (d, 11.5)
Pd-2P2
minor
major
23.4 (s)
22.9 (s)
77.7-76.9
77.7-76.9
59.4 (s)
60.8 (s)
15.3 (d (br), ∼9)
14.6 (d (br), ∼10)
a Abbreviations for multiplicity are as follows: s, singlet; d, doublet; p, pseudo; t, triplet; q, quartet; m, multiplet; br, broad. Coupling constants J are
given in Hz.
Table 3. Hydrovinylation of Styrene Catalyzed by
[Pd(L)(η3-2-MeC3H4)(nP1)]BF4 Precursorsa
selec- oligo-
catalytic
conversnb tivityc
(%)
mers
(%)
TOFd
(h-1
run precursor t (h)
(%)
)
ee (%)
1
2
Pd-1P1
Pd-2P1
Pd-3P1
2
3
38.6
62.1
96.9
93.9
0.5
0.3
97
104
68 (S)
68 (S)
3
4
2
6
31.3
55.7
97.4
77.3
0.5
1.5
77
46
63 (S)
56 (S)
5
6
2
6
34.0
53.8
95.6
77.9
0.8
0.2
85
45
65 (S)
58 (S)
1
Figure 2. Nomenclature used in H and 13C NMR of the allylic
fragment.
a Conditions: reactions carried out at 25 °C, 15 bar of initial pressure of
ethylene, 10 mL of CH2Cl2, styrene/Pd/AgBF4 ratio 500/1/1. b Conversion
is the total amount of codimers formed. c Selectivity is the percent of
3-phenyl-1-butene with respect to the codimers. d TOF is calculated as the
total amount of phenylbutenes formed.
metallic palladium in the reactor was observed. Moreover, the
isomerization of 3-phenyl-1-butene to 2-phenyl-2-butene, fa-
vored at high conversions, produced loss of selectivity. In
contrast, the catalytic properties of the mononuclear Pd-1P1
remained unaltered with an increase in the conversion.
Studies performed on Ni-catalyzed asymmetric hydrovi-
nylation by RajanBabu19c and by Leitner and co-workers19d
detected an interesting counterion effect. A similar effect has
recently been described in palladium-catalyzed hydrovinyla-
tion,23 showing that the catalysis with the weakly coordinating
anion triflate, TfO-, gives poorer results in terms of reactivity
and enantioselectivity than do bulkier and even more weakly
coordinating anions, such as BF4-, PF6-, and SbF6-. The highest
enantioselectivity was achieved with the (fluoroaryl)borate anion
B[3,5-(CF3)2C6H3]4- (BARF-). Therefore, we tried to optimize
the reaction conditions for asymmetric hydrovinylation of
styrene by using the sodium salt of this coactivator. Thus, the
chloride anion was extracted by stirring the styrene/precursor
(23) Shi, W.; Xie, J.; Zhou, Q. Tetrahedron: Asymmetry 2005, 16, 705.

Carbosilane Dendrimers
Organometallics, Vol. 25, No. 6, 2006 1373
Table 4. Hydrovinylation of Styrene Catalyzed by
Table 5. Hydrovinylation of Styrene Catalyzed by
[Pd(L)(η3-2-MeC3H4)(nP1)]BARF Precursorsa
[Pd(L)(η3-2-MeC3H4)(nP2)]BF4 Precursorsa
selec- oligo-
selec- oligo-
catalytic
conversnb tivityc
(%)
mers
(%)
TOFd
catalytic
run precursor (h)
t
conversnb tivityc
(%)
mers
(%)
TOFd
(h-1
run precursor t (h)
(%)
(h-1
)
ee (%)
(%)
)
ee (%)
1e
2
3
Pd-2P1
2
2
6
19.8
29.5
58.4
98.0
98.5
92.0
0.5
1.0
1.8
47
74
48
77 (S)
75 (S)
75 (S)
1e
2f
3
Pd-1P2
Pd-2P2
2
92.9g
94.4g
59.5
0
11.7
95.6
7.1
5.6
6.3
1
16 (S)
1
/
1785 ∼0
2
2
4
Pd-3P1
2
27.4
98.6
1.1
69
79 (S)
4
5
1
80.8
47.4
89.7
96.9
3.0
3.4
1214 ∼0
1
/
1425 ∼0
a Conditions (unless otherwise noted): reactions carried out at 25 °C,
15 bar of initial pressure of ethylene, 10 mL of CH2Cl2, styrene/Pd/NaBARF
ratio 500/1/2. b Conversion is the total amount of codimers formed.
c Selectivity is the percent of 3-phenyl-1-butene with respect to the codimers.
d TOF is calculated as the total amount of phenylbutenes formed. e Styrene/
Pd/NaBARF ratio 500/1/1.
a Conditions (unless otherwise noted): reactions carried out at 15 °C,
15 bar of initial pressure of ethylene, 10 mL of CH2Cl2, styrene/Pd/AgBF4
ratio 1500/1/1. b Conversion is the total amount of codimers formed.
c Selectivity is the percent of 3-phenyl-1-butene with respect to the codimers.
d TOF is calculated as the total amount of phenylbutenes formed. e Styrene/
Pd/AgBF4 ratio 500/1/1, 25 °C. f Styrene/Pd/AgBF4 ratio 1000/1/1. g Total
conversion of starting styrene.
mixture with the stoichiometric amount of NaBARF for 20 min.
The catalytic results are listed in Table 4.
Table 6. Hydrovinylation of Styrene Catalyzed by
[Pd(L)(η3-2-MeC3H4)(nP2)]BARF Precursorsa
The analysis of Table 4 (run 1) shows that better selectivity
(98%) and enantiomeric excess (77% ee) were achieved.
However, in contrast with the results reported in the literature,
the activity of the catalyst decreased. One possible explanation
could be that the concentration of the cationic precursor is lower
than that expected, due to incomplete halide abstraction. Thus,
the reaction was repeated using double the amount of NaBARF
with the same stirring time to avoid the deactivation of the
catalyst. Under these conditions, the activity of the system was
comparable to that found with the use of the silver salt, whereas
the selectivity and the enantioselectivity were maintained at
excellent levels (75% for Pd-2P1 and 79% for Pd-3P1). The
behavior of Pd-2P1 at higher conversion was also examined
(run 3, Table 4) and compared with that exhibited by using
AgBF4. As can be seen, the use of NaBARF improved the
selectivity (92% versus 77%), while the enantioselectivity
continued to be higher (77% ee versus 56% ee). However, the
use of the sodium salt did not avoid the destabilization of the
catalyst, evidenced by the decrease of the TOF. In conclusion,
the Pd-P1 dendrimers/NaBARF catalyst constitutes a very
selective and enantioselective system for the hydrovinylation
reaction and is comparable to the best palladium systems
reported so far,24 but making use, in this case, of more accessible
systems.
selec- oligo-
catalytic
run precursor (h)
t
conversnb tivityc
(%)
mers
(%)
TOFd
(h-1
(%)
)
ee (%)
1
1
Pd-1P2
Pd-2P2
/
87.5e
6.9
12.5
38 (S)
2
2
1
2
3
/
17.4
40.6
93.5
93.2
4.3
5.2
524
610
16 (R)
18 (R)
1
a Conditions: reactions carried out at 15 °C, 15 bar of initial pressure of
ethylene, 10 mL of CH2Cl2, styrene/Pd/NaBARF ratio 1500/1/2. b Conver-
sion is the total amount of codimers formed. c Selectivity is the percent of
3-phenyl-1-butene with respect to the codimers. d TOF is calculated as the
total amount of phenylbutenes formed. e Total conversion of starting styrene.
The use of NaBARF did not improve the results (Table 6).
For the model compound Pd-1P2, the reaction was extremely
rapid, producing total conversion, so that a study of the process
could not be performed. Moreover, a large amount of styrene
dimers was observed. The results obtained with the dendrimer
were more fruitful. By using Pd-2P2 the rate of the process
decreased significantly, the selectivity was good (93.2%), and
the ratio of styrene dimers was comparable with that found with
the silver salt. The most remarkable difference, however, lies
in the enantioselectivity of the process. In all the experiments
described above, the major enantiomer of the 3-phenyl-1-butene
had the absolute configuration S, but surprisingly, in this case
the R isomer was found to be predominant. At this point, there
is no evidence of how the formation of ionic pairs can modify
the nature of the dendritic system in comparison with the simple
molecular one. In fact, in the present report and in others,26 the
results obtained with NaBARF as halide abstractor are in some
cases erratic and unreliable. Therefore, much work is still needed
to establish the implications of its use. Finally, it should be noted
that the dendritic system Pd-2P2/NaBARF remarkably decreases
the amount of styrene dimers formed.
(b) Systems Based on P2. The palladium precursors based
on P2 were analogously prepared as described for those based
on P1.
The catalytic results obtained using AgBF4 as halide abstractor
are listed in Table 5.
The most remarkable feature is the extraordinary activity of
Pd-1P2, already observed with similar phosphines.10 Thus, run
1 shows that all the 3-phenyl-1-butene formed was consumed
and run 2 demonstrates that the enantiomeric excess is the result
of the kinetic resolution of the isomerization to 2-phenyl-2-
butene.23,25 Run 3 shows moderate selectivity and permits an
estimation of the TOF value, although the enantioselectivity is
null. The activity of Pd-2P2 was somewhat more reduced, the
selectivity was consequently better, and as in the case of Pd-
1P2, it was unable to induce chirality (0% ee). In both systems,
the amount of styrene dimers formed was considerable (3-7%),
but less for the dendritic system, as expected on the basis of
steric arguments.
Conclusions
In summary, we have established a new efficient system for
palladium-catalyzed asymmetric hydrovinylation of styrene
using carbosilane dendrimers peripherally functionalized with
P-stereogenic monophosphines. The results in terms of activity,
selectivity, and enantiomeric excess strongly depend on the
nature of the phosphine and the halide abstractor. Thus, for the
palladium species containing the 2-biphenylyl-substituted phos-
(24) (a) Bayersdo¨rfer, R.; Ganter, B.; Englert, U.; Keim, W.; Vogt, D.
J. Organomet. Chem. 1998, 552, 187. (b) Albert, J.; Bosque, R.; Cadena,
J. M.; Delgado, S.; Granell, J.; Muller, G.; Ordinas, J. I.; Font-Bardia, M.;
Solans, X. Chem. Eur. J. 2002, 8, 2279.
(25) Eggeling, E.; Vogt, D.; Englert, U.; Haerter, R.; Vasen, D.; Salzer,
A. Organometallics 1999, 18, 4390.
(26) (a) Nandi, M.; Jin, J.; RajanBabu, T. V. J. Am. Chem. Soc. 1999,
121, 9899. (b) RajanBabu, T. V.; Nomura, N.; Jin, J.; Nandi, M.; Park, H.;
Sun, X. J. Org. Chem. 2003, 68, 8431. (c) Park, H.; Kumareswaran, R.;
RajanBabu, T. V. Tetrahedron 2005, 61, 6352.

1374 Organometallics, Vol. 25, No. 6, 2006
Rodr´ıguez et al.
(Ar), 10.0 (d, 1JCP ) 24.6 Hz, CH2P), 0.1 (s, CH3Si). 11B{1H} NMR
(80.2 MHz, CDCl3, 298 K; δ (ppm)): -35.3 (d, JBP ) 54.3 Hz).
Anal. Calcd for BC22H28PSi: C, 72.93; H, 7.79. Found: C, 72.26;
H, 7.61. [R]D ) -2.7° (c ) 0.945, CHCl3). HPLC (tR): 8.5 min.
phine (P1), the use of the sodium salt of BARF- instead of
AgBF4 increased notably the chemoselectivity and the enanti-
oselectivity of the process. The best results in terms of ee (79%
toward the S isomer) were obtained with Pd-3P1. On the other
hand, the systems Pd-P2/AgBF4 were found to be extraordinarily
active, although they were unable to induce enantioselectivity.
Surprisingly, the system Pd-2P2/NaBARF gave (R)-3-phenyl-
1-butene as the predominant isomer, in contrast to its analogous
model system Pd-1P2/NaBARF, which yielded (S)-3-phenyl-
1-butene, as did the other systems studied in this paper. More
experiments are needed to elucidate this fact.
1P2-BH3. This compound was prepared analogously to 1P1-BH3.
From the phosphine-borane P2-BH3 (0.600 g, 1.910 mmol), sec-
butyllithium (2.35 mL, 1.3 M cyclohexane/hexane solution, 3.056
mmol), and 1Cl (0.7 mL, 0.857 g/mL, 5.539 mmol), the product
was obtained as a white solid. Yield: 0.719 g (97%). 31P{1H} NMR
(121.6 MHz, CDCl3, 298 K; δ (ppm)): 13.9 (pd (br),1JBP ≈ 64
1
Hz). H NMR (400.1 MHz, CDCl3, 298 K; δ (ppm)): 8.74-7.26
(m, Ar, 14H), 2.00 (pt, J ≈ 13.6 Hz, CH2P, 1H), 1.78 (pt, J ≈ 13.6
Hz, CH2P, 1H), 1.60-0.80 (m, BH3, 3H), -0.13 (s, CH3Si, 9H).
13C{1H} NMR (50.0 MHz, CDCl3, 298 K; δ (ppm)): 138.2-122.6
(Ar), 12.8 (d, 1JCP ) 25.0 Hz, CH2P), 0.4 (s, CH3Si). 11B{1H} NMR
(80.2 MHz, CDCl3, 298 K; δ (ppm)): -35.0 (s (br)). Anal. Calcd
for BC24H28PSi: C, 74.61; H, 7.30. Found: C, 74.53; H, 7.51. [R]D
) -47.7° (c ) 1.010, CHCl3). HPLC (tR): 21.3 min.
1P1. 1P1-BH3 (0.120 g, 0.331 mmol) was dissolved in morpholine
(15 g, 15 mL), and the solution was stirred for 14 h at room
temperature. The morpholine was then removed in vacuo, and the
crude product was passed through a short column of alumina with
toluene as eluent. Evaporation of the solvent furnished the product
as a colorless oil. Yield: 0.100 g (87%). 31P{1H} NMR (101.3 MHz,
CDCl3, 298 K; δ (ppm)): -33.6 (s). 1H NMR (250.1 MHz, CDCl3,
298 K; δ (ppm)): 7.60-7.15 (m, Ar, 14H), 1.21 (pq, J ≈ 7.5 Hz,
CH2P, 2H), -0.20 (s, CH3Si, 9H). 13C{1H} NMR (62.9 MHz,
CDCl3, 298 K; δ (ppm)): 148.1-127.4 (Ar), 15.1 (d, 1JCP ) 28.4
Hz, CH2P), 0.1 (s, CH3). Anal. Calcd for C22H25PSi: C, 75.82; H,
7.23. Found: C, 75.63; H, 7.16. [R]D ) -108.8° (c ) 0.85, CH2-
Cl2). MS (MALDI-TOF; m/z): 349.1 (349.5 calcd) [M + H]+.
Experimental Section
General Data. All manipulations were performed under purified
nitrogen using standard Schlenk techniques. All solvents were
distilled from appropriate drying agents. 1H, 13C{1H}, 31P{1H}, 11B-
{1H}, and 29Si{1H} NMR spectra were obtained on Varian Gemini
200, Bruker DRX 250, Varian Unity 300, and Varian Mercury 400
spectrometers. 2D NMR spectra (NOESY 1H-1H and HSQC 1H-
13C) were recorded on a Varian Mercury 400 spectrometer.
Chemical shifts are reported in ppm relative to external standards
(SiMe4 for H, 13C, and 29Si, BF3‚Et2O for 11B, and 85% H3PO4
1
for 31P), and coupling constants are given in Hz. MS (FAB and
ES) spectra were recorded with a Fisions VGQuattro spectrometer
using NBA (3-nitrobenzyl alcohol) as a matrix for FAB spectra.
MALDI-TOF spectra were recorded with a Voyager DE-RP
(Perspective Biosystems) spectrometer using DTH (dithranol; 1,8,9-
trihydroxianthracene) as a matrix. The routine GC analyses were
performed on a Hewlett-Packard 5890 Series II gas chromatograph
(50 m Ultra 2 capillary column, 5% phenylmethylsilicone and 95%
dimethylsilicone) with an FID detector. HPLC analyses were carried
out in a Waters 717 Plus autosampler chromatograph with a Waters
996 multidiode array detector, fitted with a Chiracel OD-H chiral
column. The eluent, in all the determinations, was a mixture of
n-hexane and iPrOH (95/5). Optical rotations were measured on a
Perkin-Elmer 241MC spectropolarimeter at 23 °C. Enantiomeric
excesses were determined by GC on a Hewlett-Packard 5890 Series
II gas chromatograph (30 m Chiraldex DM column) with an FID
detector. Elemental analyses (C, H) were performed at the Servicio
de Microana´lisis del Centro de Investigacio´n y Desarrollo del
Consejo Superior de Investigaciones Cient´ıficas (CSIC) or at the
Serveis Cientificote`cnics of the Universitat Rovira i Virgili. The
palladium dimer [Pd(η3-2-Me-C3H4)(µ-Cl)]2 and the starting car-
bosilane dendrimers 2Cl and 3Cl as well as the chiral phosphines
P1-BH3 and P2-BH3 were prepared as previously described.10,11,27
Other reagents were used as received from commercial suppliers.
Synthesis. 1P1-BH3. The phosphine-borane P1-BH3 (0.400 g,
1.380 mmol) was dissolved in 15 mL of thf and cooled to -78 °C.
sec-Butyllithium (1.70 mL of 1.3 M cyclohexane/hexane solution,
2.210 mmol) was added slowly. After the resulting violet mixture
was stirred for 2 h, 0.5 mL of the silane 1Cl (0.857 g/mL, 3.944
mmol) was added by syringe. The temperature was maintained at
-78 °C for 4 h, and then the mixture was stirred for 14 h, slowly
reaching room temperature. Afterward, 20 mL of a solution HCl 1
M was added and the thf was removed in vacuo. The remaining
aqueous suspension was extracted with dichloromethane (3 × 10
mL), and the combined organic portions were dried with anhydrous
sodium sulfate. The solution was concentrated, and the addition of
ethanol caused the precipitation of 1P1-BH3 as a white solid.
Yield: 0.230 g (46%). 31P{1H} NMR (101.3 MHz, CDCl3, 298 K;
1P2. This product was prepared using the same procedure as for
1P1. With 1P2-BH3 (0.350 g, 0.906 mmol) and morpholine (20 g,
20 mL) as starting materials, the product was obtained as a colorless
oil. Yield: 0.270 g (80%). 31P{1H} NMR (101.3 MHz, CDCl3, 298
1
K; δ (ppm)): -33.2 (s). H NMR (400.1 MHz, CDCl3, 298 K; δ
(ppm)): 8.65-7.23 (m, Ar, 14H), 1.53 (s (br), CH2P, 2H), 0.03 (s,
CH3Si, 9H). 13C{1H} NMR (100.6 MHz, CDCl3, 298 K; δ (ppm)):
140.6-122.9 (Ar), 14.6 (d, 1JCP ) 29.9 Hz, CH2P), 0.3 (d, 3JCP
)
4.5 Hz, CH3Si). Anal. Calcd for C24H25PSi: C, 77.38; H, 6.76.
Found: C, 77.51; H, 6.80. [R]D ) +87.9° (c ) 0.85, CH2Cl2). MS
(MALDI-TOF; m/z): 597.3 (598.6 calcd) [M + DTH]•+ (matrix
aggregation, DTH), 373.2 (373.5 calcd) [M + H]+.
2P1. The phosphine-borane P1-BH3 (0.722 g, 2.487 mmol) was
dissolved in 20 mL of thf, and the solution was cooled to -78 °C.
sec-Butyllithium (1.84 mL of 1.3 M cyclohexane/hexane solution,
2.431 mmol) was added slowly. After the violet mixture that formed
was stirred for 2 h, a precooled solution of the silane 2Cl (0.246 g,
0.482 mmol) in thf was added. The temperature was maintained at
-78 °C for 4 h, and after that the mixture was stirred for 14 h,
slowly achieving room temperature. Afterward, 25 mL of a 0.5 M
HCl solution was added and the thf was removed in vacuo. The
remaining aqueous suspension was extracted with dichloromethane
(3 × 10 mL), and the combined organic portions were dried with
anhydrous sodium sulfate. After the CH2Cl2 was evaporated to
dryness, the crude product was dissolved in morpholine (20 g, 20
mL) and the solution was stirred for 14 h at room temperature.
Morpholine was then removed, and the crude product was passed
through a short column of alumina with toluene as eluent. A mixture
of the dendrimer 1P1 and the free phosphine P1 was obtained after
evaporating the toluene. The product was purified by flash
chromatography under N2 on a silica gel column with hexane/thf
(10/1) as eluent. The title compound was finally obtained as a white
foam. Yield: 0.290 g (41%). 31P{1H} NMR (101.3 MHz, CDCl3,
298 K; δ (ppm)): -33.5 (s). 1H NMR (400.1 MHz, CDCl3, 298 K;
δ (ppm)): 7.50-7.16 (m, Ar, 56H), 1.18 (pq, J ≈ 15.6 Hz, CH2P,
8H), 0.11-0.01 (m, CH2Si, 16H), -0.23 (s, CH3Si, 12H), -0.28
1
δ (ppm)): 17.1 (pd (br),1JBP ≈ 74 Hz). H NMR (250.1 MHz,
CDCl3, 298 K; δ (ppm)): 8.21-6.75 (m, Ar, 14H), 1.60-0.30 (m,
BH3, 3H), 1.19-0.89 (m, CH2P, 2H), -0.11 (s, CH3Si, 9H). 13C-
{1H} NMR (50.0 MHz, CDCl3, 298 K; δ (ppm)): 135.2-127.8
(27) Dent, W. T.; Long, R.; Wilkinson, A. J. J. Chem. Soc. 1964, 1585.

Carbosilane Dendrimers
Organometallics, Vol. 25, No. 6, 2006 1375
(s, CH3Si, 12H). 13C{1H} NMR (100.6 MHz, CDCl3, 298 K; δ
allyl-Me, major isomer), 23.5 (s, allyl-Me, minor isomer), 18.3 (d
1
1
1
(ppm)): 147.7-127.0 (Ar), 13.2 (d, JCP ) 31.5 Hz, CH2P), 8.7
(br), JCP ) 10.8 Hz, CH2P, minor isomer), 16.2 (d (br), JCP )
3
3
(d, JCP ) 3.8 Hz, CH2Si1), 2.5 (s, CH2Si0), -2.6 (d, JCP ) 4.5
10.8 Hz, CH2P, major isomer), 0.8 (d, 3JCP ) 3.8 Hz, CH3Si, both
isomers). Anal. Calcd for C26H32ClPPdSi: C, 57.25; H, 5.91.
Found: C, 57.31; H, 5.99. MS (FAB(+); m/z): 509.0 (510.0 calcd)
[M - Cl]+.
Hz, CH3Si). 29Si{1H} NMR (49.7 MHz, CDCl3, 298 K; δ (ppm)):
9.17 (s, Si0), 3.49 (d, JSiP ) 14.5 Hz, Si1). Anal. Calcd for
2
C92H104P4Si5: C, 74.96; H, 7.11. Found: C, 75.12; H, 7.20. [R]D
) -74.3° (c ) 0.65, CH2Cl2). MS (MALDI-TOF; m/z): 1473.5
(1474.2 calcd) [M]•+, 1214.4 (1213.9 calcd) [M - phosphine +
H]+.
Pd-1P2. This complex was obtained in the same way as for Pd-
1P1. With 1P2 (0.210 g, 0.558 mmol) and the palladium dimer [Pd-
(η3-2-Me-C3H4)(µ-Cl)]2 (0.110 g, 0.279 mmol) as starting materials,
a pale yellow solid was obtained. Yield: 0.305 g (96%). 31P{1H}
NMR (101.3 MHz, CDCl3, 298 K; δ (ppm)): 7.9 (s, minor isomer),
2P2. The procedure was analogous to that used for 2P1. In the
purification by chromatography, the eluent used was a mixture of
hexane and thf (10/3). With P2-BH3 (0.956 g, 3.032 mmol), sec-
butyllithium (2.24 mL of 1.3 M cyclohexane/hexane solution, 2.915
mmol), and 2Cl (0.300 g, 0.583 mmol) as starting materials, the
product was obtained as a white foam. Yield: 0.510 g (56%). 31P-
1
4.0 (s, major isomer). H NMR (400.1 MHz, CDCl3, 298 K; δ
(ppm)): 8.69-7.25 (m, Ar, both isomers), 4.41 (dd, J1 ) 10.0 Hz,
J2 ) 2.8 Hz, Hsyn-tP, minor isomer), 4.37 (dd, J1 ) 9.6 Hz, J2 )
2.8 Hz, Hsyn-tP, major isomer), 3.47 (d, J ) 10.0 Hz, Hanti-tP, minor
isomer), 3.41 (d, J ) 10.4 Hz, Hanti-tP, major isomer), 3.24 (s,
1
{1H} NMR (101.3 MHz, CDCl3, 298 K; δ (ppm)): -36.8 (s). H
NMR (400.1 MHz, CDCl3, 298 K; δ (ppm)): 8.85-7.21 (m, Ar,
56H), 1.54 (s (br), CH2P, 8H), 0.41 (m, CH2Si, 16H), 0.00 (s, CH3-
Si, 12H), -0.02 (s, CH3Si, 12H). 13C{1H} NMR (100.6 MHz,
CDCl3, 298 K; δ (ppm)): 140.6-122.8 (Ar), 12.7 (d, 1JCP ) 30.7
H
H
syn-cP, minor isomer), 2.83 (s, Hsyn-cP, major isomer), 2.54 (s,
anti-cP, major isomer), 2.53 (s, Hanti-cP, minor isomer), 2.17 (pt, J
) 12.8 Hz, CH2P, major isomer), 2.10-1.92 (m, CH2P, both
isomers), 1.82 (s, allyl-Me, minor isomer), 1.53 (s, allyl-Me, major
isomer), 0.08 (s, CH3Si, major isomer), 0.00 (s, CH3Si, minor
isomer). 13C{1H} NMR (100.6 MHz, CDCl3, 298 K; δ (ppm)):
135.5-122.8 (Ar + allyl-Cq, both isomers), 77.7-77.0 (m, allyl-
CtP, both isomers), 60.3 (s, allyl-CcP, major isomer), 59.3 (s, allyl-
CcP, minor isomer), 23.4 (s, allyl-Me, minor isomer), 23.0 (s, allyl-
Me, major isomer), 16.7 (d, 1JCP ) 10.8 Hz, CH2P, minor isomer),
3
Hz, CH2P), 9.0 (d, JCP ) 4.6 Hz, CH2Si1), 2.9 (s, CH2Si0), -2.1
(pt, 3JCP ≈ 5.4 Hz, CH3Si). 29Si{1H} NMR (49.7 MHz, CDCl3, 298
2
K; δ (ppm)): 9.55 (s, Si0), 3.96 (d, JSiP ) 14.6 Hz, Si1). Anal.
Calcd for C100H104P4Si5: C, 76.49; H, 6.68. Found: C, 76.52; H,
6.70. [R]D ) +65.5° (c ) 2.1, CH2Cl2). MS (MALDI-TOF; m/z):
1570.9 (1570.2 calcd) [M]•+, 1793.9 (1796.3 calcd) [M + DTH]+
(matrix aggregation, DTH), 1285.8 (1285.9 calcd) [M - phosphine
+ H]+.
1
3
16.0 (d, JCP ) 11.5 Hz, CH2P, major isomer), 1.0 (d, JCP ) 3.8
3
Hz, CH3Si, major isomer), 0.9 (d, JCP ) 3.0 Hz, CH3Si, minor
isomer). Anal. Calcd for C28H32ClPPdSi: C, 59.05; H, 5.66.
Found: C, 59.27; H, 5.78%. MS (FAB(+); m/z): 533.0 (534.0
calcd) [M - Cl]+.
Pd-2P1. This complex was obtained using the same procedure
as for Pd-1P1. With 2P1 (0.182 g, 0.123 mmol) and the palladium
dimer [Pd(η3-2-Me-C3H4)(µ-Cl)]2 (0.097 g, 0.246 mmol) as starting
materials, a yellow solid was obtained. Yield: 0.265 g (95%). 31P-
{1H} NMR (101.3 MHz, CDCl3, 298 K; δ (ppm)): 7.3 (s, minor
isomer), 6.4 (s, major isomer). 1H NMR (400.1 MHz, CDCl3, 298
K; δ (ppm)): 8.00-7.00 (m, Ar, both isomers), 4.42 (d (br), J )
3P1. This was prepared in the same way as 2P1. In the purification
by chromatography, the eluent used was a mixture of hexane and
thf (10/3). With P1-BH3 (0.714 g, 2.462 mmol), sec-butyllithium
(1.81 mL of 1.3 M cyclohexane/hexane solution, 2.350 mmol), and
3Cl (0.365 g, 0.224 mmol) as starting materials, the product was
obtained as a white foam. Yield: 0.120 g (15%). 31P{1H} NMR
(101.3 MHz, CDCl3, 298 K; δ (ppm)): -33.1 (s). 1H NMR (400.1
MHz, CDCl3, 298 K; δ (ppm)): 7.48-7.18 (m, Ar, 112H), 1.20
(pq, J ≈ 14.8 Hz, CH2P, 16H), 0.40-0.00 (m, CH2Si, 64H), -0.09
(s, CH3Si1, 48H), -0.24 (s (br), CH3Si3 + CH3Si2, 24H + 12H),
-0.27 (s, CH3Si3, 24H). 13C{1H} NMR (100.6 MHz, CDCl3, 298
6.4 Hz, Hsyn-tP, minor isomer), 4.37 (d (br), J ) 7.2 Hz, Hsyn-tP
,
1
K; δ (ppm)): 147.7-127.2 (Ar), 13.3 (d, JCP ) 31.4 Hz, CH2P),
major isomer), 3.41 (d, J ) 10.0 Hz, Hanti-tP, minor isomer), 3.33
8.8 (d, 3JCP ) 4.6 Hz, CH2Si3), 7.0-2.8 (m, CH2Si), -2.4 (d, 3JCP
) 5.3 Hz, CH3Si3), -4.1 (s, CH3Si1), -6.4 (s, CH3Si2). 29Si{1H}
NMR (49.7 MHz, CDCl3, 298 K; δ (ppm)): 9.43 (s, Si0), 7.88 (s,
(s (br), Hsyn-cP, major isomer), 3.28 (s (br), Hsyn-cP, minor isomer),
3.18 (d, J ) 9.6 Hz, Hanti-tP, major isomer), 2.47 (s (br), Hanti-cP
,
minor isomer), 1.97 (s, allyl-Me, minor isomer), 1.96-1.87 (m,
CH2P both isomers + Hanti-cP major isomer), 1.87 (s, allyl-Me,
major isomer), 1.67-1.53 (m, CH2P, both isomers), 0.10-(-0.10)
(m, CH2Si + CH3Si, both isomers), -0.37 (s, CH3Si, minor isomer),
-0.38 (s, CH3Si, major isomer). 13C{1H} NMR (100.6 MHz,
CDCl3, 298 K; δ (ppm)): 146.5-127.2 (Ar + allyl-Cq, both
isomers), 77.8-77.0 (m, allyl-CtP, both isomers), 58.4 (s (br), allyl-
CcP, minor isomer), 57.0 (s (br), allyl-CcP, major isomer), 23.8 (s,
allyl-Me, major isomer), 23.5 (s, allyl-Me, minor isomer), 16.9 (d
2
Si2), 5.66 (s, Si1), 3.55 (d, JSiP ) 14.0 Hz, Si3). Anal. Calcd for
C
212H276P8Si17: C, 71.73; H, 7.84. Found: C, 71.89; H, 7.87. [R]D
) -37.5° (c ) 1.90, CH2Cl2). MS (MALDI-TOF; m/z): 3549.6
(3549.8 calcd) [M]•+.
Pd-1P1. The model compound 1P1 (0.100 g, 0.286 mmol) was
dissolved in 15 mL of CH2Cl2, and the palladium dimer [Pd(η3-
2-Me-C3H4)(µ-Cl)]2 (0.056 g, 0.143 mmol) was added. After the
mixture was stirred for 20 min, the solvent was removed and the
resulting pasty solid was recrystallized from CH2Cl2/hexane. The
product Pd-1P1 was obtained as a yellow solid. Yield: 0.150 g
(96%). 31P{1H} NMR (101.3 MHz, CDCl3, 298 K; δ (ppm)): 7.6
1
1
(br), JCP ≈ 10 Hz, CH2P, minor isomer), 14.6 (d (br), JCP ≈ 10
3
Hz, CH2P, major isomer), 9.4 (d, JCP ) 4.5 Hz, CH2Si1, major
3
isomer), 9.3 (d, JCP ≈ 4 Hz, CH2Si1, minor isomer), 2.7 (s, CH2-
1
Si, both isomers), -1.3-(-2.1) (m, CH3Si, both isomers). Anal.
Calcd for C108H132Cl4P4Pd4Si5: C, 57.35; H, 5.88. Found: C, 57.56;
H, 5.98. MS (ES(+); m/z): 2226.9 (2226.5 calcd) [M - Cl]+.
(s, minor isomer), 6.7 (s, major isomer). H NMR (400.1 MHz,
CDCl3, 298 K; δ (ppm)): 8.00-6.90 (m, Ar, both isomers), 4.45
(m, Hsyn-tP, minor isomer), 4.41 (m, Hsyn-tP, major isomer), 3.44
(d, J ) 9.6 Hz, Hanti-tP, minor isomer), 3.37 (s (br), Hsyn-cP, major
isomer), 3.27 (s (br), Hsyn-cP, minor isomer), 3.21 (d, J ) 10.4 Hz,
Pd-2P2. This procedure was analogous to that used for Pd-1P1.
With 2P2 (0.191 g, 0.122 mmol) and the palladium dimer [Pd(η3-
2-Me-C3H4)(µ-Cl)]2 (0.096 g, 0.244 mmol) as starting materials, a
pale yellow solid was obtained using toluene instead of hexane to
precipitate the product. Yield: 0.280 g (98%). 31P{1H} NMR (101.3
MHz, CDCl3, 298 K; δ (ppm)): 7.5 (s, minor isomer), 2.7 (s, major
Hanti-tP, major isomer), 2.49 (s (br), Hanti-cP, minor isomer), 1.99
(s, allyl-Me, minor isomer), 1.99-1.87 (m, CH2P both isomers +
Hanti-cP minor isomer), 1.89 (s, allyl-Me, major isomer), 1.70-
1.50 (m, CH2P both isomers), -0.11 (s, CH3Si, major isomer),
-0.14 (s, CH3Si, minor isomer). 13C{1H} NMR (100.6 MHz,
CDCl3, 298 K; δ (ppm)): 146.6-127.1 (Ar + allyl-Cq, both
isomers), 77.8-77.0 (m, allyl-CtP, both isomers), 58.3 (s (br), allyl-
CcP, minor isomer), 56.0 (s (br), allyl-CcP, major isomer), 23.7 (s,
1
isomer). H NMR (400.1 MHz, CDCl3, 298 K; δ (ppm)): 8.75-
7.33 (m, Ar, both isomers), 4.39-4.29 (m, Hsyn-tP, both isomers),
3.42 (d, J ) 10.0 Hz, Hanti-tP, minor isomer), 3.38 (d, J ) 10.0
Hz, Hanti-tP, major isomer), 3.24 (s, Hsyn-cP, minor isomer), 2.70

1376 Organometallics, Vol. 25, No. 6, 2006
Rodr´ıguez et al.
(s, Hsyn-cP, major isomer), 2.56 (s, Hanti-cP, major isomer), 2.49 (s,
monoclinic, space group P21, a ) 10.373(2) Å, b ) 9.943(2) Å, c
) 11.265(2) Å, â ) 107.692(4)°, V ) 1106.9(4) Å3, Z ) 2, Dcalcd
Hanti-cP, minor isomer), 2.23 (pt, J ) 12.8 Hz, CH2P, major isomer),
2.17-1.95 (m, CH2P, both isomers), 1.79 (s, allyl-Me, minor
isomer), 1.42 (s, allyl-Me, major isomer), 0.50-0.18 (m, CH2Si,
both isomers), 0.20 (s, CH3Si, major isomer), 0.09 (s, CH3Si, minor
isomer), 0.02 (s, CH3Si, major isomer), -0.08 (s, CH3Si, minor
isomer). 13C{1H} NMR (100.6 MHz, CDCl3, 298 K; δ (ppm)):
135.6-122.9 (Ar + allyl-Cq, both isomers), 77.7-76.9 (m, allyl-
CtP, both isomers), 60.8 (s, allyl-CcP, major isomer), 59.4 (s, allyl-
CcP, minor isomer), 23.4 (s, allyl-Me, minor isomer), 22.9 (s, allyl-
Me, major isomer), 15.3 (d (br), 1JCP ≈ 9 Hz, CH2P, minor isomer),
) 1.159 g cm-3
.
Hydrovinylation Reactions. Hydrovinylation reactions were
performed in a stainless steel autoclave fitted with an external jacket
connected to an isobutyl alcohol bath, and the temperature was
controlled using a thermostat to (0.5 °C. The internal temperature
was monitored using a Thermopar coupled to a digital recorder,
whereas the internal pressure was continuously measured as a
function of time with a Linseis L-200 recorder.
The catalytic solutions were prepared with styrene/Pd molar ratios
of 500/1 and 1000/1, using 0.02 and 0.04 mol of styrene,
respectively, and 4.0 × 10-5 mol of Pd (4.0 × 10-5 mol of Pd-1P
compounds, 1.0 × 10-5 mol of Pd-2P metallodendrimers, or 5 ×
10-6 mol for Pd-3P1). Catalytic solutions with the styrene/Pd molar
ratio 1500/1 were prepared with 0.04 mol of styrene and 2.7 ×
10-5 mol of Pd (2.7 × 10-5 mol of Pd-1P2 or 6.7 × 10-6 mol of
Pd-2P2).
(a) Catalytic Solutions Prepared with AgBF4 as Halide
Abstractor. A mixture of the suitable neutral palladium precursor,
styrene, and AgBF4 (AgBF4/Pd ratio 1/1) in 10 mL of dry and
freshly distilled CH2Cl2 was stirred for 10 min in the dark. After
the AgCl that formed was filtered off, the solution was placed in
the autoclave, which had previously been purged by successive
vacuum/nitrogen cycles and thermostated at the desired temperature.
Ethylene was admitted until a pressure of 15 bar was reached. After
the time indicated for each reaction, the autoclave was slowly
depressurized and HCl 10% solution (10 cm3) was added. The
mixture was stirred for 10 min in order to quench the catalyst. The
CH2Cl2 layer was decanted off and dried with Na2SO4. The
quantitative distribution of products and their ee values were
determined by GC analysis.
(b) Catalytic Solutions Prepared with NaBARF as Halide
Abstractor. A mixture of the suitable neutral palladium complex,
styrene, and NaBARF (NaBARF/Pd ratio 2/1) in 10 mL of dry
and freshly distilled CH2Cl2 was stirred for 20 min in the dark.
After the NaCl that formed was filtered off, the solution was placed
in the autoclave, which had previously been purged by successive
vacuum/nitrogen cycles and thermostated at the desired temperature.
Ethylene was admitted until a pressure of 15 bar was reached. After
the time indicated for each reaction, the autoclave was slowly
depressurized and HCl 10% solution (10 cm3) was added. The
mixture was stirred for 10 min in order to quench the catalyst. The
CH2Cl2 layer was decanted off and dried with Na2SO4. The
quantitative distribution of products and their ee values were
determined by GC analysis.
1
3
14.6 (d (br), JCP ≈ 10 Hz, CH2P, major isomer), 9.6 (d (br), JCP
≈ 4 Hz, CH2Si1, both isomers), 3.0 (s (br), CH2Si0, both isomers),
-1.1 (s (br), CH3Si, major isomer), -1.2 (d, 3JCP ) 4.0 Hz, CH3-
Si, minor isomer), -1.6 (s (br), CH3Si, major isomer), -1.7 (m,
CH3Si, minor isomer). Anal. Calcd for C116H132Cl4P4Pd4Si5: C,
59.08; H, 5.64. Found: C, 59.30; H, 5.78. MS (ES(+); m/z): 2323.4
(2322.6 calcd) [M - Cl]+, 2125.4 (2125.6 calcd) [M - Pd(2-Me-
C3H4)Cl - Cl]+.
Pd-3P1. This complex was obtained using the same procedure
as for Pd-1P1. With 3P1 (0.111 g, 0.031 mmol) and the palladium
dimer [Pd(η3-2-Me-C3H4)(µ-Cl)]2 (0.049 g, 0.125 mmol) as starting
materials, a yellow solid was obtained. Yield: 0.155 g (97%). 31P-
{1H} NMR (101.3 MHz, CDCl3, 298 K; δ (ppm)): 7.9 (s, minor
isomer), 6.7 (s, major isomer). 1H NMR (400.1 MHz, CDCl3, 298
K; δ (ppm)): 7.95-7.00 (m, Ar, both isomers), 4.44 (d (br), J )
4.4 Hz, Hsyn-tP, minor isomer), 4.39 (d (br), J ) 4.4 Hz, Hsyn-tP
,
major isomer), 3.43 (d, J ) 9.6 Hz, Hanti-tP, minor isomer), 3.35 (s
(br), Hsyn-cP, major isomer), 3.28 (s (br), Hsyn-cP, minor isomer),
3.19 (d, J ) 10.0 Hz, Hanti-tP, major isomer), 2.49 (s (br), Hanti-cP
,
minor isomer), 1.97 (s, allyl-Me, minor isomer), 1.97-1.87 (m,
CH2P both isomers + Hanti-cP major isomer), 1.87 (s, allyl-Me,
major isomer), 1.70-1.50 (m, CH2P, both isomers), 0.40-(-0.40)
(m, CH2Si + CH3Si, both isomers). 13C{1H} NMR (100.6 MHz,
CDCl3, 298 K; δ (ppm)):146.4-127.2 (Ar + allyl-Cq, both isomers),
77.6-76.9 (m, allyl-CtP, both isomers CH2), 58.1 (s (br), allyl-CcP,
minor isomer), 56.7 (s (br), allyl-CcP, major isomer), 23.7 (s, allyl-
Me, major isomer), 23.4 (s, allyl-Me, minor isomer), 16.6 (d (br),
1JCP ≈ 10 Hz, CH2P, minor isomer), 14.4 (d (br), 1JCP ) 11.0 Hz,
CH2P, major isomer), 9.2-2.8 (m, CH2Si, both isomers), -1.4-
(-6.4) (m, CH3Si, both isomers). Anal. Calcd for C244H332Cl8P8-
Pd8Si17: C, 57.17; H, 6.53. Found: C, 57.32; H, 6.67.
Structural Characterization. A colorless crystal of 1P2-BH3
(0.86 × 0.65 × 0.54 mm) was mounted in a Bruker SMART CCD
diffractometer. Intensities were collected at 293(2) K with graphite-
monochromated Mo KR radiation (λ ) 0.710 73 Å). A total of
3701 unique reflections were collected, of which 3556 with I >
2σ(I) were used in refinement. SHELXTL software was used for
solution and refinement.28 Absortion corrections were made with
the SADABS program.29 The structure was solved by direct
methods and refined using full-matrix least squares on F2. R )
0.039 and Rw ) 0.098, with the Flack parameter30 ø ) 0.06(8).
Crystal data for 1P2-BH3: BC22H28PSi, molecular weight 386.33,
Acknowledgment. We acknowledge support from the
Ministerio de Ciencia y Tecnolog´ıa (Projects BQU2003-01131
and CTQ2004-01546) and the CIRIT (Generalitat de Catalunya)
(Project 2001SGR 00054). L-I.R. and A.G. are indebted to the
Ministerio de Ciencia y Tecnolog´ıa for a scholarship. We also
thank Mr. Sebastian Gischig for the crystal structure determina-
tions performed at the Department of Chemistry, ETH Ho¨ng-
gerberg, Zu¨rich, Switzerland.
(28) (a) Sheldrick, G. M. SHELXS 97: A Computer Program for Crystal
Structural Determination; University of Go¨ttingen, Go¨ttingen, Germany,
1997. (b) Sheldrick, G. M. SHELXS 97: A Computer Program for Crystal
Structural Refinement; University of Go¨ttingen, Go¨ttingen, Germany, 1997.
(29) Sheldrick, G. M. SADABS: A Program for Empirical Absorption
Correction of Area Detector Data; University of Go¨ttingen, Go¨ttingen,
Germany, 1996. Based on the method of: Blessing, R. H. Acta Crystallogr.
1995, A51, 33.
Supporting Information Available: CIF file giving crystal data
1
for the phosphine 1P2-BH3 and tables showing the NOESY H-
1H cross-peaks between isomers of compounds Pd-3P1 and Pd-
2P2. This material is available free of charge via the Internet at
http://pubs.acs.org.
(30) Flack, H. D. Acta Crystallogr. 1983, A39, 876.
OM050915S