Better performance of monodentate P-stereogenic phosphanes compared to bidentate analogues in Pd-catalyzed asymmetric allylic alkylations

Article abstract of DOI:10.1002/ejic.201000308

The cationic allylpalladium complexes 3a-3f, 4a, 4e, 5e of type [Pd(η³-2-Me-C₃H₄)P₂]PF ₆ were synthesized using a group of monodentate P-stereogenic phosphanes, P=PPhRR' (a-f) and diphosphanes (PhRPCH₂)₂ (1a, 1e) or PhRPCH₂Si(Me)₂CH₂PPhR (2e). The analogous cationic complexes with the disubstituted allyl group (η³-1,3-Ph₂-C₃H₃) and monodentate phosphanes were not isolated as stable solids: only [PdCl(η³-1,3-Ph₂-C₃H₃)P] (6a, 6d) were obtained. Palladium allyl complexes were screened as precatalysts in the allylic substitution of rac-3-acetoxy-1,3-diphenyl-1-propene (I) and (E)-3-acetoxy-1-phenyl-1-propene (III) with dimethyl malonate as the nucleophile. The various catalytic precursors showed a wide range of activity and selectivity. The bismonodentate phosphane complexes 3 are more active than the bidentate analogues. With regard to the regioselectivity, precursors containing monodentate phosphanes favour the formation of the linear product in the allylic substitution of cinnamyl acetate (III) compared with those containing bidentate phosphanes. With substrate I, compounds with the diphosphanes 1a and 1e, containing a five-membered chelate ring, gave low enantioselectivities (less than 10% ee), but those with the diphosphane 2e, forming a six-membered chelate ring or with two monodentate phosphanes, afforded products with moderate enantioselectivity under standard conditions (ee up to 74 %). The results show that the performance of precursors containing monodentate phosphanes was superior to those containing bidentate ligands in both activity and selectivity.

Full text of DOI:10.1002/ejic.201000308

FULL PAPER
DOI: 10.1002/ejic.201000308
Better Performance of Monodentate P-Stereogenic Phosphanes Compared to
Bidentate Analogues in Pd-Catalyzed Asymmetric Allylic Alkylations
Arnald Grabulosa,[a] Guillermo Muller,*[a] Rosa Ceder,[a] and Miguel Ángel Maestro[b]
Keywords: Palladium / Allylic compounds / Asymmetric catalysis / Nucleophilic substitution
The cationic allylpalladium complexes 3a–3f, 4a, 4e, 5e of
type [Pd(η3-2-Me-C3H4)P2]PF6 were synthesized using a
group of monodentate P-stereogenic phosphanes, P=PPhRRЈ
(a–f) and diphosphanes (PhRPCH2)2 (1a, 1e) or
than the bidentate analogues. With regard to the regioselec-
tivity, precursors containing monodentate phosphanes favour
the formation of the linear product in the allylic substitution
of cinnamyl acetate (III) compared with those containing bi-
PhRPCH2Si(Me)2CH2PPhR (2e). The analogous cationic com- dentate phosphanes. With substrate I, compounds with the
plexes with the disubstituted allyl group (η3-1,3-Ph2-C3H3)
and monodentate phosphanes were not isolated as stable sol-
ids; only [PdCl(η3-1,3-Ph2-C3H3)P] (6a, 6d) were obtained.
Palladium allyl complexes were screened as precatalysts in
diphosphanes 1a and 1e, containing a five-membered che-
late ring, gave low enantioselectivities (less than 10% ee),
but those with the diphosphane 2e, forming a six-membered
chelate ring or with two monodentate phosphanes, afforded
the allylic substitution of rac-3-acetoxy-1,3-diphenyl-1-pro- products with moderate enantioselectivity under standard
pene (I) and (E)-3-acetoxy-1-phenyl-1-propene (III) with di-
methyl malonate as the nucleophile. The various catalytic
precursors showed a wide range of activity and selectivity.
The bismonodentate phosphane complexes 3 are more active
conditions (ee up to 74%). The results show that the perform-
ance of precursors containing monodentate phosphanes was
superior to those containing bidentate ligands in both activity
and selectivity.
palladium(I) complexes formed by the interaction of the
Pd0 and allyl-PdII species of the standard catalytic cycle,[4]
careful kinetic studies of the ion-pair implications when dif-
ferent stabilizing anions are present,[5] observations of the
chloride effect in both systems, the consequences of strong
regioretention in the allylic substitution[6] and the non-
equivalence of the catalytic precursors prepared using mix-
tures of [PdCl(µ-Cl)(allyl)]2 plus ligand or ionic [Pd(allyl)-
(ligand)2]X compounds.[7] Impressive turnover numbers
have been obtained using chiral diphosphite ligands in the
allylic alkylation and amination of rac-1,3-diphenyl-3-acet-
oxyprop-1-ene,[8a] and the origin of enantioselectivities has
been explored using a library of phosphite-phosphoramid-
ite ligands.[8b] Furthermore, the cationic nature of the palla-
dium allyl intermediates allowed the use of mass spectro-
metric screening (ESI-MS) to evaluate the enantioselectivity
of a chiral catalyst or to measure the discrimination power
of several chiral ligands in a single experiment.[9] Other met-
als have also been used successfully in allylic substitution
reactions: for example, high regioselectivity and enantio-
selectivity have been obtained with Ir complexes containing
a single phosphoramidite ligand.[10]
Introduction
Palladium-catalyzed asymmetric allylic substitution has
been thoroughly investigated in recent years. A large
number of ligands containing mainly phosphorus-, nitro-
gen- or sulfur-coordinating atoms have been prepared and
tested in catalysis.[1,2] In particular, the use of P-stereogenic
phosphanes has been widely studied, initially with limited
success, like those obtained with (R,R)-DIPAMP.[3] Today,
however, several P-stereogenic monodentate or bidentate
phosphanes produce good results in the benchmark allylic
alkylation of 1,3-diphenylallyl acetate (see examples in
Table 1 and in ref.[2]).
The reaction is characterized by a well-established ge-
neric catalytic cycle involving an oxidative addition step fol-
lowed by a nucleophilic attack on an allylpalladium(II) in-
termediate. It is normally assumed that the resting state of
the process is the allylpalladium intermediate but recent fin-
dings have improved our understanding of the reaction.
These include the observation of allyl-bridged dinuclear
[a] Departament de Química Inorgànica, Universitat de Barcelona,
Martí i Franquès 1–11, 08028 Barcelona, Spain
Fax: +34-934907725
The effect of monodentate phosphanes on the regioselec-
tivity and enantioselectivity of symmetric and asymmetric
allylic substrates has been studied in some detail. For exam-
ple, some monodentate phosphoramidites show over 90%
ee in the allylic alkylation of 1,3-diphenylallyl acetate.[19] In
the regioselectivity for asymmetric substrates like (E)-3-
E-mail: guillermo.muller@qi.ub.es
[b] Área de Química Orgánica, Departamento de Química
Fundamental, Facultade de Ciencias, Campus da Zapateira,
Universidade da Coruña,
15071 A Coruña, Spain
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201000308.
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P-Stereogenic Phosphanes in Asymmetric Allylic Alkylations
Table 1. Asymmetric allylic alkylation of rac-3-acetoxy-1,3-di- acetoxy-1-phenyl-1-propene (cinnamyl acetate), the linear
phenyl-1-propene with dimethyl malonate catalyzed by Pd/P-
product of substitution is usually favoured. However, if
PCy3 is used the stereochemistry of the starting allylic acet-
stereogenic phosphane complexes.[a]
ate is retained (“memory effect”).[20] This effect is also ob-
served when MOP is used.[21] With monodentate diami-
dophosphites[22] or 9-PBN[23] the ee obtained in the bench-
mark reaction can be 97%. When it is possible to compare
the results of palladium catalysts stabilized by a bidentate
or two monodentate phosphanes containing the same sub-
stituents, the rate observed is usually faster in the systems
that contain monodentate ligands, whereas the selectivity is
similar in both cases.[14] When the palladium/monodentate
phosphane ratio is reduced to 1:1 the enantioselectivity of
the reaction severely decreases.[14,24] In this reaction the 3,5-
dialkylphenyl effect has also been observed, which increases
the ee in the alkylation of cyclohexenyl acetate by 20%.[25]
In this study we have applied cationic palladium com-
plexes containing two monodentate or a bidentate P-
stereogenic phosphane as catalytic precursors in the allylic
substitution reaction of rac-3-acetoxy-1,3-diphenyl-1-pro-
pene (I) and (E)-3-acetoxy-1-phenyl-1-propene (III) with di-
methyl malonate as the nucleophile. From the results of ac-
tivity and selectivity it has been possible to compare the
performance of catalytic systems containing monodentate
phosphanes with those containing bidentate phosphanes
with analogous substituents at the phosphorus atoms.
Results and Discussion
Ligand Synthesis
Monodentate P-stereogenic phosphanes a–f have already
been described (Scheme 1).[26] From borane-protected
methylphosphanes aЈ, cЈ and eЈ diphosphanes were pre-
pared by the activation of a methyl proton by sec-BuLi,
followed by a coupling reaction using CuCl2, or directly
with SiCl2Me2. Both methods have been described else-
where.[27–30]
[a] Reaction conditions were not the same for all the entries. The
results shown are the best reported for each ligand. [b] Absolute
configuration not reported.
Scheme 1. Monodentate phosphanes a–f, the corresponding bo-
rane-protected phosphanes are indicated with primes.
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A. Grabulosa, G. Muller, R. Ceder, M. Á. Maestro
FULL PAPER
(1)
(2)
CuII-promoted oxidative coupling is widely used [Equa- Preparation of Allyl Palladium Complexes
tion (1)]. Careful adjustment of the excess of the alkyllith-
ium compound is needed to ensure that mixtures of the
Reaction of [Pd(η3-2-Me-C3H4)(µ-Cl)]2 with the appro-
desired diphosphane and the starting monophosphane are priate amount of ligand (a–f, 1a, 1e and 2e) in the presence
not obtained. The preparation of 1aЈ and 1eЈ was success- of an excess of ammonium hexafluorophosphate afforded
ful, but we were unable to obtain the pure diphosphane ionic allylic palladium complexes of the general formula
containing the o-biphenylyl group, possibly because this [Pd(η3-2-Me-C3H4)(P2)]PF6 (see 3a–3f, 4a, 4e, 5e in
group is more sterically demanding. Several signals between Scheme 2). The yields were in the range 40–60%. These
–27 and +35 ppm were observed in the 31P{1H} NMR spec- compounds are soluble in coordinating solvents (acetoni-
trum of the reaction mixture from cЈ, indicating the decom- trile, acetone, DMF), but only scarcely soluble in nonco-
position of the phosphane.
ordinating solvents such as toluene, chloroform or dichloro-
By the methodology depicted in Equation (2) the diphos- methane. Complexes 3c, 3d and 3f containing phosphanes
phanes containing 1-naphthyl (2a) and 9-phenanthryl (2e) with the 2-biphenylyl substituent decomposed in solution,
groups were obtained in excellent yields. Phosphanes 1a and precluding the acquisition of their 13C NMR spectra.
2a have already been reported by Mezzetti and cowork-
All these complexes were fully characterized by the usual
techniques (see Exp. Section). From IR spectroscopy data,
ers.[29,30]
The mixtures can be purified by column chromatography. the most interesting absorption is the C–C stretch of the
Starting from monodentate phosphanes of the S-absolute allylic moiety: for these complexes, one signal of medium
configuration, the diphosphanes 1 and 2 are expected to intensity is observed in the range 1440–1420 cm–1. As ex-
retain the same configuration (S,S) as reported for analo- pected, the intense ν(P–F) vibration band is present at
gous ligands. The diastereomeric ratio of around 98:2 was 750Ϯ5 cm–1.
improved by a single recrystallization. The crystal structure
Since all the allylic complexes contain two stereogenic
of allyl complex 3e (vide infra) confirms the configuration phosphorus atoms with the same absolute configuration,
of the stereogenic phosphorus atoms proposed for 1e.
the PdP2 fragment displays C2 symmetry. Accordingly, only
Scheme 2.
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P-Stereogenic Phosphanes in Asymmetric Allylic Alkylations
one isomer is expected to appear in solution, as was con-
firmed by 31P NMR spectroscopy. However, because the C2
symmetry is lost in the presence of the allyl ligand, two
coupled signals are observed in all compounds showing a
second-order effect.[31a] Interestingly, one of the doublets
shows a considerable broadening, enhanced in nonpolar
Some 1H 2D NOESY experiments were performed at
solvents, as was also reported by Filipuzzi et al.[31b] (see room temperature to examine the nuclear Overhauser ef-
Supporting Information). This broadening is more pro- fects between different protons and proton-exchange pro-
nounced in the complexes of the more crowded phosphanes, cesses. The most relevant NOE interactions were observed
1
in accordance with the different lability of each ligand. H between the syn and anti protons of each terminal allyl car-
NMR spectroscopic data were acquired in CDCl3 or [D6]- bon, and also between the syn protons and the central
acetone at room temperature. The spectra revealed a single methyl-allyl group. No contacts were found between the
stereoisomer, showing different chemical shifts for the two phosphanes and the allylic protons. Furthermore, no off-
halves of the symmetric allyl group (Hanti ϶ HantiЈ; Hsyn
϶
diagonal exchange signals were observed and therefore no
H
synЈ). The signals of the anti protons appeared as doublets interconversion between the allyl protons was detected un-
because of the coupling with the phosphorus atom in the der the conditions of measurement.
trans position. Table 2 and Table 3 list relevant 31P NMR
When 13C NMR spectra of 3c, 3d and 3f containing the
1
and H NMR spectroscopic data. 13C NMR spectra show phosphanes with the 2-biphenylyl substituent were recorded
the same pattern: the terminal allylic atoms appear as dou- an unexpected number of low intensity signals appeared.
blets because of the coupling with the phosphorus atom in Proton spectra showed the decomposition of the initial
the trans position, and only complex 4a shows coupling complex after a few hours, suggesting the decoordination
with both the trans- and cis-phosphorus atoms (see Sup- of one phosphane. This process would be favoured with the
porting Information). The maximum differences between more sterically demanding phosphanes and is supported by
the chemical shifts of the terminal allylic carbon atoms are the different pattern of the 31P signals of the two phos-
less than 3 ppm. Other effects of the allyl fragment include phanes in several ionic complexes of type 3.
the nonequivalence of the two methyl groups in the silyl
Acceptable crystals for X-ray determination were ob-
linker of the bridge in 5e, and the nonequivalence of the tained for complex 4e. The data obtained for the organome-
pair of protons of each methylene bridge in the other di- tallic cation were sufficient to establish the atom connectiv-
phosphanes.
ity although disordered CH2Cl2 and toluene molecules are
1
Table 2. 31P NMR and selected H NMR spectroscopic data[a] (δ in ppm, J [Hz]) for complexes [Pd(η3-(2-Me-C3H4))P2]PF6.
Complex
δ31P
P–CHn
P–X–CH3
allyl CH3
syn
anti
3a
–0.4
(d, 38.4)
2.2
1.74
(d, 8.0)
1.97
–
1.65
3.53
(s, br.)
3.74
3.65
(d, 10.0)
3.34
–
(d, 38.4)
21.3
(d, 32.4)
(d, 8.0)
1.20 –
1.72 (m)
(s, br.)
3.96
(s, br.)
(d, 9.6)
3.60
(d, 9.6)
3b
0.24, 0.47
(d, 14.8),
(d, 14.8)
1.89
24.2
(d, 32.9)
0.59, 0.67
(dd, 14.0, 6.8),
(dd, 14.4, 6.4)
–
4.43
(s, br.)
3.48
(d, 9.2)
3c[b]
3d[c]
3e
10.5
(d, 39.5)
12.4
(d, 39.5)
39.4
(d, 31.0)
40.0
(d, 31.0)
0.5
(d, 37.8)
3.7
(d, 37.8)
120.7
0.98
(d, 7.8)
1.33
(d, 7.7)
1.26 –
1.68 (m)
1.95
2.20
1.81
1.61
3.54
(s, br.)
3.75
(s, br.)
4.13
(s, br.)
4.42
(s, br.)
3.76
(s, br.)
3.92
(s, br.)
3.71
3.14
(d, 9.2)
3.00
(d, 9.1)
3.60
(d, 9.5)
3.36
(d, 8.8)
3.78
(d, 10.0)
3.47
(d, 9.6)
1.96
–
0.61 –
0.91 (m)
1.80
(d, 8.0)
2.09
(d, 7.6)
–
–
–
3f[d]
3.11
(d, 53.9)
124.7
(d, 10.4)
3.21
(s, br.)
3.85
(d, 8.8)
2.38
–
(d, 53.9)
(d, 10.0)
(s, br.)
(d, 8.8)
1
[a] CDCl3, 298 K, 31P NMR and H NMR spectra measured at 101.2 and 400.1 MHz, respectively. [b] 1H NMR spectra measured in
CD3COCD3 and at 250.1 MHz. [c] 1H NMR spectra measured at 250.1 MHz. [d] 1H NMR spectra measured at 500.1 MHz.
Eur. J. Inorg. Chem. 2010, 3372–3383
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A. Grabulosa, G. Muller, R. Ceder, M. Á. Maestro
Table 3. 31P NMR and selected H NMR spectroscopic data[a] (δ in ppm, J [Hz]) for complexes [Pd(η3-(2-Me-C3H4))(P–P)]PF6.
FULL PAPER
1
Complex
δ31P
P–CH2–
–Si–CH3
allyl CH3
Hsyn
Hanti
4a
44.2
(d, 29.7)
45.6
(d, 29.7)
44.7
(d, 29.8)
45.4
(d, 29.98)
12.2
(d, 47.9)
13.4
2.38–2.59
(m, 2 H)
3.14–3.30
(m, 2 H)
2.40–2.70
(m, 2 H)
3.18–3.33
(m, 2 H)
2.36–2.44
(m)
–
1.71
4.11
(s, br.)
4.54
(s, br.)
4.11
(s, br.)
4.52
(s, br.)
3.63
(t, br., 4.0)
3.79
3.27
(d, 10.4)
2.95
(d, 10.0)
3.31
(d, 9.6)
3.03
(d, 10.0)
3.46
(d, 10.4)
3.23
4e
–
1.69
1.78
5g[b]
–0.56
–0.48
(d, 47.6)
(t, br., 4.0)
(d, 10.0)
1
[a] CDCl3, 298 K, 31P NMR and H NMR spectra recorded at 101.2 and 400.1 MHz, resectively. [b] Measured in CD3COCD3.
included in the crystal. The ORTEP representation of the plexes present in solution was investigated in one case[33]
cation is given in Figure 1. Table 4 contains selected bond and the ratio between the two homocombinations and the
lengths and angles. Pd–P and Pd–C allylic bond lengths heterocombination observed was 1:1:16. We have checked
were in good agreement with other π-allylic PdII complexes the combination of the chiral phosphane a and tribenzyl-
containing either two monodentate or one bidentate phos- phosphane in detail, and the result is shown in Scheme 3.
phane and the 2-Me-allyl fragment reported in the litera- All the possible combinations of cationic complexes were
ture.[32]
observed by 31P NMR spectroscopy. The two isomers of the
complex corresponding to the heterocombination of ligands
accounted for 65% of the mixture. The precipitate from tol-
uene solutions mainly contained the achiral ligand homo-
combination and the heterocombination. Finally, by pen-
tane precipitation we separated the chiral ligand homocom-
bination, which was only slightly contaminated by the other
complexes. The amount of the precursor containing the
heterocombination of ligands was too small to be used in
catalysis and no further essays were performed.
Figure 1. ORTEP view of the molecular structure of 4e. Hydrogen
atoms, solvents and hexafluorophosphate anion have been omitted
for clarity.
Table 4. Selected bond lengths [Å] and angles [°] for complex 4e.
Pd(1)–C(3)
Pd(1)–C(1)
Pd(1)–C(2)
Pd(1)–P(1)
Pd(1)–P(2)
P(1)–C(5)
P(2)–C(6)
C(1)–C(2)
C(2)–C(3)
C(2)–C(4)
C(5)–C(6)
2.135(9)
2.158(10)
2.178(9)
2.285(2)
2.297(2)
1.826(10)
1.817(10)
1.402(14)
1.425(13)
1.436(16)
1.575(15)
C(3)–Pd(1)–C(1) 67.8(4)
P(1)–Pd(1)–P(2) 87.11(9)
C(1)–C(2)–C(3)
115.6(9)
Combination of Phosphanes
Scheme 3. Relative amounts of homo-/heterocombination of palla-
dium allyl complexes type 3 with a 1:1 ratio of PBn3 and a phos-
phanes.
Heterocombinations of monodentate chiral phosphonites
with achiral phosphites or phosphanes[33] and chiral phos-
phoramidites with achiral phosphanes[34] improved the con-
version and enantioselectivity in the Rh-catalyzed hydro-
genation reactions compared to the systems formed by
homocombination of two chiral ligands. This strategy has
Palladium-Catalyzed Asymmetric Allylic Alkylation of rac-
3-Acetoxy-1,3-diphenyl-1-propene (rac-I)
Palladium complexes 3, 4 and 5 were tested as precata-
been further extended.[35] The relative amounts of the com- lysts in the allylic alkylation of rac-I, the model substrate
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P-Stereogenic Phosphanes in Asymmetric Allylic Alkylations
for the allylic substitution processes. This group of com- rection of the asymmetric induction was inverted for the
plexes was suitable for the comparison of the importance more hindered isopropylphosphanes (entries 1 vs. 2 and 3
of the metallacycle size and the consequences of the mono- vs. 4). The origin of this inversion must be produced in the
dentate or bidentate nature of the ligands (electronically very crowded allyl intermediate that could not be isolated
analogous) and their influence on the activity and selectiv- since the crystal structures of the phosphane–boranes c and
ity of the process. The fragment PdP2 displays C2 symmetry d do not show any remarkable differences.[26] For this
in all complexes.
reason the neutral allylic complex [PdCl(η3-2-Me-C3H4)(f)]
was tested as a precursor in the reaction (entries 7 and 8).
It showed a lower but still remarkable ee and an initially
lower rate of reaction, as expected for the less favoured ini-
tial nucleophilic attack on a neutral intermediate. The reor-
ganization of the neutral complex [PdCl(η3-2-Me-C3H4)(f)]
affording cationic species that may be suitable as catalytic
precursors can be considered.[39] Similar results have been
reported when the ratio Pd/L is reduced to 1:1, with a severe
decrease of the ee.[24]
Complexes of type 3 with two monodentate phosphanes
showed higher activity than those we observed with dithio-
ethers or bis(oxazolines), and similar activity to that re-
ported for phosphane-oxazolines[37] or phosphane-phos-
phoramidite ligands[38] (entries 1–6, Table 5). Complexes 4
and 5 containing bidentate phosphanes showed lower rates
of reaction, which is consistent with the findings of
Imamoto[14] and Mezzetti.[12] Complex 3e, which contains
two monodentate phosphanes, showed a higher selectivity
than 4e or 5e, which have the same group of substituents
at the phosphorus atom. Complexes 4 containing a five-
membered metallic cycle gave almost racemic mixtures of
the substitution products, as reported by Bosnich,[3] who
used bis aryl-substituted phosphanes. The results showed a
clear dependence of the enantioselectivity on the phos-
phorus substitution in the MePhPR series. The enantio-
meric excesses follow the trend: 2-biphenylyl Ͻ 1-naphthyl
Ͻ 9-phenanthryl (entries 1, 3 and 5, respectively). The in-
crease of steric hindrance of the sp3 arm is more sensitive.
When the methyl group (entry 3 phosphane S-c) was substi-
tuted by a methoxy (entry 6 phosphane R-f) or an isopropyl
group (entry 4 phosphane S-d) the ee improved but the di-
Preparation of η3-1,3-Diphenylallyl Palladium Complexes
The synthesis of palladium η3-1,3-diphenylallyl bisphos-
phane intermediates were attempted by reaction among the
palladium dimer, monodentate phosphane and NH4PF6.[40]
Only neutral [PdCl(η3-1,3-diphenylallyl)(P)] complexes
were obtained. The use of an excess of phosphane and
AgPF6 did not afford any stable species. Possibly, the more
sterically demanding 1,3-diphenylallyl group hinders the
stabilization of the desired ionic compounds. The neutral
complexes were fully characterized by the usual techniques.
1H NMR signals from the CDCl3 solution of complex 6a
at room temperature showed broad, poorly defined signals.
Therefore, spectra were recorded at temperatures ranging
from 25 to –40 °C (see Supporting Information). In con-
trast, the spectrum of compound 6d is well defined at room
temperature.
1D and 2D NMR spectroscopic data indicate that the
number of isomers observed in these solutions are limited
to those with the phenyl groups of the allyl ligand in syn-
positions.[40,41] So, two isomers were observed in complexes
6a and 6d in the relative proportions shown in Table 6
[Equation (3)]. 31P NMR spectra of both complexes show
two signals, which is consistent with the presence of the two
isomers. Discrimination between them increases with the
size of the phosphane (6d Ͼ 6a), but it is similar to that
observed in the analogous [PdCl(η3-2-Me-C3H4)(P)] com-
plexes.[26] NOESY spectra showed dynamic exchange be-
tween the groups of hydrogen atoms. In particular, the ex-
change between anti-allylic protons of the two isomers indi-
cates that the allyl pseudorotation is the main operating
mechanism of exchange.[42]
A set of signals is observed for each isomer. The central
allylic hydrogen appears as a triplet at a lower field than
the terminal allylic hydrogen atoms. In addition, the anti-
allylic hydrogen atom located on the carbon atom trans to
the phosphorus atom appears (coupled with the central hy-
drogen and phosphorus atoms) at lower fields than those in
the cis position (which are only coupled to the central hy-
drogen atom). This is also observed for similar com-
pounds.[14]
Table 5. Results of asymmetric allylic alkylation of rac-3-acetoxy-
1,3-diphenyl-1-propene (I) with dimethyl malonate catalyzed by
type 3, 4 and 5 complexes.[a]
Entry
Complex
t [h]
Conversion [%][b] ee [%][c]
1
2
3
4
5
6
7
8
3a
1
1
1
1
1
1
1
24
1
24
1
Ͼ99.0
92.6
89.5
28 (R)
45 (S)
8 (R)
14 (S)
68 (R)
74 (S)
– (–)
60 (S)
– (–)
5 (S)
3b
3c
3d
87.5
3e
Ͼ99.0
Ͼ99.0
Ͻ2.0
Ͼ99.0
2.0
Ͼ99.0
4.1
Ͼ99.0
99
12.3
3f
[PdCl(allyl)(f)]
[PdCl(allyl)(f)]
9
4a
4a
4e
10
11
12
13
14
15
– (–)
4e
24
4
1
8 (R)
27 (R)
58 (R)
60 (R)
5a[d]
5e
5e
24
Ͼ99.0
[a] Catalytic conditions: 0.02 mmol of [Pd], complex 3, 4 or 5,
1 mmol of rac-1,3-diphenyl-2-propenyl acetate, 3 mmol of dimethyl
malonate, 3 mmol of BSA and a catalytic amount of KOAc in 4 mL
of CH2Cl2. [b] Conversion percentage based on the substrate.
[c] Enantiomeric excesses determined by HPLC with a Chiralcel-
OD column. Absolute configuration, in parentheses, determined by
optical rotation: ref.[36] [d] Ref.[12]
Eur. J. Inorg. Chem. 2010, 3372–3383
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3377

A. Grabulosa, G. Muller, R. Ceder, M. Á. Maestro
FULL PAPER
Table 6. 31P NMR and selected allyl 1H NMR and 13C NMR spectroscopic data[a] (δ in ppm, J [Hz]) for complexes [PdCl(η3-1,3-
Ph2C3H3)(P)] 6a and 6d.
Complex
31P NMR
δ
1H NMR
anti-tP
1H NMR
anti-cP
1H NMR
central
13C NMR
anti-tP
13C NMR
anti-cP
13C NMR
central
6a
(253 K)
major
1.2
7.8
7.7
5.44
(dd, 13.5, 10)
4.08
(d, 11)
6.19
(ps-t, 11.5)
97.7
(d, 25.2)
58.6
(s)
109.1
(s)
minor
1
5.49
(dd, 13.5, 10)
3.97
(d, 11.5)
–6.34
(ov.)
96.7
(d, 25.2)
59.2
(s)
108.4
(s)
6d
(298 K)
major
1.4
33.6
31.4
4.75
(ps-t, 10.5)
3.88
(d, 11)
6.21
(ps-t, 12)
98.1
(d, 24.4)
80.0
(s)
106.8
(s)
minor
1
4.88
(ps-t, 10.5)
3.57
(d, 11)
6.13
(ps-t, 12)
96.2
(d, 25.2)
80.3
(s)
107.4
(s)
[a] CDCl3, 31P NMR, 1H NMR and 13C NMR spectra measured at 101.2, 500 and 100.6 MHz, respectively; ps-t: pseudo triplet, ov.:
overlapped.
(3)
13C chemical shifts for the allylic carbon atoms show that
the central atom resonates at a lower field than the terminal
Figure 2. ORTEP view of the molecular structure of 6d. Hydrogen
atoms have been omitted for clarity.
ones and that the carbon atom located at a position trans
to phosphorus is less shielded than the cis atom, and is allylic ligand with respect to the plane defined by the palla-
coupled to the phosphorus atom. Compared with the anal- dium, chlorine and phosphorus atoms is heavily distorted:
ogous [PdCl(η3-2-Me-C3H4)(P)] complexes,[26] the carbon C(3) lies –0.021 Å away from the plane, while C(1) is at
atoms trans to phosphorus are about 10 ppm more de- 0.577 Å, probably because of the disposition of the biphenyl
shielded in the diphenylallyl complexes. Complex 6d shows substituent of the coordinated phosphane. This distortion
a large shift to lower fields in the allylic carbon atom cis to is similar to those observed in the [Pd(η3-1,3-
phosphorus, possibly as a result of the proximity of the o- Ph2C3H3)(PPh3)2]+ cation.[43] However, in the crystal struc-
phenyl group of the phosphane, as reflected in the crystal ture of the analogous [PdCl(η3-2-Me-C3H4)(P(iPr)(o-Ph2)-
structure (see below).
Ph)] complex,[26] the allyl moiety (C1 and C3) remains in
Suitable crystals for X-ray diffraction measurements were the plane defined by the same three atoms. These features
obtained from dichloromethane solutions of 6d by slow dif- suggest that the steric hindrance of the P(iPr)(o-Ph2)Ph
fusion of hexane at 4 °C (Figure 2).
phosphane blocks the formation of the [Pd(η3-1,3-
The crystal structure shows only the diastereoisomer Ph2C3H3)P2]+ cation. The difference between the two Pd–C
with R configuration at the palladium centre with the sub- bond lengths, trans to the P and trans to the Cl atom (2.253
stituted allyl ligand in syn,syn geometry. The palladium vs. 2.194 Å), indicates a major trans influence of the phos-
atom shows
a distorted square-planar coordination, phane ligand, and consequently a different double bond
bonded to one chlorine ligand, one phosphorus ligand and character of the C(1)–C(2) and C(2)–C(3) allylic bonds (see
the three allylic carbon atoms (Table 7). The position of the Table 7).
3378
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© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2010, 3372–3383

P-Stereogenic Phosphanes in Asymmetric Allylic Alkylations
Table 7. Selected bond lengths [Å] and bond angles [°] for 6d.
Table 8. Results obtained in the allylic alkylation of (E)-3-acetoxy-
1-phenyl-1-propene (III) with dimethyl malonate catalyzed by type
3, 4 and 5 complexes.[a]
Pd(1)–Cl(1)
Pd(1)–P(1)
Pd(1)–C(1)
Pd(1)–C(2)
Pd(1)–C(3)
C(1)–C(2)
C(2)–C(3)
2.4202(10)
2.3308(11)
2.253(4)
2.180(4)
2.194(4)
1.387(6)
1.429(6)
Cl(1)–Pd(1)–P(1)
C(1)–Pd(1)–C(3)
C(2)–Pd(1)–P(1)
C(2)–Pd(1)–Cl(1) 117.43(11)
C(1)–C(2)–C(3) 119.7(4)
103.22(4)
66.41(15)
138.24(11)
Entry Complex
t [min] Conv. [%][b] Branched/linear[c]
[e]
1
2
3
4
5
6
3a
10
20
60
60
60
60
30
45
30
45
60
60
150
60
60
60
6.2
–
3a
Ͼ99.0
Ͼ99.0
Ͼ99.0
Ͼ99.0
Ͼ99.0
37.2
Ͼ99.0
4.0
Ͼ99.0
Ͼ99.0
Ͻ2.0
10.0
1:15
1:Ͼ20
1:15
1:16
1:Ͼ20
1:17
1:16
3b
3c
3e
3f
7[d]
8[d]
9
[PdCl(allyl)(a)]
[PdCl(allyl)(a)]
[PdCl(allyl)(a)]
[PdCl(allyl)(a)]
[PdCl(allyl)(b)]
[PdCl(allyl)(d)]
[PdCl(allyl)(d)]
4a
Palladium-Catalyzed Asymmetric Allylic Alkylation of
(E)-3-Acetoxy-1-phenyl-1-propene (III)
[e]
–
In order to compare the regioselectivity of the allylic alk-
ylation reaction catalyzed by these palladium complexes,
the substrate (E)-3-acetoxy-1-phenyl-1-propene (III) was
used (Table 8). The reaction for this substrate was faster
than for I and total conversion was achieved in less than
10
11
12
13
14
15
1:18
1:Ͼ20
[e]
–
–
[e]
86.2
Ͼ99.0
85.1
1:9
1:8
1:13
4e
5e
one hour. The main difference was that for III a similar 16
activity was observed with catalytic precursors containing
bidentate phosphanes (4 and 5, entries 14–16) and those
stabilized by monodentate phosphanes (3, entries 1–6). A
short induction time for the activation of the catalytic pre-
cursor is necessary (entries 1 and 2, 7 and 8 or 9 and 10)
as indicated by the colour change from pale yellow to
orange. A similar induction time was observed when the
catalytic precursor was prepared in a ratio Pd/ligand: 1:1
(entries 7 and 8). Furthermore, the initially inactive neutral
allylic complex [PdCl(η3-2-Me-C3H4)(a)] achieved complete
conversion in 45 min (entries 9 and 10). Only the neutral
complex, which contained the most hindered phosphane
(d), showed limited activity (entries 12 and 13).
[a] Reaction conditions: 0.02 mmol of palladium complex, 1 mmol
of cinnamyl acetate, 3 mmol BSA and a catalytic amount of KOAc
in 4 mL of CH2Cl2. [b] Conversion percentage based on the sub-
strate, determined by GC. [c] Branched/linear ratio of isomers ob-
tained by GC. [d] Palladium precursor obtained by reaction of the
[PdCl(allyl)(phosphane)] complex with AgBF4 in the presence of
cinnamyl acetate. [e] The small conversion observed precludes the
formulation of a confident ratio of isomers.
100.0°.[43,45] The low amounts of branched product ob-
tained precluded the measurement of enantiomeric excesses.
A similar range of selectivity was observed when bulky
monodentate phosphoramidites were used.[19]
When the cationic precursor species were obtained from
[PdCl(η3-2-Me-C3H4), a], where the ratio Pd/P was 1:1, the
reaction was slower (entries 1, 2, 7, 8) but the regioselectiv-
ity was similar. The use of the neutral complexes (Pd/P =
1:1) as precursors led to the same regioselectivity as that
observed for the cationic complexes 3 (Pd/P = 1:2).
Conclusions
All precursors favoured the formation of the linear prod-
In summary, we have obtained a group of cationic palla-
uct, but the amount of branched compound b-IV obtained dium compounds 3, 4 and 5 containing P-stereogenic
with type-4 precursors (entries 14 and 15) was larger than monodentate and bidentate phosphanes that have two dif-
the amount obtained with types 3 or 5 (Table 8). The bite ferent aryl substituents at each phosphorus atom. The dif-
angle of bidentate ligands strongly affects the regioselectiv- ferent labilities of the two coordinated phosphorus atoms
ity. Van Leeuwen et al. studied the palladium-catalyzed al- were dependent on the size of the substituents, as is clearly
lylic alkylation of 2-hexenyl acetate, and showed that the demonstrated by comparing the 31P NMR spectra of the
increase in the bite angle of the diphosphanes leads to the complexes in which a methyl group was substituted by an
increase in the proportion of the linear isomer.[44] When isopropyl group or in the sequence 3a, 3c, 3e (see Support-
the phosphane substituents are analogous, the pure steric ing Information).
interaction of the diphosphane and the allyl fragment deter-
All the cationic complexes were tested in Pd-catalyzed
mines the outcome.[44] Our results with complexes 4 and 5 allylic substitution reactions. The alkylation of 3-acetoxy-
follow the same trend. The selectivity observed with com- 1-phenyl-1-propene showed that the monodentate ligands
pounds 3, which contain two monodentate phosphanes, can favour the formation of the linear product. When alkylation
be explained in the same way, bearing in mind that the co- was tested with rac-3-acetoxy-1,3-diphenyl-1 propene some
ordination of two bulky monodentate phosphanes will noteworthy results were obtained. Complexes 3 containing
produce large P–Pd–P angles. For example the angles for two monodentate phosphanes were more active than 4 and
palladium allyl bis(triphenylphosphane) complexes are 5.
Eur. J. Inorg. Chem. 2010, 3372–3383
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3379

A. Grabulosa, G. Muller, R. Ceder, M. Á. Maestro
FULL PAPER
Synthesis
With regard to the asymmetric induction, the enantio-
selectivity with catalysts 3 increases with the size of the sub-
stituents of the phosphane, achieving the best result of 74%
ee with the phosphinite ligand f. The sequence of ee ob-
served was as follows: P(2-biphenylyl)PhMe (3c, 8%), P(2-
biphenylyl)Ph(iPr) (3d, 14%), P(2-biphenylyl)Ph(OMe) (3f,
74%), P(2-biphenylyl)(tBu)Me (81%)[11] and P(2-biphen-
ylyl)CyMe (96%).[11] This sequence illustrates the diversity
and subtlety of factors determining the discrimination abil-
ity of apparently similar ligands. The lack of enantio-
selectivity observed for bidentate ligands with an ethylene
bridge (1a and 1e) is similar to the results reported for DI-
PAMP,[3] all of which contain two different aryl substitu-
ents. However, with the same bridge but with methyl and
tert-butyl substituents, 88% ee has been obtained,[14] and
with a completely planar bridge, 92% ee has been re-
ported.[18] In both cases bisalkylaryl-monodentate or biden-
tate phosphanes gave the best selectivities. Bidentate ligands
with three atoms in the bridge (2) showed a similar discrimi-
nation ability to that obtained with monodentate phos-
phanes.
(S,S)-1,2-Bis[(1-naphthyl)phenylphosphanyl]ethane–Borane(P) (S,S)-
1aЈ: The phosphane–borane (S)-aЈ (0.816 g, 3.1 mmol) was dis-
solved in THF (30 mL) and the solution was cooled to –78 °C. Sec-
butyllithium (2.9 mL of a 1.3  solution in hexane/cyclohexane,
3.7 mmol) was added by syringe and the mixture was stirred for
2 h. A precooled (–78 °C) suspension of CuCl2 (1.25 g, 9.2 mmol)
in THF (50 mL) was added and the mixture was warmed slowly to
room temperature. A HCl solution (1 , 10 mL) was added and the
mixture was extracted with ethyl acetate. The combined organic
fractions were washed with a 10% NaOH solution (3ϫ10 mL) and
eventually with an ammonia solution. The organic fraction was
washed with brine and dried with anhydrous sodium sulfate. Fil-
tration and evaporation of the solvent furnished the product as a
white foam that could appear contaminated with small amounts of
the methylmonophosphane–borane (S)-aЈ (Ͻ10%). The monosub-
stituted product was removed by flash chromatography (SiO2,
CH2Cl2). Combined yield 0.800 g (99%). 1H NMR (250.1 MHz,
CDCl3, 298 K): δ = 0.20–2.10 (s, br., 6 H), 2.60 (s, br., 4 H), 7.37–
7.98 (m, 24 H, Ar) ppm. 13C{1H} NMR (62.9 MHz, CDCl3,
298 K): δ = 20.2 (d, JCP = 37.5 Hz, CH2), 125.2–134.8 (m, 1 C, CH,
Ar) ppm. 31P{1H} NMR (101.1 MHz, CDCl3, 298 K): δ = +18.6 (s,
br.) ppm.
The results of this study confirm that P-stereogenic
monodentate phosphanes show higher activity and an anal-
ogous or better discrimination ability than bidentate phos-
phanes in the catalytic asymmetric allylic substitution reac-
tion.
(S,S)-1,2-Bis[(9-phenanthryl)phenylphosphanyl]ethane–Borane(P)
(1/2), (S,S)-1eЈ: This diphosphane–borane was obtained by the
same method as that used for (S,S)-1aЈ. From (S)-eЈ (0.942 g,
3 mmol), the desired product was obtained as a white foam that
could appear contaminated with the monophosphane–borane (S)-
1
eЈ (Ͻ15%). Combined yield 0.795 g (79%). H NMR (250.1 MHz,
CDCl3, 298 K: δ = 0.60–2.10 (s, br., 6 H), 2.65 (s, br., 4 H), 7.00–
8.88 (m, 28 H, Ar) ppm. 31P{1H} NMR (101.1 MHz, CDCl3,
298 K): δ = +21.0 (s, br.) ppm.
Experimental Section
General Data: All compounds were prepared under a purified ni-
trogen atmosphere using standard Schlenk and vacuum-line tech-
niques. The solvents were purified by standard procedures and dis-
tilled under nitrogen. [Pd(η3-2-Me-C3H4)(µ-Cl)]2 and [Pd(η3-1,3-
Ph2-C3H3)(µ-Cl)]2 were prepared as described previously.[40,46] The
routine 1H, 13C and 31P NMR spectra were recorded with a Varian
XL-500 or Mer-400 MHz (1H NMR, standard SiMe4), Varian
Gemini (13C NMR, 50.3 MHz, standard SiMe4) and Bruker DRX-
250 (31P NMR, 101.2 MHz) spectrometer in CDCl3 unless other-
wise specified. Chemical shifts were reported downfield from stan-
dards. The two-dimensional experiments were carried out with a
Bruker DMX-500 or a Varian XL-500 instrument. IR spectra were
recorded with the following spectrometers: FTIR Nicolet 520,
FTIR Nicolet Impact 400, FTIR Avatar 330 and FTIR Nicolet
5700. FAB mass chromatograms were obtained with a Fisons V6-
Quattro instrument. The routine GC analyses were performed with
a Hewlett–Packard 5890 Series II gas chromatograph (50-m Ultra
2 capillary column 5% phenylmethylsilicone and 95% dimethylsili-
cone) with a FID detector. The GC–MS analyses were performed
with a Hewlett–Packard 5890 Series II gas chromatograph (50-m
Ultra 2 capillary column) interfaced to a Hewlett–Packard 5971
mass selective detector. HPLC analyses were carried out with a
Waters 717 plus autosampler chromatograph with a Waters 996
multidiode array detector, fitted with a Chiracel OD-H chiral col-
umn (25 cmϫ0.46 cm). The eluent, in all the determinations, was
a mixture of n-hexane/iPrOH, 95:5. Optical rotations were mea-
sured with a Perkin–Elmer 241MC spectropolarimeter at 23 °C.
Enantiomeric excesses were determined by GC with a Hewlett–
Packard 5890 Series II gas chromatograph (30-m Chiraldex DM
column) with a FID detector. Elemental analyses were carried out
by the Serveis Científicotècnics of the Universitat Rovira i Virgili
with an Eager 1108 microanalyzer.
(S,S)-2,2-Dimethyl-1,3-bis[(9-phenanthryl)phenylphosphanyl]-2-sila-
propane–Borane(P) (1/2) (S,S)-2eЈ: The phosphane–borane (S)-eЈ
(0.628 g, 2.0 mmol) was dissolved in THF (5 mL) and cooled to
–78 °C. sec-Butyllithium (1.70 mL of a 1.3  solution in hexane/
cyclohexane, 2.2 mmol) was added and the solution was stirred for
2 h. Dichlorodimethylsilane (0.129 g, 1 mmol) was quickly added
by syringe and the mixture was warmed slowly to room tempera-
ture. A HCl solution (1 , 10 mL) was added and the THF was
removed. The aqueous suspension was extracted with dichloro-
methane (3ϫ10 mL) and the combined organic layers were washed
with brine and dried with anhydrous sodium sulfate and filtered.
Evaporation of the solvent yielded the title compound as a yellow-
ish foam that could appear contaminated with the monophos-
phane–borane (S)-eЈ (Ͻ10%). Combined yield 0.650 g (95%). 1H
NMR (250.1 MHz, CDCl3, 298 K): δ = –0.31 (s, 6 H), 0.20–1.80
(s, br., 6 H), 1.60–2.15 (s, br., 4 H), 7.29–8.75 (m, 28 H, Ar) ppm.
31P{1H} NMR (101.1 MHz, CDCl3, 298 K): δ = +14.3 (s, br.) ppm.
(S,S)-1,2-Bis[(1-naphthyl)phenylphosphane]ethane (S,S)-1a: The di-
phosphane–borane (S,S)-1aЈ (0.263 g, 0.5 mmol) was dissolved in
degassed morpholine (15 mL) and stirred for 14 h at room tempera-
ture. The morpholine was removed and the pasty residue was
passed through a short column of alumina with toluene as eluent.
Evaporation of toluene furnished the free diphosphane as a white
pasty solid; yield 0.120 g (48%). 1H NMR (250.1 MHz, CDCl3,
298 K): δ = 2.06–2.36 (br., s, 4 H), 7.16–8.48 (m, 24 H, Ar) ppm.
31P{1H} NMR (101.1 MHz, CDCl3, 298 K): δ = –23.4 (s) ppm.
(S,S)-1,2-Bis[(9-phenanthryl)phenylphosphanyl]ethane (S,S)-1e: This
diphosphane–borane was obtained by the same method as that
used for (S,S)-1a. From (S,S)-1eЈ (0.795 g, 1.27 mmol), the desired
product was obtained as a white pasty solid that could appear con-
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P-Stereogenic Phosphanes in Asymmetric Allylic Alkylations
taminated with the methylmonophosphane (S)-e (Ͻ10%). Com-
H) ppm. 3.92 (s, 1 H), 7.01–8.53 (m, 28 H, Ar) ppm. 13C{1H}
1
bined yield 0.356 g (47%). H NMR (250.1 MHz, CDCl3, 298 K): NMR (100.0 MHz, CDCl3, 298 K): δ = 14.3 (d, JCP = 27.4 Hz,
δ = 2.10–2.78 (br., s, 4 H), 7.16–8.48 (m, 24 H, Ar) ppm. 31P{1H}
NMR (121.5 MHz, CDCl3, 298 K): δ = –26.9 (s) ppm.
CH3), 16.1 (d, JCP = 28.2 Hz, CH3), 23.7 (s, CH3), 74.2 (d, JCP =
28.9 Hz, CH2), 76.4 (d, JCP = 29.0 Hz, CH2), 122.6–138.3 (m, 1 C,
CH, Ar) ppm. 31P{1H} NMR (101.1 MHz, CDCl3, 298 K): δ =
+0.5 (d, J = 37.9 Hz, 1 P), +3.7 (d, J = 37.7 Hz, 1 P) ppm.
C46F6H41P3Pd (907.15): calcd. C 60.90, H 4.56; found C 60.13, H
5.33.
(S,S)-2,2-Dimethyl-1,3-bis[(9-phenanthryl)phenylphosphanyl]-2-
silapropane (S,S)-2e: This diphosphane–borane was obtained by
the same method as that used for (S,S)-1a. From (S,S)-2eЈ (0.650 g,
0.95 mmol), the free diphosphane was obtained as a viscous oil
that could appear contaminated with the monophosphane (S)-e
(Ͻ15%). Combined yield 0.234 g (38%). 1H NMR (250.1 MHz,
(η3-2-Methylallyl)bis[(R)-(2-biphenylyl)methylphenylphosphane]-
palladium(II) Hexafluorophosphate (3c): This complex was obtained
CDCl3, 298 K): δ = –0.05 (s, 6 H), 0.90–0.95 (m, 4 H), 7.20–8.69 by the same method as that used for 3a. From the phosphane (S)-
(m, 28 H, Ar) ppm. 31P{1H} NMR (101.1 MHz, CDCl3, 298 K): δ
= –32.9 (s) ppm.
c (0.539 g, 1.95 mmol), ammonium hexafluorophosphate (0.454 g,
2.79 mmol) and the dimer [PdCl(µ-Cl)η3-(2-CH3-C3H4)] (0.183 g,
0.46 mmol), the product was obtained as a red solid; yield 0.485 g
(62%). 1H NMR (250.1 MHz, CDCl3, 298 K): δ = 0.98 (d, J =
7.8 Hz, 3 H), 1.33 (d, J = 7.7 Hz, 3 H), 1.95 (s, 3 H), 3.00 (d, J =
9.1 Hz, 1 H), 3.14 (d, J = 9.2 Hz, 1 H), 3.54 (s, 1 H), 3.75 (s, 1 H),
6.86–8.17 (m, 28 H, Ar) ppm. 31P{1H} NMR (101.1 MHz,
CD3COCD3, 298 K): δ = +10.5 (d, J = 39.5 Hz, 1 P), +12.4 (d, J
= 39.5 Hz, 1 P) ppm. C42F6H41P3Pd (859.11): calcd. C 58.72, H
4.81; found C 59.27, H 4.98 H.
(η3-2-Methylallyl)bis[(R)-methyl(1-naphthyl)phenylphosphane]palla-
dium(II) Hexafluorophosphate (3a): The phosphane (S)-a (0.299 g,
1.19 mmol) was dissolved in CH2Cl2 (20 mL). Ammonium hexaflu-
orophosphate (0.278 g, 1.71 mmol) and the palladium dimer
[PdCl(µ-Cl)η3-(2-CH3-C3H4)] (0.112 g, 0.28 mmol) were added and
the yellow solution was stirred for 1 h. Water (20 mL) was added
and the resulting mixture was extracted with dichloromethane
(3ϫ10 mL). The combined organic fractions were washed with
water and dried with sodium sulfate. The solvent was then removed
and the resulting yellowish foam was suspended in pentane, filtered
and washed with more pentane. The product was finally obtained
as a yellow solid; yield 0.310 g (66 %). 1H NMR (400.1 MHz,
CDCl3, 298 K): δ = 1.65 (s, 3 H), 1.74 (d, J = 8.0 Hz, 3 H), 1.97
(d, J = 8.0 Hz, 3 H), 3.34 (d, J = 9.6 Hz, 1 H), 3.53 (s, 1 H), 3.65
(η3-2-Methylallyl)bis[(R)-(2-biphenylyl)isopropylphenylphosphane]-
palladium(II) Hexafluorophosphate (3d): This complex was ob-
tained by the same method as that used for 3a. From the phos-
phane (S)-d (0.140 g, 0.46 mmol), ammonium hexafluorophosphate
(0.0937 g, 0.57 mmol) and the dimer [PdCl(µ-Cl)η3-(2-CH3-C3H4)]
(0.0442 g, 0.11 mmol), the title product was isolated as a yellow
1
(d, J = 10.0 Hz, 1 H), 3.74 (s, 1 H), 6.96–8.10 (m, 24 H, Ar) ppm. solid; yield 0.100 g (50%). H NMR (250.1 MHz, CDCl3, 298 K):
13C{1H} NMR (100.0 MHz, CDCl3, 298 K): δ = 13.6 (d, JCP
=
δ = 0.61–0.91 (m, 12 H), 1.26–168 (m, 2 H), 2.20 (s, 3 H), 3.36 (d,
J = 8.8 Hz, 1 H), 3.60 (d, J = 9.5 Hz, 1 H), 4.13 (s, 1 H), 4.42 (s,
1 H), 6.79–7.48 (m, 28 H, Ar) ppm. 31P{1H} NMR (101.1 MHz,
28.2 Hz, CH3), 15.0 (d, JCP = 28.2 Hz, CH3), 23.5 (s, CH3), 74.3
(d, JCP = 28.2 Hz, CH2), 76.1 (d, JCP = 29.7 Hz, CH2), 125.2–138.3
(m, 1 C, CH, Ar) ppm. 31P{1H} NMR (101.1 MHz, CDCl3, CD3COCD3, 298 K): δ = +39.4 (d, J = 31.0 Hz, 1 P), +40.0 (d, J
298 K): δ = –0.4 (d, J = 38.4 Hz, 1 P), +2.2 (d, J = 38.4 Hz, 1
P) ppm. C38F6H37P3Pd (807,03): calcd. C 56.56, H 4.62; found C
57.16, H 5.04.
= 31.0 Hz, 1 P) ppm. C46F6H49P3Pd (915.21): calcd. C 60.37, H
5.40; found C 60.77, H 5.94.
(η3-2-Methylallyl)bis[(S)-(2-biphenylyl)methoxyphenylphosphane]-
palladium(II) Hexafluorophosphate (3f): This complex was obtained
by the same method as that used for 3a. From the phosphinite (R)-
f (0.265 g, 0.99 mmol), ammonium hexafluorophosphate (0.231 g,
1.42 mmol) and the dimer [PdCl(µ-Cl)η3-(2-CH3-C3H4)] (0.093 g,
0.24 mmol), the desired complex was obtained as a red solid; yield
(η3-2-Methylallyl)bis[(R)-isopropyl(1-naphthyl)phenylphosphane]-
palladium(II) Hexafluorophosphate (3b): This complex was ob-
tained by the same method as that used for 3a. From (S)-b (0.200 g,
0.72 mmol), ammonium hexafluorophosphate (0.168 g, 1.03 mmol)
and the dimer [PdCl(µ-Cl)η3-(2-CH3-C3H4)] (0.068 g, 0.17 mmol),
the title complex was obtained as a red solid; yield 0.125 g (42%).
1H NMR (400.1 MHz, CDCl3, 298 K): δ = 0.24 (d, J = 14.8 Hz, 3
H, br.), 0.47 (d, J = 14.8 Hz, 3 H, br.), 0.59 (dd, J = 14.0, 6.8 Hz,
3 H), 0.67 (dd, J = 14.4, 6.4 Hz, 3 H), 1.20–1.72 (m, 2 H), 1.89 (s,
3 H), 3.48 (d, J = 9.2 Hz, 1 H), 3.60 (d, J = 9.6 Hz, 1 H) ppm. 3.96
1
0.233 g (58%). H NMR (500.1 MHz, CDCl3, 298 K): δ = 1.61 (s,
3 H), 1.96 (d, J = 8.8 Hz, 1 H), 2.38 (d, J = 8.8 Hz, 1 H), 3.11 (d,
J = 10.4 Hz, 3 H), 3.21 (d, J = 10.0 Hz, 3 H), 3.71 (s, 1 H), 3.84–
3.86 (m, 1 H), 6.81–7.62 (m, 28 H, Ar) ppm. 31P{1H} NMR
(101.1 MHz, CDCl3, 298 K): δ = +120.7 (d, J = 53.9 Hz, 1 P),
(s, 1 H), 4.43 (s, 1 H), 7.02–8.12 (m, 24 H, Ar) ppm. 13C{1H} NMR +124.7 (d, J = 53.9 Hz, 1 P) ppm. C38F6H37O2P3Pd (839.03): calcd.
(100.0 MHz, CDCl3, 298 K): δ = 18.4 (d, JCP = 3.8 Hz, CH3), 18.5
(s, CH3), 19.2 (d, JCP = 6.9 Hz, CH3), 19.6 (d, JCP = 8.4 Hz, CH3),
23.1 (s, CH3), 25.2–25.8 (br., CH), 75.4 (d, JCP = 26.6 Hz, CH2),
125.4–137.6 (m, 1 C, CH, Ar) ppm. 31P{1H} NMR (101.1 MHz,
CDCl3, 298 K): δ = +21.3 (d, J = 32.4 Hz, 1 P), +24.2 (d, J =
32.9 Hz, 1 P) ppm. C42F6H45P3Pd (863.14): calcd. C 58.45, H 5.26;
found C 58.55, H 5.82.
C 54.40, H 4.44; found C 57.00, H 5.19.
(η3-2-Methylallyl){(R,R)-1,2-bis[(1-naphthyl)phenylphosphanyl]-
ethane}palladium(II) Hexafluorophosphate (4a): The phosphane 1a
(0.110 g, 0.22 mmol) was dissolved in CH2Cl2 (10 mL). Ammo-
nium hexafluorophosphate (0.059 g, 0.36 mmol) and the dimer
[PdCl(µ-Cl)η3-(2-CH3-C3H4)] (0.047 g, 0.12 mmol) were added and
the mixture was stirred for 1 h. Water (10 mL) was added and the
(η3-2-Methylallyl)bis[(R)-methyl(9-phenanthryl)phenyphosphane]- mixture was extracted with dichloromethane (3 ϫ 10 mL). The
palladium(II) Hexafluorophosphate (3e): This complex was obtained
by the same method as that used for 3a. From the phosphane (S)-
e (0.442 g, 1.47 mmol), ammonium hexafluorophosphate (0.343 g,
2.10 mmol) and the dimer [PdCl(µ-Cl)η3-(2-CH3-C3H4)] (0.138 g,
0.35 mmol), the desired compound was obtained as a red solid;
yield 0.330 g (52%). 1H NMR (400.1 MHz, CDCl3, 298 K): δ =
1.80 (d, J = 8.0 Hz, 3 H), 1.81 (s, 3 H), 2.09 (d, J = 7.6 Hz, 3 H),
3.47 (d, J = 9.6 Hz, 1 H), 3.76 (s, 1 H), 3.78 (d, J = 10.0 Hz, 1
combined organic fraction was washed with water and dried with
anhydrous sodium sulfate. The solvent was removed and the re-
maining yellowish foam was recrystallized from toluene/dichloro-
methane to yield the title product as a white crystalline solid; yield
1
0.110 g (57%). H NMR (400.1 MHz, CDCl3, 298 K): δ = 1.71 (s,
3 H), 2.38–2.59 (m, 2 H), 2.95 (d, J = 10.0 Hz, 1 H), 3.14–3.30 (m,
2 H), 3.27 (d, J = 10.4 Hz, 1 H), 4.11 (s, 1 H), 4.54 (s, 1 H), 6.98–
8.00 (m, 26 H, Ar) ppm. 13C{1H} NMR (100.0 MHz, CDCl3,
Eur. J. Inorg. Chem. 2010, 3372–3383
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
3381

A. Grabulosa, G. Muller, R. Ceder, M. Á. Maestro
FULL PAPER
298 K): δ = 24.1 (s, CH3), 26.6 (d, JCP = 12.9 Hz, CH2), 27.0 (d,
JCP = 12.9 Hz, CH2), 69.8 (dd, JCP = 29.8, 3.8 Hz, CH2), 70.6 (dd,
JCP = 29.0, 3.8 Hz, CH2), 124.1–138.2 (m, 1 C, CH, Ar) ppm.
Allyl system: see discussion. 13C{1H} NMR (100.0 MHz, CDCl3,
298 K): δ = 13.8 (s, CH3), 14.1 (s, CH3), 72.0 (s, CH3), 96.6 (d, JCP
= 25.4 Hz, CH), 97.7 (d, JCP = 25.4 Hz, CH), 108.4 (s, CH), 109.1
31P{1H} NMR (101.1 MHz, CDCl3, 298 K): δ = +44.2 (d, J = (s, CH), 124.8–138.1 (m, 1 C, CH, Ar) ppm. 31P{1H} NMR
29.7 Hz, 1 P), +45.6 (d, J = 29.6 Hz, 1 P) ppm. C37F6H35P3Pd (101.1 MHz, CDCl3, 298 K): δ = 3.4 (b) ppm. 31P{1H} NMR
(793.01): calcd. C 56.04, H 4.45; found C 58.28, H 5.08.
(11.1 MHz, CDCl3, 253 K): δ = 7.7 (45 %), 7.8 (55 %) ppm.
C32ClH28PPd (585.41): calcd. C 65.66, H 4.82; found C 65.90, H
5.30.
(η3-2-Methylallyl){(R,R)-1,2-bis[(9-phenanthryl)phenylphosphanyl]-
ethane}palladium(II) Hexafluorophosphate (4e): This complex was
obtained by the same method as that used for 4a. From the diphos-
phane (S,S)-1e (0.271 g, 0.45 mmol), ammonium hexafluorophos-
phate (0.147 g, 0.90 mmol) and the dimer [PdCl(µ-Cl)η3-(2-CH3-
C3H4)] (0.087 g, 0.23 mmol), the desired product was obtained as
a pale yellow solid; yield 0.222 g (55%). 1H NMR (400.1 MHz,
CDCl3, 298 K): δ = 1.69 (s, 3 H), 2.40–2.70 (m, 2 H), 3.03 (d, J =
10.0 Hz, 1 H), 3.18–3.33 (m, 2 H), 3.31 (d, J = 9.6 Hz, 1 H), 4.11
(s, 1 H), 4.52 (s, 1 H), 7.06–8.71 (m, 28 H, Ar) ppm. 13C{1H} NMR
Chloro(η3-1,3-diphenylallyl)[(R)-(2-biphenylyl)isopropylphenylphos-
phane]palladium(II) (6d): This complex was obtained by the same
method as that used for 6a. From the phosphane (S)-d (0.215 g,
0.706 mmol) and the dimer [PdCl(µ-Cl)(η3-1,3-diphenylallyl)]2
(0.235 g, 0.350 mmol), the desired product was obtained as a pale
orange solid; yield 0.320 g (71%). IR: ν = 3056 ν(C–H), 3030 ν(C–
˜
H), 2984 ν(C–H), 2964 ν(C–H), 2928 ν(C–H), 1548, 1490, 1463,
1434, 1385, 1183, 1091, 761, 752, 738, 709, 697, 690, 649, 508 cm–1.
1H NMR (500.1 MHz, CDCl3, 298 K): δ = P–CH–(CH3)2 major
1.48 (m), minor 2.55 (m), P–CH–(CH3)2 major 0.65, 0.88 (dd, J =
13, 7 Hz), minor 0.90, 1.1 (dd, J = 18.5, 7 Hz, 3 H) ppm. Allyl
system: see discussion. 13C{1H} NMR (100.0 MHz, CDCl3,
298 K): δ = 19.0 (d, JCP = 43.5 Hz, CH3), 19.5 (d, JCP = 37.4 Hz,
CH3), 21.2 (d, JCP = 6.1 Hz, CH3), 21.6 (d, JCP = 9.2 Hz, CH3),
25.1 (d, JCP = 20.6 Hz, CH), 27.1 (d, JCP = 21.4 Hz, CH), 71.8 (s,
CH), 72.3 (d, JCP = 5.4 Hz, CH), 96.2 (d, JCP = 25.2 Hz, CH), 98.1
(d, JCP = 24.4 Hz, CH), 106.8 (d, JCP = 4.6 Hz, CH), 107.4 (s, CH),
126.2–147.1 (C, CH, Ar) ppm. 31P{1H} NMR (11.1 MHz, CDCl3,
298 K): δ = 31.4 (43%), 33.6 (57%) ppm. C36ClH34PPd (639.50):
calcd. C 67.62, H 5.36; found C 67.05, H 5.90.
(100.0 MHz, CDCl3, 298 K): δ = 24.2 (s, CH3), 26.6 (d, JCP
13.7 Hz, CH2), 27.0 (d, JCP = 13.7 Hz, CH2), 70.2 (d, JCP
=
=
28.9 Hz, CH2), 71.0 (d, JCP = 29.8 Hz, CH2), 122.7–138.3 (m, 1 C,
CH, Ar) ppm. 31P{1H} NMR (121.5 MHz, CDCl3, 298 K): δ =
+44.7 (d, J = 29.8 Hz, 1 P), +45.4 (d, J = 29.8 Hz, 1 P) ppm.
C46F6H39P3Pd (905.13): calcd. C 61.04, H 4.34; found C 62.96, H
4.51.
Crystal Structure Determination of 4e: Colourless crystals, suitable
to perform X-ray diffraction studies, were obtained by slow dif-
fusion of toluene over a solution of the complex in dichlorometh-
ane at 4 °C. C50H44ClF6P3Pd (1/2 toluene, 1/2 CH2Cl2) Mr =
993.69 g mol– 1 , orthorhombic, a = 19.9089(11) Å, b =
19.9089(11) Å, c = 66.178(5) Å, U = 22716(2) Å3, T = 298(2) K,
space group R32n, Z = 18, 38579 reflections measured, 11451
unique (Rint = 0.1321), which were used in all calculations. The
final wR(F2) was 0.2402 (all data).
Crystal Structure Determination for 6d: Orange crystals, suitable to
perform X-ray diffraction studies, were obtained by slow diffusion
of hexane over a solution of the complex in dichloromethane at
4 °C. C36H34ClPPd, Mr = 947.66 gmol–1, orthorhombic, a =
12.991(3) Å, b = 13.684(3) Å, c = 16.864(3) Å, U = 2997.7(10) Å3,
T = 173 K, space group P212121 (no. 19), Z = 4, 17564 reflections
measured, 6129 unique (Rint = 0.0208), which were used in all cal-
culations. The final wR(F2) was 0.1062 (all data).
CCDC-753099 contains the supplementary crystallographic data
for 4e. These data can be obtained free of charge from The Cam-
bridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
(η3-2-Methylallyl){(R,R)-2,2-dimethyl-1,3-bis[(9-phenathryl)phenyl]-
2-silapropane}palladium(II) Hexafluorophosphate (5e): This com-
plex was obtained by the same method as that used for 4a. From
the diphosphane (S,S)-2e (0.200 g, 0.30 mmol), ammonium hexa-
fluorophosphate (0.196 g, 1.20 mmol) and the dimer [PdCl(µ-
Cl)η3-(2-CH3-C3H4)] (0.059 g, 0.15 mmol), the title complex was
isolated as a white solid; yield 0.104 g (36 %). 1 H NMR
(400.1 MHz, CD3COCD3, 298 K): δ = –0.56 (s, 3 H), –0.48 (s, 3
H), 1.78 (s, 3 H), 2.36–2.55 (m, 4 H), 3.23 (d, 1 H, J = 10.0 Hz),
3.46 (d, 1 H, J = 10.4 Hz), 3.63 (t, 1 H, J = 4.0 Hz), 3.79 (t, 1 H,
J = 4.0 Hz), 7.13–9.05 (m, 28 H, Ar) ppm. 13C{1H} NMR
(100.0 MHz, CD3COCD3, 298 K): δ = –0.3 (s, CH3), –0.2 (s, CH3),
11.0–11.3 (m, 2CH2), 23.5 (s, CH3), 74.0 (d, JCP = 32.7 Hz, CH2),
76.6 (d, JCP = 31.2 Hz, CH2), 123.6–139.9 (m, 1 C, CH, Ar) ppm.
31P{1H} NMR (101.1 MHz, CD3COCD3, 298 K): δ = +12.2 (d, J
= 47.9 Hz, 1 P), +13.4 (d, J = 47.6 Hz, 1 P) ppm. C48F6H45P3PdSi
(963.29): calcd. C 59.85, H 4.71; found C 60.05, H 4.35.
CCDC-753100 contains the supplementary crystallographic data
for 6d. These data can be obtained free of charge from The Cam-
bridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
Supporting Information (see also the footnote on the first page of
this article): Selected 13C NMR spectroscopic data of complexes 3,
1
4 and 5. Crystal data and structure refinement for 4e and 6d. H
NMR spectra of 6a in CDCl3 at different temperatures. 31P{1H}
NMR spectra for selected palladium complexes.
Acknowledgments
The authors thanks the Ministerio de Educación y Ciencia (MEC)
(CTQ2007-61058/BQU) for financial support of this work.
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Sometimes it is possible to observe this exchange by NMR
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Received: March 17, 2010
Published Online: June 2, 2010
Eur. J. Inorg. Chem. 2010, 3372–3383
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
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