Phosphaalkenes palladium(II) complexes in the Suzuki and Sonogashira cross-coupling reactions

Article abstract of DOI:10.1002/hc.20307

The 1-methoxy-2-(supermesitylphos-phanylidenemethyl)-benzene ligand (1) was prepared by reacting the phospha-Wittig reagent [Mes*P=PMe₃] with o-methoxybenzaldehyde. Reaction of 1 with one equivalent of the [Pd(allyl)Cl]₂ aimer in the presence of Ag(OTf) affords a neutral complex (4) in which the triflate ligand is coordinated to the palladium atom. DFT calculations show that the formation of complex 4 is favored by 22.4 kcal/mol with respect to that of a chelate species involving coordination of the ligand through the phosphorus atom of one lone pair at the oxygen of the pendant methoxy group. Reaction of two equivalents of ligand 1 with the [Pd(allyl)Cl]₂ dimer affords complex 5, in which the two ligands are coordinated through their phosphorus atom. The catalytic activity of complex 5 was compared to that of the 1, 3-bis[2-(supermesityl)phosphanediylmethyl]benzene palladium chloride complex (6). Performances of the two catalysts were found to be similar in the Suzuki cross-coupling reaction between phenylboronic acid and some arylbromides (TON between 55.10⁵ and 99.10⁵) as well as in the Sonogashira coupling between phenylacetylene and arylbromides (TON between 400 and 950).

Full text of DOI:10.1002/hc.20307

Heteroatom Chemistry
Volume 18, Number 4, 2007
Phosphaalkenes Palladium(II) Complexes
in the Suzuki and Sonogashira
Cross-Coupling Reactions
Bernard Deschamps, Xavier Le Goff, Louis Ricard,
and Pascal Le Floch
De´partement de Chimie, Ecole Polytechnique, Laboratoire ꢀꢀ He´te´roe´le´ments et Coordinationꢁꢁ,
UMR CNRS 7653, 91128 Palaiseau Ce´dex, France
Received 3 May 2006; revised 29 May 2006
ꢂ
C
between 400 and 950).
2007 Wiley Periodicals, Inc.
ABSTRACT: The 1-methoxy-2-(supermesitylphos-
phanylidenemethyl)-benzene ligand (1) was prepared
by reacting the phospha-Wittig reagent [Mes∗P PMe3]
with o-methoxybenzaldehyde. Reaction of 1 with
one equivalent of the [Pd(allyl)Cl]2 dimer in the
presence of Ag(OTf) affords a neutral complex (4)
in which the triflate ligand is coordinated to the
palladium atom. DFT calculations show that the
formation of complex 4 is favored by 22.4 kcal/mol
with respect to that of a chelate species involving
coordination of the ligand through the phosphorus
atom of one lone pair at the oxygen of the pendant
methoxy group. Reaction of two equivalents of ligand
1 with the [Pd(allyl)Cl]2 dimer affords complex 5, in
which the two ligands are coordinated through their
phosphorus atom. The catalytic activity of complex
5 was compared to that of the 1,3-bis[2-(super-
Heteroatom Chem 18:363–371, 2007; Published online in
Wiley InterScience (www.interscience.wiley.com). DOI
10.1002/hc.20307
INTRODUCTION
Low-coordinated phosphorus compounds display
unusual electronic properties that make them very
attractive ligands in coordination chemistry [1].
Thus, their good π-accepting capacity has been
exploited for the stabilization of highly electron-
rich or electron-excessive transition metal frag-
ments [2]. However, these molecules have not been
widely used as ligands in catalysis so far. This sit-
uation mainly results from their limited stability.
Thus, without appropriate kinetic (use of bulky
groups at phosphorus) or thermodynamic (conju-
gation, aromaticity) stabilization, most low coor-
dinated phosphorus compounds are too reactive
to be engaged in the elaboration of viable cata-
lysts. This explains why studies were only limited to
derivatives such as phosphaferrocenes (stabilization
through π-coordination), sterically protected phos-
phaalkenes (kinetic stabilization), and phosphinines
(stabilized by aromaticity) in some cases. With phos-
phaalkenes, most of the developments have been re-
ported by the groups of Yoshifuji and Ozawa, who
published a series of articles on the use of DCPB
ligands (1,2-diaryl-3,4-diphosphinidenecyclobutene
mesityl)phosphanediylmethyl]benzene
palladium
chloride complex (6). Performances of the two
catalysts were found to be similar in the Suzuki
cross-coupling reaction between phenylboronic acid
and some arylbromides (TON between 55.105 and
99.105) as well as in the Sonogashira coupling
between phenylacetylene and arylbromides (TON
Correspondence to: Pascal Le Floch; e-mail: lefloch@poly.
polytechnique.fr.
For further details on the theoretical structure of complexes
I and II and the X-ray structural data for complexes 4 and 5,
contact Pascal Le Floch.
c
ꢀ
2007 Wiley Periodicals, Inc.
363

364 Deschamps et al.
ligands) [3]. Group 10 and 11 complexes of these
ligands proved to be very efficient catalysts in pro-
cesses such as the polymerization of ethylene [4],
the dehydrogenative silylation of ketones [5], the al-
lylation of amines [6], the hydroamination of 1,3-
dienes [7], the cyanation of arylbromides [8], the
cyclodehydration of diols [9], and the amination
of bromoarenes [10]. As part of a program aimed
at exploring the use of mono-, bi-, and tridentate
ligands featuring phosphaalkenes as ancillary lig-
ands in catalysis, we have recently investigated their
use in two very popular palladium-mediated cross-
coupling processes, the Suzuki [11] and the Sono-
gashira reactions [12]. The use of low-coordinated
phosphorus compounds in these two processes is
not totally unprecedented. In 1995, Yoshifuji re-
ported on the use of a [(DCPB)PdCl2] complex in the
Sonogashira coupling between trimethylsilylacety-
lene and p-bromonitrobenzene (TON about 75) [13].
In 2000, we reported on the very good activity (TON
about 1.106) of an octaethyldiphosphaferrocene
Pd(0) complex in the Suzuki coupling of arylio-
dides [14] with phenylboronic acid. Later the group
of Yoshifuji reported on the coupling of iodoben-
zene with phenylboronic acid or phenylacetylene
catalyzed by DCPB and 1,3-diphosphapropene (and
their P S derivatives) palladium complexes in a se-
ries of consecutive papers [15]. All these couplings
afforded the expected biaryl derivatives and func-
tional alkynes in fair to good yields and were car-
ried out with 1 to 4 mol% of catalyst. Note that a
report also mentions that polymers featuring DCPB-
based ligands were also employed in the coupling of
trimethylsilylacetylene with p-bromonitrobenzene
[16]. Herein we wish to report on our most recent
results.
ligand that features two phosphaalkene units grafted
on a dibenzofurane skeleton [17]. Finally, in view of
the importance of palladacycles in catalysis [18] we
have also explored the reactivity of ligand 3, whose
synthesis was reported by the group of Stephan and
Geoffroy some years ago. As will be seen further a
new synthetic approach toward this interesting lig-
and has been developed.
Synthesis of phosphaalkene 1 was conven-
tionally achieved through the phospha-Wittig ap-
proach by reacting the Mes*P PMe3 reagent with
o-methoxybenzaldehyde in THF at 0◦C for 3 hours
[19]. After usual workup, 1 (only the E isomer) was
isolated as an air-stable white powder whose NMR
data compared with other related species (Scheme 2)
[20].
Ligand 3 was synthesized by the group of
Geoffroy in 1992 using the Yoshifuji procedure [21]
(phospha-Petersen reaction) using Mes*PH(SiMe2-
t-Bu) as starting precursor [22]. The group of
Stephan later proposed an alternative pathway that
relied on the reaction of the metalla-Wittig reagent
[Cp2Zr( PMes*)(PMe3)] complex with isophtalalde-
hyde [23]. We found here the classical phospha-
Wittig reaction to be the most straightforward ap-
proach, and bidentate ligand 3 was readily obtained
by reacting 2.5 equivalents of Mes*P PMe3 with
isophtalaldehyde at 0◦C for 3 hours. Following this
procedure, compound 3 was obtained with a 70%
yield as a very stable yellow solid (Scheme 3). Note
that, in this case again, only the E,E-isomer was
formed.
Ligand 1 was reacted with half an equiva-
lent of [Pd(COD)Cl2] in dichloromethane at room
RESULTS AND DISCUSSION
MeO
Three types of phosphaalkene ligands were selected
for this study. We selected ligand 1, which features
one methoxy group at the α-position on the aryl
group in order to test the ability of this methoxy
group to act as an hemilabile ligand. Compound 2,
whose synthesis we recently reported, is a bidentate
H
O
P
PMe3
1
THF, 3 h, 0°C
Mes*
SCHEME 2 Synthesis of ligand 1.
H
H
H
Mes*
P
O
P
P
O
H
H
Mes*
*Mes
P
P
Me
3
1
2
Mes*
*Mes
SCHEME 1 Ligands studied.
Heteroatom Chemistry DOI 10.1002/hc

Phosphaalkenes Palladium(II) Complexes 365
H
H
O
O
P
PMe3
3
THF, 3 h, 0°C
Mes*
SCHEME 3 Synthesis of ligand 3.
temperature to afford a highly insoluble com-
plex within minutes for which only a weak signal
(δ(CH2Cl2) = 189.0 ppm) could be observed in 31P
NMR. Although elemental analyses confirm the pres-
ence of two phosphaalkene ligands for one PdCl2
fragment, the lack of other NMR data precluded the
determination of the stereochemistry of the com-
plex (cis or trans) or the monomeric nature of the
complex. An interesting result was obtained by re-
acting half an equivalent of [Pd(allyl)Cl]2 with one
equivalent of 1 in the presence of AgOTf as chlo-
ride abstractor in dichloromethane at room tem-
perature. After filtration of AgCl salts, complex 4
was isolated in excellent yield as a white powder.
However, the structure of 4 was difficult to estab-
lish on the sole basis of NMR data, which indicate
that only one phosphaalkene ligand is present in the
molecule. Single crystals were thus grown by diffus-
ing a solution of hexanes (mixture of isomers) into
a dichloromethane solution of the complex at room
temperature (Scheme 4).
A view of one molecule of 4 is presented in Fig. 1.
Crystal data and structure refinement parameters
are listed in Table 1. As can be seen, in this com-
plex, ligand 1 does not behave as a chelate. Only
the phosphorus atom is coordinated to the palla-
dium center and the triflate couteranion completes
the coordination sphere. Apart from this, the struc-
ture of 4 does not deserve further remarks, metric pa-
rameters being comparable with other palladium(II)
phosphaalkene complexes reported in the literature.
Calculations were carried out to estimate the en-
ergetic difference between a complex featuring lig-
and 1 as chelate species and the isolated complex
FIGURE 1 One molecule of complex 4.
4 that features the triflate as ligand. Optimizations
were carried out using the ONIOM method and the
Gaussian set of programs. The B3PW91 functional
was used in combination with the 6-31G* basis set
for all nonmetallic atoms and the LANL2DZ basis set
for palladium. Two tertiobutyl groups of the Mes*
group were computed at the molecular mechanics
level of theory using the UFF force field to save com-
putation time. The third tertiobutyl group located at
the para position was replaced by a H atom. Energies
of the complexes were given by single-point calcu-
lations (quantum level for all atoms) of the ONIOM
optimized structures. The two optimized structures I
(coordinated triflate) and II (uncoordinated triflate)
are presented in Fig. 2. Note that metric parameters
in complex I are very close to those of the exper-
imental structure (complex 4). The structure of II
proved to be very difficult to optimize and we found
that the issue of optimization depends on the ini-
tial location of the triflate anion. Thus, preliminary
calculations in which the triflate anion was initially
positioned in close proximity to the cationic palla-
dium atom (above the plane of the anisole ligand)
invariably yielded structure I as minimum, a ligand
displacement reaction taking place along the opti-
mization process. Finally, a structure of II could
be computed by initially locating the triflate in an
area where no interaction with the cationic palla-
dium can occur. In line with experimental obser-
vations, we found that the energetic difference be-
tween the two complexes is indeed very important
(I–II = −22.4 kcal/mol) and thus explains why the
formation of the chelate species is never observed.
Reaction of two equivalents of ligand 1 with
[Pd(allyl)Cl]2 afforded complex 5, which was iso-
lated as a very stable white solid (Scheme 5). All
NMR data and elemental analyses confirm the pro-
posed structure. Additional evidence was provided
Pd
TfO
*Mes
P
(1) 1/2 [Pd(allyl)Cl]2
(2) AgOTf
H
1
Me
CH2Cl2, 1 h, RT
O
4
SCHEME 4 Synthesis of complex 4.
Heteroatom Chemistry DOI 10.1002/hc

366 Deschamps et al.
TABLE 1 Crystal Data and Structure Refinement Parameters for complexes 4 and 5
Compound
4
5
Empirical formula
M
T (K)
C30H42O4F3SPPd
693.07
C55
H
79O2P2Pd.CF3O2S
1073.59
150(1)
150(1)
Crystal system
Space group
Monoclinic
P21/c
Triclinic
P–1
˚
a (A)
10.027(1)
30.878(1)
10.245(1)
19.195(1)
˚
b (A)
˚
c (A)
11.001(1)
90.00
110.35(1)
90.00
3193.5(4)
4
0.746
19.405(1)
116.51(1)
100.96(1)
94.40(1)
3295.0(4)
2
α (◦)
β (◦)
γ (◦)
3
˚
V (A )
Z
–1
µ (cm
)
0.406
F(000)
Dcalc (g cm
1432
1.442
1132
1.082
–1
)
Index range
−14 < h < 14
−40 < k < 43
−15 < l < 15
Phi and omega scans
30.03
−12 < h < 12
−23 < k < 23
−24 < l < 24
Scan type
Phi and omega scans
2θ
(◦)
26.37
22036
13349
0.0248
99.1
max
Reflectance measured
Independent reflectance
Rint
16503
9295
0.0207
99.5
Completeness to θ
(%)
max
Parameters
381
0.0379
0.1124
1.096
555
R1(Fhkl
ωR2
)
0.0481
0.1454
1.043
GOF
−3
˚
ρ
max/ρ
(eA
)
0.861/–0.838
0.734/–0.543
min
by an X-ray crystallographic study. A view of one
molecule of 5 is presented in Fig. 2. Crystal data
and structure refinement parameters are listed in
Table 1. As can be seen, despite their bulkiness the
two phosphaalkene ligands adopt a spatial arrange-
ment that minimizes steric repulsion between the
tertiobutyl groups without dramatically expanding
the P Pd P angle, which is comparable to those
recorded in other structures of Pd(allyl) complexes
(110.9◦) [24] (Fig. 2).
FIGURE 2 Optimized geometries of model complexes I and II as given by ONIOM calculations.
Heteroatom Chemistry DOI 10.1002/hc

Phosphaalkenes Palladium(II) Complexes 367
O
TfO
Me
H
H
H
[PdCl2(PhCN)2]
3
(1) 1/2 [Pd(allyl)Cl]
(2) AgOTf
2
P
Pd
P
P
P
CH2Cl2, 40°C, 10 h
Mes*
*Mes
*Mes
*Mes
2
Pd
H
Cl
CH2Cl2, 1 h, RT
6
P
O
Mes*
Me
H
SCHEME 6 Synthesis of complex 6 from 3.
Me
O
5
SCHEME 5 Synthesis of complex 5.
R
R
5 or 6
(HO)2B
+
Br
K2CO3
toluene, 100°C, 2 h
Less satisfying results were obtained when one
equivalent of ligand 2 was reacted with both metal-
lic precursors. Thus, reaction with [Pd(COD)Cl2]
afforded an insoluble material that could neither
be crystallized nor characterized by NMR tech-
niques. On the other hand, reaction of 2 with the
[Pd(allyl)Cl]2 yielded a complicated mixture of com-
plexes whose formulation could not be established,
as attested by the 31P NMR spectrum of the crude
mixture.
Complex 6, which had previously been charac-
terized by the group of Geoffroy, was conventionally
prepared by heating one equivalent of the ligand 3
with [(PhCN)2PdCl2] in dichloromethane. Contrary
to the initially reported procedure, we found that a
longer heating period was needed to complete the
reaction (40◦C for 10 h) (Scheme 6).
TON between 40 × 105 and 99 × 105
R
R
5 or 6
+
Br
H
Ph
Et3N
toluene, 90°C, 24 h
TON between 400 and 900
SCHEME 7 Suzuki and Sonogashira cross-coupling reac-
tions using complexes 5 or 6 as catalysts.
most important activity in both processes. Thus, in
the Suzuki coupling, TON fall in the range from
40 × 105 to 99 × 105. To the best of our knowledge,
these yields are the most important recorded so far
for low-coordinated phosphorus ligands and the per-
formance of these two catalysts compare with those
of the most efficient systems. Interestingly, we found
that the Sonogashira coupling could be carried out
without the presence of copper(I) salts. Unfortu-
nately, as previously observed with phosphaferocene
ligands, this coupling process could not be trans-
posed to the conversion of chloroaromatics, most
experiments resulting in the recovery of starting
materials and/or reduced compounds (see Table 2).
Both complexes also exhibited an interesting activ-
ity in the Sonogashira coupling, which is known to
be much more difficult to catalyze than the Suzuki
coupling, and TONs ranging from 400 to 950 were
obtained (see Table 3).
The catalytic activity of complexes 4, 5, and
6 was evaluated in two well-known transforma-
tions that allow the formation of C–C bonds: the
Suzuki and the Sonogashira cross-coupling reac-
tions (Scheme 7). Complexes 5 and 6 exhibited the
In
conclusion,
we
have
shown
that
phosphaalkene-based palladium complexes such
as 5 and 6 can lead to important conversions in
the Suzuki and the Sonogashira cross-coupling
processes. Further studies will now focus on the use
of ligands 1 and 3 in other catalytic transformations
with different metals.
FIGURE 3 One molecule of complex 5.
Heteroatom Chemistry DOI 10.1002/hc

368 Deschamps et al.
TABLE 2 Results Obtained in the Coupling of Phenylboronic
Acid with Some Bromoarenes
Synthesis of the Phospha-Wittig Reagent
Mes*P PPh3
Entry
Arylbromide
Catalyst Yield
TON
To a mixture of Mes*PCl2 (1.0 g, 2.9 mmol) and Zn
(1.0 g, 15.0 mmol) in THF (10 mL) at 0◦C, was sy-
ringed PMe3(1 M, 7.5 mmol, 7.5 mL). The crude mix-
ture was allowed to warm to room temperature and
was stirred for 3 h. The 31P NMR spectrum showed
the formation of the desired reagent, which was used
without further purification.
1
2
3
4
5
6
7
8
9
Bromobenzene
5
6
5
6
5
6
5
6
5
99
88
40
54
99
68
99
87
99
99 × 105
88 × 105
40 × 105
54 × 105
99 × 105
68 × 105
99 × 105
87 × 105
99 × 105
p-Bromoacetophenone
p-Bromoanisole
31P NMR (121.5 MHz, THF, 298K): δ 6.6 ppm
(1 J(P P) = 577.9, Mes*P), −132.5 ppm (1 J(P P) =
577.9, PMe3).
p-Bromotoluene
1-Bromo-3,5-
dimethylbenzene
10
6
55
55 × 105
Synthesis of 1-Methoxy-2-(supermesitylphos-
phanylidenemethyl)-benzene (1)
TABLE 3 Results Obtained in the Coupling of Phenylacety-
lene with Some Bromoarenes
5
Entry
Arylbromide
Bromobenzene
Catalyst Yield TON
6
4
3
H3C
1
2
3
4
5
6
7
8
5
6
5
6
6
6
5
6
85
78
95
95
40
76
78
68
850
780
950
950
400
760
780
680
1
O
2
7
P
p-Bromoacetophenone
8
13
9
p-Bromoanisole
p-Bromotoluene
1-Bromo-3,5-dimethylbenzene
12
10
11
The phospha-Wittig reagent [Mes*P PMe3] was
cooled to 0◦C and cannulated onto a suspension of o-
methoxybenzaldehyde (0.165 g, 1.2 mmol, 0.4 equiv)
at 0◦C in THF (10 mL). The crude mixture was stirred
for 3 h. CH2Cl2(10 mL), water (10 mL), and ice were
then added. The organic phase was separated, dried
over MgSO4, and filtered. The solvent was then evap-
orated and MeOH (10 mL) was added, resulting in
the formation of a precipitate, which was filtered off
and dried under vacuum. The title compound was
obtained as a white solid (between 0.60 and 0.72 g,
yield: 50–60%).
EXPERIMENTAL
General
All reactions were routinely performed under an
inert atmosphere of argon or nitrogen by using
Schlenk and glove-box techniques and dry de-
oxygenated solvents. Dry THF and hexanes were
obtained by distillation from Na/benzophenone.
Dry dichloromethane was distilled from P2O5, dry
toluene and THF from Na. NMR spectra were
recorded on a Bruker Avance 300 spectrometer op-
1H NMR (300 MHz, CD2Cl2, 298 K : δ 1.28 (s,
9H, para C(CH3)3), 1.45 (s, 18H, ortho C(CH3)3),
1
3
erating at 300 MHz for H, 75.5 MHz for 13C, and
3.72 (s, 3H, OCH3), 6.77 (d, 1H, J(H H) = 8.2 Hz,
121.5 MHz for 31P. Solvent peaks are used as inter-
nal reference relative to Me4Si for 1H and 13C chem-
ical shifts (ppm); 31P chemical shifts are relative to
an 85% H3PO4 external reference and coupling con-
stants are expressed in Hertz. The following abbre-
viations are used: b, broad; s, singlet; d, doublet;
t, triplet; m, multiplet; p, pentuplet; sext, sextuplet;
sept, septuplet; v, virtual. Elemental analyses were
performed by the “Service d’analyse du CNRS,” at
Gif sur Yvette, France. [Pd(COD)Cl2], [Pd(allyl)Cl]2,
and [(PhCN)2PdCl2] were prepared according to lit-
erature procedures. All other reagents and chemicals
were obtained commercially and used as received.
H6), 6.83 (t, 1H, 3 J(H H) = 7.5 Hz, H4), 7.13 (tt, 1H,
ꢀJ(H H) = 17.4, H5), 7.36 (s, 2H, H10, H12), 7.65, 1H,
2
ꢀJ = 11.9 Hz, H3), 8.28 (d, 1H, J(H P) = 25.6 Hz,
H7) ; 31P NMR (121.5 MHz, CD2Cl2, 298 K): δ 259.0;
13C NMR (75.5 MHz, CD2Cl2, 298 K) : δ 0.3 (s, para
C(CH3)3), 32.9 (d, 3 J(C P) = 7.4 Hz, ortho C(CH3)3),
34.1 (s, para C(CH3)3), 37.4 (s, ortho C(CH3)3), 54.5
(s, OCH3), 110.2 (d, 4 J(C P) = 2.8 Hz, C6), 119.8
(d, 4 J(C P) = 3.0 Hz, C4), 121.0 (s, C10, C12), 125.5
(d, 3 J(C P) = 24.6 Hz, C3), 128.3 (d, 5 J(C P) = 7.0
2
Hz, C5), 128.5 (d, J(C P) = 10.6 Hz, C2), 140.1 (d,
1 J(C P) = 55.2 Hz, C8), 148.7 (s, C9, C13), 153.3 (d,
3
4 J(C P) = 1.1 Hz, C11), 154.8 (d, J(C P) = 12.2 Hz,
Heteroatom Chemistry DOI 10.1002/hc

Phosphaalkenes Palladium(II) Complexes 369
C1), 169.8 (d, 1 J(C P) = 37.1 Hz, C7). Mass spectrum
m/z (%) 396 (M+, 100%). Anal. C26H37OP (396.55): C
78.75, H 9.40; found C 78.50, H 9.55.
Synthesis of Complex 5
To ligand 1 (158.6 mg, 0.4 mmol, 2 equiv) in
dichloromethane (3 mL) was added, at room temper-
ature, [Pd(Allyl)Cl]2 (36.7 mg, 0.1 mmol, 0.5 equiv).
The reaction was followed by 31P NMR. After check-
ing the formation of the corresponding cationic com-
plex (with a chloride as counteranion), AgOTf (51.4
mg, 0.2 mmol, 1 equiv) was added and the mixture
was stirred for 1 hour. The precipitate (AgCl) was fil-
tered under vacuum and the solvent was evaporated.
A white solid was obtained (0.185 g, yield: 85%).
1H NMR (300 MHz, CD2Cl2, 298 K) 1.29 (s, t-Bu),
1.34 (s, t-Bu), 1.45 (s, t-Bu), 3.11 (s, 2H, CH2allyl),
3.71 (s, 3H, OCH3), 5.24 (broad s, 2H, CH2 allyl),
5.40 (m, 1H, CH allyl), 6.85 (m, 2H, H6, H4), 7.13 (m,
1H,H5), 7.33 (m, 1H, H3), 7.52 (s, 2H, H10, H12), 8.71
(pseudo t, 1H, ꢀJ(H P) = 29.3 Hz, H7); 31P NMR
(121.5 MHz, CD2Cl2, 298 K) δ 188.0 ppm. ; 13C NMR
(75.5 MHz, CD2Cl2, 298 K) δ 30.1 (s, para C(CH3)3),
33.5 (s, ortho C(CH3)3), 34.5 (s, para C(CH3)3), 38.1
(ortho C(CH3)3), 55.0 (s, OCH3), 76.0 (broad s, CH2
allyl), 110.5 (s, C6), 119.3 (s, CH allyl), 123.1 (s, C10,
C12), 125.7 (s,) 126.2 (s, C2), 127.6 (d, J = 13.3 Hz, C3),
131.9 (s, C5), 153.0 (s, C9, C13), 154.4 (broad s, C11),
155.2 (pseudo t, ꢀJ = 18.8 Hz, C1), 169.9 (pseudo t,
ꢀJ = 43.6 Hz, C7). Anal. C56H79F3O5P2PdS (1089.65):
C 61.73, H 7.31; found C 61.49, H 7.28.
Synthesis of 1,3-Bis[2-(supermesityl)phos
phanediylmethyl]benzene (3)
The phospha-Wittig reagent [Mes*P PMe3] was
cooled to 0◦C and cannulated on a suspension of
isophtalaldehyde (0.160 g, 1.2 mmol, 0.4 equiv) at
0◦C in THF (10 mL). The crude mixture was stirred
for 3 h. CH2Cl2 (10 mL), water (10 mL), and ice were
then added. The organic phase was separated, dried
over MgSO4, and filtered. The solvent was then evap-
orated and MeOH (10 mL) was added, resulting in
the formation of a precipitate, which was filtered
off and dried under vacuum. The title compound
was obtained as a white solid (0.33–0.46 g, yield: 50–
70%). For complete characterization, see reference
20.
Synthesis of Complex 4
To ligand 1 (79.8 mg, 0.2 mmol, 1 equiv) in
dichloromethane (3 mL) was added, at room temper-
ature, [Pd(Allyl)Cl]2 (36.7 mg, 0.1 mmol, 0.5 equiv.).
The reaction was followed by 31P NMR. After check-
ing the formation of the corresponding cationic
complex (with a chloride as counteranion), AgOTf
(51.4 mg, 0.2 mmol, 1 equiv) was added and the
mixture was stirred for 1 hour. The precipitate (AgCl)
was filtered under vacuum and the solvent was evap-
orated. A white solid was obtained (0.125 g, yield:
90%).
Synthesis of Complex 6
A solution of ligand 3 (100 mg, 0.15 mmol)
in dichloromethane (5 mL) was added to [PdCl2
(PhCN)2] (58 mg, 0.15 mmol). The orange mixture
obtained was stirred for 10 hours at 40◦C. Then,
EtOH (3 mL) was added to precipitate the complex.
Orange crystals of 6 were grown after slow evapo-
ration of the solution under nitrogen atmosphere:
yield 75–85 mg (62–70%).
1H NMR (300 MHz, CD2Cl2, 298 K): δ 1.29 (s,
9H, para C(CH3)3), 1.54 (s, 9H, ortho C(CH3)3), 3.69
(s, 3H, OCH3), 5.48 (m, 1H, CH allyle), 6.81 (d,
3 J(H H) = 7.7 Hz, H6), 6.91 (t, ꢀJ(H H) = 7.4 Hz,
H4), 7.31 ( m, ꢀJ(H H) = 9.4 Hz, H5), 7.46 (s,
H10, H12), 7.75 (m, ꢀJ(H H) = 10.3 Hz, H3), 8.20
(d, 2 J(H P) = 27.3 Hz, H7); 31P NMR (121.5 MHz,
CD2Cl2, 298 K) δ 206.0 ppm; 13C NMR (75.5
MHz, CD2Cl2, 298 K) δ 30.1 (s, para C(CH3)3),
33.6 (d, 3 J(C P) = 1.5 Hz, ortho C(CH3)3), 34.3
(para C(CH3)3), 37.3 (s, ortho C(CH3)3), 54.8 (s,
OCH3), 110.03 (d, 4 J(C P) = 3.9 Hz, C6), 116.2 (d,
5 J(C P) = 6.0 Hz C5), 119.6 (s, C10, C12), 125.9
(d, 4 J(C P) = 1.7 Hz, C4), 127.5 (d, 3 J(C P) = 22.5
Hz, C3), 128.4 (s, C2), 130.7 (d, 5 J(C P) = 6.3 Hz,
C5), 151.8 (d, 2 J(C P) = 2.1 Hz, C9, C13), 155.1 (d,
3 J(C P) = 17.3 Hz, C1), 163.4 (d, 2 J(C P) = 46.0 Hz,
C7). Anal. C30H42F3O4PPdS (693.11): C 51.99, H 6.11;
found C 51.60, H 6.24.
General Procedures for the Coupling Reactions
Suzuki Reaction. The catalysts were prepared
by dilution of the precursor in dichloromethane at
room temperature under an inert atmosphere. For
example, 2.6 mg (0.0024 mmol) of complex 5 were
diluted in CH2Cl2 (10 mL), and 85 µL (0.00002 mmol,
0.00001%) of the solution was poured into a Sch-
lenck tube with a syringe and the solvent was evap-
orated. To the Schlenck tube, phenylboronic acid (3
mmol, 0.366 mg), K2CO3 (4 mmol, 0.55 g), and the
halogenoarene (2 mmol) in toluene (20 mL) were
added. The mixture was heated at 110◦C for 2 h.
The reaction was monitored by GC. The products
were isolated by column chromatography on silica
Heteroatom Chemistry DOI 10.1002/hc

370 Deschamps et al.
gel (petroleum ether 40–65◦C) and characterized by
comparison with literature data.
Cambridge CB2 1EZ, UK, on request (fax: +44-1223-
336-033; E-mail: deposit@ccdc.cam.ac.uk or URL:
http://www.ccdc.cam.ac.uk), quoting the deposition
numbers for 4 and 5.
Sonogashira Reaction. A solution of the cata-
lyst (0.1%) was added to a mixture of the aryl halide
(1.0 mmol), phenylacetylene (220 µL, 2 mmol), and
triethylamine (3 mL). The resultant mixture was
heated at 90◦C for 24 h. The progress of the reaction
was monitored by GC. At the end of the reaction, the
flask was cooled to room temperature. The workup
consists of quenching with water (5 mL), extraction
with dichloromethane (10 mL) and drying of the re-
sulting solution over MgSO4. The solution was then
filtered and the solvent was removed under reduced
pressure. NMR data of the isolated compounds were
compared with those reported in literature.
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Views of the optimized structures with the com-
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and bond angles for complexes 4 and 5 have
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