Cavity-shaped ligands: Calix[4]arene-based monophosphanes for fast Suzuki-Miyaura cross-coupling

Article abstract of DOI:10.1002/chem.200903390

Five conical calix[4]arenes that have a PPh₂ group as the sole functional group anchored at their upper rim were assessed in palladiumcatalysed cross-coupling reactions of phenylboronic acid with aryl halides (dioxane, 100°C, NaH). With arylbromides, remarkably high activities were obtained with the catalytic systems remaining stable for several days. The performance of the ligands is comparable to a Buchwald-type triarylphosphane, namely, (2'-methyl[1,1'-biphenyl]-2-yl)diphenylphosphane, which in contrast to the calixarenyl phosphanes tested may display chelating behaviour in solution. With the fastest ligand, 5-diphenylphosphanyl-25,26,27,28-tetra(p-methoxy)benzyloxy- calix[4]arene (8), the reaction turnover frequency for the arylation of 4-bromotoluene was 321000 versus 214000 mol-(ArBr).mol(Pd)^-1.h ^-1 for the reference ligand. The calixarene ligands were also efficient in Suzuki cross-coupling reactions with aryl chlorides. Thus, by using 1 mol% of [Pd(OAc)₂] associated with one of the phosphanes, full conversion of the deactivated arenes 4-chloroanisole and 4-chlorotoluene was observed after 16 h. The high performance of the calixarenyl-phosphanes in Suzuki-Miyaura coupling of aryl bromides possibly relies on their ability to stabilise a monoligand [Pd⁰L(ArBr)] species through supramolecular binding of the Pd-bound arene inside the calixarene cavity.

Full text of DOI:10.1002/chem.200903390

FULL PAPER
DOI: 10.1002/chem.200903390
Cavity-Shaped Ligands: Calix[4]arene-Based Monophosphanes for Fast
Suzuki–Miyaura Cross-Coupling
Laure Monnereau,[a] David Sꢀmeril,*[a] Dominique Matt,*[a] and Loꢁc Toupet[b]
Abstract: Five conical calix[4]arenes
that have a PPh2 group as the sole
functional group anchored at their
upper rim were assessed in palladium-
catalysed cross-coupling reactions of
phenylboronic acid with aryl halides
(dioxane, 1008C, NaH). With arylbro-
mides, remarkably high activities were
obtained with the catalytic systems re-
maining stable for several days. The
performance of the ligands is compara-
ble to a Buchwald-type triarylphos-
phane, namely, (2’-methyl[1,1’-biphen-
yl]-2-yl)diphenylphosphane, which in
contrast to the calixarenyl phosphanes
tested may display chelating behaviour
in solution. With the fastest ligand, 5-
diphenylphosphanyl-25,26,27,28-
tetra(p-methoxy)benzyloxy-calix[4]ar-
ene (8), the reaction turnover frequen-
cy for the arylation of 4-bromotoluene
reactions with aryl chlorides. Thus, by
using 1 mol% of [Pd(OAc)2] associated
AHCTUNGTRENNUNG
with one of the phosphanes, full con-
version of the deactivated arenes 4-
chloroanisole and 4-chlorotoluene was
observed after 16 h. The high perfor-
mance of the calixarenyl–phosphanes
in Suzuki–Miyaura coupling of aryl
bromides possibly relies on their ability
was
AHCTUNGTRENNUNG
321000
versus
214000 mol-
(ArBr).mol(Pd)À1.hÀ1 for the reference
ligand. The calixarene ligands were
also efficient in Suzuki cross-coupling
gand [Pd0L
to stabilise a monoCAHTUNGTERNlNNUG iAHCTUNGTERNUNNG ACHTUNGTRENNUNG(ArBr)]
species through supramolecular binding
of the Pd-bound arene inside the calix-
arene cavity.
Keywords: bulky monophosphanes ·
calixarenes · cross-coupling · palla-
dium · supramolecular catalysis
Introduction
phosphane complex as the most active catalyst as well as to
promote reductive elimination.[5,6] Buchwald has shown that
high activities can be induced with phosphanes containing
the sterically demanding 2,2’-biphenyl motif (Scheme 1).[7–9]
Since the discovery by Suzuki and Miyaura in 1981 that [Pd-
ACHTUNGTRENNUNG(PPh3)4] catalyses the coupling of phenyl boronic acid with
aryl halides,[1] many efforts have been spent to find variants
of this catalyst based on ligands that accelerate the reaction
and/or make the reaction proceed with less-reactive aryl
chlorides or extremely hindered aryl halides.[2,3] Although it
is now commonly accepted that strongly basic phosphanes
promote the oxidative addition step,[4] the use of bulky phos-
phanes possibly serves to favour the formation of a mono-
[a] Dr. L. Monnereau, Dr. D. Sꢀmeril, Dr. D. Matt
Laboratoire de Chimie Inorganique Molꢀculaire et Catalyse
Institut de Chimie UMR 7177 CNRS, Universitꢀ de Strasbourg
67008 Strasbourg Cedex (France)
Fax : (+33)3-68-851-637
E-mail: dsemeril@chimie.u-strasbg.fr
dmatt@chimie.u-strasbg.fr
[b] Dr. L. Toupet
Groupe Matiꢁre Condensꢀe et Matꢀriaux
UMR 6626 CNRS, Universitꢀ de Rennes 1
35042 Rennes Cedex (France)
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.200903390.
Scheme 1.
Chem. Eur. J. 2010, 16, 9237 – 9247
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9237

Similar observations were made
by Beller and Zapf with closely
related ligands, the so-called N-
aryl-phosphanylpyrroles
(Scheme 1).[10] The way that the
Buchwald ligands operate is
still not fully understood, but it
was suggested that coordination
of the ipso carbon atom of the
remote aryl ring is likely to
play a key role, that is, the li-
gands may display hemilability
during catalysis.[11–13] Interest-
ingly, the increased activity of
such ligands in Suzuki–Miyaura
arylations was shown to arise
for tertiary phosphanes of both
Scheme 2. Synthesis of monophosphanes 6–10.
types,
PACHTUNGTRENNUNG(alkyl)2(2,2’-C6H4Ar)
and PPh2(2,2’-C6H4Ar), but the
air-sensitive dialkyl-substituted
ligands are the better ones for the reactions with aryl chlor-
ides.[14] Wondering whether high productivity might also be
observed with triarylphosphanes that cannot function as
hemilabile/chelating ligands, we decided to assess a series of
encumbered monodentate arylphosphanes, namely, ligands
6–10 (Scheme 1), which are all based on a conical calix[4]ar-
ene backbone. These phosphanes must, of course, be regard-
ed as ligands of medium basicity. It is worth mentioning that
bowl-shaped triarylphosphanes with no auxiliary binding
group in which the phosphorus atom sits deep in a molecu-
lar pocket[15] were recently shown to catalyse the Suzuki–
Miyaura coupling of unactivated aryl chlorides at low tem-
peratures efficiently.[16] Bulky, dendritic triarylphosphanes
that display high efficiency in Suzuki cross-coupling were
also reported, but the latter may all potentially behave as
hemilabile ligands so that their efficiency possibly relies on
secondary ligating groups.[17,18] Note that the coordination
chemistry of calixarenyl monophosphanes related to those
described in this paper has recently been studied thoroughly.
A striking feature of these ligands concerns their ability to
behave as supramolecular chelators towards metal–arene
moieties.[19,20]
In the first step precursor 1 was alkylated in DMF with the
appropriate alkylbromide by using NaH as base. The phos-
phanyl group was then introduced by halogen–lithium ex-
change followed by reaction with PPh2Cl. The deprotected
calixarene 10 was obtained quantitatively from the tetraben-
zylated derivative 7 upon treatment with AlCl3 in toluene.
Each phosphane is characterised by a singlet near À5.5 ppm
in its 31P NMR spectrum (see also d=À4.5 ppm for PPh3).
1
The corresponding H NMR spectra are in keeping with Cs-
symmetrical ligands, each of them showing the presence of
two distinct AB patterns for the diastereotopic ArCH2Ar
protons. For each ligand, the ArCH2Ar signals appear near
31.5 ppm in the corresponding 13C NMR spectrum, a value
which is typical for calixarenes that adopt a cone conforma-
tion.[25]
To gain insight into the coordinative properties of these
phosphanes, we investigated the reaction of 7 with [PdCl2-
(cod)] (cod=1,5-cyclooctadiene) in CH2Cl2 at À788C
(Scheme 3). This reaction led to trans-[PdCl2(7)2] (11), the
stereochemistry of which was determined by an X-ray dif-
fraction study (Figure 1). In the 31P NMR spectrum of 11,
the phosphorus signal is seen at 22.7 ppm, a value that, ac-
cording to the Bartik and Himmler scale, indicates that the
electronic properties of 7 should be close to those of P
ACHTUNGTRENNUNG
Results and Discussion
tolyl)3 (see also the 31P chemical shift of trans-[PdCl2{P
ACHTUNGTRENNUNG
tolyl)3}2]: d=22.2 ppm).[27] Repeating the above reaction at
408C instead of À788C afforded the corresponding cis
isomer 12, which also formed when a CDCl3 solution of the
trans complex was allowed to stand for several days. These
findings unambiguously demonstrate the ability of a palladi-
um centre to coordinate two bulky calixarene monophos-
phanes. The X-ray structural study carried out for trans-
[PdCl2(7)2] further revealed that in the solid state the palla-
dium atom sits on the centre of symmetry of a molecule that
has a length of approximately 28 ꢃ. The calixarene skele-
tons adopt a typically flattened cone conformation. Within
each calixarene fragment, the distances between the cent-
The phosphanes presented in this study all contain a phos-
phorus atom that has three aryl substituents, one of which is
a bulky calixarenyl unit. Our choice to focus on medium-
basic phosphane ligands rather than strongly basic ones was
made to isolate steric effects from electronic ones in
Suzuki–Miyaura cross-couplings because phosphanes with
alkyl substituents are known to accelerate these reactions
drastically.[4,8,21] Note that calixarene monophosphanes have
only been sparingly used in homogeneous catalysis.[22–26]
Monophosphanes 6–9 were synthesised readily in two
steps from monobromo calixarene 1 according to Scheme 2.
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Chem. Eur. J. 2010, 16, 9237 – 9247

Cavity-Shaped Ligands
FULL PAPER
Reaction of 7 with [Pd(o-
C6H4NMe2)Cl]2 quantitatively
gave the monophosphane com-
plex 13 (see the Experimental
Section; Scheme 4). Coordina-
tion of the phosphorus atom
was unambiguously deduced
from
the
corresponding
which
1H NMR
spectrum,
shows a doublet for the NMe2
protons (4J
AHCTUNGTRENNUNG
ment of 13 with AgBF4 in THF
gave the cationic complex 14.
1
The H NMR spectrum of 14 is,
as for 13, consistent with a Cs-
symmetrical molecule. During
recristallisation of 14 from a di-
chlorohexane solution, an aquo
complex 15 formed owing to
the presence of trace amounts
of water. Interestingly, two
types of crystals, 15a and 15b,
were obtained for this complex,
which were both studied by X-
ray diffraction. The main differ-
ence between the correspond-
Scheme 3. Synthesis of trans-11 and cis-12.
ing solid-state structures con-
cerns the positioning of the Pd
atom, which is located near the
receptor entrance in 15a, and is pushed away from the
cavity in 15b (Figure 2). A rough determination of the
Figure 1. Molecular structure of trans-[PdCl2·72] (11). Important bond
À
À
lengths [ꢃ] and angles [8]: Pd P 2.3285(5), Pd Cl 2.3028(5); Cl(1)-Pd-
P(1) 89.72(2), P(1)-Pd-Cl(2) 90.28(2).
roids of distal phenol rings are 4.83 and 7.75 ꢃ, respectively.
À
The P M vectors are nearly tangentially oriented with re-
spect to the cone delineated by the corresponding calixarene
moiety, but with the metal atom still lying inside the cone.
Note that it is not appropriate to attempt to determine a
cone-angle value for 7. Indeed, given that the PPh2 moiety
À
can freely rotate about the P Ccalix axis (see below), the
cone-angle value does considerably change by varying the
orientation of the phosphorus lone pair. The cone angle
clearly reaches its highest value when the P lone pair points
towards the calixarene axis, that is, when a coordinated
metal ion sits exactly above the cavity entrance.
Scheme 4. Synthesis of complexes 13–15.
Chem. Eur. J. 2010, 16, 9237 – 9247
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9239

D. Matt, D. Sꢀmeril et al.
86.5% for the other salts (Table 1). This complex was used
in all following tests.
Table 1. Influence of the palladium precursor on Suzuki–Miyaura cross-
coupling by using monophosphane 6.[a]
Entry
Palladium precursor
Conversion [%]
1
2
3
4
[Pd
[Pd
A
N
86.5
78.2
48.7
94.9
CHTUNGTRENNUNG
[a] [Pd] (5ꢅ10À5 mmol, 1ꢅ10À2 mol%, ArBr/Pd=10000),
6
(1ꢅ
10À4 mmol, 2 equiv/Pd), 4-bromoanisole (0.094 g, 0.5 mmol), PhB(OH)2
(0.122 g, 1.0 mmol), NaH (60% dispersion in mineral oil, 0.040 g,
1.0 mmol), dioxane (1.5 mL), decane (0.050 mL), 1008C, 1 h. The conver-
sions were determined by GC; the calibrations were based on decane.
Figure 2. Molecular structures of the cationic complexes 15a and 15b.
For clarity, the BF4 anions and the CH2Cl2 solvate molecule of 15a are
À
not shown. Important bond lengths [ꢃ] and angles [8]: 15a: Pd P
In a second series of runs, we determined the optimal
base from Cs2CO3, K2CO3, CsF, CsCl, NaH, NaOH, KOH
and NEt3. As can be inferred from Table 2, the most effi-
cient base was NaH, which led to a conversion of 94.9%
(Table 2, entry 5).
À
À
2.2659(7), Pd O 2.171(2), P 2.151(2); N-Pd-O 91.41(7), N-Pd-P
À
À
À
177.55(7), O-Pd-P 89.88 (5); 15b: Pd P 2.264(1), Pd O 2.186(2), P N
2.158(3); N-Pd-O 89.1(1), N-Pd-P 174.99(9), O-Pd-P 93.32 (7).
ligand encumbrance according to Tolmanꢄs definition[28]
shows that when the phosphorus is oriented as in 15a, the
corresponding cone angle is larger than that determined
from 15b by approximately 358. Note that within the tem-
Table 2. Research of the optimal base for the Suzuki–Miyaura cross-cou-
pling catalysed by [Pd
(OAc)2]/calix[4]arene monophosphane 6.[a]
ACHTUNGTRENNUNG
1
perature range +25 to À808C the H NMR (CD2Cl2) spec-
Entry
Base
Conversion [%]
trum of 14 (that has coordinated THF instead of H2O) re-
mained sharp, revealing the presence of only one species in
solution. Thus, it was not possible to freeze-out the possible
1
2
3
4
5
6
7
8
Cs2CO3
K2CO3
CsF
CsCl
NaH
NaOH
KOH
NEt3
75.5
86.9
64.7
28.7
94.9
57.7
93.6
35.3
À
rotation of the {Ph2PPd(Me2NCH2C6H4)} unit about the P
C(calixarene) bond.
Catalytic Suzuki–Miyaura cross-coupling—Optimising the
reaction conditions: Monophosphanes 6–10 were assessed in
the palladium-catalysed Suzuki–Miyaura cross-coupling re-
actions (Scheme 5). The catalysts were generated in situ by
[a] [PdACHTUNGTRNEUNG
(OAc)2] (5ꢅ10À5 mmol, 1ꢅ10À2 mol%, ArBr/Pd=10000), 6 (1ꢅ
10À4 mmol, 2 equiv/Pd), 4-bromoanisole (0.094 g, 0.5 mmol), PhB(OH)2
(0.122 g, 1.0 mmol), base (1.0 mmol), dioxane (1.5 mL), decane
(0.050 mL), 1008C, 1 h. The conversions were determined by GC; the cal-
ibrations were based on decane.
Suzuki–Miyaura cross-coupling of arylbromides: By using
the above optimised reaction parameters (dioxane, 1008C,
[PdACTHNUTRGNE(UGN OAc)2] and NaH; 1 h reaction time), the runs were car-
Scheme 5. Suzuki–Miyaura cross-coupling.
ried out applying an ArBr/Pd ratio of 100000:1 (which cor-
responds to a palladium loading of 10À3 mol%). As found
by other authors,[14] no significant differences in activity
were observed when using either 1 or 2 equivalents of phos-
phane per palladium. This suggests that the active species of
the reaction is an intermediate containing only one mono-
phosphane per palladium. Nevertheless, to increase the cata-
lyst lifetime and also to allow comparison with published
work, a L/Pd ratio of 2:1 was used in all catalytic tests. For
each substrate, except for mesitylbromide, at least one of
the ligands tested was found to be suitable for a conversion
higher than 80% after 1 h reaction time (Table 3, entries 1–
8). For the less-reactive mesitylbromide, all phosphanes
were of comparable efficiency (Table 3, entry 9).
mixing the palladium precursor with two equivalents of
monophosphane per palladium. We noted that, as expected
for bulky phosphines, higher phosphine/Pd ratios did not sig-
nificantly modify the catalytic outcome (see the Supporting
Information).
Determination of the optimal catalytic system was carried
out with ligand 6 by studying the cross-coupling reaction be-
tween 4-bromoanisole and phenylboronic acid at 1008C in
1,4-dioxane. In a first series of runs we investigated the in-
fluence on the reactivity of the following palladium precur-
sors: [Pd
(OAc)2]. The highest conversion was obtained with [Pd-
ACHTUNGTRENNUNG(OAc)2], which led to a conversion of 94.9% versus 48.7–
ACHTUNGTRENNUNG ACHTUNRTGEG(NNNU dba)2], [PdCl2CAHTNUGTNER(NUGN cod)] and [Pd-
(h3-C3H5)Cl]2, [Pd
ACHTUNGTRENNUNG
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Cavity-Shaped Ligands
FULL PAPER
Table 3. Palladium-catalysed Suzuki–Miyaura cross-coupling of arylbromides by using monophosphanes 6–10
substituents,
which
might
and by applying an ArBr/Pd ratio of 100 000:1.[a]
modify the shape of the calixar-
ene backbone, and incidentally
its overall encumbrance. This
interpretation, however, does
not hold if the results obtained
with phosphane 8 are consid-
ered, which performs only with
Calix[4]arene monophosphane
Entry
1
ArBr
6
7
8
9
10
conv. [%]
TOF
99.7
99700
95.4
49.8
89.4
94.4
94400
95400
49800
89400
conv. [%]
TOF
80.3
80300
27.1
27100
40.0
40000
42.0
42000
76.1
76100
2
3
non-methoxylated
substrates.
conv. [%]
TOF
95.0
95000
94.7
94700
47.6
47600
99.3
99300
98.8
98800
The observation that methoxy-
containing arylbromides lower
the reactivity of catalytic sys-
tems based on this particular
phosphane was corroborated by
another test. Thus, repeating
the run described in entry 8 of
Table 4 (substrate: 4-bromoto-
luene) in the presence of 1,4-di-
conv. [%]
TOF
100
100000
48.7
48700
91.4
91400
96.2
96200
100
100000
4
conv. [%]
TOF
46.1
46100
38.0
38000
88.0
88000
51.9
51900
83.2
83200
5
6
conv. [%]
TOF
49.1
49100
26.7
26700
99.2
99200
58.5
58500
26.4
26400
methoxybenzene
(0.5 equiv
conv. [%]
TOF
92.9
92900
64.1
64100
99.0
99000
93.1
93100
77.6
77600
with respect to the substrate),
led to a significant activity de-
crease (ca. 30%). We have no
rational explanation for the
lower activities of the sole
ligand 8 in the presence of ani-
sole derivatives. Possibly, the
methoxy substituents of 8 form
a ternary complex with anisole
derivatives and the sodium ions
present in solution in which the
shape of the calixarene core is
strongly modified, and inciden-
tally also the bulkiness of the
ligand.
7
8
conv. [%]
TOF
97.9
97900
100
100000
99.2
99200
100
100000
92.0
92000
conv. [%]
TOF
47.0
4700
38.1
3810
52.7
5270
42.0
4200
36.1
3610
9[b]
[a] [PdACHTUNGTRENNUNG
(OAc)2] (5ꢅ10À6 mmol, 1ꢅ10À3 mol%), monophosphane (1ꢅ10À5 mmol, 2 equiv/Pd), ArBr (0.5 mmol),
PhB(OH)2 (0.122 g, 1.0 mmol), NaH (60% dispersion in mineral oil; 0.040 g, 1.0 mmol), dioxane (1.5 mL),
decane (0.050 mL), 1008C, 1 h. The conversions were determined by GC; the calibrations were based on
decane. The TOFs were expressed in molACHTUNTRGNEUNG . Conv.=conversion [b] [PdACTHGNURTEN(NGUN OAc)2] (5ꢅ
(ArBr).mol(Pd)À1.hÀ1
10À5 mmol, 1ꢅ10À2 mol%), monophosphane (1ꢅ10À4 mmol, 2 equiv/Pd).
To find the highest catalytic activity, the ArBr/Pd ratio
was raised to 106:1 (Table 4). With this catalyst loading, the
conversions remained significant; moreover, the differences
in activity between the five monophosphanes tested (6–10)
were more pronounced. Monophosphane 6, which has O-
hexyl substituents, was the one that gave the highest activi-
ties for substrates substituted by a methoxy function (4-bro-
moanisole, 2-bromoanisole, 2-bromo-6-methoxynaphtha-
lene; Table 4, entries 1–3). The p-methoxybenzyl-substituted
monophosphane 8 gave the higher conversions for bromo-
benzene as well as for 2-, 3-, and 4-bromotoluene (Table 4,
entries 5–8). 1-Bromonaphthalene was converted more effi-
ciently with monophosphane 9, which has four m-methoxy-
benzyl substituents (Table 4, entry 4). The tetrabenzylated
monophosphane 7 gave, in general, lower conversions than
the other phosphanes, this trend being particularly marked
with the two hindered substrates 2-bromoanisole and 2-bro-
motoluene (Table 4, entries 2 and 6). The highest catalytic
activity of all runs was measured for monophosphane 8
when used in the arylation of 4-bromotoluene (TOF=
We further observed that all the catalytic systems present-
ed above displayed remarkably long lifetimes. For example,
carrying out the arylation of 4-bromotoluene with ligand 8
and a palladium loading of 2.10À6 mol% led to a conversion
of 10.3% after 16 h (Table 5, entry 1). This corresponds to a
TOF of 322000 molACTHNUTRGNEUNG
(ArBr).mol(Pd)À1.hÀ1, a value that is
nearly identical with the one measured after 1 h (Table 4,
entry 8). After three days, the activity was still high, the
TON having then reached
a
value of 14.55ꢅ106 mol-
AHCTUNGTRENNUNG
Finally, several runs that used a low Pd concentration
(ArBr/Pd=106) were repeated in the presence of a drop of
mercury. No significant change in activities were observed,
suggesting that no palladium nanoparticles were present.[18]
Suzuki–Miyaura cross-coupling at room temperature: The
monophosphanes were further assessed for use in reactions
that were carried out at room temperature. These runs were
performed with an ArBr/Pd ratio of 1000 (0.1 mol%). In
Table 6 the results obtained for various arylbromides are
listed, with each entry corresponding to a test achieved in
the presence of the ligand that gave the best results at
1008C. Under these conditions, good conversions were ob-
321000 mol(converted
ArBr).mol(Pd)À1.hÀ1
;
Table 4,
entry 8). The observed activity differences between the indi-
vidual phosphanes could, subsequently, reflect differences in
the strength of the steric interactions between the lower-rim
Chem. Eur. J. 2010, 16, 9237 – 9247
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9241

D. Matt, D. Sꢀmeril et al.
Table 4. Palladium-catalysed Suzuki–Miyaura cross-coupling of arylbromides by using monophosphanes 6–10
For example, for 1-chloro-4-ni-
trobenzene, the conversion was
41.0% after 1 hour (Table 7,
entry 1). The higher reactivity
of 1-chloro-4-nitrobenzene with
respect to the other substrates
arises from an easier oxidative
addition step with this particu-
lar arylchloride. Increasing the
reaction time allowed full trans-
formation of all substrates.
Thus by using 7, for example,
100% conversions were ob-
served after approximately 5 h
in the case of 1-chloro-4-nitro-
benzene and chlorobenzene,
and after 16 h for 4-chloroani-
sole and 4-chlorotoluene.
and applying a ArBr/Pd ratio of 106:1.[a]
Calix[4]arene monophosphane
Entry
1
ArBr
6
7
8
9
10
conv. [%]
TOF
25.4
254000
21.1
6.2
20.8
21.2
212000
211000
62000
208000
conv. [%]
TOF
13.0
130000
3.8
38000
5.7
57000
11.6
116000
4.5
45000
2
3
conv. [%]
TOF
26.1
261000
20.6
206000
6.4
64000
21.6
216000
20.3
203000
conv. [%]
TOF
13.7
137000
6.5
65000
16.6
166000
17.0
170000
10.5
105000
4
conv. [%]
TOF
6.7
67000
5.3
53000
14.5
145000
8.8
88000
10.8
108000
5
6
conv. [%]
TOF
5.4
54000
3.6
36000
16.4
164000
7.9
79000
3.2
32000
conv. [%]
TOF
16.2
162000
9.8
98000
20.1
201000
14.6
146000
10.5
105000
Comparison with other aryl-
phosphanes: The results out-
lined above demonstrate that
7
conv. [%]
TOF
21.4
214000
15.2
152000
32.1
18.8
188000
20.9
209000
8
321000[b]
the combination of [PdACHTUNGTRENNUNG(OAc)2]
with monophosphanes 6–10 re-
sults in highly active catalysts
for Suzuki–Miyaura cross-cou-
pling reactions of arylbromides.
Ligands 6 and 8, which were
the ligands that gave the best
results for the arylation of bro-
moanisole and bromotoluene,
respectively, were compared
with two non-bulky arylphos-
phanes, PPh3 and (4-benzyloxy-
phenyl)diphenylphosphane
[a] [PdACHTUNGTRENNUNG
(OAc)2] (5ꢅ10À7 mmol, 1ꢅ10À4 mol%), monophosphane (1ꢅ10À6 mmol, 2 equiv/Pd), ArBr (0.5 mmol),
PhB(OH)2 (0.122 g, 1.0 mmol), NaH (60% dispersion in mineral oil; 0.040 g, 1.0 mmol), dioxane (1.5 mL),
decane (0.050 mL), 1008C, 1 h. The conversions were determined by GC; the calibrations were based on
decane. The TOFs were expressed in molACTHNUTRGNEUNG
(ArBr).mol(Pd)À1.hÀ1. Conv.=conversion. [b] Repeating this experi-
ment during a 5 h reaction period led to full conversion.
Table 5. Stability of the catalytic species formed with monophosphane 8.[a]
Entry
Time [h]
Conversion [%]
TON
[mol
(ArBr).mol(Pd)À1
TOF
[mol
(ArBr).mol(Pd)À1.hÀ1
G
R
]
G
U
]
1
2
3
4
16
24
48
72
10.3
14.5
25.3
29.1
5150000
7250000
12660000
14550000
322000
302000
264000
202000
(16), and two sterically de-
manding ones, PACHTNUGRTENUNG(o-tolyl)3 and
[a] [Pd
(OAc)2](2ꢅ10À8 mmol, 2ꢅ10À6 mol%, 4-bromotoluene/Pd ratio=50ꢅ106), monophosphane
8
(4ꢅ
2-diphenylphosphanyl-2ꢄ-meth-
ylbiphenyl (17; see Scheme 6).
The results of the runs per-
formed with these ligands are
reported in Table 8.
served for the whole range of substrates employed. The
highest conversion was again observed in the arylation of 4-
bromotoluene in the presence of ligand 8 (TOF=490 mol-
The systems based on 6 and 8
led to activities that were ap-
proximately 3–4 times higher
than those obtained with PPh3
and 16 (Table 8, entries 1 and
2). Interestingly, the activities
are comparable with those of
phosphane 17, which belongs to
the very efficient Buchwald-
type phosphanes.[14] In the case
of 4-bromotoluene, monophos-
phane 8 led to conversions that
were even significantly higher
than those obtained with 17
ACHTUNGTRENNUNG
(ArBr).mol(Pd)À1.hÀ1). Note that the systems based on
monophosphanes 6 and 8 were particularly efficient towards
the sterically hindered 2-bromoanisole and 2-bromotoluene
(conversions of 32.9 and 24.2%, respectively, after one
hour; see Table 6, entries 2 and 6).
Suzuki–Miyaura cross-coupling of arylchlorides: The more
challenging arylchlorides could also be converted conven-
iently into biaryls, as long as a catalyst loading of 1 mol%
was applied (Table 7). For all the substrates tested (4-chlor-
oanisole, 1-chloro-4-nitrobenzene, 4-chlorotoluene and
chlorobenzene), monophosphane 8 led to good conversions.
Scheme 6. Ligands used for
ranking the calixarene mono-
(conversion: 32.1% vs. 21.4%; phosphanes.
9242
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Chem. Eur. J. 2010, 16, 9237 – 9247

Cavity-Shaped Ligands
FULL PAPER
Table 6. Suzuki–Miyaura cross-coupling reactions carried out at room
efficient than Buchwald phosphanes of comparable steric
temperature by using monophosphanes 6, 8 and 9.[a]
encumbrance. In keeping with this belief, we found that P-
[31]
entry ArBr
Calix[4]arene
Conversion [%] TOF
AHCTUNGTREG(NNUN o-tolyl)3 led to activities that were approximately three
monophosphane
times lower than those of monophosphanes
(Table 8, entries 1 and 2).
6 and 8
1
2
6
6
44.3
32.9
440
330
To rationalise the abnormal high performance towards ar-
ylbromides of monophosphanes 6 and 8, which unlike 17 are
unable to coordinate metals in a hemilabile/chelating fash-
ion, it might be considered that in the corresponding catalyt-
À
ic intermediates, the P M vector remains preferentially di-
3
4
6
9
44.8
38.6
450
390
rected towards the calixarene axis rather than pointing away
from the cavity. In such a species the conical calixarenyl
fragment would then considerably increase the time-aver-
aged bulkiness of the phosphane (over, for example, that of
16), and therefore favour the formation of a zerovalent
5
6
8
8
22.8
24.2
230
240
mono
activation of aryl bromides.[29] With Buchwald-type ligands
such as 17, the formation of monoligand complexes is seem-
ACHUTGTNRNEUGlN iACTHNGUTRENgUNG and species, which is regarded as the key step in the
A
A
ingly promoted by transient binding of the remote aryl ring,
which then makes the phosphane artificially more bulky.
7
8
8
8
37.3
48.7
370
490
One factor that could contribute to the formation of mono
ACHTUNGTRENNUNGli-
AHCTUNGTREGgNNUN and phosphane complexes with 6–10 is the ability of the
latter ligands to bind metal–p–arene fragments, thereby
À
forming complexes in which the M arene unit is permanent-
[a] [PdACHTUNGTRENNUNG
(OAc)2] (5ꢅ10À4 mmol, 0.1 mol%, ArBr/Pd ratio of 1000), mono-
phosphane (1ꢅ10À3 mmol, 2 equiv/Pd), ArBr (0.5 mmol), PhB(OH)2
(0.122 g, 1.0 mmol), NaH (60% dispersion in mineral oil; 0.040 g,
1.0 mmol), dioxane (1.5 mL), decane (0.050 mL), room temperature, 1 h.
The conversions were determined by GC; the calibrations were based on
ly held inside the calixarene cavity. This finding was made
recently by Jeunesse et al. for some ruthenium-(p-cymene)
complexes obtained from closely related ligands (Scheme 7).
(ArBr).mol(Pd)À1.hÀ1
decane. The TOFs are expressed in molACHTNUGTERNUNNG .
Table 7. Palladium-catalysed Suzuki–Miyaura cross-coupling of arylchlor-
ides in the presence of monophosphanes 6–10.[a]
Entry ArCl
Calix[4]arene monophosphane
6
7
8
9
10
1
2
3
4
conv. [%] 5.0
36.2
41.0
25.7
4.2
conv. [%] 1.9
conv. [%] 5.6
conv. [%] 9.8
9.4
9.9
12.0
26.6
34.7
7.6
16.4
33.8
3.0
7.3
Scheme 7. a) Typical structure of RuCl2ACTHUNRGTNE(NUG p-cymene) complexes that were
obtained from calixarenyl monophosphanes;[19] b) Proposed monophos-
phane palladium(0) intermediate formed in Suzuki–Miyaura cross-cou-
pling before the oxidative addition step.
37.1
19.6
[a] [PdACHTUNGTRENNUNG
(OAc)2] (2.5ꢅ10À3 mmol, 1 mol%, ArCl/Pd ratio of 100), mono-
phosphane (5ꢅ10À3 mmol, 2 equiv/Pd), ArCl (0.25 mmol), PhB(OH)2
(0.061 g, 0.5 mmol), NaH (60% dispersion in mineral oil) (0.020 g,
0.5 mmol), dioxane (0.75 mL), decane (0.050 mL), 1008C, 1 h. The con-
versions were determined by GC; the calibrations were based on decane.
Conv.=conversion.
The entrapment of the h6-bonded arene results from p–p in-
teractions between the p-cymene ligand and two phenolic
rings of the calixarene backbone.[20,32] A similar supramolec-
ular interaction may, in principle, also occur in transient
[Pd0
ACTHNUTRGNE(NUG ArX)L] complexes obtained from the calixarenyl phos-
see Table 8, entry 2). The efficiency of Buchwald phos-
phanes is generally attributed to their ability to bind the pal-
ladium centre in a hemilabile manner, thereby stabilising a
reactive monophosphane palladium(0) precursor.[12,29] Possi-
bly, the activation barrier of the oxidative addition step is
phanes 6–10 (Scheme 7). Although this hypothesis remains
speculative, it is consistent with the observation that subtle
size modifications of the lower-rim substituents do improve
the catalytic outcome, probably as a result of an induced
shape modification of the calixarene receptor, which may
then operate as a better receptor.
lower for this monoACTHUNRGTENNlUG iACHUTNGTRENNUGgand species than for the correspond-
ing bis(phosphane) complex.[30] Note that bulky arylphos-
phanes with no secondary binding function are usually less
Of course, it may be questioned why 17 is more effi-
cient[33] than monophosphanes 6–10 in cross-coupling reac-
Chem. Eur. J. 2010, 16, 9237 – 9247
ꢂ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
9243

D. Matt, D. Sꢀmeril et al.
Table 8. Comparison of monophosphanes in Suzuki–Miyura cross-coupling of arylbromides.[a]
termine a cone angle value for
this kind of bulky ligands
worthless. Combining any of
these monophosphanes with
Entry
ArBr
PPh3
16
P
G
17
Calixarene
monophosphane
conv. [%]
TOF
7.0
70000
8.6
86000
9.6
96000
35.5
355000
25.4 (6)
254000
1
2
[PdACTHNUTRGNE(NUG OAc)2] and NaH at 1008C
conv. [%]
TOF
6.5
65000
7.5
75000
10.3
103000
21.4
214000
32.1 (8)
321000
in 1,4-dioxane gave a highly ef-
ficient catalytic system for the
Suzuki–Miyaura cross-coupling
of phenylboronic acid with aryl
bromides, which moreover was
stable over several days. The
observed activities, which com-
pare with those of another triar-
ylphosphane, the Buchwald-
type ligand 17, were found to
be three times higher than
those of systems based on the
conv. [%]
TOF
–
–
–
–
–
–
11.9
119000
16.4 (8)
164000
3
conv. [%]
TOF
–
–
–
–
–
–
9.7
97000
20.1 (8)
201000
4
[a] [PdACHTUNGTRENNUNG
(OAc)2] (5ꢅ10À6 mmol, 1ꢅ10À4 mol%), monophosphane (1ꢅ10À5 mmol, 2 equiv/Pd), ArBr (0.5 mmol),
PhB(OH)2 (0.122 g, 1.0 mmol), NaH (60% dispersion in mineral oil; 0.040 g, 1.0 mmol), dioxane (1.5 mL),
decane (0.050 mL), 1008C, 1 h. The conversions were determined by GC; the calibrations were based on
decane. The TOFs were expressed in molACTHNUTRGNEUNG
(ArBr).mol(Pd)À1.hÀ1. Conv.=conversion.
bulky phosphane
PACTHNGUTERU(NNG o-tolyl)3.
tions with aryl chlorides. According to Hartwig, the rate-lim-
iting step with aryl chlorides is the oxidative addition step
Because, unlike Buchwald-type ligands, the reported calixar-
enyl phosphanes cannot act as chelators, it is likely that
their high efficiency relies on the ability of the calixarene to
act as a second-sphere ligand towards a P-coordinated {Pd0-
that occurs after formation of the monoACTHNUTRGENNlUG iACHTUTGNRENNUG
gand species.[29] Ac-
tually, 17 may act as a chelator, and when behaving so it be-
comes a better donor than its P monodentate counterpart,
hence the oxidative addition step should be facilitated with
respect to systems based on purely monodentate phosphanes
such as 6–10. Note, however, that recent investigations on
bowl-shaped triarylphosphanes in which the P atom sits
deep inside a pocket[13,15,16,34] have clearly demonstrated that
the presence of additional donors that may render the phos-
phane a chelating ligand is not a prerequisite for the oxida-
tive addition to occur effectively. It is likely that with these
extremely crowded ligands, the palladium(0) complexes that
may form are exclusively monophosphane species, the for-
mation of the less-reactive PdL2 intermediate being totally
prevented. These findings suggest that, in principle, any
phosphane (L) of medium basicity that is able to shift the
equilibrium shown in Scheme 8 towards the formation of
AHCTUNGTRENNUNG
A
A
A
A
dative addition step is probably not sufficient to make
theses phosphanes competitive with the formally more elec-
tron rich 17 in cross-coupling reactions with aryl chlorides.
Further work is aimed at modifying the calixarene backbone
to get new triarylphosphane ligands that operate in a supra-
molecular fashion for the efficient activation of aryl chlor-
ides.
Experimental Section
the Pd0L
N
General methods: All syntheses were performed in Schlenk-type flasks
under dry nitrogen. Solvents were dried by conventional methods and
were distilled immediately prior to use. Routine 1H, 13C{1H} and 31P{1H}
NMR spectra were recorded by using a Bruker AVANCE 300 spectrome-
ter. 1H NMR spectra were referenced to residual protonated solvents
(7.26 ppm for CDCl3), 13C chemical shifts are reported relative to deuter-
ated solvents (77.16 ppm for CDCl3) and the 31P NMR data are given rel-
ative to external H3PO4. Elemental analyses were performed by the Ser-
vice de Microanalyse, Institut de Chimie, Universitꢀ de Strasbourg. The
catalytic solutions were analysed by using a Varian 3900 gas chromato-
graph equipped with a WCOT fused-silica column (25 mꢅ0.25 mm). 5-
Bromo-25,26,27,28-tetrahydroxy-calix[4]arene (1),[35] and (4-benzyloxy-
phenyl)diphenylphosphane (16)[36] were prepared according to literature
procedures. In the NMR data given hereafter, the bridging CH2 groups
of the calixarene backbone are designated by the abreviation ArCH2Ar.
Suzuki–Miyaura cross-coupling of aryl chlorides.
Scheme 8. Possible key equilibrium preceding the oxidative addition step
in Suzuki–Miyaura cross-coupling.
Conclusion
We have described the synthesis of five new, conical p-(H)3-
calix[4]arenes that have a PPh2 group anchored at their
upper rim. X-ray diffraction studies carried out on three pal-
ladium complexes containing monophosphane 7 suggest that
General procedure for the synthesis of 5-bromo-25,26,27,28-tetraalky-
loxy-calix[4]arenes (2–5): A solution of 1 (1.000 g, 2.0 mmol), NaH (60%
in mineral oil; 0.357 g, 8.9 mmol) and the corresponding alkylbromide
(8,9 mmol) in DMF (50 mL) was heated at 608C during 3 h. After cool-
ing to room temperature, excess NaH was hydrolysed with water (2 mL)
and the reaction mixture was evaporated to dryness. The resulting oily
À
the PPh2 moiety may freely rotate in solution about the P
Ccalix axis, and therefore position a coordinated metal ion
either above or outside the cone that is delineated by the
calixarene cavity. This peculiarity makes any attempt to de-
product was treated with
a mixture of CH2Cl2 (50 mL) and water
(20 mL). After extraction of the aqueous layer with CH2Cl2 (2ꢅ50 mL),
the organic phases were combined. The resulting solution was washed
9244
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ꢂ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2010, 16, 9237 – 9247

Cavity-Shaped Ligands
FULL PAPER
with water (4ꢅ50 mL), then dried over Na2SO4 and evaporated under re-
duced pressure. The products 2–5 were purified by column chromatogra-
phy on silica gel by using petroleum ether (100%) as the eluent for 2 and
3 or ethyl acetate/petroleum ether (20:80, v/v) as the eluent for 4 and 5.
mental analysis calcd (%) for C60H55O8Br (Mr =983.98): C 73.24, H 5.63;
found: C 73.28, H 5.75.
General procedure for the synthesis of 5-diphenylphosphanyl-25,26,27,28-
tetraalkyloxy-calix[4]arenes (6–9): n-Butyllithium (2.1 mmol) was slowly
added to a solution of 5-bromo-25,26,27,28-tetraalkyloxy-calix[4]arene
(1 mmol) in THF (50 mL) at À788C. After 0.5 h, the generated carbanion
was quenched with chlorodiphenylphosphane (2.5 mmol). The mixture
was stirred at room temperature for 3 h. After completion of the reaction
(monitored by TLC), water (20 mL) was added. The aqueous phase was
washed with CH2Cl2 (2ꢅ50 mL). The combined organic phases were
dried over Na2SO4 and were evaporated under reduced pressure. The cal-
ixarene monophosphanes 6–9 were purified by column chromatography
on silica gel by using petroleum ether (100%) as the eluent for 6 and 7
and ethyl acetate/petroleum ether (20:80, v/v) as the eluent for 8 and 9.
5-Bromo-25,26,27,28-tetrahexyloxy-calix[4]arene (2): Yield: 1.529 g,
1
91%; Rf =0.73 (AcOEt/petroleum ether, 20:80, v/v); H NMR (300 MHz,
CDCl3): d=6.82–6.68 (6H; Ar H), 6.58 (d, 3J=7.5 Hz, 1H; Ar H), 6.49
(s, 2H; Ar H ortho to Br), 6.41 (d, 3J=7.5 Hz, 2H; Ar H), 4.44 and 3.16
(2ꢅd, 2J=13.6 Hz, 4H; AB spin system, ArCH2Ar), 4.39 and 3.09 (2ꢅd,
2J=13.6 Hz, 4H; AB spin system, ArCH2Ar), 3.96–3.89 (m, 4H; OCH2),
3.83 (t, 3J=7.3 Hz, 2H; OCH2), 3.80 (t, 3J=7.3 Hz, 2H; OCH2), 1.92–
1.85 (m, 8H; OCH2CH2), 1.50–1.31 (m, 24H; CH2CH2CH2CH3), 0.96–
0.89 ppm (m, 12H; CH2CH3); 13C{1H} NMR (75 MHz, CDCl3): d=
157.21, 156.24 and 155.51 (3ꢅs; Ar Cq-O), 137.04–114.82 (Ar C), 75.29
(s; OCH2), 75.17 (s; 2ꢅOCH2), 32.26 (s; CH3CH2CH2), 32.18 (s;
CH3CH2CH2), 32.14 (s; CH3CH2CH2), 31.17 (s; ArCH2Ar), 31.04 (s;
ArCH2Ar), 30.51 (s; OCH2CH2), 30.39 (s; OCH2CH2), 30.32 (s;
OCH2CH2), 26.24 (s; OCH2CH2CH2), 26.18 (s; OCH2CH2CH2), 25.97 (s;
OCH2CH2CH2), 23.02 (s; CH2CH3), 22.96 (s; CH2CH3), 22.94 (s;
CH2CH3), 14.23 (s; CH2CH3), 14.22 ppm (s; CH2CH3); elemental analysis
calcd (%) for C52H71O4Br (Mr =840.02): C 74.35, H 8.52; found: C 74.20,
H 8.67.
5-Diphenylphosphanyl-25,26,27,28-tetrahexyloxy-calix[4]arene (6): Yield:
0.850 g, 90%; Rf =0.80 (CH2Cl2-petroleum ether, 40:60, v/v); 1H NMR
(300 MHz, CDCl3): d=7.35–7.29 (m, 6H; PPh2 Ar H), 7.22–7.17 (m, 4H;
3
PPh2 Ar H), 6.80 (d, J=7.3 Hz, 2H; calix Ar H), 6.72–6.65 (m, 5H; calix
Ar H), 6.61–6.52 (m, 4H; Ar H of calix), 4.53 and 3.24 (2ꢅd, 2J=
13.3 Hz, 4H; AB spin system, ArCH2Ar), 4.48 and 3.12 (2ꢅd, 2J=
3
13.2 Hz, 4H; AB spin system, ArCH2Ar), 3.96 (pseudo t, J=7.3 Hz, 8H;
OCH2), 2.05–1.94 (m, 8H; OCH2CH2), 1.50–1.39 (m, 24H;
CH2CH2CH2CH3), 0.99 ppm (t, 3J=6.0 Hz, 12H; CH2CH3); 13C{1H}
NMR (75 MHz, CDCl3): d=157.58, 156.66 and 156.48 (3ꢅs; Ar Cq-O),
138.50–122.18 (Ar C), 75.50 (s; OCH2), 75.42 (s; OCH2), 75.33 (s;
OCH2), 32.23 (s; 2ꢅCH2CH2CH3), 32.19 (s; CH2CH2CH3), 31.13 (s;
ArCH2Ar), 30.99 (s; ArCH2Ar), 30.48 (s; OCH2CH2), 30.43 (s;
OCH2CH2), 30.38 (s; OCH2CH2), 26.12 (s; 2ꢅOCH2CH2CH2), 26.07 (s;
OCH2CH2CH2), 23.00 (s; 2ꢅCH2CH3), 22.96 (s; CH2CH3), 14.23 ppm (s;
CH2CH3); 31P{1H} NMR (121 MHz, CDCl3): d=À5.4 ppm (s; PPh2); ele-
mental analysis calcd (%) for C64H81O4P (Mr =945.30): C 81.32, H 8.64;
found: C 81.41, H 8.75.
5-Bromo-25,26,27,28-tetrabenzyloxy-calix[4]arene (3): Yield: 1.624 g,
1
94%; Rf =0.75 (CH2Cl2-petroleum ether, 50:50, v/v); H NMR (300 MHz,
CDCl3): d=7.38–7.35 (2H; benzyl Ar H), 7.30–7.22 (14H; benzyl Ar H),
7.16 (d, 3J=7.1 Hz, 4H; benzyl Ar H), 6.76–6.60 (m, 7H; calix Ar H),
3
6.43 (s, 2H; Ar H ortho to Br), 6.37 (d, J=7.5 Hz, 2H; calix Ar H), 5.02
and 4.97 (2ꢅd, 2J=11.9 Hz, 4H; AB spin system, CH2Ph), 4.86 (s, 2H;
H2Ph), 4.80 (s, 2H; CH2Ph), 4.25 and 3.00 (2ꢅd, 2J=13.7 Hz, 4H; AB
spin system, ArCH2Ar), 4.10 and 2.83 ppm (2ꢅd, 2J=13.7 Hz, 4H;
ArCH2Ar, AB spin system); 13C{1H} NMR (75 MHz, CDCl3): d=155.71,
155.39 and 154.54 (3ꢅs; Ar Cq-O), 137.99–115.28 (Ar C), 76.95 (s;
OCH2Ph), 76.89 (s; OCH2Ph), 76.31 (s; OCH2Ph), 31.56 (s; ArCH2Ar),
31.41 ppm (s; ArCH2Ar); elemental analysis calcd (%) for C56H47O4Br
(Mr =863.87): C 77.86, H 5.48; found: C 77.67, H 5.61.
5-Diphenylphosphanyl-25,26,27,28-tetrabenzyloxy-calix[4]arene
(7):
Yield: 0.727 g, 75%; Rf =0.37 (CH2Cl2-petroleum ether, 40:60, v/v);
1H NMR (300 MHz, CDCl3): d=7.39–7.17 (m, 30H; benzyl and PPh2
Ar H), 6.78–6.73 (m, 3H; calix Ar H), 6.67 (d, 3J=7.9 Hz, 2H; calix
Ar H), 6.58–6.52 (s, 4H; calix Ar H), 6.42–6.38 (m, 2H; calix Ar H), 5.04
(s, 4H; CH2Ph), 5.00 and 4.95 (2ꢅd, 2J=11.5 Hz, 4H; AB spin system,
CH2Ph), 4.30 and 3.03 (2ꢅd, 2J=13.3 Hz, 4H; AB spin system,
ArCH2Ar), 4.22 and 2.88 ppm (2ꢅd, 2J=13.4 Hz, 4H; AB spin system,
ArCH2Ar); 13C{1H} NMR (75 MHz, CDCl3): d=156.35, 155.56 and
155.17 (3ꢅs; Ar Cq-O), 138.31–122.39 (Ar C), 76.57 (s; OCH2Ph), 76.46
(s; OCH2Ph), 76.21 (s; OCH2Ph), 31.44 (s; ArCH2Ar), 31.37 ppm (s;
ArCH2Ar); 31P{1H} NMR (121 MHz, CDCl3): d=À5.9 ppm (s; PPh2); el-
emental analysis calcd (%) for C68H57O4P (Mr =969.15): C 84.27, H 5.93;
found: C 84.39, H 5.92.
5-Bromo-25,26,27,28-tetra(p-methoxy)benzyloxy-calix[4]arene (4): Yield:
1.751 g, 89%; Rf =0.52 (CH2Cl2-petroleum ether, 60:40, v/v); 1H NMR
(300 MHz, CDCl3): d=7.31 (d, 3J=8.6 Hz, 2H; benzyl Ar H), 7.23 (d,
3J=8.5 Hz, 2H; benzyl Ar H), 7.18 (d, 3J=8.6 Hz, 4H; benzyl Ar H),
6.84 (d, 3J=8.5 Hz, 2H; benzyl Ar H), 6.82 (d, 3J=8.5 Hz, 2H; benzyl
Ar H), 6.78–6.69 (m, 10H; benzyl and calix Ar H), 6.64 (t, 3J=7.6 Hz,
1H; calix Ar H of), 6.46 (s, 2H; calix Ar H ortho to Br), 6.40 (d, 3J=
7.6 Hz, 2H; calix Ar H), 4.96 and 4.92 (2ꢅd, 2J=12.1 Hz, 4H; AB spin
system, CH2Ar), 4.83 (s, 2H; CH2Ar), 4.77 (s, 2H; CH2Ar), 4.27 and 3.01
(2ꢅd, 2J=13.7 Hz, 4H; AB spin system, ArCH2Ar), 4.12 and 2.85 (2ꢅd,
2J=13.7 Hz, 4H; AB spin system, ArCH2Ar), 3.82 (s, 3H; CH3OAr),
3.81 (s, 3H; CH3OAr), 3.78 ppm (s, 6H; CH3OAr); 13C{1H} NMR
(75 MHz, CDCl3): d=159.61, 159.49 and 159.43 (3ꢅs; Ar Cq-OMe),
155.71, 155.40 and 154.54 (3ꢅs; Ar Cq-Ocalix), 137.43–113.40 (Ar C),
76.44 (s; OCH2Ar), 76.34 (s; OCH2Ar), 75.70 (s; OCH2Ar), 55.44 (s;
CH3OAr), 55.37 (s; CH3OAr), 31.60 (s; ArCH2Ar), 31.48 ppm (s;
ArCH2Ar); elemental analysis calcd (%) for C60H55O8Br (Mr =983.98): C
73.24, H 5.63; found: C 73.16, H 5.72.
5-Diphenylphosphanyl-25,26,27,28-tetra(p-methoxy)benzyloxy-calix[4]ar-
ene (8): Yield: 0.163 g, 15%; Rf =0.90 (CH2Cl2); 1H NMR (300 MHz,
CDCl3): d=7.30 (d, 4H; PPh2 Ar H), 7.24 (3J=8.6 Hz, d, 4H; methoxy-
benzyl Ar H), 7.23–7.12 (m, 4H; PPh2 Ar H), 7.22 (d, 3J=8.6 Hz, 2H;
methoxybenzyl Ar H), 7.16 (d, 3J=8.0 Hz, 2H; methoxybenzyl Ar H),
6.80 (d, 3J=8.6 Hz, 4H; methoxybenzyl Ar H), 6.77–6.67 (m, 4H; PPh2
and calix Ar H), 6.72 (d, 3J=8.6 Hz, 4H; methoxybenzyl Ar H), 6.62 (d,
3J=7.9 Hz, 2H; calix Ar H), 6.56–6.46 (m, 5H; calix Ar H), 6.37–6.34
(m, 2H; calix Ar H), 4.92 (s, 4H; CH2Ar), 4.87 and 4.83 (2ꢅd, 2J=
12 Hz, 4H; AB spin system, CH2Ar), 4.24 and 2.98 (2ꢅd, 2J=13.3 Hz,
4H; AB spin system, ArCH2Ar), 4.16 and 2.83 (2ꢅd, 2J=13.4 Hz, 4H;
AB spin system, ArCH2Ar), 3.80 (s, 6H; CH3OAr), 3.79 ppm (s, 6H;
CH3OAr); 13C{1H} NMR (75 MHz, CDCl3): d=159.49 and 159.44 (2ꢅs;
Ar Cq-OMe), 156.52, 155.70 and 155.32 (3ꢅs; Ar Cq-Ocalix), 138.48–
113.41 (Ar C), 76.16 (s; OCH2Ar), 76.01 (s; OCH2Ar), 75.76 (s;
OCH2Ar), 55.50 (s; CH3OAr), 55.42 (s; CH3OAr), 55.40 (s; CH3OAr),
31.64 (s; ArCH2Ar), 31.59 ppm (s; ArCH2Ar); 31P{1H} NMR (121 MHz,
CDCl3): d=À5.8 ppm (s; PPh2); elemental analysis calcd (%) for
5-Bromo-25,26,27,28-tetra(m-methoxy)benzyloxy-calix[4]arene
(5):
Yield: 1.732 g, 88%; Rf =0.5 (CH2Cl2-petroleum ether, 60:40, v/v);
1H NMR (300 MHz, CDCl3): d=7.24 (t, 3J=7.2 Hz, 1H; benzyl Ar H),
7.21 (t, 3J=7.5 Hz, 1H; benzyl Ar H), 7.13 (t, 3J=7.9 Hz, 2H; benzyl
Ar H), 7.04–6.64 (m, 19H; benzyl and calix Ar H), 6.48 (s, 2H; calix
Ar H ortho to Br), 6.42 (d, 3J=7.5 Hz, 2H; calix Ar H), 5.10 and 5.04
(2ꢅd, 2J=11.9 Hz, 4H; AB spin system, CH2Ar), 5.02 (s, 2H; CH2Ar),
4.93 (s, 2H; CH2Ar), 4.28 and 3.02 (2ꢅd, 2J=13.6 Hz, 4H; AB spin
system, ArCH2Ar), 4.12 and 2.83 (2ꢅd, 2J=13.7 Hz, 4H; AB spin
system, ArCH2Ar), 3.73 (s, 3H; CH3OAr), 3.73 (s, 3H; CH3OAr),
3.68 ppm (s, 6H; CH3OAr); 13C{1H} NMR (75 MHz, CDCl3): d=159.51,
159.47 and 159.22 (3ꢅs; Ar Cq-OMe), 155.65, 155.32 and 154.45 (3ꢅs;
Ar Cq-Ocalix), 139.45–113.62 (Ar C), 76.70 (s; OCH2Ar), 76.62 (s;
OCH2Ar), 76.12 (s; OCH2Ar), 55.27 (s; CH3OAr), 55.26 (s; CH3OAr),
55.20 (s; CH3OAr), 31.59 (s; ArCH2Ar), 31.45 ppm (s; ArCH2Ar); ele-
C72H65O8P·1= CH2Cl2 (Mr =1089.25+42.47): C 76.94, H 5.88; found: C
2
76.87, H 5.76.
5-Diphenylphosphanyl-25,26,27,28-tetra(meta-methoxy)benzyloxy-cal-
ix[4]arene (9): Yield: 0.272 g, 25%; Rf =0.70 (AcOEt-petroleum ether,
Chem. Eur. J. 2010, 16, 9237 – 9247
ꢂ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
9245

D. Matt, D. Sꢀmeril et al.
1
40:60, v/v); H NMR (300 MHz, CDCl3): d=7.40–7.20 (12H; Ar H), 7.09
2079.52 [MÀCl]+ expected isotopic profiles; elemental analysis calcd (%)
for C136H114Cl2O8P2Pd (Mr =2115.63): C 77.21, H 5.43; found: C 77.15, H
5.56.
3
(t, J=6.8 Hz, 6H; Ar H), 6.97–6.88 (m, 13H; Ar H), 7.80–6.60 (m, 14H;
Ar H), 6.51 (d, 3J=6.2 Hz, 2H; Ar H), 5.13–5.06 (m, 8H; CH2Ar), 4.36
and 3.08 (2ꢅd, 2J=13.4 Hz, 4H; AB spin system, ArCH2Ar), 4.27 and
2.92 (2ꢅd, 2J=13.4 Hz, 4H; AB spin system, ArCH2Ar), 3.77 (s, 6H;
CH3OAr), 3.76 ppm (s, 6H; CH3OAr); 13C{1H} NMR (75 MHz, CDCl3):
d=159.29, 159.25 and 159.22 (3ꢅs; Ar Cq-OMe), 156.26, 155.42 and
155.17 (3ꢅs; Ar Cq-Ocalix), 139.35–113.50 (Ar C), 76.31 (s; OCH2Ar),
76.22 (s; OCH2Ar), 76.18 (s; OCH2Ar), 55.10 (s; CH3OAr), 31.53 (s;
ArCH2Ar), 31.43 ppm (s; ArCH2Ar); 31P{1H} NMR (121 MHz, CDCl3):
d=À5.6 ppm (s; PPh2); elemental analysis calcd (%) for C72H65O8P
(Mr =1089.25): C 79.39, H 6.01; found: C 79.34, H 5.93.
Chlorido-(o-dimethylaminomethylphenyl-C,N)-{5-diphenylphosphanyl-
25,26,27,28-tetra benzyloxy-calix[4]arene} palladium(II) (13): A solution
of [PdCl(o-C6H4CH2NMe2]2 (0.035 g, 0.06 mmol) in CH2Cl2 (5 mL) was
added to a stirred solution of 7 (0.122 g, 0.13 mmol) in CH2Cl2 (5 mL).
After stirring for 0.5 h, the reaction mixture was concentrated to ca.
2 mL, upon which n-hexane (20 mL) was added. The yellow precipitate
that formed was separated by filtration and was dried under vacuum
1
(yield: 0.157 g, 97%). H NMR (CDCl3, 300 MHz): d=7.58–7.54 (m, 4H;
Ar CH), 7.52–7.10 (m, 27H; Ar CH), 6.99 (d, 3J=7.1 Hz, 1H; Ar CH),
6.87 (d, 3J=7.1 Hz, 4H; Ar CH), 6.74 (t, 3J=7.4 Hz, 1H; Ar CH), 6.51–
5-Diphenylphosphanyl-25,26,27,28-tetrahydroxy-calix[4]arene (10):
A
3
6.42 (m, 2H; Ar CH), 6.26–6.23 (m, 4H; Ar CH), 5.78 (t, J=4.6 Hz, 2H;
Schlenk tube was filled with phosphane 7 (0.500 g, 0.5 mmol), AlCl3
(0.267 g, 2.0 mmol) and toluene (50 mL). After stirring this suspension
for 16 h, a saturated solution of NaCl (15 mL) was slowly added. The
aqueous layer was extracted with CH2Cl2 (2ꢅ15 mL), then the combined
organic layers were dried over Na2SO4. Evaporation under vacuum af-
forded a pale-yellow solid, which was recrystallised from diethylether/pe-
troleum ether (1:1, v/v). The product was collected by filtration and dried
under vacuum (yield: 0.314 g, 100%); 1H NMR (300 MHz, CDCl3): d=
10.18 (s, 4H; OH), 7.33–6.67 (m, 21H; Ar H), 4.20 and 3.49 ppm (2ꢅ
brsignals, 8H; AB spin system, ArCH2Ar); 13C{1H} NMR (75 MHz,
CDCl3): d=150.05, 149.21 and 148.67 (3ꢅs; Ar Cq-OH), 137.94–122.32
(Ar C), 31.85 (s; ArCH2Ar), 31.74 ppm (s; ArCH2Ar); 31P{1H} NMR
(121 MHz, CDCl3): d=À5.9 ppm (s; PPh2); elemental analysis calcd (%)
for C40H33O4P (Mr =608.66): C 78.93, H 5.46; found: C 78.84, H 5.33.
Ar CH), 5.07 (s, 2H; OCH2Ph), 5.04 (s, 2H; OCH2Ph), 4.81 and 4.74 (2ꢅ
d, 2J=11.3 Hz, 4H; AB spin system, OCH2Ph), 4.19 and 2.95 (2ꢅd, 2J=
13.5 Hz, 4H; AB spin system, ArCH2Ar), 4.07 and 2.80 (2ꢅd, 2J=
13.4 Hz, 4H; AB spin system, ArCH2Ar), 4.03 (brs, 2H; CH2N),
2.85 ppm (d, 4J (CH3)2); 13C{1H} NMR (CDCl3,
ACTHNUTRGENN(GU P,H)=2 Hz, 6H; NACHTNUGTRENNUNG
75 MHz): d=157.80, 155.87 and 154.94 (3ꢅs; Ar Cq-O), 150.97 (s;
Ar Cq-CH2N), 148.52 (d; Ar Cq-Pd), 138.37–122.32 (Ar C), 76.99 (s;
OCH2Ph), 76.21 (s; OCH2Ph), 75.71 (s; OCH2Ph), 73.21 (s; CH2N), 50.64
(s; NACHTNUGRTNEUNG
(CH3)2), 31.43 ppm (s; ArCH2Ar); 31P{1H} NMR (CDCl3, 121 MHz):
d=43.1 ppm (s; PPh2); MS (MALDITOF): m/z: 1208.86 [MÀCl]+ ex-
pected isotopic profiles; elemental analysis calcd (%) for
C77H69ClNO4PPd·CH2Cl2 (Mr =1245.22
+ 84.93): C 70.43, H 5.38, N
1.05; found: C 70.56, H 5.12, N 0.96.
(o-Dimethylaminomethylphenyl-C,N)-{5-diphenylphosphanyl-25,26,27,28-
tetrabenzyloxy-calix[4]arene}-tetrahydrofurane palladium(II) tetrafluoro-
borate (14): Asolution of AgBF4 (0.024 g, 0.13 mmol) in THF (2 mL) was
added to a solution of 13 (0.161 g, 0.13 mmol) in CH2Cl2 (5 mL). After
0.5 h, the solution was filtered through Celite and concentrated to ca.
2 mL. Addition of n-hexane (20 mL) afforded 14 as a brown precipitate,
which was filtered off and dried under vacuum (yield: 0.168 g, 98%).
1H NMR (CDCl3, 300 MHz): d=7.42–7.12 (m, 30H; Ar CH), 6.97–6.93
(m, 3H; Ar CH), 6.88 (d, 3J=7.2 Hz, 1H; Ar CH), 6.68 (d, 3J=6.9 Hz,
2H; Ar CH), 6.58–6.31 (m, 6H; Ar CH), 6.23 (t, 3J=7.0 Hz, 1H;
Ar CH), 5.98 (d, 3J=7.0 Hz, 2H; Ar CH), 4.95 (s, 2H; OCH2Ph), 4.93
trans-P,P-Dichlorido-bis{5-diphenylphosphanyl-25,26,27,28-tetrabenzy-
loxy-calix[4]are ne}-palladium(II) (11):
A solution of [PdCl2CAHTUNTGNRUEN(G cod)]
(0.012 g, 0.04 mmol) in CH2Cl2 (5 mL) was added to a solution of 7
(0.079 g, 0.08 mmol) in CH2Cl2 (5 mL) that was maintained at À788C.
After stirring the solution for a further 0.5 h at À788C, the reaction mix-
ture was concentrated to ca. 2 mL, upon which n-hexane (20 mL) was
added. The yellow precipitate was separated by filtration and dried under
vacuum (yield: 0.085 g, 99%). 1H NMR (CDCl3, 300 MHz): d=7.62–7.56
(m, 8H; Ar CH), 7.45–7.12 (m, 52H; Ar CH), 6.81 (d, 3J=7.5 Hz, 8H;
Ar CH), 6.64 (t, 3J=7.4 Hz, 2H; Ar CH), 6.44–6.40 (m, 8H; Ar CH),
6.34–6.30 (m, 4H; Ar CH), 5.05 (s, 4H; OCH2Ph), 5.02 (s, 4H;
OCH2Ph), 4.87 and 4.81 (2ꢅd, 2J=11.5 Hz, 8H; AB spin system,
OCH2Ph), 4.24 and 2.97 (2ꢅd, 2J=13.6 Hz, 8H; AB spin system,
ArCH2Ar), 4.18 and 2.79 ppm (2ꢅd, 2J=13.6 Hz, 8H; AB spin system,
ArCH2Ar); 13C{1H} NMR (CDCl3, 75 MHz): d=157.81, 155.70 and
155.00 (3ꢅs; Ar Cq-O), 137.83–122.20 (Ar C), 76.78 (s; OCH2Ph), 76.33
(s; OCH2Ph), 76.17 (s; OCH2Ph), 31.47 ppm (s; ArCH2Ar) (only one
signal is seen of the ArCH2Ar carbon atoms); 31P{1H} NMR (CDCl3,
121 MHz): d=22.7 ppm (s; PPh2); MS (MALDITOF): m/z: 2079.52
[MÀCl]+ expected isotopic profiles; elemental analysis calcd (%) for
2
and 4.84 (2ꢅd, J=11.5 Hz, 4H; AB spin system, OCH2Ph), 4.89 (s, 2H;
OCH2Ph), 4.19 and 2.93 (2ꢅd, 2J=13.3 Hz, 4H; AB spin system,
ArCH2Ar), 4.09 and 2.76 (2ꢅd, 2J=13.3 Hz, 4H; AB spin system,
ArCH2Ar), 3.95 (brs, 2H; CH2N), 3.67–3.63 (m, 4H; CH2O of THF),
4
2.74 (s, J (P,H)<1 Hz, 6H; N
G
of THF); 13C{1H} NMR (CDCl3, 75 MHz): d=158.30, 155.66 and 155.10
(3ꢅs; Ar Cq-O), 148.07 (s; Ar Cq-CH2N), 139.30 (d; Cq-Pd), 137.87–
122.30 (Ar C), 76.71 (s; OCH2Ph), 76.61 (s; OCH2Ph), 76.18 (s;
OCH2Ph), 71.07 (s; CH2N), 68.50 (s; CH2O of THF), 49.67 (s; NACHTUNGTRENNUNG(CH3)2),
31.45 (s; ArCH2Ar), 25.65 ppm (s; CH2CH2O of THF); 31P{1H} NMR
(CDCl3, 121 MHz): d=39.1 ppm (s; PPh2); elemental analysis calcd (%)
for C81H77BF4NO5PPd (Mr =1337.71): C 72.73, H 5.80, N 1.05; found: C
72.85, H 5.71, N 0.99.
C
136H114 Cl2O8P2Pd (Mr =2115.63): C 77.21, H 5.43; found: C 77.29, H
5.56.
cis-P,P-Dichlorido-bis{5-diphenylphosphanyl-25,26,27,28-tetrabenzyloxy-
calix[4]arene}-palladium(II) (12): A solution of [PdCl2ACHTNUTRGNEUNG(cod)] (0.012 g,
General procedure for palladium-catalysed Suzuki–Miyaura cross-cou-
0.04 mmol) in CH2Cl2 (5 mL) was added to a stirred solution of 7
(0.079 g, 0.08 mmol) in CH2Cl2 (5 mL) at 408C. After stirring for 0.5 h at
408C, the reaction mixture was concentrated to ca. 2 mL, upon which n-
hexane (20 mL) was added. The orange precipitate that formed was sepa-
rated by filtration and dried under vacuum (yield: 0.084 g, 98%).
1H NMR (CDCl3, 300 MHz): d=7.44–7.38 (m, 12H; Ar CH), 7.29–7.20
(m, 44H; Ar CH), 7.13–7.11 (m, 4H; Ar CH), 6.71–6.66 (m, 8H;
Ar CH), 6.56 (t, 3J=7.4 Hz, 4H; Ar CH), 6.49 (d, 3J=7.5 Hz, 4H;
Ar CH), 6.45 (d, 3J=7.5 Hz, 4H; Ar CH), 6.22 (t, 3J=7.4 Hz, 2H;
Ar CH), 5.02 and 4.95 (2ꢅd, 2J=11.6 Hz, 8H; AB spin system,
OCH2Ph), 4.83 (s, 4H; OCH2Ph), 4.82 (s, 4H; OCH2Ph), 4.19 and 2.92
(2ꢅd, 2J=13.3 Hz, 8H; AB spin system, ArCH2Ar), 3.99 and 2.72 ppm
(2ꢅd, 2J=13.5 Hz, 8H; AB spin system, ArCH2Ar); 13C{1H} NMR
(CDCl3, 75 MHz): d=157.87, 155.26 and 155.02 (3ꢅs; Ar Cq-O), 137.64–
122.34 (Ar C), 77.07 (s; OCH2Ph), 76.95 (s; OCH2Ph), 76.16 (s;
OCH2Ph), 31.41 (s; ArCH2Ar), 31.26 ppm (s; ArCH2Ar); 31P{1H} NMR
(CDCl3, 121 MHz): d=31.9 ppm (s; PPh2); MS (MALDITOF): m/z:
pling reactions: In a Schlenk tube in an inert atmosphere a solution of
[PdACTHNUTRGNE(NUG OAc)2] in dioxane, a solution of the ligand (2 equiv/Pd) in dioxane,
aryl halide (0.5 mmol), phenylboronic acid (0.122 g, 1.0 mmol), base
(1.0 mmol), decane (0.05 mL, internal reference) and a complementary
amount of dioxane were introduced so that the total reaction volume was
1.5 mL. The reaction mixture was then heated for 1 h at 1008C. After
cooling to room temperature, a small amount (0.5 mL) of the resulting
solution was passed through a Millipore filter and analyzed by GC.
Crystal structure of 11: Single crystals of 11 that were suitable for diffrac-
tion study were obtained by slow diffusion of hexane into a dichlorome-
¯
thane solution of the complex. Mr =1057.76; triclinic; space group P1;
a=12.6332(4), b=14.0161(3), c=15.2785(3) ꢃ; a=88.749(2), b=
77.488(2), g=87.409(2)8; V=2636.10(11) ꢃ3; Z=2; Dx =1.333 mgmÀ3; l
(MoKa)=0.71073 ꢃ; m=0.32 mmÀ1
; FACHTUNTGERNUG(N 000)=1104; T=120(2) K. Data
were collected on an Oxford Diffraction Xcalibur Saphir 3 diffractometer
(graphite MoKa radiation, l=0.71073 ꢃ). The structure was solved with
9246
www.chemeurj.org
ꢂ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2010, 16, 9237 – 9247

Cavity-Shaped Ligands
FULL PAPER
SIR-97,[37] which revealed the non-hydrogen atoms of the molecule. After
anisotropic refinement, many hydrogen atoms were found with a Fourier
difference analysis. The whole structure was refined with SHELX-97[38]
and full-matrix least-square techniques (use of F2; x, y, z, bij for C, Cl, O,
[8] J. Yin, M. P. Rainka, X.-X. Zhang, S. L. Buchwald, J. Am. Chem.
Soc. 2002, 124, 1162–1163.
[9] K. Billingsley, S. L. Buchwald, J. Am. Chem. Soc. 2007, 129, 3358–
3366.
P and Pd atoms; x, y, z in riding mode for H atoms; 673 variables and
[10] A. Zapf, R. Jackstell, F. Rataboul, T. Riermeier, A. Monsees, C.
Fuhrmann, N. Shaikh, U. Dingerdissen, M. Beller, Chem. Commun.
2004, 38–39.
[11] S. D. Walker, T. E. Barder, J. R. Martinelli, S. L. Buchwald, Angew.
Chem. 2004, 116, 1907–1912; Angew. Chem. Int. Ed. 2004, 43, 1871–
1876.
2
8124 observations with [I>2.0s(I)]; calcd w=1/[s
G
which P=(Fo2 +2Fc2)/3; R1=0.036, wR2=0.071, Sw =0.887; D1<
0.63 eꢃÀ3
.
Crystal structure of 15a: Single crystals of 15a suitable for diffraction
study were obtained by slow diffusion of hexane into a commercial (un-
dried) dichloromethane solution of the complex. Mr =1312.51; triclinic;
[12] T. E. Barder, S. D. Walker, J. R. Martinelli, S. L. Buchwald, J. Am.
Chem. Soc. 2005, 127, 4685–4696.
¯
space group P1; a=13.5768(6), b=14.6696(4), c=18.9840(6) ꢃ; a=
94.706(3), b=110.158(4), g=111.821(4)8; V=3197.83(19) ꢃ3; Z=2; Dx =
[13] T. Iwasawa, T. Komano, A. Tajima, M. Tokunaga, Y. Obora, T. Fuji-
hara, Y. Tsuji, Organometallics 2006, 25, 4665–4669.
[14] R. Martin, S. L. Buchwald, Acc. Chem. Res. 2008, 41, 1461–1473.
[15] Y. Ohzu, K. Goto, T. Kawashima, Angew. Chem. 2003, 42, 5714–
5717; Angew. Chem. Int. Ed. 2003, 115, 5892–5895.
[16] H. Ohta, M. Tokunaga, Y. Obora, T. Iwai, T. Iwasawa, T. Fujihara,
Y. Tsuji, Org. Lett. 2007, 9, 89–92.
[17] T. Fujihara, S. Yoshida, H. Ohta, Y. Tsuji, Angew. Chem. 2008, 120,
8434–8438; Angew. Chem. Int. Ed. 2008, 47, 8310–8314.
[18] D. J. M. Snelders, G. van Koten, R. J. M. Klein Gebbink, J. Am.
Chem. Soc. 2009, 131, 11407–11416.
[19] M. Lejeune, C. Jeunesse, D. Matt, N. Kyritsakas, R. Welter, J.-P.
Kintzinger, Dalton Trans. 2002, 1642–1650.
[20] S. Sameni, C. Jeunesse, D. Matt, R. Welter, Dalton Trans. 2009,
7912–7923.
[21] A. F. Littke, G. C. Fu, Angew. Chem. 2002, 114, 4350–4386; Angew.
Chem. Int. Ed. 2002, 41, 4176–4211.
[22] C. Wieser, C. B. Dieleman, D. Matt, Coord. Chem. Rev. 1997, 165,
93–161.
1.363 mgmÀ3; l(MoKa)=0.71073 ꢃ; m=0.381 mmÀ1; F
ACHTUNGTRENNUNG ACHTUTGNREN(NUGN 000)=1360; T=
150(2) K. Data were collected on an Oxford Diffraction Xcalibur Saphir
3 diffractometer (graphite MoKa radiation, l=0.71073 ꢃ). The structure
was solved with SIR-97,[37] which revealed the non-hydrogen atoms of the
molecule. After anisotropic refinement, many hydrogen atoms were
found with a Fourier difference analysis. The whole structure was refined
with SHELX-97[38] and full-matrix least-square techniques (use of F2; x,
y, z, bij for C, B, F, N, O, P and Pd atoms; x, y, z in riding mode for H
atoms; 811 variables and 6709 observations with [I>2.0s(I)]; calcd w=1/
2
[s
G
Sw =0.795; D1<0.643 eꢃÀ3
Crystal structure of 15b: Single crystals of 15b·CH2Cl2 that were suitable
for diffraction were obtained by slow diffusion of hexane into a commer-
cial (undried) dichloromethane solution of the complex. Mr =1397.44; tri-
¯
clinic; space group P1; a=13.3935(3), b=14.9355(3), c=18.1936(4) ꢃ;
a=90.332(2), b=110.253(2), g=98.837(2)8; V=3367.04(13) ꢃ3, Z=2;
Dx =1.378 mgmÀ3; l(MoKa)=0.71069 ꢃ; m=0.443 mmÀ1; F
ACHTUNGTRENNUNG ACHTUGNTREN(NUGN 000)=1444;
T=150(2) K. Data were collected on an Oxford Diffraction Xcalibur
Saphir 3 diffractometer (graphite MoKa radiation, l=0.71069 ꢃ). The
structure was solved with SIR-97,[37] which revealed the non-hydrogen
atoms of the molecule. After anisotropic refinement, many hydrogen
atoms were found with a Fourier difference analysis. The whole structure
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Received: December 10, 2009
Published online: June 25, 2010
Chem. Eur. J. 2010, 16, 9237 – 9247
ꢂ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
9247