Self-assembly of a cavitand-based heteronuclear coordination cage

Article abstract of DOI:10.1016/j.tet.2008.11.111

A new self-assembly protocol leading to the formation of heteronuclear coordination cage 10 is reported. Reaction of tetradentate cavitand ligand 1, bearing one ethynylpyridine and three benzonitriles at the apical positions, with Pt(dppp)OTf₂

Full text of DOI:10.1016/j.tet.2008.11.111

Tetrahedron 65 (2009) 7289–7295
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Tetrahedron
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Self-assembly of a cavitand-based heteronuclear coordination cage
,
Francesca Gruppi a, Francesca Boccini a, Lisa Elviri b, Enrico Dalcanale a
*
a
`
`
Dipartimento di Chimica Organica ed Industriale and Unita INSTM, Universita di Parma, Viale Usberti 17/A, 43100 Parma, Italy
Dipartimento di Chimica Generale ed Inorganica, Chimica Analitica, Chimica Fisica, Universita di Parma, Viale Usberti 17/A, 43100 Parma, Italy
b
`
a r t i c l e i n f o
a b s t r a c t
Article history:
A new self-assembly protocol leading to the formation of heteronuclear coordination cage 10 is reported.
Reaction of tetradentate cavitand ligand 1, bearing one ethynylpyridine and three benzonitriles at the
apical positions, with Pt(dppp)OTf2 and Pd(dppp)OTf2 in a 1:3 ratio yields 10 as the thermodynamic
product. Under the same conditions, the self-assembly of 1 with either Pt or Pd metal precursors gives
a mixture of isomeric homonuclear cages 8a–c or 9a–c, respectively.
Received 9 September 2008
Accepted 5 November 2008
Available online 24 March 2009
In memory of Dmitry M. Rudkevich
Ó 2009 Elsevier Ltd. All rights reserved.
Keywords:
Heteronuclear coordination cages
Cavitands
Self-assembly
1. Introduction
to differentiate their cross-reactivity. At the same time, the different
coordinating groups must be inserted at a single macrocyclic ligand
The self-assembly of coordination cages has reached a high level
of sophistication with regard to ligand design and selection of metal
precursors.1 As a result, the shape, dimensions, and polarity of the
internal cavity can be engineered, allowing for inclusion of diverse
neutral2 and charged guests3 in different solvents. The compart-
mentalization of these guests imparts a wide spectrum of useful
properties, including catalysis,4,5 storage,6 and the stabilization of
labile chemical species.7
site and organized in a precise relative spatial orientation.
In this paper we report a thermodynamically controlled self-
assembly protocol leading to the exclusive formation of a Pd/Pt
heteronuclear cage. The protocol is based on a tetradentate cav-
itand ligand functionalized with three nitriles and one pyridine at
the upper rim.
2. Result and discussion
A missing feature in these self-assembly protocols is the dif-
ferentiation in metal/ligand reactivity necessary for the genera-
tion of heteronuclear coordination cages. As a first step in this
direction, Kobayashi and co-workers reported the preparation of
heterocages, coordination cages featuring two different ligands.8,9
Two complementary tetradentate cavitand ligands were pre-
pared, each bearing four identical coordination groups at the
apical positions, either nitriles10 or pyridines.8 By utilizing the
two cavitand’s different coordination ability, they devised
self-assembly conditions leading to the formation of either ho-
monuclear Pd or Pt heterocages as the dominant product under
kinetic control.
2.1. Synthesis of cavitand 1
The tetradentate cavitand ligand 1, designed for the self-as-
sembly of heteronuclear coordination cages, presents three
benzonitrile and one ethynylpyridine ligands, all of which
inserted at the apical positions of a methylene-bridged cavitand
(Fig. 1). The choice of these different ligands at the upper rim of
the cavitand was dictated by two factors: (i) their different co-
ordination ability toward transition metals like Pt or Pd and (ii)
their almost identical distance and orientation with respect to
the cavitand scaffold, in order to avoid mismatch during self-
assembly.11
The four-step synthesis of cavitand 1 is presented in Scheme 1.
Resorcinarene 2, equipped with hexyl feet to assure solubility in
organic solvents, was synthesized according to published pro-
cedure.12 Tetraiodo-resorcinarene 3 was obtained from the reaction
of resorcinarene 2 with iodine in the presence of sodium hydro-
gencarbonate.13 The reaction was carried out at room temperature
in a 1:1 mixture of water and diethyl ether. The desired product
The formation of heteronuclear cages introduces a further level
of complexity, where at least two metal/ligand couples must un-
dergo self-sorting during the assembly procedure. For instance, the
choice of coordinating ligands and metal precursors must be well-defined
* Corresponding author. Tel.: þ39 0521 905 463; fax: þ39 0521 905 472.
E-mail address: enrico.dalcanale@unipr.it (E. Dalcanale).
0040-4020/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2008.11.111

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F. Gruppi et al. / Tetrahedron 65 (2009) 7289–7295
Figure 1. Structure of cavitand 1 and Spartan modeling showing the distance and orientation of the two ligands with respect to the cavitand scaffold.
precipitated in pure form at the water–organic interface (36%
yield). Reaction of 3 with CH2ClBr in a Schlenk apparatus14 afforded
methylene-bridged tetraiodo-cavitand 4 in very high yield (88%).
Sonogashira coupling on 4 gave monoethynylpyridine derivative 5,
which underwent a multiple Suzuki coupling to give the desired
cavitand 1.
The addition of further 1.5 equiv of Pt(dppp)OTf2 led to com-
plete closure of the cage, as confirmed by ESI MS. The mass spec-
trum evidenced a prominent signal at 2938.2 m/z, corresponding to
the doubly charged cage ion. However, as shown in Figure 2c and d,
two NMR signals corresponding to the ethynylpyridine a-H were
present at 8.81 and 8.61 ppm. The intensity ratio of the two peaks
was 1:1 immediately after the addition of the metal complex, but
became 1:3 after 48 h and remained stable thereafter. Moreover,
a splitting of the signals corresponding to Hin and Hout of the
methylene bridges was observed. After completion of the reaction,
the 31P NMR spectrum presented a second signal at ꢀ10.02 ppm, in
addition to ꢀ15.60 ppm peak in a 3:1 ratio.
2.2. Self-assembly of cage 8
We first explored the complexation behavior of tetradentate
ligand 1 against a single metal precursor of general structure
M(dppp)OTf2, where dppp is 1,3-bis(diphenylphosphino)propane.
A stepwise protocol, depicted in Scheme 2, was devised for both
Pt(dppp)OTf2 and Pd(dppp)OTf2.
Taken together these observations indicate the presence of more
than one isomeric cage in solution. As shown in Figure 3, in addition
to the structure in which the two ethynylpyridines are coordinated
to the same metal center (8a), the formation of two other isomers is
conceivable. In such isomers (8b and 8c), one Pt(dppp)OTf2 com-
plex is coordinated to an ethynylpyridine and a benzonitrile ligand.
In the case of 8b, 2 equiv structures are possible, obtained by ro-
tating one cavitand ligand in 8a by ꢁ90ꢂ.
Metal complex (0.5 equiv) was added to a 5 mM solution of
cavitand 1 in a mixture of CD2Cl2 (400 mL) and CD3NO2 (100 mL).
CD3NO2 was added to accelerate the ligand exchange15 in order to
reach the thermodynamic equilibrium in reasonable time. Sub-
sequently, the remaining 1.5 equiv of metal precursor was added to
the solution. 1H and 31P NMR spectra were used to track the self-
assembly process. The cages were identified by ESI mass
spectrometry.
As reported by Kobayashi and co-workers,8 the 1H NMR signal
corresponding to the a-H protons of the ethynylpyridine ligand is
Scheme 1. Synthesis of tetradentate cavitand ligand 1.

F. Gruppi et al. / Tetrahedron 65 (2009) 7289–7295
7291
Scheme 2. Stepwise self-assembly protocol.
slightly upfield shifted for the EtPy–Pt–NCPh system compared to
the EtPy–Pt–EtPy system. Therefore, the new signal detected at
8.61 ppm is consistent with cages 8b and 8c, which cannot be
differentiated by NMR.
ethynylpyridines to the same metal center, as opposed to binding
them to two different Pt complexes. Therefore, the three possible
structures are energetically equivalent, as demonstrated by the 3:1
observed 8b,c/8a ratio.
Kobayashi and co-workers demonstrated that heterocages can
be formed as kinetic products, whereas the thermodynamic prod-
ucts were always the homocages of ethynylpyridine and benzoni-
trile.8 The driving force of the self-assembly was the higher
coordination ability of the ethynylpyridine ligand. The homocage
composed by two identical tetraethynylpyridine cavitand was the
thermodynamically favored product.
However, in our system all isomeric cages require the formation
of the same set of coordinative bonds, namely two EtPy–Pt and six
PhCN–Pt bonds. There is no energy gain in binding two
2.3. Self-assembly of cage 9
The same protocol was utilized for the formation of Pd cages 9a–c
starting from Pd(dppp)OTf2. Just as with the Pt cages, when
0.5 equiv of Pd(dppp)OTf2 was added to a 5 mM solution of cav-
itand 1 in CD2Cl2/CD3NO2, hemicage 7 was formed. Due to its higher
coordination ability, ethynylpyridine sequestrated the whole
amount of metal complex added and led to the exclusive formation
of 7. The 1H NMR spectrum showed the characteristic downfield
Figure 2. 1H NMR (300 MHz, 400
Pt(dppp)OTf2, (d) 5 mM cavitand 1 and 2 equiv Pt(dppp)OTf2 after 48 h. ; ethynylpyridine
m
L CD2Cl2 and 100
m
L CD3NO2) spectra of (a) 5 mM cavitand 1, (b) 5 mM cavitand 1 and 0.5 equiv Pt(dppp)OTf2, (c) 5 mM cavitand 1 and 2 equiv
-H protons, 7 Hin and Hout methylene bridges protons, C residual solvent peaks.
a

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F. Gruppi et al. / Tetrahedron 65 (2009) 7289–7295
Figure 3. Isomeric coordination cages 8a–c and 9a–c.
shift of the peak corresponding to the
a
-H of the ethynylpyridine
8.81 and 8.59 ppm, as was the splitting of the Hin and Hout signals
of the methylene bridges. The intensity of the two signals
reached a ratio of 1:3 after ca. 48 h (Fig. 4c). Two of the six 31P
(
Dd
¼
dhemicage
ꢀ
dfree
¼0.26 ppm, from 8.51 to 8.77 ppm). In
cavitand
addition, the Hout and Hin signals of the methylene bridges adjacent
to the ethynylpyridine shifted upfield from 5.60 to 5.49 ppm and
from 4.12 to 4.08 ppm (Fig. 4). The 31P NMR signal shifted upfield
2
signals showed the JP–P¼25 Hz, which is characteristic for the
desymmetrization of the dppp signal in EtPy–CNPh systems.8 The
diagnostic M2þ ion of coordination cages was observed via ESI
MS at 2760.1 m/z (Fig. 5). Those data confirmed the formation
of three isomeric cages, as previously reported for the Pt
experiment.
from 17.26 to 6.14 ppm
11.12 ppm).
(
Dd¼
dhemicage
ꢀdfree
¼
Pd metal complex
After the addition of 1.5 further equivalents of metal complex,
two signals for the -H of the ethynylpyridine were observed at
a
Figure 4. 1H NMR (300 MHz, 400
Pt(dppp)OTf2 after 48 h. ; ethynylpyridine
m
L CD2Cl2 and 100
mL CD3NO2) spectra of (a) 5 mM cavitand 1, (b) 5 mM cavitand 1 and 0.5 equiv Pd(dppp)OTf2, (c) 5 mM cavitand 1 and 2 equiv
a
-H protons, 7 Hin and Hout methylene bridges protons, C residual solvent peaks.

F. Gruppi et al. / Tetrahedron 65 (2009) 7289–7295
7293
Figure 5. Selected region of the experimental (top) and calculated (bottom) ESI MS spectrum of CD2Cl2/CD3NO2 solution of cage 9 showing [Mꢀ2CF3SO3]2þ signal at m/z 2760.1.
The different coordination ability of the ligands in 1 could only
be exploited for the first step of the self-assembly protocol,
leading to homocages 6 and 7. Further addition of the same metal
led to ligand scrambling during subsequent cage closure,
regardless of the metal used. We can conclude that, in itself, the
presence of different ligands at the upper rim of the cavitand is
not sufficient to drive self-assembly toward the formation of
a single molecular cage. Therefore, an additional strategy was
Figure 6. 1H NMR (300 MHz, 400
cavitand 1, 0.5 equiv Pt(dppp)OTf2, and 1.5 equiv Pd(dppp)OTf2 after one week. ; ethynylpyridine
m
L CD2Cl2 and 100
m
L CD3NO2) spectra of (a) 5 mM cavitand 1, (b) 5 mM cavitand 1, 0.5 equiv Pt(dppp)OTf2, and 1.5 equiv Pd(dppp)OTf2, (c) 5 mM
-H protons, 7 Hin and Hout methylene bridges protons, C residual solvent peaks.
a

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F. Gruppi et al. / Tetrahedron 65 (2009) 7289–7295
devised, involving two different metal centers, to obtain selec-
tively a single cage.
Waters 74 spectrometer or on a LTQ-linear ion trap mass spec-
trometer (Thermo Fisher Corp.) equipped with an electrospray
source.
2.4. Self-assembly of heteronuclear cage 10
4.2. Tetraiodo-resorcinarene (3)
Addition of 1.5 equiv of Pd(dppp)OTf2 to a solution of Pt-hemi-
cage 6 led to the exclusive formation of the heterocage 10. Only one
To a solution of 0.496 g of resorcinarene 1 (6.02ꢃ10ꢀ4 mol) in
a 1:1 mixture of water and diethyl ether (16 mL), 0.202 g of NaHCO3
(2.41ꢃ10ꢀ4 mol), and 0.614 g of I2 (2.41ꢃ10ꢀ4 mol) were added. The
solution was stirred overnight at room temperature. Following
Buchner filtration, the precipitate was washed with cold ethanol.
The pure product was collected as white solid (Yield 36%). 1H NMR
signal for the a-H protons of ethynylpyridine groups and two sig-
nals for Hin and Hout, respectively, were observed in the 1H NMR
spectrum.
Moreover,
a-H protons of the ethynylpyridine and Hin signals
were shifted slightly upfield with respect to hemicage 6 due to the
complete closure of the cage (Dd
ethynypyridine group and Dd dcage
¼
dcage
ꢀ
dhemicage¼0.06 ppm for
(acetone-d6, 300 MHz)
d
¼8.16 (s, 8H, ArOH), 7.65 (s, 4H, ArH), 4.43
¼
ꢀ
demicage¼0.05ppm for Hin). 31
P
(t, 4H, ArCH, J¼8.6 Hz), 2.29 (m, 8H, ArCHCH2), 1.24 (m, 32H,
CH2CH2CH2CH2CH2CH3), 0.85 (t, 12H, CH2CH3, J¼7.4 Hz); ESI MS (m/z):
1327 [M]ꢀ [M¼C52H68I4O8].
NMR exhibited three peaks at ꢀ15.48 (EtPy–Pt–PyEt), 11.82 (PhCN–
Pd–CNPh), and 15.36 ppm (PhCN–Pd–CNPh) in a 1:2:1 ratio, con-
sistent with the structure of 10. The presence of the M2þ ion in the
ESI MS at m/z¼2803.5 confirmed the formation of the hetero-
nuclear cage. The absence of the M2þ ions corresponding to 8 and 9
excluded their presence in solution.
The thermodynamic versus kinetic stability of cage 10 was de-
termined by using a one-pot procedure. Cavitand 1 was reacted
with a mixture of Pd(dppp)OTf2 and Pt(dppp)OTf2 in a 3:1 ratio in
the standard CD2Cl2/CD3NO2 solution. Initially, two peaks corre-
4.3. Tetraiodo-cavitand (4)
Compound 1 (0.593 g, 4.46ꢃ10ꢀ4 mol) was dissolved in dry DMF
(8 mL) in a dry Schlenk tube. To the solution were added 1.208 mL
of CH2ClBr (1.78ꢃ10ꢀ2 mol) and 0.493 g of K2CO3 (3.57ꢃ10ꢀ3 mol).
The mixture was stirred at 85 ꢂC for 3 h. After neutralization with
HCl 2%, a precipitate formed; following Buchner filtration, the
resulting solid was the pure product (Yield 88%). 1H NMR (CDCl3,
sponding to the a-H protons of the ethynylpyridine appeared at
8.82 and 8.64 ppm, as did broad signals corresponding to Hin and
Hout, suggesting the formation of a mixture of different cages
(Fig. 6b). Within several hours, however, the 8.64 ppm signal dis-
appeared, and the broad Hin and Hout signals evolved into four
doublets at 5.47, 5.05, 4.22 (partially obscured by residual nitro-
methane solvent signal), and 4.08 ppm. The 1H NMR spectrum
remained unchanged after one week (Fig. 6c). These results indicate
the initial formation of several isomeric cages (kinetic products),
which interconvert into cage 10 (the thermodynamic product) over
time. 1H and 31P NMR confirmed a complete transformation of the
isomeric cages into structure 10.
300 MHz)
d
¼7.05 (s, 4H, ArH), 5.96 (d, 4H, OCHinHoutO, J2¼8.2 Hz),
4.84 (t, 4H, ArCH, J¼9.0 Hz), 4.30 (d, 4H, OCHinHoutO, J2¼8.2 Hz),
2.18 (m, 8H, ArCHCH2), 1.31 (m, 32H, CH2CH2CH2CH2CH2CH3), 0.89
(t, 12H, CH2CH3, J¼7.4 Hz); ESI MS (m/z): 1399 [MþNa]þ
[M¼C56H68I4O8].
4.4. Monoethynylpyridine-cavitand (5)
Dry Et3N (10 mL) was degassed in a dry flask for 30 min; 0.5 g of
2
(3.63ꢃ10ꢀ4 mol), 0.084 g of ethynylpyridinehydrochloride
(6.25ꢃ10ꢀ4 mol), 0.0102 g of Pd(PPh3)2Cl2 (1.45ꢃ10ꢀ5 mol),
0.0051 g of CuI (3.5ꢃ10ꢀ5 mol), and 0.0057 g of PPh3
(2.2ꢃ10ꢀ5 mol) were added and the mixture was stirred for 1 h at
60 ꢂC and for 48 h at 90 ꢂC. After cooling to room temperature,
CHCl3 was added and the crude product was washed with water
and extracted with CHCl3. The pure product was obtained by pu-
rification with silica gel flash chromatography with CH2Cl2/AcOEt
3. Conclusion
The exclusive formation of heteronuclear coordination cage 10
demonstrates the versatility of this type of self-assembly pro-
cedure. The design of the appropriate tetradentate cavitand ligand
is the key element in driving the self-assembly toward the forma-
tion of the desired product. In the specific case of the heteronuclear
coordination cages reported here, it is crucial to differentiate the
type, number, and position of the ligands, to reach the correct
metal/ligand cross-reactivity. A single ligand substitution with re-
spect to the parent tetrabenzonitrile cavitand10 is sufficient to shift
completely the outcome of the self-assembly protocol from ho-
monuclear to heteronuclear cages. For the same reason, cavitand 1
is unfit for homocage self-assembly, as it leads to the formation of
a set of isomeric cages. Efforts to extend this strategy to the self-
assembly of large cage networks16 are underway.
(95:5) as eluent (Yield 35%). 1H NMR (CDCl3, 300 MHz)
d¼8.60 (d,
2H, PyHo, J¼6.0 Hz), 7.30 (d, 2H, PyHm, J¼6.0 Hz), 7.11 (s, 1H, ArH),
7.08 (s, 1H, ArH), 7.06 (s, 1H, ArH), 5.95 (m, 4H, OCHinHoutO), 4.84
(m, 4H, ArCH), 4.48 (d, 2H, OCHinHoutO, J2¼8.1 Hz), 4.29 (d, 2H,
OCHinHoutO, J2¼8.2 Hz), 2.21 (m, 8H, ArCHCH2), 1.28 (m, 40H,
CH2CH2CH2CH2CH2CH3), 0.88 (t,12H, CH2CH3, J¼7.2 Hz); ESI MS (m/z):
1352.7 [MH]þ [M¼C63H72I3NO8].
4.5. Monoethynylpyridine-tribenzonitrile cavitand (1)
To a solution of 0.1088 g of 5 (7.45ꢃ10ꢀ5 mol) in 10 mL of di-
oxane 0.0157 g of Pd(PPh3)2Cl2 (2.24ꢃ10ꢀ5 mol), 0.208 g of 4-
(cyanophenyl)boronic acid pinacol ester, (9.07ꢃ10ꢀ4 mol), 0.057 of
AsPh3 (1.86ꢃ10ꢀ4 mol), and 0.4748 g of Cs2CO3 previously dissolved
in 0.25 mL of water were added. The mixture was stirred under
Argon for 40 h at 110 ꢂC. The solution was cooled at room tem-
perature and concentrated under vacuum. Cavitand 1 was obtained
as white solid by precipitation with diethylether in 36% yield. 1H
4. Experimental
4.1. General
Reagents and solvents were purchased as reagent grade and
used without further purification. Analytical TLC was performed
on Merck silica gel 60 F254 precoated plates. Column chromatog-
raphy was performed using silica gel (Merck 70–230 mesh). 1H
NMR spectra were recorded at 300 MHz on a Bruker AC 300
Avance spectrometer with solvent peaks as reference. 31P NMR
spectra were recorded at 162 MHz, on a Bruker 400 spectrometer.
Mass spectra were measured either on a Helwett–Packard 3395
NMR (CDCl3, 300 MHz)
d¼8.51 (d, 2H, PyHo, J¼6.0 Hz), 7.65 (d, 4H,
NCArHo, J¼9.1 Hz), 7.59 (d, 2H, NCArHo, J¼9.1 Hz), 7.29 (s, 4H, ArH),
7.21 (d, 2H, PyHm, J¼6.0 Hz), 7.15 (d, 4H, NCArHm, J¼9.1 Hz), 7.09 (d,
2H, NCArHm, J¼9.1 Hz), 5.60 (d, 2H, OCHinHoutO, J2¼7.8 Hz), 5.17 (d,
2H, OCHinHoutO, J2¼7.7 Hz), 4.80 (m, 4H, ArCH), 4.38 (d, 2H,
OCHinHoutO, J2¼7.8 Hz), 4.12 (d, 2H, OCHinHoutO, J2¼7.7 Hz), 2.30 (m,

F. Gruppi et al. / Tetrahedron 65 (2009) 7289–7295
7295
8H, ArCHCH2), 1.22 (m, 32H, CH2CH2CH2CH2CH2CH3), 0.90 (t, 12H,
CH2CH3, J¼7.3 Hz); ESI MS (m/z): 1278.6 [MH]þ, [M¼C84H84N4O8].
and 31P NMR spectra were recorded. 1H NMR (CD2Cl2, 300 MHz):
d
¼8.89 (d, 4H, PyHo), 7.73–7.30 (m, 92H, PPh2þNCArHo), 7.13–7.07
(m, 12H, NCArHm), 6.98 (d, 4H, PyHm), 5.47 (d, 4H, OCHinHoutO), 5.05
(d, 4H, OCHinHoutO), 4.80–4.72 (m, 8H, ArCH), 4.28–4.26 (m, 4H,
OCHinHoutO), 4.08 (d, 4H, OCHinHoutO), 3.24 (m, 8H, dppp), 2.90 (m,
8H, dppp), 2.30 (m, 24H, dpppþArCHCH2), 1.42–1.34 (m, 64H,
CH2CH2CH2CH2CH2CH3), 0.93 (br t, 24H, CH2CH3); 31P NMR (CD2Cl2,
4.6. Stepwise self-assembly of Pt-hemicage (6) and Pt cage (8)
To a solution of 3.2 mg of 1 (5.0ꢃ10ꢀ3 M) in CD2Cl2 (0.4 mL) and
CD3NO2 (0.1 mL) in the NMR tube 1.1 mg of Pt(dppp)OTf2 was
added to give hemicage 6 and 1H NMR and 31P NMR spectra were
162 MHz):
d¼15.36, 11.82, ꢀ15.48 (JP–Pt¼3189 Hz).
recorded. 1H NMR (CD2Cl2þCD3NO2, 300 MHz):
d
¼8.82 (d, 4H,
PyHo), 7.76–6.98 (m, 48H, PPh2þNCArHoþPyHmþNCArHm), 5.49 (d,
4H, OCHinHoutO), 5.07 (d, 4H, OCHinHoutO), 4.80–4.78 (m, 8H, ArCH),
4.20 (d, 4H, OCHinHoutO partially under residual solvent peak), 4.10
(d, 4H, OCHinHoutO), 2.29 (m, 16H, ArCHCH2), 1.29 (m, 64H,
CH2CH2CH2CH2CH2CH3), 0.90 (br t, 24H, CH2CH3); 31P NMR
(CD2Cl2þCD3NO2, 162 MHz): ꢀ15.60 ppm (JP–Pt¼3033 Hz).
4.8.2. One-pot procedure
To a solution of 3.5 mg of 1 (5.4ꢃ10ꢀ3 M) in CD2Cl2 (0.4 mL) and
CD3NO2 (0.1 mL) in the NMR tube 1.25 mg of Pt(dppp)OTf2, and
3.3 mg of Pd(dppp)OTf2 were added. 1H NMR and 31P NMR spectra
were recorded. 1H NMR (CD2Cl2þCD3NO2, 300 MHz):
¼8.82 (d, 4H,
d
PyHo), 7.72–7.25 (m, 92H, PPh2þNCArHo), 7.07–6.94 (m, 16H,
PyHmþNCArHm), 5.46 (d, 4H, OCHinHoutO), 5.03 (d, 4H, OCHinHoutO),
4.79–4.74 (m, 8H, ArCH), 4.20 (d, 4H, OCHinHoutO partially under
residual solventpeak), 4.07 (d, 4H, OCHinHoutO), 3.23–2.83 (m, dppp),
2.30 (m, 16H, ArCHCH2), 1.40–1.29 (m, 64H, CH2CH2CH2CH2CH2CH3),
0.87 (br t, 24H, CH2CH3); 31P NMR (CD2Cl2þCD3NO2, 162 MHz):
An additional 3.4 mg of Pt(dppp)OTf2 was added to same solu-
tion and 1H NMR and 31P NMR spectra were recorded again. 1H
NMR (CD2Cl2þCD3NO2, 300 MHz): ¼8.81 (d, 4H, PyHo), 8.61 (d,
d
12H, PyHo), 7.82–6.98 (m, 416H, PPh2þNCArHmþNCArHo), 6.92 (d,
4H, PyHm), 6.72 (d, 12H, PyHm), 5.55–5.42 (m, 16H, OCHinHoutO),
5.08 (d, 8H, OCHinHoutO), 4.98 (d, 8H, OCHinHoutO), 4.75–4.65
(m, 32H, ArCH), 4.26–4.22 (m, 16H, OCHinHoutO), 4.23 (d, 8H,
OCHinHoutO partially under residual solvent peak), 4.18 (d, 16H,
OCHinHoutO), 2.90 (m, 64H, dppp), 2.75 (m, 32H, dppp), 2.29 (m,
64H, ArCHCH2), 1.29 (m, 256H, CH2CH2CH2CH2CH2CH3), 0.90 (br t,
96H, CH2CH3); 31P NMR (CD2Cl2þCD3NO2, 162 MHz): ꢀ15.60, ꢀ10.02
(JP–Pt¼3444 Hz).
d
¼15.84, 12.35, ꢀ15.07 (JP–Pt¼3075 Hz).
ESI MS (m/z): 2803.51 [(Mꢀ2OTf)]2þ, [M¼C284H272F24N8O40
-
Pd3P8PtS8].
Acknowledgements
This work was supported by the EU through NoE MAGMANet (3-
NMP 515767-2). The instrumental facilities at the Centro Inter-
ESI MS (m/z): 2938.2 [(Mꢀ2OTf)]2þ, [M¼C284H272F24N8O40
-
P8Pt4S8].
`
facolta di Misure G. Casnati of the University of Parma were utilized.
4.7. Stepwise self-assembly of Pd hemicage (7) and Pd cage (9)
References and notes
To a solution of 3.1 mg of 1 (4.85ꢃ10ꢀ3 M) in CD2Cl2 (0.4 mL) and
CD3NO2 (0.1 mL) in the NMR tube 1 mg of Pd(dppp)OTf2 was added
to give hemicage 7 and 1H NMR and 31P NMR spectra were recor-
1. Pirondini, L.; Dalcanale, E. In Modern Supramolecular Chemistry, Diedrich, F., Stang,
P.J., Tykwinski, R.R., Eds.; Wiley-VCH: Weinhem, 2008; Chapter 7, pp 233–276.
2. (a) Harrison, R. G.; Burrows, J. L.; Hansen, L. D. Chem.dEur. J. 2005, 11, 2881–
2888; (b) Haino, T.; Kobayashi, M.; Fukazawa, Y. Chem.dEur. J. 2006, 12, 3310–
3319.
3. (a) Caulder, D. L.; Powers, K. N.; Parac, T. N.; Raymond, K. N. Angew. Chem., Int.
Ed. 1998, 37, 1840–1843; (b) Fochi, F.; Jacopozzi, P.; Wegelius, E.; Rissanen, K.;
Cozzini, P.; Marastoni, E.; Fisicaro, E.; Manini, P.; Fokkens, R.; Dalcanale, E. J. Am.
Chem. Soc. 2001, 123, 7539–7552; (c) Fujita, M.; Yoshizawa, M. In Modern Su-
pramolecular Chemistry, Diedrich, F., Stang, P.J., Tykwinski, R.R., Eds.; Wiley-
VCH: Weinhem, 2008; Chapter 8, pp 277–313.
4. (a) Chen, J.; Ko¨ner, S.; Craig, S. L.; Rudkevich, D. M.; Rebek, J., Jr. Nature 2002,
415, 385–386; (b) Yoshizawa, M.; Sato, N.; Fujita, M. Chem. Lett. 2005, 34, 1392–
1393.
5. Koblenz, T. S.; Dekker, H. L.; de Koster, C. G.; van Leeuwen, P. W. N. M.; Reek,
J. N. H. Chem. Commun. 2006, 1700–1702.
6. Rudkevich, D. M. Angew. Chem., Int. Ed. 2004, 43, 558–571.
7. (a) Warmuth, R. Eur. J. Org. Chem. 2001, 423–437; (b) Yoshizawa, M.; Kusukawa,
T.; Fujita, M.; Yamaguchi, K. J. Am. Chem. Soc. 2000, 122, 6311–6312.
8. Yamanaka, M.; Yamada, Y.; Sei, Y.; Yamaguchi, K.; Kobayashi, K. J. Am. Chem. Soc.
2006, 128, 1531–1539.
9. For the self-assembly of heterocages on surfaces, see: (a) Menozzi, E.; Pinalli, R.;
Speets, E. A.; Ravoo, B. J.; Dalcanale, E.; Reinhoudt, D. N. Chem.dEur. J. 2004, 10,
2199–2206; (b) Busi, M.; Laurenti, M.; Condorelli, G. G.; Motta, A.; Favazza, M.;
ded. 1H NMR (CD2Cl2þCD3NO2, 300 MHz):
¼8.77 (d, 4H, PyHo),
d
7.67–7.30 (m, 32H, PPh2þNCArHo), 7.06 (d, 12H, NCArHm), 6.94 (d,
4H, PyHm), 5.49 (d, 4H, OCHinHoutO), 5.05 (d, 4H, OCHinHoutO), 4.81–
4.75 (m, 8H, ArCH), 4.22–4.19 (m, 4H, OCHinHoutO, partially under
residual solvent peak), 4.08 (d, 4H, OCHinHoutO), 3.12–2.91 (dppp
signals),
2.32
(m,
16H,
ArCHCH2),
1.29
(m,
64H,
CH2CH2CH2CH2CH2CH3), 0.87 (br t, 24H, CH2CH3); 31P NMR:
(CD2Cl2þCD3NO2, 162 MHz): ¼6.14 ppm.
d
An additional 2.9 mg of Pd(dppp)OTf2 was added to same so-
lution and 1H NMR and 31P NMR spectra were recorded again. 1H
NMR (CD2Cl2þCD3NO2, 300 MHz): ¼8.81 (d, 4H, PyHo), 8.59 (d,
d
12H, PyHo), 7.84–6.89 (m, PPh2þNCArHmþNCArHoþPyHm), 5.51–
5.46 (m, 16H, OCHinHoutO), 5.07–4.99 (m, 16H, OCHinHoutO), 4.77–
4.66 (m, 32H, ArCH), 4.19–4.07 (m, 32H, OCHinHoutO partially under
residual solvent peak), 2.90–2.75 (m, three signals of dppp), 2.29
(m, 64H, ArCHCH2), 1.40–1.29 (m, 256H, CH2CH2CH2CH2CH2CH3),
0.87 (br t, 96H, CH2CH3); 31P NMR (CD2Cl2þCD3NO2, 162 MHz):
`
Fragala, I. L.; Montalti, M.; Prodi, L.; Dalcanale, E. Chem.dEur. J. 2007, 13, 6891–
6898.
2
2
d
¼15.77, 12.41, 11.50 (d, JP–P¼25 Hz), 10.90 (d, JP–P¼25 Hz), 6.14,
10. Cuminetti, N.; Ebbing, M. H. K.; Prados, P.; de Mendoza, J.; Dalcanale, E. Tetra-
hedron Lett. 2001, 42, 527–530.
11. Pinalli, R.; Cristini, V.; Sottili, V.; Geremia, S.; Campagnolo, M.; Caneschi, A.;
Dalcanale, E. J. Am. Chem. Soc. 2004, 126, 6516–6517.
12. Tunstad, L. M.; Tucker, J. A.; Dalcanale, E.; Weiser, J.; Bryant, J. A.; Sherman, C. J.;
Helgeson, R. C.; Knobler, C. B.; Cram, D. J. Org. Chem. 1989, 54, 1305–1312.
13. Tanaka, Y.; Sasada, A.; Fujita, Y. Proceedings of 9th International Conference on
Calixarene Chemistry, 2007; p 96.
4.91 ppm.
ESI MS (m/z): 2760.16 [(Mꢀ2OTf)]2þ, [M¼C284H272F24N8O40
-
P8Pd4S8].
4.8. Self-assembly of heteronuclear cage (10)
4.8.1. Stepwise procedure
´
14. Roman, E.; Peinador, C.; Mendoza, S.; Kaifer, A. E. J. Org. Chem. 1999, 64, 2577–
2578.
To a solution of 3.2 mg of 1 (5ꢃ10ꢀ3 M) in CD2Cl2 (0.5 mL) in the
NMR tube 1.1 mg of Pt(dppp)OTf2 was added to form Pt-hemicage
6. Pd(dppp)OTf2 (3 mg) was added to same solution and 1H NMR
15. Zuccaccia, D.; Pirondini, L.; Pinalli, R.; Dalcanale, E.; Macchioni, A. J. Am. Chem.
Soc. 2005, 127, 7025–7032.
16. Menozzi, E.; Busi, M.; Massera, C.; Ugozzoli, F.; Zuccaccia, D.; Macchioni, A.;
Dalcanale, E. J. Org. Chem. 2006, 71, 2617–2624.