Angewandte
Chemie
8.98 (br, 24H), 8.59 (br, 24H), 8.33 (br, 48H), 8.29 (br, 24H), 8.08 (br,
Table 1: Suzuki–Miyaura coupling reaction between aryl iodide and p-
tolylboronic acid catalyzed by 4a or 5.[a]
48H), 7.93 (br, 24H), 7.74 (br, 48H), 2.65 ppm (br, 144H).13C NMR
(100 MHz, [D6]DMSO, 300 K) d = 151.26, 149.89, 147.06, 145.08,
141.28, 130.64, 127.85, 126.66, 126.26, 125.53, 115.78, 13.71 ppm.
Diffusion coefficient ([D6]DMSO, 300 K): D = 6.29 10À11 m2 sÀ1
À
(Log D = À10.25). ESI-TOF-MS (PF6 salt, CH3CN): The following
picked signals are those at the highest intensities. m/z Calcd for
[MÀ9(PF6À)]9+ 1729.3246, found 1729.3325; Calcd for [MÀ10-
(PF6À)]10+ 1541.8957, found 1541.9005; Calcd for [MÀ11(PF6À)]11+
1388.5448, found 1388.5525; Calcd for [MÀ12(PF6À)]12+ 1260.7523,
found 1260.7610; Calcd for [MÀ13(PF6À)]13+ 1152.6202, found
1152.7812; Calcd for [MÀ14(PF6À)]14+ 1059.9356, found 1059.9398;
Calcd for [MÀ15(PF6À)]15+ 976.6089, found 976.6175. IR (KBr) u˜ =
3652, 3420, 3092, 1619, 1540, 1430, 1343, 1222, 1029, 840, 716,
Entry
Ar
Pd [mol%]
Yield [%][b]
for 4a
Yield [%][b]
for 5
1
2
3
4
5
phenyl
0.45
0.45
0.45
0.45
0.45
60
58
59
56
43
98
99
98
98
58
4-acetylphenyl
4-fluorophenyl
4-methoxyphenyl
2-pyridyl
557 cmÀ1
.
À
À
[a] All reactions were performed on a 0.1 mmol scale using 300 mol%
K3PO4 and 0.015 mol% 4a or 0.018 mol% 5 (empirical formula weight
based on one barrel segment unite of the tube as shown in Figure 3B) in
1,4-dioxane (5 mL) at 908C for 12 h. [b] Yields were determined by
400 MHz 1H NMR spectroscopy with the aid of CH2Cl2 as an internal
standard.
Synthesis of 4b (BF4 salt): Ligand 3b (BF4 salt) (21.52 mg,
20.60 mmol) was treated with [Pd(CH3CN)4](BF4)2 (4.56 mg,
10.3 mmol) in [D6]DMSO (1.0 mL) at 508C for 5 h. 1H NMR
confirmed the quantitative formation of 4b. An excess amount of
a mixture of ethyl acetate and diethyl ether (1:1 in volume) was added
to the solution of barrel 4b and the precipitate was collected by
centrifugation and dried in vacuo to give 4b as a white solid
(17.01 mg, 1.42 mmol, 83% yield). M.p. > 3208C (decomposed).
1H NMR (400 MHz, [D6]DMSO, 300 K) d = 9.27 (br, 48H), 8.63
(br, 48H), 8.41 (br, 24H), 8.33 (br,24H), 8.20 (br, 24H), 7.94 (br,
24H), 7.72 (br, 24H), 7.61 (br, 48H), 7.56 (br, 24H), 2.46 ppm (br,
144H). 13C NMR (100 MHz, [D6]DMSO, 300 K) d = 156.89, 150.20,
149.48, 144.98, 142.53, 128.19, 125.46, 124.46, 118.23, 115.60,
22.37 ppm. Diffusion coefficient ([D6]DMSO, 300 K): D = 6.28
samples of 5 and 4a were tested for catalyzing the Suzuki–
Miyaura cross-coupling reactions between aryl iodide and
aryl boronic acid (Table 1). The reactions were heterogeneous
in nature as they were performed in 1,4-dioxane, a solvent
from which the crystals of 5 and 4a were obtained. Sub-
stituted aryl iodides were screened which confirmed that both
electron-donating and electron-withdrawing groups could be
tolerated (entries 1–5). With as low as a 0.45 mol% loading
based on Pd, desirable products were obtained in high yields
with 5 as the catalyst, whereas only moderate yields were
observed using 4a instead. Besides, preliminary kinetic
studies (Supporting Information, Figures S31–33) revealed
that the catalysis by 5 was over 10-fold faster than 4a. This
obvious catalytic difference between 4a and 5 was attributed
to the coordination-unsaturated Pd sites on the ends of
tubular 5.
In summary, the construction of unique MMONT struc-
tures has been accomplished by a rational coordination-
directed bottom-up fabrication process featuring an unpre-
cedented barrel-to-tube conversion. Formation of either
segmental or continuous MMONTs can be easily controlled
by choosing appropriate starting materials. This study pro-
vides a new strategy for the construction of artificial nano-
tubular materials through a modular self-assembly method.
The synthesis of heterometallic nanotubes with adjustable
pore sizes using this strategy and the detailed study of their
catalytic properties are currently underway.
À
10À11 m2 sÀ1 (Log D = À10.20) ESI-TOF-MS (BF4 salt, CH3CN):
The following picked signals are those at the highest intensities. m/z
Calcd for [MÀ8(BF4À)]8+ 1687.9987, found 1687.7384; Calcd for
[MÀ9(BF4À)]9+ 1490.7766, found 1490.7647; Calcd for [MÀ10-
(BF4À)]10+ 1332.9981, found 1332.9780; Calcd for [MÀ11(BF4À)]11+
1203.9978, found 1204.0711; Calcd for [MÀ12(BF4À)]12+ 1096.4144,
found 1096.4067. IR (KBr) u˜ = 3604, 3413, 2904, 1614, 1540, 1503,
1474, 1455, 1428, 1381, 1351, 1221, 1050, 843, 772, 723, 658, 585,
517 cmÀ1
Synthesis of 5: Single crystals of 5 were obtained by the slow
vapor diffusion of 1,4-dioxane into DMSO solution of 4b
.
a
(16.6 mmol) over two weeks. The prism yellow crystals was collected
by filtration, washed with 1,4-dioxane several times and dried in
vacuo to give 5 (115 mg, 10.4 mmol, 50.1% yield based on Pd).
Elemental analysis calcd for C300H298N84B24F96Pd24·(C4H8O2)6·-
((CH3)2SO)10: C 37.5, H 3.63, N 10.68%; found C 37.0, H 3.71,
N 10.58%. IR (KBr) u˜ = 3445, 2920, 2851, 1751, 1611, 1535, 1457,
1424, 1381, 1311, 1255, 1083, 1027,875, 762, 723, 646, 517 cmÀ1
Crystal data for 4a: Space group R3/m, a = b = 66.460(9) , c =
30.056(6) , V= 114970(45) 3, Z = 3, T= 293 K. Anisotropic least-
squares refinement for the framework atoms and isotropic refinement
.
¯
for the other atoms on 10274 independent merged reflections (Rint
=
0.042) converged at residual wR2 = 0.2708 for all data; residual R1 =
0.0781 for 19780 observed data [I > 2s(I)], and goodness of fit
(GOF) = 1.264.
Crystal data for 5: Space group P6/m, a = b = 39.2398(10) , c =
14.9993(5) , V= 20001.2(14) 3, Z = 6, T= 293 K. Anisotropic
least-squares refinement for the framework atoms and isotropic
refinement for the other atoms on 13794 independent merged
reflections (Rint = 0.0613) converged at residual wR2 = 0.4451 for all
data; residual R1 = 0.1477 for 46043 observed data [I > 2s(I)], and
goodness of fit (GOF) = 1.157.
Full experimental details and crystallographic analysis are given
the supplementary crystallographic data for this paper. These data
Experimental Section
À
À
Synthesis of 4a (PF6 salt): Ligand 3a (PF6 salt) (24.12 mg,
19.97 mmol) was treated with Pd(PF6)2 (3.95 mg, 9.96 mmol) in
[D6]DMSO (1.0 mL) at 508C for 5 h. 1H NMR spectroscopy con-
firmed the quantitative formation of 4a. An excess amount of
a mixture of ethyl acetate and diethyl ether (1:1 in volume) was added
to the solution of barrel 4a and the precipitate was collected by
centrifugation and dried in vacuo to give 4a as a white solid (22.46 mg,
1.33 mmol, 80% yield). M.p. > 3208C (decomposed). 1H NMR
(400 MHz, [D6]DMSO, 300 K) d = 9.38 (br, 48H), 9.05 (br, 48H),
Angew. Chem. Int. Ed. 2015, 54, 9844 –9848
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