The Wittig reaction as a key step in the preparation of triangular ligands for the self-assembly of molecular M4L4 tetrahedra

Article abstract of DOI:10.1055/s-2007-990826

Triangular ligands based on a central C₃-symmetric backbone, ethylene linkages, and catechol ligand units, are prepared by a Wittig approach. The ligands form, in metal-directed self-assembly processes, tetrahedral coordination compounds of the

Full text of DOI:10.1055/s-2007-990826

3736
PAPER
The Wittig Reaction as a Key Step in the Preparation of Triangular Ligands
for the Self-Assembly of Molecular M4L4 Tetrahedra
Preparation of
T
riangu
a
lar
L
igands
r
for Self
k
a
b
c
Institut für Organische Chemie, RWTH-Aachen, Landoltweg 1, 52074 Aachen, Germany
Institut für Physikalische Chemie, Universität Karlsruhe, Fritz-Haber-Weg, 76128 Karlsruhe, Germany
Institut für Chemie und Biochemie – Organische Chemie, FU Berlin, Takustraße 3, 14195 Berlin, Germany
E-mail: markus.albrecht@oc.rwth-aachen.de; fax +49(241)8092385
Received 14 August 2007; revised 17 August 2007
OH
HN
Abstract: Triangular ligands based on a central C3-symmetric
backbone, ethylene linkages, and catechol ligand units, are prepared
by a Wittig approach. The ligands form, in metal-directed self-
assembly processes, tetrahedral coordination compounds of the
composition M4L4.
OH
O
N
H
N
N
Key words: Wittig reaction, catechol, ligands, self-assembly, tetra-
hedra
N
N
N
BH
N
OH
O
N
O
HO
NH
N
HO
Metallosupramolecular chemistry provides an opportuni-
ty to prepare huge heteronuclear coordination compounds
with different structural features in self-assembly process-
es. Although the self-assembly step is simple, the prepara-
tion of the necessary organic ligands is often challenging.1
A
B
N
HO
OH
HO
HO
N
For example, triangular ligand systems with pyridines as
metal-binding units at the corners are able to form con-
tainer molecules as demonstrated by the work of Fujita2
and Stang.1a
HO
O
OtBu
N
t
O
CO2 Bu
N
O
Figure 1 presents some ligands with chelating binding
sites, which form tetrahedral M4L4 complexes in self-as-
sembly processes. The coordination compounds of
ligands A–C are small, providing virtually no internal
space for guest uptake.3,4 Ligand D, which is obtained in
a simple imine condensation, was introduced by our group
and forms an M4L4 complex with titanium(IV) ions which
possesses a huge cavity and is able to encapsulate organic
guest species.5
O
D
OtBu
tBuO2C
tBuO2C
tBuO
N
O
C
OH
O
OH
Figure 1 Selected ligands that form M4L4 molecular tetrahedra
Unfortunately, ligand D and its titanium(IV) complex
show some disadvantages compared to ligands A–C. The
most important one is the lability of the connecting imine
units in the presence of water. However, in order to use
such containers for transport processes, phase-transfer ca-
talysis, or to promote chemical reactions, as it was recent-
ly demonstrated by Fujita6 or Raymond,7 the compounds
should be water-stable.
paper, we present the synthesis of the ligands and show
that they form tetranuclear [Ti4L4]8– tetrahedra.
For the preparation of the ligands by a Wittig approach,
two different strategies can be envisaged: (1) A central tri-
angular trisphosphonium salt is transformed into a tris-
ylide, which then reacts with three equivalents of 2,3-
dimethoxybenzaldehyde. (2) In an alternative protocol, a
trialdehyde reacts with three equivalents of 2,3-dimeth-
oxybenzylidene triphenylphosphonium ylide. It will be
shown that both reaction sequences are feasible.
Thus, we have undertaken a study to substitute the imine
linkage in ligands like D by ethylene units. The new spac-
ers are introduced in a Wittig-type approach followed by
hydrogenation of the resulting C=C double bonds. In this
[Benzene-1,3,5-triyltris(methylene)]tris(triphenylphos-
phonium) tribromide (1) is easily prepared in a three-step
procedure in 26% yield starting from benzene-1,3,5-tri-
carboxylic acid trimethyl ester.8 In situ, it is converted
into the tris-ylide by deprotonation with potassium tert-
butoxide in THF and immediately is trapped by the addi-
SYNTHESIS 2007, No. 23, pp 3736–3740
x
x.
x
x
.
2
0
0
7
Advanced online publication: 10.10.2007
DOI: 10.1055/s-2007-990826; Art ID: Z19507SS
© Georg Thieme Verlag Stuttgart · New York

PAPER
Preparation of Triangular Ligands for Self-Assembly
3737
1) KOtBu, THF
1) KOtBu, THF
2)
O
O
2)
OMe
OMe
7
3
Ph3P
2
Br
N
PPh3
OMe
63%
Ph3P
PPh3
O
O
3
1
3 Br
32%
OMe
RO
OR
6
OR
OMe
OMe
OR
MeO
MeO
H2 (35 bar),
Pd/C, EtOAc
quant.
H2 (35 bar),
Pd/C, CH2Cl2
OR
76%
OR
N
MeO
MeO
MeO
OMe
OMe
OMe
OMe
R = Me (4)
BBr3
89%
MeO
3
R = H (5-H6)
8
Scheme 1 Preparation of the triscatechol 5-H6
OR
OR
tion of three equivalents of 2,3-dimethoxybenzaldehyde
(2). The trialkene 3 is obtained as a mixture of E/Z isomers
in 63% yield (Scheme 1).
Hydrogenation of the double bonds of 3 at 35 bar using
Pd/C in ethyl acetate affords 4 in quantitative yield, which
is deprotected to liberate the triscatechol ligand 5-H6 in
89% yield. The ligand is characterized by standard tech-
niques (1H NMR, IR, MS, elemental analysis). For exam-
N
OR
OR
OR
1
RO
ple, the H NMR spectrum in CD3OD provides the
expected signals of the central benzene ring as a singlet at
d = 6.75 (3 H), the aromatic CH protons of the catechol
units at d = 6.54 (dd, J = 1.65, 7.69 Hz, 3 H), 6.47 (t,
J = 7.69 Hz, 3 H), and 6.42 (dd, J = 1.65, 7.69 Hz, 3 H),
and the resonance of the alkyl spacer at d = 2.71 (s, 12 H).
MS (EI) shows the molar peak at m/z = 486.
R = Me (9)
R = H (10-H6)
BBr3
98%
Scheme 2 Preparation of the triscatechol 10-H6
In an alternative approach, the (2,3-dimethoxyben-
zyl)triphenylphosphonium bromide (6) is deprotonated
with potassium tert-butoxide to generate the correspond-
ing ylide. Three equivalents of this ylide react with the tri-
aldehyde 7 (prepared from triphenylamine by Vilsmaier
reaction).9 The trialkene is obtained in 32% and subse-
quently reduced by hydrogen at 35 bar using Pd/C as the
catalyst, resulting in the methylated ligand 9 in 72%.
Deprotection with BBr3 affords the triscatechol 10-H6 in
98% (Scheme 2). MS shows the corresponding molar
1
peak at m/z = 653. H NMR in CD3OD reveals the dou-
blets of the internal aromatics at d = 7.09 (d, 3J = 8.2 Hz,
6 H) and 6.89 (d, 3J = 8.2 Hz, 6 H); resonances of the cat-
echol units are observed at d = 6.62–6.54 (m, 9 H, CHarom
and the alkyl protons appear at d = 2.83 (br s, 12 H).
)
Scheme 3 Formation of tetranuclear complexes with ligands 5-H6
and 10-H6. The structure of the tetrahedron is only indicated.
The two ligands 5-H6 and 10-H6 were applied in coordina-
tion studies with titanium(IV) ions using different alkali
metal carbonates (for 5) or hydroxides (for 10) as the base.
Synthesis 2007, No. 23, 3736–3740 © Thieme Stuttgart · New York

3738
M. Albrecht et al.
PAPER
The reactions are performed in DMF or methanol and pro- tative example Figure 2, bottom shows the spectrum of
vide the tetranuclear complexes M8[(5)4Ti4] (M = Li, Na) Na8[(10)4Ti4]. Differently charged ions of the M4L4 com-
and M8[(10)4Ti4] (M = Li, Na, K) in quantitative yields plex can be detected in the negative mode. Substitution of
(Scheme 3).
the sodium cations by protons is observed.
The complexes are well soluble in DMF or methanol and In this paper, we have presented the synthesis of two new
show reasonable solubility in water. In the latter solvent triscatechol ligands in which the ligand units are connect-
they possess long-term stability. Elemental analysis indi- ed to the backbone by alkyl spacers. The geometry of the
cates the presence of huge amounts of solvent in the solid ligands is ideal for the formation of tetrahedral complex-
material (e.g., 50 molecules of water per Li8[(5)4Ti4]). es, while steric restrictions prevent the coordination of the
This is probably due to the inclusion of the solvents in the three catecholates to only one metal. The preliminary
interior of the containers as already observed in the crystal complexation studies show that the supramolecular con-
structure of the titanium complex of ligand D.5
tainers assemble easily and can be characterized by a
combination of NMR spectroscopy and mass spectrome-
try. The obtained complexes are soluble and stable in wa-
ter and therefore should be ideal candidates for host/guest
chemistry in this solvent. This investigation is now in
progress in our laboratories.
1H NMR spectroscopy provides information on the sym-
metry of the coordination compounds. The very simple
spectra show that complexes with high symmetry are
formed, indicating the tetrahedral structures (for an exam-
ple of a spectrum see Figure 2, top).
NMR spectra were recorded on a Varian Mercury 300 or Inova 400
spectrometer. FT-IR spectra were recorded on a Bruker IFS spec-
trometer. ESI FT-ICR mass spectra were measured on a Bruker Bio-
apex II FTMS equipped with a 7 Tesla magnet or a Bruker APEX
IV Fourier-transform ion cyclotron resonance (FT-ICR) mass spec-
trometer with an Apollo electrospray ion source. Elemental analy-
ses were obtained with a Heraeus CHN-O-Rapid analyzer. Melting
points: Büchi B-540 (uncorrected). The starting materials 1,8 6,12
and 79 were prepared as described before.
1,3,5-Tris(2,3-dimethoxystyryl)benzene (3)
The tris(triphenylphosphonium) tribromide 1 (0.500 g, 0.440
mmol) was dissolved in anhyd THF (20 mL). The solution was
cooled to 0 °C and first t-BuOK (0.148 g, 1.320 mmol) in THF (10
mL) and after 0.5 h, 2,3-dimethoxybenzaldehyde (2; 0.217 g, 1.320
mmol) were added. The mixture was stirred overnight and then
poured into H2O (10 mL). The trialkene was purified by extraction
with toluene (3 × 20 mL), drying (Na2SO4), and column chromatog-
raphy (SiO2; EtOAc–pentane, 1:1). Pure 3 (as a mixture of E/Z iso-
mers) was obtained after a second chromatographic purification
(SiO2; CH2Cl2–pentane, 1:1) as a yellow oil (0.157 g, 63%).
IR (CHCl3): 3527, 2939, 2834, 1584, 1471, 1271, 1224, 1172, 1076,
1007, 895, 752 cm–1.
1H NMR (300 MHz, DMSO-d6, mixture of isomers): d = 7.6–6.4
(m, 18 H, CHolefinic + CHarom), 3.9–3.5 (m, 18 H, CHalkyl).
MS (EI, 70 eV): m/z = 564.3 (M+).
Anal. Calcd for C36H36O6·4.5 H2O (645.74): C, 72.41; H, 6.68.
Found: C, 72.50; H, 6.97.
1
Figure 2 Top: H NMR spectrum of Na8[(10)4Ti4] in CD3OD at
room temperature showing the assignment of the signals to the ligand.
Bottom: ESI FT-ICR MS of Na8[(10)4Ti4] (M) sprayed from meth-
anol.
1,3,5-Tris[2-(2,3-dimethoxyphenyl)ethyl]benzene (4)
1,3,5-Tris(2,3-dimethoxystyryl)benzene 3 (157 mg, 0.78 mmol) as
well as 10% Pd/C (5 mg) were suspended in EtOAc (5 mL). The
mixture was hydrogenated in an autoclave overnight at 35 bar H2
pressure. The mixture was filtered and the solvent was removed un-
der vacuum. The crude product was purified by column chromatog-
raphy (EtOAc–pentane, 1:1) to give a viscous oil (0.159 g, quant).
Diastereotopic behavior is expected for the methylene
protons of the alkyl spacers. This is not observed at room
temperature due to fast epimerization of the metal com-
plex units. Only in water broad resonances are found for
the alkyl protons at room temperature. Cooling a solution
of Na8[(10)4Ti4] in CD3OD in the NMR spectrometer to
220 K does not lead to a splitting of the resonances but
significant broadening is observed for the alkyl signals.10
IR (CHCl3): 3492, 3400, 3007, 2936, 2836, 1591, 1476, 1271, 1222,
1172, 1081, 1010, 754, 569, 537 cm–1.
1H NMR (300 MHz, DMSO-d6): d = 6.98 (t, J = 7.9 Hz, 3 H,
CHarom), 6.87 (dd, J = 1.5, 8.4 Hz, 3 H, CHarom), 6.86 (s, 3 H,
CHarom), 6.87 (dd, J = 1.7, 7.7 Hz, 3 H, CHarom), 3.78 (s, 9 H,
CHalkyl), 3.69 (s, 9 H, CHalkyl), 2.75 (m, 12 H, CHalkyl).
The composition of the coordination compounds is shown
by ESI FT-ICR MS11 to be 4:4 complexes. As a represen-
Synthesis 2007, No. 23, 3736–3740 © Thieme Stuttgart · New York

PAPER
Preparation of Triangular Ligands for Self-Assembly
3739
+
MS (EI, 70 eV): m/z = 571.2 (MH+), 435.1 (C28H35O4 ), 419.0
(C27H31O4 ).
by the addition of MeOH (1 mL) in EtOAc (20 mL) at 0 °C. The or-
ganic phase was washed with dilute HCl (10 mL) and dried
(Na2SO4). The solvent was removed to give a dark oil (0.112 g,
98%).
+
Anal. Calcd for C36H42O6·1.5 H2O (597.74): C, 72.34; H, 7.59.
Found: C, 72.11; H, 7.23.
IR (CHCl3): 3539, 3390, 3019, 2936, 1707, 1600, 1505, 1479, 1279,
1217, 1076, 758 cm–1.
1H NMR (CD3OD, 300 MHz): d = 7.09 (d, J = 8.2 Hz, 6 H, CHarom),
6.89 (d, J = 8.2 Hz, 6 H, CHarom), 6.62–6.54 (m, 9 H, CHarom), 2.83
(br s, 12 H, CHalkyl).
1,3,5-Tris[2-(2,3-dihydroxyphenyl)ethyl]benzene (5-H6)
At 4 °C, BBr3 (2 mL) was added to 4 (0.117 g, 0.210 mol) in CH2Cl2
(30 mL). After stirring overnight, MeOH–H2O mixture (1:1, 5 mL)
was added and the product was extracted with EtOAc (3 × 20 mL).
The combined organic phases were dried (Na2SO4) and the solvent
was removed under vacuum to obtain a waxy red solid (0.089 g,
89%).
MS (EI): m/z = 653.4 (M+), 530.3 (C35H32NO4 ), 394.2
+
+
+
(C27H24NO2 ), 530.3 (C35H32NO4 ), 285.2 (C21H19N+), 246.1
(C18H15N+), 228.1 (C14H14NO2 ), 213.1 (C14H13O2 ), 194.1
+
+
IR (CHCl3): 3765, 3016, 2931, 2860, 1620, 1359, 1158, 1071, 950,
863, 830, 668, 569, 537 cm–1.
1H NMR (300 MHz, CD3OD): d = 6.75 (s, 3 H, CHarom), 6.54 (dd,
J = 1.65, 7.69 Hz, 3 H, CHarom), 6.47 (t, J = 7.69 Hz, 3 H, CHarom),
6.42 (dd, J = 1.65, 7.69 Hz, 3 H, CHarom), 2.71 (s, 12 H, CHalkyl).
(C14H12N+), 110.2 (C6H6O2 ), 91.2 (C6H5N+).
+
Anal. Calcd for C42H39NO6·5 H2O (698.80): C, 67.82; H, 6.64; N,
1.88. Found: C, 67.53; H, 6.05; N, 1.63.
Complexes of Ligand 5; General Procedure
MS (EI): m/z = 486.1 (M+), 363.1 (C23H23O4 ), 123 (C7H8O2 ).
Ligand 5-H6 (0.045 g, 0.092 mmol), TiO(acac)2 (0.024 g, 0.092
mmol) and M2CO3 (M = Li, Na, 0.092 mmol) were dissolved in
DMF (40 mL) and stirred overnight. The solvent was removed and
the residue was dried under vacuum.
+
+
Anal. Calcd for C30H30O6·4 H2O (558.62): C, 65.50; H, 6.86. Found:
C, 65.49; H, 7.11.
Tris[4-(2,3-dimethoxystyryl)phenyl]amine (8)
Li8[(5)4Ti4]
Yield: 0.075 g (quant).
The triphenylphosphonium bromide 6 (1.327 g, 2.690 mmol, 4
equiv) and t-BuOK (0.403 g, 3.590 mmol, 5.4 equiv) were dissolved
in anhyd THF (20 mL). After 1 h, compound 7 (0.222 g, 0.670
mmol, 1 equiv) was added. After stirring overnight at 50 °C, the re-
action was quenched with 3 N HCl (2 mL) followed by concd aq
NH3 (1 mL). Filtration, removal of solvent and chromatography
(EtOAc–hexane, 2:3) afforded the product as a yellow oil; mixture
of E/Z isomers (0.166 g, 32%).
IR (KBr): 3879, 3430, 2920, 2372, 2345, 1662, 1570, 1521, 1441,
1252, 1099, 1062, 1023, 971, 856, 738, 667, 489 cm–1.
1H NMR (400 MHz, CD3OD): d = 6.83 (s, 12 H, CHarom), 6.43 (dd,
J = 7.8, 1.4 Hz, 12 H, CHarom), 6.35 (dd, J = 7.7, 7.8 Hz, 12 H,
CHarom), 6.16 (dd, J = 7.7, 1.4 Hz, 12 H, CHarom), 2.86 (m, 12 H,
CHalkyl), 2.73 (m, 12 H, CHalkyl), 2.50 (m, 24 H, CHalkyl).
IR (KBr): 3989, 3931, 3869, 3617, 3566, 3483, 3420, 3369, 3274,
2931, 1590, 1504, 1472, 1424, 1318, 1270, 1220, 1069, 1004, 743
cm–1.
1H NMR (CDCl3, 400 MHz): d (major isomer) = 7.26 (m, 8 H,
CHarom), 7.06 (dd, J = 8.0, 1.5 Hz, 6 H, CHarom), 6.99 (t, J = 8.0 Hz,
6 H, CHarom), 6.78 (dd, J = 8.0, 1.5 Hz, 6 H, CHarom), 6.74 (d,
J = 15.9 Hz, 3 H, CHalken), 6.25 (dt, 3J = 15.9 Hz, 4J = 6.9 Hz, 3 H,
CHalkene), 3.86 (s, 9 H, CHalkyl), 3.80 (s, 9 H, CHalkyl).
MS (ESI–): m/z = 1065.3 [M – 6 Li + 2 H]2–, 1062.8 [M – 7 Li + 5
H]2–, 1059.3 [M – 8 Li + 6 H]2–, 529.6 [M – 7 Li + 3 H]4–, 530.1
[M – 8 Li + 4 H]4–.
Anal. Calcd for C120H96Li8O24Ti4·11 DMF·18 H2O (3297.33): C,
53.64; H, 6.15; N, 4.50. Found: C, 53.59; H, 5.90; N, 4.48.
Na8[(5)4Ti4]
Yield: 0.068 g (quant).
+
MS (EI): m/z = 731.4 (M+), 365.8 (C25H22NO2 ).
IR (KBr): 3903, 3839, 3751, 3676, 3655, 3629, 3551, 3438, 3278,
2929, 1655, 1637, 473 cm–1.
1H NMR (400 MHz, CD3OD): d = 6.79 (s, 12 H, CHarom), 6.43 (d,
J = 7.6 Hz, 12 H, CHarom), 6.36 (dd, J = 7.6, 7.5 Hz, 12 H, CHarom),
6.18 (d, J = 7.5 Hz, 12 H, CHarom), 2.96 (m, 12 H, CHalkyl), 2.74 (m,
12 H, CHalkyl), 2.44 (d, 3J = 9.1 Hz, 24 H, CHalkyl).
MS (ESI–): m/z = 1125.3 [M – 2 Na]2–, 1114.8 [M – 3 Na + H]2–,
1103.3 [M – 4 Na + 2 H]2–, 1092.8 [M – 3 Na + 3 H]2–, 742.8 [M –
3 Na]3–, 735.5 [M – 4 Na + H]3–, 728.2 [M – 5 Na + 2 H]3–, 720.5
[M – 6 Na + 3 H]3–, 545.9 [M – 5 Na + H]4–, 535.1 [M – 7 Na + 3
H]4–.
Anal. Calcd for C48H45NO6·0.5 EtOAc (775.93): C, 77.08; H, 6.62;
N, 1.32. Found: C, 77.40; H, 6.37; N, 1.81.
Tris{4-[(2,3-dimethoxyphenyl)ethyl]phenyl}amine (9)
Compound 8 (0.166 g, 0.230 mol) was hydrogenated (30 bar) in an
autoclave in CH2Cl2 (10 mL) in the presence of 10% Pd/C (5 mg).
The mixture was filtered and the solvent removed to obtain a yellow
oil (0.134 g, 76%).
IR (CHCl3): 3011, 2936, 2832, 1588, 1505, 1477, 1272, 1220, 1079,
1009, 814, 754 cm–1.
1H NMR (CD3OD, 300 MHz): d = 7.10 (d, J = 8.5 Hz, 6 H, CHarom),
6.99 (d, J = 8.5 Hz, 6 H, CHarom), 7.03–6.97 (m, 3 H, CHarom), 7.85–
6.77 (m, 6 H, CHarom), 3.89 (s, 9 H, CHalkyl), 3.83 (s, 9 H, CHalkyl),
2.98–6.84 (m, 12 H, CHalkyl).
Anal. Calcd for C120H96Na8O24Ti4·7 DMF·16 H2O (2968.93): C,
57.04; H, 6.01; N, 3.30. Found: C 56.89; H, 6.15; N, 3.38.
Complexes of Ligand 10; General Procedure
+
MS (EI): m/z = 737.3 (M+), 586.2 (C39H40NO4 ), 573.2
Ligand 10-H6 (0.030 g, 0.046 mmol), TiO(acac)2 (0.012 g, 0.046
mmol) and MOH (M = Li, Na, K, 0.093 mmol) were dissolved in
MeOH (40 mL) and stirred overnight. The solvent was removed and
the residue was dried under vacuum.
+
+
+
(C38H39NO4 ), 436.2 (C30H31NO2 ), 422.1 (C29H28NO2 ), 271.1
(C20H17N+).
Anal. Calcd for C48H51NO6·1.5 H2O (764.95): C, 75.37; H, 7.12; N,
1.83. Found: C, 75.43; H, 7.35; N, 2.15.
Li8[(10)4Ti4]
Yield: 0.043 g (quant).
Tris{4-[(2,3-dihydroxyphenyl)ethyl]phenyl}amine (10-H6)
BBr3 (0.3 mL) was added to the amine 9 (0.124 g, 0.170 mol) in
CH2Cl2 (15 mL). After stirring overnight, the mixture was quenched
IR (KBr): 3438, 2923, 1601, 1509, 1450, 1256, 1061, 1026, 847,
738, 622, 487 cm–1.
Synthesis 2007, No. 23, 3736–3740 © Thieme Stuttgart · New York

3740
M. Albrecht et al.
PAPER
1H NMR (300 MHz, CD3OD): d = 7.04 (d, J = 8.2 Hz, 24 H,
CHarom), 6.78 (d, J = 8.2 Hz, 24 H, CHarom), 6.37 (d, J = 7.7 Hz, 12
H, CHarom), 6.31 (dd, J = 7.7, 7.4 Hz, 12 H, CHarom), 6.16 (d, J = 7.4
Hz, 12 H, CHarom), 2.65 (br s, 48 H, CHalkyl).
Acknowledgment
This work was supported by the Deutsche Forschungsgemeinschaft
(SPP 1118) and the Fonds der Chemischen Industrie.
MS (ESI–): m/z = 1018.5 [M – 8 Li + 4 K + Na + 3 CH3OH]3–, 997.2
[M – 8 Li + 4 K + Na + CH3OH]3–, 991.8 [M – 8 Li + 5 K]3–, 970.5
[M – 8 Li + K + 4 Na]3–, 965.2 [M – 8 Li + 5 Na]3–, 943.9 [M – 4 Li
+ Na]3–, 942.5 [M – 5 Li + Na + H]3–, 938.6 [M – 3 Li]3–, 782.6 [M
– 8 Li + 4 K + 4 CH3OH]4–, 770.7 [M – 8 Li + 3 K + Na + 5
CH3OH]4–, 766.2 [M – 8 Li + 4 K + 4 CH3OH]4–, 762.7 [M – 8 Li +
3 K + Na + 4 CH3OH]4–, 762.5 [M – 7 Li + 3 Na + 6 CH3OH]4–,
759.4 [M – 8 Li + 2 K + 2 Na + 2 CH3OH]4–, 751.0 [M – 8 Li + 2 K
+ 2 Na + 3 CH3OH]4–, 750.2 [M – 8 Li + 4 K + 2 CH3OH]4–, 746.1
[M – 8 Li + 3 Na + K + 3 CH3OH]4–, 742.2 [M – 8 Li + 4 K +
CH3OH]4–, 726.2 [M – 8 Li + 2 K + 2 Na]4–, 724.9 [M – 5 Li + H +
3 CH3OH]4–, 722.2 [M – 8 Li + K + 3 Na]4–, 720.7 [M – 8 Li + 3 Na
+ H + CH3OH]4–, 719.2 [M – 8 Li + 4 H + 5 H2O]4–, 718.2 [M – 8
Li + 4 Na]4–, 706.4 [M – 5 Li + Na]4–, 704.7 [M – 6 Li + Na + H]4–,
702.2 [M – 4 Li]4–, 700.7 [M – 5 Li + H]4–, 699.2 [M – 6 Li + 2 H]4–.
References
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Soc., Dalton Trans. 1998, 1707. (b) Swiegers, G. F.;
Malefetse, T. J. Chem. Rev. 2000, 100, 3483. (c) Constable,
E. C. Tetrahedron 1992, 48, 10013. (d) Albrecht, M.;
Fröhlich, R. Bull. Chem. Soc. Jpn. 2007, 80, 797.
(2) Fujita, M. Chem. Soc. Rev. 1998, 27, 417.
(3) (a) Amoroso, A. J.; Jefferey, J. C.; Jones, P. L.; McCleverty,
J. A.; Thornton, P.; Ward, M. D. Angew. Chem., Int. Ed.
Engl. 1995, 34, 1443; Angew. Chem. 1995, 107, 1577.
(b) Paul, R. L.; Amoroso, A. J.; Jones, P. L.; Couchman, S.
M.; Reeves, Z. R.; Rees, L. H.; Jefferey, J. C.; McCleverty,
J. A.; Ward, M. D. Dalton Trans. 1999, 1563. (c)Brückner,
C.; Powers, R. E.; Raymond, K. N. Angew. Chem. Int. Ed.
1998, 37, 1837; Angew. Chem. 1998, 110, 1937.
(d) Caulder, D.; Brückner, C.; Powers, R. E.; König, S.;
Parac, T. N.; Leary, J. A.; Raymond, K. N. J. Am. Chem. Soc.
2001, 123, 8923. (e) Saalfrank, R. W.; Glaser, H.;
Demleitner, B.; Hampel, F.; Chowdhry, M. M.;
Schünemann, V.; Trautwein, A. X.; Vaughan, G. B. M.;
Yeh, R.; Davis, A. V.; Raymond, K. N. Chem. Eur. J. 2001,
8, 493.
Anal. Calcd for C168H132Li8N4O24Ti4·50 H2O (3738.62): C, 53.97;
H, 6.25; N, 1.50. Found: C, 53.65; H, 5.92; N, 1.39.
Na8[(10)4Ti4]
Yield: 0.040 g (quant).
IR (KBr): 3407, 2923, 1661, 1506, 1450, 1387, 1320, 1257, 1103,
1060, 1027, 968, 843, 738, 625, 484 cm–1.
1H NMR (300 MHz, CD3OD): d = 7.15 (d, J = 7.2 Hz, 24 H,
CHarom), 6.88 (d, J = 7.2 Hz, 24 H, CHarom), 6.42 (m, 24 H, CHarom),
6.25 (d, 3J = 6.2 Hz, 12 H, CHarom), 2.75 (s, 48 H, CHalkyl).
MS (ESI–): m/z = 965.2 [M – 3 Na]3–, 718.4 [M – 4 Na]4–, 712.9
[M – 5 Na + H]4–, 707.7 [M – 6 Na + 2 H]4–, 702.2 [M – 7 Na +
3 H]4–, 696.2 [M – 8 Na + 4 H]4–.
(4) For big M4L4 tetrahedra see: Yeh, R. M.; Xu, J.; Seeber, G.;
Raymond, K. N. Inorg. Chem. 2005, 44, 6228.
(5) (a) Albrecht, M.; Janser, I.; Meyer, S.; Weis, P.; Fröhlich, R.
Chem. Commun. 2003, 2854. (b) Albrecht, M.; Janser, I.;
Fröhlich, R. Synthesis 2004, 1977. (c) Albrecht, M.; Janser,
I.; Burk, S.; Weis, P. Dalton Trans. 2006, 2727.
(6) Fujita, M.; Tominaga, M.; Hori, A.; Therrien, B. Acc. Chem.
Res. 2005, 38, 369.
Anal. Calcd for C168H132N4Na8O24Ti4·30 H2O (3506.70): C, 57.54;
H, 5.52; N, 1.60. Found: C, 57.33; H, 5.36; N, 1.94.
(7) Fiedler, D.; Leung, D. H.; Bergman, R. G.; Raymond, K. N.
Acc. Chem. Res. 2005, 38, 349.
K8[(10)4Ti4]
(8) (a) Stork, W.; Manecke, G. Macromol. Chem. 1975, 176,
97. (b) Formigni, M.; Johannsen, I.; Boubekeur, K.; Nelsen,
C.; Batail, P. J. Am. Chem. Soc. 1993, 115, 3752.
(9) Mongin, O. Synthesis 2005, 1771.
Yield: 0.043 g (quant).
IR (KBr): 3756, 3436, 2927, 2345, 1616, 1506, 1448, 1255, 1059,
1029, 841, 732, 626, 573, 474 cm–1.
1H NMR (300 MHz, CD3OD): d = 7.15 (d, J = 8.2 Hz, 24 H,
CHarom), 6.88 (d, J = 8.2 Hz, 24 H, CHarom), 6.47 (d, J = 7.4 Hz, 12
H, CHarom), 6.43 (dd, J = 7.4, 7.7 Hz, 12 H, CHarom), 6.26 (d, J = 7.7
Hz, 12 H, CHarom), 2.74 (br s, 48 H, CHalkyl).
MS (ESI–): m/z = 760.7 [M – 6 K + Na + H + 5 CH3OH]4–, 750.7
[M – 8 K + 4 Na + 4 CH3OH]4–, 741.2 [M – 6 K + Li + H + 3
CH3OH]4–, 740.7 [M – 5 K + H + 2 CH3OH]4–, 736.9 [M – 6 K + Na
+ H + 2 CH3OH]4–, 731.7 [M – 6 K + 2 H + 2 CH3OH]4–, 721.2 [M
– 8 K + 3 Na + H + CH3OH]4–, 711.4 [M – 8 K + Na + Li + 2 H +
CH3OH]4–, 702.2 [M – 8 K + 4 Li]4–.
(10) See for comparison: Albrecht, M.; Schneider, M.; Röttele,
H. Chem. Ber. 1997, 130, 615.
(11) For MS techniques in supramolecular chemistry, see:
(a) Schalley, C. A. Int. J. Mass Spectrom. 2000, 194, 11.
(b) Schalley, C. A. Mass Spectrom. Rev. 2001, 20, 253.
(c) Baytekin, B.; Baytekin, H. T.; Schalley, C. A. Org.
Biomol. Chem. 2006, 4, 2825.
(12) Albrecht, M.; Witt, K.; Blau, O. J. Prakt. Chem. 1998, 340,
562.
Anal. Calcd for C168H132K8N4O24Ti4·35 H2O·35 CH3OH (3757.69):
C, 53.09; H, 5.92; N, 1.41. Found: C, 53.17; H, 5.90; N, 1.99.
Synthesis 2007, No. 23, 3736–3740 © Thieme Stuttgart · New York