Convenient, zirconocene-coupling routes to germole- and thiophene-containing macrocycles with triangular geometries

Article abstract of DOI:10.1016/S0022-328X(02)02028-4

Reactions of zirconacyclopentadiene-coupled macrocycles with S₂Cl₂ or GeCl₄ gave new macrocycles containing thiophene and dichlorogermole groups, respectively. The germoles, synthesized in high yields, possess labile chloride substituents that are readily displaced via nucleophilic substitution reactions. These germole-containing macrocycles are potentially useful as supramolecular building blocks. A macrocyclic trithiophene compound, with 1,4-phenylene groups that bridge the thiophene rings, was characterized by X-ray crystallography. The X-ray structure of a related trigermole macrocycle, with bridging biphenylene groups, is also presented.

Full text of DOI:10.1016/S0022-328X(02)02028-4

Journal of Organometallic Chemistry 666 (2003) 15ꢀ22
/
www.elsevier.com/locate/jorganchem
Convenient, zirconocene-coupling routes to germole- and thiophene-
containing macrocycles with triangular geometries
Jonathan R. Nitschke, T. Don Tilley *
Department of Chemistry, Center for New Directions in Organic Synthesis, University of California, Berkeley, Berkeley, CA 94720-1460, USA
Received 28 June 2002
Dedicated to Professor Jerry Atwood on the occasion of his 60th birthday
Abstract
Reactions of zirconacyclopentadiene-coupled macrocycles with S2Cl2 or GeCl4 gave new macrocycles containing thiophene and
dichlorogermole groups, respectively. The germoles, synthesized in high yields, possess labile chloride substituents that are readily
displaced via nucleophilic substitution reactions. These germole-containing macrocycles are potentially useful as supramolecular
building blocks. A macrocyclic trithiophene compound, with 1,4-phenylene groups that bridge the thiophene rings, was
characterized by X-ray crystallography. The X-ray structure of a related trigermole macrocycle, with bridging biphenylene groups,
is also presented.
# 2002 Elsevier Science B.V. All rights reserved.
Keywords: Germole; Macrocyclization; Tecton; Thiophene; Zirconocene
1. Introduction
relies on the reversible formation of a zirconacyclopen-
tadiene ring from a zirconocene fragment and two
alkyne groups. This reaction therefore allows the self-
assembly of complex structures via reactions of a labile
Macrocycles are important synthons and building
blocks in supramolecular chemistry [1]. Macrocyclic
compounds that incorporate a number of donor atoms
serve as highly selective hosts and receptors [2]. Re-
cently, macrocycles that feature ‘exterior’ functional
groups have been shown to serve as building blocks
(or tectons) for discrete supramolecular assemblies [3]
and designed crystal lattices [4].
CÃ/C bond.
Many of the macrocycles synthesized via zirconocene
coupling are rigid and highly symmetrical. The number
of monomeric diyne units incorporated into each
macrocycle is a function of the geometry and flexibility
of the diyne unit [6ꢀ8], and the reaction allows the
/
incorporation of functional groups of proven use in
supramolecular chemistry, such as perfluorophenylene
[7] and bipyridyl [9]. Treatment of the zirconocene-
containing macrocycles with acid allows the high-yield-
ing syntheses of air-stable cyclophanes that contain
bis(trimethylsilyl)butadiene groups.
Here we report the incorporation of germole and
thiophene functionalities into the ‘corners’ of triangular
macrocycles obtained by zirconocene coupling. The
germole-producing reactions, in particular, are remark-
able for the high yields observed and the ease of
subsequent nucleophilic displacement of the chlorine
The synthesis of macrocyclic tectons for supramole-
cular chemistry is often a challenging problem. The
cyclization reactions employed are often low yielding,
requiring high-dilution conditions and lengthy separa-
tions to remove oligomeric co-products. We have
recently developed a zirconocene-coupling macrocycle
synthesis as an alternative to traditional macrocycliza-
tion reactions [5ꢀ9]. This high-yielding macrocyclization
/
* Corresponding author. Fax: ꢁ
/
1-510-6428940
E-mail address: tdtilley@socrates.berkeley.edu (T. Don Tilley).
0022-328X/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved.
PII: S 0 0 2 2 - 3 2 8 X ( 0 2 ) 0 2 0 2 8 - 4

16
J.R. Nitschke, T. Don Tilley / Journal of Organometallic Chemistry 666 (2003) 15ꢀ22
/
atoms bound to germanium. The symmetrical arrange-
ment of these groups around the periphery of these rigid
macrocycles is expected to allow their use as tectons for
supramolecular networks and discrete assemblies.
2. Results and discussion
The presence of a trimethylsilyl substituent a to
zirconium on a zirconacyclopentadiene ring presents a
formidable steric barrier to substitution at zirconium.
This results in limitations to the functionalization of
macrocycles via reactions at zirconacyclopentadiene
rings, especially since the SiMe3 substituent appears to
be necessary for the formation of macrocycles via
zirconocene coupling [6]. Thus, reported methods of
carrying out electrophilic substitutions on zirconacyclo-
pentadienes [10,11] have generally not worked with
macrocyclic substrates. However, reactions of zircono-
cene-containing macrocycles with S2Cl2 and GeCl4 have
yielded new cyclic products, as detailed below.
Fig. 1. ORTEP diagram (50% probability ellipsoids) of 2; atoms of the
asymmetric unit are labeled.
phenylene rings. This molecule might therefore host a
number of different guest ions, coordinated by the p
clouds of the phenylenes, in a fashion similar to that of
the 2.2.2-paracyclophane complexes of Schmidbaur [12].
2.1. Synthesis of trithiophene 2
The reaction of sulfur monochloride with zirconacycle
1 gave a complex mixture of products, from which
trithiophene 2 was isolated in 10% overall yield after two
recrystallizations (Eq. (1)). Examination of the 1H-
NMR spectrum of the crude reaction mixture suggested
that 2 comprised ca. 20% of the overall soluble product.
2.2. Syntheses of hexachlorotrigermoles 5, 6, and 7
Reactions of germanium tetrachloride with the tri-
meric macrocycles 1, 3, and 4 provided high yields of
ð1Þ
The X-ray crystal structure of 2 was solved from a
crystal obtained by vapor diffusion of Et2O into a
toluene solution of the macrocycle. An ORTEP diagram
of this structure is shown in Fig. 1, and crystallographic
details are given in Table 1. Much of the molecular
symmetry of 2 is reflected in this crystal structure; the
space group P63/m places the macrocycle on a special
position of C3h point symmetry that lacks only the
vertical mirror planes of the molecule’s D3h point group.
The central cavity of 2 could accommodate a sphere
trigermoles 5, 6, and 7, as shown in Scheme 1. The high
yields observed in this substitution reaction suggest that
the three sequential germanium-for-zirconium substitu-
tion steps occur in near-quantitative yield. Under
identical conditions silicon tetrachloride reacted with 2
to give multiple unidentified products, and tin tetra-
chloride reacted with 2 to induce a decyclization
reaction, with formation of 4,4?-bis(trimethylsilylalky-
nyl)biphenyl.
Although zirconacyclopentadiene to germole substi-
tution reactions are known [11,13], this transformation
˚
of radius 1.06 A in van der Waals contact with the three

J.R. Nitschke, T. Don Tilley / Journal of Organometallic Chemistry 666 (2003) 15ꢀ
/22
17
Table 1
Crystallographic data and refinement details for 2 and 6
Compound 2
Compound 6
Empirical formula
Crystal color, habit
Temperature (8C)
Reflections used for
unit cell determination
(2u range)
C48H66Si6S3
Colorless, Prism
C195H228Cl12Ge6Si12
ꢂ102
ꢂ105
5351 (0ꢀ/458)
4674 (0ꢀ458)
/
Space group
˚
P63/m (#176)
17.2222(2)
17.2222(2)
10.5342(1)
90
P21 (#4)
a (A)
˚
18.8975(3)
20.7900(3)
24.3797(7)
90
b (A)
˚
c (A)
a (8)
b (8)
g (8)
V (A )
Z value
90
120
90.229(2)
90
3
˚
2705.88(5)
2
2.99
9578.2(3)
2
12.21
m(Moꢀ
/
Ka) (cmꢂ1
)
Fig. 2. ORTEP diagram (50% probability ellipsoids) of one of the two
independent molecules of 6 present in the asymmetric unit; heteroa-
toms are labeled.
Diffractometer
Radiation
Monochromator
Siemens SMART
Siemens SMART
Moꢀ/Ka
MoꢀKa
/
Graphite
Graphite
60 mm
Crystal to detector dis- 60 mm
tance (mm)
Scan type (8)
Frame collection time 30
(s)
v, 0.3
v, 0.3
30
has rarely been reported for cases involving a-trimethyl-
silyl substituents on the metallacyclic ring [14]. Further-
more, to our knowledge none of these substitutions have
involved zirconacyclopentadienyl rings in which any-
thing bulker than a methyl group occupies the b-
position. The rigid geometry imposed by the macro-
cyclic framework may thus be an important factor in the
success of this reaction.
Macrocycle 5 is less soluble than its precursor 1 [6],
rendering characterization by NMR spectroscopy in-
feasible. Its hexabutyl derivative (vide infra), however, is
readily soluble in hydrocarbon solvents. Macrocycle 6
has similar solubility properties to the Cp2ZrCl2 by-
product, necessitating removal of the latter by sublima-
Crystal dimensions
(mm)
0.15ꢃ0.18ꢃ0.08
0.05ꢃ0.08ꢃ0.15
2u Range (8)
Reflections measured
2ꢀ52.3
/
2ꢀ52.2
/
12 842
1794
46 536
31 320
13 120
Unique reflections
Observations (I ꢀ3s) 1066
Refinement
Full-matrix least-
Full-matrix least-
squares on F2
977
squares on F2
103
10.35
Variables
Reflection/parameter
ratio
13.43
Residuals: Rint; R; Rw 0.059; 0.068; 0.069
Hydrogen atom treat- Idealized positions
ment
0.058; 0.069; 0.073
Idealized positions
Goodness-of-fit indica- 1.90
tor
1.82
tion. The syntheses of trigermoles 5ꢀ7 may be carried
out in the same reaction flask used for the macrocycliza-
tion, which improves the overall isolated yields.
/
Largest difference peak 0.47 and ꢂ0.47
1.04 and ꢂ0.56
ꢂ3
and hole (eꢂ
A
˚
Scheme 1. Syntheses of trigermole macrocycles from the corresponding zirconacycles.

18
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/
To verify the identity of trigermole 6, its X-ray crystal
The reaction of 6 with a slight excess (6.6 equivalents)
of hexamethyldisilathiane in toluene gave the macro-
cyclic hexakis(trimethylsilylsulfido)trigermole 9 in 87%
yield (Eq. 3). The trimethylsilylsulfido groups desilylate
very readily in the presence of protic media, as evidenced
by the FAB mass spectrum of 9 in a matrix of 3-
nitrobenzyl alcohol. No peak higher in mass than
completely proteodesilylated 9 was present.
structure was determined. An ORTEP diagram is shown
in Fig. 2, and crystallographic details are given in Table
1. Unlike 2, none of the molecular symmetry of 6 was
reflected in this structure; in fact, two symmetry-
independent chemically identical macrocycles constitute
the asymmetric unit. However, the NMR spectra reflect
D3h molecular symmetry.
ð3Þ
2.3. Reactions of hexachlorotrigermoles with nucleophiles
Initial attempts to synthesize hexacyano trigermole 10
mimicked the synthesis of 9, using Me3SiCN in place of
(Me3Si)2S. However, these toluene reaction solutions
darkened in color and became viscous above 60 8C,
suggesting that 10 may have limited thermal stability.
Acetonitrile was then used as the reaction solvent, based
on the idea that a more polar solvent might facilitate the
desired nucleophilic displacement reaction at lower
temperatures. Complex mixtures of products were
obtained from this solvent, possibly resulting from the
extremely low solubility of 6 in acetonitrile. The reaction
of 6 with Me3SiCN in pyridine finally yielded the desired
product 10 in 75% isolated yield (Eq. 4).
The presence of six symmetry-equivalent, readily
displaced [15] chlorine atoms of 5, 6, and 7 suggested
that derivatives of these molecules might be linked
together into coordination networks. In order to in-
vestigate this possibility, and to explore the substitution
chemistry of these germoles, reactions with nucleophilic
reagents were investigated.
The reaction of 5 with excess n-BuLi (nine equiva-
lents) gave hexabutyl trigermole 8 in 61% yield (Eq. 2).
In contrast to 5, macrocycle 8 is highly soluble in
hydrocarbon solvents, allowing its characterization by
NMR spectroscopy.
ð2Þ

J.R. Nitschke, T. Don Tilley / Journal of Organometallic Chemistry 666 (2003) 15ꢀ
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19
ð4Þ
The slow removal of volatile material over 12 h as the
reaction mixture refluxed at 40 8C was crucial to the
success of this reaction. Rapid evaporation of the
reaction mixture to dryness gave a mixture of products,
as evidenced by broad features in the proton NMR
spectrum. The substantial difference in the boiling
points of Me3SiCl (57 8C) and Me3SiCN (118 8C)
appears to lead to the preferential evacuation of
Me3SiCl from the reaction mixture, forcing the reaction
solution in hexanes. Zirconium-containing macrocycles
1 [6], 3 [5d], and 4 [6] were synthesized as previously
described.
All NMR spectra were recorded at room temperature.
Chemical shifts are referenced to the residual proton or
carbon resonance of the deuterated solvent. In some
cases, DEPT [16] was used to assign carbon resonances.
Mass spectra and combustion analyses were provided by
the Micro-Mass Facility of the University of California,
Berkeley.
of Eq. 4 to completion. The GeÃ
/
CN bonds are quite
moisture sensitive, as the molecule evolves HCN gas in
contact with moist air.
4.2. Trithiophene 2
Macrocycle 1 (1.00 g, 0.678 mmol) was loaded into a
100 ml Teflon-stoppered Schlenk flask in a glovebox.
On a Schlenk line, dry THF (75 ml) was added. This
mixture was stirred rapidly for 1 h, giving a finely
3. Conclusions
In conclusion, electrophilic substitution at zirconium
has been employed to synthesize thiophene and germole-
containing macrocycles, the latter in high yields. Nu-
cleophilic substitution of the chloride ligands bonded to
germanium provides a means to introduce exocyclic
binding sites into these macrocycles, making them
potential tectons for supramolecular self-assembly. The
use of these molecules as ‘preformed macropores’ to
construct supramolecular assemblies and networks is a
focus of current investigations.
divided suspension. This suspension was chilled to ꢂ
/
5 8C in an ice/brine bath, and S2Cl2 (2 ml of 1 M CH2Cl2
solution, 2 mmol) was added dropwise via syringe with
rapid stirring. The precipitate slowly dissolved over 30
min, as the color of the reaction mixture deepened from
yellow to orange. The cold bath was then removed, and
stirring was continued for 30 min. The volatile material
was then removed under dynamic vacuum (30 mmHg
over 12 h) and the solid residue was suspended in C5H12
(100 ml). The C5H12 suspension was sonicated for 10
min and then filtered through a plug of celite (10 ml),
and the volatile components of the filtrate were removed
under dynamic vacuum. The product was recrystallized
4. Experimental
4.1. General
twice from C6H5CH3ꢀC5H12. The yield of white crystals
/
was 0.061 g, 10%. 1H-NMR (500 MHz, C6H6-d6) d 0.26
(s, 18H, Si(CH3)3), 7.02 (s, 4H, phenylene). 13C{1H}-
NMR (125 MHz, C6H6-d6) d 1.1 (Si(CH3)3), 130.2
(phenylene), 138.0, 140.9, 153.4. EI MS m/z 906 [Mꢁ],
All reactions involving air-sensitive compounds were
carried out under nitrogen or argon using standard
Schlenk techniques and dry, oxygen-free solvents. Pen-
tane, Et2O, C6H6, and tetrahydrofuran were distilled
under nitrogen from sodium benzophenone ketyl. Tol-
uene, C6H5CH3-d8, and C6H6-d6 were distilled under
nitrogen from Na/K. Methylene chloride-d2 was distilled
under vacuum from CaH2. n-BuLi was used as a 1.6 M
891 [Mꢁꢂ
CH3]. Anal. Calc. for C48H66S3Si6: C, 63.51;
/
H, 7.33. Found: C, 63.60; H, 7.22%. X-ray quality
crystals of 2 were obtained through vapor diffusion of
Et2O into a C6H5CH3 solution. Details of the crystal
structure are given in Table 1.

20
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/
4.3. Trigermole 5
through vapor diffusion of hexamethyldisiloxane into a
toluene solution. Details are given in Table 1.
Macrocycle 1 (1.00 g, 0.678 mmol) was loaded into a
100 ml Teflon-stoppered Schlenk flask in a glovebox.
On a Schlenk line, dry THF (75 ml) was added. This
mixture was stirred rapidly for 1 h, giving a finely
divided suspension. Germanium tetrachloride (0.116 ml,
1.02 mmol) was added at room temperature (r.t.)
dropwise via syringe with rapid stirring. The reaction
mixture bleached to an ivory color over 12 h at r.t. The
finely divided product was allowed to stand for 12 h,
and then the supernatant was removed by cannula
filtration. The product was washed with dry THF
4.5. Trigermole 7
Macrocycle 4 (2.54 g, 3.84 mmol) was loaded into a
100 ml Teflon-stoppered Schlenk flask in a glovebox.
On a Schlenk line, dry THF (75 ml) was added. This
mixture was stirred rapidly for 1 h, giving a finely
divided suspension. Germanium tetrachloride (0.656 ml,
5.76 mmol) was added at r.t. dropwise via syringe with
rapid stirring. The reaction mixture bleached to an ivory
color over 6 h at r.t., as much of the solid dissolved. The
volatile material was removed under dynamic vacuum,
and the ivory-colored residue was washed with dry
(2ꢃ100 ml) and dried under dynamic vacuum. The
/
yield of off-white powder was 0.862 g; 93% as a THF
solvate. Extremely poor solubility precluded NMR
1
characterization. THF was noted in the H spectrum
C6H5CH3 (2ꢃ100 ml) and dried under dynamic va-
/
cuum. The yield of white microcrystals was 2.10 g; 89%
1
as a bis(THF) solvate. H NMR (500 MHz, C6H6-d6) d
of a suspension of the dried product, however, EI-MS
m/z 1242 ([Mꢁ], this peak matches an isotopic simula-
0.20 (s, 18H, Si(CH3)3), 6.93 (d, Jꢄ
phenylene), 7.20 (d, Jꢄ8.5 Hz, 4H, phenylene), 7.27
(s, 4H, central phenylene). FAB-MS m/z 1698 [Mꢁ],
1555 [Mꢁꢂ
2
/
8.5 Hz, 4H,
tion well), 1227 [Mꢁꢂ
/CH3]. Anal. Calc. for
/
C48H66Cl6Ge3Si6×
/C4H8O: C, 47.52; H, 5.68. Found: C,
47.63; H, 5.64%.
/
GeCl2]. Anal. Calc. for C84H90Cl6Ge3Si6×
/
C4H8O: C, 59.96; H, 5.80. Found: C, 60.14; H, 5.53%.
4.4. Trigermole 6
4.6. Tetrabutyl trigermole 8
Macrocycle 3 (0.568 g, 0.333 mmol) was loaded into a
100 ml Teflon-stoppered Schlenk flask in a glovebox.
On a Schlenk line, dry THF (50 ml) was added. This
mixture was stirred for 5 min, giving an orange solution.
Germanium tetrachloride (0.116 ml, 1.02 mmol) was
added at r.t. dropwise via syringe with rapid stirring.
The reaction solution became colorless over 20 min at
r.t. After stirring for 1 h, the volatile material was
removed under dynamic vacuum. Dry C6H6 (50 ml) was
added to the reaction flask, and the resulting solution
was then sonicated until a finely divided suspension was
obtained (20 min). The product suspension was then
transferred via cannula to a N2-purged sublimator, and
the reaction flask was rinsed with an additional portion
of dry C6H6 (25 ml), which was also transferred to the
sublimator. The product suspension was flash-frozen
with liquid N2, and the benzene was lyophylized under
dynamic vacuum (6 h). The byproduct Cp2ZrCl2 was
then sublimed away from the desired product (12 h,
75 8C) under dynamic vacuum. The product was washed
with dry Et2O (25 ml) and dried under dynamic vacuum.
The yield of white microcrystalline powder was 0.450 g,
92%. 1H-NMR (500 MHz, C6H6-d6) d 0.10 (s, 18H,
Macrocycle 5 (0.371 g, 0.894 mmol) was loaded into a
100 ml Teflon-stoppered Schlenk flask in a glovebox.
On a Schlenk line, dry Et2O (70 ml) was added. This
mixture was stirred rapidly for 1 h, giving a finely
divided suspension. Using a syringe, n-BuLi in hexanes
(1.1 ml, 2.7 mmol) was added at r.t. dropwise with rapid
stirring. The solid present in the reaction mixture
dissolved over 5 min, giving a reddish solution. This
solution was filtered through a plug of silica (10 ml)
under aerobic conditions. The volatile material was
removed under dynamic vacuum, and the product was
recrystallized from C5H12 (50 ml) at ꢂ80 8C. The yield
/
1
of white microcrystals was 0.250 g, 61%. H-NMR (500
MHz, C6H6-d6) d 0.14 (s, 18H, Si(CH3)3), 0.98 (t, Jꢄ
7.5 Hz, 3H, GeCH2CH2CH2CH3), 1.32 (t, Jꢄ7.5 Hz,
2H, GeCH2CH2CH2CH3), 1.42 (m, Jꢄ7.5 Hz, 2H,
/
/
/
GeCH2CH2CH2CH3), 1.61 (m, 2H, GeCH2CH2-
CH2CH3), 6.71 (s, 4H, phenylene). 13C{1H}-NMR
(125 MHz, C6H6-d6) d 2.0 (Si(CH3)3), 14.5 (butyl),
16.8 (butyl), 26.6 (butyl), 28.9 (butyl), 128.7 (phenylene),
141.6, 146.2, 168.6. High Resolution ES-MS m/z
1395.564 [Mꢂ
Naꢁ], calculated 1395.559; the calculated
isotope pattern was in good agreement with experiment.
/
Si(CH3)3), 6.59 (d, Jꢄ
/
8.5 Hz, 4H, phenylene), 6.88 (d,
8.5 Hz, 4H, phenylene). 13C{1H}-NMR (125 MHz,
Jꢄ
/
C6H6-d6) d 0.74 (Si(CH3)3), 126.0 (phenylene), 129.6
(phenylene), 138.0, 138.3, 139.2, 164.2. EI-MS m/z 1470
4.7. Hexakis(trimethylsilylsulfido) trigermole 9
[Mꢁ], 1326 [Mꢁꢂ
C66H78Cl6Ge3Si6: C, 53.91; H, 5.35. Found: C, 53.65;
H, 5.24%. X-ray quality crystals of 6 were obtained
/GeCl2]. Anal. Calc. for
Macrocycle 6 (0.490 g, 1 mmol) and hexamethyldisi-
lathiane (0.464 ml, 2.2 mmol) were loaded into a 100 ml
Teflon-stoppered Schlenk flask in a glovebox. On a

J.R. Nitschke, T. Don Tilley / Journal of Organometallic Chemistry 666 (2003) 15ꢀ
/22
21
Schlenk line, dry C6H5CH3 (10 ml) was added. This
mixture was heated to 85 8C with stirring, giving a
colorless solution. The reaction mixture was kept at
85 8C for 72 h, and then the volatile components were
removed under dynamic vacuum over 12 h. Dry C5H12
(100 ml) was added to the crude product, and this
suspension was sonicated for 30 min and allowed to
stand for 6 h. The supernatant was removed by cannula
filtration, and the product was dried under dynamic
vacuum. The yield of white microcrystals was 0.548 g,
87%. 1H-NMR (500 MHz, C6H6-d6) d 0.24 (s, 18H,
Acknowledgements
We thank the National Science Foundation for their
generous support of this work. The Center for New
Directions in Organic Synthesis is supported by Bristol-
Myers Squibb as Sponsoring Member. We thank
Frederick Hollander of the U.C. Berkeley College of
Chemistry X-ray Crystallographic Facility for help with
solving the crystal structures.
Si(CH3)3 a to germanium), 0.49 (s, 18H, SÃ
/
Si(CH3)3),
8.5 Hz,
6.95 (d, Jꢄ
/
8.5 Hz, 4H, phenylene), 7.11 (d, Jꢄ
/
References
4H, phenylene). 13C{1H}-NMR (125 MHz, C6H6-d6,
not all resonances observed) d 2.0 (Si(CH3)3), 4.7
(Si(CH3)3), 126.0 (phenylene), 129.7 (phenylene). FAB-
MS, 3-nitrobenzyl alcohol matrix m/z 1456 (proteode-
silylated 9ꢁ, calculated isotope pattern in good agree-
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many, 1993.
[2] F. Vogtle, Host Guest Complex Chemistry: Macrocycles: Synth-
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ment with experiment), 1423 (proteodesilylated 9ꢁꢂ
/
SH). Anal. Calc. for C84H132Ge3S6Si12: C, 53.40; H,
7.04; S, 10.18. Found: C, 53.37; H, 6.78; S, 10.02%.
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4.8. Hexacyano trigermole 10
Macrocycle 6 (0.100 g, 0.204 mmol), trimethylsilyl-
cyanide (0.544 ml, 4.08 mmol), and dry pyridine (20 ml)
were loaded into a 100 ml Teflon-stoppered Schlenk
flask in a glovebox. The clear, slightly yellow reaction
mixture was stirred for 20 min at r.t., then placed in a
40 8C oil bath such that the bottom of the reaction flask
was just touching the oil. The Teflon stopcock was
cracked open very slightly, such that reflux occurred on
the walls of the reaction flask within several minutes.
The volatile material was removed through the slightly
open stopcock over 12 h, and then the tan solid product
was washed with dry Et2O (70 ml). The yield of white
microcrystalline product was 0.072 g, 75%. 1H-NMR
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(500 MHz, C6H6-d6) d ꢂ
/
0.01 (s, 18H, Si(CH3)3), 6.50
8.5 Hz, 4H,
(d, Jꢄ
/
8.5 Hz, 4H, phenylene), 6.87 (d, Jꢄ
/
phenylene). 13C{1H}-NMR (125 MHz, C6H6-d6) d 0.8
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5. Supplementary material
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Crystallographic data for the structural analyses have
been deposited with the Cambridge Crystallographic
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compounds 2 and 6. Copies of this information may
be obtained free of charge from The Director, CCDC,
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