Porous siloxane linked phenylacetylene nitrile silver salts from solid state dimerization and low polymerization

Article abstract of DOI:10.1021/ja0009119

Three 3-fold symmetric rigid backbone phenylacetylene nitrile molecules have been prepared to which one to six hydroxy side chains have been attached. These molecules were cocrystallized with silver(I) trifluoromethanesulfonate (triflate) to form microcrystalline porous solids. X-ray powder data show that all three crystal structures are isotypic to the crystal structures found in previous single crystal studies on related systems. Structural models based on these earlier single crystal structures have theoretical powder patterns in reasonable agreement with the experimentally observed patterns. These crystalline materials were allowed to react with silyl triflates. ¹H NMR and X-ray powder studies show that the silyl triflate groups react with the alcohol terminated side chains to form siloxane linkages with retention of the initial crystal structure. In the case of 1,3,5-tris(4-((4-cyanophenyl)ethynyl)-2-((4-hydroxybutoxy)methyl) phenylethynyl)benzene, a phenylacetylene nitrile molecule with three alcohol side chains, the introduction of di-tert-butylsilyl bis(trifluoromethanesulfonate) resulted in the formation of low polymers with average weight molecular weight of 7 x 10⁴. This polymerized material shows increased chemical robustness in contrast to the unpolymerized material. It is stable in a variety of solvents, including overnight exposure to boiling water. Exchange experiments with toluene show that this final material is still porous.

Full text of DOI:10.1021/ja0009119

J. Am. Chem. Soc. 2000, 122, 6871-6883
6871
Porous Siloxane Linked Phenylacetylene Nitrile Silver Salts from
Solid State Dimerization and Low Polymerization
Y.-H. Kiang, Geoffrey B. Gardner, Stephen Lee,* and Zhengtao Xu
Contribution from the Department of Chemistry and Chemical Biology, Baker Laboratory,
Cornell UniVersity, Ithaca, New York 14853-1301
ReceiVed March 14, 2000
Abstract: Three 3-fold symmetric rigid backbone phenylacetylene nitrile molecules have been prepared to
which one to six hydroxy side chains have been attached. These molecules were cocrystallized with silver(I)
trifluoromethanesulfonate (triflate) to form microcrystalline porous solids. X-ray powder data show that all
three crystal structures are isotypic to the crystal structures found in previous single crystal studies on related
systems. Structural models based on these earlier single crystal structures have theoretical powder patterns
in reasonable agreement with the experimentally observed patterns. These crystalline materials were allowed
1
to react with silyl triflates. H NMR and X-ray powder studies show that the silyl triflate groups react with
the alcohol terminated side chains to form siloxane linkages with retention of the initial crystal structure.
In the case of 1,3,5-tris(4-((4-cyanophenyl)ethynyl)-2-((4-hydroxybutoxy)methyl)phenylethynyl)benzene, a
phenylacetylene nitrile molecule with three alcohol side chains, the introduction of di-tert-butylsilyl
bis(trifluoromethanesulfonate) resulted in the formation of low polymers with average weight molecular weight
of 7 × 104. This polymerized material shows increased chemical robustness in contrast to the unpolymerized
material. It is stable in a variety of solvents, including overnight exposure to boiling water. Exchange experiments
with toluene show that this final material is still porous.
Introduction
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10.1021/ja0009119 CCC: $19.00 © 2000 American Chemical Society
Published on Web 07/06/2000

6872 J. Am. Chem. Soc., Vol. 122, No. 29, 2000
Kiang et al.
conductivity,57-60 and other electronic properties.61-65 Despite
the scope of the advances, critical problems remain. Chief
among them is the inherent stability of the organic or organo-
metallic network. All too often the condition of crystal growth,
which in general requires reversible intermolecular bond forma-
tion during crystallization, leads to the use of rather fragile
coordination or hydrogen bonds to link the organic molecular
constituents.66 It is these same weak intermolecular bonds which
are responsible for the poor chemical and thermal stability of
the resultant materials.
One approach has been to replace such weak intermolecular
bonds by more robust ones such as Ti-O, V-O, Zn-O, and
Al-O linkages. The Cambridge Structural Database (CSD)
reports respectively 4, 7, 23, and 6 single-crystal structures
where organic molecules are joined together into extended
networks through these metal-oxygen bonds. Using such
bonding, Wolzcanski, Yaghi, and co-workers have recently
reported remarkable and promising thermally stable porous
solids.16-24
O-Si-O bonds involve instead the covalent grafting of organic
molecules to preformed silicate and aluminosilicate networks
or through the inclusion of an organic component in mesoporous
silicate synthesis.68-74 This absence of atomic length scale
crystalline examples in which both organic bonds and Si-O,
P-O, or S-O bonds lie in the backbone of the extended
framework is all the more noteworthy when one recalls the
dominant role that the latter bonds play in the inorganic,
biological, and macromolecular literature.
In this paper we report a synthetic methodology for micro-
crystalline solids in which the organic molecules are bonded
to one another through single O-Si-O linkages. This meth-
odology has two parts. In the first step we use fairly weak
Ag-N coordination bonds to link 3-fold symmetric rigid
phenylacetylene nitrile molecules into a porous honeycomb
structure. These phenylacetylene nitrile molecules additionally
have covalently attached alkoxymethyl side chains which
terminate in hydroxy groups (see Figure 1). In the second step
we introduce into these solids reactive silyl triflate (SiRn-
(SO3CF3)m) guest molecules. The alcohol functionality is
nucleophilic and the triflate ion a good leaving group, the result
is the displacement of the silyl triflate bond by an Si-O bond
involving guest and host. For SiR2(SO3CF3)2 with two triflate
leaving groups, this leads to covalent O-Si-O bonds between
adjacent phenylacetylene molecules. We find that these reactions
occur with retention of the original crystal structure as demon-
strated by X-ray powder data. In the case of 1,3,5-tris(4-((4-
cyanophenyl)ethynyl)-2-((4-hydroxybutoxy)methyl)phenyl-
ethynyl)benzene, a phenylacetylene molecule with three alcohol
side chains, the introduction of di-tert-butylsilyl bis(trifluoro-
methanesulfonate) results in the formation of oligomers and low
weight polymers with molecular weights up to 105.
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is extremely difficult to construct crystalline extended solids
where the organic molecules are linked to one another through
main group bonds such as Si-O, P-O, or S-O close contacts.
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framework67 and none for either P-O or S-O joined moieties.
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detector (all Waters), a differential refractive index detector (Milton
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(Polymer Standards Service) with porosities of 100 Å, 1000 Å, and
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Phenylacetylene Nitrile SilVer Salts
J. Am. Chem. Soc., Vol. 122, No. 29, 2000 6873
Figure 1. Tritopic phenylacetylene nitrile ligands 1-5 and 13. 1 has a pentoxy side chain, 2-5 have hydroxy side chains, and 13 has a silyl ether
side chain.
equipped with a CPS 120 detector at 20 kV, 15 mA, for Cu KR1; λ )
1.5406 Å. RbZn4Ga5S1275 was used as internal standard for the Guinier
camera while for the Inel diffractometer a mixture of silver bohenate76
and silicon was used as an external standard. Lattice constants were
fitted and powder data were indexed by a least-squares method.
Thermogravimetric analysis (TGA) was performed on a SEIKO
Thermo-Gravimetric Differential Thermal Analyzer (TG/DTA 220)
under nitrogen flow and at a rate of 20 deg/min.
(250 mL). The flask was capped with a septum, evacuated, back-filled
with nitrogen three times, sealed with a Teflon screw cap, and stirred
at 80-90 °C overnight. The reaction mixture was then allowed to cool
to room temperature and filtered through a fritted glass funnel. The
filtrate was evaporated to dryness under reduced pressure on a rotary
evaporator and the residue was purified by column chromatography
on silica gel (1:1 dichloromethane-hexanes) to yield 6 as a yellow
solid (9.84 g, 50%): 1H NMR(200 MHz, acetone-d6 δ 7.72-7.48 (m,
14H), 4.50 (t, J ) 4.8 Hz, 2H), 3.99 (t, J ) 4.8 Hz, 2H), 0.25 (s, 27H).
13C NMR(100 MHz, acetone-d6) δ 213.5, 137.1, 132.7, 132.4, 124.3,
124.1, 123.8, 123.7, 119.5, 118.9, 105.2, 97.0, 96.9, 94.9, 90.1, 87.1,
77.1, 62.3, 0.06, 0.05.
4-Bromo-2,6-bis((2-hydroxyethoxy)methyl)benzonitrile (7). To a
solution of ethylene glycol (3.1 g, 0.05 mol) in anhydrous tetrahydro-
furan (30 mL) was added sodium hydride (60% dispersion in mineral
oil, 0.23 g, 5.6 mmol) in an ice bath over a period of 5 min. After the
hydrogen gas stopped evolving, a solution of 4-bromo-2,6-bis(bromo-
methyl)benzonitrile78 (10.6 g, 0.028 mol) in anhydrous tetrahydrofuran
(10 mL) was added. The mixture was allowed to stir for 15 min at
room temperature, poured into HCl (3 M, 30 mL), and extracted with
ether (3 × 75 mL). The combined organic layer was dried over
Na2SO4, evaporated under reduced pressure, and purified by column
chromatography on silica gel (1:4 dichloromethane-ethyl acetate) to
yield 7 as a white solid (0.81 g, 90%): 1H NMR (300 MHz, CDCl3)
δ 7.68 (s, 2H), 4.73 (s, 4H), 3.86-3.82 (m, 4H), 3.73-3.71 (m, 4H).
1H NMR (200 MHz, DMSO-d6) δ 7.82 (s, 2H), 4.67 (s, 4H), 3.55 (s,
8H). 13C NMR (75 MHz, CDCl3) δ 144.3, 131.0, 128.4, 115.6, 109.1,
72.8, 70.5, 52.0.
2-(2,4,6-Tris(4-(trimethylsilylethynyl)phenylethynyl)phenoxy)-
ethanol (6). A Schlenk flask equipped with a magnetic stirrer was
charged with (2,4,6-tris(trimethylsilylethynyl)phenoxy)ethanol (10.5 g,
0.026 mol) and tetrahydrofuran (50 mL). The mixture was capped with
a septum, evacuated, back-filled with nitrogen three times, and cooled
to 5 °C in an ice bath. A 1.0 M solution of tetrabutylammonium fluoride
in 9:1 tetrahydrofuran-water (5.0 mL, 5.0 mmol) was added rapidly
via syringe. After 5 min the solution was concentrated to near dryness
under reduced pressure on a rotary evaporator and the residue was eluted
with chloroform through a plug of silica gel. The combined filtrate
was evaporated to dryness under reduced pressure on a rotary evaporator
and transferred to a heavy-walled Schlenk flask equipped with a
magnetic stirrer. To this flask was added (4-bromophenylethynl)-
trimethylsilane77 (20.8 g, 0.0082 mol), copper(I) iodide (0.145 g, 0.76
mmol), triphenylphosphine (0.804 g, 3.1 mmol), bis(triphenylphos-
phine)palladium(II) chloride (0.539 g, 0.77 mmol), and triethylamine
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6874 J. Am. Chem. Soc., Vol. 122, No. 29, 2000
Kiang et al.
1-Bromo-4-iodo-2-methylbenzene (8). A suspension of 4-bromo-
3-methylaniline (9.3 g, 0.05 mol) in 6 M HCl (200 mL) was stirred
and heated at 90-95 °C in an Erlenmeyer flask for 1.5 h. The mixture
was then cooled to 0 °C with an ice-bath. A solution of NaNO2 (3.9 g,
56.5 mmol) in water (18 mL) was added dropwise with stirring to the
reaction mixture. The mixture was stirred at 0 °C for aother 30 min,
then added to a stirred solution of KI (83.5 g, 0.5 mol) in water (138
mL). After the reaction mixture was stirred overnight at room
temperature, 1 M Na2S2O3 (150 mL) was added. The mixture was
extracted with ether (3 × 100 mL) and dried over Na2SO4. Column
chromatography on silica gel (hexanes) afforded 8 as a colorless liquid
(11 g, 74%): 1H NMR (300 MHz, CDCl3) δ 7.55 (d, J ) 2.2 Hz, 1H),
7.33 (dd, J ) 8.6, 2.2 Hz, 1H), 7.22 (d, J ) 8.6 Hz, 1H), 2.3 (s, 3H).
13C NMR (75 MHz, CDCl3) δ 140.2, 139.4, 136.2, 133.9, 124.7, 92.3,
22.6. GC-MS m/z 298 (M + 1), 296 (M - 1).
fritted glass funnel. The filtrate was evaporated to dryness under reduced
pressure on a rotary evaporator and the residue was purified by column
chromatography on silica gel (2:3 ethyl acetate-hexanes) to yield 3 as
a yellow solid (4.53 g, 81%): IR (KBr, cm-1) 2228, 2215, 1684, 1653,
1615, 1599, 1576, 1570, 1559, 1514, 1457, 1440, 1406, 1362, 1240,
1104, 1017, 836, 668, 539, 431, 422, 418, 411. 1H NMR (200 MHz,
CDCl3) δ 7.88-7.65 (m, 26H), 4.58 (t, J ) 4.8 Hz, 2H), 4.04 (t, J )
4.8 Hz, 2H). 13C NMR (100 MHz, CDCl3) δ 162.2, 137.3, 133.1, 133.0,
132.7, 132.6, 132.5, 128.4, 124.5, 123.6, 123.4, 119.6, 119.1, 118.8,
113.1, 95.0, 93.5, 90.6, 90.4, 90.2, 87.6, 77.3, 62.4, 30.7, 25.7, 25.5,
25.3, 25.1, 24.9. HRMS-FAB ( m/z) [M + H]+ calcd 814.2495, found
814.2492.
1,3,5-Tris(4-cyano-3,5-bis((2-hydroxyethoxy)methyl)phenylethynyl)-
benzene (4). A heavy-walled Schlenk flask was charged with 7 (0.21
g, 0.64 mmol), 1,3,5-triethynylbenzene (30 mg, 0.2 mmol), copper(I)
iodide (3 mg, 15 µmol), triphenylphosphine (15 mg, 57 µmol), bis-
(triphenylphosphine)palladium(II) chloride (10 mg, 14 µmol), and
triethylamine (13 mL). The flask was capped with a septum, evacuated,
and back-filled with nitrogen, sealed with a Teflon cap, and stirred at
85 °C for 16 h. The reaction mixture was then allowed to cool to room
temperature and evaporated under reduced pressure on a rotary
evaporator. The residue was purified by column chromatography on
silica gel (5:1 ethyl acetate-triethylamine) to yield 4 as a palm yellow
solid (0.14 g, 80%): 1H NMR (300 MHz, DMSO-d6) δ 7.95 (s, 3H),
7.79 (s, 6H), 4.71 (s, 12H), 3.59 (s, 24H). 13C NMR (75 MHz, DMSO-
d6) δ 139.1, 126.2, 124.3, 122.0, 119.1, 111.0, 105.8, 86.8, 85.8, 68.6,
65.7, 56.3. HRMS (ES) m/z calcd 898.3551, found 898.3577.
1,3,5-Tris(4-((4-cyanophenyl)ethynyl)-2-((4-hydroxybutoxy)meth-
yl)phenylethynyl)benzene (5). A heavy-walled Schlenk flask was
charged with 11 (5.2 g, 0.014 mol), 1,3,5-triethynylbenzene (0.58 g,
3.8 mmol), copper(I) iodide (25 mg, 0.13 mmol), triphenylphosphine
(350 mg, 1.34 mmol), bis(triphenylphosphine)palladium(II) chloride
(189 mg, 0.27 mmol), and triethylamine (45 mL). The flask was capped
with a septum, evacuated, and back-filled with nitrogen, sealed with a
Teflon cap, and stirred at 75 °C for 36 h. The reaction mixture was
then allowed to cool to room temperature and evaporated under reduced
pressure on a rotary evaporator. The residue was purified by column
chromatography on silica gel (2:1 ethyl acetate-CH2 Cl2) to yield 5
as a yellow solid (1.1 g, 27%): IR (KBr, cm-1) 3387, 2634, 2853,
2228, 2210, 1600, 1579, 1505, 1121, 836. 1H NMR (300 MHz, CDCl3)
δ 7.66-7.58 (m, 18H), 7.53 (d, J ) 8.1 Hz, 3H), 7.45 (dd, J )
8.1, 1.6 Hz, 3H), 3.67 (d, J ) 5.9 Hz, 6H), 3.64 (d, J ) 5.9 Hz, 6H),
1.83-1.66 (m, 12H). 13C NMR (75 MHz, CDCl3) δ 140.6, 134.2,
132.3, 132.1, 130.8, 130.6, 127.8, 123.9, 122.8, 121.7, 118.4, 111.8,
94.0, 93.3, 89.7, 88.1, 71.0, 70.6, 62.6, 29.9, 26.6. HRMS-FAB ( m/z)
[M + H]+ calcd 1060.4326, found 1060.4323.
tert-Butyl((2,4,6-tris((4-cyanophenyl)ethynyl)phenoxy)ethoxy)-
dimethylsilane (12). A heavy-walled Schlenk flask equipped with a
magnetic stirrer was charged with 2 (10 mg, 1.9 µmol), tert-
butyldimethylsilyl chloride (20 mg, 0.13 mmol), imidazole (20 mg,
0.29 mmol), and dichloromethane (15 mL) and stirred under nitrogen
for 3 h at room temperature. The reaction flask was then charged
with tert-butyldimethylsilyl chloride (20 mg, 0.13 mmol) and (dimethyl-
amino)pyridine (20 mg, 1.6 mmol) and allowed to stir overnight. The
reaction mixture was then washed with water (2 × 50 mL) and dried
over magnesium sulfate, and the filtrate was evacuated to dryness to
yield 12 as a yellow solid (100% by thin-layer chromatography). An
alternative silylation reaction is as follows: A heavy-walled Schlenk
flask equipped with a magnetic stirrer was charged with 2 (5 mg, 0.95
µmol), tert-butyldimethyltrifluoromethane sulfonate (30 mg, 0.11
mmol), 2,6-di-ertt-butylpyridine (50 mg, 0.26 mmol), and anhydrous
benzene (3 mL) and stirred under nitrogen for 1 h at room temperature.
After 1 h, thin-layer chromatography indicated complete conversion
to 12: 1H NMR (200 MHz, DMSO-d6) δ 7.97-7.73 (m, 14H), 4.53
(t, J ) 4.8 Hz, 2H), 4.01 (t, J ) 4.8 Hz, 2H), 0.74 (s, 9H), -0.36 (s,
6H). MS (EI, 70 eV) m/z 57 (11.1), 59 (12.5), 73 (36.2), 75 (28.2),
101 (15.7), 263 (29.4), 264 (15.3), 526 (100), 527 (45.8), 528 (15.8),
570 (74.3), 571 (37.4), 572 (12.7).
1-Bromo-2-bromomethyl-4-iodobenzene (9). A heavy-walled Schlenk
flask was charged with 8 (10.2 g, 0.035 mol), N-bromosuccinimide
(9.5 g, 0.053 mol), and benzoyl peroxide (60 mg, 0.25 mmol). The
mixture was evacuated, back-filled with nitrogen, sealed with a Teflon
cap, and stirred at 80 °C for 24 h. After being cooled to room
temperature, the mixture was poured into 5% NaHSO3 (120 mL),
extracted with ether (3 × 75 mL), and then dried over Na2 SO4.
Recrystallization from hot hexanes afforded 9 as white crystals (8.1 g,
62%): 1H NMR (300 MHz, CDCl3) δ 7.75 (d, J ) 2.15 Hz, 1H), 7.44
(dd, J ) 8.6, 2.15 Hz, 1H), 7.27 (d, J ) 8.6 Hz, 1H), 4.48 (s, 3H). 13
C
NMR (75 MHz, CDCl3) δ 139.8, 139.2, 139.0, 134.8, 124.2, 92.4, 31.9.
4-(2-Bromo-5-iodobenzyloxyl)butan-1-ol (10). To a solution of 1,4-
butadiol (25 g, 0.28 mol) in anhydrous tetrahydrofuran (30 mL) was
added sodium hydride (60% dispersion in mineral oil, 1.34 g, 0.033
mol) in an ice bath over a period of 5 min. After the suspension was
stirred for another 10 min in an ice-bath, a solution of 9 (10.6 g, 0.028
mol) in anhydrous tetrahydrofuran (10 mL) was added to the suspension.
The mixture was then stirred for 2 h at 60 °C. After the reaction mixture
was cooled to room temperature, it was added to HCl (3 M, 100 mL)
and extracted with ether (3 × 75 mL). The combined organic layer
was dried over Na2SO4, evaporated under reduced pressure, and purified
by column chromatography on silica gel (4:1 dichloromethane-ethyl
acetate) to yield 10 as a viscous liquid (9.6 g, 89%): 1H NMR (300
MHz, CDCl3) δ 7.76 (d, J ) 2.15 Hz 1H), 7.43 (dd, J ) 8.3, 2.15 Hz,
1H), 7.22 (d, J ) 8.3 Hz, 1H), 4.48 (s, 2H) 3.68 (t, J 5.9 Hz, 2H), 3.58
(t, J ) 5.9 Hz, 2H), 1.74-1.67 (m, 4H). 13C NMR (75 MHz, CDCl3)
δ 139.9, 137.8, 137.6, 134.5, 122.2, 92.6, 71.5, 71.0, 62.7, 29.8, 26.3.
4-(4-Bromo-3-((4-hydroxybutoxy)methyl)phenylethynyl)benzo-
nitrile (11). A Schlenk flask was charged with 10 (7.54 g, 0.02 mol),
4-ethynylbenzonitrile (3.05 g, 0.02 mol), copper(I) iodide (38 mg, 0.2
mmol), triphenylphosphine (524 mg, 2.0 mmol), bis(dibenzylidene-
acetone)palladium(0) (214 mg, 0.4 mmol), and triethylamine (70 mL).
The flask was capped with a septum, evacuated, back-filled with
nitrogen, sealed with a Teflon cap, and heated at 50 °C for 16 h. The
reaction mixture was then allowed to cool to room temperature and
evaporated under reduced pressure on a rotary evaporator. The residue
was purified by column chromatography on silica gel (2:1 hexanes-
THF) to yield 11 as a beige solid (5.2 g, 70%): 1H NMR (300 MHz,
CDCl3) δ 7.64-7.57 (m, 5H), 7.53 (d, J ) 8.6 Hz, 1H), 7.26 (dd, J )
8.3, 2.15 Hz, 1H), 4.55 (s, 2H), 3.68 (t, J ) 5.9 Hz, 2H), 3.62 (t, J )
5.9 Hz, 2H), 1.77-1.69 (m, 4H). 13C NMR (75 MHz, CDCl3) δ 138.3,
132.7, 132.1, 131.9, 131.8, 127.9, 123.5, 121.6, 118.5, 111.7, 92.8,
88.6, 71.8, 71.1, 62.7, 29.9, 26.4.
(2,4,6-Tris(4-((4-cyanophenyl)enthynyl)phenylethynyl)phenoxy)-
ethanol (3). A Schlenk flask equipped with a magnetic stirrer was
charged with 7 (5.0 g, 6.86 mmol), potassium carbonate (5.0 g, 36
mmol), and a methanol/dichloromethane 1-3 solution (50 mL) and
stirred under nitrogen for 3 h at room temperature. The mixture was
then transferred via syringe to a heavy-walled Schlenk flask. To this
flask was added 4-bromobenzonitrile (4.36 g, 0.024 mol), copper(I)
iodide (65 mg, 0.34 mmol), triphenylphosphine (0.227 g, 8.7 mmol),
bis(triphenylphosphine)palladium(II) chloride (0.227 g, 0.0.32 mmol),
and triethylamine (100 mL). The flask was capped with a septum,
evacuated, back-filled with nitrogen three times, sealed with a Teflon
screw cap, and stirred at 80-90 °C overnight. The reaction mixture
was then allowed to cool to room temperature and filtered through a
tert-Butyl((2,4,6-tris(4-((4-cyanophenyl)ethynyl)phenylethynyl)-
phenoxy)ethoxy)dimethylsilane (13). A heavy-walled Schlenk flask
equipped with a magnetic stirrer was charged with 3 (0.498 g, 0.61

Phenylacetylene Nitrile SilVer Salts
J. Am. Chem. Soc., Vol. 122, No. 29, 2000 6875
mmol), tert-butyldimethylsilyl chloride (92 mg, 0.61 mmol), (dimethyl-
amino)pyridine (0.224 g, 1.8 mmol), and anhydrous tetrahydrofuran
(50 mL) and stirred under nitrogen for 4 h at room temperature. The
flask was again charged with tert-butyldimethylsilyl chloride (92 mg,
0.61 mmol) and (dimethylamino)pyridine (0.224 g, 1.8 mmol) and
allowed to stir overnight. The reaction mixture was then evacuated to
dryness on a rotary evaporator, and the residue was chromatographed
on silica gel to yield 13 as a yellow solid (0.60 g, 100%). An alternative
silylation reaction is as follows: A heavy-walled Schlenk flask equipped
with a magnetic stirrer was charged with 3 (5 mg, 0.62 µmol), tert-
butyldimethyltrifluoromethane sulfonate (30 mg, 0.11 mmol), 2,6-di-
tert-butylpyridine (50 mg, 0.26 mmol), and anhydrous benzene (3 mL)
and stirred under nitrogen for 1 h at room temperature. After 1 h, thin-
layer chromatography indicated complete conversion to 13: IR (KBr,
cm-1) 2953, 2928, 2902, 2895, 2882, 2856, 2362, 2228, 2215, 1600,
1514, 1440, 1106, 835, 666, 434, 421, 411, 394. 1H NMR (200 MHz,
acetone-d6) δ 7.88-7.66 (m, 26H), 4.60 (t, J ) 4.6 Hz, 2H), 4.17 (t,
J ) 4.8 Hz, 2H), 0.86 (s, 9H), 0.08 (s, 6H). 13C NMR (100 MHz,
THF-d6) δ 160.9, 136.4. 131.9, 131.6, 131.5, 127.7, 12.35, 122.2, 122.0,
118.3, 117.6, 111.5, 93.9, 93.2, 93.1, 89.7, 89.6, 89.3, 86.8, 62.7, 25.9,
25.7, 18.2, -5.4. HRMS-FAB ( m/z) [M + H]+ calcd 928.3359, found
928.3353.
acetonitrile (0.3 mL) was then added to the vial to dissolve the white
solids. The vial was then left undisturbed and exposed to the argon
atmosphere to allow escape of solvent. Crystalline precipitate formed
after 24 h.
Preparation of Microcrystalline Powders 4‚AgOTf. 4 (4.5 mg,
5.0 µmol) was dissolved in acetone (1.0 mL) in a capped vial heated
in an oil-bath at 50 °C. The vial was then taken out of the bath and a
solution of silver(I) trifluoromethanesulfonate (1.3 mg, 5.0 µmol) in
benzene (1.0 mL) was added. The mixture was allowed to cool to room
temperature to yield crystalline powder.
Preparation of Microcrystalline Powders 5‚AgOTf. To a solution
of 5 (30 mg, 0.03 mmol) in anhydrous benzene (8 mL) was added a
solution of silver(I) trifluoromethanesulfonate (8 mg, 0.03 mmol) in
anhydrous benzene (2 mL) in a Schlenk flask sealed with a Teflon-
lined screw cap. This flask was then placed in a furnace equipped with
an Eurotherm temperature controller and heated from room temperature
to 110 °C at 0.5 deg/min, held at 110 °C for 70 min, then slowly cooled
to room temperature at 0.02 deg/min to yield crystalline powder.
Preparation of Microcrystalline Powders 13‚AgOTf. To a solution
of 13 (20 mg, 0.02 mmol) in benzene (1.8 mL) was added silver(I)
trifluoromethanesulfonate (5 mg, 0.02 mg) in benzene (1 mL) in a vial
with a Teflon-lined screw cap. This vial was then placed in a furnace
equipped with an Eurotherm temperature controller and heated from
room temperature to 98 °C at 0.5 deg/min, held at 98 °C for 70 min,
then slowly cooled to room temperature at 0.1 deg/min to yield
crystalline powder.
Di-tert-butylbis((2,4,6-tris(4-((4-cyanophenyl)ethynyl)phenyl-
ethynyl)phenoxy)ethoxy)silane (14). A heavy-walled Schlenk flask
equipped with a magnetic stirrer was charged with 3 (0.405 g, 0.50
mmol), 2,6-di-tert-butylpyridine (0.852 g, 4.4 mmol), di-tert-butylsilyl
bis(trifluoromethanesulfonate) (0.109 g, 0.25 mmol), and anhydrous
tetrahydrofuran (5 mL) and the reaction mixture was stirred at room
temperature overnight. Excess tert-butyldimethylsilyl chloride (>0.5
g, 3.3 mmol) was added and the mixture was stirred at room temperature
for an additional 3 days. The tetrahydrofuran was then removed in
vacuo, the residue dissolved in dichloromethane, and the insoluble solid
separated by filtration. The filtrate was then evaporated to dryness on
the rotary evaporator and the solid was washed with a minimum of
cold acetone (3 × 5 mL), leaving behind 14 as a yellow solid (0.29 g,
33%): IR (KBr cm-1) 3068, 2935, 2861, 2228, 2215, 1599, 1558, 1514,
Solid State Monosilylation of 3‚AgOTf. The crystalline powder
sample 3‚AgOTf (50 mg, 0.06 mmol) grown in anhydrous benzene
was exposed to 2,6-di-tert-butylpyridine (0.3 g, 1.6 mmol) and tert-
butyldimethylsilyl (trifluoromethanesulfonate) (60 mg, 0.05 mmol) in
a glovebox. After 3 days, a small amount of the reaction mixture was
sealed in a 1.0 mm special glass capillary tube, removed from the
glovebox, and mounted on a Guinier camera for X-ray diffraction
pattern collection. Another small amount of the reaction mixture was
filtered and removed from the glovebox. This sample was then placed
on a vacuum line for 2 h, quenched with ethanol to further remove
any possible unreacted tert-butyldimethylsilyl bis(trifluoromethane-
1
1473, 1456, 1437, 1406, 1271, 1136, 1106, 1031, 1017, 834, 730. H
1
NMR (200 MHz, acetone-d6) δ 7.88-7.52 (m, 52H), 4.59 (t, J ) 5.2
Hz, 4H), 4.17 (t, J ) 5.2 Hz, 4H), 1.11 (s, 18H). 13C NMR (100 MHz,
CDCl3) δ 217.7, 160.7, 154.0, 144.1, 136.4, 131.9, 131.8, 131.6, 131.5,
131.4, 131.3, 127.6, 124.3, 123.3, 122.1, 118.2, 117.4, 111.6, 93.9,
93.2, 93.1, 89.7, 89.6, 89.5, 89.3, 86.9, 27.8, 27.4, 21.1, 21.1. MS (FAB)
m/z 1768 [M + H]+.
sulfonate), and dissolved in acetone-d6 for H NMR characterization.
To the remaining reaction mixture in the glovebox was added 2,6-di-
tert-butylpyridine (0.3 g, 1.6 mmol), and tert-butyldimethylsilyl (tri-
fluoromethanesulfonate) (60 mg, 0.05 mmol). The reaction mixture was
stirred for a week. It was filtered, removed from the glovebox, placed
on vacuum line for 2 h, quenched with ethanol, and was then divided
into two portions. One portion was dissolved in acetone-d6 for 1H NMR
characterization. A second portion of the reaction mixture was again
filtered and washed thoroughly with water, and a small sample was
sealed in a special glass capillary tube for X-ray powder pattern
collection.
Di-tert-butyl(2,4,6-tris((4-((4-cyanophenyl)ethynyl)phenylethynyl)-
phenoxy)ethoxy)silanol (15). A heavy-walled Schlenk flask equipped
with a magnetic stirrer was charged with 3 (0.100 g, 0.013 mmol),
2,6-di-tert-butylpyridine (0.50 g, 2.9 mmol), di-tert-butylsilyl bis-
(trifluoromethanesulfonate) (0.50 g, 1.1 mmol), and anhydrous tetrahydro-
furan (5 mL) and the reaction mixture was allowed to stir overnight at
room temperature. The flask was then charged with water (300 mL),
the mixture was evaporated to dryness on a rotary evaporator, and the
residue was placed in a sublimator under vacuum at 80 °C. After the
crystalline byproduct was removed by sublimation, the flask was cooled
and the residue was recovered to yield 15 (60 mg, 46%): IR (KBr
cm-1) 3484, 3416, 2962, 2932, 2856, 2227, 2216, 1599, 1515, 1439,
Solid State Disilylation of 3‚AgOTf. The crystalline powder sample
3‚AgOTf (300 mg, 0.37 mmol) grown in anhydrous benzene was placed
in a Schlenk tube capped with a septum. The reaction tube was
evacuated and back-filled with nitrogen and 2,6-di-tert-butylpyridine
(0.7 g, 3.7 mmol) and di-tert-butylsilyl bis(trifluoromethanesulfonate)
(82 mg, 0.19 mmol) were added via syringe. The septum was then
replaced by a Teflon-lined screw cap and the reaction mixture stirred
under nitrogen. After a week, a small portion of the reaction mixture
was removed from the Schlenk tube, filtered, washed thoroughly with
1
1260, 1108, 835. H NMR (200 MHz, acetone-d6) δ 7.81-7.67 (m,
26H), 5.18 (s, 1H), 4.67 (t, J ) 5.4 Hz, 2H), 4.34 (t, J ) 5.4 Hz, 2H),
0.98 (s, 18H). MS (FAB) m/z 972 (M+).
1
water, and dissolved in acetone-d6 for H NMR characterization. The
Preparation of Microcrystalline Powders 2‚AgOTf. To a solution
of 2 (0.3 g, 0.37 mmol) in anhydrous benzene (15 mL) was added a
solution of silver(I) trifluoromethanesulfonate (0.1 g, 0.37 mmol) in
anhydrous benzene (15 mL) in a vial with a Teflon-lined screw cap.
This vial was then placed in a furnace equipped with an Eurotherm
temperature controller and heated from room temperature to 98 °C at
0.5 deg/min, held at 98 °C for 60 min, then slowly cooled to room
temperature at 0.02°Cdeg/min to yield crystalline powder.
Preparation of Microcrystalline Powders 3‚AgOTf. In a glovebox
with argon atmosphere, a solution of silver(I) trifluoromethanesulfonate
(25 mg, 0.1 mmol) in anhydrous benzene (1 mL) was added to a
solution of 3 (40 mg, 0.1 mmol) in anhydrous benzene (1 mL) in a
vial. Upon addition white precipitate formed immediately. Anhydrous
remaining reaction mixture was stirred under nitrogen for another week,
then monitored with 1H NMR again. After verifying by 1H NMR that
3 had reacted completely, the reaction mixture was filtered and the
solid was washed with water. A portion of the solid thus obtained was
then sealed in a 1.0 mm special glass capillary tube and mounted on
an X-ray diffractometer for powder pattern collection.
Solid State Polymerization of 5‚AgOTf. The crystalline powder
sample of 5‚AgOTf (62 mg, 0.047 mmol) grown in anhydrous benzene
was placed in a Schlenk tube capped with a septum. The reaction
tube was evacuated and back-filled with nitrogen and 2,6-di-tert-
butylpyridine (46 mg, 0.24 mmol) and di-tert-butylsilyl bis(trifluoro-
methanesulfonate) (31 mg, 0.07 mmol) was added via syringe. The
septum was then replaced by a Teflon-lined screw cap. The reaction

6876 J. Am. Chem. Soc., Vol. 122, No. 29, 2000
Kiang et al.
Figure 2. Stereoview of the single-crystal structure of 1‚AgOTf. Silver
atoms are represented as black spheres and sulfur atoms as gray spheres.
flask was again evacuated and back-filled with nitrogen, then stirred
at room temperature. The course of this solid state reaction was
monitored by size exclusion chromatography. After 3 weeks of stirring
at room temperature under nitrogen, the reaction mixture was filtered,
washed thoroughly with water, and divided into two portions. The first
portion was sealed in a 1.0 mm special glass capillary tube and mounted
on an X-ray diffractometer for powder pattern collection. The second
portion was dissolved in tetrahydrofuran (10 mg to 1 mL) for size
exclusion chromatography.
Vapor Exchange of Polymerized 5‚AgOTf. The polymerized 5‚
AgOTf was placed in a thermogravimetric analyzer and heated to
150 °C at a rate of 20 deg/min to void the solid of initially included
solvent. The apohost was then suspended above a solution of toluene
molecules, taking care to maintain spatial separation between host and
guest, and sealed in a vial. The vial was heated to 50 °C for 48 h. The
sample was then analyzed by both TGA and X-ray powder diffraction.
Results and Discussion
In earlier work11,26,78,79 we have explored the crystalline
structure of 3-fold symmetric phenylacetylene nitriles and silver
triflate complexes. From a study of 20 such systems (including
eight single-crystal structures), a common structural theme has
emerged. In all cases such 3-fold symmetric molecules form a
honeycomb extended network in which every organic molecule
is bonded to three silver ions and each silver ion is trigonally
planar coordinated to three organic molecules. A typical single-
crystal 1‚AgOTf is illustrated in Figure 2. Its corresponding
X-ray powder diffraction pattern is shown in Figure 3c. In this
crystal structure, parallel layers of a two-dimensional honeycomb
network are stacked along the c axis. The interlayer distance is
3.52 Å. This c axis is not normal to the ab plane of the crystal.
Instead, as can be seen in Figure 2, the individual honeycomb
sheets are rotated out of the normal plane by a small rotation.
The b axis is the axis of rotation. Had there been no such
rotation, all the axes could be mutually orthogonal and the unit
cell would have appeared orthorhombic. This orthorhombic cell
would have a b/a ratio of x3 as it is a C-centered super-cell
corresponding to a hexagonal primitive cell. With the observed
rotation the b axis remains unchanged, the a axis becomes
significantly shorter, R and â stay at 90°, and the resulting crystal
is monoclinic.
Figure 3. (a) Observed and (b) calculated X-ray diffraction patterns
for 3‚AgOTf. (c) Calculated X-ray diffraction pattern based on the
single-crystal structure of 1‚AgOTf.
opposed to the channel interior. Large 110 and 200 peaks are
the hallmark of a channel type porous solid. Finally, in Figure
3c, it can be observed that while diffraction peaks appear to be
fused double peaks at low angle, at higher angles these double
peaks resolve into separate but closely spaced signals. This
splitting is due to the rotation of the honeycomb sheets away
from the plane normal to the c axis, and the consequent lowering
of the unit cell symmetry from hexagonal to monoclinic.
3‚AgOTf. The X-ray powder pattern of 3‚AgOTf is shown
in Figure 3a. Shown here are the low-angle features. The full
powder data set is given in the Supporting Information. The
similarity between this powder pattern and the one in Figure
3c based on the single-crystal data is clear. There are, however,
two notable differences. First it may be seen that near 15° there
is the onset of an extremely broad feature. This feature can be
attributed to diffraction from the benzene solvent in which the
sample was immersed during data collection. Second, the 2θ
angle scales of the two patterns are different. This difference
in diffraction angles can be understood if one notes the
difference in size of the organic molecules in the two samples.
Compared to 1, the organic molecule 3 has an additional three
aromatic rings. This larger size results in a larger real space
unit cell, smaller reciprocal lattice cell, and correspondingly
smaller 2θ angles for equivalent reflections.
Each of these structural features affects the resulting powder
pattern. Most important is the interlayer spacing of 3.52 Å. This
distance corresponds to a 2 θ angle (Cu KR radiation) of 25.3°,
hence all powder pattern reflections below this angle are due
to hk0 reflections. As Figure 3 shows, the predominant hk0
reflections, 110 and 200, partially fuse together to form the
largest reflection, a reflection significantly more intense than
any other. The strength of this reflection is due to the contrast
in crystallinity and electron density of the channel walls as
(79) Choe, W.; Kiang, Y.-H.; Xu, Z.; Lee, S. Chem. Mater. 1999, 11,
1776.

Phenylacetylene Nitrile SilVer Salts
J. Am. Chem. Soc., Vol. 122, No. 29, 2000 6877
Figure 4. View down the channel direction of the model structure for
3‚AgOTf. The calculated diffraction pattern in Figure 3c is based on
this model. Large spheres, Ag; medium spheres, N; small spheres, C.
Recalling that data with 2θ angles less than 25° are hk0
reflections, we refined the low-angle data given in Figure 3a
and the Supporting Information to a two-dimensional C-centered
rectangular cell. This projected rectangular cell was refined to
an a ) 52.37(9) Å and b ) 33.99(4) Å. Given the low-angle
nature of the data and the comparatively large cell constants of
these data, the low standard deviation suggests the validity of
this rectangular cell. We further note the honeycomb net
illustrated in Figure 2 is based on a rigid hexagonal net of
organic molecules linked to silver ions. Using knowledge of
the molecular structure of 3, tabulated bond lengths,80 and an
Ag-N bond distance of 2.2 Å, we find the calculated distance
for the Ag ions to the centroid of the central aromatic ring in 3
to be 19.9 Å. This corresponds to a b axis of 34 Å, in good
agreement with the experimentally observed value.
Figure 5. (a) Observed and (b) calculated X-ray diffraction patterns
for 5‚AgOTf.
structure leads to a powder pattern similar to the one observed
experimentally even in the absence of atomic parameter refine-
ment.
Following the single-crystal model illustrated in Figure 2,
we use the b axis as an axis of rotation to rotate these rigid
hexagonal nets. In this way we generated an a axis correspond-
ing to the experimentally observed a axis of 52.4 Å. This
provides us with the necessary data to generate the crystal model
shown in Figure 4. The atomic coordinates of this model are
given in the Supporting Information. As in the initial crystal
structure illustrated in Figure 2, only the rigid backbone, the
Ag ions, and the sulfur atoms of the triflate ions are located.
Even though solvent, the alkoxy side chains, and the remaining
triflate atoms are not included, nor has there been refinement
of any atomic parameters, the powder pattern generated from
this model (see Figure 3b) is reasonably similar to the pattern
found experimentally (Figure 3a). While the angular resolution
of our data is only 4 Å, this length is significantly smaller than
the channel diameters of 20-30 Å and therefore the data support
the presence of channels in the structure. Finally, as we have
only two reflections which correspond to hkl (l * 0), it seemed
prudent to consider here only the projection of the crystal
structure onto the two-dimensional plane normal to the c axis.
5‚AgOTf. The X-ray powder pattern of 5‚AgOTf is shown
in Figure 5. It may be seen that while this powder pattern retains
many features in common with the earlier powder patterns, the
splitting between pairs of peaks is significantly smaller. Only
at higher angles can one see the separation between pairs.
Besides the main reflections, a number of weak reflections also
appear. These additional reflections suggest that the crystal has
a super-cell, caused by the stacking pattern of honeycomb layers
on top of one another. We were able to refine the 31 observed
reflections into a monoclinic cell with a ) 59.46(6) Å, b )
33.81(2) Å, c ) )14.283(7) Å, and â ) 103.8(1)°. The
refinement is given in the Supporting Information. Given the
low angles in the observed data as well as the large unit cell
lengths, the small standard deviations in cell lengths strongly
support the validity of this refined cell. The systematic absences
found in these reflections suggest the crystal is in the C2, Cm,
or C2/m space group.81
The b axis length of 33.81 Å is in substantial agreement with
the 34 Å axis estimated from tabulated organic bond lengths
and the b axis of 33.99 Å found in 3‚AgOTf. The c axis of
14.28 Å is four times 3.57 Å, suggesting a stacking of four
layers within the unit cell. We have seen such 4-fold stacking
sequences in our earlier single-crystal structures. These earlier
structures showed that in such cases the layers shift with respect
to one another so that the triflate ions, which are coordinated
to the Ag atoms, lie in the cleft of the adjacent layers either
above or beneath them in the stacking sequence. Furthermore,
the layers stack in such a way as to place as many aromatic
We base the validity of our structural assignment on three
points. First, the observed powder pattern is similar to those
found in previously studied single-crystal structures. In the
inorganic solid state literature this is generally considered proof
of an isotypic structure. Second, the observed lattice constants
are in agreement with the cell constants of a chemically
reasonable model based on standard organic bond lengths.
Finally, the generation of a crystal model based on this proposed
(80) March, J. AdVanced Organic Chemistry, 4th ed.; Wiley: New York,
1992; p 21.
(81) Hahn, T., Ed. International Tables for Crystallography, 4th revised
ed.; Kluwer Academic Publishers: Boston, 1995; Vol. A.

6878 J. Am. Chem. Soc., Vol. 122, No. 29, 2000
Kiang et al.
Figure 6. View down the channel direction of the model structure for
5‚AgOTf. The calculated diffraction pattern in Figure 5b is obtained
from this model. Molecule 5 is shown in green, silver in red, and sulfur
in yellow.
rings as possible on top of each other in a staggered arrangement.
We therefore constructed a model using these facts. We chose
to place the model in C2/m symmetry, not just because for
extended solids it is the most common of the three possible
space groups,82 but also because it seemed pointless not to
assume the presence of an inversion center. This inversion center
enforces a pairing of the honeycomb layers in which the triflate
ions of neighboring layers lie in the cleft of the adjacent pair.
The staggering of the aromatic rings and the C2/m mirror plane
symmetry dictate how these pairs lie with respect to neighboring
pairs. The constructed model is shown in Figure 6. The atomic
coordinates for this model are given in the Supporting Informa-
tion. In this model the triflate ions are represented by the sulfur
atoms and the bridging oxygen atoms. The resultant powder
pattern is shown in Figure 5b. The agreement between calculated
and observed patterns is reasonably good. This agreement is of
special interest as no atomic parameters were refined to improve
the agreement. Furthermore, the side chains, the remaining
triflate components, and solvent molecules were not located in
our model and hence their influence on peak intensities could
not be assessed.
Figure 7. (a) Observed and (b) calculated X-ray diffraction patterns
for 4‚AgOTf.
4‚AgOTf. The X-ray powder pattern of 4‚AgOTf is illustrated
in Figure 7. Shown here are the low-angle features. The full
powder data set is given in the Supporting Information. The
observed powder pattern bears several features in common with
the previously discussed ones. The principal reflection is found
at the lowest angle, followed by four or five smaller peaks. A
broad feature attributable to the solvent benzene is found for
2θ values between 15 and 25°. As in 5‚AgOTf, the splitting
between pairs of peaks is quite small. Even at higher angles
there is no clear evidence of irregular peak shape. We therefore
refined the data with a two-dimensional hexagonal cell with an
a axis of 22.30(5) Å. This refinement is given in the Supporting
Information. This a axis is in substantial agreement with that
obtained using standard bond lengths as well as those found in
earlier single-crystal work. The former distance was calculated
to be 22.5 Å while the latter data range from 22.1 to 22.7 Å.78
Figure 8. View down the channel direction of the model for 4‚AgOTf.
The calculated diffraction pattern in Figure 7b is obtained from this
model. Carbon atoms are shown in green, nitrogen in blue, oxygen in
red, silver in brown, and triflate ions in yellow.
We have previously studied by X-ray methods a phenylacet-
ylene nitrile‚AgOTf single crystal whose molecular composition
is the same as that of 4‚AgOTf except that the alcohol group
of 4 is replaced by a methoxy group.78 We therefore used this
single-crystal structure to prepare a model for 4‚AgOTf. This
structure was modified by removing the capping methoxy groups
and then superimposing the remaining structure onto the refined
hexagonally shaped cell. This model is shown in Figure 8. Due
(82) For extended solids: C/2m, 163 compounds; Cmn, 13 compounds;
C2, 15 compounds. See: Villars, P.; Calvart, L. D. Pearson’s Handbook
of Crystallographic Data for Intermetallic Phases, 2nd ed.; ASM Inter-
national: Materails Park, 1991.

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J. Am. Chem. Soc., Vol. 122, No. 29, 2000 6879
Figure 10. X-ray diffraction patterns for (a) 3‚AgOTf, (b) 13‚AgOTf,
and (c) 3‚AgOTf after solid-state reaction with tert-butyldimethylsilyl
trifluoromethanesulfonate. Patterns shown above are densitometer traces
obtained from Guinier camera film.
1
Figure 9. Portion of the 200 MHz H NMR spectra in acetone-d6
of (a) 3, (b) 13, and (c) 3 after solid-state reaction with tert-
butyldimethylsilyl trifluoromethanesulfonate.
to the absence of symmetry in the side chains the model is
oblique. The powder pattern based on this model is shown in
Figure 7b. The agreement is fair. No refinement of any atomic
parameters was made to improve the agreement between model
and experiment. Furthermore, given that the side chains in 4‚
AgOTf are probably involved in a hydrogen-bonded network
and hence would adopt conformations different from those found
in the methoxy derivative, the deviations found in Figure 7
appear understandable.
Solid-State Reaction of 3‚AgOTf and tert-Butyldimethyl-
silyl Trifluoromethanesulfonate. As described in the Experi-
mental Section, the solution reaction of molecule3 and tert-
butyldimethylsilyl trifluoromethanesulfonate occurs in quantitative
yield at room temperature. The product is 13. In Figure 9 we
show the 4.0 to 5.0 ppm region of the 1H NMR for both 3 and13.
The peaks correspond to the side chain methylene group
hydrogen atoms of these molecules.
By contrast the equivalent solid-state reaction between this
same silyl monotriflate and 3‚AgOTf is slower and requires
several days of 3‚AgOTf exposed to neat liquid tert-butyl-
dimethylsilyl trifluoromethanesulfonate and 2,6-di-tert-butyl-
pyridine, the neutralizing base used in the reaction. As described
in the Experimental Section, after this time the solid-state portion
is dried, the reaction mixture is quenched, and the resultant solid
Figure 11. Portion of the 300 MHz 1H NMR spectra in acetone-d6 of
(a) 3, (b) 15, (c) 14, and (d) 3 after solid-state reaction with di-tert-
butylsilyl bis(trifluoromethanesulfonate).
1
is dissolved in deuterated acetone. The H NMR in the 4.0-
In Figure 10 we compare the Guinier camera powder pattern
of the solid-state samples. Figure 10a gives the original X-ray
pattern of unreacted 3‚AgOTf, Figure 10b corresponds to
solution prepared molecule 13 subsequently crystallized with
AgOTf, and Figure 10c shows the powder pattern of 3‚AgOTf
after reaction with tert-butyldimethylsilyl trifluoromethane-
sulfonate. It may be seen that the three powder patterns shown
here have the same general appearance. These results demon-
strate that the solid-state portion retains the same crystal structure
type during the 3‚AgOTf and silyl monotriflate reaction. Least-
5.0 ppm region of this dissolved material is shown in Figure 9.
While the major compound found in Figure 9 is the silyl ether
1
13, some unreacted 3 is also present based on the H NMR
data. The ratio of product to starting material is 4.5:1. Neither
prolonged reaction time (up to three weeks) nor the addition of
additional tert-butyldimethylsilyl trifluoromethanesulfonate to
the reaction changes this ratio. Presumably in the solid state,
there are alcohol sites which become inaccessible to attack by
the guest silyl monotriflate.

6880 J. Am. Chem. Soc., Vol. 122, No. 29, 2000
Kiang et al.
Figure 12. Organic molecules 14 and 15.
squares refinement of these data shows though some variation
in cell axis lengths. Between the three patterns, the a and b
axes vary by respectively 1.0 and 0.5 Å, values 15 to 20 times
greater than the standard deviations. These least-squares refine-
ments are given in the Supporting Information.
instead of the seven found in 3. As reported earlier,26 2‚AgOTf
also crystallizes in a honeycomb structure. While the solution
reaction of 2 and tert-butyldimethylsilyl trifluoromethane-
sulfonate is facile and occurs in quantitative yield to form
1
compound 12, by H NMR the solid-state reaction mixture of
2‚AgOTf and tert-butyldimethylsilyl trifluoromethanesulfonate
shows no sign of reaction after 5 days. Furthermore, as is
expected for a smaller molecule, 2 is generally more soluble
than 3. Were the previous reaction of 3‚AgOTf and tert-
butyldimethylsilyl trifluoromethanesulfonate to have occurred
by a dissolution, reaction, and subsequent recrystallization
mechanism, it would be reasonable to expect that 2‚AgOTf
would similarly react with the silyl monotriflate. That the
reaction does not occur suggests a crystalline property of 2‚
AgOTf is important. Recalling the initial sluggishness of the
reaction between 3‚AgOTf and the silyl monotriflate, it is
reasonable to suppose that in the more spatial constrained
channels of 2‚AgOTf, reaction might not occur at all.
The question remains as to whether the solid-state reaction
truly occurs in the solid sate or whether some portion of the
solid-state sample dissolves into solution, reacts with the silyl
monotriflate in solution, and then recrystallizes into the honey-
comb structure. The following point against this latter possibility.
The reaction itself takes place in a minimum of liquid. No extra
solvent is present, only the reactants themselves. Care was also
taken to prevent reaction during the quenching of the excess
silyl monotriflate. The quenching solvents, water and ethanol,
were chosen as 3‚AgOTf is quite insoluble in these media, the
solid product was subsequently dried under vacuum to pre-
remove as much silyl monotriflate as possible, and finally
ethanol and water are highly reactive with silyl monotriflate
and thus during quenching there is little time for a reaction
between 3 and silyl monotriflate to occur.
These results further exclude the possibility of the dissolution,
reaction, and subsequent recrystallization mechanism.
In this light, it is also of interest that we attempted the same
solid-state silylation reaction with 2 (see Figure 1), a smaller
phenylacetylene nitrile ligand with only four aromatic rings
Solid-State Dimerization of 3‚AgOTf and Di-tert-butylsilyl
Bis(trifluoromethanesulfonate). We now turn to the reaction
of 3 and 3‚AgOTf with the silyl di-triflate molecule, di-tert-

Phenylacetylene Nitrile SilVer Salts
J. Am. Chem. Soc., Vol. 122, No. 29, 2000 6881
Figure 14. (a) Observed and (b) calculated X-ray diffraction patterns
for 5‚AgOTf after solid-state reaction with di-tert-butylsilyl bis-
(trifluoromethanesulfonate).
Figure 13. (a) Observed and (b) calculated X-ray diffraction patterns
for 3‚AgOTf after solid-state reaction with di-tert-butylsilyl bis-
(trifluoromethanesulfonate).
butylsilyl bis(trifluoromethanesulfonate). The reaction is sub-
stantially the same as in the previous example. However, the
use of a di-triflate compound allows for two possible products,
the monomer with a single Si-O linkage and the dimer with
two 3 molecules linked to the same silicon atom. In Figure 11,
1
we show the H NMR signals for the hydrogen atoms of the
methylene sites. Figure 11a,b shows the data for the solution-
prepared monosubstituted and disubstituted compounds, respec-
tively 14 and 15 (see Figure 12), while Figure 11c shows the
pattern after the solid-state reaction of 3‚AgOTf with di-tert-
butylsilyl bis(trifluoromethanesulfonate). The results indicate
that the initial molecule 3‚AgOTf has completely reacted with
an approximate 3:2 product ratio of dimer to monomer.
In Figure 13 we see the powder pattern of the solid-state
portion of the reaction product. A comparison of Figures 3 and
13 shows that the overall crystal structure is maintained under
these reaction conditions. Nevertheless, there are several
substantial changes. In Figure 13 the major reflection s110 and
200 are much closer in d-spacing. It is not possible to separate
these two reflections from one another. The second pair of peaks,
the 020 and 301 found near 2θ ) 5.3° are similarly fused. This
change is reflected in the refined lattice constants. These lattice
constants a ) 59.1(1) Å and b ) 31.95(7) Å are significantly
different from those found for 3‚AgOTf. The a axis has
increased by 7 Å, while the b axis has shortened by 2 Å. This
a axis is reasonably close to the a axis of 59.5 Å found for the
equivalently sized 5‚AgOTf. It also corresponds quite closely
to the 60 Å length based on tabulated organic bond lengths. By
contrast, in going from reactant to product, the b axis is
shortened by 2 Å. These results suggest that vis-a´-vis the two-
dimensional projected crystal model, a rotation has occurred
where the a axis is the axis of rotation. This same rotation in a
Figure 15. SEC trace for 5‚AgOTf after solid-state reaction with di-
tert-butylsilyl bis(trifluoromethanesulfonate).
projected cell has been found in one of our previously studied
single-crystal structures.11
These results indicate a bulk property of the material has
changed during the reaction. The least-squares refinement data
are given in the Supporting Information and a calculated powder
pattern based on this refinement is also given in Figure 13.
Another change observed in the powder pattern is peak
broadening of the reflections. Were 3‚AgOTf and di-tert-
butylsilyl bis(trifluoromethanesulfonate) to have reacted in the
multistep process of dissolution, reaction in the solution phase,
and recrystallization, we would expect reasonably sharp reflec-
tions. The broadening of the peaks is suggestive that the reaction
is occurring in the solid state and as the conditions of the
reaction are not those of crystal annealing, damage to the crystal
and subsequent line broadening occurs.

6882 J. Am. Chem. Soc., Vol. 122, No. 29, 2000
Kiang et al.
Figure 16. X-ray diffraction patterns for polymerized 5‚AgOTf immersed in (a) boiling water, (b) t-BuOH, and (c) acetone and for unpolymerized
5‚AgOTf immersed in (d) boiling water, (e) t-BuOH, and (f) acetone.
Solid-State Polymerization of 5‚AgOTf and Di-tert-butyl-
silyl Bis(trifluoromethanesulfonate). This reaction was carried
out under substantially the same conditions as in the previous
two examples. However, a prolonged reaction time of three
weeks was needed to drive the reaction to completion. Unlike
the previous organic ligands, molecule 5 has three pendant
alcohol groups. The number of possible products after reaction
with the silyl ditriflate, di-tert-butylsilyl bis(trifluoromethane-
sulfonate), is therefore quite large, ranging from the monomer
of 3‚AgOTf in which two of the three side chains have joined
into one large macrocycle to oligomers and polymers of 5 with
a statistical distribution of oxygen-silicon-oxygen linkages.
The powder pattern of the reacted product is shown in Figure
14a. In comparing Figures 5 and 14a one sees significant
changes in the crystal structure have occurred. While in Figure
5 there were two dozen identifiable reflections corresponding
to a full three-dimensional cell, in Figure 14a no hkl (l * 0)
reflections can be found below 25°. The c axis superstructure
is therefore no longer observed. Even many of the hk0
reflections have broadened out and become indistinct. Besides
the main 110 and 200 reflections only four additional peaks
are found. The least-squares refinement in this refined data leads
to an a axis of 57.3(3) Å and a b axis of 33.76(6) Å. The a
lattice constant has changed by over 2 Å from the initial
crystalline material, while the b axis is more or less constant.
molecular weights Mw are respectively 6 × 104 and 7 × 104.
Polydispersities are calculated to be 12 and 16.
As the data in Figure 15 are plotted on a log scale, there is
considerably less monomer in the final product mixture than
the peak profiles suggest. To verify that the quantity of monomer
was low, we added to the product an additional amount of
monomer equal in weight to half of the original product and
then performed a size exclusion separation. These results are
shown in the Supporting Information. From these data we can
infer that the amount of monomer in the original reaction product
is by weight just two or three percent of the total reaction
product.
Finally, to verify that silver ions and silver-nitrogen bonds
did not alter our weight distribution profiles we also performed
a size exclusion separation on both pure 5 and 5‚AgOTf. These
samples showed only the original monomer peak.
Exchange Properties of Polymerized 5‚AgOTf. Our previ-
ous results indicate we have prepared microcrystalline materials
in which the original 5 molecules in the crystal are now linked
on the average to two of their neighbors. The interest in such a
material is that by the inclusion of these covalent bonds we
may have substantially improved the chemical stability of the
crystalline material. We therefore exposed both the polymerized
and original 5‚AgOTf to a variety of solvents which destroy
related honeycomb structures. Solvents studied include acetone,
t-BuOH, nitrobenzene, and boiling water. We also considered
the thermal stability of the polymerized honeycomb structure,
by heating a sample for a short time to 150 °C, a tempera-
ture just below the molecular decomposition temperature of
5‚AgOTf.
A few illustrative powder patterns are given in Figure 16.
The remaining are given in the Supporting Information. As a
comparison of Figures 14 and 16a-c shows, under these
conditions, overall crystallinity is retained in the polymerized
sample of 5‚AgOTf. By contrast as is seen in Figure 16d,e, both
t-BuOH and boiling water turn unpolymerized 5‚AgOTf into
An examination of the molecular weight of the reaction
product is instructive. In Figure 15 we show size exclusion
chromatography data of this product mixture. Monomer through
tetramer peaks are clearly visible. These first four peaks are
linearly spaced apart. The tetramer has an estimated molecular
weight of 7 × 103, in reasonable agreement with what would
be expected for a tetramer of molecule 5, coupled through
O-Si-O linkages and with all terminal hydroxy groups coupled
to silyl di-tert-butyl groups (MW 5.5-6.0 × 103). Both
fluorescence and refractive index measurements of sample
mass are in fair agreement. The calculated average weight

Phenylacetylene Nitrile SilVer Salts
J. Am. Chem. Soc., Vol. 122, No. 29, 2000 6883
amorphous solids with practically no discernible diffraction
peaks.
molecules) was prepared by heating the polymerized 5‚AgOTf
in a Thermal Gravimetric Analysis (TGA) furnace to 150 °C
for 10 min. This product was then exposed to two cycles of
first being exposed to toluene vapor and subsequently being
placed in a TGA furnace. The TGA data as well as the resultant
powder data are given in the Supporting Information. These
results indicate the polymerized material is still porous and
absorbs 12-13 wt % of toluene molecules. The powder patterns
of the final material show that the overall structure is retained,
albeit with a significant reduction in the crystalline particle size.
We further note that for the polymerized sample subjecting
the material to boiling water or t-BuOH actually improves the
overall crystallinity of the sample (compare Figures 14 and 16).
These relatively strong conditions apparently allow for the
annealing of the original polymerized crystals.
Finally in Figure 16c,f we show the powder patterns for both
the original 5‚AgOTf and polymerized 5‚AgOTf after contact
with acetone. For both samples, reasonably sharp powder
patterns are observed. The first peak of the polymerized
5‚AgOTf has a full width half-maximum (fwhm) value of 0.15°.
This fwhm value is fully the equal of any of the previously
discussed powder patterns. We can find a lower estimate of
particle size by assuming the entire line broadening is due to
particle size. The classic Guinier formula83 results in a minimum
particle length of 530 Å. As there is substantial broadening due
to both instrument factors and overlapping peak positions,
particle size is expected to be significantly greater.
Acknowledgment. This work was supported by the National
Science Foundation (Grant DMR-9812351). We thank Profes-
sors Geoffrey Coates and D. Venkataraman for advice and Dr.
Ivan Gistov for assistance in obtaining the SEC results. We also
thank Mr. Abhijit Basu Mallik for assistance in preparing
compounds 8-11.
Supporting Information Available: Tables and figures of
X-ray powder diffraction data, tables of atomic coordinates for
structure models of 3-5‚AgOTf, and SEC and TGA data (PDF).
This material is avaliable free of charge via the Internet at
http://pubs.acs.org.
As a final characterization of porosity, we performed the
vapor exchange experiments with toluene as described in the
Experimental Section. An apohost (a host without included guest
(83) Guinier, A. X-ray Diffraction in Crystals, Imperfect Crystals, and
Amorphous Bodies; Dover Publications: New York, 1994; p 143.
JA0009119