Assembly of organosilver(I) frameworks with terminal ethynide and ethenyl groups on separate pendent arms attached to an aromatic ring

Article abstract of DOI:10.1016/j.poly.2012.06.082

A series of eight silver(I) trifluoroacetate complexes based on aromatic ligands bearing terminal ethynyl and ethenyl groups on separate pendent arms has been synthesized. Single-crystal X-ray analysis of the complexes provided detailed information on the

Full text of DOI:10.1016/j.poly.2012.06.082

Polyhedron 52 (2013) 992–1008
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Polyhedron
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Assembly of organosilver(I) frameworks with terminal ethynide and ethenyl
groups on separate pendent arms attached to an aromatic ring
⇑
Sam C.K. Hau, Ping-Shing Cheng, Thomas C.W. Mak
Department of Chemistry, Center of Novel Functional Molecules, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong Special Administrative Region
a r t i c l e i n f o
a b s t r a c t
Article history:
Available online 26 July 2012
A series of eight silver(I) trifluoroacetate complexes based on aromatic ligands bearing terminal ethynyl
and ethenyl groups on separate pendent arms has been synthesized. Single-crystal X-ray analysis of the
complexes provided detailed information on the influence of argentophilicity, ligand disposition and ori-
entation, and the co-existence of three types of silver–carbon bonding (silver–ethynide, silver–ethenyl
Keywords:
Argentophilicity
Silver–ethenyl bonding
Silver–ethynide bonding
Silver–aromatic interaction
and silver–aromatic) in coordination network construction, as well as the roles played by weak
stacking and anion– interactions in supramolecular assembly.
p–p
p
Ó 2012 Elsevier Ltd. All rights reserved.
Anion–p interactions
p–p
Stacking
1. Introduction
tion of these two functional groups on the aromatic system, we aim
to investigate their combination with silver(I) trifluorocarboxylate
for the construction of new metal–organic frameworks (MOFs)
consolidated by silver(I)–ethynide plus silver(I)–olefin binding.
Herein, we report our synthetic and structural studies of a series
of eight silver(I) complexes of phenyl/naphthylethynide-based
ligands with an ethenyl group tethered to a pendent arm at
variable positions on the aromatic ring: AgL1ꢁ6AgCF3CO2ꢁ3H2O (1),
AgL2ꢁ7AgCF3CO2ꢁ2H2OꢁCH3CN (2), AgL3ꢁ6AgCF3CO2ꢁ5H2O (3), AgL3ꢁ
3AgCF3CO2ꢁH2OꢁCH3CN (4), AgL4ꢁ4AgCF3CO2ꢁH2O (5), AgL5ꢁ3AgCF3
CO2 (6), AgL6ꢁ6AgCF3CO2ꢁH2O (7), AgL7ꢁ7AgCF3CO2ꢁ4H2O (8)
(Scheme 1). On the basis of our previous experience, the reaction
of crude starting materials [AgL1]n (9), [AgL2]n (10), [AgL3]n (11),
[AgL4]n (12), [AgL5]n (13), [AgL6]n (14) and [AgL7]n (15) with
water-soluble silver salts is expected to generate MOFs stabilized
by argentophilic, silver(I)–ethynide and silver(I)–ethenyl interac-
tions, and the naphthyl or phenyl ring is potentially capable of
Metal–ethynyl complexes have caught much attention in recent
years owing to their structural diversity [1–3] and potential appli-
cations as precursors of nonlinear optical materials [4], lumines-
cence materials [5] and rigid-rod molecular wires [6]. Utilizing
appropriate metal–ligand supramolecular synthons, the designed
engineering of organometallic frameworks has come of age [7].
Our systematic studies on the syntheses and characterization of
silver(I) ethynide [8] complexes have led to the recognition and
demonstrated utility of two kinds of multinuclear supramolecular
synthons symbolized by Ar–C„CꢀAgn and Ar–OCH2C„CꢀAgn [9].
Making use of such rigid and flexible metal–ligand supramolecular
synthons in combination with various anionic and/or neutral
ancillary ligands, we have achieved the construction of a wide
variety of two- and three-dimensional silver(I) coordination net-
works exhibiting an interplay of argentophilicity, silver(I)–ethy-
nide, silver(I)–aromatic, hydrogen bonding,
p
–
p
and anion–
p
partaking in weaker silver–aromatic,
interactions.
p–p stacking and anion–p
interactions [9]. In addition, we have undertaken a systematic
study of bi-/tri-dentate phenylethynide [10] or heteroaromatic
ethynide silver(I) complexes [11].
As the ethenyl functional group –CH@CH2 is known to serve as a
2. Experimental
p-ligand site [12], our conceived idea is to investigate the coordi-
nation behavior of newly designed ligands HLn (n = 1–7) each hav-
ing ethynyl and ethenyl groups at the terminals of separate
pendent arms attached to two variable positions on an aromatic
skeleton (Scheme 1). By tuning the relative separation and orienta-
All reagents and solvents used were reagent grade. Further puri-
fication and drying followed the guidelines of Armarego [13] when
necessary. Organic solvents were concentrated under reduced
pressure on a rotary evaporator. Chromatographic purification of
the products was performed on Macherey Nagel Kieselgel 60 M
(230–400 mesh). Thin-layer chromatography (TLC) was conducted
on E. Merck silica gel 60 F254 (0.1 mm thickness) coated on
aluminum plates. Visualization of the developed chromatogram
⇑
Corresponding author.
E-mail address: tcwmak@cuhk.edu.hk (T.C.W. Mak).
0277-5387/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.poly.2012.06.082

S.C.K. Hau et al. / Polyhedron 52 (2013) 992–1008
993
2.1. Synthesis of ligands (HL1–HL7)
2.1.1. Synthesis of 2-(prop-2-ynyloxy)benzaldehyde
2-Hydroxybenzaldehyde (1.7 mL, 16.4 mmol) was dissolved in
acetone (40 mL) in a round bottom flask followed by the addition
of K2CO3 (4.5 g, 32.8 mmol) at 25 °C. After stirring for 10 min, prop-
argyl bromide solution (2.8 mL, 24.6 mmol) was injected. The reac-
tion mixture was then heated for reflux until TLC monitoring
indicated the disappearance of starting material. Followed by cool-
ing to room temperature, the mixture was filtered through a small
pad of silica gel and the pad was further washed with dichloro-
methane (3ꢂ 40 mL). The collected filtrate was concentrated and
purified by column chromatography (EtOAc/n-hexanes, 1:12).
The desired product was collected as white solids (2.5 g,
15.3 mmol). Yield: 93%; Rf = 0.5 (EtOAc/n-hexanes, 1:10); 1H NMR
(CDCl3, 400 MHz) d 2.57 (t, J = 2.4 Hz, 1H), 4.81 (d, J = 2.4 Hz, 2H),
7.04–7.11 (m, 2H), 7.53–7.57 (m, 1H), 7.84 (dd, J = 1.7, 7.7, 1H),
10.46 (s, 1H); 13C NMR (CDCl3, 100 MHz) d 56.5, 76.6, 77.8, 113.3,
121.8, 125.6, 128.6, 135.8, 159.8, 189.6; HRMS (ESI) m/z Calc. for
C
10H8O2 [M+H]+ 161.0597. Found: 161.0598.
2.1.2. Synthesis of 1-(prop-2-ynyloxy)-2-vinylbenzene (HL1)
As shown in Scheme 2, methyltriphenylphosphonium iodide
(3.0 g, 7.5 mmol) was added to a THF solution (15 mL) in a round
bottom flask. The white suspension was cooled to 0 °C in an ice
bath. After 5 min, tBuOK (806 mg, 7.2 mmol) was added to the mix-
ture to form yellow slurry. The mixture was stirred for another
30 min followed by the slow injection of a solution of 2-(prop-2-
ynyloxy)benzaldehyde (1.0 g, 6.3 mmol) in THF (5 mL). TLC moni-
toring indicated the completion of the reaction. The heterogeneous
mixture was diluted with diethyl ether and filtered through a pad
of silica gel, which was further washed with diethyl ether (40 mL).
The collected filtrate was concentrated and purified by column
chromatography (EtOAc/n-hexanes, 1:20) to give the desired prod-
uct as white powder (900 mg, 6.0 mmol). Yield: 96%; Rf = 0.4
(EtOAc/n-hexanes, 1:15); 1H NMR (CDCl3, 400 MHz) d 2.52 (t,
J = 2.4 Hz, 1H), 4.73 (d, J = 2.4 Hz, 2H), 5.27 (dd, J = 1.3, 11.2 Hz,
1H), 5.75 (dd, J = 1.4, 17.8 Hz, 1H), 6.98–7.11 (m, 3H), 7.23–7.27
(m, 1H), 7.51 (dd, J = 1.3, 7.8 Hz, 1H); 13C NMR (CDCl3, 100 MHz)
d 56.4, 75.6, 78.8, 112.8, 114.9, 121.8, 126.8, 127.6, 128.8, 131.5,
154.8.
Scheme 1. Ligands HL1–HL7 synthesized for the present study.
was performed by a spray of 5% w/v dodecamolybdophosphoric
acid in ethanol and subsequent heating. Melting points (uncor-
rected) were measured with a Reichert apparatus in degrees
Celsius. Nuclear magnetic resonance (NMR) spectra were recorded
with a Bruker ADVANCE-III NMR spectrometer at 400 MHz (1H)
and 100 MHz (13C). All NMR measurements were carried out at
room temperature in deuterated solution and were internally ref-
erenced to residual proton solvent signals (note: CDCl3 referenced
at d 7.26 in 1H, and d 77.16 for central line of the triplet in 13C).
Data for 1H NMR are reported as follows: chemical shift (d ppm),
multiplicity (s, singlet; d, doublet; t, triplet; brs, broad singlet;
dd, doublet of doublets; m, multiplet), integration, coupling
constant (Hz) and assignment. Mass spectrometry (MS) and high
resolution mass spectrometry (HRMS) measurements were made
on a ThermoFinnigan MAT 95XL instrument.
Scheme 2. Synthetic scheme for ligand HL1.
Scheme 3. Synthetic scheme for ligand HL4.

994
S.C.K. Hau et al. / Polyhedron 52 (2013) 992–1008
Table 1
Crystallography data and structure refinement parameters of complex 1–8.
Complex
1
2
3
4
Structural formula
Formula weight
Crystal system
Space group
a (Å)
C
23H15Ag7F18O16
C27H16Ag8F21NO17
1888.32
C23H19Ag7F18O18
1680.43
C19H14Ag4F9NO8
986.77
1644.40
triclinic
triclinic
triclinic
triclinic
ꢀ
ꢀ
ꢀ
ꢀ
P1 (No. 2)
P1 (No. 2)
P1 (No. 2)
P1 (No. 2)
12.583(6)
13.233(6)
13.396(6)
76.965(1)
78.434(1)
64.796(1)
1952.6(1)
2
2.797
3.589
0.0248
0.0637
11.458(6)
13.707(8)
17.101(9)
71.392(1)
75.057(1)
66.680(1)
2310.8(2)
2
2.714
3.467
0.0249
0.0632
13.091(6)
13.528(6)
14.144(6)
97.664(1)
106.305(1)
116.085(1)
2061.3(16)
2
2.708
3.406
0.0408
0.1157
9.987(4)
11.554(5)
13.113(9)
103.869(1)
101.074(1)
107.193(1)
1346.0(12)
2
2.435
2.973
0.0292
0.0746
b (Å)
c (Å)
a
(°)
b (°)
c
(°)
V (Å3)
Z
qc (g cmꢃ3
)
l
(mmꢃ1
)
r
a
R1 (I > 2
wR2 (all data)
)
b
Goodness-of-fit (GOF) on F2
1.097
1.033
1.055
1.037
5
6
7
8
Structural formula
Formula weight
Crystal system
Space group
a (Å)
C24H15Ag5F12O11
1246.69
C22H13Ag4F9O8
1007.79
monoclinic
P2/n (No. 13)c
14.551(1)
12.076(1)
15.220(1)
90
105.959(2)
90
2571.5(5)
4
C28H15Ag7F18O15
1688.46
C30H21Ag8F21O20
1963.40
triclinic
triclinic
triclinic
ꢀ
ꢀ
ꢀ
P1 (No. 2)
P1 (No. 2)
P1 (No. 2)
10.486(7)
10.969(8)
13.574(9)
83.833(1)
82.421(1)
77.626(1)
1506.8(1)
2
2.748
3.326
0.0230
0.0576
13.516(6)
13.829(6)
14.144(6)
82.156(1)
69.040(1)
71.419(1)
2339.4(1)
2
2.397
2.998
0.0408
0.1090
12.494(7)
12.763(7)
17.126(9)
81.747(1)
89.677(1)
69.244(1)
2524.5(2)
2
2.583
3.185
0.0760
0.2417
b (Å)
c (Å)
a
(°)
b (°)
c
(°)
V (Å3)
Z
qc (g cmꢃ3
)
2.603
3.115
0.0368
0.0875
l
(mmꢃ1
)
r
a
R1 (I > 2
wR2 (all data)
)
b
Goodness-of-fit (GOF) on F2
1.094
1.110
1.080
1.049
P
P
a
b
c
R1
=
||Fo| ꢃ |Fc||/ |Fo|.
P
P
2
2
1=2
wR2 ¼ f ½wðF2o ꢃ Fc2Þ ꢄ= ½wðF2oÞ ꢄg
.
Space group P2/n is equivalent to standard P2/b by an axial transformation.
2.1.3. Synthesis of 3-(prop-2-ynyloxy)benzaldehyde
5.5 mmol) at 25 °C. After stirring for 10 min, allyl bromide
(475 L, 5.5 mmol) was added dropwise to the solution mixture.
The mixture was allowed to stir for an overnight. TLC indicated
the disappearance of the starting material. The mixture was then
filtered through a small pad of silica gel, which was further washed
3-(Prop-2-ynyloxy)benzaldehyde was prepared from 3-hydro-
xybenzaldehyde (2.0 g, 16.4 mmol) according to the synthetic
procedures for 2-(prop-2-ynyloxy)benzaldehyde and purified as
colorless oil (2.3 g, 14.3 mmol). Yield: 87%; Rf = 0.5 (EtOAc/n-hex-
anes, 1:15); 1H NMR (CDCl3, 400 MHz) d 2.55 (t, J = 2.2 Hz, 1H),
4.76 (d, J = 2.1 Hz, 2H), 7.25 (d, J = 1.0 Hz, 1H), 7.46–7.53 (m, 3H),
9.98 (s, 1H); 13C NMR (CDCl3, 100 MHz) d 56.1, 76.3, 78.0, 113.6,
122.3, 124.3, 130.3, 137.9, 158.2, 192.1; HRMS (ESI) m/z Calc. for
l
C
10H8O2 [M+H]+ 161.0597. Found: 161.0595.
2.1.4. Synthesis of 1-(prop-2-ynyloxy)-3-vinylbenzene (HL2)
HL2 was prepared from 3-(prop-2-ynyloxy)benzaldehyde
(1.0 g, 6.25 mmol) as the preparation of 1-(prop-2-ynyloxy)-2-
vinylbenzene and purified as white solids (808 mg, 5.11 mmol).
Yield: 82%; Rf = 0.4 (DCM/n-hexanes, 1:3); 1H NMR (CDCl3,
400 MHz) d 2.53 (t, J = 2.4 Hz, 1H), 4.71 (d, J = 2.4 Hz, 2H), 5.27
(d, J = 10.8 Hz, 1H), 5.75 (dd, J = 0.6, 17.6 Hz, 1H), 6.66–6.73 (m,
1H), 6.88–6.90 (m, 1H), 7.03–7.07 (m, 2H), 7.24–7.28 (m, 1H);
13C NMR (CDCl3, 100 MHz) d 56.0, 75.7, 78.7, 112.8, 114.4, 114.5,
119.9, 129.7, 136.7, 139.3, 157.9.
2.1.5. Synthesis of 1-(prop-2-ynyloxy)-4-vinylbenzene (HL3)
HL3 was prepared according to literature procedures [14].
Fig. 1. Coordination environment of the silver(I) atoms in the double salt
AgL1ꢁ6AgCF3CO2ꢁ3H2O (1). The argentophilic Agꢁ ꢁ ꢁAg distances shown as thick
rods lie in the range 2.70–3.40 Å, and the hydrogen atoms and fluorine atoms are
omitted for clarity. Silver atoms are drawn as thermal ellipsoids (50% probability
level) with atom labeling. Color scheme: dark gray, silver atoms; gray, oxygen
atoms; broken line, Ag–C bond.
2.1.6. Synthesis of 7-(allyloxy)naphthalen-2-ol
2,7-Dihydroxynaphthalene (800 mg, 5.0 mmol) was dissolved
in acetone (15 mL) followed by the addition of K2CO3 (759 mg,

S.C.K. Hau et al. / Polyhedron 52 (2013) 992–1008
995
Fig. 2. (a) Perspective view of the crystal packing in 1 viewed from the direction of the a-axis, showing all notable H-bond between water molecules and trifluoroacetate
ligands, Symmetry code: A: 1 ꢃ x, 1 ꢃ y, 2 ꢃ z; B: 1 ꢃ x, 2 ꢃ y, 2 ꢃ z; (b) perspective view of crystal packing of 1 from the direction of the c-axis, indicating the additional H-
bonds (O3WBꢁ ꢁ ꢁO9A) within metal–organic layers, which lead to the formation of a 3D supramolecular structure. (b) Perspective view of the crystal packing viewed from the
direction of the c-axis. Symmetry code: A: x, y, 1 + z; B: ꢃx, 2 ꢃ y, 2 ꢃ z; C: 1 ꢃ x, 1 ꢃ y, 2 ꢃ z; D: x, ꢃ1 + y, z. The hydrogen atoms and fluorine atoms are omitted for clarity.
Color scheme: dark gray, silver atoms; gray, oxygen atoms; black ball and stick, C„C bond; bold black line, C@C bond; black broken line, Ag–C bond; gray broken line, H-bond
interactions.
with dichloromethane. After that, the collected filtrate was
concentrated and purified by column chromatography to give the
product as colorless oil (346 mg, 1.7 mmol). Yield: 34%; Rf = 0.5
(EtOAc/n-hexanes, 1:6); 1H NMR (CDCl3, 400 MHz) d 4.63 (d,
J = 5.3 Hz, 2H), 5.13 (brs, 1H), 5.32 (dd, J = 0.9, 10.5 Hz, 1H), 5.47
(dd, J = 1.3, 17.3 Hz, 1H), 6.07–6.17 (m, 1H), 6.94 (dd, J = 2.4,
8.8 Hz, 1H), 6.98–7.04 (m, 3H), 7.66 (d, J = 8.8 Hz, 2H); 13C NMR
(CDCl3, 100 MHz) d 68.9, 106.0, 108.9, 115.4, 116.7, 118.0, 124.5,
129.4, 129.7, 133.3, 136.0, 154.1, 157.3; HRMS (ESI) m/z Calc. for
2.1.7. Synthesis of 2-(allyloxy)-7-(prop-2-ynyloxy)naphthalene (HL4)
7-(Allyloxy)naphthalen-2-ol (346 mg, 1.7 mmol) was dissolved
in acetone (5 mL) followed by the addition of K2CO3 (287 mg,
2.1 mmol) at 25 °C (Scheme 3). After stirring for 15 min, propar-
gyl bromide (233 lL, 2.1 mmol) was injected slowly to the solu-
tion mixture. The mixture was then heated to reflux until TLC
monitoring indicated the disappearance of the starting material.
The mixture was cooled to room temperature and filtered
through a small pad of silica gel. The collected filtrate was con-
centrated and purified by column chromatography to give the
C
13H12O2 [M+H]+ 201.0910. Found: 201.0913.

996
S.C.K. Hau et al. / Polyhedron 52 (2013) 992–1008
117.9, 124.8, 129.3, 129.4, 133.3, 135.7, 156.2, 157.3;
HRMS (ESI) m/z Calc. for C16H14O2 [M+H]+ 239.1067. Found:
239.1068.
2.1.8. Synthesis of 6-(allyloxy)naphthalen-2-ol
6-(Allyloxy)naphthalen-2-ol was prepared from 2,6-dihydroxy-
naphthalene (500 mg, 3.1 mmol) according to the synthetic proce-
dures for 7-(allyloxy)naphthalene-2-ol and purified as colorless oil
(272 mg, 1.4 mmol). Yield: 45%; Rf = 0.4 (EtOAc/n-hexanes, 1:3); 1H
NMR (CDCl3, 400 MHz) d 4.63 (d, J = 5.3 Hz, 2H), 4.90 (brs, 1H), 5.32
(dd, J = 1.3, 10.5 Hz, 1H), 5.47 (dd, J = 1.5, 17.3 Hz, 1H), 6.07–6.17
(m, 1H), 7.06–7.17 (m, 4H), 7.61 (dd, J = 9.0, 15.7 Hz, 2H); 13C
NMR (CDCl3, 100 MHz) d 69.1, 107.5, 109.8, 117.9, 118.2, 119.7,
127.9, 128.6, 129.8, 130.1, 133.5, 152.0, 155.2.
2.1.9. Synthesis of 2-(allyloxy)-6-(prop-2-ynyloxy)naphthalene (HL5)
HL5 was prepared from 6-(allyloxy)naphthalen-2-ol (272 mg,
1.4 mmol) as the preparation of 2-(Allyloxy)-7-(prop-2-ynyl-
oxy)naphthalene and purified as white solids (257 mg, 1.1 mmol).
Yield: 79%; Rf = 0.7 (EtOAc/n-hexanes, 1:6); 1H NMR (CDCl3,
400 MHz) d 2.55 (t, J = 2.3 Hz, 1H), 4.63 (d, J = 5.2 Hz, 2H), 4.79
(d, J = 2.3 Hz, 2H), 5.32 (d, J = 10.5 Hz, 1H), 5.47 (dd, J = 1.2,
17.3 Hz, 1H), 6.08–6.17 (m, 1H), 7.11 (d, J = 2.2 Hz, 1H), 7.16–7.21
(m, 3H), 7.66 (dd, J = 6.2, 8.8 Hz, 2H); 13C NMR (CDCl3, 100 MHz)
d 56.1, 69.0, 75.7, 78.8, 107.4, 108.0, 117.9, 119.2, 119.5, 128.4,
128.5, 129.7, 130.3, 133.4, 154.2, 155.5; HRMS (ESI) m/z Calc. for
Fig. 3. Perspective view of the coordination geometry in the silver double salt
AgL2ꢁ7AgCF3CO2ꢁ2H2OꢁCH3CN (2). The argentophilic Agꢁ ꢁ ꢁAg distances shown as
thick rods lie in the range 2.70–3.40 Å, and the hydrogen atoms and fluorine atoms
are omitted for clarity. Silver atoms are drawn as thermal ellipsoids (50%
probability level) with atom labeling. Symmetry code: ꢃ1 ꢃ x, ꢃy, ꢃ1 ꢃ z. Color
scheme: dark gray, silver atoms; gray, oxygen atoms, broken line, Ag–C bond.
C
16H14O2 [M+H]+ 239.1067. Found: 239.1064.
2.1.10. Synthesis of 3-(allyloxy)naphthalen-2-ol
3-(Allyloxy)naphthalen-2-ol was prepared from 2,3-dihydroxy-
naphthalene (2.0 g, 12.5 mmol) according to the synthetic proce-
dures for 7-(allyloxy)naphthalene-2-ol and purified as colorless
oil (1.8 g, 9.1 mmol). Yield: 72%; Rf = 0.5 (EtOAc/n-hexanes, 1:3);
1H NMR (CDCl3, 400 MHz) d 4.74 (dt, J = 1.3, 5.5 Hz, 2H), 5.38 (dd,
J = 1.2, 10.5 Hz, 1H), 5.48 (dq, J = 1.4, 17.2 Hz, 1H), 5.96 (brs, 1H),
6.09–6.19 (m, 1H), 7.13 (s, 1H), 7.28 (s, 1H), 7.29–7.36 (m, 2H),
7.66 (dd, J = 1.6, 4.6 Hz, 2H); 13C NMR (CDCl3, 100 MHz) d 69.8,
desired product as white solids (294 mg, 1.2 mmol). Yield: 71%;
Rf = 0.6 (EtOAc/n-hexanes, 1:8); 1H NMR (CDCl3, 400 MHz) d
2.57 (t, J = 2.3 Hz, 1H), 4.65 (dd, J = 1.3, 4.0 Hz, 2H), 4.80 (d,
J = 2.4 Hz, 2H), 5.34 (dd, J = 1.3, 10.5 Hz, 1H), 5.48 (dd, J = 1.5,
17.2 Hz, 1H), 6.09–6.19 (m, 1H), 7.04–7.08 (m, 3H), 7.15 (d,
J = 2.4 Hz, 1H), 7.68 (dd, J = 2.6, 8.8 Hz, 2H); 13C NMR (CDCl3,
100 MHz) d 55.9, 68.9, 75.7, 78.7, 106.7, 107.0, 116.3, 116.9,
Fig. 4. Perspective view of the centrosymmetric silver–organic cycle in the crystal structure of 2, showing that it is further stabilized by the existence of H-bonds between
water molecules and trifluoroacetate ligands (O1Wꢁ ꢁ ꢁO6A and O1Wꢁ ꢁ ꢁO12A), as well as the significant anion– interaction. Symmetry code: A: ꢃ1 ꢃ x, ꢃy, ꢃ1 ꢃ z. The
hydrogen atoms and fluorine atoms are omitted for clarity. Color scheme: dark gray, silver atoms; gray, oxygen atoms; black ball and stick, C„C bond; bold black line, C@C
bond; black broken line, Ag–C bond; gray broken line, H-bond interactions; light gray broken line, anion– interactions.
p
p

S.C.K. Hau et al. / Polyhedron 52 (2013) 992–1008
997
107.1, 109.7, 118.9, 124.0, 124.5, 126.5, 126.6, 129.0, 129.9, 132.5,
145.9, 146.4; HRMS (ESI) m/z Calc. for C13H12O2 [M+H]+ 201.0910.
Found: 201.0910.
17.3 Hz, 1H), 6.12–6.22 (m, 1H), 7.17 (s, 1H), 7.32–7.38 (m, 3H),
7.67–7.73 (m, 2H); 13C NMR (CDCl3, 100 MHz) d 56.7, 69.7, 76.2,
78.5, 108.6, 109.6, 118.3, 124.4, 124.7, 126.5, 126.7, 129.1, 129.8,
133.1, 147.6, 148.8; HRMS (ESI) m/z Calc. for C16H14O2 [M+Na]+
261.0886. Found: 261.0886.
2.1.11. Synthesis of 2-(allyloxy)-3-(prop-2-ynyloxy)naphthalene (HL6)
HL6 was prepared from 3-(allyloxy)naphthalen-2-ol (1.8 g,
9.1 mmol) as the preparation of 2-(Allyloxy)-7-(prop-2-ynyl-
oxy)naphthalene and purified as white solids (1.9, 7.9 mmol).
Yield: 87%; Rf = 0.4 (EtOAc/n-hexanes, 1:20); 1H NMR (CDCl3,
400 MHz) d 2.55 (t, J = 2.3 Hz, 1H), 4.73 (d, J = 5.4 Hz, 2H), 4.89
(d, J = 2.3 Hz, 2H), 5.35 (dd, J = 1.0, 10.5 Hz, 1H), 5.49 (dd, J = 1.3,
2.1.12. Synthesis of 5-(allyloxy)naphthalen-1-ol
5-(Allyloxy)naphthalen-1-ol was prepared from 1,5-dihydroxy-
naphthalene (2.0 g, 12.5 mmol) according to the synthetic proce-
dures for 7-(allyloxy)naphthalene-2-ol and purified as yellowish
oil (638 mg, 3.21 mmol). Yield: 26%; Rf = 0.3 (EtOAc/n-hexanes,
Fig. 5. (a) Perspective view of the grid-like metal–organic network layer structure in 2. The zigzag infinite silver chains are separated into two groups labeled in gray and light
gray color, respectively. Symmetry code: A: x, y, z; B: x, y, 1 + z. (b) Perspective view of the crystal packing along the a-axis, indicating the additional H-bonds (C27–
H27Aꢁ ꢁ ꢁO2A) and off-set
1 + x, 1 + y, z; B: ꢃx, 1 ꢃ y, 1 ꢃ z. The hydrogen atoms and fluorine atoms are omitted for clarity. Color scheme: dark gray, silver atoms; gray, oxygen atoms; black ball and
stick, C„C bond; bold black line, C@C bond; black broken line, Ag–C bond; gray broken line, H-bond interactions; light gray broken line, stacking interactions.
p–p stacking interaction within metal–organic layers, which lead to the formation of the supramolecular network structure. Symmetry code: A:
p–p

998
S.C.K. Hau et al. / Polyhedron 52 (2013) 992–1008
127.0, 133.4, 153.3, 154.2; HRMS (ESI) m/z Calc. for C16H14O2
[M+H]+ 239.1067. Found: 239.1066.
2.2. Preparation of polymeric silver ethynides as synthetic precursors
Caution: Silver ethynides are potentially explosive and should
be handled in small amounts with extreme care!
Ligand HL1 (1 mmol) was first dissolved in acetonitrile (10 mL).
Silver nitrate (1 mmol) and triethylamine (1 mmol) were added
subsequently with vigorous stirring, and the mixture was allowed
to stir for 2 h in darkness. The resulted pale yellow slurry was di-
luted with methanol (20 mL) and filtered by suction filtration to
collection a pale yellow precipitate of polymeric [AgL1]n (9), which
was washed thoroughly with methanol (3ꢂ 10 mL) and then stored
in wet form at ꢃ10 °C in a refrigerator. Silver complexes of HL2–
HL7 were prepared in the same manner, the yields and infra-red
absorption data are displayed below:
[AgL1]n (9) yield: 95%; IR:
m
2054 cmꢃ1 (w,
m
C„C).
Fig. 6. Perspective view of the coordination geometry in the silver double salt
AgL3ꢁ6AgCF3CO2ꢁ5H2O (3). The argentophilic Agꢁ ꢁ ꢁAg distances shown as thick rods
lie in the range 2.70–3.40 Å, and the hydrogen atoms and fluorine atoms are
omitted for clarity. Silver atom Ag4 exhibits twofold positional disorder, and only
that the atom position with a higher occupancy (51%) is shown. Silver atoms are
represented as thermal ellipsoids (30% probability level) with atom labeling.
Symmetry code: A: ꢃx, ꢃy, 1 ꢃ z. Color scheme: dark gray, silver atoms; gray,
oxygen atoms; broken line, Ag–C bond.
[AgL2]n (10) yield: 93%; IR:
[AgL3]n (11) yield: 85%; IR:
[AgL4]n (12) yield: 91%; IR:
[AgL5]n (13) yield: 90%; IR:
[AgL6]n (14) yield: 88%; IR:
[AgL7]n (15) yield: 83%; IR:
m
m
m
m
m
m
2052 cmꢃ1 (w,
2045 cmꢃ1 (w,
2038 cmꢃ1 (w,
2046 cmꢃ1 (w,
2006 cmꢃ1 (w,
2045 cmꢃ1 (w,
m
m
m
m
m
m
C„C).
C„C).
C„C).
C„C).
C„C).
C„C).
1:5); 1H NMR (CDCl3, 400 MHz) d 4.72 (d, J = 5.1 Hz, 2H), 5.37 (d,
J = 10.5 Hz, 1H), 5.55 (dd, J = 1.0, 16.8 Hz, 1H), 6.15–6.25 (m, 2H),
6.84–6.87 (m, 2H), 7.32 (t, J = 8 Hz, 1H), 7.39 (t, J = 8.1 Hz, 1H),
7.82 (d, J = 8.4 Hz, 1H), 7.95 (d, J = 8.5 Hz, 1H); 13C NMR (CDCl3,
100 MHz) d 69.1, 105.9, 109.6, 114.1, 114.7, 117.5, 125.2, 125.3,
125.6, 127.2, 133.4, 151.4, 154.3; HRMS (ESI) m/z Calc. for
2.3. Synthesis of silver ethynide complexes
2.3.1. Synthesis of AgL1ꢁ6AgCF3CO2ꢁ3H2O (1)
AgCF3CO2 (440 mg, 2 mmol) and AgBF4 (38 mg, 0.2 mmol) were
dissolved in a mixed solution of methanol (1 mL) and deionized
water (0.1 mL). Complex 9 (16 mg) was then added to the solution
mixture with stirring until all the solids were dissolved. After that,
the solution was filtered and left to stand in the dark at room tem-
perature. After several days, colorless block crystals of 1 were
deposited in about 60% yield. Anal. Calc. for C23H15Ag7F18O16: C,
C
13H12O2 [M+H]+ 201.0910. Found: 201.0912.
2.1.13. Synthesis of 5-(allyloxy)-1-(prop-2-ynyloxy)naphthalene
(HL7)
16.80; H, 0.92. Found: C, 16.92; H, 1.06%; IR:
m mC„C).
2026 cmꢃ1 (w,
HL7 was prepared from 5-(allyloxy)naphthalen-1-ol (638 mg,
3.21 mmol) as the preparation of 2-(allyloxy)-7-(prop-2-ynyl-
oxy)naphthalene and purified as yellowish oil (600 mg,
2.53 mmol). Yield: 79%; Rf = 0.6 (EtOAc/n-hexanes, 1:15); 1H NMR
(CDCl3, 400 MHz) d 2.55 (t, J = 2.3 Hz, 1H), 4.71 (d, J = 5.1 Hz, 2H),
4.89 (d, J = 2.3 Hz, 2H), 5.34 (dd, J = 1.3, 10.6 Hz, 1H), 5.53 (dd,
J = 1.5, 17.3 Hz, 1H), 6.13–6.23 (m, 1H), 6.86 (d, J = 7.6 Hz, 1H),
6.98 (d, J = 7.6 Hz, 1H), 7.36–7.41 (m, 2H), 7.86 (d, J = 8.5 Hz, 1H),
7.96 (d, J = 8.5 Hz, 1H); 13C NMR (CDCl3, 100 MHz) d 56.3, 69.1,
75.7, 78.8, 106.0, 106.4, 114.5, 115.5, 117.5, 125.0, 125.5, 126.9,
2.3.2. Synthesis of AgL2ꢁ7AgCF3CO2ꢁ2H2OꢁCH3CN (2)
AgCF3CO2 (440 mg, 2 mmol) and AgBF4 (76 mg, 0.4 mmol) were
dissolved in a mixed solution of methanol (1 mL) and deionized
water (0.2 mL). Complex 10 (11 mg) was then added to the solu-
tion mixture with stirring until all the solids were dissolved. After
that, the solution was filtered and left to stand in the dark at room
temperature. After several days, colorless block crystals of 2 were
deposited in about 53% yield. Anal. Calc. for C27H16Ag8F21NO17: C,
Fig. 7. Perspective view of the silver–organic cycle in 3 with an inversion center between Ag2 and Ag2A. Symmetry code: A: ꢃx, ꢃy, 1 ꢃ z. Color scheme: dark gray, silver
atoms; gray, oxygen atoms; black ball and stick, C„C bond; bold black line, C@C bond; black broken line, Ag–C bond; gray broken line, H-bond interactions; light gray broken
line, anion–p interactions.

S.C.K. Hau et al. / Polyhedron 52 (2013) 992–1008
999
17.17; H, 0.85; N, 0.74. Found: C, 17.15; H, 1.14; N, 0.58%. IR:
m
2.3.5. Synthesis of AgL4ꢁ4AgCF3CO2ꢁH2O (5)
2040 cmꢃ1 (w,
mC„C). (Powder of complex 10 prepared may contain
AgCF3CO2 (440 mg, 2 mmol) were dissolved in a mixed solution
of methanol (1 mL) and deionized water (0.5 mL). Complex 12
(15 mg) was then added to the solution mixture with stirring until
all the solids were dissolved. After that, the solution was filtered
and left to stand in the dark at room temperature. After several
days, colorless block crystals of 5 were deposited in about 54%
yield. Anal. Calc. for C24H15Ag5F12O11: C, 21.44; H, 0.37. Found: C,
some acetonitrile as contaminates.)
2.3.3. Synthesis of AgL3ꢁ6AgCF3CO2ꢁ5H2O (3)
AgCF3CO2 (440 mg, 2 mmol) and AgBF4 (382 mg, 2 mmol) were
dissolved in deionized water (1 mL). Complex 11 (40 mg) was then
added to the solution mixture with stirring until all the solids were
dissolved. After that, the solution was filtered and stored at ꢃ10 °C
in a refrigerator. After several days, colorless block crystals of 3
21.65; H, 0.61%. IR:
m mC„C).
2039 cmꢃ1 (w,
2.3.6. Synthesis of AgL5ꢁ3AgCF3CO2 (6)
were deposited in about 60% yield. Anal. Calc. for C23H19Ag7F18O18
C, 16.44; H, 1.14. Found: C, 16.60; H, 0.92%. IR:
2016 cmꢃ1 (w,
C„C).
:
AgCF3CO2 (220 mg, 1 mmol) were dissolved in deionized water
(1 mL). Complex 13 (8 mg) was then added to the solution mixture
with stirring until all the solids were dissolved. After that, the solu-
tion was filtered and left to stand in the dark at room temperature.
After several days, colorless block crystals of 6 were deposited in
about 23% yield. Anal. Calc. for C22H13Ag4F9O8: C, 23.90; H, 0.27%.
m
m
2.3.4. Synthesis of AgL336AgCF3CO2ꢁH2OꢁCH3CN (4)
AgCF3CO2 (440 mg, 2 mmol) and AgBF4 (382 mg, 2 mmol) were
dissolved in a mixed solution of acetonitrile (0.2 mL) and deionized
water (1 mL). Complex 11 (40 mg) was then added to the solution
mixture with stirring until all the solids were dissolved. After that,
the solution was filtered and stored at ꢃ10 °C in a refrigerator.
After several days, colorless block crystals of 4 were deposited in
about 80% yield. Anal. Calc. for C19H14Ag4F9NO8: C, 23.13; H,
Found: C, 24.21; H, 0.34%. IR:
m mC„C).
2043 cmꢃ1 (w,
2.3.7. Synthesis of AgL6ꢁ6AgCF3CO2ꢁH2O (7)
AgCF3CO2 (440 mg, 2 mmol) were dissolved in a mixed solution
of methanol (3 mL) and deionized water (0.5 mL). Complex 14
(12 mg) was then added to the solution mixture with stirring until
all the solids were dissolved. After that, the solution was filtered
and left to stand in the dark at room temperature. After several
1.43; N, 1.42. Found: C, 23.28; H, 1.71; N, 1.65%. IR:
(w, C„C).
m
2039 cmꢃ1
m
Fig. 8. (a) Perspective view of a portion of the grid-like metal–organic layer structure in the crystal packing of 3, showing notable H-bonds. Symmetry code: A: ꢃx, ꢃy, ꢃz; B:
stacking
ꢃx, ꢃ1 ꢃ y, ꢃz. (b) Perspective view of the crystal packing of 3 from the direction of the c-axis, indicating the additional H-bond (O3Wꢁ ꢁ ꢁO7A) and aromatic
p–p
interaction within metal–organic layers. Symmetry code: A: 1 ꢃ x, ꢃy, 1ꢃz. The hydrogen atoms and fluorine atoms are omitted for clarity. Color scheme: dark gray, silver
atoms; gray, oxygen atoms; black ball and stick, C„C bond; bold black line, C@C bond; black broken line, Ag–C bond; gray broken line, H-bond interactions; light gray broken
line, p–p stacking interaction.

1000
S.C.K. Hau et al. / Polyhedron 52 (2013) 992–1008
days, colorless block crystals of 7 were deposited in about 64%
yield. Anal. Calc. for C28H15Ag7F18O15: C, 19.92; H, 0.90. Found: C,
this Ag5 segment through five trifluoroacetate groups, O2^O3,
O6^O7, O8^O9, O10^O11 and O12^O13 via the l4
2 and l4 2 modes, respectively. Carbon
–
g2 g2
, , l2–
20.15; H, 1.05%. IR:
m
2035 cmꢃ1 (w,
m
C„C).
g1
,
g1
,
l3–
g1
,
g2
,
l3–
g1
,g
– ,g
g2
atom C5 of the phenyl ring is attached to Ag2 at a bond distance of
2.815(4) Å, which is indicative of significant silver–aromatic
interaction (under 2.9 Å) [19–24]. Furthermore, silver atom Ag6
is coordinated by the vinyl group in the g2 mode with a bond
length of 2.218(3) Å, which indicates a strong silver–ethenyl inter-
action (under 2.7 Å) [7a,25–31]. All three independent water mol-
ecules are coordinated to this segment in the l1 mode.
2.3.8. Synthesis of AgL7ꢁ7AgCF3CO2ꢁ4H2O (8)
AgCF3CO2 (440 mg, 2 mmol) and AgBF4 (382 mg, 2 mmol) were
dissolved in deionized water (1 mL). Complex 15 (15 mg) was then
added to the solution mixture with stirring until all the solids were
dissolved. After that, the solution was filtered and left to stand in
the dark at room temperature. After several days, colorless block
crystals of 8 were deposited in about 35% yield. Anal. Calc. for
The Ag5 segments are linked together by two pairs of inver-
sion-related trifluoroacetate groups (O2^O3 and O12^O13) in
C
30H21Ag8F21O20: C, 18.35; H, 1.08. Found: C, 18.55; H, 1.33%. IR:
l4– ,g
g2 2–CF3CO2)2 mode to form an infinite zigzag chain along
m
2135 cmꢃ1 (w,
m
C„C).
(
the c-axis (Fig. 2a; also see Fig. S1 in Supplementary Information).
Adjacent silver(I) chains are further cross-bridged by the external
2.4. X-ray crystallography
silver atoms (Ag7 and Ag7A) and trifluoroacetate groups [l2
–
(O6^O7) and 2–(O6A^O7A)] to give a two-dimensional coordina-
l
Selected crystals were used for data collection on a Bruker AXS
Kappa ApexII Duo diffractometer at 123 K (1 and 2), at 150 K (5), at
173 K (6 and 7), and at 293 K (3, 4 and 8) using frames of oscillation
range 0.3°, with 2° < h < 28°. An empirical absorption correction
was applied using the SADABS program [15]. The structures were
solved by the direct method and refined by full-matrix least-
squares on F2 using the SHELXTL program package [16]. The crystal-
lographic data are summarized in Table 1.
tion network parallel to the bc plane, which is stabilized by hydro-
gen bonds (O1Wꢁ ꢁ ꢁO6, 2.801(3) Å; O2Wꢁ ꢁ ꢁO7, 2.915(3) Å;
O1Wꢁ ꢁ ꢁO4B, 2.867(4) Å). Such metal–organic layers are further
associated together through formation of additional hydrogen
bonding (O3WBꢁ ꢁ ꢁO9A, 2.771(4) Å) to form a 3D supramolecular
structure (Fig. 2b).
3.2.2. AgL2ꢁ7AgCF3CO2ꢁ2H2OꢁCH3CN (2)
In the crystal structure of 2, 3-(2-vinylphenoxy)propynide also
adopts a non-planar conformation, in which the torsion angles
C5–C4–O1–C3 and C4–O1–C3–C2 are 123.1(4)° and ꢃ67.2(4)°,
respectively (Fig. 3). The vinyl group is twisted out of the plane
of the phenyl ring, the torsion angle C7–C8–C10–C11 being
23.5(6)°. As shown in Fig. 3, the ethynide group (C1„C2) is bound
3. Results
3.1. Crystallization
The neutral ligands HL1–HL7 were synthesized from the
respective reactions using the corresponding hydroxybenzalde-
hyde and dihydoxynaphthalene as starting materials. Double salts
1–8 were obtained from room-temperature crystallization of the
corresponding crude polymeric compounds [AgL1]n (9), [AgL2]n
(10), [AgL3]n (11), [AgL4]n (12), [AgL5]n (13), [AgL6]n (14) and
[AgL7]n (15) in a concentrated aqueous, water/acetonitrile or
water/methanol solution of AgCF3CO2/AgBF4 (1:1 or 5:1)ꢃ. AgCF3-
CO2 and AgBF4 were used to provide the auxiliary CF3CO2 ligand
and increase the silver(I) ion concentration, respectively.
to a square-pyramidal Ag5 basket in the l5– , , , ,g
g1 g1 g1 g2 2 coordina-
tion mode with Agꢁ ꢁ ꢁAg bond distances with a range of 2.845(5) to
3.017(5) Å. Two peripheral silver(I) atoms (Ag7 and Ag8) are
hitched to the Ag5 basket by two pairs of trifluoroacetate groups
(O2^O3 and O14^O15 for Ag7; O6^O7 and O10^O11 for Ag8) in
the l3
ligands coordinate to the Ag8 atom. The Ag6 atom is attached to
the Ag5 basket by two l3
g2 trifluoroacetate groups (O4^O5
and O8^O9) and bridging water molecule O1W in the 2 mode. Sil-
– ,
g1 g2 mode, and the l1 acetonitrile (N1) and aqua (O2W)
–
g1
,
l
The high concentration of silver ions and their aggregation
through argentophilicity ensure that the ethynide moiety mostly
achieves a high ligation number of 4 or 5 within a butterfly-shaped
Ag4 or square-pyramidal Ag5 basket [17], as opposed to most tran-
sition-metal alkyl and aryl ethynide complexes with ligation num-
bers ranging from 1 to 4, and such baskets can be mutually
connected by bridging trifluoroacetate ligands to yield higher-
dimensional MOFs.
ver atom Ag6A is also bonded to the vinyl group (C10@C11), with
bond length 2.245(4) Å to form a centrosymmetric silver–organic
3.2. Description of crystal structures
3.2.1. AgL1ꢁ6AgCF3CO2ꢁ3H2O (1)
In the crystal structure of 1, the vinyl group is conjugated with
the phenyl ring with a torsion angle C8–C9–C10–C11 = 1.7(6)°. As
expected, the 3-(2-vinylphenoxy)propynide chain adopts a non-
planar conformation, in which the C3 and O1 atoms are nearly
co-planar with the phenyl ring, and the torsion angles C5–C4–
O1–C3 and C4–O1–C3–C2 are ꢃ12.4(5)° and ꢃ63.7(4)°, respec-
tively (Fig. 1). The ethynide group is encapsulated in a Ag4 butter-
fly-shaped basket in the l4– , , ,
g1 g1 g1 g2 coordination mode. The
silver atom Ag5 is connected to the Ag4 silver aggregates through
argentophilic interaction to form a Ag5 segment, with Agꢁ ꢁ ꢁAg bond
distances range from 2.801(4) to 3.337(4) Å, which are comparable
to those observed in a wide variety of silver double and multiple
salts reported by our group and attributed to argentophilic interac-
tions [18]. The peripheral silver atoms Ag6 and Ag7 are attached to
Fig. 9. Perspective view of the coordination geometry in the silver double salt
AgL3ꢁ3AgCF3CO2ꢁH2OꢁCH3CN (4). The argentophilic Agꢁ ꢁ ꢁAg distances shown as
thick rods lie in the range 2.70–3.40 Å, and the hydrogen atoms and fluorine atoms
are omitted for clarity. Silver atoms are represented as thermal ellipsoids (30%
probability level) with atom labeling. Symmetry code: A: 1 ꢃ x, 1 ꢃ y, ꢃz; B: 1 ꢃ x,
1 ꢃ y, 1 ꢃ z. Color scheme: dark gray, silver atoms; gray, oxygen atoms; broken line,
Ag–C bond.

S.C.K. Hau et al. / Polyhedron 52 (2013) 992–1008
1001
cycle, which is stabilized by the formation of hydrogen bonds
O1Wꢁ ꢁ ꢁO6A (2.705(4) Å) and O1Wꢁ ꢁ ꢁO12A (2.758(4) Å). Within
this cycle, the distance between O6 and the center of the phenyl
ring is about 3.681(3) Å, implying the possibility of significant
square-pyramidal Ag5 basket in the l5
–
g1
,
g1
,
g1
,
g2
,
g2 coordination
mode, and the argentophilic Agꢁ ꢁ ꢁAg interactions range from
2.806(1) to 3.169(5) Å. Atom Ag6 is attached to the Ag5 basket by
two
one
l
3–O,O0,O0 trifluoroacetate groups (O2^O3 and O6^O7) and
anion–
p
interaction (Fig. 4).
g
2-bridged water ligand (O1W). Silver atom Ag4 is also found
The association of silver–organic cycles by a pair of inversion-
related trifluoroacetate groups (O12^O13 and O12B^O13B) pro-
duces an infinite zigzag chain along the c-axis direction (Fig. 5a).
to exhibit site-occupancy disorder in a ratio of 51:49. Symmetry-
related atom Ag6A from a neighboring chain is coordinated by
the conjugated vinyl group in the g2 mode with a bond length of
2.286(8) Å. The exterior silver atom Ag7 is linked with the Ag5 seg-
ment through coordination by two trifluoroacetate ligands (O4^O5
Such chains are connected together by two types of l3– ,
g1 g2
trifluoroacetate groups (O2^O3 and O14^O15) to give a grid-like
metal–organic layer corresponding to the ac plane (Fig. 5a), and
such networks are further united together through off-set face-
and O6^O7) via the
l
3–O,O0,O0 mode and one trifluoroacetate
ligand (O12^O13) by the
l
2–O,O0 binding mode.
to-face
p
–
p
interactions (inter-centroid distance 3.879(2) Å)
As shown in Fig. 7, the silver atom Ag6 is bonded simulta-
neously to the vinyl group (C10B and C11B) to form a silver–
organic cycle with an inversion center between Ag2 and Ag2B.
This cycle is stabilized by the formation of hydrogen bonds
O1Wꢁ ꢁ ꢁO8B (2.732(8) Å) and O1Wꢁ ꢁ ꢁO10B (2.815(9) Å). Notably,
the short distance between the oxygen atom O10B of the coordi-
nated trifluoroacetate group (O10B^O11B) and the center of the
between adjacent phenyl rings and C27–H27Aꢁ ꢁ ꢁO2A hydrogen
bonding (2.245(3) Å) to give
(Fig. 5b).
a 3D supramolecular structure
3.2.3. AgL3ꢁ6AgCF3CO2ꢁ5H2O (3)
In the crystal structure of 3, 3-(4-vinylphenoxy)propynide
adopts a non-planar conformation, in which the C3 and O1 atoms
are nearly perpendicular to the benzene ring with torsion angles
C5–C4–O1–C3 = ꢃ177.6(7)° and C4–O1–C3–C2 = ꢃ73.8(9)°. As
show in Fig. 6, the ethynide group (C1„C2) is bound to a
benzene ring (3.570(5) Å) indicate the existence of weak anion–
p
interaction. The remaining water molecules are coordinated to
different silver atoms via the l1 mode (O2W to Ag4 and O3W
to Ag5).
Fig. 10. (a) Perspective view of a portion of the infinite chain structure in 4 along the a-axis, showing notable H-bond and anion–
p
interaction. Symmetry code: A: 1 ꢃ x,
interaction between metal–
1 ꢃ y, ꢃz; B: 1 ꢃ x, 1 ꢃ y, 1 ꢃ z; C: ꢃx, 1 ꢃ y, ꢃz. (b) Crystal packing of 4 viewed from the direction of the a-axis, indicating the additional C–Hꢁ ꢁ ꢁ
p
organic layers, which leads to the formation of a three-dimensional supramolecular structure. The hydrogen atoms and fluorine atoms are omitted for clarity. Color scheme:
dark gray, silver atoms; gray, oxygen atoms; black ball and stick, C„C bond; bold black line, C@C bond; black broken line, Ag–C bond; gray broken line, H-bond interactions;
light gray broken line, anion–
p interactions; dark gray broken line, C–Hꢁ ꢁ ꢁp interactions.

1002
S.C.K. Hau et al. / Polyhedron 52 (2013) 992–1008
Two pairs of inversion-related trifluoroacetate groups (O2^O3,
O4^O5, O2A^O3A, and O4A^O5A) are utilized to bridge two
adjacent cycles to yield a metal–organic chain along the c-axis.
Adjacent chains are associated through a pair of inversion-related
trifluoroacetate groups (O12^O13 and O12D^O13D) acting in the
l
2–O,O0 mode on silver atoms Ag7 and Ag7D to produce a grid-like
layer structure. And such layer structure is further stabilized by
additional hydrogen bonding between water molecules and
trifluoroacetate ligands (O2Wꢁ ꢁ ꢁO9A, 2.978(1) Å; O2Wꢁ ꢁ ꢁO5W,
2.704(3) Å; O4Wꢁ ꢁ ꢁO5W, 2.693(3) Å; O4Wꢁ ꢁ ꢁO12, 2.877(1) Å)
(Fig. 8a).
Adjacent sheets are further linked together through the hydro-
gen bond (O3Wꢁ ꢁ ꢁO7 2.901(6) Å) and weak aromatic
p–p stacking
interaction between the phenyl rings from different layers
(4.134(1) Å) to generate a 3D supramolecular structure (Fig. 8b).
3.2.4. AgL3ꢁ3AgCF3CO2ꢁH2OꢁCH3CN (4)
By changing the crystal-growing medium from a concentrated
aqueous solution of AgCF3CO2 to a mixed water–acetonitrile solu-
tion of AgCF3CO2, complex 4 was obtained from the crystallization
of AgL3.
In the crystal structure of 4, 3-(4-vinylphenoxy)propynide
adopts a nearly co-planar conformation, and the torsion angles
C5–C4–O1–C3 and C4–O1–C3–C2 are ꢃ1.4(7)° and ꢃ170.0(3)°,
respectively. As shown in Fig. 9, the ethynide group (C1„C2) is
bound to a square-pyramidal Ag5 basket in the l5
coordination mode, and the argentophilic Agꢁ ꢁ ꢁAg bond distances
Fig. 11. Perspective view of the coordination geometry in the silver double salt
AgL4ꢁ4AgCF3CO2ꢁH2O (5). The argentophilic Agꢁ ꢁ ꢁAg distances shown as thick rods
lie in the range 2.70–3.40 Å. The hydrogen atoms and fluorine atoms are omitted for
clarity. Silver atoms are shown as thermal ellipsoids (50% probability level) with
atom labeling. Symmetry code: A: ꢃ1 ꢃ x, 1 ꢃ y, ꢃz. Color scheme: dark gray, silver
atoms; gray, oxygen atoms; broken line, Ag–C bond.
– , , , ,
g1 g1 g1 g2 g2
Fig. 12. (a) A portion of the infinite column of linked Ag8 fragments in 5 along the b-axis. The hydrogen atoms and fluorine atoms are omitted for clarity. Symmetry code: A:
ꢃ1 ꢃ x, 1 ꢃ y, ꢃz; B: ꢃ1 ꢃ x, 2 ꢃ y, ꢃz. (b) Perspective view of packing in 5 from the direction of the b-axis. The hydrogen atoms and fluorine atoms are omitted for clarity.
Symmetry code: A: ꢃ1 ꢃ x, 1 ꢃ y, ꢃ1 ꢃ z. Color scheme: dark gray, silver atoms; gray, oxygen atoms; black ball and stick, C„C bond; bold black line, C@C bond; black broken
line, Ag–C bond; gray broken line, H-bond interactions; light gray broken line, anion–p interactions; pale gray broken line, p–p stacking interactions.

S.C.K. Hau et al. / Polyhedron 52 (2013) 992–1008
1003
are in
a range of 2.818(6) to 3.186(5) Å. The vinyl group
(C10@C11), which is slightly twisted out of the plane of the phenyl
ring with a torsion angle (C6–C7–C10–C11) of 164.5(5)°, coordi-
nates to atom Ag4B by the g2 mode with a bond distance of
2.352(5) Å.
As shown in Fig. 10a, with an inversion center located at the
center of the Ag2–Ag2A bond, two Ag5 baskets share an edge to
engender a Ag8 aggregate. Two adjacent Ag8 aggregates are linked
by an inversion-related pair of trifluoroacetate ligands (O2^O3 and
O2B^O3B) via l
3–O,O,O0 mode to generate an infinite metal–organ-
ic column along the a axis. The column is further stabilized by
additional hydrogen bonds of type O4ꢁ ꢁ ꢁO1WB at a distance of
2.823(6) Å.
Such columns are cross-bridged through silver–olefin interac-
tion to form a metal–organic layer with an inversion center be-
tween Ag4 and Ag4B. (Fig. 10a). Notably, the short distance
(O1ꢁ ꢁ ꢁring center, 3.649(4) Å) between oxygen atom O1 of the
prop-2-ynyloxy group and the proximal phenyl ring indicates the
Fig. 13. Perspective view of the coordination geometry in the silver double salt
AgL5ꢁ3AgCF3CO2 (6). The argentophilic Agꢁ ꢁ ꢁAg distances shown as thick rods lie in
the range 2.70–3.40 Å, and the hydrogen atoms and fluorine atoms are omitted for
clarity. Silver atoms are represented as thermal ellipsoids (50% probability level)
with atom labeling. Symmetry code: A: 0.5 + x, 1 ꢃ y, 0.5 + z. Color scheme: dark
gray, silver atoms; gray, oxygen atoms; broken line, Ag–C bond.
existence of a weak anion–p interaction.
Water molecule O1W and molecule N1 are coordinated to silver
atoms Ag1 and Ag3, respectively (Fig. 10a). Adjacent layers are fur-
ther linked together through C–Hꢁ ꢁ ꢁ
p
interaction (C19–
H19Aꢁ ꢁ ꢁring center, 3.003(1) Å) between acetonitrile methyl and
phenyl groups to generate a three-dimensional supramolecular
network (Fig. 10b).
3.2.5. AgL4ꢁ4AgCF3CO2ꢁH2O (5)
In the crystal structure of 5, ligand L4 exhibits a non-planar con-
formation with both the prop-2-ynyloxy group and the allyloxy
group twisted out of the plane of the naphthyl ring, and the torsion
angles C5–C4–O1–C3, C4–O1–C3–C2, C9–C8–O2–C14, C8–O2–
C14–C15 and O2–C14–C15–C16 are 135.8(3)°, ꢃ56.2(3)°,
161.9(3)°, ꢃ79.7(3)° and ꢃ19.6(5)°, respectively. As shown in
Fig. 11, the ethynide group composed of C1 and C2 is bound to a
Ag4 basket (Ag1–Ag4) in the l4– , , ,
g1 g1 g2 g2 coordination mode
with Agꢁ ꢁ ꢁAg interaction distances in the range of 2.814(4)–
Fig. 14. (a) Perspective view of the crystal packing of 6. Symmetry code: A: 1.5 ꢃ x,
y, 0.5 ꢃ z; B: 1 ꢃ x, 1 ꢃ y, ꢃz. (b) Perspective view of the crystal packing of 6
showing the existence of weak
p
–p
stacking interaction (3.775 Å), which leads to
Fig. 15. Perspective view of the coordination geometry in the silver double salt
AgL6ꢁ6AgCF3CO2ꢁH2O (7). The argentophilic Agꢁ ꢁ ꢁAg distances shown as thick rods
lie in the range 2.70–3.40 Å, and the hydrogen atoms and fluorine atoms are
omitted for clarity. Silver atoms are shown as thermal ellipsoids (50% probability
level) with atom labeling. Symmetry code: A: ꢃx, 2 ꢃ y, 1 ꢃ z; B: 1 ꢃ x, 2 ꢃ y, ꢃz.
Color scheme: dark gray, silver atoms; gray, oxygen atoms; broken line, Ag–C bond.
the formation of layer structure. The hydrogen atoms and fluorine atoms are
omitted for clarity. Symmetry code: A: 1.5 ꢃ x, y, 0.5 ꢃ z; B: ꢃ1 + x, y, z. Color
scheme: dark gray, silver atoms; gray, oxygen atoms; black ball and stick, C„C
bond; bold black line, C@C bond; black broken line, Ag–C bond; light gray broken
line, p–p stacking interactions.

1004
S.C.K. Hau et al. / Polyhedron 52 (2013) 992–1008
3.163(5) Å. Inversion-related silver atom Ag4A is linked with the
Ag4 basket by three trifluoroacetate groups (O5^O6, O7^O8 and
ring (O2Aꢁ ꢁ ꢁring center = 3.417(2) Å), leading to the formation of a
close-packed layer structure, which is further stabilized by addi-
tional H-bonding (O1Wꢁ ꢁ ꢁO9, 2.766(3) Å).
O9^O10) via l l l
4–O,O,O0,O0, 2–O,O0 and 2–O,O0 coordination modes,
respectively. An exterior silver atom Ag5 is attached to the Ag2–
Ag1–Ag4A segment through two trifluoroacetate groups (O3^O4
and O5^O6) via the
modes, respectively (Fig. 11). Notably, silver atom Ag2 is
dinated by C12 and C13 of the naphthyl ring with a Ag–Ccent bond
distance of 2.601(3) Å. Atom Ag5 is coordinated by the
2–ethenyl
l
3–O,O0,O0 and
l
4–O,O,O0,O0 coordination
2-coor-
3.2.6. AgL5ꢁ3AgCF3CO2 (6)
g
In the crystal structure of complex 6, the ethynide moiety
C1–C2, which is also twisted out of the plane of the naphthyl
ring with torsion angles (C5–C4–O1–C3, C4–O1–C3–C2) of
142.6(6)° and ꢃ160.0(5)°, respectively, is capped by a butterfly-
g
group (C15 and C16) with a Ag–Ccent bond length of 2.288(3) Å; it
also interacts with the naphthyl ring via the g1 mode at a Ag5–C7
bond distance of 2.843(3) Å. Adjacent Ag8 aggregates with an
inversion center located at the center of the Ag4ꢁ ꢁ ꢁAg4A bond are
shaped Ag4 segment taking the l4– , , ,
g1 g1 g2 g2 coordination mode
with Agꢁ ꢁ ꢁAg distances in a range of 2.789(7) to 3.000(5) Å. The
allyloxy moiety is twisted out of the plane of the naphthyl ring
with torsion angles C8–C9–O2–C14 = 170.8(5)°, C9–O2–C14–
C15 = ꢃ91.6(6)° and O2–C14–C15–C16 = ꢃ12.9(8)°. Utilizing
linked by trifluoroacetate group (O3^O4) via the l
4–O,O,O0,O0 coor-
dination mode to generate an infinite chain composed of linked
Ag8 segments along the b-axis (Fig. 12a). Viewing from the direc-
tion of the b-axis (Fig. 12b), adjacent infinite chains are seen to
three
l
3–O,O,O0 trifluoroacetate groups as linkage components,
external silver atom Ag5 is connected with the trigonal pyrami-
dal Ag4 basket. Silver atom Ag2A is coordinated by the ethenyl
group (C15 and C16) in the g2 mode with a Ag–Ccent bond dis-
tance of 2.335(5) Å (Fig. 13).
be connected by
naphthyl rings of L4 ligands, together with an anion–
between oxygen atom O2A of the allyloxy group and a C6 aromatic
p–p
stacking interactions (3.842(3) Å) between
p
interaction
Fig. 16. (a) Perspective view of interconnection between the infinite chains through Ag–aromatic interactions in the crystal structure of 7 viewed from the direction of the c-
axis. (b) Perspective view of the crystal packing showing the aromatic stacking interactions (3.665 Å) between the naphthalene rings. The hydrogen atoms and fluorine
atoms are omitted for clarity. Symmetry code: A: ꢃx, 2 ꢃ y, ꢃz; B: 1 ꢃ x, 2 ꢃ y, ꢃz. Color scheme: dark gray, silver atoms; gray, oxygen atoms; black ball and stick, C„C bond;
bold black line, C@C bond; black broken line, Ag–C bond; gray broken line, H-bond interactions; light gray broken line, stacking interactions.
p–p
p–p

S.C.K. Hau et al. / Polyhedron 52 (2013) 992–1008
1005
With Ag4 lying on a C2 axis, two Ag4 baskets share a common
vertex to form a Ag7 aggregate (Fig. 14a). Linkage of adjacent Ag7
aggregates by a pair of inversion-related trifluoroacetate groups
Ag7 atoms and the naphthyl rings to assemble a silver layer
structure (Fig. 16a). Such association is further supported by
notable H-bonding between water molecule and trifluoroacetate
ligands (O1Wꢁ ꢁ ꢁO9B, 2.775(5) Å and O1Wꢁ ꢁ ꢁO11B, 2.744(5) Å). In
(O5^O6 and O5B^O6B) produce a Ag7–(l4– ,g
g2 2–CF3CO2)2–Ag7
building unit, which leads to the formation of a zigzag infinite
between the silver layer structures, notable aromatic p–p stacking
chain along the a-axis direction (see Fig. S2 in Supplementary
interactions (3.665(1) Å) are found to support such three-
Information). With the presence of aromatic p–p stacking interac-
dimensional supramolecular structure (Fig. 16b).
tions (3.775(3) Å) between proximal naphthyl rings, adjacent
infinite zigzag silver chains are interconnected to form a wavy
layer structure (Fig. 14b).
3.2.8. AgL7ꢁ7AgCF3CO2ꢁ4H2O (8)
In the crystal structure of 8, both the prop-2-ynyloxy group
(torsion angles C5–C4–O1–C3 = ꢃ22.4(16)° and C4–O1–C3–
C2 = ꢃ76.7(11)°) and the allyloxy group (torsion angles
C8–C9–O2–C14 = ꢃ178.3(1)°, C9–O2–C14–C15 = 168.0(1)° and
O2–C14–C15–C16 = ꢃ16.4(3)°) are twisted out of the naphthalene
plane (Fig. 17). The ethynide group is capped by a Ag5 square-pyra-
3.2.7. AgL6ꢁ6AgCF3CO2ꢁH2O (7)
As shown in Fig. 15, the alkyl ethynide moiety (C1„C2) of L7 in
the crystal structure of AgL6ꢁ6AgCF3CO2ꢁH2O (7) is capped by a
square-pyramidal Ag5 (Ag1–Ag5) basket in a l5– , , , ,
g1 g1 g1 g2 g2
midal basket in a l5– , , , ,
g1 g1 g1 g2 g2 coordination mode, and the
coordination mode, and the Agꢁ ꢁ ꢁAg interaction distances range
from 2.843(6) to 3.176(8) Å. Besides, the prop-2-ynyloxy group
deviates from the plane of the naphthyl ring by torsion angles
C5–C4–O1–C3 = ꢃ6.0(8)° and C4–O1–C3–C2 = 74.3(6)°, while the
torsion angles between the allyloxy group and the naphthyl ring
are C4–C13–O2–C14 = ꢃ168.2(5)°, C13–O2–C14–C15 = 163.0(5)°
and O2–C14–C15–C16 = ꢃ19.8(9)°. The silver atom Ag6 is con-
nected to the Ag5 silver aggregates through argentophilic interac-
tion to form a Ag6 segment. A peripheral silver atom Ag7 is
attached to this Ag6 segment through two trifluoroacetate groups
distance of Agꢁ ꢁ ꢁAg argentophilic interaction ranges from 2.847(1)
to 3.116(1) Å. Atom Ag6 is attached to the Ag5 silver basket through
two trifluoroacetate groups O9^O10 and O11^O12 via the l3
mode, and is also
2-coordinated by the center of the C11–C12 edge
– ,
g1 g2
g
of the naphthyl ring at a bond distance of 2.363(1) Å. Atom Ag7
exhibits site-occupancy disorder in a ratio of 86:14; it is coordinated
by aqua ligand O3W and the ethenyl group (C15@C16) in the g2
mode at a bond length of 2.206(2) Å. Furthermore, silver atom Ag8
is coordinated to the Ag5 aggregates through coordination by two
trifluoroacetate groups O3^O4 and O7^O8 via the l3– ,
g1 g2 mode
and an aqua ligand, O3^O4, O5^O6 and O1W via the
4–O,O,O0,O0 and
2–O,O modes, respectively. Silver atom Ag7B is
2-coordinated by the center of the C9–C10 edge of the naphthyl
ring with a bond distance of 2.428(6) Å. In addition, symmetry-
related atom Ag6A is
2-coordinated by the ethenyl group (C15
l
3–O,O,O0,
and two water molecules O1W and O2W in the l2 and l1 modes,
respectively. A solvated water molecule O4W contributes to
stabilization of the crystal structure via hydrogen bonding.
Adjacent Ag5 segments are linked together by a pair of inver-
l
l
g
g
sion-related trifluoroacetate group (O13^O14) in
(l4– , –
g2 g2
and C16) with a bond distance of 2.252(7) Å.
CF3CO2)2 mode to form an infinite zigzag chain composed of Ag5
segments along the b-axis (Fig. 18a). Water molecule O1W shows
strong H-bond interactions with adjacent trifluoroacetate ligands
(O1WBꢁ ꢁ ꢁO5B, 3.084(1) Å; O1WBꢁ ꢁ ꢁO5C, 2.864(1) Å; O1Wꢁ ꢁ ꢁO7C,
3.007(1) Å). Similarly, water molecule O2W has rather strong
H-bond interaction with trifluoroacetate ligand (O2Wꢁ ꢁ ꢁO13,
2.857(2) Å) and it is found to exhibit site-occupancy disorder in a
ratio of 59:41. Water molecule O3W is interacted with adjacent
trifluoroacetate ligands through H-bondings (O3WDꢁ ꢁ ꢁO6C,
2.791(3) Å; O3WDꢁ ꢁ ꢁO10C, 3.102(3) Å). Finally, water molecule
O4W exhibits notable H-bond interaction with a nearby trifluoro-
acetate ligand (O15^O16) at a distance of 2.865(3) Å.
Two independent Ag6 aggregates are connected together
through two different pairs of inversion-related trifluoroacetate
ligands (O5^O6 and O7^O8) to engender a Ag12 segment. Such
Ag12 segments are further interconnected by another pairs of
inversion-related trifluoroacetate ligands (O13^O14 and
O13a^O14a) to generate an infinite chain of linked Ag12 segments
(Fig. S3 in Supporting Information). Adjacent chains are seen to
associate with each other by silver aromatic interaction between
Adjacent silver(I) chains are further cross-bridged by the coor-
dination of O1W with silver atoms Ag4B and Ag8A to assemble a
wavy metal–organic supramolecular layer structure (Fig. S4 in
Supporting Information). Silver atoms Ag7 are bonded to the
allyloxy group simultaneously, which generate a centrosymmet-
ric metal–organic cycle (Fig. S5 in Supporting Information shows
that an inversion center is located between Ag7A and Ag7B). As a
result, such cyclic structural elements act as cross-linkers to join
two adjacent layers to generate a three-dimensional supramolec-
ular framework. This network structure is further supported by
the additional H-bondings between water molecules and trifluo-
roacetate ligands (O4WBꢁ ꢁ ꢁO16C, 2.865(3) Å) (Fig. 18b).
4. Discussion
Fig. 17. Perspective view of the coordination geometry in the silver double salt
AgL7ꢁ7AgCF3CO2ꢁ4H2O (8). The argentophilic Agꢁ ꢁ ꢁAg distances shown lie in the
range 2.70–3.40 Å, and the hydrogen atoms and fluorine atoms are omitted for
clarity. Silver atoms are represented by thermal ellipsoids (20% probability level)
with atom labeling. The silver atom Ag7 exhibits site-occupancy disorder, and only
position Ag7 with the higher occupancy (86%) is shown. Similarly, water molecule
O2W exhibits site-occupancy disorder, and only position O2W with the higher
occupancy (59%) is shown. Color scheme: dark gray, silver atoms; gray, oxygen
atoms; broken line, Ag–C bond; gray broken line, H-bond interactions.
4.1. Silver–carbon linkage modes
Systematic investigation of the present series of eight silver
complexes (1–8) reaffirms the general utility of the silver–ethynide
supramolecular synthon R–C„CꢀAgn (n = 4, 5) in coordination
network assembly [32]. The coordination modes of ethynide
ligands L1–L8 in their silver double-salts are displayed in Fig. 19.

1006
S.C.K. Hau et al. / Polyhedron 52 (2013) 992–1008
Fig. 18. (a) Perspective view of a portion of the zigzag chains composed of Ag5 segments in 8, showing all notable H-bondings within water molecules and those between
water molecules and trifluoroacetate ligands. Symmetry code: A: 2 ꢃ x, 1 ꢃ y, ꢃz; B: 1 ꢃ x, 1 ꢃ y, ꢃ1 ꢃ z; C: ꢃ1 + x, y, z; D: 1 ꢃ x, 1 ꢃ y, ꢃz. (b) Perspective view of wavy metal–
organic layer structure viewed from the direction of the a-axis, adjacent layer structures are differentiated by purple and turquoise colors, showing notable H-bondings
within water molecules and those between water molecules and trifluoroacetate ligands. Symmetry code: A: 1 ꢃ x, 1 ꢃ y, ꢃ1 ꢃ z; B: ꢃ1 + x, y, z; C: 2 ꢃ x, 1 ꢃ y, ꢃz. The
hydrogen atoms and fluorine atoms are omitted for clarity. Color scheme: dark gray, silver atoms; gray, oxygen atoms; black ball and stick, C„C bond; bold black line, C@C
bond; black broken line, Ag–C bond; gray broken line, H-bond interactions.
Fig. 19. Coordination modes of anionic ligands in their corresponding silver complexes: L1 in 1(a), L2 in 2(b), L3 in 3(c) and 4(d), L4 in 5(e), L5 in 6(f), L6 in 7(g) and L7 in
8(h).
In each complex, the terminal olefinic group of the L ligand is
p
-
supramolecular assembly of silver(I) coordination chains and
layers.
Among the eight complexes reported herein, half are found to
exhibit significant silver–aromatic (Agꢁ ꢁ ꢁAr) interactions ranging
from 2.363(1) to 2.843(3) Å in either the g1 or g2 coordination
bonded to a silver atom at a Ag–ethenyl bond distance that varies
from 2.206(2) to 2.352(5) Å. This finding shows that an ethenyl
moiety at the end of either a pendant arm or directly attached to
an aromatic ring invariably serves as a g2 ligation site for the

S.C.K. Hau et al. / Polyhedron 52 (2013) 992–1008
1007
Table 2
Summary of the different types of silver(I)–carbon interactions and other weak interactions that exist in complex 1–8.
Complex
1
2
3
4
Solvated molecules in the crystal structure (No.)
H2O (3)
H2O (2); CH3CN (1)
H2O (5)
H2O (1); CH3CN (1)
Silver–ethynide
Silver–ethenyl
Silver–aromatic
l4–
g1
,
g1
,
g1
,
g2
l5
–
g1
,
g1
,
g1
,
g2
,
g2
l5
–
g1
,
g1
,
g1
,
g2
,
g2
l5– , , , ,
g1 g1 g1 g2 g2
g2 (2.218(3) Å)
g1 (2.815(4) Å)
p
g2 (2.245(4) Å)
g2 (2.286(8) Å)
g2 (2.352(5) Å)
–
p
–
p
–
p
Hydrogen bonding
p
–
p
Stacking
–
–
–
3.879(2) Å
3.681(3) Å
–
4.134(1) Å
3.570(5) Å
–
–
Anion–
C–Hꢁ ꢁ ꢁ
p
interaction
interaction
3.649(4) Å
3.003(1) Å
p
Complex
5
6
7
8
Solvated molecules in the crystal structure (No.)
H2O (1)
–
H2O (1)
H2O (4)
Silver–ethynide
Silver–ethenyl
Silver–aromatic
l4–
g1
,
g1
,
g2
,
g2
l4
–
g1
,
g1
,
g2
,
g2
l5
–
g1
,
g1
,
g1
,
g2
,
g2
l5– , , , ,
g1 g1 g1 g2 g2
g2 (2.288(3) Å)
g2 (2.601(3) Å)
g1 (2.843(3) Å)
p
g2 (2.335(5) Å)
g2 (2.252(7) Å)
g2 (2.428(6) Å)
g2 (2.206(2) Å)
g2 (2.363(1) Å)
–
p
p
Hydrogen bonding
–
p
–
p
Stacking
3.842(3) Å
3.417(2) Å
–
3.775(3) Å
–
–
3.665(1) Å
–
–
–
–
–
Anion–
C–Hꢁ ꢁ ꢁ
p
interaction
interaction
p
mode, and an interesting structure-dependent relationship is ob-
served. Comparing the results of complex 5–8, it is noted that
when the prop-2-ynyloxy and allyloxy groups are far apart
(complex 6, substitution at 2,6-positions in the naphthalene ring),
dominant hydrogen-bonding interactions, such as in complex 1
and 8. In such crystal structures, the aromatic systems are much
engulfed within the coordination network by silver atoms and
bridging trifluoroacetate ligands, which prevent them from coming
into close contact. When the crystal structures exhibit rather weak
coordination network construction is dominated by
p–p stacking
to yield a centrosymmetric metal–organic cycle, making it unfa-
vorable for silver atoms to get close to the aromatic system for
significant Agꢁ ꢁ ꢁAr interaction. When both functional moieties
are suitably oriented and closely spaced (complex 7 and 8, 2,3-
and 1,5-positions, respectively), the possibility of Agꢁ ꢁ ꢁAr interac-
tion will be enhanced. In complex 1 and 5, the pendant arm bear-
ing the terminal ethynide group of the respective ligand (L1 and L4,
respectively) attached to the 2-position is favorably oriented to
facilitate both silver–ethynide and silver–aromatic binding to the
same Ag5 basket.
Agꢁ ꢁ ꢁAr interactions (>2.6 Å), as in complex 5 and 7, significant
stacking interactions can co-exist. In the crystal structure of 7,
notable aromatic stacking serves as the only interaction to
associate adjacent layers by forming a distorted centrosymmetric
metal–organic cycle. In the structure of 5, both ethynide and eth-
enyl functional moieties lie above the same face of the naphthyl
p–p
p–p
ring, exposing the other face (b-side) for
p–p
stacking interactions.
Moreover, the occurrence of aromatic
the co-existence of uncommon anion–
p–p stacking is abetted by
p
interactions; for instance,
complex 2–4 each possesses a centrosymmetric metal–organic
cycle in their crystal structures, so that the phenyl rings are
constrained to be close to the oxygen atoms of the pendant arms.
The size of the aromatic skeleton in the L ligand also plays a sig-
nificant role in influencing the onset of silver–aromatic interaction.
In comparison with the phenyl ring, the naphthyl ring has a more
In the structure of 4, significant C–Hꢁ ꢁ ꢁ
p interaction with the
acetonitrile ligand as the donor serves to connect adjacent layers.
extensive delocalized
p
-electron system that facilitates stronger
Agꢁ ꢁ ꢁAr interaction. This is reflected by the shorter Agꢁ ꢁ ꢁAr dis-
tances observed in complex 5, 7 and 8 in comparison that in 1.
The coordination mode of the trifluoroacetate groups varies
5. Conclusion
from the common l2– , , l3– , – ,
g1 g1 g1 g2 and l4 g2 g2 varieties. The
The present work reports the synthesis and structural charac-
terization of a series of eight silver(I) trifluoroacetate complexes
containing newly designed ligands each composed of an aromatic
nucleus with two flexible pendant arms attached to variable posi-
tions: one bearing a terminal ethynyl group and the other an eth-
enyl group. Single-crystal X-ray analysis of the complexes provided
detailed information on the influence of ligand disposition and ori-
entation, the onset and co-existence of three types of silver–carbon
bonding (silver–ethynide, silver–ethenyl and silver–aromatic) in
coordination network construction, as well as the roles played by
weak interactions in supramolecular assembly. Different types of
silver(I)–carbon interactions and other weak interactions that exist
in complex 1–8 are summarized in Table 2.
trifluoroacetate ligand generally plays two important roles: one
type spans an edge of the Agn basket to stabilize the [AgnC„C](nꢃ1)+
cationic moiety, whereas the other type bridges adjacent Agn bas-
kets or Ag atoms coordinated to the olefin/aromatic moieties to
generate an infinite chain or a layer-type network.
4.2. Weak intermolecular interactions
With the lone exception of 6, all other complexes incorporate
solvated water molecules or acetonitrile or both in their crystalline
lattices. In these solvent-containing complexes, hydrogen-bonds
confer extra stability to a coordination layer structure or connect
the layers into a three-dimensional supramolecular network.
When a crystal structure contains a centrosymmetric metal–or-
ganic cycle as a building block, as in complex 2, 3, and 6, offset
Acknowledgements
face-to-face
tance in the range 3.3–4.2 Å) [33] serve to associate adjacent coor-
dination layers to yield three-dimensional supramolecular
network. On the other hand, stacking interaction is usually
absent in those complexes that show strong Agꢁ ꢁ ꢁAr (<2.4 Å) or
p
–
p
stacking interactions (ring center-to-center dis-
We gratefully acknowledge financial support by the Hong Kong
Research Grants Council (GRF CUHK 402408 and 402710) and the
Wei Lun Foundation, and the award of a Studentship to P.-C. Cheng
and a Postdoctoral Research Fellowship to S.C.K. Hau, respectively,
by The Chinese University of Hong Kong.
a
p–p

1008
S.C.K. Hau et al. / Polyhedron 52 (2013) 992–1008
[8] (a) T.C.W. Mak, L. Zhao, Chem. Asian J. 2 (2007) 456. and references therein;
Appendix A. Supplementary data
(b) T.C.W. Mak, L. Zhao, X.-L. Zhao, in: E.R.T. Tiekink, J. Zukerman-Schpector
(Eds.), The Importance of Pi-Interactions in Crystal Engineering, Wiley,
Chichester, 2012, pp. 323–366 (Chapter 13). The term ‘‘silver-ethynide’’ is
preferred to ‘‘silver-ethynyl’’ because the silver-carbon bonding interaction is
considered to be mainly ionic with minor covalent s and p components; the
negative charge residing mainly on the terminal C atom draws neighboring
Ag(I) atoms close to one another to facilitate the onset of argentophilic Ag...Ag
interactions.
CCDC 873473–873480 contain the supplementary crystallo-
graphic data for 1–8. These data can be obtained free of charge
via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or from the
Cambridge Crystallographic Data Centre, 12 Union Road, Cam-
bridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail: depos-
it@ccdc.cam.ac.uk. Supplementary data associated with this
article can be found, in the online version, at http://dx.doi.org/
10.1016/j.poly.2012.06.082.
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