Systematic investigation of silver-carbon bonding in coordination frameworks with aryl ligands that contain ethynyl and ethenyl substituents

Article abstract of DOI:10.1002/chem.201204225

Single-crystal X-ray diffraction of a series of ten crystalline silver(I)-trifluoroacetate complexes that contained designed ligands, each of which was composed of an aromatic system that was functionalized with terminal and internal ethynyl groups and a

Full text of DOI:10.1002/chem.201204225

FULL PAPER
DOI: 10.1002/chem.201204225
Systematic Investigation of Silver–Carbon Bonding in Coordination
Frameworks with Aryl Ligands That Contain Ethynyl and Ethenyl
Substituents
Sam C. K. Hau and Thomas C. W. Mak*[a]
Dedicated to Professor James Trotter on the occasion of his 80th birthday
Abstract: Single-crystal X-ray diffrac-
tion of a series of ten crystalline sil-
ver(I)–trifluoroacetate complexes that
contained designed ligands, each of
which was composed of an aromatic
system that was functionalized with ter-
minal and internal ethynyl groups and
a vinyl substituent, provided detailed
information on the influence of ligand
disposition and orientation, coordina-
tion preferences, and the co-existence
of different types of silver(I)–carbon
bonding interactions (silver–ethynide,
solidated by argentophilic and weak
inter/intramolecular interactions. The
silver–ethynyl,
silver–ethenyl,
and
complex
MeOH
AgL10·6AgCF3CO2·H2O·
(HL10=1-{[4-(prop-2-ynyl-
silver–aromatic) on the construction of
coordination networks that were con-
AHCTUNGTRENNoGUN xy)-3-vinylphenyl]ethynyl}naphtha-
lene) is the first reported example that
exhibits all four kinds of silver(I)–
carbon bonding interactions in the
solid state.
Keywords: coordination modes
·
crystal engineering · metal–organic
frameworks · silver · X-ray diffrac-
tion
Introduction
ver(I)–ethynide aggregates may be represented as C2@Agn
ꢁ À ꢁ
À ꢁ
(n=6–8), Ag4ꢀC C C CꢂAg4, and R C CꢂAgn (n=3–
6), respectively, with the overall charge in each case omitted
for simplicity. Such structural patterns have been shown to
be robust multinuclear metal–ligand supramolecular syn-
thons[9] for the construction of a wide variety of organosil-
ver(I) compounds that are composed of discrete molecules
and large-nuclearity clusters,[10] as well as 1D-to-3D metal–
organic frameworks (MOFs).[11]
Metal–ethynyl complexes have been intensively studied in
recent years because their structural diversity[1–3] leads to po-
tentially useful applications as precursors for nonlinear opti-
cal materials,[4] luminescent materials,[5] and rigid-rod molec-
ular wires.[6] It is widely accepted that organometallic frame-
works can be rationally designed through a judicious choice
of appropriate metal–ligand building blocks and supramo-
lecular synthons.[7]
In crystalline silver(I) complexes that contain various
ethynide-containing ligands, including the all-carbon di-
ACHTUNGTRENNUNGanions C2 and C4 and carbon-rich monoanions of the
type R C2 (R=alkyl, aryl, heteroaryl), a terminal carbon
atom that carries a formal negative charge is invariably in-
serted into a pocket that is composed of three-to-six silver(I)
centers, which are consolidated by mutual argentophilic in-
teractions.[8] The corresponding polynuclear cationic sil-
ver(I)–ethynediide, silver(I)–1,3-butadiene-1,4-diide, and sil-
The construction of conventional MOFs that are based on
transition-metal centers and pre-fabricated organic building
blocks of proper dimensions and functionality takes full ad-
vantage of their directional bonding characteristics; this
strategy can be used to generate structures that exhibit de-
sired connectivities, topologies, and pores.[12] In contrast, the
multinuclear silver(I)–ethynide supramolecular synthons can
adopt various shapes and compositions (within limits) and
their intrinsic non-directional characteristic of argentophili-
2À
2À
À
À
AHCTUNGTREGcNNUN ity (the aggregation of silver(I) centers induced by attach-
ment onto an ethynide group) precludes the assembly of
structures with predictable geometrical properties and the
generation of microporous cavities. Nevertheless, the supra-
[a] Dr. S. C. K. Hau, Prof. Dr. T. C. W. Mak
Department of Chemistry and Center of Novel Functional Molecules
The Chinese University of Hong Kong, Shatin, New Territories
Hong Kong SAR (P.R. China)
À ꢁ
À
ꢁ
molecular synthons Ar C CꢂAgn and Ar OCH2C CꢂAgn
(n=4, 5)[13] have been demonstrated to be useful for the
construction of a wide variety of 1D, 2D, and 3D MOFs
with various anionic and/or neutral ancillary ligands, which
are often found to be consolidated by weaker intermolecular
interactions, such as silver(I)–aromatic, p–p, anion–p, and
hydrogen-bonding interactions, apart from cooperative sil-
ver(I)–ethynide and argentophilic bonding interactions.
Fax: (+852)2603-5057
E-mail: tcwmak@cuhk.edu.hk
Supporting information for this article, including detailed structural
description of complexes 5, 6, 8, and 9, the synthesis of ligands HL1–
HL10 and their precursors, 1H and 13C NMR spectra, and X-ray crys-
tallographic data, is available on the WWW under http://dx.doi.org/
10.1002/chem.201204225.
Chem. Eur. J. 2013, 19, 5387 – 5400
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
5387

Unlike a terminal ethynide moiety, an internal ethynyl
to generate MOFs that were stabilized by argentophilic,
silver–ethynide, silver–ethynyl, and silver–ethenyl interac-
tions and the phenyl or naphthyl rings were potentially ca-
pable of partaking in weaker silver–aromatic, p–p-stacking,
and anion–p interactions.
À ꢁ À
group (R C C R’) is expected to function as a potential p-
ligand site. In the present context, we considered it worth-
while to perform a systematic investigation of the coordina-
tion behavior of several newly designed ligands, HLn (n=1–
10), each of which contained an aromatic core with a rigid/
flexible terminal ethynyl group, an internal ethynyl group,
and a vinyl group at various positions on the aromatic ring
(Scheme 1). By altering the relative separation and orienta-
Results and Discussion
Structural description: The
crystal structures of complexes
1–10 were determined by
single-crystal X-ray diffraction.
The crystal data and refinement
parameters are presented in the
Supporting
Table S1.
Information,
As expected, the trifluoroace-
tate ligands in all of these com-
plexes exhibit bridging ligation
modes. The silver–ethynide
“bonds” within either the but-
terfly-shaped Ag4 or square-
pyramidal Ag5 baskets can be
classified into three types: s, p,
and
mixed
(s,p)
bonds
(Scheme 2).[14] In general, the s-
À
type Ag C bond between the
terminal carbon atom (C1) of
the ethynide moiety and its ap-
proximately co-linear silver
ꢁ
À
atom (aC2 C1 Ag (q) set to
Scheme 1. Structures of ligands HL1–HL10 that were designed and synthesized for this study.
tion of these three functional groups on the aromatic
system, we aimed to study their combination with silver(I)
trifluorocarboxylate for the construction of new metal–or-
ganic frameworks (MOFs) that were consolidated by sil-
ver(I)–ethynide, silver(I)–ethynyl, silver(I)–olefin, and
silver–aromatic bonding interactions.
Herein, we report our synthetic and structural studies of a
series of 10 silver(I)–trifluoroacetate complexes of substitut-
ed ethynylbenzene ligands that contained a terminal ethynyl
group that was tethered to a pendant arm and a vinyl group
at various positions on the aromatic ring: (AgL1)2·
6AgCF3CO2·0.5H2O·2MeCN (1), AgL2·4AgCF3CO2·3H2O·
2MeOH (2), AgL3·5AgCF3CO2·2H2O (3), AgL4·6Ag-
be 160–1808) is much shorter
À
than the other Ag C bonds.
The p-type bonds, which are
ꢁ
À
taken to be those with C2 C1
Ag angles of less than 908, are
generally the longest among all
Scheme 2. Classification of dif-
ferent types of silver–ethynide
interaction.
À
of the Ag C bonds, whereas
the remaining mixed (s,p)-type
bonds correspond to those with
ꢁ
À
C2 C1 Ag angles that lie between 908 and 1608. As listed
in the Supporting Information, Table S2, the measured s, p,
À
and mixed (s,p) Ag C bond lengths in complexes 1–10 lie
within the ranges 2.185(6)–2.208(5), 2.328(3)–2.696(10), and
2.154(6)–2.605(8) ꢁ, respectively.
ACHTUNGTRENNUNGCF3CO2·5H2O (4), AgL5·6AgCF3CO2·2H2O·MeOH (5),
AgL6·6AgCF3CO2·2H2O·MeOH (6), AgL7·6AgCF3CO2·
2H2O·MeOH (7), AgL8·6AgCF3CO2·H2O·2MeOH (8),
AgL9·ACHTUNGTRENNUNG5AgCF3CO2·ACHTUNGTRENNUNG5.5H2O (9), and AgL10·6AgCF3CO2·
H2O·MeOH (10). On the basis of our previous experience,
the reactions of crude starting materials [AgL1]n (11),
[AgL2]n (12), [AgL3]n (13), [AgL4]n (14), [AgL5]n (15),
[AgL6]n (16), [AgL7]n (17), [AgL8]n (18), [AgL9]n (19), and
[AgL10]n (20) with water-soluble silver salts were expected
In view of the similarities between the supramolecular
layered structures of complexes 5, 6, 8, and 9 and those of
complexes 3 and 7, the crystal structures of complexes 5, 6,
8, and 9 are reported in detail in the Supporting Informa-
tion.
AHCTUNGTRENNUNG
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Chem. Eur. J. 2013, 19, 5387 – 5400

Silver–Carbon Bonding in Coordination Frameworks
FULL PAPER
Two Ag8 segments are linked together by two pairs of in-
version-related trifluoroacetate groups (O1^O2 and
O5^O6) in m3-h1,h2 and m4-h2,h2 modes, respectively, to form
a discrete molecule (Figure 2a). Adjacent molecules are fur-
ther associated together by offset face-to-face p–p interac-
tions
(ring II’···ring III
3.690(2) ꢁ,
ring I’···ring IV
3.713(2) ꢁ) to form a supramolecular layered structure that
is orientated parallel to the bc plane (Figure 2b).
Figure 1. Coordination environment of the silver(I) atoms in double salt
AgL1·6AgCF3CO2·0.5H2O·2MeCN (1); the argentophilic Ag···Ag dis-
ACHTUNGTRENNUNGtances, represented as thick rods, lie within the range 2.70–3.40 ꢁ and the
hydrogen and fluorine atoms are omitted for clarity. Color scheme: Ag:
À
purple; O: orange; Ag C bonds: broken lines; p–p-stacking interactions:
turquoise broken lines. This color scheme for the atoms and bonds ap-
plies to all other figures.
ent L1 ligands each deviate from co-planarity with respect
to their corresponding phenyl rings, with torsion angles of
C11-C16-C17-C18=À170.4(4)8 and C29-C34-C35-C36=
170.8(5)8, respectively (Figure 1). As expected, the diACHTUNTRGNEUNGphen-
ACHTUNGTRENNUNGyl–ethyne backbone of each ligand adopts a non-planar con-
formation, in which the torsion angles C8-C9-C10-C11 and
C26-C27-C28-C29 are À18.9(5)8 and 4.1(9)8, respectively.
ꢁ
ꢁ
The terminal ethynide groups (C1 C2 and C19 C20) of
ligand L1 are each inserted into a Ag4 butterfly-shaped
basket in the m4-h1,h1,h1,h2 coordination mode. Despite shar-
ing the same vertex silver atom (Ag4), two Ag4 segments
are fused together to form a Ag7 aggregate through argento-
philic interactions, with Ag···Ag distances that range from
2.729(5) to 3.067(5) ꢁ, which are comparable to those
values have been observed in a wide variety of silver double
and multiple salts and are attributable to argentophilic inter-
actions.[15] Peripheral silver atom Ag8 is hitched onto the
Ag7 segment through two pairs of m4-h2,h2-coordinated tri-
fluoroacetate groups (O5^O6 and O7^O8) and two MeCN
Figure 2. a) Crystal packing in compound 1, viewed along the a axis,
which shows all of the notable offset face-to-face p–p-stacking interac-
tions. Symmetry code: A: 1Àx, 1Ày, 1Àz. b) Crystal packing in com-
pound 1, viewed along the a axis, which shows all of the notable offset
face-to-face p–p interactions between independent molecular structures,
which form a 2D coordination network parallel to the bc plane. Symme-
try code: A: 1Àx, 0.5+y, 0.5Àz. The hydrogen and fluorine atoms are
omitted for clarity.
AgL2·4AgCF3CO2·3H2O·2MeOH (2). Ligand L2 in the
crystal structure of compound 2 adopts a non-planar confor-
mation with a torsion angle of C6-C9-C10-C11=35.8(9)8
(Figure 3) and the vinyl group (C17=C18) is twisted out of
the plane of the conjugated phenyl ring with a torsion angle
ligands (N1 and N2). Silver atom Ag3 is bonded to the inter-
2
ꢁ
nal h -ethynyl group (C9 C10) with a bond length of
2.400(4) ꢁ, which is indicative of a significant silver–alkyne
p-interaction (under 2.9 ꢁ),[16–21] whilst silver atom Ag7 is
ꢁ
ꢁ
attached onto the C27 C28 ethynyl group in the same fash-
of C13-C14-C17-C18=165.8(4)8. The ethynide group (C1
ion, with a bond length of 2.397(3) ꢁ. The two independent
L1 ligands are held tightly to each other through offset face-
to-face p–p-stacking interactions[22] (inter-centroid distances:
ring I···ring III 3.858(2) ꢁ, ring II···ring IV 3.695(2) ꢁ, and
C2) is bound to a butterfly-shaped Ag4 basket in the m4-
h1,h1,h1,h2 coordination mode (see the Supporting Informa-
tion, Table S1). One peripheral silver atom (Ag5) is attached
onto the Ag4 basket through two trifluoroacetate groups
(O1^O2 and O3^O4) in the m3-h1,h2 and m4-h2,h2 coordina-
tion modes, respectively. An independent aqua ligand
(O1W) is m1-coordinated to the Ag2 atom. The remaining
aqua ligand (O2W), which is m1-coordinated to the Ag5
C
cent(of C17=C18)···Ccent(of C35=C36) 3.809(1) ꢁ). The co-
crystallized water molecule O1W, which has a half site-occu-
pancy, is not involved in donor hydrogen-bonding interac-
tions with any trifluoroacetate group.
Chem. Eur. J. 2013, 19, 5387 – 5400
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5389

T. C. W. Mak and S. C. K. Hau
Figure 3. Coordination geometry in silver double salt AgL2·4Ag-
CF3CO2·3H2O·2MeOH (2); the argentophilic Ag···Ag distances, repre-
A
ACHTUNGTRENNUNG
sented as thick rods, lie within the range 2.70–3.40 ꢁ and the hydrogen
and fluorine atoms are omitted for clarity. Silver atoms are represented
as thermal ellipsoids (50% probability) with atom labeling. Symmetry
code: A: Àx, 1Ày, Àz. Green broken lines indicate H-bonding interac-
tions; henceforth, the same notation applies to the other figures.
atom, forms a hydrogen bond (O2W···O10 2.757(5) ꢁ) with
À
an independent MeOH ligand (O10 C28). The m1-coordinat-
Figure 4. a) Crystal packing in compound 2, viewed along the a axis,
which shows all of the notable H bonds and offset face-to-face p–p inter-
actions that lead to the formation of infinite zigzag silver chains. Symme-
try codes: A: Àx, 1Ày, Àz; B: 1Àx, 1Ày, 1Àz. b) A portion of the grid-
like metal–organic layered structure in the crystal packing of compound
2, which shows the notable H bonds. Symmetry codes: A: Àx, 1Ày, Àz;
B: 1Àx, Ày, 1Àz; C: À1+x, y, z. The hydrogen and fluorine atoms are
omitted for clarity.
ed MeOH molecule (O9) on silver atom Ag4 interacts with
an independent O3W ligand through a hydrogen-bonding
interaction (O9···O3W 2.764(4) ꢁ).
Symmetry-related silver atom Ag5A is coordinated by the
h2-vinyl group (C17=C18) with a bond length of 2.245(3) ꢁ,
which indicates a strong silver–ethenyl interaction (under
2.7 ꢁ).[7c,23–29] An inversion center between silver atoms Ag5
and Ag5A generates a centrosymmetric silver–organic cycle,
which is consolidated by the formation of a significant
silver–aromatic interaction (Ag1A···C12 2.749(2) ꢁ, under
2.9 ꢁ),[30–39] along with an offset face-to-face p–p-stacking
interaction (inter-centroid distance 3.720(2) ꢁ) between the
phenyl rings of adjacent ligands (Figure 4a).
one aqua ligand (O1W). The allyl moiety, which is twisted
out of the plane of the phenyl ring with torsion angles C20-
C19-C18-C5=À109.4(6)8 and C19-C18-C5-C6=114.7(4)8,
coordinates to a symmetry-related Ag5B atom on a neigh-
boring chain through a h2 mode with a bond length of
The association of neighboring silver–organic cycles
through two pairs of inversion-related trifluoroacetate
groups (O3^O4 and O3B^O4B, O7^O8 and O7B^O8B)
produces an infinite zigzag chain along the b axis (Fig-
ure 4a). Such chains are interconnected through additional
hydrogen-bonding interaction between water and MeOH
2.207(3) ꢁ. Notably, silver atom Ag6A from an adjacent
2
ꢁ
chain is h -coordinated by the internal ethynyl moiety (C10
À
C11), with a Ag Ccent bond length of 2.249(4) ꢁ.
Adjacent Ag10 aggregates with an inversion center at the
center of the Ag1···Ag1C bond (Figure 5b) are interconnect-
ed with the assistance of additional hydrogen-bonding inter-
actions between the trifluoroacetate groups (O6^O7 and
O10^O11) and water molecules (O1WC···O7 2.766(3) ꢁ,
and O1WC···O10 2.689(3) ꢁ) to generate an infinite chain
that is composed of linked Ag10 segments along the a axis
(Figure 6a). Notably, significant anion–p interactions
(3.560(3) ꢁ) between coordinated trifluoroacetate groups
(O10^O11) and the center of the benzene ring help to con-
solidate the centrosymmetric metal–organic cyclic struc-
ture.[40]
molecules
(O3W···O10A
2.720(4) ꢁ,
O3W···O10B
2.807(5) ꢁ) to give a supramolecular layered structure (Fig-
ure 4b).
AgL3·5AgCF3CO2·2H2O (3). As shown in Figure 5a, the
ꢁ
ethynide moiety C1 C2 of ligand L3 is twisted out of the
plane of the phenyl ring, with torsion angles C2-C3-O1-C4
and C3-O1-C4-C5 of 70.9(4)8 and À168.6(3)8, respectively.
This group is capped by a butterfly-shaped Ag5 segment,
which includes a symmetry-related silver atom (Ag1C).
Silver atom Ag5 is linked to the Ag4 basket by two trifluoro-
By viewing along the a axis, we can observe the associa-
tion of adjacent infinite chains through silver–alkenyl inter-
actions, as well as through H-bonding between the aqua li-
gands and the trifluoroacetate groups (O2W···O9B
2.891(5) ꢁ), thereby leading to the formation of a close-
packed coordination-layer structure (Figure 6b).
ACHTUNGTRENNUNGacetate groups (O6^O7 and O8^O9) through m3-O,O,O’ and
m2-O,O’ coordination modes, respectively. An exterior silver
atom (Ag6) is linked to the Ag5 segment through two m4-
O,O,O’,O’-trifluoroacetate groups (O2^O3 and O4^O5) and
5390
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Silver–Carbon Bonding in Coordination Frameworks
FULL PAPER
Figure 5. a) Coordination geometry in silver double salt AgL3·5Ag-
ACHTUNGTRENNUNGCF3CO2·2H2O (3); the argentophilic Ag···Ag distances, represented as
Figure 6. a) A portion of the infinite chains of linked Ag10 fragments in
compound 3, viewed along the a axis. Symmetry codes: A: 1Àx, 2Ày,
1Àz; B: 0.5Àx, À0.5+y, 0.5Àz; C: Àx, 2Ày, 1Àz. b) Packing in compound
3, viewed along the a axis. Symmetry codes: A: 1Àx, 2Ày, 1Àz; B: 0.5Àx,
À0.5+y, 0.5Àz. The hydrogen and fluorine atoms are omitted for clarity.
thick rods, lie within the range 2.70–3.40 ꢁ. Silver atoms are represented
as thermal ellipsoids (50% probability) with atom labeling. Symmetry
codes: A: Àx, 2Ày, 1Àz; B: 0.5Àx, 0.5+y, 0.5Àz. b) The Ag10 segment in
À
compound 3 has an inversion center at the center of the Ag1 Ag1C
bond. The hydrogen and fluorine atoms are omitted for clarity. Symmetry
codes: A: Àx, 2Ày, 1Àz; B: 0.5Àx, 0.5+y, 0.5Àz; C: 1Àx, 2Ày, 1Àz; D:
1+x, y, z; E: 0.5+x, 2.5Ày, 0.5+z.
2.799(3) ꢁ, and O3W···O5 2.778(1) ꢁ) also occur between
trifluoroacetate ligands and aqua molecules within the crys-
tal structure.
As shown in Figure 7b, silver atom Ag6 is bonded to the
ꢁ
AgL4·6AgCF3CO2·5H2O (4). In the crystal structure of
compound 4, ligand L4 adopts a non-planar conformation,
in which the C3 and O1 atoms lie almost perpendicular to
the phenyl ring, with torsion angles of C5-C4-O1-C3=
À167.7(7)8 and C4-O1-C3-C2=69.9(9)8. As shown in Fig-
internal ethynyl group (C10 A C11A) to form a silver–or-
ganic cycle with an inversion center between atoms Ag3 and
Ag3A. This cycle is stabilized by the formation of
O9···O1WA (2.722(11) ꢁ) and O10···O1WA hydrogen bonds
(2.734(6) ꢁ). Notably, the short distance between oxygen
atom O10 of the coordinated trifluoroacetate group
(O10^O11) and the center of the phenyl ring (3.643(4) ꢁ)
indicates the existence of a weak anion–p interaction.
Two pairs of inversion-related trifluoroacetate groups
(O2^O3 and O6^O7 and O2C^O3C and O6C^O7C) are
utilized to bridge two adjacent cycles to yield an infinite
metal–organic chain along the c axis (Figure 8a). Adjacent
silver chains are associated through a silver–ethenyl interac-
tion between silver atom Ag7 in one chain and vinyl group
C18B=C19B in an adjacent chain to generate a grid-like co-
ordination-layer structure (Figure 8b).
ꢁ
ure 7a, the ethynide group (C1 C2) is clasped by a square-
pyramidal Ag5 basket. Peripheral silver atom Ag6 is hitched
to the Ag5 basket by two trifluoroacetate groups (O2^O3
and O4^O5) through m4-h2,h2 and m3-h1,h2 modes, respective-
ly, as well as by one m2-bridged water ligand (O1W), where-
as silver atom Ag7 is attached to the Ag5 basket through
one m3-h1,h2-coordinated trifluoroacetate ligand (O10^O11)
and
one
m2-h2-coordinated
trifluoroacetate
ligand
(O12^O13). Symmetry-related silver atom Ag6A from an
adjacent chain is bound by the conjugated ethynyl group
2
ꢁ
(C10 C11) through an h mode with a bond length of
2.236(6) ꢁ. In a similar fashion, symmetry-related silver
atom Ag7B is coordinated to the conjugated vinyl group
(C18=C19) with a bond length of 2.255(10) ꢁ. Two inde-
pendent aqua ligands are coordinated to different silver
AgL5·6AgCF3CO2·2H2O·MeOH (5). In complex 5, the ter-
minal ethynide group on ligand L5 (C1 C2) is grasped by a
Ag5 basket and this aggregate is further linked to two exteri-
or silver atoms, Ag6 and Ag7 (see the Supporting Informa-
tion, Figure S1), which are h2-coordinated to vinyl group
ꢁ
À
À
atoms (O2W Ag5 and O3W Ag7) and significant hydrogen
bonding interactions (O2W···O13 2.825(2) ꢁ, O2W···O5W
Chem. Eur. J. 2013, 19, 5387 – 5400
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T. C. W. Mak and S. C. K. Hau
Figure 7. a) Coordination
geometry
in
silver
double
salt
AgL4·6AgCF3CO2·5H2O (4); the argentophilic Ag···Ag distances, repre-
sented as thick rods, lie within the range 2.70–3.40 ꢁ. Silver atoms are
represented as thermal ellipsoids (50% probability) with atom labeling.
Symmetry codes: A: 2Àx, 1Ày, Àz; B: 2Àx, Ày, Àz. b) The silver–organic
cycle in compound 4, with an inversion center between atoms Ag3 and
Ag3A. Symmetry codes: A: 2Àx, 1Ày, Àz; B: 2Àx, Ày, Àz; C: x, 1+y, z.
The hydrogen and fluorine atoms are omitted for clarity. Turquoise
broken lines indicate anion–p interactions.
Figure 8. a) A portion of the infinite chain structure of compound 4. Sym-
metry codes: A: 2Àx, 1Ày, Àz; B: 2Àx, Ày, Àz; C: 2Àx, 1Ày, 1Àz. b) A
portion of the grid-like layered structure in the crystal packing of com-
pound 4, viewed along the c axis. Symmetry codes: A: 2Àx, 1Ày, Àz; B:
2Àx, Ày, Àz; C: x, À1+y, z. The hydrogen and fluorine atoms are omit-
ted for clarity.
ciated together to generate a grid-like supramolecular lay-
ered structure through additional H-bonding interactions
(O2W···O7B 2.806(6) ꢁ, O2W···O12A 2.847(11) ꢁ; Fig-
ure 10b).
C18=C19 (2.262ACHTUNGTRENNUNG(6 ꢁ) and are bound by a symmetry-related
ꢁ
internal ethynyl group (C10A C11A, 2.263(7) ꢁ), respec-
tively. With the assistance of additional H-bonding and
anion–p interactions, a silver–organic cycle is formed with
an inversion center between atoms Ag3 and Ag3A (see the
Supporting Information, Figure S2).
AgL7·6AgCF3CO2·2H2O·MeOH (7). As shown in
ꢁ
Figure 11, the alkyl–ethynide moiety (C1 C2) of ligand L7
À
Then, adjacent cycles are interconnected by two pairs of
inversion-related trifluoroacetate groups (O4^O5 and
O6^O7) to yield an infinite metal–organic chain along the
a axis (Figure 9a); these chains are further associated
is clasped by a square-pyramidal Ag5 (Ag1 Ag5) basket.
The prop-2-ynyloxy group deviates from the plane of the
phenyl ring with torsion angles C5-C4-O1-C3=176.1(7)8
and C4-O1-C3-C2=À67.5(9)8, whilst the torsion angle be-
tween the conjugated ethenyl group and the phenyl ring
(C6-C7-C18-C19) is À4.4(1)8. Silver atom Ag6 is linked to
the Ag5 silver segment through a pair of m3-h1,h2 trifluoro-
through
additional
hydrogen-bonding
interactions
(O2WA···O3B, 2.770(6) ꢁ and O2WA···O12B, 2.823(13) ꢁ)
to generate a grid-like supramolecular layered structure
(Figure 9b).
AHCTUNGTREGaNNUN cetate ligands (O10^O11 and O12^O13) and a bridging
aqua ligand (O2W). Silver atom Ag6 is coordinated by the
2
ꢁ
AgL6·6AgCF3CO2·2H2O·MeOH (6). Similar to complex 5,
a silver–organic cycle, which has an inversion center be-
tween atoms Ag6 and Ag6A, is formed with L6 ligands,
aided by additional H-bonding and weak anion–p interac-
tions (Figure 10a). Neighboring cycles are interconnected
through two pairs of inversion-related trifluoroacetate
groups (O2^O3 and O4^O5) to further extend it into an in-
finite silver–organic chain along the a axis (see the Support-
ing Information, Figure S6a). Then, adjacent chains are asso-
internal h -ethynyl group (C10 C11) with a bond length of
2.285(6) ꢁ. A peripheral silver atom (Ag7) is hitched onto
the Ag5 aggregates through two trifluoroacetate groups
(O2^O3 and O6^O7) and one aqua ligand (O1W) through
m3-O,O,O’, m3-O,O,O’, and m2-O,O modes, respectively, whilst
symmetry-related Ag7A from an adjacent chain is coordi-
nated by the h2-ethenyl group (C18=C19) with a bond
length of 2.273(8) ꢁ.
5392
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Chem. Eur. J. 2013, 19, 5387 – 5400

Silver–Carbon Bonding in Coordination Frameworks
FULL PAPER
Figure 9. a) A portion of the grid-like layered structure in the crystal
packing of compound 5, viewed along the c axis. Symmetry codes: A:
2Àx, 1Ày, Àz; B: 2Àx, Ày, Àz; C: x, À1+y, z. b) A portion of the infinite
chain structure of compound 5. Symmetry codes: A: 3Àx, À1Ày, 2Àz; B:
2Àx, À1Ày, 2Àz; C: À1+x, y, z. The hydrogen and fluorine atoms are
omitted for clarity.
Figure 10. a) The silver–organic cycle in compound 6, with an inversion
center between atoms Ag6 and Ag6A. Symmetry code: A: Àx, Ày, 1Àz.
b) A portion of the grid-like supramolecular layered structure in the crys-
tal packing of compound 6, viewed along the a axis. Symmetry codes: A:
Àx, Ày, 1Àz; B: Àx, 1Ày, Àz. The hydrogen and fluorine atoms are omit-
ted for clarity.
As shown in Figure 12a, silver atom Ag6 is bonded to
ꢁ
ethynyl group C10 C11 to form a silver–organic cycle with
an inversion center between atoms Ag2 and Ag2A. This
cycle is stabilized by the formation of hydrogen bonds
O1W···O8A (2.744(10) ꢁ) and O1W···>O10A (2.738(7) ꢁ).
Two adjacent cycles are bridged through two pairs of inver-
sion-related trifluoroacetate groups (O2^O3 and O2B^O3B
and O4^O5 and O4B^O5B) to yield a metal–organic chain
along the c axis. Such coordination chains are further stabi-
lized by additional hydrogen bonds (O12···O14B,
2.832(13) ꢁ). Notably, the short distance between oxygen
atom O10 of the coordinated trifluoroacetate group
(O10^O11) and the center of the phenyl ring (3.656(5) ꢁ)
indicates the existence of a weak anion–p interaction (Fig-
ure 12b). Two adjacent chains are associated through hydro-
gen bonds between the water molecules and trifluoroacetate
ligands (O2W···O7B, 2.942(9) ꢁ) to produce a grid-like su-
pramolecular layered structure (Figure 12b).
Figure 11. Coordination geometry in silver double salt AgL7·6Ag-
AHCTNUGTERCGNNUN F3CO2·2H2O·MeOH (7); the argentophilic Ag···Ag distances, shown as
thick rods, lie within the range 2.70–3.40 ꢁ and the hydrogen and fluo-
rine atoms are omitted for clarity. Silver atoms are represented as ther-
mal ellipsoids (50% probability) with atom labeling. Symmetry code: A:
3Àx, À1Ày, 2Àz.
AgL8·6AgCF3CO2·H2O·2MeOH (8). As shown in Fig-
ꢁ
ure 13a, silver atom Ag6 is bonded to ethynyl group C12
C13 to form a silver–organic cycle with an inversion center
between atoms Ag6 and Ag6A, as is the case in complex 6.
The cycle is further consolidated by additional hydrogen
bonds
(O1W···O9A
2.763(5) ꢁ
and
O1W···O10A
2.790(5) ꢁ) and a weak anion–p interaction (3.726(6) ꢁ,
Chem. Eur. J. 2013, 19, 5387 – 5400
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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5393

T. C. W. Mak and S. C. K. Hau
Figure 13. a) The silver–organic cycle in compound 8, with an inversion
center between atoms Ag6 and Ag6A. Symmetry code: A: 0.5Àx, 1.5Ày,
Àz. b) A portion of the grid-like layered structure in the crystal packing
of compound 8, viewing along the b axis. Symmetry codes: A: 0.5Àx,
1.5Ày, Àz; B: 1Àx, y, 0.5Àz. The hydrogen and fluorine atoms are omit-
ted for clarity.
Figure 12. a) A portion of the infinite chain structure of compound 7.
Symmetry codes: A: 2Àx, 1Ày, 2Àz; B: 2Àx, 1Ày, 1Àz. b) A portion of
the grid-like layered structure in the crystal packing of compound 7,
viewed along the c axis. Symmetry codes: A: 2Àx, 1Ày, 2Àz; B: 2Àx,
2Ày, 1Àz. The hydrogen and fluorine atoms are omitted for clarity.
lecular layered structure through H-bonding interactions
(O3A···O1WB 2.864(6) ꢁ and O6A···O1WB 2.817(5) ꢁ).
Figure 13a). Such metal–organic cycles are associated with
each other through two pairs of inversion-related trifluoro-
ꢁ
AgL10·6AgCF3CO2·H2O·MeOH (10). Ethynide moiety C1
A
C2 is inserted into a square-pyramidal Ag5 (Ag1 to Ag5)
basket (Figure 15). The pro-2-ynyloxy group deviates from
the plane of the phenyl ring with torsion angles of C5-C4-
O1-C3=178.6(5)8 and C4-O1-C3-C2=70.4(6)8, whilst that
between ethenyl group C22=C23 and the conjugated phenyl
ring, that is, C4-C5-C22-C23, is 155.8(8)8. The naphthyl ring
is twisted out of the plane of the phenyl ring with a C7-C10-
C11-C12 torsion angle of À22.0(7)8. An exterior silver atom
(Ag6) is linked with the Ag5 silver segment through two m3-
h1,h2-coordinated trifluoroacetate groups (O4^O5 and
O6^O7) and one m2-bridged aqua ligand (O1W). In a similar
fashion, peripheral silver atom Ag7, which is h2-coordinated
by the ethenyl group (C22=C23) with a bond length of
2.081(7) ꢁ, is attached onto the Ag5 silver aggregate
through two m3-h1,h2-coordinated trifluoroacetate groups
(O8^O9 and O10^O11). In addition, symmetry-related
ite silver–organic chain along the b axis, in cooperation with
additional hydrogen-bonding interactions (see the Support-
ing Information, Figure S9a). Adjacent chains are further
linked together through hydrogen-bonding interactions
(O15···O3B 2.797(6) ꢁ and O15···O15B 2.858(8) ꢁ) to pro-
duce a 2D supramolecular structure (Figure 13b).
AgL9·5AgCF3CO2·5.5H2O (9). Similar to the crystal struc-
ture of compound 8, a silver–organic cycle that contains an
inversion center is constructed through silver–ethynyl inter-
actions between two L9 ligands (see the Supporting Infor-
mation, Figure S11). With the cooperation of additional hy-
drogen-bond interactions (O2W···O8B 2.799(6) ꢁ), neigh-
boring cycles are interconnected through two pairs of inver-
sion-related trifluoroacetate groups (O4^O5 and O10^O11)
to yield an infinite silver coordination chain along the b axis
(Figure 14a). As shown in Figure 14b, adjacent chains are
further associated with one another to generate a supramo-
atom Ag6A from an adjacent chain is coordinated by inter-
nal h -ethynyl group C10 C11 with a bond length of
2.259(4) ꢁ, whilst another symmetry-related atom (Ag5B) is
2
ꢁ
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Chem. Eur. J. 2013, 19, 5387 – 5400

Silver–Carbon Bonding in Coordination Frameworks
FULL PAPER
As shown in the Supporting Information, Figure S13, ad-
jacent independent Ag5 aggregates coalesce together to
afford a Ag10 aggregate through argentophilic interactions
within a pair of inversion-related silver atoms (Ag2 and
Ag2C), with the assistance of a pair of inversion-related m3-
h1,h2-coordinated trifluoroacetate groups (O2^O3 and
O2C^O3C). Moreover, both silver atoms Ag6 and Ag7 are
ꢁ
bonded to ethynyl group C10 C11 and vinyl group C22=
C23 to form a silver–organic cycle with an inversion center
between atoms Ag4 and Ag4A (see the Supporting Informa-
tion, Figure S14). This cycle is consolidated by the formation
of hydrogen bonds O1W···O11A (2.714(4) ꢁ) and
O1W···O12A (2.703(6) ꢁ) and a weak anion–p interaction
(O11···ring-center 3.643(3) ꢁ).
Such metal–organic cycles are associated together through
À
À
a silver–aromatic interaction (Ag5B Ccent of the C19 C20
edge in the naphthyl ring) and a weak edge-to-edge p–p-
stacking interaction between adjacent symmetry-related
À
À
phenyl rings (C
centACHTUNGTERNNUG(C8 C9)···CcentHCATUNGTREN(NUGN C8B C9B) 3.549(2) ꢁ) to
generate grid-like coordination-layer structure (Fig-
a
ure 16a). Adjacent layers are interconnected through addi-
tional hydrogen-bonding interactions between MeOH mole-
cules and coordinated trifluoroacetate groups (O14A···O5B
Figure 14. a) A portion of the infinite chain structure of compound 9.
Symmetry codes: A: 1Àx, 4Ày, 3Àz; B: 1Àx, 3Ày, 3Àz. b) A portion of
the grid-like layered structure in the crystal packing of compound 9,
viewed along the b axis. Symmetry codes: A: 1Àx, 4Ày, 3Àz; B: 1+x, y,
z. The hydrogen and fluorine atoms are omitted for clarity.
Figure 15. Coordination geometry in silver double salt AgL10·6Ag-
ACHTUNGTRENNUNGCF3CO2·H2O·MeOH (10); the argentophilic Ag···Ag distances, represent-
ed as thick rods, lie within the range 2.70–3.40 ꢁ and the hydrogen and
fluorine atoms are omitted for clarity. Silver atoms are represented as
thermal ellipsoids (50% probability) with atom labeling. Symmetry
codes: A: 1Àx, 4Ày, 3Àz; B: 2Àx, 4Ày, 3Àz.
Figure 16. a) A portion of the grid-like layered structure of compound 10,
which shows all of the notable p–p-stacking interactions. Symmetry
codes: A: 1Àx, 4Ày, 3Àz; B: 2Àx, 4Ày, 3Àz; C: 1+x, y, z. b) A portion of
the 3D supramolecular network in the crystal packing of compound 10,
viewed along the a axis, which shows all of the notable H bonds. Symme-
try codes: A: 1Àx, 4Ày, 3Àz; B: x, y, 1+z. The hydrogen and fluorine
atoms are omitted for clarity.
2
À
h -coordinated by an edge (C19 C20) of the naphthyl ring
with a bond length of 2.564(5) ꢁ. The remaining MeOH
À
molecule (O14 C36) is coordinated to silver atom Ag7.
Chem. Eur. J. 2013, 19, 5387 – 5400
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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5395

T. C. W. Mak and S. C. K. Hau
Figure 17. Coordination modes of the anionic ligands in their corresponding silver complexes: a) ligand L1 in complex 1; b) ligand L2 in complex 2;
c) ligand L3 in complex 3; d) ligand L4 in complex 4; e) ligand L5 in complex 5; f) ligand L6 in complex 6; g) ligand L7 in complex 7; h) ligand L8 in
complex 8; i) ligand L9 in complex 9; and j) ligand L10 in complex 10.
2.848(10) ꢁ) to produce a 3D supramolecular network (Fig-
ure 16b).
of the four principal types of silver–carbon interactions in
the construction of coordination networks can be general-
ized as follows: silver–ethynide@silver–ethenyl^silver–
ethynyl@silver–aromatic.
To the best of our knowledge, complex 10 represents the
first example of a complex that is stabilized by all four kinds
of silver(I)–carbon bonding interactions, that is, silver–ethy-
nide, silver–ethynyl, silver–ethenyl, and silver–aromatic in-
teractions, in the crystalline state.
Structure–correlation relationships: Notably, in complexes 1
and 2, in which the terminal ethynyl and vinyl groups of li-
gands L1 or L2 are far apart, the formation of a coordina-
tion-layer structure is dominated by silver–ethenyl, silver–ar-
omatic, and aromatic p–p stacking interactions to yield a
centrosymmetric silver–organic cycle, thus making it unfa-
Discussion
Silver–ethynide linkage modes: A systematic investigation
of this series of 10 silver complexes (1–10) reaffirms the gen-
eral utility of the silver–ethynide supramolecular synthon
ACHTUNGTRENvNUGN orable for other silver atoms to get close to the internal
ethynyl group to form significant silver–ethynyl interactions.
When the rigid terminal ethynide group in ligand L2 (com-
plex 2) is attached onto a pendant arm, as in ligand L4
(complex 4), silver–ethynyl and anion–p interactions drive
the formation of the metal–organic cycle. The extra flexibili-
ty that is conferred by the pendant arm allows the ethynide
moiety to be embraced by a higher-nuclearity silver aggre-
gate. When the terminal ethynide and vinyl moieties are
positioned closer to each other, as in ligand L5 (compared
with the situation in ligand L4), both the silver–ethynyl and
silver–ethenyl interactions in compound 5 are weakened
with respect to those in compound 4, owing to the steric
congestion of the silver atoms over the central phenyl ring.
Such a finding is further affirmed by the structural results
for complexes 3 and 5. Compared to ligand L5, the terminal
ethenyl group on ligand L3 is connected to the phenyl ring
through an intermediate methylene group; the shorter
silver–ethenyl and silver–ethynyl interactions in complex 3
than in complex 5 indicate that the L3 ligand sites are more
accessible to the silver atoms.
À ꢁ
R C CꢂAgn (n=4, 5) in the assembly of coordination net-
works. The coordination modes of ethynide ligands L1–L10
in their silver double salts are displayed in Figure 17.
Among the 10 complexes reported herein, nine exhibit sig-
ꢁ
nificant silver–ethynyl (Ag···C Ccent) p-interactions that
range from 2.236(6) to 2.400(4) ꢁ. This finding indicates
that an internal ethynyl moiety consistently serves as a h2-li-
gation site for the supramolecular assembly of silver(I) coor-
dination chains and layers. On the other hand, eight out of
the ten complexes show p-type coordination of their corre-
sponding terminal olefinic group, which is either located on
the end of a pendant arm or is directly attached onto an aro-
matic ring, with bond lengths in the range 2.081(7) to
2.289(6) ꢁ. This result confirms the notion that an ethenyl
moiety functions as an even stronger h2-ligation site than an
internal ethynyl group. Notably, a silver–aromatic (Ag···Ar)
interaction was only found in two complexes in this series
and their coordination modes were m1-h1 (2) and m1-h2 (10).
Comparing complexes 6 and 7, the location of the prop-2-
ynyloxy group with respect to either the vinyl group or the
internal ethynyl group has a negligible effect on the corre-
sponding silver–ethenyl or silver–ethynyl interactions. When
both vinyl and internal ethynyl groups are located far from
Principal types of silver–carbon bonding and weak interac-
tions: Detailed analysis of the X-ray data of complexes 1–10
yielded metric parameters for silver–carbon bonding interac-
tions, as well as weak intra- and intermolecular interactions,
which are listed in Table 1. The order of decreasing strength
À ꢁ
the C CꢂAgn aggregate (complex 9), the silver atom is
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Chem. Eur. J. 2013, 19, 5387 – 5400

Silver–Carbon Bonding in Coordination Frameworks
FULL PAPER
Table 1. Summary of the different types of silver(I)–carbon bonding and weak interactions in complex 1–10.
1
2
3
4
5
solvated molecules in
the crystal structure (no.)
silver–ethynide
silver–ethynyl
silver–ethenyl
MeCN (2), H2O (0.5)
MeOH (2), H2O (3)
H2O (2)
H2O (5)
MeOH (1), H2O (2)
m4-h1,h1,h1,h2
m4-h1,h1,h1,h2
m5-h1,h1,h2,h2,h2
m5-h1,h1,h1,h2,h2
m5-h1,h1,h1,h2,h2
h2 [2.400
N
–
h2 [2.249
h2 [2.207
–
U
h2 [2.236
A
h2 [2.263
h2 [2.262
–
ACHTUNGTRENNUNG
–
–
h2 [2.245
h1 [2.749
U
h2 [2.255
A
ACHTUNGTRENNUNG
silver–aromatic
–
hydrogen-bonding interaction
p–p-stacking interaction
anion–p interaction
centrosymmetric
no
yes
yes
no
yes
no
yes
yes
yes
no
yes
yes
yes
no
yes
yes
yes
no
no
yes
silver–organic cycle
silver–organic structure
2D supramolecular
layered structure
2D supramolecular
layered structure
2D coordination-
layer structure
2D coordination-
layer structure
2D supramolecular
layered structure
6
7
8
9
10
solvated molecules in
the crystal structure (no.)
silver–ethynide
silver–ethynyl
silver–ethenyl
MeOH (1), H2O (2)
MeOH (1), H2O (2)
MeOH (2), H2O (1)
H2O (6)
MeOH (1), H2O (1)
m5-h1,h1,h1,h2,h2
m5-h1,h1,h1,h1,h2
m5-h1,h1,h1,h2,h2
m5-h1,h1,h1,h2,h2
m5-h1,h1,h1,h2,h2
h2 [2.274
h2 [2.289
–
U
h2 [2.285
h2 [2.273
–
U
h2 [2.262
h2 [2.248
–
U
h2 [2.247
N
h2 [2.259
h2 [2.081
h2 [2.564
ACHTUNGTRENNUNG
–
–
ACHTUNGTRENNUNG
silver–aromatic
ACHTUNGTRENNUNG
hydrogen-bonding interaction
p–p-stacking interaction
anion–p interaction
silver–organic structure
yes
no
yes
yes
no
yes
yes
no
yes
yes
no
yes
yes
yes
yes
2D supramolecular
layered structure
2D supramolecular
layered structure
2D supramolecular
layered structure
2D supramolecular
layered structure
3D supramolecular
network
preferably coordinated by the internal ethynyl group over
the vinyl group.
Furthermore, variation in the size of a terminal substitu-
ent on the internal ethynyl group in the L ligand plays a sig-
nificant role in influencing the onset of silver–ethynyl and
silver–ethenyl interactions. The order of increasing bond
3.72 ꢁ), which are a major contributing factor to the con-
struction of such metal–organic cycles. Silver–ethynyl inter-
actions are another dominant factor for the establishment of
such a cycle. When the phenyl nucleus in ligand L contains
a rigid terminal ethynyl substituent (as in complexes 1 and
2), close contacts between neighboring phenyl rings from
adjacent coordination chains or layers facilitate the forma-
tion of p–p-stacking interactions. On the other hand, p–p-
stacking interactions are more likely to occur in those com-
plexes that lack hydrogen-bonding interactions, such as com-
plex 1. In the crystal structure of complex 10, the co-exis-
tence of all four different types of silver–carbon interactions
allows the occurrence of aromatic p–p-stacking interactions.
With the aid of hydrogen-bonding and anion–p interactions,
ligand L10 maximizes its linkage efficiency to generate a tri-
fluoroacetate-bridged 3D supramolecular network structure.
Complexes 1–10 all contain solvated water molecules and
MeCN or MeOH molecules in their crystalline lattices. In
these complexes, hydrogen bonds confer enhanced stability
onto a coordination-chain structure or connect the chains
into a 2D or 3D supramolecular structure. The weak intra-
and intermolecular interactions that exist in their crystalline
forms are listed in Table 1.
À
À
lengths for both Ag ethynyl and Ag ethenyl interactions in
complexes 5, 6, and 8 consistently reflect the relative steric
bulkiness of the corresponding substituents (i.e., isopropyl<
phenyl<cyclohexyl). For complex 10, although the naphthyl
substituent is much larger than these above-mentioned
groups, the presence of a strong silver–aromatic interaction
facilitates the formation of silver–ethynyl and silver–ethenyl
interactions and overcomes the effects that are caused by its
steric bulk.
The coordination modes of the trifluoroacetate groups
vary from the common m2-h2 mode to the m2-h1,h1, m3-h1,h2,
and m4-h2,h2 modes. In these complexes, the trifluoroacetate
ligand generally plays two important roles: One ligand type
ꢁ
spans an edge of the Agn basket to consolidate the [AgnC
C](nÀ1)+ cationic moiety, whereas the other ligand type
bridges adjacent Agn baskets or Ag atoms that are coordi-
nated by olefin/ethynyl/aromatic-moieties to generate an in-
finite chain or a layer-type structure.
Role of weak intra- and intermolecular interactions: When
ligand L contains a pendant prop-2-ynyloxy group, a centro-
symmetric metal–organic cycle is often formed as a building
block in its crystal structure, as in complexes 3–10. The
extra flexibility that is provided by the propynyloxy group
enhances the formation of weak anion–p interactions (3.56–
Conclusion
This work reports the synthesis and structural characteriza-
tion of a series of 10 silver(I)–trifluoroacetate complexes of
newly-designed ligands, each of which was composed of an
aromatic system that was functionalized with terminal and
Chem. Eur. J. 2013, 19, 5387 – 5400
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5397

T. C. W. Mak and S. C. K. Hau
AgL4·6AgCF3CO2·5H2O (4). First, silver salt AgCF3CO2 (0.440 g,
2 mmol) was dissolved in MeOH (1 mL) and deionized water (0.3 mL).
Then, complex 14 (about 20 mg) was added to the solution. After stirring
for about 30 min, the solution was filtered and left to stand in the dark at
RT. After several days, colorless block crystals of compound 4 had been
internal ethynyl groups and a vinyl substituent. Single-crys-
tal X-ray analysis of these complexes provided detailed in-
formation on the influence of the ligand disposition and ori-
entation, coordination preference, and the co-existence of
different kinds of silver(I)–carbon bonding interactions
(silver–ethynide, silver–ethynyl, silver–ethenyl, and silver–
aromatic) in the construction of these coordination net-
works, as well as of the roles that were played by weak in-
teractions in these supramolecular assemblies. In AgL10·
6AgCF3CO2·H2O·MeOH, we have accomplished the charac-
terization of the first complex that exhibits all four principal
types of silver–carbon bonding interactions in the solid
state.
deposited in about 75% yield. IR (KBr): n˜ =2046 cmÀ1 (C C, w); ele-
ꢁ
mental analysis calcd (%) for C31H23Ag7F18O18: C 20.91, H 1.30; found:
C 21.20, H 1.35.
AgL5·6AgCF3CO2·2H2O·MeOH (5). First, silver salts AgCF3CO2
(0.440 g, 2 mmol) and AgBF4 (0.382 g, 2 mmol) were dissolved in a mixed
solution of MeOH (1 mL) and deionized water (1 mL). Then, complex 15
(about 25 mg) was added to the solution. After stirring until the complex
had completely dissolved, the solution was filtered and left to stand in
the dark at RT. After several days, colorless block crystals of compound
5 had been deposited in about 80% yield. IR (KBr): n˜ =2039 cmÀ1 (C C,
ꢁ
w); elemental analysis calcd (%) for C32H20Ag7F18O16: C 21.87, H 1.15;
found: C 21.70, H 1.25.
AgL6·6AgCF3CO2·2H2O·MeOH (6). First, silver salt AgCF3CO2
(0.440 g, 2 mmol) was dissolved in MeOH (1 mL) and deionized water
(0.3 mL). Then, complex 16 (about 15 mg) was added to the solution.
After stirring for about 30 min, the solution was filtered and left to stand
in the dark at RT. After several days, colorless block crystals of com-
pound 6 had been deposited in about 65% yield. IR (KBr): n˜ =2037 cmÀ1
Experimental Section
X-ray crystallography: Selected single crystals were used for data collec-
tion on a Bruker AXS Kappa Apex II Duo diffractometer at 123 K (1,
3), at 173 K (2, 4, 5, 9, and 10), at 243 K (6, 8), or 293 K (7) by using
frames of oscillation range 0.38, with 2<q<288. An empirical absorption
correction was applied by using the SADABS program.[41] The structures
were solved by using direct methods and refined by using full-matrix
least-squares on F2 with the SHELXTL program package.[42]
ꢁ
(C C, w); elemental analysis calcd (%) for C32H26Ag7F18O16: C 21.79,
H 1.49; found: C 21.66, H 1.37.
AgL7·6AgCF3CO2·2H2O·MeOH (7). First, silver salt AgCF3CO2
(0.440 g, 2 mmol) was dissolved in a mixed solution of MeOH (1 mL)
and deionized water (0.3 mL). Then, complex 17 (about 25 mg) was
added to the solution. After stirring for about 30 min, the solution was
filtered and left to stand in the dark at RT. After several days, colorless
block crystals of compound 7 had been deposited in about 75% yield. IR
Preparation of polymeric silver ethynides as synthetic precursors: CAU-
TION! Silver ethynides are potentially explosive and should be handled
in small amounts with extreme care.
(KBr): n˜ =2056 cmÀ1 (C C, w); elemental analysis calcd (%) for
ꢁ
First, ligand HL1 (1 mmol) was dissolved in MeCN (10 mL). Silver ni-
trate (1 mmol) and triethylamine (1 mmol) were subsequently added
under vigorous stirring and the mixture was stirred for 2 h in the dark.
The resultant pale-yellow slurry was diluted with MeOH (20 mL) and fil-
tered by suction filtration to collection a pale-yellow precipitate of poly-
meric [AgL1]n (11), which was washed thoroughly with MeOH (3ꢂ
10 mL) and then stored in its wet form at À108C in a refrigerator. Silver
complexes of ligands HL2–HL10 were prepared in the same manner. IR
ꢁ
C32H26Ag7F18O16: C 21.79, H 1.49; found: C 21.86, H 1.57.
AgL8·6AgCF3CO2·H2O·2MeOH (8). First, silver salts AgCF3CO2
(0.440 g, 2 mmol) and AgBF4 (0.038 g, 0.2 mmol) were dissolved in
MeOH (1 mL) and deionized water (0.1 mL). Then, complex 18 (about
20 mg) was added to the solution. After stirring for about 30 min, the sol-
ution was filtered and left to stand in the dark at RT. After several days,
colorless block crystals of compound 8 had been deposited in about 65%
ꢁ
(KBr): n˜
(C C, w)=2012 [AgL1]n (11), 2035 [AgL2]n (12), 2024 [AgL3]n
yield. IR (KBr): n˜ =2039 cmÀ1 (C C, w); elemental analysis calcd (%)
(13), 2052 [AgL4]n (14), 2037 [AgL5]n (15), 2044 [AgL6]n (16), 2049
[AgL7]n (17), 2033 [AgL8]n (18), 2044 [AgL9]n (19), 2034 cmÀ1 [AgL10]n
(20).
for C30H23Ag7F18O16: C 20.75, H 1.33; found: C 20.94, H 1.46.
AgL9·5AgCF3CO2·5.5H2O (9). First, silver salt AgCF3CO2 (0.440 g,
2 mmol) was dissolved in a mixed solution of MeOH (1 mL) and deion-
ized water (0.1 mL). Then, complex 19 (about 20 mg) was added to the
solution. After stirring for about 30 min, the solution was filtered and left
to stand in the dark at RT. After several days, colorless block crystals of
compound 9 had been deposited in about 75% yield. IR (KBr): n˜ =
ꢁ
Synthesis of silver ethynide complexes:
2ACHTUNGRETNNU{G (AgL1)2·6AgCF3CO2·
0.5H2O·2MeCN} (1). First, silver salt AgCF3CO2 (0.440 g, 2 mmol) was
dissolved in MeCN (1 mL) and deionized water (0.1 mL). Then, complex
11 (about 20 mg) was then added to the solution. After stirring for about
30 min, the solution was filtered and left to stand in the dark at RT.
After several days, colorless block crystals of compound 1 had been de-
2051 cmÀ1 (C C, w); elemental analysis calcd (%) for C27H29Ag6F15O16.5
C 20.93, H 1.89; found: C 21.12, H 1.76.
:
posited in about 30% yield. IR (KBr): n˜ =2016 cmÀ1 (C C, w); elemental
ꢁ
AgL10·6AgCF3CO2·H2O·MeOH (10). First, silver salt AgCF3CO2
(0.660 g, 3 mmol) was dissolved in MeOH (2 mL) and deionized water
(0.5 mL). Then, complex 20 (about 20 mg) was added to the solution.
After stirring for about 30 min, the solution was filtered and left to stand
in the dark at RT. After several days, colorless block crystals of com-
pound 10 had been deposited in about 55% yield. IR (KBr): n˜ =
ꢁ
analysis calcd (%) for
C
104H58Ag16F36N4O25
:
C 29.93, H 1.40, N 1.34;
found: C 29.85, H 1.25, N 1.30.
AgL2·4AgCF3CO2·3H2O·2MeOH (2). First, silver salts AgCF3CO2
(0.660 g, 3 mmol) and AgBF4 (0.382 g, 2 mmol) were dissolved in MeOH
(2 mL) and deionized water (1 mL). The, complex 12 (about 20 mg) was
added to the solution. After stirring for about 30 min, the solution was
filtered and left to stand in the dark at RT. After several days, colorless
block crystals of compound 2 had been deposited in about 65% yield. IR
2036 cmÀ1 (C C, w); elemental analysis calcd (%) for C36H20Ag7F18O15
C 24.16, H 1.13; found: C 24.33, H 1.27.
:
CCDC-924000 (1), CCDC-924001 (2), CCDC-924002 (3), CCDC-924003
(4), CCDC-924004 (5), CCDC-924005 (6), CCDC-924006 (7), CCDC-
924007 (8), CCDC-924008 (9), and CCDC-924009 (10) contain the sup-
plementary crystallographic data for this paper. These data can be ob-
tained free of charge from The Cambridge Crystallographic Data Centre
via www.ccdc.cam.ac.uk/data_request/cif.
(KBr): n˜ =2014 cmÀ1 (C C, w); elemental analysis calcd (%) for
ꢁ
C28H24Ag5F12O13: C 25.18, H 1.81; found: C 25.30, H 1.65.
AgL3·5AgCF3CO2·2H2O (3). First, silver salt AgCF3CO2 (0.440 g,
2 mmol) was dissolved in MeCN (3 mL) and deionized water (0.5 mL).
Then, complex 13 (about 10 mg) was added to the solution. After stirring
until the complex had complete dissolved, the solution was filtered and
left to stand in the dark at RT. After several days, colorless block crystals
of compound 3 had been deposited in about 25% yield. IR (KBr): n˜ =
ꢁ
2054 cmÀ1 (C C, w); elemental analysis calcd (%) for C30H19Ag6F15O13
C 23.71, H 1.26; found: C 23.70, H 1.43.
:
5398
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Chem. Eur. J. 2013, 19, 5387 – 5400

Silver–Carbon Bonding in Coordination Frameworks
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Acknowledgements
We gratefully acknowledge financial support from the Hong Kong Re-
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Received: November 27, 2012
Published online: February 28, 2013
5400
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