Structural studies of silver(I) coordination polymers with aryl iodide derived ligands

Article abstract of DOI:10.1021/ic991261g

This paper reports novel silver polymers, built with iodine-silver interactions, with interesting structural motifs. Four silver(I) coordination polymers of the aryl iodide derived ligands, triiodobenzoic acid (HL¹), tris(4-iodophenyl)-amine (L²), and 5,7-diiodo-8-hydroxyquinoline (HL³), have been synthesized and characterized by X-ray crystallography. Treatment of Ag(CH₃COO) with HL¹ yielded [Ag(L¹)] (1), whose structural analysis revealed 2D layers of ladders connected through weak Ag···I interaction. Reactions of AgClO₄ and L² in benzene and nitrobenzene afforded, respectively, two different products, [Ag(L²)(H₂O)]ClO₄-C₆H₆ (2) and [Ag(L₂)(ClO₄)] (3). While the structure of 2 could be described as a 2D layer of square and octagons perpendicular to [100], complex . 3 is formed by 2D layers of the same topology of 2 (8²·4), alternating as ABAB. In contrast, complex 4, [Ag₂-(H₂L³)(CF₃SO₃)₃], obtained by reaction of Ag(CF₃SO₃) and HL₃, was found to consist of a 2D layer based on columnar arrays AgH₂L³-Ag(triflate). The solid-state FT-IR and ¹⁰⁹Ag NMR spectra of theses complexes are discussed on the basis of their crystal structures.

Full text of DOI:10.1021/ic991261g

2146
Inorg. Chem. 2000, 39, 2146-2151
Structural Studies of Silver(I) Coordination Polymers with Aryl Iodide Derived Ligands
Ichiro Ino,† Liang Ping Wu,‡ Megumu Munakata,*,† Masahiko Maekawa,† Yusaku Suenaga,†
Takayoshi Kuroda-Sowa,† and Yoshinobu Kitamori†
Department of Chemistry, Kinki University, Kowakae, Higashi-Osaka, Osaka 577-8502, Japan, and East
China Normal University, Shanghai 200062, China
ReceiVed October 26, 1999
This paper reports novel silver polymers, built with iodine-silver interactions, with interesting structural motifs.
Four silver(I) coordination polymers of the aryl iodide derived ligands, triiodobenzoic acid (HL1), tris(4-iodophenyl)-
amine (L2), and 5,7-diiodo-8-hydroxyquinoline (HL3), have been synthesized and characterized by X-ray
crystallography. Treatment of Ag(CH3COO) with HL1 yielded [Ag(L1)] (1), whose structural analysis revealed
2D layers of ladders connected through weak Ag‚‚‚I interaction. Reactions of AgClO4 and L2 in benzene and
nitrobenzene afforded, respectively, two different products, [Ag(L2)(H2O)]ClO4‚C6H6 (2) and [Ag(L2)(ClO4)] (3).
While the structure of 2 could be described as a 2D layer of square and octagons perpendicular to [100], complex
3 is formed by 2D layers of the same topology of 2 (82‚4), alternating as ABAB. In contrast, complex 4, [Ag2-
(H2L3)(CF3SO3)3], obtained by reaction of Ag(CF3SO3) and HL3, was found to consist of a 2D layer based on
columnar arrays AgH2L3-Ag(triflate). The solid-state FT-IR and 109Ag NMR spectra of theses complexes are
discussed on the basis of their crystal structures.
Introduction
halocarbon ligands with Ag(I) ions are mainly restricted to alkyl
halides,9,10 To date, the utility of the aryl halide ligands in the
synthesis of high-nuclearity coinage metal complexes remains
virtually unexplored.10 This is surprising in that aryl halides
appear to be equally extremely versatile and easily handled
ligands. Compared with other halogen elements in the group,
the iodine atom possesses stronger nucleophilic character and
is expected to form stable coordination compounds with the
soft acid silver(I) ion.11 In addition, our research into the
supramolecular architectures created by self-assembly of copper-
(I) and silver(I) complexes with multidentate organic ligands1,12
The design of new functional polymeric coordination com-
plexes consisting of one-, two-, and three-dimensional networks
from the assembly of metal ions and suitable multidentate
ligands is of intense current interest.1,2 Halocarbons RX, where
R is an alkyl or aryl group and X is a halogen atom, constitute
a unique type of ligand in coordination chemistry.3 They are
very weak bases so that the coordination to transition metal
centers is labile and the RX-M bonds can be easily broken by
nucleophilic attack.4-7 Recent research results from different
research groups have shown that silver(I) is a favorable and
fashionable building block for coordination polymers.8 However,
fully characterized examples of coordination complexes of
(8) (a) Powell, J.; Horvath, M. J.; Lough, A. J. Chem. Soc., Dalton Trans.
1996, 1669. (b) Powell, J.; Horvath, M.; Lough, A. J. Chem. Soc.,
Chem. Commun. 1993, 733. (c) Powell, J.; Horvath, M.; Lough, A. J.
Organomet. Chem. 1993, 456, C27.
* To whom correspondence should be addressed. E-mail: munakata@
chem.kindai.ac.jp.
(9) (a) Akakero¨y, C. B.; Beatty, A. M. Chem. Commun. 1998, 1067. (b)
Wu, H.-P.; Janiak, C.; Rheinwald, G.; Lang, H. J. Chem. Soc., Dalton
Trans. 1999, 183. (c) Kaes, C.; Hosseini, M. W.; Rickard, C. E. F.;
Skelton, B. W.; While, A. H. Angew. Chem., Int. Ed. Engl. 1998, 37,
920. (d) Bowyer, P. K.; Porter, K. A.; Rae, A. D.; Willis, A. C.; Wild,
S. B. Chem. Commun. 1998, 1153. (e) Hirsch, K. A.; Wilson, S. R.;
Moore, J. S. Chem. Commun. 1998, 13. (f) Hirsch, K. A.; Wilson, S.
R.; Moore, J. S. Chem. Eur. J. 1997, 3, 765. (g) Hirsch, K. A.; Wilson,
S. R.; Moore, J. S. Inorg. Chem. 1997, 36, 2960. (h) Carlucci, L.;
Ciani, G.; Gudenberg, D. W. v.; Proserpio, D. M.; Sironi, A. Chem.
Commun. 1997, 631. (i) Blake, A. J.; Champness, N. R.; Khlobystov,
A.; Lemenovskii, D. A.; Li, W.-S.; Schro¨der, M. Chem. Commun.
1997, 2027. (j) Carlucci, L.; Ciani, G.; Proserpio, D. M.; Sironi, A.
Chem. Commun. 1996, 1393. (k) Venkataraman, D.; Lee, S.; Moore,
J. S.; Zhang, P.; Hirsch, K. A.; Gardner, G. B.; Covey, A. C.; Prentice,
C. L. Chem. Mater. 1996, 8, 2030. (l) Janiak, C.; Scharman, T. G.;
Albrecht, P.; Marlow, F.; Macdonald, R. J. Am. Chem. Soc. 1996,
118, 6307. (m) Carlucci, L.; Ciani, G.; Proserpio, D. M.; Sironi, A. J.
Am. Chem. Soc. 1995, 117, 4562.
(10) (a) Seggen, D. M. V.; Hurlburt, P. K.; Anderson, O. P.; Strauss, S. H.
Inorg. Chem. 1995, 34, 3453. (b) Colsman, M. R.; Noirot, M. D.;
Miller, M. M.; Anderson, O. P.; Strauss, S. H. J. Am. Chem. Soc.
1988, 110, 6886. (c) Newbound, T. D.; Colsman, M. R.; Miller, M.
M.; Wulfsberg, G. P.; Anderson, O. P.; Strauss, S. H. J. Am. Chem.
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(11) Lancashire, R. J. In ComprehensiVe Coordination Chemistry; Wilkin-
son, G., Gillard, R. D., McCleverty, J. A., Eds.; Pergamon Press:
Oxford, 1987; Vol. 5, pp 775-859.
† Kinki University.
‡ East China Normal University.
(1) (a) Munakata, M.; Wu, L. P.; Kuroda-Sowa, T. Bull. Chem. Soc. Jpn.
1997, 70, 1727. (b) Munakata, M.; Wu, L. P.; Kuroda-Sowa, T. AdV.
Inorg. Chem. 1998, 46, 173.
(2) (a) Robson, R.; Abrahams, B. F.; Batten, S. R.; Gable, R. W.; Hoskins,
B. F.; Liu, J. Supramolecular Architecture; American Chemical
Society: Washington, DC, 1992; Chapter 19. (b) Janiak, C. Angew.
Chem., Int. Ed. Engl. 1997, 36, 1431. (c) Bowes, C. L.; Ozin, G. A.
AdV. Mater. 1996, 8, 13. (d) Zaworotko, M. J. Chem. Soc. ReV. 1994,
283.
(3) Kulawiec, R. J.; Crabtree, R. H. Coord. Chem. ReV. 1990, 99, 89.
(4) (a) Kulawiec, R. J.; Faller, J. W.; Crabtree, R. H. Organometallics
1990, 9, 745. (b) Burk, M. J.; Segmuller, B.; Crabtree, R. H.
Organometallics 1987, 6, 2241.
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118, 11831. (b) Casas, J. M.; Falvello, L. R.; Fornie´s, J.; Mart´ın, A.
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10.1021/ic991261g CCC: $19.00 © 2000 American Chemical Society
Published on Web 04/25/2000

Silver(I) Coordination Polymers
Inorganic Chemistry, Vol. 39, No. 10, 2000 2147
at room-temperature, colorless block crystals of 2 were obtained (33
mg, 39%). Anal. Calcd for C18H14AgI3NClO5 (the formula without
benzene molecule): C, 25.46; H, 1.65; N, 1.65. Found: C, 25.30; H,
1.51; N, 1.59. Main IR bands (cm-1): 3495(m), 2926(w), 2363(w),
1680(s), 1572(s), 1485(s), 1319(s), 1086(s), 1032(s), 828(s), and
625(s).
Synthesis of [Ag(L2)(ClO4)] (3). This compound was synthesized
by the manner similar to that for 2 with nitrobenzene in place of benzene
as the solvent. Anal. Calcd for C18H12AgI3NClO4: C, 26.01; H, 1.45;
N, 1.69. Found: C, 25.88; H, 1.46; N, 1.61. Main IR bands (cm-1):
1572(m), 1485(s), 1319(s), 1292(m), 1271(m), 1120(m), 1099(s), 1030-
(m), 1003(m), 916(w), 828(m), 808(m), 717(w), 621(m), 525(m), and
451(w).
generated a curiosity as to what binding mode an aryl iodide
derived ligand with more than two metal coordination sites
would adopt when bound to a labile metal center. Here, we
describe the preparation and single-crystal structures of four
distinct and highly unusual polymeric silver(I) complexes of
the aryl iodide derived ligands triiodobenzoic acid (HL1), tris-
(4-iodophenyl)amine (L2), and 5,7-diiodo-8-hydroxyquinoline
(HL3). The versatility of these iodocarbon derived species in
Synthesis of [Ag2(H2L3)(CF3SO3)3] (4). To a toluene solution (5
mL) containing silver triflate (25.7 mg, 0.1 mmol) was added
5,7-diiodo-8-hydroxyquinoline (10 mg, 0.025 mmol). The mixture was
stirred for 10 min and filtered. A portion of the filtrate (3 mL) was
transferred to a 7 mm diameter glass tube and gently layered with 3
mL of n-hexane as a diffusion solvent. After standing for 2 weeks at
5 °C yellow plate crystals of 4 were obtained (11 mg, 48%). Anal.
Calcd for C12H6Ag2I2NS3F9O10: C, 13.57; H, 0.57; N, 1.32. Found:
C, 13.81; H, 0.51; N, 1.49. Main IR bands (cm-1): 3061(s), 2498(w),
2375(w), 1557(m), 1483(w), 1455(m), 1389(s), 1331(m), 1267(m),
1134(m), 924(w), 870(w), 806(w), 783(w), 721(w), 650(m), and 548-
(w).
X-ray Data Collection and Structure Solutions and Refinements.
For 1-3 a suitable single crystal was mounted on a glass fiber, while
that for 4 was enclosed in a glass capillary. Diffraction data were
collected at room temperature on a Quantum CCD area detector coupled
with a Rigaku AFC7 diffractometer with graphite monochromated Mo
KR radiation. Periodic remeasurement of three standard reflections,
collected every 150, revealed no significant changes in intensities.
Azimuthal scans of several reflections for each compound indicated
no need for an absorption correction. Intensities were measured from
continuous ω-2θ scans. All intensity data were corrected for Lorentz
polarization effects.
The structures were solved by direct methods followed by subsequent
Fourier difference calculation and refined by a full-matrix least-squares
analysis on F2, using the TEXSAN package.13All the full-occupancy
non-hydrogen atoms were refined anisotropically. Hydrogen atoms of
the four structures were introduced in their calculated positions; they
were included, but not refined, in the refinement. The counteranions
ClO4- and CF3SO3- were found to have high thermal motions in 2-4.
The highest residual peaks for 4 resulted from this disorder. Details
of the X-ray experiments and crystal data are summarized in Table 1.
Selected bond lengths and bond angles are given in Table 2.
complexing metal ions makes them especially interesting
candidates for formation of self-assembly of a wide range of
infinite frameworks.
Experimental Section
General Methods. All chemicals were reagent grade. Reactions and
manipulations were carried out under an argon atmosphere by using
the standard Schlenk vacuum line techniques. Solvents were dried using
standard procedures and distilled under an argon atmosphere prior to
use. High-purity argon was used to deoxygenate solvents. Triiodoben-
zoic acid, 5,7-diiodo-8-hydroxyquinoline, silver acetate, and silver
perchlorate were purchased from Aldrich. Tris(4-iodophenyl)amine was
purchased from Tokyo Chemical Industry Co., Ltd. All chemicals were
used as received. The IR spectra were recorded as KBr disks on a
JASCO FT-IR-8000 spectrometer, and ESR spectra were recorded on
a JEOL JES-TE200 ESR spectrometer. Solid-state 109Ag NMR spectra
were obtained with a JEOL GX 500 FT NMR spectrometer at 27 °C.
Safety Note. Perchlorate salts of metal complexes with organic
ligands are potentially explosiVe! Only small amounts of materials
should be prepared, and these should be handled with great caution.
Synthesis of [Ag(L1)] (1). An aqueous solution (10 mL) containing
16.6 mg (0.1 mmol) of AgCH3COO in a glass tube was layered with
a methanolic solution (10 mL) of triiodobenzoic acid (50 mg, 0.1 mmol).
The glass tube, sealed under Ar and wrapped with aluminum foil, was
left standing at room temperature for 1 day; colorless slab crystals of
1 were isolated (38 mg, 57%). Anal. Calcd for C7H2AgI3O2: C, 13.85;
H, 0.33. Found: C, 13.68; H, 0.36. Main IR bands (cm-1): 2926(s),
2857(s), 1590(m), 1551(m), 1462(m), 1379(m), 1346(m), 1200(w),
1100(w), and 457(w). 109Ag NMR (ppm): δAg ) 378.
Results and Discussion
Structure of [Ag(L1)] (1). An ORTEP drawing of the
complex with the atom numbering scheme is shown in Figure
1. The structure of 1 in the crystalline state features a two-
dimensional arrangement of ladders constructed from silver
atoms linked by carboxylate anions. Except for the coordination
of Ag-I, the coordination environment of each metal atom is
almost trigonal planar, comprising three carboxylate oxygen
atoms from three different ligand groups. Each I3C6H2COO-
moiety in turn employs its carboxylate group to interact with
three metal centers. The unique structural feature of the ligand
is its tridentate binding of the carboxylate group to three metal
centers with Ag-O bond distances varying widely, ranging from
2.229(3) to 2.518(3) Å. Nevertheless, they are well within the
range 2.17-2.61 Å observed in silver(I) carboxylate and oxalate
complexes.11 The two symmetry-related metal centers are
coupled by two ligand groups with a Ag‚‚‚Ag separation of
2.8898(8) Å. This results in an eight-membered macrocycle,
which is further linked to its neighboring counterpart by two
Synthesis of [Ag(L2)(H2O)]ClO4‚C6H6 (2). To a benzene solution
(5 mL) containing silver perchlorate (22.5 mg, 0.1 mmol) was added
tris(4-iodophenyl)amine (62.3 mg, 0.1 mmol). The mixture was stirred
for 10 min and filtered. A portion of the filtrate (3 mL) was transferred
to a 7 mm diameter glass tube and gently layered with 3 mL of
n-pentane as a diffusion solvent. After the solution stood for 3 weeks
(12) (a) Munakata, M.; Wu, L. P.; Kuroda-Sowa, T.; Maekawa, M.;
Suenaga, Y.; Ning, G. L.; Kojima, T. J. Am. Chem. Soc. 1998, 120,
8610. (b) Wu, L. P.; Dai, J.; Munakata, M.; Kuroda-Sowa, T.;
Maekawa, M.; Suenaga, Y.; Ohno, Y. J. Chem. Soc., Dalton Trans.
1998, 3255.
(13) TEXSAN-TEXRAY Structural Analysis Package; Molecular Structure
Corp.: The Woodlands, TX, 1985.

2148 Inorganic Chemistry, Vol. 39, No. 10, 2000
Ino et al.
Table 1. Crystallographic Data for Complexes 1-4
1
2
3
4
formula
fw
space group
a, Å
b, Å
c, Å
C7H2AgI3O2
606.67
P21/n
13.33(2)
5.72(2)
14.90(3)
108.83(4)
1075(4)
4
C24H20AgI3NClO5
926.46
P21/c
10.6675(7)
10.537(1)
25.5279(6)
93.7476(6)
2863.3(3)
4
C18H12AgI3NClO4
830.33
P21/n
10.854(4)
20.176(6)
10.9803(3)
116.080(2)
2159.7(8)
4
C12H6Ag2I2NS3F9O10
1060.89
P21/c
11.611(1)
22.806(3)
11.9415(1)
110.0051(3)
2971.3(3)
4
â, deg
V, Å3
Z
temp, °C
λ (Mo KR), Å
F, g/cm3
µ, cm-1
Ra
23
0.710 69
3.746
104.46
0.028
0.098
23
0.710 69
2.149
40.64
0.042
23
0.710 69
2.553
53.69
0.034
23
0.710 69
2.371
37.03
0.075
b
Rw
0.130
0.123
0.235
a ∑(Fo - Fc2)/∑Fo . b [∑w(Fo - Fc2)2/∑w(Fo )2]1/2
.
2
2
2
2
Table 2. Selected Bond Lengths (Å) and Angles (deg) for
Complexes 1-4
1
Ag-I(1)
Ag-O(2)
Ag‚‚‚Ag′
3.053(4)
2.518(3)
2.8898(8)
Ag-O(1)
Ag-O(2′)
2.229(3)
2.268(3)
I(1)-Ag-O(1)
I(1)-Ag-O(2′)
O(1)-Ag-O(2′)
99.8(1)
105.7(1)
154.3(1)
I(1)-Ag-O(2)
O(1)-Ag-O(2)
O(2)-Ag-O(2′)
74.1(1)
115.0(1)
75.9(1)
2
3
4
Ag-I(1)
Ag-I(3)
2.8439(6)
3.0103(7)
Ag-I(2)
2.7932(6)
2.344(4)
Ag-O(5)
I(1)-Ag-I(2)
I(1)-Ag-O(5)
I(2)-Ag-O(5)
112.71(2)
99.88(9)
113.14(10)
I(1)-Ag-I(3)
I(2)-Ag-I(3)
I(3)-Ag-O(5)
107.60(2)
108.45(2)
114.80(9)
Ag-I(1)
Ag-I(3)
2.7849(5)
2.8195(6)
Ag-I(2)
Ag-O(1)
2.9119(7)
2.483(5)
Figure 1. (a) ORTEP view of the structure of 1, showing 50% thermal
ellipsoids. (b) Schematic view of the framework in 1 consisting of
square and pentagons.
I(1)-Ag-I(2)
I(1)-Ag-O(1)
I(2)-Ag-O(1)
119.18(2)
95.1(1)
102.2(1)
I(1)-Ag-I(3)
I(2)-Ag-I(3)
I(3)-Ag-O(1)
133.03(2)
101.42(2)
98.6(1)
two Ag atoms (2.884 Å),14 presumably as a consequence of
the requirements of the formation of the dinuclear core. This
distance is slightly shorter than those found in disilver(I)
complexes [AgCH2P(S)Ph2]2 (2.990(2) Å),15 [Ag(O2CCF3)]2
(2.967(3) Å),16 [Ag{CH(COOC2H5}2PPh2]2 (2.953(1) Å),17 and
[Ag(O2CC6H5)]2 (2.902(3) Å)18 and recently reported triazopy-
rimidine complexes (3.089(1)-3.127(1) Å).19 However, much
shorter Ag‚‚‚Ag interactions have been observed in [Ag{o-(Me3-
Si)2CC5H4N}]2 (2.654(1) Å),20 [Ag(PhN3Ph)]2 (2.669(1) Å),21
and [Ag(p-CH3C6H4NCHNC6H4-p-CH3]2 (2.705(1) Å).22 We
Ag-I(1)
2.908(1)
2.423(7)
2.946(1)
2.373(9)
Ag(1)-I(2)
Ag(1)-O(9)
Ag(2)-O(1)
Ag(2)-O(5)
3.046(1)
2.64(2)
2.380(9)
2.501(8)
Ag(1)-O(4)
Ag(2)-I(2)
Ag(2)-O(3)
I(1)-Ag(1)-I(2)
I(1)-Ag(1)-O(9)
I(2)-Ag(1)-O(9)
I(2)-Ag(2)-O(1)
I(2)-Ag(2)-O(5)
O(1)-Ag(2)-O(5)
150.76(5)
113.3(3)
95.0(3)
144.8(2)
81.4(2)
I(1)-Ag(1)-O(4)
I(2)-Ag(1)-O(4)
O(4)-Ag(1)-O(9)
I(2)-Ag(2)-O(3)
O(1)-Ag(2)-O(3)
O(3)-Ag(2)-O(5)
89.3(2)
77.2(2)
101.9(4)
102.1(3)
112.1(3)
122.9(3)
86.7(3)
bridging oxygen atoms O(2) and O(2′), giving rise to a rhombic
AgOAgO plane with a negligible Ag‚‚‚Ag interaction of 3.78
Å. The Ag2O2 rhomboid is not coplanar with the eight-
membered macrocycle; instead, they are slightly tilted against
each other at a dihedral angle of 18.43°. The overall result of
this arrangement is a supramolecular ladderlike network virtually
based on covalent bonding interactions. The Ag-I(1) bond
length of 3.053(4) Å is extra long compared with those in
previously reported iodocarbon-silver complexes (2.8-3.0 Å).10
Thus, we would consider the Ag-I as a weak, nondirectional
interaction, and the structure could be described as 2D layers
of ladders connected through weak Ag‚‚‚I interaction running
parallel to [010] (Figure 2).
(14) Pauling, L. The Nature of the Chemical Bond, 3rd ed.; Cornell
University Press: Ithaca, NY, 1960.
(15) Wang, S.; Fackler, J. P., Jr.; Carlson, T. F. Organometallics 1990, 9,
1973.
(16) Griffin, R. G.; Ellett, J. D., Jr.; Mehring, M.; Bullitt, J. G.; Waugh, J.
S. J. Chem. Phys. 1972, 57, 2147.
(17) Vicente, J.; Chicote, M. T.; Saura-Llamas, I. Organometallics 1989,
8, 767.
(18) Usubaliev, B. T.; Movsumov, E. M.; Amiraslanov, I. R.; Akhmedov,
A. I.; Musaev, A. A.; Mamedov, K. H. S. Zh. Strukt. Khim. 1981, 22,
98.
(19) Navarro, J. A. R.; Salas, J. M.; Romero, M. A.; Faure, R. J. Chem.
Soc., Dalton Trans. 1998, 901.
(20) Papasergio, R. I.; Raston, C. L.; White, A. H. J. Chem. Soc., Dalton
Trans. 1987, 3085.
(21) Beck, J.; Stra¨hle, J. Z. Naturforsch. B: Anorg. Chem., Org. Chem.
1986, 41, 4.
The intramacrocycle Ag‚‚‚Ag separation (2.8898(8) Å)
observed in 1 is very close to the sum of the metallic radii of
(22) Cotton, F. A.; Feng, X.; Matusz, M.; Poli, R. J. Am. Chem. Soc. 1988,
110, 7077.

Silver(I) Coordination Polymers
Inorganic Chemistry, Vol. 39, No. 10, 2000 2149
Figure 2. Perspective views of the ladderlike network in 1: (a) top
view and (b) side view.
Figure 4. Perspective views of the packing of 2: (a) top view, (b)
schematic view of the framework (solid line is for upper layer and
dotted line for lower layer), and (c) side view.
as a 2D layer of square and octagons (82‚4) perpendicular to
[100]. A two-dimensional porous structure is formed in which
the larger cavity consisting of four metal ions and four ligand
groups incorporates one solvated benzene molecule as shown
-
in Figure 4. Discrete ClO4 anions maintain electroneutrality.
Complex 2 was found to be unstable under atmosphere
possibly because of release of the solvated benzene molecule
from the lattice. Therefore, the theoretical value for elemental
analysis is based on the formula without benzene molecules.
The colorless crystals were also very sensitive to light and
readily changed to black color under light irradiation.
Figure 3. ORTEP view of the structure of 2, showing 50% thermal
ellipsoids.
conclude that 1, like those dinuclear silver compounds with very
short Ag‚‚‚Ag separations,20-22 has little or no formal metal-
metal bonding, and hence, no special physicochemical properties
derived from metal-metal interactions have been detected.
Structure of [Ag(L2)(H2O)]ClO4‚C6H6 (2). The structure
determination of 2 reveals an infinite cationic lattice of formula
[Ag(C18H12I3N)(H2O)]nn+ and noninteracting perchlorate anions.
The cation comprises a dimeric unit as shown in Figure 3, in
which each metal center is tetrahedrally coordinated to one
iodine atom of three distinct ligand groups and the fourth
coordination is accomplished by interaction with one crystallized
water molecule. Half of the molecule is related to the other half
by a center of symmetry. Each ligand molecule exhibits
tridentate coordination, employing all three iodine binding sites
to link three metal centers. Here, all the Ag-I interactions are
comparable and the topology of the network is easily described
Structure of [Ag(L2)(ClO4)] (3). Although colorless single
crystals of 3 were synthesized by the manner similar to that for
2, employment of nitrobenzene as the solvent gave a different
compound involving coordination of the perchlorate anions,
which was confirmed by X-ray analysis and infrared spectrum.
A view of the molecular structure with atom numbering scheme
is shown in Figure 5. The formation of the macrocyclic dinuclear
unit is directly analogous to that in 2. Each metal center basically
involves a trigonal pyramidal coordination geometry rather than
a tetrahedron as observed in 2, comprising one iodine atom of
three distinct ligand groups to form the base, and the apex site
is occupied by one ClO4- ion. The three I-Ag-I angles range
from 101.42(2)° to 133.03(2)° and the three I-Ag-O angles
from 95.1(1)° to 102.2(1)°. As in 2, each ligand group uses all
three iodine binding sites to link three silver atoms with Ag-I

2150 Inorganic Chemistry, Vol. 39, No. 10, 2000
Ino et al.
Figure 5. ORTEP view of the structure of 3, showing 50% thermal
ellipsoids.
Figure 7. (a) Overall view of the extended structure of 4 where
CF3SO3- is represented as O-O for clarity. (b) Schematic view of 2D
layer structure in 4.
HL3 moiety, consistent with the stoichiometry decided by
structure analysis.
The structure is based on columnar arrays of two crystallo-
graphically independent silver(I) ions bridged by +H2L3 groups
and CF3SO3 anions (Figure 7). On the Ag(1) column the two
symmetry-related ligand groups each bind two metal atoms with
two iodine atoms, giving a dinuclear core in which each Ag(1)
atom is coordinated to two H2L3 groups, one bridging and one
-
terminal CF3SO3 ions. In contrast, on the Ag(2) column the
two adjacent metal atoms are linked together by CF3SO3- ions,
affording a zigzag chain. The one-atom bridging of I(2) between
Ag(1) and Ag(2) connects the columnar arrays of metal ions
together, leading to an alternate arrangement of 2D layers of
Ag2(H2L3)2 and Ag2(CF3SO3)2. The packing diagram shows that
there is no interaction between the adjacent columns in the cell,
suggestive of a stronger interaction between the molecules
stacked within a chain than between chains. Such a columnar
structure may have larger electrical or magnetic interactions
along the column than perpendicular to the column, leading to
anisotropic (one-dimensional) properties.23
Figure 6. Perspective views of the packing of 3: (a) top view, (b)
schematic view of the framework (solid line is for upper layer and
dotted line for lower layer), and (c) side view.
ESR, Conductivity, and Solid-State Multinuclear NMR
Studies. At ambient temperature complexes 1, 2, and 4 show
an isotropic ESR signal with g ) 2.005-2.007, whose origin
is not immediately clear. In contrast, 3 did not exhibit such
strong ESR resonance. The electrical conductivity of compacted
pellets was measured by the conventional two-probe technique
employing gold or silver paste coated probes. All the compounds
are electrically nonconducting, whereas the light-irradiated
samples display semiconducting behavior at ambient temperature
bond lengths varying from 2.7849(5) to 2.9119(7) Å. Following
the above description of 2, the relation with 3 is straightforward.
Indeed, 3 is formed by 2D layers of the same topology of 2
(82‚4), running perpendicular to [101] and alternating as ABAB.
This again deprives the possibility of formation of the channel
structure. The layers have a different corrugation compared to
2 and are interdigitated as shown in Figure 6. In contrast to
clathration of solvent molecules in 2, the octagon consisting of
four metal ions and four ligand groups includes the coordinated
perchlorate ion as guest species.
with a σ300 value ranging from 6.3 × 10-5 to 2.1 × 10-4
S
cm-1. This behavior clearly implies that electron transfer
between the Ag(I) ion and the ligand in the solid state is
enhanced by irradiation of light.
Structure of [Ag2(H2L3)(CF3SO3)3] (4). Yellow plate single
crystals of 4 were obtained by the reaction of HL3 with an excess
of Ag(CF3SO3). The compound was formulated on the basis of
the IR spectrum as well the elemental analysis and single-crystal
X-ray structure determination. The infrared spectrum shows the
strong ν(NH) stretching frequency at 3061 cm-1, indicating that
the ligand exists as a monocation +H2L3 rather than the neutral
Since many silver compounds are light-sensitive and quite
labile in solution, solid-state 109Ag NMR spectroscopy seems
to be an especially attractive method in chemical structure
(23) Miller, J. S.; Spstein, A. J. Prog. Inorg. Chem. 1976, 20, 1.

Silver(I) Coordination Polymers
Inorganic Chemistry, Vol. 39, No. 10, 2000 2151
ligand-dependent and that the 109Ag resonance substantially
shifts downfield with coordination to soft ligands,24 for example,
Ag[CH3CHC(OH)CO2] (345.9, 320.2, 219.7, and 210.7 ppm),
Ag(CH3CO2) (401.2 and 382.7 ppm), AgCl (370 ppm), AgBr
(350 ppm), AgI (710 ppm), and KAg4I5 (810 ppm). The
chemical shift observed in 1 conforms to this pattern when the
four-coordinate silver ion in the complex bonding to one iodine
and three carboxylate oxygen atoms is taken into consideration.
The single peak and the δ value observed for 1 are both
consistent with the structural data determined by X-ray analysis.
Conclusions
Of all the common organic functional groups, halocarbons
have been by far the least studied in coordination chemistry.
To our knowledge, this work represents the first structural
characterization of silver(I) polymers with simple aryl iodide
derived ligands, triiodobenzoic acid, tris(4-iodophenyl)amine,
and 5,7-diiodo-8-hydroxyquinoline. The average Ag-I bond
distances of 3.053, 2.882, 2.839, and 2.967 Å observed in 1, 2,
3, and 4, respectively, are slightly longer or shorter than those
Figure 8. Solid-state 109Ag spectrum of complex 1 at 300 K and 23.28
MHz.
analysis, especially for polymeric complexes. Unfortunately,
while the solid-state 109Ag chemical shift data for several simple
silver(I) salts have been measured,24 those for silver(I) com-
plexes have not been extensively studied yet. NMR spectra of
complexes 2 and 3 are not possible for safety reasons, whereas
complex 4 was unstable upon extended exposure to light and
gradually decomposed, which also prevented a 109Ag spectrum
from being obtained. Therefore, in this work only complex 1
was selected for a tentative study.
-
found in inorganic silver(I) iodide compounds such as [Ag2I3]n
2-
(2.851 Å) and [AgI3]n
(2.847 Å),25 indicating that the
interaction of the aryl iodide with the silver(I) ion is almost of
the same extent as those of the inorganic iodide species. The
study demonstrates that the iodocarbon-derived ligands may
have a rich coordination chemistry, possessing unique coordi-
native versatility and diversity and bridging the metal centers
to form a supramolecular architecture brought about by covalent
bonding interactions. Further studies are directed toward the
development of various self-assembly process involving other
aryl halide derivatives such as 2,4,6-triiodophenol and 3,5-
diiodosalicylic acid, as well as the elucidation of spectroscopic
and conductive properties observed in such systems.
Silver-109 has I ) 1/2, but direct observation of the solid 109
-
Ag NMR resonance is difficult because of its low magnetogyric
ratio, low receptivity, and long relaxation times. However, in
this work we measured the solid 109Ag NMR of 1 at 300 K and
23.28 MHz in natural abundance and were able to obtain the
resonance by operating the Fourier transfer of the free induction
decay (FID) by the window function with a broadening factor
of 300 MHz (Figure 8). The spectrum consists of a peak and a
much broader line, suggestive of only one metal coordination
environment present in the compound. The 109Ag resonance at
δ ) 378 ppm is referenced to aqueous Ag(ClO4) solution (δ ≡
0 ppm.) It is well-known that the silver chemical shifts are
Acknowledgment. This work was partially supported by a
Grant-in-Aid for Science Research [Nos. 10440201, 11874092,
and 10016743 (priority areas “Metal-Assembled Complexes”)]
from the Ministry of Education, Science, Sports and Culture in
Japan.
Supporting Information Available: X-ray crystallographic files
in CIF format for the structure determination of 1-4. This material is
available free of charge via the Internet at http://pubs.acs.org.
(24) (a) Merwin, L. H.; Sebald, A. J. Magn. Reson. 1992, 97, 628. (b)
Looser, H.; Brinkmann, D. J. Magn. Reson. 1985, 64, 76. (c) Becker,
K. D.; Von Goldammer, E. Chem. Phys. 1980, 48, 193.
(25) Wells, A. F. Structural Inorganic Chemistry, 5th ed.; Oxford University
Press: Oxford, 1993; p 1109 and the references therein.
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